1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
24 @include asconfig.texi
29 @c common OR combinations of conditions
52 @set abnormal-separator
56 @settitle Using @value{AS}
59 @settitle Using @value{AS} (@value{TARGET})
61 @setchapternewpage odd
66 @c WARE! Some of the machine-dependent sections contain tables of machine
67 @c instructions. Except in multi-column format, these tables look silly.
68 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
69 @c the multi-col format is faked within @example sections.
71 @c Again unfortunately, the natural size that fits on a page, for these tables,
72 @c is different depending on whether or not smallbook is turned on.
73 @c This matters, because of order: text flow switches columns at each page
76 @c The format faked in this source works reasonably well for smallbook,
77 @c not well for the default large-page format. This manual expects that if you
78 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
79 @c tables in question. You can turn on one without the other at your
80 @c discretion, of course.
83 @c the insn tables look just as silly in info files regardless of smallbook,
84 @c might as well show 'em anyways.
90 * As: (as). The GNU assembler.
91 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
104 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
106 Permission is granted to copy, distribute and/or modify this document
107 under the terms of the GNU Free Documentation License, Version 1.3
108 or any later version published by the Free Software Foundation;
109 with no Invariant Sections, with no Front-Cover Texts, and with no
110 Back-Cover Texts. A copy of the license is included in the
111 section entitled ``GNU Free Documentation License''.
117 @title Using @value{AS}
118 @subtitle The @sc{gnu} Assembler
120 @subtitle for the @value{TARGET} family
122 @ifset VERSION_PACKAGE
124 @subtitle @value{VERSION_PACKAGE}
127 @subtitle Version @value{VERSION}
130 The Free Software Foundation Inc.@: thanks The Nice Computer
131 Company of Australia for loaning Dean Elsner to write the
132 first (Vax) version of @command{as} for Project @sc{gnu}.
133 The proprietors, management and staff of TNCCA thank FSF for
134 distracting the boss while they got some work
137 @author Dean Elsner, Jay Fenlason & friends
141 \hfill {\it Using {\tt @value{AS}}}\par
142 \hfill Edited by Cygnus Support\par
144 %"boxit" macro for figures:
145 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
146 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
147 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
148 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
149 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
152 @vskip 0pt plus 1filll
153 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002,
154 2006, 2007, 2008, 2009 Free Software Foundation, Inc.
156 Permission is granted to copy, distribute and/or modify this document
157 under the terms of the GNU Free Documentation License, Version 1.3
158 or any later version published by the Free Software Foundation;
159 with no Invariant Sections, with no Front-Cover Texts, and with no
160 Back-Cover Texts. A copy of the license is included in the
161 section entitled ``GNU Free Documentation License''.
168 @top Using @value{AS}
170 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
171 @ifset VERSION_PACKAGE
172 @value{VERSION_PACKAGE}
174 version @value{VERSION}.
176 This version of the file describes @command{@value{AS}} configured to generate
177 code for @value{TARGET} architectures.
180 This document is distributed under the terms of the GNU Free
181 Documentation License. A copy of the license is included in the
182 section entitled ``GNU Free Documentation License''.
185 * Overview:: Overview
186 * Invoking:: Command-Line Options
188 * Sections:: Sections and Relocation
190 * Expressions:: Expressions
191 * Pseudo Ops:: Assembler Directives
193 * Object Attributes:: Object Attributes
195 * Machine Dependencies:: Machine Dependent Features
196 * Reporting Bugs:: Reporting Bugs
197 * Acknowledgements:: Who Did What
198 * GNU Free Documentation License:: GNU Free Documentation License
199 * AS Index:: AS Index
206 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
208 This version of the manual describes @command{@value{AS}} configured to generate
209 code for @value{TARGET} architectures.
213 @cindex invocation summary
214 @cindex option summary
215 @cindex summary of options
216 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
217 see @ref{Invoking,,Command-Line Options}.
219 @c man title AS the portable GNU assembler.
223 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
227 @c We don't use deffn and friends for the following because they seem
228 @c to be limited to one line for the header.
230 @c man begin SYNOPSIS
231 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
232 [@b{--debug-prefix-map} @var{old}=@var{new}]
233 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
234 [@b{--gstabs+}] [@b{--gdwarf-2}] [@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{--target-help}] [@var{target-options}]
242 [@b{--}|@var{files} @dots{}]
244 @c Target dependent options are listed below. Keep the list sorted.
245 @c Add an empty line for separation.
248 @emph{Target Alpha options:}
250 [@b{-mdebug} | @b{-no-mdebug}]
251 [@b{-replace} | @b{-noreplace}]
252 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
253 [@b{-F}] [@b{-32addr}]
257 @emph{Target ARC options:}
263 @emph{Target ARM options:}
264 @c Don't document the deprecated options
265 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
266 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
267 [@b{-mfpu}=@var{floating-point-format}]
268 [@b{-mfloat-abi}=@var{abi}]
269 [@b{-meabi}=@var{ver}]
272 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
273 @b{-mapcs-reentrant}]
274 [@b{-mthumb-interwork}] [@b{-k}]
278 @emph{Target CRIS options:}
279 [@b{--underscore} | @b{--no-underscore}]
281 [@b{--emulation=criself} | @b{--emulation=crisaout}]
282 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
283 @c Deprecated -- deliberately not documented.
288 @emph{Target D10V options:}
293 @emph{Target D30V options:}
294 [@b{-O}|@b{-n}|@b{-N}]
298 @emph{Target H8/300 options:}
302 @c HPPA has no machine-dependent assembler options (yet).
306 @emph{Target i386 options:}
307 [@b{--32}|@b{--64}] [@b{-n}]
308 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
312 @emph{Target i960 options:}
313 @c see md_parse_option in tc-i960.c
314 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
316 [@b{-b}] [@b{-no-relax}]
320 @emph{Target IA-64 options:}
321 [@b{-mconstant-gp}|@b{-mauto-pic}]
322 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
324 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
325 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
326 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
327 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
331 @emph{Target IP2K options:}
332 [@b{-mip2022}|@b{-mip2022ext}]
336 @emph{Target M32C options:}
337 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
341 @emph{Target M32R options:}
342 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
347 @emph{Target M680X0 options:}
348 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
352 @emph{Target M68HC11 options:}
353 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
354 [@b{-mshort}|@b{-mlong}]
355 [@b{-mshort-double}|@b{-mlong-double}]
356 [@b{--force-long-branches}] [@b{--short-branches}]
357 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
358 [@b{--print-opcodes}] [@b{--generate-example}]
362 @emph{Target MCORE options:}
363 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
364 [@b{-mcpu=[210|340]}]
368 @emph{Target MIPS options:}
369 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
370 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
371 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
372 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
373 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
374 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
375 [@b{-mips64}] [@b{-mips64r2}]
376 [@b{-construct-floats}] [@b{-no-construct-floats}]
377 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
378 [@b{-mfix7000}] [@b{-mno-fix7000}]
379 [@b{-mips16}] [@b{-no-mips16}]
380 [@b{-msmartmips}] [@b{-mno-smartmips}]
381 [@b{-mips3d}] [@b{-no-mips3d}]
382 [@b{-mdmx}] [@b{-no-mdmx}]
383 [@b{-mdsp}] [@b{-mno-dsp}]
384 [@b{-mdspr2}] [@b{-mno-dspr2}]
385 [@b{-mmt}] [@b{-mno-mt}]
386 [@b{-mdebug}] [@b{-no-mdebug}]
387 [@b{-mpdr}] [@b{-mno-pdr}]
391 @emph{Target MMIX options:}
392 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
393 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
394 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
395 [@b{--linker-allocated-gregs}]
399 @emph{Target PDP11 options:}
400 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
401 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
402 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
406 @emph{Target picoJava options:}
411 @emph{Target PowerPC options:}
412 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
413 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}]
414 [@b{-mcom}|@b{-many}|@b{-maltivec}|@b{-mvsx}] [@b{-memb}]
415 [@b{-mregnames}|@b{-mno-regnames}]
416 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
417 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
418 [@b{-msolaris}|@b{-mno-solaris}]
422 @emph{Target s390 options:}
423 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
424 [@b{-mregnames}|@b{-mno-regnames}]
425 [@b{-mwarn-areg-zero}]
429 @emph{Target SCORE options:}
430 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
431 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
432 [@b{-march=score7}][@b{-march=score3}]
433 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
437 @emph{Target SPARC options:}
438 @c The order here is important. See c-sparc.texi.
439 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
440 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
441 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
446 @emph{Target TIC54X options:}
447 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
448 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
453 @emph{Target Z80 options:}
454 [@b{-z80}] [@b{-r800}]
455 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
456 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
457 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
458 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
459 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
460 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
464 @c Z8000 has no machine-dependent assembler options
468 @emph{Target Xtensa options:}
469 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
470 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
471 [@b{--[no-]transform}]
472 [@b{--rename-section} @var{oldname}=@var{newname}]
480 @include at-file.texi
483 Turn on listings, in any of a variety of ways:
487 omit false conditionals
490 omit debugging directives
493 include general information, like @value{AS} version and options passed
496 include high-level source
502 include macro expansions
505 omit forms processing
511 set the name of the listing file
514 You may combine these options; for example, use @samp{-aln} for assembly
515 listing without forms processing. The @samp{=file} option, if used, must be
516 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
519 Begin in alternate macro mode.
521 @xref{Altmacro,,@code{.altmacro}}.
525 Ignored. This option is accepted for script compatibility with calls to
528 @item --debug-prefix-map @var{old}=@var{new}
529 When assembling files in directory @file{@var{old}}, record debugging
530 information describing them as in @file{@var{new}} instead.
532 @item --defsym @var{sym}=@var{value}
533 Define the symbol @var{sym} to be @var{value} before assembling the input file.
534 @var{value} must be an integer constant. As in C, a leading @samp{0x}
535 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
536 value. The value of the symbol can be overridden inside a source file via the
537 use of a @code{.set} pseudo-op.
540 ``fast''---skip whitespace and comment preprocessing (assume source is
545 Generate debugging information for each assembler source line using whichever
546 debug format is preferred by the target. This currently means either STABS,
550 Generate stabs debugging information for each assembler line. This
551 may help debugging assembler code, if the debugger can handle it.
554 Generate stabs debugging information for each assembler line, with GNU
555 extensions that probably only gdb can handle, and that could make other
556 debuggers crash or refuse to read your program. This
557 may help debugging assembler code. Currently the only GNU extension is
558 the location of the current working directory at assembling time.
561 Generate DWARF2 debugging information for each assembler line. This
562 may help debugging assembler code, if the debugger can handle it. Note---this
563 option is only supported by some targets, not all of them.
566 Print a summary of the command line options and exit.
569 Print a summary of all target specific options and exit.
572 Add directory @var{dir} to the search list for @code{.include} directives.
575 Don't warn about signed overflow.
578 @ifclear DIFF-TBL-KLUGE
579 This option is accepted but has no effect on the @value{TARGET} family.
581 @ifset DIFF-TBL-KLUGE
582 Issue warnings when difference tables altered for long displacements.
587 Keep (in the symbol table) local symbols. These symbols start with
588 system-specific local label prefixes, typically @samp{.L} for ELF systems
589 or @samp{L} for traditional a.out systems.
594 @item --listing-lhs-width=@var{number}
595 Set the maximum width, in words, of the output data column for an assembler
596 listing to @var{number}.
598 @item --listing-lhs-width2=@var{number}
599 Set the maximum width, in words, of the output data column for continuation
600 lines in an assembler listing to @var{number}.
602 @item --listing-rhs-width=@var{number}
603 Set the maximum width of an input source line, as displayed in a listing, to
606 @item --listing-cont-lines=@var{number}
607 Set the maximum number of lines printed in a listing for a single line of input
610 @item -o @var{objfile}
611 Name the object-file output from @command{@value{AS}} @var{objfile}.
614 Fold the data section into the text section.
616 @kindex --hash-size=@var{number}
617 Set the default size of GAS's hash tables to a prime number close to
618 @var{number}. Increasing this value can reduce the length of time it takes the
619 assembler to perform its tasks, at the expense of increasing the assembler's
620 memory requirements. Similarly reducing this value can reduce the memory
621 requirements at the expense of speed.
623 @item --reduce-memory-overheads
624 This option reduces GAS's memory requirements, at the expense of making the
625 assembly processes slower. Currently this switch is a synonym for
626 @samp{--hash-size=4051}, but in the future it may have other effects as well.
629 Print the maximum space (in bytes) and total time (in seconds) used by
632 @item --strip-local-absolute
633 Remove local absolute symbols from the outgoing symbol table.
637 Print the @command{as} version.
640 Print the @command{as} version and exit.
644 Suppress warning messages.
646 @item --fatal-warnings
647 Treat warnings as errors.
650 Don't suppress warning messages or treat them as errors.
659 Generate an object file even after errors.
661 @item -- | @var{files} @dots{}
662 Standard input, or source files to assemble.
667 The following options are available when @value{AS} is configured for
672 This option selects the core processor variant.
674 Select either big-endian (-EB) or little-endian (-EL) output.
679 The following options are available when @value{AS} is configured for the ARM
683 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
684 Specify which ARM processor variant is the target.
685 @item -march=@var{architecture}[+@var{extension}@dots{}]
686 Specify which ARM architecture variant is used by the target.
687 @item -mfpu=@var{floating-point-format}
688 Select which Floating Point architecture is the target.
689 @item -mfloat-abi=@var{abi}
690 Select which floating point ABI is in use.
692 Enable Thumb only instruction decoding.
693 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
694 Select which procedure calling convention is in use.
696 Select either big-endian (-EB) or little-endian (-EL) output.
697 @item -mthumb-interwork
698 Specify that the code has been generated with interworking between Thumb and
701 Specify that PIC code has been generated.
706 See the info pages for documentation of the CRIS-specific options.
710 The following options are available when @value{AS} is configured for
713 @cindex D10V optimization
714 @cindex optimization, D10V
716 Optimize output by parallelizing instructions.
721 The following options are available when @value{AS} is configured for a D30V
724 @cindex D30V optimization
725 @cindex optimization, D30V
727 Optimize output by parallelizing instructions.
731 Warn when nops are generated.
733 @cindex D30V nops after 32-bit multiply
735 Warn when a nop after a 32-bit multiply instruction is generated.
740 The following options are available when @value{AS} is configured for the
741 Intel 80960 processor.
744 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
745 Specify which variant of the 960 architecture is the target.
748 Add code to collect statistics about branches taken.
751 Do not alter compare-and-branch instructions for long displacements;
758 The following options are available when @value{AS} is configured for the
764 Specifies that the extended IP2022 instructions are allowed.
767 Restores the default behaviour, which restricts the permitted instructions to
768 just the basic IP2022 ones.
774 The following options are available when @value{AS} is configured for the
775 Renesas M32C and M16C processors.
780 Assemble M32C instructions.
783 Assemble M16C instructions (the default).
786 Enable support for link-time relaxations.
789 Support H'00 style hex constants in addition to 0x00 style.
795 The following options are available when @value{AS} is configured for the
796 Renesas M32R (formerly Mitsubishi M32R) series.
801 Specify which processor in the M32R family is the target. The default
802 is normally the M32R, but this option changes it to the M32RX.
804 @item --warn-explicit-parallel-conflicts or --Wp
805 Produce warning messages when questionable parallel constructs are
808 @item --no-warn-explicit-parallel-conflicts or --Wnp
809 Do not produce warning messages when questionable parallel constructs are
816 The following options are available when @value{AS} is configured for the
817 Motorola 68000 series.
822 Shorten references to undefined symbols, to one word instead of two.
824 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
825 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
826 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
827 Specify what processor in the 68000 family is the target. The default
828 is normally the 68020, but this can be changed at configuration time.
830 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
831 The target machine does (or does not) have a floating-point coprocessor.
832 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
833 the basic 68000 is not compatible with the 68881, a combination of the
834 two can be specified, since it's possible to do emulation of the
835 coprocessor instructions with the main processor.
837 @item -m68851 | -mno-68851
838 The target machine does (or does not) have a memory-management
839 unit coprocessor. The default is to assume an MMU for 68020 and up.
846 For details about the PDP-11 machine dependent features options,
847 see @ref{PDP-11-Options}.
850 @item -mpic | -mno-pic
851 Generate position-independent (or position-dependent) code. The
852 default is @option{-mpic}.
855 @itemx -mall-extensions
856 Enable all instruction set extensions. This is the default.
858 @item -mno-extensions
859 Disable all instruction set extensions.
861 @item -m@var{extension} | -mno-@var{extension}
862 Enable (or disable) a particular instruction set extension.
865 Enable the instruction set extensions supported by a particular CPU, and
866 disable all other extensions.
868 @item -m@var{machine}
869 Enable the instruction set extensions supported by a particular machine
870 model, and disable all other extensions.
876 The following options are available when @value{AS} is configured for
877 a picoJava processor.
881 @cindex PJ endianness
882 @cindex endianness, PJ
883 @cindex big endian output, PJ
885 Generate ``big endian'' format output.
887 @cindex little endian output, PJ
889 Generate ``little endian'' format output.
895 The following options are available when @value{AS} is configured for the
896 Motorola 68HC11 or 68HC12 series.
900 @item -m68hc11 | -m68hc12 | -m68hcs12
901 Specify what processor is the target. The default is
902 defined by the configuration option when building the assembler.
905 Specify to use the 16-bit integer ABI.
908 Specify to use the 32-bit integer ABI.
911 Specify to use the 32-bit double ABI.
914 Specify to use the 64-bit double ABI.
916 @item --force-long-branches
917 Relative branches are turned into absolute ones. This concerns
918 conditional branches, unconditional branches and branches to a
921 @item -S | --short-branches
922 Do not turn relative branches into absolute ones
923 when the offset is out of range.
925 @item --strict-direct-mode
926 Do not turn the direct addressing mode into extended addressing mode
927 when the instruction does not support direct addressing mode.
929 @item --print-insn-syntax
930 Print the syntax of instruction in case of error.
932 @item --print-opcodes
933 print the list of instructions with syntax and then exit.
935 @item --generate-example
936 print an example of instruction for each possible instruction and then exit.
937 This option is only useful for testing @command{@value{AS}}.
943 The following options are available when @command{@value{AS}} is configured
944 for the SPARC architecture:
947 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
948 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
949 Explicitly select a variant of the SPARC architecture.
951 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
952 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
954 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
955 UltraSPARC extensions.
957 @item -xarch=v8plus | -xarch=v8plusa
958 For compatibility with the Solaris v9 assembler. These options are
959 equivalent to -Av8plus and -Av8plusa, respectively.
962 Warn when the assembler switches to another architecture.
967 The following options are available when @value{AS} is configured for the 'c54x
972 Enable extended addressing mode. All addresses and relocations will assume
973 extended addressing (usually 23 bits).
974 @item -mcpu=@var{CPU_VERSION}
975 Sets the CPU version being compiled for.
976 @item -merrors-to-file @var{FILENAME}
977 Redirect error output to a file, for broken systems which don't support such
978 behaviour in the shell.
983 The following options are available when @value{AS} is configured for
984 a @sc{mips} processor.
988 This option sets the largest size of an object that can be referenced
989 implicitly with the @code{gp} register. It is only accepted for targets that
990 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
992 @cindex MIPS endianness
993 @cindex endianness, MIPS
994 @cindex big endian output, MIPS
996 Generate ``big endian'' format output.
998 @cindex little endian output, MIPS
1000 Generate ``little endian'' format output.
1012 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1013 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1014 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1015 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1016 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1018 correspond to generic
1019 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1020 and @samp{MIPS64 Release 2}
1021 ISA processors, respectively.
1023 @item -march=@var{CPU}
1024 Generate code for a particular @sc{mips} cpu.
1026 @item -mtune=@var{cpu}
1027 Schedule and tune for a particular @sc{mips} cpu.
1031 Cause nops to be inserted if the read of the destination register
1032 of an mfhi or mflo instruction occurs in the following two instructions.
1036 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1037 section instead of the standard ELF .stabs sections.
1041 Control generation of @code{.pdr} sections.
1045 The register sizes are normally inferred from the ISA and ABI, but these
1046 flags force a certain group of registers to be treated as 32 bits wide at
1047 all times. @samp{-mgp32} controls the size of general-purpose registers
1048 and @samp{-mfp32} controls the size of floating-point registers.
1052 Generate code for the MIPS 16 processor. This is equivalent to putting
1053 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1054 turns off this option.
1057 @itemx -mno-smartmips
1058 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1059 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1060 @samp{-mno-smartmips} turns off this option.
1064 Generate code for the MIPS-3D Application Specific Extension.
1065 This tells the assembler to accept MIPS-3D instructions.
1066 @samp{-no-mips3d} turns off this option.
1070 Generate code for the MDMX Application Specific Extension.
1071 This tells the assembler to accept MDMX instructions.
1072 @samp{-no-mdmx} turns off this option.
1076 Generate code for the DSP Release 1 Application Specific Extension.
1077 This tells the assembler to accept DSP Release 1 instructions.
1078 @samp{-mno-dsp} turns off this option.
1082 Generate code for the DSP Release 2 Application Specific Extension.
1083 This option implies -mdsp.
1084 This tells the assembler to accept DSP Release 2 instructions.
1085 @samp{-mno-dspr2} turns off this option.
1089 Generate code for the MT Application Specific Extension.
1090 This tells the assembler to accept MT instructions.
1091 @samp{-mno-mt} turns off this option.
1093 @item --construct-floats
1094 @itemx --no-construct-floats
1095 The @samp{--no-construct-floats} option disables the construction of
1096 double width floating point constants by loading the two halves of the
1097 value into the two single width floating point registers that make up
1098 the double width register. By default @samp{--construct-floats} is
1099 selected, allowing construction of these floating point constants.
1102 @item --emulation=@var{name}
1103 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1104 for some other target, in all respects, including output format (choosing
1105 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1106 debugging information or store symbol table information, and default
1107 endianness. The available configuration names are: @samp{mipsecoff},
1108 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1109 @samp{mipsbelf}. The first two do not alter the default endianness from that
1110 of the primary target for which the assembler was configured; the others change
1111 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1112 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1113 selection in any case.
1115 This option is currently supported only when the primary target
1116 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1117 Furthermore, the primary target or others specified with
1118 @samp{--enable-targets=@dots{}} at configuration time must include support for
1119 the other format, if both are to be available. For example, the Irix 5
1120 configuration includes support for both.
1122 Eventually, this option will support more configurations, with more
1123 fine-grained control over the assembler's behavior, and will be supported for
1127 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1134 Control how to deal with multiplication overflow and division by zero.
1135 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1136 (and only work for Instruction Set Architecture level 2 and higher);
1137 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1141 When this option is used, @command{@value{AS}} will issue a warning every
1142 time it generates a nop instruction from a macro.
1147 The following options are available when @value{AS} is configured for
1153 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1154 The command line option @samp{-nojsri2bsr} can be used to disable it.
1158 Enable or disable the silicon filter behaviour. By default this is disabled.
1159 The default can be overridden by the @samp{-sifilter} command line option.
1162 Alter jump instructions for long displacements.
1164 @item -mcpu=[210|340]
1165 Select the cpu type on the target hardware. This controls which instructions
1169 Assemble for a big endian target.
1172 Assemble for a little endian target.
1178 See the info pages for documentation of the MMIX-specific options.
1182 The following options are available when @value{AS} is configured for the s390
1188 Select the word size, either 31/32 bits or 64 bits.
1191 Select the architecture mode, either the Enterprise System
1192 Architecture (esa) or the z/Architecture mode (zarch).
1193 @item -march=@var{processor}
1194 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1195 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1197 @itemx -mno-regnames
1198 Allow or disallow symbolic names for registers.
1199 @item -mwarn-areg-zero
1200 Warn whenever the operand for a base or index register has been specified
1201 but evaluates to zero.
1206 The following options are available when @value{AS} is configured for
1207 an Xtensa processor.
1210 @item --text-section-literals | --no-text-section-literals
1211 With @option{--text-@-section-@-literals}, literal pools are interspersed
1212 in the text section. The default is
1213 @option{--no-@-text-@-section-@-literals}, which places literals in a
1214 separate section in the output file. These options only affect literals
1215 referenced via PC-relative @code{L32R} instructions; literals for
1216 absolute mode @code{L32R} instructions are handled separately.
1218 @item --absolute-literals | --no-absolute-literals
1219 Indicate to the assembler whether @code{L32R} instructions use absolute
1220 or PC-relative addressing. The default is to assume absolute addressing
1221 if the Xtensa processor includes the absolute @code{L32R} addressing
1222 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1224 @item --target-align | --no-target-align
1225 Enable or disable automatic alignment to reduce branch penalties at the
1226 expense of some code density. The default is @option{--target-@-align}.
1228 @item --longcalls | --no-longcalls
1229 Enable or disable transformation of call instructions to allow calls
1230 across a greater range of addresses. The default is
1231 @option{--no-@-longcalls}.
1233 @item --transform | --no-transform
1234 Enable or disable all assembler transformations of Xtensa instructions.
1235 The default is @option{--transform};
1236 @option{--no-transform} should be used only in the rare cases when the
1237 instructions must be exactly as specified in the assembly source.
1239 @item --rename-section @var{oldname}=@var{newname}
1240 When generating output sections, rename the @var{oldname} section to
1246 The following options are available when @value{AS} is configured for
1247 a Z80 family processor.
1250 Assemble for Z80 processor.
1252 Assemble for R800 processor.
1253 @item -ignore-undocumented-instructions
1255 Assemble undocumented Z80 instructions that also work on R800 without warning.
1256 @item -ignore-unportable-instructions
1258 Assemble all undocumented Z80 instructions without warning.
1259 @item -warn-undocumented-instructions
1261 Issue a warning for undocumented Z80 instructions that also work on R800.
1262 @item -warn-unportable-instructions
1264 Issue a warning for undocumented Z80 instructions that do not work on R800.
1265 @item -forbid-undocumented-instructions
1267 Treat all undocumented instructions as errors.
1268 @item -forbid-unportable-instructions
1270 Treat undocumented Z80 instructions that do not work on R800 as errors.
1277 * Manual:: Structure of this Manual
1278 * GNU Assembler:: The GNU Assembler
1279 * Object Formats:: Object File Formats
1280 * Command Line:: Command Line
1281 * Input Files:: Input Files
1282 * Object:: Output (Object) File
1283 * Errors:: Error and Warning Messages
1287 @section Structure of this Manual
1289 @cindex manual, structure and purpose
1290 This manual is intended to describe what you need to know to use
1291 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1292 notation for symbols, constants, and expressions; the directives that
1293 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1296 We also cover special features in the @value{TARGET}
1297 configuration of @command{@value{AS}}, including assembler directives.
1300 This manual also describes some of the machine-dependent features of
1301 various flavors of the assembler.
1304 @cindex machine instructions (not covered)
1305 On the other hand, this manual is @emph{not} intended as an introduction
1306 to programming in assembly language---let alone programming in general!
1307 In a similar vein, we make no attempt to introduce the machine
1308 architecture; we do @emph{not} describe the instruction set, standard
1309 mnemonics, registers or addressing modes that are standard to a
1310 particular architecture.
1312 You may want to consult the manufacturer's
1313 machine architecture manual for this information.
1317 For information on the H8/300 machine instruction set, see @cite{H8/300
1318 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1319 Programming Manual} (Renesas).
1322 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1323 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1324 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1325 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1328 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1332 @c I think this is premature---doc@cygnus.com, 17jan1991
1334 Throughout this manual, we assume that you are running @dfn{GNU},
1335 the portable operating system from the @dfn{Free Software
1336 Foundation, Inc.}. This restricts our attention to certain kinds of
1337 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1338 once this assumption is granted examples and definitions need less
1341 @command{@value{AS}} is part of a team of programs that turn a high-level
1342 human-readable series of instructions into a low-level
1343 computer-readable series of instructions. Different versions of
1344 @command{@value{AS}} are used for different kinds of computer.
1347 @c There used to be a section "Terminology" here, which defined
1348 @c "contents", "byte", "word", and "long". Defining "word" to any
1349 @c particular size is confusing when the .word directive may generate 16
1350 @c bits on one machine and 32 bits on another; in general, for the user
1351 @c version of this manual, none of these terms seem essential to define.
1352 @c They were used very little even in the former draft of the manual;
1353 @c this draft makes an effort to avoid them (except in names of
1357 @section The GNU Assembler
1359 @c man begin DESCRIPTION
1361 @sc{gnu} @command{as} is really a family of assemblers.
1363 This manual describes @command{@value{AS}}, a member of that family which is
1364 configured for the @value{TARGET} architectures.
1366 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1367 should find a fairly similar environment when you use it on another
1368 architecture. Each version has much in common with the others,
1369 including object file formats, most assembler directives (often called
1370 @dfn{pseudo-ops}) and assembler syntax.@refill
1372 @cindex purpose of @sc{gnu} assembler
1373 @command{@value{AS}} is primarily intended to assemble the output of the
1374 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1375 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1376 assemble correctly everything that other assemblers for the same
1377 machine would assemble.
1379 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1382 @c This remark should appear in generic version of manual; assumption
1383 @c here is that generic version sets M680x0.
1384 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1385 assembler for the same architecture; for example, we know of several
1386 incompatible versions of 680x0 assembly language syntax.
1391 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1392 program in one pass of the source file. This has a subtle impact on the
1393 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1395 @node Object Formats
1396 @section Object File Formats
1398 @cindex object file format
1399 The @sc{gnu} assembler can be configured to produce several alternative
1400 object file formats. For the most part, this does not affect how you
1401 write assembly language programs; but directives for debugging symbols
1402 are typically different in different file formats. @xref{Symbol
1403 Attributes,,Symbol Attributes}.
1406 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1407 @value{OBJ-NAME} format object files.
1409 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1411 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1412 @code{b.out} or COFF format object files.
1415 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1416 SOM or ELF format object files.
1421 @section Command Line
1423 @cindex command line conventions
1425 After the program name @command{@value{AS}}, the command line may contain
1426 options and file names. Options may appear in any order, and may be
1427 before, after, or between file names. The order of file names is
1430 @cindex standard input, as input file
1432 @file{--} (two hyphens) by itself names the standard input file
1433 explicitly, as one of the files for @command{@value{AS}} to assemble.
1435 @cindex options, command line
1436 Except for @samp{--} any command line argument that begins with a
1437 hyphen (@samp{-}) is an option. Each option changes the behavior of
1438 @command{@value{AS}}. No option changes the way another option works. An
1439 option is a @samp{-} followed by one or more letters; the case of
1440 the letter is important. All options are optional.
1442 Some options expect exactly one file name to follow them. The file
1443 name may either immediately follow the option's letter (compatible
1444 with older assemblers) or it may be the next command argument (@sc{gnu}
1445 standard). These two command lines are equivalent:
1448 @value{AS} -o my-object-file.o mumble.s
1449 @value{AS} -omy-object-file.o mumble.s
1453 @section Input Files
1456 @cindex source program
1457 @cindex files, input
1458 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1459 describe the program input to one run of @command{@value{AS}}. The program may
1460 be in one or more files; how the source is partitioned into files
1461 doesn't change the meaning of the source.
1463 @c I added "con" prefix to "catenation" just to prove I can overcome my
1464 @c APL training... doc@cygnus.com
1465 The source program is a concatenation of the text in all the files, in the
1468 @c man begin DESCRIPTION
1469 Each time you run @command{@value{AS}} it assembles exactly one source
1470 program. The source program is made up of one or more files.
1471 (The standard input is also a file.)
1473 You give @command{@value{AS}} a command line that has zero or more input file
1474 names. The input files are read (from left file name to right). A
1475 command line argument (in any position) that has no special meaning
1476 is taken to be an input file name.
1478 If you give @command{@value{AS}} no file names it attempts to read one input file
1479 from the @command{@value{AS}} standard input, which is normally your terminal. You
1480 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1483 Use @samp{--} if you need to explicitly name the standard input file
1484 in your command line.
1486 If the source is empty, @command{@value{AS}} produces a small, empty object
1491 @subheading Filenames and Line-numbers
1493 @cindex input file linenumbers
1494 @cindex line numbers, in input files
1495 There are two ways of locating a line in the input file (or files) and
1496 either may be used in reporting error messages. One way refers to a line
1497 number in a physical file; the other refers to a line number in a
1498 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1500 @dfn{Physical files} are those files named in the command line given
1501 to @command{@value{AS}}.
1503 @dfn{Logical files} are simply names declared explicitly by assembler
1504 directives; they bear no relation to physical files. Logical file names help
1505 error messages reflect the original source file, when @command{@value{AS}} source
1506 is itself synthesized from other files. @command{@value{AS}} understands the
1507 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1508 @ref{File,,@code{.file}}.
1511 @section Output (Object) File
1517 Every time you run @command{@value{AS}} it produces an output file, which is
1518 your assembly language program translated into numbers. This file
1519 is the object file. Its default name is
1527 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1529 You can give it another name by using the @option{-o} option. Conventionally,
1530 object file names end with @file{.o}. The default name is used for historical
1531 reasons: older assemblers were capable of assembling self-contained programs
1532 directly into a runnable program. (For some formats, this isn't currently
1533 possible, but it can be done for the @code{a.out} format.)
1537 The object file is meant for input to the linker @code{@value{LD}}. It contains
1538 assembled program code, information to help @code{@value{LD}} integrate
1539 the assembled program into a runnable file, and (optionally) symbolic
1540 information for the debugger.
1542 @c link above to some info file(s) like the description of a.out.
1543 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1546 @section Error and Warning Messages
1548 @c man begin DESCRIPTION
1550 @cindex error messages
1551 @cindex warning messages
1552 @cindex messages from assembler
1553 @command{@value{AS}} may write warnings and error messages to the standard error
1554 file (usually your terminal). This should not happen when a compiler
1555 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1556 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1557 grave problem that stops the assembly.
1561 @cindex format of warning messages
1562 Warning messages have the format
1565 file_name:@b{NNN}:Warning Message Text
1569 @cindex line numbers, in warnings/errors
1570 (where @b{NNN} is a line number). If a logical file name has been given
1571 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1572 the current input file is used. If a logical line number was given
1574 (@pxref{Line,,@code{.line}})
1576 then it is used to calculate the number printed,
1577 otherwise the actual line in the current source file is printed. The
1578 message text is intended to be self explanatory (in the grand Unix
1581 @cindex format of error messages
1582 Error messages have the format
1584 file_name:@b{NNN}:FATAL:Error Message Text
1586 The file name and line number are derived as for warning
1587 messages. The actual message text may be rather less explanatory
1588 because many of them aren't supposed to happen.
1591 @chapter Command-Line Options
1593 @cindex options, all versions of assembler
1594 This chapter describes command-line options available in @emph{all}
1595 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1596 for options specific
1598 to the @value{TARGET} target.
1601 to particular machine architectures.
1604 @c man begin DESCRIPTION
1606 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1607 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1608 The assembler arguments must be separated from each other (and the @samp{-Wa})
1609 by commas. For example:
1612 gcc -c -g -O -Wa,-alh,-L file.c
1616 This passes two options to the assembler: @samp{-alh} (emit a listing to
1617 standard output with high-level and assembly source) and @samp{-L} (retain
1618 local symbols in the symbol table).
1620 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1621 command-line options are automatically passed to the assembler by the compiler.
1622 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1623 precisely what options it passes to each compilation pass, including the
1629 * a:: -a[cdghlns] enable listings
1630 * alternate:: --alternate enable alternate macro syntax
1631 * D:: -D for compatibility
1632 * f:: -f to work faster
1633 * I:: -I for .include search path
1634 @ifclear DIFF-TBL-KLUGE
1635 * K:: -K for compatibility
1637 @ifset DIFF-TBL-KLUGE
1638 * K:: -K for difference tables
1641 * L:: -L to retain local symbols
1642 * listing:: --listing-XXX to configure listing output
1643 * M:: -M or --mri to assemble in MRI compatibility mode
1644 * MD:: --MD for dependency tracking
1645 * o:: -o to name the object file
1646 * R:: -R to join data and text sections
1647 * statistics:: --statistics to see statistics about assembly
1648 * traditional-format:: --traditional-format for compatible output
1649 * v:: -v to announce version
1650 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1651 * Z:: -Z to make object file even after errors
1655 @section Enable Listings: @option{-a[cdghlns]}
1665 @cindex listings, enabling
1666 @cindex assembly listings, enabling
1668 These options enable listing output from the assembler. By itself,
1669 @samp{-a} requests high-level, assembly, and symbols listing.
1670 You can use other letters to select specific options for the list:
1671 @samp{-ah} requests a high-level language listing,
1672 @samp{-al} requests an output-program assembly listing, and
1673 @samp{-as} requests a symbol table listing.
1674 High-level listings require that a compiler debugging option like
1675 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1678 Use the @samp{-ag} option to print a first section with general assembly
1679 information, like @value{AS} version, switches passed, or time stamp.
1681 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1682 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1683 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1684 omitted from the listing.
1686 Use the @samp{-ad} option to omit debugging directives from the
1689 Once you have specified one of these options, you can further control
1690 listing output and its appearance using the directives @code{.list},
1691 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1693 The @samp{-an} option turns off all forms processing.
1694 If you do not request listing output with one of the @samp{-a} options, the
1695 listing-control directives have no effect.
1697 The letters after @samp{-a} may be combined into one option,
1698 @emph{e.g.}, @samp{-aln}.
1700 Note if the assembler source is coming from the standard input (e.g.,
1702 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1703 is being used) then the listing will not contain any comments or preprocessor
1704 directives. This is because the listing code buffers input source lines from
1705 stdin only after they have been preprocessed by the assembler. This reduces
1706 memory usage and makes the code more efficient.
1709 @section @option{--alternate}
1712 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1715 @section @option{-D}
1718 This option has no effect whatsoever, but it is accepted to make it more
1719 likely that scripts written for other assemblers also work with
1720 @command{@value{AS}}.
1723 @section Work Faster: @option{-f}
1726 @cindex trusted compiler
1727 @cindex faster processing (@option{-f})
1728 @samp{-f} should only be used when assembling programs written by a
1729 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1730 and comment preprocessing on
1731 the input file(s) before assembling them. @xref{Preprocessing,
1735 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1736 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1741 @section @code{.include} Search Path: @option{-I} @var{path}
1743 @kindex -I @var{path}
1744 @cindex paths for @code{.include}
1745 @cindex search path for @code{.include}
1746 @cindex @code{include} directive search path
1747 Use this option to add a @var{path} to the list of directories
1748 @command{@value{AS}} searches for files specified in @code{.include}
1749 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1750 many times as necessary to include a variety of paths. The current
1751 working directory is always searched first; after that, @command{@value{AS}}
1752 searches any @samp{-I} directories in the same order as they were
1753 specified (left to right) on the command line.
1756 @section Difference Tables: @option{-K}
1759 @ifclear DIFF-TBL-KLUGE
1760 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1761 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1762 where it can be used to warn when the assembler alters the machine code
1763 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1764 family does not have the addressing limitations that sometimes lead to this
1765 alteration on other platforms.
1768 @ifset DIFF-TBL-KLUGE
1769 @cindex difference tables, warning
1770 @cindex warning for altered difference tables
1771 @command{@value{AS}} sometimes alters the code emitted for directives of the
1772 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1773 You can use the @samp{-K} option if you want a warning issued when this
1778 @section Include Local Symbols: @option{-L}
1781 @cindex local symbols, retaining in output
1782 Symbols beginning with system-specific local label prefixes, typically
1783 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1784 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1785 such symbols when debugging, because they are intended for the use of
1786 programs (like compilers) that compose assembler programs, not for your
1787 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1788 such symbols, so you do not normally debug with them.
1790 This option tells @command{@value{AS}} to retain those local symbols
1791 in the object file. Usually if you do this you also tell the linker
1792 @code{@value{LD}} to preserve those symbols.
1795 @section Configuring listing output: @option{--listing}
1797 The listing feature of the assembler can be enabled via the command line switch
1798 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1799 hex dump of the corresponding locations in the output object file, and displays
1800 them as a listing file. The format of this listing can be controlled by
1801 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1802 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1803 @code{.psize} (@pxref{Psize}), and
1804 @code{.eject} (@pxref{Eject}) and also by the following switches:
1807 @item --listing-lhs-width=@samp{number}
1808 @kindex --listing-lhs-width
1809 @cindex Width of first line disassembly output
1810 Sets the maximum width, in words, of the first line of the hex byte dump. This
1811 dump appears on the left hand side of the listing output.
1813 @item --listing-lhs-width2=@samp{number}
1814 @kindex --listing-lhs-width2
1815 @cindex Width of continuation lines of disassembly output
1816 Sets the maximum width, in words, of any further lines of the hex byte dump for
1817 a given input source line. If this value is not specified, it defaults to being
1818 the same as the value specified for @samp{--listing-lhs-width}. If neither
1819 switch is used the default is to one.
1821 @item --listing-rhs-width=@samp{number}
1822 @kindex --listing-rhs-width
1823 @cindex Width of source line output
1824 Sets the maximum width, in characters, of the source line that is displayed
1825 alongside the hex dump. The default value for this parameter is 100. The
1826 source line is displayed on the right hand side of the listing output.
1828 @item --listing-cont-lines=@samp{number}
1829 @kindex --listing-cont-lines
1830 @cindex Maximum number of continuation lines
1831 Sets the maximum number of continuation lines of hex dump that will be
1832 displayed for a given single line of source input. The default value is 4.
1836 @section Assemble in MRI Compatibility Mode: @option{-M}
1839 @cindex MRI compatibility mode
1840 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1841 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1842 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1843 configured target) assembler from Microtec Research. The exact nature of the
1844 MRI syntax will not be documented here; see the MRI manuals for more
1845 information. Note in particular that the handling of macros and macro
1846 arguments is somewhat different. The purpose of this option is to permit
1847 assembling existing MRI assembler code using @command{@value{AS}}.
1849 The MRI compatibility is not complete. Certain operations of the MRI assembler
1850 depend upon its object file format, and can not be supported using other object
1851 file formats. Supporting these would require enhancing each object file format
1852 individually. These are:
1855 @item global symbols in common section
1857 The m68k MRI assembler supports common sections which are merged by the linker.
1858 Other object file formats do not support this. @command{@value{AS}} handles
1859 common sections by treating them as a single common symbol. It permits local
1860 symbols to be defined within a common section, but it can not support global
1861 symbols, since it has no way to describe them.
1863 @item complex relocations
1865 The MRI assemblers support relocations against a negated section address, and
1866 relocations which combine the start addresses of two or more sections. These
1867 are not support by other object file formats.
1869 @item @code{END} pseudo-op specifying start address
1871 The MRI @code{END} pseudo-op permits the specification of a start address.
1872 This is not supported by other object file formats. The start address may
1873 instead be specified using the @option{-e} option to the linker, or in a linker
1876 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1878 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1879 name to the output file. This is not supported by other object file formats.
1881 @item @code{ORG} pseudo-op
1883 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1884 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1885 which changes the location within the current section. Absolute sections are
1886 not supported by other object file formats. The address of a section may be
1887 assigned within a linker script.
1890 There are some other features of the MRI assembler which are not supported by
1891 @command{@value{AS}}, typically either because they are difficult or because they
1892 seem of little consequence. Some of these may be supported in future releases.
1896 @item EBCDIC strings
1898 EBCDIC strings are not supported.
1900 @item packed binary coded decimal
1902 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1903 and @code{DCB.P} pseudo-ops are not supported.
1905 @item @code{FEQU} pseudo-op
1907 The m68k @code{FEQU} pseudo-op is not supported.
1909 @item @code{NOOBJ} pseudo-op
1911 The m68k @code{NOOBJ} pseudo-op is not supported.
1913 @item @code{OPT} branch control options
1915 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1916 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1917 relaxes all branches, whether forward or backward, to an appropriate size, so
1918 these options serve no purpose.
1920 @item @code{OPT} list control options
1922 The following m68k @code{OPT} list control options are ignored: @code{C},
1923 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1924 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1926 @item other @code{OPT} options
1928 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1929 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1931 @item @code{OPT} @code{D} option is default
1933 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1934 @code{OPT NOD} may be used to turn it off.
1936 @item @code{XREF} pseudo-op.
1938 The m68k @code{XREF} pseudo-op is ignored.
1940 @item @code{.debug} pseudo-op
1942 The i960 @code{.debug} pseudo-op is not supported.
1944 @item @code{.extended} pseudo-op
1946 The i960 @code{.extended} pseudo-op is not supported.
1948 @item @code{.list} pseudo-op.
1950 The various options of the i960 @code{.list} pseudo-op are not supported.
1952 @item @code{.optimize} pseudo-op
1954 The i960 @code{.optimize} pseudo-op is not supported.
1956 @item @code{.output} pseudo-op
1958 The i960 @code{.output} pseudo-op is not supported.
1960 @item @code{.setreal} pseudo-op
1962 The i960 @code{.setreal} pseudo-op is not supported.
1967 @section Dependency Tracking: @option{--MD}
1970 @cindex dependency tracking
1973 @command{@value{AS}} can generate a dependency file for the file it creates. This
1974 file consists of a single rule suitable for @code{make} describing the
1975 dependencies of the main source file.
