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{--no-pad-sections}]
239 [@b{-o} @var{objfile}] [@b{-R}]
240 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
242 [@b{-v}] [@b{-version}] [@b{--version}]
243 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
244 [@b{-Z}] [@b{@@@var{FILE}}]
245 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
246 [@b{--elf-stt-common=[no|yes]}]
247 [@b{--target-help}] [@var{target-options}]
248 [@b{--}|@var{files} @dots{}]
251 @c Target dependent options are listed below. Keep the list sorted.
252 @c Add an empty line for separation.
256 @emph{Target AArch64 options:}
258 [@b{-mabi}=@var{ABI}]
262 @emph{Target Alpha options:}
264 [@b{-mdebug} | @b{-no-mdebug}]
265 [@b{-replace} | @b{-noreplace}]
266 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
267 [@b{-F}] [@b{-32addr}]
271 @emph{Target ARC options:}
272 [@b{-mcpu=@var{cpu}}]
273 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
280 @emph{Target ARM options:}
281 @c Don't document the deprecated options
282 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
283 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
284 [@b{-mfpu}=@var{floating-point-format}]
285 [@b{-mfloat-abi}=@var{abi}]
286 [@b{-meabi}=@var{ver}]
289 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
290 @b{-mapcs-reentrant}]
291 [@b{-mthumb-interwork}] [@b{-k}]
295 @emph{Target Blackfin options:}
296 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
303 @emph{Target CRIS options:}
304 [@b{--underscore} | @b{--no-underscore}]
306 [@b{--emulation=criself} | @b{--emulation=crisaout}]
307 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
308 @c Deprecated -- deliberately not documented.
313 @emph{Target D10V options:}
318 @emph{Target D30V options:}
319 [@b{-O}|@b{-n}|@b{-N}]
323 @emph{Target EPIPHANY options:}
324 [@b{-mepiphany}|@b{-mepiphany16}]
328 @emph{Target H8/300 options:}
332 @c HPPA has no machine-dependent assembler options (yet).
336 @emph{Target i386 options:}
337 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
338 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
342 @emph{Target i960 options:}
343 @c see md_parse_option in tc-i960.c
344 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
346 [@b{-b}] [@b{-no-relax}]
350 @emph{Target IA-64 options:}
351 [@b{-mconstant-gp}|@b{-mauto-pic}]
352 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
354 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
355 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
356 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
357 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
361 @emph{Target IP2K options:}
362 [@b{-mip2022}|@b{-mip2022ext}]
366 @emph{Target M32C options:}
367 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
371 @emph{Target M32R options:}
372 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
377 @emph{Target M680X0 options:}
378 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
382 @emph{Target M68HC11 options:}
383 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
384 [@b{-mshort}|@b{-mlong}]
385 [@b{-mshort-double}|@b{-mlong-double}]
386 [@b{--force-long-branches}] [@b{--short-branches}]
387 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
388 [@b{--print-opcodes}] [@b{--generate-example}]
392 @emph{Target MCORE options:}
393 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
394 [@b{-mcpu=[210|340]}]
398 @emph{Target Meta options:}
399 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
402 @emph{Target MICROBLAZE options:}
403 @c MicroBlaze has no machine-dependent assembler options.
407 @emph{Target MIPS options:}
408 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
409 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
410 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
411 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
412 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
413 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
414 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
415 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
416 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
417 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
418 [@b{-construct-floats}] [@b{-no-construct-floats}]
419 [@b{-mnan=@var{encoding}}]
420 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
421 [@b{-mips16}] [@b{-no-mips16}]
422 [@b{-mmicromips}] [@b{-mno-micromips}]
423 [@b{-msmartmips}] [@b{-mno-smartmips}]
424 [@b{-mips3d}] [@b{-no-mips3d}]
425 [@b{-mdmx}] [@b{-no-mdmx}]
426 [@b{-mdsp}] [@b{-mno-dsp}]
427 [@b{-mdspr2}] [@b{-mno-dspr2}]
428 [@b{-mdspr3}] [@b{-mno-dspr3}]
429 [@b{-mmsa}] [@b{-mno-msa}]
430 [@b{-mxpa}] [@b{-mno-xpa}]
431 [@b{-mmt}] [@b{-mno-mt}]
432 [@b{-mmcu}] [@b{-mno-mcu}]
433 [@b{-minsn32}] [@b{-mno-insn32}]
434 [@b{-mfix7000}] [@b{-mno-fix7000}]
435 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
436 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
437 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
438 [@b{-mdebug}] [@b{-no-mdebug}]
439 [@b{-mpdr}] [@b{-mno-pdr}]
443 @emph{Target MMIX options:}
444 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
445 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
446 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
447 [@b{--linker-allocated-gregs}]
451 @emph{Target Nios II options:}
452 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
457 @emph{Target NDS32 options:}
458 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
459 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
460 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
461 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
462 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
463 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
464 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
469 @emph{Target PDP11 options:}
470 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
471 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
472 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
476 @emph{Target picoJava options:}
481 @emph{Target PowerPC options:}
483 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
484 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
485 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
486 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
487 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-mpower9}|@b{-mpwr9}@b{-ma2}|
488 @b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
489 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
490 [@b{-mregnames}|@b{-mno-regnames}]
491 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
492 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
493 [@b{-msolaris}|@b{-mno-solaris}]
494 [@b{-nops=@var{count}}]
498 @emph{Target RL78 options:}
500 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
504 @emph{Target RX options:}
505 [@b{-mlittle-endian}|@b{-mbig-endian}]
506 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
507 [@b{-muse-conventional-section-names}]
508 [@b{-msmall-data-limit}]
511 [@b{-mint-register=@var{number}}]
512 [@b{-mgcc-abi}|@b{-mrx-abi}]
516 @emph{Target s390 options:}
517 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
518 [@b{-mregnames}|@b{-mno-regnames}]
519 [@b{-mwarn-areg-zero}]
523 @emph{Target SCORE options:}
524 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
525 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
526 [@b{-march=score7}][@b{-march=score3}]
527 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
531 @emph{Target SPARC options:}
532 @c The order here is important. See c-sparc.texi.
533 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
534 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
535 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
540 @emph{Target TIC54X options:}
541 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
542 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
546 @emph{Target TIC6X options:}
547 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
548 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
549 [@b{-mpic}|@b{-mno-pic}]
553 @emph{Target TILE-Gx options:}
554 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
557 @c TILEPro has no machine-dependent assembler options
561 @emph{Target Visium options:}
562 [@b{-mtune=@var{arch}}]
566 @emph{Target Xtensa options:}
567 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
568 [@b{--[no-]absolute-literals}]
569 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
570 [@b{--[no-]transform}]
571 [@b{--rename-section} @var{oldname}=@var{newname}]
572 [@b{--[no-]trampolines}]
576 @emph{Target Z80 options:}
577 [@b{-z80}] [@b{-r800}]
578 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
579 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
580 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
581 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
582 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
583 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
587 @c Z8000 has no machine-dependent assembler options
596 @include at-file.texi
599 Turn on listings, in any of a variety of ways:
603 omit false conditionals
606 omit debugging directives
609 include general information, like @value{AS} version and options passed
612 include high-level source
618 include macro expansions
621 omit forms processing
627 set the name of the listing file
630 You may combine these options; for example, use @samp{-aln} for assembly
631 listing without forms processing. The @samp{=file} option, if used, must be
632 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
635 Begin in alternate macro mode.
637 @xref{Altmacro,,@code{.altmacro}}.
640 @item --compress-debug-sections
641 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
642 ELF ABI. The resulting object file may not be compatible with older
643 linkers and object file utilities. Note if compression would make a
644 given section @emph{larger} then it is not compressed.
647 @cindex @samp{--compress-debug-sections=} option
648 @item --compress-debug-sections=none
649 @itemx --compress-debug-sections=zlib
650 @itemx --compress-debug-sections=zlib-gnu
651 @itemx --compress-debug-sections=zlib-gabi
652 These options control how DWARF debug sections are compressed.
653 @option{--compress-debug-sections=none} is equivalent to
654 @option{--nocompress-debug-sections}.
655 @option{--compress-debug-sections=zlib} and
656 @option{--compress-debug-sections=zlib-gabi} are equivalent to
657 @option{--compress-debug-sections}.
658 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
659 sections using zlib. The debug sections are renamed to begin with
660 @samp{.zdebug}. Note if compression would make a given section
661 @emph{larger} then it is not compressed nor renamed.
665 @item --nocompress-debug-sections
666 Do not compress DWARF debug sections. This is usually the default for all
667 targets except the x86/x86_64, but a configure time option can be used to
671 Ignored. This option is accepted for script compatibility with calls to
674 @item --debug-prefix-map @var{old}=@var{new}
675 When assembling files in directory @file{@var{old}}, record debugging
676 information describing them as in @file{@var{new}} instead.
678 @item --defsym @var{sym}=@var{value}
679 Define the symbol @var{sym} to be @var{value} before assembling the input file.
680 @var{value} must be an integer constant. As in C, a leading @samp{0x}
681 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
682 value. The value of the symbol can be overridden inside a source file via the
683 use of a @code{.set} pseudo-op.
686 ``fast''---skip whitespace and comment preprocessing (assume source is
691 Generate debugging information for each assembler source line using whichever
692 debug format is preferred by the target. This currently means either STABS,
696 Generate stabs debugging information for each assembler line. This
697 may help debugging assembler code, if the debugger can handle it.
700 Generate stabs debugging information for each assembler line, with GNU
701 extensions that probably only gdb can handle, and that could make other
702 debuggers crash or refuse to read your program. This
703 may help debugging assembler code. Currently the only GNU extension is
704 the location of the current working directory at assembling time.
707 Generate DWARF2 debugging information for each assembler line. This
708 may help debugging assembler code, if the debugger can handle it. Note---this
709 option is only supported by some targets, not all of them.
711 @item --gdwarf-sections
712 Instead of creating a .debug_line section, create a series of
713 .debug_line.@var{foo} sections where @var{foo} is the name of the
714 corresponding code section. For example a code section called @var{.text.func}
715 will have its dwarf line number information placed into a section called
716 @var{.debug_line.text.func}. If the code section is just called @var{.text}
717 then debug line section will still be called just @var{.debug_line} without any
721 @item --size-check=error
722 @itemx --size-check=warning
723 Issue an error or warning for invalid ELF .size directive.
725 @item --elf-stt-common=no
726 @itemx --elf-stt-common=yes
727 These options control whether the ELF assembler should generate common
728 symbols with the @code{STT_COMMON} type. The default can be controlled
729 by a configure option @option{--enable-elf-stt-common}.
733 Print a summary of the command line options and exit.
736 Print a summary of all target specific options and exit.
739 Add directory @var{dir} to the search list for @code{.include} directives.
742 Don't warn about signed overflow.
745 @ifclear DIFF-TBL-KLUGE
746 This option is accepted but has no effect on the @value{TARGET} family.
748 @ifset DIFF-TBL-KLUGE
749 Issue warnings when difference tables altered for long displacements.
754 Keep (in the symbol table) local symbols. These symbols start with
755 system-specific local label prefixes, typically @samp{.L} for ELF systems
756 or @samp{L} for traditional a.out systems.
761 @item --listing-lhs-width=@var{number}
762 Set the maximum width, in words, of the output data column for an assembler
763 listing to @var{number}.
765 @item --listing-lhs-width2=@var{number}
766 Set the maximum width, in words, of the output data column for continuation
767 lines in an assembler listing to @var{number}.
769 @item --listing-rhs-width=@var{number}
770 Set the maximum width of an input source line, as displayed in a listing, to
773 @item --listing-cont-lines=@var{number}
774 Set the maximum number of lines printed in a listing for a single line of input
777 @item --no-pad-sections
778 Stop the assembler for padding the ends of output sections to the alignment
779 of that section. The default is to pad the sections, but this can waste space
780 which might be needed on targets which have tight memory constraints.
782 @item -o @var{objfile}
783 Name the object-file output from @command{@value{AS}} @var{objfile}.
786 Fold the data section into the text section.
788 @item --hash-size=@var{number}
789 Set the default size of GAS's hash tables to a prime number close to
790 @var{number}. Increasing this value can reduce the length of time it takes the
791 assembler to perform its tasks, at the expense of increasing the assembler's
792 memory requirements. Similarly reducing this value can reduce the memory
793 requirements at the expense of speed.
795 @item --reduce-memory-overheads
796 This option reduces GAS's memory requirements, at the expense of making the
797 assembly processes slower. Currently this switch is a synonym for
798 @samp{--hash-size=4051}, but in the future it may have other effects as well.
801 @item --sectname-subst
802 Honor substitution sequences in section names.
804 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
809 Print the maximum space (in bytes) and total time (in seconds) used by
812 @item --strip-local-absolute
813 Remove local absolute symbols from the outgoing symbol table.
817 Print the @command{as} version.
820 Print the @command{as} version and exit.
824 Suppress warning messages.
826 @item --fatal-warnings
827 Treat warnings as errors.
830 Don't suppress warning messages or treat them as errors.
839 Generate an object file even after errors.
841 @item -- | @var{files} @dots{}
842 Standard input, or source files to assemble.
850 @xref{AArch64 Options}, for the options available when @value{AS} is configured
851 for the 64-bit mode of the ARM Architecture (AArch64).
856 The following options are available when @value{AS} is configured for the
857 64-bit mode of the ARM Architecture (AArch64).
860 @include c-aarch64.texi
861 @c ended inside the included file
869 @xref{Alpha Options}, for the options available when @value{AS} is configured
870 for an Alpha processor.
875 The following options are available when @value{AS} is configured for an Alpha
879 @include c-alpha.texi
880 @c ended inside the included file
887 The following options are available when @value{AS} is configured for an ARC
891 @item -mcpu=@var{cpu}
892 This option selects the core processor variant.
894 Select either big-endian (-EB) or little-endian (-EL) output.
896 Enable Code Density extenssion instructions.
901 The following options are available when @value{AS} is configured for the ARM
905 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
906 Specify which ARM processor variant is the target.
907 @item -march=@var{architecture}[+@var{extension}@dots{}]
908 Specify which ARM architecture variant is used by the target.
909 @item -mfpu=@var{floating-point-format}
910 Select which Floating Point architecture is the target.
911 @item -mfloat-abi=@var{abi}
912 Select which floating point ABI is in use.
914 Enable Thumb only instruction decoding.
915 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
916 Select which procedure calling convention is in use.
918 Select either big-endian (-EB) or little-endian (-EL) output.
919 @item -mthumb-interwork
920 Specify that the code has been generated with interworking between Thumb and
923 Turns on CodeComposer Studio assembly syntax compatibility mode.
925 Specify that PIC code has been generated.
933 @xref{Blackfin Options}, for the options available when @value{AS} is
934 configured for the Blackfin processor family.
939 The following options are available when @value{AS} is configured for
940 the Blackfin processor family.
944 @c ended inside the included file
951 See the info pages for documentation of the CRIS-specific options.
955 The following options are available when @value{AS} is configured for
958 @cindex D10V optimization
959 @cindex optimization, D10V
961 Optimize output by parallelizing instructions.
966 The following options are available when @value{AS} is configured for a D30V
969 @cindex D30V optimization
970 @cindex optimization, D30V
972 Optimize output by parallelizing instructions.
976 Warn when nops are generated.
978 @cindex D30V nops after 32-bit multiply
980 Warn when a nop after a 32-bit multiply instruction is generated.
986 The following options are available when @value{AS} is configured for the
987 Adapteva EPIPHANY series.
990 @xref{Epiphany Options}, for the options available when @value{AS} is
991 configured for an Epiphany processor.
996 The following options are available when @value{AS} is configured for
997 an Epiphany processor.
1000 @include c-epiphany.texi
1001 @c ended inside the included file
1009 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1010 for an H8/300 processor.
1014 @c man begin OPTIONS
1015 The following options are available when @value{AS} is configured for an H8/300
1018 @c man begin INCLUDE
1019 @include c-h8300.texi
1020 @c ended inside the included file
1028 @xref{i386-Options}, for the options available when @value{AS} is
1029 configured for an i386 processor.
1033 @c man begin OPTIONS
1034 The following options are available when @value{AS} is configured for
1037 @c man begin INCLUDE
1038 @include c-i386.texi
1039 @c ended inside the included file
1044 @c man begin OPTIONS
1046 The following options are available when @value{AS} is configured for the
1047 Intel 80960 processor.
1050 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1051 Specify which variant of the 960 architecture is the target.
1054 Add code to collect statistics about branches taken.
1057 Do not alter compare-and-branch instructions for long displacements;
1064 The following options are available when @value{AS} is configured for the
1070 Specifies that the extended IP2022 instructions are allowed.
1073 Restores the default behaviour, which restricts the permitted instructions to
1074 just the basic IP2022 ones.
1080 The following options are available when @value{AS} is configured for the
1081 Renesas M32C and M16C processors.
1086 Assemble M32C instructions.
1089 Assemble M16C instructions (the default).
1092 Enable support for link-time relaxations.
1095 Support H'00 style hex constants in addition to 0x00 style.
1101 The following options are available when @value{AS} is configured for the
1102 Renesas M32R (formerly Mitsubishi M32R) series.
1107 Specify which processor in the M32R family is the target. The default
1108 is normally the M32R, but this option changes it to the M32RX.
1110 @item --warn-explicit-parallel-conflicts or --Wp
1111 Produce warning messages when questionable parallel constructs are
1114 @item --no-warn-explicit-parallel-conflicts or --Wnp
1115 Do not produce warning messages when questionable parallel constructs are
1122 The following options are available when @value{AS} is configured for the
1123 Motorola 68000 series.
1128 Shorten references to undefined symbols, to one word instead of two.
1130 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1131 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1132 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1133 Specify what processor in the 68000 family is the target. The default
1134 is normally the 68020, but this can be changed at configuration time.
1136 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1137 The target machine does (or does not) have a floating-point coprocessor.
1138 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1139 the basic 68000 is not compatible with the 68881, a combination of the
1140 two can be specified, since it's possible to do emulation of the
1141 coprocessor instructions with the main processor.
1143 @item -m68851 | -mno-68851
1144 The target machine does (or does not) have a memory-management
1145 unit coprocessor. The default is to assume an MMU for 68020 and up.
1153 @xref{Nios II Options}, for the options available when @value{AS} is configured
1154 for an Altera Nios II processor.
1158 @c man begin OPTIONS
1159 The following options are available when @value{AS} is configured for an
1160 Altera Nios II processor.
1162 @c man begin INCLUDE
1163 @include c-nios2.texi
1164 @c ended inside the included file
1170 For details about the PDP-11 machine dependent features options,
1171 see @ref{PDP-11-Options}.
1174 @item -mpic | -mno-pic
1175 Generate position-independent (or position-dependent) code. The
1176 default is @option{-mpic}.
1179 @itemx -mall-extensions
1180 Enable all instruction set extensions. This is the default.
1182 @item -mno-extensions
1183 Disable all instruction set extensions.
1185 @item -m@var{extension} | -mno-@var{extension}
1186 Enable (or disable) a particular instruction set extension.
1189 Enable the instruction set extensions supported by a particular CPU, and
1190 disable all other extensions.
1192 @item -m@var{machine}
1193 Enable the instruction set extensions supported by a particular machine
1194 model, and disable all other extensions.
1200 The following options are available when @value{AS} is configured for
1201 a picoJava processor.
1205 @cindex PJ endianness
1206 @cindex endianness, PJ
1207 @cindex big endian output, PJ
1209 Generate ``big endian'' format output.
1211 @cindex little endian output, PJ
1213 Generate ``little endian'' format output.
1219 The following options are available when @value{AS} is configured for the
1220 Motorola 68HC11 or 68HC12 series.
1224 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1225 Specify what processor is the target. The default is
1226 defined by the configuration option when building the assembler.
1228 @item --xgate-ramoffset
1229 Instruct the linker to offset RAM addresses from S12X address space into
1230 XGATE address space.
1233 Specify to use the 16-bit integer ABI.
1236 Specify to use the 32-bit integer ABI.
1238 @item -mshort-double
1239 Specify to use the 32-bit double ABI.
1242 Specify to use the 64-bit double ABI.
1244 @item --force-long-branches
1245 Relative branches are turned into absolute ones. This concerns
1246 conditional branches, unconditional branches and branches to a
1249 @item -S | --short-branches
1250 Do not turn relative branches into absolute ones
1251 when the offset is out of range.
1253 @item --strict-direct-mode
1254 Do not turn the direct addressing mode into extended addressing mode
1255 when the instruction does not support direct addressing mode.
1257 @item --print-insn-syntax
1258 Print the syntax of instruction in case of error.
1260 @item --print-opcodes
1261 Print the list of instructions with syntax and then exit.
1263 @item --generate-example
1264 Print an example of instruction for each possible instruction and then exit.
1265 This option is only useful for testing @command{@value{AS}}.
1271 The following options are available when @command{@value{AS}} is configured
1272 for the SPARC architecture:
1275 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1276 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1277 Explicitly select a variant of the SPARC architecture.
1279 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1280 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1282 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1283 UltraSPARC extensions.
1285 @item -xarch=v8plus | -xarch=v8plusa
1286 For compatibility with the Solaris v9 assembler. These options are
1287 equivalent to -Av8plus and -Av8plusa, respectively.
1290 Warn when the assembler switches to another architecture.
1295 The following options are available when @value{AS} is configured for the 'c54x
1300 Enable extended addressing mode. All addresses and relocations will assume
1301 extended addressing (usually 23 bits).
1302 @item -mcpu=@var{CPU_VERSION}
1303 Sets the CPU version being compiled for.
1304 @item -merrors-to-file @var{FILENAME}
1305 Redirect error output to a file, for broken systems which don't support such
1306 behaviour in the shell.
1311 The following options are available when @value{AS} is configured for
1316 This option sets the largest size of an object that can be referenced
1317 implicitly with the @code{gp} register. It is only accepted for targets that
1318 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1320 @cindex MIPS endianness
1321 @cindex endianness, MIPS
1322 @cindex big endian output, MIPS
1324 Generate ``big endian'' format output.
1326 @cindex little endian output, MIPS
1328 Generate ``little endian'' format output.
1346 Generate code for a particular MIPS Instruction Set Architecture level.
1347 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1348 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1349 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1350 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1351 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1352 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1353 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1354 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1355 MIPS64 Release 6 ISA processors, respectively.
1357 @item -march=@var{cpu}
1358 Generate code for a particular MIPS CPU.
1360 @item -mtune=@var{cpu}
1361 Schedule and tune for a particular MIPS CPU.
1365 Cause nops to be inserted if the read of the destination register
1366 of an mfhi or mflo instruction occurs in the following two instructions.
1369 @itemx -mno-fix-rm7000
1370 Cause nops to be inserted if a dmult or dmultu instruction is
1371 followed by a load instruction.
1375 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1376 section instead of the standard ELF .stabs sections.
1380 Control generation of @code{.pdr} sections.
1384 The register sizes are normally inferred from the ISA and ABI, but these
1385 flags force a certain group of registers to be treated as 32 bits wide at
1386 all times. @samp{-mgp32} controls the size of general-purpose registers
1387 and @samp{-mfp32} controls the size of floating-point registers.
1391 The register sizes are normally inferred from the ISA and ABI, but these
1392 flags force a certain group of registers to be treated as 64 bits wide at
1393 all times. @samp{-mgp64} controls the size of general-purpose registers
1394 and @samp{-mfp64} controls the size of floating-point registers.
1397 The register sizes are normally inferred from the ISA and ABI, but using
1398 this flag in combination with @samp{-mabi=32} enables an ABI variant
1399 which will operate correctly with floating-point registers which are
1403 @itemx -mno-odd-spreg
1404 Enable use of floating-point operations on odd-numbered single-precision
1405 registers when supported by the ISA. @samp{-mfpxx} implies
1406 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1410 Generate code for the MIPS 16 processor. This is equivalent to putting
1411 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1412 turns off this option.
1415 @itemx -mno-micromips
1416 Generate code for the microMIPS processor. This is equivalent to putting
1417 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1418 turns off this option. This is equivalent to putting @code{.set nomicromips}
1419 at the start of the assembly file.
1422 @itemx -mno-smartmips
1423 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1424 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1425 @samp{-mno-smartmips} turns off this option.
1429 Generate code for the MIPS-3D Application Specific Extension.
1430 This tells the assembler to accept MIPS-3D instructions.
1431 @samp{-no-mips3d} turns off this option.
1435 Generate code for the MDMX Application Specific Extension.
1436 This tells the assembler to accept MDMX instructions.
1437 @samp{-no-mdmx} turns off this option.
1441 Generate code for the DSP Release 1 Application Specific Extension.
1442 This tells the assembler to accept DSP Release 1 instructions.
1443 @samp{-mno-dsp} turns off this option.
1447 Generate code for the DSP Release 2 Application Specific Extension.
1448 This option implies @samp{-mdsp}.
1449 This tells the assembler to accept DSP Release 2 instructions.
1450 @samp{-mno-dspr2} turns off this option.
1454 Generate code for the DSP Release 3 Application Specific Extension.
1455 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1456 This tells the assembler to accept DSP Release 3 instructions.
1457 @samp{-mno-dspr3} turns off this option.
1461 Generate code for the MIPS SIMD Architecture Extension.
1462 This tells the assembler to accept MSA instructions.
1463 @samp{-mno-msa} turns off this option.
1467 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1468 This tells the assembler to accept XPA instructions.
1469 @samp{-mno-xpa} turns off this option.
1473 Generate code for the MT Application Specific Extension.
1474 This tells the assembler to accept MT instructions.
1475 @samp{-mno-mt} turns off this option.
1479 Generate code for the MCU Application Specific Extension.
1480 This tells the assembler to accept MCU instructions.
1481 @samp{-mno-mcu} turns off this option.
1485 Only use 32-bit instruction encodings when generating code for the
1486 microMIPS processor. This option inhibits the use of any 16-bit
1487 instructions. This is equivalent to putting @code{.set insn32} at
1488 the start of the assembly file. @samp{-mno-insn32} turns off this
1489 option. This is equivalent to putting @code{.set noinsn32} at the
1490 start of the assembly file. By default @samp{-mno-insn32} is
1491 selected, allowing all instructions to be used.
1493 @item --construct-floats
1494 @itemx --no-construct-floats
1495 The @samp{--no-construct-floats} option disables the construction of
1496 double width floating point constants by loading the two halves of the
1497 value into the two single width floating point registers that make up
1498 the double width register. By default @samp{--construct-floats} is
1499 selected, allowing construction of these floating point constants.
1501 @item --relax-branch
1502 @itemx --no-relax-branch
1503 The @samp{--relax-branch} option enables the relaxation of out-of-range
1504 branches. By default @samp{--no-relax-branch} is selected, causing any
1505 out-of-range branches to produce an error.
1507 @item -mnan=@var{encoding}
1508 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1509 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1512 @item --emulation=@var{name}
1513 This option was formerly used to switch between ELF and ECOFF output
1514 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1515 removed in GAS 2.24, so the option now serves little purpose.
1516 It is retained for backwards compatibility.
1518 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1519 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1520 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1521 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1522 preferred options instead.
1525 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1532 Control how to deal with multiplication overflow and division by zero.
1533 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1534 (and only work for Instruction Set Architecture level 2 and higher);
1535 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1539 When this option is used, @command{@value{AS}} will issue a warning every
1540 time it generates a nop instruction from a macro.
1545 The following options are available when @value{AS} is configured for
1551 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1552 The command line option @samp{-nojsri2bsr} can be used to disable it.
1556 Enable or disable the silicon filter behaviour. By default this is disabled.
1557 The default can be overridden by the @samp{-sifilter} command line option.
1560 Alter jump instructions for long displacements.
1562 @item -mcpu=[210|340]
1563 Select the cpu type on the target hardware. This controls which instructions
1567 Assemble for a big endian target.
1570 Assemble for a little endian target.
1579 @xref{Meta Options}, for the options available when @value{AS} is configured
1580 for a Meta processor.
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-metag.texi
1590 @c ended inside the included file
1595 @c man begin OPTIONS
1597 See the info pages for documentation of the MMIX-specific options.
1603 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1604 for a NDS32 processor.
1606 @c ended inside the included file
1610 @c man begin OPTIONS
1611 The following options are available when @value{AS} is configured for a
1614 @c man begin INCLUDE
1615 @include c-nds32.texi
1616 @c ended inside the included file
1623 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1624 for a PowerPC processor.
1628 @c man begin OPTIONS
1629 The following options are available when @value{AS} is configured for a
1632 @c man begin INCLUDE
1634 @c ended inside the included file
1639 @c man begin OPTIONS
1641 See the info pages for documentation of the RX-specific options.
1645 The following options are available when @value{AS} is configured for the s390
1651 Select the word size, either 31/32 bits or 64 bits.
1654 Select the architecture mode, either the Enterprise System
1655 Architecture (esa) or the z/Architecture mode (zarch).
1656 @item -march=@var{processor}
1657 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1658 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1659 @samp{z196}, @samp{zEC12}, or @samp{z13}.
1661 @itemx -mno-regnames
1662 Allow or disallow symbolic names for registers.
1663 @item -mwarn-areg-zero
1664 Warn whenever the operand for a base or index register has been specified
1665 but evaluates to zero.
1673 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1674 for a TMS320C6000 processor.
1678 @c man begin OPTIONS
1679 The following options are available when @value{AS} is configured for a
1680 TMS320C6000 processor.
1682 @c man begin INCLUDE
1683 @include c-tic6x.texi
1684 @c ended inside the included file
1692 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1693 for a TILE-Gx processor.
1697 @c man begin OPTIONS
1698 The following options are available when @value{AS} is configured for a TILE-Gx
1701 @c man begin INCLUDE
1702 @include c-tilegx.texi
1703 @c ended inside the included file
1711 @xref{Visium Options}, for the options available when @value{AS} is configured
1712 for a Visium processor.
1716 @c man begin OPTIONS
1717 The following option is available when @value{AS} is configured for a Visium
1720 @c man begin INCLUDE
1721 @include c-visium.texi
1722 @c ended inside the included file
1730 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1731 for an Xtensa processor.
1735 @c man begin OPTIONS
1736 The following options are available when @value{AS} is configured for an
1739 @c man begin INCLUDE
1740 @include c-xtensa.texi
1741 @c ended inside the included file
1746 @c man begin OPTIONS
1749 The following options are available when @value{AS} is configured for
1750 a Z80 family processor.
1753 Assemble for Z80 processor.
1755 Assemble for R800 processor.
1756 @item -ignore-undocumented-instructions
1758 Assemble undocumented Z80 instructions that also work on R800 without warning.
1759 @item -ignore-unportable-instructions
1761 Assemble all undocumented Z80 instructions without warning.
1762 @item -warn-undocumented-instructions
1764 Issue a warning for undocumented Z80 instructions that also work on R800.
1765 @item -warn-unportable-instructions
1767 Issue a warning for undocumented Z80 instructions that do not work on R800.
1768 @item -forbid-undocumented-instructions
1770 Treat all undocumented instructions as errors.
1771 @item -forbid-unportable-instructions
1773 Treat undocumented Z80 instructions that do not work on R800 as errors.
1780 * Manual:: Structure of this Manual
1781 * GNU Assembler:: The GNU Assembler
1782 * Object Formats:: Object File Formats
1783 * Command Line:: Command Line
1784 * Input Files:: Input Files
1785 * Object:: Output (Object) File
1786 * Errors:: Error and Warning Messages
1790 @section Structure of this Manual
1792 @cindex manual, structure and purpose
1793 This manual is intended to describe what you need to know to use
1794 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1795 notation for symbols, constants, and expressions; the directives that
1796 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1799 We also cover special features in the @value{TARGET}
1800 configuration of @command{@value{AS}}, including assembler directives.
1803 This manual also describes some of the machine-dependent features of
1804 various flavors of the assembler.
1807 @cindex machine instructions (not covered)
1808 On the other hand, this manual is @emph{not} intended as an introduction
1809 to programming in assembly language---let alone programming in general!
1810 In a similar vein, we make no attempt to introduce the machine
1811 architecture; we do @emph{not} describe the instruction set, standard
1812 mnemonics, registers or addressing modes that are standard to a
1813 particular architecture.
1815 You may want to consult the manufacturer's
1816 machine architecture manual for this information.
1820 For information on the H8/300 machine instruction set, see @cite{H8/300
1821 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1822 Programming Manual} (Renesas).
1825 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1826 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1827 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1828 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1831 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1835 @c I think this is premature---doc@cygnus.com, 17jan1991
1837 Throughout this manual, we assume that you are running @dfn{GNU},
1838 the portable operating system from the @dfn{Free Software
1839 Foundation, Inc.}. This restricts our attention to certain kinds of
1840 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1841 once this assumption is granted examples and definitions need less
1844 @command{@value{AS}} is part of a team of programs that turn a high-level
1845 human-readable series of instructions into a low-level
1846 computer-readable series of instructions. Different versions of
1847 @command{@value{AS}} are used for different kinds of computer.
1850 @c There used to be a section "Terminology" here, which defined
1851 @c "contents", "byte", "word", and "long". Defining "word" to any
1852 @c particular size is confusing when the .word directive may generate 16
1853 @c bits on one machine and 32 bits on another; in general, for the user
1854 @c version of this manual, none of these terms seem essential to define.
1855 @c They were used very little even in the former draft of the manual;
1856 @c this draft makes an effort to avoid them (except in names of
1860 @section The GNU Assembler
1862 @c man begin DESCRIPTION
1864 @sc{gnu} @command{as} is really a family of assemblers.
1866 This manual describes @command{@value{AS}}, a member of that family which is
1867 configured for the @value{TARGET} architectures.
1869 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1870 should find a fairly similar environment when you use it on another
1871 architecture. Each version has much in common with the others,
1872 including object file formats, most assembler directives (often called
1873 @dfn{pseudo-ops}) and assembler syntax.@refill
1875 @cindex purpose of @sc{gnu} assembler
1876 @command{@value{AS}} is primarily intended to assemble the output of the
1877 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1878 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1879 assemble correctly everything that other assemblers for the same
1880 machine would assemble.
1882 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1885 @c This remark should appear in generic version of manual; assumption
1886 @c here is that generic version sets M680x0.
1887 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1888 assembler for the same architecture; for example, we know of several
1889 incompatible versions of 680x0 assembly language syntax.
1894 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1895 program in one pass of the source file. This has a subtle impact on the
1896 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1898 @node Object Formats
1899 @section Object File Formats
1901 @cindex object file format
1902 The @sc{gnu} assembler can be configured to produce several alternative
1903 object file formats. For the most part, this does not affect how you
1904 write assembly language programs; but directives for debugging symbols
1905 are typically different in different file formats. @xref{Symbol
1906 Attributes,,Symbol Attributes}.
1909 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1910 @value{OBJ-NAME} format object files.
1912 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1914 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1915 @code{b.out} or COFF format object files.
1918 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1919 SOM or ELF format object files.
1924 @section Command Line
1926 @cindex command line conventions
1928 After the program name @command{@value{AS}}, the command line may contain
1929 options and file names. Options may appear in any order, and may be
1930 before, after, or between file names. The order of file names is
1933 @cindex standard input, as input file
1935 @file{--} (two hyphens) by itself names the standard input file
1936 explicitly, as one of the files for @command{@value{AS}} to assemble.
1938 @cindex options, command line
1939 Except for @samp{--} any command line argument that begins with a
1940 hyphen (@samp{-}) is an option. Each option changes the behavior of
1941 @command{@value{AS}}. No option changes the way another option works. An
1942 option is a @samp{-} followed by one or more letters; the case of
1943 the letter is important. All options are optional.
1945 Some options expect exactly one file name to follow them. The file
1946 name may either immediately follow the option's letter (compatible
1947 with older assemblers) or it may be the next command argument (@sc{gnu}
1948 standard). These two command lines are equivalent:
1951 @value{AS} -o my-object-file.o mumble.s
1952 @value{AS} -omy-object-file.o mumble.s
1956 @section Input Files
1959 @cindex source program
1960 @cindex files, input
1961 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1962 describe the program input to one run of @command{@value{AS}}. The program may
1963 be in one or more files; how the source is partitioned into files
1964 doesn't change the meaning of the source.
1966 @c I added "con" prefix to "catenation" just to prove I can overcome my
1967 @c APL training... doc@cygnus.com
1968 The source program is a concatenation of the text in all the files, in the
1971 @c man begin DESCRIPTION
1972 Each time you run @command{@value{AS}} it assembles exactly one source
1973 program. The source program is made up of one or more files.
1974 (The standard input is also a file.)
1976 You give @command{@value{AS}} a command line that has zero or more input file
1977 names. The input files are read (from left file name to right). A
1978 command line argument (in any position) that has no special meaning
1979 is taken to be an input file name.
1981 If you give @command{@value{AS}} no file names it attempts to read one input file
1982 from the @command{@value{AS}} standard input, which is normally your terminal. You
1983 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1986 Use @samp{--} if you need to explicitly name the standard input file
1987 in your command line.
1989 If the source is empty, @command{@value{AS}} produces a small, empty object
1994 @subheading Filenames and Line-numbers
1996 @cindex input file linenumbers
1997 @cindex line numbers, in input files
1998 There are two ways of locating a line in the input file (or files) and
1999 either may be used in reporting error messages. One way refers to a line
2000 number in a physical file; the other refers to a line number in a
2001 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2003 @dfn{Physical files} are those files named in the command line given
2004 to @command{@value{AS}}.
2006 @dfn{Logical files} are simply names declared explicitly by assembler
2007 directives; they bear no relation to physical files. Logical file names help
2008 error messages reflect the original source file, when @command{@value{AS}} source
2009 is itself synthesized from other files. @command{@value{AS}} understands the
2010 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2011 @ref{File,,@code{.file}}.
2014 @section Output (Object) File
2020 Every time you run @command{@value{AS}} it produces an output file, which is
2021 your assembly language program translated into numbers. This file
2022 is the object file. Its default name is
2030 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2032 You can give it another name by using the @option{-o} option. Conventionally,
2033 object file names end with @file{.o}. The default name is used for historical
2034 reasons: older assemblers were capable of assembling self-contained programs
2035 directly into a runnable program. (For some formats, this isn't currently
2036 possible, but it can be done for the @code{a.out} format.)
2040 The object file is meant for input to the linker @code{@value{LD}}. It contains
2041 assembled program code, information to help @code{@value{LD}} integrate
2042 the assembled program into a runnable file, and (optionally) symbolic
2043 information for the debugger.
2045 @c link above to some info file(s) like the description of a.out.
2046 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2049 @section Error and Warning Messages
2051 @c man begin DESCRIPTION
2053 @cindex error messages
2054 @cindex warning messages
2055 @cindex messages from assembler
2056 @command{@value{AS}} may write warnings and error messages to the standard error
2057 file (usually your terminal). This should not happen when a compiler
2058 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2059 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2060 grave problem that stops the assembly.
2064 @cindex format of warning messages
2065 Warning messages have the format
2068 file_name:@b{NNN}:Warning Message Text
2072 @cindex file names and line numbers, in warnings/errors
2073 (where @b{NNN} is a line number). If both a logical file name
2074 (@pxref{File,,@code{.file}}) and a logical line number
2076 (@pxref{Line,,@code{.line}})
2078 have been given then they will be used, otherwise the file name and line number
2079 in the current assembler source file will be used. The message text is
2080 intended to be self explanatory (in the grand Unix tradition).
2082 Note the file name must be set via the logical version of the @code{.file}
2083 directive, not the DWARF2 version of the @code{.file} directive. For example:
2087 error_assembler_source
2093 produces this output:
2097 asm.s:2: Error: no such instruction: `error_assembler_source'
2098 foo.c:31: Error: no such instruction: `error_c_source'
2101 @cindex format of error messages
2102 Error messages have the format
2105 file_name:@b{NNN}:FATAL:Error Message Text
2108 The file name and line number are derived as for warning
2109 messages. The actual message text may be rather less explanatory
2110 because many of them aren't supposed to happen.
2113 @chapter Command-Line Options
2115 @cindex options, all versions of assembler
2116 This chapter describes command-line options available in @emph{all}
2117 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2118 for options specific
2120 to the @value{TARGET} target.
2123 to particular machine architectures.
2126 @c man begin DESCRIPTION
2128 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2129 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2130 The assembler arguments must be separated from each other (and the @samp{-Wa})
2131 by commas. For example:
2134 gcc -c -g -O -Wa,-alh,-L file.c
2138 This passes two options to the assembler: @samp{-alh} (emit a listing to
2139 standard output with high-level and assembly source) and @samp{-L} (retain
2140 local symbols in the symbol table).
2142 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2143 command-line options are automatically passed to the assembler by the compiler.
2144 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2145 precisely what options it passes to each compilation pass, including the
2151 * a:: -a[cdghlns] enable listings
2152 * alternate:: --alternate enable alternate macro syntax
2153 * D:: -D for compatibility
2154 * f:: -f to work faster
2155 * I:: -I for .include search path
2156 @ifclear DIFF-TBL-KLUGE
2157 * K:: -K for compatibility
2159 @ifset DIFF-TBL-KLUGE
2160 * K:: -K for difference tables
2163 * L:: -L to retain local symbols
2164 * listing:: --listing-XXX to configure listing output
2165 * M:: -M or --mri to assemble in MRI compatibility mode
2166 * MD:: --MD for dependency tracking
2167 * no-pad-sections:: --no-pad-sections to stop section padding
2168 * o:: -o to name the object file
2169 * R:: -R to join data and text sections
2170 * statistics:: --statistics to see statistics about assembly
2171 * traditional-format:: --traditional-format for compatible output
2172 * v:: -v to announce version
2173 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2174 * Z:: -Z to make object file even after errors
2178 @section Enable Listings: @option{-a[cdghlns]}
2188 @cindex listings, enabling
2189 @cindex assembly listings, enabling
2191 These options enable listing output from the assembler. By itself,
2192 @samp{-a} requests high-level, assembly, and symbols listing.
2193 You can use other letters to select specific options for the list:
2194 @samp{-ah} requests a high-level language listing,
2195 @samp{-al} requests an output-program assembly listing, and
2196 @samp{-as} requests a symbol table listing.
2197 High-level listings require that a compiler debugging option like
2198 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2201 Use the @samp{-ag} option to print a first section with general assembly
2202 information, like @value{AS} version, switches passed, or time stamp.
2204 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2205 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2206 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2207 omitted from the listing.
2209 Use the @samp{-ad} option to omit debugging directives from the
2212 Once you have specified one of these options, you can further control
2213 listing output and its appearance using the directives @code{.list},
2214 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2216 The @samp{-an} option turns off all forms processing.
2217 If you do not request listing output with one of the @samp{-a} options, the
2218 listing-control directives have no effect.
2220 The letters after @samp{-a} may be combined into one option,
2221 @emph{e.g.}, @samp{-aln}.
2223 Note if the assembler source is coming from the standard input (e.g.,
2225 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2226 is being used) then the listing will not contain any comments or preprocessor
2227 directives. This is because the listing code buffers input source lines from
2228 stdin only after they have been preprocessed by the assembler. This reduces
2229 memory usage and makes the code more efficient.
2232 @section @option{--alternate}
2235 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2238 @section @option{-D}
2241 This option has no effect whatsoever, but it is accepted to make it more
2242 likely that scripts written for other assemblers also work with
2243 @command{@value{AS}}.
2246 @section Work Faster: @option{-f}
2249 @cindex trusted compiler
2250 @cindex faster processing (@option{-f})
2251 @samp{-f} should only be used when assembling programs written by a
2252 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2253 and comment preprocessing on
2254 the input file(s) before assembling them. @xref{Preprocessing,
2258 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2259 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2264 @section @code{.include} Search Path: @option{-I} @var{path}
2266 @kindex -I @var{path}
2267 @cindex paths for @code{.include}
2268 @cindex search path for @code{.include}
2269 @cindex @code{include} directive search path
2270 Use this option to add a @var{path} to the list of directories
2271 @command{@value{AS}} searches for files specified in @code{.include}
2272 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2273 many times as necessary to include a variety of paths. The current
2274 working directory is always searched first; after that, @command{@value{AS}}
2275 searches any @samp{-I} directories in the same order as they were
2276 specified (left to right) on the command line.
2279 @section Difference Tables: @option{-K}
2282 @ifclear DIFF-TBL-KLUGE
2283 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2284 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2285 where it can be used to warn when the assembler alters the machine code
2286 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2287 family does not have the addressing limitations that sometimes lead to this
2288 alteration on other platforms.
2291 @ifset DIFF-TBL-KLUGE
2292 @cindex difference tables, warning
2293 @cindex warning for altered difference tables
2294 @command{@value{AS}} sometimes alters the code emitted for directives of the
2295 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2296 You can use the @samp{-K} option if you want a warning issued when this
2301 @section Include Local Symbols: @option{-L}
2304 @cindex local symbols, retaining in output
2305 Symbols beginning with system-specific local label prefixes, typically
2306 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2307 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2308 such symbols when debugging, because they are intended for the use of
2309 programs (like compilers) that compose assembler programs, not for your
2310 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2311 such symbols, so you do not normally debug with them.
2313 This option tells @command{@value{AS}} to retain those local symbols
2314 in the object file. Usually if you do this you also tell the linker
2315 @code{@value{LD}} to preserve those symbols.
2318 @section Configuring listing output: @option{--listing}
2320 The listing feature of the assembler can be enabled via the command line switch
2321 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2322 hex dump of the corresponding locations in the output object file, and displays
2323 them as a listing file. The format of this listing can be controlled by
2324 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2325 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2326 @code{.psize} (@pxref{Psize}), and
2327 @code{.eject} (@pxref{Eject}) and also by the following switches:
2330 @item --listing-lhs-width=@samp{number}
2331 @kindex --listing-lhs-width
2332 @cindex Width of first line disassembly output
2333 Sets the maximum width, in words, of the first line of the hex byte dump. This
2334 dump appears on the left hand side of the listing output.
2336 @item --listing-lhs-width2=@samp{number}
2337 @kindex --listing-lhs-width2
2338 @cindex Width of continuation lines of disassembly output
2339 Sets the maximum width, in words, of any further lines of the hex byte dump for
2340 a given input source line. If this value is not specified, it defaults to being
2341 the same as the value specified for @samp{--listing-lhs-width}. If neither
2342 switch is used the default is to one.
2344 @item --listing-rhs-width=@samp{number}
2345 @kindex --listing-rhs-width
2346 @cindex Width of source line output
2347 Sets the maximum width, in characters, of the source line that is displayed
2348 alongside the hex dump. The default value for this parameter is 100. The
2349 source line is displayed on the right hand side of the listing output.
2351 @item --listing-cont-lines=@samp{number}
2352 @kindex --listing-cont-lines
2353 @cindex Maximum number of continuation lines
2354 Sets the maximum number of continuation lines of hex dump that will be
2355 displayed for a given single line of source input. The default value is 4.
2359 @section Assemble in MRI Compatibility Mode: @option{-M}
2362 @cindex MRI compatibility mode
2363 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2364 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2365 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2366 configured target) assembler from Microtec Research. The exact nature of the
2367 MRI syntax will not be documented here; see the MRI manuals for more
2368 information. Note in particular that the handling of macros and macro
2369 arguments is somewhat different. The purpose of this option is to permit
2370 assembling existing MRI assembler code using @command{@value{AS}}.
2372 The MRI compatibility is not complete. Certain operations of the MRI assembler
2373 depend upon its object file format, and can not be supported using other object
2374 file formats. Supporting these would require enhancing each object file format
2375 individually. These are:
2378 @item global symbols in common section
2380 The m68k MRI assembler supports common sections which are merged by the linker.
2381 Other object file formats do not support this. @command{@value{AS}} handles
2382 common sections by treating them as a single common symbol. It permits local
2383 symbols to be defined within a common section, but it can not support global
2384 symbols, since it has no way to describe them.
2386 @item complex relocations
2388 The MRI assemblers support relocations against a negated section address, and
2389 relocations which combine the start addresses of two or more sections. These
2390 are not support by other object file formats.
2392 @item @code{END} pseudo-op specifying start address
2394 The MRI @code{END} pseudo-op permits the specification of a start address.
2395 This is not supported by other object file formats. The start address may
2396 instead be specified using the @option{-e} option to the linker, or in a linker
2399 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2401 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2402 name to the output file. This is not supported by other object file formats.
2404 @item @code{ORG} pseudo-op
2406 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2407 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2408 which changes the location within the current section. Absolute sections are
2409 not supported by other object file formats. The address of a section may be
2410 assigned within a linker script.
2413 There are some other features of the MRI assembler which are not supported by
2414 @command{@value{AS}}, typically either because they are difficult or because they
2415 seem of little consequence. Some of these may be supported in future releases.
2419 @item EBCDIC strings
2421 EBCDIC strings are not supported.
2423 @item packed binary coded decimal
2425 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2426 and @code{DCB.P} pseudo-ops are not supported.
2428 @item @code{FEQU} pseudo-op
2430 The m68k @code{FEQU} pseudo-op is not supported.
2432 @item @code{NOOBJ} pseudo-op
2434 The m68k @code{NOOBJ} pseudo-op is not supported.
2436 @item @code{OPT} branch control options
2438 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2439 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2440 relaxes all branches, whether forward or backward, to an appropriate size, so
2441 these options serve no purpose.
2443 @item @code{OPT} list control options
2445 The following m68k @code{OPT} list control options are ignored: @code{C},
2446 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2447 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2449 @item other @code{OPT} options
2451 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2452 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2454 @item @code{OPT} @code{D} option is default
2456 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2457 @code{OPT NOD} may be used to turn it off.
2459 @item @code{XREF} pseudo-op.
2461 The m68k @code{XREF} pseudo-op is ignored.
2463 @item @code{.debug} pseudo-op
2465 The i960 @code{.debug} pseudo-op is not supported.
2467 @item @code{.extended} pseudo-op
2469 The i960 @code{.extended} pseudo-op is not supported.
2471 @item @code{.list} pseudo-op.
2473 The various options of the i960 @code{.list} pseudo-op are not supported.
2475 @item @code{.optimize} pseudo-op
2477 The i960 @code{.optimize} pseudo-op is not supported.
2479 @item @code{.output} pseudo-op
2481 The i960 @code{.output} pseudo-op is not supported.
2483 @item @code{.setreal} pseudo-op
2485 The i960 @code{.setreal} pseudo-op is not supported.
2490 @section Dependency Tracking: @option{--MD}
2493 @cindex dependency tracking
2496 @command{@value{AS}} can generate a dependency file for the file it creates. This
2497 file consists of a single rule suitable for @code{make} describing the
2498 dependencies of the main source file.
2500 The rule is written to the file named in its argument.
2502 This feature is used in the automatic updating of makefiles.
2504 @node no-pad-sections
2505 @section Output Section Padding
2506 @kindex --no-pad-sections
2507 @cindex output section padding
2508 Normally the assembler will pad the end of each output section up to its
2509 alignment boundary. But this can waste space, which can be significant on
2510 memory constrained targets. So the @option{--no-pad-sections} option will
2511 disable this behaviour.
2514 @section Name the Object File: @option{-o}
2517 @cindex naming object file
2518 @cindex object file name
2519 There is always one object file output when you run @command{@value{AS}}. By
2520 default it has the name
2523 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2537 You use this option (which takes exactly one filename) to give the
2538 object file a different name.
2540 Whatever the object file is called, @command{@value{AS}} overwrites any
2541 existing file of the same name.
2544 @section Join Data and Text Sections: @option{-R}
2547 @cindex data and text sections, joining
2548 @cindex text and data sections, joining
2549 @cindex joining text and data sections
2550 @cindex merging text and data sections
2551 @option{-R} tells @command{@value{AS}} to write the object file as if all
2552 data-section data lives in the text section. This is only done at
2553 the very last moment: your binary data are the same, but data
2554 section parts are relocated differently. The data section part of
2555 your object file is zero bytes long because all its bytes are
2556 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2558 When you specify @option{-R} it would be possible to generate shorter
2559 address displacements (because we do not have to cross between text and
2560 data section). We refrain from doing this simply for compatibility with
2561 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2564 When @command{@value{AS}} is configured for COFF or ELF output,
2565 this option is only useful if you use sections named @samp{.text} and
2570 @option{-R} is not supported for any of the HPPA targets. Using
2571 @option{-R} generates a warning from @command{@value{AS}}.
2575 @section Display Assembly Statistics: @option{--statistics}
2577 @kindex --statistics
2578 @cindex statistics, about assembly
2579 @cindex time, total for assembly
2580 @cindex space used, maximum for assembly
2581 Use @samp{--statistics} to display two statistics about the resources used by
2582 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2583 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2586 @node traditional-format
2587 @section Compatible Output: @option{--traditional-format}
2589 @kindex --traditional-format
2590 For some targets, the output of @command{@value{AS}} is different in some ways
2591 from the output of some existing assembler. This switch requests
2592 @command{@value{AS}} to use the traditional format instead.
2594 For example, it disables the exception frame optimizations which
2595 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2598 @section Announce Version: @option{-v}
2602 @cindex assembler version
2603 @cindex version of assembler
2604 You can find out what version of as is running by including the
2605 option @samp{-v} (which you can also spell as @samp{-version}) on the
2609 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2611 @command{@value{AS}} should never give a warning or error message when
2612 assembling compiler output. But programs written by people often
2613 cause @command{@value{AS}} to give a warning that a particular assumption was
2614 made. All such warnings are directed to the standard error file.
2618 @cindex suppressing warnings
2619 @cindex warnings, suppressing
2620 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2621 This only affects the warning messages: it does not change any particular of
2622 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2625 @kindex --fatal-warnings
2626 @cindex errors, caused by warnings
2627 @cindex warnings, causing error
2628 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2629 files that generate warnings to be in error.
2632 @cindex warnings, switching on
2633 You can switch these options off again by specifying @option{--warn}, which
2634 causes warnings to be output as usual.
2637 @section Generate Object File in Spite of Errors: @option{-Z}
2638 @cindex object file, after errors
2639 @cindex errors, continuing after
2640 After an error message, @command{@value{AS}} normally produces no output. If for
2641 some reason you are interested in object file output even after
2642 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2643 option. If there are any errors, @command{@value{AS}} continues anyways, and
2644 writes an object file after a final warning message of the form @samp{@var{n}
2645 errors, @var{m} warnings, generating bad object file.}
2650 @cindex machine-independent syntax
2651 @cindex syntax, machine-independent
2652 This chapter describes the machine-independent syntax allowed in a
2653 source file. @command{@value{AS}} syntax is similar to what many other
2654 assemblers use; it is inspired by the BSD 4.2
2659 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2663 * Preprocessing:: Preprocessing
2664 * Whitespace:: Whitespace
2665 * Comments:: Comments
2666 * Symbol Intro:: Symbols
2667 * Statements:: Statements
2668 * Constants:: Constants
2672 @section Preprocessing
2674 @cindex preprocessing
2675 The @command{@value{AS}} internal preprocessor:
2677 @cindex whitespace, removed by preprocessor
2679 adjusts and removes extra whitespace. It leaves one space or tab before
2680 the keywords on a line, and turns any other whitespace on the line into
2683 @cindex comments, removed by preprocessor
2685 removes all comments, replacing them with a single space, or an
2686 appropriate number of newlines.
2688 @cindex constants, converted by preprocessor
2690 converts character constants into the appropriate numeric values.
2693 It does not do macro processing, include file handling, or
2694 anything else you may get from your C compiler's preprocessor. You can
2695 do include file processing with the @code{.include} directive
2696 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2697 to get other ``CPP'' style preprocessing by giving the input file a
2698 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2699 Output, gcc info, Using GNU CC}.
2701 Excess whitespace, comments, and character constants
2702 cannot be used in the portions of the input text that are not
2705 @cindex turning preprocessing on and off
2706 @cindex preprocessing, turning on and off
2709 If the first line of an input file is @code{#NO_APP} or if you use the
2710 @samp{-f} option, whitespace and comments are not removed from the input file.
2711 Within an input file, you can ask for whitespace and comment removal in
2712 specific portions of the by putting a line that says @code{#APP} before the
2713 text that may contain whitespace or comments, and putting a line that says
2714 @code{#NO_APP} after this text. This feature is mainly intend to support
2715 @code{asm} statements in compilers whose output is otherwise free of comments
2722 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2723 Whitespace is used to separate symbols, and to make programs neater for
2724 people to read. Unless within character constants
2725 (@pxref{Characters,,Character Constants}), any whitespace means the same
2726 as exactly one space.
2732 There are two ways of rendering comments to @command{@value{AS}}. In both
2733 cases the comment is equivalent to one space.
2735 Anything from @samp{/*} through the next @samp{*/} is a comment.
2736 This means you may not nest these comments.
2740 The only way to include a newline ('\n') in a comment
2741 is to use this sort of comment.
2744 /* This sort of comment does not nest. */
2747 @cindex line comment character
2748 Anything from a @dfn{line comment} character up to the next newline is
2749 considered a comment and is ignored. The line comment character is target
2750 specific, and some targets multiple comment characters. Some targets also have
2751 line comment characters that only work if they are the first character on a
2752 line. Some targets use a sequence of two characters to introduce a line
2753 comment. Some targets can also change their line comment characters depending
2754 upon command line options that have been used. For more details see the
2755 @emph{Syntax} section in the documentation for individual targets.
2757 If the line comment character is the hash sign (@samp{#}) then it still has the
2758 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2759 to specify logical line numbers:
2762 @cindex lines starting with @code{#}
2763 @cindex logical line numbers
2764 To be compatible with past assemblers, lines that begin with @samp{#} have a
2765 special interpretation. Following the @samp{#} should be an absolute
2766 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2767 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2768 new logical file name. The rest of the line, if any, should be whitespace.
2770 If the first non-whitespace characters on the line are not numeric,
2771 the line is ignored. (Just like a comment.)
2774 # This is an ordinary comment.
2775 # 42-6 "new_file_name" # New logical file name
2776 # This is logical line # 36.
2778 This feature is deprecated, and may disappear from future versions
2779 of @command{@value{AS}}.
2784 @cindex characters used in symbols
2785 @ifclear SPECIAL-SYMS
2786 A @dfn{symbol} is one or more characters chosen from the set of all
2787 letters (both upper and lower case), digits and the three characters
2793 A @dfn{symbol} is one or more characters chosen from the set of all
2794 letters (both upper and lower case), digits and the three characters
2795 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2801 On most machines, you can also use @code{$} in symbol names; exceptions
2802 are noted in @ref{Machine Dependencies}.
2804 No symbol may begin with a digit. Case is significant.
2805 There is no length limit; all characters are significant. Multibyte characters
2806 are supported. Symbols are delimited by characters not in that set, or by the
2807 beginning of a file (since the source program must end with a newline, the end
2808 of a file is not a possible symbol delimiter). @xref{Symbols}.
2810 Symbol names may also be enclosed in double quote @code{"} characters. In such
2811 cases any characters are allowed, except for the NUL character. If a double
2812 quote character is to be included in the symbol name it must be preceeded by a
2813 backslash @code{\} character.
2814 @cindex length of symbols
2819 @cindex statements, structure of
2820 @cindex line separator character
2821 @cindex statement separator character
2823 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2824 @dfn{line separator character}. The line separator character is target
2825 specific and described in the @emph{Syntax} section of each
2826 target's documentation. Not all targets support a line separator character.
2827 The newline or line separator character is considered to be part of the
2828 preceding statement. Newlines and separators within character constants are an
2829 exception: they do not end statements.
2831 @cindex newline, required at file end
2832 @cindex EOF, newline must precede
2833 It is an error to end any statement with end-of-file: the last
2834 character of any input file should be a newline.@refill
2836 An empty statement is allowed, and may include whitespace. It is ignored.
2838 @cindex instructions and directives
2839 @cindex directives and instructions
2840 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2841 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2843 A statement begins with zero or more labels, optionally followed by a
2844 key symbol which determines what kind of statement it is. The key
2845 symbol determines the syntax of the rest of the statement. If the
2846 symbol begins with a dot @samp{.} then the statement is an assembler
2847 directive: typically valid for any computer. If the symbol begins with
2848 a letter the statement is an assembly language @dfn{instruction}: it
2849 assembles into a machine language instruction.
2851 Different versions of @command{@value{AS}} for different computers
2852 recognize different instructions. In fact, the same symbol may
2853 represent a different instruction in a different computer's assembly
2857 @cindex @code{:} (label)
2858 @cindex label (@code{:})
2859 A label is a symbol immediately followed by a colon (@code{:}).
2860 Whitespace before a label or after a colon is permitted, but you may not
2861 have whitespace between a label's symbol and its colon. @xref{Labels}.
2864 For HPPA targets, labels need not be immediately followed by a colon, but
2865 the definition of a label must begin in column zero. This also implies that
2866 only one label may be defined on each line.
2870 label: .directive followed by something
2871 another_label: # This is an empty statement.
2872 instruction operand_1, operand_2, @dots{}
2879 A constant is a number, written so that its value is known by
2880 inspection, without knowing any context. Like this:
2883 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2884 .ascii "Ring the bell\7" # A string constant.
2885 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2886 .float 0f-314159265358979323846264338327\
2887 95028841971.693993751E-40 # - pi, a flonum.
2892 * Characters:: Character Constants
2893 * Numbers:: Number Constants
2897 @subsection Character Constants
2899 @cindex character constants
2900 @cindex constants, character
2901 There are two kinds of character constants. A @dfn{character} stands
2902 for one character in one byte and its value may be used in
2903 numeric expressions. String constants (properly called string
2904 @emph{literals}) are potentially many bytes and their values may not be
2905 used in arithmetic expressions.
2909 * Chars:: Characters
2913 @subsubsection Strings
2915 @cindex string constants
2916 @cindex constants, string
2917 A @dfn{string} is written between double-quotes. It may contain
2918 double-quotes or null characters. The way to get special characters
2919 into a string is to @dfn{escape} these characters: precede them with
2920 a backslash @samp{\} character. For example @samp{\\} represents
2921 one backslash: the first @code{\} is an escape which tells
2922 @command{@value{AS}} to interpret the second character literally as a backslash
2923 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2924 escape character). The complete list of escapes follows.
2926 @cindex escape codes, character
2927 @cindex character escape codes
2928 @c NOTE: Cindex entries must not start with a backlash character.
2929 @c NOTE: This confuses the pdf2texi script when it is creating the
2930 @c NOTE: index based upon the first character and so it generates:
2931 @c NOTE: \initial {\\}
2932 @c NOTE: which then results in the error message:
2933 @c NOTE: Argument of \\ has an extra }.
2934 @c NOTE: So in the index entries below a space character has been
2935 @c NOTE: prepended to avoid this problem.
2938 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2940 @cindex @code{ \b} (backspace character)
2941 @cindex backspace (@code{\b})
2943 Mnemonic for backspace; for ASCII this is octal code 010.
2946 @c Mnemonic for EOText; for ASCII this is octal code 004.
2948 @cindex @code{ \f} (formfeed character)
2949 @cindex formfeed (@code{\f})
2951 Mnemonic for FormFeed; for ASCII this is octal code 014.
2953 @cindex @code{ \n} (newline character)
2954 @cindex newline (@code{\n})
2956 Mnemonic for newline; for ASCII this is octal code 012.
2959 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2961 @cindex @code{ \r} (carriage return character)
2962 @cindex carriage return (@code{backslash-r})
2964 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2967 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2968 @c other assemblers.
2970 @cindex @code{ \t} (tab)
2971 @cindex tab (@code{\t})
2973 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2976 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2977 @c @item \x @var{digit} @var{digit} @var{digit}
2978 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2980 @cindex @code{ \@var{ddd}} (octal character code)
2981 @cindex octal character code (@code{\@var{ddd}})
2982 @item \ @var{digit} @var{digit} @var{digit}
2983 An octal character code. The numeric code is 3 octal digits.
2984 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2985 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2987 @cindex @code{ \@var{xd...}} (hex character code)
2988 @cindex hex character code (@code{\@var{xd...}})
2989 @item \@code{x} @var{hex-digits...}
2990 A hex character code. All trailing hex digits are combined. Either upper or
2991 lower case @code{x} works.
2993 @cindex @code{ \\} (@samp{\} character)
2994 @cindex backslash (@code{\\})
2996 Represents one @samp{\} character.
2999 @c Represents one @samp{'} (accent acute) character.
3000 @c This is needed in single character literals
3001 @c (@xref{Characters,,Character Constants}.) to represent
3004 @cindex @code{ \"} (doublequote character)
3005 @cindex doublequote (@code{\"})
3007 Represents one @samp{"} character. Needed in strings to represent
3008 this character, because an unescaped @samp{"} would end the string.
3010 @item \ @var{anything-else}
3011 Any other character when escaped by @kbd{\} gives a warning, but
3012 assembles as if the @samp{\} was not present. The idea is that if
3013 you used an escape sequence you clearly didn't want the literal
3014 interpretation of the following character. However @command{@value{AS}} has no
3015 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3016 code and warns you of the fact.
3019 Which characters are escapable, and what those escapes represent,
3020 varies widely among assemblers. The current set is what we think
3021 the BSD 4.2 assembler recognizes, and is a subset of what most C
3022 compilers recognize. If you are in doubt, do not use an escape
3026 @subsubsection Characters
3028 @cindex single character constant
3029 @cindex character, single
3030 @cindex constant, single character
3031 A single character may be written as a single quote immediately
3032 followed by that character. The same escapes apply to characters as
3033 to strings. So if you want to write the character backslash, you
3034 must write @kbd{'\\} where the first @code{\} escapes the second
3035 @code{\}. As you can see, the quote is an acute accent, not a
3036 grave accent. A newline
3038 @ifclear abnormal-separator
3039 (or semicolon @samp{;})
3041 @ifset abnormal-separator
3043 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3048 immediately following an acute accent is taken as a literal character
3049 and does not count as the end of a statement. The value of a character
3050 constant in a numeric expression is the machine's byte-wide code for
3051 that character. @command{@value{AS}} assumes your character code is ASCII:
3052 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3055 @subsection Number Constants
3057 @cindex constants, number
3058 @cindex number constants
3059 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3060 are stored in the target machine. @emph{Integers} are numbers that
3061 would fit into an @code{int} in the C language. @emph{Bignums} are
3062 integers, but they are stored in more than 32 bits. @emph{Flonums}
3063 are floating point numbers, described below.
3066 * Integers:: Integers
3071 * Bit Fields:: Bit Fields
3077 @subsubsection Integers
3079 @cindex constants, integer
3081 @cindex binary integers
3082 @cindex integers, binary
3083 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3084 the binary digits @samp{01}.
3086 @cindex octal integers
3087 @cindex integers, octal
3088 An octal integer is @samp{0} followed by zero or more of the octal
3089 digits (@samp{01234567}).
3091 @cindex decimal integers
3092 @cindex integers, decimal
3093 A decimal integer starts with a non-zero digit followed by zero or
3094 more digits (@samp{0123456789}).
3096 @cindex hexadecimal integers
3097 @cindex integers, hexadecimal
3098 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3099 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3101 Integers have the usual values. To denote a negative integer, use
3102 the prefix operator @samp{-} discussed under expressions
3103 (@pxref{Prefix Ops,,Prefix Operators}).
3106 @subsubsection Bignums
3109 @cindex constants, bignum
3110 A @dfn{bignum} has the same syntax and semantics as an integer
3111 except that the number (or its negative) takes more than 32 bits to
3112 represent in binary. The distinction is made because in some places
3113 integers are permitted while bignums are not.
3116 @subsubsection Flonums
3118 @cindex floating point numbers
3119 @cindex constants, floating point
3121 @cindex precision, floating point
3122 A @dfn{flonum} represents a floating point number. The translation is
3123 indirect: a decimal floating point number from the text is converted by
3124 @command{@value{AS}} to a generic binary floating point number of more than
3125 sufficient precision. This generic floating point number is converted
3126 to a particular computer's floating point format (or formats) by a
3127 portion of @command{@value{AS}} specialized to that computer.
3129 A flonum is written by writing (in order)
3134 (@samp{0} is optional on the HPPA.)
3138 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3140 @kbd{e} is recommended. Case is not important.
3142 @c FIXME: verify if flonum syntax really this vague for most cases
3143 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3144 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3147 On the H8/300, Renesas / SuperH SH,
3148 and AMD 29K architectures, the letter must be
3149 one of the letters @samp{DFPRSX} (in upper or lower case).
3151 On the ARC, the letter must be one of the letters @samp{DFRS}
3152 (in upper or lower case).
3154 On the Intel 960 architecture, the letter must be
3155 one of the letters @samp{DFT} (in upper or lower case).
3157 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3161 One of the letters @samp{DFRS} (in upper or lower case).
3164 One of the letters @samp{DFPRSX} (in upper or lower case).
3167 The letter @samp{E} (upper case only).
3170 One of the letters @samp{DFT} (in upper or lower case).
3175 An optional sign: either @samp{+} or @samp{-}.
3178 An optional @dfn{integer part}: zero or more decimal digits.
3181 An optional @dfn{fractional part}: @samp{.} followed by zero
3182 or more decimal digits.
3185 An optional exponent, consisting of:
3189 An @samp{E} or @samp{e}.
3190 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3191 @c principle this can perfectly well be different on different targets.
3193 Optional sign: either @samp{+} or @samp{-}.
3195 One or more decimal digits.
3200 At least one of the integer part or the fractional part must be
3201 present. The floating point number has the usual base-10 value.
3203 @command{@value{AS}} does all processing using integers. Flonums are computed
3204 independently of any floating point hardware in the computer running
3205 @command{@value{AS}}.
3209 @c Bit fields are written as a general facility but are also controlled
3210 @c by a conditional-compilation flag---which is as of now (21mar91)
3211 @c turned on only by the i960 config of GAS.
3213 @subsubsection Bit Fields
3216 @cindex constants, bit field
3217 You can also define numeric constants as @dfn{bit fields}.
3218 Specify two numbers separated by a colon---
3220 @var{mask}:@var{value}
3223 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3226 The resulting number is then packed
3228 @c this conditional paren in case bit fields turned on elsewhere than 960
3229 (in host-dependent byte order)
3231 into a field whose width depends on which assembler directive has the
3232 bit-field as its argument. Overflow (a result from the bitwise and
3233 requiring more binary digits to represent) is not an error; instead,
3234 more constants are generated, of the specified width, beginning with the
3235 least significant digits.@refill
3237 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3238 @code{.short}, and @code{.word} accept bit-field arguments.
3243 @chapter Sections and Relocation
3248 * Secs Background:: Background
3249 * Ld Sections:: Linker Sections
3250 * As Sections:: Assembler Internal Sections
3251 * Sub-Sections:: Sub-Sections
3255 @node Secs Background
3258 Roughly, a section is a range of addresses, with no gaps; all data
3259 ``in'' those addresses is treated the same for some particular purpose.
3260 For example there may be a ``read only'' section.
3262 @cindex linker, and assembler
3263 @cindex assembler, and linker
3264 The linker @code{@value{LD}} reads many object files (partial programs) and
3265 combines their contents to form a runnable program. When @command{@value{AS}}
3266 emits an object file, the partial program is assumed to start at address 0.
3267 @code{@value{LD}} assigns the final addresses for the partial program, so that
3268 different partial programs do not overlap. This is actually an
3269 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3272 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3273 addresses. These blocks slide to their run-time addresses as rigid
3274 units; their length does not change and neither does the order of bytes
3275 within them. Such a rigid unit is called a @emph{section}. Assigning
3276 run-time addresses to sections is called @dfn{relocation}. It includes
3277 the task of adjusting mentions of object-file addresses so they refer to
3278 the proper run-time addresses.
3280 For the H8/300, and for the Renesas / SuperH SH,
3281 @command{@value{AS}} pads sections if needed to
3282 ensure they end on a word (sixteen bit) boundary.
3285 @cindex standard assembler sections
3286 An object file written by @command{@value{AS}} has at least three sections, any
3287 of which may be empty. These are named @dfn{text}, @dfn{data} and
3292 When it generates COFF or ELF output,
3294 @command{@value{AS}} can also generate whatever other named sections you specify
3295 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3296 If you do not use any directives that place output in the @samp{.text}
3297 or @samp{.data} sections, these sections still exist, but are empty.
3302 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3304 @command{@value{AS}} can also generate whatever other named sections you
3305 specify using the @samp{.space} and @samp{.subspace} directives. See
3306 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3307 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3308 assembler directives.
3311 Additionally, @command{@value{AS}} uses different names for the standard
3312 text, data, and bss sections when generating SOM output. Program text
3313 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3314 BSS into @samp{$BSS$}.
3318 Within the object file, the text section starts at address @code{0}, the
3319 data section follows, and the bss section follows the data section.
3322 When generating either SOM or ELF output files on the HPPA, the text
3323 section starts at address @code{0}, the data section at address
3324 @code{0x4000000}, and the bss section follows the data section.
3327 To let @code{@value{LD}} know which data changes when the sections are
3328 relocated, and how to change that data, @command{@value{AS}} also writes to the
3329 object file details of the relocation needed. To perform relocation
3330 @code{@value{LD}} must know, each time an address in the object
3334 Where in the object file is the beginning of this reference to
3337 How long (in bytes) is this reference?
3339 Which section does the address refer to? What is the numeric value of
3341 (@var{address}) @minus{} (@var{start-address of section})?
3344 Is the reference to an address ``Program-Counter relative''?
3347 @cindex addresses, format of
3348 @cindex section-relative addressing
3349 In fact, every address @command{@value{AS}} ever uses is expressed as
3351 (@var{section}) + (@var{offset into section})
3354 Further, most expressions @command{@value{AS}} computes have this section-relative
3357 (For some object formats, such as SOM for the HPPA, some expressions are
3358 symbol-relative instead.)
3361 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3362 @var{N} into section @var{secname}.''
3364 Apart from text, data and bss sections you need to know about the
3365 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3366 addresses in the absolute section remain unchanged. For example, address
3367 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3368 @code{@value{LD}}. Although the linker never arranges two partial programs'
3369 data sections with overlapping addresses after linking, @emph{by definition}
3370 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3371 part of a program is always the same address when the program is running as
3372 address @code{@{absolute@ 239@}} in any other part of the program.
3374 The idea of sections is extended to the @dfn{undefined} section. Any
3375 address whose section is unknown at assembly time is by definition
3376 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3377 Since numbers are always defined, the only way to generate an undefined
3378 address is to mention an undefined symbol. A reference to a named
3379 common block would be such a symbol: its value is unknown at assembly
3380 time so it has section @emph{undefined}.
3382 By analogy the word @emph{section} is used to describe groups of sections in
3383 the linked program. @code{@value{LD}} puts all partial programs' text
3384 sections in contiguous addresses in the linked program. It is
3385 customary to refer to the @emph{text section} of a program, meaning all
3386 the addresses of all partial programs' text sections. Likewise for
3387 data and bss sections.
3389 Some sections are manipulated by @code{@value{LD}}; others are invented for
3390 use of @command{@value{AS}} and have no meaning except during assembly.
3393 @section Linker Sections
3394 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3399 @cindex named sections
3400 @cindex sections, named
3401 @item named sections
3404 @cindex text section
3405 @cindex data section
3409 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3410 separate but equal sections. Anything you can say of one section is
3413 When the program is running, however, it is
3414 customary for the text section to be unalterable. The
3415 text section is often shared among processes: it contains
3416 instructions, constants and the like. The data section of a running
3417 program is usually alterable: for example, C variables would be stored
3418 in the data section.
3423 This section contains zeroed bytes when your program begins running. It
3424 is used to hold uninitialized variables or common storage. The length of
3425 each partial program's bss section is important, but because it starts
3426 out containing zeroed bytes there is no need to store explicit zero
3427 bytes in the object file. The bss section was invented to eliminate
3428 those explicit zeros from object files.
3430 @cindex absolute section
3431 @item absolute section
3432 Address 0 of this section is always ``relocated'' to runtime address 0.
3433 This is useful if you want to refer to an address that @code{@value{LD}} must
3434 not change when relocating. In this sense we speak of absolute
3435 addresses being ``unrelocatable'': they do not change during relocation.
3437 @cindex undefined section
3438 @item undefined section
3439 This ``section'' is a catch-all for address references to objects not in
3440 the preceding sections.
3441 @c FIXME: ref to some other doc on obj-file formats could go here.
3444 @cindex relocation example
3445 An idealized example of three relocatable sections follows.
3447 The example uses the traditional section names @samp{.text} and @samp{.data}.
3449 Memory addresses are on the horizontal axis.
3453 @c END TEXI2ROFF-KILL
3456 partial program # 1: |ttttt|dddd|00|
3463 partial program # 2: |TTT|DDD|000|
3466 +--+---+-----+--+----+---+-----+~~
3467 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3468 +--+---+-----+--+----+---+-----+~~
3470 addresses: 0 @dots{}
3477 \line{\it Partial program \#1: \hfil}
3478 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3479 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3481 \line{\it Partial program \#2: \hfil}
3482 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3483 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3485 \line{\it linked program: \hfil}
3486 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3487 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3488 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3489 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3491 \line{\it addresses: \hfil}
3495 @c END TEXI2ROFF-KILL
3498 @section Assembler Internal Sections
3500 @cindex internal assembler sections
3501 @cindex sections in messages, internal
3502 These sections are meant only for the internal use of @command{@value{AS}}. They
3503 have no meaning at run-time. You do not really need to know about these
3504 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3505 warning messages, so it might be helpful to have an idea of their
3506 meanings to @command{@value{AS}}. These sections are used to permit the
3507 value of every expression in your assembly language program to be a
3508 section-relative address.
3511 @cindex assembler internal logic error
3512 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3513 An internal assembler logic error has been found. This means there is a
3514 bug in the assembler.
3516 @cindex expr (internal section)
3518 The assembler stores complex expression internally as combinations of
3519 symbols. When it needs to represent an expression as a symbol, it puts
3520 it in the expr section.
3522 @c FIXME item transfer[t] vector preload
3523 @c FIXME item transfer[t] vector postload
3524 @c FIXME item register
3528 @section Sub-Sections
3530 @cindex numbered subsections
3531 @cindex grouping data
3537 fall into two sections: text and data.
3539 You may have separate groups of
3541 data in named sections
3545 data in named sections
3551 that you want to end up near to each other in the object file, even though they
3552 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3553 use @dfn{subsections} for this purpose. Within each section, there can be
3554 numbered subsections with values from 0 to 8192. Objects assembled into the
3555 same subsection go into the object file together with other objects in the same
3556 subsection. For example, a compiler might want to store constants in the text
3557 section, but might not want to have them interspersed with the program being
3558 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3559 section of code being output, and a @samp{.text 1} before each group of
3560 constants being output.
3562 Subsections are optional. If you do not use subsections, everything
3563 goes in subsection number zero.
3566 Each subsection is zero-padded up to a multiple of four bytes.
3567 (Subsections may be padded a different amount on different flavors
3568 of @command{@value{AS}}.)
3572 On the H8/300 platform, each subsection is zero-padded to a word
3573 boundary (two bytes).
3574 The same is true on the Renesas SH.
3577 @c FIXME section padding (alignment)?
3578 @c Rich Pixley says padding here depends on target obj code format; that
3579 @c doesn't seem particularly useful to say without further elaboration,
3580 @c so for now I say nothing about it. If this is a generic BFD issue,
3581 @c these paragraphs might need to vanish from this manual, and be
3582 @c discussed in BFD chapter of binutils (or some such).
3586 Subsections appear in your object file in numeric order, lowest numbered
3587 to highest. (All this to be compatible with other people's assemblers.)
3588 The object file contains no representation of subsections; @code{@value{LD}} and
3589 other programs that manipulate object files see no trace of them.
3590 They just see all your text subsections as a text section, and all your
3591 data subsections as a data section.
3593 To specify which subsection you want subsequent statements assembled
3594 into, use a numeric argument to specify it, in a @samp{.text
3595 @var{expression}} or a @samp{.data @var{expression}} statement.
3598 When generating COFF output, you
3603 can also use an extra subsection
3604 argument with arbitrary named sections: @samp{.section @var{name},
3609 When generating ELF output, you
3614 can also use the @code{.subsection} directive (@pxref{SubSection})
3615 to specify a subsection: @samp{.subsection @var{expression}}.
3617 @var{Expression} should be an absolute expression
3618 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3619 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3620 begins in @code{text 0}. For instance:
3622 .text 0 # The default subsection is text 0 anyway.
3623 .ascii "This lives in the first text subsection. *"
3625 .ascii "But this lives in the second text subsection."
3627 .ascii "This lives in the data section,"
3628 .ascii "in the first data subsection."
3630 .ascii "This lives in the first text section,"
3631 .ascii "immediately following the asterisk (*)."
3634 Each section has a @dfn{location counter} incremented by one for every byte
3635 assembled into that section. Because subsections are merely a convenience
3636 restricted to @command{@value{AS}} there is no concept of a subsection location
3637 counter. There is no way to directly manipulate a location counter---but the
3638 @code{.align} directive changes it, and any label definition captures its
3639 current value. The location counter of the section where statements are being
3640 assembled is said to be the @dfn{active} location counter.
3643 @section bss Section
3646 @cindex common variable storage
3647 The bss section is used for local common variable storage.
3648 You may allocate address space in the bss section, but you may
3649 not dictate data to load into it before your program executes. When
3650 your program starts running, all the contents of the bss
3651 section are zeroed bytes.
3653 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3654 @ref{Lcomm,,@code{.lcomm}}.
3656 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3657 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3660 When assembling for a target which supports multiple sections, such as ELF or
3661 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3662 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3663 section. Typically the section will only contain symbol definitions and
3664 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3671 Symbols are a central concept: the programmer uses symbols to name
3672 things, the linker uses symbols to link, and the debugger uses symbols
3676 @cindex debuggers, and symbol order
3677 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3678 the same order they were declared. This may break some debuggers.
3683 * Setting Symbols:: Giving Symbols Other Values
3684 * Symbol Names:: Symbol Names
3685 * Dot:: The Special Dot Symbol
3686 * Symbol Attributes:: Symbol Attributes
3693 A @dfn{label} is written as a symbol immediately followed by a colon
3694 @samp{:}. The symbol then represents the current value of the
3695 active location counter, and is, for example, a suitable instruction
3696 operand. You are warned if you use the same symbol to represent two
3697 different locations: the first definition overrides any other
3701 On the HPPA, the usual form for a label need not be immediately followed by a
3702 colon, but instead must start in column zero. Only one label may be defined on
3703 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3704 provides a special directive @code{.label} for defining labels more flexibly.
3707 @node Setting Symbols
3708 @section Giving Symbols Other Values
3710 @cindex assigning values to symbols
3711 @cindex symbol values, assigning
3712 A symbol can be given an arbitrary value by writing a symbol, followed
3713 by an equals sign @samp{=}, followed by an expression
3714 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3715 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3716 equals sign @samp{=}@samp{=} here represents an equivalent of the
3717 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3720 Blackfin does not support symbol assignment with @samp{=}.
3724 @section Symbol Names
3726 @cindex symbol names
3727 @cindex names, symbol
3728 @ifclear SPECIAL-SYMS
3729 Symbol names begin with a letter or with one of @samp{._}. On most
3730 machines, you can also use @code{$} in symbol names; exceptions are
3731 noted in @ref{Machine Dependencies}. That character may be followed by any
3732 string of digits, letters, dollar signs (unless otherwise noted for a
3733 particular target machine), and underscores.
3737 Symbol names begin with a letter or with one of @samp{._}. On the
3738 Renesas SH you can also use @code{$} in symbol names. That
3739 character may be followed by any string of digits, letters, dollar signs (save
3740 on the H8/300), and underscores.
3744 Case of letters is significant: @code{foo} is a different symbol name
3747 Symbol names do not start with a digit. An exception to this rule is made for
3748 Local Labels. See below.
3750 Multibyte characters are supported. To generate a symbol name containing
3751 multibyte characters enclose it within double quotes and use escape codes. cf
3752 @xref{Strings}. Generating a multibyte symbol name from a label is not
3753 currently supported.
3755 Each symbol has exactly one name. Each name in an assembly language program
3756 refers to exactly one symbol. You may use that symbol name any number of times
3759 @subheading Local Symbol Names
3761 @cindex local symbol names
3762 @cindex symbol names, local
3763 A local symbol is any symbol beginning with certain local label prefixes.
3764 By default, the local label prefix is @samp{.L} for ELF systems or
3765 @samp{L} for traditional a.out systems, but each target may have its own
3766 set of local label prefixes.
3768 On the HPPA local symbols begin with @samp{L$}.
3771 Local symbols are defined and used within the assembler, but they are
3772 normally not saved in object files. Thus, they are not visible when debugging.
3773 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3774 to retain the local symbols in the object files.
3776 @subheading Local Labels
3778 @cindex local labels
3779 @cindex temporary symbol names
3780 @cindex symbol names, temporary
3781 Local labels are different from local symbols. Local labels help compilers and
3782 programmers use names temporarily. They create symbols which are guaranteed to
3783 be unique over the entire scope of the input source code and which can be
3784 referred to by a simple notation. To define a local label, write a label of
3785 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3786 To refer to the most recent previous definition of that label write
3787 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3788 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3789 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3791 There is no restriction on how you can use these labels, and you can reuse them
3792 too. So that it is possible to repeatedly define the same local label (using
3793 the same number @samp{@b{N}}), although you can only refer to the most recently
3794 defined local label of that number (for a backwards reference) or the next
3795 definition of a specific local label for a forward reference. It is also worth
3796 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3797 implemented in a slightly more efficient manner than the others.
3808 Which is the equivalent of:
3811 label_1: branch label_3
3812 label_2: branch label_1
3813 label_3: branch label_4
3814 label_4: branch label_3
3817 Local label names are only a notational device. They are immediately
3818 transformed into more conventional symbol names before the assembler uses them.
3819 The symbol names are stored in the symbol table, appear in error messages, and
3820 are optionally emitted to the object file. The names are constructed using
3824 @item @emph{local label prefix}
3825 All local symbols begin with the system-specific local label prefix.
3826 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3827 that start with the local label prefix. These labels are
3828 used for symbols you are never intended to see. If you use the
3829 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3830 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3831 you may use them in debugging.
3834 This is the number that was used in the local label definition. So if the
3835 label is written @samp{55:} then the number is @samp{55}.
3838 This unusual character is included so you do not accidentally invent a symbol
3839 of the same name. The character has ASCII value of @samp{\002} (control-B).
3841 @item @emph{ordinal number}
3842 This is a serial number to keep the labels distinct. The first definition of
3843 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3844 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3845 the number @samp{1} and its 15th definition gets @samp{15} as well.
3848 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3849 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3851 @subheading Dollar Local Labels
3852 @cindex dollar local symbols
3854 On some targets @code{@value{AS}} also supports an even more local form of
3855 local labels called dollar labels. These labels go out of scope (i.e., they
3856 become undefined) as soon as a non-local label is defined. Thus they remain
3857 valid for only a small region of the input source code. Normal local labels,
3858 by contrast, remain in scope for the entire file, or until they are redefined
3859 by another occurrence of the same local label.
3861 Dollar labels are defined in exactly the same way as ordinary local labels,
3862 except that they have a dollar sign suffix to their numeric value, e.g.,
3865 They can also be distinguished from ordinary local labels by their transformed
3866 names which use ASCII character @samp{\001} (control-A) as the magic character
3867 to distinguish them from ordinary labels. For example, the fifth definition of
3868 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3871 @section The Special Dot Symbol
3873 @cindex dot (symbol)
3874 @cindex @code{.} (symbol)
3875 @cindex current address
3876 @cindex location counter
3877 The special symbol @samp{.} refers to the current address that
3878 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3879 .long .} defines @code{melvin} to contain its own address.
3880 Assigning a value to @code{.} is treated the same as a @code{.org}
3882 @ifclear no-space-dir
3883 Thus, the expression @samp{.=.+4} is the same as saying
3887 @node Symbol Attributes
3888 @section Symbol Attributes
3890 @cindex symbol attributes
3891 @cindex attributes, symbol
3892 Every symbol has, as well as its name, the attributes ``Value'' and
3893 ``Type''. Depending on output format, symbols can also have auxiliary
3896 The detailed definitions are in @file{a.out.h}.
3899 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3900 all these attributes, and probably won't warn you. This makes the
3901 symbol an externally defined symbol, which is generally what you
3905 * Symbol Value:: Value
3906 * Symbol Type:: Type
3909 * a.out Symbols:: Symbol Attributes: @code{a.out}
3913 * a.out Symbols:: Symbol Attributes: @code{a.out}
3916 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3921 * COFF Symbols:: Symbol Attributes for COFF
3924 * SOM Symbols:: Symbol Attributes for SOM
3931 @cindex value of a symbol
3932 @cindex symbol value
3933 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3934 location in the text, data, bss or absolute sections the value is the
3935 number of addresses from the start of that section to the label.
3936 Naturally for text, data and bss sections the value of a symbol changes
3937 as @code{@value{LD}} changes section base addresses during linking. Absolute
3938 symbols' values do not change during linking: that is why they are
3941 The value of an undefined symbol is treated in a special way. If it is
3942 0 then the symbol is not defined in this assembler source file, and
3943 @code{@value{LD}} tries to determine its value from other files linked into the
3944 same program. You make this kind of symbol simply by mentioning a symbol
3945 name without defining it. A non-zero value represents a @code{.comm}
3946 common declaration. The value is how much common storage to reserve, in
3947 bytes (addresses). The symbol refers to the first address of the
3953 @cindex type of a symbol
3955 The type attribute of a symbol contains relocation (section)
3956 information, any flag settings indicating that a symbol is external, and
3957 (optionally), other information for linkers and debuggers. The exact
3958 format depends on the object-code output format in use.
3963 @c The following avoids a "widow" subsection title. @group would be
3964 @c better if it were available outside examples.
3967 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3969 @cindex @code{b.out} symbol attributes
3970 @cindex symbol attributes, @code{b.out}
3971 These symbol attributes appear only when @command{@value{AS}} is configured for
3972 one of the Berkeley-descended object output formats---@code{a.out} or
3978 @subsection Symbol Attributes: @code{a.out}
3980 @cindex @code{a.out} symbol attributes
3981 @cindex symbol attributes, @code{a.out}
3987 @subsection Symbol Attributes: @code{a.out}
3989 @cindex @code{a.out} symbol attributes
3990 @cindex symbol attributes, @code{a.out}
3994 * Symbol Desc:: Descriptor
3995 * Symbol Other:: Other
3999 @subsubsection Descriptor
4001 @cindex descriptor, of @code{a.out} symbol
4002 This is an arbitrary 16-bit value. You may establish a symbol's
4003 descriptor value by using a @code{.desc} statement
4004 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4005 @command{@value{AS}}.
4008 @subsubsection Other
4010 @cindex other attribute, of @code{a.out} symbol
4011 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4016 @subsection Symbol Attributes for COFF
4018 @cindex COFF symbol attributes
4019 @cindex symbol attributes, COFF
4021 The COFF format supports a multitude of auxiliary symbol attributes;
4022 like the primary symbol attributes, they are set between @code{.def} and
4023 @code{.endef} directives.
4025 @subsubsection Primary Attributes
4027 @cindex primary attributes, COFF symbols
4028 The symbol name is set with @code{.def}; the value and type,
4029 respectively, with @code{.val} and @code{.type}.
4031 @subsubsection Auxiliary Attributes
4033 @cindex auxiliary attributes, COFF symbols
4034 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4035 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4036 table information for COFF.
4041 @subsection Symbol Attributes for SOM
4043 @cindex SOM symbol attributes
4044 @cindex symbol attributes, SOM
4046 The SOM format for the HPPA supports a multitude of symbol attributes set with
4047 the @code{.EXPORT} and @code{.IMPORT} directives.
4049 The attributes are described in @cite{HP9000 Series 800 Assembly
4050 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4051 @code{EXPORT} assembler directive documentation.
4055 @chapter Expressions
4059 @cindex numeric values
4060 An @dfn{expression} specifies an address or numeric value.
4061 Whitespace may precede and/or follow an expression.
4063 The result of an expression must be an absolute number, or else an offset into
4064 a particular section. If an expression is not absolute, and there is not
4065 enough information when @command{@value{AS}} sees the expression to know its
4066 section, a second pass over the source program might be necessary to interpret
4067 the expression---but the second pass is currently not implemented.
4068 @command{@value{AS}} aborts with an error message in this situation.
4071 * Empty Exprs:: Empty Expressions
4072 * Integer Exprs:: Integer Expressions
4076 @section Empty Expressions
4078 @cindex empty expressions
4079 @cindex expressions, empty
4080 An empty expression has no value: it is just whitespace or null.
4081 Wherever an absolute expression is required, you may omit the
4082 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4083 is compatible with other assemblers.
4086 @section Integer Expressions
4088 @cindex integer expressions
4089 @cindex expressions, integer
4090 An @dfn{integer expression} is one or more @emph{arguments} delimited
4091 by @emph{operators}.
4094 * Arguments:: Arguments
4095 * Operators:: Operators
4096 * Prefix Ops:: Prefix Operators
4097 * Infix Ops:: Infix Operators
4101 @subsection Arguments
4103 @cindex expression arguments
4104 @cindex arguments in expressions
4105 @cindex operands in expressions
4106 @cindex arithmetic operands
4107 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4108 contexts arguments are sometimes called ``arithmetic operands''. In
4109 this manual, to avoid confusing them with the ``instruction operands'' of
4110 the machine language, we use the term ``argument'' to refer to parts of
4111 expressions only, reserving the word ``operand'' to refer only to machine
4112 instruction operands.
4114 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4115 @var{section} is one of text, data, bss, absolute,
4116 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4119 Numbers are usually integers.
4121 A number can be a flonum or bignum. In this case, you are warned
4122 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4123 these 32 bits are an integer. You may write integer-manipulating
4124 instructions that act on exotic constants, compatible with other
4127 @cindex subexpressions
4128 Subexpressions are a left parenthesis @samp{(} followed by an integer
4129 expression, followed by a right parenthesis @samp{)}; or a prefix
4130 operator followed by an argument.
4133 @subsection Operators
4135 @cindex operators, in expressions
4136 @cindex arithmetic functions
4137 @cindex functions, in expressions
4138 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4139 operators are followed by an argument. Infix operators appear
4140 between their arguments. Operators may be preceded and/or followed by
4144 @subsection Prefix Operator
4146 @cindex prefix operators
4147 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4148 one argument, which must be absolute.
4150 @c the tex/end tex stuff surrounding this small table is meant to make
4151 @c it align, on the printed page, with the similar table in the next
4152 @c section (which is inside an enumerate).
4154 \global\advance\leftskip by \itemindent
4159 @dfn{Negation}. Two's complement negation.
4161 @dfn{Complementation}. Bitwise not.
4165 \global\advance\leftskip by -\itemindent
4169 @subsection Infix Operators
4171 @cindex infix operators
4172 @cindex operators, permitted arguments
4173 @dfn{Infix operators} take two arguments, one on either side. Operators
4174 have precedence, but operations with equal precedence are performed left
4175 to right. Apart from @code{+} or @option{-}, both arguments must be
4176 absolute, and the result is absolute.
4179 @cindex operator precedence
4180 @cindex precedence of operators
4187 @dfn{Multiplication}.
4190 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4196 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4199 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4203 Intermediate precedence
4208 @dfn{Bitwise Inclusive Or}.
4214 @dfn{Bitwise Exclusive Or}.
4217 @dfn{Bitwise Or Not}.
4224 @cindex addition, permitted arguments
4225 @cindex plus, permitted arguments
4226 @cindex arguments for addition
4228 @dfn{Addition}. If either argument is absolute, the result has the section of
4229 the other argument. You may not add together arguments from different
4232 @cindex subtraction, permitted arguments
4233 @cindex minus, permitted arguments
4234 @cindex arguments for subtraction
4236 @dfn{Subtraction}. If the right argument is absolute, the
4237 result has the section of the left argument.
4238 If both arguments are in the same section, the result is absolute.
4239 You may not subtract arguments from different sections.
4240 @c FIXME is there still something useful to say about undefined - undefined ?
4242 @cindex comparison expressions
4243 @cindex expressions, comparison
4248 @dfn{Is Not Equal To}
4252 @dfn{Is Greater Than}
4254 @dfn{Is Greater Than Or Equal To}
4256 @dfn{Is Less Than Or Equal To}
4258 The comparison operators can be used as infix operators. A true results has a
4259 value of -1 whereas a false result has a value of 0. Note, these operators
4260 perform signed comparisons.
4263 @item Lowest Precedence
4272 These two logical operations can be used to combine the results of sub
4273 expressions. Note, unlike the comparison operators a true result returns a
4274 value of 1 but a false results does still return 0. Also note that the logical
4275 or operator has a slightly lower precedence than logical and.
4280 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4281 address; you can only have a defined section in one of the two arguments.
4284 @chapter Assembler Directives
4286 @cindex directives, machine independent
4287 @cindex pseudo-ops, machine independent
4288 @cindex machine independent directives
4289 All assembler directives have names that begin with a period (@samp{.}).
4290 The names are case insensitive for most targets, and usually written
4293 This chapter discusses directives that are available regardless of the
4294 target machine configuration for the @sc{gnu} assembler.
4296 Some machine configurations provide additional directives.
4297 @xref{Machine Dependencies}.
4300 @ifset machine-directives
4301 @xref{Machine Dependencies}, for additional directives.
4306 * Abort:: @code{.abort}
4308 * ABORT (COFF):: @code{.ABORT}
4311 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4312 * Altmacro:: @code{.altmacro}
4313 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4314 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4315 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4316 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4317 * Byte:: @code{.byte @var{expressions}}
4318 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4319 * Comm:: @code{.comm @var{symbol} , @var{length} }
4320 * Data:: @code{.data @var{subsection}}
4322 * Def:: @code{.def @var{name}}
4325 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4331 * Double:: @code{.double @var{flonums}}
4332 * Eject:: @code{.eject}
4333 * Else:: @code{.else}
4334 * Elseif:: @code{.elseif}
4337 * Endef:: @code{.endef}
4340 * Endfunc:: @code{.endfunc}
4341 * Endif:: @code{.endif}
4342 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4343 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4344 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4346 * Error:: @code{.error @var{string}}
4347 * Exitm:: @code{.exitm}
4348 * Extern:: @code{.extern}
4349 * Fail:: @code{.fail}
4350 * File:: @code{.file}
4351 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4352 * Float:: @code{.float @var{flonums}}
4353 * Func:: @code{.func}
4354 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4356 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4357 * Hidden:: @code{.hidden @var{names}}
4360 * hword:: @code{.hword @var{expressions}}
4361 * Ident:: @code{.ident}
4362 * If:: @code{.if @var{absolute expression}}
4363 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4364 * Include:: @code{.include "@var{file}"}
4365 * Int:: @code{.int @var{expressions}}
4367 * Internal:: @code{.internal @var{names}}
4370 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4371 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4372 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4373 * Lflags:: @code{.lflags}
4374 @ifclear no-line-dir
4375 * Line:: @code{.line @var{line-number}}
4378 * Linkonce:: @code{.linkonce [@var{type}]}
4379 * List:: @code{.list}
4380 * Ln:: @code{.ln @var{line-number}}
4381 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4382 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4384 * Local:: @code{.local @var{names}}
4387 * Long:: @code{.long @var{expressions}}
4389 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4392 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4393 * MRI:: @code{.mri @var{val}}
4394 * Noaltmacro:: @code{.noaltmacro}
4395 * Nolist:: @code{.nolist}
4396 * Octa:: @code{.octa @var{bignums}}
4397 * Offset:: @code{.offset @var{loc}}
4398 * Org:: @code{.org @var{new-lc}, @var{fill}}
4399 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4401 * PopSection:: @code{.popsection}
4402 * Previous:: @code{.previous}
4405 * Print:: @code{.print @var{string}}
4407 * Protected:: @code{.protected @var{names}}
4410 * Psize:: @code{.psize @var{lines}, @var{columns}}
4411 * Purgem:: @code{.purgem @var{name}}
4413 * PushSection:: @code{.pushsection @var{name}}
4416 * Quad:: @code{.quad @var{bignums}}
4417 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4418 * Rept:: @code{.rept @var{count}}
4419 * Sbttl:: @code{.sbttl "@var{subheading}"}
4421 * Scl:: @code{.scl @var{class}}
4424 * Section:: @code{.section @var{name}[, @var{flags}]}
4427 * Set:: @code{.set @var{symbol}, @var{expression}}
4428 * Short:: @code{.short @var{expressions}}
4429 * Single:: @code{.single @var{flonums}}
4431 * Size:: @code{.size [@var{name} , @var{expression}]}
4433 @ifclear no-space-dir
4434 * Skip:: @code{.skip @var{size} , @var{fill}}
4437 * Sleb128:: @code{.sleb128 @var{expressions}}
4438 @ifclear no-space-dir
4439 * Space:: @code{.space @var{size} , @var{fill}}
4442 * Stab:: @code{.stabd, .stabn, .stabs}
4445 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4446 * Struct:: @code{.struct @var{expression}}
4448 * SubSection:: @code{.subsection}
4449 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4453 * Tag:: @code{.tag @var{structname}}
4456 * Text:: @code{.text @var{subsection}}
4457 * Title:: @code{.title "@var{heading}"}
4459 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4462 * Uleb128:: @code{.uleb128 @var{expressions}}
4464 * Val:: @code{.val @var{addr}}
4468 * Version:: @code{.version "@var{string}"}
4469 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4470 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4473 * Warning:: @code{.warning @var{string}}
4474 * Weak:: @code{.weak @var{names}}
4475 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4476 * Word:: @code{.word @var{expressions}}
4477 @ifclear no-space-dir
4478 * Zero:: @code{.zero @var{size}}
4480 * Deprecated:: Deprecated Directives
4484 @section @code{.abort}
4486 @cindex @code{abort} directive
4487 @cindex stopping the assembly
4488 This directive stops the assembly immediately. It is for
4489 compatibility with other assemblers. The original idea was that the
4490 assembly language source would be piped into the assembler. If the sender
4491 of the source quit, it could use this directive tells @command{@value{AS}} to
4492 quit also. One day @code{.abort} will not be supported.
4496 @section @code{.ABORT} (COFF)
4498 @cindex @code{ABORT} directive
4499 When producing COFF output, @command{@value{AS}} accepts this directive as a
4500 synonym for @samp{.abort}.
4503 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4509 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4511 @cindex padding the location counter
4512 @cindex @code{align} directive
4513 Pad the location counter (in the current subsection) to a particular storage
4514 boundary. The first expression (which must be absolute) is the alignment
4515 required, as described below.
4517 The second expression (also absolute) gives the fill value to be stored in the
4518 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4519 padding bytes are normally zero. However, on some systems, if the section is
4520 marked as containing code and the fill value is omitted, the space is filled
4521 with no-op instructions.
4523 The third expression is also absolute, and is also optional. If it is present,
4524 it is the maximum number of bytes that should be skipped by this alignment
4525 directive. If doing the alignment would require skipping more bytes than the
4526 specified maximum, then the alignment is not done at all. You can omit the
4527 fill value (the second argument) entirely by simply using two commas after the
4528 required alignment; this can be useful if you want the alignment to be filled
4529 with no-op instructions when appropriate.
4531 The way the required alignment is specified varies from system to system.
4532 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4533 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4534 alignment request in bytes. For example @samp{.align 8} advances
4535 the location counter until it is a multiple of 8. If the location counter
4536 is already a multiple of 8, no change is needed. For the tic54x, the
4537 first expression is the alignment request in words.
4539 For other systems, including ppc, i386 using a.out format, arm and
4540 strongarm, it is the
4541 number of low-order zero bits the location counter must have after
4542 advancement. For example @samp{.align 3} advances the location
4543 counter until it a multiple of 8. If the location counter is already a
4544 multiple of 8, no change is needed.
4546 This inconsistency is due to the different behaviors of the various
4547 native assemblers for these systems which GAS must emulate.
4548 GAS also provides @code{.balign} and @code{.p2align} directives,
4549 described later, which have a consistent behavior across all
4550 architectures (but are specific to GAS).
4553 @section @code{.altmacro}
4554 Enable alternate macro mode, enabling:
4557 @item LOCAL @var{name} [ , @dots{} ]
4558 One additional directive, @code{LOCAL}, is available. It is used to
4559 generate a string replacement for each of the @var{name} arguments, and
4560 replace any instances of @var{name} in each macro expansion. The
4561 replacement string is unique in the assembly, and different for each
4562 separate macro expansion. @code{LOCAL} allows you to write macros that
4563 define symbols, without fear of conflict between separate macro expansions.
4565 @item String delimiters
4566 You can write strings delimited in these other ways besides
4567 @code{"@var{string}"}:
4570 @item '@var{string}'
4571 You can delimit strings with single-quote characters.
4573 @item <@var{string}>
4574 You can delimit strings with matching angle brackets.
4577 @item single-character string escape
4578 To include any single character literally in a string (even if the
4579 character would otherwise have some special meaning), you can prefix the
4580 character with @samp{!} (an exclamation mark). For example, you can
4581 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4583 @item Expression results as strings
4584 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4585 and use the result as a string.
4589 @section @code{.ascii "@var{string}"}@dots{}
4591 @cindex @code{ascii} directive
4592 @cindex string literals
4593 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4594 separated by commas. It assembles each string (with no automatic
4595 trailing zero byte) into consecutive addresses.
4598 @section @code{.asciz "@var{string}"}@dots{}
4600 @cindex @code{asciz} directive
4601 @cindex zero-terminated strings
4602 @cindex null-terminated strings
4603 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4604 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4607 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4609 @cindex padding the location counter given number of bytes
4610 @cindex @code{balign} directive
4611 Pad the location counter (in the current subsection) to a particular
4612 storage boundary. The first expression (which must be absolute) is the
4613 alignment request in bytes. For example @samp{.balign 8} advances
4614 the location counter until it is a multiple of 8. If the location counter
4615 is already a multiple of 8, no change is needed.
4617 The second expression (also absolute) gives the fill value to be stored in the
4618 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4619 padding bytes are normally zero. However, on some systems, if the section is
4620 marked as containing code and the fill value is omitted, the space is filled
4621 with no-op instructions.
4623 The third expression is also absolute, and is also optional. If it is present,
4624 it is the maximum number of bytes that should be skipped by this alignment
4625 directive. If doing the alignment would require skipping more bytes than the
4626 specified maximum, then the alignment is not done at all. You can omit the
4627 fill value (the second argument) entirely by simply using two commas after the
4628 required alignment; this can be useful if you want the alignment to be filled
4629 with no-op instructions when appropriate.
4631 @cindex @code{balignw} directive
4632 @cindex @code{balignl} directive
4633 The @code{.balignw} and @code{.balignl} directives are variants of the
4634 @code{.balign} directive. The @code{.balignw} directive treats the fill
4635 pattern as a two byte word value. The @code{.balignl} directives treats the
4636 fill pattern as a four byte longword value. For example, @code{.balignw
4637 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4638 filled in with the value 0x368d (the exact placement of the bytes depends upon
4639 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4642 @node Bundle directives
4643 @section Bundle directives
4644 @subsection @code{.bundle_align_mode @var{abs-expr}}
4645 @cindex @code{bundle_align_mode} directive
4647 @cindex instruction bundle
4648 @cindex aligned instruction bundle
4649 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4650 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4651 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4652 disabled (which is the default state). If the argument it not zero, it
4653 gives the size of an instruction bundle as a power of two (as for the
4654 @code{.p2align} directive, @pxref{P2align}).
4656 For some targets, it's an ABI requirement that no instruction may span a
4657 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4658 instructions that starts on an aligned boundary. For example, if
4659 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4660 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4661 effect, no single instruction may span a boundary between bundles. If an
4662 instruction would start too close to the end of a bundle for the length of
4663 that particular instruction to fit within the bundle, then the space at the
4664 end of that bundle is filled with no-op instructions so the instruction
4665 starts in the next bundle. As a corollary, it's an error if any single
4666 instruction's encoding is longer than the bundle size.
4668 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4669 @cindex @code{bundle_lock} directive
4670 @cindex @code{bundle_unlock} directive
4671 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4672 allow explicit control over instruction bundle padding. These directives
4673 are only valid when @code{.bundle_align_mode} has been used to enable
4674 aligned instruction bundle mode. It's an error if they appear when
4675 @code{.bundle_align_mode} has not been used at all, or when the last
4676 directive was @w{@code{.bundle_align_mode 0}}.
4678 @cindex bundle-locked
4679 For some targets, it's an ABI requirement that certain instructions may
4680 appear only as part of specified permissible sequences of multiple
4681 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4682 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4683 instruction sequence. For purposes of aligned instruction bundle mode, a
4684 sequence starting with @code{.bundle_lock} and ending with
4685 @code{.bundle_unlock} is treated as a single instruction. That is, the
4686 entire sequence must fit into a single bundle and may not span a bundle
4687 boundary. If necessary, no-op instructions will be inserted before the
4688 first instruction of the sequence so that the whole sequence starts on an
4689 aligned bundle boundary. It's an error if the sequence is longer than the
4692 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4693 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4694 nested. That is, a second @code{.bundle_lock} directive before the next
4695 @code{.bundle_unlock} directive has no effect except that it must be
4696 matched by another closing @code{.bundle_unlock} so that there is the
4697 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4700 @section @code{.byte @var{expressions}}
4702 @cindex @code{byte} directive
4703 @cindex integers, one byte
4704 @code{.byte} expects zero or more expressions, separated by commas.
4705 Each expression is assembled into the next byte.
4707 @node CFI directives
4708 @section CFI directives
4709 @subsection @code{.cfi_sections @var{section_list}}
4710 @cindex @code{cfi_sections} directive
4711 @code{.cfi_sections} may be used to specify whether CFI directives
4712 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4713 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4714 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4715 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4716 directive is not used is @code{.cfi_sections .eh_frame}.
4718 On targets that support compact unwinding tables these can be generated
4719 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4721 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4722 which is used by the @value{TIC6X} target.
4724 The @code{.cfi_sections} directive can be repeated, with the same or different
4725 arguments, provided that CFI generation has not yet started. Once CFI
4726 generation has started however the section list is fixed and any attempts to
4727 redefine it will result in an error.
4729 @subsection @code{.cfi_startproc [simple]}
4730 @cindex @code{cfi_startproc} directive
4731 @code{.cfi_startproc} is used at the beginning of each function that
4732 should have an entry in @code{.eh_frame}. It initializes some internal
4733 data structures. Don't forget to close the function by
4734 @code{.cfi_endproc}.
4736 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4737 it also emits some architecture dependent initial CFI instructions.
4739 @subsection @code{.cfi_endproc}
4740 @cindex @code{cfi_endproc} directive
4741 @code{.cfi_endproc} is used at the end of a function where it closes its
4742 unwind entry previously opened by
4743 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4745 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4746 @cindex @code{cfi_personality} directive
4747 @code{.cfi_personality} defines personality routine and its encoding.
4748 @var{encoding} must be a constant determining how the personality
4749 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4750 argument is not present, otherwise second argument should be
4751 a constant or a symbol name. When using indirect encodings,
4752 the symbol provided should be the location where personality
4753 can be loaded from, not the personality routine itself.
4754 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4755 no personality routine.
4757 @subsection @code{.cfi_personality_id @var{id}}
4758 @cindex @code{cfi_personality_id} directive
4759 @code{cfi_personality_id} defines a personality routine by its index as
4760 defined in a compact unwinding format.
4761 Only valid when generating compact EH frames (i.e.
4762 with @code{.cfi_sections eh_frame_entry}.
4764 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4765 @cindex @code{cfi_fde_data} directive
4766 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4767 used for the current function. These are emitted inline in the
4768 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4769 in the @code{.gnu.extab} section otherwise.
4770 Only valid when generating compact EH frames (i.e.
4771 with @code{.cfi_sections eh_frame_entry}.
4773 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4774 @code{.cfi_lsda} defines LSDA and its encoding.
4775 @var{encoding} must be a constant determining how the LSDA
4776 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4777 argument is not present, otherwise the second argument should be a constant
4778 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4779 meaning that no LSDA is present.
4781 @subsection @code{.cfi_inline_lsda} [@var{align}]
4782 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4783 switches to the corresponding @code{.gnu.extab} section.
4784 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4785 Only valid when generating compact EH frames (i.e.
4786 with @code{.cfi_sections eh_frame_entry}.
4788 The table header and unwinding opcodes will be generated at this point,
4789 so that they are immediately followed by the LSDA data. The symbol
4790 referenced by the @code{.cfi_lsda} directive should still be defined
4791 in case a fallback FDE based encoding is used. The LSDA data is terminated
4792 by a section directive.
4794 The optional @var{align} argument specifies the alignment required.
4795 The alignment is specified as a power of two, as with the
4796 @code{.p2align} directive.
4798 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4799 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4800 address from @var{register} and add @var{offset} to it}.
4802 @subsection @code{.cfi_def_cfa_register @var{register}}
4803 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4804 now on @var{register} will be used instead of the old one. Offset
4807 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4808 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4809 remains the same, but @var{offset} is new. Note that it is the
4810 absolute offset that will be added to a defined register to compute
4813 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4814 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4815 value that is added/substracted from the previous offset.
4817 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4818 Previous value of @var{register} is saved at offset @var{offset} from
4821 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4822 Previous value of @var{register} is saved at offset @var{offset} from
4823 the current CFA register. This is transformed to @code{.cfi_offset}
4824 using the known displacement of the CFA register from the CFA.
4825 This is often easier to use, because the number will match the
4826 code it's annotating.
4828 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4829 Previous value of @var{register1} is saved in register @var{register2}.
4831 @subsection @code{.cfi_restore @var{register}}
4832 @code{.cfi_restore} says that the rule for @var{register} is now the
4833 same as it was at the beginning of the function, after all initial
4834 instruction added by @code{.cfi_startproc} were executed.
4836 @subsection @code{.cfi_undefined @var{register}}
4837 From now on the previous value of @var{register} can't be restored anymore.
4839 @subsection @code{.cfi_same_value @var{register}}
4840 Current value of @var{register} is the same like in the previous frame,
4841 i.e. no restoration needed.
4843 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4844 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4845 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4846 places them in the current row. This is useful for situations where you have
4847 multiple @code{.cfi_*} directives that need to be undone due to the control
4848 flow of the program. For example, we could have something like this (assuming
4849 the CFA is the value of @code{rbp}):
4859 .cfi_def_cfa %rsp, 8
4862 /* Do something else */
4865 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4866 to the instructions before @code{label}. This means we'd have to add multiple
4867 @code{.cfi} directives after @code{label} to recreate the original save
4868 locations of the registers, as well as setting the CFA back to the value of
4869 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4881 .cfi_def_cfa %rsp, 8
4885 /* Do something else */
4888 That way, the rules for the instructions after @code{label} will be the same
4889 as before the first @code{.cfi_restore} without having to use multiple
4890 @code{.cfi} directives.
4892 @subsection @code{.cfi_return_column @var{register}}
4893 Change return column @var{register}, i.e. the return address is either
4894 directly in @var{register} or can be accessed by rules for @var{register}.
4896 @subsection @code{.cfi_signal_frame}
4897 Mark current function as signal trampoline.
4899 @subsection @code{.cfi_window_save}
4900 SPARC register window has been saved.
4902 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4903 Allows the user to add arbitrary bytes to the unwind info. One
4904 might use this to add OS-specific CFI opcodes, or generic CFI
4905 opcodes that GAS does not yet support.
4907 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4908 The current value of @var{register} is @var{label}. The value of @var{label}
4909 will be encoded in the output file according to @var{encoding}; see the
4910 description of @code{.cfi_personality} for details on this encoding.
4912 The usefulness of equating a register to a fixed label is probably
4913 limited to the return address register. Here, it can be useful to
4914 mark a code segment that has only one return address which is reached
4915 by a direct branch and no copy of the return address exists in memory
4916 or another register.
4919 @section @code{.comm @var{symbol} , @var{length} }
4921 @cindex @code{comm} directive
4922 @cindex symbol, common
4923 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4924 common symbol in one object file may be merged with a defined or common symbol
4925 of the same name in another object file. If @code{@value{LD}} does not see a
4926 definition for the symbol--just one or more common symbols--then it will
4927 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4928 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4929 the same name, and they do not all have the same size, it will allocate space
4930 using the largest size.
4933 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4934 an optional third argument. This is the desired alignment of the symbol,
4935 specified for ELF as a byte boundary (for example, an alignment of 16 means
4936 that the least significant 4 bits of the address should be zero), and for PE
4937 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4938 boundary). The alignment must be an absolute expression, and it must be a
4939 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4940 common symbol, it will use the alignment when placing the symbol. If no
4941 alignment is specified, @command{@value{AS}} will set the alignment to the
4942 largest power of two less than or equal to the size of the symbol, up to a
4943 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4944 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4945 @samp{--section-alignment} option; image file sections in PE are aligned to
4946 multiples of 4096, which is far too large an alignment for ordinary variables.
4947 It is rather the default alignment for (non-debug) sections within object
4948 (@samp{*.o}) files, which are less strictly aligned.}.
4952 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4953 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4957 @section @code{.data @var{subsection}}
4959 @cindex @code{data} directive
4960 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4961 end of the data subsection numbered @var{subsection} (which is an
4962 absolute expression). If @var{subsection} is omitted, it defaults
4967 @section @code{.def @var{name}}
4969 @cindex @code{def} directive
4970 @cindex COFF symbols, debugging
4971 @cindex debugging COFF symbols
4972 Begin defining debugging information for a symbol @var{name}; the
4973 definition extends until the @code{.endef} directive is encountered.
4976 This directive is only observed when @command{@value{AS}} is configured for COFF
4977 format output; when producing @code{b.out}, @samp{.def} is recognized,
4984 @section @code{.desc @var{symbol}, @var{abs-expression}}
4986 @cindex @code{desc} directive
4987 @cindex COFF symbol descriptor
4988 @cindex symbol descriptor, COFF
4989 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4990 to the low 16 bits of an absolute expression.
4993 The @samp{.desc} directive is not available when @command{@value{AS}} is
4994 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4995 object format. For the sake of compatibility, @command{@value{AS}} accepts
4996 it, but produces no output, when configured for COFF.
5002 @section @code{.dim}
5004 @cindex @code{dim} directive
5005 @cindex COFF auxiliary symbol information
5006 @cindex auxiliary symbol information, COFF
5007 This directive is generated by compilers to include auxiliary debugging
5008 information in the symbol table. It is only permitted inside
5009 @code{.def}/@code{.endef} pairs.
5012 @samp{.dim} is only meaningful when generating COFF format output; when
5013 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5019 @section @code{.double @var{flonums}}
5021 @cindex @code{double} directive
5022 @cindex floating point numbers (double)
5023 @code{.double} expects zero or more flonums, separated by commas. It
5024 assembles floating point numbers.
5026 The exact kind of floating point numbers emitted depends on how
5027 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5031 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5032 in @sc{ieee} format.
5037 @section @code{.eject}
5039 @cindex @code{eject} directive
5040 @cindex new page, in listings
5041 @cindex page, in listings
5042 @cindex listing control: new page
5043 Force a page break at this point, when generating assembly listings.
5046 @section @code{.else}
5048 @cindex @code{else} directive
5049 @code{.else} is part of the @command{@value{AS}} support for conditional
5050 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5051 of code to be assembled if the condition for the preceding @code{.if}
5055 @section @code{.elseif}
5057 @cindex @code{elseif} directive
5058 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5059 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5060 @code{.if} block that would otherwise fill the entire @code{.else} section.
5063 @section @code{.end}
5065 @cindex @code{end} directive
5066 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5067 process anything in the file past the @code{.end} directive.
5071 @section @code{.endef}
5073 @cindex @code{endef} directive
5074 This directive flags the end of a symbol definition begun with
5078 @samp{.endef} is only meaningful when generating COFF format output; if
5079 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5080 directive but ignores it.
5085 @section @code{.endfunc}
5086 @cindex @code{endfunc} directive
5087 @code{.endfunc} marks the end of a function specified with @code{.func}.
5090 @section @code{.endif}
5092 @cindex @code{endif} directive
5093 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5094 it marks the end of a block of code that is only assembled
5095 conditionally. @xref{If,,@code{.if}}.
5098 @section @code{.equ @var{symbol}, @var{expression}}
5100 @cindex @code{equ} directive
5101 @cindex assigning values to symbols
5102 @cindex symbols, assigning values to
5103 This directive sets the value of @var{symbol} to @var{expression}.
5104 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5107 The syntax for @code{equ} on the HPPA is
5108 @samp{@var{symbol} .equ @var{expression}}.
5112 The syntax for @code{equ} on the Z80 is
5113 @samp{@var{symbol} equ @var{expression}}.
5114 On the Z80 it is an eror if @var{symbol} is already defined,
5115 but the symbol is not protected from later redefinition.
5116 Compare @ref{Equiv}.
5120 @section @code{.equiv @var{symbol}, @var{expression}}
5121 @cindex @code{equiv} directive
5122 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5123 the assembler will signal an error if @var{symbol} is already defined. Note a
5124 symbol which has been referenced but not actually defined is considered to be
5127 Except for the contents of the error message, this is roughly equivalent to
5134 plus it protects the symbol from later redefinition.
5137 @section @code{.eqv @var{symbol}, @var{expression}}
5138 @cindex @code{eqv} directive
5139 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5140 evaluate the expression or any part of it immediately. Instead each time
5141 the resulting symbol is used in an expression, a snapshot of its current
5145 @section @code{.err}
5146 @cindex @code{err} directive
5147 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5148 message and, unless the @option{-Z} option was used, it will not generate an
5149 object file. This can be used to signal an error in conditionally compiled code.
5152 @section @code{.error "@var{string}"}
5153 @cindex error directive
5155 Similarly to @code{.err}, this directive emits an error, but you can specify a
5156 string that will be emitted as the error message. If you don't specify the
5157 message, it defaults to @code{".error directive invoked in source file"}.
5158 @xref{Errors, ,Error and Warning Messages}.
5161 .error "This code has not been assembled and tested."
5165 @section @code{.exitm}
5166 Exit early from the current macro definition. @xref{Macro}.
5169 @section @code{.extern}
5171 @cindex @code{extern} directive
5172 @code{.extern} is accepted in the source program---for compatibility
5173 with other assemblers---but it is ignored. @command{@value{AS}} treats
5174 all undefined symbols as external.
5177 @section @code{.fail @var{expression}}
5179 @cindex @code{fail} directive
5180 Generates an error or a warning. If the value of the @var{expression} is 500
5181 or more, @command{@value{AS}} will print a warning message. If the value is less
5182 than 500, @command{@value{AS}} will print an error message. The message will
5183 include the value of @var{expression}. This can occasionally be useful inside
5184 complex nested macros or conditional assembly.
5187 @section @code{.file}
5188 @cindex @code{file} directive
5190 @ifclear no-file-dir
5191 There are two different versions of the @code{.file} directive. Targets
5192 that support DWARF2 line number information use the DWARF2 version of
5193 @code{.file}. Other targets use the default version.
5195 @subheading Default Version
5197 @cindex logical file name
5198 @cindex file name, logical
5199 This version of the @code{.file} directive tells @command{@value{AS}} that we
5200 are about to start a new logical file. The syntax is:
5206 @var{string} is the new file name. In general, the filename is
5207 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5208 to specify an empty file name, you must give the quotes--@code{""}. This
5209 statement may go away in future: it is only recognized to be compatible with
5210 old @command{@value{AS}} programs.
5212 @subheading DWARF2 Version
5215 When emitting DWARF2 line number information, @code{.file} assigns filenames
5216 to the @code{.debug_line} file name table. The syntax is:
5219 .file @var{fileno} @var{filename}
5222 The @var{fileno} operand should be a unique positive integer to use as the
5223 index of the entry in the table. The @var{filename} operand is a C string
5226 The detail of filename indices is exposed to the user because the filename
5227 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5228 information, and thus the user must know the exact indices that table
5232 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5234 @cindex @code{fill} directive
5235 @cindex writing patterns in memory
5236 @cindex patterns, writing in memory
5237 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5238 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5239 may be zero or more. @var{Size} may be zero or more, but if it is
5240 more than 8, then it is deemed to have the value 8, compatible with
5241 other people's assemblers. The contents of each @var{repeat} bytes
5242 is taken from an 8-byte number. The highest order 4 bytes are
5243 zero. The lowest order 4 bytes are @var{value} rendered in the
5244 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5245 Each @var{size} bytes in a repetition is taken from the lowest order
5246 @var{size} bytes of this number. Again, this bizarre behavior is
5247 compatible with other people's assemblers.
5249 @var{size} and @var{value} are optional.
5250 If the second comma and @var{value} are absent, @var{value} is
5251 assumed zero. If the first comma and following tokens are absent,
5252 @var{size} is assumed to be 1.
5255 @section @code{.float @var{flonums}}
5257 @cindex floating point numbers (single)
5258 @cindex @code{float} directive
5259 This directive assembles zero or more flonums, separated by commas. It
5260 has the same effect as @code{.single}.
5262 The exact kind of floating point numbers emitted depends on how
5263 @command{@value{AS}} is configured.
5264 @xref{Machine Dependencies}.
5268 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5269 in @sc{ieee} format.
5274 @section @code{.func @var{name}[,@var{label}]}
5275 @cindex @code{func} directive
5276 @code{.func} emits debugging information to denote function @var{name}, and
5277 is ignored unless the file is assembled with debugging enabled.
5278 Only @samp{--gstabs[+]} is currently supported.
5279 @var{label} is the entry point of the function and if omitted @var{name}
5280 prepended with the @samp{leading char} is used.
5281 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5282 All functions are currently defined to have @code{void} return type.
5283 The function must be terminated with @code{.endfunc}.
5286 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5288 @cindex @code{global} directive
5289 @cindex symbol, making visible to linker
5290 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5291 @var{symbol} in your partial program, its value is made available to
5292 other partial programs that are linked with it. Otherwise,
5293 @var{symbol} takes its attributes from a symbol of the same name
5294 from another file linked into the same program.
5296 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5297 compatibility with other assemblers.
5300 On the HPPA, @code{.global} is not always enough to make it accessible to other
5301 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5302 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5307 @section @code{.gnu_attribute @var{tag},@var{value}}
5308 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5311 @section @code{.hidden @var{names}}
5313 @cindex @code{hidden} directive
5315 This is one of the ELF visibility directives. The other two are
5316 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5317 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5319 This directive overrides the named symbols default visibility (which is set by
5320 their binding: local, global or weak). The directive sets the visibility to
5321 @code{hidden} which means that the symbols are not visible to other components.
5322 Such symbols are always considered to be @code{protected} as well.
5326 @section @code{.hword @var{expressions}}
5328 @cindex @code{hword} directive
5329 @cindex integers, 16-bit
5330 @cindex numbers, 16-bit
5331 @cindex sixteen bit integers
5332 This expects zero or more @var{expressions}, and emits
5333 a 16 bit number for each.
5336 This directive is a synonym for @samp{.short}; depending on the target
5337 architecture, it may also be a synonym for @samp{.word}.
5341 This directive is a synonym for @samp{.short}.
5344 This directive is a synonym for both @samp{.short} and @samp{.word}.
5349 @section @code{.ident}
5351 @cindex @code{ident} directive
5353 This directive is used by some assemblers to place tags in object files. The
5354 behavior of this directive varies depending on the target. When using the
5355 a.out object file format, @command{@value{AS}} simply accepts the directive for
5356 source-file compatibility with existing assemblers, but does not emit anything
5357 for it. When using COFF, comments are emitted to the @code{.comment} or
5358 @code{.rdata} section, depending on the target. When using ELF, comments are
5359 emitted to the @code{.comment} section.
5362 @section @code{.if @var{absolute expression}}
5364 @cindex conditional assembly
5365 @cindex @code{if} directive
5366 @code{.if} marks the beginning of a section of code which is only
5367 considered part of the source program being assembled if the argument
5368 (which must be an @var{absolute expression}) is non-zero. The end of
5369 the conditional section of code must be marked by @code{.endif}
5370 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5371 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5372 If you have several conditions to check, @code{.elseif} may be used to avoid
5373 nesting blocks if/else within each subsequent @code{.else} block.
5375 The following variants of @code{.if} are also supported:
5377 @cindex @code{ifdef} directive
5378 @item .ifdef @var{symbol}
5379 Assembles the following section of code if the specified @var{symbol}
5380 has been defined. Note a symbol which has been referenced but not yet defined
5381 is considered to be undefined.
5383 @cindex @code{ifb} directive
5384 @item .ifb @var{text}
5385 Assembles the following section of code if the operand is blank (empty).
5387 @cindex @code{ifc} directive
5388 @item .ifc @var{string1},@var{string2}
5389 Assembles the following section of code if the two strings are the same. The
5390 strings may be optionally quoted with single quotes. If they are not quoted,
5391 the first string stops at the first comma, and the second string stops at the
5392 end of the line. Strings which contain whitespace should be quoted. The
5393 string comparison is case sensitive.
5395 @cindex @code{ifeq} directive
5396 @item .ifeq @var{absolute expression}
5397 Assembles the following section of code if the argument is zero.
5399 @cindex @code{ifeqs} directive
5400 @item .ifeqs @var{string1},@var{string2}
5401 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5403 @cindex @code{ifge} directive
5404 @item .ifge @var{absolute expression}
5405 Assembles the following section of code if the argument is greater than or
5408 @cindex @code{ifgt} directive
5409 @item .ifgt @var{absolute expression}
5410 Assembles the following section of code if the argument is greater than zero.
5412 @cindex @code{ifle} directive
5413 @item .ifle @var{absolute expression}
5414 Assembles the following section of code if the argument is less than or equal
5417 @cindex @code{iflt} directive
5418 @item .iflt @var{absolute expression}
5419 Assembles the following section of code if the argument is less than zero.
5421 @cindex @code{ifnb} directive
5422 @item .ifnb @var{text}
5423 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5424 following section of code if the operand is non-blank (non-empty).
5426 @cindex @code{ifnc} directive
5427 @item .ifnc @var{string1},@var{string2}.
5428 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5429 following section of code if the two strings are not the same.
5431 @cindex @code{ifndef} directive
5432 @cindex @code{ifnotdef} directive
5433 @item .ifndef @var{symbol}
5434 @itemx .ifnotdef @var{symbol}
5435 Assembles the following section of code if the specified @var{symbol}
5436 has not been defined. Both spelling variants are equivalent. Note a symbol
5437 which has been referenced but not yet defined is considered to be undefined.
5439 @cindex @code{ifne} directive
5440 @item .ifne @var{absolute expression}
5441 Assembles the following section of code if the argument is not equal to zero
5442 (in other words, this is equivalent to @code{.if}).
5444 @cindex @code{ifnes} directive
5445 @item .ifnes @var{string1},@var{string2}
5446 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5447 following section of code if the two strings are not the same.
5451 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5453 @cindex @code{incbin} directive
5454 @cindex binary files, including
5455 The @code{incbin} directive includes @var{file} verbatim at the current
5456 location. You can control the search paths used with the @samp{-I} command-line
5457 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5460 The @var{skip} argument skips a number of bytes from the start of the
5461 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5462 read. Note that the data is not aligned in any way, so it is the user's
5463 responsibility to make sure that proper alignment is provided both before and
5464 after the @code{incbin} directive.
5467 @section @code{.include "@var{file}"}
5469 @cindex @code{include} directive
5470 @cindex supporting files, including
5471 @cindex files, including
5472 This directive provides a way to include supporting files at specified
5473 points in your source program. The code from @var{file} is assembled as
5474 if it followed the point of the @code{.include}; when the end of the
5475 included file is reached, assembly of the original file continues. You
5476 can control the search paths used with the @samp{-I} command-line option
5477 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5481 @section @code{.int @var{expressions}}
5483 @cindex @code{int} directive
5484 @cindex integers, 32-bit
5485 Expect zero or more @var{expressions}, of any section, separated by commas.
5486 For each expression, emit a number that, at run time, is the value of that
5487 expression. The byte order and bit size of the number depends on what kind
5488 of target the assembly is for.
5492 On most forms of the H8/300, @code{.int} emits 16-bit
5493 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5500 @section @code{.internal @var{names}}
5502 @cindex @code{internal} directive
5504 This is one of the ELF visibility directives. The other two are
5505 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5506 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5508 This directive overrides the named symbols default visibility (which is set by
5509 their binding: local, global or weak). The directive sets the visibility to
5510 @code{internal} which means that the symbols are considered to be @code{hidden}
5511 (i.e., not visible to other components), and that some extra, processor specific
5512 processing must also be performed upon the symbols as well.
5516 @section @code{.irp @var{symbol},@var{values}}@dots{}
5518 @cindex @code{irp} directive
5519 Evaluate a sequence of statements assigning different values to @var{symbol}.
5520 The sequence of statements starts at the @code{.irp} directive, and is
5521 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5522 set to @var{value}, and the sequence of statements is assembled. If no
5523 @var{value} is listed, the sequence of statements is assembled once, with
5524 @var{symbol} set to the null string. To refer to @var{symbol} within the
5525 sequence of statements, use @var{\symbol}.
5527 For example, assembling
5535 is equivalent to assembling
5543 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5546 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5548 @cindex @code{irpc} directive
5549 Evaluate a sequence of statements assigning different values to @var{symbol}.
5550 The sequence of statements starts at the @code{.irpc} directive, and is
5551 terminated by an @code{.endr} directive. For each character in @var{value},
5552 @var{symbol} is set to the character, and the sequence of statements is
5553 assembled. If no @var{value} is listed, the sequence of statements is
5554 assembled once, with @var{symbol} set to the null string. To refer to
5555 @var{symbol} within the sequence of statements, use @var{\symbol}.
5557 For example, assembling
5565 is equivalent to assembling
5573 For some caveats with the spelling of @var{symbol}, see also the discussion
5577 @section @code{.lcomm @var{symbol} , @var{length}}
5579 @cindex @code{lcomm} directive
5580 @cindex local common symbols
5581 @cindex symbols, local common
5582 Reserve @var{length} (an absolute expression) bytes for a local common
5583 denoted by @var{symbol}. The section and value of @var{symbol} are
5584 those of the new local common. The addresses are allocated in the bss
5585 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5586 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5587 not visible to @code{@value{LD}}.
5590 Some targets permit a third argument to be used with @code{.lcomm}. This
5591 argument specifies the desired alignment of the symbol in the bss section.
5595 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5596 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5600 @section @code{.lflags}
5602 @cindex @code{lflags} directive (ignored)
5603 @command{@value{AS}} accepts this directive, for compatibility with other
5604 assemblers, but ignores it.
5606 @ifclear no-line-dir
5608 @section @code{.line @var{line-number}}
5610 @cindex @code{line} directive
5611 @cindex logical line number
5613 Change the logical line number. @var{line-number} must be an absolute
5614 expression. The next line has that logical line number. Therefore any other
5615 statements on the current line (after a statement separator character) are
5616 reported as on logical line number @var{line-number} @minus{} 1. One day
5617 @command{@value{AS}} will no longer support this directive: it is recognized only
5618 for compatibility with existing assembler programs.
5621 Even though this is a directive associated with the @code{a.out} or
5622 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5623 when producing COFF output, and treats @samp{.line} as though it
5624 were the COFF @samp{.ln} @emph{if} it is found outside a
5625 @code{.def}/@code{.endef} pair.
5627 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5628 used by compilers to generate auxiliary symbol information for
5633 @section @code{.linkonce [@var{type}]}
5635 @cindex @code{linkonce} directive
5636 @cindex common sections
5637 Mark the current section so that the linker only includes a single copy of it.
5638 This may be used to include the same section in several different object files,
5639 but ensure that the linker will only include it once in the final output file.
5640 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5641 Duplicate sections are detected based on the section name, so it should be
5644 This directive is only supported by a few object file formats; as of this
5645 writing, the only object file format which supports it is the Portable
5646 Executable format used on Windows NT.
5648 The @var{type} argument is optional. If specified, it must be one of the
5649 following strings. For example:
5653 Not all types may be supported on all object file formats.
5657 Silently discard duplicate sections. This is the default.
5660 Warn if there are duplicate sections, but still keep only one copy.
5663 Warn if any of the duplicates have different sizes.
5666 Warn if any of the duplicates do not have exactly the same contents.
5670 @section @code{.list}
5672 @cindex @code{list} directive
5673 @cindex listing control, turning on
5674 Control (in conjunction with the @code{.nolist} directive) whether or
5675 not assembly listings are generated. These two directives maintain an
5676 internal counter (which is zero initially). @code{.list} increments the
5677 counter, and @code{.nolist} decrements it. Assembly listings are
5678 generated whenever the counter is greater than zero.
5680 By default, listings are disabled. When you enable them (with the
5681 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5682 the initial value of the listing counter is one.
5685 @section @code{.ln @var{line-number}}
5687 @cindex @code{ln} directive
5688 @ifclear no-line-dir
5689 @samp{.ln} is a synonym for @samp{.line}.
5692 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5693 must be an absolute expression. The next line has that logical
5694 line number, so any other statements on the current line (after a
5695 statement separator character @code{;}) are reported as on logical
5696 line number @var{line-number} @minus{} 1.
5699 This directive is accepted, but ignored, when @command{@value{AS}} is
5700 configured for @code{b.out}; its effect is only associated with COFF
5706 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5707 @cindex @code{loc} directive
5708 When emitting DWARF2 line number information,
5709 the @code{.loc} directive will add a row to the @code{.debug_line} line
5710 number matrix corresponding to the immediately following assembly
5711 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5712 arguments will be applied to the @code{.debug_line} state machine before
5715 The @var{options} are a sequence of the following tokens in any order:
5719 This option will set the @code{basic_block} register in the
5720 @code{.debug_line} state machine to @code{true}.
5723 This option will set the @code{prologue_end} register in the
5724 @code{.debug_line} state machine to @code{true}.
5726 @item epilogue_begin
5727 This option will set the @code{epilogue_begin} register in the
5728 @code{.debug_line} state machine to @code{true}.
5730 @item is_stmt @var{value}
5731 This option will set the @code{is_stmt} register in the
5732 @code{.debug_line} state machine to @code{value}, which must be
5735 @item isa @var{value}
5736 This directive will set the @code{isa} register in the @code{.debug_line}
5737 state machine to @var{value}, which must be an unsigned integer.
5739 @item discriminator @var{value}
5740 This directive will set the @code{discriminator} register in the @code{.debug_line}
5741 state machine to @var{value}, which must be an unsigned integer.
5745 @node Loc_mark_labels
5746 @section @code{.loc_mark_labels @var{enable}}
5747 @cindex @code{loc_mark_labels} directive
5748 When emitting DWARF2 line number information,
5749 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5750 to the @code{.debug_line} line number matrix with the @code{basic_block}
5751 register in the state machine set whenever a code label is seen.
5752 The @var{enable} argument should be either 1 or 0, to enable or disable
5753 this function respectively.
5757 @section @code{.local @var{names}}
5759 @cindex @code{local} directive
5760 This directive, which is available for ELF targets, marks each symbol in
5761 the comma-separated list of @code{names} as a local symbol so that it
5762 will not be externally visible. If the symbols do not already exist,
5763 they will be created.
5765 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5766 accept an alignment argument, which is the case for most ELF targets,
5767 the @code{.local} directive can be used in combination with @code{.comm}
5768 (@pxref{Comm}) to define aligned local common data.
5772 @section @code{.long @var{expressions}}
5774 @cindex @code{long} directive
5775 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5778 @c no one seems to know what this is for or whether this description is
5779 @c what it really ought to do
5781 @section @code{.lsym @var{symbol}, @var{expression}}
5783 @cindex @code{lsym} directive
5784 @cindex symbol, not referenced in assembly
5785 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5786 the hash table, ensuring it cannot be referenced by name during the
5787 rest of the assembly. This sets the attributes of the symbol to be
5788 the same as the expression value:
5790 @var{other} = @var{descriptor} = 0
5791 @var{type} = @r{(section of @var{expression})}
5792 @var{value} = @var{expression}
5795 The new symbol is not flagged as external.
5799 @section @code{.macro}
5802 The commands @code{.macro} and @code{.endm} allow you to define macros that
5803 generate assembly output. For example, this definition specifies a macro
5804 @code{sum} that puts a sequence of numbers into memory:
5807 .macro sum from=0, to=5
5816 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5828 @item .macro @var{macname}
5829 @itemx .macro @var{macname} @var{macargs} @dots{}
5830 @cindex @code{macro} directive
5831 Begin the definition of a macro called @var{macname}. If your macro
5832 definition requires arguments, specify their names after the macro name,
5833 separated by commas or spaces. You can qualify the macro argument to
5834 indicate whether all invocations must specify a non-blank value (through
5835 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5836 (through @samp{:@code{vararg}}). You can supply a default value for any
5837 macro argument by following the name with @samp{=@var{deflt}}. You
5838 cannot define two macros with the same @var{macname} unless it has been
5839 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5840 definitions. For example, these are all valid @code{.macro} statements:
5844 Begin the definition of a macro called @code{comm}, which takes no
5847 @item .macro plus1 p, p1
5848 @itemx .macro plus1 p p1
5849 Either statement begins the definition of a macro called @code{plus1},
5850 which takes two arguments; within the macro definition, write
5851 @samp{\p} or @samp{\p1} to evaluate the arguments.
5853 @item .macro reserve_str p1=0 p2
5854 Begin the definition of a macro called @code{reserve_str}, with two
5855 arguments. The first argument has a default value, but not the second.
5856 After the definition is complete, you can call the macro either as
5857 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5858 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5859 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5860 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5862 @item .macro m p1:req, p2=0, p3:vararg
5863 Begin the definition of a macro called @code{m}, with at least three
5864 arguments. The first argument must always have a value specified, but
5865 not the second, which instead has a default value. The third formal
5866 will get assigned all remaining arguments specified at invocation time.
5868 When you call a macro, you can specify the argument values either by
5869 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5870 @samp{sum to=17, from=9}.
5874 Note that since each of the @var{macargs} can be an identifier exactly
5875 as any other one permitted by the target architecture, there may be
5876 occasional problems if the target hand-crafts special meanings to certain
5877 characters when they occur in a special position. For example, if the colon
5878 (@code{:}) is generally permitted to be part of a symbol name, but the
5879 architecture specific code special-cases it when occurring as the final
5880 character of a symbol (to denote a label), then the macro parameter
5881 replacement code will have no way of knowing that and consider the whole
5882 construct (including the colon) an identifier, and check only this
5883 identifier for being the subject to parameter substitution. So for example
5884 this macro definition:
5892 might not work as expected. Invoking @samp{label foo} might not create a label
5893 called @samp{foo} but instead just insert the text @samp{\l:} into the
5894 assembler source, probably generating an error about an unrecognised
5897 Similarly problems might occur with the period character (@samp{.})
5898 which is often allowed inside opcode names (and hence identifier names). So
5899 for example constructing a macro to build an opcode from a base name and a
5900 length specifier like this:
5903 .macro opcode base length
5908 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5909 instruction but instead generate some kind of error as the assembler tries to
5910 interpret the text @samp{\base.\length}.
5912 There are several possible ways around this problem:
5915 @item Insert white space
5916 If it is possible to use white space characters then this is the simplest
5925 @item Use @samp{\()}
5926 The string @samp{\()} can be used to separate the end of a macro argument from
5927 the following text. eg:
5930 .macro opcode base length
5935 @item Use the alternate macro syntax mode
5936 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5937 used as a separator. eg:
5947 Note: this problem of correctly identifying string parameters to pseudo ops
5948 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5949 and @code{.irpc} (@pxref{Irpc}) as well.
5952 @cindex @code{endm} directive
5953 Mark the end of a macro definition.
5956 @cindex @code{exitm} directive
5957 Exit early from the current macro definition.
5959 @cindex number of macros executed
5960 @cindex macros, count executed
5962 @command{@value{AS}} maintains a counter of how many macros it has
5963 executed in this pseudo-variable; you can copy that number to your
5964 output with @samp{\@@}, but @emph{only within a macro definition}.
5966 @item LOCAL @var{name} [ , @dots{} ]
5967 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5968 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5969 @xref{Altmacro,,@code{.altmacro}}.
5973 @section @code{.mri @var{val}}
5975 @cindex @code{mri} directive
5976 @cindex MRI mode, temporarily
5977 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5978 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5979 affects code assembled until the next @code{.mri} directive, or until the end
5980 of the file. @xref{M, MRI mode, MRI mode}.
5983 @section @code{.noaltmacro}
5984 Disable alternate macro mode. @xref{Altmacro}.
5987 @section @code{.nolist}
5989 @cindex @code{nolist} directive
5990 @cindex listing control, turning off
5991 Control (in conjunction with the @code{.list} directive) whether or
5992 not assembly listings are generated. These two directives maintain an
5993 internal counter (which is zero initially). @code{.list} increments the
5994 counter, and @code{.nolist} decrements it. Assembly listings are
5995 generated whenever the counter is greater than zero.
5998 @section @code{.octa @var{bignums}}
6000 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6001 @cindex @code{octa} directive
6002 @cindex integer, 16-byte
6003 @cindex sixteen byte integer
6004 This directive expects zero or more bignums, separated by commas. For each
6005 bignum, it emits a 16-byte integer.
6007 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6008 hence @emph{octa}-word for 16 bytes.
6011 @section @code{.offset @var{loc}}
6013 @cindex @code{offset} directive
6014 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6015 be an absolute expression. This directive may be useful for defining
6016 symbols with absolute values. Do not confuse it with the @code{.org}
6020 @section @code{.org @var{new-lc} , @var{fill}}
6022 @cindex @code{org} directive
6023 @cindex location counter, advancing
6024 @cindex advancing location counter
6025 @cindex current address, advancing
6026 Advance the location counter of the current section to
6027 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6028 expression with the same section as the current subsection. That is,
6029 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6030 wrong section, the @code{.org} directive is ignored. To be compatible
6031 with former assemblers, if the section of @var{new-lc} is absolute,
6032 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6033 is the same as the current subsection.
6035 @code{.org} may only increase the location counter, or leave it
6036 unchanged; you cannot use @code{.org} to move the location counter
6039 @c double negative used below "not undefined" because this is a specific
6040 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6041 @c section. doc@cygnus.com 18feb91
6042 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6043 may not be undefined. If you really detest this restriction we eagerly await
6044 a chance to share your improved assembler.
6046 Beware that the origin is relative to the start of the section, not
6047 to the start of the subsection. This is compatible with other
6048 people's assemblers.
6050 When the location counter (of the current subsection) is advanced, the
6051 intervening bytes are filled with @var{fill} which should be an
6052 absolute expression. If the comma and @var{fill} are omitted,
6053 @var{fill} defaults to zero.
6056 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6058 @cindex padding the location counter given a power of two
6059 @cindex @code{p2align} directive
6060 Pad the location counter (in the current subsection) to a particular
6061 storage boundary. The first expression (which must be absolute) is the
6062 number of low-order zero bits the location counter must have after
6063 advancement. For example @samp{.p2align 3} advances the location
6064 counter until it a multiple of 8. If the location counter is already a
6065 multiple of 8, no change is needed.
6067 The second expression (also absolute) gives the fill value to be stored in the
6068 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6069 padding bytes are normally zero. However, on some systems, if the section is
6070 marked as containing code and the fill value is omitted, the space is filled
6071 with no-op instructions.
6073 The third expression is also absolute, and is also optional. If it is present,
6074 it is the maximum number of bytes that should be skipped by this alignment
6075 directive. If doing the alignment would require skipping more bytes than the
6076 specified maximum, then the alignment is not done at all. You can omit the
6077 fill value (the second argument) entirely by simply using two commas after the
6078 required alignment; this can be useful if you want the alignment to be filled
6079 with no-op instructions when appropriate.
6081 @cindex @code{p2alignw} directive
6082 @cindex @code{p2alignl} directive
6083 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6084 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6085 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6086 fill pattern as a four byte longword value. For example, @code{.p2alignw
6087 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6088 filled in with the value 0x368d (the exact placement of the bytes depends upon
6089 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6094 @section @code{.popsection}
6096 @cindex @code{popsection} directive
6097 @cindex Section Stack
6098 This is one of the ELF section stack manipulation directives. The others are
6099 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6100 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6103 This directive replaces the current section (and subsection) with the top
6104 section (and subsection) on the section stack. This section is popped off the
6110 @section @code{.previous}
6112 @cindex @code{previous} directive
6113 @cindex Section Stack
6114 This is one of the ELF section stack manipulation directives. The others are
6115 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6116 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6117 (@pxref{PopSection}).
6119 This directive swaps the current section (and subsection) with most recently
6120 referenced section/subsection pair prior to this one. Multiple
6121 @code{.previous} directives in a row will flip between two sections (and their
6122 subsections). For example:
6134 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6140 # Now in section A subsection 1
6144 # Now in section B subsection 0
6147 # Now in section B subsection 1
6150 # Now in section B subsection 0
6154 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6155 section B and 0x9abc into subsection 1 of section B.
6157 In terms of the section stack, this directive swaps the current section with
6158 the top section on the section stack.
6162 @section @code{.print @var{string}}
6164 @cindex @code{print} directive
6165 @command{@value{AS}} will print @var{string} on the standard output during
6166 assembly. You must put @var{string} in double quotes.
6170 @section @code{.protected @var{names}}
6172 @cindex @code{protected} directive
6174 This is one of the ELF visibility directives. The other two are
6175 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6177 This directive overrides the named symbols default visibility (which is set by
6178 their binding: local, global or weak). The directive sets the visibility to
6179 @code{protected} which means that any references to the symbols from within the
6180 components that defines them must be resolved to the definition in that
6181 component, even if a definition in another component would normally preempt
6186 @section @code{.psize @var{lines} , @var{columns}}
6188 @cindex @code{psize} directive
6189 @cindex listing control: paper size
6190 @cindex paper size, for listings
6191 Use this directive to declare the number of lines---and, optionally, the
6192 number of columns---to use for each page, when generating listings.
6194 If you do not use @code{.psize}, listings use a default line-count
6195 of 60. You may omit the comma and @var{columns} specification; the
6196 default width is 200 columns.
6198 @command{@value{AS}} generates formfeeds whenever the specified number of
6199 lines is exceeded (or whenever you explicitly request one, using
6202 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6203 those explicitly specified with @code{.eject}.
6206 @section @code{.purgem @var{name}}
6208 @cindex @code{purgem} directive
6209 Undefine the macro @var{name}, so that later uses of the string will not be
6210 expanded. @xref{Macro}.
6214 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6216 @cindex @code{pushsection} directive
6217 @cindex Section Stack
6218 This is one of the ELF section stack manipulation directives. The others are
6219 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6220 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6223 This directive pushes the current section (and subsection) onto the
6224 top of the section stack, and then replaces the current section and
6225 subsection with @code{name} and @code{subsection}. The optional
6226 @code{flags}, @code{type} and @code{arguments} are treated the same
6227 as in the @code{.section} (@pxref{Section}) directive.
6231 @section @code{.quad @var{bignums}}
6233 @cindex @code{quad} directive
6234 @code{.quad} expects zero or more bignums, separated by commas. For
6235 each bignum, it emits
6237 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6238 warning message; and just takes the lowest order 8 bytes of the bignum.
6239 @cindex eight-byte integer
6240 @cindex integer, 8-byte
6242 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6243 hence @emph{quad}-word for 8 bytes.
6246 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6247 warning message; and just takes the lowest order 16 bytes of the bignum.
6248 @cindex sixteen-byte integer
6249 @cindex integer, 16-byte
6253 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6255 @cindex @code{reloc} directive
6256 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6257 @var{expression}. If @var{offset} is a number, the relocation is generated in
6258 the current section. If @var{offset} is an expression that resolves to a
6259 symbol plus offset, the relocation is generated in the given symbol's section.
6260 @var{expression}, if present, must resolve to a symbol plus addend or to an
6261 absolute value, but note that not all targets support an addend. e.g. ELF REL
6262 targets such as i386 store an addend in the section contents rather than in the
6263 relocation. This low level interface does not support addends stored in the
6267 @section @code{.rept @var{count}}
6269 @cindex @code{rept} directive
6270 Repeat the sequence of lines between the @code{.rept} directive and the next
6271 @code{.endr} directive @var{count} times.
6273 For example, assembling
6281 is equivalent to assembling
6290 @section @code{.sbttl "@var{subheading}"}
6292 @cindex @code{sbttl} directive
6293 @cindex subtitles for listings
6294 @cindex listing control: subtitle
6295 Use @var{subheading} as the title (third line, immediately after the
6296 title line) when generating assembly listings.
6298 This directive affects subsequent pages, as well as the current page if
6299 it appears within ten lines of the top of a page.
6303 @section @code{.scl @var{class}}
6305 @cindex @code{scl} directive
6306 @cindex symbol storage class (COFF)
6307 @cindex COFF symbol storage class
6308 Set the storage-class value for a symbol. This directive may only be
6309 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6310 whether a symbol is static or external, or it may record further
6311 symbolic debugging information.
6314 The @samp{.scl} directive is primarily associated with COFF output; when
6315 configured to generate @code{b.out} output format, @command{@value{AS}}
6316 accepts this directive but ignores it.
6322 @section @code{.section @var{name}}
6324 @cindex named section
6325 Use the @code{.section} directive to assemble the following code into a section
6328 This directive is only supported for targets that actually support arbitrarily
6329 named sections; on @code{a.out} targets, for example, it is not accepted, even
6330 with a standard @code{a.out} section name.
6334 @c only print the extra heading if both COFF and ELF are set
6335 @subheading COFF Version
6338 @cindex @code{section} directive (COFF version)
6339 For COFF targets, the @code{.section} directive is used in one of the following
6343 .section @var{name}[, "@var{flags}"]
6344 .section @var{name}[, @var{subsection}]
6347 If the optional argument is quoted, it is taken as flags to use for the
6348 section. Each flag is a single character. The following flags are recognized:
6352 bss section (uninitialized data)
6354 section is not loaded
6360 exclude section from linking
6366 shared section (meaningful for PE targets)
6368 ignored. (For compatibility with the ELF version)
6370 section is not readable (meaningful for PE targets)
6372 single-digit power-of-two section alignment (GNU extension)
6375 If no flags are specified, the default flags depend upon the section name. If
6376 the section name is not recognized, the default will be for the section to be
6377 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6378 from the section, rather than adding them, so if they are used on their own it
6379 will be as if no flags had been specified at all.
6381 If the optional argument to the @code{.section} directive is not quoted, it is
6382 taken as a subsection number (@pxref{Sub-Sections}).
6387 @c only print the extra heading if both COFF and ELF are set
6388 @subheading ELF Version
6391 @cindex Section Stack
6392 This is one of the ELF section stack manipulation directives. The others are
6393 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6394 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6395 @code{.previous} (@pxref{Previous}).
6397 @cindex @code{section} directive (ELF version)
6398 For ELF targets, the @code{.section} directive is used like this:
6401 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6404 @anchor{Section Name Substitutions}
6405 @kindex --sectname-subst
6406 @cindex section name substitution
6407 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6408 argument may contain a substitution sequence. Only @code{%S} is supported
6409 at the moment, and substitutes the current section name. For example:
6412 .macro exception_code
6413 .section %S.exception
6414 [exception code here]
6429 The two @code{exception_code} invocations above would create the
6430 @code{.text.exception} and @code{.init.exception} sections respectively.
6431 This is useful e.g. to discriminate between anciliary sections that are
6432 tied to setup code to be discarded after use from anciliary sections that
6433 need to stay resident without having to define multiple @code{exception_code}
6434 macros just for that purpose.
6436 The optional @var{flags} argument is a quoted string which may contain any
6437 combination of the following characters:
6441 section is allocatable
6443 section is excluded from executable and shared library.
6447 section is executable
6449 section is mergeable
6451 section contains zero terminated strings
6453 section is a member of a section group
6455 section is used for thread-local-storage
6457 section is a member of the previously-current section's group, if any
6458 @item @code{<number>}
6459 a numeric value indicating the bits to be set in the ELF section header's flags
6460 field. Note - if one or more of the alphabetic characters described above is
6461 also included in the flags field, their bit values will be ORed into the
6463 @item @code{<target specific>}
6464 some targets extend this list with their own flag characters
6467 Note - once a section's flags have been set they cannot be changed. There are
6468 a few exceptions to this rule however. Processor and application specific
6469 flags can be added to an already defined section. The @code{.interp},
6470 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6471 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6472 section may have the executable (@code{x}) flag added.
6474 The optional @var{type} argument may contain one of the following constants:
6478 section contains data
6480 section does not contain data (i.e., section only occupies space)
6482 section contains data which is used by things other than the program
6484 section contains an array of pointers to init functions
6486 section contains an array of pointers to finish functions
6487 @item @@preinit_array
6488 section contains an array of pointers to pre-init functions
6489 @item @@@code{<number>}
6490 a numeric value to be set as the ELF section header's type field.
6491 @item @@@code{<target specific>}
6492 some targets extend this list with their own types
6495 Many targets only support the first three section types. The type may be
6496 enclosed in double quotes if necessary.
6498 Note on targets where the @code{@@} character is the start of a comment (eg
6499 ARM) then another character is used instead. For example the ARM port uses the
6502 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6503 special and have fixed types. Any attempt to declare them with a different
6504 type will generate an error from the assembler.
6506 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6507 be specified as well as an extra argument---@var{entsize}---like this:
6510 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6513 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6514 constants, each @var{entsize} octets long. Sections with both @code{M} and
6515 @code{S} must contain zero terminated strings where each character is
6516 @var{entsize} bytes long. The linker may remove duplicates within sections with
6517 the same name, same entity size and same flags. @var{entsize} must be an
6518 absolute expression. For sections with both @code{M} and @code{S}, a string
6519 which is a suffix of a larger string is considered a duplicate. Thus
6520 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6521 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6523 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6524 be present along with an additional field like this:
6527 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6530 The @var{GroupName} field specifies the name of the section group to which this
6531 particular section belongs. The optional linkage field can contain:
6535 indicates that only one copy of this section should be retained
6540 Note: if both the @var{M} and @var{G} flags are present then the fields for
6541 the Merge flag should come first, like this:
6544 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6547 If @var{flags} contains the @code{?} symbol then it may not also contain the
6548 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6549 present. Instead, @code{?} says to consider the section that's current before
6550 this directive. If that section used @code{G}, then the new section will use
6551 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6552 If not, then the @code{?} symbol has no effect.
6554 If no flags are specified, the default flags depend upon the section name. If
6555 the section name is not recognized, the default will be for the section to have
6556 none of the above flags: it will not be allocated in memory, nor writable, nor
6557 executable. The section will contain data.
6559 For ELF targets, the assembler supports another type of @code{.section}
6560 directive for compatibility with the Solaris assembler:
6563 .section "@var{name}"[, @var{flags}...]
6566 Note that the section name is quoted. There may be a sequence of comma
6571 section is allocatable
6575 section is executable
6577 section is excluded from executable and shared library.
6579 section is used for thread local storage
6582 This directive replaces the current section and subsection. See the
6583 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6584 some examples of how this directive and the other section stack directives
6590 @section @code{.set @var{symbol}, @var{expression}}
6592 @cindex @code{set} directive
6593 @cindex symbol value, setting
6594 Set the value of @var{symbol} to @var{expression}. This
6595 changes @var{symbol}'s value and type to conform to
6596 @var{expression}. If @var{symbol} was flagged as external, it remains
6597 flagged (@pxref{Symbol Attributes}).
6599 You may @code{.set} a symbol many times in the same assembly provided that the
6600 values given to the symbol are constants. Values that are based on expressions
6601 involving other symbols are allowed, but some targets may restrict this to only
6602 being done once per assembly. This is because those targets do not set the
6603 addresses of symbols at assembly time, but rather delay the assignment until a
6604 final link is performed. This allows the linker a chance to change the code in
6605 the files, changing the location of, and the relative distance between, various
6608 If you @code{.set} a global symbol, the value stored in the object
6609 file is the last value stored into it.
6612 On Z80 @code{set} is a real instruction, use
6613 @samp{@var{symbol} defl @var{expression}} instead.
6617 @section @code{.short @var{expressions}}
6619 @cindex @code{short} directive
6621 @code{.short} is normally the same as @samp{.word}.
6622 @xref{Word,,@code{.word}}.
6624 In some configurations, however, @code{.short} and @code{.word} generate
6625 numbers of different lengths. @xref{Machine Dependencies}.
6629 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6632 This expects zero or more @var{expressions}, and emits
6633 a 16 bit number for each.
6638 @section @code{.single @var{flonums}}
6640 @cindex @code{single} directive
6641 @cindex floating point numbers (single)
6642 This directive assembles zero or more flonums, separated by commas. It
6643 has the same effect as @code{.float}.
6645 The exact kind of floating point numbers emitted depends on how
6646 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6650 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6651 numbers in @sc{ieee} format.
6657 @section @code{.size}
6659 This directive is used to set the size associated with a symbol.
6663 @c only print the extra heading if both COFF and ELF are set
6664 @subheading COFF Version
6667 @cindex @code{size} directive (COFF version)
6668 For COFF targets, the @code{.size} directive is only permitted inside
6669 @code{.def}/@code{.endef} pairs. It is used like this:
6672 .size @var{expression}
6676 @samp{.size} is only meaningful when generating COFF format output; when
6677 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6684 @c only print the extra heading if both COFF and ELF are set
6685 @subheading ELF Version
6688 @cindex @code{size} directive (ELF version)
6689 For ELF targets, the @code{.size} directive is used like this:
6692 .size @var{name} , @var{expression}
6695 This directive sets the size associated with a symbol @var{name}.
6696 The size in bytes is computed from @var{expression} which can make use of label
6697 arithmetic. This directive is typically used to set the size of function
6702 @ifclear no-space-dir
6704 @section @code{.skip @var{size} , @var{fill}}
6706 @cindex @code{skip} directive
6707 @cindex filling memory
6708 This directive emits @var{size} bytes, each of value @var{fill}. Both
6709 @var{size} and @var{fill} are absolute expressions. If the comma and
6710 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6715 @section @code{.sleb128 @var{expressions}}
6717 @cindex @code{sleb128} directive
6718 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6719 compact, variable length representation of numbers used by the DWARF
6720 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6722 @ifclear no-space-dir
6724 @section @code{.space @var{size} , @var{fill}}
6726 @cindex @code{space} directive
6727 @cindex filling memory
6728 This directive emits @var{size} bytes, each of value @var{fill}. Both
6729 @var{size} and @var{fill} are absolute expressions. If the comma
6730 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6735 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6736 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6737 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6738 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6746 @section @code{.stabd, .stabn, .stabs}
6748 @cindex symbolic debuggers, information for
6749 @cindex @code{stab@var{x}} directives
6750 There are three directives that begin @samp{.stab}.
6751 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6752 The symbols are not entered in the @command{@value{AS}} hash table: they
6753 cannot be referenced elsewhere in the source file.
6754 Up to five fields are required:
6758 This is the symbol's name. It may contain any character except
6759 @samp{\000}, so is more general than ordinary symbol names. Some
6760 debuggers used to code arbitrarily complex structures into symbol names
6764 An absolute expression. The symbol's type is set to the low 8 bits of
6765 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6766 and debuggers choke on silly bit patterns.
6769 An absolute expression. The symbol's ``other'' attribute is set to the
6770 low 8 bits of this expression.
6773 An absolute expression. The symbol's descriptor is set to the low 16
6774 bits of this expression.
6777 An absolute expression which becomes the symbol's value.
6780 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6781 or @code{.stabs} statement, the symbol has probably already been created;
6782 you get a half-formed symbol in your object file. This is
6783 compatible with earlier assemblers!
6786 @cindex @code{stabd} directive
6787 @item .stabd @var{type} , @var{other} , @var{desc}
6789 The ``name'' of the symbol generated is not even an empty string.
6790 It is a null pointer, for compatibility. Older assemblers used a
6791 null pointer so they didn't waste space in object files with empty
6794 The symbol's value is set to the location counter,
6795 relocatably. When your program is linked, the value of this symbol
6796 is the address of the location counter when the @code{.stabd} was
6799 @cindex @code{stabn} directive
6800 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6801 The name of the symbol is set to the empty string @code{""}.
6803 @cindex @code{stabs} directive
6804 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6805 All five fields are specified.
6811 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6812 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6814 @cindex string, copying to object file
6815 @cindex string8, copying to object file
6816 @cindex string16, copying to object file
6817 @cindex string32, copying to object file
6818 @cindex string64, copying to object file
6819 @cindex @code{string} directive
6820 @cindex @code{string8} directive
6821 @cindex @code{string16} directive
6822 @cindex @code{string32} directive
6823 @cindex @code{string64} directive
6825 Copy the characters in @var{str} to the object file. You may specify more than
6826 one string to copy, separated by commas. Unless otherwise specified for a
6827 particular machine, the assembler marks the end of each string with a 0 byte.
6828 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6830 The variants @code{string16}, @code{string32} and @code{string64} differ from
6831 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6832 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6833 are stored in target endianness byte order.
6839 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6840 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6845 @section @code{.struct @var{expression}}
6847 @cindex @code{struct} directive
6848 Switch to the absolute section, and set the section offset to @var{expression},
6849 which must be an absolute expression. You might use this as follows:
6858 This would define the symbol @code{field1} to have the value 0, the symbol
6859 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6860 value 8. Assembly would be left in the absolute section, and you would need to
6861 use a @code{.section} directive of some sort to change to some other section
6862 before further assembly.
6866 @section @code{.subsection @var{name}}
6868 @cindex @code{subsection} directive
6869 @cindex Section Stack
6870 This is one of the ELF section stack manipulation directives. The others are
6871 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6872 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6875 This directive replaces the current subsection with @code{name}. The current
6876 section is not changed. The replaced subsection is put onto the section stack
6877 in place of the then current top of stack subsection.
6882 @section @code{.symver}
6883 @cindex @code{symver} directive
6884 @cindex symbol versioning
6885 @cindex versions of symbols
6886 Use the @code{.symver} directive to bind symbols to specific version nodes
6887 within a source file. This is only supported on ELF platforms, and is
6888 typically used when assembling files to be linked into a shared library.
6889 There are cases where it may make sense to use this in objects to be bound
6890 into an application itself so as to override a versioned symbol from a
6893 For ELF targets, the @code{.symver} directive can be used like this:
6895 .symver @var{name}, @var{name2@@nodename}
6897 If the symbol @var{name} is defined within the file
6898 being assembled, the @code{.symver} directive effectively creates a symbol
6899 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6900 just don't try and create a regular alias is that the @var{@@} character isn't
6901 permitted in symbol names. The @var{name2} part of the name is the actual name
6902 of the symbol by which it will be externally referenced. The name @var{name}
6903 itself is merely a name of convenience that is used so that it is possible to
6904 have definitions for multiple versions of a function within a single source
6905 file, and so that the compiler can unambiguously know which version of a
6906 function is being mentioned. The @var{nodename} portion of the alias should be
6907 the name of a node specified in the version script supplied to the linker when
6908 building a shared library. If you are attempting to override a versioned
6909 symbol from a shared library, then @var{nodename} should correspond to the
6910 nodename of the symbol you are trying to override.
6912 If the symbol @var{name} is not defined within the file being assembled, all
6913 references to @var{name} will be changed to @var{name2@@nodename}. If no
6914 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6917 Another usage of the @code{.symver} directive is:
6919 .symver @var{name}, @var{name2@@@@nodename}
6921 In this case, the symbol @var{name} must exist and be defined within
6922 the file being assembled. It is similar to @var{name2@@nodename}. The
6923 difference is @var{name2@@@@nodename} will also be used to resolve
6924 references to @var{name2} by the linker.
6926 The third usage of the @code{.symver} directive is:
6928 .symver @var{name}, @var{name2@@@@@@nodename}
6930 When @var{name} is not defined within the
6931 file being assembled, it is treated as @var{name2@@nodename}. When
6932 @var{name} is defined within the file being assembled, the symbol
6933 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6938 @section @code{.tag @var{structname}}
6940 @cindex COFF structure debugging
6941 @cindex structure debugging, COFF
6942 @cindex @code{tag} directive
6943 This directive is generated by compilers to include auxiliary debugging
6944 information in the symbol table. It is only permitted inside
6945 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6946 definitions in the symbol table with instances of those structures.
6949 @samp{.tag} is only used when generating COFF format output; when
6950 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6956 @section @code{.text @var{subsection}}
6958 @cindex @code{text} directive
6959 Tells @command{@value{AS}} to assemble the following statements onto the end of
6960 the text subsection numbered @var{subsection}, which is an absolute
6961 expression. If @var{subsection} is omitted, subsection number zero
6965 @section @code{.title "@var{heading}"}
6967 @cindex @code{title} directive
6968 @cindex listing control: title line
6969 Use @var{heading} as the title (second line, immediately after the
6970 source file name and pagenumber) when generating assembly listings.
6972 This directive affects subsequent pages, as well as the current page if
6973 it appears within ten lines of the top of a page.
6977 @section @code{.type}
6979 This directive is used to set the type of a symbol.
6983 @c only print the extra heading if both COFF and ELF are set
6984 @subheading COFF Version
6987 @cindex COFF symbol type
6988 @cindex symbol type, COFF
6989 @cindex @code{type} directive (COFF version)
6990 For COFF targets, this directive is permitted only within
6991 @code{.def}/@code{.endef} pairs. It is used like this:
6997 This records the integer @var{int} as the type attribute of a symbol table
7001 @samp{.type} is associated only with COFF format output; when
7002 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7003 directive but ignores it.
7009 @c only print the extra heading if both COFF and ELF are set
7010 @subheading ELF Version
7013 @cindex ELF symbol type
7014 @cindex symbol type, ELF
7015 @cindex @code{type} directive (ELF version)
7016 For ELF targets, the @code{.type} directive is used like this:
7019 .type @var{name} , @var{type description}
7022 This sets the type of symbol @var{name} to be either a
7023 function symbol or an object symbol. There are five different syntaxes
7024 supported for the @var{type description} field, in order to provide
7025 compatibility with various other assemblers.
7027 Because some of the characters used in these syntaxes (such as @samp{@@} and
7028 @samp{#}) are comment characters for some architectures, some of the syntaxes
7029 below do not work on all architectures. The first variant will be accepted by
7030 the GNU assembler on all architectures so that variant should be used for
7031 maximum portability, if you do not need to assemble your code with other
7034 The syntaxes supported are:
7037 .type <name> STT_<TYPE_IN_UPPER_CASE>
7038 .type <name>,#<type>
7039 .type <name>,@@<type>
7040 .type <name>,%<type>
7041 .type <name>,"<type>"
7044 The types supported are:
7049 Mark the symbol as being a function name.
7052 @itemx gnu_indirect_function
7053 Mark the symbol as an indirect function when evaluated during reloc
7054 processing. (This is only supported on assemblers targeting GNU systems).
7058 Mark the symbol as being a data object.
7062 Mark the symbol as being a thead-local data object.
7066 Mark the symbol as being a common data object.
7070 Does not mark the symbol in any way. It is supported just for completeness.
7072 @item gnu_unique_object
7073 Marks the symbol as being a globally unique data object. The dynamic linker
7074 will make sure that in the entire process there is just one symbol with this
7075 name and type in use. (This is only supported on assemblers targeting GNU
7080 Note: Some targets support extra types in addition to those listed above.
7086 @section @code{.uleb128 @var{expressions}}
7088 @cindex @code{uleb128} directive
7089 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7090 compact, variable length representation of numbers used by the DWARF
7091 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7095 @section @code{.val @var{addr}}
7097 @cindex @code{val} directive
7098 @cindex COFF value attribute
7099 @cindex value attribute, COFF
7100 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7101 records the address @var{addr} as the value attribute of a symbol table
7105 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7106 configured for @code{b.out}, it accepts this directive but ignores it.
7112 @section @code{.version "@var{string}"}
7114 @cindex @code{version} directive
7115 This directive creates a @code{.note} section and places into it an ELF
7116 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7121 @section @code{.vtable_entry @var{table}, @var{offset}}
7123 @cindex @code{vtable_entry} directive
7124 This directive finds or creates a symbol @code{table} and creates a
7125 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7128 @section @code{.vtable_inherit @var{child}, @var{parent}}
7130 @cindex @code{vtable_inherit} directive
7131 This directive finds the symbol @code{child} and finds or creates the symbol
7132 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7133 parent whose addend is the value of the child symbol. As a special case the
7134 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7138 @section @code{.warning "@var{string}"}
7139 @cindex warning directive
7140 Similar to the directive @code{.error}
7141 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7144 @section @code{.weak @var{names}}
7146 @cindex @code{weak} directive
7147 This directive sets the weak attribute on the comma separated list of symbol
7148 @code{names}. If the symbols do not already exist, they will be created.
7150 On COFF targets other than PE, weak symbols are a GNU extension. This
7151 directive sets the weak attribute on the comma separated list of symbol
7152 @code{names}. If the symbols do not already exist, they will be created.
7154 On the PE target, weak symbols are supported natively as weak aliases.
7155 When a weak symbol is created that is not an alias, GAS creates an
7156 alternate symbol to hold the default value.
7159 @section @code{.weakref @var{alias}, @var{target}}
7161 @cindex @code{weakref} directive
7162 This directive creates an alias to the target symbol that enables the symbol to
7163 be referenced with weak-symbol semantics, but without actually making it weak.
7164 If direct references or definitions of the symbol are present, then the symbol
7165 will not be weak, but if all references to it are through weak references, the
7166 symbol will be marked as weak in the symbol table.
7168 The effect is equivalent to moving all references to the alias to a separate
7169 assembly source file, renaming the alias to the symbol in it, declaring the
7170 symbol as weak there, and running a reloadable link to merge the object files
7171 resulting from the assembly of the new source file and the old source file that
7172 had the references to the alias removed.
7174 The alias itself never makes to the symbol table, and is entirely handled
7175 within the assembler.
7178 @section @code{.word @var{expressions}}
7180 @cindex @code{word} directive
7181 This directive expects zero or more @var{expressions}, of any section,
7182 separated by commas.
7185 For each expression, @command{@value{AS}} emits a 32-bit number.
7188 For each expression, @command{@value{AS}} emits a 16-bit number.
7193 The size of the number emitted, and its byte order,
7194 depend on what target computer the assembly is for.
7197 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7198 @c happen---32-bit addressability, period; no long/short jumps.
7199 @ifset DIFF-TBL-KLUGE
7200 @cindex difference tables altered
7201 @cindex altered difference tables
7203 @emph{Warning: Special Treatment to support Compilers}
7207 Machines with a 32-bit address space, but that do less than 32-bit
7208 addressing, require the following special treatment. If the machine of
7209 interest to you does 32-bit addressing (or doesn't require it;
7210 @pxref{Machine Dependencies}), you can ignore this issue.
7213 In order to assemble compiler output into something that works,
7214 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7215 Directives of the form @samp{.word sym1-sym2} are often emitted by
7216 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7217 directive of the form @samp{.word sym1-sym2}, and the difference between
7218 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7219 creates a @dfn{secondary jump table}, immediately before the next label.
7220 This secondary jump table is preceded by a short-jump to the
7221 first byte after the secondary table. This short-jump prevents the flow
7222 of control from accidentally falling into the new table. Inside the
7223 table is a long-jump to @code{sym2}. The original @samp{.word}
7224 contains @code{sym1} minus the address of the long-jump to
7227 If there were several occurrences of @samp{.word sym1-sym2} before the
7228 secondary jump table, all of them are adjusted. If there was a
7229 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7230 long-jump to @code{sym4} is included in the secondary jump table,
7231 and the @code{.word} directives are adjusted to contain @code{sym3}
7232 minus the address of the long-jump to @code{sym4}; and so on, for as many
7233 entries in the original jump table as necessary.
7236 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7237 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7238 assembly language programmers.
7241 @c end DIFF-TBL-KLUGE
7243 @ifclear no-space-dir
7245 @section @code{.zero @var{size}}
7247 @cindex @code{zero} directive
7248 @cindex filling memory with zero bytes
7249 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7250 expression. This directive is actually an alias for the @samp{.skip} directive
7251 so in can take an optional second argument of the value to store in the bytes
7252 instead of zero. Using @samp{.zero} in this way would be confusing however.
7256 @section Deprecated Directives
7258 @cindex deprecated directives
7259 @cindex obsolescent directives
7260 One day these directives won't work.
7261 They are included for compatibility with older assemblers.
7268 @node Object Attributes
7269 @chapter Object Attributes
7270 @cindex object attributes
7272 @command{@value{AS}} assembles source files written for a specific architecture
7273 into object files for that architecture. But not all object files are alike.
7274 Many architectures support incompatible variations. For instance, floating
7275 point arguments might be passed in floating point registers if the object file
7276 requires hardware floating point support---or floating point arguments might be
7277 passed in integer registers if the object file supports processors with no
7278 hardware floating point unit. Or, if two objects are built for different
7279 generations of the same architecture, the combination may require the
7280 newer generation at run-time.
7282 This information is useful during and after linking. At link time,
7283 @command{@value{LD}} can warn about incompatible object files. After link
7284 time, tools like @command{gdb} can use it to process the linked file
7287 Compatibility information is recorded as a series of object attributes. Each
7288 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7289 string, and indicates who sets the meaning of the tag. The tag is an integer,
7290 and indicates what property the attribute describes. The value may be a string
7291 or an integer, and indicates how the property affects this object. Missing
7292 attributes are the same as attributes with a zero value or empty string value.
7294 Object attributes were developed as part of the ABI for the ARM Architecture.
7295 The file format is documented in @cite{ELF for the ARM Architecture}.
7298 * GNU Object Attributes:: @sc{gnu} Object Attributes
7299 * Defining New Object Attributes:: Defining New Object Attributes
7302 @node GNU Object Attributes
7303 @section @sc{gnu} Object Attributes
7305 The @code{.gnu_attribute} directive records an object attribute
7306 with vendor @samp{gnu}.
7308 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7309 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7310 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7311 2} is set for architecture-independent attributes and clear for
7312 architecture-dependent ones.
7314 @subsection Common @sc{gnu} attributes
7316 These attributes are valid on all architectures.
7319 @item Tag_compatibility (32)
7320 The compatibility attribute takes an integer flag value and a vendor name. If
7321 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7322 then the file is only compatible with the named toolchain. If it is greater
7323 than 1, the file can only be processed by other toolchains under some private
7324 arrangement indicated by the flag value and the vendor name.
7327 @subsection MIPS Attributes
7330 @item Tag_GNU_MIPS_ABI_FP (4)
7331 The floating-point ABI used by this object file. The value will be:
7335 0 for files not affected by the floating-point ABI.
7337 1 for files using the hardware floating-point ABI with a standard
7338 double-precision FPU.
7340 2 for files using the hardware floating-point ABI with a single-precision FPU.
7342 3 for files using the software floating-point ABI.
7344 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7345 floating-point registers, 32-bit general-purpose registers and increased the
7346 number of callee-saved floating-point registers.
7348 5 for files using the hardware floating-point ABI with a double-precision FPU
7349 with either 32-bit or 64-bit floating-point registers and 32-bit
7350 general-purpose registers.
7352 6 for files using the hardware floating-point ABI with 64-bit floating-point
7353 registers and 32-bit general-purpose registers.
7355 7 for files using the hardware floating-point ABI with 64-bit floating-point
7356 registers, 32-bit general-purpose registers and a rule that forbids the
7357 direct use of odd-numbered single-precision floating-point registers.
7361 @subsection PowerPC Attributes
7364 @item Tag_GNU_Power_ABI_FP (4)
7365 The floating-point ABI used by this object file. The value will be:
7369 0 for files not affected by the floating-point ABI.
7371 1 for files using double-precision hardware floating-point ABI.
7373 2 for files using the software floating-point ABI.
7375 3 for files using single-precision hardware floating-point ABI.
7378 @item Tag_GNU_Power_ABI_Vector (8)
7379 The vector ABI used by this object file. The value will be:
7383 0 for files not affected by the vector ABI.
7385 1 for files using general purpose registers to pass vectors.
7387 2 for files using AltiVec registers to pass vectors.
7389 3 for files using SPE registers to pass vectors.
7393 @subsection IBM z Systems Attributes
7396 @item Tag_GNU_S390_ABI_Vector (8)
7397 The vector ABI used by this object file. The value will be:
7401 0 for files not affected by the vector ABI.
7403 1 for files using software vector ABI.
7405 2 for files using hardware vector ABI.
7409 @node Defining New Object Attributes
7410 @section Defining New Object Attributes
7412 If you want to define a new @sc{gnu} object attribute, here are the places you
7413 will need to modify. New attributes should be discussed on the @samp{binutils}
7418 This manual, which is the official register of attributes.
7420 The header for your architecture @file{include/elf}, to define the tag.
7422 The @file{bfd} support file for your architecture, to merge the attribute
7423 and issue any appropriate link warnings.
7425 Test cases in @file{ld/testsuite} for merging and link warnings.
7427 @file{binutils/readelf.c} to display your attribute.
7429 GCC, if you want the compiler to mark the attribute automatically.
7435 @node Machine Dependencies
7436 @chapter Machine Dependent Features
7438 @cindex machine dependencies
7439 The machine instruction sets are (almost by definition) different on
7440 each machine where @command{@value{AS}} runs. Floating point representations
7441 vary as well, and @command{@value{AS}} often supports a few additional
7442 directives or command-line options for compatibility with other
7443 assemblers on a particular platform. Finally, some versions of
7444 @command{@value{AS}} support special pseudo-instructions for branch
7447 This chapter discusses most of these differences, though it does not
7448 include details on any machine's instruction set. For details on that
7449 subject, see the hardware manufacturer's manual.
7453 * AArch64-Dependent:: AArch64 Dependent Features
7456 * Alpha-Dependent:: Alpha Dependent Features
7459 * ARC-Dependent:: ARC Dependent Features
7462 * ARM-Dependent:: ARM Dependent Features
7465 * AVR-Dependent:: AVR Dependent Features
7468 * Blackfin-Dependent:: Blackfin Dependent Features
7471 * CR16-Dependent:: CR16 Dependent Features
7474 * CRIS-Dependent:: CRIS Dependent Features
7477 * D10V-Dependent:: D10V Dependent Features
7480 * D30V-Dependent:: D30V Dependent Features
7483 * Epiphany-Dependent:: EPIPHANY Dependent Features
7486 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7489 * HPPA-Dependent:: HPPA Dependent Features
7492 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7495 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7498 * i860-Dependent:: Intel 80860 Dependent Features
7501 * i960-Dependent:: Intel 80960 Dependent Features
7504 * IA-64-Dependent:: Intel IA-64 Dependent Features
7507 * IP2K-Dependent:: IP2K Dependent Features
7510 * LM32-Dependent:: LM32 Dependent Features
7513 * M32C-Dependent:: M32C Dependent Features
7516 * M32R-Dependent:: M32R Dependent Features
7519 * M68K-Dependent:: M680x0 Dependent Features
7522 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7525 * Meta-Dependent :: Meta Dependent Features
7528 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7531 * MIPS-Dependent:: MIPS Dependent Features
7534 * MMIX-Dependent:: MMIX Dependent Features
7537 * MSP430-Dependent:: MSP430 Dependent Features
7540 * NDS32-Dependent:: Andes NDS32 Dependent Features
7543 * NiosII-Dependent:: Altera Nios II Dependent Features
7546 * NS32K-Dependent:: NS32K Dependent Features
7549 * PDP-11-Dependent:: PDP-11 Dependent Features
7552 * PJ-Dependent:: picoJava Dependent Features
7555 * PPC-Dependent:: PowerPC Dependent Features
7558 * RL78-Dependent:: RL78 Dependent Features
7561 * RX-Dependent:: RX Dependent Features
7564 * S/390-Dependent:: IBM S/390 Dependent Features
7567 * SCORE-Dependent:: SCORE Dependent Features
7570 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7571 * SH64-Dependent:: SuperH SH64 Dependent Features
7574 * Sparc-Dependent:: SPARC Dependent Features
7577 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7580 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7583 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7586 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7589 * V850-Dependent:: V850 Dependent Features
7592 * Vax-Dependent:: VAX Dependent Features
7595 * Visium-Dependent:: Visium Dependent Features
7598 * XGATE-Dependent:: XGATE Features
7601 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7604 * Xtensa-Dependent:: Xtensa Dependent Features
7607 * Z80-Dependent:: Z80 Dependent Features
7610 * Z8000-Dependent:: Z8000 Dependent Features
7617 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7618 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7619 @c peculiarity: to preserve cross-references, there must be a node called
7620 @c "Machine Dependencies". Hence the conditional nodenames in each
7621 @c major node below. Node defaulting in makeinfo requires adjacency of
7622 @c node and sectioning commands; hence the repetition of @chapter BLAH
7623 @c in both conditional blocks.
7626 @include c-aarch64.texi
7630 @include c-alpha.texi
7646 @include c-bfin.texi
7650 @include c-cr16.texi
7654 @include c-cris.texi
7659 @node Machine Dependencies
7660 @chapter Machine Dependent Features
7662 The machine instruction sets are different on each Renesas chip family,
7663 and there are also some syntax differences among the families. This
7664 chapter describes the specific @command{@value{AS}} features for each
7668 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7669 * SH-Dependent:: Renesas SH Dependent Features
7676 @include c-d10v.texi
7680 @include c-d30v.texi
7684 @include c-epiphany.texi
7688 @include c-h8300.texi
7692 @include c-hppa.texi
7696 @include c-i370.texi
7700 @include c-i386.texi
7704 @include c-i860.texi
7708 @include c-i960.texi
7712 @include c-ia64.texi
7716 @include c-ip2k.texi
7720 @include c-lm32.texi
7724 @include c-m32c.texi
7728 @include c-m32r.texi
7732 @include c-m68k.texi
7736 @include c-m68hc11.texi
7740 @include c-metag.texi
7744 @include c-microblaze.texi
7748 @include c-mips.texi
7752 @include c-mmix.texi
7756 @include c-msp430.texi
7760 @include c-nds32.texi
7764 @include c-nios2.texi
7768 @include c-ns32k.texi
7772 @include c-pdp11.texi
7784 @include c-rl78.texi
7792 @include c-s390.texi
7796 @include c-score.texi
7801 @include c-sh64.texi
7805 @include c-sparc.texi
7809 @include c-tic54x.texi
7813 @include c-tic6x.texi
7817 @include c-tilegx.texi
7821 @include c-tilepro.texi
7825 @include c-v850.texi
7833 @include c-visium.texi
7837 @include c-xgate.texi
7841 @include c-xstormy16.texi
7845 @include c-xtensa.texi
7857 @c reverse effect of @down at top of generic Machine-Dep chapter
7861 @node Reporting Bugs
7862 @chapter Reporting Bugs
7863 @cindex bugs in assembler
7864 @cindex reporting bugs in assembler
7866 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7868 Reporting a bug may help you by bringing a solution to your problem, or it may
7869 not. But in any case the principal function of a bug report is to help the
7870 entire community by making the next version of @command{@value{AS}} work better.
7871 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7873 In order for a bug report to serve its purpose, you must include the
7874 information that enables us to fix the bug.
7877 * Bug Criteria:: Have you found a bug?
7878 * Bug Reporting:: How to report bugs
7882 @section Have You Found a Bug?
7883 @cindex bug criteria
7885 If you are not sure whether you have found a bug, here are some guidelines:
7888 @cindex fatal signal
7889 @cindex assembler crash
7890 @cindex crash of assembler
7892 If the assembler gets a fatal signal, for any input whatever, that is a
7893 @command{@value{AS}} bug. Reliable assemblers never crash.
7895 @cindex error on valid input
7897 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7899 @cindex invalid input
7901 If @command{@value{AS}} does not produce an error message for invalid input, that
7902 is a bug. However, you should note that your idea of ``invalid input'' might
7903 be our idea of ``an extension'' or ``support for traditional practice''.
7906 If you are an experienced user of assemblers, your suggestions for improvement
7907 of @command{@value{AS}} are welcome in any case.
7911 @section How to Report Bugs
7913 @cindex assembler bugs, reporting
7915 A number of companies and individuals offer support for @sc{gnu} products. If
7916 you obtained @command{@value{AS}} from a support organization, we recommend you
7917 contact that organization first.
7919 You can find contact information for many support companies and
7920 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7924 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7928 The fundamental principle of reporting bugs usefully is this:
7929 @strong{report all the facts}. If you are not sure whether to state a
7930 fact or leave it out, state it!
7932 Often people omit facts because they think they know what causes the problem
7933 and assume that some details do not matter. Thus, you might assume that the
7934 name of a symbol you use in an example does not matter. Well, probably it does
7935 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7936 happens to fetch from the location where that name is stored in memory;
7937 perhaps, if the name were different, the contents of that location would fool
7938 the assembler into doing the right thing despite the bug. Play it safe and
7939 give a specific, complete example. That is the easiest thing for you to do,
7940 and the most helpful.
7942 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7943 it is new to us. Therefore, always write your bug reports on the assumption
7944 that the bug has not been reported previously.
7946 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7947 bell?'' This cannot help us fix a bug, so it is basically useless. We
7948 respond by asking for enough details to enable us to investigate.
7949 You might as well expedite matters by sending them to begin with.
7951 To enable us to fix the bug, you should include all these things:
7955 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7956 it with the @samp{--version} argument.
7958 Without this, we will not know whether there is any point in looking for
7959 the bug in the current version of @command{@value{AS}}.
7962 Any patches you may have applied to the @command{@value{AS}} source.
7965 The type of machine you are using, and the operating system name and
7969 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7973 The command arguments you gave the assembler to assemble your example and
7974 observe the bug. To guarantee you will not omit something important, list them
7975 all. A copy of the Makefile (or the output from make) is sufficient.
7977 If we were to try to guess the arguments, we would probably guess wrong
7978 and then we might not encounter the bug.
7981 A complete input file that will reproduce the bug. If the bug is observed when
7982 the assembler is invoked via a compiler, send the assembler source, not the
7983 high level language source. Most compilers will produce the assembler source
7984 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7985 the options @samp{-v --save-temps}; this will save the assembler source in a
7986 file with an extension of @file{.s}, and also show you exactly how
7987 @command{@value{AS}} is being run.
7990 A description of what behavior you observe that you believe is
7991 incorrect. For example, ``It gets a fatal signal.''
7993 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7994 will certainly notice it. But if the bug is incorrect output, we might not
7995 notice unless it is glaringly wrong. You might as well not give us a chance to
7998 Even if the problem you experience is a fatal signal, you should still say so
7999 explicitly. Suppose something strange is going on, such as, your copy of
8000 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8001 library on your system. (This has happened!) Your copy might crash and ours
8002 would not. If you told us to expect a crash, then when ours fails to crash, we
8003 would know that the bug was not happening for us. If you had not told us to
8004 expect a crash, then we would not be able to draw any conclusion from our
8008 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8009 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8010 option. Always send diffs from the old file to the new file. If you even
8011 discuss something in the @command{@value{AS}} source, refer to it by context, not
8014 The line numbers in our development sources will not match those in your
8015 sources. Your line numbers would convey no useful information to us.
8018 Here are some things that are not necessary:
8022 A description of the envelope of the bug.
8024 Often people who encounter a bug spend a lot of time investigating
8025 which changes to the input file will make the bug go away and which
8026 changes will not affect it.
8028 This is often time consuming and not very useful, because the way we
8029 will find the bug is by running a single example under the debugger
8030 with breakpoints, not by pure deduction from a series of examples.
8031 We recommend that you save your time for something else.
8033 Of course, if you can find a simpler example to report @emph{instead}
8034 of the original one, that is a convenience for us. Errors in the
8035 output will be easier to spot, running under the debugger will take
8036 less time, and so on.
8038 However, simplification is not vital; if you do not want to do this,
8039 report the bug anyway and send us the entire test case you used.
8042 A patch for the bug.
8044 A patch for the bug does help us if it is a good one. But do not omit
8045 the necessary information, such as the test case, on the assumption that
8046 a patch is all we need. We might see problems with your patch and decide
8047 to fix the problem another way, or we might not understand it at all.
8049 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8050 construct an example that will make the program follow a certain path through
8051 the code. If you do not send us the example, we will not be able to construct
8052 one, so we will not be able to verify that the bug is fixed.
8054 And if we cannot understand what bug you are trying to fix, or why your
8055 patch should be an improvement, we will not install it. A test case will
8056 help us to understand.
8059 A guess about what the bug is or what it depends on.
8061 Such guesses are usually wrong. Even we cannot guess right about such
8062 things without first using the debugger to find the facts.
8065 @node Acknowledgements
8066 @chapter Acknowledgements
8068 If you have contributed to GAS and your name isn't listed here,
8069 it is not meant as a slight. We just don't know about it. Send mail to the
8070 maintainer, and we'll correct the situation. Currently
8072 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8074 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8077 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8078 information and the 68k series machines, most of the preprocessing pass, and
8079 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8081 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8082 many bug fixes, including merging support for several processors, breaking GAS
8083 up to handle multiple object file format back ends (including heavy rewrite,
8084 testing, an integration of the coff and b.out back ends), adding configuration
8085 including heavy testing and verification of cross assemblers and file splits
8086 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8087 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8088 port (including considerable amounts of reverse engineering), a SPARC opcode
8089 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8090 assertions and made them work, much other reorganization, cleanup, and lint.
8092 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8093 in format-specific I/O modules.
8095 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8096 has done much work with it since.
8098 The Intel 80386 machine description was written by Eliot Dresselhaus.
8100 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8102 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8103 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8105 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8106 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8107 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8108 support a.out format.
8110 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8111 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8112 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8113 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8116 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8117 simplified the configuration of which versions accept which directives. He
8118 updated the 68k machine description so that Motorola's opcodes always produced
8119 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8120 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8121 cross-compilation support, and one bug in relaxation that took a week and
8122 required the proverbial one-bit fix.
8124 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8125 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8126 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8127 PowerPC assembler, and made a few other minor patches.
8129 Steve Chamberlain made GAS able to generate listings.
8131 Hewlett-Packard contributed support for the HP9000/300.
8133 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8134 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8135 formats). This work was supported by both the Center for Software Science at
8136 the University of Utah and Cygnus Support.
8138 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8139 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8140 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8141 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8142 and some initial 64-bit support).
8144 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8146 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8147 support for openVMS/Alpha.
8149 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8152 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8153 Inc.@: added support for Xtensa processors.
8155 Several engineers at Cygnus Support have also provided many small bug fixes and
8156 configuration enhancements.
8158 Jon Beniston added support for the Lattice Mico32 architecture.
8160 Many others have contributed large or small bugfixes and enhancements. If
8161 you have contributed significant work and are not mentioned on this list, and
8162 want to be, let us know. Some of the history has been lost; we are not
8163 intentionally leaving anyone out.
8165 @node GNU Free Documentation License
8166 @appendix GNU Free Documentation License
8170 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob