1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2017 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{} 1991-2017 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{} 1991-2017 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 PRU options:}
501 [@b{-mno-warn-regname-label}]
505 @emph{Target RL78 options:}
507 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
511 @emph{Target RX options:}
512 [@b{-mlittle-endian}|@b{-mbig-endian}]
513 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
514 [@b{-muse-conventional-section-names}]
515 [@b{-msmall-data-limit}]
518 [@b{-mint-register=@var{number}}]
519 [@b{-mgcc-abi}|@b{-mrx-abi}]
523 @emph{Target RISC-V options:}
524 [@b{-march}=@var{ISA}]
525 [@b{-mabi}=@var{ABI}]
529 @emph{Target s390 options:}
530 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
531 [@b{-mregnames}|@b{-mno-regnames}]
532 [@b{-mwarn-areg-zero}]
536 @emph{Target SCORE options:}
537 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
538 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
539 [@b{-march=score7}][@b{-march=score3}]
540 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
544 @emph{Target SPARC options:}
545 @c The order here is important. See c-sparc.texi.
546 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Aleon}|@b{-Asparclet}|@b{-Asparclite}
547 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av8plusb}|@b{-Av8plusc}|@b{-Av8plusd}
548 @b{-Av8plusv}|@b{-Av8plusm}|@b{-Av9}|@b{-Av9a}|@b{-Av9b}|@b{-Av9c}
549 @b{-Av9d}|@b{-Av9e}|@b{-Av9v}|@b{-Av9m}|@b{-Asparc}|@b{-Asparcvis}
550 @b{-Asparcvis2}|@b{-Asparcfmaf}|@b{-Asparcima}|@b{-Asparcvis3}
551 @b{-Asparcvisr}|@b{-Asparc5}]
552 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}]|@b{-xarch=v8plusb}|@b{-xarch=v8plusc}
553 @b{-xarch=v8plusd}|@b{-xarch=v8plusv}|@b{-xarch=v8plusm}|@b{-xarch=v9}
554 @b{-xarch=v9a}|@b{-xarch=v9b}|@b{-xarch=v9c}|@b{-xarch=v9d}|@b{-xarch=v9e}
555 @b{-xarch=v9v}|@b{-xarch=v9m}|@b{-xarch=sparc}|@b{-xarch=sparcvis}
556 @b{-xarch=sparcvis2}|@b{-xarch=sparcfmaf}|@b{-xarch=sparcima}
557 @b{-xarch=sparcvis3}|@b{-xarch=sparcvisr}|@b{-xarch=sparc5}
560 [@b{--enforce-aligned-data}][@b{--dcti-couples-detect}]
564 @emph{Target TIC54X options:}
565 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
566 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
570 @emph{Target TIC6X options:}
571 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
572 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
573 [@b{-mpic}|@b{-mno-pic}]
577 @emph{Target TILE-Gx options:}
578 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
581 @c TILEPro has no machine-dependent assembler options
585 @emph{Target Visium options:}
586 [@b{-mtune=@var{arch}}]
590 @emph{Target Xtensa options:}
591 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
592 [@b{--[no-]absolute-literals}]
593 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
594 [@b{--[no-]transform}]
595 [@b{--rename-section} @var{oldname}=@var{newname}]
596 [@b{--[no-]trampolines}]
600 @emph{Target Z80 options:}
601 [@b{-z80}] [@b{-r800}]
602 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
603 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
604 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
605 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
606 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
607 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
611 @c Z8000 has no machine-dependent assembler options
620 @include at-file.texi
623 Turn on listings, in any of a variety of ways:
627 omit false conditionals
630 omit debugging directives
633 include general information, like @value{AS} version and options passed
636 include high-level source
642 include macro expansions
645 omit forms processing
651 set the name of the listing file
654 You may combine these options; for example, use @samp{-aln} for assembly
655 listing without forms processing. The @samp{=file} option, if used, must be
656 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
659 Begin in alternate macro mode.
661 @xref{Altmacro,,@code{.altmacro}}.
664 @item --compress-debug-sections
665 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
666 ELF ABI. The resulting object file may not be compatible with older
667 linkers and object file utilities. Note if compression would make a
668 given section @emph{larger} then it is not compressed.
671 @cindex @samp{--compress-debug-sections=} option
672 @item --compress-debug-sections=none
673 @itemx --compress-debug-sections=zlib
674 @itemx --compress-debug-sections=zlib-gnu
675 @itemx --compress-debug-sections=zlib-gabi
676 These options control how DWARF debug sections are compressed.
677 @option{--compress-debug-sections=none} is equivalent to
678 @option{--nocompress-debug-sections}.
679 @option{--compress-debug-sections=zlib} and
680 @option{--compress-debug-sections=zlib-gabi} are equivalent to
681 @option{--compress-debug-sections}.
682 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
683 sections using zlib. The debug sections are renamed to begin with
684 @samp{.zdebug}. Note if compression would make a given section
685 @emph{larger} then it is not compressed nor renamed.
689 @item --nocompress-debug-sections
690 Do not compress DWARF debug sections. This is usually the default for all
691 targets except the x86/x86_64, but a configure time option can be used to
695 Ignored. This option is accepted for script compatibility with calls to
698 @item --debug-prefix-map @var{old}=@var{new}
699 When assembling files in directory @file{@var{old}}, record debugging
700 information describing them as in @file{@var{new}} instead.
702 @item --defsym @var{sym}=@var{value}
703 Define the symbol @var{sym} to be @var{value} before assembling the input file.
704 @var{value} must be an integer constant. As in C, a leading @samp{0x}
705 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
706 value. The value of the symbol can be overridden inside a source file via the
707 use of a @code{.set} pseudo-op.
710 ``fast''---skip whitespace and comment preprocessing (assume source is
715 Generate debugging information for each assembler source line using whichever
716 debug format is preferred by the target. This currently means either STABS,
720 Generate stabs debugging information for each assembler line. This
721 may help debugging assembler code, if the debugger can handle it.
724 Generate stabs debugging information for each assembler line, with GNU
725 extensions that probably only gdb can handle, and that could make other
726 debuggers crash or refuse to read your program. This
727 may help debugging assembler code. Currently the only GNU extension is
728 the location of the current working directory at assembling time.
731 Generate DWARF2 debugging information for each assembler line. This
732 may help debugging assembler code, if the debugger can handle it. Note---this
733 option is only supported by some targets, not all of them.
735 @item --gdwarf-sections
736 Instead of creating a .debug_line section, create a series of
737 .debug_line.@var{foo} sections where @var{foo} is the name of the
738 corresponding code section. For example a code section called @var{.text.func}
739 will have its dwarf line number information placed into a section called
740 @var{.debug_line.text.func}. If the code section is just called @var{.text}
741 then debug line section will still be called just @var{.debug_line} without any
745 @item --size-check=error
746 @itemx --size-check=warning
747 Issue an error or warning for invalid ELF .size directive.
749 @item --elf-stt-common=no
750 @itemx --elf-stt-common=yes
751 These options control whether the ELF assembler should generate common
752 symbols with the @code{STT_COMMON} type. The default can be controlled
753 by a configure option @option{--enable-elf-stt-common}.
757 Print a summary of the command line options and exit.
760 Print a summary of all target specific options and exit.
763 Add directory @var{dir} to the search list for @code{.include} directives.
766 Don't warn about signed overflow.
769 @ifclear DIFF-TBL-KLUGE
770 This option is accepted but has no effect on the @value{TARGET} family.
772 @ifset DIFF-TBL-KLUGE
773 Issue warnings when difference tables altered for long displacements.
778 Keep (in the symbol table) local symbols. These symbols start with
779 system-specific local label prefixes, typically @samp{.L} for ELF systems
780 or @samp{L} for traditional a.out systems.
785 @item --listing-lhs-width=@var{number}
786 Set the maximum width, in words, of the output data column for an assembler
787 listing to @var{number}.
789 @item --listing-lhs-width2=@var{number}
790 Set the maximum width, in words, of the output data column for continuation
791 lines in an assembler listing to @var{number}.
793 @item --listing-rhs-width=@var{number}
794 Set the maximum width of an input source line, as displayed in a listing, to
797 @item --listing-cont-lines=@var{number}
798 Set the maximum number of lines printed in a listing for a single line of input
801 @item --no-pad-sections
802 Stop the assembler for padding the ends of output sections to the alignment
803 of that section. The default is to pad the sections, but this can waste space
804 which might be needed on targets which have tight memory constraints.
806 @item -o @var{objfile}
807 Name the object-file output from @command{@value{AS}} @var{objfile}.
810 Fold the data section into the text section.
812 @item --hash-size=@var{number}
813 Set the default size of GAS's hash tables to a prime number close to
814 @var{number}. Increasing this value can reduce the length of time it takes the
815 assembler to perform its tasks, at the expense of increasing the assembler's
816 memory requirements. Similarly reducing this value can reduce the memory
817 requirements at the expense of speed.
819 @item --reduce-memory-overheads
820 This option reduces GAS's memory requirements, at the expense of making the
821 assembly processes slower. Currently this switch is a synonym for
822 @samp{--hash-size=4051}, but in the future it may have other effects as well.
825 @item --sectname-subst
826 Honor substitution sequences in section names.
828 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
833 Print the maximum space (in bytes) and total time (in seconds) used by
836 @item --strip-local-absolute
837 Remove local absolute symbols from the outgoing symbol table.
841 Print the @command{as} version.
844 Print the @command{as} version and exit.
848 Suppress warning messages.
850 @item --fatal-warnings
851 Treat warnings as errors.
854 Don't suppress warning messages or treat them as errors.
863 Generate an object file even after errors.
865 @item -- | @var{files} @dots{}
866 Standard input, or source files to assemble.
874 @xref{AArch64 Options}, for the options available when @value{AS} is configured
875 for the 64-bit mode of the ARM Architecture (AArch64).
880 The following options are available when @value{AS} is configured for the
881 64-bit mode of the ARM Architecture (AArch64).
884 @include c-aarch64.texi
885 @c ended inside the included file
893 @xref{Alpha Options}, for the options available when @value{AS} is configured
894 for an Alpha processor.
899 The following options are available when @value{AS} is configured for an Alpha
903 @include c-alpha.texi
904 @c ended inside the included file
911 The following options are available when @value{AS} is configured for an ARC
915 @item -mcpu=@var{cpu}
916 This option selects the core processor variant.
918 Select either big-endian (-EB) or little-endian (-EL) output.
920 Enable Code Density extenssion instructions.
925 The following options are available when @value{AS} is configured for the ARM
929 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
930 Specify which ARM processor variant is the target.
931 @item -march=@var{architecture}[+@var{extension}@dots{}]
932 Specify which ARM architecture variant is used by the target.
933 @item -mfpu=@var{floating-point-format}
934 Select which Floating Point architecture is the target.
935 @item -mfloat-abi=@var{abi}
936 Select which floating point ABI is in use.
938 Enable Thumb only instruction decoding.
939 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
940 Select which procedure calling convention is in use.
942 Select either big-endian (-EB) or little-endian (-EL) output.
943 @item -mthumb-interwork
944 Specify that the code has been generated with interworking between Thumb and
947 Turns on CodeComposer Studio assembly syntax compatibility mode.
949 Specify that PIC code has been generated.
957 @xref{Blackfin Options}, for the options available when @value{AS} is
958 configured for the Blackfin processor family.
963 The following options are available when @value{AS} is configured for
964 the Blackfin processor family.
968 @c ended inside the included file
975 See the info pages for documentation of the CRIS-specific options.
979 The following options are available when @value{AS} is configured for
982 @cindex D10V optimization
983 @cindex optimization, D10V
985 Optimize output by parallelizing instructions.
990 The following options are available when @value{AS} is configured for a D30V
993 @cindex D30V optimization
994 @cindex optimization, D30V
996 Optimize output by parallelizing instructions.
1000 Warn when nops are generated.
1002 @cindex D30V nops after 32-bit multiply
1004 Warn when a nop after a 32-bit multiply instruction is generated.
1010 The following options are available when @value{AS} is configured for the
1011 Adapteva EPIPHANY series.
1014 @xref{Epiphany Options}, for the options available when @value{AS} is
1015 configured for an Epiphany processor.
1019 @c man begin OPTIONS
1020 The following options are available when @value{AS} is configured for
1021 an Epiphany processor.
1023 @c man begin INCLUDE
1024 @include c-epiphany.texi
1025 @c ended inside the included file
1033 @xref{H8/300 Options}, for the options available when @value{AS} is configured
1034 for an H8/300 processor.
1038 @c man begin OPTIONS
1039 The following options are available when @value{AS} is configured for an H8/300
1042 @c man begin INCLUDE
1043 @include c-h8300.texi
1044 @c ended inside the included file
1052 @xref{i386-Options}, for the options available when @value{AS} is
1053 configured for an i386 processor.
1057 @c man begin OPTIONS
1058 The following options are available when @value{AS} is configured for
1061 @c man begin INCLUDE
1062 @include c-i386.texi
1063 @c ended inside the included file
1068 @c man begin OPTIONS
1070 The following options are available when @value{AS} is configured for the
1071 Intel 80960 processor.
1074 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1075 Specify which variant of the 960 architecture is the target.
1078 Add code to collect statistics about branches taken.
1081 Do not alter compare-and-branch instructions for long displacements;
1088 The following options are available when @value{AS} is configured for the
1094 Specifies that the extended IP2022 instructions are allowed.
1097 Restores the default behaviour, which restricts the permitted instructions to
1098 just the basic IP2022 ones.
1104 The following options are available when @value{AS} is configured for the
1105 Renesas M32C and M16C processors.
1110 Assemble M32C instructions.
1113 Assemble M16C instructions (the default).
1116 Enable support for link-time relaxations.
1119 Support H'00 style hex constants in addition to 0x00 style.
1125 The following options are available when @value{AS} is configured for the
1126 Renesas M32R (formerly Mitsubishi M32R) series.
1131 Specify which processor in the M32R family is the target. The default
1132 is normally the M32R, but this option changes it to the M32RX.
1134 @item --warn-explicit-parallel-conflicts or --Wp
1135 Produce warning messages when questionable parallel constructs are
1138 @item --no-warn-explicit-parallel-conflicts or --Wnp
1139 Do not produce warning messages when questionable parallel constructs are
1146 The following options are available when @value{AS} is configured for the
1147 Motorola 68000 series.
1152 Shorten references to undefined symbols, to one word instead of two.
1154 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1155 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1156 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1157 Specify what processor in the 68000 family is the target. The default
1158 is normally the 68020, but this can be changed at configuration time.
1160 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1161 The target machine does (or does not) have a floating-point coprocessor.
1162 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1163 the basic 68000 is not compatible with the 68881, a combination of the
1164 two can be specified, since it's possible to do emulation of the
1165 coprocessor instructions with the main processor.
1167 @item -m68851 | -mno-68851
1168 The target machine does (or does not) have a memory-management
1169 unit coprocessor. The default is to assume an MMU for 68020 and up.
1177 @xref{Nios II Options}, for the options available when @value{AS} is configured
1178 for an Altera Nios II processor.
1182 @c man begin OPTIONS
1183 The following options are available when @value{AS} is configured for an
1184 Altera Nios II processor.
1186 @c man begin INCLUDE
1187 @include c-nios2.texi
1188 @c ended inside the included file
1194 For details about the PDP-11 machine dependent features options,
1195 see @ref{PDP-11-Options}.
1198 @item -mpic | -mno-pic
1199 Generate position-independent (or position-dependent) code. The
1200 default is @option{-mpic}.
1203 @itemx -mall-extensions
1204 Enable all instruction set extensions. This is the default.
1206 @item -mno-extensions
1207 Disable all instruction set extensions.
1209 @item -m@var{extension} | -mno-@var{extension}
1210 Enable (or disable) a particular instruction set extension.
1213 Enable the instruction set extensions supported by a particular CPU, and
1214 disable all other extensions.
1216 @item -m@var{machine}
1217 Enable the instruction set extensions supported by a particular machine
1218 model, and disable all other extensions.
1224 The following options are available when @value{AS} is configured for
1225 a picoJava processor.
1229 @cindex PJ endianness
1230 @cindex endianness, PJ
1231 @cindex big endian output, PJ
1233 Generate ``big endian'' format output.
1235 @cindex little endian output, PJ
1237 Generate ``little endian'' format output.
1245 @xref{PRU Options}, for the options available when @value{AS} is configured
1246 for a PRU processor.
1250 @c man begin OPTIONS
1251 The following options are available when @value{AS} is configured for a
1254 @c man begin INCLUDE
1256 @c ended inside the included file
1261 The following options are available when @value{AS} is configured for the
1262 Motorola 68HC11 or 68HC12 series.
1266 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1267 Specify what processor is the target. The default is
1268 defined by the configuration option when building the assembler.
1270 @item --xgate-ramoffset
1271 Instruct the linker to offset RAM addresses from S12X address space into
1272 XGATE address space.
1275 Specify to use the 16-bit integer ABI.
1278 Specify to use the 32-bit integer ABI.
1280 @item -mshort-double
1281 Specify to use the 32-bit double ABI.
1284 Specify to use the 64-bit double ABI.
1286 @item --force-long-branches
1287 Relative branches are turned into absolute ones. This concerns
1288 conditional branches, unconditional branches and branches to a
1291 @item -S | --short-branches
1292 Do not turn relative branches into absolute ones
1293 when the offset is out of range.
1295 @item --strict-direct-mode
1296 Do not turn the direct addressing mode into extended addressing mode
1297 when the instruction does not support direct addressing mode.
1299 @item --print-insn-syntax
1300 Print the syntax of instruction in case of error.
1302 @item --print-opcodes
1303 Print the list of instructions with syntax and then exit.
1305 @item --generate-example
1306 Print an example of instruction for each possible instruction and then exit.
1307 This option is only useful for testing @command{@value{AS}}.
1313 The following options are available when @command{@value{AS}} is configured
1314 for the SPARC architecture:
1317 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1318 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1319 Explicitly select a variant of the SPARC architecture.
1321 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1322 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1324 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1325 UltraSPARC extensions.
1327 @item -xarch=v8plus | -xarch=v8plusa
1328 For compatibility with the Solaris v9 assembler. These options are
1329 equivalent to -Av8plus and -Av8plusa, respectively.
1332 Warn when the assembler switches to another architecture.
1337 The following options are available when @value{AS} is configured for the 'c54x
1342 Enable extended addressing mode. All addresses and relocations will assume
1343 extended addressing (usually 23 bits).
1344 @item -mcpu=@var{CPU_VERSION}
1345 Sets the CPU version being compiled for.
1346 @item -merrors-to-file @var{FILENAME}
1347 Redirect error output to a file, for broken systems which don't support such
1348 behaviour in the shell.
1353 The following options are available when @value{AS} is configured for
1358 This option sets the largest size of an object that can be referenced
1359 implicitly with the @code{gp} register. It is only accepted for targets that
1360 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1362 @cindex MIPS endianness
1363 @cindex endianness, MIPS
1364 @cindex big endian output, MIPS
1366 Generate ``big endian'' format output.
1368 @cindex little endian output, MIPS
1370 Generate ``little endian'' format output.
1388 Generate code for a particular MIPS Instruction Set Architecture level.
1389 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1390 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1391 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1392 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1393 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1394 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1395 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1396 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1397 MIPS64 Release 6 ISA processors, respectively.
1399 @item -march=@var{cpu}
1400 Generate code for a particular MIPS CPU.
1402 @item -mtune=@var{cpu}
1403 Schedule and tune for a particular MIPS CPU.
1407 Cause nops to be inserted if the read of the destination register
1408 of an mfhi or mflo instruction occurs in the following two instructions.
1411 @itemx -mno-fix-rm7000
1412 Cause nops to be inserted if a dmult or dmultu instruction is
1413 followed by a load instruction.
1417 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1418 section instead of the standard ELF .stabs sections.
1422 Control generation of @code{.pdr} sections.
1426 The register sizes are normally inferred from the ISA and ABI, but these
1427 flags force a certain group of registers to be treated as 32 bits wide at
1428 all times. @samp{-mgp32} controls the size of general-purpose registers
1429 and @samp{-mfp32} controls the size of floating-point registers.
1433 The register sizes are normally inferred from the ISA and ABI, but these
1434 flags force a certain group of registers to be treated as 64 bits wide at
1435 all times. @samp{-mgp64} controls the size of general-purpose registers
1436 and @samp{-mfp64} controls the size of floating-point registers.
1439 The register sizes are normally inferred from the ISA and ABI, but using
1440 this flag in combination with @samp{-mabi=32} enables an ABI variant
1441 which will operate correctly with floating-point registers which are
1445 @itemx -mno-odd-spreg
1446 Enable use of floating-point operations on odd-numbered single-precision
1447 registers when supported by the ISA. @samp{-mfpxx} implies
1448 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1452 Generate code for the MIPS 16 processor. This is equivalent to putting
1453 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1454 turns off this option.
1457 @itemx -mno-micromips
1458 Generate code for the microMIPS processor. This is equivalent to putting
1459 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1460 turns off this option. This is equivalent to putting @code{.set nomicromips}
1461 at the start of the assembly file.
1464 @itemx -mno-smartmips
1465 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1466 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1467 @samp{-mno-smartmips} turns off this option.
1471 Generate code for the MIPS-3D Application Specific Extension.
1472 This tells the assembler to accept MIPS-3D instructions.
1473 @samp{-no-mips3d} turns off this option.
1477 Generate code for the MDMX Application Specific Extension.
1478 This tells the assembler to accept MDMX instructions.
1479 @samp{-no-mdmx} turns off this option.
1483 Generate code for the DSP Release 1 Application Specific Extension.
1484 This tells the assembler to accept DSP Release 1 instructions.
1485 @samp{-mno-dsp} turns off this option.
1489 Generate code for the DSP Release 2 Application Specific Extension.
1490 This option implies @samp{-mdsp}.
1491 This tells the assembler to accept DSP Release 2 instructions.
1492 @samp{-mno-dspr2} turns off this option.
1496 Generate code for the DSP Release 3 Application Specific Extension.
1497 This option implies @samp{-mdsp} and @samp{-mdspr2}.
1498 This tells the assembler to accept DSP Release 3 instructions.
1499 @samp{-mno-dspr3} turns off this option.
1503 Generate code for the MIPS SIMD Architecture Extension.
1504 This tells the assembler to accept MSA instructions.
1505 @samp{-mno-msa} turns off this option.
1509 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1510 This tells the assembler to accept XPA instructions.
1511 @samp{-mno-xpa} turns off this option.
1515 Generate code for the MT Application Specific Extension.
1516 This tells the assembler to accept MT instructions.
1517 @samp{-mno-mt} turns off this option.
1521 Generate code for the MCU Application Specific Extension.
1522 This tells the assembler to accept MCU instructions.
1523 @samp{-mno-mcu} turns off this option.
1527 Only use 32-bit instruction encodings when generating code for the
1528 microMIPS processor. This option inhibits the use of any 16-bit
1529 instructions. This is equivalent to putting @code{.set insn32} at
1530 the start of the assembly file. @samp{-mno-insn32} turns off this
1531 option. This is equivalent to putting @code{.set noinsn32} at the
1532 start of the assembly file. By default @samp{-mno-insn32} is
1533 selected, allowing all instructions to be used.
1535 @item --construct-floats
1536 @itemx --no-construct-floats
1537 The @samp{--no-construct-floats} option disables the construction of
1538 double width floating point constants by loading the two halves of the
1539 value into the two single width floating point registers that make up
1540 the double width register. By default @samp{--construct-floats} is
1541 selected, allowing construction of these floating point constants.
1543 @item --relax-branch
1544 @itemx --no-relax-branch
1545 The @samp{--relax-branch} option enables the relaxation of out-of-range
1546 branches. By default @samp{--no-relax-branch} is selected, causing any
1547 out-of-range branches to produce an error.
1549 @item -mnan=@var{encoding}
1550 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1551 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1554 @item --emulation=@var{name}
1555 This option was formerly used to switch between ELF and ECOFF output
1556 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1557 removed in GAS 2.24, so the option now serves little purpose.
1558 It is retained for backwards compatibility.
1560 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1561 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1562 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1563 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1564 preferred options instead.
1567 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1574 Control how to deal with multiplication overflow and division by zero.
1575 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1576 (and only work for Instruction Set Architecture level 2 and higher);
1577 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1581 When this option is used, @command{@value{AS}} will issue a warning every
1582 time it generates a nop instruction from a macro.
1587 The following options are available when @value{AS} is configured for
1593 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1594 The command line option @samp{-nojsri2bsr} can be used to disable it.
