1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2015 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{} 1991-2015 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{} 1991-2015 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}]
238 [@b{-o} @var{objfile}] [@b{-R}]
239 [@b{--hash-size}=@var{NUM}] [@b{--reduce-memory-overheads}]
241 [@b{-v}] [@b{-version}] [@b{--version}]
242 [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}] [@b{-w}] [@b{-x}]
243 [@b{-Z}] [@b{@@@var{FILE}}]
244 [@b{--sectname-subst}] [@b{--size-check=[error|warning]}]
245 [@b{--target-help}] [@var{target-options}]
246 [@b{--}|@var{files} @dots{}]
248 @c Target dependent options are listed below. Keep the list sorted.
249 @c Add an empty line for separation.
252 @emph{Target AArch64 options:}
254 [@b{-mabi}=@var{ABI}]
258 @emph{Target Alpha options:}
260 [@b{-mdebug} | @b{-no-mdebug}]
261 [@b{-replace} | @b{-noreplace}]
262 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
263 [@b{-F}] [@b{-32addr}]
267 @emph{Target ARC options:}
268 [@b{-mcpu=@var{cpu}}]
269 [@b{-mA6}|@b{-mARC600}|@b{-mARC601}|@b{-mA7}|@b{-mARC700}|@b{-mEM}|@b{-mHS}]
275 @emph{Target ARM options:}
276 @c Don't document the deprecated options
277 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
278 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
279 [@b{-mfpu}=@var{floating-point-format}]
280 [@b{-mfloat-abi}=@var{abi}]
281 [@b{-meabi}=@var{ver}]
284 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
285 @b{-mapcs-reentrant}]
286 [@b{-mthumb-interwork}] [@b{-k}]
290 @emph{Target Blackfin options:}
291 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
298 @emph{Target CRIS options:}
299 [@b{--underscore} | @b{--no-underscore}]
301 [@b{--emulation=criself} | @b{--emulation=crisaout}]
302 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
303 @c Deprecated -- deliberately not documented.
308 @emph{Target D10V options:}
313 @emph{Target D30V options:}
314 [@b{-O}|@b{-n}|@b{-N}]
318 @emph{Target EPIPHANY options:}
319 [@b{-mepiphany}|@b{-mepiphany16}]
323 @emph{Target H8/300 options:}
327 @c HPPA has no machine-dependent assembler options (yet).
331 @emph{Target i386 options:}
332 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
333 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
337 @emph{Target i960 options:}
338 @c see md_parse_option in tc-i960.c
339 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
341 [@b{-b}] [@b{-no-relax}]
345 @emph{Target IA-64 options:}
346 [@b{-mconstant-gp}|@b{-mauto-pic}]
347 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
349 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
350 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
351 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
352 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
356 @emph{Target IP2K options:}
357 [@b{-mip2022}|@b{-mip2022ext}]
361 @emph{Target M32C options:}
362 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
366 @emph{Target M32R options:}
367 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
372 @emph{Target M680X0 options:}
373 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
377 @emph{Target M68HC11 options:}
378 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
379 [@b{-mshort}|@b{-mlong}]
380 [@b{-mshort-double}|@b{-mlong-double}]
381 [@b{--force-long-branches}] [@b{--short-branches}]
382 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
383 [@b{--print-opcodes}] [@b{--generate-example}]
387 @emph{Target MCORE options:}
388 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
389 [@b{-mcpu=[210|340]}]
393 @emph{Target Meta options:}
394 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
397 @emph{Target MICROBLAZE options:}
398 @c MicroBlaze has no machine-dependent assembler options.
402 @emph{Target MIPS options:}
403 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
404 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
405 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
406 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
407 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
408 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
409 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
410 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
411 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
412 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
413 [@b{-construct-floats}] [@b{-no-construct-floats}]
414 [@b{-mnan=@var{encoding}}]
415 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
416 [@b{-mips16}] [@b{-no-mips16}]
417 [@b{-mmicromips}] [@b{-mno-micromips}]
418 [@b{-msmartmips}] [@b{-mno-smartmips}]
419 [@b{-mips3d}] [@b{-no-mips3d}]
420 [@b{-mdmx}] [@b{-no-mdmx}]
421 [@b{-mdsp}] [@b{-mno-dsp}]
422 [@b{-mdspr2}] [@b{-mno-dspr2}]
423 [@b{-mmsa}] [@b{-mno-msa}]
424 [@b{-mxpa}] [@b{-mno-xpa}]
425 [@b{-mmt}] [@b{-mno-mt}]
426 [@b{-mmcu}] [@b{-mno-mcu}]
427 [@b{-minsn32}] [@b{-mno-insn32}]
428 [@b{-mfix7000}] [@b{-mno-fix7000}]
429 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
430 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
431 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
432 [@b{-mdebug}] [@b{-no-mdebug}]
433 [@b{-mpdr}] [@b{-mno-pdr}]
437 @emph{Target MMIX options:}
438 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
439 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
440 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
441 [@b{--linker-allocated-gregs}]
445 @emph{Target Nios II options:}
446 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
451 @emph{Target NDS32 options:}
452 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
453 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
454 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
455 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
456 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
457 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
458 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
463 @emph{Target PDP11 options:}
464 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
465 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
466 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
470 @emph{Target picoJava options:}
475 @emph{Target PowerPC options:}
477 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
478 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
479 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
480 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
481 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
482 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
483 [@b{-mregnames}|@b{-mno-regnames}]
484 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
485 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
486 [@b{-msolaris}|@b{-mno-solaris}]
487 [@b{-nops=@var{count}}]
491 @emph{Target RL78 options:}
493 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
497 @emph{Target RX options:}
498 [@b{-mlittle-endian}|@b{-mbig-endian}]
499 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
500 [@b{-muse-conventional-section-names}]
501 [@b{-msmall-data-limit}]
504 [@b{-mint-register=@var{number}}]
505 [@b{-mgcc-abi}|@b{-mrx-abi}]
509 @emph{Target s390 options:}
510 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
511 [@b{-mregnames}|@b{-mno-regnames}]
512 [@b{-mwarn-areg-zero}]
516 @emph{Target SCORE options:}
517 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
518 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
519 [@b{-march=score7}][@b{-march=score3}]
520 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
524 @emph{Target SPARC options:}
525 @c The order here is important. See c-sparc.texi.
526 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
527 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
528 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
533 @emph{Target TIC54X options:}
534 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
535 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
539 @emph{Target TIC6X options:}
540 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
541 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
542 [@b{-mpic}|@b{-mno-pic}]
546 @emph{Target TILE-Gx options:}
547 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
550 @c TILEPro has no machine-dependent assembler options
554 @emph{Target Visium options:}
555 [@b{-mtune=@var{arch}}]
559 @emph{Target Xtensa options:}
560 [@b{--[no-]text-section-literals}] [@b{--[no-]auto-litpools}]
561 [@b{--[no-]absolute-literals}]
562 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
563 [@b{--[no-]transform}]
564 [@b{--rename-section} @var{oldname}=@var{newname}]
565 [@b{--[no-]trampolines}]
569 @emph{Target Z80 options:}
570 [@b{-z80}] [@b{-r800}]
571 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
572 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
573 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
574 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
575 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
576 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
580 @c Z8000 has no machine-dependent assembler options
589 @include at-file.texi
592 Turn on listings, in any of a variety of ways:
596 omit false conditionals
599 omit debugging directives
602 include general information, like @value{AS} version and options passed
605 include high-level source
611 include macro expansions
614 omit forms processing
620 set the name of the listing file
623 You may combine these options; for example, use @samp{-aln} for assembly
624 listing without forms processing. The @samp{=file} option, if used, must be
625 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
628 Begin in alternate macro mode.
630 @xref{Altmacro,,@code{.altmacro}}.
633 @item --compress-debug-sections
634 Compress DWARF debug sections using zlib with SHF_COMPRESSED from the
635 ELF ABI. The resulting object file may not be compatible with older
636 linkers and object file utilities. Note if compression would make a
637 given section @emph{larger} then it is not compressed.
640 @cindex @samp{--compress-debug-sections=} option
641 @item --compress-debug-sections=none
642 @itemx --compress-debug-sections=zlib
643 @itemx --compress-debug-sections=zlib-gnu
644 @itemx --compress-debug-sections=zlib-gabi
645 These options control how DWARF debug sections are compressed.
646 @option{--compress-debug-sections=none} is equivalent to
647 @option{--nocompress-debug-sections}.
648 @option{--compress-debug-sections=zlib} and
649 @option{--compress-debug-sections=zlib-gabi} are equivalent to
650 @option{--compress-debug-sections}.
651 @option{--compress-debug-sections=zlib-gnu} compresses DWARF debug
652 sections using zlib. The debug sections are renamed to begin with
653 @samp{.zdebug}. Note if compression would make a given section
654 @emph{larger} then it is not compressed nor renamed.
658 @item --nocompress-debug-sections
659 Do not compress DWARF debug sections. This is usually the default for all
660 targets except the x86/x86_64, but a configure time option can be used to
664 Ignored. This option is accepted for script compatibility with calls to
667 @item --debug-prefix-map @var{old}=@var{new}
668 When assembling files in directory @file{@var{old}}, record debugging
669 information describing them as in @file{@var{new}} instead.
671 @item --defsym @var{sym}=@var{value}
672 Define the symbol @var{sym} to be @var{value} before assembling the input file.
673 @var{value} must be an integer constant. As in C, a leading @samp{0x}
674 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
675 value. The value of the symbol can be overridden inside a source file via the
676 use of a @code{.set} pseudo-op.
679 ``fast''---skip whitespace and comment preprocessing (assume source is
684 Generate debugging information for each assembler source line using whichever
685 debug format is preferred by the target. This currently means either STABS,
689 Generate stabs debugging information for each assembler line. This
690 may help debugging assembler code, if the debugger can handle it.
693 Generate stabs debugging information for each assembler line, with GNU
694 extensions that probably only gdb can handle, and that could make other
695 debuggers crash or refuse to read your program. This
696 may help debugging assembler code. Currently the only GNU extension is
697 the location of the current working directory at assembling time.
700 Generate DWARF2 debugging information for each assembler line. This
701 may help debugging assembler code, if the debugger can handle it. Note---this
702 option is only supported by some targets, not all of them.
704 @item --gdwarf-sections
705 Instead of creating a .debug_line section, create a series of
706 .debug_line.@var{foo} sections where @var{foo} is the name of the
707 corresponding code section. For example a code section called @var{.text.func}
708 will have its dwarf line number information placed into a section called
709 @var{.debug_line.text.func}. If the code section is just called @var{.text}
710 then debug line section will still be called just @var{.debug_line} without any
713 @item --size-check=error
714 @itemx --size-check=warning
715 Issue an error or warning for invalid ELF .size directive.
718 Print a summary of the command line options and exit.
721 Print a summary of all target specific options and exit.
724 Add directory @var{dir} to the search list for @code{.include} directives.
727 Don't warn about signed overflow.
730 @ifclear DIFF-TBL-KLUGE
731 This option is accepted but has no effect on the @value{TARGET} family.
733 @ifset DIFF-TBL-KLUGE
734 Issue warnings when difference tables altered for long displacements.
739 Keep (in the symbol table) local symbols. These symbols start with
740 system-specific local label prefixes, typically @samp{.L} for ELF systems
741 or @samp{L} for traditional a.out systems.
746 @item --listing-lhs-width=@var{number}
747 Set the maximum width, in words, of the output data column for an assembler
748 listing to @var{number}.
750 @item --listing-lhs-width2=@var{number}
751 Set the maximum width, in words, of the output data column for continuation
752 lines in an assembler listing to @var{number}.
754 @item --listing-rhs-width=@var{number}
755 Set the maximum width of an input source line, as displayed in a listing, to
758 @item --listing-cont-lines=@var{number}
759 Set the maximum number of lines printed in a listing for a single line of input
762 @item -o @var{objfile}
763 Name the object-file output from @command{@value{AS}} @var{objfile}.
766 Fold the data section into the text section.
768 @item --hash-size=@var{number}
769 Set the default size of GAS's hash tables to a prime number close to
770 @var{number}. Increasing this value can reduce the length of time it takes the
771 assembler to perform its tasks, at the expense of increasing the assembler's
772 memory requirements. Similarly reducing this value can reduce the memory
773 requirements at the expense of speed.
775 @item --reduce-memory-overheads
776 This option reduces GAS's memory requirements, at the expense of making the
777 assembly processes slower. Currently this switch is a synonym for
778 @samp{--hash-size=4051}, but in the future it may have other effects as well.
781 @item --sectname-subst
782 Honor substitution sequences in section names.
784 @xref{Section Name Substitutions,,@code{.section @var{name}}}.
789 Print the maximum space (in bytes) and total time (in seconds) used by
792 @item --strip-local-absolute
793 Remove local absolute symbols from the outgoing symbol table.
797 Print the @command{as} version.
800 Print the @command{as} version and exit.
804 Suppress warning messages.
806 @item --fatal-warnings
807 Treat warnings as errors.
810 Don't suppress warning messages or treat them as errors.
819 Generate an object file even after errors.
821 @item -- | @var{files} @dots{}
822 Standard input, or source files to assemble.
830 @xref{AArch64 Options}, for the options available when @value{AS} is configured
831 for the 64-bit mode of the ARM Architecture (AArch64).
836 The following options are available when @value{AS} is configured for the
837 64-bit mode of the ARM Architecture (AArch64).
840 @include c-aarch64.texi
841 @c ended inside the included file
849 @xref{Alpha Options}, for the options available when @value{AS} is configured
850 for an Alpha processor.
855 The following options are available when @value{AS} is configured for an Alpha
859 @include c-alpha.texi
860 @c ended inside the included file
867 The following options are available when @value{AS} is configured for an ARC
871 @item -mcpu=@var{cpu}
872 This option selects the core processor variant.
874 Select either big-endian (-EB) or little-endian (-EL) output.
876 Enable Code Density extenssion instructions.
881 The following options are available when @value{AS} is configured for the ARM
885 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
886 Specify which ARM processor variant is the target.
887 @item -march=@var{architecture}[+@var{extension}@dots{}]
888 Specify which ARM architecture variant is used by the target.
889 @item -mfpu=@var{floating-point-format}
890 Select which Floating Point architecture is the target.
891 @item -mfloat-abi=@var{abi}
892 Select which floating point ABI is in use.
894 Enable Thumb only instruction decoding.
895 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
896 Select which procedure calling convention is in use.
898 Select either big-endian (-EB) or little-endian (-EL) output.
899 @item -mthumb-interwork
900 Specify that the code has been generated with interworking between Thumb and
903 Turns on CodeComposer Studio assembly syntax compatibility mode.
905 Specify that PIC code has been generated.
913 @xref{Blackfin Options}, for the options available when @value{AS} is
914 configured for the Blackfin processor family.
919 The following options are available when @value{AS} is configured for
920 the Blackfin processor family.
924 @c ended inside the included file
931 See the info pages for documentation of the CRIS-specific options.
935 The following options are available when @value{AS} is configured for
938 @cindex D10V optimization
939 @cindex optimization, D10V
941 Optimize output by parallelizing instructions.
946 The following options are available when @value{AS} is configured for a D30V
949 @cindex D30V optimization
950 @cindex optimization, D30V
952 Optimize output by parallelizing instructions.
956 Warn when nops are generated.
958 @cindex D30V nops after 32-bit multiply
960 Warn when a nop after a 32-bit multiply instruction is generated.
966 The following options are available when @value{AS} is configured for the
967 Adapteva EPIPHANY series.
970 @xref{Epiphany Options}, for the options available when @value{AS} is
971 configured for an Epiphany processor.
976 The following options are available when @value{AS} is configured for
977 an Epiphany processor.
980 @include c-epiphany.texi
981 @c ended inside the included file
989 @xref{H8/300 Options}, for the options available when @value{AS} is configured
990 for an H8/300 processor.
995 The following options are available when @value{AS} is configured for an H8/300
999 @include c-h8300.texi
1000 @c ended inside the included file
1008 @xref{i386-Options}, for the options available when @value{AS} is
1009 configured for an i386 processor.
1013 @c man begin OPTIONS
1014 The following options are available when @value{AS} is configured for
1017 @c man begin INCLUDE
1018 @include c-i386.texi
1019 @c ended inside the included file
1024 @c man begin OPTIONS
1026 The following options are available when @value{AS} is configured for the
1027 Intel 80960 processor.
1030 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
1031 Specify which variant of the 960 architecture is the target.
1034 Add code to collect statistics about branches taken.
1037 Do not alter compare-and-branch instructions for long displacements;
1044 The following options are available when @value{AS} is configured for the
1050 Specifies that the extended IP2022 instructions are allowed.
1053 Restores the default behaviour, which restricts the permitted instructions to
1054 just the basic IP2022 ones.
1060 The following options are available when @value{AS} is configured for the
1061 Renesas M32C and M16C processors.
1066 Assemble M32C instructions.
1069 Assemble M16C instructions (the default).
1072 Enable support for link-time relaxations.
1075 Support H'00 style hex constants in addition to 0x00 style.
1081 The following options are available when @value{AS} is configured for the
1082 Renesas M32R (formerly Mitsubishi M32R) series.
1087 Specify which processor in the M32R family is the target. The default
1088 is normally the M32R, but this option changes it to the M32RX.
1090 @item --warn-explicit-parallel-conflicts or --Wp
1091 Produce warning messages when questionable parallel constructs are
1094 @item --no-warn-explicit-parallel-conflicts or --Wnp
1095 Do not produce warning messages when questionable parallel constructs are
1102 The following options are available when @value{AS} is configured for the
1103 Motorola 68000 series.
1108 Shorten references to undefined symbols, to one word instead of two.
1110 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1111 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1112 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1113 Specify what processor in the 68000 family is the target. The default
1114 is normally the 68020, but this can be changed at configuration time.
1116 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1117 The target machine does (or does not) have a floating-point coprocessor.
1118 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1119 the basic 68000 is not compatible with the 68881, a combination of the
1120 two can be specified, since it's possible to do emulation of the
1121 coprocessor instructions with the main processor.
1123 @item -m68851 | -mno-68851
1124 The target machine does (or does not) have a memory-management
1125 unit coprocessor. The default is to assume an MMU for 68020 and up.
1133 @xref{Nios II Options}, for the options available when @value{AS} is configured
1134 for an Altera Nios II processor.
1138 @c man begin OPTIONS
1139 The following options are available when @value{AS} is configured for an
1140 Altera Nios II processor.
1142 @c man begin INCLUDE
1143 @include c-nios2.texi
1144 @c ended inside the included file
1150 For details about the PDP-11 machine dependent features options,
1151 see @ref{PDP-11-Options}.
1154 @item -mpic | -mno-pic
1155 Generate position-independent (or position-dependent) code. The
1156 default is @option{-mpic}.
1159 @itemx -mall-extensions
1160 Enable all instruction set extensions. This is the default.
1162 @item -mno-extensions
1163 Disable all instruction set extensions.
1165 @item -m@var{extension} | -mno-@var{extension}
1166 Enable (or disable) a particular instruction set extension.
1169 Enable the instruction set extensions supported by a particular CPU, and
1170 disable all other extensions.
1172 @item -m@var{machine}
1173 Enable the instruction set extensions supported by a particular machine
1174 model, and disable all other extensions.
1180 The following options are available when @value{AS} is configured for
1181 a picoJava processor.
1185 @cindex PJ endianness
1186 @cindex endianness, PJ
1187 @cindex big endian output, PJ
1189 Generate ``big endian'' format output.
1191 @cindex little endian output, PJ
1193 Generate ``little endian'' format output.
1199 The following options are available when @value{AS} is configured for the
1200 Motorola 68HC11 or 68HC12 series.
1204 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1205 Specify what processor is the target. The default is
1206 defined by the configuration option when building the assembler.
1208 @item --xgate-ramoffset
1209 Instruct the linker to offset RAM addresses from S12X address space into
1210 XGATE address space.
1213 Specify to use the 16-bit integer ABI.
1216 Specify to use the 32-bit integer ABI.
1218 @item -mshort-double
1219 Specify to use the 32-bit double ABI.
1222 Specify to use the 64-bit double ABI.
1224 @item --force-long-branches
1225 Relative branches are turned into absolute ones. This concerns
1226 conditional branches, unconditional branches and branches to a
1229 @item -S | --short-branches
1230 Do not turn relative branches into absolute ones
1231 when the offset is out of range.
1233 @item --strict-direct-mode
1234 Do not turn the direct addressing mode into extended addressing mode
1235 when the instruction does not support direct addressing mode.
1237 @item --print-insn-syntax
1238 Print the syntax of instruction in case of error.
1240 @item --print-opcodes
1241 Print the list of instructions with syntax and then exit.
1243 @item --generate-example
1244 Print an example of instruction for each possible instruction and then exit.
1245 This option is only useful for testing @command{@value{AS}}.
1251 The following options are available when @command{@value{AS}} is configured
1252 for the SPARC architecture:
1255 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1256 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1257 Explicitly select a variant of the SPARC architecture.
1259 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1260 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1262 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1263 UltraSPARC extensions.
1265 @item -xarch=v8plus | -xarch=v8plusa
1266 For compatibility with the Solaris v9 assembler. These options are
1267 equivalent to -Av8plus and -Av8plusa, respectively.
1270 Warn when the assembler switches to another architecture.
1275 The following options are available when @value{AS} is configured for the 'c54x
1280 Enable extended addressing mode. All addresses and relocations will assume
1281 extended addressing (usually 23 bits).
1282 @item -mcpu=@var{CPU_VERSION}
1283 Sets the CPU version being compiled for.
1284 @item -merrors-to-file @var{FILENAME}
1285 Redirect error output to a file, for broken systems which don't support such
1286 behaviour in the shell.
1291 The following options are available when @value{AS} is configured for
1296 This option sets the largest size of an object that can be referenced
1297 implicitly with the @code{gp} register. It is only accepted for targets that
1298 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1300 @cindex MIPS endianness
1301 @cindex endianness, MIPS
1302 @cindex big endian output, MIPS
1304 Generate ``big endian'' format output.
1306 @cindex little endian output, MIPS
1308 Generate ``little endian'' format output.
1326 Generate code for a particular MIPS Instruction Set Architecture level.
1327 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1328 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1329 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1330 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1331 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1332 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1333 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1334 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1335 MIPS64 Release 6 ISA processors, respectively.
1337 @item -march=@var{cpu}
1338 Generate code for a particular MIPS CPU.
1340 @item -mtune=@var{cpu}
1341 Schedule and tune for a particular MIPS CPU.
1345 Cause nops to be inserted if the read of the destination register
1346 of an mfhi or mflo instruction occurs in the following two instructions.
1349 @itemx -mno-fix-rm7000
1350 Cause nops to be inserted if a dmult or dmultu instruction is
1351 followed by a load instruction.
1355 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1356 section instead of the standard ELF .stabs sections.
1360 Control generation of @code{.pdr} sections.
1364 The register sizes are normally inferred from the ISA and ABI, but these
1365 flags force a certain group of registers to be treated as 32 bits wide at
1366 all times. @samp{-mgp32} controls the size of general-purpose registers
1367 and @samp{-mfp32} controls the size of floating-point registers.
1371 The register sizes are normally inferred from the ISA and ABI, but these
1372 flags force a certain group of registers to be treated as 64 bits wide at
1373 all times. @samp{-mgp64} controls the size of general-purpose registers
1374 and @samp{-mfp64} controls the size of floating-point registers.
1377 The register sizes are normally inferred from the ISA and ABI, but using
1378 this flag in combination with @samp{-mabi=32} enables an ABI variant
1379 which will operate correctly with floating-point registers which are
1383 @itemx -mno-odd-spreg
1384 Enable use of floating-point operations on odd-numbered single-precision
1385 registers when supported by the ISA. @samp{-mfpxx} implies
1386 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1390 Generate code for the MIPS 16 processor. This is equivalent to putting
1391 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1392 turns off this option.
1395 @itemx -mno-micromips
1396 Generate code for the microMIPS processor. This is equivalent to putting
1397 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1398 turns off this option. This is equivalent to putting @code{.set nomicromips}
1399 at the start of the assembly file.
1402 @itemx -mno-smartmips
1403 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1404 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1405 @samp{-mno-smartmips} turns off this option.
1409 Generate code for the MIPS-3D Application Specific Extension.
1410 This tells the assembler to accept MIPS-3D instructions.
1411 @samp{-no-mips3d} turns off this option.
1415 Generate code for the MDMX Application Specific Extension.
1416 This tells the assembler to accept MDMX instructions.
1417 @samp{-no-mdmx} turns off this option.
1421 Generate code for the DSP Release 1 Application Specific Extension.
1422 This tells the assembler to accept DSP Release 1 instructions.
1423 @samp{-mno-dsp} turns off this option.
1427 Generate code for the DSP Release 2 Application Specific Extension.
1428 This option implies -mdsp.
1429 This tells the assembler to accept DSP Release 2 instructions.
1430 @samp{-mno-dspr2} turns off this option.
1434 Generate code for the MIPS SIMD Architecture Extension.
1435 This tells the assembler to accept MSA instructions.
1436 @samp{-mno-msa} turns off this option.
1440 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1441 This tells the assembler to accept XPA instructions.
1442 @samp{-mno-xpa} turns off this option.
1446 Generate code for the MT Application Specific Extension.
1447 This tells the assembler to accept MT instructions.
1448 @samp{-mno-mt} turns off this option.
1452 Generate code for the MCU Application Specific Extension.
1453 This tells the assembler to accept MCU instructions.
1454 @samp{-mno-mcu} turns off this option.
1458 Only use 32-bit instruction encodings when generating code for the
1459 microMIPS processor. This option inhibits the use of any 16-bit
1460 instructions. This is equivalent to putting @code{.set insn32} at
1461 the start of the assembly file. @samp{-mno-insn32} turns off this
1462 option. This is equivalent to putting @code{.set noinsn32} at the
1463 start of the assembly file. By default @samp{-mno-insn32} is
1464 selected, allowing all instructions to be used.
1466 @item --construct-floats
1467 @itemx --no-construct-floats
1468 The @samp{--no-construct-floats} option disables the construction of
1469 double width floating point constants by loading the two halves of the
1470 value into the two single width floating point registers that make up
1471 the double width register. By default @samp{--construct-floats} is
1472 selected, allowing construction of these floating point constants.
1474 @item --relax-branch
1475 @itemx --no-relax-branch
1476 The @samp{--relax-branch} option enables the relaxation of out-of-range
1477 branches. By default @samp{--no-relax-branch} is selected, causing any
1478 out-of-range branches to produce an error.
1480 @item -mnan=@var{encoding}
1481 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1482 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1485 @item --emulation=@var{name}
1486 This option was formerly used to switch between ELF and ECOFF output
1487 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1488 removed in GAS 2.24, so the option now serves little purpose.
1489 It is retained for backwards compatibility.
1491 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1492 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1493 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1494 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1495 preferred options instead.
1498 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1505 Control how to deal with multiplication overflow and division by zero.
1506 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1507 (and only work for Instruction Set Architecture level 2 and higher);
1508 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1512 When this option is used, @command{@value{AS}} will issue a warning every
1513 time it generates a nop instruction from a macro.
1518 The following options are available when @value{AS} is configured for
1524 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1525 The command line option @samp{-nojsri2bsr} can be used to disable it.
1529 Enable or disable the silicon filter behaviour. By default this is disabled.
1530 The default can be overridden by the @samp{-sifilter} command line option.
1533 Alter jump instructions for long displacements.
1535 @item -mcpu=[210|340]
1536 Select the cpu type on the target hardware. This controls which instructions
1540 Assemble for a big endian target.
1543 Assemble for a little endian target.
1552 @xref{Meta Options}, for the options available when @value{AS} is configured
1553 for a Meta processor.
1557 @c man begin OPTIONS
1558 The following options are available when @value{AS} is configured for a
1561 @c man begin INCLUDE
1562 @include c-metag.texi
1563 @c ended inside the included file
1568 @c man begin OPTIONS
1570 See the info pages for documentation of the MMIX-specific options.
1576 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1577 for a NDS32 processor.
1579 @c ended inside the included file
1583 @c man begin OPTIONS
1584 The following options are available when @value{AS} is configured for a
1587 @c man begin INCLUDE
1588 @include c-nds32.texi
1589 @c ended inside the included file
1596 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1597 for a PowerPC processor.
1601 @c man begin OPTIONS
1602 The following options are available when @value{AS} is configured for a
1605 @c man begin INCLUDE
1607 @c ended inside the included file
1612 @c man begin OPTIONS
1614 See the info pages for documentation of the RX-specific options.
1618 The following options are available when @value{AS} is configured for the s390
1624 Select the word size, either 31/32 bits or 64 bits.
1627 Select the architecture mode, either the Enterprise System
1628 Architecture (esa) or the z/Architecture mode (zarch).
1629 @item -march=@var{processor}
1630 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1631 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1632 @samp{z196}, @samp{zEC12}, or @samp{z13}.
1634 @itemx -mno-regnames
1635 Allow or disallow symbolic names for registers.
1636 @item -mwarn-areg-zero
1637 Warn whenever the operand for a base or index register has been specified
1638 but evaluates to zero.
1646 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1647 for a TMS320C6000 processor.
1651 @c man begin OPTIONS
1652 The following options are available when @value{AS} is configured for a
1653 TMS320C6000 processor.
1655 @c man begin INCLUDE
1656 @include c-tic6x.texi
1657 @c ended inside the included file
1665 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1666 for a TILE-Gx processor.
1670 @c man begin OPTIONS
1671 The following options are available when @value{AS} is configured for a TILE-Gx
1674 @c man begin INCLUDE
1675 @include c-tilegx.texi
1676 @c ended inside the included file
1684 @xref{Visium Options}, for the options available when @value{AS} is configured
1685 for a Visium processor.
1689 @c man begin OPTIONS
1690 The following option is available when @value{AS} is configured for a Visium
1693 @c man begin INCLUDE
1694 @include c-visium.texi
1695 @c ended inside the included file
1703 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1704 for an Xtensa processor.
1708 @c man begin OPTIONS
1709 The following options are available when @value{AS} is configured for an
1712 @c man begin INCLUDE
1713 @include c-xtensa.texi
1714 @c ended inside the included file
1719 @c man begin OPTIONS
1722 The following options are available when @value{AS} is configured for
1723 a Z80 family processor.
1726 Assemble for Z80 processor.
1728 Assemble for R800 processor.
1729 @item -ignore-undocumented-instructions
1731 Assemble undocumented Z80 instructions that also work on R800 without warning.
1732 @item -ignore-unportable-instructions
1734 Assemble all undocumented Z80 instructions without warning.
1735 @item -warn-undocumented-instructions
1737 Issue a warning for undocumented Z80 instructions that also work on R800.
1738 @item -warn-unportable-instructions
1740 Issue a warning for undocumented Z80 instructions that do not work on R800.
1741 @item -forbid-undocumented-instructions
1743 Treat all undocumented instructions as errors.
1744 @item -forbid-unportable-instructions
1746 Treat undocumented Z80 instructions that do not work on R800 as errors.
1753 * Manual:: Structure of this Manual
1754 * GNU Assembler:: The GNU Assembler
1755 * Object Formats:: Object File Formats
1756 * Command Line:: Command Line
1757 * Input Files:: Input Files
1758 * Object:: Output (Object) File
1759 * Errors:: Error and Warning Messages
1763 @section Structure of this Manual
1765 @cindex manual, structure and purpose
1766 This manual is intended to describe what you need to know to use
1767 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1768 notation for symbols, constants, and expressions; the directives that
1769 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1772 We also cover special features in the @value{TARGET}
1773 configuration of @command{@value{AS}}, including assembler directives.
1776 This manual also describes some of the machine-dependent features of
1777 various flavors of the assembler.
1780 @cindex machine instructions (not covered)
1781 On the other hand, this manual is @emph{not} intended as an introduction
1782 to programming in assembly language---let alone programming in general!
1783 In a similar vein, we make no attempt to introduce the machine
1784 architecture; we do @emph{not} describe the instruction set, standard
1785 mnemonics, registers or addressing modes that are standard to a
1786 particular architecture.
1788 You may want to consult the manufacturer's
1789 machine architecture manual for this information.
1793 For information on the H8/300 machine instruction set, see @cite{H8/300
1794 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1795 Programming Manual} (Renesas).
1798 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1799 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1800 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1801 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1804 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1808 @c I think this is premature---doc@cygnus.com, 17jan1991
1810 Throughout this manual, we assume that you are running @dfn{GNU},
1811 the portable operating system from the @dfn{Free Software
1812 Foundation, Inc.}. This restricts our attention to certain kinds of
1813 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1814 once this assumption is granted examples and definitions need less
1817 @command{@value{AS}} is part of a team of programs that turn a high-level
1818 human-readable series of instructions into a low-level
1819 computer-readable series of instructions. Different versions of
1820 @command{@value{AS}} are used for different kinds of computer.
1823 @c There used to be a section "Terminology" here, which defined
1824 @c "contents", "byte", "word", and "long". Defining "word" to any
1825 @c particular size is confusing when the .word directive may generate 16
1826 @c bits on one machine and 32 bits on another; in general, for the user
1827 @c version of this manual, none of these terms seem essential to define.
1828 @c They were used very little even in the former draft of the manual;
1829 @c this draft makes an effort to avoid them (except in names of
1833 @section The GNU Assembler
1835 @c man begin DESCRIPTION
1837 @sc{gnu} @command{as} is really a family of assemblers.
1839 This manual describes @command{@value{AS}}, a member of that family which is
1840 configured for the @value{TARGET} architectures.
1842 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1843 should find a fairly similar environment when you use it on another
1844 architecture. Each version has much in common with the others,
1845 including object file formats, most assembler directives (often called
1846 @dfn{pseudo-ops}) and assembler syntax.@refill
1848 @cindex purpose of @sc{gnu} assembler
1849 @command{@value{AS}} is primarily intended to assemble the output of the
1850 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1851 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1852 assemble correctly everything that other assemblers for the same
1853 machine would assemble.
1855 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1858 @c This remark should appear in generic version of manual; assumption
1859 @c here is that generic version sets M680x0.
1860 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1861 assembler for the same architecture; for example, we know of several
1862 incompatible versions of 680x0 assembly language syntax.
1867 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1868 program in one pass of the source file. This has a subtle impact on the
1869 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1871 @node Object Formats
1872 @section Object File Formats
1874 @cindex object file format
1875 The @sc{gnu} assembler can be configured to produce several alternative
1876 object file formats. For the most part, this does not affect how you
1877 write assembly language programs; but directives for debugging symbols
1878 are typically different in different file formats. @xref{Symbol
1879 Attributes,,Symbol Attributes}.
1882 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1883 @value{OBJ-NAME} format object files.
1885 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1887 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1888 @code{b.out} or COFF format object files.
1891 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1892 SOM or ELF format object files.
1897 @section Command Line
1899 @cindex command line conventions
1901 After the program name @command{@value{AS}}, the command line may contain
1902 options and file names. Options may appear in any order, and may be
1903 before, after, or between file names. The order of file names is
1906 @cindex standard input, as input file
1908 @file{--} (two hyphens) by itself names the standard input file
1909 explicitly, as one of the files for @command{@value{AS}} to assemble.
1911 @cindex options, command line
1912 Except for @samp{--} any command line argument that begins with a
1913 hyphen (@samp{-}) is an option. Each option changes the behavior of
1914 @command{@value{AS}}. No option changes the way another option works. An
1915 option is a @samp{-} followed by one or more letters; the case of
1916 the letter is important. All options are optional.
1918 Some options expect exactly one file name to follow them. The file
1919 name may either immediately follow the option's letter (compatible
1920 with older assemblers) or it may be the next command argument (@sc{gnu}
1921 standard). These two command lines are equivalent:
1924 @value{AS} -o my-object-file.o mumble.s
1925 @value{AS} -omy-object-file.o mumble.s
1929 @section Input Files
1932 @cindex source program
1933 @cindex files, input
1934 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1935 describe the program input to one run of @command{@value{AS}}. The program may
1936 be in one or more files; how the source is partitioned into files
1937 doesn't change the meaning of the source.
1939 @c I added "con" prefix to "catenation" just to prove I can overcome my
1940 @c APL training... doc@cygnus.com
1941 The source program is a concatenation of the text in all the files, in the
1944 @c man begin DESCRIPTION
1945 Each time you run @command{@value{AS}} it assembles exactly one source
1946 program. The source program is made up of one or more files.
1947 (The standard input is also a file.)
1949 You give @command{@value{AS}} a command line that has zero or more input file
1950 names. The input files are read (from left file name to right). A
1951 command line argument (in any position) that has no special meaning
1952 is taken to be an input file name.
1954 If you give @command{@value{AS}} no file names it attempts to read one input file
1955 from the @command{@value{AS}} standard input, which is normally your terminal. You
1956 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1959 Use @samp{--} if you need to explicitly name the standard input file
1960 in your command line.
1962 If the source is empty, @command{@value{AS}} produces a small, empty object
1967 @subheading Filenames and Line-numbers
1969 @cindex input file linenumbers
1970 @cindex line numbers, in input files
1971 There are two ways of locating a line in the input file (or files) and
1972 either may be used in reporting error messages. One way refers to a line
1973 number in a physical file; the other refers to a line number in a
1974 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1976 @dfn{Physical files} are those files named in the command line given
1977 to @command{@value{AS}}.
1979 @dfn{Logical files} are simply names declared explicitly by assembler
1980 directives; they bear no relation to physical files. Logical file names help
1981 error messages reflect the original source file, when @command{@value{AS}} source
1982 is itself synthesized from other files. @command{@value{AS}} understands the
1983 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1984 @ref{File,,@code{.file}}.
1987 @section Output (Object) File
1993 Every time you run @command{@value{AS}} it produces an output file, which is
1994 your assembly language program translated into numbers. This file
1995 is the object file. Its default name is
2003 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
2005 You can give it another name by using the @option{-o} option. Conventionally,
2006 object file names end with @file{.o}. The default name is used for historical
2007 reasons: older assemblers were capable of assembling self-contained programs
2008 directly into a runnable program. (For some formats, this isn't currently
2009 possible, but it can be done for the @code{a.out} format.)
2013 The object file is meant for input to the linker @code{@value{LD}}. It contains
2014 assembled program code, information to help @code{@value{LD}} integrate
2015 the assembled program into a runnable file, and (optionally) symbolic
2016 information for the debugger.
2018 @c link above to some info file(s) like the description of a.out.
2019 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
2022 @section Error and Warning Messages
2024 @c man begin DESCRIPTION
2026 @cindex error messages
2027 @cindex warning messages
2028 @cindex messages from assembler
2029 @command{@value{AS}} may write warnings and error messages to the standard error
2030 file (usually your terminal). This should not happen when a compiler
2031 runs @command{@value{AS}} automatically. Warnings report an assumption made so
2032 that @command{@value{AS}} could keep assembling a flawed program; errors report a
2033 grave problem that stops the assembly.
2037 @cindex format of warning messages
2038 Warning messages have the format
2041 file_name:@b{NNN}:Warning Message Text
2045 @cindex line numbers, in warnings/errors
2046 (where @b{NNN} is a line number). If a logical file name has been given
2047 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
2048 the current input file is used. If a logical line number was given
2050 (@pxref{Line,,@code{.line}})
2052 then it is used to calculate the number printed,
2053 otherwise the actual line in the current source file is printed. The
2054 message text is intended to be self explanatory (in the grand Unix
2057 @cindex format of error messages
2058 Error messages have the format
2060 file_name:@b{NNN}:FATAL:Error Message Text
2062 The file name and line number are derived as for warning
2063 messages. The actual message text may be rather less explanatory
2064 because many of them aren't supposed to happen.
2067 @chapter Command-Line Options
2069 @cindex options, all versions of assembler
2070 This chapter describes command-line options available in @emph{all}
2071 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2072 for options specific
2074 to the @value{TARGET} target.
2077 to particular machine architectures.
2080 @c man begin DESCRIPTION
2082 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2083 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2084 The assembler arguments must be separated from each other (and the @samp{-Wa})
2085 by commas. For example:
2088 gcc -c -g -O -Wa,-alh,-L file.c
2092 This passes two options to the assembler: @samp{-alh} (emit a listing to
2093 standard output with high-level and assembly source) and @samp{-L} (retain
2094 local symbols in the symbol table).
2096 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2097 command-line options are automatically passed to the assembler by the compiler.
2098 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2099 precisely what options it passes to each compilation pass, including the
2105 * a:: -a[cdghlns] enable listings
2106 * alternate:: --alternate enable alternate macro syntax
2107 * D:: -D for compatibility
2108 * f:: -f to work faster
2109 * I:: -I for .include search path
2110 @ifclear DIFF-TBL-KLUGE
2111 * K:: -K for compatibility
2113 @ifset DIFF-TBL-KLUGE
2114 * K:: -K for difference tables
2117 * L:: -L to retain local symbols
2118 * listing:: --listing-XXX to configure listing output
2119 * M:: -M or --mri to assemble in MRI compatibility mode
2120 * MD:: --MD for dependency tracking
2121 * o:: -o to name the object file
2122 * R:: -R to join data and text sections
2123 * statistics:: --statistics to see statistics about assembly
2124 * traditional-format:: --traditional-format for compatible output
2125 * v:: -v to announce version
2126 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2127 * Z:: -Z to make object file even after errors
2131 @section Enable Listings: @option{-a[cdghlns]}
2141 @cindex listings, enabling
2142 @cindex assembly listings, enabling
2144 These options enable listing output from the assembler. By itself,
2145 @samp{-a} requests high-level, assembly, and symbols listing.
2146 You can use other letters to select specific options for the list:
2147 @samp{-ah} requests a high-level language listing,
2148 @samp{-al} requests an output-program assembly listing, and
2149 @samp{-as} requests a symbol table listing.
2150 High-level listings require that a compiler debugging option like
2151 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2154 Use the @samp{-ag} option to print a first section with general assembly
2155 information, like @value{AS} version, switches passed, or time stamp.
2157 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2158 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2159 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2160 omitted from the listing.
2162 Use the @samp{-ad} option to omit debugging directives from the
2165 Once you have specified one of these options, you can further control
2166 listing output and its appearance using the directives @code{.list},
2167 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2169 The @samp{-an} option turns off all forms processing.
2170 If you do not request listing output with one of the @samp{-a} options, the
2171 listing-control directives have no effect.
2173 The letters after @samp{-a} may be combined into one option,
2174 @emph{e.g.}, @samp{-aln}.
2176 Note if the assembler source is coming from the standard input (e.g.,
2178 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2179 is being used) then the listing will not contain any comments or preprocessor
2180 directives. This is because the listing code buffers input source lines from
2181 stdin only after they have been preprocessed by the assembler. This reduces
2182 memory usage and makes the code more efficient.
2185 @section @option{--alternate}
2188 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2191 @section @option{-D}
2194 This option has no effect whatsoever, but it is accepted to make it more
2195 likely that scripts written for other assemblers also work with
2196 @command{@value{AS}}.
2199 @section Work Faster: @option{-f}
2202 @cindex trusted compiler
2203 @cindex faster processing (@option{-f})
2204 @samp{-f} should only be used when assembling programs written by a
2205 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2206 and comment preprocessing on
2207 the input file(s) before assembling them. @xref{Preprocessing,
2211 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2212 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2217 @section @code{.include} Search Path: @option{-I} @var{path}
2219 @kindex -I @var{path}
2220 @cindex paths for @code{.include}
2221 @cindex search path for @code{.include}
2222 @cindex @code{include} directive search path
2223 Use this option to add a @var{path} to the list of directories
2224 @command{@value{AS}} searches for files specified in @code{.include}
2225 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2226 many times as necessary to include a variety of paths. The current
2227 working directory is always searched first; after that, @command{@value{AS}}
2228 searches any @samp{-I} directories in the same order as they were
2229 specified (left to right) on the command line.
2232 @section Difference Tables: @option{-K}
2235 @ifclear DIFF-TBL-KLUGE
2236 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2237 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2238 where it can be used to warn when the assembler alters the machine code
2239 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2240 family does not have the addressing limitations that sometimes lead to this
2241 alteration on other platforms.
2244 @ifset DIFF-TBL-KLUGE
2245 @cindex difference tables, warning
2246 @cindex warning for altered difference tables
2247 @command{@value{AS}} sometimes alters the code emitted for directives of the
2248 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2249 You can use the @samp{-K} option if you want a warning issued when this
2254 @section Include Local Symbols: @option{-L}
2257 @cindex local symbols, retaining in output
2258 Symbols beginning with system-specific local label prefixes, typically
2259 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2260 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2261 such symbols when debugging, because they are intended for the use of
2262 programs (like compilers) that compose assembler programs, not for your
2263 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2264 such symbols, so you do not normally debug with them.
2266 This option tells @command{@value{AS}} to retain those local symbols
2267 in the object file. Usually if you do this you also tell the linker
2268 @code{@value{LD}} to preserve those symbols.
2271 @section Configuring listing output: @option{--listing}
2273 The listing feature of the assembler can be enabled via the command line switch
2274 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2275 hex dump of the corresponding locations in the output object file, and displays
2276 them as a listing file. The format of this listing can be controlled by
2277 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2278 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2279 @code{.psize} (@pxref{Psize}), and
2280 @code{.eject} (@pxref{Eject}) and also by the following switches:
2283 @item --listing-lhs-width=@samp{number}
2284 @kindex --listing-lhs-width
2285 @cindex Width of first line disassembly output
2286 Sets the maximum width, in words, of the first line of the hex byte dump. This
2287 dump appears on the left hand side of the listing output.
2289 @item --listing-lhs-width2=@samp{number}
2290 @kindex --listing-lhs-width2
2291 @cindex Width of continuation lines of disassembly output
2292 Sets the maximum width, in words, of any further lines of the hex byte dump for
2293 a given input source line. If this value is not specified, it defaults to being
2294 the same as the value specified for @samp{--listing-lhs-width}. If neither
2295 switch is used the default is to one.
2297 @item --listing-rhs-width=@samp{number}
2298 @kindex --listing-rhs-width
2299 @cindex Width of source line output
2300 Sets the maximum width, in characters, of the source line that is displayed
2301 alongside the hex dump. The default value for this parameter is 100. The
2302 source line is displayed on the right hand side of the listing output.
2304 @item --listing-cont-lines=@samp{number}
2305 @kindex --listing-cont-lines
2306 @cindex Maximum number of continuation lines
2307 Sets the maximum number of continuation lines of hex dump that will be
2308 displayed for a given single line of source input. The default value is 4.
2312 @section Assemble in MRI Compatibility Mode: @option{-M}
2315 @cindex MRI compatibility mode
2316 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2317 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2318 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2319 configured target) assembler from Microtec Research. The exact nature of the
2320 MRI syntax will not be documented here; see the MRI manuals for more
2321 information. Note in particular that the handling of macros and macro
2322 arguments is somewhat different. The purpose of this option is to permit
2323 assembling existing MRI assembler code using @command{@value{AS}}.
2325 The MRI compatibility is not complete. Certain operations of the MRI assembler
2326 depend upon its object file format, and can not be supported using other object
2327 file formats. Supporting these would require enhancing each object file format
2328 individually. These are:
2331 @item global symbols in common section
2333 The m68k MRI assembler supports common sections which are merged by the linker.
2334 Other object file formats do not support this. @command{@value{AS}} handles
2335 common sections by treating them as a single common symbol. It permits local
2336 symbols to be defined within a common section, but it can not support global
2337 symbols, since it has no way to describe them.
2339 @item complex relocations
2341 The MRI assemblers support relocations against a negated section address, and
2342 relocations which combine the start addresses of two or more sections. These
2343 are not support by other object file formats.
2345 @item @code{END} pseudo-op specifying start address
2347 The MRI @code{END} pseudo-op permits the specification of a start address.
2348 This is not supported by other object file formats. The start address may
2349 instead be specified using the @option{-e} option to the linker, or in a linker
2352 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2354 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2355 name to the output file. This is not supported by other object file formats.
2357 @item @code{ORG} pseudo-op
2359 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2360 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2361 which changes the location within the current section. Absolute sections are
2362 not supported by other object file formats. The address of a section may be
2363 assigned within a linker script.
2366 There are some other features of the MRI assembler which are not supported by
2367 @command{@value{AS}}, typically either because they are difficult or because they
2368 seem of little consequence. Some of these may be supported in future releases.
2372 @item EBCDIC strings
2374 EBCDIC strings are not supported.
2376 @item packed binary coded decimal
2378 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2379 and @code{DCB.P} pseudo-ops are not supported.
2381 @item @code{FEQU} pseudo-op
2383 The m68k @code{FEQU} pseudo-op is not supported.
2385 @item @code{NOOBJ} pseudo-op
2387 The m68k @code{NOOBJ} pseudo-op is not supported.
2389 @item @code{OPT} branch control options
2391 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2392 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2393 relaxes all branches, whether forward or backward, to an appropriate size, so
2394 these options serve no purpose.
2396 @item @code{OPT} list control options
2398 The following m68k @code{OPT} list control options are ignored: @code{C},
2399 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2400 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2402 @item other @code{OPT} options
2404 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2405 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2407 @item @code{OPT} @code{D} option is default
2409 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2410 @code{OPT NOD} may be used to turn it off.
2412 @item @code{XREF} pseudo-op.
2414 The m68k @code{XREF} pseudo-op is ignored.
2416 @item @code{.debug} pseudo-op
2418 The i960 @code{.debug} pseudo-op is not supported.
2420 @item @code{.extended} pseudo-op
2422 The i960 @code{.extended} pseudo-op is not supported.
2424 @item @code{.list} pseudo-op.
2426 The various options of the i960 @code{.list} pseudo-op are not supported.
2428 @item @code{.optimize} pseudo-op
2430 The i960 @code{.optimize} pseudo-op is not supported.
2432 @item @code{.output} pseudo-op
2434 The i960 @code{.output} pseudo-op is not supported.
2436 @item @code{.setreal} pseudo-op
2438 The i960 @code{.setreal} pseudo-op is not supported.
2443 @section Dependency Tracking: @option{--MD}
2446 @cindex dependency tracking
2449 @command{@value{AS}} can generate a dependency file for the file it creates. This
2450 file consists of a single rule suitable for @code{make} describing the
2451 dependencies of the main source file.
2453 The rule is written to the file named in its argument.
2455 This feature is used in the automatic updating of makefiles.
2458 @section Name the Object File: @option{-o}
2461 @cindex naming object file
2462 @cindex object file name
2463 There is always one object file output when you run @command{@value{AS}}. By
2464 default it has the name
2467 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2481 You use this option (which takes exactly one filename) to give the
2482 object file a different name.
2484 Whatever the object file is called, @command{@value{AS}} overwrites any
2485 existing file of the same name.
2488 @section Join Data and Text Sections: @option{-R}
2491 @cindex data and text sections, joining
2492 @cindex text and data sections, joining
2493 @cindex joining text and data sections
2494 @cindex merging text and data sections
2495 @option{-R} tells @command{@value{AS}} to write the object file as if all
2496 data-section data lives in the text section. This is only done at
2497 the very last moment: your binary data are the same, but data
2498 section parts are relocated differently. The data section part of
2499 your object file is zero bytes long because all its bytes are
2500 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2502 When you specify @option{-R} it would be possible to generate shorter
2503 address displacements (because we do not have to cross between text and
2504 data section). We refrain from doing this simply for compatibility with
2505 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2508 When @command{@value{AS}} is configured for COFF or ELF output,
2509 this option is only useful if you use sections named @samp{.text} and
2514 @option{-R} is not supported for any of the HPPA targets. Using
2515 @option{-R} generates a warning from @command{@value{AS}}.
2519 @section Display Assembly Statistics: @option{--statistics}
2521 @kindex --statistics
2522 @cindex statistics, about assembly
2523 @cindex time, total for assembly
2524 @cindex space used, maximum for assembly
2525 Use @samp{--statistics} to display two statistics about the resources used by
2526 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2527 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2530 @node traditional-format
2531 @section Compatible Output: @option{--traditional-format}
2533 @kindex --traditional-format
2534 For some targets, the output of @command{@value{AS}} is different in some ways
2535 from the output of some existing assembler. This switch requests
2536 @command{@value{AS}} to use the traditional format instead.
2538 For example, it disables the exception frame optimizations which
2539 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2542 @section Announce Version: @option{-v}
2546 @cindex assembler version
2547 @cindex version of assembler
2548 You can find out what version of as is running by including the
2549 option @samp{-v} (which you can also spell as @samp{-version}) on the
2553 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2555 @command{@value{AS}} should never give a warning or error message when
2556 assembling compiler output. But programs written by people often
2557 cause @command{@value{AS}} to give a warning that a particular assumption was
2558 made. All such warnings are directed to the standard error file.
2562 @cindex suppressing warnings
2563 @cindex warnings, suppressing
2564 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2565 This only affects the warning messages: it does not change any particular of
2566 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2569 @kindex --fatal-warnings
2570 @cindex errors, caused by warnings
2571 @cindex warnings, causing error
2572 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2573 files that generate warnings to be in error.
2576 @cindex warnings, switching on
2577 You can switch these options off again by specifying @option{--warn}, which
2578 causes warnings to be output as usual.
2581 @section Generate Object File in Spite of Errors: @option{-Z}
2582 @cindex object file, after errors
2583 @cindex errors, continuing after
2584 After an error message, @command{@value{AS}} normally produces no output. If for
2585 some reason you are interested in object file output even after
2586 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2587 option. If there are any errors, @command{@value{AS}} continues anyways, and
2588 writes an object file after a final warning message of the form @samp{@var{n}
2589 errors, @var{m} warnings, generating bad object file.}
2594 @cindex machine-independent syntax
2595 @cindex syntax, machine-independent
2596 This chapter describes the machine-independent syntax allowed in a
2597 source file. @command{@value{AS}} syntax is similar to what many other
2598 assemblers use; it is inspired by the BSD 4.2
2603 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2607 * Preprocessing:: Preprocessing
2608 * Whitespace:: Whitespace
2609 * Comments:: Comments
2610 * Symbol Intro:: Symbols
2611 * Statements:: Statements
2612 * Constants:: Constants
2616 @section Preprocessing
2618 @cindex preprocessing
2619 The @command{@value{AS}} internal preprocessor:
2621 @cindex whitespace, removed by preprocessor
2623 adjusts and removes extra whitespace. It leaves one space or tab before
2624 the keywords on a line, and turns any other whitespace on the line into
2627 @cindex comments, removed by preprocessor
2629 removes all comments, replacing them with a single space, or an
2630 appropriate number of newlines.
2632 @cindex constants, converted by preprocessor
2634 converts character constants into the appropriate numeric values.
2637 It does not do macro processing, include file handling, or
2638 anything else you may get from your C compiler's preprocessor. You can
2639 do include file processing with the @code{.include} directive
2640 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2641 to get other ``CPP'' style preprocessing by giving the input file a
2642 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2643 Output, gcc.info, Using GNU CC}.
2645 Excess whitespace, comments, and character constants
2646 cannot be used in the portions of the input text that are not
2649 @cindex turning preprocessing on and off
2650 @cindex preprocessing, turning on and off
2653 If the first line of an input file is @code{#NO_APP} or if you use the
2654 @samp{-f} option, whitespace and comments are not removed from the input file.
2655 Within an input file, you can ask for whitespace and comment removal in
2656 specific portions of the by putting a line that says @code{#APP} before the
2657 text that may contain whitespace or comments, and putting a line that says
2658 @code{#NO_APP} after this text. This feature is mainly intend to support
2659 @code{asm} statements in compilers whose output is otherwise free of comments
2666 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2667 Whitespace is used to separate symbols, and to make programs neater for
2668 people to read. Unless within character constants
2669 (@pxref{Characters,,Character Constants}), any whitespace means the same
2670 as exactly one space.
2676 There are two ways of rendering comments to @command{@value{AS}}. In both
2677 cases the comment is equivalent to one space.
2679 Anything from @samp{/*} through the next @samp{*/} is a comment.
2680 This means you may not nest these comments.
2684 The only way to include a newline ('\n') in a comment
2685 is to use this sort of comment.
2688 /* This sort of comment does not nest. */
2691 @cindex line comment character
2692 Anything from a @dfn{line comment} character up to the next newline is
2693 considered a comment and is ignored. The line comment character is target
2694 specific, and some targets multiple comment characters. Some targets also have
2695 line comment characters that only work if they are the first character on a
2696 line. Some targets use a sequence of two characters to introduce a line
2697 comment. Some targets can also change their line comment characters depending
2698 upon command line options that have been used. For more details see the
2699 @emph{Syntax} section in the documentation for individual targets.
2701 If the line comment character is the hash sign (@samp{#}) then it still has the
2702 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2703 to specify logical line numbers:
2706 @cindex lines starting with @code{#}
2707 @cindex logical line numbers
2708 To be compatible with past assemblers, lines that begin with @samp{#} have a
2709 special interpretation. Following the @samp{#} should be an absolute
2710 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2711 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2712 new logical file name. The rest of the line, if any, should be whitespace.
2714 If the first non-whitespace characters on the line are not numeric,
2715 the line is ignored. (Just like a comment.)
2718 # This is an ordinary comment.
2719 # 42-6 "new_file_name" # New logical file name
2720 # This is logical line # 36.
2722 This feature is deprecated, and may disappear from future versions
2723 of @command{@value{AS}}.
2728 @cindex characters used in symbols
2729 @ifclear SPECIAL-SYMS
2730 A @dfn{symbol} is one or more characters chosen from the set of all
2731 letters (both upper and lower case), digits and the three characters
2737 A @dfn{symbol} is one or more characters chosen from the set of all
2738 letters (both upper and lower case), digits and the three characters
2739 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2745 On most machines, you can also use @code{$} in symbol names; exceptions
2746 are noted in @ref{Machine Dependencies}.
2748 No symbol may begin with a digit. Case is significant.
2749 There is no length limit; all characters are significant. Multibyte characters
2750 are supported. Symbols are delimited by characters not in that set, or by the
2751 beginning of a file (since the source program must end with a newline, the end
2752 of a file is not a possible symbol delimiter). @xref{Symbols}.
2754 Symbol names may also be enclosed in double quote @code{"} characters. In such
2755 cases any characters are allowed, except for the NUL character. If a double
2756 quote character is to be included in the symbol name it must be preceeded by a
2757 backslash @code{\} character.
2758 @cindex length of symbols
2763 @cindex statements, structure of
2764 @cindex line separator character
2765 @cindex statement separator character
2767 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2768 @dfn{line separator character}. The line separator character is target
2769 specific and described in the @emph{Syntax} section of each
2770 target's documentation. Not all targets support a line separator character.
2771 The newline or line separator character is considered to be part of the
2772 preceding statement. Newlines and separators within character constants are an
2773 exception: they do not end statements.
2775 @cindex newline, required at file end
2776 @cindex EOF, newline must precede
2777 It is an error to end any statement with end-of-file: the last
2778 character of any input file should be a newline.@refill
2780 An empty statement is allowed, and may include whitespace. It is ignored.
2782 @cindex instructions and directives
2783 @cindex directives and instructions
2784 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2785 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2787 A statement begins with zero or more labels, optionally followed by a
2788 key symbol which determines what kind of statement it is. The key
2789 symbol determines the syntax of the rest of the statement. If the
2790 symbol begins with a dot @samp{.} then the statement is an assembler
2791 directive: typically valid for any computer. If the symbol begins with
2792 a letter the statement is an assembly language @dfn{instruction}: it
2793 assembles into a machine language instruction.
2795 Different versions of @command{@value{AS}} for different computers
2796 recognize different instructions. In fact, the same symbol may
2797 represent a different instruction in a different computer's assembly
2801 @cindex @code{:} (label)
2802 @cindex label (@code{:})
2803 A label is a symbol immediately followed by a colon (@code{:}).
2804 Whitespace before a label or after a colon is permitted, but you may not
2805 have whitespace between a label's symbol and its colon. @xref{Labels}.
2808 For HPPA targets, labels need not be immediately followed by a colon, but
2809 the definition of a label must begin in column zero. This also implies that
2810 only one label may be defined on each line.
2814 label: .directive followed by something
2815 another_label: # This is an empty statement.
2816 instruction operand_1, operand_2, @dots{}
2823 A constant is a number, written so that its value is known by
2824 inspection, without knowing any context. Like this:
2827 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2828 .ascii "Ring the bell\7" # A string constant.
2829 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2830 .float 0f-314159265358979323846264338327\
2831 95028841971.693993751E-40 # - pi, a flonum.
2836 * Characters:: Character Constants
2837 * Numbers:: Number Constants
2841 @subsection Character Constants
2843 @cindex character constants
2844 @cindex constants, character
2845 There are two kinds of character constants. A @dfn{character} stands
2846 for one character in one byte and its value may be used in
2847 numeric expressions. String constants (properly called string
2848 @emph{literals}) are potentially many bytes and their values may not be
2849 used in arithmetic expressions.
2853 * Chars:: Characters
2857 @subsubsection Strings
2859 @cindex string constants
2860 @cindex constants, string
2861 A @dfn{string} is written between double-quotes. It may contain
2862 double-quotes or null characters. The way to get special characters
2863 into a string is to @dfn{escape} these characters: precede them with
2864 a backslash @samp{\} character. For example @samp{\\} represents
2865 one backslash: the first @code{\} is an escape which tells
2866 @command{@value{AS}} to interpret the second character literally as a backslash
2867 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2868 escape character). The complete list of escapes follows.
2870 @cindex escape codes, character
2871 @cindex character escape codes
2874 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2876 @cindex @code{\b} (backspace character)
2877 @cindex backspace (@code{\b})
2879 Mnemonic for backspace; for ASCII this is octal code 010.
2882 @c Mnemonic for EOText; for ASCII this is octal code 004.
2884 @cindex @code{\f} (formfeed character)
2885 @cindex formfeed (@code{\f})
2887 Mnemonic for FormFeed; for ASCII this is octal code 014.
2889 @cindex @code{\n} (newline character)
2890 @cindex newline (@code{\n})
2892 Mnemonic for newline; for ASCII this is octal code 012.
2895 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2897 @cindex @code{\r} (carriage return character)
2898 @cindex carriage return (@code{\r})
2900 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2903 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2904 @c other assemblers.
2906 @cindex @code{\t} (tab)
2907 @cindex tab (@code{\t})
2909 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2912 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2913 @c @item \x @var{digit} @var{digit} @var{digit}
2914 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2916 @cindex @code{\@var{ddd}} (octal character code)
2917 @cindex octal character code (@code{\@var{ddd}})
2918 @item \ @var{digit} @var{digit} @var{digit}
2919 An octal character code. The numeric code is 3 octal digits.
2920 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2921 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2923 @cindex @code{\@var{xd...}} (hex character code)
2924 @cindex hex character code (@code{\@var{xd...}})
2925 @item \@code{x} @var{hex-digits...}
2926 A hex character code. All trailing hex digits are combined. Either upper or
2927 lower case @code{x} works.
2929 @cindex @code{\\} (@samp{\} character)
2930 @cindex backslash (@code{\\})
2932 Represents one @samp{\} character.
2935 @c Represents one @samp{'} (accent acute) character.
2936 @c This is needed in single character literals
2937 @c (@xref{Characters,,Character Constants}.) to represent
2940 @cindex @code{\"} (doublequote character)
2941 @cindex doublequote (@code{\"})
2943 Represents one @samp{"} character. Needed in strings to represent
2944 this character, because an unescaped @samp{"} would end the string.
2946 @item \ @var{anything-else}
2947 Any other character when escaped by @kbd{\} gives a warning, but
2948 assembles as if the @samp{\} was not present. The idea is that if
2949 you used an escape sequence you clearly didn't want the literal
2950 interpretation of the following character. However @command{@value{AS}} has no
2951 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2952 code and warns you of the fact.
2955 Which characters are escapable, and what those escapes represent,
2956 varies widely among assemblers. The current set is what we think
2957 the BSD 4.2 assembler recognizes, and is a subset of what most C
2958 compilers recognize. If you are in doubt, do not use an escape
2962 @subsubsection Characters
2964 @cindex single character constant
2965 @cindex character, single
2966 @cindex constant, single character
2967 A single character may be written as a single quote immediately
2968 followed by that character. The same escapes apply to characters as
2969 to strings. So if you want to write the character backslash, you
2970 must write @kbd{'\\} where the first @code{\} escapes the second
2971 @code{\}. As you can see, the quote is an acute accent, not a
2972 grave accent. A newline
2974 @ifclear abnormal-separator
2975 (or semicolon @samp{;})
2977 @ifset abnormal-separator
2979 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2984 immediately following an acute accent is taken as a literal character
2985 and does not count as the end of a statement. The value of a character
2986 constant in a numeric expression is the machine's byte-wide code for
2987 that character. @command{@value{AS}} assumes your character code is ASCII:
2988 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2991 @subsection Number Constants
2993 @cindex constants, number
2994 @cindex number constants
2995 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2996 are stored in the target machine. @emph{Integers} are numbers that
2997 would fit into an @code{int} in the C language. @emph{Bignums} are
2998 integers, but they are stored in more than 32 bits. @emph{Flonums}
2999 are floating point numbers, described below.
3002 * Integers:: Integers
3007 * Bit Fields:: Bit Fields
3013 @subsubsection Integers
3015 @cindex constants, integer
3017 @cindex binary integers
3018 @cindex integers, binary
3019 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
3020 the binary digits @samp{01}.
3022 @cindex octal integers
3023 @cindex integers, octal
3024 An octal integer is @samp{0} followed by zero or more of the octal
3025 digits (@samp{01234567}).
3027 @cindex decimal integers
3028 @cindex integers, decimal
3029 A decimal integer starts with a non-zero digit followed by zero or
3030 more digits (@samp{0123456789}).
3032 @cindex hexadecimal integers
3033 @cindex integers, hexadecimal
3034 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
3035 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
3037 Integers have the usual values. To denote a negative integer, use
3038 the prefix operator @samp{-} discussed under expressions
3039 (@pxref{Prefix Ops,,Prefix Operators}).
3042 @subsubsection Bignums
3045 @cindex constants, bignum
3046 A @dfn{bignum} has the same syntax and semantics as an integer
3047 except that the number (or its negative) takes more than 32 bits to
3048 represent in binary. The distinction is made because in some places
3049 integers are permitted while bignums are not.
3052 @subsubsection Flonums
3054 @cindex floating point numbers
3055 @cindex constants, floating point
3057 @cindex precision, floating point
3058 A @dfn{flonum} represents a floating point number. The translation is
3059 indirect: a decimal floating point number from the text is converted by
3060 @command{@value{AS}} to a generic binary floating point number of more than
3061 sufficient precision. This generic floating point number is converted
3062 to a particular computer's floating point format (or formats) by a
3063 portion of @command{@value{AS}} specialized to that computer.
3065 A flonum is written by writing (in order)
3070 (@samp{0} is optional on the HPPA.)
3074 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3076 @kbd{e} is recommended. Case is not important.
3078 @c FIXME: verify if flonum syntax really this vague for most cases
3079 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3080 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3083 On the H8/300, Renesas / SuperH SH,
3084 and AMD 29K architectures, the letter must be
3085 one of the letters @samp{DFPRSX} (in upper or lower case).
3087 On the ARC, the letter must be one of the letters @samp{DFRS}
3088 (in upper or lower case).
3090 On the Intel 960 architecture, the letter must be
3091 one of the letters @samp{DFT} (in upper or lower case).
3093 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3097 One of the letters @samp{DFRS} (in upper or lower case).
3100 One of the letters @samp{DFPRSX} (in upper or lower case).
3103 The letter @samp{E} (upper case only).
3106 One of the letters @samp{DFT} (in upper or lower case).
3111 An optional sign: either @samp{+} or @samp{-}.
3114 An optional @dfn{integer part}: zero or more decimal digits.
3117 An optional @dfn{fractional part}: @samp{.} followed by zero
3118 or more decimal digits.
3121 An optional exponent, consisting of:
3125 An @samp{E} or @samp{e}.
3126 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3127 @c principle this can perfectly well be different on different targets.
3129 Optional sign: either @samp{+} or @samp{-}.
3131 One or more decimal digits.
3136 At least one of the integer part or the fractional part must be
3137 present. The floating point number has the usual base-10 value.
3139 @command{@value{AS}} does all processing using integers. Flonums are computed
3140 independently of any floating point hardware in the computer running
3141 @command{@value{AS}}.
3145 @c Bit fields are written as a general facility but are also controlled
3146 @c by a conditional-compilation flag---which is as of now (21mar91)
3147 @c turned on only by the i960 config of GAS.
3149 @subsubsection Bit Fields
3152 @cindex constants, bit field
3153 You can also define numeric constants as @dfn{bit fields}.
3154 Specify two numbers separated by a colon---
3156 @var{mask}:@var{value}
3159 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3162 The resulting number is then packed
3164 @c this conditional paren in case bit fields turned on elsewhere than 960
3165 (in host-dependent byte order)
3167 into a field whose width depends on which assembler directive has the
3168 bit-field as its argument. Overflow (a result from the bitwise and
3169 requiring more binary digits to represent) is not an error; instead,
3170 more constants are generated, of the specified width, beginning with the
3171 least significant digits.@refill
3173 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3174 @code{.short}, and @code{.word} accept bit-field arguments.
3179 @chapter Sections and Relocation
3184 * Secs Background:: Background
3185 * Ld Sections:: Linker Sections
3186 * As Sections:: Assembler Internal Sections
3187 * Sub-Sections:: Sub-Sections
3191 @node Secs Background
3194 Roughly, a section is a range of addresses, with no gaps; all data
3195 ``in'' those addresses is treated the same for some particular purpose.
3196 For example there may be a ``read only'' section.
3198 @cindex linker, and assembler
3199 @cindex assembler, and linker
3200 The linker @code{@value{LD}} reads many object files (partial programs) and
3201 combines their contents to form a runnable program. When @command{@value{AS}}
3202 emits an object file, the partial program is assumed to start at address 0.
3203 @code{@value{LD}} assigns the final addresses for the partial program, so that
3204 different partial programs do not overlap. This is actually an
3205 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3208 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3209 addresses. These blocks slide to their run-time addresses as rigid
3210 units; their length does not change and neither does the order of bytes
3211 within them. Such a rigid unit is called a @emph{section}. Assigning
3212 run-time addresses to sections is called @dfn{relocation}. It includes
3213 the task of adjusting mentions of object-file addresses so they refer to
3214 the proper run-time addresses.
3216 For the H8/300, and for the Renesas / SuperH SH,
3217 @command{@value{AS}} pads sections if needed to
3218 ensure they end on a word (sixteen bit) boundary.
3221 @cindex standard assembler sections
3222 An object file written by @command{@value{AS}} has at least three sections, any
3223 of which may be empty. These are named @dfn{text}, @dfn{data} and
3228 When it generates COFF or ELF output,
3230 @command{@value{AS}} can also generate whatever other named sections you specify
3231 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3232 If you do not use any directives that place output in the @samp{.text}
3233 or @samp{.data} sections, these sections still exist, but are empty.
3238 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3240 @command{@value{AS}} can also generate whatever other named sections you
3241 specify using the @samp{.space} and @samp{.subspace} directives. See
3242 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3243 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3244 assembler directives.
3247 Additionally, @command{@value{AS}} uses different names for the standard
3248 text, data, and bss sections when generating SOM output. Program text
3249 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3250 BSS into @samp{$BSS$}.
3254 Within the object file, the text section starts at address @code{0}, the
3255 data section follows, and the bss section follows the data section.
3258 When generating either SOM or ELF output files on the HPPA, the text
3259 section starts at address @code{0}, the data section at address
3260 @code{0x4000000}, and the bss section follows the data section.
3263 To let @code{@value{LD}} know which data changes when the sections are
3264 relocated, and how to change that data, @command{@value{AS}} also writes to the
3265 object file details of the relocation needed. To perform relocation
3266 @code{@value{LD}} must know, each time an address in the object
3270 Where in the object file is the beginning of this reference to
3273 How long (in bytes) is this reference?
3275 Which section does the address refer to? What is the numeric value of
3277 (@var{address}) @minus{} (@var{start-address of section})?
3280 Is the reference to an address ``Program-Counter relative''?
3283 @cindex addresses, format of
3284 @cindex section-relative addressing
3285 In fact, every address @command{@value{AS}} ever uses is expressed as
3287 (@var{section}) + (@var{offset into section})
3290 Further, most expressions @command{@value{AS}} computes have this section-relative
3293 (For some object formats, such as SOM for the HPPA, some expressions are
3294 symbol-relative instead.)
3297 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3298 @var{N} into section @var{secname}.''
3300 Apart from text, data and bss sections you need to know about the
3301 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3302 addresses in the absolute section remain unchanged. For example, address
3303 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3304 @code{@value{LD}}. Although the linker never arranges two partial programs'
3305 data sections with overlapping addresses after linking, @emph{by definition}
3306 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3307 part of a program is always the same address when the program is running as
3308 address @code{@{absolute@ 239@}} in any other part of the program.
3310 The idea of sections is extended to the @dfn{undefined} section. Any
3311 address whose section is unknown at assembly time is by definition
3312 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3313 Since numbers are always defined, the only way to generate an undefined
3314 address is to mention an undefined symbol. A reference to a named
3315 common block would be such a symbol: its value is unknown at assembly
3316 time so it has section @emph{undefined}.
3318 By analogy the word @emph{section} is used to describe groups of sections in
3319 the linked program. @code{@value{LD}} puts all partial programs' text
3320 sections in contiguous addresses in the linked program. It is
3321 customary to refer to the @emph{text section} of a program, meaning all
3322 the addresses of all partial programs' text sections. Likewise for
3323 data and bss sections.
3325 Some sections are manipulated by @code{@value{LD}}; others are invented for
3326 use of @command{@value{AS}} and have no meaning except during assembly.
3329 @section Linker Sections
3330 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3335 @cindex named sections
3336 @cindex sections, named
3337 @item named sections
3340 @cindex text section
3341 @cindex data section
3345 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3346 separate but equal sections. Anything you can say of one section is
3349 When the program is running, however, it is
3350 customary for the text section to be unalterable. The
3351 text section is often shared among processes: it contains
3352 instructions, constants and the like. The data section of a running
3353 program is usually alterable: for example, C variables would be stored
3354 in the data section.
3359 This section contains zeroed bytes when your program begins running. It
3360 is used to hold uninitialized variables or common storage. The length of
3361 each partial program's bss section is important, but because it starts
3362 out containing zeroed bytes there is no need to store explicit zero
3363 bytes in the object file. The bss section was invented to eliminate
3364 those explicit zeros from object files.
3366 @cindex absolute section
3367 @item absolute section
3368 Address 0 of this section is always ``relocated'' to runtime address 0.
3369 This is useful if you want to refer to an address that @code{@value{LD}} must
3370 not change when relocating. In this sense we speak of absolute
3371 addresses being ``unrelocatable'': they do not change during relocation.
3373 @cindex undefined section
3374 @item undefined section
3375 This ``section'' is a catch-all for address references to objects not in
3376 the preceding sections.
3377 @c FIXME: ref to some other doc on obj-file formats could go here.
3380 @cindex relocation example
3381 An idealized example of three relocatable sections follows.
3383 The example uses the traditional section names @samp{.text} and @samp{.data}.
3385 Memory addresses are on the horizontal axis.
3389 @c END TEXI2ROFF-KILL
3392 partial program # 1: |ttttt|dddd|00|
3399 partial program # 2: |TTT|DDD|000|
3402 +--+---+-----+--+----+---+-----+~~
3403 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3404 +--+---+-----+--+----+---+-----+~~
3406 addresses: 0 @dots{}
3413 \line{\it Partial program \#1: \hfil}
3414 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3415 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3417 \line{\it Partial program \#2: \hfil}
3418 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3419 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3421 \line{\it linked program: \hfil}
3422 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3423 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3424 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3425 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3427 \line{\it addresses: \hfil}
3431 @c END TEXI2ROFF-KILL
3434 @section Assembler Internal Sections
3436 @cindex internal assembler sections
3437 @cindex sections in messages, internal
3438 These sections are meant only for the internal use of @command{@value{AS}}. They
3439 have no meaning at run-time. You do not really need to know about these
3440 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3441 warning messages, so it might be helpful to have an idea of their
3442 meanings to @command{@value{AS}}. These sections are used to permit the
3443 value of every expression in your assembly language program to be a
3444 section-relative address.
3447 @cindex assembler internal logic error
3448 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3449 An internal assembler logic error has been found. This means there is a
3450 bug in the assembler.
3452 @cindex expr (internal section)
3454 The assembler stores complex expression internally as combinations of
3455 symbols. When it needs to represent an expression as a symbol, it puts
3456 it in the expr section.
3458 @c FIXME item transfer[t] vector preload
3459 @c FIXME item transfer[t] vector postload
3460 @c FIXME item register
3464 @section Sub-Sections
3466 @cindex numbered subsections
3467 @cindex grouping data
3473 fall into two sections: text and data.
3475 You may have separate groups of
3477 data in named sections
3481 data in named sections
3487 that you want to end up near to each other in the object file, even though they
3488 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3489 use @dfn{subsections} for this purpose. Within each section, there can be
3490 numbered subsections with values from 0 to 8192. Objects assembled into the
3491 same subsection go into the object file together with other objects in the same
3492 subsection. For example, a compiler might want to store constants in the text
3493 section, but might not want to have them interspersed with the program being
3494 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3495 section of code being output, and a @samp{.text 1} before each group of
3496 constants being output.
3498 Subsections are optional. If you do not use subsections, everything
3499 goes in subsection number zero.
3502 Each subsection is zero-padded up to a multiple of four bytes.
3503 (Subsections may be padded a different amount on different flavors
3504 of @command{@value{AS}}.)
3508 On the H8/300 platform, each subsection is zero-padded to a word
3509 boundary (two bytes).
3510 The same is true on the Renesas SH.
3513 @c FIXME section padding (alignment)?
3514 @c Rich Pixley says padding here depends on target obj code format; that
3515 @c doesn't seem particularly useful to say without further elaboration,
3516 @c so for now I say nothing about it. If this is a generic BFD issue,
3517 @c these paragraphs might need to vanish from this manual, and be
3518 @c discussed in BFD chapter of binutils (or some such).
3522 Subsections appear in your object file in numeric order, lowest numbered
3523 to highest. (All this to be compatible with other people's assemblers.)
3524 The object file contains no representation of subsections; @code{@value{LD}} and
3525 other programs that manipulate object files see no trace of them.
3526 They just see all your text subsections as a text section, and all your
3527 data subsections as a data section.
3529 To specify which subsection you want subsequent statements assembled
3530 into, use a numeric argument to specify it, in a @samp{.text
3531 @var{expression}} or a @samp{.data @var{expression}} statement.
3534 When generating COFF output, you
3539 can also use an extra subsection
3540 argument with arbitrary named sections: @samp{.section @var{name},
3545 When generating ELF output, you
3550 can also use the @code{.subsection} directive (@pxref{SubSection})
3551 to specify a subsection: @samp{.subsection @var{expression}}.
3553 @var{Expression} should be an absolute expression
3554 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3555 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3556 begins in @code{text 0}. For instance:
3558 .text 0 # The default subsection is text 0 anyway.
3559 .ascii "This lives in the first text subsection. *"
3561 .ascii "But this lives in the second text subsection."
3563 .ascii "This lives in the data section,"
3564 .ascii "in the first data subsection."
3566 .ascii "This lives in the first text section,"
3567 .ascii "immediately following the asterisk (*)."
3570 Each section has a @dfn{location counter} incremented by one for every byte
3571 assembled into that section. Because subsections are merely a convenience
3572 restricted to @command{@value{AS}} there is no concept of a subsection location
3573 counter. There is no way to directly manipulate a location counter---but the
3574 @code{.align} directive changes it, and any label definition captures its
3575 current value. The location counter of the section where statements are being
3576 assembled is said to be the @dfn{active} location counter.
3579 @section bss Section
3582 @cindex common variable storage
3583 The bss section is used for local common variable storage.
3584 You may allocate address space in the bss section, but you may
3585 not dictate data to load into it before your program executes. When
3586 your program starts running, all the contents of the bss
3587 section are zeroed bytes.
3589 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3590 @ref{Lcomm,,@code{.lcomm}}.
3592 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3593 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3596 When assembling for a target which supports multiple sections, such as ELF or
3597 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3598 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3599 section. Typically the section will only contain symbol definitions and
3600 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3607 Symbols are a central concept: the programmer uses symbols to name
3608 things, the linker uses symbols to link, and the debugger uses symbols
3612 @cindex debuggers, and symbol order
3613 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3614 the same order they were declared. This may break some debuggers.
3619 * Setting Symbols:: Giving Symbols Other Values
3620 * Symbol Names:: Symbol Names
3621 * Dot:: The Special Dot Symbol
3622 * Symbol Attributes:: Symbol Attributes
3629 A @dfn{label} is written as a symbol immediately followed by a colon
3630 @samp{:}. The symbol then represents the current value of the
3631 active location counter, and is, for example, a suitable instruction
3632 operand. You are warned if you use the same symbol to represent two
3633 different locations: the first definition overrides any other
3637 On the HPPA, the usual form for a label need not be immediately followed by a
3638 colon, but instead must start in column zero. Only one label may be defined on
3639 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3640 provides a special directive @code{.label} for defining labels more flexibly.
3643 @node Setting Symbols
3644 @section Giving Symbols Other Values
3646 @cindex assigning values to symbols
3647 @cindex symbol values, assigning
3648 A symbol can be given an arbitrary value by writing a symbol, followed
3649 by an equals sign @samp{=}, followed by an expression
3650 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3651 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3652 equals sign @samp{=}@samp{=} here represents an equivalent of the
3653 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3656 Blackfin does not support symbol assignment with @samp{=}.
3660 @section Symbol Names
3662 @cindex symbol names
3663 @cindex names, symbol
3664 @ifclear SPECIAL-SYMS
3665 Symbol names begin with a letter or with one of @samp{._}. On most
3666 machines, you can also use @code{$} in symbol names; exceptions are
3667 noted in @ref{Machine Dependencies}. That character may be followed by any
3668 string of digits, letters, dollar signs (unless otherwise noted for a
3669 particular target machine), and underscores.
3673 Symbol names begin with a letter or with one of @samp{._}. On the
3674 Renesas SH you can also use @code{$} in symbol names. That
3675 character may be followed by any string of digits, letters, dollar signs (save
3676 on the H8/300), and underscores.
3680 Case of letters is significant: @code{foo} is a different symbol name
3683 Symbol names do not start with a digit. An exception to this rule is made for
3684 Local Labels. See below.
3686 Multibyte characters are supported. To generate a symbol name containing
3687 multibyte characters enclose it within double quotes and use escape codes. cf
3688 @xref{Strings}. Generating a multibyte symbol name from a label is not
3689 currently supported.
3691 Each symbol has exactly one name. Each name in an assembly language program
3692 refers to exactly one symbol. You may use that symbol name any number of times
3695 @subheading Local Symbol Names
3697 @cindex local symbol names
3698 @cindex symbol names, local
3699 A local symbol is any symbol beginning with certain local label prefixes.
3700 By default, the local label prefix is @samp{.L} for ELF systems or
3701 @samp{L} for traditional a.out systems, but each target may have its own
3702 set of local label prefixes.
3704 On the HPPA local symbols begin with @samp{L$}.
3707 Local symbols are defined and used within the assembler, but they are
3708 normally not saved in object files. Thus, they are not visible when debugging.
3709 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols})
3710 to retain the local symbols in the object files.
3712 @subheading Local Labels
3714 @cindex local labels
3715 @cindex temporary symbol names
3716 @cindex symbol names, temporary
3717 Local labels are different from local symbols. Local labels help compilers and
3718 programmers use names temporarily. They create symbols which are guaranteed to
3719 be unique over the entire scope of the input source code and which can be
3720 referred to by a simple notation. To define a local label, write a label of
3721 the form @samp{@b{N}:} (where @b{N} represents any non-negative integer).
3722 To refer to the most recent previous definition of that label write
3723 @samp{@b{N}b}, using the same number as when you defined the label. To refer
3724 to the next definition of a local label, write @samp{@b{N}f}. The @samp{b}
3725 stands for ``backwards'' and the @samp{f} stands for ``forwards''.
3727 There is no restriction on how you can use these labels, and you can reuse them
3728 too. So that it is possible to repeatedly define the same local label (using
3729 the same number @samp{@b{N}}), although you can only refer to the most recently
3730 defined local label of that number (for a backwards reference) or the next
3731 definition of a specific local label for a forward reference. It is also worth
3732 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3733 implemented in a slightly more efficient manner than the others.
3744 Which is the equivalent of:
3747 label_1: branch label_3
3748 label_2: branch label_1
3749 label_3: branch label_4
3750 label_4: branch label_3
3753 Local label names are only a notational device. They are immediately
3754 transformed into more conventional symbol names before the assembler uses them.
3755 The symbol names are stored in the symbol table, appear in error messages, and
3756 are optionally emitted to the object file. The names are constructed using
3760 @item @emph{local label prefix}
3761 All local symbols begin with the system-specific local label prefix.
3762 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3763 that start with the local label prefix. These labels are
3764 used for symbols you are never intended to see. If you use the
3765 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3766 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3767 you may use them in debugging.
3770 This is the number that was used in the local label definition. So if the
3771 label is written @samp{55:} then the number is @samp{55}.
3774 This unusual character is included so you do not accidentally invent a symbol
3775 of the same name. The character has ASCII value of @samp{\002} (control-B).
3777 @item @emph{ordinal number}
3778 This is a serial number to keep the labels distinct. The first definition of
3779 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3780 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3781 the number @samp{1} and its 15th definition gets @samp{15} as well.
3784 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3785 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3787 @subheading Dollar Local Labels
3788 @cindex dollar local symbols
3790 On some targets @code{@value{AS}} also supports an even more local form of
3791 local labels called dollar labels. These labels go out of scope (i.e., they
3792 become undefined) as soon as a non-local label is defined. Thus they remain
3793 valid for only a small region of the input source code. Normal local labels,
3794 by contrast, remain in scope for the entire file, or until they are redefined
3795 by another occurrence of the same local label.
3797 Dollar labels are defined in exactly the same way as ordinary local labels,
3798 except that they have a dollar sign suffix to their numeric value, e.g.,
3801 They can also be distinguished from ordinary local labels by their transformed
3802 names which use ASCII character @samp{\001} (control-A) as the magic character
3803 to distinguish them from ordinary labels. For example, the fifth definition of
3804 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3807 @section The Special Dot Symbol
3809 @cindex dot (symbol)
3810 @cindex @code{.} (symbol)
3811 @cindex current address
3812 @cindex location counter
3813 The special symbol @samp{.} refers to the current address that
3814 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3815 .long .} defines @code{melvin} to contain its own address.
3816 Assigning a value to @code{.} is treated the same as a @code{.org}
3818 @ifclear no-space-dir
3819 Thus, the expression @samp{.=.+4} is the same as saying
3823 @node Symbol Attributes
3824 @section Symbol Attributes
3826 @cindex symbol attributes
3827 @cindex attributes, symbol
3828 Every symbol has, as well as its name, the attributes ``Value'' and
3829 ``Type''. Depending on output format, symbols can also have auxiliary
3832 The detailed definitions are in @file{a.out.h}.
3835 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3836 all these attributes, and probably won't warn you. This makes the
3837 symbol an externally defined symbol, which is generally what you
3841 * Symbol Value:: Value
3842 * Symbol Type:: Type
3845 * a.out Symbols:: Symbol Attributes: @code{a.out}
3849 * a.out Symbols:: Symbol Attributes: @code{a.out}
3852 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3857 * COFF Symbols:: Symbol Attributes for COFF
3860 * SOM Symbols:: Symbol Attributes for SOM
3867 @cindex value of a symbol
3868 @cindex symbol value
3869 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3870 location in the text, data, bss or absolute sections the value is the
3871 number of addresses from the start of that section to the label.
3872 Naturally for text, data and bss sections the value of a symbol changes
3873 as @code{@value{LD}} changes section base addresses during linking. Absolute
3874 symbols' values do not change during linking: that is why they are
3877 The value of an undefined symbol is treated in a special way. If it is
3878 0 then the symbol is not defined in this assembler source file, and
3879 @code{@value{LD}} tries to determine its value from other files linked into the
3880 same program. You make this kind of symbol simply by mentioning a symbol
3881 name without defining it. A non-zero value represents a @code{.comm}
3882 common declaration. The value is how much common storage to reserve, in
3883 bytes (addresses). The symbol refers to the first address of the
3889 @cindex type of a symbol
3891 The type attribute of a symbol contains relocation (section)
3892 information, any flag settings indicating that a symbol is external, and
3893 (optionally), other information for linkers and debuggers. The exact
3894 format depends on the object-code output format in use.
3899 @c The following avoids a "widow" subsection title. @group would be
3900 @c better if it were available outside examples.
3903 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3905 @cindex @code{b.out} symbol attributes
3906 @cindex symbol attributes, @code{b.out}
3907 These symbol attributes appear only when @command{@value{AS}} is configured for
3908 one of the Berkeley-descended object output formats---@code{a.out} or
3914 @subsection Symbol Attributes: @code{a.out}
3916 @cindex @code{a.out} symbol attributes
3917 @cindex symbol attributes, @code{a.out}
3923 @subsection Symbol Attributes: @code{a.out}
3925 @cindex @code{a.out} symbol attributes
3926 @cindex symbol attributes, @code{a.out}
3930 * Symbol Desc:: Descriptor
3931 * Symbol Other:: Other
3935 @subsubsection Descriptor
3937 @cindex descriptor, of @code{a.out} symbol
3938 This is an arbitrary 16-bit value. You may establish a symbol's
3939 descriptor value by using a @code{.desc} statement
3940 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3941 @command{@value{AS}}.
3944 @subsubsection Other
3946 @cindex other attribute, of @code{a.out} symbol
3947 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3952 @subsection Symbol Attributes for COFF
3954 @cindex COFF symbol attributes
3955 @cindex symbol attributes, COFF
3957 The COFF format supports a multitude of auxiliary symbol attributes;
3958 like the primary symbol attributes, they are set between @code{.def} and
3959 @code{.endef} directives.
3961 @subsubsection Primary Attributes
3963 @cindex primary attributes, COFF symbols
3964 The symbol name is set with @code{.def}; the value and type,
3965 respectively, with @code{.val} and @code{.type}.
3967 @subsubsection Auxiliary Attributes
3969 @cindex auxiliary attributes, COFF symbols
3970 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3971 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3972 table information for COFF.
3977 @subsection Symbol Attributes for SOM
3979 @cindex SOM symbol attributes
3980 @cindex symbol attributes, SOM
3982 The SOM format for the HPPA supports a multitude of symbol attributes set with
3983 the @code{.EXPORT} and @code{.IMPORT} directives.
3985 The attributes are described in @cite{HP9000 Series 800 Assembly
3986 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3987 @code{EXPORT} assembler directive documentation.
3991 @chapter Expressions
3995 @cindex numeric values
3996 An @dfn{expression} specifies an address or numeric value.
3997 Whitespace may precede and/or follow an expression.
3999 The result of an expression must be an absolute number, or else an offset into
4000 a particular section. If an expression is not absolute, and there is not
4001 enough information when @command{@value{AS}} sees the expression to know its
4002 section, a second pass over the source program might be necessary to interpret
4003 the expression---but the second pass is currently not implemented.
4004 @command{@value{AS}} aborts with an error message in this situation.
4007 * Empty Exprs:: Empty Expressions
4008 * Integer Exprs:: Integer Expressions
4012 @section Empty Expressions
4014 @cindex empty expressions
4015 @cindex expressions, empty
4016 An empty expression has no value: it is just whitespace or null.
4017 Wherever an absolute expression is required, you may omit the
4018 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
4019 is compatible with other assemblers.
4022 @section Integer Expressions
4024 @cindex integer expressions
4025 @cindex expressions, integer
4026 An @dfn{integer expression} is one or more @emph{arguments} delimited
4027 by @emph{operators}.
4030 * Arguments:: Arguments
4031 * Operators:: Operators
4032 * Prefix Ops:: Prefix Operators
4033 * Infix Ops:: Infix Operators
4037 @subsection Arguments
4039 @cindex expression arguments
4040 @cindex arguments in expressions
4041 @cindex operands in expressions
4042 @cindex arithmetic operands
4043 @dfn{Arguments} are symbols, numbers or subexpressions. In other
4044 contexts arguments are sometimes called ``arithmetic operands''. In
4045 this manual, to avoid confusing them with the ``instruction operands'' of
4046 the machine language, we use the term ``argument'' to refer to parts of
4047 expressions only, reserving the word ``operand'' to refer only to machine
4048 instruction operands.
4050 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
4051 @var{section} is one of text, data, bss, absolute,
4052 or undefined. @var{NNN} is a signed, 2's complement 32 bit
4055 Numbers are usually integers.
4057 A number can be a flonum or bignum. In this case, you are warned
4058 that only the low order 32 bits are used, and @command{@value{AS}} pretends
4059 these 32 bits are an integer. You may write integer-manipulating
4060 instructions that act on exotic constants, compatible with other
4063 @cindex subexpressions
4064 Subexpressions are a left parenthesis @samp{(} followed by an integer
4065 expression, followed by a right parenthesis @samp{)}; or a prefix
4066 operator followed by an argument.
4069 @subsection Operators
4071 @cindex operators, in expressions
4072 @cindex arithmetic functions
4073 @cindex functions, in expressions
4074 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4075 operators are followed by an argument. Infix operators appear
4076 between their arguments. Operators may be preceded and/or followed by
4080 @subsection Prefix Operator
4082 @cindex prefix operators
4083 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4084 one argument, which must be absolute.
4086 @c the tex/end tex stuff surrounding this small table is meant to make
4087 @c it align, on the printed page, with the similar table in the next
4088 @c section (which is inside an enumerate).
4090 \global\advance\leftskip by \itemindent
4095 @dfn{Negation}. Two's complement negation.
4097 @dfn{Complementation}. Bitwise not.
4101 \global\advance\leftskip by -\itemindent
4105 @subsection Infix Operators
4107 @cindex infix operators
4108 @cindex operators, permitted arguments
4109 @dfn{Infix operators} take two arguments, one on either side. Operators
4110 have precedence, but operations with equal precedence are performed left
4111 to right. Apart from @code{+} or @option{-}, both arguments must be
4112 absolute, and the result is absolute.
4115 @cindex operator precedence
4116 @cindex precedence of operators
4123 @dfn{Multiplication}.
4126 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4132 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4135 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4139 Intermediate precedence
4144 @dfn{Bitwise Inclusive Or}.
4150 @dfn{Bitwise Exclusive Or}.
4153 @dfn{Bitwise Or Not}.
4160 @cindex addition, permitted arguments
4161 @cindex plus, permitted arguments
4162 @cindex arguments for addition
4164 @dfn{Addition}. If either argument is absolute, the result has the section of
4165 the other argument. You may not add together arguments from different
4168 @cindex subtraction, permitted arguments
4169 @cindex minus, permitted arguments
4170 @cindex arguments for subtraction
4172 @dfn{Subtraction}. If the right argument is absolute, the
4173 result has the section of the left argument.
4174 If both arguments are in the same section, the result is absolute.
4175 You may not subtract arguments from different sections.
4176 @c FIXME is there still something useful to say about undefined - undefined ?
4178 @cindex comparison expressions
4179 @cindex expressions, comparison
4184 @dfn{Is Not Equal To}
4188 @dfn{Is Greater Than}
4190 @dfn{Is Greater Than Or Equal To}
4192 @dfn{Is Less Than Or Equal To}
4194 The comparison operators can be used as infix operators. A true results has a
4195 value of -1 whereas a false result has a value of 0. Note, these operators
4196 perform signed comparisons.
4199 @item Lowest Precedence
4208 These two logical operations can be used to combine the results of sub
4209 expressions. Note, unlike the comparison operators a true result returns a
4210 value of 1 but a false results does still return 0. Also note that the logical
4211 or operator has a slightly lower precedence than logical and.
4216 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4217 address; you can only have a defined section in one of the two arguments.
4220 @chapter Assembler Directives
4222 @cindex directives, machine independent
4223 @cindex pseudo-ops, machine independent
4224 @cindex machine independent directives
4225 All assembler directives have names that begin with a period (@samp{.}).
4226 The names are case insensitive for most targets, and usually written
4229 This chapter discusses directives that are available regardless of the
4230 target machine configuration for the @sc{gnu} assembler.
4232 Some machine configurations provide additional directives.
4233 @xref{Machine Dependencies}.
4236 @ifset machine-directives
4237 @xref{Machine Dependencies}, for additional directives.
4242 * Abort:: @code{.abort}
4244 * ABORT (COFF):: @code{.ABORT}
4247 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4248 * Altmacro:: @code{.altmacro}
4249 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4250 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4251 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4252 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, etc
4253 * Byte:: @code{.byte @var{expressions}}
4254 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4255 * Comm:: @code{.comm @var{symbol} , @var{length} }
4256 * Data:: @code{.data @var{subsection}}
4258 * Def:: @code{.def @var{name}}
4261 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4267 * Double:: @code{.double @var{flonums}}
4268 * Eject:: @code{.eject}
4269 * Else:: @code{.else}
4270 * Elseif:: @code{.elseif}
4273 * Endef:: @code{.endef}
4276 * Endfunc:: @code{.endfunc}
4277 * Endif:: @code{.endif}
4278 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4279 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4280 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4282 * Error:: @code{.error @var{string}}
4283 * Exitm:: @code{.exitm}
4284 * Extern:: @code{.extern}
4285 * Fail:: @code{.fail}
4286 * File:: @code{.file}
4287 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4288 * Float:: @code{.float @var{flonums}}
4289 * Func:: @code{.func}
4290 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4292 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4293 * Hidden:: @code{.hidden @var{names}}
4296 * hword:: @code{.hword @var{expressions}}
4297 * Ident:: @code{.ident}
4298 * If:: @code{.if @var{absolute expression}}
4299 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4300 * Include:: @code{.include "@var{file}"}
4301 * Int:: @code{.int @var{expressions}}
4303 * Internal:: @code{.internal @var{names}}
4306 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4307 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4308 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4309 * Lflags:: @code{.lflags}
4310 @ifclear no-line-dir
4311 * Line:: @code{.line @var{line-number}}
4314 * Linkonce:: @code{.linkonce [@var{type}]}
4315 * List:: @code{.list}
4316 * Ln:: @code{.ln @var{line-number}}
4317 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4318 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4320 * Local:: @code{.local @var{names}}
4323 * Long:: @code{.long @var{expressions}}
4325 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4328 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4329 * MRI:: @code{.mri @var{val}}
4330 * Noaltmacro:: @code{.noaltmacro}
4331 * Nolist:: @code{.nolist}
4332 * Octa:: @code{.octa @var{bignums}}
4333 * Offset:: @code{.offset @var{loc}}
4334 * Org:: @code{.org @var{new-lc}, @var{fill}}
4335 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4337 * PopSection:: @code{.popsection}
4338 * Previous:: @code{.previous}
4341 * Print:: @code{.print @var{string}}
4343 * Protected:: @code{.protected @var{names}}
4346 * Psize:: @code{.psize @var{lines}, @var{columns}}
4347 * Purgem:: @code{.purgem @var{name}}
4349 * PushSection:: @code{.pushsection @var{name}}
4352 * Quad:: @code{.quad @var{bignums}}
4353 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4354 * Rept:: @code{.rept @var{count}}
4355 * Sbttl:: @code{.sbttl "@var{subheading}"}
4357 * Scl:: @code{.scl @var{class}}
4360 * Section:: @code{.section @var{name}[, @var{flags}]}
4363 * Set:: @code{.set @var{symbol}, @var{expression}}
4364 * Short:: @code{.short @var{expressions}}
4365 * Single:: @code{.single @var{flonums}}
4367 * Size:: @code{.size [@var{name} , @var{expression}]}
4369 @ifclear no-space-dir
4370 * Skip:: @code{.skip @var{size} , @var{fill}}
4373 * Sleb128:: @code{.sleb128 @var{expressions}}
4374 @ifclear no-space-dir
4375 * Space:: @code{.space @var{size} , @var{fill}}
4378 * Stab:: @code{.stabd, .stabn, .stabs}
4381 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4382 * Struct:: @code{.struct @var{expression}}
4384 * SubSection:: @code{.subsection}
4385 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4389 * Tag:: @code{.tag @var{structname}}
4392 * Text:: @code{.text @var{subsection}}
4393 * Title:: @code{.title "@var{heading}"}
4395 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4398 * Uleb128:: @code{.uleb128 @var{expressions}}
4400 * Val:: @code{.val @var{addr}}
4404 * Version:: @code{.version "@var{string}"}
4405 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4406 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4409 * Warning:: @code{.warning @var{string}}
4410 * Weak:: @code{.weak @var{names}}
4411 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4412 * Word:: @code{.word @var{expressions}}
4413 @ifclear no-space-dir
4414 * Zero:: @code{.zero @var{size}}
4416 * Deprecated:: Deprecated Directives
4420 @section @code{.abort}
4422 @cindex @code{abort} directive
4423 @cindex stopping the assembly
4424 This directive stops the assembly immediately. It is for
4425 compatibility with other assemblers. The original idea was that the
4426 assembly language source would be piped into the assembler. If the sender
4427 of the source quit, it could use this directive tells @command{@value{AS}} to
4428 quit also. One day @code{.abort} will not be supported.
4432 @section @code{.ABORT} (COFF)
4434 @cindex @code{ABORT} directive
4435 When producing COFF output, @command{@value{AS}} accepts this directive as a
4436 synonym for @samp{.abort}.
4439 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4445 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4447 @cindex padding the location counter
4448 @cindex @code{align} directive
4449 Pad the location counter (in the current subsection) to a particular storage
4450 boundary. The first expression (which must be absolute) is the alignment
4451 required, as described below.
4453 The second expression (also absolute) gives the fill value to be stored in the
4454 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4455 padding bytes are normally zero. However, on some systems, if the section is
4456 marked as containing code and the fill value is omitted, the space is filled
4457 with no-op instructions.
4459 The third expression is also absolute, and is also optional. If it is present,
4460 it is the maximum number of bytes that should be skipped by this alignment
4461 directive. If doing the alignment would require skipping more bytes than the
4462 specified maximum, then the alignment is not done at all. You can omit the
4463 fill value (the second argument) entirely by simply using two commas after the
4464 required alignment; this can be useful if you want the alignment to be filled
4465 with no-op instructions when appropriate.
4467 The way the required alignment is specified varies from system to system.
4468 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4469 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4470 alignment request in bytes. For example @samp{.align 8} advances
4471 the location counter until it is a multiple of 8. If the location counter
4472 is already a multiple of 8, no change is needed. For the tic54x, the
4473 first expression is the alignment request in words.
4475 For other systems, including ppc, i386 using a.out format, arm and
4476 strongarm, it is the
4477 number of low-order zero bits the location counter must have after
4478 advancement. For example @samp{.align 3} advances the location
4479 counter until it a multiple of 8. If the location counter is already a
4480 multiple of 8, no change is needed.
4482 This inconsistency is due to the different behaviors of the various
4483 native assemblers for these systems which GAS must emulate.
4484 GAS also provides @code{.balign} and @code{.p2align} directives,
4485 described later, which have a consistent behavior across all
4486 architectures (but are specific to GAS).
4489 @section @code{.altmacro}
4490 Enable alternate macro mode, enabling:
4493 @item LOCAL @var{name} [ , @dots{} ]
4494 One additional directive, @code{LOCAL}, is available. It is used to
4495 generate a string replacement for each of the @var{name} arguments, and
4496 replace any instances of @var{name} in each macro expansion. The
4497 replacement string is unique in the assembly, and different for each
4498 separate macro expansion. @code{LOCAL} allows you to write macros that
4499 define symbols, without fear of conflict between separate macro expansions.
4501 @item String delimiters
4502 You can write strings delimited in these other ways besides
4503 @code{"@var{string}"}:
4506 @item '@var{string}'
4507 You can delimit strings with single-quote characters.
4509 @item <@var{string}>
4510 You can delimit strings with matching angle brackets.
4513 @item single-character string escape
4514 To include any single character literally in a string (even if the
4515 character would otherwise have some special meaning), you can prefix the
4516 character with @samp{!} (an exclamation mark). For example, you can
4517 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4519 @item Expression results as strings
4520 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4521 and use the result as a string.
4525 @section @code{.ascii "@var{string}"}@dots{}
4527 @cindex @code{ascii} directive
4528 @cindex string literals
4529 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4530 separated by commas. It assembles each string (with no automatic
4531 trailing zero byte) into consecutive addresses.
4534 @section @code{.asciz "@var{string}"}@dots{}
4536 @cindex @code{asciz} directive
4537 @cindex zero-terminated strings
4538 @cindex null-terminated strings
4539 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4540 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4543 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4545 @cindex padding the location counter given number of bytes
4546 @cindex @code{balign} directive
4547 Pad the location counter (in the current subsection) to a particular
4548 storage boundary. The first expression (which must be absolute) is the
4549 alignment request in bytes. For example @samp{.balign 8} advances
4550 the location counter until it is a multiple of 8. If the location counter
4551 is already a multiple of 8, no change is needed.
4553 The second expression (also absolute) gives the fill value to be stored in the
4554 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4555 padding bytes are normally zero. However, on some systems, if the section is
4556 marked as containing code and the fill value is omitted, the space is filled
4557 with no-op instructions.
4559 The third expression is also absolute, and is also optional. If it is present,
4560 it is the maximum number of bytes that should be skipped by this alignment
4561 directive. If doing the alignment would require skipping more bytes than the
4562 specified maximum, then the alignment is not done at all. You can omit the
4563 fill value (the second argument) entirely by simply using two commas after the
4564 required alignment; this can be useful if you want the alignment to be filled
4565 with no-op instructions when appropriate.
4567 @cindex @code{balignw} directive
4568 @cindex @code{balignl} directive
4569 The @code{.balignw} and @code{.balignl} directives are variants of the
4570 @code{.balign} directive. The @code{.balignw} directive treats the fill
4571 pattern as a two byte word value. The @code{.balignl} directives treats the
4572 fill pattern as a four byte longword value. For example, @code{.balignw
4573 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4574 filled in with the value 0x368d (the exact placement of the bytes depends upon
4575 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4578 @node Bundle directives
4579 @section Bundle directives
4580 @subsection @code{.bundle_align_mode @var{abs-expr}}
4581 @cindex @code{bundle_align_mode} directive
4583 @cindex instruction bundle
4584 @cindex aligned instruction bundle
4585 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4586 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4587 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4588 disabled (which is the default state). If the argument it not zero, it
4589 gives the size of an instruction bundle as a power of two (as for the
4590 @code{.p2align} directive, @pxref{P2align}).
4592 For some targets, it's an ABI requirement that no instruction may span a
4593 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4594 instructions that starts on an aligned boundary. For example, if
4595 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4596 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4597 effect, no single instruction may span a boundary between bundles. If an
4598 instruction would start too close to the end of a bundle for the length of
4599 that particular instruction to fit within the bundle, then the space at the
4600 end of that bundle is filled with no-op instructions so the instruction
4601 starts in the next bundle. As a corollary, it's an error if any single
4602 instruction's encoding is longer than the bundle size.
4604 @subsection @code{.bundle_lock} and @code{.bundle_unlock}
4605 @cindex @code{bundle_lock} directive
4606 @cindex @code{bundle_unlock} directive
4607 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4608 allow explicit control over instruction bundle padding. These directives
4609 are only valid when @code{.bundle_align_mode} has been used to enable
4610 aligned instruction bundle mode. It's an error if they appear when
4611 @code{.bundle_align_mode} has not been used at all, or when the last
4612 directive was @w{@code{.bundle_align_mode 0}}.
4614 @cindex bundle-locked
4615 For some targets, it's an ABI requirement that certain instructions may
4616 appear only as part of specified permissible sequences of multiple
4617 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4618 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4619 instruction sequence. For purposes of aligned instruction bundle mode, a
4620 sequence starting with @code{.bundle_lock} and ending with
4621 @code{.bundle_unlock} is treated as a single instruction. That is, the
4622 entire sequence must fit into a single bundle and may not span a bundle
4623 boundary. If necessary, no-op instructions will be inserted before the
4624 first instruction of the sequence so that the whole sequence starts on an
4625 aligned bundle boundary. It's an error if the sequence is longer than the
4628 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4629 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4630 nested. That is, a second @code{.bundle_lock} directive before the next
4631 @code{.bundle_unlock} directive has no effect except that it must be
4632 matched by another closing @code{.bundle_unlock} so that there is the
4633 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4636 @section @code{.byte @var{expressions}}
4638 @cindex @code{byte} directive
4639 @cindex integers, one byte
4640 @code{.byte} expects zero or more expressions, separated by commas.
4641 Each expression is assembled into the next byte.
4643 @node CFI directives
4644 @section CFI directives
4645 @subsection @code{.cfi_sections @var{section_list}}
4646 @cindex @code{cfi_sections} directive
4647 @code{.cfi_sections} may be used to specify whether CFI directives
4648 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4649 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4650 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4651 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4652 directive is not used is @code{.cfi_sections .eh_frame}.
4654 On targets that support compact unwinding tables these can be generated
4655 by specifying @code{.eh_frame_entry} instead of @code{.eh_frame}.
4657 @subsection @code{.cfi_startproc [simple]}
4658 @cindex @code{cfi_startproc} directive
4659 @code{.cfi_startproc} is used at the beginning of each function that
4660 should have an entry in @code{.eh_frame}. It initializes some internal
4661 data structures. Don't forget to close the function by
4662 @code{.cfi_endproc}.
4664 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4665 it also emits some architecture dependent initial CFI instructions.
4667 @subsection @code{.cfi_endproc}
4668 @cindex @code{cfi_endproc} directive
4669 @code{.cfi_endproc} is used at the end of a function where it closes its
4670 unwind entry previously opened by
4671 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4673 @subsection @code{.cfi_personality @var{encoding} [, @var{exp}]}
4674 @cindex @code{cfi_personality} directive
4675 @code{.cfi_personality} defines personality routine and its encoding.
4676 @var{encoding} must be a constant determining how the personality
4677 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4678 argument is not present, otherwise second argument should be
4679 a constant or a symbol name. When using indirect encodings,
4680 the symbol provided should be the location where personality
4681 can be loaded from, not the personality routine itself.
4682 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4683 no personality routine.
4685 @subsection @code{.cfi_personality_id @var{id}}
4686 @cindex @code{cfi_personality_id} directive
4687 @code{cfi_personality_id} defines a personality routine by its index as
4688 defined in a compact unwinding format.
4689 Only valid when generating compact EH frames (i.e.
4690 with @code{.cfi_sections eh_frame_entry}.
4692 @subsection @code{.cfi_fde_data [@var{opcode1} [, @dots{}]]}
4693 @cindex @code{cfi_fde_data} directive
4694 @code{cfi_fde_data} is used to describe the compact unwind opcodes to be
4695 used for the current function. These are emitted inline in the
4696 @code{.eh_frame_entry} section if small enough and there is no LSDA, or
4697 in the @code{.gnu.extab} section otherwise.
4698 Only valid when generating compact EH frames (i.e.
4699 with @code{.cfi_sections eh_frame_entry}.
4701 @subsection @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4702 @code{.cfi_lsda} defines LSDA and its encoding.
4703 @var{encoding} must be a constant determining how the LSDA
4704 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), the second
4705 argument is not present, otherwise the second argument should be a constant
4706 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4707 meaning that no LSDA is present.
4709 @subsection @code{.cfi_inline_lsda} [@var{align}]
4710 @code{.cfi_inline_lsda} marks the start of a LSDA data section and
4711 switches to the corresponding @code{.gnu.extab} section.
4712 Must be preceded by a CFI block containing a @code{.cfi_lsda} directive.
4713 Only valid when generating compact EH frames (i.e.
4714 with @code{.cfi_sections eh_frame_entry}.
4716 The table header and unwinding opcodes will be generated at this point,
4717 so that they are immediately followed by the LSDA data. The symbol
4718 referenced by the @code{.cfi_lsda} directive should still be defined
4719 in case a fallback FDE based encoding is used. The LSDA data is terminated
4720 by a section directive.
4722 The optional @var{align} argument specifies the alignment required.
4723 The alignment is specified as a power of two, as with the
4724 @code{.p2align} directive.
4726 @subsection @code{.cfi_def_cfa @var{register}, @var{offset}}
4727 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4728 address from @var{register} and add @var{offset} to it}.
4730 @subsection @code{.cfi_def_cfa_register @var{register}}
4731 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4732 now on @var{register} will be used instead of the old one. Offset
4735 @subsection @code{.cfi_def_cfa_offset @var{offset}}
4736 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4737 remains the same, but @var{offset} is new. Note that it is the
4738 absolute offset that will be added to a defined register to compute
4741 @subsection @code{.cfi_adjust_cfa_offset @var{offset}}
4742 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4743 value that is added/substracted from the previous offset.
4745 @subsection @code{.cfi_offset @var{register}, @var{offset}}
4746 Previous value of @var{register} is saved at offset @var{offset} from
4749 @subsection @code{.cfi_rel_offset @var{register}, @var{offset}}
4750 Previous value of @var{register} is saved at offset @var{offset} from
4751 the current CFA register. This is transformed to @code{.cfi_offset}
4752 using the known displacement of the CFA register from the CFA.
4753 This is often easier to use, because the number will match the
4754 code it's annotating.
4756 @subsection @code{.cfi_register @var{register1}, @var{register2}}
4757 Previous value of @var{register1} is saved in register @var{register2}.
4759 @subsection @code{.cfi_restore @var{register}}
4760 @code{.cfi_restore} says that the rule for @var{register} is now the
4761 same as it was at the beginning of the function, after all initial
4762 instruction added by @code{.cfi_startproc} were executed.
4764 @subsection @code{.cfi_undefined @var{register}}
4765 From now on the previous value of @var{register} can't be restored anymore.
4767 @subsection @code{.cfi_same_value @var{register}}
4768 Current value of @var{register} is the same like in the previous frame,
4769 i.e. no restoration needed.
4771 @subsection @code{.cfi_remember_state},
4772 First save all current rules for all registers by @code{.cfi_remember_state},
4773 then totally screw them up by subsequent @code{.cfi_*} directives and when
4774 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4775 the previous saved state.
4777 @subsection @code{.cfi_return_column @var{register}}
4778 Change return column @var{register}, i.e. the return address is either
4779 directly in @var{register} or can be accessed by rules for @var{register}.
4781 @subsection @code{.cfi_signal_frame}
4782 Mark current function as signal trampoline.
4784 @subsection @code{.cfi_window_save}
4785 SPARC register window has been saved.
4787 @subsection @code{.cfi_escape} @var{expression}[, @dots{}]
4788 Allows the user to add arbitrary bytes to the unwind info. One
4789 might use this to add OS-specific CFI opcodes, or generic CFI
4790 opcodes that GAS does not yet support.
4792 @subsection @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4793 The current value of @var{register} is @var{label}. The value of @var{label}
4794 will be encoded in the output file according to @var{encoding}; see the
4795 description of @code{.cfi_personality} for details on this encoding.
4797 The usefulness of equating a register to a fixed label is probably
4798 limited to the return address register. Here, it can be useful to
4799 mark a code segment that has only one return address which is reached
4800 by a direct branch and no copy of the return address exists in memory
4801 or another register.
4804 @section @code{.comm @var{symbol} , @var{length} }
4806 @cindex @code{comm} directive
4807 @cindex symbol, common
4808 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4809 common symbol in one object file may be merged with a defined or common symbol
4810 of the same name in another object file. If @code{@value{LD}} does not see a
4811 definition for the symbol--just one or more common symbols--then it will
4812 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4813 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4814 the same name, and they do not all have the same size, it will allocate space
4815 using the largest size.
4818 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4819 an optional third argument. This is the desired alignment of the symbol,
4820 specified for ELF as a byte boundary (for example, an alignment of 16 means
4821 that the least significant 4 bits of the address should be zero), and for PE
4822 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4823 boundary). The alignment must be an absolute expression, and it must be a
4824 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4825 common symbol, it will use the alignment when placing the symbol. If no
4826 alignment is specified, @command{@value{AS}} will set the alignment to the
4827 largest power of two less than or equal to the size of the symbol, up to a
4828 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4829 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4830 @samp{--section-alignment} option; image file sections in PE are aligned to
4831 multiples of 4096, which is far too large an alignment for ordinary variables.
4832 It is rather the default alignment for (non-debug) sections within object
4833 (@samp{*.o}) files, which are less strictly aligned.}.
4837 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4838 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4842 @section @code{.data @var{subsection}}
4844 @cindex @code{data} directive
4845 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4846 end of the data subsection numbered @var{subsection} (which is an
4847 absolute expression). If @var{subsection} is omitted, it defaults
4852 @section @code{.def @var{name}}
4854 @cindex @code{def} directive
4855 @cindex COFF symbols, debugging
4856 @cindex debugging COFF symbols
4857 Begin defining debugging information for a symbol @var{name}; the
4858 definition extends until the @code{.endef} directive is encountered.
4861 This directive is only observed when @command{@value{AS}} is configured for COFF
4862 format output; when producing @code{b.out}, @samp{.def} is recognized,
4869 @section @code{.desc @var{symbol}, @var{abs-expression}}
4871 @cindex @code{desc} directive
4872 @cindex COFF symbol descriptor
4873 @cindex symbol descriptor, COFF
4874 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4875 to the low 16 bits of an absolute expression.
4878 The @samp{.desc} directive is not available when @command{@value{AS}} is
4879 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4880 object format. For the sake of compatibility, @command{@value{AS}} accepts
4881 it, but produces no output, when configured for COFF.
4887 @section @code{.dim}
4889 @cindex @code{dim} directive
4890 @cindex COFF auxiliary symbol information
4891 @cindex auxiliary symbol information, COFF
4892 This directive is generated by compilers to include auxiliary debugging
4893 information in the symbol table. It is only permitted inside
4894 @code{.def}/@code{.endef} pairs.
4897 @samp{.dim} is only meaningful when generating COFF format output; when
4898 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4904 @section @code{.double @var{flonums}}
4906 @cindex @code{double} directive
4907 @cindex floating point numbers (double)
4908 @code{.double} expects zero or more flonums, separated by commas. It
4909 assembles floating point numbers.
4911 The exact kind of floating point numbers emitted depends on how
4912 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4916 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4917 in @sc{ieee} format.
4922 @section @code{.eject}
4924 @cindex @code{eject} directive
4925 @cindex new page, in listings
4926 @cindex page, in listings
4927 @cindex listing control: new page
4928 Force a page break at this point, when generating assembly listings.
4931 @section @code{.else}
4933 @cindex @code{else} directive
4934 @code{.else} is part of the @command{@value{AS}} support for conditional
4935 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4936 of code to be assembled if the condition for the preceding @code{.if}
4940 @section @code{.elseif}
4942 @cindex @code{elseif} directive
4943 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4944 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4945 @code{.if} block that would otherwise fill the entire @code{.else} section.
4948 @section @code{.end}
4950 @cindex @code{end} directive
4951 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4952 process anything in the file past the @code{.end} directive.
4956 @section @code{.endef}
4958 @cindex @code{endef} directive
4959 This directive flags the end of a symbol definition begun with
4963 @samp{.endef} is only meaningful when generating COFF format output; if
4964 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4965 directive but ignores it.
4970 @section @code{.endfunc}
4971 @cindex @code{endfunc} directive
4972 @code{.endfunc} marks the end of a function specified with @code{.func}.
4975 @section @code{.endif}
4977 @cindex @code{endif} directive
4978 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4979 it marks the end of a block of code that is only assembled
4980 conditionally. @xref{If,,@code{.if}}.
4983 @section @code{.equ @var{symbol}, @var{expression}}
4985 @cindex @code{equ} directive
4986 @cindex assigning values to symbols
4987 @cindex symbols, assigning values to
4988 This directive sets the value of @var{symbol} to @var{expression}.
4989 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4992 The syntax for @code{equ} on the HPPA is
4993 @samp{@var{symbol} .equ @var{expression}}.
4997 The syntax for @code{equ} on the Z80 is
4998 @samp{@var{symbol} equ @var{expression}}.
4999 On the Z80 it is an eror if @var{symbol} is already defined,
5000 but the symbol is not protected from later redefinition.
5001 Compare @ref{Equiv}.
5005 @section @code{.equiv @var{symbol}, @var{expression}}
5006 @cindex @code{equiv} directive
5007 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
5008 the assembler will signal an error if @var{symbol} is already defined. Note a
5009 symbol which has been referenced but not actually defined is considered to be
5012 Except for the contents of the error message, this is roughly equivalent to
5019 plus it protects the symbol from later redefinition.
5022 @section @code{.eqv @var{symbol}, @var{expression}}
5023 @cindex @code{eqv} directive
5024 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
5025 evaluate the expression or any part of it immediately. Instead each time
5026 the resulting symbol is used in an expression, a snapshot of its current
5030 @section @code{.err}
5031 @cindex @code{err} directive
5032 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
5033 message and, unless the @option{-Z} option was used, it will not generate an
5034 object file. This can be used to signal an error in conditionally compiled code.
5037 @section @code{.error "@var{string}"}
5038 @cindex error directive
5040 Similarly to @code{.err}, this directive emits an error, but you can specify a
5041 string that will be emitted as the error message. If you don't specify the
5042 message, it defaults to @code{".error directive invoked in source file"}.
5043 @xref{Errors, ,Error and Warning Messages}.
5046 .error "This code has not been assembled and tested."
5050 @section @code{.exitm}
5051 Exit early from the current macro definition. @xref{Macro}.
5054 @section @code{.extern}
5056 @cindex @code{extern} directive
5057 @code{.extern} is accepted in the source program---for compatibility
5058 with other assemblers---but it is ignored. @command{@value{AS}} treats
5059 all undefined symbols as external.
5062 @section @code{.fail @var{expression}}
5064 @cindex @code{fail} directive
5065 Generates an error or a warning. If the value of the @var{expression} is 500
5066 or more, @command{@value{AS}} will print a warning message. If the value is less
5067 than 500, @command{@value{AS}} will print an error message. The message will
5068 include the value of @var{expression}. This can occasionally be useful inside
5069 complex nested macros or conditional assembly.
5072 @section @code{.file}
5073 @cindex @code{file} directive
5075 @ifclear no-file-dir
5076 There are two different versions of the @code{.file} directive. Targets
5077 that support DWARF2 line number information use the DWARF2 version of
5078 @code{.file}. Other targets use the default version.
5080 @subheading Default Version
5082 @cindex logical file name
5083 @cindex file name, logical
5084 This version of the @code{.file} directive tells @command{@value{AS}} that we
5085 are about to start a new logical file. The syntax is:
5091 @var{string} is the new file name. In general, the filename is
5092 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
5093 to specify an empty file name, you must give the quotes--@code{""}. This
5094 statement may go away in future: it is only recognized to be compatible with
5095 old @command{@value{AS}} programs.
5097 @subheading DWARF2 Version
5100 When emitting DWARF2 line number information, @code{.file} assigns filenames
5101 to the @code{.debug_line} file name table. The syntax is:
5104 .file @var{fileno} @var{filename}
5107 The @var{fileno} operand should be a unique positive integer to use as the
5108 index of the entry in the table. The @var{filename} operand is a C string
5111 The detail of filename indices is exposed to the user because the filename
5112 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5113 information, and thus the user must know the exact indices that table
5117 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5119 @cindex @code{fill} directive
5120 @cindex writing patterns in memory
5121 @cindex patterns, writing in memory
5122 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5123 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5124 may be zero or more. @var{Size} may be zero or more, but if it is
5125 more than 8, then it is deemed to have the value 8, compatible with
5126 other people's assemblers. The contents of each @var{repeat} bytes
5127 is taken from an 8-byte number. The highest order 4 bytes are
5128 zero. The lowest order 4 bytes are @var{value} rendered in the
5129 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5130 Each @var{size} bytes in a repetition is taken from the lowest order
5131 @var{size} bytes of this number. Again, this bizarre behavior is
5132 compatible with other people's assemblers.
5134 @var{size} and @var{value} are optional.
5135 If the second comma and @var{value} are absent, @var{value} is
5136 assumed zero. If the first comma and following tokens are absent,
5137 @var{size} is assumed to be 1.
5140 @section @code{.float @var{flonums}}
5142 @cindex floating point numbers (single)
5143 @cindex @code{float} directive
5144 This directive assembles zero or more flonums, separated by commas. It
5145 has the same effect as @code{.single}.
5147 The exact kind of floating point numbers emitted depends on how
5148 @command{@value{AS}} is configured.
5149 @xref{Machine Dependencies}.
5153 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5154 in @sc{ieee} format.
5159 @section @code{.func @var{name}[,@var{label}]}
5160 @cindex @code{func} directive
5161 @code{.func} emits debugging information to denote function @var{name}, and
5162 is ignored unless the file is assembled with debugging enabled.
5163 Only @samp{--gstabs[+]} is currently supported.
5164 @var{label} is the entry point of the function and if omitted @var{name}
5165 prepended with the @samp{leading char} is used.
5166 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5167 All functions are currently defined to have @code{void} return type.
5168 The function must be terminated with @code{.endfunc}.
5171 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5173 @cindex @code{global} directive
5174 @cindex symbol, making visible to linker
5175 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5176 @var{symbol} in your partial program, its value is made available to
5177 other partial programs that are linked with it. Otherwise,
5178 @var{symbol} takes its attributes from a symbol of the same name
5179 from another file linked into the same program.
5181 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5182 compatibility with other assemblers.
5185 On the HPPA, @code{.global} is not always enough to make it accessible to other
5186 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5187 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5192 @section @code{.gnu_attribute @var{tag},@var{value}}
5193 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5196 @section @code{.hidden @var{names}}
5198 @cindex @code{hidden} directive
5200 This is one of the ELF visibility directives. The other two are
5201 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5202 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5204 This directive overrides the named symbols default visibility (which is set by
5205 their binding: local, global or weak). The directive sets the visibility to
5206 @code{hidden} which means that the symbols are not visible to other components.
5207 Such symbols are always considered to be @code{protected} as well.
5211 @section @code{.hword @var{expressions}}
5213 @cindex @code{hword} directive
5214 @cindex integers, 16-bit
5215 @cindex numbers, 16-bit
5216 @cindex sixteen bit integers
5217 This expects zero or more @var{expressions}, and emits
5218 a 16 bit number for each.
5221 This directive is a synonym for @samp{.short}; depending on the target
5222 architecture, it may also be a synonym for @samp{.word}.
5226 This directive is a synonym for @samp{.short}.
5229 This directive is a synonym for both @samp{.short} and @samp{.word}.
5234 @section @code{.ident}
5236 @cindex @code{ident} directive
5238 This directive is used by some assemblers to place tags in object files. The
5239 behavior of this directive varies depending on the target. When using the
5240 a.out object file format, @command{@value{AS}} simply accepts the directive for
5241 source-file compatibility with existing assemblers, but does not emit anything
5242 for it. When using COFF, comments are emitted to the @code{.comment} or
5243 @code{.rdata} section, depending on the target. When using ELF, comments are
5244 emitted to the @code{.comment} section.
5247 @section @code{.if @var{absolute expression}}
5249 @cindex conditional assembly
5250 @cindex @code{if} directive
5251 @code{.if} marks the beginning of a section of code which is only
5252 considered part of the source program being assembled if the argument
5253 (which must be an @var{absolute expression}) is non-zero. The end of
5254 the conditional section of code must be marked by @code{.endif}
5255 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5256 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5257 If you have several conditions to check, @code{.elseif} may be used to avoid
5258 nesting blocks if/else within each subsequent @code{.else} block.
5260 The following variants of @code{.if} are also supported:
5262 @cindex @code{ifdef} directive
5263 @item .ifdef @var{symbol}
5264 Assembles the following section of code if the specified @var{symbol}
5265 has been defined. Note a symbol which has been referenced but not yet defined
5266 is considered to be undefined.
5268 @cindex @code{ifb} directive
5269 @item .ifb @var{text}
5270 Assembles the following section of code if the operand is blank (empty).
5272 @cindex @code{ifc} directive
5273 @item .ifc @var{string1},@var{string2}
5274 Assembles the following section of code if the two strings are the same. The
5275 strings may be optionally quoted with single quotes. If they are not quoted,
5276 the first string stops at the first comma, and the second string stops at the
5277 end of the line. Strings which contain whitespace should be quoted. The
5278 string comparison is case sensitive.
5280 @cindex @code{ifeq} directive
5281 @item .ifeq @var{absolute expression}
5282 Assembles the following section of code if the argument is zero.
5284 @cindex @code{ifeqs} directive
5285 @item .ifeqs @var{string1},@var{string2}
5286 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5288 @cindex @code{ifge} directive
5289 @item .ifge @var{absolute expression}
5290 Assembles the following section of code if the argument is greater than or
5293 @cindex @code{ifgt} directive
5294 @item .ifgt @var{absolute expression}
5295 Assembles the following section of code if the argument is greater than zero.
5297 @cindex @code{ifle} directive
5298 @item .ifle @var{absolute expression}
5299 Assembles the following section of code if the argument is less than or equal
5302 @cindex @code{iflt} directive
5303 @item .iflt @var{absolute expression}
5304 Assembles the following section of code if the argument is less than zero.
5306 @cindex @code{ifnb} directive
5307 @item .ifnb @var{text}
5308 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5309 following section of code if the operand is non-blank (non-empty).
5311 @cindex @code{ifnc} directive
5312 @item .ifnc @var{string1},@var{string2}.
5313 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5314 following section of code if the two strings are not the same.
5316 @cindex @code{ifndef} directive
5317 @cindex @code{ifnotdef} directive
5318 @item .ifndef @var{symbol}
5319 @itemx .ifnotdef @var{symbol}
5320 Assembles the following section of code if the specified @var{symbol}
5321 has not been defined. Both spelling variants are equivalent. Note a symbol
5322 which has been referenced but not yet defined is considered to be undefined.
5324 @cindex @code{ifne} directive
5325 @item .ifne @var{absolute expression}
5326 Assembles the following section of code if the argument is not equal to zero
5327 (in other words, this is equivalent to @code{.if}).
5329 @cindex @code{ifnes} directive
5330 @item .ifnes @var{string1},@var{string2}
5331 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5332 following section of code if the two strings are not the same.
5336 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5338 @cindex @code{incbin} directive
5339 @cindex binary files, including
5340 The @code{incbin} directive includes @var{file} verbatim at the current
5341 location. You can control the search paths used with the @samp{-I} command-line
5342 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5345 The @var{skip} argument skips a number of bytes from the start of the
5346 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5347 read. Note that the data is not aligned in any way, so it is the user's
5348 responsibility to make sure that proper alignment is provided both before and
5349 after the @code{incbin} directive.
5352 @section @code{.include "@var{file}"}
5354 @cindex @code{include} directive
5355 @cindex supporting files, including
5356 @cindex files, including
5357 This directive provides a way to include supporting files at specified
5358 points in your source program. The code from @var{file} is assembled as
5359 if it followed the point of the @code{.include}; when the end of the
5360 included file is reached, assembly of the original file continues. You
5361 can control the search paths used with the @samp{-I} command-line option
5362 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5366 @section @code{.int @var{expressions}}
5368 @cindex @code{int} directive
5369 @cindex integers, 32-bit
5370 Expect zero or more @var{expressions}, of any section, separated by commas.
5371 For each expression, emit a number that, at run time, is the value of that
5372 expression. The byte order and bit size of the number depends on what kind
5373 of target the assembly is for.
5377 On most forms of the H8/300, @code{.int} emits 16-bit
5378 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5385 @section @code{.internal @var{names}}
5387 @cindex @code{internal} directive
5389 This is one of the ELF visibility directives. The other two are
5390 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5391 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5393 This directive overrides the named symbols default visibility (which is set by
5394 their binding: local, global or weak). The directive sets the visibility to
5395 @code{internal} which means that the symbols are considered to be @code{hidden}
5396 (i.e., not visible to other components), and that some extra, processor specific
5397 processing must also be performed upon the symbols as well.
5401 @section @code{.irp @var{symbol},@var{values}}@dots{}
5403 @cindex @code{irp} directive
5404 Evaluate a sequence of statements assigning different values to @var{symbol}.
5405 The sequence of statements starts at the @code{.irp} directive, and is
5406 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5407 set to @var{value}, and the sequence of statements is assembled. If no
5408 @var{value} is listed, the sequence of statements is assembled once, with
5409 @var{symbol} set to the null string. To refer to @var{symbol} within the
5410 sequence of statements, use @var{\symbol}.
5412 For example, assembling
5420 is equivalent to assembling
5428 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5431 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5433 @cindex @code{irpc} directive
5434 Evaluate a sequence of statements assigning different values to @var{symbol}.
5435 The sequence of statements starts at the @code{.irpc} directive, and is
5436 terminated by an @code{.endr} directive. For each character in @var{value},
5437 @var{symbol} is set to the character, and the sequence of statements is
5438 assembled. If no @var{value} is listed, the sequence of statements is
5439 assembled once, with @var{symbol} set to the null string. To refer to
5440 @var{symbol} within the sequence of statements, use @var{\symbol}.
5442 For example, assembling
5450 is equivalent to assembling
5458 For some caveats with the spelling of @var{symbol}, see also the discussion
5462 @section @code{.lcomm @var{symbol} , @var{length}}
5464 @cindex @code{lcomm} directive
5465 @cindex local common symbols
5466 @cindex symbols, local common
5467 Reserve @var{length} (an absolute expression) bytes for a local common
5468 denoted by @var{symbol}. The section and value of @var{symbol} are
5469 those of the new local common. The addresses are allocated in the bss
5470 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5471 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5472 not visible to @code{@value{LD}}.
5475 Some targets permit a third argument to be used with @code{.lcomm}. This
5476 argument specifies the desired alignment of the symbol in the bss section.
5480 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5481 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5485 @section @code{.lflags}
5487 @cindex @code{lflags} directive (ignored)
5488 @command{@value{AS}} accepts this directive, for compatibility with other
5489 assemblers, but ignores it.
5491 @ifclear no-line-dir
5493 @section @code{.line @var{line-number}}
5495 @cindex @code{line} directive
5496 @cindex logical line number
5498 Change the logical line number. @var{line-number} must be an absolute
5499 expression. The next line has that logical line number. Therefore any other
5500 statements on the current line (after a statement separator character) are
5501 reported as on logical line number @var{line-number} @minus{} 1. One day
5502 @command{@value{AS}} will no longer support this directive: it is recognized only
5503 for compatibility with existing assembler programs.
5506 Even though this is a directive associated with the @code{a.out} or
5507 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5508 when producing COFF output, and treats @samp{.line} as though it
5509 were the COFF @samp{.ln} @emph{if} it is found outside a
5510 @code{.def}/@code{.endef} pair.
5512 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5513 used by compilers to generate auxiliary symbol information for
5518 @section @code{.linkonce [@var{type}]}
5520 @cindex @code{linkonce} directive
5521 @cindex common sections
5522 Mark the current section so that the linker only includes a single copy of it.
5523 This may be used to include the same section in several different object files,
5524 but ensure that the linker will only include it once in the final output file.
5525 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5526 Duplicate sections are detected based on the section name, so it should be
5529 This directive is only supported by a few object file formats; as of this
5530 writing, the only object file format which supports it is the Portable
5531 Executable format used on Windows NT.
5533 The @var{type} argument is optional. If specified, it must be one of the
5534 following strings. For example:
5538 Not all types may be supported on all object file formats.
5542 Silently discard duplicate sections. This is the default.
5545 Warn if there are duplicate sections, but still keep only one copy.
5548 Warn if any of the duplicates have different sizes.
5551 Warn if any of the duplicates do not have exactly the same contents.
5555 @section @code{.list}
5557 @cindex @code{list} directive
5558 @cindex listing control, turning on
5559 Control (in conjunction with the @code{.nolist} directive) whether or
5560 not assembly listings are generated. These two directives maintain an
5561 internal counter (which is zero initially). @code{.list} increments the
5562 counter, and @code{.nolist} decrements it. Assembly listings are
5563 generated whenever the counter is greater than zero.
5565 By default, listings are disabled. When you enable them (with the
5566 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5567 the initial value of the listing counter is one.
5570 @section @code{.ln @var{line-number}}
5572 @cindex @code{ln} directive
5573 @ifclear no-line-dir
5574 @samp{.ln} is a synonym for @samp{.line}.
5577 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5578 must be an absolute expression. The next line has that logical
5579 line number, so any other statements on the current line (after a
5580 statement separator character @code{;}) are reported as on logical
5581 line number @var{line-number} @minus{} 1.
5584 This directive is accepted, but ignored, when @command{@value{AS}} is
5585 configured for @code{b.out}; its effect is only associated with COFF
5591 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5592 @cindex @code{loc} directive
5593 When emitting DWARF2 line number information,
5594 the @code{.loc} directive will add a row to the @code{.debug_line} line
5595 number matrix corresponding to the immediately following assembly
5596 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5597 arguments will be applied to the @code{.debug_line} state machine before
5600 The @var{options} are a sequence of the following tokens in any order:
5604 This option will set the @code{basic_block} register in the
5605 @code{.debug_line} state machine to @code{true}.
5608 This option will set the @code{prologue_end} register in the
5609 @code{.debug_line} state machine to @code{true}.
5611 @item epilogue_begin
5612 This option will set the @code{epilogue_begin} register in the
5613 @code{.debug_line} state machine to @code{true}.
5615 @item is_stmt @var{value}
5616 This option will set the @code{is_stmt} register in the
5617 @code{.debug_line} state machine to @code{value}, which must be
5620 @item isa @var{value}
5621 This directive will set the @code{isa} register in the @code{.debug_line}
5622 state machine to @var{value}, which must be an unsigned integer.
5624 @item discriminator @var{value}
5625 This directive will set the @code{discriminator} register in the @code{.debug_line}
5626 state machine to @var{value}, which must be an unsigned integer.
5630 @node Loc_mark_labels
5631 @section @code{.loc_mark_labels @var{enable}}
5632 @cindex @code{loc_mark_labels} directive
5633 When emitting DWARF2 line number information,
5634 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5635 to the @code{.debug_line} line number matrix with the @code{basic_block}
5636 register in the state machine set whenever a code label is seen.
5637 The @var{enable} argument should be either 1 or 0, to enable or disable
5638 this function respectively.
5642 @section @code{.local @var{names}}
5644 @cindex @code{local} directive
5645 This directive, which is available for ELF targets, marks each symbol in
5646 the comma-separated list of @code{names} as a local symbol so that it
5647 will not be externally visible. If the symbols do not already exist,
5648 they will be created.
5650 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5651 accept an alignment argument, which is the case for most ELF targets,
5652 the @code{.local} directive can be used in combination with @code{.comm}
5653 (@pxref{Comm}) to define aligned local common data.
5657 @section @code{.long @var{expressions}}
5659 @cindex @code{long} directive
5660 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5663 @c no one seems to know what this is for or whether this description is
5664 @c what it really ought to do
5666 @section @code{.lsym @var{symbol}, @var{expression}}
5668 @cindex @code{lsym} directive
5669 @cindex symbol, not referenced in assembly
5670 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5671 the hash table, ensuring it cannot be referenced by name during the
5672 rest of the assembly. This sets the attributes of the symbol to be
5673 the same as the expression value:
5675 @var{other} = @var{descriptor} = 0
5676 @var{type} = @r{(section of @var{expression})}
5677 @var{value} = @var{expression}
5680 The new symbol is not flagged as external.
5684 @section @code{.macro}
5687 The commands @code{.macro} and @code{.endm} allow you to define macros that
5688 generate assembly output. For example, this definition specifies a macro
5689 @code{sum} that puts a sequence of numbers into memory:
5692 .macro sum from=0, to=5
5701 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5713 @item .macro @var{macname}
5714 @itemx .macro @var{macname} @var{macargs} @dots{}
5715 @cindex @code{macro} directive
5716 Begin the definition of a macro called @var{macname}. If your macro
5717 definition requires arguments, specify their names after the macro name,
5718 separated by commas or spaces. You can qualify the macro argument to
5719 indicate whether all invocations must specify a non-blank value (through
5720 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5721 (through @samp{:@code{vararg}}). You can supply a default value for any
5722 macro argument by following the name with @samp{=@var{deflt}}. You
5723 cannot define two macros with the same @var{macname} unless it has been
5724 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5725 definitions. For example, these are all valid @code{.macro} statements:
5729 Begin the definition of a macro called @code{comm}, which takes no
5732 @item .macro plus1 p, p1
5733 @itemx .macro plus1 p p1
5734 Either statement begins the definition of a macro called @code{plus1},
5735 which takes two arguments; within the macro definition, write
5736 @samp{\p} or @samp{\p1} to evaluate the arguments.
5738 @item .macro reserve_str p1=0 p2
5739 Begin the definition of a macro called @code{reserve_str}, with two
5740 arguments. The first argument has a default value, but not the second.
5741 After the definition is complete, you can call the macro either as
5742 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5743 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5744 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5745 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5747 @item .macro m p1:req, p2=0, p3:vararg
5748 Begin the definition of a macro called @code{m}, with at least three
5749 arguments. The first argument must always have a value specified, but
5750 not the second, which instead has a default value. The third formal
5751 will get assigned all remaining arguments specified at invocation time.
5753 When you call a macro, you can specify the argument values either by
5754 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5755 @samp{sum to=17, from=9}.
5759 Note that since each of the @var{macargs} can be an identifier exactly
5760 as any other one permitted by the target architecture, there may be
5761 occasional problems if the target hand-crafts special meanings to certain
5762 characters when they occur in a special position. For example, if the colon
5763 (@code{:}) is generally permitted to be part of a symbol name, but the
5764 architecture specific code special-cases it when occurring as the final
5765 character of a symbol (to denote a label), then the macro parameter
5766 replacement code will have no way of knowing that and consider the whole
5767 construct (including the colon) an identifier, and check only this
5768 identifier for being the subject to parameter substitution. So for example
5769 this macro definition:
5777 might not work as expected. Invoking @samp{label foo} might not create a label
5778 called @samp{foo} but instead just insert the text @samp{\l:} into the
5779 assembler source, probably generating an error about an unrecognised
5782 Similarly problems might occur with the period character (@samp{.})
5783 which is often allowed inside opcode names (and hence identifier names). So
5784 for example constructing a macro to build an opcode from a base name and a
5785 length specifier like this:
5788 .macro opcode base length
5793 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5794 instruction but instead generate some kind of error as the assembler tries to
5795 interpret the text @samp{\base.\length}.
5797 There are several possible ways around this problem:
5800 @item Insert white space
5801 If it is possible to use white space characters then this is the simplest
5810 @item Use @samp{\()}
5811 The string @samp{\()} can be used to separate the end of a macro argument from
5812 the following text. eg:
5815 .macro opcode base length
5820 @item Use the alternate macro syntax mode
5821 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5822 used as a separator. eg:
5832 Note: this problem of correctly identifying string parameters to pseudo ops
5833 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5834 and @code{.irpc} (@pxref{Irpc}) as well.
5837 @cindex @code{endm} directive
5838 Mark the end of a macro definition.
5841 @cindex @code{exitm} directive
5842 Exit early from the current macro definition.
5844 @cindex number of macros executed
5845 @cindex macros, count executed
5847 @command{@value{AS}} maintains a counter of how many macros it has
5848 executed in this pseudo-variable; you can copy that number to your
5849 output with @samp{\@@}, but @emph{only within a macro definition}.
5851 @item LOCAL @var{name} [ , @dots{} ]
5852 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5853 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5854 @xref{Altmacro,,@code{.altmacro}}.
5858 @section @code{.mri @var{val}}
5860 @cindex @code{mri} directive
5861 @cindex MRI mode, temporarily
5862 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5863 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5864 affects code assembled until the next @code{.mri} directive, or until the end
5865 of the file. @xref{M, MRI mode, MRI mode}.
5868 @section @code{.noaltmacro}
5869 Disable alternate macro mode. @xref{Altmacro}.
5872 @section @code{.nolist}
5874 @cindex @code{nolist} directive
5875 @cindex listing control, turning off
5876 Control (in conjunction with the @code{.list} directive) whether or
5877 not assembly listings are generated. These two directives maintain an
5878 internal counter (which is zero initially). @code{.list} increments the
5879 counter, and @code{.nolist} decrements it. Assembly listings are
5880 generated whenever the counter is greater than zero.
5883 @section @code{.octa @var{bignums}}
5885 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5886 @cindex @code{octa} directive
5887 @cindex integer, 16-byte
5888 @cindex sixteen byte integer
5889 This directive expects zero or more bignums, separated by commas. For each
5890 bignum, it emits a 16-byte integer.
5892 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5893 hence @emph{octa}-word for 16 bytes.
5896 @section @code{.offset @var{loc}}
5898 @cindex @code{offset} directive
5899 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5900 be an absolute expression. This directive may be useful for defining
5901 symbols with absolute values. Do not confuse it with the @code{.org}
5905 @section @code{.org @var{new-lc} , @var{fill}}
5907 @cindex @code{org} directive
5908 @cindex location counter, advancing
5909 @cindex advancing location counter
5910 @cindex current address, advancing
5911 Advance the location counter of the current section to
5912 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5913 expression with the same section as the current subsection. That is,
5914 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5915 wrong section, the @code{.org} directive is ignored. To be compatible
5916 with former assemblers, if the section of @var{new-lc} is absolute,
5917 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5918 is the same as the current subsection.
5920 @code{.org} may only increase the location counter, or leave it
5921 unchanged; you cannot use @code{.org} to move the location counter
5924 @c double negative used below "not undefined" because this is a specific
5925 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5926 @c section. doc@cygnus.com 18feb91
5927 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5928 may not be undefined. If you really detest this restriction we eagerly await
5929 a chance to share your improved assembler.
5931 Beware that the origin is relative to the start of the section, not
5932 to the start of the subsection. This is compatible with other
5933 people's assemblers.
5935 When the location counter (of the current subsection) is advanced, the
5936 intervening bytes are filled with @var{fill} which should be an
5937 absolute expression. If the comma and @var{fill} are omitted,
5938 @var{fill} defaults to zero.
5941 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5943 @cindex padding the location counter given a power of two
5944 @cindex @code{p2align} directive
5945 Pad the location counter (in the current subsection) to a particular
5946 storage boundary. The first expression (which must be absolute) is the
5947 number of low-order zero bits the location counter must have after
5948 advancement. For example @samp{.p2align 3} advances the location
5949 counter until it a multiple of 8. If the location counter is already a
5950 multiple of 8, no change is needed.
5952 The second expression (also absolute) gives the fill value to be stored in the
5953 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5954 padding bytes are normally zero. However, on some systems, if the section is
5955 marked as containing code and the fill value is omitted, the space is filled
5956 with no-op instructions.
5958 The third expression is also absolute, and is also optional. If it is present,
5959 it is the maximum number of bytes that should be skipped by this alignment
5960 directive. If doing the alignment would require skipping more bytes than the
5961 specified maximum, then the alignment is not done at all. You can omit the
5962 fill value (the second argument) entirely by simply using two commas after the
5963 required alignment; this can be useful if you want the alignment to be filled
5964 with no-op instructions when appropriate.
5966 @cindex @code{p2alignw} directive
5967 @cindex @code{p2alignl} directive
5968 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5969 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5970 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5971 fill pattern as a four byte longword value. For example, @code{.p2alignw
5972 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5973 filled in with the value 0x368d (the exact placement of the bytes depends upon
5974 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5979 @section @code{.popsection}
5981 @cindex @code{popsection} directive
5982 @cindex Section Stack
5983 This is one of the ELF section stack manipulation directives. The others are
5984 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5985 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5988 This directive replaces the current section (and subsection) with the top
5989 section (and subsection) on the section stack. This section is popped off the
5995 @section @code{.previous}
5997 @cindex @code{previous} directive
5998 @cindex Section Stack
5999 This is one of the ELF section stack manipulation directives. The others are
6000 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6001 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
6002 (@pxref{PopSection}).
6004 This directive swaps the current section (and subsection) with most recently
6005 referenced section/subsection pair prior to this one. Multiple
6006 @code{.previous} directives in a row will flip between two sections (and their
6007 subsections). For example:
6019 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
6025 # Now in section A subsection 1
6029 # Now in section B subsection 0
6032 # Now in section B subsection 1
6035 # Now in section B subsection 0
6039 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
6040 section B and 0x9abc into subsection 1 of section B.
6042 In terms of the section stack, this directive swaps the current section with
6043 the top section on the section stack.
6047 @section @code{.print @var{string}}
6049 @cindex @code{print} directive
6050 @command{@value{AS}} will print @var{string} on the standard output during
6051 assembly. You must put @var{string} in double quotes.
6055 @section @code{.protected @var{names}}
6057 @cindex @code{protected} directive
6059 This is one of the ELF visibility directives. The other two are
6060 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
6062 This directive overrides the named symbols default visibility (which is set by
6063 their binding: local, global or weak). The directive sets the visibility to
6064 @code{protected} which means that any references to the symbols from within the
6065 components that defines them must be resolved to the definition in that
6066 component, even if a definition in another component would normally preempt
6071 @section @code{.psize @var{lines} , @var{columns}}
6073 @cindex @code{psize} directive
6074 @cindex listing control: paper size
6075 @cindex paper size, for listings
6076 Use this directive to declare the number of lines---and, optionally, the
6077 number of columns---to use for each page, when generating listings.
6079 If you do not use @code{.psize}, listings use a default line-count
6080 of 60. You may omit the comma and @var{columns} specification; the
6081 default width is 200 columns.
6083 @command{@value{AS}} generates formfeeds whenever the specified number of
6084 lines is exceeded (or whenever you explicitly request one, using
6087 If you specify @var{lines} as @code{0}, no formfeeds are generated save
6088 those explicitly specified with @code{.eject}.
6091 @section @code{.purgem @var{name}}
6093 @cindex @code{purgem} directive
6094 Undefine the macro @var{name}, so that later uses of the string will not be
6095 expanded. @xref{Macro}.
6099 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
6101 @cindex @code{pushsection} directive
6102 @cindex Section Stack
6103 This is one of the ELF section stack manipulation directives. The others are
6104 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
6105 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6108 This directive pushes the current section (and subsection) onto the
6109 top of the section stack, and then replaces the current section and
6110 subsection with @code{name} and @code{subsection}. The optional
6111 @code{flags}, @code{type} and @code{arguments} are treated the same
6112 as in the @code{.section} (@pxref{Section}) directive.
6116 @section @code{.quad @var{bignums}}
6118 @cindex @code{quad} directive
6119 @code{.quad} expects zero or more bignums, separated by commas. For
6120 each bignum, it emits
6122 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6123 warning message; and just takes the lowest order 8 bytes of the bignum.
6124 @cindex eight-byte integer
6125 @cindex integer, 8-byte
6127 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6128 hence @emph{quad}-word for 8 bytes.
6131 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6132 warning message; and just takes the lowest order 16 bytes of the bignum.
6133 @cindex sixteen-byte integer
6134 @cindex integer, 16-byte
6138 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6140 @cindex @code{reloc} directive
6141 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6142 @var{expression}. If @var{offset} is a number, the relocation is generated in
6143 the current section. If @var{offset} is an expression that resolves to a
6144 symbol plus offset, the relocation is generated in the given symbol's section.
6145 @var{expression}, if present, must resolve to a symbol plus addend or to an
6146 absolute value, but note that not all targets support an addend. e.g. ELF REL
6147 targets such as i386 store an addend in the section contents rather than in the
6148 relocation. This low level interface does not support addends stored in the
6152 @section @code{.rept @var{count}}
6154 @cindex @code{rept} directive
6155 Repeat the sequence of lines between the @code{.rept} directive and the next
6156 @code{.endr} directive @var{count} times.
6158 For example, assembling
6166 is equivalent to assembling
6175 @section @code{.sbttl "@var{subheading}"}
6177 @cindex @code{sbttl} directive
6178 @cindex subtitles for listings
6179 @cindex listing control: subtitle
6180 Use @var{subheading} as the title (third line, immediately after the
6181 title line) when generating assembly listings.
6183 This directive affects subsequent pages, as well as the current page if
6184 it appears within ten lines of the top of a page.
6188 @section @code{.scl @var{class}}
6190 @cindex @code{scl} directive
6191 @cindex symbol storage class (COFF)
6192 @cindex COFF symbol storage class
6193 Set the storage-class value for a symbol. This directive may only be
6194 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6195 whether a symbol is static or external, or it may record further
6196 symbolic debugging information.
6199 The @samp{.scl} directive is primarily associated with COFF output; when
6200 configured to generate @code{b.out} output format, @command{@value{AS}}
6201 accepts this directive but ignores it.
6207 @section @code{.section @var{name}}
6209 @cindex named section
6210 Use the @code{.section} directive to assemble the following code into a section
6213 This directive is only supported for targets that actually support arbitrarily
6214 named sections; on @code{a.out} targets, for example, it is not accepted, even
6215 with a standard @code{a.out} section name.
6219 @c only print the extra heading if both COFF and ELF are set
6220 @subheading COFF Version
6223 @cindex @code{section} directive (COFF version)
6224 For COFF targets, the @code{.section} directive is used in one of the following
6228 .section @var{name}[, "@var{flags}"]
6229 .section @var{name}[, @var{subsection}]
6232 If the optional argument is quoted, it is taken as flags to use for the
6233 section. Each flag is a single character. The following flags are recognized:
6236 bss section (uninitialized data)
6238 section is not loaded
6244 exclude section from linking
6250 shared section (meaningful for PE targets)
6252 ignored. (For compatibility with the ELF version)
6254 section is not readable (meaningful for PE targets)
6256 single-digit power-of-two section alignment (GNU extension)
6259 If no flags are specified, the default flags depend upon the section name. If
6260 the section name is not recognized, the default will be for the section to be
6261 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6262 from the section, rather than adding them, so if they are used on their own it
6263 will be as if no flags had been specified at all.
6265 If the optional argument to the @code{.section} directive is not quoted, it is
6266 taken as a subsection number (@pxref{Sub-Sections}).
6271 @c only print the extra heading if both COFF and ELF are set
6272 @subheading ELF Version
6275 @cindex Section Stack
6276 This is one of the ELF section stack manipulation directives. The others are
6277 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6278 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6279 @code{.previous} (@pxref{Previous}).
6281 @cindex @code{section} directive (ELF version)
6282 For ELF targets, the @code{.section} directive is used like this:
6285 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6288 @anchor{Section Name Substitutions}
6289 @kindex --sectname-subst
6290 @cindex section name substitution
6291 If the @samp{--sectname-subst} command-line option is provided, the @var{name}
6292 argument may contain a substitution sequence. Only @code{%S} is supported
6293 at the moment, and substitutes the current section name. For example:
6296 .macro exception_code
6297 .section %S.exception
6298 [exception code here]
6313 The two @code{exception_code} invocations above would create the
6314 @code{.text.exception} and @code{.init.exception} sections respectively.
6315 This is useful e.g. to discriminate between anciliary sections that are
6316 tied to setup code to be discarded after use from anciliary sections that
6317 need to stay resident without having to define multiple @code{exception_code}
6318 macros just for that purpose.
6320 The optional @var{flags} argument is a quoted string which may contain any
6321 combination of the following characters:
6324 section is allocatable
6326 section is excluded from executable and shared library.
6330 section is executable
6332 section is mergeable
6334 section contains zero terminated strings
6336 section is a member of a section group
6338 section is used for thread-local-storage
6340 section is a member of the previously-current section's group, if any
6343 The optional @var{type} argument may contain one of the following constants:
6346 section contains data
6348 section does not contain data (i.e., section only occupies space)
6350 section contains data which is used by things other than the program
6352 section contains an array of pointers to init functions
6354 section contains an array of pointers to finish functions
6355 @item @@preinit_array
6356 section contains an array of pointers to pre-init functions
6359 Many targets only support the first three section types.
6361 Note on targets where the @code{@@} character is the start of a comment (eg
6362 ARM) then another character is used instead. For example the ARM port uses the
6365 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6366 be specified as well as an extra argument---@var{entsize}---like this:
6369 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6372 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6373 constants, each @var{entsize} octets long. Sections with both @code{M} and
6374 @code{S} must contain zero terminated strings where each character is
6375 @var{entsize} bytes long. The linker may remove duplicates within sections with
6376 the same name, same entity size and same flags. @var{entsize} must be an
6377 absolute expression. For sections with both @code{M} and @code{S}, a string
6378 which is a suffix of a larger string is considered a duplicate. Thus
6379 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6380 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6382 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6383 be present along with an additional field like this:
6386 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6389 The @var{GroupName} field specifies the name of the section group to which this
6390 particular section belongs. The optional linkage field can contain:
6393 indicates that only one copy of this section should be retained
6398 Note: if both the @var{M} and @var{G} flags are present then the fields for
6399 the Merge flag should come first, like this:
6402 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6405 If @var{flags} contains the @code{?} symbol then it may not also contain the
6406 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6407 present. Instead, @code{?} says to consider the section that's current before
6408 this directive. If that section used @code{G}, then the new section will use
6409 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6410 If not, then the @code{?} symbol has no effect.
6412 If no flags are specified, the default flags depend upon the section name. If
6413 the section name is not recognized, the default will be for the section to have
6414 none of the above flags: it will not be allocated in memory, nor writable, nor
6415 executable. The section will contain data.
6417 For ELF targets, the assembler supports another type of @code{.section}
6418 directive for compatibility with the Solaris assembler:
6421 .section "@var{name}"[, @var{flags}...]
6424 Note that the section name is quoted. There may be a sequence of comma
6428 section is allocatable
6432 section is executable
6434 section is excluded from executable and shared library.
6436 section is used for thread local storage
6439 This directive replaces the current section and subsection. See the
6440 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6441 some examples of how this directive and the other section stack directives
6447 @section @code{.set @var{symbol}, @var{expression}}
6449 @cindex @code{set} directive
6450 @cindex symbol value, setting
6451 Set the value of @var{symbol} to @var{expression}. This
6452 changes @var{symbol}'s value and type to conform to
6453 @var{expression}. If @var{symbol} was flagged as external, it remains
6454 flagged (@pxref{Symbol Attributes}).
6456 You may @code{.set} a symbol many times in the same assembly provided that the
6457 values given to the symbol are constants. Values that are based on expressions
6458 involving other symbols are allowed, but some targets may restrict this to only
6459 being done once per assembly. This is because those targets do not set the
6460 addresses of symbols at assembly time, but rather delay the assignment until a
6461 final link is performed. This allows the linker a chance to change the code in
6462 the files, changing the location of, and the relative distance between, various
6465 If you @code{.set} a global symbol, the value stored in the object
6466 file is the last value stored into it.
6469 On Z80 @code{set} is a real instruction, use
6470 @samp{@var{symbol} defl @var{expression}} instead.
6474 @section @code{.short @var{expressions}}
6476 @cindex @code{short} directive
6478 @code{.short} is normally the same as @samp{.word}.
6479 @xref{Word,,@code{.word}}.
6481 In some configurations, however, @code{.short} and @code{.word} generate
6482 numbers of different lengths. @xref{Machine Dependencies}.
6486 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6489 This expects zero or more @var{expressions}, and emits
6490 a 16 bit number for each.
6495 @section @code{.single @var{flonums}}
6497 @cindex @code{single} directive
6498 @cindex floating point numbers (single)
6499 This directive assembles zero or more flonums, separated by commas. It
6500 has the same effect as @code{.float}.
6502 The exact kind of floating point numbers emitted depends on how
6503 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6507 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6508 numbers in @sc{ieee} format.
6514 @section @code{.size}
6516 This directive is used to set the size associated with a symbol.
6520 @c only print the extra heading if both COFF and ELF are set
6521 @subheading COFF Version
6524 @cindex @code{size} directive (COFF version)
6525 For COFF targets, the @code{.size} directive is only permitted inside
6526 @code{.def}/@code{.endef} pairs. It is used like this:
6529 .size @var{expression}
6533 @samp{.size} is only meaningful when generating COFF format output; when
6534 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6541 @c only print the extra heading if both COFF and ELF are set
6542 @subheading ELF Version
6545 @cindex @code{size} directive (ELF version)
6546 For ELF targets, the @code{.size} directive is used like this:
6549 .size @var{name} , @var{expression}
6552 This directive sets the size associated with a symbol @var{name}.
6553 The size in bytes is computed from @var{expression} which can make use of label
6554 arithmetic. This directive is typically used to set the size of function
6559 @ifclear no-space-dir
6561 @section @code{.skip @var{size} , @var{fill}}
6563 @cindex @code{skip} directive
6564 @cindex filling memory
6565 This directive emits @var{size} bytes, each of value @var{fill}. Both
6566 @var{size} and @var{fill} are absolute expressions. If the comma and
6567 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6572 @section @code{.sleb128 @var{expressions}}
6574 @cindex @code{sleb128} directive
6575 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6576 compact, variable length representation of numbers used by the DWARF
6577 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6579 @ifclear no-space-dir
6581 @section @code{.space @var{size} , @var{fill}}
6583 @cindex @code{space} directive
6584 @cindex filling memory
6585 This directive emits @var{size} bytes, each of value @var{fill}. Both
6586 @var{size} and @var{fill} are absolute expressions. If the comma
6587 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6592 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6593 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6594 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6595 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6603 @section @code{.stabd, .stabn, .stabs}
6605 @cindex symbolic debuggers, information for
6606 @cindex @code{stab@var{x}} directives
6607 There are three directives that begin @samp{.stab}.
6608 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6609 The symbols are not entered in the @command{@value{AS}} hash table: they
6610 cannot be referenced elsewhere in the source file.
6611 Up to five fields are required:
6615 This is the symbol's name. It may contain any character except
6616 @samp{\000}, so is more general than ordinary symbol names. Some
6617 debuggers used to code arbitrarily complex structures into symbol names
6621 An absolute expression. The symbol's type is set to the low 8 bits of
6622 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6623 and debuggers choke on silly bit patterns.
6626 An absolute expression. The symbol's ``other'' attribute is set to the
6627 low 8 bits of this expression.
6630 An absolute expression. The symbol's descriptor is set to the low 16
6631 bits of this expression.
6634 An absolute expression which becomes the symbol's value.
6637 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6638 or @code{.stabs} statement, the symbol has probably already been created;
6639 you get a half-formed symbol in your object file. This is
6640 compatible with earlier assemblers!
6643 @cindex @code{stabd} directive
6644 @item .stabd @var{type} , @var{other} , @var{desc}
6646 The ``name'' of the symbol generated is not even an empty string.
6647 It is a null pointer, for compatibility. Older assemblers used a
6648 null pointer so they didn't waste space in object files with empty
6651 The symbol's value is set to the location counter,
6652 relocatably. When your program is linked, the value of this symbol
6653 is the address of the location counter when the @code{.stabd} was
6656 @cindex @code{stabn} directive
6657 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6658 The name of the symbol is set to the empty string @code{""}.
6660 @cindex @code{stabs} directive
6661 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6662 All five fields are specified.
6668 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6669 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6671 @cindex string, copying to object file
6672 @cindex string8, copying to object file
6673 @cindex string16, copying to object file
6674 @cindex string32, copying to object file
6675 @cindex string64, copying to object file
6676 @cindex @code{string} directive
6677 @cindex @code{string8} directive
6678 @cindex @code{string16} directive
6679 @cindex @code{string32} directive
6680 @cindex @code{string64} directive
6682 Copy the characters in @var{str} to the object file. You may specify more than
6683 one string to copy, separated by commas. Unless otherwise specified for a
6684 particular machine, the assembler marks the end of each string with a 0 byte.
6685 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6687 The variants @code{string16}, @code{string32} and @code{string64} differ from
6688 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6689 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6690 are stored in target endianness byte order.
6696 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6697 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6702 @section @code{.struct @var{expression}}
6704 @cindex @code{struct} directive
6705 Switch to the absolute section, and set the section offset to @var{expression},
6706 which must be an absolute expression. You might use this as follows:
6715 This would define the symbol @code{field1} to have the value 0, the symbol
6716 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6717 value 8. Assembly would be left in the absolute section, and you would need to
6718 use a @code{.section} directive of some sort to change to some other section
6719 before further assembly.
6723 @section @code{.subsection @var{name}}
6725 @cindex @code{subsection} directive
6726 @cindex Section Stack
6727 This is one of the ELF section stack manipulation directives. The others are
6728 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6729 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6732 This directive replaces the current subsection with @code{name}. The current
6733 section is not changed. The replaced subsection is put onto the section stack
6734 in place of the then current top of stack subsection.
6739 @section @code{.symver}
6740 @cindex @code{symver} directive
6741 @cindex symbol versioning
6742 @cindex versions of symbols
6743 Use the @code{.symver} directive to bind symbols to specific version nodes
6744 within a source file. This is only supported on ELF platforms, and is
6745 typically used when assembling files to be linked into a shared library.
6746 There are cases where it may make sense to use this in objects to be bound
6747 into an application itself so as to override a versioned symbol from a
6750 For ELF targets, the @code{.symver} directive can be used like this:
6752 .symver @var{name}, @var{name2@@nodename}
6754 If the symbol @var{name} is defined within the file
6755 being assembled, the @code{.symver} directive effectively creates a symbol
6756 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6757 just don't try and create a regular alias is that the @var{@@} character isn't
6758 permitted in symbol names. The @var{name2} part of the name is the actual name
6759 of the symbol by which it will be externally referenced. The name @var{name}
6760 itself is merely a name of convenience that is used so that it is possible to
6761 have definitions for multiple versions of a function within a single source
6762 file, and so that the compiler can unambiguously know which version of a
6763 function is being mentioned. The @var{nodename} portion of the alias should be
6764 the name of a node specified in the version script supplied to the linker when
6765 building a shared library. If you are attempting to override a versioned
6766 symbol from a shared library, then @var{nodename} should correspond to the
6767 nodename of the symbol you are trying to override.
6769 If the symbol @var{name} is not defined within the file being assembled, all
6770 references to @var{name} will be changed to @var{name2@@nodename}. If no
6771 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6774 Another usage of the @code{.symver} directive is:
6776 .symver @var{name}, @var{name2@@@@nodename}
6778 In this case, the symbol @var{name} must exist and be defined within
6779 the file being assembled. It is similar to @var{name2@@nodename}. The
6780 difference is @var{name2@@@@nodename} will also be used to resolve
6781 references to @var{name2} by the linker.
6783 The third usage of the @code{.symver} directive is:
6785 .symver @var{name}, @var{name2@@@@@@nodename}
6787 When @var{name} is not defined within the
6788 file being assembled, it is treated as @var{name2@@nodename}. When
6789 @var{name} is defined within the file being assembled, the symbol
6790 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6795 @section @code{.tag @var{structname}}
6797 @cindex COFF structure debugging
6798 @cindex structure debugging, COFF
6799 @cindex @code{tag} directive
6800 This directive is generated by compilers to include auxiliary debugging
6801 information in the symbol table. It is only permitted inside
6802 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6803 definitions in the symbol table with instances of those structures.
6806 @samp{.tag} is only used when generating COFF format output; when
6807 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6813 @section @code{.text @var{subsection}}
6815 @cindex @code{text} directive
6816 Tells @command{@value{AS}} to assemble the following statements onto the end of
6817 the text subsection numbered @var{subsection}, which is an absolute
6818 expression. If @var{subsection} is omitted, subsection number zero
6822 @section @code{.title "@var{heading}"}
6824 @cindex @code{title} directive
6825 @cindex listing control: title line
6826 Use @var{heading} as the title (second line, immediately after the
6827 source file name and pagenumber) when generating assembly listings.
6829 This directive affects subsequent pages, as well as the current page if
6830 it appears within ten lines of the top of a page.
6834 @section @code{.type}
6836 This directive is used to set the type of a symbol.
6840 @c only print the extra heading if both COFF and ELF are set
6841 @subheading COFF Version
6844 @cindex COFF symbol type
6845 @cindex symbol type, COFF
6846 @cindex @code{type} directive (COFF version)
6847 For COFF targets, this directive is permitted only within
6848 @code{.def}/@code{.endef} pairs. It is used like this:
6854 This records the integer @var{int} as the type attribute of a symbol table
6858 @samp{.type} is associated only with COFF format output; when
6859 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6860 directive but ignores it.
6866 @c only print the extra heading if both COFF and ELF are set
6867 @subheading ELF Version
6870 @cindex ELF symbol type
6871 @cindex symbol type, ELF
6872 @cindex @code{type} directive (ELF version)
6873 For ELF targets, the @code{.type} directive is used like this:
6876 .type @var{name} , @var{type description}
6879 This sets the type of symbol @var{name} to be either a
6880 function symbol or an object symbol. There are five different syntaxes
6881 supported for the @var{type description} field, in order to provide
6882 compatibility with various other assemblers.
6884 Because some of the characters used in these syntaxes (such as @samp{@@} and
6885 @samp{#}) are comment characters for some architectures, some of the syntaxes
6886 below do not work on all architectures. The first variant will be accepted by
6887 the GNU assembler on all architectures so that variant should be used for
6888 maximum portability, if you do not need to assemble your code with other
6891 The syntaxes supported are:
6894 .type <name> STT_<TYPE_IN_UPPER_CASE>
6895 .type <name>,#<type>
6896 .type <name>,@@<type>
6897 .type <name>,%<type>
6898 .type <name>,"<type>"
6901 The types supported are:
6906 Mark the symbol as being a function name.
6909 @itemx gnu_indirect_function
6910 Mark the symbol as an indirect function when evaluated during reloc
6911 processing. (This is only supported on assemblers targeting GNU systems).
6915 Mark the symbol as being a data object.
6919 Mark the symbol as being a thead-local data object.
6923 Mark the symbol as being a common data object.
6927 Does not mark the symbol in any way. It is supported just for completeness.
6929 @item gnu_unique_object
6930 Marks the symbol as being a globally unique data object. The dynamic linker
6931 will make sure that in the entire process there is just one symbol with this
6932 name and type in use. (This is only supported on assemblers targeting GNU
6937 Note: Some targets support extra types in addition to those listed above.
6943 @section @code{.uleb128 @var{expressions}}
6945 @cindex @code{uleb128} directive
6946 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6947 compact, variable length representation of numbers used by the DWARF
6948 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6952 @section @code{.val @var{addr}}
6954 @cindex @code{val} directive
6955 @cindex COFF value attribute
6956 @cindex value attribute, COFF
6957 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6958 records the address @var{addr} as the value attribute of a symbol table
6962 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6963 configured for @code{b.out}, it accepts this directive but ignores it.
6969 @section @code{.version "@var{string}"}
6971 @cindex @code{version} directive
6972 This directive creates a @code{.note} section and places into it an ELF
6973 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6978 @section @code{.vtable_entry @var{table}, @var{offset}}
6980 @cindex @code{vtable_entry} directive
6981 This directive finds or creates a symbol @code{table} and creates a
6982 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6985 @section @code{.vtable_inherit @var{child}, @var{parent}}
6987 @cindex @code{vtable_inherit} directive
6988 This directive finds the symbol @code{child} and finds or creates the symbol
6989 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6990 parent whose addend is the value of the child symbol. As a special case the
6991 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6995 @section @code{.warning "@var{string}"}
6996 @cindex warning directive
6997 Similar to the directive @code{.error}
6998 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
7001 @section @code{.weak @var{names}}
7003 @cindex @code{weak} directive
7004 This directive sets the weak attribute on the comma separated list of symbol
7005 @code{names}. If the symbols do not already exist, they will be created.
7007 On COFF targets other than PE, weak symbols are a GNU extension. This
7008 directive sets the weak attribute on the comma separated list of symbol
7009 @code{names}. If the symbols do not already exist, they will be created.
7011 On the PE target, weak symbols are supported natively as weak aliases.
7012 When a weak symbol is created that is not an alias, GAS creates an
7013 alternate symbol to hold the default value.
7016 @section @code{.weakref @var{alias}, @var{target}}
7018 @cindex @code{weakref} directive
7019 This directive creates an alias to the target symbol that enables the symbol to
7020 be referenced with weak-symbol semantics, but without actually making it weak.
7021 If direct references or definitions of the symbol are present, then the symbol
7022 will not be weak, but if all references to it are through weak references, the
7023 symbol will be marked as weak in the symbol table.
7025 The effect is equivalent to moving all references to the alias to a separate
7026 assembly source file, renaming the alias to the symbol in it, declaring the
7027 symbol as weak there, and running a reloadable link to merge the object files
7028 resulting from the assembly of the new source file and the old source file that
7029 had the references to the alias removed.
7031 The alias itself never makes to the symbol table, and is entirely handled
7032 within the assembler.
7035 @section @code{.word @var{expressions}}
7037 @cindex @code{word} directive
7038 This directive expects zero or more @var{expressions}, of any section,
7039 separated by commas.
7042 For each expression, @command{@value{AS}} emits a 32-bit number.
7045 For each expression, @command{@value{AS}} emits a 16-bit number.
7050 The size of the number emitted, and its byte order,
7051 depend on what target computer the assembly is for.
7054 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
7055 @c happen---32-bit addressability, period; no long/short jumps.
7056 @ifset DIFF-TBL-KLUGE
7057 @cindex difference tables altered
7058 @cindex altered difference tables
7060 @emph{Warning: Special Treatment to support Compilers}
7064 Machines with a 32-bit address space, but that do less than 32-bit
7065 addressing, require the following special treatment. If the machine of
7066 interest to you does 32-bit addressing (or doesn't require it;
7067 @pxref{Machine Dependencies}), you can ignore this issue.
7070 In order to assemble compiler output into something that works,
7071 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
7072 Directives of the form @samp{.word sym1-sym2} are often emitted by
7073 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
7074 directive of the form @samp{.word sym1-sym2}, and the difference between
7075 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
7076 creates a @dfn{secondary jump table}, immediately before the next label.
7077 This secondary jump table is preceded by a short-jump to the
7078 first byte after the secondary table. This short-jump prevents the flow
7079 of control from accidentally falling into the new table. Inside the
7080 table is a long-jump to @code{sym2}. The original @samp{.word}
7081 contains @code{sym1} minus the address of the long-jump to
7084 If there were several occurrences of @samp{.word sym1-sym2} before the
7085 secondary jump table, all of them are adjusted. If there was a
7086 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
7087 long-jump to @code{sym4} is included in the secondary jump table,
7088 and the @code{.word} directives are adjusted to contain @code{sym3}
7089 minus the address of the long-jump to @code{sym4}; and so on, for as many
7090 entries in the original jump table as necessary.
7093 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
7094 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
7095 assembly language programmers.
7098 @c end DIFF-TBL-KLUGE
7100 @ifclear no-space-dir
7102 @section @code{.zero @var{size}}
7104 @cindex @code{zero} directive
7105 @cindex filling memory with zero bytes
7106 This directive emits @var{size} 0-valued bytes. @var{size} must be an absolute
7107 expression. This directive is actually an alias for the @samp{.skip} directive
7108 so in can take an optional second argument of the value to store in the bytes
7109 instead of zero. Using @samp{.zero} in this way would be confusing however.
7113 @section Deprecated Directives
7115 @cindex deprecated directives
7116 @cindex obsolescent directives
7117 One day these directives won't work.
7118 They are included for compatibility with older assemblers.
7125 @node Object Attributes
7126 @chapter Object Attributes
7127 @cindex object attributes
7129 @command{@value{AS}} assembles source files written for a specific architecture
7130 into object files for that architecture. But not all object files are alike.
7131 Many architectures support incompatible variations. For instance, floating
7132 point arguments might be passed in floating point registers if the object file
7133 requires hardware floating point support---or floating point arguments might be
7134 passed in integer registers if the object file supports processors with no
7135 hardware floating point unit. Or, if two objects are built for different
7136 generations of the same architecture, the combination may require the
7137 newer generation at run-time.
7139 This information is useful during and after linking. At link time,
7140 @command{@value{LD}} can warn about incompatible object files. After link
7141 time, tools like @command{gdb} can use it to process the linked file
7144 Compatibility information is recorded as a series of object attributes. Each
7145 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
7146 string, and indicates who sets the meaning of the tag. The tag is an integer,
7147 and indicates what property the attribute describes. The value may be a string
7148 or an integer, and indicates how the property affects this object. Missing
7149 attributes are the same as attributes with a zero value or empty string value.
7151 Object attributes were developed as part of the ABI for the ARM Architecture.
7152 The file format is documented in @cite{ELF for the ARM Architecture}.
7155 * GNU Object Attributes:: @sc{gnu} Object Attributes
7156 * Defining New Object Attributes:: Defining New Object Attributes
7159 @node GNU Object Attributes
7160 @section @sc{gnu} Object Attributes
7162 The @code{.gnu_attribute} directive records an object attribute
7163 with vendor @samp{gnu}.
7165 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7166 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7167 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7168 2} is set for architecture-independent attributes and clear for
7169 architecture-dependent ones.
7171 @subsection Common @sc{gnu} attributes
7173 These attributes are valid on all architectures.
7176 @item Tag_compatibility (32)
7177 The compatibility attribute takes an integer flag value and a vendor name. If
7178 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7179 then the file is only compatible with the named toolchain. If it is greater
7180 than 1, the file can only be processed by other toolchains under some private
7181 arrangement indicated by the flag value and the vendor name.
7184 @subsection MIPS Attributes
7187 @item Tag_GNU_MIPS_ABI_FP (4)
7188 The floating-point ABI used by this object file. The value will be:
7192 0 for files not affected by the floating-point ABI.
7194 1 for files using the hardware floating-point ABI with a standard
7195 double-precision FPU.
7197 2 for files using the hardware floating-point ABI with a single-precision FPU.
7199 3 for files using the software floating-point ABI.
7201 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7202 floating-point registers, 32-bit general-purpose registers and increased the
7203 number of callee-saved floating-point registers.
7205 5 for files using the hardware floating-point ABI with a double-precision FPU
7206 with either 32-bit or 64-bit floating-point registers and 32-bit
7207 general-purpose registers.
7209 6 for files using the hardware floating-point ABI with 64-bit floating-point
7210 registers and 32-bit general-purpose registers.
7212 7 for files using the hardware floating-point ABI with 64-bit floating-point
7213 registers, 32-bit general-purpose registers and a rule that forbids the
7214 direct use of odd-numbered single-precision floating-point registers.
7218 @subsection PowerPC Attributes
7221 @item Tag_GNU_Power_ABI_FP (4)
7222 The floating-point ABI used by this object file. The value will be:
7226 0 for files not affected by the floating-point ABI.
7228 1 for files using double-precision hardware floating-point ABI.
7230 2 for files using the software floating-point ABI.
7232 3 for files using single-precision hardware floating-point ABI.
7235 @item Tag_GNU_Power_ABI_Vector (8)
7236 The vector ABI used by this object file. The value will be:
7240 0 for files not affected by the vector ABI.
7242 1 for files using general purpose registers to pass vectors.
7244 2 for files using AltiVec registers to pass vectors.
7246 3 for files using SPE registers to pass vectors.
7250 @subsection IBM z Systems Attributes
7253 @item Tag_GNU_S390_ABI_Vector (8)
7254 The vector ABI used by this object file. The value will be:
7258 0 for files not affected by the vector ABI.
7260 1 for files using software vector ABI.
7262 2 for files using hardware vector ABI.
7266 @node Defining New Object Attributes
7267 @section Defining New Object Attributes
7269 If you want to define a new @sc{gnu} object attribute, here are the places you
7270 will need to modify. New attributes should be discussed on the @samp{binutils}
7275 This manual, which is the official register of attributes.
7277 The header for your architecture @file{include/elf}, to define the tag.
7279 The @file{bfd} support file for your architecture, to merge the attribute
7280 and issue any appropriate link warnings.
7282 Test cases in @file{ld/testsuite} for merging and link warnings.
7284 @file{binutils/readelf.c} to display your attribute.
7286 GCC, if you want the compiler to mark the attribute automatically.
7292 @node Machine Dependencies
7293 @chapter Machine Dependent Features
7295 @cindex machine dependencies
7296 The machine instruction sets are (almost by definition) different on
7297 each machine where @command{@value{AS}} runs. Floating point representations
7298 vary as well, and @command{@value{AS}} often supports a few additional
7299 directives or command-line options for compatibility with other
7300 assemblers on a particular platform. Finally, some versions of
7301 @command{@value{AS}} support special pseudo-instructions for branch
7304 This chapter discusses most of these differences, though it does not
7305 include details on any machine's instruction set. For details on that
7306 subject, see the hardware manufacturer's manual.
7310 * AArch64-Dependent:: AArch64 Dependent Features
7313 * Alpha-Dependent:: Alpha Dependent Features
7316 * ARC-Dependent:: ARC Dependent Features
7319 * ARM-Dependent:: ARM Dependent Features
7322 * AVR-Dependent:: AVR Dependent Features
7325 * Blackfin-Dependent:: Blackfin Dependent Features
7328 * CR16-Dependent:: CR16 Dependent Features
7331 * CRIS-Dependent:: CRIS Dependent Features
7334 * D10V-Dependent:: D10V Dependent Features
7337 * D30V-Dependent:: D30V Dependent Features
7340 * Epiphany-Dependent:: EPIPHANY Dependent Features
7343 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7346 * HPPA-Dependent:: HPPA Dependent Features
7349 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7352 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7355 * i860-Dependent:: Intel 80860 Dependent Features
7358 * i960-Dependent:: Intel 80960 Dependent Features
7361 * IA-64-Dependent:: Intel IA-64 Dependent Features
7364 * IP2K-Dependent:: IP2K Dependent Features
7367 * LM32-Dependent:: LM32 Dependent Features
7370 * M32C-Dependent:: M32C Dependent Features
7373 * M32R-Dependent:: M32R Dependent Features
7376 * M68K-Dependent:: M680x0 Dependent Features
7379 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7382 * Meta-Dependent :: Meta Dependent Features
7385 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7388 * MIPS-Dependent:: MIPS Dependent Features
7391 * MMIX-Dependent:: MMIX Dependent Features
7394 * MSP430-Dependent:: MSP430 Dependent Features
7397 * NDS32-Dependent:: Andes NDS32 Dependent Features
7400 * NiosII-Dependent:: Altera Nios II Dependent Features
7403 * NS32K-Dependent:: NS32K Dependent Features
7406 * PDP-11-Dependent:: PDP-11 Dependent Features
7409 * PJ-Dependent:: picoJava Dependent Features
7412 * PPC-Dependent:: PowerPC Dependent Features
7415 * RL78-Dependent:: RL78 Dependent Features
7418 * RX-Dependent:: RX Dependent Features
7421 * S/390-Dependent:: IBM S/390 Dependent Features
7424 * SCORE-Dependent:: SCORE Dependent Features
7427 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7428 * SH64-Dependent:: SuperH SH64 Dependent Features
7431 * Sparc-Dependent:: SPARC Dependent Features
7434 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7437 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7440 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7443 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7446 * V850-Dependent:: V850 Dependent Features
7449 * Vax-Dependent:: VAX Dependent Features
7452 * Visium-Dependent:: Visium Dependent Features
7455 * XGATE-Dependent:: XGATE Features
7458 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7461 * Xtensa-Dependent:: Xtensa Dependent Features
7464 * Z80-Dependent:: Z80 Dependent Features
7467 * Z8000-Dependent:: Z8000 Dependent Features
7474 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7475 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7476 @c peculiarity: to preserve cross-references, there must be a node called
7477 @c "Machine Dependencies". Hence the conditional nodenames in each
7478 @c major node below. Node defaulting in makeinfo requires adjacency of
7479 @c node and sectioning commands; hence the repetition of @chapter BLAH
7480 @c in both conditional blocks.
7483 @include c-aarch64.texi
7487 @include c-alpha.texi
7503 @include c-bfin.texi
7507 @include c-cr16.texi
7511 @include c-cris.texi
7516 @node Machine Dependencies
7517 @chapter Machine Dependent Features
7519 The machine instruction sets are different on each Renesas chip family,
7520 and there are also some syntax differences among the families. This
7521 chapter describes the specific @command{@value{AS}} features for each
7525 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7526 * SH-Dependent:: Renesas SH Dependent Features
7533 @include c-d10v.texi
7537 @include c-d30v.texi
7541 @include c-epiphany.texi
7545 @include c-h8300.texi
7549 @include c-hppa.texi
7553 @include c-i370.texi
7557 @include c-i386.texi
7561 @include c-i860.texi
7565 @include c-i960.texi
7569 @include c-ia64.texi
7573 @include c-ip2k.texi
7577 @include c-lm32.texi
7581 @include c-m32c.texi
7585 @include c-m32r.texi
7589 @include c-m68k.texi
7593 @include c-m68hc11.texi
7597 @include c-metag.texi
7601 @include c-microblaze.texi
7605 @include c-mips.texi
7609 @include c-mmix.texi
7613 @include c-msp430.texi
7617 @include c-nds32.texi
7621 @include c-nios2.texi
7625 @include c-ns32k.texi
7629 @include c-pdp11.texi
7641 @include c-rl78.texi
7649 @include c-s390.texi
7653 @include c-score.texi
7658 @include c-sh64.texi
7662 @include c-sparc.texi
7666 @include c-tic54x.texi
7670 @include c-tic6x.texi
7674 @include c-tilegx.texi
7678 @include c-tilepro.texi
7682 @include c-v850.texi
7690 @include c-visium.texi
7694 @include c-xgate.texi
7698 @include c-xstormy16.texi
7702 @include c-xtensa.texi
7714 @c reverse effect of @down at top of generic Machine-Dep chapter
7718 @node Reporting Bugs
7719 @chapter Reporting Bugs
7720 @cindex bugs in assembler
7721 @cindex reporting bugs in assembler
7723 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7725 Reporting a bug may help you by bringing a solution to your problem, or it may
7726 not. But in any case the principal function of a bug report is to help the
7727 entire community by making the next version of @command{@value{AS}} work better.
7728 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7730 In order for a bug report to serve its purpose, you must include the
7731 information that enables us to fix the bug.
7734 * Bug Criteria:: Have you found a bug?
7735 * Bug Reporting:: How to report bugs
7739 @section Have You Found a Bug?
7740 @cindex bug criteria
7742 If you are not sure whether you have found a bug, here are some guidelines:
7745 @cindex fatal signal
7746 @cindex assembler crash
7747 @cindex crash of assembler
7749 If the assembler gets a fatal signal, for any input whatever, that is a
7750 @command{@value{AS}} bug. Reliable assemblers never crash.
7752 @cindex error on valid input
7754 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7756 @cindex invalid input
7758 If @command{@value{AS}} does not produce an error message for invalid input, that
7759 is a bug. However, you should note that your idea of ``invalid input'' might
7760 be our idea of ``an extension'' or ``support for traditional practice''.
7763 If you are an experienced user of assemblers, your suggestions for improvement
7764 of @command{@value{AS}} are welcome in any case.
7768 @section How to Report Bugs
7770 @cindex assembler bugs, reporting
7772 A number of companies and individuals offer support for @sc{gnu} products. If
7773 you obtained @command{@value{AS}} from a support organization, we recommend you
7774 contact that organization first.
7776 You can find contact information for many support companies and
7777 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7781 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7785 The fundamental principle of reporting bugs usefully is this:
7786 @strong{report all the facts}. If you are not sure whether to state a
7787 fact or leave it out, state it!
7789 Often people omit facts because they think they know what causes the problem
7790 and assume that some details do not matter. Thus, you might assume that the
7791 name of a symbol you use in an example does not matter. Well, probably it does
7792 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7793 happens to fetch from the location where that name is stored in memory;
7794 perhaps, if the name were different, the contents of that location would fool
7795 the assembler into doing the right thing despite the bug. Play it safe and
7796 give a specific, complete example. That is the easiest thing for you to do,
7797 and the most helpful.
7799 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7800 it is new to us. Therefore, always write your bug reports on the assumption
7801 that the bug has not been reported previously.
7803 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7804 bell?'' This cannot help us fix a bug, so it is basically useless. We
7805 respond by asking for enough details to enable us to investigate.
7806 You might as well expedite matters by sending them to begin with.
7808 To enable us to fix the bug, you should include all these things:
7812 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7813 it with the @samp{--version} argument.
7815 Without this, we will not know whether there is any point in looking for
7816 the bug in the current version of @command{@value{AS}}.
7819 Any patches you may have applied to the @command{@value{AS}} source.
7822 The type of machine you are using, and the operating system name and
7826 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7830 The command arguments you gave the assembler to assemble your example and
7831 observe the bug. To guarantee you will not omit something important, list them
7832 all. A copy of the Makefile (or the output from make) is sufficient.
7834 If we were to try to guess the arguments, we would probably guess wrong
7835 and then we might not encounter the bug.
7838 A complete input file that will reproduce the bug. If the bug is observed when
7839 the assembler is invoked via a compiler, send the assembler source, not the
7840 high level language source. Most compilers will produce the assembler source
7841 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7842 the options @samp{-v --save-temps}; this will save the assembler source in a
7843 file with an extension of @file{.s}, and also show you exactly how
7844 @command{@value{AS}} is being run.
7847 A description of what behavior you observe that you believe is
7848 incorrect. For example, ``It gets a fatal signal.''
7850 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7851 will certainly notice it. But if the bug is incorrect output, we might not
7852 notice unless it is glaringly wrong. You might as well not give us a chance to
7855 Even if the problem you experience is a fatal signal, you should still say so
7856 explicitly. Suppose something strange is going on, such as, your copy of
7857 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7858 library on your system. (This has happened!) Your copy might crash and ours
7859 would not. If you told us to expect a crash, then when ours fails to crash, we
7860 would know that the bug was not happening for us. If you had not told us to
7861 expect a crash, then we would not be able to draw any conclusion from our
7865 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7866 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7867 option. Always send diffs from the old file to the new file. If you even
7868 discuss something in the @command{@value{AS}} source, refer to it by context, not
7871 The line numbers in our development sources will not match those in your
7872 sources. Your line numbers would convey no useful information to us.
7875 Here are some things that are not necessary:
7879 A description of the envelope of the bug.
7881 Often people who encounter a bug spend a lot of time investigating
7882 which changes to the input file will make the bug go away and which
7883 changes will not affect it.
7885 This is often time consuming and not very useful, because the way we
7886 will find the bug is by running a single example under the debugger
7887 with breakpoints, not by pure deduction from a series of examples.
7888 We recommend that you save your time for something else.
7890 Of course, if you can find a simpler example to report @emph{instead}
7891 of the original one, that is a convenience for us. Errors in the
7892 output will be easier to spot, running under the debugger will take
7893 less time, and so on.
7895 However, simplification is not vital; if you do not want to do this,
7896 report the bug anyway and send us the entire test case you used.
7899 A patch for the bug.
7901 A patch for the bug does help us if it is a good one. But do not omit
7902 the necessary information, such as the test case, on the assumption that
7903 a patch is all we need. We might see problems with your patch and decide
7904 to fix the problem another way, or we might not understand it at all.
7906 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7907 construct an example that will make the program follow a certain path through
7908 the code. If you do not send us the example, we will not be able to construct
7909 one, so we will not be able to verify that the bug is fixed.
7911 And if we cannot understand what bug you are trying to fix, or why your
7912 patch should be an improvement, we will not install it. A test case will
7913 help us to understand.
7916 A guess about what the bug is or what it depends on.
7918 Such guesses are usually wrong. Even we cannot guess right about such
7919 things without first using the debugger to find the facts.
7922 @node Acknowledgements
7923 @chapter Acknowledgements
7925 If you have contributed to GAS and your name isn't listed here,
7926 it is not meant as a slight. We just don't know about it. Send mail to the
7927 maintainer, and we'll correct the situation. Currently
7929 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7931 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7934 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7935 information and the 68k series machines, most of the preprocessing pass, and
7936 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7938 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7939 many bug fixes, including merging support for several processors, breaking GAS
7940 up to handle multiple object file format back ends (including heavy rewrite,
7941 testing, an integration of the coff and b.out back ends), adding configuration
7942 including heavy testing and verification of cross assemblers and file splits
7943 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7944 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7945 port (including considerable amounts of reverse engineering), a SPARC opcode
7946 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7947 assertions and made them work, much other reorganization, cleanup, and lint.
7949 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7950 in format-specific I/O modules.
7952 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7953 has done much work with it since.
7955 The Intel 80386 machine description was written by Eliot Dresselhaus.
7957 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7959 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7960 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7962 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7963 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7964 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7965 support a.out format.
7967 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7968 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7969 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7970 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7973 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7974 simplified the configuration of which versions accept which directives. He
7975 updated the 68k machine description so that Motorola's opcodes always produced
7976 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7977 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7978 cross-compilation support, and one bug in relaxation that took a week and
7979 required the proverbial one-bit fix.
7981 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7982 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7983 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7984 PowerPC assembler, and made a few other minor patches.
7986 Steve Chamberlain made GAS able to generate listings.
7988 Hewlett-Packard contributed support for the HP9000/300.
7990 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7991 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7992 formats). This work was supported by both the Center for Software Science at
7993 the University of Utah and Cygnus Support.
7995 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7996 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7997 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7998 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7999 and some initial 64-bit support).
8001 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
8003 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
8004 support for openVMS/Alpha.
8006 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
8009 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
8010 Inc.@: added support for Xtensa processors.
8012 Several engineers at Cygnus Support have also provided many small bug fixes and
8013 configuration enhancements.
8015 Jon Beniston added support for the Lattice Mico32 architecture.
8017 Many others have contributed large or small bugfixes and enhancements. If
8018 you have contributed significant work and are not mentioned on this list, and
8019 want to be, let us know. Some of the history has been lost; we are not
8020 intentionally leaving anyone out.
8022 @node GNU Free Documentation License
8023 @appendix GNU Free Documentation License
8027 @unnumbered AS Index