1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2014 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{} 1991-2014 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{} 1991-2014 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}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
251 [@b{-mabi}=@var{ABI}]
255 @emph{Target Alpha options:}
257 [@b{-mdebug} | @b{-no-mdebug}]
258 [@b{-replace} | @b{-noreplace}]
259 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
260 [@b{-F}] [@b{-32addr}]
264 @emph{Target ARC options:}
270 @emph{Target ARM options:}
271 @c Don't document the deprecated options
272 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
273 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
274 [@b{-mfpu}=@var{floating-point-format}]
275 [@b{-mfloat-abi}=@var{abi}]
276 [@b{-meabi}=@var{ver}]
279 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
280 @b{-mapcs-reentrant}]
281 [@b{-mthumb-interwork}] [@b{-k}]
285 @emph{Target Blackfin options:}
286 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
293 @emph{Target CRIS options:}
294 [@b{--underscore} | @b{--no-underscore}]
296 [@b{--emulation=criself} | @b{--emulation=crisaout}]
297 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
298 @c Deprecated -- deliberately not documented.
303 @emph{Target D10V options:}
308 @emph{Target D30V options:}
309 [@b{-O}|@b{-n}|@b{-N}]
313 @emph{Target EPIPHANY options:}
314 [@b{-mepiphany}|@b{-mepiphany16}]
318 @emph{Target H8/300 options:}
322 @c HPPA has no machine-dependent assembler options (yet).
326 @emph{Target i386 options:}
327 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
328 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
332 @emph{Target i960 options:}
333 @c see md_parse_option in tc-i960.c
334 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
336 [@b{-b}] [@b{-no-relax}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
345 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
346 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
347 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
351 @emph{Target IP2K options:}
352 [@b{-mip2022}|@b{-mip2022ext}]
356 @emph{Target M32C options:}
357 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
361 @emph{Target M32R options:}
362 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
367 @emph{Target M680X0 options:}
368 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
372 @emph{Target M68HC11 options:}
373 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
374 [@b{-mshort}|@b{-mlong}]
375 [@b{-mshort-double}|@b{-mlong-double}]
376 [@b{--force-long-branches}] [@b{--short-branches}]
377 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
378 [@b{--print-opcodes}] [@b{--generate-example}]
382 @emph{Target MCORE options:}
383 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
384 [@b{-mcpu=[210|340]}]
388 @emph{Target Meta options:}
389 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
392 @emph{Target MICROBLAZE options:}
393 @c MicroBlaze has no machine-dependent assembler options.
397 @emph{Target MIPS options:}
398 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
399 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
400 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
401 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
402 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
403 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
404 [@b{-mips64}] [@b{-mips64r2}]
405 [@b{-construct-floats}] [@b{-no-construct-floats}]
406 [@b{-mnan=@var{encoding}}]
407 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
408 [@b{-mips16}] [@b{-no-mips16}]
409 [@b{-mmicromips}] [@b{-mno-micromips}]
410 [@b{-msmartmips}] [@b{-mno-smartmips}]
411 [@b{-mips3d}] [@b{-no-mips3d}]
412 [@b{-mdmx}] [@b{-no-mdmx}]
413 [@b{-mdsp}] [@b{-mno-dsp}]
414 [@b{-mdspr2}] [@b{-mno-dspr2}]
415 [@b{-mmsa}] [@b{-mno-msa}]
416 [@b{-mxpa}] [@b{-mno-xpa}]
417 [@b{-mmt}] [@b{-mno-mt}]
418 [@b{-mmcu}] [@b{-mno-mcu}]
419 [@b{-minsn32}] [@b{-mno-insn32}]
420 [@b{-mfix7000}] [@b{-mno-fix7000}]
421 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
422 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
423 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
424 [@b{-mdebug}] [@b{-no-mdebug}]
425 [@b{-mpdr}] [@b{-mno-pdr}]
429 @emph{Target MMIX options:}
430 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
431 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
432 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
433 [@b{--linker-allocated-gregs}]
437 @emph{Target Nios II options:}
438 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
443 @emph{Target NDS32 options:}
444 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
445 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
446 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
447 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
448 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
449 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
450 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
455 @emph{Target PDP11 options:}
456 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
457 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
458 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
462 @emph{Target picoJava options:}
467 @emph{Target PowerPC options:}
469 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
470 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
471 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
472 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
473 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
474 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
475 [@b{-mregnames}|@b{-mno-regnames}]
476 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
477 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
478 [@b{-msolaris}|@b{-mno-solaris}]
479 [@b{-nops=@var{count}}]
483 @emph{Target RX options:}
484 [@b{-mlittle-endian}|@b{-mbig-endian}]
485 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
486 [@b{-muse-conventional-section-names}]
487 [@b{-msmall-data-limit}]
490 [@b{-mint-register=@var{number}}]
491 [@b{-mgcc-abi}|@b{-mrx-abi}]
495 @emph{Target s390 options:}
496 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
497 [@b{-mregnames}|@b{-mno-regnames}]
498 [@b{-mwarn-areg-zero}]
502 @emph{Target SCORE options:}
503 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
504 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
505 [@b{-march=score7}][@b{-march=score3}]
506 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
510 @emph{Target SPARC options:}
511 @c The order here is important. See c-sparc.texi.
512 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
513 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
514 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
519 @emph{Target TIC54X options:}
520 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
521 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
526 @emph{Target TIC6X options:}
527 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
528 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
529 [@b{-mpic}|@b{-mno-pic}]
533 @emph{Target TILE-Gx options:}
534 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
537 @c TILEPro has no machine-dependent assembler options
542 @emph{Target Xtensa options:}
543 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
544 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
545 [@b{--[no-]transform}]
546 [@b{--rename-section} @var{oldname}=@var{newname}]
547 [@b{--[no-]trampolines}]
552 @emph{Target Z80 options:}
553 [@b{-z80}] [@b{-r800}]
554 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
555 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
556 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
557 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
558 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
559 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
563 @c Z8000 has no machine-dependent assembler options
572 @include at-file.texi
575 Turn on listings, in any of a variety of ways:
579 omit false conditionals
582 omit debugging directives
585 include general information, like @value{AS} version and options passed
588 include high-level source
594 include macro expansions
597 omit forms processing
603 set the name of the listing file
606 You may combine these options; for example, use @samp{-aln} for assembly
607 listing without forms processing. The @samp{=file} option, if used, must be
608 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
611 Begin in alternate macro mode.
613 @xref{Altmacro,,@code{.altmacro}}.
616 @item --compress-debug-sections
617 Compress DWARF debug sections using zlib. The debug sections are renamed
618 to begin with @samp{.zdebug}, and the resulting object file may not be
619 compatible with older linkers and object file utilities.
621 @item --nocompress-debug-sections
622 Do not compress DWARF debug sections. This is the default.
625 Ignored. This option is accepted for script compatibility with calls to
628 @item --debug-prefix-map @var{old}=@var{new}
629 When assembling files in directory @file{@var{old}}, record debugging
630 information describing them as in @file{@var{new}} instead.
632 @item --defsym @var{sym}=@var{value}
633 Define the symbol @var{sym} to be @var{value} before assembling the input file.
634 @var{value} must be an integer constant. As in C, a leading @samp{0x}
635 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
636 value. The value of the symbol can be overridden inside a source file via the
637 use of a @code{.set} pseudo-op.
640 ``fast''---skip whitespace and comment preprocessing (assume source is
645 Generate debugging information for each assembler source line using whichever
646 debug format is preferred by the target. This currently means either STABS,
650 Generate stabs debugging information for each assembler line. This
651 may help debugging assembler code, if the debugger can handle it.
654 Generate stabs debugging information for each assembler line, with GNU
655 extensions that probably only gdb can handle, and that could make other
656 debuggers crash or refuse to read your program. This
657 may help debugging assembler code. Currently the only GNU extension is
658 the location of the current working directory at assembling time.
661 Generate DWARF2 debugging information for each assembler line. This
662 may help debugging assembler code, if the debugger can handle it. Note---this
663 option is only supported by some targets, not all of them.
665 @item --gdwarf-sections
666 Instead of creating a .debug_line section, create a series of
667 .debug_line.@var{foo} sections where @var{foo} is the name of the
668 corresponding code section. For example a code section called @var{.text.func}
669 will have its dwarf line number information placed into a section called
670 @var{.debug_line.text.func}. If the code section is just called @var{.text}
671 then debug line section will still be called just @var{.debug_line} without any
674 @item --size-check=error
675 @itemx --size-check=warning
676 Issue an error or warning for invalid ELF .size directive.
679 Print a summary of the command line options and exit.
682 Print a summary of all target specific options and exit.
685 Add directory @var{dir} to the search list for @code{.include} directives.
688 Don't warn about signed overflow.
691 @ifclear DIFF-TBL-KLUGE
692 This option is accepted but has no effect on the @value{TARGET} family.
694 @ifset DIFF-TBL-KLUGE
695 Issue warnings when difference tables altered for long displacements.
700 Keep (in the symbol table) local symbols. These symbols start with
701 system-specific local label prefixes, typically @samp{.L} for ELF systems
702 or @samp{L} for traditional a.out systems.
707 @item --listing-lhs-width=@var{number}
708 Set the maximum width, in words, of the output data column for an assembler
709 listing to @var{number}.
711 @item --listing-lhs-width2=@var{number}
712 Set the maximum width, in words, of the output data column for continuation
713 lines in an assembler listing to @var{number}.
715 @item --listing-rhs-width=@var{number}
716 Set the maximum width of an input source line, as displayed in a listing, to
719 @item --listing-cont-lines=@var{number}
720 Set the maximum number of lines printed in a listing for a single line of input
723 @item -o @var{objfile}
724 Name the object-file output from @command{@value{AS}} @var{objfile}.
727 Fold the data section into the text section.
729 @kindex --hash-size=@var{number}
730 Set the default size of GAS's hash tables to a prime number close to
731 @var{number}. Increasing this value can reduce the length of time it takes the
732 assembler to perform its tasks, at the expense of increasing the assembler's
733 memory requirements. Similarly reducing this value can reduce the memory
734 requirements at the expense of speed.
736 @item --reduce-memory-overheads
737 This option reduces GAS's memory requirements, at the expense of making the
738 assembly processes slower. Currently this switch is a synonym for
739 @samp{--hash-size=4051}, but in the future it may have other effects as well.
742 Print the maximum space (in bytes) and total time (in seconds) used by
745 @item --strip-local-absolute
746 Remove local absolute symbols from the outgoing symbol table.
750 Print the @command{as} version.
753 Print the @command{as} version and exit.
757 Suppress warning messages.
759 @item --fatal-warnings
760 Treat warnings as errors.
763 Don't suppress warning messages or treat them as errors.
772 Generate an object file even after errors.
774 @item -- | @var{files} @dots{}
775 Standard input, or source files to assemble.
783 @xref{AArch64 Options}, for the options available when @value{AS} is configured
784 for the 64-bit mode of the ARM Architecture (AArch64).
789 The following options are available when @value{AS} is configured for the
790 64-bit mode of the ARM Architecture (AArch64).
793 @include c-aarch64.texi
794 @c ended inside the included file
802 @xref{Alpha Options}, for the options available when @value{AS} is configured
803 for an Alpha processor.
808 The following options are available when @value{AS} is configured for an Alpha
812 @include c-alpha.texi
813 @c ended inside the included file
820 The following options are available when @value{AS} is configured for
825 This option selects the core processor variant.
827 Select either big-endian (-EB) or little-endian (-EL) output.
832 The following options are available when @value{AS} is configured for the ARM
836 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
837 Specify which ARM processor variant is the target.
838 @item -march=@var{architecture}[+@var{extension}@dots{}]
839 Specify which ARM architecture variant is used by the target.
840 @item -mfpu=@var{floating-point-format}
841 Select which Floating Point architecture is the target.
842 @item -mfloat-abi=@var{abi}
843 Select which floating point ABI is in use.
845 Enable Thumb only instruction decoding.
846 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
847 Select which procedure calling convention is in use.
849 Select either big-endian (-EB) or little-endian (-EL) output.
850 @item -mthumb-interwork
851 Specify that the code has been generated with interworking between Thumb and
854 Turns on CodeComposer Studio assembly syntax compatibility mode.
856 Specify that PIC code has been generated.
864 @xref{Blackfin Options}, for the options available when @value{AS} is
865 configured for the Blackfin processor family.
870 The following options are available when @value{AS} is configured for
871 the Blackfin processor family.
875 @c ended inside the included file
882 See the info pages for documentation of the CRIS-specific options.
886 The following options are available when @value{AS} is configured for
889 @cindex D10V optimization
890 @cindex optimization, D10V
892 Optimize output by parallelizing instructions.
897 The following options are available when @value{AS} is configured for a D30V
900 @cindex D30V optimization
901 @cindex optimization, D30V
903 Optimize output by parallelizing instructions.
907 Warn when nops are generated.
909 @cindex D30V nops after 32-bit multiply
911 Warn when a nop after a 32-bit multiply instruction is generated.
917 The following options are available when @value{AS} is configured for the
918 Adapteva EPIPHANY series.
921 @xref{Epiphany Options}, for the options available when @value{AS} is
922 configured for an Epiphany processor.
927 The following options are available when @value{AS} is configured for
928 an Epiphany processor.
931 @include c-epiphany.texi
932 @c ended inside the included file
940 @xref{H8/300 Options}, for the options available when @value{AS} is configured
941 for an H8/300 processor.
946 The following options are available when @value{AS} is configured for an H8/300
950 @include c-h8300.texi
951 @c ended inside the included file
959 @xref{i386-Options}, for the options available when @value{AS} is
960 configured for an i386 processor.
965 The following options are available when @value{AS} is configured for
970 @c ended inside the included file
977 The following options are available when @value{AS} is configured for the
978 Intel 80960 processor.
981 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
982 Specify which variant of the 960 architecture is the target.
985 Add code to collect statistics about branches taken.
988 Do not alter compare-and-branch instructions for long displacements;
995 The following options are available when @value{AS} is configured for the
1001 Specifies that the extended IP2022 instructions are allowed.
1004 Restores the default behaviour, which restricts the permitted instructions to
1005 just the basic IP2022 ones.
1011 The following options are available when @value{AS} is configured for the
1012 Renesas M32C and M16C processors.
1017 Assemble M32C instructions.
1020 Assemble M16C instructions (the default).
1023 Enable support for link-time relaxations.
1026 Support H'00 style hex constants in addition to 0x00 style.
1032 The following options are available when @value{AS} is configured for the
1033 Renesas M32R (formerly Mitsubishi M32R) series.
1038 Specify which processor in the M32R family is the target. The default
1039 is normally the M32R, but this option changes it to the M32RX.
1041 @item --warn-explicit-parallel-conflicts or --Wp
1042 Produce warning messages when questionable parallel constructs are
1045 @item --no-warn-explicit-parallel-conflicts or --Wnp
1046 Do not produce warning messages when questionable parallel constructs are
1053 The following options are available when @value{AS} is configured for the
1054 Motorola 68000 series.
1059 Shorten references to undefined symbols, to one word instead of two.
1061 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1062 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1063 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1064 Specify what processor in the 68000 family is the target. The default
1065 is normally the 68020, but this can be changed at configuration time.
1067 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1068 The target machine does (or does not) have a floating-point coprocessor.
1069 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1070 the basic 68000 is not compatible with the 68881, a combination of the
1071 two can be specified, since it's possible to do emulation of the
1072 coprocessor instructions with the main processor.
1074 @item -m68851 | -mno-68851
1075 The target machine does (or does not) have a memory-management
1076 unit coprocessor. The default is to assume an MMU for 68020 and up.
1084 @xref{Nios II Options}, for the options available when @value{AS} is configured
1085 for an Altera Nios II processor.
1089 @c man begin OPTIONS
1090 The following options are available when @value{AS} is configured for an
1091 Altera Nios II processor.
1093 @c man begin INCLUDE
1094 @include c-nios2.texi
1095 @c ended inside the included file
1101 For details about the PDP-11 machine dependent features options,
1102 see @ref{PDP-11-Options}.
1105 @item -mpic | -mno-pic
1106 Generate position-independent (or position-dependent) code. The
1107 default is @option{-mpic}.
1110 @itemx -mall-extensions
1111 Enable all instruction set extensions. This is the default.
1113 @item -mno-extensions
1114 Disable all instruction set extensions.
1116 @item -m@var{extension} | -mno-@var{extension}
1117 Enable (or disable) a particular instruction set extension.
1120 Enable the instruction set extensions supported by a particular CPU, and
1121 disable all other extensions.
1123 @item -m@var{machine}
1124 Enable the instruction set extensions supported by a particular machine
1125 model, and disable all other extensions.
1131 The following options are available when @value{AS} is configured for
1132 a picoJava processor.
1136 @cindex PJ endianness
1137 @cindex endianness, PJ
1138 @cindex big endian output, PJ
1140 Generate ``big endian'' format output.
1142 @cindex little endian output, PJ
1144 Generate ``little endian'' format output.
1150 The following options are available when @value{AS} is configured for the
1151 Motorola 68HC11 or 68HC12 series.
1155 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1156 Specify what processor is the target. The default is
1157 defined by the configuration option when building the assembler.
1159 @item --xgate-ramoffset
1160 Instruct the linker to offset RAM addresses from S12X address space into
1161 XGATE address space.
1164 Specify to use the 16-bit integer ABI.
1167 Specify to use the 32-bit integer ABI.
1169 @item -mshort-double
1170 Specify to use the 32-bit double ABI.
1173 Specify to use the 64-bit double ABI.
1175 @item --force-long-branches
1176 Relative branches are turned into absolute ones. This concerns
1177 conditional branches, unconditional branches and branches to a
1180 @item -S | --short-branches
1181 Do not turn relative branches into absolute ones
1182 when the offset is out of range.
1184 @item --strict-direct-mode
1185 Do not turn the direct addressing mode into extended addressing mode
1186 when the instruction does not support direct addressing mode.
1188 @item --print-insn-syntax
1189 Print the syntax of instruction in case of error.
1191 @item --print-opcodes
1192 Print the list of instructions with syntax and then exit.
1194 @item --generate-example
1195 Print an example of instruction for each possible instruction and then exit.
1196 This option is only useful for testing @command{@value{AS}}.
1202 The following options are available when @command{@value{AS}} is configured
1203 for the SPARC architecture:
1206 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1207 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1208 Explicitly select a variant of the SPARC architecture.
1210 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1211 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1213 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1214 UltraSPARC extensions.
1216 @item -xarch=v8plus | -xarch=v8plusa
1217 For compatibility with the Solaris v9 assembler. These options are
1218 equivalent to -Av8plus and -Av8plusa, respectively.
1221 Warn when the assembler switches to another architecture.
1226 The following options are available when @value{AS} is configured for the 'c54x
1231 Enable extended addressing mode. All addresses and relocations will assume
1232 extended addressing (usually 23 bits).
1233 @item -mcpu=@var{CPU_VERSION}
1234 Sets the CPU version being compiled for.
1235 @item -merrors-to-file @var{FILENAME}
1236 Redirect error output to a file, for broken systems which don't support such
1237 behaviour in the shell.
1242 The following options are available when @value{AS} is configured for
1247 This option sets the largest size of an object that can be referenced
1248 implicitly with the @code{gp} register. It is only accepted for targets that
1249 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1251 @cindex MIPS endianness
1252 @cindex endianness, MIPS
1253 @cindex big endian output, MIPS
1255 Generate ``big endian'' format output.
1257 @cindex little endian output, MIPS
1259 Generate ``little endian'' format output.
1271 Generate code for a particular MIPS Instruction Set Architecture level.
1272 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1273 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1274 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1275 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1276 @samp{-mips64r2} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1277 MIPS64, and MIPS64 Release 2 ISA processors, respectively.
1279 @item -march=@var{cpu}
1280 Generate code for a particular MIPS CPU.
1282 @item -mtune=@var{cpu}
1283 Schedule and tune for a particular MIPS CPU.
1287 Cause nops to be inserted if the read of the destination register
1288 of an mfhi or mflo instruction occurs in the following two instructions.
1291 @itemx -mno-fix-rm7000
1292 Cause nops to be inserted if a dmult or dmultu instruction is
1293 followed by a load instruction.
1297 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1298 section instead of the standard ELF .stabs sections.
1302 Control generation of @code{.pdr} sections.
1306 The register sizes are normally inferred from the ISA and ABI, but these
1307 flags force a certain group of registers to be treated as 32 bits wide at
1308 all times. @samp{-mgp32} controls the size of general-purpose registers
1309 and @samp{-mfp32} controls the size of floating-point registers.
1313 Generate code for the MIPS 16 processor. This is equivalent to putting
1314 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1315 turns off this option.
1318 @itemx -mno-micromips
1319 Generate code for the microMIPS processor. This is equivalent to putting
1320 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1321 turns off this option. This is equivalent to putting @code{.set nomicromips}
1322 at the start of the assembly file.
1325 @itemx -mno-smartmips
1326 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1327 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1328 @samp{-mno-smartmips} turns off this option.
1332 Generate code for the MIPS-3D Application Specific Extension.
1333 This tells the assembler to accept MIPS-3D instructions.
1334 @samp{-no-mips3d} turns off this option.
1338 Generate code for the MDMX Application Specific Extension.
1339 This tells the assembler to accept MDMX instructions.
1340 @samp{-no-mdmx} turns off this option.
1344 Generate code for the DSP Release 1 Application Specific Extension.
1345 This tells the assembler to accept DSP Release 1 instructions.
1346 @samp{-mno-dsp} turns off this option.
1350 Generate code for the DSP Release 2 Application Specific Extension.
1351 This option implies -mdsp.
1352 This tells the assembler to accept DSP Release 2 instructions.
1353 @samp{-mno-dspr2} turns off this option.
1357 Generate code for the MIPS SIMD Architecture Extension.
1358 This tells the assembler to accept MSA instructions.
1359 @samp{-mno-msa} turns off this option.
1363 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1364 This tells the assembler to accept XPA instructions.
1365 @samp{-mno-xpa} turns off this option.
1369 Generate code for the MT Application Specific Extension.
1370 This tells the assembler to accept MT instructions.
1371 @samp{-mno-mt} turns off this option.
1375 Generate code for the MCU Application Specific Extension.
1376 This tells the assembler to accept MCU instructions.
1377 @samp{-mno-mcu} turns off this option.
1381 Only use 32-bit instruction encodings when generating code for the
1382 microMIPS processor. This option inhibits the use of any 16-bit
1383 instructions. This is equivalent to putting @code{.set insn32} at
1384 the start of the assembly file. @samp{-mno-insn32} turns off this
1385 option. This is equivalent to putting @code{.set noinsn32} at the
1386 start of the assembly file. By default @samp{-mno-insn32} is
1387 selected, allowing all instructions to be used.
1389 @item --construct-floats
1390 @itemx --no-construct-floats
1391 The @samp{--no-construct-floats} option disables the construction of
1392 double width floating point constants by loading the two halves of the
1393 value into the two single width floating point registers that make up
1394 the double width register. By default @samp{--construct-floats} is
1395 selected, allowing construction of these floating point constants.
1397 @item --relax-branch
1398 @itemx --no-relax-branch
1399 The @samp{--relax-branch} option enables the relaxation of out-of-range
1400 branches. By default @samp{--no-relax-branch} is selected, causing any
1401 out-of-range branches to produce an error.
1403 @item -mnan=@var{encoding}
1404 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1405 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1408 @item --emulation=@var{name}
1409 This option was formerly used to switch between ELF and ECOFF output
1410 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1411 removed in GAS 2.24, so the option now serves little purpose.
1412 It is retained for backwards compatibility.
1414 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1415 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1416 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1417 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1418 preferred options instead.
1421 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1428 Control how to deal with multiplication overflow and division by zero.
1429 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1430 (and only work for Instruction Set Architecture level 2 and higher);
1431 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1435 When this option is used, @command{@value{AS}} will issue a warning every
1436 time it generates a nop instruction from a macro.
1441 The following options are available when @value{AS} is configured for
1447 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1448 The command line option @samp{-nojsri2bsr} can be used to disable it.
1452 Enable or disable the silicon filter behaviour. By default this is disabled.
1453 The default can be overridden by the @samp{-sifilter} command line option.
1456 Alter jump instructions for long displacements.
1458 @item -mcpu=[210|340]
1459 Select the cpu type on the target hardware. This controls which instructions
1463 Assemble for a big endian target.
1466 Assemble for a little endian target.
1475 @xref{Meta Options}, for the options available when @value{AS} is configured
1476 for a Meta processor.
1480 @c man begin OPTIONS
1481 The following options are available when @value{AS} is configured for a
1484 @c man begin INCLUDE
1485 @include c-metag.texi
1486 @c ended inside the included file
1491 @c man begin OPTIONS
1493 See the info pages for documentation of the MMIX-specific options.
1499 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1500 for a NDS32 processor.
1502 @c ended inside the included file
1506 @c man begin OPTIONS
1507 The following options are available when @value{AS} is configured for a
1510 @c man begin INCLUDE
1511 @include c-nds32.texi
1512 @c ended inside the included file
1519 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1520 for a PowerPC processor.
1524 @c man begin OPTIONS
1525 The following options are available when @value{AS} is configured for a
1528 @c man begin INCLUDE
1530 @c ended inside the included file
1535 @c man begin OPTIONS
1537 See the info pages for documentation of the RX-specific options.
1541 The following options are available when @value{AS} is configured for the s390
1547 Select the word size, either 31/32 bits or 64 bits.
1550 Select the architecture mode, either the Enterprise System
1551 Architecture (esa) or the z/Architecture mode (zarch).
1552 @item -march=@var{processor}
1553 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1554 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1555 @samp{z196}, or @samp{zEC12}.
1557 @itemx -mno-regnames
1558 Allow or disallow symbolic names for registers.
1559 @item -mwarn-areg-zero
1560 Warn whenever the operand for a base or index register has been specified
1561 but evaluates to zero.
1569 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1570 for a TMS320C6000 processor.
1574 @c man begin OPTIONS
1575 The following options are available when @value{AS} is configured for a
1576 TMS320C6000 processor.
1578 @c man begin INCLUDE
1579 @include c-tic6x.texi
1580 @c ended inside the included file
1588 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1589 for a TILE-Gx processor.
1593 @c man begin OPTIONS
1594 The following options are available when @value{AS} is configured for a TILE-Gx
1597 @c man begin INCLUDE
1598 @include c-tilegx.texi
1599 @c ended inside the included file
1607 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1608 for an Xtensa processor.
1612 @c man begin OPTIONS
1613 The following options are available when @value{AS} is configured for an
1616 @c man begin INCLUDE
1617 @include c-xtensa.texi
1618 @c ended inside the included file
1623 @c man begin OPTIONS
1626 The following options are available when @value{AS} is configured for
1627 a Z80 family processor.
1630 Assemble for Z80 processor.
1632 Assemble for R800 processor.
1633 @item -ignore-undocumented-instructions
1635 Assemble undocumented Z80 instructions that also work on R800 without warning.
1636 @item -ignore-unportable-instructions
1638 Assemble all undocumented Z80 instructions without warning.
1639 @item -warn-undocumented-instructions
1641 Issue a warning for undocumented Z80 instructions that also work on R800.
1642 @item -warn-unportable-instructions
1644 Issue a warning for undocumented Z80 instructions that do not work on R800.
1645 @item -forbid-undocumented-instructions
1647 Treat all undocumented instructions as errors.
1648 @item -forbid-unportable-instructions
1650 Treat undocumented Z80 instructions that do not work on R800 as errors.
1657 * Manual:: Structure of this Manual
1658 * GNU Assembler:: The GNU Assembler
1659 * Object Formats:: Object File Formats
1660 * Command Line:: Command Line
1661 * Input Files:: Input Files
1662 * Object:: Output (Object) File
1663 * Errors:: Error and Warning Messages
1667 @section Structure of this Manual
1669 @cindex manual, structure and purpose
1670 This manual is intended to describe what you need to know to use
1671 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1672 notation for symbols, constants, and expressions; the directives that
1673 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1676 We also cover special features in the @value{TARGET}
1677 configuration of @command{@value{AS}}, including assembler directives.
1680 This manual also describes some of the machine-dependent features of
1681 various flavors of the assembler.
1684 @cindex machine instructions (not covered)
1685 On the other hand, this manual is @emph{not} intended as an introduction
1686 to programming in assembly language---let alone programming in general!
1687 In a similar vein, we make no attempt to introduce the machine
1688 architecture; we do @emph{not} describe the instruction set, standard
1689 mnemonics, registers or addressing modes that are standard to a
1690 particular architecture.
1692 You may want to consult the manufacturer's
1693 machine architecture manual for this information.
1697 For information on the H8/300 machine instruction set, see @cite{H8/300
1698 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1699 Programming Manual} (Renesas).
1702 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1703 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1704 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1705 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1708 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1712 @c I think this is premature---doc@cygnus.com, 17jan1991
1714 Throughout this manual, we assume that you are running @dfn{GNU},
1715 the portable operating system from the @dfn{Free Software
1716 Foundation, Inc.}. This restricts our attention to certain kinds of
1717 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1718 once this assumption is granted examples and definitions need less
1721 @command{@value{AS}} is part of a team of programs that turn a high-level
1722 human-readable series of instructions into a low-level
1723 computer-readable series of instructions. Different versions of
1724 @command{@value{AS}} are used for different kinds of computer.
1727 @c There used to be a section "Terminology" here, which defined
1728 @c "contents", "byte", "word", and "long". Defining "word" to any
1729 @c particular size is confusing when the .word directive may generate 16
1730 @c bits on one machine and 32 bits on another; in general, for the user
1731 @c version of this manual, none of these terms seem essential to define.
1732 @c They were used very little even in the former draft of the manual;
1733 @c this draft makes an effort to avoid them (except in names of
1737 @section The GNU Assembler
1739 @c man begin DESCRIPTION
1741 @sc{gnu} @command{as} is really a family of assemblers.
1743 This manual describes @command{@value{AS}}, a member of that family which is
1744 configured for the @value{TARGET} architectures.
1746 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1747 should find a fairly similar environment when you use it on another
1748 architecture. Each version has much in common with the others,
1749 including object file formats, most assembler directives (often called
1750 @dfn{pseudo-ops}) and assembler syntax.@refill
1752 @cindex purpose of @sc{gnu} assembler
1753 @command{@value{AS}} is primarily intended to assemble the output of the
1754 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1755 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1756 assemble correctly everything that other assemblers for the same
1757 machine would assemble.
1759 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1762 @c This remark should appear in generic version of manual; assumption
1763 @c here is that generic version sets M680x0.
1764 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1765 assembler for the same architecture; for example, we know of several
1766 incompatible versions of 680x0 assembly language syntax.
1771 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1772 program in one pass of the source file. This has a subtle impact on the
1773 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1775 @node Object Formats
1776 @section Object File Formats
1778 @cindex object file format
1779 The @sc{gnu} assembler can be configured to produce several alternative
1780 object file formats. For the most part, this does not affect how you
1781 write assembly language programs; but directives for debugging symbols
1782 are typically different in different file formats. @xref{Symbol
1783 Attributes,,Symbol Attributes}.
1786 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1787 @value{OBJ-NAME} format object files.
1789 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1791 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1792 @code{b.out} or COFF format object files.
1795 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1796 SOM or ELF format object files.
1801 @section Command Line
1803 @cindex command line conventions
1805 After the program name @command{@value{AS}}, the command line may contain
1806 options and file names. Options may appear in any order, and may be
1807 before, after, or between file names. The order of file names is
1810 @cindex standard input, as input file
1812 @file{--} (two hyphens) by itself names the standard input file
1813 explicitly, as one of the files for @command{@value{AS}} to assemble.
1815 @cindex options, command line
1816 Except for @samp{--} any command line argument that begins with a
1817 hyphen (@samp{-}) is an option. Each option changes the behavior of
1818 @command{@value{AS}}. No option changes the way another option works. An
1819 option is a @samp{-} followed by one or more letters; the case of
1820 the letter is important. All options are optional.
1822 Some options expect exactly one file name to follow them. The file
1823 name may either immediately follow the option's letter (compatible
1824 with older assemblers) or it may be the next command argument (@sc{gnu}
1825 standard). These two command lines are equivalent:
1828 @value{AS} -o my-object-file.o mumble.s
1829 @value{AS} -omy-object-file.o mumble.s
1833 @section Input Files
1836 @cindex source program
1837 @cindex files, input
1838 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1839 describe the program input to one run of @command{@value{AS}}. The program may
1840 be in one or more files; how the source is partitioned into files
1841 doesn't change the meaning of the source.
1843 @c I added "con" prefix to "catenation" just to prove I can overcome my
1844 @c APL training... doc@cygnus.com
1845 The source program is a concatenation of the text in all the files, in the
1848 @c man begin DESCRIPTION
1849 Each time you run @command{@value{AS}} it assembles exactly one source
1850 program. The source program is made up of one or more files.
1851 (The standard input is also a file.)
1853 You give @command{@value{AS}} a command line that has zero or more input file
1854 names. The input files are read (from left file name to right). A
1855 command line argument (in any position) that has no special meaning
1856 is taken to be an input file name.
1858 If you give @command{@value{AS}} no file names it attempts to read one input file
1859 from the @command{@value{AS}} standard input, which is normally your terminal. You
1860 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1863 Use @samp{--} if you need to explicitly name the standard input file
1864 in your command line.
1866 If the source is empty, @command{@value{AS}} produces a small, empty object
1871 @subheading Filenames and Line-numbers
1873 @cindex input file linenumbers
1874 @cindex line numbers, in input files
1875 There are two ways of locating a line in the input file (or files) and
1876 either may be used in reporting error messages. One way refers to a line
1877 number in a physical file; the other refers to a line number in a
1878 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1880 @dfn{Physical files} are those files named in the command line given
1881 to @command{@value{AS}}.
1883 @dfn{Logical files} are simply names declared explicitly by assembler
1884 directives; they bear no relation to physical files. Logical file names help
1885 error messages reflect the original source file, when @command{@value{AS}} source
1886 is itself synthesized from other files. @command{@value{AS}} understands the
1887 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1888 @ref{File,,@code{.file}}.
1891 @section Output (Object) File
1897 Every time you run @command{@value{AS}} it produces an output file, which is
1898 your assembly language program translated into numbers. This file
1899 is the object file. Its default name is
1907 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1909 You can give it another name by using the @option{-o} option. Conventionally,
1910 object file names end with @file{.o}. The default name is used for historical
1911 reasons: older assemblers were capable of assembling self-contained programs
1912 directly into a runnable program. (For some formats, this isn't currently
1913 possible, but it can be done for the @code{a.out} format.)
1917 The object file is meant for input to the linker @code{@value{LD}}. It contains
1918 assembled program code, information to help @code{@value{LD}} integrate
1919 the assembled program into a runnable file, and (optionally) symbolic
1920 information for the debugger.
1922 @c link above to some info file(s) like the description of a.out.
1923 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1926 @section Error and Warning Messages
1928 @c man begin DESCRIPTION
1930 @cindex error messages
1931 @cindex warning messages
1932 @cindex messages from assembler
1933 @command{@value{AS}} may write warnings and error messages to the standard error
1934 file (usually your terminal). This should not happen when a compiler
1935 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1936 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1937 grave problem that stops the assembly.
1941 @cindex format of warning messages
1942 Warning messages have the format
1945 file_name:@b{NNN}:Warning Message Text
1949 @cindex line numbers, in warnings/errors
1950 (where @b{NNN} is a line number). If a logical file name has been given
1951 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1952 the current input file is used. If a logical line number was given
1954 (@pxref{Line,,@code{.line}})
1956 then it is used to calculate the number printed,
1957 otherwise the actual line in the current source file is printed. The
1958 message text is intended to be self explanatory (in the grand Unix
1961 @cindex format of error messages
1962 Error messages have the format
1964 file_name:@b{NNN}:FATAL:Error Message Text
1966 The file name and line number are derived as for warning
1967 messages. The actual message text may be rather less explanatory
1968 because many of them aren't supposed to happen.
1971 @chapter Command-Line Options
1973 @cindex options, all versions of assembler
1974 This chapter describes command-line options available in @emph{all}
1975 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1976 for options specific
1978 to the @value{TARGET} target.
1981 to particular machine architectures.
1984 @c man begin DESCRIPTION
1986 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1987 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1988 The assembler arguments must be separated from each other (and the @samp{-Wa})
1989 by commas. For example:
1992 gcc -c -g -O -Wa,-alh,-L file.c
1996 This passes two options to the assembler: @samp{-alh} (emit a listing to
1997 standard output with high-level and assembly source) and @samp{-L} (retain
1998 local symbols in the symbol table).
2000 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2001 command-line options are automatically passed to the assembler by the compiler.
2002 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2003 precisely what options it passes to each compilation pass, including the
2009 * a:: -a[cdghlns] enable listings
2010 * alternate:: --alternate enable alternate macro syntax
2011 * D:: -D for compatibility
2012 * f:: -f to work faster
2013 * I:: -I for .include search path
2014 @ifclear DIFF-TBL-KLUGE
2015 * K:: -K for compatibility
2017 @ifset DIFF-TBL-KLUGE
2018 * K:: -K for difference tables
2021 * L:: -L to retain local symbols
2022 * listing:: --listing-XXX to configure listing output
2023 * M:: -M or --mri to assemble in MRI compatibility mode
2024 * MD:: --MD for dependency tracking
2025 * o:: -o to name the object file
2026 * R:: -R to join data and text sections
2027 * statistics:: --statistics to see statistics about assembly
2028 * traditional-format:: --traditional-format for compatible output
2029 * v:: -v to announce version
2030 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2031 * Z:: -Z to make object file even after errors
2035 @section Enable Listings: @option{-a[cdghlns]}
2045 @cindex listings, enabling
2046 @cindex assembly listings, enabling
2048 These options enable listing output from the assembler. By itself,
2049 @samp{-a} requests high-level, assembly, and symbols listing.
2050 You can use other letters to select specific options for the list:
2051 @samp{-ah} requests a high-level language listing,
2052 @samp{-al} requests an output-program assembly listing, and
2053 @samp{-as} requests a symbol table listing.
2054 High-level listings require that a compiler debugging option like
2055 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2058 Use the @samp{-ag} option to print a first section with general assembly
2059 information, like @value{AS} version, switches passed, or time stamp.
2061 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2062 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2063 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2064 omitted from the listing.
2066 Use the @samp{-ad} option to omit debugging directives from the
2069 Once you have specified one of these options, you can further control
2070 listing output and its appearance using the directives @code{.list},
2071 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2073 The @samp{-an} option turns off all forms processing.
2074 If you do not request listing output with one of the @samp{-a} options, the
2075 listing-control directives have no effect.
2077 The letters after @samp{-a} may be combined into one option,
2078 @emph{e.g.}, @samp{-aln}.
2080 Note if the assembler source is coming from the standard input (e.g.,
2082 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2083 is being used) then the listing will not contain any comments or preprocessor
2084 directives. This is because the listing code buffers input source lines from
2085 stdin only after they have been preprocessed by the assembler. This reduces
2086 memory usage and makes the code more efficient.
2089 @section @option{--alternate}
2092 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2095 @section @option{-D}
2098 This option has no effect whatsoever, but it is accepted to make it more
2099 likely that scripts written for other assemblers also work with
2100 @command{@value{AS}}.
2103 @section Work Faster: @option{-f}
2106 @cindex trusted compiler
2107 @cindex faster processing (@option{-f})
2108 @samp{-f} should only be used when assembling programs written by a
2109 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2110 and comment preprocessing on
2111 the input file(s) before assembling them. @xref{Preprocessing,
2115 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2116 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2121 @section @code{.include} Search Path: @option{-I} @var{path}
2123 @kindex -I @var{path}
2124 @cindex paths for @code{.include}
2125 @cindex search path for @code{.include}
2126 @cindex @code{include} directive search path
2127 Use this option to add a @var{path} to the list of directories
2128 @command{@value{AS}} searches for files specified in @code{.include}
2129 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2130 many times as necessary to include a variety of paths. The current
2131 working directory is always searched first; after that, @command{@value{AS}}
2132 searches any @samp{-I} directories in the same order as they were
2133 specified (left to right) on the command line.
2136 @section Difference Tables: @option{-K}
2139 @ifclear DIFF-TBL-KLUGE
2140 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2141 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2142 where it can be used to warn when the assembler alters the machine code
2143 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2144 family does not have the addressing limitations that sometimes lead to this
2145 alteration on other platforms.
2148 @ifset DIFF-TBL-KLUGE
2149 @cindex difference tables, warning
2150 @cindex warning for altered difference tables
2151 @command{@value{AS}} sometimes alters the code emitted for directives of the
2152 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2153 You can use the @samp{-K} option if you want a warning issued when this
2158 @section Include Local Symbols: @option{-L}
2161 @cindex local symbols, retaining in output
2162 Symbols beginning with system-specific local label prefixes, typically
2163 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2164 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2165 such symbols when debugging, because they are intended for the use of
2166 programs (like compilers) that compose assembler programs, not for your
2167 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2168 such symbols, so you do not normally debug with them.
2170 This option tells @command{@value{AS}} to retain those local symbols
2171 in the object file. Usually if you do this you also tell the linker
2172 @code{@value{LD}} to preserve those symbols.
2175 @section Configuring listing output: @option{--listing}
2177 The listing feature of the assembler can be enabled via the command line switch
2178 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2179 hex dump of the corresponding locations in the output object file, and displays
2180 them as a listing file. The format of this listing can be controlled by
2181 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2182 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2183 @code{.psize} (@pxref{Psize}), and
2184 @code{.eject} (@pxref{Eject}) and also by the following switches:
2187 @item --listing-lhs-width=@samp{number}
2188 @kindex --listing-lhs-width
2189 @cindex Width of first line disassembly output
2190 Sets the maximum width, in words, of the first line of the hex byte dump. This
2191 dump appears on the left hand side of the listing output.
2193 @item --listing-lhs-width2=@samp{number}
2194 @kindex --listing-lhs-width2
2195 @cindex Width of continuation lines of disassembly output
2196 Sets the maximum width, in words, of any further lines of the hex byte dump for
2197 a given input source line. If this value is not specified, it defaults to being
2198 the same as the value specified for @samp{--listing-lhs-width}. If neither
2199 switch is used the default is to one.
2201 @item --listing-rhs-width=@samp{number}
2202 @kindex --listing-rhs-width
2203 @cindex Width of source line output
2204 Sets the maximum width, in characters, of the source line that is displayed
2205 alongside the hex dump. The default value for this parameter is 100. The
2206 source line is displayed on the right hand side of the listing output.
2208 @item --listing-cont-lines=@samp{number}
2209 @kindex --listing-cont-lines
2210 @cindex Maximum number of continuation lines
2211 Sets the maximum number of continuation lines of hex dump that will be
2212 displayed for a given single line of source input. The default value is 4.
2216 @section Assemble in MRI Compatibility Mode: @option{-M}
2219 @cindex MRI compatibility mode
2220 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2221 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2222 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2223 configured target) assembler from Microtec Research. The exact nature of the
2224 MRI syntax will not be documented here; see the MRI manuals for more
2225 information. Note in particular that the handling of macros and macro
2226 arguments is somewhat different. The purpose of this option is to permit
2227 assembling existing MRI assembler code using @command{@value{AS}}.
2229 The MRI compatibility is not complete. Certain operations of the MRI assembler
2230 depend upon its object file format, and can not be supported using other object
2231 file formats. Supporting these would require enhancing each object file format
2232 individually. These are:
2235 @item global symbols in common section
2237 The m68k MRI assembler supports common sections which are merged by the linker.
2238 Other object file formats do not support this. @command{@value{AS}} handles
2239 common sections by treating them as a single common symbol. It permits local
2240 symbols to be defined within a common section, but it can not support global
2241 symbols, since it has no way to describe them.
2243 @item complex relocations
2245 The MRI assemblers support relocations against a negated section address, and
2246 relocations which combine the start addresses of two or more sections. These
2247 are not support by other object file formats.
2249 @item @code{END} pseudo-op specifying start address
2251 The MRI @code{END} pseudo-op permits the specification of a start address.
2252 This is not supported by other object file formats. The start address may
2253 instead be specified using the @option{-e} option to the linker, or in a linker
2256 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2258 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2259 name to the output file. This is not supported by other object file formats.
2261 @item @code{ORG} pseudo-op
2263 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2264 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2265 which changes the location within the current section. Absolute sections are
2266 not supported by other object file formats. The address of a section may be
2267 assigned within a linker script.
2270 There are some other features of the MRI assembler which are not supported by
2271 @command{@value{AS}}, typically either because they are difficult or because they
2272 seem of little consequence. Some of these may be supported in future releases.
2276 @item EBCDIC strings
2278 EBCDIC strings are not supported.
2280 @item packed binary coded decimal
2282 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2283 and @code{DCB.P} pseudo-ops are not supported.
2285 @item @code{FEQU} pseudo-op
2287 The m68k @code{FEQU} pseudo-op is not supported.
2289 @item @code{NOOBJ} pseudo-op
2291 The m68k @code{NOOBJ} pseudo-op is not supported.
2293 @item @code{OPT} branch control options
2295 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2296 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2297 relaxes all branches, whether forward or backward, to an appropriate size, so
2298 these options serve no purpose.
2300 @item @code{OPT} list control options
2302 The following m68k @code{OPT} list control options are ignored: @code{C},
2303 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2304 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2306 @item other @code{OPT} options
2308 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2309 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2311 @item @code{OPT} @code{D} option is default
2313 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2314 @code{OPT NOD} may be used to turn it off.
2316 @item @code{XREF} pseudo-op.
2318 The m68k @code{XREF} pseudo-op is ignored.
2320 @item @code{.debug} pseudo-op
2322 The i960 @code{.debug} pseudo-op is not supported.
2324 @item @code{.extended} pseudo-op
2326 The i960 @code{.extended} pseudo-op is not supported.
2328 @item @code{.list} pseudo-op.
2330 The various options of the i960 @code{.list} pseudo-op are not supported.
2332 @item @code{.optimize} pseudo-op
2334 The i960 @code{.optimize} pseudo-op is not supported.
2336 @item @code{.output} pseudo-op
2338 The i960 @code{.output} pseudo-op is not supported.
2340 @item @code{.setreal} pseudo-op
2342 The i960 @code{.setreal} pseudo-op is not supported.
2347 @section Dependency Tracking: @option{--MD}
2350 @cindex dependency tracking
2353 @command{@value{AS}} can generate a dependency file for the file it creates. This
2354 file consists of a single rule suitable for @code{make} describing the
2355 dependencies of the main source file.
2357 The rule is written to the file named in its argument.
2359 This feature is used in the automatic updating of makefiles.
2362 @section Name the Object File: @option{-o}
2365 @cindex naming object file
2366 @cindex object file name
2367 There is always one object file output when you run @command{@value{AS}}. By
2368 default it has the name
2371 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2385 You use this option (which takes exactly one filename) to give the
2386 object file a different name.
2388 Whatever the object file is called, @command{@value{AS}} overwrites any
2389 existing file of the same name.
2392 @section Join Data and Text Sections: @option{-R}
2395 @cindex data and text sections, joining
2396 @cindex text and data sections, joining
2397 @cindex joining text and data sections
2398 @cindex merging text and data sections
2399 @option{-R} tells @command{@value{AS}} to write the object file as if all
2400 data-section data lives in the text section. This is only done at
2401 the very last moment: your binary data are the same, but data
2402 section parts are relocated differently. The data section part of
2403 your object file is zero bytes long because all its bytes are
2404 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2406 When you specify @option{-R} it would be possible to generate shorter
2407 address displacements (because we do not have to cross between text and
2408 data section). We refrain from doing this simply for compatibility with
2409 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2412 When @command{@value{AS}} is configured for COFF or ELF output,
2413 this option is only useful if you use sections named @samp{.text} and
2418 @option{-R} is not supported for any of the HPPA targets. Using
2419 @option{-R} generates a warning from @command{@value{AS}}.
2423 @section Display Assembly Statistics: @option{--statistics}
2425 @kindex --statistics
2426 @cindex statistics, about assembly
2427 @cindex time, total for assembly
2428 @cindex space used, maximum for assembly
2429 Use @samp{--statistics} to display two statistics about the resources used by
2430 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2431 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2434 @node traditional-format
2435 @section Compatible Output: @option{--traditional-format}
2437 @kindex --traditional-format
2438 For some targets, the output of @command{@value{AS}} is different in some ways
2439 from the output of some existing assembler. This switch requests
2440 @command{@value{AS}} to use the traditional format instead.
2442 For example, it disables the exception frame optimizations which
2443 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2446 @section Announce Version: @option{-v}
2450 @cindex assembler version
2451 @cindex version of assembler
2452 You can find out what version of as is running by including the
2453 option @samp{-v} (which you can also spell as @samp{-version}) on the
2457 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2459 @command{@value{AS}} should never give a warning or error message when
2460 assembling compiler output. But programs written by people often
2461 cause @command{@value{AS}} to give a warning that a particular assumption was
2462 made. All such warnings are directed to the standard error file.
2466 @cindex suppressing warnings
2467 @cindex warnings, suppressing
2468 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2469 This only affects the warning messages: it does not change any particular of
2470 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2473 @kindex --fatal-warnings
2474 @cindex errors, caused by warnings
2475 @cindex warnings, causing error
2476 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2477 files that generate warnings to be in error.
2480 @cindex warnings, switching on
2481 You can switch these options off again by specifying @option{--warn}, which
2482 causes warnings to be output as usual.
2485 @section Generate Object File in Spite of Errors: @option{-Z}
2486 @cindex object file, after errors
2487 @cindex errors, continuing after
2488 After an error message, @command{@value{AS}} normally produces no output. If for
2489 some reason you are interested in object file output even after
2490 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2491 option. If there are any errors, @command{@value{AS}} continues anyways, and
2492 writes an object file after a final warning message of the form @samp{@var{n}
2493 errors, @var{m} warnings, generating bad object file.}
2498 @cindex machine-independent syntax
2499 @cindex syntax, machine-independent
2500 This chapter describes the machine-independent syntax allowed in a
2501 source file. @command{@value{AS}} syntax is similar to what many other
2502 assemblers use; it is inspired by the BSD 4.2
2507 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2511 * Preprocessing:: Preprocessing
2512 * Whitespace:: Whitespace
2513 * Comments:: Comments
2514 * Symbol Intro:: Symbols
2515 * Statements:: Statements
2516 * Constants:: Constants
2520 @section Preprocessing
2522 @cindex preprocessing
2523 The @command{@value{AS}} internal preprocessor:
2525 @cindex whitespace, removed by preprocessor
2527 adjusts and removes extra whitespace. It leaves one space or tab before
2528 the keywords on a line, and turns any other whitespace on the line into
2531 @cindex comments, removed by preprocessor
2533 removes all comments, replacing them with a single space, or an
2534 appropriate number of newlines.
2536 @cindex constants, converted by preprocessor
2538 converts character constants into the appropriate numeric values.
2541 It does not do macro processing, include file handling, or
2542 anything else you may get from your C compiler's preprocessor. You can
2543 do include file processing with the @code{.include} directive
2544 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2545 to get other ``CPP'' style preprocessing by giving the input file a
2546 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2547 Output, gcc.info, Using GNU CC}.
2549 Excess whitespace, comments, and character constants
2550 cannot be used in the portions of the input text that are not
2553 @cindex turning preprocessing on and off
2554 @cindex preprocessing, turning on and off
2557 If the first line of an input file is @code{#NO_APP} or if you use the
2558 @samp{-f} option, whitespace and comments are not removed from the input file.
2559 Within an input file, you can ask for whitespace and comment removal in
2560 specific portions of the by putting a line that says @code{#APP} before the
2561 text that may contain whitespace or comments, and putting a line that says
2562 @code{#NO_APP} after this text. This feature is mainly intend to support
2563 @code{asm} statements in compilers whose output is otherwise free of comments
2570 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2571 Whitespace is used to separate symbols, and to make programs neater for
2572 people to read. Unless within character constants
2573 (@pxref{Characters,,Character Constants}), any whitespace means the same
2574 as exactly one space.
2580 There are two ways of rendering comments to @command{@value{AS}}. In both
2581 cases the comment is equivalent to one space.
2583 Anything from @samp{/*} through the next @samp{*/} is a comment.
2584 This means you may not nest these comments.
2588 The only way to include a newline ('\n') in a comment
2589 is to use this sort of comment.
2592 /* This sort of comment does not nest. */
2595 @cindex line comment character
2596 Anything from a @dfn{line comment} character up to the next newline is
2597 considered a comment and is ignored. The line comment character is target
2598 specific, and some targets multiple comment characters. Some targets also have
2599 line comment characters that only work if they are the first character on a
2600 line. Some targets use a sequence of two characters to introduce a line
2601 comment. Some targets can also change their line comment characters depending
2602 upon command line options that have been used. For more details see the
2603 @emph{Syntax} section in the documentation for individual targets.
2605 If the line comment character is the hash sign (@samp{#}) then it still has the
2606 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2607 to specify logical line numbers:
2610 @cindex lines starting with @code{#}
2611 @cindex logical line numbers
2612 To be compatible with past assemblers, lines that begin with @samp{#} have a
2613 special interpretation. Following the @samp{#} should be an absolute
2614 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2615 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2616 new logical file name. The rest of the line, if any, should be whitespace.
2618 If the first non-whitespace characters on the line are not numeric,
2619 the line is ignored. (Just like a comment.)
2622 # This is an ordinary comment.
2623 # 42-6 "new_file_name" # New logical file name
2624 # This is logical line # 36.
2626 This feature is deprecated, and may disappear from future versions
2627 of @command{@value{AS}}.
2632 @cindex characters used in symbols
2633 @ifclear SPECIAL-SYMS
2634 A @dfn{symbol} is one or more characters chosen from the set of all
2635 letters (both upper and lower case), digits and the three characters
2641 A @dfn{symbol} is one or more characters chosen from the set of all
2642 letters (both upper and lower case), digits and the three characters
2643 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2649 On most machines, you can also use @code{$} in symbol names; exceptions
2650 are noted in @ref{Machine Dependencies}.
2652 No symbol may begin with a digit. Case is significant.
2653 There is no length limit: all characters are significant. Multibyte characters
2654 are supported. Symbols are delimited by characters not in that set, or by the
2655 beginning of a file (since the source program must end with a newline, the end
2656 of a file is not a possible symbol delimiter). @xref{Symbols}.
2657 @cindex length of symbols
2662 @cindex statements, structure of
2663 @cindex line separator character
2664 @cindex statement separator character
2666 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2667 @dfn{line separator character}. The line separator character is target
2668 specific and described in the @emph{Syntax} section of each
2669 target's documentation. Not all targets support a line separator character.
2670 The newline or line separator character is considered to be part of the
2671 preceding statement. Newlines and separators within character constants are an
2672 exception: they do not end statements.
2674 @cindex newline, required at file end
2675 @cindex EOF, newline must precede
2676 It is an error to end any statement with end-of-file: the last
2677 character of any input file should be a newline.@refill
2679 An empty statement is allowed, and may include whitespace. It is ignored.
2681 @cindex instructions and directives
2682 @cindex directives and instructions
2683 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2684 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2686 A statement begins with zero or more labels, optionally followed by a
2687 key symbol which determines what kind of statement it is. The key
2688 symbol determines the syntax of the rest of the statement. If the
2689 symbol begins with a dot @samp{.} then the statement is an assembler
2690 directive: typically valid for any computer. If the symbol begins with
2691 a letter the statement is an assembly language @dfn{instruction}: it
2692 assembles into a machine language instruction.
2694 Different versions of @command{@value{AS}} for different computers
2695 recognize different instructions. In fact, the same symbol may
2696 represent a different instruction in a different computer's assembly
2700 @cindex @code{:} (label)
2701 @cindex label (@code{:})
2702 A label is a symbol immediately followed by a colon (@code{:}).
2703 Whitespace before a label or after a colon is permitted, but you may not
2704 have whitespace between a label's symbol and its colon. @xref{Labels}.
2707 For HPPA targets, labels need not be immediately followed by a colon, but
2708 the definition of a label must begin in column zero. This also implies that
2709 only one label may be defined on each line.
2713 label: .directive followed by something
2714 another_label: # This is an empty statement.
2715 instruction operand_1, operand_2, @dots{}
2722 A constant is a number, written so that its value is known by
2723 inspection, without knowing any context. Like this:
2726 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2727 .ascii "Ring the bell\7" # A string constant.
2728 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2729 .float 0f-314159265358979323846264338327\
2730 95028841971.693993751E-40 # - pi, a flonum.
2735 * Characters:: Character Constants
2736 * Numbers:: Number Constants
2740 @subsection Character Constants
2742 @cindex character constants
2743 @cindex constants, character
2744 There are two kinds of character constants. A @dfn{character} stands
2745 for one character in one byte and its value may be used in
2746 numeric expressions. String constants (properly called string
2747 @emph{literals}) are potentially many bytes and their values may not be
2748 used in arithmetic expressions.
2752 * Chars:: Characters
2756 @subsubsection Strings
2758 @cindex string constants
2759 @cindex constants, string
2760 A @dfn{string} is written between double-quotes. It may contain
2761 double-quotes or null characters. The way to get special characters
2762 into a string is to @dfn{escape} these characters: precede them with
2763 a backslash @samp{\} character. For example @samp{\\} represents
2764 one backslash: the first @code{\} is an escape which tells
2765 @command{@value{AS}} to interpret the second character literally as a backslash
2766 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2767 escape character). The complete list of escapes follows.
2769 @cindex escape codes, character
2770 @cindex character escape codes
2773 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2775 @cindex @code{\b} (backspace character)
2776 @cindex backspace (@code{\b})
2778 Mnemonic for backspace; for ASCII this is octal code 010.
2781 @c Mnemonic for EOText; for ASCII this is octal code 004.
2783 @cindex @code{\f} (formfeed character)
2784 @cindex formfeed (@code{\f})
2786 Mnemonic for FormFeed; for ASCII this is octal code 014.
2788 @cindex @code{\n} (newline character)
2789 @cindex newline (@code{\n})
2791 Mnemonic for newline; for ASCII this is octal code 012.
2794 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2796 @cindex @code{\r} (carriage return character)
2797 @cindex carriage return (@code{\r})
2799 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2802 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2803 @c other assemblers.
2805 @cindex @code{\t} (tab)
2806 @cindex tab (@code{\t})
2808 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2811 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2812 @c @item \x @var{digit} @var{digit} @var{digit}
2813 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2815 @cindex @code{\@var{ddd}} (octal character code)
2816 @cindex octal character code (@code{\@var{ddd}})
2817 @item \ @var{digit} @var{digit} @var{digit}
2818 An octal character code. The numeric code is 3 octal digits.
2819 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2820 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2822 @cindex @code{\@var{xd...}} (hex character code)
2823 @cindex hex character code (@code{\@var{xd...}})
2824 @item \@code{x} @var{hex-digits...}
2825 A hex character code. All trailing hex digits are combined. Either upper or
2826 lower case @code{x} works.
2828 @cindex @code{\\} (@samp{\} character)
2829 @cindex backslash (@code{\\})
2831 Represents one @samp{\} character.
2834 @c Represents one @samp{'} (accent acute) character.
2835 @c This is needed in single character literals
2836 @c (@xref{Characters,,Character Constants}.) to represent
2839 @cindex @code{\"} (doublequote character)
2840 @cindex doublequote (@code{\"})
2842 Represents one @samp{"} character. Needed in strings to represent
2843 this character, because an unescaped @samp{"} would end the string.
2845 @item \ @var{anything-else}
2846 Any other character when escaped by @kbd{\} gives a warning, but
2847 assembles as if the @samp{\} was not present. The idea is that if
2848 you used an escape sequence you clearly didn't want the literal
2849 interpretation of the following character. However @command{@value{AS}} has no
2850 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2851 code and warns you of the fact.
2854 Which characters are escapable, and what those escapes represent,
2855 varies widely among assemblers. The current set is what we think
2856 the BSD 4.2 assembler recognizes, and is a subset of what most C
2857 compilers recognize. If you are in doubt, do not use an escape
2861 @subsubsection Characters
2863 @cindex single character constant
2864 @cindex character, single
2865 @cindex constant, single character
2866 A single character may be written as a single quote immediately
2867 followed by that character. The same escapes apply to characters as
2868 to strings. So if you want to write the character backslash, you
2869 must write @kbd{'\\} where the first @code{\} escapes the second
2870 @code{\}. As you can see, the quote is an acute accent, not a
2871 grave accent. A newline
2873 @ifclear abnormal-separator
2874 (or semicolon @samp{;})
2876 @ifset abnormal-separator
2878 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2883 immediately following an acute accent is taken as a literal character
2884 and does not count as the end of a statement. The value of a character
2885 constant in a numeric expression is the machine's byte-wide code for
2886 that character. @command{@value{AS}} assumes your character code is ASCII:
2887 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2890 @subsection Number Constants
2892 @cindex constants, number
2893 @cindex number constants
2894 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2895 are stored in the target machine. @emph{Integers} are numbers that
2896 would fit into an @code{int} in the C language. @emph{Bignums} are
2897 integers, but they are stored in more than 32 bits. @emph{Flonums}
2898 are floating point numbers, described below.
2901 * Integers:: Integers
2906 * Bit Fields:: Bit Fields
2912 @subsubsection Integers
2914 @cindex constants, integer
2916 @cindex binary integers
2917 @cindex integers, binary
2918 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2919 the binary digits @samp{01}.
2921 @cindex octal integers
2922 @cindex integers, octal
2923 An octal integer is @samp{0} followed by zero or more of the octal
2924 digits (@samp{01234567}).
2926 @cindex decimal integers
2927 @cindex integers, decimal
2928 A decimal integer starts with a non-zero digit followed by zero or
2929 more digits (@samp{0123456789}).
2931 @cindex hexadecimal integers
2932 @cindex integers, hexadecimal
2933 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2934 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2936 Integers have the usual values. To denote a negative integer, use
2937 the prefix operator @samp{-} discussed under expressions
2938 (@pxref{Prefix Ops,,Prefix Operators}).
2941 @subsubsection Bignums
2944 @cindex constants, bignum
2945 A @dfn{bignum} has the same syntax and semantics as an integer
2946 except that the number (or its negative) takes more than 32 bits to
2947 represent in binary. The distinction is made because in some places
2948 integers are permitted while bignums are not.
2951 @subsubsection Flonums
2953 @cindex floating point numbers
2954 @cindex constants, floating point
2956 @cindex precision, floating point
2957 A @dfn{flonum} represents a floating point number. The translation is
2958 indirect: a decimal floating point number from the text is converted by
2959 @command{@value{AS}} to a generic binary floating point number of more than
2960 sufficient precision. This generic floating point number is converted
2961 to a particular computer's floating point format (or formats) by a
2962 portion of @command{@value{AS}} specialized to that computer.
2964 A flonum is written by writing (in order)
2969 (@samp{0} is optional on the HPPA.)
2973 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2975 @kbd{e} is recommended. Case is not important.
2977 @c FIXME: verify if flonum syntax really this vague for most cases
2978 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2979 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2982 On the H8/300, Renesas / SuperH SH,
2983 and AMD 29K architectures, the letter must be
2984 one of the letters @samp{DFPRSX} (in upper or lower case).
2986 On the ARC, the letter must be one of the letters @samp{DFRS}
2987 (in upper or lower case).
2989 On the Intel 960 architecture, the letter must be
2990 one of the letters @samp{DFT} (in upper or lower case).
2992 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2996 One of the letters @samp{DFRS} (in upper or lower case).
2999 One of the letters @samp{DFPRSX} (in upper or lower case).
3002 The letter @samp{E} (upper case only).
3005 One of the letters @samp{DFT} (in upper or lower case).
3010 An optional sign: either @samp{+} or @samp{-}.
3013 An optional @dfn{integer part}: zero or more decimal digits.
3016 An optional @dfn{fractional part}: @samp{.} followed by zero
3017 or more decimal digits.
3020 An optional exponent, consisting of:
3024 An @samp{E} or @samp{e}.
3025 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3026 @c principle this can perfectly well be different on different targets.
3028 Optional sign: either @samp{+} or @samp{-}.
3030 One or more decimal digits.
3035 At least one of the integer part or the fractional part must be
3036 present. The floating point number has the usual base-10 value.
3038 @command{@value{AS}} does all processing using integers. Flonums are computed
3039 independently of any floating point hardware in the computer running
3040 @command{@value{AS}}.
3044 @c Bit fields are written as a general facility but are also controlled
3045 @c by a conditional-compilation flag---which is as of now (21mar91)
3046 @c turned on only by the i960 config of GAS.
3048 @subsubsection Bit Fields
3051 @cindex constants, bit field
3052 You can also define numeric constants as @dfn{bit fields}.
3053 Specify two numbers separated by a colon---
3055 @var{mask}:@var{value}
3058 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3061 The resulting number is then packed
3063 @c this conditional paren in case bit fields turned on elsewhere than 960
3064 (in host-dependent byte order)
3066 into a field whose width depends on which assembler directive has the
3067 bit-field as its argument. Overflow (a result from the bitwise and
3068 requiring more binary digits to represent) is not an error; instead,
3069 more constants are generated, of the specified width, beginning with the
3070 least significant digits.@refill
3072 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3073 @code{.short}, and @code{.word} accept bit-field arguments.
3078 @chapter Sections and Relocation
3083 * Secs Background:: Background
3084 * Ld Sections:: Linker Sections
3085 * As Sections:: Assembler Internal Sections
3086 * Sub-Sections:: Sub-Sections
3090 @node Secs Background
3093 Roughly, a section is a range of addresses, with no gaps; all data
3094 ``in'' those addresses is treated the same for some particular purpose.
3095 For example there may be a ``read only'' section.
3097 @cindex linker, and assembler
3098 @cindex assembler, and linker
3099 The linker @code{@value{LD}} reads many object files (partial programs) and
3100 combines their contents to form a runnable program. When @command{@value{AS}}
3101 emits an object file, the partial program is assumed to start at address 0.
3102 @code{@value{LD}} assigns the final addresses for the partial program, so that
3103 different partial programs do not overlap. This is actually an
3104 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3107 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3108 addresses. These blocks slide to their run-time addresses as rigid
3109 units; their length does not change and neither does the order of bytes
3110 within them. Such a rigid unit is called a @emph{section}. Assigning
3111 run-time addresses to sections is called @dfn{relocation}. It includes
3112 the task of adjusting mentions of object-file addresses so they refer to
3113 the proper run-time addresses.
3115 For the H8/300, and for the Renesas / SuperH SH,
3116 @command{@value{AS}} pads sections if needed to
3117 ensure they end on a word (sixteen bit) boundary.
3120 @cindex standard assembler sections
3121 An object file written by @command{@value{AS}} has at least three sections, any
3122 of which may be empty. These are named @dfn{text}, @dfn{data} and
3127 When it generates COFF or ELF output,
3129 @command{@value{AS}} can also generate whatever other named sections you specify
3130 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3131 If you do not use any directives that place output in the @samp{.text}
3132 or @samp{.data} sections, these sections still exist, but are empty.
3137 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3139 @command{@value{AS}} can also generate whatever other named sections you
3140 specify using the @samp{.space} and @samp{.subspace} directives. See
3141 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3142 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3143 assembler directives.
3146 Additionally, @command{@value{AS}} uses different names for the standard
3147 text, data, and bss sections when generating SOM output. Program text
3148 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3149 BSS into @samp{$BSS$}.
3153 Within the object file, the text section starts at address @code{0}, the
3154 data section follows, and the bss section follows the data section.
3157 When generating either SOM or ELF output files on the HPPA, the text
3158 section starts at address @code{0}, the data section at address
3159 @code{0x4000000}, and the bss section follows the data section.
3162 To let @code{@value{LD}} know which data changes when the sections are
3163 relocated, and how to change that data, @command{@value{AS}} also writes to the
3164 object file details of the relocation needed. To perform relocation
3165 @code{@value{LD}} must know, each time an address in the object
3169 Where in the object file is the beginning of this reference to
3172 How long (in bytes) is this reference?
3174 Which section does the address refer to? What is the numeric value of
3176 (@var{address}) @minus{} (@var{start-address of section})?
3179 Is the reference to an address ``Program-Counter relative''?
3182 @cindex addresses, format of
3183 @cindex section-relative addressing
3184 In fact, every address @command{@value{AS}} ever uses is expressed as
3186 (@var{section}) + (@var{offset into section})
3189 Further, most expressions @command{@value{AS}} computes have this section-relative
3192 (For some object formats, such as SOM for the HPPA, some expressions are
3193 symbol-relative instead.)
3196 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3197 @var{N} into section @var{secname}.''
3199 Apart from text, data and bss sections you need to know about the
3200 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3201 addresses in the absolute section remain unchanged. For example, address
3202 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3203 @code{@value{LD}}. Although the linker never arranges two partial programs'
3204 data sections with overlapping addresses after linking, @emph{by definition}
3205 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3206 part of a program is always the same address when the program is running as
3207 address @code{@{absolute@ 239@}} in any other part of the program.
3209 The idea of sections is extended to the @dfn{undefined} section. Any
3210 address whose section is unknown at assembly time is by definition
3211 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3212 Since numbers are always defined, the only way to generate an undefined
3213 address is to mention an undefined symbol. A reference to a named
3214 common block would be such a symbol: its value is unknown at assembly
3215 time so it has section @emph{undefined}.
3217 By analogy the word @emph{section} is used to describe groups of sections in
3218 the linked program. @code{@value{LD}} puts all partial programs' text
3219 sections in contiguous addresses in the linked program. It is
3220 customary to refer to the @emph{text section} of a program, meaning all
3221 the addresses of all partial programs' text sections. Likewise for
3222 data and bss sections.
3224 Some sections are manipulated by @code{@value{LD}}; others are invented for
3225 use of @command{@value{AS}} and have no meaning except during assembly.
3228 @section Linker Sections
3229 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3234 @cindex named sections
3235 @cindex sections, named
3236 @item named sections
3239 @cindex text section
3240 @cindex data section
3244 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3245 separate but equal sections. Anything you can say of one section is
3248 When the program is running, however, it is
3249 customary for the text section to be unalterable. The
3250 text section is often shared among processes: it contains
3251 instructions, constants and the like. The data section of a running
3252 program is usually alterable: for example, C variables would be stored
3253 in the data section.
3258 This section contains zeroed bytes when your program begins running. It
3259 is used to hold uninitialized variables or common storage. The length of
3260 each partial program's bss section is important, but because it starts
3261 out containing zeroed bytes there is no need to store explicit zero
3262 bytes in the object file. The bss section was invented to eliminate
3263 those explicit zeros from object files.
3265 @cindex absolute section
3266 @item absolute section
3267 Address 0 of this section is always ``relocated'' to runtime address 0.
3268 This is useful if you want to refer to an address that @code{@value{LD}} must
3269 not change when relocating. In this sense we speak of absolute
3270 addresses being ``unrelocatable'': they do not change during relocation.
3272 @cindex undefined section
3273 @item undefined section
3274 This ``section'' is a catch-all for address references to objects not in
3275 the preceding sections.
3276 @c FIXME: ref to some other doc on obj-file formats could go here.
3279 @cindex relocation example
3280 An idealized example of three relocatable sections follows.
3282 The example uses the traditional section names @samp{.text} and @samp{.data}.
3284 Memory addresses are on the horizontal axis.
3288 @c END TEXI2ROFF-KILL
3291 partial program # 1: |ttttt|dddd|00|
3298 partial program # 2: |TTT|DDD|000|
3301 +--+---+-----+--+----+---+-----+~~
3302 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3303 +--+---+-----+--+----+---+-----+~~
3305 addresses: 0 @dots{}
3312 \line{\it Partial program \#1: \hfil}
3313 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3314 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3316 \line{\it Partial program \#2: \hfil}
3317 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3318 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3320 \line{\it linked program: \hfil}
3321 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3322 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3323 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3324 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3326 \line{\it addresses: \hfil}
3330 @c END TEXI2ROFF-KILL
3333 @section Assembler Internal Sections
3335 @cindex internal assembler sections
3336 @cindex sections in messages, internal
3337 These sections are meant only for the internal use of @command{@value{AS}}. They
3338 have no meaning at run-time. You do not really need to know about these
3339 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3340 warning messages, so it might be helpful to have an idea of their
3341 meanings to @command{@value{AS}}. These sections are used to permit the
3342 value of every expression in your assembly language program to be a
3343 section-relative address.
3346 @cindex assembler internal logic error
3347 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3348 An internal assembler logic error has been found. This means there is a
3349 bug in the assembler.
3351 @cindex expr (internal section)
3353 The assembler stores complex expression internally as combinations of
3354 symbols. When it needs to represent an expression as a symbol, it puts
3355 it in the expr section.
3357 @c FIXME item transfer[t] vector preload
3358 @c FIXME item transfer[t] vector postload
3359 @c FIXME item register
3363 @section Sub-Sections
3365 @cindex numbered subsections
3366 @cindex grouping data
3372 fall into two sections: text and data.
3374 You may have separate groups of
3376 data in named sections
3380 data in named sections
3386 that you want to end up near to each other in the object file, even though they
3387 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3388 use @dfn{subsections} for this purpose. Within each section, there can be
3389 numbered subsections with values from 0 to 8192. Objects assembled into the
3390 same subsection go into the object file together with other objects in the same
3391 subsection. For example, a compiler might want to store constants in the text
3392 section, but might not want to have them interspersed with the program being
3393 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3394 section of code being output, and a @samp{.text 1} before each group of
3395 constants being output.
3397 Subsections are optional. If you do not use subsections, everything
3398 goes in subsection number zero.
3401 Each subsection is zero-padded up to a multiple of four bytes.
3402 (Subsections may be padded a different amount on different flavors
3403 of @command{@value{AS}}.)
3407 On the H8/300 platform, each subsection is zero-padded to a word
3408 boundary (two bytes).
3409 The same is true on the Renesas SH.
3412 @c FIXME section padding (alignment)?
3413 @c Rich Pixley says padding here depends on target obj code format; that
3414 @c doesn't seem particularly useful to say without further elaboration,
3415 @c so for now I say nothing about it. If this is a generic BFD issue,
3416 @c these paragraphs might need to vanish from this manual, and be
3417 @c discussed in BFD chapter of binutils (or some such).
3421 Subsections appear in your object file in numeric order, lowest numbered
3422 to highest. (All this to be compatible with other people's assemblers.)
3423 The object file contains no representation of subsections; @code{@value{LD}} and
3424 other programs that manipulate object files see no trace of them.
3425 They just see all your text subsections as a text section, and all your
3426 data subsections as a data section.
3428 To specify which subsection you want subsequent statements assembled
3429 into, use a numeric argument to specify it, in a @samp{.text
3430 @var{expression}} or a @samp{.data @var{expression}} statement.
3433 When generating COFF output, you
3438 can also use an extra subsection
3439 argument with arbitrary named sections: @samp{.section @var{name},
3444 When generating ELF output, you
3449 can also use the @code{.subsection} directive (@pxref{SubSection})
3450 to specify a subsection: @samp{.subsection @var{expression}}.
3452 @var{Expression} should be an absolute expression
3453 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3454 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3455 begins in @code{text 0}. For instance:
3457 .text 0 # The default subsection is text 0 anyway.
3458 .ascii "This lives in the first text subsection. *"
3460 .ascii "But this lives in the second text subsection."
3462 .ascii "This lives in the data section,"
3463 .ascii "in the first data subsection."
3465 .ascii "This lives in the first text section,"
3466 .ascii "immediately following the asterisk (*)."
3469 Each section has a @dfn{location counter} incremented by one for every byte
3470 assembled into that section. Because subsections are merely a convenience
3471 restricted to @command{@value{AS}} there is no concept of a subsection location
3472 counter. There is no way to directly manipulate a location counter---but the
3473 @code{.align} directive changes it, and any label definition captures its
3474 current value. The location counter of the section where statements are being
3475 assembled is said to be the @dfn{active} location counter.
3478 @section bss Section
3481 @cindex common variable storage
3482 The bss section is used for local common variable storage.
3483 You may allocate address space in the bss section, but you may
3484 not dictate data to load into it before your program executes. When
3485 your program starts running, all the contents of the bss
3486 section are zeroed bytes.
3488 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3489 @ref{Lcomm,,@code{.lcomm}}.
3491 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3492 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3495 When assembling for a target which supports multiple sections, such as ELF or
3496 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3497 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3498 section. Typically the section will only contain symbol definitions and
3499 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3506 Symbols are a central concept: the programmer uses symbols to name
3507 things, the linker uses symbols to link, and the debugger uses symbols
3511 @cindex debuggers, and symbol order
3512 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3513 the same order they were declared. This may break some debuggers.
3518 * Setting Symbols:: Giving Symbols Other Values
3519 * Symbol Names:: Symbol Names
3520 * Dot:: The Special Dot Symbol
3521 * Symbol Attributes:: Symbol Attributes
3528 A @dfn{label} is written as a symbol immediately followed by a colon
3529 @samp{:}. The symbol then represents the current value of the
3530 active location counter, and is, for example, a suitable instruction
3531 operand. You are warned if you use the same symbol to represent two
3532 different locations: the first definition overrides any other
3536 On the HPPA, the usual form for a label need not be immediately followed by a
3537 colon, but instead must start in column zero. Only one label may be defined on
3538 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3539 provides a special directive @code{.label} for defining labels more flexibly.
3542 @node Setting Symbols
3543 @section Giving Symbols Other Values
3545 @cindex assigning values to symbols
3546 @cindex symbol values, assigning
3547 A symbol can be given an arbitrary value by writing a symbol, followed
3548 by an equals sign @samp{=}, followed by an expression
3549 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3550 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3551 equals sign @samp{=}@samp{=} here represents an equivalent of the
3552 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3555 Blackfin does not support symbol assignment with @samp{=}.
3559 @section Symbol Names
3561 @cindex symbol names
3562 @cindex names, symbol
3563 @ifclear SPECIAL-SYMS
3564 Symbol names begin with a letter or with one of @samp{._}. On most
3565 machines, you can also use @code{$} in symbol names; exceptions are
3566 noted in @ref{Machine Dependencies}. That character may be followed by any
3567 string of digits, letters, dollar signs (unless otherwise noted for a
3568 particular target machine), and underscores.
3572 Symbol names begin with a letter or with one of @samp{._}. On the
3573 Renesas SH you can also use @code{$} in symbol names. That
3574 character may be followed by any string of digits, letters, dollar signs (save
3575 on the H8/300), and underscores.
3579 Case of letters is significant: @code{foo} is a different symbol name
3582 Multibyte characters are supported. To generate a symbol name containing
3583 multibyte characters enclose it within double quotes and use escape codes. cf
3584 @xref{Strings}. Generating a multibyte symbol name from a label is not
3585 currently supported.
3587 Each symbol has exactly one name. Each name in an assembly language program
3588 refers to exactly one symbol. You may use that symbol name any number of times
3591 @subheading Local Symbol Names
3593 @cindex local symbol names
3594 @cindex symbol names, local
3595 A local symbol is any symbol beginning with certain local label prefixes.
3596 By default, the local label prefix is @samp{.L} for ELF systems or
3597 @samp{L} for traditional a.out systems, but each target may have its own
3598 set of local label prefixes.
3600 On the HPPA local symbols begin with @samp{L$}.
3603 Local symbols are defined and used within the assembler, but they are
3604 normally not saved in object files. Thus, they are not visible when debugging.
3605 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3606 @option{-L}}) to retain the local symbols in the object files.
3608 @subheading Local Labels
3610 @cindex local labels
3611 @cindex temporary symbol names
3612 @cindex symbol names, temporary
3613 Local labels help compilers and programmers use names temporarily.
3614 They create symbols which are guaranteed to be unique over the entire scope of
3615 the input source code and which can be referred to by a simple notation.
3616 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3617 represents any positive integer). To refer to the most recent previous
3618 definition of that label write @samp{@b{N}b}, using the same number as when
3619 you defined the label. To refer to the next definition of a local label, write
3620 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3623 There is no restriction on how you can use these labels, and you can reuse them
3624 too. So that it is possible to repeatedly define the same local label (using
3625 the same number @samp{@b{N}}), although you can only refer to the most recently
3626 defined local label of that number (for a backwards reference) or the next
3627 definition of a specific local label for a forward reference. It is also worth
3628 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3629 implemented in a slightly more efficient manner than the others.
3640 Which is the equivalent of:
3643 label_1: branch label_3
3644 label_2: branch label_1
3645 label_3: branch label_4
3646 label_4: branch label_3
3649 Local label names are only a notational device. They are immediately
3650 transformed into more conventional symbol names before the assembler uses them.
3651 The symbol names are stored in the symbol table, appear in error messages, and
3652 are optionally emitted to the object file. The names are constructed using
3656 @item @emph{local label prefix}
3657 All local symbols begin with the system-specific local label prefix.
3658 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3659 that start with the local label prefix. These labels are
3660 used for symbols you are never intended to see. If you use the
3661 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3662 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3663 you may use them in debugging.
3666 This is the number that was used in the local label definition. So if the
3667 label is written @samp{55:} then the number is @samp{55}.
3670 This unusual character is included so you do not accidentally invent a symbol
3671 of the same name. The character has ASCII value of @samp{\002} (control-B).
3673 @item @emph{ordinal number}
3674 This is a serial number to keep the labels distinct. The first definition of
3675 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3676 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3677 the number @samp{1} and its 15th definition gets @samp{15} as well.
3680 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3681 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3683 @subheading Dollar Local Labels
3684 @cindex dollar local symbols
3686 @code{@value{AS}} also supports an even more local form of local labels called
3687 dollar labels. These labels go out of scope (i.e., they become undefined) as
3688 soon as a non-local label is defined. Thus they remain valid for only a small
3689 region of the input source code. Normal local labels, by contrast, remain in
3690 scope for the entire file, or until they are redefined by another occurrence of
3691 the same local label.
3693 Dollar labels are defined in exactly the same way as ordinary local labels,
3694 except that they have a dollar sign suffix to their numeric value, e.g.,
3697 They can also be distinguished from ordinary local labels by their transformed
3698 names which use ASCII character @samp{\001} (control-A) as the magic character
3699 to distinguish them from ordinary labels. For example, the fifth definition of
3700 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3703 @section The Special Dot Symbol
3705 @cindex dot (symbol)
3706 @cindex @code{.} (symbol)
3707 @cindex current address
3708 @cindex location counter
3709 The special symbol @samp{.} refers to the current address that
3710 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3711 .long .} defines @code{melvin} to contain its own address.
3712 Assigning a value to @code{.} is treated the same as a @code{.org}
3714 @ifclear no-space-dir
3715 Thus, the expression @samp{.=.+4} is the same as saying
3719 @node Symbol Attributes
3720 @section Symbol Attributes
3722 @cindex symbol attributes
3723 @cindex attributes, symbol
3724 Every symbol has, as well as its name, the attributes ``Value'' and
3725 ``Type''. Depending on output format, symbols can also have auxiliary
3728 The detailed definitions are in @file{a.out.h}.
3731 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3732 all these attributes, and probably won't warn you. This makes the
3733 symbol an externally defined symbol, which is generally what you
3737 * Symbol Value:: Value
3738 * Symbol Type:: Type
3741 * a.out Symbols:: Symbol Attributes: @code{a.out}
3745 * a.out Symbols:: Symbol Attributes: @code{a.out}
3748 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3753 * COFF Symbols:: Symbol Attributes for COFF
3756 * SOM Symbols:: Symbol Attributes for SOM
3763 @cindex value of a symbol
3764 @cindex symbol value
3765 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3766 location in the text, data, bss or absolute sections the value is the
3767 number of addresses from the start of that section to the label.
3768 Naturally for text, data and bss sections the value of a symbol changes
3769 as @code{@value{LD}} changes section base addresses during linking. Absolute
3770 symbols' values do not change during linking: that is why they are
3773 The value of an undefined symbol is treated in a special way. If it is
3774 0 then the symbol is not defined in this assembler source file, and
3775 @code{@value{LD}} tries to determine its value from other files linked into the
3776 same program. You make this kind of symbol simply by mentioning a symbol
3777 name without defining it. A non-zero value represents a @code{.comm}
3778 common declaration. The value is how much common storage to reserve, in
3779 bytes (addresses). The symbol refers to the first address of the
3785 @cindex type of a symbol
3787 The type attribute of a symbol contains relocation (section)
3788 information, any flag settings indicating that a symbol is external, and
3789 (optionally), other information for linkers and debuggers. The exact
3790 format depends on the object-code output format in use.
3795 @c The following avoids a "widow" subsection title. @group would be
3796 @c better if it were available outside examples.
3799 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3801 @cindex @code{b.out} symbol attributes
3802 @cindex symbol attributes, @code{b.out}
3803 These symbol attributes appear only when @command{@value{AS}} is configured for
3804 one of the Berkeley-descended object output formats---@code{a.out} or
3810 @subsection Symbol Attributes: @code{a.out}
3812 @cindex @code{a.out} symbol attributes
3813 @cindex symbol attributes, @code{a.out}
3819 @subsection Symbol Attributes: @code{a.out}
3821 @cindex @code{a.out} symbol attributes
3822 @cindex symbol attributes, @code{a.out}
3826 * Symbol Desc:: Descriptor
3827 * Symbol Other:: Other
3831 @subsubsection Descriptor
3833 @cindex descriptor, of @code{a.out} symbol
3834 This is an arbitrary 16-bit value. You may establish a symbol's
3835 descriptor value by using a @code{.desc} statement
3836 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3837 @command{@value{AS}}.
3840 @subsubsection Other
3842 @cindex other attribute, of @code{a.out} symbol
3843 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3848 @subsection Symbol Attributes for COFF
3850 @cindex COFF symbol attributes
3851 @cindex symbol attributes, COFF
3853 The COFF format supports a multitude of auxiliary symbol attributes;
3854 like the primary symbol attributes, they are set between @code{.def} and
3855 @code{.endef} directives.
3857 @subsubsection Primary Attributes
3859 @cindex primary attributes, COFF symbols
3860 The symbol name is set with @code{.def}; the value and type,
3861 respectively, with @code{.val} and @code{.type}.
3863 @subsubsection Auxiliary Attributes
3865 @cindex auxiliary attributes, COFF symbols
3866 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3867 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3868 table information for COFF.
3873 @subsection Symbol Attributes for SOM
3875 @cindex SOM symbol attributes
3876 @cindex symbol attributes, SOM
3878 The SOM format for the HPPA supports a multitude of symbol attributes set with
3879 the @code{.EXPORT} and @code{.IMPORT} directives.
3881 The attributes are described in @cite{HP9000 Series 800 Assembly
3882 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3883 @code{EXPORT} assembler directive documentation.
3887 @chapter Expressions
3891 @cindex numeric values
3892 An @dfn{expression} specifies an address or numeric value.
3893 Whitespace may precede and/or follow an expression.
3895 The result of an expression must be an absolute number, or else an offset into
3896 a particular section. If an expression is not absolute, and there is not
3897 enough information when @command{@value{AS}} sees the expression to know its
3898 section, a second pass over the source program might be necessary to interpret
3899 the expression---but the second pass is currently not implemented.
3900 @command{@value{AS}} aborts with an error message in this situation.
3903 * Empty Exprs:: Empty Expressions
3904 * Integer Exprs:: Integer Expressions
3908 @section Empty Expressions
3910 @cindex empty expressions
3911 @cindex expressions, empty
3912 An empty expression has no value: it is just whitespace or null.
3913 Wherever an absolute expression is required, you may omit the
3914 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3915 is compatible with other assemblers.
3918 @section Integer Expressions
3920 @cindex integer expressions
3921 @cindex expressions, integer
3922 An @dfn{integer expression} is one or more @emph{arguments} delimited
3923 by @emph{operators}.
3926 * Arguments:: Arguments
3927 * Operators:: Operators
3928 * Prefix Ops:: Prefix Operators
3929 * Infix Ops:: Infix Operators
3933 @subsection Arguments
3935 @cindex expression arguments
3936 @cindex arguments in expressions
3937 @cindex operands in expressions
3938 @cindex arithmetic operands
3939 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3940 contexts arguments are sometimes called ``arithmetic operands''. In
3941 this manual, to avoid confusing them with the ``instruction operands'' of
3942 the machine language, we use the term ``argument'' to refer to parts of
3943 expressions only, reserving the word ``operand'' to refer only to machine
3944 instruction operands.
3946 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3947 @var{section} is one of text, data, bss, absolute,
3948 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3951 Numbers are usually integers.
3953 A number can be a flonum or bignum. In this case, you are warned
3954 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3955 these 32 bits are an integer. You may write integer-manipulating
3956 instructions that act on exotic constants, compatible with other
3959 @cindex subexpressions
3960 Subexpressions are a left parenthesis @samp{(} followed by an integer
3961 expression, followed by a right parenthesis @samp{)}; or a prefix
3962 operator followed by an argument.
3965 @subsection Operators
3967 @cindex operators, in expressions
3968 @cindex arithmetic functions
3969 @cindex functions, in expressions
3970 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3971 operators are followed by an argument. Infix operators appear
3972 between their arguments. Operators may be preceded and/or followed by
3976 @subsection Prefix Operator
3978 @cindex prefix operators
3979 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3980 one argument, which must be absolute.
3982 @c the tex/end tex stuff surrounding this small table is meant to make
3983 @c it align, on the printed page, with the similar table in the next
3984 @c section (which is inside an enumerate).
3986 \global\advance\leftskip by \itemindent
3991 @dfn{Negation}. Two's complement negation.
3993 @dfn{Complementation}. Bitwise not.
3997 \global\advance\leftskip by -\itemindent
4001 @subsection Infix Operators
4003 @cindex infix operators
4004 @cindex operators, permitted arguments
4005 @dfn{Infix operators} take two arguments, one on either side. Operators
4006 have precedence, but operations with equal precedence are performed left
4007 to right. Apart from @code{+} or @option{-}, both arguments must be
4008 absolute, and the result is absolute.
4011 @cindex operator precedence
4012 @cindex precedence of operators
4019 @dfn{Multiplication}.
4022 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4028 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4031 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4035 Intermediate precedence
4040 @dfn{Bitwise Inclusive Or}.
4046 @dfn{Bitwise Exclusive Or}.
4049 @dfn{Bitwise Or Not}.
4056 @cindex addition, permitted arguments
4057 @cindex plus, permitted arguments
4058 @cindex arguments for addition
4060 @dfn{Addition}. If either argument is absolute, the result has the section of
4061 the other argument. You may not add together arguments from different
4064 @cindex subtraction, permitted arguments
4065 @cindex minus, permitted arguments
4066 @cindex arguments for subtraction
4068 @dfn{Subtraction}. If the right argument is absolute, the
4069 result has the section of the left argument.
4070 If both arguments are in the same section, the result is absolute.
4071 You may not subtract arguments from different sections.
4072 @c FIXME is there still something useful to say about undefined - undefined ?
4074 @cindex comparison expressions
4075 @cindex expressions, comparison
4080 @dfn{Is Not Equal To}
4084 @dfn{Is Greater Than}
4086 @dfn{Is Greater Than Or Equal To}
4088 @dfn{Is Less Than Or Equal To}
4090 The comparison operators can be used as infix operators. A true results has a
4091 value of -1 whereas a false result has a value of 0. Note, these operators
4092 perform signed comparisons.
4095 @item Lowest Precedence
4104 These two logical operations can be used to combine the results of sub
4105 expressions. Note, unlike the comparison operators a true result returns a
4106 value of 1 but a false results does still return 0. Also note that the logical
4107 or operator has a slightly lower precedence than logical and.
4112 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4113 address; you can only have a defined section in one of the two arguments.
4116 @chapter Assembler Directives
4118 @cindex directives, machine independent
4119 @cindex pseudo-ops, machine independent
4120 @cindex machine independent directives
4121 All assembler directives have names that begin with a period (@samp{.}).
4122 The rest of the name is letters, usually in lower case.
4124 This chapter discusses directives that are available regardless of the
4125 target machine configuration for the @sc{gnu} assembler.
4127 Some machine configurations provide additional directives.
4128 @xref{Machine Dependencies}.
4131 @ifset machine-directives
4132 @xref{Machine Dependencies}, for additional directives.
4137 * Abort:: @code{.abort}
4139 * ABORT (COFF):: @code{.ABORT}
4142 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4143 * Altmacro:: @code{.altmacro}
4144 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4145 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4146 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4147 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4148 * Byte:: @code{.byte @var{expressions}}
4149 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4150 * Comm:: @code{.comm @var{symbol} , @var{length} }
4151 * Data:: @code{.data @var{subsection}}
4153 * Def:: @code{.def @var{name}}
4156 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4162 * Double:: @code{.double @var{flonums}}
4163 * Eject:: @code{.eject}
4164 * Else:: @code{.else}
4165 * Elseif:: @code{.elseif}
4168 * Endef:: @code{.endef}
4171 * Endfunc:: @code{.endfunc}
4172 * Endif:: @code{.endif}
4173 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4174 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4175 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4177 * Error:: @code{.error @var{string}}
4178 * Exitm:: @code{.exitm}
4179 * Extern:: @code{.extern}
4180 * Fail:: @code{.fail}
4181 * File:: @code{.file}
4182 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4183 * Float:: @code{.float @var{flonums}}
4184 * Func:: @code{.func}
4185 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4187 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4188 * Hidden:: @code{.hidden @var{names}}
4191 * hword:: @code{.hword @var{expressions}}
4192 * Ident:: @code{.ident}
4193 * If:: @code{.if @var{absolute expression}}
4194 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4195 * Include:: @code{.include "@var{file}"}
4196 * Int:: @code{.int @var{expressions}}
4198 * Internal:: @code{.internal @var{names}}
4201 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4202 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4203 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4204 * Lflags:: @code{.lflags}
4205 @ifclear no-line-dir
4206 * Line:: @code{.line @var{line-number}}
4209 * Linkonce:: @code{.linkonce [@var{type}]}
4210 * List:: @code{.list}
4211 * Ln:: @code{.ln @var{line-number}}
4212 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4213 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4215 * Local:: @code{.local @var{names}}
4218 * Long:: @code{.long @var{expressions}}
4220 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4223 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4224 * MRI:: @code{.mri @var{val}}
4225 * Noaltmacro:: @code{.noaltmacro}
4226 * Nolist:: @code{.nolist}
4227 * Octa:: @code{.octa @var{bignums}}
4228 * Offset:: @code{.offset @var{loc}}
4229 * Org:: @code{.org @var{new-lc}, @var{fill}}
4230 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4232 * PopSection:: @code{.popsection}
4233 * Previous:: @code{.previous}
4236 * Print:: @code{.print @var{string}}
4238 * Protected:: @code{.protected @var{names}}
4241 * Psize:: @code{.psize @var{lines}, @var{columns}}
4242 * Purgem:: @code{.purgem @var{name}}
4244 * PushSection:: @code{.pushsection @var{name}}
4247 * Quad:: @code{.quad @var{bignums}}
4248 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4249 * Rept:: @code{.rept @var{count}}
4250 * Sbttl:: @code{.sbttl "@var{subheading}"}
4252 * Scl:: @code{.scl @var{class}}
4255 * Section:: @code{.section @var{name}[, @var{flags}]}
4258 * Set:: @code{.set @var{symbol}, @var{expression}}
4259 * Short:: @code{.short @var{expressions}}
4260 * Single:: @code{.single @var{flonums}}
4262 * Size:: @code{.size [@var{name} , @var{expression}]}
4264 @ifclear no-space-dir
4265 * Skip:: @code{.skip @var{size} , @var{fill}}
4268 * Sleb128:: @code{.sleb128 @var{expressions}}
4269 @ifclear no-space-dir
4270 * Space:: @code{.space @var{size} , @var{fill}}
4273 * Stab:: @code{.stabd, .stabn, .stabs}
4276 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4277 * Struct:: @code{.struct @var{expression}}
4279 * SubSection:: @code{.subsection}
4280 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4284 * Tag:: @code{.tag @var{structname}}
4287 * Text:: @code{.text @var{subsection}}
4288 * Title:: @code{.title "@var{heading}"}
4290 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4293 * Uleb128:: @code{.uleb128 @var{expressions}}
4295 * Val:: @code{.val @var{addr}}
4299 * Version:: @code{.version "@var{string}"}
4300 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4301 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4304 * Warning:: @code{.warning @var{string}}
4305 * Weak:: @code{.weak @var{names}}
4306 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4307 * Word:: @code{.word @var{expressions}}
4308 * Deprecated:: Deprecated Directives
4312 @section @code{.abort}
4314 @cindex @code{abort} directive
4315 @cindex stopping the assembly
4316 This directive stops the assembly immediately. It is for
4317 compatibility with other assemblers. The original idea was that the
4318 assembly language source would be piped into the assembler. If the sender
4319 of the source quit, it could use this directive tells @command{@value{AS}} to
4320 quit also. One day @code{.abort} will not be supported.
4324 @section @code{.ABORT} (COFF)
4326 @cindex @code{ABORT} directive
4327 When producing COFF output, @command{@value{AS}} accepts this directive as a
4328 synonym for @samp{.abort}.
4331 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4337 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4339 @cindex padding the location counter
4340 @cindex @code{align} directive
4341 Pad the location counter (in the current subsection) to a particular storage
4342 boundary. The first expression (which must be absolute) is the alignment
4343 required, as described below.
4345 The second expression (also absolute) gives the fill value to be stored in the
4346 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4347 padding bytes are normally zero. However, on some systems, if the section is
4348 marked as containing code and the fill value is omitted, the space is filled
4349 with no-op instructions.
4351 The third expression is also absolute, and is also optional. If it is present,
4352 it is the maximum number of bytes that should be skipped by this alignment
4353 directive. If doing the alignment would require skipping more bytes than the
4354 specified maximum, then the alignment is not done at all. You can omit the
4355 fill value (the second argument) entirely by simply using two commas after the
4356 required alignment; this can be useful if you want the alignment to be filled
4357 with no-op instructions when appropriate.
4359 The way the required alignment is specified varies from system to system.
4360 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4361 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4362 alignment request in bytes. For example @samp{.align 8} advances
4363 the location counter until it is a multiple of 8. If the location counter
4364 is already a multiple of 8, no change is needed. For the tic54x, the
4365 first expression is the alignment request in words.
4367 For other systems, including ppc, i386 using a.out format, arm and
4368 strongarm, it is the
4369 number of low-order zero bits the location counter must have after
4370 advancement. For example @samp{.align 3} advances the location
4371 counter until it a multiple of 8. If the location counter is already a
4372 multiple of 8, no change is needed.
4374 This inconsistency is due to the different behaviors of the various
4375 native assemblers for these systems which GAS must emulate.
4376 GAS also provides @code{.balign} and @code{.p2align} directives,
4377 described later, which have a consistent behavior across all
4378 architectures (but are specific to GAS).
4381 @section @code{.altmacro}
4382 Enable alternate macro mode, enabling:
4385 @item LOCAL @var{name} [ , @dots{} ]
4386 One additional directive, @code{LOCAL}, is available. It is used to
4387 generate a string replacement for each of the @var{name} arguments, and
4388 replace any instances of @var{name} in each macro expansion. The
4389 replacement string is unique in the assembly, and different for each
4390 separate macro expansion. @code{LOCAL} allows you to write macros that
4391 define symbols, without fear of conflict between separate macro expansions.
4393 @item String delimiters
4394 You can write strings delimited in these other ways besides
4395 @code{"@var{string}"}:
4398 @item '@var{string}'
4399 You can delimit strings with single-quote characters.
4401 @item <@var{string}>
4402 You can delimit strings with matching angle brackets.
4405 @item single-character string escape
4406 To include any single character literally in a string (even if the
4407 character would otherwise have some special meaning), you can prefix the
4408 character with @samp{!} (an exclamation mark). For example, you can
4409 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4411 @item Expression results as strings
4412 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4413 and use the result as a string.
4417 @section @code{.ascii "@var{string}"}@dots{}
4419 @cindex @code{ascii} directive
4420 @cindex string literals
4421 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4422 separated by commas. It assembles each string (with no automatic
4423 trailing zero byte) into consecutive addresses.
4426 @section @code{.asciz "@var{string}"}@dots{}
4428 @cindex @code{asciz} directive
4429 @cindex zero-terminated strings
4430 @cindex null-terminated strings
4431 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4432 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4435 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4437 @cindex padding the location counter given number of bytes
4438 @cindex @code{balign} directive
4439 Pad the location counter (in the current subsection) to a particular
4440 storage boundary. The first expression (which must be absolute) is the
4441 alignment request in bytes. For example @samp{.balign 8} advances
4442 the location counter until it is a multiple of 8. If the location counter
4443 is already a multiple of 8, no change is needed.
4445 The second expression (also absolute) gives the fill value to be stored in the
4446 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4447 padding bytes are normally zero. However, on some systems, if the section is
4448 marked as containing code and the fill value is omitted, the space is filled
4449 with no-op instructions.
4451 The third expression is also absolute, and is also optional. If it is present,
4452 it is the maximum number of bytes that should be skipped by this alignment
4453 directive. If doing the alignment would require skipping more bytes than the
4454 specified maximum, then the alignment is not done at all. You can omit the
4455 fill value (the second argument) entirely by simply using two commas after the
4456 required alignment; this can be useful if you want the alignment to be filled
4457 with no-op instructions when appropriate.
4459 @cindex @code{balignw} directive
4460 @cindex @code{balignl} directive
4461 The @code{.balignw} and @code{.balignl} directives are variants of the
4462 @code{.balign} directive. The @code{.balignw} directive treats the fill
4463 pattern as a two byte word value. The @code{.balignl} directives treats the
4464 fill pattern as a four byte longword value. For example, @code{.balignw
4465 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4466 filled in with the value 0x368d (the exact placement of the bytes depends upon
4467 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4470 @node Bundle directives
4471 @section @code{.bundle_align_mode @var{abs-expr}}
4472 @cindex @code{bundle_align_mode} directive
4474 @cindex instruction bundle
4475 @cindex aligned instruction bundle
4476 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4477 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4478 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4479 disabled (which is the default state). If the argument it not zero, it
4480 gives the size of an instruction bundle as a power of two (as for the
4481 @code{.p2align} directive, @pxref{P2align}).
4483 For some targets, it's an ABI requirement that no instruction may span a
4484 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4485 instructions that starts on an aligned boundary. For example, if
4486 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4487 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4488 effect, no single instruction may span a boundary between bundles. If an
4489 instruction would start too close to the end of a bundle for the length of
4490 that particular instruction to fit within the bundle, then the space at the
4491 end of that bundle is filled with no-op instructions so the instruction
4492 starts in the next bundle. As a corollary, it's an error if any single
4493 instruction's encoding is longer than the bundle size.
4495 @section @code{.bundle_lock} and @code{.bundle_unlock}
4496 @cindex @code{bundle_lock} directive
4497 @cindex @code{bundle_unlock} directive
4498 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4499 allow explicit control over instruction bundle padding. These directives
4500 are only valid when @code{.bundle_align_mode} has been used to enable
4501 aligned instruction bundle mode. It's an error if they appear when
4502 @code{.bundle_align_mode} has not been used at all, or when the last
4503 directive was @w{@code{.bundle_align_mode 0}}.
4505 @cindex bundle-locked
4506 For some targets, it's an ABI requirement that certain instructions may
4507 appear only as part of specified permissible sequences of multiple
4508 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4509 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4510 instruction sequence. For purposes of aligned instruction bundle mode, a
4511 sequence starting with @code{.bundle_lock} and ending with
4512 @code{.bundle_unlock} is treated as a single instruction. That is, the
4513 entire sequence must fit into a single bundle and may not span a bundle
4514 boundary. If necessary, no-op instructions will be inserted before the
4515 first instruction of the sequence so that the whole sequence starts on an
4516 aligned bundle boundary. It's an error if the sequence is longer than the
4519 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4520 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4521 nested. That is, a second @code{.bundle_lock} directive before the next
4522 @code{.bundle_unlock} directive has no effect except that it must be
4523 matched by another closing @code{.bundle_unlock} so that there is the
4524 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4527 @section @code{.byte @var{expressions}}
4529 @cindex @code{byte} directive
4530 @cindex integers, one byte
4531 @code{.byte} expects zero or more expressions, separated by commas.
4532 Each expression is assembled into the next byte.
4534 @node CFI directives
4535 @section @code{.cfi_sections @var{section_list}}
4536 @cindex @code{cfi_sections} directive
4537 @code{.cfi_sections} may be used to specify whether CFI directives
4538 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4539 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4540 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4541 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4542 directive is not used is @code{.cfi_sections .eh_frame}.
4544 @section @code{.cfi_startproc [simple]}
4545 @cindex @code{cfi_startproc} directive
4546 @code{.cfi_startproc} is used at the beginning of each function that
4547 should have an entry in @code{.eh_frame}. It initializes some internal
4548 data structures. Don't forget to close the function by
4549 @code{.cfi_endproc}.
4551 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4552 it also emits some architecture dependent initial CFI instructions.
4554 @section @code{.cfi_endproc}
4555 @cindex @code{cfi_endproc} directive
4556 @code{.cfi_endproc} is used at the end of a function where it closes its
4557 unwind entry previously opened by
4558 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4560 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4561 @code{.cfi_personality} defines personality routine and its encoding.
4562 @var{encoding} must be a constant determining how the personality
4563 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4564 argument is not present, otherwise second argument should be
4565 a constant or a symbol name. When using indirect encodings,
4566 the symbol provided should be the location where personality
4567 can be loaded from, not the personality routine itself.
4568 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4569 no personality routine.
4571 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4572 @code{.cfi_lsda} defines LSDA and its encoding.
4573 @var{encoding} must be a constant determining how the LSDA
4574 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4575 argument is not present, otherwise second argument should be a constant
4576 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4579 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4580 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4581 address from @var{register} and add @var{offset} to it}.
4583 @section @code{.cfi_def_cfa_register @var{register}}
4584 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4585 now on @var{register} will be used instead of the old one. Offset
4588 @section @code{.cfi_def_cfa_offset @var{offset}}
4589 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4590 remains the same, but @var{offset} is new. Note that it is the
4591 absolute offset that will be added to a defined register to compute
4594 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4595 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4596 value that is added/substracted from the previous offset.
4598 @section @code{.cfi_offset @var{register}, @var{offset}}
4599 Previous value of @var{register} is saved at offset @var{offset} from
4602 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4603 Previous value of @var{register} is saved at offset @var{offset} from
4604 the current CFA register. This is transformed to @code{.cfi_offset}
4605 using the known displacement of the CFA register from the CFA.
4606 This is often easier to use, because the number will match the
4607 code it's annotating.
4609 @section @code{.cfi_register @var{register1}, @var{register2}}
4610 Previous value of @var{register1} is saved in register @var{register2}.
4612 @section @code{.cfi_restore @var{register}}
4613 @code{.cfi_restore} says that the rule for @var{register} is now the
4614 same as it was at the beginning of the function, after all initial
4615 instruction added by @code{.cfi_startproc} were executed.
4617 @section @code{.cfi_undefined @var{register}}
4618 From now on the previous value of @var{register} can't be restored anymore.
4620 @section @code{.cfi_same_value @var{register}}
4621 Current value of @var{register} is the same like in the previous frame,
4622 i.e. no restoration needed.
4624 @section @code{.cfi_remember_state},
4625 First save all current rules for all registers by @code{.cfi_remember_state},
4626 then totally screw them up by subsequent @code{.cfi_*} directives and when
4627 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4628 the previous saved state.
4630 @section @code{.cfi_return_column @var{register}}
4631 Change return column @var{register}, i.e. the return address is either
4632 directly in @var{register} or can be accessed by rules for @var{register}.
4634 @section @code{.cfi_signal_frame}
4635 Mark current function as signal trampoline.
4637 @section @code{.cfi_window_save}
4638 SPARC register window has been saved.
4640 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4641 Allows the user to add arbitrary bytes to the unwind info. One
4642 might use this to add OS-specific CFI opcodes, or generic CFI
4643 opcodes that GAS does not yet support.
4645 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4646 The current value of @var{register} is @var{label}. The value of @var{label}
4647 will be encoded in the output file according to @var{encoding}; see the
4648 description of @code{.cfi_personality} for details on this encoding.
4650 The usefulness of equating a register to a fixed label is probably
4651 limited to the return address register. Here, it can be useful to
4652 mark a code segment that has only one return address which is reached
4653 by a direct branch and no copy of the return address exists in memory
4654 or another register.
4657 @section @code{.comm @var{symbol} , @var{length} }
4659 @cindex @code{comm} directive
4660 @cindex symbol, common
4661 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4662 common symbol in one object file may be merged with a defined or common symbol
4663 of the same name in another object file. If @code{@value{LD}} does not see a
4664 definition for the symbol--just one or more common symbols--then it will
4665 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4666 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4667 the same name, and they do not all have the same size, it will allocate space
4668 using the largest size.
4671 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4672 an optional third argument. This is the desired alignment of the symbol,
4673 specified for ELF as a byte boundary (for example, an alignment of 16 means
4674 that the least significant 4 bits of the address should be zero), and for PE
4675 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4676 boundary). The alignment must be an absolute expression, and it must be a
4677 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4678 common symbol, it will use the alignment when placing the symbol. If no
4679 alignment is specified, @command{@value{AS}} will set the alignment to the
4680 largest power of two less than or equal to the size of the symbol, up to a
4681 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4682 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4683 @samp{--section-alignment} option; image file sections in PE are aligned to
4684 multiples of 4096, which is far too large an alignment for ordinary variables.
4685 It is rather the default alignment for (non-debug) sections within object
4686 (@samp{*.o}) files, which are less strictly aligned.}.
4690 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4691 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4695 @section @code{.data @var{subsection}}
4697 @cindex @code{data} directive
4698 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4699 end of the data subsection numbered @var{subsection} (which is an
4700 absolute expression). If @var{subsection} is omitted, it defaults
4705 @section @code{.def @var{name}}
4707 @cindex @code{def} directive
4708 @cindex COFF symbols, debugging
4709 @cindex debugging COFF symbols
4710 Begin defining debugging information for a symbol @var{name}; the
4711 definition extends until the @code{.endef} directive is encountered.
4714 This directive is only observed when @command{@value{AS}} is configured for COFF
4715 format output; when producing @code{b.out}, @samp{.def} is recognized,
4722 @section @code{.desc @var{symbol}, @var{abs-expression}}
4724 @cindex @code{desc} directive
4725 @cindex COFF symbol descriptor
4726 @cindex symbol descriptor, COFF
4727 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4728 to the low 16 bits of an absolute expression.
4731 The @samp{.desc} directive is not available when @command{@value{AS}} is
4732 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4733 object format. For the sake of compatibility, @command{@value{AS}} accepts
4734 it, but produces no output, when configured for COFF.
4740 @section @code{.dim}
4742 @cindex @code{dim} directive
4743 @cindex COFF auxiliary symbol information
4744 @cindex auxiliary symbol information, COFF
4745 This directive is generated by compilers to include auxiliary debugging
4746 information in the symbol table. It is only permitted inside
4747 @code{.def}/@code{.endef} pairs.
4750 @samp{.dim} is only meaningful when generating COFF format output; when
4751 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4757 @section @code{.double @var{flonums}}
4759 @cindex @code{double} directive
4760 @cindex floating point numbers (double)
4761 @code{.double} expects zero or more flonums, separated by commas. It
4762 assembles floating point numbers.
4764 The exact kind of floating point numbers emitted depends on how
4765 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4769 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4770 in @sc{ieee} format.
4775 @section @code{.eject}
4777 @cindex @code{eject} directive
4778 @cindex new page, in listings
4779 @cindex page, in listings
4780 @cindex listing control: new page
4781 Force a page break at this point, when generating assembly listings.
4784 @section @code{.else}
4786 @cindex @code{else} directive
4787 @code{.else} is part of the @command{@value{AS}} support for conditional
4788 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4789 of code to be assembled if the condition for the preceding @code{.if}
4793 @section @code{.elseif}
4795 @cindex @code{elseif} directive
4796 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4797 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4798 @code{.if} block that would otherwise fill the entire @code{.else} section.
4801 @section @code{.end}
4803 @cindex @code{end} directive
4804 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4805 process anything in the file past the @code{.end} directive.
4809 @section @code{.endef}
4811 @cindex @code{endef} directive
4812 This directive flags the end of a symbol definition begun with
4816 @samp{.endef} is only meaningful when generating COFF format output; if
4817 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4818 directive but ignores it.
4823 @section @code{.endfunc}
4824 @cindex @code{endfunc} directive
4825 @code{.endfunc} marks the end of a function specified with @code{.func}.
4828 @section @code{.endif}
4830 @cindex @code{endif} directive
4831 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4832 it marks the end of a block of code that is only assembled
4833 conditionally. @xref{If,,@code{.if}}.
4836 @section @code{.equ @var{symbol}, @var{expression}}
4838 @cindex @code{equ} directive
4839 @cindex assigning values to symbols
4840 @cindex symbols, assigning values to
4841 This directive sets the value of @var{symbol} to @var{expression}.
4842 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4845 The syntax for @code{equ} on the HPPA is
4846 @samp{@var{symbol} .equ @var{expression}}.
4850 The syntax for @code{equ} on the Z80 is
4851 @samp{@var{symbol} equ @var{expression}}.
4852 On the Z80 it is an eror if @var{symbol} is already defined,
4853 but the symbol is not protected from later redefinition.
4854 Compare @ref{Equiv}.
4858 @section @code{.equiv @var{symbol}, @var{expression}}
4859 @cindex @code{equiv} directive
4860 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4861 the assembler will signal an error if @var{symbol} is already defined. Note a
4862 symbol which has been referenced but not actually defined is considered to be
4865 Except for the contents of the error message, this is roughly equivalent to
4872 plus it protects the symbol from later redefinition.
4875 @section @code{.eqv @var{symbol}, @var{expression}}
4876 @cindex @code{eqv} directive
4877 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4878 evaluate the expression or any part of it immediately. Instead each time
4879 the resulting symbol is used in an expression, a snapshot of its current
4883 @section @code{.err}
4884 @cindex @code{err} directive
4885 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4886 message and, unless the @option{-Z} option was used, it will not generate an
4887 object file. This can be used to signal an error in conditionally compiled code.
4890 @section @code{.error "@var{string}"}
4891 @cindex error directive
4893 Similarly to @code{.err}, this directive emits an error, but you can specify a
4894 string that will be emitted as the error message. If you don't specify the
4895 message, it defaults to @code{".error directive invoked in source file"}.
4896 @xref{Errors, ,Error and Warning Messages}.
4899 .error "This code has not been assembled and tested."
4903 @section @code{.exitm}
4904 Exit early from the current macro definition. @xref{Macro}.
4907 @section @code{.extern}
4909 @cindex @code{extern} directive
4910 @code{.extern} is accepted in the source program---for compatibility
4911 with other assemblers---but it is ignored. @command{@value{AS}} treats
4912 all undefined symbols as external.
4915 @section @code{.fail @var{expression}}
4917 @cindex @code{fail} directive
4918 Generates an error or a warning. If the value of the @var{expression} is 500
4919 or more, @command{@value{AS}} will print a warning message. If the value is less
4920 than 500, @command{@value{AS}} will print an error message. The message will
4921 include the value of @var{expression}. This can occasionally be useful inside
4922 complex nested macros or conditional assembly.
