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, 2010
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
55 @set abnormal-separator
59 @settitle Using @value{AS}
62 @settitle Using @value{AS} (@value{TARGET})
64 @setchapternewpage odd
69 @c WARE! Some of the machine-dependent sections contain tables of machine
70 @c instructions. Except in multi-column format, these tables look silly.
71 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
72 @c the multi-col format is faked within @example sections.
74 @c Again unfortunately, the natural size that fits on a page, for these tables,
75 @c is different depending on whether or not smallbook is turned on.
76 @c This matters, because of order: text flow switches columns at each page
79 @c The format faked in this source works reasonably well for smallbook,
80 @c not well for the default large-page format. This manual expects that if you
81 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
82 @c tables in question. You can turn on one without the other at your
83 @c discretion, of course.
86 @c the insn tables look just as silly in info files regardless of smallbook,
87 @c might as well show 'em anyways.
91 @dircategory Software development
93 * As: (as). The GNU assembler.
94 * Gas: (as). The GNU assembler.
102 This file documents the GNU Assembler "@value{AS}".
104 @c man begin COPYRIGHT
105 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
106 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
108 Permission is granted to copy, distribute and/or modify this document
109 under the terms of the GNU Free Documentation License, Version 1.3
110 or any later version published by the Free Software Foundation;
111 with no Invariant Sections, with no Front-Cover Texts, and with no
112 Back-Cover Texts. A copy of the license is included in the
113 section entitled ``GNU Free Documentation License''.
119 @title Using @value{AS}
120 @subtitle The @sc{gnu} Assembler
122 @subtitle for the @value{TARGET} family
124 @ifset VERSION_PACKAGE
126 @subtitle @value{VERSION_PACKAGE}
129 @subtitle Version @value{VERSION}
132 The Free Software Foundation Inc.@: thanks The Nice Computer
133 Company of Australia for loaning Dean Elsner to write the
134 first (Vax) version of @command{as} for Project @sc{gnu}.
135 The proprietors, management and staff of TNCCA thank FSF for
136 distracting the boss while they got some work
139 @author Dean Elsner, Jay Fenlason & friends
143 \hfill {\it Using {\tt @value{AS}}}\par
144 \hfill Edited by Cygnus Support\par
146 %"boxit" macro for figures:
147 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
148 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
149 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
150 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
151 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
154 @vskip 0pt plus 1filll
155 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
156 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
158 Permission is granted to copy, distribute and/or modify this document
159 under the terms of the GNU Free Documentation License, Version 1.3
160 or any later version published by the Free Software Foundation;
161 with no Invariant Sections, with no Front-Cover Texts, and with no
162 Back-Cover Texts. A copy of the license is included in the
163 section entitled ``GNU Free Documentation License''.
170 @top Using @value{AS}
172 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
173 @ifset VERSION_PACKAGE
174 @value{VERSION_PACKAGE}
176 version @value{VERSION}.
178 This version of the file describes @command{@value{AS}} configured to generate
179 code for @value{TARGET} architectures.
182 This document is distributed under the terms of the GNU Free
183 Documentation License. A copy of the license is included in the
184 section entitled ``GNU Free Documentation License''.
187 * Overview:: Overview
188 * Invoking:: Command-Line Options
190 * Sections:: Sections and Relocation
192 * Expressions:: Expressions
193 * Pseudo Ops:: Assembler Directives
195 * Object Attributes:: Object Attributes
197 * Machine Dependencies:: Machine Dependent Features
198 * Reporting Bugs:: Reporting Bugs
199 * Acknowledgements:: Who Did What
200 * GNU Free Documentation License:: GNU Free Documentation License
201 * AS Index:: AS Index
208 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
210 This version of the manual describes @command{@value{AS}} configured to generate
211 code for @value{TARGET} architectures.
215 @cindex invocation summary
216 @cindex option summary
217 @cindex summary of options
218 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
219 see @ref{Invoking,,Command-Line Options}.
221 @c man title AS the portable GNU assembler.
225 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
229 @c We don't use deffn and friends for the following because they seem
230 @c to be limited to one line for the header.
232 @c man begin SYNOPSIS
233 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
234 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
235 [@b{--debug-prefix-map} @var{old}=@var{new}]
236 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
237 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
238 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
239 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
240 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
241 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
242 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
243 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
244 [@b{--target-help}] [@var{target-options}]
245 [@b{--}|@var{files} @dots{}]
247 @c Target dependent options are listed below. Keep the list sorted.
248 @c Add an empty line for separation.
251 @emph{Target Alpha options:}
253 [@b{-mdebug} | @b{-no-mdebug}]
254 [@b{-replace} | @b{-noreplace}]
255 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
256 [@b{-F}] [@b{-32addr}]
260 @emph{Target ARC options:}
266 @emph{Target ARM options:}
267 @c Don't document the deprecated options
268 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
269 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
270 [@b{-mfpu}=@var{floating-point-format}]
271 [@b{-mfloat-abi}=@var{abi}]
272 [@b{-meabi}=@var{ver}]
275 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
276 @b{-mapcs-reentrant}]
277 [@b{-mthumb-interwork}] [@b{-k}]
281 @emph{Target Blackfin options:}
282 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
289 @emph{Target CRIS options:}
290 [@b{--underscore} | @b{--no-underscore}]
292 [@b{--emulation=criself} | @b{--emulation=crisaout}]
293 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
294 @c Deprecated -- deliberately not documented.
299 @emph{Target D10V options:}
304 @emph{Target D30V options:}
305 [@b{-O}|@b{-n}|@b{-N}]
309 @emph{Target H8/300 options:}
313 @c HPPA has no machine-dependent assembler options (yet).
317 @emph{Target i386 options:}
318 [@b{--32}|@b{--64}] [@b{-n}]
319 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
323 @emph{Target i960 options:}
324 @c see md_parse_option in tc-i960.c
325 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
327 [@b{-b}] [@b{-no-relax}]
331 @emph{Target IA-64 options:}
332 [@b{-mconstant-gp}|@b{-mauto-pic}]
333 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
335 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
336 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
337 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
338 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
342 @emph{Target IP2K options:}
343 [@b{-mip2022}|@b{-mip2022ext}]
347 @emph{Target M32C options:}
348 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
352 @emph{Target M32R options:}
353 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
358 @emph{Target M680X0 options:}
359 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
363 @emph{Target M68HC11 options:}
364 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
365 [@b{-mshort}|@b{-mlong}]
366 [@b{-mshort-double}|@b{-mlong-double}]
367 [@b{--force-long-branches}] [@b{--short-branches}]
368 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
369 [@b{--print-opcodes}] [@b{--generate-example}]
373 @emph{Target MCORE options:}
374 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
375 [@b{-mcpu=[210|340]}]
378 @emph{Target MICROBLAZE options:}
379 @c MicroBlaze has no machine-dependent assembler options.
383 @emph{Target MIPS options:}
384 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
385 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
386 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
387 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
388 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
389 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
390 [@b{-mips64}] [@b{-mips64r2}]
391 [@b{-construct-floats}] [@b{-no-construct-floats}]
392 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
393 [@b{-mips16}] [@b{-no-mips16}]
394 [@b{-msmartmips}] [@b{-mno-smartmips}]
395 [@b{-mips3d}] [@b{-no-mips3d}]
396 [@b{-mdmx}] [@b{-no-mdmx}]
397 [@b{-mdsp}] [@b{-mno-dsp}]
398 [@b{-mdspr2}] [@b{-mno-dspr2}]
399 [@b{-mmt}] [@b{-mno-mt}]
400 [@b{-mfix7000}] [@b{-mno-fix7000}]
401 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
402 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
403 [@b{-mdebug}] [@b{-no-mdebug}]
404 [@b{-mpdr}] [@b{-mno-pdr}]
408 @emph{Target MMIX options:}
409 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
410 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
411 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
412 [@b{--linker-allocated-gregs}]
416 @emph{Target PDP11 options:}
417 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
418 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
419 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
423 @emph{Target picoJava options:}
428 @emph{Target PowerPC options:}
429 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
430 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}]
431 [@b{-mcom}|@b{-many}|@b{-maltivec}|@b{-mvsx}] [@b{-memb}]
432 [@b{-mregnames}|@b{-mno-regnames}]
433 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
434 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
435 [@b{-msolaris}|@b{-mno-solaris}]
439 @emph{Target RX options:}
440 [@b{-mlittle-endian}|@b{-mbig-endian}]
441 [@b{-m32bit-ints}|@b{-m16bit-ints}]
442 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
446 @emph{Target s390 options:}
447 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
448 [@b{-mregnames}|@b{-mno-regnames}]
449 [@b{-mwarn-areg-zero}]
453 @emph{Target SCORE options:}
454 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
455 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
456 [@b{-march=score7}][@b{-march=score3}]
457 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
461 @emph{Target SPARC options:}
462 @c The order here is important. See c-sparc.texi.
463 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
464 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
465 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
470 @emph{Target TIC54X options:}
471 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
472 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
477 @emph{Target TIC6X options:}
478 [@b{-march=@var{arch}}] [@b{-matomic}|@b{-mno-atomic}]
479 [@b{-mbig-endian}|@b{-mlittle-endian}] [@b{-mdsbt}|@b{-mno-dsbt}]
480 [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}] [@b{-mpic}|@b{-mno-pic}]
485 @emph{Target Xtensa options:}
486 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
487 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
488 [@b{--[no-]transform}]
489 [@b{--rename-section} @var{oldname}=@var{newname}]
494 @emph{Target Z80 options:}
495 [@b{-z80}] [@b{-r800}]
496 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
497 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
498 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
499 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
500 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
501 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
505 @c Z8000 has no machine-dependent assembler options
514 @include at-file.texi
517 Turn on listings, in any of a variety of ways:
521 omit false conditionals
524 omit debugging directives
527 include general information, like @value{AS} version and options passed
530 include high-level source
536 include macro expansions
539 omit forms processing
545 set the name of the listing file
548 You may combine these options; for example, use @samp{-aln} for assembly
549 listing without forms processing. The @samp{=file} option, if used, must be
550 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
553 Begin in alternate macro mode.
555 @xref{Altmacro,,@code{.altmacro}}.
558 @item --compress-debug-sections
559 Compress DWARF debug sections using zlib. The debug sections are renamed
560 to begin with @samp{.zdebug}, and the resulting object file may not be
561 compatible with older linkers and object file utilities.
563 @item --nocompress-debug-sections
564 Do not compress DWARF debug sections. This is the default.
567 Ignored. This option is accepted for script compatibility with calls to
570 @item --debug-prefix-map @var{old}=@var{new}
571 When assembling files in directory @file{@var{old}}, record debugging
572 information describing them as in @file{@var{new}} instead.
574 @item --defsym @var{sym}=@var{value}
575 Define the symbol @var{sym} to be @var{value} before assembling the input file.
576 @var{value} must be an integer constant. As in C, a leading @samp{0x}
577 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
578 value. The value of the symbol can be overridden inside a source file via the
579 use of a @code{.set} pseudo-op.
582 ``fast''---skip whitespace and comment preprocessing (assume source is
587 Generate debugging information for each assembler source line using whichever
588 debug format is preferred by the target. This currently means either STABS,
592 Generate stabs debugging information for each assembler line. This
593 may help debugging assembler code, if the debugger can handle it.
596 Generate stabs debugging information for each assembler line, with GNU
597 extensions that probably only gdb can handle, and that could make other
598 debuggers crash or refuse to read your program. This
599 may help debugging assembler code. Currently the only GNU extension is
600 the location of the current working directory at assembling time.
603 Generate DWARF2 debugging information for each assembler line. This
604 may help debugging assembler code, if the debugger can handle it. Note---this
605 option is only supported by some targets, not all of them.
608 Print a summary of the command line options and exit.
611 Print a summary of all target specific options and exit.
614 Add directory @var{dir} to the search list for @code{.include} directives.
617 Don't warn about signed overflow.
620 @ifclear DIFF-TBL-KLUGE
621 This option is accepted but has no effect on the @value{TARGET} family.
623 @ifset DIFF-TBL-KLUGE
624 Issue warnings when difference tables altered for long displacements.
629 Keep (in the symbol table) local symbols. These symbols start with
630 system-specific local label prefixes, typically @samp{.L} for ELF systems
631 or @samp{L} for traditional a.out systems.
636 @item --listing-lhs-width=@var{number}
637 Set the maximum width, in words, of the output data column for an assembler
638 listing to @var{number}.
640 @item --listing-lhs-width2=@var{number}
641 Set the maximum width, in words, of the output data column for continuation
642 lines in an assembler listing to @var{number}.
644 @item --listing-rhs-width=@var{number}
645 Set the maximum width of an input source line, as displayed in a listing, to
648 @item --listing-cont-lines=@var{number}
649 Set the maximum number of lines printed in a listing for a single line of input
652 @item -o @var{objfile}
653 Name the object-file output from @command{@value{AS}} @var{objfile}.
656 Fold the data section into the text section.
658 @kindex --hash-size=@var{number}
659 Set the default size of GAS's hash tables to a prime number close to
660 @var{number}. Increasing this value can reduce the length of time it takes the
661 assembler to perform its tasks, at the expense of increasing the assembler's
662 memory requirements. Similarly reducing this value can reduce the memory
663 requirements at the expense of speed.
665 @item --reduce-memory-overheads
666 This option reduces GAS's memory requirements, at the expense of making the
667 assembly processes slower. Currently this switch is a synonym for
668 @samp{--hash-size=4051}, but in the future it may have other effects as well.
671 Print the maximum space (in bytes) and total time (in seconds) used by
674 @item --strip-local-absolute
675 Remove local absolute symbols from the outgoing symbol table.
679 Print the @command{as} version.
682 Print the @command{as} version and exit.
686 Suppress warning messages.
688 @item --fatal-warnings
689 Treat warnings as errors.
692 Don't suppress warning messages or treat them as errors.
701 Generate an object file even after errors.
703 @item -- | @var{files} @dots{}
704 Standard input, or source files to assemble.
712 @xref{Alpha Options}, for the options available when @value{AS} is configured
713 for an Alpha processor.
718 The following options are available when @value{AS} is configured for an Alpha
722 @include c-alpha.texi
723 @c ended inside the included file
730 The following options are available when @value{AS} is configured for
735 This option selects the core processor variant.
737 Select either big-endian (-EB) or little-endian (-EL) output.
742 The following options are available when @value{AS} is configured for the ARM
746 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
747 Specify which ARM processor variant is the target.
748 @item -march=@var{architecture}[+@var{extension}@dots{}]
749 Specify which ARM architecture variant is used by the target.
750 @item -mfpu=@var{floating-point-format}
751 Select which Floating Point architecture is the target.
752 @item -mfloat-abi=@var{abi}
753 Select which floating point ABI is in use.
755 Enable Thumb only instruction decoding.
756 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
757 Select which procedure calling convention is in use.
759 Select either big-endian (-EB) or little-endian (-EL) output.
760 @item -mthumb-interwork
761 Specify that the code has been generated with interworking between Thumb and
764 Specify that PIC code has been generated.
771 @xref{Blackfin Options}, for the options available when @value{AS} is
772 configured for the Blackfin processor family.
777 The following options are available when @value{AS} is configured for
778 the Blackfin processor family.
782 @c ended inside the included file
788 See the info pages for documentation of the CRIS-specific options.
792 The following options are available when @value{AS} is configured for
795 @cindex D10V optimization
796 @cindex optimization, D10V
798 Optimize output by parallelizing instructions.
803 The following options are available when @value{AS} is configured for a D30V
806 @cindex D30V optimization
807 @cindex optimization, D30V
809 Optimize output by parallelizing instructions.
813 Warn when nops are generated.
815 @cindex D30V nops after 32-bit multiply
817 Warn when a nop after a 32-bit multiply instruction is generated.
825 @xref{i386-Options}, for the options available when @value{AS} is
826 configured for an i386 processor.
831 The following options are available when @value{AS} is configured for
836 @c ended inside the included file
843 The following options are available when @value{AS} is configured for the
844 Intel 80960 processor.
847 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
848 Specify which variant of the 960 architecture is the target.
851 Add code to collect statistics about branches taken.
854 Do not alter compare-and-branch instructions for long displacements;
861 The following options are available when @value{AS} is configured for the
867 Specifies that the extended IP2022 instructions are allowed.
870 Restores the default behaviour, which restricts the permitted instructions to
871 just the basic IP2022 ones.
877 The following options are available when @value{AS} is configured for the
878 Renesas M32C and M16C processors.
883 Assemble M32C instructions.
886 Assemble M16C instructions (the default).
889 Enable support for link-time relaxations.
892 Support H'00 style hex constants in addition to 0x00 style.
898 The following options are available when @value{AS} is configured for the
899 Renesas M32R (formerly Mitsubishi M32R) series.
904 Specify which processor in the M32R family is the target. The default
905 is normally the M32R, but this option changes it to the M32RX.
907 @item --warn-explicit-parallel-conflicts or --Wp
908 Produce warning messages when questionable parallel constructs are
911 @item --no-warn-explicit-parallel-conflicts or --Wnp
912 Do not produce warning messages when questionable parallel constructs are
919 The following options are available when @value{AS} is configured for the
920 Motorola 68000 series.
925 Shorten references to undefined symbols, to one word instead of two.
927 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
928 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
929 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
930 Specify what processor in the 68000 family is the target. The default
931 is normally the 68020, but this can be changed at configuration time.
933 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
934 The target machine does (or does not) have a floating-point coprocessor.
935 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
936 the basic 68000 is not compatible with the 68881, a combination of the
937 two can be specified, since it's possible to do emulation of the
938 coprocessor instructions with the main processor.
940 @item -m68851 | -mno-68851
941 The target machine does (or does not) have a memory-management
942 unit coprocessor. The default is to assume an MMU for 68020 and up.
949 For details about the PDP-11 machine dependent features options,
950 see @ref{PDP-11-Options}.
953 @item -mpic | -mno-pic
954 Generate position-independent (or position-dependent) code. The
955 default is @option{-mpic}.
958 @itemx -mall-extensions
959 Enable all instruction set extensions. This is the default.
961 @item -mno-extensions
962 Disable all instruction set extensions.
964 @item -m@var{extension} | -mno-@var{extension}
965 Enable (or disable) a particular instruction set extension.
968 Enable the instruction set extensions supported by a particular CPU, and
969 disable all other extensions.
971 @item -m@var{machine}
972 Enable the instruction set extensions supported by a particular machine
973 model, and disable all other extensions.
979 The following options are available when @value{AS} is configured for
980 a picoJava processor.
984 @cindex PJ endianness
985 @cindex endianness, PJ
986 @cindex big endian output, PJ
988 Generate ``big endian'' format output.
990 @cindex little endian output, PJ
992 Generate ``little endian'' format output.
998 The following options are available when @value{AS} is configured for the
999 Motorola 68HC11 or 68HC12 series.
1003 @item -m68hc11 | -m68hc12 | -m68hcs12
1004 Specify what processor is the target. The default is
1005 defined by the configuration option when building the assembler.
1008 Specify to use the 16-bit integer ABI.
1011 Specify to use the 32-bit integer ABI.
1013 @item -mshort-double
1014 Specify to use the 32-bit double ABI.
1017 Specify to use the 64-bit double ABI.
1019 @item --force-long-branches
1020 Relative branches are turned into absolute ones. This concerns
1021 conditional branches, unconditional branches and branches to a
1024 @item -S | --short-branches
1025 Do not turn relative branches into absolute ones
1026 when the offset is out of range.
1028 @item --strict-direct-mode
1029 Do not turn the direct addressing mode into extended addressing mode
1030 when the instruction does not support direct addressing mode.
1032 @item --print-insn-syntax
1033 Print the syntax of instruction in case of error.
1035 @item --print-opcodes
1036 print the list of instructions with syntax and then exit.
1038 @item --generate-example
1039 print an example of instruction for each possible instruction and then exit.
1040 This option is only useful for testing @command{@value{AS}}.
1046 The following options are available when @command{@value{AS}} is configured
1047 for the SPARC architecture:
1050 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1051 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1052 Explicitly select a variant of the SPARC architecture.
1054 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1055 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1057 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1058 UltraSPARC extensions.
1060 @item -xarch=v8plus | -xarch=v8plusa
1061 For compatibility with the Solaris v9 assembler. These options are
1062 equivalent to -Av8plus and -Av8plusa, respectively.
1065 Warn when the assembler switches to another architecture.
1070 The following options are available when @value{AS} is configured for the 'c54x
1075 Enable extended addressing mode. All addresses and relocations will assume
1076 extended addressing (usually 23 bits).
1077 @item -mcpu=@var{CPU_VERSION}
1078 Sets the CPU version being compiled for.
1079 @item -merrors-to-file @var{FILENAME}
1080 Redirect error output to a file, for broken systems which don't support such
1081 behaviour in the shell.
1086 The following options are available when @value{AS} is configured for
1087 a @sc{mips} processor.
1091 This option sets the largest size of an object that can be referenced
1092 implicitly with the @code{gp} register. It is only accepted for targets that
1093 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1095 @cindex MIPS endianness
1096 @cindex endianness, MIPS
1097 @cindex big endian output, MIPS
1099 Generate ``big endian'' format output.
1101 @cindex little endian output, MIPS
1103 Generate ``little endian'' format output.
1115 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1116 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1117 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1118 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1119 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1121 correspond to generic
1122 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1123 and @samp{MIPS64 Release 2}
1124 ISA processors, respectively.
1126 @item -march=@var{CPU}
1127 Generate code for a particular @sc{mips} cpu.
1129 @item -mtune=@var{cpu}
1130 Schedule and tune for a particular @sc{mips} cpu.
1134 Cause nops to be inserted if the read of the destination register
1135 of an mfhi or mflo instruction occurs in the following two instructions.
1139 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1140 section instead of the standard ELF .stabs sections.
1144 Control generation of @code{.pdr} sections.
1148 The register sizes are normally inferred from the ISA and ABI, but these
1149 flags force a certain group of registers to be treated as 32 bits wide at
1150 all times. @samp{-mgp32} controls the size of general-purpose registers
1151 and @samp{-mfp32} controls the size of floating-point registers.
1155 Generate code for the MIPS 16 processor. This is equivalent to putting
1156 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1157 turns off this option.
1160 @itemx -mno-smartmips
1161 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1162 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1163 @samp{-mno-smartmips} turns off this option.
1167 Generate code for the MIPS-3D Application Specific Extension.
1168 This tells the assembler to accept MIPS-3D instructions.
1169 @samp{-no-mips3d} turns off this option.
1173 Generate code for the MDMX Application Specific Extension.
1174 This tells the assembler to accept MDMX instructions.
1175 @samp{-no-mdmx} turns off this option.
1179 Generate code for the DSP Release 1 Application Specific Extension.
1180 This tells the assembler to accept DSP Release 1 instructions.
1181 @samp{-mno-dsp} turns off this option.
1185 Generate code for the DSP Release 2 Application Specific Extension.
1186 This option implies -mdsp.
1187 This tells the assembler to accept DSP Release 2 instructions.
1188 @samp{-mno-dspr2} turns off this option.
1192 Generate code for the MT Application Specific Extension.
1193 This tells the assembler to accept MT instructions.
1194 @samp{-mno-mt} turns off this option.
1196 @item --construct-floats
1197 @itemx --no-construct-floats
1198 The @samp{--no-construct-floats} option disables the construction of
1199 double width floating point constants by loading the two halves of the
1200 value into the two single width floating point registers that make up
1201 the double width register. By default @samp{--construct-floats} is
1202 selected, allowing construction of these floating point constants.
1205 @item --emulation=@var{name}
1206 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1207 for some other target, in all respects, including output format (choosing
1208 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1209 debugging information or store symbol table information, and default
1210 endianness. The available configuration names are: @samp{mipsecoff},
1211 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1212 @samp{mipsbelf}. The first two do not alter the default endianness from that
1213 of the primary target for which the assembler was configured; the others change
1214 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1215 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1216 selection in any case.
1218 This option is currently supported only when the primary target
1219 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1220 Furthermore, the primary target or others specified with
1221 @samp{--enable-targets=@dots{}} at configuration time must include support for
1222 the other format, if both are to be available. For example, the Irix 5
1223 configuration includes support for both.
1225 Eventually, this option will support more configurations, with more
1226 fine-grained control over the assembler's behavior, and will be supported for
1230 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1237 Control how to deal with multiplication overflow and division by zero.
1238 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1239 (and only work for Instruction Set Architecture level 2 and higher);
1240 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1244 When this option is used, @command{@value{AS}} will issue a warning every
1245 time it generates a nop instruction from a macro.
1250 The following options are available when @value{AS} is configured for
1256 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1257 The command line option @samp{-nojsri2bsr} can be used to disable it.
1261 Enable or disable the silicon filter behaviour. By default this is disabled.
1262 The default can be overridden by the @samp{-sifilter} command line option.
1265 Alter jump instructions for long displacements.
1267 @item -mcpu=[210|340]
1268 Select the cpu type on the target hardware. This controls which instructions
1272 Assemble for a big endian target.
1275 Assemble for a little endian target.
1281 See the info pages for documentation of the MMIX-specific options.
1285 See the info pages for documentation of the RX-specific options.
1289 The following options are available when @value{AS} is configured for the s390
1295 Select the word size, either 31/32 bits or 64 bits.
1298 Select the architecture mode, either the Enterprise System
1299 Architecture (esa) or the z/Architecture mode (zarch).
1300 @item -march=@var{processor}
1301 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1302 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1304 @itemx -mno-regnames
1305 Allow or disallow symbolic names for registers.
1306 @item -mwarn-areg-zero
1307 Warn whenever the operand for a base or index register has been specified
1308 but evaluates to zero.
1316 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1317 for a TMS320C6000 processor.
1321 @c man begin OPTIONS
1322 The following options are available when @value{AS} is configured for a
1323 TMS320C6000 processor.
1325 @c man begin INCLUDE
1326 @include c-tic6x.texi
1327 @c ended inside the included file
1335 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1336 for an Xtensa processor.
1340 @c man begin OPTIONS
1341 The following options are available when @value{AS} is configured for an
1344 @c man begin INCLUDE
1345 @include c-xtensa.texi
1346 @c ended inside the included file
1351 @c man begin OPTIONS
1354 The following options are available when @value{AS} is configured for
1355 a Z80 family processor.
1358 Assemble for Z80 processor.
1360 Assemble for R800 processor.
1361 @item -ignore-undocumented-instructions
1363 Assemble undocumented Z80 instructions that also work on R800 without warning.
1364 @item -ignore-unportable-instructions
1366 Assemble all undocumented Z80 instructions without warning.
1367 @item -warn-undocumented-instructions
1369 Issue a warning for undocumented Z80 instructions that also work on R800.
1370 @item -warn-unportable-instructions
1372 Issue a warning for undocumented Z80 instructions that do not work on R800.
1373 @item -forbid-undocumented-instructions
1375 Treat all undocumented instructions as errors.
1376 @item -forbid-unportable-instructions
1378 Treat undocumented Z80 instructions that do not work on R800 as errors.
1385 * Manual:: Structure of this Manual
1386 * GNU Assembler:: The GNU Assembler
1387 * Object Formats:: Object File Formats
1388 * Command Line:: Command Line
1389 * Input Files:: Input Files
1390 * Object:: Output (Object) File
1391 * Errors:: Error and Warning Messages
1395 @section Structure of this Manual
1397 @cindex manual, structure and purpose
1398 This manual is intended to describe what you need to know to use
1399 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1400 notation for symbols, constants, and expressions; the directives that
1401 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1404 We also cover special features in the @value{TARGET}
1405 configuration of @command{@value{AS}}, including assembler directives.
1408 This manual also describes some of the machine-dependent features of
1409 various flavors of the assembler.
1412 @cindex machine instructions (not covered)
1413 On the other hand, this manual is @emph{not} intended as an introduction
1414 to programming in assembly language---let alone programming in general!
1415 In a similar vein, we make no attempt to introduce the machine
1416 architecture; we do @emph{not} describe the instruction set, standard
1417 mnemonics, registers or addressing modes that are standard to a
1418 particular architecture.
1420 You may want to consult the manufacturer's
1421 machine architecture manual for this information.
1425 For information on the H8/300 machine instruction set, see @cite{H8/300
1426 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1427 Programming Manual} (Renesas).
1430 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1431 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1432 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1433 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1436 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1440 @c I think this is premature---doc@cygnus.com, 17jan1991
1442 Throughout this manual, we assume that you are running @dfn{GNU},
1443 the portable operating system from the @dfn{Free Software
1444 Foundation, Inc.}. This restricts our attention to certain kinds of
1445 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1446 once this assumption is granted examples and definitions need less
1449 @command{@value{AS}} is part of a team of programs that turn a high-level
1450 human-readable series of instructions into a low-level
1451 computer-readable series of instructions. Different versions of
1452 @command{@value{AS}} are used for different kinds of computer.
1455 @c There used to be a section "Terminology" here, which defined
1456 @c "contents", "byte", "word", and "long". Defining "word" to any
1457 @c particular size is confusing when the .word directive may generate 16
1458 @c bits on one machine and 32 bits on another; in general, for the user
1459 @c version of this manual, none of these terms seem essential to define.
1460 @c They were used very little even in the former draft of the manual;
1461 @c this draft makes an effort to avoid them (except in names of
1465 @section The GNU Assembler
1467 @c man begin DESCRIPTION
1469 @sc{gnu} @command{as} is really a family of assemblers.
1471 This manual describes @command{@value{AS}}, a member of that family which is
1472 configured for the @value{TARGET} architectures.
1474 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1475 should find a fairly similar environment when you use it on another
1476 architecture. Each version has much in common with the others,
1477 including object file formats, most assembler directives (often called
1478 @dfn{pseudo-ops}) and assembler syntax.@refill
1480 @cindex purpose of @sc{gnu} assembler
1481 @command{@value{AS}} is primarily intended to assemble the output of the
1482 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1483 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1484 assemble correctly everything that other assemblers for the same
1485 machine would assemble.
1487 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1490 @c This remark should appear in generic version of manual; assumption
1491 @c here is that generic version sets M680x0.
1492 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1493 assembler for the same architecture; for example, we know of several
1494 incompatible versions of 680x0 assembly language syntax.
1499 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1500 program in one pass of the source file. This has a subtle impact on the
1501 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1503 @node Object Formats
1504 @section Object File Formats
1506 @cindex object file format
1507 The @sc{gnu} assembler can be configured to produce several alternative
1508 object file formats. For the most part, this does not affect how you
1509 write assembly language programs; but directives for debugging symbols
1510 are typically different in different file formats. @xref{Symbol
1511 Attributes,,Symbol Attributes}.
1514 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1515 @value{OBJ-NAME} format object files.
1517 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1519 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1520 @code{b.out} or COFF format object files.
1523 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1524 SOM or ELF format object files.
1529 @section Command Line
1531 @cindex command line conventions
1533 After the program name @command{@value{AS}}, the command line may contain
1534 options and file names. Options may appear in any order, and may be
1535 before, after, or between file names. The order of file names is
1538 @cindex standard input, as input file
1540 @file{--} (two hyphens) by itself names the standard input file
1541 explicitly, as one of the files for @command{@value{AS}} to assemble.
1543 @cindex options, command line
1544 Except for @samp{--} any command line argument that begins with a
1545 hyphen (@samp{-}) is an option. Each option changes the behavior of
1546 @command{@value{AS}}. No option changes the way another option works. An
1547 option is a @samp{-} followed by one or more letters; the case of
1548 the letter is important. All options are optional.
1550 Some options expect exactly one file name to follow them. The file
1551 name may either immediately follow the option's letter (compatible
1552 with older assemblers) or it may be the next command argument (@sc{gnu}
1553 standard). These two command lines are equivalent:
1556 @value{AS} -o my-object-file.o mumble.s
1557 @value{AS} -omy-object-file.o mumble.s
1561 @section Input Files
1564 @cindex source program
1565 @cindex files, input
1566 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1567 describe the program input to one run of @command{@value{AS}}. The program may
1568 be in one or more files; how the source is partitioned into files
1569 doesn't change the meaning of the source.
1571 @c I added "con" prefix to "catenation" just to prove I can overcome my
1572 @c APL training... doc@cygnus.com
1573 The source program is a concatenation of the text in all the files, in the
1576 @c man begin DESCRIPTION
1577 Each time you run @command{@value{AS}} it assembles exactly one source
1578 program. The source program is made up of one or more files.
1579 (The standard input is also a file.)
1581 You give @command{@value{AS}} a command line that has zero or more input file
1582 names. The input files are read (from left file name to right). A
1583 command line argument (in any position) that has no special meaning
1584 is taken to be an input file name.
1586 If you give @command{@value{AS}} no file names it attempts to read one input file
1587 from the @command{@value{AS}} standard input, which is normally your terminal. You
1588 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1591 Use @samp{--} if you need to explicitly name the standard input file
1592 in your command line.
1594 If the source is empty, @command{@value{AS}} produces a small, empty object
1599 @subheading Filenames and Line-numbers
1601 @cindex input file linenumbers
1602 @cindex line numbers, in input files
1603 There are two ways of locating a line in the input file (or files) and
1604 either may be used in reporting error messages. One way refers to a line
1605 number in a physical file; the other refers to a line number in a
1606 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1608 @dfn{Physical files} are those files named in the command line given
1609 to @command{@value{AS}}.
1611 @dfn{Logical files} are simply names declared explicitly by assembler
1612 directives; they bear no relation to physical files. Logical file names help
1613 error messages reflect the original source file, when @command{@value{AS}} source
1614 is itself synthesized from other files. @command{@value{AS}} understands the
1615 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1616 @ref{File,,@code{.file}}.
1619 @section Output (Object) File
1625 Every time you run @command{@value{AS}} it produces an output file, which is
1626 your assembly language program translated into numbers. This file
1627 is the object file. Its default name is
1635 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1637 You can give it another name by using the @option{-o} option. Conventionally,
1638 object file names end with @file{.o}. The default name is used for historical
1639 reasons: older assemblers were capable of assembling self-contained programs
1640 directly into a runnable program. (For some formats, this isn't currently
1641 possible, but it can be done for the @code{a.out} format.)
1645 The object file is meant for input to the linker @code{@value{LD}}. It contains
1646 assembled program code, information to help @code{@value{LD}} integrate
1647 the assembled program into a runnable file, and (optionally) symbolic
1648 information for the debugger.
1650 @c link above to some info file(s) like the description of a.out.
1651 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1654 @section Error and Warning Messages
1656 @c man begin DESCRIPTION
1658 @cindex error messages
1659 @cindex warning messages
1660 @cindex messages from assembler
1661 @command{@value{AS}} may write warnings and error messages to the standard error
1662 file (usually your terminal). This should not happen when a compiler
1663 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1664 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1665 grave problem that stops the assembly.
1669 @cindex format of warning messages
1670 Warning messages have the format
1673 file_name:@b{NNN}:Warning Message Text
1677 @cindex line numbers, in warnings/errors
1678 (where @b{NNN} is a line number). If a logical file name has been given
1679 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1680 the current input file is used. If a logical line number was given
1682 (@pxref{Line,,@code{.line}})
1684 then it is used to calculate the number printed,
1685 otherwise the actual line in the current source file is printed. The
1686 message text is intended to be self explanatory (in the grand Unix
1689 @cindex format of error messages
1690 Error messages have the format
1692 file_name:@b{NNN}:FATAL:Error Message Text
1694 The file name and line number are derived as for warning
1695 messages. The actual message text may be rather less explanatory
1696 because many of them aren't supposed to happen.
1699 @chapter Command-Line Options
1701 @cindex options, all versions of assembler
1702 This chapter describes command-line options available in @emph{all}
1703 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1704 for options specific
1706 to the @value{TARGET} target.
1709 to particular machine architectures.
1712 @c man begin DESCRIPTION
1714 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1715 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1716 The assembler arguments must be separated from each other (and the @samp{-Wa})
1717 by commas. For example:
1720 gcc -c -g -O -Wa,-alh,-L file.c
1724 This passes two options to the assembler: @samp{-alh} (emit a listing to
1725 standard output with high-level and assembly source) and @samp{-L} (retain
1726 local symbols in the symbol table).
1728 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1729 command-line options are automatically passed to the assembler by the compiler.
1730 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1731 precisely what options it passes to each compilation pass, including the
1737 * a:: -a[cdghlns] enable listings
1738 * alternate:: --alternate enable alternate macro syntax
1739 * D:: -D for compatibility
1740 * f:: -f to work faster
1741 * I:: -I for .include search path
1742 @ifclear DIFF-TBL-KLUGE
1743 * K:: -K for compatibility
1745 @ifset DIFF-TBL-KLUGE
1746 * K:: -K for difference tables
1749 * L:: -L to retain local symbols
1750 * listing:: --listing-XXX to configure listing output
1751 * M:: -M or --mri to assemble in MRI compatibility mode
1752 * MD:: --MD for dependency tracking
1753 * o:: -o to name the object file
1754 * R:: -R to join data and text sections
1755 * statistics:: --statistics to see statistics about assembly
1756 * traditional-format:: --traditional-format for compatible output
1757 * v:: -v to announce version
1758 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1759 * Z:: -Z to make object file even after errors
1763 @section Enable Listings: @option{-a[cdghlns]}
1773 @cindex listings, enabling
1774 @cindex assembly listings, enabling
1776 These options enable listing output from the assembler. By itself,
1777 @samp{-a} requests high-level, assembly, and symbols listing.
1778 You can use other letters to select specific options for the list:
1779 @samp{-ah} requests a high-level language listing,
1780 @samp{-al} requests an output-program assembly listing, and
1781 @samp{-as} requests a symbol table listing.
1782 High-level listings require that a compiler debugging option like
1783 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1786 Use the @samp{-ag} option to print a first section with general assembly
1787 information, like @value{AS} version, switches passed, or time stamp.
1789 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1790 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1791 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1792 omitted from the listing.
1794 Use the @samp{-ad} option to omit debugging directives from the
1797 Once you have specified one of these options, you can further control
1798 listing output and its appearance using the directives @code{.list},
1799 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1801 The @samp{-an} option turns off all forms processing.
1802 If you do not request listing output with one of the @samp{-a} options, the
1803 listing-control directives have no effect.
1805 The letters after @samp{-a} may be combined into one option,
1806 @emph{e.g.}, @samp{-aln}.
1808 Note if the assembler source is coming from the standard input (e.g.,
1810 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1811 is being used) then the listing will not contain any comments or preprocessor
1812 directives. This is because the listing code buffers input source lines from
1813 stdin only after they have been preprocessed by the assembler. This reduces
1814 memory usage and makes the code more efficient.
1817 @section @option{--alternate}
1820 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1823 @section @option{-D}
1826 This option has no effect whatsoever, but it is accepted to make it more
1827 likely that scripts written for other assemblers also work with
1828 @command{@value{AS}}.
1831 @section Work Faster: @option{-f}
1834 @cindex trusted compiler
1835 @cindex faster processing (@option{-f})
1836 @samp{-f} should only be used when assembling programs written by a
1837 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1838 and comment preprocessing on
1839 the input file(s) before assembling them. @xref{Preprocessing,
1843 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1844 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1849 @section @code{.include} Search Path: @option{-I} @var{path}
1851 @kindex -I @var{path}
1852 @cindex paths for @code{.include}
1853 @cindex search path for @code{.include}
1854 @cindex @code{include} directive search path
1855 Use this option to add a @var{path} to the list of directories
1856 @command{@value{AS}} searches for files specified in @code{.include}
1857 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1858 many times as necessary to include a variety of paths. The current
1859 working directory is always searched first; after that, @command{@value{AS}}
1860 searches any @samp{-I} directories in the same order as they were
1861 specified (left to right) on the command line.
1864 @section Difference Tables: @option{-K}
1867 @ifclear DIFF-TBL-KLUGE
1868 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1869 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1870 where it can be used to warn when the assembler alters the machine code
1871 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1872 family does not have the addressing limitations that sometimes lead to this
1873 alteration on other platforms.
1876 @ifset DIFF-TBL-KLUGE
1877 @cindex difference tables, warning
1878 @cindex warning for altered difference tables
1879 @command{@value{AS}} sometimes alters the code emitted for directives of the
1880 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1881 You can use the @samp{-K} option if you want a warning issued when this
1886 @section Include Local Symbols: @option{-L}
1889 @cindex local symbols, retaining in output
1890 Symbols beginning with system-specific local label prefixes, typically
1891 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1892 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1893 such symbols when debugging, because they are intended for the use of
1894 programs (like compilers) that compose assembler programs, not for your
1895 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1896 such symbols, so you do not normally debug with them.
1898 This option tells @command{@value{AS}} to retain those local symbols
1899 in the object file. Usually if you do this you also tell the linker
1900 @code{@value{LD}} to preserve those symbols.
1903 @section Configuring listing output: @option{--listing}
1905 The listing feature of the assembler can be enabled via the command line switch
1906 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1907 hex dump of the corresponding locations in the output object file, and displays
1908 them as a listing file. The format of this listing can be controlled by
1909 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1910 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1911 @code{.psize} (@pxref{Psize}), and
1912 @code{.eject} (@pxref{Eject}) and also by the following switches:
1915 @item --listing-lhs-width=@samp{number}
1916 @kindex --listing-lhs-width
1917 @cindex Width of first line disassembly output
1918 Sets the maximum width, in words, of the first line of the hex byte dump. This
1919 dump appears on the left hand side of the listing output.
1921 @item --listing-lhs-width2=@samp{number}
1922 @kindex --listing-lhs-width2
1923 @cindex Width of continuation lines of disassembly output
1924 Sets the maximum width, in words, of any further lines of the hex byte dump for
1925 a given input source line. If this value is not specified, it defaults to being
1926 the same as the value specified for @samp{--listing-lhs-width}. If neither
1927 switch is used the default is to one.
1929 @item --listing-rhs-width=@samp{number}
1930 @kindex --listing-rhs-width
1931 @cindex Width of source line output
1932 Sets the maximum width, in characters, of the source line that is displayed
1933 alongside the hex dump. The default value for this parameter is 100. The
1934 source line is displayed on the right hand side of the listing output.
1936 @item --listing-cont-lines=@samp{number}
1937 @kindex --listing-cont-lines
1938 @cindex Maximum number of continuation lines
1939 Sets the maximum number of continuation lines of hex dump that will be
1940 displayed for a given single line of source input. The default value is 4.
1944 @section Assemble in MRI Compatibility Mode: @option{-M}
1947 @cindex MRI compatibility mode
1948 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1949 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1950 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1951 configured target) assembler from Microtec Research. The exact nature of the
1952 MRI syntax will not be documented here; see the MRI manuals for more
1953 information. Note in particular that the handling of macros and macro
1954 arguments is somewhat different. The purpose of this option is to permit
1955 assembling existing MRI assembler code using @command{@value{AS}}.
1957 The MRI compatibility is not complete. Certain operations of the MRI assembler
1958 depend upon its object file format, and can not be supported using other object
1959 file formats. Supporting these would require enhancing each object file format
1960 individually. These are:
1963 @item global symbols in common section
1965 The m68k MRI assembler supports common sections which are merged by the linker.
1966 Other object file formats do not support this. @command{@value{AS}} handles
1967 common sections by treating them as a single common symbol. It permits local
1968 symbols to be defined within a common section, but it can not support global
1969 symbols, since it has no way to describe them.
1971 @item complex relocations
1973 The MRI assemblers support relocations against a negated section address, and
1974 relocations which combine the start addresses of two or more sections. These
1975 are not support by other object file formats.
1977 @item @code{END} pseudo-op specifying start address
1979 The MRI @code{END} pseudo-op permits the specification of a start address.
1980 This is not supported by other object file formats. The start address may
1981 instead be specified using the @option{-e} option to the linker, or in a linker
1984 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1986 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1987 name to the output file. This is not supported by other object file formats.
1989 @item @code{ORG} pseudo-op
1991 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1992 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1993 which changes the location within the current section. Absolute sections are
1994 not supported by other object file formats. The address of a section may be
1995 assigned within a linker script.
1998 There are some other features of the MRI assembler which are not supported by
1999 @command{@value{AS}}, typically either because they are difficult or because they
2000 seem of little consequence. Some of these may be supported in future releases.
2004 @item EBCDIC strings
2006 EBCDIC strings are not supported.
2008 @item packed binary coded decimal
2010 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2011 and @code{DCB.P} pseudo-ops are not supported.
2013 @item @code{FEQU} pseudo-op
2015 The m68k @code{FEQU} pseudo-op is not supported.
2017 @item @code{NOOBJ} pseudo-op
2019 The m68k @code{NOOBJ} pseudo-op is not supported.
2021 @item @code{OPT} branch control options
2023 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2024 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2025 relaxes all branches, whether forward or backward, to an appropriate size, so
2026 these options serve no purpose.
2028 @item @code{OPT} list control options
2030 The following m68k @code{OPT} list control options are ignored: @code{C},
2031 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2032 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2034 @item other @code{OPT} options
2036 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2037 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2039 @item @code{OPT} @code{D} option is default
2041 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2042 @code{OPT NOD} may be used to turn it off.
2044 @item @code{XREF} pseudo-op.
2046 The m68k @code{XREF} pseudo-op is ignored.
2048 @item @code{.debug} pseudo-op
2050 The i960 @code{.debug} pseudo-op is not supported.
2052 @item @code{.extended} pseudo-op
2054 The i960 @code{.extended} pseudo-op is not supported.
2056 @item @code{.list} pseudo-op.
2058 The various options of the i960 @code{.list} pseudo-op are not supported.
2060 @item @code{.optimize} pseudo-op
2062 The i960 @code{.optimize} pseudo-op is not supported.
2064 @item @code{.output} pseudo-op
2066 The i960 @code{.output} pseudo-op is not supported.
2068 @item @code{.setreal} pseudo-op
2070 The i960 @code{.setreal} pseudo-op is not supported.
2075 @section Dependency Tracking: @option{--MD}
2078 @cindex dependency tracking
2081 @command{@value{AS}} can generate a dependency file for the file it creates. This
2082 file consists of a single rule suitable for @code{make} describing the
2083 dependencies of the main source file.
2085 The rule is written to the file named in its argument.
2087 This feature is used in the automatic updating of makefiles.
2090 @section Name the Object File: @option{-o}
2093 @cindex naming object file
2094 @cindex object file name
2095 There is always one object file output when you run @command{@value{AS}}. By
2096 default it has the name
2099 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2113 You use this option (which takes exactly one filename) to give the
2114 object file a different name.
2116 Whatever the object file is called, @command{@value{AS}} overwrites any
2117 existing file of the same name.
2120 @section Join Data and Text Sections: @option{-R}
2123 @cindex data and text sections, joining
2124 @cindex text and data sections, joining
2125 @cindex joining text and data sections
2126 @cindex merging text and data sections
2127 @option{-R} tells @command{@value{AS}} to write the object file as if all
2128 data-section data lives in the text section. This is only done at
2129 the very last moment: your binary data are the same, but data
2130 section parts are relocated differently. The data section part of
2131 your object file is zero bytes long because all its bytes are
2132 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2134 When you specify @option{-R} it would be possible to generate shorter
2135 address displacements (because we do not have to cross between text and
2136 data section). We refrain from doing this simply for compatibility with
2137 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2140 When @command{@value{AS}} is configured for COFF or ELF output,
2141 this option is only useful if you use sections named @samp{.text} and
2146 @option{-R} is not supported for any of the HPPA targets. Using
2147 @option{-R} generates a warning from @command{@value{AS}}.
2151 @section Display Assembly Statistics: @option{--statistics}
2153 @kindex --statistics
2154 @cindex statistics, about assembly
2155 @cindex time, total for assembly
2156 @cindex space used, maximum for assembly
2157 Use @samp{--statistics} to display two statistics about the resources used by
2158 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2159 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2162 @node traditional-format
2163 @section Compatible Output: @option{--traditional-format}
2165 @kindex --traditional-format
2166 For some targets, the output of @command{@value{AS}} is different in some ways
2167 from the output of some existing assembler. This switch requests
2168 @command{@value{AS}} to use the traditional format instead.
2170 For example, it disables the exception frame optimizations which
2171 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2174 @section Announce Version: @option{-v}
2178 @cindex assembler version
2179 @cindex version of assembler
2180 You can find out what version of as is running by including the
2181 option @samp{-v} (which you can also spell as @samp{-version}) on the
2185 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2187 @command{@value{AS}} should never give a warning or error message when
2188 assembling compiler output. But programs written by people often
2189 cause @command{@value{AS}} to give a warning that a particular assumption was
2190 made. All such warnings are directed to the standard error file.
2194 @cindex suppressing warnings
2195 @cindex warnings, suppressing
2196 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2197 This only affects the warning messages: it does not change any particular of
2198 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2201 @kindex --fatal-warnings
2202 @cindex errors, caused by warnings
2203 @cindex warnings, causing error
2204 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2205 files that generate warnings to be in error.
2208 @cindex warnings, switching on
2209 You can switch these options off again by specifying @option{--warn}, which
2210 causes warnings to be output as usual.
2213 @section Generate Object File in Spite of Errors: @option{-Z}
2214 @cindex object file, after errors
2215 @cindex errors, continuing after
2216 After an error message, @command{@value{AS}} normally produces no output. If for
2217 some reason you are interested in object file output even after
2218 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2219 option. If there are any errors, @command{@value{AS}} continues anyways, and
2220 writes an object file after a final warning message of the form @samp{@var{n}
2221 errors, @var{m} warnings, generating bad object file.}
2226 @cindex machine-independent syntax
2227 @cindex syntax, machine-independent
2228 This chapter describes the machine-independent syntax allowed in a
2229 source file. @command{@value{AS}} syntax is similar to what many other
2230 assemblers use; it is inspired by the BSD 4.2
2235 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2239 * Preprocessing:: Preprocessing
2240 * Whitespace:: Whitespace
2241 * Comments:: Comments
2242 * Symbol Intro:: Symbols
2243 * Statements:: Statements
2244 * Constants:: Constants
2248 @section Preprocessing
2250 @cindex preprocessing
2251 The @command{@value{AS}} internal preprocessor:
2253 @cindex whitespace, removed by preprocessor
2255 adjusts and removes extra whitespace. It leaves one space or tab before
2256 the keywords on a line, and turns any other whitespace on the line into
2259 @cindex comments, removed by preprocessor
2261 removes all comments, replacing them with a single space, or an
2262 appropriate number of newlines.
2264 @cindex constants, converted by preprocessor
2266 converts character constants into the appropriate numeric values.
2269 It does not do macro processing, include file handling, or
2270 anything else you may get from your C compiler's preprocessor. You can
2271 do include file processing with the @code{.include} directive
2272 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2273 to get other ``CPP'' style preprocessing by giving the input file a
2274 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2275 Output, gcc.info, Using GNU CC}.
2277 Excess whitespace, comments, and character constants
2278 cannot be used in the portions of the input text that are not
2281 @cindex turning preprocessing on and off
2282 @cindex preprocessing, turning on and off
2285 If the first line of an input file is @code{#NO_APP} or if you use the
2286 @samp{-f} option, whitespace and comments are not removed from the input file.
2287 Within an input file, you can ask for whitespace and comment removal in
2288 specific portions of the by putting a line that says @code{#APP} before the
2289 text that may contain whitespace or comments, and putting a line that says
2290 @code{#NO_APP} after this text. This feature is mainly intend to support
2291 @code{asm} statements in compilers whose output is otherwise free of comments
2298 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2299 Whitespace is used to separate symbols, and to make programs neater for
2300 people to read. Unless within character constants
2301 (@pxref{Characters,,Character Constants}), any whitespace means the same
2302 as exactly one space.
2308 There are two ways of rendering comments to @command{@value{AS}}. In both
2309 cases the comment is equivalent to one space.
2311 Anything from @samp{/*} through the next @samp{*/} is a comment.
2312 This means you may not nest these comments.
2316 The only way to include a newline ('\n') in a comment
2317 is to use this sort of comment.
2320 /* This sort of comment does not nest. */
2323 @cindex line comment character
2324 Anything from the @dfn{line comment} character to the next newline
2325 is considered a comment and is ignored. The line comment character is
2327 @samp{;} on the ARC;
2330 @samp{@@} on the ARM;
2333 @samp{;} for the H8/300 family;
2336 @samp{;} for the HPPA;
2339 @samp{#} on the i386 and x86-64;
2342 @samp{#} on the i960;
2345 @samp{;} for the PDP-11;
2348 @samp{;} for picoJava;
2351 @samp{#} for Motorola PowerPC;
2354 @samp{#} for IBM S/390;
2357 @samp{#} for the Sunplus SCORE;
2360 @samp{!} for the Renesas / SuperH SH;
2363 @samp{!} on the SPARC;
2366 @samp{#} on the ip2k;
2369 @samp{#} on the m32c;
2372 @samp{#} on the m32r;
2375 @samp{|} on the 680x0;
2378 @samp{#} on the 68HC11 and 68HC12;
2384 @samp{;} on the TMS320C6X;
2387 @samp{#} on the Vax;
2390 @samp{;} for the Z80;
2393 @samp{!} for the Z8000;
2396 @samp{#} on the V850;
2399 @samp{#} for Xtensa systems;
2401 see @ref{Machine Dependencies}. @refill
2402 @c FIXME What about i860?
2405 On some machines there are two different line comment characters. One
2406 character only begins a comment if it is the first non-whitespace character on
2407 a line, while the other always begins a comment.
2411 The V850 assembler also supports a double dash as starting a comment that
2412 extends to the end of the line.
2418 @cindex lines starting with @code{#}
2419 @cindex logical line numbers
2420 To be compatible with past assemblers, lines that begin with @samp{#} have a
2421 special interpretation. Following the @samp{#} should be an absolute
2422 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2423 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2424 new logical file name. The rest of the line, if any, should be whitespace.
2426 If the first non-whitespace characters on the line are not numeric,
2427 the line is ignored. (Just like a comment.)
2430 # This is an ordinary comment.
2431 # 42-6 "new_file_name" # New logical file name
2432 # This is logical line # 36.
2434 This feature is deprecated, and may disappear from future versions
2435 of @command{@value{AS}}.
2440 @cindex characters used in symbols
2441 @ifclear SPECIAL-SYMS
2442 A @dfn{symbol} is one or more characters chosen from the set of all
2443 letters (both upper and lower case), digits and the three characters
2449 A @dfn{symbol} is one or more characters chosen from the set of all
2450 letters (both upper and lower case), digits and the three characters
2451 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2457 On most machines, you can also use @code{$} in symbol names; exceptions
2458 are noted in @ref{Machine Dependencies}.
2460 No symbol may begin with a digit. Case is significant.
2461 There is no length limit: all characters are significant. Symbols are
2462 delimited by characters not in that set, or by the beginning of a file
2463 (since the source program must end with a newline, the end of a file is
2464 not a possible symbol delimiter). @xref{Symbols}.
2465 @cindex length of symbols
2470 @cindex statements, structure of
2471 @cindex line separator character
2472 @cindex statement separator character
2474 @ifclear abnormal-separator
2475 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2476 semicolon (@samp{;}). The newline or semicolon is considered part of
2477 the preceding statement. Newlines and semicolons within character
2478 constants are an exception: they do not end statements.
2480 @ifset abnormal-separator
2482 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2483 point (@samp{!}). The newline or exclamation point is considered part of the
2484 preceding statement. Newlines and exclamation points within character
2485 constants are an exception: they do not end statements.
2488 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2489 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2490 (@samp{;}). The newline or separator character is considered part of
2491 the preceding statement. Newlines and separators within character
2492 constants are an exception: they do not end statements.
2497 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2498 separator character. (The line separator is usually @samp{;}, unless this
2499 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2500 newline or separator character is considered part of the preceding
2501 statement. Newlines and separators within character constants are an
2502 exception: they do not end statements.
2505 @cindex newline, required at file end
2506 @cindex EOF, newline must precede
2507 It is an error to end any statement with end-of-file: the last
2508 character of any input file should be a newline.@refill
2510 An empty statement is allowed, and may include whitespace. It is ignored.
2512 @cindex instructions and directives
2513 @cindex directives and instructions
2514 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2515 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2517 A statement begins with zero or more labels, optionally followed by a
2518 key symbol which determines what kind of statement it is. The key
2519 symbol determines the syntax of the rest of the statement. If the
2520 symbol begins with a dot @samp{.} then the statement is an assembler
2521 directive: typically valid for any computer. If the symbol begins with
2522 a letter the statement is an assembly language @dfn{instruction}: it
2523 assembles into a machine language instruction.
2525 Different versions of @command{@value{AS}} for different computers
2526 recognize different instructions. In fact, the same symbol may
2527 represent a different instruction in a different computer's assembly
2531 @cindex @code{:} (label)
2532 @cindex label (@code{:})
2533 A label is a symbol immediately followed by a colon (@code{:}).
2534 Whitespace before a label or after a colon is permitted, but you may not
2535 have whitespace between a label's symbol and its colon. @xref{Labels}.
2538 For HPPA targets, labels need not be immediately followed by a colon, but
2539 the definition of a label must begin in column zero. This also implies that
2540 only one label may be defined on each line.
2544 label: .directive followed by something
2545 another_label: # This is an empty statement.
2546 instruction operand_1, operand_2, @dots{}
2553 A constant is a number, written so that its value is known by
2554 inspection, without knowing any context. Like this:
2557 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2558 .ascii "Ring the bell\7" # A string constant.
2559 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2560 .float 0f-314159265358979323846264338327\
2561 95028841971.693993751E-40 # - pi, a flonum.
2566 * Characters:: Character Constants
2567 * Numbers:: Number Constants
2571 @subsection Character Constants
2573 @cindex character constants
2574 @cindex constants, character
2575 There are two kinds of character constants. A @dfn{character} stands
2576 for one character in one byte and its value may be used in
2577 numeric expressions. String constants (properly called string
2578 @emph{literals}) are potentially many bytes and their values may not be
2579 used in arithmetic expressions.
2583 * Chars:: Characters
2587 @subsubsection Strings
2589 @cindex string constants
2590 @cindex constants, string
2591 A @dfn{string} is written between double-quotes. It may contain
2592 double-quotes or null characters. The way to get special characters
2593 into a string is to @dfn{escape} these characters: precede them with
2594 a backslash @samp{\} character. For example @samp{\\} represents
2595 one backslash: the first @code{\} is an escape which tells
2596 @command{@value{AS}} to interpret the second character literally as a backslash
2597 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2598 escape character). The complete list of escapes follows.
2600 @cindex escape codes, character
2601 @cindex character escape codes
2604 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2606 @cindex @code{\b} (backspace character)
2607 @cindex backspace (@code{\b})
2609 Mnemonic for backspace; for ASCII this is octal code 010.
2612 @c Mnemonic for EOText; for ASCII this is octal code 004.
2614 @cindex @code{\f} (formfeed character)
2615 @cindex formfeed (@code{\f})
2617 Mnemonic for FormFeed; for ASCII this is octal code 014.
2619 @cindex @code{\n} (newline character)
2620 @cindex newline (@code{\n})
2622 Mnemonic for newline; for ASCII this is octal code 012.
2625 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2627 @cindex @code{\r} (carriage return character)
2628 @cindex carriage return (@code{\r})
2630 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2633 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2634 @c other assemblers.
2636 @cindex @code{\t} (tab)
2637 @cindex tab (@code{\t})
2639 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2642 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2643 @c @item \x @var{digit} @var{digit} @var{digit}
2644 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2646 @cindex @code{\@var{ddd}} (octal character code)
2647 @cindex octal character code (@code{\@var{ddd}})
2648 @item \ @var{digit} @var{digit} @var{digit}
2649 An octal character code. The numeric code is 3 octal digits.
2650 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2651 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2653 @cindex @code{\@var{xd...}} (hex character code)
2654 @cindex hex character code (@code{\@var{xd...}})
2655 @item \@code{x} @var{hex-digits...}
2656 A hex character code. All trailing hex digits are combined. Either upper or
2657 lower case @code{x} works.
2659 @cindex @code{\\} (@samp{\} character)
2660 @cindex backslash (@code{\\})
2662 Represents one @samp{\} character.
2665 @c Represents one @samp{'} (accent acute) character.
2666 @c This is needed in single character literals
2667 @c (@xref{Characters,,Character Constants}.) to represent
2670 @cindex @code{\"} (doublequote character)
2671 @cindex doublequote (@code{\"})
2673 Represents one @samp{"} character. Needed in strings to represent
2674 this character, because an unescaped @samp{"} would end the string.
2676 @item \ @var{anything-else}
2677 Any other character when escaped by @kbd{\} gives a warning, but
2678 assembles as if the @samp{\} was not present. The idea is that if
2679 you used an escape sequence you clearly didn't want the literal
2680 interpretation of the following character. However @command{@value{AS}} has no
2681 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2682 code and warns you of the fact.
2685 Which characters are escapable, and what those escapes represent,
2686 varies widely among assemblers. The current set is what we think
2687 the BSD 4.2 assembler recognizes, and is a subset of what most C
2688 compilers recognize. If you are in doubt, do not use an escape
2692 @subsubsection Characters
2694 @cindex single character constant
2695 @cindex character, single
2696 @cindex constant, single character
2697 A single character may be written as a single quote immediately
2698 followed by that character. The same escapes apply to characters as
2699 to strings. So if you want to write the character backslash, you
2700 must write @kbd{'\\} where the first @code{\} escapes the second
2701 @code{\}. As you can see, the quote is an acute accent, not a
2702 grave accent. A newline
2704 @ifclear abnormal-separator
2705 (or semicolon @samp{;})
2707 @ifset abnormal-separator
2709 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2714 immediately following an acute accent is taken as a literal character
2715 and does not count as the end of a statement. The value of a character
2716 constant in a numeric expression is the machine's byte-wide code for
2717 that character. @command{@value{AS}} assumes your character code is ASCII:
2718 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2721 @subsection Number Constants
2723 @cindex constants, number
2724 @cindex number constants
2725 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2726 are stored in the target machine. @emph{Integers} are numbers that
2727 would fit into an @code{int} in the C language. @emph{Bignums} are
2728 integers, but they are stored in more than 32 bits. @emph{Flonums}
2729 are floating point numbers, described below.
2732 * Integers:: Integers
2737 * Bit Fields:: Bit Fields
2743 @subsubsection Integers
2745 @cindex constants, integer
2747 @cindex binary integers
2748 @cindex integers, binary
2749 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2750 the binary digits @samp{01}.
2752 @cindex octal integers
2753 @cindex integers, octal
2754 An octal integer is @samp{0} followed by zero or more of the octal
2755 digits (@samp{01234567}).
2757 @cindex decimal integers
2758 @cindex integers, decimal
2759 A decimal integer starts with a non-zero digit followed by zero or
2760 more digits (@samp{0123456789}).
2762 @cindex hexadecimal integers
2763 @cindex integers, hexadecimal
2764 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2765 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2767 Integers have the usual values. To denote a negative integer, use
2768 the prefix operator @samp{-} discussed under expressions
2769 (@pxref{Prefix Ops,,Prefix Operators}).
2772 @subsubsection Bignums
2775 @cindex constants, bignum
2776 A @dfn{bignum} has the same syntax and semantics as an integer
2777 except that the number (or its negative) takes more than 32 bits to
2778 represent in binary. The distinction is made because in some places
2779 integers are permitted while bignums are not.
2782 @subsubsection Flonums
2784 @cindex floating point numbers
2785 @cindex constants, floating point
2787 @cindex precision, floating point
2788 A @dfn{flonum} represents a floating point number. The translation is
2789 indirect: a decimal floating point number from the text is converted by
2790 @command{@value{AS}} to a generic binary floating point number of more than
2791 sufficient precision. This generic floating point number is converted
2792 to a particular computer's floating point format (or formats) by a
2793 portion of @command{@value{AS}} specialized to that computer.
2795 A flonum is written by writing (in order)
2800 (@samp{0} is optional on the HPPA.)
2804 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2806 @kbd{e} is recommended. Case is not important.
2808 @c FIXME: verify if flonum syntax really this vague for most cases
2809 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2810 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2813 On the H8/300, Renesas / SuperH SH,
2814 and AMD 29K architectures, the letter must be
2815 one of the letters @samp{DFPRSX} (in upper or lower case).
2817 On the ARC, the letter must be one of the letters @samp{DFRS}
2818 (in upper or lower case).
2820 On the Intel 960 architecture, the letter must be
2821 one of the letters @samp{DFT} (in upper or lower case).
2823 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2827 One of the letters @samp{DFRS} (in upper or lower case).
2830 One of the letters @samp{DFPRSX} (in upper or lower case).
2833 The letter @samp{E} (upper case only).
2836 One of the letters @samp{DFT} (in upper or lower case).
2841 An optional sign: either @samp{+} or @samp{-}.
2844 An optional @dfn{integer part}: zero or more decimal digits.
2847 An optional @dfn{fractional part}: @samp{.} followed by zero
2848 or more decimal digits.
2851 An optional exponent, consisting of:
2855 An @samp{E} or @samp{e}.
2856 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2857 @c principle this can perfectly well be different on different targets.
2859 Optional sign: either @samp{+} or @samp{-}.
2861 One or more decimal digits.
2866 At least one of the integer part or the fractional part must be
2867 present. The floating point number has the usual base-10 value.
2869 @command{@value{AS}} does all processing using integers. Flonums are computed
2870 independently of any floating point hardware in the computer running
2871 @command{@value{AS}}.
2875 @c Bit fields are written as a general facility but are also controlled
2876 @c by a conditional-compilation flag---which is as of now (21mar91)
2877 @c turned on only by the i960 config of GAS.
2879 @subsubsection Bit Fields
2882 @cindex constants, bit field
2883 You can also define numeric constants as @dfn{bit fields}.
2884 Specify two numbers separated by a colon---
2886 @var{mask}:@var{value}
2889 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2892 The resulting number is then packed
2894 @c this conditional paren in case bit fields turned on elsewhere than 960
2895 (in host-dependent byte order)
2897 into a field whose width depends on which assembler directive has the
2898 bit-field as its argument. Overflow (a result from the bitwise and
2899 requiring more binary digits to represent) is not an error; instead,
2900 more constants are generated, of the specified width, beginning with the
2901 least significant digits.@refill
2903 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2904 @code{.short}, and @code{.word} accept bit-field arguments.
2909 @chapter Sections and Relocation
2914 * Secs Background:: Background
2915 * Ld Sections:: Linker Sections
2916 * As Sections:: Assembler Internal Sections
2917 * Sub-Sections:: Sub-Sections
2921 @node Secs Background
2924 Roughly, a section is a range of addresses, with no gaps; all data
2925 ``in'' those addresses is treated the same for some particular purpose.
2926 For example there may be a ``read only'' section.
2928 @cindex linker, and assembler
2929 @cindex assembler, and linker
2930 The linker @code{@value{LD}} reads many object files (partial programs) and
2931 combines their contents to form a runnable program. When @command{@value{AS}}
2932 emits an object file, the partial program is assumed to start at address 0.
2933 @code{@value{LD}} assigns the final addresses for the partial program, so that
2934 different partial programs do not overlap. This is actually an
2935 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2938 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2939 addresses. These blocks slide to their run-time addresses as rigid
2940 units; their length does not change and neither does the order of bytes
2941 within them. Such a rigid unit is called a @emph{section}. Assigning
2942 run-time addresses to sections is called @dfn{relocation}. It includes
2943 the task of adjusting mentions of object-file addresses so they refer to
2944 the proper run-time addresses.
2946 For the H8/300, and for the Renesas / SuperH SH,
2947 @command{@value{AS}} pads sections if needed to
2948 ensure they end on a word (sixteen bit) boundary.
2951 @cindex standard assembler sections
2952 An object file written by @command{@value{AS}} has at least three sections, any
2953 of which may be empty. These are named @dfn{text}, @dfn{data} and
2958 When it generates COFF or ELF output,
2960 @command{@value{AS}} can also generate whatever other named sections you specify
2961 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2962 If you do not use any directives that place output in the @samp{.text}
2963 or @samp{.data} sections, these sections still exist, but are empty.
2968 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2970 @command{@value{AS}} can also generate whatever other named sections you
2971 specify using the @samp{.space} and @samp{.subspace} directives. See
2972 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2973 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2974 assembler directives.
2977 Additionally, @command{@value{AS}} uses different names for the standard
2978 text, data, and bss sections when generating SOM output. Program text
2979 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2980 BSS into @samp{$BSS$}.
2984 Within the object file, the text section starts at address @code{0}, the
2985 data section follows, and the bss section follows the data section.
2988 When generating either SOM or ELF output files on the HPPA, the text
2989 section starts at address @code{0}, the data section at address
2990 @code{0x4000000}, and the bss section follows the data section.
2993 To let @code{@value{LD}} know which data changes when the sections are
2994 relocated, and how to change that data, @command{@value{AS}} also writes to the
2995 object file details of the relocation needed. To perform relocation
2996 @code{@value{LD}} must know, each time an address in the object
3000 Where in the object file is the beginning of this reference to
3003 How long (in bytes) is this reference?
3005 Which section does the address refer to? What is the numeric value of
3007 (@var{address}) @minus{} (@var{start-address of section})?
3010 Is the reference to an address ``Program-Counter relative''?
3013 @cindex addresses, format of
3014 @cindex section-relative addressing
3015 In fact, every address @command{@value{AS}} ever uses is expressed as
3017 (@var{section}) + (@var{offset into section})
3020 Further, most expressions @command{@value{AS}} computes have this section-relative
3023 (For some object formats, such as SOM for the HPPA, some expressions are
3024 symbol-relative instead.)
3027 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3028 @var{N} into section @var{secname}.''
3030 Apart from text, data and bss sections you need to know about the
3031 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3032 addresses in the absolute section remain unchanged. For example, address
3033 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3034 @code{@value{LD}}. Although the linker never arranges two partial programs'
3035 data sections with overlapping addresses after linking, @emph{by definition}
3036 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3037 part of a program is always the same address when the program is running as
3038 address @code{@{absolute@ 239@}} in any other part of the program.
3040 The idea of sections is extended to the @dfn{undefined} section. Any
3041 address whose section is unknown at assembly time is by definition
3042 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3043 Since numbers are always defined, the only way to generate an undefined
3044 address is to mention an undefined symbol. A reference to a named
3045 common block would be such a symbol: its value is unknown at assembly
3046 time so it has section @emph{undefined}.
3048 By analogy the word @emph{section} is used to describe groups of sections in
3049 the linked program. @code{@value{LD}} puts all partial programs' text
3050 sections in contiguous addresses in the linked program. It is
3051 customary to refer to the @emph{text section} of a program, meaning all
3052 the addresses of all partial programs' text sections. Likewise for
3053 data and bss sections.
3055 Some sections are manipulated by @code{@value{LD}}; others are invented for
3056 use of @command{@value{AS}} and have no meaning except during assembly.
3059 @section Linker Sections
3060 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3065 @cindex named sections
3066 @cindex sections, named
3067 @item named sections
3070 @cindex text section
3071 @cindex data section
3075 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3076 separate but equal sections. Anything you can say of one section is
3079 When the program is running, however, it is
3080 customary for the text section to be unalterable. The
3081 text section is often shared among processes: it contains
3082 instructions, constants and the like. The data section of a running
3083 program is usually alterable: for example, C variables would be stored
3084 in the data section.
3089 This section contains zeroed bytes when your program begins running. It
3090 is used to hold uninitialized variables or common storage. The length of
3091 each partial program's bss section is important, but because it starts
3092 out containing zeroed bytes there is no need to store explicit zero
3093 bytes in the object file. The bss section was invented to eliminate
3094 those explicit zeros from object files.
3096 @cindex absolute section
3097 @item absolute section
3098 Address 0 of this section is always ``relocated'' to runtime address 0.
3099 This is useful if you want to refer to an address that @code{@value{LD}} must
3100 not change when relocating. In this sense we speak of absolute
3101 addresses being ``unrelocatable'': they do not change during relocation.
3103 @cindex undefined section
3104 @item undefined section
3105 This ``section'' is a catch-all for address references to objects not in
3106 the preceding sections.
3107 @c FIXME: ref to some other doc on obj-file formats could go here.
3110 @cindex relocation example
3111 An idealized example of three relocatable sections follows.
3113 The example uses the traditional section names @samp{.text} and @samp{.data}.
3115 Memory addresses are on the horizontal axis.
3119 @c END TEXI2ROFF-KILL
3122 partial program # 1: |ttttt|dddd|00|
3129 partial program # 2: |TTT|DDD|000|
3132 +--+---+-----+--+----+---+-----+~~
3133 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3134 +--+---+-----+--+----+---+-----+~~
3136 addresses: 0 @dots{}
3143 \line{\it Partial program \#1: \hfil}
3144 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3145 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3147 \line{\it Partial program \#2: \hfil}
3148 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3149 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3151 \line{\it linked program: \hfil}
3152 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3153 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3154 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3155 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3157 \line{\it addresses: \hfil}
3161 @c END TEXI2ROFF-KILL
3164 @section Assembler Internal Sections
3166 @cindex internal assembler sections
3167 @cindex sections in messages, internal
3168 These sections are meant only for the internal use of @command{@value{AS}}. They
3169 have no meaning at run-time. You do not really need to know about these
3170 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3171 warning messages, so it might be helpful to have an idea of their
3172 meanings to @command{@value{AS}}. These sections are used to permit the
3173 value of every expression in your assembly language program to be a
3174 section-relative address.
3177 @cindex assembler internal logic error
3178 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3179 An internal assembler logic error has been found. This means there is a
3180 bug in the assembler.
3182 @cindex expr (internal section)
3184 The assembler stores complex expression internally as combinations of
3185 symbols. When it needs to represent an expression as a symbol, it puts
3186 it in the expr section.
3188 @c FIXME item transfer[t] vector preload
3189 @c FIXME item transfer[t] vector postload
3190 @c FIXME item register
3194 @section Sub-Sections
3196 @cindex numbered subsections
3197 @cindex grouping data
3203 fall into two sections: text and data.
3205 You may have separate groups of
3207 data in named sections
3211 data in named sections
3217 that you want to end up near to each other in the object file, even though they
3218 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3219 use @dfn{subsections} for this purpose. Within each section, there can be
3220 numbered subsections with values from 0 to 8192. Objects assembled into the
3221 same subsection go into the object file together with other objects in the same
3222 subsection. For example, a compiler might want to store constants in the text
3223 section, but might not want to have them interspersed with the program being
3224 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3225 section of code being output, and a @samp{.text 1} before each group of
3226 constants being output.
3228 Subsections are optional. If you do not use subsections, everything
3229 goes in subsection number zero.
3232 Each subsection is zero-padded up to a multiple of four bytes.
3233 (Subsections may be padded a different amount on different flavors
3234 of @command{@value{AS}}.)
3238 On the H8/300 platform, each subsection is zero-padded to a word
3239 boundary (two bytes).
3240 The same is true on the Renesas SH.
3243 @c FIXME section padding (alignment)?
3244 @c Rich Pixley says padding here depends on target obj code format; that
3245 @c doesn't seem particularly useful to say without further elaboration,
3246 @c so for now I say nothing about it. If this is a generic BFD issue,
3247 @c these paragraphs might need to vanish from this manual, and be
3248 @c discussed in BFD chapter of binutils (or some such).
3252 Subsections appear in your object file in numeric order, lowest numbered
3253 to highest. (All this to be compatible with other people's assemblers.)
3254 The object file contains no representation of subsections; @code{@value{LD}} and
3255 other programs that manipulate object files see no trace of them.
3256 They just see all your text subsections as a text section, and all your
3257 data subsections as a data section.
3259 To specify which subsection you want subsequent statements assembled
3260 into, use a numeric argument to specify it, in a @samp{.text
3261 @var{expression}} or a @samp{.data @var{expression}} statement.
3264 When generating COFF output, you
3269 can also use an extra subsection
3270 argument with arbitrary named sections: @samp{.section @var{name},
3275 When generating ELF output, you
3280 can also use the @code{.subsection} directive (@pxref{SubSection})
3281 to specify a subsection: @samp{.subsection @var{expression}}.
3283 @var{Expression} should be an absolute expression
3284 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3285 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3286 begins in @code{text 0}. For instance:
3288 .text 0 # The default subsection is text 0 anyway.
3289 .ascii "This lives in the first text subsection. *"
3291 .ascii "But this lives in the second text subsection."
3293 .ascii "This lives in the data section,"
3294 .ascii "in the first data subsection."
3296 .ascii "This lives in the first text section,"
3297 .ascii "immediately following the asterisk (*)."
3300 Each section has a @dfn{location counter} incremented by one for every byte
3301 assembled into that section. Because subsections are merely a convenience
3302 restricted to @command{@value{AS}} there is no concept of a subsection location
3303 counter. There is no way to directly manipulate a location counter---but the
3304 @code{.align} directive changes it, and any label definition captures its
3305 current value. The location counter of the section where statements are being
3306 assembled is said to be the @dfn{active} location counter.
3309 @section bss Section
3312 @cindex common variable storage
3313 The bss section is used for local common variable storage.
3314 You may allocate address space in the bss section, but you may
3315 not dictate data to load into it before your program executes. When
3316 your program starts running, all the contents of the bss
3317 section are zeroed bytes.
3319 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3320 @ref{Lcomm,,@code{.lcomm}}.
3322 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3323 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3326 When assembling for a target which supports multiple sections, such as ELF or
3327 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3328 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3329 section. Typically the section will only contain symbol definitions and
3330 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3337 Symbols are a central concept: the programmer uses symbols to name
3338 things, the linker uses symbols to link, and the debugger uses symbols
3342 @cindex debuggers, and symbol order
3343 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3344 the same order they were declared. This may break some debuggers.
3349 * Setting Symbols:: Giving Symbols Other Values
3350 * Symbol Names:: Symbol Names
3351 * Dot:: The Special Dot Symbol
3352 * Symbol Attributes:: Symbol Attributes
3359 A @dfn{label} is written as a symbol immediately followed by a colon
3360 @samp{:}. The symbol then represents the current value of the
3361 active location counter, and is, for example, a suitable instruction
3362 operand. You are warned if you use the same symbol to represent two
3363 different locations: the first definition overrides any other
3367 On the HPPA, the usual form for a label need not be immediately followed by a
3368 colon, but instead must start in column zero. Only one label may be defined on
3369 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3370 provides a special directive @code{.label} for defining labels more flexibly.
3373 @node Setting Symbols
3374 @section Giving Symbols Other Values
3376 @cindex assigning values to symbols
3377 @cindex symbol values, assigning
3378 A symbol can be given an arbitrary value by writing a symbol, followed
3379 by an equals sign @samp{=}, followed by an expression
3380 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3381 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3382 equals sign @samp{=}@samp{=} here represents an equivalent of the
3383 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3386 Blackfin does not support symbol assignment with @samp{=}.
3390 @section Symbol Names
3392 @cindex symbol names
3393 @cindex names, symbol
3394 @ifclear SPECIAL-SYMS
3395 Symbol names begin with a letter or with one of @samp{._}. On most
3396 machines, you can also use @code{$} in symbol names; exceptions are
3397 noted in @ref{Machine Dependencies}. That character may be followed by any
3398 string of digits, letters, dollar signs (unless otherwise noted for a
3399 particular target machine), and underscores.
3403 Symbol names begin with a letter or with one of @samp{._}. On the
3404 Renesas SH you can also use @code{$} in symbol names. That
3405 character may be followed by any string of digits, letters, dollar signs (save
3406 on the H8/300), and underscores.
3410 Case of letters is significant: @code{foo} is a different symbol name
3413 Each symbol has exactly one name. Each name in an assembly language program
3414 refers to exactly one symbol. You may use that symbol name any number of times
3417 @subheading Local Symbol Names
3419 @cindex local symbol names
3420 @cindex symbol names, local
3421 A local symbol is any symbol beginning with certain local label prefixes.
3422 By default, the local label prefix is @samp{.L} for ELF systems or
3423 @samp{L} for traditional a.out systems, but each target may have its own
3424 set of local label prefixes.
3426 On the HPPA local symbols begin with @samp{L$}.
3429 Local symbols are defined and used within the assembler, but they are
3430 normally not saved in object files. Thus, they are not visible when debugging.
3431 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3432 @option{-L}}) to retain the local symbols in the object files.
3434 @subheading Local Labels
3436 @cindex local labels
3437 @cindex temporary symbol names
3438 @cindex symbol names, temporary
3439 Local labels help compilers and programmers use names temporarily.
3440 They create symbols which are guaranteed to be unique over the entire scope of
3441 the input source code and which can be referred to by a simple notation.
3442 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3443 represents any positive integer). To refer to the most recent previous
3444 definition of that label write @samp{@b{N}b}, using the same number as when
3445 you defined the label. To refer to the next definition of a local label, write
3446 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3449 There is no restriction on how you can use these labels, and you can reuse them
3450 too. So that it is possible to repeatedly define the same local label (using
3451 the same number @samp{@b{N}}), although you can only refer to the most recently
3452 defined local label of that number (for a backwards reference) or the next
3453 definition of a specific local label for a forward reference. It is also worth
3454 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3455 implemented in a slightly more efficient manner than the others.
3466 Which is the equivalent of:
3469 label_1: branch label_3
3470 label_2: branch label_1
3471 label_3: branch label_4
3472 label_4: branch label_3
3475 Local label names are only a notational device. They are immediately
3476 transformed into more conventional symbol names before the assembler uses them.
3477 The symbol names are stored in the symbol table, appear in error messages, and
3478 are optionally emitted to the object file. The names are constructed using
3482 @item @emph{local label prefix}
3483 All local symbols begin with the system-specific local label prefix.
3484 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3485 that start with the local label prefix. These labels are
3486 used for symbols you are never intended to see. If you use the
3487 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3488 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3489 you may use them in debugging.
3492 This is the number that was used in the local label definition. So if the
3493 label is written @samp{55:} then the number is @samp{55}.
3496 This unusual character is included so you do not accidentally invent a symbol
3497 of the same name. The character has ASCII value of @samp{\002} (control-B).
3499 @item @emph{ordinal number}
3500 This is a serial number to keep the labels distinct. The first definition of
3501 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3502 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3503 the number @samp{1} and its 15th definition gets @samp{15} as well.
3506 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3507 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3509 @subheading Dollar Local Labels
3510 @cindex dollar local symbols
3512 @code{@value{AS}} also supports an even more local form of local labels called
3513 dollar labels. These labels go out of scope (i.e., they become undefined) as
3514 soon as a non-local label is defined. Thus they remain valid for only a small
3515 region of the input source code. Normal local labels, by contrast, remain in
3516 scope for the entire file, or until they are redefined by another occurrence of
3517 the same local label.
3519 Dollar labels are defined in exactly the same way as ordinary local labels,
3520 except that they have a dollar sign suffix to their numeric value, e.g.,
3523 They can also be distinguished from ordinary local labels by their transformed
3524 names which use ASCII character @samp{\001} (control-A) as the magic character
3525 to distinguish them from ordinary labels. For example, the fifth definition of
3526 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3529 @section The Special Dot Symbol
3531 @cindex dot (symbol)
3532 @cindex @code{.} (symbol)
3533 @cindex current address
3534 @cindex location counter
3535 The special symbol @samp{.} refers to the current address that
3536 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3537 .long .} defines @code{melvin} to contain its own address.
3538 Assigning a value to @code{.} is treated the same as a @code{.org}
3540 @ifclear no-space-dir
3541 Thus, the expression @samp{.=.+4} is the same as saying
3545 @node Symbol Attributes
3546 @section Symbol Attributes
3548 @cindex symbol attributes
3549 @cindex attributes, symbol
3550 Every symbol has, as well as its name, the attributes ``Value'' and
3551 ``Type''. Depending on output format, symbols can also have auxiliary
3554 The detailed definitions are in @file{a.out.h}.
3557 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3558 all these attributes, and probably won't warn you. This makes the
3559 symbol an externally defined symbol, which is generally what you
3563 * Symbol Value:: Value
3564 * Symbol Type:: Type
3567 * a.out Symbols:: Symbol Attributes: @code{a.out}
3571 * a.out Symbols:: Symbol Attributes: @code{a.out}
3574 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3579 * COFF Symbols:: Symbol Attributes for COFF
3582 * SOM Symbols:: Symbol Attributes for SOM
3589 @cindex value of a symbol
3590 @cindex symbol value
3591 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3592 location in the text, data, bss or absolute sections the value is the
3593 number of addresses from the start of that section to the label.
3594 Naturally for text, data and bss sections the value of a symbol changes
3595 as @code{@value{LD}} changes section base addresses during linking. Absolute
3596 symbols' values do not change during linking: that is why they are
3599 The value of an undefined symbol is treated in a special way. If it is
3600 0 then the symbol is not defined in this assembler source file, and
3601 @code{@value{LD}} tries to determine its value from other files linked into the
3602 same program. You make this kind of symbol simply by mentioning a symbol
3603 name without defining it. A non-zero value represents a @code{.comm}
3604 common declaration. The value is how much common storage to reserve, in
3605 bytes (addresses). The symbol refers to the first address of the
3611 @cindex type of a symbol
3613 The type attribute of a symbol contains relocation (section)
3614 information, any flag settings indicating that a symbol is external, and
3615 (optionally), other information for linkers and debuggers. The exact
3616 format depends on the object-code output format in use.
3621 @c The following avoids a "widow" subsection title. @group would be
3622 @c better if it were available outside examples.
3625 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3627 @cindex @code{b.out} symbol attributes
3628 @cindex symbol attributes, @code{b.out}
3629 These symbol attributes appear only when @command{@value{AS}} is configured for
3630 one of the Berkeley-descended object output formats---@code{a.out} or
3636 @subsection Symbol Attributes: @code{a.out}
3638 @cindex @code{a.out} symbol attributes
3639 @cindex symbol attributes, @code{a.out}
3645 @subsection Symbol Attributes: @code{a.out}
3647 @cindex @code{a.out} symbol attributes
3648 @cindex symbol attributes, @code{a.out}
3652 * Symbol Desc:: Descriptor
3653 * Symbol Other:: Other
3657 @subsubsection Descriptor
3659 @cindex descriptor, of @code{a.out} symbol
3660 This is an arbitrary 16-bit value. You may establish a symbol's
3661 descriptor value by using a @code{.desc} statement
3662 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3663 @command{@value{AS}}.
3666 @subsubsection Other
3668 @cindex other attribute, of @code{a.out} symbol
3669 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3674 @subsection Symbol Attributes for COFF
3676 @cindex COFF symbol attributes
3677 @cindex symbol attributes, COFF
3679 The COFF format supports a multitude of auxiliary symbol attributes;
3680 like the primary symbol attributes, they are set between @code{.def} and
3681 @code{.endef} directives.
3683 @subsubsection Primary Attributes
3685 @cindex primary attributes, COFF symbols
3686 The symbol name is set with @code{.def}; the value and type,
3687 respectively, with @code{.val} and @code{.type}.
3689 @subsubsection Auxiliary Attributes
3691 @cindex auxiliary attributes, COFF symbols
3692 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3693 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3694 table information for COFF.
3699 @subsection Symbol Attributes for SOM
3701 @cindex SOM symbol attributes
3702 @cindex symbol attributes, SOM
3704 The SOM format for the HPPA supports a multitude of symbol attributes set with
3705 the @code{.EXPORT} and @code{.IMPORT} directives.
3707 The attributes are described in @cite{HP9000 Series 800 Assembly
3708 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3709 @code{EXPORT} assembler directive documentation.
3713 @chapter Expressions
3717 @cindex numeric values
3718 An @dfn{expression} specifies an address or numeric value.
3719 Whitespace may precede and/or follow an expression.
3721 The result of an expression must be an absolute number, or else an offset into
3722 a particular section. If an expression is not absolute, and there is not
3723 enough information when @command{@value{AS}} sees the expression to know its
3724 section, a second pass over the source program might be necessary to interpret
3725 the expression---but the second pass is currently not implemented.
3726 @command{@value{AS}} aborts with an error message in this situation.
3729 * Empty Exprs:: Empty Expressions
3730 * Integer Exprs:: Integer Expressions
3734 @section Empty Expressions
3736 @cindex empty expressions
3737 @cindex expressions, empty
3738 An empty expression has no value: it is just whitespace or null.
3739 Wherever an absolute expression is required, you may omit the
3740 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3741 is compatible with other assemblers.
3744 @section Integer Expressions
3746 @cindex integer expressions
3747 @cindex expressions, integer
3748 An @dfn{integer expression} is one or more @emph{arguments} delimited
3749 by @emph{operators}.
3752 * Arguments:: Arguments
3753 * Operators:: Operators
3754 * Prefix Ops:: Prefix Operators
3755 * Infix Ops:: Infix Operators
3759 @subsection Arguments
3761 @cindex expression arguments
3762 @cindex arguments in expressions
3763 @cindex operands in expressions
3764 @cindex arithmetic operands
3765 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3766 contexts arguments are sometimes called ``arithmetic operands''. In
3767 this manual, to avoid confusing them with the ``instruction operands'' of
3768 the machine language, we use the term ``argument'' to refer to parts of
3769 expressions only, reserving the word ``operand'' to refer only to machine
3770 instruction operands.
3772 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3773 @var{section} is one of text, data, bss, absolute,
3774 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3777 Numbers are usually integers.
3779 A number can be a flonum or bignum. In this case, you are warned
3780 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3781 these 32 bits are an integer. You may write integer-manipulating
3782 instructions that act on exotic constants, compatible with other
3785 @cindex subexpressions
3786 Subexpressions are a left parenthesis @samp{(} followed by an integer
3787 expression, followed by a right parenthesis @samp{)}; or a prefix
3788 operator followed by an argument.
3791 @subsection Operators
3793 @cindex operators, in expressions
3794 @cindex arithmetic functions
3795 @cindex functions, in expressions
3796 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3797 operators are followed by an argument. Infix operators appear
3798 between their arguments. Operators may be preceded and/or followed by
3802 @subsection Prefix Operator
3804 @cindex prefix operators
3805 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3806 one argument, which must be absolute.
3808 @c the tex/end tex stuff surrounding this small table is meant to make
3809 @c it align, on the printed page, with the similar table in the next
3810 @c section (which is inside an enumerate).
3812 \global\advance\leftskip by \itemindent
3817 @dfn{Negation}. Two's complement negation.
3819 @dfn{Complementation}. Bitwise not.
3823 \global\advance\leftskip by -\itemindent
3827 @subsection Infix Operators
3829 @cindex infix operators
3830 @cindex operators, permitted arguments
3831 @dfn{Infix operators} take two arguments, one on either side. Operators
3832 have precedence, but operations with equal precedence are performed left
3833 to right. Apart from @code{+} or @option{-}, both arguments must be
3834 absolute, and the result is absolute.
3837 @cindex operator precedence
3838 @cindex precedence of operators
3845 @dfn{Multiplication}.
3848 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3854 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3857 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3861 Intermediate precedence
3866 @dfn{Bitwise Inclusive Or}.
3872 @dfn{Bitwise Exclusive Or}.
3875 @dfn{Bitwise Or Not}.
3882 @cindex addition, permitted arguments
3883 @cindex plus, permitted arguments
3884 @cindex arguments for addition
3886 @dfn{Addition}. If either argument is absolute, the result has the section of
3887 the other argument. You may not add together arguments from different
3890 @cindex subtraction, permitted arguments
3891 @cindex minus, permitted arguments
3892 @cindex arguments for subtraction
3894 @dfn{Subtraction}. If the right argument is absolute, the
3895 result has the section of the left argument.
3896 If both arguments are in the same section, the result is absolute.
3897 You may not subtract arguments from different sections.
3898 @c FIXME is there still something useful to say about undefined - undefined ?
3900 @cindex comparison expressions
3901 @cindex expressions, comparison
3906 @dfn{Is Not Equal To}
3910 @dfn{Is Greater Than}
3912 @dfn{Is Greater Than Or Equal To}
3914 @dfn{Is Less Than Or Equal To}
3916 The comparison operators can be used as infix operators. A true results has a
3917 value of -1 whereas a false result has a value of 0. Note, these operators
3918 perform signed comparisons.
3921 @item Lowest Precedence
3930 These two logical operations can be used to combine the results of sub
3931 expressions. Note, unlike the comparison operators a true result returns a
3932 value of 1 but a false results does still return 0. Also note that the logical
3933 or operator has a slightly lower precedence than logical and.
3938 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3939 address; you can only have a defined section in one of the two arguments.
3942 @chapter Assembler Directives
3944 @cindex directives, machine independent
3945 @cindex pseudo-ops, machine independent
3946 @cindex machine independent directives
3947 All assembler directives have names that begin with a period (@samp{.}).
3948 The rest of the name is letters, usually in lower case.
3950 This chapter discusses directives that are available regardless of the
3951 target machine configuration for the @sc{gnu} assembler.
3953 Some machine configurations provide additional directives.
3954 @xref{Machine Dependencies}.
3957 @ifset machine-directives
3958 @xref{Machine Dependencies}, for additional directives.
3963 * Abort:: @code{.abort}
3965 * ABORT (COFF):: @code{.ABORT}
3968 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3969 * Altmacro:: @code{.altmacro}
3970 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3971 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3972 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3973 * Byte:: @code{.byte @var{expressions}}
3974 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3975 * Comm:: @code{.comm @var{symbol} , @var{length} }
3976 * Data:: @code{.data @var{subsection}}
3978 * Def:: @code{.def @var{name}}
3981 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3987 * Double:: @code{.double @var{flonums}}
3988 * Eject:: @code{.eject}
3989 * Else:: @code{.else}
3990 * Elseif:: @code{.elseif}
3993 * Endef:: @code{.endef}
3996 * Endfunc:: @code{.endfunc}
3997 * Endif:: @code{.endif}
3998 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3999 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4000 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4002 * Error:: @code{.error @var{string}}
4003 * Exitm:: @code{.exitm}
4004 * Extern:: @code{.extern}
4005 * Fail:: @code{.fail}
4006 * File:: @code{.file}
4007 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4008 * Float:: @code{.float @var{flonums}}
4009 * Func:: @code{.func}
4010 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4012 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4013 * Hidden:: @code{.hidden @var{names}}
4016 * hword:: @code{.hword @var{expressions}}
4017 * Ident:: @code{.ident}
4018 * If:: @code{.if @var{absolute expression}}
4019 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4020 * Include:: @code{.include "@var{file}"}
4021 * Int:: @code{.int @var{expressions}}
4023 * Internal:: @code{.internal @var{names}}
4026 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4027 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4028 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4029 * Lflags:: @code{.lflags}
4030 @ifclear no-line-dir
4031 * Line:: @code{.line @var{line-number}}
4034 * Linkonce:: @code{.linkonce [@var{type}]}
4035 * List:: @code{.list}
4036 * Ln:: @code{.ln @var{line-number}}
4037 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4038 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4040 * Local:: @code{.local @var{names}}
4043 * Long:: @code{.long @var{expressions}}
4045 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4048 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4049 * MRI:: @code{.mri @var{val}}
4050 * Noaltmacro:: @code{.noaltmacro}
4051 * Nolist:: @code{.nolist}
4052 * Octa:: @code{.octa @var{bignums}}
4053 * Org:: @code{.org @var{new-lc}, @var{fill}}
4054 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4056 * PopSection:: @code{.popsection}
4057 * Previous:: @code{.previous}
4060 * Print:: @code{.print @var{string}}
4062 * Protected:: @code{.protected @var{names}}
4065 * Psize:: @code{.psize @var{lines}, @var{columns}}
4066 * Purgem:: @code{.purgem @var{name}}
4068 * PushSection:: @code{.pushsection @var{name}}
4071 * Quad:: @code{.quad @var{bignums}}
4072 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4073 * Rept:: @code{.rept @var{count}}
4074 * Sbttl:: @code{.sbttl "@var{subheading}"}
4076 * Scl:: @code{.scl @var{class}}
4079 * Section:: @code{.section @var{name}[, @var{flags}]}
4082 * Set:: @code{.set @var{symbol}, @var{expression}}
4083 * Short:: @code{.short @var{expressions}}
4084 * Single:: @code{.single @var{flonums}}
4086 * Size:: @code{.size [@var{name} , @var{expression}]}
4088 @ifclear no-space-dir
4089 * Skip:: @code{.skip @var{size} , @var{fill}}
4092 * Sleb128:: @code{.sleb128 @var{expressions}}
4093 @ifclear no-space-dir
4094 * Space:: @code{.space @var{size} , @var{fill}}
4097 * Stab:: @code{.stabd, .stabn, .stabs}
4100 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4101 * Struct:: @code{.struct @var{expression}}
4103 * SubSection:: @code{.subsection}
4104 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4108 * Tag:: @code{.tag @var{structname}}
4111 * Text:: @code{.text @var{subsection}}
4112 * Title:: @code{.title "@var{heading}"}
4114 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4117 * Uleb128:: @code{.uleb128 @var{expressions}}
4119 * Val:: @code{.val @var{addr}}
4123 * Version:: @code{.version "@var{string}"}
4124 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4125 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4128 * Warning:: @code{.warning @var{string}}
4129 * Weak:: @code{.weak @var{names}}
4130 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4131 * Word:: @code{.word @var{expressions}}
4132 * Deprecated:: Deprecated Directives
4136 @section @code{.abort}
4138 @cindex @code{abort} directive
4139 @cindex stopping the assembly
4140 This directive stops the assembly immediately. It is for
4141 compatibility with other assemblers. The original idea was that the
4142 assembly language source would be piped into the assembler. If the sender
4143 of the source quit, it could use this directive tells @command{@value{AS}} to
4144 quit also. One day @code{.abort} will not be supported.
4148 @section @code{.ABORT} (COFF)
4150 @cindex @code{ABORT} directive
4151 When producing COFF output, @command{@value{AS}} accepts this directive as a
4152 synonym for @samp{.abort}.
4155 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4161 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4163 @cindex padding the location counter
4164 @cindex @code{align} directive
4165 Pad the location counter (in the current subsection) to a particular storage
4166 boundary. The first expression (which must be absolute) is the alignment
4167 required, as described below.
4169 The second expression (also absolute) gives the fill value to be stored in the
4170 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4171 padding bytes are normally zero. However, on some systems, if the section is
4172 marked as containing code and the fill value is omitted, the space is filled
4173 with no-op instructions.
4175 The third expression is also absolute, and is also optional. If it is present,
4176 it is the maximum number of bytes that should be skipped by this alignment
4177 directive. If doing the alignment would require skipping more bytes than the
4178 specified maximum, then the alignment is not done at all. You can omit the
4179 fill value (the second argument) entirely by simply using two commas after the
4180 required alignment; this can be useful if you want the alignment to be filled
4181 with no-op instructions when appropriate.
4183 The way the required alignment is specified varies from system to system.
4184 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4185 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4186 alignment request in bytes. For example @samp{.align 8} advances
4187 the location counter until it is a multiple of 8. If the location counter
4188 is already a multiple of 8, no change is needed. For the tic54x, the
4189 first expression is the alignment request in words.
4191 For other systems, including ppc, i386 using a.out format, arm and
4192 strongarm, it is the
4193 number of low-order zero bits the location counter must have after
4194 advancement. For example @samp{.align 3} advances the location
4195 counter until it a multiple of 8. If the location counter is already a
4196 multiple of 8, no change is needed.
4198 This inconsistency is due to the different behaviors of the various
4199 native assemblers for these systems which GAS must emulate.
4200 GAS also provides @code{.balign} and @code{.p2align} directives,
4201 described later, which have a consistent behavior across all
4202 architectures (but are specific to GAS).
4205 @section @code{.altmacro}
4206 Enable alternate macro mode, enabling:
4209 @item LOCAL @var{name} [ , @dots{} ]
4210 One additional directive, @code{LOCAL}, is available. It is used to
4211 generate a string replacement for each of the @var{name} arguments, and
4212 replace any instances of @var{name} in each macro expansion. The
4213 replacement string is unique in the assembly, and different for each
4214 separate macro expansion. @code{LOCAL} allows you to write macros that
4215 define symbols, without fear of conflict between separate macro expansions.
4217 @item String delimiters
4218 You can write strings delimited in these other ways besides
4219 @code{"@var{string}"}:
4222 @item '@var{string}'
4223 You can delimit strings with single-quote characters.
4225 @item <@var{string}>
4226 You can delimit strings with matching angle brackets.
4229 @item single-character string escape
4230 To include any single character literally in a string (even if the
4231 character would otherwise have some special meaning), you can prefix the
4232 character with @samp{!} (an exclamation mark). For example, you can
4233 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4235 @item Expression results as strings
4236 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4237 and use the result as a string.
4241 @section @code{.ascii "@var{string}"}@dots{}
4243 @cindex @code{ascii} directive
4244 @cindex string literals
4245 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4246 separated by commas. It assembles each string (with no automatic
4247 trailing zero byte) into consecutive addresses.
4250 @section @code{.asciz "@var{string}"}@dots{}
4252 @cindex @code{asciz} directive
4253 @cindex zero-terminated strings
4254 @cindex null-terminated strings
4255 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4256 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4259 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4261 @cindex padding the location counter given number of bytes
4262 @cindex @code{balign} directive
4263 Pad the location counter (in the current subsection) to a particular
4264 storage boundary. The first expression (which must be absolute) is the
4265 alignment request in bytes. For example @samp{.balign 8} advances
4266 the location counter until it is a multiple of 8. If the location counter
4267 is already a multiple of 8, no change is needed.
4269 The second expression (also absolute) gives the fill value to be stored in the
4270 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4271 padding bytes are normally zero. However, on some systems, if the section is
4272 marked as containing code and the fill value is omitted, the space is filled
4273 with no-op instructions.
4275 The third expression is also absolute, and is also optional. If it is present,
4276 it is the maximum number of bytes that should be skipped by this alignment
4277 directive. If doing the alignment would require skipping more bytes than the
4278 specified maximum, then the alignment is not done at all. You can omit the
4279 fill value (the second argument) entirely by simply using two commas after the
4280 required alignment; this can be useful if you want the alignment to be filled
4281 with no-op instructions when appropriate.
4283 @cindex @code{balignw} directive
4284 @cindex @code{balignl} directive
4285 The @code{.balignw} and @code{.balignl} directives are variants of the
4286 @code{.balign} directive. The @code{.balignw} directive treats the fill
4287 pattern as a two byte word value. The @code{.balignl} directives treats the
4288 fill pattern as a four byte longword value. For example, @code{.balignw
4289 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4290 filled in with the value 0x368d (the exact placement of the bytes depends upon
4291 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4295 @section @code{.byte @var{expressions}}
4297 @cindex @code{byte} directive
4298 @cindex integers, one byte
4299 @code{.byte} expects zero or more expressions, separated by commas.
4300 Each expression is assembled into the next byte.
4302 @node CFI directives
4303 @section @code{.cfi_sections @var{section_list}}
4304 @cindex @code{cfi_sections} directive
4305 @code{.cfi_sections} may be used to specify whether CFI directives
4306 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4307 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4308 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4309 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4310 directive is not used is @code{.cfi_sections .eh_frame}.
4312 @section @code{.cfi_startproc [simple]}
4313 @cindex @code{cfi_startproc} directive
4314 @code{.cfi_startproc} is used at the beginning of each function that
4315 should have an entry in @code{.eh_frame}. It initializes some internal
4316 data structures. Don't forget to close the function by
4317 @code{.cfi_endproc}.
4319 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4320 it also emits some architecture dependent initial CFI instructions.
4322 @section @code{.cfi_endproc}
4323 @cindex @code{cfi_endproc} directive
4324 @code{.cfi_endproc} is used at the end of a function where it closes its
4325 unwind entry previously opened by
4326 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4328 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4329 @code{.cfi_personality} defines personality routine and its encoding.
4330 @var{encoding} must be a constant determining how the personality
4331 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4332 argument is not present, otherwise second argument should be
4333 a constant or a symbol name. When using indirect encodings,
4334 the symbol provided should be the location where personality
4335 can be loaded from, not the personality routine itself.
4336 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4337 no personality routine.
4339 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4340 @code{.cfi_lsda} defines LSDA and its encoding.
4341 @var{encoding} must be a constant determining how the LSDA
4342 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4343 argument is not present, otherwise second argument should be a constant
4344 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4347 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4348 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4349 address from @var{register} and add @var{offset} to it}.
4351 @section @code{.cfi_def_cfa_register @var{register}}
4352 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4353 now on @var{register} will be used instead of the old one. Offset
4356 @section @code{.cfi_def_cfa_offset @var{offset}}
4357 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4358 remains the same, but @var{offset} is new. Note that it is the
4359 absolute offset that will be added to a defined register to compute
4362 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4363 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4364 value that is added/substracted from the previous offset.
4366 @section @code{.cfi_offset @var{register}, @var{offset}}
4367 Previous value of @var{register} is saved at offset @var{offset} from
4370 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4371 Previous value of @var{register} is saved at offset @var{offset} from
4372 the current CFA register. This is transformed to @code{.cfi_offset}
4373 using the known displacement of the CFA register from the CFA.
4374 This is often easier to use, because the number will match the
4375 code it's annotating.
4377 @section @code{.cfi_register @var{register1}, @var{register2}}
4378 Previous value of @var{register1} is saved in register @var{register2}.
4380 @section @code{.cfi_restore @var{register}}
4381 @code{.cfi_restore} says that the rule for @var{register} is now the
4382 same as it was at the beginning of the function, after all initial
4383 instruction added by @code{.cfi_startproc} were executed.
4385 @section @code{.cfi_undefined @var{register}}
4386 From now on the previous value of @var{register} can't be restored anymore.
4388 @section @code{.cfi_same_value @var{register}}
4389 Current value of @var{register} is the same like in the previous frame,
4390 i.e. no restoration needed.
4392 @section @code{.cfi_remember_state},
4393 First save all current rules for all registers by @code{.cfi_remember_state},
4394 then totally screw them up by subsequent @code{.cfi_*} directives and when
4395 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4396 the previous saved state.
4398 @section @code{.cfi_return_column @var{register}}
4399 Change return column @var{register}, i.e. the return address is either
4400 directly in @var{register} or can be accessed by rules for @var{register}.
4402 @section @code{.cfi_signal_frame}
4403 Mark current function as signal trampoline.
4405 @section @code{.cfi_window_save}
4406 SPARC register window has been saved.
4408 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4409 Allows the user to add arbitrary bytes to the unwind info. One
4410 might use this to add OS-specific CFI opcodes, or generic CFI
4411 opcodes that GAS does not yet support.
4413 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4414 The current value of @var{register} is @var{label}. The value of @var{label}
4415 will be encoded in the output file according to @var{encoding}; see the
4416 description of @code{.cfi_personality} for details on this encoding.
4418 The usefulness of equating a register to a fixed label is probably
4419 limited to the return address register. Here, it can be useful to
4420 mark a code segment that has only one return address which is reached
4421 by a direct branch and no copy of the return address exists in memory
4422 or another register.
4425 @section @code{.comm @var{symbol} , @var{length} }
4427 @cindex @code{comm} directive
4428 @cindex symbol, common
4429 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4430 common symbol in one object file may be merged with a defined or common symbol
4431 of the same name in another object file. If @code{@value{LD}} does not see a
4432 definition for the symbol--just one or more common symbols--then it will
4433 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4434 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4435 the same name, and they do not all have the same size, it will allocate space
4436 using the largest size.
4439 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4440 an optional third argument. This is the desired alignment of the symbol,
4441 specified for ELF as a byte boundary (for example, an alignment of 16 means
4442 that the least significant 4 bits of the address should be zero), and for PE
4443 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4444 boundary). The alignment must be an absolute expression, and it must be a
4445 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4446 common symbol, it will use the alignment when placing the symbol. If no
4447 alignment is specified, @command{@value{AS}} will set the alignment to the
4448 largest power of two less than or equal to the size of the symbol, up to a
4449 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4450 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4451 @samp{--section-alignment} option; image file sections in PE are aligned to
4452 multiples of 4096, which is far too large an alignment for ordinary variables.
4453 It is rather the default alignment for (non-debug) sections within object
4454 (@samp{*.o}) files, which are less strictly aligned.}.
4458 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4459 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4463 @section @code{.data @var{subsection}}
4465 @cindex @code{data} directive
4466 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4467 end of the data subsection numbered @var{subsection} (which is an
4468 absolute expression). If @var{subsection} is omitted, it defaults
4473 @section @code{.def @var{name}}
4475 @cindex @code{def} directive
4476 @cindex COFF symbols, debugging
4477 @cindex debugging COFF symbols
4478 Begin defining debugging information for a symbol @var{name}; the
4479 definition extends until the @code{.endef} directive is encountered.
4482 This directive is only observed when @command{@value{AS}} is configured for COFF
4483 format output; when producing @code{b.out}, @samp{.def} is recognized,
4490 @section @code{.desc @var{symbol}, @var{abs-expression}}
4492 @cindex @code{desc} directive
4493 @cindex COFF symbol descriptor
4494 @cindex symbol descriptor, COFF
4495 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4496 to the low 16 bits of an absolute expression.
4499 The @samp{.desc} directive is not available when @command{@value{AS}} is
4500 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4501 object format. For the sake of compatibility, @command{@value{AS}} accepts
4502 it, but produces no output, when configured for COFF.
4508 @section @code{.dim}
4510 @cindex @code{dim} directive
4511 @cindex COFF auxiliary symbol information
4512 @cindex auxiliary symbol information, COFF
4513 This directive is generated by compilers to include auxiliary debugging
4514 information in the symbol table. It is only permitted inside
4515 @code{.def}/@code{.endef} pairs.
4518 @samp{.dim} is only meaningful when generating COFF format output; when
4519 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4525 @section @code{.double @var{flonums}}
4527 @cindex @code{double} directive
4528 @cindex floating point numbers (double)
4529 @code{.double} expects zero or more flonums, separated by commas. It
4530 assembles floating point numbers.
4532 The exact kind of floating point numbers emitted depends on how
4533 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4537 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4538 in @sc{ieee} format.
4543 @section @code{.eject}
4545 @cindex @code{eject} directive
4546 @cindex new page, in listings
4547 @cindex page, in listings
4548 @cindex listing control: new page
4549 Force a page break at this point, when generating assembly listings.
4552 @section @code{.else}
4554 @cindex @code{else} directive
4555 @code{.else} is part of the @command{@value{AS}} support for conditional
4556 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4557 of code to be assembled if the condition for the preceding @code{.if}
4561 @section @code{.elseif}
4563 @cindex @code{elseif} directive
4564 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4565 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4566 @code{.if} block that would otherwise fill the entire @code{.else} section.
4569 @section @code{.end}
4571 @cindex @code{end} directive
4572 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4573 process anything in the file past the @code{.end} directive.
4577 @section @code{.endef}
4579 @cindex @code{endef} directive
4580 This directive flags the end of a symbol definition begun with
4584 @samp{.endef} is only meaningful when generating COFF format output; if
4585 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4586 directive but ignores it.
4591 @section @code{.endfunc}
4592 @cindex @code{endfunc} directive
4593 @code{.endfunc} marks the end of a function specified with @code{.func}.
4596 @section @code{.endif}
4598 @cindex @code{endif} directive
4599 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4600 it marks the end of a block of code that is only assembled
4601 conditionally. @xref{If,,@code{.if}}.
4604 @section @code{.equ @var{symbol}, @var{expression}}
4606 @cindex @code{equ} directive
4607 @cindex assigning values to symbols
4608 @cindex symbols, assigning values to
4609 This directive sets the value of @var{symbol} to @var{expression}.
4610 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4613 The syntax for @code{equ} on the HPPA is
4614 @samp{@var{symbol} .equ @var{expression}}.
4618 The syntax for @code{equ} on the Z80 is
4619 @samp{@var{symbol} equ @var{expression}}.
4620 On the Z80 it is an eror if @var{symbol} is already defined,
4621 but the symbol is not protected from later redefinition.
4622 Compare @ref{Equiv}.
4626 @section @code{.equiv @var{symbol}, @var{expression}}
4627 @cindex @code{equiv} directive
4628 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4629 the assembler will signal an error if @var{symbol} is already defined. Note a
4630 symbol which has been referenced but not actually defined is considered to be
4633 Except for the contents of the error message, this is roughly equivalent to
4640 plus it protects the symbol from later redefinition.
4643 @section @code{.eqv @var{symbol}, @var{expression}}
4644 @cindex @code{eqv} directive
4645 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4646 evaluate the expression or any part of it immediately. Instead each time
4647 the resulting symbol is used in an expression, a snapshot of its current
4651 @section @code{.err}
4652 @cindex @code{err} directive
4653 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4654 message and, unless the @option{-Z} option was used, it will not generate an
4655 object file. This can be used to signal an error in conditionally compiled code.
4658 @section @code{.error "@var{string}"}
4659 @cindex error directive
4661 Similarly to @code{.err}, this directive emits an error, but you can specify a
4662 string that will be emitted as the error message. If you don't specify the
4663 message, it defaults to @code{".error directive invoked in source file"}.
4664 @xref{Errors, ,Error and Warning Messages}.
4667 .error "This code has not been assembled and tested."
4671 @section @code{.exitm}
4672 Exit early from the current macro definition. @xref{Macro}.
4675 @section @code{.extern}
4677 @cindex @code{extern} directive
4678 @code{.extern} is accepted in the source program---for compatibility
4679 with other assemblers---but it is ignored. @command{@value{AS}} treats
4680 all undefined symbols as external.
4683 @section @code{.fail @var{expression}}
4685 @cindex @code{fail} directive
4686 Generates an error or a warning. If the value of the @var{expression} is 500
4687 or more, @command{@value{AS}} will print a warning message. If the value is less
4688 than 500, @command{@value{AS}} will print an error message. The message will
4689 include the value of @var{expression}. This can occasionally be useful inside
4690 complex nested macros or conditional assembly.
4693 @section @code{.file}
4694 @cindex @code{file} directive
4696 @ifclear no-file-dir
4697 There are two different versions of the @code{.file} directive. Targets
4698 that support DWARF2 line number information use the DWARF2 version of
4699 @code{.file}. Other targets use the default version.
4701 @subheading Default Version
4703 @cindex logical file name
4704 @cindex file name, logical
4705 This version of the @code{.file} directive tells @command{@value{AS}} that we
4706 are about to start a new logical file. The syntax is:
4712 @var{string} is the new file name. In general, the filename is
4713 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4714 to specify an empty file name, you must give the quotes--@code{""}. This
4715 statement may go away in future: it is only recognized to be compatible with
4716 old @command{@value{AS}} programs.
4718 @subheading DWARF2 Version
4721 When emitting DWARF2 line number information, @code{.file} assigns filenames
4722 to the @code{.debug_line} file name table. The syntax is:
4725 .file @var{fileno} @var{filename}
4728 The @var{fileno} operand should be a unique positive integer to use as the
4729 index of the entry in the table. The @var{filename} operand is a C string
4732 The detail of filename indices is exposed to the user because the filename
4733 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4734 information, and thus the user must know the exact indices that table
4738 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4740 @cindex @code{fill} directive
4741 @cindex writing patterns in memory
4742 @cindex patterns, writing in memory
4743 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4744 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4745 may be zero or more. @var{Size} may be zero or more, but if it is
4746 more than 8, then it is deemed to have the value 8, compatible with
4747 other people's assemblers. The contents of each @var{repeat} bytes
4748 is taken from an 8-byte number. The highest order 4 bytes are
4749 zero. The lowest order 4 bytes are @var{value} rendered in the
4750 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4751 Each @var{size} bytes in a repetition is taken from the lowest order
4752 @var{size} bytes of this number. Again, this bizarre behavior is
4753 compatible with other people's assemblers.
4755 @var{size} and @var{value} are optional.
4756 If the second comma and @var{value} are absent, @var{value} is
4757 assumed zero. If the first comma and following tokens are absent,
4758 @var{size} is assumed to be 1.
4761 @section @code{.float @var{flonums}}
4763 @cindex floating point numbers (single)
4764 @cindex @code{float} directive
4765 This directive assembles zero or more flonums, separated by commas. It
4766 has the same effect as @code{.single}.
4768 The exact kind of floating point numbers emitted depends on how
4769 @command{@value{AS}} is configured.
4770 @xref{Machine Dependencies}.
4774 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4775 in @sc{ieee} format.
4780 @section @code{.func @var{name}[,@var{label}]}
4781 @cindex @code{func} directive
4782 @code{.func} emits debugging information to denote function @var{name}, and
4783 is ignored unless the file is assembled with debugging enabled.
4784 Only @samp{--gstabs[+]} is currently supported.
4785 @var{label} is the entry point of the function and if omitted @var{name}
4786 prepended with the @samp{leading char} is used.
4787 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4788 All functions are currently defined to have @code{void} return type.
4789 The function must be terminated with @code{.endfunc}.
4792 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4794 @cindex @code{global} directive
4795 @cindex symbol, making visible to linker
4796 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4797 @var{symbol} in your partial program, its value is made available to
4798 other partial programs that are linked with it. Otherwise,
4799 @var{symbol} takes its attributes from a symbol of the same name
4800 from another file linked into the same program.
4802 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4803 compatibility with other assemblers.
4806 On the HPPA, @code{.global} is not always enough to make it accessible to other
4807 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4808 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4813 @section @code{.gnu_attribute @var{tag},@var{value}}
4814 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4817 @section @code{.hidden @var{names}}
4819 @cindex @code{hidden} directive
4821 This is one of the ELF visibility directives. The other two are
4822 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4823 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4825 This directive overrides the named symbols default visibility (which is set by
4826 their binding: local, global or weak). The directive sets the visibility to
4827 @code{hidden} which means that the symbols are not visible to other components.
4828 Such symbols are always considered to be @code{protected} as well.
4832 @section @code{.hword @var{expressions}}
4834 @cindex @code{hword} directive
4835 @cindex integers, 16-bit
4836 @cindex numbers, 16-bit
4837 @cindex sixteen bit integers
4838 This expects zero or more @var{expressions}, and emits
4839 a 16 bit number for each.
4842 This directive is a synonym for @samp{.short}; depending on the target
4843 architecture, it may also be a synonym for @samp{.word}.
4847 This directive is a synonym for @samp{.short}.
4850 This directive is a synonym for both @samp{.short} and @samp{.word}.
4855 @section @code{.ident}
4857 @cindex @code{ident} directive
4859 This directive is used by some assemblers to place tags in object files. The
4860 behavior of this directive varies depending on the target. When using the
4861 a.out object file format, @command{@value{AS}} simply accepts the directive for
4862 source-file compatibility with existing assemblers, but does not emit anything
4863 for it. When using COFF, comments are emitted to the @code{.comment} or
4864 @code{.rdata} section, depending on the target. When using ELF, comments are
4865 emitted to the @code{.comment} section.
4868 @section @code{.if @var{absolute expression}}
4870 @cindex conditional assembly
4871 @cindex @code{if} directive
4872 @code{.if} marks the beginning of a section of code which is only
4873 considered part of the source program being assembled if the argument
4874 (which must be an @var{absolute expression}) is non-zero. The end of
4875 the conditional section of code must be marked by @code{.endif}
4876 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4877 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4878 If you have several conditions to check, @code{.elseif} may be used to avoid
4879 nesting blocks if/else within each subsequent @code{.else} block.
4881 The following variants of @code{.if} are also supported:
4883 @cindex @code{ifdef} directive
4884 @item .ifdef @var{symbol}
4885 Assembles the following section of code if the specified @var{symbol}
4886 has been defined. Note a symbol which has been referenced but not yet defined
4887 is considered to be undefined.
4889 @cindex @code{ifb} directive
4890 @item .ifb @var{text}
4891 Assembles the following section of code if the operand is blank (empty).
4893 @cindex @code{ifc} directive
4894 @item .ifc @var{string1},@var{string2}
4895 Assembles the following section of code if the two strings are the same. The
4896 strings may be optionally quoted with single quotes. If they are not quoted,
4897 the first string stops at the first comma, and the second string stops at the
4898 end of the line. Strings which contain whitespace should be quoted. The
4899 string comparison is case sensitive.
4901 @cindex @code{ifeq} directive
4902 @item .ifeq @var{absolute expression}
4903 Assembles the following section of code if the argument is zero.
4905 @cindex @code{ifeqs} directive
4906 @item .ifeqs @var{string1},@var{string2}
4907 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4909 @cindex @code{ifge} directive
4910 @item .ifge @var{absolute expression}
4911 Assembles the following section of code if the argument is greater than or
4914 @cindex @code{ifgt} directive
4915 @item .ifgt @var{absolute expression}
4916 Assembles the following section of code if the argument is greater than zero.
4918 @cindex @code{ifle} directive
4919 @item .ifle @var{absolute expression}
4920 Assembles the following section of code if the argument is less than or equal
4923 @cindex @code{iflt} directive
4924 @item .iflt @var{absolute expression}
4925 Assembles the following section of code if the argument is less than zero.
4927 @cindex @code{ifnb} directive
4928 @item .ifnb @var{text}
4929 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4930 following section of code if the operand is non-blank (non-empty).
4932 @cindex @code{ifnc} directive
4933 @item .ifnc @var{string1},@var{string2}.
4934 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4935 following section of code if the two strings are not the same.
4937 @cindex @code{ifndef} directive
4938 @cindex @code{ifnotdef} directive
4939 @item .ifndef @var{symbol}
4940 @itemx .ifnotdef @var{symbol}
4941 Assembles the following section of code if the specified @var{symbol}
4942 has not been defined. Both spelling variants are equivalent. Note a symbol
4943 which has been referenced but not yet defined is considered to be undefined.
4945 @cindex @code{ifne} directive
4946 @item .ifne @var{absolute expression}
4947 Assembles the following section of code if the argument is not equal to zero
4948 (in other words, this is equivalent to @code{.if}).
4950 @cindex @code{ifnes} directive
4951 @item .ifnes @var{string1},@var{string2}
4952 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4953 following section of code if the two strings are not the same.
4957 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4959 @cindex @code{incbin} directive
4960 @cindex binary files, including
4961 The @code{incbin} directive includes @var{file} verbatim at the current
4962 location. You can control the search paths used with the @samp{-I} command-line
4963 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4966 The @var{skip} argument skips a number of bytes from the start of the
4967 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4968 read. Note that the data is not aligned in any way, so it is the user's
4969 responsibility to make sure that proper alignment is provided both before and
4970 after the @code{incbin} directive.
4973 @section @code{.include "@var{file}"}
4975 @cindex @code{include} directive
4976 @cindex supporting files, including
4977 @cindex files, including
4978 This directive provides a way to include supporting files at specified
4979 points in your source program. The code from @var{file} is assembled as
4980 if it followed the point of the @code{.include}; when the end of the
4981 included file is reached, assembly of the original file continues. You
4982 can control the search paths used with the @samp{-I} command-line option
4983 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4987 @section @code{.int @var{expressions}}
4989 @cindex @code{int} directive
4990 @cindex integers, 32-bit
4991 Expect zero or more @var{expressions}, of any section, separated by commas.
4992 For each expression, emit a number that, at run time, is the value of that
4993 expression. The byte order and bit size of the number depends on what kind
4994 of target the assembly is for.
4998 On most forms of the H8/300, @code{.int} emits 16-bit
4999 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5006 @section @code{.internal @var{names}}
5008 @cindex @code{internal} directive
5010 This is one of the ELF visibility directives. The other two are
5011 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5012 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5014 This directive overrides the named symbols default visibility (which is set by
5015 their binding: local, global or weak). The directive sets the visibility to
5016 @code{internal} which means that the symbols are considered to be @code{hidden}
5017 (i.e., not visible to other components), and that some extra, processor specific
5018 processing must also be performed upon the symbols as well.
5022 @section @code{.irp @var{symbol},@var{values}}@dots{}
5024 @cindex @code{irp} directive
5025 Evaluate a sequence of statements assigning different values to @var{symbol}.
5026 The sequence of statements starts at the @code{.irp} directive, and is
5027 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5028 set to @var{value}, and the sequence of statements is assembled. If no
5029 @var{value} is listed, the sequence of statements is assembled once, with
5030 @var{symbol} set to the null string. To refer to @var{symbol} within the
5031 sequence of statements, use @var{\symbol}.
5033 For example, assembling
5041 is equivalent to assembling
5049 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5052 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5054 @cindex @code{irpc} directive
5055 Evaluate a sequence of statements assigning different values to @var{symbol}.
5056 The sequence of statements starts at the @code{.irpc} directive, and is
5057 terminated by an @code{.endr} directive. For each character in @var{value},
5058 @var{symbol} is set to the character, and the sequence of statements is
5059 assembled. If no @var{value} is listed, the sequence of statements is
5060 assembled once, with @var{symbol} set to the null string. To refer to
5061 @var{symbol} within the sequence of statements, use @var{\symbol}.
5063 For example, assembling
5071 is equivalent to assembling
5079 For some caveats with the spelling of @var{symbol}, see also the discussion
5083 @section @code{.lcomm @var{symbol} , @var{length}}
5085 @cindex @code{lcomm} directive
5086 @cindex local common symbols
5087 @cindex symbols, local common
5088 Reserve @var{length} (an absolute expression) bytes for a local common
5089 denoted by @var{symbol}. The section and value of @var{symbol} are
5090 those of the new local common. The addresses are allocated in the bss
5091 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5092 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5093 not visible to @code{@value{LD}}.
5096 Some targets permit a third argument to be used with @code{.lcomm}. This
5097 argument specifies the desired alignment of the symbol in the bss section.
5101 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5102 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5106 @section @code{.lflags}
5108 @cindex @code{lflags} directive (ignored)
5109 @command{@value{AS}} accepts this directive, for compatibility with other
5110 assemblers, but ignores it.
5112 @ifclear no-line-dir
5114 @section @code{.line @var{line-number}}
5116 @cindex @code{line} directive
5117 @cindex logical line number
5119 Change the logical line number. @var{line-number} must be an absolute
5120 expression. The next line has that logical line number. Therefore any other
5121 statements on the current line (after a statement separator character) are
5122 reported as on logical line number @var{line-number} @minus{} 1. One day
5123 @command{@value{AS}} will no longer support this directive: it is recognized only
5124 for compatibility with existing assembler programs.
5127 Even though this is a directive associated with the @code{a.out} or
5128 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5129 when producing COFF output, and treats @samp{.line} as though it
5130 were the COFF @samp{.ln} @emph{if} it is found outside a
5131 @code{.def}/@code{.endef} pair.
5133 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5134 used by compilers to generate auxiliary symbol information for
5139 @section @code{.linkonce [@var{type}]}
5141 @cindex @code{linkonce} directive
5142 @cindex common sections
5143 Mark the current section so that the linker only includes a single copy of it.
5144 This may be used to include the same section in several different object files,
5145 but ensure that the linker will only include it once in the final output file.
5146 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5147 Duplicate sections are detected based on the section name, so it should be
5150 This directive is only supported by a few object file formats; as of this
5151 writing, the only object file format which supports it is the Portable
5152 Executable format used on Windows NT.
5154 The @var{type} argument is optional. If specified, it must be one of the
5155 following strings. For example:
5159 Not all types may be supported on all object file formats.
5163 Silently discard duplicate sections. This is the default.
5166 Warn if there are duplicate sections, but still keep only one copy.
5169 Warn if any of the duplicates have different sizes.
5172 Warn if any of the duplicates do not have exactly the same contents.
5176 @section @code{.list}
5178 @cindex @code{list} directive
5179 @cindex listing control, turning on
5180 Control (in conjunction with the @code{.nolist} directive) whether or
5181 not assembly listings are generated. These two directives maintain an
5182 internal counter (which is zero initially). @code{.list} increments the
5183 counter, and @code{.nolist} decrements it. Assembly listings are
5184 generated whenever the counter is greater than zero.
5186 By default, listings are disabled. When you enable them (with the
5187 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5188 the initial value of the listing counter is one.
5191 @section @code{.ln @var{line-number}}
5193 @cindex @code{ln} directive
5194 @ifclear no-line-dir
5195 @samp{.ln} is a synonym for @samp{.line}.
5198 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5199 must be an absolute expression. The next line has that logical
5200 line number, so any other statements on the current line (after a
5201 statement separator character @code{;}) are reported as on logical
5202 line number @var{line-number} @minus{} 1.
5205 This directive is accepted, but ignored, when @command{@value{AS}} is
5206 configured for @code{b.out}; its effect is only associated with COFF
5212 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5213 @cindex @code{loc} directive
5214 When emitting DWARF2 line number information,
5215 the @code{.loc} directive will add a row to the @code{.debug_line} line
5216 number matrix corresponding to the immediately following assembly
5217 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5218 arguments will be applied to the @code{.debug_line} state machine before
5221 The @var{options} are a sequence of the following tokens in any order:
5225 This option will set the @code{basic_block} register in the
5226 @code{.debug_line} state machine to @code{true}.
5229 This option will set the @code{prologue_end} register in the
5230 @code{.debug_line} state machine to @code{true}.
5232 @item epilogue_begin
5233 This option will set the @code{epilogue_begin} register in the
5234 @code{.debug_line} state machine to @code{true}.
5236 @item is_stmt @var{value}
5237 This option will set the @code{is_stmt} register in the
5238 @code{.debug_line} state machine to @code{value}, which must be
5241 @item isa @var{value}
5242 This directive will set the @code{isa} register in the @code{.debug_line}
5243 state machine to @var{value}, which must be an unsigned integer.
5245 @item discriminator @var{value}
5246 This directive will set the @code{discriminator} register in the @code{.debug_line}
5247 state machine to @var{value}, which must be an unsigned integer.
5251 @node Loc_mark_labels
5252 @section @code{.loc_mark_labels @var{enable}}
5253 @cindex @code{loc_mark_labels} directive
5254 When emitting DWARF2 line number information,
5255 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5256 to the @code{.debug_line} line number matrix with the @code{basic_block}
5257 register in the state machine set whenever a code label is seen.
5258 The @var{enable} argument should be either 1 or 0, to enable or disable
5259 this function respectively.
5263 @section @code{.local @var{names}}
5265 @cindex @code{local} directive
5266 This directive, which is available for ELF targets, marks each symbol in
5267 the comma-separated list of @code{names} as a local symbol so that it
5268 will not be externally visible. If the symbols do not already exist,
5269 they will be created.
5271 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5272 accept an alignment argument, which is the case for most ELF targets,
5273 the @code{.local} directive can be used in combination with @code{.comm}
5274 (@pxref{Comm}) to define aligned local common data.
5278 @section @code{.long @var{expressions}}
5280 @cindex @code{long} directive
5281 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5284 @c no one seems to know what this is for or whether this description is
5285 @c what it really ought to do
5287 @section @code{.lsym @var{symbol}, @var{expression}}
5289 @cindex @code{lsym} directive
5290 @cindex symbol, not referenced in assembly
5291 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5292 the hash table, ensuring it cannot be referenced by name during the
5293 rest of the assembly. This sets the attributes of the symbol to be
5294 the same as the expression value:
5296 @var{other} = @var{descriptor} = 0
5297 @var{type} = @r{(section of @var{expression})}
5298 @var{value} = @var{expression}
5301 The new symbol is not flagged as external.
5305 @section @code{.macro}
5308 The commands @code{.macro} and @code{.endm} allow you to define macros that
5309 generate assembly output. For example, this definition specifies a macro
5310 @code{sum} that puts a sequence of numbers into memory:
5313 .macro sum from=0, to=5
5322 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5334 @item .macro @var{macname}
5335 @itemx .macro @var{macname} @var{macargs} @dots{}
5336 @cindex @code{macro} directive
5337 Begin the definition of a macro called @var{macname}. If your macro
5338 definition requires arguments, specify their names after the macro name,
5339 separated by commas or spaces. You can qualify the macro argument to
5340 indicate whether all invocations must specify a non-blank value (through
5341 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5342 (through @samp{:@code{vararg}}). You can supply a default value for any
5343 macro argument by following the name with @samp{=@var{deflt}}. You
5344 cannot define two macros with the same @var{macname} unless it has been
5345 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5346 definitions. For example, these are all valid @code{.macro} statements:
5350 Begin the definition of a macro called @code{comm}, which takes no
5353 @item .macro plus1 p, p1
5354 @itemx .macro plus1 p p1
5355 Either statement begins the definition of a macro called @code{plus1},
5356 which takes two arguments; within the macro definition, write
5357 @samp{\p} or @samp{\p1} to evaluate the arguments.
5359 @item .macro reserve_str p1=0 p2
5360 Begin the definition of a macro called @code{reserve_str}, with two
5361 arguments. The first argument has a default value, but not the second.
5362 After the definition is complete, you can call the macro either as
5363 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5364 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5365 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5366 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5368 @item .macro m p1:req, p2=0, p3:vararg
5369 Begin the definition of a macro called @code{m}, with at least three
5370 arguments. The first argument must always have a value specified, but
5371 not the second, which instead has a default value. The third formal
5372 will get assigned all remaining arguments specified at invocation time.
5374 When you call a macro, you can specify the argument values either by
5375 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5376 @samp{sum to=17, from=9}.
5380 Note that since each of the @var{macargs} can be an identifier exactly
5381 as any other one permitted by the target architecture, there may be
5382 occasional problems if the target hand-crafts special meanings to certain
5383 characters when they occur in a special position. For example, if the colon
5384 (@code{:}) is generally permitted to be part of a symbol name, but the
5385 architecture specific code special-cases it when occurring as the final
5386 character of a symbol (to denote a label), then the macro parameter
5387 replacement code will have no way of knowing that and consider the whole
5388 construct (including the colon) an identifier, and check only this
5389 identifier for being the subject to parameter substitution. So for example
5390 this macro definition:
5398 might not work as expected. Invoking @samp{label foo} might not create a label
5399 called @samp{foo} but instead just insert the text @samp{\l:} into the
5400 assembler source, probably generating an error about an unrecognised
5403 Similarly problems might occur with the period character (@samp{.})
5404 which is often allowed inside opcode names (and hence identifier names). So
5405 for example constructing a macro to build an opcode from a base name and a
5406 length specifier like this:
5409 .macro opcode base length
5414 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5415 instruction but instead generate some kind of error as the assembler tries to
5416 interpret the text @samp{\base.\length}.
5418 There are several possible ways around this problem:
5421 @item Insert white space
5422 If it is possible to use white space characters then this is the simplest
5431 @item Use @samp{\()}
5432 The string @samp{\()} can be used to separate the end of a macro argument from
5433 the following text. eg:
5436 .macro opcode base length
5441 @item Use the alternate macro syntax mode
5442 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5443 used as a separator. eg:
5453 Note: this problem of correctly identifying string parameters to pseudo ops
5454 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5455 and @code{.irpc} (@pxref{Irpc}) as well.
5458 @cindex @code{endm} directive
5459 Mark the end of a macro definition.
5462 @cindex @code{exitm} directive
5463 Exit early from the current macro definition.
5465 @cindex number of macros executed
5466 @cindex macros, count executed
5468 @command{@value{AS}} maintains a counter of how many macros it has
5469 executed in this pseudo-variable; you can copy that number to your
5470 output with @samp{\@@}, but @emph{only within a macro definition}.
5472 @item LOCAL @var{name} [ , @dots{} ]
5473 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5474 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5475 @xref{Altmacro,,@code{.altmacro}}.
5479 @section @code{.mri @var{val}}
5481 @cindex @code{mri} directive
5482 @cindex MRI mode, temporarily
5483 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5484 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5485 affects code assembled until the next @code{.mri} directive, or until the end
5486 of the file. @xref{M, MRI mode, MRI mode}.
5489 @section @code{.noaltmacro}
5490 Disable alternate macro mode. @xref{Altmacro}.
5493 @section @code{.nolist}
5495 @cindex @code{nolist} directive
5496 @cindex listing control, turning off
5497 Control (in conjunction with the @code{.list} directive) whether or
5498 not assembly listings are generated. These two directives maintain an
5499 internal counter (which is zero initially). @code{.list} increments the
5500 counter, and @code{.nolist} decrements it. Assembly listings are
5501 generated whenever the counter is greater than zero.
5504 @section @code{.octa @var{bignums}}
5506 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5507 @cindex @code{octa} directive
5508 @cindex integer, 16-byte
5509 @cindex sixteen byte integer
5510 This directive expects zero or more bignums, separated by commas. For each
5511 bignum, it emits a 16-byte integer.
5513 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5514 hence @emph{octa}-word for 16 bytes.
5517 @section @code{.org @var{new-lc} , @var{fill}}
5519 @cindex @code{org} directive
5520 @cindex location counter, advancing
5521 @cindex advancing location counter
5522 @cindex current address, advancing
5523 Advance the location counter of the current section to
5524 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5525 expression with the same section as the current subsection. That is,
5526 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5527 wrong section, the @code{.org} directive is ignored. To be compatible
5528 with former assemblers, if the section of @var{new-lc} is absolute,
5529 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5530 is the same as the current subsection.
5532 @code{.org} may only increase the location counter, or leave it
5533 unchanged; you cannot use @code{.org} to move the location counter
5536 @c double negative used below "not undefined" because this is a specific
5537 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5538 @c section. doc@cygnus.com 18feb91
5539 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5540 may not be undefined. If you really detest this restriction we eagerly await
5541 a chance to share your improved assembler.
5543 Beware that the origin is relative to the start of the section, not
5544 to the start of the subsection. This is compatible with other
5545 people's assemblers.
5547 When the location counter (of the current subsection) is advanced, the
5548 intervening bytes are filled with @var{fill} which should be an
5549 absolute expression. If the comma and @var{fill} are omitted,
5550 @var{fill} defaults to zero.
5553 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5555 @cindex padding the location counter given a power of two
5556 @cindex @code{p2align} directive
5557 Pad the location counter (in the current subsection) to a particular
5558 storage boundary. The first expression (which must be absolute) is the
5559 number of low-order zero bits the location counter must have after
5560 advancement. For example @samp{.p2align 3} advances the location
5561 counter until it a multiple of 8. If the location counter is already a
5562 multiple of 8, no change is needed.
5564 The second expression (also absolute) gives the fill value to be stored in the
5565 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5566 padding bytes are normally zero. However, on some systems, if the section is
5567 marked as containing code and the fill value is omitted, the space is filled
5568 with no-op instructions.
5570 The third expression is also absolute, and is also optional. If it is present,
5571 it is the maximum number of bytes that should be skipped by this alignment
5572 directive. If doing the alignment would require skipping more bytes than the
5573 specified maximum, then the alignment is not done at all. You can omit the
5574 fill value (the second argument) entirely by simply using two commas after the
5575 required alignment; this can be useful if you want the alignment to be filled
5576 with no-op instructions when appropriate.
5578 @cindex @code{p2alignw} directive
5579 @cindex @code{p2alignl} directive
5580 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5581 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5582 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5583 fill pattern as a four byte longword value. For example, @code{.p2alignw
5584 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5585 filled in with the value 0x368d (the exact placement of the bytes depends upon
5586 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5591 @section @code{.popsection}
5593 @cindex @code{popsection} directive
5594 @cindex Section Stack
5595 This is one of the ELF section stack manipulation directives. The others are
5596 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5597 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5600 This directive replaces the current section (and subsection) with the top
5601 section (and subsection) on the section stack. This section is popped off the
5607 @section @code{.previous}
5609 @cindex @code{previous} directive
5610 @cindex Section Stack
5611 This is one of the ELF section stack manipulation directives. The others are
5612 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5613 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5614 (@pxref{PopSection}).
5616 This directive swaps the current section (and subsection) with most recently
5617 referenced section/subsection pair prior to this one. Multiple
5618 @code{.previous} directives in a row will flip between two sections (and their
5619 subsections). For example:
5631 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5637 # Now in section A subsection 1
5641 # Now in section B subsection 0
5644 # Now in section B subsection 1
5647 # Now in section B subsection 0
5651 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5652 section B and 0x9abc into subsection 1 of section B.
5654 In terms of the section stack, this directive swaps the current section with
5655 the top section on the section stack.
5659 @section @code{.print @var{string}}
5661 @cindex @code{print} directive
5662 @command{@value{AS}} will print @var{string} on the standard output during
5663 assembly. You must put @var{string} in double quotes.
5667 @section @code{.protected @var{names}}
5669 @cindex @code{protected} directive
5671 This is one of the ELF visibility directives. The other two are
5672 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5674 This directive overrides the named symbols default visibility (which is set by
5675 their binding: local, global or weak). The directive sets the visibility to
5676 @code{protected} which means that any references to the symbols from within the
5677 components that defines them must be resolved to the definition in that
5678 component, even if a definition in another component would normally preempt
5683 @section @code{.psize @var{lines} , @var{columns}}
5685 @cindex @code{psize} directive
5686 @cindex listing control: paper size
5687 @cindex paper size, for listings
5688 Use this directive to declare the number of lines---and, optionally, the
5689 number of columns---to use for each page, when generating listings.
5691 If you do not use @code{.psize}, listings use a default line-count
5692 of 60. You may omit the comma and @var{columns} specification; the
5693 default width is 200 columns.
5695 @command{@value{AS}} generates formfeeds whenever the specified number of
5696 lines is exceeded (or whenever you explicitly request one, using
5699 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5700 those explicitly specified with @code{.eject}.
5703 @section @code{.purgem @var{name}}
5705 @cindex @code{purgem} directive
5706 Undefine the macro @var{name}, so that later uses of the string will not be
5707 expanded. @xref{Macro}.
5711 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5713 @cindex @code{pushsection} directive
5714 @cindex Section Stack
5715 This is one of the ELF section stack manipulation directives. The others are
5716 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5717 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5720 This directive pushes the current section (and subsection) onto the
5721 top of the section stack, and then replaces the current section and
5722 subsection with @code{name} and @code{subsection}. The optional
5723 @code{flags}, @code{type} and @code{arguments} are treated the same
5724 as in the @code{.section} (@pxref{Section}) directive.
5728 @section @code{.quad @var{bignums}}
5730 @cindex @code{quad} directive
5731 @code{.quad} expects zero or more bignums, separated by commas. For
5732 each bignum, it emits
5734 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5735 warning message; and just takes the lowest order 8 bytes of the bignum.
5736 @cindex eight-byte integer
5737 @cindex integer, 8-byte
5739 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5740 hence @emph{quad}-word for 8 bytes.
5743 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5744 warning message; and just takes the lowest order 16 bytes of the bignum.
5745 @cindex sixteen-byte integer
5746 @cindex integer, 16-byte
5750 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5752 @cindex @code{reloc} directive
5753 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5754 @var{expression}. If @var{offset} is a number, the relocation is generated in
5755 the current section. If @var{offset} is an expression that resolves to a
5756 symbol plus offset, the relocation is generated in the given symbol's section.
5757 @var{expression}, if present, must resolve to a symbol plus addend or to an
5758 absolute value, but note that not all targets support an addend. e.g. ELF REL
5759 targets such as i386 store an addend in the section contents rather than in the
5760 relocation. This low level interface does not support addends stored in the
5764 @section @code{.rept @var{count}}
5766 @cindex @code{rept} directive
5767 Repeat the sequence of lines between the @code{.rept} directive and the next
5768 @code{.endr} directive @var{count} times.
5770 For example, assembling
5778 is equivalent to assembling
5787 @section @code{.sbttl "@var{subheading}"}
5789 @cindex @code{sbttl} directive
5790 @cindex subtitles for listings
5791 @cindex listing control: subtitle
5792 Use @var{subheading} as the title (third line, immediately after the
5793 title line) when generating assembly listings.
5795 This directive affects subsequent pages, as well as the current page if
5796 it appears within ten lines of the top of a page.
5800 @section @code{.scl @var{class}}
5802 @cindex @code{scl} directive
5803 @cindex symbol storage class (COFF)
5804 @cindex COFF symbol storage class
5805 Set the storage-class value for a symbol. This directive may only be
5806 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5807 whether a symbol is static or external, or it may record further
5808 symbolic debugging information.
5811 The @samp{.scl} directive is primarily associated with COFF output; when
5812 configured to generate @code{b.out} output format, @command{@value{AS}}
5813 accepts this directive but ignores it.
5819 @section @code{.section @var{name}}
5821 @cindex named section
5822 Use the @code{.section} directive to assemble the following code into a section
5825 This directive is only supported for targets that actually support arbitrarily
5826 named sections; on @code{a.out} targets, for example, it is not accepted, even
5827 with a standard @code{a.out} section name.
5831 @c only print the extra heading if both COFF and ELF are set
5832 @subheading COFF Version
5835 @cindex @code{section} directive (COFF version)
5836 For COFF targets, the @code{.section} directive is used in one of the following
5840 .section @var{name}[, "@var{flags}"]
5841 .section @var{name}[, @var{subsection}]
5844 If the optional argument is quoted, it is taken as flags to use for the
5845 section. Each flag is a single character. The following flags are recognized:
5848 bss section (uninitialized data)
5850 section is not loaded
5860 shared section (meaningful for PE targets)
5862 ignored. (For compatibility with the ELF version)
5864 section is not readable (meaningful for PE targets)
5866 single-digit power-of-two section alignment (GNU extension)
5869 If no flags are specified, the default flags depend upon the section name. If
5870 the section name is not recognized, the default will be for the section to be
5871 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5872 from the section, rather than adding them, so if they are used on their own it
5873 will be as if no flags had been specified at all.
5875 If the optional argument to the @code{.section} directive is not quoted, it is
5876 taken as a subsection number (@pxref{Sub-Sections}).
5881 @c only print the extra heading if both COFF and ELF are set
5882 @subheading ELF Version
5885 @cindex Section Stack
5886 This is one of the ELF section stack manipulation directives. The others are
5887 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5888 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5889 @code{.previous} (@pxref{Previous}).
5891 @cindex @code{section} directive (ELF version)
5892 For ELF targets, the @code{.section} directive is used like this:
5895 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5898 The optional @var{flags} argument is a quoted string which may contain any
5899 combination of the following characters:
5902 section is allocatable
5904 section is excluded from executable and shared library.
5908 section is executable
5910 section is mergeable
5912 section contains zero terminated strings
5914 section is a member of a section group
5916 section is used for thread-local-storage
5918 section is a member of the previously-current section's group, if any
5921 The optional @var{type} argument may contain one of the following constants:
5924 section contains data
5926 section does not contain data (i.e., section only occupies space)
5928 section contains data which is used by things other than the program
5930 section contains an array of pointers to init functions
5932 section contains an array of pointers to finish functions
5933 @item @@preinit_array
5934 section contains an array of pointers to pre-init functions
5937 Many targets only support the first three section types.
5939 Note on targets where the @code{@@} character is the start of a comment (eg
5940 ARM) then another character is used instead. For example the ARM port uses the
5943 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5944 be specified as well as an extra argument---@var{entsize}---like this:
5947 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5950 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5951 constants, each @var{entsize} octets long. Sections with both @code{M} and
5952 @code{S} must contain zero terminated strings where each character is
5953 @var{entsize} bytes long. The linker may remove duplicates within sections with
5954 the same name, same entity size and same flags. @var{entsize} must be an
5955 absolute expression. For sections with both @code{M} and @code{S}, a string
5956 which is a suffix of a larger string is considered a duplicate. Thus
5957 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5958 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5960 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5961 be present along with an additional field like this:
5964 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5967 The @var{GroupName} field specifies the name of the section group to which this
5968 particular section belongs. The optional linkage field can contain:
5971 indicates that only one copy of this section should be retained
5976 Note: if both the @var{M} and @var{G} flags are present then the fields for
5977 the Merge flag should come first, like this:
5980 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5983 If @var{flags} contains the @code{?} symbol then it may not also contain the
5984 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
5985 present. Instead, @code{?} says to consider the section that's current before
5986 this directive. If that section used @code{G}, then the new section will use
5987 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
5988 If not, then the @code{?} symbol has no effect.
5990 If no flags are specified, the default flags depend upon the section name. If
5991 the section name is not recognized, the default will be for the section to have
5992 none of the above flags: it will not be allocated in memory, nor writable, nor
5993 executable. The section will contain data.
5995 For ELF targets, the assembler supports another type of @code{.section}
5996 directive for compatibility with the Solaris assembler:
5999 .section "@var{name}"[, @var{flags}...]
6002 Note that the section name is quoted. There may be a sequence of comma
6006 section is allocatable
6010 section is executable
6012 section is excluded from executable and shared library.
6014 section is used for thread local storage
6017 This directive replaces the current section and subsection. See the
6018 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6019 some examples of how this directive and the other section stack directives
6025 @section @code{.set @var{symbol}, @var{expression}}
6027 @cindex @code{set} directive
6028 @cindex symbol value, setting
6029 Set the value of @var{symbol} to @var{expression}. This
6030 changes @var{symbol}'s value and type to conform to
6031 @var{expression}. If @var{symbol} was flagged as external, it remains
6032 flagged (@pxref{Symbol Attributes}).
6034 You may @code{.set} a symbol many times in the same assembly.
6036 If you @code{.set} a global symbol, the value stored in the object
6037 file is the last value stored into it.
6040 On Z80 @code{set} is a real instruction, use
6041 @samp{@var{symbol} defl @var{expression}} instead.
6045 @section @code{.short @var{expressions}}
6047 @cindex @code{short} directive
6049 @code{.short} is normally the same as @samp{.word}.
6050 @xref{Word,,@code{.word}}.
6052 In some configurations, however, @code{.short} and @code{.word} generate
6053 numbers of different lengths. @xref{Machine Dependencies}.
6057 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6060 This expects zero or more @var{expressions}, and emits
6061 a 16 bit number for each.
6066 @section @code{.single @var{flonums}}
6068 @cindex @code{single} directive
6069 @cindex floating point numbers (single)
6070 This directive assembles zero or more flonums, separated by commas. It
6071 has the same effect as @code{.float}.
6073 The exact kind of floating point numbers emitted depends on how
6074 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6078 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6079 numbers in @sc{ieee} format.
6085 @section @code{.size}
6087 This directive is used to set the size associated with a symbol.
6091 @c only print the extra heading if both COFF and ELF are set
6092 @subheading COFF Version
6095 @cindex @code{size} directive (COFF version)
6096 For COFF targets, the @code{.size} directive is only permitted inside
6097 @code{.def}/@code{.endef} pairs. It is used like this:
6100 .size @var{expression}
6104 @samp{.size} is only meaningful when generating COFF format output; when
6105 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6112 @c only print the extra heading if both COFF and ELF are set
6113 @subheading ELF Version
6116 @cindex @code{size} directive (ELF version)
6117 For ELF targets, the @code{.size} directive is used like this:
6120 .size @var{name} , @var{expression}
6123 This directive sets the size associated with a symbol @var{name}.
6124 The size in bytes is computed from @var{expression} which can make use of label
6125 arithmetic. This directive is typically used to set the size of function
6130 @ifclear no-space-dir
6132 @section @code{.skip @var{size} , @var{fill}}
6134 @cindex @code{skip} directive
6135 @cindex filling memory
6136 This directive emits @var{size} bytes, each of value @var{fill}. Both
6137 @var{size} and @var{fill} are absolute expressions. If the comma and
6138 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6143 @section @code{.sleb128 @var{expressions}}
6145 @cindex @code{sleb128} directive
6146 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6147 compact, variable length representation of numbers used by the DWARF
6148 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6150 @ifclear no-space-dir
6152 @section @code{.space @var{size} , @var{fill}}
6154 @cindex @code{space} directive
6155 @cindex filling memory
6156 This directive emits @var{size} bytes, each of value @var{fill}. Both
6157 @var{size} and @var{fill} are absolute expressions. If the comma
6158 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6163 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6164 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6165 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6166 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6174 @section @code{.stabd, .stabn, .stabs}
6176 @cindex symbolic debuggers, information for
6177 @cindex @code{stab@var{x}} directives
6178 There are three directives that begin @samp{.stab}.
6179 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6180 The symbols are not entered in the @command{@value{AS}} hash table: they
6181 cannot be referenced elsewhere in the source file.
6182 Up to five fields are required:
6186 This is the symbol's name. It may contain any character except
6187 @samp{\000}, so is more general than ordinary symbol names. Some
6188 debuggers used to code arbitrarily complex structures into symbol names
6192 An absolute expression. The symbol's type is set to the low 8 bits of
6193 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6194 and debuggers choke on silly bit patterns.
6197 An absolute expression. The symbol's ``other'' attribute is set to the
6198 low 8 bits of this expression.
6201 An absolute expression. The symbol's descriptor is set to the low 16
6202 bits of this expression.
6205 An absolute expression which becomes the symbol's value.
6208 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6209 or @code{.stabs} statement, the symbol has probably already been created;
6210 you get a half-formed symbol in your object file. This is
6211 compatible with earlier assemblers!
6214 @cindex @code{stabd} directive
6215 @item .stabd @var{type} , @var{other} , @var{desc}
6217 The ``name'' of the symbol generated is not even an empty string.
6218 It is a null pointer, for compatibility. Older assemblers used a
6219 null pointer so they didn't waste space in object files with empty
6222 The symbol's value is set to the location counter,
6223 relocatably. When your program is linked, the value of this symbol
6224 is the address of the location counter when the @code{.stabd} was
6227 @cindex @code{stabn} directive
6228 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6229 The name of the symbol is set to the empty string @code{""}.
6231 @cindex @code{stabs} directive
6232 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6233 All five fields are specified.
6239 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6240 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6242 @cindex string, copying to object file
6243 @cindex string8, copying to object file
6244 @cindex string16, copying to object file
6245 @cindex string32, copying to object file
6246 @cindex string64, copying to object file
6247 @cindex @code{string} directive
6248 @cindex @code{string8} directive
6249 @cindex @code{string16} directive
6250 @cindex @code{string32} directive
6251 @cindex @code{string64} directive
6253 Copy the characters in @var{str} to the object file. You may specify more than
6254 one string to copy, separated by commas. Unless otherwise specified for a
6255 particular machine, the assembler marks the end of each string with a 0 byte.
6256 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6258 The variants @code{string16}, @code{string32} and @code{string64} differ from
6259 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6260 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6261 are stored in target endianness byte order.
6267 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6268 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6273 @section @code{.struct @var{expression}}
6275 @cindex @code{struct} directive
6276 Switch to the absolute section, and set the section offset to @var{expression},
6277 which must be an absolute expression. You might use this as follows:
6286 This would define the symbol @code{field1} to have the value 0, the symbol
6287 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6288 value 8. Assembly would be left in the absolute section, and you would need to
6289 use a @code{.section} directive of some sort to change to some other section
6290 before further assembly.
6294 @section @code{.subsection @var{name}}
6296 @cindex @code{subsection} directive
6297 @cindex Section Stack
6298 This is one of the ELF section stack manipulation directives. The others are
6299 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6300 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6303 This directive replaces the current subsection with @code{name}. The current
6304 section is not changed. The replaced subsection is put onto the section stack
6305 in place of the then current top of stack subsection.
6310 @section @code{.symver}
6311 @cindex @code{symver} directive
6312 @cindex symbol versioning
6313 @cindex versions of symbols
6314 Use the @code{.symver} directive to bind symbols to specific version nodes
6315 within a source file. This is only supported on ELF platforms, and is
6316 typically used when assembling files to be linked into a shared library.
6317 There are cases where it may make sense to use this in objects to be bound
6318 into an application itself so as to override a versioned symbol from a
6321 For ELF targets, the @code{.symver} directive can be used like this:
6323 .symver @var{name}, @var{name2@@nodename}
6325 If the symbol @var{name} is defined within the file
6326 being assembled, the @code{.symver} directive effectively creates a symbol
6327 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6328 just don't try and create a regular alias is that the @var{@@} character isn't
6329 permitted in symbol names. The @var{name2} part of the name is the actual name
6330 of the symbol by which it will be externally referenced. The name @var{name}
6331 itself is merely a name of convenience that is used so that it is possible to
6332 have definitions for multiple versions of a function within a single source
6333 file, and so that the compiler can unambiguously know which version of a
6334 function is being mentioned. The @var{nodename} portion of the alias should be
6335 the name of a node specified in the version script supplied to the linker when
6336 building a shared library. If you are attempting to override a versioned
6337 symbol from a shared library, then @var{nodename} should correspond to the
6338 nodename of the symbol you are trying to override.
6340 If the symbol @var{name} is not defined within the file being assembled, all
6341 references to @var{name} will be changed to @var{name2@@nodename}. If no
6342 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6345 Another usage of the @code{.symver} directive is:
6347 .symver @var{name}, @var{name2@@@@nodename}
6349 In this case, the symbol @var{name} must exist and be defined within
6350 the file being assembled. It is similar to @var{name2@@nodename}. The
6351 difference is @var{name2@@@@nodename} will also be used to resolve
6352 references to @var{name2} by the linker.
6354 The third usage of the @code{.symver} directive is:
6356 .symver @var{name}, @var{name2@@@@@@nodename}
6358 When @var{name} is not defined within the
6359 file being assembled, it is treated as @var{name2@@nodename}. When
6360 @var{name} is defined within the file being assembled, the symbol
6361 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6366 @section @code{.tag @var{structname}}
6368 @cindex COFF structure debugging
6369 @cindex structure debugging, COFF
6370 @cindex @code{tag} directive
6371 This directive is generated by compilers to include auxiliary debugging
6372 information in the symbol table. It is only permitted inside
6373 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6374 definitions in the symbol table with instances of those structures.
6377 @samp{.tag} is only used when generating COFF format output; when
6378 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6384 @section @code{.text @var{subsection}}
6386 @cindex @code{text} directive
6387 Tells @command{@value{AS}} to assemble the following statements onto the end of
6388 the text subsection numbered @var{subsection}, which is an absolute
6389 expression. If @var{subsection} is omitted, subsection number zero
6393 @section @code{.title "@var{heading}"}
6395 @cindex @code{title} directive
6396 @cindex listing control: title line
6397 Use @var{heading} as the title (second line, immediately after the
6398 source file name and pagenumber) when generating assembly listings.
6400 This directive affects subsequent pages, as well as the current page if
6401 it appears within ten lines of the top of a page.
6405 @section @code{.type}
6407 This directive is used to set the type of a symbol.
6411 @c only print the extra heading if both COFF and ELF are set
6412 @subheading COFF Version
6415 @cindex COFF symbol type
6416 @cindex symbol type, COFF
6417 @cindex @code{type} directive (COFF version)
6418 For COFF targets, this directive is permitted only within
6419 @code{.def}/@code{.endef} pairs. It is used like this:
6425 This records the integer @var{int} as the type attribute of a symbol table
6429 @samp{.type} is associated only with COFF format output; when
6430 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6431 directive but ignores it.
6437 @c only print the extra heading if both COFF and ELF are set
6438 @subheading ELF Version
6441 @cindex ELF symbol type
6442 @cindex symbol type, ELF
6443 @cindex @code{type} directive (ELF version)
6444 For ELF targets, the @code{.type} directive is used like this:
6447 .type @var{name} , @var{type description}
6450 This sets the type of symbol @var{name} to be either a
6451 function symbol or an object symbol. There are five different syntaxes
6452 supported for the @var{type description} field, in order to provide
6453 compatibility with various other assemblers.
6455 Because some of the characters used in these syntaxes (such as @samp{@@} and
6456 @samp{#}) are comment characters for some architectures, some of the syntaxes
6457 below do not work on all architectures. The first variant will be accepted by
6458 the GNU assembler on all architectures so that variant should be used for
6459 maximum portability, if you do not need to assemble your code with other
6462 The syntaxes supported are:
6465 .type <name> STT_<TYPE_IN_UPPER_CASE>
6466 .type <name>,#<type>
6467 .type <name>,@@<type>
6468 .type <name>,%<type>
6469 .type <name>,"<type>"
6472 The types supported are:
6477 Mark the symbol as being a function name.
6480 @itemx gnu_indirect_function
6481 Mark the symbol as an indirect function when evaluated during reloc
6482 processing. (This is only supported on Linux targeted assemblers).
6486 Mark the symbol as being a data object.
6490 Mark the symbol as being a thead-local data object.
6494 Mark the symbol as being a common data object.
6498 Does not mark the symbol in any way. It is supported just for completeness.
6500 @item gnu_unique_object
6501 Marks the symbol as being a globally unique data object. The dynamic linker
6502 will make sure that in the entire process there is just one symbol with this
6503 name and type in use. (This is only supported on Linux targeted assemblers).
6507 Note: Some targets support extra types in addition to those listed above.
6513 @section @code{.uleb128 @var{expressions}}
6515 @cindex @code{uleb128} directive
6516 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6517 compact, variable length representation of numbers used by the DWARF
6518 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6522 @section @code{.val @var{addr}}
6524 @cindex @code{val} directive
6525 @cindex COFF value attribute
6526 @cindex value attribute, COFF
6527 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6528 records the address @var{addr} as the value attribute of a symbol table
6532 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6533 configured for @code{b.out}, it accepts this directive but ignores it.
6539 @section @code{.version "@var{string}"}
6541 @cindex @code{version} directive
6542 This directive creates a @code{.note} section and places into it an ELF
6543 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6548 @section @code{.vtable_entry @var{table}, @var{offset}}
6550 @cindex @code{vtable_entry} directive
6551 This directive finds or creates a symbol @code{table} and creates a
6552 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6555 @section @code{.vtable_inherit @var{child}, @var{parent}}
6557 @cindex @code{vtable_inherit} directive
6558 This directive finds the symbol @code{child} and finds or creates the symbol
6559 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6560 parent whose addend is the value of the child symbol. As a special case the
6561 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6565 @section @code{.warning "@var{string}"}
6566 @cindex warning directive
6567 Similar to the directive @code{.error}
6568 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6571 @section @code{.weak @var{names}}
6573 @cindex @code{weak} directive
6574 This directive sets the weak attribute on the comma separated list of symbol
6575 @code{names}. If the symbols do not already exist, they will be created.
6577 On COFF targets other than PE, weak symbols are a GNU extension. This
6578 directive sets the weak attribute on the comma separated list of symbol
6579 @code{names}. If the symbols do not already exist, they will be created.
6581 On the PE target, weak symbols are supported natively as weak aliases.
6582 When a weak symbol is created that is not an alias, GAS creates an
6583 alternate symbol to hold the default value.
6586 @section @code{.weakref @var{alias}, @var{target}}
6588 @cindex @code{weakref} directive
6589 This directive creates an alias to the target symbol that enables the symbol to
6590 be referenced with weak-symbol semantics, but without actually making it weak.
6591 If direct references or definitions of the symbol are present, then the symbol
6592 will not be weak, but if all references to it are through weak references, the
6593 symbol will be marked as weak in the symbol table.
6595 The effect is equivalent to moving all references to the alias to a separate
6596 assembly source file, renaming the alias to the symbol in it, declaring the
6597 symbol as weak there, and running a reloadable link to merge the object files
6598 resulting from the assembly of the new source file and the old source file that
6599 had the references to the alias removed.
6601 The alias itself never makes to the symbol table, and is entirely handled
6602 within the assembler.
6605 @section @code{.word @var{expressions}}
6607 @cindex @code{word} directive
6608 This directive expects zero or more @var{expressions}, of any section,
6609 separated by commas.
6612 For each expression, @command{@value{AS}} emits a 32-bit number.
6615 For each expression, @command{@value{AS}} emits a 16-bit number.
6620 The size of the number emitted, and its byte order,
6621 depend on what target computer the assembly is for.
6624 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6625 @c happen---32-bit addressability, period; no long/short jumps.
6626 @ifset DIFF-TBL-KLUGE
6627 @cindex difference tables altered
6628 @cindex altered difference tables
6630 @emph{Warning: Special Treatment to support Compilers}
6634 Machines with a 32-bit address space, but that do less than 32-bit
6635 addressing, require the following special treatment. If the machine of
6636 interest to you does 32-bit addressing (or doesn't require it;
6637 @pxref{Machine Dependencies}), you can ignore this issue.
6640 In order to assemble compiler output into something that works,
6641 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6642 Directives of the form @samp{.word sym1-sym2} are often emitted by
6643 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6644 directive of the form @samp{.word sym1-sym2}, and the difference between
6645 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6646 creates a @dfn{secondary jump table}, immediately before the next label.
6647 This secondary jump table is preceded by a short-jump to the
6648 first byte after the secondary table. This short-jump prevents the flow
6649 of control from accidentally falling into the new table. Inside the
6650 table is a long-jump to @code{sym2}. The original @samp{.word}
6651 contains @code{sym1} minus the address of the long-jump to
6654 If there were several occurrences of @samp{.word sym1-sym2} before the
6655 secondary jump table, all of them are adjusted. If there was a
6656 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6657 long-jump to @code{sym4} is included in the secondary jump table,
6658 and the @code{.word} directives are adjusted to contain @code{sym3}
6659 minus the address of the long-jump to @code{sym4}; and so on, for as many
6660 entries in the original jump table as necessary.
6663 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6664 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6665 assembly language programmers.
6668 @c end DIFF-TBL-KLUGE
6671 @section Deprecated Directives
6673 @cindex deprecated directives
6674 @cindex obsolescent directives
6675 One day these directives won't work.
6676 They are included for compatibility with older assemblers.
6683 @node Object Attributes
6684 @chapter Object Attributes
6685 @cindex object attributes
6687 @command{@value{AS}} assembles source files written for a specific architecture
6688 into object files for that architecture. But not all object files are alike.
6689 Many architectures support incompatible variations. For instance, floating
6690 point arguments might be passed in floating point registers if the object file
6691 requires hardware floating point support---or floating point arguments might be
6692 passed in integer registers if the object file supports processors with no
6693 hardware floating point unit. Or, if two objects are built for different
6694 generations of the same architecture, the combination may require the
6695 newer generation at run-time.
6697 This information is useful during and after linking. At link time,
6698 @command{@value{LD}} can warn about incompatible object files. After link
6699 time, tools like @command{gdb} can use it to process the linked file
6702 Compatibility information is recorded as a series of object attributes. Each
6703 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6704 string, and indicates who sets the meaning of the tag. The tag is an integer,
6705 and indicates what property the attribute describes. The value may be a string
6706 or an integer, and indicates how the property affects this object. Missing
6707 attributes are the same as attributes with a zero value or empty string value.
6709 Object attributes were developed as part of the ABI for the ARM Architecture.
6710 The file format is documented in @cite{ELF for the ARM Architecture}.
6713 * GNU Object Attributes:: @sc{gnu} Object Attributes
6714 * Defining New Object Attributes:: Defining New Object Attributes
6717 @node GNU Object Attributes
6718 @section @sc{gnu} Object Attributes
6720 The @code{.gnu_attribute} directive records an object attribute
6721 with vendor @samp{gnu}.
6723 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6724 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6725 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6726 2} is set for architecture-independent attributes and clear for
6727 architecture-dependent ones.
6729 @subsection Common @sc{gnu} attributes
6731 These attributes are valid on all architectures.
6734 @item Tag_compatibility (32)
6735 The compatibility attribute takes an integer flag value and a vendor name. If
6736 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6737 then the file is only compatible with the named toolchain. If it is greater
6738 than 1, the file can only be processed by other toolchains under some private
6739 arrangement indicated by the flag value and the vendor name.
6742 @subsection MIPS Attributes
6745 @item Tag_GNU_MIPS_ABI_FP (4)
6746 The floating-point ABI used by this object file. The value will be:
6750 0 for files not affected by the floating-point ABI.
6752 1 for files using the hardware floating-point with a standard double-precision
6755 2 for files using the hardware floating-point ABI with a single-precision FPU.
6757 3 for files using the software floating-point ABI.
6759 4 for files using the hardware floating-point ABI with 64-bit wide
6760 double-precision floating-point registers and 32-bit wide general
6765 @subsection PowerPC Attributes
6768 @item Tag_GNU_Power_ABI_FP (4)
6769 The floating-point ABI used by this object file. The value will be:
6773 0 for files not affected by the floating-point ABI.
6775 1 for files using double-precision hardware floating-point ABI.
6777 2 for files using the software floating-point ABI.
6779 3 for files using single-precision hardware floating-point ABI.
6782 @item Tag_GNU_Power_ABI_Vector (8)
6783 The vector ABI used by this object file. The value will be:
6787 0 for files not affected by the vector ABI.
6789 1 for files using general purpose registers to pass vectors.
6791 2 for files using AltiVec registers to pass vectors.
6793 3 for files using SPE registers to pass vectors.
6797 @node Defining New Object Attributes
6798 @section Defining New Object Attributes
6800 If you want to define a new @sc{gnu} object attribute, here are the places you
6801 will need to modify. New attributes should be discussed on the @samp{binutils}
6806 This manual, which is the official register of attributes.
6808 The header for your architecture @file{include/elf}, to define the tag.
6810 The @file{bfd} support file for your architecture, to merge the attribute
6811 and issue any appropriate link warnings.
6813 Test cases in @file{ld/testsuite} for merging and link warnings.
6815 @file{binutils/readelf.c} to display your attribute.
6817 GCC, if you want the compiler to mark the attribute automatically.
6823 @node Machine Dependencies
6824 @chapter Machine Dependent Features
6826 @cindex machine dependencies
6827 The machine instruction sets are (almost by definition) different on
6828 each machine where @command{@value{AS}} runs. Floating point representations
6829 vary as well, and @command{@value{AS}} often supports a few additional
6830 directives or command-line options for compatibility with other
6831 assemblers on a particular platform. Finally, some versions of
6832 @command{@value{AS}} support special pseudo-instructions for branch
6835 This chapter discusses most of these differences, though it does not
6836 include details on any machine's instruction set. For details on that
6837 subject, see the hardware manufacturer's manual.
6841 * Alpha-Dependent:: Alpha Dependent Features
6844 * ARC-Dependent:: ARC Dependent Features
6847 * ARM-Dependent:: ARM Dependent Features
6850 * AVR-Dependent:: AVR Dependent Features
6853 * Blackfin-Dependent:: Blackfin Dependent Features
6856 * CR16-Dependent:: CR16 Dependent Features
6859 * CRIS-Dependent:: CRIS Dependent Features
6862 * D10V-Dependent:: D10V Dependent Features
6865 * D30V-Dependent:: D30V Dependent Features
6868 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6871 * HPPA-Dependent:: HPPA Dependent Features
6874 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6877 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6880 * i860-Dependent:: Intel 80860 Dependent Features
6883 * i960-Dependent:: Intel 80960 Dependent Features
6886 * IA-64-Dependent:: Intel IA-64 Dependent Features
6889 * IP2K-Dependent:: IP2K Dependent Features
6892 * LM32-Dependent:: LM32 Dependent Features
6895 * M32C-Dependent:: M32C Dependent Features
6898 * M32R-Dependent:: M32R Dependent Features
6901 * M68K-Dependent:: M680x0 Dependent Features
6904 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6907 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6910 * MIPS-Dependent:: MIPS Dependent Features
6913 * MMIX-Dependent:: MMIX Dependent Features
6916 * MSP430-Dependent:: MSP430 Dependent Features
6919 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6920 * SH64-Dependent:: SuperH SH64 Dependent Features
6923 * PDP-11-Dependent:: PDP-11 Dependent Features
6926 * PJ-Dependent:: picoJava Dependent Features
6929 * PPC-Dependent:: PowerPC Dependent Features
6932 * RX-Dependent:: RX Dependent Features
6935 * S/390-Dependent:: IBM S/390 Dependent Features
6938 * SCORE-Dependent:: SCORE Dependent Features
6941 * Sparc-Dependent:: SPARC Dependent Features
6944 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6947 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6950 * V850-Dependent:: V850 Dependent Features
6953 * Xtensa-Dependent:: Xtensa Dependent Features
6956 * Z80-Dependent:: Z80 Dependent Features
6959 * Z8000-Dependent:: Z8000 Dependent Features
6962 * Vax-Dependent:: VAX Dependent Features
6969 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6970 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6971 @c peculiarity: to preserve cross-references, there must be a node called
6972 @c "Machine Dependencies". Hence the conditional nodenames in each
6973 @c major node below. Node defaulting in makeinfo requires adjacency of
6974 @c node and sectioning commands; hence the repetition of @chapter BLAH
6975 @c in both conditional blocks.
6978 @include c-alpha.texi
6994 @include c-bfin.texi
6998 @include c-cr16.texi
7002 @include c-cris.texi
7007 @node Machine Dependencies
7008 @chapter Machine Dependent Features
7010 The machine instruction sets are different on each Renesas chip family,
7011 and there are also some syntax differences among the families. This
7012 chapter describes the specific @command{@value{AS}} features for each
7016 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7017 * SH-Dependent:: Renesas SH Dependent Features
7024 @include c-d10v.texi
7028 @include c-d30v.texi
7032 @include c-h8300.texi
7036 @include c-hppa.texi
7040 @include c-i370.texi
7044 @include c-i386.texi
7048 @include c-i860.texi
7052 @include c-i960.texi
7056 @include c-ia64.texi
7060 @include c-ip2k.texi
7064 @include c-lm32.texi
7068 @include c-m32c.texi
7072 @include c-m32r.texi
7076 @include c-m68k.texi
7080 @include c-m68hc11.texi
7084 @include c-microblaze.texi
7088 @include c-mips.texi
7092 @include c-mmix.texi
7096 @include c-msp430.texi
7100 @include c-ns32k.texi
7104 @include c-pdp11.texi
7120 @include c-s390.texi
7124 @include c-score.texi
7129 @include c-sh64.texi
7133 @include c-sparc.texi
7137 @include c-tic54x.texi
7141 @include c-tic6x.texi
7157 @include c-v850.texi
7161 @include c-xtensa.texi
7165 @c reverse effect of @down at top of generic Machine-Dep chapter
7169 @node Reporting Bugs
7170 @chapter Reporting Bugs
7171 @cindex bugs in assembler
7172 @cindex reporting bugs in assembler
7174 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7176 Reporting a bug may help you by bringing a solution to your problem, or it may
7177 not. But in any case the principal function of a bug report is to help the
7178 entire community by making the next version of @command{@value{AS}} work better.
7179 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7181 In order for a bug report to serve its purpose, you must include the
7182 information that enables us to fix the bug.
7185 * Bug Criteria:: Have you found a bug?
7186 * Bug Reporting:: How to report bugs
7190 @section Have You Found a Bug?
7191 @cindex bug criteria
7193 If you are not sure whether you have found a bug, here are some guidelines:
7196 @cindex fatal signal
7197 @cindex assembler crash
7198 @cindex crash of assembler
7200 If the assembler gets a fatal signal, for any input whatever, that is a
7201 @command{@value{AS}} bug. Reliable assemblers never crash.
7203 @cindex error on valid input
7205 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7207 @cindex invalid input
7209 If @command{@value{AS}} does not produce an error message for invalid input, that
7210 is a bug. However, you should note that your idea of ``invalid input'' might
7211 be our idea of ``an extension'' or ``support for traditional practice''.
7214 If you are an experienced user of assemblers, your suggestions for improvement
7215 of @command{@value{AS}} are welcome in any case.
7219 @section How to Report Bugs
7221 @cindex assembler bugs, reporting
7223 A number of companies and individuals offer support for @sc{gnu} products. If
7224 you obtained @command{@value{AS}} from a support organization, we recommend you
7225 contact that organization first.
7227 You can find contact information for many support companies and
7228 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7232 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7236 The fundamental principle of reporting bugs usefully is this:
7237 @strong{report all the facts}. If you are not sure whether to state a
7238 fact or leave it out, state it!
7240 Often people omit facts because they think they know what causes the problem
7241 and assume that some details do not matter. Thus, you might assume that the
7242 name of a symbol you use in an example does not matter. Well, probably it does
7243 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7244 happens to fetch from the location where that name is stored in memory;
7245 perhaps, if the name were different, the contents of that location would fool
7246 the assembler into doing the right thing despite the bug. Play it safe and
7247 give a specific, complete example. That is the easiest thing for you to do,
7248 and the most helpful.
7250 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7251 it is new to us. Therefore, always write your bug reports on the assumption
7252 that the bug has not been reported previously.
7254 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7255 bell?'' This cannot help us fix a bug, so it is basically useless. We
7256 respond by asking for enough details to enable us to investigate.
7257 You might as well expedite matters by sending them to begin with.
7259 To enable us to fix the bug, you should include all these things:
7263 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7264 it with the @samp{--version} argument.
7266 Without this, we will not know whether there is any point in looking for
7267 the bug in the current version of @command{@value{AS}}.
7270 Any patches you may have applied to the @command{@value{AS}} source.
7273 The type of machine you are using, and the operating system name and
7277 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7281 The command arguments you gave the assembler to assemble your example and
7282 observe the bug. To guarantee you will not omit something important, list them
7283 all. A copy of the Makefile (or the output from make) is sufficient.
7285 If we were to try to guess the arguments, we would probably guess wrong
7286 and then we might not encounter the bug.
7289 A complete input file that will reproduce the bug. If the bug is observed when
7290 the assembler is invoked via a compiler, send the assembler source, not the
7291 high level language source. Most compilers will produce the assembler source
7292 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7293 the options @samp{-v --save-temps}; this will save the assembler source in a
7294 file with an extension of @file{.s}, and also show you exactly how
7295 @command{@value{AS}} is being run.
7298 A description of what behavior you observe that you believe is
7299 incorrect. For example, ``It gets a fatal signal.''
7301 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7302 will certainly notice it. But if the bug is incorrect output, we might not
7303 notice unless it is glaringly wrong. You might as well not give us a chance to
7306 Even if the problem you experience is a fatal signal, you should still say so
7307 explicitly. Suppose something strange is going on, such as, your copy of
7308 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7309 library on your system. (This has happened!) Your copy might crash and ours
7310 would not. If you told us to expect a crash, then when ours fails to crash, we
7311 would know that the bug was not happening for us. If you had not told us to
7312 expect a crash, then we would not be able to draw any conclusion from our
7316 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7317 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7318 option. Always send diffs from the old file to the new file. If you even
7319 discuss something in the @command{@value{AS}} source, refer to it by context, not
7322 The line numbers in our development sources will not match those in your
7323 sources. Your line numbers would convey no useful information to us.
7326 Here are some things that are not necessary:
7330 A description of the envelope of the bug.
7332 Often people who encounter a bug spend a lot of time investigating
7333 which changes to the input file will make the bug go away and which
7334 changes will not affect it.
7336 This is often time consuming and not very useful, because the way we
7337 will find the bug is by running a single example under the debugger
7338 with breakpoints, not by pure deduction from a series of examples.
7339 We recommend that you save your time for something else.
7341 Of course, if you can find a simpler example to report @emph{instead}
7342 of the original one, that is a convenience for us. Errors in the
7343 output will be easier to spot, running under the debugger will take
7344 less time, and so on.
7346 However, simplification is not vital; if you do not want to do this,
7347 report the bug anyway and send us the entire test case you used.
7350 A patch for the bug.
7352 A patch for the bug does help us if it is a good one. But do not omit
7353 the necessary information, such as the test case, on the assumption that
7354 a patch is all we need. We might see problems with your patch and decide
7355 to fix the problem another way, or we might not understand it at all.
7357 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7358 construct an example that will make the program follow a certain path through
7359 the code. If you do not send us the example, we will not be able to construct
7360 one, so we will not be able to verify that the bug is fixed.
7362 And if we cannot understand what bug you are trying to fix, or why your
7363 patch should be an improvement, we will not install it. A test case will
7364 help us to understand.
7367 A guess about what the bug is or what it depends on.
7369 Such guesses are usually wrong. Even we cannot guess right about such
7370 things without first using the debugger to find the facts.
7373 @node Acknowledgements
7374 @chapter Acknowledgements
7376 If you have contributed to GAS and your name isn't listed here,
7377 it is not meant as a slight. We just don't know about it. Send mail to the
7378 maintainer, and we'll correct the situation. Currently
7380 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7382 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7385 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7386 information and the 68k series machines, most of the preprocessing pass, and
7387 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7389 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7390 many bug fixes, including merging support for several processors, breaking GAS
7391 up to handle multiple object file format back ends (including heavy rewrite,
7392 testing, an integration of the coff and b.out back ends), adding configuration
7393 including heavy testing and verification of cross assemblers and file splits
7394 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7395 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7396 port (including considerable amounts of reverse engineering), a SPARC opcode
7397 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7398 assertions and made them work, much other reorganization, cleanup, and lint.
7400 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7401 in format-specific I/O modules.
7403 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7404 has done much work with it since.
7406 The Intel 80386 machine description was written by Eliot Dresselhaus.
7408 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7410 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7411 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7413 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7414 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7415 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7416 support a.out format.
7418 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7419 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7420 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7421 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7424 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7425 simplified the configuration of which versions accept which directives. He
7426 updated the 68k machine description so that Motorola's opcodes always produced
7427 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7428 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7429 cross-compilation support, and one bug in relaxation that took a week and
7430 required the proverbial one-bit fix.
7432 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7433 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7434 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7435 PowerPC assembler, and made a few other minor patches.
7437 Steve Chamberlain made GAS able to generate listings.
7439 Hewlett-Packard contributed support for the HP9000/300.
7441 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7442 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7443 formats). This work was supported by both the Center for Software Science at
7444 the University of Utah and Cygnus Support.
7446 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7447 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7448 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7449 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7450 and some initial 64-bit support).
7452 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7454 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7455 support for openVMS/Alpha.
7457 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7460 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7461 Inc.@: added support for Xtensa processors.
7463 Several engineers at Cygnus Support have also provided many small bug fixes and
7464 configuration enhancements.
7466 Jon Beniston added support for the Lattice Mico32 architecture.
7468 Many others have contributed large or small bugfixes and enhancements. If
7469 you have contributed significant work and are not mentioned on this list, and
7470 want to be, let us know. Some of the history has been lost; we are not
7471 intentionally leaving anyone out.
7473 @node GNU Free Documentation License
7474 @appendix GNU Free Documentation License
7478 @unnumbered AS Index