1598 Enable or disable the silicon filter behaviour. By default this is disabled.
1599 The default can be overridden by the @samp{-sifilter} command line option.
1602 Alter jump instructions for long displacements.
1604 @item -mcpu=[210|340]
1605 Select the cpu type on the target hardware. This controls which instructions
1609 Assemble for a big endian target.
1612 Assemble for a little endian target.
1621 @xref{Meta Options}, for the options available when @value{AS} is configured
1622 for a Meta processor.
1626 @c man begin OPTIONS
1627 The following options are available when @value{AS} is configured for a
1630 @c man begin INCLUDE
1631 @include c-metag.texi
1632 @c ended inside the included file
1637 @c man begin OPTIONS
1639 See the info pages for documentation of the MMIX-specific options.
1645 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1646 for a NDS32 processor.
1648 @c ended inside the included file
1652 @c man begin OPTIONS
1653 The following options are available when @value{AS} is configured for a
1656 @c man begin INCLUDE
1657 @include c-nds32.texi
1658 @c ended inside the included file
1665 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1666 for a PowerPC processor.
1670 @c man begin OPTIONS
1671 The following options are available when @value{AS} is configured for a
1674 @c man begin INCLUDE
1676 @c ended inside the included file
1684 @xref{RISC-V-Opts}, for the options available when @value{AS} is configured
1685 for a RISC-V processor.
1689 @c man begin OPTIONS
1690 The following options are available when @value{AS} is configured for a
1693 @c man begin INCLUDE
1694 @include c-riscv.texi
1695 @c ended inside the included file
1700 @c man begin OPTIONS
1702 See the info pages for documentation of the RX-specific options.
1706 The following options are available when @value{AS} is configured for the s390
1712 Select the word size, either 31/32 bits or 64 bits.
1715 Select the architecture mode, either the Enterprise System
1716 Architecture (esa) or the z/Architecture mode (zarch).
1717 @item -march=@var{processor}
1718 Specify which s390 processor variant is the target, @samp{g5} (or
1719 @samp{arch3}), @samp{g6}, @samp{z900} (or @samp{arch5}), @samp{z990} (or
1720 @samp{arch6}), @samp{z9-109}, @samp{z9-ec} (or @samp{arch7}), @samp{z10} (or
1721 @samp{arch8}), @samp{z196} (or @samp{arch9}), @samp{zEC12} (or @samp{arch10}),
1722 or @samp{z13} (or @samp{arch11}).
1724 @itemx -mno-regnames
1725 Allow or disallow symbolic names for registers.
1726 @item -mwarn-areg-zero
1727 Warn whenever the operand for a base or index register has been specified
1728 but evaluates to zero.
1736 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1737 for a TMS320C6000 processor.
1741 @c man begin OPTIONS
1742 The following options are available when @value{AS} is configured for a
1743 TMS320C6000 processor.
1745 @c man begin INCLUDE
1746 @include c-tic6x.texi
1747 @c ended inside the included file
1755 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1756 for a TILE-Gx processor.
1760 @c man begin OPTIONS
1761 The following options are available when @value{AS} is configured for a TILE-Gx
1764 @c man begin INCLUDE
1765 @include c-tilegx.texi
1766 @c ended inside the included file
1774 @xref{Visium Options}, for the options available when @value{AS} is configured
1775 for a Visium processor.
1779 @c man begin OPTIONS
1780 The following option is available when @value{AS} is configured for a Visium
1783 @c man begin INCLUDE
1784 @include c-visium.texi
1785 @c ended inside the included file
1793 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1794 for an Xtensa processor.
1798 @c man begin OPTIONS
1799 The following options are available when @value{AS} is configured for an
1802 @c man begin INCLUDE
1803 @include c-xtensa.texi
1804 @c ended inside the included file
1809 @c man begin OPTIONS
1812 The following options are available when @value{AS} is configured for
1813 a Z80 family processor.
1816 Assemble for Z80 processor.
1818 Assemble for R800 processor.
1819 @item -ignore-undocumented-instructions
1821 Assemble undocumented Z80 instructions that also work on R800 without warning.
1822 @item -ignore-unportable-instructions
1824 Assemble all undocumented Z80 instructions without warning.
1825 @item -warn-undocumented-instructions
1827 Issue a warning for undocumented Z80 instructions that also work on R800.
1828 @item -warn-unportable-instructions
1830 Issue a warning for undocumented Z80 instructions that do not work on R800.
1831 @item -forbid-undocumented-instructions
1833 Treat all undocumented instructions as errors.
1834 @item -forbid-unportable-instructions
1836 Treat undocumented Z80 instructions that do not work on R800 as errors.
1843 * Manual:: Structure of this Manual
1844 * GNU Assembler:: The GNU Assembler
1845 * Object Formats:: Object File Formats
1846 * Command Line:: Command Line
1847 * Input Files:: Input Files
1848 * Object:: Output (Object) File
1849 * Errors:: Error and Warning Messages
1853 @section Structure of this Manual
1855 @cindex manual, structure and purpose
1856 This manual is intended to describe what you need to know to use
1857 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1858 notation for symbols, constants, and expressions; the directives that
1859 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1862 We also cover special features in the @value{TARGET}
1863 configuration of @command{@value{AS}}, including assembler directives.
1866 This manual also describes some of the machine-dependent features of
1867 various flavors of the assembler.
1870 @cindex machine instructions (not covered)
1871 On the other hand, this manual is @emph{not} intended as an introduction
1872 to programming in assembly language---let alone programming in general!
1873 In a similar vein, we make no attempt to introduce the machine
1874 architecture; we do @emph{not} describe the instruction set, standard
1875 mnemonics, registers or addressing modes that are standard to a
1876 particular architecture.
1878 You may want to consult the manufacturer's
1879 machine architecture manual for this information.
1883 For information on the H8/300 machine instruction set, see @cite{H8/300
1884 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1885 Programming Manual} (Renesas).
1888 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1889 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1890 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1891 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1894 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1898 @c I think this is premature---doc@cygnus.com, 17jan1991
1900 Throughout this manual, we assume that you are running @dfn{GNU},
1901 the portable operating system from the @dfn{Free Software
1902 Foundation, Inc.}. This restricts our attention to certain kinds of
1903 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1904 once this assumption is granted examples and definitions need less
1907 @command{@value{AS}} is part of a team of programs that turn a high-level
1908 human-readable series of instructions into a low-level
1909 computer-readable series of instructions. Different versions of
1910 @command{@value{AS}} are used for different kinds of computer.
1913 @c There used to be a section "Terminology" here, which defined
1914 @c "contents", "byte", "word", and "long". Defining "word" to any
1915 @c particular size is confusing when the .word directive may generate 16
1916 @c bits on one machine and 32 bits on another; in general, for the user
1917 @c version of this manual, none of these terms seem essential to define.
1918 @c They were used very little even in the former draft of the manual;
1919 @c this draft makes an effort to avoid them (except in names of
1923 @section The GNU Assembler
1925 @c man begin DESCRIPTION
1927 @sc{gnu} @command{as} is really a family of assemblers.
1929 This manual describes @command{@value{AS}}, a member of that family which is
1930 configured for the @value{TARGET} architectures.
1932 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1933 should find a fairly similar environment when you use it on another
1934 architecture. Each version has much in common with the others,
1935 including object file formats, most assembler directives (often called
1936 @dfn{pseudo-ops}) and assembler syntax.@refill
1938 @cindex purpose of @sc{gnu} assembler
1939 @command{@value{AS}} is primarily intended to assemble the output of the
1940 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1941 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1942 assemble correctly everything that other assemblers for the same
1943 machine would assemble.
1945 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1948 @c This remark should appear in generic version of manual; assumption
1949 @c here is that generic version sets M680x0.
1950 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1951 assembler for the same architecture; for example, we know of several
1952 incompatible versions of 680x0 assembly language syntax.
1957 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1958 program in one pass of the source file. This has a subtle impact on the
1959 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1961 @node Object Formats
1962 @section Object File Formats
1964 @cindex object file format
1965 The @sc{gnu} assembler can be configured to produce several alternative
1966 object file formats. For the most part, this does not affect how you
1967 write assembly language programs; but directives for debugging symbols
1968 are typically different in different file formats. @xref{Symbol
1969 Attributes,,Symbol Attributes}.
1972 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1973 @value{OBJ-NAME} format object files.
1975 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1977 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1978 @code{b.out} or COFF format object files.
1981 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1982 SOM or ELF format object files.
1987 @section Command Line
1989 @cindex command line conventions
1991 After the program name @command{@value{AS}}, the command line may contain
1992 options and file names. Options may appear in any order, and may be
1993 before, after, or between file names. The order of file names is
1996 @cindex standard input, as input file
1998 @file{--} (two hyphens) by itself names the standard input file
1999 explicitly, as one of the files for @command{@value{AS}} to assemble.
2001 @cindex options, command line
2002 Except for @samp{--} any command line argument that begins with a
2003 hyphen (@samp{-}) is an option. Each option changes the behavior of
2004 @command{@value{AS}}. No option changes the way another option works. An
2005 option is a @samp{-} followed by one or more letters; the case of
2006 the letter is important. All options are optional.
2008 Some options expect exactly one file name to follow them. The file
2009 name may either immediately follow the option's letter (compatible
2010 with older assemblers) or it may be the next command argument (@sc{gnu}
2011 standard). These two command lines are equivalent:
2014 @value{AS} -o my-object-file.o mumble.s
2015 @value{AS} -omy-object-file.o mumble.s
2019 @section Input Files
2022 @cindex source program
2023 @cindex files, input
2024 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
2025 describe the program input to one run of @command{@value{AS}}. The program may
2026 be in one or more files; how the source is partitioned into files
2027 doesn't change the meaning of the source.
2029 @c I added "con" prefix to "catenation" just to prove I can overcome my
2030 @c APL training... doc@cygnus.com
2031 The source program is a concatenation of the text in all the files, in the
2034 @c man begin DESCRIPTION
2035 Each time you run @command{@value{AS}} it assembles exactly one source
2036 program. The source program is made up of one or more files.
2037 (The standard input is also a file.)
2039 You give @command{@value{AS}} a command line that has zero or more input file
2040 names. The input files are read (from left file name to right). A
2041 command line argument (in any position) that has no special meaning
2042 is taken to be an input file name.
2044 If you give @command{@value{AS}} no file names it attempts to read one input file
2045 from the @command{@value{AS}} standard input, which is normally your terminal. You
2046 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
2049 Use @samp{--} if you need to explicitly name the standard input file
2050 in your command line.
2052 If the source is empty, @command{@value{AS}} produces a small, empty object
2057 @subheading Filenames and Line-numbers
2059 @cindex input file linenumbers
2060 @cindex line numbers, in input files
2061 There are two ways of locating a line in the input file (or files) and
2062 either may be used in reporting error messages. One way refers to a line
2063 number in a physical file; the other refers to a line number in a
2064 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
2066 @dfn{Physical files} are those files named in the command line given
2067 to @command{@value{AS}}.
2069 @dfn{Logical files} are simply names declared explicitly by assembler
2070 directives; they bear no relation to physical files. Logical file names help
2071 error messages reflect the original source file, when @command{@value{AS}} source
2072 is itself synthesized from other files. @command{@value{AS}} understands the
2073 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
2074 @ref{File,,@code{.file}}.
2077 @section Output (Object) File
2083 Every time you run @command{@value{AS}} it produces an output file, which is
2084 your assembly language program translated into numbers. This file
2085 is the object file. Its default name is
2093 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2095 You can give it another name by using the @option{-o} option. Conventionally,
2096 object file names end with @file{.o}. The default name is used for historical
2097 reasons: older assemblers were capable of assembling self-contained programs
2098 directly into a runnable program. (For some formats, this isn't currently
2099 possible, but it can be done for the @code{a.out} format.)
2103 The object file is meant for input to the linker @code{@value{LD}}. It contains
2104 assembled program code, information to help @code{@value{LD}} integrate
2105 the assembled program into a runnable file, and (optionally) symbolic
2106 information for the debugger.
2108 @c link above to some info file(s) like the description of a.out.
2109 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2112 @section Error and Warning Messages
2114 @c man begin DESCRIPTION
2116 @cindex error messages
2117 @cindex warning messages
2118 @cindex messages from assembler
2119 @command{@value{AS}} may write warnings and error messages to the standard error
2120 file (usually your terminal). This should not happen when a compiler
2121 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2122 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2123 grave problem that stops the assembly.
2127 @cindex format of warning messages
2128 Warning messages have the format
2131 file_name:@b{NNN}:Warning Message Text
2135 @cindex file names and line numbers, in warnings/errors
2136 (where @b{NNN} is a line number). If both a logical file name
2137 (@pxref{File,,@code{.file}}) and a logical line number
2139 (@pxref{Line,,@code{.line}})
2141 have been given then they will be used, otherwise the file name and line number
2142 in the current assembler source file will be used. The message text is
2143 intended to be self explanatory (in the grand Unix tradition).
2145 Note the file name must be set via the logical version of the @code{.file}
2146 directive, not the DWARF2 version of the @code{.file} directive. For example:
2150 error_assembler_source
2156 produces this output:
2160 asm.s:2: Error: no such instruction: `error_assembler_source'
2161 foo.c:31: Error: no such instruction: `error_c_source'
2164 @cindex format of error messages
2165 Error messages have the format
2168 file_name:@b{NNN}:FATAL:Error Message Text
2171 The file name and line number are derived as for warning
2172 messages. The actual message text may be rather less explanatory
2173 because many of them aren't supposed to happen.
2176 @chapter Command-Line Options
2178 @cindex options, all versions of assembler
2179 This chapter describes command-line options available in @emph{all}
2180 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2181 for options specific
2183 to the @value{TARGET} target.
2186 to particular machine architectures.
2189 @c man begin DESCRIPTION
2191 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2192 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2193 The assembler arguments must be separated from each other (and the @samp{-Wa})
2194 by commas. For example:
2197 gcc -c -g -O -Wa,-alh,-L file.c
2201 This passes two options to the assembler: @samp{-alh} (emit a listing to
2202 standard output with high-level and assembly source) and @samp{-L} (retain
2203 local symbols in the symbol table).
2205 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2206 command-line options are automatically passed to the assembler by the compiler.
2207 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2208 precisely what options it passes to each compilation pass, including the
2214 * a:: -a[cdghlns] enable listings
2215 * alternate:: --alternate enable alternate macro syntax
2216 * D:: -D for compatibility
2217 * f:: -f to work faster
2218 * I:: -I for .include search path
2219 @ifclear DIFF-TBL-KLUGE
2220 * K:: -K for compatibility
2222 @ifset DIFF-TBL-KLUGE
2223 * K:: -K for difference tables
2226 * L:: -L to retain local symbols
2227 * listing:: --listing-XXX to configure listing output
2228 * M:: -M or --mri to assemble in MRI compatibility mode
2229 * MD:: --MD for dependency tracking
2230 * no-pad-sections:: --no-pad-sections to stop section padding
2231 * o:: -o to name the object file
2232 * R:: -R to join data and text sections
2233 * statistics:: --statistics to see statistics about assembly
2234 * traditional-format:: --traditional-format for compatible output
2235 * v:: -v to announce version
2236 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2237 * Z:: -Z to make object file even after errors
2241 @section Enable Listings: @option{-a[cdghlns]}
2251 @cindex listings, enabling
2252 @cindex assembly listings, enabling
2254 These options enable listing output from the assembler. By itself,
2255 @samp{-a} requests high-level, assembly, and symbols listing.
2256 You can use other letters to select specific options for the list:
2257 @samp{-ah} requests a high-level language listing,
2258 @samp{-al} requests an output-program assembly listing, and
2259 @samp{-as} requests a symbol table listing.
2260 High-level listings require that a compiler debugging option like
2261 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2264 Use the @samp{-ag} option to print a first section with general assembly
2265 information, like @value{AS} version, switches passed, or time stamp.
2267 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2268 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2269 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2270 omitted from the listing.
2272 Use the @samp{-ad} option to omit debugging directives from the
2275 Once you have specified one of these options, you can further control
2276 listing output and its appearance using the directives @code{.list},
2277 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2279 The @samp{-an} option turns off all forms processing.
2280 If you do not request listing output with one of the @samp{-a} options, the
2281 listing-control directives have no effect.
2283 The letters after @samp{-a} may be combined into one option,
2284 @emph{e.g.}, @samp{-aln}.
2286 Note if the assembler source is coming from the standard input (e.g.,
2288 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2289 is being used) then the listing will not contain any comments or preprocessor
2290 directives. This is because the listing code buffers input source lines from
2291 stdin only after they have been preprocessed by the assembler. This reduces
2292 memory usage and makes the code more efficient.
2295 @section @option{--alternate}
2298 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2301 @section @option{-D}
2304 This option has no effect whatsoever, but it is accepted to make it more
2305 likely that scripts written for other assemblers also work with
2306 @command{@value{AS}}.
2309 @section Work Faster: @option{-f}
2312 @cindex trusted compiler
2313 @cindex faster processing (@option{-f})
2314 @samp{-f} should only be used when assembling programs written by a
2315 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2316 and comment preprocessing on
2317 the input file(s) before assembling them. @xref{Preprocessing,
2321 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2322 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2327 @section @code{.include} Search Path: @option{-I} @var{path}
2329 @kindex -I @var{path}
2330 @cindex paths for @code{.include}
2331 @cindex search path for @code{.include}
2332 @cindex @code{include} directive search path
2333 Use this option to add a @var{path} to the list of directories
2334 @command{@value{AS}} searches for files specified in @code{.include}
2335 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2336 many times as necessary to include a variety of paths. The current
2337 working directory is always searched first; after that, @command{@value{AS}}
2338 searches any @samp{-I} directories in the same order as they were
2339 specified (left to right) on the command line.
2342 @section Difference Tables: @option{-K}
2345 @ifclear DIFF-TBL-KLUGE
2346 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2347 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2348 where it can be used to warn when the assembler alters the machine code
2349 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2350 family does not have the addressing limitations that sometimes lead to this
2351 alteration on other platforms.
2354 @ifset DIFF-TBL-KLUGE
2355 @cindex difference tables, warning
2356 @cindex warning for altered difference tables
2357 @command{@value{AS}} sometimes alters the code emitted for directives of the
2358 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2359 You can use the @samp{-K} option if you want a warning issued when this
2364 @section Include Local Symbols: @option{-L}
2367 @cindex local symbols, retaining in output
2368 Symbols beginning with system-specific local label prefixes, typically
2369 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2370 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2371 such symbols when debugging, because they are intended for the use of
2372 programs (like compilers) that compose assembler programs, not for your
2373 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2374 such symbols, so you do not normally debug with them.
2376 This option tells @command{@value{AS}} to retain those local symbols
2377 in the object file. Usually if you do this you also tell the linker
2378 @code{@value{LD}} to preserve those symbols.
2381 @section Configuring listing output: @option{--listing}
2383 The listing feature of the assembler can be enabled via the command line switch
2384 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2385 hex dump of the corresponding locations in the output object file, and displays
2386 them as a listing file. The format of this listing can be controlled by
2387 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2388 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2389 @code{.psize} (@pxref{Psize}), and
2390 @code{.eject} (@pxref{Eject}) and also by the following switches:
2393 @item --listing-lhs-width=@samp{number}
2394 @kindex --listing-lhs-width
2395 @cindex Width of first line disassembly output
2396 Sets the maximum width, in words, of the first line of the hex byte dump. This
2397 dump appears on the left hand side of the listing output.
2399 @item --listing-lhs-width2=@samp{number}
2400 @kindex --listing-lhs-width2
2401 @cindex Width of continuation lines of disassembly output
2402 Sets the maximum width, in words, of any further lines of the hex byte dump for
2403 a given input source line. If this value is not specified, it defaults to being
2404 the same as the value specified for @samp{--listing-lhs-width}. If neither
2405 switch is used the default is to one.
2407 @item --listing-rhs-width=@samp{number}
2408 @kindex --listing-rhs-width
2409 @cindex Width of source line output
2410 Sets the maximum width, in characters, of the source line that is displayed
2411 alongside the hex dump. The default value for this parameter is 100. The
2412 source line is displayed on the right hand side of the listing output.
2414 @item --listing-cont-lines=@samp{number}
2415 @kindex --listing-cont-lines
2416 @cindex Maximum number of continuation lines
2417 Sets the maximum number of continuation lines of hex dump that will be
2418 displayed for a given single line of source input. The default value is 4.
2422 @section Assemble in MRI Compatibility Mode: @option{-M}
2425 @cindex MRI compatibility mode
2426 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2427 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2428 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2429 configured target) assembler from Microtec Research. The exact nature of the
2430 MRI syntax will not be documented here; see the MRI manuals for more
2431 information. Note in particular that the handling of macros and macro
2432 arguments is somewhat different. The purpose of this option is to permit
2433 assembling existing MRI assembler code using @command{@value{AS}}.
2435 The MRI compatibility is not complete. Certain operations of the MRI assembler
2436 depend upon its object file format, and can not be supported using other object
2437 file formats. Supporting these would require enhancing each object file format
2438 individually. These are:
2441 @item global symbols in common section
2443 The m68k MRI assembler supports common sections which are merged by the linker.
2444 Other object file formats do not support this. @command{@value{AS}} handles
2445 common sections by treating them as a single common symbol. It permits local
2446 symbols to be defined within a common section, but it can not support global
2447 symbols, since it has no way to describe them.
2449 @item complex relocations
2451 The MRI assemblers support relocations against a negated section address, and
2452 relocations which combine the start addresses of two or more sections. These
2453 are not support by other object file formats.
2455 @item @code{END} pseudo-op specifying start address
2457 The MRI @code{END} pseudo-op permits the specification of a start address.
2458 This is not supported by other object file formats. The start address may
2459 instead be specified using the @option{-e} option to the linker, or in a linker
2462 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2464 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2465 name to the output file. This is not supported by other object file formats.
2467 @item @code{ORG} pseudo-op
2469 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2470 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2471 which changes the location within the current section. Absolute sections are
2472 not supported by other object file formats. The address of a section may be
2473 assigned within a linker script.
2476 There are some other features of the MRI assembler which are not supported by
2477 @command{@value{AS}}, typically either because they are difficult or because they
2478 seem of little consequence. Some of these may be supported in future releases.
2482 @item EBCDIC strings
2484 EBCDIC strings are not supported.
2486 @item packed binary coded decimal
2488 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2489 and @code{DCB.P} pseudo-ops are not supported.
2491 @item @code{FEQU} pseudo-op
2493 The m68k @code{FEQU} pseudo-op is not supported.
2495 @item @code{NOOBJ} pseudo-op
2497 The m68k @code{NOOBJ} pseudo-op is not supported.
2499 @item @code{OPT} branch control options
2501 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2502 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2503 relaxes all branches, whether forward or backward, to an appropriate size, so
2504 these options serve no purpose.
2506 @item @code{OPT} list control options
2508 The following m68k @code{OPT} list control options are ignored: @code{C},
2509 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2510 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2512 @item other @code{OPT} options
2514 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2515 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2517 @item @code{OPT} @code{D} option is default
2519 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2520 @code{OPT NOD} may be used to turn it off.
2522 @item @code{XREF} pseudo-op.
2524 The m68k @code{XREF} pseudo-op is ignored.
2526 @item @code{.debug} pseudo-op
2528 The i960 @code{.debug} pseudo-op is not supported.
2530 @item @code{.extended} pseudo-op
2532 The i960 @code{.extended} pseudo-op is not supported.
2534 @item @code{.list} pseudo-op.
2536 The various options of the i960 @code{.list} pseudo-op are not supported.
2538 @item @code{.optimize} pseudo-op
2540 The i960 @code{.optimize} pseudo-op is not supported.
2542 @item @code{.output} pseudo-op
2544 The i960 @code{.output} pseudo-op is not supported.
2546 @item @code{.setreal} pseudo-op
2548 The i960 @code{.setreal} pseudo-op is not supported.
2553 @section Dependency Tracking: @option{--MD}
2556 @cindex dependency tracking
2559 @command{@value{AS}} can generate a dependency file for the file it creates. This
2560 file consists of a single rule suitable for @code{make} describing the
2561 dependencies of the main source file.
2563 The rule is written to the file named in its argument.
2565 This feature is used in the automatic updating of makefiles.
2567 @node no-pad-sections
2568 @section Output Section Padding
2569 @kindex --no-pad-sections
2570 @cindex output section padding
2571 Normally the assembler will pad the end of each output section up to its
2572 alignment boundary. But this can waste space, which can be significant on
2573 memory constrained targets. So the @option{--no-pad-sections} option will
2574 disable this behaviour.
2577 @section Name the Object File: @option{-o}
2580 @cindex naming object file
2581 @cindex object file name
2582 There is always one object file output when you run @command{@value{AS}}. By
2583 default it has the name
2586 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2600 You use this option (which takes exactly one filename) to give the
2601 object file a different name.
2603 Whatever the object file is called, @command{@value{AS}} overwrites any
2604 existing file of the same name.
2607 @section Join Data and Text Sections: @option{-R}
2610 @cindex data and text sections, joining
2611 @cindex text and data sections, joining
2612 @cindex joining text and data sections
2613 @cindex merging text and data sections
2614 @option{-R} tells @command{@value{AS}} to write the object file as if all
2615 data-section data lives in the text section. This is only done at
2616 the very last moment: your binary data are the same, but data
2617 section parts are relocated differently. The data section part of
2618 your object file is zero bytes long because all its bytes are
2619 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2621 When you specify @option{-R} it would be possible to generate shorter
2622 address displacements (because we do not have to cross between text and
2623 data section). We refrain from doing this simply for compatibility with
2624 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2627 When @command{@value{AS}} is configured for COFF or ELF output,
2628 this option is only useful if you use sections named @samp{.text} and
2633 @option{-R} is not supported for any of the HPPA targets. Using
2634 @option{-R} generates a warning from @command{@value{AS}}.
2638 @section Display Assembly Statistics: @option{--statistics}
2640 @kindex --statistics
2641 @cindex statistics, about assembly
2642 @cindex time, total for assembly
2643 @cindex space used, maximum for assembly
2644 Use @samp{--statistics} to display two statistics about the resources used by
2645 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2646 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2649 @node traditional-format
2650 @section Compatible Output: @option{--traditional-format}
2652 @kindex --traditional-format
2653 For some targets, the output of @command{@value{AS}} is different in some ways
2654 from the output of some existing assembler. This switch requests
2655 @command{@value{AS}} to use the traditional format instead.
2657 For example, it disables the exception frame optimizations which
2658 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2661 @section Announce Version: @option{-v}
2665 @cindex assembler version
2666 @cindex version of assembler
2667 You can find out what version of as is running by including the
2668 option @samp{-v} (which you can also spell as @samp{-version}) on the
2672 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2674 @command{@value{AS}} should never give a warning or error message when
2675 assembling compiler output. But programs written by people often
2676 cause @command{@value{AS}} to give a warning that a particular assumption was
2677 made. All such warnings are directed to the standard error file.
2681 @cindex suppressing warnings
2682 @cindex warnings, suppressing
2683 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2684 This only affects the warning messages: it does not change any particular of
2685 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2688 @kindex --fatal-warnings
2689 @cindex errors, caused by warnings
2690 @cindex warnings, causing error
2691 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2692 files that generate warnings to be in error.
2695 @cindex warnings, switching on
2696 You can switch these options off again by specifying @option{--warn}, which
2697 causes warnings to be output as usual.
2700 @section Generate Object File in Spite of Errors: @option{-Z}
2701 @cindex object file, after errors
2702 @cindex errors, continuing after
2703 After an error message, @command{@value{AS}} normally produces no output. If for
2704 some reason you are interested in object file output even after
2705 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2706 option. If there are any errors, @command{@value{AS}} continues anyways, and
2707 writes an object file after a final warning message of the form @samp{@var{n}
2708 errors, @var{m} warnings, generating bad object file.}
2713 @cindex machine-independent syntax
2714 @cindex syntax, machine-independent
2715 This chapter describes the machine-independent syntax allowed in a
2716 source file. @command{@value{AS}} syntax is similar to what many other
2717 assemblers use; it is inspired by the BSD 4.2
2722 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2726 * Preprocessing:: Preprocessing
2727 * Whitespace:: Whitespace
2728 * Comments:: Comments
2729 * Symbol Intro:: Symbols
2730 * Statements:: Statements
2731 * Constants:: Constants
2735 @section Preprocessing
2737 @cindex preprocessing
2738 The @command{@value{AS}} internal preprocessor:
2740 @cindex whitespace, removed by preprocessor
2742 adjusts and removes extra whitespace. It leaves one space or tab before
2743 the keywords on a line, and turns any other whitespace on the line into
2746 @cindex comments, removed by preprocessor
2748 removes all comments, replacing them with a single space, or an
2749 appropriate number of newlines.
2751 @cindex constants, converted by preprocessor
2753 converts character constants into the appropriate numeric values.
2756 It does not do macro processing, include file handling, or
2757 anything else you may get from your C compiler's preprocessor. You can
2758 do include file processing with the @code{.include} directive
2759 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2760 to get other ``CPP'' style preprocessing by giving the input file a
2761 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2762 Output, gcc info, Using GNU CC}.
2764 Excess whitespace, comments, and character constants
2765 cannot be used in the portions of the input text that are not
2768 @cindex turning preprocessing on and off
2769 @cindex preprocessing, turning on and off
2772 If the first line of an input file is @code{#NO_APP} or if you use the
2773 @samp{-f} option, whitespace and comments are not removed from the input file.
2774 Within an input file, you can ask for whitespace and comment removal in
2775 specific portions of the by putting a line that says @code{#APP} before the
2776 text that may contain whitespace or comments, and putting a line that says
2777 @code{#NO_APP} after this text. This feature is mainly intend to support
2778 @code{asm} statements in compilers whose output is otherwise free of comments
2785 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2786 Whitespace is used to separate symbols, and to make programs neater for
2787 people to read. Unless within character constants
2788 (@pxref{Characters,,Character Constants}), any whitespace means the same
2789 as exactly one space.
2795 There are two ways of rendering comments to @command{@value{AS}}. In both
2796 cases the comment is equivalent to one space.
2798 Anything from @samp{/*} through the next @samp{*/} is a comment.
2799 This means you may not nest these comments.
2803 The only way to include a newline ('\n') in a comment
2804 is to use this sort of comment.
2807 /* This sort of comment does not nest. */
2810 @cindex line comment character
2811 Anything from a @dfn{line comment} character up to the next newline is
2812 considered a comment and is ignored. The line comment character is target
2813 specific, and some targets multiple comment characters. Some targets also have
2814 line comment characters that only work if they are the first character on a
2815 line. Some targets use a sequence of two characters to introduce a line
2816 comment. Some targets can also change their line comment characters depending
2817 upon command line options that have been used. For more details see the
2818 @emph{Syntax} section in the documentation for individual targets.
2820 If the line comment character is the hash sign (@samp{#}) then it still has the
2821 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2822 to specify logical line numbers:
2825 @cindex lines starting with @code{#}
2826 @cindex logical line numbers
2827 To be compatible with past assemblers, lines that begin with @samp{#} have a
2828 special interpretation. Following the @samp{#} should be an absolute
2829 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2830 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2831 new logical file name. The rest of the line, if any, should be whitespace.
2833 If the first non-whitespace characters on the line are not numeric,
2834 the line is ignored. (Just like a comment.)
2837 # This is an ordinary comment.
2838 # 42-6 "new_file_name" # New logical file name
2839 # This is logical line # 36.
2841 This feature is deprecated, and may disappear from future versions
2842 of @command{@value{AS}}.
2847 @cindex characters used in symbols
2848 @ifclear SPECIAL-SYMS
2849 A @dfn{symbol} is one or more characters chosen from the set of all
2850 letters (both upper and lower case), digits and the three characters
2856 A @dfn{symbol} is one or more characters chosen from the set of all
2857 letters (both upper and lower case), digits and the three characters
2858 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2864 On most machines, you can also use @code{$} in symbol names; exceptions
2865 are noted in @ref{Machine Dependencies}.
2867 No symbol may begin with a digit. Case is significant.
2868 There is no length limit; all characters are significant. Multibyte characters
2869 are supported. Symbols are delimited by characters not in that set, or by the
2870 beginning of a file (since the source program must end with a newline, the end
2871 of a file is not a possible symbol delimiter). @xref{Symbols}.
2873 Symbol names may also be enclosed in double quote @code{"} characters. In such
2874 cases any characters are allowed, except for the NUL character. If a double
2875 quote character is to be included in the symbol name it must be preceeded by a
2876 backslash @code{\} character.
2877 @cindex length of symbols
2882 @cindex statements, structure of
2883 @cindex line separator character
2884 @cindex statement separator character
2886 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2887 @dfn{line separator character}. The line separator character is target
2888 specific and described in the @emph{Syntax} section of each
2889 target's documentation. Not all targets support a line separator character.
2890 The newline or line separator character is considered to be part of the
2891 preceding statement. Newlines and separators within character constants are an
2892 exception: they do not end statements.
2894 @cindex newline, required at file end
2895 @cindex EOF, newline must precede
2896 It is an error to end any statement with end-of-file: the last
2897 character of any input file should be a newline.@refill
2899 An empty statement is allowed, and may include whitespace. It is ignored.
2901 @cindex instructions and directives
2902 @cindex directives and instructions
2903 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2904 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2906 A statement begins with zero or more labels, optionally followed by a
2907 key symbol which determines what kind of statement it is. The key
2908 symbol determines the syntax of the rest of the statement. If the
2909 symbol begins with a dot @samp{.} then the statement is an assembler
2910 directive: typically valid for any computer. If the symbol begins with
2911 a letter the statement is an assembly language @dfn{instruction}: it
2912 assembles into a machine language instruction.
2914 Different versions of @command{@value{AS}} for different computers
2915 recognize different instructions. In fact, the same symbol may
2916 represent a different instruction in a different computer's assembly
2920 @cindex @code{:} (label)
2921 @cindex label (@code{:})
2922 A label is a symbol immediately followed by a colon (@code{:}).
2923 Whitespace before a label or after a colon is permitted, but you may not
2924 have whitespace between a label's symbol and its colon. @xref{Labels}.
2927 For HPPA targets, labels need not be immediately followed by a colon, but
2928 the definition of a label must begin in column zero. This also implies that
2929 only one label may be defined on each line.
2933 label: .directive followed by something
2934 another_label: # This is an empty statement.
2935 instruction operand_1, operand_2, @dots{}
2942 A constant is a number, written so that its value is known by
2943 inspection, without knowing any context. Like this:
2946 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2947 .ascii "Ring the bell\7" # A string constant.
2948 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2949 .float 0f-314159265358979323846264338327\
2950 95028841971.693993751E-40 # - pi, a flonum.
2955 * Characters:: Character Constants
2956 * Numbers:: Number Constants
2960 @subsection Character Constants
2962 @cindex character constants
2963 @cindex constants, character
2964 There are two kinds of character constants. A @dfn{character} stands
2965 for one character in one byte and its value may be used in
2966 numeric expressions. String constants (properly called string
2967 @emph{literals}) are potentially many bytes and their values may not be
2968 used in arithmetic expressions.
2972 * Chars:: Characters
2976 @subsubsection Strings
2978 @cindex string constants
2979 @cindex constants, string
2980 A @dfn{string} is written between double-quotes. It may contain
2981 double-quotes or null characters. The way to get special characters
2982 into a string is to @dfn{escape} these characters: precede them with
2983 a backslash @samp{\} character. For example @samp{\\} represents
2984 one backslash: the first @code{\} is an escape which tells
2985 @command{@value{AS}} to interpret the second character literally as a backslash
2986 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2987 escape character). The complete list of escapes follows.
2989 @cindex escape codes, character
2990 @cindex character escape codes
2991 @c NOTE: Cindex entries must not start with a backlash character.
2992 @c NOTE: This confuses the pdf2texi script when it is creating the
2993 @c NOTE: index based upon the first character and so it generates:
2994 @c NOTE: \initial {\\}
2995 @c NOTE: which then results in the error message:
2996 @c NOTE: Argument of \\ has an extra }.
2997 @c NOTE: So in the index entries below a space character has been
2998 @c NOTE: prepended to avoid this problem.
3001 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
3003 @cindex @code{ \b} (backspace character)
3004 @cindex backspace (@code{\b})
3006 Mnemonic for backspace; for ASCII this is octal code 010.
3009 @c Mnemonic for EOText; for ASCII this is octal code 004.
3011 @cindex @code{ \f} (formfeed character)
3012 @cindex formfeed (@code{\f})
3014 Mnemonic for FormFeed; for ASCII this is octal code 014.
3016 @cindex @code{ \n} (newline character)
3017 @cindex newline (@code{\n})
3019 Mnemonic for newline; for ASCII this is octal code 012.
3022 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
3024 @cindex @code{ \r} (carriage return character)
3025 @cindex carriage return (@code{backslash-r})
3027 Mnemonic for carriage-Return; for ASCII this is octal code 015.
3030 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
3031 @c other assemblers.
3033 @cindex @code{ \t} (tab)
3034 @cindex tab (@code{\t})
3036 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
3039 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
3040 @c @item \x @var{digit} @var{digit} @var{digit}
3041 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
3043 @cindex @code{ \@var{ddd}} (octal character code)
3044 @cindex octal character code (@code{\@var{ddd}})
3045 @item \ @var{digit} @var{digit} @var{digit}
3046 An octal character code. The numeric code is 3 octal digits.
3047 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
3048 for example, @code{\008} has the value 010, and @code{\009} the value 011.
3050 @cindex @code{ \@var{xd...}} (hex character code)
3051 @cindex hex character code (@code{\@var{xd...}})
3052 @item \@code{x} @var{hex-digits...}
3053 A hex character code. All trailing hex digits are combined. Either upper or
3054 lower case @code{x} works.
3056 @cindex @code{ \\} (@samp{\} character)
3057 @cindex backslash (@code{\\})
3059 Represents one @samp{\} character.
3062 @c Represents one @samp{'} (accent acute) character.
3063 @c This is needed in single character literals
3064 @c (@xref{Characters,,Character Constants}.) to represent
3067 @cindex @code{ \"} (doublequote character)
3068 @cindex doublequote (@code{\"})
3070 Represents one @samp{"} character. Needed in strings to represent
3071 this character, because an unescaped @samp{"} would end the string.
3073 @item \ @var{anything-else}
3074 Any other character when escaped by @kbd{\} gives a warning, but
3075 assembles as if the @samp{\} was not present. The idea is that if
3076 you used an escape sequence you clearly didn't want the literal
3077 interpretation of the following character. However @command{@value{AS}} has no
3078 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
3079 code and warns you of the fact.
3082 Which characters are escapable, and what those escapes represent,
3083 varies widely among assemblers. The current set is what we think
3084 the BSD 4.2 assembler recognizes, and is a subset of what most C
3085 compilers recognize. If you are in doubt, do not use an escape
3089 @subsubsection Characters
3091 @cindex single character constant
3092 @cindex character, single
3093 @cindex constant, single character
3094 A single character may be written as a single quote immediately followed by
3095 that character. Some backslash escapes apply to characters, @code{\b},
3096 @code{\f}, @code{\n}, @code{\r}, @code{\t}, and @code{\"} with the same meaning
3097 as for strings, plus @code{\'} for a single quote. So if you want to write the
3098 character backslash, you must write @kbd{'\\} where the first @code{\} escapes
3099 the second @code{\}. As you can see, the quote is an acute accent, not a grave
3102 @ifclear abnormal-separator
3103 (or semicolon @samp{;})
3105 @ifset abnormal-separator
3107 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
3112 immediately following an acute accent is taken as a literal character
3113 and does not count as the end of a statement. The value of a character
3114 constant in a numeric expression is the machine's byte-wide code for
3115 that character. @command{@value{AS}} assumes your character code is ASCII:
3116 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
3119 @subsection Number Constants
3121 @cindex constants, number
3122 @cindex number constants
3123 @command{@value{AS}} distinguishes three kinds of numbers according to how they
3124 are stored in the target machine. @emph{Integers} are numbers that
3125 would fit into an @code{int} in the C language. @emph{Bignums} are
3126 integers, but they are stored in more than 32 bits. @emph{Flonums}
3127 are floating point numbers, described below.
3130 * Integers:: Integers
3135 * Bit Fields:: Bit Fields
3141 @subsubsection Integers
3143 @cindex constants, integer
3145 @cindex binary integers
3146 @cindex integers, binary
3147 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3148 the binary digits @samp{01}.
3150 @cindex octal integers
3151 @cindex integers, octal
3152 An octal integer is @samp{0} followed by zero or more of the octal
3153 digits (@samp{01234567}).
3155 @cindex decimal integers
3156 @cindex integers, decimal
3157 A decimal integer starts with a non-zero digit followed by zero or
3158 more digits (@samp{0123456789}).
3160 @cindex hexadecimal integers
3161 @cindex integers, hexadecimal
3162 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3163 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3165 Integers have the usual values. To denote a negative integer, use
3166 the prefix operator @samp{-} discussed under expressions
3167 (@pxref{Prefix Ops,,Prefix Operators}).
3170 @subsubsection Bignums
3173 @cindex constants, bignum
3174 A @dfn{bignum} has the same syntax and semantics as an integer
3175 except that the number (or its negative) takes more than 32 bits to
3176 represent in binary. The distinction is made because in some places
3177 integers are permitted while bignums are not.
3180 @subsubsection Flonums
3182 @cindex floating point numbers
3183 @cindex constants, floating point
3185 @cindex precision, floating point
3186 A @dfn{flonum} represents a floating point number. The translation is
3187 indirect: a decimal floating point number from the text is converted by
3188 @command{@value{AS}} to a generic binary floating point number of more than
3189 sufficient precision. This generic floating point number is converted
3190 to a particular computer's floating point format (or formats) by a
3191 portion of @command{@value{AS}} specialized to that computer.
3193 A flonum is written by writing (in order)
3198 (@samp{0} is optional on the HPPA.)
3202 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3204 @kbd{e} is recommended. Case is not important.
3206 @c FIXME: verify if flonum syntax really this vague for most cases
3207 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3208 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3211 On the H8/300, Renesas / SuperH SH,
3212 and AMD 29K architectures, the letter must be
3213 one of the letters @samp{DFPRSX} (in upper or lower case).
3215 On the ARC, the letter must be one of the letters @samp{DFRS}
3216 (in upper or lower case).
3218 On the Intel 960 architecture, the letter must be
3219 one of the letters @samp{DFT} (in upper or lower case).
3221 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3225 One of the letters @samp{DFRS} (in upper or lower case).
3228 One of the letters @samp{DFPRSX} (in upper or lower case).
3231 The letter @samp{E} (upper case only).
3234 One of the letters @samp{DFT} (in upper or lower case).
3239 An optional sign: either @samp{+} or @samp{-}.
3242 An optional @dfn{integer part}: zero or more decimal digits.
3245 An optional @dfn{fractional part}: @samp{.} followed by zero
3246 or more decimal digits.
3249 An optional exponent, consisting of:
3253 An @samp{E} or @samp{e}.
3254 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3255 @c principle this can perfectly well be different on different targets.
3257 Optional sign: either @samp{+} or @samp{-}.
3259 One or more decimal digits.
3264 At least one of the integer part or the fractional part must be
3265 present. The floating point number has the usual base-10 value.
3267 @command{@value{AS}} does all processing using integers. Flonums are computed
3268 independently of any floating point hardware in the computer running
3269 @command{@value{AS}}.
3273 @c Bit fields are written as a general facility but are also controlled
3274 @c by a conditional-compilation flag---which is as of now (21mar91)
3275 @c turned on only by the i960 config of GAS.
3277 @subsubsection Bit Fields
3280 @cindex constants, bit field
3281 You can also define numeric constants as @dfn{bit fields}.
3282 Specify two numbers separated by a colon---
3284 @var{mask}:@var{value}
3287 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3290 The resulting number is then packed
3292 @c this conditional paren in case bit fields turned on elsewhere than 960
3293 (in host-dependent byte order)
3295 into a field whose width depends on which assembler directive has the
3296 bit-field as its argument. Overflow (a result from the bitwise and
3297 requiring more binary digits to represent) is not an error; instead,
3298 more constants are generated, of the specified width, beginning with the
3299 least significant digits.@refill
3301 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3302 @code{.short}, and @code{.word} accept bit-field arguments.
3307 @chapter Sections and Relocation
3312 * Secs Background:: Background
3313 * Ld Sections:: Linker Sections
3314 * As Sections:: Assembler Internal Sections
3315 * Sub-Sections:: Sub-Sections
3319 @node Secs Background
3322 Roughly, a section is a range of addresses, with no gaps; all data
3323 ``in'' those addresses is treated the same for some particular purpose.
3324 For example there may be a ``read only'' section.
3326 @cindex linker, and assembler
3327 @cindex assembler, and linker
3328 The linker @code{@value{LD}} reads many object files (partial programs) and
3329 combines their contents to form a runnable program. When @command{@value{AS}}
3330 emits an object file, the partial program is assumed to start at address 0.
3331 @code{@value{LD}} assigns the final addresses for the partial program, so that
3332 different partial programs do not overlap. This is actually an
3333 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3336 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3337 addresses. These blocks slide to their run-time addresses as rigid
3338 units; their length does not change and neither does the order of bytes
3339 within them. Such a rigid unit is called a @emph{section}. Assigning
3340 run-time addresses to sections is called @dfn{relocation}. It includes
3341 the task of adjusting mentions of object-file addresses so they refer to
3342 the proper run-time addresses.
3344 For the H8/300, and for the Renesas / SuperH SH,
3345 @command{@value{AS}} pads sections if needed to
3346 ensure they end on a word (sixteen bit) boundary.
3349 @cindex standard assembler sections
3350 An object file written by @command{@value{AS}} has at least three sections, any
3351 of which may be empty. These are named @dfn{text}, @dfn{data} and
3356 When it generates COFF or ELF output,
3358 @command{@value{AS}} can also generate whatever other named sections you specify
3359 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3360 If you do not use any directives that place output in the @samp{.text}
3361 or @samp{.data} sections, these sections still exist, but are empty.
3366 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3368 @command{@value{AS}} can also generate whatever other named sections you
3369 specify using the @samp{.space} and @samp{.subspace} directives. See
3370 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3371 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3372 assembler directives.
3375 Additionally, @command{@value{AS}} uses different names for the standard
3376 text, data, and bss sections when generating SOM output. Program text
3377 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3378 BSS into @samp{$BSS$}.
3382 Within the object file, the text section starts at address @code{0}, the
3383 data section follows, and the bss section follows the data section.
3386 When generating either SOM or ELF output files on the HPPA, the text
3387 section starts at address @code{0}, the data section at address
3388 @code{0x4000000}, and the bss section follows the data section.
3391 To let @code{@value{LD}} know which data changes when the sections are
3392 relocated, and how to change that data, @command{@value{AS}} also writes to the
3393 object file details of the relocation needed. To perform relocation
3394 @code{@value{LD}} must know, each time an address in the object
3398 Where in the object file is the beginning of this reference to
3401 How long (in bytes) is this reference?
3403 Which section does the address refer to? What is the numeric value of
3405 (@var{address}) @minus{} (@var{start-address of section})?
3408 Is the reference to an address ``Program-Counter relative''?
3411 @cindex addresses, format of
3412 @cindex section-relative addressing
3413 In fact, every address @command{@value{AS}} ever uses is expressed as
3415 (@var{section}) + (@var{offset into section})
3418 Further, most expressions @command{@value{AS}} computes have this section-relative
3421 (For some object formats, such as SOM for the HPPA, some expressions are
3422 symbol-relative instead.)
3425 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3426 @var{N} into section @var{secname}.''
3428 Apart from text, data and bss sections you need to know about the
3429 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3430 addresses in the absolute section remain unchanged. For example, address
3431 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3432 @code{@value{LD}}. Although the linker never arranges two partial programs'
3433 data sections with overlapping addresses after linking, @emph{by definition}
3434 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3435 part of a program is always the same address when the program is running as
3436 address @code{@{absolute@ 239@}} in any other part of the program.
3438 The idea of sections is extended to the @dfn{undefined} section. Any
3439 address whose section is unknown at assembly time is by definition
3440 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3441 Since numbers are always defined, the only way to generate an undefined
3442 address is to mention an undefined symbol. A reference to a named
3443 common block would be such a symbol: its value is unknown at assembly
3444 time so it has section @emph{undefined}.
3446 By analogy the word @emph{section} is used to describe groups of sections in
3447 the linked program. @code{@value{LD}} puts all partial programs' text
3448 sections in contiguous addresses in the linked program. It is
3449 customary to refer to the @emph{text section} of a program, meaning all
3450 the addresses of all partial programs' text sections. Likewise for
3451 data and bss sections.
3453 Some sections are manipulated by @code{@value{LD}}; others are invented for
3454 use of @command{@value{AS}} and have no meaning except during assembly.
3457 @section Linker Sections
3458 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3463 @cindex named sections
3464 @cindex sections, named
3465 @item named sections
3468 @cindex text section
3469 @cindex data section
3473 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3474 separate but equal sections. Anything you can say of one section is
3477 When the program is running, however, it is
3478 customary for the text section to be unalterable. The
3479 text section is often shared among processes: it contains
3480 instructions, constants and the like. The data section of a running
3481 program is usually alterable: for example, C variables would be stored
3482 in the data section.
3487 This section contains zeroed bytes when your program begins running. It
3488 is used to hold uninitialized variables or common storage. The length of
3489 each partial program's bss section is important, but because it starts
3490 out containing zeroed bytes there is no need to store explicit zero
3491 bytes in the object file. The bss section was invented to eliminate
3492 those explicit zeros from object files.
3494 @cindex absolute section
3495 @item absolute section
3496 Address 0 of this section is always ``relocated'' to runtime address 0.
3497 This is useful if you want to refer to an address that @code{@value{LD}} must
3498 not change when relocating. In this sense we speak of absolute
3499 addresses being ``unrelocatable'': they do not change during relocation.
3501 @cindex undefined section
3502 @item undefined section
3503 This ``section'' is a catch-all for address references to objects not in
3504 the preceding sections.
3505 @c FIXME: ref to some other doc on obj-file formats could go here.
3508 @cindex relocation example
3509 An idealized example of three relocatable sections follows.
3511 The example uses the traditional section names @samp{.text} and @samp{.data}.
3513 Memory addresses are on the horizontal axis.
3517 @c END TEXI2ROFF-KILL
3520 partial program # 1: |ttttt|dddd|00|
3527 partial program # 2: |TTT|DDD|000|
3530 +--+---+-----+--+----+---+-----+~~
3531 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3532 +--+---+-----+--+----+---+-----+~~
3534 addresses: 0 @dots{}
3541 \line{\it Partial program \#1: \hfil}
3542 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3543 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3545 \line{\it Partial program \#2: \hfil}
3546 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3547 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3549 \line{\it linked program: \hfil}
3550 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3551 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3552 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3553 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3555 \line{\it addresses: \hfil}
3559 @c END TEXI2ROFF-KILL
3562 @section Assembler Internal Sections
3564 @cindex internal assembler sections
3565 @cindex sections in messages, internal
3566 These sections are meant only for the internal use of @command{@value{AS}}. They
3567 have no meaning at run-time. You do not really need to know about these
3568 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3569 warning messages, so it might be helpful to have an idea of their
3570 meanings to @command{@value{AS}}. These sections are used to permit the
3571 value of every expression in your assembly language program to be a
3572 section-relative address.
3575 @cindex assembler internal logic error
3576 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3577 An internal assembler logic error has been found. This means there is a
3578 bug in the assembler.
3580 @cindex expr (internal section)
3582 The assembler stores complex expression internally as combinations of
3583 symbols. When it needs to represent an expression as a symbol, it puts
3584 it in the expr section.
3586 @c FIXME item transfer[t] vector preload
3587 @c FIXME item transfer[t] vector postload
3588 @c FIXME item register
3592 @section Sub-Sections
3594 @cindex numbered subsections
3595 @cindex grouping data
3601 fall into two sections: text and data.
3603 You may have separate groups of
3605 data in named sections
3609 data in named sections
3615 that you want to end up near to each other in the object file, even though they
3616 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3617 use @dfn{subsections} for this purpose. Within each section, there can be
3618 numbered subsections with values from 0 to 8192. Objects assembled into the
3619 same subsection go into the object file together with other objects in the same
3620 subsection. For example, a compiler might want to store constants in the text
3621 section, but might not want to have them interspersed with the program being
3622 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3623 section of code being output, and a @samp{.text 1} before each group of
3624 constants being output.
3626 Subsections are optional. If you do not use subsections, everything
3627 goes in subsection number zero.
3630 Each subsection is zero-padded up to a multiple of four bytes.
3631 (Subsections may be padded a different amount on different flavors
3632 of @command{@value{AS}}.)
3636 On the H8/300 platform, each subsection is zero-padded to a word
3637 boundary (two bytes).
3638 The same is true on the Renesas SH.
3641 @c FIXME section padding (alignment)?
3642 @c Rich Pixley says padding here depends on target obj code format; that
3643 @c doesn't seem particularly useful to say without further elaboration,
3644 @c so for now I say nothing about it. If this is a generic BFD issue,
3645 @c these paragraphs might need to vanish from this manual, and be
3646 @c discussed in BFD chapter of binutils (or some such).
3650 Subsections appear in your object file in numeric order, lowest numbered
3651 to highest. (All this to be compatible with other people's assemblers.)
3652 The object file contains no representation of subsections; @code{@value{LD}} and
3653 other programs that manipulate object files see no trace of them.
3654 They just see all your text subsections as a text section, and all your
3655 data subsections as a data section.
3657 To specify which subsection you want subsequent statements assembled
3658 into, use a numeric argument to specify it, in a @samp{.text
3659 @var{expression}} or a @samp{.data @var{expression}} statement.
3662 When generating COFF output, you
3667 can also use an extra subsection
3668 argument with arbitrary named sections: @samp{.section @var{name},
3673 When generating ELF output, you
3678 can also use the @code{.subsection} directive (@pxref{SubSection})
3679 to specify a subsection: @samp{.subsection @var{expression}}.
3681 @var{Expression} should be an absolute expression
3682 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3683 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3684 begins in @code{text 0}. For instance:
3686 .text 0 # The default subsection is text 0 anyway.
3687 .ascii "This lives in the first text subsection. *"
3689 .ascii "But this lives in the second text subsection."
3691 .ascii "This lives in the data section,"
3692 .ascii "in the first data subsection."
3694 .ascii "This lives in the first text section,"
3695 .ascii "immediately following the asterisk (*)."
3698 Each section has a @dfn{location counter} incremented by one for every byte
3699 assembled into that section. Because subsections are merely a convenience
3700 restricted to @command{@value{AS}} there is no concept of a subsection location
3701 counter. There is no way to directly manipulate a location counter---but the
3702 @code{.align} directive changes it, and any label definition captures its
3703 current value. The location counter of the section where statements are being
3704 assembled is said to be the @dfn{active} location counter.
3707 @section bss Section
3710 @cindex common variable storage
3711 The bss section is used for local common variable storage.
3712 You may allocate address space in the bss section, but you may
3713 not dictate data to load into it before your program executes. When
3714 your program starts running, all the contents of the bss
3715 section are zeroed bytes.
3717 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3718 @ref{Lcomm,,@code{.lcomm}}.
3720 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3721 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3724 When assembling for a target which supports multiple sections, such as ELF or
3725 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3726 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3727 section. Typically the section will only contain symbol definitions and
3728 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3735 Symbols are a central concept: the programmer uses symbols to name
3736 things, the linker uses symbols to link, and the debugger uses symbols
3740 @cindex debuggers, and symbol order
3741 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3742 the same order they were declared. This may break some debuggers.
3747 * Setting Symbols:: Giving Symbols Other Values
3748 * Symbol Names:: Symbol Names
3749 * Dot:: The Special Dot Symbol
3750 * Symbol Attributes:: Symbol Attributes
3757 A @dfn{label} is written as a symbol immediately followed by a colon
3758 @samp{:}. The symbol then represents the current value of the
3759 active location counter, and is, for example, a suitable instruction
3760 operand. You are warned if you use the same symbol to represent two
3761 different locations: the first definition overrides any other
3765 On the HPPA, the usual form for a label need not be immediately followed by a
3766 colon, but instead must start in column zero. Only one label may be defined on
3767 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3768 provides a special directive @code{.label} for defining labels more flexibly.
3771 @node Setting Symbols
3772 @section Giving Symbols Other Values
3774 @cindex assigning values to symbols
3775 @cindex symbol values, assigning
3776 A symbol can be given an arbitrary value by writing a symbol, followed
3777 by an equals sign @samp{=}, followed by an expression
3778 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3779 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3780 equals sign @samp{=}@samp{=} here represents an equivalent of the
3781 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3784 Blackfin does not support symbol assignment with @samp{=}.
3788 @section Symbol Names
3790 @cindex symbol names
3791 @cindex names, symbol
3792 @ifclear SPECIAL-SYMS
3793 Symbol names begin with a letter or with one of @samp{._}. On most
3794 machines, you can also use @code{$} in symbol names; exceptions are
3795 noted in @ref{Machine Dependencies}. That character may be followed by any
3796 string of digits, letters, dollar signs (unless otherwise noted for a
3797 particular target machine), and underscores.
3801 Symbol names begin with a letter or with one of @samp{._}. On the
3802 Renesas SH you can also use @code{$} in symbol names. That
3803 character may be followed by any string of digits, letters, dollar signs (save
3804 on the H8/300), and underscores.
3808 Case of letters is significant: @code{foo} is a different symbol name
3811 Symbol names do not start with a digit. An exception to this rule is made for
3812 Local Labels. See below.
3814 Multibyte characters are supported. To generate a symbol name containing
3815 multibyte characters enclose it within double quotes and use escape codes. cf
3816 @xref{Strings}. Generating a multibyte symbol name from a label is not
3817 currently supported.
3819 Each symbol has exactly one name. Each name in an assembly language program
3820 refers to exactly one symbol. You may use that symbol name any number of times
3823 @subheading Local Symbol Names
3825 @cindex local symbol names
3826 @cindex symbol names, local
3827 A local symbol is any symbol beginning with certain local label prefixes.
3828 By default, the local label prefix is @samp{.L} for ELF systems or
3829 @samp{L} for traditional a.out systems, but each target may have its own
3830 set of local label prefixes.
3832 On the HPPA local symbols begin with @samp{L$}.
3835 Local symbols are defined and used within the assembler, but they are
3836 normally not saved in object files. Thus, they are not visible when debugging.
3837 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3838 to retain the local symbols in the object files.
3840 @subheading Local Labels
3842 @cindex local labels
3843 @cindex temporary symbol names
3844 @cindex symbol names, temporary
3845 Local labels are different from local symbols. Local labels help compilers and
3846 programmers use names temporarily. They create symbols which are guaranteed to
3847 be unique over the entire scope of the input source code and which can be
3848 referred to by a simple notation. To define a local label, write a label of
3849 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3850 To refer to the most recent previous definition of that label write
3851 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3852 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3853 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3855 There is no restriction on how you can use these labels, and you can reuse them
3856 too. So that it is possible to repeatedly define the same local label (using
3857 the same number @samp{@b{N}}), although you can only refer to the most recently
3858 defined local label of that number (for a backwards reference) or the next
3859 definition of a specific local label for a forward reference. It is also worth
3860 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3861 implemented in a slightly more efficient manner than the others.
3872 Which is the equivalent of:
3875 label_1: branch label_3
3876 label_2: branch label_1
3877 label_3: branch label_4
3878 label_4: branch label_3
3881 Local label names are only a notational device. They are immediately
3882 transformed into more conventional symbol names before the assembler uses them.
3883 The symbol names are stored in the symbol table, appear in error messages, and
3884 are optionally emitted to the object file. The names are constructed using
3888 @item @emph{local label prefix}
3889 All local symbols begin with the system-specific local label prefix.
3890 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3891 that start with the local label prefix. These labels are
3892 used for symbols you are never intended to see. If you use the
3893 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3894 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3895 you may use them in debugging.
3898 This is the number that was used in the local label definition. So if the
3899 label is written @samp{55:} then the number is @samp{55}.
3902 This unusual character is included so you do not accidentally invent a symbol
3903 of the same name. The character has ASCII value of @samp{\002} (control-B).
3905 @item @emph{ordinal number}
3906 This is a serial number to keep the labels distinct. The first definition of
3907 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3908 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3909 the number @samp{1} and its 15th definition gets @samp{15} as well.
3912 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3913 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3915 @subheading Dollar Local Labels
3916 @cindex dollar local symbols
3918 On some targets @code{@value{AS}} also supports an even more local form of
3919 local labels called dollar labels. These labels go out of scope (i.e., they
3920 become undefined) as soon as a non-local label is defined. Thus they remain
3921 valid for only a small region of the input source code. Normal local labels,
3922 by contrast, remain in scope for the entire file, or until they are redefined
3923 by another occurrence of the same local label.
3925 Dollar labels are defined in exactly the same way as ordinary local labels,
3926 except that they have a dollar sign suffix to their numeric value, e.g.,
3929 They can also be distinguished from ordinary local labels by their transformed
3930 names which use ASCII character @samp{\001} (control-A) as the magic character
3931 to distinguish them from ordinary labels. For example, the fifth definition of
3932 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3935 @section The Special Dot Symbol
3937 @cindex dot (symbol)
3938 @cindex @code{.} (symbol)
3939 @cindex current address
3940 @cindex location counter
3941 The special symbol @samp{.} refers to the current address that
3942 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3943 .long .} defines @code{melvin} to contain its own address.
3944 Assigning a value to @code{.} is treated the same as a @code{.org}
3946 @ifclear no-space-dir
3947 Thus, the expression @samp{.=.+4} is the same as saying
3951 @node Symbol Attributes
3952 @section Symbol Attributes
3954 @cindex symbol attributes
3955 @cindex attributes, symbol
3956 Every symbol has, as well as its name, the attributes ``Value'' and
3957 ``Type''. Depending on output format, symbols can also have auxiliary
3960 The detailed definitions are in @file{a.out.h}.
3963 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3964 all these attributes, and probably won't warn you. This makes the
3965 symbol an externally defined symbol, which is generally what you
3969 * Symbol Value:: Value
3970 * Symbol Type:: Type
3973 * a.out Symbols:: Symbol Attributes: @code{a.out}
3977 * a.out Symbols:: Symbol Attributes: @code{a.out}
3980 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3985 * COFF Symbols:: Symbol Attributes for COFF
3988 * SOM Symbols:: Symbol Attributes for SOM
3995 @cindex value of a symbol
3996 @cindex symbol value
3997 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3998 location in the text, data, bss or absolute sections the value is the
3999 number of addresses from the start of that section to the label.
4000 Naturally for text, data and bss sections the value of a symbol changes
4001 as @code{@value{LD}} changes section base addresses during linking. Absolute
4002 symbols' values do not change during linking: that is why they are
4005 The value of an undefined symbol is treated in a special way. If it is
4006 0 then the symbol is not defined in this assembler source file, and
4007 @code{@value{LD}} tries to determine its value from other files linked into the
4008 same program. You make this kind of symbol simply by mentioning a symbol
4009 name without defining it. A non-zero value represents a @code{.comm}
4010 common declaration. The value is how much common storage to reserve, in
4011 bytes (addresses). The symbol refers to the first address of the
4017 @cindex type of a symbol
4019 The type attribute of a symbol contains relocation (section)
4020 information, any flag settings indicating that a symbol is external, and
4021 (optionally), other information for linkers and debuggers. The exact
4022 format depends on the object-code output format in use.
4027 @c The following avoids a "widow" subsection title. @group would be
4028 @c better if it were available outside examples.
4031 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
4033 @cindex @code{b.out} symbol attributes
4034 @cindex symbol attributes, @code{b.out}
4035 These symbol attributes appear only when @command{@value{AS}} is configured for
4036 one of the Berkeley-descended object output formats---@code{a.out} or
4042 @subsection Symbol Attributes: @code{a.out}
4044 @cindex @code{a.out} symbol attributes
4045 @cindex symbol attributes, @code{a.out}
4051 @subsection Symbol Attributes: @code{a.out}
4053 @cindex @code{a.out} symbol attributes
4054 @cindex symbol attributes, @code{a.out}
4058 * Symbol Desc:: Descriptor
4059 * Symbol Other:: Other
4063 @subsubsection Descriptor
4065 @cindex descriptor, of @code{a.out} symbol
4066 This is an arbitrary 16-bit value. You may establish a symbol's
4067 descriptor value by using a @code{.desc} statement
4068 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
4069 @command{@value{AS}}.
4072 @subsubsection Other
4074 @cindex other attribute, of @code{a.out} symbol
4075 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
4080 @subsection Symbol Attributes for COFF
4082 @cindex COFF symbol attributes
4083 @cindex symbol attributes, COFF
4085 The COFF format supports a multitude of auxiliary symbol attributes;
4086 like the primary symbol attributes, they are set between @code{.def} and
4087 @code{.endef} directives.
4089 @subsubsection Primary Attributes
4091 @cindex primary attributes, COFF symbols
4092 The symbol name is set with @code{.def}; the value and type,
4093 respectively, with @code{.val} and @code{.type}.
4095 @subsubsection Auxiliary Attributes
4097 @cindex auxiliary attributes, COFF symbols
4098 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
4099 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
4100 table information for COFF.
4105 @subsection Symbol Attributes for SOM
4107 @cindex SOM symbol attributes
4108 @cindex symbol attributes, SOM
4110 The SOM format for the HPPA supports a multitude of symbol attributes set with
4111 the @code{.EXPORT} and @code{.IMPORT} directives.
4113 The attributes are described in @cite{HP9000 Series 800 Assembly
4114 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
4115 @code{EXPORT} assembler directive documentation.
4119 @chapter Expressions
4123 @cindex numeric values
4124 An @dfn{expression} specifies an address or numeric value.
4125 Whitespace may precede and/or follow an expression.
4127 The result of an expression must be an absolute number, or else an offset into
4128 a particular section. If an expression is not absolute, and there is not
4129 enough information when @command{@value{AS}} sees the expression to know its
4130 section, a second pass over the source program might be necessary to interpret
4131 the expression---but the second pass is currently not implemented.
4132 @command{@value{AS}} aborts with an error message in this situation.
4135 * Empty Exprs:: Empty Expressions
4136 * Integer Exprs:: Integer Expressions
4140 @section Empty Expressions
4142 @cindex empty expressions
4143 @cindex expressions, empty
4144 An empty expression has no value: it is just whitespace or null.
4145 Wherever an absolute expression is required, you may omit the
4146 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4147 is compatible with other assemblers.
4150 @section Integer Expressions
4152 @cindex integer expressions
4153 @cindex expressions, integer
4154 An @dfn{integer expression} is one or more @emph{arguments} delimited
4155 by @emph{operators}.
4158 * Arguments:: Arguments
4159 * Operators:: Operators
4160 * Prefix Ops:: Prefix Operators
4161 * Infix Ops:: Infix Operators
4165 @subsection Arguments
4167 @cindex expression arguments
4168 @cindex arguments in expressions
4169 @cindex operands in expressions
4170 @cindex arithmetic operands
4171 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4172 contexts arguments are sometimes called ``arithmetic operands''. In
4173 this manual, to avoid confusing them with the ``instruction operands'' of
4174 the machine language, we use the term ``argument'' to refer to parts of
4175 expressions only, reserving the word ``operand'' to refer only to machine
4176 instruction operands.
4178 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4179 @var{section} is one of text, data, bss, absolute,
4180 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4183 Numbers are usually integers.
4185 A number can be a flonum or bignum. In this case, you are warned
4186 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4187 these 32 bits are an integer. You may write integer-manipulating
4188 instructions that act on exotic constants, compatible with other
4191 @cindex subexpressions
4192 Subexpressions are a left parenthesis @samp{(} followed by an integer
4193 expression, followed by a right parenthesis @samp{)}; or a prefix
4194 operator followed by an argument.
4197 @subsection Operators
4199 @cindex operators, in expressions
4200 @cindex arithmetic functions
4201 @cindex functions, in expressions
4202 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4203 operators are followed by an argument. Infix operators appear
4204 between their arguments. Operators may be preceded and/or followed by
4208 @subsection Prefix Operator
4210 @cindex prefix operators
4211 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4212 one argument, which must be absolute.
4214 @c the tex/end tex stuff surrounding this small table is meant to make
4215 @c it align, on the printed page, with the similar table in the next
4216 @c section (which is inside an enumerate).
4218 \global\advance\leftskip by \itemindent
4223 @dfn{Negation}. Two's complement negation.
4225 @dfn{Complementation}. Bitwise not.
4229 \global\advance\leftskip by -\itemindent
4233 @subsection Infix Operators
4235 @cindex infix operators
4236 @cindex operators, permitted arguments
4237 @dfn{Infix operators} take two arguments, one on either side. Operators
4238 have precedence, but operations with equal precedence are performed left
4239 to right. Apart from @code{+} or @option{-}, both arguments must be
4240 absolute, and the result is absolute.
4243 @cindex operator precedence
4244 @cindex precedence of operators
4251 @dfn{Multiplication}.
4254 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4260 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4263 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4267 Intermediate precedence
4272 @dfn{Bitwise Inclusive Or}.
4278 @dfn{Bitwise Exclusive Or}.
4281 @dfn{Bitwise Or Not}.
4288 @cindex addition, permitted arguments
4289 @cindex plus, permitted arguments
4290 @cindex arguments for addition
4292 @dfn{Addition}. If either argument is absolute, the result has the section of
4293 the other argument. You may not add together arguments from different
4296 @cindex subtraction, permitted arguments
4297 @cindex minus, permitted arguments
4298 @cindex arguments for subtraction
4300 @dfn{Subtraction}. If the right argument is absolute, the
4301 result has the section of the left argument.
4302 If both arguments are in the same section, the result is absolute.
4303 You may not subtract arguments from different sections.
4304 @c FIXME is there still something useful to say about undefined - undefined ?
4306 @cindex comparison expressions
4307 @cindex expressions, comparison
4312 @dfn{Is Not Equal To}
4316 @dfn{Is Greater Than}
4318 @dfn{Is Greater Than Or Equal To}
4320 @dfn{Is Less Than Or Equal To}
4322 The comparison operators can be used as infix operators. A true results has a
4323 value of -1 whereas a false result has a value of 0. Note, these operators
4324 perform signed comparisons.
4327 @item Lowest Precedence
4336 These two logical operations can be used to combine the results of sub
4337 expressions. Note, unlike the comparison operators a true result returns a
4338 value of 1 but a false results does still return 0. Also note that the logical
4339 or operator has a slightly lower precedence than logical and.
4344 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4345 address; you can only have a defined section in one of the two arguments.
4348 @chapter Assembler Directives
4350 @cindex directives, machine independent
4351 @cindex pseudo-ops, machine independent
4352 @cindex machine independent directives
4353 All assembler directives have names that begin with a period (@samp{.}).
4354 The names are case insensitive for most targets, and usually written
4357 This chapter discusses directives that are available regardless of the
4358 target machine configuration for the @sc{gnu} assembler.
4360 Some machine configurations provide additional directives.
4361 @xref{Machine Dependencies}.
4364 @ifset machine-directives
4365 @xref{Machine Dependencies}, for additional directives.
4370 * Abort:: @code{.abort}
4372 * ABORT (COFF):: @code{.ABORT}
4375 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4376 * Altmacro:: @code{.altmacro}
4377 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4378 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4379 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4380 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4381 * Byte:: @code{.byte @var{expressions}}
4382 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4383 * Comm:: @code{.comm @var{symbol} , @var{length} }
4384 * Data:: @code{.data @var{subsection}}
4386 * Def:: @code{.def @var{name}}
4389 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4395 * Double:: @code{.double @var{flonums}}
4396 * Eject:: @code{.eject}
4397 * Else:: @code{.else}
4398 * Elseif:: @code{.elseif}
4401 * Endef:: @code{.endef}
4404 * Endfunc:: @code{.endfunc}
4405 * Endif:: @code{.endif}
4406 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4407 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4408 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4410 * Error:: @code{.error @var{string}}
4411 * Exitm:: @code{.exitm}
4412 * Extern:: @code{.extern}
4413 * Fail:: @code{.fail}
4414 * File:: @code{.file}
4415 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4416 * Float:: @code{.float @var{flonums}}
4417 * Func:: @code{.func}
4418 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4420 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4421 * Hidden:: @code{.hidden @var{names}}
4424 * hword:: @code{.hword @var{expressions}}
4425 * Ident:: @code{.ident}
4426 * If:: @code{.if @var{absolute expression}}
4427 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4428 * Include:: @code{.include "@var{file}"}
4429 * Int:: @code{.int @var{expressions}}
4431 * Internal:: @code{.internal @var{names}}
4434 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4435 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4436 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4437 * Lflags:: @code{.lflags}
4438 @ifclear no-line-dir
4439 * Line:: @code{.line @var{line-number}}
4442 * Linkonce:: @code{.linkonce [@var{type}]}
4443 * List:: @code{.list}
4444 * Ln:: @code{.ln @var{line-number}}
4445 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4446 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4448 * Local:: @code{.local @var{names}}
4451 * Long:: @code{.long @var{expressions}}
4453 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4456 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4457 * MRI:: @code{.mri @var{val}}
4458 * Noaltmacro:: @code{.noaltmacro}
4459 * Nolist:: @code{.nolist}
4460 * Octa:: @code{.octa @var{bignums}}
4461 * Offset:: @code{.offset @var{loc}}
4462 * Org:: @code{.org @var{new-lc}, @var{fill}}
4463 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4465 * PopSection:: @code{.popsection}
4466 * Previous:: @code{.previous}
4469 * Print:: @code{.print @var{string}}
4471 * Protected:: @code{.protected @var{names}}
4474 * Psize:: @code{.psize @var{lines}, @var{columns}}
4475 * Purgem:: @code{.purgem @var{name}}
4477 * PushSection:: @code{.pushsection @var{name}}
4480 * Quad:: @code{.quad @var{bignums}}
4481 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4482 * Rept:: @code{.rept @var{count}}
4483 * Sbttl:: @code{.sbttl "@var{subheading}"}
4485 * Scl:: @code{.scl @var{class}}
4488 * Section:: @code{.section @var{name}[, @var{flags}]}
4491 * Set:: @code{.set @var{symbol}, @var{expression}}
4492 * Short:: @code{.short @var{expressions}}
4493 * Single:: @code{.single @var{flonums}}
4495 * Size:: @code{.size [@var{name} , @var{expression}]}
4497 @ifclear no-space-dir
4498 * Skip:: @code{.skip @var{size} , @var{fill}}
4501 * Sleb128:: @code{.sleb128 @var{expressions}}
4502 @ifclear no-space-dir
4503 * Space:: @code{.space @var{size} , @var{fill}}
4506 * Stab:: @code{.stabd, .stabn, .stabs}
4509 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4510 * Struct:: @code{.struct @var{expression}}
4512 * SubSection:: @code{.subsection}
4513 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4517 * Tag:: @code{.tag @var{structname}}
4520 * Text:: @code{.text @var{subsection}}
4521 * Title:: @code{.title "@var{heading}"}
4523 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4526 * Uleb128:: @code{.uleb128 @var{expressions}}
4528 * Val:: @code{.val @var{addr}}
4532 * Version:: @code{.version "@var{string}"}
4533 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4534 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4537 * Warning:: @code{.warning @var{string}}
4538 * Weak:: @code{.weak @var{names}}
4539 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4540 * Word:: @code{.word @var{expressions}}
4541 @ifclear no-space-dir
4542 * Zero:: @code{.zero @var{size}}
4544 * Deprecated:: Deprecated Directives
4548 @section @code{.abort}
4550 @cindex @code{abort} directive
4551 @cindex stopping the assembly
4552 This directive stops the assembly immediately. It is for
4553 compatibility with other assemblers. The original idea was that the
4554 assembly language source would be piped into the assembler. If the sender
4555 of the source quit, it could use this directive tells @command{@value{AS}} to
4556 quit also. One day @code{.abort} will not be supported.
4560 @section @code{.ABORT} (COFF)
4562 @cindex @code{ABORT} directive
4563 When producing COFF output, @command{@value{AS}} accepts this directive as a
4564 synonym for @samp{.abort}.
4567 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4573 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4575 @cindex padding the location counter
4576 @cindex @code{align} directive
4577 Pad the location counter (in the current subsection) to a particular storage
4578 boundary. The first expression (which must be absolute) is the alignment
4579 required, as described below.
4581 The second expression (also absolute) gives the fill value to be stored in the
4582 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4583 padding bytes are normally zero. However, on some systems, if the section is
4584 marked as containing code and the fill value is omitted, the space is filled
4585 with no-op instructions.
4587 The third expression is also absolute, and is also optional. If it is present,
4588 it is the maximum number of bytes that should be skipped by this alignment
4589 directive. If doing the alignment would require skipping more bytes than the
4590 specified maximum, then the alignment is not done at all. You can omit the
4591 fill value (the second argument) entirely by simply using two commas after the
4592 required alignment; this can be useful if you want the alignment to be filled
4593 with no-op instructions when appropriate.
4595 The way the required alignment is specified varies from system to system.
4596 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4597 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4598 alignment request in bytes. For example @samp{.align 8} advances
4599 the location counter until it is a multiple of 8. If the location counter
4600 is already a multiple of 8, no change is needed. For the tic54x, the
4601 first expression is the alignment request in words.
4603 For other systems, including ppc, i386 using a.out format, arm and
4604 strongarm, it is the
4605 number of low-order zero bits the location counter must have after
4606 advancement. For example @samp{.align 3} advances the location
4607 counter until it a multiple of 8. If the location counter is already a
4608 multiple of 8, no change is needed.
4610 This inconsistency is due to the different behaviors of the various
4611 native assemblers for these systems which GAS must emulate.
4612 GAS also provides @code{.balign} and @code{.p2align} directives,
4613 described later, which have a consistent behavior across all
4614 architectures (but are specific to GAS).
4617 @section @code{.altmacro}
4618 Enable alternate macro mode, enabling:
4621 @item LOCAL @var{name} [ , @dots{} ]
4622 One additional directive, @code{LOCAL}, is available. It is used to
4623 generate a string replacement for each of the @var{name} arguments, and
4624 replace any instances of @var{name} in each macro expansion. The
4625 replacement string is unique in the assembly, and different for each
4626 separate macro expansion. @code{LOCAL} allows you to write macros that
4627 define symbols, without fear of conflict between separate macro expansions.
4629 @item String delimiters
4630 You can write strings delimited in these other ways besides
4631 @code{"@var{string}"}:
4634 @item '@var{string}'
4635 You can delimit strings with single-quote characters.
4637 @item <@var{string}>
4638 You can delimit strings with matching angle brackets.
4641 @item single-character string escape
4642 To include any single character literally in a string (even if the
4643 character would otherwise have some special meaning), you can prefix the
4644 character with @samp{!} (an exclamation mark). For example, you can
4645 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4647 @item Expression results as strings
4648 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4649 and use the result as a string.
4653 @section @code{.ascii "@var{string}"}@dots{}
4655 @cindex @code{ascii} directive
4656 @cindex string literals
4657 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4658 separated by commas. It assembles each string (with no automatic
4659 trailing zero byte) into consecutive addresses.
4662 @section @code{.asciz "@var{string}"}@dots{}
4664 @cindex @code{asciz} directive
4665 @cindex zero-terminated strings
4666 @cindex null-terminated strings
4667 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4668 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4671 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4673 @cindex padding the location counter given number of bytes
4674 @cindex @code{balign} directive
4675 Pad the location counter (in the current subsection) to a particular
4676 storage boundary. The first expression (which must be absolute) is the
4677 alignment request in bytes. For example @samp{.balign 8} advances
4678 the location counter until it is a multiple of 8. If the location counter
4679 is already a multiple of 8, no change is needed.
4681 The second expression (also absolute) gives the fill value to be stored in the
4682 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4683 padding bytes are normally zero. However, on some systems, if the section is
4684 marked as containing code and the fill value is omitted, the space is filled
4685 with no-op instructions.
4687 The third expression is also absolute, and is also optional. If it is present,
4688 it is the maximum number of bytes that should be skipped by this alignment
4689 directive. If doing the alignment would require skipping more bytes than the
4690 specified maximum, then the alignment is not done at all. You can omit the
4691 fill value (the second argument) entirely by simply using two commas after the
4692 required alignment; this can be useful if you want the alignment to be filled
4693 with no-op instructions when appropriate.
4695 @cindex @code{balignw} directive
4696 @cindex @code{balignl} directive
4697 The @code{.balignw} and @code{.balignl} directives are variants of the
4698 @code{.balign} directive. The @code{.balignw} directive treats the fill
4699 pattern as a two byte word value. The @code{.balignl} directives treats the
4700 fill pattern as a four byte longword value. For example, @code{.balignw
4701 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4702 filled in with the value 0x368d (the exact placement of the bytes depends upon
4703 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4706 @node Bundle directives
4707 @section Bundle directives
4708 @subsection @code{.bundle_align_mode @var{abs-expr}}
4709 @cindex @code{bundle_align_mode} directive
4711 @cindex instruction bundle
4712 @cindex aligned instruction bundle
4713 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4714 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4715 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4716 disabled (which is the default state). If the argument it not zero, it
4717 gives the size of an instruction bundle as a power of two (as for the
4718 @code{.p2align} directive, @pxref{P2align}).
4720 For some targets, it's an ABI requirement that no instruction may span a
4721 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4722 instructions that starts on an aligned boundary. For example, if
4723 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4724 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4725 effect, no single instruction may span a boundary between bundles. If an
4726 instruction would start too close to the end of a bundle for the length of
4727 that particular instruction to fit within the bundle, then the space at the
4728 end of that bundle is filled with no-op instructions so the instruction
4729 starts in the next bundle. As a corollary, it's an error if any single
4730 instruction's encoding is longer than the bundle size.
4732 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4733 @cindex @code{bundle_lock} directive
4734 @cindex @code{bundle_unlock} directive
4735 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4736 allow explicit control over instruction bundle padding. These directives
4737 are only valid when @code{.bundle_align_mode} has been used to enable
4738 aligned instruction bundle mode. It's an error if they appear when
4739 @code{.bundle_align_mode} has not been used at all, or when the last
4740 directive was @w{@code{.bundle_align_mode 0}}.
4742 @cindex bundle-locked
4743 For some targets, it's an ABI requirement that certain instructions may
4744 appear only as part of specified permissible sequences of multiple
4745 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4746 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4747 instruction sequence. For purposes of aligned instruction bundle mode, a
4748 sequence starting with @code{.bundle_lock} and ending with
4749 @code{.bundle_unlock} is treated as a single instruction. That is, the
4750 entire sequence must fit into a single bundle and may not span a bundle
4751 boundary. If necessary, no-op instructions will be inserted before the
4752 first instruction of the sequence so that the whole sequence starts on an
4753 aligned bundle boundary. It's an error if the sequence is longer than the
4756 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4757 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4758 nested. That is, a second @code{.bundle_lock} directive before the next
4759 @code{.bundle_unlock} directive has no effect except that it must be
4760 matched by another closing @code{.bundle_unlock} so that there is the
4761 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4764 @section @code{.byte @var{expressions}}
4766 @cindex @code{byte} directive
4767 @cindex integers, one byte
4768 @code{.byte} expects zero or more expressions, separated by commas.
4769 Each expression is assembled into the next byte.
4771 @node CFI directives
4772 @section CFI directives
4773 @subsection @code{.cfi_sections @var{section_list}}
4774 @cindex @code{cfi_sections} directive
4775 @code{.cfi_sections} may be used to specify whether CFI directives
4776 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4777 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4778 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4779 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4780 directive is not used is @code{.cfi_sections .eh_frame}.
4782 On targets that support compact unwinding tables these can be generated
4783 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4785 Some targets may support an additional name, such as @code{.c6xabi.exidx}
4786 which is used by the @value{TIC6X} target.
4788 The @code{.cfi_sections} directive can be repeated, with the same or different
4789 arguments, provided that CFI generation has not yet started. Once CFI
4790 generation has started however the section list is fixed and any attempts to
4791 redefine it will result in an error.
4793 @subsection @code{.cfi_startproc [simple]}
4794 @cindex @code{cfi_startproc} directive
4795 @code{.cfi_startproc} is used at the beginning of each function that
4796 should have an entry in @code{.eh_frame}. It initializes some internal
4797 data structures. Don't forget to close the function by
4798 @code{.cfi_endproc}.
4800 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4801 it also emits some architecture dependent initial CFI instructions.
4803 @subsection @code{.cfi_endproc}
4804 @cindex @code{cfi_endproc} directive
4805 @code{.cfi_endproc} is used at the end of a function where it closes its
4806 unwind entry previously opened by
4807 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4809 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4810 @cindex @code{cfi_personality} directive
4811 @code{.cfi_personality} defines personality routine and its encoding.
4812 @var{encoding} must be a constant determining how the personality
4813 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4814 argument is not present, otherwise second argument should be
4815 a constant or a symbol name. When using indirect encodings,
4816 the symbol provided should be the location where personality
4817 can be loaded from, not the personality routine itself.
4818 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4819 no personality routine.
4821 @subsection @code{.cfi_personality_id @var{id}}
4822 @cindex @code{cfi_personality_id} directive
4823 @code{cfi_personality_id} defines a personality routine by its index as
4824 defined in a compact unwinding format.
4825 Only valid when generating compact EH frames (i.e.
4826 with @code{.cfi_sections eh_frame_entry}.
4828 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4829 @cindex @code{cfi_fde_data} directive
4830 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4831 used for the current function. These are emitted inline in the
4832 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4833 in the @code{.gnu.extab} section otherwise.
4834 Only valid when generating compact EH frames (i.e.
4835 with @code{.cfi_sections eh_frame_entry}.
4837 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4838 @code{.cfi_lsda} defines LSDA and its encoding.
4839 @var{encoding} must be a constant determining how the LSDA
4840 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4841 argument is not present, otherwise the second argument should be a constant
4842 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4843 meaning that no LSDA is present.
4845 @subsection @code{.cfi_inline_lsda} [@var{align}]
4846 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4847 switches to the corresponding @code{.gnu.extab} section.
4848 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4849 Only valid when generating compact EH frames (i.e.
4850 with @code{.cfi_sections eh_frame_entry}.
4852 The table header and unwinding opcodes will be generated at this point,
4853 so that they are immediately followed by the LSDA data. The symbol
4854 referenced by the @code{.cfi_lsda} directive should still be defined
4855 in case a fallback FDE based encoding is used. The LSDA data is terminated
4856 by a section directive.
4858 The optional @var{align} argument specifies the alignment required.
4859 The alignment is specified as a power of two, as with the
4860 @code{.p2align} directive.
4862 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4863 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4864 address from @var{register} and add @var{offset} to it}.
4866 @subsection @code{.cfi_def_cfa_register @var{register}}
4867 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4868 now on @var{register} will be used instead of the old one. Offset
4871 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4872 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4873 remains the same, but @var{offset} is new. Note that it is the
4874 absolute offset that will be added to a defined register to compute
4877 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4878 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4879 value that is added/subtracted from the previous offset.
4881 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4882 Previous value of @var{register} is saved at offset @var{offset} from
4885 @subsection @code{.cfi_val_offset @var{register}, @var{offset}}
4886 Previous value of @var{register} is CFA + @var{offset}.
4888 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4889 Previous value of @var{register} is saved at offset @var{offset} from
4890 the current CFA register. This is transformed to @code{.cfi_offset}
4891 using the known displacement of the CFA register from the CFA.
4892 This is often easier to use, because the number will match the
4893 code it's annotating.
4895 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4896 Previous value of @var{register1} is saved in register @var{register2}.
4898 @subsection @code{.cfi_restore @var{register}}
4899 @code{.cfi_restore} says that the rule for @var{register} is now the
4900 same as it was at the beginning of the function, after all initial
4901 instruction added by @code{.cfi_startproc} were executed.
4903 @subsection @code{.cfi_undefined @var{register}}
4904 From now on the previous value of @var{register} can't be restored anymore.
4906 @subsection @code{.cfi_same_value @var{register}}
4907 Current value of @var{register} is the same like in the previous frame,
4908 i.e. no restoration needed.
4910 @subsection @code{.cfi_remember_state} and @code{.cfi_restore_state}
4911 @code{.cfi_remember_state} pushes the set of rules for every register onto an
4912 implicit stack, while @code{.cfi_restore_state} pops them off the stack and
4913 places them in the current row. This is useful for situations where you have
4914 multiple @code{.cfi_*} directives that need to be undone due to the control
4915 flow of the program. For example, we could have something like this (assuming
4916 the CFA is the value of @code{rbp}):
4926 .cfi_def_cfa %rsp, 8
4929 /* Do something else */
4932 Here, we want the @code{.cfi} directives to affect only the rows corresponding
4933 to the instructions before @code{label}. This means we'd have to add multiple
4934 @code{.cfi} directives after @code{label} to recreate the original save
4935 locations of the registers, as well as setting the CFA back to the value of
4936 @code{rbp}. This would be clumsy, and result in a larger binary size. Instead,
4948 .cfi_def_cfa %rsp, 8
4952 /* Do something else */
4955 That way, the rules for the instructions after @code{label} will be the same
4956 as before the first @code{.cfi_restore} without having to use multiple
4957 @code{.cfi} directives.
4959 @subsection @code{.cfi_return_column @var{register}}
4960 Change return column @var{register}, i.e. the return address is either
4961 directly in @var{register} or can be accessed by rules for @var{register}.
4963 @subsection @code{.cfi_signal_frame}
4964 Mark current function as signal trampoline.
4966 @subsection @code{.cfi_window_save}
4967 SPARC register window has been saved.
4969 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4970 Allows the user to add arbitrary bytes to the unwind info. One
4971 might use this to add OS-specific CFI opcodes, or generic CFI
4972 opcodes that GAS does not yet support.
4974 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4975 The current value of @var{register} is @var{label}. The value of @var{label}
4976 will be encoded in the output file according to @var{encoding}; see the
4977 description of @code{.cfi_personality} for details on this encoding.
4979 The usefulness of equating a register to a fixed label is probably
4980 limited to the return address register. Here, it can be useful to
4981 mark a code segment that has only one return address which is reached
4982 by a direct branch and no copy of the return address exists in memory
4983 or another register.
4986 @section @code{.comm @var{symbol} , @var{length} }
4988 @cindex @code{comm} directive
4989 @cindex symbol, common
4990 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4991 common symbol in one object file may be merged with a defined or common symbol
4992 of the same name in another object file. If @code{@value{LD}} does not see a
4993 definition for the symbol--just one or more common symbols--then it will
4994 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4995 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4996 the same name, and they do not all have the same size, it will allocate space
4997 using the largest size.
5000 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
5001 an optional third argument. This is the desired alignment of the symbol,
5002 specified for ELF as a byte boundary (for example, an alignment of 16 means
5003 that the least significant 4 bits of the address should be zero), and for PE
5004 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
5005 boundary). The alignment must be an absolute expression, and it must be a
5006 power of two. If @code{@value{LD}} allocates uninitialized memory for the
5007 common symbol, it will use the alignment when placing the symbol. If no
5008 alignment is specified, @command{@value{AS}} will set the alignment to the
5009 largest power of two less than or equal to the size of the symbol, up to a
5010 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
5011 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
5012 @samp{--section-alignment} option; image file sections in PE are aligned to
5013 multiples of 4096, which is far too large an alignment for ordinary variables.
5014 It is rather the default alignment for (non-debug) sections within object
5015 (@samp{*.o}) files, which are less strictly aligned.}.
5019 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
5020 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
5024 @section @code{.data @var{subsection}}
5026 @cindex @code{data} directive
5027 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
5028 end of the data subsection numbered @var{subsection} (which is an
5029 absolute expression). If @var{subsection} is omitted, it defaults
5034 @section @code{.def @var{name}}
5036 @cindex @code{def} directive
5037 @cindex COFF symbols, debugging
5038 @cindex debugging COFF symbols
5039 Begin defining debugging information for a symbol @var{name}; the
5040 definition extends until the @code{.endef} directive is encountered.
5043 This directive is only observed when @command{@value{AS}} is configured for COFF
5044 format output; when producing @code{b.out}, @samp{.def} is recognized,
5051 @section @code{.desc @var{symbol}, @var{abs-expression}}
5053 @cindex @code{desc} directive
5054 @cindex COFF symbol descriptor
5055 @cindex symbol descriptor, COFF
5056 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
5057 to the low 16 bits of an absolute expression.
5060 The @samp{.desc} directive is not available when @command{@value{AS}} is
5061 configured for COFF output; it is only for @code{a.out} or @code{b.out}
5062 object format. For the sake of compatibility, @command{@value{AS}} accepts
5063 it, but produces no output, when configured for COFF.
5069 @section @code{.dim}
5071 @cindex @code{dim} directive
5072 @cindex COFF auxiliary symbol information
5073 @cindex auxiliary symbol information, COFF
5074 This directive is generated by compilers to include auxiliary debugging
5075 information in the symbol table. It is only permitted inside
5076 @code{.def}/@code{.endef} pairs.
5079 @samp{.dim} is only meaningful when generating COFF format output; when
5080 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5086 @section @code{.double @var{flonums}}
5088 @cindex @code{double} directive
5089 @cindex floating point numbers (double)
5090 @code{.double} expects zero or more flonums, separated by commas. It
5091 assembles floating point numbers.
5093 The exact kind of floating point numbers emitted depends on how
5094 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5098 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
5099 in @sc{ieee} format.
5104 @section @code{.eject}
5106 @cindex @code{eject} directive
5107 @cindex new page, in listings
5108 @cindex page, in listings
5109 @cindex listing control: new page
5110 Force a page break at this point, when generating assembly listings.
5113 @section @code{.else}
5115 @cindex @code{else} directive
5116 @code{.else} is part of the @command{@value{AS}} support for conditional
5117 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
5118 of code to be assembled if the condition for the preceding @code{.if}
5122 @section @code{.elseif}
5124 @cindex @code{elseif} directive
5125 @code{.elseif} is part of the @command{@value{AS}} support for conditional
5126 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
5127 @code{.if} block that would otherwise fill the entire @code{.else} section.
5130 @section @code{.end}
5132 @cindex @code{end} directive
5133 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
5134 process anything in the file past the @code{.end} directive.
5138 @section @code{.endef}
5140 @cindex @code{endef} directive
5141 This directive flags the end of a symbol definition begun with
5145 @samp{.endef} is only meaningful when generating COFF format output; if
5146 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
5147 directive but ignores it.
5152 @section @code{.endfunc}
5153 @cindex @code{endfunc} directive
5154 @code{.endfunc} marks the end of a function specified with @code{.func}.
5157 @section @code{.endif}
5159 @cindex @code{endif} directive
5160 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
5161 it marks the end of a block of code that is only assembled
5162 conditionally. @xref{If,,@code{.if}}.
5165 @section @code{.equ @var{symbol}, @var{expression}}
5167 @cindex @code{equ} directive
5168 @cindex assigning values to symbols
5169 @cindex symbols, assigning values to
5170 This directive sets the value of @var{symbol} to @var{expression}.
5171 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
5174 The syntax for @code{equ} on the HPPA is
5175 @samp{@var{symbol} .equ @var{expression}}.
5179 The syntax for @code{equ} on the Z80 is
5180 @samp{@var{symbol} equ @var{expression}}.
5181 On the Z80 it is an error if @var{symbol} is already defined,
5182 but the symbol is not protected from later redefinition.
5183 Compare @ref{Equiv}.
5187 @section @code{.equiv @var{symbol}, @var{expression}}
5188 @cindex @code{equiv} directive
5189 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5190 the assembler will signal an error if @var{symbol} is already defined. Note a
5191 symbol which has been referenced but not actually defined is considered to be
5194 Except for the contents of the error message, this is roughly equivalent to
5201 plus it protects the symbol from later redefinition.
5204 @section @code{.eqv @var{symbol}, @var{expression}}
5205 @cindex @code{eqv} directive
5206 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5207 evaluate the expression or any part of it immediately. Instead each time
5208 the resulting symbol is used in an expression, a snapshot of its current
5212 @section @code{.err}
5213 @cindex @code{err} directive
5214 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5215 message and, unless the @option{-Z} option was used, it will not generate an
5216 object file. This can be used to signal an error in conditionally compiled code.
5219 @section @code{.error "@var{string}"}
5220 @cindex error directive
5222 Similarly to @code{.err}, this directive emits an error, but you can specify a
5223 string that will be emitted as the error message. If you don't specify the
5224 message, it defaults to @code{".error directive invoked in source file"}.
5225 @xref{Errors, ,Error and Warning Messages}.
5228 .error "This code has not been assembled and tested."
5232 @section @code{.exitm}
5233 Exit early from the current macro definition. @xref{Macro}.
5236 @section @code{.extern}
5238 @cindex @code{extern} directive
5239 @code{.extern} is accepted in the source program---for compatibility
5240 with other assemblers---but it is ignored. @command{@value{AS}} treats
5241 all undefined symbols as external.
5244 @section @code{.fail @var{expression}}
5246 @cindex @code{fail} directive
5247 Generates an error or a warning. If the value of the @var{expression} is 500
5248 or more, @command{@value{AS}} will print a warning message. If the value is less
5249 than 500, @command{@value{AS}} will print an error message. The message will
5250 include the value of @var{expression}. This can occasionally be useful inside
5251 complex nested macros or conditional assembly.
5254 @section @code{.file}
5255 @cindex @code{file} directive
5257 @ifclear no-file-dir
5258 There are two different versions of the @code{.file} directive. Targets
5259 that support DWARF2 line number information use the DWARF2 version of
5260 @code{.file}. Other targets use the default version.
