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]}]
391 @emph{Target MICROBLAZE options:}
392 @c MicroBlaze has no machine-dependent assembler options.
396 @emph{Target MIPS options:}
397 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
398 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
399 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
400 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
401 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
402 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
403 [@b{-mips64}] [@b{-mips64r2}]
404 [@b{-construct-floats}] [@b{-no-construct-floats}]
405 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
406 [@b{-mips16}] [@b{-no-mips16}]
407 [@b{-mmicromips}] [@b{-mno-micromips}]
408 [@b{-msmartmips}] [@b{-mno-smartmips}]
409 [@b{-mips3d}] [@b{-no-mips3d}]
410 [@b{-mdmx}] [@b{-no-mdmx}]
411 [@b{-mdsp}] [@b{-mno-dsp}]
412 [@b{-mdspr2}] [@b{-mno-dspr2}]
413 [@b{-mmt}] [@b{-mno-mt}]
414 [@b{-mmcu}] [@b{-mno-mcu}]
415 [@b{-mfix7000}] [@b{-mno-fix7000}]
416 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
417 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
418 [@b{-mdebug}] [@b{-no-mdebug}]
419 [@b{-mpdr}] [@b{-mno-pdr}]
423 @emph{Target MMIX options:}
424 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
425 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
426 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
427 [@b{--linker-allocated-gregs}]
431 @emph{Target PDP11 options:}
432 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
433 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
434 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
438 @emph{Target picoJava options:}
443 @emph{Target PowerPC options:}
445 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
446 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
447 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
448 @b{-mbooke}|@b{-mpower4}|@b{-mpr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
449 @b{-mpower7}|@b{-mpw7}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mvle}|@b{-mcom}]
450 [@b{-many}] [@b{-maltivec}|@b{-mvsx}]
451 [@b{-mregnames}|@b{-mno-regnames}]
452 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
453 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
454 [@b{-msolaris}|@b{-mno-solaris}]
455 [@b{-nops=@var{count}}]
459 @emph{Target RX options:}
460 [@b{-mlittle-endian}|@b{-mbig-endian}]
461 [@b{-m32bit-ints}|@b{-m16bit-ints}]
462 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
466 @emph{Target s390 options:}
467 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
468 [@b{-mregnames}|@b{-mno-regnames}]
469 [@b{-mwarn-areg-zero}]
473 @emph{Target SCORE options:}
474 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
475 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
476 [@b{-march=score7}][@b{-march=score3}]
477 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
481 @emph{Target SPARC options:}
482 @c The order here is important. See c-sparc.texi.
483 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
484 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
485 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
490 @emph{Target TIC54X options:}
491 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
492 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
497 @emph{Target TIC6X options:}
498 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
499 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
500 [@b{-mpic}|@b{-mno-pic}]
504 @emph{Target TILE-Gx options:}
505 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
508 @c TILEPro has no machine-dependent assembler options
513 @emph{Target Xtensa options:}
514 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
515 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
516 [@b{--[no-]transform}]
517 [@b{--rename-section} @var{oldname}=@var{newname}]
522 @emph{Target Z80 options:}
523 [@b{-z80}] [@b{-r800}]
524 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
525 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
526 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
527 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
528 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
529 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
533 @c Z8000 has no machine-dependent assembler options
542 @include at-file.texi
545 Turn on listings, in any of a variety of ways:
549 omit false conditionals
552 omit debugging directives
555 include general information, like @value{AS} version and options passed
558 include high-level source
564 include macro expansions
567 omit forms processing
573 set the name of the listing file
576 You may combine these options; for example, use @samp{-aln} for assembly
577 listing without forms processing. The @samp{=file} option, if used, must be
578 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
581 Begin in alternate macro mode.
583 @xref{Altmacro,,@code{.altmacro}}.
586 @item --compress-debug-sections
587 Compress DWARF debug sections using zlib. The debug sections are renamed
588 to begin with @samp{.zdebug}, and the resulting object file may not be
589 compatible with older linkers and object file utilities.
591 @item --nocompress-debug-sections
592 Do not compress DWARF debug sections. This is the default.
595 Ignored. This option is accepted for script compatibility with calls to
598 @item --debug-prefix-map @var{old}=@var{new}
599 When assembling files in directory @file{@var{old}}, record debugging
600 information describing them as in @file{@var{new}} instead.
602 @item --defsym @var{sym}=@var{value}
603 Define the symbol @var{sym} to be @var{value} before assembling the input file.
604 @var{value} must be an integer constant. As in C, a leading @samp{0x}
605 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
606 value. The value of the symbol can be overridden inside a source file via the
607 use of a @code{.set} pseudo-op.
610 ``fast''---skip whitespace and comment preprocessing (assume source is
615 Generate debugging information for each assembler source line using whichever
616 debug format is preferred by the target. This currently means either STABS,
620 Generate stabs debugging information for each assembler line. This
621 may help debugging assembler code, if the debugger can handle it.
624 Generate stabs debugging information for each assembler line, with GNU
625 extensions that probably only gdb can handle, and that could make other
626 debuggers crash or refuse to read your program. This
627 may help debugging assembler code. Currently the only GNU extension is
628 the location of the current working directory at assembling time.
631 Generate DWARF2 debugging information for each assembler line. This
632 may help debugging assembler code, if the debugger can handle it. Note---this
633 option is only supported by some targets, not all of them.
635 @item --size-check=error
636 @itemx --size-check=warning
637 Issue an error or warning for invalid ELF .size directive.
640 Print a summary of the command line options and exit.
643 Print a summary of all target specific options and exit.
646 Add directory @var{dir} to the search list for @code{.include} directives.
649 Don't warn about signed overflow.
652 @ifclear DIFF-TBL-KLUGE
653 This option is accepted but has no effect on the @value{TARGET} family.
655 @ifset DIFF-TBL-KLUGE
656 Issue warnings when difference tables altered for long displacements.
661 Keep (in the symbol table) local symbols. These symbols start with
662 system-specific local label prefixes, typically @samp{.L} for ELF systems
663 or @samp{L} for traditional a.out systems.
668 @item --listing-lhs-width=@var{number}
669 Set the maximum width, in words, of the output data column for an assembler
670 listing to @var{number}.
672 @item --listing-lhs-width2=@var{number}
673 Set the maximum width, in words, of the output data column for continuation
674 lines in an assembler listing to @var{number}.
676 @item --listing-rhs-width=@var{number}
677 Set the maximum width of an input source line, as displayed in a listing, to
680 @item --listing-cont-lines=@var{number}
681 Set the maximum number of lines printed in a listing for a single line of input
684 @item -o @var{objfile}
685 Name the object-file output from @command{@value{AS}} @var{objfile}.
688 Fold the data section into the text section.
690 @kindex --hash-size=@var{number}
691 Set the default size of GAS's hash tables to a prime number close to
692 @var{number}. Increasing this value can reduce the length of time it takes the
693 assembler to perform its tasks, at the expense of increasing the assembler's
694 memory requirements. Similarly reducing this value can reduce the memory
695 requirements at the expense of speed.
697 @item --reduce-memory-overheads
698 This option reduces GAS's memory requirements, at the expense of making the
699 assembly processes slower. Currently this switch is a synonym for
700 @samp{--hash-size=4051}, but in the future it may have other effects as well.
703 Print the maximum space (in bytes) and total time (in seconds) used by
706 @item --strip-local-absolute
707 Remove local absolute symbols from the outgoing symbol table.
711 Print the @command{as} version.
714 Print the @command{as} version and exit.
718 Suppress warning messages.
720 @item --fatal-warnings
721 Treat warnings as errors.
724 Don't suppress warning messages or treat them as errors.
733 Generate an object file even after errors.
735 @item -- | @var{files} @dots{}
736 Standard input, or source files to assemble.
744 @xref{AArch64 Options}, for the options available when @value{AS} is configured
745 for the 64-bit mode of the ARM Architecture (AArch64).
750 The following options are available when @value{AS} is configured for the
751 64-bit mode of the ARM Architecture (AArch64).
754 @include c-aarch64.texi
755 @c ended inside the included file
763 @xref{Alpha Options}, for the options available when @value{AS} is configured
764 for an Alpha processor.
769 The following options are available when @value{AS} is configured for an Alpha
773 @include c-alpha.texi
774 @c ended inside the included file
781 The following options are available when @value{AS} is configured for
786 This option selects the core processor variant.
788 Select either big-endian (-EB) or little-endian (-EL) output.
793 The following options are available when @value{AS} is configured for the ARM
797 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
798 Specify which ARM processor variant is the target.
799 @item -march=@var{architecture}[+@var{extension}@dots{}]
800 Specify which ARM architecture variant is used by the target.
801 @item -mfpu=@var{floating-point-format}
802 Select which Floating Point architecture is the target.
803 @item -mfloat-abi=@var{abi}
804 Select which floating point ABI is in use.
806 Enable Thumb only instruction decoding.
807 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
808 Select which procedure calling convention is in use.
810 Select either big-endian (-EB) or little-endian (-EL) output.
811 @item -mthumb-interwork
812 Specify that the code has been generated with interworking between Thumb and
815 Specify that PIC code has been generated.
823 @xref{Blackfin Options}, for the options available when @value{AS} is
824 configured for the Blackfin processor family.
829 The following options are available when @value{AS} is configured for
830 the Blackfin processor family.
834 @c ended inside the included file
841 See the info pages for documentation of the CRIS-specific options.
845 The following options are available when @value{AS} is configured for
848 @cindex D10V optimization
849 @cindex optimization, D10V
851 Optimize output by parallelizing instructions.
856 The following options are available when @value{AS} is configured for a D30V
859 @cindex D30V optimization
860 @cindex optimization, D30V
862 Optimize output by parallelizing instructions.
866 Warn when nops are generated.
868 @cindex D30V nops after 32-bit multiply
870 Warn when a nop after a 32-bit multiply instruction is generated.
876 The following options are available when @value{AS} is configured for the
877 Adapteva EPIPHANY series.
880 @xref{Epiphany Options}, for the options available when @value{AS} is
881 configured for an Epiphany processor.
886 The following options are available when @value{AS} is configured for
887 an Epiphany processor.
890 @include c-epiphany.texi
891 @c ended inside the included file
899 @xref{i386-Options}, for the options available when @value{AS} is
900 configured for an i386 processor.
905 The following options are available when @value{AS} is configured for
910 @c ended inside the included file
917 The following options are available when @value{AS} is configured for the
918 Intel 80960 processor.
921 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
922 Specify which variant of the 960 architecture is the target.
925 Add code to collect statistics about branches taken.
928 Do not alter compare-and-branch instructions for long displacements;
935 The following options are available when @value{AS} is configured for the
941 Specifies that the extended IP2022 instructions are allowed.
944 Restores the default behaviour, which restricts the permitted instructions to
945 just the basic IP2022 ones.
951 The following options are available when @value{AS} is configured for the
952 Renesas M32C and M16C processors.
957 Assemble M32C instructions.
960 Assemble M16C instructions (the default).
963 Enable support for link-time relaxations.
966 Support H'00 style hex constants in addition to 0x00 style.
972 The following options are available when @value{AS} is configured for the
973 Renesas M32R (formerly Mitsubishi M32R) series.
978 Specify which processor in the M32R family is the target. The default
979 is normally the M32R, but this option changes it to the M32RX.
981 @item --warn-explicit-parallel-conflicts or --Wp
982 Produce warning messages when questionable parallel constructs are
985 @item --no-warn-explicit-parallel-conflicts or --Wnp
986 Do not produce warning messages when questionable parallel constructs are
993 The following options are available when @value{AS} is configured for the
994 Motorola 68000 series.
999 Shorten references to undefined symbols, to one word instead of two.
1001 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1002 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1003 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1004 Specify what processor in the 68000 family is the target. The default
1005 is normally the 68020, but this can be changed at configuration time.
1007 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1008 The target machine does (or does not) have a floating-point coprocessor.
1009 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1010 the basic 68000 is not compatible with the 68881, a combination of the
1011 two can be specified, since it's possible to do emulation of the
1012 coprocessor instructions with the main processor.
1014 @item -m68851 | -mno-68851
1015 The target machine does (or does not) have a memory-management
1016 unit coprocessor. The default is to assume an MMU for 68020 and up.
1023 For details about the PDP-11 machine dependent features options,
1024 see @ref{PDP-11-Options}.
1027 @item -mpic | -mno-pic
1028 Generate position-independent (or position-dependent) code. The
1029 default is @option{-mpic}.
1032 @itemx -mall-extensions
1033 Enable all instruction set extensions. This is the default.
1035 @item -mno-extensions
1036 Disable all instruction set extensions.
1038 @item -m@var{extension} | -mno-@var{extension}
1039 Enable (or disable) a particular instruction set extension.
1042 Enable the instruction set extensions supported by a particular CPU, and
1043 disable all other extensions.
1045 @item -m@var{machine}
1046 Enable the instruction set extensions supported by a particular machine
1047 model, and disable all other extensions.
1053 The following options are available when @value{AS} is configured for
1054 a picoJava processor.
1058 @cindex PJ endianness
1059 @cindex endianness, PJ
1060 @cindex big endian output, PJ
1062 Generate ``big endian'' format output.
1064 @cindex little endian output, PJ
1066 Generate ``little endian'' format output.
1072 The following options are available when @value{AS} is configured for the
1073 Motorola 68HC11 or 68HC12 series.
1077 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1078 Specify what processor is the target. The default is
1079 defined by the configuration option when building the assembler.
1081 @item --xgate-ramoffset
1082 Instruct the linker to offset RAM addresses from S12X address space into
1083 XGATE address space.
1086 Specify to use the 16-bit integer ABI.
1089 Specify to use the 32-bit integer ABI.
1091 @item -mshort-double
1092 Specify to use the 32-bit double ABI.
1095 Specify to use the 64-bit double ABI.
1097 @item --force-long-branches
1098 Relative branches are turned into absolute ones. This concerns
1099 conditional branches, unconditional branches and branches to a
1102 @item -S | --short-branches
1103 Do not turn relative branches into absolute ones
1104 when the offset is out of range.
1106 @item --strict-direct-mode
1107 Do not turn the direct addressing mode into extended addressing mode
1108 when the instruction does not support direct addressing mode.
1110 @item --print-insn-syntax
1111 Print the syntax of instruction in case of error.
1113 @item --print-opcodes
1114 Print the list of instructions with syntax and then exit.
1116 @item --generate-example
1117 Print an example of instruction for each possible instruction and then exit.
1118 This option is only useful for testing @command{@value{AS}}.
1124 The following options are available when @command{@value{AS}} is configured
1125 for the SPARC architecture:
1128 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1129 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1130 Explicitly select a variant of the SPARC architecture.
1132 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1133 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1135 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1136 UltraSPARC extensions.
1138 @item -xarch=v8plus | -xarch=v8plusa
1139 For compatibility with the Solaris v9 assembler. These options are
1140 equivalent to -Av8plus and -Av8plusa, respectively.
1143 Warn when the assembler switches to another architecture.
1148 The following options are available when @value{AS} is configured for the 'c54x
1153 Enable extended addressing mode. All addresses and relocations will assume
1154 extended addressing (usually 23 bits).
1155 @item -mcpu=@var{CPU_VERSION}
1156 Sets the CPU version being compiled for.
1157 @item -merrors-to-file @var{FILENAME}
1158 Redirect error output to a file, for broken systems which don't support such
1159 behaviour in the shell.
1164 The following options are available when @value{AS} is configured for
1165 a @sc{mips} processor.
1169 This option sets the largest size of an object that can be referenced
1170 implicitly with the @code{gp} register. It is only accepted for targets that
1171 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1173 @cindex MIPS endianness
1174 @cindex endianness, MIPS
1175 @cindex big endian output, MIPS
1177 Generate ``big endian'' format output.
1179 @cindex little endian output, MIPS
1181 Generate ``little endian'' format output.
1193 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1194 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1195 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1196 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1197 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1199 correspond to generic
1200 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1201 and @samp{MIPS64 Release 2}
1202 ISA processors, respectively.
1204 @item -march=@var{CPU}
1205 Generate code for a particular @sc{mips} cpu.
1207 @item -mtune=@var{cpu}
1208 Schedule and tune for a particular @sc{mips} cpu.
1212 Cause nops to be inserted if the read of the destination register
1213 of an mfhi or mflo instruction occurs in the following two instructions.
1217 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1218 section instead of the standard ELF .stabs sections.
1222 Control generation of @code{.pdr} sections.
1226 The register sizes are normally inferred from the ISA and ABI, but these
1227 flags force a certain group of registers to be treated as 32 bits wide at
1228 all times. @samp{-mgp32} controls the size of general-purpose registers
1229 and @samp{-mfp32} controls the size of floating-point registers.
1233 Generate code for the MIPS 16 processor. This is equivalent to putting
1234 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1235 turns off this option.
1238 @itemx -mno-micromips
1239 Generate code for the microMIPS processor. This is equivalent to putting
1240 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1241 turns off this option. This is equivalent to putting @code{.set nomicromips}
1242 at the start of the assembly file.
1245 @itemx -mno-smartmips
1246 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1247 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1248 @samp{-mno-smartmips} turns off this option.
1252 Generate code for the MIPS-3D Application Specific Extension.
1253 This tells the assembler to accept MIPS-3D instructions.
1254 @samp{-no-mips3d} turns off this option.
1258 Generate code for the MDMX Application Specific Extension.
1259 This tells the assembler to accept MDMX instructions.
1260 @samp{-no-mdmx} turns off this option.
1264 Generate code for the DSP Release 1 Application Specific Extension.
1265 This tells the assembler to accept DSP Release 1 instructions.
1266 @samp{-mno-dsp} turns off this option.
1270 Generate code for the DSP Release 2 Application Specific Extension.
1271 This option implies -mdsp.
1272 This tells the assembler to accept DSP Release 2 instructions.
1273 @samp{-mno-dspr2} turns off this option.
1277 Generate code for the MT Application Specific Extension.
1278 This tells the assembler to accept MT instructions.
1279 @samp{-mno-mt} turns off this option.
1283 Generate code for the MCU Application Specific Extension.
1284 This tells the assembler to accept MCU instructions.
1285 @samp{-mno-mcu} turns off this option.
1287 @item --construct-floats
1288 @itemx --no-construct-floats
1289 The @samp{--no-construct-floats} option disables the construction of
1290 double width floating point constants by loading the two halves of the
1291 value into the two single width floating point registers that make up
1292 the double width register. By default @samp{--construct-floats} is
1293 selected, allowing construction of these floating point constants.
1296 @item --emulation=@var{name}
1297 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1298 for some other target, in all respects, including output format (choosing
1299 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1300 debugging information or store symbol table information, and default
1301 endianness. The available configuration names are: @samp{mipsecoff},
1302 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1303 @samp{mipsbelf}. The first two do not alter the default endianness from that
1304 of the primary target for which the assembler was configured; the others change
1305 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1306 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1307 selection in any case.
1309 This option is currently supported only when the primary target
1310 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1311 Furthermore, the primary target or others specified with
1312 @samp{--enable-targets=@dots{}} at configuration time must include support for
1313 the other format, if both are to be available. For example, the Irix 5
1314 configuration includes support for both.
1316 Eventually, this option will support more configurations, with more
1317 fine-grained control over the assembler's behavior, and will be supported for
1321 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1328 Control how to deal with multiplication overflow and division by zero.
1329 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1330 (and only work for Instruction Set Architecture level 2 and higher);
1331 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1335 When this option is used, @command{@value{AS}} will issue a warning every
1336 time it generates a nop instruction from a macro.
1341 The following options are available when @value{AS} is configured for
1347 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1348 The command line option @samp{-nojsri2bsr} can be used to disable it.
1352 Enable or disable the silicon filter behaviour. By default this is disabled.
1353 The default can be overridden by the @samp{-sifilter} command line option.
1356 Alter jump instructions for long displacements.
1358 @item -mcpu=[210|340]
1359 Select the cpu type on the target hardware. This controls which instructions
1363 Assemble for a big endian target.
1366 Assemble for a little endian target.
1372 See the info pages for documentation of the MMIX-specific options.
1379 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1380 for a PowerPC processor.
1384 @c man begin OPTIONS
1385 The following options are available when @value{AS} is configured for a
1388 @c man begin INCLUDE
1390 @c ended inside the included file
1395 @c man begin OPTIONS
1397 See the info pages for documentation of the RX-specific options.
1401 The following options are available when @value{AS} is configured for the s390
1407 Select the word size, either 31/32 bits or 64 bits.
1410 Select the architecture mode, either the Enterprise System
1411 Architecture (esa) or the z/Architecture mode (zarch).
1412 @item -march=@var{processor}
1413 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1414 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1416 @itemx -mno-regnames
1417 Allow or disallow symbolic names for registers.
1418 @item -mwarn-areg-zero
1419 Warn whenever the operand for a base or index register has been specified
1420 but evaluates to zero.
1428 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1429 for a TMS320C6000 processor.
1433 @c man begin OPTIONS
1434 The following options are available when @value{AS} is configured for a
1435 TMS320C6000 processor.
1437 @c man begin INCLUDE
1438 @include c-tic6x.texi
1439 @c ended inside the included file
1447 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1448 for a TILE-Gx processor.
1452 @c man begin OPTIONS
1453 The following options are available when @value{AS} is configured for a TILE-Gx
1456 @c man begin INCLUDE
1457 @include c-tilegx.texi
1458 @c ended inside the included file
1466 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1467 for an Xtensa processor.
1471 @c man begin OPTIONS
1472 The following options are available when @value{AS} is configured for an
1475 @c man begin INCLUDE
1476 @include c-xtensa.texi
1477 @c ended inside the included file
1482 @c man begin OPTIONS
1485 The following options are available when @value{AS} is configured for
1486 a Z80 family processor.
1489 Assemble for Z80 processor.
1491 Assemble for R800 processor.
1492 @item -ignore-undocumented-instructions
1494 Assemble undocumented Z80 instructions that also work on R800 without warning.
1495 @item -ignore-unportable-instructions
1497 Assemble all undocumented Z80 instructions without warning.
1498 @item -warn-undocumented-instructions
1500 Issue a warning for undocumented Z80 instructions that also work on R800.
1501 @item -warn-unportable-instructions
1503 Issue a warning for undocumented Z80 instructions that do not work on R800.
1504 @item -forbid-undocumented-instructions
1506 Treat all undocumented instructions as errors.
1507 @item -forbid-unportable-instructions
1509 Treat undocumented Z80 instructions that do not work on R800 as errors.
1516 * Manual:: Structure of this Manual
1517 * GNU Assembler:: The GNU Assembler
1518 * Object Formats:: Object File Formats
1519 * Command Line:: Command Line
1520 * Input Files:: Input Files
1521 * Object:: Output (Object) File
1522 * Errors:: Error and Warning Messages
1526 @section Structure of this Manual
1528 @cindex manual, structure and purpose
1529 This manual is intended to describe what you need to know to use
1530 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1531 notation for symbols, constants, and expressions; the directives that
1532 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1535 We also cover special features in the @value{TARGET}
1536 configuration of @command{@value{AS}}, including assembler directives.
1539 This manual also describes some of the machine-dependent features of
1540 various flavors of the assembler.
1543 @cindex machine instructions (not covered)
1544 On the other hand, this manual is @emph{not} intended as an introduction
1545 to programming in assembly language---let alone programming in general!
1546 In a similar vein, we make no attempt to introduce the machine
1547 architecture; we do @emph{not} describe the instruction set, standard
1548 mnemonics, registers or addressing modes that are standard to a
1549 particular architecture.
1551 You may want to consult the manufacturer's
1552 machine architecture manual for this information.
1556 For information on the H8/300 machine instruction set, see @cite{H8/300
1557 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1558 Programming Manual} (Renesas).
1561 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1562 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1563 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1564 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1567 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1573 Throughout this manual, we assume that you are running @dfn{GNU},
1574 the portable operating system from the @dfn{Free Software
1575 Foundation, Inc.}. This restricts our attention to certain kinds of
1576 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1577 once this assumption is granted examples and definitions need less
1580 @command{@value{AS}} is part of a team of programs that turn a high-level
1581 human-readable series of instructions into a low-level
1582 computer-readable series of instructions. Different versions of
1583 @command{@value{AS}} are used for different kinds of computer.
1586 @c There used to be a section "Terminology" here, which defined
1587 @c "contents", "byte", "word", and "long". Defining "word" to any
1588 @c particular size is confusing when the .word directive may generate 16
1589 @c bits on one machine and 32 bits on another; in general, for the user
1590 @c version of this manual, none of these terms seem essential to define.
1591 @c They were used very little even in the former draft of the manual;
1592 @c this draft makes an effort to avoid them (except in names of
1596 @section The GNU Assembler
1598 @c man begin DESCRIPTION
1600 @sc{gnu} @command{as} is really a family of assemblers.
1602 This manual describes @command{@value{AS}}, a member of that family which is
1603 configured for the @value{TARGET} architectures.
1605 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1606 should find a fairly similar environment when you use it on another
1607 architecture. Each version has much in common with the others,
1608 including object file formats, most assembler directives (often called
1609 @dfn{pseudo-ops}) and assembler syntax.@refill
1611 @cindex purpose of @sc{gnu} assembler
1612 @command{@value{AS}} is primarily intended to assemble the output of the
1613 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1614 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1615 assemble correctly everything that other assemblers for the same
1616 machine would assemble.
1618 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1621 @c This remark should appear in generic version of manual; assumption
1622 @c here is that generic version sets M680x0.
1623 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1624 assembler for the same architecture; for example, we know of several
1625 incompatible versions of 680x0 assembly language syntax.
1630 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1631 program in one pass of the source file. This has a subtle impact on the
1632 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1634 @node Object Formats
1635 @section Object File Formats
1637 @cindex object file format
1638 The @sc{gnu} assembler can be configured to produce several alternative
1639 object file formats. For the most part, this does not affect how you
1640 write assembly language programs; but directives for debugging symbols
1641 are typically different in different file formats. @xref{Symbol
1642 Attributes,,Symbol Attributes}.
1645 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1646 @value{OBJ-NAME} format object files.
1648 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1650 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1651 @code{b.out} or COFF format object files.
1654 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1655 SOM or ELF format object files.
1660 @section Command Line
1662 @cindex command line conventions
1664 After the program name @command{@value{AS}}, the command line may contain
1665 options and file names. Options may appear in any order, and may be
1666 before, after, or between file names. The order of file names is
1669 @cindex standard input, as input file
1671 @file{--} (two hyphens) by itself names the standard input file
1672 explicitly, as one of the files for @command{@value{AS}} to assemble.
1674 @cindex options, command line
1675 Except for @samp{--} any command line argument that begins with a
1676 hyphen (@samp{-}) is an option. Each option changes the behavior of
1677 @command{@value{AS}}. No option changes the way another option works. An
1678 option is a @samp{-} followed by one or more letters; the case of
1679 the letter is important. All options are optional.
1681 Some options expect exactly one file name to follow them. The file
1682 name may either immediately follow the option's letter (compatible
1683 with older assemblers) or it may be the next command argument (@sc{gnu}
1684 standard). These two command lines are equivalent:
1687 @value{AS} -o my-object-file.o mumble.s
1688 @value{AS} -omy-object-file.o mumble.s
1692 @section Input Files
1695 @cindex source program
1696 @cindex files, input
1697 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1698 describe the program input to one run of @command{@value{AS}}. The program may
1699 be in one or more files; how the source is partitioned into files
1700 doesn't change the meaning of the source.
1702 @c I added "con" prefix to "catenation" just to prove I can overcome my
1704 The source program is a concatenation of the text in all the files, in the
1707 @c man begin DESCRIPTION
1708 Each time you run @command{@value{AS}} it assembles exactly one source
1709 program. The source program is made up of one or more files.
1710 (The standard input is also a file.)
1712 You give @command{@value{AS}} a command line that has zero or more input file
1713 names. The input files are read (from left file name to right). A
1714 command line argument (in any position) that has no special meaning
1715 is taken to be an input file name.
1717 If you give @command{@value{AS}} no file names it attempts to read one input file
1718 from the @command{@value{AS}} standard input, which is normally your terminal. You
1719 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1722 Use @samp{--} if you need to explicitly name the standard input file
1723 in your command line.
1725 If the source is empty, @command{@value{AS}} produces a small, empty object
1730 @subheading Filenames and Line-numbers
1732 @cindex input file linenumbers
1733 @cindex line numbers, in input files
1734 There are two ways of locating a line in the input file (or files) and
1735 either may be used in reporting error messages. One way refers to a line
1736 number in a physical file; the other refers to a line number in a
1737 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1739 @dfn{Physical files} are those files named in the command line given
1740 to @command{@value{AS}}.
1742 @dfn{Logical files} are simply names declared explicitly by assembler
1743 directives; they bear no relation to physical files. Logical file names help
1744 error messages reflect the original source file, when @command{@value{AS}} source
1745 is itself synthesized from other files. @command{@value{AS}} understands the
1746 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1747 @ref{File,,@code{.file}}.
1750 @section Output (Object) File
1756 Every time you run @command{@value{AS}} it produces an output file, which is
1757 your assembly language program translated into numbers. This file
1758 is the object file. Its default name is
1766 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1768 You can give it another name by using the @option{-o} option. Conventionally,
1769 object file names end with @file{.o}. The default name is used for historical
1770 reasons: older assemblers were capable of assembling self-contained programs
1771 directly into a runnable program. (For some formats, this isn't currently
1772 possible, but it can be done for the @code{a.out} format.)
1776 The object file is meant for input to the linker @code{@value{LD}}. It contains
1777 assembled program code, information to help @code{@value{LD}} integrate
1778 the assembled program into a runnable file, and (optionally) symbolic
1779 information for the debugger.
1781 @c link above to some info file(s) like the description of a.out.
1782 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1785 @section Error and Warning Messages
1787 @c man begin DESCRIPTION
1789 @cindex error messages
1790 @cindex warning messages
1791 @cindex messages from assembler
1792 @command{@value{AS}} may write warnings and error messages to the standard error
1793 file (usually your terminal). This should not happen when a compiler
1794 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1795 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1796 grave problem that stops the assembly.
1800 @cindex format of warning messages
1801 Warning messages have the format
1804 file_name:@b{NNN}:Warning Message Text
1808 @cindex line numbers, in warnings/errors
1809 (where @b{NNN} is a line number). If a logical file name has been given
1810 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1811 the current input file is used. If a logical line number was given
1813 (@pxref{Line,,@code{.line}})
1815 then it is used to calculate the number printed,
1816 otherwise the actual line in the current source file is printed. The
1817 message text is intended to be self explanatory (in the grand Unix
1820 @cindex format of error messages
1821 Error messages have the format
1823 file_name:@b{NNN}:FATAL:Error Message Text
1825 The file name and line number are derived as for warning
1826 messages. The actual message text may be rather less explanatory
1827 because many of them aren't supposed to happen.
1830 @chapter Command-Line Options
1832 @cindex options, all versions of assembler
1833 This chapter describes command-line options available in @emph{all}
1834 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1835 for options specific
1837 to the @value{TARGET} target.
1840 to particular machine architectures.
1843 @c man begin DESCRIPTION
1845 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1846 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1847 The assembler arguments must be separated from each other (and the @samp{-Wa})
1848 by commas. For example:
1851 gcc -c -g -O -Wa,-alh,-L file.c
1855 This passes two options to the assembler: @samp{-alh} (emit a listing to
1856 standard output with high-level and assembly source) and @samp{-L} (retain
1857 local symbols in the symbol table).
1859 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1860 command-line options are automatically passed to the assembler by the compiler.
1861 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1862 precisely what options it passes to each compilation pass, including the
1868 * a:: -a[cdghlns] enable listings
1869 * alternate:: --alternate enable alternate macro syntax
1870 * D:: -D for compatibility
1871 * f:: -f to work faster
1872 * I:: -I for .include search path
1873 @ifclear DIFF-TBL-KLUGE
1874 * K:: -K for compatibility
1876 @ifset DIFF-TBL-KLUGE
1877 * K:: -K for difference tables
1880 * L:: -L to retain local symbols
1881 * listing:: --listing-XXX to configure listing output
1882 * M:: -M or --mri to assemble in MRI compatibility mode
1883 * MD:: --MD for dependency tracking
1884 * o:: -o to name the object file
1885 * R:: -R to join data and text sections
1886 * statistics:: --statistics to see statistics about assembly
1887 * traditional-format:: --traditional-format for compatible output
1888 * v:: -v to announce version
1889 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1890 * Z:: -Z to make object file even after errors
1894 @section Enable Listings: @option{-a[cdghlns]}
1904 @cindex listings, enabling
1905 @cindex assembly listings, enabling
1907 These options enable listing output from the assembler. By itself,
1908 @samp{-a} requests high-level, assembly, and symbols listing.
1909 You can use other letters to select specific options for the list:
1910 @samp{-ah} requests a high-level language listing,
1911 @samp{-al} requests an output-program assembly listing, and
1912 @samp{-as} requests a symbol table listing.
1913 High-level listings require that a compiler debugging option like
1914 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1917 Use the @samp{-ag} option to print a first section with general assembly
1918 information, like @value{AS} version, switches passed, or time stamp.
1920 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1921 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1922 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1923 omitted from the listing.
1925 Use the @samp{-ad} option to omit debugging directives from the
1928 Once you have specified one of these options, you can further control
1929 listing output and its appearance using the directives @code{.list},
1930 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1932 The @samp{-an} option turns off all forms processing.
1933 If you do not request listing output with one of the @samp{-a} options, the
1934 listing-control directives have no effect.
1936 The letters after @samp{-a} may be combined into one option,
1937 @emph{e.g.}, @samp{-aln}.
1939 Note if the assembler source is coming from the standard input (e.g.,
1941 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1942 is being used) then the listing will not contain any comments or preprocessor
1943 directives. This is because the listing code buffers input source lines from
1944 stdin only after they have been preprocessed by the assembler. This reduces
1945 memory usage and makes the code more efficient.
1948 @section @option{--alternate}
1951 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1954 @section @option{-D}
1957 This option has no effect whatsoever, but it is accepted to make it more
1958 likely that scripts written for other assemblers also work with
1959 @command{@value{AS}}.
1962 @section Work Faster: @option{-f}
1965 @cindex trusted compiler
1966 @cindex faster processing (@option{-f})
1967 @samp{-f} should only be used when assembling programs written by a
1968 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1969 and comment preprocessing on
1970 the input file(s) before assembling them. @xref{Preprocessing,
1974 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1975 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1980 @section @code{.include} Search Path: @option{-I} @var{path}
1982 @kindex -I @var{path}
1983 @cindex paths for @code{.include}
1984 @cindex search path for @code{.include}
1985 @cindex @code{include} directive search path
1986 Use this option to add a @var{path} to the list of directories
1987 @command{@value{AS}} searches for files specified in @code{.include}
1988 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1989 many times as necessary to include a variety of paths. The current
1990 working directory is always searched first; after that, @command{@value{AS}}
1991 searches any @samp{-I} directories in the same order as they were
1992 specified (left to right) on the command line.
1995 @section Difference Tables: @option{-K}
1998 @ifclear DIFF-TBL-KLUGE
1999 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2000 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2001 where it can be used to warn when the assembler alters the machine code
2002 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2003 family does not have the addressing limitations that sometimes lead to this
2004 alteration on other platforms.
2007 @ifset DIFF-TBL-KLUGE
2008 @cindex difference tables, warning
2009 @cindex warning for altered difference tables
2010 @command{@value{AS}} sometimes alters the code emitted for directives of the
2011 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2012 You can use the @samp{-K} option if you want a warning issued when this
2017 @section Include Local Symbols: @option{-L}
2020 @cindex local symbols, retaining in output
2021 Symbols beginning with system-specific local label prefixes, typically
2022 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2023 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2024 such symbols when debugging, because they are intended for the use of
2025 programs (like compilers) that compose assembler programs, not for your
2026 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2027 such symbols, so you do not normally debug with them.
2029 This option tells @command{@value{AS}} to retain those local symbols
2030 in the object file. Usually if you do this you also tell the linker
2031 @code{@value{LD}} to preserve those symbols.
2034 @section Configuring listing output: @option{--listing}
2036 The listing feature of the assembler can be enabled via the command line switch
2037 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2038 hex dump of the corresponding locations in the output object file, and displays
2039 them as a listing file. The format of this listing can be controlled by
2040 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2041 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2042 @code{.psize} (@pxref{Psize}), and
2043 @code{.eject} (@pxref{Eject}) and also by the following switches:
2046 @item --listing-lhs-width=@samp{number}
2047 @kindex --listing-lhs-width
2048 @cindex Width of first line disassembly output
2049 Sets the maximum width, in words, of the first line of the hex byte dump. This
2050 dump appears on the left hand side of the listing output.
2052 @item --listing-lhs-width2=@samp{number}
2053 @kindex --listing-lhs-width2
2054 @cindex Width of continuation lines of disassembly output
2055 Sets the maximum width, in words, of any further lines of the hex byte dump for
2056 a given input source line. If this value is not specified, it defaults to being
2057 the same as the value specified for @samp{--listing-lhs-width}. If neither
2058 switch is used the default is to one.
2060 @item --listing-rhs-width=@samp{number}
2061 @kindex --listing-rhs-width
2062 @cindex Width of source line output
2063 Sets the maximum width, in characters, of the source line that is displayed
2064 alongside the hex dump. The default value for this parameter is 100. The
2065 source line is displayed on the right hand side of the listing output.
2067 @item --listing-cont-lines=@samp{number}
2068 @kindex --listing-cont-lines
2069 @cindex Maximum number of continuation lines
2070 Sets the maximum number of continuation lines of hex dump that will be
2071 displayed for a given single line of source input. The default value is 4.
2075 @section Assemble in MRI Compatibility Mode: @option{-M}
2078 @cindex MRI compatibility mode
2079 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2080 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2081 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2082 configured target) assembler from Microtec Research. The exact nature of the
2083 MRI syntax will not be documented here; see the MRI manuals for more
2084 information. Note in particular that the handling of macros and macro
2085 arguments is somewhat different. The purpose of this option is to permit
2086 assembling existing MRI assembler code using @command{@value{AS}}.
2088 The MRI compatibility is not complete. Certain operations of the MRI assembler
2089 depend upon its object file format, and can not be supported using other object
2090 file formats. Supporting these would require enhancing each object file format
2091 individually. These are:
2094 @item global symbols in common section
2096 The m68k MRI assembler supports common sections which are merged by the linker.
2097 Other object file formats do not support this. @command{@value{AS}} handles
2098 common sections by treating them as a single common symbol. It permits local
2099 symbols to be defined within a common section, but it can not support global
2100 symbols, since it has no way to describe them.
2102 @item complex relocations
2104 The MRI assemblers support relocations against a negated section address, and
2105 relocations which combine the start addresses of two or more sections. These
2106 are not support by other object file formats.
2108 @item @code{END} pseudo-op specifying start address
2110 The MRI @code{END} pseudo-op permits the specification of a start address.
2111 This is not supported by other object file formats. The start address may
2112 instead be specified using the @option{-e} option to the linker, or in a linker
2115 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2117 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2118 name to the output file. This is not supported by other object file formats.
2120 @item @code{ORG} pseudo-op
2122 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2123 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2124 which changes the location within the current section. Absolute sections are
2125 not supported by other object file formats. The address of a section may be
2126 assigned within a linker script.
2129 There are some other features of the MRI assembler which are not supported by
2130 @command{@value{AS}}, typically either because they are difficult or because they
2131 seem of little consequence. Some of these may be supported in future releases.
2135 @item EBCDIC strings
2137 EBCDIC strings are not supported.
2139 @item packed binary coded decimal
2141 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2142 and @code{DCB.P} pseudo-ops are not supported.
2144 @item @code{FEQU} pseudo-op
2146 The m68k @code{FEQU} pseudo-op is not supported.
2148 @item @code{NOOBJ} pseudo-op
2150 The m68k @code{NOOBJ} pseudo-op is not supported.
2152 @item @code{OPT} branch control options
2154 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2155 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2156 relaxes all branches, whether forward or backward, to an appropriate size, so
2157 these options serve no purpose.
2159 @item @code{OPT} list control options
2161 The following m68k @code{OPT} list control options are ignored: @code{C},
2162 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2163 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2165 @item other @code{OPT} options
2167 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2168 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2170 @item @code{OPT} @code{D} option is default
2172 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2173 @code{OPT NOD} may be used to turn it off.
2175 @item @code{XREF} pseudo-op.
2177 The m68k @code{XREF} pseudo-op is ignored.
2179 @item @code{.debug} pseudo-op
2181 The i960 @code{.debug} pseudo-op is not supported.
2183 @item @code{.extended} pseudo-op
2185 The i960 @code{.extended} pseudo-op is not supported.
2187 @item @code{.list} pseudo-op.
2189 The various options of the i960 @code{.list} pseudo-op are not supported.
2191 @item @code{.optimize} pseudo-op
2193 The i960 @code{.optimize} pseudo-op is not supported.
2195 @item @code{.output} pseudo-op
2197 The i960 @code{.output} pseudo-op is not supported.
2199 @item @code{.setreal} pseudo-op
2201 The i960 @code{.setreal} pseudo-op is not supported.
2206 @section Dependency Tracking: @option{--MD}
2209 @cindex dependency tracking
2212 @command{@value{AS}} can generate a dependency file for the file it creates. This
2213 file consists of a single rule suitable for @code{make} describing the
2214 dependencies of the main source file.
2216 The rule is written to the file named in its argument.
2218 This feature is used in the automatic updating of makefiles.
2221 @section Name the Object File: @option{-o}
2224 @cindex naming object file
2225 @cindex object file name
2226 There is always one object file output when you run @command{@value{AS}}. By
2227 default it has the name
2230 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2244 You use this option (which takes exactly one filename) to give the
2245 object file a different name.
2247 Whatever the object file is called, @command{@value{AS}} overwrites any
2248 existing file of the same name.
2251 @section Join Data and Text Sections: @option{-R}
2254 @cindex data and text sections, joining
2255 @cindex text and data sections, joining
2256 @cindex joining text and data sections
2257 @cindex merging text and data sections
2258 @option{-R} tells @command{@value{AS}} to write the object file as if all
2259 data-section data lives in the text section. This is only done at
2260 the very last moment: your binary data are the same, but data
2261 section parts are relocated differently. The data section part of
2262 your object file is zero bytes long because all its bytes are
2263 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2265 When you specify @option{-R} it would be possible to generate shorter
2266 address displacements (because we do not have to cross between text and
2267 data section). We refrain from doing this simply for compatibility with
2268 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2271 When @command{@value{AS}} is configured for COFF or ELF output,
2272 this option is only useful if you use sections named @samp{.text} and
2277 @option{-R} is not supported for any of the HPPA targets. Using
2278 @option{-R} generates a warning from @command{@value{AS}}.
2282 @section Display Assembly Statistics: @option{--statistics}
2284 @kindex --statistics
2285 @cindex statistics, about assembly
2286 @cindex time, total for assembly
2287 @cindex space used, maximum for assembly
2288 Use @samp{--statistics} to display two statistics about the resources used by
2289 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2290 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2293 @node traditional-format
2294 @section Compatible Output: @option{--traditional-format}
2296 @kindex --traditional-format
2297 For some targets, the output of @command{@value{AS}} is different in some ways
2298 from the output of some existing assembler. This switch requests
2299 @command{@value{AS}} to use the traditional format instead.
2301 For example, it disables the exception frame optimizations which
2302 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2305 @section Announce Version: @option{-v}
2309 @cindex assembler version
2310 @cindex version of assembler
2311 You can find out what version of as is running by including the
2312 option @samp{-v} (which you can also spell as @samp{-version}) on the
2316 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2318 @command{@value{AS}} should never give a warning or error message when
2319 assembling compiler output. But programs written by people often
2320 cause @command{@value{AS}} to give a warning that a particular assumption was
2321 made. All such warnings are directed to the standard error file.
2325 @cindex suppressing warnings
2326 @cindex warnings, suppressing
2327 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2328 This only affects the warning messages: it does not change any particular of
2329 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2332 @kindex --fatal-warnings
2333 @cindex errors, caused by warnings
2334 @cindex warnings, causing error
2335 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2336 files that generate warnings to be in error.
2339 @cindex warnings, switching on
2340 You can switch these options off again by specifying @option{--warn}, which
2341 causes warnings to be output as usual.
2344 @section Generate Object File in Spite of Errors: @option{-Z}
2345 @cindex object file, after errors
2346 @cindex errors, continuing after
2347 After an error message, @command{@value{AS}} normally produces no output. If for
2348 some reason you are interested in object file output even after
2349 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2350 option. If there are any errors, @command{@value{AS}} continues anyways, and
2351 writes an object file after a final warning message of the form @samp{@var{n}
2352 errors, @var{m} warnings, generating bad object file.}
2357 @cindex machine-independent syntax
2358 @cindex syntax, machine-independent
2359 This chapter describes the machine-independent syntax allowed in a
2360 source file. @command{@value{AS}} syntax is similar to what many other
2361 assemblers use; it is inspired by the BSD 4.2
2366 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2370 * Preprocessing:: Preprocessing
2371 * Whitespace:: Whitespace
2372 * Comments:: Comments
2373 * Symbol Intro:: Symbols
2374 * Statements:: Statements
2375 * Constants:: Constants
2379 @section Preprocessing
2381 @cindex preprocessing
2382 The @command{@value{AS}} internal preprocessor:
2384 @cindex whitespace, removed by preprocessor
2386 adjusts and removes extra whitespace. It leaves one space or tab before
2387 the keywords on a line, and turns any other whitespace on the line into
2390 @cindex comments, removed by preprocessor
2392 removes all comments, replacing them with a single space, or an
2393 appropriate number of newlines.
2395 @cindex constants, converted by preprocessor
2397 converts character constants into the appropriate numeric values.
2400 It does not do macro processing, include file handling, or
2401 anything else you may get from your C compiler's preprocessor. You can
2402 do include file processing with the @code{.include} directive
2403 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2404 to get other ``CPP'' style preprocessing by giving the input file a
2405 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2406 Output, gcc.info, Using GNU CC}.
2408 Excess whitespace, comments, and character constants
2409 cannot be used in the portions of the input text that are not
2412 @cindex turning preprocessing on and off
2413 @cindex preprocessing, turning on and off
2416 If the first line of an input file is @code{#NO_APP} or if you use the
2417 @samp{-f} option, whitespace and comments are not removed from the input file.
2418 Within an input file, you can ask for whitespace and comment removal in
2419 specific portions of the by putting a line that says @code{#APP} before the
2420 text that may contain whitespace or comments, and putting a line that says
2421 @code{#NO_APP} after this text. This feature is mainly intend to support
2422 @code{asm} statements in compilers whose output is otherwise free of comments
2429 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2430 Whitespace is used to separate symbols, and to make programs neater for
2431 people to read. Unless within character constants
2432 (@pxref{Characters,,Character Constants}), any whitespace means the same
2433 as exactly one space.
2439 There are two ways of rendering comments to @command{@value{AS}}. In both
2440 cases the comment is equivalent to one space.
2442 Anything from @samp{/*} through the next @samp{*/} is a comment.
2443 This means you may not nest these comments.
2447 The only way to include a newline ('\n') in a comment
2448 is to use this sort of comment.
2451 /* This sort of comment does not nest. */
2454 @cindex line comment character
2455 Anything from a @dfn{line comment} character up to the next newline is
2456 considered a comment and is ignored. The line comment character is target
2457 specific, and some targets multiple comment characters. Some targets also have
2458 line comment characters that only work if they are the first character on a
2459 line. Some targets use a sequence of two characters to introduce a line
2460 comment. Some targets can also change their line comment characters depending
2461 upon command line options that have been used. For more details see the
2462 @emph{Syntax} section in the documentation for individual targets.
2464 If the line comment character is the hash sign (@samp{#}) then it still has the
2465 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2466 to specify logical line numbers:
2469 @cindex lines starting with @code{#}
2470 @cindex logical line numbers
2471 To be compatible with past assemblers, lines that begin with @samp{#} have a
2472 special interpretation. Following the @samp{#} should be an absolute
2473 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2474 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2475 new logical file name. The rest of the line, if any, should be whitespace.
2477 If the first non-whitespace characters on the line are not numeric,
2478 the line is ignored. (Just like a comment.)
2481 # This is an ordinary comment.
2482 # 42-6 "new_file_name" # New logical file name
2483 # This is logical line # 36.
2485 This feature is deprecated, and may disappear from future versions
2486 of @command{@value{AS}}.
2491 @cindex characters used in symbols
2492 @ifclear SPECIAL-SYMS
2493 A @dfn{symbol} is one or more characters chosen from the set of all
2494 letters (both upper and lower case), digits and the three characters
2500 A @dfn{symbol} is one or more characters chosen from the set of all
2501 letters (both upper and lower case), digits and the three characters
2502 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2508 On most machines, you can also use @code{$} in symbol names; exceptions
2509 are noted in @ref{Machine Dependencies}.
2511 No symbol may begin with a digit. Case is significant.
2512 There is no length limit: all characters are significant. Multibyte characters
2513 are supported. Symbols are delimited by characters not in that set, or by the
2514 beginning of a file (since the source program must end with a newline, the end
2515 of a file is not a possible symbol delimiter). @xref{Symbols}.
2516 @cindex length of symbols
2521 @cindex statements, structure of
2522 @cindex line separator character
2523 @cindex statement separator character
2525 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2526 @dfn{line separator character}. The line separator character is target
2527 specific and described in the @emph{Syntax} section of each
2528 target's documentation. Not all targets support a line separator character.
2529 The newline or line separator character is considered to be part of the
2530 preceding statement. Newlines and separators within character constants are an
2531 exception: they do not end statements.
2533 @cindex newline, required at file end
2534 @cindex EOF, newline must precede
2535 It is an error to end any statement with end-of-file: the last
2536 character of any input file should be a newline.@refill
2538 An empty statement is allowed, and may include whitespace. It is ignored.
2540 @cindex instructions and directives
2541 @cindex directives and instructions
2542 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2545 A statement begins with zero or more labels, optionally followed by a
2546 key symbol which determines what kind of statement it is. The key
2547 symbol determines the syntax of the rest of the statement. If the
2548 symbol begins with a dot @samp{.} then the statement is an assembler
2549 directive: typically valid for any computer. If the symbol begins with
2550 a letter the statement is an assembly language @dfn{instruction}: it
2551 assembles into a machine language instruction.
2553 Different versions of @command{@value{AS}} for different computers
2554 recognize different instructions. In fact, the same symbol may
2555 represent a different instruction in a different computer's assembly
2559 @cindex @code{:} (label)
2560 @cindex label (@code{:})
2561 A label is a symbol immediately followed by a colon (@code{:}).
2562 Whitespace before a label or after a colon is permitted, but you may not
2563 have whitespace between a label's symbol and its colon. @xref{Labels}.
2566 For HPPA targets, labels need not be immediately followed by a colon, but
2567 the definition of a label must begin in column zero. This also implies that
2568 only one label may be defined on each line.
2572 label: .directive followed by something
2573 another_label: # This is an empty statement.
2574 instruction operand_1, operand_2, @dots{}
2581 A constant is a number, written so that its value is known by
2582 inspection, without knowing any context. Like this:
2585 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2586 .ascii "Ring the bell\7" # A string constant.
2587 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2588 .float 0f-314159265358979323846264338327\
2589 95028841971.693993751E-40 # - pi, a flonum.
2594 * Characters:: Character Constants
2595 * Numbers:: Number Constants
2599 @subsection Character Constants
2601 @cindex character constants
2602 @cindex constants, character
2603 There are two kinds of character constants. A @dfn{character} stands
2604 for one character in one byte and its value may be used in
2605 numeric expressions. String constants (properly called string
2606 @emph{literals}) are potentially many bytes and their values may not be
2607 used in arithmetic expressions.
2611 * Chars:: Characters
2615 @subsubsection Strings
2617 @cindex string constants
2618 @cindex constants, string
2619 A @dfn{string} is written between double-quotes. It may contain
2620 double-quotes or null characters. The way to get special characters
2621 into a string is to @dfn{escape} these characters: precede them with
2622 a backslash @samp{\} character. For example @samp{\\} represents
2623 one backslash: the first @code{\} is an escape which tells
2624 @command{@value{AS}} to interpret the second character literally as a backslash
2625 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2626 escape character). The complete list of escapes follows.
2628 @cindex escape codes, character
2629 @cindex character escape codes
2632 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2634 @cindex @code{\b} (backspace character)
2635 @cindex backspace (@code{\b})
2637 Mnemonic for backspace; for ASCII this is octal code 010.
2640 @c Mnemonic for EOText; for ASCII this is octal code 004.
2642 @cindex @code{\f} (formfeed character)
2643 @cindex formfeed (@code{\f})
2645 Mnemonic for FormFeed; for ASCII this is octal code 014.
2647 @cindex @code{\n} (newline character)
2648 @cindex newline (@code{\n})
2650 Mnemonic for newline; for ASCII this is octal code 012.
2653 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2655 @cindex @code{\r} (carriage return character)
2656 @cindex carriage return (@code{\r})
2658 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2661 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2662 @c other assemblers.
2664 @cindex @code{\t} (tab)
2665 @cindex tab (@code{\t})
2667 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2670 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2671 @c @item \x @var{digit} @var{digit} @var{digit}
2672 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2674 @cindex @code{\@var{ddd}} (octal character code)
2675 @cindex octal character code (@code{\@var{ddd}})
2676 @item \ @var{digit} @var{digit} @var{digit}
2677 An octal character code. The numeric code is 3 octal digits.
2678 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2679 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2681 @cindex @code{\@var{xd...}} (hex character code)
2682 @cindex hex character code (@code{\@var{xd...}})
2683 @item \@code{x} @var{hex-digits...}
2684 A hex character code. All trailing hex digits are combined. Either upper or
2685 lower case @code{x} works.
2687 @cindex @code{\\} (@samp{\} character)
2688 @cindex backslash (@code{\\})
2690 Represents one @samp{\} character.
2693 @c Represents one @samp{'} (accent acute) character.
2694 @c This is needed in single character literals
2695 @c (@xref{Characters,,Character Constants}.) to represent
2698 @cindex @code{\"} (doublequote character)
2699 @cindex doublequote (@code{\"})
2701 Represents one @samp{"} character. Needed in strings to represent
2702 this character, because an unescaped @samp{"} would end the string.
2704 @item \ @var{anything-else}
2705 Any other character when escaped by @kbd{\} gives a warning, but
2706 assembles as if the @samp{\} was not present. The idea is that if
2707 you used an escape sequence you clearly didn't want the literal
2708 interpretation of the following character. However @command{@value{AS}} has no
2709 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2710 code and warns you of the fact.
2713 Which characters are escapable, and what those escapes represent,
2714 varies widely among assemblers. The current set is what we think
2715 the BSD 4.2 assembler recognizes, and is a subset of what most C
2716 compilers recognize. If you are in doubt, do not use an escape
2720 @subsubsection Characters
2722 @cindex single character constant
2723 @cindex character, single
2724 @cindex constant, single character
2725 A single character may be written as a single quote immediately
2726 followed by that character. The same escapes apply to characters as
2727 to strings. So if you want to write the character backslash, you
2728 must write @kbd{'\\} where the first @code{\} escapes the second
2729 @code{\}. As you can see, the quote is an acute accent, not a
2730 grave accent. A newline
2732 @ifclear abnormal-separator
2733 (or semicolon @samp{;})
2735 @ifset abnormal-separator
2737 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2742 immediately following an acute accent is taken as a literal character
2743 and does not count as the end of a statement. The value of a character
2744 constant in a numeric expression is the machine's byte-wide code for
2745 that character. @command{@value{AS}} assumes your character code is ASCII:
2746 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2749 @subsection Number Constants
2751 @cindex constants, number
2752 @cindex number constants
2753 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2754 are stored in the target machine. @emph{Integers} are numbers that
2755 would fit into an @code{int} in the C language. @emph{Bignums} are
2756 integers, but they are stored in more than 32 bits. @emph{Flonums}
2757 are floating point numbers, described below.
2760 * Integers:: Integers
2765 * Bit Fields:: Bit Fields
2771 @subsubsection Integers
2773 @cindex constants, integer
2775 @cindex binary integers
2776 @cindex integers, binary
2777 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2778 the binary digits @samp{01}.
2780 @cindex octal integers
2781 @cindex integers, octal
2782 An octal integer is @samp{0} followed by zero or more of the octal
2783 digits (@samp{01234567}).
2785 @cindex decimal integers
2786 @cindex integers, decimal
2787 A decimal integer starts with a non-zero digit followed by zero or
2788 more digits (@samp{0123456789}).
2790 @cindex hexadecimal integers
2791 @cindex integers, hexadecimal
2792 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2793 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2795 Integers have the usual values. To denote a negative integer, use
2796 the prefix operator @samp{-} discussed under expressions
2797 (@pxref{Prefix Ops,,Prefix Operators}).
2800 @subsubsection Bignums
2803 @cindex constants, bignum
2804 A @dfn{bignum} has the same syntax and semantics as an integer
2805 except that the number (or its negative) takes more than 32 bits to
2806 represent in binary. The distinction is made because in some places
2807 integers are permitted while bignums are not.
2810 @subsubsection Flonums
2812 @cindex floating point numbers
2813 @cindex constants, floating point
2815 @cindex precision, floating point
2816 A @dfn{flonum} represents a floating point number. The translation is
2817 indirect: a decimal floating point number from the text is converted by
2818 @command{@value{AS}} to a generic binary floating point number of more than
2819 sufficient precision. This generic floating point number is converted
2820 to a particular computer's floating point format (or formats) by a
2821 portion of @command{@value{AS}} specialized to that computer.
2823 A flonum is written by writing (in order)
2828 (@samp{0} is optional on the HPPA.)
2832 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2834 @kbd{e} is recommended. Case is not important.
2836 @c FIXME: verify if flonum syntax really this vague for most cases
2837 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2838 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2841 On the H8/300, Renesas / SuperH SH,
2842 and AMD 29K architectures, the letter must be
2843 one of the letters @samp{DFPRSX} (in upper or lower case).
2845 On the ARC, the letter must be one of the letters @samp{DFRS}
2846 (in upper or lower case).
2848 On the Intel 960 architecture, the letter must be
2849 one of the letters @samp{DFT} (in upper or lower case).
2851 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2855 One of the letters @samp{DFRS} (in upper or lower case).
2858 One of the letters @samp{DFPRSX} (in upper or lower case).
2861 The letter @samp{E} (upper case only).
2864 One of the letters @samp{DFT} (in upper or lower case).
2869 An optional sign: either @samp{+} or @samp{-}.
2872 An optional @dfn{integer part}: zero or more decimal digits.
2875 An optional @dfn{fractional part}: @samp{.} followed by zero
2876 or more decimal digits.
2879 An optional exponent, consisting of:
2883 An @samp{E} or @samp{e}.
2884 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2885 @c principle this can perfectly well be different on different targets.
2887 Optional sign: either @samp{+} or @samp{-}.
2889 One or more decimal digits.
2894 At least one of the integer part or the fractional part must be
2895 present. The floating point number has the usual base-10 value.
2897 @command{@value{AS}} does all processing using integers. Flonums are computed
2898 independently of any floating point hardware in the computer running
2899 @command{@value{AS}}.
2903 @c Bit fields are written as a general facility but are also controlled
2904 @c by a conditional-compilation flag---which is as of now (21mar91)
2905 @c turned on only by the i960 config of GAS.
2907 @subsubsection Bit Fields
2910 @cindex constants, bit field
2911 You can also define numeric constants as @dfn{bit fields}.
2912 Specify two numbers separated by a colon---
2914 @var{mask}:@var{value}
2917 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2920 The resulting number is then packed
2922 @c this conditional paren in case bit fields turned on elsewhere than 960
2923 (in host-dependent byte order)
2925 into a field whose width depends on which assembler directive has the
2926 bit-field as its argument. Overflow (a result from the bitwise and
2927 requiring more binary digits to represent) is not an error; instead,
2928 more constants are generated, of the specified width, beginning with the
2929 least significant digits.@refill
2931 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2932 @code{.short}, and @code{.word} accept bit-field arguments.
2937 @chapter Sections and Relocation
2942 * Secs Background:: Background
2943 * Ld Sections:: Linker Sections
2944 * As Sections:: Assembler Internal Sections
2945 * Sub-Sections:: Sub-Sections
2949 @node Secs Background
2952 Roughly, a section is a range of addresses, with no gaps; all data
2953 ``in'' those addresses is treated the same for some particular purpose.
2954 For example there may be a ``read only'' section.
2956 @cindex linker, and assembler
2957 @cindex assembler, and linker
2958 The linker @code{@value{LD}} reads many object files (partial programs) and
2959 combines their contents to form a runnable program. When @command{@value{AS}}
2960 emits an object file, the partial program is assumed to start at address 0.
2961 @code{@value{LD}} assigns the final addresses for the partial program, so that
2962 different partial programs do not overlap. This is actually an
2963 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2966 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2967 addresses. These blocks slide to their run-time addresses as rigid
2968 units; their length does not change and neither does the order of bytes
2969 within them. Such a rigid unit is called a @emph{section}. Assigning
2970 run-time addresses to sections is called @dfn{relocation}. It includes
2971 the task of adjusting mentions of object-file addresses so they refer to
2972 the proper run-time addresses.
2974 For the H8/300, and for the Renesas / SuperH SH,
2975 @command{@value{AS}} pads sections if needed to
2976 ensure they end on a word (sixteen bit) boundary.
2979 @cindex standard assembler sections
2980 An object file written by @command{@value{AS}} has at least three sections, any
2981 of which may be empty. These are named @dfn{text}, @dfn{data} and
2986 When it generates COFF or ELF output,
2988 @command{@value{AS}} can also generate whatever other named sections you specify
2989 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2990 If you do not use any directives that place output in the @samp{.text}
2991 or @samp{.data} sections, these sections still exist, but are empty.
2996 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2998 @command{@value{AS}} can also generate whatever other named sections you
2999 specify using the @samp{.space} and @samp{.subspace} directives. See
3000 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3001 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3002 assembler directives.
3005 Additionally, @command{@value{AS}} uses different names for the standard
3006 text, data, and bss sections when generating SOM output. Program text
3007 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3008 BSS into @samp{$BSS$}.
3012 Within the object file, the text section starts at address @code{0}, the
3013 data section follows, and the bss section follows the data section.
3016 When generating either SOM or ELF output files on the HPPA, the text
3017 section starts at address @code{0}, the data section at address
3018 @code{0x4000000}, and the bss section follows the data section.
3021 To let @code{@value{LD}} know which data changes when the sections are
3022 relocated, and how to change that data, @command{@value{AS}} also writes to the
3023 object file details of the relocation needed. To perform relocation
3024 @code{@value{LD}} must know, each time an address in the object
3028 Where in the object file is the beginning of this reference to
3031 How long (in bytes) is this reference?
3033 Which section does the address refer to? What is the numeric value of
3035 (@var{address}) @minus{} (@var{start-address of section})?
3038 Is the reference to an address ``Program-Counter relative''?
3041 @cindex addresses, format of
3042 @cindex section-relative addressing
3043 In fact, every address @command{@value{AS}} ever uses is expressed as
3045 (@var{section}) + (@var{offset into section})
3048 Further, most expressions @command{@value{AS}} computes have this section-relative
3051 (For some object formats, such as SOM for the HPPA, some expressions are
3052 symbol-relative instead.)
3055 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3056 @var{N} into section @var{secname}.''
3058 Apart from text, data and bss sections you need to know about the
3059 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3060 addresses in the absolute section remain unchanged. For example, address
3061 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3062 @code{@value{LD}}. Although the linker never arranges two partial programs'
3063 data sections with overlapping addresses after linking, @emph{by definition}
3064 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3065 part of a program is always the same address when the program is running as
3066 address @code{@{absolute@ 239@}} in any other part of the program.
3068 The idea of sections is extended to the @dfn{undefined} section. Any
3069 address whose section is unknown at assembly time is by definition
3070 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3071 Since numbers are always defined, the only way to generate an undefined
3072 address is to mention an undefined symbol. A reference to a named
3073 common block would be such a symbol: its value is unknown at assembly
3074 time so it has section @emph{undefined}.
3076 By analogy the word @emph{section} is used to describe groups of sections in
3077 the linked program. @code{@value{LD}} puts all partial programs' text
3078 sections in contiguous addresses in the linked program. It is
3079 customary to refer to the @emph{text section} of a program, meaning all
3080 the addresses of all partial programs' text sections. Likewise for
3081 data and bss sections.
3083 Some sections are manipulated by @code{@value{LD}}; others are invented for
3084 use of @command{@value{AS}} and have no meaning except during assembly.
3087 @section Linker Sections
3088 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3093 @cindex named sections
3094 @cindex sections, named
3095 @item named sections
3098 @cindex text section
3099 @cindex data section
3103 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3104 separate but equal sections. Anything you can say of one section is
3107 When the program is running, however, it is
3108 customary for the text section to be unalterable. The
3109 text section is often shared among processes: it contains
3110 instructions, constants and the like. The data section of a running
3111 program is usually alterable: for example, C variables would be stored
3112 in the data section.
3117 This section contains zeroed bytes when your program begins running. It
3118 is used to hold uninitialized variables or common storage. The length of
3119 each partial program's bss section is important, but because it starts
3120 out containing zeroed bytes there is no need to store explicit zero
3121 bytes in the object file. The bss section was invented to eliminate
3122 those explicit zeros from object files.
3124 @cindex absolute section
3125 @item absolute section
3126 Address 0 of this section is always ``relocated'' to runtime address 0.
3127 This is useful if you want to refer to an address that @code{@value{LD}} must
3128 not change when relocating. In this sense we speak of absolute
3129 addresses being ``unrelocatable'': they do not change during relocation.
3131 @cindex undefined section
3132 @item undefined section
3133 This ``section'' is a catch-all for address references to objects not in
3134 the preceding sections.
3135 @c FIXME: ref to some other doc on obj-file formats could go here.
3138 @cindex relocation example
3139 An idealized example of three relocatable sections follows.
3141 The example uses the traditional section names @samp{.text} and @samp{.data}.
3143 Memory addresses are on the horizontal axis.
3147 @c END TEXI2ROFF-KILL
3150 partial program # 1: |ttttt|dddd|00|
3157 partial program # 2: |TTT|DDD|000|
3160 +--+---+-----+--+----+---+-----+~~
3161 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3162 +--+---+-----+--+----+---+-----+~~
3164 addresses: 0 @dots{}
3171 \line{\it Partial program \#1: \hfil}
3172 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3173 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3175 \line{\it Partial program \#2: \hfil}
3176 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3177 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3179 \line{\it linked program: \hfil}
3180 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3181 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3182 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3183 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3185 \line{\it addresses: \hfil}
3189 @c END TEXI2ROFF-KILL
3192 @section Assembler Internal Sections
3194 @cindex internal assembler sections
3195 @cindex sections in messages, internal
3196 These sections are meant only for the internal use of @command{@value{AS}}. They
3197 have no meaning at run-time. You do not really need to know about these
3198 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3199 warning messages, so it might be helpful to have an idea of their
3200 meanings to @command{@value{AS}}. These sections are used to permit the
3201 value of every expression in your assembly language program to be a
3202 section-relative address.
3205 @cindex assembler internal logic error
3206 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3207 An internal assembler logic error has been found. This means there is a
3208 bug in the assembler.
3210 @cindex expr (internal section)
3212 The assembler stores complex expression internally as combinations of
3213 symbols. When it needs to represent an expression as a symbol, it puts
3214 it in the expr section.
3216 @c FIXME item transfer[t] vector preload
3217 @c FIXME item transfer[t] vector postload
3218 @c FIXME item register
3222 @section Sub-Sections
3224 @cindex numbered subsections
3225 @cindex grouping data
3231 fall into two sections: text and data.
3233 You may have separate groups of
3235 data in named sections
3239 data in named sections
3245 that you want to end up near to each other in the object file, even though they
3246 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3247 use @dfn{subsections} for this purpose. Within each section, there can be
3248 numbered subsections with values from 0 to 8192. Objects assembled into the
3249 same subsection go into the object file together with other objects in the same
3250 subsection. For example, a compiler might want to store constants in the text
3251 section, but might not want to have them interspersed with the program being
3252 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3253 section of code being output, and a @samp{.text 1} before each group of
3254 constants being output.
3256 Subsections are optional. If you do not use subsections, everything
3257 goes in subsection number zero.
3260 Each subsection is zero-padded up to a multiple of four bytes.
3261 (Subsections may be padded a different amount on different flavors
3262 of @command{@value{AS}}.)
3266 On the H8/300 platform, each subsection is zero-padded to a word
3267 boundary (two bytes).
3268 The same is true on the Renesas SH.
3271 @c FIXME section padding (alignment)?
3272 @c Rich Pixley says padding here depends on target obj code format; that
3273 @c doesn't seem particularly useful to say without further elaboration,
3274 @c so for now I say nothing about it. If this is a generic BFD issue,
3275 @c these paragraphs might need to vanish from this manual, and be
3276 @c discussed in BFD chapter of binutils (or some such).
3280 Subsections appear in your object file in numeric order, lowest numbered
3281 to highest. (All this to be compatible with other people's assemblers.)
3282 The object file contains no representation of subsections; @code{@value{LD}} and
3283 other programs that manipulate object files see no trace of them.
3284 They just see all your text subsections as a text section, and all your
3285 data subsections as a data section.
3287 To specify which subsection you want subsequent statements assembled
3288 into, use a numeric argument to specify it, in a @samp{.text
3289 @var{expression}} or a @samp{.data @var{expression}} statement.
3292 When generating COFF output, you
3297 can also use an extra subsection
3298 argument with arbitrary named sections: @samp{.section @var{name},
3303 When generating ELF output, you
3308 can also use the @code{.subsection} directive (@pxref{SubSection})
3309 to specify a subsection: @samp{.subsection @var{expression}}.
3311 @var{Expression} should be an absolute expression
3312 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3313 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3314 begins in @code{text 0}. For instance:
3316 .text 0 # The default subsection is text 0 anyway.
3317 .ascii "This lives in the first text subsection. *"
3319 .ascii "But this lives in the second text subsection."
3321 .ascii "This lives in the data section,"
3322 .ascii "in the first data subsection."
3324 .ascii "This lives in the first text section,"
3325 .ascii "immediately following the asterisk (*)."
3328 Each section has a @dfn{location counter} incremented by one for every byte
3329 assembled into that section. Because subsections are merely a convenience
3330 restricted to @command{@value{AS}} there is no concept of a subsection location
3331 counter. There is no way to directly manipulate a location counter---but the
3332 @code{.align} directive changes it, and any label definition captures its
3333 current value. The location counter of the section where statements are being
3334 assembled is said to be the @dfn{active} location counter.
3337 @section bss Section
3340 @cindex common variable storage
3341 The bss section is used for local common variable storage.
3342 You may allocate address space in the bss section, but you may
3343 not dictate data to load into it before your program executes. When
3344 your program starts running, all the contents of the bss
3345 section are zeroed bytes.
3347 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3348 @ref{Lcomm,,@code{.lcomm}}.
3350 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3351 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3354 When assembling for a target which supports multiple sections, such as ELF or
3355 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3356 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3357 section. Typically the section will only contain symbol definitions and
3358 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3365 Symbols are a central concept: the programmer uses symbols to name
3366 things, the linker uses symbols to link, and the debugger uses symbols
3370 @cindex debuggers, and symbol order
3371 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3372 the same order they were declared. This may break some debuggers.
3377 * Setting Symbols:: Giving Symbols Other Values
3378 * Symbol Names:: Symbol Names
3379 * Dot:: The Special Dot Symbol
3380 * Symbol Attributes:: Symbol Attributes
3387 A @dfn{label} is written as a symbol immediately followed by a colon
3388 @samp{:}. The symbol then represents the current value of the
3389 active location counter, and is, for example, a suitable instruction
3390 operand. You are warned if you use the same symbol to represent two
3391 different locations: the first definition overrides any other
3395 On the HPPA, the usual form for a label need not be immediately followed by a
3396 colon, but instead must start in column zero. Only one label may be defined on
3397 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3398 provides a special directive @code{.label} for defining labels more flexibly.
3401 @node Setting Symbols
3402 @section Giving Symbols Other Values
3404 @cindex assigning values to symbols
3405 @cindex symbol values, assigning
3406 A symbol can be given an arbitrary value by writing a symbol, followed
3407 by an equals sign @samp{=}, followed by an expression
3408 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3409 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3410 equals sign @samp{=}@samp{=} here represents an equivalent of the
3411 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3414 Blackfin does not support symbol assignment with @samp{=}.
3418 @section Symbol Names
3420 @cindex symbol names
3421 @cindex names, symbol
3422 @ifclear SPECIAL-SYMS
3423 Symbol names begin with a letter or with one of @samp{._}. On most
3424 machines, you can also use @code{$} in symbol names; exceptions are
3425 noted in @ref{Machine Dependencies}. That character may be followed by any
3426 string of digits, letters, dollar signs (unless otherwise noted for a
3427 particular target machine), and underscores.
3431 Symbol names begin with a letter or with one of @samp{._}. On the
3432 Renesas SH you can also use @code{$} in symbol names. That
3433 character may be followed by any string of digits, letters, dollar signs (save
3434 on the H8/300), and underscores.
3438 Case of letters is significant: @code{foo} is a different symbol name
3441 Multibyte characters are supported. To generate a symbol name containing
3442 multibyte characters enclose it within double quotes and use escape codes. cf
3443 @xref{Strings}. Generating a multibyte symbol name from a label is not
3444 currently supported.
3446 Each symbol has exactly one name. Each name in an assembly language program
3447 refers to exactly one symbol. You may use that symbol name any number of times
3450 @subheading Local Symbol Names
3452 @cindex local symbol names
3453 @cindex symbol names, local
3454 A local symbol is any symbol beginning with certain local label prefixes.
3455 By default, the local label prefix is @samp{.L} for ELF systems or
3456 @samp{L} for traditional a.out systems, but each target may have its own
3457 set of local label prefixes.
3459 On the HPPA local symbols begin with @samp{L$}.
3462 Local symbols are defined and used within the assembler, but they are
3463 normally not saved in object files. Thus, they are not visible when debugging.
3464 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3465 @option{-L}}) to retain the local symbols in the object files.
3467 @subheading Local Labels
3469 @cindex local labels
3470 @cindex temporary symbol names
3471 @cindex symbol names, temporary
3472 Local labels help compilers and programmers use names temporarily.
3473 They create symbols which are guaranteed to be unique over the entire scope of
3474 the input source code and which can be referred to by a simple notation.
3475 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3476 represents any positive integer). To refer to the most recent previous
3477 definition of that label write @samp{@b{N}b}, using the same number as when
3478 you defined the label. To refer to the next definition of a local label, write
3479 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3482 There is no restriction on how you can use these labels, and you can reuse them
3483 too. So that it is possible to repeatedly define the same local label (using
3484 the same number @samp{@b{N}}), although you can only refer to the most recently
3485 defined local label of that number (for a backwards reference) or the next
3486 definition of a specific local label for a forward reference. It is also worth
3487 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3488 implemented in a slightly more efficient manner than the others.
3499 Which is the equivalent of:
3502 label_1: branch label_3
3503 label_2: branch label_1
3504 label_3: branch label_4
3505 label_4: branch label_3
3508 Local label names are only a notational device. They are immediately
3509 transformed into more conventional symbol names before the assembler uses them.
3510 The symbol names are stored in the symbol table, appear in error messages, and
3511 are optionally emitted to the object file. The names are constructed using
3515 @item @emph{local label prefix}
3516 All local symbols begin with the system-specific local label prefix.
3517 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3518 that start with the local label prefix. These labels are
3519 used for symbols you are never intended to see. If you use the
3520 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3521 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3522 you may use them in debugging.
3525 This is the number that was used in the local label definition. So if the
3526 label is written @samp{55:} then the number is @samp{55}.
3529 This unusual character is included so you do not accidentally invent a symbol
3530 of the same name. The character has ASCII value of @samp{\002} (control-B).
3532 @item @emph{ordinal number}
3533 This is a serial number to keep the labels distinct. The first definition of
3534 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3535 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3536 the number @samp{1} and its 15th definition gets @samp{15} as well.
3539 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3540 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3542 @subheading Dollar Local Labels
3543 @cindex dollar local symbols
3545 @code{@value{AS}} also supports an even more local form of local labels called
3546 dollar labels. These labels go out of scope (i.e., they become undefined) as
3547 soon as a non-local label is defined. Thus they remain valid for only a small
3548 region of the input source code. Normal local labels, by contrast, remain in
3549 scope for the entire file, or until they are redefined by another occurrence of
3550 the same local label.
3552 Dollar labels are defined in exactly the same way as ordinary local labels,
3553 except that they have a dollar sign suffix to their numeric value, e.g.,
3556 They can also be distinguished from ordinary local labels by their transformed
3557 names which use ASCII character @samp{\001} (control-A) as the magic character
3558 to distinguish them from ordinary labels. For example, the fifth definition of
3559 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3562 @section The Special Dot Symbol
3564 @cindex dot (symbol)
3565 @cindex @code{.} (symbol)
3566 @cindex current address
3567 @cindex location counter
3568 The special symbol @samp{.} refers to the current address that
3569 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3570 .long .} defines @code{melvin} to contain its own address.
3571 Assigning a value to @code{.} is treated the same as a @code{.org}
3573 @ifclear no-space-dir
3574 Thus, the expression @samp{.=.+4} is the same as saying
3578 @node Symbol Attributes
3579 @section Symbol Attributes
3581 @cindex symbol attributes
3582 @cindex attributes, symbol
3583 Every symbol has, as well as its name, the attributes ``Value'' and
3584 ``Type''. Depending on output format, symbols can also have auxiliary
3587 The detailed definitions are in @file{a.out.h}.
3590 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3591 all these attributes, and probably won't warn you. This makes the
3592 symbol an externally defined symbol, which is generally what you
3596 * Symbol Value:: Value
3597 * Symbol Type:: Type
3600 * a.out Symbols:: Symbol Attributes: @code{a.out}
3604 * a.out Symbols:: Symbol Attributes: @code{a.out}
3607 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3612 * COFF Symbols:: Symbol Attributes for COFF
3615 * SOM Symbols:: Symbol Attributes for SOM
3622 @cindex value of a symbol
3623 @cindex symbol value
3624 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3625 location in the text, data, bss or absolute sections the value is the
3626 number of addresses from the start of that section to the label.
3627 Naturally for text, data and bss sections the value of a symbol changes
3628 as @code{@value{LD}} changes section base addresses during linking. Absolute
3629 symbols' values do not change during linking: that is why they are
3632 The value of an undefined symbol is treated in a special way. If it is
3633 0 then the symbol is not defined in this assembler source file, and
3634 @code{@value{LD}} tries to determine its value from other files linked into the
3635 same program. You make this kind of symbol simply by mentioning a symbol
3636 name without defining it. A non-zero value represents a @code{.comm}
3637 common declaration. The value is how much common storage to reserve, in
3638 bytes (addresses). The symbol refers to the first address of the
3644 @cindex type of a symbol
3646 The type attribute of a symbol contains relocation (section)
3647 information, any flag settings indicating that a symbol is external, and
3648 (optionally), other information for linkers and debuggers. The exact
3649 format depends on the object-code output format in use.
3654 @c The following avoids a "widow" subsection title. @group would be
3655 @c better if it were available outside examples.
3658 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3660 @cindex @code{b.out} symbol attributes
3661 @cindex symbol attributes, @code{b.out}
3662 These symbol attributes appear only when @command{@value{AS}} is configured for
3663 one of the Berkeley-descended object output formats---@code{a.out} or
3669 @subsection Symbol Attributes: @code{a.out}
3671 @cindex @code{a.out} symbol attributes
3672 @cindex symbol attributes, @code{a.out}
3678 @subsection Symbol Attributes: @code{a.out}
3680 @cindex @code{a.out} symbol attributes
3681 @cindex symbol attributes, @code{a.out}
3685 * Symbol Desc:: Descriptor
3686 * Symbol Other:: Other
3690 @subsubsection Descriptor
3692 @cindex descriptor, of @code{a.out} symbol
3693 This is an arbitrary 16-bit value. You may establish a symbol's
3694 descriptor value by using a @code{.desc} statement
3695 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3696 @command{@value{AS}}.
3699 @subsubsection Other
3701 @cindex other attribute, of @code{a.out} symbol
3702 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3707 @subsection Symbol Attributes for COFF
3709 @cindex COFF symbol attributes
3710 @cindex symbol attributes, COFF
3712 The COFF format supports a multitude of auxiliary symbol attributes;
3713 like the primary symbol attributes, they are set between @code{.def} and
3714 @code{.endef} directives.
3716 @subsubsection Primary Attributes
3718 @cindex primary attributes, COFF symbols
3719 The symbol name is set with @code{.def}; the value and type,
3720 respectively, with @code{.val} and @code{.type}.
3722 @subsubsection Auxiliary Attributes
3724 @cindex auxiliary attributes, COFF symbols
3725 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3726 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3727 table information for COFF.
3732 @subsection Symbol Attributes for SOM
3734 @cindex SOM symbol attributes
3735 @cindex symbol attributes, SOM
3737 The SOM format for the HPPA supports a multitude of symbol attributes set with
3738 the @code{.EXPORT} and @code{.IMPORT} directives.
3740 The attributes are described in @cite{HP9000 Series 800 Assembly
3741 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3742 @code{EXPORT} assembler directive documentation.
3746 @chapter Expressions
3750 @cindex numeric values
3751 An @dfn{expression} specifies an address or numeric value.
3752 Whitespace may precede and/or follow an expression.
3754 The result of an expression must be an absolute number, or else an offset into
3755 a particular section. If an expression is not absolute, and there is not
3756 enough information when @command{@value{AS}} sees the expression to know its
3757 section, a second pass over the source program might be necessary to interpret
3758 the expression---but the second pass is currently not implemented.
3759 @command{@value{AS}} aborts with an error message in this situation.
3762 * Empty Exprs:: Empty Expressions
3763 * Integer Exprs:: Integer Expressions
3767 @section Empty Expressions
3769 @cindex empty expressions
3770 @cindex expressions, empty
3771 An empty expression has no value: it is just whitespace or null.
3772 Wherever an absolute expression is required, you may omit the
3773 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3774 is compatible with other assemblers.
3777 @section Integer Expressions
3779 @cindex integer expressions
3780 @cindex expressions, integer
3781 An @dfn{integer expression} is one or more @emph{arguments} delimited
3782 by @emph{operators}.
3785 * Arguments:: Arguments
3786 * Operators:: Operators
3787 * Prefix Ops:: Prefix Operators
3788 * Infix Ops:: Infix Operators
3792 @subsection Arguments
3794 @cindex expression arguments
3795 @cindex arguments in expressions
3796 @cindex operands in expressions
3797 @cindex arithmetic operands
3798 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3799 contexts arguments are sometimes called ``arithmetic operands''. In
3800 this manual, to avoid confusing them with the ``instruction operands'' of
3801 the machine language, we use the term ``argument'' to refer to parts of
3802 expressions only, reserving the word ``operand'' to refer only to machine
3803 instruction operands.
3805 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3806 @var{section} is one of text, data, bss, absolute,
3807 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3810 Numbers are usually integers.
3812 A number can be a flonum or bignum. In this case, you are warned
3813 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3814 these 32 bits are an integer. You may write integer-manipulating
3815 instructions that act on exotic constants, compatible with other
3818 @cindex subexpressions
3819 Subexpressions are a left parenthesis @samp{(} followed by an integer
3820 expression, followed by a right parenthesis @samp{)}; or a prefix
3821 operator followed by an argument.
3824 @subsection Operators
3826 @cindex operators, in expressions
3827 @cindex arithmetic functions
3828 @cindex functions, in expressions
3829 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3830 operators are followed by an argument. Infix operators appear
3831 between their arguments. Operators may be preceded and/or followed by
3835 @subsection Prefix Operator
3837 @cindex prefix operators
3838 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3839 one argument, which must be absolute.
3841 @c the tex/end tex stuff surrounding this small table is meant to make
3842 @c it align, on the printed page, with the similar table in the next
3843 @c section (which is inside an enumerate).
3845 \global\advance\leftskip by \itemindent
3850 @dfn{Negation}. Two's complement negation.
3852 @dfn{Complementation}. Bitwise not.
3856 \global\advance\leftskip by -\itemindent
3860 @subsection Infix Operators
3862 @cindex infix operators
3863 @cindex operators, permitted arguments
3864 @dfn{Infix operators} take two arguments, one on either side. Operators
3865 have precedence, but operations with equal precedence are performed left
3866 to right. Apart from @code{+} or @option{-}, both arguments must be
3867 absolute, and the result is absolute.
3870 @cindex operator precedence
3871 @cindex precedence of operators
3878 @dfn{Multiplication}.
3881 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3887 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3890 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3894 Intermediate precedence
3899 @dfn{Bitwise Inclusive Or}.
3905 @dfn{Bitwise Exclusive Or}.
3908 @dfn{Bitwise Or Not}.
3915 @cindex addition, permitted arguments
3916 @cindex plus, permitted arguments
3917 @cindex arguments for addition
3919 @dfn{Addition}. If either argument is absolute, the result has the section of
3920 the other argument. You may not add together arguments from different
3923 @cindex subtraction, permitted arguments
3924 @cindex minus, permitted arguments
3925 @cindex arguments for subtraction
3927 @dfn{Subtraction}. If the right argument is absolute, the
3928 result has the section of the left argument.
3929 If both arguments are in the same section, the result is absolute.
3930 You may not subtract arguments from different sections.
3931 @c FIXME is there still something useful to say about undefined - undefined ?
3933 @cindex comparison expressions
3934 @cindex expressions, comparison
3939 @dfn{Is Not Equal To}
3943 @dfn{Is Greater Than}
3945 @dfn{Is Greater Than Or Equal To}
3947 @dfn{Is Less Than Or Equal To}
3949 The comparison operators can be used as infix operators. A true results has a
3950 value of -1 whereas a false result has a value of 0. Note, these operators
3951 perform signed comparisons.
3954 @item Lowest Precedence
3963 These two logical operations can be used to combine the results of sub
3964 expressions. Note, unlike the comparison operators a true result returns a
3965 value of 1 but a false results does still return 0. Also note that the logical
3966 or operator has a slightly lower precedence than logical and.
3971 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3972 address; you can only have a defined section in one of the two arguments.
3975 @chapter Assembler Directives
3977 @cindex directives, machine independent
3978 @cindex pseudo-ops, machine independent
3979 @cindex machine independent directives
3980 All assembler directives have names that begin with a period (@samp{.}).
3981 The rest of the name is letters, usually in lower case.
3983 This chapter discusses directives that are available regardless of the
3984 target machine configuration for the @sc{gnu} assembler.
3986 Some machine configurations provide additional directives.
3987 @xref{Machine Dependencies}.
3990 @ifset machine-directives
3991 @xref{Machine Dependencies}, for additional directives.
3996 * Abort:: @code{.abort}
3998 * ABORT (COFF):: @code{.ABORT}
4001 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4002 * Altmacro:: @code{.altmacro}
4003 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4004 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4005 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4006 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4007 * Byte:: @code{.byte @var{expressions}}
4008 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4009 * Comm:: @code{.comm @var{symbol} , @var{length} }
4010 * Data:: @code{.data @var{subsection}}
4012 * Def:: @code{.def @var{name}}
4015 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4021 * Double:: @code{.double @var{flonums}}
4022 * Eject:: @code{.eject}
4023 * Else:: @code{.else}
4024 * Elseif:: @code{.elseif}
4027 * Endef:: @code{.endef}
4030 * Endfunc:: @code{.endfunc}
4031 * Endif:: @code{.endif}
4032 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4033 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4034 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4036 * Error:: @code{.error @var{string}}
4037 * Exitm:: @code{.exitm}
4038 * Extern:: @code{.extern}
4039 * Fail:: @code{.fail}
4040 * File:: @code{.file}
4041 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4042 * Float:: @code{.float @var{flonums}}
4043 * Func:: @code{.func}
4044 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4046 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4047 * Hidden:: @code{.hidden @var{names}}
4050 * hword:: @code{.hword @var{expressions}}
4051 * Ident:: @code{.ident}
4052 * If:: @code{.if @var{absolute expression}}
4053 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4054 * Include:: @code{.include "@var{file}"}
4055 * Int:: @code{.int @var{expressions}}
4057 * Internal:: @code{.internal @var{names}}
4060 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4061 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4062 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4063 * Lflags:: @code{.lflags}
4064 @ifclear no-line-dir
4065 * Line:: @code{.line @var{line-number}}
4068 * Linkonce:: @code{.linkonce [@var{type}]}
4069 * List:: @code{.list}
4070 * Ln:: @code{.ln @var{line-number}}
4071 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4072 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4074 * Local:: @code{.local @var{names}}
4077 * Long:: @code{.long @var{expressions}}
4079 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4082 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4083 * MRI:: @code{.mri @var{val}}
4084 * Noaltmacro:: @code{.noaltmacro}
4085 * Nolist:: @code{.nolist}
4086 * Octa:: @code{.octa @var{bignums}}
4087 * Offset:: @code{.offset @var{loc}}
4088 * Org:: @code{.org @var{new-lc}, @var{fill}}
4089 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4091 * PopSection:: @code{.popsection}
4092 * Previous:: @code{.previous}
4095 * Print:: @code{.print @var{string}}
4097 * Protected:: @code{.protected @var{names}}
4100 * Psize:: @code{.psize @var{lines}, @var{columns}}
4101 * Purgem:: @code{.purgem @var{name}}
4103 * PushSection:: @code{.pushsection @var{name}}
4106 * Quad:: @code{.quad @var{bignums}}
4107 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4108 * Rept:: @code{.rept @var{count}}
4109 * Sbttl:: @code{.sbttl "@var{subheading}"}
4111 * Scl:: @code{.scl @var{class}}
4114 * Section:: @code{.section @var{name}[, @var{flags}]}
4117 * Set:: @code{.set @var{symbol}, @var{expression}}
4118 * Short:: @code{.short @var{expressions}}
4119 * Single:: @code{.single @var{flonums}}
4121 * Size:: @code{.size [@var{name} , @var{expression}]}
4123 @ifclear no-space-dir
4124 * Skip:: @code{.skip @var{size} , @var{fill}}
4127 * Sleb128:: @code{.sleb128 @var{expressions}}
4128 @ifclear no-space-dir
4129 * Space:: @code{.space @var{size} , @var{fill}}
4132 * Stab:: @code{.stabd, .stabn, .stabs}
4135 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4136 * Struct:: @code{.struct @var{expression}}
4138 * SubSection:: @code{.subsection}
4139 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4143 * Tag:: @code{.tag @var{structname}}
4146 * Text:: @code{.text @var{subsection}}
4147 * Title:: @code{.title "@var{heading}"}
4149 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4152 * Uleb128:: @code{.uleb128 @var{expressions}}
4154 * Val:: @code{.val @var{addr}}
4158 * Version:: @code{.version "@var{string}"}
4159 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4160 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4163 * Warning:: @code{.warning @var{string}}
4164 * Weak:: @code{.weak @var{names}}
4165 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4166 * Word:: @code{.word @var{expressions}}
4167 * Deprecated:: Deprecated Directives
4171 @section @code{.abort}
4173 @cindex @code{abort} directive
4174 @cindex stopping the assembly
4175 This directive stops the assembly immediately. It is for
4176 compatibility with other assemblers. The original idea was that the
4177 assembly language source would be piped into the assembler. If the sender
4178 of the source quit, it could use this directive tells @command{@value{AS}} to
4179 quit also. One day @code{.abort} will not be supported.
