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}]
484 @emph{Target Z80 options:}
485 [@b{-z80}] [@b{-r800}]
486 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
487 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
488 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
489 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
490 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
491 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
495 @c Z8000 has no machine-dependent assembler options
499 @emph{Target Xtensa options:}
500 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
501 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
502 [@b{--[no-]transform}]
503 [@b{--rename-section} @var{oldname}=@var{newname}]
511 @include at-file.texi
514 Turn on listings, in any of a variety of ways:
518 omit false conditionals
521 omit debugging directives
524 include general information, like @value{AS} version and options passed
527 include high-level source
533 include macro expansions
536 omit forms processing
542 set the name of the listing file
545 You may combine these options; for example, use @samp{-aln} for assembly
546 listing without forms processing. The @samp{=file} option, if used, must be
547 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
550 Begin in alternate macro mode.
552 @xref{Altmacro,,@code{.altmacro}}.
555 @item --compress-debug-sections
556 Compress DWARF debug sections using zlib. The debug sections are renamed
557 to begin with @samp{.zdebug}, and the resulting object file may not be
558 compatible with older linkers and object file utilities.
560 @item --nocompress-debug-sections
561 Do not compress DWARF debug sections. This is the default.
564 Ignored. This option is accepted for script compatibility with calls to
567 @item --debug-prefix-map @var{old}=@var{new}
568 When assembling files in directory @file{@var{old}}, record debugging
569 information describing them as in @file{@var{new}} instead.
571 @item --defsym @var{sym}=@var{value}
572 Define the symbol @var{sym} to be @var{value} before assembling the input file.
573 @var{value} must be an integer constant. As in C, a leading @samp{0x}
574 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
575 value. The value of the symbol can be overridden inside a source file via the
576 use of a @code{.set} pseudo-op.
579 ``fast''---skip whitespace and comment preprocessing (assume source is
584 Generate debugging information for each assembler source line using whichever
585 debug format is preferred by the target. This currently means either STABS,
589 Generate stabs debugging information for each assembler line. This
590 may help debugging assembler code, if the debugger can handle it.
593 Generate stabs debugging information for each assembler line, with GNU
594 extensions that probably only gdb can handle, and that could make other
595 debuggers crash or refuse to read your program. This
596 may help debugging assembler code. Currently the only GNU extension is
597 the location of the current working directory at assembling time.
600 Generate DWARF2 debugging information for each assembler line. This
601 may help debugging assembler code, if the debugger can handle it. Note---this
602 option is only supported by some targets, not all of them.
605 Print a summary of the command line options and exit.
608 Print a summary of all target specific options and exit.
611 Add directory @var{dir} to the search list for @code{.include} directives.
614 Don't warn about signed overflow.
617 @ifclear DIFF-TBL-KLUGE
618 This option is accepted but has no effect on the @value{TARGET} family.
620 @ifset DIFF-TBL-KLUGE
621 Issue warnings when difference tables altered for long displacements.
626 Keep (in the symbol table) local symbols. These symbols start with
627 system-specific local label prefixes, typically @samp{.L} for ELF systems
628 or @samp{L} for traditional a.out systems.
633 @item --listing-lhs-width=@var{number}
634 Set the maximum width, in words, of the output data column for an assembler
635 listing to @var{number}.
637 @item --listing-lhs-width2=@var{number}
638 Set the maximum width, in words, of the output data column for continuation
639 lines in an assembler listing to @var{number}.
641 @item --listing-rhs-width=@var{number}
642 Set the maximum width of an input source line, as displayed in a listing, to
645 @item --listing-cont-lines=@var{number}
646 Set the maximum number of lines printed in a listing for a single line of input
649 @item -o @var{objfile}
650 Name the object-file output from @command{@value{AS}} @var{objfile}.
653 Fold the data section into the text section.
655 @kindex --hash-size=@var{number}
656 Set the default size of GAS's hash tables to a prime number close to
657 @var{number}. Increasing this value can reduce the length of time it takes the
658 assembler to perform its tasks, at the expense of increasing the assembler's
659 memory requirements. Similarly reducing this value can reduce the memory
660 requirements at the expense of speed.
662 @item --reduce-memory-overheads
663 This option reduces GAS's memory requirements, at the expense of making the
664 assembly processes slower. Currently this switch is a synonym for
665 @samp{--hash-size=4051}, but in the future it may have other effects as well.
668 Print the maximum space (in bytes) and total time (in seconds) used by
671 @item --strip-local-absolute
672 Remove local absolute symbols from the outgoing symbol table.
676 Print the @command{as} version.
679 Print the @command{as} version and exit.
683 Suppress warning messages.
685 @item --fatal-warnings
686 Treat warnings as errors.
689 Don't suppress warning messages or treat them as errors.
698 Generate an object file even after errors.
700 @item -- | @var{files} @dots{}
701 Standard input, or source files to assemble.
706 The following options are available when @value{AS} is configured for
711 This option selects the core processor variant.
713 Select either big-endian (-EB) or little-endian (-EL) output.
718 The following options are available when @value{AS} is configured for the ARM
722 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
723 Specify which ARM processor variant is the target.
724 @item -march=@var{architecture}[+@var{extension}@dots{}]
725 Specify which ARM architecture variant is used by the target.
726 @item -mfpu=@var{floating-point-format}
727 Select which Floating Point architecture is the target.
728 @item -mfloat-abi=@var{abi}
729 Select which floating point ABI is in use.
731 Enable Thumb only instruction decoding.
732 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
733 Select which procedure calling convention is in use.
735 Select either big-endian (-EB) or little-endian (-EL) output.
736 @item -mthumb-interwork
737 Specify that the code has been generated with interworking between Thumb and
740 Specify that PIC code has been generated.
745 The following options are available when @value{AS} is configured for
746 the Blackfin processor family.
749 @item -mcpu=@var{processor}@r{[}-@var{sirevision}@r{]}
750 This option specifies the target processor. The optional @var{sirevision}
751 is not used in assembler.
753 Assemble for the FDPIC ABI.
761 See the info pages for documentation of the CRIS-specific options.
765 The following options are available when @value{AS} is configured for
768 @cindex D10V optimization
769 @cindex optimization, D10V
771 Optimize output by parallelizing instructions.
776 The following options are available when @value{AS} is configured for a D30V
779 @cindex D30V optimization
780 @cindex optimization, D30V
782 Optimize output by parallelizing instructions.
786 Warn when nops are generated.
788 @cindex D30V nops after 32-bit multiply
790 Warn when a nop after a 32-bit multiply instruction is generated.
795 The following options are available when @value{AS} is configured for the
796 Intel 80960 processor.
799 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
800 Specify which variant of the 960 architecture is the target.
803 Add code to collect statistics about branches taken.
806 Do not alter compare-and-branch instructions for long displacements;
813 The following options are available when @value{AS} is configured for the
819 Specifies that the extended IP2022 instructions are allowed.
822 Restores the default behaviour, which restricts the permitted instructions to
823 just the basic IP2022 ones.
829 The following options are available when @value{AS} is configured for the
830 Renesas M32C and M16C processors.
835 Assemble M32C instructions.
838 Assemble M16C instructions (the default).
841 Enable support for link-time relaxations.
844 Support H'00 style hex constants in addition to 0x00 style.
850 The following options are available when @value{AS} is configured for the
851 Renesas M32R (formerly Mitsubishi M32R) series.
856 Specify which processor in the M32R family is the target. The default
857 is normally the M32R, but this option changes it to the M32RX.
859 @item --warn-explicit-parallel-conflicts or --Wp
860 Produce warning messages when questionable parallel constructs are
863 @item --no-warn-explicit-parallel-conflicts or --Wnp
864 Do not produce warning messages when questionable parallel constructs are
871 The following options are available when @value{AS} is configured for the
872 Motorola 68000 series.
877 Shorten references to undefined symbols, to one word instead of two.
879 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
880 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
881 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
882 Specify what processor in the 68000 family is the target. The default
883 is normally the 68020, but this can be changed at configuration time.
885 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
886 The target machine does (or does not) have a floating-point coprocessor.
887 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
888 the basic 68000 is not compatible with the 68881, a combination of the
889 two can be specified, since it's possible to do emulation of the
890 coprocessor instructions with the main processor.
892 @item -m68851 | -mno-68851
893 The target machine does (or does not) have a memory-management
894 unit coprocessor. The default is to assume an MMU for 68020 and up.
901 For details about the PDP-11 machine dependent features options,
902 see @ref{PDP-11-Options}.
905 @item -mpic | -mno-pic
906 Generate position-independent (or position-dependent) code. The
907 default is @option{-mpic}.
910 @itemx -mall-extensions
911 Enable all instruction set extensions. This is the default.
913 @item -mno-extensions
914 Disable all instruction set extensions.
916 @item -m@var{extension} | -mno-@var{extension}
917 Enable (or disable) a particular instruction set extension.
920 Enable the instruction set extensions supported by a particular CPU, and
921 disable all other extensions.
923 @item -m@var{machine}
924 Enable the instruction set extensions supported by a particular machine
925 model, and disable all other extensions.
931 The following options are available when @value{AS} is configured for
932 a picoJava processor.
936 @cindex PJ endianness
937 @cindex endianness, PJ
938 @cindex big endian output, PJ
940 Generate ``big endian'' format output.
942 @cindex little endian output, PJ
944 Generate ``little endian'' format output.
950 The following options are available when @value{AS} is configured for the
951 Motorola 68HC11 or 68HC12 series.
955 @item -m68hc11 | -m68hc12 | -m68hcs12
956 Specify what processor is the target. The default is
957 defined by the configuration option when building the assembler.
960 Specify to use the 16-bit integer ABI.
963 Specify to use the 32-bit integer ABI.
966 Specify to use the 32-bit double ABI.
969 Specify to use the 64-bit double ABI.
971 @item --force-long-branches
972 Relative branches are turned into absolute ones. This concerns
973 conditional branches, unconditional branches and branches to a
976 @item -S | --short-branches
977 Do not turn relative branches into absolute ones
978 when the offset is out of range.
980 @item --strict-direct-mode
981 Do not turn the direct addressing mode into extended addressing mode
982 when the instruction does not support direct addressing mode.
984 @item --print-insn-syntax
985 Print the syntax of instruction in case of error.
987 @item --print-opcodes
988 print the list of instructions with syntax and then exit.
990 @item --generate-example
991 print an example of instruction for each possible instruction and then exit.
992 This option is only useful for testing @command{@value{AS}}.
998 The following options are available when @command{@value{AS}} is configured
999 for the SPARC architecture:
1002 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1003 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1004 Explicitly select a variant of the SPARC architecture.
1006 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1007 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1009 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1010 UltraSPARC extensions.
1012 @item -xarch=v8plus | -xarch=v8plusa
1013 For compatibility with the Solaris v9 assembler. These options are
1014 equivalent to -Av8plus and -Av8plusa, respectively.
1017 Warn when the assembler switches to another architecture.
1022 The following options are available when @value{AS} is configured for the 'c54x
1027 Enable extended addressing mode. All addresses and relocations will assume
1028 extended addressing (usually 23 bits).
1029 @item -mcpu=@var{CPU_VERSION}
1030 Sets the CPU version being compiled for.
1031 @item -merrors-to-file @var{FILENAME}
1032 Redirect error output to a file, for broken systems which don't support such
1033 behaviour in the shell.
1038 The following options are available when @value{AS} is configured for
1039 a @sc{mips} processor.
1043 This option sets the largest size of an object that can be referenced
1044 implicitly with the @code{gp} register. It is only accepted for targets that
1045 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1047 @cindex MIPS endianness
1048 @cindex endianness, MIPS
1049 @cindex big endian output, MIPS
1051 Generate ``big endian'' format output.
1053 @cindex little endian output, MIPS
1055 Generate ``little endian'' format output.
1067 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1068 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1069 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1070 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1071 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1073 correspond to generic
1074 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1075 and @samp{MIPS64 Release 2}
1076 ISA processors, respectively.
1078 @item -march=@var{CPU}
1079 Generate code for a particular @sc{mips} cpu.
1081 @item -mtune=@var{cpu}
1082 Schedule and tune for a particular @sc{mips} cpu.
1086 Cause nops to be inserted if the read of the destination register
1087 of an mfhi or mflo instruction occurs in the following two instructions.
1091 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1092 section instead of the standard ELF .stabs sections.
1096 Control generation of @code{.pdr} sections.
1100 The register sizes are normally inferred from the ISA and ABI, but these
1101 flags force a certain group of registers to be treated as 32 bits wide at
1102 all times. @samp{-mgp32} controls the size of general-purpose registers
1103 and @samp{-mfp32} controls the size of floating-point registers.
1107 Generate code for the MIPS 16 processor. This is equivalent to putting
1108 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1109 turns off this option.
1112 @itemx -mno-smartmips
1113 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1114 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1115 @samp{-mno-smartmips} turns off this option.
1119 Generate code for the MIPS-3D Application Specific Extension.
1120 This tells the assembler to accept MIPS-3D instructions.
1121 @samp{-no-mips3d} turns off this option.
1125 Generate code for the MDMX Application Specific Extension.
1126 This tells the assembler to accept MDMX instructions.
1127 @samp{-no-mdmx} turns off this option.
1131 Generate code for the DSP Release 1 Application Specific Extension.
1132 This tells the assembler to accept DSP Release 1 instructions.
1133 @samp{-mno-dsp} turns off this option.
1137 Generate code for the DSP Release 2 Application Specific Extension.
1138 This option implies -mdsp.
1139 This tells the assembler to accept DSP Release 2 instructions.
1140 @samp{-mno-dspr2} turns off this option.
1144 Generate code for the MT Application Specific Extension.
1145 This tells the assembler to accept MT instructions.
1146 @samp{-mno-mt} turns off this option.
1148 @item --construct-floats
1149 @itemx --no-construct-floats
1150 The @samp{--no-construct-floats} option disables the construction of
1151 double width floating point constants by loading the two halves of the
1152 value into the two single width floating point registers that make up
1153 the double width register. By default @samp{--construct-floats} is
1154 selected, allowing construction of these floating point constants.
1157 @item --emulation=@var{name}
1158 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1159 for some other target, in all respects, including output format (choosing
1160 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1161 debugging information or store symbol table information, and default
1162 endianness. The available configuration names are: @samp{mipsecoff},
1163 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1164 @samp{mipsbelf}. The first two do not alter the default endianness from that
1165 of the primary target for which the assembler was configured; the others change
1166 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1167 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1168 selection in any case.
1170 This option is currently supported only when the primary target
1171 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1172 Furthermore, the primary target or others specified with
1173 @samp{--enable-targets=@dots{}} at configuration time must include support for
1174 the other format, if both are to be available. For example, the Irix 5
1175 configuration includes support for both.
1177 Eventually, this option will support more configurations, with more
1178 fine-grained control over the assembler's behavior, and will be supported for
1182 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1189 Control how to deal with multiplication overflow and division by zero.
1190 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1191 (and only work for Instruction Set Architecture level 2 and higher);
1192 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1196 When this option is used, @command{@value{AS}} will issue a warning every
1197 time it generates a nop instruction from a macro.
1202 The following options are available when @value{AS} is configured for
1208 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1209 The command line option @samp{-nojsri2bsr} can be used to disable it.
1213 Enable or disable the silicon filter behaviour. By default this is disabled.
1214 The default can be overridden by the @samp{-sifilter} command line option.
1217 Alter jump instructions for long displacements.
1219 @item -mcpu=[210|340]
1220 Select the cpu type on the target hardware. This controls which instructions
1224 Assemble for a big endian target.
1227 Assemble for a little endian target.
1233 See the info pages for documentation of the MMIX-specific options.
1237 See the info pages for documentation of the RX-specific options.
1241 The following options are available when @value{AS} is configured for the s390
1247 Select the word size, either 31/32 bits or 64 bits.
1250 Select the architecture mode, either the Enterprise System
1251 Architecture (esa) or the z/Architecture mode (zarch).
1252 @item -march=@var{processor}
1253 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1254 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1256 @itemx -mno-regnames
1257 Allow or disallow symbolic names for registers.
1258 @item -mwarn-areg-zero
1259 Warn whenever the operand for a base or index register has been specified
1260 but evaluates to zero.
1265 The following options are available when @value{AS} is configured for a
1266 TMS320C6000 processor.
1269 @item -march=@var{arch}
1270 Enable (only) instructions from architecture @var{arch}. By default,
1271 all instructions are permitted.
1273 The following values of @var{arch} are accepted: @code{c62x},
1274 @code{c64x}, @code{c64x+}, @code{c67x}, @code{c67x+}, @code{c674x}.
1278 Enable or disable the optional C64x+ atomic operation instructions.
1279 By default, they are enabled if no @option{-march} option is given, or
1280 if an architecture is specified with @option{-march} that implies
1281 these instructions are present (currently, there are no such
1282 architectures); they are disabled if an architecture is specified with
1283 @option{-march} on which the instructions are optional or not
1284 present. This option overrides such a default from the architecture,
1285 independent of the order in which the @option{-march} or
1286 @option{-matomic} or @option{-mno-atomic} options are passed.
1289 @itemx -mlittle-endian
1290 Generate code for the specified endianness. The default is
1297 The following options are available when @value{AS} is configured for
1298 an Xtensa processor.
1301 @item --text-section-literals | --no-text-section-literals
1302 With @option{--text-@-section-@-literals}, literal pools are interspersed
1303 in the text section. The default is
1304 @option{--no-@-text-@-section-@-literals}, which places literals in a
1305 separate section in the output file. These options only affect literals
1306 referenced via PC-relative @code{L32R} instructions; literals for
1307 absolute mode @code{L32R} instructions are handled separately.
1309 @item --absolute-literals | --no-absolute-literals
1310 Indicate to the assembler whether @code{L32R} instructions use absolute
1311 or PC-relative addressing. The default is to assume absolute addressing
1312 if the Xtensa processor includes the absolute @code{L32R} addressing
1313 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1315 @item --target-align | --no-target-align
1316 Enable or disable automatic alignment to reduce branch penalties at the
1317 expense of some code density. The default is @option{--target-@-align}.
1319 @item --longcalls | --no-longcalls
1320 Enable or disable transformation of call instructions to allow calls
1321 across a greater range of addresses. The default is
1322 @option{--no-@-longcalls}.
1324 @item --transform | --no-transform
1325 Enable or disable all assembler transformations of Xtensa instructions.
1326 The default is @option{--transform};
1327 @option{--no-transform} should be used only in the rare cases when the
1328 instructions must be exactly as specified in the assembly source.
1330 @item --rename-section @var{oldname}=@var{newname}
1331 When generating output sections, rename the @var{oldname} section to
1337 The following options are available when @value{AS} is configured for
1338 a Z80 family processor.
1341 Assemble for Z80 processor.
1343 Assemble for R800 processor.
1344 @item -ignore-undocumented-instructions
1346 Assemble undocumented Z80 instructions that also work on R800 without warning.
1347 @item -ignore-unportable-instructions
1349 Assemble all undocumented Z80 instructions without warning.
1350 @item -warn-undocumented-instructions
1352 Issue a warning for undocumented Z80 instructions that also work on R800.
1353 @item -warn-unportable-instructions
1355 Issue a warning for undocumented Z80 instructions that do not work on R800.
1356 @item -forbid-undocumented-instructions
1358 Treat all undocumented instructions as errors.
1359 @item -forbid-unportable-instructions
1361 Treat undocumented Z80 instructions that do not work on R800 as errors.
1368 * Manual:: Structure of this Manual
1369 * GNU Assembler:: The GNU Assembler
1370 * Object Formats:: Object File Formats
1371 * Command Line:: Command Line
1372 * Input Files:: Input Files
1373 * Object:: Output (Object) File
1374 * Errors:: Error and Warning Messages
1378 @section Structure of this Manual
1380 @cindex manual, structure and purpose
1381 This manual is intended to describe what you need to know to use
1382 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1383 notation for symbols, constants, and expressions; the directives that
1384 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1387 We also cover special features in the @value{TARGET}
1388 configuration of @command{@value{AS}}, including assembler directives.
1391 This manual also describes some of the machine-dependent features of
1392 various flavors of the assembler.
1395 @cindex machine instructions (not covered)
1396 On the other hand, this manual is @emph{not} intended as an introduction
1397 to programming in assembly language---let alone programming in general!
1398 In a similar vein, we make no attempt to introduce the machine
1399 architecture; we do @emph{not} describe the instruction set, standard
1400 mnemonics, registers or addressing modes that are standard to a
1401 particular architecture.
1403 You may want to consult the manufacturer's
1404 machine architecture manual for this information.
1408 For information on the H8/300 machine instruction set, see @cite{H8/300
1409 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1410 Programming Manual} (Renesas).
1413 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1414 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1415 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1416 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1419 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1423 @c I think this is premature---doc@cygnus.com, 17jan1991
1425 Throughout this manual, we assume that you are running @dfn{GNU},
1426 the portable operating system from the @dfn{Free Software
1427 Foundation, Inc.}. This restricts our attention to certain kinds of
1428 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1429 once this assumption is granted examples and definitions need less
1432 @command{@value{AS}} is part of a team of programs that turn a high-level
1433 human-readable series of instructions into a low-level
1434 computer-readable series of instructions. Different versions of
1435 @command{@value{AS}} are used for different kinds of computer.
1438 @c There used to be a section "Terminology" here, which defined
1439 @c "contents", "byte", "word", and "long". Defining "word" to any
1440 @c particular size is confusing when the .word directive may generate 16
1441 @c bits on one machine and 32 bits on another; in general, for the user
1442 @c version of this manual, none of these terms seem essential to define.
1443 @c They were used very little even in the former draft of the manual;
1444 @c this draft makes an effort to avoid them (except in names of
1448 @section The GNU Assembler
1450 @c man begin DESCRIPTION
1452 @sc{gnu} @command{as} is really a family of assemblers.
1454 This manual describes @command{@value{AS}}, a member of that family which is
1455 configured for the @value{TARGET} architectures.
1457 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1458 should find a fairly similar environment when you use it on another
1459 architecture. Each version has much in common with the others,
1460 including object file formats, most assembler directives (often called
1461 @dfn{pseudo-ops}) and assembler syntax.@refill
1463 @cindex purpose of @sc{gnu} assembler
1464 @command{@value{AS}} is primarily intended to assemble the output of the
1465 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1466 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1467 assemble correctly everything that other assemblers for the same
1468 machine would assemble.
1470 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1473 @c This remark should appear in generic version of manual; assumption
1474 @c here is that generic version sets M680x0.
1475 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1476 assembler for the same architecture; for example, we know of several
1477 incompatible versions of 680x0 assembly language syntax.
1482 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1483 program in one pass of the source file. This has a subtle impact on the
1484 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1486 @node Object Formats
1487 @section Object File Formats
1489 @cindex object file format
1490 The @sc{gnu} assembler can be configured to produce several alternative
1491 object file formats. For the most part, this does not affect how you
1492 write assembly language programs; but directives for debugging symbols
1493 are typically different in different file formats. @xref{Symbol
1494 Attributes,,Symbol Attributes}.
1497 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1498 @value{OBJ-NAME} format object files.
1500 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1502 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1503 @code{b.out} or COFF format object files.
1506 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1507 SOM or ELF format object files.
1512 @section Command Line
1514 @cindex command line conventions
1516 After the program name @command{@value{AS}}, the command line may contain
1517 options and file names. Options may appear in any order, and may be
1518 before, after, or between file names. The order of file names is
1521 @cindex standard input, as input file
1523 @file{--} (two hyphens) by itself names the standard input file
1524 explicitly, as one of the files for @command{@value{AS}} to assemble.
1526 @cindex options, command line
1527 Except for @samp{--} any command line argument that begins with a
1528 hyphen (@samp{-}) is an option. Each option changes the behavior of
1529 @command{@value{AS}}. No option changes the way another option works. An
1530 option is a @samp{-} followed by one or more letters; the case of
1531 the letter is important. All options are optional.
1533 Some options expect exactly one file name to follow them. The file
1534 name may either immediately follow the option's letter (compatible
1535 with older assemblers) or it may be the next command argument (@sc{gnu}
1536 standard). These two command lines are equivalent:
1539 @value{AS} -o my-object-file.o mumble.s
1540 @value{AS} -omy-object-file.o mumble.s
1544 @section Input Files
1547 @cindex source program
1548 @cindex files, input
1549 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1550 describe the program input to one run of @command{@value{AS}}. The program may
1551 be in one or more files; how the source is partitioned into files
1552 doesn't change the meaning of the source.
1554 @c I added "con" prefix to "catenation" just to prove I can overcome my
1555 @c APL training... doc@cygnus.com
1556 The source program is a concatenation of the text in all the files, in the
1559 @c man begin DESCRIPTION
1560 Each time you run @command{@value{AS}} it assembles exactly one source
1561 program. The source program is made up of one or more files.
1562 (The standard input is also a file.)
1564 You give @command{@value{AS}} a command line that has zero or more input file
1565 names. The input files are read (from left file name to right). A
1566 command line argument (in any position) that has no special meaning
1567 is taken to be an input file name.
1569 If you give @command{@value{AS}} no file names it attempts to read one input file
1570 from the @command{@value{AS}} standard input, which is normally your terminal. You
1571 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1574 Use @samp{--} if you need to explicitly name the standard input file
1575 in your command line.
1577 If the source is empty, @command{@value{AS}} produces a small, empty object
1582 @subheading Filenames and Line-numbers
1584 @cindex input file linenumbers
1585 @cindex line numbers, in input files
1586 There are two ways of locating a line in the input file (or files) and
1587 either may be used in reporting error messages. One way refers to a line
1588 number in a physical file; the other refers to a line number in a
1589 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1591 @dfn{Physical files} are those files named in the command line given
1592 to @command{@value{AS}}.
1594 @dfn{Logical files} are simply names declared explicitly by assembler
1595 directives; they bear no relation to physical files. Logical file names help
1596 error messages reflect the original source file, when @command{@value{AS}} source
1597 is itself synthesized from other files. @command{@value{AS}} understands the
1598 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1599 @ref{File,,@code{.file}}.
1602 @section Output (Object) File
1608 Every time you run @command{@value{AS}} it produces an output file, which is
1609 your assembly language program translated into numbers. This file
1610 is the object file. Its default name is
1618 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1620 You can give it another name by using the @option{-o} option. Conventionally,
1621 object file names end with @file{.o}. The default name is used for historical
1622 reasons: older assemblers were capable of assembling self-contained programs
1623 directly into a runnable program. (For some formats, this isn't currently
1624 possible, but it can be done for the @code{a.out} format.)
1628 The object file is meant for input to the linker @code{@value{LD}}. It contains
1629 assembled program code, information to help @code{@value{LD}} integrate
1630 the assembled program into a runnable file, and (optionally) symbolic
1631 information for the debugger.
1633 @c link above to some info file(s) like the description of a.out.
1634 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1637 @section Error and Warning Messages
1639 @c man begin DESCRIPTION
1641 @cindex error messages
1642 @cindex warning messages
1643 @cindex messages from assembler
1644 @command{@value{AS}} may write warnings and error messages to the standard error
1645 file (usually your terminal). This should not happen when a compiler
1646 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1647 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1648 grave problem that stops the assembly.
1652 @cindex format of warning messages
1653 Warning messages have the format
1656 file_name:@b{NNN}:Warning Message Text
1660 @cindex line numbers, in warnings/errors
1661 (where @b{NNN} is a line number). If a logical file name has been given
1662 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1663 the current input file is used. If a logical line number was given
1665 (@pxref{Line,,@code{.line}})
1667 then it is used to calculate the number printed,
1668 otherwise the actual line in the current source file is printed. The
1669 message text is intended to be self explanatory (in the grand Unix
1672 @cindex format of error messages
1673 Error messages have the format
1675 file_name:@b{NNN}:FATAL:Error Message Text
1677 The file name and line number are derived as for warning
1678 messages. The actual message text may be rather less explanatory
1679 because many of them aren't supposed to happen.
1682 @chapter Command-Line Options
1684 @cindex options, all versions of assembler
1685 This chapter describes command-line options available in @emph{all}
1686 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1687 for options specific
1689 to the @value{TARGET} target.
1692 to particular machine architectures.
1695 @c man begin DESCRIPTION
1697 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1698 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1699 The assembler arguments must be separated from each other (and the @samp{-Wa})
1700 by commas. For example:
1703 gcc -c -g -O -Wa,-alh,-L file.c
1707 This passes two options to the assembler: @samp{-alh} (emit a listing to
1708 standard output with high-level and assembly source) and @samp{-L} (retain
1709 local symbols in the symbol table).
1711 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1712 command-line options are automatically passed to the assembler by the compiler.
1713 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1714 precisely what options it passes to each compilation pass, including the
1720 * a:: -a[cdghlns] enable listings
1721 * alternate:: --alternate enable alternate macro syntax
1722 * D:: -D for compatibility
1723 * f:: -f to work faster
1724 * I:: -I for .include search path
1725 @ifclear DIFF-TBL-KLUGE
1726 * K:: -K for compatibility
1728 @ifset DIFF-TBL-KLUGE
1729 * K:: -K for difference tables
1732 * L:: -L to retain local symbols
1733 * listing:: --listing-XXX to configure listing output
1734 * M:: -M or --mri to assemble in MRI compatibility mode
1735 * MD:: --MD for dependency tracking
1736 * o:: -o to name the object file
1737 * R:: -R to join data and text sections
1738 * statistics:: --statistics to see statistics about assembly
1739 * traditional-format:: --traditional-format for compatible output
1740 * v:: -v to announce version
1741 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1742 * Z:: -Z to make object file even after errors
1746 @section Enable Listings: @option{-a[cdghlns]}
1756 @cindex listings, enabling
1757 @cindex assembly listings, enabling
1759 These options enable listing output from the assembler. By itself,
1760 @samp{-a} requests high-level, assembly, and symbols listing.
1761 You can use other letters to select specific options for the list:
1762 @samp{-ah} requests a high-level language listing,
1763 @samp{-al} requests an output-program assembly listing, and
1764 @samp{-as} requests a symbol table listing.
1765 High-level listings require that a compiler debugging option like
1766 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1769 Use the @samp{-ag} option to print a first section with general assembly
1770 information, like @value{AS} version, switches passed, or time stamp.
1772 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1773 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1774 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1775 omitted from the listing.
1777 Use the @samp{-ad} option to omit debugging directives from the
1780 Once you have specified one of these options, you can further control
1781 listing output and its appearance using the directives @code{.list},
1782 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1784 The @samp{-an} option turns off all forms processing.
1785 If you do not request listing output with one of the @samp{-a} options, the
1786 listing-control directives have no effect.
1788 The letters after @samp{-a} may be combined into one option,
1789 @emph{e.g.}, @samp{-aln}.
1791 Note if the assembler source is coming from the standard input (e.g.,
1793 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1794 is being used) then the listing will not contain any comments or preprocessor
1795 directives. This is because the listing code buffers input source lines from
1796 stdin only after they have been preprocessed by the assembler. This reduces
1797 memory usage and makes the code more efficient.
1800 @section @option{--alternate}
1803 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1806 @section @option{-D}
1809 This option has no effect whatsoever, but it is accepted to make it more
1810 likely that scripts written for other assemblers also work with
1811 @command{@value{AS}}.
1814 @section Work Faster: @option{-f}
1817 @cindex trusted compiler
1818 @cindex faster processing (@option{-f})
1819 @samp{-f} should only be used when assembling programs written by a
1820 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1821 and comment preprocessing on
1822 the input file(s) before assembling them. @xref{Preprocessing,
1826 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1827 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1832 @section @code{.include} Search Path: @option{-I} @var{path}
1834 @kindex -I @var{path}
1835 @cindex paths for @code{.include}
1836 @cindex search path for @code{.include}
1837 @cindex @code{include} directive search path
1838 Use this option to add a @var{path} to the list of directories
1839 @command{@value{AS}} searches for files specified in @code{.include}
1840 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1841 many times as necessary to include a variety of paths. The current
1842 working directory is always searched first; after that, @command{@value{AS}}
1843 searches any @samp{-I} directories in the same order as they were
1844 specified (left to right) on the command line.
1847 @section Difference Tables: @option{-K}
1850 @ifclear DIFF-TBL-KLUGE
1851 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1852 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1853 where it can be used to warn when the assembler alters the machine code
1854 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1855 family does not have the addressing limitations that sometimes lead to this
1856 alteration on other platforms.
1859 @ifset DIFF-TBL-KLUGE
1860 @cindex difference tables, warning
1861 @cindex warning for altered difference tables
1862 @command{@value{AS}} sometimes alters the code emitted for directives of the
1863 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1864 You can use the @samp{-K} option if you want a warning issued when this
1869 @section Include Local Symbols: @option{-L}
1872 @cindex local symbols, retaining in output
1873 Symbols beginning with system-specific local label prefixes, typically
1874 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1875 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1876 such symbols when debugging, because they are intended for the use of
1877 programs (like compilers) that compose assembler programs, not for your
1878 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1879 such symbols, so you do not normally debug with them.
1881 This option tells @command{@value{AS}} to retain those local symbols
1882 in the object file. Usually if you do this you also tell the linker
1883 @code{@value{LD}} to preserve those symbols.
1886 @section Configuring listing output: @option{--listing}
1888 The listing feature of the assembler can be enabled via the command line switch
1889 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1890 hex dump of the corresponding locations in the output object file, and displays
1891 them as a listing file. The format of this listing can be controlled by
1892 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1893 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1894 @code{.psize} (@pxref{Psize}), and
1895 @code{.eject} (@pxref{Eject}) and also by the following switches:
1898 @item --listing-lhs-width=@samp{number}
1899 @kindex --listing-lhs-width
1900 @cindex Width of first line disassembly output
1901 Sets the maximum width, in words, of the first line of the hex byte dump. This
1902 dump appears on the left hand side of the listing output.
1904 @item --listing-lhs-width2=@samp{number}
1905 @kindex --listing-lhs-width2
1906 @cindex Width of continuation lines of disassembly output
1907 Sets the maximum width, in words, of any further lines of the hex byte dump for
1908 a given input source line. If this value is not specified, it defaults to being
1909 the same as the value specified for @samp{--listing-lhs-width}. If neither
1910 switch is used the default is to one.
1912 @item --listing-rhs-width=@samp{number}
1913 @kindex --listing-rhs-width
1914 @cindex Width of source line output
1915 Sets the maximum width, in characters, of the source line that is displayed
1916 alongside the hex dump. The default value for this parameter is 100. The
1917 source line is displayed on the right hand side of the listing output.
1919 @item --listing-cont-lines=@samp{number}
1920 @kindex --listing-cont-lines
1921 @cindex Maximum number of continuation lines
1922 Sets the maximum number of continuation lines of hex dump that will be
1923 displayed for a given single line of source input. The default value is 4.
1927 @section Assemble in MRI Compatibility Mode: @option{-M}
1930 @cindex MRI compatibility mode
1931 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1932 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1933 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1934 configured target) assembler from Microtec Research. The exact nature of the
1935 MRI syntax will not be documented here; see the MRI manuals for more
1936 information. Note in particular that the handling of macros and macro
1937 arguments is somewhat different. The purpose of this option is to permit
1938 assembling existing MRI assembler code using @command{@value{AS}}.
1940 The MRI compatibility is not complete. Certain operations of the MRI assembler
1941 depend upon its object file format, and can not be supported using other object
1942 file formats. Supporting these would require enhancing each object file format
1943 individually. These are:
1946 @item global symbols in common section
1948 The m68k MRI assembler supports common sections which are merged by the linker.
1949 Other object file formats do not support this. @command{@value{AS}} handles
1950 common sections by treating them as a single common symbol. It permits local
1951 symbols to be defined within a common section, but it can not support global
1952 symbols, since it has no way to describe them.
1954 @item complex relocations
1956 The MRI assemblers support relocations against a negated section address, and
1957 relocations which combine the start addresses of two or more sections. These
1958 are not support by other object file formats.
1960 @item @code{END} pseudo-op specifying start address
1962 The MRI @code{END} pseudo-op permits the specification of a start address.
1963 This is not supported by other object file formats. The start address may
1964 instead be specified using the @option{-e} option to the linker, or in a linker
1967 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1969 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1970 name to the output file. This is not supported by other object file formats.
1972 @item @code{ORG} pseudo-op
1974 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1975 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1976 which changes the location within the current section. Absolute sections are
1977 not supported by other object file formats. The address of a section may be
1978 assigned within a linker script.
1981 There are some other features of the MRI assembler which are not supported by
1982 @command{@value{AS}}, typically either because they are difficult or because they
1983 seem of little consequence. Some of these may be supported in future releases.
1987 @item EBCDIC strings
1989 EBCDIC strings are not supported.
1991 @item packed binary coded decimal
1993 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1994 and @code{DCB.P} pseudo-ops are not supported.
1996 @item @code{FEQU} pseudo-op
1998 The m68k @code{FEQU} pseudo-op is not supported.
2000 @item @code{NOOBJ} pseudo-op
2002 The m68k @code{NOOBJ} pseudo-op is not supported.
2004 @item @code{OPT} branch control options
2006 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2007 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2008 relaxes all branches, whether forward or backward, to an appropriate size, so
2009 these options serve no purpose.
2011 @item @code{OPT} list control options
2013 The following m68k @code{OPT} list control options are ignored: @code{C},
2014 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2015 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2017 @item other @code{OPT} options
2019 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2020 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2022 @item @code{OPT} @code{D} option is default
2024 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2025 @code{OPT NOD} may be used to turn it off.
2027 @item @code{XREF} pseudo-op.
2029 The m68k @code{XREF} pseudo-op is ignored.
2031 @item @code{.debug} pseudo-op
2033 The i960 @code{.debug} pseudo-op is not supported.
2035 @item @code{.extended} pseudo-op
2037 The i960 @code{.extended} pseudo-op is not supported.
2039 @item @code{.list} pseudo-op.
2041 The various options of the i960 @code{.list} pseudo-op are not supported.
2043 @item @code{.optimize} pseudo-op
2045 The i960 @code{.optimize} pseudo-op is not supported.
2047 @item @code{.output} pseudo-op
2049 The i960 @code{.output} pseudo-op is not supported.
2051 @item @code{.setreal} pseudo-op
2053 The i960 @code{.setreal} pseudo-op is not supported.
2058 @section Dependency Tracking: @option{--MD}
2061 @cindex dependency tracking
2064 @command{@value{AS}} can generate a dependency file for the file it creates. This
2065 file consists of a single rule suitable for @code{make} describing the
2066 dependencies of the main source file.
2068 The rule is written to the file named in its argument.
2070 This feature is used in the automatic updating of makefiles.
2073 @section Name the Object File: @option{-o}
2076 @cindex naming object file
2077 @cindex object file name
2078 There is always one object file output when you run @command{@value{AS}}. By
2079 default it has the name
2082 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2096 You use this option (which takes exactly one filename) to give the
2097 object file a different name.
2099 Whatever the object file is called, @command{@value{AS}} overwrites any
2100 existing file of the same name.
2103 @section Join Data and Text Sections: @option{-R}
2106 @cindex data and text sections, joining
2107 @cindex text and data sections, joining
2108 @cindex joining text and data sections
2109 @cindex merging text and data sections
2110 @option{-R} tells @command{@value{AS}} to write the object file as if all
2111 data-section data lives in the text section. This is only done at
2112 the very last moment: your binary data are the same, but data
2113 section parts are relocated differently. The data section part of
2114 your object file is zero bytes long because all its bytes are
2115 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2117 When you specify @option{-R} it would be possible to generate shorter
2118 address displacements (because we do not have to cross between text and
2119 data section). We refrain from doing this simply for compatibility with
2120 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2123 When @command{@value{AS}} is configured for COFF or ELF output,
2124 this option is only useful if you use sections named @samp{.text} and
2129 @option{-R} is not supported for any of the HPPA targets. Using
2130 @option{-R} generates a warning from @command{@value{AS}}.
2134 @section Display Assembly Statistics: @option{--statistics}
2136 @kindex --statistics
2137 @cindex statistics, about assembly
2138 @cindex time, total for assembly
2139 @cindex space used, maximum for assembly
2140 Use @samp{--statistics} to display two statistics about the resources used by
2141 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2142 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2145 @node traditional-format
2146 @section Compatible Output: @option{--traditional-format}
2148 @kindex --traditional-format
2149 For some targets, the output of @command{@value{AS}} is different in some ways
2150 from the output of some existing assembler. This switch requests
2151 @command{@value{AS}} to use the traditional format instead.
2153 For example, it disables the exception frame optimizations which
2154 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2157 @section Announce Version: @option{-v}
2161 @cindex assembler version
2162 @cindex version of assembler
2163 You can find out what version of as is running by including the
2164 option @samp{-v} (which you can also spell as @samp{-version}) on the
2168 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2170 @command{@value{AS}} should never give a warning or error message when
2171 assembling compiler output. But programs written by people often
2172 cause @command{@value{AS}} to give a warning that a particular assumption was
2173 made. All such warnings are directed to the standard error file.
2177 @cindex suppressing warnings
2178 @cindex warnings, suppressing
2179 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2180 This only affects the warning messages: it does not change any particular of
2181 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2184 @kindex --fatal-warnings
2185 @cindex errors, caused by warnings
2186 @cindex warnings, causing error
2187 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2188 files that generate warnings to be in error.
2191 @cindex warnings, switching on
2192 You can switch these options off again by specifying @option{--warn}, which
2193 causes warnings to be output as usual.
2196 @section Generate Object File in Spite of Errors: @option{-Z}
2197 @cindex object file, after errors
2198 @cindex errors, continuing after
2199 After an error message, @command{@value{AS}} normally produces no output. If for
2200 some reason you are interested in object file output even after
2201 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2202 option. If there are any errors, @command{@value{AS}} continues anyways, and
2203 writes an object file after a final warning message of the form @samp{@var{n}
2204 errors, @var{m} warnings, generating bad object file.}
2209 @cindex machine-independent syntax
2210 @cindex syntax, machine-independent
2211 This chapter describes the machine-independent syntax allowed in a
2212 source file. @command{@value{AS}} syntax is similar to what many other
2213 assemblers use; it is inspired by the BSD 4.2
2218 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2222 * Preprocessing:: Preprocessing
2223 * Whitespace:: Whitespace
2224 * Comments:: Comments
2225 * Symbol Intro:: Symbols
2226 * Statements:: Statements
2227 * Constants:: Constants
2231 @section Preprocessing
2233 @cindex preprocessing
2234 The @command{@value{AS}} internal preprocessor:
2236 @cindex whitespace, removed by preprocessor
2238 adjusts and removes extra whitespace. It leaves one space or tab before
2239 the keywords on a line, and turns any other whitespace on the line into
2242 @cindex comments, removed by preprocessor
2244 removes all comments, replacing them with a single space, or an
2245 appropriate number of newlines.
2247 @cindex constants, converted by preprocessor
2249 converts character constants into the appropriate numeric values.
2252 It does not do macro processing, include file handling, or
2253 anything else you may get from your C compiler's preprocessor. You can
2254 do include file processing with the @code{.include} directive
2255 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2256 to get other ``CPP'' style preprocessing by giving the input file a
2257 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2258 Output, gcc.info, Using GNU CC}.
2260 Excess whitespace, comments, and character constants
2261 cannot be used in the portions of the input text that are not
2264 @cindex turning preprocessing on and off
2265 @cindex preprocessing, turning on and off
2268 If the first line of an input file is @code{#NO_APP} or if you use the
2269 @samp{-f} option, whitespace and comments are not removed from the input file.
2270 Within an input file, you can ask for whitespace and comment removal in
2271 specific portions of the by putting a line that says @code{#APP} before the
2272 text that may contain whitespace or comments, and putting a line that says
2273 @code{#NO_APP} after this text. This feature is mainly intend to support
2274 @code{asm} statements in compilers whose output is otherwise free of comments
2281 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2282 Whitespace is used to separate symbols, and to make programs neater for
2283 people to read. Unless within character constants
2284 (@pxref{Characters,,Character Constants}), any whitespace means the same
2285 as exactly one space.
2291 There are two ways of rendering comments to @command{@value{AS}}. In both
2292 cases the comment is equivalent to one space.
2294 Anything from @samp{/*} through the next @samp{*/} is a comment.
2295 This means you may not nest these comments.
2299 The only way to include a newline ('\n') in a comment
2300 is to use this sort of comment.
2303 /* This sort of comment does not nest. */
2306 @cindex line comment character
2307 Anything from the @dfn{line comment} character to the next newline
2308 is considered a comment and is ignored. The line comment character is
2310 @samp{;} on the ARC;
2313 @samp{@@} on the ARM;
2316 @samp{;} for the H8/300 family;
2319 @samp{;} for the HPPA;
2322 @samp{#} on the i386 and x86-64;
2325 @samp{#} on the i960;
2328 @samp{;} for the PDP-11;
2331 @samp{;} for picoJava;
2334 @samp{#} for Motorola PowerPC;
2337 @samp{#} for IBM S/390;
2340 @samp{#} for the Sunplus SCORE;
2343 @samp{!} for the Renesas / SuperH SH;
2346 @samp{!} on the SPARC;
2349 @samp{#} on the ip2k;
2352 @samp{#} on the m32c;
2355 @samp{#} on the m32r;
2358 @samp{|} on the 680x0;
2361 @samp{#} on the 68HC11 and 68HC12;
2367 @samp{;} on the TMS320C6X;
2370 @samp{#} on the Vax;
2373 @samp{;} for the Z80;
2376 @samp{!} for the Z8000;
2379 @samp{#} on the V850;
2382 @samp{#} for Xtensa systems;
2384 see @ref{Machine Dependencies}. @refill
2385 @c FIXME What about i860?
2388 On some machines there are two different line comment characters. One
2389 character only begins a comment if it is the first non-whitespace character on
2390 a line, while the other always begins a comment.
2394 The V850 assembler also supports a double dash as starting a comment that
2395 extends to the end of the line.
2401 @cindex lines starting with @code{#}
2402 @cindex logical line numbers
2403 To be compatible with past assemblers, lines that begin with @samp{#} have a
2404 special interpretation. Following the @samp{#} should be an absolute
2405 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2406 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2407 new logical file name. The rest of the line, if any, should be whitespace.
2409 If the first non-whitespace characters on the line are not numeric,
2410 the line is ignored. (Just like a comment.)
2413 # This is an ordinary comment.
2414 # 42-6 "new_file_name" # New logical file name
2415 # This is logical line # 36.
2417 This feature is deprecated, and may disappear from future versions
2418 of @command{@value{AS}}.
2423 @cindex characters used in symbols
2424 @ifclear SPECIAL-SYMS
2425 A @dfn{symbol} is one or more characters chosen from the set of all
2426 letters (both upper and lower case), digits and the three characters
2432 A @dfn{symbol} is one or more characters chosen from the set of all
2433 letters (both upper and lower case), digits and the three characters
2434 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2440 On most machines, you can also use @code{$} in symbol names; exceptions
2441 are noted in @ref{Machine Dependencies}.
2443 No symbol may begin with a digit. Case is significant.
2444 There is no length limit: all characters are significant. Symbols are
2445 delimited by characters not in that set, or by the beginning of a file
2446 (since the source program must end with a newline, the end of a file is
2447 not a possible symbol delimiter). @xref{Symbols}.
2448 @cindex length of symbols
2453 @cindex statements, structure of
2454 @cindex line separator character
2455 @cindex statement separator character
2457 @ifclear abnormal-separator
2458 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2459 semicolon (@samp{;}). The newline or semicolon is considered part of
2460 the preceding statement. Newlines and semicolons within character
2461 constants are an exception: they do not end statements.
2463 @ifset abnormal-separator
2465 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2466 point (@samp{!}). The newline or exclamation point is considered part of the
2467 preceding statement. Newlines and exclamation points within character
2468 constants are an exception: they do not end statements.
2471 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2472 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2473 (@samp{;}). The newline or separator character is considered part of
2474 the preceding statement. Newlines and separators within character
2475 constants are an exception: they do not end statements.
2480 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2481 separator character. (The line separator is usually @samp{;}, unless this
2482 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2483 newline or separator character is considered part of the preceding
2484 statement. Newlines and separators within character constants are an
2485 exception: they do not end statements.
2488 @cindex newline, required at file end
2489 @cindex EOF, newline must precede
2490 It is an error to end any statement with end-of-file: the last
2491 character of any input file should be a newline.@refill
2493 An empty statement is allowed, and may include whitespace. It is ignored.
2495 @cindex instructions and directives
2496 @cindex directives and instructions
2497 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2498 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2500 A statement begins with zero or more labels, optionally followed by a
2501 key symbol which determines what kind of statement it is. The key
2502 symbol determines the syntax of the rest of the statement. If the
2503 symbol begins with a dot @samp{.} then the statement is an assembler
2504 directive: typically valid for any computer. If the symbol begins with
2505 a letter the statement is an assembly language @dfn{instruction}: it
2506 assembles into a machine language instruction.
2508 Different versions of @command{@value{AS}} for different computers
2509 recognize different instructions. In fact, the same symbol may
2510 represent a different instruction in a different computer's assembly
2514 @cindex @code{:} (label)
2515 @cindex label (@code{:})
2516 A label is a symbol immediately followed by a colon (@code{:}).
2517 Whitespace before a label or after a colon is permitted, but you may not
2518 have whitespace between a label's symbol and its colon. @xref{Labels}.
2521 For HPPA targets, labels need not be immediately followed by a colon, but
2522 the definition of a label must begin in column zero. This also implies that
2523 only one label may be defined on each line.
2527 label: .directive followed by something
2528 another_label: # This is an empty statement.
2529 instruction operand_1, operand_2, @dots{}
2536 A constant is a number, written so that its value is known by
2537 inspection, without knowing any context. Like this:
2540 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2541 .ascii "Ring the bell\7" # A string constant.
2542 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2543 .float 0f-314159265358979323846264338327\
2544 95028841971.693993751E-40 # - pi, a flonum.
2549 * Characters:: Character Constants
2550 * Numbers:: Number Constants
2554 @subsection Character Constants
2556 @cindex character constants
2557 @cindex constants, character
2558 There are two kinds of character constants. A @dfn{character} stands
2559 for one character in one byte and its value may be used in
2560 numeric expressions. String constants (properly called string
2561 @emph{literals}) are potentially many bytes and their values may not be
2562 used in arithmetic expressions.
2566 * Chars:: Characters
2570 @subsubsection Strings
2572 @cindex string constants
2573 @cindex constants, string
2574 A @dfn{string} is written between double-quotes. It may contain
2575 double-quotes or null characters. The way to get special characters
2576 into a string is to @dfn{escape} these characters: precede them with
2577 a backslash @samp{\} character. For example @samp{\\} represents
2578 one backslash: the first @code{\} is an escape which tells
2579 @command{@value{AS}} to interpret the second character literally as a backslash
2580 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2581 escape character). The complete list of escapes follows.
2583 @cindex escape codes, character
2584 @cindex character escape codes
2587 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2589 @cindex @code{\b} (backspace character)
2590 @cindex backspace (@code{\b})
2592 Mnemonic for backspace; for ASCII this is octal code 010.
2595 @c Mnemonic for EOText; for ASCII this is octal code 004.
2597 @cindex @code{\f} (formfeed character)
2598 @cindex formfeed (@code{\f})
2600 Mnemonic for FormFeed; for ASCII this is octal code 014.
2602 @cindex @code{\n} (newline character)
2603 @cindex newline (@code{\n})
2605 Mnemonic for newline; for ASCII this is octal code 012.
2608 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2610 @cindex @code{\r} (carriage return character)
2611 @cindex carriage return (@code{\r})
2613 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2616 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2617 @c other assemblers.
2619 @cindex @code{\t} (tab)
2620 @cindex tab (@code{\t})
2622 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2625 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2626 @c @item \x @var{digit} @var{digit} @var{digit}
2627 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2629 @cindex @code{\@var{ddd}} (octal character code)
2630 @cindex octal character code (@code{\@var{ddd}})
2631 @item \ @var{digit} @var{digit} @var{digit}
2632 An octal character code. The numeric code is 3 octal digits.
2633 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2634 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2636 @cindex @code{\@var{xd...}} (hex character code)
2637 @cindex hex character code (@code{\@var{xd...}})
2638 @item \@code{x} @var{hex-digits...}
2639 A hex character code. All trailing hex digits are combined. Either upper or
2640 lower case @code{x} works.
2642 @cindex @code{\\} (@samp{\} character)
2643 @cindex backslash (@code{\\})
2645 Represents one @samp{\} character.
2648 @c Represents one @samp{'} (accent acute) character.
2649 @c This is needed in single character literals
2650 @c (@xref{Characters,,Character Constants}.) to represent
2653 @cindex @code{\"} (doublequote character)
2654 @cindex doublequote (@code{\"})
2656 Represents one @samp{"} character. Needed in strings to represent
2657 this character, because an unescaped @samp{"} would end the string.
2659 @item \ @var{anything-else}
2660 Any other character when escaped by @kbd{\} gives a warning, but
2661 assembles as if the @samp{\} was not present. The idea is that if
2662 you used an escape sequence you clearly didn't want the literal
2663 interpretation of the following character. However @command{@value{AS}} has no
2664 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2665 code and warns you of the fact.
2668 Which characters are escapable, and what those escapes represent,
2669 varies widely among assemblers. The current set is what we think
2670 the BSD 4.2 assembler recognizes, and is a subset of what most C
2671 compilers recognize. If you are in doubt, do not use an escape
2675 @subsubsection Characters
2677 @cindex single character constant
2678 @cindex character, single
2679 @cindex constant, single character
2680 A single character may be written as a single quote immediately
2681 followed by that character. The same escapes apply to characters as
2682 to strings. So if you want to write the character backslash, you
2683 must write @kbd{'\\} where the first @code{\} escapes the second
2684 @code{\}. As you can see, the quote is an acute accent, not a
2685 grave accent. A newline
2687 @ifclear abnormal-separator
2688 (or semicolon @samp{;})
2690 @ifset abnormal-separator
2692 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2697 immediately following an acute accent is taken as a literal character
2698 and does not count as the end of a statement. The value of a character
2699 constant in a numeric expression is the machine's byte-wide code for
2700 that character. @command{@value{AS}} assumes your character code is ASCII:
2701 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2704 @subsection Number Constants
2706 @cindex constants, number
2707 @cindex number constants
2708 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2709 are stored in the target machine. @emph{Integers} are numbers that
2710 would fit into an @code{int} in the C language. @emph{Bignums} are
2711 integers, but they are stored in more than 32 bits. @emph{Flonums}
2712 are floating point numbers, described below.
2715 * Integers:: Integers
2720 * Bit Fields:: Bit Fields
2726 @subsubsection Integers
2728 @cindex constants, integer
2730 @cindex binary integers
2731 @cindex integers, binary
2732 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2733 the binary digits @samp{01}.
2735 @cindex octal integers
2736 @cindex integers, octal
2737 An octal integer is @samp{0} followed by zero or more of the octal
2738 digits (@samp{01234567}).
2740 @cindex decimal integers
2741 @cindex integers, decimal
2742 A decimal integer starts with a non-zero digit followed by zero or
2743 more digits (@samp{0123456789}).
2745 @cindex hexadecimal integers
2746 @cindex integers, hexadecimal
2747 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2748 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2750 Integers have the usual values. To denote a negative integer, use
2751 the prefix operator @samp{-} discussed under expressions
2752 (@pxref{Prefix Ops,,Prefix Operators}).
2755 @subsubsection Bignums
2758 @cindex constants, bignum
2759 A @dfn{bignum} has the same syntax and semantics as an integer
2760 except that the number (or its negative) takes more than 32 bits to
2761 represent in binary. The distinction is made because in some places
2762 integers are permitted while bignums are not.
2765 @subsubsection Flonums
2767 @cindex floating point numbers
2768 @cindex constants, floating point
2770 @cindex precision, floating point
2771 A @dfn{flonum} represents a floating point number. The translation is
2772 indirect: a decimal floating point number from the text is converted by
2773 @command{@value{AS}} to a generic binary floating point number of more than
2774 sufficient precision. This generic floating point number is converted
2775 to a particular computer's floating point format (or formats) by a
2776 portion of @command{@value{AS}} specialized to that computer.
2778 A flonum is written by writing (in order)
2783 (@samp{0} is optional on the HPPA.)
2787 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2789 @kbd{e} is recommended. Case is not important.
2791 @c FIXME: verify if flonum syntax really this vague for most cases
2792 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2793 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2796 On the H8/300, Renesas / SuperH SH,
2797 and AMD 29K architectures, the letter must be
2798 one of the letters @samp{DFPRSX} (in upper or lower case).
2800 On the ARC, the letter must be one of the letters @samp{DFRS}
2801 (in upper or lower case).
2803 On the Intel 960 architecture, the letter must be
2804 one of the letters @samp{DFT} (in upper or lower case).
2806 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2810 One of the letters @samp{DFRS} (in upper or lower case).
2813 One of the letters @samp{DFPRSX} (in upper or lower case).
2816 The letter @samp{E} (upper case only).
2819 One of the letters @samp{DFT} (in upper or lower case).
2824 An optional sign: either @samp{+} or @samp{-}.
2827 An optional @dfn{integer part}: zero or more decimal digits.
2830 An optional @dfn{fractional part}: @samp{.} followed by zero
2831 or more decimal digits.
2834 An optional exponent, consisting of:
2838 An @samp{E} or @samp{e}.
2839 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2840 @c principle this can perfectly well be different on different targets.
2842 Optional sign: either @samp{+} or @samp{-}.
2844 One or more decimal digits.
2849 At least one of the integer part or the fractional part must be
2850 present. The floating point number has the usual base-10 value.
2852 @command{@value{AS}} does all processing using integers. Flonums are computed
2853 independently of any floating point hardware in the computer running
2854 @command{@value{AS}}.
2858 @c Bit fields are written as a general facility but are also controlled
2859 @c by a conditional-compilation flag---which is as of now (21mar91)
2860 @c turned on only by the i960 config of GAS.
2862 @subsubsection Bit Fields
2865 @cindex constants, bit field
2866 You can also define numeric constants as @dfn{bit fields}.
2867 Specify two numbers separated by a colon---
2869 @var{mask}:@var{value}
2872 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2875 The resulting number is then packed
2877 @c this conditional paren in case bit fields turned on elsewhere than 960
2878 (in host-dependent byte order)
2880 into a field whose width depends on which assembler directive has the
2881 bit-field as its argument. Overflow (a result from the bitwise and
2882 requiring more binary digits to represent) is not an error; instead,
2883 more constants are generated, of the specified width, beginning with the
2884 least significant digits.@refill
2886 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2887 @code{.short}, and @code{.word} accept bit-field arguments.
2892 @chapter Sections and Relocation
2897 * Secs Background:: Background
2898 * Ld Sections:: Linker Sections
2899 * As Sections:: Assembler Internal Sections
2900 * Sub-Sections:: Sub-Sections
2904 @node Secs Background
2907 Roughly, a section is a range of addresses, with no gaps; all data
2908 ``in'' those addresses is treated the same for some particular purpose.
2909 For example there may be a ``read only'' section.
2911 @cindex linker, and assembler
2912 @cindex assembler, and linker
2913 The linker @code{@value{LD}} reads many object files (partial programs) and
2914 combines their contents to form a runnable program. When @command{@value{AS}}
2915 emits an object file, the partial program is assumed to start at address 0.
2916 @code{@value{LD}} assigns the final addresses for the partial program, so that
2917 different partial programs do not overlap. This is actually an
2918 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2921 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2922 addresses. These blocks slide to their run-time addresses as rigid
2923 units; their length does not change and neither does the order of bytes
2924 within them. Such a rigid unit is called a @emph{section}. Assigning
2925 run-time addresses to sections is called @dfn{relocation}. It includes
2926 the task of adjusting mentions of object-file addresses so they refer to
2927 the proper run-time addresses.
2929 For the H8/300, and for the Renesas / SuperH SH,
2930 @command{@value{AS}} pads sections if needed to
2931 ensure they end on a word (sixteen bit) boundary.
2934 @cindex standard assembler sections
2935 An object file written by @command{@value{AS}} has at least three sections, any
2936 of which may be empty. These are named @dfn{text}, @dfn{data} and
2941 When it generates COFF or ELF output,
2943 @command{@value{AS}} can also generate whatever other named sections you specify
2944 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2945 If you do not use any directives that place output in the @samp{.text}
2946 or @samp{.data} sections, these sections still exist, but are empty.
2951 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2953 @command{@value{AS}} can also generate whatever other named sections you
2954 specify using the @samp{.space} and @samp{.subspace} directives. See
2955 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2956 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2957 assembler directives.
2960 Additionally, @command{@value{AS}} uses different names for the standard
2961 text, data, and bss sections when generating SOM output. Program text
2962 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2963 BSS into @samp{$BSS$}.
2967 Within the object file, the text section starts at address @code{0}, the
2968 data section follows, and the bss section follows the data section.
2971 When generating either SOM or ELF output files on the HPPA, the text
2972 section starts at address @code{0}, the data section at address
2973 @code{0x4000000}, and the bss section follows the data section.
2976 To let @code{@value{LD}} know which data changes when the sections are
2977 relocated, and how to change that data, @command{@value{AS}} also writes to the
2978 object file details of the relocation needed. To perform relocation
2979 @code{@value{LD}} must know, each time an address in the object
2983 Where in the object file is the beginning of this reference to
2986 How long (in bytes) is this reference?
2988 Which section does the address refer to? What is the numeric value of
2990 (@var{address}) @minus{} (@var{start-address of section})?
2993 Is the reference to an address ``Program-Counter relative''?
2996 @cindex addresses, format of
2997 @cindex section-relative addressing
2998 In fact, every address @command{@value{AS}} ever uses is expressed as
3000 (@var{section}) + (@var{offset into section})
3003 Further, most expressions @command{@value{AS}} computes have this section-relative
3006 (For some object formats, such as SOM for the HPPA, some expressions are
3007 symbol-relative instead.)
3010 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3011 @var{N} into section @var{secname}.''
3013 Apart from text, data and bss sections you need to know about the
3014 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3015 addresses in the absolute section remain unchanged. For example, address
3016 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3017 @code{@value{LD}}. Although the linker never arranges two partial programs'
3018 data sections with overlapping addresses after linking, @emph{by definition}
3019 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3020 part of a program is always the same address when the program is running as
3021 address @code{@{absolute@ 239@}} in any other part of the program.
3023 The idea of sections is extended to the @dfn{undefined} section. Any
3024 address whose section is unknown at assembly time is by definition
3025 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3026 Since numbers are always defined, the only way to generate an undefined
3027 address is to mention an undefined symbol. A reference to a named
3028 common block would be such a symbol: its value is unknown at assembly
3029 time so it has section @emph{undefined}.
3031 By analogy the word @emph{section} is used to describe groups of sections in
3032 the linked program. @code{@value{LD}} puts all partial programs' text
3033 sections in contiguous addresses in the linked program. It is
3034 customary to refer to the @emph{text section} of a program, meaning all
3035 the addresses of all partial programs' text sections. Likewise for
3036 data and bss sections.
3038 Some sections are manipulated by @code{@value{LD}}; others are invented for
3039 use of @command{@value{AS}} and have no meaning except during assembly.
3042 @section Linker Sections
3043 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3048 @cindex named sections
3049 @cindex sections, named
3050 @item named sections
3053 @cindex text section
3054 @cindex data section
3058 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3059 separate but equal sections. Anything you can say of one section is
3062 When the program is running, however, it is
3063 customary for the text section to be unalterable. The
3064 text section is often shared among processes: it contains
3065 instructions, constants and the like. The data section of a running
3066 program is usually alterable: for example, C variables would be stored
3067 in the data section.
3072 This section contains zeroed bytes when your program begins running. It
3073 is used to hold uninitialized variables or common storage. The length of
3074 each partial program's bss section is important, but because it starts
3075 out containing zeroed bytes there is no need to store explicit zero
3076 bytes in the object file. The bss section was invented to eliminate
3077 those explicit zeros from object files.
3079 @cindex absolute section
3080 @item absolute section
3081 Address 0 of this section is always ``relocated'' to runtime address 0.
3082 This is useful if you want to refer to an address that @code{@value{LD}} must
3083 not change when relocating. In this sense we speak of absolute
3084 addresses being ``unrelocatable'': they do not change during relocation.
3086 @cindex undefined section
3087 @item undefined section
3088 This ``section'' is a catch-all for address references to objects not in
3089 the preceding sections.
3090 @c FIXME: ref to some other doc on obj-file formats could go here.
3093 @cindex relocation example
3094 An idealized example of three relocatable sections follows.
3096 The example uses the traditional section names @samp{.text} and @samp{.data}.
3098 Memory addresses are on the horizontal axis.
3102 @c END TEXI2ROFF-KILL
3105 partial program # 1: |ttttt|dddd|00|
3112 partial program # 2: |TTT|DDD|000|
3115 +--+---+-----+--+----+---+-----+~~
3116 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3117 +--+---+-----+--+----+---+-----+~~
3119 addresses: 0 @dots{}
3126 \line{\it Partial program \#1: \hfil}
3127 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3128 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3130 \line{\it Partial program \#2: \hfil}
3131 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3132 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3134 \line{\it linked program: \hfil}
3135 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3136 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3137 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3138 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3140 \line{\it addresses: \hfil}
3144 @c END TEXI2ROFF-KILL
3147 @section Assembler Internal Sections
3149 @cindex internal assembler sections
3150 @cindex sections in messages, internal
3151 These sections are meant only for the internal use of @command{@value{AS}}. They
3152 have no meaning at run-time. You do not really need to know about these
3153 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3154 warning messages, so it might be helpful to have an idea of their
3155 meanings to @command{@value{AS}}. These sections are used to permit the
3156 value of every expression in your assembly language program to be a
3157 section-relative address.
3160 @cindex assembler internal logic error
3161 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3162 An internal assembler logic error has been found. This means there is a
3163 bug in the assembler.
3165 @cindex expr (internal section)
3167 The assembler stores complex expression internally as combinations of
3168 symbols. When it needs to represent an expression as a symbol, it puts
3169 it in the expr section.
3171 @c FIXME item transfer[t] vector preload
3172 @c FIXME item transfer[t] vector postload
3173 @c FIXME item register
3177 @section Sub-Sections
3179 @cindex numbered subsections
3180 @cindex grouping data
3186 fall into two sections: text and data.
3188 You may have separate groups of
3190 data in named sections
3194 data in named sections
3200 that you want to end up near to each other in the object file, even though they
3201 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3202 use @dfn{subsections} for this purpose. Within each section, there can be
3203 numbered subsections with values from 0 to 8192. Objects assembled into the
3204 same subsection go into the object file together with other objects in the same
3205 subsection. For example, a compiler might want to store constants in the text
3206 section, but might not want to have them interspersed with the program being
3207 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3208 section of code being output, and a @samp{.text 1} before each group of
3209 constants being output.
3211 Subsections are optional. If you do not use subsections, everything
3212 goes in subsection number zero.
3215 Each subsection is zero-padded up to a multiple of four bytes.
3216 (Subsections may be padded a different amount on different flavors
3217 of @command{@value{AS}}.)
3221 On the H8/300 platform, each subsection is zero-padded to a word
3222 boundary (two bytes).
3223 The same is true on the Renesas SH.
3226 @c FIXME section padding (alignment)?
3227 @c Rich Pixley says padding here depends on target obj code format; that
3228 @c doesn't seem particularly useful to say without further elaboration,
3229 @c so for now I say nothing about it. If this is a generic BFD issue,
3230 @c these paragraphs might need to vanish from this manual, and be
3231 @c discussed in BFD chapter of binutils (or some such).
3235 Subsections appear in your object file in numeric order, lowest numbered
3236 to highest. (All this to be compatible with other people's assemblers.)
3237 The object file contains no representation of subsections; @code{@value{LD}} and
3238 other programs that manipulate object files see no trace of them.
3239 They just see all your text subsections as a text section, and all your
3240 data subsections as a data section.
3242 To specify which subsection you want subsequent statements assembled
3243 into, use a numeric argument to specify it, in a @samp{.text
3244 @var{expression}} or a @samp{.data @var{expression}} statement.
3247 When generating COFF output, you
3252 can also use an extra subsection
3253 argument with arbitrary named sections: @samp{.section @var{name},
3258 When generating ELF output, you
3263 can also use the @code{.subsection} directive (@pxref{SubSection})
3264 to specify a subsection: @samp{.subsection @var{expression}}.
3266 @var{Expression} should be an absolute expression
3267 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3268 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3269 begins in @code{text 0}. For instance:
3271 .text 0 # The default subsection is text 0 anyway.
3272 .ascii "This lives in the first text subsection. *"
3274 .ascii "But this lives in the second text subsection."
3276 .ascii "This lives in the data section,"
3277 .ascii "in the first data subsection."
3279 .ascii "This lives in the first text section,"
3280 .ascii "immediately following the asterisk (*)."
3283 Each section has a @dfn{location counter} incremented by one for every byte
3284 assembled into that section. Because subsections are merely a convenience
3285 restricted to @command{@value{AS}} there is no concept of a subsection location
3286 counter. There is no way to directly manipulate a location counter---but the
3287 @code{.align} directive changes it, and any label definition captures its
3288 current value. The location counter of the section where statements are being
3289 assembled is said to be the @dfn{active} location counter.
3292 @section bss Section
3295 @cindex common variable storage
3296 The bss section is used for local common variable storage.
3297 You may allocate address space in the bss section, but you may
3298 not dictate data to load into it before your program executes. When
3299 your program starts running, all the contents of the bss
3300 section are zeroed bytes.
3302 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3303 @ref{Lcomm,,@code{.lcomm}}.
3305 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3306 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3309 When assembling for a target which supports multiple sections, such as ELF or
3310 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3311 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3312 section. Typically the section will only contain symbol definitions and
3313 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3320 Symbols are a central concept: the programmer uses symbols to name
3321 things, the linker uses symbols to link, and the debugger uses symbols
3325 @cindex debuggers, and symbol order
3326 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3327 the same order they were declared. This may break some debuggers.
3332 * Setting Symbols:: Giving Symbols Other Values
3333 * Symbol Names:: Symbol Names
3334 * Dot:: The Special Dot Symbol
3335 * Symbol Attributes:: Symbol Attributes
3342 A @dfn{label} is written as a symbol immediately followed by a colon
3343 @samp{:}. The symbol then represents the current value of the
3344 active location counter, and is, for example, a suitable instruction
3345 operand. You are warned if you use the same symbol to represent two
3346 different locations: the first definition overrides any other
3350 On the HPPA, the usual form for a label need not be immediately followed by a
3351 colon, but instead must start in column zero. Only one label may be defined on
3352 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3353 provides a special directive @code{.label} for defining labels more flexibly.
3356 @node Setting Symbols
3357 @section Giving Symbols Other Values
3359 @cindex assigning values to symbols
3360 @cindex symbol values, assigning
3361 A symbol can be given an arbitrary value by writing a symbol, followed
3362 by an equals sign @samp{=}, followed by an expression
3363 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3364 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3365 equals sign @samp{=}@samp{=} here represents an equivalent of the
3366 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3369 Blackfin does not support symbol assignment with @samp{=}.
3373 @section Symbol Names
3375 @cindex symbol names
3376 @cindex names, symbol
3377 @ifclear SPECIAL-SYMS
3378 Symbol names begin with a letter or with one of @samp{._}. On most
3379 machines, you can also use @code{$} in symbol names; exceptions are
3380 noted in @ref{Machine Dependencies}. That character may be followed by any
3381 string of digits, letters, dollar signs (unless otherwise noted for a
3382 particular target machine), and underscores.
3386 Symbol names begin with a letter or with one of @samp{._}. On the
3387 Renesas SH you can also use @code{$} in symbol names. That
3388 character may be followed by any string of digits, letters, dollar signs (save
3389 on the H8/300), and underscores.
3393 Case of letters is significant: @code{foo} is a different symbol name
3396 Each symbol has exactly one name. Each name in an assembly language program
3397 refers to exactly one symbol. You may use that symbol name any number of times
3400 @subheading Local Symbol Names
3402 @cindex local symbol names
3403 @cindex symbol names, local
3404 A local symbol is any symbol beginning with certain local label prefixes.
3405 By default, the local label prefix is @samp{.L} for ELF systems or
3406 @samp{L} for traditional a.out systems, but each target may have its own
3407 set of local label prefixes.
3409 On the HPPA local symbols begin with @samp{L$}.
3412 Local symbols are defined and used within the assembler, but they are
3413 normally not saved in object files. Thus, they are not visible when debugging.
3414 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3415 @option{-L}}) to retain the local symbols in the object files.
3417 @subheading Local Labels
3419 @cindex local labels
3420 @cindex temporary symbol names
3421 @cindex symbol names, temporary
3422 Local labels help compilers and programmers use names temporarily.
3423 They create symbols which are guaranteed to be unique over the entire scope of
3424 the input source code and which can be referred to by a simple notation.
3425 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3426 represents any positive integer). To refer to the most recent previous
3427 definition of that label write @samp{@b{N}b}, using the same number as when
3428 you defined the label. To refer to the next definition of a local label, write
3429 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3432 There is no restriction on how you can use these labels, and you can reuse them
3433 too. So that it is possible to repeatedly define the same local label (using
3434 the same number @samp{@b{N}}), although you can only refer to the most recently
3435 defined local label of that number (for a backwards reference) or the next
3436 definition of a specific local label for a forward reference. It is also worth
3437 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3438 implemented in a slightly more efficient manner than the others.
3449 Which is the equivalent of:
3452 label_1: branch label_3
3453 label_2: branch label_1
3454 label_3: branch label_4
3455 label_4: branch label_3
3458 Local label names are only a notational device. They are immediately
3459 transformed into more conventional symbol names before the assembler uses them.
3460 The symbol names are stored in the symbol table, appear in error messages, and
3461 are optionally emitted to the object file. The names are constructed using
3465 @item @emph{local label prefix}
3466 All local symbols begin with the system-specific local label prefix.
3467 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3468 that start with the local label prefix. These labels are
3469 used for symbols you are never intended to see. If you use the
3470 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3471 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3472 you may use them in debugging.
3475 This is the number that was used in the local label definition. So if the
3476 label is written @samp{55:} then the number is @samp{55}.
3479 This unusual character is included so you do not accidentally invent a symbol
3480 of the same name. The character has ASCII value of @samp{\002} (control-B).
3482 @item @emph{ordinal number}
3483 This is a serial number to keep the labels distinct. The first definition of
3484 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3485 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3486 the number @samp{1} and its 15th definition gets @samp{15} as well.
3489 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3490 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3492 @subheading Dollar Local Labels
3493 @cindex dollar local symbols
3495 @code{@value{AS}} also supports an even more local form of local labels called
3496 dollar labels. These labels go out of scope (i.e., they become undefined) as
3497 soon as a non-local label is defined. Thus they remain valid for only a small
3498 region of the input source code. Normal local labels, by contrast, remain in
3499 scope for the entire file, or until they are redefined by another occurrence of
3500 the same local label.
3502 Dollar labels are defined in exactly the same way as ordinary local labels,
3503 except that they have a dollar sign suffix to their numeric value, e.g.,
3506 They can also be distinguished from ordinary local labels by their transformed
3507 names which use ASCII character @samp{\001} (control-A) as the magic character
3508 to distinguish them from ordinary labels. For example, the fifth definition of
3509 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3512 @section The Special Dot Symbol
3514 @cindex dot (symbol)
3515 @cindex @code{.} (symbol)
3516 @cindex current address
3517 @cindex location counter
3518 The special symbol @samp{.} refers to the current address that
3519 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3520 .long .} defines @code{melvin} to contain its own address.
3521 Assigning a value to @code{.} is treated the same as a @code{.org}
3523 @ifclear no-space-dir
3524 Thus, the expression @samp{.=.+4} is the same as saying
3528 @node Symbol Attributes
3529 @section Symbol Attributes
3531 @cindex symbol attributes
3532 @cindex attributes, symbol
3533 Every symbol has, as well as its name, the attributes ``Value'' and
3534 ``Type''. Depending on output format, symbols can also have auxiliary
3537 The detailed definitions are in @file{a.out.h}.
3540 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3541 all these attributes, and probably won't warn you. This makes the
3542 symbol an externally defined symbol, which is generally what you
3546 * Symbol Value:: Value
3547 * Symbol Type:: Type
3550 * a.out Symbols:: Symbol Attributes: @code{a.out}
3554 * a.out Symbols:: Symbol Attributes: @code{a.out}
3557 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3562 * COFF Symbols:: Symbol Attributes for COFF
3565 * SOM Symbols:: Symbol Attributes for SOM
3572 @cindex value of a symbol
3573 @cindex symbol value
3574 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3575 location in the text, data, bss or absolute sections the value is the
3576 number of addresses from the start of that section to the label.
3577 Naturally for text, data and bss sections the value of a symbol changes
3578 as @code{@value{LD}} changes section base addresses during linking. Absolute
3579 symbols' values do not change during linking: that is why they are
3582 The value of an undefined symbol is treated in a special way. If it is
3583 0 then the symbol is not defined in this assembler source file, and
3584 @code{@value{LD}} tries to determine its value from other files linked into the
3585 same program. You make this kind of symbol simply by mentioning a symbol
3586 name without defining it. A non-zero value represents a @code{.comm}
3587 common declaration. The value is how much common storage to reserve, in
3588 bytes (addresses). The symbol refers to the first address of the
3594 @cindex type of a symbol
3596 The type attribute of a symbol contains relocation (section)
3597 information, any flag settings indicating that a symbol is external, and
3598 (optionally), other information for linkers and debuggers. The exact
3599 format depends on the object-code output format in use.
3604 @c The following avoids a "widow" subsection title. @group would be
3605 @c better if it were available outside examples.
3608 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3610 @cindex @code{b.out} symbol attributes
3611 @cindex symbol attributes, @code{b.out}
3612 These symbol attributes appear only when @command{@value{AS}} is configured for
3613 one of the Berkeley-descended object output formats---@code{a.out} or
3619 @subsection Symbol Attributes: @code{a.out}
3621 @cindex @code{a.out} symbol attributes
3622 @cindex symbol attributes, @code{a.out}
3628 @subsection Symbol Attributes: @code{a.out}
3630 @cindex @code{a.out} symbol attributes
3631 @cindex symbol attributes, @code{a.out}
3635 * Symbol Desc:: Descriptor
3636 * Symbol Other:: Other
3640 @subsubsection Descriptor
3642 @cindex descriptor, of @code{a.out} symbol
3643 This is an arbitrary 16-bit value. You may establish a symbol's
3644 descriptor value by using a @code{.desc} statement
3645 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3646 @command{@value{AS}}.
3649 @subsubsection Other
3651 @cindex other attribute, of @code{a.out} symbol
3652 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3657 @subsection Symbol Attributes for COFF
3659 @cindex COFF symbol attributes
3660 @cindex symbol attributes, COFF
3662 The COFF format supports a multitude of auxiliary symbol attributes;
3663 like the primary symbol attributes, they are set between @code{.def} and
3664 @code{.endef} directives.
3666 @subsubsection Primary Attributes
3668 @cindex primary attributes, COFF symbols
3669 The symbol name is set with @code{.def}; the value and type,
3670 respectively, with @code{.val} and @code{.type}.
3672 @subsubsection Auxiliary Attributes
3674 @cindex auxiliary attributes, COFF symbols
3675 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3676 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3677 table information for COFF.
3682 @subsection Symbol Attributes for SOM
3684 @cindex SOM symbol attributes
3685 @cindex symbol attributes, SOM
3687 The SOM format for the HPPA supports a multitude of symbol attributes set with
3688 the @code{.EXPORT} and @code{.IMPORT} directives.
3690 The attributes are described in @cite{HP9000 Series 800 Assembly
3691 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3692 @code{EXPORT} assembler directive documentation.
3696 @chapter Expressions
3700 @cindex numeric values
3701 An @dfn{expression} specifies an address or numeric value.
3702 Whitespace may precede and/or follow an expression.
3704 The result of an expression must be an absolute number, or else an offset into
3705 a particular section. If an expression is not absolute, and there is not
3706 enough information when @command{@value{AS}} sees the expression to know its
3707 section, a second pass over the source program might be necessary to interpret
3708 the expression---but the second pass is currently not implemented.
3709 @command{@value{AS}} aborts with an error message in this situation.
3712 * Empty Exprs:: Empty Expressions
3713 * Integer Exprs:: Integer Expressions
3717 @section Empty Expressions
3719 @cindex empty expressions
3720 @cindex expressions, empty
3721 An empty expression has no value: it is just whitespace or null.
3722 Wherever an absolute expression is required, you may omit the
3723 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3724 is compatible with other assemblers.
3727 @section Integer Expressions
3729 @cindex integer expressions
3730 @cindex expressions, integer
3731 An @dfn{integer expression} is one or more @emph{arguments} delimited
3732 by @emph{operators}.
3735 * Arguments:: Arguments
3736 * Operators:: Operators
3737 * Prefix Ops:: Prefix Operators
3738 * Infix Ops:: Infix Operators
3742 @subsection Arguments
3744 @cindex expression arguments
3745 @cindex arguments in expressions
3746 @cindex operands in expressions
3747 @cindex arithmetic operands
3748 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3749 contexts arguments are sometimes called ``arithmetic operands''. In
3750 this manual, to avoid confusing them with the ``instruction operands'' of
3751 the machine language, we use the term ``argument'' to refer to parts of
3752 expressions only, reserving the word ``operand'' to refer only to machine
3753 instruction operands.
3755 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3756 @var{section} is one of text, data, bss, absolute,
3757 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3760 Numbers are usually integers.
3762 A number can be a flonum or bignum. In this case, you are warned
3763 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3764 these 32 bits are an integer. You may write integer-manipulating
3765 instructions that act on exotic constants, compatible with other
3768 @cindex subexpressions
3769 Subexpressions are a left parenthesis @samp{(} followed by an integer
3770 expression, followed by a right parenthesis @samp{)}; or a prefix
3771 operator followed by an argument.
3774 @subsection Operators
3776 @cindex operators, in expressions
3777 @cindex arithmetic functions
3778 @cindex functions, in expressions
3779 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3780 operators are followed by an argument. Infix operators appear
3781 between their arguments. Operators may be preceded and/or followed by
3785 @subsection Prefix Operator
3787 @cindex prefix operators
3788 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3789 one argument, which must be absolute.
3791 @c the tex/end tex stuff surrounding this small table is meant to make
3792 @c it align, on the printed page, with the similar table in the next
3793 @c section (which is inside an enumerate).
3795 \global\advance\leftskip by \itemindent
3800 @dfn{Negation}. Two's complement negation.
3802 @dfn{Complementation}. Bitwise not.
3806 \global\advance\leftskip by -\itemindent
3810 @subsection Infix Operators
3812 @cindex infix operators
3813 @cindex operators, permitted arguments
3814 @dfn{Infix operators} take two arguments, one on either side. Operators
3815 have precedence, but operations with equal precedence are performed left
3816 to right. Apart from @code{+} or @option{-}, both arguments must be
3817 absolute, and the result is absolute.
3820 @cindex operator precedence
3821 @cindex precedence of operators
3828 @dfn{Multiplication}.
3831 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3837 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3840 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3844 Intermediate precedence
3849 @dfn{Bitwise Inclusive Or}.
3855 @dfn{Bitwise Exclusive Or}.
3858 @dfn{Bitwise Or Not}.
3865 @cindex addition, permitted arguments
3866 @cindex plus, permitted arguments
3867 @cindex arguments for addition
3869 @dfn{Addition}. If either argument is absolute, the result has the section of
3870 the other argument. You may not add together arguments from different
3873 @cindex subtraction, permitted arguments
3874 @cindex minus, permitted arguments
3875 @cindex arguments for subtraction
3877 @dfn{Subtraction}. If the right argument is absolute, the
3878 result has the section of the left argument.
3879 If both arguments are in the same section, the result is absolute.
3880 You may not subtract arguments from different sections.
3881 @c FIXME is there still something useful to say about undefined - undefined ?
3883 @cindex comparison expressions
3884 @cindex expressions, comparison
3889 @dfn{Is Not Equal To}
3893 @dfn{Is Greater Than}
3895 @dfn{Is Greater Than Or Equal To}
3897 @dfn{Is Less Than Or Equal To}
3899 The comparison operators can be used as infix operators. A true results has a
3900 value of -1 whereas a false result has a value of 0. Note, these operators
3901 perform signed comparisons.
3904 @item Lowest Precedence
3913 These two logical operations can be used to combine the results of sub
3914 expressions. Note, unlike the comparison operators a true result returns a
3915 value of 1 but a false results does still return 0. Also note that the logical
3916 or operator has a slightly lower precedence than logical and.
3921 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3922 address; you can only have a defined section in one of the two arguments.
3925 @chapter Assembler Directives
3927 @cindex directives, machine independent
3928 @cindex pseudo-ops, machine independent
3929 @cindex machine independent directives
3930 All assembler directives have names that begin with a period (@samp{.}).
3931 The rest of the name is letters, usually in lower case.
3933 This chapter discusses directives that are available regardless of the
3934 target machine configuration for the @sc{gnu} assembler.
3936 Some machine configurations provide additional directives.
3937 @xref{Machine Dependencies}.
3940 @ifset machine-directives
3941 @xref{Machine Dependencies}, for additional directives.
3946 * Abort:: @code{.abort}
3948 * ABORT (COFF):: @code{.ABORT}
3951 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3952 * Altmacro:: @code{.altmacro}
3953 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3954 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3955 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3956 * Byte:: @code{.byte @var{expressions}}
3957 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3958 * Comm:: @code{.comm @var{symbol} , @var{length} }
3959 * Data:: @code{.data @var{subsection}}
3961 * Def:: @code{.def @var{name}}
3964 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3970 * Double:: @code{.double @var{flonums}}
3971 * Eject:: @code{.eject}
3972 * Else:: @code{.else}
3973 * Elseif:: @code{.elseif}
3976 * Endef:: @code{.endef}
3979 * Endfunc:: @code{.endfunc}
3980 * Endif:: @code{.endif}
3981 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3982 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3983 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3985 * Error:: @code{.error @var{string}}
3986 * Exitm:: @code{.exitm}
3987 * Extern:: @code{.extern}
3988 * Fail:: @code{.fail}
3989 * File:: @code{.file}
3990 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3991 * Float:: @code{.float @var{flonums}}
3992 * Func:: @code{.func}
3993 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3995 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3996 * Hidden:: @code{.hidden @var{names}}
3999 * hword:: @code{.hword @var{expressions}}
4000 * Ident:: @code{.ident}
4001 * If:: @code{.if @var{absolute expression}}
4002 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4003 * Include:: @code{.include "@var{file}"}
4004 * Int:: @code{.int @var{expressions}}
4006 * Internal:: @code{.internal @var{names}}
4009 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4010 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4011 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4012 * Lflags:: @code{.lflags}
4013 @ifclear no-line-dir
4014 * Line:: @code{.line @var{line-number}}
4017 * Linkonce:: @code{.linkonce [@var{type}]}
4018 * List:: @code{.list}
4019 * Ln:: @code{.ln @var{line-number}}
4020 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4021 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4023 * Local:: @code{.local @var{names}}
4026 * Long:: @code{.long @var{expressions}}
4028 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4031 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4032 * MRI:: @code{.mri @var{val}}
4033 * Noaltmacro:: @code{.noaltmacro}
4034 * Nolist:: @code{.nolist}
4035 * Octa:: @code{.octa @var{bignums}}
4036 * Org:: @code{.org @var{new-lc}, @var{fill}}
4037 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4039 * PopSection:: @code{.popsection}
4040 * Previous:: @code{.previous}
4043 * Print:: @code{.print @var{string}}
4045 * Protected:: @code{.protected @var{names}}
4048 * Psize:: @code{.psize @var{lines}, @var{columns}}
4049 * Purgem:: @code{.purgem @var{name}}
4051 * PushSection:: @code{.pushsection @var{name}}
4054 * Quad:: @code{.quad @var{bignums}}
4055 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4056 * Rept:: @code{.rept @var{count}}
4057 * Sbttl:: @code{.sbttl "@var{subheading}"}
4059 * Scl:: @code{.scl @var{class}}
4062 * Section:: @code{.section @var{name}[, @var{flags}]}
4065 * Set:: @code{.set @var{symbol}, @var{expression}}
4066 * Short:: @code{.short @var{expressions}}
4067 * Single:: @code{.single @var{flonums}}
4069 * Size:: @code{.size [@var{name} , @var{expression}]}
4071 @ifclear no-space-dir
4072 * Skip:: @code{.skip @var{size} , @var{fill}}
4075 * Sleb128:: @code{.sleb128 @var{expressions}}
4076 @ifclear no-space-dir
4077 * Space:: @code{.space @var{size} , @var{fill}}
4080 * Stab:: @code{.stabd, .stabn, .stabs}
4083 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4084 * Struct:: @code{.struct @var{expression}}
4086 * SubSection:: @code{.subsection}
4087 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4091 * Tag:: @code{.tag @var{structname}}
4094 * Text:: @code{.text @var{subsection}}
4095 * Title:: @code{.title "@var{heading}"}
4097 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4100 * Uleb128:: @code{.uleb128 @var{expressions}}
4102 * Val:: @code{.val @var{addr}}
4106 * Version:: @code{.version "@var{string}"}
4107 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4108 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4111 * Warning:: @code{.warning @var{string}}
4112 * Weak:: @code{.weak @var{names}}
4113 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4114 * Word:: @code{.word @var{expressions}}
4115 * Deprecated:: Deprecated Directives
4119 @section @code{.abort}
4121 @cindex @code{abort} directive
4122 @cindex stopping the assembly
4123 This directive stops the assembly immediately. It is for
4124 compatibility with other assemblers. The original idea was that the
4125 assembly language source would be piped into the assembler. If the sender
4126 of the source quit, it could use this directive tells @command{@value{AS}} to
4127 quit also. One day @code{.abort} will not be supported.
4131 @section @code{.ABORT} (COFF)
4133 @cindex @code{ABORT} directive
4134 When producing COFF output, @command{@value{AS}} accepts this directive as a
4135 synonym for @samp{.abort}.
4138 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4144 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4146 @cindex padding the location counter
4147 @cindex @code{align} directive
4148 Pad the location counter (in the current subsection) to a particular storage
4149 boundary. The first expression (which must be absolute) is the alignment
4150 required, as described below.
4152 The second expression (also absolute) gives the fill value to be stored in the
4153 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4154 padding bytes are normally zero. However, on some systems, if the section is
4155 marked as containing code and the fill value is omitted, the space is filled
4156 with no-op instructions.
4158 The third expression is also absolute, and is also optional. If it is present,
4159 it is the maximum number of bytes that should be skipped by this alignment
4160 directive. If doing the alignment would require skipping more bytes than the
4161 specified maximum, then the alignment is not done at all. You can omit the
4162 fill value (the second argument) entirely by simply using two commas after the
4163 required alignment; this can be useful if you want the alignment to be filled
4164 with no-op instructions when appropriate.
4166 The way the required alignment is specified varies from system to system.
4167 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4168 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4169 alignment request in bytes. For example @samp{.align 8} advances
4170 the location counter until it is a multiple of 8. If the location counter
4171 is already a multiple of 8, no change is needed. For the tic54x, the
4172 first expression is the alignment request in words.
4174 For other systems, including ppc, i386 using a.out format, arm and
4175 strongarm, it is the
4176 number of low-order zero bits the location counter must have after
4177 advancement. For example @samp{.align 3} advances the location
4178 counter until it a multiple of 8. If the location counter is already a
4179 multiple of 8, no change is needed.
4181 This inconsistency is due to the different behaviors of the various
4182 native assemblers for these systems which GAS must emulate.
4183 GAS also provides @code{.balign} and @code{.p2align} directives,
4184 described later, which have a consistent behavior across all
4185 architectures (but are specific to GAS).
4188 @section @code{.altmacro}
4189 Enable alternate macro mode, enabling:
4192 @item LOCAL @var{name} [ , @dots{} ]
4193 One additional directive, @code{LOCAL}, is available. It is used to
4194 generate a string replacement for each of the @var{name} arguments, and
4195 replace any instances of @var{name} in each macro expansion. The
4196 replacement string is unique in the assembly, and different for each
4197 separate macro expansion. @code{LOCAL} allows you to write macros that
4198 define symbols, without fear of conflict between separate macro expansions.
4200 @item String delimiters
4201 You can write strings delimited in these other ways besides
4202 @code{"@var{string}"}:
4205 @item '@var{string}'
4206 You can delimit strings with single-quote characters.
4208 @item <@var{string}>
4209 You can delimit strings with matching angle brackets.
4212 @item single-character string escape
4213 To include any single character literally in a string (even if the
4214 character would otherwise have some special meaning), you can prefix the
4215 character with @samp{!} (an exclamation mark). For example, you can
4216 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4218 @item Expression results as strings
4219 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4220 and use the result as a string.
4224 @section @code{.ascii "@var{string}"}@dots{}
4226 @cindex @code{ascii} directive
4227 @cindex string literals
4228 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4229 separated by commas. It assembles each string (with no automatic
4230 trailing zero byte) into consecutive addresses.
4233 @section @code{.asciz "@var{string}"}@dots{}
4235 @cindex @code{asciz} directive
4236 @cindex zero-terminated strings
4237 @cindex null-terminated strings
4238 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4239 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4242 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4244 @cindex padding the location counter given number of bytes
4245 @cindex @code{balign} directive
4246 Pad the location counter (in the current subsection) to a particular
4247 storage boundary. The first expression (which must be absolute) is the
4248 alignment request in bytes. For example @samp{.balign 8} advances
4249 the location counter until it is a multiple of 8. If the location counter
4250 is already a multiple of 8, no change is needed.
4252 The second expression (also absolute) gives the fill value to be stored in the
4253 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4254 padding bytes are normally zero. However, on some systems, if the section is
4255 marked as containing code and the fill value is omitted, the space is filled
4256 with no-op instructions.
4258 The third expression is also absolute, and is also optional. If it is present,
4259 it is the maximum number of bytes that should be skipped by this alignment
4260 directive. If doing the alignment would require skipping more bytes than the
4261 specified maximum, then the alignment is not done at all. You can omit the
4262 fill value (the second argument) entirely by simply using two commas after the
4263 required alignment; this can be useful if you want the alignment to be filled
4264 with no-op instructions when appropriate.
4266 @cindex @code{balignw} directive
4267 @cindex @code{balignl} directive
4268 The @code{.balignw} and @code{.balignl} directives are variants of the
4269 @code{.balign} directive. The @code{.balignw} directive treats the fill
4270 pattern as a two byte word value. The @code{.balignl} directives treats the
4271 fill pattern as a four byte longword value. For example, @code{.balignw
4272 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4273 filled in with the value 0x368d (the exact placement of the bytes depends upon
4274 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4278 @section @code{.byte @var{expressions}}
4280 @cindex @code{byte} directive
4281 @cindex integers, one byte
4282 @code{.byte} expects zero or more expressions, separated by commas.
4283 Each expression is assembled into the next byte.
4285 @node CFI directives
4286 @section @code{.cfi_sections @var{section_list}}
4287 @cindex @code{cfi_sections} directive
4288 @code{.cfi_sections} may be used to specify whether CFI directives
4289 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4290 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4291 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4292 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4293 directive is not used is @code{.cfi_sections .eh_frame}.
4295 @section @code{.cfi_startproc [simple]}
4296 @cindex @code{cfi_startproc} directive
4297 @code{.cfi_startproc} is used at the beginning of each function that
4298 should have an entry in @code{.eh_frame}. It initializes some internal
4299 data structures. Don't forget to close the function by
4300 @code{.cfi_endproc}.
4302 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4303 it also emits some architecture dependent initial CFI instructions.
4305 @section @code{.cfi_endproc}
4306 @cindex @code{cfi_endproc} directive
4307 @code{.cfi_endproc} is used at the end of a function where it closes its
4308 unwind entry previously opened by
4309 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4311 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4312 @code{.cfi_personality} defines personality routine and its encoding.
4313 @var{encoding} must be a constant determining how the personality
4314 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4315 argument is not present, otherwise second argument should be
4316 a constant or a symbol name. When using indirect encodings,
4317 the symbol provided should be the location where personality
4318 can be loaded from, not the personality routine itself.
4319 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4320 no personality routine.
4322 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4323 @code{.cfi_lsda} defines LSDA and its encoding.
4324 @var{encoding} must be a constant determining how the LSDA
4325 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4326 argument is not present, otherwise second argument should be a constant
4327 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4330 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4331 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4332 address from @var{register} and add @var{offset} to it}.
4334 @section @code{.cfi_def_cfa_register @var{register}}
4335 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4336 now on @var{register} will be used instead of the old one. Offset
4339 @section @code{.cfi_def_cfa_offset @var{offset}}
4340 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4341 remains the same, but @var{offset} is new. Note that it is the
4342 absolute offset that will be added to a defined register to compute
4345 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4346 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4347 value that is added/substracted from the previous offset.
4349 @section @code{.cfi_offset @var{register}, @var{offset}}
4350 Previous value of @var{register} is saved at offset @var{offset} from
4353 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4354 Previous value of @var{register} is saved at offset @var{offset} from
4355 the current CFA register. This is transformed to @code{.cfi_offset}
4356 using the known displacement of the CFA register from the CFA.
4357 This is often easier to use, because the number will match the
4358 code it's annotating.
4360 @section @code{.cfi_register @var{register1}, @var{register2}}
4361 Previous value of @var{register1} is saved in register @var{register2}.
4363 @section @code{.cfi_restore @var{register}}
4364 @code{.cfi_restore} says that the rule for @var{register} is now the
4365 same as it was at the beginning of the function, after all initial
4366 instruction added by @code{.cfi_startproc} were executed.
4368 @section @code{.cfi_undefined @var{register}}
4369 From now on the previous value of @var{register} can't be restored anymore.
4371 @section @code{.cfi_same_value @var{register}}
4372 Current value of @var{register} is the same like in the previous frame,
4373 i.e. no restoration needed.
4375 @section @code{.cfi_remember_state},
4376 First save all current rules for all registers by @code{.cfi_remember_state},
4377 then totally screw them up by subsequent @code{.cfi_*} directives and when
4378 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4379 the previous saved state.
4381 @section @code{.cfi_return_column @var{register}}
4382 Change return column @var{register}, i.e. the return address is either
4383 directly in @var{register} or can be accessed by rules for @var{register}.
4385 @section @code{.cfi_signal_frame}
4386 Mark current function as signal trampoline.
4388 @section @code{.cfi_window_save}
4389 SPARC register window has been saved.
4391 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4392 Allows the user to add arbitrary bytes to the unwind info. One
4393 might use this to add OS-specific CFI opcodes, or generic CFI
4394 opcodes that GAS does not yet support.
4396 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4397 The current value of @var{register} is @var{label}. The value of @var{label}
4398 will be encoded in the output file according to @var{encoding}; see the
4399 description of @code{.cfi_personality} for details on this encoding.
4401 The usefulness of equating a register to a fixed label is probably
4402 limited to the return address register. Here, it can be useful to
4403 mark a code segment that has only one return address which is reached
4404 by a direct branch and no copy of the return address exists in memory
4405 or another register.
4408 @section @code{.comm @var{symbol} , @var{length} }
4410 @cindex @code{comm} directive
4411 @cindex symbol, common
4412 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4413 common symbol in one object file may be merged with a defined or common symbol
4414 of the same name in another object file. If @code{@value{LD}} does not see a
4415 definition for the symbol--just one or more common symbols--then it will
4416 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4417 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4418 the same name, and they do not all have the same size, it will allocate space
4419 using the largest size.
4422 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4423 an optional third argument. This is the desired alignment of the symbol,
4424 specified for ELF as a byte boundary (for example, an alignment of 16 means
4425 that the least significant 4 bits of the address should be zero), and for PE
4426 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4427 boundary). The alignment must be an absolute expression, and it must be a
4428 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4429 common symbol, it will use the alignment when placing the symbol. If no
4430 alignment is specified, @command{@value{AS}} will set the alignment to the
4431 largest power of two less than or equal to the size of the symbol, up to a
4432 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4433 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4434 @samp{--section-alignment} option; image file sections in PE are aligned to
4435 multiples of 4096, which is far too large an alignment for ordinary variables.
4436 It is rather the default alignment for (non-debug) sections within object
4437 (@samp{*.o}) files, which are less strictly aligned.}.
4441 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4442 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4446 @section @code{.data @var{subsection}}
4448 @cindex @code{data} directive
4449 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4450 end of the data subsection numbered @var{subsection} (which is an
4451 absolute expression). If @var{subsection} is omitted, it defaults
4456 @section @code{.def @var{name}}
4458 @cindex @code{def} directive
4459 @cindex COFF symbols, debugging
4460 @cindex debugging COFF symbols
4461 Begin defining debugging information for a symbol @var{name}; the
4462 definition extends until the @code{.endef} directive is encountered.
4465 This directive is only observed when @command{@value{AS}} is configured for COFF
4466 format output; when producing @code{b.out}, @samp{.def} is recognized,
4473 @section @code{.desc @var{symbol}, @var{abs-expression}}
4475 @cindex @code{desc} directive
4476 @cindex COFF symbol descriptor
4477 @cindex symbol descriptor, COFF
4478 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4479 to the low 16 bits of an absolute expression.
4482 The @samp{.desc} directive is not available when @command{@value{AS}} is
4483 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4484 object format. For the sake of compatibility, @command{@value{AS}} accepts
4485 it, but produces no output, when configured for COFF.
4491 @section @code{.dim}
4493 @cindex @code{dim} directive
4494 @cindex COFF auxiliary symbol information
4495 @cindex auxiliary symbol information, COFF
4496 This directive is generated by compilers to include auxiliary debugging
4497 information in the symbol table. It is only permitted inside
4498 @code{.def}/@code{.endef} pairs.
4501 @samp{.dim} is only meaningful when generating COFF format output; when
4502 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4508 @section @code{.double @var{flonums}}
4510 @cindex @code{double} directive
4511 @cindex floating point numbers (double)
4512 @code{.double} expects zero or more flonums, separated by commas. It
4513 assembles floating point numbers.
4515 The exact kind of floating point numbers emitted depends on how
4516 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4520 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4521 in @sc{ieee} format.
4526 @section @code{.eject}
4528 @cindex @code{eject} directive
4529 @cindex new page, in listings
4530 @cindex page, in listings
4531 @cindex listing control: new page
4532 Force a page break at this point, when generating assembly listings.
4535 @section @code{.else}
4537 @cindex @code{else} directive
4538 @code{.else} is part of the @command{@value{AS}} support for conditional
4539 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4540 of code to be assembled if the condition for the preceding @code{.if}
4544 @section @code{.elseif}
4546 @cindex @code{elseif} directive
4547 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4548 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4549 @code{.if} block that would otherwise fill the entire @code{.else} section.
4552 @section @code{.end}
4554 @cindex @code{end} directive
4555 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4556 process anything in the file past the @code{.end} directive.
4560 @section @code{.endef}
4562 @cindex @code{endef} directive
4563 This directive flags the end of a symbol definition begun with
4567 @samp{.endef} is only meaningful when generating COFF format output; if
4568 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4569 directive but ignores it.
4574 @section @code{.endfunc}
4575 @cindex @code{endfunc} directive
4576 @code{.endfunc} marks the end of a function specified with @code{.func}.
4579 @section @code{.endif}
4581 @cindex @code{endif} directive
4582 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4583 it marks the end of a block of code that is only assembled
4584 conditionally. @xref{If,,@code{.if}}.
4587 @section @code{.equ @var{symbol}, @var{expression}}
4589 @cindex @code{equ} directive
4590 @cindex assigning values to symbols
4591 @cindex symbols, assigning values to
4592 This directive sets the value of @var{symbol} to @var{expression}.
4593 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4596 The syntax for @code{equ} on the HPPA is
4597 @samp{@var{symbol} .equ @var{expression}}.
4601 The syntax for @code{equ} on the Z80 is
4602 @samp{@var{symbol} equ @var{expression}}.
4603 On the Z80 it is an eror if @var{symbol} is already defined,
4604 but the symbol is not protected from later redefinition.
4605 Compare @ref{Equiv}.
4609 @section @code{.equiv @var{symbol}, @var{expression}}
4610 @cindex @code{equiv} directive
4611 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4612 the assembler will signal an error if @var{symbol} is already defined. Note a
4613 symbol which has been referenced but not actually defined is considered to be
4616 Except for the contents of the error message, this is roughly equivalent to
4623 plus it protects the symbol from later redefinition.
4626 @section @code{.eqv @var{symbol}, @var{expression}}
4627 @cindex @code{eqv} directive
4628 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4629 evaluate the expression or any part of it immediately. Instead each time
4630 the resulting symbol is used in an expression, a snapshot of its current
4634 @section @code{.err}
4635 @cindex @code{err} directive
4636 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4637 message and, unless the @option{-Z} option was used, it will not generate an
4638 object file. This can be used to signal an error in conditionally compiled code.
4641 @section @code{.error "@var{string}"}
4642 @cindex error directive
4644 Similarly to @code{.err}, this directive emits an error, but you can specify a
4645 string that will be emitted as the error message. If you don't specify the
4646 message, it defaults to @code{".error directive invoked in source file"}.
4647 @xref{Errors, ,Error and Warning Messages}.
4650 .error "This code has not been assembled and tested."
4654 @section @code{.exitm}
4655 Exit early from the current macro definition. @xref{Macro}.
4658 @section @code{.extern}
4660 @cindex @code{extern} directive
4661 @code{.extern} is accepted in the source program---for compatibility
4662 with other assemblers---but it is ignored. @command{@value{AS}} treats
4663 all undefined symbols as external.
4666 @section @code{.fail @var{expression}}
4668 @cindex @code{fail} directive
4669 Generates an error or a warning. If the value of the @var{expression} is 500
4670 or more, @command{@value{AS}} will print a warning message. If the value is less
4671 than 500, @command{@value{AS}} will print an error message. The message will
4672 include the value of @var{expression}. This can occasionally be useful inside
4673 complex nested macros or conditional assembly.
4676 @section @code{.file}
4677 @cindex @code{file} directive
4679 @ifclear no-file-dir
4680 There are two different versions of the @code{.file} directive. Targets
4681 that support DWARF2 line number information use the DWARF2 version of
4682 @code{.file}. Other targets use the default version.
4684 @subheading Default Version
4686 @cindex logical file name
4687 @cindex file name, logical
4688 This version of the @code{.file} directive tells @command{@value{AS}} that we
4689 are about to start a new logical file. The syntax is:
4695 @var{string} is the new file name. In general, the filename is
4696 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4697 to specify an empty file name, you must give the quotes--@code{""}. This
4698 statement may go away in future: it is only recognized to be compatible with
4699 old @command{@value{AS}} programs.
4701 @subheading DWARF2 Version
4704 When emitting DWARF2 line number information, @code{.file} assigns filenames
4705 to the @code{.debug_line} file name table. The syntax is:
4708 .file @var{fileno} @var{filename}
4711 The @var{fileno} operand should be a unique positive integer to use as the
4712 index of the entry in the table. The @var{filename} operand is a C string
4715 The detail of filename indices is exposed to the user because the filename
4716 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4717 information, and thus the user must know the exact indices that table
4721 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4723 @cindex @code{fill} directive
4724 @cindex writing patterns in memory
4725 @cindex patterns, writing in memory
4726 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4727 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4728 may be zero or more. @var{Size} may be zero or more, but if it is
4729 more than 8, then it is deemed to have the value 8, compatible with
4730 other people's assemblers. The contents of each @var{repeat} bytes
4731 is taken from an 8-byte number. The highest order 4 bytes are
4732 zero. The lowest order 4 bytes are @var{value} rendered in the
4733 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4734 Each @var{size} bytes in a repetition is taken from the lowest order
4735 @var{size} bytes of this number. Again, this bizarre behavior is
4736 compatible with other people's assemblers.
4738 @var{size} and @var{value} are optional.
4739 If the second comma and @var{value} are absent, @var{value} is
4740 assumed zero. If the first comma and following tokens are absent,
4741 @var{size} is assumed to be 1.
4744 @section @code{.float @var{flonums}}
4746 @cindex floating point numbers (single)
4747 @cindex @code{float} directive
4748 This directive assembles zero or more flonums, separated by commas. It
4749 has the same effect as @code{.single}.
4751 The exact kind of floating point numbers emitted depends on how
4752 @command{@value{AS}} is configured.
4753 @xref{Machine Dependencies}.
4757 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4758 in @sc{ieee} format.
4763 @section @code{.func @var{name}[,@var{label}]}
4764 @cindex @code{func} directive
4765 @code{.func} emits debugging information to denote function @var{name}, and
4766 is ignored unless the file is assembled with debugging enabled.
4767 Only @samp{--gstabs[+]} is currently supported.
4768 @var{label} is the entry point of the function and if omitted @var{name}
4769 prepended with the @samp{leading char} is used.
4770 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4771 All functions are currently defined to have @code{void} return type.
4772 The function must be terminated with @code{.endfunc}.
4775 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4777 @cindex @code{global} directive
4778 @cindex symbol, making visible to linker
4779 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4780 @var{symbol} in your partial program, its value is made available to
4781 other partial programs that are linked with it. Otherwise,
4782 @var{symbol} takes its attributes from a symbol of the same name
4783 from another file linked into the same program.
4785 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4786 compatibility with other assemblers.
4789 On the HPPA, @code{.global} is not always enough to make it accessible to other
4790 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4791 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4796 @section @code{.gnu_attribute @var{tag},@var{value}}
4797 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4800 @section @code{.hidden @var{names}}
4802 @cindex @code{hidden} directive
4804 This is one of the ELF visibility directives. The other two are
4805 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4806 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4808 This directive overrides the named symbols default visibility (which is set by
4809 their binding: local, global or weak). The directive sets the visibility to
4810 @code{hidden} which means that the symbols are not visible to other components.
4811 Such symbols are always considered to be @code{protected} as well.
4815 @section @code{.hword @var{expressions}}
4817 @cindex @code{hword} directive
4818 @cindex integers, 16-bit
4819 @cindex numbers, 16-bit
4820 @cindex sixteen bit integers
4821 This expects zero or more @var{expressions}, and emits
4822 a 16 bit number for each.
4825 This directive is a synonym for @samp{.short}; depending on the target
4826 architecture, it may also be a synonym for @samp{.word}.
4830 This directive is a synonym for @samp{.short}.
4833 This directive is a synonym for both @samp{.short} and @samp{.word}.
4838 @section @code{.ident}
4840 @cindex @code{ident} directive
4842 This directive is used by some assemblers to place tags in object files. The
4843 behavior of this directive varies depending on the target. When using the
4844 a.out object file format, @command{@value{AS}} simply accepts the directive for
4845 source-file compatibility with existing assemblers, but does not emit anything
4846 for it. When using COFF, comments are emitted to the @code{.comment} or
4847 @code{.rdata} section, depending on the target. When using ELF, comments are
4848 emitted to the @code{.comment} section.
4851 @section @code{.if @var{absolute expression}}
4853 @cindex conditional assembly
4854 @cindex @code{if} directive
4855 @code{.if} marks the beginning of a section of code which is only
4856 considered part of the source program being assembled if the argument
4857 (which must be an @var{absolute expression}) is non-zero. The end of
4858 the conditional section of code must be marked by @code{.endif}
4859 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4860 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4861 If you have several conditions to check, @code{.elseif} may be used to avoid
4862 nesting blocks if/else within each subsequent @code{.else} block.
4864 The following variants of @code{.if} are also supported:
4866 @cindex @code{ifdef} directive
4867 @item .ifdef @var{symbol}
4868 Assembles the following section of code if the specified @var{symbol}
4869 has been defined. Note a symbol which has been referenced but not yet defined
4870 is considered to be undefined.
4872 @cindex @code{ifb} directive
4873 @item .ifb @var{text}
4874 Assembles the following section of code if the operand is blank (empty).
4876 @cindex @code{ifc} directive
4877 @item .ifc @var{string1},@var{string2}
4878 Assembles the following section of code if the two strings are the same. The
4879 strings may be optionally quoted with single quotes. If they are not quoted,
4880 the first string stops at the first comma, and the second string stops at the
4881 end of the line. Strings which contain whitespace should be quoted. The
4882 string comparison is case sensitive.
4884 @cindex @code{ifeq} directive
4885 @item .ifeq @var{absolute expression}
4886 Assembles the following section of code if the argument is zero.
4888 @cindex @code{ifeqs} directive
4889 @item .ifeqs @var{string1},@var{string2}
4890 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4892 @cindex @code{ifge} directive
4893 @item .ifge @var{absolute expression}
4894 Assembles the following section of code if the argument is greater than or
4897 @cindex @code{ifgt} directive
4898 @item .ifgt @var{absolute expression}
4899 Assembles the following section of code if the argument is greater than zero.
4901 @cindex @code{ifle} directive
4902 @item .ifle @var{absolute expression}
4903 Assembles the following section of code if the argument is less than or equal
4906 @cindex @code{iflt} directive
4907 @item .iflt @var{absolute expression}
4908 Assembles the following section of code if the argument is less than zero.
4910 @cindex @code{ifnb} directive
4911 @item .ifnb @var{text}
4912 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4913 following section of code if the operand is non-blank (non-empty).
4915 @cindex @code{ifnc} directive
4916 @item .ifnc @var{string1},@var{string2}.
4917 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4918 following section of code if the two strings are not the same.
4920 @cindex @code{ifndef} directive
4921 @cindex @code{ifnotdef} directive
4922 @item .ifndef @var{symbol}
4923 @itemx .ifnotdef @var{symbol}
4924 Assembles the following section of code if the specified @var{symbol}
4925 has not been defined. Both spelling variants are equivalent. Note a symbol
4926 which has been referenced but not yet defined is considered to be undefined.
4928 @cindex @code{ifne} directive
4929 @item .ifne @var{absolute expression}
4930 Assembles the following section of code if the argument is not equal to zero
4931 (in other words, this is equivalent to @code{.if}).
4933 @cindex @code{ifnes} directive
4934 @item .ifnes @var{string1},@var{string2}
4935 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4936 following section of code if the two strings are not the same.
4940 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4942 @cindex @code{incbin} directive
4943 @cindex binary files, including
4944 The @code{incbin} directive includes @var{file} verbatim at the current
4945 location. You can control the search paths used with the @samp{-I} command-line
4946 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4949 The @var{skip} argument skips a number of bytes from the start of the
4950 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4951 read. Note that the data is not aligned in any way, so it is the user's
4952 responsibility to make sure that proper alignment is provided both before and
4953 after the @code{incbin} directive.
4956 @section @code{.include "@var{file}"}
4958 @cindex @code{include} directive
4959 @cindex supporting files, including
4960 @cindex files, including
4961 This directive provides a way to include supporting files at specified
4962 points in your source program. The code from @var{file} is assembled as
4963 if it followed the point of the @code{.include}; when the end of the
4964 included file is reached, assembly of the original file continues. You
4965 can control the search paths used with the @samp{-I} command-line option
4966 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4970 @section @code{.int @var{expressions}}
4972 @cindex @code{int} directive
4973 @cindex integers, 32-bit
4974 Expect zero or more @var{expressions}, of any section, separated by commas.
4975 For each expression, emit a number that, at run time, is the value of that
4976 expression. The byte order and bit size of the number depends on what kind
4977 of target the assembly is for.
4981 On most forms of the H8/300, @code{.int} emits 16-bit
4982 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4989 @section @code{.internal @var{names}}
4991 @cindex @code{internal} directive
4993 This is one of the ELF visibility directives. The other two are
4994 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4995 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4997 This directive overrides the named symbols default visibility (which is set by
4998 their binding: local, global or weak). The directive sets the visibility to
4999 @code{internal} which means that the symbols are considered to be @code{hidden}
5000 (i.e., not visible to other components), and that some extra, processor specific
5001 processing must also be performed upon the symbols as well.
5005 @section @code{.irp @var{symbol},@var{values}}@dots{}
5007 @cindex @code{irp} directive
5008 Evaluate a sequence of statements assigning different values to @var{symbol}.
5009 The sequence of statements starts at the @code{.irp} directive, and is
5010 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5011 set to @var{value}, and the sequence of statements is assembled. If no
5012 @var{value} is listed, the sequence of statements is assembled once, with
5013 @var{symbol} set to the null string. To refer to @var{symbol} within the
5014 sequence of statements, use @var{\symbol}.
5016 For example, assembling
5024 is equivalent to assembling
5032 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5035 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5037 @cindex @code{irpc} directive
5038 Evaluate a sequence of statements assigning different values to @var{symbol}.
5039 The sequence of statements starts at the @code{.irpc} directive, and is
5040 terminated by an @code{.endr} directive. For each character in @var{value},
5041 @var{symbol} is set to the character, and the sequence of statements is
5042 assembled. If no @var{value} is listed, the sequence of statements is
5043 assembled once, with @var{symbol} set to the null string. To refer to
5044 @var{symbol} within the sequence of statements, use @var{\symbol}.
5046 For example, assembling
5054 is equivalent to assembling
5062 For some caveats with the spelling of @var{symbol}, see also the discussion
5066 @section @code{.lcomm @var{symbol} , @var{length}}
5068 @cindex @code{lcomm} directive
5069 @cindex local common symbols
5070 @cindex symbols, local common
5071 Reserve @var{length} (an absolute expression) bytes for a local common
5072 denoted by @var{symbol}. The section and value of @var{symbol} are
5073 those of the new local common. The addresses are allocated in the bss
5074 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5075 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5076 not visible to @code{@value{LD}}.
5079 Some targets permit a third argument to be used with @code{.lcomm}. This
5080 argument specifies the desired alignment of the symbol in the bss section.
5084 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5085 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5089 @section @code{.lflags}
5091 @cindex @code{lflags} directive (ignored)
5092 @command{@value{AS}} accepts this directive, for compatibility with other
5093 assemblers, but ignores it.
5095 @ifclear no-line-dir
5097 @section @code{.line @var{line-number}}
5099 @cindex @code{line} directive
5100 @cindex logical line number
5102 Change the logical line number. @var{line-number} must be an absolute
5103 expression. The next line has that logical line number. Therefore any other
5104 statements on the current line (after a statement separator character) are
5105 reported as on logical line number @var{line-number} @minus{} 1. One day
5106 @command{@value{AS}} will no longer support this directive: it is recognized only
5107 for compatibility with existing assembler programs.
5110 Even though this is a directive associated with the @code{a.out} or
5111 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5112 when producing COFF output, and treats @samp{.line} as though it
5113 were the COFF @samp{.ln} @emph{if} it is found outside a
5114 @code{.def}/@code{.endef} pair.
5116 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5117 used by compilers to generate auxiliary symbol information for
5122 @section @code{.linkonce [@var{type}]}
5124 @cindex @code{linkonce} directive
5125 @cindex common sections
5126 Mark the current section so that the linker only includes a single copy of it.
5127 This may be used to include the same section in several different object files,
5128 but ensure that the linker will only include it once in the final output file.
5129 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5130 Duplicate sections are detected based on the section name, so it should be
5133 This directive is only supported by a few object file formats; as of this
5134 writing, the only object file format which supports it is the Portable
5135 Executable format used on Windows NT.
5137 The @var{type} argument is optional. If specified, it must be one of the
5138 following strings. For example:
5142 Not all types may be supported on all object file formats.
5146 Silently discard duplicate sections. This is the default.
5149 Warn if there are duplicate sections, but still keep only one copy.
5152 Warn if any of the duplicates have different sizes.
5155 Warn if any of the duplicates do not have exactly the same contents.
5159 @section @code{.list}
5161 @cindex @code{list} directive
5162 @cindex listing control, turning on
5163 Control (in conjunction with the @code{.nolist} directive) whether or
5164 not assembly listings are generated. These two directives maintain an
5165 internal counter (which is zero initially). @code{.list} increments the
5166 counter, and @code{.nolist} decrements it. Assembly listings are
5167 generated whenever the counter is greater than zero.
5169 By default, listings are disabled. When you enable them (with the
5170 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5171 the initial value of the listing counter is one.
5174 @section @code{.ln @var{line-number}}
5176 @cindex @code{ln} directive
5177 @ifclear no-line-dir
5178 @samp{.ln} is a synonym for @samp{.line}.
5181 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5182 must be an absolute expression. The next line has that logical
5183 line number, so any other statements on the current line (after a
5184 statement separator character @code{;}) are reported as on logical
5185 line number @var{line-number} @minus{} 1.
5188 This directive is accepted, but ignored, when @command{@value{AS}} is
5189 configured for @code{b.out}; its effect is only associated with COFF
5195 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5196 @cindex @code{loc} directive
5197 When emitting DWARF2 line number information,
5198 the @code{.loc} directive will add a row to the @code{.debug_line} line
5199 number matrix corresponding to the immediately following assembly
5200 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5201 arguments will be applied to the @code{.debug_line} state machine before
5204 The @var{options} are a sequence of the following tokens in any order:
5208 This option will set the @code{basic_block} register in the
5209 @code{.debug_line} state machine to @code{true}.
5212 This option will set the @code{prologue_end} register in the
5213 @code{.debug_line} state machine to @code{true}.
5215 @item epilogue_begin
5216 This option will set the @code{epilogue_begin} register in the
5217 @code{.debug_line} state machine to @code{true}.
5219 @item is_stmt @var{value}
5220 This option will set the @code{is_stmt} register in the
5221 @code{.debug_line} state machine to @code{value}, which must be
5224 @item isa @var{value}
5225 This directive will set the @code{isa} register in the @code{.debug_line}
5226 state machine to @var{value}, which must be an unsigned integer.
5228 @item discriminator @var{value}
5229 This directive will set the @code{discriminator} register in the @code{.debug_line}
5230 state machine to @var{value}, which must be an unsigned integer.
5234 @node Loc_mark_labels
5235 @section @code{.loc_mark_labels @var{enable}}
5236 @cindex @code{loc_mark_labels} directive
5237 When emitting DWARF2 line number information,
5238 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5239 to the @code{.debug_line} line number matrix with the @code{basic_block}
5240 register in the state machine set whenever a code label is seen.
5241 The @var{enable} argument should be either 1 or 0, to enable or disable
5242 this function respectively.
5246 @section @code{.local @var{names}}
5248 @cindex @code{local} directive
5249 This directive, which is available for ELF targets, marks each symbol in
5250 the comma-separated list of @code{names} as a local symbol so that it
5251 will not be externally visible. If the symbols do not already exist,
5252 they will be created.
5254 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5255 accept an alignment argument, which is the case for most ELF targets,
5256 the @code{.local} directive can be used in combination with @code{.comm}
5257 (@pxref{Comm}) to define aligned local common data.
5261 @section @code{.long @var{expressions}}
5263 @cindex @code{long} directive
5264 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5267 @c no one seems to know what this is for or whether this description is
5268 @c what it really ought to do
5270 @section @code{.lsym @var{symbol}, @var{expression}}
5272 @cindex @code{lsym} directive
5273 @cindex symbol, not referenced in assembly
5274 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5275 the hash table, ensuring it cannot be referenced by name during the
5276 rest of the assembly. This sets the attributes of the symbol to be
5277 the same as the expression value:
5279 @var{other} = @var{descriptor} = 0
5280 @var{type} = @r{(section of @var{expression})}
5281 @var{value} = @var{expression}
5284 The new symbol is not flagged as external.
5288 @section @code{.macro}
5291 The commands @code{.macro} and @code{.endm} allow you to define macros that
5292 generate assembly output. For example, this definition specifies a macro
5293 @code{sum} that puts a sequence of numbers into memory:
5296 .macro sum from=0, to=5
5305 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5317 @item .macro @var{macname}
5318 @itemx .macro @var{macname} @var{macargs} @dots{}
5319 @cindex @code{macro} directive
5320 Begin the definition of a macro called @var{macname}. If your macro
5321 definition requires arguments, specify their names after the macro name,
5322 separated by commas or spaces. You can qualify the macro argument to
5323 indicate whether all invocations must specify a non-blank value (through
5324 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5325 (through @samp{:@code{vararg}}). You can supply a default value for any
5326 macro argument by following the name with @samp{=@var{deflt}}. You
5327 cannot define two macros with the same @var{macname} unless it has been
5328 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5329 definitions. For example, these are all valid @code{.macro} statements:
5333 Begin the definition of a macro called @code{comm}, which takes no
5336 @item .macro plus1 p, p1
5337 @itemx .macro plus1 p p1
5338 Either statement begins the definition of a macro called @code{plus1},
5339 which takes two arguments; within the macro definition, write
5340 @samp{\p} or @samp{\p1} to evaluate the arguments.
5342 @item .macro reserve_str p1=0 p2
5343 Begin the definition of a macro called @code{reserve_str}, with two
5344 arguments. The first argument has a default value, but not the second.
5345 After the definition is complete, you can call the macro either as
5346 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5347 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5348 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5349 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5351 @item .macro m p1:req, p2=0, p3:vararg
5352 Begin the definition of a macro called @code{m}, with at least three
5353 arguments. The first argument must always have a value specified, but
5354 not the second, which instead has a default value. The third formal
5355 will get assigned all remaining arguments specified at invocation time.
5357 When you call a macro, you can specify the argument values either by
5358 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5359 @samp{sum to=17, from=9}.
5363 Note that since each of the @var{macargs} can be an identifier exactly
5364 as any other one permitted by the target architecture, there may be
5365 occasional problems if the target hand-crafts special meanings to certain
5366 characters when they occur in a special position. For example, if the colon
5367 (@code{:}) is generally permitted to be part of a symbol name, but the
5368 architecture specific code special-cases it when occurring as the final
5369 character of a symbol (to denote a label), then the macro parameter
5370 replacement code will have no way of knowing that and consider the whole
5371 construct (including the colon) an identifier, and check only this
5372 identifier for being the subject to parameter substitution. So for example
5373 this macro definition:
5381 might not work as expected. Invoking @samp{label foo} might not create a label
5382 called @samp{foo} but instead just insert the text @samp{\l:} into the
5383 assembler source, probably generating an error about an unrecognised
5386 Similarly problems might occur with the period character (@samp{.})
5387 which is often allowed inside opcode names (and hence identifier names). So
5388 for example constructing a macro to build an opcode from a base name and a
5389 length specifier like this:
5392 .macro opcode base length
5397 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5398 instruction but instead generate some kind of error as the assembler tries to
5399 interpret the text @samp{\base.\length}.
5401 There are several possible ways around this problem:
5404 @item Insert white space
5405 If it is possible to use white space characters then this is the simplest
5414 @item Use @samp{\()}
5415 The string @samp{\()} can be used to separate the end of a macro argument from
5416 the following text. eg:
5419 .macro opcode base length
5424 @item Use the alternate macro syntax mode
5425 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5426 used as a separator. eg:
5436 Note: this problem of correctly identifying string parameters to pseudo ops
5437 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5438 and @code{.irpc} (@pxref{Irpc}) as well.
5441 @cindex @code{endm} directive
5442 Mark the end of a macro definition.
5445 @cindex @code{exitm} directive
5446 Exit early from the current macro definition.
5448 @cindex number of macros executed
5449 @cindex macros, count executed
5451 @command{@value{AS}} maintains a counter of how many macros it has
5452 executed in this pseudo-variable; you can copy that number to your
5453 output with @samp{\@@}, but @emph{only within a macro definition}.
5455 @item LOCAL @var{name} [ , @dots{} ]
5456 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5457 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5458 @xref{Altmacro,,@code{.altmacro}}.
5462 @section @code{.mri @var{val}}
5464 @cindex @code{mri} directive
5465 @cindex MRI mode, temporarily
5466 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5467 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5468 affects code assembled until the next @code{.mri} directive, or until the end
5469 of the file. @xref{M, MRI mode, MRI mode}.
5472 @section @code{.noaltmacro}
5473 Disable alternate macro mode. @xref{Altmacro}.
5476 @section @code{.nolist}
5478 @cindex @code{nolist} directive
5479 @cindex listing control, turning off
5480 Control (in conjunction with the @code{.list} directive) whether or
5481 not assembly listings are generated. These two directives maintain an
5482 internal counter (which is zero initially). @code{.list} increments the
5483 counter, and @code{.nolist} decrements it. Assembly listings are
5484 generated whenever the counter is greater than zero.
5487 @section @code{.octa @var{bignums}}
5489 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5490 @cindex @code{octa} directive
5491 @cindex integer, 16-byte
5492 @cindex sixteen byte integer
5493 This directive expects zero or more bignums, separated by commas. For each
5494 bignum, it emits a 16-byte integer.
5496 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5497 hence @emph{octa}-word for 16 bytes.
5500 @section @code{.org @var{new-lc} , @var{fill}}
5502 @cindex @code{org} directive
5503 @cindex location counter, advancing
5504 @cindex advancing location counter
5505 @cindex current address, advancing
5506 Advance the location counter of the current section to
5507 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5508 expression with the same section as the current subsection. That is,
5509 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5510 wrong section, the @code{.org} directive is ignored. To be compatible
5511 with former assemblers, if the section of @var{new-lc} is absolute,
5512 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5513 is the same as the current subsection.
5515 @code{.org} may only increase the location counter, or leave it
5516 unchanged; you cannot use @code{.org} to move the location counter
5519 @c double negative used below "not undefined" because this is a specific
5520 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5521 @c section. doc@cygnus.com 18feb91
5522 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5523 may not be undefined. If you really detest this restriction we eagerly await
5524 a chance to share your improved assembler.
5526 Beware that the origin is relative to the start of the section, not
5527 to the start of the subsection. This is compatible with other
5528 people's assemblers.
5530 When the location counter (of the current subsection) is advanced, the
5531 intervening bytes are filled with @var{fill} which should be an
5532 absolute expression. If the comma and @var{fill} are omitted,
5533 @var{fill} defaults to zero.
5536 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5538 @cindex padding the location counter given a power of two
5539 @cindex @code{p2align} directive
5540 Pad the location counter (in the current subsection) to a particular
5541 storage boundary. The first expression (which must be absolute) is the
5542 number of low-order zero bits the location counter must have after
5543 advancement. For example @samp{.p2align 3} advances the location
5544 counter until it a multiple of 8. If the location counter is already a
5545 multiple of 8, no change is needed.
5547 The second expression (also absolute) gives the fill value to be stored in the
5548 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5549 padding bytes are normally zero. However, on some systems, if the section is
5550 marked as containing code and the fill value is omitted, the space is filled
5551 with no-op instructions.
5553 The third expression is also absolute, and is also optional. If it is present,
5554 it is the maximum number of bytes that should be skipped by this alignment
5555 directive. If doing the alignment would require skipping more bytes than the
5556 specified maximum, then the alignment is not done at all. You can omit the
5557 fill value (the second argument) entirely by simply using two commas after the
5558 required alignment; this can be useful if you want the alignment to be filled
5559 with no-op instructions when appropriate.
5561 @cindex @code{p2alignw} directive
5562 @cindex @code{p2alignl} directive
5563 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5564 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5565 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5566 fill pattern as a four byte longword value. For example, @code{.p2alignw
5567 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5568 filled in with the value 0x368d (the exact placement of the bytes depends upon
5569 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5574 @section @code{.popsection}
5576 @cindex @code{popsection} directive
5577 @cindex Section Stack
5578 This is one of the ELF section stack manipulation directives. The others are
5579 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5580 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5583 This directive replaces the current section (and subsection) with the top
5584 section (and subsection) on the section stack. This section is popped off the
5590 @section @code{.previous}
5592 @cindex @code{previous} directive
5593 @cindex Section Stack
5594 This is one of the ELF section stack manipulation directives. The others are
5595 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5596 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5597 (@pxref{PopSection}).
5599 This directive swaps the current section (and subsection) with most recently
5600 referenced section/subsection pair prior to this one. Multiple
5601 @code{.previous} directives in a row will flip between two sections (and their
5602 subsections). For example:
5614 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5620 # Now in section A subsection 1
5624 # Now in section B subsection 0
5627 # Now in section B subsection 1
5630 # Now in section B subsection 0
5634 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5635 section B and 0x9abc into subsection 1 of section B.
5637 In terms of the section stack, this directive swaps the current section with
5638 the top section on the section stack.
5642 @section @code{.print @var{string}}
5644 @cindex @code{print} directive
5645 @command{@value{AS}} will print @var{string} on the standard output during
5646 assembly. You must put @var{string} in double quotes.
5650 @section @code{.protected @var{names}}
5652 @cindex @code{protected} directive
5654 This is one of the ELF visibility directives. The other two are
5655 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5657 This directive overrides the named symbols default visibility (which is set by
5658 their binding: local, global or weak). The directive sets the visibility to
5659 @code{protected} which means that any references to the symbols from within the
5660 components that defines them must be resolved to the definition in that
5661 component, even if a definition in another component would normally preempt
5666 @section @code{.psize @var{lines} , @var{columns}}
5668 @cindex @code{psize} directive
5669 @cindex listing control: paper size
5670 @cindex paper size, for listings
5671 Use this directive to declare the number of lines---and, optionally, the
5672 number of columns---to use for each page, when generating listings.
5674 If you do not use @code{.psize}, listings use a default line-count
5675 of 60. You may omit the comma and @var{columns} specification; the
5676 default width is 200 columns.
5678 @command{@value{AS}} generates formfeeds whenever the specified number of
5679 lines is exceeded (or whenever you explicitly request one, using
5682 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5683 those explicitly specified with @code{.eject}.
5686 @section @code{.purgem @var{name}}
5688 @cindex @code{purgem} directive
5689 Undefine the macro @var{name}, so that later uses of the string will not be
5690 expanded. @xref{Macro}.
5694 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5696 @cindex @code{pushsection} directive
5697 @cindex Section Stack
5698 This is one of the ELF section stack manipulation directives. The others are
5699 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5700 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5703 This directive pushes the current section (and subsection) onto the
5704 top of the section stack, and then replaces the current section and
5705 subsection with @code{name} and @code{subsection}. The optional
5706 @code{flags}, @code{type} and @code{arguments} are treated the same
5707 as in the @code{.section} (@pxref{Section}) directive.
5711 @section @code{.quad @var{bignums}}
5713 @cindex @code{quad} directive
5714 @code{.quad} expects zero or more bignums, separated by commas. For
5715 each bignum, it emits
5717 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5718 warning message; and just takes the lowest order 8 bytes of the bignum.
5719 @cindex eight-byte integer
5720 @cindex integer, 8-byte
5722 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5723 hence @emph{quad}-word for 8 bytes.
5726 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5727 warning message; and just takes the lowest order 16 bytes of the bignum.
5728 @cindex sixteen-byte integer
5729 @cindex integer, 16-byte
5733 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5735 @cindex @code{reloc} directive
5736 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5737 @var{expression}. If @var{offset} is a number, the relocation is generated in
5738 the current section. If @var{offset} is an expression that resolves to a
5739 symbol plus offset, the relocation is generated in the given symbol's section.
5740 @var{expression}, if present, must resolve to a symbol plus addend or to an
5741 absolute value, but note that not all targets support an addend. e.g. ELF REL
5742 targets such as i386 store an addend in the section contents rather than in the
5743 relocation. This low level interface does not support addends stored in the
5747 @section @code{.rept @var{count}}
5749 @cindex @code{rept} directive
5750 Repeat the sequence of lines between the @code{.rept} directive and the next
5751 @code{.endr} directive @var{count} times.
5753 For example, assembling
5761 is equivalent to assembling
5770 @section @code{.sbttl "@var{subheading}"}
5772 @cindex @code{sbttl} directive
5773 @cindex subtitles for listings
5774 @cindex listing control: subtitle
5775 Use @var{subheading} as the title (third line, immediately after the
5776 title line) when generating assembly listings.
5778 This directive affects subsequent pages, as well as the current page if
5779 it appears within ten lines of the top of a page.
5783 @section @code{.scl @var{class}}
5785 @cindex @code{scl} directive
5786 @cindex symbol storage class (COFF)
5787 @cindex COFF symbol storage class
5788 Set the storage-class value for a symbol. This directive may only be
5789 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5790 whether a symbol is static or external, or it may record further
5791 symbolic debugging information.
5794 The @samp{.scl} directive is primarily associated with COFF output; when
5795 configured to generate @code{b.out} output format, @command{@value{AS}}
5796 accepts this directive but ignores it.
5802 @section @code{.section @var{name}}
5804 @cindex named section
5805 Use the @code{.section} directive to assemble the following code into a section
5808 This directive is only supported for targets that actually support arbitrarily
5809 named sections; on @code{a.out} targets, for example, it is not accepted, even
5810 with a standard @code{a.out} section name.
5814 @c only print the extra heading if both COFF and ELF are set
5815 @subheading COFF Version
5818 @cindex @code{section} directive (COFF version)
5819 For COFF targets, the @code{.section} directive is used in one of the following
5823 .section @var{name}[, "@var{flags}"]
5824 .section @var{name}[, @var{subsection}]
5827 If the optional argument is quoted, it is taken as flags to use for the
5828 section. Each flag is a single character. The following flags are recognized:
5831 bss section (uninitialized data)
5833 section is not loaded
5843 shared section (meaningful for PE targets)
5845 ignored. (For compatibility with the ELF version)
5847 section is not readable (meaningful for PE targets)
5849 single-digit power-of-two section alignment (GNU extension)
5852 If no flags are specified, the default flags depend upon the section name. If
5853 the section name is not recognized, the default will be for the section to be
5854 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5855 from the section, rather than adding them, so if they are used on their own it
5856 will be as if no flags had been specified at all.
5858 If the optional argument to the @code{.section} directive is not quoted, it is
5859 taken as a subsection number (@pxref{Sub-Sections}).
5864 @c only print the extra heading if both COFF and ELF are set
5865 @subheading ELF Version
5868 @cindex Section Stack
5869 This is one of the ELF section stack manipulation directives. The others are
5870 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5871 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5872 @code{.previous} (@pxref{Previous}).
5874 @cindex @code{section} directive (ELF version)
5875 For ELF targets, the @code{.section} directive is used like this:
5878 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5881 The optional @var{flags} argument is a quoted string which may contain any
5882 combination of the following characters:
5885 section is allocatable
5887 section is excluded from executable and shared library.
5891 section is executable
5893 section is mergeable
5895 section contains zero terminated strings
5897 section is a member of a section group
5899 section is used for thread-local-storage
5901 section is a member of the previously-current section's group, if any
5904 The optional @var{type} argument may contain one of the following constants:
5907 section contains data
5909 section does not contain data (i.e., section only occupies space)
5911 section contains data which is used by things other than the program
5913 section contains an array of pointers to init functions
5915 section contains an array of pointers to finish functions
5916 @item @@preinit_array
5917 section contains an array of pointers to pre-init functions
5920 Many targets only support the first three section types.
5922 Note on targets where the @code{@@} character is the start of a comment (eg
5923 ARM) then another character is used instead. For example the ARM port uses the
5926 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5927 be specified as well as an extra argument---@var{entsize}---like this:
5930 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5933 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5934 constants, each @var{entsize} octets long. Sections with both @code{M} and
5935 @code{S} must contain zero terminated strings where each character is
5936 @var{entsize} bytes long. The linker may remove duplicates within sections with
5937 the same name, same entity size and same flags. @var{entsize} must be an
5938 absolute expression. For sections with both @code{M} and @code{S}, a string
5939 which is a suffix of a larger string is considered a duplicate. Thus
5940 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5941 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5943 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5944 be present along with an additional field like this:
5947 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5950 The @var{GroupName} field specifies the name of the section group to which this
5951 particular section belongs. The optional linkage field can contain:
5954 indicates that only one copy of this section should be retained
5959 Note: if both the @var{M} and @var{G} flags are present then the fields for
5960 the Merge flag should come first, like this:
5963 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5966 If @var{flags} contains the @code{?} symbol then it may not also contain the
5967 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
5968 present. Instead, @code{?} says to consider the section that's current before
5969 this directive. If that section used @code{G}, then the new section will use
5970 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
5971 If not, then the @code{?} symbol has no effect.
5973 If no flags are specified, the default flags depend upon the section name. If
5974 the section name is not recognized, the default will be for the section to have
5975 none of the above flags: it will not be allocated in memory, nor writable, nor
5976 executable. The section will contain data.
5978 For ELF targets, the assembler supports another type of @code{.section}
5979 directive for compatibility with the Solaris assembler:
5982 .section "@var{name}"[, @var{flags}...]
5985 Note that the section name is quoted. There may be a sequence of comma
5989 section is allocatable
5993 section is executable
5995 section is excluded from executable and shared library.
5997 section is used for thread local storage
6000 This directive replaces the current section and subsection. See the
6001 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6002 some examples of how this directive and the other section stack directives
6008 @section @code{.set @var{symbol}, @var{expression}}
6010 @cindex @code{set} directive
6011 @cindex symbol value, setting
6012 Set the value of @var{symbol} to @var{expression}. This
6013 changes @var{symbol}'s value and type to conform to
6014 @var{expression}. If @var{symbol} was flagged as external, it remains
6015 flagged (@pxref{Symbol Attributes}).
6017 You may @code{.set} a symbol many times in the same assembly.
6019 If you @code{.set} a global symbol, the value stored in the object
6020 file is the last value stored into it.
6023 On Z80 @code{set} is a real instruction, use
6024 @samp{@var{symbol} defl @var{expression}} instead.
6028 @section @code{.short @var{expressions}}
6030 @cindex @code{short} directive
6032 @code{.short} is normally the same as @samp{.word}.
6033 @xref{Word,,@code{.word}}.
6035 In some configurations, however, @code{.short} and @code{.word} generate
6036 numbers of different lengths. @xref{Machine Dependencies}.
6040 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6043 This expects zero or more @var{expressions}, and emits
6044 a 16 bit number for each.
6049 @section @code{.single @var{flonums}}
6051 @cindex @code{single} directive
6052 @cindex floating point numbers (single)
6053 This directive assembles zero or more flonums, separated by commas. It
6054 has the same effect as @code{.float}.
6056 The exact kind of floating point numbers emitted depends on how
6057 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6061 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6062 numbers in @sc{ieee} format.
6068 @section @code{.size}
6070 This directive is used to set the size associated with a symbol.
6074 @c only print the extra heading if both COFF and ELF are set
6075 @subheading COFF Version
6078 @cindex @code{size} directive (COFF version)
6079 For COFF targets, the @code{.size} directive is only permitted inside
6080 @code{.def}/@code{.endef} pairs. It is used like this:
6083 .size @var{expression}
6087 @samp{.size} is only meaningful when generating COFF format output; when
6088 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6095 @c only print the extra heading if both COFF and ELF are set
6096 @subheading ELF Version
6099 @cindex @code{size} directive (ELF version)
6100 For ELF targets, the @code{.size} directive is used like this:
6103 .size @var{name} , @var{expression}
6106 This directive sets the size associated with a symbol @var{name}.
6107 The size in bytes is computed from @var{expression} which can make use of label
6108 arithmetic. This directive is typically used to set the size of function
6113 @ifclear no-space-dir
6115 @section @code{.skip @var{size} , @var{fill}}
6117 @cindex @code{skip} directive
6118 @cindex filling memory
6119 This directive emits @var{size} bytes, each of value @var{fill}. Both
6120 @var{size} and @var{fill} are absolute expressions. If the comma and
6121 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6126 @section @code{.sleb128 @var{expressions}}
6128 @cindex @code{sleb128} directive
6129 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6130 compact, variable length representation of numbers used by the DWARF
6131 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6133 @ifclear no-space-dir
6135 @section @code{.space @var{size} , @var{fill}}
6137 @cindex @code{space} directive
6138 @cindex filling memory
6139 This directive emits @var{size} bytes, each of value @var{fill}. Both
6140 @var{size} and @var{fill} are absolute expressions. If the comma
6141 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6146 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6147 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6148 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6149 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6157 @section @code{.stabd, .stabn, .stabs}
6159 @cindex symbolic debuggers, information for
6160 @cindex @code{stab@var{x}} directives
6161 There are three directives that begin @samp{.stab}.
6162 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6163 The symbols are not entered in the @command{@value{AS}} hash table: they
6164 cannot be referenced elsewhere in the source file.
6165 Up to five fields are required:
6169 This is the symbol's name. It may contain any character except
6170 @samp{\000}, so is more general than ordinary symbol names. Some
6171 debuggers used to code arbitrarily complex structures into symbol names
6175 An absolute expression. The symbol's type is set to the low 8 bits of
6176 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6177 and debuggers choke on silly bit patterns.
6180 An absolute expression. The symbol's ``other'' attribute is set to the
6181 low 8 bits of this expression.
6184 An absolute expression. The symbol's descriptor is set to the low 16
6185 bits of this expression.
6188 An absolute expression which becomes the symbol's value.
6191 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6192 or @code{.stabs} statement, the symbol has probably already been created;
6193 you get a half-formed symbol in your object file. This is
6194 compatible with earlier assemblers!
6197 @cindex @code{stabd} directive
6198 @item .stabd @var{type} , @var{other} , @var{desc}
6200 The ``name'' of the symbol generated is not even an empty string.
6201 It is a null pointer, for compatibility. Older assemblers used a
6202 null pointer so they didn't waste space in object files with empty
6205 The symbol's value is set to the location counter,
6206 relocatably. When your program is linked, the value of this symbol
6207 is the address of the location counter when the @code{.stabd} was
6210 @cindex @code{stabn} directive
6211 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6212 The name of the symbol is set to the empty string @code{""}.
6214 @cindex @code{stabs} directive
6215 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6216 All five fields are specified.
6222 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6223 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6225 @cindex string, copying to object file
6226 @cindex string8, copying to object file
6227 @cindex string16, copying to object file
6228 @cindex string32, copying to object file
6229 @cindex string64, copying to object file
6230 @cindex @code{string} directive
6231 @cindex @code{string8} directive
6232 @cindex @code{string16} directive
6233 @cindex @code{string32} directive
6234 @cindex @code{string64} directive
6236 Copy the characters in @var{str} to the object file. You may specify more than
6237 one string to copy, separated by commas. Unless otherwise specified for a
6238 particular machine, the assembler marks the end of each string with a 0 byte.
6239 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6241 The variants @code{string16}, @code{string32} and @code{string64} differ from
6242 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6243 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6244 are stored in target endianness byte order.
6250 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6251 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6256 @section @code{.struct @var{expression}}
6258 @cindex @code{struct} directive
6259 Switch to the absolute section, and set the section offset to @var{expression},
6260 which must be an absolute expression. You might use this as follows:
6269 This would define the symbol @code{field1} to have the value 0, the symbol
6270 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6271 value 8. Assembly would be left in the absolute section, and you would need to
6272 use a @code{.section} directive of some sort to change to some other section
6273 before further assembly.
6277 @section @code{.subsection @var{name}}
6279 @cindex @code{subsection} directive
6280 @cindex Section Stack
6281 This is one of the ELF section stack manipulation directives. The others are
6282 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6283 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6286 This directive replaces the current subsection with @code{name}. The current
6287 section is not changed. The replaced subsection is put onto the section stack
6288 in place of the then current top of stack subsection.
6293 @section @code{.symver}
6294 @cindex @code{symver} directive
6295 @cindex symbol versioning
6296 @cindex versions of symbols
6297 Use the @code{.symver} directive to bind symbols to specific version nodes
6298 within a source file. This is only supported on ELF platforms, and is
6299 typically used when assembling files to be linked into a shared library.
6300 There are cases where it may make sense to use this in objects to be bound
6301 into an application itself so as to override a versioned symbol from a
6304 For ELF targets, the @code{.symver} directive can be used like this:
6306 .symver @var{name}, @var{name2@@nodename}
6308 If the symbol @var{name} is defined within the file
6309 being assembled, the @code{.symver} directive effectively creates a symbol
6310 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6311 just don't try and create a regular alias is that the @var{@@} character isn't
6312 permitted in symbol names. The @var{name2} part of the name is the actual name
6313 of the symbol by which it will be externally referenced. The name @var{name}
6314 itself is merely a name of convenience that is used so that it is possible to
6315 have definitions for multiple versions of a function within a single source
6316 file, and so that the compiler can unambiguously know which version of a
6317 function is being mentioned. The @var{nodename} portion of the alias should be
6318 the name of a node specified in the version script supplied to the linker when
6319 building a shared library. If you are attempting to override a versioned
6320 symbol from a shared library, then @var{nodename} should correspond to the
6321 nodename of the symbol you are trying to override.
6323 If the symbol @var{name} is not defined within the file being assembled, all
6324 references to @var{name} will be changed to @var{name2@@nodename}. If no
6325 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6328 Another usage of the @code{.symver} directive is:
6330 .symver @var{name}, @var{name2@@@@nodename}
6332 In this case, the symbol @var{name} must exist and be defined within
6333 the file being assembled. It is similar to @var{name2@@nodename}. The
6334 difference is @var{name2@@@@nodename} will also be used to resolve
6335 references to @var{name2} by the linker.
6337 The third usage of the @code{.symver} directive is:
6339 .symver @var{name}, @var{name2@@@@@@nodename}
6341 When @var{name} is not defined within the
6342 file being assembled, it is treated as @var{name2@@nodename}. When
6343 @var{name} is defined within the file being assembled, the symbol
6344 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6349 @section @code{.tag @var{structname}}
6351 @cindex COFF structure debugging
6352 @cindex structure debugging, COFF
6353 @cindex @code{tag} directive
6354 This directive is generated by compilers to include auxiliary debugging
6355 information in the symbol table. It is only permitted inside
6356 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6357 definitions in the symbol table with instances of those structures.
6360 @samp{.tag} is only used when generating COFF format output; when
6361 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6367 @section @code{.text @var{subsection}}
6369 @cindex @code{text} directive
6370 Tells @command{@value{AS}} to assemble the following statements onto the end of
6371 the text subsection numbered @var{subsection}, which is an absolute
6372 expression. If @var{subsection} is omitted, subsection number zero
6376 @section @code{.title "@var{heading}"}
6378 @cindex @code{title} directive
6379 @cindex listing control: title line
6380 Use @var{heading} as the title (second line, immediately after the
6381 source file name and pagenumber) when generating assembly listings.
6383 This directive affects subsequent pages, as well as the current page if
6384 it appears within ten lines of the top of a page.
6388 @section @code{.type}
6390 This directive is used to set the type of a symbol.
6394 @c only print the extra heading if both COFF and ELF are set
6395 @subheading COFF Version
6398 @cindex COFF symbol type
6399 @cindex symbol type, COFF
6400 @cindex @code{type} directive (COFF version)
6401 For COFF targets, this directive is permitted only within
6402 @code{.def}/@code{.endef} pairs. It is used like this:
6408 This records the integer @var{int} as the type attribute of a symbol table
6412 @samp{.type} is associated only with COFF format output; when
6413 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6414 directive but ignores it.
6420 @c only print the extra heading if both COFF and ELF are set
6421 @subheading ELF Version
6424 @cindex ELF symbol type
6425 @cindex symbol type, ELF
6426 @cindex @code{type} directive (ELF version)
6427 For ELF targets, the @code{.type} directive is used like this:
6430 .type @var{name} , @var{type description}
6433 This sets the type of symbol @var{name} to be either a
6434 function symbol or an object symbol. There are five different syntaxes
6435 supported for the @var{type description} field, in order to provide
6436 compatibility with various other assemblers.
6438 Because some of the characters used in these syntaxes (such as @samp{@@} and
6439 @samp{#}) are comment characters for some architectures, some of the syntaxes
6440 below do not work on all architectures. The first variant will be accepted by
6441 the GNU assembler on all architectures so that variant should be used for
6442 maximum portability, if you do not need to assemble your code with other
6445 The syntaxes supported are:
6448 .type <name> STT_<TYPE_IN_UPPER_CASE>
6449 .type <name>,#<type>
6450 .type <name>,@@<type>
6451 .type <name>,%<type>
6452 .type <name>,"<type>"
6455 The types supported are:
6460 Mark the symbol as being a function name.
6463 @itemx gnu_indirect_function
6464 Mark the symbol as an indirect function when evaluated during reloc
6465 processing. (This is only supported on Linux targeted assemblers).
6469 Mark the symbol as being a data object.
6473 Mark the symbol as being a thead-local data object.
6477 Mark the symbol as being a common data object.
6481 Does not mark the symbol in any way. It is supported just for completeness.
6483 @item gnu_unique_object
6484 Marks the symbol as being a globally unique data object. The dynamic linker
6485 will make sure that in the entire process there is just one symbol with this
6486 name and type in use. (This is only supported on Linux targeted assemblers).
6490 Note: Some targets support extra types in addition to those listed above.
6496 @section @code{.uleb128 @var{expressions}}
6498 @cindex @code{uleb128} directive
6499 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6500 compact, variable length representation of numbers used by the DWARF
6501 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6505 @section @code{.val @var{addr}}
6507 @cindex @code{val} directive
6508 @cindex COFF value attribute
6509 @cindex value attribute, COFF
6510 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6511 records the address @var{addr} as the value attribute of a symbol table
6515 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6516 configured for @code{b.out}, it accepts this directive but ignores it.
6522 @section @code{.version "@var{string}"}
6524 @cindex @code{version} directive
6525 This directive creates a @code{.note} section and places into it an ELF
6526 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6531 @section @code{.vtable_entry @var{table}, @var{offset}}
6533 @cindex @code{vtable_entry} directive
6534 This directive finds or creates a symbol @code{table} and creates a
6535 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6538 @section @code{.vtable_inherit @var{child}, @var{parent}}
6540 @cindex @code{vtable_inherit} directive
6541 This directive finds the symbol @code{child} and finds or creates the symbol
6542 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6543 parent whose addend is the value of the child symbol. As a special case the
6544 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6548 @section @code{.warning "@var{string}"}
6549 @cindex warning directive
6550 Similar to the directive @code{.error}
6551 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6554 @section @code{.weak @var{names}}
6556 @cindex @code{weak} directive
6557 This directive sets the weak attribute on the comma separated list of symbol
6558 @code{names}. If the symbols do not already exist, they will be created.
6560 On COFF targets other than PE, weak symbols are a GNU extension. This
6561 directive sets the weak attribute on the comma separated list of symbol
6562 @code{names}. If the symbols do not already exist, they will be created.
6564 On the PE target, weak symbols are supported natively as weak aliases.
6565 When a weak symbol is created that is not an alias, GAS creates an
6566 alternate symbol to hold the default value.
6569 @section @code{.weakref @var{alias}, @var{target}}
6571 @cindex @code{weakref} directive
6572 This directive creates an alias to the target symbol that enables the symbol to
6573 be referenced with weak-symbol semantics, but without actually making it weak.
6574 If direct references or definitions of the symbol are present, then the symbol
6575 will not be weak, but if all references to it are through weak references, the
6576 symbol will be marked as weak in the symbol table.
6578 The effect is equivalent to moving all references to the alias to a separate
6579 assembly source file, renaming the alias to the symbol in it, declaring the
6580 symbol as weak there, and running a reloadable link to merge the object files
6581 resulting from the assembly of the new source file and the old source file that
6582 had the references to the alias removed.
6584 The alias itself never makes to the symbol table, and is entirely handled
6585 within the assembler.
6588 @section @code{.word @var{expressions}}
6590 @cindex @code{word} directive
6591 This directive expects zero or more @var{expressions}, of any section,
6592 separated by commas.
6595 For each expression, @command{@value{AS}} emits a 32-bit number.
6598 For each expression, @command{@value{AS}} emits a 16-bit number.
6603 The size of the number emitted, and its byte order,
6604 depend on what target computer the assembly is for.
6607 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6608 @c happen---32-bit addressability, period; no long/short jumps.
6609 @ifset DIFF-TBL-KLUGE
6610 @cindex difference tables altered
6611 @cindex altered difference tables
6613 @emph{Warning: Special Treatment to support Compilers}
6617 Machines with a 32-bit address space, but that do less than 32-bit
6618 addressing, require the following special treatment. If the machine of
6619 interest to you does 32-bit addressing (or doesn't require it;
6620 @pxref{Machine Dependencies}), you can ignore this issue.
6623 In order to assemble compiler output into something that works,
6624 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6625 Directives of the form @samp{.word sym1-sym2} are often emitted by
6626 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6627 directive of the form @samp{.word sym1-sym2}, and the difference between
6628 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6629 creates a @dfn{secondary jump table}, immediately before the next label.
6630 This secondary jump table is preceded by a short-jump to the
6631 first byte after the secondary table. This short-jump prevents the flow
6632 of control from accidentally falling into the new table. Inside the
6633 table is a long-jump to @code{sym2}. The original @samp{.word}
6634 contains @code{sym1} minus the address of the long-jump to
6637 If there were several occurrences of @samp{.word sym1-sym2} before the
6638 secondary jump table, all of them are adjusted. If there was a
6639 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6640 long-jump to @code{sym4} is included in the secondary jump table,
6641 and the @code{.word} directives are adjusted to contain @code{sym3}
6642 minus the address of the long-jump to @code{sym4}; and so on, for as many
6643 entries in the original jump table as necessary.
6646 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6647 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6648 assembly language programmers.
6651 @c end DIFF-TBL-KLUGE
6654 @section Deprecated Directives
6656 @cindex deprecated directives
6657 @cindex obsolescent directives
6658 One day these directives won't work.
6659 They are included for compatibility with older assemblers.
6666 @node Object Attributes
6667 @chapter Object Attributes
6668 @cindex object attributes
6670 @command{@value{AS}} assembles source files written for a specific architecture
6671 into object files for that architecture. But not all object files are alike.
6672 Many architectures support incompatible variations. For instance, floating
6673 point arguments might be passed in floating point registers if the object file
6674 requires hardware floating point support---or floating point arguments might be
6675 passed in integer registers if the object file supports processors with no
6676 hardware floating point unit. Or, if two objects are built for different
6677 generations of the same architecture, the combination may require the
6678 newer generation at run-time.
6680 This information is useful during and after linking. At link time,
6681 @command{@value{LD}} can warn about incompatible object files. After link
6682 time, tools like @command{gdb} can use it to process the linked file
6685 Compatibility information is recorded as a series of object attributes. Each
6686 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6687 string, and indicates who sets the meaning of the tag. The tag is an integer,
6688 and indicates what property the attribute describes. The value may be a string
6689 or an integer, and indicates how the property affects this object. Missing
6690 attributes are the same as attributes with a zero value or empty string value.
6692 Object attributes were developed as part of the ABI for the ARM Architecture.
6693 The file format is documented in @cite{ELF for the ARM Architecture}.
6696 * GNU Object Attributes:: @sc{gnu} Object Attributes
6697 * Defining New Object Attributes:: Defining New Object Attributes
6700 @node GNU Object Attributes
6701 @section @sc{gnu} Object Attributes
6703 The @code{.gnu_attribute} directive records an object attribute
6704 with vendor @samp{gnu}.
6706 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6707 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6708 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6709 2} is set for architecture-independent attributes and clear for
6710 architecture-dependent ones.
6712 @subsection Common @sc{gnu} attributes
6714 These attributes are valid on all architectures.
6717 @item Tag_compatibility (32)
6718 The compatibility attribute takes an integer flag value and a vendor name. If
6719 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6720 then the file is only compatible with the named toolchain. If it is greater
6721 than 1, the file can only be processed by other toolchains under some private
6722 arrangement indicated by the flag value and the vendor name.
6725 @subsection MIPS Attributes
6728 @item Tag_GNU_MIPS_ABI_FP (4)
6729 The floating-point ABI used by this object file. The value will be:
6733 0 for files not affected by the floating-point ABI.
6735 1 for files using the hardware floating-point with a standard double-precision
6738 2 for files using the hardware floating-point ABI with a single-precision FPU.
6740 3 for files using the software floating-point ABI.
6742 4 for files using the hardware floating-point ABI with 64-bit wide
6743 double-precision floating-point registers and 32-bit wide general
6748 @subsection PowerPC Attributes
6751 @item Tag_GNU_Power_ABI_FP (4)
6752 The floating-point ABI used by this object file. The value will be:
6756 0 for files not affected by the floating-point ABI.
6758 1 for files using double-precision hardware floating-point ABI.
6760 2 for files using the software floating-point ABI.
6762 3 for files using single-precision hardware floating-point ABI.
6765 @item Tag_GNU_Power_ABI_Vector (8)
6766 The vector ABI used by this object file. The value will be:
6770 0 for files not affected by the vector ABI.
6772 1 for files using general purpose registers to pass vectors.
6774 2 for files using AltiVec registers to pass vectors.
6776 3 for files using SPE registers to pass vectors.
6780 @node Defining New Object Attributes
6781 @section Defining New Object Attributes
6783 If you want to define a new @sc{gnu} object attribute, here are the places you
6784 will need to modify. New attributes should be discussed on the @samp{binutils}
6789 This manual, which is the official register of attributes.
6791 The header for your architecture @file{include/elf}, to define the tag.
6793 The @file{bfd} support file for your architecture, to merge the attribute
6794 and issue any appropriate link warnings.
6796 Test cases in @file{ld/testsuite} for merging and link warnings.
6798 @file{binutils/readelf.c} to display your attribute.
6800 GCC, if you want the compiler to mark the attribute automatically.
6806 @node Machine Dependencies
6807 @chapter Machine Dependent Features
6809 @cindex machine dependencies
6810 The machine instruction sets are (almost by definition) different on
6811 each machine where @command{@value{AS}} runs. Floating point representations
6812 vary as well, and @command{@value{AS}} often supports a few additional
6813 directives or command-line options for compatibility with other
6814 assemblers on a particular platform. Finally, some versions of
6815 @command{@value{AS}} support special pseudo-instructions for branch
6818 This chapter discusses most of these differences, though it does not
6819 include details on any machine's instruction set. For details on that
6820 subject, see the hardware manufacturer's manual.
6824 * Alpha-Dependent:: Alpha Dependent Features
6827 * ARC-Dependent:: ARC Dependent Features
6830 * ARM-Dependent:: ARM Dependent Features
6833 * AVR-Dependent:: AVR Dependent Features
6836 * Blackfin-Dependent:: Blackfin Dependent Features
6839 * CR16-Dependent:: CR16 Dependent Features
6842 * CRIS-Dependent:: CRIS Dependent Features
6845 * D10V-Dependent:: D10V Dependent Features
6848 * D30V-Dependent:: D30V Dependent Features
6851 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6854 * HPPA-Dependent:: HPPA Dependent Features
6857 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6860 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6863 * i860-Dependent:: Intel 80860 Dependent Features
6866 * i960-Dependent:: Intel 80960 Dependent Features
6869 * IA-64-Dependent:: Intel IA-64 Dependent Features
6872 * IP2K-Dependent:: IP2K Dependent Features
6875 * LM32-Dependent:: LM32 Dependent Features
6878 * M32C-Dependent:: M32C Dependent Features
6881 * M32R-Dependent:: M32R Dependent Features
6884 * M68K-Dependent:: M680x0 Dependent Features
6887 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6890 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6893 * MIPS-Dependent:: MIPS Dependent Features
6896 * MMIX-Dependent:: MMIX Dependent Features
6899 * MSP430-Dependent:: MSP430 Dependent Features
6902 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6903 * SH64-Dependent:: SuperH SH64 Dependent Features
6906 * PDP-11-Dependent:: PDP-11 Dependent Features
6909 * PJ-Dependent:: picoJava Dependent Features
6912 * PPC-Dependent:: PowerPC Dependent Features
6915 * RX-Dependent:: RX Dependent Features
6918 * S/390-Dependent:: IBM S/390 Dependent Features
6921 * SCORE-Dependent:: SCORE Dependent Features
6924 * Sparc-Dependent:: SPARC Dependent Features
6927 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6930 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6933 * V850-Dependent:: V850 Dependent Features
6936 * Xtensa-Dependent:: Xtensa Dependent Features
6939 * Z80-Dependent:: Z80 Dependent Features
6942 * Z8000-Dependent:: Z8000 Dependent Features
6945 * Vax-Dependent:: VAX Dependent Features
6952 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6953 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6954 @c peculiarity: to preserve cross-references, there must be a node called
6955 @c "Machine Dependencies". Hence the conditional nodenames in each
6956 @c major node below. Node defaulting in makeinfo requires adjacency of
6957 @c node and sectioning commands; hence the repetition of @chapter BLAH
6958 @c in both conditional blocks.
6961 @include c-alpha.texi
6977 @include c-bfin.texi
6981 @include c-cr16.texi
6985 @include c-cris.texi
6990 @node Machine Dependencies
6991 @chapter Machine Dependent Features
6993 The machine instruction sets are different on each Renesas chip family,
6994 and there are also some syntax differences among the families. This
6995 chapter describes the specific @command{@value{AS}} features for each
6999 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7000 * SH-Dependent:: Renesas SH Dependent Features
7007 @include c-d10v.texi
7011 @include c-d30v.texi
7015 @include c-h8300.texi
7019 @include c-hppa.texi
7023 @include c-i370.texi
7027 @include c-i386.texi
7031 @include c-i860.texi
7035 @include c-i960.texi
7039 @include c-ia64.texi
7043 @include c-ip2k.texi
7047 @include c-lm32.texi
7051 @include c-m32c.texi
7055 @include c-m32r.texi
7059 @include c-m68k.texi
7063 @include c-m68hc11.texi
7067 @include c-microblaze.texi
7071 @include c-mips.texi
7075 @include c-mmix.texi
7079 @include c-msp430.texi
7083 @include c-ns32k.texi
7087 @include c-pdp11.texi
7103 @include c-s390.texi
7107 @include c-score.texi
7112 @include c-sh64.texi
7116 @include c-sparc.texi
7120 @include c-tic54x.texi
7124 @include c-tic6x.texi
7140 @include c-v850.texi
7144 @include c-xtensa.texi
7148 @c reverse effect of @down at top of generic Machine-Dep chapter
7152 @node Reporting Bugs
7153 @chapter Reporting Bugs
7154 @cindex bugs in assembler
7155 @cindex reporting bugs in assembler
7157 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7159 Reporting a bug may help you by bringing a solution to your problem, or it may
7160 not. But in any case the principal function of a bug report is to help the
7161 entire community by making the next version of @command{@value{AS}} work better.
7162 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7164 In order for a bug report to serve its purpose, you must include the
7165 information that enables us to fix the bug.
7168 * Bug Criteria:: Have you found a bug?
7169 * Bug Reporting:: How to report bugs
7173 @section Have You Found a Bug?
7174 @cindex bug criteria
7176 If you are not sure whether you have found a bug, here are some guidelines:
7179 @cindex fatal signal
7180 @cindex assembler crash
7181 @cindex crash of assembler
7183 If the assembler gets a fatal signal, for any input whatever, that is a
7184 @command{@value{AS}} bug. Reliable assemblers never crash.
7186 @cindex error on valid input
7188 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7190 @cindex invalid input
7192 If @command{@value{AS}} does not produce an error message for invalid input, that
7193 is a bug. However, you should note that your idea of ``invalid input'' might
7194 be our idea of ``an extension'' or ``support for traditional practice''.
7197 If you are an experienced user of assemblers, your suggestions for improvement
7198 of @command{@value{AS}} are welcome in any case.
7202 @section How to Report Bugs
7204 @cindex assembler bugs, reporting
7206 A number of companies and individuals offer support for @sc{gnu} products. If
7207 you obtained @command{@value{AS}} from a support organization, we recommend you
7208 contact that organization first.
7210 You can find contact information for many support companies and
7211 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7215 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7219 The fundamental principle of reporting bugs usefully is this:
7220 @strong{report all the facts}. If you are not sure whether to state a
7221 fact or leave it out, state it!
7223 Often people omit facts because they think they know what causes the problem
7224 and assume that some details do not matter. Thus, you might assume that the
7225 name of a symbol you use in an example does not matter. Well, probably it does
7226 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7227 happens to fetch from the location where that name is stored in memory;
7228 perhaps, if the name were different, the contents of that location would fool
7229 the assembler into doing the right thing despite the bug. Play it safe and
7230 give a specific, complete example. That is the easiest thing for you to do,
7231 and the most helpful.
7233 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7234 it is new to us. Therefore, always write your bug reports on the assumption
7235 that the bug has not been reported previously.
7237 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7238 bell?'' This cannot help us fix a bug, so it is basically useless. We
7239 respond by asking for enough details to enable us to investigate.
7240 You might as well expedite matters by sending them to begin with.
7242 To enable us to fix the bug, you should include all these things:
7246 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7247 it with the @samp{--version} argument.
7249 Without this, we will not know whether there is any point in looking for
7250 the bug in the current version of @command{@value{AS}}.
7253 Any patches you may have applied to the @command{@value{AS}} source.
7256 The type of machine you are using, and the operating system name and
7260 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7264 The command arguments you gave the assembler to assemble your example and
7265 observe the bug. To guarantee you will not omit something important, list them
7266 all. A copy of the Makefile (or the output from make) is sufficient.
7268 If we were to try to guess the arguments, we would probably guess wrong
7269 and then we might not encounter the bug.
7272 A complete input file that will reproduce the bug. If the bug is observed when
7273 the assembler is invoked via a compiler, send the assembler source, not the
7274 high level language source. Most compilers will produce the assembler source
7275 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7276 the options @samp{-v --save-temps}; this will save the assembler source in a
7277 file with an extension of @file{.s}, and also show you exactly how
7278 @command{@value{AS}} is being run.
7281 A description of what behavior you observe that you believe is
7282 incorrect. For example, ``It gets a fatal signal.''
7284 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7285 will certainly notice it. But if the bug is incorrect output, we might not
7286 notice unless it is glaringly wrong. You might as well not give us a chance to
7289 Even if the problem you experience is a fatal signal, you should still say so
7290 explicitly. Suppose something strange is going on, such as, your copy of
7291 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7292 library on your system. (This has happened!) Your copy might crash and ours
7293 would not. If you told us to expect a crash, then when ours fails to crash, we
7294 would know that the bug was not happening for us. If you had not told us to
7295 expect a crash, then we would not be able to draw any conclusion from our
7299 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7300 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7301 option. Always send diffs from the old file to the new file. If you even
7302 discuss something in the @command{@value{AS}} source, refer to it by context, not
7305 The line numbers in our development sources will not match those in your
7306 sources. Your line numbers would convey no useful information to us.
7309 Here are some things that are not necessary:
7313 A description of the envelope of the bug.
7315 Often people who encounter a bug spend a lot of time investigating
7316 which changes to the input file will make the bug go away and which
7317 changes will not affect it.
7319 This is often time consuming and not very useful, because the way we
7320 will find the bug is by running a single example under the debugger
7321 with breakpoints, not by pure deduction from a series of examples.
7322 We recommend that you save your time for something else.
7324 Of course, if you can find a simpler example to report @emph{instead}
7325 of the original one, that is a convenience for us. Errors in the
7326 output will be easier to spot, running under the debugger will take
7327 less time, and so on.
7329 However, simplification is not vital; if you do not want to do this,
7330 report the bug anyway and send us the entire test case you used.
7333 A patch for the bug.
7335 A patch for the bug does help us if it is a good one. But do not omit
7336 the necessary information, such as the test case, on the assumption that
7337 a patch is all we need. We might see problems with your patch and decide
7338 to fix the problem another way, or we might not understand it at all.
7340 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7341 construct an example that will make the program follow a certain path through
7342 the code. If you do not send us the example, we will not be able to construct
7343 one, so we will not be able to verify that the bug is fixed.
7345 And if we cannot understand what bug you are trying to fix, or why your
7346 patch should be an improvement, we will not install it. A test case will
7347 help us to understand.
7350 A guess about what the bug is or what it depends on.
7352 Such guesses are usually wrong. Even we cannot guess right about such
7353 things without first using the debugger to find the facts.
7356 @node Acknowledgements
7357 @chapter Acknowledgements
7359 If you have contributed to GAS and your name isn't listed here,
7360 it is not meant as a slight. We just don't know about it. Send mail to the
7361 maintainer, and we'll correct the situation. Currently
7363 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7365 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7368 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7369 information and the 68k series machines, most of the preprocessing pass, and
7370 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7372 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7373 many bug fixes, including merging support for several processors, breaking GAS
7374 up to handle multiple object file format back ends (including heavy rewrite,
7375 testing, an integration of the coff and b.out back ends), adding configuration
7376 including heavy testing and verification of cross assemblers and file splits
7377 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7378 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7379 port (including considerable amounts of reverse engineering), a SPARC opcode
7380 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7381 assertions and made them work, much other reorganization, cleanup, and lint.
7383 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7384 in format-specific I/O modules.
7386 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7387 has done much work with it since.
7389 The Intel 80386 machine description was written by Eliot Dresselhaus.
7391 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7393 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7394 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7396 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7397 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7398 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7399 support a.out format.
7401 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7402 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7403 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7404 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7407 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7408 simplified the configuration of which versions accept which directives. He
7409 updated the 68k machine description so that Motorola's opcodes always produced
7410 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7411 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7412 cross-compilation support, and one bug in relaxation that took a week and
7413 required the proverbial one-bit fix.
7415 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7416 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7417 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7418 PowerPC assembler, and made a few other minor patches.
7420 Steve Chamberlain made GAS able to generate listings.
7422 Hewlett-Packard contributed support for the HP9000/300.
7424 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7425 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7426 formats). This work was supported by both the Center for Software Science at
7427 the University of Utah and Cygnus Support.
7429 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7430 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7431 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7432 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7433 and some initial 64-bit support).
7435 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7437 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7438 support for openVMS/Alpha.
7440 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7443 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7444 Inc.@: added support for Xtensa processors.
7446 Several engineers at Cygnus Support have also provided many small bug fixes and
7447 configuration enhancements.
7449 Jon Beniston added support for the Lattice Mico32 architecture.
7451 Many others have contributed large or small bugfixes and enhancements. If
7452 you have contributed significant work and are not mentioned on this list, and
7453 want to be, let us know. Some of the history has been lost; we are not
7454 intentionally leaving anyone out.
7456 @node GNU Free Documentation License
7457 @appendix GNU Free Documentation License
7461 @unnumbered AS Index