5262 @subheading Default Version
5264 @cindex logical file name
5265 @cindex file name, logical
5266 This version of the @code{.file} directive tells @command{@value{AS}} that we
5267 are about to start a new logical file. The syntax is:
5273 @var{string} is the new file name. In general, the filename is
5274 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5275 to specify an empty file name, you must give the quotes--@code{""}. This
5276 statement may go away in future: it is only recognized to be compatible with
5277 old @command{@value{AS}} programs.
5279 @subheading DWARF2 Version
5282 When emitting DWARF2 line number information, @code{.file} assigns filenames
5283 to the @code{.debug_line} file name table. The syntax is:
5286 .file @var{fileno} @var{filename}
5289 The @var{fileno} operand should be a unique positive integer to use as the
5290 index of the entry in the table. The @var{filename} operand is a C string
5293 The detail of filename indices is exposed to the user because the filename
5294 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5295 information, and thus the user must know the exact indices that table
5299 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5301 @cindex @code{fill} directive
5302 @cindex writing patterns in memory
5303 @cindex patterns, writing in memory
5304 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5305 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5306 may be zero or more. @var{Size} may be zero or more, but if it is
5307 more than 8, then it is deemed to have the value 8, compatible with
5308 other people's assemblers. The contents of each @var{repeat} bytes
5309 is taken from an 8-byte number. The highest order 4 bytes are
5310 zero. The lowest order 4 bytes are @var{value} rendered in the
5311 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5312 Each @var{size} bytes in a repetition is taken from the lowest order
5313 @var{size} bytes of this number. Again, this bizarre behavior is
5314 compatible with other people's assemblers.
5316 @var{size} and @var{value} are optional.
5317 If the second comma and @var{value} are absent, @var{value} is
5318 assumed zero. If the first comma and following tokens are absent,
5319 @var{size} is assumed to be 1.
5322 @section @code{.float @var{flonums}}
5324 @cindex floating point numbers (single)
5325 @cindex @code{float} directive
5326 This directive assembles zero or more flonums, separated by commas. It
5327 has the same effect as @code{.single}.
5329 The exact kind of floating point numbers emitted depends on how
5330 @command{@value{AS}} is configured.
5331 @xref{Machine Dependencies}.
5335 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5336 in @sc{ieee} format.
5341 @section @code{.func @var{name}[,@var{label}]}
5342 @cindex @code{func} directive
5343 @code{.func} emits debugging information to denote function @var{name}, and
5344 is ignored unless the file is assembled with debugging enabled.
5345 Only @samp{--gstabs[+]} is currently supported.
5346 @var{label} is the entry point of the function and if omitted @var{name}
5347 prepended with the @samp{leading char} is used.
5348 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5349 All functions are currently defined to have @code{void} return type.
5350 The function must be terminated with @code{.endfunc}.
5353 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5355 @cindex @code{global} directive
5356 @cindex symbol, making visible to linker
5357 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5358 @var{symbol} in your partial program, its value is made available to
5359 other partial programs that are linked with it. Otherwise,
5360 @var{symbol} takes its attributes from a symbol of the same name
5361 from another file linked into the same program.
5363 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5364 compatibility with other assemblers.
5367 On the HPPA, @code{.global} is not always enough to make it accessible to other
5368 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5369 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5374 @section @code{.gnu_attribute @var{tag},@var{value}}
5375 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5378 @section @code{.hidden @var{names}}
5380 @cindex @code{hidden} directive
5382 This is one of the ELF visibility directives. The other two are
5383 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5384 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5386 This directive overrides the named symbols default visibility (which is set by
5387 their binding: local, global or weak). The directive sets the visibility to
5388 @code{hidden} which means that the symbols are not visible to other components.
5389 Such symbols are always considered to be @code{protected} as well.
5393 @section @code{.hword @var{expressions}}
5395 @cindex @code{hword} directive
5396 @cindex integers, 16-bit
5397 @cindex numbers, 16-bit
5398 @cindex sixteen bit integers
5399 This expects zero or more @var{expressions}, and emits
5400 a 16 bit number for each.
5403 This directive is a synonym for @samp{.short}; depending on the target
5404 architecture, it may also be a synonym for @samp{.word}.
5408 This directive is a synonym for @samp{.short}.
5411 This directive is a synonym for both @samp{.short} and @samp{.word}.
5416 @section @code{.ident}
5418 @cindex @code{ident} directive
5420 This directive is used by some assemblers to place tags in object files. The
5421 behavior of this directive varies depending on the target. When using the
5422 a.out object file format, @command{@value{AS}} simply accepts the directive for
5423 source-file compatibility with existing assemblers, but does not emit anything
5424 for it. When using COFF, comments are emitted to the @code{.comment} or
5425 @code{.rdata} section, depending on the target. When using ELF, comments are
5426 emitted to the @code{.comment} section.
5429 @section @code{.if @var{absolute expression}}
5431 @cindex conditional assembly
5432 @cindex @code{if} directive
5433 @code{.if} marks the beginning of a section of code which is only
5434 considered part of the source program being assembled if the argument
5435 (which must be an @var{absolute expression}) is non-zero. The end of
5436 the conditional section of code must be marked by @code{.endif}
5437 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5438 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5439 If you have several conditions to check, @code{.elseif} may be used to avoid
5440 nesting blocks if/else within each subsequent @code{.else} block.
5442 The following variants of @code{.if} are also supported:
5444 @cindex @code{ifdef} directive
5445 @item .ifdef @var{symbol}
5446 Assembles the following section of code if the specified @var{symbol}
5447 has been defined. Note a symbol which has been referenced but not yet defined
5448 is considered to be undefined.
5450 @cindex @code{ifb} directive
5451 @item .ifb @var{text}
5452 Assembles the following section of code if the operand is blank (empty).
5454 @cindex @code{ifc} directive
5455 @item .ifc @var{string1},@var{string2}
5456 Assembles the following section of code if the two strings are the same. The
5457 strings may be optionally quoted with single quotes. If they are not quoted,
5458 the first string stops at the first comma, and the second string stops at the
5459 end of the line. Strings which contain whitespace should be quoted. The
5460 string comparison is case sensitive.
5462 @cindex @code{ifeq} directive
5463 @item .ifeq @var{absolute expression}
5464 Assembles the following section of code if the argument is zero.
5466 @cindex @code{ifeqs} directive
5467 @item .ifeqs @var{string1},@var{string2}
5468 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5470 @cindex @code{ifge} directive
5471 @item .ifge @var{absolute expression}
5472 Assembles the following section of code if the argument is greater than or
5475 @cindex @code{ifgt} directive
5476 @item .ifgt @var{absolute expression}
5477 Assembles the following section of code if the argument is greater than zero.
5479 @cindex @code{ifle} directive
5480 @item .ifle @var{absolute expression}
5481 Assembles the following section of code if the argument is less than or equal
5484 @cindex @code{iflt} directive
5485 @item .iflt @var{absolute expression}
5486 Assembles the following section of code if the argument is less than zero.
5488 @cindex @code{ifnb} directive
5489 @item .ifnb @var{text}
5490 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5491 following section of code if the operand is non-blank (non-empty).
5493 @cindex @code{ifnc} directive
5494 @item .ifnc @var{string1},@var{string2}.
5495 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5496 following section of code if the two strings are not the same.
5498 @cindex @code{ifndef} directive
5499 @cindex @code{ifnotdef} directive
5500 @item .ifndef @var{symbol}
5501 @itemx .ifnotdef @var{symbol}
5502 Assembles the following section of code if the specified @var{symbol}
5503 has not been defined. Both spelling variants are equivalent. Note a symbol
5504 which has been referenced but not yet defined is considered to be undefined.
5506 @cindex @code{ifne} directive
5507 @item .ifne @var{absolute expression}
5508 Assembles the following section of code if the argument is not equal to zero
5509 (in other words, this is equivalent to @code{.if}).
5511 @cindex @code{ifnes} directive
5512 @item .ifnes @var{string1},@var{string2}
5513 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5514 following section of code if the two strings are not the same.
5518 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5520 @cindex @code{incbin} directive
5521 @cindex binary files, including
5522 The @code{incbin} directive includes @var{file} verbatim at the current
5523 location. You can control the search paths used with the @samp{-I} command-line
5524 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5527 The @var{skip} argument skips a number of bytes from the start of the
5528 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5529 read. Note that the data is not aligned in any way, so it is the user's
5530 responsibility to make sure that proper alignment is provided both before and
5531 after the @code{incbin} directive.
5534 @section @code{.include "@var{file}"}
5536 @cindex @code{include} directive
5537 @cindex supporting files, including
5538 @cindex files, including
5539 This directive provides a way to include supporting files at specified
5540 points in your source program. The code from @var{file} is assembled as
5541 if it followed the point of the @code{.include}; when the end of the
5542 included file is reached, assembly of the original file continues. You
5543 can control the search paths used with the @samp{-I} command-line option
5544 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5548 @section @code{.int @var{expressions}}
5550 @cindex @code{int} directive
5551 @cindex integers, 32-bit
5552 Expect zero or more @var{expressions}, of any section, separated by commas.
5553 For each expression, emit a number that, at run time, is the value of that
5554 expression. The byte order and bit size of the number depends on what kind
5555 of target the assembly is for.
5559 On most forms of the H8/300, @code{.int} emits 16-bit
5560 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5567 @section @code{.internal @var{names}}
5569 @cindex @code{internal} directive
5571 This is one of the ELF visibility directives. The other two are
5572 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5573 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5575 This directive overrides the named symbols default visibility (which is set by
5576 their binding: local, global or weak). The directive sets the visibility to
5577 @code{internal} which means that the symbols are considered to be @code{hidden}
5578 (i.e., not visible to other components), and that some extra, processor specific
5579 processing must also be performed upon the symbols as well.
5583 @section @code{.irp @var{symbol},@var{values}}@dots{}
5585 @cindex @code{irp} directive
5586 Evaluate a sequence of statements assigning different values to @var{symbol}.
5587 The sequence of statements starts at the @code{.irp} directive, and is
5588 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5589 set to @var{value}, and the sequence of statements is assembled. If no
5590 @var{value} is listed, the sequence of statements is assembled once, with
5591 @var{symbol} set to the null string. To refer to @var{symbol} within the
5592 sequence of statements, use @var{\symbol}.
5594 For example, assembling
5602 is equivalent to assembling
5610 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5613 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5615 @cindex @code{irpc} directive
5616 Evaluate a sequence of statements assigning different values to @var{symbol}.
5617 The sequence of statements starts at the @code{.irpc} directive, and is
5618 terminated by an @code{.endr} directive. For each character in @var{value},
5619 @var{symbol} is set to the character, and the sequence of statements is
5620 assembled. If no @var{value} is listed, the sequence of statements is
5621 assembled once, with @var{symbol} set to the null string. To refer to
5622 @var{symbol} within the sequence of statements, use @var{\symbol}.
5624 For example, assembling
5632 is equivalent to assembling
5640 For some caveats with the spelling of @var{symbol}, see also the discussion
5644 @section @code{.lcomm @var{symbol} , @var{length}}
5646 @cindex @code{lcomm} directive
5647 @cindex local common symbols
5648 @cindex symbols, local common
5649 Reserve @var{length} (an absolute expression) bytes for a local common
5650 denoted by @var{symbol}. The section and value of @var{symbol} are
5651 those of the new local common. The addresses are allocated in the bss
5652 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5653 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5654 not visible to @code{@value{LD}}.
5657 Some targets permit a third argument to be used with @code{.lcomm}. This
5658 argument specifies the desired alignment of the symbol in the bss section.
5662 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5663 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5667 @section @code{.lflags}
5669 @cindex @code{lflags} directive (ignored)
5670 @command{@value{AS}} accepts this directive, for compatibility with other
5671 assemblers, but ignores it.
5673 @ifclear no-line-dir
5675 @section @code{.line @var{line-number}}
5677 @cindex @code{line} directive
5678 @cindex logical line number
5680 Change the logical line number. @var{line-number} must be an absolute
5681 expression. The next line has that logical line number. Therefore any other
5682 statements on the current line (after a statement separator character) are
5683 reported as on logical line number @var{line-number} @minus{} 1. One day
5684 @command{@value{AS}} will no longer support this directive: it is recognized only
5685 for compatibility with existing assembler programs.
5688 Even though this is a directive associated with the @code{a.out} or
5689 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5690 when producing COFF output, and treats @samp{.line} as though it
5691 were the COFF @samp{.ln} @emph{if} it is found outside a
5692 @code{.def}/@code{.endef} pair.
5694 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5695 used by compilers to generate auxiliary symbol information for
5700 @section @code{.linkonce [@var{type}]}
5702 @cindex @code{linkonce} directive
5703 @cindex common sections
5704 Mark the current section so that the linker only includes a single copy of it.
5705 This may be used to include the same section in several different object files,
5706 but ensure that the linker will only include it once in the final output file.
5707 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5708 Duplicate sections are detected based on the section name, so it should be
5711 This directive is only supported by a few object file formats; as of this
5712 writing, the only object file format which supports it is the Portable
5713 Executable format used on Windows NT.
5715 The @var{type} argument is optional. If specified, it must be one of the
5716 following strings. For example:
5720 Not all types may be supported on all object file formats.
5724 Silently discard duplicate sections. This is the default.
5727 Warn if there are duplicate sections, but still keep only one copy.
5730 Warn if any of the duplicates have different sizes.
5733 Warn if any of the duplicates do not have exactly the same contents.
5737 @section @code{.list}
5739 @cindex @code{list} directive
5740 @cindex listing control, turning on
5741 Control (in conjunction with the @code{.nolist} directive) whether or
5742 not assembly listings are generated. These two directives maintain an
5743 internal counter (which is zero initially). @code{.list} increments the
5744 counter, and @code{.nolist} decrements it. Assembly listings are
5745 generated whenever the counter is greater than zero.
5747 By default, listings are disabled. When you enable them (with the
5748 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5749 the initial value of the listing counter is one.
5752 @section @code{.ln @var{line-number}}
5754 @cindex @code{ln} directive
5755 @ifclear no-line-dir
5756 @samp{.ln} is a synonym for @samp{.line}.
5759 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5760 must be an absolute expression. The next line has that logical
5761 line number, so any other statements on the current line (after a
5762 statement separator character @code{;}) are reported as on logical
5763 line number @var{line-number} @minus{} 1.
5766 This directive is accepted, but ignored, when @command{@value{AS}} is
5767 configured for @code{b.out}; its effect is only associated with COFF
5773 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5774 @cindex @code{loc} directive
5775 When emitting DWARF2 line number information,
5776 the @code{.loc} directive will add a row to the @code{.debug_line} line
5777 number matrix corresponding to the immediately following assembly
5778 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5779 arguments will be applied to the @code{.debug_line} state machine before
5782 The @var{options} are a sequence of the following tokens in any order:
5786 This option will set the @code{basic_block} register in the
5787 @code{.debug_line} state machine to @code{true}.
5790 This option will set the @code{prologue_end} register in the
5791 @code{.debug_line} state machine to @code{true}.
5793 @item epilogue_begin
5794 This option will set the @code{epilogue_begin} register in the
5795 @code{.debug_line} state machine to @code{true}.
5797 @item is_stmt @var{value}
5798 This option will set the @code{is_stmt} register in the
5799 @code{.debug_line} state machine to @code{value}, which must be
5802 @item isa @var{value}
5803 This directive will set the @code{isa} register in the @code{.debug_line}
5804 state machine to @var{value}, which must be an unsigned integer.
5806 @item discriminator @var{value}
5807 This directive will set the @code{discriminator} register in the @code{.debug_line}
5808 state machine to @var{value}, which must be an unsigned integer.
5812 @node Loc_mark_labels
5813 @section @code{.loc_mark_labels @var{enable}}
5814 @cindex @code{loc_mark_labels} directive
5815 When emitting DWARF2 line number information,
5816 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5817 to the @code{.debug_line} line number matrix with the @code{basic_block}
5818 register in the state machine set whenever a code label is seen.
5819 The @var{enable} argument should be either 1 or 0, to enable or disable
5820 this function respectively.
5824 @section @code{.local @var{names}}
5826 @cindex @code{local} directive
5827 This directive, which is available for ELF targets, marks each symbol in
5828 the comma-separated list of @code{names} as a local symbol so that it
5829 will not be externally visible. If the symbols do not already exist,
5830 they will be created.
5832 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5833 accept an alignment argument, which is the case for most ELF targets,
5834 the @code{.local} directive can be used in combination with @code{.comm}
5835 (@pxref{Comm}) to define aligned local common data.
5839 @section @code{.long @var{expressions}}
5841 @cindex @code{long} directive
5842 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5845 @c no one seems to know what this is for or whether this description is
5846 @c what it really ought to do
5848 @section @code{.lsym @var{symbol}, @var{expression}}
5850 @cindex @code{lsym} directive
5851 @cindex symbol, not referenced in assembly
5852 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5853 the hash table, ensuring it cannot be referenced by name during the
5854 rest of the assembly. This sets the attributes of the symbol to be
5855 the same as the expression value:
5857 @var{other} = @var{descriptor} = 0
5858 @var{type} = @r{(section of @var{expression})}
5859 @var{value} = @var{expression}
5862 The new symbol is not flagged as external.
5866 @section @code{.macro}
5869 The commands @code{.macro} and @code{.endm} allow you to define macros that
5870 generate assembly output. For example, this definition specifies a macro
5871 @code{sum} that puts a sequence of numbers into memory:
5874 .macro sum from=0, to=5
5883 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5895 @item .macro @var{macname}
5896 @itemx .macro @var{macname} @var{macargs} @dots{}
5897 @cindex @code{macro} directive
5898 Begin the definition of a macro called @var{macname}. If your macro
5899 definition requires arguments, specify their names after the macro name,
5900 separated by commas or spaces. You can qualify the macro argument to
5901 indicate whether all invocations must specify a non-blank value (through
5902 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5903 (through @samp{:@code{vararg}}). You can supply a default value for any
5904 macro argument by following the name with @samp{=@var{deflt}}. You
5905 cannot define two macros with the same @var{macname} unless it has been
5906 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5907 definitions. For example, these are all valid @code{.macro} statements:
5911 Begin the definition of a macro called @code{comm}, which takes no
5914 @item .macro plus1 p, p1
5915 @itemx .macro plus1 p p1
5916 Either statement begins the definition of a macro called @code{plus1},
5917 which takes two arguments; within the macro definition, write
5918 @samp{\p} or @samp{\p1} to evaluate the arguments.
5920 @item .macro reserve_str p1=0 p2
5921 Begin the definition of a macro called @code{reserve_str}, with two
5922 arguments. The first argument has a default value, but not the second.
5923 After the definition is complete, you can call the macro either as
5924 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5925 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5926 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5927 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5929 @item .macro m p1:req, p2=0, p3:vararg
5930 Begin the definition of a macro called @code{m}, with at least three
5931 arguments. The first argument must always have a value specified, but
5932 not the second, which instead has a default value. The third formal
5933 will get assigned all remaining arguments specified at invocation time.
5935 When you call a macro, you can specify the argument values either by
5936 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5937 @samp{sum to=17, from=9}.
5941 Note that since each of the @var{macargs} can be an identifier exactly
5942 as any other one permitted by the target architecture, there may be
5943 occasional problems if the target hand-crafts special meanings to certain
5944 characters when they occur in a special position. For example, if the colon
5945 (@code{:}) is generally permitted to be part of a symbol name, but the
5946 architecture specific code special-cases it when occurring as the final
5947 character of a symbol (to denote a label), then the macro parameter
5948 replacement code will have no way of knowing that and consider the whole
5949 construct (including the colon) an identifier, and check only this
5950 identifier for being the subject to parameter substitution. So for example
5951 this macro definition:
5959 might not work as expected. Invoking @samp{label foo} might not create a label
5960 called @samp{foo} but instead just insert the text @samp{\l:} into the
5961 assembler source, probably generating an error about an unrecognised
5964 Similarly problems might occur with the period character (@samp{.})
5965 which is often allowed inside opcode names (and hence identifier names). So
5966 for example constructing a macro to build an opcode from a base name and a
5967 length specifier like this:
5970 .macro opcode base length
5975 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5976 instruction but instead generate some kind of error as the assembler tries to
5977 interpret the text @samp{\base.\length}.
5979 There are several possible ways around this problem:
5982 @item Insert white space
5983 If it is possible to use white space characters then this is the simplest
5992 @item Use @samp{\()}
5993 The string @samp{\()} can be used to separate the end of a macro argument from
5994 the following text. eg:
5997 .macro opcode base length
6002 @item Use the alternate macro syntax mode
6003 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
6004 used as a separator. eg:
6014 Note: this problem of correctly identifying string parameters to pseudo ops
6015 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
6016 and @code{.irpc} (@pxref{Irpc}) as well.
6019 @cindex @code{endm} directive
6020 Mark the end of a macro definition.
6023 @cindex @code{exitm} directive
6024 Exit early from the current macro definition.
6026 @cindex number of macros executed
6027 @cindex macros, count executed
6029 @command{@value{AS}} maintains a counter of how many macros it has
6030 executed in this pseudo-variable; you can copy that number to your
6031 output with @samp{\@@}, but @emph{only within a macro definition}.
6033 @item LOCAL @var{name} [ , @dots{} ]
6034 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
6035 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
6036 @xref{Altmacro,,@code{.altmacro}}.
6040 @section @code{.mri @var{val}}
6042 @cindex @code{mri} directive
6043 @cindex MRI mode, temporarily
6044 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
6045 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
6046 affects code assembled until the next @code{.mri} directive, or until the end
6047 of the file. @xref{M, MRI mode, MRI mode}.
6050 @section @code{.noaltmacro}
6051 Disable alternate macro mode. @xref{Altmacro}.
6054 @section @code{.nolist}
6056 @cindex @code{nolist} directive
6057 @cindex listing control, turning off
6058 Control (in conjunction with the @code{.list} directive) whether or
6059 not assembly listings are generated. These two directives maintain an
6060 internal counter (which is zero initially). @code{.list} increments the
6061 counter, and @code{.nolist} decrements it. Assembly listings are
6062 generated whenever the counter is greater than zero.
6065 @section @code{.octa @var{bignums}}
6067 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
6068 @cindex @code{octa} directive
6069 @cindex integer, 16-byte
6070 @cindex sixteen byte integer
6071 This directive expects zero or more bignums, separated by commas. For each
6072 bignum, it emits a 16-byte integer.
6074 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
6075 hence @emph{octa}-word for 16 bytes.
6078 @section @code{.offset @var{loc}}
6080 @cindex @code{offset} directive
6081 Set the location counter to @var{loc} in the absolute section. @var{loc} must
6082 be an absolute expression. This directive may be useful for defining
6083 symbols with absolute values. Do not confuse it with the @code{.org}
6087 @section @code{.org @var{new-lc} , @var{fill}}
6089 @cindex @code{org} directive
6090 @cindex location counter, advancing
6091 @cindex advancing location counter
6092 @cindex current address, advancing
6093 Advance the location counter of the current section to
6094 @var{new-lc}. @var{new-lc} is either an absolute expression or an
6095 expression with the same section as the current subsection. That is,
6096 you can't use @code{.org} to cross sections: if @var{new-lc} has the
6097 wrong section, the @code{.org} directive is ignored. To be compatible
6098 with former assemblers, if the section of @var{new-lc} is absolute,
6099 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
6100 is the same as the current subsection.
6102 @code{.org} may only increase the location counter, or leave it
6103 unchanged; you cannot use @code{.org} to move the location counter
6106 @c double negative used below "not undefined" because this is a specific
6107 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
6108 @c section. doc@cygnus.com 18feb91
6109 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
6110 may not be undefined. If you really detest this restriction we eagerly await
6111 a chance to share your improved assembler.
6113 Beware that the origin is relative to the start of the section, not
6114 to the start of the subsection. This is compatible with other
6115 people's assemblers.
6117 When the location counter (of the current subsection) is advanced, the
6118 intervening bytes are filled with @var{fill} which should be an
6119 absolute expression. If the comma and @var{fill} are omitted,
6120 @var{fill} defaults to zero.
6123 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
6125 @cindex padding the location counter given a power of two
6126 @cindex @code{p2align} directive
6127 Pad the location counter (in the current subsection) to a particular
6128 storage boundary. The first expression (which must be absolute) is the
6129 number of low-order zero bits the location counter must have after
6130 advancement. For example @samp{.p2align 3} advances the location
6131 counter until it a multiple of 8. If the location counter is already a
6132 multiple of 8, no change is needed.
6134 The second expression (also absolute) gives the fill value to be stored in the
6135 padding bytes. It (and the comma) may be omitted. If it is omitted, the
6136 padding bytes are normally zero. However, on some systems, if the section is
6137 marked as containing code and the fill value is omitted, the space is filled
6138 with no-op instructions.
6140 The third expression is also absolute, and is also optional. If it is present,
6141 it is the maximum number of bytes that should be skipped by this alignment
6142 directive. If doing the alignment would require skipping more bytes than the
6143 specified maximum, then the alignment is not done at all. You can omit the
6144 fill value (the second argument) entirely by simply using two commas after the
6145 required alignment; this can be useful if you want the alignment to be filled
6146 with no-op instructions when appropriate.
6148 @cindex @code{p2alignw} directive
6149 @cindex @code{p2alignl} directive
6150 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
6151 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
6152 pattern as a two byte word value. The @code{.p2alignl} directives treats the
6153 fill pattern as a four byte longword value. For example, @code{.p2alignw
6154 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
6155 filled in with the value 0x368d (the exact placement of the bytes depends upon
6156 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
6161 @section @code{.popsection}
6163 @cindex @code{popsection} directive
6164 @cindex Section Stack
6165 This is one of the ELF section stack manipulation directives. The others are
6166 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6167 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
6170 This directive replaces the current section (and subsection) with the top
6171 section (and subsection) on the section stack. This section is popped off the
6177 @section @code{.previous}
6179 @cindex @code{previous} directive
6180 @cindex Section Stack
6181 This is one of the ELF section stack manipulation directives. The others are
6182 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6183 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6184 (@pxref{PopSection}).
6186 This directive swaps the current section (and subsection) with most recently
6187 referenced section/subsection pair prior to this one. Multiple
6188 @code{.previous} directives in a row will flip between two sections (and their
6189 subsections). For example:
6201 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6207 # Now in section A subsection 1
6211 # Now in section B subsection 0
6214 # Now in section B subsection 1
6217 # Now in section B subsection 0
6221 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6222 section B and 0x9abc into subsection 1 of section B.
6224 In terms of the section stack, this directive swaps the current section with
6225 the top section on the section stack.
6229 @section @code{.print @var{string}}
6231 @cindex @code{print} directive
6232 @command{@value{AS}} will print @var{string} on the standard output during
6233 assembly. You must put @var{string} in double quotes.
6237 @section @code{.protected @var{names}}
6239 @cindex @code{protected} directive
6241 This is one of the ELF visibility directives. The other two are
6242 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6244 This directive overrides the named symbols default visibility (which is set by
6245 their binding: local, global or weak). The directive sets the visibility to
6246 @code{protected} which means that any references to the symbols from within the
6247 components that defines them must be resolved to the definition in that
6248 component, even if a definition in another component would normally preempt
6253 @section @code{.psize @var{lines} , @var{columns}}
6255 @cindex @code{psize} directive
6256 @cindex listing control: paper size
6257 @cindex paper size, for listings
6258 Use this directive to declare the number of lines---and, optionally, the
6259 number of columns---to use for each page, when generating listings.
6261 If you do not use @code{.psize}, listings use a default line-count
6262 of 60. You may omit the comma and @var{columns} specification; the
6263 default width is 200 columns.
6265 @command{@value{AS}} generates formfeeds whenever the specified number of
6266 lines is exceeded (or whenever you explicitly request one, using
6269 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6270 those explicitly specified with @code{.eject}.
6273 @section @code{.purgem @var{name}}
6275 @cindex @code{purgem} directive
6276 Undefine the macro @var{name}, so that later uses of the string will not be
6277 expanded. @xref{Macro}.
6281 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6283 @cindex @code{pushsection} directive
6284 @cindex Section Stack
6285 This is one of the ELF section stack manipulation directives. The others are
6286 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6287 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6290 This directive pushes the current section (and subsection) onto the
6291 top of the section stack, and then replaces the current section and
6292 subsection with @code{name} and @code{subsection}. The optional
6293 @code{flags}, @code{type} and @code{arguments} are treated the same
6294 as in the @code{.section} (@pxref{Section}) directive.
6298 @section @code{.quad @var{bignums}}
6300 @cindex @code{quad} directive
6301 @code{.quad} expects zero or more bignums, separated by commas. For
6302 each bignum, it emits
6304 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6305 warning message; and just takes the lowest order 8 bytes of the bignum.
6306 @cindex eight-byte integer
6307 @cindex integer, 8-byte
6309 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6310 hence @emph{quad}-word for 8 bytes.
6313 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6314 warning message; and just takes the lowest order 16 bytes of the bignum.
6315 @cindex sixteen-byte integer
6316 @cindex integer, 16-byte
6320 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6322 @cindex @code{reloc} directive
6323 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6324 @var{expression}. If @var{offset} is a number, the relocation is generated in
6325 the current section. If @var{offset} is an expression that resolves to a
6326 symbol plus offset, the relocation is generated in the given symbol's section.
6327 @var{expression}, if present, must resolve to a symbol plus addend or to an
6328 absolute value, but note that not all targets support an addend. e.g. ELF REL
6329 targets such as i386 store an addend in the section contents rather than in the
6330 relocation. This low level interface does not support addends stored in the
6334 @section @code{.rept @var{count}}
6336 @cindex @code{rept} directive
6337 Repeat the sequence of lines between the @code{.rept} directive and the next
6338 @code{.endr} directive @var{count} times.
6340 For example, assembling
6348 is equivalent to assembling
6357 @section @code{.sbttl "@var{subheading}"}
6359 @cindex @code{sbttl} directive
6360 @cindex subtitles for listings
6361 @cindex listing control: subtitle
6362 Use @var{subheading} as the title (third line, immediately after the
6363 title line) when generating assembly listings.
6365 This directive affects subsequent pages, as well as the current page if
6366 it appears within ten lines of the top of a page.
6370 @section @code{.scl @var{class}}
6372 @cindex @code{scl} directive
6373 @cindex symbol storage class (COFF)
6374 @cindex COFF symbol storage class
6375 Set the storage-class value for a symbol. This directive may only be
6376 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6377 whether a symbol is static or external, or it may record further
6378 symbolic debugging information.
6381 The @samp{.scl} directive is primarily associated with COFF output; when
6382 configured to generate @code{b.out} output format, @command{@value{AS}}
6383 accepts this directive but ignores it.
6389 @section @code{.section @var{name}}
6391 @cindex named section
6392 Use the @code{.section} directive to assemble the following code into a section
6395 This directive is only supported for targets that actually support arbitrarily
6396 named sections; on @code{a.out} targets, for example, it is not accepted, even
6397 with a standard @code{a.out} section name.
6401 @c only print the extra heading if both COFF and ELF are set
6402 @subheading COFF Version
6405 @cindex @code{section} directive (COFF version)
6406 For COFF targets, the @code{.section} directive is used in one of the following
6410 .section @var{name}[, "@var{flags}"]
6411 .section @var{name}[, @var{subsection}]
6414 If the optional argument is quoted, it is taken as flags to use for the
6415 section. Each flag is a single character. The following flags are recognized:
6419 bss section (uninitialized data)
6421 section is not loaded
6427 exclude section from linking
6433 shared section (meaningful for PE targets)
6435 ignored. (For compatibility with the ELF version)
6437 section is not readable (meaningful for PE targets)
6439 single-digit power-of-two section alignment (GNU extension)
6442 If no flags are specified, the default flags depend upon the section name. If
6443 the section name is not recognized, the default will be for the section to be
6444 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6445 from the section, rather than adding them, so if they are used on their own it
6446 will be as if no flags had been specified at all.
6448 If the optional argument to the @code{.section} directive is not quoted, it is
6449 taken as a subsection number (@pxref{Sub-Sections}).
6454 @c only print the extra heading if both COFF and ELF are set
6455 @subheading ELF Version
6458 @cindex Section Stack
6459 This is one of the ELF section stack manipulation directives. The others are
6460 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6461 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6462 @code{.previous} (@pxref{Previous}).
6464 @cindex @code{section} directive (ELF version)
6465 For ELF targets, the @code{.section} directive is used like this:
6468 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6471 @anchor{Section Name Substitutions}
6472 @kindex --sectname-subst
6473 @cindex section name substitution
6474 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6475 argument may contain a substitution sequence. Only @code{%S} is supported
6476 at the moment, and substitutes the current section name. For example:
6479 .macro exception_code
6480 .section %S.exception
6481 [exception code here]
6496 The two @code{exception_code} invocations above would create the
6497 @code{.text.exception} and @code{.init.exception} sections respectively.
6498 This is useful e.g. to discriminate between ancillary sections that are
6499 tied to setup code to be discarded after use from ancillary sections that
6500 need to stay resident without having to define multiple @code{exception_code}
6501 macros just for that purpose.
6503 The optional @var{flags} argument is a quoted string which may contain any
6504 combination of the following characters:
6508 section is allocatable
6510 section is excluded from executable and shared library.
6514 section is executable
6516 section is mergeable
6518 section contains zero terminated strings
6520 section is a member of a section group
6522 section is used for thread-local-storage
6524 section is a member of the previously-current section's group, if any
6525 @item @code{<number>}
6526 a numeric value indicating the bits to be set in the ELF section header's flags
6527 field. Note - if one or more of the alphabetic characters described above is
6528 also included in the flags field, their bit values will be ORed into the
6530 @item @code{<target specific>}
6531 some targets extend this list with their own flag characters
6534 Note - once a section's flags have been set they cannot be changed. There are
6535 a few exceptions to this rule however. Processor and application specific
6536 flags can be added to an already defined section. The @code{.interp},
6537 @code{.strtab} and @code{.symtab} sections can have the allocate flag
6538 (@code{a}) set after they are initially defined, and the @code{.note-GNU-stack}
6539 section may have the executable (@code{x}) flag added.
6541 The optional @var{type} argument may contain one of the following constants:
6545 section contains data
6547 section does not contain data (i.e., section only occupies space)
6549 section contains data which is used by things other than the program
6551 section contains an array of pointers to init functions
6553 section contains an array of pointers to finish functions
6554 @item @@preinit_array
6555 section contains an array of pointers to pre-init functions
6556 @item @@@code{<number>}
6557 a numeric value to be set as the ELF section header's type field.
6558 @item @@@code{<target specific>}
6559 some targets extend this list with their own types
6562 Many targets only support the first three section types. The type may be
6563 enclosed in double quotes if necessary.
6565 Note on targets where the @code{@@} character is the start of a comment (eg
6566 ARM) then another character is used instead. For example the ARM port uses the
6569 Note - some sections, eg @code{.text} and @code{.data} are considered to be
6570 special and have fixed types. Any attempt to declare them with a different
6571 type will generate an error from the assembler.
6573 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6574 be specified as well as an extra argument---@var{entsize}---like this:
6577 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6580 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6581 constants, each @var{entsize} octets long. Sections with both @code{M} and
6582 @code{S} must contain zero terminated strings where each character is
6583 @var{entsize} bytes long. The linker may remove duplicates within sections with
6584 the same name, same entity size and same flags. @var{entsize} must be an
6585 absolute expression. For sections with both @code{M} and @code{S}, a string
6586 which is a suffix of a larger string is considered a duplicate. Thus
6587 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6588 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6590 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6591 be present along with an additional field like this:
6594 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6597 The @var{GroupName} field specifies the name of the section group to which this
6598 particular section belongs. The optional linkage field can contain:
6602 indicates that only one copy of this section should be retained
6607 Note: if both the @var{M} and @var{G} flags are present then the fields for
6608 the Merge flag should come first, like this:
6611 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6614 If @var{flags} contains the @code{?} symbol then it may not also contain the
6615 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6616 present. Instead, @code{?} says to consider the section that's current before
6617 this directive. If that section used @code{G}, then the new section will use
6618 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6619 If not, then the @code{?} symbol has no effect.
6621 If no flags are specified, the default flags depend upon the section name. If
6622 the section name is not recognized, the default will be for the section to have
6623 none of the above flags: it will not be allocated in memory, nor writable, nor
6624 executable. The section will contain data.
6626 For ELF targets, the assembler supports another type of @code{.section}
6627 directive for compatibility with the Solaris assembler:
6630 .section "@var{name}"[, @var{flags}...]
6633 Note that the section name is quoted. There may be a sequence of comma
6638 section is allocatable
6642 section is executable
6644 section is excluded from executable and shared library.
6646 section is used for thread local storage
6649 This directive replaces the current section and subsection. See the
6650 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6651 some examples of how this directive and the other section stack directives
6657 @section @code{.set @var{symbol}, @var{expression}}
6659 @cindex @code{set} directive
6660 @cindex symbol value, setting
6661 Set the value of @var{symbol} to @var{expression}. This
6662 changes @var{symbol}'s value and type to conform to
6663 @var{expression}. If @var{symbol} was flagged as external, it remains
6664 flagged (@pxref{Symbol Attributes}).
6666 You may @code{.set} a symbol many times in the same assembly provided that the
6667 values given to the symbol are constants. Values that are based on expressions
6668 involving other symbols are allowed, but some targets may restrict this to only
6669 being done once per assembly. This is because those targets do not set the
6670 addresses of symbols at assembly time, but rather delay the assignment until a
6671 final link is performed. This allows the linker a chance to change the code in
6672 the files, changing the location of, and the relative distance between, various
6675 If you @code{.set} a global symbol, the value stored in the object
6676 file is the last value stored into it.
6679 On Z80 @code{set} is a real instruction, use
6680 @samp{@var{symbol} defl @var{expression}} instead.
6684 @section @code{.short @var{expressions}}
6686 @cindex @code{short} directive
6688 @code{.short} is normally the same as @samp{.word}.
6689 @xref{Word,,@code{.word}}.
6691 In some configurations, however, @code{.short} and @code{.word} generate
6692 numbers of different lengths. @xref{Machine Dependencies}.
6696 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6699 This expects zero or more @var{expressions}, and emits
6700 a 16 bit number for each.
6705 @section @code{.single @var{flonums}}
6707 @cindex @code{single} directive
6708 @cindex floating point numbers (single)
6709 This directive assembles zero or more flonums, separated by commas. It
6710 has the same effect as @code{.float}.
6712 The exact kind of floating point numbers emitted depends on how
6713 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6717 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6718 numbers in @sc{ieee} format.
6724 @section @code{.size}
6726 This directive is used to set the size associated with a symbol.
6730 @c only print the extra heading if both COFF and ELF are set
6731 @subheading COFF Version
6734 @cindex @code{size} directive (COFF version)
6735 For COFF targets, the @code{.size} directive is only permitted inside
6736 @code{.def}/@code{.endef} pairs. It is used like this:
6739 .size @var{expression}
6743 @samp{.size} is only meaningful when generating COFF format output; when
6744 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6751 @c only print the extra heading if both COFF and ELF are set
6752 @subheading ELF Version
6755 @cindex @code{size} directive (ELF version)
6756 For ELF targets, the @code{.size} directive is used like this:
6759 .size @var{name} , @var{expression}
6762 This directive sets the size associated with a symbol @var{name}.
6763 The size in bytes is computed from @var{expression} which can make use of label
6764 arithmetic. This directive is typically used to set the size of function
6769 @ifclear no-space-dir
6771 @section @code{.skip @var{size} , @var{fill}}
6773 @cindex @code{skip} directive
6774 @cindex filling memory
6775 This directive emits @var{size} bytes, each of value @var{fill}. Both
6776 @var{size} and @var{fill} are absolute expressions. If the comma and
6777 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6782 @section @code{.sleb128 @var{expressions}}
6784 @cindex @code{sleb128} directive
6785 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6786 compact, variable length representation of numbers used by the DWARF
6787 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6789 @ifclear no-space-dir
6791 @section @code{.space @var{size} , @var{fill}}
6793 @cindex @code{space} directive
6794 @cindex filling memory
6795 This directive emits @var{size} bytes, each of value @var{fill}. Both
6796 @var{size} and @var{fill} are absolute expressions. If the comma
6797 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6802 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6803 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6804 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6805 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6813 @section @code{.stabd, .stabn, .stabs}
6815 @cindex symbolic debuggers, information for
6816 @cindex @code{stab@var{x}} directives
6817 There are three directives that begin @samp{.stab}.
6818 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6819 The symbols are not entered in the @command{@value{AS}} hash table: they
6820 cannot be referenced elsewhere in the source file.
6821 Up to five fields are required:
6825 This is the symbol's name. It may contain any character except
6826 @samp{\000}, so is more general than ordinary symbol names. Some
6827 debuggers used to code arbitrarily complex structures into symbol names
6831 An absolute expression. The symbol's type is set to the low 8 bits of
6832 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6833 and debuggers choke on silly bit patterns.
6836 An absolute expression. The symbol's ``other'' attribute is set to the
6837 low 8 bits of this expression.
6840 An absolute expression. The symbol's descriptor is set to the low 16
6841 bits of this expression.
6844 An absolute expression which becomes the symbol's value.
6847 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6848 or @code{.stabs} statement, the symbol has probably already been created;
6849 you get a half-formed symbol in your object file. This is
6850 compatible with earlier assemblers!
6853 @cindex @code{stabd} directive
6854 @item .stabd @var{type} , @var{other} , @var{desc}
6856 The ``name'' of the symbol generated is not even an empty string.
6857 It is a null pointer, for compatibility. Older assemblers used a
6858 null pointer so they didn't waste space in object files with empty
6861 The symbol's value is set to the location counter,
6862 relocatably. When your program is linked, the value of this symbol
6863 is the address of the location counter when the @code{.stabd} was
6866 @cindex @code{stabn} directive
6867 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6868 The name of the symbol is set to the empty string @code{""}.
6870 @cindex @code{stabs} directive
6871 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6872 All five fields are specified.
6878 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6879 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6881 @cindex string, copying to object file
6882 @cindex string8, copying to object file
6883 @cindex string16, copying to object file
6884 @cindex string32, copying to object file
6885 @cindex string64, copying to object file
6886 @cindex @code{string} directive
6887 @cindex @code{string8} directive
6888 @cindex @code{string16} directive
6889 @cindex @code{string32} directive
6890 @cindex @code{string64} directive
6892 Copy the characters in @var{str} to the object file. You may specify more than
6893 one string to copy, separated by commas. Unless otherwise specified for a
6894 particular machine, the assembler marks the end of each string with a 0 byte.
6895 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6897 The variants @code{string16}, @code{string32} and @code{string64} differ from
6898 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6899 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6900 are stored in target endianness byte order.
6906 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6907 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6912 @section @code{.struct @var{expression}}
6914 @cindex @code{struct} directive
6915 Switch to the absolute section, and set the section offset to @var{expression},
6916 which must be an absolute expression. You might use this as follows:
6925 This would define the symbol @code{field1} to have the value 0, the symbol
6926 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6927 value 8. Assembly would be left in the absolute section, and you would need to
6928 use a @code{.section} directive of some sort to change to some other section
6929 before further assembly.
6933 @section @code{.subsection @var{name}}
6935 @cindex @code{subsection} directive
6936 @cindex Section Stack
6937 This is one of the ELF section stack manipulation directives. The others are
6938 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6939 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6942 This directive replaces the current subsection with @code{name}. The current
6943 section is not changed. The replaced subsection is put onto the section stack
6944 in place of the then current top of stack subsection.
6949 @section @code{.symver}
6950 @cindex @code{symver} directive
6951 @cindex symbol versioning
6952 @cindex versions of symbols
6953 Use the @code{.symver} directive to bind symbols to specific version nodes
6954 within a source file. This is only supported on ELF platforms, and is
6955 typically used when assembling files to be linked into a shared library.
6956 There are cases where it may make sense to use this in objects to be bound
6957 into an application itself so as to override a versioned symbol from a
6960 For ELF targets, the @code{.symver} directive can be used like this:
6962 .symver @var{name}, @var{name2@@nodename}
6964 If the symbol @var{name} is defined within the file
6965 being assembled, the @code{.symver} directive effectively creates a symbol
6966 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6967 just don't try and create a regular alias is that the @var{@@} character isn't
6968 permitted in symbol names. The @var{name2} part of the name is the actual name
6969 of the symbol by which it will be externally referenced. The name @var{name}
6970 itself is merely a name of convenience that is used so that it is possible to
6971 have definitions for multiple versions of a function within a single source
6972 file, and so that the compiler can unambiguously know which version of a
6973 function is being mentioned. The @var{nodename} portion of the alias should be
6974 the name of a node specified in the version script supplied to the linker when
6975 building a shared library. If you are attempting to override a versioned
6976 symbol from a shared library, then @var{nodename} should correspond to the
6977 nodename of the symbol you are trying to override.
6979 If the symbol @var{name} is not defined within the file being assembled, all
6980 references to @var{name} will be changed to @var{name2@@nodename}. If no
6981 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6984 Another usage of the @code{.symver} directive is:
6986 .symver @var{name}, @var{name2@@@@nodename}
6988 In this case, the symbol @var{name} must exist and be defined within
6989 the file being assembled. It is similar to @var{name2@@nodename}. The
6990 difference is @var{name2@@@@nodename} will also be used to resolve
6991 references to @var{name2} by the linker.
6993 The third usage of the @code{.symver} directive is:
6995 .symver @var{name}, @var{name2@@@@@@nodename}
6997 When @var{name} is not defined within the
6998 file being assembled, it is treated as @var{name2@@nodename}. When
6999 @var{name} is defined within the file being assembled, the symbol
7000 name, @var{name}, will be changed to @var{name2@@@@nodename}.
7005 @section @code{.tag @var{structname}}
7007 @cindex COFF structure debugging
7008 @cindex structure debugging, COFF
7009 @cindex @code{tag} directive
7010 This directive is generated by compilers to include auxiliary debugging
7011 information in the symbol table. It is only permitted inside
7012 @code{.def}/@code{.endef} pairs. Tags are used to link structure
7013 definitions in the symbol table with instances of those structures.
7016 @samp{.tag} is only used when generating COFF format output; when
7017 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
7023 @section @code{.text @var{subsection}}
7025 @cindex @code{text} directive
7026 Tells @command{@value{AS}} to assemble the following statements onto the end of
7027 the text subsection numbered @var{subsection}, which is an absolute
7028 expression. If @var{subsection} is omitted, subsection number zero
7032 @section @code{.title "@var{heading}"}
7034 @cindex @code{title} directive
7035 @cindex listing control: title line
7036 Use @var{heading} as the title (second line, immediately after the
7037 source file name and pagenumber) when generating assembly listings.
7039 This directive affects subsequent pages, as well as the current page if
7040 it appears within ten lines of the top of a page.
7044 @section @code{.type}
7046 This directive is used to set the type of a symbol.
7050 @c only print the extra heading if both COFF and ELF are set
7051 @subheading COFF Version
7054 @cindex COFF symbol type
7055 @cindex symbol type, COFF
7056 @cindex @code{type} directive (COFF version)
7057 For COFF targets, this directive is permitted only within
7058 @code{.def}/@code{.endef} pairs. It is used like this:
7064 This records the integer @var{int} as the type attribute of a symbol table
7068 @samp{.type} is associated only with COFF format output; when
7069 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
7070 directive but ignores it.
7076 @c only print the extra heading if both COFF and ELF are set
7077 @subheading ELF Version
7080 @cindex ELF symbol type
7081 @cindex symbol type, ELF
7082 @cindex @code{type} directive (ELF version)
7083 For ELF targets, the @code{.type} directive is used like this:
7086 .type @var{name} , @var{type description}
7089 This sets the type of symbol @var{name} to be either a
7090 function symbol or an object symbol. There are five different syntaxes
7091 supported for the @var{type description} field, in order to provide
7092 compatibility with various other assemblers.
7094 Because some of the characters used in these syntaxes (such as @samp{@@} and
7095 @samp{#}) are comment characters for some architectures, some of the syntaxes
7096 below do not work on all architectures. The first variant will be accepted by
7097 the GNU assembler on all architectures so that variant should be used for
7098 maximum portability, if you do not need to assemble your code with other
7101 The syntaxes supported are:
7104 .type <name> STT_<TYPE_IN_UPPER_CASE>
7105 .type <name>,#<type>
7106 .type <name>,@@<type>
7107 .type <name>,%<type>
7108 .type <name>,"<type>"
7111 The types supported are:
7116 Mark the symbol as being a function name.
7119 @itemx gnu_indirect_function
7120 Mark the symbol as an indirect function when evaluated during reloc
7121 processing. (This is only supported on assemblers targeting GNU systems).
7125 Mark the symbol as being a data object.
7129 Mark the symbol as being a thread-local data object.
7133 Mark the symbol as being a common data object.
7137 Does not mark the symbol in any way. It is supported just for completeness.
7139 @item gnu_unique_object
7140 Marks the symbol as being a globally unique data object. The dynamic linker
7141 will make sure that in the entire process there is just one symbol with this
7142 name and type in use. (This is only supported on assemblers targeting GNU
7147 Note: Some targets support extra types in addition to those listed above.
7153 @section @code{.uleb128 @var{expressions}}
7155 @cindex @code{uleb128} directive
7156 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
7157 compact, variable length representation of numbers used by the DWARF
7158 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
7162 @section @code{.val @var{addr}}
7164 @cindex @code{val} directive
7165 @cindex COFF value attribute
7166 @cindex value attribute, COFF
7167 This directive, permitted only within @code{.def}/@code{.endef} pairs,
7168 records the address @var{addr} as the value attribute of a symbol table
7172 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
7173 configured for @code{b.out}, it accepts this directive but ignores it.
7179 @section @code{.version "@var{string}"}
7181 @cindex @code{version} directive
7182 This directive creates a @code{.note} section and places into it an ELF
7183 formatted note of type NT_VERSION. The note's name is set to @code{string}.
7188 @section @code{.vtable_entry @var{table}, @var{offset}}
7190 @cindex @code{vtable_entry} directive
7191 This directive finds or creates a symbol @code{table} and creates a
7192 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
7195 @section @code{.vtable_inherit @var{child}, @var{parent}}
7197 @cindex @code{vtable_inherit} directive
7198 This directive finds the symbol @code{child} and finds or creates the symbol
7199 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
7200 parent whose addend is the value of the child symbol. As a special case the
7201 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
7205 @section @code{.warning "@var{string}"}
7206 @cindex warning directive
7207 Similar to the directive @code{.error}
7208 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7211 @section @code{.weak @var{names}}
7213 @cindex @code{weak} directive
7214 This directive sets the weak attribute on the comma separated list of symbol
7215 @code{names}. If the symbols do not already exist, they will be created.
7217 On COFF targets other than PE, weak symbols are a GNU extension. This
7218 directive sets the weak attribute on the comma separated list of symbol
7219 @code{names}. If the symbols do not already exist, they will be created.
7221 On the PE target, weak symbols are supported natively as weak aliases.
7222 When a weak symbol is created that is not an alias, GAS creates an
7223 alternate symbol to hold the default value.
7226 @section @code{.weakref @var{alias}, @var{target}}
7228 @cindex @code{weakref} directive
7229 This directive creates an alias to the target symbol that enables the symbol to
7230 be referenced with weak-symbol semantics, but without actually making it weak.
7231 If direct references or definitions of the symbol are present, then the symbol
7232 will not be weak, but if all references to it are through weak references, the
7233 symbol will be marked as weak in the symbol table.
7235 The effect is equivalent to moving all references to the alias to a separate
7236 assembly source file, renaming the alias to the symbol in it, declaring the
7237 symbol as weak there, and running a reloadable link to merge the object files
7238 resulting from the assembly of the new source file and the old source file that
7239 had the references to the alias removed.
7241 The alias itself never makes to the symbol table, and is entirely handled
7242 within the assembler.
7245 @section @code{.word @var{expressions}}
7247 @cindex @code{word} directive
7248 This directive expects zero or more @var{expressions}, of any section,
7249 separated by commas.
7252 For each expression, @command{@value{AS}} emits a 32-bit number.
7255 For each expression, @command{@value{AS}} emits a 16-bit number.
7260 The size of the number emitted, and its byte order,
7261 depend on what target computer the assembly is for.
7264 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7265 @c happen---32-bit addressability, period; no long/short jumps.
7266 @ifset DIFF-TBL-KLUGE
7267 @cindex difference tables altered
7268 @cindex altered difference tables
7270 @emph{Warning: Special Treatment to support Compilers}
7274 Machines with a 32-bit address space, but that do less than 32-bit
7275 addressing, require the following special treatment. If the machine of
7276 interest to you does 32-bit addressing (or doesn't require it;
7277 @pxref{Machine Dependencies}), you can ignore this issue.
7280 In order to assemble compiler output into something that works,
7281 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7282 Directives of the form @samp{.word sym1-sym2} are often emitted by
7283 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7284 directive of the form @samp{.word sym1-sym2}, and the difference between
7285 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7286 creates a @dfn{secondary jump table}, immediately before the next label.
7287 This secondary jump table is preceded by a short-jump to the
7288 first byte after the secondary table. This short-jump prevents the flow
7289 of control from accidentally falling into the new table. Inside the
7290 table is a long-jump to @code{sym2}. The original @samp{.word}
7291 contains @code{sym1} minus the address of the long-jump to
7294 If there were several occurrences of @samp{.word sym1-sym2} before the
7295 secondary jump table, all of them are adjusted. If there was a
7296 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7297 long-jump to @code{sym4} is included in the secondary jump table,
7298 and the @code{.word} directives are adjusted to contain @code{sym3}
7299 minus the address of the long-jump to @code{sym4}; and so on, for as many
7300 entries in the original jump table as necessary.
7303 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7304 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7305 assembly language programmers.
7308 @c end DIFF-TBL-KLUGE
7310 @ifclear no-space-dir
7312 @section @code{.zero @var{size}}
7314 @cindex @code{zero} directive
7315 @cindex filling memory with zero bytes
7316 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7317 expression. This directive is actually an alias for the @samp{.skip} directive
7318 so in can take an optional second argument of the value to store in the bytes
7319 instead of zero. Using @samp{.zero} in this way would be confusing however.
7323 @section Deprecated Directives
7325 @cindex deprecated directives
7326 @cindex obsolescent directives
7327 One day these directives won't work.
7328 They are included for compatibility with older assemblers.
7335 @node Object Attributes
7336 @chapter Object Attributes
7337 @cindex object attributes
7339 @command{@value{AS}} assembles source files written for a specific architecture
7340 into object files for that architecture. But not all object files are alike.
7341 Many architectures support incompatible variations. For instance, floating
7342 point arguments might be passed in floating point registers if the object file
7343 requires hardware floating point support---or floating point arguments might be
7344 passed in integer registers if the object file supports processors with no
7345 hardware floating point unit. Or, if two objects are built for different
7346 generations of the same architecture, the combination may require the
7347 newer generation at run-time.
7349 This information is useful during and after linking. At link time,
7350 @command{@value{LD}} can warn about incompatible object files. After link
7351 time, tools like @command{gdb} can use it to process the linked file
7354 Compatibility information is recorded as a series of object attributes. Each
7355 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7356 string, and indicates who sets the meaning of the tag. The tag is an integer,
7357 and indicates what property the attribute describes. The value may be a string
7358 or an integer, and indicates how the property affects this object. Missing
7359 attributes are the same as attributes with a zero value or empty string value.
7361 Object attributes were developed as part of the ABI for the ARM Architecture.
7362 The file format is documented in @cite{ELF for the ARM Architecture}.
7365 * GNU Object Attributes:: @sc{gnu} Object Attributes
7366 * Defining New Object Attributes:: Defining New Object Attributes
7369 @node GNU Object Attributes
7370 @section @sc{gnu} Object Attributes
7372 The @code{.gnu_attribute} directive records an object attribute
7373 with vendor @samp{gnu}.
7375 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7376 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7377 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7378 2} is set for architecture-independent attributes and clear for
7379 architecture-dependent ones.
7381 @subsection Common @sc{gnu} attributes
7383 These attributes are valid on all architectures.
7386 @item Tag_compatibility (32)
7387 The compatibility attribute takes an integer flag value and a vendor name. If
7388 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7389 then the file is only compatible with the named toolchain. If it is greater
7390 than 1, the file can only be processed by other toolchains under some private
7391 arrangement indicated by the flag value and the vendor name.
7394 @subsection MIPS Attributes
7397 @item Tag_GNU_MIPS_ABI_FP (4)
7398 The floating-point ABI used by this object file. The value will be:
7402 0 for files not affected by the floating-point ABI.
7404 1 for files using the hardware floating-point ABI with a standard
7405 double-precision FPU.
7407 2 for files using the hardware floating-point ABI with a single-precision FPU.
7409 3 for files using the software floating-point ABI.
7411 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7412 floating-point registers, 32-bit general-purpose registers and increased the
7413 number of callee-saved floating-point registers.
7415 5 for files using the hardware floating-point ABI with a double-precision FPU
7416 with either 32-bit or 64-bit floating-point registers and 32-bit
7417 general-purpose registers.
7419 6 for files using the hardware floating-point ABI with 64-bit floating-point
7420 registers and 32-bit general-purpose registers.
7422 7 for files using the hardware floating-point ABI with 64-bit floating-point
7423 registers, 32-bit general-purpose registers and a rule that forbids the
7424 direct use of odd-numbered single-precision floating-point registers.
7428 @subsection PowerPC Attributes
7431 @item Tag_GNU_Power_ABI_FP (4)
7432 The floating-point ABI used by this object file. The value will be:
7436 0 for files not affected by the floating-point ABI.
7438 1 for files using double-precision hardware floating-point ABI.
7440 2 for files using the software floating-point ABI.
7442 3 for files using single-precision hardware floating-point ABI.
7445 @item Tag_GNU_Power_ABI_Vector (8)
7446 The vector ABI used by this object file. The value will be:
7450 0 for files not affected by the vector ABI.
7452 1 for files using general purpose registers to pass vectors.
7454 2 for files using AltiVec registers to pass vectors.
7456 3 for files using SPE registers to pass vectors.
7460 @subsection IBM z Systems Attributes
7463 @item Tag_GNU_S390_ABI_Vector (8)
7464 The vector ABI used by this object file. The value will be:
7468 0 for files not affected by the vector ABI.
7470 1 for files using software vector ABI.
7472 2 for files using hardware vector ABI.
7476 @node Defining New Object Attributes
7477 @section Defining New Object Attributes
7479 If you want to define a new @sc{gnu} object attribute, here are the places you
7480 will need to modify. New attributes should be discussed on the @samp{binutils}
7485 This manual, which is the official register of attributes.
7487 The header for your architecture @file{include/elf}, to define the tag.
7489 The @file{bfd} support file for your architecture, to merge the attribute
7490 and issue any appropriate link warnings.
7492 Test cases in @file{ld/testsuite} for merging and link warnings.
7494 @file{binutils/readelf.c} to display your attribute.
7496 GCC, if you want the compiler to mark the attribute automatically.
7502 @node Machine Dependencies
7503 @chapter Machine Dependent Features
7505 @cindex machine dependencies
7506 The machine instruction sets are (almost by definition) different on
7507 each machine where @command{@value{AS}} runs. Floating point representations
7508 vary as well, and @command{@value{AS}} often supports a few additional
7509 directives or command-line options for compatibility with other
7510 assemblers on a particular platform. Finally, some versions of
7511 @command{@value{AS}} support special pseudo-instructions for branch
7514 This chapter discusses most of these differences, though it does not
7515 include details on any machine's instruction set. For details on that
7516 subject, see the hardware manufacturer's manual.
7520 * AArch64-Dependent:: AArch64 Dependent Features
7523 * Alpha-Dependent:: Alpha Dependent Features
7526 * ARC-Dependent:: ARC Dependent Features
7529 * ARM-Dependent:: ARM Dependent Features
7532 * AVR-Dependent:: AVR Dependent Features
7535 * Blackfin-Dependent:: Blackfin Dependent Features
7538 * CR16-Dependent:: CR16 Dependent Features
7541 * CRIS-Dependent:: CRIS Dependent Features
7544 * D10V-Dependent:: D10V Dependent Features
7547 * D30V-Dependent:: D30V Dependent Features
7550 * Epiphany-Dependent:: EPIPHANY Dependent Features
7553 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7556 * HPPA-Dependent:: HPPA Dependent Features
7559 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7562 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7565 * i860-Dependent:: Intel 80860 Dependent Features
7568 * i960-Dependent:: Intel 80960 Dependent Features
7571 * IA-64-Dependent:: Intel IA-64 Dependent Features
7574 * IP2K-Dependent:: IP2K Dependent Features
7577 * LM32-Dependent:: LM32 Dependent Features
7580 * M32C-Dependent:: M32C Dependent Features
7583 * M32R-Dependent:: M32R Dependent Features
7586 * M68K-Dependent:: M680x0 Dependent Features
7589 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7592 * Meta-Dependent :: Meta Dependent Features
7595 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7598 * MIPS-Dependent:: MIPS Dependent Features
7601 * MMIX-Dependent:: MMIX Dependent Features
7604 * MSP430-Dependent:: MSP430 Dependent Features
7607 * NDS32-Dependent:: Andes NDS32 Dependent Features
7610 * NiosII-Dependent:: Altera Nios II Dependent Features
7613 * NS32K-Dependent:: NS32K Dependent Features
7616 * PDP-11-Dependent:: PDP-11 Dependent Features
7619 * PJ-Dependent:: picoJava Dependent Features
7622 * PPC-Dependent:: PowerPC Dependent Features
7625 * PRU-Dependent:: PRU Dependent Features
7628 * RL78-Dependent:: RL78 Dependent Features
7631 * RISC-V-Dependent:: RISC-V Dependent Features
7634 * RX-Dependent:: RX Dependent Features
7637 * S/390-Dependent:: IBM S/390 Dependent Features
7640 * SCORE-Dependent:: SCORE Dependent Features
7643 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7644 * SH64-Dependent:: SuperH SH64 Dependent Features
7647 * Sparc-Dependent:: SPARC Dependent Features
7650 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7653 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7656 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7659 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7662 * V850-Dependent:: V850 Dependent Features
7665 * Vax-Dependent:: VAX Dependent Features
7668 * Visium-Dependent:: Visium Dependent Features
7671 * XGATE-Dependent:: XGATE Features
7674 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7677 * Xtensa-Dependent:: Xtensa Dependent Features
7680 * Z80-Dependent:: Z80 Dependent Features
7683 * Z8000-Dependent:: Z8000 Dependent Features
7690 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7691 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7692 @c peculiarity: to preserve cross-references, there must be a node called
7693 @c "Machine Dependencies". Hence the conditional nodenames in each
7694 @c major node below. Node defaulting in makeinfo requires adjacency of
7695 @c node and sectioning commands; hence the repetition of @chapter BLAH
7696 @c in both conditional blocks.
7699 @include c-aarch64.texi
7703 @include c-alpha.texi
7719 @include c-bfin.texi
7723 @include c-cr16.texi
7727 @include c-cris.texi
7732 @node Machine Dependencies
7733 @chapter Machine Dependent Features
7735 The machine instruction sets are different on each Renesas chip family,
7736 and there are also some syntax differences among the families. This
7737 chapter describes the specific @command{@value{AS}} features for each
7741 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7742 * SH-Dependent:: Renesas SH Dependent Features
7749 @include c-d10v.texi
7753 @include c-d30v.texi
7757 @include c-epiphany.texi
7761 @include c-h8300.texi
7765 @include c-hppa.texi
7769 @include c-i370.texi
7773 @include c-i386.texi
7777 @include c-i860.texi
7781 @include c-i960.texi
7785 @include c-ia64.texi
7789 @include c-ip2k.texi
7793 @include c-lm32.texi
7797 @include c-m32c.texi
7801 @include c-m32r.texi
7805 @include c-m68k.texi
7809 @include c-m68hc11.texi
7813 @include c-metag.texi
7817 @include c-microblaze.texi
7821 @include c-mips.texi
7825 @include c-mmix.texi
7829 @include c-msp430.texi
7833 @include c-nds32.texi
7837 @include c-nios2.texi
7841 @include c-ns32k.texi
7845 @include c-pdp11.texi
7861 @include c-rl78.texi
7865 @include c-riscv.texi
7873 @include c-s390.texi
7877 @include c-score.texi
7882 @include c-sh64.texi
7886 @include c-sparc.texi
7890 @include c-tic54x.texi
7894 @include c-tic6x.texi
7898 @include c-tilegx.texi
7902 @include c-tilepro.texi
7906 @include c-v850.texi
7914 @include c-visium.texi
7918 @include c-xgate.texi
7922 @include c-xstormy16.texi
7926 @include c-xtensa.texi
7938 @c reverse effect of @down at top of generic Machine-Dep chapter
7942 @node Reporting Bugs
7943 @chapter Reporting Bugs
7944 @cindex bugs in assembler
7945 @cindex reporting bugs in assembler
7947 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7949 Reporting a bug may help you by bringing a solution to your problem, or it may
7950 not. But in any case the principal function of a bug report is to help the
7951 entire community by making the next version of @command{@value{AS}} work better.
7952 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7954 In order for a bug report to serve its purpose, you must include the
7955 information that enables us to fix the bug.
7958 * Bug Criteria:: Have you found a bug?
7959 * Bug Reporting:: How to report bugs
7963 @section Have You Found a Bug?
7964 @cindex bug criteria
7966 If you are not sure whether you have found a bug, here are some guidelines:
7969 @cindex fatal signal
7970 @cindex assembler crash
7971 @cindex crash of assembler
7973 If the assembler gets a fatal signal, for any input whatever, that is a
7974 @command{@value{AS}} bug. Reliable assemblers never crash.
7976 @cindex error on valid input
7978 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7980 @cindex invalid input
7982 If @command{@value{AS}} does not produce an error message for invalid input, that
7983 is a bug. However, you should note that your idea of ``invalid input'' might
7984 be our idea of ``an extension'' or ``support for traditional practice''.
7987 If you are an experienced user of assemblers, your suggestions for improvement
7988 of @command{@value{AS}} are welcome in any case.
7992 @section How to Report Bugs
7994 @cindex assembler bugs, reporting
7996 A number of companies and individuals offer support for @sc{gnu} products. If
7997 you obtained @command{@value{AS}} from a support organization, we recommend you
7998 contact that organization first.
8000 You can find contact information for many support companies and
8001 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
8005 In any event, we also recommend that you send bug reports for @command{@value{AS}}
8009 The fundamental principle of reporting bugs usefully is this:
8010 @strong{report all the facts}. If you are not sure whether to state a
8011 fact or leave it out, state it!
8013 Often people omit facts because they think they know what causes the problem
8014 and assume that some details do not matter. Thus, you might assume that the
8015 name of a symbol you use in an example does not matter. Well, probably it does
8016 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
8017 happens to fetch from the location where that name is stored in memory;
8018 perhaps, if the name were different, the contents of that location would fool
8019 the assembler into doing the right thing despite the bug. Play it safe and
8020 give a specific, complete example. That is the easiest thing for you to do,
8021 and the most helpful.
8023 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
8024 it is new to us. Therefore, always write your bug reports on the assumption
8025 that the bug has not been reported previously.
8027 Sometimes people give a few sketchy facts and ask, ``Does this ring a
8028 bell?'' This cannot help us fix a bug, so it is basically useless. We
8029 respond by asking for enough details to enable us to investigate.
8030 You might as well expedite matters by sending them to begin with.
8032 To enable us to fix the bug, you should include all these things:
8036 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
8037 it with the @samp{--version} argument.
8039 Without this, we will not know whether there is any point in looking for
8040 the bug in the current version of @command{@value{AS}}.
8043 Any patches you may have applied to the @command{@value{AS}} source.
8046 The type of machine you are using, and the operating system name and
8050 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
8054 The command arguments you gave the assembler to assemble your example and
8055 observe the bug. To guarantee you will not omit something important, list them
8056 all. A copy of the Makefile (or the output from make) is sufficient.
8058 If we were to try to guess the arguments, we would probably guess wrong
8059 and then we might not encounter the bug.
8062 A complete input file that will reproduce the bug. If the bug is observed when
8063 the assembler is invoked via a compiler, send the assembler source, not the
8064 high level language source. Most compilers will produce the assembler source
8065 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
8066 the options @samp{-v --save-temps}; this will save the assembler source in a
8067 file with an extension of @file{.s}, and also show you exactly how
8068 @command{@value{AS}} is being run.
8071 A description of what behavior you observe that you believe is
8072 incorrect. For example, ``It gets a fatal signal.''
8074 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
8075 will certainly notice it. But if the bug is incorrect output, we might not
8076 notice unless it is glaringly wrong. You might as well not give us a chance to
8079 Even if the problem you experience is a fatal signal, you should still say so
8080 explicitly. Suppose something strange is going on, such as, your copy of
8081 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
8082 library on your system. (This has happened!) Your copy might crash and ours
8083 would not. If you told us to expect a crash, then when ours fails to crash, we
8084 would know that the bug was not happening for us. If you had not told us to
8085 expect a crash, then we would not be able to draw any conclusion from our
8089 If you wish to suggest changes to the @command{@value{AS}} source, send us context
8090 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
8091 option. Always send diffs from the old file to the new file. If you even
8092 discuss something in the @command{@value{AS}} source, refer to it by context, not
8095 The line numbers in our development sources will not match those in your
8096 sources. Your line numbers would convey no useful information to us.
8099 Here are some things that are not necessary:
8103 A description of the envelope of the bug.
8105 Often people who encounter a bug spend a lot of time investigating
8106 which changes to the input file will make the bug go away and which
8107 changes will not affect it.
8109 This is often time consuming and not very useful, because the way we
8110 will find the bug is by running a single example under the debugger
8111 with breakpoints, not by pure deduction from a series of examples.
8112 We recommend that you save your time for something else.
8114 Of course, if you can find a simpler example to report @emph{instead}
8115 of the original one, that is a convenience for us. Errors in the
8116 output will be easier to spot, running under the debugger will take
8117 less time, and so on.
8119 However, simplification is not vital; if you do not want to do this,
8120 report the bug anyway and send us the entire test case you used.
8123 A patch for the bug.
8125 A patch for the bug does help us if it is a good one. But do not omit
8126 the necessary information, such as the test case, on the assumption that
8127 a patch is all we need. We might see problems with your patch and decide
8128 to fix the problem another way, or we might not understand it at all.
8130 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
8131 construct an example that will make the program follow a certain path through
8132 the code. If you do not send us the example, we will not be able to construct
8133 one, so we will not be able to verify that the bug is fixed.
8135 And if we cannot understand what bug you are trying to fix, or why your
8136 patch should be an improvement, we will not install it. A test case will
8137 help us to understand.
8140 A guess about what the bug is or what it depends on.
8142 Such guesses are usually wrong. Even we cannot guess right about such
8143 things without first using the debugger to find the facts.
8146 @node Acknowledgements
8147 @chapter Acknowledgements
8149 If you have contributed to GAS and your name isn't listed here,
8150 it is not meant as a slight. We just don't know about it. Send mail to the
8151 maintainer, and we'll correct the situation. Currently
8153 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
8155 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
8158 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
8159 information and the 68k series machines, most of the preprocessing pass, and
8160 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
8162 K. Richard Pixley maintained GAS for a while, adding various enhancements and
8163 many bug fixes, including merging support for several processors, breaking GAS
8164 up to handle multiple object file format back ends (including heavy rewrite,
8165 testing, an integration of the coff and b.out back ends), adding configuration
8166 including heavy testing and verification of cross assemblers and file splits
8167 and renaming, converted GAS to strictly ANSI C including full prototypes, added
8168 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
8169 port (including considerable amounts of reverse engineering), a SPARC opcode
8170 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
8171 assertions and made them work, much other reorganization, cleanup, and lint.
8173 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
8174 in format-specific I/O modules.
8176 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
8177 has done much work with it since.
8179 The Intel 80386 machine description was written by Eliot Dresselhaus.
8181 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
8183 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
8184 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
8186 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
8187 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
8188 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
8189 support a.out format.
8191 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
8192 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
8193 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
8194 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
8197 John Gilmore built the AMD 29000 support, added @code{.include} support, and
8198 simplified the configuration of which versions accept which directives. He
8199 updated the 68k machine description so that Motorola's opcodes always produced
8200 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
8201 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
8202 cross-compilation support, and one bug in relaxation that took a week and
8203 required the proverbial one-bit fix.
8205 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
8206 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
8207 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
8208 PowerPC assembler, and made a few other minor patches.
8210 Steve Chamberlain made GAS able to generate listings.
8212 Hewlett-Packard contributed support for the HP9000/300.
8214 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
8215 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
8216 formats). This work was supported by both the Center for Software Science at
8217 the University of Utah and Cygnus Support.
8219 Support for ELF format files has been worked on by Mark Eichin of Cygnus
8220 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
8221 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
8222 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
8223 and some initial 64-bit support).
8225 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8227 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8228 support for openVMS/Alpha.
8230 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8233 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8234 Inc.@: added support for Xtensa processors.
8236 Several engineers at Cygnus Support have also provided many small bug fixes and
8237 configuration enhancements.
8239 Jon Beniston added support for the Lattice Mico32 architecture.
8241 Many others have contributed large or small bugfixes and enhancements. If
8242 you have contributed significant work and are not mentioned on this list, and
8243 want to be, let us know. Some of the history has been lost; we are not
8244 intentionally leaving anyone out.
8246 @node GNU Free Documentation License
8247 @appendix GNU Free Documentation License
8251 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob