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, 2012
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 AArch64 options:}
259 @emph{Target Alpha options:}
261 [@b{-mdebug} | @b{-no-mdebug}]
262 [@b{-replace} | @b{-noreplace}]
263 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
264 [@b{-F}] [@b{-32addr}]
268 @emph{Target ARC options:}
274 @emph{Target ARM options:}
275 @c Don't document the deprecated options
276 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
277 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
278 [@b{-mfpu}=@var{floating-point-format}]
279 [@b{-mfloat-abi}=@var{abi}]
280 [@b{-meabi}=@var{ver}]
283 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
284 @b{-mapcs-reentrant}]
285 [@b{-mthumb-interwork}] [@b{-k}]
289 @emph{Target Blackfin options:}
290 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
297 @emph{Target CRIS options:}
298 [@b{--underscore} | @b{--no-underscore}]
300 [@b{--emulation=criself} | @b{--emulation=crisaout}]
301 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
302 @c Deprecated -- deliberately not documented.
307 @emph{Target D10V options:}
312 @emph{Target D30V options:}
313 [@b{-O}|@b{-n}|@b{-N}]
317 @emph{Target EPIPHANY options:}
318 [@b{-mepiphany}|@b{-mepiphany16}]
322 @emph{Target H8/300 options:}
326 @c HPPA has no machine-dependent assembler options (yet).
330 @emph{Target i386 options:}
331 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
332 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
336 @emph{Target i960 options:}
337 @c see md_parse_option in tc-i960.c
338 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
340 [@b{-b}] [@b{-no-relax}]
344 @emph{Target IA-64 options:}
345 [@b{-mconstant-gp}|@b{-mauto-pic}]
346 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
348 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
349 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
350 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
351 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
355 @emph{Target IP2K options:}
356 [@b{-mip2022}|@b{-mip2022ext}]
360 @emph{Target M32C options:}
361 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
365 @emph{Target M32R options:}
366 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
371 @emph{Target M680X0 options:}
372 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
376 @emph{Target M68HC11 options:}
377 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
378 [@b{-mshort}|@b{-mlong}]
379 [@b{-mshort-double}|@b{-mlong-double}]
380 [@b{--force-long-branches}] [@b{--short-branches}]
381 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
382 [@b{--print-opcodes}] [@b{--generate-example}]
386 @emph{Target MCORE options:}
387 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
388 [@b{-mcpu=[210|340]}]
392 @emph{Target Meta options:}
393 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
396 @emph{Target MICROBLAZE options:}
397 @c MicroBlaze has no machine-dependent assembler options.
401 @emph{Target MIPS options:}
402 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
403 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
404 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
405 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
406 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
407 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
408 [@b{-mips64}] [@b{-mips64r2}]
409 [@b{-construct-floats}] [@b{-no-construct-floats}]
410 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
411 [@b{-mips16}] [@b{-no-mips16}]
412 [@b{-mmicromips}] [@b{-mno-micromips}]
413 [@b{-msmartmips}] [@b{-mno-smartmips}]
414 [@b{-mips3d}] [@b{-no-mips3d}]
415 [@b{-mdmx}] [@b{-no-mdmx}]
416 [@b{-mdsp}] [@b{-mno-dsp}]
417 [@b{-mdspr2}] [@b{-mno-dspr2}]
418 [@b{-mmt}] [@b{-mno-mt}]
419 [@b{-mmcu}] [@b{-mno-mcu}]
420 [@b{-mfix7000}] [@b{-mno-fix7000}]
421 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
422 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
423 [@b{-mdebug}] [@b{-no-mdebug}]
424 [@b{-mpdr}] [@b{-mno-pdr}]
428 @emph{Target MMIX options:}
429 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
430 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
431 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
432 [@b{--linker-allocated-gregs}]
436 @emph{Target PDP11 options:}
437 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
438 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
439 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
443 @emph{Target picoJava options:}
448 @emph{Target PowerPC options:}
450 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
451 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
452 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
453 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
454 @b{-mpower7}|@b{-mpwr7}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mvle}|@b{-mcom}]
455 [@b{-many}] [@b{-maltivec}|@b{-mvsx}]
456 [@b{-mregnames}|@b{-mno-regnames}]
457 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
458 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
459 [@b{-msolaris}|@b{-mno-solaris}]
460 [@b{-nops=@var{count}}]
464 @emph{Target RX options:}
465 [@b{-mlittle-endian}|@b{-mbig-endian}]
466 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
467 [@b{-muse-conventional-section-names}]
468 [@b{-msmall-data-limit}]
471 [@b{-mint-register=@var{number}}]
472 [@b{-mgcc-abi}|@b{-mrx-abi}]
476 @emph{Target s390 options:}
477 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
478 [@b{-mregnames}|@b{-mno-regnames}]
479 [@b{-mwarn-areg-zero}]
483 @emph{Target SCORE options:}
484 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
485 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
486 [@b{-march=score7}][@b{-march=score3}]
487 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
491 @emph{Target SPARC options:}
492 @c The order here is important. See c-sparc.texi.
493 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
494 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
495 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
500 @emph{Target TIC54X options:}
501 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
502 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
507 @emph{Target TIC6X options:}
508 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
509 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
510 [@b{-mpic}|@b{-mno-pic}]
514 @emph{Target TILE-Gx options:}
515 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
518 @c TILEPro has no machine-dependent assembler options
523 @emph{Target Xtensa options:}
524 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
525 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
526 [@b{--[no-]transform}]
527 [@b{--rename-section} @var{oldname}=@var{newname}]
532 @emph{Target Z80 options:}
533 [@b{-z80}] [@b{-r800}]
534 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
535 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
536 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
537 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
538 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
539 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
543 @c Z8000 has no machine-dependent assembler options
552 @include at-file.texi
555 Turn on listings, in any of a variety of ways:
559 omit false conditionals
562 omit debugging directives
565 include general information, like @value{AS} version and options passed
568 include high-level source
574 include macro expansions
577 omit forms processing
583 set the name of the listing file
586 You may combine these options; for example, use @samp{-aln} for assembly
587 listing without forms processing. The @samp{=file} option, if used, must be
588 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
591 Begin in alternate macro mode.
593 @xref{Altmacro,,@code{.altmacro}}.
596 @item --compress-debug-sections
597 Compress DWARF debug sections using zlib. The debug sections are renamed
598 to begin with @samp{.zdebug}, and the resulting object file may not be
599 compatible with older linkers and object file utilities.
601 @item --nocompress-debug-sections
602 Do not compress DWARF debug sections. This is the default.
605 Ignored. This option is accepted for script compatibility with calls to
608 @item --debug-prefix-map @var{old}=@var{new}
609 When assembling files in directory @file{@var{old}}, record debugging
610 information describing them as in @file{@var{new}} instead.
612 @item --defsym @var{sym}=@var{value}
613 Define the symbol @var{sym} to be @var{value} before assembling the input file.
614 @var{value} must be an integer constant. As in C, a leading @samp{0x}
615 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
616 value. The value of the symbol can be overridden inside a source file via the
617 use of a @code{.set} pseudo-op.
620 ``fast''---skip whitespace and comment preprocessing (assume source is
625 Generate debugging information for each assembler source line using whichever
626 debug format is preferred by the target. This currently means either STABS,
630 Generate stabs debugging information for each assembler line. This
631 may help debugging assembler code, if the debugger can handle it.
634 Generate stabs debugging information for each assembler line, with GNU
635 extensions that probably only gdb can handle, and that could make other
636 debuggers crash or refuse to read your program. This
637 may help debugging assembler code. Currently the only GNU extension is
638 the location of the current working directory at assembling time.
641 Generate DWARF2 debugging information for each assembler line. This
642 may help debugging assembler code, if the debugger can handle it. Note---this
643 option is only supported by some targets, not all of them.
645 @item --size-check=error
646 @itemx --size-check=warning
647 Issue an error or warning for invalid ELF .size directive.
650 Print a summary of the command line options and exit.
653 Print a summary of all target specific options and exit.
656 Add directory @var{dir} to the search list for @code{.include} directives.
659 Don't warn about signed overflow.
662 @ifclear DIFF-TBL-KLUGE
663 This option is accepted but has no effect on the @value{TARGET} family.
665 @ifset DIFF-TBL-KLUGE
666 Issue warnings when difference tables altered for long displacements.
671 Keep (in the symbol table) local symbols. These symbols start with
672 system-specific local label prefixes, typically @samp{.L} for ELF systems
673 or @samp{L} for traditional a.out systems.
678 @item --listing-lhs-width=@var{number}
679 Set the maximum width, in words, of the output data column for an assembler
680 listing to @var{number}.
682 @item --listing-lhs-width2=@var{number}
683 Set the maximum width, in words, of the output data column for continuation
684 lines in an assembler listing to @var{number}.
686 @item --listing-rhs-width=@var{number}
687 Set the maximum width of an input source line, as displayed in a listing, to
690 @item --listing-cont-lines=@var{number}
691 Set the maximum number of lines printed in a listing for a single line of input
694 @item -o @var{objfile}
695 Name the object-file output from @command{@value{AS}} @var{objfile}.
698 Fold the data section into the text section.
700 @kindex --hash-size=@var{number}
701 Set the default size of GAS's hash tables to a prime number close to
702 @var{number}. Increasing this value can reduce the length of time it takes the
703 assembler to perform its tasks, at the expense of increasing the assembler's
704 memory requirements. Similarly reducing this value can reduce the memory
705 requirements at the expense of speed.
707 @item --reduce-memory-overheads
708 This option reduces GAS's memory requirements, at the expense of making the
709 assembly processes slower. Currently this switch is a synonym for
710 @samp{--hash-size=4051}, but in the future it may have other effects as well.
713 Print the maximum space (in bytes) and total time (in seconds) used by
716 @item --strip-local-absolute
717 Remove local absolute symbols from the outgoing symbol table.
721 Print the @command{as} version.
724 Print the @command{as} version and exit.
728 Suppress warning messages.
730 @item --fatal-warnings
731 Treat warnings as errors.
734 Don't suppress warning messages or treat them as errors.
743 Generate an object file even after errors.
745 @item -- | @var{files} @dots{}
746 Standard input, or source files to assemble.
754 @xref{AArch64 Options}, for the options available when @value{AS} is configured
755 for the 64-bit mode of the ARM Architecture (AArch64).
760 The following options are available when @value{AS} is configured for the
761 64-bit mode of the ARM Architecture (AArch64).
764 @include c-aarch64.texi
765 @c ended inside the included file
773 @xref{Alpha Options}, for the options available when @value{AS} is configured
774 for an Alpha processor.
779 The following options are available when @value{AS} is configured for an Alpha
783 @include c-alpha.texi
784 @c ended inside the included file
791 The following options are available when @value{AS} is configured for
796 This option selects the core processor variant.
798 Select either big-endian (-EB) or little-endian (-EL) output.
803 The following options are available when @value{AS} is configured for the ARM
807 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
808 Specify which ARM processor variant is the target.
809 @item -march=@var{architecture}[+@var{extension}@dots{}]
810 Specify which ARM architecture variant is used by the target.
811 @item -mfpu=@var{floating-point-format}
812 Select which Floating Point architecture is the target.
813 @item -mfloat-abi=@var{abi}
814 Select which floating point ABI is in use.
816 Enable Thumb only instruction decoding.
817 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
818 Select which procedure calling convention is in use.
820 Select either big-endian (-EB) or little-endian (-EL) output.
821 @item -mthumb-interwork
822 Specify that the code has been generated with interworking between Thumb and
825 Specify that PIC code has been generated.
833 @xref{Blackfin Options}, for the options available when @value{AS} is
834 configured for the Blackfin processor family.
839 The following options are available when @value{AS} is configured for
840 the Blackfin processor family.
844 @c ended inside the included file
851 See the info pages for documentation of the CRIS-specific options.
855 The following options are available when @value{AS} is configured for
858 @cindex D10V optimization
859 @cindex optimization, D10V
861 Optimize output by parallelizing instructions.
866 The following options are available when @value{AS} is configured for a D30V
869 @cindex D30V optimization
870 @cindex optimization, D30V
872 Optimize output by parallelizing instructions.
876 Warn when nops are generated.
878 @cindex D30V nops after 32-bit multiply
880 Warn when a nop after a 32-bit multiply instruction is generated.
886 The following options are available when @value{AS} is configured for the
887 Adapteva EPIPHANY series.
890 @xref{Epiphany Options}, for the options available when @value{AS} is
891 configured for an Epiphany processor.
896 The following options are available when @value{AS} is configured for
897 an Epiphany processor.
900 @include c-epiphany.texi
901 @c ended inside the included file
909 @xref{i386-Options}, for the options available when @value{AS} is
910 configured for an i386 processor.
915 The following options are available when @value{AS} is configured for
920 @c ended inside the included file
927 The following options are available when @value{AS} is configured for the
928 Intel 80960 processor.
931 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
932 Specify which variant of the 960 architecture is the target.
935 Add code to collect statistics about branches taken.
938 Do not alter compare-and-branch instructions for long displacements;
945 The following options are available when @value{AS} is configured for the
951 Specifies that the extended IP2022 instructions are allowed.
954 Restores the default behaviour, which restricts the permitted instructions to
955 just the basic IP2022 ones.
961 The following options are available when @value{AS} is configured for the
962 Renesas M32C and M16C processors.
967 Assemble M32C instructions.
970 Assemble M16C instructions (the default).
973 Enable support for link-time relaxations.
976 Support H'00 style hex constants in addition to 0x00 style.
982 The following options are available when @value{AS} is configured for the
983 Renesas M32R (formerly Mitsubishi M32R) series.
988 Specify which processor in the M32R family is the target. The default
989 is normally the M32R, but this option changes it to the M32RX.
991 @item --warn-explicit-parallel-conflicts or --Wp
992 Produce warning messages when questionable parallel constructs are
995 @item --no-warn-explicit-parallel-conflicts or --Wnp
996 Do not produce warning messages when questionable parallel constructs are
1003 The following options are available when @value{AS} is configured for the
1004 Motorola 68000 series.
1009 Shorten references to undefined symbols, to one word instead of two.
1011 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1012 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1013 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1014 Specify what processor in the 68000 family is the target. The default
1015 is normally the 68020, but this can be changed at configuration time.
1017 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1018 The target machine does (or does not) have a floating-point coprocessor.
1019 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1020 the basic 68000 is not compatible with the 68881, a combination of the
1021 two can be specified, since it's possible to do emulation of the
1022 coprocessor instructions with the main processor.
1024 @item -m68851 | -mno-68851
1025 The target machine does (or does not) have a memory-management
1026 unit coprocessor. The default is to assume an MMU for 68020 and up.
1033 For details about the PDP-11 machine dependent features options,
1034 see @ref{PDP-11-Options}.
1037 @item -mpic | -mno-pic
1038 Generate position-independent (or position-dependent) code. The
1039 default is @option{-mpic}.
1042 @itemx -mall-extensions
1043 Enable all instruction set extensions. This is the default.
1045 @item -mno-extensions
1046 Disable all instruction set extensions.
1048 @item -m@var{extension} | -mno-@var{extension}
1049 Enable (or disable) a particular instruction set extension.
1052 Enable the instruction set extensions supported by a particular CPU, and
1053 disable all other extensions.
1055 @item -m@var{machine}
1056 Enable the instruction set extensions supported by a particular machine
1057 model, and disable all other extensions.
1063 The following options are available when @value{AS} is configured for
1064 a picoJava processor.
1068 @cindex PJ endianness
1069 @cindex endianness, PJ
1070 @cindex big endian output, PJ
1072 Generate ``big endian'' format output.
1074 @cindex little endian output, PJ
1076 Generate ``little endian'' format output.
1082 The following options are available when @value{AS} is configured for the
1083 Motorola 68HC11 or 68HC12 series.
1087 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1088 Specify what processor is the target. The default is
1089 defined by the configuration option when building the assembler.
1091 @item --xgate-ramoffset
1092 Instruct the linker to offset RAM addresses from S12X address space into
1093 XGATE address space.
1096 Specify to use the 16-bit integer ABI.
1099 Specify to use the 32-bit integer ABI.
1101 @item -mshort-double
1102 Specify to use the 32-bit double ABI.
1105 Specify to use the 64-bit double ABI.
1107 @item --force-long-branches
1108 Relative branches are turned into absolute ones. This concerns
1109 conditional branches, unconditional branches and branches to a
1112 @item -S | --short-branches
1113 Do not turn relative branches into absolute ones
1114 when the offset is out of range.
1116 @item --strict-direct-mode
1117 Do not turn the direct addressing mode into extended addressing mode
1118 when the instruction does not support direct addressing mode.
1120 @item --print-insn-syntax
1121 Print the syntax of instruction in case of error.
1123 @item --print-opcodes
1124 Print the list of instructions with syntax and then exit.
1126 @item --generate-example
1127 Print an example of instruction for each possible instruction and then exit.
1128 This option is only useful for testing @command{@value{AS}}.
1134 The following options are available when @command{@value{AS}} is configured
1135 for the SPARC architecture:
1138 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1139 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1140 Explicitly select a variant of the SPARC architecture.
1142 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1143 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1145 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1146 UltraSPARC extensions.
1148 @item -xarch=v8plus | -xarch=v8plusa
1149 For compatibility with the Solaris v9 assembler. These options are
1150 equivalent to -Av8plus and -Av8plusa, respectively.
1153 Warn when the assembler switches to another architecture.
1158 The following options are available when @value{AS} is configured for the 'c54x
1163 Enable extended addressing mode. All addresses and relocations will assume
1164 extended addressing (usually 23 bits).
1165 @item -mcpu=@var{CPU_VERSION}
1166 Sets the CPU version being compiled for.
1167 @item -merrors-to-file @var{FILENAME}
1168 Redirect error output to a file, for broken systems which don't support such
1169 behaviour in the shell.
1174 The following options are available when @value{AS} is configured for
1175 a @sc{mips} processor.
1179 This option sets the largest size of an object that can be referenced
1180 implicitly with the @code{gp} register. It is only accepted for targets that
1181 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1183 @cindex MIPS endianness
1184 @cindex endianness, MIPS
1185 @cindex big endian output, MIPS
1187 Generate ``big endian'' format output.
1189 @cindex little endian output, MIPS
1191 Generate ``little endian'' format output.
1203 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1204 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1205 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1206 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1207 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1209 correspond to generic
1210 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1211 and @samp{MIPS64 Release 2}
1212 ISA processors, respectively.
1214 @item -march=@var{CPU}
1215 Generate code for a particular @sc{mips} cpu.
1217 @item -mtune=@var{cpu}
1218 Schedule and tune for a particular @sc{mips} cpu.
1222 Cause nops to be inserted if the read of the destination register
1223 of an mfhi or mflo instruction occurs in the following two instructions.
1227 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1228 section instead of the standard ELF .stabs sections.
1232 Control generation of @code{.pdr} sections.
1236 The register sizes are normally inferred from the ISA and ABI, but these
1237 flags force a certain group of registers to be treated as 32 bits wide at
1238 all times. @samp{-mgp32} controls the size of general-purpose registers
1239 and @samp{-mfp32} controls the size of floating-point registers.
1243 Generate code for the MIPS 16 processor. This is equivalent to putting
1244 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1245 turns off this option.
1248 @itemx -mno-micromips
1249 Generate code for the microMIPS processor. This is equivalent to putting
1250 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1251 turns off this option. This is equivalent to putting @code{.set nomicromips}
1252 at the start of the assembly file.
1255 @itemx -mno-smartmips
1256 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1257 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1258 @samp{-mno-smartmips} turns off this option.
1262 Generate code for the MIPS-3D Application Specific Extension.
1263 This tells the assembler to accept MIPS-3D instructions.
1264 @samp{-no-mips3d} turns off this option.
1268 Generate code for the MDMX Application Specific Extension.
1269 This tells the assembler to accept MDMX instructions.
1270 @samp{-no-mdmx} turns off this option.
1274 Generate code for the DSP Release 1 Application Specific Extension.
1275 This tells the assembler to accept DSP Release 1 instructions.
1276 @samp{-mno-dsp} turns off this option.
1280 Generate code for the DSP Release 2 Application Specific Extension.
1281 This option implies -mdsp.
1282 This tells the assembler to accept DSP Release 2 instructions.
1283 @samp{-mno-dspr2} turns off this option.
1287 Generate code for the MT Application Specific Extension.
1288 This tells the assembler to accept MT instructions.
1289 @samp{-mno-mt} turns off this option.
1293 Generate code for the MCU Application Specific Extension.
1294 This tells the assembler to accept MCU instructions.
1295 @samp{-mno-mcu} turns off this option.
1297 @item --construct-floats
1298 @itemx --no-construct-floats
1299 The @samp{--no-construct-floats} option disables the construction of
1300 double width floating point constants by loading the two halves of the
1301 value into the two single width floating point registers that make up
1302 the double width register. By default @samp{--construct-floats} is
1303 selected, allowing construction of these floating point constants.
1306 @item --emulation=@var{name}
1307 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1308 for some other target, in all respects, including output format (choosing
1309 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1310 debugging information or store symbol table information, and default
1311 endianness. The available configuration names are: @samp{mipsecoff},
1312 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1313 @samp{mipsbelf}. The first two do not alter the default endianness from that
1314 of the primary target for which the assembler was configured; the others change
1315 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1316 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1317 selection in any case.
1319 This option is currently supported only when the primary target
1320 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1321 Furthermore, the primary target or others specified with
1322 @samp{--enable-targets=@dots{}} at configuration time must include support for
1323 the other format, if both are to be available. For example, the Irix 5
1324 configuration includes support for both.
1326 Eventually, this option will support more configurations, with more
1327 fine-grained control over the assembler's behavior, and will be supported for
1331 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1338 Control how to deal with multiplication overflow and division by zero.
1339 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1340 (and only work for Instruction Set Architecture level 2 and higher);
1341 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1345 When this option is used, @command{@value{AS}} will issue a warning every
1346 time it generates a nop instruction from a macro.
1351 The following options are available when @value{AS} is configured for
1357 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1358 The command line option @samp{-nojsri2bsr} can be used to disable it.
1362 Enable or disable the silicon filter behaviour. By default this is disabled.
1363 The default can be overridden by the @samp{-sifilter} command line option.
1366 Alter jump instructions for long displacements.
1368 @item -mcpu=[210|340]
1369 Select the cpu type on the target hardware. This controls which instructions
1373 Assemble for a big endian target.
1376 Assemble for a little endian target.
1385 @xref{Meta Options}, for the options available when @value{AS} is configured
1386 for a Meta processor.
1390 @c man begin OPTIONS
1391 The following options are available when @value{AS} is configured for a
1394 @c man begin INCLUDE
1395 @include c-metag.texi
1396 @c ended inside the included file
1401 @c man begin OPTIONS
1403 See the info pages for documentation of the MMIX-specific options.
1410 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1411 for a PowerPC processor.
1415 @c man begin OPTIONS
1416 The following options are available when @value{AS} is configured for a
1419 @c man begin INCLUDE
1421 @c ended inside the included file
1426 @c man begin OPTIONS
1428 See the info pages for documentation of the RX-specific options.
1432 The following options are available when @value{AS} is configured for the s390
1438 Select the word size, either 31/32 bits or 64 bits.
1441 Select the architecture mode, either the Enterprise System
1442 Architecture (esa) or the z/Architecture mode (zarch).
1443 @item -march=@var{processor}
1444 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1445 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1446 @samp{z196}, or @samp{zEC12}.
1448 @itemx -mno-regnames
1449 Allow or disallow symbolic names for registers.
1450 @item -mwarn-areg-zero
1451 Warn whenever the operand for a base or index register has been specified
1452 but evaluates to zero.
1460 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1461 for a TMS320C6000 processor.
1465 @c man begin OPTIONS
1466 The following options are available when @value{AS} is configured for a
1467 TMS320C6000 processor.
1469 @c man begin INCLUDE
1470 @include c-tic6x.texi
1471 @c ended inside the included file
1479 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1480 for a TILE-Gx processor.
1484 @c man begin OPTIONS
1485 The following options are available when @value{AS} is configured for a TILE-Gx
1488 @c man begin INCLUDE
1489 @include c-tilegx.texi
1490 @c ended inside the included file
1498 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1499 for an Xtensa processor.
1503 @c man begin OPTIONS
1504 The following options are available when @value{AS} is configured for an
1507 @c man begin INCLUDE
1508 @include c-xtensa.texi
1509 @c ended inside the included file
1514 @c man begin OPTIONS
1517 The following options are available when @value{AS} is configured for
1518 a Z80 family processor.
1521 Assemble for Z80 processor.
1523 Assemble for R800 processor.
1524 @item -ignore-undocumented-instructions
1526 Assemble undocumented Z80 instructions that also work on R800 without warning.
1527 @item -ignore-unportable-instructions
1529 Assemble all undocumented Z80 instructions without warning.
1530 @item -warn-undocumented-instructions
1532 Issue a warning for undocumented Z80 instructions that also work on R800.
1533 @item -warn-unportable-instructions
1535 Issue a warning for undocumented Z80 instructions that do not work on R800.
1536 @item -forbid-undocumented-instructions
1538 Treat all undocumented instructions as errors.
1539 @item -forbid-unportable-instructions
1541 Treat undocumented Z80 instructions that do not work on R800 as errors.
1548 * Manual:: Structure of this Manual
1549 * GNU Assembler:: The GNU Assembler
1550 * Object Formats:: Object File Formats
1551 * Command Line:: Command Line
1552 * Input Files:: Input Files
1553 * Object:: Output (Object) File
1554 * Errors:: Error and Warning Messages
1558 @section Structure of this Manual
1560 @cindex manual, structure and purpose
1561 This manual is intended to describe what you need to know to use
1562 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1563 notation for symbols, constants, and expressions; the directives that
1564 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1567 We also cover special features in the @value{TARGET}
1568 configuration of @command{@value{AS}}, including assembler directives.
1571 This manual also describes some of the machine-dependent features of
1572 various flavors of the assembler.
1575 @cindex machine instructions (not covered)
1576 On the other hand, this manual is @emph{not} intended as an introduction
1577 to programming in assembly language---let alone programming in general!
1578 In a similar vein, we make no attempt to introduce the machine
1579 architecture; we do @emph{not} describe the instruction set, standard
1580 mnemonics, registers or addressing modes that are standard to a
1581 particular architecture.
1583 You may want to consult the manufacturer's
1584 machine architecture manual for this information.
1588 For information on the H8/300 machine instruction set, see @cite{H8/300
1589 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1590 Programming Manual} (Renesas).
1593 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1594 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1595 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1596 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1599 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1603 @c I think this is premature---doc@cygnus.com, 17jan1991
1605 Throughout this manual, we assume that you are running @dfn{GNU},
1606 the portable operating system from the @dfn{Free Software
1607 Foundation, Inc.}. This restricts our attention to certain kinds of
1608 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1609 once this assumption is granted examples and definitions need less
1612 @command{@value{AS}} is part of a team of programs that turn a high-level
1613 human-readable series of instructions into a low-level
1614 computer-readable series of instructions. Different versions of
1615 @command{@value{AS}} are used for different kinds of computer.
1618 @c There used to be a section "Terminology" here, which defined
1619 @c "contents", "byte", "word", and "long". Defining "word" to any
1620 @c particular size is confusing when the .word directive may generate 16
1621 @c bits on one machine and 32 bits on another; in general, for the user
1622 @c version of this manual, none of these terms seem essential to define.
1623 @c They were used very little even in the former draft of the manual;
1624 @c this draft makes an effort to avoid them (except in names of
1628 @section The GNU Assembler
1630 @c man begin DESCRIPTION
1632 @sc{gnu} @command{as} is really a family of assemblers.
1634 This manual describes @command{@value{AS}}, a member of that family which is
1635 configured for the @value{TARGET} architectures.
1637 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1638 should find a fairly similar environment when you use it on another
1639 architecture. Each version has much in common with the others,
1640 including object file formats, most assembler directives (often called
1641 @dfn{pseudo-ops}) and assembler syntax.@refill
1643 @cindex purpose of @sc{gnu} assembler
1644 @command{@value{AS}} is primarily intended to assemble the output of the
1645 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1646 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1647 assemble correctly everything that other assemblers for the same
1648 machine would assemble.
1650 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1653 @c This remark should appear in generic version of manual; assumption
1654 @c here is that generic version sets M680x0.
1655 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1656 assembler for the same architecture; for example, we know of several
1657 incompatible versions of 680x0 assembly language syntax.
1662 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1663 program in one pass of the source file. This has a subtle impact on the
1664 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1666 @node Object Formats
1667 @section Object File Formats
1669 @cindex object file format
1670 The @sc{gnu} assembler can be configured to produce several alternative
1671 object file formats. For the most part, this does not affect how you
1672 write assembly language programs; but directives for debugging symbols
1673 are typically different in different file formats. @xref{Symbol
1674 Attributes,,Symbol Attributes}.
1677 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1678 @value{OBJ-NAME} format object files.
1680 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1682 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1683 @code{b.out} or COFF format object files.
1686 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1687 SOM or ELF format object files.
1692 @section Command Line
1694 @cindex command line conventions
1696 After the program name @command{@value{AS}}, the command line may contain
1697 options and file names. Options may appear in any order, and may be
1698 before, after, or between file names. The order of file names is
1701 @cindex standard input, as input file
1703 @file{--} (two hyphens) by itself names the standard input file
1704 explicitly, as one of the files for @command{@value{AS}} to assemble.
1706 @cindex options, command line
1707 Except for @samp{--} any command line argument that begins with a
1708 hyphen (@samp{-}) is an option. Each option changes the behavior of
1709 @command{@value{AS}}. No option changes the way another option works. An
1710 option is a @samp{-} followed by one or more letters; the case of
1711 the letter is important. All options are optional.
1713 Some options expect exactly one file name to follow them. The file
1714 name may either immediately follow the option's letter (compatible
1715 with older assemblers) or it may be the next command argument (@sc{gnu}
1716 standard). These two command lines are equivalent:
1719 @value{AS} -o my-object-file.o mumble.s
1720 @value{AS} -omy-object-file.o mumble.s
1724 @section Input Files
1727 @cindex source program
1728 @cindex files, input
1729 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1730 describe the program input to one run of @command{@value{AS}}. The program may
1731 be in one or more files; how the source is partitioned into files
1732 doesn't change the meaning of the source.
1734 @c I added "con" prefix to "catenation" just to prove I can overcome my
1735 @c APL training... doc@cygnus.com
1736 The source program is a concatenation of the text in all the files, in the
1739 @c man begin DESCRIPTION
1740 Each time you run @command{@value{AS}} it assembles exactly one source
1741 program. The source program is made up of one or more files.
1742 (The standard input is also a file.)
1744 You give @command{@value{AS}} a command line that has zero or more input file
1745 names. The input files are read (from left file name to right). A
1746 command line argument (in any position) that has no special meaning
1747 is taken to be an input file name.
1749 If you give @command{@value{AS}} no file names it attempts to read one input file
1750 from the @command{@value{AS}} standard input, which is normally your terminal. You
1751 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1754 Use @samp{--} if you need to explicitly name the standard input file
1755 in your command line.
1757 If the source is empty, @command{@value{AS}} produces a small, empty object
1762 @subheading Filenames and Line-numbers
1764 @cindex input file linenumbers
1765 @cindex line numbers, in input files
1766 There are two ways of locating a line in the input file (or files) and
1767 either may be used in reporting error messages. One way refers to a line
1768 number in a physical file; the other refers to a line number in a
1769 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1771 @dfn{Physical files} are those files named in the command line given
1772 to @command{@value{AS}}.
1774 @dfn{Logical files} are simply names declared explicitly by assembler
1775 directives; they bear no relation to physical files. Logical file names help
1776 error messages reflect the original source file, when @command{@value{AS}} source
1777 is itself synthesized from other files. @command{@value{AS}} understands the
1778 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1779 @ref{File,,@code{.file}}.
1782 @section Output (Object) File
1788 Every time you run @command{@value{AS}} it produces an output file, which is
1789 your assembly language program translated into numbers. This file
1790 is the object file. Its default name is
1798 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1800 You can give it another name by using the @option{-o} option. Conventionally,
1801 object file names end with @file{.o}. The default name is used for historical
1802 reasons: older assemblers were capable of assembling self-contained programs
1803 directly into a runnable program. (For some formats, this isn't currently
1804 possible, but it can be done for the @code{a.out} format.)
1808 The object file is meant for input to the linker @code{@value{LD}}. It contains
1809 assembled program code, information to help @code{@value{LD}} integrate
1810 the assembled program into a runnable file, and (optionally) symbolic
1811 information for the debugger.
1813 @c link above to some info file(s) like the description of a.out.
1814 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1817 @section Error and Warning Messages
1819 @c man begin DESCRIPTION
1821 @cindex error messages
1822 @cindex warning messages
1823 @cindex messages from assembler
1824 @command{@value{AS}} may write warnings and error messages to the standard error
1825 file (usually your terminal). This should not happen when a compiler
1826 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1827 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1828 grave problem that stops the assembly.
1832 @cindex format of warning messages
1833 Warning messages have the format
1836 file_name:@b{NNN}:Warning Message Text
1840 @cindex line numbers, in warnings/errors
1841 (where @b{NNN} is a line number). If a logical file name has been given
1842 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1843 the current input file is used. If a logical line number was given
1845 (@pxref{Line,,@code{.line}})
1847 then it is used to calculate the number printed,
1848 otherwise the actual line in the current source file is printed. The
1849 message text is intended to be self explanatory (in the grand Unix
1852 @cindex format of error messages
1853 Error messages have the format
1855 file_name:@b{NNN}:FATAL:Error Message Text
1857 The file name and line number are derived as for warning
1858 messages. The actual message text may be rather less explanatory
1859 because many of them aren't supposed to happen.
1862 @chapter Command-Line Options
1864 @cindex options, all versions of assembler
1865 This chapter describes command-line options available in @emph{all}
1866 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1867 for options specific
1869 to the @value{TARGET} target.
1872 to particular machine architectures.
1875 @c man begin DESCRIPTION
1877 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1878 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1879 The assembler arguments must be separated from each other (and the @samp{-Wa})
1880 by commas. For example:
1883 gcc -c -g -O -Wa,-alh,-L file.c
1887 This passes two options to the assembler: @samp{-alh} (emit a listing to
1888 standard output with high-level and assembly source) and @samp{-L} (retain
1889 local symbols in the symbol table).
1891 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1892 command-line options are automatically passed to the assembler by the compiler.
1893 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1894 precisely what options it passes to each compilation pass, including the
1900 * a:: -a[cdghlns] enable listings
1901 * alternate:: --alternate enable alternate macro syntax
1902 * D:: -D for compatibility
1903 * f:: -f to work faster
1904 * I:: -I for .include search path
1905 @ifclear DIFF-TBL-KLUGE
1906 * K:: -K for compatibility
1908 @ifset DIFF-TBL-KLUGE
1909 * K:: -K for difference tables
1912 * L:: -L to retain local symbols
1913 * listing:: --listing-XXX to configure listing output
1914 * M:: -M or --mri to assemble in MRI compatibility mode
1915 * MD:: --MD for dependency tracking
1916 * o:: -o to name the object file
1917 * R:: -R to join data and text sections
1918 * statistics:: --statistics to see statistics about assembly
1919 * traditional-format:: --traditional-format for compatible output
1920 * v:: -v to announce version
1921 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1922 * Z:: -Z to make object file even after errors
1926 @section Enable Listings: @option{-a[cdghlns]}
1936 @cindex listings, enabling
1937 @cindex assembly listings, enabling
1939 These options enable listing output from the assembler. By itself,
1940 @samp{-a} requests high-level, assembly, and symbols listing.
1941 You can use other letters to select specific options for the list:
1942 @samp{-ah} requests a high-level language listing,
1943 @samp{-al} requests an output-program assembly listing, and
1944 @samp{-as} requests a symbol table listing.
1945 High-level listings require that a compiler debugging option like
1946 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1949 Use the @samp{-ag} option to print a first section with general assembly
1950 information, like @value{AS} version, switches passed, or time stamp.
1952 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1953 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1954 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1955 omitted from the listing.
1957 Use the @samp{-ad} option to omit debugging directives from the
1960 Once you have specified one of these options, you can further control
1961 listing output and its appearance using the directives @code{.list},
1962 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1964 The @samp{-an} option turns off all forms processing.
1965 If you do not request listing output with one of the @samp{-a} options, the
1966 listing-control directives have no effect.
1968 The letters after @samp{-a} may be combined into one option,
1969 @emph{e.g.}, @samp{-aln}.
1971 Note if the assembler source is coming from the standard input (e.g.,
1973 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1974 is being used) then the listing will not contain any comments or preprocessor
1975 directives. This is because the listing code buffers input source lines from
1976 stdin only after they have been preprocessed by the assembler. This reduces
1977 memory usage and makes the code more efficient.
1980 @section @option{--alternate}
1983 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1986 @section @option{-D}
1989 This option has no effect whatsoever, but it is accepted to make it more
1990 likely that scripts written for other assemblers also work with
1991 @command{@value{AS}}.
1994 @section Work Faster: @option{-f}
1997 @cindex trusted compiler
1998 @cindex faster processing (@option{-f})
1999 @samp{-f} should only be used when assembling programs written by a
2000 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2001 and comment preprocessing on
2002 the input file(s) before assembling them. @xref{Preprocessing,
2006 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2007 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2012 @section @code{.include} Search Path: @option{-I} @var{path}
2014 @kindex -I @var{path}
2015 @cindex paths for @code{.include}
2016 @cindex search path for @code{.include}
2017 @cindex @code{include} directive search path
2018 Use this option to add a @var{path} to the list of directories
2019 @command{@value{AS}} searches for files specified in @code{.include}
2020 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2021 many times as necessary to include a variety of paths. The current
2022 working directory is always searched first; after that, @command{@value{AS}}
2023 searches any @samp{-I} directories in the same order as they were
2024 specified (left to right) on the command line.
2027 @section Difference Tables: @option{-K}
2030 @ifclear DIFF-TBL-KLUGE
2031 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2032 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2033 where it can be used to warn when the assembler alters the machine code
2034 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2035 family does not have the addressing limitations that sometimes lead to this
2036 alteration on other platforms.
2039 @ifset DIFF-TBL-KLUGE
2040 @cindex difference tables, warning
2041 @cindex warning for altered difference tables
2042 @command{@value{AS}} sometimes alters the code emitted for directives of the
2043 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2044 You can use the @samp{-K} option if you want a warning issued when this
2049 @section Include Local Symbols: @option{-L}
2052 @cindex local symbols, retaining in output
2053 Symbols beginning with system-specific local label prefixes, typically
2054 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2055 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2056 such symbols when debugging, because they are intended for the use of
2057 programs (like compilers) that compose assembler programs, not for your
2058 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2059 such symbols, so you do not normally debug with them.
2061 This option tells @command{@value{AS}} to retain those local symbols
2062 in the object file. Usually if you do this you also tell the linker
2063 @code{@value{LD}} to preserve those symbols.
2066 @section Configuring listing output: @option{--listing}
2068 The listing feature of the assembler can be enabled via the command line switch
2069 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2070 hex dump of the corresponding locations in the output object file, and displays
2071 them as a listing file. The format of this listing can be controlled by
2072 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2073 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2074 @code{.psize} (@pxref{Psize}), and
2075 @code{.eject} (@pxref{Eject}) and also by the following switches:
2078 @item --listing-lhs-width=@samp{number}
2079 @kindex --listing-lhs-width
2080 @cindex Width of first line disassembly output
2081 Sets the maximum width, in words, of the first line of the hex byte dump. This
2082 dump appears on the left hand side of the listing output.
2084 @item --listing-lhs-width2=@samp{number}
2085 @kindex --listing-lhs-width2
2086 @cindex Width of continuation lines of disassembly output
2087 Sets the maximum width, in words, of any further lines of the hex byte dump for
2088 a given input source line. If this value is not specified, it defaults to being
2089 the same as the value specified for @samp{--listing-lhs-width}. If neither
2090 switch is used the default is to one.
2092 @item --listing-rhs-width=@samp{number}
2093 @kindex --listing-rhs-width
2094 @cindex Width of source line output
2095 Sets the maximum width, in characters, of the source line that is displayed
2096 alongside the hex dump. The default value for this parameter is 100. The
2097 source line is displayed on the right hand side of the listing output.
2099 @item --listing-cont-lines=@samp{number}
2100 @kindex --listing-cont-lines
2101 @cindex Maximum number of continuation lines
2102 Sets the maximum number of continuation lines of hex dump that will be
2103 displayed for a given single line of source input. The default value is 4.
2107 @section Assemble in MRI Compatibility Mode: @option{-M}
2110 @cindex MRI compatibility mode
2111 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2112 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2113 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2114 configured target) assembler from Microtec Research. The exact nature of the
2115 MRI syntax will not be documented here; see the MRI manuals for more
2116 information. Note in particular that the handling of macros and macro
2117 arguments is somewhat different. The purpose of this option is to permit
2118 assembling existing MRI assembler code using @command{@value{AS}}.
2120 The MRI compatibility is not complete. Certain operations of the MRI assembler
2121 depend upon its object file format, and can not be supported using other object
2122 file formats. Supporting these would require enhancing each object file format
2123 individually. These are:
2126 @item global symbols in common section
2128 The m68k MRI assembler supports common sections which are merged by the linker.
2129 Other object file formats do not support this. @command{@value{AS}} handles
2130 common sections by treating them as a single common symbol. It permits local
2131 symbols to be defined within a common section, but it can not support global
2132 symbols, since it has no way to describe them.
2134 @item complex relocations
2136 The MRI assemblers support relocations against a negated section address, and
2137 relocations which combine the start addresses of two or more sections. These
2138 are not support by other object file formats.
2140 @item @code{END} pseudo-op specifying start address
2142 The MRI @code{END} pseudo-op permits the specification of a start address.
2143 This is not supported by other object file formats. The start address may
2144 instead be specified using the @option{-e} option to the linker, or in a linker
2147 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2149 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2150 name to the output file. This is not supported by other object file formats.
2152 @item @code{ORG} pseudo-op
2154 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2155 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2156 which changes the location within the current section. Absolute sections are
2157 not supported by other object file formats. The address of a section may be
2158 assigned within a linker script.
2161 There are some other features of the MRI assembler which are not supported by
2162 @command{@value{AS}}, typically either because they are difficult or because they
2163 seem of little consequence. Some of these may be supported in future releases.
2167 @item EBCDIC strings
2169 EBCDIC strings are not supported.
2171 @item packed binary coded decimal
2173 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2174 and @code{DCB.P} pseudo-ops are not supported.
2176 @item @code{FEQU} pseudo-op
2178 The m68k @code{FEQU} pseudo-op is not supported.
2180 @item @code{NOOBJ} pseudo-op
2182 The m68k @code{NOOBJ} pseudo-op is not supported.
2184 @item @code{OPT} branch control options
2186 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2187 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2188 relaxes all branches, whether forward or backward, to an appropriate size, so
2189 these options serve no purpose.
2191 @item @code{OPT} list control options
2193 The following m68k @code{OPT} list control options are ignored: @code{C},
2194 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2195 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2197 @item other @code{OPT} options
2199 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2200 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2202 @item @code{OPT} @code{D} option is default
2204 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2205 @code{OPT NOD} may be used to turn it off.
2207 @item @code{XREF} pseudo-op.
2209 The m68k @code{XREF} pseudo-op is ignored.
2211 @item @code{.debug} pseudo-op
2213 The i960 @code{.debug} pseudo-op is not supported.
2215 @item @code{.extended} pseudo-op
2217 The i960 @code{.extended} pseudo-op is not supported.
2219 @item @code{.list} pseudo-op.
2221 The various options of the i960 @code{.list} pseudo-op are not supported.
2223 @item @code{.optimize} pseudo-op
2225 The i960 @code{.optimize} pseudo-op is not supported.
2227 @item @code{.output} pseudo-op
2229 The i960 @code{.output} pseudo-op is not supported.
2231 @item @code{.setreal} pseudo-op
2233 The i960 @code{.setreal} pseudo-op is not supported.
2238 @section Dependency Tracking: @option{--MD}
2241 @cindex dependency tracking
2244 @command{@value{AS}} can generate a dependency file for the file it creates. This
2245 file consists of a single rule suitable for @code{make} describing the
2246 dependencies of the main source file.
2248 The rule is written to the file named in its argument.
2250 This feature is used in the automatic updating of makefiles.
2253 @section Name the Object File: @option{-o}
2256 @cindex naming object file
2257 @cindex object file name
2258 There is always one object file output when you run @command{@value{AS}}. By
2259 default it has the name
2262 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2276 You use this option (which takes exactly one filename) to give the
2277 object file a different name.
2279 Whatever the object file is called, @command{@value{AS}} overwrites any
2280 existing file of the same name.
2283 @section Join Data and Text Sections: @option{-R}
2286 @cindex data and text sections, joining
2287 @cindex text and data sections, joining
2288 @cindex joining text and data sections
2289 @cindex merging text and data sections
2290 @option{-R} tells @command{@value{AS}} to write the object file as if all
2291 data-section data lives in the text section. This is only done at
2292 the very last moment: your binary data are the same, but data
2293 section parts are relocated differently. The data section part of
2294 your object file is zero bytes long because all its bytes are
2295 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2297 When you specify @option{-R} it would be possible to generate shorter
2298 address displacements (because we do not have to cross between text and
2299 data section). We refrain from doing this simply for compatibility with
2300 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2303 When @command{@value{AS}} is configured for COFF or ELF output,
2304 this option is only useful if you use sections named @samp{.text} and
2309 @option{-R} is not supported for any of the HPPA targets. Using
2310 @option{-R} generates a warning from @command{@value{AS}}.
2314 @section Display Assembly Statistics: @option{--statistics}
2316 @kindex --statistics
2317 @cindex statistics, about assembly
2318 @cindex time, total for assembly
2319 @cindex space used, maximum for assembly
2320 Use @samp{--statistics} to display two statistics about the resources used by
2321 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2322 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2325 @node traditional-format
2326 @section Compatible Output: @option{--traditional-format}
2328 @kindex --traditional-format
2329 For some targets, the output of @command{@value{AS}} is different in some ways
2330 from the output of some existing assembler. This switch requests
2331 @command{@value{AS}} to use the traditional format instead.
2333 For example, it disables the exception frame optimizations which
2334 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2337 @section Announce Version: @option{-v}
2341 @cindex assembler version
2342 @cindex version of assembler
2343 You can find out what version of as is running by including the
2344 option @samp{-v} (which you can also spell as @samp{-version}) on the
2348 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2350 @command{@value{AS}} should never give a warning or error message when
2351 assembling compiler output. But programs written by people often
2352 cause @command{@value{AS}} to give a warning that a particular assumption was
2353 made. All such warnings are directed to the standard error file.
2357 @cindex suppressing warnings
2358 @cindex warnings, suppressing
2359 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2360 This only affects the warning messages: it does not change any particular of
2361 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2364 @kindex --fatal-warnings
2365 @cindex errors, caused by warnings
2366 @cindex warnings, causing error
2367 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2368 files that generate warnings to be in error.
2371 @cindex warnings, switching on
2372 You can switch these options off again by specifying @option{--warn}, which
2373 causes warnings to be output as usual.
2376 @section Generate Object File in Spite of Errors: @option{-Z}
2377 @cindex object file, after errors
2378 @cindex errors, continuing after
2379 After an error message, @command{@value{AS}} normally produces no output. If for
2380 some reason you are interested in object file output even after
2381 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2382 option. If there are any errors, @command{@value{AS}} continues anyways, and
2383 writes an object file after a final warning message of the form @samp{@var{n}
2384 errors, @var{m} warnings, generating bad object file.}
2389 @cindex machine-independent syntax
2390 @cindex syntax, machine-independent
2391 This chapter describes the machine-independent syntax allowed in a
2392 source file. @command{@value{AS}} syntax is similar to what many other
2393 assemblers use; it is inspired by the BSD 4.2
2398 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2402 * Preprocessing:: Preprocessing
2403 * Whitespace:: Whitespace
2404 * Comments:: Comments
2405 * Symbol Intro:: Symbols
2406 * Statements:: Statements
2407 * Constants:: Constants
2411 @section Preprocessing
2413 @cindex preprocessing
2414 The @command{@value{AS}} internal preprocessor:
2416 @cindex whitespace, removed by preprocessor
2418 adjusts and removes extra whitespace. It leaves one space or tab before
2419 the keywords on a line, and turns any other whitespace on the line into
2422 @cindex comments, removed by preprocessor
2424 removes all comments, replacing them with a single space, or an
2425 appropriate number of newlines.
2427 @cindex constants, converted by preprocessor
2429 converts character constants into the appropriate numeric values.
2432 It does not do macro processing, include file handling, or
2433 anything else you may get from your C compiler's preprocessor. You can
2434 do include file processing with the @code{.include} directive
2435 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2436 to get other ``CPP'' style preprocessing by giving the input file a
2437 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2438 Output, gcc.info, Using GNU CC}.
2440 Excess whitespace, comments, and character constants
2441 cannot be used in the portions of the input text that are not
2444 @cindex turning preprocessing on and off
2445 @cindex preprocessing, turning on and off
2448 If the first line of an input file is @code{#NO_APP} or if you use the
2449 @samp{-f} option, whitespace and comments are not removed from the input file.
2450 Within an input file, you can ask for whitespace and comment removal in
2451 specific portions of the by putting a line that says @code{#APP} before the
2452 text that may contain whitespace or comments, and putting a line that says
2453 @code{#NO_APP} after this text. This feature is mainly intend to support
2454 @code{asm} statements in compilers whose output is otherwise free of comments
2461 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2462 Whitespace is used to separate symbols, and to make programs neater for
2463 people to read. Unless within character constants
2464 (@pxref{Characters,,Character Constants}), any whitespace means the same
2465 as exactly one space.
2471 There are two ways of rendering comments to @command{@value{AS}}. In both
2472 cases the comment is equivalent to one space.
2474 Anything from @samp{/*} through the next @samp{*/} is a comment.
2475 This means you may not nest these comments.
2479 The only way to include a newline ('\n') in a comment
2480 is to use this sort of comment.
2483 /* This sort of comment does not nest. */
2486 @cindex line comment character
2487 Anything from a @dfn{line comment} character up to the next newline is
2488 considered a comment and is ignored. The line comment character is target
2489 specific, and some targets multiple comment characters. Some targets also have
2490 line comment characters that only work if they are the first character on a
2491 line. Some targets use a sequence of two characters to introduce a line
2492 comment. Some targets can also change their line comment characters depending
2493 upon command line options that have been used. For more details see the
2494 @emph{Syntax} section in the documentation for individual targets.
2496 If the line comment character is the hash sign (@samp{#}) then it still has the
2497 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2498 to specify logical line numbers:
2501 @cindex lines starting with @code{#}
2502 @cindex logical line numbers
2503 To be compatible with past assemblers, lines that begin with @samp{#} have a
2504 special interpretation. Following the @samp{#} should be an absolute
2505 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2506 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2507 new logical file name. The rest of the line, if any, should be whitespace.
2509 If the first non-whitespace characters on the line are not numeric,
2510 the line is ignored. (Just like a comment.)
2513 # This is an ordinary comment.
2514 # 42-6 "new_file_name" # New logical file name
2515 # This is logical line # 36.
2517 This feature is deprecated, and may disappear from future versions
2518 of @command{@value{AS}}.
2523 @cindex characters used in symbols
2524 @ifclear SPECIAL-SYMS
2525 A @dfn{symbol} is one or more characters chosen from the set of all
2526 letters (both upper and lower case), digits and the three characters
2532 A @dfn{symbol} is one or more characters chosen from the set of all
2533 letters (both upper and lower case), digits and the three characters
2534 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2540 On most machines, you can also use @code{$} in symbol names; exceptions
2541 are noted in @ref{Machine Dependencies}.
2543 No symbol may begin with a digit. Case is significant.
2544 There is no length limit: all characters are significant. Multibyte characters
2545 are supported. Symbols are delimited by characters not in that set, or by the
2546 beginning of a file (since the source program must end with a newline, the end
2547 of a file is not a possible symbol delimiter). @xref{Symbols}.
2548 @cindex length of symbols
2553 @cindex statements, structure of
2554 @cindex line separator character
2555 @cindex statement separator character
2557 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2558 @dfn{line separator character}. The line separator character is target
2559 specific and described in the @emph{Syntax} section of each
2560 target's documentation. Not all targets support a line separator character.
2561 The newline or line separator character is considered to be part of the
2562 preceding statement. Newlines and separators within character constants are an
2563 exception: they do not end statements.
2565 @cindex newline, required at file end
2566 @cindex EOF, newline must precede
2567 It is an error to end any statement with end-of-file: the last
2568 character of any input file should be a newline.@refill
2570 An empty statement is allowed, and may include whitespace. It is ignored.
2572 @cindex instructions and directives
2573 @cindex directives and instructions
2574 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2575 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2577 A statement begins with zero or more labels, optionally followed by a
2578 key symbol which determines what kind of statement it is. The key
2579 symbol determines the syntax of the rest of the statement. If the
2580 symbol begins with a dot @samp{.} then the statement is an assembler
2581 directive: typically valid for any computer. If the symbol begins with
2582 a letter the statement is an assembly language @dfn{instruction}: it
2583 assembles into a machine language instruction.
2585 Different versions of @command{@value{AS}} for different computers
2586 recognize different instructions. In fact, the same symbol may
2587 represent a different instruction in a different computer's assembly
2591 @cindex @code{:} (label)
2592 @cindex label (@code{:})
2593 A label is a symbol immediately followed by a colon (@code{:}).
2594 Whitespace before a label or after a colon is permitted, but you may not
2595 have whitespace between a label's symbol and its colon. @xref{Labels}.
2598 For HPPA targets, labels need not be immediately followed by a colon, but
2599 the definition of a label must begin in column zero. This also implies that
2600 only one label may be defined on each line.
2604 label: .directive followed by something
2605 another_label: # This is an empty statement.
2606 instruction operand_1, operand_2, @dots{}
2613 A constant is a number, written so that its value is known by
2614 inspection, without knowing any context. Like this:
2617 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2618 .ascii "Ring the bell\7" # A string constant.
2619 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2620 .float 0f-314159265358979323846264338327\
2621 95028841971.693993751E-40 # - pi, a flonum.
2626 * Characters:: Character Constants
2627 * Numbers:: Number Constants
2631 @subsection Character Constants
2633 @cindex character constants
2634 @cindex constants, character
2635 There are two kinds of character constants. A @dfn{character} stands
2636 for one character in one byte and its value may be used in
2637 numeric expressions. String constants (properly called string
2638 @emph{literals}) are potentially many bytes and their values may not be
2639 used in arithmetic expressions.
2643 * Chars:: Characters
2647 @subsubsection Strings
2649 @cindex string constants
2650 @cindex constants, string
2651 A @dfn{string} is written between double-quotes. It may contain
2652 double-quotes or null characters. The way to get special characters
2653 into a string is to @dfn{escape} these characters: precede them with
2654 a backslash @samp{\} character. For example @samp{\\} represents
2655 one backslash: the first @code{\} is an escape which tells
2656 @command{@value{AS}} to interpret the second character literally as a backslash
2657 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2658 escape character). The complete list of escapes follows.
2660 @cindex escape codes, character
2661 @cindex character escape codes
2664 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2666 @cindex @code{\b} (backspace character)
2667 @cindex backspace (@code{\b})
2669 Mnemonic for backspace; for ASCII this is octal code 010.
2672 @c Mnemonic for EOText; for ASCII this is octal code 004.
2674 @cindex @code{\f} (formfeed character)
2675 @cindex formfeed (@code{\f})
2677 Mnemonic for FormFeed; for ASCII this is octal code 014.
2679 @cindex @code{\n} (newline character)
2680 @cindex newline (@code{\n})
2682 Mnemonic for newline; for ASCII this is octal code 012.
2685 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2687 @cindex @code{\r} (carriage return character)
2688 @cindex carriage return (@code{\r})
2690 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2693 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2694 @c other assemblers.
2696 @cindex @code{\t} (tab)
2697 @cindex tab (@code{\t})
2699 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2702 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2703 @c @item \x @var{digit} @var{digit} @var{digit}
2704 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2706 @cindex @code{\@var{ddd}} (octal character code)
2707 @cindex octal character code (@code{\@var{ddd}})
2708 @item \ @var{digit} @var{digit} @var{digit}
2709 An octal character code. The numeric code is 3 octal digits.
2710 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2711 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2713 @cindex @code{\@var{xd...}} (hex character code)
2714 @cindex hex character code (@code{\@var{xd...}})
2715 @item \@code{x} @var{hex-digits...}
2716 A hex character code. All trailing hex digits are combined. Either upper or
2717 lower case @code{x} works.
2719 @cindex @code{\\} (@samp{\} character)
2720 @cindex backslash (@code{\\})
2722 Represents one @samp{\} character.
2725 @c Represents one @samp{'} (accent acute) character.
2726 @c This is needed in single character literals
2727 @c (@xref{Characters,,Character Constants}.) to represent
2730 @cindex @code{\"} (doublequote character)
2731 @cindex doublequote (@code{\"})
2733 Represents one @samp{"} character. Needed in strings to represent
2734 this character, because an unescaped @samp{"} would end the string.
2736 @item \ @var{anything-else}
2737 Any other character when escaped by @kbd{\} gives a warning, but
2738 assembles as if the @samp{\} was not present. The idea is that if
2739 you used an escape sequence you clearly didn't want the literal
2740 interpretation of the following character. However @command{@value{AS}} has no
2741 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2742 code and warns you of the fact.
2745 Which characters are escapable, and what those escapes represent,
2746 varies widely among assemblers. The current set is what we think
2747 the BSD 4.2 assembler recognizes, and is a subset of what most C
2748 compilers recognize. If you are in doubt, do not use an escape
2752 @subsubsection Characters
2754 @cindex single character constant
2755 @cindex character, single
2756 @cindex constant, single character
2757 A single character may be written as a single quote immediately
2758 followed by that character. The same escapes apply to characters as
2759 to strings. So if you want to write the character backslash, you
2760 must write @kbd{'\\} where the first @code{\} escapes the second
2761 @code{\}. As you can see, the quote is an acute accent, not a
2762 grave accent. A newline
2764 @ifclear abnormal-separator
2765 (or semicolon @samp{;})
2767 @ifset abnormal-separator
2769 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2774 immediately following an acute accent is taken as a literal character
2775 and does not count as the end of a statement. The value of a character
2776 constant in a numeric expression is the machine's byte-wide code for
2777 that character. @command{@value{AS}} assumes your character code is ASCII:
2778 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2781 @subsection Number Constants
2783 @cindex constants, number
2784 @cindex number constants
2785 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2786 are stored in the target machine. @emph{Integers} are numbers that
2787 would fit into an @code{int} in the C language. @emph{Bignums} are
2788 integers, but they are stored in more than 32 bits. @emph{Flonums}
2789 are floating point numbers, described below.
2792 * Integers:: Integers
2797 * Bit Fields:: Bit Fields
2803 @subsubsection Integers
2805 @cindex constants, integer
2807 @cindex binary integers
2808 @cindex integers, binary
2809 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2810 the binary digits @samp{01}.
2812 @cindex octal integers
2813 @cindex integers, octal
2814 An octal integer is @samp{0} followed by zero or more of the octal
2815 digits (@samp{01234567}).
2817 @cindex decimal integers
2818 @cindex integers, decimal
2819 A decimal integer starts with a non-zero digit followed by zero or
2820 more digits (@samp{0123456789}).
2822 @cindex hexadecimal integers
2823 @cindex integers, hexadecimal
2824 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2825 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2827 Integers have the usual values. To denote a negative integer, use
2828 the prefix operator @samp{-} discussed under expressions
2829 (@pxref{Prefix Ops,,Prefix Operators}).
2832 @subsubsection Bignums
2835 @cindex constants, bignum
2836 A @dfn{bignum} has the same syntax and semantics as an integer
2837 except that the number (or its negative) takes more than 32 bits to
2838 represent in binary. The distinction is made because in some places
2839 integers are permitted while bignums are not.
2842 @subsubsection Flonums
2844 @cindex floating point numbers
2845 @cindex constants, floating point
2847 @cindex precision, floating point
2848 A @dfn{flonum} represents a floating point number. The translation is
2849 indirect: a decimal floating point number from the text is converted by
2850 @command{@value{AS}} to a generic binary floating point number of more than
2851 sufficient precision. This generic floating point number is converted
2852 to a particular computer's floating point format (or formats) by a
2853 portion of @command{@value{AS}} specialized to that computer.
2855 A flonum is written by writing (in order)
2860 (@samp{0} is optional on the HPPA.)
2864 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2866 @kbd{e} is recommended. Case is not important.
2868 @c FIXME: verify if flonum syntax really this vague for most cases
2869 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2870 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2873 On the H8/300, Renesas / SuperH SH,
2874 and AMD 29K architectures, the letter must be
2875 one of the letters @samp{DFPRSX} (in upper or lower case).
2877 On the ARC, the letter must be one of the letters @samp{DFRS}
2878 (in upper or lower case).
2880 On the Intel 960 architecture, the letter must be
2881 one of the letters @samp{DFT} (in upper or lower case).
2883 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2887 One of the letters @samp{DFRS} (in upper or lower case).
2890 One of the letters @samp{DFPRSX} (in upper or lower case).
2893 The letter @samp{E} (upper case only).
2896 One of the letters @samp{DFT} (in upper or lower case).
2901 An optional sign: either @samp{+} or @samp{-}.
2904 An optional @dfn{integer part}: zero or more decimal digits.
2907 An optional @dfn{fractional part}: @samp{.} followed by zero
2908 or more decimal digits.
2911 An optional exponent, consisting of:
2915 An @samp{E} or @samp{e}.
2916 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2917 @c principle this can perfectly well be different on different targets.
2919 Optional sign: either @samp{+} or @samp{-}.
2921 One or more decimal digits.
2926 At least one of the integer part or the fractional part must be
2927 present. The floating point number has the usual base-10 value.
2929 @command{@value{AS}} does all processing using integers. Flonums are computed
2930 independently of any floating point hardware in the computer running
2931 @command{@value{AS}}.
2935 @c Bit fields are written as a general facility but are also controlled
2936 @c by a conditional-compilation flag---which is as of now (21mar91)
2937 @c turned on only by the i960 config of GAS.
2939 @subsubsection Bit Fields
2942 @cindex constants, bit field
2943 You can also define numeric constants as @dfn{bit fields}.
2944 Specify two numbers separated by a colon---
2946 @var{mask}:@var{value}
2949 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2952 The resulting number is then packed
2954 @c this conditional paren in case bit fields turned on elsewhere than 960
2955 (in host-dependent byte order)
2957 into a field whose width depends on which assembler directive has the
2958 bit-field as its argument. Overflow (a result from the bitwise and
2959 requiring more binary digits to represent) is not an error; instead,
2960 more constants are generated, of the specified width, beginning with the
2961 least significant digits.@refill
2963 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2964 @code{.short}, and @code{.word} accept bit-field arguments.
2969 @chapter Sections and Relocation
2974 * Secs Background:: Background
2975 * Ld Sections:: Linker Sections
2976 * As Sections:: Assembler Internal Sections
2977 * Sub-Sections:: Sub-Sections
2981 @node Secs Background
2984 Roughly, a section is a range of addresses, with no gaps; all data
2985 ``in'' those addresses is treated the same for some particular purpose.
2986 For example there may be a ``read only'' section.
2988 @cindex linker, and assembler
2989 @cindex assembler, and linker
2990 The linker @code{@value{LD}} reads many object files (partial programs) and
2991 combines their contents to form a runnable program. When @command{@value{AS}}
2992 emits an object file, the partial program is assumed to start at address 0.
2993 @code{@value{LD}} assigns the final addresses for the partial program, so that
2994 different partial programs do not overlap. This is actually an
2995 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2998 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2999 addresses. These blocks slide to their run-time addresses as rigid
3000 units; their length does not change and neither does the order of bytes
3001 within them. Such a rigid unit is called a @emph{section}. Assigning
3002 run-time addresses to sections is called @dfn{relocation}. It includes
3003 the task of adjusting mentions of object-file addresses so they refer to
3004 the proper run-time addresses.
3006 For the H8/300, and for the Renesas / SuperH SH,
3007 @command{@value{AS}} pads sections if needed to
3008 ensure they end on a word (sixteen bit) boundary.
3011 @cindex standard assembler sections
3012 An object file written by @command{@value{AS}} has at least three sections, any
3013 of which may be empty. These are named @dfn{text}, @dfn{data} and
3018 When it generates COFF or ELF output,
3020 @command{@value{AS}} can also generate whatever other named sections you specify
3021 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3022 If you do not use any directives that place output in the @samp{.text}
3023 or @samp{.data} sections, these sections still exist, but are empty.
3028 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3030 @command{@value{AS}} can also generate whatever other named sections you
3031 specify using the @samp{.space} and @samp{.subspace} directives. See
3032 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3033 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3034 assembler directives.
3037 Additionally, @command{@value{AS}} uses different names for the standard
3038 text, data, and bss sections when generating SOM output. Program text
3039 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3040 BSS into @samp{$BSS$}.
3044 Within the object file, the text section starts at address @code{0}, the
3045 data section follows, and the bss section follows the data section.
3048 When generating either SOM or ELF output files on the HPPA, the text
3049 section starts at address @code{0}, the data section at address
3050 @code{0x4000000}, and the bss section follows the data section.
3053 To let @code{@value{LD}} know which data changes when the sections are
3054 relocated, and how to change that data, @command{@value{AS}} also writes to the
3055 object file details of the relocation needed. To perform relocation
3056 @code{@value{LD}} must know, each time an address in the object
3060 Where in the object file is the beginning of this reference to
3063 How long (in bytes) is this reference?
3065 Which section does the address refer to? What is the numeric value of
3067 (@var{address}) @minus{} (@var{start-address of section})?
3070 Is the reference to an address ``Program-Counter relative''?
3073 @cindex addresses, format of
3074 @cindex section-relative addressing
3075 In fact, every address @command{@value{AS}} ever uses is expressed as
3077 (@var{section}) + (@var{offset into section})
3080 Further, most expressions @command{@value{AS}} computes have this section-relative
3083 (For some object formats, such as SOM for the HPPA, some expressions are
3084 symbol-relative instead.)
3087 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3088 @var{N} into section @var{secname}.''
3090 Apart from text, data and bss sections you need to know about the
3091 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3092 addresses in the absolute section remain unchanged. For example, address
3093 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3094 @code{@value{LD}}. Although the linker never arranges two partial programs'
3095 data sections with overlapping addresses after linking, @emph{by definition}
3096 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3097 part of a program is always the same address when the program is running as
3098 address @code{@{absolute@ 239@}} in any other part of the program.
3100 The idea of sections is extended to the @dfn{undefined} section. Any
3101 address whose section is unknown at assembly time is by definition
3102 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3103 Since numbers are always defined, the only way to generate an undefined
3104 address is to mention an undefined symbol. A reference to a named
3105 common block would be such a symbol: its value is unknown at assembly
3106 time so it has section @emph{undefined}.
3108 By analogy the word @emph{section} is used to describe groups of sections in
3109 the linked program. @code{@value{LD}} puts all partial programs' text
3110 sections in contiguous addresses in the linked program. It is
3111 customary to refer to the @emph{text section} of a program, meaning all
3112 the addresses of all partial programs' text sections. Likewise for
3113 data and bss sections.
3115 Some sections are manipulated by @code{@value{LD}}; others are invented for
3116 use of @command{@value{AS}} and have no meaning except during assembly.
3119 @section Linker Sections
3120 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3125 @cindex named sections
3126 @cindex sections, named
3127 @item named sections
3130 @cindex text section
3131 @cindex data section
3135 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3136 separate but equal sections. Anything you can say of one section is
3139 When the program is running, however, it is
3140 customary for the text section to be unalterable. The
3141 text section is often shared among processes: it contains
3142 instructions, constants and the like. The data section of a running
3143 program is usually alterable: for example, C variables would be stored
3144 in the data section.
3149 This section contains zeroed bytes when your program begins running. It
3150 is used to hold uninitialized variables or common storage. The length of
3151 each partial program's bss section is important, but because it starts
3152 out containing zeroed bytes there is no need to store explicit zero
3153 bytes in the object file. The bss section was invented to eliminate
3154 those explicit zeros from object files.
3156 @cindex absolute section
3157 @item absolute section
3158 Address 0 of this section is always ``relocated'' to runtime address 0.
3159 This is useful if you want to refer to an address that @code{@value{LD}} must
3160 not change when relocating. In this sense we speak of absolute
3161 addresses being ``unrelocatable'': they do not change during relocation.
3163 @cindex undefined section
3164 @item undefined section
3165 This ``section'' is a catch-all for address references to objects not in
3166 the preceding sections.
3167 @c FIXME: ref to some other doc on obj-file formats could go here.
3170 @cindex relocation example
3171 An idealized example of three relocatable sections follows.
3173 The example uses the traditional section names @samp{.text} and @samp{.data}.
3175 Memory addresses are on the horizontal axis.
3179 @c END TEXI2ROFF-KILL
3182 partial program # 1: |ttttt|dddd|00|
3189 partial program # 2: |TTT|DDD|000|
3192 +--+---+-----+--+----+---+-----+~~
3193 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3194 +--+---+-----+--+----+---+-----+~~
3196 addresses: 0 @dots{}
3203 \line{\it Partial program \#1: \hfil}
3204 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3205 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3207 \line{\it Partial program \#2: \hfil}
3208 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3209 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3211 \line{\it linked program: \hfil}
3212 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3213 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3214 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3215 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3217 \line{\it addresses: \hfil}
3221 @c END TEXI2ROFF-KILL
3224 @section Assembler Internal Sections
3226 @cindex internal assembler sections
3227 @cindex sections in messages, internal
3228 These sections are meant only for the internal use of @command{@value{AS}}. They
3229 have no meaning at run-time. You do not really need to know about these
3230 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3231 warning messages, so it might be helpful to have an idea of their
3232 meanings to @command{@value{AS}}. These sections are used to permit the
3233 value of every expression in your assembly language program to be a
3234 section-relative address.
3237 @cindex assembler internal logic error
3238 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3239 An internal assembler logic error has been found. This means there is a
3240 bug in the assembler.
3242 @cindex expr (internal section)
3244 The assembler stores complex expression internally as combinations of
3245 symbols. When it needs to represent an expression as a symbol, it puts
3246 it in the expr section.
3248 @c FIXME item transfer[t] vector preload
3249 @c FIXME item transfer[t] vector postload
3250 @c FIXME item register
3254 @section Sub-Sections
3256 @cindex numbered subsections
3257 @cindex grouping data
3263 fall into two sections: text and data.
3265 You may have separate groups of
3267 data in named sections
3271 data in named sections
3277 that you want to end up near to each other in the object file, even though they
3278 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3279 use @dfn{subsections} for this purpose. Within each section, there can be
3280 numbered subsections with values from 0 to 8192. Objects assembled into the
3281 same subsection go into the object file together with other objects in the same
3282 subsection. For example, a compiler might want to store constants in the text
3283 section, but might not want to have them interspersed with the program being
3284 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3285 section of code being output, and a @samp{.text 1} before each group of
3286 constants being output.
3288 Subsections are optional. If you do not use subsections, everything
3289 goes in subsection number zero.
3292 Each subsection is zero-padded up to a multiple of four bytes.
3293 (Subsections may be padded a different amount on different flavors
3294 of @command{@value{AS}}.)
3298 On the H8/300 platform, each subsection is zero-padded to a word
3299 boundary (two bytes).
3300 The same is true on the Renesas SH.
3303 @c FIXME section padding (alignment)?
3304 @c Rich Pixley says padding here depends on target obj code format; that
3305 @c doesn't seem particularly useful to say without further elaboration,
3306 @c so for now I say nothing about it. If this is a generic BFD issue,
3307 @c these paragraphs might need to vanish from this manual, and be
3308 @c discussed in BFD chapter of binutils (or some such).
3312 Subsections appear in your object file in numeric order, lowest numbered
3313 to highest. (All this to be compatible with other people's assemblers.)
3314 The object file contains no representation of subsections; @code{@value{LD}} and
3315 other programs that manipulate object files see no trace of them.
3316 They just see all your text subsections as a text section, and all your
3317 data subsections as a data section.
3319 To specify which subsection you want subsequent statements assembled
3320 into, use a numeric argument to specify it, in a @samp{.text
3321 @var{expression}} or a @samp{.data @var{expression}} statement.
3324 When generating COFF output, you
3329 can also use an extra subsection
3330 argument with arbitrary named sections: @samp{.section @var{name},
3335 When generating ELF output, you
3340 can also use the @code{.subsection} directive (@pxref{SubSection})
3341 to specify a subsection: @samp{.subsection @var{expression}}.
3343 @var{Expression} should be an absolute expression
3344 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3345 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3346 begins in @code{text 0}. For instance:
3348 .text 0 # The default subsection is text 0 anyway.
3349 .ascii "This lives in the first text subsection. *"
3351 .ascii "But this lives in the second text subsection."
3353 .ascii "This lives in the data section,"
3354 .ascii "in the first data subsection."
3356 .ascii "This lives in the first text section,"
3357 .ascii "immediately following the asterisk (*)."
3360 Each section has a @dfn{location counter} incremented by one for every byte
3361 assembled into that section. Because subsections are merely a convenience
3362 restricted to @command{@value{AS}} there is no concept of a subsection location
3363 counter. There is no way to directly manipulate a location counter---but the
3364 @code{.align} directive changes it, and any label definition captures its
3365 current value. The location counter of the section where statements are being
3366 assembled is said to be the @dfn{active} location counter.
3369 @section bss Section
3372 @cindex common variable storage
3373 The bss section is used for local common variable storage.
3374 You may allocate address space in the bss section, but you may
3375 not dictate data to load into it before your program executes. When
3376 your program starts running, all the contents of the bss
3377 section are zeroed bytes.
3379 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3380 @ref{Lcomm,,@code{.lcomm}}.
3382 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3383 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3386 When assembling for a target which supports multiple sections, such as ELF or
3387 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3388 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3389 section. Typically the section will only contain symbol definitions and
3390 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3397 Symbols are a central concept: the programmer uses symbols to name
3398 things, the linker uses symbols to link, and the debugger uses symbols
3402 @cindex debuggers, and symbol order
3403 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3404 the same order they were declared. This may break some debuggers.
3409 * Setting Symbols:: Giving Symbols Other Values
3410 * Symbol Names:: Symbol Names
3411 * Dot:: The Special Dot Symbol
3412 * Symbol Attributes:: Symbol Attributes
3419 A @dfn{label} is written as a symbol immediately followed by a colon
3420 @samp{:}. The symbol then represents the current value of the
3421 active location counter, and is, for example, a suitable instruction
3422 operand. You are warned if you use the same symbol to represent two
3423 different locations: the first definition overrides any other
3427 On the HPPA, the usual form for a label need not be immediately followed by a
3428 colon, but instead must start in column zero. Only one label may be defined on
3429 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3430 provides a special directive @code{.label} for defining labels more flexibly.
3433 @node Setting Symbols
3434 @section Giving Symbols Other Values
3436 @cindex assigning values to symbols
3437 @cindex symbol values, assigning
3438 A symbol can be given an arbitrary value by writing a symbol, followed
3439 by an equals sign @samp{=}, followed by an expression
3440 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3441 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3442 equals sign @samp{=}@samp{=} here represents an equivalent of the
3443 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3446 Blackfin does not support symbol assignment with @samp{=}.
3450 @section Symbol Names
3452 @cindex symbol names
3453 @cindex names, symbol
3454 @ifclear SPECIAL-SYMS
3455 Symbol names begin with a letter or with one of @samp{._}. On most
3456 machines, you can also use @code{$} in symbol names; exceptions are
3457 noted in @ref{Machine Dependencies}. That character may be followed by any
3458 string of digits, letters, dollar signs (unless otherwise noted for a
3459 particular target machine), and underscores.
3463 Symbol names begin with a letter or with one of @samp{._}. On the
3464 Renesas SH you can also use @code{$} in symbol names. That
3465 character may be followed by any string of digits, letters, dollar signs (save
3466 on the H8/300), and underscores.
3470 Case of letters is significant: @code{foo} is a different symbol name
3473 Multibyte characters are supported. To generate a symbol name containing
3474 multibyte characters enclose it within double quotes and use escape codes. cf
3475 @xref{Strings}. Generating a multibyte symbol name from a label is not
3476 currently supported.
3478 Each symbol has exactly one name. Each name in an assembly language program
3479 refers to exactly one symbol. You may use that symbol name any number of times
3482 @subheading Local Symbol Names
3484 @cindex local symbol names
3485 @cindex symbol names, local
3486 A local symbol is any symbol beginning with certain local label prefixes.
3487 By default, the local label prefix is @samp{.L} for ELF systems or
3488 @samp{L} for traditional a.out systems, but each target may have its own
3489 set of local label prefixes.
3491 On the HPPA local symbols begin with @samp{L$}.
3494 Local symbols are defined and used within the assembler, but they are
3495 normally not saved in object files. Thus, they are not visible when debugging.
3496 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3497 @option{-L}}) to retain the local symbols in the object files.
3499 @subheading Local Labels
3501 @cindex local labels
3502 @cindex temporary symbol names
3503 @cindex symbol names, temporary
3504 Local labels help compilers and programmers use names temporarily.
3505 They create symbols which are guaranteed to be unique over the entire scope of
3506 the input source code and which can be referred to by a simple notation.
3507 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3508 represents any positive integer). To refer to the most recent previous
3509 definition of that label write @samp{@b{N}b}, using the same number as when
3510 you defined the label. To refer to the next definition of a local label, write
3511 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3514 There is no restriction on how you can use these labels, and you can reuse them
3515 too. So that it is possible to repeatedly define the same local label (using
3516 the same number @samp{@b{N}}), although you can only refer to the most recently
3517 defined local label of that number (for a backwards reference) or the next
3518 definition of a specific local label for a forward reference. It is also worth
3519 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3520 implemented in a slightly more efficient manner than the others.
3531 Which is the equivalent of:
3534 label_1: branch label_3
3535 label_2: branch label_1
3536 label_3: branch label_4
3537 label_4: branch label_3
3540 Local label names are only a notational device. They are immediately
3541 transformed into more conventional symbol names before the assembler uses them.
3542 The symbol names are stored in the symbol table, appear in error messages, and
3543 are optionally emitted to the object file. The names are constructed using
3547 @item @emph{local label prefix}
3548 All local symbols begin with the system-specific local label prefix.
3549 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3550 that start with the local label prefix. These labels are
3551 used for symbols you are never intended to see. If you use the
3552 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3553 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3554 you may use them in debugging.
3557 This is the number that was used in the local label definition. So if the
3558 label is written @samp{55:} then the number is @samp{55}.
3561 This unusual character is included so you do not accidentally invent a symbol
3562 of the same name. The character has ASCII value of @samp{\002} (control-B).
3564 @item @emph{ordinal number}
3565 This is a serial number to keep the labels distinct. The first definition of
3566 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3567 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3568 the number @samp{1} and its 15th definition gets @samp{15} as well.
3571 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3572 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3574 @subheading Dollar Local Labels
3575 @cindex dollar local symbols
3577 @code{@value{AS}} also supports an even more local form of local labels called
3578 dollar labels. These labels go out of scope (i.e., they become undefined) as
3579 soon as a non-local label is defined. Thus they remain valid for only a small
3580 region of the input source code. Normal local labels, by contrast, remain in
3581 scope for the entire file, or until they are redefined by another occurrence of
3582 the same local label.
3584 Dollar labels are defined in exactly the same way as ordinary local labels,
3585 except that they have a dollar sign suffix to their numeric value, e.g.,
3588 They can also be distinguished from ordinary local labels by their transformed
3589 names which use ASCII character @samp{\001} (control-A) as the magic character
3590 to distinguish them from ordinary labels. For example, the fifth definition of
3591 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3594 @section The Special Dot Symbol
3596 @cindex dot (symbol)
3597 @cindex @code{.} (symbol)
3598 @cindex current address
3599 @cindex location counter
3600 The special symbol @samp{.} refers to the current address that
3601 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3602 .long .} defines @code{melvin} to contain its own address.
3603 Assigning a value to @code{.} is treated the same as a @code{.org}
3605 @ifclear no-space-dir
3606 Thus, the expression @samp{.=.+4} is the same as saying
3610 @node Symbol Attributes
3611 @section Symbol Attributes
3613 @cindex symbol attributes
3614 @cindex attributes, symbol
3615 Every symbol has, as well as its name, the attributes ``Value'' and
3616 ``Type''. Depending on output format, symbols can also have auxiliary
3619 The detailed definitions are in @file{a.out.h}.
3622 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3623 all these attributes, and probably won't warn you. This makes the
3624 symbol an externally defined symbol, which is generally what you
3628 * Symbol Value:: Value
3629 * Symbol Type:: Type
3632 * a.out Symbols:: Symbol Attributes: @code{a.out}
3636 * a.out Symbols:: Symbol Attributes: @code{a.out}
3639 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3644 * COFF Symbols:: Symbol Attributes for COFF
3647 * SOM Symbols:: Symbol Attributes for SOM
3654 @cindex value of a symbol
3655 @cindex symbol value
3656 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3657 location in the text, data, bss or absolute sections the value is the
3658 number of addresses from the start of that section to the label.
3659 Naturally for text, data and bss sections the value of a symbol changes
3660 as @code{@value{LD}} changes section base addresses during linking. Absolute
3661 symbols' values do not change during linking: that is why they are
3664 The value of an undefined symbol is treated in a special way. If it is
3665 0 then the symbol is not defined in this assembler source file, and
3666 @code{@value{LD}} tries to determine its value from other files linked into the
3667 same program. You make this kind of symbol simply by mentioning a symbol
3668 name without defining it. A non-zero value represents a @code{.comm}
3669 common declaration. The value is how much common storage to reserve, in
3670 bytes (addresses). The symbol refers to the first address of the
3676 @cindex type of a symbol
3678 The type attribute of a symbol contains relocation (section)
3679 information, any flag settings indicating that a symbol is external, and
3680 (optionally), other information for linkers and debuggers. The exact
3681 format depends on the object-code output format in use.
3686 @c The following avoids a "widow" subsection title. @group would be
3687 @c better if it were available outside examples.
3690 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3692 @cindex @code{b.out} symbol attributes
3693 @cindex symbol attributes, @code{b.out}
3694 These symbol attributes appear only when @command{@value{AS}} is configured for
3695 one of the Berkeley-descended object output formats---@code{a.out} or
3701 @subsection Symbol Attributes: @code{a.out}
3703 @cindex @code{a.out} symbol attributes
3704 @cindex symbol attributes, @code{a.out}
3710 @subsection Symbol Attributes: @code{a.out}
3712 @cindex @code{a.out} symbol attributes
3713 @cindex symbol attributes, @code{a.out}
3717 * Symbol Desc:: Descriptor
3718 * Symbol Other:: Other
3722 @subsubsection Descriptor
3724 @cindex descriptor, of @code{a.out} symbol
3725 This is an arbitrary 16-bit value. You may establish a symbol's
3726 descriptor value by using a @code{.desc} statement
3727 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3728 @command{@value{AS}}.
3731 @subsubsection Other
3733 @cindex other attribute, of @code{a.out} symbol
3734 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3739 @subsection Symbol Attributes for COFF
3741 @cindex COFF symbol attributes
3742 @cindex symbol attributes, COFF
3744 The COFF format supports a multitude of auxiliary symbol attributes;
3745 like the primary symbol attributes, they are set between @code{.def} and
3746 @code{.endef} directives.
3748 @subsubsection Primary Attributes
3750 @cindex primary attributes, COFF symbols
3751 The symbol name is set with @code{.def}; the value and type,
3752 respectively, with @code{.val} and @code{.type}.
3754 @subsubsection Auxiliary Attributes
3756 @cindex auxiliary attributes, COFF symbols
3757 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3758 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3759 table information for COFF.
3764 @subsection Symbol Attributes for SOM
3766 @cindex SOM symbol attributes
3767 @cindex symbol attributes, SOM
3769 The SOM format for the HPPA supports a multitude of symbol attributes set with
3770 the @code{.EXPORT} and @code{.IMPORT} directives.
3772 The attributes are described in @cite{HP9000 Series 800 Assembly
3773 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3774 @code{EXPORT} assembler directive documentation.
3778 @chapter Expressions
3782 @cindex numeric values
3783 An @dfn{expression} specifies an address or numeric value.
3784 Whitespace may precede and/or follow an expression.
3786 The result of an expression must be an absolute number, or else an offset into
3787 a particular section. If an expression is not absolute, and there is not
3788 enough information when @command{@value{AS}} sees the expression to know its
3789 section, a second pass over the source program might be necessary to interpret
3790 the expression---but the second pass is currently not implemented.
3791 @command{@value{AS}} aborts with an error message in this situation.
3794 * Empty Exprs:: Empty Expressions
3795 * Integer Exprs:: Integer Expressions
3799 @section Empty Expressions
3801 @cindex empty expressions
3802 @cindex expressions, empty
3803 An empty expression has no value: it is just whitespace or null.
3804 Wherever an absolute expression is required, you may omit the
3805 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3806 is compatible with other assemblers.
3809 @section Integer Expressions
3811 @cindex integer expressions
3812 @cindex expressions, integer
3813 An @dfn{integer expression} is one or more @emph{arguments} delimited
3814 by @emph{operators}.
3817 * Arguments:: Arguments
3818 * Operators:: Operators
3819 * Prefix Ops:: Prefix Operators
3820 * Infix Ops:: Infix Operators
3824 @subsection Arguments
3826 @cindex expression arguments
3827 @cindex arguments in expressions
3828 @cindex operands in expressions
3829 @cindex arithmetic operands
3830 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3831 contexts arguments are sometimes called ``arithmetic operands''. In
3832 this manual, to avoid confusing them with the ``instruction operands'' of
3833 the machine language, we use the term ``argument'' to refer to parts of
3834 expressions only, reserving the word ``operand'' to refer only to machine
3835 instruction operands.
3837 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3838 @var{section} is one of text, data, bss, absolute,
3839 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3842 Numbers are usually integers.
3844 A number can be a flonum or bignum. In this case, you are warned
3845 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3846 these 32 bits are an integer. You may write integer-manipulating
3847 instructions that act on exotic constants, compatible with other
3850 @cindex subexpressions
3851 Subexpressions are a left parenthesis @samp{(} followed by an integer
3852 expression, followed by a right parenthesis @samp{)}; or a prefix
3853 operator followed by an argument.
3856 @subsection Operators
3858 @cindex operators, in expressions
3859 @cindex arithmetic functions
3860 @cindex functions, in expressions
3861 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3862 operators are followed by an argument. Infix operators appear
3863 between their arguments. Operators may be preceded and/or followed by
3867 @subsection Prefix Operator
3869 @cindex prefix operators
3870 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3871 one argument, which must be absolute.
3873 @c the tex/end tex stuff surrounding this small table is meant to make
3874 @c it align, on the printed page, with the similar table in the next
3875 @c section (which is inside an enumerate).
3877 \global\advance\leftskip by \itemindent
3882 @dfn{Negation}. Two's complement negation.
3884 @dfn{Complementation}. Bitwise not.
3888 \global\advance\leftskip by -\itemindent
3892 @subsection Infix Operators
3894 @cindex infix operators
3895 @cindex operators, permitted arguments
3896 @dfn{Infix operators} take two arguments, one on either side. Operators
3897 have precedence, but operations with equal precedence are performed left
3898 to right. Apart from @code{+} or @option{-}, both arguments must be
3899 absolute, and the result is absolute.
3902 @cindex operator precedence
3903 @cindex precedence of operators
3910 @dfn{Multiplication}.
3913 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3919 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3922 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3926 Intermediate precedence
3931 @dfn{Bitwise Inclusive Or}.
3937 @dfn{Bitwise Exclusive Or}.
3940 @dfn{Bitwise Or Not}.
3947 @cindex addition, permitted arguments
3948 @cindex plus, permitted arguments
3949 @cindex arguments for addition
3951 @dfn{Addition}. If either argument is absolute, the result has the section of
3952 the other argument. You may not add together arguments from different
3955 @cindex subtraction, permitted arguments
3956 @cindex minus, permitted arguments
3957 @cindex arguments for subtraction
3959 @dfn{Subtraction}. If the right argument is absolute, the
3960 result has the section of the left argument.
3961 If both arguments are in the same section, the result is absolute.
3962 You may not subtract arguments from different sections.
3963 @c FIXME is there still something useful to say about undefined - undefined ?
3965 @cindex comparison expressions
3966 @cindex expressions, comparison
3971 @dfn{Is Not Equal To}
3975 @dfn{Is Greater Than}
3977 @dfn{Is Greater Than Or Equal To}
3979 @dfn{Is Less Than Or Equal To}
3981 The comparison operators can be used as infix operators. A true results has a
3982 value of -1 whereas a false result has a value of 0. Note, these operators
3983 perform signed comparisons.
3986 @item Lowest Precedence
3995 These two logical operations can be used to combine the results of sub
3996 expressions. Note, unlike the comparison operators a true result returns a
3997 value of 1 but a false results does still return 0. Also note that the logical
3998 or operator has a slightly lower precedence than logical and.
4003 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4004 address; you can only have a defined section in one of the two arguments.
4007 @chapter Assembler Directives
4009 @cindex directives, machine independent
4010 @cindex pseudo-ops, machine independent
4011 @cindex machine independent directives
4012 All assembler directives have names that begin with a period (@samp{.}).
4013 The rest of the name is letters, usually in lower case.
4015 This chapter discusses directives that are available regardless of the
4016 target machine configuration for the @sc{gnu} assembler.
4018 Some machine configurations provide additional directives.
4019 @xref{Machine Dependencies}.
4022 @ifset machine-directives
4023 @xref{Machine Dependencies}, for additional directives.
4028 * Abort:: @code{.abort}
4030 * ABORT (COFF):: @code{.ABORT}
4033 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4034 * Altmacro:: @code{.altmacro}
4035 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4036 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4037 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4038 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4039 * Byte:: @code{.byte @var{expressions}}
4040 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4041 * Comm:: @code{.comm @var{symbol} , @var{length} }
4042 * Data:: @code{.data @var{subsection}}
4044 * Def:: @code{.def @var{name}}
4047 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4053 * Double:: @code{.double @var{flonums}}
4054 * Eject:: @code{.eject}
4055 * Else:: @code{.else}
4056 * Elseif:: @code{.elseif}
4059 * Endef:: @code{.endef}
4062 * Endfunc:: @code{.endfunc}
4063 * Endif:: @code{.endif}
4064 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4065 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4066 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4068 * Error:: @code{.error @var{string}}
4069 * Exitm:: @code{.exitm}
4070 * Extern:: @code{.extern}
4071 * Fail:: @code{.fail}
4072 * File:: @code{.file}
4073 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4074 * Float:: @code{.float @var{flonums}}
4075 * Func:: @code{.func}
4076 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4078 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4079 * Hidden:: @code{.hidden @var{names}}
4082 * hword:: @code{.hword @var{expressions}}
4083 * Ident:: @code{.ident}
4084 * If:: @code{.if @var{absolute expression}}
4085 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4086 * Include:: @code{.include "@var{file}"}
4087 * Int:: @code{.int @var{expressions}}
4089 * Internal:: @code{.internal @var{names}}
4092 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4093 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4094 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4095 * Lflags:: @code{.lflags}
4096 @ifclear no-line-dir
4097 * Line:: @code{.line @var{line-number}}
4100 * Linkonce:: @code{.linkonce [@var{type}]}
4101 * List:: @code{.list}
4102 * Ln:: @code{.ln @var{line-number}}
4103 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4104 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4106 * Local:: @code{.local @var{names}}
4109 * Long:: @code{.long @var{expressions}}
4111 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4114 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4115 * MRI:: @code{.mri @var{val}}
4116 * Noaltmacro:: @code{.noaltmacro}
4117 * Nolist:: @code{.nolist}
4118 * Octa:: @code{.octa @var{bignums}}
4119 * Offset:: @code{.offset @var{loc}}
4120 * Org:: @code{.org @var{new-lc}, @var{fill}}
4121 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4123 * PopSection:: @code{.popsection}
4124 * Previous:: @code{.previous}
4127 * Print:: @code{.print @var{string}}
4129 * Protected:: @code{.protected @var{names}}
4132 * Psize:: @code{.psize @var{lines}, @var{columns}}
4133 * Purgem:: @code{.purgem @var{name}}
4135 * PushSection:: @code{.pushsection @var{name}}
4138 * Quad:: @code{.quad @var{bignums}}
4139 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4140 * Rept:: @code{.rept @var{count}}
4141 * Sbttl:: @code{.sbttl "@var{subheading}"}
4143 * Scl:: @code{.scl @var{class}}
4146 * Section:: @code{.section @var{name}[, @var{flags}]}
4149 * Set:: @code{.set @var{symbol}, @var{expression}}
4150 * Short:: @code{.short @var{expressions}}
4151 * Single:: @code{.single @var{flonums}}
4153 * Size:: @code{.size [@var{name} , @var{expression}]}
4155 @ifclear no-space-dir
4156 * Skip:: @code{.skip @var{size} , @var{fill}}
4159 * Sleb128:: @code{.sleb128 @var{expressions}}
4160 @ifclear no-space-dir
4161 * Space:: @code{.space @var{size} , @var{fill}}
4164 * Stab:: @code{.stabd, .stabn, .stabs}
4167 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4168 * Struct:: @code{.struct @var{expression}}
4170 * SubSection:: @code{.subsection}
4171 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4175 * Tag:: @code{.tag @var{structname}}
4178 * Text:: @code{.text @var{subsection}}
4179 * Title:: @code{.title "@var{heading}"}
4181 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4184 * Uleb128:: @code{.uleb128 @var{expressions}}
4186 * Val:: @code{.val @var{addr}}
4190 * Version:: @code{.version "@var{string}"}
4191 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4192 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4195 * Warning:: @code{.warning @var{string}}
4196 * Weak:: @code{.weak @var{names}}
4197 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4198 * Word:: @code{.word @var{expressions}}
4199 * Deprecated:: Deprecated Directives
4203 @section @code{.abort}
4205 @cindex @code{abort} directive
4206 @cindex stopping the assembly
4207 This directive stops the assembly immediately. It is for
4208 compatibility with other assemblers. The original idea was that the
4209 assembly language source would be piped into the assembler. If the sender
4210 of the source quit, it could use this directive tells @command{@value{AS}} to
4211 quit also. One day @code{.abort} will not be supported.
4215 @section @code{.ABORT} (COFF)
4217 @cindex @code{ABORT} directive
4218 When producing COFF output, @command{@value{AS}} accepts this directive as a
4219 synonym for @samp{.abort}.
4222 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4228 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4230 @cindex padding the location counter
4231 @cindex @code{align} directive
4232 Pad the location counter (in the current subsection) to a particular storage
4233 boundary. The first expression (which must be absolute) is the alignment
4234 required, as described below.
4236 The second expression (also absolute) gives the fill value to be stored in the
4237 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4238 padding bytes are normally zero. However, on some systems, if the section is
4239 marked as containing code and the fill value is omitted, the space is filled
4240 with no-op instructions.
4242 The third expression is also absolute, and is also optional. If it is present,
4243 it is the maximum number of bytes that should be skipped by this alignment
4244 directive. If doing the alignment would require skipping more bytes than the
4245 specified maximum, then the alignment is not done at all. You can omit the
4246 fill value (the second argument) entirely by simply using two commas after the
4247 required alignment; this can be useful if you want the alignment to be filled
4248 with no-op instructions when appropriate.
4250 The way the required alignment is specified varies from system to system.
4251 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4252 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4253 alignment request in bytes. For example @samp{.align 8} advances
4254 the location counter until it is a multiple of 8. If the location counter
4255 is already a multiple of 8, no change is needed. For the tic54x, the
4256 first expression is the alignment request in words.
4258 For other systems, including ppc, i386 using a.out format, arm and
4259 strongarm, it is the
4260 number of low-order zero bits the location counter must have after
4261 advancement. For example @samp{.align 3} advances the location
4262 counter until it a multiple of 8. If the location counter is already a
4263 multiple of 8, no change is needed.
4265 This inconsistency is due to the different behaviors of the various
4266 native assemblers for these systems which GAS must emulate.
4267 GAS also provides @code{.balign} and @code{.p2align} directives,
4268 described later, which have a consistent behavior across all
4269 architectures (but are specific to GAS).
4272 @section @code{.altmacro}
4273 Enable alternate macro mode, enabling:
4276 @item LOCAL @var{name} [ , @dots{} ]
4277 One additional directive, @code{LOCAL}, is available. It is used to
4278 generate a string replacement for each of the @var{name} arguments, and
4279 replace any instances of @var{name} in each macro expansion. The
4280 replacement string is unique in the assembly, and different for each
4281 separate macro expansion. @code{LOCAL} allows you to write macros that
4282 define symbols, without fear of conflict between separate macro expansions.
4284 @item String delimiters
4285 You can write strings delimited in these other ways besides
4286 @code{"@var{string}"}:
4289 @item '@var{string}'
4290 You can delimit strings with single-quote characters.
4292 @item <@var{string}>
4293 You can delimit strings with matching angle brackets.
4296 @item single-character string escape
4297 To include any single character literally in a string (even if the
4298 character would otherwise have some special meaning), you can prefix the
4299 character with @samp{!} (an exclamation mark). For example, you can
4300 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4302 @item Expression results as strings
4303 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4304 and use the result as a string.
4308 @section @code{.ascii "@var{string}"}@dots{}
4310 @cindex @code{ascii} directive
4311 @cindex string literals
4312 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4313 separated by commas. It assembles each string (with no automatic
4314 trailing zero byte) into consecutive addresses.
4317 @section @code{.asciz "@var{string}"}@dots{}
4319 @cindex @code{asciz} directive
4320 @cindex zero-terminated strings
4321 @cindex null-terminated strings
4322 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4323 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4326 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4328 @cindex padding the location counter given number of bytes
4329 @cindex @code{balign} directive
4330 Pad the location counter (in the current subsection) to a particular
4331 storage boundary. The first expression (which must be absolute) is the
4332 alignment request in bytes. For example @samp{.balign 8} advances
4333 the location counter until it is a multiple of 8. If the location counter
4334 is already a multiple of 8, no change is needed.
4336 The second expression (also absolute) gives the fill value to be stored in the
4337 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4338 padding bytes are normally zero. However, on some systems, if the section is
4339 marked as containing code and the fill value is omitted, the space is filled
4340 with no-op instructions.
4342 The third expression is also absolute, and is also optional. If it is present,
4343 it is the maximum number of bytes that should be skipped by this alignment
4344 directive. If doing the alignment would require skipping more bytes than the
4345 specified maximum, then the alignment is not done at all. You can omit the
4346 fill value (the second argument) entirely by simply using two commas after the
4347 required alignment; this can be useful if you want the alignment to be filled
4348 with no-op instructions when appropriate.
4350 @cindex @code{balignw} directive
4351 @cindex @code{balignl} directive
4352 The @code{.balignw} and @code{.balignl} directives are variants of the
4353 @code{.balign} directive. The @code{.balignw} directive treats the fill
4354 pattern as a two byte word value. The @code{.balignl} directives treats the
4355 fill pattern as a four byte longword value. For example, @code{.balignw
4356 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4357 filled in with the value 0x368d (the exact placement of the bytes depends upon
4358 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4361 @node Bundle directives
4362 @section @code{.bundle_align_mode @var{abs-expr}}
4363 @cindex @code{bundle_align_mode} directive
4365 @cindex instruction bundle
4366 @cindex aligned instruction bundle
4367 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4368 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4369 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4370 disabled (which is the default state). If the argument it not zero, it
4371 gives the size of an instruction bundle as a power of two (as for the
4372 @code{.p2align} directive, @pxref{P2align}).
4374 For some targets, it's an ABI requirement that no instruction may span a
4375 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4376 instructions that starts on an aligned boundary. For example, if
4377 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4378 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4379 effect, no single instruction may span a boundary between bundles. If an
4380 instruction would start too close to the end of a bundle for the length of
4381 that particular instruction to fit within the bundle, then the space at the
4382 end of that bundle is filled with no-op instructions so the instruction
4383 starts in the next bundle. As a corollary, it's an error if any single
4384 instruction's encoding is longer than the bundle size.
4386 @section @code{.bundle_lock} and @code{.bundle_unlock}
4387 @cindex @code{bundle_lock} directive
4388 @cindex @code{bundle_unlock} directive
4389 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4390 allow explicit control over instruction bundle padding. These directives
4391 are only valid when @code{.bundle_align_mode} has been used to enable
4392 aligned instruction bundle mode. It's an error if they appear when
4393 @code{.bundle_align_mode} has not been used at all, or when the last
4394 directive was @w{@code{.bundle_align_mode 0}}.
4396 @cindex bundle-locked
4397 For some targets, it's an ABI requirement that certain instructions may
4398 appear only as part of specified permissible sequences of multiple
4399 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4400 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4401 instruction sequence. For purposes of aligned instruction bundle mode, a
4402 sequence starting with @code{.bundle_lock} and ending with
4403 @code{.bundle_unlock} is treated as a single instruction. That is, the
4404 entire sequence must fit into a single bundle and may not span a bundle
4405 boundary. If necessary, no-op instructions will be inserted before the
4406 first instruction of the sequence so that the whole sequence starts on an
4407 aligned bundle boundary. It's an error if the sequence is longer than the
4410 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4411 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4412 nested. That is, a second @code{.bundle_lock} directive before the next
4413 @code{.bundle_unlock} directive has no effect except that it must be
4414 matched by another closing @code{.bundle_unlock} so that there is the
4415 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4418 @section @code{.byte @var{expressions}}
4420 @cindex @code{byte} directive
4421 @cindex integers, one byte
4422 @code{.byte} expects zero or more expressions, separated by commas.
4423 Each expression is assembled into the next byte.
4425 @node CFI directives
4426 @section @code{.cfi_sections @var{section_list}}
4427 @cindex @code{cfi_sections} directive
4428 @code{.cfi_sections} may be used to specify whether CFI directives
4429 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4430 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4431 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4432 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4433 directive is not used is @code{.cfi_sections .eh_frame}.
4435 @section @code{.cfi_startproc [simple]}
4436 @cindex @code{cfi_startproc} directive
4437 @code{.cfi_startproc} is used at the beginning of each function that
4438 should have an entry in @code{.eh_frame}. It initializes some internal
4439 data structures. Don't forget to close the function by
4440 @code{.cfi_endproc}.
4442 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4443 it also emits some architecture dependent initial CFI instructions.
4445 @section @code{.cfi_endproc}
4446 @cindex @code{cfi_endproc} directive
4447 @code{.cfi_endproc} is used at the end of a function where it closes its
4448 unwind entry previously opened by
4449 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4451 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4452 @code{.cfi_personality} defines personality routine and its encoding.
4453 @var{encoding} must be a constant determining how the personality
4454 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4455 argument is not present, otherwise second argument should be
4456 a constant or a symbol name. When using indirect encodings,
4457 the symbol provided should be the location where personality
4458 can be loaded from, not the personality routine itself.
4459 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4460 no personality routine.
4462 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4463 @code{.cfi_lsda} defines LSDA and its encoding.
4464 @var{encoding} must be a constant determining how the LSDA
4465 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4466 argument is not present, otherwise second argument should be a constant
4467 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4470 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4471 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4472 address from @var{register} and add @var{offset} to it}.
4474 @section @code{.cfi_def_cfa_register @var{register}}
4475 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4476 now on @var{register} will be used instead of the old one. Offset
4479 @section @code{.cfi_def_cfa_offset @var{offset}}
4480 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4481 remains the same, but @var{offset} is new. Note that it is the
4482 absolute offset that will be added to a defined register to compute
4485 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4486 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4487 value that is added/substracted from the previous offset.
4489 @section @code{.cfi_offset @var{register}, @var{offset}}
4490 Previous value of @var{register} is saved at offset @var{offset} from
4493 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4494 Previous value of @var{register} is saved at offset @var{offset} from
4495 the current CFA register. This is transformed to @code{.cfi_offset}
4496 using the known displacement of the CFA register from the CFA.
4497 This is often easier to use, because the number will match the
4498 code it's annotating.
4500 @section @code{.cfi_register @var{register1}, @var{register2}}
4501 Previous value of @var{register1} is saved in register @var{register2}.
4503 @section @code{.cfi_restore @var{register}}
4504 @code{.cfi_restore} says that the rule for @var{register} is now the
4505 same as it was at the beginning of the function, after all initial
4506 instruction added by @code{.cfi_startproc} were executed.
4508 @section @code{.cfi_undefined @var{register}}
4509 From now on the previous value of @var{register} can't be restored anymore.
4511 @section @code{.cfi_same_value @var{register}}
4512 Current value of @var{register} is the same like in the previous frame,
4513 i.e. no restoration needed.
4515 @section @code{.cfi_remember_state},
4516 First save all current rules for all registers by @code{.cfi_remember_state},
4517 then totally screw them up by subsequent @code{.cfi_*} directives and when
4518 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4519 the previous saved state.
4521 @section @code{.cfi_return_column @var{register}}
4522 Change return column @var{register}, i.e. the return address is either
4523 directly in @var{register} or can be accessed by rules for @var{register}.
4525 @section @code{.cfi_signal_frame}
4526 Mark current function as signal trampoline.
4528 @section @code{.cfi_window_save}
4529 SPARC register window has been saved.
4531 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4532 Allows the user to add arbitrary bytes to the unwind info. One
4533 might use this to add OS-specific CFI opcodes, or generic CFI
4534 opcodes that GAS does not yet support.
4536 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4537 The current value of @var{register} is @var{label}. The value of @var{label}
4538 will be encoded in the output file according to @var{encoding}; see the
4539 description of @code{.cfi_personality} for details on this encoding.
4541 The usefulness of equating a register to a fixed label is probably
4542 limited to the return address register. Here, it can be useful to
4543 mark a code segment that has only one return address which is reached
4544 by a direct branch and no copy of the return address exists in memory
4545 or another register.
4548 @section @code{.comm @var{symbol} , @var{length} }
4550 @cindex @code{comm} directive
4551 @cindex symbol, common
4552 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4553 common symbol in one object file may be merged with a defined or common symbol
4554 of the same name in another object file. If @code{@value{LD}} does not see a
4555 definition for the symbol--just one or more common symbols--then it will
4556 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4557 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4558 the same name, and they do not all have the same size, it will allocate space
4559 using the largest size.
4562 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4563 an optional third argument. This is the desired alignment of the symbol,
4564 specified for ELF as a byte boundary (for example, an alignment of 16 means
4565 that the least significant 4 bits of the address should be zero), and for PE
4566 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4567 boundary). The alignment must be an absolute expression, and it must be a
4568 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4569 common symbol, it will use the alignment when placing the symbol. If no
4570 alignment is specified, @command{@value{AS}} will set the alignment to the
4571 largest power of two less than or equal to the size of the symbol, up to a
4572 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4573 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4574 @samp{--section-alignment} option; image file sections in PE are aligned to
4575 multiples of 4096, which is far too large an alignment for ordinary variables.
4576 It is rather the default alignment for (non-debug) sections within object
4577 (@samp{*.o}) files, which are less strictly aligned.}.
4581 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4582 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4586 @section @code{.data @var{subsection}}
4588 @cindex @code{data} directive
4589 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4590 end of the data subsection numbered @var{subsection} (which is an
4591 absolute expression). If @var{subsection} is omitted, it defaults
4596 @section @code{.def @var{name}}
4598 @cindex @code{def} directive
4599 @cindex COFF symbols, debugging
4600 @cindex debugging COFF symbols
4601 Begin defining debugging information for a symbol @var{name}; the
4602 definition extends until the @code{.endef} directive is encountered.
4605 This directive is only observed when @command{@value{AS}} is configured for COFF
4606 format output; when producing @code{b.out}, @samp{.def} is recognized,
4613 @section @code{.desc @var{symbol}, @var{abs-expression}}
4615 @cindex @code{desc} directive
4616 @cindex COFF symbol descriptor
4617 @cindex symbol descriptor, COFF
4618 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4619 to the low 16 bits of an absolute expression.
4622 The @samp{.desc} directive is not available when @command{@value{AS}} is
4623 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4624 object format. For the sake of compatibility, @command{@value{AS}} accepts
4625 it, but produces no output, when configured for COFF.
4631 @section @code{.dim}
4633 @cindex @code{dim} directive
4634 @cindex COFF auxiliary symbol information
4635 @cindex auxiliary symbol information, COFF
4636 This directive is generated by compilers to include auxiliary debugging
4637 information in the symbol table. It is only permitted inside
4638 @code{.def}/@code{.endef} pairs.
4641 @samp{.dim} is only meaningful when generating COFF format output; when
4642 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4648 @section @code{.double @var{flonums}}
4650 @cindex @code{double} directive
4651 @cindex floating point numbers (double)
4652 @code{.double} expects zero or more flonums, separated by commas. It
4653 assembles floating point numbers.
4655 The exact kind of floating point numbers emitted depends on how
4656 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4660 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4661 in @sc{ieee} format.
4666 @section @code{.eject}
4668 @cindex @code{eject} directive
4669 @cindex new page, in listings
4670 @cindex page, in listings
4671 @cindex listing control: new page
4672 Force a page break at this point, when generating assembly listings.
4675 @section @code{.else}
4677 @cindex @code{else} directive
4678 @code{.else} is part of the @command{@value{AS}} support for conditional
4679 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4680 of code to be assembled if the condition for the preceding @code{.if}
4684 @section @code{.elseif}
4686 @cindex @code{elseif} directive
4687 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4688 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4689 @code{.if} block that would otherwise fill the entire @code{.else} section.
4692 @section @code{.end}
4694 @cindex @code{end} directive
4695 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4696 process anything in the file past the @code{.end} directive.
4700 @section @code{.endef}
4702 @cindex @code{endef} directive
4703 This directive flags the end of a symbol definition begun with
4707 @samp{.endef} is only meaningful when generating COFF format output; if
4708 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4709 directive but ignores it.
4714 @section @code{.endfunc}
4715 @cindex @code{endfunc} directive
4716 @code{.endfunc} marks the end of a function specified with @code{.func}.
4719 @section @code{.endif}
4721 @cindex @code{endif} directive
4722 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4723 it marks the end of a block of code that is only assembled
4724 conditionally. @xref{If,,@code{.if}}.
4727 @section @code{.equ @var{symbol}, @var{expression}}
4729 @cindex @code{equ} directive
4730 @cindex assigning values to symbols
4731 @cindex symbols, assigning values to
4732 This directive sets the value of @var{symbol} to @var{expression}.
4733 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4736 The syntax for @code{equ} on the HPPA is
4737 @samp{@var{symbol} .equ @var{expression}}.
4741 The syntax for @code{equ} on the Z80 is
4742 @samp{@var{symbol} equ @var{expression}}.
4743 On the Z80 it is an eror if @var{symbol} is already defined,
4744 but the symbol is not protected from later redefinition.
4745 Compare @ref{Equiv}.
4749 @section @code{.equiv @var{symbol}, @var{expression}}
4750 @cindex @code{equiv} directive
4751 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4752 the assembler will signal an error if @var{symbol} is already defined. Note a
4753 symbol which has been referenced but not actually defined is considered to be
4756 Except for the contents of the error message, this is roughly equivalent to
4763 plus it protects the symbol from later redefinition.
4766 @section @code{.eqv @var{symbol}, @var{expression}}
4767 @cindex @code{eqv} directive
4768 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4769 evaluate the expression or any part of it immediately. Instead each time
4770 the resulting symbol is used in an expression, a snapshot of its current
4774 @section @code{.err}
4775 @cindex @code{err} directive
4776 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4777 message and, unless the @option{-Z} option was used, it will not generate an
4778 object file. This can be used to signal an error in conditionally compiled code.
4781 @section @code{.error "@var{string}"}
4782 @cindex error directive
4784 Similarly to @code{.err}, this directive emits an error, but you can specify a
4785 string that will be emitted as the error message. If you don't specify the
4786 message, it defaults to @code{".error directive invoked in source file"}.
4787 @xref{Errors, ,Error and Warning Messages}.
4790 .error "This code has not been assembled and tested."
4794 @section @code{.exitm}
4795 Exit early from the current macro definition. @xref{Macro}.
4798 @section @code{.extern}
4800 @cindex @code{extern} directive
4801 @code{.extern} is accepted in the source program---for compatibility
4802 with other assemblers---but it is ignored. @command{@value{AS}} treats
4803 all undefined symbols as external.
4806 @section @code{.fail @var{expression}}
4808 @cindex @code{fail} directive
4809 Generates an error or a warning. If the value of the @var{expression} is 500
4810 or more, @command{@value{AS}} will print a warning message. If the value is less
4811 than 500, @command{@value{AS}} will print an error message. The message will
4812 include the value of @var{expression}. This can occasionally be useful inside
4813 complex nested macros or conditional assembly.
4816 @section @code{.file}
4817 @cindex @code{file} directive
4819 @ifclear no-file-dir
4820 There are two different versions of the @code{.file} directive. Targets
4821 that support DWARF2 line number information use the DWARF2 version of
4822 @code{.file}. Other targets use the default version.
4824 @subheading Default Version
4826 @cindex logical file name
4827 @cindex file name, logical
4828 This version of the @code{.file} directive tells @command{@value{AS}} that we
4829 are about to start a new logical file. The syntax is:
4835 @var{string} is the new file name. In general, the filename is
4836 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4837 to specify an empty file name, you must give the quotes--@code{""}. This
4838 statement may go away in future: it is only recognized to be compatible with
4839 old @command{@value{AS}} programs.
4841 @subheading DWARF2 Version
4844 When emitting DWARF2 line number information, @code{.file} assigns filenames
4845 to the @code{.debug_line} file name table. The syntax is:
4848 .file @var{fileno} @var{filename}
4851 The @var{fileno} operand should be a unique positive integer to use as the
4852 index of the entry in the table. The @var{filename} operand is a C string
4855 The detail of filename indices is exposed to the user because the filename
4856 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4857 information, and thus the user must know the exact indices that table
4861 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4863 @cindex @code{fill} directive
4864 @cindex writing patterns in memory
4865 @cindex patterns, writing in memory
4866 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4867 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4868 may be zero or more. @var{Size} may be zero or more, but if it is
4869 more than 8, then it is deemed to have the value 8, compatible with
4870 other people's assemblers. The contents of each @var{repeat} bytes
4871 is taken from an 8-byte number. The highest order 4 bytes are
4872 zero. The lowest order 4 bytes are @var{value} rendered in the
4873 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4874 Each @var{size} bytes in a repetition is taken from the lowest order
4875 @var{size} bytes of this number. Again, this bizarre behavior is
4876 compatible with other people's assemblers.
4878 @var{size} and @var{value} are optional.
4879 If the second comma and @var{value} are absent, @var{value} is
4880 assumed zero. If the first comma and following tokens are absent,
4881 @var{size} is assumed to be 1.
4884 @section @code{.float @var{flonums}}
4886 @cindex floating point numbers (single)
4887 @cindex @code{float} directive
4888 This directive assembles zero or more flonums, separated by commas. It
4889 has the same effect as @code{.single}.
4891 The exact kind of floating point numbers emitted depends on how
4892 @command{@value{AS}} is configured.
4893 @xref{Machine Dependencies}.
4897 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4898 in @sc{ieee} format.
4903 @section @code{.func @var{name}[,@var{label}]}
4904 @cindex @code{func} directive
4905 @code{.func} emits debugging information to denote function @var{name}, and
4906 is ignored unless the file is assembled with debugging enabled.
4907 Only @samp{--gstabs[+]} is currently supported.
4908 @var{label} is the entry point of the function and if omitted @var{name}
4909 prepended with the @samp{leading char} is used.
4910 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4911 All functions are currently defined to have @code{void} return type.
4912 The function must be terminated with @code{.endfunc}.
4915 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4917 @cindex @code{global} directive
4918 @cindex symbol, making visible to linker
4919 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4920 @var{symbol} in your partial program, its value is made available to
4921 other partial programs that are linked with it. Otherwise,
4922 @var{symbol} takes its attributes from a symbol of the same name
4923 from another file linked into the same program.
4925 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4926 compatibility with other assemblers.
4929 On the HPPA, @code{.global} is not always enough to make it accessible to other
4930 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4931 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4936 @section @code{.gnu_attribute @var{tag},@var{value}}
4937 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4940 @section @code{.hidden @var{names}}
4942 @cindex @code{hidden} directive
4944 This is one of the ELF visibility directives. The other two are
4945 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4946 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4948 This directive overrides the named symbols default visibility (which is set by
4949 their binding: local, global or weak). The directive sets the visibility to
4950 @code{hidden} which means that the symbols are not visible to other components.
4951 Such symbols are always considered to be @code{protected} as well.
4955 @section @code{.hword @var{expressions}}
4957 @cindex @code{hword} directive
4958 @cindex integers, 16-bit
4959 @cindex numbers, 16-bit
4960 @cindex sixteen bit integers
4961 This expects zero or more @var{expressions}, and emits
4962 a 16 bit number for each.
4965 This directive is a synonym for @samp{.short}; depending on the target
4966 architecture, it may also be a synonym for @samp{.word}.
4970 This directive is a synonym for @samp{.short}.
4973 This directive is a synonym for both @samp{.short} and @samp{.word}.
4978 @section @code{.ident}
4980 @cindex @code{ident} directive
4982 This directive is used by some assemblers to place tags in object files. The
4983 behavior of this directive varies depending on the target. When using the
4984 a.out object file format, @command{@value{AS}} simply accepts the directive for
4985 source-file compatibility with existing assemblers, but does not emit anything
4986 for it. When using COFF, comments are emitted to the @code{.comment} or
4987 @code{.rdata} section, depending on the target. When using ELF, comments are
4988 emitted to the @code{.comment} section.
4991 @section @code{.if @var{absolute expression}}
4993 @cindex conditional assembly
4994 @cindex @code{if} directive
4995 @code{.if} marks the beginning of a section of code which is only
4996 considered part of the source program being assembled if the argument
4997 (which must be an @var{absolute expression}) is non-zero. The end of
4998 the conditional section of code must be marked by @code{.endif}
4999 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5000 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5001 If you have several conditions to check, @code{.elseif} may be used to avoid
5002 nesting blocks if/else within each subsequent @code{.else} block.
5004 The following variants of @code{.if} are also supported:
5006 @cindex @code{ifdef} directive
5007 @item .ifdef @var{symbol}
5008 Assembles the following section of code if the specified @var{symbol}
5009 has been defined. Note a symbol which has been referenced but not yet defined
5010 is considered to be undefined.
5012 @cindex @code{ifb} directive
5013 @item .ifb @var{text}
5014 Assembles the following section of code if the operand is blank (empty).
5016 @cindex @code{ifc} directive
5017 @item .ifc @var{string1},@var{string2}
5018 Assembles the following section of code if the two strings are the same. The
5019 strings may be optionally quoted with single quotes. If they are not quoted,
5020 the first string stops at the first comma, and the second string stops at the
5021 end of the line. Strings which contain whitespace should be quoted. The
5022 string comparison is case sensitive.
5024 @cindex @code{ifeq} directive
5025 @item .ifeq @var{absolute expression}
5026 Assembles the following section of code if the argument is zero.
5028 @cindex @code{ifeqs} directive
5029 @item .ifeqs @var{string1},@var{string2}
5030 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5032 @cindex @code{ifge} directive
5033 @item .ifge @var{absolute expression}
5034 Assembles the following section of code if the argument is greater than or
5037 @cindex @code{ifgt} directive
5038 @item .ifgt @var{absolute expression}
5039 Assembles the following section of code if the argument is greater than zero.
5041 @cindex @code{ifle} directive
5042 @item .ifle @var{absolute expression}
5043 Assembles the following section of code if the argument is less than or equal
5046 @cindex @code{iflt} directive
5047 @item .iflt @var{absolute expression}
5048 Assembles the following section of code if the argument is less than zero.
5050 @cindex @code{ifnb} directive
5051 @item .ifnb @var{text}
5052 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5053 following section of code if the operand is non-blank (non-empty).
5055 @cindex @code{ifnc} directive
5056 @item .ifnc @var{string1},@var{string2}.
5057 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5058 following section of code if the two strings are not the same.
5060 @cindex @code{ifndef} directive
5061 @cindex @code{ifnotdef} directive
5062 @item .ifndef @var{symbol}
5063 @itemx .ifnotdef @var{symbol}
5064 Assembles the following section of code if the specified @var{symbol}
5065 has not been defined. Both spelling variants are equivalent. Note a symbol
5066 which has been referenced but not yet defined is considered to be undefined.
5068 @cindex @code{ifne} directive
5069 @item .ifne @var{absolute expression}
5070 Assembles the following section of code if the argument is not equal to zero
5071 (in other words, this is equivalent to @code{.if}).
5073 @cindex @code{ifnes} directive
5074 @item .ifnes @var{string1},@var{string2}
5075 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5076 following section of code if the two strings are not the same.
5080 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5082 @cindex @code{incbin} directive
5083 @cindex binary files, including
5084 The @code{incbin} directive includes @var{file} verbatim at the current
5085 location. You can control the search paths used with the @samp{-I} command-line
5086 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5089 The @var{skip} argument skips a number of bytes from the start of the
5090 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5091 read. Note that the data is not aligned in any way, so it is the user's
5092 responsibility to make sure that proper alignment is provided both before and
5093 after the @code{incbin} directive.
5096 @section @code{.include "@var{file}"}
5098 @cindex @code{include} directive
5099 @cindex supporting files, including
5100 @cindex files, including
5101 This directive provides a way to include supporting files at specified
5102 points in your source program. The code from @var{file} is assembled as
5103 if it followed the point of the @code{.include}; when the end of the
5104 included file is reached, assembly of the original file continues. You
5105 can control the search paths used with the @samp{-I} command-line option
5106 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5110 @section @code{.int @var{expressions}}
5112 @cindex @code{int} directive
5113 @cindex integers, 32-bit
5114 Expect zero or more @var{expressions}, of any section, separated by commas.
5115 For each expression, emit a number that, at run time, is the value of that
5116 expression. The byte order and bit size of the number depends on what kind
5117 of target the assembly is for.
5121 On most forms of the H8/300, @code{.int} emits 16-bit
5122 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5129 @section @code{.internal @var{names}}
5131 @cindex @code{internal} directive
5133 This is one of the ELF visibility directives. The other two are
5134 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5135 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5137 This directive overrides the named symbols default visibility (which is set by
5138 their binding: local, global or weak). The directive sets the visibility to
5139 @code{internal} which means that the symbols are considered to be @code{hidden}
5140 (i.e., not visible to other components), and that some extra, processor specific
5141 processing must also be performed upon the symbols as well.
5145 @section @code{.irp @var{symbol},@var{values}}@dots{}
5147 @cindex @code{irp} directive
5148 Evaluate a sequence of statements assigning different values to @var{symbol}.
5149 The sequence of statements starts at the @code{.irp} directive, and is
5150 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5151 set to @var{value}, and the sequence of statements is assembled. If no
5152 @var{value} is listed, the sequence of statements is assembled once, with
5153 @var{symbol} set to the null string. To refer to @var{symbol} within the
5154 sequence of statements, use @var{\symbol}.
5156 For example, assembling
5164 is equivalent to assembling
5172 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5175 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5177 @cindex @code{irpc} directive
5178 Evaluate a sequence of statements assigning different values to @var{symbol}.
5179 The sequence of statements starts at the @code{.irpc} directive, and is
5180 terminated by an @code{.endr} directive. For each character in @var{value},
5181 @var{symbol} is set to the character, and the sequence of statements is
5182 assembled. If no @var{value} is listed, the sequence of statements is
5183 assembled once, with @var{symbol} set to the null string. To refer to
5184 @var{symbol} within the sequence of statements, use @var{\symbol}.
5186 For example, assembling
5194 is equivalent to assembling
5202 For some caveats with the spelling of @var{symbol}, see also the discussion
5206 @section @code{.lcomm @var{symbol} , @var{length}}
5208 @cindex @code{lcomm} directive
5209 @cindex local common symbols
5210 @cindex symbols, local common
5211 Reserve @var{length} (an absolute expression) bytes for a local common
5212 denoted by @var{symbol}. The section and value of @var{symbol} are
5213 those of the new local common. The addresses are allocated in the bss
5214 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5215 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5216 not visible to @code{@value{LD}}.
5219 Some targets permit a third argument to be used with @code{.lcomm}. This
5220 argument specifies the desired alignment of the symbol in the bss section.
5224 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5225 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5229 @section @code{.lflags}
5231 @cindex @code{lflags} directive (ignored)
5232 @command{@value{AS}} accepts this directive, for compatibility with other
5233 assemblers, but ignores it.
5235 @ifclear no-line-dir
5237 @section @code{.line @var{line-number}}
5239 @cindex @code{line} directive
5240 @cindex logical line number
5242 Change the logical line number. @var{line-number} must be an absolute
5243 expression. The next line has that logical line number. Therefore any other
5244 statements on the current line (after a statement separator character) are
5245 reported as on logical line number @var{line-number} @minus{} 1. One day
5246 @command{@value{AS}} will no longer support this directive: it is recognized only
5247 for compatibility with existing assembler programs.
5250 Even though this is a directive associated with the @code{a.out} or
5251 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5252 when producing COFF output, and treats @samp{.line} as though it
5253 were the COFF @samp{.ln} @emph{if} it is found outside a
5254 @code{.def}/@code{.endef} pair.
5256 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5257 used by compilers to generate auxiliary symbol information for
5262 @section @code{.linkonce [@var{type}]}
5264 @cindex @code{linkonce} directive
5265 @cindex common sections
5266 Mark the current section so that the linker only includes a single copy of it.
5267 This may be used to include the same section in several different object files,
5268 but ensure that the linker will only include it once in the final output file.
5269 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5270 Duplicate sections are detected based on the section name, so it should be
5273 This directive is only supported by a few object file formats; as of this
5274 writing, the only object file format which supports it is the Portable
5275 Executable format used on Windows NT.
5277 The @var{type} argument is optional. If specified, it must be one of the
5278 following strings. For example:
5282 Not all types may be supported on all object file formats.
5286 Silently discard duplicate sections. This is the default.
5289 Warn if there are duplicate sections, but still keep only one copy.
5292 Warn if any of the duplicates have different sizes.
5295 Warn if any of the duplicates do not have exactly the same contents.
5299 @section @code{.list}
5301 @cindex @code{list} directive
5302 @cindex listing control, turning on
5303 Control (in conjunction with the @code{.nolist} directive) whether or
5304 not assembly listings are generated. These two directives maintain an
5305 internal counter (which is zero initially). @code{.list} increments the
5306 counter, and @code{.nolist} decrements it. Assembly listings are
5307 generated whenever the counter is greater than zero.
5309 By default, listings are disabled. When you enable them (with the
5310 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5311 the initial value of the listing counter is one.
5314 @section @code{.ln @var{line-number}}
5316 @cindex @code{ln} directive
5317 @ifclear no-line-dir
5318 @samp{.ln} is a synonym for @samp{.line}.
5321 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5322 must be an absolute expression. The next line has that logical
5323 line number, so any other statements on the current line (after a
5324 statement separator character @code{;}) are reported as on logical
5325 line number @var{line-number} @minus{} 1.
5328 This directive is accepted, but ignored, when @command{@value{AS}} is
5329 configured for @code{b.out}; its effect is only associated with COFF
5335 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5336 @cindex @code{loc} directive
5337 When emitting DWARF2 line number information,
5338 the @code{.loc} directive will add a row to the @code{.debug_line} line
5339 number matrix corresponding to the immediately following assembly
5340 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5341 arguments will be applied to the @code{.debug_line} state machine before
5344 The @var{options} are a sequence of the following tokens in any order:
5348 This option will set the @code{basic_block} register in the
5349 @code{.debug_line} state machine to @code{true}.
5352 This option will set the @code{prologue_end} register in the
5353 @code{.debug_line} state machine to @code{true}.
5355 @item epilogue_begin
5356 This option will set the @code{epilogue_begin} register in the
5357 @code{.debug_line} state machine to @code{true}.
5359 @item is_stmt @var{value}
5360 This option will set the @code{is_stmt} register in the
5361 @code{.debug_line} state machine to @code{value}, which must be
5364 @item isa @var{value}
5365 This directive will set the @code{isa} register in the @code{.debug_line}
5366 state machine to @var{value}, which must be an unsigned integer.
5368 @item discriminator @var{value}
5369 This directive will set the @code{discriminator} register in the @code{.debug_line}
5370 state machine to @var{value}, which must be an unsigned integer.
5374 @node Loc_mark_labels
5375 @section @code{.loc_mark_labels @var{enable}}
5376 @cindex @code{loc_mark_labels} directive
5377 When emitting DWARF2 line number information,
5378 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5379 to the @code{.debug_line} line number matrix with the @code{basic_block}
5380 register in the state machine set whenever a code label is seen.
5381 The @var{enable} argument should be either 1 or 0, to enable or disable
5382 this function respectively.
5386 @section @code{.local @var{names}}
5388 @cindex @code{local} directive
5389 This directive, which is available for ELF targets, marks each symbol in
5390 the comma-separated list of @code{names} as a local symbol so that it
5391 will not be externally visible. If the symbols do not already exist,
5392 they will be created.
5394 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5395 accept an alignment argument, which is the case for most ELF targets,
5396 the @code{.local} directive can be used in combination with @code{.comm}
5397 (@pxref{Comm}) to define aligned local common data.
5401 @section @code{.long @var{expressions}}
5403 @cindex @code{long} directive
5404 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5407 @c no one seems to know what this is for or whether this description is
5408 @c what it really ought to do
5410 @section @code{.lsym @var{symbol}, @var{expression}}
5412 @cindex @code{lsym} directive
5413 @cindex symbol, not referenced in assembly
5414 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5415 the hash table, ensuring it cannot be referenced by name during the
5416 rest of the assembly. This sets the attributes of the symbol to be
5417 the same as the expression value:
5419 @var{other} = @var{descriptor} = 0
5420 @var{type} = @r{(section of @var{expression})}
5421 @var{value} = @var{expression}
5424 The new symbol is not flagged as external.
5428 @section @code{.macro}
5431 The commands @code{.macro} and @code{.endm} allow you to define macros that
5432 generate assembly output. For example, this definition specifies a macro
5433 @code{sum} that puts a sequence of numbers into memory:
5436 .macro sum from=0, to=5
5445 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5457 @item .macro @var{macname}
5458 @itemx .macro @var{macname} @var{macargs} @dots{}
5459 @cindex @code{macro} directive
5460 Begin the definition of a macro called @var{macname}. If your macro
5461 definition requires arguments, specify their names after the macro name,
5462 separated by commas or spaces. You can qualify the macro argument to
5463 indicate whether all invocations must specify a non-blank value (through
5464 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5465 (through @samp{:@code{vararg}}). You can supply a default value for any
5466 macro argument by following the name with @samp{=@var{deflt}}. You
5467 cannot define two macros with the same @var{macname} unless it has been
5468 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5469 definitions. For example, these are all valid @code{.macro} statements:
5473 Begin the definition of a macro called @code{comm}, which takes no
5476 @item .macro plus1 p, p1
5477 @itemx .macro plus1 p p1
5478 Either statement begins the definition of a macro called @code{plus1},
5479 which takes two arguments; within the macro definition, write
5480 @samp{\p} or @samp{\p1} to evaluate the arguments.
5482 @item .macro reserve_str p1=0 p2
5483 Begin the definition of a macro called @code{reserve_str}, with two
5484 arguments. The first argument has a default value, but not the second.
5485 After the definition is complete, you can call the macro either as
5486 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5487 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5488 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5489 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5491 @item .macro m p1:req, p2=0, p3:vararg
5492 Begin the definition of a macro called @code{m}, with at least three
5493 arguments. The first argument must always have a value specified, but
5494 not the second, which instead has a default value. The third formal
5495 will get assigned all remaining arguments specified at invocation time.
5497 When you call a macro, you can specify the argument values either by
5498 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5499 @samp{sum to=17, from=9}.
5503 Note that since each of the @var{macargs} can be an identifier exactly
5504 as any other one permitted by the target architecture, there may be
5505 occasional problems if the target hand-crafts special meanings to certain
5506 characters when they occur in a special position. For example, if the colon
5507 (@code{:}) is generally permitted to be part of a symbol name, but the
5508 architecture specific code special-cases it when occurring as the final
5509 character of a symbol (to denote a label), then the macro parameter
5510 replacement code will have no way of knowing that and consider the whole
5511 construct (including the colon) an identifier, and check only this
5512 identifier for being the subject to parameter substitution. So for example
5513 this macro definition:
5521 might not work as expected. Invoking @samp{label foo} might not create a label
5522 called @samp{foo} but instead just insert the text @samp{\l:} into the
5523 assembler source, probably generating an error about an unrecognised
5526 Similarly problems might occur with the period character (@samp{.})
5527 which is often allowed inside opcode names (and hence identifier names). So
5528 for example constructing a macro to build an opcode from a base name and a
5529 length specifier like this:
5532 .macro opcode base length
5537 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5538 instruction but instead generate some kind of error as the assembler tries to
5539 interpret the text @samp{\base.\length}.
5541 There are several possible ways around this problem:
5544 @item Insert white space
5545 If it is possible to use white space characters then this is the simplest
5554 @item Use @samp{\()}
5555 The string @samp{\()} can be used to separate the end of a macro argument from
5556 the following text. eg:
5559 .macro opcode base length
5564 @item Use the alternate macro syntax mode
5565 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5566 used as a separator. eg:
5576 Note: this problem of correctly identifying string parameters to pseudo ops
5577 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5578 and @code{.irpc} (@pxref{Irpc}) as well.
5581 @cindex @code{endm} directive
5582 Mark the end of a macro definition.
5585 @cindex @code{exitm} directive
5586 Exit early from the current macro definition.
5588 @cindex number of macros executed
5589 @cindex macros, count executed
5591 @command{@value{AS}} maintains a counter of how many macros it has
5592 executed in this pseudo-variable; you can copy that number to your
5593 output with @samp{\@@}, but @emph{only within a macro definition}.
5595 @item LOCAL @var{name} [ , @dots{} ]
5596 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5597 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5598 @xref{Altmacro,,@code{.altmacro}}.
5602 @section @code{.mri @var{val}}
5604 @cindex @code{mri} directive
5605 @cindex MRI mode, temporarily
5606 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5607 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5608 affects code assembled until the next @code{.mri} directive, or until the end
5609 of the file. @xref{M, MRI mode, MRI mode}.
5612 @section @code{.noaltmacro}
5613 Disable alternate macro mode. @xref{Altmacro}.
5616 @section @code{.nolist}
5618 @cindex @code{nolist} directive
5619 @cindex listing control, turning off
5620 Control (in conjunction with the @code{.list} directive) whether or
5621 not assembly listings are generated. These two directives maintain an
5622 internal counter (which is zero initially). @code{.list} increments the
5623 counter, and @code{.nolist} decrements it. Assembly listings are
5624 generated whenever the counter is greater than zero.
5627 @section @code{.octa @var{bignums}}
5629 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5630 @cindex @code{octa} directive
5631 @cindex integer, 16-byte
5632 @cindex sixteen byte integer
5633 This directive expects zero or more bignums, separated by commas. For each
5634 bignum, it emits a 16-byte integer.
5636 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5637 hence @emph{octa}-word for 16 bytes.
5640 @section @code{.offset @var{loc}}
5642 @cindex @code{offset} directive
5643 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5644 be an absolute expression. This directive may be useful for defining
5645 symbols with absolute values. Do not confuse it with the @code{.org}
5649 @section @code{.org @var{new-lc} , @var{fill}}
5651 @cindex @code{org} directive
5652 @cindex location counter, advancing
5653 @cindex advancing location counter
5654 @cindex current address, advancing
5655 Advance the location counter of the current section to
5656 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5657 expression with the same section as the current subsection. That is,
5658 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5659 wrong section, the @code{.org} directive is ignored. To be compatible
5660 with former assemblers, if the section of @var{new-lc} is absolute,
5661 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5662 is the same as the current subsection.
5664 @code{.org} may only increase the location counter, or leave it
5665 unchanged; you cannot use @code{.org} to move the location counter
5668 @c double negative used below "not undefined" because this is a specific
5669 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5670 @c section. doc@cygnus.com 18feb91
5671 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5672 may not be undefined. If you really detest this restriction we eagerly await
5673 a chance to share your improved assembler.
5675 Beware that the origin is relative to the start of the section, not
5676 to the start of the subsection. This is compatible with other
5677 people's assemblers.
5679 When the location counter (of the current subsection) is advanced, the
5680 intervening bytes are filled with @var{fill} which should be an
5681 absolute expression. If the comma and @var{fill} are omitted,
5682 @var{fill} defaults to zero.
5685 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5687 @cindex padding the location counter given a power of two
5688 @cindex @code{p2align} directive
5689 Pad the location counter (in the current subsection) to a particular
5690 storage boundary. The first expression (which must be absolute) is the
5691 number of low-order zero bits the location counter must have after
5692 advancement. For example @samp{.p2align 3} advances the location
5693 counter until it a multiple of 8. If the location counter is already a
5694 multiple of 8, no change is needed.
5696 The second expression (also absolute) gives the fill value to be stored in the
5697 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5698 padding bytes are normally zero. However, on some systems, if the section is
5699 marked as containing code and the fill value is omitted, the space is filled
5700 with no-op instructions.
5702 The third expression is also absolute, and is also optional. If it is present,
5703 it is the maximum number of bytes that should be skipped by this alignment
5704 directive. If doing the alignment would require skipping more bytes than the
5705 specified maximum, then the alignment is not done at all. You can omit the
5706 fill value (the second argument) entirely by simply using two commas after the
5707 required alignment; this can be useful if you want the alignment to be filled
5708 with no-op instructions when appropriate.
5710 @cindex @code{p2alignw} directive
5711 @cindex @code{p2alignl} directive
5712 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5713 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5714 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5715 fill pattern as a four byte longword value. For example, @code{.p2alignw
5716 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5717 filled in with the value 0x368d (the exact placement of the bytes depends upon
5718 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5723 @section @code{.popsection}
5725 @cindex @code{popsection} directive
5726 @cindex Section Stack
5727 This is one of the ELF section stack manipulation directives. The others are
5728 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5729 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5732 This directive replaces the current section (and subsection) with the top
5733 section (and subsection) on the section stack. This section is popped off the
5739 @section @code{.previous}
5741 @cindex @code{previous} directive
5742 @cindex Section Stack
5743 This is one of the ELF section stack manipulation directives. The others are
5744 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5745 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5746 (@pxref{PopSection}).
5748 This directive swaps the current section (and subsection) with most recently
5749 referenced section/subsection pair prior to this one. Multiple
5750 @code{.previous} directives in a row will flip between two sections (and their
5751 subsections). For example:
5763 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5769 # Now in section A subsection 1
5773 # Now in section B subsection 0
5776 # Now in section B subsection 1
5779 # Now in section B subsection 0
5783 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5784 section B and 0x9abc into subsection 1 of section B.
5786 In terms of the section stack, this directive swaps the current section with
5787 the top section on the section stack.
5791 @section @code{.print @var{string}}
5793 @cindex @code{print} directive
5794 @command{@value{AS}} will print @var{string} on the standard output during
5795 assembly. You must put @var{string} in double quotes.
5799 @section @code{.protected @var{names}}
5801 @cindex @code{protected} directive
5803 This is one of the ELF visibility directives. The other two are
5804 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5806 This directive overrides the named symbols default visibility (which is set by
5807 their binding: local, global or weak). The directive sets the visibility to
5808 @code{protected} which means that any references to the symbols from within the
5809 components that defines them must be resolved to the definition in that
5810 component, even if a definition in another component would normally preempt
5815 @section @code{.psize @var{lines} , @var{columns}}
5817 @cindex @code{psize} directive
5818 @cindex listing control: paper size
5819 @cindex paper size, for listings
5820 Use this directive to declare the number of lines---and, optionally, the
5821 number of columns---to use for each page, when generating listings.
5823 If you do not use @code{.psize}, listings use a default line-count
5824 of 60. You may omit the comma and @var{columns} specification; the
5825 default width is 200 columns.
5827 @command{@value{AS}} generates formfeeds whenever the specified number of
5828 lines is exceeded (or whenever you explicitly request one, using
5831 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5832 those explicitly specified with @code{.eject}.
5835 @section @code{.purgem @var{name}}
5837 @cindex @code{purgem} directive
5838 Undefine the macro @var{name}, so that later uses of the string will not be
5839 expanded. @xref{Macro}.
5843 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5845 @cindex @code{pushsection} directive
5846 @cindex Section Stack
5847 This is one of the ELF section stack manipulation directives. The others are
5848 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5849 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5852 This directive pushes the current section (and subsection) onto the
5853 top of the section stack, and then replaces the current section and
5854 subsection with @code{name} and @code{subsection}. The optional
5855 @code{flags}, @code{type} and @code{arguments} are treated the same
5856 as in the @code{.section} (@pxref{Section}) directive.
5860 @section @code{.quad @var{bignums}}
5862 @cindex @code{quad} directive
5863 @code{.quad} expects zero or more bignums, separated by commas. For
5864 each bignum, it emits
5866 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5867 warning message; and just takes the lowest order 8 bytes of the bignum.
5868 @cindex eight-byte integer
5869 @cindex integer, 8-byte
5871 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5872 hence @emph{quad}-word for 8 bytes.
5875 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5876 warning message; and just takes the lowest order 16 bytes of the bignum.
5877 @cindex sixteen-byte integer
5878 @cindex integer, 16-byte
5882 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5884 @cindex @code{reloc} directive
5885 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5886 @var{expression}. If @var{offset} is a number, the relocation is generated in
5887 the current section. If @var{offset} is an expression that resolves to a
5888 symbol plus offset, the relocation is generated in the given symbol's section.
5889 @var{expression}, if present, must resolve to a symbol plus addend or to an
5890 absolute value, but note that not all targets support an addend. e.g. ELF REL
5891 targets such as i386 store an addend in the section contents rather than in the
5892 relocation. This low level interface does not support addends stored in the
5896 @section @code{.rept @var{count}}
5898 @cindex @code{rept} directive
5899 Repeat the sequence of lines between the @code{.rept} directive and the next
5900 @code{.endr} directive @var{count} times.
5902 For example, assembling
5910 is equivalent to assembling
5919 @section @code{.sbttl "@var{subheading}"}
5921 @cindex @code{sbttl} directive
5922 @cindex subtitles for listings
5923 @cindex listing control: subtitle
5924 Use @var{subheading} as the title (third line, immediately after the
5925 title line) when generating assembly listings.
5927 This directive affects subsequent pages, as well as the current page if
5928 it appears within ten lines of the top of a page.
5932 @section @code{.scl @var{class}}
5934 @cindex @code{scl} directive
5935 @cindex symbol storage class (COFF)
5936 @cindex COFF symbol storage class
5937 Set the storage-class value for a symbol. This directive may only be
5938 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5939 whether a symbol is static or external, or it may record further
5940 symbolic debugging information.
5943 The @samp{.scl} directive is primarily associated with COFF output; when
5944 configured to generate @code{b.out} output format, @command{@value{AS}}
5945 accepts this directive but ignores it.
5951 @section @code{.section @var{name}}
5953 @cindex named section
5954 Use the @code{.section} directive to assemble the following code into a section
5957 This directive is only supported for targets that actually support arbitrarily
5958 named sections; on @code{a.out} targets, for example, it is not accepted, even
5959 with a standard @code{a.out} section name.
5963 @c only print the extra heading if both COFF and ELF are set
5964 @subheading COFF Version
5967 @cindex @code{section} directive (COFF version)
5968 For COFF targets, the @code{.section} directive is used in one of the following
5972 .section @var{name}[, "@var{flags}"]
5973 .section @var{name}[, @var{subsection}]
5976 If the optional argument is quoted, it is taken as flags to use for the
5977 section. Each flag is a single character. The following flags are recognized:
5980 bss section (uninitialized data)
5982 section is not loaded
5988 exclude section from linking
5994 shared section (meaningful for PE targets)
5996 ignored. (For compatibility with the ELF version)
5998 section is not readable (meaningful for PE targets)
6000 single-digit power-of-two section alignment (GNU extension)
6003 If no flags are specified, the default flags depend upon the section name. If
6004 the section name is not recognized, the default will be for the section to be
6005 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6006 from the section, rather than adding them, so if they are used on their own it
6007 will be as if no flags had been specified at all.
6009 If the optional argument to the @code{.section} directive is not quoted, it is
6010 taken as a subsection number (@pxref{Sub-Sections}).
6015 @c only print the extra heading if both COFF and ELF are set
6016 @subheading ELF Version
6019 @cindex Section Stack
6020 This is one of the ELF section stack manipulation directives. The others are
6021 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6022 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6023 @code{.previous} (@pxref{Previous}).
6025 @cindex @code{section} directive (ELF version)
6026 For ELF targets, the @code{.section} directive is used like this:
6029 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6032 The optional @var{flags} argument is a quoted string which may contain any
6033 combination of the following characters:
6036 section is allocatable
6038 section is excluded from executable and shared library.
6042 section is executable
6044 section is mergeable
6046 section contains zero terminated strings
6048 section is a member of a section group
6050 section is used for thread-local-storage
6052 section is a member of the previously-current section's group, if any
6055 The optional @var{type} argument may contain one of the following constants:
6058 section contains data
6060 section does not contain data (i.e., section only occupies space)
6062 section contains data which is used by things other than the program
6064 section contains an array of pointers to init functions
6066 section contains an array of pointers to finish functions
6067 @item @@preinit_array
6068 section contains an array of pointers to pre-init functions
6071 Many targets only support the first three section types.
6073 Note on targets where the @code{@@} character is the start of a comment (eg
6074 ARM) then another character is used instead. For example the ARM port uses the
6077 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6078 be specified as well as an extra argument---@var{entsize}---like this:
6081 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6084 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6085 constants, each @var{entsize} octets long. Sections with both @code{M} and
6086 @code{S} must contain zero terminated strings where each character is
6087 @var{entsize} bytes long. The linker may remove duplicates within sections with
6088 the same name, same entity size and same flags. @var{entsize} must be an
6089 absolute expression. For sections with both @code{M} and @code{S}, a string
6090 which is a suffix of a larger string is considered a duplicate. Thus
6091 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6092 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6094 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6095 be present along with an additional field like this:
6098 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6101 The @var{GroupName} field specifies the name of the section group to which this
6102 particular section belongs. The optional linkage field can contain:
6105 indicates that only one copy of this section should be retained
6110 Note: if both the @var{M} and @var{G} flags are present then the fields for
6111 the Merge flag should come first, like this:
6114 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6117 If @var{flags} contains the @code{?} symbol then it may not also contain the
6118 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6119 present. Instead, @code{?} says to consider the section that's current before
6120 this directive. If that section used @code{G}, then the new section will use
6121 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6122 If not, then the @code{?} symbol has no effect.
6124 If no flags are specified, the default flags depend upon the section name. If
6125 the section name is not recognized, the default will be for the section to have
6126 none of the above flags: it will not be allocated in memory, nor writable, nor
6127 executable. The section will contain data.
6129 For ELF targets, the assembler supports another type of @code{.section}
6130 directive for compatibility with the Solaris assembler:
6133 .section "@var{name}"[, @var{flags}...]
6136 Note that the section name is quoted. There may be a sequence of comma
6140 section is allocatable
6144 section is executable
6146 section is excluded from executable and shared library.
6148 section is used for thread local storage
6151 This directive replaces the current section and subsection. See the
6152 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6153 some examples of how this directive and the other section stack directives
6159 @section @code{.set @var{symbol}, @var{expression}}
6161 @cindex @code{set} directive
6162 @cindex symbol value, setting
6163 Set the value of @var{symbol} to @var{expression}. This
6164 changes @var{symbol}'s value and type to conform to
6165 @var{expression}. If @var{symbol} was flagged as external, it remains
6166 flagged (@pxref{Symbol Attributes}).
6168 You may @code{.set} a symbol many times in the same assembly.
6170 If you @code{.set} a global symbol, the value stored in the object
6171 file is the last value stored into it.
6174 On Z80 @code{set} is a real instruction, use
6175 @samp{@var{symbol} defl @var{expression}} instead.
6179 @section @code{.short @var{expressions}}
6181 @cindex @code{short} directive
6183 @code{.short} is normally the same as @samp{.word}.
6184 @xref{Word,,@code{.word}}.
6186 In some configurations, however, @code{.short} and @code{.word} generate
6187 numbers of different lengths. @xref{Machine Dependencies}.
6191 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6194 This expects zero or more @var{expressions}, and emits
6195 a 16 bit number for each.
6200 @section @code{.single @var{flonums}}
6202 @cindex @code{single} directive
6203 @cindex floating point numbers (single)
6204 This directive assembles zero or more flonums, separated by commas. It
6205 has the same effect as @code{.float}.
6207 The exact kind of floating point numbers emitted depends on how
6208 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6212 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6213 numbers in @sc{ieee} format.
6219 @section @code{.size}
6221 This directive is used to set the size associated with a symbol.
6225 @c only print the extra heading if both COFF and ELF are set
6226 @subheading COFF Version
6229 @cindex @code{size} directive (COFF version)
6230 For COFF targets, the @code{.size} directive is only permitted inside
6231 @code{.def}/@code{.endef} pairs. It is used like this:
6234 .size @var{expression}
6238 @samp{.size} is only meaningful when generating COFF format output; when
6239 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6246 @c only print the extra heading if both COFF and ELF are set
6247 @subheading ELF Version
6250 @cindex @code{size} directive (ELF version)
6251 For ELF targets, the @code{.size} directive is used like this:
6254 .size @var{name} , @var{expression}
6257 This directive sets the size associated with a symbol @var{name}.
6258 The size in bytes is computed from @var{expression} which can make use of label
6259 arithmetic. This directive is typically used to set the size of function
6264 @ifclear no-space-dir
6266 @section @code{.skip @var{size} , @var{fill}}
6268 @cindex @code{skip} directive
6269 @cindex filling memory
6270 This directive emits @var{size} bytes, each of value @var{fill}. Both
6271 @var{size} and @var{fill} are absolute expressions. If the comma and
6272 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6277 @section @code{.sleb128 @var{expressions}}
6279 @cindex @code{sleb128} directive
6280 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6281 compact, variable length representation of numbers used by the DWARF
6282 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6284 @ifclear no-space-dir
6286 @section @code{.space @var{size} , @var{fill}}
6288 @cindex @code{space} directive
6289 @cindex filling memory
6290 This directive emits @var{size} bytes, each of value @var{fill}. Both
6291 @var{size} and @var{fill} are absolute expressions. If the comma
6292 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6297 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6298 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6299 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6300 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6308 @section @code{.stabd, .stabn, .stabs}
6310 @cindex symbolic debuggers, information for
6311 @cindex @code{stab@var{x}} directives
6312 There are three directives that begin @samp{.stab}.
6313 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6314 The symbols are not entered in the @command{@value{AS}} hash table: they
6315 cannot be referenced elsewhere in the source file.
6316 Up to five fields are required:
6320 This is the symbol's name. It may contain any character except
6321 @samp{\000}, so is more general than ordinary symbol names. Some
6322 debuggers used to code arbitrarily complex structures into symbol names
6326 An absolute expression. The symbol's type is set to the low 8 bits of
6327 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6328 and debuggers choke on silly bit patterns.
6331 An absolute expression. The symbol's ``other'' attribute is set to the
6332 low 8 bits of this expression.
6335 An absolute expression. The symbol's descriptor is set to the low 16
6336 bits of this expression.
6339 An absolute expression which becomes the symbol's value.
6342 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6343 or @code{.stabs} statement, the symbol has probably already been created;
6344 you get a half-formed symbol in your object file. This is
6345 compatible with earlier assemblers!
6348 @cindex @code{stabd} directive
6349 @item .stabd @var{type} , @var{other} , @var{desc}
6351 The ``name'' of the symbol generated is not even an empty string.
6352 It is a null pointer, for compatibility. Older assemblers used a
6353 null pointer so they didn't waste space in object files with empty
6356 The symbol's value is set to the location counter,
6357 relocatably. When your program is linked, the value of this symbol
6358 is the address of the location counter when the @code{.stabd} was
6361 @cindex @code{stabn} directive
6362 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6363 The name of the symbol is set to the empty string @code{""}.
6365 @cindex @code{stabs} directive
6366 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6367 All five fields are specified.
6373 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6374 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6376 @cindex string, copying to object file
6377 @cindex string8, copying to object file
6378 @cindex string16, copying to object file
6379 @cindex string32, copying to object file
6380 @cindex string64, copying to object file
6381 @cindex @code{string} directive
6382 @cindex @code{string8} directive
6383 @cindex @code{string16} directive
6384 @cindex @code{string32} directive
6385 @cindex @code{string64} directive
6387 Copy the characters in @var{str} to the object file. You may specify more than
6388 one string to copy, separated by commas. Unless otherwise specified for a
6389 particular machine, the assembler marks the end of each string with a 0 byte.
6390 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6392 The variants @code{string16}, @code{string32} and @code{string64} differ from
6393 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6394 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6395 are stored in target endianness byte order.
6401 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6402 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6407 @section @code{.struct @var{expression}}
6409 @cindex @code{struct} directive
6410 Switch to the absolute section, and set the section offset to @var{expression},
6411 which must be an absolute expression. You might use this as follows:
6420 This would define the symbol @code{field1} to have the value 0, the symbol
6421 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6422 value 8. Assembly would be left in the absolute section, and you would need to
6423 use a @code{.section} directive of some sort to change to some other section
6424 before further assembly.
6428 @section @code{.subsection @var{name}}
6430 @cindex @code{subsection} directive
6431 @cindex Section Stack
6432 This is one of the ELF section stack manipulation directives. The others are
6433 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6434 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6437 This directive replaces the current subsection with @code{name}. The current
6438 section is not changed. The replaced subsection is put onto the section stack
6439 in place of the then current top of stack subsection.
6444 @section @code{.symver}
6445 @cindex @code{symver} directive
6446 @cindex symbol versioning
6447 @cindex versions of symbols
6448 Use the @code{.symver} directive to bind symbols to specific version nodes
6449 within a source file. This is only supported on ELF platforms, and is
6450 typically used when assembling files to be linked into a shared library.
6451 There are cases where it may make sense to use this in objects to be bound
6452 into an application itself so as to override a versioned symbol from a
6455 For ELF targets, the @code{.symver} directive can be used like this:
6457 .symver @var{name}, @var{name2@@nodename}
6459 If the symbol @var{name} is defined within the file
6460 being assembled, the @code{.symver} directive effectively creates a symbol
6461 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6462 just don't try and create a regular alias is that the @var{@@} character isn't
6463 permitted in symbol names. The @var{name2} part of the name is the actual name
6464 of the symbol by which it will be externally referenced. The name @var{name}
6465 itself is merely a name of convenience that is used so that it is possible to
6466 have definitions for multiple versions of a function within a single source
6467 file, and so that the compiler can unambiguously know which version of a
6468 function is being mentioned. The @var{nodename} portion of the alias should be
6469 the name of a node specified in the version script supplied to the linker when
6470 building a shared library. If you are attempting to override a versioned
6471 symbol from a shared library, then @var{nodename} should correspond to the
6472 nodename of the symbol you are trying to override.
6474 If the symbol @var{name} is not defined within the file being assembled, all
6475 references to @var{name} will be changed to @var{name2@@nodename}. If no
6476 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6479 Another usage of the @code{.symver} directive is:
6481 .symver @var{name}, @var{name2@@@@nodename}
6483 In this case, the symbol @var{name} must exist and be defined within
6484 the file being assembled. It is similar to @var{name2@@nodename}. The
6485 difference is @var{name2@@@@nodename} will also be used to resolve
6486 references to @var{name2} by the linker.
6488 The third usage of the @code{.symver} directive is:
6490 .symver @var{name}, @var{name2@@@@@@nodename}
6492 When @var{name} is not defined within the
6493 file being assembled, it is treated as @var{name2@@nodename}. When
6494 @var{name} is defined within the file being assembled, the symbol
6495 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6500 @section @code{.tag @var{structname}}
6502 @cindex COFF structure debugging
6503 @cindex structure debugging, COFF
6504 @cindex @code{tag} directive
6505 This directive is generated by compilers to include auxiliary debugging
6506 information in the symbol table. It is only permitted inside
6507 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6508 definitions in the symbol table with instances of those structures.
6511 @samp{.tag} is only used when generating COFF format output; when
6512 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6518 @section @code{.text @var{subsection}}
6520 @cindex @code{text} directive
6521 Tells @command{@value{AS}} to assemble the following statements onto the end of
6522 the text subsection numbered @var{subsection}, which is an absolute
6523 expression. If @var{subsection} is omitted, subsection number zero
6527 @section @code{.title "@var{heading}"}
6529 @cindex @code{title} directive
6530 @cindex listing control: title line
6531 Use @var{heading} as the title (second line, immediately after the
6532 source file name and pagenumber) when generating assembly listings.
6534 This directive affects subsequent pages, as well as the current page if
6535 it appears within ten lines of the top of a page.
6539 @section @code{.type}
6541 This directive is used to set the type of a symbol.
6545 @c only print the extra heading if both COFF and ELF are set
6546 @subheading COFF Version
6549 @cindex COFF symbol type
6550 @cindex symbol type, COFF
6551 @cindex @code{type} directive (COFF version)
6552 For COFF targets, this directive is permitted only within
6553 @code{.def}/@code{.endef} pairs. It is used like this:
6559 This records the integer @var{int} as the type attribute of a symbol table
6563 @samp{.type} is associated only with COFF format output; when
6564 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6565 directive but ignores it.
6571 @c only print the extra heading if both COFF and ELF are set
6572 @subheading ELF Version
6575 @cindex ELF symbol type
6576 @cindex symbol type, ELF
6577 @cindex @code{type} directive (ELF version)
6578 For ELF targets, the @code{.type} directive is used like this:
6581 .type @var{name} , @var{type description}
6584 This sets the type of symbol @var{name} to be either a
6585 function symbol or an object symbol. There are five different syntaxes
6586 supported for the @var{type description} field, in order to provide
6587 compatibility with various other assemblers.
6589 Because some of the characters used in these syntaxes (such as @samp{@@} and
6590 @samp{#}) are comment characters for some architectures, some of the syntaxes
6591 below do not work on all architectures. The first variant will be accepted by
6592 the GNU assembler on all architectures so that variant should be used for
6593 maximum portability, if you do not need to assemble your code with other
6596 The syntaxes supported are:
6599 .type <name> STT_<TYPE_IN_UPPER_CASE>
6600 .type <name>,#<type>
6601 .type <name>,@@<type>
6602 .type <name>,%<type>
6603 .type <name>,"<type>"
6606 The types supported are:
6611 Mark the symbol as being a function name.
6614 @itemx gnu_indirect_function
6615 Mark the symbol as an indirect function when evaluated during reloc
6616 processing. (This is only supported on assemblers targeting GNU systems).
6620 Mark the symbol as being a data object.
6624 Mark the symbol as being a thead-local data object.
6628 Mark the symbol as being a common data object.
6632 Does not mark the symbol in any way. It is supported just for completeness.
6634 @item gnu_unique_object
6635 Marks the symbol as being a globally unique data object. The dynamic linker
6636 will make sure that in the entire process there is just one symbol with this
6637 name and type in use. (This is only supported on assemblers targeting GNU
6642 Note: Some targets support extra types in addition to those listed above.
6648 @section @code{.uleb128 @var{expressions}}
6650 @cindex @code{uleb128} directive
6651 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6652 compact, variable length representation of numbers used by the DWARF
6653 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6657 @section @code{.val @var{addr}}
6659 @cindex @code{val} directive
6660 @cindex COFF value attribute
6661 @cindex value attribute, COFF
6662 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6663 records the address @var{addr} as the value attribute of a symbol table
6667 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6668 configured for @code{b.out}, it accepts this directive but ignores it.
6674 @section @code{.version "@var{string}"}
6676 @cindex @code{version} directive
6677 This directive creates a @code{.note} section and places into it an ELF
6678 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6683 @section @code{.vtable_entry @var{table}, @var{offset}}
6685 @cindex @code{vtable_entry} directive
6686 This directive finds or creates a symbol @code{table} and creates a
6687 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6690 @section @code{.vtable_inherit @var{child}, @var{parent}}
6692 @cindex @code{vtable_inherit} directive
6693 This directive finds the symbol @code{child} and finds or creates the symbol
6694 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6695 parent whose addend is the value of the child symbol. As a special case the
6696 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6700 @section @code{.warning "@var{string}"}
6701 @cindex warning directive
6702 Similar to the directive @code{.error}
6703 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6706 @section @code{.weak @var{names}}
6708 @cindex @code{weak} directive
6709 This directive sets the weak attribute on the comma separated list of symbol
6710 @code{names}. If the symbols do not already exist, they will be created.
6712 On COFF targets other than PE, weak symbols are a GNU extension. This
6713 directive sets the weak attribute on the comma separated list of symbol
6714 @code{names}. If the symbols do not already exist, they will be created.
6716 On the PE target, weak symbols are supported natively as weak aliases.
6717 When a weak symbol is created that is not an alias, GAS creates an
6718 alternate symbol to hold the default value.
6721 @section @code{.weakref @var{alias}, @var{target}}
6723 @cindex @code{weakref} directive
6724 This directive creates an alias to the target symbol that enables the symbol to
6725 be referenced with weak-symbol semantics, but without actually making it weak.
6726 If direct references or definitions of the symbol are present, then the symbol
6727 will not be weak, but if all references to it are through weak references, the
6728 symbol will be marked as weak in the symbol table.
6730 The effect is equivalent to moving all references to the alias to a separate
6731 assembly source file, renaming the alias to the symbol in it, declaring the
6732 symbol as weak there, and running a reloadable link to merge the object files
6733 resulting from the assembly of the new source file and the old source file that
6734 had the references to the alias removed.
6736 The alias itself never makes to the symbol table, and is entirely handled
6737 within the assembler.
6740 @section @code{.word @var{expressions}}
6742 @cindex @code{word} directive
6743 This directive expects zero or more @var{expressions}, of any section,
6744 separated by commas.
6747 For each expression, @command{@value{AS}} emits a 32-bit number.
6750 For each expression, @command{@value{AS}} emits a 16-bit number.
6755 The size of the number emitted, and its byte order,
6756 depend on what target computer the assembly is for.
6759 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6760 @c happen---32-bit addressability, period; no long/short jumps.
6761 @ifset DIFF-TBL-KLUGE
6762 @cindex difference tables altered
6763 @cindex altered difference tables
6765 @emph{Warning: Special Treatment to support Compilers}
6769 Machines with a 32-bit address space, but that do less than 32-bit
6770 addressing, require the following special treatment. If the machine of
6771 interest to you does 32-bit addressing (or doesn't require it;
6772 @pxref{Machine Dependencies}), you can ignore this issue.
6775 In order to assemble compiler output into something that works,
6776 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6777 Directives of the form @samp{.word sym1-sym2} are often emitted by
6778 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6779 directive of the form @samp{.word sym1-sym2}, and the difference between
6780 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6781 creates a @dfn{secondary jump table}, immediately before the next label.
6782 This secondary jump table is preceded by a short-jump to the
6783 first byte after the secondary table. This short-jump prevents the flow
6784 of control from accidentally falling into the new table. Inside the
6785 table is a long-jump to @code{sym2}. The original @samp{.word}
6786 contains @code{sym1} minus the address of the long-jump to
6789 If there were several occurrences of @samp{.word sym1-sym2} before the
6790 secondary jump table, all of them are adjusted. If there was a
6791 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6792 long-jump to @code{sym4} is included in the secondary jump table,
6793 and the @code{.word} directives are adjusted to contain @code{sym3}
6794 minus the address of the long-jump to @code{sym4}; and so on, for as many
6795 entries in the original jump table as necessary.
6798 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6799 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6800 assembly language programmers.
6803 @c end DIFF-TBL-KLUGE
6806 @section Deprecated Directives
6808 @cindex deprecated directives
6809 @cindex obsolescent directives
6810 One day these directives won't work.
6811 They are included for compatibility with older assemblers.
6818 @node Object Attributes
6819 @chapter Object Attributes
6820 @cindex object attributes
6822 @command{@value{AS}} assembles source files written for a specific architecture
6823 into object files for that architecture. But not all object files are alike.
6824 Many architectures support incompatible variations. For instance, floating
6825 point arguments might be passed in floating point registers if the object file
6826 requires hardware floating point support---or floating point arguments might be
6827 passed in integer registers if the object file supports processors with no
6828 hardware floating point unit. Or, if two objects are built for different
6829 generations of the same architecture, the combination may require the
6830 newer generation at run-time.
6832 This information is useful during and after linking. At link time,
6833 @command{@value{LD}} can warn about incompatible object files. After link
6834 time, tools like @command{gdb} can use it to process the linked file
6837 Compatibility information is recorded as a series of object attributes. Each
6838 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6839 string, and indicates who sets the meaning of the tag. The tag is an integer,
6840 and indicates what property the attribute describes. The value may be a string
6841 or an integer, and indicates how the property affects this object. Missing
6842 attributes are the same as attributes with a zero value or empty string value.
6844 Object attributes were developed as part of the ABI for the ARM Architecture.
6845 The file format is documented in @cite{ELF for the ARM Architecture}.
6848 * GNU Object Attributes:: @sc{gnu} Object Attributes
6849 * Defining New Object Attributes:: Defining New Object Attributes
6852 @node GNU Object Attributes
6853 @section @sc{gnu} Object Attributes
6855 The @code{.gnu_attribute} directive records an object attribute
6856 with vendor @samp{gnu}.
6858 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6859 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6860 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6861 2} is set for architecture-independent attributes and clear for
6862 architecture-dependent ones.
6864 @subsection Common @sc{gnu} attributes
6866 These attributes are valid on all architectures.
6869 @item Tag_compatibility (32)
6870 The compatibility attribute takes an integer flag value and a vendor name. If
6871 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6872 then the file is only compatible with the named toolchain. If it is greater
6873 than 1, the file can only be processed by other toolchains under some private
6874 arrangement indicated by the flag value and the vendor name.
6877 @subsection MIPS Attributes
6880 @item Tag_GNU_MIPS_ABI_FP (4)
6881 The floating-point ABI used by this object file. The value will be:
6885 0 for files not affected by the floating-point ABI.
6887 1 for files using the hardware floating-point with a standard double-precision
6890 2 for files using the hardware floating-point ABI with a single-precision FPU.
6892 3 for files using the software floating-point ABI.
6894 4 for files using the hardware floating-point ABI with 64-bit wide
6895 double-precision floating-point registers and 32-bit wide general
6900 @subsection PowerPC Attributes
6903 @item Tag_GNU_Power_ABI_FP (4)
6904 The floating-point ABI used by this object file. The value will be:
6908 0 for files not affected by the floating-point ABI.
6910 1 for files using double-precision hardware floating-point ABI.
6912 2 for files using the software floating-point ABI.
6914 3 for files using single-precision hardware floating-point ABI.
6917 @item Tag_GNU_Power_ABI_Vector (8)
6918 The vector ABI used by this object file. The value will be:
6922 0 for files not affected by the vector ABI.
6924 1 for files using general purpose registers to pass vectors.
6926 2 for files using AltiVec registers to pass vectors.
6928 3 for files using SPE registers to pass vectors.
6932 @node Defining New Object Attributes
6933 @section Defining New Object Attributes
6935 If you want to define a new @sc{gnu} object attribute, here are the places you
6936 will need to modify. New attributes should be discussed on the @samp{binutils}
6941 This manual, which is the official register of attributes.
6943 The header for your architecture @file{include/elf}, to define the tag.
6945 The @file{bfd} support file for your architecture, to merge the attribute
6946 and issue any appropriate link warnings.
6948 Test cases in @file{ld/testsuite} for merging and link warnings.
6950 @file{binutils/readelf.c} to display your attribute.
6952 GCC, if you want the compiler to mark the attribute automatically.
6958 @node Machine Dependencies
6959 @chapter Machine Dependent Features
6961 @cindex machine dependencies
6962 The machine instruction sets are (almost by definition) different on
6963 each machine where @command{@value{AS}} runs. Floating point representations
6964 vary as well, and @command{@value{AS}} often supports a few additional
6965 directives or command-line options for compatibility with other
6966 assemblers on a particular platform. Finally, some versions of
6967 @command{@value{AS}} support special pseudo-instructions for branch
6970 This chapter discusses most of these differences, though it does not
6971 include details on any machine's instruction set. For details on that
6972 subject, see the hardware manufacturer's manual.
6976 * AArch64-Dependent:: AArch64 Dependent Features
6979 * Alpha-Dependent:: Alpha Dependent Features
6982 * ARC-Dependent:: ARC Dependent Features
6985 * ARM-Dependent:: ARM Dependent Features
6988 * AVR-Dependent:: AVR Dependent Features
6991 * Blackfin-Dependent:: Blackfin Dependent Features
6994 * CR16-Dependent:: CR16 Dependent Features
6997 * CRIS-Dependent:: CRIS Dependent Features
7000 * D10V-Dependent:: D10V Dependent Features
7003 * D30V-Dependent:: D30V Dependent Features
7006 * Epiphany-Dependent:: EPIPHANY Dependent Features
7009 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7012 * HPPA-Dependent:: HPPA Dependent Features
7015 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7018 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7021 * i860-Dependent:: Intel 80860 Dependent Features
7024 * i960-Dependent:: Intel 80960 Dependent Features
7027 * IA-64-Dependent:: Intel IA-64 Dependent Features
7030 * IP2K-Dependent:: IP2K Dependent Features
7033 * LM32-Dependent:: LM32 Dependent Features
7036 * M32C-Dependent:: M32C Dependent Features
7039 * M32R-Dependent:: M32R Dependent Features
7042 * M68K-Dependent:: M680x0 Dependent Features
7045 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7048 * Meta-Dependent :: Meta Dependent Features
7051 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7054 * MIPS-Dependent:: MIPS Dependent Features
7057 * MMIX-Dependent:: MMIX Dependent Features
7060 * MSP430-Dependent:: MSP430 Dependent Features
7063 * NS32K-Dependent:: NS32K Dependent Features
7066 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7067 * SH64-Dependent:: SuperH SH64 Dependent Features
7070 * PDP-11-Dependent:: PDP-11 Dependent Features
7073 * PJ-Dependent:: picoJava Dependent Features
7076 * PPC-Dependent:: PowerPC Dependent Features
7079 * RL78-Dependent:: RL78 Dependent Features
7082 * RX-Dependent:: RX Dependent Features
7085 * S/390-Dependent:: IBM S/390 Dependent Features
7088 * SCORE-Dependent:: SCORE Dependent Features
7091 * Sparc-Dependent:: SPARC Dependent Features
7094 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7097 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7100 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7103 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7106 * V850-Dependent:: V850 Dependent Features
7109 * XGATE-Dependent:: XGATE Features
7112 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7115 * Xtensa-Dependent:: Xtensa Dependent Features
7118 * Z80-Dependent:: Z80 Dependent Features
7121 * Z8000-Dependent:: Z8000 Dependent Features
7124 * Vax-Dependent:: VAX Dependent Features
7131 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7132 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7133 @c peculiarity: to preserve cross-references, there must be a node called
7134 @c "Machine Dependencies". Hence the conditional nodenames in each
7135 @c major node below. Node defaulting in makeinfo requires adjacency of
7136 @c node and sectioning commands; hence the repetition of @chapter BLAH
7137 @c in both conditional blocks.
7140 @include c-aarch64.texi
7144 @include c-alpha.texi
7160 @include c-bfin.texi
7164 @include c-cr16.texi
7168 @include c-cris.texi
7173 @node Machine Dependencies
7174 @chapter Machine Dependent Features
7176 The machine instruction sets are different on each Renesas chip family,
7177 and there are also some syntax differences among the families. This
7178 chapter describes the specific @command{@value{AS}} features for each
7182 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7183 * SH-Dependent:: Renesas SH Dependent Features
7190 @include c-d10v.texi
7194 @include c-d30v.texi
7198 @include c-epiphany.texi
7202 @include c-h8300.texi
7206 @include c-hppa.texi
7210 @include c-i370.texi
7214 @include c-i386.texi
7218 @include c-i860.texi
7222 @include c-i960.texi
7226 @include c-ia64.texi
7230 @include c-ip2k.texi
7234 @include c-lm32.texi
7238 @include c-m32c.texi
7242 @include c-m32r.texi
7246 @include c-m68k.texi
7250 @include c-m68hc11.texi
7254 @include c-metag.texi
7258 @include c-microblaze.texi
7262 @include c-mips.texi
7266 @include c-mmix.texi
7270 @include c-msp430.texi
7274 @include c-ns32k.texi
7278 @include c-pdp11.texi
7290 @include c-rl78.texi
7298 @include c-s390.texi
7302 @include c-score.texi
7307 @include c-sh64.texi
7311 @include c-sparc.texi
7315 @include c-tic54x.texi
7319 @include c-tic6x.texi
7323 @include c-tilegx.texi
7327 @include c-tilepro.texi
7343 @include c-v850.texi
7347 @include c-xgate.texi
7351 @include c-xstormy16.texi
7355 @include c-xtensa.texi
7359 @c reverse effect of @down at top of generic Machine-Dep chapter
7363 @node Reporting Bugs
7364 @chapter Reporting Bugs
7365 @cindex bugs in assembler
7366 @cindex reporting bugs in assembler
7368 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7370 Reporting a bug may help you by bringing a solution to your problem, or it may
7371 not. But in any case the principal function of a bug report is to help the
7372 entire community by making the next version of @command{@value{AS}} work better.
7373 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7375 In order for a bug report to serve its purpose, you must include the
7376 information that enables us to fix the bug.
7379 * Bug Criteria:: Have you found a bug?
7380 * Bug Reporting:: How to report bugs
7384 @section Have You Found a Bug?
7385 @cindex bug criteria
7387 If you are not sure whether you have found a bug, here are some guidelines:
7390 @cindex fatal signal
7391 @cindex assembler crash
7392 @cindex crash of assembler
7394 If the assembler gets a fatal signal, for any input whatever, that is a
7395 @command{@value{AS}} bug. Reliable assemblers never crash.
7397 @cindex error on valid input
7399 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7401 @cindex invalid input
7403 If @command{@value{AS}} does not produce an error message for invalid input, that
7404 is a bug. However, you should note that your idea of ``invalid input'' might
7405 be our idea of ``an extension'' or ``support for traditional practice''.
7408 If you are an experienced user of assemblers, your suggestions for improvement
7409 of @command{@value{AS}} are welcome in any case.
7413 @section How to Report Bugs
7415 @cindex assembler bugs, reporting
7417 A number of companies and individuals offer support for @sc{gnu} products. If
7418 you obtained @command{@value{AS}} from a support organization, we recommend you
7419 contact that organization first.
7421 You can find contact information for many support companies and
7422 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7426 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7430 The fundamental principle of reporting bugs usefully is this:
7431 @strong{report all the facts}. If you are not sure whether to state a
7432 fact or leave it out, state it!
7434 Often people omit facts because they think they know what causes the problem
7435 and assume that some details do not matter. Thus, you might assume that the
7436 name of a symbol you use in an example does not matter. Well, probably it does
7437 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7438 happens to fetch from the location where that name is stored in memory;
7439 perhaps, if the name were different, the contents of that location would fool
7440 the assembler into doing the right thing despite the bug. Play it safe and
7441 give a specific, complete example. That is the easiest thing for you to do,
7442 and the most helpful.
7444 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7445 it is new to us. Therefore, always write your bug reports on the assumption
7446 that the bug has not been reported previously.
7448 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7449 bell?'' This cannot help us fix a bug, so it is basically useless. We
7450 respond by asking for enough details to enable us to investigate.
7451 You might as well expedite matters by sending them to begin with.
7453 To enable us to fix the bug, you should include all these things:
7457 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7458 it with the @samp{--version} argument.
7460 Without this, we will not know whether there is any point in looking for
7461 the bug in the current version of @command{@value{AS}}.
7464 Any patches you may have applied to the @command{@value{AS}} source.
7467 The type of machine you are using, and the operating system name and
7471 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7475 The command arguments you gave the assembler to assemble your example and
7476 observe the bug. To guarantee you will not omit something important, list them
7477 all. A copy of the Makefile (or the output from make) is sufficient.
7479 If we were to try to guess the arguments, we would probably guess wrong
7480 and then we might not encounter the bug.
7483 A complete input file that will reproduce the bug. If the bug is observed when
7484 the assembler is invoked via a compiler, send the assembler source, not the
7485 high level language source. Most compilers will produce the assembler source
7486 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7487 the options @samp{-v --save-temps}; this will save the assembler source in a
7488 file with an extension of @file{.s}, and also show you exactly how
7489 @command{@value{AS}} is being run.
7492 A description of what behavior you observe that you believe is
7493 incorrect. For example, ``It gets a fatal signal.''
7495 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7496 will certainly notice it. But if the bug is incorrect output, we might not
7497 notice unless it is glaringly wrong. You might as well not give us a chance to
7500 Even if the problem you experience is a fatal signal, you should still say so
7501 explicitly. Suppose something strange is going on, such as, your copy of
7502 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7503 library on your system. (This has happened!) Your copy might crash and ours
7504 would not. If you told us to expect a crash, then when ours fails to crash, we
7505 would know that the bug was not happening for us. If you had not told us to
7506 expect a crash, then we would not be able to draw any conclusion from our
7510 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7511 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7512 option. Always send diffs from the old file to the new file. If you even
7513 discuss something in the @command{@value{AS}} source, refer to it by context, not
7516 The line numbers in our development sources will not match those in your
7517 sources. Your line numbers would convey no useful information to us.
7520 Here are some things that are not necessary:
7524 A description of the envelope of the bug.
7526 Often people who encounter a bug spend a lot of time investigating
7527 which changes to the input file will make the bug go away and which
7528 changes will not affect it.
7530 This is often time consuming and not very useful, because the way we
7531 will find the bug is by running a single example under the debugger
7532 with breakpoints, not by pure deduction from a series of examples.
7533 We recommend that you save your time for something else.
7535 Of course, if you can find a simpler example to report @emph{instead}
7536 of the original one, that is a convenience for us. Errors in the
7537 output will be easier to spot, running under the debugger will take
7538 less time, and so on.
7540 However, simplification is not vital; if you do not want to do this,
7541 report the bug anyway and send us the entire test case you used.
7544 A patch for the bug.
7546 A patch for the bug does help us if it is a good one. But do not omit
7547 the necessary information, such as the test case, on the assumption that
7548 a patch is all we need. We might see problems with your patch and decide
7549 to fix the problem another way, or we might not understand it at all.
7551 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7552 construct an example that will make the program follow a certain path through
7553 the code. If you do not send us the example, we will not be able to construct
7554 one, so we will not be able to verify that the bug is fixed.
7556 And if we cannot understand what bug you are trying to fix, or why your
7557 patch should be an improvement, we will not install it. A test case will
7558 help us to understand.
7561 A guess about what the bug is or what it depends on.
7563 Such guesses are usually wrong. Even we cannot guess right about such
7564 things without first using the debugger to find the facts.
7567 @node Acknowledgements
7568 @chapter Acknowledgements
7570 If you have contributed to GAS and your name isn't listed here,
7571 it is not meant as a slight. We just don't know about it. Send mail to the
7572 maintainer, and we'll correct the situation. Currently
7574 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7576 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7579 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7580 information and the 68k series machines, most of the preprocessing pass, and
7581 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7583 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7584 many bug fixes, including merging support for several processors, breaking GAS
7585 up to handle multiple object file format back ends (including heavy rewrite,
7586 testing, an integration of the coff and b.out back ends), adding configuration
7587 including heavy testing and verification of cross assemblers and file splits
7588 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7589 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7590 port (including considerable amounts of reverse engineering), a SPARC opcode
7591 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7592 assertions and made them work, much other reorganization, cleanup, and lint.
7594 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7595 in format-specific I/O modules.
7597 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7598 has done much work with it since.
7600 The Intel 80386 machine description was written by Eliot Dresselhaus.
7602 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7604 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7605 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7607 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7608 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7609 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7610 support a.out format.
7612 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7613 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7614 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7615 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7618 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7619 simplified the configuration of which versions accept which directives. He
7620 updated the 68k machine description so that Motorola's opcodes always produced
7621 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7622 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7623 cross-compilation support, and one bug in relaxation that took a week and
7624 required the proverbial one-bit fix.
7626 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7627 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7628 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7629 PowerPC assembler, and made a few other minor patches.
7631 Steve Chamberlain made GAS able to generate listings.
7633 Hewlett-Packard contributed support for the HP9000/300.
7635 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7636 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7637 formats). This work was supported by both the Center for Software Science at
7638 the University of Utah and Cygnus Support.
7640 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7641 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7642 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7643 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7644 and some initial 64-bit support).
7646 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7648 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7649 support for openVMS/Alpha.
7651 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7654 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7655 Inc.@: added support for Xtensa processors.
7657 Several engineers at Cygnus Support have also provided many small bug fixes and
7658 configuration enhancements.
7660 Jon Beniston added support for the Lattice Mico32 architecture.
7662 Many others have contributed large or small bugfixes and enhancements. If
7663 you have contributed significant work and are not mentioned on this list, and
7664 want to be, let us know. Some of the history has been lost; we are not
7665 intentionally leaving anyone out.
7667 @node GNU Free Documentation License
7668 @appendix GNU Free Documentation License
7672 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob