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, 2011
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, 2011 Free Software Foundation,
109 Permission is granted to copy, distribute and/or modify this document
110 under the terms of the GNU Free Documentation License, Version 1.3
111 or any later version published by the Free Software Foundation;
112 with no Invariant Sections, with no Front-Cover Texts, and with no
113 Back-Cover Texts. A copy of the license is included in the
114 section entitled ``GNU Free Documentation License''.
120 @title Using @value{AS}
121 @subtitle The @sc{gnu} Assembler
123 @subtitle for the @value{TARGET} family
125 @ifset VERSION_PACKAGE
127 @subtitle @value{VERSION_PACKAGE}
130 @subtitle Version @value{VERSION}
133 The Free Software Foundation Inc.@: thanks The Nice Computer
134 Company of Australia for loaning Dean Elsner to write the
135 first (Vax) version of @command{as} for Project @sc{gnu}.
136 The proprietors, management and staff of TNCCA thank FSF for
137 distracting the boss while they got some work
140 @author Dean Elsner, Jay Fenlason & friends
144 \hfill {\it Using {\tt @value{AS}}}\par
145 \hfill Edited by Cygnus Support\par
147 %"boxit" macro for figures:
148 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
149 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
150 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
151 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
152 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
155 @vskip 0pt plus 1filll
156 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
157 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
160 Permission is granted to copy, distribute and/or modify this document
161 under the terms of the GNU Free Documentation License, Version 1.3
162 or any later version published by the Free Software Foundation;
163 with no Invariant Sections, with no Front-Cover Texts, and with no
164 Back-Cover Texts. A copy of the license is included in the
165 section entitled ``GNU Free Documentation License''.
172 @top Using @value{AS}
174 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
175 @ifset VERSION_PACKAGE
176 @value{VERSION_PACKAGE}
178 version @value{VERSION}.
180 This version of the file describes @command{@value{AS}} configured to generate
181 code for @value{TARGET} architectures.
184 This document is distributed under the terms of the GNU Free
185 Documentation License. A copy of the license is included in the
186 section entitled ``GNU Free Documentation License''.
189 * Overview:: Overview
190 * Invoking:: Command-Line Options
192 * Sections:: Sections and Relocation
194 * Expressions:: Expressions
195 * Pseudo Ops:: Assembler Directives
197 * Object Attributes:: Object Attributes
199 * Machine Dependencies:: Machine Dependent Features
200 * Reporting Bugs:: Reporting Bugs
201 * Acknowledgements:: Who Did What
202 * GNU Free Documentation License:: GNU Free Documentation License
203 * AS Index:: AS Index
210 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
212 This version of the manual describes @command{@value{AS}} configured to generate
213 code for @value{TARGET} architectures.
217 @cindex invocation summary
218 @cindex option summary
219 @cindex summary of options
220 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
221 see @ref{Invoking,,Command-Line Options}.
223 @c man title AS the portable GNU assembler.
227 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
231 @c We don't use deffn and friends for the following because they seem
232 @c to be limited to one line for the header.
234 @c man begin SYNOPSIS
235 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
236 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
237 [@b{--debug-prefix-map} @var{old}=@var{new}]
238 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
239 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
240 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
241 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
242 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
243 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
244 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
245 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
246 [@b{--size-check=[error|warning]}]
247 [@b{--target-help}] [@var{target-options}]
248 [@b{--}|@var{files} @dots{}]
250 @c Target dependent options are listed below. Keep the list sorted.
251 @c Add an empty line for separation.
254 @emph{Target Alpha options:}
256 [@b{-mdebug} | @b{-no-mdebug}]
257 [@b{-replace} | @b{-noreplace}]
258 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
259 [@b{-F}] [@b{-32addr}]
263 @emph{Target ARC options:}
269 @emph{Target ARM options:}
270 @c Don't document the deprecated options
271 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
272 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
273 [@b{-mfpu}=@var{floating-point-format}]
274 [@b{-mfloat-abi}=@var{abi}]
275 [@b{-meabi}=@var{ver}]
278 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
279 @b{-mapcs-reentrant}]
280 [@b{-mthumb-interwork}] [@b{-k}]
284 @emph{Target Blackfin options:}
285 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
292 @emph{Target CRIS options:}
293 [@b{--underscore} | @b{--no-underscore}]
295 [@b{--emulation=criself} | @b{--emulation=crisaout}]
296 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
297 @c Deprecated -- deliberately not documented.
302 @emph{Target D10V options:}
307 @emph{Target D30V options:}
308 [@b{-O}|@b{-n}|@b{-N}]
312 @emph{Target H8/300 options:}
316 @c HPPA has no machine-dependent assembler options (yet).
320 @emph{Target i386 options:}
321 [@b{--32}|@b{--n32}|@b{--64}] [@b{-n}]
322 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
326 @emph{Target i960 options:}
327 @c see md_parse_option in tc-i960.c
328 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
330 [@b{-b}] [@b{-no-relax}]
334 @emph{Target IA-64 options:}
335 [@b{-mconstant-gp}|@b{-mauto-pic}]
336 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
338 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
339 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
340 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
341 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
345 @emph{Target IP2K options:}
346 [@b{-mip2022}|@b{-mip2022ext}]
350 @emph{Target M32C options:}
351 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
355 @emph{Target M32R options:}
356 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
361 @emph{Target M680X0 options:}
362 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
366 @emph{Target M68HC11 options:}
367 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
368 [@b{-mshort}|@b{-mlong}]
369 [@b{-mshort-double}|@b{-mlong-double}]
370 [@b{--force-long-branches}] [@b{--short-branches}]
371 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
372 [@b{--print-opcodes}] [@b{--generate-example}]
376 @emph{Target MCORE options:}
377 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
378 [@b{-mcpu=[210|340]}]
381 @emph{Target MICROBLAZE options:}
382 @c MicroBlaze has no machine-dependent assembler options.
386 @emph{Target MIPS options:}
387 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
388 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
389 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
390 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
391 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
392 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
393 [@b{-mips64}] [@b{-mips64r2}]
394 [@b{-construct-floats}] [@b{-no-construct-floats}]
395 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
396 [@b{-mips16}] [@b{-no-mips16}]
397 [@b{-mmicromips}] [@b{-mno-micromips}]
398 [@b{-msmartmips}] [@b{-mno-smartmips}]
399 [@b{-mips3d}] [@b{-no-mips3d}]
400 [@b{-mdmx}] [@b{-no-mdmx}]
401 [@b{-mdsp}] [@b{-mno-dsp}]
402 [@b{-mdspr2}] [@b{-mno-dspr2}]
403 [@b{-mmt}] [@b{-mno-mt}]
404 [@b{-mmcu}] [@b{-mno-mcu}]
405 [@b{-mfix7000}] [@b{-mno-fix7000}]
406 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
407 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
408 [@b{-mdebug}] [@b{-no-mdebug}]
409 [@b{-mpdr}] [@b{-mno-pdr}]
413 @emph{Target MMIX options:}
414 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
415 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
416 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
417 [@b{--linker-allocated-gregs}]
421 @emph{Target PDP11 options:}
422 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
423 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
424 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
428 @emph{Target picoJava options:}
433 @emph{Target PowerPC options:}
435 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
436 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
437 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-mppc64bridge}|@b{-mbooke}|
438 @b{-mpower4}|@b{-mpr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
439 @b{-mpower7}|@b{-mpw7}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
440 [@b{-many}] [@b{-maltivec}|@b{-mvsx}]
441 [@b{-mregnames}|@b{-mno-regnames}]
442 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
443 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
444 [@b{-msolaris}|@b{-mno-solaris}]
445 [@b{-nops=@var{count}}]
449 @emph{Target RX options:}
450 [@b{-mlittle-endian}|@b{-mbig-endian}]
451 [@b{-m32bit-ints}|@b{-m16bit-ints}]
452 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
456 @emph{Target s390 options:}
457 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
458 [@b{-mregnames}|@b{-mno-regnames}]
459 [@b{-mwarn-areg-zero}]
463 @emph{Target SCORE options:}
464 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
465 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
466 [@b{-march=score7}][@b{-march=score3}]
467 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
471 @emph{Target SPARC options:}
472 @c The order here is important. See c-sparc.texi.
473 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
474 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
475 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
480 @emph{Target TIC54X options:}
481 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
482 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
487 @emph{Target TIC6X options:}
488 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
489 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
490 [@b{-mpic}|@b{-mno-pic}]
494 @emph{Target TILE-Gx options:}
498 @c TILEPro has no machine-dependent assembler options
503 @emph{Target Xtensa options:}
504 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
505 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
506 [@b{--[no-]transform}]
507 [@b{--rename-section} @var{oldname}=@var{newname}]
512 @emph{Target Z80 options:}
513 [@b{-z80}] [@b{-r800}]
514 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
515 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
516 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
517 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
518 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
519 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
523 @c Z8000 has no machine-dependent assembler options
532 @include at-file.texi
535 Turn on listings, in any of a variety of ways:
539 omit false conditionals
542 omit debugging directives
545 include general information, like @value{AS} version and options passed
548 include high-level source
554 include macro expansions
557 omit forms processing
563 set the name of the listing file
566 You may combine these options; for example, use @samp{-aln} for assembly
567 listing without forms processing. The @samp{=file} option, if used, must be
568 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
571 Begin in alternate macro mode.
573 @xref{Altmacro,,@code{.altmacro}}.
576 @item --compress-debug-sections
577 Compress DWARF debug sections using zlib. The debug sections are renamed
578 to begin with @samp{.zdebug}, and the resulting object file may not be
579 compatible with older linkers and object file utilities.
581 @item --nocompress-debug-sections
582 Do not compress DWARF debug sections. This is the default.
585 Ignored. This option is accepted for script compatibility with calls to
588 @item --debug-prefix-map @var{old}=@var{new}
589 When assembling files in directory @file{@var{old}}, record debugging
590 information describing them as in @file{@var{new}} instead.
592 @item --defsym @var{sym}=@var{value}
593 Define the symbol @var{sym} to be @var{value} before assembling the input file.
594 @var{value} must be an integer constant. As in C, a leading @samp{0x}
595 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
596 value. The value of the symbol can be overridden inside a source file via the
597 use of a @code{.set} pseudo-op.
600 ``fast''---skip whitespace and comment preprocessing (assume source is
605 Generate debugging information for each assembler source line using whichever
606 debug format is preferred by the target. This currently means either STABS,
610 Generate stabs debugging information for each assembler line. This
611 may help debugging assembler code, if the debugger can handle it.
614 Generate stabs debugging information for each assembler line, with GNU
615 extensions that probably only gdb can handle, and that could make other
616 debuggers crash or refuse to read your program. This
617 may help debugging assembler code. Currently the only GNU extension is
618 the location of the current working directory at assembling time.
621 Generate DWARF2 debugging information for each assembler line. This
622 may help debugging assembler code, if the debugger can handle it. Note---this
623 option is only supported by some targets, not all of them.
625 @item --size-check=error
626 @itemx --size-check=warning
627 Issue an error or warning for invalid ELF .size directive.
630 Print a summary of the command line options and exit.
633 Print a summary of all target specific options and exit.
636 Add directory @var{dir} to the search list for @code{.include} directives.
639 Don't warn about signed overflow.
642 @ifclear DIFF-TBL-KLUGE
643 This option is accepted but has no effect on the @value{TARGET} family.
645 @ifset DIFF-TBL-KLUGE
646 Issue warnings when difference tables altered for long displacements.
651 Keep (in the symbol table) local symbols. These symbols start with
652 system-specific local label prefixes, typically @samp{.L} for ELF systems
653 or @samp{L} for traditional a.out systems.
658 @item --listing-lhs-width=@var{number}
659 Set the maximum width, in words, of the output data column for an assembler
660 listing to @var{number}.
662 @item --listing-lhs-width2=@var{number}
663 Set the maximum width, in words, of the output data column for continuation
664 lines in an assembler listing to @var{number}.
666 @item --listing-rhs-width=@var{number}
667 Set the maximum width of an input source line, as displayed in a listing, to
670 @item --listing-cont-lines=@var{number}
671 Set the maximum number of lines printed in a listing for a single line of input
674 @item -o @var{objfile}
675 Name the object-file output from @command{@value{AS}} @var{objfile}.
678 Fold the data section into the text section.
680 @kindex --hash-size=@var{number}
681 Set the default size of GAS's hash tables to a prime number close to
682 @var{number}. Increasing this value can reduce the length of time it takes the
683 assembler to perform its tasks, at the expense of increasing the assembler's
684 memory requirements. Similarly reducing this value can reduce the memory
685 requirements at the expense of speed.
687 @item --reduce-memory-overheads
688 This option reduces GAS's memory requirements, at the expense of making the
689 assembly processes slower. Currently this switch is a synonym for
690 @samp{--hash-size=4051}, but in the future it may have other effects as well.
693 Print the maximum space (in bytes) and total time (in seconds) used by
696 @item --strip-local-absolute
697 Remove local absolute symbols from the outgoing symbol table.
701 Print the @command{as} version.
704 Print the @command{as} version and exit.
708 Suppress warning messages.
710 @item --fatal-warnings
711 Treat warnings as errors.
714 Don't suppress warning messages or treat them as errors.
723 Generate an object file even after errors.
725 @item -- | @var{files} @dots{}
726 Standard input, or source files to assemble.
734 @xref{Alpha Options}, for the options available when @value{AS} is configured
735 for an Alpha processor.
740 The following options are available when @value{AS} is configured for an Alpha
744 @include c-alpha.texi
745 @c ended inside the included file
752 The following options are available when @value{AS} is configured for
757 This option selects the core processor variant.
759 Select either big-endian (-EB) or little-endian (-EL) output.
764 The following options are available when @value{AS} is configured for the ARM
768 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
769 Specify which ARM processor variant is the target.
770 @item -march=@var{architecture}[+@var{extension}@dots{}]
771 Specify which ARM architecture variant is used by the target.
772 @item -mfpu=@var{floating-point-format}
773 Select which Floating Point architecture is the target.
774 @item -mfloat-abi=@var{abi}
775 Select which floating point ABI is in use.
777 Enable Thumb only instruction decoding.
778 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
779 Select which procedure calling convention is in use.
781 Select either big-endian (-EB) or little-endian (-EL) output.
782 @item -mthumb-interwork
783 Specify that the code has been generated with interworking between Thumb and
786 Specify that PIC code has been generated.
794 @xref{Blackfin Options}, for the options available when @value{AS} is
795 configured for the Blackfin processor family.
800 The following options are available when @value{AS} is configured for
801 the Blackfin processor family.
805 @c ended inside the included file
812 See the info pages for documentation of the CRIS-specific options.
816 The following options are available when @value{AS} is configured for
819 @cindex D10V optimization
820 @cindex optimization, D10V
822 Optimize output by parallelizing instructions.
827 The following options are available when @value{AS} is configured for a D30V
830 @cindex D30V optimization
831 @cindex optimization, D30V
833 Optimize output by parallelizing instructions.
837 Warn when nops are generated.
839 @cindex D30V nops after 32-bit multiply
841 Warn when a nop after a 32-bit multiply instruction is generated.
849 @xref{i386-Options}, for the options available when @value{AS} is
850 configured for an i386 processor.
855 The following options are available when @value{AS} is configured for
860 @c ended inside the included file
867 The following options are available when @value{AS} is configured for the
868 Intel 80960 processor.
871 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
872 Specify which variant of the 960 architecture is the target.
875 Add code to collect statistics about branches taken.
878 Do not alter compare-and-branch instructions for long displacements;
885 The following options are available when @value{AS} is configured for the
891 Specifies that the extended IP2022 instructions are allowed.
894 Restores the default behaviour, which restricts the permitted instructions to
895 just the basic IP2022 ones.
901 The following options are available when @value{AS} is configured for the
902 Renesas M32C and M16C processors.
907 Assemble M32C instructions.
910 Assemble M16C instructions (the default).
913 Enable support for link-time relaxations.
916 Support H'00 style hex constants in addition to 0x00 style.
922 The following options are available when @value{AS} is configured for the
923 Renesas M32R (formerly Mitsubishi M32R) series.
928 Specify which processor in the M32R family is the target. The default
929 is normally the M32R, but this option changes it to the M32RX.
931 @item --warn-explicit-parallel-conflicts or --Wp
932 Produce warning messages when questionable parallel constructs are
935 @item --no-warn-explicit-parallel-conflicts or --Wnp
936 Do not produce warning messages when questionable parallel constructs are
943 The following options are available when @value{AS} is configured for the
944 Motorola 68000 series.
949 Shorten references to undefined symbols, to one word instead of two.
951 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
952 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
953 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
954 Specify what processor in the 68000 family is the target. The default
955 is normally the 68020, but this can be changed at configuration time.
957 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
958 The target machine does (or does not) have a floating-point coprocessor.
959 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
960 the basic 68000 is not compatible with the 68881, a combination of the
961 two can be specified, since it's possible to do emulation of the
962 coprocessor instructions with the main processor.
964 @item -m68851 | -mno-68851
965 The target machine does (or does not) have a memory-management
966 unit coprocessor. The default is to assume an MMU for 68020 and up.
973 For details about the PDP-11 machine dependent features options,
974 see @ref{PDP-11-Options}.
977 @item -mpic | -mno-pic
978 Generate position-independent (or position-dependent) code. The
979 default is @option{-mpic}.
982 @itemx -mall-extensions
983 Enable all instruction set extensions. This is the default.
985 @item -mno-extensions
986 Disable all instruction set extensions.
988 @item -m@var{extension} | -mno-@var{extension}
989 Enable (or disable) a particular instruction set extension.
992 Enable the instruction set extensions supported by a particular CPU, and
993 disable all other extensions.
995 @item -m@var{machine}
996 Enable the instruction set extensions supported by a particular machine
997 model, and disable all other extensions.
1003 The following options are available when @value{AS} is configured for
1004 a picoJava processor.
1008 @cindex PJ endianness
1009 @cindex endianness, PJ
1010 @cindex big endian output, PJ
1012 Generate ``big endian'' format output.
1014 @cindex little endian output, PJ
1016 Generate ``little endian'' format output.
1022 The following options are available when @value{AS} is configured for the
1023 Motorola 68HC11 or 68HC12 series.
1027 @item -m68hc11 | -m68hc12 | -m68hcs12
1028 Specify what processor is the target. The default is
1029 defined by the configuration option when building the assembler.
1032 Specify to use the 16-bit integer ABI.
1035 Specify to use the 32-bit integer ABI.
1037 @item -mshort-double
1038 Specify to use the 32-bit double ABI.
1041 Specify to use the 64-bit double ABI.
1043 @item --force-long-branches
1044 Relative branches are turned into absolute ones. This concerns
1045 conditional branches, unconditional branches and branches to a
1048 @item -S | --short-branches
1049 Do not turn relative branches into absolute ones
1050 when the offset is out of range.
1052 @item --strict-direct-mode
1053 Do not turn the direct addressing mode into extended addressing mode
1054 when the instruction does not support direct addressing mode.
1056 @item --print-insn-syntax
1057 Print the syntax of instruction in case of error.
1059 @item --print-opcodes
1060 print the list of instructions with syntax and then exit.
1062 @item --generate-example
1063 print an example of instruction for each possible instruction and then exit.
1064 This option is only useful for testing @command{@value{AS}}.
1070 The following options are available when @command{@value{AS}} is configured
1071 for the SPARC architecture:
1074 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1075 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1076 Explicitly select a variant of the SPARC architecture.
1078 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1079 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1081 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1082 UltraSPARC extensions.
1084 @item -xarch=v8plus | -xarch=v8plusa
1085 For compatibility with the Solaris v9 assembler. These options are
1086 equivalent to -Av8plus and -Av8plusa, respectively.
1089 Warn when the assembler switches to another architecture.
1094 The following options are available when @value{AS} is configured for the 'c54x
1099 Enable extended addressing mode. All addresses and relocations will assume
1100 extended addressing (usually 23 bits).
1101 @item -mcpu=@var{CPU_VERSION}
1102 Sets the CPU version being compiled for.
1103 @item -merrors-to-file @var{FILENAME}
1104 Redirect error output to a file, for broken systems which don't support such
1105 behaviour in the shell.
1110 The following options are available when @value{AS} is configured for
1111 a @sc{mips} processor.
1115 This option sets the largest size of an object that can be referenced
1116 implicitly with the @code{gp} register. It is only accepted for targets that
1117 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1119 @cindex MIPS endianness
1120 @cindex endianness, MIPS
1121 @cindex big endian output, MIPS
1123 Generate ``big endian'' format output.
1125 @cindex little endian output, MIPS
1127 Generate ``little endian'' format output.
1139 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1140 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1141 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1142 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1143 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1145 correspond to generic
1146 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1147 and @samp{MIPS64 Release 2}
1148 ISA processors, respectively.
1150 @item -march=@var{CPU}
1151 Generate code for a particular @sc{mips} cpu.
1153 @item -mtune=@var{cpu}
1154 Schedule and tune for a particular @sc{mips} cpu.
1158 Cause nops to be inserted if the read of the destination register
1159 of an mfhi or mflo instruction occurs in the following two instructions.
1163 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1164 section instead of the standard ELF .stabs sections.
1168 Control generation of @code{.pdr} sections.
1172 The register sizes are normally inferred from the ISA and ABI, but these
1173 flags force a certain group of registers to be treated as 32 bits wide at
1174 all times. @samp{-mgp32} controls the size of general-purpose registers
1175 and @samp{-mfp32} controls the size of floating-point registers.
1179 Generate code for the MIPS 16 processor. This is equivalent to putting
1180 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1181 turns off this option.
1184 @itemx -mno-micromips
1185 Generate code for the microMIPS processor. This is equivalent to putting
1186 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1187 turns off this option. This is equivalent to putting @code{.set nomicromips}
1188 at the start of the assembly file.
1191 @itemx -mno-smartmips
1192 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1193 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1194 @samp{-mno-smartmips} turns off this option.
1198 Generate code for the MIPS-3D Application Specific Extension.
1199 This tells the assembler to accept MIPS-3D instructions.
1200 @samp{-no-mips3d} turns off this option.
1204 Generate code for the MDMX Application Specific Extension.
1205 This tells the assembler to accept MDMX instructions.
1206 @samp{-no-mdmx} turns off this option.
1210 Generate code for the DSP Release 1 Application Specific Extension.
1211 This tells the assembler to accept DSP Release 1 instructions.
1212 @samp{-mno-dsp} turns off this option.
1216 Generate code for the DSP Release 2 Application Specific Extension.
1217 This option implies -mdsp.
1218 This tells the assembler to accept DSP Release 2 instructions.
1219 @samp{-mno-dspr2} turns off this option.
1223 Generate code for the MT Application Specific Extension.
1224 This tells the assembler to accept MT instructions.
1225 @samp{-mno-mt} turns off this option.
1229 Generate code for the MCU Application Specific Extension.
1230 This tells the assembler to accept MCU instructions.
1231 @samp{-mno-mcu} turns off this option.
1233 @item --construct-floats
1234 @itemx --no-construct-floats
1235 The @samp{--no-construct-floats} option disables the construction of
1236 double width floating point constants by loading the two halves of the
1237 value into the two single width floating point registers that make up
1238 the double width register. By default @samp{--construct-floats} is
1239 selected, allowing construction of these floating point constants.
1242 @item --emulation=@var{name}
1243 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1244 for some other target, in all respects, including output format (choosing
1245 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1246 debugging information or store symbol table information, and default
1247 endianness. The available configuration names are: @samp{mipsecoff},
1248 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1249 @samp{mipsbelf}. The first two do not alter the default endianness from that
1250 of the primary target for which the assembler was configured; the others change
1251 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1252 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1253 selection in any case.
1255 This option is currently supported only when the primary target
1256 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1257 Furthermore, the primary target or others specified with
1258 @samp{--enable-targets=@dots{}} at configuration time must include support for
1259 the other format, if both are to be available. For example, the Irix 5
1260 configuration includes support for both.
1262 Eventually, this option will support more configurations, with more
1263 fine-grained control over the assembler's behavior, and will be supported for
1267 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1274 Control how to deal with multiplication overflow and division by zero.
1275 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1276 (and only work for Instruction Set Architecture level 2 and higher);
1277 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1281 When this option is used, @command{@value{AS}} will issue a warning every
1282 time it generates a nop instruction from a macro.
1287 The following options are available when @value{AS} is configured for
1293 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1294 The command line option @samp{-nojsri2bsr} can be used to disable it.
1298 Enable or disable the silicon filter behaviour. By default this is disabled.
1299 The default can be overridden by the @samp{-sifilter} command line option.
1302 Alter jump instructions for long displacements.
1304 @item -mcpu=[210|340]
1305 Select the cpu type on the target hardware. This controls which instructions
1309 Assemble for a big endian target.
1312 Assemble for a little endian target.
1318 See the info pages for documentation of the MMIX-specific options.
1325 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1326 for a PowerPC processor.
1330 @c man begin OPTIONS
1331 The following options are available when @value{AS} is configured for a
1334 @c man begin INCLUDE
1336 @c ended inside the included file
1341 @c man begin OPTIONS
1343 See the info pages for documentation of the RX-specific options.
1347 The following options are available when @value{AS} is configured for the s390
1353 Select the word size, either 31/32 bits or 64 bits.
1356 Select the architecture mode, either the Enterprise System
1357 Architecture (esa) or the z/Architecture mode (zarch).
1358 @item -march=@var{processor}
1359 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1360 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1362 @itemx -mno-regnames
1363 Allow or disallow symbolic names for registers.
1364 @item -mwarn-areg-zero
1365 Warn whenever the operand for a base or index register has been specified
1366 but evaluates to zero.
1374 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1375 for a TMS320C6000 processor.
1379 @c man begin OPTIONS
1380 The following options are available when @value{AS} is configured for a
1381 TMS320C6000 processor.
1383 @c man begin INCLUDE
1384 @include c-tic6x.texi
1385 @c ended inside the included file
1393 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1394 for a TILE-Gx processor.
1398 @c man begin OPTIONS
1399 The following options are available when @value{AS} is configured for a TILE-Gx
1402 @c man begin INCLUDE
1403 @include c-tilegx.texi
1404 @c ended inside the included file
1412 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1413 for an Xtensa processor.
1417 @c man begin OPTIONS
1418 The following options are available when @value{AS} is configured for an
1421 @c man begin INCLUDE
1422 @include c-xtensa.texi
1423 @c ended inside the included file
1428 @c man begin OPTIONS
1431 The following options are available when @value{AS} is configured for
1432 a Z80 family processor.
1435 Assemble for Z80 processor.
1437 Assemble for R800 processor.
1438 @item -ignore-undocumented-instructions
1440 Assemble undocumented Z80 instructions that also work on R800 without warning.
1441 @item -ignore-unportable-instructions
1443 Assemble all undocumented Z80 instructions without warning.
1444 @item -warn-undocumented-instructions
1446 Issue a warning for undocumented Z80 instructions that also work on R800.
1447 @item -warn-unportable-instructions
1449 Issue a warning for undocumented Z80 instructions that do not work on R800.
1450 @item -forbid-undocumented-instructions
1452 Treat all undocumented instructions as errors.
1453 @item -forbid-unportable-instructions
1455 Treat undocumented Z80 instructions that do not work on R800 as errors.
1462 * Manual:: Structure of this Manual
1463 * GNU Assembler:: The GNU Assembler
1464 * Object Formats:: Object File Formats
1465 * Command Line:: Command Line
1466 * Input Files:: Input Files
1467 * Object:: Output (Object) File
1468 * Errors:: Error and Warning Messages
1472 @section Structure of this Manual
1474 @cindex manual, structure and purpose
1475 This manual is intended to describe what you need to know to use
1476 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1477 notation for symbols, constants, and expressions; the directives that
1478 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1481 We also cover special features in the @value{TARGET}
1482 configuration of @command{@value{AS}}, including assembler directives.
1485 This manual also describes some of the machine-dependent features of
1486 various flavors of the assembler.
1489 @cindex machine instructions (not covered)
1490 On the other hand, this manual is @emph{not} intended as an introduction
1491 to programming in assembly language---let alone programming in general!
1492 In a similar vein, we make no attempt to introduce the machine
1493 architecture; we do @emph{not} describe the instruction set, standard
1494 mnemonics, registers or addressing modes that are standard to a
1495 particular architecture.
1497 You may want to consult the manufacturer's
1498 machine architecture manual for this information.
1502 For information on the H8/300 machine instruction set, see @cite{H8/300
1503 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1504 Programming Manual} (Renesas).
1507 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1508 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1509 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1510 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1513 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1517 @c I think this is premature---doc@cygnus.com, 17jan1991
1519 Throughout this manual, we assume that you are running @dfn{GNU},
1520 the portable operating system from the @dfn{Free Software
1521 Foundation, Inc.}. This restricts our attention to certain kinds of
1522 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1523 once this assumption is granted examples and definitions need less
1526 @command{@value{AS}} is part of a team of programs that turn a high-level
1527 human-readable series of instructions into a low-level
1528 computer-readable series of instructions. Different versions of
1529 @command{@value{AS}} are used for different kinds of computer.
1532 @c There used to be a section "Terminology" here, which defined
1533 @c "contents", "byte", "word", and "long". Defining "word" to any
1534 @c particular size is confusing when the .word directive may generate 16
1535 @c bits on one machine and 32 bits on another; in general, for the user
1536 @c version of this manual, none of these terms seem essential to define.
1537 @c They were used very little even in the former draft of the manual;
1538 @c this draft makes an effort to avoid them (except in names of
1542 @section The GNU Assembler
1544 @c man begin DESCRIPTION
1546 @sc{gnu} @command{as} is really a family of assemblers.
1548 This manual describes @command{@value{AS}}, a member of that family which is
1549 configured for the @value{TARGET} architectures.
1551 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1552 should find a fairly similar environment when you use it on another
1553 architecture. Each version has much in common with the others,
1554 including object file formats, most assembler directives (often called
1555 @dfn{pseudo-ops}) and assembler syntax.@refill
1557 @cindex purpose of @sc{gnu} assembler
1558 @command{@value{AS}} is primarily intended to assemble the output of the
1559 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1560 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1561 assemble correctly everything that other assemblers for the same
1562 machine would assemble.
1564 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1567 @c This remark should appear in generic version of manual; assumption
1568 @c here is that generic version sets M680x0.
1569 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1570 assembler for the same architecture; for example, we know of several
1571 incompatible versions of 680x0 assembly language syntax.
1576 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1577 program in one pass of the source file. This has a subtle impact on the
1578 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1580 @node Object Formats
1581 @section Object File Formats
1583 @cindex object file format
1584 The @sc{gnu} assembler can be configured to produce several alternative
1585 object file formats. For the most part, this does not affect how you
1586 write assembly language programs; but directives for debugging symbols
1587 are typically different in different file formats. @xref{Symbol
1588 Attributes,,Symbol Attributes}.
1591 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1592 @value{OBJ-NAME} format object files.
1594 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1596 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1597 @code{b.out} or COFF format object files.
1600 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1601 SOM or ELF format object files.
1606 @section Command Line
1608 @cindex command line conventions
1610 After the program name @command{@value{AS}}, the command line may contain
1611 options and file names. Options may appear in any order, and may be
1612 before, after, or between file names. The order of file names is
1615 @cindex standard input, as input file
1617 @file{--} (two hyphens) by itself names the standard input file
1618 explicitly, as one of the files for @command{@value{AS}} to assemble.
1620 @cindex options, command line
1621 Except for @samp{--} any command line argument that begins with a
1622 hyphen (@samp{-}) is an option. Each option changes the behavior of
1623 @command{@value{AS}}. No option changes the way another option works. An
1624 option is a @samp{-} followed by one or more letters; the case of
1625 the letter is important. All options are optional.
1627 Some options expect exactly one file name to follow them. The file
1628 name may either immediately follow the option's letter (compatible
1629 with older assemblers) or it may be the next command argument (@sc{gnu}
1630 standard). These two command lines are equivalent:
1633 @value{AS} -o my-object-file.o mumble.s
1634 @value{AS} -omy-object-file.o mumble.s
1638 @section Input Files
1641 @cindex source program
1642 @cindex files, input
1643 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1644 describe the program input to one run of @command{@value{AS}}. The program may
1645 be in one or more files; how the source is partitioned into files
1646 doesn't change the meaning of the source.
1648 @c I added "con" prefix to "catenation" just to prove I can overcome my
1649 @c APL training... doc@cygnus.com
1650 The source program is a concatenation of the text in all the files, in the
1653 @c man begin DESCRIPTION
1654 Each time you run @command{@value{AS}} it assembles exactly one source
1655 program. The source program is made up of one or more files.
1656 (The standard input is also a file.)
1658 You give @command{@value{AS}} a command line that has zero or more input file
1659 names. The input files are read (from left file name to right). A
1660 command line argument (in any position) that has no special meaning
1661 is taken to be an input file name.
1663 If you give @command{@value{AS}} no file names it attempts to read one input file
1664 from the @command{@value{AS}} standard input, which is normally your terminal. You
1665 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1668 Use @samp{--} if you need to explicitly name the standard input file
1669 in your command line.
1671 If the source is empty, @command{@value{AS}} produces a small, empty object
1676 @subheading Filenames and Line-numbers
1678 @cindex input file linenumbers
1679 @cindex line numbers, in input files
1680 There are two ways of locating a line in the input file (or files) and
1681 either may be used in reporting error messages. One way refers to a line
1682 number in a physical file; the other refers to a line number in a
1683 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1685 @dfn{Physical files} are those files named in the command line given
1686 to @command{@value{AS}}.
1688 @dfn{Logical files} are simply names declared explicitly by assembler
1689 directives; they bear no relation to physical files. Logical file names help
1690 error messages reflect the original source file, when @command{@value{AS}} source
1691 is itself synthesized from other files. @command{@value{AS}} understands the
1692 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1693 @ref{File,,@code{.file}}.
1696 @section Output (Object) File
1702 Every time you run @command{@value{AS}} it produces an output file, which is
1703 your assembly language program translated into numbers. This file
1704 is the object file. Its default name is
1712 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1714 You can give it another name by using the @option{-o} option. Conventionally,
1715 object file names end with @file{.o}. The default name is used for historical
1716 reasons: older assemblers were capable of assembling self-contained programs
1717 directly into a runnable program. (For some formats, this isn't currently
1718 possible, but it can be done for the @code{a.out} format.)
1722 The object file is meant for input to the linker @code{@value{LD}}. It contains
1723 assembled program code, information to help @code{@value{LD}} integrate
1724 the assembled program into a runnable file, and (optionally) symbolic
1725 information for the debugger.
1727 @c link above to some info file(s) like the description of a.out.
1728 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1731 @section Error and Warning Messages
1733 @c man begin DESCRIPTION
1735 @cindex error messages
1736 @cindex warning messages
1737 @cindex messages from assembler
1738 @command{@value{AS}} may write warnings and error messages to the standard error
1739 file (usually your terminal). This should not happen when a compiler
1740 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1741 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1742 grave problem that stops the assembly.
1746 @cindex format of warning messages
1747 Warning messages have the format
1750 file_name:@b{NNN}:Warning Message Text
1754 @cindex line numbers, in warnings/errors
1755 (where @b{NNN} is a line number). If a logical file name has been given
1756 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1757 the current input file is used. If a logical line number was given
1759 (@pxref{Line,,@code{.line}})
1761 then it is used to calculate the number printed,
1762 otherwise the actual line in the current source file is printed. The
1763 message text is intended to be self explanatory (in the grand Unix
1766 @cindex format of error messages
1767 Error messages have the format
1769 file_name:@b{NNN}:FATAL:Error Message Text
1771 The file name and line number are derived as for warning
1772 messages. The actual message text may be rather less explanatory
1773 because many of them aren't supposed to happen.
1776 @chapter Command-Line Options
1778 @cindex options, all versions of assembler
1779 This chapter describes command-line options available in @emph{all}
1780 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1781 for options specific
1783 to the @value{TARGET} target.
1786 to particular machine architectures.
1789 @c man begin DESCRIPTION
1791 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1792 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1793 The assembler arguments must be separated from each other (and the @samp{-Wa})
1794 by commas. For example:
1797 gcc -c -g -O -Wa,-alh,-L file.c
1801 This passes two options to the assembler: @samp{-alh} (emit a listing to
1802 standard output with high-level and assembly source) and @samp{-L} (retain
1803 local symbols in the symbol table).
1805 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1806 command-line options are automatically passed to the assembler by the compiler.
1807 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1808 precisely what options it passes to each compilation pass, including the
1814 * a:: -a[cdghlns] enable listings
1815 * alternate:: --alternate enable alternate macro syntax
1816 * D:: -D for compatibility
1817 * f:: -f to work faster
1818 * I:: -I for .include search path
1819 @ifclear DIFF-TBL-KLUGE
1820 * K:: -K for compatibility
1822 @ifset DIFF-TBL-KLUGE
1823 * K:: -K for difference tables
1826 * L:: -L to retain local symbols
1827 * listing:: --listing-XXX to configure listing output
1828 * M:: -M or --mri to assemble in MRI compatibility mode
1829 * MD:: --MD for dependency tracking
1830 * o:: -o to name the object file
1831 * R:: -R to join data and text sections
1832 * statistics:: --statistics to see statistics about assembly
1833 * traditional-format:: --traditional-format for compatible output
1834 * v:: -v to announce version
1835 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1836 * Z:: -Z to make object file even after errors
1840 @section Enable Listings: @option{-a[cdghlns]}
1850 @cindex listings, enabling
1851 @cindex assembly listings, enabling
1853 These options enable listing output from the assembler. By itself,
1854 @samp{-a} requests high-level, assembly, and symbols listing.
1855 You can use other letters to select specific options for the list:
1856 @samp{-ah} requests a high-level language listing,
1857 @samp{-al} requests an output-program assembly listing, and
1858 @samp{-as} requests a symbol table listing.
1859 High-level listings require that a compiler debugging option like
1860 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1863 Use the @samp{-ag} option to print a first section with general assembly
1864 information, like @value{AS} version, switches passed, or time stamp.
1866 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1867 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1868 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1869 omitted from the listing.
1871 Use the @samp{-ad} option to omit debugging directives from the
1874 Once you have specified one of these options, you can further control
1875 listing output and its appearance using the directives @code{.list},
1876 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1878 The @samp{-an} option turns off all forms processing.
1879 If you do not request listing output with one of the @samp{-a} options, the
1880 listing-control directives have no effect.
1882 The letters after @samp{-a} may be combined into one option,
1883 @emph{e.g.}, @samp{-aln}.
1885 Note if the assembler source is coming from the standard input (e.g.,
1887 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1888 is being used) then the listing will not contain any comments or preprocessor
1889 directives. This is because the listing code buffers input source lines from
1890 stdin only after they have been preprocessed by the assembler. This reduces
1891 memory usage and makes the code more efficient.
1894 @section @option{--alternate}
1897 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1900 @section @option{-D}
1903 This option has no effect whatsoever, but it is accepted to make it more
1904 likely that scripts written for other assemblers also work with
1905 @command{@value{AS}}.
1908 @section Work Faster: @option{-f}
1911 @cindex trusted compiler
1912 @cindex faster processing (@option{-f})
1913 @samp{-f} should only be used when assembling programs written by a
1914 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1915 and comment preprocessing on
1916 the input file(s) before assembling them. @xref{Preprocessing,
1920 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1921 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1926 @section @code{.include} Search Path: @option{-I} @var{path}
1928 @kindex -I @var{path}
1929 @cindex paths for @code{.include}
1930 @cindex search path for @code{.include}
1931 @cindex @code{include} directive search path
1932 Use this option to add a @var{path} to the list of directories
1933 @command{@value{AS}} searches for files specified in @code{.include}
1934 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1935 many times as necessary to include a variety of paths. The current
1936 working directory is always searched first; after that, @command{@value{AS}}
1937 searches any @samp{-I} directories in the same order as they were
1938 specified (left to right) on the command line.
1941 @section Difference Tables: @option{-K}
1944 @ifclear DIFF-TBL-KLUGE
1945 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1946 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1947 where it can be used to warn when the assembler alters the machine code
1948 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1949 family does not have the addressing limitations that sometimes lead to this
1950 alteration on other platforms.
1953 @ifset DIFF-TBL-KLUGE
1954 @cindex difference tables, warning
1955 @cindex warning for altered difference tables
1956 @command{@value{AS}} sometimes alters the code emitted for directives of the
1957 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1958 You can use the @samp{-K} option if you want a warning issued when this
1963 @section Include Local Symbols: @option{-L}
1966 @cindex local symbols, retaining in output
1967 Symbols beginning with system-specific local label prefixes, typically
1968 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1969 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1970 such symbols when debugging, because they are intended for the use of
1971 programs (like compilers) that compose assembler programs, not for your
1972 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1973 such symbols, so you do not normally debug with them.
1975 This option tells @command{@value{AS}} to retain those local symbols
1976 in the object file. Usually if you do this you also tell the linker
1977 @code{@value{LD}} to preserve those symbols.
1980 @section Configuring listing output: @option{--listing}
1982 The listing feature of the assembler can be enabled via the command line switch
1983 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1984 hex dump of the corresponding locations in the output object file, and displays
1985 them as a listing file. The format of this listing can be controlled by
1986 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1987 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1988 @code{.psize} (@pxref{Psize}), and
1989 @code{.eject} (@pxref{Eject}) and also by the following switches:
1992 @item --listing-lhs-width=@samp{number}
1993 @kindex --listing-lhs-width
1994 @cindex Width of first line disassembly output
1995 Sets the maximum width, in words, of the first line of the hex byte dump. This
1996 dump appears on the left hand side of the listing output.
1998 @item --listing-lhs-width2=@samp{number}
1999 @kindex --listing-lhs-width2
2000 @cindex Width of continuation lines of disassembly output
2001 Sets the maximum width, in words, of any further lines of the hex byte dump for
2002 a given input source line. If this value is not specified, it defaults to being
2003 the same as the value specified for @samp{--listing-lhs-width}. If neither
2004 switch is used the default is to one.
2006 @item --listing-rhs-width=@samp{number}
2007 @kindex --listing-rhs-width
2008 @cindex Width of source line output
2009 Sets the maximum width, in characters, of the source line that is displayed
2010 alongside the hex dump. The default value for this parameter is 100. The
2011 source line is displayed on the right hand side of the listing output.
2013 @item --listing-cont-lines=@samp{number}
2014 @kindex --listing-cont-lines
2015 @cindex Maximum number of continuation lines
2016 Sets the maximum number of continuation lines of hex dump that will be
2017 displayed for a given single line of source input. The default value is 4.
2021 @section Assemble in MRI Compatibility Mode: @option{-M}
2024 @cindex MRI compatibility mode
2025 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2026 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2027 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2028 configured target) assembler from Microtec Research. The exact nature of the
2029 MRI syntax will not be documented here; see the MRI manuals for more
2030 information. Note in particular that the handling of macros and macro
2031 arguments is somewhat different. The purpose of this option is to permit
2032 assembling existing MRI assembler code using @command{@value{AS}}.
2034 The MRI compatibility is not complete. Certain operations of the MRI assembler
2035 depend upon its object file format, and can not be supported using other object
2036 file formats. Supporting these would require enhancing each object file format
2037 individually. These are:
2040 @item global symbols in common section
2042 The m68k MRI assembler supports common sections which are merged by the linker.
2043 Other object file formats do not support this. @command{@value{AS}} handles
2044 common sections by treating them as a single common symbol. It permits local
2045 symbols to be defined within a common section, but it can not support global
2046 symbols, since it has no way to describe them.
2048 @item complex relocations
2050 The MRI assemblers support relocations against a negated section address, and
2051 relocations which combine the start addresses of two or more sections. These
2052 are not support by other object file formats.
2054 @item @code{END} pseudo-op specifying start address
2056 The MRI @code{END} pseudo-op permits the specification of a start address.
2057 This is not supported by other object file formats. The start address may
2058 instead be specified using the @option{-e} option to the linker, or in a linker
2061 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2063 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2064 name to the output file. This is not supported by other object file formats.
2066 @item @code{ORG} pseudo-op
2068 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2069 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2070 which changes the location within the current section. Absolute sections are
2071 not supported by other object file formats. The address of a section may be
2072 assigned within a linker script.
2075 There are some other features of the MRI assembler which are not supported by
2076 @command{@value{AS}}, typically either because they are difficult or because they
2077 seem of little consequence. Some of these may be supported in future releases.
2081 @item EBCDIC strings
2083 EBCDIC strings are not supported.
2085 @item packed binary coded decimal
2087 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2088 and @code{DCB.P} pseudo-ops are not supported.
2090 @item @code{FEQU} pseudo-op
2092 The m68k @code{FEQU} pseudo-op is not supported.
2094 @item @code{NOOBJ} pseudo-op
2096 The m68k @code{NOOBJ} pseudo-op is not supported.
2098 @item @code{OPT} branch control options
2100 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2101 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2102 relaxes all branches, whether forward or backward, to an appropriate size, so
2103 these options serve no purpose.
2105 @item @code{OPT} list control options
2107 The following m68k @code{OPT} list control options are ignored: @code{C},
2108 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2109 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2111 @item other @code{OPT} options
2113 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2114 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2116 @item @code{OPT} @code{D} option is default
2118 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2119 @code{OPT NOD} may be used to turn it off.
2121 @item @code{XREF} pseudo-op.
2123 The m68k @code{XREF} pseudo-op is ignored.
2125 @item @code{.debug} pseudo-op
2127 The i960 @code{.debug} pseudo-op is not supported.
2129 @item @code{.extended} pseudo-op
2131 The i960 @code{.extended} pseudo-op is not supported.
2133 @item @code{.list} pseudo-op.
2135 The various options of the i960 @code{.list} pseudo-op are not supported.
2137 @item @code{.optimize} pseudo-op
2139 The i960 @code{.optimize} pseudo-op is not supported.
2141 @item @code{.output} pseudo-op
2143 The i960 @code{.output} pseudo-op is not supported.
2145 @item @code{.setreal} pseudo-op
2147 The i960 @code{.setreal} pseudo-op is not supported.
2152 @section Dependency Tracking: @option{--MD}
2155 @cindex dependency tracking
2158 @command{@value{AS}} can generate a dependency file for the file it creates. This
2159 file consists of a single rule suitable for @code{make} describing the
2160 dependencies of the main source file.
2162 The rule is written to the file named in its argument.
2164 This feature is used in the automatic updating of makefiles.
2167 @section Name the Object File: @option{-o}
2170 @cindex naming object file
2171 @cindex object file name
2172 There is always one object file output when you run @command{@value{AS}}. By
2173 default it has the name
2176 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2190 You use this option (which takes exactly one filename) to give the
2191 object file a different name.
2193 Whatever the object file is called, @command{@value{AS}} overwrites any
2194 existing file of the same name.
2197 @section Join Data and Text Sections: @option{-R}
2200 @cindex data and text sections, joining
2201 @cindex text and data sections, joining
2202 @cindex joining text and data sections
2203 @cindex merging text and data sections
2204 @option{-R} tells @command{@value{AS}} to write the object file as if all
2205 data-section data lives in the text section. This is only done at
2206 the very last moment: your binary data are the same, but data
2207 section parts are relocated differently. The data section part of
2208 your object file is zero bytes long because all its bytes are
2209 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2211 When you specify @option{-R} it would be possible to generate shorter
2212 address displacements (because we do not have to cross between text and
2213 data section). We refrain from doing this simply for compatibility with
2214 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2217 When @command{@value{AS}} is configured for COFF or ELF output,
2218 this option is only useful if you use sections named @samp{.text} and
2223 @option{-R} is not supported for any of the HPPA targets. Using
2224 @option{-R} generates a warning from @command{@value{AS}}.
2228 @section Display Assembly Statistics: @option{--statistics}
2230 @kindex --statistics
2231 @cindex statistics, about assembly
2232 @cindex time, total for assembly
2233 @cindex space used, maximum for assembly
2234 Use @samp{--statistics} to display two statistics about the resources used by
2235 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2236 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2239 @node traditional-format
2240 @section Compatible Output: @option{--traditional-format}
2242 @kindex --traditional-format
2243 For some targets, the output of @command{@value{AS}} is different in some ways
2244 from the output of some existing assembler. This switch requests
2245 @command{@value{AS}} to use the traditional format instead.
2247 For example, it disables the exception frame optimizations which
2248 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2251 @section Announce Version: @option{-v}
2255 @cindex assembler version
2256 @cindex version of assembler
2257 You can find out what version of as is running by including the
2258 option @samp{-v} (which you can also spell as @samp{-version}) on the
2262 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2264 @command{@value{AS}} should never give a warning or error message when
2265 assembling compiler output. But programs written by people often
2266 cause @command{@value{AS}} to give a warning that a particular assumption was
2267 made. All such warnings are directed to the standard error file.
2271 @cindex suppressing warnings
2272 @cindex warnings, suppressing
2273 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2274 This only affects the warning messages: it does not change any particular of
2275 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2278 @kindex --fatal-warnings
2279 @cindex errors, caused by warnings
2280 @cindex warnings, causing error
2281 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2282 files that generate warnings to be in error.
2285 @cindex warnings, switching on
2286 You can switch these options off again by specifying @option{--warn}, which
2287 causes warnings to be output as usual.
2290 @section Generate Object File in Spite of Errors: @option{-Z}
2291 @cindex object file, after errors
2292 @cindex errors, continuing after
2293 After an error message, @command{@value{AS}} normally produces no output. If for
2294 some reason you are interested in object file output even after
2295 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2296 option. If there are any errors, @command{@value{AS}} continues anyways, and
2297 writes an object file after a final warning message of the form @samp{@var{n}
2298 errors, @var{m} warnings, generating bad object file.}
2303 @cindex machine-independent syntax
2304 @cindex syntax, machine-independent
2305 This chapter describes the machine-independent syntax allowed in a
2306 source file. @command{@value{AS}} syntax is similar to what many other
2307 assemblers use; it is inspired by the BSD 4.2
2312 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2316 * Preprocessing:: Preprocessing
2317 * Whitespace:: Whitespace
2318 * Comments:: Comments
2319 * Symbol Intro:: Symbols
2320 * Statements:: Statements
2321 * Constants:: Constants
2325 @section Preprocessing
2327 @cindex preprocessing
2328 The @command{@value{AS}} internal preprocessor:
2330 @cindex whitespace, removed by preprocessor
2332 adjusts and removes extra whitespace. It leaves one space or tab before
2333 the keywords on a line, and turns any other whitespace on the line into
2336 @cindex comments, removed by preprocessor
2338 removes all comments, replacing them with a single space, or an
2339 appropriate number of newlines.
2341 @cindex constants, converted by preprocessor
2343 converts character constants into the appropriate numeric values.
2346 It does not do macro processing, include file handling, or
2347 anything else you may get from your C compiler's preprocessor. You can
2348 do include file processing with the @code{.include} directive
2349 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2350 to get other ``CPP'' style preprocessing by giving the input file a
2351 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2352 Output, gcc.info, Using GNU CC}.
2354 Excess whitespace, comments, and character constants
2355 cannot be used in the portions of the input text that are not
2358 @cindex turning preprocessing on and off
2359 @cindex preprocessing, turning on and off
2362 If the first line of an input file is @code{#NO_APP} or if you use the
2363 @samp{-f} option, whitespace and comments are not removed from the input file.
2364 Within an input file, you can ask for whitespace and comment removal in
2365 specific portions of the by putting a line that says @code{#APP} before the
2366 text that may contain whitespace or comments, and putting a line that says
2367 @code{#NO_APP} after this text. This feature is mainly intend to support
2368 @code{asm} statements in compilers whose output is otherwise free of comments
2375 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2376 Whitespace is used to separate symbols, and to make programs neater for
2377 people to read. Unless within character constants
2378 (@pxref{Characters,,Character Constants}), any whitespace means the same
2379 as exactly one space.
2385 There are two ways of rendering comments to @command{@value{AS}}. In both
2386 cases the comment is equivalent to one space.
2388 Anything from @samp{/*} through the next @samp{*/} is a comment.
2389 This means you may not nest these comments.
2393 The only way to include a newline ('\n') in a comment
2394 is to use this sort of comment.
2397 /* This sort of comment does not nest. */
2400 @cindex line comment character
2401 Anything from a @dfn{line comment} character up to the next newline is
2402 considered a comment and is ignored. The line comment character is target
2403 specific, and some targets multiple comment characters. Some targets also have
2404 line comment characters that only work if they are the first character on a
2405 line. Some targets use a sequence of two characters to introduce a line
2406 comment. Some targets can also change their line comment characters depending
2407 upon command line options that have been used. For more details see the
2408 @emph{Syntax} section in the documentation for individual targets.
2410 If the line comment character is the hash sign (@samp{#}) then it still has the
2411 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2412 to specify logical line numbers:
2415 @cindex lines starting with @code{#}
2416 @cindex logical line numbers
2417 To be compatible with past assemblers, lines that begin with @samp{#} have a
2418 special interpretation. Following the @samp{#} should be an absolute
2419 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2420 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2421 new logical file name. The rest of the line, if any, should be whitespace.
2423 If the first non-whitespace characters on the line are not numeric,
2424 the line is ignored. (Just like a comment.)
2427 # This is an ordinary comment.
2428 # 42-6 "new_file_name" # New logical file name
2429 # This is logical line # 36.
2431 This feature is deprecated, and may disappear from future versions
2432 of @command{@value{AS}}.
2437 @cindex characters used in symbols
2438 @ifclear SPECIAL-SYMS
2439 A @dfn{symbol} is one or more characters chosen from the set of all
2440 letters (both upper and lower case), digits and the three characters
2446 A @dfn{symbol} is one or more characters chosen from the set of all
2447 letters (both upper and lower case), digits and the three characters
2448 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2454 On most machines, you can also use @code{$} in symbol names; exceptions
2455 are noted in @ref{Machine Dependencies}.
2457 No symbol may begin with a digit. Case is significant.
2458 There is no length limit: all characters are significant. Symbols are
2459 delimited by characters not in that set, or by the beginning of a file
2460 (since the source program must end with a newline, the end of a file is
2461 not a possible symbol delimiter). @xref{Symbols}.
2462 @cindex length of symbols
2467 @cindex statements, structure of
2468 @cindex line separator character
2469 @cindex statement separator character
2471 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2472 @dfn{line separator character}. The line separator character is target
2473 specific and described in the @emph{Syntax} section of each
2474 target's documentation. Not all targets support a line separator character.
2475 The newline or line separator character is considered to be part of the
2476 preceding statement. Newlines and separators within character constants are an
2477 exception: they do not end statements.
2479 @cindex newline, required at file end
2480 @cindex EOF, newline must precede
2481 It is an error to end any statement with end-of-file: the last
2482 character of any input file should be a newline.@refill
2484 An empty statement is allowed, and may include whitespace. It is ignored.
2486 @cindex instructions and directives
2487 @cindex directives and instructions
2488 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2489 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2491 A statement begins with zero or more labels, optionally followed by a
2492 key symbol which determines what kind of statement it is. The key
2493 symbol determines the syntax of the rest of the statement. If the
2494 symbol begins with a dot @samp{.} then the statement is an assembler
2495 directive: typically valid for any computer. If the symbol begins with
2496 a letter the statement is an assembly language @dfn{instruction}: it
2497 assembles into a machine language instruction.
2499 Different versions of @command{@value{AS}} for different computers
2500 recognize different instructions. In fact, the same symbol may
2501 represent a different instruction in a different computer's assembly
2505 @cindex @code{:} (label)
2506 @cindex label (@code{:})
2507 A label is a symbol immediately followed by a colon (@code{:}).
2508 Whitespace before a label or after a colon is permitted, but you may not
2509 have whitespace between a label's symbol and its colon. @xref{Labels}.
2512 For HPPA targets, labels need not be immediately followed by a colon, but
2513 the definition of a label must begin in column zero. This also implies that
2514 only one label may be defined on each line.
2518 label: .directive followed by something
2519 another_label: # This is an empty statement.
2520 instruction operand_1, operand_2, @dots{}
2527 A constant is a number, written so that its value is known by
2528 inspection, without knowing any context. Like this:
2531 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2532 .ascii "Ring the bell\7" # A string constant.
2533 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2534 .float 0f-314159265358979323846264338327\
2535 95028841971.693993751E-40 # - pi, a flonum.
2540 * Characters:: Character Constants
2541 * Numbers:: Number Constants
2545 @subsection Character Constants
2547 @cindex character constants
2548 @cindex constants, character
2549 There are two kinds of character constants. A @dfn{character} stands
2550 for one character in one byte and its value may be used in
2551 numeric expressions. String constants (properly called string
2552 @emph{literals}) are potentially many bytes and their values may not be
2553 used in arithmetic expressions.
2557 * Chars:: Characters
2561 @subsubsection Strings
2563 @cindex string constants
2564 @cindex constants, string
2565 A @dfn{string} is written between double-quotes. It may contain
2566 double-quotes or null characters. The way to get special characters
2567 into a string is to @dfn{escape} these characters: precede them with
2568 a backslash @samp{\} character. For example @samp{\\} represents
2569 one backslash: the first @code{\} is an escape which tells
2570 @command{@value{AS}} to interpret the second character literally as a backslash
2571 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2572 escape character). The complete list of escapes follows.
2574 @cindex escape codes, character
2575 @cindex character escape codes
2578 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2580 @cindex @code{\b} (backspace character)
2581 @cindex backspace (@code{\b})
2583 Mnemonic for backspace; for ASCII this is octal code 010.
2586 @c Mnemonic for EOText; for ASCII this is octal code 004.
2588 @cindex @code{\f} (formfeed character)
2589 @cindex formfeed (@code{\f})
2591 Mnemonic for FormFeed; for ASCII this is octal code 014.
2593 @cindex @code{\n} (newline character)
2594 @cindex newline (@code{\n})
2596 Mnemonic for newline; for ASCII this is octal code 012.
2599 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2601 @cindex @code{\r} (carriage return character)
2602 @cindex carriage return (@code{\r})
2604 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2607 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2608 @c other assemblers.
2610 @cindex @code{\t} (tab)
2611 @cindex tab (@code{\t})
2613 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2616 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2617 @c @item \x @var{digit} @var{digit} @var{digit}
2618 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2620 @cindex @code{\@var{ddd}} (octal character code)
2621 @cindex octal character code (@code{\@var{ddd}})
2622 @item \ @var{digit} @var{digit} @var{digit}
2623 An octal character code. The numeric code is 3 octal digits.
2624 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2625 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2627 @cindex @code{\@var{xd...}} (hex character code)
2628 @cindex hex character code (@code{\@var{xd...}})
2629 @item \@code{x} @var{hex-digits...}
2630 A hex character code. All trailing hex digits are combined. Either upper or
2631 lower case @code{x} works.
2633 @cindex @code{\\} (@samp{\} character)
2634 @cindex backslash (@code{\\})
2636 Represents one @samp{\} character.
2639 @c Represents one @samp{'} (accent acute) character.
2640 @c This is needed in single character literals
2641 @c (@xref{Characters,,Character Constants}.) to represent
2644 @cindex @code{\"} (doublequote character)
2645 @cindex doublequote (@code{\"})
2647 Represents one @samp{"} character. Needed in strings to represent
2648 this character, because an unescaped @samp{"} would end the string.
2650 @item \ @var{anything-else}
2651 Any other character when escaped by @kbd{\} gives a warning, but
2652 assembles as if the @samp{\} was not present. The idea is that if
2653 you used an escape sequence you clearly didn't want the literal
2654 interpretation of the following character. However @command{@value{AS}} has no
2655 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2656 code and warns you of the fact.
2659 Which characters are escapable, and what those escapes represent,
2660 varies widely among assemblers. The current set is what we think
2661 the BSD 4.2 assembler recognizes, and is a subset of what most C
2662 compilers recognize. If you are in doubt, do not use an escape
2666 @subsubsection Characters
2668 @cindex single character constant
2669 @cindex character, single
2670 @cindex constant, single character
2671 A single character may be written as a single quote immediately
2672 followed by that character. The same escapes apply to characters as
2673 to strings. So if you want to write the character backslash, you
2674 must write @kbd{'\\} where the first @code{\} escapes the second
2675 @code{\}. As you can see, the quote is an acute accent, not a
2676 grave accent. A newline
2678 @ifclear abnormal-separator
2679 (or semicolon @samp{;})
2681 @ifset abnormal-separator
2683 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2688 immediately following an acute accent is taken as a literal character
2689 and does not count as the end of a statement. The value of a character
2690 constant in a numeric expression is the machine's byte-wide code for
2691 that character. @command{@value{AS}} assumes your character code is ASCII:
2692 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2695 @subsection Number Constants
2697 @cindex constants, number
2698 @cindex number constants
2699 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2700 are stored in the target machine. @emph{Integers} are numbers that
2701 would fit into an @code{int} in the C language. @emph{Bignums} are
2702 integers, but they are stored in more than 32 bits. @emph{Flonums}
2703 are floating point numbers, described below.
2706 * Integers:: Integers
2711 * Bit Fields:: Bit Fields
2717 @subsubsection Integers
2719 @cindex constants, integer
2721 @cindex binary integers
2722 @cindex integers, binary
2723 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2724 the binary digits @samp{01}.
2726 @cindex octal integers
2727 @cindex integers, octal
2728 An octal integer is @samp{0} followed by zero or more of the octal
2729 digits (@samp{01234567}).
2731 @cindex decimal integers
2732 @cindex integers, decimal
2733 A decimal integer starts with a non-zero digit followed by zero or
2734 more digits (@samp{0123456789}).
2736 @cindex hexadecimal integers
2737 @cindex integers, hexadecimal
2738 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2739 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2741 Integers have the usual values. To denote a negative integer, use
2742 the prefix operator @samp{-} discussed under expressions
2743 (@pxref{Prefix Ops,,Prefix Operators}).
2746 @subsubsection Bignums
2749 @cindex constants, bignum
2750 A @dfn{bignum} has the same syntax and semantics as an integer
2751 except that the number (or its negative) takes more than 32 bits to
2752 represent in binary. The distinction is made because in some places
2753 integers are permitted while bignums are not.
2756 @subsubsection Flonums
2758 @cindex floating point numbers
2759 @cindex constants, floating point
2761 @cindex precision, floating point
2762 A @dfn{flonum} represents a floating point number. The translation is
2763 indirect: a decimal floating point number from the text is converted by
2764 @command{@value{AS}} to a generic binary floating point number of more than
2765 sufficient precision. This generic floating point number is converted
2766 to a particular computer's floating point format (or formats) by a
2767 portion of @command{@value{AS}} specialized to that computer.
2769 A flonum is written by writing (in order)
2774 (@samp{0} is optional on the HPPA.)
2778 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2780 @kbd{e} is recommended. Case is not important.
2782 @c FIXME: verify if flonum syntax really this vague for most cases
2783 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2784 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2787 On the H8/300, Renesas / SuperH SH,
2788 and AMD 29K architectures, the letter must be
2789 one of the letters @samp{DFPRSX} (in upper or lower case).
2791 On the ARC, the letter must be one of the letters @samp{DFRS}
2792 (in upper or lower case).
2794 On the Intel 960 architecture, the letter must be
2795 one of the letters @samp{DFT} (in upper or lower case).
2797 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2801 One of the letters @samp{DFRS} (in upper or lower case).
2804 One of the letters @samp{DFPRSX} (in upper or lower case).
2807 The letter @samp{E} (upper case only).
2810 One of the letters @samp{DFT} (in upper or lower case).
2815 An optional sign: either @samp{+} or @samp{-}.
2818 An optional @dfn{integer part}: zero or more decimal digits.
2821 An optional @dfn{fractional part}: @samp{.} followed by zero
2822 or more decimal digits.
2825 An optional exponent, consisting of:
2829 An @samp{E} or @samp{e}.
2830 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2831 @c principle this can perfectly well be different on different targets.
2833 Optional sign: either @samp{+} or @samp{-}.
2835 One or more decimal digits.
2840 At least one of the integer part or the fractional part must be
2841 present. The floating point number has the usual base-10 value.
2843 @command{@value{AS}} does all processing using integers. Flonums are computed
2844 independently of any floating point hardware in the computer running
2845 @command{@value{AS}}.
2849 @c Bit fields are written as a general facility but are also controlled
2850 @c by a conditional-compilation flag---which is as of now (21mar91)
2851 @c turned on only by the i960 config of GAS.
2853 @subsubsection Bit Fields
2856 @cindex constants, bit field
2857 You can also define numeric constants as @dfn{bit fields}.
2858 Specify two numbers separated by a colon---
2860 @var{mask}:@var{value}
2863 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2866 The resulting number is then packed
2868 @c this conditional paren in case bit fields turned on elsewhere than 960
2869 (in host-dependent byte order)
2871 into a field whose width depends on which assembler directive has the
2872 bit-field as its argument. Overflow (a result from the bitwise and
2873 requiring more binary digits to represent) is not an error; instead,
2874 more constants are generated, of the specified width, beginning with the
2875 least significant digits.@refill
2877 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2878 @code{.short}, and @code{.word} accept bit-field arguments.
2883 @chapter Sections and Relocation
2888 * Secs Background:: Background
2889 * Ld Sections:: Linker Sections
2890 * As Sections:: Assembler Internal Sections
2891 * Sub-Sections:: Sub-Sections
2895 @node Secs Background
2898 Roughly, a section is a range of addresses, with no gaps; all data
2899 ``in'' those addresses is treated the same for some particular purpose.
2900 For example there may be a ``read only'' section.
2902 @cindex linker, and assembler
2903 @cindex assembler, and linker
2904 The linker @code{@value{LD}} reads many object files (partial programs) and
2905 combines their contents to form a runnable program. When @command{@value{AS}}
2906 emits an object file, the partial program is assumed to start at address 0.
2907 @code{@value{LD}} assigns the final addresses for the partial program, so that
2908 different partial programs do not overlap. This is actually an
2909 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2912 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2913 addresses. These blocks slide to their run-time addresses as rigid
2914 units; their length does not change and neither does the order of bytes
2915 within them. Such a rigid unit is called a @emph{section}. Assigning
2916 run-time addresses to sections is called @dfn{relocation}. It includes
2917 the task of adjusting mentions of object-file addresses so they refer to
2918 the proper run-time addresses.
2920 For the H8/300, and for the Renesas / SuperH SH,
2921 @command{@value{AS}} pads sections if needed to
2922 ensure they end on a word (sixteen bit) boundary.
2925 @cindex standard assembler sections
2926 An object file written by @command{@value{AS}} has at least three sections, any
2927 of which may be empty. These are named @dfn{text}, @dfn{data} and
2932 When it generates COFF or ELF output,
2934 @command{@value{AS}} can also generate whatever other named sections you specify
2935 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2936 If you do not use any directives that place output in the @samp{.text}
2937 or @samp{.data} sections, these sections still exist, but are empty.
2942 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2944 @command{@value{AS}} can also generate whatever other named sections you
2945 specify using the @samp{.space} and @samp{.subspace} directives. See
2946 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2947 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2948 assembler directives.
2951 Additionally, @command{@value{AS}} uses different names for the standard
2952 text, data, and bss sections when generating SOM output. Program text
2953 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2954 BSS into @samp{$BSS$}.
2958 Within the object file, the text section starts at address @code{0}, the
2959 data section follows, and the bss section follows the data section.
2962 When generating either SOM or ELF output files on the HPPA, the text
2963 section starts at address @code{0}, the data section at address
2964 @code{0x4000000}, and the bss section follows the data section.
2967 To let @code{@value{LD}} know which data changes when the sections are
2968 relocated, and how to change that data, @command{@value{AS}} also writes to the
2969 object file details of the relocation needed. To perform relocation
2970 @code{@value{LD}} must know, each time an address in the object
2974 Where in the object file is the beginning of this reference to
2977 How long (in bytes) is this reference?
2979 Which section does the address refer to? What is the numeric value of
2981 (@var{address}) @minus{} (@var{start-address of section})?
2984 Is the reference to an address ``Program-Counter relative''?
2987 @cindex addresses, format of
2988 @cindex section-relative addressing
2989 In fact, every address @command{@value{AS}} ever uses is expressed as
2991 (@var{section}) + (@var{offset into section})
2994 Further, most expressions @command{@value{AS}} computes have this section-relative
2997 (For some object formats, such as SOM for the HPPA, some expressions are
2998 symbol-relative instead.)
3001 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3002 @var{N} into section @var{secname}.''
3004 Apart from text, data and bss sections you need to know about the
3005 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3006 addresses in the absolute section remain unchanged. For example, address
3007 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3008 @code{@value{LD}}. Although the linker never arranges two partial programs'
3009 data sections with overlapping addresses after linking, @emph{by definition}
3010 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3011 part of a program is always the same address when the program is running as
3012 address @code{@{absolute@ 239@}} in any other part of the program.
3014 The idea of sections is extended to the @dfn{undefined} section. Any
3015 address whose section is unknown at assembly time is by definition
3016 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3017 Since numbers are always defined, the only way to generate an undefined
3018 address is to mention an undefined symbol. A reference to a named
3019 common block would be such a symbol: its value is unknown at assembly
3020 time so it has section @emph{undefined}.
3022 By analogy the word @emph{section} is used to describe groups of sections in
3023 the linked program. @code{@value{LD}} puts all partial programs' text
3024 sections in contiguous addresses in the linked program. It is
3025 customary to refer to the @emph{text section} of a program, meaning all
3026 the addresses of all partial programs' text sections. Likewise for
3027 data and bss sections.
3029 Some sections are manipulated by @code{@value{LD}}; others are invented for
3030 use of @command{@value{AS}} and have no meaning except during assembly.
3033 @section Linker Sections
3034 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3039 @cindex named sections
3040 @cindex sections, named
3041 @item named sections
3044 @cindex text section
3045 @cindex data section
3049 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3050 separate but equal sections. Anything you can say of one section is
3053 When the program is running, however, it is
3054 customary for the text section to be unalterable. The
3055 text section is often shared among processes: it contains
3056 instructions, constants and the like. The data section of a running
3057 program is usually alterable: for example, C variables would be stored
3058 in the data section.
3063 This section contains zeroed bytes when your program begins running. It
3064 is used to hold uninitialized variables or common storage. The length of
3065 each partial program's bss section is important, but because it starts
3066 out containing zeroed bytes there is no need to store explicit zero
3067 bytes in the object file. The bss section was invented to eliminate
3068 those explicit zeros from object files.
3070 @cindex absolute section
3071 @item absolute section
3072 Address 0 of this section is always ``relocated'' to runtime address 0.
3073 This is useful if you want to refer to an address that @code{@value{LD}} must
3074 not change when relocating. In this sense we speak of absolute
3075 addresses being ``unrelocatable'': they do not change during relocation.
3077 @cindex undefined section
3078 @item undefined section
3079 This ``section'' is a catch-all for address references to objects not in
3080 the preceding sections.
3081 @c FIXME: ref to some other doc on obj-file formats could go here.
3084 @cindex relocation example
3085 An idealized example of three relocatable sections follows.
3087 The example uses the traditional section names @samp{.text} and @samp{.data}.
3089 Memory addresses are on the horizontal axis.
3093 @c END TEXI2ROFF-KILL
3096 partial program # 1: |ttttt|dddd|00|
3103 partial program # 2: |TTT|DDD|000|
3106 +--+---+-----+--+----+---+-----+~~
3107 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3108 +--+---+-----+--+----+---+-----+~~
3110 addresses: 0 @dots{}
3117 \line{\it Partial program \#1: \hfil}
3118 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3119 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3121 \line{\it Partial program \#2: \hfil}
3122 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3123 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3125 \line{\it linked program: \hfil}
3126 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3127 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3128 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3129 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3131 \line{\it addresses: \hfil}
3135 @c END TEXI2ROFF-KILL
3138 @section Assembler Internal Sections
3140 @cindex internal assembler sections
3141 @cindex sections in messages, internal
3142 These sections are meant only for the internal use of @command{@value{AS}}. They
3143 have no meaning at run-time. You do not really need to know about these
3144 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3145 warning messages, so it might be helpful to have an idea of their
3146 meanings to @command{@value{AS}}. These sections are used to permit the
3147 value of every expression in your assembly language program to be a
3148 section-relative address.
3151 @cindex assembler internal logic error
3152 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3153 An internal assembler logic error has been found. This means there is a
3154 bug in the assembler.
3156 @cindex expr (internal section)
3158 The assembler stores complex expression internally as combinations of
3159 symbols. When it needs to represent an expression as a symbol, it puts
3160 it in the expr section.
3162 @c FIXME item transfer[t] vector preload
3163 @c FIXME item transfer[t] vector postload
3164 @c FIXME item register
3168 @section Sub-Sections
3170 @cindex numbered subsections
3171 @cindex grouping data
3177 fall into two sections: text and data.
3179 You may have separate groups of
3181 data in named sections
3185 data in named sections
3191 that you want to end up near to each other in the object file, even though they
3192 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3193 use @dfn{subsections} for this purpose. Within each section, there can be
3194 numbered subsections with values from 0 to 8192. Objects assembled into the
3195 same subsection go into the object file together with other objects in the same
3196 subsection. For example, a compiler might want to store constants in the text
3197 section, but might not want to have them interspersed with the program being
3198 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3199 section of code being output, and a @samp{.text 1} before each group of
3200 constants being output.
3202 Subsections are optional. If you do not use subsections, everything
3203 goes in subsection number zero.
3206 Each subsection is zero-padded up to a multiple of four bytes.
3207 (Subsections may be padded a different amount on different flavors
3208 of @command{@value{AS}}.)
3212 On the H8/300 platform, each subsection is zero-padded to a word
3213 boundary (two bytes).
3214 The same is true on the Renesas SH.
3217 @c FIXME section padding (alignment)?
3218 @c Rich Pixley says padding here depends on target obj code format; that
3219 @c doesn't seem particularly useful to say without further elaboration,
3220 @c so for now I say nothing about it. If this is a generic BFD issue,
3221 @c these paragraphs might need to vanish from this manual, and be
3222 @c discussed in BFD chapter of binutils (or some such).
3226 Subsections appear in your object file in numeric order, lowest numbered
3227 to highest. (All this to be compatible with other people's assemblers.)
3228 The object file contains no representation of subsections; @code{@value{LD}} and
3229 other programs that manipulate object files see no trace of them.
3230 They just see all your text subsections as a text section, and all your
3231 data subsections as a data section.
3233 To specify which subsection you want subsequent statements assembled
3234 into, use a numeric argument to specify it, in a @samp{.text
3235 @var{expression}} or a @samp{.data @var{expression}} statement.
3238 When generating COFF output, you
3243 can also use an extra subsection
3244 argument with arbitrary named sections: @samp{.section @var{name},
3249 When generating ELF output, you
3254 can also use the @code{.subsection} directive (@pxref{SubSection})
3255 to specify a subsection: @samp{.subsection @var{expression}}.
3257 @var{Expression} should be an absolute expression
3258 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3259 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3260 begins in @code{text 0}. For instance:
3262 .text 0 # The default subsection is text 0 anyway.
3263 .ascii "This lives in the first text subsection. *"
3265 .ascii "But this lives in the second text subsection."
3267 .ascii "This lives in the data section,"
3268 .ascii "in the first data subsection."
3270 .ascii "This lives in the first text section,"
3271 .ascii "immediately following the asterisk (*)."
3274 Each section has a @dfn{location counter} incremented by one for every byte
3275 assembled into that section. Because subsections are merely a convenience
3276 restricted to @command{@value{AS}} there is no concept of a subsection location
3277 counter. There is no way to directly manipulate a location counter---but the
3278 @code{.align} directive changes it, and any label definition captures its
3279 current value. The location counter of the section where statements are being
3280 assembled is said to be the @dfn{active} location counter.
3283 @section bss Section
3286 @cindex common variable storage
3287 The bss section is used for local common variable storage.
3288 You may allocate address space in the bss section, but you may
3289 not dictate data to load into it before your program executes. When
3290 your program starts running, all the contents of the bss
3291 section are zeroed bytes.
3293 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3294 @ref{Lcomm,,@code{.lcomm}}.
3296 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3297 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3300 When assembling for a target which supports multiple sections, such as ELF or
3301 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3302 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3303 section. Typically the section will only contain symbol definitions and
3304 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3311 Symbols are a central concept: the programmer uses symbols to name
3312 things, the linker uses symbols to link, and the debugger uses symbols
3316 @cindex debuggers, and symbol order
3317 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3318 the same order they were declared. This may break some debuggers.
3323 * Setting Symbols:: Giving Symbols Other Values
3324 * Symbol Names:: Symbol Names
3325 * Dot:: The Special Dot Symbol
3326 * Symbol Attributes:: Symbol Attributes
3333 A @dfn{label} is written as a symbol immediately followed by a colon
3334 @samp{:}. The symbol then represents the current value of the
3335 active location counter, and is, for example, a suitable instruction
3336 operand. You are warned if you use the same symbol to represent two
3337 different locations: the first definition overrides any other
3341 On the HPPA, the usual form for a label need not be immediately followed by a
3342 colon, but instead must start in column zero. Only one label may be defined on
3343 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3344 provides a special directive @code{.label} for defining labels more flexibly.
3347 @node Setting Symbols
3348 @section Giving Symbols Other Values
3350 @cindex assigning values to symbols
3351 @cindex symbol values, assigning
3352 A symbol can be given an arbitrary value by writing a symbol, followed
3353 by an equals sign @samp{=}, followed by an expression
3354 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3355 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3356 equals sign @samp{=}@samp{=} here represents an equivalent of the
3357 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3360 Blackfin does not support symbol assignment with @samp{=}.
3364 @section Symbol Names
3366 @cindex symbol names
3367 @cindex names, symbol
3368 @ifclear SPECIAL-SYMS
3369 Symbol names begin with a letter or with one of @samp{._}. On most
3370 machines, you can also use @code{$} in symbol names; exceptions are
3371 noted in @ref{Machine Dependencies}. That character may be followed by any
3372 string of digits, letters, dollar signs (unless otherwise noted for a
3373 particular target machine), and underscores.
3377 Symbol names begin with a letter or with one of @samp{._}. On the
3378 Renesas SH you can also use @code{$} in symbol names. That
3379 character may be followed by any string of digits, letters, dollar signs (save
3380 on the H8/300), and underscores.
3384 Case of letters is significant: @code{foo} is a different symbol name
3387 Each symbol has exactly one name. Each name in an assembly language program
3388 refers to exactly one symbol. You may use that symbol name any number of times
3391 @subheading Local Symbol Names
3393 @cindex local symbol names
3394 @cindex symbol names, local
3395 A local symbol is any symbol beginning with certain local label prefixes.
3396 By default, the local label prefix is @samp{.L} for ELF systems or
3397 @samp{L} for traditional a.out systems, but each target may have its own
3398 set of local label prefixes.
3400 On the HPPA local symbols begin with @samp{L$}.
3403 Local symbols are defined and used within the assembler, but they are
3404 normally not saved in object files. Thus, they are not visible when debugging.
3405 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3406 @option{-L}}) to retain the local symbols in the object files.
3408 @subheading Local Labels
3410 @cindex local labels
3411 @cindex temporary symbol names
3412 @cindex symbol names, temporary
3413 Local labels help compilers and programmers use names temporarily.
3414 They create symbols which are guaranteed to be unique over the entire scope of
3415 the input source code and which can be referred to by a simple notation.
3416 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3417 represents any positive integer). To refer to the most recent previous
3418 definition of that label write @samp{@b{N}b}, using the same number as when
3419 you defined the label. To refer to the next definition of a local label, write
3420 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3423 There is no restriction on how you can use these labels, and you can reuse them
3424 too. So that it is possible to repeatedly define the same local label (using
3425 the same number @samp{@b{N}}), although you can only refer to the most recently
3426 defined local label of that number (for a backwards reference) or the next
3427 definition of a specific local label for a forward reference. It is also worth
3428 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3429 implemented in a slightly more efficient manner than the others.
3440 Which is the equivalent of:
3443 label_1: branch label_3
3444 label_2: branch label_1
3445 label_3: branch label_4
3446 label_4: branch label_3
3449 Local label names are only a notational device. They are immediately
3450 transformed into more conventional symbol names before the assembler uses them.
3451 The symbol names are stored in the symbol table, appear in error messages, and
3452 are optionally emitted to the object file. The names are constructed using
3456 @item @emph{local label prefix}
3457 All local symbols begin with the system-specific local label prefix.
3458 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3459 that start with the local label prefix. These labels are
3460 used for symbols you are never intended to see. If you use the
3461 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3462 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3463 you may use them in debugging.
3466 This is the number that was used in the local label definition. So if the
3467 label is written @samp{55:} then the number is @samp{55}.
3470 This unusual character is included so you do not accidentally invent a symbol
3471 of the same name. The character has ASCII value of @samp{\002} (control-B).
3473 @item @emph{ordinal number}
3474 This is a serial number to keep the labels distinct. The first definition of
3475 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3476 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3477 the number @samp{1} and its 15th definition gets @samp{15} as well.
3480 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3481 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3483 @subheading Dollar Local Labels
3484 @cindex dollar local symbols
3486 @code{@value{AS}} also supports an even more local form of local labels called
3487 dollar labels. These labels go out of scope (i.e., they become undefined) as
3488 soon as a non-local label is defined. Thus they remain valid for only a small
3489 region of the input source code. Normal local labels, by contrast, remain in
3490 scope for the entire file, or until they are redefined by another occurrence of
3491 the same local label.
3493 Dollar labels are defined in exactly the same way as ordinary local labels,
3494 except that they have a dollar sign suffix to their numeric value, e.g.,
3497 They can also be distinguished from ordinary local labels by their transformed
3498 names which use ASCII character @samp{\001} (control-A) as the magic character
3499 to distinguish them from ordinary labels. For example, the fifth definition of
3500 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3503 @section The Special Dot Symbol
3505 @cindex dot (symbol)
3506 @cindex @code{.} (symbol)
3507 @cindex current address
3508 @cindex location counter
3509 The special symbol @samp{.} refers to the current address that
3510 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3511 .long .} defines @code{melvin} to contain its own address.
3512 Assigning a value to @code{.} is treated the same as a @code{.org}
3514 @ifclear no-space-dir
3515 Thus, the expression @samp{.=.+4} is the same as saying
3519 @node Symbol Attributes
3520 @section Symbol Attributes
3522 @cindex symbol attributes
3523 @cindex attributes, symbol
3524 Every symbol has, as well as its name, the attributes ``Value'' and
3525 ``Type''. Depending on output format, symbols can also have auxiliary
3528 The detailed definitions are in @file{a.out.h}.
3531 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3532 all these attributes, and probably won't warn you. This makes the
3533 symbol an externally defined symbol, which is generally what you
3537 * Symbol Value:: Value
3538 * Symbol Type:: Type
3541 * a.out Symbols:: Symbol Attributes: @code{a.out}
3545 * a.out Symbols:: Symbol Attributes: @code{a.out}
3548 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3553 * COFF Symbols:: Symbol Attributes for COFF
3556 * SOM Symbols:: Symbol Attributes for SOM
3563 @cindex value of a symbol
3564 @cindex symbol value
3565 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3566 location in the text, data, bss or absolute sections the value is the
3567 number of addresses from the start of that section to the label.
3568 Naturally for text, data and bss sections the value of a symbol changes
3569 as @code{@value{LD}} changes section base addresses during linking. Absolute
3570 symbols' values do not change during linking: that is why they are
3573 The value of an undefined symbol is treated in a special way. If it is
3574 0 then the symbol is not defined in this assembler source file, and
3575 @code{@value{LD}} tries to determine its value from other files linked into the
3576 same program. You make this kind of symbol simply by mentioning a symbol
3577 name without defining it. A non-zero value represents a @code{.comm}
3578 common declaration. The value is how much common storage to reserve, in
3579 bytes (addresses). The symbol refers to the first address of the
3585 @cindex type of a symbol
3587 The type attribute of a symbol contains relocation (section)
3588 information, any flag settings indicating that a symbol is external, and
3589 (optionally), other information for linkers and debuggers. The exact
3590 format depends on the object-code output format in use.
3595 @c The following avoids a "widow" subsection title. @group would be
3596 @c better if it were available outside examples.
3599 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3601 @cindex @code{b.out} symbol attributes
3602 @cindex symbol attributes, @code{b.out}
3603 These symbol attributes appear only when @command{@value{AS}} is configured for
3604 one of the Berkeley-descended object output formats---@code{a.out} or
3610 @subsection Symbol Attributes: @code{a.out}
3612 @cindex @code{a.out} symbol attributes
3613 @cindex symbol attributes, @code{a.out}
3619 @subsection Symbol Attributes: @code{a.out}
3621 @cindex @code{a.out} symbol attributes
3622 @cindex symbol attributes, @code{a.out}
3626 * Symbol Desc:: Descriptor
3627 * Symbol Other:: Other
3631 @subsubsection Descriptor
3633 @cindex descriptor, of @code{a.out} symbol
3634 This is an arbitrary 16-bit value. You may establish a symbol's
3635 descriptor value by using a @code{.desc} statement
3636 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3637 @command{@value{AS}}.
3640 @subsubsection Other
3642 @cindex other attribute, of @code{a.out} symbol
3643 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3648 @subsection Symbol Attributes for COFF
3650 @cindex COFF symbol attributes
3651 @cindex symbol attributes, COFF
3653 The COFF format supports a multitude of auxiliary symbol attributes;
3654 like the primary symbol attributes, they are set between @code{.def} and
3655 @code{.endef} directives.
3657 @subsubsection Primary Attributes
3659 @cindex primary attributes, COFF symbols
3660 The symbol name is set with @code{.def}; the value and type,
3661 respectively, with @code{.val} and @code{.type}.
3663 @subsubsection Auxiliary Attributes
3665 @cindex auxiliary attributes, COFF symbols
3666 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3667 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3668 table information for COFF.
3673 @subsection Symbol Attributes for SOM
3675 @cindex SOM symbol attributes
3676 @cindex symbol attributes, SOM
3678 The SOM format for the HPPA supports a multitude of symbol attributes set with
3679 the @code{.EXPORT} and @code{.IMPORT} directives.
3681 The attributes are described in @cite{HP9000 Series 800 Assembly
3682 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3683 @code{EXPORT} assembler directive documentation.
3687 @chapter Expressions
3691 @cindex numeric values
3692 An @dfn{expression} specifies an address or numeric value.
3693 Whitespace may precede and/or follow an expression.
3695 The result of an expression must be an absolute number, or else an offset into
3696 a particular section. If an expression is not absolute, and there is not
3697 enough information when @command{@value{AS}} sees the expression to know its
3698 section, a second pass over the source program might be necessary to interpret
3699 the expression---but the second pass is currently not implemented.
3700 @command{@value{AS}} aborts with an error message in this situation.
3703 * Empty Exprs:: Empty Expressions
3704 * Integer Exprs:: Integer Expressions
3708 @section Empty Expressions
3710 @cindex empty expressions
3711 @cindex expressions, empty
3712 An empty expression has no value: it is just whitespace or null.
3713 Wherever an absolute expression is required, you may omit the
3714 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3715 is compatible with other assemblers.
3718 @section Integer Expressions
3720 @cindex integer expressions
3721 @cindex expressions, integer
3722 An @dfn{integer expression} is one or more @emph{arguments} delimited
3723 by @emph{operators}.
3726 * Arguments:: Arguments
3727 * Operators:: Operators
3728 * Prefix Ops:: Prefix Operators
3729 * Infix Ops:: Infix Operators
3733 @subsection Arguments
3735 @cindex expression arguments
3736 @cindex arguments in expressions
3737 @cindex operands in expressions
3738 @cindex arithmetic operands
3739 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3740 contexts arguments are sometimes called ``arithmetic operands''. In
3741 this manual, to avoid confusing them with the ``instruction operands'' of
3742 the machine language, we use the term ``argument'' to refer to parts of
3743 expressions only, reserving the word ``operand'' to refer only to machine
3744 instruction operands.
3746 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3747 @var{section} is one of text, data, bss, absolute,
3748 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3751 Numbers are usually integers.
3753 A number can be a flonum or bignum. In this case, you are warned
3754 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3755 these 32 bits are an integer. You may write integer-manipulating
3756 instructions that act on exotic constants, compatible with other
3759 @cindex subexpressions
3760 Subexpressions are a left parenthesis @samp{(} followed by an integer
3761 expression, followed by a right parenthesis @samp{)}; or a prefix
3762 operator followed by an argument.
3765 @subsection Operators
3767 @cindex operators, in expressions
3768 @cindex arithmetic functions
3769 @cindex functions, in expressions
3770 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3771 operators are followed by an argument. Infix operators appear
3772 between their arguments. Operators may be preceded and/or followed by
3776 @subsection Prefix Operator
3778 @cindex prefix operators
3779 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3780 one argument, which must be absolute.
3782 @c the tex/end tex stuff surrounding this small table is meant to make
3783 @c it align, on the printed page, with the similar table in the next
3784 @c section (which is inside an enumerate).
3786 \global\advance\leftskip by \itemindent
3791 @dfn{Negation}. Two's complement negation.
3793 @dfn{Complementation}. Bitwise not.
3797 \global\advance\leftskip by -\itemindent
3801 @subsection Infix Operators
3803 @cindex infix operators
3804 @cindex operators, permitted arguments
3805 @dfn{Infix operators} take two arguments, one on either side. Operators
3806 have precedence, but operations with equal precedence are performed left
3807 to right. Apart from @code{+} or @option{-}, both arguments must be
3808 absolute, and the result is absolute.
3811 @cindex operator precedence
3812 @cindex precedence of operators
3819 @dfn{Multiplication}.
3822 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3828 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3831 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3835 Intermediate precedence
3840 @dfn{Bitwise Inclusive Or}.
3846 @dfn{Bitwise Exclusive Or}.
3849 @dfn{Bitwise Or Not}.
3856 @cindex addition, permitted arguments
3857 @cindex plus, permitted arguments
3858 @cindex arguments for addition
3860 @dfn{Addition}. If either argument is absolute, the result has the section of
3861 the other argument. You may not add together arguments from different
3864 @cindex subtraction, permitted arguments
3865 @cindex minus, permitted arguments
3866 @cindex arguments for subtraction
3868 @dfn{Subtraction}. If the right argument is absolute, the
3869 result has the section of the left argument.
3870 If both arguments are in the same section, the result is absolute.
3871 You may not subtract arguments from different sections.
3872 @c FIXME is there still something useful to say about undefined - undefined ?
3874 @cindex comparison expressions
3875 @cindex expressions, comparison
3880 @dfn{Is Not Equal To}
3884 @dfn{Is Greater Than}
3886 @dfn{Is Greater Than Or Equal To}
3888 @dfn{Is Less Than Or Equal To}
3890 The comparison operators can be used as infix operators. A true results has a
3891 value of -1 whereas a false result has a value of 0. Note, these operators
3892 perform signed comparisons.
3895 @item Lowest Precedence
3904 These two logical operations can be used to combine the results of sub
3905 expressions. Note, unlike the comparison operators a true result returns a
3906 value of 1 but a false results does still return 0. Also note that the logical
3907 or operator has a slightly lower precedence than logical and.
3912 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3913 address; you can only have a defined section in one of the two arguments.
3916 @chapter Assembler Directives
3918 @cindex directives, machine independent
3919 @cindex pseudo-ops, machine independent
3920 @cindex machine independent directives
3921 All assembler directives have names that begin with a period (@samp{.}).
3922 The rest of the name is letters, usually in lower case.
3924 This chapter discusses directives that are available regardless of the
3925 target machine configuration for the @sc{gnu} assembler.
3927 Some machine configurations provide additional directives.
3928 @xref{Machine Dependencies}.
3931 @ifset machine-directives
3932 @xref{Machine Dependencies}, for additional directives.
3937 * Abort:: @code{.abort}
3939 * ABORT (COFF):: @code{.ABORT}
3942 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3943 * Altmacro:: @code{.altmacro}
3944 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3945 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3946 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3947 * Byte:: @code{.byte @var{expressions}}
3948 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3949 * Comm:: @code{.comm @var{symbol} , @var{length} }
3950 * Data:: @code{.data @var{subsection}}
3952 * Def:: @code{.def @var{name}}
3955 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3961 * Double:: @code{.double @var{flonums}}
3962 * Eject:: @code{.eject}
3963 * Else:: @code{.else}
3964 * Elseif:: @code{.elseif}
3967 * Endef:: @code{.endef}
3970 * Endfunc:: @code{.endfunc}
3971 * Endif:: @code{.endif}
3972 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3973 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3974 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3976 * Error:: @code{.error @var{string}}
3977 * Exitm:: @code{.exitm}
3978 * Extern:: @code{.extern}
3979 * Fail:: @code{.fail}
3980 * File:: @code{.file}
3981 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3982 * Float:: @code{.float @var{flonums}}
3983 * Func:: @code{.func}
3984 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3986 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3987 * Hidden:: @code{.hidden @var{names}}
3990 * hword:: @code{.hword @var{expressions}}
3991 * Ident:: @code{.ident}
3992 * If:: @code{.if @var{absolute expression}}
3993 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3994 * Include:: @code{.include "@var{file}"}
3995 * Int:: @code{.int @var{expressions}}
3997 * Internal:: @code{.internal @var{names}}
4000 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4001 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4002 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4003 * Lflags:: @code{.lflags}
4004 @ifclear no-line-dir
4005 * Line:: @code{.line @var{line-number}}
4008 * Linkonce:: @code{.linkonce [@var{type}]}
4009 * List:: @code{.list}
4010 * Ln:: @code{.ln @var{line-number}}
4011 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4012 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4014 * Local:: @code{.local @var{names}}
4017 * Long:: @code{.long @var{expressions}}
4019 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4022 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4023 * MRI:: @code{.mri @var{val}}
4024 * Noaltmacro:: @code{.noaltmacro}
4025 * Nolist:: @code{.nolist}
4026 * Octa:: @code{.octa @var{bignums}}
4027 * Offset:: @code{.offset @var{loc}}
4028 * Org:: @code{.org @var{new-lc}, @var{fill}}
4029 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4031 * PopSection:: @code{.popsection}
4032 * Previous:: @code{.previous}
4035 * Print:: @code{.print @var{string}}
4037 * Protected:: @code{.protected @var{names}}
4040 * Psize:: @code{.psize @var{lines}, @var{columns}}
4041 * Purgem:: @code{.purgem @var{name}}
4043 * PushSection:: @code{.pushsection @var{name}}
4046 * Quad:: @code{.quad @var{bignums}}
4047 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4048 * Rept:: @code{.rept @var{count}}
4049 * Sbttl:: @code{.sbttl "@var{subheading}"}
4051 * Scl:: @code{.scl @var{class}}
4054 * Section:: @code{.section @var{name}[, @var{flags}]}
4057 * Set:: @code{.set @var{symbol}, @var{expression}}
4058 * Short:: @code{.short @var{expressions}}
4059 * Single:: @code{.single @var{flonums}}
4061 * Size:: @code{.size [@var{name} , @var{expression}]}
4063 @ifclear no-space-dir
4064 * Skip:: @code{.skip @var{size} , @var{fill}}
4067 * Sleb128:: @code{.sleb128 @var{expressions}}
4068 @ifclear no-space-dir
4069 * Space:: @code{.space @var{size} , @var{fill}}
4072 * Stab:: @code{.stabd, .stabn, .stabs}
4075 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4076 * Struct:: @code{.struct @var{expression}}
4078 * SubSection:: @code{.subsection}
4079 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4083 * Tag:: @code{.tag @var{structname}}
4086 * Text:: @code{.text @var{subsection}}
4087 * Title:: @code{.title "@var{heading}"}
4089 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4092 * Uleb128:: @code{.uleb128 @var{expressions}}
4094 * Val:: @code{.val @var{addr}}
4098 * Version:: @code{.version "@var{string}"}
4099 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4100 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4103 * Warning:: @code{.warning @var{string}}
4104 * Weak:: @code{.weak @var{names}}
4105 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4106 * Word:: @code{.word @var{expressions}}
4107 * Deprecated:: Deprecated Directives
4111 @section @code{.abort}
4113 @cindex @code{abort} directive
4114 @cindex stopping the assembly
4115 This directive stops the assembly immediately. It is for
4116 compatibility with other assemblers. The original idea was that the
4117 assembly language source would be piped into the assembler. If the sender
4118 of the source quit, it could use this directive tells @command{@value{AS}} to
4119 quit also. One day @code{.abort} will not be supported.
4123 @section @code{.ABORT} (COFF)
4125 @cindex @code{ABORT} directive
4126 When producing COFF output, @command{@value{AS}} accepts this directive as a
4127 synonym for @samp{.abort}.
4130 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4136 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4138 @cindex padding the location counter
4139 @cindex @code{align} directive
4140 Pad the location counter (in the current subsection) to a particular storage
4141 boundary. The first expression (which must be absolute) is the alignment
4142 required, as described below.
4144 The second expression (also absolute) gives the fill value to be stored in the
4145 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4146 padding bytes are normally zero. However, on some systems, if the section is
4147 marked as containing code and the fill value is omitted, the space is filled
4148 with no-op instructions.
4150 The third expression is also absolute, and is also optional. If it is present,
4151 it is the maximum number of bytes that should be skipped by this alignment
4152 directive. If doing the alignment would require skipping more bytes than the
4153 specified maximum, then the alignment is not done at all. You can omit the
4154 fill value (the second argument) entirely by simply using two commas after the
4155 required alignment; this can be useful if you want the alignment to be filled
4156 with no-op instructions when appropriate.
4158 The way the required alignment is specified varies from system to system.
4159 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4160 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4161 alignment request in bytes. For example @samp{.align 8} advances
4162 the location counter until it is a multiple of 8. If the location counter
4163 is already a multiple of 8, no change is needed. For the tic54x, the
4164 first expression is the alignment request in words.
4166 For other systems, including ppc, i386 using a.out format, arm and
4167 strongarm, it is the
4168 number of low-order zero bits the location counter must have after
4169 advancement. For example @samp{.align 3} advances the location
4170 counter until it a multiple of 8. If the location counter is already a
4171 multiple of 8, no change is needed.
4173 This inconsistency is due to the different behaviors of the various
4174 native assemblers for these systems which GAS must emulate.
4175 GAS also provides @code{.balign} and @code{.p2align} directives,
4176 described later, which have a consistent behavior across all
4177 architectures (but are specific to GAS).
4180 @section @code{.altmacro}
4181 Enable alternate macro mode, enabling:
4184 @item LOCAL @var{name} [ , @dots{} ]
4185 One additional directive, @code{LOCAL}, is available. It is used to
4186 generate a string replacement for each of the @var{name} arguments, and
4187 replace any instances of @var{name} in each macro expansion. The
4188 replacement string is unique in the assembly, and different for each
4189 separate macro expansion. @code{LOCAL} allows you to write macros that
4190 define symbols, without fear of conflict between separate macro expansions.
4192 @item String delimiters
4193 You can write strings delimited in these other ways besides
4194 @code{"@var{string}"}:
4197 @item '@var{string}'
4198 You can delimit strings with single-quote characters.
4200 @item <@var{string}>
4201 You can delimit strings with matching angle brackets.
4204 @item single-character string escape
4205 To include any single character literally in a string (even if the
4206 character would otherwise have some special meaning), you can prefix the
4207 character with @samp{!} (an exclamation mark). For example, you can
4208 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4210 @item Expression results as strings
4211 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4212 and use the result as a string.
4216 @section @code{.ascii "@var{string}"}@dots{}
4218 @cindex @code{ascii} directive
4219 @cindex string literals
4220 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4221 separated by commas. It assembles each string (with no automatic
4222 trailing zero byte) into consecutive addresses.
4225 @section @code{.asciz "@var{string}"}@dots{}
4227 @cindex @code{asciz} directive
4228 @cindex zero-terminated strings
4229 @cindex null-terminated strings
4230 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4231 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4234 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4236 @cindex padding the location counter given number of bytes
4237 @cindex @code{balign} directive
4238 Pad the location counter (in the current subsection) to a particular
4239 storage boundary. The first expression (which must be absolute) is the
4240 alignment request in bytes. For example @samp{.balign 8} advances
4241 the location counter until it is a multiple of 8. If the location counter
4242 is already a multiple of 8, no change is needed.
4244 The second expression (also absolute) gives the fill value to be stored in the
4245 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4246 padding bytes are normally zero. However, on some systems, if the section is
4247 marked as containing code and the fill value is omitted, the space is filled
4248 with no-op instructions.
4250 The third expression is also absolute, and is also optional. If it is present,
4251 it is the maximum number of bytes that should be skipped by this alignment
4252 directive. If doing the alignment would require skipping more bytes than the
4253 specified maximum, then the alignment is not done at all. You can omit the
4254 fill value (the second argument) entirely by simply using two commas after the
4255 required alignment; this can be useful if you want the alignment to be filled
4256 with no-op instructions when appropriate.
4258 @cindex @code{balignw} directive
4259 @cindex @code{balignl} directive
4260 The @code{.balignw} and @code{.balignl} directives are variants of the
4261 @code{.balign} directive. The @code{.balignw} directive treats the fill
4262 pattern as a two byte word value. The @code{.balignl} directives treats the
4263 fill pattern as a four byte longword value. For example, @code{.balignw
4264 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4265 filled in with the value 0x368d (the exact placement of the bytes depends upon
4266 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4270 @section @code{.byte @var{expressions}}
4272 @cindex @code{byte} directive
4273 @cindex integers, one byte
4274 @code{.byte} expects zero or more expressions, separated by commas.
4275 Each expression is assembled into the next byte.
4277 @node CFI directives
4278 @section @code{.cfi_sections @var{section_list}}
4279 @cindex @code{cfi_sections} directive
4280 @code{.cfi_sections} may be used to specify whether CFI directives
4281 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4282 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4283 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4284 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4285 directive is not used is @code{.cfi_sections .eh_frame}.
4287 @section @code{.cfi_startproc [simple]}
4288 @cindex @code{cfi_startproc} directive
4289 @code{.cfi_startproc} is used at the beginning of each function that
4290 should have an entry in @code{.eh_frame}. It initializes some internal
4291 data structures. Don't forget to close the function by
4292 @code{.cfi_endproc}.
4294 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4295 it also emits some architecture dependent initial CFI instructions.
4297 @section @code{.cfi_endproc}
4298 @cindex @code{cfi_endproc} directive
4299 @code{.cfi_endproc} is used at the end of a function where it closes its
4300 unwind entry previously opened by
4301 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4303 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4304 @code{.cfi_personality} defines personality routine and its encoding.
4305 @var{encoding} must be a constant determining how the personality
4306 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4307 argument is not present, otherwise second argument should be
4308 a constant or a symbol name. When using indirect encodings,
4309 the symbol provided should be the location where personality
4310 can be loaded from, not the personality routine itself.
4311 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4312 no personality routine.
4314 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4315 @code{.cfi_lsda} defines LSDA and its encoding.
4316 @var{encoding} must be a constant determining how the LSDA
4317 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4318 argument is not present, otherwise second argument should be a constant
4319 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4322 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4323 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4324 address from @var{register} and add @var{offset} to it}.
4326 @section @code{.cfi_def_cfa_register @var{register}}
4327 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4328 now on @var{register} will be used instead of the old one. Offset
4331 @section @code{.cfi_def_cfa_offset @var{offset}}
4332 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4333 remains the same, but @var{offset} is new. Note that it is the
4334 absolute offset that will be added to a defined register to compute
4337 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4338 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4339 value that is added/substracted from the previous offset.
4341 @section @code{.cfi_offset @var{register}, @var{offset}}
4342 Previous value of @var{register} is saved at offset @var{offset} from
4345 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4346 Previous value of @var{register} is saved at offset @var{offset} from
4347 the current CFA register. This is transformed to @code{.cfi_offset}
4348 using the known displacement of the CFA register from the CFA.
4349 This is often easier to use, because the number will match the
4350 code it's annotating.
4352 @section @code{.cfi_register @var{register1}, @var{register2}}
4353 Previous value of @var{register1} is saved in register @var{register2}.
4355 @section @code{.cfi_restore @var{register}}
4356 @code{.cfi_restore} says that the rule for @var{register} is now the
4357 same as it was at the beginning of the function, after all initial
4358 instruction added by @code{.cfi_startproc} were executed.
4360 @section @code{.cfi_undefined @var{register}}
4361 From now on the previous value of @var{register} can't be restored anymore.
4363 @section @code{.cfi_same_value @var{register}}
4364 Current value of @var{register} is the same like in the previous frame,
4365 i.e. no restoration needed.
4367 @section @code{.cfi_remember_state},
4368 First save all current rules for all registers by @code{.cfi_remember_state},
4369 then totally screw them up by subsequent @code{.cfi_*} directives and when
4370 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4371 the previous saved state.
4373 @section @code{.cfi_return_column @var{register}}
4374 Change return column @var{register}, i.e. the return address is either
4375 directly in @var{register} or can be accessed by rules for @var{register}.
4377 @section @code{.cfi_signal_frame}
4378 Mark current function as signal trampoline.
4380 @section @code{.cfi_window_save}
4381 SPARC register window has been saved.
4383 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4384 Allows the user to add arbitrary bytes to the unwind info. One
4385 might use this to add OS-specific CFI opcodes, or generic CFI
4386 opcodes that GAS does not yet support.
4388 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4389 The current value of @var{register} is @var{label}. The value of @var{label}
4390 will be encoded in the output file according to @var{encoding}; see the
4391 description of @code{.cfi_personality} for details on this encoding.
4393 The usefulness of equating a register to a fixed label is probably
4394 limited to the return address register. Here, it can be useful to
4395 mark a code segment that has only one return address which is reached
4396 by a direct branch and no copy of the return address exists in memory
4397 or another register.
4400 @section @code{.comm @var{symbol} , @var{length} }
4402 @cindex @code{comm} directive
4403 @cindex symbol, common
4404 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4405 common symbol in one object file may be merged with a defined or common symbol
4406 of the same name in another object file. If @code{@value{LD}} does not see a
4407 definition for the symbol--just one or more common symbols--then it will
4408 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4409 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4410 the same name, and they do not all have the same size, it will allocate space
4411 using the largest size.
4414 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4415 an optional third argument. This is the desired alignment of the symbol,
4416 specified for ELF as a byte boundary (for example, an alignment of 16 means
4417 that the least significant 4 bits of the address should be zero), and for PE
4418 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4419 boundary). The alignment must be an absolute expression, and it must be a
4420 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4421 common symbol, it will use the alignment when placing the symbol. If no
4422 alignment is specified, @command{@value{AS}} will set the alignment to the
4423 largest power of two less than or equal to the size of the symbol, up to a
4424 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4425 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4426 @samp{--section-alignment} option; image file sections in PE are aligned to
4427 multiples of 4096, which is far too large an alignment for ordinary variables.
4428 It is rather the default alignment for (non-debug) sections within object
4429 (@samp{*.o}) files, which are less strictly aligned.}.
4433 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4434 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4438 @section @code{.data @var{subsection}}
4440 @cindex @code{data} directive
4441 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4442 end of the data subsection numbered @var{subsection} (which is an
4443 absolute expression). If @var{subsection} is omitted, it defaults
4448 @section @code{.def @var{name}}
4450 @cindex @code{def} directive
4451 @cindex COFF symbols, debugging
4452 @cindex debugging COFF symbols
4453 Begin defining debugging information for a symbol @var{name}; the
4454 definition extends until the @code{.endef} directive is encountered.
4457 This directive is only observed when @command{@value{AS}} is configured for COFF
4458 format output; when producing @code{b.out}, @samp{.def} is recognized,
4465 @section @code{.desc @var{symbol}, @var{abs-expression}}
4467 @cindex @code{desc} directive
4468 @cindex COFF symbol descriptor
4469 @cindex symbol descriptor, COFF
4470 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4471 to the low 16 bits of an absolute expression.
4474 The @samp{.desc} directive is not available when @command{@value{AS}} is
4475 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4476 object format. For the sake of compatibility, @command{@value{AS}} accepts
4477 it, but produces no output, when configured for COFF.
4483 @section @code{.dim}
4485 @cindex @code{dim} directive
4486 @cindex COFF auxiliary symbol information
4487 @cindex auxiliary symbol information, COFF
4488 This directive is generated by compilers to include auxiliary debugging
4489 information in the symbol table. It is only permitted inside
4490 @code{.def}/@code{.endef} pairs.
4493 @samp{.dim} is only meaningful when generating COFF format output; when
4494 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4500 @section @code{.double @var{flonums}}
4502 @cindex @code{double} directive
4503 @cindex floating point numbers (double)
4504 @code{.double} expects zero or more flonums, separated by commas. It
4505 assembles floating point numbers.
4507 The exact kind of floating point numbers emitted depends on how
4508 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4512 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4513 in @sc{ieee} format.
4518 @section @code{.eject}
4520 @cindex @code{eject} directive
4521 @cindex new page, in listings
4522 @cindex page, in listings
4523 @cindex listing control: new page
4524 Force a page break at this point, when generating assembly listings.
4527 @section @code{.else}
4529 @cindex @code{else} directive
4530 @code{.else} is part of the @command{@value{AS}} support for conditional
4531 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4532 of code to be assembled if the condition for the preceding @code{.if}
4536 @section @code{.elseif}
4538 @cindex @code{elseif} directive
4539 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4540 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4541 @code{.if} block that would otherwise fill the entire @code{.else} section.
4544 @section @code{.end}
4546 @cindex @code{end} directive
4547 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4548 process anything in the file past the @code{.end} directive.
4552 @section @code{.endef}
4554 @cindex @code{endef} directive
4555 This directive flags the end of a symbol definition begun with
4559 @samp{.endef} is only meaningful when generating COFF format output; if
4560 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4561 directive but ignores it.
4566 @section @code{.endfunc}
4567 @cindex @code{endfunc} directive
4568 @code{.endfunc} marks the end of a function specified with @code{.func}.
4571 @section @code{.endif}
4573 @cindex @code{endif} directive
4574 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4575 it marks the end of a block of code that is only assembled
4576 conditionally. @xref{If,,@code{.if}}.
4579 @section @code{.equ @var{symbol}, @var{expression}}
4581 @cindex @code{equ} directive
4582 @cindex assigning values to symbols
4583 @cindex symbols, assigning values to
4584 This directive sets the value of @var{symbol} to @var{expression}.
4585 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4588 The syntax for @code{equ} on the HPPA is
4589 @samp{@var{symbol} .equ @var{expression}}.
4593 The syntax for @code{equ} on the Z80 is
4594 @samp{@var{symbol} equ @var{expression}}.
4595 On the Z80 it is an eror if @var{symbol} is already defined,
4596 but the symbol is not protected from later redefinition.
4597 Compare @ref{Equiv}.
4601 @section @code{.equiv @var{symbol}, @var{expression}}
4602 @cindex @code{equiv} directive
4603 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4604 the assembler will signal an error if @var{symbol} is already defined. Note a
4605 symbol which has been referenced but not actually defined is considered to be
4608 Except for the contents of the error message, this is roughly equivalent to
4615 plus it protects the symbol from later redefinition.
4618 @section @code{.eqv @var{symbol}, @var{expression}}
4619 @cindex @code{eqv} directive
4620 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4621 evaluate the expression or any part of it immediately. Instead each time
4622 the resulting symbol is used in an expression, a snapshot of its current
4626 @section @code{.err}
4627 @cindex @code{err} directive
4628 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4629 message and, unless the @option{-Z} option was used, it will not generate an
4630 object file. This can be used to signal an error in conditionally compiled code.
4633 @section @code{.error "@var{string}"}
4634 @cindex error directive
4636 Similarly to @code{.err}, this directive emits an error, but you can specify a
4637 string that will be emitted as the error message. If you don't specify the
4638 message, it defaults to @code{".error directive invoked in source file"}.
4639 @xref{Errors, ,Error and Warning Messages}.
4642 .error "This code has not been assembled and tested."
4646 @section @code{.exitm}
4647 Exit early from the current macro definition. @xref{Macro}.
4650 @section @code{.extern}
4652 @cindex @code{extern} directive
4653 @code{.extern} is accepted in the source program---for compatibility
4654 with other assemblers---but it is ignored. @command{@value{AS}} treats
4655 all undefined symbols as external.
4658 @section @code{.fail @var{expression}}
4660 @cindex @code{fail} directive
4661 Generates an error or a warning. If the value of the @var{expression} is 500
4662 or more, @command{@value{AS}} will print a warning message. If the value is less
4663 than 500, @command{@value{AS}} will print an error message. The message will
4664 include the value of @var{expression}. This can occasionally be useful inside
4665 complex nested macros or conditional assembly.
4668 @section @code{.file}
4669 @cindex @code{file} directive
4671 @ifclear no-file-dir
4672 There are two different versions of the @code{.file} directive. Targets
4673 that support DWARF2 line number information use the DWARF2 version of
4674 @code{.file}. Other targets use the default version.
4676 @subheading Default Version
4678 @cindex logical file name
4679 @cindex file name, logical
4680 This version of the @code{.file} directive tells @command{@value{AS}} that we
4681 are about to start a new logical file. The syntax is:
4687 @var{string} is the new file name. In general, the filename is
4688 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4689 to specify an empty file name, you must give the quotes--@code{""}. This
4690 statement may go away in future: it is only recognized to be compatible with
4691 old @command{@value{AS}} programs.
4693 @subheading DWARF2 Version
4696 When emitting DWARF2 line number information, @code{.file} assigns filenames
4697 to the @code{.debug_line} file name table. The syntax is:
4700 .file @var{fileno} @var{filename}
4703 The @var{fileno} operand should be a unique positive integer to use as the
4704 index of the entry in the table. The @var{filename} operand is a C string
4707 The detail of filename indices is exposed to the user because the filename
4708 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4709 information, and thus the user must know the exact indices that table
4713 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4715 @cindex @code{fill} directive
4716 @cindex writing patterns in memory
4717 @cindex patterns, writing in memory
4718 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4719 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4720 may be zero or more. @var{Size} may be zero or more, but if it is
4721 more than 8, then it is deemed to have the value 8, compatible with
4722 other people's assemblers. The contents of each @var{repeat} bytes
4723 is taken from an 8-byte number. The highest order 4 bytes are
4724 zero. The lowest order 4 bytes are @var{value} rendered in the
4725 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4726 Each @var{size} bytes in a repetition is taken from the lowest order
4727 @var{size} bytes of this number. Again, this bizarre behavior is
4728 compatible with other people's assemblers.
4730 @var{size} and @var{value} are optional.
4731 If the second comma and @var{value} are absent, @var{value} is
4732 assumed zero. If the first comma and following tokens are absent,
4733 @var{size} is assumed to be 1.
4736 @section @code{.float @var{flonums}}
4738 @cindex floating point numbers (single)
4739 @cindex @code{float} directive
4740 This directive assembles zero or more flonums, separated by commas. It
4741 has the same effect as @code{.single}.
4743 The exact kind of floating point numbers emitted depends on how
4744 @command{@value{AS}} is configured.
4745 @xref{Machine Dependencies}.
4749 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4750 in @sc{ieee} format.
4755 @section @code{.func @var{name}[,@var{label}]}
4756 @cindex @code{func} directive
4757 @code{.func} emits debugging information to denote function @var{name}, and
4758 is ignored unless the file is assembled with debugging enabled.
4759 Only @samp{--gstabs[+]} is currently supported.
4760 @var{label} is the entry point of the function and if omitted @var{name}
4761 prepended with the @samp{leading char} is used.
4762 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4763 All functions are currently defined to have @code{void} return type.
4764 The function must be terminated with @code{.endfunc}.
4767 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4769 @cindex @code{global} directive
4770 @cindex symbol, making visible to linker
4771 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4772 @var{symbol} in your partial program, its value is made available to
4773 other partial programs that are linked with it. Otherwise,
4774 @var{symbol} takes its attributes from a symbol of the same name
4775 from another file linked into the same program.
4777 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4778 compatibility with other assemblers.
4781 On the HPPA, @code{.global} is not always enough to make it accessible to other
4782 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4783 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4788 @section @code{.gnu_attribute @var{tag},@var{value}}
4789 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4792 @section @code{.hidden @var{names}}
4794 @cindex @code{hidden} directive
4796 This is one of the ELF visibility directives. The other two are
4797 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4798 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4800 This directive overrides the named symbols default visibility (which is set by
4801 their binding: local, global or weak). The directive sets the visibility to
4802 @code{hidden} which means that the symbols are not visible to other components.
4803 Such symbols are always considered to be @code{protected} as well.
4807 @section @code{.hword @var{expressions}}
4809 @cindex @code{hword} directive
4810 @cindex integers, 16-bit
4811 @cindex numbers, 16-bit
4812 @cindex sixteen bit integers
4813 This expects zero or more @var{expressions}, and emits
4814 a 16 bit number for each.
4817 This directive is a synonym for @samp{.short}; depending on the target
4818 architecture, it may also be a synonym for @samp{.word}.
4822 This directive is a synonym for @samp{.short}.
4825 This directive is a synonym for both @samp{.short} and @samp{.word}.
4830 @section @code{.ident}
4832 @cindex @code{ident} directive
4834 This directive is used by some assemblers to place tags in object files. The
4835 behavior of this directive varies depending on the target. When using the
4836 a.out object file format, @command{@value{AS}} simply accepts the directive for
4837 source-file compatibility with existing assemblers, but does not emit anything
4838 for it. When using COFF, comments are emitted to the @code{.comment} or
4839 @code{.rdata} section, depending on the target. When using ELF, comments are
4840 emitted to the @code{.comment} section.
4843 @section @code{.if @var{absolute expression}}
4845 @cindex conditional assembly
4846 @cindex @code{if} directive
4847 @code{.if} marks the beginning of a section of code which is only
4848 considered part of the source program being assembled if the argument
4849 (which must be an @var{absolute expression}) is non-zero. The end of
4850 the conditional section of code must be marked by @code{.endif}
4851 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4852 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4853 If you have several conditions to check, @code{.elseif} may be used to avoid
4854 nesting blocks if/else within each subsequent @code{.else} block.
4856 The following variants of @code{.if} are also supported:
4858 @cindex @code{ifdef} directive
4859 @item .ifdef @var{symbol}
4860 Assembles the following section of code if the specified @var{symbol}
4861 has been defined. Note a symbol which has been referenced but not yet defined
4862 is considered to be undefined.
4864 @cindex @code{ifb} directive
4865 @item .ifb @var{text}
4866 Assembles the following section of code if the operand is blank (empty).
4868 @cindex @code{ifc} directive
4869 @item .ifc @var{string1},@var{string2}
4870 Assembles the following section of code if the two strings are the same. The
4871 strings may be optionally quoted with single quotes. If they are not quoted,
4872 the first string stops at the first comma, and the second string stops at the
4873 end of the line. Strings which contain whitespace should be quoted. The
4874 string comparison is case sensitive.
4876 @cindex @code{ifeq} directive
4877 @item .ifeq @var{absolute expression}
4878 Assembles the following section of code if the argument is zero.
4880 @cindex @code{ifeqs} directive
4881 @item .ifeqs @var{string1},@var{string2}
4882 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4884 @cindex @code{ifge} directive
4885 @item .ifge @var{absolute expression}
4886 Assembles the following section of code if the argument is greater than or
4889 @cindex @code{ifgt} directive
4890 @item .ifgt @var{absolute expression}
4891 Assembles the following section of code if the argument is greater than zero.
4893 @cindex @code{ifle} directive
4894 @item .ifle @var{absolute expression}
4895 Assembles the following section of code if the argument is less than or equal
4898 @cindex @code{iflt} directive
4899 @item .iflt @var{absolute expression}
4900 Assembles the following section of code if the argument is less than zero.
4902 @cindex @code{ifnb} directive
4903 @item .ifnb @var{text}
4904 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4905 following section of code if the operand is non-blank (non-empty).
4907 @cindex @code{ifnc} directive
4908 @item .ifnc @var{string1},@var{string2}.
4909 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4910 following section of code if the two strings are not the same.
4912 @cindex @code{ifndef} directive
4913 @cindex @code{ifnotdef} directive
4914 @item .ifndef @var{symbol}
4915 @itemx .ifnotdef @var{symbol}
4916 Assembles the following section of code if the specified @var{symbol}
4917 has not been defined. Both spelling variants are equivalent. Note a symbol
4918 which has been referenced but not yet defined is considered to be undefined.
4920 @cindex @code{ifne} directive
4921 @item .ifne @var{absolute expression}
4922 Assembles the following section of code if the argument is not equal to zero
4923 (in other words, this is equivalent to @code{.if}).
4925 @cindex @code{ifnes} directive
4926 @item .ifnes @var{string1},@var{string2}
4927 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4928 following section of code if the two strings are not the same.
4932 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4934 @cindex @code{incbin} directive
4935 @cindex binary files, including
4936 The @code{incbin} directive includes @var{file} verbatim at the current
4937 location. You can control the search paths used with the @samp{-I} command-line
4938 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4941 The @var{skip} argument skips a number of bytes from the start of the
4942 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4943 read. Note that the data is not aligned in any way, so it is the user's
4944 responsibility to make sure that proper alignment is provided both before and
4945 after the @code{incbin} directive.
4948 @section @code{.include "@var{file}"}
4950 @cindex @code{include} directive
4951 @cindex supporting files, including
4952 @cindex files, including
4953 This directive provides a way to include supporting files at specified
4954 points in your source program. The code from @var{file} is assembled as
4955 if it followed the point of the @code{.include}; when the end of the
4956 included file is reached, assembly of the original file continues. You
4957 can control the search paths used with the @samp{-I} command-line option
4958 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4962 @section @code{.int @var{expressions}}
4964 @cindex @code{int} directive
4965 @cindex integers, 32-bit
4966 Expect zero or more @var{expressions}, of any section, separated by commas.
4967 For each expression, emit a number that, at run time, is the value of that
4968 expression. The byte order and bit size of the number depends on what kind
4969 of target the assembly is for.
4973 On most forms of the H8/300, @code{.int} emits 16-bit
4974 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4981 @section @code{.internal @var{names}}
4983 @cindex @code{internal} directive
4985 This is one of the ELF visibility directives. The other two are
4986 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4987 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4989 This directive overrides the named symbols default visibility (which is set by
4990 their binding: local, global or weak). The directive sets the visibility to
4991 @code{internal} which means that the symbols are considered to be @code{hidden}
4992 (i.e., not visible to other components), and that some extra, processor specific
4993 processing must also be performed upon the symbols as well.
4997 @section @code{.irp @var{symbol},@var{values}}@dots{}
4999 @cindex @code{irp} directive
5000 Evaluate a sequence of statements assigning different values to @var{symbol}.
5001 The sequence of statements starts at the @code{.irp} directive, and is
5002 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5003 set to @var{value}, and the sequence of statements is assembled. If no
5004 @var{value} is listed, the sequence of statements is assembled once, with
5005 @var{symbol} set to the null string. To refer to @var{symbol} within the
5006 sequence of statements, use @var{\symbol}.
5008 For example, assembling
5016 is equivalent to assembling
5024 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5027 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5029 @cindex @code{irpc} directive
5030 Evaluate a sequence of statements assigning different values to @var{symbol}.
5031 The sequence of statements starts at the @code{.irpc} directive, and is
5032 terminated by an @code{.endr} directive. For each character in @var{value},
5033 @var{symbol} is set to the character, and the sequence of statements is
5034 assembled. If no @var{value} is listed, the sequence of statements is
5035 assembled once, with @var{symbol} set to the null string. To refer to
5036 @var{symbol} within the sequence of statements, use @var{\symbol}.
5038 For example, assembling
5046 is equivalent to assembling
5054 For some caveats with the spelling of @var{symbol}, see also the discussion
5058 @section @code{.lcomm @var{symbol} , @var{length}}
5060 @cindex @code{lcomm} directive
5061 @cindex local common symbols
5062 @cindex symbols, local common
5063 Reserve @var{length} (an absolute expression) bytes for a local common
5064 denoted by @var{symbol}. The section and value of @var{symbol} are
5065 those of the new local common. The addresses are allocated in the bss
5066 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5067 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5068 not visible to @code{@value{LD}}.
5071 Some targets permit a third argument to be used with @code{.lcomm}. This
5072 argument specifies the desired alignment of the symbol in the bss section.
5076 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5077 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5081 @section @code{.lflags}
5083 @cindex @code{lflags} directive (ignored)
5084 @command{@value{AS}} accepts this directive, for compatibility with other
5085 assemblers, but ignores it.
5087 @ifclear no-line-dir
5089 @section @code{.line @var{line-number}}
5091 @cindex @code{line} directive
5092 @cindex logical line number
5094 Change the logical line number. @var{line-number} must be an absolute
5095 expression. The next line has that logical line number. Therefore any other
5096 statements on the current line (after a statement separator character) are
5097 reported as on logical line number @var{line-number} @minus{} 1. One day
5098 @command{@value{AS}} will no longer support this directive: it is recognized only
5099 for compatibility with existing assembler programs.
5102 Even though this is a directive associated with the @code{a.out} or
5103 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5104 when producing COFF output, and treats @samp{.line} as though it
5105 were the COFF @samp{.ln} @emph{if} it is found outside a
5106 @code{.def}/@code{.endef} pair.
5108 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5109 used by compilers to generate auxiliary symbol information for
5114 @section @code{.linkonce [@var{type}]}
5116 @cindex @code{linkonce} directive
5117 @cindex common sections
5118 Mark the current section so that the linker only includes a single copy of it.
5119 This may be used to include the same section in several different object files,
5120 but ensure that the linker will only include it once in the final output file.
5121 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5122 Duplicate sections are detected based on the section name, so it should be
5125 This directive is only supported by a few object file formats; as of this
5126 writing, the only object file format which supports it is the Portable
5127 Executable format used on Windows NT.
5129 The @var{type} argument is optional. If specified, it must be one of the
5130 following strings. For example:
5134 Not all types may be supported on all object file formats.
5138 Silently discard duplicate sections. This is the default.
5141 Warn if there are duplicate sections, but still keep only one copy.
5144 Warn if any of the duplicates have different sizes.
5147 Warn if any of the duplicates do not have exactly the same contents.
5151 @section @code{.list}
5153 @cindex @code{list} directive
5154 @cindex listing control, turning on
5155 Control (in conjunction with the @code{.nolist} directive) whether or
5156 not assembly listings are generated. These two directives maintain an
5157 internal counter (which is zero initially). @code{.list} increments the
5158 counter, and @code{.nolist} decrements it. Assembly listings are
5159 generated whenever the counter is greater than zero.
5161 By default, listings are disabled. When you enable them (with the
5162 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5163 the initial value of the listing counter is one.
5166 @section @code{.ln @var{line-number}}
5168 @cindex @code{ln} directive
5169 @ifclear no-line-dir
5170 @samp{.ln} is a synonym for @samp{.line}.
5173 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5174 must be an absolute expression. The next line has that logical
5175 line number, so any other statements on the current line (after a
5176 statement separator character @code{;}) are reported as on logical
5177 line number @var{line-number} @minus{} 1.
5180 This directive is accepted, but ignored, when @command{@value{AS}} is
5181 configured for @code{b.out}; its effect is only associated with COFF
5187 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5188 @cindex @code{loc} directive
5189 When emitting DWARF2 line number information,
5190 the @code{.loc} directive will add a row to the @code{.debug_line} line
5191 number matrix corresponding to the immediately following assembly
5192 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5193 arguments will be applied to the @code{.debug_line} state machine before
5196 The @var{options} are a sequence of the following tokens in any order:
5200 This option will set the @code{basic_block} register in the
5201 @code{.debug_line} state machine to @code{true}.
5204 This option will set the @code{prologue_end} register in the
5205 @code{.debug_line} state machine to @code{true}.
5207 @item epilogue_begin
5208 This option will set the @code{epilogue_begin} register in the
5209 @code{.debug_line} state machine to @code{true}.
5211 @item is_stmt @var{value}
5212 This option will set the @code{is_stmt} register in the
5213 @code{.debug_line} state machine to @code{value}, which must be
5216 @item isa @var{value}
5217 This directive will set the @code{isa} register in the @code{.debug_line}
5218 state machine to @var{value}, which must be an unsigned integer.
5220 @item discriminator @var{value}
5221 This directive will set the @code{discriminator} register in the @code{.debug_line}
5222 state machine to @var{value}, which must be an unsigned integer.
5226 @node Loc_mark_labels
5227 @section @code{.loc_mark_labels @var{enable}}
5228 @cindex @code{loc_mark_labels} directive
5229 When emitting DWARF2 line number information,
5230 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5231 to the @code{.debug_line} line number matrix with the @code{basic_block}
5232 register in the state machine set whenever a code label is seen.
5233 The @var{enable} argument should be either 1 or 0, to enable or disable
5234 this function respectively.
5238 @section @code{.local @var{names}}
5240 @cindex @code{local} directive
5241 This directive, which is available for ELF targets, marks each symbol in
5242 the comma-separated list of @code{names} as a local symbol so that it
5243 will not be externally visible. If the symbols do not already exist,
5244 they will be created.
5246 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5247 accept an alignment argument, which is the case for most ELF targets,
5248 the @code{.local} directive can be used in combination with @code{.comm}
5249 (@pxref{Comm}) to define aligned local common data.
5253 @section @code{.long @var{expressions}}
5255 @cindex @code{long} directive
5256 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5259 @c no one seems to know what this is for or whether this description is
5260 @c what it really ought to do
5262 @section @code{.lsym @var{symbol}, @var{expression}}
5264 @cindex @code{lsym} directive
5265 @cindex symbol, not referenced in assembly
5266 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5267 the hash table, ensuring it cannot be referenced by name during the
5268 rest of the assembly. This sets the attributes of the symbol to be
5269 the same as the expression value:
5271 @var{other} = @var{descriptor} = 0
5272 @var{type} = @r{(section of @var{expression})}
5273 @var{value} = @var{expression}
5276 The new symbol is not flagged as external.
5280 @section @code{.macro}
5283 The commands @code{.macro} and @code{.endm} allow you to define macros that
5284 generate assembly output. For example, this definition specifies a macro
5285 @code{sum} that puts a sequence of numbers into memory:
5288 .macro sum from=0, to=5
5297 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5309 @item .macro @var{macname}
5310 @itemx .macro @var{macname} @var{macargs} @dots{}
5311 @cindex @code{macro} directive
5312 Begin the definition of a macro called @var{macname}. If your macro
5313 definition requires arguments, specify their names after the macro name,
5314 separated by commas or spaces. You can qualify the macro argument to
5315 indicate whether all invocations must specify a non-blank value (through
5316 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5317 (through @samp{:@code{vararg}}). You can supply a default value for any
5318 macro argument by following the name with @samp{=@var{deflt}}. You
5319 cannot define two macros with the same @var{macname} unless it has been
5320 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5321 definitions. For example, these are all valid @code{.macro} statements:
5325 Begin the definition of a macro called @code{comm}, which takes no
5328 @item .macro plus1 p, p1
5329 @itemx .macro plus1 p p1
5330 Either statement begins the definition of a macro called @code{plus1},
5331 which takes two arguments; within the macro definition, write
5332 @samp{\p} or @samp{\p1} to evaluate the arguments.
5334 @item .macro reserve_str p1=0 p2
5335 Begin the definition of a macro called @code{reserve_str}, with two
5336 arguments. The first argument has a default value, but not the second.
5337 After the definition is complete, you can call the macro either as
5338 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5339 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5340 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5341 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5343 @item .macro m p1:req, p2=0, p3:vararg
5344 Begin the definition of a macro called @code{m}, with at least three
5345 arguments. The first argument must always have a value specified, but
5346 not the second, which instead has a default value. The third formal
5347 will get assigned all remaining arguments specified at invocation time.
5349 When you call a macro, you can specify the argument values either by
5350 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5351 @samp{sum to=17, from=9}.
5355 Note that since each of the @var{macargs} can be an identifier exactly
5356 as any other one permitted by the target architecture, there may be
5357 occasional problems if the target hand-crafts special meanings to certain
5358 characters when they occur in a special position. For example, if the colon
5359 (@code{:}) is generally permitted to be part of a symbol name, but the
5360 architecture specific code special-cases it when occurring as the final
5361 character of a symbol (to denote a label), then the macro parameter
5362 replacement code will have no way of knowing that and consider the whole
5363 construct (including the colon) an identifier, and check only this
5364 identifier for being the subject to parameter substitution. So for example
5365 this macro definition:
5373 might not work as expected. Invoking @samp{label foo} might not create a label
5374 called @samp{foo} but instead just insert the text @samp{\l:} into the
5375 assembler source, probably generating an error about an unrecognised
5378 Similarly problems might occur with the period character (@samp{.})
5379 which is often allowed inside opcode names (and hence identifier names). So
5380 for example constructing a macro to build an opcode from a base name and a
5381 length specifier like this:
5384 .macro opcode base length
5389 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5390 instruction but instead generate some kind of error as the assembler tries to
5391 interpret the text @samp{\base.\length}.
5393 There are several possible ways around this problem:
5396 @item Insert white space
5397 If it is possible to use white space characters then this is the simplest
5406 @item Use @samp{\()}
5407 The string @samp{\()} can be used to separate the end of a macro argument from
5408 the following text. eg:
5411 .macro opcode base length
5416 @item Use the alternate macro syntax mode
5417 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5418 used as a separator. eg:
5428 Note: this problem of correctly identifying string parameters to pseudo ops
5429 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5430 and @code{.irpc} (@pxref{Irpc}) as well.
5433 @cindex @code{endm} directive
5434 Mark the end of a macro definition.
5437 @cindex @code{exitm} directive
5438 Exit early from the current macro definition.
5440 @cindex number of macros executed
5441 @cindex macros, count executed
5443 @command{@value{AS}} maintains a counter of how many macros it has
5444 executed in this pseudo-variable; you can copy that number to your
5445 output with @samp{\@@}, but @emph{only within a macro definition}.
5447 @item LOCAL @var{name} [ , @dots{} ]
5448 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5449 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5450 @xref{Altmacro,,@code{.altmacro}}.
5454 @section @code{.mri @var{val}}
5456 @cindex @code{mri} directive
5457 @cindex MRI mode, temporarily
5458 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5459 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5460 affects code assembled until the next @code{.mri} directive, or until the end
5461 of the file. @xref{M, MRI mode, MRI mode}.
5464 @section @code{.noaltmacro}
5465 Disable alternate macro mode. @xref{Altmacro}.
5468 @section @code{.nolist}
5470 @cindex @code{nolist} directive
5471 @cindex listing control, turning off
5472 Control (in conjunction with the @code{.list} directive) whether or
5473 not assembly listings are generated. These two directives maintain an
5474 internal counter (which is zero initially). @code{.list} increments the
5475 counter, and @code{.nolist} decrements it. Assembly listings are
5476 generated whenever the counter is greater than zero.
5479 @section @code{.octa @var{bignums}}
5481 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5482 @cindex @code{octa} directive
5483 @cindex integer, 16-byte
5484 @cindex sixteen byte integer
5485 This directive expects zero or more bignums, separated by commas. For each
5486 bignum, it emits a 16-byte integer.
5488 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5489 hence @emph{octa}-word for 16 bytes.
5492 @section @code{.offset @var{loc}}
5494 @cindex @code{offset} directive
5495 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5496 be an absolute expression. This directive may be useful for defining
5497 symbols with absolute values. Do not confuse it with the @code{.org}
5501 @section @code{.org @var{new-lc} , @var{fill}}
5503 @cindex @code{org} directive
5504 @cindex location counter, advancing
5505 @cindex advancing location counter
5506 @cindex current address, advancing
5507 Advance the location counter of the current section to
5508 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5509 expression with the same section as the current subsection. That is,
5510 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5511 wrong section, the @code{.org} directive is ignored. To be compatible
5512 with former assemblers, if the section of @var{new-lc} is absolute,
5513 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5514 is the same as the current subsection.
5516 @code{.org} may only increase the location counter, or leave it
5517 unchanged; you cannot use @code{.org} to move the location counter
5520 @c double negative used below "not undefined" because this is a specific
5521 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5522 @c section. doc@cygnus.com 18feb91
5523 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5524 may not be undefined. If you really detest this restriction we eagerly await
5525 a chance to share your improved assembler.
5527 Beware that the origin is relative to the start of the section, not
5528 to the start of the subsection. This is compatible with other
5529 people's assemblers.
5531 When the location counter (of the current subsection) is advanced, the
5532 intervening bytes are filled with @var{fill} which should be an
5533 absolute expression. If the comma and @var{fill} are omitted,
5534 @var{fill} defaults to zero.
5537 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5539 @cindex padding the location counter given a power of two
5540 @cindex @code{p2align} directive
5541 Pad the location counter (in the current subsection) to a particular
5542 storage boundary. The first expression (which must be absolute) is the
5543 number of low-order zero bits the location counter must have after
5544 advancement. For example @samp{.p2align 3} advances the location
5545 counter until it a multiple of 8. If the location counter is already a
5546 multiple of 8, no change is needed.
5548 The second expression (also absolute) gives the fill value to be stored in the
5549 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5550 padding bytes are normally zero. However, on some systems, if the section is
5551 marked as containing code and the fill value is omitted, the space is filled
5552 with no-op instructions.
5554 The third expression is also absolute, and is also optional. If it is present,
5555 it is the maximum number of bytes that should be skipped by this alignment
5556 directive. If doing the alignment would require skipping more bytes than the
5557 specified maximum, then the alignment is not done at all. You can omit the
5558 fill value (the second argument) entirely by simply using two commas after the
5559 required alignment; this can be useful if you want the alignment to be filled
5560 with no-op instructions when appropriate.
5562 @cindex @code{p2alignw} directive
5563 @cindex @code{p2alignl} directive
5564 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5565 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5566 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5567 fill pattern as a four byte longword value. For example, @code{.p2alignw
5568 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5569 filled in with the value 0x368d (the exact placement of the bytes depends upon
5570 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5575 @section @code{.popsection}
5577 @cindex @code{popsection} directive
5578 @cindex Section Stack
5579 This is one of the ELF section stack manipulation directives. The others are
5580 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5581 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5584 This directive replaces the current section (and subsection) with the top
5585 section (and subsection) on the section stack. This section is popped off the
5591 @section @code{.previous}
5593 @cindex @code{previous} directive
5594 @cindex Section Stack
5595 This is one of the ELF section stack manipulation directives. The others are
5596 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5597 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5598 (@pxref{PopSection}).
5600 This directive swaps the current section (and subsection) with most recently
5601 referenced section/subsection pair prior to this one. Multiple
5602 @code{.previous} directives in a row will flip between two sections (and their
5603 subsections). For example:
5615 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5621 # Now in section A subsection 1
5625 # Now in section B subsection 0
5628 # Now in section B subsection 1
5631 # Now in section B subsection 0
5635 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5636 section B and 0x9abc into subsection 1 of section B.
5638 In terms of the section stack, this directive swaps the current section with
5639 the top section on the section stack.
5643 @section @code{.print @var{string}}
5645 @cindex @code{print} directive
5646 @command{@value{AS}} will print @var{string} on the standard output during
5647 assembly. You must put @var{string} in double quotes.
5651 @section @code{.protected @var{names}}
5653 @cindex @code{protected} directive
5655 This is one of the ELF visibility directives. The other two are
5656 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5658 This directive overrides the named symbols default visibility (which is set by
5659 their binding: local, global or weak). The directive sets the visibility to
5660 @code{protected} which means that any references to the symbols from within the
5661 components that defines them must be resolved to the definition in that
5662 component, even if a definition in another component would normally preempt
5667 @section @code{.psize @var{lines} , @var{columns}}
5669 @cindex @code{psize} directive
5670 @cindex listing control: paper size
5671 @cindex paper size, for listings
5672 Use this directive to declare the number of lines---and, optionally, the
5673 number of columns---to use for each page, when generating listings.
5675 If you do not use @code{.psize}, listings use a default line-count
5676 of 60. You may omit the comma and @var{columns} specification; the
5677 default width is 200 columns.
5679 @command{@value{AS}} generates formfeeds whenever the specified number of
5680 lines is exceeded (or whenever you explicitly request one, using
5683 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5684 those explicitly specified with @code{.eject}.
5687 @section @code{.purgem @var{name}}
5689 @cindex @code{purgem} directive
5690 Undefine the macro @var{name}, so that later uses of the string will not be
5691 expanded. @xref{Macro}.
5695 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5697 @cindex @code{pushsection} directive
5698 @cindex Section Stack
5699 This is one of the ELF section stack manipulation directives. The others are
5700 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5701 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5704 This directive pushes the current section (and subsection) onto the
5705 top of the section stack, and then replaces the current section and
5706 subsection with @code{name} and @code{subsection}. The optional
5707 @code{flags}, @code{type} and @code{arguments} are treated the same
5708 as in the @code{.section} (@pxref{Section}) directive.
5712 @section @code{.quad @var{bignums}}
5714 @cindex @code{quad} directive
5715 @code{.quad} expects zero or more bignums, separated by commas. For
5716 each bignum, it emits
5718 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5719 warning message; and just takes the lowest order 8 bytes of the bignum.
5720 @cindex eight-byte integer
5721 @cindex integer, 8-byte
5723 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5724 hence @emph{quad}-word for 8 bytes.
5727 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5728 warning message; and just takes the lowest order 16 bytes of the bignum.
5729 @cindex sixteen-byte integer
5730 @cindex integer, 16-byte
5734 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5736 @cindex @code{reloc} directive
5737 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5738 @var{expression}. If @var{offset} is a number, the relocation is generated in
5739 the current section. If @var{offset} is an expression that resolves to a
5740 symbol plus offset, the relocation is generated in the given symbol's section.
5741 @var{expression}, if present, must resolve to a symbol plus addend or to an
5742 absolute value, but note that not all targets support an addend. e.g. ELF REL
5743 targets such as i386 store an addend in the section contents rather than in the
5744 relocation. This low level interface does not support addends stored in the
5748 @section @code{.rept @var{count}}
5750 @cindex @code{rept} directive
5751 Repeat the sequence of lines between the @code{.rept} directive and the next
5752 @code{.endr} directive @var{count} times.
5754 For example, assembling
5762 is equivalent to assembling
5771 @section @code{.sbttl "@var{subheading}"}
5773 @cindex @code{sbttl} directive
5774 @cindex subtitles for listings
5775 @cindex listing control: subtitle
5776 Use @var{subheading} as the title (third line, immediately after the
5777 title line) when generating assembly listings.
5779 This directive affects subsequent pages, as well as the current page if
5780 it appears within ten lines of the top of a page.
5784 @section @code{.scl @var{class}}
5786 @cindex @code{scl} directive
5787 @cindex symbol storage class (COFF)
5788 @cindex COFF symbol storage class
5789 Set the storage-class value for a symbol. This directive may only be
5790 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5791 whether a symbol is static or external, or it may record further
5792 symbolic debugging information.
5795 The @samp{.scl} directive is primarily associated with COFF output; when
5796 configured to generate @code{b.out} output format, @command{@value{AS}}
5797 accepts this directive but ignores it.
5803 @section @code{.section @var{name}}
5805 @cindex named section
5806 Use the @code{.section} directive to assemble the following code into a section
5809 This directive is only supported for targets that actually support arbitrarily
5810 named sections; on @code{a.out} targets, for example, it is not accepted, even
5811 with a standard @code{a.out} section name.
5815 @c only print the extra heading if both COFF and ELF are set
5816 @subheading COFF Version
5819 @cindex @code{section} directive (COFF version)
5820 For COFF targets, the @code{.section} directive is used in one of the following
5824 .section @var{name}[, "@var{flags}"]
5825 .section @var{name}[, @var{subsection}]
5828 If the optional argument is quoted, it is taken as flags to use for the
5829 section. Each flag is a single character. The following flags are recognized:
5832 bss section (uninitialized data)
5834 section is not loaded
5844 shared section (meaningful for PE targets)
5846 ignored. (For compatibility with the ELF version)
5848 section is not readable (meaningful for PE targets)
5850 single-digit power-of-two section alignment (GNU extension)
5853 If no flags are specified, the default flags depend upon the section name. If
5854 the section name is not recognized, the default will be for the section to be
5855 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5856 from the section, rather than adding them, so if they are used on their own it
5857 will be as if no flags had been specified at all.
5859 If the optional argument to the @code{.section} directive is not quoted, it is
5860 taken as a subsection number (@pxref{Sub-Sections}).
5865 @c only print the extra heading if both COFF and ELF are set
5866 @subheading ELF Version
5869 @cindex Section Stack
5870 This is one of the ELF section stack manipulation directives. The others are
5871 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5872 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5873 @code{.previous} (@pxref{Previous}).
5875 @cindex @code{section} directive (ELF version)
5876 For ELF targets, the @code{.section} directive is used like this:
5879 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5882 The optional @var{flags} argument is a quoted string which may contain any
5883 combination of the following characters:
5886 section is allocatable
5888 section is excluded from executable and shared library.
5892 section is executable
5894 section is mergeable
5896 section contains zero terminated strings
5898 section is a member of a section group
5900 section is used for thread-local-storage
5902 section is a member of the previously-current section's group, if any
5905 The optional @var{type} argument may contain one of the following constants:
5908 section contains data
5910 section does not contain data (i.e., section only occupies space)
5912 section contains data which is used by things other than the program
5914 section contains an array of pointers to init functions
5916 section contains an array of pointers to finish functions
5917 @item @@preinit_array
5918 section contains an array of pointers to pre-init functions
5921 Many targets only support the first three section types.
5923 Note on targets where the @code{@@} character is the start of a comment (eg
5924 ARM) then another character is used instead. For example the ARM port uses the
5927 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5928 be specified as well as an extra argument---@var{entsize}---like this:
5931 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5934 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5935 constants, each @var{entsize} octets long. Sections with both @code{M} and
5936 @code{S} must contain zero terminated strings where each character is
5937 @var{entsize} bytes long. The linker may remove duplicates within sections with
5938 the same name, same entity size and same flags. @var{entsize} must be an
5939 absolute expression. For sections with both @code{M} and @code{S}, a string
5940 which is a suffix of a larger string is considered a duplicate. Thus
5941 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5942 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5944 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5945 be present along with an additional field like this:
5948 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5951 The @var{GroupName} field specifies the name of the section group to which this
5952 particular section belongs. The optional linkage field can contain:
5955 indicates that only one copy of this section should be retained
5960 Note: if both the @var{M} and @var{G} flags are present then the fields for
5961 the Merge flag should come first, like this:
5964 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5967 If @var{flags} contains the @code{?} symbol then it may not also contain the
5968 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
5969 present. Instead, @code{?} says to consider the section that's current before
5970 this directive. If that section used @code{G}, then the new section will use
5971 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
5972 If not, then the @code{?} symbol has no effect.
5974 If no flags are specified, the default flags depend upon the section name. If
5975 the section name is not recognized, the default will be for the section to have
5976 none of the above flags: it will not be allocated in memory, nor writable, nor
5977 executable. The section will contain data.
5979 For ELF targets, the assembler supports another type of @code{.section}
5980 directive for compatibility with the Solaris assembler:
5983 .section "@var{name}"[, @var{flags}...]
5986 Note that the section name is quoted. There may be a sequence of comma
5990 section is allocatable
5994 section is executable
5996 section is excluded from executable and shared library.
5998 section is used for thread local storage
6001 This directive replaces the current section and subsection. See the
6002 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6003 some examples of how this directive and the other section stack directives
6009 @section @code{.set @var{symbol}, @var{expression}}
6011 @cindex @code{set} directive
6012 @cindex symbol value, setting
6013 Set the value of @var{symbol} to @var{expression}. This
6014 changes @var{symbol}'s value and type to conform to
6015 @var{expression}. If @var{symbol} was flagged as external, it remains
6016 flagged (@pxref{Symbol Attributes}).
6018 You may @code{.set} a symbol many times in the same assembly.
6020 If you @code{.set} a global symbol, the value stored in the object
6021 file is the last value stored into it.
6024 On Z80 @code{set} is a real instruction, use
6025 @samp{@var{symbol} defl @var{expression}} instead.
6029 @section @code{.short @var{expressions}}
6031 @cindex @code{short} directive
6033 @code{.short} is normally the same as @samp{.word}.
6034 @xref{Word,,@code{.word}}.
6036 In some configurations, however, @code{.short} and @code{.word} generate
6037 numbers of different lengths. @xref{Machine Dependencies}.
6041 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6044 This expects zero or more @var{expressions}, and emits
6045 a 16 bit number for each.
6050 @section @code{.single @var{flonums}}
6052 @cindex @code{single} directive
6053 @cindex floating point numbers (single)
6054 This directive assembles zero or more flonums, separated by commas. It
6055 has the same effect as @code{.float}.
6057 The exact kind of floating point numbers emitted depends on how
6058 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6062 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6063 numbers in @sc{ieee} format.
6069 @section @code{.size}
6071 This directive is used to set the size associated with a symbol.
6075 @c only print the extra heading if both COFF and ELF are set
6076 @subheading COFF Version
6079 @cindex @code{size} directive (COFF version)
6080 For COFF targets, the @code{.size} directive is only permitted inside
6081 @code{.def}/@code{.endef} pairs. It is used like this:
6084 .size @var{expression}
6088 @samp{.size} is only meaningful when generating COFF format output; when
6089 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6096 @c only print the extra heading if both COFF and ELF are set
6097 @subheading ELF Version
6100 @cindex @code{size} directive (ELF version)
6101 For ELF targets, the @code{.size} directive is used like this:
6104 .size @var{name} , @var{expression}
6107 This directive sets the size associated with a symbol @var{name}.
6108 The size in bytes is computed from @var{expression} which can make use of label
6109 arithmetic. This directive is typically used to set the size of function
6114 @ifclear no-space-dir
6116 @section @code{.skip @var{size} , @var{fill}}
6118 @cindex @code{skip} directive
6119 @cindex filling memory
6120 This directive emits @var{size} bytes, each of value @var{fill}. Both
6121 @var{size} and @var{fill} are absolute expressions. If the comma and
6122 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6127 @section @code{.sleb128 @var{expressions}}
6129 @cindex @code{sleb128} directive
6130 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6131 compact, variable length representation of numbers used by the DWARF
6132 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6134 @ifclear no-space-dir
6136 @section @code{.space @var{size} , @var{fill}}
6138 @cindex @code{space} directive
6139 @cindex filling memory
6140 This directive emits @var{size} bytes, each of value @var{fill}. Both
6141 @var{size} and @var{fill} are absolute expressions. If the comma
6142 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6147 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6148 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6149 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6150 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6158 @section @code{.stabd, .stabn, .stabs}
6160 @cindex symbolic debuggers, information for
6161 @cindex @code{stab@var{x}} directives
6162 There are three directives that begin @samp{.stab}.
6163 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6164 The symbols are not entered in the @command{@value{AS}} hash table: they
6165 cannot be referenced elsewhere in the source file.
6166 Up to five fields are required:
6170 This is the symbol's name. It may contain any character except
6171 @samp{\000}, so is more general than ordinary symbol names. Some
6172 debuggers used to code arbitrarily complex structures into symbol names
6176 An absolute expression. The symbol's type is set to the low 8 bits of
6177 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6178 and debuggers choke on silly bit patterns.
6181 An absolute expression. The symbol's ``other'' attribute is set to the
6182 low 8 bits of this expression.
6185 An absolute expression. The symbol's descriptor is set to the low 16
6186 bits of this expression.
6189 An absolute expression which becomes the symbol's value.
6192 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6193 or @code{.stabs} statement, the symbol has probably already been created;
6194 you get a half-formed symbol in your object file. This is
6195 compatible with earlier assemblers!
6198 @cindex @code{stabd} directive
6199 @item .stabd @var{type} , @var{other} , @var{desc}
6201 The ``name'' of the symbol generated is not even an empty string.
6202 It is a null pointer, for compatibility. Older assemblers used a
6203 null pointer so they didn't waste space in object files with empty
6206 The symbol's value is set to the location counter,
6207 relocatably. When your program is linked, the value of this symbol
6208 is the address of the location counter when the @code{.stabd} was
6211 @cindex @code{stabn} directive
6212 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6213 The name of the symbol is set to the empty string @code{""}.
6215 @cindex @code{stabs} directive
6216 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6217 All five fields are specified.
6223 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6224 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6226 @cindex string, copying to object file
6227 @cindex string8, copying to object file
6228 @cindex string16, copying to object file
6229 @cindex string32, copying to object file
6230 @cindex string64, copying to object file
6231 @cindex @code{string} directive
6232 @cindex @code{string8} directive
6233 @cindex @code{string16} directive
6234 @cindex @code{string32} directive
6235 @cindex @code{string64} directive
6237 Copy the characters in @var{str} to the object file. You may specify more than
6238 one string to copy, separated by commas. Unless otherwise specified for a
6239 particular machine, the assembler marks the end of each string with a 0 byte.
6240 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6242 The variants @code{string16}, @code{string32} and @code{string64} differ from
6243 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6244 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6245 are stored in target endianness byte order.
6251 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6252 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6257 @section @code{.struct @var{expression}}
6259 @cindex @code{struct} directive
6260 Switch to the absolute section, and set the section offset to @var{expression},
6261 which must be an absolute expression. You might use this as follows:
6270 This would define the symbol @code{field1} to have the value 0, the symbol
6271 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6272 value 8. Assembly would be left in the absolute section, and you would need to
6273 use a @code{.section} directive of some sort to change to some other section
6274 before further assembly.
6278 @section @code{.subsection @var{name}}
6280 @cindex @code{subsection} directive
6281 @cindex Section Stack
6282 This is one of the ELF section stack manipulation directives. The others are
6283 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6284 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6287 This directive replaces the current subsection with @code{name}. The current
6288 section is not changed. The replaced subsection is put onto the section stack
6289 in place of the then current top of stack subsection.
6294 @section @code{.symver}
6295 @cindex @code{symver} directive
6296 @cindex symbol versioning
6297 @cindex versions of symbols
6298 Use the @code{.symver} directive to bind symbols to specific version nodes
6299 within a source file. This is only supported on ELF platforms, and is
6300 typically used when assembling files to be linked into a shared library.
6301 There are cases where it may make sense to use this in objects to be bound
6302 into an application itself so as to override a versioned symbol from a
6305 For ELF targets, the @code{.symver} directive can be used like this:
6307 .symver @var{name}, @var{name2@@nodename}
6309 If the symbol @var{name} is defined within the file
6310 being assembled, the @code{.symver} directive effectively creates a symbol
6311 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6312 just don't try and create a regular alias is that the @var{@@} character isn't
6313 permitted in symbol names. The @var{name2} part of the name is the actual name
6314 of the symbol by which it will be externally referenced. The name @var{name}
6315 itself is merely a name of convenience that is used so that it is possible to
6316 have definitions for multiple versions of a function within a single source
6317 file, and so that the compiler can unambiguously know which version of a
6318 function is being mentioned. The @var{nodename} portion of the alias should be
6319 the name of a node specified in the version script supplied to the linker when
6320 building a shared library. If you are attempting to override a versioned
6321 symbol from a shared library, then @var{nodename} should correspond to the
6322 nodename of the symbol you are trying to override.
6324 If the symbol @var{name} is not defined within the file being assembled, all
6325 references to @var{name} will be changed to @var{name2@@nodename}. If no
6326 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6329 Another usage of the @code{.symver} directive is:
6331 .symver @var{name}, @var{name2@@@@nodename}
6333 In this case, the symbol @var{name} must exist and be defined within
6334 the file being assembled. It is similar to @var{name2@@nodename}. The
6335 difference is @var{name2@@@@nodename} will also be used to resolve
6336 references to @var{name2} by the linker.
6338 The third usage of the @code{.symver} directive is:
6340 .symver @var{name}, @var{name2@@@@@@nodename}
6342 When @var{name} is not defined within the
6343 file being assembled, it is treated as @var{name2@@nodename}. When
6344 @var{name} is defined within the file being assembled, the symbol
6345 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6350 @section @code{.tag @var{structname}}
6352 @cindex COFF structure debugging
6353 @cindex structure debugging, COFF
6354 @cindex @code{tag} directive
6355 This directive is generated by compilers to include auxiliary debugging
6356 information in the symbol table. It is only permitted inside
6357 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6358 definitions in the symbol table with instances of those structures.
6361 @samp{.tag} is only used when generating COFF format output; when
6362 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6368 @section @code{.text @var{subsection}}
6370 @cindex @code{text} directive
6371 Tells @command{@value{AS}} to assemble the following statements onto the end of
6372 the text subsection numbered @var{subsection}, which is an absolute
6373 expression. If @var{subsection} is omitted, subsection number zero
6377 @section @code{.title "@var{heading}"}
6379 @cindex @code{title} directive
6380 @cindex listing control: title line
6381 Use @var{heading} as the title (second line, immediately after the
6382 source file name and pagenumber) when generating assembly listings.
6384 This directive affects subsequent pages, as well as the current page if
6385 it appears within ten lines of the top of a page.
6389 @section @code{.type}
6391 This directive is used to set the type of a symbol.
6395 @c only print the extra heading if both COFF and ELF are set
6396 @subheading COFF Version
6399 @cindex COFF symbol type
6400 @cindex symbol type, COFF
6401 @cindex @code{type} directive (COFF version)
6402 For COFF targets, this directive is permitted only within
6403 @code{.def}/@code{.endef} pairs. It is used like this:
6409 This records the integer @var{int} as the type attribute of a symbol table
6413 @samp{.type} is associated only with COFF format output; when
6414 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6415 directive but ignores it.
6421 @c only print the extra heading if both COFF and ELF are set
6422 @subheading ELF Version
6425 @cindex ELF symbol type
6426 @cindex symbol type, ELF
6427 @cindex @code{type} directive (ELF version)
6428 For ELF targets, the @code{.type} directive is used like this:
6431 .type @var{name} , @var{type description}
6434 This sets the type of symbol @var{name} to be either a
6435 function symbol or an object symbol. There are five different syntaxes
6436 supported for the @var{type description} field, in order to provide
6437 compatibility with various other assemblers.
6439 Because some of the characters used in these syntaxes (such as @samp{@@} and
6440 @samp{#}) are comment characters for some architectures, some of the syntaxes
6441 below do not work on all architectures. The first variant will be accepted by
6442 the GNU assembler on all architectures so that variant should be used for
6443 maximum portability, if you do not need to assemble your code with other
6446 The syntaxes supported are:
6449 .type <name> STT_<TYPE_IN_UPPER_CASE>
6450 .type <name>,#<type>
6451 .type <name>,@@<type>
6452 .type <name>,%<type>
6453 .type <name>,"<type>"
6456 The types supported are:
6461 Mark the symbol as being a function name.
6464 @itemx gnu_indirect_function
6465 Mark the symbol as an indirect function when evaluated during reloc
6466 processing. (This is only supported on assemblers targeting GNU systems).
6470 Mark the symbol as being a data object.
6474 Mark the symbol as being a thead-local data object.
6478 Mark the symbol as being a common data object.
6482 Does not mark the symbol in any way. It is supported just for completeness.
6484 @item gnu_unique_object
6485 Marks the symbol as being a globally unique data object. The dynamic linker
6486 will make sure that in the entire process there is just one symbol with this
6487 name and type in use. (This is only supported on assemblers targeting GNU
6492 Note: Some targets support extra types in addition to those listed above.
6498 @section @code{.uleb128 @var{expressions}}
6500 @cindex @code{uleb128} directive
6501 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6502 compact, variable length representation of numbers used by the DWARF
6503 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6507 @section @code{.val @var{addr}}
6509 @cindex @code{val} directive
6510 @cindex COFF value attribute
6511 @cindex value attribute, COFF
6512 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6513 records the address @var{addr} as the value attribute of a symbol table
6517 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6518 configured for @code{b.out}, it accepts this directive but ignores it.
6524 @section @code{.version "@var{string}"}
6526 @cindex @code{version} directive
6527 This directive creates a @code{.note} section and places into it an ELF
6528 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6533 @section @code{.vtable_entry @var{table}, @var{offset}}
6535 @cindex @code{vtable_entry} directive
6536 This directive finds or creates a symbol @code{table} and creates a
6537 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6540 @section @code{.vtable_inherit @var{child}, @var{parent}}
6542 @cindex @code{vtable_inherit} directive
6543 This directive finds the symbol @code{child} and finds or creates the symbol
6544 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6545 parent whose addend is the value of the child symbol. As a special case the
6546 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6550 @section @code{.warning "@var{string}"}
6551 @cindex warning directive
6552 Similar to the directive @code{.error}
6553 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6556 @section @code{.weak @var{names}}
6558 @cindex @code{weak} directive
6559 This directive sets the weak attribute on the comma separated list of symbol
6560 @code{names}. If the symbols do not already exist, they will be created.
6562 On COFF targets other than PE, weak symbols are a GNU extension. This
6563 directive sets the weak attribute on the comma separated list of symbol
6564 @code{names}. If the symbols do not already exist, they will be created.
6566 On the PE target, weak symbols are supported natively as weak aliases.
6567 When a weak symbol is created that is not an alias, GAS creates an
6568 alternate symbol to hold the default value.
6571 @section @code{.weakref @var{alias}, @var{target}}
6573 @cindex @code{weakref} directive
6574 This directive creates an alias to the target symbol that enables the symbol to
6575 be referenced with weak-symbol semantics, but without actually making it weak.
6576 If direct references or definitions of the symbol are present, then the symbol
6577 will not be weak, but if all references to it are through weak references, the
6578 symbol will be marked as weak in the symbol table.
6580 The effect is equivalent to moving all references to the alias to a separate
6581 assembly source file, renaming the alias to the symbol in it, declaring the
6582 symbol as weak there, and running a reloadable link to merge the object files
6583 resulting from the assembly of the new source file and the old source file that
6584 had the references to the alias removed.
6586 The alias itself never makes to the symbol table, and is entirely handled
6587 within the assembler.
6590 @section @code{.word @var{expressions}}
6592 @cindex @code{word} directive
6593 This directive expects zero or more @var{expressions}, of any section,
6594 separated by commas.
6597 For each expression, @command{@value{AS}} emits a 32-bit number.
6600 For each expression, @command{@value{AS}} emits a 16-bit number.
6605 The size of the number emitted, and its byte order,
6606 depend on what target computer the assembly is for.
6609 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6610 @c happen---32-bit addressability, period; no long/short jumps.
6611 @ifset DIFF-TBL-KLUGE
6612 @cindex difference tables altered
6613 @cindex altered difference tables
6615 @emph{Warning: Special Treatment to support Compilers}
6619 Machines with a 32-bit address space, but that do less than 32-bit
6620 addressing, require the following special treatment. If the machine of
6621 interest to you does 32-bit addressing (or doesn't require it;
6622 @pxref{Machine Dependencies}), you can ignore this issue.
6625 In order to assemble compiler output into something that works,
6626 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6627 Directives of the form @samp{.word sym1-sym2} are often emitted by
6628 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6629 directive of the form @samp{.word sym1-sym2}, and the difference between
6630 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6631 creates a @dfn{secondary jump table}, immediately before the next label.
6632 This secondary jump table is preceded by a short-jump to the
6633 first byte after the secondary table. This short-jump prevents the flow
6634 of control from accidentally falling into the new table. Inside the
6635 table is a long-jump to @code{sym2}. The original @samp{.word}
6636 contains @code{sym1} minus the address of the long-jump to
6639 If there were several occurrences of @samp{.word sym1-sym2} before the
6640 secondary jump table, all of them are adjusted. If there was a
6641 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6642 long-jump to @code{sym4} is included in the secondary jump table,
6643 and the @code{.word} directives are adjusted to contain @code{sym3}
6644 minus the address of the long-jump to @code{sym4}; and so on, for as many
6645 entries in the original jump table as necessary.
6648 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6649 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6650 assembly language programmers.
6653 @c end DIFF-TBL-KLUGE
6656 @section Deprecated Directives
6658 @cindex deprecated directives
6659 @cindex obsolescent directives
6660 One day these directives won't work.
6661 They are included for compatibility with older assemblers.
6668 @node Object Attributes
6669 @chapter Object Attributes
6670 @cindex object attributes
6672 @command{@value{AS}} assembles source files written for a specific architecture
6673 into object files for that architecture. But not all object files are alike.
6674 Many architectures support incompatible variations. For instance, floating
6675 point arguments might be passed in floating point registers if the object file
6676 requires hardware floating point support---or floating point arguments might be
6677 passed in integer registers if the object file supports processors with no
6678 hardware floating point unit. Or, if two objects are built for different
6679 generations of the same architecture, the combination may require the
6680 newer generation at run-time.
6682 This information is useful during and after linking. At link time,
6683 @command{@value{LD}} can warn about incompatible object files. After link
6684 time, tools like @command{gdb} can use it to process the linked file
6687 Compatibility information is recorded as a series of object attributes. Each
6688 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6689 string, and indicates who sets the meaning of the tag. The tag is an integer,
6690 and indicates what property the attribute describes. The value may be a string
6691 or an integer, and indicates how the property affects this object. Missing
6692 attributes are the same as attributes with a zero value or empty string value.
6694 Object attributes were developed as part of the ABI for the ARM Architecture.
6695 The file format is documented in @cite{ELF for the ARM Architecture}.
6698 * GNU Object Attributes:: @sc{gnu} Object Attributes
6699 * Defining New Object Attributes:: Defining New Object Attributes
6702 @node GNU Object Attributes
6703 @section @sc{gnu} Object Attributes
6705 The @code{.gnu_attribute} directive records an object attribute
6706 with vendor @samp{gnu}.
6708 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6709 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6710 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6711 2} is set for architecture-independent attributes and clear for
6712 architecture-dependent ones.
6714 @subsection Common @sc{gnu} attributes
6716 These attributes are valid on all architectures.
6719 @item Tag_compatibility (32)
6720 The compatibility attribute takes an integer flag value and a vendor name. If
6721 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6722 then the file is only compatible with the named toolchain. If it is greater
6723 than 1, the file can only be processed by other toolchains under some private
6724 arrangement indicated by the flag value and the vendor name.
6727 @subsection MIPS Attributes
6730 @item Tag_GNU_MIPS_ABI_FP (4)
6731 The floating-point ABI used by this object file. The value will be:
6735 0 for files not affected by the floating-point ABI.
6737 1 for files using the hardware floating-point with a standard double-precision
6740 2 for files using the hardware floating-point ABI with a single-precision FPU.
6742 3 for files using the software floating-point ABI.
6744 4 for files using the hardware floating-point ABI with 64-bit wide
6745 double-precision floating-point registers and 32-bit wide general
6750 @subsection PowerPC Attributes
6753 @item Tag_GNU_Power_ABI_FP (4)
6754 The floating-point ABI used by this object file. The value will be:
6758 0 for files not affected by the floating-point ABI.
6760 1 for files using double-precision hardware floating-point ABI.
6762 2 for files using the software floating-point ABI.
6764 3 for files using single-precision hardware floating-point ABI.
6767 @item Tag_GNU_Power_ABI_Vector (8)
6768 The vector ABI used by this object file. The value will be:
6772 0 for files not affected by the vector ABI.
6774 1 for files using general purpose registers to pass vectors.
6776 2 for files using AltiVec registers to pass vectors.
6778 3 for files using SPE registers to pass vectors.
6782 @node Defining New Object Attributes
6783 @section Defining New Object Attributes
6785 If you want to define a new @sc{gnu} object attribute, here are the places you
6786 will need to modify. New attributes should be discussed on the @samp{binutils}
6791 This manual, which is the official register of attributes.
6793 The header for your architecture @file{include/elf}, to define the tag.
6795 The @file{bfd} support file for your architecture, to merge the attribute
6796 and issue any appropriate link warnings.
6798 Test cases in @file{ld/testsuite} for merging and link warnings.
6800 @file{binutils/readelf.c} to display your attribute.
6802 GCC, if you want the compiler to mark the attribute automatically.
6808 @node Machine Dependencies
6809 @chapter Machine Dependent Features
6811 @cindex machine dependencies
6812 The machine instruction sets are (almost by definition) different on
6813 each machine where @command{@value{AS}} runs. Floating point representations
6814 vary as well, and @command{@value{AS}} often supports a few additional
6815 directives or command-line options for compatibility with other
6816 assemblers on a particular platform. Finally, some versions of
6817 @command{@value{AS}} support special pseudo-instructions for branch
6820 This chapter discusses most of these differences, though it does not
6821 include details on any machine's instruction set. For details on that
6822 subject, see the hardware manufacturer's manual.
6826 * Alpha-Dependent:: Alpha Dependent Features
6829 * ARC-Dependent:: ARC Dependent Features
6832 * ARM-Dependent:: ARM Dependent Features
6835 * AVR-Dependent:: AVR Dependent Features
6838 * Blackfin-Dependent:: Blackfin Dependent Features
6841 * CR16-Dependent:: CR16 Dependent Features
6844 * CRIS-Dependent:: CRIS Dependent Features
6847 * D10V-Dependent:: D10V Dependent Features
6850 * D30V-Dependent:: D30V Dependent Features
6853 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6856 * HPPA-Dependent:: HPPA Dependent Features
6859 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6862 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6865 * i860-Dependent:: Intel 80860 Dependent Features
6868 * i960-Dependent:: Intel 80960 Dependent Features
6871 * IA-64-Dependent:: Intel IA-64 Dependent Features
6874 * IP2K-Dependent:: IP2K Dependent Features
6877 * LM32-Dependent:: LM32 Dependent Features
6880 * M32C-Dependent:: M32C Dependent Features
6883 * M32R-Dependent:: M32R Dependent Features
6886 * M68K-Dependent:: M680x0 Dependent Features
6889 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6892 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6895 * MIPS-Dependent:: MIPS Dependent Features
6898 * MMIX-Dependent:: MMIX Dependent Features
6901 * MSP430-Dependent:: MSP430 Dependent Features
6904 * NS32K-Dependent:: NS32K Dependent Features
6907 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6908 * SH64-Dependent:: SuperH SH64 Dependent Features
6911 * PDP-11-Dependent:: PDP-11 Dependent Features
6914 * PJ-Dependent:: picoJava Dependent Features
6917 * PPC-Dependent:: PowerPC Dependent Features
6920 * RX-Dependent:: RX Dependent Features
6923 * S/390-Dependent:: IBM S/390 Dependent Features
6926 * SCORE-Dependent:: SCORE Dependent Features
6929 * Sparc-Dependent:: SPARC Dependent Features
6932 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6935 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6938 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
6941 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
6944 * V850-Dependent:: V850 Dependent Features
6947 * XSTORMY16-Dependent:: XStormy16 Dependent Features
6950 * Xtensa-Dependent:: Xtensa Dependent Features
6953 * Z80-Dependent:: Z80 Dependent Features
6956 * Z8000-Dependent:: Z8000 Dependent Features
6959 * Vax-Dependent:: VAX Dependent Features
6966 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6967 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6968 @c peculiarity: to preserve cross-references, there must be a node called
6969 @c "Machine Dependencies". Hence the conditional nodenames in each
6970 @c major node below. Node defaulting in makeinfo requires adjacency of
6971 @c node and sectioning commands; hence the repetition of @chapter BLAH
6972 @c in both conditional blocks.
6975 @include c-alpha.texi
6991 @include c-bfin.texi
6995 @include c-cr16.texi
6999 @include c-cris.texi
7004 @node Machine Dependencies
7005 @chapter Machine Dependent Features
7007 The machine instruction sets are different on each Renesas chip family,
7008 and there are also some syntax differences among the families. This
7009 chapter describes the specific @command{@value{AS}} features for each
7013 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7014 * SH-Dependent:: Renesas SH Dependent Features
7021 @include c-d10v.texi
7025 @include c-d30v.texi
7029 @include c-h8300.texi
7033 @include c-hppa.texi
7037 @include c-i370.texi
7041 @include c-i386.texi
7045 @include c-i860.texi
7049 @include c-i960.texi
7053 @include c-ia64.texi
7057 @include c-ip2k.texi
7061 @include c-lm32.texi
7065 @include c-m32c.texi
7069 @include c-m32r.texi
7073 @include c-m68k.texi
7077 @include c-m68hc11.texi
7081 @include c-microblaze.texi
7085 @include c-mips.texi
7089 @include c-mmix.texi
7093 @include c-msp430.texi
7097 @include c-ns32k.texi
7101 @include c-pdp11.texi
7117 @include c-s390.texi
7121 @include c-score.texi
7126 @include c-sh64.texi
7130 @include c-sparc.texi
7134 @include c-tic54x.texi
7138 @include c-tic6x.texi
7142 @include c-tilegx.texi
7146 @include c-tilepro.texi
7162 @include c-v850.texi
7166 @include c-xstormy16.texi
7170 @include c-xtensa.texi
7174 @c reverse effect of @down at top of generic Machine-Dep chapter
7178 @node Reporting Bugs
7179 @chapter Reporting Bugs
7180 @cindex bugs in assembler
7181 @cindex reporting bugs in assembler
7183 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7185 Reporting a bug may help you by bringing a solution to your problem, or it may
7186 not. But in any case the principal function of a bug report is to help the
7187 entire community by making the next version of @command{@value{AS}} work better.
7188 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7190 In order for a bug report to serve its purpose, you must include the
7191 information that enables us to fix the bug.
7194 * Bug Criteria:: Have you found a bug?
7195 * Bug Reporting:: How to report bugs
7199 @section Have You Found a Bug?
7200 @cindex bug criteria
7202 If you are not sure whether you have found a bug, here are some guidelines:
7205 @cindex fatal signal
7206 @cindex assembler crash
7207 @cindex crash of assembler
7209 If the assembler gets a fatal signal, for any input whatever, that is a
7210 @command{@value{AS}} bug. Reliable assemblers never crash.
7212 @cindex error on valid input
7214 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7216 @cindex invalid input
7218 If @command{@value{AS}} does not produce an error message for invalid input, that
7219 is a bug. However, you should note that your idea of ``invalid input'' might
7220 be our idea of ``an extension'' or ``support for traditional practice''.
7223 If you are an experienced user of assemblers, your suggestions for improvement
7224 of @command{@value{AS}} are welcome in any case.
7228 @section How to Report Bugs
7230 @cindex assembler bugs, reporting
7232 A number of companies and individuals offer support for @sc{gnu} products. If
7233 you obtained @command{@value{AS}} from a support organization, we recommend you
7234 contact that organization first.
7236 You can find contact information for many support companies and
7237 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7241 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7245 The fundamental principle of reporting bugs usefully is this:
7246 @strong{report all the facts}. If you are not sure whether to state a
7247 fact or leave it out, state it!
7249 Often people omit facts because they think they know what causes the problem
7250 and assume that some details do not matter. Thus, you might assume that the
7251 name of a symbol you use in an example does not matter. Well, probably it does
7252 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7253 happens to fetch from the location where that name is stored in memory;
7254 perhaps, if the name were different, the contents of that location would fool
7255 the assembler into doing the right thing despite the bug. Play it safe and
7256 give a specific, complete example. That is the easiest thing for you to do,
7257 and the most helpful.
7259 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7260 it is new to us. Therefore, always write your bug reports on the assumption
7261 that the bug has not been reported previously.
7263 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7264 bell?'' This cannot help us fix a bug, so it is basically useless. We
7265 respond by asking for enough details to enable us to investigate.
7266 You might as well expedite matters by sending them to begin with.
7268 To enable us to fix the bug, you should include all these things:
7272 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7273 it with the @samp{--version} argument.
7275 Without this, we will not know whether there is any point in looking for
7276 the bug in the current version of @command{@value{AS}}.
7279 Any patches you may have applied to the @command{@value{AS}} source.
7282 The type of machine you are using, and the operating system name and
7286 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7290 The command arguments you gave the assembler to assemble your example and
7291 observe the bug. To guarantee you will not omit something important, list them
7292 all. A copy of the Makefile (or the output from make) is sufficient.
7294 If we were to try to guess the arguments, we would probably guess wrong
7295 and then we might not encounter the bug.
7298 A complete input file that will reproduce the bug. If the bug is observed when
7299 the assembler is invoked via a compiler, send the assembler source, not the
7300 high level language source. Most compilers will produce the assembler source
7301 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7302 the options @samp{-v --save-temps}; this will save the assembler source in a
7303 file with an extension of @file{.s}, and also show you exactly how
7304 @command{@value{AS}} is being run.
7307 A description of what behavior you observe that you believe is
7308 incorrect. For example, ``It gets a fatal signal.''
7310 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7311 will certainly notice it. But if the bug is incorrect output, we might not
7312 notice unless it is glaringly wrong. You might as well not give us a chance to
7315 Even if the problem you experience is a fatal signal, you should still say so
7316 explicitly. Suppose something strange is going on, such as, your copy of
7317 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7318 library on your system. (This has happened!) Your copy might crash and ours
7319 would not. If you told us to expect a crash, then when ours fails to crash, we
7320 would know that the bug was not happening for us. If you had not told us to
7321 expect a crash, then we would not be able to draw any conclusion from our
7325 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7326 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7327 option. Always send diffs from the old file to the new file. If you even
7328 discuss something in the @command{@value{AS}} source, refer to it by context, not
7331 The line numbers in our development sources will not match those in your
7332 sources. Your line numbers would convey no useful information to us.
7335 Here are some things that are not necessary:
7339 A description of the envelope of the bug.
7341 Often people who encounter a bug spend a lot of time investigating
7342 which changes to the input file will make the bug go away and which
7343 changes will not affect it.
7345 This is often time consuming and not very useful, because the way we
7346 will find the bug is by running a single example under the debugger
7347 with breakpoints, not by pure deduction from a series of examples.
7348 We recommend that you save your time for something else.
7350 Of course, if you can find a simpler example to report @emph{instead}
7351 of the original one, that is a convenience for us. Errors in the
7352 output will be easier to spot, running under the debugger will take
7353 less time, and so on.
7355 However, simplification is not vital; if you do not want to do this,
7356 report the bug anyway and send us the entire test case you used.
7359 A patch for the bug.
7361 A patch for the bug does help us if it is a good one. But do not omit
7362 the necessary information, such as the test case, on the assumption that
7363 a patch is all we need. We might see problems with your patch and decide
7364 to fix the problem another way, or we might not understand it at all.
7366 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7367 construct an example that will make the program follow a certain path through
7368 the code. If you do not send us the example, we will not be able to construct
7369 one, so we will not be able to verify that the bug is fixed.
7371 And if we cannot understand what bug you are trying to fix, or why your
7372 patch should be an improvement, we will not install it. A test case will
7373 help us to understand.
7376 A guess about what the bug is or what it depends on.
7378 Such guesses are usually wrong. Even we cannot guess right about such
7379 things without first using the debugger to find the facts.
7382 @node Acknowledgements
7383 @chapter Acknowledgements
7385 If you have contributed to GAS and your name isn't listed here,
7386 it is not meant as a slight. We just don't know about it. Send mail to the
7387 maintainer, and we'll correct the situation. Currently
7389 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7391 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7394 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7395 information and the 68k series machines, most of the preprocessing pass, and
7396 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7398 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7399 many bug fixes, including merging support for several processors, breaking GAS
7400 up to handle multiple object file format back ends (including heavy rewrite,
7401 testing, an integration of the coff and b.out back ends), adding configuration
7402 including heavy testing and verification of cross assemblers and file splits
7403 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7404 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7405 port (including considerable amounts of reverse engineering), a SPARC opcode
7406 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7407 assertions and made them work, much other reorganization, cleanup, and lint.
7409 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7410 in format-specific I/O modules.
7412 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7413 has done much work with it since.
7415 The Intel 80386 machine description was written by Eliot Dresselhaus.
7417 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7419 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7420 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7422 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7423 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7424 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7425 support a.out format.
7427 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7428 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7429 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7430 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7433 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7434 simplified the configuration of which versions accept which directives. He
7435 updated the 68k machine description so that Motorola's opcodes always produced
7436 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7437 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7438 cross-compilation support, and one bug in relaxation that took a week and
7439 required the proverbial one-bit fix.
7441 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7442 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7443 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7444 PowerPC assembler, and made a few other minor patches.
7446 Steve Chamberlain made GAS able to generate listings.
7448 Hewlett-Packard contributed support for the HP9000/300.
7450 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7451 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7452 formats). This work was supported by both the Center for Software Science at
7453 the University of Utah and Cygnus Support.
7455 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7456 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7457 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7458 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7459 and some initial 64-bit support).
7461 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7463 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7464 support for openVMS/Alpha.
7466 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7469 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7470 Inc.@: added support for Xtensa processors.
7472 Several engineers at Cygnus Support have also provided many small bug fixes and
7473 configuration enhancements.
7475 Jon Beniston added support for the Lattice Mico32 architecture.
7477 Many others have contributed large or small bugfixes and enhancements. If
7478 you have contributed significant work and are not mentioned on this list, and
7479 want to be, let us know. Some of the history has been lost; we are not
7480 intentionally leaving anyone out.
7482 @node GNU Free Documentation License
7483 @appendix GNU Free Documentation License
7487 @unnumbered AS Index