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{--target-help}] [@var{target-options}]
246 [@b{--}|@var{files} @dots{}]
248 @c Target dependent options are listed below. Keep the list sorted.
249 @c Add an empty line for separation.
252 @emph{Target AArch64 options:}
254 [@b{-mabi}=@var{ABI}]
258 @emph{Target Alpha options:}
260 [@b{-mdebug} | @b{-no-mdebug}]
261 [@b{-replace} | @b{-noreplace}]
262 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
263 [@b{-F}] [@b{-32addr}]
267 @emph{Target ARC options:}
268 [@b{-mcpu=@var{cpu}}]
269 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
275 @emph{Target ARM options:}
276 @c Don't document the deprecated options
277 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
278 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
279 [@b{-mfpu}=@var{floating-point-format}]
280 [@b{-mfloat-abi}=@var{abi}]
281 [@b{-meabi}=@var{ver}]
284 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
285 @b{-mapcs-reentrant}]
286 [@b{-mthumb-interwork}] [@b{-k}]
290 @emph{Target Blackfin options:}
291 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
298 @emph{Target CRIS options:}
299 [@b{--underscore} | @b{--no-underscore}]
301 [@b{--emulation=criself} | @b{--emulation=crisaout}]
302 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
303 @c Deprecated -- deliberately not documented.
308 @emph{Target D10V options:}
313 @emph{Target D30V options:}
314 [@b{-O}|@b{-n}|@b{-N}]
318 @emph{Target EPIPHANY options:}
319 [@b{-mepiphany}|@b{-mepiphany16}]
323 @emph{Target H8/300 options:}
327 @c HPPA has no machine-dependent assembler options (yet).
331 @emph{Target i386 options:}
332 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
333 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
337 @emph{Target i960 options:}
338 @c see md_parse_option in tc-i960.c
339 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
341 [@b{-b}] [@b{-no-relax}]
345 @emph{Target IA-64 options:}
346 [@b{-mconstant-gp}|@b{-mauto-pic}]
347 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
349 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
350 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
351 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
352 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
356 @emph{Target IP2K options:}
357 [@b{-mip2022}|@b{-mip2022ext}]
361 @emph{Target M32C options:}
362 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
366 @emph{Target M32R options:}
367 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
372 @emph{Target M680X0 options:}
373 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
377 @emph{Target M68HC11 options:}
378 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
379 [@b{-mshort}|@b{-mlong}]
380 [@b{-mshort-double}|@b{-mlong-double}]
381 [@b{--force-long-branches}] [@b{--short-branches}]
382 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
383 [@b{--print-opcodes}] [@b{--generate-example}]
387 @emph{Target MCORE options:}
388 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
389 [@b{-mcpu=[210|340]}]
393 @emph{Target Meta options:}
394 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
397 @emph{Target MICROBLAZE options:}
398 @c MicroBlaze has no machine-dependent assembler options.
402 @emph{Target MIPS options:}
403 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
404 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
405 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
406 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
407 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
408 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
409 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
410 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
411 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
412 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
413 [@b{-construct-floats}] [@b{-no-construct-floats}]
414 [@b{-mnan=@var{encoding}}]
415 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
416 [@b{-mips16}] [@b{-no-mips16}]
417 [@b{-mmicromips}] [@b{-mno-micromips}]
418 [@b{-msmartmips}] [@b{-mno-smartmips}]
419 [@b{-mips3d}] [@b{-no-mips3d}]
420 [@b{-mdmx}] [@b{-no-mdmx}]
421 [@b{-mdsp}] [@b{-mno-dsp}]
422 [@b{-mdspr2}] [@b{-mno-dspr2}]
423 [@b{-mmsa}] [@b{-mno-msa}]
424 [@b{-mxpa}] [@b{-mno-xpa}]
425 [@b{-mmt}] [@b{-mno-mt}]
426 [@b{-mmcu}] [@b{-mno-mcu}]
427 [@b{-minsn32}] [@b{-mno-insn32}]
428 [@b{-mfix7000}] [@b{-mno-fix7000}]
429 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
430 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
431 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
432 [@b{-mdebug}] [@b{-no-mdebug}]
433 [@b{-mpdr}] [@b{-mno-pdr}]
437 @emph{Target MMIX options:}
438 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
439 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
440 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
441 [@b{--linker-allocated-gregs}]
445 @emph{Target Nios II options:}
446 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
451 @emph{Target NDS32 options:}
452 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
453 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
454 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
455 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
456 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
457 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
458 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
463 @emph{Target PDP11 options:}
464 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
465 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
466 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
470 @emph{Target picoJava options:}
475 @emph{Target PowerPC options:}
477 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
478 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
479 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
480 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
481 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
482 @b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
483 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
484 [@b{-mregnames}|@b{-mno-regnames}]
485 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
486 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
487 [@b{-msolaris}|@b{-mno-solaris}]
488 [@b{-nops=@var{count}}]
492 @emph{Target RL78 options:}
494 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
498 @emph{Target RX options:}
499 [@b{-mlittle-endian}|@b{-mbig-endian}]
500 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
501 [@b{-muse-conventional-section-names}]
502 [@b{-msmall-data-limit}]
505 [@b{-mint-register=@var{number}}]
506 [@b{-mgcc-abi}|@b{-mrx-abi}]
510 @emph{Target s390 options:}
511 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
512 [@b{-mregnames}|@b{-mno-regnames}]
513 [@b{-mwarn-areg-zero}]
517 @emph{Target SCORE options:}
518 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
519 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
520 [@b{-march=score7}][@b{-march=score3}]
521 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
525 @emph{Target SPARC options:}
526 @c The order here is important. See c-sparc.texi.
527 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
528 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
529 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
534 @emph{Target TIC54X options:}
535 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
536 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
540 @emph{Target TIC6X options:}
541 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
542 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
543 [@b{-mpic}|@b{-mno-pic}]
547 @emph{Target TILE-Gx options:}
548 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
551 @c TILEPro has no machine-dependent assembler options
555 @emph{Target Visium options:}
556 [@b{-mtune=@var{arch}}]
560 @emph{Target Xtensa options:}
561 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
562 [@b{--[no-]absolute-literals}]
563 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
564 [@b{--[no-]transform}]
565 [@b{--rename-section} @var{oldname}=@var{newname}]
566 [@b{--[no-]trampolines}]
570 @emph{Target Z80 options:}
571 [@b{-z80}] [@b{-r800}]
572 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
573 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
574 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
575 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
576 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
577 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
581 @c Z8000 has no machine-dependent assembler options
590 @include at-file.texi
593 Turn on listings, in any of a variety of ways:
597 omit false conditionals
600 omit debugging directives
603 include general information, like @value{AS} version and options passed
606 include high-level source
612 include macro expansions
615 omit forms processing
621 set the name of the listing file
624 You may combine these options; for example, use @samp{-aln} for assembly
625 listing without forms processing. The @samp{=file} option, if used, must be
626 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
629 Begin in alternate macro mode.
631 @xref{Altmacro,,@code{.altmacro}}.
634 @item --compress-debug-sections
635 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
636 ELF ABI. The resulting object file may not be compatible with older
637 linkers and object file utilities. Note if compression would make a
638 given section @emph{larger} then it is not compressed.
641 @cindex @samp{--compress-debug-sections=} option
642 @item --compress-debug-sections=none
643 @itemx --compress-debug-sections=zlib
644 @itemx --compress-debug-sections=zlib-gnu
645 @itemx --compress-debug-sections=zlib-gabi
646 These options control how DWARF debug sections are compressed.
647 @option{--compress-debug-sections=none} is equivalent to
648 @option{--nocompress-debug-sections}.
649 @option{--compress-debug-sections=zlib} and
650 @option{--compress-debug-sections=zlib-gabi} are equivalent to
651 @option{--compress-debug-sections}.
652 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
653 sections using zlib. The debug sections are renamed to begin with
654 @samp{.zdebug}. Note if compression would make a given section
655 @emph{larger} then it is not compressed nor renamed.
659 @item --nocompress-debug-sections
660 Do not compress DWARF debug sections. This is usually the default for all
661 targets except the x86/x86_64, but a configure time option can be used to
665 Ignored. This option is accepted for script compatibility with calls to
668 @item --debug-prefix-map @var{old}=@var{new}
669 When assembling files in directory @file{@var{old}}, record debugging
670 information describing them as in @file{@var{new}} instead.
672 @item --defsym @var{sym}=@var{value}
673 Define the symbol @var{sym} to be @var{value} before assembling the input file.
674 @var{value} must be an integer constant. As in C, a leading @samp{0x}
675 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
676 value. The value of the symbol can be overridden inside a source file via the
677 use of a @code{.set} pseudo-op.
680 ``fast''---skip whitespace and comment preprocessing (assume source is
685 Generate debugging information for each assembler source line using whichever
686 debug format is preferred by the target. This currently means either STABS,
690 Generate stabs debugging information for each assembler line. This
691 may help debugging assembler code, if the debugger can handle it.
694 Generate stabs debugging information for each assembler line, with GNU
695 extensions that probably only gdb can handle, and that could make other
696 debuggers crash or refuse to read your program. This
697 may help debugging assembler code. Currently the only GNU extension is
698 the location of the current working directory at assembling time.
701 Generate DWARF2 debugging information for each assembler line. This
702 may help debugging assembler code, if the debugger can handle it. Note---this
703 option is only supported by some targets, not all of them.
705 @item --gdwarf-sections
706 Instead of creating a .debug_line section, create a series of
707 .debug_line.@var{foo} sections where @var{foo} is the name of the
708 corresponding code section. For example a code section called @var{.text.func}
709 will have its dwarf line number information placed into a section called
710 @var{.debug_line.text.func}. If the code section is just called @var{.text}
711 then debug line section will still be called just @var{.debug_line} without any
714 @item --size-check=error
715 @itemx --size-check=warning
716 Issue an error or warning for invalid ELF .size directive.
719 Print a summary of the command line options and exit.
722 Print a summary of all target specific options and exit.
725 Add directory @var{dir} to the search list for @code{.include} directives.
728 Don't warn about signed overflow.
731 @ifclear DIFF-TBL-KLUGE
732 This option is accepted but has no effect on the @value{TARGET} family.
734 @ifset DIFF-TBL-KLUGE
735 Issue warnings when difference tables altered for long displacements.
740 Keep (in the symbol table) local symbols. These symbols start with
741 system-specific local label prefixes, typically @samp{.L} for ELF systems
742 or @samp{L} for traditional a.out systems.
747 @item --listing-lhs-width=@var{number}
748 Set the maximum width, in words, of the output data column for an assembler
749 listing to @var{number}.
751 @item --listing-lhs-width2=@var{number}
752 Set the maximum width, in words, of the output data column for continuation
753 lines in an assembler listing to @var{number}.
755 @item --listing-rhs-width=@var{number}
756 Set the maximum width of an input source line, as displayed in a listing, to
759 @item --listing-cont-lines=@var{number}
760 Set the maximum number of lines printed in a listing for a single line of input
763 @item -o @var{objfile}
764 Name the object-file output from @command{@value{AS}} @var{objfile}.
767 Fold the data section into the text section.
769 @item --hash-size=@var{number}
770 Set the default size of GAS's hash tables to a prime number close to
771 @var{number}. Increasing this value can reduce the length of time it takes the
772 assembler to perform its tasks, at the expense of increasing the assembler's
773 memory requirements. Similarly reducing this value can reduce the memory
774 requirements at the expense of speed.
776 @item --reduce-memory-overheads
777 This option reduces GAS's memory requirements, at the expense of making the
778 assembly processes slower. Currently this switch is a synonym for
779 @samp{--hash-size=4051}, but in the future it may have other effects as well.
782 @item --sectname-subst
783 Honor substitution sequences in section names.
785 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
790 Print the maximum space (in bytes) and total time (in seconds) used by
793 @item --strip-local-absolute
794 Remove local absolute symbols from the outgoing symbol table.
798 Print the @command{as} version.
801 Print the @command{as} version and exit.
805 Suppress warning messages.
807 @item --fatal-warnings
808 Treat warnings as errors.
811 Don't suppress warning messages or treat them as errors.
820 Generate an object file even after errors.
822 @item -- | @var{files} @dots{}
823 Standard input, or source files to assemble.
831 @xref{AArch64 Options}, for the options available when @value{AS} is configured
832 for the 64-bit mode of the ARM Architecture (AArch64).
837 The following options are available when @value{AS} is configured for the
838 64-bit mode of the ARM Architecture (AArch64).
841 @include c-aarch64.texi
842 @c ended inside the included file
850 @xref{Alpha Options}, for the options available when @value{AS} is configured
851 for an Alpha processor.
856 The following options are available when @value{AS} is configured for an Alpha
860 @include c-alpha.texi
861 @c ended inside the included file
868 The following options are available when @value{AS} is configured for an ARC
872 @item -mcpu=@var{cpu}
873 This option selects the core processor variant.
875 Select either big-endian (-EB) or little-endian (-EL) output.
877 Enable Code Density extenssion instructions.
882 The following options are available when @value{AS} is configured for the ARM
886 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
887 Specify which ARM processor variant is the target.
888 @item -march=@var{architecture}[+@var{extension}@dots{}]
889 Specify which ARM architecture variant is used by the target.
890 @item -mfpu=@var{floating-point-format}
891 Select which Floating Point architecture is the target.
892 @item -mfloat-abi=@var{abi}
893 Select which floating point ABI is in use.
895 Enable Thumb only instruction decoding.
896 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
897 Select which procedure calling convention is in use.
899 Select either big-endian (-EB) or little-endian (-EL) output.
900 @item -mthumb-interwork
901 Specify that the code has been generated with interworking between Thumb and
904 Turns on CodeComposer Studio assembly syntax compatibility mode.
906 Specify that PIC code has been generated.
914 @xref{Blackfin Options}, for the options available when @value{AS} is
915 configured for the Blackfin processor family.
920 The following options are available when @value{AS} is configured for
921 the Blackfin processor family.
925 @c ended inside the included file
932 See the info pages for documentation of the CRIS-specific options.
936 The following options are available when @value{AS} is configured for
939 @cindex D10V optimization
940 @cindex optimization, D10V
942 Optimize output by parallelizing instructions.
947 The following options are available when @value{AS} is configured for a D30V
950 @cindex D30V optimization
951 @cindex optimization, D30V
953 Optimize output by parallelizing instructions.
957 Warn when nops are generated.
959 @cindex D30V nops after 32-bit multiply
961 Warn when a nop after a 32-bit multiply instruction is generated.
967 The following options are available when @value{AS} is configured for the
968 Adapteva EPIPHANY series.
971 @xref{Epiphany Options}, for the options available when @value{AS} is
972 configured for an Epiphany processor.
977 The following options are available when @value{AS} is configured for
978 an Epiphany processor.
981 @include c-epiphany.texi
982 @c ended inside the included file
990 @xref{H8/300 Options}, for the options available when @value{AS} is configured
991 for an H8/300 processor.
996 The following options are available when @value{AS} is configured for an H8/300
1000 @include c-h8300.texi
1001 @c ended inside the included file
1009 @xref{i386-Options}, for the options available when @value{AS} is
1010 configured for an i386 processor.
1014 @c man begin OPTIONS
1015 The following options are available when @value{AS} is configured for
1018 @c man begin INCLUDE
1019 @include c-i386.texi
1020 @c ended inside the included file
1025 @c man begin OPTIONS
1027 The following options are available when @value{AS} is configured for the
1028 Intel 80960 processor.
1031 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1032 Specify which variant of the 960 architecture is the target.
1035 Add code to collect statistics about branches taken.
1038 Do not alter compare-and-branch instructions for long displacements;
1045 The following options are available when @value{AS} is configured for the
1051 Specifies that the extended IP2022 instructions are allowed.
1054 Restores the default behaviour, which restricts the permitted instructions to
1055 just the basic IP2022 ones.
1061 The following options are available when @value{AS} is configured for the
1062 Renesas M32C and M16C processors.
1067 Assemble M32C instructions.
1070 Assemble M16C instructions (the default).
1073 Enable support for link-time relaxations.
1076 Support H'00 style hex constants in addition to 0x00 style.
1082 The following options are available when @value{AS} is configured for the
1083 Renesas M32R (formerly Mitsubishi M32R) series.
1088 Specify which processor in the M32R family is the target. The default
1089 is normally the M32R, but this option changes it to the M32RX.
1091 @item --warn-explicit-parallel-conflicts or --Wp
1092 Produce warning messages when questionable parallel constructs are
1095 @item --no-warn-explicit-parallel-conflicts or --Wnp
1096 Do not produce warning messages when questionable parallel constructs are
1103 The following options are available when @value{AS} is configured for the
1104 Motorola 68000 series.
1109 Shorten references to undefined symbols, to one word instead of two.
1111 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1112 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1113 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1114 Specify what processor in the 68000 family is the target. The default
1115 is normally the 68020, but this can be changed at configuration time.
1117 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1118 The target machine does (or does not) have a floating-point coprocessor.
1119 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1120 the basic 68000 is not compatible with the 68881, a combination of the
1121 two can be specified, since it's possible to do emulation of the
1122 coprocessor instructions with the main processor.
1124 @item -m68851 | -mno-68851
1125 The target machine does (or does not) have a memory-management
1126 unit coprocessor. The default is to assume an MMU for 68020 and up.
1134 @xref{Nios II Options}, for the options available when @value{AS} is configured
1135 for an Altera Nios II processor.
1139 @c man begin OPTIONS
1140 The following options are available when @value{AS} is configured for an
1141 Altera Nios II processor.
1143 @c man begin INCLUDE
1144 @include c-nios2.texi
1145 @c ended inside the included file
1151 For details about the PDP-11 machine dependent features options,
1152 see @ref{PDP-11-Options}.
1155 @item -mpic | -mno-pic
1156 Generate position-independent (or position-dependent) code. The
1157 default is @option{-mpic}.
1160 @itemx -mall-extensions
1161 Enable all instruction set extensions. This is the default.
1163 @item -mno-extensions
1164 Disable all instruction set extensions.
1166 @item -m@var{extension} | -mno-@var{extension}
1167 Enable (or disable) a particular instruction set extension.
1170 Enable the instruction set extensions supported by a particular CPU, and
1171 disable all other extensions.
1173 @item -m@var{machine}
1174 Enable the instruction set extensions supported by a particular machine
1175 model, and disable all other extensions.
1181 The following options are available when @value{AS} is configured for
1182 a picoJava processor.
1186 @cindex PJ endianness
1187 @cindex endianness, PJ
1188 @cindex big endian output, PJ
1190 Generate ``big endian'' format output.
1192 @cindex little endian output, PJ
1194 Generate ``little endian'' format output.
1200 The following options are available when @value{AS} is configured for the
1201 Motorola 68HC11 or 68HC12 series.
1205 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1206 Specify what processor is the target. The default is
1207 defined by the configuration option when building the assembler.
1209 @item --xgate-ramoffset
1210 Instruct the linker to offset RAM addresses from S12X address space into
1211 XGATE address space.
1214 Specify to use the 16-bit integer ABI.
1217 Specify to use the 32-bit integer ABI.
1219 @item -mshort-double
1220 Specify to use the 32-bit double ABI.
1223 Specify to use the 64-bit double ABI.
1225 @item --force-long-branches
1226 Relative branches are turned into absolute ones. This concerns
1227 conditional branches, unconditional branches and branches to a
1230 @item -S | --short-branches
1231 Do not turn relative branches into absolute ones
1232 when the offset is out of range.
1234 @item --strict-direct-mode
1235 Do not turn the direct addressing mode into extended addressing mode
1236 when the instruction does not support direct addressing mode.
1238 @item --print-insn-syntax
1239 Print the syntax of instruction in case of error.
1241 @item --print-opcodes
1242 Print the list of instructions with syntax and then exit.
1244 @item --generate-example
1245 Print an example of instruction for each possible instruction and then exit.
1246 This option is only useful for testing @command{@value{AS}}.
1252 The following options are available when @command{@value{AS}} is configured
1253 for the SPARC architecture:
1256 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1257 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1258 Explicitly select a variant of the SPARC architecture.
1260 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1261 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1263 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1264 UltraSPARC extensions.
1266 @item -xarch=v8plus | -xarch=v8plusa
1267 For compatibility with the Solaris v9 assembler. These options are
1268 equivalent to -Av8plus and -Av8plusa, respectively.
1271 Warn when the assembler switches to another architecture.
1276 The following options are available when @value{AS} is configured for the 'c54x
1281 Enable extended addressing mode. All addresses and relocations will assume
1282 extended addressing (usually 23 bits).
1283 @item -mcpu=@var{CPU_VERSION}
1284 Sets the CPU version being compiled for.
1285 @item -merrors-to-file @var{FILENAME}
1286 Redirect error output to a file, for broken systems which don't support such
1287 behaviour in the shell.
1292 The following options are available when @value{AS} is configured for
1297 This option sets the largest size of an object that can be referenced
1298 implicitly with the @code{gp} register. It is only accepted for targets that
1299 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1301 @cindex MIPS endianness
1302 @cindex endianness, MIPS
1303 @cindex big endian output, MIPS
1305 Generate ``big endian'' format output.
1307 @cindex little endian output, MIPS
1309 Generate ``little endian'' format output.
1327 Generate code for a particular MIPS Instruction Set Architecture level.
1328 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1329 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1330 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1331 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1332 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1333 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1334 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1335 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1336 MIPS64 Release 6 ISA processors, respectively.
1338 @item -march=@var{cpu}
1339 Generate code for a particular MIPS CPU.
1341 @item -mtune=@var{cpu}
1342 Schedule and tune for a particular MIPS CPU.
1346 Cause nops to be inserted if the read of the destination register
1347 of an mfhi or mflo instruction occurs in the following two instructions.
1350 @itemx -mno-fix-rm7000
1351 Cause nops to be inserted if a dmult or dmultu instruction is
1352 followed by a load instruction.
1356 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1357 section instead of the standard ELF .stabs sections.
1361 Control generation of @code{.pdr} sections.
1365 The register sizes are normally inferred from the ISA and ABI, but these
1366 flags force a certain group of registers to be treated as 32 bits wide at
1367 all times. @samp{-mgp32} controls the size of general-purpose registers
1368 and @samp{-mfp32} controls the size of floating-point registers.
1372 The register sizes are normally inferred from the ISA and ABI, but these
1373 flags force a certain group of registers to be treated as 64 bits wide at
1374 all times. @samp{-mgp64} controls the size of general-purpose registers
1375 and @samp{-mfp64} controls the size of floating-point registers.
1378 The register sizes are normally inferred from the ISA and ABI, but using
1379 this flag in combination with @samp{-mabi=32} enables an ABI variant
1380 which will operate correctly with floating-point registers which are
1384 @itemx -mno-odd-spreg
1385 Enable use of floating-point operations on odd-numbered single-precision
1386 registers when supported by the ISA. @samp{-mfpxx} implies
1387 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1391 Generate code for the MIPS 16 processor. This is equivalent to putting
1392 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1393 turns off this option.
1396 @itemx -mno-micromips
1397 Generate code for the microMIPS processor. This is equivalent to putting
1398 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1399 turns off this option. This is equivalent to putting @code{.set nomicromips}
1400 at the start of the assembly file.
1403 @itemx -mno-smartmips
1404 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1405 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1406 @samp{-mno-smartmips} turns off this option.
1410 Generate code for the MIPS-3D Application Specific Extension.
1411 This tells the assembler to accept MIPS-3D instructions.
1412 @samp{-no-mips3d} turns off this option.
1416 Generate code for the MDMX Application Specific Extension.
1417 This tells the assembler to accept MDMX instructions.
1418 @samp{-no-mdmx} turns off this option.
1422 Generate code for the DSP Release 1 Application Specific Extension.
1423 This tells the assembler to accept DSP Release 1 instructions.
1424 @samp{-mno-dsp} turns off this option.
1428 Generate code for the DSP Release 2 Application Specific Extension.
1429 This option implies -mdsp.
1430 This tells the assembler to accept DSP Release 2 instructions.
1431 @samp{-mno-dspr2} turns off this option.
1435 Generate code for the MIPS SIMD Architecture Extension.
1436 This tells the assembler to accept MSA instructions.
1437 @samp{-mno-msa} turns off this option.
1441 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1442 This tells the assembler to accept XPA instructions.
1443 @samp{-mno-xpa} turns off this option.
1447 Generate code for the MT Application Specific Extension.
1448 This tells the assembler to accept MT instructions.
1449 @samp{-mno-mt} turns off this option.
1453 Generate code for the MCU Application Specific Extension.
1454 This tells the assembler to accept MCU instructions.
1455 @samp{-mno-mcu} turns off this option.
1459 Only use 32-bit instruction encodings when generating code for the
1460 microMIPS processor. This option inhibits the use of any 16-bit
1461 instructions. This is equivalent to putting @code{.set insn32} at
1462 the start of the assembly file. @samp{-mno-insn32} turns off this
1463 option. This is equivalent to putting @code{.set noinsn32} at the
1464 start of the assembly file. By default @samp{-mno-insn32} is
1465 selected, allowing all instructions to be used.
1467 @item --construct-floats
1468 @itemx --no-construct-floats
1469 The @samp{--no-construct-floats} option disables the construction of
1470 double width floating point constants by loading the two halves of the
1471 value into the two single width floating point registers that make up
1472 the double width register. By default @samp{--construct-floats} is
1473 selected, allowing construction of these floating point constants.
1475 @item --relax-branch
1476 @itemx --no-relax-branch
1477 The @samp{--relax-branch} option enables the relaxation of out-of-range
1478 branches. By default @samp{--no-relax-branch} is selected, causing any
1479 out-of-range branches to produce an error.
1481 @item -mnan=@var{encoding}
1482 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1483 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1486 @item --emulation=@var{name}
1487 This option was formerly used to switch between ELF and ECOFF output
1488 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1489 removed in GAS 2.24, so the option now serves little purpose.
1490 It is retained for backwards compatibility.
1492 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1493 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1494 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1495 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1496 preferred options instead.
1499 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1506 Control how to deal with multiplication overflow and division by zero.
1507 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1508 (and only work for Instruction Set Architecture level 2 and higher);
1509 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1513 When this option is used, @command{@value{AS}} will issue a warning every
1514 time it generates a nop instruction from a macro.
1519 The following options are available when @value{AS} is configured for
1525 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1526 The command line option @samp{-nojsri2bsr} can be used to disable it.
1530 Enable or disable the silicon filter behaviour. By default this is disabled.
1531 The default can be overridden by the @samp{-sifilter} command line option.
1534 Alter jump instructions for long displacements.
1536 @item -mcpu=[210|340]
1537 Select the cpu type on the target hardware. This controls which instructions
1541 Assemble for a big endian target.
1544 Assemble for a little endian target.
1553 @xref{Meta Options}, for the options available when @value{AS} is configured
1554 for a Meta processor.
1558 @c man begin OPTIONS
1559 The following options are available when @value{AS} is configured for a
1562 @c man begin INCLUDE
1563 @include c-metag.texi
1564 @c ended inside the included file
1569 @c man begin OPTIONS
1571 See the info pages for documentation of the MMIX-specific options.
1577 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1578 for a NDS32 processor.
1580 @c ended inside the included file
1584 @c man begin OPTIONS
1585 The following options are available when @value{AS} is configured for a
1588 @c man begin INCLUDE
1589 @include c-nds32.texi
1590 @c ended inside the included file
1597 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1598 for a PowerPC processor.
1602 @c man begin OPTIONS
1603 The following options are available when @value{AS} is configured for a
1606 @c man begin INCLUDE
1608 @c ended inside the included file
1613 @c man begin OPTIONS
1615 See the info pages for documentation of the RX-specific options.
1619 The following options are available when @value{AS} is configured for the s390
1625 Select the word size, either 31/32 bits or 64 bits.
1628 Select the architecture mode, either the Enterprise System
1629 Architecture (esa) or the z/Architecture mode (zarch).
1630 @item -march=@var{processor}
1631 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1632 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1633 @samp{z196}, @samp{zEC12}, or @samp{z13}.
1635 @itemx -mno-regnames
1636 Allow or disallow symbolic names for registers.
1637 @item -mwarn-areg-zero
1638 Warn whenever the operand for a base or index register has been specified
1639 but evaluates to zero.
1647 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1648 for a TMS320C6000 processor.
1652 @c man begin OPTIONS
1653 The following options are available when @value{AS} is configured for a
1654 TMS320C6000 processor.
1656 @c man begin INCLUDE
1657 @include c-tic6x.texi
1658 @c ended inside the included file
1666 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1667 for a TILE-Gx processor.
1671 @c man begin OPTIONS
1672 The following options are available when @value{AS} is configured for a TILE-Gx
1675 @c man begin INCLUDE
1676 @include c-tilegx.texi
1677 @c ended inside the included file
1685 @xref{Visium Options}, for the options available when @value{AS} is configured
1686 for a Visium processor.
1690 @c man begin OPTIONS
1691 The following option is available when @value{AS} is configured for a Visium
1694 @c man begin INCLUDE
1695 @include c-visium.texi
1696 @c ended inside the included file
1704 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1705 for an Xtensa processor.
1709 @c man begin OPTIONS
1710 The following options are available when @value{AS} is configured for an
1713 @c man begin INCLUDE
1714 @include c-xtensa.texi
1715 @c ended inside the included file
1720 @c man begin OPTIONS
1723 The following options are available when @value{AS} is configured for
1724 a Z80 family processor.
1727 Assemble for Z80 processor.
1729 Assemble for R800 processor.
1730 @item -ignore-undocumented-instructions
1732 Assemble undocumented Z80 instructions that also work on R800 without warning.
1733 @item -ignore-unportable-instructions
1735 Assemble all undocumented Z80 instructions without warning.
1736 @item -warn-undocumented-instructions
1738 Issue a warning for undocumented Z80 instructions that also work on R800.
1739 @item -warn-unportable-instructions
1741 Issue a warning for undocumented Z80 instructions that do not work on R800.
1742 @item -forbid-undocumented-instructions
1744 Treat all undocumented instructions as errors.
1745 @item -forbid-unportable-instructions
1747 Treat undocumented Z80 instructions that do not work on R800 as errors.
1754 * Manual:: Structure of this Manual
1755 * GNU Assembler:: The GNU Assembler
1756 * Object Formats:: Object File Formats
1757 * Command Line:: Command Line
1758 * Input Files:: Input Files
1759 * Object:: Output (Object) File
1760 * Errors:: Error and Warning Messages
1764 @section Structure of this Manual
1766 @cindex manual, structure and purpose
1767 This manual is intended to describe what you need to know to use
1768 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1769 notation for symbols, constants, and expressions; the directives that
1770 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1773 We also cover special features in the @value{TARGET}
1774 configuration of @command{@value{AS}}, including assembler directives.
1777 This manual also describes some of the machine-dependent features of
1778 various flavors of the assembler.
1781 @cindex machine instructions (not covered)
1782 On the other hand, this manual is @emph{not} intended as an introduction
1783 to programming in assembly language---let alone programming in general!
1784 In a similar vein, we make no attempt to introduce the machine
1785 architecture; we do @emph{not} describe the instruction set, standard
1786 mnemonics, registers or addressing modes that are standard to a
1787 particular architecture.
1789 You may want to consult the manufacturer's
1790 machine architecture manual for this information.
1794 For information on the H8/300 machine instruction set, see @cite{H8/300
1795 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1796 Programming Manual} (Renesas).
1799 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1800 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1801 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1802 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1805 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1809 @c I think this is premature---doc@cygnus.com, 17jan1991
1811 Throughout this manual, we assume that you are running @dfn{GNU},
1812 the portable operating system from the @dfn{Free Software
1813 Foundation, Inc.}. This restricts our attention to certain kinds of
1814 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1815 once this assumption is granted examples and definitions need less
1818 @command{@value{AS}} is part of a team of programs that turn a high-level
1819 human-readable series of instructions into a low-level
1820 computer-readable series of instructions. Different versions of
1821 @command{@value{AS}} are used for different kinds of computer.
1824 @c There used to be a section "Terminology" here, which defined
1825 @c "contents", "byte", "word", and "long". Defining "word" to any
1826 @c particular size is confusing when the .word directive may generate 16
1827 @c bits on one machine and 32 bits on another; in general, for the user
1828 @c version of this manual, none of these terms seem essential to define.
1829 @c They were used very little even in the former draft of the manual;
1830 @c this draft makes an effort to avoid them (except in names of
1834 @section The GNU Assembler
1836 @c man begin DESCRIPTION
1838 @sc{gnu} @command{as} is really a family of assemblers.
1840 This manual describes @command{@value{AS}}, a member of that family which is
1841 configured for the @value{TARGET} architectures.
1843 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1844 should find a fairly similar environment when you use it on another
1845 architecture. Each version has much in common with the others,
1846 including object file formats, most assembler directives (often called
1847 @dfn{pseudo-ops}) and assembler syntax.@refill
1849 @cindex purpose of @sc{gnu} assembler
1850 @command{@value{AS}} is primarily intended to assemble the output of the
1851 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1852 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1853 assemble correctly everything that other assemblers for the same
1854 machine would assemble.
1856 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1859 @c This remark should appear in generic version of manual; assumption
1860 @c here is that generic version sets M680x0.
1861 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1862 assembler for the same architecture; for example, we know of several
1863 incompatible versions of 680x0 assembly language syntax.
1868 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1869 program in one pass of the source file. This has a subtle impact on the
1870 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1872 @node Object Formats
1873 @section Object File Formats
1875 @cindex object file format
1876 The @sc{gnu} assembler can be configured to produce several alternative
1877 object file formats. For the most part, this does not affect how you
1878 write assembly language programs; but directives for debugging symbols
1879 are typically different in different file formats. @xref{Symbol
1880 Attributes,,Symbol Attributes}.
1883 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1884 @value{OBJ-NAME} format object files.
1886 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1888 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1889 @code{b.out} or COFF format object files.
1892 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1893 SOM or ELF format object files.
1898 @section Command Line
1900 @cindex command line conventions
1902 After the program name @command{@value{AS}}, the command line may contain
1903 options and file names. Options may appear in any order, and may be
1904 before, after, or between file names. The order of file names is
1907 @cindex standard input, as input file
1909 @file{--} (two hyphens) by itself names the standard input file
1910 explicitly, as one of the files for @command{@value{AS}} to assemble.
1912 @cindex options, command line
1913 Except for @samp{--} any command line argument that begins with a
1914 hyphen (@samp{-}) is an option. Each option changes the behavior of
1915 @command{@value{AS}}. No option changes the way another option works. An
1916 option is a @samp{-} followed by one or more letters; the case of
1917 the letter is important. All options are optional.
1919 Some options expect exactly one file name to follow them. The file
1920 name may either immediately follow the option's letter (compatible
1921 with older assemblers) or it may be the next command argument (@sc{gnu}
1922 standard). These two command lines are equivalent:
1925 @value{AS} -o my-object-file.o mumble.s
1926 @value{AS} -omy-object-file.o mumble.s
1930 @section Input Files
1933 @cindex source program
1934 @cindex files, input
1935 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1936 describe the program input to one run of @command{@value{AS}}. The program may
1937 be in one or more files; how the source is partitioned into files
1938 doesn't change the meaning of the source.
1940 @c I added "con" prefix to "catenation" just to prove I can overcome my
1941 @c APL training... doc@cygnus.com
1942 The source program is a concatenation of the text in all the files, in the
1945 @c man begin DESCRIPTION
1946 Each time you run @command{@value{AS}} it assembles exactly one source
1947 program. The source program is made up of one or more files.
1948 (The standard input is also a file.)
1950 You give @command{@value{AS}} a command line that has zero or more input file
1951 names. The input files are read (from left file name to right). A
1952 command line argument (in any position) that has no special meaning
1953 is taken to be an input file name.
1955 If you give @command{@value{AS}} no file names it attempts to read one input file
1956 from the @command{@value{AS}} standard input, which is normally your terminal. You
1957 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1960 Use @samp{--} if you need to explicitly name the standard input file
1961 in your command line.
1963 If the source is empty, @command{@value{AS}} produces a small, empty object
1968 @subheading Filenames and Line-numbers
1970 @cindex input file linenumbers
1971 @cindex line numbers, in input files
1972 There are two ways of locating a line in the input file (or files) and
1973 either may be used in reporting error messages. One way refers to a line
1974 number in a physical file; the other refers to a line number in a
1975 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1977 @dfn{Physical files} are those files named in the command line given
1978 to @command{@value{AS}}.
1980 @dfn{Logical files} are simply names declared explicitly by assembler
1981 directives; they bear no relation to physical files. Logical file names help
1982 error messages reflect the original source file, when @command{@value{AS}} source
1983 is itself synthesized from other files. @command{@value{AS}} understands the
1984 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1985 @ref{File,,@code{.file}}.
1988 @section Output (Object) File
1994 Every time you run @command{@value{AS}} it produces an output file, which is
1995 your assembly language program translated into numbers. This file
1996 is the object file. Its default name is
2004 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2006 You can give it another name by using the @option{-o} option. Conventionally,
2007 object file names end with @file{.o}. The default name is used for historical
2008 reasons: older assemblers were capable of assembling self-contained programs
2009 directly into a runnable program. (For some formats, this isn't currently
2010 possible, but it can be done for the @code{a.out} format.)
2014 The object file is meant for input to the linker @code{@value{LD}}. It contains
2015 assembled program code, information to help @code{@value{LD}} integrate
2016 the assembled program into a runnable file, and (optionally) symbolic
2017 information for the debugger.
2019 @c link above to some info file(s) like the description of a.out.
2020 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2023 @section Error and Warning Messages
2025 @c man begin DESCRIPTION
2027 @cindex error messages
2028 @cindex warning messages
2029 @cindex messages from assembler
2030 @command{@value{AS}} may write warnings and error messages to the standard error
2031 file (usually your terminal). This should not happen when a compiler
2032 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2033 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2034 grave problem that stops the assembly.
2038 @cindex format of warning messages
2039 Warning messages have the format
2042 file_name:@b{NNN}:Warning Message Text
2046 @cindex line numbers, in warnings/errors
2047 (where @b{NNN} is a line number). If a logical file name has been given
2048 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
2049 the current input file is used. If a logical line number was given
2051 (@pxref{Line,,@code{.line}})
2053 then it is used to calculate the number printed,
2054 otherwise the actual line in the current source file is printed. The
2055 message text is intended to be self explanatory (in the grand Unix
2058 @cindex format of error messages
2059 Error messages have the format
2061 file_name:@b{NNN}:FATAL:Error Message Text
2063 The file name and line number are derived as for warning
2064 messages. The actual message text may be rather less explanatory
2065 because many of them aren't supposed to happen.
2068 @chapter Command-Line Options
2070 @cindex options, all versions of assembler
2071 This chapter describes command-line options available in @emph{all}
2072 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2073 for options specific
2075 to the @value{TARGET} target.
2078 to particular machine architectures.
2081 @c man begin DESCRIPTION
2083 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2084 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2085 The assembler arguments must be separated from each other (and the @samp{-Wa})
2086 by commas. For example:
2089 gcc -c -g -O -Wa,-alh,-L file.c
2093 This passes two options to the assembler: @samp{-alh} (emit a listing to
2094 standard output with high-level and assembly source) and @samp{-L} (retain
2095 local symbols in the symbol table).
2097 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2098 command-line options are automatically passed to the assembler by the compiler.
2099 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2100 precisely what options it passes to each compilation pass, including the
2106 * a:: -a[cdghlns] enable listings
2107 * alternate:: --alternate enable alternate macro syntax
2108 * D:: -D for compatibility
2109 * f:: -f to work faster
2110 * I:: -I for .include search path
2111 @ifclear DIFF-TBL-KLUGE
2112 * K:: -K for compatibility
2114 @ifset DIFF-TBL-KLUGE
2115 * K:: -K for difference tables
2118 * L:: -L to retain local symbols
2119 * listing:: --listing-XXX to configure listing output
2120 * M:: -M or --mri to assemble in MRI compatibility mode
2121 * MD:: --MD for dependency tracking
2122 * o:: -o to name the object file
2123 * R:: -R to join data and text sections
2124 * statistics:: --statistics to see statistics about assembly
2125 * traditional-format:: --traditional-format for compatible output
2126 * v:: -v to announce version
2127 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2128 * Z:: -Z to make object file even after errors
2132 @section Enable Listings: @option{-a[cdghlns]}
2142 @cindex listings, enabling
2143 @cindex assembly listings, enabling
2145 These options enable listing output from the assembler. By itself,
2146 @samp{-a} requests high-level, assembly, and symbols listing.
2147 You can use other letters to select specific options for the list:
2148 @samp{-ah} requests a high-level language listing,
2149 @samp{-al} requests an output-program assembly listing, and
2150 @samp{-as} requests a symbol table listing.
2151 High-level listings require that a compiler debugging option like
2152 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2155 Use the @samp{-ag} option to print a first section with general assembly
2156 information, like @value{AS} version, switches passed, or time stamp.
2158 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2159 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2160 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2161 omitted from the listing.
2163 Use the @samp{-ad} option to omit debugging directives from the
2166 Once you have specified one of these options, you can further control
2167 listing output and its appearance using the directives @code{.list},
2168 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2170 The @samp{-an} option turns off all forms processing.
2171 If you do not request listing output with one of the @samp{-a} options, the
2172 listing-control directives have no effect.
2174 The letters after @samp{-a} may be combined into one option,
2175 @emph{e.g.}, @samp{-aln}.
2177 Note if the assembler source is coming from the standard input (e.g.,
2179 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2180 is being used) then the listing will not contain any comments or preprocessor
2181 directives. This is because the listing code buffers input source lines from
2182 stdin only after they have been preprocessed by the assembler. This reduces
2183 memory usage and makes the code more efficient.
2186 @section @option{--alternate}
2189 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2192 @section @option{-D}
2195 This option has no effect whatsoever, but it is accepted to make it more
2196 likely that scripts written for other assemblers also work with
2197 @command{@value{AS}}.
2200 @section Work Faster: @option{-f}
2203 @cindex trusted compiler
2204 @cindex faster processing (@option{-f})
2205 @samp{-f} should only be used when assembling programs written by a
2206 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2207 and comment preprocessing on
2208 the input file(s) before assembling them. @xref{Preprocessing,
2212 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2213 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2218 @section @code{.include} Search Path: @option{-I} @var{path}
2220 @kindex -I @var{path}
2221 @cindex paths for @code{.include}
2222 @cindex search path for @code{.include}
2223 @cindex @code{include} directive search path
2224 Use this option to add a @var{path} to the list of directories
2225 @command{@value{AS}} searches for files specified in @code{.include}
2226 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2227 many times as necessary to include a variety of paths. The current
2228 working directory is always searched first; after that, @command{@value{AS}}
2229 searches any @samp{-I} directories in the same order as they were
2230 specified (left to right) on the command line.
2233 @section Difference Tables: @option{-K}
2236 @ifclear DIFF-TBL-KLUGE
2237 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2238 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2239 where it can be used to warn when the assembler alters the machine code
2240 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2241 family does not have the addressing limitations that sometimes lead to this
2242 alteration on other platforms.
2245 @ifset DIFF-TBL-KLUGE
2246 @cindex difference tables, warning
2247 @cindex warning for altered difference tables
2248 @command{@value{AS}} sometimes alters the code emitted for directives of the
2249 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2250 You can use the @samp{-K} option if you want a warning issued when this
2255 @section Include Local Symbols: @option{-L}
2258 @cindex local symbols, retaining in output
2259 Symbols beginning with system-specific local label prefixes, typically
2260 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2261 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2262 such symbols when debugging, because they are intended for the use of
2263 programs (like compilers) that compose assembler programs, not for your
2264 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2265 such symbols, so you do not normally debug with them.
2267 This option tells @command{@value{AS}} to retain those local symbols
2268 in the object file. Usually if you do this you also tell the linker
2269 @code{@value{LD}} to preserve those symbols.
2272 @section Configuring listing output: @option{--listing}
2274 The listing feature of the assembler can be enabled via the command line switch
2275 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2276 hex dump of the corresponding locations in the output object file, and displays
2277 them as a listing file. The format of this listing can be controlled by
2278 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2279 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2280 @code{.psize} (@pxref{Psize}), and
2281 @code{.eject} (@pxref{Eject}) and also by the following switches:
2284 @item --listing-lhs-width=@samp{number}
2285 @kindex --listing-lhs-width
2286 @cindex Width of first line disassembly output
2287 Sets the maximum width, in words, of the first line of the hex byte dump. This
2288 dump appears on the left hand side of the listing output.
2290 @item --listing-lhs-width2=@samp{number}
2291 @kindex --listing-lhs-width2
2292 @cindex Width of continuation lines of disassembly output
2293 Sets the maximum width, in words, of any further lines of the hex byte dump for
2294 a given input source line. If this value is not specified, it defaults to being
2295 the same as the value specified for @samp{--listing-lhs-width}. If neither
2296 switch is used the default is to one.
2298 @item --listing-rhs-width=@samp{number}
2299 @kindex --listing-rhs-width
2300 @cindex Width of source line output
2301 Sets the maximum width, in characters, of the source line that is displayed
2302 alongside the hex dump. The default value for this parameter is 100. The
2303 source line is displayed on the right hand side of the listing output.
2305 @item --listing-cont-lines=@samp{number}
2306 @kindex --listing-cont-lines
2307 @cindex Maximum number of continuation lines
2308 Sets the maximum number of continuation lines of hex dump that will be
2309 displayed for a given single line of source input. The default value is 4.
2313 @section Assemble in MRI Compatibility Mode: @option{-M}
2316 @cindex MRI compatibility mode
2317 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2318 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2319 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2320 configured target) assembler from Microtec Research. The exact nature of the
2321 MRI syntax will not be documented here; see the MRI manuals for more
2322 information. Note in particular that the handling of macros and macro
2323 arguments is somewhat different. The purpose of this option is to permit
2324 assembling existing MRI assembler code using @command{@value{AS}}.
2326 The MRI compatibility is not complete. Certain operations of the MRI assembler
2327 depend upon its object file format, and can not be supported using other object
2328 file formats. Supporting these would require enhancing each object file format
2329 individually. These are:
2332 @item global symbols in common section
2334 The m68k MRI assembler supports common sections which are merged by the linker.
2335 Other object file formats do not support this. @command{@value{AS}} handles
2336 common sections by treating them as a single common symbol. It permits local
2337 symbols to be defined within a common section, but it can not support global
2338 symbols, since it has no way to describe them.
2340 @item complex relocations
2342 The MRI assemblers support relocations against a negated section address, and
2343 relocations which combine the start addresses of two or more sections. These
2344 are not support by other object file formats.
2346 @item @code{END} pseudo-op specifying start address
2348 The MRI @code{END} pseudo-op permits the specification of a start address.
2349 This is not supported by other object file formats. The start address may
2350 instead be specified using the @option{-e} option to the linker, or in a linker
2353 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2355 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2356 name to the output file. This is not supported by other object file formats.
2358 @item @code{ORG} pseudo-op
2360 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2361 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2362 which changes the location within the current section. Absolute sections are
2363 not supported by other object file formats. The address of a section may be
2364 assigned within a linker script.
2367 There are some other features of the MRI assembler which are not supported by
2368 @command{@value{AS}}, typically either because they are difficult or because they
2369 seem of little consequence. Some of these may be supported in future releases.
2373 @item EBCDIC strings
2375 EBCDIC strings are not supported.
2377 @item packed binary coded decimal
2379 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2380 and @code{DCB.P} pseudo-ops are not supported.
2382 @item @code{FEQU} pseudo-op
2384 The m68k @code{FEQU} pseudo-op is not supported.
2386 @item @code{NOOBJ} pseudo-op
2388 The m68k @code{NOOBJ} pseudo-op is not supported.
2390 @item @code{OPT} branch control options
2392 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2393 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2394 relaxes all branches, whether forward or backward, to an appropriate size, so
2395 these options serve no purpose.
2397 @item @code{OPT} list control options
2399 The following m68k @code{OPT} list control options are ignored: @code{C},
2400 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2401 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2403 @item other @code{OPT} options
2405 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2406 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2408 @item @code{OPT} @code{D} option is default
2410 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2411 @code{OPT NOD} may be used to turn it off.
2413 @item @code{XREF} pseudo-op.
2415 The m68k @code{XREF} pseudo-op is ignored.
2417 @item @code{.debug} pseudo-op
2419 The i960 @code{.debug} pseudo-op is not supported.
2421 @item @code{.extended} pseudo-op
2423 The i960 @code{.extended} pseudo-op is not supported.
2425 @item @code{.list} pseudo-op.
2427 The various options of the i960 @code{.list} pseudo-op are not supported.
2429 @item @code{.optimize} pseudo-op
2431 The i960 @code{.optimize} pseudo-op is not supported.
2433 @item @code{.output} pseudo-op
2435 The i960 @code{.output} pseudo-op is not supported.
2437 @item @code{.setreal} pseudo-op
2439 The i960 @code{.setreal} pseudo-op is not supported.
2444 @section Dependency Tracking: @option{--MD}
2447 @cindex dependency tracking
2450 @command{@value{AS}} can generate a dependency file for the file it creates. This
2451 file consists of a single rule suitable for @code{make} describing the
2452 dependencies of the main source file.
2454 The rule is written to the file named in its argument.
2456 This feature is used in the automatic updating of makefiles.
2459 @section Name the Object File: @option{-o}
2462 @cindex naming object file
2463 @cindex object file name
2464 There is always one object file output when you run @command{@value{AS}}. By
2465 default it has the name
2468 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2482 You use this option (which takes exactly one filename) to give the
2483 object file a different name.
2485 Whatever the object file is called, @command{@value{AS}} overwrites any
2486 existing file of the same name.
2489 @section Join Data and Text Sections: @option{-R}
2492 @cindex data and text sections, joining
2493 @cindex text and data sections, joining
2494 @cindex joining text and data sections
2495 @cindex merging text and data sections
2496 @option{-R} tells @command{@value{AS}} to write the object file as if all
2497 data-section data lives in the text section. This is only done at
2498 the very last moment: your binary data are the same, but data
2499 section parts are relocated differently. The data section part of
2500 your object file is zero bytes long because all its bytes are
2501 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2503 When you specify @option{-R} it would be possible to generate shorter
2504 address displacements (because we do not have to cross between text and
2505 data section). We refrain from doing this simply for compatibility with
2506 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2509 When @command{@value{AS}} is configured for COFF or ELF output,
2510 this option is only useful if you use sections named @samp{.text} and
2515 @option{-R} is not supported for any of the HPPA targets. Using
2516 @option{-R} generates a warning from @command{@value{AS}}.
2520 @section Display Assembly Statistics: @option{--statistics}
2522 @kindex --statistics
2523 @cindex statistics, about assembly
2524 @cindex time, total for assembly
2525 @cindex space used, maximum for assembly
2526 Use @samp{--statistics} to display two statistics about the resources used by
2527 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2528 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2531 @node traditional-format
2532 @section Compatible Output: @option{--traditional-format}
2534 @kindex --traditional-format
2535 For some targets, the output of @command{@value{AS}} is different in some ways
2536 from the output of some existing assembler. This switch requests
2537 @command{@value{AS}} to use the traditional format instead.
2539 For example, it disables the exception frame optimizations which
2540 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2543 @section Announce Version: @option{-v}
2547 @cindex assembler version
2548 @cindex version of assembler
2549 You can find out what version of as is running by including the
2550 option @samp{-v} (which you can also spell as @samp{-version}) on the
2554 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2556 @command{@value{AS}} should never give a warning or error message when
2557 assembling compiler output. But programs written by people often
2558 cause @command{@value{AS}} to give a warning that a particular assumption was
2559 made. All such warnings are directed to the standard error file.
2563 @cindex suppressing warnings
2564 @cindex warnings, suppressing
2565 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2566 This only affects the warning messages: it does not change any particular of
2567 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2570 @kindex --fatal-warnings
2571 @cindex errors, caused by warnings
2572 @cindex warnings, causing error
2573 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2574 files that generate warnings to be in error.
2577 @cindex warnings, switching on
2578 You can switch these options off again by specifying @option{--warn}, which
2579 causes warnings to be output as usual.
2582 @section Generate Object File in Spite of Errors: @option{-Z}
2583 @cindex object file, after errors
2584 @cindex errors, continuing after
2585 After an error message, @command{@value{AS}} normally produces no output. If for
2586 some reason you are interested in object file output even after
2587 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2588 option. If there are any errors, @command{@value{AS}} continues anyways, and
2589 writes an object file after a final warning message of the form @samp{@var{n}
2590 errors, @var{m} warnings, generating bad object file.}
2595 @cindex machine-independent syntax
2596 @cindex syntax, machine-independent
2597 This chapter describes the machine-independent syntax allowed in a
2598 source file. @command{@value{AS}} syntax is similar to what many other
2599 assemblers use; it is inspired by the BSD 4.2
2604 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2608 * Preprocessing:: Preprocessing
2609 * Whitespace:: Whitespace
2610 * Comments:: Comments
2611 * Symbol Intro:: Symbols
2612 * Statements:: Statements
2613 * Constants:: Constants
2617 @section Preprocessing
2619 @cindex preprocessing
2620 The @command{@value{AS}} internal preprocessor:
2622 @cindex whitespace, removed by preprocessor
2624 adjusts and removes extra whitespace. It leaves one space or tab before
2625 the keywords on a line, and turns any other whitespace on the line into
2628 @cindex comments, removed by preprocessor
2630 removes all comments, replacing them with a single space, or an
2631 appropriate number of newlines.
2633 @cindex constants, converted by preprocessor
2635 converts character constants into the appropriate numeric values.
2638 It does not do macro processing, include file handling, or
2639 anything else you may get from your C compiler's preprocessor. You can
2640 do include file processing with the @code{.include} directive
2641 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2642 to get other ``CPP'' style preprocessing by giving the input file a
2643 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2644 Output, gcc.info, Using GNU CC}.
2646 Excess whitespace, comments, and character constants
2647 cannot be used in the portions of the input text that are not
2650 @cindex turning preprocessing on and off
2651 @cindex preprocessing, turning on and off
2654 If the first line of an input file is @code{#NO_APP} or if you use the
2655 @samp{-f} option, whitespace and comments are not removed from the input file.
2656 Within an input file, you can ask for whitespace and comment removal in
2657 specific portions of the by putting a line that says @code{#APP} before the
2658 text that may contain whitespace or comments, and putting a line that says
2659 @code{#NO_APP} after this text. This feature is mainly intend to support
2660 @code{asm} statements in compilers whose output is otherwise free of comments
2667 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2668 Whitespace is used to separate symbols, and to make programs neater for
2669 people to read. Unless within character constants
2670 (@pxref{Characters,,Character Constants}), any whitespace means the same
2671 as exactly one space.
2677 There are two ways of rendering comments to @command{@value{AS}}. In both
2678 cases the comment is equivalent to one space.
2680 Anything from @samp{/*} through the next @samp{*/} is a comment.
2681 This means you may not nest these comments.
2685 The only way to include a newline ('\n') in a comment
2686 is to use this sort of comment.
2689 /* This sort of comment does not nest. */
2692 @cindex line comment character
2693 Anything from a @dfn{line comment} character up to the next newline is
2694 considered a comment and is ignored. The line comment character is target
2695 specific, and some targets multiple comment characters. Some targets also have
2696 line comment characters that only work if they are the first character on a
2697 line. Some targets use a sequence of two characters to introduce a line
2698 comment. Some targets can also change their line comment characters depending
2699 upon command line options that have been used. For more details see the
2700 @emph{Syntax} section in the documentation for individual targets.
2702 If the line comment character is the hash sign (@samp{#}) then it still has the
2703 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2704 to specify logical line numbers:
2707 @cindex lines starting with @code{#}
2708 @cindex logical line numbers
2709 To be compatible with past assemblers, lines that begin with @samp{#} have a
2710 special interpretation. Following the @samp{#} should be an absolute
2711 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2712 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2713 new logical file name. The rest of the line, if any, should be whitespace.
2715 If the first non-whitespace characters on the line are not numeric,
2716 the line is ignored. (Just like a comment.)
2719 # This is an ordinary comment.
2720 # 42-6 "new_file_name" # New logical file name
2721 # This is logical line # 36.
2723 This feature is deprecated, and may disappear from future versions
2724 of @command{@value{AS}}.
2729 @cindex characters used in symbols
2730 @ifclear SPECIAL-SYMS
2731 A @dfn{symbol} is one or more characters chosen from the set of all
2732 letters (both upper and lower case), digits and the three characters
2738 A @dfn{symbol} is one or more characters chosen from the set of all
2739 letters (both upper and lower case), digits and the three characters
2740 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2746 On most machines, you can also use @code{$} in symbol names; exceptions
2747 are noted in @ref{Machine Dependencies}.
2749 No symbol may begin with a digit. Case is significant.
2750 There is no length limit; all characters are significant. Multibyte characters
2751 are supported. Symbols are delimited by characters not in that set, or by the
2752 beginning of a file (since the source program must end with a newline, the end
2753 of a file is not a possible symbol delimiter). @xref{Symbols}.
2755 Symbol names may also be enclosed in double quote @code{"} characters. In such
2756 cases any characters are allowed, except for the NUL character. If a double
2757 quote character is to be included in the symbol name it must be preceeded by a
2758 backslash @code{\} character.
2759 @cindex length of symbols
2764 @cindex statements, structure of
2765 @cindex line separator character
2766 @cindex statement separator character
2768 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2769 @dfn{line separator character}. The line separator character is target
2770 specific and described in the @emph{Syntax} section of each
2771 target's documentation. Not all targets support a line separator character.
2772 The newline or line separator character is considered to be part of the
2773 preceding statement. Newlines and separators within character constants are an
2774 exception: they do not end statements.
2776 @cindex newline, required at file end
2777 @cindex EOF, newline must precede
2778 It is an error to end any statement with end-of-file: the last
2779 character of any input file should be a newline.@refill
2781 An empty statement is allowed, and may include whitespace. It is ignored.
2783 @cindex instructions and directives
2784 @cindex directives and instructions
2785 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2786 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2788 A statement begins with zero or more labels, optionally followed by a
2789 key symbol which determines what kind of statement it is. The key
2790 symbol determines the syntax of the rest of the statement. If the
2791 symbol begins with a dot @samp{.} then the statement is an assembler
2792 directive: typically valid for any computer. If the symbol begins with
2793 a letter the statement is an assembly language @dfn{instruction}: it
2794 assembles into a machine language instruction.
2796 Different versions of @command{@value{AS}} for different computers
2797 recognize different instructions. In fact, the same symbol may
2798 represent a different instruction in a different computer's assembly
2802 @cindex @code{:} (label)
2803 @cindex label (@code{:})
2804 A label is a symbol immediately followed by a colon (@code{:}).
2805 Whitespace before a label or after a colon is permitted, but you may not
2806 have whitespace between a label's symbol and its colon. @xref{Labels}.
2809 For HPPA targets, labels need not be immediately followed by a colon, but
2810 the definition of a label must begin in column zero. This also implies that
2811 only one label may be defined on each line.
2815 label: .directive followed by something
2816 another_label: # This is an empty statement.
2817 instruction operand_1, operand_2, @dots{}
2824 A constant is a number, written so that its value is known by
2825 inspection, without knowing any context. Like this:
2828 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2829 .ascii "Ring the bell\7" # A string constant.
2830 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2831 .float 0f-314159265358979323846264338327\
2832 95028841971.693993751E-40 # - pi, a flonum.
2837 * Characters:: Character Constants
2838 * Numbers:: Number Constants
2842 @subsection Character Constants
2844 @cindex character constants
2845 @cindex constants, character
2846 There are two kinds of character constants. A @dfn{character} stands
2847 for one character in one byte and its value may be used in
2848 numeric expressions. String constants (properly called string
2849 @emph{literals}) are potentially many bytes and their values may not be
2850 used in arithmetic expressions.
2854 * Chars:: Characters
2858 @subsubsection Strings
2860 @cindex string constants
2861 @cindex constants, string
2862 A @dfn{string} is written between double-quotes. It may contain
2863 double-quotes or null characters. The way to get special characters
2864 into a string is to @dfn{escape} these characters: precede them with
2865 a backslash @samp{\} character. For example @samp{\\} represents
2866 one backslash: the first @code{\} is an escape which tells
2867 @command{@value{AS}} to interpret the second character literally as a backslash
2868 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2869 escape character). The complete list of escapes follows.
2871 @cindex escape codes, character
2872 @cindex character escape codes
2873 @c NOTE: Cindex entries must not start with a backlash character.
2874 @c NOTE: This confuses the pdf2texi script when it is creating the
2875 @c NOTE: index based upon the first character and so it generates:
2876 @c NOTE: \initial {\\}
2877 @c NOTE: which then results in the error message:
2878 @c NOTE: Argument of \\ has an extra }.
2879 @c NOTE: So in the index entries below a space character has been
2880 @c NOTE: prepended to avoid this problem.
2883 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2885 @cindex @code{ \b} (backspace character)
2886 @cindex backspace (@code{\b})
2888 Mnemonic for backspace; for ASCII this is octal code 010.
2891 @c Mnemonic for EOText; for ASCII this is octal code 004.
2893 @cindex @code{ \f} (formfeed character)
2894 @cindex formfeed (@code{\f})
2896 Mnemonic for FormFeed; for ASCII this is octal code 014.
2898 @cindex @code{ \n} (newline character)
2899 @cindex newline (@code{\n})
2901 Mnemonic for newline; for ASCII this is octal code 012.
2904 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2906 @cindex @code{ \r} (carriage return character)
2907 @cindex carriage return (@code{backslash-r})
2909 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2912 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2913 @c other assemblers.
2915 @cindex @code{ \t} (tab)
2916 @cindex tab (@code{\t})
2918 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2921 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2922 @c @item \x @var{digit} @var{digit} @var{digit}
2923 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2925 @cindex @code{ \@var{ddd}} (octal character code)
2926 @cindex octal character code (@code{\@var{ddd}})
2927 @item \ @var{digit} @var{digit} @var{digit}
2928 An octal character code. The numeric code is 3 octal digits.
2929 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2930 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2932 @cindex @code{ \@var{xd...}} (hex character code)
2933 @cindex hex character code (@code{\@var{xd...}})
2934 @item \@code{x} @var{hex-digits...}
2935 A hex character code. All trailing hex digits are combined. Either upper or
2936 lower case @code{x} works.
2938 @cindex @code{ \\} (@samp{\} character)
2939 @cindex backslash (@code{\\})
2941 Represents one @samp{\} character.
2944 @c Represents one @samp{'} (accent acute) character.
2945 @c This is needed in single character literals
2946 @c (@xref{Characters,,Character Constants}.) to represent
2949 @cindex @code{ \"} (doublequote character)
2950 @cindex doublequote (@code{\"})
2952 Represents one @samp{"} character. Needed in strings to represent
2953 this character, because an unescaped @samp{"} would end the string.
2955 @item \ @var{anything-else}
2956 Any other character when escaped by @kbd{\} gives a warning, but
2957 assembles as if the @samp{\} was not present. The idea is that if
2958 you used an escape sequence you clearly didn't want the literal
2959 interpretation of the following character. However @command{@value{AS}} has no
2960 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2961 code and warns you of the fact.
2964 Which characters are escapable, and what those escapes represent,
2965 varies widely among assemblers. The current set is what we think
2966 the BSD 4.2 assembler recognizes, and is a subset of what most C
2967 compilers recognize. If you are in doubt, do not use an escape
2971 @subsubsection Characters
2973 @cindex single character constant
2974 @cindex character, single
2975 @cindex constant, single character
2976 A single character may be written as a single quote immediately
2977 followed by that character. The same escapes apply to characters as
2978 to strings. So if you want to write the character backslash, you
2979 must write @kbd{'\\} where the first @code{\} escapes the second
2980 @code{\}. As you can see, the quote is an acute accent, not a
2981 grave accent. A newline
2983 @ifclear abnormal-separator
2984 (or semicolon @samp{;})
2986 @ifset abnormal-separator
2988 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2993 immediately following an acute accent is taken as a literal character
2994 and does not count as the end of a statement. The value of a character
2995 constant in a numeric expression is the machine's byte-wide code for
2996 that character. @command{@value{AS}} assumes your character code is ASCII:
2997 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3000 @subsection Number Constants
3002 @cindex constants, number
3003 @cindex number constants
3004 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3005 are stored in the target machine. @emph{Integers} are numbers that
3006 would fit into an @code{int} in the C language. @emph{Bignums} are
3007 integers, but they are stored in more than 32 bits. @emph{Flonums}
3008 are floating point numbers, described below.
3011 * Integers:: Integers
3016 * Bit Fields:: Bit Fields
3022 @subsubsection Integers
3024 @cindex constants, integer
3026 @cindex binary integers
3027 @cindex integers, binary
3028 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3029 the binary digits @samp{01}.
3031 @cindex octal integers
3032 @cindex integers, octal
3033 An octal integer is @samp{0} followed by zero or more of the octal
3034 digits (@samp{01234567}).
3036 @cindex decimal integers
3037 @cindex integers, decimal
3038 A decimal integer starts with a non-zero digit followed by zero or
3039 more digits (@samp{0123456789}).
3041 @cindex hexadecimal integers
3042 @cindex integers, hexadecimal
3043 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3044 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3046 Integers have the usual values. To denote a negative integer, use
3047 the prefix operator @samp{-} discussed under expressions
3048 (@pxref{Prefix Ops,,Prefix Operators}).
3051 @subsubsection Bignums
3054 @cindex constants, bignum
3055 A @dfn{bignum} has the same syntax and semantics as an integer
3056 except that the number (or its negative) takes more than 32 bits to
3057 represent in binary. The distinction is made because in some places
3058 integers are permitted while bignums are not.
3061 @subsubsection Flonums
3063 @cindex floating point numbers
3064 @cindex constants, floating point
3066 @cindex precision, floating point
3067 A @dfn{flonum} represents a floating point number. The translation is
3068 indirect: a decimal floating point number from the text is converted by
3069 @command{@value{AS}} to a generic binary floating point number of more than
3070 sufficient precision. This generic floating point number is converted
3071 to a particular computer's floating point format (or formats) by a
3072 portion of @command{@value{AS}} specialized to that computer.
3074 A flonum is written by writing (in order)
3079 (@samp{0} is optional on the HPPA.)
3083 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3085 @kbd{e} is recommended. Case is not important.
3087 @c FIXME: verify if flonum syntax really this vague for most cases
3088 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3089 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3092 On the H8/300, Renesas / SuperH SH,
3093 and AMD 29K architectures, the letter must be
3094 one of the letters @samp{DFPRSX} (in upper or lower case).
3096 On the ARC, the letter must be one of the letters @samp{DFRS}
3097 (in upper or lower case).
3099 On the Intel 960 architecture, the letter must be
3100 one of the letters @samp{DFT} (in upper or lower case).
3102 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3106 One of the letters @samp{DFRS} (in upper or lower case).
3109 One of the letters @samp{DFPRSX} (in upper or lower case).
3112 The letter @samp{E} (upper case only).
3115 One of the letters @samp{DFT} (in upper or lower case).
3120 An optional sign: either @samp{+} or @samp{-}.
3123 An optional @dfn{integer part}: zero or more decimal digits.
3126 An optional @dfn{fractional part}: @samp{.} followed by zero
3127 or more decimal digits.
3130 An optional exponent, consisting of:
3134 An @samp{E} or @samp{e}.
3135 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3136 @c principle this can perfectly well be different on different targets.
3138 Optional sign: either @samp{+} or @samp{-}.
3140 One or more decimal digits.
3145 At least one of the integer part or the fractional part must be
3146 present. The floating point number has the usual base-10 value.
3148 @command{@value{AS}} does all processing using integers. Flonums are computed
3149 independently of any floating point hardware in the computer running
3150 @command{@value{AS}}.
3154 @c Bit fields are written as a general facility but are also controlled
3155 @c by a conditional-compilation flag---which is as of now (21mar91)
3156 @c turned on only by the i960 config of GAS.
3158 @subsubsection Bit Fields
3161 @cindex constants, bit field
3162 You can also define numeric constants as @dfn{bit fields}.
3163 Specify two numbers separated by a colon---
3165 @var{mask}:@var{value}
3168 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3171 The resulting number is then packed
3173 @c this conditional paren in case bit fields turned on elsewhere than 960
3174 (in host-dependent byte order)
3176 into a field whose width depends on which assembler directive has the
3177 bit-field as its argument. Overflow (a result from the bitwise and
3178 requiring more binary digits to represent) is not an error; instead,
3179 more constants are generated, of the specified width, beginning with the
3180 least significant digits.@refill
3182 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3183 @code{.short}, and @code{.word} accept bit-field arguments.
3188 @chapter Sections and Relocation
3193 * Secs Background:: Background
3194 * Ld Sections:: Linker Sections
3195 * As Sections:: Assembler Internal Sections
3196 * Sub-Sections:: Sub-Sections
3200 @node Secs Background
3203 Roughly, a section is a range of addresses, with no gaps; all data
3204 ``in'' those addresses is treated the same for some particular purpose.
3205 For example there may be a ``read only'' section.
3207 @cindex linker, and assembler
3208 @cindex assembler, and linker
3209 The linker @code{@value{LD}} reads many object files (partial programs) and
3210 combines their contents to form a runnable program. When @command{@value{AS}}
3211 emits an object file, the partial program is assumed to start at address 0.
3212 @code{@value{LD}} assigns the final addresses for the partial program, so that
3213 different partial programs do not overlap. This is actually an
3214 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3217 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3218 addresses. These blocks slide to their run-time addresses as rigid
3219 units; their length does not change and neither does the order of bytes
3220 within them. Such a rigid unit is called a @emph{section}. Assigning
3221 run-time addresses to sections is called @dfn{relocation}. It includes
3222 the task of adjusting mentions of object-file addresses so they refer to
3223 the proper run-time addresses.
3225 For the H8/300, and for the Renesas / SuperH SH,
3226 @command{@value{AS}} pads sections if needed to
3227 ensure they end on a word (sixteen bit) boundary.
3230 @cindex standard assembler sections
3231 An object file written by @command{@value{AS}} has at least three sections, any
3232 of which may be empty. These are named @dfn{text}, @dfn{data} and
3237 When it generates COFF or ELF output,
3239 @command{@value{AS}} can also generate whatever other named sections you specify
3240 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3241 If you do not use any directives that place output in the @samp{.text}
3242 or @samp{.data} sections, these sections still exist, but are empty.
3247 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3249 @command{@value{AS}} can also generate whatever other named sections you
3250 specify using the @samp{.space} and @samp{.subspace} directives. See
3251 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3252 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3253 assembler directives.
3256 Additionally, @command{@value{AS}} uses different names for the standard
3257 text, data, and bss sections when generating SOM output. Program text
3258 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3259 BSS into @samp{$BSS$}.
3263 Within the object file, the text section starts at address @code{0}, the
3264 data section follows, and the bss section follows the data section.
3267 When generating either SOM or ELF output files on the HPPA, the text
3268 section starts at address @code{0}, the data section at address
3269 @code{0x4000000}, and the bss section follows the data section.
3272 To let @code{@value{LD}} know which data changes when the sections are
3273 relocated, and how to change that data, @command{@value{AS}} also writes to the
3274 object file details of the relocation needed. To perform relocation
3275 @code{@value{LD}} must know, each time an address in the object
3279 Where in the object file is the beginning of this reference to
3282 How long (in bytes) is this reference?
3284 Which section does the address refer to? What is the numeric value of
3286 (@var{address}) @minus{} (@var{start-address of section})?
3289 Is the reference to an address ``Program-Counter relative''?
3292 @cindex addresses, format of
3293 @cindex section-relative addressing
3294 In fact, every address @command{@value{AS}} ever uses is expressed as
3296 (@var{section}) + (@var{offset into section})
3299 Further, most expressions @command{@value{AS}} computes have this section-relative
3302 (For some object formats, such as SOM for the HPPA, some expressions are
3303 symbol-relative instead.)
3306 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3307 @var{N} into section @var{secname}.''
3309 Apart from text, data and bss sections you need to know about the
3310 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3311 addresses in the absolute section remain unchanged. For example, address
3312 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3313 @code{@value{LD}}. Although the linker never arranges two partial programs'
3314 data sections with overlapping addresses after linking, @emph{by definition}
3315 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3316 part of a program is always the same address when the program is running as
3317 address @code{@{absolute@ 239@}} in any other part of the program.
3319 The idea of sections is extended to the @dfn{undefined} section. Any
3320 address whose section is unknown at assembly time is by definition
3321 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3322 Since numbers are always defined, the only way to generate an undefined
3323 address is to mention an undefined symbol. A reference to a named
3324 common block would be such a symbol: its value is unknown at assembly
3325 time so it has section @emph{undefined}.
3327 By analogy the word @emph{section} is used to describe groups of sections in
3328 the linked program. @code{@value{LD}} puts all partial programs' text
3329 sections in contiguous addresses in the linked program. It is
3330 customary to refer to the @emph{text section} of a program, meaning all
3331 the addresses of all partial programs' text sections. Likewise for
3332 data and bss sections.
3334 Some sections are manipulated by @code{@value{LD}}; others are invented for
3335 use of @command{@value{AS}} and have no meaning except during assembly.
3338 @section Linker Sections
3339 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3344 @cindex named sections
3345 @cindex sections, named
3346 @item named sections
3349 @cindex text section
3350 @cindex data section
3354 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3355 separate but equal sections. Anything you can say of one section is
3358 When the program is running, however, it is
3359 customary for the text section to be unalterable. The
3360 text section is often shared among processes: it contains
3361 instructions, constants and the like. The data section of a running
3362 program is usually alterable: for example, C variables would be stored
3363 in the data section.
3368 This section contains zeroed bytes when your program begins running. It
3369 is used to hold uninitialized variables or common storage. The length of
3370 each partial program's bss section is important, but because it starts
3371 out containing zeroed bytes there is no need to store explicit zero
3372 bytes in the object file. The bss section was invented to eliminate
3373 those explicit zeros from object files.
3375 @cindex absolute section
3376 @item absolute section
3377 Address 0 of this section is always ``relocated'' to runtime address 0.
3378 This is useful if you want to refer to an address that @code{@value{LD}} must
3379 not change when relocating. In this sense we speak of absolute
3380 addresses being ``unrelocatable'': they do not change during relocation.
3382 @cindex undefined section
3383 @item undefined section
3384 This ``section'' is a catch-all for address references to objects not in
3385 the preceding sections.
3386 @c FIXME: ref to some other doc on obj-file formats could go here.
3389 @cindex relocation example
3390 An idealized example of three relocatable sections follows.
3392 The example uses the traditional section names @samp{.text} and @samp{.data}.
3394 Memory addresses are on the horizontal axis.
3398 @c END TEXI2ROFF-KILL
3401 partial program # 1: |ttttt|dddd|00|
3408 partial program # 2: |TTT|DDD|000|
3411 +--+---+-----+--+----+---+-----+~~
3412 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3413 +--+---+-----+--+----+---+-----+~~
3415 addresses: 0 @dots{}
3422 \line{\it Partial program \#1: \hfil}
3423 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3424 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3426 \line{\it Partial program \#2: \hfil}
3427 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3428 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3430 \line{\it linked program: \hfil}
3431 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3432 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3433 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3434 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3436 \line{\it addresses: \hfil}
3440 @c END TEXI2ROFF-KILL
3443 @section Assembler Internal Sections
3445 @cindex internal assembler sections
3446 @cindex sections in messages, internal
3447 These sections are meant only for the internal use of @command{@value{AS}}. They
3448 have no meaning at run-time. You do not really need to know about these
3449 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3450 warning messages, so it might be helpful to have an idea of their
3451 meanings to @command{@value{AS}}. These sections are used to permit the
3452 value of every expression in your assembly language program to be a
3453 section-relative address.
3456 @cindex assembler internal logic error
3457 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3458 An internal assembler logic error has been found. This means there is a
3459 bug in the assembler.
3461 @cindex expr (internal section)
3463 The assembler stores complex expression internally as combinations of
3464 symbols. When it needs to represent an expression as a symbol, it puts
3465 it in the expr section.
3467 @c FIXME item transfer[t] vector preload
3468 @c FIXME item transfer[t] vector postload
3469 @c FIXME item register
3473 @section Sub-Sections
3475 @cindex numbered subsections
3476 @cindex grouping data
3482 fall into two sections: text and data.
3484 You may have separate groups of
3486 data in named sections
3490 data in named sections
3496 that you want to end up near to each other in the object file, even though they
3497 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3498 use @dfn{subsections} for this purpose. Within each section, there can be
3499 numbered subsections with values from 0 to 8192. Objects assembled into the
3500 same subsection go into the object file together with other objects in the same
3501 subsection. For example, a compiler might want to store constants in the text
3502 section, but might not want to have them interspersed with the program being
3503 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3504 section of code being output, and a @samp{.text 1} before each group of
3505 constants being output.
3507 Subsections are optional. If you do not use subsections, everything
3508 goes in subsection number zero.
3511 Each subsection is zero-padded up to a multiple of four bytes.
3512 (Subsections may be padded a different amount on different flavors
3513 of @command{@value{AS}}.)
3517 On the H8/300 platform, each subsection is zero-padded to a word
3518 boundary (two bytes).
3519 The same is true on the Renesas SH.
3522 @c FIXME section padding (alignment)?
3523 @c Rich Pixley says padding here depends on target obj code format; that
3524 @c doesn't seem particularly useful to say without further elaboration,
3525 @c so for now I say nothing about it. If this is a generic BFD issue,
3526 @c these paragraphs might need to vanish from this manual, and be
3527 @c discussed in BFD chapter of binutils (or some such).
3531 Subsections appear in your object file in numeric order, lowest numbered
3532 to highest. (All this to be compatible with other people's assemblers.)
3533 The object file contains no representation of subsections; @code{@value{LD}} and
3534 other programs that manipulate object files see no trace of them.
3535 They just see all your text subsections as a text section, and all your
3536 data subsections as a data section.
3538 To specify which subsection you want subsequent statements assembled
3539 into, use a numeric argument to specify it, in a @samp{.text
3540 @var{expression}} or a @samp{.data @var{expression}} statement.
3543 When generating COFF output, you
3548 can also use an extra subsection
3549 argument with arbitrary named sections: @samp{.section @var{name},
3554 When generating ELF output, you
3559 can also use the @code{.subsection} directive (@pxref{SubSection})
3560 to specify a subsection: @samp{.subsection @var{expression}}.
3562 @var{Expression} should be an absolute expression
3563 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3564 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3565 begins in @code{text 0}. For instance:
3567 .text 0 # The default subsection is text 0 anyway.
3568 .ascii "This lives in the first text subsection. *"
3570 .ascii "But this lives in the second text subsection."
3572 .ascii "This lives in the data section,"
3573 .ascii "in the first data subsection."
3575 .ascii "This lives in the first text section,"
3576 .ascii "immediately following the asterisk (*)."
3579 Each section has a @dfn{location counter} incremented by one for every byte
3580 assembled into that section. Because subsections are merely a convenience
3581 restricted to @command{@value{AS}} there is no concept of a subsection location
3582 counter. There is no way to directly manipulate a location counter---but the
3583 @code{.align} directive changes it, and any label definition captures its
3584 current value. The location counter of the section where statements are being
3585 assembled is said to be the @dfn{active} location counter.
3588 @section bss Section
3591 @cindex common variable storage
3592 The bss section is used for local common variable storage.
3593 You may allocate address space in the bss section, but you may
3594 not dictate data to load into it before your program executes. When
3595 your program starts running, all the contents of the bss
3596 section are zeroed bytes.
3598 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3599 @ref{Lcomm,,@code{.lcomm}}.
3601 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3602 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3605 When assembling for a target which supports multiple sections, such as ELF or
3606 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3607 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3608 section. Typically the section will only contain symbol definitions and
3609 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3616 Symbols are a central concept: the programmer uses symbols to name
3617 things, the linker uses symbols to link, and the debugger uses symbols
3621 @cindex debuggers, and symbol order
3622 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3623 the same order they were declared. This may break some debuggers.
3628 * Setting Symbols:: Giving Symbols Other Values
3629 * Symbol Names:: Symbol Names
3630 * Dot:: The Special Dot Symbol
3631 * Symbol Attributes:: Symbol Attributes
3638 A @dfn{label} is written as a symbol immediately followed by a colon
3639 @samp{:}. The symbol then represents the current value of the
3640 active location counter, and is, for example, a suitable instruction
3641 operand. You are warned if you use the same symbol to represent two
3642 different locations: the first definition overrides any other
3646 On the HPPA, the usual form for a label need not be immediately followed by a
3647 colon, but instead must start in column zero. Only one label may be defined on
3648 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3649 provides a special directive @code{.label} for defining labels more flexibly.
3652 @node Setting Symbols
3653 @section Giving Symbols Other Values
3655 @cindex assigning values to symbols
3656 @cindex symbol values, assigning
3657 A symbol can be given an arbitrary value by writing a symbol, followed
3658 by an equals sign @samp{=}, followed by an expression
3659 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3660 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3661 equals sign @samp{=}@samp{=} here represents an equivalent of the
3662 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3665 Blackfin does not support symbol assignment with @samp{=}.
3669 @section Symbol Names
3671 @cindex symbol names
3672 @cindex names, symbol
3673 @ifclear SPECIAL-SYMS
3674 Symbol names begin with a letter or with one of @samp{._}. On most
3675 machines, you can also use @code{$} in symbol names; exceptions are
3676 noted in @ref{Machine Dependencies}. That character may be followed by any
3677 string of digits, letters, dollar signs (unless otherwise noted for a
3678 particular target machine), and underscores.
3682 Symbol names begin with a letter or with one of @samp{._}. On the
3683 Renesas SH you can also use @code{$} in symbol names. That
3684 character may be followed by any string of digits, letters, dollar signs (save
3685 on the H8/300), and underscores.
3689 Case of letters is significant: @code{foo} is a different symbol name
3692 Symbol names do not start with a digit. An exception to this rule is made for
3693 Local Labels. See below.
3695 Multibyte characters are supported. To generate a symbol name containing
3696 multibyte characters enclose it within double quotes and use escape codes. cf
3697 @xref{Strings}. Generating a multibyte symbol name from a label is not
3698 currently supported.
3700 Each symbol has exactly one name. Each name in an assembly language program
3701 refers to exactly one symbol. You may use that symbol name any number of times
3704 @subheading Local Symbol Names
3706 @cindex local symbol names
3707 @cindex symbol names, local
3708 A local symbol is any symbol beginning with certain local label prefixes.
3709 By default, the local label prefix is @samp{.L} for ELF systems or
3710 @samp{L} for traditional a.out systems, but each target may have its own
3711 set of local label prefixes.
3713 On the HPPA local symbols begin with @samp{L$}.
3716 Local symbols are defined and used within the assembler, but they are
3717 normally not saved in object files. Thus, they are not visible when debugging.
3718 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3719 to retain the local symbols in the object files.
3721 @subheading Local Labels
3723 @cindex local labels
3724 @cindex temporary symbol names
3725 @cindex symbol names, temporary
3726 Local labels are different from local symbols. Local labels help compilers and
3727 programmers use names temporarily. They create symbols which are guaranteed to
3728 be unique over the entire scope of the input source code and which can be
3729 referred to by a simple notation. To define a local label, write a label of
3730 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3731 To refer to the most recent previous definition of that label write
3732 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3733 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3734 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3736 There is no restriction on how you can use these labels, and you can reuse them
3737 too. So that it is possible to repeatedly define the same local label (using
3738 the same number @samp{@b{N}}), although you can only refer to the most recently
3739 defined local label of that number (for a backwards reference) or the next
3740 definition of a specific local label for a forward reference. It is also worth
3741 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3742 implemented in a slightly more efficient manner than the others.
3753 Which is the equivalent of:
3756 label_1: branch label_3
3757 label_2: branch label_1
3758 label_3: branch label_4
3759 label_4: branch label_3
3762 Local label names are only a notational device. They are immediately
3763 transformed into more conventional symbol names before the assembler uses them.
3764 The symbol names are stored in the symbol table, appear in error messages, and
3765 are optionally emitted to the object file. The names are constructed using
3769 @item @emph{local label prefix}
3770 All local symbols begin with the system-specific local label prefix.
3771 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3772 that start with the local label prefix. These labels are
3773 used for symbols you are never intended to see. If you use the
3774 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3775 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3776 you may use them in debugging.
3779 This is the number that was used in the local label definition. So if the
3780 label is written @samp{55:} then the number is @samp{55}.
3783 This unusual character is included so you do not accidentally invent a symbol
3784 of the same name. The character has ASCII value of @samp{\002} (control-B).
3786 @item @emph{ordinal number}
3787 This is a serial number to keep the labels distinct. The first definition of
3788 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3789 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3790 the number @samp{1} and its 15th definition gets @samp{15} as well.
3793 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3794 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3796 @subheading Dollar Local Labels
3797 @cindex dollar local symbols
3799 On some targets @code{@value{AS}} also supports an even more local form of
3800 local labels called dollar labels. These labels go out of scope (i.e., they
3801 become undefined) as soon as a non-local label is defined. Thus they remain
3802 valid for only a small region of the input source code. Normal local labels,
3803 by contrast, remain in scope for the entire file, or until they are redefined
3804 by another occurrence of the same local label.
3806 Dollar labels are defined in exactly the same way as ordinary local labels,
3807 except that they have a dollar sign suffix to their numeric value, e.g.,
3810 They can also be distinguished from ordinary local labels by their transformed
3811 names which use ASCII character @samp{\001} (control-A) as the magic character
3812 to distinguish them from ordinary labels. For example, the fifth definition of
3813 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3816 @section The Special Dot Symbol
3818 @cindex dot (symbol)
3819 @cindex @code{.} (symbol)
3820 @cindex current address
3821 @cindex location counter
3822 The special symbol @samp{.} refers to the current address that
3823 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3824 .long .} defines @code{melvin} to contain its own address.
3825 Assigning a value to @code{.} is treated the same as a @code{.org}
3827 @ifclear no-space-dir
3828 Thus, the expression @samp{.=.+4} is the same as saying
3832 @node Symbol Attributes
3833 @section Symbol Attributes
3835 @cindex symbol attributes
3836 @cindex attributes, symbol
3837 Every symbol has, as well as its name, the attributes ``Value'' and
3838 ``Type''. Depending on output format, symbols can also have auxiliary
3841 The detailed definitions are in @file{a.out.h}.
3844 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3845 all these attributes, and probably won't warn you. This makes the
3846 symbol an externally defined symbol, which is generally what you
3850 * Symbol Value:: Value
3851 * Symbol Type:: Type
3854 * a.out Symbols:: Symbol Attributes: @code{a.out}
3858 * a.out Symbols:: Symbol Attributes: @code{a.out}
3861 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3866 * COFF Symbols:: Symbol Attributes for COFF
3869 * SOM Symbols:: Symbol Attributes for SOM
3876 @cindex value of a symbol
3877 @cindex symbol value
3878 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3879 location in the text, data, bss or absolute sections the value is the
3880 number of addresses from the start of that section to the label.
3881 Naturally for text, data and bss sections the value of a symbol changes
3882 as @code{@value{LD}} changes section base addresses during linking. Absolute
3883 symbols' values do not change during linking: that is why they are
3886 The value of an undefined symbol is treated in a special way. If it is
3887 0 then the symbol is not defined in this assembler source file, and
3888 @code{@value{LD}} tries to determine its value from other files linked into the
3889 same program. You make this kind of symbol simply by mentioning a symbol
3890 name without defining it. A non-zero value represents a @code{.comm}
3891 common declaration. The value is how much common storage to reserve, in
3892 bytes (addresses). The symbol refers to the first address of the
3898 @cindex type of a symbol
3900 The type attribute of a symbol contains relocation (section)
3901 information, any flag settings indicating that a symbol is external, and
3902 (optionally), other information for linkers and debuggers. The exact
3903 format depends on the object-code output format in use.
3908 @c The following avoids a "widow" subsection title. @group would be
3909 @c better if it were available outside examples.
3912 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3914 @cindex @code{b.out} symbol attributes
3915 @cindex symbol attributes, @code{b.out}
3916 These symbol attributes appear only when @command{@value{AS}} is configured for
3917 one of the Berkeley-descended object output formats---@code{a.out} or
3923 @subsection Symbol Attributes: @code{a.out}
3925 @cindex @code{a.out} symbol attributes
3926 @cindex symbol attributes, @code{a.out}
3932 @subsection Symbol Attributes: @code{a.out}
3934 @cindex @code{a.out} symbol attributes
3935 @cindex symbol attributes, @code{a.out}
3939 * Symbol Desc:: Descriptor
3940 * Symbol Other:: Other
3944 @subsubsection Descriptor
3946 @cindex descriptor, of @code{a.out} symbol
3947 This is an arbitrary 16-bit value. You may establish a symbol's
3948 descriptor value by using a @code{.desc} statement
3949 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3950 @command{@value{AS}}.
3953 @subsubsection Other
3955 @cindex other attribute, of @code{a.out} symbol
3956 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3961 @subsection Symbol Attributes for COFF
3963 @cindex COFF symbol attributes
3964 @cindex symbol attributes, COFF
3966 The COFF format supports a multitude of auxiliary symbol attributes;
3967 like the primary symbol attributes, they are set between @code{.def} and
3968 @code{.endef} directives.
3970 @subsubsection Primary Attributes
3972 @cindex primary attributes, COFF symbols
3973 The symbol name is set with @code{.def}; the value and type,
3974 respectively, with @code{.val} and @code{.type}.
3976 @subsubsection Auxiliary Attributes
3978 @cindex auxiliary attributes, COFF symbols
3979 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3980 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3981 table information for COFF.
3986 @subsection Symbol Attributes for SOM
3988 @cindex SOM symbol attributes
3989 @cindex symbol attributes, SOM
3991 The SOM format for the HPPA supports a multitude of symbol attributes set with
3992 the @code{.EXPORT} and @code{.IMPORT} directives.
3994 The attributes are described in @cite{HP9000 Series 800 Assembly
3995 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3996 @code{EXPORT} assembler directive documentation.
4000 @chapter Expressions
4004 @cindex numeric values
4005 An @dfn{expression} specifies an address or numeric value.
4006 Whitespace may precede and/or follow an expression.
4008 The result of an expression must be an absolute number, or else an offset into
4009 a particular section. If an expression is not absolute, and there is not
4010 enough information when @command{@value{AS}} sees the expression to know its
4011 section, a second pass over the source program might be necessary to interpret
4012 the expression---but the second pass is currently not implemented.
4013 @command{@value{AS}} aborts with an error message in this situation.
4016 * Empty Exprs:: Empty Expressions
4017 * Integer Exprs:: Integer Expressions
4021 @section Empty Expressions
4023 @cindex empty expressions
4024 @cindex expressions, empty
4025 An empty expression has no value: it is just whitespace or null.
4026 Wherever an absolute expression is required, you may omit the
4027 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4028 is compatible with other assemblers.
4031 @section Integer Expressions
4033 @cindex integer expressions
4034 @cindex expressions, integer
4035 An @dfn{integer expression} is one or more @emph{arguments} delimited
4036 by @emph{operators}.
4039 * Arguments:: Arguments
4040 * Operators:: Operators
4041 * Prefix Ops:: Prefix Operators
4042 * Infix Ops:: Infix Operators
4046 @subsection Arguments
4048 @cindex expression arguments
4049 @cindex arguments in expressions
4050 @cindex operands in expressions
4051 @cindex arithmetic operands
4052 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4053 contexts arguments are sometimes called ``arithmetic operands''. In
4054 this manual, to avoid confusing them with the ``instruction operands'' of
4055 the machine language, we use the term ``argument'' to refer to parts of
4056 expressions only, reserving the word ``operand'' to refer only to machine
4057 instruction operands.
4059 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4060 @var{section} is one of text, data, bss, absolute,
4061 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4064 Numbers are usually integers.
4066 A number can be a flonum or bignum. In this case, you are warned
4067 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4068 these 32 bits are an integer. You may write integer-manipulating
4069 instructions that act on exotic constants, compatible with other
4072 @cindex subexpressions
4073 Subexpressions are a left parenthesis @samp{(} followed by an integer
4074 expression, followed by a right parenthesis @samp{)}; or a prefix
4075 operator followed by an argument.
4078 @subsection Operators
4080 @cindex operators, in expressions
4081 @cindex arithmetic functions
4082 @cindex functions, in expressions
4083 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4084 operators are followed by an argument. Infix operators appear
4085 between their arguments. Operators may be preceded and/or followed by
4089 @subsection Prefix Operator
4091 @cindex prefix operators
4092 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4093 one argument, which must be absolute.
4095 @c the tex/end tex stuff surrounding this small table is meant to make
4096 @c it align, on the printed page, with the similar table in the next
4097 @c section (which is inside an enumerate).
4099 \global\advance\leftskip by \itemindent
4104 @dfn{Negation}. Two's complement negation.
4106 @dfn{Complementation}. Bitwise not.
4110 \global\advance\leftskip by -\itemindent
4114 @subsection Infix Operators
4116 @cindex infix operators
4117 @cindex operators, permitted arguments
4118 @dfn{Infix operators} take two arguments, one on either side. Operators
4119 have precedence, but operations with equal precedence are performed left
4120 to right. Apart from @code{+} or @option{-}, both arguments must be
4121 absolute, and the result is absolute.
4124 @cindex operator precedence
4125 @cindex precedence of operators
4132 @dfn{Multiplication}.
4135 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4141 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4144 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4148 Intermediate precedence
4153 @dfn{Bitwise Inclusive Or}.
4159 @dfn{Bitwise Exclusive Or}.
4162 @dfn{Bitwise Or Not}.
4169 @cindex addition, permitted arguments
4170 @cindex plus, permitted arguments
4171 @cindex arguments for addition
4173 @dfn{Addition}. If either argument is absolute, the result has the section of
4174 the other argument. You may not add together arguments from different
4177 @cindex subtraction, permitted arguments
4178 @cindex minus, permitted arguments
4179 @cindex arguments for subtraction
4181 @dfn{Subtraction}. If the right argument is absolute, the
4182 result has the section of the left argument.
4183 If both arguments are in the same section, the result is absolute.
4184 You may not subtract arguments from different sections.
4185 @c FIXME is there still something useful to say about undefined - undefined ?
4187 @cindex comparison expressions
4188 @cindex expressions, comparison
4193 @dfn{Is Not Equal To}
4197 @dfn{Is Greater Than}
4199 @dfn{Is Greater Than Or Equal To}
4201 @dfn{Is Less Than Or Equal To}
4203 The comparison operators can be used as infix operators. A true results has a
4204 value of -1 whereas a false result has a value of 0. Note, these operators
4205 perform signed comparisons.
4208 @item Lowest Precedence
4217 These two logical operations can be used to combine the results of sub
4218 expressions. Note, unlike the comparison operators a true result returns a
4219 value of 1 but a false results does still return 0. Also note that the logical
4220 or operator has a slightly lower precedence than logical and.
4225 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4226 address; you can only have a defined section in one of the two arguments.
4229 @chapter Assembler Directives
4231 @cindex directives, machine independent
4232 @cindex pseudo-ops, machine independent
4233 @cindex machine independent directives
4234 All assembler directives have names that begin with a period (@samp{.}).
4235 The names are case insensitive for most targets, and usually written
4238 This chapter discusses directives that are available regardless of the
4239 target machine configuration for the @sc{gnu} assembler.
4241 Some machine configurations provide additional directives.
4242 @xref{Machine Dependencies}.
4245 @ifset machine-directives
4246 @xref{Machine Dependencies}, for additional directives.
4251 * Abort:: @code{.abort}
4253 * ABORT (COFF):: @code{.ABORT}
4256 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4257 * Altmacro:: @code{.altmacro}
4258 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4259 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4260 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4261 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4262 * Byte:: @code{.byte @var{expressions}}
4263 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4264 * Comm:: @code{.comm @var{symbol} , @var{length} }
4265 * Data:: @code{.data @var{subsection}}
4267 * Def:: @code{.def @var{name}}
4270 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4276 * Double:: @code{.double @var{flonums}}
4277 * Eject:: @code{.eject}
4278 * Else:: @code{.else}
4279 * Elseif:: @code{.elseif}
4282 * Endef:: @code{.endef}
4285 * Endfunc:: @code{.endfunc}
4286 * Endif:: @code{.endif}
4287 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4288 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4289 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4291 * Error:: @code{.error @var{string}}
4292 * Exitm:: @code{.exitm}
4293 * Extern:: @code{.extern}
4294 * Fail:: @code{.fail}
4295 * File:: @code{.file}
4296 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4297 * Float:: @code{.float @var{flonums}}
4298 * Func:: @code{.func}
4299 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4301 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4302 * Hidden:: @code{.hidden @var{names}}
4305 * hword:: @code{.hword @var{expressions}}
4306 * Ident:: @code{.ident}
4307 * If:: @code{.if @var{absolute expression}}
4308 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4309 * Include:: @code{.include "@var{file}"}
4310 * Int:: @code{.int @var{expressions}}
4312 * Internal:: @code{.internal @var{names}}
4315 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4316 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4317 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4318 * Lflags:: @code{.lflags}
4319 @ifclear no-line-dir
4320 * Line:: @code{.line @var{line-number}}
4323 * Linkonce:: @code{.linkonce [@var{type}]}
4324 * List:: @code{.list}
4325 * Ln:: @code{.ln @var{line-number}}
4326 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4327 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4329 * Local:: @code{.local @var{names}}
4332 * Long:: @code{.long @var{expressions}}
4334 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4337 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4338 * MRI:: @code{.mri @var{val}}
4339 * Noaltmacro:: @code{.noaltmacro}
4340 * Nolist:: @code{.nolist}
4341 * Octa:: @code{.octa @var{bignums}}
4342 * Offset:: @code{.offset @var{loc}}
4343 * Org:: @code{.org @var{new-lc}, @var{fill}}
4344 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4346 * PopSection:: @code{.popsection}
4347 * Previous:: @code{.previous}
4350 * Print:: @code{.print @var{string}}
4352 * Protected:: @code{.protected @var{names}}
4355 * Psize:: @code{.psize @var{lines}, @var{columns}}
4356 * Purgem:: @code{.purgem @var{name}}
4358 * PushSection:: @code{.pushsection @var{name}}
4361 * Quad:: @code{.quad @var{bignums}}
4362 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4363 * Rept:: @code{.rept @var{count}}
4364 * Sbttl:: @code{.sbttl "@var{subheading}"}
4366 * Scl:: @code{.scl @var{class}}
4369 * Section:: @code{.section @var{name}[, @var{flags}]}
4372 * Set:: @code{.set @var{symbol}, @var{expression}}
4373 * Short:: @code{.short @var{expressions}}
4374 * Single:: @code{.single @var{flonums}}
4376 * Size:: @code{.size [@var{name} , @var{expression}]}
4378 @ifclear no-space-dir
4379 * Skip:: @code{.skip @var{size} , @var{fill}}
4382 * Sleb128:: @code{.sleb128 @var{expressions}}
4383 @ifclear no-space-dir
4384 * Space:: @code{.space @var{size} , @var{fill}}
4387 * Stab:: @code{.stabd, .stabn, .stabs}
4390 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4391 * Struct:: @code{.struct @var{expression}}
4393 * SubSection:: @code{.subsection}
4394 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4398 * Tag:: @code{.tag @var{structname}}
4401 * Text:: @code{.text @var{subsection}}
4402 * Title:: @code{.title "@var{heading}"}
4404 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4407 * Uleb128:: @code{.uleb128 @var{expressions}}
4409 * Val:: @code{.val @var{addr}}
4413 * Version:: @code{.version "@var{string}"}
4414 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4415 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4418 * Warning:: @code{.warning @var{string}}
4419 * Weak:: @code{.weak @var{names}}
4420 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4421 * Word:: @code{.word @var{expressions}}
4422 @ifclear no-space-dir
4423 * Zero:: @code{.zero @var{size}}
4425 * Deprecated:: Deprecated Directives
4429 @section @code{.abort}
4431 @cindex @code{abort} directive
4432 @cindex stopping the assembly
4433 This directive stops the assembly immediately. It is for
4434 compatibility with other assemblers. The original idea was that the
4435 assembly language source would be piped into the assembler. If the sender
4436 of the source quit, it could use this directive tells @command{@value{AS}} to
4437 quit also. One day @code{.abort} will not be supported.
4441 @section @code{.ABORT} (COFF)
4443 @cindex @code{ABORT} directive
4444 When producing COFF output, @command{@value{AS}} accepts this directive as a
4445 synonym for @samp{.abort}.
4448 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4454 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4456 @cindex padding the location counter
4457 @cindex @code{align} directive
4458 Pad the location counter (in the current subsection) to a particular storage
4459 boundary. The first expression (which must be absolute) is the alignment
4460 required, as described below.
4462 The second expression (also absolute) gives the fill value to be stored in the
4463 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4464 padding bytes are normally zero. However, on some systems, if the section is
4465 marked as containing code and the fill value is omitted, the space is filled
4466 with no-op instructions.
4468 The third expression is also absolute, and is also optional. If it is present,
4469 it is the maximum number of bytes that should be skipped by this alignment
4470 directive. If doing the alignment would require skipping more bytes than the
4471 specified maximum, then the alignment is not done at all. You can omit the
4472 fill value (the second argument) entirely by simply using two commas after the
4473 required alignment; this can be useful if you want the alignment to be filled
4474 with no-op instructions when appropriate.
4476 The way the required alignment is specified varies from system to system.
4477 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4478 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4479 alignment request in bytes. For example @samp{.align 8} advances
4480 the location counter until it is a multiple of 8. If the location counter
4481 is already a multiple of 8, no change is needed. For the tic54x, the
4482 first expression is the alignment request in words.
4484 For other systems, including ppc, i386 using a.out format, arm and
4485 strongarm, it is the
4486 number of low-order zero bits the location counter must have after
4487 advancement. For example @samp{.align 3} advances the location
4488 counter until it a multiple of 8. If the location counter is already a
4489 multiple of 8, no change is needed.
4491 This inconsistency is due to the different behaviors of the various
4492 native assemblers for these systems which GAS must emulate.
4493 GAS also provides @code{.balign} and @code{.p2align} directives,
4494 described later, which have a consistent behavior across all
4495 architectures (but are specific to GAS).
4498 @section @code{.altmacro}
4499 Enable alternate macro mode, enabling:
4502 @item LOCAL @var{name} [ , @dots{} ]
4503 One additional directive, @code{LOCAL}, is available. It is used to
4504 generate a string replacement for each of the @var{name} arguments, and
4505 replace any instances of @var{name} in each macro expansion. The
4506 replacement string is unique in the assembly, and different for each
4507 separate macro expansion. @code{LOCAL} allows you to write macros that
4508 define symbols, without fear of conflict between separate macro expansions.
4510 @item String delimiters
4511 You can write strings delimited in these other ways besides
4512 @code{"@var{string}"}:
4515 @item '@var{string}'
4516 You can delimit strings with single-quote characters.
4518 @item <@var{string}>
4519 You can delimit strings with matching angle brackets.
4522 @item single-character string escape
4523 To include any single character literally in a string (even if the
4524 character would otherwise have some special meaning), you can prefix the
4525 character with @samp{!} (an exclamation mark). For example, you can
4526 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4528 @item Expression results as strings
4529 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4530 and use the result as a string.
4534 @section @code{.ascii "@var{string}"}@dots{}
4536 @cindex @code{ascii} directive
4537 @cindex string literals
4538 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4539 separated by commas. It assembles each string (with no automatic
4540 trailing zero byte) into consecutive addresses.
4543 @section @code{.asciz "@var{string}"}@dots{}
4545 @cindex @code{asciz} directive
4546 @cindex zero-terminated strings
4547 @cindex null-terminated strings
4548 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4549 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4552 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4554 @cindex padding the location counter given number of bytes
4555 @cindex @code{balign} directive
4556 Pad the location counter (in the current subsection) to a particular
4557 storage boundary. The first expression (which must be absolute) is the
4558 alignment request in bytes. For example @samp{.balign 8} advances
4559 the location counter until it is a multiple of 8. If the location counter
4560 is already a multiple of 8, no change is needed.
4562 The second expression (also absolute) gives the fill value to be stored in the
4563 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4564 padding bytes are normally zero. However, on some systems, if the section is
4565 marked as containing code and the fill value is omitted, the space is filled
4566 with no-op instructions.
4568 The third expression is also absolute, and is also optional. If it is present,
4569 it is the maximum number of bytes that should be skipped by this alignment
4570 directive. If doing the alignment would require skipping more bytes than the
4571 specified maximum, then the alignment is not done at all. You can omit the
4572 fill value (the second argument) entirely by simply using two commas after the
4573 required alignment; this can be useful if you want the alignment to be filled
4574 with no-op instructions when appropriate.
4576 @cindex @code{balignw} directive
4577 @cindex @code{balignl} directive
4578 The @code{.balignw} and @code{.balignl} directives are variants of the
4579 @code{.balign} directive. The @code{.balignw} directive treats the fill
4580 pattern as a two byte word value. The @code{.balignl} directives treats the
4581 fill pattern as a four byte longword value. For example, @code{.balignw
4582 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4583 filled in with the value 0x368d (the exact placement of the bytes depends upon
4584 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4587 @node Bundle directives
4588 @section Bundle directives
4589 @subsection @code{.bundle_align_mode @var{abs-expr}}
4590 @cindex @code{bundle_align_mode} directive
4592 @cindex instruction bundle
4593 @cindex aligned instruction bundle
4594 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4595 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4596 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4597 disabled (which is the default state). If the argument it not zero, it
4598 gives the size of an instruction bundle as a power of two (as for the
4599 @code{.p2align} directive, @pxref{P2align}).
4601 For some targets, it's an ABI requirement that no instruction may span a
4602 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4603 instructions that starts on an aligned boundary. For example, if
4604 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4605 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4606 effect, no single instruction may span a boundary between bundles. If an
4607 instruction would start too close to the end of a bundle for the length of
4608 that particular instruction to fit within the bundle, then the space at the
4609 end of that bundle is filled with no-op instructions so the instruction
4610 starts in the next bundle. As a corollary, it's an error if any single
4611 instruction's encoding is longer than the bundle size.
4613 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4614 @cindex @code{bundle_lock} directive
4615 @cindex @code{bundle_unlock} directive
4616 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4617 allow explicit control over instruction bundle padding. These directives
4618 are only valid when @code{.bundle_align_mode} has been used to enable
4619 aligned instruction bundle mode. It's an error if they appear when
4620 @code{.bundle_align_mode} has not been used at all, or when the last
4621 directive was @w{@code{.bundle_align_mode 0}}.
4623 @cindex bundle-locked
4624 For some targets, it's an ABI requirement that certain instructions may
4625 appear only as part of specified permissible sequences of multiple
4626 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4627 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4628 instruction sequence. For purposes of aligned instruction bundle mode, a
4629 sequence starting with @code{.bundle_lock} and ending with
4630 @code{.bundle_unlock} is treated as a single instruction. That is, the
4631 entire sequence must fit into a single bundle and may not span a bundle
4632 boundary. If necessary, no-op instructions will be inserted before the
4633 first instruction of the sequence so that the whole sequence starts on an
4634 aligned bundle boundary. It's an error if the sequence is longer than the
4637 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4638 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4639 nested. That is, a second @code{.bundle_lock} directive before the next
4640 @code{.bundle_unlock} directive has no effect except that it must be
4641 matched by another closing @code{.bundle_unlock} so that there is the
4642 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4645 @section @code{.byte @var{expressions}}
4647 @cindex @code{byte} directive
4648 @cindex integers, one byte
4649 @code{.byte} expects zero or more expressions, separated by commas.
4650 Each expression is assembled into the next byte.
4652 @node CFI directives
4653 @section CFI directives
4654 @subsection @code{.cfi_sections @var{section_list}}
4655 @cindex @code{cfi_sections} directive
4656 @code{.cfi_sections} may be used to specify whether CFI directives
4657 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4658 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4659 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4660 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4661 directive is not used is @code{.cfi_sections .eh_frame}.
4663 On targets that support compact unwinding tables these can be generated
4664 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4666 @subsection @code{.cfi_startproc [simple]}
4667 @cindex @code{cfi_startproc} directive
4668 @code{.cfi_startproc} is used at the beginning of each function that
4669 should have an entry in @code{.eh_frame}. It initializes some internal
4670 data structures. Don't forget to close the function by
4671 @code{.cfi_endproc}.
4673 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4674 it also emits some architecture dependent initial CFI instructions.
4676 @subsection @code{.cfi_endproc}
4677 @cindex @code{cfi_endproc} directive
4678 @code{.cfi_endproc} is used at the end of a function where it closes its
4679 unwind entry previously opened by
4680 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4682 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4683 @cindex @code{cfi_personality} directive
4684 @code{.cfi_personality} defines personality routine and its encoding.
4685 @var{encoding} must be a constant determining how the personality
4686 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4687 argument is not present, otherwise second argument should be
4688 a constant or a symbol name. When using indirect encodings,
4689 the symbol provided should be the location where personality
4690 can be loaded from, not the personality routine itself.
4691 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4692 no personality routine.
4694 @subsection @code{.cfi_personality_id @var{id}}
4695 @cindex @code{cfi_personality_id} directive
4696 @code{cfi_personality_id} defines a personality routine by its index as
4697 defined in a compact unwinding format.
4698 Only valid when generating compact EH frames (i.e.
4699 with @code{.cfi_sections eh_frame_entry}.
4701 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4702 @cindex @code{cfi_fde_data} directive
4703 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4704 used for the current function. These are emitted inline in the
4705 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4706 in the @code{.gnu.extab} section otherwise.
4707 Only valid when generating compact EH frames (i.e.
4708 with @code{.cfi_sections eh_frame_entry}.
4710 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4711 @code{.cfi_lsda} defines LSDA and its encoding.
4712 @var{encoding} must be a constant determining how the LSDA
4713 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4714 argument is not present, otherwise the second argument should be a constant
4715 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4716 meaning that no LSDA is present.
4718 @subsection @code{.cfi_inline_lsda} [@var{align}]
4719 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4720 switches to the corresponding @code{.gnu.extab} section.
4721 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4722 Only valid when generating compact EH frames (i.e.
4723 with @code{.cfi_sections eh_frame_entry}.
4725 The table header and unwinding opcodes will be generated at this point,
4726 so that they are immediately followed by the LSDA data. The symbol
4727 referenced by the @code{.cfi_lsda} directive should still be defined
4728 in case a fallback FDE based encoding is used. The LSDA data is terminated
4729 by a section directive.
4731 The optional @var{align} argument specifies the alignment required.
4732 The alignment is specified as a power of two, as with the
4733 @code{.p2align} directive.
4735 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4736 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4737 address from @var{register} and add @var{offset} to it}.
4739 @subsection @code{.cfi_def_cfa_register @var{register}}
4740 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4741 now on @var{register} will be used instead of the old one. Offset
4744 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4745 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4746 remains the same, but @var{offset} is new. Note that it is the
4747 absolute offset that will be added to a defined register to compute
4750 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4751 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4752 value that is added/substracted from the previous offset.
4754 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4755 Previous value of @var{register} is saved at offset @var{offset} from
4758 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4759 Previous value of @var{register} is saved at offset @var{offset} from
4760 the current CFA register. This is transformed to @code{.cfi_offset}
4761 using the known displacement of the CFA register from the CFA.
4762 This is often easier to use, because the number will match the
4763 code it's annotating.
4765 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4766 Previous value of @var{register1} is saved in register @var{register2}.
4768 @subsection @code{.cfi_restore @var{register}}
4769 @code{.cfi_restore} says that the rule for @var{register} is now the
4770 same as it was at the beginning of the function, after all initial
4771 instruction added by @code{.cfi_startproc} were executed.
4773 @subsection @code{.cfi_undefined @var{register}}
4774 From now on the previous value of @var{register} can't be restored anymore.
4776 @subsection @code{.cfi_same_value @var{register}}
4777 Current value of @var{register} is the same like in the previous frame,
4778 i.e. no restoration needed.
4780 @subsection @code{.cfi_remember_state},
4781 First save all current rules for all registers by @code{.cfi_remember_state},
4782 then totally screw them up by subsequent @code{.cfi_*} directives and when
4783 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4784 the previous saved state.
4786 @subsection @code{.cfi_return_column @var{register}}
4787 Change return column @var{register}, i.e. the return address is either
4788 directly in @var{register} or can be accessed by rules for @var{register}.
4790 @subsection @code{.cfi_signal_frame}
4791 Mark current function as signal trampoline.
4793 @subsection @code{.cfi_window_save}
4794 SPARC register window has been saved.
4796 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4797 Allows the user to add arbitrary bytes to the unwind info. One
4798 might use this to add OS-specific CFI opcodes, or generic CFI
4799 opcodes that GAS does not yet support.
4801 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4802 The current value of @var{register} is @var{label}. The value of @var{label}
4803 will be encoded in the output file according to @var{encoding}; see the
4804 description of @code{.cfi_personality} for details on this encoding.
4806 The usefulness of equating a register to a fixed label is probably
4807 limited to the return address register. Here, it can be useful to
4808 mark a code segment that has only one return address which is reached
4809 by a direct branch and no copy of the return address exists in memory
4810 or another register.
4813 @section @code{.comm @var{symbol} , @var{length} }
4815 @cindex @code{comm} directive
4816 @cindex symbol, common
4817 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4818 common symbol in one object file may be merged with a defined or common symbol
4819 of the same name in another object file. If @code{@value{LD}} does not see a
4820 definition for the symbol--just one or more common symbols--then it will
4821 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4822 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4823 the same name, and they do not all have the same size, it will allocate space
4824 using the largest size.
4827 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4828 an optional third argument. This is the desired alignment of the symbol,
4829 specified for ELF as a byte boundary (for example, an alignment of 16 means
4830 that the least significant 4 bits of the address should be zero), and for PE
4831 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4832 boundary). The alignment must be an absolute expression, and it must be a
4833 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4834 common symbol, it will use the alignment when placing the symbol. If no
4835 alignment is specified, @command{@value{AS}} will set the alignment to the
4836 largest power of two less than or equal to the size of the symbol, up to a
4837 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4838 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4839 @samp{--section-alignment} option; image file sections in PE are aligned to
4840 multiples of 4096, which is far too large an alignment for ordinary variables.
4841 It is rather the default alignment for (non-debug) sections within object
4842 (@samp{*.o}) files, which are less strictly aligned.}.
4846 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4847 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4851 @section @code{.data @var{subsection}}
4853 @cindex @code{data} directive
4854 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4855 end of the data subsection numbered @var{subsection} (which is an
4856 absolute expression). If @var{subsection} is omitted, it defaults
4861 @section @code{.def @var{name}}
4863 @cindex @code{def} directive
4864 @cindex COFF symbols, debugging
4865 @cindex debugging COFF symbols
4866 Begin defining debugging information for a symbol @var{name}; the
4867 definition extends until the @code{.endef} directive is encountered.
4870 This directive is only observed when @command{@value{AS}} is configured for COFF
4871 format output; when producing @code{b.out}, @samp{.def} is recognized,
4878 @section @code{.desc @var{symbol}, @var{abs-expression}}
4880 @cindex @code{desc} directive
4881 @cindex COFF symbol descriptor
4882 @cindex symbol descriptor, COFF
4883 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4884 to the low 16 bits of an absolute expression.
4887 The @samp{.desc} directive is not available when @command{@value{AS}} is
4888 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4889 object format. For the sake of compatibility, @command{@value{AS}} accepts
4890 it, but produces no output, when configured for COFF.
4896 @section @code{.dim}
4898 @cindex @code{dim} directive
4899 @cindex COFF auxiliary symbol information
4900 @cindex auxiliary symbol information, COFF
4901 This directive is generated by compilers to include auxiliary debugging
4902 information in the symbol table. It is only permitted inside
4903 @code{.def}/@code{.endef} pairs.
4906 @samp{.dim} is only meaningful when generating COFF format output; when
4907 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4913 @section @code{.double @var{flonums}}
4915 @cindex @code{double} directive
4916 @cindex floating point numbers (double)
4917 @code{.double} expects zero or more flonums, separated by commas. It
4918 assembles floating point numbers.
4920 The exact kind of floating point numbers emitted depends on how
4921 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4925 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4926 in @sc{ieee} format.
4931 @section @code{.eject}
4933 @cindex @code{eject} directive
4934 @cindex new page, in listings
4935 @cindex page, in listings
4936 @cindex listing control: new page
4937 Force a page break at this point, when generating assembly listings.
4940 @section @code{.else}
4942 @cindex @code{else} directive
4943 @code{.else} is part of the @command{@value{AS}} support for conditional
4944 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4945 of code to be assembled if the condition for the preceding @code{.if}
4949 @section @code{.elseif}
4951 @cindex @code{elseif} directive
4952 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4953 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4954 @code{.if} block that would otherwise fill the entire @code{.else} section.
4957 @section @code{.end}
4959 @cindex @code{end} directive
4960 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4961 process anything in the file past the @code{.end} directive.
4965 @section @code{.endef}
4967 @cindex @code{endef} directive
4968 This directive flags the end of a symbol definition begun with
4972 @samp{.endef} is only meaningful when generating COFF format output; if
4973 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4974 directive but ignores it.
4979 @section @code{.endfunc}
4980 @cindex @code{endfunc} directive
4981 @code{.endfunc} marks the end of a function specified with @code{.func}.
4984 @section @code{.endif}
4986 @cindex @code{endif} directive
4987 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4988 it marks the end of a block of code that is only assembled
4989 conditionally. @xref{If,,@code{.if}}.
4992 @section @code{.equ @var{symbol}, @var{expression}}
4994 @cindex @code{equ} directive
4995 @cindex assigning values to symbols
4996 @cindex symbols, assigning values to
4997 This directive sets the value of @var{symbol} to @var{expression}.
4998 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5001 The syntax for @code{equ} on the HPPA is
5002 @samp{@var{symbol} .equ @var{expression}}.
5006 The syntax for @code{equ} on the Z80 is
5007 @samp{@var{symbol} equ @var{expression}}.
5008 On the Z80 it is an eror if @var{symbol} is already defined,
5009 but the symbol is not protected from later redefinition.
5010 Compare @ref{Equiv}.
5014 @section @code{.equiv @var{symbol}, @var{expression}}
5015 @cindex @code{equiv} directive
5016 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5017 the assembler will signal an error if @var{symbol} is already defined. Note a
5018 symbol which has been referenced but not actually defined is considered to be
5021 Except for the contents of the error message, this is roughly equivalent to
5028 plus it protects the symbol from later redefinition.
5031 @section @code{.eqv @var{symbol}, @var{expression}}
5032 @cindex @code{eqv} directive
5033 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5034 evaluate the expression or any part of it immediately. Instead each time
5035 the resulting symbol is used in an expression, a snapshot of its current
5039 @section @code{.err}
5040 @cindex @code{err} directive
5041 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5042 message and, unless the @option{-Z} option was used, it will not generate an
5043 object file. This can be used to signal an error in conditionally compiled code.
5046 @section @code{.error "@var{string}"}
5047 @cindex error directive
5049 Similarly to @code{.err}, this directive emits an error, but you can specify a
5050 string that will be emitted as the error message. If you don't specify the
5051 message, it defaults to @code{".error directive invoked in source file"}.
5052 @xref{Errors, ,Error and Warning Messages}.
5055 .error "This code has not been assembled and tested."
5059 @section @code{.exitm}
5060 Exit early from the current macro definition. @xref{Macro}.
5063 @section @code{.extern}
5065 @cindex @code{extern} directive
5066 @code{.extern} is accepted in the source program---for compatibility
5067 with other assemblers---but it is ignored. @command{@value{AS}} treats
5068 all undefined symbols as external.
5071 @section @code{.fail @var{expression}}
5073 @cindex @code{fail} directive
5074 Generates an error or a warning. If the value of the @var{expression} is 500
5075 or more, @command{@value{AS}} will print a warning message. If the value is less
5076 than 500, @command{@value{AS}} will print an error message. The message will
5077 include the value of @var{expression}. This can occasionally be useful inside
5078 complex nested macros or conditional assembly.
5081 @section @code{.file}
5082 @cindex @code{file} directive
5084 @ifclear no-file-dir
5085 There are two different versions of the @code{.file} directive. Targets
5086 that support DWARF2 line number information use the DWARF2 version of
5087 @code{.file}. Other targets use the default version.
5089 @subheading Default Version
5091 @cindex logical file name
5092 @cindex file name, logical
5093 This version of the @code{.file} directive tells @command{@value{AS}} that we
5094 are about to start a new logical file. The syntax is:
5100 @var{string} is the new file name. In general, the filename is
5101 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5102 to specify an empty file name, you must give the quotes--@code{""}. This
5103 statement may go away in future: it is only recognized to be compatible with
5104 old @command{@value{AS}} programs.
5106 @subheading DWARF2 Version
5109 When emitting DWARF2 line number information, @code{.file} assigns filenames
5110 to the @code{.debug_line} file name table. The syntax is:
5113 .file @var{fileno} @var{filename}
5116 The @var{fileno} operand should be a unique positive integer to use as the
5117 index of the entry in the table. The @var{filename} operand is a C string
5120 The detail of filename indices is exposed to the user because the filename
5121 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5122 information, and thus the user must know the exact indices that table
5126 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5128 @cindex @code{fill} directive
5129 @cindex writing patterns in memory
5130 @cindex patterns, writing in memory
5131 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5132 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5133 may be zero or more. @var{Size} may be zero or more, but if it is
5134 more than 8, then it is deemed to have the value 8, compatible with
5135 other people's assemblers. The contents of each @var{repeat} bytes
5136 is taken from an 8-byte number. The highest order 4 bytes are
5137 zero. The lowest order 4 bytes are @var{value} rendered in the
5138 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5139 Each @var{size} bytes in a repetition is taken from the lowest order
5140 @var{size} bytes of this number. Again, this bizarre behavior is
5141 compatible with other people's assemblers.
5143 @var{size} and @var{value} are optional.
5144 If the second comma and @var{value} are absent, @var{value} is
5145 assumed zero. If the first comma and following tokens are absent,
5146 @var{size} is assumed to be 1.
5149 @section @code{.float @var{flonums}}
5151 @cindex floating point numbers (single)
5152 @cindex @code{float} directive
5153 This directive assembles zero or more flonums, separated by commas. It
5154 has the same effect as @code{.single}.
5156 The exact kind of floating point numbers emitted depends on how
5157 @command{@value{AS}} is configured.
5158 @xref{Machine Dependencies}.
5162 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5163 in @sc{ieee} format.
5168 @section @code{.func @var{name}[,@var{label}]}
5169 @cindex @code{func} directive
5170 @code{.func} emits debugging information to denote function @var{name}, and
5171 is ignored unless the file is assembled with debugging enabled.
5172 Only @samp{--gstabs[+]} is currently supported.
5173 @var{label} is the entry point of the function and if omitted @var{name}
5174 prepended with the @samp{leading char} is used.
5175 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5176 All functions are currently defined to have @code{void} return type.
5177 The function must be terminated with @code{.endfunc}.
5180 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5182 @cindex @code{global} directive
5183 @cindex symbol, making visible to linker
5184 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5185 @var{symbol} in your partial program, its value is made available to
5186 other partial programs that are linked with it. Otherwise,
5187 @var{symbol} takes its attributes from a symbol of the same name
5188 from another file linked into the same program.
5190 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5191 compatibility with other assemblers.
5194 On the HPPA, @code{.global} is not always enough to make it accessible to other
5195 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5196 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5201 @section @code{.gnu_attribute @var{tag},@var{value}}
5202 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5205 @section @code{.hidden @var{names}}
5207 @cindex @code{hidden} directive
5209 This is one of the ELF visibility directives. The other two are
5210 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5211 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5213 This directive overrides the named symbols default visibility (which is set by
5214 their binding: local, global or weak). The directive sets the visibility to
5215 @code{hidden} which means that the symbols are not visible to other components.
5216 Such symbols are always considered to be @code{protected} as well.
5220 @section @code{.hword @var{expressions}}
5222 @cindex @code{hword} directive
5223 @cindex integers, 16-bit
5224 @cindex numbers, 16-bit
5225 @cindex sixteen bit integers
5226 This expects zero or more @var{expressions}, and emits
5227 a 16 bit number for each.
5230 This directive is a synonym for @samp{.short}; depending on the target
5231 architecture, it may also be a synonym for @samp{.word}.
5235 This directive is a synonym for @samp{.short}.
5238 This directive is a synonym for both @samp{.short} and @samp{.word}.
5243 @section @code{.ident}
5245 @cindex @code{ident} directive
5247 This directive is used by some assemblers to place tags in object files. The
5248 behavior of this directive varies depending on the target. When using the
5249 a.out object file format, @command{@value{AS}} simply accepts the directive for
5250 source-file compatibility with existing assemblers, but does not emit anything
5251 for it. When using COFF, comments are emitted to the @code{.comment} or
5252 @code{.rdata} section, depending on the target. When using ELF, comments are
5253 emitted to the @code{.comment} section.
5256 @section @code{.if @var{absolute expression}}
5258 @cindex conditional assembly
5259 @cindex @code{if} directive
5260 @code{.if} marks the beginning of a section of code which is only
5261 considered part of the source program being assembled if the argument
5262 (which must be an @var{absolute expression}) is non-zero. The end of
5263 the conditional section of code must be marked by @code{.endif}
5264 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5265 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5266 If you have several conditions to check, @code{.elseif} may be used to avoid
5267 nesting blocks if/else within each subsequent @code{.else} block.
5269 The following variants of @code{.if} are also supported:
5271 @cindex @code{ifdef} directive
5272 @item .ifdef @var{symbol}
5273 Assembles the following section of code if the specified @var{symbol}
5274 has been defined. Note a symbol which has been referenced but not yet defined
5275 is considered to be undefined.
5277 @cindex @code{ifb} directive
5278 @item .ifb @var{text}
5279 Assembles the following section of code if the operand is blank (empty).
5281 @cindex @code{ifc} directive
5282 @item .ifc @var{string1},@var{string2}
5283 Assembles the following section of code if the two strings are the same. The
5284 strings may be optionally quoted with single quotes. If they are not quoted,
5285 the first string stops at the first comma, and the second string stops at the
5286 end of the line. Strings which contain whitespace should be quoted. The
5287 string comparison is case sensitive.
5289 @cindex @code{ifeq} directive
5290 @item .ifeq @var{absolute expression}
5291 Assembles the following section of code if the argument is zero.
5293 @cindex @code{ifeqs} directive
5294 @item .ifeqs @var{string1},@var{string2}
5295 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5297 @cindex @code{ifge} directive
5298 @item .ifge @var{absolute expression}
5299 Assembles the following section of code if the argument is greater than or
5302 @cindex @code{ifgt} directive
5303 @item .ifgt @var{absolute expression}
5304 Assembles the following section of code if the argument is greater than zero.
5306 @cindex @code{ifle} directive
5307 @item .ifle @var{absolute expression}
5308 Assembles the following section of code if the argument is less than or equal
5311 @cindex @code{iflt} directive
5312 @item .iflt @var{absolute expression}
5313 Assembles the following section of code if the argument is less than zero.
5315 @cindex @code{ifnb} directive
5316 @item .ifnb @var{text}
5317 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5318 following section of code if the operand is non-blank (non-empty).
5320 @cindex @code{ifnc} directive
5321 @item .ifnc @var{string1},@var{string2}.
5322 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5323 following section of code if the two strings are not the same.
5325 @cindex @code{ifndef} directive
5326 @cindex @code{ifnotdef} directive
5327 @item .ifndef @var{symbol}
5328 @itemx .ifnotdef @var{symbol}
5329 Assembles the following section of code if the specified @var{symbol}
5330 has not been defined. Both spelling variants are equivalent. Note a symbol
5331 which has been referenced but not yet defined is considered to be undefined.
5333 @cindex @code{ifne} directive
5334 @item .ifne @var{absolute expression}
5335 Assembles the following section of code if the argument is not equal to zero
5336 (in other words, this is equivalent to @code{.if}).
5338 @cindex @code{ifnes} directive
5339 @item .ifnes @var{string1},@var{string2}
5340 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5341 following section of code if the two strings are not the same.
5345 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5347 @cindex @code{incbin} directive
5348 @cindex binary files, including
5349 The @code{incbin} directive includes @var{file} verbatim at the current
5350 location. You can control the search paths used with the @samp{-I} command-line
5351 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5354 The @var{skip} argument skips a number of bytes from the start of the
5355 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5356 read. Note that the data is not aligned in any way, so it is the user's
5357 responsibility to make sure that proper alignment is provided both before and
5358 after the @code{incbin} directive.
5361 @section @code{.include "@var{file}"}
5363 @cindex @code{include} directive
5364 @cindex supporting files, including
5365 @cindex files, including
5366 This directive provides a way to include supporting files at specified
5367 points in your source program. The code from @var{file} is assembled as
5368 if it followed the point of the @code{.include}; when the end of the
5369 included file is reached, assembly of the original file continues. You
5370 can control the search paths used with the @samp{-I} command-line option
5371 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5375 @section @code{.int @var{expressions}}
5377 @cindex @code{int} directive
5378 @cindex integers, 32-bit
5379 Expect zero or more @var{expressions}, of any section, separated by commas.
5380 For each expression, emit a number that, at run time, is the value of that
5381 expression. The byte order and bit size of the number depends on what kind
5382 of target the assembly is for.
5386 On most forms of the H8/300, @code{.int} emits 16-bit
5387 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5394 @section @code{.internal @var{names}}
5396 @cindex @code{internal} directive
5398 This is one of the ELF visibility directives. The other two are
5399 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5400 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5402 This directive overrides the named symbols default visibility (which is set by
5403 their binding: local, global or weak). The directive sets the visibility to
5404 @code{internal} which means that the symbols are considered to be @code{hidden}
5405 (i.e., not visible to other components), and that some extra, processor specific
5406 processing must also be performed upon the symbols as well.
5410 @section @code{.irp @var{symbol},@var{values}}@dots{}
5412 @cindex @code{irp} directive
5413 Evaluate a sequence of statements assigning different values to @var{symbol}.
5414 The sequence of statements starts at the @code{.irp} directive, and is
5415 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5416 set to @var{value}, and the sequence of statements is assembled. If no
5417 @var{value} is listed, the sequence of statements is assembled once, with
5418 @var{symbol} set to the null string. To refer to @var{symbol} within the
5419 sequence of statements, use @var{\symbol}.
5421 For example, assembling
5429 is equivalent to assembling
5437 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5440 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5442 @cindex @code{irpc} directive
5443 Evaluate a sequence of statements assigning different values to @var{symbol}.
5444 The sequence of statements starts at the @code{.irpc} directive, and is
5445 terminated by an @code{.endr} directive. For each character in @var{value},
5446 @var{symbol} is set to the character, and the sequence of statements is
5447 assembled. If no @var{value} is listed, the sequence of statements is
5448 assembled once, with @var{symbol} set to the null string. To refer to
5449 @var{symbol} within the sequence of statements, use @var{\symbol}.
5451 For example, assembling
5459 is equivalent to assembling
5467 For some caveats with the spelling of @var{symbol}, see also the discussion
5471 @section @code{.lcomm @var{symbol} , @var{length}}
5473 @cindex @code{lcomm} directive
5474 @cindex local common symbols
5475 @cindex symbols, local common
5476 Reserve @var{length} (an absolute expression) bytes for a local common
5477 denoted by @var{symbol}. The section and value of @var{symbol} are
5478 those of the new local common. The addresses are allocated in the bss
5479 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5480 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5481 not visible to @code{@value{LD}}.
5484 Some targets permit a third argument to be used with @code{.lcomm}. This
5485 argument specifies the desired alignment of the symbol in the bss section.
5489 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5490 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5494 @section @code{.lflags}
5496 @cindex @code{lflags} directive (ignored)
5497 @command{@value{AS}} accepts this directive, for compatibility with other
5498 assemblers, but ignores it.
5500 @ifclear no-line-dir
5502 @section @code{.line @var{line-number}}
5504 @cindex @code{line} directive
5505 @cindex logical line number
5507 Change the logical line number. @var{line-number} must be an absolute
5508 expression. The next line has that logical line number. Therefore any other
5509 statements on the current line (after a statement separator character) are
5510 reported as on logical line number @var{line-number} @minus{} 1. One day
5511 @command{@value{AS}} will no longer support this directive: it is recognized only
5512 for compatibility with existing assembler programs.
5515 Even though this is a directive associated with the @code{a.out} or
5516 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5517 when producing COFF output, and treats @samp{.line} as though it
5518 were the COFF @samp{.ln} @emph{if} it is found outside a
5519 @code{.def}/@code{.endef} pair.
5521 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5522 used by compilers to generate auxiliary symbol information for
5527 @section @code{.linkonce [@var{type}]}
5529 @cindex @code{linkonce} directive
5530 @cindex common sections
5531 Mark the current section so that the linker only includes a single copy of it.
5532 This may be used to include the same section in several different object files,
5533 but ensure that the linker will only include it once in the final output file.
5534 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5535 Duplicate sections are detected based on the section name, so it should be
5538 This directive is only supported by a few object file formats; as of this
5539 writing, the only object file format which supports it is the Portable
5540 Executable format used on Windows NT.
5542 The @var{type} argument is optional. If specified, it must be one of the
5543 following strings. For example:
5547 Not all types may be supported on all object file formats.
5551 Silently discard duplicate sections. This is the default.
5554 Warn if there are duplicate sections, but still keep only one copy.
5557 Warn if any of the duplicates have different sizes.
5560 Warn if any of the duplicates do not have exactly the same contents.
5564 @section @code{.list}
5566 @cindex @code{list} directive
5567 @cindex listing control, turning on
5568 Control (in conjunction with the @code{.nolist} directive) whether or
5569 not assembly listings are generated. These two directives maintain an
5570 internal counter (which is zero initially). @code{.list} increments the
5571 counter, and @code{.nolist} decrements it. Assembly listings are
5572 generated whenever the counter is greater than zero.
5574 By default, listings are disabled. When you enable them (with the
5575 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5576 the initial value of the listing counter is one.
5579 @section @code{.ln @var{line-number}}
5581 @cindex @code{ln} directive
5582 @ifclear no-line-dir
5583 @samp{.ln} is a synonym for @samp{.line}.
5586 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5587 must be an absolute expression. The next line has that logical
5588 line number, so any other statements on the current line (after a
5589 statement separator character @code{;}) are reported as on logical
5590 line number @var{line-number} @minus{} 1.
5593 This directive is accepted, but ignored, when @command{@value{AS}} is
5594 configured for @code{b.out}; its effect is only associated with COFF
5600 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5601 @cindex @code{loc} directive
5602 When emitting DWARF2 line number information,
5603 the @code{.loc} directive will add a row to the @code{.debug_line} line
5604 number matrix corresponding to the immediately following assembly
5605 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5606 arguments will be applied to the @code{.debug_line} state machine before
5609 The @var{options} are a sequence of the following tokens in any order:
5613 This option will set the @code{basic_block} register in the
5614 @code{.debug_line} state machine to @code{true}.
5617 This option will set the @code{prologue_end} register in the
5618 @code{.debug_line} state machine to @code{true}.
5620 @item epilogue_begin
5621 This option will set the @code{epilogue_begin} register in the
5622 @code{.debug_line} state machine to @code{true}.
5624 @item is_stmt @var{value}
5625 This option will set the @code{is_stmt} register in the
5626 @code{.debug_line} state machine to @code{value}, which must be
5629 @item isa @var{value}
5630 This directive will set the @code{isa} register in the @code{.debug_line}
5631 state machine to @var{value}, which must be an unsigned integer.
5633 @item discriminator @var{value}
5634 This directive will set the @code{discriminator} register in the @code{.debug_line}
5635 state machine to @var{value}, which must be an unsigned integer.
5639 @node Loc_mark_labels
5640 @section @code{.loc_mark_labels @var{enable}}
5641 @cindex @code{loc_mark_labels} directive
5642 When emitting DWARF2 line number information,
5643 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5644 to the @code{.debug_line} line number matrix with the @code{basic_block}
5645 register in the state machine set whenever a code label is seen.
5646 The @var{enable} argument should be either 1 or 0, to enable or disable
5647 this function respectively.
5651 @section @code{.local @var{names}}
5653 @cindex @code{local} directive
5654 This directive, which is available for ELF targets, marks each symbol in
5655 the comma-separated list of @code{names} as a local symbol so that it
5656 will not be externally visible. If the symbols do not already exist,
5657 they will be created.
5659 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5660 accept an alignment argument, which is the case for most ELF targets,
5661 the @code{.local} directive can be used in combination with @code{.comm}
5662 (@pxref{Comm}) to define aligned local common data.
5666 @section @code{.long @var{expressions}}
5668 @cindex @code{long} directive
5669 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5672 @c no one seems to know what this is for or whether this description is
5673 @c what it really ought to do
5675 @section @code{.lsym @var{symbol}, @var{expression}}
5677 @cindex @code{lsym} directive
5678 @cindex symbol, not referenced in assembly
5679 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5680 the hash table, ensuring it cannot be referenced by name during the
5681 rest of the assembly. This sets the attributes of the symbol to be
5682 the same as the expression value:
5684 @var{other} = @var{descriptor} = 0
5685 @var{type} = @r{(section of @var{expression})}
5686 @var{value} = @var{expression}
5689 The new symbol is not flagged as external.
5693 @section @code{.macro}
5696 The commands @code{.macro} and @code{.endm} allow you to define macros that
5697 generate assembly output. For example, this definition specifies a macro
5698 @code{sum} that puts a sequence of numbers into memory:
5701 .macro sum from=0, to=5
5710 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5722 @item .macro @var{macname}
5723 @itemx .macro @var{macname} @var{macargs} @dots{}
5724 @cindex @code{macro} directive
5725 Begin the definition of a macro called @var{macname}. If your macro
5726 definition requires arguments, specify their names after the macro name,
5727 separated by commas or spaces. You can qualify the macro argument to
5728 indicate whether all invocations must specify a non-blank value (through
5729 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5730 (through @samp{:@code{vararg}}). You can supply a default value for any
5731 macro argument by following the name with @samp{=@var{deflt}}. You
5732 cannot define two macros with the same @var{macname} unless it has been
5733 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5734 definitions. For example, these are all valid @code{.macro} statements:
5738 Begin the definition of a macro called @code{comm}, which takes no
5741 @item .macro plus1 p, p1
5742 @itemx .macro plus1 p p1
5743 Either statement begins the definition of a macro called @code{plus1},
5744 which takes two arguments; within the macro definition, write
5745 @samp{\p} or @samp{\p1} to evaluate the arguments.
5747 @item .macro reserve_str p1=0 p2
5748 Begin the definition of a macro called @code{reserve_str}, with two
5749 arguments. The first argument has a default value, but not the second.
5750 After the definition is complete, you can call the macro either as
5751 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5752 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5753 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5754 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5756 @item .macro m p1:req, p2=0, p3:vararg
5757 Begin the definition of a macro called @code{m}, with at least three
5758 arguments. The first argument must always have a value specified, but
5759 not the second, which instead has a default value. The third formal
5760 will get assigned all remaining arguments specified at invocation time.
5762 When you call a macro, you can specify the argument values either by
5763 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5764 @samp{sum to=17, from=9}.
5768 Note that since each of the @var{macargs} can be an identifier exactly
5769 as any other one permitted by the target architecture, there may be
5770 occasional problems if the target hand-crafts special meanings to certain
5771 characters when they occur in a special position. For example, if the colon
5772 (@code{:}) is generally permitted to be part of a symbol name, but the
5773 architecture specific code special-cases it when occurring as the final
5774 character of a symbol (to denote a label), then the macro parameter
5775 replacement code will have no way of knowing that and consider the whole
5776 construct (including the colon) an identifier, and check only this
5777 identifier for being the subject to parameter substitution. So for example
5778 this macro definition:
5786 might not work as expected. Invoking @samp{label foo} might not create a label
5787 called @samp{foo} but instead just insert the text @samp{\l:} into the
5788 assembler source, probably generating an error about an unrecognised
5791 Similarly problems might occur with the period character (@samp{.})
5792 which is often allowed inside opcode names (and hence identifier names). So
5793 for example constructing a macro to build an opcode from a base name and a
5794 length specifier like this:
5797 .macro opcode base length
5802 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5803 instruction but instead generate some kind of error as the assembler tries to
5804 interpret the text @samp{\base.\length}.
5806 There are several possible ways around this problem:
5809 @item Insert white space
5810 If it is possible to use white space characters then this is the simplest
5819 @item Use @samp{\()}
5820 The string @samp{\()} can be used to separate the end of a macro argument from
5821 the following text. eg:
5824 .macro opcode base length
5829 @item Use the alternate macro syntax mode
5830 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5831 used as a separator. eg:
5841 Note: this problem of correctly identifying string parameters to pseudo ops
5842 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5843 and @code{.irpc} (@pxref{Irpc}) as well.
5846 @cindex @code{endm} directive
5847 Mark the end of a macro definition.
5850 @cindex @code{exitm} directive
5851 Exit early from the current macro definition.
5853 @cindex number of macros executed
5854 @cindex macros, count executed
5856 @command{@value{AS}} maintains a counter of how many macros it has
5857 executed in this pseudo-variable; you can copy that number to your
5858 output with @samp{\@@}, but @emph{only within a macro definition}.
5860 @item LOCAL @var{name} [ , @dots{} ]
5861 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5862 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5863 @xref{Altmacro,,@code{.altmacro}}.
5867 @section @code{.mri @var{val}}
5869 @cindex @code{mri} directive
5870 @cindex MRI mode, temporarily
5871 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5872 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5873 affects code assembled until the next @code{.mri} directive, or until the end
5874 of the file. @xref{M, MRI mode, MRI mode}.
5877 @section @code{.noaltmacro}
5878 Disable alternate macro mode. @xref{Altmacro}.
5881 @section @code{.nolist}
5883 @cindex @code{nolist} directive
5884 @cindex listing control, turning off
5885 Control (in conjunction with the @code{.list} directive) whether or
5886 not assembly listings are generated. These two directives maintain an
5887 internal counter (which is zero initially). @code{.list} increments the
5888 counter, and @code{.nolist} decrements it. Assembly listings are
5889 generated whenever the counter is greater than zero.
5892 @section @code{.octa @var{bignums}}
5894 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5895 @cindex @code{octa} directive
5896 @cindex integer, 16-byte
5897 @cindex sixteen byte integer
5898 This directive expects zero or more bignums, separated by commas. For each
5899 bignum, it emits a 16-byte integer.
5901 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5902 hence @emph{octa}-word for 16 bytes.
5905 @section @code{.offset @var{loc}}
5907 @cindex @code{offset} directive
5908 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5909 be an absolute expression. This directive may be useful for defining
5910 symbols with absolute values. Do not confuse it with the @code{.org}
5914 @section @code{.org @var{new-lc} , @var{fill}}
5916 @cindex @code{org} directive
5917 @cindex location counter, advancing
5918 @cindex advancing location counter
5919 @cindex current address, advancing
5920 Advance the location counter of the current section to
5921 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5922 expression with the same section as the current subsection. That is,
5923 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5924 wrong section, the @code{.org} directive is ignored. To be compatible
5925 with former assemblers, if the section of @var{new-lc} is absolute,
5926 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5927 is the same as the current subsection.
5929 @code{.org} may only increase the location counter, or leave it
5930 unchanged; you cannot use @code{.org} to move the location counter
5933 @c double negative used below "not undefined" because this is a specific
5934 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5935 @c section. doc@cygnus.com 18feb91
5936 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5937 may not be undefined. If you really detest this restriction we eagerly await
5938 a chance to share your improved assembler.
5940 Beware that the origin is relative to the start of the section, not
5941 to the start of the subsection. This is compatible with other
5942 people's assemblers.
5944 When the location counter (of the current subsection) is advanced, the
5945 intervening bytes are filled with @var{fill} which should be an
5946 absolute expression. If the comma and @var{fill} are omitted,
5947 @var{fill} defaults to zero.
5950 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5952 @cindex padding the location counter given a power of two
5953 @cindex @code{p2align} directive
5954 Pad the location counter (in the current subsection) to a particular
5955 storage boundary. The first expression (which must be absolute) is the
5956 number of low-order zero bits the location counter must have after
5957 advancement. For example @samp{.p2align 3} advances the location
5958 counter until it a multiple of 8. If the location counter is already a
5959 multiple of 8, no change is needed.
5961 The second expression (also absolute) gives the fill value to be stored in the
5962 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5963 padding bytes are normally zero. However, on some systems, if the section is
5964 marked as containing code and the fill value is omitted, the space is filled
5965 with no-op instructions.
5967 The third expression is also absolute, and is also optional. If it is present,
5968 it is the maximum number of bytes that should be skipped by this alignment
5969 directive. If doing the alignment would require skipping more bytes than the
5970 specified maximum, then the alignment is not done at all. You can omit the
5971 fill value (the second argument) entirely by simply using two commas after the
5972 required alignment; this can be useful if you want the alignment to be filled
5973 with no-op instructions when appropriate.
5975 @cindex @code{p2alignw} directive
5976 @cindex @code{p2alignl} directive
5977 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5978 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5979 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5980 fill pattern as a four byte longword value. For example, @code{.p2alignw
5981 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5982 filled in with the value 0x368d (the exact placement of the bytes depends upon
5983 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5988 @section @code{.popsection}
5990 @cindex @code{popsection} directive
5991 @cindex Section Stack
5992 This is one of the ELF section stack manipulation directives. The others are
5993 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5994 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5997 This directive replaces the current section (and subsection) with the top
5998 section (and subsection) on the section stack. This section is popped off the
6004 @section @code{.previous}
6006 @cindex @code{previous} directive
6007 @cindex Section Stack
6008 This is one of the ELF section stack manipulation directives. The others are
6009 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6010 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6011 (@pxref{PopSection}).
6013 This directive swaps the current section (and subsection) with most recently
6014 referenced section/subsection pair prior to this one. Multiple
6015 @code{.previous} directives in a row will flip between two sections (and their
6016 subsections). For example:
6028 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6034 # Now in section A subsection 1
6038 # Now in section B subsection 0
6041 # Now in section B subsection 1
6044 # Now in section B subsection 0
6048 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6049 section B and 0x9abc into subsection 1 of section B.
6051 In terms of the section stack, this directive swaps the current section with
6052 the top section on the section stack.
6056 @section @code{.print @var{string}}
6058 @cindex @code{print} directive
6059 @command{@value{AS}} will print @var{string} on the standard output during
6060 assembly. You must put @var{string} in double quotes.
6064 @section @code{.protected @var{names}}
6066 @cindex @code{protected} directive
6068 This is one of the ELF visibility directives. The other two are
6069 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6071 This directive overrides the named symbols default visibility (which is set by
6072 their binding: local, global or weak). The directive sets the visibility to
6073 @code{protected} which means that any references to the symbols from within the
6074 components that defines them must be resolved to the definition in that
6075 component, even if a definition in another component would normally preempt
6080 @section @code{.psize @var{lines} , @var{columns}}
6082 @cindex @code{psize} directive
6083 @cindex listing control: paper size
6084 @cindex paper size, for listings
6085 Use this directive to declare the number of lines---and, optionally, the
6086 number of columns---to use for each page, when generating listings.
6088 If you do not use @code{.psize}, listings use a default line-count
6089 of 60. You may omit the comma and @var{columns} specification; the
6090 default width is 200 columns.
6092 @command{@value{AS}} generates formfeeds whenever the specified number of
6093 lines is exceeded (or whenever you explicitly request one, using
6096 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6097 those explicitly specified with @code{.eject}.
6100 @section @code{.purgem @var{name}}
6102 @cindex @code{purgem} directive
6103 Undefine the macro @var{name}, so that later uses of the string will not be
6104 expanded. @xref{Macro}.
6108 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6110 @cindex @code{pushsection} directive
6111 @cindex Section Stack
6112 This is one of the ELF section stack manipulation directives. The others are
6113 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6114 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6117 This directive pushes the current section (and subsection) onto the
6118 top of the section stack, and then replaces the current section and
6119 subsection with @code{name} and @code{subsection}. The optional
6120 @code{flags}, @code{type} and @code{arguments} are treated the same
6121 as in the @code{.section} (@pxref{Section}) directive.
6125 @section @code{.quad @var{bignums}}
6127 @cindex @code{quad} directive
6128 @code{.quad} expects zero or more bignums, separated by commas. For
6129 each bignum, it emits
6131 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6132 warning message; and just takes the lowest order 8 bytes of the bignum.
6133 @cindex eight-byte integer
6134 @cindex integer, 8-byte
6136 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6137 hence @emph{quad}-word for 8 bytes.
6140 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6141 warning message; and just takes the lowest order 16 bytes of the bignum.
6142 @cindex sixteen-byte integer
6143 @cindex integer, 16-byte
6147 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6149 @cindex @code{reloc} directive
6150 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6151 @var{expression}. If @var{offset} is a number, the relocation is generated in
6152 the current section. If @var{offset} is an expression that resolves to a
6153 symbol plus offset, the relocation is generated in the given symbol's section.
6154 @var{expression}, if present, must resolve to a symbol plus addend or to an
6155 absolute value, but note that not all targets support an addend. e.g. ELF REL
6156 targets such as i386 store an addend in the section contents rather than in the
6157 relocation. This low level interface does not support addends stored in the
6161 @section @code{.rept @var{count}}
6163 @cindex @code{rept} directive
6164 Repeat the sequence of lines between the @code{.rept} directive and the next
6165 @code{.endr} directive @var{count} times.
6167 For example, assembling
6175 is equivalent to assembling
6184 @section @code{.sbttl "@var{subheading}"}
6186 @cindex @code{sbttl} directive
6187 @cindex subtitles for listings
6188 @cindex listing control: subtitle
6189 Use @var{subheading} as the title (third line, immediately after the
6190 title line) when generating assembly listings.
6192 This directive affects subsequent pages, as well as the current page if
6193 it appears within ten lines of the top of a page.
6197 @section @code{.scl @var{class}}
6199 @cindex @code{scl} directive
6200 @cindex symbol storage class (COFF)
6201 @cindex COFF symbol storage class
6202 Set the storage-class value for a symbol. This directive may only be
6203 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6204 whether a symbol is static or external, or it may record further
6205 symbolic debugging information.
6208 The @samp{.scl} directive is primarily associated with COFF output; when
6209 configured to generate @code{b.out} output format, @command{@value{AS}}
6210 accepts this directive but ignores it.
6216 @section @code{.section @var{name}}
6218 @cindex named section
6219 Use the @code{.section} directive to assemble the following code into a section
6222 This directive is only supported for targets that actually support arbitrarily
6223 named sections; on @code{a.out} targets, for example, it is not accepted, even
6224 with a standard @code{a.out} section name.
6228 @c only print the extra heading if both COFF and ELF are set
6229 @subheading COFF Version
6232 @cindex @code{section} directive (COFF version)
6233 For COFF targets, the @code{.section} directive is used in one of the following
6237 .section @var{name}[, "@var{flags}"]
6238 .section @var{name}[, @var{subsection}]
6241 If the optional argument is quoted, it is taken as flags to use for the
6242 section. Each flag is a single character. The following flags are recognized:
6245 bss section (uninitialized data)
6247 section is not loaded
6253 exclude section from linking
6259 shared section (meaningful for PE targets)
6261 ignored. (For compatibility with the ELF version)
6263 section is not readable (meaningful for PE targets)
6265 single-digit power-of-two section alignment (GNU extension)
6268 If no flags are specified, the default flags depend upon the section name. If
6269 the section name is not recognized, the default will be for the section to be
6270 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6271 from the section, rather than adding them, so if they are used on their own it
6272 will be as if no flags had been specified at all.
6274 If the optional argument to the @code{.section} directive is not quoted, it is
6275 taken as a subsection number (@pxref{Sub-Sections}).
6280 @c only print the extra heading if both COFF and ELF are set
6281 @subheading ELF Version
6284 @cindex Section Stack
6285 This is one of the ELF section stack manipulation directives. The others are
6286 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6287 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6288 @code{.previous} (@pxref{Previous}).
6290 @cindex @code{section} directive (ELF version)
6291 For ELF targets, the @code{.section} directive is used like this:
6294 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6297 @anchor{Section Name Substitutions}
6298 @kindex --sectname-subst
6299 @cindex section name substitution
6300 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6301 argument may contain a substitution sequence. Only @code{%S} is supported
6302 at the moment, and substitutes the current section name. For example:
6305 .macro exception_code
6306 .section %S.exception
6307 [exception code here]
6322 The two @code{exception_code} invocations above would create the
6323 @code{.text.exception} and @code{.init.exception} sections respectively.
6324 This is useful e.g. to discriminate between anciliary sections that are
6325 tied to setup code to be discarded after use from anciliary sections that
6326 need to stay resident without having to define multiple @code{exception_code}
6327 macros just for that purpose.
6329 The optional @var{flags} argument is a quoted string which may contain any
6330 combination of the following characters:
6333 section is allocatable
6335 section is excluded from executable and shared library.
6339 section is executable
6341 section is mergeable
6343 section contains zero terminated strings
6345 section is a member of a section group
6347 section is used for thread-local-storage
6349 section is a member of the previously-current section's group, if any
6352 The optional @var{type} argument may contain one of the following constants:
6355 section contains data
6357 section does not contain data (i.e., section only occupies space)
6359 section contains data which is used by things other than the program
6361 section contains an array of pointers to init functions
6363 section contains an array of pointers to finish functions
6364 @item @@preinit_array
6365 section contains an array of pointers to pre-init functions
6368 Many targets only support the first three section types.
6370 Note on targets where the @code{@@} character is the start of a comment (eg
6371 ARM) then another character is used instead. For example the ARM port uses the
6374 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6375 be specified as well as an extra argument---@var{entsize}---like this:
6378 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6381 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6382 constants, each @var{entsize} octets long. Sections with both @code{M} and
6383 @code{S} must contain zero terminated strings where each character is
6384 @var{entsize} bytes long. The linker may remove duplicates within sections with
6385 the same name, same entity size and same flags. @var{entsize} must be an
6386 absolute expression. For sections with both @code{M} and @code{S}, a string
6387 which is a suffix of a larger string is considered a duplicate. Thus
6388 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6389 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6391 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6392 be present along with an additional field like this:
6395 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6398 The @var{GroupName} field specifies the name of the section group to which this
6399 particular section belongs. The optional linkage field can contain:
6402 indicates that only one copy of this section should be retained
6407 Note: if both the @var{M} and @var{G} flags are present then the fields for
6408 the Merge flag should come first, like this:
6411 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6414 If @var{flags} contains the @code{?} symbol then it may not also contain the
6415 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6416 present. Instead, @code{?} says to consider the section that's current before
6417 this directive. If that section used @code{G}, then the new section will use
6418 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6419 If not, then the @code{?} symbol has no effect.
6421 If no flags are specified, the default flags depend upon the section name. If
6422 the section name is not recognized, the default will be for the section to have
6423 none of the above flags: it will not be allocated in memory, nor writable, nor
6424 executable. The section will contain data.
6426 For ELF targets, the assembler supports another type of @code{.section}
6427 directive for compatibility with the Solaris assembler:
6430 .section "@var{name}"[, @var{flags}...]
6433 Note that the section name is quoted. There may be a sequence of comma
6437 section is allocatable
6441 section is executable
6443 section is excluded from executable and shared library.
6445 section is used for thread local storage
6448 This directive replaces the current section and subsection. See the
6449 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6450 some examples of how this directive and the other section stack directives
6456 @section @code{.set @var{symbol}, @var{expression}}
6458 @cindex @code{set} directive
6459 @cindex symbol value, setting
6460 Set the value of @var{symbol} to @var{expression}. This
6461 changes @var{symbol}'s value and type to conform to
6462 @var{expression}. If @var{symbol} was flagged as external, it remains
6463 flagged (@pxref{Symbol Attributes}).
6465 You may @code{.set} a symbol many times in the same assembly provided that the
6466 values given to the symbol are constants. Values that are based on expressions
6467 involving other symbols are allowed, but some targets may restrict this to only
6468 being done once per assembly. This is because those targets do not set the
6469 addresses of symbols at assembly time, but rather delay the assignment until a
6470 final link is performed. This allows the linker a chance to change the code in
6471 the files, changing the location of, and the relative distance between, various
6474 If you @code{.set} a global symbol, the value stored in the object
6475 file is the last value stored into it.
6478 On Z80 @code{set} is a real instruction, use
6479 @samp{@var{symbol} defl @var{expression}} instead.
6483 @section @code{.short @var{expressions}}
6485 @cindex @code{short} directive
6487 @code{.short} is normally the same as @samp{.word}.
6488 @xref{Word,,@code{.word}}.
6490 In some configurations, however, @code{.short} and @code{.word} generate
6491 numbers of different lengths. @xref{Machine Dependencies}.
6495 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6498 This expects zero or more @var{expressions}, and emits
6499 a 16 bit number for each.
6504 @section @code{.single @var{flonums}}
6506 @cindex @code{single} directive
6507 @cindex floating point numbers (single)
6508 This directive assembles zero or more flonums, separated by commas. It
6509 has the same effect as @code{.float}.
6511 The exact kind of floating point numbers emitted depends on how
6512 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6516 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6517 numbers in @sc{ieee} format.
6523 @section @code{.size}
6525 This directive is used to set the size associated with a symbol.
6529 @c only print the extra heading if both COFF and ELF are set
6530 @subheading COFF Version
6533 @cindex @code{size} directive (COFF version)
6534 For COFF targets, the @code{.size} directive is only permitted inside
6535 @code{.def}/@code{.endef} pairs. It is used like this:
6538 .size @var{expression}
6542 @samp{.size} is only meaningful when generating COFF format output; when
6543 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6550 @c only print the extra heading if both COFF and ELF are set
6551 @subheading ELF Version
6554 @cindex @code{size} directive (ELF version)
6555 For ELF targets, the @code{.size} directive is used like this:
6558 .size @var{name} , @var{expression}
6561 This directive sets the size associated with a symbol @var{name}.
6562 The size in bytes is computed from @var{expression} which can make use of label
6563 arithmetic. This directive is typically used to set the size of function
6568 @ifclear no-space-dir
6570 @section @code{.skip @var{size} , @var{fill}}
6572 @cindex @code{skip} directive
6573 @cindex filling memory
6574 This directive emits @var{size} bytes, each of value @var{fill}. Both
6575 @var{size} and @var{fill} are absolute expressions. If the comma and
6576 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6581 @section @code{.sleb128 @var{expressions}}
6583 @cindex @code{sleb128} directive
6584 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6585 compact, variable length representation of numbers used by the DWARF
6586 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6588 @ifclear no-space-dir
6590 @section @code{.space @var{size} , @var{fill}}
6592 @cindex @code{space} directive
6593 @cindex filling memory
6594 This directive emits @var{size} bytes, each of value @var{fill}. Both
6595 @var{size} and @var{fill} are absolute expressions. If the comma
6596 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6601 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6602 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6603 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6604 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6612 @section @code{.stabd, .stabn, .stabs}
6614 @cindex symbolic debuggers, information for
6615 @cindex @code{stab@var{x}} directives
6616 There are three directives that begin @samp{.stab}.
6617 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6618 The symbols are not entered in the @command{@value{AS}} hash table: they
6619 cannot be referenced elsewhere in the source file.
6620 Up to five fields are required:
6624 This is the symbol's name. It may contain any character except
6625 @samp{\000}, so is more general than ordinary symbol names. Some
6626 debuggers used to code arbitrarily complex structures into symbol names
6630 An absolute expression. The symbol's type is set to the low 8 bits of
6631 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6632 and debuggers choke on silly bit patterns.
6635 An absolute expression. The symbol's ``other'' attribute is set to the
6636 low 8 bits of this expression.
6639 An absolute expression. The symbol's descriptor is set to the low 16
6640 bits of this expression.
6643 An absolute expression which becomes the symbol's value.
6646 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6647 or @code{.stabs} statement, the symbol has probably already been created;
6648 you get a half-formed symbol in your object file. This is
6649 compatible with earlier assemblers!
6652 @cindex @code{stabd} directive
6653 @item .stabd @var{type} , @var{other} , @var{desc}
6655 The ``name'' of the symbol generated is not even an empty string.
6656 It is a null pointer, for compatibility. Older assemblers used a
6657 null pointer so they didn't waste space in object files with empty
6660 The symbol's value is set to the location counter,
6661 relocatably. When your program is linked, the value of this symbol
6662 is the address of the location counter when the @code{.stabd} was
6665 @cindex @code{stabn} directive
6666 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6667 The name of the symbol is set to the empty string @code{""}.
6669 @cindex @code{stabs} directive
6670 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6671 All five fields are specified.
6677 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6678 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6680 @cindex string, copying to object file
6681 @cindex string8, copying to object file
6682 @cindex string16, copying to object file
6683 @cindex string32, copying to object file
6684 @cindex string64, copying to object file
6685 @cindex @code{string} directive
6686 @cindex @code{string8} directive
6687 @cindex @code{string16} directive
6688 @cindex @code{string32} directive
6689 @cindex @code{string64} directive
6691 Copy the characters in @var{str} to the object file. You may specify more than
6692 one string to copy, separated by commas. Unless otherwise specified for a
6693 particular machine, the assembler marks the end of each string with a 0 byte.
6694 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6696 The variants @code{string16}, @code{string32} and @code{string64} differ from
6697 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6698 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6699 are stored in target endianness byte order.
6705 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6706 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6711 @section @code{.struct @var{expression}}
6713 @cindex @code{struct} directive
6714 Switch to the absolute section, and set the section offset to @var{expression},
6715 which must be an absolute expression. You might use this as follows:
6724 This would define the symbol @code{field1} to have the value 0, the symbol
6725 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6726 value 8. Assembly would be left in the absolute section, and you would need to
6727 use a @code{.section} directive of some sort to change to some other section
6728 before further assembly.
6732 @section @code{.subsection @var{name}}
6734 @cindex @code{subsection} directive
6735 @cindex Section Stack
6736 This is one of the ELF section stack manipulation directives. The others are
6737 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6738 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6741 This directive replaces the current subsection with @code{name}. The current
6742 section is not changed. The replaced subsection is put onto the section stack
6743 in place of the then current top of stack subsection.
6748 @section @code{.symver}
6749 @cindex @code{symver} directive
6750 @cindex symbol versioning
6751 @cindex versions of symbols
6752 Use the @code{.symver} directive to bind symbols to specific version nodes
6753 within a source file. This is only supported on ELF platforms, and is
6754 typically used when assembling files to be linked into a shared library.
6755 There are cases where it may make sense to use this in objects to be bound
6756 into an application itself so as to override a versioned symbol from a
6759 For ELF targets, the @code{.symver} directive can be used like this:
6761 .symver @var{name}, @var{name2@@nodename}
6763 If the symbol @var{name} is defined within the file
6764 being assembled, the @code{.symver} directive effectively creates a symbol
6765 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6766 just don't try and create a regular alias is that the @var{@@} character isn't
6767 permitted in symbol names. The @var{name2} part of the name is the actual name
6768 of the symbol by which it will be externally referenced. The name @var{name}
6769 itself is merely a name of convenience that is used so that it is possible to
6770 have definitions for multiple versions of a function within a single source
6771 file, and so that the compiler can unambiguously know which version of a
6772 function is being mentioned. The @var{nodename} portion of the alias should be
6773 the name of a node specified in the version script supplied to the linker when
6774 building a shared library. If you are attempting to override a versioned
6775 symbol from a shared library, then @var{nodename} should correspond to the
6776 nodename of the symbol you are trying to override.
6778 If the symbol @var{name} is not defined within the file being assembled, all
6779 references to @var{name} will be changed to @var{name2@@nodename}. If no
6780 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6783 Another usage of the @code{.symver} directive is:
6785 .symver @var{name}, @var{name2@@@@nodename}
6787 In this case, the symbol @var{name} must exist and be defined within
6788 the file being assembled. It is similar to @var{name2@@nodename}. The
6789 difference is @var{name2@@@@nodename} will also be used to resolve
6790 references to @var{name2} by the linker.
6792 The third usage of the @code{.symver} directive is:
6794 .symver @var{name}, @var{name2@@@@@@nodename}
6796 When @var{name} is not defined within the
6797 file being assembled, it is treated as @var{name2@@nodename}. When
6798 @var{name} is defined within the file being assembled, the symbol
6799 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6804 @section @code{.tag @var{structname}}
6806 @cindex COFF structure debugging
6807 @cindex structure debugging, COFF
6808 @cindex @code{tag} directive
6809 This directive is generated by compilers to include auxiliary debugging
6810 information in the symbol table. It is only permitted inside
6811 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6812 definitions in the symbol table with instances of those structures.
6815 @samp{.tag} is only used when generating COFF format output; when
6816 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6822 @section @code{.text @var{subsection}}
6824 @cindex @code{text} directive
6825 Tells @command{@value{AS}} to assemble the following statements onto the end of
6826 the text subsection numbered @var{subsection}, which is an absolute
6827 expression. If @var{subsection} is omitted, subsection number zero
6831 @section @code{.title "@var{heading}"}
6833 @cindex @code{title} directive
6834 @cindex listing control: title line
6835 Use @var{heading} as the title (second line, immediately after the
6836 source file name and pagenumber) when generating assembly listings.
6838 This directive affects subsequent pages, as well as the current page if
6839 it appears within ten lines of the top of a page.
6843 @section @code{.type}
6845 This directive is used to set the type of a symbol.
6849 @c only print the extra heading if both COFF and ELF are set
6850 @subheading COFF Version
6853 @cindex COFF symbol type
6854 @cindex symbol type, COFF
6855 @cindex @code{type} directive (COFF version)
6856 For COFF targets, this directive is permitted only within
6857 @code{.def}/@code{.endef} pairs. It is used like this:
6863 This records the integer @var{int} as the type attribute of a symbol table
6867 @samp{.type} is associated only with COFF format output; when
6868 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6869 directive but ignores it.
6875 @c only print the extra heading if both COFF and ELF are set
6876 @subheading ELF Version
6879 @cindex ELF symbol type
6880 @cindex symbol type, ELF
6881 @cindex @code{type} directive (ELF version)
6882 For ELF targets, the @code{.type} directive is used like this:
6885 .type @var{name} , @var{type description}
6888 This sets the type of symbol @var{name} to be either a
6889 function symbol or an object symbol. There are five different syntaxes
6890 supported for the @var{type description} field, in order to provide
6891 compatibility with various other assemblers.
6893 Because some of the characters used in these syntaxes (such as @samp{@@} and
6894 @samp{#}) are comment characters for some architectures, some of the syntaxes
6895 below do not work on all architectures. The first variant will be accepted by
6896 the GNU assembler on all architectures so that variant should be used for
6897 maximum portability, if you do not need to assemble your code with other
6900 The syntaxes supported are:
6903 .type <name> STT_<TYPE_IN_UPPER_CASE>
6904 .type <name>,#<type>
6905 .type <name>,@@<type>
6906 .type <name>,%<type>
6907 .type <name>,"<type>"
6910 The types supported are:
6915 Mark the symbol as being a function name.
6918 @itemx gnu_indirect_function
6919 Mark the symbol as an indirect function when evaluated during reloc
6920 processing. (This is only supported on assemblers targeting GNU systems).
6924 Mark the symbol as being a data object.
6928 Mark the symbol as being a thead-local data object.
6932 Mark the symbol as being a common data object.
6936 Does not mark the symbol in any way. It is supported just for completeness.
6938 @item gnu_unique_object
6939 Marks the symbol as being a globally unique data object. The dynamic linker
6940 will make sure that in the entire process there is just one symbol with this
6941 name and type in use. (This is only supported on assemblers targeting GNU
6946 Note: Some targets support extra types in addition to those listed above.
6952 @section @code{.uleb128 @var{expressions}}
6954 @cindex @code{uleb128} directive
6955 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6956 compact, variable length representation of numbers used by the DWARF
6957 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6961 @section @code{.val @var{addr}}
6963 @cindex @code{val} directive
6964 @cindex COFF value attribute
6965 @cindex value attribute, COFF
6966 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6967 records the address @var{addr} as the value attribute of a symbol table
6971 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6972 configured for @code{b.out}, it accepts this directive but ignores it.
6978 @section @code{.version "@var{string}"}
6980 @cindex @code{version} directive
6981 This directive creates a @code{.note} section and places into it an ELF
6982 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6987 @section @code{.vtable_entry @var{table}, @var{offset}}
6989 @cindex @code{vtable_entry} directive
6990 This directive finds or creates a symbol @code{table} and creates a
6991 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6994 @section @code{.vtable_inherit @var{child}, @var{parent}}
6996 @cindex @code{vtable_inherit} directive
6997 This directive finds the symbol @code{child} and finds or creates the symbol
6998 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6999 parent whose addend is the value of the child symbol. As a special case the
7000 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7004 @section @code{.warning "@var{string}"}
7005 @cindex warning directive
7006 Similar to the directive @code{.error}
7007 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7010 @section @code{.weak @var{names}}
7012 @cindex @code{weak} directive
7013 This directive sets the weak attribute on the comma separated list of symbol
7014 @code{names}. If the symbols do not already exist, they will be created.
7016 On COFF targets other than PE, weak symbols are a GNU extension. This
7017 directive sets the weak attribute on the comma separated list of symbol
7018 @code{names}. If the symbols do not already exist, they will be created.
7020 On the PE target, weak symbols are supported natively as weak aliases.
7021 When a weak symbol is created that is not an alias, GAS creates an
7022 alternate symbol to hold the default value.
7025 @section @code{.weakref @var{alias}, @var{target}}
7027 @cindex @code{weakref} directive
7028 This directive creates an alias to the target symbol that enables the symbol to
7029 be referenced with weak-symbol semantics, but without actually making it weak.
7030 If direct references or definitions of the symbol are present, then the symbol
7031 will not be weak, but if all references to it are through weak references, the
7032 symbol will be marked as weak in the symbol table.
7034 The effect is equivalent to moving all references to the alias to a separate
7035 assembly source file, renaming the alias to the symbol in it, declaring the
7036 symbol as weak there, and running a reloadable link to merge the object files
7037 resulting from the assembly of the new source file and the old source file that
7038 had the references to the alias removed.
7040 The alias itself never makes to the symbol table, and is entirely handled
7041 within the assembler.
7044 @section @code{.word @var{expressions}}
7046 @cindex @code{word} directive
7047 This directive expects zero or more @var{expressions}, of any section,
7048 separated by commas.
7051 For each expression, @command{@value{AS}} emits a 32-bit number.
7054 For each expression, @command{@value{AS}} emits a 16-bit number.
7059 The size of the number emitted, and its byte order,
7060 depend on what target computer the assembly is for.
7063 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7064 @c happen---32-bit addressability, period; no long/short jumps.
7065 @ifset DIFF-TBL-KLUGE
7066 @cindex difference tables altered
7067 @cindex altered difference tables
7069 @emph{Warning: Special Treatment to support Compilers}
7073 Machines with a 32-bit address space, but that do less than 32-bit
7074 addressing, require the following special treatment. If the machine of
7075 interest to you does 32-bit addressing (or doesn't require it;
7076 @pxref{Machine Dependencies}), you can ignore this issue.
7079 In order to assemble compiler output into something that works,
7080 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7081 Directives of the form @samp{.word sym1-sym2} are often emitted by
7082 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7083 directive of the form @samp{.word sym1-sym2}, and the difference between
7084 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7085 creates a @dfn{secondary jump table}, immediately before the next label.
7086 This secondary jump table is preceded by a short-jump to the
7087 first byte after the secondary table. This short-jump prevents the flow
7088 of control from accidentally falling into the new table. Inside the
7089 table is a long-jump to @code{sym2}. The original @samp{.word}
7090 contains @code{sym1} minus the address of the long-jump to
7093 If there were several occurrences of @samp{.word sym1-sym2} before the
7094 secondary jump table, all of them are adjusted. If there was a
7095 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7096 long-jump to @code{sym4} is included in the secondary jump table,
7097 and the @code{.word} directives are adjusted to contain @code{sym3}
7098 minus the address of the long-jump to @code{sym4}; and so on, for as many
7099 entries in the original jump table as necessary.
7102 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7103 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7104 assembly language programmers.
7107 @c end DIFF-TBL-KLUGE
7109 @ifclear no-space-dir
7111 @section @code{.zero @var{size}}
7113 @cindex @code{zero} directive
7114 @cindex filling memory with zero bytes
7115 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7116 expression. This directive is actually an alias for the @samp{.skip} directive
7117 so in can take an optional second argument of the value to store in the bytes
7118 instead of zero. Using @samp{.zero} in this way would be confusing however.
7122 @section Deprecated Directives
7124 @cindex deprecated directives
7125 @cindex obsolescent directives
7126 One day these directives won't work.
7127 They are included for compatibility with older assemblers.
7134 @node Object Attributes
7135 @chapter Object Attributes
7136 @cindex object attributes
7138 @command{@value{AS}} assembles source files written for a specific architecture
7139 into object files for that architecture. But not all object files are alike.
7140 Many architectures support incompatible variations. For instance, floating
7141 point arguments might be passed in floating point registers if the object file
7142 requires hardware floating point support---or floating point arguments might be
7143 passed in integer registers if the object file supports processors with no
7144 hardware floating point unit. Or, if two objects are built for different
7145 generations of the same architecture, the combination may require the
7146 newer generation at run-time.
7148 This information is useful during and after linking. At link time,
7149 @command{@value{LD}} can warn about incompatible object files. After link
7150 time, tools like @command{gdb} can use it to process the linked file
7153 Compatibility information is recorded as a series of object attributes. Each
7154 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7155 string, and indicates who sets the meaning of the tag. The tag is an integer,
7156 and indicates what property the attribute describes. The value may be a string
7157 or an integer, and indicates how the property affects this object. Missing
7158 attributes are the same as attributes with a zero value or empty string value.
7160 Object attributes were developed as part of the ABI for the ARM Architecture.
7161 The file format is documented in @cite{ELF for the ARM Architecture}.
7164 * GNU Object Attributes:: @sc{gnu} Object Attributes
7165 * Defining New Object Attributes:: Defining New Object Attributes
7168 @node GNU Object Attributes
7169 @section @sc{gnu} Object Attributes
7171 The @code{.gnu_attribute} directive records an object attribute
7172 with vendor @samp{gnu}.
7174 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7175 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7176 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7177 2} is set for architecture-independent attributes and clear for
7178 architecture-dependent ones.
7180 @subsection Common @sc{gnu} attributes
7182 These attributes are valid on all architectures.
7185 @item Tag_compatibility (32)
7186 The compatibility attribute takes an integer flag value and a vendor name. If
7187 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7188 then the file is only compatible with the named toolchain. If it is greater
7189 than 1, the file can only be processed by other toolchains under some private
7190 arrangement indicated by the flag value and the vendor name.
7193 @subsection MIPS Attributes
7196 @item Tag_GNU_MIPS_ABI_FP (4)
7197 The floating-point ABI used by this object file. The value will be:
7201 0 for files not affected by the floating-point ABI.
7203 1 for files using the hardware floating-point ABI with a standard
7204 double-precision FPU.
7206 2 for files using the hardware floating-point ABI with a single-precision FPU.
7208 3 for files using the software floating-point ABI.
7210 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7211 floating-point registers, 32-bit general-purpose registers and increased the
7212 number of callee-saved floating-point registers.
7214 5 for files using the hardware floating-point ABI with a double-precision FPU
7215 with either 32-bit or 64-bit floating-point registers and 32-bit
7216 general-purpose registers.
7218 6 for files using the hardware floating-point ABI with 64-bit floating-point
7219 registers and 32-bit general-purpose registers.
7221 7 for files using the hardware floating-point ABI with 64-bit floating-point
7222 registers, 32-bit general-purpose registers and a rule that forbids the
7223 direct use of odd-numbered single-precision floating-point registers.
7227 @subsection PowerPC Attributes
7230 @item Tag_GNU_Power_ABI_FP (4)
7231 The floating-point ABI used by this object file. The value will be:
7235 0 for files not affected by the floating-point ABI.
7237 1 for files using double-precision hardware floating-point ABI.
7239 2 for files using the software floating-point ABI.
7241 3 for files using single-precision hardware floating-point ABI.
7244 @item Tag_GNU_Power_ABI_Vector (8)
7245 The vector ABI used by this object file. The value will be:
7249 0 for files not affected by the vector ABI.
7251 1 for files using general purpose registers to pass vectors.
7253 2 for files using AltiVec registers to pass vectors.
7255 3 for files using SPE registers to pass vectors.
7259 @subsection IBM z Systems Attributes
7262 @item Tag_GNU_S390_ABI_Vector (8)
7263 The vector ABI used by this object file. The value will be:
7267 0 for files not affected by the vector ABI.
7269 1 for files using software vector ABI.
7271 2 for files using hardware vector ABI.
7275 @node Defining New Object Attributes
7276 @section Defining New Object Attributes
7278 If you want to define a new @sc{gnu} object attribute, here are the places you
7279 will need to modify. New attributes should be discussed on the @samp{binutils}
7284 This manual, which is the official register of attributes.
7286 The header for your architecture @file{include/elf}, to define the tag.
7288 The @file{bfd} support file for your architecture, to merge the attribute
7289 and issue any appropriate link warnings.
7291 Test cases in @file{ld/testsuite} for merging and link warnings.
7293 @file{binutils/readelf.c} to display your attribute.
7295 GCC, if you want the compiler to mark the attribute automatically.
7301 @node Machine Dependencies
7302 @chapter Machine Dependent Features
7304 @cindex machine dependencies
7305 The machine instruction sets are (almost by definition) different on
7306 each machine where @command{@value{AS}} runs. Floating point representations
7307 vary as well, and @command{@value{AS}} often supports a few additional
7308 directives or command-line options for compatibility with other
7309 assemblers on a particular platform. Finally, some versions of
7310 @command{@value{AS}} support special pseudo-instructions for branch
7313 This chapter discusses most of these differences, though it does not
7314 include details on any machine's instruction set. For details on that
7315 subject, see the hardware manufacturer's manual.
7319 * AArch64-Dependent:: AArch64 Dependent Features
7322 * Alpha-Dependent:: Alpha Dependent Features
7325 * ARC-Dependent:: ARC Dependent Features
7328 * ARM-Dependent:: ARM Dependent Features
7331 * AVR-Dependent:: AVR Dependent Features
7334 * Blackfin-Dependent:: Blackfin Dependent Features
7337 * CR16-Dependent:: CR16 Dependent Features
7340 * CRIS-Dependent:: CRIS Dependent Features
7343 * D10V-Dependent:: D10V Dependent Features
7346 * D30V-Dependent:: D30V Dependent Features
7349 * Epiphany-Dependent:: EPIPHANY Dependent Features
7352 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7355 * HPPA-Dependent:: HPPA Dependent Features
7358 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7361 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7364 * i860-Dependent:: Intel 80860 Dependent Features
7367 * i960-Dependent:: Intel 80960 Dependent Features
7370 * IA-64-Dependent:: Intel IA-64 Dependent Features
7373 * IP2K-Dependent:: IP2K Dependent Features
7376 * LM32-Dependent:: LM32 Dependent Features
7379 * M32C-Dependent:: M32C Dependent Features
7382 * M32R-Dependent:: M32R Dependent Features
7385 * M68K-Dependent:: M680x0 Dependent Features
7388 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7391 * Meta-Dependent :: Meta Dependent Features
7394 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7397 * MIPS-Dependent:: MIPS Dependent Features
7400 * MMIX-Dependent:: MMIX Dependent Features
7403 * MSP430-Dependent:: MSP430 Dependent Features
7406 * NDS32-Dependent:: Andes NDS32 Dependent Features
7409 * NiosII-Dependent:: Altera Nios II Dependent Features
7412 * NS32K-Dependent:: NS32K Dependent Features
7415 * PDP-11-Dependent:: PDP-11 Dependent Features
7418 * PJ-Dependent:: picoJava Dependent Features
7421 * PPC-Dependent:: PowerPC Dependent Features
7424 * RL78-Dependent:: RL78 Dependent Features
7427 * RX-Dependent:: RX Dependent Features
7430 * S/390-Dependent:: IBM S/390 Dependent Features
7433 * SCORE-Dependent:: SCORE Dependent Features
7436 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7437 * SH64-Dependent:: SuperH SH64 Dependent Features
7440 * Sparc-Dependent:: SPARC Dependent Features
7443 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7446 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7449 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7452 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7455 * V850-Dependent:: V850 Dependent Features
7458 * Vax-Dependent:: VAX Dependent Features
7461 * Visium-Dependent:: Visium Dependent Features
7464 * XGATE-Dependent:: XGATE Features
7467 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7470 * Xtensa-Dependent:: Xtensa Dependent Features
7473 * Z80-Dependent:: Z80 Dependent Features
7476 * Z8000-Dependent:: Z8000 Dependent Features
7483 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7484 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7485 @c peculiarity: to preserve cross-references, there must be a node called
7486 @c "Machine Dependencies". Hence the conditional nodenames in each
7487 @c major node below. Node defaulting in makeinfo requires adjacency of
7488 @c node and sectioning commands; hence the repetition of @chapter BLAH
7489 @c in both conditional blocks.
7492 @include c-aarch64.texi
7496 @include c-alpha.texi
7512 @include c-bfin.texi
7516 @include c-cr16.texi
7520 @include c-cris.texi
7525 @node Machine Dependencies
7526 @chapter Machine Dependent Features
7528 The machine instruction sets are different on each Renesas chip family,
7529 and there are also some syntax differences among the families. This
7530 chapter describes the specific @command{@value{AS}} features for each
7534 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7535 * SH-Dependent:: Renesas SH Dependent Features
7542 @include c-d10v.texi
7546 @include c-d30v.texi
7550 @include c-epiphany.texi
7554 @include c-h8300.texi
7558 @include c-hppa.texi
7562 @include c-i370.texi
7566 @include c-i386.texi
7570 @include c-i860.texi
7574 @include c-i960.texi
7578 @include c-ia64.texi
7582 @include c-ip2k.texi
7586 @include c-lm32.texi
7590 @include c-m32c.texi
7594 @include c-m32r.texi
7598 @include c-m68k.texi
7602 @include c-m68hc11.texi
7606 @include c-metag.texi
7610 @include c-microblaze.texi
7614 @include c-mips.texi
7618 @include c-mmix.texi
7622 @include c-msp430.texi
7626 @include c-nds32.texi
7630 @include c-nios2.texi
7634 @include c-ns32k.texi
7638 @include c-pdp11.texi
7650 @include c-rl78.texi
7658 @include c-s390.texi
7662 @include c-score.texi
7667 @include c-sh64.texi
7671 @include c-sparc.texi
7675 @include c-tic54x.texi
7679 @include c-tic6x.texi
7683 @include c-tilegx.texi
7687 @include c-tilepro.texi
7691 @include c-v850.texi
7699 @include c-visium.texi
7703 @include c-xgate.texi
7707 @include c-xstormy16.texi
7711 @include c-xtensa.texi
7723 @c reverse effect of @down at top of generic Machine-Dep chapter
7727 @node Reporting Bugs
7728 @chapter Reporting Bugs
7729 @cindex bugs in assembler
7730 @cindex reporting bugs in assembler
7732 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7734 Reporting a bug may help you by bringing a solution to your problem, or it may
7735 not. But in any case the principal function of a bug report is to help the
7736 entire community by making the next version of @command{@value{AS}} work better.
7737 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7739 In order for a bug report to serve its purpose, you must include the
7740 information that enables us to fix the bug.
7743 * Bug Criteria:: Have you found a bug?
7744 * Bug Reporting:: How to report bugs
7748 @section Have You Found a Bug?
7749 @cindex bug criteria
7751 If you are not sure whether you have found a bug, here are some guidelines:
7754 @cindex fatal signal
7755 @cindex assembler crash
7756 @cindex crash of assembler
7758 If the assembler gets a fatal signal, for any input whatever, that is a
7759 @command{@value{AS}} bug. Reliable assemblers never crash.
7761 @cindex error on valid input
7763 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7765 @cindex invalid input
7767 If @command{@value{AS}} does not produce an error message for invalid input, that
7768 is a bug. However, you should note that your idea of ``invalid input'' might
7769 be our idea of ``an extension'' or ``support for traditional practice''.
7772 If you are an experienced user of assemblers, your suggestions for improvement
7773 of @command{@value{AS}} are welcome in any case.
7777 @section How to Report Bugs
7779 @cindex assembler bugs, reporting
7781 A number of companies and individuals offer support for @sc{gnu} products. If
7782 you obtained @command{@value{AS}} from a support organization, we recommend you
7783 contact that organization first.
7785 You can find contact information for many support companies and
7786 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7790 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7794 The fundamental principle of reporting bugs usefully is this:
7795 @strong{report all the facts}. If you are not sure whether to state a
7796 fact or leave it out, state it!
7798 Often people omit facts because they think they know what causes the problem
7799 and assume that some details do not matter. Thus, you might assume that the
7800 name of a symbol you use in an example does not matter. Well, probably it does
7801 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7802 happens to fetch from the location where that name is stored in memory;
7803 perhaps, if the name were different, the contents of that location would fool
7804 the assembler into doing the right thing despite the bug. Play it safe and
7805 give a specific, complete example. That is the easiest thing for you to do,
7806 and the most helpful.
7808 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7809 it is new to us. Therefore, always write your bug reports on the assumption
7810 that the bug has not been reported previously.
7812 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7813 bell?'' This cannot help us fix a bug, so it is basically useless. We
7814 respond by asking for enough details to enable us to investigate.
7815 You might as well expedite matters by sending them to begin with.
7817 To enable us to fix the bug, you should include all these things:
7821 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7822 it with the @samp{--version} argument.
7824 Without this, we will not know whether there is any point in looking for
7825 the bug in the current version of @command{@value{AS}}.
7828 Any patches you may have applied to the @command{@value{AS}} source.
7831 The type of machine you are using, and the operating system name and
7835 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7839 The command arguments you gave the assembler to assemble your example and
7840 observe the bug. To guarantee you will not omit something important, list them
7841 all. A copy of the Makefile (or the output from make) is sufficient.
7843 If we were to try to guess the arguments, we would probably guess wrong
7844 and then we might not encounter the bug.
7847 A complete input file that will reproduce the bug. If the bug is observed when
7848 the assembler is invoked via a compiler, send the assembler source, not the
7849 high level language source. Most compilers will produce the assembler source
7850 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7851 the options @samp{-v --save-temps}; this will save the assembler source in a
7852 file with an extension of @file{.s}, and also show you exactly how
7853 @command{@value{AS}} is being run.
7856 A description of what behavior you observe that you believe is
7857 incorrect. For example, ``It gets a fatal signal.''
7859 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7860 will certainly notice it. But if the bug is incorrect output, we might not
7861 notice unless it is glaringly wrong. You might as well not give us a chance to
7864 Even if the problem you experience is a fatal signal, you should still say so
7865 explicitly. Suppose something strange is going on, such as, your copy of
7866 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7867 library on your system. (This has happened!) Your copy might crash and ours
7868 would not. If you told us to expect a crash, then when ours fails to crash, we
7869 would know that the bug was not happening for us. If you had not told us to
7870 expect a crash, then we would not be able to draw any conclusion from our
7874 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7875 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7876 option. Always send diffs from the old file to the new file. If you even
7877 discuss something in the @command{@value{AS}} source, refer to it by context, not
7880 The line numbers in our development sources will not match those in your
7881 sources. Your line numbers would convey no useful information to us.
7884 Here are some things that are not necessary:
7888 A description of the envelope of the bug.
7890 Often people who encounter a bug spend a lot of time investigating
7891 which changes to the input file will make the bug go away and which
7892 changes will not affect it.
7894 This is often time consuming and not very useful, because the way we
7895 will find the bug is by running a single example under the debugger
7896 with breakpoints, not by pure deduction from a series of examples.
7897 We recommend that you save your time for something else.
7899 Of course, if you can find a simpler example to report @emph{instead}
7900 of the original one, that is a convenience for us. Errors in the
7901 output will be easier to spot, running under the debugger will take
7902 less time, and so on.
7904 However, simplification is not vital; if you do not want to do this,
7905 report the bug anyway and send us the entire test case you used.
7908 A patch for the bug.
7910 A patch for the bug does help us if it is a good one. But do not omit
7911 the necessary information, such as the test case, on the assumption that
7912 a patch is all we need. We might see problems with your patch and decide
7913 to fix the problem another way, or we might not understand it at all.
7915 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7916 construct an example that will make the program follow a certain path through
7917 the code. If you do not send us the example, we will not be able to construct
7918 one, so we will not be able to verify that the bug is fixed.
7920 And if we cannot understand what bug you are trying to fix, or why your
7921 patch should be an improvement, we will not install it. A test case will
7922 help us to understand.
7925 A guess about what the bug is or what it depends on.
7927 Such guesses are usually wrong. Even we cannot guess right about such
7928 things without first using the debugger to find the facts.
7931 @node Acknowledgements
7932 @chapter Acknowledgements
7934 If you have contributed to GAS and your name isn't listed here,
7935 it is not meant as a slight. We just don't know about it. Send mail to the
7936 maintainer, and we'll correct the situation. Currently
7938 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7940 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7943 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7944 information and the 68k series machines, most of the preprocessing pass, and
7945 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7947 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7948 many bug fixes, including merging support for several processors, breaking GAS
7949 up to handle multiple object file format back ends (including heavy rewrite,
7950 testing, an integration of the coff and b.out back ends), adding configuration
7951 including heavy testing and verification of cross assemblers and file splits
7952 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7953 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7954 port (including considerable amounts of reverse engineering), a SPARC opcode
7955 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7956 assertions and made them work, much other reorganization, cleanup, and lint.
7958 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7959 in format-specific I/O modules.
7961 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7962 has done much work with it since.
7964 The Intel 80386 machine description was written by Eliot Dresselhaus.
7966 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7968 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7969 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7971 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7972 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7973 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7974 support a.out format.
7976 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7977 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7978 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7979 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7982 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7983 simplified the configuration of which versions accept which directives. He
7984 updated the 68k machine description so that Motorola's opcodes always produced
7985 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7986 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7987 cross-compilation support, and one bug in relaxation that took a week and
7988 required the proverbial one-bit fix.
7990 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7991 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7992 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7993 PowerPC assembler, and made a few other minor patches.
7995 Steve Chamberlain made GAS able to generate listings.
7997 Hewlett-Packard contributed support for the HP9000/300.
7999 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8000 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8001 formats). This work was supported by both the Center for Software Science at
8002 the University of Utah and Cygnus Support.
8004 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8005 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8006 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8007 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8008 and some initial 64-bit support).
8010 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8012 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8013 support for openVMS/Alpha.
8015 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8018 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8019 Inc.@: added support for Xtensa processors.
8021 Several engineers at Cygnus Support have also provided many small bug fixes and
8022 configuration enhancements.
8024 Jon Beniston added support for the Lattice Mico32 architecture.
8026 Many others have contributed large or small bugfixes and enhancements. If
8027 you have contributed significant work and are not mentioned on this list, and
8028 want to be, let us know. Some of the history has been lost; we are not
8029 intentionally leaving anyone out.
8031 @node GNU Free Documentation License
8032 @appendix GNU Free Documentation License
8036 @unnumbered AS Index