4925 @section @code{.file}
4926 @cindex @code{file} directive
4928 @ifclear no-file-dir
4929 There are two different versions of the @code{.file} directive. Targets
4930 that support DWARF2 line number information use the DWARF2 version of
4931 @code{.file}. Other targets use the default version.
4933 @subheading Default Version
4935 @cindex logical file name
4936 @cindex file name, logical
4937 This version of the @code{.file} directive tells @command{@value{AS}} that we
4938 are about to start a new logical file. The syntax is:
4944 @var{string} is the new file name. In general, the filename is
4945 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4946 to specify an empty file name, you must give the quotes--@code{""}. This
4947 statement may go away in future: it is only recognized to be compatible with
4948 old @command{@value{AS}} programs.
4950 @subheading DWARF2 Version
4953 When emitting DWARF2 line number information, @code{.file} assigns filenames
4954 to the @code{.debug_line} file name table. The syntax is:
4957 .file @var{fileno} @var{filename}
4960 The @var{fileno} operand should be a unique positive integer to use as the
4961 index of the entry in the table. The @var{filename} operand is a C string
4964 The detail of filename indices is exposed to the user because the filename
4965 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4966 information, and thus the user must know the exact indices that table
4970 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4972 @cindex @code{fill} directive
4973 @cindex writing patterns in memory
4974 @cindex patterns, writing in memory
4975 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4976 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4977 may be zero or more. @var{Size} may be zero or more, but if it is
4978 more than 8, then it is deemed to have the value 8, compatible with
4979 other people's assemblers. The contents of each @var{repeat} bytes
4980 is taken from an 8-byte number. The highest order 4 bytes are
4981 zero. The lowest order 4 bytes are @var{value} rendered in the
4982 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4983 Each @var{size} bytes in a repetition is taken from the lowest order
4984 @var{size} bytes of this number. Again, this bizarre behavior is
4985 compatible with other people's assemblers.
4987 @var{size} and @var{value} are optional.
4988 If the second comma and @var{value} are absent, @var{value} is
4989 assumed zero. If the first comma and following tokens are absent,
4990 @var{size} is assumed to be 1.
4993 @section @code{.float @var{flonums}}
4995 @cindex floating point numbers (single)
4996 @cindex @code{float} directive
4997 This directive assembles zero or more flonums, separated by commas. It
4998 has the same effect as @code{.single}.
5000 The exact kind of floating point numbers emitted depends on how
5001 @command{@value{AS}} is configured.
5002 @xref{Machine Dependencies}.
5006 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5007 in @sc{ieee} format.
5012 @section @code{.func @var{name}[,@var{label}]}
5013 @cindex @code{func} directive
5014 @code{.func} emits debugging information to denote function @var{name}, and
5015 is ignored unless the file is assembled with debugging enabled.
5016 Only @samp{--gstabs[+]} is currently supported.
5017 @var{label} is the entry point of the function and if omitted @var{name}
5018 prepended with the @samp{leading char} is used.
5019 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5020 All functions are currently defined to have @code{void} return type.
5021 The function must be terminated with @code{.endfunc}.
5024 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5026 @cindex @code{global} directive
5027 @cindex symbol, making visible to linker
5028 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5029 @var{symbol} in your partial program, its value is made available to
5030 other partial programs that are linked with it. Otherwise,
5031 @var{symbol} takes its attributes from a symbol of the same name
5032 from another file linked into the same program.
5034 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5035 compatibility with other assemblers.
5038 On the HPPA, @code{.global} is not always enough to make it accessible to other
5039 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5040 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5045 @section @code{.gnu_attribute @var{tag},@var{value}}
5046 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5049 @section @code{.hidden @var{names}}
5051 @cindex @code{hidden} directive
5053 This is one of the ELF visibility directives. The other two are
5054 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5055 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5057 This directive overrides the named symbols default visibility (which is set by
5058 their binding: local, global or weak). The directive sets the visibility to
5059 @code{hidden} which means that the symbols are not visible to other components.
5060 Such symbols are always considered to be @code{protected} as well.
5064 @section @code{.hword @var{expressions}}
5066 @cindex @code{hword} directive
5067 @cindex integers, 16-bit
5068 @cindex numbers, 16-bit
5069 @cindex sixteen bit integers
5070 This expects zero or more @var{expressions}, and emits
5071 a 16 bit number for each.
5074 This directive is a synonym for @samp{.short}; depending on the target
5075 architecture, it may also be a synonym for @samp{.word}.
5079 This directive is a synonym for @samp{.short}.
5082 This directive is a synonym for both @samp{.short} and @samp{.word}.
5087 @section @code{.ident}
5089 @cindex @code{ident} directive
5091 This directive is used by some assemblers to place tags in object files. The
5092 behavior of this directive varies depending on the target. When using the
5093 a.out object file format, @command{@value{AS}} simply accepts the directive for
5094 source-file compatibility with existing assemblers, but does not emit anything
5095 for it. When using COFF, comments are emitted to the @code{.comment} or
5096 @code{.rdata} section, depending on the target. When using ELF, comments are
5097 emitted to the @code{.comment} section.
5100 @section @code{.if @var{absolute expression}}
5102 @cindex conditional assembly
5103 @cindex @code{if} directive
5104 @code{.if} marks the beginning of a section of code which is only
5105 considered part of the source program being assembled if the argument
5106 (which must be an @var{absolute expression}) is non-zero. The end of
5107 the conditional section of code must be marked by @code{.endif}
5108 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5109 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5110 If you have several conditions to check, @code{.elseif} may be used to avoid
5111 nesting blocks if/else within each subsequent @code{.else} block.
5113 The following variants of @code{.if} are also supported:
5115 @cindex @code{ifdef} directive
5116 @item .ifdef @var{symbol}
5117 Assembles the following section of code if the specified @var{symbol}
5118 has been defined. Note a symbol which has been referenced but not yet defined
5119 is considered to be undefined.
5121 @cindex @code{ifb} directive
5122 @item .ifb @var{text}
5123 Assembles the following section of code if the operand is blank (empty).
5125 @cindex @code{ifc} directive
5126 @item .ifc @var{string1},@var{string2}
5127 Assembles the following section of code if the two strings are the same. The
5128 strings may be optionally quoted with single quotes. If they are not quoted,
5129 the first string stops at the first comma, and the second string stops at the
5130 end of the line. Strings which contain whitespace should be quoted. The
5131 string comparison is case sensitive.
5133 @cindex @code{ifeq} directive
5134 @item .ifeq @var{absolute expression}
5135 Assembles the following section of code if the argument is zero.
5137 @cindex @code{ifeqs} directive
5138 @item .ifeqs @var{string1},@var{string2}
5139 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5141 @cindex @code{ifge} directive
5142 @item .ifge @var{absolute expression}
5143 Assembles the following section of code if the argument is greater than or
5146 @cindex @code{ifgt} directive
5147 @item .ifgt @var{absolute expression}
5148 Assembles the following section of code if the argument is greater than zero.
5150 @cindex @code{ifle} directive
5151 @item .ifle @var{absolute expression}
5152 Assembles the following section of code if the argument is less than or equal
5155 @cindex @code{iflt} directive
5156 @item .iflt @var{absolute expression}
5157 Assembles the following section of code if the argument is less than zero.
5159 @cindex @code{ifnb} directive
5160 @item .ifnb @var{text}
5161 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5162 following section of code if the operand is non-blank (non-empty).
5164 @cindex @code{ifnc} directive
5165 @item .ifnc @var{string1},@var{string2}.
5166 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5167 following section of code if the two strings are not the same.
5169 @cindex @code{ifndef} directive
5170 @cindex @code{ifnotdef} directive
5171 @item .ifndef @var{symbol}
5172 @itemx .ifnotdef @var{symbol}
5173 Assembles the following section of code if the specified @var{symbol}
5174 has not been defined. Both spelling variants are equivalent. Note a symbol
5175 which has been referenced but not yet defined is considered to be undefined.
5177 @cindex @code{ifne} directive
5178 @item .ifne @var{absolute expression}
5179 Assembles the following section of code if the argument is not equal to zero
5180 (in other words, this is equivalent to @code{.if}).
5182 @cindex @code{ifnes} directive
5183 @item .ifnes @var{string1},@var{string2}
5184 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5185 following section of code if the two strings are not the same.
5189 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5191 @cindex @code{incbin} directive
5192 @cindex binary files, including
5193 The @code{incbin} directive includes @var{file} verbatim at the current
5194 location. You can control the search paths used with the @samp{-I} command-line
5195 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5198 The @var{skip} argument skips a number of bytes from the start of the
5199 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5200 read. Note that the data is not aligned in any way, so it is the user's
5201 responsibility to make sure that proper alignment is provided both before and
5202 after the @code{incbin} directive.
5205 @section @code{.include "@var{file}"}
5207 @cindex @code{include} directive
5208 @cindex supporting files, including
5209 @cindex files, including
5210 This directive provides a way to include supporting files at specified
5211 points in your source program. The code from @var{file} is assembled as
5212 if it followed the point of the @code{.include}; when the end of the
5213 included file is reached, assembly of the original file continues. You
5214 can control the search paths used with the @samp{-I} command-line option
5215 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5219 @section @code{.int @var{expressions}}
5221 @cindex @code{int} directive
5222 @cindex integers, 32-bit
5223 Expect zero or more @var{expressions}, of any section, separated by commas.
5224 For each expression, emit a number that, at run time, is the value of that
5225 expression. The byte order and bit size of the number depends on what kind
5226 of target the assembly is for.
5230 On most forms of the H8/300, @code{.int} emits 16-bit
5231 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5238 @section @code{.internal @var{names}}
5240 @cindex @code{internal} directive
5242 This is one of the ELF visibility directives. The other two are
5243 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5244 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5246 This directive overrides the named symbols default visibility (which is set by
5247 their binding: local, global or weak). The directive sets the visibility to
5248 @code{internal} which means that the symbols are considered to be @code{hidden}
5249 (i.e., not visible to other components), and that some extra, processor specific
5250 processing must also be performed upon the symbols as well.
5254 @section @code{.irp @var{symbol},@var{values}}@dots{}
5256 @cindex @code{irp} directive
5257 Evaluate a sequence of statements assigning different values to @var{symbol}.
5258 The sequence of statements starts at the @code{.irp} directive, and is
5259 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5260 set to @var{value}, and the sequence of statements is assembled. If no
5261 @var{value} is listed, the sequence of statements is assembled once, with
5262 @var{symbol} set to the null string. To refer to @var{symbol} within the
5263 sequence of statements, use @var{\symbol}.
5265 For example, assembling
5273 is equivalent to assembling
5281 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5284 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5286 @cindex @code{irpc} directive
5287 Evaluate a sequence of statements assigning different values to @var{symbol}.
5288 The sequence of statements starts at the @code{.irpc} directive, and is
5289 terminated by an @code{.endr} directive. For each character in @var{value},
5290 @var{symbol} is set to the character, and the sequence of statements is
5291 assembled. If no @var{value} is listed, the sequence of statements is
5292 assembled once, with @var{symbol} set to the null string. To refer to
5293 @var{symbol} within the sequence of statements, use @var{\symbol}.
5295 For example, assembling
5303 is equivalent to assembling
5311 For some caveats with the spelling of @var{symbol}, see also the discussion
5315 @section @code{.lcomm @var{symbol} , @var{length}}
5317 @cindex @code{lcomm} directive
5318 @cindex local common symbols
5319 @cindex symbols, local common
5320 Reserve @var{length} (an absolute expression) bytes for a local common
5321 denoted by @var{symbol}. The section and value of @var{symbol} are
5322 those of the new local common. The addresses are allocated in the bss
5323 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5324 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5325 not visible to @code{@value{LD}}.
5328 Some targets permit a third argument to be used with @code{.lcomm}. This
5329 argument specifies the desired alignment of the symbol in the bss section.
5333 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5334 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5338 @section @code{.lflags}
5340 @cindex @code{lflags} directive (ignored)
5341 @command{@value{AS}} accepts this directive, for compatibility with other
5342 assemblers, but ignores it.
5344 @ifclear no-line-dir
5346 @section @code{.line @var{line-number}}
5348 @cindex @code{line} directive
5349 @cindex logical line number
5351 Change the logical line number. @var{line-number} must be an absolute
5352 expression. The next line has that logical line number. Therefore any other
5353 statements on the current line (after a statement separator character) are
5354 reported as on logical line number @var{line-number} @minus{} 1. One day
5355 @command{@value{AS}} will no longer support this directive: it is recognized only
5356 for compatibility with existing assembler programs.
5359 Even though this is a directive associated with the @code{a.out} or
5360 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5361 when producing COFF output, and treats @samp{.line} as though it
5362 were the COFF @samp{.ln} @emph{if} it is found outside a
5363 @code{.def}/@code{.endef} pair.
5365 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5366 used by compilers to generate auxiliary symbol information for
5371 @section @code{.linkonce [@var{type}]}
5373 @cindex @code{linkonce} directive
5374 @cindex common sections
5375 Mark the current section so that the linker only includes a single copy of it.
5376 This may be used to include the same section in several different object files,
5377 but ensure that the linker will only include it once in the final output file.
5378 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5379 Duplicate sections are detected based on the section name, so it should be
5382 This directive is only supported by a few object file formats; as of this
5383 writing, the only object file format which supports it is the Portable
5384 Executable format used on Windows NT.
5386 The @var{type} argument is optional. If specified, it must be one of the
5387 following strings. For example:
5391 Not all types may be supported on all object file formats.
5395 Silently discard duplicate sections. This is the default.
5398 Warn if there are duplicate sections, but still keep only one copy.
5401 Warn if any of the duplicates have different sizes.
5404 Warn if any of the duplicates do not have exactly the same contents.
5408 @section @code{.list}
5410 @cindex @code{list} directive
5411 @cindex listing control, turning on
5412 Control (in conjunction with the @code{.nolist} directive) whether or
5413 not assembly listings are generated. These two directives maintain an
5414 internal counter (which is zero initially). @code{.list} increments the
5415 counter, and @code{.nolist} decrements it. Assembly listings are
5416 generated whenever the counter is greater than zero.
5418 By default, listings are disabled. When you enable them (with the
5419 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5420 the initial value of the listing counter is one.
5423 @section @code{.ln @var{line-number}}
5425 @cindex @code{ln} directive
5426 @ifclear no-line-dir
5427 @samp{.ln} is a synonym for @samp{.line}.
5430 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5431 must be an absolute expression. The next line has that logical
5432 line number, so any other statements on the current line (after a
5433 statement separator character @code{;}) are reported as on logical
5434 line number @var{line-number} @minus{} 1.
5437 This directive is accepted, but ignored, when @command{@value{AS}} is
5438 configured for @code{b.out}; its effect is only associated with COFF
5444 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5445 @cindex @code{loc} directive
5446 When emitting DWARF2 line number information,
5447 the @code{.loc} directive will add a row to the @code{.debug_line} line
5448 number matrix corresponding to the immediately following assembly
5449 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5450 arguments will be applied to the @code{.debug_line} state machine before
5453 The @var{options} are a sequence of the following tokens in any order:
5457 This option will set the @code{basic_block} register in the
5458 @code{.debug_line} state machine to @code{true}.
5461 This option will set the @code{prologue_end} register in the
5462 @code{.debug_line} state machine to @code{true}.
5464 @item epilogue_begin
5465 This option will set the @code{epilogue_begin} register in the
5466 @code{.debug_line} state machine to @code{true}.
5468 @item is_stmt @var{value}
5469 This option will set the @code{is_stmt} register in the
5470 @code{.debug_line} state machine to @code{value}, which must be
5473 @item isa @var{value}
5474 This directive will set the @code{isa} register in the @code{.debug_line}
5475 state machine to @var{value}, which must be an unsigned integer.
5477 @item discriminator @var{value}
5478 This directive will set the @code{discriminator} register in the @code{.debug_line}
5479 state machine to @var{value}, which must be an unsigned integer.
5483 @node Loc_mark_labels
5484 @section @code{.loc_mark_labels @var{enable}}
5485 @cindex @code{loc_mark_labels} directive
5486 When emitting DWARF2 line number information,
5487 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5488 to the @code{.debug_line} line number matrix with the @code{basic_block}
5489 register in the state machine set whenever a code label is seen.
5490 The @var{enable} argument should be either 1 or 0, to enable or disable
5491 this function respectively.
5495 @section @code{.local @var{names}}
5497 @cindex @code{local} directive
5498 This directive, which is available for ELF targets, marks each symbol in
5499 the comma-separated list of @code{names} as a local symbol so that it
5500 will not be externally visible. If the symbols do not already exist,
5501 they will be created.
5503 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5504 accept an alignment argument, which is the case for most ELF targets,
5505 the @code{.local} directive can be used in combination with @code{.comm}
5506 (@pxref{Comm}) to define aligned local common data.
5510 @section @code{.long @var{expressions}}
5512 @cindex @code{long} directive
5513 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5516 @c no one seems to know what this is for or whether this description is
5517 @c what it really ought to do
5519 @section @code{.lsym @var{symbol}, @var{expression}}
5521 @cindex @code{lsym} directive
5522 @cindex symbol, not referenced in assembly
5523 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5524 the hash table, ensuring it cannot be referenced by name during the
5525 rest of the assembly. This sets the attributes of the symbol to be
5526 the same as the expression value:
5528 @var{other} = @var{descriptor} = 0
5529 @var{type} = @r{(section of @var{expression})}
5530 @var{value} = @var{expression}
5533 The new symbol is not flagged as external.
5537 @section @code{.macro}
5540 The commands @code{.macro} and @code{.endm} allow you to define macros that
5541 generate assembly output. For example, this definition specifies a macro
5542 @code{sum} that puts a sequence of numbers into memory:
5545 .macro sum from=0, to=5
5554 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5566 @item .macro @var{macname}
5567 @itemx .macro @var{macname} @var{macargs} @dots{}
5568 @cindex @code{macro} directive
5569 Begin the definition of a macro called @var{macname}. If your macro
5570 definition requires arguments, specify their names after the macro name,
5571 separated by commas or spaces. You can qualify the macro argument to
5572 indicate whether all invocations must specify a non-blank value (through
5573 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5574 (through @samp{:@code{vararg}}). You can supply a default value for any
5575 macro argument by following the name with @samp{=@var{deflt}}. You
5576 cannot define two macros with the same @var{macname} unless it has been
5577 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5578 definitions. For example, these are all valid @code{.macro} statements:
5582 Begin the definition of a macro called @code{comm}, which takes no
5585 @item .macro plus1 p, p1
5586 @itemx .macro plus1 p p1
5587 Either statement begins the definition of a macro called @code{plus1},
5588 which takes two arguments; within the macro definition, write
5589 @samp{\p} or @samp{\p1} to evaluate the arguments.
5591 @item .macro reserve_str p1=0 p2
5592 Begin the definition of a macro called @code{reserve_str}, with two
5593 arguments. The first argument has a default value, but not the second.
5594 After the definition is complete, you can call the macro either as
5595 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5596 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5597 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5598 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5600 @item .macro m p1:req, p2=0, p3:vararg
5601 Begin the definition of a macro called @code{m}, with at least three
5602 arguments. The first argument must always have a value specified, but
5603 not the second, which instead has a default value. The third formal
5604 will get assigned all remaining arguments specified at invocation time.
5606 When you call a macro, you can specify the argument values either by
5607 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5608 @samp{sum to=17, from=9}.
5612 Note that since each of the @var{macargs} can be an identifier exactly
5613 as any other one permitted by the target architecture, there may be
5614 occasional problems if the target hand-crafts special meanings to certain
5615 characters when they occur in a special position. For example, if the colon
5616 (@code{:}) is generally permitted to be part of a symbol name, but the
5617 architecture specific code special-cases it when occurring as the final
5618 character of a symbol (to denote a label), then the macro parameter
5619 replacement code will have no way of knowing that and consider the whole
5620 construct (including the colon) an identifier, and check only this
5621 identifier for being the subject to parameter substitution. So for example
5622 this macro definition:
5630 might not work as expected. Invoking @samp{label foo} might not create a label
5631 called @samp{foo} but instead just insert the text @samp{\l:} into the
5632 assembler source, probably generating an error about an unrecognised
5635 Similarly problems might occur with the period character (@samp{.})
5636 which is often allowed inside opcode names (and hence identifier names). So
5637 for example constructing a macro to build an opcode from a base name and a
5638 length specifier like this:
5641 .macro opcode base length
5646 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5647 instruction but instead generate some kind of error as the assembler tries to
5648 interpret the text @samp{\base.\length}.
5650 There are several possible ways around this problem:
5653 @item Insert white space
5654 If it is possible to use white space characters then this is the simplest
5663 @item Use @samp{\()}
5664 The string @samp{\()} can be used to separate the end of a macro argument from
5665 the following text. eg:
5668 .macro opcode base length
5673 @item Use the alternate macro syntax mode
5674 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5675 used as a separator. eg:
5685 Note: this problem of correctly identifying string parameters to pseudo ops
5686 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5687 and @code{.irpc} (@pxref{Irpc}) as well.
5690 @cindex @code{endm} directive
5691 Mark the end of a macro definition.
5694 @cindex @code{exitm} directive
5695 Exit early from the current macro definition.
5697 @cindex number of macros executed
5698 @cindex macros, count executed
5700 @command{@value{AS}} maintains a counter of how many macros it has
5701 executed in this pseudo-variable; you can copy that number to your
5702 output with @samp{\@@}, but @emph{only within a macro definition}.
5704 @item LOCAL @var{name} [ , @dots{} ]
5705 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5706 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5707 @xref{Altmacro,,@code{.altmacro}}.
5711 @section @code{.mri @var{val}}
5713 @cindex @code{mri} directive
5714 @cindex MRI mode, temporarily
5715 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5716 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5717 affects code assembled until the next @code{.mri} directive, or until the end
5718 of the file. @xref{M, MRI mode, MRI mode}.
5721 @section @code{.noaltmacro}
5722 Disable alternate macro mode. @xref{Altmacro}.
5725 @section @code{.nolist}
5727 @cindex @code{nolist} directive
5728 @cindex listing control, turning off
5729 Control (in conjunction with the @code{.list} directive) whether or
5730 not assembly listings are generated. These two directives maintain an
5731 internal counter (which is zero initially). @code{.list} increments the
5732 counter, and @code{.nolist} decrements it. Assembly listings are
5733 generated whenever the counter is greater than zero.
5736 @section @code{.octa @var{bignums}}
5738 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5739 @cindex @code{octa} directive
5740 @cindex integer, 16-byte
5741 @cindex sixteen byte integer
5742 This directive expects zero or more bignums, separated by commas. For each
5743 bignum, it emits a 16-byte integer.
5745 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5746 hence @emph{octa}-word for 16 bytes.
5749 @section @code{.offset @var{loc}}
5751 @cindex @code{offset} directive
5752 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5753 be an absolute expression. This directive may be useful for defining
5754 symbols with absolute values. Do not confuse it with the @code{.org}
5758 @section @code{.org @var{new-lc} , @var{fill}}
5760 @cindex @code{org} directive
5761 @cindex location counter, advancing
5762 @cindex advancing location counter
5763 @cindex current address, advancing
5764 Advance the location counter of the current section to
5765 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5766 expression with the same section as the current subsection. That is,
5767 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5768 wrong section, the @code{.org} directive is ignored. To be compatible
5769 with former assemblers, if the section of @var{new-lc} is absolute,
5770 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5771 is the same as the current subsection.
5773 @code{.org} may only increase the location counter, or leave it
5774 unchanged; you cannot use @code{.org} to move the location counter
5777 @c double negative used below "not undefined" because this is a specific
5778 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5779 @c section. doc@cygnus.com 18feb91
5780 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5781 may not be undefined. If you really detest this restriction we eagerly await
5782 a chance to share your improved assembler.
5784 Beware that the origin is relative to the start of the section, not
5785 to the start of the subsection. This is compatible with other
5786 people's assemblers.
5788 When the location counter (of the current subsection) is advanced, the
5789 intervening bytes are filled with @var{fill} which should be an
5790 absolute expression. If the comma and @var{fill} are omitted,
5791 @var{fill} defaults to zero.
5794 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5796 @cindex padding the location counter given a power of two
5797 @cindex @code{p2align} directive
5798 Pad the location counter (in the current subsection) to a particular
5799 storage boundary. The first expression (which must be absolute) is the
5800 number of low-order zero bits the location counter must have after
5801 advancement. For example @samp{.p2align 3} advances the location
5802 counter until it a multiple of 8. If the location counter is already a
5803 multiple of 8, no change is needed.
5805 The second expression (also absolute) gives the fill value to be stored in the
5806 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5807 padding bytes are normally zero. However, on some systems, if the section is
5808 marked as containing code and the fill value is omitted, the space is filled
5809 with no-op instructions.
5811 The third expression is also absolute, and is also optional. If it is present,
5812 it is the maximum number of bytes that should be skipped by this alignment
5813 directive. If doing the alignment would require skipping more bytes than the
5814 specified maximum, then the alignment is not done at all. You can omit the
5815 fill value (the second argument) entirely by simply using two commas after the
5816 required alignment; this can be useful if you want the alignment to be filled
5817 with no-op instructions when appropriate.
5819 @cindex @code{p2alignw} directive
5820 @cindex @code{p2alignl} directive
5821 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5822 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5823 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5824 fill pattern as a four byte longword value. For example, @code{.p2alignw
5825 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5826 filled in with the value 0x368d (the exact placement of the bytes depends upon
5827 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5832 @section @code{.popsection}
5834 @cindex @code{popsection} directive
5835 @cindex Section Stack
5836 This is one of the ELF section stack manipulation directives. The others are
5837 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5838 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5841 This directive replaces the current section (and subsection) with the top
5842 section (and subsection) on the section stack. This section is popped off the
5848 @section @code{.previous}
5850 @cindex @code{previous} directive
5851 @cindex Section Stack
5852 This is one of the ELF section stack manipulation directives. The others are
5853 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5854 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5855 (@pxref{PopSection}).
5857 This directive swaps the current section (and subsection) with most recently
5858 referenced section/subsection pair prior to this one. Multiple
5859 @code{.previous} directives in a row will flip between two sections (and their
5860 subsections). For example:
5872 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5878 # Now in section A subsection 1
5882 # Now in section B subsection 0
5885 # Now in section B subsection 1
5888 # Now in section B subsection 0
5892 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5893 section B and 0x9abc into subsection 1 of section B.
5895 In terms of the section stack, this directive swaps the current section with
5896 the top section on the section stack.
5900 @section @code{.print @var{string}}
5902 @cindex @code{print} directive
5903 @command{@value{AS}} will print @var{string} on the standard output during
5904 assembly. You must put @var{string} in double quotes.
5908 @section @code{.protected @var{names}}
5910 @cindex @code{protected} directive
5912 This is one of the ELF visibility directives. The other two are
5913 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5915 This directive overrides the named symbols default visibility (which is set by
5916 their binding: local, global or weak). The directive sets the visibility to
5917 @code{protected} which means that any references to the symbols from within the
5918 components that defines them must be resolved to the definition in that
5919 component, even if a definition in another component would normally preempt
5924 @section @code{.psize @var{lines} , @var{columns}}
5926 @cindex @code{psize} directive
5927 @cindex listing control: paper size
5928 @cindex paper size, for listings
5929 Use this directive to declare the number of lines---and, optionally, the
5930 number of columns---to use for each page, when generating listings.
5932 If you do not use @code{.psize}, listings use a default line-count
5933 of 60. You may omit the comma and @var{columns} specification; the
5934 default width is 200 columns.
5936 @command{@value{AS}} generates formfeeds whenever the specified number of
5937 lines is exceeded (or whenever you explicitly request one, using
5940 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5941 those explicitly specified with @code{.eject}.
5944 @section @code{.purgem @var{name}}
5946 @cindex @code{purgem} directive
5947 Undefine the macro @var{name}, so that later uses of the string will not be
5948 expanded. @xref{Macro}.
5952 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5954 @cindex @code{pushsection} directive
5955 @cindex Section Stack
5956 This is one of the ELF section stack manipulation directives. The others are
5957 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5958 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5961 This directive pushes the current section (and subsection) onto the
5962 top of the section stack, and then replaces the current section and
5963 subsection with @code{name} and @code{subsection}. The optional
5964 @code{flags}, @code{type} and @code{arguments} are treated the same
5965 as in the @code{.section} (@pxref{Section}) directive.
5969 @section @code{.quad @var{bignums}}
5971 @cindex @code{quad} directive
5972 @code{.quad} expects zero or more bignums, separated by commas. For
5973 each bignum, it emits
5975 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5976 warning message; and just takes the lowest order 8 bytes of the bignum.
5977 @cindex eight-byte integer
5978 @cindex integer, 8-byte
5980 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5981 hence @emph{quad}-word for 8 bytes.
5984 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5985 warning message; and just takes the lowest order 16 bytes of the bignum.
5986 @cindex sixteen-byte integer
5987 @cindex integer, 16-byte
5991 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5993 @cindex @code{reloc} directive
5994 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5995 @var{expression}. If @var{offset} is a number, the relocation is generated in
5996 the current section. If @var{offset} is an expression that resolves to a
5997 symbol plus offset, the relocation is generated in the given symbol's section.
5998 @var{expression}, if present, must resolve to a symbol plus addend or to an
5999 absolute value, but note that not all targets support an addend. e.g. ELF REL
6000 targets such as i386 store an addend in the section contents rather than in the
6001 relocation. This low level interface does not support addends stored in the
6005 @section @code{.rept @var{count}}
6007 @cindex @code{rept} directive
6008 Repeat the sequence of lines between the @code{.rept} directive and the next
6009 @code{.endr} directive @var{count} times.
6011 For example, assembling
6019 is equivalent to assembling
6028 @section @code{.sbttl "@var{subheading}"}
6030 @cindex @code{sbttl} directive
6031 @cindex subtitles for listings
6032 @cindex listing control: subtitle
6033 Use @var{subheading} as the title (third line, immediately after the
6034 title line) when generating assembly listings.
6036 This directive affects subsequent pages, as well as the current page if
6037 it appears within ten lines of the top of a page.
6041 @section @code{.scl @var{class}}
6043 @cindex @code{scl} directive
6044 @cindex symbol storage class (COFF)
6045 @cindex COFF symbol storage class
6046 Set the storage-class value for a symbol. This directive may only be
6047 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6048 whether a symbol is static or external, or it may record further
6049 symbolic debugging information.
6052 The @samp{.scl} directive is primarily associated with COFF output; when
6053 configured to generate @code{b.out} output format, @command{@value{AS}}
6054 accepts this directive but ignores it.
6060 @section @code{.section @var{name}}
6062 @cindex named section
6063 Use the @code{.section} directive to assemble the following code into a section
6066 This directive is only supported for targets that actually support arbitrarily
6067 named sections; on @code{a.out} targets, for example, it is not accepted, even
6068 with a standard @code{a.out} section name.
6072 @c only print the extra heading if both COFF and ELF are set
6073 @subheading COFF Version
6076 @cindex @code{section} directive (COFF version)
6077 For COFF targets, the @code{.section} directive is used in one of the following
6081 .section @var{name}[, "@var{flags}"]
6082 .section @var{name}[, @var{subsection}]
6085 If the optional argument is quoted, it is taken as flags to use for the
6086 section. Each flag is a single character. The following flags are recognized:
6089 bss section (uninitialized data)
6091 section is not loaded
6097 exclude section from linking
6103 shared section (meaningful for PE targets)
6105 ignored. (For compatibility with the ELF version)
6107 section is not readable (meaningful for PE targets)
6109 single-digit power-of-two section alignment (GNU extension)
6112 If no flags are specified, the default flags depend upon the section name. If
6113 the section name is not recognized, the default will be for the section to be
6114 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6115 from the section, rather than adding them, so if they are used on their own it
6116 will be as if no flags had been specified at all.
6118 If the optional argument to the @code{.section} directive is not quoted, it is
6119 taken as a subsection number (@pxref{Sub-Sections}).
6124 @c only print the extra heading if both COFF and ELF are set
6125 @subheading ELF Version
6128 @cindex Section Stack
6129 This is one of the ELF section stack manipulation directives. The others are
6130 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6131 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6132 @code{.previous} (@pxref{Previous}).
6134 @cindex @code{section} directive (ELF version)
6135 For ELF targets, the @code{.section} directive is used like this:
6138 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6141 The optional @var{flags} argument is a quoted string which may contain any
6142 combination of the following characters:
6145 section is allocatable
6147 section is excluded from executable and shared library.
6151 section is executable
6153 section is mergeable
6155 section contains zero terminated strings
6157 section is a member of a section group
6159 section is used for thread-local-storage
6161 section is a member of the previously-current section's group, if any
6164 The optional @var{type} argument may contain one of the following constants:
6167 section contains data
6169 section does not contain data (i.e., section only occupies space)
6171 section contains data which is used by things other than the program
6173 section contains an array of pointers to init functions
6175 section contains an array of pointers to finish functions
6176 @item @@preinit_array
6177 section contains an array of pointers to pre-init functions
6180 Many targets only support the first three section types.
6182 Note on targets where the @code{@@} character is the start of a comment (eg
6183 ARM) then another character is used instead. For example the ARM port uses the
6186 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6187 be specified as well as an extra argument---@var{entsize}---like this:
6190 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6193 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6194 constants, each @var{entsize} octets long. Sections with both @code{M} and
6195 @code{S} must contain zero terminated strings where each character is
6196 @var{entsize} bytes long. The linker may remove duplicates within sections with
6197 the same name, same entity size and same flags. @var{entsize} must be an
6198 absolute expression. For sections with both @code{M} and @code{S}, a string
6199 which is a suffix of a larger string is considered a duplicate. Thus
6200 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6201 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6203 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6204 be present along with an additional field like this:
6207 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6210 The @var{GroupName} field specifies the name of the section group to which this
6211 particular section belongs. The optional linkage field can contain:
6214 indicates that only one copy of this section should be retained
6219 Note: if both the @var{M} and @var{G} flags are present then the fields for
6220 the Merge flag should come first, like this:
6223 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6226 If @var{flags} contains the @code{?} symbol then it may not also contain the
6227 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6228 present. Instead, @code{?} says to consider the section that's current before
6229 this directive. If that section used @code{G}, then the new section will use
6230 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6231 If not, then the @code{?} symbol has no effect.
6233 If no flags are specified, the default flags depend upon the section name. If
6234 the section name is not recognized, the default will be for the section to have
6235 none of the above flags: it will not be allocated in memory, nor writable, nor
6236 executable. The section will contain data.
6238 For ELF targets, the assembler supports another type of @code{.section}
6239 directive for compatibility with the Solaris assembler:
6242 .section "@var{name}"[, @var{flags}...]
6245 Note that the section name is quoted. There may be a sequence of comma
6249 section is allocatable
6253 section is executable
6255 section is excluded from executable and shared library.
6257 section is used for thread local storage
6260 This directive replaces the current section and subsection. See the
6261 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6262 some examples of how this directive and the other section stack directives
6268 @section @code{.set @var{symbol}, @var{expression}}
6270 @cindex @code{set} directive
6271 @cindex symbol value, setting
6272 Set the value of @var{symbol} to @var{expression}. This
6273 changes @var{symbol}'s value and type to conform to
6274 @var{expression}. If @var{symbol} was flagged as external, it remains
6275 flagged (@pxref{Symbol Attributes}).
6277 You may @code{.set} a symbol many times in the same assembly.
6279 If you @code{.set} a global symbol, the value stored in the object
6280 file is the last value stored into it.
6283 On Z80 @code{set} is a real instruction, use
6284 @samp{@var{symbol} defl @var{expression}} instead.
6288 @section @code{.short @var{expressions}}
6290 @cindex @code{short} directive
6292 @code{.short} is normally the same as @samp{.word}.
6293 @xref{Word,,@code{.word}}.
6295 In some configurations, however, @code{.short} and @code{.word} generate
6296 numbers of different lengths. @xref{Machine Dependencies}.
6300 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6303 This expects zero or more @var{expressions}, and emits
6304 a 16 bit number for each.
6309 @section @code{.single @var{flonums}}
6311 @cindex @code{single} directive
6312 @cindex floating point numbers (single)
6313 This directive assembles zero or more flonums, separated by commas. It
6314 has the same effect as @code{.float}.
6316 The exact kind of floating point numbers emitted depends on how
6317 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6321 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6322 numbers in @sc{ieee} format.
6328 @section @code{.size}
6330 This directive is used to set the size associated with a symbol.
6334 @c only print the extra heading if both COFF and ELF are set
6335 @subheading COFF Version
6338 @cindex @code{size} directive (COFF version)
6339 For COFF targets, the @code{.size} directive is only permitted inside
6340 @code{.def}/@code{.endef} pairs. It is used like this:
6343 .size @var{expression}
6347 @samp{.size} is only meaningful when generating COFF format output; when
6348 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6355 @c only print the extra heading if both COFF and ELF are set
6356 @subheading ELF Version
6359 @cindex @code{size} directive (ELF version)
6360 For ELF targets, the @code{.size} directive is used like this:
6363 .size @var{name} , @var{expression}
6366 This directive sets the size associated with a symbol @var{name}.
6367 The size in bytes is computed from @var{expression} which can make use of label
6368 arithmetic. This directive is typically used to set the size of function
6373 @ifclear no-space-dir
6375 @section @code{.skip @var{size} , @var{fill}}
6377 @cindex @code{skip} directive
6378 @cindex filling memory
6379 This directive emits @var{size} bytes, each of value @var{fill}. Both
6380 @var{size} and @var{fill} are absolute expressions. If the comma and
6381 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6386 @section @code{.sleb128 @var{expressions}}
6388 @cindex @code{sleb128} directive
6389 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6390 compact, variable length representation of numbers used by the DWARF
6391 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6393 @ifclear no-space-dir
6395 @section @code{.space @var{size} , @var{fill}}
6397 @cindex @code{space} directive
6398 @cindex filling memory
6399 This directive emits @var{size} bytes, each of value @var{fill}. Both
6400 @var{size} and @var{fill} are absolute expressions. If the comma
6401 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6406 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6407 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6408 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6409 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6417 @section @code{.stabd, .stabn, .stabs}
6419 @cindex symbolic debuggers, information for
6420 @cindex @code{stab@var{x}} directives
6421 There are three directives that begin @samp{.stab}.
6422 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6423 The symbols are not entered in the @command{@value{AS}} hash table: they
6424 cannot be referenced elsewhere in the source file.
6425 Up to five fields are required:
6429 This is the symbol's name. It may contain any character except
6430 @samp{\000}, so is more general than ordinary symbol names. Some
6431 debuggers used to code arbitrarily complex structures into symbol names
6435 An absolute expression. The symbol's type is set to the low 8 bits of
6436 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6437 and debuggers choke on silly bit patterns.
6440 An absolute expression. The symbol's ``other'' attribute is set to the
6441 low 8 bits of this expression.
6444 An absolute expression. The symbol's descriptor is set to the low 16
6445 bits of this expression.
6448 An absolute expression which becomes the symbol's value.
6451 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6452 or @code{.stabs} statement, the symbol has probably already been created;
6453 you get a half-formed symbol in your object file. This is
6454 compatible with earlier assemblers!
6457 @cindex @code{stabd} directive
6458 @item .stabd @var{type} , @var{other} , @var{desc}
6460 The ``name'' of the symbol generated is not even an empty string.
6461 It is a null pointer, for compatibility. Older assemblers used a
6462 null pointer so they didn't waste space in object files with empty
6465 The symbol's value is set to the location counter,
6466 relocatably. When your program is linked, the value of this symbol
6467 is the address of the location counter when the @code{.stabd} was
6470 @cindex @code{stabn} directive
6471 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6472 The name of the symbol is set to the empty string @code{""}.
6474 @cindex @code{stabs} directive
6475 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6476 All five fields are specified.
6482 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6483 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6485 @cindex string, copying to object file
6486 @cindex string8, copying to object file
6487 @cindex string16, copying to object file
6488 @cindex string32, copying to object file
6489 @cindex string64, copying to object file
6490 @cindex @code{string} directive
6491 @cindex @code{string8} directive
6492 @cindex @code{string16} directive
6493 @cindex @code{string32} directive
6494 @cindex @code{string64} directive
6496 Copy the characters in @var{str} to the object file. You may specify more than
6497 one string to copy, separated by commas. Unless otherwise specified for a
6498 particular machine, the assembler marks the end of each string with a 0 byte.
6499 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6501 The variants @code{string16}, @code{string32} and @code{string64} differ from
6502 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6503 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6504 are stored in target endianness byte order.
6510 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6511 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6516 @section @code{.struct @var{expression}}
6518 @cindex @code{struct} directive
6519 Switch to the absolute section, and set the section offset to @var{expression},
6520 which must be an absolute expression. You might use this as follows:
6529 This would define the symbol @code{field1} to have the value 0, the symbol
6530 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6531 value 8. Assembly would be left in the absolute section, and you would need to
6532 use a @code{.section} directive of some sort to change to some other section
6533 before further assembly.
6537 @section @code{.subsection @var{name}}
6539 @cindex @code{subsection} directive
6540 @cindex Section Stack
6541 This is one of the ELF section stack manipulation directives. The others are
6542 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6543 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6546 This directive replaces the current subsection with @code{name}. The current
6547 section is not changed. The replaced subsection is put onto the section stack
6548 in place of the then current top of stack subsection.
6553 @section @code{.symver}
6554 @cindex @code{symver} directive
6555 @cindex symbol versioning
6556 @cindex versions of symbols
6557 Use the @code{.symver} directive to bind symbols to specific version nodes
6558 within a source file. This is only supported on ELF platforms, and is
6559 typically used when assembling files to be linked into a shared library.
6560 There are cases where it may make sense to use this in objects to be bound
6561 into an application itself so as to override a versioned symbol from a
6564 For ELF targets, the @code{.symver} directive can be used like this:
6566 .symver @var{name}, @var{name2@@nodename}
6568 If the symbol @var{name} is defined within the file
6569 being assembled, the @code{.symver} directive effectively creates a symbol
6570 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6571 just don't try and create a regular alias is that the @var{@@} character isn't
6572 permitted in symbol names. The @var{name2} part of the name is the actual name
6573 of the symbol by which it will be externally referenced. The name @var{name}
6574 itself is merely a name of convenience that is used so that it is possible to
6575 have definitions for multiple versions of a function within a single source
6576 file, and so that the compiler can unambiguously know which version of a
6577 function is being mentioned. The @var{nodename} portion of the alias should be
6578 the name of a node specified in the version script supplied to the linker when
6579 building a shared library. If you are attempting to override a versioned
6580 symbol from a shared library, then @var{nodename} should correspond to the
6581 nodename of the symbol you are trying to override.
6583 If the symbol @var{name} is not defined within the file being assembled, all
6584 references to @var{name} will be changed to @var{name2@@nodename}. If no
6585 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6588 Another usage of the @code{.symver} directive is:
6590 .symver @var{name}, @var{name2@@@@nodename}
6592 In this case, the symbol @var{name} must exist and be defined within
6593 the file being assembled. It is similar to @var{name2@@nodename}. The
6594 difference is @var{name2@@@@nodename} will also be used to resolve
6595 references to @var{name2} by the linker.
6597 The third usage of the @code{.symver} directive is:
6599 .symver @var{name}, @var{name2@@@@@@nodename}
6601 When @var{name} is not defined within the
6602 file being assembled, it is treated as @var{name2@@nodename}. When
6603 @var{name} is defined within the file being assembled, the symbol
6604 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6609 @section @code{.tag @var{structname}}
6611 @cindex COFF structure debugging
6612 @cindex structure debugging, COFF
6613 @cindex @code{tag} directive
6614 This directive is generated by compilers to include auxiliary debugging
6615 information in the symbol table. It is only permitted inside
6616 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6617 definitions in the symbol table with instances of those structures.
6620 @samp{.tag} is only used when generating COFF format output; when
6621 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6627 @section @code{.text @var{subsection}}
6629 @cindex @code{text} directive
6630 Tells @command{@value{AS}} to assemble the following statements onto the end of
6631 the text subsection numbered @var{subsection}, which is an absolute
6632 expression. If @var{subsection} is omitted, subsection number zero
6636 @section @code{.title "@var{heading}"}
6638 @cindex @code{title} directive
6639 @cindex listing control: title line
6640 Use @var{heading} as the title (second line, immediately after the
6641 source file name and pagenumber) when generating assembly listings.
6643 This directive affects subsequent pages, as well as the current page if
6644 it appears within ten lines of the top of a page.
6648 @section @code{.type}
6650 This directive is used to set the type of a symbol.
6654 @c only print the extra heading if both COFF and ELF are set
6655 @subheading COFF Version
6658 @cindex COFF symbol type
6659 @cindex symbol type, COFF
6660 @cindex @code{type} directive (COFF version)
6661 For COFF targets, this directive is permitted only within
6662 @code{.def}/@code{.endef} pairs. It is used like this:
6668 This records the integer @var{int} as the type attribute of a symbol table
6672 @samp{.type} is associated only with COFF format output; when
6673 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6674 directive but ignores it.
6680 @c only print the extra heading if both COFF and ELF are set
6681 @subheading ELF Version
6684 @cindex ELF symbol type
6685 @cindex symbol type, ELF
6686 @cindex @code{type} directive (ELF version)
6687 For ELF targets, the @code{.type} directive is used like this:
6690 .type @var{name} , @var{type description}
6693 This sets the type of symbol @var{name} to be either a
6694 function symbol or an object symbol. There are five different syntaxes
6695 supported for the @var{type description} field, in order to provide
6696 compatibility with various other assemblers.
6698 Because some of the characters used in these syntaxes (such as @samp{@@} and
6699 @samp{#}) are comment characters for some architectures, some of the syntaxes
6700 below do not work on all architectures. The first variant will be accepted by
6701 the GNU assembler on all architectures so that variant should be used for
6702 maximum portability, if you do not need to assemble your code with other
6705 The syntaxes supported are:
6708 .type <name> STT_<TYPE_IN_UPPER_CASE>
6709 .type <name>,#<type>
6710 .type <name>,@@<type>
6711 .type <name>,%<type>
6712 .type <name>,"<type>"
6715 The types supported are:
6720 Mark the symbol as being a function name.
6723 @itemx gnu_indirect_function
6724 Mark the symbol as an indirect function when evaluated during reloc
6725 processing. (This is only supported on assemblers targeting GNU systems).
6729 Mark the symbol as being a data object.
6733 Mark the symbol as being a thead-local data object.
6737 Mark the symbol as being a common data object.
6741 Does not mark the symbol in any way. It is supported just for completeness.
6743 @item gnu_unique_object
6744 Marks the symbol as being a globally unique data object. The dynamic linker
6745 will make sure that in the entire process there is just one symbol with this
6746 name and type in use. (This is only supported on assemblers targeting GNU
6751 Note: Some targets support extra types in addition to those listed above.
6757 @section @code{.uleb128 @var{expressions}}
6759 @cindex @code{uleb128} directive
6760 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6761 compact, variable length representation of numbers used by the DWARF
6762 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6766 @section @code{.val @var{addr}}
6768 @cindex @code{val} directive
6769 @cindex COFF value attribute
6770 @cindex value attribute, COFF
6771 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6772 records the address @var{addr} as the value attribute of a symbol table
6776 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6777 configured for @code{b.out}, it accepts this directive but ignores it.
6783 @section @code{.version "@var{string}"}
6785 @cindex @code{version} directive
6786 This directive creates a @code{.note} section and places into it an ELF
6787 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6792 @section @code{.vtable_entry @var{table}, @var{offset}}
6794 @cindex @code{vtable_entry} directive
6795 This directive finds or creates a symbol @code{table} and creates a
6796 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6799 @section @code{.vtable_inherit @var{child}, @var{parent}}
6801 @cindex @code{vtable_inherit} directive
6802 This directive finds the symbol @code{child} and finds or creates the symbol
6803 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6804 parent whose addend is the value of the child symbol. As a special case the
6805 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6809 @section @code{.warning "@var{string}"}
6810 @cindex warning directive
6811 Similar to the directive @code{.error}
6812 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6815 @section @code{.weak @var{names}}
6817 @cindex @code{weak} directive
6818 This directive sets the weak attribute on the comma separated list of symbol
6819 @code{names}. If the symbols do not already exist, they will be created.
6821 On COFF targets other than PE, weak symbols are a GNU extension. This
6822 directive sets the weak attribute on the comma separated list of symbol
6823 @code{names}. If the symbols do not already exist, they will be created.
6825 On the PE target, weak symbols are supported natively as weak aliases.
6826 When a weak symbol is created that is not an alias, GAS creates an
6827 alternate symbol to hold the default value.
6830 @section @code{.weakref @var{alias}, @var{target}}
6832 @cindex @code{weakref} directive
6833 This directive creates an alias to the target symbol that enables the symbol to
6834 be referenced with weak-symbol semantics, but without actually making it weak.
6835 If direct references or definitions of the symbol are present, then the symbol
6836 will not be weak, but if all references to it are through weak references, the
6837 symbol will be marked as weak in the symbol table.
6839 The effect is equivalent to moving all references to the alias to a separate
6840 assembly source file, renaming the alias to the symbol in it, declaring the
6841 symbol as weak there, and running a reloadable link to merge the object files
6842 resulting from the assembly of the new source file and the old source file that
6843 had the references to the alias removed.
6845 The alias itself never makes to the symbol table, and is entirely handled
6846 within the assembler.
6849 @section @code{.word @var{expressions}}
6851 @cindex @code{word} directive
6852 This directive expects zero or more @var{expressions}, of any section,
6853 separated by commas.
6856 For each expression, @command{@value{AS}} emits a 32-bit number.
6859 For each expression, @command{@value{AS}} emits a 16-bit number.
6864 The size of the number emitted, and its byte order,
6865 depend on what target computer the assembly is for.
6868 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6869 @c happen---32-bit addressability, period; no long/short jumps.
6870 @ifset DIFF-TBL-KLUGE
6871 @cindex difference tables altered
6872 @cindex altered difference tables
6874 @emph{Warning: Special Treatment to support Compilers}
6878 Machines with a 32-bit address space, but that do less than 32-bit
6879 addressing, require the following special treatment. If the machine of
6880 interest to you does 32-bit addressing (or doesn't require it;
6881 @pxref{Machine Dependencies}), you can ignore this issue.
6884 In order to assemble compiler output into something that works,
6885 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6886 Directives of the form @samp{.word sym1-sym2} are often emitted by
6887 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6888 directive of the form @samp{.word sym1-sym2}, and the difference between
6889 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6890 creates a @dfn{secondary jump table}, immediately before the next label.
6891 This secondary jump table is preceded by a short-jump to the
6892 first byte after the secondary table. This short-jump prevents the flow
6893 of control from accidentally falling into the new table. Inside the
6894 table is a long-jump to @code{sym2}. The original @samp{.word}
6895 contains @code{sym1} minus the address of the long-jump to
6898 If there were several occurrences of @samp{.word sym1-sym2} before the
6899 secondary jump table, all of them are adjusted. If there was a
6900 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6901 long-jump to @code{sym4} is included in the secondary jump table,
6902 and the @code{.word} directives are adjusted to contain @code{sym3}
6903 minus the address of the long-jump to @code{sym4}; and so on, for as many
6904 entries in the original jump table as necessary.
6907 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6908 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6909 assembly language programmers.
6912 @c end DIFF-TBL-KLUGE
6915 @section Deprecated Directives
6917 @cindex deprecated directives
6918 @cindex obsolescent directives
6919 One day these directives won't work.
6920 They are included for compatibility with older assemblers.
6927 @node Object Attributes
6928 @chapter Object Attributes
6929 @cindex object attributes
6931 @command{@value{AS}} assembles source files written for a specific architecture
6932 into object files for that architecture. But not all object files are alike.
6933 Many architectures support incompatible variations. For instance, floating
6934 point arguments might be passed in floating point registers if the object file
6935 requires hardware floating point support---or floating point arguments might be
6936 passed in integer registers if the object file supports processors with no
6937 hardware floating point unit. Or, if two objects are built for different
6938 generations of the same architecture, the combination may require the
6939 newer generation at run-time.
6941 This information is useful during and after linking. At link time,
6942 @command{@value{LD}} can warn about incompatible object files. After link
6943 time, tools like @command{gdb} can use it to process the linked file
6946 Compatibility information is recorded as a series of object attributes. Each
6947 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6948 string, and indicates who sets the meaning of the tag. The tag is an integer,
6949 and indicates what property the attribute describes. The value may be a string
6950 or an integer, and indicates how the property affects this object. Missing
6951 attributes are the same as attributes with a zero value or empty string value.
6953 Object attributes were developed as part of the ABI for the ARM Architecture.
6954 The file format is documented in @cite{ELF for the ARM Architecture}.
6957 * GNU Object Attributes:: @sc{gnu} Object Attributes
6958 * Defining New Object Attributes:: Defining New Object Attributes
6961 @node GNU Object Attributes
6962 @section @sc{gnu} Object Attributes
6964 The @code{.gnu_attribute} directive records an object attribute
6965 with vendor @samp{gnu}.
6967 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6968 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6969 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6970 2} is set for architecture-independent attributes and clear for
6971 architecture-dependent ones.
6973 @subsection Common @sc{gnu} attributes
6975 These attributes are valid on all architectures.
6978 @item Tag_compatibility (32)
6979 The compatibility attribute takes an integer flag value and a vendor name. If
6980 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6981 then the file is only compatible with the named toolchain. If it is greater
6982 than 1, the file can only be processed by other toolchains under some private
6983 arrangement indicated by the flag value and the vendor name.
6986 @subsection MIPS Attributes
6989 @item Tag_GNU_MIPS_ABI_FP (4)
6990 The floating-point ABI used by this object file. The value will be:
6994 0 for files not affected by the floating-point ABI.
6996 1 for files using the hardware floating-point with a standard double-precision
6999 2 for files using the hardware floating-point ABI with a single-precision FPU.
7001 3 for files using the software floating-point ABI.
7003 4 for files using the hardware floating-point ABI with 64-bit wide
7004 double-precision floating-point registers and 32-bit wide general
7009 @subsection PowerPC Attributes
7012 @item Tag_GNU_Power_ABI_FP (4)
7013 The floating-point ABI used by this object file. The value will be:
7017 0 for files not affected by the floating-point ABI.
7019 1 for files using double-precision hardware floating-point ABI.
7021 2 for files using the software floating-point ABI.
7023 3 for files using single-precision hardware floating-point ABI.
7026 @item Tag_GNU_Power_ABI_Vector (8)
7027 The vector ABI used by this object file. The value will be:
7031 0 for files not affected by the vector ABI.
7033 1 for files using general purpose registers to pass vectors.
7035 2 for files using AltiVec registers to pass vectors.
7037 3 for files using SPE registers to pass vectors.
7041 @node Defining New Object Attributes
7042 @section Defining New Object Attributes
7044 If you want to define a new @sc{gnu} object attribute, here are the places you
7045 will need to modify. New attributes should be discussed on the @samp{binutils}
7050 This manual, which is the official register of attributes.
7052 The header for your architecture @file{include/elf}, to define the tag.
7054 The @file{bfd} support file for your architecture, to merge the attribute
7055 and issue any appropriate link warnings.
7057 Test cases in @file{ld/testsuite} for merging and link warnings.
7059 @file{binutils/readelf.c} to display your attribute.
7061 GCC, if you want the compiler to mark the attribute automatically.
7067 @node Machine Dependencies
7068 @chapter Machine Dependent Features
7070 @cindex machine dependencies
7071 The machine instruction sets are (almost by definition) different on
7072 each machine where @command{@value{AS}} runs. Floating point representations
7073 vary as well, and @command{@value{AS}} often supports a few additional
7074 directives or command-line options for compatibility with other
7075 assemblers on a particular platform. Finally, some versions of
7076 @command{@value{AS}} support special pseudo-instructions for branch
7079 This chapter discusses most of these differences, though it does not
7080 include details on any machine's instruction set. For details on that
7081 subject, see the hardware manufacturer's manual.
7085 * AArch64-Dependent:: AArch64 Dependent Features
7088 * Alpha-Dependent:: Alpha Dependent Features
7091 * ARC-Dependent:: ARC Dependent Features
7094 * ARM-Dependent:: ARM Dependent Features
7097 * AVR-Dependent:: AVR Dependent Features
7100 * Blackfin-Dependent:: Blackfin Dependent Features
7103 * CR16-Dependent:: CR16 Dependent Features
7106 * CRIS-Dependent:: CRIS Dependent Features
7109 * D10V-Dependent:: D10V Dependent Features
7112 * D30V-Dependent:: D30V Dependent Features
7115 * Epiphany-Dependent:: EPIPHANY Dependent Features
7118 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7121 * HPPA-Dependent:: HPPA Dependent Features
7124 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7127 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7130 * i860-Dependent:: Intel 80860 Dependent Features
7133 * i960-Dependent:: Intel 80960 Dependent Features
7136 * IA-64-Dependent:: Intel IA-64 Dependent Features
7139 * IP2K-Dependent:: IP2K Dependent Features
7142 * LM32-Dependent:: LM32 Dependent Features
7145 * M32C-Dependent:: M32C Dependent Features
7148 * M32R-Dependent:: M32R Dependent Features
7151 * M68K-Dependent:: M680x0 Dependent Features
7154 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7157 * Meta-Dependent :: Meta Dependent Features
7160 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7163 * MIPS-Dependent:: MIPS Dependent Features
7166 * MMIX-Dependent:: MMIX Dependent Features
7169 * MSP430-Dependent:: MSP430 Dependent Features
7172 * NDS32-Dependent:: Andes NDS32 Dependent Features
7175 * NiosII-Dependent:: Altera Nios II Dependent Features
7178 * NS32K-Dependent:: NS32K Dependent Features
7181 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7182 * SH64-Dependent:: SuperH SH64 Dependent Features
7185 * PDP-11-Dependent:: PDP-11 Dependent Features
7188 * PJ-Dependent:: picoJava Dependent Features
7191 * PPC-Dependent:: PowerPC Dependent Features
7194 * RL78-Dependent:: RL78 Dependent Features
7197 * RX-Dependent:: RX Dependent Features
7200 * S/390-Dependent:: IBM S/390 Dependent Features
7203 * SCORE-Dependent:: SCORE Dependent Features
7206 * Sparc-Dependent:: SPARC Dependent Features
7209 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7212 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7215 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7218 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7221 * V850-Dependent:: V850 Dependent Features
7224 * XGATE-Dependent:: XGATE Features
7227 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7230 * Xtensa-Dependent:: Xtensa Dependent Features
7233 * Z80-Dependent:: Z80 Dependent Features
7236 * Z8000-Dependent:: Z8000 Dependent Features
7239 * Vax-Dependent:: VAX Dependent Features
7246 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7247 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7248 @c peculiarity: to preserve cross-references, there must be a node called
7249 @c "Machine Dependencies". Hence the conditional nodenames in each
7250 @c major node below. Node defaulting in makeinfo requires adjacency of
7251 @c node and sectioning commands; hence the repetition of @chapter BLAH
7252 @c in both conditional blocks.
7255 @include c-aarch64.texi
7259 @include c-alpha.texi
7275 @include c-bfin.texi
7279 @include c-cr16.texi
7283 @include c-cris.texi
7288 @node Machine Dependencies
7289 @chapter Machine Dependent Features
7291 The machine instruction sets are different on each Renesas chip family,
7292 and there are also some syntax differences among the families. This
7293 chapter describes the specific @command{@value{AS}} features for each
7297 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7298 * SH-Dependent:: Renesas SH Dependent Features
7305 @include c-d10v.texi
7309 @include c-d30v.texi
7313 @include c-epiphany.texi
7317 @include c-h8300.texi
7321 @include c-hppa.texi
7325 @include c-i370.texi
7329 @include c-i386.texi
7333 @include c-i860.texi
7337 @include c-i960.texi
7341 @include c-ia64.texi
7345 @include c-ip2k.texi
7349 @include c-lm32.texi
7353 @include c-m32c.texi
7357 @include c-m32r.texi
7361 @include c-m68k.texi
7365 @include c-m68hc11.texi
7369 @include c-metag.texi
7373 @include c-microblaze.texi
7377 @include c-mips.texi
7381 @include c-mmix.texi
7385 @include c-msp430.texi
7389 @include c-nds32.texi
7393 @include c-nios2.texi
7397 @include c-ns32k.texi
7401 @include c-pdp11.texi
7413 @include c-rl78.texi
7421 @include c-s390.texi
7425 @include c-score.texi
7430 @include c-sh64.texi
7434 @include c-sparc.texi
7438 @include c-tic54x.texi
7442 @include c-tic6x.texi
7446 @include c-tilegx.texi
7450 @include c-tilepro.texi
7466 @include c-v850.texi
7470 @include c-xgate.texi
7474 @include c-xstormy16.texi
7478 @include c-xtensa.texi
7482 @c reverse effect of @down at top of generic Machine-Dep chapter
7486 @node Reporting Bugs
7487 @chapter Reporting Bugs
7488 @cindex bugs in assembler
7489 @cindex reporting bugs in assembler
7491 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7493 Reporting a bug may help you by bringing a solution to your problem, or it may
7494 not. But in any case the principal function of a bug report is to help the
7495 entire community by making the next version of @command{@value{AS}} work better.
7496 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7498 In order for a bug report to serve its purpose, you must include the
7499 information that enables us to fix the bug.
7502 * Bug Criteria:: Have you found a bug?
7503 * Bug Reporting:: How to report bugs
7507 @section Have You Found a Bug?
7508 @cindex bug criteria
7510 If you are not sure whether you have found a bug, here are some guidelines:
7513 @cindex fatal signal
7514 @cindex assembler crash
7515 @cindex crash of assembler
7517 If the assembler gets a fatal signal, for any input whatever, that is a
7518 @command{@value{AS}} bug. Reliable assemblers never crash.
7520 @cindex error on valid input
7522 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7524 @cindex invalid input
7526 If @command{@value{AS}} does not produce an error message for invalid input, that
7527 is a bug. However, you should note that your idea of ``invalid input'' might
7528 be our idea of ``an extension'' or ``support for traditional practice''.
7531 If you are an experienced user of assemblers, your suggestions for improvement
7532 of @command{@value{AS}} are welcome in any case.
7536 @section How to Report Bugs
7538 @cindex assembler bugs, reporting
7540 A number of companies and individuals offer support for @sc{gnu} products. If
7541 you obtained @command{@value{AS}} from a support organization, we recommend you
7542 contact that organization first.
7544 You can find contact information for many support companies and
7545 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7549 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7553 The fundamental principle of reporting bugs usefully is this:
7554 @strong{report all the facts}. If you are not sure whether to state a
7555 fact or leave it out, state it!
7557 Often people omit facts because they think they know what causes the problem
7558 and assume that some details do not matter. Thus, you might assume that the
7559 name of a symbol you use in an example does not matter. Well, probably it does
7560 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7561 happens to fetch from the location where that name is stored in memory;
7562 perhaps, if the name were different, the contents of that location would fool
7563 the assembler into doing the right thing despite the bug. Play it safe and
7564 give a specific, complete example. That is the easiest thing for you to do,
7565 and the most helpful.
7567 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7568 it is new to us. Therefore, always write your bug reports on the assumption
7569 that the bug has not been reported previously.
7571 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7572 bell?'' This cannot help us fix a bug, so it is basically useless. We
7573 respond by asking for enough details to enable us to investigate.
7574 You might as well expedite matters by sending them to begin with.
7576 To enable us to fix the bug, you should include all these things:
7580 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7581 it with the @samp{--version} argument.
7583 Without this, we will not know whether there is any point in looking for
7584 the bug in the current version of @command{@value{AS}}.
7587 Any patches you may have applied to the @command{@value{AS}} source.
7590 The type of machine you are using, and the operating system name and
7594 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7598 The command arguments you gave the assembler to assemble your example and
7599 observe the bug. To guarantee you will not omit something important, list them
7600 all. A copy of the Makefile (or the output from make) is sufficient.
7602 If we were to try to guess the arguments, we would probably guess wrong
7603 and then we might not encounter the bug.
7606 A complete input file that will reproduce the bug. If the bug is observed when
7607 the assembler is invoked via a compiler, send the assembler source, not the
7608 high level language source. Most compilers will produce the assembler source
7609 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7610 the options @samp{-v --save-temps}; this will save the assembler source in a
7611 file with an extension of @file{.s}, and also show you exactly how
7612 @command{@value{AS}} is being run.
7615 A description of what behavior you observe that you believe is
7616 incorrect. For example, ``It gets a fatal signal.''
7618 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7619 will certainly notice it. But if the bug is incorrect output, we might not
7620 notice unless it is glaringly wrong. You might as well not give us a chance to
7623 Even if the problem you experience is a fatal signal, you should still say so
7624 explicitly. Suppose something strange is going on, such as, your copy of
7625 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7626 library on your system. (This has happened!) Your copy might crash and ours
7627 would not. If you told us to expect a crash, then when ours fails to crash, we
7628 would know that the bug was not happening for us. If you had not told us to
7629 expect a crash, then we would not be able to draw any conclusion from our
7633 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7634 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7635 option. Always send diffs from the old file to the new file. If you even
7636 discuss something in the @command{@value{AS}} source, refer to it by context, not
7639 The line numbers in our development sources will not match those in your
7640 sources. Your line numbers would convey no useful information to us.
7643 Here are some things that are not necessary:
7647 A description of the envelope of the bug.
7649 Often people who encounter a bug spend a lot of time investigating
7650 which changes to the input file will make the bug go away and which
7651 changes will not affect it.
7653 This is often time consuming and not very useful, because the way we
7654 will find the bug is by running a single example under the debugger
7655 with breakpoints, not by pure deduction from a series of examples.
7656 We recommend that you save your time for something else.
7658 Of course, if you can find a simpler example to report @emph{instead}
7659 of the original one, that is a convenience for us. Errors in the
7660 output will be easier to spot, running under the debugger will take
7661 less time, and so on.
7663 However, simplification is not vital; if you do not want to do this,
7664 report the bug anyway and send us the entire test case you used.
7667 A patch for the bug.
7669 A patch for the bug does help us if it is a good one. But do not omit
7670 the necessary information, such as the test case, on the assumption that
7671 a patch is all we need. We might see problems with your patch and decide
7672 to fix the problem another way, or we might not understand it at all.
7674 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7675 construct an example that will make the program follow a certain path through
7676 the code. If you do not send us the example, we will not be able to construct
7677 one, so we will not be able to verify that the bug is fixed.
7679 And if we cannot understand what bug you are trying to fix, or why your
7680 patch should be an improvement, we will not install it. A test case will
7681 help us to understand.
7684 A guess about what the bug is or what it depends on.
7686 Such guesses are usually wrong. Even we cannot guess right about such
7687 things without first using the debugger to find the facts.
7690 @node Acknowledgements
7691 @chapter Acknowledgements
7693 If you have contributed to GAS and your name isn't listed here,
7694 it is not meant as a slight. We just don't know about it. Send mail to the
7695 maintainer, and we'll correct the situation. Currently
7697 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7699 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7702 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7703 information and the 68k series machines, most of the preprocessing pass, and
7704 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7706 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7707 many bug fixes, including merging support for several processors, breaking GAS
7708 up to handle multiple object file format back ends (including heavy rewrite,
7709 testing, an integration of the coff and b.out back ends), adding configuration
7710 including heavy testing and verification of cross assemblers and file splits
7711 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7712 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7713 port (including considerable amounts of reverse engineering), a SPARC opcode
7714 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7715 assertions and made them work, much other reorganization, cleanup, and lint.
7717 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7718 in format-specific I/O modules.
7720 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7721 has done much work with it since.
7723 The Intel 80386 machine description was written by Eliot Dresselhaus.
7725 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7727 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7728 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7730 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7731 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7732 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7733 support a.out format.
7735 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7736 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7737 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7738 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7741 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7742 simplified the configuration of which versions accept which directives. He
7743 updated the 68k machine description so that Motorola's opcodes always produced
7744 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7745 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7746 cross-compilation support, and one bug in relaxation that took a week and
7747 required the proverbial one-bit fix.
7749 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7750 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7751 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7752 PowerPC assembler, and made a few other minor patches.
7754 Steve Chamberlain made GAS able to generate listings.
7756 Hewlett-Packard contributed support for the HP9000/300.
7758 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7759 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7760 formats). This work was supported by both the Center for Software Science at
7761 the University of Utah and Cygnus Support.
7763 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7764 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7765 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7766 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7767 and some initial 64-bit support).
7769 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7771 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7772 support for openVMS/Alpha.
7774 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7777 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7778 Inc.@: added support for Xtensa processors.
7780 Several engineers at Cygnus Support have also provided many small bug fixes and
7781 configuration enhancements.
7783 Jon Beniston added support for the Lattice Mico32 architecture.
7785 Many others have contributed large or small bugfixes and enhancements. If
7786 you have contributed significant work and are not mentioned on this list, and
7787 want to be, let us know. Some of the history has been lost; we are not
7788 intentionally leaving anyone out.
7790 @node GNU Free Documentation License
7791 @appendix GNU Free Documentation License
7795 @unnumbered AS Index