1977 The rule is written to the file named in its argument.
1979 This feature is used in the automatic updating of makefiles.
1982 @section Name the Object File: @option{-o}
1985 @cindex naming object file
1986 @cindex object file name
1987 There is always one object file output when you run @command{@value{AS}}. By
1988 default it has the name
1991 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2005 You use this option (which takes exactly one filename) to give the
2006 object file a different name.
2008 Whatever the object file is called, @command{@value{AS}} overwrites any
2009 existing file of the same name.
2012 @section Join Data and Text Sections: @option{-R}
2015 @cindex data and text sections, joining
2016 @cindex text and data sections, joining
2017 @cindex joining text and data sections
2018 @cindex merging text and data sections
2019 @option{-R} tells @command{@value{AS}} to write the object file as if all
2020 data-section data lives in the text section. This is only done at
2021 the very last moment: your binary data are the same, but data
2022 section parts are relocated differently. The data section part of
2023 your object file is zero bytes long because all its bytes are
2024 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2026 When you specify @option{-R} it would be possible to generate shorter
2027 address displacements (because we do not have to cross between text and
2028 data section). We refrain from doing this simply for compatibility with
2029 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2032 When @command{@value{AS}} is configured for COFF or ELF output,
2033 this option is only useful if you use sections named @samp{.text} and
2038 @option{-R} is not supported for any of the HPPA targets. Using
2039 @option{-R} generates a warning from @command{@value{AS}}.
2043 @section Display Assembly Statistics: @option{--statistics}
2045 @kindex --statistics
2046 @cindex statistics, about assembly
2047 @cindex time, total for assembly
2048 @cindex space used, maximum for assembly
2049 Use @samp{--statistics} to display two statistics about the resources used by
2050 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2051 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2054 @node traditional-format
2055 @section Compatible Output: @option{--traditional-format}
2057 @kindex --traditional-format
2058 For some targets, the output of @command{@value{AS}} is different in some ways
2059 from the output of some existing assembler. This switch requests
2060 @command{@value{AS}} to use the traditional format instead.
2062 For example, it disables the exception frame optimizations which
2063 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2066 @section Announce Version: @option{-v}
2070 @cindex assembler version
2071 @cindex version of assembler
2072 You can find out what version of as is running by including the
2073 option @samp{-v} (which you can also spell as @samp{-version}) on the
2077 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2079 @command{@value{AS}} should never give a warning or error message when
2080 assembling compiler output. But programs written by people often
2081 cause @command{@value{AS}} to give a warning that a particular assumption was
2082 made. All such warnings are directed to the standard error file.
2086 @cindex suppressing warnings
2087 @cindex warnings, suppressing
2088 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2089 This only affects the warning messages: it does not change any particular of
2090 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2093 @kindex --fatal-warnings
2094 @cindex errors, caused by warnings
2095 @cindex warnings, causing error
2096 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2097 files that generate warnings to be in error.
2100 @cindex warnings, switching on
2101 You can switch these options off again by specifying @option{--warn}, which
2102 causes warnings to be output as usual.
2105 @section Generate Object File in Spite of Errors: @option{-Z}
2106 @cindex object file, after errors
2107 @cindex errors, continuing after
2108 After an error message, @command{@value{AS}} normally produces no output. If for
2109 some reason you are interested in object file output even after
2110 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2111 option. If there are any errors, @command{@value{AS}} continues anyways, and
2112 writes an object file after a final warning message of the form @samp{@var{n}
2113 errors, @var{m} warnings, generating bad object file.}
2118 @cindex machine-independent syntax
2119 @cindex syntax, machine-independent
2120 This chapter describes the machine-independent syntax allowed in a
2121 source file. @command{@value{AS}} syntax is similar to what many other
2122 assemblers use; it is inspired by the BSD 4.2
2127 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2131 * Preprocessing:: Preprocessing
2132 * Whitespace:: Whitespace
2133 * Comments:: Comments
2134 * Symbol Intro:: Symbols
2135 * Statements:: Statements
2136 * Constants:: Constants
2140 @section Preprocessing
2142 @cindex preprocessing
2143 The @command{@value{AS}} internal preprocessor:
2145 @cindex whitespace, removed by preprocessor
2147 adjusts and removes extra whitespace. It leaves one space or tab before
2148 the keywords on a line, and turns any other whitespace on the line into
2151 @cindex comments, removed by preprocessor
2153 removes all comments, replacing them with a single space, or an
2154 appropriate number of newlines.
2156 @cindex constants, converted by preprocessor
2158 converts character constants into the appropriate numeric values.
2161 It does not do macro processing, include file handling, or
2162 anything else you may get from your C compiler's preprocessor. You can
2163 do include file processing with the @code{.include} directive
2164 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2165 to get other ``CPP'' style preprocessing by giving the input file a
2166 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2167 Output, gcc.info, Using GNU CC}.
2169 Excess whitespace, comments, and character constants
2170 cannot be used in the portions of the input text that are not
2173 @cindex turning preprocessing on and off
2174 @cindex preprocessing, turning on and off
2177 If the first line of an input file is @code{#NO_APP} or if you use the
2178 @samp{-f} option, whitespace and comments are not removed from the input file.
2179 Within an input file, you can ask for whitespace and comment removal in
2180 specific portions of the by putting a line that says @code{#APP} before the
2181 text that may contain whitespace or comments, and putting a line that says
2182 @code{#NO_APP} after this text. This feature is mainly intend to support
2183 @code{asm} statements in compilers whose output is otherwise free of comments
2190 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2191 Whitespace is used to separate symbols, and to make programs neater for
2192 people to read. Unless within character constants
2193 (@pxref{Characters,,Character Constants}), any whitespace means the same
2194 as exactly one space.
2200 There are two ways of rendering comments to @command{@value{AS}}. In both
2201 cases the comment is equivalent to one space.
2203 Anything from @samp{/*} through the next @samp{*/} is a comment.
2204 This means you may not nest these comments.
2208 The only way to include a newline ('\n') in a comment
2209 is to use this sort of comment.
2212 /* This sort of comment does not nest. */
2215 @cindex line comment character
2216 Anything from the @dfn{line comment} character to the next newline
2217 is considered a comment and is ignored. The line comment character is
2219 @samp{;} on the ARC;
2222 @samp{@@} on the ARM;
2225 @samp{;} for the H8/300 family;
2228 @samp{;} for the HPPA;
2231 @samp{#} on the i386 and x86-64;
2234 @samp{#} on the i960;
2237 @samp{;} for the PDP-11;
2240 @samp{;} for picoJava;
2243 @samp{#} for Motorola PowerPC;
2247 @samp{#} for the Sunplus SCORE;
2251 @samp{#} for IBM S/390;
2255 @samp{!} for the Renesas / SuperH SH;
2258 @samp{!} on the SPARC;
2261 @samp{#} on the ip2k;
2264 @samp{#} on the m32c;
2267 @samp{#} on the m32r;
2270 @samp{|} on the 680x0;
2273 @samp{#} on the 68HC11 and 68HC12;
2276 @samp{#} on the Vax;
2279 @samp{;} for the Z80;
2282 @samp{!} for the Z8000;
2285 @samp{#} on the V850;
2288 @samp{#} for Xtensa systems;
2290 see @ref{Machine Dependencies}. @refill
2291 @c FIXME What about i860?
2294 On some machines there are two different line comment characters. One
2295 character only begins a comment if it is the first non-whitespace character on
2296 a line, while the other always begins a comment.
2300 The V850 assembler also supports a double dash as starting a comment that
2301 extends to the end of the line.
2307 @cindex lines starting with @code{#}
2308 @cindex logical line numbers
2309 To be compatible with past assemblers, lines that begin with @samp{#} have a
2310 special interpretation. Following the @samp{#} should be an absolute
2311 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2312 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2313 new logical file name. The rest of the line, if any, should be whitespace.
2315 If the first non-whitespace characters on the line are not numeric,
2316 the line is ignored. (Just like a comment.)
2319 # This is an ordinary comment.
2320 # 42-6 "new_file_name" # New logical file name
2321 # This is logical line # 36.
2323 This feature is deprecated, and may disappear from future versions
2324 of @command{@value{AS}}.
2329 @cindex characters used in symbols
2330 @ifclear SPECIAL-SYMS
2331 A @dfn{symbol} is one or more characters chosen from the set of all
2332 letters (both upper and lower case), digits and the three characters
2338 A @dfn{symbol} is one or more characters chosen from the set of all
2339 letters (both upper and lower case), digits and the three characters
2340 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2346 On most machines, you can also use @code{$} in symbol names; exceptions
2347 are noted in @ref{Machine Dependencies}.
2349 No symbol may begin with a digit. Case is significant.
2350 There is no length limit: all characters are significant. Symbols are
2351 delimited by characters not in that set, or by the beginning of a file
2352 (since the source program must end with a newline, the end of a file is
2353 not a possible symbol delimiter). @xref{Symbols}.
2354 @cindex length of symbols
2359 @cindex statements, structure of
2360 @cindex line separator character
2361 @cindex statement separator character
2363 @ifclear abnormal-separator
2364 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2365 semicolon (@samp{;}). The newline or semicolon is considered part of
2366 the preceding statement. Newlines and semicolons within character
2367 constants are an exception: they do not end statements.
2369 @ifset abnormal-separator
2371 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2372 point (@samp{!}). The newline or exclamation point is considered part of the
2373 preceding statement. Newlines and exclamation points within character
2374 constants are an exception: they do not end statements.
2377 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2378 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2379 (@samp{;}). The newline or separator character is considered part of
2380 the preceding statement. Newlines and separators within character
2381 constants are an exception: they do not end statements.
2386 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2387 separator character. (The line separator is usually @samp{;}, unless this
2388 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2389 newline or separator character is considered part of the preceding
2390 statement. Newlines and separators within character constants are an
2391 exception: they do not end statements.
2394 @cindex newline, required at file end
2395 @cindex EOF, newline must precede
2396 It is an error to end any statement with end-of-file: the last
2397 character of any input file should be a newline.@refill
2399 An empty statement is allowed, and may include whitespace. It is ignored.
2401 @cindex instructions and directives
2402 @cindex directives and instructions
2403 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2404 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2406 A statement begins with zero or more labels, optionally followed by a
2407 key symbol which determines what kind of statement it is. The key
2408 symbol determines the syntax of the rest of the statement. If the
2409 symbol begins with a dot @samp{.} then the statement is an assembler
2410 directive: typically valid for any computer. If the symbol begins with
2411 a letter the statement is an assembly language @dfn{instruction}: it
2412 assembles into a machine language instruction.
2414 Different versions of @command{@value{AS}} for different computers
2415 recognize different instructions. In fact, the same symbol may
2416 represent a different instruction in a different computer's assembly
2420 @cindex @code{:} (label)
2421 @cindex label (@code{:})
2422 A label is a symbol immediately followed by a colon (@code{:}).
2423 Whitespace before a label or after a colon is permitted, but you may not
2424 have whitespace between a label's symbol and its colon. @xref{Labels}.
2427 For HPPA targets, labels need not be immediately followed by a colon, but
2428 the definition of a label must begin in column zero. This also implies that
2429 only one label may be defined on each line.
2433 label: .directive followed by something
2434 another_label: # This is an empty statement.
2435 instruction operand_1, operand_2, @dots{}
2442 A constant is a number, written so that its value is known by
2443 inspection, without knowing any context. Like this:
2446 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2447 .ascii "Ring the bell\7" # A string constant.
2448 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2449 .float 0f-314159265358979323846264338327\
2450 95028841971.693993751E-40 # - pi, a flonum.
2455 * Characters:: Character Constants
2456 * Numbers:: Number Constants
2460 @subsection Character Constants
2462 @cindex character constants
2463 @cindex constants, character
2464 There are two kinds of character constants. A @dfn{character} stands
2465 for one character in one byte and its value may be used in
2466 numeric expressions. String constants (properly called string
2467 @emph{literals}) are potentially many bytes and their values may not be
2468 used in arithmetic expressions.
2472 * Chars:: Characters
2476 @subsubsection Strings
2478 @cindex string constants
2479 @cindex constants, string
2480 A @dfn{string} is written between double-quotes. It may contain
2481 double-quotes or null characters. The way to get special characters
2482 into a string is to @dfn{escape} these characters: precede them with
2483 a backslash @samp{\} character. For example @samp{\\} represents
2484 one backslash: the first @code{\} is an escape which tells
2485 @command{@value{AS}} to interpret the second character literally as a backslash
2486 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2487 escape character). The complete list of escapes follows.
2489 @cindex escape codes, character
2490 @cindex character escape codes
2493 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2495 @cindex @code{\b} (backspace character)
2496 @cindex backspace (@code{\b})
2498 Mnemonic for backspace; for ASCII this is octal code 010.
2501 @c Mnemonic for EOText; for ASCII this is octal code 004.
2503 @cindex @code{\f} (formfeed character)
2504 @cindex formfeed (@code{\f})
2506 Mnemonic for FormFeed; for ASCII this is octal code 014.
2508 @cindex @code{\n} (newline character)
2509 @cindex newline (@code{\n})
2511 Mnemonic for newline; for ASCII this is octal code 012.
2514 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2516 @cindex @code{\r} (carriage return character)
2517 @cindex carriage return (@code{\r})
2519 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2522 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2523 @c other assemblers.
2525 @cindex @code{\t} (tab)
2526 @cindex tab (@code{\t})
2528 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2531 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2532 @c @item \x @var{digit} @var{digit} @var{digit}
2533 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2535 @cindex @code{\@var{ddd}} (octal character code)
2536 @cindex octal character code (@code{\@var{ddd}})
2537 @item \ @var{digit} @var{digit} @var{digit}
2538 An octal character code. The numeric code is 3 octal digits.
2539 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2540 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2542 @cindex @code{\@var{xd...}} (hex character code)
2543 @cindex hex character code (@code{\@var{xd...}})
2544 @item \@code{x} @var{hex-digits...}
2545 A hex character code. All trailing hex digits are combined. Either upper or
2546 lower case @code{x} works.
2548 @cindex @code{\\} (@samp{\} character)
2549 @cindex backslash (@code{\\})
2551 Represents one @samp{\} character.
2554 @c Represents one @samp{'} (accent acute) character.
2555 @c This is needed in single character literals
2556 @c (@xref{Characters,,Character Constants}.) to represent
2559 @cindex @code{\"} (doublequote character)
2560 @cindex doublequote (@code{\"})
2562 Represents one @samp{"} character. Needed in strings to represent
2563 this character, because an unescaped @samp{"} would end the string.
2565 @item \ @var{anything-else}
2566 Any other character when escaped by @kbd{\} gives a warning, but
2567 assembles as if the @samp{\} was not present. The idea is that if
2568 you used an escape sequence you clearly didn't want the literal
2569 interpretation of the following character. However @command{@value{AS}} has no
2570 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2571 code and warns you of the fact.
2574 Which characters are escapable, and what those escapes represent,
2575 varies widely among assemblers. The current set is what we think
2576 the BSD 4.2 assembler recognizes, and is a subset of what most C
2577 compilers recognize. If you are in doubt, do not use an escape
2581 @subsubsection Characters
2583 @cindex single character constant
2584 @cindex character, single
2585 @cindex constant, single character
2586 A single character may be written as a single quote immediately
2587 followed by that character. The same escapes apply to characters as
2588 to strings. So if you want to write the character backslash, you
2589 must write @kbd{'\\} where the first @code{\} escapes the second
2590 @code{\}. As you can see, the quote is an acute accent, not a
2591 grave accent. A newline
2593 @ifclear abnormal-separator
2594 (or semicolon @samp{;})
2596 @ifset abnormal-separator
2598 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2603 immediately following an acute accent is taken as a literal character
2604 and does not count as the end of a statement. The value of a character
2605 constant in a numeric expression is the machine's byte-wide code for
2606 that character. @command{@value{AS}} assumes your character code is ASCII:
2607 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2610 @subsection Number Constants
2612 @cindex constants, number
2613 @cindex number constants
2614 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2615 are stored in the target machine. @emph{Integers} are numbers that
2616 would fit into an @code{int} in the C language. @emph{Bignums} are
2617 integers, but they are stored in more than 32 bits. @emph{Flonums}
2618 are floating point numbers, described below.
2621 * Integers:: Integers
2626 * Bit Fields:: Bit Fields
2632 @subsubsection Integers
2634 @cindex constants, integer
2636 @cindex binary integers
2637 @cindex integers, binary
2638 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2639 the binary digits @samp{01}.
2641 @cindex octal integers
2642 @cindex integers, octal
2643 An octal integer is @samp{0} followed by zero or more of the octal
2644 digits (@samp{01234567}).
2646 @cindex decimal integers
2647 @cindex integers, decimal
2648 A decimal integer starts with a non-zero digit followed by zero or
2649 more digits (@samp{0123456789}).
2651 @cindex hexadecimal integers
2652 @cindex integers, hexadecimal
2653 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2654 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2656 Integers have the usual values. To denote a negative integer, use
2657 the prefix operator @samp{-} discussed under expressions
2658 (@pxref{Prefix Ops,,Prefix Operators}).
2661 @subsubsection Bignums
2664 @cindex constants, bignum
2665 A @dfn{bignum} has the same syntax and semantics as an integer
2666 except that the number (or its negative) takes more than 32 bits to
2667 represent in binary. The distinction is made because in some places
2668 integers are permitted while bignums are not.
2671 @subsubsection Flonums
2673 @cindex floating point numbers
2674 @cindex constants, floating point
2676 @cindex precision, floating point
2677 A @dfn{flonum} represents a floating point number. The translation is
2678 indirect: a decimal floating point number from the text is converted by
2679 @command{@value{AS}} to a generic binary floating point number of more than
2680 sufficient precision. This generic floating point number is converted
2681 to a particular computer's floating point format (or formats) by a
2682 portion of @command{@value{AS}} specialized to that computer.
2684 A flonum is written by writing (in order)
2689 (@samp{0} is optional on the HPPA.)
2693 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2695 @kbd{e} is recommended. Case is not important.
2697 @c FIXME: verify if flonum syntax really this vague for most cases
2698 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2699 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2702 On the H8/300, Renesas / SuperH SH,
2703 and AMD 29K architectures, the letter must be
2704 one of the letters @samp{DFPRSX} (in upper or lower case).
2706 On the ARC, the letter must be one of the letters @samp{DFRS}
2707 (in upper or lower case).
2709 On the Intel 960 architecture, the letter must be
2710 one of the letters @samp{DFT} (in upper or lower case).
2712 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2716 One of the letters @samp{DFRS} (in upper or lower case).
2719 One of the letters @samp{DFPRSX} (in upper or lower case).
2722 The letter @samp{E} (upper case only).
2725 One of the letters @samp{DFT} (in upper or lower case).
2730 An optional sign: either @samp{+} or @samp{-}.
2733 An optional @dfn{integer part}: zero or more decimal digits.
2736 An optional @dfn{fractional part}: @samp{.} followed by zero
2737 or more decimal digits.
2740 An optional exponent, consisting of:
2744 An @samp{E} or @samp{e}.
2745 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2746 @c principle this can perfectly well be different on different targets.
2748 Optional sign: either @samp{+} or @samp{-}.
2750 One or more decimal digits.
2755 At least one of the integer part or the fractional part must be
2756 present. The floating point number has the usual base-10 value.
2758 @command{@value{AS}} does all processing using integers. Flonums are computed
2759 independently of any floating point hardware in the computer running
2760 @command{@value{AS}}.
2764 @c Bit fields are written as a general facility but are also controlled
2765 @c by a conditional-compilation flag---which is as of now (21mar91)
2766 @c turned on only by the i960 config of GAS.
2768 @subsubsection Bit Fields
2771 @cindex constants, bit field
2772 You can also define numeric constants as @dfn{bit fields}.
2773 Specify two numbers separated by a colon---
2775 @var{mask}:@var{value}
2778 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2781 The resulting number is then packed
2783 @c this conditional paren in case bit fields turned on elsewhere than 960
2784 (in host-dependent byte order)
2786 into a field whose width depends on which assembler directive has the
2787 bit-field as its argument. Overflow (a result from the bitwise and
2788 requiring more binary digits to represent) is not an error; instead,
2789 more constants are generated, of the specified width, beginning with the
2790 least significant digits.@refill
2792 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2793 @code{.short}, and @code{.word} accept bit-field arguments.
2798 @chapter Sections and Relocation
2803 * Secs Background:: Background
2804 * Ld Sections:: Linker Sections
2805 * As Sections:: Assembler Internal Sections
2806 * Sub-Sections:: Sub-Sections
2810 @node Secs Background
2813 Roughly, a section is a range of addresses, with no gaps; all data
2814 ``in'' those addresses is treated the same for some particular purpose.
2815 For example there may be a ``read only'' section.
2817 @cindex linker, and assembler
2818 @cindex assembler, and linker
2819 The linker @code{@value{LD}} reads many object files (partial programs) and
2820 combines their contents to form a runnable program. When @command{@value{AS}}
2821 emits an object file, the partial program is assumed to start at address 0.
2822 @code{@value{LD}} assigns the final addresses for the partial program, so that
2823 different partial programs do not overlap. This is actually an
2824 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2827 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2828 addresses. These blocks slide to their run-time addresses as rigid
2829 units; their length does not change and neither does the order of bytes
2830 within them. Such a rigid unit is called a @emph{section}. Assigning
2831 run-time addresses to sections is called @dfn{relocation}. It includes
2832 the task of adjusting mentions of object-file addresses so they refer to
2833 the proper run-time addresses.
2835 For the H8/300, and for the Renesas / SuperH SH,
2836 @command{@value{AS}} pads sections if needed to
2837 ensure they end on a word (sixteen bit) boundary.
2840 @cindex standard assembler sections
2841 An object file written by @command{@value{AS}} has at least three sections, any
2842 of which may be empty. These are named @dfn{text}, @dfn{data} and
2847 When it generates COFF or ELF output,
2849 @command{@value{AS}} can also generate whatever other named sections you specify
2850 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2851 If you do not use any directives that place output in the @samp{.text}
2852 or @samp{.data} sections, these sections still exist, but are empty.
2857 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2859 @command{@value{AS}} can also generate whatever other named sections you
2860 specify using the @samp{.space} and @samp{.subspace} directives. See
2861 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2862 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2863 assembler directives.
2866 Additionally, @command{@value{AS}} uses different names for the standard
2867 text, data, and bss sections when generating SOM output. Program text
2868 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2869 BSS into @samp{$BSS$}.
2873 Within the object file, the text section starts at address @code{0}, the
2874 data section follows, and the bss section follows the data section.
2877 When generating either SOM or ELF output files on the HPPA, the text
2878 section starts at address @code{0}, the data section at address
2879 @code{0x4000000}, and the bss section follows the data section.
2882 To let @code{@value{LD}} know which data changes when the sections are
2883 relocated, and how to change that data, @command{@value{AS}} also writes to the
2884 object file details of the relocation needed. To perform relocation
2885 @code{@value{LD}} must know, each time an address in the object
2889 Where in the object file is the beginning of this reference to
2892 How long (in bytes) is this reference?
2894 Which section does the address refer to? What is the numeric value of
2896 (@var{address}) @minus{} (@var{start-address of section})?
2899 Is the reference to an address ``Program-Counter relative''?
2902 @cindex addresses, format of
2903 @cindex section-relative addressing
2904 In fact, every address @command{@value{AS}} ever uses is expressed as
2906 (@var{section}) + (@var{offset into section})
2909 Further, most expressions @command{@value{AS}} computes have this section-relative
2912 (For some object formats, such as SOM for the HPPA, some expressions are
2913 symbol-relative instead.)
2916 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2917 @var{N} into section @var{secname}.''
2919 Apart from text, data and bss sections you need to know about the
2920 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2921 addresses in the absolute section remain unchanged. For example, address
2922 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2923 @code{@value{LD}}. Although the linker never arranges two partial programs'
2924 data sections with overlapping addresses after linking, @emph{by definition}
2925 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2926 part of a program is always the same address when the program is running as
2927 address @code{@{absolute@ 239@}} in any other part of the program.
2929 The idea of sections is extended to the @dfn{undefined} section. Any
2930 address whose section is unknown at assembly time is by definition
2931 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2932 Since numbers are always defined, the only way to generate an undefined
2933 address is to mention an undefined symbol. A reference to a named
2934 common block would be such a symbol: its value is unknown at assembly
2935 time so it has section @emph{undefined}.
2937 By analogy the word @emph{section} is used to describe groups of sections in
2938 the linked program. @code{@value{LD}} puts all partial programs' text
2939 sections in contiguous addresses in the linked program. It is
2940 customary to refer to the @emph{text section} of a program, meaning all
2941 the addresses of all partial programs' text sections. Likewise for
2942 data and bss sections.
2944 Some sections are manipulated by @code{@value{LD}}; others are invented for
2945 use of @command{@value{AS}} and have no meaning except during assembly.
2948 @section Linker Sections
2949 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2954 @cindex named sections
2955 @cindex sections, named
2956 @item named sections
2959 @cindex text section
2960 @cindex data section
2964 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2965 separate but equal sections. Anything you can say of one section is
2968 When the program is running, however, it is
2969 customary for the text section to be unalterable. The
2970 text section is often shared among processes: it contains
2971 instructions, constants and the like. The data section of a running
2972 program is usually alterable: for example, C variables would be stored
2973 in the data section.
2978 This section contains zeroed bytes when your program begins running. It
2979 is used to hold uninitialized variables or common storage. The length of
2980 each partial program's bss section is important, but because it starts
2981 out containing zeroed bytes there is no need to store explicit zero
2982 bytes in the object file. The bss section was invented to eliminate
2983 those explicit zeros from object files.
2985 @cindex absolute section
2986 @item absolute section
2987 Address 0 of this section is always ``relocated'' to runtime address 0.
2988 This is useful if you want to refer to an address that @code{@value{LD}} must
2989 not change when relocating. In this sense we speak of absolute
2990 addresses being ``unrelocatable'': they do not change during relocation.
2992 @cindex undefined section
2993 @item undefined section
2994 This ``section'' is a catch-all for address references to objects not in
2995 the preceding sections.
2996 @c FIXME: ref to some other doc on obj-file formats could go here.
2999 @cindex relocation example
3000 An idealized example of three relocatable sections follows.
3002 The example uses the traditional section names @samp{.text} and @samp{.data}.
3004 Memory addresses are on the horizontal axis.
3008 @c END TEXI2ROFF-KILL
3011 partial program # 1: |ttttt|dddd|00|
3018 partial program # 2: |TTT|DDD|000|
3021 +--+---+-----+--+----+---+-----+~~
3022 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3023 +--+---+-----+--+----+---+-----+~~
3025 addresses: 0 @dots{}
3032 \line{\it Partial program \#1: \hfil}
3033 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3034 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3036 \line{\it Partial program \#2: \hfil}
3037 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3038 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3040 \line{\it linked program: \hfil}
3041 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3042 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3043 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3044 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3046 \line{\it addresses: \hfil}
3050 @c END TEXI2ROFF-KILL
3053 @section Assembler Internal Sections
3055 @cindex internal assembler sections
3056 @cindex sections in messages, internal
3057 These sections are meant only for the internal use of @command{@value{AS}}. They
3058 have no meaning at run-time. You do not really need to know about these
3059 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3060 warning messages, so it might be helpful to have an idea of their
3061 meanings to @command{@value{AS}}. These sections are used to permit the
3062 value of every expression in your assembly language program to be a
3063 section-relative address.
3066 @cindex assembler internal logic error
3067 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3068 An internal assembler logic error has been found. This means there is a
3069 bug in the assembler.
3071 @cindex expr (internal section)
3073 The assembler stores complex expression internally as combinations of
3074 symbols. When it needs to represent an expression as a symbol, it puts
3075 it in the expr section.
3077 @c FIXME item transfer[t] vector preload
3078 @c FIXME item transfer[t] vector postload
3079 @c FIXME item register
3083 @section Sub-Sections
3085 @cindex numbered subsections
3086 @cindex grouping data
3092 fall into two sections: text and data.
3094 You may have separate groups of
3096 data in named sections
3100 data in named sections
3106 that you want to end up near to each other in the object file, even though they
3107 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3108 use @dfn{subsections} for this purpose. Within each section, there can be
3109 numbered subsections with values from 0 to 8192. Objects assembled into the
3110 same subsection go into the object file together with other objects in the same
3111 subsection. For example, a compiler might want to store constants in the text
3112 section, but might not want to have them interspersed with the program being
3113 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3114 section of code being output, and a @samp{.text 1} before each group of
3115 constants being output.
3117 Subsections are optional. If you do not use subsections, everything
3118 goes in subsection number zero.
3121 Each subsection is zero-padded up to a multiple of four bytes.
3122 (Subsections may be padded a different amount on different flavors
3123 of @command{@value{AS}}.)
3127 On the H8/300 platform, each subsection is zero-padded to a word
3128 boundary (two bytes).
3129 The same is true on the Renesas SH.
3132 @c FIXME section padding (alignment)?
3133 @c Rich Pixley says padding here depends on target obj code format; that
3134 @c doesn't seem particularly useful to say without further elaboration,
3135 @c so for now I say nothing about it. If this is a generic BFD issue,
3136 @c these paragraphs might need to vanish from this manual, and be
3137 @c discussed in BFD chapter of binutils (or some such).
3141 Subsections appear in your object file in numeric order, lowest numbered
3142 to highest. (All this to be compatible with other people's assemblers.)
3143 The object file contains no representation of subsections; @code{@value{LD}} and
3144 other programs that manipulate object files see no trace of them.
3145 They just see all your text subsections as a text section, and all your
3146 data subsections as a data section.
3148 To specify which subsection you want subsequent statements assembled
3149 into, use a numeric argument to specify it, in a @samp{.text
3150 @var{expression}} or a @samp{.data @var{expression}} statement.
3153 When generating COFF output, you
3158 can also use an extra subsection
3159 argument with arbitrary named sections: @samp{.section @var{name},
3164 When generating ELF output, you
3169 can also use the @code{.subsection} directive (@pxref{SubSection})
3170 to specify a subsection: @samp{.subsection @var{expression}}.
3172 @var{Expression} should be an absolute expression
3173 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3174 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3175 begins in @code{text 0}. For instance:
3177 .text 0 # The default subsection is text 0 anyway.
3178 .ascii "This lives in the first text subsection. *"
3180 .ascii "But this lives in the second text subsection."
3182 .ascii "This lives in the data section,"
3183 .ascii "in the first data subsection."
3185 .ascii "This lives in the first text section,"
3186 .ascii "immediately following the asterisk (*)."
3189 Each section has a @dfn{location counter} incremented by one for every byte
3190 assembled into that section. Because subsections are merely a convenience
3191 restricted to @command{@value{AS}} there is no concept of a subsection location
3192 counter. There is no way to directly manipulate a location counter---but the
3193 @code{.align} directive changes it, and any label definition captures its
3194 current value. The location counter of the section where statements are being
3195 assembled is said to be the @dfn{active} location counter.
3198 @section bss Section
3201 @cindex common variable storage
3202 The bss section is used for local common variable storage.
3203 You may allocate address space in the bss section, but you may
3204 not dictate data to load into it before your program executes. When
3205 your program starts running, all the contents of the bss
3206 section are zeroed bytes.
3208 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3209 @ref{Lcomm,,@code{.lcomm}}.
3211 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3212 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3215 When assembling for a target which supports multiple sections, such as ELF or
3216 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3217 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3218 section. Typically the section will only contain symbol definitions and
3219 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3226 Symbols are a central concept: the programmer uses symbols to name
3227 things, the linker uses symbols to link, and the debugger uses symbols
3231 @cindex debuggers, and symbol order
3232 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3233 the same order they were declared. This may break some debuggers.
3238 * Setting Symbols:: Giving Symbols Other Values
3239 * Symbol Names:: Symbol Names
3240 * Dot:: The Special Dot Symbol
3241 * Symbol Attributes:: Symbol Attributes
3248 A @dfn{label} is written as a symbol immediately followed by a colon
3249 @samp{:}. The symbol then represents the current value of the
3250 active location counter, and is, for example, a suitable instruction
3251 operand. You are warned if you use the same symbol to represent two
3252 different locations: the first definition overrides any other
3256 On the HPPA, the usual form for a label need not be immediately followed by a
3257 colon, but instead must start in column zero. Only one label may be defined on
3258 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3259 provides a special directive @code{.label} for defining labels more flexibly.
3262 @node Setting Symbols
3263 @section Giving Symbols Other Values
3265 @cindex assigning values to symbols
3266 @cindex symbol values, assigning
3267 A symbol can be given an arbitrary value by writing a symbol, followed
3268 by an equals sign @samp{=}, followed by an expression
3269 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3270 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3271 equals sign @samp{=}@samp{=} here represents an equivalent of the
3272 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3275 @section Symbol Names
3277 @cindex symbol names
3278 @cindex names, symbol
3279 @ifclear SPECIAL-SYMS
3280 Symbol names begin with a letter or with one of @samp{._}. On most
3281 machines, you can also use @code{$} in symbol names; exceptions are
3282 noted in @ref{Machine Dependencies}. That character may be followed by any
3283 string of digits, letters, dollar signs (unless otherwise noted for a
3284 particular target machine), and underscores.
3288 Symbol names begin with a letter or with one of @samp{._}. On the
3289 Renesas SH you can also use @code{$} in symbol names. That
3290 character may be followed by any string of digits, letters, dollar signs (save
3291 on the H8/300), and underscores.
3295 Case of letters is significant: @code{foo} is a different symbol name
3298 Each symbol has exactly one name. Each name in an assembly language program
3299 refers to exactly one symbol. You may use that symbol name any number of times
3302 @subheading Local Symbol Names
3304 @cindex local symbol names
3305 @cindex symbol names, local
3306 A local symbol is any symbol beginning with certain local label prefixes.
3307 By default, the local label prefix is @samp{.L} for ELF systems or
3308 @samp{L} for traditional a.out systems, but each target may have its own
3309 set of local label prefixes.
3311 On the HPPA local symbols begin with @samp{L$}.
3314 Local symbols are defined and used within the assembler, but they are
3315 normally not saved in object files. Thus, they are not visible when debugging.
3316 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3317 @option{-L}}) to retain the local symbols in the object files.
3319 @subheading Local Labels
3321 @cindex local labels
3322 @cindex temporary symbol names
3323 @cindex symbol names, temporary
3324 Local labels help compilers and programmers use names temporarily.
3325 They create symbols which are guaranteed to be unique over the entire scope of
3326 the input source code and which can be referred to by a simple notation.
3327 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3328 represents any positive integer). To refer to the most recent previous
3329 definition of that label write @samp{@b{N}b}, using the same number as when
3330 you defined the label. To refer to the next definition of a local label, write
3331 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3334 There is no restriction on how you can use these labels, and you can reuse them
3335 too. So that it is possible to repeatedly define the same local label (using
3336 the same number @samp{@b{N}}), although you can only refer to the most recently
3337 defined local label of that number (for a backwards reference) or the next
3338 definition of a specific local label for a forward reference. It is also worth
3339 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3340 implemented in a slightly more efficient manner than the others.
3351 Which is the equivalent of:
3354 label_1: branch label_3
3355 label_2: branch label_1
3356 label_3: branch label_4
3357 label_4: branch label_3
3360 Local label names are only a notational device. They are immediately
3361 transformed into more conventional symbol names before the assembler uses them.
3362 The symbol names are stored in the symbol table, appear in error messages, and
3363 are optionally emitted to the object file. The names are constructed using
3367 @item @emph{local label prefix}
3368 All local symbols begin with the system-specific local label prefix.
3369 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3370 that start with the local label prefix. These labels are
3371 used for symbols you are never intended to see. If you use the
3372 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3373 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3374 you may use them in debugging.
3377 This is the number that was used in the local label definition. So if the
3378 label is written @samp{55:} then the number is @samp{55}.
3381 This unusual character is included so you do not accidentally invent a symbol
3382 of the same name. The character has ASCII value of @samp{\002} (control-B).
3384 @item @emph{ordinal number}
3385 This is a serial number to keep the labels distinct. The first definition of
3386 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3387 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3388 the number @samp{1} and its 15th definition gets @samp{15} as well.
3391 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3392 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3394 @subheading Dollar Local Labels
3395 @cindex dollar local symbols
3397 @code{@value{AS}} also supports an even more local form of local labels called
3398 dollar labels. These labels go out of scope (i.e., they become undefined) as
3399 soon as a non-local label is defined. Thus they remain valid for only a small
3400 region of the input source code. Normal local labels, by contrast, remain in
3401 scope for the entire file, or until they are redefined by another occurrence of
3402 the same local label.
3404 Dollar labels are defined in exactly the same way as ordinary local labels,
3405 except that they have a dollar sign suffix to their numeric value, e.g.,
3408 They can also be distinguished from ordinary local labels by their transformed
3409 names which use ASCII character @samp{\001} (control-A) as the magic character
3410 to distinguish them from ordinary labels. For example, the fifth definition of
3411 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3414 @section The Special Dot Symbol
3416 @cindex dot (symbol)
3417 @cindex @code{.} (symbol)
3418 @cindex current address
3419 @cindex location counter
3420 The special symbol @samp{.} refers to the current address that
3421 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3422 .long .} defines @code{melvin} to contain its own address.
3423 Assigning a value to @code{.} is treated the same as a @code{.org}
3425 @ifclear no-space-dir
3426 Thus, the expression @samp{.=.+4} is the same as saying
3430 @node Symbol Attributes
3431 @section Symbol Attributes
3433 @cindex symbol attributes
3434 @cindex attributes, symbol
3435 Every symbol has, as well as its name, the attributes ``Value'' and
3436 ``Type''. Depending on output format, symbols can also have auxiliary
3439 The detailed definitions are in @file{a.out.h}.
3442 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3443 all these attributes, and probably won't warn you. This makes the
3444 symbol an externally defined symbol, which is generally what you
3448 * Symbol Value:: Value
3449 * Symbol Type:: Type
3452 * a.out Symbols:: Symbol Attributes: @code{a.out}
3456 * a.out Symbols:: Symbol Attributes: @code{a.out}
3459 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3464 * COFF Symbols:: Symbol Attributes for COFF
3467 * SOM Symbols:: Symbol Attributes for SOM
3474 @cindex value of a symbol
3475 @cindex symbol value
3476 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3477 location in the text, data, bss or absolute sections the value is the
3478 number of addresses from the start of that section to the label.
3479 Naturally for text, data and bss sections the value of a symbol changes
3480 as @code{@value{LD}} changes section base addresses during linking. Absolute
3481 symbols' values do not change during linking: that is why they are
3484 The value of an undefined symbol is treated in a special way. If it is
3485 0 then the symbol is not defined in this assembler source file, and
3486 @code{@value{LD}} tries to determine its value from other files linked into the
3487 same program. You make this kind of symbol simply by mentioning a symbol
3488 name without defining it. A non-zero value represents a @code{.comm}
3489 common declaration. The value is how much common storage to reserve, in
3490 bytes (addresses). The symbol refers to the first address of the
3496 @cindex type of a symbol
3498 The type attribute of a symbol contains relocation (section)
3499 information, any flag settings indicating that a symbol is external, and
3500 (optionally), other information for linkers and debuggers. The exact
3501 format depends on the object-code output format in use.
3506 @c The following avoids a "widow" subsection title. @group would be
3507 @c better if it were available outside examples.
3510 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3512 @cindex @code{b.out} symbol attributes
3513 @cindex symbol attributes, @code{b.out}
3514 These symbol attributes appear only when @command{@value{AS}} is configured for
3515 one of the Berkeley-descended object output formats---@code{a.out} or
3521 @subsection Symbol Attributes: @code{a.out}
3523 @cindex @code{a.out} symbol attributes
3524 @cindex symbol attributes, @code{a.out}
3530 @subsection Symbol Attributes: @code{a.out}
3532 @cindex @code{a.out} symbol attributes
3533 @cindex symbol attributes, @code{a.out}
3537 * Symbol Desc:: Descriptor
3538 * Symbol Other:: Other
3542 @subsubsection Descriptor
3544 @cindex descriptor, of @code{a.out} symbol
3545 This is an arbitrary 16-bit value. You may establish a symbol's
3546 descriptor value by using a @code{.desc} statement
3547 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3548 @command{@value{AS}}.
3551 @subsubsection Other
3553 @cindex other attribute, of @code{a.out} symbol
3554 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3559 @subsection Symbol Attributes for COFF
3561 @cindex COFF symbol attributes
3562 @cindex symbol attributes, COFF
3564 The COFF format supports a multitude of auxiliary symbol attributes;
3565 like the primary symbol attributes, they are set between @code{.def} and
3566 @code{.endef} directives.
3568 @subsubsection Primary Attributes
3570 @cindex primary attributes, COFF symbols
3571 The symbol name is set with @code{.def}; the value and type,
3572 respectively, with @code{.val} and @code{.type}.
3574 @subsubsection Auxiliary Attributes
3576 @cindex auxiliary attributes, COFF symbols
3577 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3578 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3579 table information for COFF.
3584 @subsection Symbol Attributes for SOM
3586 @cindex SOM symbol attributes
3587 @cindex symbol attributes, SOM
3589 The SOM format for the HPPA supports a multitude of symbol attributes set with
3590 the @code{.EXPORT} and @code{.IMPORT} directives.
3592 The attributes are described in @cite{HP9000 Series 800 Assembly
3593 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3594 @code{EXPORT} assembler directive documentation.
3598 @chapter Expressions
3602 @cindex numeric values
3603 An @dfn{expression} specifies an address or numeric value.
3604 Whitespace may precede and/or follow an expression.
3606 The result of an expression must be an absolute number, or else an offset into
3607 a particular section. If an expression is not absolute, and there is not
3608 enough information when @command{@value{AS}} sees the expression to know its
3609 section, a second pass over the source program might be necessary to interpret
3610 the expression---but the second pass is currently not implemented.
3611 @command{@value{AS}} aborts with an error message in this situation.
3614 * Empty Exprs:: Empty Expressions
3615 * Integer Exprs:: Integer Expressions
3619 @section Empty Expressions
3621 @cindex empty expressions
3622 @cindex expressions, empty
3623 An empty expression has no value: it is just whitespace or null.
3624 Wherever an absolute expression is required, you may omit the
3625 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3626 is compatible with other assemblers.
3629 @section Integer Expressions
3631 @cindex integer expressions
3632 @cindex expressions, integer
3633 An @dfn{integer expression} is one or more @emph{arguments} delimited
3634 by @emph{operators}.
3637 * Arguments:: Arguments
3638 * Operators:: Operators
3639 * Prefix Ops:: Prefix Operators
3640 * Infix Ops:: Infix Operators
3644 @subsection Arguments
3646 @cindex expression arguments
3647 @cindex arguments in expressions
3648 @cindex operands in expressions
3649 @cindex arithmetic operands
3650 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3651 contexts arguments are sometimes called ``arithmetic operands''. In
3652 this manual, to avoid confusing them with the ``instruction operands'' of
3653 the machine language, we use the term ``argument'' to refer to parts of
3654 expressions only, reserving the word ``operand'' to refer only to machine
3655 instruction operands.
3657 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3658 @var{section} is one of text, data, bss, absolute,
3659 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3662 Numbers are usually integers.
3664 A number can be a flonum or bignum. In this case, you are warned
3665 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3666 these 32 bits are an integer. You may write integer-manipulating
3667 instructions that act on exotic constants, compatible with other
3670 @cindex subexpressions
3671 Subexpressions are a left parenthesis @samp{(} followed by an integer
3672 expression, followed by a right parenthesis @samp{)}; or a prefix
3673 operator followed by an argument.
3676 @subsection Operators
3678 @cindex operators, in expressions
3679 @cindex arithmetic functions
3680 @cindex functions, in expressions
3681 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3682 operators are followed by an argument. Infix operators appear
3683 between their arguments. Operators may be preceded and/or followed by
3687 @subsection Prefix Operator
3689 @cindex prefix operators
3690 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3691 one argument, which must be absolute.
3693 @c the tex/end tex stuff surrounding this small table is meant to make
3694 @c it align, on the printed page, with the similar table in the next
3695 @c section (which is inside an enumerate).
3697 \global\advance\leftskip by \itemindent
3702 @dfn{Negation}. Two's complement negation.
3704 @dfn{Complementation}. Bitwise not.
3708 \global\advance\leftskip by -\itemindent
3712 @subsection Infix Operators
3714 @cindex infix operators
3715 @cindex operators, permitted arguments
3716 @dfn{Infix operators} take two arguments, one on either side. Operators
3717 have precedence, but operations with equal precedence are performed left
3718 to right. Apart from @code{+} or @option{-}, both arguments must be
3719 absolute, and the result is absolute.
3722 @cindex operator precedence
3723 @cindex precedence of operators
3730 @dfn{Multiplication}.
3733 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3739 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3742 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3746 Intermediate precedence
3751 @dfn{Bitwise Inclusive Or}.
3757 @dfn{Bitwise Exclusive Or}.
3760 @dfn{Bitwise Or Not}.
3767 @cindex addition, permitted arguments
3768 @cindex plus, permitted arguments
3769 @cindex arguments for addition
3771 @dfn{Addition}. If either argument is absolute, the result has the section of
3772 the other argument. You may not add together arguments from different
3775 @cindex subtraction, permitted arguments
3776 @cindex minus, permitted arguments
3777 @cindex arguments for subtraction
3779 @dfn{Subtraction}. If the right argument is absolute, the
3780 result has the section of the left argument.
3781 If both arguments are in the same section, the result is absolute.
3782 You may not subtract arguments from different sections.
3783 @c FIXME is there still something useful to say about undefined - undefined ?
3785 @cindex comparison expressions
3786 @cindex expressions, comparison
3791 @dfn{Is Not Equal To}
3795 @dfn{Is Greater Than}
3797 @dfn{Is Greater Than Or Equal To}
3799 @dfn{Is Less Than Or Equal To}
3801 The comparison operators can be used as infix operators. A true results has a
3802 value of -1 whereas a false result has a value of 0. Note, these operators
3803 perform signed comparisons.
3806 @item Lowest Precedence
3815 These two logical operations can be used to combine the results of sub
3816 expressions. Note, unlike the comparison operators a true result returns a
3817 value of 1 but a false results does still return 0. Also note that the logical
3818 or operator has a slightly lower precedence than logical and.
3823 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3824 address; you can only have a defined section in one of the two arguments.
3827 @chapter Assembler Directives
3829 @cindex directives, machine independent
3830 @cindex pseudo-ops, machine independent
3831 @cindex machine independent directives
3832 All assembler directives have names that begin with a period (@samp{.}).
3833 The rest of the name is letters, usually in lower case.
3835 This chapter discusses directives that are available regardless of the
3836 target machine configuration for the @sc{gnu} assembler.
3838 Some machine configurations provide additional directives.
3839 @xref{Machine Dependencies}.
3842 @ifset machine-directives
3843 @xref{Machine Dependencies}, for additional directives.
3848 * Abort:: @code{.abort}
3850 * ABORT (COFF):: @code{.ABORT}
3853 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3854 * Altmacro:: @code{.altmacro}
3855 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3856 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3857 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3858 * Byte:: @code{.byte @var{expressions}}
3859 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3860 * Comm:: @code{.comm @var{symbol} , @var{length} }
3861 * Data:: @code{.data @var{subsection}}
3863 * Def:: @code{.def @var{name}}
3866 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3872 * Double:: @code{.double @var{flonums}}
3873 * Eject:: @code{.eject}
3874 * Else:: @code{.else}
3875 * Elseif:: @code{.elseif}
3878 * Endef:: @code{.endef}
3881 * Endfunc:: @code{.endfunc}
3882 * Endif:: @code{.endif}
3883 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3884 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3885 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3887 * Error:: @code{.error @var{string}}
3888 * Exitm:: @code{.exitm}
3889 * Extern:: @code{.extern}
3890 * Fail:: @code{.fail}
3891 * File:: @code{.file}
3892 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3893 * Float:: @code{.float @var{flonums}}
3894 * Func:: @code{.func}
3895 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3897 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3898 * Hidden:: @code{.hidden @var{names}}
3901 * hword:: @code{.hword @var{expressions}}
3902 * Ident:: @code{.ident}
3903 * If:: @code{.if @var{absolute expression}}
3904 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3905 * Include:: @code{.include "@var{file}"}
3906 * Int:: @code{.int @var{expressions}}
3908 * Internal:: @code{.internal @var{names}}
3911 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3912 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3913 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3914 * Lflags:: @code{.lflags}
3915 @ifclear no-line-dir
3916 * Line:: @code{.line @var{line-number}}
3919 * Linkonce:: @code{.linkonce [@var{type}]}
3920 * List:: @code{.list}
3921 * Ln:: @code{.ln @var{line-number}}
3922 * Loc:: @code{.loc @var{fileno} @var{lineno}}
3923 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
3925 * Local:: @code{.local @var{names}}
3928 * Long:: @code{.long @var{expressions}}
3930 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3933 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3934 * MRI:: @code{.mri @var{val}}
3935 * Noaltmacro:: @code{.noaltmacro}
3936 * Nolist:: @code{.nolist}
3937 * Octa:: @code{.octa @var{bignums}}
3938 * Org:: @code{.org @var{new-lc}, @var{fill}}
3939 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3941 * PopSection:: @code{.popsection}
3942 * Previous:: @code{.previous}
3945 * Print:: @code{.print @var{string}}
3947 * Protected:: @code{.protected @var{names}}
3950 * Psize:: @code{.psize @var{lines}, @var{columns}}
3951 * Purgem:: @code{.purgem @var{name}}
3953 * PushSection:: @code{.pushsection @var{name}}
3956 * Quad:: @code{.quad @var{bignums}}
3957 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
3958 * Rept:: @code{.rept @var{count}}
3959 * Sbttl:: @code{.sbttl "@var{subheading}"}
3961 * Scl:: @code{.scl @var{class}}
3964 * Section:: @code{.section @var{name}[, @var{flags}]}
3967 * Set:: @code{.set @var{symbol}, @var{expression}}
3968 * Short:: @code{.short @var{expressions}}
3969 * Single:: @code{.single @var{flonums}}
3971 * Size:: @code{.size [@var{name} , @var{expression}]}
3973 @ifclear no-space-dir
3974 * Skip:: @code{.skip @var{size} , @var{fill}}
3977 * Sleb128:: @code{.sleb128 @var{expressions}}
3978 @ifclear no-space-dir
3979 * Space:: @code{.space @var{size} , @var{fill}}
3982 * Stab:: @code{.stabd, .stabn, .stabs}
3985 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
3986 * Struct:: @code{.struct @var{expression}}
3988 * SubSection:: @code{.subsection}
3989 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3993 * Tag:: @code{.tag @var{structname}}
3996 * Text:: @code{.text @var{subsection}}
3997 * Title:: @code{.title "@var{heading}"}
3999 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4002 * Uleb128:: @code{.uleb128 @var{expressions}}
4004 * Val:: @code{.val @var{addr}}
4008 * Version:: @code{.version "@var{string}"}
4009 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4010 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4013 * Warning:: @code{.warning @var{string}}
4014 * Weak:: @code{.weak @var{names}}
4015 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4016 * Word:: @code{.word @var{expressions}}
4017 * Deprecated:: Deprecated Directives
4021 @section @code{.abort}
4023 @cindex @code{abort} directive
4024 @cindex stopping the assembly
4025 This directive stops the assembly immediately. It is for
4026 compatibility with other assemblers. The original idea was that the
4027 assembly language source would be piped into the assembler. If the sender
4028 of the source quit, it could use this directive tells @command{@value{AS}} to
4029 quit also. One day @code{.abort} will not be supported.
4033 @section @code{.ABORT} (COFF)
4035 @cindex @code{ABORT} directive
4036 When producing COFF output, @command{@value{AS}} accepts this directive as a
4037 synonym for @samp{.abort}.
4040 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4046 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4048 @cindex padding the location counter
4049 @cindex @code{align} directive
4050 Pad the location counter (in the current subsection) to a particular storage
4051 boundary. The first expression (which must be absolute) is the alignment
4052 required, as described below.
4054 The second expression (also absolute) gives the fill value to be stored in the
4055 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4056 padding bytes are normally zero. However, on some systems, if the section is
4057 marked as containing code and the fill value is omitted, the space is filled
4058 with no-op instructions.
4060 The third expression is also absolute, and is also optional. If it is present,
4061 it is the maximum number of bytes that should be skipped by this alignment
4062 directive. If doing the alignment would require skipping more bytes than the
4063 specified maximum, then the alignment is not done at all. You can omit the
4064 fill value (the second argument) entirely by simply using two commas after the
4065 required alignment; this can be useful if you want the alignment to be filled
4066 with no-op instructions when appropriate.
4068 The way the required alignment is specified varies from system to system.
4069 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4070 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4071 alignment request in bytes. For example @samp{.align 8} advances
4072 the location counter until it is a multiple of 8. If the location counter
4073 is already a multiple of 8, no change is needed. For the tic54x, the
4074 first expression is the alignment request in words.
4076 For other systems, including ppc, i386 using a.out format, arm and
4077 strongarm, it is the
4078 number of low-order zero bits the location counter must have after
4079 advancement. For example @samp{.align 3} advances the location
4080 counter until it a multiple of 8. If the location counter is already a
4081 multiple of 8, no change is needed.
4083 This inconsistency is due to the different behaviors of the various
4084 native assemblers for these systems which GAS must emulate.
4085 GAS also provides @code{.balign} and @code{.p2align} directives,
4086 described later, which have a consistent behavior across all
4087 architectures (but are specific to GAS).
4090 @section @code{.altmacro}
4091 Enable alternate macro mode, enabling:
4094 @item LOCAL @var{name} [ , @dots{} ]
4095 One additional directive, @code{LOCAL}, is available. It is used to
4096 generate a string replacement for each of the @var{name} arguments, and
4097 replace any instances of @var{name} in each macro expansion. The
4098 replacement string is unique in the assembly, and different for each
4099 separate macro expansion. @code{LOCAL} allows you to write macros that
4100 define symbols, without fear of conflict between separate macro expansions.
4102 @item String delimiters
4103 You can write strings delimited in these other ways besides
4104 @code{"@var{string}"}:
4107 @item '@var{string}'
4108 You can delimit strings with single-quote characters.
4110 @item <@var{string}>
4111 You can delimit strings with matching angle brackets.
4114 @item single-character string escape
4115 To include any single character literally in a string (even if the
4116 character would otherwise have some special meaning), you can prefix the
4117 character with @samp{!} (an exclamation mark). For example, you can
4118 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4120 @item Expression results as strings
4121 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4122 and use the result as a string.
4126 @section @code{.ascii "@var{string}"}@dots{}
4128 @cindex @code{ascii} directive
4129 @cindex string literals
4130 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4131 separated by commas. It assembles each string (with no automatic
4132 trailing zero byte) into consecutive addresses.
4135 @section @code{.asciz "@var{string}"}@dots{}
4137 @cindex @code{asciz} directive
4138 @cindex zero-terminated strings
4139 @cindex null-terminated strings
4140 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4141 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4144 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4146 @cindex padding the location counter given number of bytes
4147 @cindex @code{balign} directive
4148 Pad the location counter (in the current subsection) to a particular
4149 storage boundary. The first expression (which must be absolute) is the
4150 alignment request in bytes. For example @samp{.balign 8} advances
4151 the location counter until it is a multiple of 8. If the location counter
4152 is already a multiple of 8, no change is needed.
4154 The second expression (also absolute) gives the fill value to be stored in the
4155 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4156 padding bytes are normally zero. However, on some systems, if the section is
4157 marked as containing code and the fill value is omitted, the space is filled
4158 with no-op instructions.
4160 The third expression is also absolute, and is also optional. If it is present,
4161 it is the maximum number of bytes that should be skipped by this alignment
4162 directive. If doing the alignment would require skipping more bytes than the
4163 specified maximum, then the alignment is not done at all. You can omit the
4164 fill value (the second argument) entirely by simply using two commas after the
4165 required alignment; this can be useful if you want the alignment to be filled
4166 with no-op instructions when appropriate.
4168 @cindex @code{balignw} directive
4169 @cindex @code{balignl} directive
4170 The @code{.balignw} and @code{.balignl} directives are variants of the
4171 @code{.balign} directive. The @code{.balignw} directive treats the fill
4172 pattern as a two byte word value. The @code{.balignl} directives treats the
4173 fill pattern as a four byte longword value. For example, @code{.balignw
4174 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4175 filled in with the value 0x368d (the exact placement of the bytes depends upon
4176 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4180 @section @code{.byte @var{expressions}}
4182 @cindex @code{byte} directive
4183 @cindex integers, one byte
4184 @code{.byte} expects zero or more expressions, separated by commas.
4185 Each expression is assembled into the next byte.
4187 @node CFI directives
4188 @section @code{.cfi_startproc [simple]}
4189 @cindex @code{cfi_startproc} directive
4190 @code{.cfi_startproc} is used at the beginning of each function that
4191 should have an entry in @code{.eh_frame}. It initializes some internal
4192 data structures. Don't forget to close the function by
4193 @code{.cfi_endproc}.
4195 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4196 it also emits some architecture dependent initial CFI instructions.
4198 @section @code{.cfi_endproc}
4199 @cindex @code{cfi_endproc} directive
4200 @code{.cfi_endproc} is used at the end of a function where it closes its
4201 unwind entry previously opened by
4202 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4204 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4205 @code{.cfi_personality} defines personality routine and its encoding.
4206 @var{encoding} must be a constant determining how the personality
4207 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4208 argument is not present, otherwise second argument should be
4209 a constant or a symbol name. When using indirect encodings,
4210 the symbol provided should be the location where personality
4211 can be loaded from, not the personality routine itself.
4212 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4213 no personality routine.
4215 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4216 @code{.cfi_lsda} defines LSDA and its encoding.
4217 @var{encoding} must be a constant determining how the LSDA
4218 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4219 argument is not present, otherwise second argument should be a constant
4220 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4223 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4224 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4225 address from @var{register} and add @var{offset} to it}.
4227 @section @code{.cfi_def_cfa_register @var{register}}
4228 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4229 now on @var{register} will be used instead of the old one. Offset
4232 @section @code{.cfi_def_cfa_offset @var{offset}}
4233 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4234 remains the same, but @var{offset} is new. Note that it is the
4235 absolute offset that will be added to a defined register to compute
4238 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4239 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4240 value that is added/substracted from the previous offset.
4242 @section @code{.cfi_offset @var{register}, @var{offset}}
4243 Previous value of @var{register} is saved at offset @var{offset} from
4246 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4247 Previous value of @var{register} is saved at offset @var{offset} from
4248 the current CFA register. This is transformed to @code{.cfi_offset}
4249 using the known displacement of the CFA register from the CFA.
4250 This is often easier to use, because the number will match the
4251 code it's annotating.
4253 @section @code{.cfi_register @var{register1}, @var{register2}}
4254 Previous value of @var{register1} is saved in register @var{register2}.
4256 @section @code{.cfi_restore @var{register}}
4257 @code{.cfi_restore} says that the rule for @var{register} is now the
4258 same as it was at the beginning of the function, after all initial
4259 instruction added by @code{.cfi_startproc} were executed.
4261 @section @code{.cfi_undefined @var{register}}
4262 From now on the previous value of @var{register} can't be restored anymore.
4264 @section @code{.cfi_same_value @var{register}}
4265 Current value of @var{register} is the same like in the previous frame,
4266 i.e. no restoration needed.
4268 @section @code{.cfi_remember_state},
4269 First save all current rules for all registers by @code{.cfi_remember_state},
4270 then totally screw them up by subsequent @code{.cfi_*} directives and when
4271 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4272 the previous saved state.
4274 @section @code{.cfi_return_column @var{register}}
4275 Change return column @var{register}, i.e. the return address is either
4276 directly in @var{register} or can be accessed by rules for @var{register}.
4278 @section @code{.cfi_signal_frame}
4279 Mark current function as signal trampoline.
4281 @section @code{.cfi_window_save}
4282 SPARC register window has been saved.
4284 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4285 Allows the user to add arbitrary bytes to the unwind info. One
4286 might use this to add OS-specific CFI opcodes, or generic CFI
4287 opcodes that GAS does not yet support.
4289 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4290 The current value of @var{register} is @var{label}. The value of @var{label}
4291 will be encoded in the output file according to @var{encoding}; see the
4292 description of @code{.cfi_personality} for details on this encoding.
4294 The usefulness of equating a register to a fixed label is probably
4295 limited to the return address register. Here, it can be useful to
4296 mark a code segment that has only one return address which is reached
4297 by a direct branch and no copy of the return address exists in memory
4298 or another register.
4301 @section @code{.comm @var{symbol} , @var{length} }
4303 @cindex @code{comm} directive
4304 @cindex symbol, common
4305 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4306 common symbol in one object file may be merged with a defined or common symbol
4307 of the same name in another object file. If @code{@value{LD}} does not see a
4308 definition for the symbol--just one or more common symbols--then it will
4309 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4310 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4311 the same name, and they do not all have the same size, it will allocate space
4312 using the largest size.
4315 When using ELF, the @code{.comm} directive takes an optional third argument.
4316 This is the desired alignment of the symbol, specified as a byte boundary (for
4317 example, an alignment of 16 means that the least significant 4 bits of the
4318 address should be zero). The alignment must be an absolute expression, and it
4319 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4320 for the common symbol, it will use the alignment when placing the symbol. If
4321 no alignment is specified, @command{@value{AS}} will set the alignment to the
4322 largest power of two less than or equal to the size of the symbol, up to a
4327 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4328 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4332 @section @code{.data @var{subsection}}
4334 @cindex @code{data} directive
4335 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4336 end of the data subsection numbered @var{subsection} (which is an
4337 absolute expression). If @var{subsection} is omitted, it defaults
4342 @section @code{.def @var{name}}
4344 @cindex @code{def} directive
4345 @cindex COFF symbols, debugging
4346 @cindex debugging COFF symbols
4347 Begin defining debugging information for a symbol @var{name}; the
4348 definition extends until the @code{.endef} directive is encountered.
4351 This directive is only observed when @command{@value{AS}} is configured for COFF
4352 format output; when producing @code{b.out}, @samp{.def} is recognized,
4359 @section @code{.desc @var{symbol}, @var{abs-expression}}
4361 @cindex @code{desc} directive
4362 @cindex COFF symbol descriptor
4363 @cindex symbol descriptor, COFF
4364 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4365 to the low 16 bits of an absolute expression.
4368 The @samp{.desc} directive is not available when @command{@value{AS}} is
4369 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4370 object format. For the sake of compatibility, @command{@value{AS}} accepts
4371 it, but produces no output, when configured for COFF.
4377 @section @code{.dim}
4379 @cindex @code{dim} directive
4380 @cindex COFF auxiliary symbol information
4381 @cindex auxiliary symbol information, COFF
4382 This directive is generated by compilers to include auxiliary debugging
4383 information in the symbol table. It is only permitted inside
4384 @code{.def}/@code{.endef} pairs.
4387 @samp{.dim} is only meaningful when generating COFF format output; when
4388 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4394 @section @code{.double @var{flonums}}
4396 @cindex @code{double} directive
4397 @cindex floating point numbers (double)
4398 @code{.double} expects zero or more flonums, separated by commas. It
4399 assembles floating point numbers.
4401 The exact kind of floating point numbers emitted depends on how
4402 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4406 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4407 in @sc{ieee} format.
4412 @section @code{.eject}
4414 @cindex @code{eject} directive
4415 @cindex new page, in listings
4416 @cindex page, in listings
4417 @cindex listing control: new page
4418 Force a page break at this point, when generating assembly listings.
4421 @section @code{.else}
4423 @cindex @code{else} directive
4424 @code{.else} is part of the @command{@value{AS}} support for conditional
4425 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4426 of code to be assembled if the condition for the preceding @code{.if}
4430 @section @code{.elseif}
4432 @cindex @code{elseif} directive
4433 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4434 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4435 @code{.if} block that would otherwise fill the entire @code{.else} section.
4438 @section @code{.end}
4440 @cindex @code{end} directive
4441 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4442 process anything in the file past the @code{.end} directive.
4446 @section @code{.endef}
4448 @cindex @code{endef} directive
4449 This directive flags the end of a symbol definition begun with
4453 @samp{.endef} is only meaningful when generating COFF format output; if
4454 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4455 directive but ignores it.
4460 @section @code{.endfunc}
4461 @cindex @code{endfunc} directive
4462 @code{.endfunc} marks the end of a function specified with @code{.func}.
4465 @section @code{.endif}
4467 @cindex @code{endif} directive
4468 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4469 it marks the end of a block of code that is only assembled
4470 conditionally. @xref{If,,@code{.if}}.
4473 @section @code{.equ @var{symbol}, @var{expression}}
4475 @cindex @code{equ} directive
4476 @cindex assigning values to symbols
4477 @cindex symbols, assigning values to
4478 This directive sets the value of @var{symbol} to @var{expression}.
4479 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4482 The syntax for @code{equ} on the HPPA is
4483 @samp{@var{symbol} .equ @var{expression}}.
4487 The syntax for @code{equ} on the Z80 is
4488 @samp{@var{symbol} equ @var{expression}}.
4489 On the Z80 it is an eror if @var{symbol} is already defined,
4490 but the symbol is not protected from later redefinition.
4491 Compare @ref{Equiv}.
4495 @section @code{.equiv @var{symbol}, @var{expression}}
4496 @cindex @code{equiv} directive
4497 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4498 the assembler will signal an error if @var{symbol} is already defined. Note a
4499 symbol which has been referenced but not actually defined is considered to be
4502 Except for the contents of the error message, this is roughly equivalent to
4509 plus it protects the symbol from later redefinition.
4512 @section @code{.eqv @var{symbol}, @var{expression}}
4513 @cindex @code{eqv} directive
4514 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4515 evaluate the expression or any part of it immediately. Instead each time
4516 the resulting symbol is used in an expression, a snapshot of its current
4520 @section @code{.err}
4521 @cindex @code{err} directive
4522 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4523 message and, unless the @option{-Z} option was used, it will not generate an
4524 object file. This can be used to signal an error in conditionally compiled code.
4527 @section @code{.error "@var{string}"}
4528 @cindex error directive
4530 Similarly to @code{.err}, this directive emits an error, but you can specify a
4531 string that will be emitted as the error message. If you don't specify the
4532 message, it defaults to @code{".error directive invoked in source file"}.
4533 @xref{Errors, ,Error and Warning Messages}.
4536 .error "This code has not been assembled and tested."
4540 @section @code{.exitm}
4541 Exit early from the current macro definition. @xref{Macro}.
4544 @section @code{.extern}
4546 @cindex @code{extern} directive
4547 @code{.extern} is accepted in the source program---for compatibility
4548 with other assemblers---but it is ignored. @command{@value{AS}} treats
4549 all undefined symbols as external.
4552 @section @code{.fail @var{expression}}
4554 @cindex @code{fail} directive
4555 Generates an error or a warning. If the value of the @var{expression} is 500
4556 or more, @command{@value{AS}} will print a warning message. If the value is less
4557 than 500, @command{@value{AS}} will print an error message. The message will
4558 include the value of @var{expression}. This can occasionally be useful inside
4559 complex nested macros or conditional assembly.
4562 @section @code{.file}
4563 @cindex @code{file} directive
4565 @ifclear no-file-dir
4566 There are two different versions of the @code{.file} directive. Targets
4567 that support DWARF2 line number information use the DWARF2 version of
4568 @code{.file}. Other targets use the default version.
4570 @subheading Default Version
4572 @cindex logical file name
4573 @cindex file name, logical
4574 This version of the @code{.file} directive tells @command{@value{AS}} that we
4575 are about to start a new logical file. The syntax is:
4581 @var{string} is the new file name. In general, the filename is
4582 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4583 to specify an empty file name, you must give the quotes--@code{""}. This
4584 statement may go away in future: it is only recognized to be compatible with
4585 old @command{@value{AS}} programs.
4587 @subheading DWARF2 Version
4590 When emitting DWARF2 line number information, @code{.file} assigns filenames
4591 to the @code{.debug_line} file name table. The syntax is:
4594 .file @var{fileno} @var{filename}
4597 The @var{fileno} operand should be a unique positive integer to use as the
4598 index of the entry in the table. The @var{filename} operand is a C string
4601 The detail of filename indices is exposed to the user because the filename
4602 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4603 information, and thus the user must know the exact indices that table
4607 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4609 @cindex @code{fill} directive
4610 @cindex writing patterns in memory
4611 @cindex patterns, writing in memory
4612 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4613 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4614 may be zero or more. @var{Size} may be zero or more, but if it is
4615 more than 8, then it is deemed to have the value 8, compatible with
4616 other people's assemblers. The contents of each @var{repeat} bytes
4617 is taken from an 8-byte number. The highest order 4 bytes are
4618 zero. The lowest order 4 bytes are @var{value} rendered in the
4619 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4620 Each @var{size} bytes in a repetition is taken from the lowest order
4621 @var{size} bytes of this number. Again, this bizarre behavior is
4622 compatible with other people's assemblers.
4624 @var{size} and @var{value} are optional.
4625 If the second comma and @var{value} are absent, @var{value} is
4626 assumed zero. If the first comma and following tokens are absent,
4627 @var{size} is assumed to be 1.
4630 @section @code{.float @var{flonums}}
4632 @cindex floating point numbers (single)
4633 @cindex @code{float} directive
4634 This directive assembles zero or more flonums, separated by commas. It
4635 has the same effect as @code{.single}.
4637 The exact kind of floating point numbers emitted depends on how
4638 @command{@value{AS}} is configured.
4639 @xref{Machine Dependencies}.
4643 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4644 in @sc{ieee} format.
4649 @section @code{.func @var{name}[,@var{label}]}
4650 @cindex @code{func} directive
4651 @code{.func} emits debugging information to denote function @var{name}, and
4652 is ignored unless the file is assembled with debugging enabled.
4653 Only @samp{--gstabs[+]} is currently supported.
4654 @var{label} is the entry point of the function and if omitted @var{name}
4655 prepended with the @samp{leading char} is used.
4656 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4657 All functions are currently defined to have @code{void} return type.
4658 The function must be terminated with @code{.endfunc}.
4661 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4663 @cindex @code{global} directive
4664 @cindex symbol, making visible to linker
4665 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4666 @var{symbol} in your partial program, its value is made available to
4667 other partial programs that are linked with it. Otherwise,
4668 @var{symbol} takes its attributes from a symbol of the same name
4669 from another file linked into the same program.
4671 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4672 compatibility with other assemblers.
4675 On the HPPA, @code{.global} is not always enough to make it accessible to other
4676 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4677 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4682 @section @code{.gnu_attribute @var{tag},@var{value}}
4683 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4686 @section @code{.hidden @var{names}}
4688 @cindex @code{hidden} directive
4690 This is one of the ELF visibility directives. The other two are
4691 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4692 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4694 This directive overrides the named symbols default visibility (which is set by
4695 their binding: local, global or weak). The directive sets the visibility to
4696 @code{hidden} which means that the symbols are not visible to other components.
4697 Such symbols are always considered to be @code{protected} as well.
4701 @section @code{.hword @var{expressions}}
4703 @cindex @code{hword} directive
4704 @cindex integers, 16-bit
4705 @cindex numbers, 16-bit
4706 @cindex sixteen bit integers
4707 This expects zero or more @var{expressions}, and emits
4708 a 16 bit number for each.
4711 This directive is a synonym for @samp{.short}; depending on the target
4712 architecture, it may also be a synonym for @samp{.word}.
4716 This directive is a synonym for @samp{.short}.
4719 This directive is a synonym for both @samp{.short} and @samp{.word}.
4724 @section @code{.ident}
4726 @cindex @code{ident} directive
4728 This directive is used by some assemblers to place tags in object files. The
4729 behavior of this directive varies depending on the target. When using the
4730 a.out object file format, @command{@value{AS}} simply accepts the directive for
4731 source-file compatibility with existing assemblers, but does not emit anything
4732 for it. When using COFF, comments are emitted to the @code{.comment} or
4733 @code{.rdata} section, depending on the target. When using ELF, comments are
4734 emitted to the @code{.comment} section.
4737 @section @code{.if @var{absolute expression}}
4739 @cindex conditional assembly
4740 @cindex @code{if} directive
4741 @code{.if} marks the beginning of a section of code which is only
4742 considered part of the source program being assembled if the argument
4743 (which must be an @var{absolute expression}) is non-zero. The end of
4744 the conditional section of code must be marked by @code{.endif}
4745 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4746 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4747 If you have several conditions to check, @code{.elseif} may be used to avoid
4748 nesting blocks if/else within each subsequent @code{.else} block.
4750 The following variants of @code{.if} are also supported:
4752 @cindex @code{ifdef} directive
4753 @item .ifdef @var{symbol}
4754 Assembles the following section of code if the specified @var{symbol}
4755 has been defined. Note a symbol which has been referenced but not yet defined
4756 is considered to be undefined.
4758 @cindex @code{ifb} directive
4759 @item .ifb @var{text}
4760 Assembles the following section of code if the operand is blank (empty).
4762 @cindex @code{ifc} directive
4763 @item .ifc @var{string1},@var{string2}
4764 Assembles the following section of code if the two strings are the same. The
4765 strings may be optionally quoted with single quotes. If they are not quoted,
4766 the first string stops at the first comma, and the second string stops at the
4767 end of the line. Strings which contain whitespace should be quoted. The
4768 string comparison is case sensitive.
4770 @cindex @code{ifeq} directive
4771 @item .ifeq @var{absolute expression}
4772 Assembles the following section of code if the argument is zero.
4774 @cindex @code{ifeqs} directive
4775 @item .ifeqs @var{string1},@var{string2}
4776 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4778 @cindex @code{ifge} directive
4779 @item .ifge @var{absolute expression}
4780 Assembles the following section of code if the argument is greater than or
4783 @cindex @code{ifgt} directive
4784 @item .ifgt @var{absolute expression}
4785 Assembles the following section of code if the argument is greater than zero.
4787 @cindex @code{ifle} directive
4788 @item .ifle @var{absolute expression}
4789 Assembles the following section of code if the argument is less than or equal
4792 @cindex @code{iflt} directive
4793 @item .iflt @var{absolute expression}
4794 Assembles the following section of code if the argument is less than zero.
4796 @cindex @code{ifnb} directive
4797 @item .ifnb @var{text}
4798 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4799 following section of code if the operand is non-blank (non-empty).
4801 @cindex @code{ifnc} directive
4802 @item .ifnc @var{string1},@var{string2}.
4803 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4804 following section of code if the two strings are not the same.
4806 @cindex @code{ifndef} directive
4807 @cindex @code{ifnotdef} directive
4808 @item .ifndef @var{symbol}
4809 @itemx .ifnotdef @var{symbol}
4810 Assembles the following section of code if the specified @var{symbol}
4811 has not been defined. Both spelling variants are equivalent. Note a symbol
4812 which has been referenced but not yet defined is considered to be undefined.
4814 @cindex @code{ifne} directive
4815 @item .ifne @var{absolute expression}
4816 Assembles the following section of code if the argument is not equal to zero
4817 (in other words, this is equivalent to @code{.if}).
4819 @cindex @code{ifnes} directive
4820 @item .ifnes @var{string1},@var{string2}
4821 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4822 following section of code if the two strings are not the same.
4826 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4828 @cindex @code{incbin} directive
4829 @cindex binary files, including
4830 The @code{incbin} directive includes @var{file} verbatim at the current
4831 location. You can control the search paths used with the @samp{-I} command-line
4832 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4835 The @var{skip} argument skips a number of bytes from the start of the
4836 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4837 read. Note that the data is not aligned in any way, so it is the user's
4838 responsibility to make sure that proper alignment is provided both before and
4839 after the @code{incbin} directive.
4842 @section @code{.include "@var{file}"}
4844 @cindex @code{include} directive
4845 @cindex supporting files, including
4846 @cindex files, including
4847 This directive provides a way to include supporting files at specified
4848 points in your source program. The code from @var{file} is assembled as
4849 if it followed the point of the @code{.include}; when the end of the
4850 included file is reached, assembly of the original file continues. You
4851 can control the search paths used with the @samp{-I} command-line option
4852 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4856 @section @code{.int @var{expressions}}
4858 @cindex @code{int} directive
4859 @cindex integers, 32-bit
4860 Expect zero or more @var{expressions}, of any section, separated by commas.
4861 For each expression, emit a number that, at run time, is the value of that
4862 expression. The byte order and bit size of the number depends on what kind
4863 of target the assembly is for.
4867 On most forms of the H8/300, @code{.int} emits 16-bit
4868 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4875 @section @code{.internal @var{names}}
4877 @cindex @code{internal} directive
4879 This is one of the ELF visibility directives. The other two are
4880 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4881 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4883 This directive overrides the named symbols default visibility (which is set by
4884 their binding: local, global or weak). The directive sets the visibility to
4885 @code{internal} which means that the symbols are considered to be @code{hidden}
4886 (i.e., not visible to other components), and that some extra, processor specific
4887 processing must also be performed upon the symbols as well.
4891 @section @code{.irp @var{symbol},@var{values}}@dots{}
4893 @cindex @code{irp} directive
4894 Evaluate a sequence of statements assigning different values to @var{symbol}.
4895 The sequence of statements starts at the @code{.irp} directive, and is
4896 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4897 set to @var{value}, and the sequence of statements is assembled. If no
4898 @var{value} is listed, the sequence of statements is assembled once, with
4899 @var{symbol} set to the null string. To refer to @var{symbol} within the
4900 sequence of statements, use @var{\symbol}.
4902 For example, assembling
4910 is equivalent to assembling
4918 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4921 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4923 @cindex @code{irpc} directive
4924 Evaluate a sequence of statements assigning different values to @var{symbol}.
4925 The sequence of statements starts at the @code{.irpc} directive, and is
4926 terminated by an @code{.endr} directive. For each character in @var{value},
4927 @var{symbol} is set to the character, and the sequence of statements is
4928 assembled. If no @var{value} is listed, the sequence of statements is
4929 assembled once, with @var{symbol} set to the null string. To refer to
4930 @var{symbol} within the sequence of statements, use @var{\symbol}.
4932 For example, assembling
4940 is equivalent to assembling
4948 For some caveats with the spelling of @var{symbol}, see also the discussion
4952 @section @code{.lcomm @var{symbol} , @var{length}}
4954 @cindex @code{lcomm} directive
4955 @cindex local common symbols
4956 @cindex symbols, local common
4957 Reserve @var{length} (an absolute expression) bytes for a local common
4958 denoted by @var{symbol}. The section and value of @var{symbol} are
4959 those of the new local common. The addresses are allocated in the bss
4960 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4961 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4962 not visible to @code{@value{LD}}.
4965 Some targets permit a third argument to be used with @code{.lcomm}. This
4966 argument specifies the desired alignment of the symbol in the bss section.
4970 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4971 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4975 @section @code{.lflags}
4977 @cindex @code{lflags} directive (ignored)
4978 @command{@value{AS}} accepts this directive, for compatibility with other
4979 assemblers, but ignores it.
4981 @ifclear no-line-dir
4983 @section @code{.line @var{line-number}}
4985 @cindex @code{line} directive
4986 @cindex logical line number
4988 Change the logical line number. @var{line-number} must be an absolute
4989 expression. The next line has that logical line number. Therefore any other
4990 statements on the current line (after a statement separator character) are
4991 reported as on logical line number @var{line-number} @minus{} 1. One day
4992 @command{@value{AS}} will no longer support this directive: it is recognized only
4993 for compatibility with existing assembler programs.
4996 Even though this is a directive associated with the @code{a.out} or
4997 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4998 when producing COFF output, and treats @samp{.line} as though it
4999 were the COFF @samp{.ln} @emph{if} it is found outside a
5000 @code{.def}/@code{.endef} pair.
5002 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5003 used by compilers to generate auxiliary symbol information for
5008 @section @code{.linkonce [@var{type}]}
5010 @cindex @code{linkonce} directive
5011 @cindex common sections
5012 Mark the current section so that the linker only includes a single copy of it.
5013 This may be used to include the same section in several different object files,
5014 but ensure that the linker will only include it once in the final output file.
5015 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5016 Duplicate sections are detected based on the section name, so it should be
5019 This directive is only supported by a few object file formats; as of this
5020 writing, the only object file format which supports it is the Portable
5021 Executable format used on Windows NT.
5023 The @var{type} argument is optional. If specified, it must be one of the
5024 following strings. For example:
5028 Not all types may be supported on all object file formats.
5032 Silently discard duplicate sections. This is the default.
5035 Warn if there are duplicate sections, but still keep only one copy.
5038 Warn if any of the duplicates have different sizes.
5041 Warn if any of the duplicates do not have exactly the same contents.
5045 @section @code{.list}
5047 @cindex @code{list} directive
5048 @cindex listing control, turning on
5049 Control (in conjunction with the @code{.nolist} directive) whether or
5050 not assembly listings are generated. These two directives maintain an
5051 internal counter (which is zero initially). @code{.list} increments the
5052 counter, and @code{.nolist} decrements it. Assembly listings are
5053 generated whenever the counter is greater than zero.
5055 By default, listings are disabled. When you enable them (with the
5056 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5057 the initial value of the listing counter is one.
5060 @section @code{.ln @var{line-number}}
5062 @cindex @code{ln} directive
5063 @ifclear no-line-dir
5064 @samp{.ln} is a synonym for @samp{.line}.
5067 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5068 must be an absolute expression. The next line has that logical
5069 line number, so any other statements on the current line (after a
5070 statement separator character @code{;}) are reported as on logical
5071 line number @var{line-number} @minus{} 1.
5074 This directive is accepted, but ignored, when @command{@value{AS}} is
5075 configured for @code{b.out}; its effect is only associated with COFF
5081 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5082 @cindex @code{loc} directive
5083 When emitting DWARF2 line number information,
5084 the @code{.loc} directive will add a row to the @code{.debug_line} line
5085 number matrix corresponding to the immediately following assembly
5086 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5087 arguments will be applied to the @code{.debug_line} state machine before
5090 The @var{options} are a sequence of the following tokens in any order:
5094 This option will set the @code{basic_block} register in the
5095 @code{.debug_line} state machine to @code{true}.
5098 This option will set the @code{prologue_end} register in the
5099 @code{.debug_line} state machine to @code{true}.
5101 @item epilogue_begin
5102 This option will set the @code{epilogue_begin} register in the
5103 @code{.debug_line} state machine to @code{true}.
5105 @item is_stmt @var{value}
5106 This option will set the @code{is_stmt} register in the
5107 @code{.debug_line} state machine to @code{value}, which must be
5110 @item isa @var{value}
5111 This directive will set the @code{isa} register in the @code{.debug_line}
5112 state machine to @var{value}, which must be an unsigned integer.
5116 @node Loc_mark_labels
5117 @section @code{.loc_mark_labels @var{enable}}
5118 @cindex @code{loc_mark_labels} directive
5119 When emitting DWARF2 line number information,
5120 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5121 to the @code{.debug_line} line number matrix with the @code{basic_block}
5122 register in the state machine set whenever a code label is seen.
5123 The @var{enable} argument should be either 1 or 0, to enable or disable
5124 this function respectively.
5128 @section @code{.local @var{names}}
5130 @cindex @code{local} directive
5131 This directive, which is available for ELF targets, marks each symbol in
5132 the comma-separated list of @code{names} as a local symbol so that it
5133 will not be externally visible. If the symbols do not already exist,
5134 they will be created.
5136 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5137 accept an alignment argument, which is the case for most ELF targets,
5138 the @code{.local} directive can be used in combination with @code{.comm}
5139 (@pxref{Comm}) to define aligned local common data.
5143 @section @code{.long @var{expressions}}
5145 @cindex @code{long} directive
5146 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5149 @c no one seems to know what this is for or whether this description is
5150 @c what it really ought to do
5152 @section @code{.lsym @var{symbol}, @var{expression}}
5154 @cindex @code{lsym} directive
5155 @cindex symbol, not referenced in assembly
5156 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5157 the hash table, ensuring it cannot be referenced by name during the
5158 rest of the assembly. This sets the attributes of the symbol to be
5159 the same as the expression value:
5161 @var{other} = @var{descriptor} = 0
5162 @var{type} = @r{(section of @var{expression})}
5163 @var{value} = @var{expression}
5166 The new symbol is not flagged as external.
5170 @section @code{.macro}
5173 The commands @code{.macro} and @code{.endm} allow you to define macros that
5174 generate assembly output. For example, this definition specifies a macro
5175 @code{sum} that puts a sequence of numbers into memory:
5178 .macro sum from=0, to=5
5187 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5199 @item .macro @var{macname}
5200 @itemx .macro @var{macname} @var{macargs} @dots{}
5201 @cindex @code{macro} directive
5202 Begin the definition of a macro called @var{macname}. If your macro
5203 definition requires arguments, specify their names after the macro name,
5204 separated by commas or spaces. You can qualify the macro argument to
5205 indicate whether all invocations must specify a non-blank value (through
5206 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5207 (through @samp{:@code{vararg}}). You can supply a default value for any
5208 macro argument by following the name with @samp{=@var{deflt}}. You
5209 cannot define two macros with the same @var{macname} unless it has been
5210 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5211 definitions. For example, these are all valid @code{.macro} statements:
5215 Begin the definition of a macro called @code{comm}, which takes no
5218 @item .macro plus1 p, p1
5219 @itemx .macro plus1 p p1
5220 Either statement begins the definition of a macro called @code{plus1},
5221 which takes two arguments; within the macro definition, write
5222 @samp{\p} or @samp{\p1} to evaluate the arguments.
5224 @item .macro reserve_str p1=0 p2
5225 Begin the definition of a macro called @code{reserve_str}, with two
5226 arguments. The first argument has a default value, but not the second.
5227 After the definition is complete, you can call the macro either as
5228 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5229 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5230 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5231 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5233 @item .macro m p1:req, p2=0, p3:vararg
5234 Begin the definition of a macro called @code{m}, with at least three
5235 arguments. The first argument must always have a value specified, but
5236 not the second, which instead has a default value. The third formal
5237 will get assigned all remaining arguments specified at invocation time.
5239 When you call a macro, you can specify the argument values either by
5240 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5241 @samp{sum to=17, from=9}.
5245 Note that since each of the @var{macargs} can be an identifier exactly
5246 as any other one permitted by the target architecture, there may be
5247 occasional problems if the target hand-crafts special meanings to certain
5248 characters when they occur in a special position. For example, if the colon
5249 (@code{:}) is generally permitted to be part of a symbol name, but the
5250 architecture specific code special-cases it when occurring as the final
5251 character of a symbol (to denote a label), then the macro parameter
5252 replacement code will have no way of knowing that and consider the whole
5253 construct (including the colon) an identifier, and check only this
5254 identifier for being the subject to parameter substitution. So for example
5255 this macro definition:
5263 might not work as expected. Invoking @samp{label foo} might not create a label
5264 called @samp{foo} but instead just insert the text @samp{\l:} into the
5265 assembler source, probably generating an error about an unrecognised
5268 Similarly problems might occur with the period character (@samp{.})
5269 which is often allowed inside opcode names (and hence identifier names). So
5270 for example constructing a macro to build an opcode from a base name and a
5271 length specifier like this:
5274 .macro opcode base length
5279 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5280 instruction but instead generate some kind of error as the assembler tries to
5281 interpret the text @samp{\base.\length}.
5283 There are several possible ways around this problem:
5286 @item Insert white space
5287 If it is possible to use white space characters then this is the simplest
5296 @item Use @samp{\()}
5297 The string @samp{\()} can be used to separate the end of a macro argument from
5298 the following text. eg:
5301 .macro opcode base length
5306 @item Use the alternate macro syntax mode
5307 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5308 used as a separator. eg:
5318 Note: this problem of correctly identifying string parameters to pseudo ops
5319 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5320 and @code{.irpc} (@pxref{Irpc}) as well.
5323 @cindex @code{endm} directive
5324 Mark the end of a macro definition.
5327 @cindex @code{exitm} directive
5328 Exit early from the current macro definition.
5330 @cindex number of macros executed
5331 @cindex macros, count executed
5333 @command{@value{AS}} maintains a counter of how many macros it has
5334 executed in this pseudo-variable; you can copy that number to your
5335 output with @samp{\@@}, but @emph{only within a macro definition}.
5337 @item LOCAL @var{name} [ , @dots{} ]
5338 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5339 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5340 @xref{Altmacro,,@code{.altmacro}}.
5344 @section @code{.mri @var{val}}
5346 @cindex @code{mri} directive
5347 @cindex MRI mode, temporarily
5348 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5349 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5350 affects code assembled until the next @code{.mri} directive, or until the end
5351 of the file. @xref{M, MRI mode, MRI mode}.
5354 @section @code{.noaltmacro}
5355 Disable alternate macro mode. @xref{Altmacro}.
5358 @section @code{.nolist}
5360 @cindex @code{nolist} directive
5361 @cindex listing control, turning off
5362 Control (in conjunction with the @code{.list} directive) whether or
5363 not assembly listings are generated. These two directives maintain an
5364 internal counter (which is zero initially). @code{.list} increments the
5365 counter, and @code{.nolist} decrements it. Assembly listings are
5366 generated whenever the counter is greater than zero.
5369 @section @code{.octa @var{bignums}}
5371 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5372 @cindex @code{octa} directive
5373 @cindex integer, 16-byte
5374 @cindex sixteen byte integer
5375 This directive expects zero or more bignums, separated by commas. For each
5376 bignum, it emits a 16-byte integer.
5378 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5379 hence @emph{octa}-word for 16 bytes.
5382 @section @code{.org @var{new-lc} , @var{fill}}
5384 @cindex @code{org} directive
5385 @cindex location counter, advancing
5386 @cindex advancing location counter
5387 @cindex current address, advancing
5388 Advance the location counter of the current section to
5389 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5390 expression with the same section as the current subsection. That is,
5391 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5392 wrong section, the @code{.org} directive is ignored. To be compatible
5393 with former assemblers, if the section of @var{new-lc} is absolute,
5394 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5395 is the same as the current subsection.
5397 @code{.org} may only increase the location counter, or leave it
5398 unchanged; you cannot use @code{.org} to move the location counter
5401 @c double negative used below "not undefined" because this is a specific
5402 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5403 @c section. doc@cygnus.com 18feb91
5404 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5405 may not be undefined. If you really detest this restriction we eagerly await
5406 a chance to share your improved assembler.
5408 Beware that the origin is relative to the start of the section, not
5409 to the start of the subsection. This is compatible with other
5410 people's assemblers.
5412 When the location counter (of the current subsection) is advanced, the
5413 intervening bytes are filled with @var{fill} which should be an
5414 absolute expression. If the comma and @var{fill} are omitted,
5415 @var{fill} defaults to zero.
5418 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5420 @cindex padding the location counter given a power of two
5421 @cindex @code{p2align} directive
5422 Pad the location counter (in the current subsection) to a particular
5423 storage boundary. The first expression (which must be absolute) is the
5424 number of low-order zero bits the location counter must have after
5425 advancement. For example @samp{.p2align 3} advances the location
5426 counter until it a multiple of 8. If the location counter is already a
5427 multiple of 8, no change is needed.
5429 The second expression (also absolute) gives the fill value to be stored in the
5430 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5431 padding bytes are normally zero. However, on some systems, if the section is
5432 marked as containing code and the fill value is omitted, the space is filled
5433 with no-op instructions.
5435 The third expression is also absolute, and is also optional. If it is present,
5436 it is the maximum number of bytes that should be skipped by this alignment
5437 directive. If doing the alignment would require skipping more bytes than the
5438 specified maximum, then the alignment is not done at all. You can omit the
5439 fill value (the second argument) entirely by simply using two commas after the
5440 required alignment; this can be useful if you want the alignment to be filled
5441 with no-op instructions when appropriate.
5443 @cindex @code{p2alignw} directive
5444 @cindex @code{p2alignl} directive
5445 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5446 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5447 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5448 fill pattern as a four byte longword value. For example, @code{.p2alignw
5449 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5450 filled in with the value 0x368d (the exact placement of the bytes depends upon
5451 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5456 @section @code{.popsection}
5458 @cindex @code{popsection} directive
5459 @cindex Section Stack
5460 This is one of the ELF section stack manipulation directives. The others are
5461 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5462 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5465 This directive replaces the current section (and subsection) with the top
5466 section (and subsection) on the section stack. This section is popped off the
5472 @section @code{.previous}
5474 @cindex @code{previous} directive
5475 @cindex Section Stack
5476 This is one of the ELF section stack manipulation directives. The others are
5477 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5478 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5479 (@pxref{PopSection}).
5481 This directive swaps the current section (and subsection) with most recently
5482 referenced section/subsection pair prior to this one. Multiple
5483 @code{.previous} directives in a row will flip between two sections (and their
5484 subsections). For example:
5496 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5502 # Now in section A subsection 1
5506 # Now in section B subsection 0
5509 # Now in section B subsection 1
5512 # Now in section B subsection 0
5516 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5517 section B and 0x9abc into subsection 1 of section B.
5519 In terms of the section stack, this directive swaps the current section with
5520 the top section on the section stack.
5524 @section @code{.print @var{string}}
5526 @cindex @code{print} directive
5527 @command{@value{AS}} will print @var{string} on the standard output during
5528 assembly. You must put @var{string} in double quotes.
5532 @section @code{.protected @var{names}}
5534 @cindex @code{protected} directive
5536 This is one of the ELF visibility directives. The other two are
5537 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5539 This directive overrides the named symbols default visibility (which is set by
5540 their binding: local, global or weak). The directive sets the visibility to
5541 @code{protected} which means that any references to the symbols from within the
5542 components that defines them must be resolved to the definition in that
5543 component, even if a definition in another component would normally preempt
5548 @section @code{.psize @var{lines} , @var{columns}}
5550 @cindex @code{psize} directive
5551 @cindex listing control: paper size
5552 @cindex paper size, for listings
5553 Use this directive to declare the number of lines---and, optionally, the
5554 number of columns---to use for each page, when generating listings.
5556 If you do not use @code{.psize}, listings use a default line-count
5557 of 60. You may omit the comma and @var{columns} specification; the
5558 default width is 200 columns.
5560 @command{@value{AS}} generates formfeeds whenever the specified number of
5561 lines is exceeded (or whenever you explicitly request one, using
5564 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5565 those explicitly specified with @code{.eject}.
5568 @section @code{.purgem @var{name}}
5570 @cindex @code{purgem} directive
5571 Undefine the macro @var{name}, so that later uses of the string will not be
5572 expanded. @xref{Macro}.
5576 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5578 @cindex @code{pushsection} directive
5579 @cindex Section Stack
5580 This is one of the ELF section stack manipulation directives. The others are
5581 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5582 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5585 This directive pushes the current section (and subsection) onto the
5586 top of the section stack, and then replaces the current section and
5587 subsection with @code{name} and @code{subsection}. The optional
5588 @code{flags}, @code{type} and @code{arguments} are treated the same
5589 as in the @code{.section} (@pxref{Section}) directive.
5593 @section @code{.quad @var{bignums}}
5595 @cindex @code{quad} directive
5596 @code{.quad} expects zero or more bignums, separated by commas. For
5597 each bignum, it emits
5599 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5600 warning message; and just takes the lowest order 8 bytes of the bignum.
5601 @cindex eight-byte integer
5602 @cindex integer, 8-byte
5604 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5605 hence @emph{quad}-word for 8 bytes.
5608 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5609 warning message; and just takes the lowest order 16 bytes of the bignum.
5610 @cindex sixteen-byte integer
5611 @cindex integer, 16-byte
5615 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5617 @cindex @code{reloc} directive
5618 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5619 @var{expression}. If @var{offset} is a number, the relocation is generated in
5620 the current section. If @var{offset} is an expression that resolves to a
5621 symbol plus offset, the relocation is generated in the given symbol's section.
5622 @var{expression}, if present, must resolve to a symbol plus addend or to an
5623 absolute value, but note that not all targets support an addend. e.g. ELF REL
5624 targets such as i386 store an addend in the section contents rather than in the
5625 relocation. This low level interface does not support addends stored in the
5629 @section @code{.rept @var{count}}
5631 @cindex @code{rept} directive
5632 Repeat the sequence of lines between the @code{.rept} directive and the next
5633 @code{.endr} directive @var{count} times.
5635 For example, assembling
5643 is equivalent to assembling
5652 @section @code{.sbttl "@var{subheading}"}
5654 @cindex @code{sbttl} directive
5655 @cindex subtitles for listings
5656 @cindex listing control: subtitle
5657 Use @var{subheading} as the title (third line, immediately after the
5658 title line) when generating assembly listings.
5660 This directive affects subsequent pages, as well as the current page if
5661 it appears within ten lines of the top of a page.
5665 @section @code{.scl @var{class}}
5667 @cindex @code{scl} directive
5668 @cindex symbol storage class (COFF)
5669 @cindex COFF symbol storage class
5670 Set the storage-class value for a symbol. This directive may only be
5671 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5672 whether a symbol is static or external, or it may record further
5673 symbolic debugging information.
5676 The @samp{.scl} directive is primarily associated with COFF output; when
5677 configured to generate @code{b.out} output format, @command{@value{AS}}
5678 accepts this directive but ignores it.
5684 @section @code{.section @var{name}}
5686 @cindex named section
5687 Use the @code{.section} directive to assemble the following code into a section
5690 This directive is only supported for targets that actually support arbitrarily
5691 named sections; on @code{a.out} targets, for example, it is not accepted, even
5692 with a standard @code{a.out} section name.
5696 @c only print the extra heading if both COFF and ELF are set
5697 @subheading COFF Version
5700 @cindex @code{section} directive (COFF version)
5701 For COFF targets, the @code{.section} directive is used in one of the following
5705 .section @var{name}[, "@var{flags}"]
5706 .section @var{name}[, @var{subsection}]
5709 If the optional argument is quoted, it is taken as flags to use for the
5710 section. Each flag is a single character. The following flags are recognized:
5713 bss section (uninitialized data)
5715 section is not loaded
5725 shared section (meaningful for PE targets)
5727 ignored. (For compatibility with the ELF version)
5730 If no flags are specified, the default flags depend upon the section name. If
5731 the section name is not recognized, the default will be for the section to be
5732 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5733 from the section, rather than adding them, so if they are used on their own it
5734 will be as if no flags had been specified at all.
5736 If the optional argument to the @code{.section} directive is not quoted, it is
5737 taken as a subsection number (@pxref{Sub-Sections}).
5742 @c only print the extra heading if both COFF and ELF are set
5743 @subheading ELF Version
5746 @cindex Section Stack
5747 This is one of the ELF section stack manipulation directives. The others are
5748 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5749 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5750 @code{.previous} (@pxref{Previous}).
5752 @cindex @code{section} directive (ELF version)
5753 For ELF targets, the @code{.section} directive is used like this:
5756 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5759 The optional @var{flags} argument is a quoted string which may contain any
5760 combination of the following characters:
5763 section is allocatable
5767 section is executable
5769 section is mergeable
5771 section contains zero terminated strings
5773 section is a member of a section group
5775 section is used for thread-local-storage
5778 The optional @var{type} argument may contain one of the following constants:
5781 section contains data
5783 section does not contain data (i.e., section only occupies space)
5785 section contains data which is used by things other than the program
5787 section contains an array of pointers to init functions
5789 section contains an array of pointers to finish functions
5790 @item @@preinit_array
5791 section contains an array of pointers to pre-init functions
5794 Many targets only support the first three section types.
5796 Note on targets where the @code{@@} character is the start of a comment (eg
5797 ARM) then another character is used instead. For example the ARM port uses the
5800 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5801 be specified as well as an extra argument---@var{entsize}---like this:
5804 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5807 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5808 constants, each @var{entsize} octets long. Sections with both @code{M} and
5809 @code{S} must contain zero terminated strings where each character is
5810 @var{entsize} bytes long. The linker may remove duplicates within sections with
5811 the same name, same entity size and same flags. @var{entsize} must be an
5812 absolute expression.
5814 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5815 be present along with an additional field like this:
5818 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5821 The @var{GroupName} field specifies the name of the section group to which this
5822 particular section belongs. The optional linkage field can contain:
5825 indicates that only one copy of this section should be retained
5830 Note: if both the @var{M} and @var{G} flags are present then the fields for
5831 the Merge flag should come first, like this:
5834 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5837 If no flags are specified, the default flags depend upon the section name. If
5838 the section name is not recognized, the default will be for the section to have
5839 none of the above flags: it will not be allocated in memory, nor writable, nor
5840 executable. The section will contain data.
5842 For ELF targets, the assembler supports another type of @code{.section}
5843 directive for compatibility with the Solaris assembler:
5846 .section "@var{name}"[, @var{flags}...]
5849 Note that the section name is quoted. There may be a sequence of comma
5853 section is allocatable
5857 section is executable
5859 section is used for thread local storage
5862 This directive replaces the current section and subsection. See the
5863 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5864 some examples of how this directive and the other section stack directives
5870 @section @code{.set @var{symbol}, @var{expression}}
5872 @cindex @code{set} directive
5873 @cindex symbol value, setting
5874 Set the value of @var{symbol} to @var{expression}. This
5875 changes @var{symbol}'s value and type to conform to
5876 @var{expression}. If @var{symbol} was flagged as external, it remains
5877 flagged (@pxref{Symbol Attributes}).
5879 You may @code{.set} a symbol many times in the same assembly.
5881 If you @code{.set} a global symbol, the value stored in the object
5882 file is the last value stored into it.
5885 The syntax for @code{set} on the HPPA is
5886 @samp{@var{symbol} .set @var{expression}}.
5890 On Z80 @code{set} is a real instruction, use
5891 @samp{@var{symbol} defl @var{expression}} instead.
5895 @section @code{.short @var{expressions}}
5897 @cindex @code{short} directive
5899 @code{.short} is normally the same as @samp{.word}.
5900 @xref{Word,,@code{.word}}.
5902 In some configurations, however, @code{.short} and @code{.word} generate
5903 numbers of different lengths. @xref{Machine Dependencies}.
5907 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5910 This expects zero or more @var{expressions}, and emits
5911 a 16 bit number for each.
5916 @section @code{.single @var{flonums}}
5918 @cindex @code{single} directive
5919 @cindex floating point numbers (single)
5920 This directive assembles zero or more flonums, separated by commas. It
5921 has the same effect as @code{.float}.
5923 The exact kind of floating point numbers emitted depends on how
5924 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5928 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5929 numbers in @sc{ieee} format.
5935 @section @code{.size}
5937 This directive is used to set the size associated with a symbol.
5941 @c only print the extra heading if both COFF and ELF are set
5942 @subheading COFF Version
5945 @cindex @code{size} directive (COFF version)
5946 For COFF targets, the @code{.size} directive is only permitted inside
5947 @code{.def}/@code{.endef} pairs. It is used like this:
5950 .size @var{expression}
5954 @samp{.size} is only meaningful when generating COFF format output; when
5955 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5962 @c only print the extra heading if both COFF and ELF are set
5963 @subheading ELF Version
5966 @cindex @code{size} directive (ELF version)
5967 For ELF targets, the @code{.size} directive is used like this:
5970 .size @var{name} , @var{expression}
5973 This directive sets the size associated with a symbol @var{name}.
5974 The size in bytes is computed from @var{expression} which can make use of label
5975 arithmetic. This directive is typically used to set the size of function
5980 @ifclear no-space-dir
5982 @section @code{.skip @var{size} , @var{fill}}
5984 @cindex @code{skip} directive
5985 @cindex filling memory
5986 This directive emits @var{size} bytes, each of value @var{fill}. Both
5987 @var{size} and @var{fill} are absolute expressions. If the comma and
5988 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5993 @section @code{.sleb128 @var{expressions}}
5995 @cindex @code{sleb128} directive
5996 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5997 compact, variable length representation of numbers used by the DWARF
5998 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6000 @ifclear no-space-dir
6002 @section @code{.space @var{size} , @var{fill}}
6004 @cindex @code{space} directive
6005 @cindex filling memory
6006 This directive emits @var{size} bytes, each of value @var{fill}. Both
6007 @var{size} and @var{fill} are absolute expressions. If the comma
6008 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6013 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6014 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6015 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6016 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6024 @section @code{.stabd, .stabn, .stabs}
6026 @cindex symbolic debuggers, information for
6027 @cindex @code{stab@var{x}} directives
6028 There are three directives that begin @samp{.stab}.
6029 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6030 The symbols are not entered in the @command{@value{AS}} hash table: they
6031 cannot be referenced elsewhere in the source file.
6032 Up to five fields are required:
6036 This is the symbol's name. It may contain any character except
6037 @samp{\000}, so is more general than ordinary symbol names. Some
6038 debuggers used to code arbitrarily complex structures into symbol names
6042 An absolute expression. The symbol's type is set to the low 8 bits of
6043 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6044 and debuggers choke on silly bit patterns.
6047 An absolute expression. The symbol's ``other'' attribute is set to the
6048 low 8 bits of this expression.
6051 An absolute expression. The symbol's descriptor is set to the low 16
6052 bits of this expression.
6055 An absolute expression which becomes the symbol's value.
6058 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6059 or @code{.stabs} statement, the symbol has probably already been created;
6060 you get a half-formed symbol in your object file. This is
6061 compatible with earlier assemblers!
6064 @cindex @code{stabd} directive
6065 @item .stabd @var{type} , @var{other} , @var{desc}
6067 The ``name'' of the symbol generated is not even an empty string.
6068 It is a null pointer, for compatibility. Older assemblers used a
6069 null pointer so they didn't waste space in object files with empty
6072 The symbol's value is set to the location counter,
6073 relocatably. When your program is linked, the value of this symbol
6074 is the address of the location counter when the @code{.stabd} was
6077 @cindex @code{stabn} directive
6078 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6079 The name of the symbol is set to the empty string @code{""}.
6081 @cindex @code{stabs} directive
6082 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6083 All five fields are specified.
6089 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6090 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6092 @cindex string, copying to object file
6093 @cindex string8, copying to object file
6094 @cindex string16, copying to object file
6095 @cindex string32, copying to object file
6096 @cindex string64, copying to object file
6097 @cindex @code{string} directive
6098 @cindex @code{string8} directive
6099 @cindex @code{string16} directive
6100 @cindex @code{string32} directive
6101 @cindex @code{string64} directive
6103 Copy the characters in @var{str} to the object file. You may specify more than
6104 one string to copy, separated by commas. Unless otherwise specified for a
6105 particular machine, the assembler marks the end of each string with a 0 byte.
6106 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6108 The variants @code{string16}, @code{string32} and @code{string64} differ from
6109 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6110 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6111 are stored in target endianness byte order.
6117 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6118 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6123 @section @code{.struct @var{expression}}
6125 @cindex @code{struct} directive
6126 Switch to the absolute section, and set the section offset to @var{expression},
6127 which must be an absolute expression. You might use this as follows:
6136 This would define the symbol @code{field1} to have the value 0, the symbol
6137 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6138 value 8. Assembly would be left in the absolute section, and you would need to
6139 use a @code{.section} directive of some sort to change to some other section
6140 before further assembly.
6144 @section @code{.subsection @var{name}}
6146 @cindex @code{subsection} directive
6147 @cindex Section Stack
6148 This is one of the ELF section stack manipulation directives. The others are
6149 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6150 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6153 This directive replaces the current subsection with @code{name}. The current
6154 section is not changed. The replaced subsection is put onto the section stack
6155 in place of the then current top of stack subsection.
6160 @section @code{.symver}
6161 @cindex @code{symver} directive
6162 @cindex symbol versioning
6163 @cindex versions of symbols
6164 Use the @code{.symver} directive to bind symbols to specific version nodes
6165 within a source file. This is only supported on ELF platforms, and is
6166 typically used when assembling files to be linked into a shared library.
6167 There are cases where it may make sense to use this in objects to be bound
6168 into an application itself so as to override a versioned symbol from a
6171 For ELF targets, the @code{.symver} directive can be used like this:
6173 .symver @var{name}, @var{name2@@nodename}
6175 If the symbol @var{name} is defined within the file
6176 being assembled, the @code{.symver} directive effectively creates a symbol
6177 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6178 just don't try and create a regular alias is that the @var{@@} character isn't
6179 permitted in symbol names. The @var{name2} part of the name is the actual name
6180 of the symbol by which it will be externally referenced. The name @var{name}
6181 itself is merely a name of convenience that is used so that it is possible to
6182 have definitions for multiple versions of a function within a single source
6183 file, and so that the compiler can unambiguously know which version of a
6184 function is being mentioned. The @var{nodename} portion of the alias should be
6185 the name of a node specified in the version script supplied to the linker when
6186 building a shared library. If you are attempting to override a versioned
6187 symbol from a shared library, then @var{nodename} should correspond to the
6188 nodename of the symbol you are trying to override.
6190 If the symbol @var{name} is not defined within the file being assembled, all
6191 references to @var{name} will be changed to @var{name2@@nodename}. If no
6192 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6195 Another usage of the @code{.symver} directive is:
6197 .symver @var{name}, @var{name2@@@@nodename}
6199 In this case, the symbol @var{name} must exist and be defined within
6200 the file being assembled. It is similar to @var{name2@@nodename}. The
6201 difference is @var{name2@@@@nodename} will also be used to resolve
6202 references to @var{name2} by the linker.
6204 The third usage of the @code{.symver} directive is:
6206 .symver @var{name}, @var{name2@@@@@@nodename}
6208 When @var{name} is not defined within the
6209 file being assembled, it is treated as @var{name2@@nodename}. When
6210 @var{name} is defined within the file being assembled, the symbol
6211 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6216 @section @code{.tag @var{structname}}
6218 @cindex COFF structure debugging
6219 @cindex structure debugging, COFF
6220 @cindex @code{tag} directive
6221 This directive is generated by compilers to include auxiliary debugging
6222 information in the symbol table. It is only permitted inside
6223 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6224 definitions in the symbol table with instances of those structures.
6227 @samp{.tag} is only used when generating COFF format output; when
6228 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6234 @section @code{.text @var{subsection}}
6236 @cindex @code{text} directive
6237 Tells @command{@value{AS}} to assemble the following statements onto the end of
6238 the text subsection numbered @var{subsection}, which is an absolute
6239 expression. If @var{subsection} is omitted, subsection number zero
6243 @section @code{.title "@var{heading}"}
6245 @cindex @code{title} directive
6246 @cindex listing control: title line
6247 Use @var{heading} as the title (second line, immediately after the
6248 source file name and pagenumber) when generating assembly listings.
6250 This directive affects subsequent pages, as well as the current page if
6251 it appears within ten lines of the top of a page.
6255 @section @code{.type}
6257 This directive is used to set the type of a symbol.
6261 @c only print the extra heading if both COFF and ELF are set
6262 @subheading COFF Version
6265 @cindex COFF symbol type
6266 @cindex symbol type, COFF
6267 @cindex @code{type} directive (COFF version)
6268 For COFF targets, this directive is permitted only within
6269 @code{.def}/@code{.endef} pairs. It is used like this:
6275 This records the integer @var{int} as the type attribute of a symbol table
6279 @samp{.type} is associated only with COFF format output; when
6280 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6281 directive but ignores it.
6287 @c only print the extra heading if both COFF and ELF are set
6288 @subheading ELF Version
6291 @cindex ELF symbol type
6292 @cindex symbol type, ELF
6293 @cindex @code{type} directive (ELF version)
6294 For ELF targets, the @code{.type} directive is used like this:
6297 .type @var{name} , @var{type description}
6300 This sets the type of symbol @var{name} to be either a
6301 function symbol or an object symbol. There are five different syntaxes
6302 supported for the @var{type description} field, in order to provide
6303 compatibility with various other assemblers.
6305 Because some of the characters used in these syntaxes (such as @samp{@@} and
6306 @samp{#}) are comment characters for some architectures, some of the syntaxes
6307 below do not work on all architectures. The first variant will be accepted by
6308 the GNU assembler on all architectures so that variant should be used for
6309 maximum portability, if you do not need to assemble your code with other
6312 The syntaxes supported are:
6315 .type <name> STT_<TYPE_IN_UPPER_CASE>
6316 .type <name>,#<type>
6317 .type <name>,@@<type>
6318 .type <name>,%<type>
6319 .type <name>,"<type>"
6322 The types supported are:
6327 Mark the symbol as being a function name.
6331 Mark the symbol as being a data object.
6335 Mark the symbol as being a thead-local data object.
6339 Mark the symbol as being a common data object.
6343 Does not mark the symbol in any way. It is supported just for completeness.
6347 Note: Some targets support extra types in addition to those listed above.
6353 @section @code{.uleb128 @var{expressions}}
6355 @cindex @code{uleb128} directive
6356 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6357 compact, variable length representation of numbers used by the DWARF
6358 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6362 @section @code{.val @var{addr}}
6364 @cindex @code{val} directive
6365 @cindex COFF value attribute
6366 @cindex value attribute, COFF
6367 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6368 records the address @var{addr} as the value attribute of a symbol table
6372 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6373 configured for @code{b.out}, it accepts this directive but ignores it.
6379 @section @code{.version "@var{string}"}
6381 @cindex @code{version} directive
6382 This directive creates a @code{.note} section and places into it an ELF
6383 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6388 @section @code{.vtable_entry @var{table}, @var{offset}}
6390 @cindex @code{vtable_entry} directive
6391 This directive finds or creates a symbol @code{table} and creates a
6392 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6395 @section @code{.vtable_inherit @var{child}, @var{parent}}
6397 @cindex @code{vtable_inherit} directive
6398 This directive finds the symbol @code{child} and finds or creates the symbol
6399 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6400 parent whose addend is the value of the child symbol. As a special case the
6401 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6405 @section @code{.warning "@var{string}"}
6406 @cindex warning directive
6407 Similar to the directive @code{.error}
6408 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6411 @section @code{.weak @var{names}}
6413 @cindex @code{weak} directive
6414 This directive sets the weak attribute on the comma separated list of symbol
6415 @code{names}. If the symbols do not already exist, they will be created.
6417 On COFF targets other than PE, weak symbols are a GNU extension. This
6418 directive sets the weak attribute on the comma separated list of symbol
6419 @code{names}. If the symbols do not already exist, they will be created.
6421 On the PE target, weak symbols are supported natively as weak aliases.
6422 When a weak symbol is created that is not an alias, GAS creates an
6423 alternate symbol to hold the default value.
6426 @section @code{.weakref @var{alias}, @var{target}}
6428 @cindex @code{weakref} directive
6429 This directive creates an alias to the target symbol that enables the symbol to
6430 be referenced with weak-symbol semantics, but without actually making it weak.
6431 If direct references or definitions of the symbol are present, then the symbol
6432 will not be weak, but if all references to it are through weak references, the
6433 symbol will be marked as weak in the symbol table.
6435 The effect is equivalent to moving all references to the alias to a separate
6436 assembly source file, renaming the alias to the symbol in it, declaring the
6437 symbol as weak there, and running a reloadable link to merge the object files
6438 resulting from the assembly of the new source file and the old source file that
6439 had the references to the alias removed.
6441 The alias itself never makes to the symbol table, and is entirely handled
6442 within the assembler.
6445 @section @code{.word @var{expressions}}
6447 @cindex @code{word} directive
6448 This directive expects zero or more @var{expressions}, of any section,
6449 separated by commas.
6452 For each expression, @command{@value{AS}} emits a 32-bit number.
6455 For each expression, @command{@value{AS}} emits a 16-bit number.
6460 The size of the number emitted, and its byte order,
6461 depend on what target computer the assembly is for.
6464 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6465 @c happen---32-bit addressability, period; no long/short jumps.
6466 @ifset DIFF-TBL-KLUGE
6467 @cindex difference tables altered
6468 @cindex altered difference tables
6470 @emph{Warning: Special Treatment to support Compilers}
6474 Machines with a 32-bit address space, but that do less than 32-bit
6475 addressing, require the following special treatment. If the machine of
6476 interest to you does 32-bit addressing (or doesn't require it;
6477 @pxref{Machine Dependencies}), you can ignore this issue.
6480 In order to assemble compiler output into something that works,
6481 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6482 Directives of the form @samp{.word sym1-sym2} are often emitted by
6483 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6484 directive of the form @samp{.word sym1-sym2}, and the difference between
6485 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6486 creates a @dfn{secondary jump table}, immediately before the next label.
6487 This secondary jump table is preceded by a short-jump to the
6488 first byte after the secondary table. This short-jump prevents the flow
6489 of control from accidentally falling into the new table. Inside the
6490 table is a long-jump to @code{sym2}. The original @samp{.word}
6491 contains @code{sym1} minus the address of the long-jump to
6494 If there were several occurrences of @samp{.word sym1-sym2} before the
6495 secondary jump table, all of them are adjusted. If there was a
6496 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6497 long-jump to @code{sym4} is included in the secondary jump table,
6498 and the @code{.word} directives are adjusted to contain @code{sym3}
6499 minus the address of the long-jump to @code{sym4}; and so on, for as many
6500 entries in the original jump table as necessary.
6503 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6504 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6505 assembly language programmers.
6508 @c end DIFF-TBL-KLUGE
6511 @section Deprecated Directives
6513 @cindex deprecated directives
6514 @cindex obsolescent directives
6515 One day these directives won't work.
6516 They are included for compatibility with older assemblers.
6523 @node Object Attributes
6524 @chapter Object Attributes
6525 @cindex object attributes
6527 @command{@value{AS}} assembles source files written for a specific architecture
6528 into object files for that architecture. But not all object files are alike.
6529 Many architectures support incompatible variations. For instance, floating
6530 point arguments might be passed in floating point registers if the object file
6531 requires hardware floating point support---or floating point arguments might be
6532 passed in integer registers if the object file supports processors with no
6533 hardware floating point unit. Or, if two objects are built for different
6534 generations of the same architecture, the combination may require the
6535 newer generation at run-time.
6537 This information is useful during and after linking. At link time,
6538 @command{@value{LD}} can warn about incompatible object files. After link
6539 time, tools like @command{gdb} can use it to process the linked file
6542 Compatibility information is recorded as a series of object attributes. Each
6543 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6544 string, and indicates who sets the meaning of the tag. The tag is an integer,
6545 and indicates what property the attribute describes. The value may be a string
6546 or an integer, and indicates how the property affects this object. Missing
6547 attributes are the same as attributes with a zero value or empty string value.
6549 Object attributes were developed as part of the ABI for the ARM Architecture.
6550 The file format is documented in @cite{ELF for the ARM Architecture}.
6553 * GNU Object Attributes:: @sc{gnu} Object Attributes
6554 * Defining New Object Attributes:: Defining New Object Attributes
6557 @node GNU Object Attributes
6558 @section @sc{gnu} Object Attributes
6560 The @code{.gnu_attribute} directive records an object attribute
6561 with vendor @samp{gnu}.
6563 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6564 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6565 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6566 2} is set for architecture-independent attributes and clear for
6567 architecture-dependent ones.
6569 @subsection Common @sc{gnu} attributes
6571 These attributes are valid on all architectures.
6574 @item Tag_compatibility (32)
6575 The compatibility attribute takes an integer flag value and a vendor name. If
6576 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6577 then the file is only compatible with the named toolchain. If it is greater
6578 than 1, the file can only be processed by other toolchains under some private
6579 arrangement indicated by the flag value and the vendor name.
6582 @subsection MIPS Attributes
6585 @item Tag_GNU_MIPS_ABI_FP (4)
6586 The floating-point ABI used by this object file. The value will be:
6590 0 for files not affected by the floating-point ABI.
6592 1 for files using the hardware floating-point with a standard double-precision
6595 2 for files using the hardware floating-point ABI with a single-precision FPU.
6597 3 for files using the software floating-point ABI.
6599 4 for files using the hardware floating-point ABI with 64-bit wide
6600 double-precision floating-point registers and 32-bit wide general
6605 @subsection PowerPC Attributes
6608 @item Tag_GNU_Power_ABI_FP (4)
6609 The floating-point ABI used by this object file. The value will be:
6613 0 for files not affected by the floating-point ABI.
6615 1 for files using double-precision hardware floating-point ABI.
6617 2 for files using the software floating-point ABI.
6619 3 for files using single-precision hardware floating-point ABI.
6622 @item Tag_GNU_Power_ABI_Vector (8)
6623 The vector ABI used by this object file. The value will be:
6627 0 for files not affected by the vector ABI.
6629 1 for files using general purpose registers to pass vectors.
6631 2 for files using AltiVec registers to pass vectors.
6633 3 for files using SPE registers to pass vectors.
6637 @node Defining New Object Attributes
6638 @section Defining New Object Attributes
6640 If you want to define a new @sc{gnu} object attribute, here are the places you
6641 will need to modify. New attributes should be discussed on the @samp{binutils}
6646 This manual, which is the official register of attributes.
6648 The header for your architecture @file{include/elf}, to define the tag.
6650 The @file{bfd} support file for your architecture, to merge the attribute
6651 and issue any appropriate link warnings.
6653 Test cases in @file{ld/testsuite} for merging and link warnings.
6655 @file{binutils/readelf.c} to display your attribute.
6657 GCC, if you want the compiler to mark the attribute automatically.
6663 @node Machine Dependencies
6664 @chapter Machine Dependent Features
6666 @cindex machine dependencies
6667 The machine instruction sets are (almost by definition) different on
6668 each machine where @command{@value{AS}} runs. Floating point representations
6669 vary as well, and @command{@value{AS}} often supports a few additional
6670 directives or command-line options for compatibility with other
6671 assemblers on a particular platform. Finally, some versions of
6672 @command{@value{AS}} support special pseudo-instructions for branch
6675 This chapter discusses most of these differences, though it does not
6676 include details on any machine's instruction set. For details on that
6677 subject, see the hardware manufacturer's manual.
6681 * Alpha-Dependent:: Alpha Dependent Features
6684 * ARC-Dependent:: ARC Dependent Features
6687 * ARM-Dependent:: ARM Dependent Features
6690 * AVR-Dependent:: AVR Dependent Features
6693 * BFIN-Dependent:: BFIN Dependent Features
6696 * CR16-Dependent:: CR16 Dependent Features
6699 * CRIS-Dependent:: CRIS Dependent Features
6702 * D10V-Dependent:: D10V Dependent Features
6705 * D30V-Dependent:: D30V Dependent Features
6708 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6711 * HPPA-Dependent:: HPPA Dependent Features
6714 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6717 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6720 * i860-Dependent:: Intel 80860 Dependent Features
6723 * i960-Dependent:: Intel 80960 Dependent Features
6726 * IA-64-Dependent:: Intel IA-64 Dependent Features
6729 * IP2K-Dependent:: IP2K Dependent Features
6732 * LM32-Dependent:: LM32 Dependent Features
6735 * M32C-Dependent:: M32C Dependent Features
6738 * M32R-Dependent:: M32R Dependent Features
6741 * M68K-Dependent:: M680x0 Dependent Features
6744 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6747 * MIPS-Dependent:: MIPS Dependent Features
6750 * MMIX-Dependent:: MMIX Dependent Features
6753 * MSP430-Dependent:: MSP430 Dependent Features
6756 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6757 * SH64-Dependent:: SuperH SH64 Dependent Features
6760 * PDP-11-Dependent:: PDP-11 Dependent Features
6763 * PJ-Dependent:: picoJava Dependent Features
6766 * PPC-Dependent:: PowerPC Dependent Features
6770 * SCORE-Dependent:: SCORE Dependent Features
6774 * S/390-Dependent:: IBM S/390 Dependent Features
6778 * Sparc-Dependent:: SPARC Dependent Features
6781 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6784 * V850-Dependent:: V850 Dependent Features
6787 * Xtensa-Dependent:: Xtensa Dependent Features
6790 * Z80-Dependent:: Z80 Dependent Features
6793 * Z8000-Dependent:: Z8000 Dependent Features
6796 * Vax-Dependent:: VAX Dependent Features
6803 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6804 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6805 @c peculiarity: to preserve cross-references, there must be a node called
6806 @c "Machine Dependencies". Hence the conditional nodenames in each
6807 @c major node below. Node defaulting in makeinfo requires adjacency of
6808 @c node and sectioning commands; hence the repetition of @chapter BLAH
6809 @c in both conditional blocks.
6812 @include c-alpha.texi
6828 @include c-bfin.texi
6832 @include c-cr16.texi
6836 @include c-cris.texi
6841 @node Machine Dependencies
6842 @chapter Machine Dependent Features
6844 The machine instruction sets are different on each Renesas chip family,
6845 and there are also some syntax differences among the families. This
6846 chapter describes the specific @command{@value{AS}} features for each
6850 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6851 * SH-Dependent:: Renesas SH Dependent Features
6858 @include c-d10v.texi
6862 @include c-d30v.texi
6866 @include c-h8300.texi
6870 @include c-hppa.texi
6874 @include c-i370.texi
6878 @include c-i386.texi
6882 @include c-i860.texi
6886 @include c-i960.texi
6890 @include c-ia64.texi
6894 @include c-ip2k.texi
6898 @include c-lm32.texi
6902 @include c-m32c.texi
6906 @include c-m32r.texi
6910 @include c-m68k.texi
6914 @include c-m68hc11.texi
6918 @include c-mips.texi
6922 @include c-mmix.texi
6926 @include c-msp430.texi
6930 @include c-ns32k.texi
6934 @include c-pdp11.texi
6947 @include c-score.texi
6952 @include c-s390.texi
6958 @include c-sh64.texi
6962 @include c-sparc.texi
6966 @include c-tic54x.texi
6982 @include c-v850.texi
6986 @include c-xtensa.texi
6990 @c reverse effect of @down at top of generic Machine-Dep chapter
6994 @node Reporting Bugs
6995 @chapter Reporting Bugs
6996 @cindex bugs in assembler
6997 @cindex reporting bugs in assembler
6999 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7001 Reporting a bug may help you by bringing a solution to your problem, or it may
7002 not. But in any case the principal function of a bug report is to help the
7003 entire community by making the next version of @command{@value{AS}} work better.
7004 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7006 In order for a bug report to serve its purpose, you must include the
7007 information that enables us to fix the bug.
7010 * Bug Criteria:: Have you found a bug?
7011 * Bug Reporting:: How to report bugs
7015 @section Have You Found a Bug?
7016 @cindex bug criteria
7018 If you are not sure whether you have found a bug, here are some guidelines:
7021 @cindex fatal signal
7022 @cindex assembler crash
7023 @cindex crash of assembler
7025 If the assembler gets a fatal signal, for any input whatever, that is a
7026 @command{@value{AS}} bug. Reliable assemblers never crash.
7028 @cindex error on valid input
7030 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7032 @cindex invalid input
7034 If @command{@value{AS}} does not produce an error message for invalid input, that
7035 is a bug. However, you should note that your idea of ``invalid input'' might
7036 be our idea of ``an extension'' or ``support for traditional practice''.
7039 If you are an experienced user of assemblers, your suggestions for improvement
7040 of @command{@value{AS}} are welcome in any case.
7044 @section How to Report Bugs
7046 @cindex assembler bugs, reporting
7048 A number of companies and individuals offer support for @sc{gnu} products. If
7049 you obtained @command{@value{AS}} from a support organization, we recommend you
7050 contact that organization first.
7052 You can find contact information for many support companies and
7053 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7057 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7061 The fundamental principle of reporting bugs usefully is this:
7062 @strong{report all the facts}. If you are not sure whether to state a
7063 fact or leave it out, state it!
7065 Often people omit facts because they think they know what causes the problem
7066 and assume that some details do not matter. Thus, you might assume that the
7067 name of a symbol you use in an example does not matter. Well, probably it does
7068 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7069 happens to fetch from the location where that name is stored in memory;
7070 perhaps, if the name were different, the contents of that location would fool
7071 the assembler into doing the right thing despite the bug. Play it safe and
7072 give a specific, complete example. That is the easiest thing for you to do,
7073 and the most helpful.
7075 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7076 it is new to us. Therefore, always write your bug reports on the assumption
7077 that the bug has not been reported previously.
7079 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7080 bell?'' This cannot help us fix a bug, so it is basically useless. We
7081 respond by asking for enough details to enable us to investigate.
7082 You might as well expedite matters by sending them to begin with.
7084 To enable us to fix the bug, you should include all these things:
7088 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7089 it with the @samp{--version} argument.
7091 Without this, we will not know whether there is any point in looking for
7092 the bug in the current version of @command{@value{AS}}.
7095 Any patches you may have applied to the @command{@value{AS}} source.
7098 The type of machine you are using, and the operating system name and
7102 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7106 The command arguments you gave the assembler to assemble your example and
7107 observe the bug. To guarantee you will not omit something important, list them
7108 all. A copy of the Makefile (or the output from make) is sufficient.
7110 If we were to try to guess the arguments, we would probably guess wrong
7111 and then we might not encounter the bug.
7114 A complete input file that will reproduce the bug. If the bug is observed when
7115 the assembler is invoked via a compiler, send the assembler source, not the
7116 high level language source. Most compilers will produce the assembler source
7117 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7118 the options @samp{-v --save-temps}; this will save the assembler source in a
7119 file with an extension of @file{.s}, and also show you exactly how
7120 @command{@value{AS}} is being run.
7123 A description of what behavior you observe that you believe is
7124 incorrect. For example, ``It gets a fatal signal.''
7126 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7127 will certainly notice it. But if the bug is incorrect output, we might not
7128 notice unless it is glaringly wrong. You might as well not give us a chance to
7131 Even if the problem you experience is a fatal signal, you should still say so
7132 explicitly. Suppose something strange is going on, such as, your copy of
7133 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7134 library on your system. (This has happened!) Your copy might crash and ours
7135 would not. If you told us to expect a crash, then when ours fails to crash, we
7136 would know that the bug was not happening for us. If you had not told us to
7137 expect a crash, then we would not be able to draw any conclusion from our
7141 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7142 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7143 option. Always send diffs from the old file to the new file. If you even
7144 discuss something in the @command{@value{AS}} source, refer to it by context, not
7147 The line numbers in our development sources will not match those in your
7148 sources. Your line numbers would convey no useful information to us.
7151 Here are some things that are not necessary:
7155 A description of the envelope of the bug.
7157 Often people who encounter a bug spend a lot of time investigating
7158 which changes to the input file will make the bug go away and which
7159 changes will not affect it.
7161 This is often time consuming and not very useful, because the way we
7162 will find the bug is by running a single example under the debugger
7163 with breakpoints, not by pure deduction from a series of examples.
7164 We recommend that you save your time for something else.
7166 Of course, if you can find a simpler example to report @emph{instead}
7167 of the original one, that is a convenience for us. Errors in the
7168 output will be easier to spot, running under the debugger will take
7169 less time, and so on.
7171 However, simplification is not vital; if you do not want to do this,
7172 report the bug anyway and send us the entire test case you used.
7175 A patch for the bug.
7177 A patch for the bug does help us if it is a good one. But do not omit
7178 the necessary information, such as the test case, on the assumption that
7179 a patch is all we need. We might see problems with your patch and decide
7180 to fix the problem another way, or we might not understand it at all.
7182 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7183 construct an example that will make the program follow a certain path through
7184 the code. If you do not send us the example, we will not be able to construct
7185 one, so we will not be able to verify that the bug is fixed.
7187 And if we cannot understand what bug you are trying to fix, or why your
7188 patch should be an improvement, we will not install it. A test case will
7189 help us to understand.
7192 A guess about what the bug is or what it depends on.
7194 Such guesses are usually wrong. Even we cannot guess right about such
7195 things without first using the debugger to find the facts.
7198 @node Acknowledgements
7199 @chapter Acknowledgements
7201 If you have contributed to GAS and your name isn't listed here,
7202 it is not meant as a slight. We just don't know about it. Send mail to the
7203 maintainer, and we'll correct the situation. Currently
7205 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7207 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7210 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7211 information and the 68k series machines, most of the preprocessing pass, and
7212 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7214 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7215 many bug fixes, including merging support for several processors, breaking GAS
7216 up to handle multiple object file format back ends (including heavy rewrite,
7217 testing, an integration of the coff and b.out back ends), adding configuration
7218 including heavy testing and verification of cross assemblers and file splits
7219 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7220 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7221 port (including considerable amounts of reverse engineering), a SPARC opcode
7222 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7223 assertions and made them work, much other reorganization, cleanup, and lint.
7225 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7226 in format-specific I/O modules.
7228 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7229 has done much work with it since.
7231 The Intel 80386 machine description was written by Eliot Dresselhaus.
7233 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7235 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7236 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7238 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7239 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7240 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7241 support a.out format.
7243 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7244 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7245 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7246 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7249 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7250 simplified the configuration of which versions accept which directives. He
7251 updated the 68k machine description so that Motorola's opcodes always produced
7252 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7253 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7254 cross-compilation support, and one bug in relaxation that took a week and
7255 required the proverbial one-bit fix.
7257 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7258 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7259 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7260 PowerPC assembler, and made a few other minor patches.
7262 Steve Chamberlain made GAS able to generate listings.
7264 Hewlett-Packard contributed support for the HP9000/300.
7266 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7267 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7268 formats). This work was supported by both the Center for Software Science at
7269 the University of Utah and Cygnus Support.
7271 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7272 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7273 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7274 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7275 and some initial 64-bit support).
7277 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7279 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7280 support for openVMS/Alpha.
7282 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7285 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7286 Inc.@: added support for Xtensa processors.
7288 Several engineers at Cygnus Support have also provided many small bug fixes and
7289 configuration enhancements.
7291 Jon Beniston added support for the Lattice Mico32 architecture.
7293 Many others have contributed large or small bugfixes and enhancements. If
7294 you have contributed significant work and are not mentioned on this list, and
7295 want to be, let us know. Some of the history has been lost; we are not
7296 intentionally leaving anyone out.
7298 @node GNU Free Documentation License
7299 @appendix GNU Free Documentation License
7303 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob