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 file names and line numbers, in warnings/errors
2047 (where @b{NNN} is a line number). If both a logical file name
2048 (@pxref{File,,@code{.file}}) and a logical line number
2050 (@pxref{Line,,@code{.line}})
2052 have been given then they will be used, otherwise the file name and line number
2053 in the current assembler source file will be used. The message text is
2054 intended to be self explanatory (in the grand Unix tradition).
2056 Note the file name must be set via the logical version of the @code{.file}
2057 directive, not the DWARF2 version of the @code{.file} directive. For example:
2061 error_assembler_source
2067 produces this output:
2071 asm.s:2: Error: no such instruction: `error_assembler_source'
2072 foo.c:31: Error: no such instruction: `error_c_source'
2075 @cindex format of error messages
2076 Error messages have the format
2079 file_name:@b{NNN}:FATAL:Error Message Text
2082 The file name and line number are derived as for warning
2083 messages. The actual message text may be rather less explanatory
2084 because many of them aren't supposed to happen.
2087 @chapter Command-Line Options
2089 @cindex options, all versions of assembler
2090 This chapter describes command-line options available in @emph{all}
2091 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2092 for options specific
2094 to the @value{TARGET} target.
2097 to particular machine architectures.
2100 @c man begin DESCRIPTION
2102 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2103 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2104 The assembler arguments must be separated from each other (and the @samp{-Wa})
2105 by commas. For example:
2108 gcc -c -g -O -Wa,-alh,-L file.c
2112 This passes two options to the assembler: @samp{-alh} (emit a listing to
2113 standard output with high-level and assembly source) and @samp{-L} (retain
2114 local symbols in the symbol table).
2116 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2117 command-line options are automatically passed to the assembler by the compiler.
2118 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2119 precisely what options it passes to each compilation pass, including the
2125 * a:: -a[cdghlns] enable listings
2126 * alternate:: --alternate enable alternate macro syntax
2127 * D:: -D for compatibility
2128 * f:: -f to work faster
2129 * I:: -I for .include search path
2130 @ifclear DIFF-TBL-KLUGE
2131 * K:: -K for compatibility
2133 @ifset DIFF-TBL-KLUGE
2134 * K:: -K for difference tables
2137 * L:: -L to retain local symbols
2138 * listing:: --listing-XXX to configure listing output
2139 * M:: -M or --mri to assemble in MRI compatibility mode
2140 * MD:: --MD for dependency tracking
2141 * o:: -o to name the object file
2142 * R:: -R to join data and text sections
2143 * statistics:: --statistics to see statistics about assembly
2144 * traditional-format:: --traditional-format for compatible output
2145 * v:: -v to announce version
2146 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2147 * Z:: -Z to make object file even after errors
2151 @section Enable Listings: @option{-a[cdghlns]}
2161 @cindex listings, enabling
2162 @cindex assembly listings, enabling
2164 These options enable listing output from the assembler. By itself,
2165 @samp{-a} requests high-level, assembly, and symbols listing.
2166 You can use other letters to select specific options for the list:
2167 @samp{-ah} requests a high-level language listing,
2168 @samp{-al} requests an output-program assembly listing, and
2169 @samp{-as} requests a symbol table listing.
2170 High-level listings require that a compiler debugging option like
2171 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2174 Use the @samp{-ag} option to print a first section with general assembly
2175 information, like @value{AS} version, switches passed, or time stamp.
2177 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2178 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2179 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2180 omitted from the listing.
2182 Use the @samp{-ad} option to omit debugging directives from the
2185 Once you have specified one of these options, you can further control
2186 listing output and its appearance using the directives @code{.list},
2187 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2189 The @samp{-an} option turns off all forms processing.
2190 If you do not request listing output with one of the @samp{-a} options, the
2191 listing-control directives have no effect.
2193 The letters after @samp{-a} may be combined into one option,
2194 @emph{e.g.}, @samp{-aln}.
2196 Note if the assembler source is coming from the standard input (e.g.,
2198 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2199 is being used) then the listing will not contain any comments or preprocessor
2200 directives. This is because the listing code buffers input source lines from
2201 stdin only after they have been preprocessed by the assembler. This reduces
2202 memory usage and makes the code more efficient.
2205 @section @option{--alternate}
2208 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2211 @section @option{-D}
2214 This option has no effect whatsoever, but it is accepted to make it more
2215 likely that scripts written for other assemblers also work with
2216 @command{@value{AS}}.
2219 @section Work Faster: @option{-f}
2222 @cindex trusted compiler
2223 @cindex faster processing (@option{-f})
2224 @samp{-f} should only be used when assembling programs written by a
2225 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2226 and comment preprocessing on
2227 the input file(s) before assembling them. @xref{Preprocessing,
2231 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2232 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2237 @section @code{.include} Search Path: @option{-I} @var{path}
2239 @kindex -I @var{path}
2240 @cindex paths for @code{.include}
2241 @cindex search path for @code{.include}
2242 @cindex @code{include} directive search path
2243 Use this option to add a @var{path} to the list of directories
2244 @command{@value{AS}} searches for files specified in @code{.include}
2245 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2246 many times as necessary to include a variety of paths. The current
2247 working directory is always searched first; after that, @command{@value{AS}}
2248 searches any @samp{-I} directories in the same order as they were
2249 specified (left to right) on the command line.
2252 @section Difference Tables: @option{-K}
2255 @ifclear DIFF-TBL-KLUGE
2256 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2257 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2258 where it can be used to warn when the assembler alters the machine code
2259 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2260 family does not have the addressing limitations that sometimes lead to this
2261 alteration on other platforms.
2264 @ifset DIFF-TBL-KLUGE
2265 @cindex difference tables, warning
2266 @cindex warning for altered difference tables
2267 @command{@value{AS}} sometimes alters the code emitted for directives of the
2268 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2269 You can use the @samp{-K} option if you want a warning issued when this
2274 @section Include Local Symbols: @option{-L}
2277 @cindex local symbols, retaining in output
2278 Symbols beginning with system-specific local label prefixes, typically
2279 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2280 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2281 such symbols when debugging, because they are intended for the use of
2282 programs (like compilers) that compose assembler programs, not for your
2283 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2284 such symbols, so you do not normally debug with them.
2286 This option tells @command{@value{AS}} to retain those local symbols
2287 in the object file. Usually if you do this you also tell the linker
2288 @code{@value{LD}} to preserve those symbols.
2291 @section Configuring listing output: @option{--listing}
2293 The listing feature of the assembler can be enabled via the command line switch
2294 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2295 hex dump of the corresponding locations in the output object file, and displays
2296 them as a listing file. The format of this listing can be controlled by
2297 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2298 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2299 @code{.psize} (@pxref{Psize}), and
2300 @code{.eject} (@pxref{Eject}) and also by the following switches:
2303 @item --listing-lhs-width=@samp{number}
2304 @kindex --listing-lhs-width
2305 @cindex Width of first line disassembly output
2306 Sets the maximum width, in words, of the first line of the hex byte dump. This
2307 dump appears on the left hand side of the listing output.
2309 @item --listing-lhs-width2=@samp{number}
2310 @kindex --listing-lhs-width2
2311 @cindex Width of continuation lines of disassembly output
2312 Sets the maximum width, in words, of any further lines of the hex byte dump for
2313 a given input source line. If this value is not specified, it defaults to being
2314 the same as the value specified for @samp{--listing-lhs-width}. If neither
2315 switch is used the default is to one.
2317 @item --listing-rhs-width=@samp{number}
2318 @kindex --listing-rhs-width
2319 @cindex Width of source line output
2320 Sets the maximum width, in characters, of the source line that is displayed
2321 alongside the hex dump. The default value for this parameter is 100. The
2322 source line is displayed on the right hand side of the listing output.
2324 @item --listing-cont-lines=@samp{number}
2325 @kindex --listing-cont-lines
2326 @cindex Maximum number of continuation lines
2327 Sets the maximum number of continuation lines of hex dump that will be
2328 displayed for a given single line of source input. The default value is 4.
2332 @section Assemble in MRI Compatibility Mode: @option{-M}
2335 @cindex MRI compatibility mode
2336 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2337 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2338 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2339 configured target) assembler from Microtec Research. The exact nature of the
2340 MRI syntax will not be documented here; see the MRI manuals for more
2341 information. Note in particular that the handling of macros and macro
2342 arguments is somewhat different. The purpose of this option is to permit
2343 assembling existing MRI assembler code using @command{@value{AS}}.
2345 The MRI compatibility is not complete. Certain operations of the MRI assembler
2346 depend upon its object file format, and can not be supported using other object
2347 file formats. Supporting these would require enhancing each object file format
2348 individually. These are:
2351 @item global symbols in common section
2353 The m68k MRI assembler supports common sections which are merged by the linker.
2354 Other object file formats do not support this. @command{@value{AS}} handles
2355 common sections by treating them as a single common symbol. It permits local
2356 symbols to be defined within a common section, but it can not support global
2357 symbols, since it has no way to describe them.
2359 @item complex relocations
2361 The MRI assemblers support relocations against a negated section address, and
2362 relocations which combine the start addresses of two or more sections. These
2363 are not support by other object file formats.
2365 @item @code{END} pseudo-op specifying start address
2367 The MRI @code{END} pseudo-op permits the specification of a start address.
2368 This is not supported by other object file formats. The start address may
2369 instead be specified using the @option{-e} option to the linker, or in a linker
2372 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2374 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2375 name to the output file. This is not supported by other object file formats.
2377 @item @code{ORG} pseudo-op
2379 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2380 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2381 which changes the location within the current section. Absolute sections are
2382 not supported by other object file formats. The address of a section may be
2383 assigned within a linker script.
2386 There are some other features of the MRI assembler which are not supported by
2387 @command{@value{AS}}, typically either because they are difficult or because they
2388 seem of little consequence. Some of these may be supported in future releases.
2392 @item EBCDIC strings
2394 EBCDIC strings are not supported.
2396 @item packed binary coded decimal
2398 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2399 and @code{DCB.P} pseudo-ops are not supported.
2401 @item @code{FEQU} pseudo-op
2403 The m68k @code{FEQU} pseudo-op is not supported.
2405 @item @code{NOOBJ} pseudo-op
2407 The m68k @code{NOOBJ} pseudo-op is not supported.
2409 @item @code{OPT} branch control options
2411 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2412 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2413 relaxes all branches, whether forward or backward, to an appropriate size, so
2414 these options serve no purpose.
2416 @item @code{OPT} list control options
2418 The following m68k @code{OPT} list control options are ignored: @code{C},
2419 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2420 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2422 @item other @code{OPT} options
2424 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2425 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2427 @item @code{OPT} @code{D} option is default
2429 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2430 @code{OPT NOD} may be used to turn it off.
2432 @item @code{XREF} pseudo-op.
2434 The m68k @code{XREF} pseudo-op is ignored.
2436 @item @code{.debug} pseudo-op
2438 The i960 @code{.debug} pseudo-op is not supported.
2440 @item @code{.extended} pseudo-op
2442 The i960 @code{.extended} pseudo-op is not supported.
2444 @item @code{.list} pseudo-op.
2446 The various options of the i960 @code{.list} pseudo-op are not supported.
2448 @item @code{.optimize} pseudo-op
2450 The i960 @code{.optimize} pseudo-op is not supported.
2452 @item @code{.output} pseudo-op
2454 The i960 @code{.output} pseudo-op is not supported.
2456 @item @code{.setreal} pseudo-op
2458 The i960 @code{.setreal} pseudo-op is not supported.
2463 @section Dependency Tracking: @option{--MD}
2466 @cindex dependency tracking
2469 @command{@value{AS}} can generate a dependency file for the file it creates. This
2470 file consists of a single rule suitable for @code{make} describing the
2471 dependencies of the main source file.
2473 The rule is written to the file named in its argument.
2475 This feature is used in the automatic updating of makefiles.
2478 @section Name the Object File: @option{-o}
2481 @cindex naming object file
2482 @cindex object file name
2483 There is always one object file output when you run @command{@value{AS}}. By
2484 default it has the name
2487 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2501 You use this option (which takes exactly one filename) to give the
2502 object file a different name.
2504 Whatever the object file is called, @command{@value{AS}} overwrites any
2505 existing file of the same name.
2508 @section Join Data and Text Sections: @option{-R}
2511 @cindex data and text sections, joining
2512 @cindex text and data sections, joining
2513 @cindex joining text and data sections
2514 @cindex merging text and data sections
2515 @option{-R} tells @command{@value{AS}} to write the object file as if all
2516 data-section data lives in the text section. This is only done at
2517 the very last moment: your binary data are the same, but data
2518 section parts are relocated differently. The data section part of
2519 your object file is zero bytes long because all its bytes are
2520 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2522 When you specify @option{-R} it would be possible to generate shorter
2523 address displacements (because we do not have to cross between text and
2524 data section). We refrain from doing this simply for compatibility with
2525 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2528 When @command{@value{AS}} is configured for COFF or ELF output,
2529 this option is only useful if you use sections named @samp{.text} and
2534 @option{-R} is not supported for any of the HPPA targets. Using
2535 @option{-R} generates a warning from @command{@value{AS}}.
2539 @section Display Assembly Statistics: @option{--statistics}
2541 @kindex --statistics
2542 @cindex statistics, about assembly
2543 @cindex time, total for assembly
2544 @cindex space used, maximum for assembly
2545 Use @samp{--statistics} to display two statistics about the resources used by
2546 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2547 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2550 @node traditional-format
2551 @section Compatible Output: @option{--traditional-format}
2553 @kindex --traditional-format
2554 For some targets, the output of @command{@value{AS}} is different in some ways
2555 from the output of some existing assembler. This switch requests
2556 @command{@value{AS}} to use the traditional format instead.
2558 For example, it disables the exception frame optimizations which
2559 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2562 @section Announce Version: @option{-v}
2566 @cindex assembler version
2567 @cindex version of assembler
2568 You can find out what version of as is running by including the
2569 option @samp{-v} (which you can also spell as @samp{-version}) on the
2573 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2575 @command{@value{AS}} should never give a warning or error message when
2576 assembling compiler output. But programs written by people often
2577 cause @command{@value{AS}} to give a warning that a particular assumption was
2578 made. All such warnings are directed to the standard error file.
2582 @cindex suppressing warnings
2583 @cindex warnings, suppressing
2584 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2585 This only affects the warning messages: it does not change any particular of
2586 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2589 @kindex --fatal-warnings
2590 @cindex errors, caused by warnings
2591 @cindex warnings, causing error
2592 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2593 files that generate warnings to be in error.
2596 @cindex warnings, switching on
2597 You can switch these options off again by specifying @option{--warn}, which
2598 causes warnings to be output as usual.
2601 @section Generate Object File in Spite of Errors: @option{-Z}
2602 @cindex object file, after errors
2603 @cindex errors, continuing after
2604 After an error message, @command{@value{AS}} normally produces no output. If for
2605 some reason you are interested in object file output even after
2606 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2607 option. If there are any errors, @command{@value{AS}} continues anyways, and
2608 writes an object file after a final warning message of the form @samp{@var{n}
2609 errors, @var{m} warnings, generating bad object file.}
2614 @cindex machine-independent syntax
2615 @cindex syntax, machine-independent
2616 This chapter describes the machine-independent syntax allowed in a
2617 source file. @command{@value{AS}} syntax is similar to what many other
2618 assemblers use; it is inspired by the BSD 4.2
2623 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2627 * Preprocessing:: Preprocessing
2628 * Whitespace:: Whitespace
2629 * Comments:: Comments
2630 * Symbol Intro:: Symbols
2631 * Statements:: Statements
2632 * Constants:: Constants
2636 @section Preprocessing
2638 @cindex preprocessing
2639 The @command{@value{AS}} internal preprocessor:
2641 @cindex whitespace, removed by preprocessor
2643 adjusts and removes extra whitespace. It leaves one space or tab before
2644 the keywords on a line, and turns any other whitespace on the line into
2647 @cindex comments, removed by preprocessor
2649 removes all comments, replacing them with a single space, or an
2650 appropriate number of newlines.
2652 @cindex constants, converted by preprocessor
2654 converts character constants into the appropriate numeric values.
2657 It does not do macro processing, include file handling, or
2658 anything else you may get from your C compiler's preprocessor. You can
2659 do include file processing with the @code{.include} directive
2660 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2661 to get other ``CPP'' style preprocessing by giving the input file a
2662 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2663 Output, gcc.info, Using GNU CC}.
2665 Excess whitespace, comments, and character constants
2666 cannot be used in the portions of the input text that are not
2669 @cindex turning preprocessing on and off
2670 @cindex preprocessing, turning on and off
2673 If the first line of an input file is @code{#NO_APP} or if you use the
2674 @samp{-f} option, whitespace and comments are not removed from the input file.
2675 Within an input file, you can ask for whitespace and comment removal in
2676 specific portions of the by putting a line that says @code{#APP} before the
2677 text that may contain whitespace or comments, and putting a line that says
2678 @code{#NO_APP} after this text. This feature is mainly intend to support
2679 @code{asm} statements in compilers whose output is otherwise free of comments
2686 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2687 Whitespace is used to separate symbols, and to make programs neater for
2688 people to read. Unless within character constants
2689 (@pxref{Characters,,Character Constants}), any whitespace means the same
2690 as exactly one space.
2696 There are two ways of rendering comments to @command{@value{AS}}. In both
2697 cases the comment is equivalent to one space.
2699 Anything from @samp{/*} through the next @samp{*/} is a comment.
2700 This means you may not nest these comments.
2704 The only way to include a newline ('\n') in a comment
2705 is to use this sort of comment.
2708 /* This sort of comment does not nest. */
2711 @cindex line comment character
2712 Anything from a @dfn{line comment} character up to the next newline is
2713 considered a comment and is ignored. The line comment character is target
2714 specific, and some targets multiple comment characters. Some targets also have
2715 line comment characters that only work if they are the first character on a
2716 line. Some targets use a sequence of two characters to introduce a line
2717 comment. Some targets can also change their line comment characters depending
2718 upon command line options that have been used. For more details see the
2719 @emph{Syntax} section in the documentation for individual targets.
2721 If the line comment character is the hash sign (@samp{#}) then it still has the
2722 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2723 to specify logical line numbers:
2726 @cindex lines starting with @code{#}
2727 @cindex logical line numbers
2728 To be compatible with past assemblers, lines that begin with @samp{#} have a
2729 special interpretation. Following the @samp{#} should be an absolute
2730 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2731 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2732 new logical file name. The rest of the line, if any, should be whitespace.
2734 If the first non-whitespace characters on the line are not numeric,
2735 the line is ignored. (Just like a comment.)
2738 # This is an ordinary comment.
2739 # 42-6 "new_file_name" # New logical file name
2740 # This is logical line # 36.
2742 This feature is deprecated, and may disappear from future versions
2743 of @command{@value{AS}}.
2748 @cindex characters used in symbols
2749 @ifclear SPECIAL-SYMS
2750 A @dfn{symbol} is one or more characters chosen from the set of all
2751 letters (both upper and lower case), digits and the three characters
2757 A @dfn{symbol} is one or more characters chosen from the set of all
2758 letters (both upper and lower case), digits and the three characters
2759 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2765 On most machines, you can also use @code{$} in symbol names; exceptions
2766 are noted in @ref{Machine Dependencies}.
2768 No symbol may begin with a digit. Case is significant.
2769 There is no length limit; all characters are significant. Multibyte characters
2770 are supported. Symbols are delimited by characters not in that set, or by the
2771 beginning of a file (since the source program must end with a newline, the end
2772 of a file is not a possible symbol delimiter). @xref{Symbols}.
2774 Symbol names may also be enclosed in double quote @code{"} characters. In such
2775 cases any characters are allowed, except for the NUL character. If a double
2776 quote character is to be included in the symbol name it must be preceeded by a
2777 backslash @code{\} character.
2778 @cindex length of symbols
2783 @cindex statements, structure of
2784 @cindex line separator character
2785 @cindex statement separator character
2787 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2788 @dfn{line separator character}. The line separator character is target
2789 specific and described in the @emph{Syntax} section of each
2790 target's documentation. Not all targets support a line separator character.
2791 The newline or line separator character is considered to be part of the
2792 preceding statement. Newlines and separators within character constants are an
2793 exception: they do not end statements.
2795 @cindex newline, required at file end
2796 @cindex EOF, newline must precede
2797 It is an error to end any statement with end-of-file: the last
2798 character of any input file should be a newline.@refill
2800 An empty statement is allowed, and may include whitespace. It is ignored.
2802 @cindex instructions and directives
2803 @cindex directives and instructions
2804 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2805 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2807 A statement begins with zero or more labels, optionally followed by a
2808 key symbol which determines what kind of statement it is. The key
2809 symbol determines the syntax of the rest of the statement. If the
2810 symbol begins with a dot @samp{.} then the statement is an assembler
2811 directive: typically valid for any computer. If the symbol begins with
2812 a letter the statement is an assembly language @dfn{instruction}: it
2813 assembles into a machine language instruction.
2815 Different versions of @command{@value{AS}} for different computers
2816 recognize different instructions. In fact, the same symbol may
2817 represent a different instruction in a different computer's assembly
2821 @cindex @code{:} (label)
2822 @cindex label (@code{:})
2823 A label is a symbol immediately followed by a colon (@code{:}).
2824 Whitespace before a label or after a colon is permitted, but you may not
2825 have whitespace between a label's symbol and its colon. @xref{Labels}.
2828 For HPPA targets, labels need not be immediately followed by a colon, but
2829 the definition of a label must begin in column zero. This also implies that
2830 only one label may be defined on each line.
2834 label: .directive followed by something
2835 another_label: # This is an empty statement.
2836 instruction operand_1, operand_2, @dots{}
2843 A constant is a number, written so that its value is known by
2844 inspection, without knowing any context. Like this:
2847 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2848 .ascii "Ring the bell\7" # A string constant.
2849 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2850 .float 0f-314159265358979323846264338327\
2851 95028841971.693993751E-40 # - pi, a flonum.
2856 * Characters:: Character Constants
2857 * Numbers:: Number Constants
2861 @subsection Character Constants
2863 @cindex character constants
2864 @cindex constants, character
2865 There are two kinds of character constants. A @dfn{character} stands
2866 for one character in one byte and its value may be used in
2867 numeric expressions. String constants (properly called string
2868 @emph{literals}) are potentially many bytes and their values may not be
2869 used in arithmetic expressions.
2873 * Chars:: Characters
2877 @subsubsection Strings
2879 @cindex string constants
2880 @cindex constants, string
2881 A @dfn{string} is written between double-quotes. It may contain
2882 double-quotes or null characters. The way to get special characters
2883 into a string is to @dfn{escape} these characters: precede them with
2884 a backslash @samp{\} character. For example @samp{\\} represents
2885 one backslash: the first @code{\} is an escape which tells
2886 @command{@value{AS}} to interpret the second character literally as a backslash
2887 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2888 escape character). The complete list of escapes follows.
2890 @cindex escape codes, character
2891 @cindex character escape codes
2892 @c NOTE: Cindex entries must not start with a backlash character.
2893 @c NOTE: This confuses the pdf2texi script when it is creating the
2894 @c NOTE: index based upon the first character and so it generates:
2895 @c NOTE: \initial {\\}
2896 @c NOTE: which then results in the error message:
2897 @c NOTE: Argument of \\ has an extra }.
2898 @c NOTE: So in the index entries below a space character has been
2899 @c NOTE: prepended to avoid this problem.
2902 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2904 @cindex @code{ \b} (backspace character)
2905 @cindex backspace (@code{\b})
2907 Mnemonic for backspace; for ASCII this is octal code 010.
2910 @c Mnemonic for EOText; for ASCII this is octal code 004.
2912 @cindex @code{ \f} (formfeed character)
2913 @cindex formfeed (@code{\f})
2915 Mnemonic for FormFeed; for ASCII this is octal code 014.
2917 @cindex @code{ \n} (newline character)
2918 @cindex newline (@code{\n})
2920 Mnemonic for newline; for ASCII this is octal code 012.
2923 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2925 @cindex @code{ \r} (carriage return character)
2926 @cindex carriage return (@code{backslash-r})
2928 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2931 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2932 @c other assemblers.
2934 @cindex @code{ \t} (tab)
2935 @cindex tab (@code{\t})
2937 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2940 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2941 @c @item \x @var{digit} @var{digit} @var{digit}
2942 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2944 @cindex @code{ \@var{ddd}} (octal character code)
2945 @cindex octal character code (@code{\@var{ddd}})
2946 @item \ @var{digit} @var{digit} @var{digit}
2947 An octal character code. The numeric code is 3 octal digits.
2948 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2949 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2951 @cindex @code{ \@var{xd...}} (hex character code)
2952 @cindex hex character code (@code{\@var{xd...}})
2953 @item \@code{x} @var{hex-digits...}
2954 A hex character code. All trailing hex digits are combined. Either upper or
2955 lower case @code{x} works.
2957 @cindex @code{ \\} (@samp{\} character)
2958 @cindex backslash (@code{\\})
2960 Represents one @samp{\} character.
2963 @c Represents one @samp{'} (accent acute) character.
2964 @c This is needed in single character literals
2965 @c (@xref{Characters,,Character Constants}.) to represent
2968 @cindex @code{ \"} (doublequote character)
2969 @cindex doublequote (@code{\"})
2971 Represents one @samp{"} character. Needed in strings to represent
2972 this character, because an unescaped @samp{"} would end the string.
2974 @item \ @var{anything-else}
2975 Any other character when escaped by @kbd{\} gives a warning, but
2976 assembles as if the @samp{\} was not present. The idea is that if
2977 you used an escape sequence you clearly didn't want the literal
2978 interpretation of the following character. However @command{@value{AS}} has no
2979 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2980 code and warns you of the fact.
2983 Which characters are escapable, and what those escapes represent,
2984 varies widely among assemblers. The current set is what we think
2985 the BSD 4.2 assembler recognizes, and is a subset of what most C
2986 compilers recognize. If you are in doubt, do not use an escape
2990 @subsubsection Characters
2992 @cindex single character constant
2993 @cindex character, single
2994 @cindex constant, single character
2995 A single character may be written as a single quote immediately
2996 followed by that character. The same escapes apply to characters as
2997 to strings. So if you want to write the character backslash, you
2998 must write @kbd{'\\} where the first @code{\} escapes the second
2999 @code{\}. As you can see, the quote is an acute accent, not a
3000 grave accent. A newline
3002 @ifclear abnormal-separator
3003 (or semicolon @samp{;})
3005 @ifset abnormal-separator
3007 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3012 immediately following an acute accent is taken as a literal character
3013 and does not count as the end of a statement. The value of a character
3014 constant in a numeric expression is the machine's byte-wide code for
3015 that character. @command{@value{AS}} assumes your character code is ASCII:
3016 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3019 @subsection Number Constants
3021 @cindex constants, number
3022 @cindex number constants
3023 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3024 are stored in the target machine. @emph{Integers} are numbers that
3025 would fit into an @code{int} in the C language. @emph{Bignums} are
3026 integers, but they are stored in more than 32 bits. @emph{Flonums}
3027 are floating point numbers, described below.
3030 * Integers:: Integers
3035 * Bit Fields:: Bit Fields
3041 @subsubsection Integers
3043 @cindex constants, integer
3045 @cindex binary integers
3046 @cindex integers, binary
3047 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3048 the binary digits @samp{01}.
3050 @cindex octal integers
3051 @cindex integers, octal
3052 An octal integer is @samp{0} followed by zero or more of the octal
3053 digits (@samp{01234567}).
3055 @cindex decimal integers
3056 @cindex integers, decimal
3057 A decimal integer starts with a non-zero digit followed by zero or
3058 more digits (@samp{0123456789}).
3060 @cindex hexadecimal integers
3061 @cindex integers, hexadecimal
3062 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3063 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3065 Integers have the usual values. To denote a negative integer, use
3066 the prefix operator @samp{-} discussed under expressions
3067 (@pxref{Prefix Ops,,Prefix Operators}).
3070 @subsubsection Bignums
3073 @cindex constants, bignum
3074 A @dfn{bignum} has the same syntax and semantics as an integer
3075 except that the number (or its negative) takes more than 32 bits to
3076 represent in binary. The distinction is made because in some places
3077 integers are permitted while bignums are not.
3080 @subsubsection Flonums
3082 @cindex floating point numbers
3083 @cindex constants, floating point
3085 @cindex precision, floating point
3086 A @dfn{flonum} represents a floating point number. The translation is
3087 indirect: a decimal floating point number from the text is converted by
3088 @command{@value{AS}} to a generic binary floating point number of more than
3089 sufficient precision. This generic floating point number is converted
3090 to a particular computer's floating point format (or formats) by a
3091 portion of @command{@value{AS}} specialized to that computer.
3093 A flonum is written by writing (in order)
3098 (@samp{0} is optional on the HPPA.)
3102 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3104 @kbd{e} is recommended. Case is not important.
3106 @c FIXME: verify if flonum syntax really this vague for most cases
3107 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3108 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3111 On the H8/300, Renesas / SuperH SH,
3112 and AMD 29K architectures, the letter must be
3113 one of the letters @samp{DFPRSX} (in upper or lower case).
3115 On the ARC, the letter must be one of the letters @samp{DFRS}
3116 (in upper or lower case).
3118 On the Intel 960 architecture, the letter must be
3119 one of the letters @samp{DFT} (in upper or lower case).
3121 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3125 One of the letters @samp{DFRS} (in upper or lower case).
3128 One of the letters @samp{DFPRSX} (in upper or lower case).
3131 The letter @samp{E} (upper case only).
3134 One of the letters @samp{DFT} (in upper or lower case).
3139 An optional sign: either @samp{+} or @samp{-}.
3142 An optional @dfn{integer part}: zero or more decimal digits.
3145 An optional @dfn{fractional part}: @samp{.} followed by zero
3146 or more decimal digits.
3149 An optional exponent, consisting of:
3153 An @samp{E} or @samp{e}.
3154 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3155 @c principle this can perfectly well be different on different targets.
3157 Optional sign: either @samp{+} or @samp{-}.
3159 One or more decimal digits.
3164 At least one of the integer part or the fractional part must be
3165 present. The floating point number has the usual base-10 value.
3167 @command{@value{AS}} does all processing using integers. Flonums are computed
3168 independently of any floating point hardware in the computer running
3169 @command{@value{AS}}.
3173 @c Bit fields are written as a general facility but are also controlled
3174 @c by a conditional-compilation flag---which is as of now (21mar91)
3175 @c turned on only by the i960 config of GAS.
3177 @subsubsection Bit Fields
3180 @cindex constants, bit field
3181 You can also define numeric constants as @dfn{bit fields}.
3182 Specify two numbers separated by a colon---
3184 @var{mask}:@var{value}
3187 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3190 The resulting number is then packed
3192 @c this conditional paren in case bit fields turned on elsewhere than 960
3193 (in host-dependent byte order)
3195 into a field whose width depends on which assembler directive has the
3196 bit-field as its argument. Overflow (a result from the bitwise and
3197 requiring more binary digits to represent) is not an error; instead,
3198 more constants are generated, of the specified width, beginning with the
3199 least significant digits.@refill
3201 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3202 @code{.short}, and @code{.word} accept bit-field arguments.
3207 @chapter Sections and Relocation
3212 * Secs Background:: Background
3213 * Ld Sections:: Linker Sections
3214 * As Sections:: Assembler Internal Sections
3215 * Sub-Sections:: Sub-Sections
3219 @node Secs Background
3222 Roughly, a section is a range of addresses, with no gaps; all data
3223 ``in'' those addresses is treated the same for some particular purpose.
3224 For example there may be a ``read only'' section.
3226 @cindex linker, and assembler
3227 @cindex assembler, and linker
3228 The linker @code{@value{LD}} reads many object files (partial programs) and
3229 combines their contents to form a runnable program. When @command{@value{AS}}
3230 emits an object file, the partial program is assumed to start at address 0.
3231 @code{@value{LD}} assigns the final addresses for the partial program, so that
3232 different partial programs do not overlap. This is actually an
3233 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3236 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3237 addresses. These blocks slide to their run-time addresses as rigid
3238 units; their length does not change and neither does the order of bytes
3239 within them. Such a rigid unit is called a @emph{section}. Assigning
3240 run-time addresses to sections is called @dfn{relocation}. It includes
3241 the task of adjusting mentions of object-file addresses so they refer to
3242 the proper run-time addresses.
3244 For the H8/300, and for the Renesas / SuperH SH,
3245 @command{@value{AS}} pads sections if needed to
3246 ensure they end on a word (sixteen bit) boundary.
3249 @cindex standard assembler sections
3250 An object file written by @command{@value{AS}} has at least three sections, any
3251 of which may be empty. These are named @dfn{text}, @dfn{data} and
3256 When it generates COFF or ELF output,
3258 @command{@value{AS}} can also generate whatever other named sections you specify
3259 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3260 If you do not use any directives that place output in the @samp{.text}
3261 or @samp{.data} sections, these sections still exist, but are empty.
3266 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3268 @command{@value{AS}} can also generate whatever other named sections you
3269 specify using the @samp{.space} and @samp{.subspace} directives. See
3270 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3271 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3272 assembler directives.
3275 Additionally, @command{@value{AS}} uses different names for the standard
3276 text, data, and bss sections when generating SOM output. Program text
3277 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3278 BSS into @samp{$BSS$}.
3282 Within the object file, the text section starts at address @code{0}, the
3283 data section follows, and the bss section follows the data section.
3286 When generating either SOM or ELF output files on the HPPA, the text
3287 section starts at address @code{0}, the data section at address
3288 @code{0x4000000}, and the bss section follows the data section.
3291 To let @code{@value{LD}} know which data changes when the sections are
3292 relocated, and how to change that data, @command{@value{AS}} also writes to the
3293 object file details of the relocation needed. To perform relocation
3294 @code{@value{LD}} must know, each time an address in the object
3298 Where in the object file is the beginning of this reference to
3301 How long (in bytes) is this reference?
3303 Which section does the address refer to? What is the numeric value of
3305 (@var{address}) @minus{} (@var{start-address of section})?
3308 Is the reference to an address ``Program-Counter relative''?
3311 @cindex addresses, format of
3312 @cindex section-relative addressing
3313 In fact, every address @command{@value{AS}} ever uses is expressed as
3315 (@var{section}) + (@var{offset into section})
3318 Further, most expressions @command{@value{AS}} computes have this section-relative
3321 (For some object formats, such as SOM for the HPPA, some expressions are
3322 symbol-relative instead.)
3325 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3326 @var{N} into section @var{secname}.''
3328 Apart from text, data and bss sections you need to know about the
3329 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3330 addresses in the absolute section remain unchanged. For example, address
3331 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3332 @code{@value{LD}}. Although the linker never arranges two partial programs'
3333 data sections with overlapping addresses after linking, @emph{by definition}
3334 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3335 part of a program is always the same address when the program is running as
3336 address @code{@{absolute@ 239@}} in any other part of the program.
3338 The idea of sections is extended to the @dfn{undefined} section. Any
3339 address whose section is unknown at assembly time is by definition
3340 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3341 Since numbers are always defined, the only way to generate an undefined
3342 address is to mention an undefined symbol. A reference to a named
3343 common block would be such a symbol: its value is unknown at assembly
3344 time so it has section @emph{undefined}.
3346 By analogy the word @emph{section} is used to describe groups of sections in
3347 the linked program. @code{@value{LD}} puts all partial programs' text
3348 sections in contiguous addresses in the linked program. It is
3349 customary to refer to the @emph{text section} of a program, meaning all
3350 the addresses of all partial programs' text sections. Likewise for
3351 data and bss sections.
3353 Some sections are manipulated by @code{@value{LD}}; others are invented for
3354 use of @command{@value{AS}} and have no meaning except during assembly.
3357 @section Linker Sections
3358 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3363 @cindex named sections
3364 @cindex sections, named
3365 @item named sections
3368 @cindex text section
3369 @cindex data section
3373 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3374 separate but equal sections. Anything you can say of one section is
3377 When the program is running, however, it is
3378 customary for the text section to be unalterable. The
3379 text section is often shared among processes: it contains
3380 instructions, constants and the like. The data section of a running
3381 program is usually alterable: for example, C variables would be stored
3382 in the data section.
3387 This section contains zeroed bytes when your program begins running. It
3388 is used to hold uninitialized variables or common storage. The length of
3389 each partial program's bss section is important, but because it starts
3390 out containing zeroed bytes there is no need to store explicit zero
3391 bytes in the object file. The bss section was invented to eliminate
3392 those explicit zeros from object files.
3394 @cindex absolute section
3395 @item absolute section
3396 Address 0 of this section is always ``relocated'' to runtime address 0.
3397 This is useful if you want to refer to an address that @code{@value{LD}} must
3398 not change when relocating. In this sense we speak of absolute
3399 addresses being ``unrelocatable'': they do not change during relocation.
3401 @cindex undefined section
3402 @item undefined section
3403 This ``section'' is a catch-all for address references to objects not in
3404 the preceding sections.
3405 @c FIXME: ref to some other doc on obj-file formats could go here.
3408 @cindex relocation example
3409 An idealized example of three relocatable sections follows.
3411 The example uses the traditional section names @samp{.text} and @samp{.data}.
3413 Memory addresses are on the horizontal axis.
3417 @c END TEXI2ROFF-KILL
3420 partial program # 1: |ttttt|dddd|00|
3427 partial program # 2: |TTT|DDD|000|
3430 +--+---+-----+--+----+---+-----+~~
3431 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3432 +--+---+-----+--+----+---+-----+~~
3434 addresses: 0 @dots{}
3441 \line{\it Partial program \#1: \hfil}
3442 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3443 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3445 \line{\it Partial program \#2: \hfil}
3446 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3447 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3449 \line{\it linked program: \hfil}
3450 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3451 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3452 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3453 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3455 \line{\it addresses: \hfil}
3459 @c END TEXI2ROFF-KILL
3462 @section Assembler Internal Sections
3464 @cindex internal assembler sections
3465 @cindex sections in messages, internal
3466 These sections are meant only for the internal use of @command{@value{AS}}. They
3467 have no meaning at run-time. You do not really need to know about these
3468 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3469 warning messages, so it might be helpful to have an idea of their
3470 meanings to @command{@value{AS}}. These sections are used to permit the
3471 value of every expression in your assembly language program to be a
3472 section-relative address.
3475 @cindex assembler internal logic error
3476 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3477 An internal assembler logic error has been found. This means there is a
3478 bug in the assembler.
3480 @cindex expr (internal section)
3482 The assembler stores complex expression internally as combinations of
3483 symbols. When it needs to represent an expression as a symbol, it puts
3484 it in the expr section.
3486 @c FIXME item transfer[t] vector preload
3487 @c FIXME item transfer[t] vector postload
3488 @c FIXME item register
3492 @section Sub-Sections
3494 @cindex numbered subsections
3495 @cindex grouping data
3501 fall into two sections: text and data.
3503 You may have separate groups of
3505 data in named sections
3509 data in named sections
3515 that you want to end up near to each other in the object file, even though they
3516 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3517 use @dfn{subsections} for this purpose. Within each section, there can be
3518 numbered subsections with values from 0 to 8192. Objects assembled into the
3519 same subsection go into the object file together with other objects in the same
3520 subsection. For example, a compiler might want to store constants in the text
3521 section, but might not want to have them interspersed with the program being
3522 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3523 section of code being output, and a @samp{.text 1} before each group of
3524 constants being output.
3526 Subsections are optional. If you do not use subsections, everything
3527 goes in subsection number zero.
3530 Each subsection is zero-padded up to a multiple of four bytes.
3531 (Subsections may be padded a different amount on different flavors
3532 of @command{@value{AS}}.)
3536 On the H8/300 platform, each subsection is zero-padded to a word
3537 boundary (two bytes).
3538 The same is true on the Renesas SH.
3541 @c FIXME section padding (alignment)?
3542 @c Rich Pixley says padding here depends on target obj code format; that
3543 @c doesn't seem particularly useful to say without further elaboration,
3544 @c so for now I say nothing about it. If this is a generic BFD issue,
3545 @c these paragraphs might need to vanish from this manual, and be
3546 @c discussed in BFD chapter of binutils (or some such).
3550 Subsections appear in your object file in numeric order, lowest numbered
3551 to highest. (All this to be compatible with other people's assemblers.)
3552 The object file contains no representation of subsections; @code{@value{LD}} and
3553 other programs that manipulate object files see no trace of them.
3554 They just see all your text subsections as a text section, and all your
3555 data subsections as a data section.
3557 To specify which subsection you want subsequent statements assembled
3558 into, use a numeric argument to specify it, in a @samp{.text
3559 @var{expression}} or a @samp{.data @var{expression}} statement.
3562 When generating COFF output, you
3567 can also use an extra subsection
3568 argument with arbitrary named sections: @samp{.section @var{name},
3573 When generating ELF output, you
3578 can also use the @code{.subsection} directive (@pxref{SubSection})
3579 to specify a subsection: @samp{.subsection @var{expression}}.
3581 @var{Expression} should be an absolute expression
3582 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3583 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3584 begins in @code{text 0}. For instance:
3586 .text 0 # The default subsection is text 0 anyway.
3587 .ascii "This lives in the first text subsection. *"
3589 .ascii "But this lives in the second text subsection."
3591 .ascii "This lives in the data section,"
3592 .ascii "in the first data subsection."
3594 .ascii "This lives in the first text section,"
3595 .ascii "immediately following the asterisk (*)."
3598 Each section has a @dfn{location counter} incremented by one for every byte
3599 assembled into that section. Because subsections are merely a convenience
3600 restricted to @command{@value{AS}} there is no concept of a subsection location
3601 counter. There is no way to directly manipulate a location counter---but the
3602 @code{.align} directive changes it, and any label definition captures its
3603 current value. The location counter of the section where statements are being
3604 assembled is said to be the @dfn{active} location counter.
3607 @section bss Section
3610 @cindex common variable storage
3611 The bss section is used for local common variable storage.
3612 You may allocate address space in the bss section, but you may
3613 not dictate data to load into it before your program executes. When
3614 your program starts running, all the contents of the bss
3615 section are zeroed bytes.
3617 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3618 @ref{Lcomm,,@code{.lcomm}}.
3620 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3621 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3624 When assembling for a target which supports multiple sections, such as ELF or
3625 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3626 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3627 section. Typically the section will only contain symbol definitions and
3628 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3635 Symbols are a central concept: the programmer uses symbols to name
3636 things, the linker uses symbols to link, and the debugger uses symbols
3640 @cindex debuggers, and symbol order
3641 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3642 the same order they were declared. This may break some debuggers.
3647 * Setting Symbols:: Giving Symbols Other Values
3648 * Symbol Names:: Symbol Names
3649 * Dot:: The Special Dot Symbol
3650 * Symbol Attributes:: Symbol Attributes
3657 A @dfn{label} is written as a symbol immediately followed by a colon
3658 @samp{:}. The symbol then represents the current value of the
3659 active location counter, and is, for example, a suitable instruction
3660 operand. You are warned if you use the same symbol to represent two
3661 different locations: the first definition overrides any other
3665 On the HPPA, the usual form for a label need not be immediately followed by a
3666 colon, but instead must start in column zero. Only one label may be defined on
3667 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3668 provides a special directive @code{.label} for defining labels more flexibly.
3671 @node Setting Symbols
3672 @section Giving Symbols Other Values
3674 @cindex assigning values to symbols
3675 @cindex symbol values, assigning
3676 A symbol can be given an arbitrary value by writing a symbol, followed
3677 by an equals sign @samp{=}, followed by an expression
3678 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3679 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3680 equals sign @samp{=}@samp{=} here represents an equivalent of the
3681 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3684 Blackfin does not support symbol assignment with @samp{=}.
3688 @section Symbol Names
3690 @cindex symbol names
3691 @cindex names, symbol
3692 @ifclear SPECIAL-SYMS
3693 Symbol names begin with a letter or with one of @samp{._}. On most
3694 machines, you can also use @code{$} in symbol names; exceptions are
3695 noted in @ref{Machine Dependencies}. That character may be followed by any
3696 string of digits, letters, dollar signs (unless otherwise noted for a
3697 particular target machine), and underscores.
3701 Symbol names begin with a letter or with one of @samp{._}. On the
3702 Renesas SH you can also use @code{$} in symbol names. That
3703 character may be followed by any string of digits, letters, dollar signs (save
3704 on the H8/300), and underscores.
3708 Case of letters is significant: @code{foo} is a different symbol name
3711 Symbol names do not start with a digit. An exception to this rule is made for
3712 Local Labels. See below.
3714 Multibyte characters are supported. To generate a symbol name containing
3715 multibyte characters enclose it within double quotes and use escape codes. cf
3716 @xref{Strings}. Generating a multibyte symbol name from a label is not
3717 currently supported.
3719 Each symbol has exactly one name. Each name in an assembly language program
3720 refers to exactly one symbol. You may use that symbol name any number of times
3723 @subheading Local Symbol Names
3725 @cindex local symbol names
3726 @cindex symbol names, local
3727 A local symbol is any symbol beginning with certain local label prefixes.
3728 By default, the local label prefix is @samp{.L} for ELF systems or
3729 @samp{L} for traditional a.out systems, but each target may have its own
3730 set of local label prefixes.
3732 On the HPPA local symbols begin with @samp{L$}.
3735 Local symbols are defined and used within the assembler, but they are
3736 normally not saved in object files. Thus, they are not visible when debugging.
3737 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3738 to retain the local symbols in the object files.
3740 @subheading Local Labels
3742 @cindex local labels
3743 @cindex temporary symbol names
3744 @cindex symbol names, temporary
3745 Local labels are different from local symbols. Local labels help compilers and
3746 programmers use names temporarily. They create symbols which are guaranteed to
3747 be unique over the entire scope of the input source code and which can be
3748 referred to by a simple notation. To define a local label, write a label of
3749 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3750 To refer to the most recent previous definition of that label write
3751 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3752 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3753 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3755 There is no restriction on how you can use these labels, and you can reuse them
3756 too. So that it is possible to repeatedly define the same local label (using
3757 the same number @samp{@b{N}}), although you can only refer to the most recently
3758 defined local label of that number (for a backwards reference) or the next
3759 definition of a specific local label for a forward reference. It is also worth
3760 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3761 implemented in a slightly more efficient manner than the others.
3772 Which is the equivalent of:
3775 label_1: branch label_3
3776 label_2: branch label_1
3777 label_3: branch label_4
3778 label_4: branch label_3
3781 Local label names are only a notational device. They are immediately
3782 transformed into more conventional symbol names before the assembler uses them.
3783 The symbol names are stored in the symbol table, appear in error messages, and
3784 are optionally emitted to the object file. The names are constructed using
3788 @item @emph{local label prefix}
3789 All local symbols begin with the system-specific local label prefix.
3790 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3791 that start with the local label prefix. These labels are
3792 used for symbols you are never intended to see. If you use the
3793 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3794 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3795 you may use them in debugging.
3798 This is the number that was used in the local label definition. So if the
3799 label is written @samp{55:} then the number is @samp{55}.
3802 This unusual character is included so you do not accidentally invent a symbol
3803 of the same name. The character has ASCII value of @samp{\002} (control-B).
3805 @item @emph{ordinal number}
3806 This is a serial number to keep the labels distinct. The first definition of
3807 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3808 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3809 the number @samp{1} and its 15th definition gets @samp{15} as well.
3812 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3813 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3815 @subheading Dollar Local Labels
3816 @cindex dollar local symbols
3818 On some targets @code{@value{AS}} also supports an even more local form of
3819 local labels called dollar labels. These labels go out of scope (i.e., they
3820 become undefined) as soon as a non-local label is defined. Thus they remain
3821 valid for only a small region of the input source code. Normal local labels,
3822 by contrast, remain in scope for the entire file, or until they are redefined
3823 by another occurrence of the same local label.
3825 Dollar labels are defined in exactly the same way as ordinary local labels,
3826 except that they have a dollar sign suffix to their numeric value, e.g.,
3829 They can also be distinguished from ordinary local labels by their transformed
3830 names which use ASCII character @samp{\001} (control-A) as the magic character
3831 to distinguish them from ordinary labels. For example, the fifth definition of
3832 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3835 @section The Special Dot Symbol
3837 @cindex dot (symbol)
3838 @cindex @code{.} (symbol)
3839 @cindex current address
3840 @cindex location counter
3841 The special symbol @samp{.} refers to the current address that
3842 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3843 .long .} defines @code{melvin} to contain its own address.
3844 Assigning a value to @code{.} is treated the same as a @code{.org}
3846 @ifclear no-space-dir
3847 Thus, the expression @samp{.=.+4} is the same as saying
3851 @node Symbol Attributes
3852 @section Symbol Attributes
3854 @cindex symbol attributes
3855 @cindex attributes, symbol
3856 Every symbol has, as well as its name, the attributes ``Value'' and
3857 ``Type''. Depending on output format, symbols can also have auxiliary
3860 The detailed definitions are in @file{a.out.h}.
3863 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3864 all these attributes, and probably won't warn you. This makes the
3865 symbol an externally defined symbol, which is generally what you
3869 * Symbol Value:: Value
3870 * Symbol Type:: Type
3873 * a.out Symbols:: Symbol Attributes: @code{a.out}
3877 * a.out Symbols:: Symbol Attributes: @code{a.out}
3880 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3885 * COFF Symbols:: Symbol Attributes for COFF
3888 * SOM Symbols:: Symbol Attributes for SOM
3895 @cindex value of a symbol
3896 @cindex symbol value
3897 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3898 location in the text, data, bss or absolute sections the value is the
3899 number of addresses from the start of that section to the label.
3900 Naturally for text, data and bss sections the value of a symbol changes
3901 as @code{@value{LD}} changes section base addresses during linking. Absolute
3902 symbols' values do not change during linking: that is why they are
3905 The value of an undefined symbol is treated in a special way. If it is
3906 0 then the symbol is not defined in this assembler source file, and
3907 @code{@value{LD}} tries to determine its value from other files linked into the
3908 same program. You make this kind of symbol simply by mentioning a symbol
3909 name without defining it. A non-zero value represents a @code{.comm}
3910 common declaration. The value is how much common storage to reserve, in
3911 bytes (addresses). The symbol refers to the first address of the
3917 @cindex type of a symbol
3919 The type attribute of a symbol contains relocation (section)
3920 information, any flag settings indicating that a symbol is external, and
3921 (optionally), other information for linkers and debuggers. The exact
3922 format depends on the object-code output format in use.
3927 @c The following avoids a "widow" subsection title. @group would be
3928 @c better if it were available outside examples.
3931 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3933 @cindex @code{b.out} symbol attributes
3934 @cindex symbol attributes, @code{b.out}
3935 These symbol attributes appear only when @command{@value{AS}} is configured for
3936 one of the Berkeley-descended object output formats---@code{a.out} or
3942 @subsection Symbol Attributes: @code{a.out}
3944 @cindex @code{a.out} symbol attributes
3945 @cindex symbol attributes, @code{a.out}
3951 @subsection Symbol Attributes: @code{a.out}
3953 @cindex @code{a.out} symbol attributes
3954 @cindex symbol attributes, @code{a.out}
3958 * Symbol Desc:: Descriptor
3959 * Symbol Other:: Other
3963 @subsubsection Descriptor
3965 @cindex descriptor, of @code{a.out} symbol
3966 This is an arbitrary 16-bit value. You may establish a symbol's
3967 descriptor value by using a @code{.desc} statement
3968 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3969 @command{@value{AS}}.
3972 @subsubsection Other
3974 @cindex other attribute, of @code{a.out} symbol
3975 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3980 @subsection Symbol Attributes for COFF
3982 @cindex COFF symbol attributes
3983 @cindex symbol attributes, COFF
3985 The COFF format supports a multitude of auxiliary symbol attributes;
3986 like the primary symbol attributes, they are set between @code{.def} and
3987 @code{.endef} directives.
3989 @subsubsection Primary Attributes
3991 @cindex primary attributes, COFF symbols
3992 The symbol name is set with @code{.def}; the value and type,
3993 respectively, with @code{.val} and @code{.type}.
3995 @subsubsection Auxiliary Attributes
3997 @cindex auxiliary attributes, COFF symbols
3998 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3999 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4000 table information for COFF.
4005 @subsection Symbol Attributes for SOM
4007 @cindex SOM symbol attributes
4008 @cindex symbol attributes, SOM
4010 The SOM format for the HPPA supports a multitude of symbol attributes set with
4011 the @code{.EXPORT} and @code{.IMPORT} directives.
4013 The attributes are described in @cite{HP9000 Series 800 Assembly
4014 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4015 @code{EXPORT} assembler directive documentation.
4019 @chapter Expressions
4023 @cindex numeric values
4024 An @dfn{expression} specifies an address or numeric value.
4025 Whitespace may precede and/or follow an expression.
4027 The result of an expression must be an absolute number, or else an offset into
4028 a particular section. If an expression is not absolute, and there is not
4029 enough information when @command{@value{AS}} sees the expression to know its
4030 section, a second pass over the source program might be necessary to interpret
4031 the expression---but the second pass is currently not implemented.
4032 @command{@value{AS}} aborts with an error message in this situation.
4035 * Empty Exprs:: Empty Expressions
4036 * Integer Exprs:: Integer Expressions
4040 @section Empty Expressions
4042 @cindex empty expressions
4043 @cindex expressions, empty
4044 An empty expression has no value: it is just whitespace or null.
4045 Wherever an absolute expression is required, you may omit the
4046 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4047 is compatible with other assemblers.
4050 @section Integer Expressions
4052 @cindex integer expressions
4053 @cindex expressions, integer
4054 An @dfn{integer expression} is one or more @emph{arguments} delimited
4055 by @emph{operators}.
4058 * Arguments:: Arguments
4059 * Operators:: Operators
4060 * Prefix Ops:: Prefix Operators
4061 * Infix Ops:: Infix Operators
4065 @subsection Arguments
4067 @cindex expression arguments
4068 @cindex arguments in expressions
4069 @cindex operands in expressions
4070 @cindex arithmetic operands
4071 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4072 contexts arguments are sometimes called ``arithmetic operands''. In
4073 this manual, to avoid confusing them with the ``instruction operands'' of
4074 the machine language, we use the term ``argument'' to refer to parts of
4075 expressions only, reserving the word ``operand'' to refer only to machine
4076 instruction operands.
4078 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4079 @var{section} is one of text, data, bss, absolute,
4080 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4083 Numbers are usually integers.
4085 A number can be a flonum or bignum. In this case, you are warned
4086 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4087 these 32 bits are an integer. You may write integer-manipulating
4088 instructions that act on exotic constants, compatible with other
4091 @cindex subexpressions
4092 Subexpressions are a left parenthesis @samp{(} followed by an integer
4093 expression, followed by a right parenthesis @samp{)}; or a prefix
4094 operator followed by an argument.
4097 @subsection Operators
4099 @cindex operators, in expressions
4100 @cindex arithmetic functions
4101 @cindex functions, in expressions
4102 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4103 operators are followed by an argument. Infix operators appear
4104 between their arguments. Operators may be preceded and/or followed by
4108 @subsection Prefix Operator
4110 @cindex prefix operators
4111 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4112 one argument, which must be absolute.
4114 @c the tex/end tex stuff surrounding this small table is meant to make
4115 @c it align, on the printed page, with the similar table in the next
4116 @c section (which is inside an enumerate).
4118 \global\advance\leftskip by \itemindent
4123 @dfn{Negation}. Two's complement negation.
4125 @dfn{Complementation}. Bitwise not.
4129 \global\advance\leftskip by -\itemindent
4133 @subsection Infix Operators
4135 @cindex infix operators
4136 @cindex operators, permitted arguments
4137 @dfn{Infix operators} take two arguments, one on either side. Operators
4138 have precedence, but operations with equal precedence are performed left
4139 to right. Apart from @code{+} or @option{-}, both arguments must be
4140 absolute, and the result is absolute.
4143 @cindex operator precedence
4144 @cindex precedence of operators
4151 @dfn{Multiplication}.
4154 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4160 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4163 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4167 Intermediate precedence
4172 @dfn{Bitwise Inclusive Or}.
4178 @dfn{Bitwise Exclusive Or}.
4181 @dfn{Bitwise Or Not}.
4188 @cindex addition, permitted arguments
4189 @cindex plus, permitted arguments
4190 @cindex arguments for addition
4192 @dfn{Addition}. If either argument is absolute, the result has the section of
4193 the other argument. You may not add together arguments from different
4196 @cindex subtraction, permitted arguments
4197 @cindex minus, permitted arguments
4198 @cindex arguments for subtraction
4200 @dfn{Subtraction}. If the right argument is absolute, the
4201 result has the section of the left argument.
4202 If both arguments are in the same section, the result is absolute.
4203 You may not subtract arguments from different sections.
4204 @c FIXME is there still something useful to say about undefined - undefined ?
4206 @cindex comparison expressions
4207 @cindex expressions, comparison
4212 @dfn{Is Not Equal To}
4216 @dfn{Is Greater Than}
4218 @dfn{Is Greater Than Or Equal To}
4220 @dfn{Is Less Than Or Equal To}
4222 The comparison operators can be used as infix operators. A true results has a
4223 value of -1 whereas a false result has a value of 0. Note, these operators
4224 perform signed comparisons.
4227 @item Lowest Precedence
4236 These two logical operations can be used to combine the results of sub
4237 expressions. Note, unlike the comparison operators a true result returns a
4238 value of 1 but a false results does still return 0. Also note that the logical
4239 or operator has a slightly lower precedence than logical and.
4244 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4245 address; you can only have a defined section in one of the two arguments.
4248 @chapter Assembler Directives
4250 @cindex directives, machine independent
4251 @cindex pseudo-ops, machine independent
4252 @cindex machine independent directives
4253 All assembler directives have names that begin with a period (@samp{.}).
4254 The names are case insensitive for most targets, and usually written
4257 This chapter discusses directives that are available regardless of the
4258 target machine configuration for the @sc{gnu} assembler.
4260 Some machine configurations provide additional directives.
4261 @xref{Machine Dependencies}.
4264 @ifset machine-directives
4265 @xref{Machine Dependencies}, for additional directives.
4270 * Abort:: @code{.abort}
4272 * ABORT (COFF):: @code{.ABORT}
4275 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4276 * Altmacro:: @code{.altmacro}
4277 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4278 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4279 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4280 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4281 * Byte:: @code{.byte @var{expressions}}
4282 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4283 * Comm:: @code{.comm @var{symbol} , @var{length} }
4284 * Data:: @code{.data @var{subsection}}
4286 * Def:: @code{.def @var{name}}
4289 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4295 * Double:: @code{.double @var{flonums}}
4296 * Eject:: @code{.eject}
4297 * Else:: @code{.else}
4298 * Elseif:: @code{.elseif}
4301 * Endef:: @code{.endef}
4304 * Endfunc:: @code{.endfunc}
4305 * Endif:: @code{.endif}
4306 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4307 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4308 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4310 * Error:: @code{.error @var{string}}
4311 * Exitm:: @code{.exitm}
4312 * Extern:: @code{.extern}
4313 * Fail:: @code{.fail}
4314 * File:: @code{.file}
4315 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4316 * Float:: @code{.float @var{flonums}}
4317 * Func:: @code{.func}
4318 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4320 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4321 * Hidden:: @code{.hidden @var{names}}
4324 * hword:: @code{.hword @var{expressions}}
4325 * Ident:: @code{.ident}
4326 * If:: @code{.if @var{absolute expression}}
4327 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4328 * Include:: @code{.include "@var{file}"}
4329 * Int:: @code{.int @var{expressions}}
4331 * Internal:: @code{.internal @var{names}}
4334 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4335 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4336 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4337 * Lflags:: @code{.lflags}
4338 @ifclear no-line-dir
4339 * Line:: @code{.line @var{line-number}}
4342 * Linkonce:: @code{.linkonce [@var{type}]}
4343 * List:: @code{.list}
4344 * Ln:: @code{.ln @var{line-number}}
4345 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4346 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4348 * Local:: @code{.local @var{names}}
4351 * Long:: @code{.long @var{expressions}}
4353 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4356 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4357 * MRI:: @code{.mri @var{val}}
4358 * Noaltmacro:: @code{.noaltmacro}
4359 * Nolist:: @code{.nolist}
4360 * Octa:: @code{.octa @var{bignums}}
4361 * Offset:: @code{.offset @var{loc}}
4362 * Org:: @code{.org @var{new-lc}, @var{fill}}
4363 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4365 * PopSection:: @code{.popsection}
4366 * Previous:: @code{.previous}
4369 * Print:: @code{.print @var{string}}
4371 * Protected:: @code{.protected @var{names}}
4374 * Psize:: @code{.psize @var{lines}, @var{columns}}
4375 * Purgem:: @code{.purgem @var{name}}
4377 * PushSection:: @code{.pushsection @var{name}}
4380 * Quad:: @code{.quad @var{bignums}}
4381 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4382 * Rept:: @code{.rept @var{count}}
4383 * Sbttl:: @code{.sbttl "@var{subheading}"}
4385 * Scl:: @code{.scl @var{class}}
4388 * Section:: @code{.section @var{name}[, @var{flags}]}
4391 * Set:: @code{.set @var{symbol}, @var{expression}}
4392 * Short:: @code{.short @var{expressions}}
4393 * Single:: @code{.single @var{flonums}}
4395 * Size:: @code{.size [@var{name} , @var{expression}]}
4397 @ifclear no-space-dir
4398 * Skip:: @code{.skip @var{size} , @var{fill}}
4401 * Sleb128:: @code{.sleb128 @var{expressions}}
4402 @ifclear no-space-dir
4403 * Space:: @code{.space @var{size} , @var{fill}}
4406 * Stab:: @code{.stabd, .stabn, .stabs}
4409 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4410 * Struct:: @code{.struct @var{expression}}
4412 * SubSection:: @code{.subsection}
4413 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4417 * Tag:: @code{.tag @var{structname}}
4420 * Text:: @code{.text @var{subsection}}
4421 * Title:: @code{.title "@var{heading}"}
4423 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4426 * Uleb128:: @code{.uleb128 @var{expressions}}
4428 * Val:: @code{.val @var{addr}}
4432 * Version:: @code{.version "@var{string}"}
4433 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4434 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4437 * Warning:: @code{.warning @var{string}}
4438 * Weak:: @code{.weak @var{names}}
4439 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4440 * Word:: @code{.word @var{expressions}}
4441 @ifclear no-space-dir
4442 * Zero:: @code{.zero @var{size}}
4444 * Deprecated:: Deprecated Directives
4448 @section @code{.abort}
4450 @cindex @code{abort} directive
4451 @cindex stopping the assembly
4452 This directive stops the assembly immediately. It is for
4453 compatibility with other assemblers. The original idea was that the
4454 assembly language source would be piped into the assembler. If the sender
4455 of the source quit, it could use this directive tells @command{@value{AS}} to
4456 quit also. One day @code{.abort} will not be supported.
4460 @section @code{.ABORT} (COFF)
4462 @cindex @code{ABORT} directive
4463 When producing COFF output, @command{@value{AS}} accepts this directive as a
4464 synonym for @samp{.abort}.
4467 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4473 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4475 @cindex padding the location counter
4476 @cindex @code{align} directive
4477 Pad the location counter (in the current subsection) to a particular storage
4478 boundary. The first expression (which must be absolute) is the alignment
4479 required, as described below.
4481 The second expression (also absolute) gives the fill value to be stored in the
4482 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4483 padding bytes are normally zero. However, on some systems, if the section is
4484 marked as containing code and the fill value is omitted, the space is filled
4485 with no-op instructions.
4487 The third expression is also absolute, and is also optional. If it is present,
4488 it is the maximum number of bytes that should be skipped by this alignment
4489 directive. If doing the alignment would require skipping more bytes than the
4490 specified maximum, then the alignment is not done at all. You can omit the
4491 fill value (the second argument) entirely by simply using two commas after the
4492 required alignment; this can be useful if you want the alignment to be filled
4493 with no-op instructions when appropriate.
4495 The way the required alignment is specified varies from system to system.
4496 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4497 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4498 alignment request in bytes. For example @samp{.align 8} advances
4499 the location counter until it is a multiple of 8. If the location counter
4500 is already a multiple of 8, no change is needed. For the tic54x, the
4501 first expression is the alignment request in words.
4503 For other systems, including ppc, i386 using a.out format, arm and
4504 strongarm, it is the
4505 number of low-order zero bits the location counter must have after
4506 advancement. For example @samp{.align 3} advances the location
4507 counter until it a multiple of 8. If the location counter is already a
4508 multiple of 8, no change is needed.
4510 This inconsistency is due to the different behaviors of the various
4511 native assemblers for these systems which GAS must emulate.
4512 GAS also provides @code{.balign} and @code{.p2align} directives,
4513 described later, which have a consistent behavior across all
4514 architectures (but are specific to GAS).
4517 @section @code{.altmacro}
4518 Enable alternate macro mode, enabling:
4521 @item LOCAL @var{name} [ , @dots{} ]
4522 One additional directive, @code{LOCAL}, is available. It is used to
4523 generate a string replacement for each of the @var{name} arguments, and
4524 replace any instances of @var{name} in each macro expansion. The
4525 replacement string is unique in the assembly, and different for each
4526 separate macro expansion. @code{LOCAL} allows you to write macros that
4527 define symbols, without fear of conflict between separate macro expansions.
4529 @item String delimiters
4530 You can write strings delimited in these other ways besides
4531 @code{"@var{string}"}:
4534 @item '@var{string}'
4535 You can delimit strings with single-quote characters.
4537 @item <@var{string}>
4538 You can delimit strings with matching angle brackets.
4541 @item single-character string escape
4542 To include any single character literally in a string (even if the
4543 character would otherwise have some special meaning), you can prefix the
4544 character with @samp{!} (an exclamation mark). For example, you can
4545 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4547 @item Expression results as strings
4548 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4549 and use the result as a string.
4553 @section @code{.ascii "@var{string}"}@dots{}
4555 @cindex @code{ascii} directive
4556 @cindex string literals
4557 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4558 separated by commas. It assembles each string (with no automatic
4559 trailing zero byte) into consecutive addresses.
4562 @section @code{.asciz "@var{string}"}@dots{}
4564 @cindex @code{asciz} directive
4565 @cindex zero-terminated strings
4566 @cindex null-terminated strings
4567 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4568 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4571 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4573 @cindex padding the location counter given number of bytes
4574 @cindex @code{balign} directive
4575 Pad the location counter (in the current subsection) to a particular
4576 storage boundary. The first expression (which must be absolute) is the
4577 alignment request in bytes. For example @samp{.balign 8} advances
4578 the location counter until it is a multiple of 8. If the location counter
4579 is already a multiple of 8, no change is needed.
4581 The second expression (also absolute) gives the fill value to be stored in the
4582 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4583 padding bytes are normally zero. However, on some systems, if the section is
4584 marked as containing code and the fill value is omitted, the space is filled
4585 with no-op instructions.
4587 The third expression is also absolute, and is also optional. If it is present,
4588 it is the maximum number of bytes that should be skipped by this alignment
4589 directive. If doing the alignment would require skipping more bytes than the
4590 specified maximum, then the alignment is not done at all. You can omit the
4591 fill value (the second argument) entirely by simply using two commas after the
4592 required alignment; this can be useful if you want the alignment to be filled
4593 with no-op instructions when appropriate.
4595 @cindex @code{balignw} directive
4596 @cindex @code{balignl} directive
4597 The @code{.balignw} and @code{.balignl} directives are variants of the
4598 @code{.balign} directive. The @code{.balignw} directive treats the fill
4599 pattern as a two byte word value. The @code{.balignl} directives treats the
4600 fill pattern as a four byte longword value. For example, @code{.balignw
4601 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4602 filled in with the value 0x368d (the exact placement of the bytes depends upon
4603 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4606 @node Bundle directives
4607 @section Bundle directives
4608 @subsection @code{.bundle_align_mode @var{abs-expr}}
4609 @cindex @code{bundle_align_mode} directive
4611 @cindex instruction bundle
4612 @cindex aligned instruction bundle
4613 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4614 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4615 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4616 disabled (which is the default state). If the argument it not zero, it
4617 gives the size of an instruction bundle as a power of two (as for the
4618 @code{.p2align} directive, @pxref{P2align}).
4620 For some targets, it's an ABI requirement that no instruction may span a
4621 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4622 instructions that starts on an aligned boundary. For example, if
4623 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4624 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4625 effect, no single instruction may span a boundary between bundles. If an
4626 instruction would start too close to the end of a bundle for the length of
4627 that particular instruction to fit within the bundle, then the space at the
4628 end of that bundle is filled with no-op instructions so the instruction
4629 starts in the next bundle. As a corollary, it's an error if any single
4630 instruction's encoding is longer than the bundle size.
4632 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4633 @cindex @code{bundle_lock} directive
4634 @cindex @code{bundle_unlock} directive
4635 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4636 allow explicit control over instruction bundle padding. These directives
4637 are only valid when @code{.bundle_align_mode} has been used to enable
4638 aligned instruction bundle mode. It's an error if they appear when
4639 @code{.bundle_align_mode} has not been used at all, or when the last
4640 directive was @w{@code{.bundle_align_mode 0}}.
4642 @cindex bundle-locked
4643 For some targets, it's an ABI requirement that certain instructions may
4644 appear only as part of specified permissible sequences of multiple
4645 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4646 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4647 instruction sequence. For purposes of aligned instruction bundle mode, a
4648 sequence starting with @code{.bundle_lock} and ending with
4649 @code{.bundle_unlock} is treated as a single instruction. That is, the
4650 entire sequence must fit into a single bundle and may not span a bundle
4651 boundary. If necessary, no-op instructions will be inserted before the
4652 first instruction of the sequence so that the whole sequence starts on an
4653 aligned bundle boundary. It's an error if the sequence is longer than the
4656 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4657 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4658 nested. That is, a second @code{.bundle_lock} directive before the next
4659 @code{.bundle_unlock} directive has no effect except that it must be
4660 matched by another closing @code{.bundle_unlock} so that there is the
4661 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4664 @section @code{.byte @var{expressions}}
4666 @cindex @code{byte} directive
4667 @cindex integers, one byte
4668 @code{.byte} expects zero or more expressions, separated by commas.
4669 Each expression is assembled into the next byte.
4671 @node CFI directives
4672 @section CFI directives
4673 @subsection @code{.cfi_sections @var{section_list}}
4674 @cindex @code{cfi_sections} directive
4675 @code{.cfi_sections} may be used to specify whether CFI directives
4676 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4677 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4678 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4679 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4680 directive is not used is @code{.cfi_sections .eh_frame}.
4682 On targets that support compact unwinding tables these can be generated
4683 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4685 @subsection @code{.cfi_startproc [simple]}
4686 @cindex @code{cfi_startproc} directive
4687 @code{.cfi_startproc} is used at the beginning of each function that
4688 should have an entry in @code{.eh_frame}. It initializes some internal
4689 data structures. Don't forget to close the function by
4690 @code{.cfi_endproc}.
4692 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4693 it also emits some architecture dependent initial CFI instructions.
4695 @subsection @code{.cfi_endproc}
4696 @cindex @code{cfi_endproc} directive
4697 @code{.cfi_endproc} is used at the end of a function where it closes its
4698 unwind entry previously opened by
4699 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4701 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4702 @cindex @code{cfi_personality} directive
4703 @code{.cfi_personality} defines personality routine and its encoding.
4704 @var{encoding} must be a constant determining how the personality
4705 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4706 argument is not present, otherwise second argument should be
4707 a constant or a symbol name. When using indirect encodings,
4708 the symbol provided should be the location where personality
4709 can be loaded from, not the personality routine itself.
4710 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4711 no personality routine.
4713 @subsection @code{.cfi_personality_id @var{id}}
4714 @cindex @code{cfi_personality_id} directive
4715 @code{cfi_personality_id} defines a personality routine by its index as
4716 defined in a compact unwinding format.
4717 Only valid when generating compact EH frames (i.e.
4718 with @code{.cfi_sections eh_frame_entry}.
4720 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4721 @cindex @code{cfi_fde_data} directive
4722 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4723 used for the current function. These are emitted inline in the
4724 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4725 in the @code{.gnu.extab} section otherwise.
4726 Only valid when generating compact EH frames (i.e.
4727 with @code{.cfi_sections eh_frame_entry}.
4729 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4730 @code{.cfi_lsda} defines LSDA and its encoding.
4731 @var{encoding} must be a constant determining how the LSDA
4732 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4733 argument is not present, otherwise the second argument should be a constant
4734 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4735 meaning that no LSDA is present.
4737 @subsection @code{.cfi_inline_lsda} [@var{align}]
4738 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4739 switches to the corresponding @code{.gnu.extab} section.
4740 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4741 Only valid when generating compact EH frames (i.e.
4742 with @code{.cfi_sections eh_frame_entry}.
4744 The table header and unwinding opcodes will be generated at this point,
4745 so that they are immediately followed by the LSDA data. The symbol
4746 referenced by the @code{.cfi_lsda} directive should still be defined
4747 in case a fallback FDE based encoding is used. The LSDA data is terminated
4748 by a section directive.
4750 The optional @var{align} argument specifies the alignment required.
4751 The alignment is specified as a power of two, as with the
4752 @code{.p2align} directive.
4754 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4755 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4756 address from @var{register} and add @var{offset} to it}.
4758 @subsection @code{.cfi_def_cfa_register @var{register}}
4759 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4760 now on @var{register} will be used instead of the old one. Offset
4763 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4764 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4765 remains the same, but @var{offset} is new. Note that it is the
4766 absolute offset that will be added to a defined register to compute
4769 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4770 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4771 value that is added/substracted from the previous offset.
4773 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4774 Previous value of @var{register} is saved at offset @var{offset} from
4777 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4778 Previous value of @var{register} is saved at offset @var{offset} from
4779 the current CFA register. This is transformed to @code{.cfi_offset}
4780 using the known displacement of the CFA register from the CFA.
4781 This is often easier to use, because the number will match the
4782 code it's annotating.
4784 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4785 Previous value of @var{register1} is saved in register @var{register2}.
4787 @subsection @code{.cfi_restore @var{register}}
4788 @code{.cfi_restore} says that the rule for @var{register} is now the
4789 same as it was at the beginning of the function, after all initial
4790 instruction added by @code{.cfi_startproc} were executed.
4792 @subsection @code{.cfi_undefined @var{register}}
4793 From now on the previous value of @var{register} can't be restored anymore.
4795 @subsection @code{.cfi_same_value @var{register}}
4796 Current value of @var{register} is the same like in the previous frame,
4797 i.e. no restoration needed.
4799 @subsection @code{.cfi_remember_state},
4800 First save all current rules for all registers by @code{.cfi_remember_state},
4801 then totally screw them up by subsequent @code{.cfi_*} directives and when
4802 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4803 the previous saved state.
4805 @subsection @code{.cfi_return_column @var{register}}
4806 Change return column @var{register}, i.e. the return address is either
4807 directly in @var{register} or can be accessed by rules for @var{register}.
4809 @subsection @code{.cfi_signal_frame}
4810 Mark current function as signal trampoline.
4812 @subsection @code{.cfi_window_save}
4813 SPARC register window has been saved.
4815 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4816 Allows the user to add arbitrary bytes to the unwind info. One
4817 might use this to add OS-specific CFI opcodes, or generic CFI
4818 opcodes that GAS does not yet support.
4820 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4821 The current value of @var{register} is @var{label}. The value of @var{label}
4822 will be encoded in the output file according to @var{encoding}; see the
4823 description of @code{.cfi_personality} for details on this encoding.
4825 The usefulness of equating a register to a fixed label is probably
4826 limited to the return address register. Here, it can be useful to
4827 mark a code segment that has only one return address which is reached
4828 by a direct branch and no copy of the return address exists in memory
4829 or another register.
4832 @section @code{.comm @var{symbol} , @var{length} }
4834 @cindex @code{comm} directive
4835 @cindex symbol, common
4836 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4837 common symbol in one object file may be merged with a defined or common symbol
4838 of the same name in another object file. If @code{@value{LD}} does not see a
4839 definition for the symbol--just one or more common symbols--then it will
4840 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4841 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4842 the same name, and they do not all have the same size, it will allocate space
4843 using the largest size.
4846 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4847 an optional third argument. This is the desired alignment of the symbol,
4848 specified for ELF as a byte boundary (for example, an alignment of 16 means
4849 that the least significant 4 bits of the address should be zero), and for PE
4850 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4851 boundary). The alignment must be an absolute expression, and it must be a
4852 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4853 common symbol, it will use the alignment when placing the symbol. If no
4854 alignment is specified, @command{@value{AS}} will set the alignment to the
4855 largest power of two less than or equal to the size of the symbol, up to a
4856 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4857 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4858 @samp{--section-alignment} option; image file sections in PE are aligned to
4859 multiples of 4096, which is far too large an alignment for ordinary variables.
4860 It is rather the default alignment for (non-debug) sections within object
4861 (@samp{*.o}) files, which are less strictly aligned.}.
4865 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4866 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4870 @section @code{.data @var{subsection}}
4872 @cindex @code{data} directive
4873 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4874 end of the data subsection numbered @var{subsection} (which is an
4875 absolute expression). If @var{subsection} is omitted, it defaults
4880 @section @code{.def @var{name}}
4882 @cindex @code{def} directive
4883 @cindex COFF symbols, debugging
4884 @cindex debugging COFF symbols
4885 Begin defining debugging information for a symbol @var{name}; the
4886 definition extends until the @code{.endef} directive is encountered.
4889 This directive is only observed when @command{@value{AS}} is configured for COFF
4890 format output; when producing @code{b.out}, @samp{.def} is recognized,
4897 @section @code{.desc @var{symbol}, @var{abs-expression}}
4899 @cindex @code{desc} directive
4900 @cindex COFF symbol descriptor
4901 @cindex symbol descriptor, COFF
4902 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4903 to the low 16 bits of an absolute expression.
4906 The @samp{.desc} directive is not available when @command{@value{AS}} is
4907 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4908 object format. For the sake of compatibility, @command{@value{AS}} accepts
4909 it, but produces no output, when configured for COFF.
4915 @section @code{.dim}
4917 @cindex @code{dim} directive
4918 @cindex COFF auxiliary symbol information
4919 @cindex auxiliary symbol information, COFF
4920 This directive is generated by compilers to include auxiliary debugging
4921 information in the symbol table. It is only permitted inside
4922 @code{.def}/@code{.endef} pairs.
4925 @samp{.dim} is only meaningful when generating COFF format output; when
4926 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4932 @section @code{.double @var{flonums}}
4934 @cindex @code{double} directive
4935 @cindex floating point numbers (double)
4936 @code{.double} expects zero or more flonums, separated by commas. It
4937 assembles floating point numbers.
4939 The exact kind of floating point numbers emitted depends on how
4940 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4944 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4945 in @sc{ieee} format.
4950 @section @code{.eject}
4952 @cindex @code{eject} directive
4953 @cindex new page, in listings
4954 @cindex page, in listings
4955 @cindex listing control: new page
4956 Force a page break at this point, when generating assembly listings.
4959 @section @code{.else}
4961 @cindex @code{else} directive
4962 @code{.else} is part of the @command{@value{AS}} support for conditional
4963 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4964 of code to be assembled if the condition for the preceding @code{.if}
4968 @section @code{.elseif}
4970 @cindex @code{elseif} directive
4971 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4972 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4973 @code{.if} block that would otherwise fill the entire @code{.else} section.
4976 @section @code{.end}
4978 @cindex @code{end} directive
4979 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4980 process anything in the file past the @code{.end} directive.
4984 @section @code{.endef}
4986 @cindex @code{endef} directive
4987 This directive flags the end of a symbol definition begun with
4991 @samp{.endef} is only meaningful when generating COFF format output; if
4992 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4993 directive but ignores it.
4998 @section @code{.endfunc}
4999 @cindex @code{endfunc} directive
5000 @code{.endfunc} marks the end of a function specified with @code{.func}.
5003 @section @code{.endif}
5005 @cindex @code{endif} directive
5006 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5007 it marks the end of a block of code that is only assembled
5008 conditionally. @xref{If,,@code{.if}}.
5011 @section @code{.equ @var{symbol}, @var{expression}}
5013 @cindex @code{equ} directive
5014 @cindex assigning values to symbols
5015 @cindex symbols, assigning values to
5016 This directive sets the value of @var{symbol} to @var{expression}.
5017 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5020 The syntax for @code{equ} on the HPPA is
5021 @samp{@var{symbol} .equ @var{expression}}.
5025 The syntax for @code{equ} on the Z80 is
5026 @samp{@var{symbol} equ @var{expression}}.
5027 On the Z80 it is an eror if @var{symbol} is already defined,
5028 but the symbol is not protected from later redefinition.
5029 Compare @ref{Equiv}.
5033 @section @code{.equiv @var{symbol}, @var{expression}}
5034 @cindex @code{equiv} directive
5035 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5036 the assembler will signal an error if @var{symbol} is already defined. Note a
5037 symbol which has been referenced but not actually defined is considered to be
5040 Except for the contents of the error message, this is roughly equivalent to
5047 plus it protects the symbol from later redefinition.
5050 @section @code{.eqv @var{symbol}, @var{expression}}
5051 @cindex @code{eqv} directive
5052 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5053 evaluate the expression or any part of it immediately. Instead each time
5054 the resulting symbol is used in an expression, a snapshot of its current
5058 @section @code{.err}
5059 @cindex @code{err} directive
5060 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5061 message and, unless the @option{-Z} option was used, it will not generate an
5062 object file. This can be used to signal an error in conditionally compiled code.
5065 @section @code{.error "@var{string}"}
5066 @cindex error directive
5068 Similarly to @code{.err}, this directive emits an error, but you can specify a
5069 string that will be emitted as the error message. If you don't specify the
5070 message, it defaults to @code{".error directive invoked in source file"}.
5071 @xref{Errors, ,Error and Warning Messages}.
5074 .error "This code has not been assembled and tested."
5078 @section @code{.exitm}
5079 Exit early from the current macro definition. @xref{Macro}.
5082 @section @code{.extern}
5084 @cindex @code{extern} directive
5085 @code{.extern} is accepted in the source program---for compatibility
5086 with other assemblers---but it is ignored. @command{@value{AS}} treats
5087 all undefined symbols as external.
5090 @section @code{.fail @var{expression}}
5092 @cindex @code{fail} directive
5093 Generates an error or a warning. If the value of the @var{expression} is 500
5094 or more, @command{@value{AS}} will print a warning message. If the value is less
5095 than 500, @command{@value{AS}} will print an error message. The message will
5096 include the value of @var{expression}. This can occasionally be useful inside
5097 complex nested macros or conditional assembly.
5100 @section @code{.file}
5101 @cindex @code{file} directive
5103 @ifclear no-file-dir
5104 There are two different versions of the @code{.file} directive. Targets
5105 that support DWARF2 line number information use the DWARF2 version of
5106 @code{.file}. Other targets use the default version.
5108 @subheading Default Version
5110 @cindex logical file name
5111 @cindex file name, logical
5112 This version of the @code{.file} directive tells @command{@value{AS}} that we
5113 are about to start a new logical file. The syntax is:
5119 @var{string} is the new file name. In general, the filename is
5120 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5121 to specify an empty file name, you must give the quotes--@code{""}. This
5122 statement may go away in future: it is only recognized to be compatible with
5123 old @command{@value{AS}} programs.
5125 @subheading DWARF2 Version
5128 When emitting DWARF2 line number information, @code{.file} assigns filenames
5129 to the @code{.debug_line} file name table. The syntax is:
5132 .file @var{fileno} @var{filename}
5135 The @var{fileno} operand should be a unique positive integer to use as the
5136 index of the entry in the table. The @var{filename} operand is a C string
5139 The detail of filename indices is exposed to the user because the filename
5140 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5141 information, and thus the user must know the exact indices that table
5145 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5147 @cindex @code{fill} directive
5148 @cindex writing patterns in memory
5149 @cindex patterns, writing in memory
5150 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5151 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5152 may be zero or more. @var{Size} may be zero or more, but if it is
5153 more than 8, then it is deemed to have the value 8, compatible with
5154 other people's assemblers. The contents of each @var{repeat} bytes
5155 is taken from an 8-byte number. The highest order 4 bytes are
5156 zero. The lowest order 4 bytes are @var{value} rendered in the
5157 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5158 Each @var{size} bytes in a repetition is taken from the lowest order
5159 @var{size} bytes of this number. Again, this bizarre behavior is
5160 compatible with other people's assemblers.
5162 @var{size} and @var{value} are optional.
5163 If the second comma and @var{value} are absent, @var{value} is
5164 assumed zero. If the first comma and following tokens are absent,
5165 @var{size} is assumed to be 1.
5168 @section @code{.float @var{flonums}}
5170 @cindex floating point numbers (single)
5171 @cindex @code{float} directive
5172 This directive assembles zero or more flonums, separated by commas. It
5173 has the same effect as @code{.single}.
5175 The exact kind of floating point numbers emitted depends on how
5176 @command{@value{AS}} is configured.
5177 @xref{Machine Dependencies}.
5181 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5182 in @sc{ieee} format.
5187 @section @code{.func @var{name}[,@var{label}]}
5188 @cindex @code{func} directive
5189 @code{.func} emits debugging information to denote function @var{name}, and
5190 is ignored unless the file is assembled with debugging enabled.
5191 Only @samp{--gstabs[+]} is currently supported.
5192 @var{label} is the entry point of the function and if omitted @var{name}
5193 prepended with the @samp{leading char} is used.
5194 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5195 All functions are currently defined to have @code{void} return type.
5196 The function must be terminated with @code{.endfunc}.
5199 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5201 @cindex @code{global} directive
5202 @cindex symbol, making visible to linker
5203 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5204 @var{symbol} in your partial program, its value is made available to
5205 other partial programs that are linked with it. Otherwise,
5206 @var{symbol} takes its attributes from a symbol of the same name
5207 from another file linked into the same program.
5209 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5210 compatibility with other assemblers.
5213 On the HPPA, @code{.global} is not always enough to make it accessible to other
5214 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5215 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5220 @section @code{.gnu_attribute @var{tag},@var{value}}
5221 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5224 @section @code{.hidden @var{names}}
5226 @cindex @code{hidden} directive
5228 This is one of the ELF visibility directives. The other two are
5229 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5230 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5232 This directive overrides the named symbols default visibility (which is set by
5233 their binding: local, global or weak). The directive sets the visibility to
5234 @code{hidden} which means that the symbols are not visible to other components.
5235 Such symbols are always considered to be @code{protected} as well.
5239 @section @code{.hword @var{expressions}}
5241 @cindex @code{hword} directive
5242 @cindex integers, 16-bit
5243 @cindex numbers, 16-bit
5244 @cindex sixteen bit integers
5245 This expects zero or more @var{expressions}, and emits
5246 a 16 bit number for each.
5249 This directive is a synonym for @samp{.short}; depending on the target
5250 architecture, it may also be a synonym for @samp{.word}.
5254 This directive is a synonym for @samp{.short}.
5257 This directive is a synonym for both @samp{.short} and @samp{.word}.
5262 @section @code{.ident}
5264 @cindex @code{ident} directive
5266 This directive is used by some assemblers to place tags in object files. The
5267 behavior of this directive varies depending on the target. When using the
5268 a.out object file format, @command{@value{AS}} simply accepts the directive for
5269 source-file compatibility with existing assemblers, but does not emit anything
5270 for it. When using COFF, comments are emitted to the @code{.comment} or
5271 @code{.rdata} section, depending on the target. When using ELF, comments are
5272 emitted to the @code{.comment} section.
5275 @section @code{.if @var{absolute expression}}
5277 @cindex conditional assembly
5278 @cindex @code{if} directive
5279 @code{.if} marks the beginning of a section of code which is only
5280 considered part of the source program being assembled if the argument
5281 (which must be an @var{absolute expression}) is non-zero. The end of
5282 the conditional section of code must be marked by @code{.endif}
5283 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5284 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5285 If you have several conditions to check, @code{.elseif} may be used to avoid
5286 nesting blocks if/else within each subsequent @code{.else} block.
5288 The following variants of @code{.if} are also supported:
5290 @cindex @code{ifdef} directive
5291 @item .ifdef @var{symbol}
5292 Assembles the following section of code if the specified @var{symbol}
5293 has been defined. Note a symbol which has been referenced but not yet defined
5294 is considered to be undefined.
5296 @cindex @code{ifb} directive
5297 @item .ifb @var{text}
5298 Assembles the following section of code if the operand is blank (empty).
5300 @cindex @code{ifc} directive
5301 @item .ifc @var{string1},@var{string2}
5302 Assembles the following section of code if the two strings are the same. The
5303 strings may be optionally quoted with single quotes. If they are not quoted,
5304 the first string stops at the first comma, and the second string stops at the
5305 end of the line. Strings which contain whitespace should be quoted. The
5306 string comparison is case sensitive.
5308 @cindex @code{ifeq} directive
5309 @item .ifeq @var{absolute expression}
5310 Assembles the following section of code if the argument is zero.
5312 @cindex @code{ifeqs} directive
5313 @item .ifeqs @var{string1},@var{string2}
5314 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5316 @cindex @code{ifge} directive
5317 @item .ifge @var{absolute expression}
5318 Assembles the following section of code if the argument is greater than or
5321 @cindex @code{ifgt} directive
5322 @item .ifgt @var{absolute expression}
5323 Assembles the following section of code if the argument is greater than zero.
5325 @cindex @code{ifle} directive
5326 @item .ifle @var{absolute expression}
5327 Assembles the following section of code if the argument is less than or equal
5330 @cindex @code{iflt} directive
5331 @item .iflt @var{absolute expression}
5332 Assembles the following section of code if the argument is less than zero.
5334 @cindex @code{ifnb} directive
5335 @item .ifnb @var{text}
5336 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5337 following section of code if the operand is non-blank (non-empty).
5339 @cindex @code{ifnc} directive
5340 @item .ifnc @var{string1},@var{string2}.
5341 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5342 following section of code if the two strings are not the same.
5344 @cindex @code{ifndef} directive
5345 @cindex @code{ifnotdef} directive
5346 @item .ifndef @var{symbol}
5347 @itemx .ifnotdef @var{symbol}
5348 Assembles the following section of code if the specified @var{symbol}
5349 has not been defined. Both spelling variants are equivalent. Note a symbol
5350 which has been referenced but not yet defined is considered to be undefined.
5352 @cindex @code{ifne} directive
5353 @item .ifne @var{absolute expression}
5354 Assembles the following section of code if the argument is not equal to zero
5355 (in other words, this is equivalent to @code{.if}).
5357 @cindex @code{ifnes} directive
5358 @item .ifnes @var{string1},@var{string2}
5359 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5360 following section of code if the two strings are not the same.
5364 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5366 @cindex @code{incbin} directive
5367 @cindex binary files, including
5368 The @code{incbin} directive includes @var{file} verbatim at the current
5369 location. You can control the search paths used with the @samp{-I} command-line
5370 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5373 The @var{skip} argument skips a number of bytes from the start of the
5374 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5375 read. Note that the data is not aligned in any way, so it is the user's
5376 responsibility to make sure that proper alignment is provided both before and
5377 after the @code{incbin} directive.
5380 @section @code{.include "@var{file}"}
5382 @cindex @code{include} directive
5383 @cindex supporting files, including
5384 @cindex files, including
5385 This directive provides a way to include supporting files at specified
5386 points in your source program. The code from @var{file} is assembled as
5387 if it followed the point of the @code{.include}; when the end of the
5388 included file is reached, assembly of the original file continues. You
5389 can control the search paths used with the @samp{-I} command-line option
5390 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5394 @section @code{.int @var{expressions}}
5396 @cindex @code{int} directive
5397 @cindex integers, 32-bit
5398 Expect zero or more @var{expressions}, of any section, separated by commas.
5399 For each expression, emit a number that, at run time, is the value of that
5400 expression. The byte order and bit size of the number depends on what kind
5401 of target the assembly is for.
5405 On most forms of the H8/300, @code{.int} emits 16-bit
5406 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5413 @section @code{.internal @var{names}}
5415 @cindex @code{internal} directive
5417 This is one of the ELF visibility directives. The other two are
5418 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5419 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5421 This directive overrides the named symbols default visibility (which is set by
5422 their binding: local, global or weak). The directive sets the visibility to
5423 @code{internal} which means that the symbols are considered to be @code{hidden}
5424 (i.e., not visible to other components), and that some extra, processor specific
5425 processing must also be performed upon the symbols as well.
5429 @section @code{.irp @var{symbol},@var{values}}@dots{}
5431 @cindex @code{irp} directive
5432 Evaluate a sequence of statements assigning different values to @var{symbol}.
5433 The sequence of statements starts at the @code{.irp} directive, and is
5434 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5435 set to @var{value}, and the sequence of statements is assembled. If no
5436 @var{value} is listed, the sequence of statements is assembled once, with
5437 @var{symbol} set to the null string. To refer to @var{symbol} within the
5438 sequence of statements, use @var{\symbol}.
5440 For example, assembling
5448 is equivalent to assembling
5456 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5459 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5461 @cindex @code{irpc} directive
5462 Evaluate a sequence of statements assigning different values to @var{symbol}.
5463 The sequence of statements starts at the @code{.irpc} directive, and is
5464 terminated by an @code{.endr} directive. For each character in @var{value},
5465 @var{symbol} is set to the character, and the sequence of statements is
5466 assembled. If no @var{value} is listed, the sequence of statements is
5467 assembled once, with @var{symbol} set to the null string. To refer to
5468 @var{symbol} within the sequence of statements, use @var{\symbol}.
5470 For example, assembling
5478 is equivalent to assembling
5486 For some caveats with the spelling of @var{symbol}, see also the discussion
5490 @section @code{.lcomm @var{symbol} , @var{length}}
5492 @cindex @code{lcomm} directive
5493 @cindex local common symbols
5494 @cindex symbols, local common
5495 Reserve @var{length} (an absolute expression) bytes for a local common
5496 denoted by @var{symbol}. The section and value of @var{symbol} are
5497 those of the new local common. The addresses are allocated in the bss
5498 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5499 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5500 not visible to @code{@value{LD}}.
5503 Some targets permit a third argument to be used with @code{.lcomm}. This
5504 argument specifies the desired alignment of the symbol in the bss section.
5508 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5509 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5513 @section @code{.lflags}
5515 @cindex @code{lflags} directive (ignored)
5516 @command{@value{AS}} accepts this directive, for compatibility with other
5517 assemblers, but ignores it.
5519 @ifclear no-line-dir
5521 @section @code{.line @var{line-number}}
5523 @cindex @code{line} directive
5524 @cindex logical line number
5526 Change the logical line number. @var{line-number} must be an absolute
5527 expression. The next line has that logical line number. Therefore any other
5528 statements on the current line (after a statement separator character) are
5529 reported as on logical line number @var{line-number} @minus{} 1. One day
5530 @command{@value{AS}} will no longer support this directive: it is recognized only
5531 for compatibility with existing assembler programs.
5534 Even though this is a directive associated with the @code{a.out} or
5535 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5536 when producing COFF output, and treats @samp{.line} as though it
5537 were the COFF @samp{.ln} @emph{if} it is found outside a
5538 @code{.def}/@code{.endef} pair.
5540 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5541 used by compilers to generate auxiliary symbol information for
5546 @section @code{.linkonce [@var{type}]}
5548 @cindex @code{linkonce} directive
5549 @cindex common sections
5550 Mark the current section so that the linker only includes a single copy of it.
5551 This may be used to include the same section in several different object files,
5552 but ensure that the linker will only include it once in the final output file.
5553 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5554 Duplicate sections are detected based on the section name, so it should be
5557 This directive is only supported by a few object file formats; as of this
5558 writing, the only object file format which supports it is the Portable
5559 Executable format used on Windows NT.
5561 The @var{type} argument is optional. If specified, it must be one of the
5562 following strings. For example:
5566 Not all types may be supported on all object file formats.
5570 Silently discard duplicate sections. This is the default.
5573 Warn if there are duplicate sections, but still keep only one copy.
5576 Warn if any of the duplicates have different sizes.
5579 Warn if any of the duplicates do not have exactly the same contents.
5583 @section @code{.list}
5585 @cindex @code{list} directive
5586 @cindex listing control, turning on
5587 Control (in conjunction with the @code{.nolist} directive) whether or
5588 not assembly listings are generated. These two directives maintain an
5589 internal counter (which is zero initially). @code{.list} increments the
5590 counter, and @code{.nolist} decrements it. Assembly listings are
5591 generated whenever the counter is greater than zero.
5593 By default, listings are disabled. When you enable them (with the
5594 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5595 the initial value of the listing counter is one.
5598 @section @code{.ln @var{line-number}}
5600 @cindex @code{ln} directive
5601 @ifclear no-line-dir
5602 @samp{.ln} is a synonym for @samp{.line}.
5605 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5606 must be an absolute expression. The next line has that logical
5607 line number, so any other statements on the current line (after a
5608 statement separator character @code{;}) are reported as on logical
5609 line number @var{line-number} @minus{} 1.
5612 This directive is accepted, but ignored, when @command{@value{AS}} is
5613 configured for @code{b.out}; its effect is only associated with COFF
5619 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5620 @cindex @code{loc} directive
5621 When emitting DWARF2 line number information,
5622 the @code{.loc} directive will add a row to the @code{.debug_line} line
5623 number matrix corresponding to the immediately following assembly
5624 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5625 arguments will be applied to the @code{.debug_line} state machine before
5628 The @var{options} are a sequence of the following tokens in any order:
5632 This option will set the @code{basic_block} register in the
5633 @code{.debug_line} state machine to @code{true}.
5636 This option will set the @code{prologue_end} register in the
5637 @code{.debug_line} state machine to @code{true}.
5639 @item epilogue_begin
5640 This option will set the @code{epilogue_begin} register in the
5641 @code{.debug_line} state machine to @code{true}.
5643 @item is_stmt @var{value}
5644 This option will set the @code{is_stmt} register in the
5645 @code{.debug_line} state machine to @code{value}, which must be
5648 @item isa @var{value}
5649 This directive will set the @code{isa} register in the @code{.debug_line}
5650 state machine to @var{value}, which must be an unsigned integer.
5652 @item discriminator @var{value}
5653 This directive will set the @code{discriminator} register in the @code{.debug_line}
5654 state machine to @var{value}, which must be an unsigned integer.
5658 @node Loc_mark_labels
5659 @section @code{.loc_mark_labels @var{enable}}
5660 @cindex @code{loc_mark_labels} directive
5661 When emitting DWARF2 line number information,
5662 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5663 to the @code{.debug_line} line number matrix with the @code{basic_block}
5664 register in the state machine set whenever a code label is seen.
5665 The @var{enable} argument should be either 1 or 0, to enable or disable
5666 this function respectively.
5670 @section @code{.local @var{names}}
5672 @cindex @code{local} directive
5673 This directive, which is available for ELF targets, marks each symbol in
5674 the comma-separated list of @code{names} as a local symbol so that it
5675 will not be externally visible. If the symbols do not already exist,
5676 they will be created.
5678 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5679 accept an alignment argument, which is the case for most ELF targets,
5680 the @code{.local} directive can be used in combination with @code{.comm}
5681 (@pxref{Comm}) to define aligned local common data.
5685 @section @code{.long @var{expressions}}
5687 @cindex @code{long} directive
5688 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5691 @c no one seems to know what this is for or whether this description is
5692 @c what it really ought to do
5694 @section @code{.lsym @var{symbol}, @var{expression}}
5696 @cindex @code{lsym} directive
5697 @cindex symbol, not referenced in assembly
5698 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5699 the hash table, ensuring it cannot be referenced by name during the
5700 rest of the assembly. This sets the attributes of the symbol to be
5701 the same as the expression value:
5703 @var{other} = @var{descriptor} = 0
5704 @var{type} = @r{(section of @var{expression})}
5705 @var{value} = @var{expression}
5708 The new symbol is not flagged as external.
5712 @section @code{.macro}
5715 The commands @code{.macro} and @code{.endm} allow you to define macros that
5716 generate assembly output. For example, this definition specifies a macro
5717 @code{sum} that puts a sequence of numbers into memory:
5720 .macro sum from=0, to=5
5729 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5741 @item .macro @var{macname}
5742 @itemx .macro @var{macname} @var{macargs} @dots{}
5743 @cindex @code{macro} directive
5744 Begin the definition of a macro called @var{macname}. If your macro
5745 definition requires arguments, specify their names after the macro name,
5746 separated by commas or spaces. You can qualify the macro argument to
5747 indicate whether all invocations must specify a non-blank value (through
5748 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5749 (through @samp{:@code{vararg}}). You can supply a default value for any
5750 macro argument by following the name with @samp{=@var{deflt}}. You
5751 cannot define two macros with the same @var{macname} unless it has been
5752 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5753 definitions. For example, these are all valid @code{.macro} statements:
5757 Begin the definition of a macro called @code{comm}, which takes no
5760 @item .macro plus1 p, p1
5761 @itemx .macro plus1 p p1
5762 Either statement begins the definition of a macro called @code{plus1},
5763 which takes two arguments; within the macro definition, write
5764 @samp{\p} or @samp{\p1} to evaluate the arguments.
5766 @item .macro reserve_str p1=0 p2
5767 Begin the definition of a macro called @code{reserve_str}, with two
5768 arguments. The first argument has a default value, but not the second.
5769 After the definition is complete, you can call the macro either as
5770 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5771 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5772 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5773 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5775 @item .macro m p1:req, p2=0, p3:vararg
5776 Begin the definition of a macro called @code{m}, with at least three
5777 arguments. The first argument must always have a value specified, but
5778 not the second, which instead has a default value. The third formal
5779 will get assigned all remaining arguments specified at invocation time.
5781 When you call a macro, you can specify the argument values either by
5782 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5783 @samp{sum to=17, from=9}.
5787 Note that since each of the @var{macargs} can be an identifier exactly
5788 as any other one permitted by the target architecture, there may be
5789 occasional problems if the target hand-crafts special meanings to certain
5790 characters when they occur in a special position. For example, if the colon
5791 (@code{:}) is generally permitted to be part of a symbol name, but the
5792 architecture specific code special-cases it when occurring as the final
5793 character of a symbol (to denote a label), then the macro parameter
5794 replacement code will have no way of knowing that and consider the whole
5795 construct (including the colon) an identifier, and check only this
5796 identifier for being the subject to parameter substitution. So for example
5797 this macro definition:
5805 might not work as expected. Invoking @samp{label foo} might not create a label
5806 called @samp{foo} but instead just insert the text @samp{\l:} into the
5807 assembler source, probably generating an error about an unrecognised
5810 Similarly problems might occur with the period character (@samp{.})
5811 which is often allowed inside opcode names (and hence identifier names). So
5812 for example constructing a macro to build an opcode from a base name and a
5813 length specifier like this:
5816 .macro opcode base length
5821 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5822 instruction but instead generate some kind of error as the assembler tries to
5823 interpret the text @samp{\base.\length}.
5825 There are several possible ways around this problem:
5828 @item Insert white space
5829 If it is possible to use white space characters then this is the simplest
5838 @item Use @samp{\()}
5839 The string @samp{\()} can be used to separate the end of a macro argument from
5840 the following text. eg:
5843 .macro opcode base length
5848 @item Use the alternate macro syntax mode
5849 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5850 used as a separator. eg:
5860 Note: this problem of correctly identifying string parameters to pseudo ops
5861 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5862 and @code{.irpc} (@pxref{Irpc}) as well.
5865 @cindex @code{endm} directive
5866 Mark the end of a macro definition.
5869 @cindex @code{exitm} directive
5870 Exit early from the current macro definition.
5872 @cindex number of macros executed
5873 @cindex macros, count executed
5875 @command{@value{AS}} maintains a counter of how many macros it has
5876 executed in this pseudo-variable; you can copy that number to your
5877 output with @samp{\@@}, but @emph{only within a macro definition}.
5879 @item LOCAL @var{name} [ , @dots{} ]
5880 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5881 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5882 @xref{Altmacro,,@code{.altmacro}}.
5886 @section @code{.mri @var{val}}
5888 @cindex @code{mri} directive
5889 @cindex MRI mode, temporarily
5890 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5891 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5892 affects code assembled until the next @code{.mri} directive, or until the end
5893 of the file. @xref{M, MRI mode, MRI mode}.
5896 @section @code{.noaltmacro}
5897 Disable alternate macro mode. @xref{Altmacro}.
5900 @section @code{.nolist}
5902 @cindex @code{nolist} directive
5903 @cindex listing control, turning off
5904 Control (in conjunction with the @code{.list} directive) whether or
5905 not assembly listings are generated. These two directives maintain an
5906 internal counter (which is zero initially). @code{.list} increments the
5907 counter, and @code{.nolist} decrements it. Assembly listings are
5908 generated whenever the counter is greater than zero.
5911 @section @code{.octa @var{bignums}}
5913 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5914 @cindex @code{octa} directive
5915 @cindex integer, 16-byte
5916 @cindex sixteen byte integer
5917 This directive expects zero or more bignums, separated by commas. For each
5918 bignum, it emits a 16-byte integer.
5920 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5921 hence @emph{octa}-word for 16 bytes.
5924 @section @code{.offset @var{loc}}
5926 @cindex @code{offset} directive
5927 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5928 be an absolute expression. This directive may be useful for defining
5929 symbols with absolute values. Do not confuse it with the @code{.org}
5933 @section @code{.org @var{new-lc} , @var{fill}}
5935 @cindex @code{org} directive
5936 @cindex location counter, advancing
5937 @cindex advancing location counter
5938 @cindex current address, advancing
5939 Advance the location counter of the current section to
5940 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5941 expression with the same section as the current subsection. That is,
5942 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5943 wrong section, the @code{.org} directive is ignored. To be compatible
5944 with former assemblers, if the section of @var{new-lc} is absolute,
5945 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5946 is the same as the current subsection.
5948 @code{.org} may only increase the location counter, or leave it
5949 unchanged; you cannot use @code{.org} to move the location counter
5952 @c double negative used below "not undefined" because this is a specific
5953 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5954 @c section. doc@cygnus.com 18feb91
5955 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5956 may not be undefined. If you really detest this restriction we eagerly await
5957 a chance to share your improved assembler.
5959 Beware that the origin is relative to the start of the section, not
5960 to the start of the subsection. This is compatible with other
5961 people's assemblers.
5963 When the location counter (of the current subsection) is advanced, the
5964 intervening bytes are filled with @var{fill} which should be an
5965 absolute expression. If the comma and @var{fill} are omitted,
5966 @var{fill} defaults to zero.
5969 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5971 @cindex padding the location counter given a power of two
5972 @cindex @code{p2align} directive
5973 Pad the location counter (in the current subsection) to a particular
5974 storage boundary. The first expression (which must be absolute) is the
5975 number of low-order zero bits the location counter must have after
5976 advancement. For example @samp{.p2align 3} advances the location
5977 counter until it a multiple of 8. If the location counter is already a
5978 multiple of 8, no change is needed.
5980 The second expression (also absolute) gives the fill value to be stored in the
5981 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5982 padding bytes are normally zero. However, on some systems, if the section is
5983 marked as containing code and the fill value is omitted, the space is filled
5984 with no-op instructions.
5986 The third expression is also absolute, and is also optional. If it is present,
5987 it is the maximum number of bytes that should be skipped by this alignment
5988 directive. If doing the alignment would require skipping more bytes than the
5989 specified maximum, then the alignment is not done at all. You can omit the
5990 fill value (the second argument) entirely by simply using two commas after the
5991 required alignment; this can be useful if you want the alignment to be filled
5992 with no-op instructions when appropriate.
5994 @cindex @code{p2alignw} directive
5995 @cindex @code{p2alignl} directive
5996 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5997 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5998 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5999 fill pattern as a four byte longword value. For example, @code{.p2alignw
6000 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6001 filled in with the value 0x368d (the exact placement of the bytes depends upon
6002 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6007 @section @code{.popsection}
6009 @cindex @code{popsection} directive
6010 @cindex Section Stack
6011 This is one of the ELF section stack manipulation directives. The others are
6012 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6013 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6016 This directive replaces the current section (and subsection) with the top
6017 section (and subsection) on the section stack. This section is popped off the
6023 @section @code{.previous}
6025 @cindex @code{previous} directive
6026 @cindex Section Stack
6027 This is one of the ELF section stack manipulation directives. The others are
6028 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6029 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6030 (@pxref{PopSection}).
6032 This directive swaps the current section (and subsection) with most recently
6033 referenced section/subsection pair prior to this one. Multiple
6034 @code{.previous} directives in a row will flip between two sections (and their
6035 subsections). For example:
6047 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6053 # Now in section A subsection 1
6057 # Now in section B subsection 0
6060 # Now in section B subsection 1
6063 # Now in section B subsection 0
6067 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6068 section B and 0x9abc into subsection 1 of section B.
6070 In terms of the section stack, this directive swaps the current section with
6071 the top section on the section stack.
6075 @section @code{.print @var{string}}
6077 @cindex @code{print} directive
6078 @command{@value{AS}} will print @var{string} on the standard output during
6079 assembly. You must put @var{string} in double quotes.
6083 @section @code{.protected @var{names}}
6085 @cindex @code{protected} directive
6087 This is one of the ELF visibility directives. The other two are
6088 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6090 This directive overrides the named symbols default visibility (which is set by
6091 their binding: local, global or weak). The directive sets the visibility to
6092 @code{protected} which means that any references to the symbols from within the
6093 components that defines them must be resolved to the definition in that
6094 component, even if a definition in another component would normally preempt
6099 @section @code{.psize @var{lines} , @var{columns}}
6101 @cindex @code{psize} directive
6102 @cindex listing control: paper size
6103 @cindex paper size, for listings
6104 Use this directive to declare the number of lines---and, optionally, the
6105 number of columns---to use for each page, when generating listings.
6107 If you do not use @code{.psize}, listings use a default line-count
6108 of 60. You may omit the comma and @var{columns} specification; the
6109 default width is 200 columns.
6111 @command{@value{AS}} generates formfeeds whenever the specified number of
6112 lines is exceeded (or whenever you explicitly request one, using
6115 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6116 those explicitly specified with @code{.eject}.
6119 @section @code{.purgem @var{name}}
6121 @cindex @code{purgem} directive
6122 Undefine the macro @var{name}, so that later uses of the string will not be
6123 expanded. @xref{Macro}.
6127 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6129 @cindex @code{pushsection} directive
6130 @cindex Section Stack
6131 This is one of the ELF section stack manipulation directives. The others are
6132 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6133 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6136 This directive pushes the current section (and subsection) onto the
6137 top of the section stack, and then replaces the current section and
6138 subsection with @code{name} and @code{subsection}. The optional
6139 @code{flags}, @code{type} and @code{arguments} are treated the same
6140 as in the @code{.section} (@pxref{Section}) directive.
6144 @section @code{.quad @var{bignums}}
6146 @cindex @code{quad} directive
6147 @code{.quad} expects zero or more bignums, separated by commas. For
6148 each bignum, it emits
6150 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6151 warning message; and just takes the lowest order 8 bytes of the bignum.
6152 @cindex eight-byte integer
6153 @cindex integer, 8-byte
6155 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6156 hence @emph{quad}-word for 8 bytes.
6159 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6160 warning message; and just takes the lowest order 16 bytes of the bignum.
6161 @cindex sixteen-byte integer
6162 @cindex integer, 16-byte
6166 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6168 @cindex @code{reloc} directive
6169 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6170 @var{expression}. If @var{offset} is a number, the relocation is generated in
6171 the current section. If @var{offset} is an expression that resolves to a
6172 symbol plus offset, the relocation is generated in the given symbol's section.
6173 @var{expression}, if present, must resolve to a symbol plus addend or to an
6174 absolute value, but note that not all targets support an addend. e.g. ELF REL
6175 targets such as i386 store an addend in the section contents rather than in the
6176 relocation. This low level interface does not support addends stored in the
6180 @section @code{.rept @var{count}}
6182 @cindex @code{rept} directive
6183 Repeat the sequence of lines between the @code{.rept} directive and the next
6184 @code{.endr} directive @var{count} times.
6186 For example, assembling
6194 is equivalent to assembling
6203 @section @code{.sbttl "@var{subheading}"}
6205 @cindex @code{sbttl} directive
6206 @cindex subtitles for listings
6207 @cindex listing control: subtitle
6208 Use @var{subheading} as the title (third line, immediately after the
6209 title line) when generating assembly listings.
6211 This directive affects subsequent pages, as well as the current page if
6212 it appears within ten lines of the top of a page.
6216 @section @code{.scl @var{class}}
6218 @cindex @code{scl} directive
6219 @cindex symbol storage class (COFF)
6220 @cindex COFF symbol storage class
6221 Set the storage-class value for a symbol. This directive may only be
6222 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6223 whether a symbol is static or external, or it may record further
6224 symbolic debugging information.
6227 The @samp{.scl} directive is primarily associated with COFF output; when
6228 configured to generate @code{b.out} output format, @command{@value{AS}}
6229 accepts this directive but ignores it.
6235 @section @code{.section @var{name}}
6237 @cindex named section
6238 Use the @code{.section} directive to assemble the following code into a section
6241 This directive is only supported for targets that actually support arbitrarily
6242 named sections; on @code{a.out} targets, for example, it is not accepted, even
6243 with a standard @code{a.out} section name.
6247 @c only print the extra heading if both COFF and ELF are set
6248 @subheading COFF Version
6251 @cindex @code{section} directive (COFF version)
6252 For COFF targets, the @code{.section} directive is used in one of the following
6256 .section @var{name}[, "@var{flags}"]
6257 .section @var{name}[, @var{subsection}]
6260 If the optional argument is quoted, it is taken as flags to use for the
6261 section. Each flag is a single character. The following flags are recognized:
6264 bss section (uninitialized data)
6266 section is not loaded
6272 exclude section from linking
6278 shared section (meaningful for PE targets)
6280 ignored. (For compatibility with the ELF version)
6282 section is not readable (meaningful for PE targets)
6284 single-digit power-of-two section alignment (GNU extension)
6287 If no flags are specified, the default flags depend upon the section name. If
6288 the section name is not recognized, the default will be for the section to be
6289 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6290 from the section, rather than adding them, so if they are used on their own it
6291 will be as if no flags had been specified at all.
6293 If the optional argument to the @code{.section} directive is not quoted, it is
6294 taken as a subsection number (@pxref{Sub-Sections}).
6299 @c only print the extra heading if both COFF and ELF are set
6300 @subheading ELF Version
6303 @cindex Section Stack
6304 This is one of the ELF section stack manipulation directives. The others are
6305 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6306 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6307 @code{.previous} (@pxref{Previous}).
6309 @cindex @code{section} directive (ELF version)
6310 For ELF targets, the @code{.section} directive is used like this:
6313 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6316 @anchor{Section Name Substitutions}
6317 @kindex --sectname-subst
6318 @cindex section name substitution
6319 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6320 argument may contain a substitution sequence. Only @code{%S} is supported
6321 at the moment, and substitutes the current section name. For example:
6324 .macro exception_code
6325 .section %S.exception
6326 [exception code here]
6341 The two @code{exception_code} invocations above would create the
6342 @code{.text.exception} and @code{.init.exception} sections respectively.
6343 This is useful e.g. to discriminate between anciliary sections that are
6344 tied to setup code to be discarded after use from anciliary sections that
6345 need to stay resident without having to define multiple @code{exception_code}
6346 macros just for that purpose.
6348 The optional @var{flags} argument is a quoted string which may contain any
6349 combination of the following characters:
6352 section is allocatable
6354 section is excluded from executable and shared library.
6358 section is executable
6360 section is mergeable
6362 section contains zero terminated strings
6364 section is a member of a section group
6366 section is used for thread-local-storage
6368 section is a member of the previously-current section's group, if any
6371 The optional @var{type} argument may contain one of the following constants:
6374 section contains data
6376 section does not contain data (i.e., section only occupies space)
6378 section contains data which is used by things other than the program
6380 section contains an array of pointers to init functions
6382 section contains an array of pointers to finish functions
6383 @item @@preinit_array
6384 section contains an array of pointers to pre-init functions
6387 Many targets only support the first three section types.
6389 Note on targets where the @code{@@} character is the start of a comment (eg
6390 ARM) then another character is used instead. For example the ARM port uses the
6393 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6394 be specified as well as an extra argument---@var{entsize}---like this:
6397 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6400 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6401 constants, each @var{entsize} octets long. Sections with both @code{M} and
6402 @code{S} must contain zero terminated strings where each character is
6403 @var{entsize} bytes long. The linker may remove duplicates within sections with
6404 the same name, same entity size and same flags. @var{entsize} must be an
6405 absolute expression. For sections with both @code{M} and @code{S}, a string
6406 which is a suffix of a larger string is considered a duplicate. Thus
6407 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6408 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6410 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6411 be present along with an additional field like this:
6414 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6417 The @var{GroupName} field specifies the name of the section group to which this
6418 particular section belongs. The optional linkage field can contain:
6421 indicates that only one copy of this section should be retained
6426 Note: if both the @var{M} and @var{G} flags are present then the fields for
6427 the Merge flag should come first, like this:
6430 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6433 If @var{flags} contains the @code{?} symbol then it may not also contain the
6434 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6435 present. Instead, @code{?} says to consider the section that's current before
6436 this directive. If that section used @code{G}, then the new section will use
6437 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6438 If not, then the @code{?} symbol has no effect.
6440 If no flags are specified, the default flags depend upon the section name. If
6441 the section name is not recognized, the default will be for the section to have
6442 none of the above flags: it will not be allocated in memory, nor writable, nor
6443 executable. The section will contain data.
6445 For ELF targets, the assembler supports another type of @code{.section}
6446 directive for compatibility with the Solaris assembler:
6449 .section "@var{name}"[, @var{flags}...]
6452 Note that the section name is quoted. There may be a sequence of comma
6456 section is allocatable
6460 section is executable
6462 section is excluded from executable and shared library.
6464 section is used for thread local storage
6467 This directive replaces the current section and subsection. See the
6468 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6469 some examples of how this directive and the other section stack directives
6475 @section @code{.set @var{symbol}, @var{expression}}
6477 @cindex @code{set} directive
6478 @cindex symbol value, setting
6479 Set the value of @var{symbol} to @var{expression}. This
6480 changes @var{symbol}'s value and type to conform to
6481 @var{expression}. If @var{symbol} was flagged as external, it remains
6482 flagged (@pxref{Symbol Attributes}).
6484 You may @code{.set} a symbol many times in the same assembly provided that the
6485 values given to the symbol are constants. Values that are based on expressions
6486 involving other symbols are allowed, but some targets may restrict this to only
6487 being done once per assembly. This is because those targets do not set the
6488 addresses of symbols at assembly time, but rather delay the assignment until a
6489 final link is performed. This allows the linker a chance to change the code in
6490 the files, changing the location of, and the relative distance between, various
6493 If you @code{.set} a global symbol, the value stored in the object
6494 file is the last value stored into it.
6497 On Z80 @code{set} is a real instruction, use
6498 @samp{@var{symbol} defl @var{expression}} instead.
6502 @section @code{.short @var{expressions}}
6504 @cindex @code{short} directive
6506 @code{.short} is normally the same as @samp{.word}.
6507 @xref{Word,,@code{.word}}.
6509 In some configurations, however, @code{.short} and @code{.word} generate
6510 numbers of different lengths. @xref{Machine Dependencies}.
6514 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6517 This expects zero or more @var{expressions}, and emits
6518 a 16 bit number for each.
6523 @section @code{.single @var{flonums}}
6525 @cindex @code{single} directive
6526 @cindex floating point numbers (single)
6527 This directive assembles zero or more flonums, separated by commas. It
6528 has the same effect as @code{.float}.
6530 The exact kind of floating point numbers emitted depends on how
6531 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6535 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6536 numbers in @sc{ieee} format.
6542 @section @code{.size}
6544 This directive is used to set the size associated with a symbol.
6548 @c only print the extra heading if both COFF and ELF are set
6549 @subheading COFF Version
6552 @cindex @code{size} directive (COFF version)
6553 For COFF targets, the @code{.size} directive is only permitted inside
6554 @code{.def}/@code{.endef} pairs. It is used like this:
6557 .size @var{expression}
6561 @samp{.size} is only meaningful when generating COFF format output; when
6562 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6569 @c only print the extra heading if both COFF and ELF are set
6570 @subheading ELF Version
6573 @cindex @code{size} directive (ELF version)
6574 For ELF targets, the @code{.size} directive is used like this:
6577 .size @var{name} , @var{expression}
6580 This directive sets the size associated with a symbol @var{name}.
6581 The size in bytes is computed from @var{expression} which can make use of label
6582 arithmetic. This directive is typically used to set the size of function
6587 @ifclear no-space-dir
6589 @section @code{.skip @var{size} , @var{fill}}
6591 @cindex @code{skip} directive
6592 @cindex filling memory
6593 This directive emits @var{size} bytes, each of value @var{fill}. Both
6594 @var{size} and @var{fill} are absolute expressions. If the comma and
6595 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6600 @section @code{.sleb128 @var{expressions}}
6602 @cindex @code{sleb128} directive
6603 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6604 compact, variable length representation of numbers used by the DWARF
6605 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6607 @ifclear no-space-dir
6609 @section @code{.space @var{size} , @var{fill}}
6611 @cindex @code{space} directive
6612 @cindex filling memory
6613 This directive emits @var{size} bytes, each of value @var{fill}. Both
6614 @var{size} and @var{fill} are absolute expressions. If the comma
6615 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6620 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6621 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6622 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6623 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6631 @section @code{.stabd, .stabn, .stabs}
6633 @cindex symbolic debuggers, information for
6634 @cindex @code{stab@var{x}} directives
6635 There are three directives that begin @samp{.stab}.
6636 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6637 The symbols are not entered in the @command{@value{AS}} hash table: they
6638 cannot be referenced elsewhere in the source file.
6639 Up to five fields are required:
6643 This is the symbol's name. It may contain any character except
6644 @samp{\000}, so is more general than ordinary symbol names. Some
6645 debuggers used to code arbitrarily complex structures into symbol names
6649 An absolute expression. The symbol's type is set to the low 8 bits of
6650 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6651 and debuggers choke on silly bit patterns.
6654 An absolute expression. The symbol's ``other'' attribute is set to the
6655 low 8 bits of this expression.
6658 An absolute expression. The symbol's descriptor is set to the low 16
6659 bits of this expression.
6662 An absolute expression which becomes the symbol's value.
6665 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6666 or @code{.stabs} statement, the symbol has probably already been created;
6667 you get a half-formed symbol in your object file. This is
6668 compatible with earlier assemblers!
6671 @cindex @code{stabd} directive
6672 @item .stabd @var{type} , @var{other} , @var{desc}
6674 The ``name'' of the symbol generated is not even an empty string.
6675 It is a null pointer, for compatibility. Older assemblers used a
6676 null pointer so they didn't waste space in object files with empty
6679 The symbol's value is set to the location counter,
6680 relocatably. When your program is linked, the value of this symbol
6681 is the address of the location counter when the @code{.stabd} was
6684 @cindex @code{stabn} directive
6685 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6686 The name of the symbol is set to the empty string @code{""}.
6688 @cindex @code{stabs} directive
6689 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6690 All five fields are specified.
6696 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6697 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6699 @cindex string, copying to object file
6700 @cindex string8, copying to object file
6701 @cindex string16, copying to object file
6702 @cindex string32, copying to object file
6703 @cindex string64, copying to object file
6704 @cindex @code{string} directive
6705 @cindex @code{string8} directive
6706 @cindex @code{string16} directive
6707 @cindex @code{string32} directive
6708 @cindex @code{string64} directive
6710 Copy the characters in @var{str} to the object file. You may specify more than
6711 one string to copy, separated by commas. Unless otherwise specified for a
6712 particular machine, the assembler marks the end of each string with a 0 byte.
6713 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6715 The variants @code{string16}, @code{string32} and @code{string64} differ from
6716 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6717 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6718 are stored in target endianness byte order.
6724 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6725 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6730 @section @code{.struct @var{expression}}
6732 @cindex @code{struct} directive
6733 Switch to the absolute section, and set the section offset to @var{expression},
6734 which must be an absolute expression. You might use this as follows:
6743 This would define the symbol @code{field1} to have the value 0, the symbol
6744 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6745 value 8. Assembly would be left in the absolute section, and you would need to
6746 use a @code{.section} directive of some sort to change to some other section
6747 before further assembly.
6751 @section @code{.subsection @var{name}}
6753 @cindex @code{subsection} directive
6754 @cindex Section Stack
6755 This is one of the ELF section stack manipulation directives. The others are
6756 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6757 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6760 This directive replaces the current subsection with @code{name}. The current
6761 section is not changed. The replaced subsection is put onto the section stack
6762 in place of the then current top of stack subsection.
6767 @section @code{.symver}
6768 @cindex @code{symver} directive
6769 @cindex symbol versioning
6770 @cindex versions of symbols
6771 Use the @code{.symver} directive to bind symbols to specific version nodes
6772 within a source file. This is only supported on ELF platforms, and is
6773 typically used when assembling files to be linked into a shared library.
6774 There are cases where it may make sense to use this in objects to be bound
6775 into an application itself so as to override a versioned symbol from a
6778 For ELF targets, the @code{.symver} directive can be used like this:
6780 .symver @var{name}, @var{name2@@nodename}
6782 If the symbol @var{name} is defined within the file
6783 being assembled, the @code{.symver} directive effectively creates a symbol
6784 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6785 just don't try and create a regular alias is that the @var{@@} character isn't
6786 permitted in symbol names. The @var{name2} part of the name is the actual name
6787 of the symbol by which it will be externally referenced. The name @var{name}
6788 itself is merely a name of convenience that is used so that it is possible to
6789 have definitions for multiple versions of a function within a single source
6790 file, and so that the compiler can unambiguously know which version of a
6791 function is being mentioned. The @var{nodename} portion of the alias should be
6792 the name of a node specified in the version script supplied to the linker when
6793 building a shared library. If you are attempting to override a versioned
6794 symbol from a shared library, then @var{nodename} should correspond to the
6795 nodename of the symbol you are trying to override.
6797 If the symbol @var{name} is not defined within the file being assembled, all
6798 references to @var{name} will be changed to @var{name2@@nodename}. If no
6799 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6802 Another usage of the @code{.symver} directive is:
6804 .symver @var{name}, @var{name2@@@@nodename}
6806 In this case, the symbol @var{name} must exist and be defined within
6807 the file being assembled. It is similar to @var{name2@@nodename}. The
6808 difference is @var{name2@@@@nodename} will also be used to resolve
6809 references to @var{name2} by the linker.
6811 The third usage of the @code{.symver} directive is:
6813 .symver @var{name}, @var{name2@@@@@@nodename}
6815 When @var{name} is not defined within the
6816 file being assembled, it is treated as @var{name2@@nodename}. When
6817 @var{name} is defined within the file being assembled, the symbol
6818 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6823 @section @code{.tag @var{structname}}
6825 @cindex COFF structure debugging
6826 @cindex structure debugging, COFF
6827 @cindex @code{tag} directive
6828 This directive is generated by compilers to include auxiliary debugging
6829 information in the symbol table. It is only permitted inside
6830 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6831 definitions in the symbol table with instances of those structures.
6834 @samp{.tag} is only used when generating COFF format output; when
6835 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6841 @section @code{.text @var{subsection}}
6843 @cindex @code{text} directive
6844 Tells @command{@value{AS}} to assemble the following statements onto the end of
6845 the text subsection numbered @var{subsection}, which is an absolute
6846 expression. If @var{subsection} is omitted, subsection number zero
6850 @section @code{.title "@var{heading}"}
6852 @cindex @code{title} directive
6853 @cindex listing control: title line
6854 Use @var{heading} as the title (second line, immediately after the
6855 source file name and pagenumber) when generating assembly listings.
6857 This directive affects subsequent pages, as well as the current page if
6858 it appears within ten lines of the top of a page.
6862 @section @code{.type}
6864 This directive is used to set the type of a symbol.
6868 @c only print the extra heading if both COFF and ELF are set
6869 @subheading COFF Version
6872 @cindex COFF symbol type
6873 @cindex symbol type, COFF
6874 @cindex @code{type} directive (COFF version)
6875 For COFF targets, this directive is permitted only within
6876 @code{.def}/@code{.endef} pairs. It is used like this:
6882 This records the integer @var{int} as the type attribute of a symbol table
6886 @samp{.type} is associated only with COFF format output; when
6887 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6888 directive but ignores it.
6894 @c only print the extra heading if both COFF and ELF are set
6895 @subheading ELF Version
6898 @cindex ELF symbol type
6899 @cindex symbol type, ELF
6900 @cindex @code{type} directive (ELF version)
6901 For ELF targets, the @code{.type} directive is used like this:
6904 .type @var{name} , @var{type description}
6907 This sets the type of symbol @var{name} to be either a
6908 function symbol or an object symbol. There are five different syntaxes
6909 supported for the @var{type description} field, in order to provide
6910 compatibility with various other assemblers.
6912 Because some of the characters used in these syntaxes (such as @samp{@@} and
6913 @samp{#}) are comment characters for some architectures, some of the syntaxes
6914 below do not work on all architectures. The first variant will be accepted by
6915 the GNU assembler on all architectures so that variant should be used for
6916 maximum portability, if you do not need to assemble your code with other
6919 The syntaxes supported are:
6922 .type <name> STT_<TYPE_IN_UPPER_CASE>
6923 .type <name>,#<type>
6924 .type <name>,@@<type>
6925 .type <name>,%<type>
6926 .type <name>,"<type>"
6929 The types supported are:
6934 Mark the symbol as being a function name.
6937 @itemx gnu_indirect_function
6938 Mark the symbol as an indirect function when evaluated during reloc
6939 processing. (This is only supported on assemblers targeting GNU systems).
6943 Mark the symbol as being a data object.
6947 Mark the symbol as being a thead-local data object.
6951 Mark the symbol as being a common data object.
6955 Does not mark the symbol in any way. It is supported just for completeness.
6957 @item gnu_unique_object
6958 Marks the symbol as being a globally unique data object. The dynamic linker
6959 will make sure that in the entire process there is just one symbol with this
6960 name and type in use. (This is only supported on assemblers targeting GNU
6965 Note: Some targets support extra types in addition to those listed above.
6971 @section @code{.uleb128 @var{expressions}}
6973 @cindex @code{uleb128} directive
6974 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6975 compact, variable length representation of numbers used by the DWARF
6976 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6980 @section @code{.val @var{addr}}
6982 @cindex @code{val} directive
6983 @cindex COFF value attribute
6984 @cindex value attribute, COFF
6985 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6986 records the address @var{addr} as the value attribute of a symbol table
6990 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6991 configured for @code{b.out}, it accepts this directive but ignores it.
6997 @section @code{.version "@var{string}"}
6999 @cindex @code{version} directive
7000 This directive creates a @code{.note} section and places into it an ELF
7001 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7006 @section @code{.vtable_entry @var{table}, @var{offset}}
7008 @cindex @code{vtable_entry} directive
7009 This directive finds or creates a symbol @code{table} and creates a
7010 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7013 @section @code{.vtable_inherit @var{child}, @var{parent}}
7015 @cindex @code{vtable_inherit} directive
7016 This directive finds the symbol @code{child} and finds or creates the symbol
7017 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7018 parent whose addend is the value of the child symbol. As a special case the
7019 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7023 @section @code{.warning "@var{string}"}
7024 @cindex warning directive
7025 Similar to the directive @code{.error}
7026 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7029 @section @code{.weak @var{names}}
7031 @cindex @code{weak} directive
7032 This directive sets the weak attribute on the comma separated list of symbol
7033 @code{names}. If the symbols do not already exist, they will be created.
7035 On COFF targets other than PE, weak symbols are a GNU extension. This
7036 directive sets the weak attribute on the comma separated list of symbol
7037 @code{names}. If the symbols do not already exist, they will be created.
7039 On the PE target, weak symbols are supported natively as weak aliases.
7040 When a weak symbol is created that is not an alias, GAS creates an
7041 alternate symbol to hold the default value.
7044 @section @code{.weakref @var{alias}, @var{target}}
7046 @cindex @code{weakref} directive
7047 This directive creates an alias to the target symbol that enables the symbol to
7048 be referenced with weak-symbol semantics, but without actually making it weak.
7049 If direct references or definitions of the symbol are present, then the symbol
7050 will not be weak, but if all references to it are through weak references, the
7051 symbol will be marked as weak in the symbol table.
7053 The effect is equivalent to moving all references to the alias to a separate
7054 assembly source file, renaming the alias to the symbol in it, declaring the
7055 symbol as weak there, and running a reloadable link to merge the object files
7056 resulting from the assembly of the new source file and the old source file that
7057 had the references to the alias removed.
7059 The alias itself never makes to the symbol table, and is entirely handled
7060 within the assembler.
7063 @section @code{.word @var{expressions}}
7065 @cindex @code{word} directive
7066 This directive expects zero or more @var{expressions}, of any section,
7067 separated by commas.
7070 For each expression, @command{@value{AS}} emits a 32-bit number.
7073 For each expression, @command{@value{AS}} emits a 16-bit number.
7078 The size of the number emitted, and its byte order,
7079 depend on what target computer the assembly is for.
7082 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7083 @c happen---32-bit addressability, period; no long/short jumps.
7084 @ifset DIFF-TBL-KLUGE
7085 @cindex difference tables altered
7086 @cindex altered difference tables
7088 @emph{Warning: Special Treatment to support Compilers}
7092 Machines with a 32-bit address space, but that do less than 32-bit
7093 addressing, require the following special treatment. If the machine of
7094 interest to you does 32-bit addressing (or doesn't require it;
7095 @pxref{Machine Dependencies}), you can ignore this issue.
7098 In order to assemble compiler output into something that works,
7099 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7100 Directives of the form @samp{.word sym1-sym2} are often emitted by
7101 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7102 directive of the form @samp{.word sym1-sym2}, and the difference between
7103 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7104 creates a @dfn{secondary jump table}, immediately before the next label.
7105 This secondary jump table is preceded by a short-jump to the
7106 first byte after the secondary table. This short-jump prevents the flow
7107 of control from accidentally falling into the new table. Inside the
7108 table is a long-jump to @code{sym2}. The original @samp{.word}
7109 contains @code{sym1} minus the address of the long-jump to
7112 If there were several occurrences of @samp{.word sym1-sym2} before the
7113 secondary jump table, all of them are adjusted. If there was a
7114 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7115 long-jump to @code{sym4} is included in the secondary jump table,
7116 and the @code{.word} directives are adjusted to contain @code{sym3}
7117 minus the address of the long-jump to @code{sym4}; and so on, for as many
7118 entries in the original jump table as necessary.
7121 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7122 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7123 assembly language programmers.
7126 @c end DIFF-TBL-KLUGE
7128 @ifclear no-space-dir
7130 @section @code{.zero @var{size}}
7132 @cindex @code{zero} directive
7133 @cindex filling memory with zero bytes
7134 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7135 expression. This directive is actually an alias for the @samp{.skip} directive
7136 so in can take an optional second argument of the value to store in the bytes
7137 instead of zero. Using @samp{.zero} in this way would be confusing however.
7141 @section Deprecated Directives
7143 @cindex deprecated directives
7144 @cindex obsolescent directives
7145 One day these directives won't work.
7146 They are included for compatibility with older assemblers.
7153 @node Object Attributes
7154 @chapter Object Attributes
7155 @cindex object attributes
7157 @command{@value{AS}} assembles source files written for a specific architecture
7158 into object files for that architecture. But not all object files are alike.
7159 Many architectures support incompatible variations. For instance, floating
7160 point arguments might be passed in floating point registers if the object file
7161 requires hardware floating point support---or floating point arguments might be
7162 passed in integer registers if the object file supports processors with no
7163 hardware floating point unit. Or, if two objects are built for different
7164 generations of the same architecture, the combination may require the
7165 newer generation at run-time.
7167 This information is useful during and after linking. At link time,
7168 @command{@value{LD}} can warn about incompatible object files. After link
7169 time, tools like @command{gdb} can use it to process the linked file
7172 Compatibility information is recorded as a series of object attributes. Each
7173 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7174 string, and indicates who sets the meaning of the tag. The tag is an integer,
7175 and indicates what property the attribute describes. The value may be a string
7176 or an integer, and indicates how the property affects this object. Missing
7177 attributes are the same as attributes with a zero value or empty string value.
7179 Object attributes were developed as part of the ABI for the ARM Architecture.
7180 The file format is documented in @cite{ELF for the ARM Architecture}.
7183 * GNU Object Attributes:: @sc{gnu} Object Attributes
7184 * Defining New Object Attributes:: Defining New Object Attributes
7187 @node GNU Object Attributes
7188 @section @sc{gnu} Object Attributes
7190 The @code{.gnu_attribute} directive records an object attribute
7191 with vendor @samp{gnu}.
7193 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7194 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7195 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7196 2} is set for architecture-independent attributes and clear for
7197 architecture-dependent ones.
7199 @subsection Common @sc{gnu} attributes
7201 These attributes are valid on all architectures.
7204 @item Tag_compatibility (32)
7205 The compatibility attribute takes an integer flag value and a vendor name. If
7206 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7207 then the file is only compatible with the named toolchain. If it is greater
7208 than 1, the file can only be processed by other toolchains under some private
7209 arrangement indicated by the flag value and the vendor name.
7212 @subsection MIPS Attributes
7215 @item Tag_GNU_MIPS_ABI_FP (4)
7216 The floating-point ABI used by this object file. The value will be:
7220 0 for files not affected by the floating-point ABI.
7222 1 for files using the hardware floating-point ABI with a standard
7223 double-precision FPU.
7225 2 for files using the hardware floating-point ABI with a single-precision FPU.
7227 3 for files using the software floating-point ABI.
7229 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7230 floating-point registers, 32-bit general-purpose registers and increased the
7231 number of callee-saved floating-point registers.
7233 5 for files using the hardware floating-point ABI with a double-precision FPU
7234 with either 32-bit or 64-bit floating-point registers and 32-bit
7235 general-purpose registers.
7237 6 for files using the hardware floating-point ABI with 64-bit floating-point
7238 registers and 32-bit general-purpose registers.
7240 7 for files using the hardware floating-point ABI with 64-bit floating-point
7241 registers, 32-bit general-purpose registers and a rule that forbids the
7242 direct use of odd-numbered single-precision floating-point registers.
7246 @subsection PowerPC Attributes
7249 @item Tag_GNU_Power_ABI_FP (4)
7250 The floating-point ABI used by this object file. The value will be:
7254 0 for files not affected by the floating-point ABI.
7256 1 for files using double-precision hardware floating-point ABI.
7258 2 for files using the software floating-point ABI.
7260 3 for files using single-precision hardware floating-point ABI.
7263 @item Tag_GNU_Power_ABI_Vector (8)
7264 The vector ABI used by this object file. The value will be:
7268 0 for files not affected by the vector ABI.
7270 1 for files using general purpose registers to pass vectors.
7272 2 for files using AltiVec registers to pass vectors.
7274 3 for files using SPE registers to pass vectors.
7278 @subsection IBM z Systems Attributes
7281 @item Tag_GNU_S390_ABI_Vector (8)
7282 The vector ABI used by this object file. The value will be:
7286 0 for files not affected by the vector ABI.
7288 1 for files using software vector ABI.
7290 2 for files using hardware vector ABI.
7294 @node Defining New Object Attributes
7295 @section Defining New Object Attributes
7297 If you want to define a new @sc{gnu} object attribute, here are the places you
7298 will need to modify. New attributes should be discussed on the @samp{binutils}
7303 This manual, which is the official register of attributes.
7305 The header for your architecture @file{include/elf}, to define the tag.
7307 The @file{bfd} support file for your architecture, to merge the attribute
7308 and issue any appropriate link warnings.
7310 Test cases in @file{ld/testsuite} for merging and link warnings.
7312 @file{binutils/readelf.c} to display your attribute.
7314 GCC, if you want the compiler to mark the attribute automatically.
7320 @node Machine Dependencies
7321 @chapter Machine Dependent Features
7323 @cindex machine dependencies
7324 The machine instruction sets are (almost by definition) different on
7325 each machine where @command{@value{AS}} runs. Floating point representations
7326 vary as well, and @command{@value{AS}} often supports a few additional
7327 directives or command-line options for compatibility with other
7328 assemblers on a particular platform. Finally, some versions of
7329 @command{@value{AS}} support special pseudo-instructions for branch
7332 This chapter discusses most of these differences, though it does not
7333 include details on any machine's instruction set. For details on that
7334 subject, see the hardware manufacturer's manual.
7338 * AArch64-Dependent:: AArch64 Dependent Features
7341 * Alpha-Dependent:: Alpha Dependent Features
7344 * ARC-Dependent:: ARC Dependent Features
7347 * ARM-Dependent:: ARM Dependent Features
7350 * AVR-Dependent:: AVR Dependent Features
7353 * Blackfin-Dependent:: Blackfin Dependent Features
7356 * CR16-Dependent:: CR16 Dependent Features
7359 * CRIS-Dependent:: CRIS Dependent Features
7362 * D10V-Dependent:: D10V Dependent Features
7365 * D30V-Dependent:: D30V Dependent Features
7368 * Epiphany-Dependent:: EPIPHANY Dependent Features
7371 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7374 * HPPA-Dependent:: HPPA Dependent Features
7377 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7380 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7383 * i860-Dependent:: Intel 80860 Dependent Features
7386 * i960-Dependent:: Intel 80960 Dependent Features
7389 * IA-64-Dependent:: Intel IA-64 Dependent Features
7392 * IP2K-Dependent:: IP2K Dependent Features
7395 * LM32-Dependent:: LM32 Dependent Features
7398 * M32C-Dependent:: M32C Dependent Features
7401 * M32R-Dependent:: M32R Dependent Features
7404 * M68K-Dependent:: M680x0 Dependent Features
7407 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7410 * Meta-Dependent :: Meta Dependent Features
7413 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7416 * MIPS-Dependent:: MIPS Dependent Features
7419 * MMIX-Dependent:: MMIX Dependent Features
7422 * MSP430-Dependent:: MSP430 Dependent Features
7425 * NDS32-Dependent:: Andes NDS32 Dependent Features
7428 * NiosII-Dependent:: Altera Nios II Dependent Features
7431 * NS32K-Dependent:: NS32K Dependent Features
7434 * PDP-11-Dependent:: PDP-11 Dependent Features
7437 * PJ-Dependent:: picoJava Dependent Features
7440 * PPC-Dependent:: PowerPC Dependent Features
7443 * RL78-Dependent:: RL78 Dependent Features
7446 * RX-Dependent:: RX Dependent Features
7449 * S/390-Dependent:: IBM S/390 Dependent Features
7452 * SCORE-Dependent:: SCORE Dependent Features
7455 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7456 * SH64-Dependent:: SuperH SH64 Dependent Features
7459 * Sparc-Dependent:: SPARC Dependent Features
7462 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7465 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7468 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7471 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7474 * V850-Dependent:: V850 Dependent Features
7477 * Vax-Dependent:: VAX Dependent Features
7480 * Visium-Dependent:: Visium Dependent Features
7483 * XGATE-Dependent:: XGATE Features
7486 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7489 * Xtensa-Dependent:: Xtensa Dependent Features
7492 * Z80-Dependent:: Z80 Dependent Features
7495 * Z8000-Dependent:: Z8000 Dependent Features
7502 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7503 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7504 @c peculiarity: to preserve cross-references, there must be a node called
7505 @c "Machine Dependencies". Hence the conditional nodenames in each
7506 @c major node below. Node defaulting in makeinfo requires adjacency of
7507 @c node and sectioning commands; hence the repetition of @chapter BLAH
7508 @c in both conditional blocks.
7511 @include c-aarch64.texi
7515 @include c-alpha.texi
7531 @include c-bfin.texi
7535 @include c-cr16.texi
7539 @include c-cris.texi
7544 @node Machine Dependencies
7545 @chapter Machine Dependent Features
7547 The machine instruction sets are different on each Renesas chip family,
7548 and there are also some syntax differences among the families. This
7549 chapter describes the specific @command{@value{AS}} features for each
7553 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7554 * SH-Dependent:: Renesas SH Dependent Features
7561 @include c-d10v.texi
7565 @include c-d30v.texi
7569 @include c-epiphany.texi
7573 @include c-h8300.texi
7577 @include c-hppa.texi
7581 @include c-i370.texi
7585 @include c-i386.texi
7589 @include c-i860.texi
7593 @include c-i960.texi
7597 @include c-ia64.texi
7601 @include c-ip2k.texi
7605 @include c-lm32.texi
7609 @include c-m32c.texi
7613 @include c-m32r.texi
7617 @include c-m68k.texi
7621 @include c-m68hc11.texi
7625 @include c-metag.texi
7629 @include c-microblaze.texi
7633 @include c-mips.texi
7637 @include c-mmix.texi
7641 @include c-msp430.texi
7645 @include c-nds32.texi
7649 @include c-nios2.texi
7653 @include c-ns32k.texi
7657 @include c-pdp11.texi
7669 @include c-rl78.texi
7677 @include c-s390.texi
7681 @include c-score.texi
7686 @include c-sh64.texi
7690 @include c-sparc.texi
7694 @include c-tic54x.texi
7698 @include c-tic6x.texi
7702 @include c-tilegx.texi
7706 @include c-tilepro.texi
7710 @include c-v850.texi
7718 @include c-visium.texi
7722 @include c-xgate.texi
7726 @include c-xstormy16.texi
7730 @include c-xtensa.texi
7742 @c reverse effect of @down at top of generic Machine-Dep chapter
7746 @node Reporting Bugs
7747 @chapter Reporting Bugs
7748 @cindex bugs in assembler
7749 @cindex reporting bugs in assembler
7751 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7753 Reporting a bug may help you by bringing a solution to your problem, or it may
7754 not. But in any case the principal function of a bug report is to help the
7755 entire community by making the next version of @command{@value{AS}} work better.
7756 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7758 In order for a bug report to serve its purpose, you must include the
7759 information that enables us to fix the bug.
7762 * Bug Criteria:: Have you found a bug?
7763 * Bug Reporting:: How to report bugs
7767 @section Have You Found a Bug?
7768 @cindex bug criteria
7770 If you are not sure whether you have found a bug, here are some guidelines:
7773 @cindex fatal signal
7774 @cindex assembler crash
7775 @cindex crash of assembler
7777 If the assembler gets a fatal signal, for any input whatever, that is a
7778 @command{@value{AS}} bug. Reliable assemblers never crash.
7780 @cindex error on valid input
7782 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7784 @cindex invalid input
7786 If @command{@value{AS}} does not produce an error message for invalid input, that
7787 is a bug. However, you should note that your idea of ``invalid input'' might
7788 be our idea of ``an extension'' or ``support for traditional practice''.
7791 If you are an experienced user of assemblers, your suggestions for improvement
7792 of @command{@value{AS}} are welcome in any case.
7796 @section How to Report Bugs
7798 @cindex assembler bugs, reporting
7800 A number of companies and individuals offer support for @sc{gnu} products. If
7801 you obtained @command{@value{AS}} from a support organization, we recommend you
7802 contact that organization first.
7804 You can find contact information for many support companies and
7805 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7809 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7813 The fundamental principle of reporting bugs usefully is this:
7814 @strong{report all the facts}. If you are not sure whether to state a
7815 fact or leave it out, state it!
7817 Often people omit facts because they think they know what causes the problem
7818 and assume that some details do not matter. Thus, you might assume that the
7819 name of a symbol you use in an example does not matter. Well, probably it does
7820 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7821 happens to fetch from the location where that name is stored in memory;
7822 perhaps, if the name were different, the contents of that location would fool
7823 the assembler into doing the right thing despite the bug. Play it safe and
7824 give a specific, complete example. That is the easiest thing for you to do,
7825 and the most helpful.
7827 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7828 it is new to us. Therefore, always write your bug reports on the assumption
7829 that the bug has not been reported previously.
7831 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7832 bell?'' This cannot help us fix a bug, so it is basically useless. We
7833 respond by asking for enough details to enable us to investigate.
7834 You might as well expedite matters by sending them to begin with.
7836 To enable us to fix the bug, you should include all these things:
7840 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7841 it with the @samp{--version} argument.
7843 Without this, we will not know whether there is any point in looking for
7844 the bug in the current version of @command{@value{AS}}.
7847 Any patches you may have applied to the @command{@value{AS}} source.
7850 The type of machine you are using, and the operating system name and
7854 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7858 The command arguments you gave the assembler to assemble your example and
7859 observe the bug. To guarantee you will not omit something important, list them
7860 all. A copy of the Makefile (or the output from make) is sufficient.
7862 If we were to try to guess the arguments, we would probably guess wrong
7863 and then we might not encounter the bug.
7866 A complete input file that will reproduce the bug. If the bug is observed when
7867 the assembler is invoked via a compiler, send the assembler source, not the
7868 high level language source. Most compilers will produce the assembler source
7869 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7870 the options @samp{-v --save-temps}; this will save the assembler source in a
7871 file with an extension of @file{.s}, and also show you exactly how
7872 @command{@value{AS}} is being run.
7875 A description of what behavior you observe that you believe is
7876 incorrect. For example, ``It gets a fatal signal.''
7878 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7879 will certainly notice it. But if the bug is incorrect output, we might not
7880 notice unless it is glaringly wrong. You might as well not give us a chance to
7883 Even if the problem you experience is a fatal signal, you should still say so
7884 explicitly. Suppose something strange is going on, such as, your copy of
7885 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7886 library on your system. (This has happened!) Your copy might crash and ours
7887 would not. If you told us to expect a crash, then when ours fails to crash, we
7888 would know that the bug was not happening for us. If you had not told us to
7889 expect a crash, then we would not be able to draw any conclusion from our
7893 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7894 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7895 option. Always send diffs from the old file to the new file. If you even
7896 discuss something in the @command{@value{AS}} source, refer to it by context, not
7899 The line numbers in our development sources will not match those in your
7900 sources. Your line numbers would convey no useful information to us.
7903 Here are some things that are not necessary:
7907 A description of the envelope of the bug.
7909 Often people who encounter a bug spend a lot of time investigating
7910 which changes to the input file will make the bug go away and which
7911 changes will not affect it.
7913 This is often time consuming and not very useful, because the way we
7914 will find the bug is by running a single example under the debugger
7915 with breakpoints, not by pure deduction from a series of examples.
7916 We recommend that you save your time for something else.
7918 Of course, if you can find a simpler example to report @emph{instead}
7919 of the original one, that is a convenience for us. Errors in the
7920 output will be easier to spot, running under the debugger will take
7921 less time, and so on.
7923 However, simplification is not vital; if you do not want to do this,
7924 report the bug anyway and send us the entire test case you used.
7927 A patch for the bug.
7929 A patch for the bug does help us if it is a good one. But do not omit
7930 the necessary information, such as the test case, on the assumption that
7931 a patch is all we need. We might see problems with your patch and decide
7932 to fix the problem another way, or we might not understand it at all.
7934 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7935 construct an example that will make the program follow a certain path through
7936 the code. If you do not send us the example, we will not be able to construct
7937 one, so we will not be able to verify that the bug is fixed.
7939 And if we cannot understand what bug you are trying to fix, or why your
7940 patch should be an improvement, we will not install it. A test case will
7941 help us to understand.
7944 A guess about what the bug is or what it depends on.
7946 Such guesses are usually wrong. Even we cannot guess right about such
7947 things without first using the debugger to find the facts.
7950 @node Acknowledgements
7951 @chapter Acknowledgements
7953 If you have contributed to GAS and your name isn't listed here,
7954 it is not meant as a slight. We just don't know about it. Send mail to the
7955 maintainer, and we'll correct the situation. Currently
7957 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7959 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7962 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7963 information and the 68k series machines, most of the preprocessing pass, and
7964 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7966 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7967 many bug fixes, including merging support for several processors, breaking GAS
7968 up to handle multiple object file format back ends (including heavy rewrite,
7969 testing, an integration of the coff and b.out back ends), adding configuration
7970 including heavy testing and verification of cross assemblers and file splits
7971 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7972 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7973 port (including considerable amounts of reverse engineering), a SPARC opcode
7974 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7975 assertions and made them work, much other reorganization, cleanup, and lint.
7977 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7978 in format-specific I/O modules.
7980 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7981 has done much work with it since.
7983 The Intel 80386 machine description was written by Eliot Dresselhaus.
7985 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7987 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7988 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7990 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7991 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7992 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7993 support a.out format.
7995 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7996 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7997 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7998 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8001 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8002 simplified the configuration of which versions accept which directives. He
8003 updated the 68k machine description so that Motorola's opcodes always produced
8004 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8005 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8006 cross-compilation support, and one bug in relaxation that took a week and
8007 required the proverbial one-bit fix.
8009 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8010 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8011 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8012 PowerPC assembler, and made a few other minor patches.
8014 Steve Chamberlain made GAS able to generate listings.
8016 Hewlett-Packard contributed support for the HP9000/300.
8018 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8019 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8020 formats). This work was supported by both the Center for Software Science at
8021 the University of Utah and Cygnus Support.
8023 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8024 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8025 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8026 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8027 and some initial 64-bit support).
8029 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8031 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8032 support for openVMS/Alpha.
8034 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8037 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8038 Inc.@: added support for Xtensa processors.
8040 Several engineers at Cygnus Support have also provided many small bug fixes and
8041 configuration enhancements.
8043 Jon Beniston added support for the Lattice Mico32 architecture.
8045 Many others have contributed large or small bugfixes and enhancements. If
8046 you have contributed significant work and are not mentioned on this list, and
8047 want to be, let us know. Some of the history has been lost; we are not
8048 intentionally leaving anyone out.
8050 @node GNU Free Documentation License
8051 @appendix GNU Free Documentation License
8055 @unnumbered AS Index