4183 @section @code{.ABORT} (COFF)
4185 @cindex @code{ABORT} directive
4186 When producing COFF output, @command{@value{AS}} accepts this directive as a
4187 synonym for @samp{.abort}.
4190 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4196 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4198 @cindex padding the location counter
4199 @cindex @code{align} directive
4200 Pad the location counter (in the current subsection) to a particular storage
4201 boundary. The first expression (which must be absolute) is the alignment
4202 required, as described below.
4204 The second expression (also absolute) gives the fill value to be stored in the
4205 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4206 padding bytes are normally zero. However, on some systems, if the section is
4207 marked as containing code and the fill value is omitted, the space is filled
4208 with no-op instructions.
4210 The third expression is also absolute, and is also optional. If it is present,
4211 it is the maximum number of bytes that should be skipped by this alignment
4212 directive. If doing the alignment would require skipping more bytes than the
4213 specified maximum, then the alignment is not done at all. You can omit the
4214 fill value (the second argument) entirely by simply using two commas after the
4215 required alignment; this can be useful if you want the alignment to be filled
4216 with no-op instructions when appropriate.
4218 The way the required alignment is specified varies from system to system.
4219 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4220 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4221 alignment request in bytes. For example @samp{.align 8} advances
4222 the location counter until it is a multiple of 8. If the location counter
4223 is already a multiple of 8, no change is needed. For the tic54x, the
4224 first expression is the alignment request in words.
4226 For other systems, including ppc, i386 using a.out format, arm and
4227 strongarm, it is the
4228 number of low-order zero bits the location counter must have after
4229 advancement. For example @samp{.align 3} advances the location
4230 counter until it a multiple of 8. If the location counter is already a
4231 multiple of 8, no change is needed.
4233 This inconsistency is due to the different behaviors of the various
4234 native assemblers for these systems which GAS must emulate.
4235 GAS also provides @code{.balign} and @code{.p2align} directives,
4236 described later, which have a consistent behavior across all
4237 architectures (but are specific to GAS).
4240 @section @code{.altmacro}
4241 Enable alternate macro mode, enabling:
4244 @item LOCAL @var{name} [ , @dots{} ]
4245 One additional directive, @code{LOCAL}, is available. It is used to
4246 generate a string replacement for each of the @var{name} arguments, and
4247 replace any instances of @var{name} in each macro expansion. The
4248 replacement string is unique in the assembly, and different for each
4249 separate macro expansion. @code{LOCAL} allows you to write macros that
4250 define symbols, without fear of conflict between separate macro expansions.
4252 @item String delimiters
4253 You can write strings delimited in these other ways besides
4254 @code{"@var{string}"}:
4257 @item '@var{string}'
4258 You can delimit strings with single-quote characters.
4260 @item <@var{string}>
4261 You can delimit strings with matching angle brackets.
4264 @item single-character string escape
4265 To include any single character literally in a string (even if the
4266 character would otherwise have some special meaning), you can prefix the
4267 character with @samp{!} (an exclamation mark). For example, you can
4268 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4270 @item Expression results as strings
4271 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4272 and use the result as a string.
4276 @section @code{.ascii "@var{string}"}@dots{}
4278 @cindex @code{ascii} directive
4279 @cindex string literals
4280 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4281 separated by commas. It assembles each string (with no automatic
4282 trailing zero byte) into consecutive addresses.
4285 @section @code{.asciz "@var{string}"}@dots{}
4287 @cindex @code{asciz} directive
4288 @cindex zero-terminated strings
4289 @cindex null-terminated strings
4290 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4291 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4294 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4296 @cindex padding the location counter given number of bytes
4297 @cindex @code{balign} directive
4298 Pad the location counter (in the current subsection) to a particular
4299 storage boundary. The first expression (which must be absolute) is the
4300 alignment request in bytes. For example @samp{.balign 8} advances
4301 the location counter until it is a multiple of 8. If the location counter
4302 is already a multiple of 8, no change is needed.
4304 The second expression (also absolute) gives the fill value to be stored in the
4305 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4306 padding bytes are normally zero. However, on some systems, if the section is
4307 marked as containing code and the fill value is omitted, the space is filled
4308 with no-op instructions.
4310 The third expression is also absolute, and is also optional. If it is present,
4311 it is the maximum number of bytes that should be skipped by this alignment
4312 directive. If doing the alignment would require skipping more bytes than the
4313 specified maximum, then the alignment is not done at all. You can omit the
4314 fill value (the second argument) entirely by simply using two commas after the
4315 required alignment; this can be useful if you want the alignment to be filled
4316 with no-op instructions when appropriate.
4318 @cindex @code{balignw} directive
4319 @cindex @code{balignl} directive
4320 The @code{.balignw} and @code{.balignl} directives are variants of the
4321 @code{.balign} directive. The @code{.balignw} directive treats the fill
4322 pattern as a two byte word value. The @code{.balignl} directives treats the
4323 fill pattern as a four byte longword value. For example, @code{.balignw
4324 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4325 filled in with the value 0x368d (the exact placement of the bytes depends upon
4326 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4329 @node Bundle directives
4330 @section @code{.bundle_align_mode @var{abs-expr}}
4331 @cindex @code{bundle_align_mode} directive
4333 @cindex instruction bundle
4334 @cindex aligned instruction bundle
4335 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4336 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4337 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4338 disabled (which is the default state). If the argument it not zero, it
4339 gives the size of an instruction bundle as a power of two (as for the
4340 @code{.p2align} directive, @pxref{P2align}).
4342 For some targets, it's an ABI requirement that no instruction may span a
4343 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4344 instructions that starts on an aligned boundary. For example, if
4345 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4346 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4347 effect, no single instruction may span a boundary between bundles. If an
4348 instruction would start too close to the end of a bundle for the length of
4349 that particular instruction to fit within the bundle, then the space at the
4350 end of that bundle is filled with no-op instructions so the instruction
4351 starts in the next bundle. As a corollary, it's an error if any single
4352 instruction's encoding is longer than the bundle size.
4354 @section @code{.bundle_lock} and @code{.bundle_unlock}
4355 @cindex @code{bundle_lock} directive
4356 @cindex @code{bundle_unlock} directive
4357 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4358 allow explicit control over instruction bundle padding. These directives
4359 are only valid when @code{.bundle_align_mode} has been used to enable
4360 aligned instruction bundle mode. It's an error if they appear when
4361 @code{.bundle_align_mode} has not been used at all, or when the last
4362 directive was @w{@code{.bundle_align_mode 0}}.
4364 @cindex bundle-locked
4365 For some targets, it's an ABI requirement that certain instructions may
4366 appear only as part of specified permissible sequences of multiple
4367 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4368 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4369 instruction sequence. For purposes of aligned instruction bundle mode, a
4370 sequence starting with @code{.bundle_lock} and ending with
4371 @code{.bundle_unlock} is treated as a single instruction. That is, the
4372 entire sequence must fit into a single bundle and may not span a bundle
4373 boundary. If necessary, no-op instructions will be inserted before the
4374 first instruction of the sequence so that the whole sequence starts on an
4375 aligned bundle boundary. It's an error if the sequence is longer than the
4378 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4379 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4380 nested. That is, a second @code{.bundle_lock} directive before the next
4381 @code{.bundle_unlock} directive has no effect except that it must be
4382 matched by another closing @code{.bundle_unlock} so that there is the
4383 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4386 @section @code{.byte @var{expressions}}
4388 @cindex @code{byte} directive
4389 @cindex integers, one byte
4390 @code{.byte} expects zero or more expressions, separated by commas.
4391 Each expression is assembled into the next byte.
4393 @node CFI directives
4394 @section @code{.cfi_sections @var{section_list}}
4395 @cindex @code{cfi_sections} directive
4396 @code{.cfi_sections} may be used to specify whether CFI directives
4397 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4398 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4399 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4400 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4401 directive is not used is @code{.cfi_sections .eh_frame}.
4403 @section @code{.cfi_startproc [simple]}
4404 @cindex @code{cfi_startproc} directive
4405 @code{.cfi_startproc} is used at the beginning of each function that
4406 should have an entry in @code{.eh_frame}. It initializes some internal
4407 data structures. Don't forget to close the function by
4408 @code{.cfi_endproc}.
4410 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4411 it also emits some architecture dependent initial CFI instructions.
4413 @section @code{.cfi_endproc}
4414 @cindex @code{cfi_endproc} directive
4415 @code{.cfi_endproc} is used at the end of a function where it closes its
4416 unwind entry previously opened by
4417 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4419 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4420 @code{.cfi_personality} defines personality routine and its encoding.
4421 @var{encoding} must be a constant determining how the personality
4422 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4423 argument is not present, otherwise second argument should be
4424 a constant or a symbol name. When using indirect encodings,
4425 the symbol provided should be the location where personality
4426 can be loaded from, not the personality routine itself.
4427 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4428 no personality routine.
4430 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4431 @code{.cfi_lsda} defines LSDA and its encoding.
4432 @var{encoding} must be a constant determining how the LSDA
4433 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4434 argument is not present, otherwise second argument should be a constant
4435 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4438 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4439 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4440 address from @var{register} and add @var{offset} to it}.
4442 @section @code{.cfi_def_cfa_register @var{register}}
4443 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4444 now on @var{register} will be used instead of the old one. Offset
4447 @section @code{.cfi_def_cfa_offset @var{offset}}
4448 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4449 remains the same, but @var{offset} is new. Note that it is the
4450 absolute offset that will be added to a defined register to compute
4453 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4454 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4455 value that is added/substracted from the previous offset.
4457 @section @code{.cfi_offset @var{register}, @var{offset}}
4458 Previous value of @var{register} is saved at offset @var{offset} from
4461 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4462 Previous value of @var{register} is saved at offset @var{offset} from
4463 the current CFA register. This is transformed to @code{.cfi_offset}
4464 using the known displacement of the CFA register from the CFA.
4465 This is often easier to use, because the number will match the
4466 code it's annotating.
4468 @section @code{.cfi_register @var{register1}, @var{register2}}
4469 Previous value of @var{register1} is saved in register @var{register2}.
4471 @section @code{.cfi_restore @var{register}}
4472 @code{.cfi_restore} says that the rule for @var{register} is now the
4473 same as it was at the beginning of the function, after all initial
4474 instruction added by @code{.cfi_startproc} were executed.
4476 @section @code{.cfi_undefined @var{register}}
4477 From now on the previous value of @var{register} can't be restored anymore.
4479 @section @code{.cfi_same_value @var{register}}
4480 Current value of @var{register} is the same like in the previous frame,
4481 i.e. no restoration needed.
4483 @section @code{.cfi_remember_state},
4484 First save all current rules for all registers by @code{.cfi_remember_state},
4485 then totally screw them up by subsequent @code{.cfi_*} directives and when
4486 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4487 the previous saved state.
4489 @section @code{.cfi_return_column @var{register}}
4490 Change return column @var{register}, i.e. the return address is either
4491 directly in @var{register} or can be accessed by rules for @var{register}.
4493 @section @code{.cfi_signal_frame}
4494 Mark current function as signal trampoline.
4496 @section @code{.cfi_window_save}
4497 SPARC register window has been saved.
4499 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4500 Allows the user to add arbitrary bytes to the unwind info. One
4501 might use this to add OS-specific CFI opcodes, or generic CFI
4502 opcodes that GAS does not yet support.
4504 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4505 The current value of @var{register} is @var{label}. The value of @var{label}
4506 will be encoded in the output file according to @var{encoding}; see the
4507 description of @code{.cfi_personality} for details on this encoding.
4509 The usefulness of equating a register to a fixed label is probably
4510 limited to the return address register. Here, it can be useful to
4511 mark a code segment that has only one return address which is reached
4512 by a direct branch and no copy of the return address exists in memory
4513 or another register.
4516 @section @code{.comm @var{symbol} , @var{length} }
4518 @cindex @code{comm} directive
4519 @cindex symbol, common
4520 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4521 common symbol in one object file may be merged with a defined or common symbol
4522 of the same name in another object file. If @code{@value{LD}} does not see a
4523 definition for the symbol--just one or more common symbols--then it will
4524 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4525 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4526 the same name, and they do not all have the same size, it will allocate space
4527 using the largest size.
4530 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4531 an optional third argument. This is the desired alignment of the symbol,
4532 specified for ELF as a byte boundary (for example, an alignment of 16 means
4533 that the least significant 4 bits of the address should be zero), and for PE
4534 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4535 boundary). The alignment must be an absolute expression, and it must be a
4536 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4537 common symbol, it will use the alignment when placing the symbol. If no
4538 alignment is specified, @command{@value{AS}} will set the alignment to the
4539 largest power of two less than or equal to the size of the symbol, up to a
4540 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4541 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4542 @samp{--section-alignment} option; image file sections in PE are aligned to
4543 multiples of 4096, which is far too large an alignment for ordinary variables.
4544 It is rather the default alignment for (non-debug) sections within object
4545 (@samp{*.o}) files, which are less strictly aligned.}.
4549 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4550 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4554 @section @code{.data @var{subsection}}
4556 @cindex @code{data} directive
4557 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4558 end of the data subsection numbered @var{subsection} (which is an
4559 absolute expression). If @var{subsection} is omitted, it defaults
4564 @section @code{.def @var{name}}
4566 @cindex @code{def} directive
4567 @cindex COFF symbols, debugging
4568 @cindex debugging COFF symbols
4569 Begin defining debugging information for a symbol @var{name}; the
4570 definition extends until the @code{.endef} directive is encountered.
4573 This directive is only observed when @command{@value{AS}} is configured for COFF
4574 format output; when producing @code{b.out}, @samp{.def} is recognized,
4581 @section @code{.desc @var{symbol}, @var{abs-expression}}
4583 @cindex @code{desc} directive
4584 @cindex COFF symbol descriptor
4585 @cindex symbol descriptor, COFF
4586 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4587 to the low 16 bits of an absolute expression.
4590 The @samp{.desc} directive is not available when @command{@value{AS}} is
4591 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4592 object format. For the sake of compatibility, @command{@value{AS}} accepts
4593 it, but produces no output, when configured for COFF.
4599 @section @code{.dim}
4601 @cindex @code{dim} directive
4602 @cindex COFF auxiliary symbol information
4603 @cindex auxiliary symbol information, COFF
4604 This directive is generated by compilers to include auxiliary debugging
4605 information in the symbol table. It is only permitted inside
4606 @code{.def}/@code{.endef} pairs.
4609 @samp{.dim} is only meaningful when generating COFF format output; when
4610 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4616 @section @code{.double @var{flonums}}
4618 @cindex @code{double} directive
4619 @cindex floating point numbers (double)
4620 @code{.double} expects zero or more flonums, separated by commas. It
4621 assembles floating point numbers.
4623 The exact kind of floating point numbers emitted depends on how
4624 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4628 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4629 in @sc{ieee} format.
4634 @section @code{.eject}
4636 @cindex @code{eject} directive
4637 @cindex new page, in listings
4638 @cindex page, in listings
4639 @cindex listing control: new page
4640 Force a page break at this point, when generating assembly listings.
4643 @section @code{.else}
4645 @cindex @code{else} directive
4646 @code{.else} is part of the @command{@value{AS}} support for conditional
4647 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4648 of code to be assembled if the condition for the preceding @code{.if}
4652 @section @code{.elseif}
4654 @cindex @code{elseif} directive
4655 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4656 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4657 @code{.if} block that would otherwise fill the entire @code{.else} section.
4660 @section @code{.end}
4662 @cindex @code{end} directive
4663 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4664 process anything in the file past the @code{.end} directive.
4668 @section @code{.endef}
4670 @cindex @code{endef} directive
4671 This directive flags the end of a symbol definition begun with
4675 @samp{.endef} is only meaningful when generating COFF format output; if
4676 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4677 directive but ignores it.
4682 @section @code{.endfunc}
4683 @cindex @code{endfunc} directive
4684 @code{.endfunc} marks the end of a function specified with @code{.func}.
4687 @section @code{.endif}
4689 @cindex @code{endif} directive
4690 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4691 it marks the end of a block of code that is only assembled
4692 conditionally. @xref{If,,@code{.if}}.
4695 @section @code{.equ @var{symbol}, @var{expression}}
4697 @cindex @code{equ} directive
4698 @cindex assigning values to symbols
4699 @cindex symbols, assigning values to
4700 This directive sets the value of @var{symbol} to @var{expression}.
4701 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4704 The syntax for @code{equ} on the HPPA is
4705 @samp{@var{symbol} .equ @var{expression}}.
4709 The syntax for @code{equ} on the Z80 is
4710 @samp{@var{symbol} equ @var{expression}}.
4711 On the Z80 it is an eror if @var{symbol} is already defined,
4712 but the symbol is not protected from later redefinition.
4713 Compare @ref{Equiv}.
4717 @section @code{.equiv @var{symbol}, @var{expression}}
4718 @cindex @code{equiv} directive
4719 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4720 the assembler will signal an error if @var{symbol} is already defined. Note a
4721 symbol which has been referenced but not actually defined is considered to be
4724 Except for the contents of the error message, this is roughly equivalent to
4731 plus it protects the symbol from later redefinition.
4734 @section @code{.eqv @var{symbol}, @var{expression}}
4735 @cindex @code{eqv} directive
4736 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4737 evaluate the expression or any part of it immediately. Instead each time
4738 the resulting symbol is used in an expression, a snapshot of its current
4742 @section @code{.err}
4743 @cindex @code{err} directive
4744 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4745 message and, unless the @option{-Z} option was used, it will not generate an
4746 object file. This can be used to signal an error in conditionally compiled code.
4749 @section @code{.error "@var{string}"}
4750 @cindex error directive
4752 Similarly to @code{.err}, this directive emits an error, but you can specify a
4753 string that will be emitted as the error message. If you don't specify the
4754 message, it defaults to @code{".error directive invoked in source file"}.
4755 @xref{Errors, ,Error and Warning Messages}.
4758 .error "This code has not been assembled and tested."
4762 @section @code{.exitm}
4763 Exit early from the current macro definition. @xref{Macro}.
4766 @section @code{.extern}
4768 @cindex @code{extern} directive
4769 @code{.extern} is accepted in the source program---for compatibility
4770 with other assemblers---but it is ignored. @command{@value{AS}} treats
4771 all undefined symbols as external.
4774 @section @code{.fail @var{expression}}
4776 @cindex @code{fail} directive
4777 Generates an error or a warning. If the value of the @var{expression} is 500
4778 or more, @command{@value{AS}} will print a warning message. If the value is less
4779 than 500, @command{@value{AS}} will print an error message. The message will
4780 include the value of @var{expression}. This can occasionally be useful inside
4781 complex nested macros or conditional assembly.
4784 @section @code{.file}
4785 @cindex @code{file} directive
4787 @ifclear no-file-dir
4788 There are two different versions of the @code{.file} directive. Targets
4789 that support DWARF2 line number information use the DWARF2 version of
4790 @code{.file}. Other targets use the default version.
4792 @subheading Default Version
4794 @cindex logical file name
4795 @cindex file name, logical
4796 This version of the @code{.file} directive tells @command{@value{AS}} that we
4797 are about to start a new logical file. The syntax is:
4803 @var{string} is the new file name. In general, the filename is
4804 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4805 to specify an empty file name, you must give the quotes--@code{""}. This
4806 statement may go away in future: it is only recognized to be compatible with
4807 old @command{@value{AS}} programs.
4809 @subheading DWARF2 Version
4812 When emitting DWARF2 line number information, @code{.file} assigns filenames
4813 to the @code{.debug_line} file name table. The syntax is:
4816 .file @var{fileno} @var{filename}
4819 The @var{fileno} operand should be a unique positive integer to use as the
4820 index of the entry in the table. The @var{filename} operand is a C string
4823 The detail of filename indices is exposed to the user because the filename
4824 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4825 information, and thus the user must know the exact indices that table
4829 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4831 @cindex @code{fill} directive
4832 @cindex writing patterns in memory
4833 @cindex patterns, writing in memory
4834 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4835 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4836 may be zero or more. @var{Size} may be zero or more, but if it is
4837 more than 8, then it is deemed to have the value 8, compatible with
4838 other people's assemblers. The contents of each @var{repeat} bytes
4839 is taken from an 8-byte number. The highest order 4 bytes are
4840 zero. The lowest order 4 bytes are @var{value} rendered in the
4841 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4842 Each @var{size} bytes in a repetition is taken from the lowest order
4843 @var{size} bytes of this number. Again, this bizarre behavior is
4844 compatible with other people's assemblers.
4846 @var{size} and @var{value} are optional.
4847 If the second comma and @var{value} are absent, @var{value} is
4848 assumed zero. If the first comma and following tokens are absent,
4849 @var{size} is assumed to be 1.
4852 @section @code{.float @var{flonums}}
4854 @cindex floating point numbers (single)
4855 @cindex @code{float} directive
4856 This directive assembles zero or more flonums, separated by commas. It
4857 has the same effect as @code{.single}.
4859 The exact kind of floating point numbers emitted depends on how
4860 @command{@value{AS}} is configured.
4861 @xref{Machine Dependencies}.
4865 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4866 in @sc{ieee} format.
4871 @section @code{.func @var{name}[,@var{label}]}
4872 @cindex @code{func} directive
4873 @code{.func} emits debugging information to denote function @var{name}, and
4874 is ignored unless the file is assembled with debugging enabled.
4875 Only @samp{--gstabs[+]} is currently supported.
4876 @var{label} is the entry point of the function and if omitted @var{name}
4877 prepended with the @samp{leading char} is used.
4878 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4879 All functions are currently defined to have @code{void} return type.
4880 The function must be terminated with @code{.endfunc}.
4883 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4885 @cindex @code{global} directive
4886 @cindex symbol, making visible to linker
4887 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4888 @var{symbol} in your partial program, its value is made available to
4889 other partial programs that are linked with it. Otherwise,
4890 @var{symbol} takes its attributes from a symbol of the same name
4891 from another file linked into the same program.
4893 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4894 compatibility with other assemblers.
4897 On the HPPA, @code{.global} is not always enough to make it accessible to other
4898 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4899 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4904 @section @code{.gnu_attribute @var{tag},@var{value}}
4905 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4908 @section @code{.hidden @var{names}}
4910 @cindex @code{hidden} directive
4912 This is one of the ELF visibility directives. The other two are
4913 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4914 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4916 This directive overrides the named symbols default visibility (which is set by
4917 their binding: local, global or weak). The directive sets the visibility to
4918 @code{hidden} which means that the symbols are not visible to other components.
4919 Such symbols are always considered to be @code{protected} as well.
4923 @section @code{.hword @var{expressions}}
4925 @cindex @code{hword} directive
4926 @cindex integers, 16-bit
4927 @cindex numbers, 16-bit
4928 @cindex sixteen bit integers
4929 This expects zero or more @var{expressions}, and emits
4930 a 16 bit number for each.
4933 This directive is a synonym for @samp{.short}; depending on the target
4934 architecture, it may also be a synonym for @samp{.word}.
4938 This directive is a synonym for @samp{.short}.
4941 This directive is a synonym for both @samp{.short} and @samp{.word}.
4946 @section @code{.ident}
4948 @cindex @code{ident} directive
4950 This directive is used by some assemblers to place tags in object files. The
4951 behavior of this directive varies depending on the target. When using the
4952 a.out object file format, @command{@value{AS}} simply accepts the directive for
4953 source-file compatibility with existing assemblers, but does not emit anything
4954 for it. When using COFF, comments are emitted to the @code{.comment} or
4955 @code{.rdata} section, depending on the target. When using ELF, comments are
4956 emitted to the @code{.comment} section.
4959 @section @code{.if @var{absolute expression}}
4961 @cindex conditional assembly
4962 @cindex @code{if} directive
4963 @code{.if} marks the beginning of a section of code which is only
4964 considered part of the source program being assembled if the argument
4965 (which must be an @var{absolute expression}) is non-zero. The end of
4966 the conditional section of code must be marked by @code{.endif}
4967 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4968 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4969 If you have several conditions to check, @code{.elseif} may be used to avoid
4970 nesting blocks if/else within each subsequent @code{.else} block.
4972 The following variants of @code{.if} are also supported:
4974 @cindex @code{ifdef} directive
4975 @item .ifdef @var{symbol}
4976 Assembles the following section of code if the specified @var{symbol}
4977 has been defined. Note a symbol which has been referenced but not yet defined
4978 is considered to be undefined.
4980 @cindex @code{ifb} directive
4981 @item .ifb @var{text}
4982 Assembles the following section of code if the operand is blank (empty).
4984 @cindex @code{ifc} directive
4985 @item .ifc @var{string1},@var{string2}
4986 Assembles the following section of code if the two strings are the same. The
4987 strings may be optionally quoted with single quotes. If they are not quoted,
4988 the first string stops at the first comma, and the second string stops at the
4989 end of the line. Strings which contain whitespace should be quoted. The
4990 string comparison is case sensitive.
4992 @cindex @code{ifeq} directive
4993 @item .ifeq @var{absolute expression}
4994 Assembles the following section of code if the argument is zero.
4996 @cindex @code{ifeqs} directive
4997 @item .ifeqs @var{string1},@var{string2}
4998 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5000 @cindex @code{ifge} directive
5001 @item .ifge @var{absolute expression}
5002 Assembles the following section of code if the argument is greater than or
5005 @cindex @code{ifgt} directive
5006 @item .ifgt @var{absolute expression}
5007 Assembles the following section of code if the argument is greater than zero.
5009 @cindex @code{ifle} directive
5010 @item .ifle @var{absolute expression}
5011 Assembles the following section of code if the argument is less than or equal
5014 @cindex @code{iflt} directive
5015 @item .iflt @var{absolute expression}
5016 Assembles the following section of code if the argument is less than zero.
5018 @cindex @code{ifnb} directive
5019 @item .ifnb @var{text}
5020 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5021 following section of code if the operand is non-blank (non-empty).
5023 @cindex @code{ifnc} directive
5024 @item .ifnc @var{string1},@var{string2}.
5025 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5026 following section of code if the two strings are not the same.
5028 @cindex @code{ifndef} directive
5029 @cindex @code{ifnotdef} directive
5030 @item .ifndef @var{symbol}
5031 @itemx .ifnotdef @var{symbol}
5032 Assembles the following section of code if the specified @var{symbol}
5033 has not been defined. Both spelling variants are equivalent. Note a symbol
5034 which has been referenced but not yet defined is considered to be undefined.
5036 @cindex @code{ifne} directive
5037 @item .ifne @var{absolute expression}
5038 Assembles the following section of code if the argument is not equal to zero
5039 (in other words, this is equivalent to @code{.if}).
5041 @cindex @code{ifnes} directive
5042 @item .ifnes @var{string1},@var{string2}
5043 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5044 following section of code if the two strings are not the same.
5048 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5050 @cindex @code{incbin} directive
5051 @cindex binary files, including
5052 The @code{incbin} directive includes @var{file} verbatim at the current
5053 location. You can control the search paths used with the @samp{-I} command-line
5054 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5057 The @var{skip} argument skips a number of bytes from the start of the
5058 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5059 read. Note that the data is not aligned in any way, so it is the user's
5060 responsibility to make sure that proper alignment is provided both before and
5061 after the @code{incbin} directive.
5064 @section @code{.include "@var{file}"}
5066 @cindex @code{include} directive
5067 @cindex supporting files, including
5068 @cindex files, including
5069 This directive provides a way to include supporting files at specified
5070 points in your source program. The code from @var{file} is assembled as
5071 if it followed the point of the @code{.include}; when the end of the
5072 included file is reached, assembly of the original file continues. You
5073 can control the search paths used with the @samp{-I} command-line option
5074 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5078 @section @code{.int @var{expressions}}
5080 @cindex @code{int} directive
5081 @cindex integers, 32-bit
5082 Expect zero or more @var{expressions}, of any section, separated by commas.
5083 For each expression, emit a number that, at run time, is the value of that
5084 expression. The byte order and bit size of the number depends on what kind
5085 of target the assembly is for.
5089 On most forms of the H8/300, @code{.int} emits 16-bit
5090 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5097 @section @code{.internal @var{names}}
5099 @cindex @code{internal} directive
5101 This is one of the ELF visibility directives. The other two are
5102 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5103 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5105 This directive overrides the named symbols default visibility (which is set by
5106 their binding: local, global or weak). The directive sets the visibility to
5107 @code{internal} which means that the symbols are considered to be @code{hidden}
5108 (i.e., not visible to other components), and that some extra, processor specific
5109 processing must also be performed upon the symbols as well.
5113 @section @code{.irp @var{symbol},@var{values}}@dots{}
5115 @cindex @code{irp} directive
5116 Evaluate a sequence of statements assigning different values to @var{symbol}.
5117 The sequence of statements starts at the @code{.irp} directive, and is
5118 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5119 set to @var{value}, and the sequence of statements is assembled. If no
5120 @var{value} is listed, the sequence of statements is assembled once, with
5121 @var{symbol} set to the null string. To refer to @var{symbol} within the
5122 sequence of statements, use @var{\symbol}.
5124 For example, assembling
5132 is equivalent to assembling
5140 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5143 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5145 @cindex @code{irpc} directive
5146 Evaluate a sequence of statements assigning different values to @var{symbol}.
5147 The sequence of statements starts at the @code{.irpc} directive, and is
5148 terminated by an @code{.endr} directive. For each character in @var{value},
5149 @var{symbol} is set to the character, and the sequence of statements is
5150 assembled. If no @var{value} is listed, the sequence of statements is
5151 assembled once, with @var{symbol} set to the null string. To refer to
5152 @var{symbol} within the sequence of statements, use @var{\symbol}.
5154 For example, assembling
5162 is equivalent to assembling
5170 For some caveats with the spelling of @var{symbol}, see also the discussion
5174 @section @code{.lcomm @var{symbol} , @var{length}}
5176 @cindex @code{lcomm} directive
5177 @cindex local common symbols
5178 @cindex symbols, local common
5179 Reserve @var{length} (an absolute expression) bytes for a local common
5180 denoted by @var{symbol}. The section and value of @var{symbol} are
5181 those of the new local common. The addresses are allocated in the bss
5182 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5183 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5184 not visible to @code{@value{LD}}.
5187 Some targets permit a third argument to be used with @code{.lcomm}. This
5188 argument specifies the desired alignment of the symbol in the bss section.
5192 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5193 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5197 @section @code{.lflags}
5199 @cindex @code{lflags} directive (ignored)
5200 @command{@value{AS}} accepts this directive, for compatibility with other
5201 assemblers, but ignores it.
5203 @ifclear no-line-dir
5205 @section @code{.line @var{line-number}}
5207 @cindex @code{line} directive
5208 @cindex logical line number
5210 Change the logical line number. @var{line-number} must be an absolute
5211 expression. The next line has that logical line number. Therefore any other
5212 statements on the current line (after a statement separator character) are
5213 reported as on logical line number @var{line-number} @minus{} 1. One day
5214 @command{@value{AS}} will no longer support this directive: it is recognized only
5215 for compatibility with existing assembler programs.
5218 Even though this is a directive associated with the @code{a.out} or
5219 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5220 when producing COFF output, and treats @samp{.line} as though it
5221 were the COFF @samp{.ln} @emph{if} it is found outside a
5222 @code{.def}/@code{.endef} pair.
5224 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5225 used by compilers to generate auxiliary symbol information for
5230 @section @code{.linkonce [@var{type}]}
5232 @cindex @code{linkonce} directive
5233 @cindex common sections
5234 Mark the current section so that the linker only includes a single copy of it.
5235 This may be used to include the same section in several different object files,
5236 but ensure that the linker will only include it once in the final output file.
5237 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5238 Duplicate sections are detected based on the section name, so it should be
5241 This directive is only supported by a few object file formats; as of this
5242 writing, the only object file format which supports it is the Portable
5243 Executable format used on Windows NT.
5245 The @var{type} argument is optional. If specified, it must be one of the
5246 following strings. For example:
5250 Not all types may be supported on all object file formats.
5254 Silently discard duplicate sections. This is the default.
5257 Warn if there are duplicate sections, but still keep only one copy.
5260 Warn if any of the duplicates have different sizes.
5263 Warn if any of the duplicates do not have exactly the same contents.
5267 @section @code{.list}
5269 @cindex @code{list} directive
5270 @cindex listing control, turning on
5271 Control (in conjunction with the @code{.nolist} directive) whether or
5272 not assembly listings are generated. These two directives maintain an
5273 internal counter (which is zero initially). @code{.list} increments the
5274 counter, and @code{.nolist} decrements it. Assembly listings are
5275 generated whenever the counter is greater than zero.
5277 By default, listings are disabled. When you enable them (with the
5278 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5279 the initial value of the listing counter is one.
5282 @section @code{.ln @var{line-number}}
5284 @cindex @code{ln} directive
5285 @ifclear no-line-dir
5286 @samp{.ln} is a synonym for @samp{.line}.
5289 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5290 must be an absolute expression. The next line has that logical
5291 line number, so any other statements on the current line (after a
5292 statement separator character @code{;}) are reported as on logical
5293 line number @var{line-number} @minus{} 1.
5296 This directive is accepted, but ignored, when @command{@value{AS}} is
5297 configured for @code{b.out}; its effect is only associated with COFF
5303 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5304 @cindex @code{loc} directive
5305 When emitting DWARF2 line number information,
5306 the @code{.loc} directive will add a row to the @code{.debug_line} line
5307 number matrix corresponding to the immediately following assembly
5308 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5309 arguments will be applied to the @code{.debug_line} state machine before
5312 The @var{options} are a sequence of the following tokens in any order:
5316 This option will set the @code{basic_block} register in the
5317 @code{.debug_line} state machine to @code{true}.
5320 This option will set the @code{prologue_end} register in the
5321 @code{.debug_line} state machine to @code{true}.
5323 @item epilogue_begin
5324 This option will set the @code{epilogue_begin} register in the
5325 @code{.debug_line} state machine to @code{true}.
5327 @item is_stmt @var{value}
5328 This option will set the @code{is_stmt} register in the
5329 @code{.debug_line} state machine to @code{value}, which must be
5332 @item isa @var{value}
5333 This directive will set the @code{isa} register in the @code{.debug_line}
5334 state machine to @var{value}, which must be an unsigned integer.
5336 @item discriminator @var{value}
5337 This directive will set the @code{discriminator} register in the @code{.debug_line}
5338 state machine to @var{value}, which must be an unsigned integer.
5342 @node Loc_mark_labels
5343 @section @code{.loc_mark_labels @var{enable}}
5344 @cindex @code{loc_mark_labels} directive
5345 When emitting DWARF2 line number information,
5346 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5347 to the @code{.debug_line} line number matrix with the @code{basic_block}
5348 register in the state machine set whenever a code label is seen.
5349 The @var{enable} argument should be either 1 or 0, to enable or disable
5350 this function respectively.
5354 @section @code{.local @var{names}}
5356 @cindex @code{local} directive
5357 This directive, which is available for ELF targets, marks each symbol in
5358 the comma-separated list of @code{names} as a local symbol so that it
5359 will not be externally visible. If the symbols do not already exist,
5360 they will be created.
5362 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5363 accept an alignment argument, which is the case for most ELF targets,
5364 the @code{.local} directive can be used in combination with @code{.comm}
5365 (@pxref{Comm}) to define aligned local common data.
5369 @section @code{.long @var{expressions}}
5371 @cindex @code{long} directive
5372 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5375 @c no one seems to know what this is for or whether this description is
5376 @c what it really ought to do
5378 @section @code{.lsym @var{symbol}, @var{expression}}
5380 @cindex @code{lsym} directive
5381 @cindex symbol, not referenced in assembly
5382 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5383 the hash table, ensuring it cannot be referenced by name during the
5384 rest of the assembly. This sets the attributes of the symbol to be
5385 the same as the expression value:
5387 @var{other} = @var{descriptor} = 0
5388 @var{type} = @r{(section of @var{expression})}
5389 @var{value} = @var{expression}
5392 The new symbol is not flagged as external.
5396 @section @code{.macro}
5399 The commands @code{.macro} and @code{.endm} allow you to define macros that
5400 generate assembly output. For example, this definition specifies a macro
5401 @code{sum} that puts a sequence of numbers into memory:
5404 .macro sum from=0, to=5
5413 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5425 @item .macro @var{macname}
5426 @itemx .macro @var{macname} @var{macargs} @dots{}
5427 @cindex @code{macro} directive
5428 Begin the definition of a macro called @var{macname}. If your macro
5429 definition requires arguments, specify their names after the macro name,
5430 separated by commas or spaces. You can qualify the macro argument to
5431 indicate whether all invocations must specify a non-blank value (through
5432 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5433 (through @samp{:@code{vararg}}). You can supply a default value for any
5434 macro argument by following the name with @samp{=@var{deflt}}. You
5435 cannot define two macros with the same @var{macname} unless it has been
5436 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5437 definitions. For example, these are all valid @code{.macro} statements:
5441 Begin the definition of a macro called @code{comm}, which takes no
5444 @item .macro plus1 p, p1
5445 @itemx .macro plus1 p p1
5446 Either statement begins the definition of a macro called @code{plus1},
5447 which takes two arguments; within the macro definition, write
5448 @samp{\p} or @samp{\p1} to evaluate the arguments.
5450 @item .macro reserve_str p1=0 p2
5451 Begin the definition of a macro called @code{reserve_str}, with two
5452 arguments. The first argument has a default value, but not the second.
5453 After the definition is complete, you can call the macro either as
5454 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5455 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5456 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5457 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5459 @item .macro m p1:req, p2=0, p3:vararg
5460 Begin the definition of a macro called @code{m}, with at least three
5461 arguments. The first argument must always have a value specified, but
5462 not the second, which instead has a default value. The third formal
5463 will get assigned all remaining arguments specified at invocation time.
5465 When you call a macro, you can specify the argument values either by
5466 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5467 @samp{sum to=17, from=9}.
5471 Note that since each of the @var{macargs} can be an identifier exactly
5472 as any other one permitted by the target architecture, there may be
5473 occasional problems if the target hand-crafts special meanings to certain
5474 characters when they occur in a special position. For example, if the colon
5475 (@code{:}) is generally permitted to be part of a symbol name, but the
5476 architecture specific code special-cases it when occurring as the final
5477 character of a symbol (to denote a label), then the macro parameter
5478 replacement code will have no way of knowing that and consider the whole
5479 construct (including the colon) an identifier, and check only this
5480 identifier for being the subject to parameter substitution. So for example
5481 this macro definition:
5489 might not work as expected. Invoking @samp{label foo} might not create a label
5490 called @samp{foo} but instead just insert the text @samp{\l:} into the
5491 assembler source, probably generating an error about an unrecognised
5494 Similarly problems might occur with the period character (@samp{.})
5495 which is often allowed inside opcode names (and hence identifier names). So
5496 for example constructing a macro to build an opcode from a base name and a
5497 length specifier like this:
5500 .macro opcode base length
5505 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5506 instruction but instead generate some kind of error as the assembler tries to
5507 interpret the text @samp{\base.\length}.
5509 There are several possible ways around this problem:
5512 @item Insert white space
5513 If it is possible to use white space characters then this is the simplest
5522 @item Use @samp{\()}
5523 The string @samp{\()} can be used to separate the end of a macro argument from
5524 the following text. eg:
5527 .macro opcode base length
5532 @item Use the alternate macro syntax mode
5533 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5534 used as a separator. eg:
5544 Note: this problem of correctly identifying string parameters to pseudo ops
5545 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5546 and @code{.irpc} (@pxref{Irpc}) as well.
5549 @cindex @code{endm} directive
5550 Mark the end of a macro definition.
5553 @cindex @code{exitm} directive
5554 Exit early from the current macro definition.
5556 @cindex number of macros executed
5557 @cindex macros, count executed
5559 @command{@value{AS}} maintains a counter of how many macros it has
5560 executed in this pseudo-variable; you can copy that number to your
5561 output with @samp{\@@}, but @emph{only within a macro definition}.
5563 @item LOCAL @var{name} [ , @dots{} ]
5564 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5565 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5566 @xref{Altmacro,,@code{.altmacro}}.
5570 @section @code{.mri @var{val}}
5572 @cindex @code{mri} directive
5573 @cindex MRI mode, temporarily
5574 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5575 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5576 affects code assembled until the next @code{.mri} directive, or until the end
5577 of the file. @xref{M, MRI mode, MRI mode}.
5580 @section @code{.noaltmacro}
5581 Disable alternate macro mode. @xref{Altmacro}.
5584 @section @code{.nolist}
5586 @cindex @code{nolist} directive
5587 @cindex listing control, turning off
5588 Control (in conjunction with the @code{.list} directive) whether or
5589 not assembly listings are generated. These two directives maintain an
5590 internal counter (which is zero initially). @code{.list} increments the
5591 counter, and @code{.nolist} decrements it. Assembly listings are
5592 generated whenever the counter is greater than zero.
5595 @section @code{.octa @var{bignums}}
5597 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5598 @cindex @code{octa} directive
5599 @cindex integer, 16-byte
5600 @cindex sixteen byte integer
5601 This directive expects zero or more bignums, separated by commas. For each
5602 bignum, it emits a 16-byte integer.
5604 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5605 hence @emph{octa}-word for 16 bytes.
5608 @section @code{.offset @var{loc}}
5610 @cindex @code{offset} directive
5611 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5612 be an absolute expression. This directive may be useful for defining
5613 symbols with absolute values. Do not confuse it with the @code{.org}
5617 @section @code{.org @var{new-lc} , @var{fill}}
5619 @cindex @code{org} directive
5620 @cindex location counter, advancing
5621 @cindex advancing location counter
5622 @cindex current address, advancing
5623 Advance the location counter of the current section to
5624 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5625 expression with the same section as the current subsection. That is,
5626 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5627 wrong section, the @code{.org} directive is ignored. To be compatible
5628 with former assemblers, if the section of @var{new-lc} is absolute,
5629 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5630 is the same as the current subsection.
5632 @code{.org} may only increase the location counter, or leave it
5633 unchanged; you cannot use @code{.org} to move the location counter
5636 @c double negative used below "not undefined" because this is a specific
5637 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5639 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5640 may not be undefined. If you really detest this restriction we eagerly await
5641 a chance to share your improved assembler.
5643 Beware that the origin is relative to the start of the section, not
5644 to the start of the subsection. This is compatible with other
5645 people's assemblers.
5647 When the location counter (of the current subsection) is advanced, the
5648 intervening bytes are filled with @var{fill} which should be an
5649 absolute expression. If the comma and @var{fill} are omitted,
5650 @var{fill} defaults to zero.
5653 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5655 @cindex padding the location counter given a power of two
5656 @cindex @code{p2align} directive
5657 Pad the location counter (in the current subsection) to a particular
5658 storage boundary. The first expression (which must be absolute) is the
5659 number of low-order zero bits the location counter must have after
5660 advancement. For example @samp{.p2align 3} advances the location
5661 counter until it a multiple of 8. If the location counter is already a
5662 multiple of 8, no change is needed.
5664 The second expression (also absolute) gives the fill value to be stored in the
5665 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5666 padding bytes are normally zero. However, on some systems, if the section is
5667 marked as containing code and the fill value is omitted, the space is filled
5668 with no-op instructions.
5670 The third expression is also absolute, and is also optional. If it is present,
5671 it is the maximum number of bytes that should be skipped by this alignment
5672 directive. If doing the alignment would require skipping more bytes than the
5673 specified maximum, then the alignment is not done at all. You can omit the
5674 fill value (the second argument) entirely by simply using two commas after the
5675 required alignment; this can be useful if you want the alignment to be filled
5676 with no-op instructions when appropriate.
5678 @cindex @code{p2alignw} directive
5679 @cindex @code{p2alignl} directive
5680 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5681 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5682 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5683 fill pattern as a four byte longword value. For example, @code{.p2alignw
5684 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5685 filled in with the value 0x368d (the exact placement of the bytes depends upon
5686 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5691 @section @code{.popsection}
5693 @cindex @code{popsection} directive
5694 @cindex Section Stack
5695 This is one of the ELF section stack manipulation directives. The others are
5696 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5697 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5700 This directive replaces the current section (and subsection) with the top
5701 section (and subsection) on the section stack. This section is popped off the
5707 @section @code{.previous}
5709 @cindex @code{previous} directive
5710 @cindex Section Stack
5711 This is one of the ELF section stack manipulation directives. The others are
5712 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5713 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5714 (@pxref{PopSection}).
5716 This directive swaps the current section (and subsection) with most recently
5717 referenced section/subsection pair prior to this one. Multiple
5718 @code{.previous} directives in a row will flip between two sections (and their
5719 subsections). For example:
5731 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5737 # Now in section A subsection 1
5741 # Now in section B subsection 0
5744 # Now in section B subsection 1
5747 # Now in section B subsection 0
5751 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5752 section B and 0x9abc into subsection 1 of section B.
5754 In terms of the section stack, this directive swaps the current section with
5755 the top section on the section stack.
5759 @section @code{.print @var{string}}
5761 @cindex @code{print} directive
5762 @command{@value{AS}} will print @var{string} on the standard output during
5763 assembly. You must put @var{string} in double quotes.
5767 @section @code{.protected @var{names}}
5769 @cindex @code{protected} directive
5771 This is one of the ELF visibility directives. The other two are
5772 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5774 This directive overrides the named symbols default visibility (which is set by
5775 their binding: local, global or weak). The directive sets the visibility to
5776 @code{protected} which means that any references to the symbols from within the
5777 components that defines them must be resolved to the definition in that
5778 component, even if a definition in another component would normally preempt
5783 @section @code{.psize @var{lines} , @var{columns}}
5785 @cindex @code{psize} directive
5786 @cindex listing control: paper size
5787 @cindex paper size, for listings
5788 Use this directive to declare the number of lines---and, optionally, the
5789 number of columns---to use for each page, when generating listings.
5791 If you do not use @code{.psize}, listings use a default line-count
5792 of 60. You may omit the comma and @var{columns} specification; the
5793 default width is 200 columns.
5795 @command{@value{AS}} generates formfeeds whenever the specified number of
5796 lines is exceeded (or whenever you explicitly request one, using
5799 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5800 those explicitly specified with @code{.eject}.
5803 @section @code{.purgem @var{name}}
5805 @cindex @code{purgem} directive
5806 Undefine the macro @var{name}, so that later uses of the string will not be
5807 expanded. @xref{Macro}.
5811 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5813 @cindex @code{pushsection} directive
5814 @cindex Section Stack
5815 This is one of the ELF section stack manipulation directives. The others are
5816 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5817 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5820 This directive pushes the current section (and subsection) onto the
5821 top of the section stack, and then replaces the current section and
5822 subsection with @code{name} and @code{subsection}. The optional
5823 @code{flags}, @code{type} and @code{arguments} are treated the same
5824 as in the @code{.section} (@pxref{Section}) directive.
5828 @section @code{.quad @var{bignums}}
5830 @cindex @code{quad} directive
5831 @code{.quad} expects zero or more bignums, separated by commas. For
5832 each bignum, it emits
5834 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5835 warning message; and just takes the lowest order 8 bytes of the bignum.
5836 @cindex eight-byte integer
5837 @cindex integer, 8-byte
5839 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5840 hence @emph{quad}-word for 8 bytes.
5843 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5844 warning message; and just takes the lowest order 16 bytes of the bignum.
5845 @cindex sixteen-byte integer
5846 @cindex integer, 16-byte
5850 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5852 @cindex @code{reloc} directive
5853 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5854 @var{expression}. If @var{offset} is a number, the relocation is generated in
5855 the current section. If @var{offset} is an expression that resolves to a
5856 symbol plus offset, the relocation is generated in the given symbol's section.
5857 @var{expression}, if present, must resolve to a symbol plus addend or to an
5858 absolute value, but note that not all targets support an addend. e.g. ELF REL
5859 targets such as i386 store an addend in the section contents rather than in the
5860 relocation. This low level interface does not support addends stored in the
5864 @section @code{.rept @var{count}}
5866 @cindex @code{rept} directive
5867 Repeat the sequence of lines between the @code{.rept} directive and the next
5868 @code{.endr} directive @var{count} times.
5870 For example, assembling
5878 is equivalent to assembling
5887 @section @code{.sbttl "@var{subheading}"}
5889 @cindex @code{sbttl} directive
5890 @cindex subtitles for listings
5891 @cindex listing control: subtitle
5892 Use @var{subheading} as the title (third line, immediately after the
5893 title line) when generating assembly listings.
5895 This directive affects subsequent pages, as well as the current page if
5896 it appears within ten lines of the top of a page.
5900 @section @code{.scl @var{class}}
5902 @cindex @code{scl} directive
5903 @cindex symbol storage class (COFF)
5904 @cindex COFF symbol storage class
5905 Set the storage-class value for a symbol. This directive may only be
5906 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5907 whether a symbol is static or external, or it may record further
5908 symbolic debugging information.
5911 The @samp{.scl} directive is primarily associated with COFF output; when
5912 configured to generate @code{b.out} output format, @command{@value{AS}}
5913 accepts this directive but ignores it.
5919 @section @code{.section @var{name}}
5921 @cindex named section
5922 Use the @code{.section} directive to assemble the following code into a section
5925 This directive is only supported for targets that actually support arbitrarily
5926 named sections; on @code{a.out} targets, for example, it is not accepted, even
5927 with a standard @code{a.out} section name.
5931 @c only print the extra heading if both COFF and ELF are set
5932 @subheading COFF Version
5935 @cindex @code{section} directive (COFF version)
5936 For COFF targets, the @code{.section} directive is used in one of the following
5940 .section @var{name}[, "@var{flags}"]
5941 .section @var{name}[, @var{subsection}]
5944 If the optional argument is quoted, it is taken as flags to use for the
5945 section. Each flag is a single character. The following flags are recognized:
5948 bss section (uninitialized data)
5950 section is not loaded
5960 shared section (meaningful for PE targets)
5962 ignored. (For compatibility with the ELF version)
5964 section is not readable (meaningful for PE targets)
5966 single-digit power-of-two section alignment (GNU extension)
5969 If no flags are specified, the default flags depend upon the section name. If
5970 the section name is not recognized, the default will be for the section to be
5971 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5972 from the section, rather than adding them, so if they are used on their own it
5973 will be as if no flags had been specified at all.
5975 If the optional argument to the @code{.section} directive is not quoted, it is
5976 taken as a subsection number (@pxref{Sub-Sections}).
5981 @c only print the extra heading if both COFF and ELF are set
5982 @subheading ELF Version
5985 @cindex Section Stack
5986 This is one of the ELF section stack manipulation directives. The others are
5987 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5988 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5989 @code{.previous} (@pxref{Previous}).
5991 @cindex @code{section} directive (ELF version)
5992 For ELF targets, the @code{.section} directive is used like this:
5995 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5998 The optional @var{flags} argument is a quoted string which may contain any
5999 combination of the following characters:
6002 section is allocatable
6004 section is excluded from executable and shared library.
6008 section is executable
6010 section is mergeable
6012 section contains zero terminated strings
6014 section is a member of a section group
6016 section is used for thread-local-storage
6018 section is a member of the previously-current section's group, if any
6021 The optional @var{type} argument may contain one of the following constants:
6024 section contains data
6026 section does not contain data (i.e., section only occupies space)
6028 section contains data which is used by things other than the program
6030 section contains an array of pointers to init functions
6032 section contains an array of pointers to finish functions
6033 @item @@preinit_array
6034 section contains an array of pointers to pre-init functions
6037 Many targets only support the first three section types.
6039 Note on targets where the @code{@@} character is the start of a comment (eg
6040 ARM) then another character is used instead. For example the ARM port uses the
6043 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6044 be specified as well as an extra argument---@var{entsize}---like this:
6047 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6050 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6051 constants, each @var{entsize} octets long. Sections with both @code{M} and
6052 @code{S} must contain zero terminated strings where each character is
6053 @var{entsize} bytes long. The linker may remove duplicates within sections with
6054 the same name, same entity size and same flags. @var{entsize} must be an
6055 absolute expression. For sections with both @code{M} and @code{S}, a string
6056 which is a suffix of a larger string is considered a duplicate. Thus
6057 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6058 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6060 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6061 be present along with an additional field like this:
6064 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6067 The @var{GroupName} field specifies the name of the section group to which this
6068 particular section belongs. The optional linkage field can contain:
6071 indicates that only one copy of this section should be retained
6076 Note: if both the @var{M} and @var{G} flags are present then the fields for
6077 the Merge flag should come first, like this:
6080 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6083 If @var{flags} contains the @code{?} symbol then it may not also contain the
6084 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6085 present. Instead, @code{?} says to consider the section that's current before
6086 this directive. If that section used @code{G}, then the new section will use
6087 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6088 If not, then the @code{?} symbol has no effect.
6090 If no flags are specified, the default flags depend upon the section name. If
6091 the section name is not recognized, the default will be for the section to have
6092 none of the above flags: it will not be allocated in memory, nor writable, nor
6093 executable. The section will contain data.
6095 For ELF targets, the assembler supports another type of @code{.section}
6096 directive for compatibility with the Solaris assembler:
6099 .section "@var{name}"[, @var{flags}...]
6102 Note that the section name is quoted. There may be a sequence of comma
6106 section is allocatable
6110 section is executable
6112 section is excluded from executable and shared library.
6114 section is used for thread local storage
6117 This directive replaces the current section and subsection. See the
6118 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6119 some examples of how this directive and the other section stack directives
6125 @section @code{.set @var{symbol}, @var{expression}}
6127 @cindex @code{set} directive
6128 @cindex symbol value, setting
6129 Set the value of @var{symbol} to @var{expression}. This
6130 changes @var{symbol}'s value and type to conform to
6131 @var{expression}. If @var{symbol} was flagged as external, it remains
6132 flagged (@pxref{Symbol Attributes}).
6134 You may @code{.set} a symbol many times in the same assembly.
6136 If you @code{.set} a global symbol, the value stored in the object
6137 file is the last value stored into it.
6140 On Z80 @code{set} is a real instruction, use
6141 @samp{@var{symbol} defl @var{expression}} instead.
6145 @section @code{.short @var{expressions}}
6147 @cindex @code{short} directive
6149 @code{.short} is normally the same as @samp{.word}.
6150 @xref{Word,,@code{.word}}.
6152 In some configurations, however, @code{.short} and @code{.word} generate
6153 numbers of different lengths. @xref{Machine Dependencies}.
6157 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6160 This expects zero or more @var{expressions}, and emits
6161 a 16 bit number for each.
6166 @section @code{.single @var{flonums}}
6168 @cindex @code{single} directive
6169 @cindex floating point numbers (single)
6170 This directive assembles zero or more flonums, separated by commas. It
6171 has the same effect as @code{.float}.
6173 The exact kind of floating point numbers emitted depends on how
6174 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6178 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6179 numbers in @sc{ieee} format.
6185 @section @code{.size}
6187 This directive is used to set the size associated with a symbol.
6191 @c only print the extra heading if both COFF and ELF are set
6192 @subheading COFF Version
6195 @cindex @code{size} directive (COFF version)
6196 For COFF targets, the @code{.size} directive is only permitted inside
6197 @code{.def}/@code{.endef} pairs. It is used like this:
6200 .size @var{expression}
6204 @samp{.size} is only meaningful when generating COFF format output; when
6205 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6212 @c only print the extra heading if both COFF and ELF are set
6213 @subheading ELF Version
6216 @cindex @code{size} directive (ELF version)
6217 For ELF targets, the @code{.size} directive is used like this:
6220 .size @var{name} , @var{expression}
6223 This directive sets the size associated with a symbol @var{name}.
6224 The size in bytes is computed from @var{expression} which can make use of label
6225 arithmetic. This directive is typically used to set the size of function
6230 @ifclear no-space-dir
6232 @section @code{.skip @var{size} , @var{fill}}
6234 @cindex @code{skip} directive
6235 @cindex filling memory
6236 This directive emits @var{size} bytes, each of value @var{fill}. Both
6237 @var{size} and @var{fill} are absolute expressions. If the comma and
6238 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6243 @section @code{.sleb128 @var{expressions}}
6245 @cindex @code{sleb128} directive
6246 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6247 compact, variable length representation of numbers used by the DWARF
6248 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6250 @ifclear no-space-dir
6252 @section @code{.space @var{size} , @var{fill}}
6254 @cindex @code{space} directive
6255 @cindex filling memory
6256 This directive emits @var{size} bytes, each of value @var{fill}. Both
6257 @var{size} and @var{fill} are absolute expressions. If the comma
6258 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6263 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6264 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6265 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6266 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6274 @section @code{.stabd, .stabn, .stabs}
6276 @cindex symbolic debuggers, information for
6277 @cindex @code{stab@var{x}} directives
6278 There are three directives that begin @samp{.stab}.
6279 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6280 The symbols are not entered in the @command{@value{AS}} hash table: they
6281 cannot be referenced elsewhere in the source file.
6282 Up to five fields are required:
6286 This is the symbol's name. It may contain any character except
6287 @samp{\000}, so is more general than ordinary symbol names. Some
6288 debuggers used to code arbitrarily complex structures into symbol names
6292 An absolute expression. The symbol's type is set to the low 8 bits of
6293 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6294 and debuggers choke on silly bit patterns.
6297 An absolute expression. The symbol's ``other'' attribute is set to the
6298 low 8 bits of this expression.
6301 An absolute expression. The symbol's descriptor is set to the low 16
6302 bits of this expression.
6305 An absolute expression which becomes the symbol's value.
6308 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6309 or @code{.stabs} statement, the symbol has probably already been created;
6310 you get a half-formed symbol in your object file. This is
6311 compatible with earlier assemblers!
6314 @cindex @code{stabd} directive
6315 @item .stabd @var{type} , @var{other} , @var{desc}
6317 The ``name'' of the symbol generated is not even an empty string.
6318 It is a null pointer, for compatibility. Older assemblers used a
6319 null pointer so they didn't waste space in object files with empty
6322 The symbol's value is set to the location counter,
6323 relocatably. When your program is linked, the value of this symbol
6324 is the address of the location counter when the @code{.stabd} was
6327 @cindex @code{stabn} directive
6328 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6329 The name of the symbol is set to the empty string @code{""}.
6331 @cindex @code{stabs} directive
6332 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6333 All five fields are specified.
6339 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6340 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6342 @cindex string, copying to object file
6343 @cindex string8, copying to object file
6344 @cindex string16, copying to object file
6345 @cindex string32, copying to object file
6346 @cindex string64, copying to object file
6347 @cindex @code{string} directive
6348 @cindex @code{string8} directive
6349 @cindex @code{string16} directive
6350 @cindex @code{string32} directive
6351 @cindex @code{string64} directive
6353 Copy the characters in @var{str} to the object file. You may specify more than
6354 one string to copy, separated by commas. Unless otherwise specified for a
6355 particular machine, the assembler marks the end of each string with a 0 byte.
6356 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6358 The variants @code{string16}, @code{string32} and @code{string64} differ from
6359 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6360 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6361 are stored in target endianness byte order.
6367 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6368 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6373 @section @code{.struct @var{expression}}
6375 @cindex @code{struct} directive
6376 Switch to the absolute section, and set the section offset to @var{expression},
6377 which must be an absolute expression. You might use this as follows:
6386 This would define the symbol @code{field1} to have the value 0, the symbol
6387 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6388 value 8. Assembly would be left in the absolute section, and you would need to
6389 use a @code{.section} directive of some sort to change to some other section
6390 before further assembly.
6394 @section @code{.subsection @var{name}}
6396 @cindex @code{subsection} directive
6397 @cindex Section Stack
6398 This is one of the ELF section stack manipulation directives. The others are
6399 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6400 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6403 This directive replaces the current subsection with @code{name}. The current
6404 section is not changed. The replaced subsection is put onto the section stack
6405 in place of the then current top of stack subsection.
6410 @section @code{.symver}
6411 @cindex @code{symver} directive
6412 @cindex symbol versioning
6413 @cindex versions of symbols
6414 Use the @code{.symver} directive to bind symbols to specific version nodes
6415 within a source file. This is only supported on ELF platforms, and is
6416 typically used when assembling files to be linked into a shared library.
6417 There are cases where it may make sense to use this in objects to be bound
6418 into an application itself so as to override a versioned symbol from a
6421 For ELF targets, the @code{.symver} directive can be used like this:
6423 .symver @var{name}, @var{name2@@nodename}
6425 If the symbol @var{name} is defined within the file
6426 being assembled, the @code{.symver} directive effectively creates a symbol
6427 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6428 just don't try and create a regular alias is that the @var{@@} character isn't
6429 permitted in symbol names. The @var{name2} part of the name is the actual name
6430 of the symbol by which it will be externally referenced. The name @var{name}
6431 itself is merely a name of convenience that is used so that it is possible to
6432 have definitions for multiple versions of a function within a single source
6433 file, and so that the compiler can unambiguously know which version of a
6434 function is being mentioned. The @var{nodename} portion of the alias should be
6435 the name of a node specified in the version script supplied to the linker when
6436 building a shared library. If you are attempting to override a versioned
6437 symbol from a shared library, then @var{nodename} should correspond to the
6438 nodename of the symbol you are trying to override.
6440 If the symbol @var{name} is not defined within the file being assembled, all
6441 references to @var{name} will be changed to @var{name2@@nodename}. If no
6442 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6445 Another usage of the @code{.symver} directive is:
6447 .symver @var{name}, @var{name2@@@@nodename}
6449 In this case, the symbol @var{name} must exist and be defined within
6450 the file being assembled. It is similar to @var{name2@@nodename}. The
6451 difference is @var{name2@@@@nodename} will also be used to resolve
6452 references to @var{name2} by the linker.
6454 The third usage of the @code{.symver} directive is:
6456 .symver @var{name}, @var{name2@@@@@@nodename}
6458 When @var{name} is not defined within the
6459 file being assembled, it is treated as @var{name2@@nodename}. When
6460 @var{name} is defined within the file being assembled, the symbol
6461 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6466 @section @code{.tag @var{structname}}
6468 @cindex COFF structure debugging
6469 @cindex structure debugging, COFF
6470 @cindex @code{tag} directive
6471 This directive is generated by compilers to include auxiliary debugging
6472 information in the symbol table. It is only permitted inside
6473 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6474 definitions in the symbol table with instances of those structures.
6477 @samp{.tag} is only used when generating COFF format output; when
6478 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6484 @section @code{.text @var{subsection}}
6486 @cindex @code{text} directive
6487 Tells @command{@value{AS}} to assemble the following statements onto the end of
6488 the text subsection numbered @var{subsection}, which is an absolute
6489 expression. If @var{subsection} is omitted, subsection number zero
6493 @section @code{.title "@var{heading}"}
6495 @cindex @code{title} directive
6496 @cindex listing control: title line
6497 Use @var{heading} as the title (second line, immediately after the
6498 source file name and pagenumber) when generating assembly listings.
6500 This directive affects subsequent pages, as well as the current page if
6501 it appears within ten lines of the top of a page.
6505 @section @code{.type}
6507 This directive is used to set the type of a symbol.
6511 @c only print the extra heading if both COFF and ELF are set
6512 @subheading COFF Version
6515 @cindex COFF symbol type
6516 @cindex symbol type, COFF
6517 @cindex @code{type} directive (COFF version)
6518 For COFF targets, this directive is permitted only within
6519 @code{.def}/@code{.endef} pairs. It is used like this:
6525 This records the integer @var{int} as the type attribute of a symbol table
6529 @samp{.type} is associated only with COFF format output; when
6530 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6531 directive but ignores it.
6537 @c only print the extra heading if both COFF and ELF are set
6538 @subheading ELF Version
6541 @cindex ELF symbol type
6542 @cindex symbol type, ELF
6543 @cindex @code{type} directive (ELF version)
6544 For ELF targets, the @code{.type} directive is used like this:
6547 .type @var{name} , @var{type description}
6550 This sets the type of symbol @var{name} to be either a
6551 function symbol or an object symbol. There are five different syntaxes
6552 supported for the @var{type description} field, in order to provide
6553 compatibility with various other assemblers.
6555 Because some of the characters used in these syntaxes (such as @samp{@@} and
6556 @samp{#}) are comment characters for some architectures, some of the syntaxes
6557 below do not work on all architectures. The first variant will be accepted by
6558 the GNU assembler on all architectures so that variant should be used for
6559 maximum portability, if you do not need to assemble your code with other
6562 The syntaxes supported are:
6565 .type <name> STT_<TYPE_IN_UPPER_CASE>
6566 .type <name>,#<type>
6567 .type <name>,@@<type>
6568 .type <name>,%<type>
6569 .type <name>,"<type>"
6572 The types supported are:
6577 Mark the symbol as being a function name.
6580 @itemx gnu_indirect_function
6581 Mark the symbol as an indirect function when evaluated during reloc
6582 processing. (This is only supported on assemblers targeting GNU systems).
6586 Mark the symbol as being a data object.
6590 Mark the symbol as being a thead-local data object.
6594 Mark the symbol as being a common data object.
6598 Does not mark the symbol in any way. It is supported just for completeness.
6600 @item gnu_unique_object
6601 Marks the symbol as being a globally unique data object. The dynamic linker
6602 will make sure that in the entire process there is just one symbol with this
6603 name and type in use. (This is only supported on assemblers targeting GNU
6608 Note: Some targets support extra types in addition to those listed above.
6614 @section @code{.uleb128 @var{expressions}}
6616 @cindex @code{uleb128} directive
6617 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6618 compact, variable length representation of numbers used by the DWARF
6619 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6623 @section @code{.val @var{addr}}
6625 @cindex @code{val} directive
6626 @cindex COFF value attribute
6627 @cindex value attribute, COFF
6628 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6629 records the address @var{addr} as the value attribute of a symbol table
6633 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6634 configured for @code{b.out}, it accepts this directive but ignores it.
6640 @section @code{.version "@var{string}"}
6642 @cindex @code{version} directive
6643 This directive creates a @code{.note} section and places into it an ELF
6644 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6649 @section @code{.vtable_entry @var{table}, @var{offset}}
6651 @cindex @code{vtable_entry} directive
6652 This directive finds or creates a symbol @code{table} and creates a
6653 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6656 @section @code{.vtable_inherit @var{child}, @var{parent}}
6658 @cindex @code{vtable_inherit} directive
6659 This directive finds the symbol @code{child} and finds or creates the symbol
6660 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6661 parent whose addend is the value of the child symbol. As a special case the
6662 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6666 @section @code{.warning "@var{string}"}
6667 @cindex warning directive
6668 Similar to the directive @code{.error}
6669 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6672 @section @code{.weak @var{names}}
6674 @cindex @code{weak} directive
6675 This directive sets the weak attribute on the comma separated list of symbol
6676 @code{names}. If the symbols do not already exist, they will be created.
6678 On COFF targets other than PE, weak symbols are a GNU extension. This
6679 directive sets the weak attribute on the comma separated list of symbol
6680 @code{names}. If the symbols do not already exist, they will be created.
6682 On the PE target, weak symbols are supported natively as weak aliases.
6683 When a weak symbol is created that is not an alias, GAS creates an
6684 alternate symbol to hold the default value.
6687 @section @code{.weakref @var{alias}, @var{target}}
6689 @cindex @code{weakref} directive
6690 This directive creates an alias to the target symbol that enables the symbol to
6691 be referenced with weak-symbol semantics, but without actually making it weak.
6692 If direct references or definitions of the symbol are present, then the symbol
6693 will not be weak, but if all references to it are through weak references, the
6694 symbol will be marked as weak in the symbol table.
6696 The effect is equivalent to moving all references to the alias to a separate
6697 assembly source file, renaming the alias to the symbol in it, declaring the
6698 symbol as weak there, and running a reloadable link to merge the object files
6699 resulting from the assembly of the new source file and the old source file that
6700 had the references to the alias removed.
6702 The alias itself never makes to the symbol table, and is entirely handled
6703 within the assembler.
6706 @section @code{.word @var{expressions}}
6708 @cindex @code{word} directive
6709 This directive expects zero or more @var{expressions}, of any section,
6710 separated by commas.
6713 For each expression, @command{@value{AS}} emits a 32-bit number.
6716 For each expression, @command{@value{AS}} emits a 16-bit number.
6721 The size of the number emitted, and its byte order,
6722 depend on what target computer the assembly is for.
6725 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6726 @c happen---32-bit addressability, period; no long/short jumps.
6727 @ifset DIFF-TBL-KLUGE
6728 @cindex difference tables altered
6729 @cindex altered difference tables
6731 @emph{Warning: Special Treatment to support Compilers}
6735 Machines with a 32-bit address space, but that do less than 32-bit
6736 addressing, require the following special treatment. If the machine of
6737 interest to you does 32-bit addressing (or doesn't require it;
6738 @pxref{Machine Dependencies}), you can ignore this issue.
6741 In order to assemble compiler output into something that works,
6742 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6743 Directives of the form @samp{.word sym1-sym2} are often emitted by
6744 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6745 directive of the form @samp{.word sym1-sym2}, and the difference between
6746 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6747 creates a @dfn{secondary jump table}, immediately before the next label.
6748 This secondary jump table is preceded by a short-jump to the
6749 first byte after the secondary table. This short-jump prevents the flow
6750 of control from accidentally falling into the new table. Inside the
6751 table is a long-jump to @code{sym2}. The original @samp{.word}
6752 contains @code{sym1} minus the address of the long-jump to
6755 If there were several occurrences of @samp{.word sym1-sym2} before the
6756 secondary jump table, all of them are adjusted. If there was a
6757 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6758 long-jump to @code{sym4} is included in the secondary jump table,
6759 and the @code{.word} directives are adjusted to contain @code{sym3}
6760 minus the address of the long-jump to @code{sym4}; and so on, for as many
6761 entries in the original jump table as necessary.
6764 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6765 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6766 assembly language programmers.
6769 @c end DIFF-TBL-KLUGE
6772 @section Deprecated Directives
6774 @cindex deprecated directives
6775 @cindex obsolescent directives
6776 One day these directives won't work.
6777 They are included for compatibility with older assemblers.
6784 @node Object Attributes
6785 @chapter Object Attributes
6786 @cindex object attributes
6788 @command{@value{AS}} assembles source files written for a specific architecture
6789 into object files for that architecture. But not all object files are alike.
6790 Many architectures support incompatible variations. For instance, floating
6791 point arguments might be passed in floating point registers if the object file
6792 requires hardware floating point support---or floating point arguments might be
6793 passed in integer registers if the object file supports processors with no
6794 hardware floating point unit. Or, if two objects are built for different
6795 generations of the same architecture, the combination may require the
6796 newer generation at run-time.
6798 This information is useful during and after linking. At link time,
6799 @command{@value{LD}} can warn about incompatible object files. After link
6800 time, tools like @command{gdb} can use it to process the linked file
6803 Compatibility information is recorded as a series of object attributes. Each
6804 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6805 string, and indicates who sets the meaning of the tag. The tag is an integer,
6806 and indicates what property the attribute describes. The value may be a string
6807 or an integer, and indicates how the property affects this object. Missing
6808 attributes are the same as attributes with a zero value or empty string value.
6810 Object attributes were developed as part of the ABI for the ARM Architecture.
6811 The file format is documented in @cite{ELF for the ARM Architecture}.
6814 * GNU Object Attributes:: @sc{gnu} Object Attributes
6815 * Defining New Object Attributes:: Defining New Object Attributes
6818 @node GNU Object Attributes
6819 @section @sc{gnu} Object Attributes
6821 The @code{.gnu_attribute} directive records an object attribute
6822 with vendor @samp{gnu}.
6824 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6825 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6826 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6827 2} is set for architecture-independent attributes and clear for
6828 architecture-dependent ones.
6830 @subsection Common @sc{gnu} attributes
6832 These attributes are valid on all architectures.
6835 @item Tag_compatibility (32)
6836 The compatibility attribute takes an integer flag value and a vendor name. If
6837 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6838 then the file is only compatible with the named toolchain. If it is greater
6839 than 1, the file can only be processed by other toolchains under some private
6840 arrangement indicated by the flag value and the vendor name.
6843 @subsection MIPS Attributes
6846 @item Tag_GNU_MIPS_ABI_FP (4)
6847 The floating-point ABI used by this object file. The value will be:
6851 0 for files not affected by the floating-point ABI.
6853 1 for files using the hardware floating-point with a standard double-precision
6856 2 for files using the hardware floating-point ABI with a single-precision FPU.
6858 3 for files using the software floating-point ABI.
6860 4 for files using the hardware floating-point ABI with 64-bit wide
6861 double-precision floating-point registers and 32-bit wide general
6866 @subsection PowerPC Attributes
6869 @item Tag_GNU_Power_ABI_FP (4)
6870 The floating-point ABI used by this object file. The value will be:
6874 0 for files not affected by the floating-point ABI.
6876 1 for files using double-precision hardware floating-point ABI.
6878 2 for files using the software floating-point ABI.
6880 3 for files using single-precision hardware floating-point ABI.
6883 @item Tag_GNU_Power_ABI_Vector (8)
6884 The vector ABI used by this object file. The value will be:
6888 0 for files not affected by the vector ABI.
6890 1 for files using general purpose registers to pass vectors.
6892 2 for files using AltiVec registers to pass vectors.
6894 3 for files using SPE registers to pass vectors.
6898 @node Defining New Object Attributes
6899 @section Defining New Object Attributes
6901 If you want to define a new @sc{gnu} object attribute, here are the places you
6902 will need to modify. New attributes should be discussed on the @samp{binutils}
6907 This manual, which is the official register of attributes.
6909 The header for your architecture @file{include/elf}, to define the tag.
6911 The @file{bfd} support file for your architecture, to merge the attribute
6912 and issue any appropriate link warnings.
6914 Test cases in @file{ld/testsuite} for merging and link warnings.
6916 @file{binutils/readelf.c} to display your attribute.
6918 GCC, if you want the compiler to mark the attribute automatically.
6924 @node Machine Dependencies
6925 @chapter Machine Dependent Features
6927 @cindex machine dependencies
6928 The machine instruction sets are (almost by definition) different on
6929 each machine where @command{@value{AS}} runs. Floating point representations
6930 vary as well, and @command{@value{AS}} often supports a few additional
6931 directives or command-line options for compatibility with other
6932 assemblers on a particular platform. Finally, some versions of
6933 @command{@value{AS}} support special pseudo-instructions for branch
6936 This chapter discusses most of these differences, though it does not
6937 include details on any machine's instruction set. For details on that
6938 subject, see the hardware manufacturer's manual.
6942 * AArch64-Dependent:: AArch64 Dependent Features
6945 * Alpha-Dependent:: Alpha Dependent Features
6948 * ARC-Dependent:: ARC Dependent Features
6951 * ARM-Dependent:: ARM Dependent Features
6954 * AVR-Dependent:: AVR Dependent Features
6957 * Blackfin-Dependent:: Blackfin Dependent Features
6960 * CR16-Dependent:: CR16 Dependent Features
6963 * CRIS-Dependent:: CRIS Dependent Features
6966 * D10V-Dependent:: D10V Dependent Features
6969 * D30V-Dependent:: D30V Dependent Features
6972 * Epiphany-Dependent:: EPIPHANY Dependent Features
6975 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6978 * HPPA-Dependent:: HPPA Dependent Features
6981 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6984 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6987 * i860-Dependent:: Intel 80860 Dependent Features
6990 * i960-Dependent:: Intel 80960 Dependent Features
6993 * IA-64-Dependent:: Intel IA-64 Dependent Features
6996 * IP2K-Dependent:: IP2K Dependent Features
6999 * LM32-Dependent:: LM32 Dependent Features
7002 * M32C-Dependent:: M32C Dependent Features
7005 * M32R-Dependent:: M32R Dependent Features
7008 * M68K-Dependent:: M680x0 Dependent Features
7011 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7014 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7017 * MIPS-Dependent:: MIPS Dependent Features
7020 * MMIX-Dependent:: MMIX Dependent Features
7023 * MSP430-Dependent:: MSP430 Dependent Features
7026 * NS32K-Dependent:: NS32K Dependent Features
7029 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7030 * SH64-Dependent:: SuperH SH64 Dependent Features
7033 * PDP-11-Dependent:: PDP-11 Dependent Features
7036 * PJ-Dependent:: picoJava Dependent Features
7039 * PPC-Dependent:: PowerPC Dependent Features
7042 * RL78-Dependent:: RL78 Dependent Features
7045 * RX-Dependent:: RX Dependent Features
7048 * S/390-Dependent:: IBM S/390 Dependent Features
7051 * SCORE-Dependent:: SCORE Dependent Features
7054 * Sparc-Dependent:: SPARC Dependent Features
7057 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7060 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7063 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7066 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7069 * V850-Dependent:: V850 Dependent Features
7072 * XGATE-Dependent:: XGATE Features
7075 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7078 * Xtensa-Dependent:: Xtensa Dependent Features
7081 * Z80-Dependent:: Z80 Dependent Features
7084 * Z8000-Dependent:: Z8000 Dependent Features
7087 * Vax-Dependent:: VAX Dependent Features
7094 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7095 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7096 @c peculiarity: to preserve cross-references, there must be a node called
7097 @c "Machine Dependencies". Hence the conditional nodenames in each
7098 @c major node below. Node defaulting in makeinfo requires adjacency of
7099 @c node and sectioning commands; hence the repetition of @chapter BLAH
7100 @c in both conditional blocks.
7103 @include c-aarch64.texi
7107 @include c-alpha.texi
7123 @include c-bfin.texi
7127 @include c-cr16.texi
7131 @include c-cris.texi
7136 @node Machine Dependencies
7137 @chapter Machine Dependent Features
7139 The machine instruction sets are different on each Renesas chip family,
7140 and there are also some syntax differences among the families. This
7141 chapter describes the specific @command{@value{AS}} features for each
7145 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7146 * SH-Dependent:: Renesas SH Dependent Features
7153 @include c-d10v.texi
7157 @include c-d30v.texi
7161 @include c-epiphany.texi
7165 @include c-h8300.texi
7169 @include c-hppa.texi
7173 @include c-i370.texi
7177 @include c-i386.texi
7181 @include c-i860.texi
7185 @include c-i960.texi
7189 @include c-ia64.texi
7193 @include c-ip2k.texi
7197 @include c-lm32.texi
7201 @include c-m32c.texi
7205 @include c-m32r.texi
7209 @include c-m68k.texi
7213 @include c-m68hc11.texi
7217 @include c-microblaze.texi
7221 @include c-mips.texi
7225 @include c-mmix.texi
7229 @include c-msp430.texi
7233 @include c-ns32k.texi
7237 @include c-pdp11.texi
7249 @include c-rl78.texi
7257 @include c-s390.texi
7261 @include c-score.texi
7266 @include c-sh64.texi
7270 @include c-sparc.texi
7274 @include c-tic54x.texi
7278 @include c-tic6x.texi
7282 @include c-tilegx.texi
7286 @include c-tilepro.texi
7302 @include c-v850.texi
7306 @include c-xgate.texi
7310 @include c-xstormy16.texi
7314 @include c-xtensa.texi
7318 @c reverse effect of @down at top of generic Machine-Dep chapter
7322 @node Reporting Bugs
7323 @chapter Reporting Bugs
7324 @cindex bugs in assembler
7325 @cindex reporting bugs in assembler
7327 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7329 Reporting a bug may help you by bringing a solution to your problem, or it may
7330 not. But in any case the principal function of a bug report is to help the
7331 entire community by making the next version of @command{@value{AS}} work better.
7332 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7334 In order for a bug report to serve its purpose, you must include the
7335 information that enables us to fix the bug.
7338 * Bug Criteria:: Have you found a bug?
7339 * Bug Reporting:: How to report bugs
7343 @section Have You Found a Bug?
7344 @cindex bug criteria
7346 If you are not sure whether you have found a bug, here are some guidelines:
7349 @cindex fatal signal
7350 @cindex assembler crash
7351 @cindex crash of assembler
7353 If the assembler gets a fatal signal, for any input whatever, that is a
7354 @command{@value{AS}} bug. Reliable assemblers never crash.
7356 @cindex error on valid input
7358 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7360 @cindex invalid input
7362 If @command{@value{AS}} does not produce an error message for invalid input, that
7363 is a bug. However, you should note that your idea of ``invalid input'' might
7364 be our idea of ``an extension'' or ``support for traditional practice''.
7367 If you are an experienced user of assemblers, your suggestions for improvement
7368 of @command{@value{AS}} are welcome in any case.
7372 @section How to Report Bugs
7374 @cindex assembler bugs, reporting
7376 A number of companies and individuals offer support for @sc{gnu} products. If
7377 you obtained @command{@value{AS}} from a support organization, we recommend you
7378 contact that organization first.
7380 You can find contact information for many support companies and
7381 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7385 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7389 The fundamental principle of reporting bugs usefully is this:
7390 @strong{report all the facts}. If you are not sure whether to state a
7391 fact or leave it out, state it!
7393 Often people omit facts because they think they know what causes the problem
7394 and assume that some details do not matter. Thus, you might assume that the
7395 name of a symbol you use in an example does not matter. Well, probably it does
7396 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7397 happens to fetch from the location where that name is stored in memory;
7398 perhaps, if the name were different, the contents of that location would fool
7399 the assembler into doing the right thing despite the bug. Play it safe and
7400 give a specific, complete example. That is the easiest thing for you to do,
7401 and the most helpful.
7403 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7404 it is new to us. Therefore, always write your bug reports on the assumption
7405 that the bug has not been reported previously.
7407 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7408 bell?'' This cannot help us fix a bug, so it is basically useless. We
7409 respond by asking for enough details to enable us to investigate.
7410 You might as well expedite matters by sending them to begin with.
7412 To enable us to fix the bug, you should include all these things:
7416 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7417 it with the @samp{--version} argument.
7419 Without this, we will not know whether there is any point in looking for
7420 the bug in the current version of @command{@value{AS}}.
7423 Any patches you may have applied to the @command{@value{AS}} source.
7426 The type of machine you are using, and the operating system name and
7430 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7434 The command arguments you gave the assembler to assemble your example and
7435 observe the bug. To guarantee you will not omit something important, list them
7436 all. A copy of the Makefile (or the output from make) is sufficient.
7438 If we were to try to guess the arguments, we would probably guess wrong
7439 and then we might not encounter the bug.
7442 A complete input file that will reproduce the bug. If the bug is observed when
7443 the assembler is invoked via a compiler, send the assembler source, not the
7444 high level language source. Most compilers will produce the assembler source
7445 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7446 the options @samp{-v --save-temps}; this will save the assembler source in a
7447 file with an extension of @file{.s}, and also show you exactly how
7448 @command{@value{AS}} is being run.
7451 A description of what behavior you observe that you believe is
7452 incorrect. For example, ``It gets a fatal signal.''
7454 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7455 will certainly notice it. But if the bug is incorrect output, we might not
7456 notice unless it is glaringly wrong. You might as well not give us a chance to
7459 Even if the problem you experience is a fatal signal, you should still say so
7460 explicitly. Suppose something strange is going on, such as, your copy of
7461 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7462 library on your system. (This has happened!) Your copy might crash and ours
7463 would not. If you told us to expect a crash, then when ours fails to crash, we
7464 would know that the bug was not happening for us. If you had not told us to
7465 expect a crash, then we would not be able to draw any conclusion from our
7469 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7470 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7471 option. Always send diffs from the old file to the new file. If you even
7472 discuss something in the @command{@value{AS}} source, refer to it by context, not
7475 The line numbers in our development sources will not match those in your
7476 sources. Your line numbers would convey no useful information to us.
7479 Here are some things that are not necessary:
7483 A description of the envelope of the bug.
7485 Often people who encounter a bug spend a lot of time investigating
7486 which changes to the input file will make the bug go away and which
7487 changes will not affect it.
7489 This is often time consuming and not very useful, because the way we
7490 will find the bug is by running a single example under the debugger
7491 with breakpoints, not by pure deduction from a series of examples.
7492 We recommend that you save your time for something else.
7494 Of course, if you can find a simpler example to report @emph{instead}
7495 of the original one, that is a convenience for us. Errors in the
7496 output will be easier to spot, running under the debugger will take
7497 less time, and so on.
7499 However, simplification is not vital; if you do not want to do this,
7500 report the bug anyway and send us the entire test case you used.
7503 A patch for the bug.
7505 A patch for the bug does help us if it is a good one. But do not omit
7506 the necessary information, such as the test case, on the assumption that
7507 a patch is all we need. We might see problems with your patch and decide
7508 to fix the problem another way, or we might not understand it at all.
7510 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7511 construct an example that will make the program follow a certain path through
7512 the code. If you do not send us the example, we will not be able to construct
7513 one, so we will not be able to verify that the bug is fixed.
7515 And if we cannot understand what bug you are trying to fix, or why your
7516 patch should be an improvement, we will not install it. A test case will
7517 help us to understand.
7520 A guess about what the bug is or what it depends on.
7522 Such guesses are usually wrong. Even we cannot guess right about such
7523 things without first using the debugger to find the facts.
7526 @node Acknowledgements
7527 @chapter Acknowledgements
7529 If you have contributed to GAS and your name isn't listed here,
7530 it is not meant as a slight. We just don't know about it. Send mail to the
7531 maintainer, and we'll correct the situation. Currently
7533 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7535 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7538 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7539 information and the 68k series machines, most of the preprocessing pass, and
7540 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7542 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7543 many bug fixes, including merging support for several processors, breaking GAS
7544 up to handle multiple object file format back ends (including heavy rewrite,
7545 testing, an integration of the coff and b.out back ends), adding configuration
7546 including heavy testing and verification of cross assemblers and file splits
7547 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7548 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7549 port (including considerable amounts of reverse engineering), a SPARC opcode
7550 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7551 assertions and made them work, much other reorganization, cleanup, and lint.
7553 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7554 in format-specific I/O modules.
7556 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7557 has done much work with it since.
7559 The Intel 80386 machine description was written by Eliot Dresselhaus.
7561 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7563 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7564 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7566 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7567 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7568 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7569 support a.out format.
7571 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7572 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7573 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7574 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7577 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7578 simplified the configuration of which versions accept which directives. He
7579 updated the 68k machine description so that Motorola's opcodes always produced
7580 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7581 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7582 cross-compilation support, and one bug in relaxation that took a week and
7583 required the proverbial one-bit fix.
7585 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7586 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7587 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7588 PowerPC assembler, and made a few other minor patches.
7590 Steve Chamberlain made GAS able to generate listings.
7592 Hewlett-Packard contributed support for the HP9000/300.
7594 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7595 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7596 formats). This work was supported by both the Center for Software Science at
7597 the University of Utah and Cygnus Support.
7599 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7600 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7601 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7602 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7603 and some initial 64-bit support).
7605 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7607 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7608 support for openVMS/Alpha.
7610 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7613 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7614 Inc.@: added support for Xtensa processors.
7616 Several engineers at Cygnus Support have also provided many small bug fixes and
7617 configuration enhancements.
7619 Jon Beniston added support for the Lattice Mico32 architecture.
7621 Many others have contributed large or small bugfixes and enhancements. If
7622 you have contributed significant work and are not mentioned on this list, and
7623 want to be, let us know. Some of the history has been lost; we are not
7624 intentionally leaving anyone out.
7626 @node GNU Free Documentation License
7627 @appendix GNU Free Documentation License
7631 @unnumbered AS Index
projects / binutils.git / blob