1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
3 @c 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009, 2010, 2011
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
24 @include asconfig.texi
29 @c common OR combinations of conditions
55 @set abnormal-separator
59 @settitle Using @value{AS}
62 @settitle Using @value{AS} (@value{TARGET})
64 @setchapternewpage odd
69 @c WARE! Some of the machine-dependent sections contain tables of machine
70 @c instructions. Except in multi-column format, these tables look silly.
71 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
72 @c the multi-col format is faked within @example sections.
74 @c Again unfortunately, the natural size that fits on a page, for these tables,
75 @c is different depending on whether or not smallbook is turned on.
76 @c This matters, because of order: text flow switches columns at each page
79 @c The format faked in this source works reasonably well for smallbook,
80 @c not well for the default large-page format. This manual expects that if you
81 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
82 @c tables in question. You can turn on one without the other at your
83 @c discretion, of course.
86 @c the insn tables look just as silly in info files regardless of smallbook,
87 @c might as well show 'em anyways.
91 @dircategory Software development
93 * As: (as). The GNU assembler.
94 * Gas: (as). The GNU assembler.
102 This file documents the GNU Assembler "@value{AS}".
104 @c man begin COPYRIGHT
105 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
106 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
109 Permission is granted to copy, distribute and/or modify this document
110 under the terms of the GNU Free Documentation License, Version 1.3
111 or any later version published by the Free Software Foundation;
112 with no Invariant Sections, with no Front-Cover Texts, and with no
113 Back-Cover Texts. A copy of the license is included in the
114 section entitled ``GNU Free Documentation License''.
120 @title Using @value{AS}
121 @subtitle The @sc{gnu} Assembler
123 @subtitle for the @value{TARGET} family
125 @ifset VERSION_PACKAGE
127 @subtitle @value{VERSION_PACKAGE}
130 @subtitle Version @value{VERSION}
133 The Free Software Foundation Inc.@: thanks The Nice Computer
134 Company of Australia for loaning Dean Elsner to write the
135 first (Vax) version of @command{as} for Project @sc{gnu}.
136 The proprietors, management and staff of TNCCA thank FSF for
137 distracting the boss while they got some work
140 @author Dean Elsner, Jay Fenlason & friends
144 \hfill {\it Using {\tt @value{AS}}}\par
145 \hfill Edited by Cygnus Support\par
147 %"boxit" macro for figures:
148 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
149 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
150 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
151 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
152 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
155 @vskip 0pt plus 1filll
156 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
157 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010, 2011 Free Software Foundation,
160 Permission is granted to copy, distribute and/or modify this document
161 under the terms of the GNU Free Documentation License, Version 1.3
162 or any later version published by the Free Software Foundation;
163 with no Invariant Sections, with no Front-Cover Texts, and with no
164 Back-Cover Texts. A copy of the license is included in the
165 section entitled ``GNU Free Documentation License''.
172 @top Using @value{AS}
174 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
175 @ifset VERSION_PACKAGE
176 @value{VERSION_PACKAGE}
178 version @value{VERSION}.
180 This version of the file describes @command{@value{AS}} configured to generate
181 code for @value{TARGET} architectures.
184 This document is distributed under the terms of the GNU Free
185 Documentation License. A copy of the license is included in the
186 section entitled ``GNU Free Documentation License''.
189 * Overview:: Overview
190 * Invoking:: Command-Line Options
192 * Sections:: Sections and Relocation
194 * Expressions:: Expressions
195 * Pseudo Ops:: Assembler Directives
197 * Object Attributes:: Object Attributes
199 * Machine Dependencies:: Machine Dependent Features
200 * Reporting Bugs:: Reporting Bugs
201 * Acknowledgements:: Who Did What
202 * GNU Free Documentation License:: GNU Free Documentation License
203 * AS Index:: AS Index
210 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
212 This version of the manual describes @command{@value{AS}} configured to generate
213 code for @value{TARGET} architectures.
217 @cindex invocation summary
218 @cindex option summary
219 @cindex summary of options
220 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
221 see @ref{Invoking,,Command-Line Options}.
223 @c man title AS the portable GNU assembler.
227 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
231 @c We don't use deffn and friends for the following because they seem
232 @c to be limited to one line for the header.
234 @c man begin SYNOPSIS
235 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
236 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
237 [@b{--debug-prefix-map} @var{old}=@var{new}]
238 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
239 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
240 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
241 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
242 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
243 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
244 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
245 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
246 [@b{--target-help}] [@var{target-options}]
247 [@b{--}|@var{files} @dots{}]
249 @c Target dependent options are listed below. Keep the list sorted.
250 @c Add an empty line for separation.
253 @emph{Target Alpha options:}
255 [@b{-mdebug} | @b{-no-mdebug}]
256 [@b{-replace} | @b{-noreplace}]
257 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
258 [@b{-F}] [@b{-32addr}]
262 @emph{Target ARC options:}
268 @emph{Target ARM options:}
269 @c Don't document the deprecated options
270 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
271 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
272 [@b{-mfpu}=@var{floating-point-format}]
273 [@b{-mfloat-abi}=@var{abi}]
274 [@b{-meabi}=@var{ver}]
277 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
278 @b{-mapcs-reentrant}]
279 [@b{-mthumb-interwork}] [@b{-k}]
283 @emph{Target Blackfin options:}
284 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
291 @emph{Target CRIS options:}
292 [@b{--underscore} | @b{--no-underscore}]
294 [@b{--emulation=criself} | @b{--emulation=crisaout}]
295 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
296 @c Deprecated -- deliberately not documented.
301 @emph{Target D10V options:}
306 @emph{Target D30V options:}
307 [@b{-O}|@b{-n}|@b{-N}]
311 @emph{Target H8/300 options:}
315 @c HPPA has no machine-dependent assembler options (yet).
319 @emph{Target i386 options:}
320 [@b{--32}|@b{--n32}|@b{--64}] [@b{-n}]
321 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
325 @emph{Target i960 options:}
326 @c see md_parse_option in tc-i960.c
327 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
329 [@b{-b}] [@b{-no-relax}]
333 @emph{Target IA-64 options:}
334 [@b{-mconstant-gp}|@b{-mauto-pic}]
335 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
337 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
338 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
339 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
340 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
344 @emph{Target IP2K options:}
345 [@b{-mip2022}|@b{-mip2022ext}]
349 @emph{Target M32C options:}
350 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
354 @emph{Target M32R options:}
355 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
360 @emph{Target M680X0 options:}
361 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
365 @emph{Target M68HC11 options:}
366 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
367 [@b{-mshort}|@b{-mlong}]
368 [@b{-mshort-double}|@b{-mlong-double}]
369 [@b{--force-long-branches}] [@b{--short-branches}]
370 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
371 [@b{--print-opcodes}] [@b{--generate-example}]
375 @emph{Target MCORE options:}
376 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
377 [@b{-mcpu=[210|340]}]
380 @emph{Target MICROBLAZE options:}
381 @c MicroBlaze has no machine-dependent assembler options.
385 @emph{Target MIPS options:}
386 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
387 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
388 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
389 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
390 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
391 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
392 [@b{-mips64}] [@b{-mips64r2}]
393 [@b{-construct-floats}] [@b{-no-construct-floats}]
394 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
395 [@b{-mips16}] [@b{-no-mips16}]
396 [@b{-msmartmips}] [@b{-mno-smartmips}]
397 [@b{-mips3d}] [@b{-no-mips3d}]
398 [@b{-mdmx}] [@b{-no-mdmx}]
399 [@b{-mdsp}] [@b{-mno-dsp}]
400 [@b{-mdspr2}] [@b{-mno-dspr2}]
401 [@b{-mmt}] [@b{-mno-mt}]
402 [@b{-mfix7000}] [@b{-mno-fix7000}]
403 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
404 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
405 [@b{-mdebug}] [@b{-no-mdebug}]
406 [@b{-mpdr}] [@b{-mno-pdr}]
410 @emph{Target MMIX options:}
411 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
412 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
413 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
414 [@b{--linker-allocated-gregs}]
418 @emph{Target PDP11 options:}
419 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
420 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
421 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
425 @emph{Target picoJava options:}
430 @emph{Target PowerPC options:}
432 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
433 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
434 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-mppc64bridge}|@b{-mbooke}|
435 @b{-mpower4}|@b{-mpr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
436 @b{-mpower7}|@b{-mpw7}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
437 [@b{-many}] [@b{-maltivec}|@b{-mvsx}]
438 [@b{-mregnames}|@b{-mno-regnames}]
439 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
440 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
441 [@b{-msolaris}|@b{-mno-solaris}]
442 [@b{-nops=@var{count}}]
446 @emph{Target RX options:}
447 [@b{-mlittle-endian}|@b{-mbig-endian}]
448 [@b{-m32bit-ints}|@b{-m16bit-ints}]
449 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
453 @emph{Target s390 options:}
454 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
455 [@b{-mregnames}|@b{-mno-regnames}]
456 [@b{-mwarn-areg-zero}]
460 @emph{Target SCORE options:}
461 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
462 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
463 [@b{-march=score7}][@b{-march=score3}]
464 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
468 @emph{Target SPARC options:}
469 @c The order here is important. See c-sparc.texi.
470 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
471 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
472 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
477 @emph{Target TIC54X options:}
478 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
479 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
484 @emph{Target TIC6X options:}
485 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
486 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
487 [@b{-mpic}|@b{-mno-pic}]
492 @emph{Target Xtensa options:}
493 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
494 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
495 [@b{--[no-]transform}]
496 [@b{--rename-section} @var{oldname}=@var{newname}]
501 @emph{Target Z80 options:}
502 [@b{-z80}] [@b{-r800}]
503 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
504 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
505 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
506 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
507 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
508 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
512 @c Z8000 has no machine-dependent assembler options
521 @include at-file.texi
524 Turn on listings, in any of a variety of ways:
528 omit false conditionals
531 omit debugging directives
534 include general information, like @value{AS} version and options passed
537 include high-level source
543 include macro expansions
546 omit forms processing
552 set the name of the listing file
555 You may combine these options; for example, use @samp{-aln} for assembly
556 listing without forms processing. The @samp{=file} option, if used, must be
557 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
560 Begin in alternate macro mode.
562 @xref{Altmacro,,@code{.altmacro}}.
565 @item --compress-debug-sections
566 Compress DWARF debug sections using zlib. The debug sections are renamed
567 to begin with @samp{.zdebug}, and the resulting object file may not be
568 compatible with older linkers and object file utilities.
570 @item --nocompress-debug-sections
571 Do not compress DWARF debug sections. This is the default.
574 Ignored. This option is accepted for script compatibility with calls to
577 @item --debug-prefix-map @var{old}=@var{new}
578 When assembling files in directory @file{@var{old}}, record debugging
579 information describing them as in @file{@var{new}} instead.
581 @item --defsym @var{sym}=@var{value}
582 Define the symbol @var{sym} to be @var{value} before assembling the input file.
583 @var{value} must be an integer constant. As in C, a leading @samp{0x}
584 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
585 value. The value of the symbol can be overridden inside a source file via the
586 use of a @code{.set} pseudo-op.
589 ``fast''---skip whitespace and comment preprocessing (assume source is
594 Generate debugging information for each assembler source line using whichever
595 debug format is preferred by the target. This currently means either STABS,
599 Generate stabs debugging information for each assembler line. This
600 may help debugging assembler code, if the debugger can handle it.
603 Generate stabs debugging information for each assembler line, with GNU
604 extensions that probably only gdb can handle, and that could make other
605 debuggers crash or refuse to read your program. This
606 may help debugging assembler code. Currently the only GNU extension is
607 the location of the current working directory at assembling time.
610 Generate DWARF2 debugging information for each assembler line. This
611 may help debugging assembler code, if the debugger can handle it. Note---this
612 option is only supported by some targets, not all of them.
615 Print a summary of the command line options and exit.
618 Print a summary of all target specific options and exit.
621 Add directory @var{dir} to the search list for @code{.include} directives.
624 Don't warn about signed overflow.
627 @ifclear DIFF-TBL-KLUGE
628 This option is accepted but has no effect on the @value{TARGET} family.
630 @ifset DIFF-TBL-KLUGE
631 Issue warnings when difference tables altered for long displacements.
636 Keep (in the symbol table) local symbols. These symbols start with
637 system-specific local label prefixes, typically @samp{.L} for ELF systems
638 or @samp{L} for traditional a.out systems.
643 @item --listing-lhs-width=@var{number}
644 Set the maximum width, in words, of the output data column for an assembler
645 listing to @var{number}.
647 @item --listing-lhs-width2=@var{number}
648 Set the maximum width, in words, of the output data column for continuation
649 lines in an assembler listing to @var{number}.
651 @item --listing-rhs-width=@var{number}
652 Set the maximum width of an input source line, as displayed in a listing, to
655 @item --listing-cont-lines=@var{number}
656 Set the maximum number of lines printed in a listing for a single line of input
659 @item -o @var{objfile}
660 Name the object-file output from @command{@value{AS}} @var{objfile}.
663 Fold the data section into the text section.
665 @kindex --hash-size=@var{number}
666 Set the default size of GAS's hash tables to a prime number close to
667 @var{number}. Increasing this value can reduce the length of time it takes the
668 assembler to perform its tasks, at the expense of increasing the assembler's
669 memory requirements. Similarly reducing this value can reduce the memory
670 requirements at the expense of speed.
672 @item --reduce-memory-overheads
673 This option reduces GAS's memory requirements, at the expense of making the
674 assembly processes slower. Currently this switch is a synonym for
675 @samp{--hash-size=4051}, but in the future it may have other effects as well.
678 Print the maximum space (in bytes) and total time (in seconds) used by
681 @item --strip-local-absolute
682 Remove local absolute symbols from the outgoing symbol table.
686 Print the @command{as} version.
689 Print the @command{as} version and exit.
693 Suppress warning messages.
695 @item --fatal-warnings
696 Treat warnings as errors.
699 Don't suppress warning messages or treat them as errors.
708 Generate an object file even after errors.
710 @item -- | @var{files} @dots{}
711 Standard input, or source files to assemble.
719 @xref{Alpha Options}, for the options available when @value{AS} is configured
720 for an Alpha processor.
725 The following options are available when @value{AS} is configured for an Alpha
729 @include c-alpha.texi
730 @c ended inside the included file
737 The following options are available when @value{AS} is configured for
742 This option selects the core processor variant.
744 Select either big-endian (-EB) or little-endian (-EL) output.
749 The following options are available when @value{AS} is configured for the ARM
753 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
754 Specify which ARM processor variant is the target.
755 @item -march=@var{architecture}[+@var{extension}@dots{}]
756 Specify which ARM architecture variant is used by the target.
757 @item -mfpu=@var{floating-point-format}
758 Select which Floating Point architecture is the target.
759 @item -mfloat-abi=@var{abi}
760 Select which floating point ABI is in use.
762 Enable Thumb only instruction decoding.
763 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
764 Select which procedure calling convention is in use.
766 Select either big-endian (-EB) or little-endian (-EL) output.
767 @item -mthumb-interwork
768 Specify that the code has been generated with interworking between Thumb and
771 Specify that PIC code has been generated.
779 @xref{Blackfin Options}, for the options available when @value{AS} is
780 configured for the Blackfin processor family.
785 The following options are available when @value{AS} is configured for
786 the Blackfin processor family.
790 @c ended inside the included file
797 See the info pages for documentation of the CRIS-specific options.
801 The following options are available when @value{AS} is configured for
804 @cindex D10V optimization
805 @cindex optimization, D10V
807 Optimize output by parallelizing instructions.
812 The following options are available when @value{AS} is configured for a D30V
815 @cindex D30V optimization
816 @cindex optimization, D30V
818 Optimize output by parallelizing instructions.
822 Warn when nops are generated.
824 @cindex D30V nops after 32-bit multiply
826 Warn when a nop after a 32-bit multiply instruction is generated.
834 @xref{i386-Options}, for the options available when @value{AS} is
835 configured for an i386 processor.
840 The following options are available when @value{AS} is configured for
845 @c ended inside the included file
852 The following options are available when @value{AS} is configured for the
853 Intel 80960 processor.
856 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
857 Specify which variant of the 960 architecture is the target.
860 Add code to collect statistics about branches taken.
863 Do not alter compare-and-branch instructions for long displacements;
870 The following options are available when @value{AS} is configured for the
876 Specifies that the extended IP2022 instructions are allowed.
879 Restores the default behaviour, which restricts the permitted instructions to
880 just the basic IP2022 ones.
886 The following options are available when @value{AS} is configured for the
887 Renesas M32C and M16C processors.
892 Assemble M32C instructions.
895 Assemble M16C instructions (the default).
898 Enable support for link-time relaxations.
901 Support H'00 style hex constants in addition to 0x00 style.
907 The following options are available when @value{AS} is configured for the
908 Renesas M32R (formerly Mitsubishi M32R) series.
913 Specify which processor in the M32R family is the target. The default
914 is normally the M32R, but this option changes it to the M32RX.
916 @item --warn-explicit-parallel-conflicts or --Wp
917 Produce warning messages when questionable parallel constructs are
920 @item --no-warn-explicit-parallel-conflicts or --Wnp
921 Do not produce warning messages when questionable parallel constructs are
928 The following options are available when @value{AS} is configured for the
929 Motorola 68000 series.
934 Shorten references to undefined symbols, to one word instead of two.
936 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
937 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
938 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
939 Specify what processor in the 68000 family is the target. The default
940 is normally the 68020, but this can be changed at configuration time.
942 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
943 The target machine does (or does not) have a floating-point coprocessor.
944 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
945 the basic 68000 is not compatible with the 68881, a combination of the
946 two can be specified, since it's possible to do emulation of the
947 coprocessor instructions with the main processor.
949 @item -m68851 | -mno-68851
950 The target machine does (or does not) have a memory-management
951 unit coprocessor. The default is to assume an MMU for 68020 and up.
958 For details about the PDP-11 machine dependent features options,
959 see @ref{PDP-11-Options}.
962 @item -mpic | -mno-pic
963 Generate position-independent (or position-dependent) code. The
964 default is @option{-mpic}.
967 @itemx -mall-extensions
968 Enable all instruction set extensions. This is the default.
970 @item -mno-extensions
971 Disable all instruction set extensions.
973 @item -m@var{extension} | -mno-@var{extension}
974 Enable (or disable) a particular instruction set extension.
977 Enable the instruction set extensions supported by a particular CPU, and
978 disable all other extensions.
980 @item -m@var{machine}
981 Enable the instruction set extensions supported by a particular machine
982 model, and disable all other extensions.
988 The following options are available when @value{AS} is configured for
989 a picoJava processor.
993 @cindex PJ endianness
994 @cindex endianness, PJ
995 @cindex big endian output, PJ
997 Generate ``big endian'' format output.
999 @cindex little endian output, PJ
1001 Generate ``little endian'' format output.
1007 The following options are available when @value{AS} is configured for the
1008 Motorola 68HC11 or 68HC12 series.
1012 @item -m68hc11 | -m68hc12 | -m68hcs12
1013 Specify what processor is the target. The default is
1014 defined by the configuration option when building the assembler.
1017 Specify to use the 16-bit integer ABI.
1020 Specify to use the 32-bit integer ABI.
1022 @item -mshort-double
1023 Specify to use the 32-bit double ABI.
1026 Specify to use the 64-bit double ABI.
1028 @item --force-long-branches
1029 Relative branches are turned into absolute ones. This concerns
1030 conditional branches, unconditional branches and branches to a
1033 @item -S | --short-branches
1034 Do not turn relative branches into absolute ones
1035 when the offset is out of range.
1037 @item --strict-direct-mode
1038 Do not turn the direct addressing mode into extended addressing mode
1039 when the instruction does not support direct addressing mode.
1041 @item --print-insn-syntax
1042 Print the syntax of instruction in case of error.
1044 @item --print-opcodes
1045 print the list of instructions with syntax and then exit.
1047 @item --generate-example
1048 print an example of instruction for each possible instruction and then exit.
1049 This option is only useful for testing @command{@value{AS}}.
1055 The following options are available when @command{@value{AS}} is configured
1056 for the SPARC architecture:
1059 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1060 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1061 Explicitly select a variant of the SPARC architecture.
1063 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1064 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1066 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1067 UltraSPARC extensions.
1069 @item -xarch=v8plus | -xarch=v8plusa
1070 For compatibility with the Solaris v9 assembler. These options are
1071 equivalent to -Av8plus and -Av8plusa, respectively.
1074 Warn when the assembler switches to another architecture.
1079 The following options are available when @value{AS} is configured for the 'c54x
1084 Enable extended addressing mode. All addresses and relocations will assume
1085 extended addressing (usually 23 bits).
1086 @item -mcpu=@var{CPU_VERSION}
1087 Sets the CPU version being compiled for.
1088 @item -merrors-to-file @var{FILENAME}
1089 Redirect error output to a file, for broken systems which don't support such
1090 behaviour in the shell.
1095 The following options are available when @value{AS} is configured for
1096 a @sc{mips} processor.
1100 This option sets the largest size of an object that can be referenced
1101 implicitly with the @code{gp} register. It is only accepted for targets that
1102 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1104 @cindex MIPS endianness
1105 @cindex endianness, MIPS
1106 @cindex big endian output, MIPS
1108 Generate ``big endian'' format output.
1110 @cindex little endian output, MIPS
1112 Generate ``little endian'' format output.
1124 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1125 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1126 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1127 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1128 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1130 correspond to generic
1131 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1132 and @samp{MIPS64 Release 2}
1133 ISA processors, respectively.
1135 @item -march=@var{CPU}
1136 Generate code for a particular @sc{mips} cpu.
1138 @item -mtune=@var{cpu}
1139 Schedule and tune for a particular @sc{mips} cpu.
1143 Cause nops to be inserted if the read of the destination register
1144 of an mfhi or mflo instruction occurs in the following two instructions.
1148 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1149 section instead of the standard ELF .stabs sections.
1153 Control generation of @code{.pdr} sections.
1157 The register sizes are normally inferred from the ISA and ABI, but these
1158 flags force a certain group of registers to be treated as 32 bits wide at
1159 all times. @samp{-mgp32} controls the size of general-purpose registers
1160 and @samp{-mfp32} controls the size of floating-point registers.
1164 Generate code for the MIPS 16 processor. This is equivalent to putting
1165 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1166 turns off this option.
1169 @itemx -mno-smartmips
1170 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1171 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1172 @samp{-mno-smartmips} turns off this option.
1176 Generate code for the MIPS-3D Application Specific Extension.
1177 This tells the assembler to accept MIPS-3D instructions.
1178 @samp{-no-mips3d} turns off this option.
1182 Generate code for the MDMX Application Specific Extension.
1183 This tells the assembler to accept MDMX instructions.
1184 @samp{-no-mdmx} turns off this option.
1188 Generate code for the DSP Release 1 Application Specific Extension.
1189 This tells the assembler to accept DSP Release 1 instructions.
1190 @samp{-mno-dsp} turns off this option.
1194 Generate code for the DSP Release 2 Application Specific Extension.
1195 This option implies -mdsp.
1196 This tells the assembler to accept DSP Release 2 instructions.
1197 @samp{-mno-dspr2} turns off this option.
1201 Generate code for the MT Application Specific Extension.
1202 This tells the assembler to accept MT instructions.
1203 @samp{-mno-mt} turns off this option.
1205 @item --construct-floats
1206 @itemx --no-construct-floats
1207 The @samp{--no-construct-floats} option disables the construction of
1208 double width floating point constants by loading the two halves of the
1209 value into the two single width floating point registers that make up
1210 the double width register. By default @samp{--construct-floats} is
1211 selected, allowing construction of these floating point constants.
1214 @item --emulation=@var{name}
1215 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1216 for some other target, in all respects, including output format (choosing
1217 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1218 debugging information or store symbol table information, and default
1219 endianness. The available configuration names are: @samp{mipsecoff},
1220 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1221 @samp{mipsbelf}. The first two do not alter the default endianness from that
1222 of the primary target for which the assembler was configured; the others change
1223 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1224 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1225 selection in any case.
1227 This option is currently supported only when the primary target
1228 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1229 Furthermore, the primary target or others specified with
1230 @samp{--enable-targets=@dots{}} at configuration time must include support for
1231 the other format, if both are to be available. For example, the Irix 5
1232 configuration includes support for both.
1234 Eventually, this option will support more configurations, with more
1235 fine-grained control over the assembler's behavior, and will be supported for
1239 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1246 Control how to deal with multiplication overflow and division by zero.
1247 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1248 (and only work for Instruction Set Architecture level 2 and higher);
1249 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1253 When this option is used, @command{@value{AS}} will issue a warning every
1254 time it generates a nop instruction from a macro.
1259 The following options are available when @value{AS} is configured for
1265 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1266 The command line option @samp{-nojsri2bsr} can be used to disable it.
1270 Enable or disable the silicon filter behaviour. By default this is disabled.
1271 The default can be overridden by the @samp{-sifilter} command line option.
1274 Alter jump instructions for long displacements.
1276 @item -mcpu=[210|340]
1277 Select the cpu type on the target hardware. This controls which instructions
1281 Assemble for a big endian target.
1284 Assemble for a little endian target.
1290 See the info pages for documentation of the MMIX-specific options.
1297 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1298 for a PowerPC processor.
1302 @c man begin OPTIONS
1303 The following options are available when @value{AS} is configured for a
1306 @c man begin INCLUDE
1308 @c ended inside the included file
1313 @c man begin OPTIONS
1315 See the info pages for documentation of the RX-specific options.
1319 The following options are available when @value{AS} is configured for the s390
1325 Select the word size, either 31/32 bits or 64 bits.
1328 Select the architecture mode, either the Enterprise System
1329 Architecture (esa) or the z/Architecture mode (zarch).
1330 @item -march=@var{processor}
1331 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1332 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1334 @itemx -mno-regnames
1335 Allow or disallow symbolic names for registers.
1336 @item -mwarn-areg-zero
1337 Warn whenever the operand for a base or index register has been specified
1338 but evaluates to zero.
1346 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1347 for a TMS320C6000 processor.
1351 @c man begin OPTIONS
1352 The following options are available when @value{AS} is configured for a
1353 TMS320C6000 processor.
1355 @c man begin INCLUDE
1356 @include c-tic6x.texi
1357 @c ended inside the included file
1365 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1366 for an Xtensa processor.
1370 @c man begin OPTIONS
1371 The following options are available when @value{AS} is configured for an
1374 @c man begin INCLUDE
1375 @include c-xtensa.texi
1376 @c ended inside the included file
1381 @c man begin OPTIONS
1384 The following options are available when @value{AS} is configured for
1385 a Z80 family processor.
1388 Assemble for Z80 processor.
1390 Assemble for R800 processor.
1391 @item -ignore-undocumented-instructions
1393 Assemble undocumented Z80 instructions that also work on R800 without warning.
1394 @item -ignore-unportable-instructions
1396 Assemble all undocumented Z80 instructions without warning.
1397 @item -warn-undocumented-instructions
1399 Issue a warning for undocumented Z80 instructions that also work on R800.
1400 @item -warn-unportable-instructions
1402 Issue a warning for undocumented Z80 instructions that do not work on R800.
1403 @item -forbid-undocumented-instructions
1405 Treat all undocumented instructions as errors.
1406 @item -forbid-unportable-instructions
1408 Treat undocumented Z80 instructions that do not work on R800 as errors.
1415 * Manual:: Structure of this Manual
1416 * GNU Assembler:: The GNU Assembler
1417 * Object Formats:: Object File Formats
1418 * Command Line:: Command Line
1419 * Input Files:: Input Files
1420 * Object:: Output (Object) File
1421 * Errors:: Error and Warning Messages
1425 @section Structure of this Manual
1427 @cindex manual, structure and purpose
1428 This manual is intended to describe what you need to know to use
1429 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1430 notation for symbols, constants, and expressions; the directives that
1431 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1434 We also cover special features in the @value{TARGET}
1435 configuration of @command{@value{AS}}, including assembler directives.
1438 This manual also describes some of the machine-dependent features of
1439 various flavors of the assembler.
1442 @cindex machine instructions (not covered)
1443 On the other hand, this manual is @emph{not} intended as an introduction
1444 to programming in assembly language---let alone programming in general!
1445 In a similar vein, we make no attempt to introduce the machine
1446 architecture; we do @emph{not} describe the instruction set, standard
1447 mnemonics, registers or addressing modes that are standard to a
1448 particular architecture.
1450 You may want to consult the manufacturer's
1451 machine architecture manual for this information.
1455 For information on the H8/300 machine instruction set, see @cite{H8/300
1456 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1457 Programming Manual} (Renesas).
1460 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1461 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1462 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1463 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1466 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1470 @c I think this is premature---doc@cygnus.com, 17jan1991
1472 Throughout this manual, we assume that you are running @dfn{GNU},
1473 the portable operating system from the @dfn{Free Software
1474 Foundation, Inc.}. This restricts our attention to certain kinds of
1475 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1476 once this assumption is granted examples and definitions need less
1479 @command{@value{AS}} is part of a team of programs that turn a high-level
1480 human-readable series of instructions into a low-level
1481 computer-readable series of instructions. Different versions of
1482 @command{@value{AS}} are used for different kinds of computer.
1485 @c There used to be a section "Terminology" here, which defined
1486 @c "contents", "byte", "word", and "long". Defining "word" to any
1487 @c particular size is confusing when the .word directive may generate 16
1488 @c bits on one machine and 32 bits on another; in general, for the user
1489 @c version of this manual, none of these terms seem essential to define.
1490 @c They were used very little even in the former draft of the manual;
1491 @c this draft makes an effort to avoid them (except in names of
1495 @section The GNU Assembler
1497 @c man begin DESCRIPTION
1499 @sc{gnu} @command{as} is really a family of assemblers.
1501 This manual describes @command{@value{AS}}, a member of that family which is
1502 configured for the @value{TARGET} architectures.
1504 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1505 should find a fairly similar environment when you use it on another
1506 architecture. Each version has much in common with the others,
1507 including object file formats, most assembler directives (often called
1508 @dfn{pseudo-ops}) and assembler syntax.@refill
1510 @cindex purpose of @sc{gnu} assembler
1511 @command{@value{AS}} is primarily intended to assemble the output of the
1512 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1513 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1514 assemble correctly everything that other assemblers for the same
1515 machine would assemble.
1517 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1520 @c This remark should appear in generic version of manual; assumption
1521 @c here is that generic version sets M680x0.
1522 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1523 assembler for the same architecture; for example, we know of several
1524 incompatible versions of 680x0 assembly language syntax.
1529 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1530 program in one pass of the source file. This has a subtle impact on the
1531 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1533 @node Object Formats
1534 @section Object File Formats
1536 @cindex object file format
1537 The @sc{gnu} assembler can be configured to produce several alternative
1538 object file formats. For the most part, this does not affect how you
1539 write assembly language programs; but directives for debugging symbols
1540 are typically different in different file formats. @xref{Symbol
1541 Attributes,,Symbol Attributes}.
1544 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1545 @value{OBJ-NAME} format object files.
1547 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1549 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1550 @code{b.out} or COFF format object files.
1553 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1554 SOM or ELF format object files.
1559 @section Command Line
1561 @cindex command line conventions
1563 After the program name @command{@value{AS}}, the command line may contain
1564 options and file names. Options may appear in any order, and may be
1565 before, after, or between file names. The order of file names is
1568 @cindex standard input, as input file
1570 @file{--} (two hyphens) by itself names the standard input file
1571 explicitly, as one of the files for @command{@value{AS}} to assemble.
1573 @cindex options, command line
1574 Except for @samp{--} any command line argument that begins with a
1575 hyphen (@samp{-}) is an option. Each option changes the behavior of
1576 @command{@value{AS}}. No option changes the way another option works. An
1577 option is a @samp{-} followed by one or more letters; the case of
1578 the letter is important. All options are optional.
1580 Some options expect exactly one file name to follow them. The file
1581 name may either immediately follow the option's letter (compatible
1582 with older assemblers) or it may be the next command argument (@sc{gnu}
1583 standard). These two command lines are equivalent:
1586 @value{AS} -o my-object-file.o mumble.s
1587 @value{AS} -omy-object-file.o mumble.s
1591 @section Input Files
1594 @cindex source program
1595 @cindex files, input
1596 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1597 describe the program input to one run of @command{@value{AS}}. The program may
1598 be in one or more files; how the source is partitioned into files
1599 doesn't change the meaning of the source.
1601 @c I added "con" prefix to "catenation" just to prove I can overcome my
1602 @c APL training... doc@cygnus.com
1603 The source program is a concatenation of the text in all the files, in the
1606 @c man begin DESCRIPTION
1607 Each time you run @command{@value{AS}} it assembles exactly one source
1608 program. The source program is made up of one or more files.
1609 (The standard input is also a file.)
1611 You give @command{@value{AS}} a command line that has zero or more input file
1612 names. The input files are read (from left file name to right). A
1613 command line argument (in any position) that has no special meaning
1614 is taken to be an input file name.
1616 If you give @command{@value{AS}} no file names it attempts to read one input file
1617 from the @command{@value{AS}} standard input, which is normally your terminal. You
1618 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1621 Use @samp{--} if you need to explicitly name the standard input file
1622 in your command line.
1624 If the source is empty, @command{@value{AS}} produces a small, empty object
1629 @subheading Filenames and Line-numbers
1631 @cindex input file linenumbers
1632 @cindex line numbers, in input files
1633 There are two ways of locating a line in the input file (or files) and
1634 either may be used in reporting error messages. One way refers to a line
1635 number in a physical file; the other refers to a line number in a
1636 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1638 @dfn{Physical files} are those files named in the command line given
1639 to @command{@value{AS}}.
1641 @dfn{Logical files} are simply names declared explicitly by assembler
1642 directives; they bear no relation to physical files. Logical file names help
1643 error messages reflect the original source file, when @command{@value{AS}} source
1644 is itself synthesized from other files. @command{@value{AS}} understands the
1645 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1646 @ref{File,,@code{.file}}.
1649 @section Output (Object) File
1655 Every time you run @command{@value{AS}} it produces an output file, which is
1656 your assembly language program translated into numbers. This file
1657 is the object file. Its default name is
1665 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1667 You can give it another name by using the @option{-o} option. Conventionally,
1668 object file names end with @file{.o}. The default name is used for historical
1669 reasons: older assemblers were capable of assembling self-contained programs
1670 directly into a runnable program. (For some formats, this isn't currently
1671 possible, but it can be done for the @code{a.out} format.)
1675 The object file is meant for input to the linker @code{@value{LD}}. It contains
1676 assembled program code, information to help @code{@value{LD}} integrate
1677 the assembled program into a runnable file, and (optionally) symbolic
1678 information for the debugger.
1680 @c link above to some info file(s) like the description of a.out.
1681 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1684 @section Error and Warning Messages
1686 @c man begin DESCRIPTION
1688 @cindex error messages
1689 @cindex warning messages
1690 @cindex messages from assembler
1691 @command{@value{AS}} may write warnings and error messages to the standard error
1692 file (usually your terminal). This should not happen when a compiler
1693 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1694 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1695 grave problem that stops the assembly.
1699 @cindex format of warning messages
1700 Warning messages have the format
1703 file_name:@b{NNN}:Warning Message Text
1707 @cindex line numbers, in warnings/errors
1708 (where @b{NNN} is a line number). If a logical file name has been given
1709 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1710 the current input file is used. If a logical line number was given
1712 (@pxref{Line,,@code{.line}})
1714 then it is used to calculate the number printed,
1715 otherwise the actual line in the current source file is printed. The
1716 message text is intended to be self explanatory (in the grand Unix
1719 @cindex format of error messages
1720 Error messages have the format
1722 file_name:@b{NNN}:FATAL:Error Message Text
1724 The file name and line number are derived as for warning
1725 messages. The actual message text may be rather less explanatory
1726 because many of them aren't supposed to happen.
1729 @chapter Command-Line Options
1731 @cindex options, all versions of assembler
1732 This chapter describes command-line options available in @emph{all}
1733 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1734 for options specific
1736 to the @value{TARGET} target.
1739 to particular machine architectures.
1742 @c man begin DESCRIPTION
1744 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1745 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1746 The assembler arguments must be separated from each other (and the @samp{-Wa})
1747 by commas. For example:
1750 gcc -c -g -O -Wa,-alh,-L file.c
1754 This passes two options to the assembler: @samp{-alh} (emit a listing to
1755 standard output with high-level and assembly source) and @samp{-L} (retain
1756 local symbols in the symbol table).
1758 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1759 command-line options are automatically passed to the assembler by the compiler.
1760 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1761 precisely what options it passes to each compilation pass, including the
1767 * a:: -a[cdghlns] enable listings
1768 * alternate:: --alternate enable alternate macro syntax
1769 * D:: -D for compatibility
1770 * f:: -f to work faster
1771 * I:: -I for .include search path
1772 @ifclear DIFF-TBL-KLUGE
1773 * K:: -K for compatibility
1775 @ifset DIFF-TBL-KLUGE
1776 * K:: -K for difference tables
1779 * L:: -L to retain local symbols
1780 * listing:: --listing-XXX to configure listing output
1781 * M:: -M or --mri to assemble in MRI compatibility mode
1782 * MD:: --MD for dependency tracking
1783 * o:: -o to name the object file
1784 * R:: -R to join data and text sections
1785 * statistics:: --statistics to see statistics about assembly
1786 * traditional-format:: --traditional-format for compatible output
1787 * v:: -v to announce version
1788 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1789 * Z:: -Z to make object file even after errors
1793 @section Enable Listings: @option{-a[cdghlns]}
1803 @cindex listings, enabling
1804 @cindex assembly listings, enabling
1806 These options enable listing output from the assembler. By itself,
1807 @samp{-a} requests high-level, assembly, and symbols listing.
1808 You can use other letters to select specific options for the list:
1809 @samp{-ah} requests a high-level language listing,
1810 @samp{-al} requests an output-program assembly listing, and
1811 @samp{-as} requests a symbol table listing.
1812 High-level listings require that a compiler debugging option like
1813 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1816 Use the @samp{-ag} option to print a first section with general assembly
1817 information, like @value{AS} version, switches passed, or time stamp.
1819 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1820 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1821 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1822 omitted from the listing.
1824 Use the @samp{-ad} option to omit debugging directives from the
1827 Once you have specified one of these options, you can further control
1828 listing output and its appearance using the directives @code{.list},
1829 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1831 The @samp{-an} option turns off all forms processing.
1832 If you do not request listing output with one of the @samp{-a} options, the
1833 listing-control directives have no effect.
1835 The letters after @samp{-a} may be combined into one option,
1836 @emph{e.g.}, @samp{-aln}.
1838 Note if the assembler source is coming from the standard input (e.g.,
1840 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1841 is being used) then the listing will not contain any comments or preprocessor
1842 directives. This is because the listing code buffers input source lines from
1843 stdin only after they have been preprocessed by the assembler. This reduces
1844 memory usage and makes the code more efficient.
1847 @section @option{--alternate}
1850 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1853 @section @option{-D}
1856 This option has no effect whatsoever, but it is accepted to make it more
1857 likely that scripts written for other assemblers also work with
1858 @command{@value{AS}}.
1861 @section Work Faster: @option{-f}
1864 @cindex trusted compiler
1865 @cindex faster processing (@option{-f})
1866 @samp{-f} should only be used when assembling programs written by a
1867 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1868 and comment preprocessing on
1869 the input file(s) before assembling them. @xref{Preprocessing,
1873 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1874 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1879 @section @code{.include} Search Path: @option{-I} @var{path}
1881 @kindex -I @var{path}
1882 @cindex paths for @code{.include}
1883 @cindex search path for @code{.include}
1884 @cindex @code{include} directive search path
1885 Use this option to add a @var{path} to the list of directories
1886 @command{@value{AS}} searches for files specified in @code{.include}
1887 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1888 many times as necessary to include a variety of paths. The current
1889 working directory is always searched first; after that, @command{@value{AS}}
1890 searches any @samp{-I} directories in the same order as they were
1891 specified (left to right) on the command line.
1894 @section Difference Tables: @option{-K}
1897 @ifclear DIFF-TBL-KLUGE
1898 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1899 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1900 where it can be used to warn when the assembler alters the machine code
1901 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1902 family does not have the addressing limitations that sometimes lead to this
1903 alteration on other platforms.
1906 @ifset DIFF-TBL-KLUGE
1907 @cindex difference tables, warning
1908 @cindex warning for altered difference tables
1909 @command{@value{AS}} sometimes alters the code emitted for directives of the
1910 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1911 You can use the @samp{-K} option if you want a warning issued when this
1916 @section Include Local Symbols: @option{-L}
1919 @cindex local symbols, retaining in output
1920 Symbols beginning with system-specific local label prefixes, typically
1921 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1922 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1923 such symbols when debugging, because they are intended for the use of
1924 programs (like compilers) that compose assembler programs, not for your
1925 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1926 such symbols, so you do not normally debug with them.
1928 This option tells @command{@value{AS}} to retain those local symbols
1929 in the object file. Usually if you do this you also tell the linker
1930 @code{@value{LD}} to preserve those symbols.
1933 @section Configuring listing output: @option{--listing}
1935 The listing feature of the assembler can be enabled via the command line switch
1936 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1937 hex dump of the corresponding locations in the output object file, and displays
1938 them as a listing file. The format of this listing can be controlled by
1939 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1940 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1941 @code{.psize} (@pxref{Psize}), and
1942 @code{.eject} (@pxref{Eject}) and also by the following switches:
1945 @item --listing-lhs-width=@samp{number}
1946 @kindex --listing-lhs-width
1947 @cindex Width of first line disassembly output
1948 Sets the maximum width, in words, of the first line of the hex byte dump. This
1949 dump appears on the left hand side of the listing output.
1951 @item --listing-lhs-width2=@samp{number}
1952 @kindex --listing-lhs-width2
1953 @cindex Width of continuation lines of disassembly output
1954 Sets the maximum width, in words, of any further lines of the hex byte dump for
1955 a given input source line. If this value is not specified, it defaults to being
1956 the same as the value specified for @samp{--listing-lhs-width}. If neither
1957 switch is used the default is to one.
1959 @item --listing-rhs-width=@samp{number}
1960 @kindex --listing-rhs-width
1961 @cindex Width of source line output
1962 Sets the maximum width, in characters, of the source line that is displayed
1963 alongside the hex dump. The default value for this parameter is 100. The
1964 source line is displayed on the right hand side of the listing output.
1966 @item --listing-cont-lines=@samp{number}
1967 @kindex --listing-cont-lines
1968 @cindex Maximum number of continuation lines
1969 Sets the maximum number of continuation lines of hex dump that will be
1970 displayed for a given single line of source input. The default value is 4.
1974 @section Assemble in MRI Compatibility Mode: @option{-M}
1977 @cindex MRI compatibility mode
1978 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1979 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1980 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1981 configured target) assembler from Microtec Research. The exact nature of the
1982 MRI syntax will not be documented here; see the MRI manuals for more
1983 information. Note in particular that the handling of macros and macro
1984 arguments is somewhat different. The purpose of this option is to permit
1985 assembling existing MRI assembler code using @command{@value{AS}}.
1987 The MRI compatibility is not complete. Certain operations of the MRI assembler
1988 depend upon its object file format, and can not be supported using other object
1989 file formats. Supporting these would require enhancing each object file format
1990 individually. These are:
1993 @item global symbols in common section
1995 The m68k MRI assembler supports common sections which are merged by the linker.
1996 Other object file formats do not support this. @command{@value{AS}} handles
1997 common sections by treating them as a single common symbol. It permits local
1998 symbols to be defined within a common section, but it can not support global
1999 symbols, since it has no way to describe them.
2001 @item complex relocations
2003 The MRI assemblers support relocations against a negated section address, and
2004 relocations which combine the start addresses of two or more sections. These
2005 are not support by other object file formats.
2007 @item @code{END} pseudo-op specifying start address
2009 The MRI @code{END} pseudo-op permits the specification of a start address.
2010 This is not supported by other object file formats. The start address may
2011 instead be specified using the @option{-e} option to the linker, or in a linker
2014 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2016 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2017 name to the output file. This is not supported by other object file formats.
2019 @item @code{ORG} pseudo-op
2021 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2022 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2023 which changes the location within the current section. Absolute sections are
2024 not supported by other object file formats. The address of a section may be
2025 assigned within a linker script.
2028 There are some other features of the MRI assembler which are not supported by
2029 @command{@value{AS}}, typically either because they are difficult or because they
2030 seem of little consequence. Some of these may be supported in future releases.
2034 @item EBCDIC strings
2036 EBCDIC strings are not supported.
2038 @item packed binary coded decimal
2040 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2041 and @code{DCB.P} pseudo-ops are not supported.
2043 @item @code{FEQU} pseudo-op
2045 The m68k @code{FEQU} pseudo-op is not supported.
2047 @item @code{NOOBJ} pseudo-op
2049 The m68k @code{NOOBJ} pseudo-op is not supported.
2051 @item @code{OPT} branch control options
2053 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2054 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2055 relaxes all branches, whether forward or backward, to an appropriate size, so
2056 these options serve no purpose.
2058 @item @code{OPT} list control options
2060 The following m68k @code{OPT} list control options are ignored: @code{C},
2061 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2062 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2064 @item other @code{OPT} options
2066 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2067 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2069 @item @code{OPT} @code{D} option is default
2071 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2072 @code{OPT NOD} may be used to turn it off.
2074 @item @code{XREF} pseudo-op.
2076 The m68k @code{XREF} pseudo-op is ignored.
2078 @item @code{.debug} pseudo-op
2080 The i960 @code{.debug} pseudo-op is not supported.
2082 @item @code{.extended} pseudo-op
2084 The i960 @code{.extended} pseudo-op is not supported.
2086 @item @code{.list} pseudo-op.
2088 The various options of the i960 @code{.list} pseudo-op are not supported.
2090 @item @code{.optimize} pseudo-op
2092 The i960 @code{.optimize} pseudo-op is not supported.
2094 @item @code{.output} pseudo-op
2096 The i960 @code{.output} pseudo-op is not supported.
2098 @item @code{.setreal} pseudo-op
2100 The i960 @code{.setreal} pseudo-op is not supported.
2105 @section Dependency Tracking: @option{--MD}
2108 @cindex dependency tracking
2111 @command{@value{AS}} can generate a dependency file for the file it creates. This
2112 file consists of a single rule suitable for @code{make} describing the
2113 dependencies of the main source file.
2115 The rule is written to the file named in its argument.
2117 This feature is used in the automatic updating of makefiles.
2120 @section Name the Object File: @option{-o}
2123 @cindex naming object file
2124 @cindex object file name
2125 There is always one object file output when you run @command{@value{AS}}. By
2126 default it has the name
2129 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2143 You use this option (which takes exactly one filename) to give the
2144 object file a different name.
2146 Whatever the object file is called, @command{@value{AS}} overwrites any
2147 existing file of the same name.
2150 @section Join Data and Text Sections: @option{-R}
2153 @cindex data and text sections, joining
2154 @cindex text and data sections, joining
2155 @cindex joining text and data sections
2156 @cindex merging text and data sections
2157 @option{-R} tells @command{@value{AS}} to write the object file as if all
2158 data-section data lives in the text section. This is only done at
2159 the very last moment: your binary data are the same, but data
2160 section parts are relocated differently. The data section part of
2161 your object file is zero bytes long because all its bytes are
2162 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2164 When you specify @option{-R} it would be possible to generate shorter
2165 address displacements (because we do not have to cross between text and
2166 data section). We refrain from doing this simply for compatibility with
2167 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2170 When @command{@value{AS}} is configured for COFF or ELF output,
2171 this option is only useful if you use sections named @samp{.text} and
2176 @option{-R} is not supported for any of the HPPA targets. Using
2177 @option{-R} generates a warning from @command{@value{AS}}.
2181 @section Display Assembly Statistics: @option{--statistics}
2183 @kindex --statistics
2184 @cindex statistics, about assembly
2185 @cindex time, total for assembly
2186 @cindex space used, maximum for assembly
2187 Use @samp{--statistics} to display two statistics about the resources used by
2188 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2189 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2192 @node traditional-format
2193 @section Compatible Output: @option{--traditional-format}
2195 @kindex --traditional-format
2196 For some targets, the output of @command{@value{AS}} is different in some ways
2197 from the output of some existing assembler. This switch requests
2198 @command{@value{AS}} to use the traditional format instead.
2200 For example, it disables the exception frame optimizations which
2201 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2204 @section Announce Version: @option{-v}
2208 @cindex assembler version
2209 @cindex version of assembler
2210 You can find out what version of as is running by including the
2211 option @samp{-v} (which you can also spell as @samp{-version}) on the
2215 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2217 @command{@value{AS}} should never give a warning or error message when
2218 assembling compiler output. But programs written by people often
2219 cause @command{@value{AS}} to give a warning that a particular assumption was
2220 made. All such warnings are directed to the standard error file.
2224 @cindex suppressing warnings
2225 @cindex warnings, suppressing
2226 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2227 This only affects the warning messages: it does not change any particular of
2228 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2231 @kindex --fatal-warnings
2232 @cindex errors, caused by warnings
2233 @cindex warnings, causing error
2234 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2235 files that generate warnings to be in error.
2238 @cindex warnings, switching on
2239 You can switch these options off again by specifying @option{--warn}, which
2240 causes warnings to be output as usual.
2243 @section Generate Object File in Spite of Errors: @option{-Z}
2244 @cindex object file, after errors
2245 @cindex errors, continuing after
2246 After an error message, @command{@value{AS}} normally produces no output. If for
2247 some reason you are interested in object file output even after
2248 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2249 option. If there are any errors, @command{@value{AS}} continues anyways, and
2250 writes an object file after a final warning message of the form @samp{@var{n}
2251 errors, @var{m} warnings, generating bad object file.}
2256 @cindex machine-independent syntax
2257 @cindex syntax, machine-independent
2258 This chapter describes the machine-independent syntax allowed in a
2259 source file. @command{@value{AS}} syntax is similar to what many other
2260 assemblers use; it is inspired by the BSD 4.2
2265 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2269 * Preprocessing:: Preprocessing
2270 * Whitespace:: Whitespace
2271 * Comments:: Comments
2272 * Symbol Intro:: Symbols
2273 * Statements:: Statements
2274 * Constants:: Constants
2278 @section Preprocessing
2280 @cindex preprocessing
2281 The @command{@value{AS}} internal preprocessor:
2283 @cindex whitespace, removed by preprocessor
2285 adjusts and removes extra whitespace. It leaves one space or tab before
2286 the keywords on a line, and turns any other whitespace on the line into
2289 @cindex comments, removed by preprocessor
2291 removes all comments, replacing them with a single space, or an
2292 appropriate number of newlines.
2294 @cindex constants, converted by preprocessor
2296 converts character constants into the appropriate numeric values.
2299 It does not do macro processing, include file handling, or
2300 anything else you may get from your C compiler's preprocessor. You can
2301 do include file processing with the @code{.include} directive
2302 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2303 to get other ``CPP'' style preprocessing by giving the input file a
2304 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2305 Output, gcc.info, Using GNU CC}.
2307 Excess whitespace, comments, and character constants
2308 cannot be used in the portions of the input text that are not
2311 @cindex turning preprocessing on and off
2312 @cindex preprocessing, turning on and off
2315 If the first line of an input file is @code{#NO_APP} or if you use the
2316 @samp{-f} option, whitespace and comments are not removed from the input file.
2317 Within an input file, you can ask for whitespace and comment removal in
2318 specific portions of the by putting a line that says @code{#APP} before the
2319 text that may contain whitespace or comments, and putting a line that says
2320 @code{#NO_APP} after this text. This feature is mainly intend to support
2321 @code{asm} statements in compilers whose output is otherwise free of comments
2328 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2329 Whitespace is used to separate symbols, and to make programs neater for
2330 people to read. Unless within character constants
2331 (@pxref{Characters,,Character Constants}), any whitespace means the same
2332 as exactly one space.
2338 There are two ways of rendering comments to @command{@value{AS}}. In both
2339 cases the comment is equivalent to one space.
2341 Anything from @samp{/*} through the next @samp{*/} is a comment.
2342 This means you may not nest these comments.
2346 The only way to include a newline ('\n') in a comment
2347 is to use this sort of comment.
2350 /* This sort of comment does not nest. */
2353 @cindex line comment character
2354 Anything from a @dfn{line comment} character up to the next newline is
2355 considered a comment and is ignored. The line comment character is target
2356 specific, and some targets multiple comment characters. Some targets also have
2357 line comment characters that only work if they are the first character on a
2358 line. Some targets use a sequence of two characters to introduce a line
2359 comment. Some targets can also change their line comment characters depending
2360 upon command line options that have been used. For more details see the
2361 @emph{Syntax} section in the documentation for individual targets.
2363 If the line comment character is the hash sign (@samp{#}) then it still has the
2364 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2365 to specify logical line numbers:
2368 @cindex lines starting with @code{#}
2369 @cindex logical line numbers
2370 To be compatible with past assemblers, lines that begin with @samp{#} have a
2371 special interpretation. Following the @samp{#} should be an absolute
2372 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2373 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2374 new logical file name. The rest of the line, if any, should be whitespace.
2376 If the first non-whitespace characters on the line are not numeric,
2377 the line is ignored. (Just like a comment.)
2380 # This is an ordinary comment.
2381 # 42-6 "new_file_name" # New logical file name
2382 # This is logical line # 36.
2384 This feature is deprecated, and may disappear from future versions
2385 of @command{@value{AS}}.
2390 @cindex characters used in symbols
2391 @ifclear SPECIAL-SYMS
2392 A @dfn{symbol} is one or more characters chosen from the set of all
2393 letters (both upper and lower case), digits and the three characters
2399 A @dfn{symbol} is one or more characters chosen from the set of all
2400 letters (both upper and lower case), digits and the three characters
2401 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2407 On most machines, you can also use @code{$} in symbol names; exceptions
2408 are noted in @ref{Machine Dependencies}.
2410 No symbol may begin with a digit. Case is significant.
2411 There is no length limit: all characters are significant. Symbols are
2412 delimited by characters not in that set, or by the beginning of a file
2413 (since the source program must end with a newline, the end of a file is
2414 not a possible symbol delimiter). @xref{Symbols}.
2415 @cindex length of symbols
2420 @cindex statements, structure of
2421 @cindex line separator character
2422 @cindex statement separator character
2424 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2425 @dfn{line separator character}. The line separator character is target
2426 specific and described in the @emph{Syntax} section of each
2427 target's documentation. Not all targets support a line separator character.
2428 The newline or line separator character is considered to be part of the
2429 preceding statement. Newlines and separators within character constants are an
2430 exception: they do not end statements.
2432 @cindex newline, required at file end
2433 @cindex EOF, newline must precede
2434 It is an error to end any statement with end-of-file: the last
2435 character of any input file should be a newline.@refill
2437 An empty statement is allowed, and may include whitespace. It is ignored.
2439 @cindex instructions and directives
2440 @cindex directives and instructions
2441 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2442 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2444 A statement begins with zero or more labels, optionally followed by a
2445 key symbol which determines what kind of statement it is. The key
2446 symbol determines the syntax of the rest of the statement. If the
2447 symbol begins with a dot @samp{.} then the statement is an assembler
2448 directive: typically valid for any computer. If the symbol begins with
2449 a letter the statement is an assembly language @dfn{instruction}: it
2450 assembles into a machine language instruction.
2452 Different versions of @command{@value{AS}} for different computers
2453 recognize different instructions. In fact, the same symbol may
2454 represent a different instruction in a different computer's assembly
2458 @cindex @code{:} (label)
2459 @cindex label (@code{:})
2460 A label is a symbol immediately followed by a colon (@code{:}).
2461 Whitespace before a label or after a colon is permitted, but you may not
2462 have whitespace between a label's symbol and its colon. @xref{Labels}.
2465 For HPPA targets, labels need not be immediately followed by a colon, but
2466 the definition of a label must begin in column zero. This also implies that
2467 only one label may be defined on each line.
2471 label: .directive followed by something
2472 another_label: # This is an empty statement.
2473 instruction operand_1, operand_2, @dots{}
2480 A constant is a number, written so that its value is known by
2481 inspection, without knowing any context. Like this:
2484 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2485 .ascii "Ring the bell\7" # A string constant.
2486 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2487 .float 0f-314159265358979323846264338327\
2488 95028841971.693993751E-40 # - pi, a flonum.
2493 * Characters:: Character Constants
2494 * Numbers:: Number Constants
2498 @subsection Character Constants
2500 @cindex character constants
2501 @cindex constants, character
2502 There are two kinds of character constants. A @dfn{character} stands
2503 for one character in one byte and its value may be used in
2504 numeric expressions. String constants (properly called string
2505 @emph{literals}) are potentially many bytes and their values may not be
2506 used in arithmetic expressions.
2510 * Chars:: Characters
2514 @subsubsection Strings
2516 @cindex string constants
2517 @cindex constants, string
2518 A @dfn{string} is written between double-quotes. It may contain
2519 double-quotes or null characters. The way to get special characters
2520 into a string is to @dfn{escape} these characters: precede them with
2521 a backslash @samp{\} character. For example @samp{\\} represents
2522 one backslash: the first @code{\} is an escape which tells
2523 @command{@value{AS}} to interpret the second character literally as a backslash
2524 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2525 escape character). The complete list of escapes follows.
2527 @cindex escape codes, character
2528 @cindex character escape codes
2531 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2533 @cindex @code{\b} (backspace character)
2534 @cindex backspace (@code{\b})
2536 Mnemonic for backspace; for ASCII this is octal code 010.
2539 @c Mnemonic for EOText; for ASCII this is octal code 004.
2541 @cindex @code{\f} (formfeed character)
2542 @cindex formfeed (@code{\f})
2544 Mnemonic for FormFeed; for ASCII this is octal code 014.
2546 @cindex @code{\n} (newline character)
2547 @cindex newline (@code{\n})
2549 Mnemonic for newline; for ASCII this is octal code 012.
2552 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2554 @cindex @code{\r} (carriage return character)
2555 @cindex carriage return (@code{\r})
2557 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2560 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2561 @c other assemblers.
2563 @cindex @code{\t} (tab)
2564 @cindex tab (@code{\t})
2566 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2569 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2570 @c @item \x @var{digit} @var{digit} @var{digit}
2571 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2573 @cindex @code{\@var{ddd}} (octal character code)
2574 @cindex octal character code (@code{\@var{ddd}})
2575 @item \ @var{digit} @var{digit} @var{digit}
2576 An octal character code. The numeric code is 3 octal digits.
2577 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2578 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2580 @cindex @code{\@var{xd...}} (hex character code)
2581 @cindex hex character code (@code{\@var{xd...}})
2582 @item \@code{x} @var{hex-digits...}
2583 A hex character code. All trailing hex digits are combined. Either upper or
2584 lower case @code{x} works.
2586 @cindex @code{\\} (@samp{\} character)
2587 @cindex backslash (@code{\\})
2589 Represents one @samp{\} character.
2592 @c Represents one @samp{'} (accent acute) character.
2593 @c This is needed in single character literals
2594 @c (@xref{Characters,,Character Constants}.) to represent
2597 @cindex @code{\"} (doublequote character)
2598 @cindex doublequote (@code{\"})
2600 Represents one @samp{"} character. Needed in strings to represent
2601 this character, because an unescaped @samp{"} would end the string.
2603 @item \ @var{anything-else}
2604 Any other character when escaped by @kbd{\} gives a warning, but
2605 assembles as if the @samp{\} was not present. The idea is that if
2606 you used an escape sequence you clearly didn't want the literal
2607 interpretation of the following character. However @command{@value{AS}} has no
2608 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2609 code and warns you of the fact.
2612 Which characters are escapable, and what those escapes represent,
2613 varies widely among assemblers. The current set is what we think
2614 the BSD 4.2 assembler recognizes, and is a subset of what most C
2615 compilers recognize. If you are in doubt, do not use an escape
2619 @subsubsection Characters
2621 @cindex single character constant
2622 @cindex character, single
2623 @cindex constant, single character
2624 A single character may be written as a single quote immediately
2625 followed by that character. The same escapes apply to characters as
2626 to strings. So if you want to write the character backslash, you
2627 must write @kbd{'\\} where the first @code{\} escapes the second
2628 @code{\}. As you can see, the quote is an acute accent, not a
2629 grave accent. A newline
2631 @ifclear abnormal-separator
2632 (or semicolon @samp{;})
2634 @ifset abnormal-separator
2636 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2641 immediately following an acute accent is taken as a literal character
2642 and does not count as the end of a statement. The value of a character
2643 constant in a numeric expression is the machine's byte-wide code for
2644 that character. @command{@value{AS}} assumes your character code is ASCII:
2645 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2648 @subsection Number Constants
2650 @cindex constants, number
2651 @cindex number constants
2652 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2653 are stored in the target machine. @emph{Integers} are numbers that
2654 would fit into an @code{int} in the C language. @emph{Bignums} are
2655 integers, but they are stored in more than 32 bits. @emph{Flonums}
2656 are floating point numbers, described below.
2659 * Integers:: Integers
2664 * Bit Fields:: Bit Fields
2670 @subsubsection Integers
2672 @cindex constants, integer
2674 @cindex binary integers
2675 @cindex integers, binary
2676 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2677 the binary digits @samp{01}.
2679 @cindex octal integers
2680 @cindex integers, octal
2681 An octal integer is @samp{0} followed by zero or more of the octal
2682 digits (@samp{01234567}).
2684 @cindex decimal integers
2685 @cindex integers, decimal
2686 A decimal integer starts with a non-zero digit followed by zero or
2687 more digits (@samp{0123456789}).
2689 @cindex hexadecimal integers
2690 @cindex integers, hexadecimal
2691 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2692 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2694 Integers have the usual values. To denote a negative integer, use
2695 the prefix operator @samp{-} discussed under expressions
2696 (@pxref{Prefix Ops,,Prefix Operators}).
2699 @subsubsection Bignums
2702 @cindex constants, bignum
2703 A @dfn{bignum} has the same syntax and semantics as an integer
2704 except that the number (or its negative) takes more than 32 bits to
2705 represent in binary. The distinction is made because in some places
2706 integers are permitted while bignums are not.
2709 @subsubsection Flonums
2711 @cindex floating point numbers
2712 @cindex constants, floating point
2714 @cindex precision, floating point
2715 A @dfn{flonum} represents a floating point number. The translation is
2716 indirect: a decimal floating point number from the text is converted by
2717 @command{@value{AS}} to a generic binary floating point number of more than
2718 sufficient precision. This generic floating point number is converted
2719 to a particular computer's floating point format (or formats) by a
2720 portion of @command{@value{AS}} specialized to that computer.
2722 A flonum is written by writing (in order)
2727 (@samp{0} is optional on the HPPA.)
2731 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2733 @kbd{e} is recommended. Case is not important.
2735 @c FIXME: verify if flonum syntax really this vague for most cases
2736 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2737 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2740 On the H8/300, Renesas / SuperH SH,
2741 and AMD 29K architectures, the letter must be
2742 one of the letters @samp{DFPRSX} (in upper or lower case).
2744 On the ARC, the letter must be one of the letters @samp{DFRS}
2745 (in upper or lower case).
2747 On the Intel 960 architecture, the letter must be
2748 one of the letters @samp{DFT} (in upper or lower case).
2750 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2754 One of the letters @samp{DFRS} (in upper or lower case).
2757 One of the letters @samp{DFPRSX} (in upper or lower case).
2760 The letter @samp{E} (upper case only).
2763 One of the letters @samp{DFT} (in upper or lower case).
2768 An optional sign: either @samp{+} or @samp{-}.
2771 An optional @dfn{integer part}: zero or more decimal digits.
2774 An optional @dfn{fractional part}: @samp{.} followed by zero
2775 or more decimal digits.
2778 An optional exponent, consisting of:
2782 An @samp{E} or @samp{e}.
2783 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2784 @c principle this can perfectly well be different on different targets.
2786 Optional sign: either @samp{+} or @samp{-}.
2788 One or more decimal digits.
2793 At least one of the integer part or the fractional part must be
2794 present. The floating point number has the usual base-10 value.
2796 @command{@value{AS}} does all processing using integers. Flonums are computed
2797 independently of any floating point hardware in the computer running
2798 @command{@value{AS}}.
2802 @c Bit fields are written as a general facility but are also controlled
2803 @c by a conditional-compilation flag---which is as of now (21mar91)
2804 @c turned on only by the i960 config of GAS.
2806 @subsubsection Bit Fields
2809 @cindex constants, bit field
2810 You can also define numeric constants as @dfn{bit fields}.
2811 Specify two numbers separated by a colon---
2813 @var{mask}:@var{value}
2816 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2819 The resulting number is then packed
2821 @c this conditional paren in case bit fields turned on elsewhere than 960
2822 (in host-dependent byte order)
2824 into a field whose width depends on which assembler directive has the
2825 bit-field as its argument. Overflow (a result from the bitwise and
2826 requiring more binary digits to represent) is not an error; instead,
2827 more constants are generated, of the specified width, beginning with the
2828 least significant digits.@refill
2830 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2831 @code{.short}, and @code{.word} accept bit-field arguments.
2836 @chapter Sections and Relocation
2841 * Secs Background:: Background
2842 * Ld Sections:: Linker Sections
2843 * As Sections:: Assembler Internal Sections
2844 * Sub-Sections:: Sub-Sections
2848 @node Secs Background
2851 Roughly, a section is a range of addresses, with no gaps; all data
2852 ``in'' those addresses is treated the same for some particular purpose.
2853 For example there may be a ``read only'' section.
2855 @cindex linker, and assembler
2856 @cindex assembler, and linker
2857 The linker @code{@value{LD}} reads many object files (partial programs) and
2858 combines their contents to form a runnable program. When @command{@value{AS}}
2859 emits an object file, the partial program is assumed to start at address 0.
2860 @code{@value{LD}} assigns the final addresses for the partial program, so that
2861 different partial programs do not overlap. This is actually an
2862 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2865 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2866 addresses. These blocks slide to their run-time addresses as rigid
2867 units; their length does not change and neither does the order of bytes
2868 within them. Such a rigid unit is called a @emph{section}. Assigning
2869 run-time addresses to sections is called @dfn{relocation}. It includes
2870 the task of adjusting mentions of object-file addresses so they refer to
2871 the proper run-time addresses.
2873 For the H8/300, and for the Renesas / SuperH SH,
2874 @command{@value{AS}} pads sections if needed to
2875 ensure they end on a word (sixteen bit) boundary.
2878 @cindex standard assembler sections
2879 An object file written by @command{@value{AS}} has at least three sections, any
2880 of which may be empty. These are named @dfn{text}, @dfn{data} and
2885 When it generates COFF or ELF output,
2887 @command{@value{AS}} can also generate whatever other named sections you specify
2888 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2889 If you do not use any directives that place output in the @samp{.text}
2890 or @samp{.data} sections, these sections still exist, but are empty.
2895 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2897 @command{@value{AS}} can also generate whatever other named sections you
2898 specify using the @samp{.space} and @samp{.subspace} directives. See
2899 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2900 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2901 assembler directives.
2904 Additionally, @command{@value{AS}} uses different names for the standard
2905 text, data, and bss sections when generating SOM output. Program text
2906 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2907 BSS into @samp{$BSS$}.
2911 Within the object file, the text section starts at address @code{0}, the
2912 data section follows, and the bss section follows the data section.
2915 When generating either SOM or ELF output files on the HPPA, the text
2916 section starts at address @code{0}, the data section at address
2917 @code{0x4000000}, and the bss section follows the data section.
2920 To let @code{@value{LD}} know which data changes when the sections are
2921 relocated, and how to change that data, @command{@value{AS}} also writes to the
2922 object file details of the relocation needed. To perform relocation
2923 @code{@value{LD}} must know, each time an address in the object
2927 Where in the object file is the beginning of this reference to
2930 How long (in bytes) is this reference?
2932 Which section does the address refer to? What is the numeric value of
2934 (@var{address}) @minus{} (@var{start-address of section})?
2937 Is the reference to an address ``Program-Counter relative''?
2940 @cindex addresses, format of
2941 @cindex section-relative addressing
2942 In fact, every address @command{@value{AS}} ever uses is expressed as
2944 (@var{section}) + (@var{offset into section})
2947 Further, most expressions @command{@value{AS}} computes have this section-relative
2950 (For some object formats, such as SOM for the HPPA, some expressions are
2951 symbol-relative instead.)
2954 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2955 @var{N} into section @var{secname}.''
2957 Apart from text, data and bss sections you need to know about the
2958 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2959 addresses in the absolute section remain unchanged. For example, address
2960 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2961 @code{@value{LD}}. Although the linker never arranges two partial programs'
2962 data sections with overlapping addresses after linking, @emph{by definition}
2963 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2964 part of a program is always the same address when the program is running as
2965 address @code{@{absolute@ 239@}} in any other part of the program.
2967 The idea of sections is extended to the @dfn{undefined} section. Any
2968 address whose section is unknown at assembly time is by definition
2969 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2970 Since numbers are always defined, the only way to generate an undefined
2971 address is to mention an undefined symbol. A reference to a named
2972 common block would be such a symbol: its value is unknown at assembly
2973 time so it has section @emph{undefined}.
2975 By analogy the word @emph{section} is used to describe groups of sections in
2976 the linked program. @code{@value{LD}} puts all partial programs' text
2977 sections in contiguous addresses in the linked program. It is
2978 customary to refer to the @emph{text section} of a program, meaning all
2979 the addresses of all partial programs' text sections. Likewise for
2980 data and bss sections.
2982 Some sections are manipulated by @code{@value{LD}}; others are invented for
2983 use of @command{@value{AS}} and have no meaning except during assembly.
2986 @section Linker Sections
2987 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2992 @cindex named sections
2993 @cindex sections, named
2994 @item named sections
2997 @cindex text section
2998 @cindex data section
3002 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3003 separate but equal sections. Anything you can say of one section is
3006 When the program is running, however, it is
3007 customary for the text section to be unalterable. The
3008 text section is often shared among processes: it contains
3009 instructions, constants and the like. The data section of a running
3010 program is usually alterable: for example, C variables would be stored
3011 in the data section.
3016 This section contains zeroed bytes when your program begins running. It
3017 is used to hold uninitialized variables or common storage. The length of
3018 each partial program's bss section is important, but because it starts
3019 out containing zeroed bytes there is no need to store explicit zero
3020 bytes in the object file. The bss section was invented to eliminate
3021 those explicit zeros from object files.
3023 @cindex absolute section
3024 @item absolute section
3025 Address 0 of this section is always ``relocated'' to runtime address 0.
3026 This is useful if you want to refer to an address that @code{@value{LD}} must
3027 not change when relocating. In this sense we speak of absolute
3028 addresses being ``unrelocatable'': they do not change during relocation.
3030 @cindex undefined section
3031 @item undefined section
3032 This ``section'' is a catch-all for address references to objects not in
3033 the preceding sections.
3034 @c FIXME: ref to some other doc on obj-file formats could go here.
3037 @cindex relocation example
3038 An idealized example of three relocatable sections follows.
3040 The example uses the traditional section names @samp{.text} and @samp{.data}.
3042 Memory addresses are on the horizontal axis.
3046 @c END TEXI2ROFF-KILL
3049 partial program # 1: |ttttt|dddd|00|
3056 partial program # 2: |TTT|DDD|000|
3059 +--+---+-----+--+----+---+-----+~~
3060 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3061 +--+---+-----+--+----+---+-----+~~
3063 addresses: 0 @dots{}
3070 \line{\it Partial program \#1: \hfil}
3071 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3072 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3074 \line{\it Partial program \#2: \hfil}
3075 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3076 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3078 \line{\it linked program: \hfil}
3079 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3080 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3081 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3082 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3084 \line{\it addresses: \hfil}
3088 @c END TEXI2ROFF-KILL
3091 @section Assembler Internal Sections
3093 @cindex internal assembler sections
3094 @cindex sections in messages, internal
3095 These sections are meant only for the internal use of @command{@value{AS}}. They
3096 have no meaning at run-time. You do not really need to know about these
3097 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3098 warning messages, so it might be helpful to have an idea of their
3099 meanings to @command{@value{AS}}. These sections are used to permit the
3100 value of every expression in your assembly language program to be a
3101 section-relative address.
3104 @cindex assembler internal logic error
3105 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3106 An internal assembler logic error has been found. This means there is a
3107 bug in the assembler.
3109 @cindex expr (internal section)
3111 The assembler stores complex expression internally as combinations of
3112 symbols. When it needs to represent an expression as a symbol, it puts
3113 it in the expr section.
3115 @c FIXME item transfer[t] vector preload
3116 @c FIXME item transfer[t] vector postload
3117 @c FIXME item register
3121 @section Sub-Sections
3123 @cindex numbered subsections
3124 @cindex grouping data
3130 fall into two sections: text and data.
3132 You may have separate groups of
3134 data in named sections
3138 data in named sections
3144 that you want to end up near to each other in the object file, even though they
3145 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3146 use @dfn{subsections} for this purpose. Within each section, there can be
3147 numbered subsections with values from 0 to 8192. Objects assembled into the
3148 same subsection go into the object file together with other objects in the same
3149 subsection. For example, a compiler might want to store constants in the text
3150 section, but might not want to have them interspersed with the program being
3151 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3152 section of code being output, and a @samp{.text 1} before each group of
3153 constants being output.
3155 Subsections are optional. If you do not use subsections, everything
3156 goes in subsection number zero.
3159 Each subsection is zero-padded up to a multiple of four bytes.
3160 (Subsections may be padded a different amount on different flavors
3161 of @command{@value{AS}}.)
3165 On the H8/300 platform, each subsection is zero-padded to a word
3166 boundary (two bytes).
3167 The same is true on the Renesas SH.
3170 @c FIXME section padding (alignment)?
3171 @c Rich Pixley says padding here depends on target obj code format; that
3172 @c doesn't seem particularly useful to say without further elaboration,
3173 @c so for now I say nothing about it. If this is a generic BFD issue,
3174 @c these paragraphs might need to vanish from this manual, and be
3175 @c discussed in BFD chapter of binutils (or some such).
3179 Subsections appear in your object file in numeric order, lowest numbered
3180 to highest. (All this to be compatible with other people's assemblers.)
3181 The object file contains no representation of subsections; @code{@value{LD}} and
3182 other programs that manipulate object files see no trace of them.
3183 They just see all your text subsections as a text section, and all your
3184 data subsections as a data section.
3186 To specify which subsection you want subsequent statements assembled
3187 into, use a numeric argument to specify it, in a @samp{.text
3188 @var{expression}} or a @samp{.data @var{expression}} statement.
3191 When generating COFF output, you
3196 can also use an extra subsection
3197 argument with arbitrary named sections: @samp{.section @var{name},
3202 When generating ELF output, you
3207 can also use the @code{.subsection} directive (@pxref{SubSection})
3208 to specify a subsection: @samp{.subsection @var{expression}}.
3210 @var{Expression} should be an absolute expression
3211 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3212 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3213 begins in @code{text 0}. For instance:
3215 .text 0 # The default subsection is text 0 anyway.
3216 .ascii "This lives in the first text subsection. *"
3218 .ascii "But this lives in the second text subsection."
3220 .ascii "This lives in the data section,"
3221 .ascii "in the first data subsection."
3223 .ascii "This lives in the first text section,"
3224 .ascii "immediately following the asterisk (*)."
3227 Each section has a @dfn{location counter} incremented by one for every byte
3228 assembled into that section. Because subsections are merely a convenience
3229 restricted to @command{@value{AS}} there is no concept of a subsection location
3230 counter. There is no way to directly manipulate a location counter---but the
3231 @code{.align} directive changes it, and any label definition captures its
3232 current value. The location counter of the section where statements are being
3233 assembled is said to be the @dfn{active} location counter.
3236 @section bss Section
3239 @cindex common variable storage
3240 The bss section is used for local common variable storage.
3241 You may allocate address space in the bss section, but you may
3242 not dictate data to load into it before your program executes. When
3243 your program starts running, all the contents of the bss
3244 section are zeroed bytes.
3246 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3247 @ref{Lcomm,,@code{.lcomm}}.
3249 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3250 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3253 When assembling for a target which supports multiple sections, such as ELF or
3254 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3255 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3256 section. Typically the section will only contain symbol definitions and
3257 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3264 Symbols are a central concept: the programmer uses symbols to name
3265 things, the linker uses symbols to link, and the debugger uses symbols
3269 @cindex debuggers, and symbol order
3270 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3271 the same order they were declared. This may break some debuggers.
3276 * Setting Symbols:: Giving Symbols Other Values
3277 * Symbol Names:: Symbol Names
3278 * Dot:: The Special Dot Symbol
3279 * Symbol Attributes:: Symbol Attributes
3286 A @dfn{label} is written as a symbol immediately followed by a colon
3287 @samp{:}. The symbol then represents the current value of the
3288 active location counter, and is, for example, a suitable instruction
3289 operand. You are warned if you use the same symbol to represent two
3290 different locations: the first definition overrides any other
3294 On the HPPA, the usual form for a label need not be immediately followed by a
3295 colon, but instead must start in column zero. Only one label may be defined on
3296 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3297 provides a special directive @code{.label} for defining labels more flexibly.
3300 @node Setting Symbols
3301 @section Giving Symbols Other Values
3303 @cindex assigning values to symbols
3304 @cindex symbol values, assigning
3305 A symbol can be given an arbitrary value by writing a symbol, followed
3306 by an equals sign @samp{=}, followed by an expression
3307 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3308 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3309 equals sign @samp{=}@samp{=} here represents an equivalent of the
3310 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3313 Blackfin does not support symbol assignment with @samp{=}.
3317 @section Symbol Names
3319 @cindex symbol names
3320 @cindex names, symbol
3321 @ifclear SPECIAL-SYMS
3322 Symbol names begin with a letter or with one of @samp{._}. On most
3323 machines, you can also use @code{$} in symbol names; exceptions are
3324 noted in @ref{Machine Dependencies}. That character may be followed by any
3325 string of digits, letters, dollar signs (unless otherwise noted for a
3326 particular target machine), and underscores.
3330 Symbol names begin with a letter or with one of @samp{._}. On the
3331 Renesas SH you can also use @code{$} in symbol names. That
3332 character may be followed by any string of digits, letters, dollar signs (save
3333 on the H8/300), and underscores.
3337 Case of letters is significant: @code{foo} is a different symbol name
3340 Each symbol has exactly one name. Each name in an assembly language program
3341 refers to exactly one symbol. You may use that symbol name any number of times
3344 @subheading Local Symbol Names
3346 @cindex local symbol names
3347 @cindex symbol names, local
3348 A local symbol is any symbol beginning with certain local label prefixes.
3349 By default, the local label prefix is @samp{.L} for ELF systems or
3350 @samp{L} for traditional a.out systems, but each target may have its own
3351 set of local label prefixes.
3353 On the HPPA local symbols begin with @samp{L$}.
3356 Local symbols are defined and used within the assembler, but they are
3357 normally not saved in object files. Thus, they are not visible when debugging.
3358 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3359 @option{-L}}) to retain the local symbols in the object files.
3361 @subheading Local Labels
3363 @cindex local labels
3364 @cindex temporary symbol names
3365 @cindex symbol names, temporary
3366 Local labels help compilers and programmers use names temporarily.
3367 They create symbols which are guaranteed to be unique over the entire scope of
3368 the input source code and which can be referred to by a simple notation.
3369 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3370 represents any positive integer). To refer to the most recent previous
3371 definition of that label write @samp{@b{N}b}, using the same number as when
3372 you defined the label. To refer to the next definition of a local label, write
3373 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3376 There is no restriction on how you can use these labels, and you can reuse them
3377 too. So that it is possible to repeatedly define the same local label (using
3378 the same number @samp{@b{N}}), although you can only refer to the most recently
3379 defined local label of that number (for a backwards reference) or the next
3380 definition of a specific local label for a forward reference. It is also worth
3381 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3382 implemented in a slightly more efficient manner than the others.
3393 Which is the equivalent of:
3396 label_1: branch label_3
3397 label_2: branch label_1
3398 label_3: branch label_4
3399 label_4: branch label_3
3402 Local label names are only a notational device. They are immediately
3403 transformed into more conventional symbol names before the assembler uses them.
3404 The symbol names are stored in the symbol table, appear in error messages, and
3405 are optionally emitted to the object file. The names are constructed using
3409 @item @emph{local label prefix}
3410 All local symbols begin with the system-specific local label prefix.
3411 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3412 that start with the local label prefix. These labels are
3413 used for symbols you are never intended to see. If you use the
3414 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3415 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3416 you may use them in debugging.
3419 This is the number that was used in the local label definition. So if the
3420 label is written @samp{55:} then the number is @samp{55}.
3423 This unusual character is included so you do not accidentally invent a symbol
3424 of the same name. The character has ASCII value of @samp{\002} (control-B).
3426 @item @emph{ordinal number}
3427 This is a serial number to keep the labels distinct. The first definition of
3428 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3429 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3430 the number @samp{1} and its 15th definition gets @samp{15} as well.
3433 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3434 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3436 @subheading Dollar Local Labels
3437 @cindex dollar local symbols
3439 @code{@value{AS}} also supports an even more local form of local labels called
3440 dollar labels. These labels go out of scope (i.e., they become undefined) as
3441 soon as a non-local label is defined. Thus they remain valid for only a small
3442 region of the input source code. Normal local labels, by contrast, remain in
3443 scope for the entire file, or until they are redefined by another occurrence of
3444 the same local label.
3446 Dollar labels are defined in exactly the same way as ordinary local labels,
3447 except that they have a dollar sign suffix to their numeric value, e.g.,
3450 They can also be distinguished from ordinary local labels by their transformed
3451 names which use ASCII character @samp{\001} (control-A) as the magic character
3452 to distinguish them from ordinary labels. For example, the fifth definition of
3453 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3456 @section The Special Dot Symbol
3458 @cindex dot (symbol)
3459 @cindex @code{.} (symbol)
3460 @cindex current address
3461 @cindex location counter
3462 The special symbol @samp{.} refers to the current address that
3463 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3464 .long .} defines @code{melvin} to contain its own address.
3465 Assigning a value to @code{.} is treated the same as a @code{.org}
3467 @ifclear no-space-dir
3468 Thus, the expression @samp{.=.+4} is the same as saying
3472 @node Symbol Attributes
3473 @section Symbol Attributes
3475 @cindex symbol attributes
3476 @cindex attributes, symbol
3477 Every symbol has, as well as its name, the attributes ``Value'' and
3478 ``Type''. Depending on output format, symbols can also have auxiliary
3481 The detailed definitions are in @file{a.out.h}.
3484 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3485 all these attributes, and probably won't warn you. This makes the
3486 symbol an externally defined symbol, which is generally what you
3490 * Symbol Value:: Value
3491 * Symbol Type:: Type
3494 * a.out Symbols:: Symbol Attributes: @code{a.out}
3498 * a.out Symbols:: Symbol Attributes: @code{a.out}
3501 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3506 * COFF Symbols:: Symbol Attributes for COFF
3509 * SOM Symbols:: Symbol Attributes for SOM
3516 @cindex value of a symbol
3517 @cindex symbol value
3518 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3519 location in the text, data, bss or absolute sections the value is the
3520 number of addresses from the start of that section to the label.
3521 Naturally for text, data and bss sections the value of a symbol changes
3522 as @code{@value{LD}} changes section base addresses during linking. Absolute
3523 symbols' values do not change during linking: that is why they are
3526 The value of an undefined symbol is treated in a special way. If it is
3527 0 then the symbol is not defined in this assembler source file, and
3528 @code{@value{LD}} tries to determine its value from other files linked into the
3529 same program. You make this kind of symbol simply by mentioning a symbol
3530 name without defining it. A non-zero value represents a @code{.comm}
3531 common declaration. The value is how much common storage to reserve, in
3532 bytes (addresses). The symbol refers to the first address of the
3538 @cindex type of a symbol
3540 The type attribute of a symbol contains relocation (section)
3541 information, any flag settings indicating that a symbol is external, and
3542 (optionally), other information for linkers and debuggers. The exact
3543 format depends on the object-code output format in use.
3548 @c The following avoids a "widow" subsection title. @group would be
3549 @c better if it were available outside examples.
3552 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3554 @cindex @code{b.out} symbol attributes
3555 @cindex symbol attributes, @code{b.out}
3556 These symbol attributes appear only when @command{@value{AS}} is configured for
3557 one of the Berkeley-descended object output formats---@code{a.out} or
3563 @subsection Symbol Attributes: @code{a.out}
3565 @cindex @code{a.out} symbol attributes
3566 @cindex symbol attributes, @code{a.out}
3572 @subsection Symbol Attributes: @code{a.out}
3574 @cindex @code{a.out} symbol attributes
3575 @cindex symbol attributes, @code{a.out}
3579 * Symbol Desc:: Descriptor
3580 * Symbol Other:: Other
3584 @subsubsection Descriptor
3586 @cindex descriptor, of @code{a.out} symbol
3587 This is an arbitrary 16-bit value. You may establish a symbol's
3588 descriptor value by using a @code{.desc} statement
3589 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3590 @command{@value{AS}}.
3593 @subsubsection Other
3595 @cindex other attribute, of @code{a.out} symbol
3596 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3601 @subsection Symbol Attributes for COFF
3603 @cindex COFF symbol attributes
3604 @cindex symbol attributes, COFF
3606 The COFF format supports a multitude of auxiliary symbol attributes;
3607 like the primary symbol attributes, they are set between @code{.def} and
3608 @code{.endef} directives.
3610 @subsubsection Primary Attributes
3612 @cindex primary attributes, COFF symbols
3613 The symbol name is set with @code{.def}; the value and type,
3614 respectively, with @code{.val} and @code{.type}.
3616 @subsubsection Auxiliary Attributes
3618 @cindex auxiliary attributes, COFF symbols
3619 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3620 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3621 table information for COFF.
3626 @subsection Symbol Attributes for SOM
3628 @cindex SOM symbol attributes
3629 @cindex symbol attributes, SOM
3631 The SOM format for the HPPA supports a multitude of symbol attributes set with
3632 the @code{.EXPORT} and @code{.IMPORT} directives.
3634 The attributes are described in @cite{HP9000 Series 800 Assembly
3635 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3636 @code{EXPORT} assembler directive documentation.
3640 @chapter Expressions
3644 @cindex numeric values
3645 An @dfn{expression} specifies an address or numeric value.
3646 Whitespace may precede and/or follow an expression.
3648 The result of an expression must be an absolute number, or else an offset into
3649 a particular section. If an expression is not absolute, and there is not
3650 enough information when @command{@value{AS}} sees the expression to know its
3651 section, a second pass over the source program might be necessary to interpret
3652 the expression---but the second pass is currently not implemented.
3653 @command{@value{AS}} aborts with an error message in this situation.
3656 * Empty Exprs:: Empty Expressions
3657 * Integer Exprs:: Integer Expressions
3661 @section Empty Expressions
3663 @cindex empty expressions
3664 @cindex expressions, empty
3665 An empty expression has no value: it is just whitespace or null.
3666 Wherever an absolute expression is required, you may omit the
3667 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3668 is compatible with other assemblers.
3671 @section Integer Expressions
3673 @cindex integer expressions
3674 @cindex expressions, integer
3675 An @dfn{integer expression} is one or more @emph{arguments} delimited
3676 by @emph{operators}.
3679 * Arguments:: Arguments
3680 * Operators:: Operators
3681 * Prefix Ops:: Prefix Operators
3682 * Infix Ops:: Infix Operators
3686 @subsection Arguments
3688 @cindex expression arguments
3689 @cindex arguments in expressions
3690 @cindex operands in expressions
3691 @cindex arithmetic operands
3692 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3693 contexts arguments are sometimes called ``arithmetic operands''. In
3694 this manual, to avoid confusing them with the ``instruction operands'' of
3695 the machine language, we use the term ``argument'' to refer to parts of
3696 expressions only, reserving the word ``operand'' to refer only to machine
3697 instruction operands.
3699 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3700 @var{section} is one of text, data, bss, absolute,
3701 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3704 Numbers are usually integers.
3706 A number can be a flonum or bignum. In this case, you are warned
3707 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3708 these 32 bits are an integer. You may write integer-manipulating
3709 instructions that act on exotic constants, compatible with other
3712 @cindex subexpressions
3713 Subexpressions are a left parenthesis @samp{(} followed by an integer
3714 expression, followed by a right parenthesis @samp{)}; or a prefix
3715 operator followed by an argument.
3718 @subsection Operators
3720 @cindex operators, in expressions
3721 @cindex arithmetic functions
3722 @cindex functions, in expressions
3723 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3724 operators are followed by an argument. Infix operators appear
3725 between their arguments. Operators may be preceded and/or followed by
3729 @subsection Prefix Operator
3731 @cindex prefix operators
3732 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3733 one argument, which must be absolute.
3735 @c the tex/end tex stuff surrounding this small table is meant to make
3736 @c it align, on the printed page, with the similar table in the next
3737 @c section (which is inside an enumerate).
3739 \global\advance\leftskip by \itemindent
3744 @dfn{Negation}. Two's complement negation.
3746 @dfn{Complementation}. Bitwise not.
3750 \global\advance\leftskip by -\itemindent
3754 @subsection Infix Operators
3756 @cindex infix operators
3757 @cindex operators, permitted arguments
3758 @dfn{Infix operators} take two arguments, one on either side. Operators
3759 have precedence, but operations with equal precedence are performed left
3760 to right. Apart from @code{+} or @option{-}, both arguments must be
3761 absolute, and the result is absolute.
3764 @cindex operator precedence
3765 @cindex precedence of operators
3772 @dfn{Multiplication}.
3775 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3781 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3784 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3788 Intermediate precedence
3793 @dfn{Bitwise Inclusive Or}.
3799 @dfn{Bitwise Exclusive Or}.
3802 @dfn{Bitwise Or Not}.
3809 @cindex addition, permitted arguments
3810 @cindex plus, permitted arguments
3811 @cindex arguments for addition
3813 @dfn{Addition}. If either argument is absolute, the result has the section of
3814 the other argument. You may not add together arguments from different
3817 @cindex subtraction, permitted arguments
3818 @cindex minus, permitted arguments
3819 @cindex arguments for subtraction
3821 @dfn{Subtraction}. If the right argument is absolute, the
3822 result has the section of the left argument.
3823 If both arguments are in the same section, the result is absolute.
3824 You may not subtract arguments from different sections.
3825 @c FIXME is there still something useful to say about undefined - undefined ?
3827 @cindex comparison expressions
3828 @cindex expressions, comparison
3833 @dfn{Is Not Equal To}
3837 @dfn{Is Greater Than}
3839 @dfn{Is Greater Than Or Equal To}
3841 @dfn{Is Less Than Or Equal To}
3843 The comparison operators can be used as infix operators. A true results has a
3844 value of -1 whereas a false result has a value of 0. Note, these operators
3845 perform signed comparisons.
3848 @item Lowest Precedence
3857 These two logical operations can be used to combine the results of sub
3858 expressions. Note, unlike the comparison operators a true result returns a
3859 value of 1 but a false results does still return 0. Also note that the logical
3860 or operator has a slightly lower precedence than logical and.
3865 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3866 address; you can only have a defined section in one of the two arguments.
3869 @chapter Assembler Directives
3871 @cindex directives, machine independent
3872 @cindex pseudo-ops, machine independent
3873 @cindex machine independent directives
3874 All assembler directives have names that begin with a period (@samp{.}).
3875 The rest of the name is letters, usually in lower case.
3877 This chapter discusses directives that are available regardless of the
3878 target machine configuration for the @sc{gnu} assembler.
3880 Some machine configurations provide additional directives.
3881 @xref{Machine Dependencies}.
3884 @ifset machine-directives
3885 @xref{Machine Dependencies}, for additional directives.
3890 * Abort:: @code{.abort}
3892 * ABORT (COFF):: @code{.ABORT}
3895 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3896 * Altmacro:: @code{.altmacro}
3897 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3898 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3899 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3900 * Byte:: @code{.byte @var{expressions}}
3901 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3902 * Comm:: @code{.comm @var{symbol} , @var{length} }
3903 * Data:: @code{.data @var{subsection}}
3905 * Def:: @code{.def @var{name}}
3908 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3914 * Double:: @code{.double @var{flonums}}
3915 * Eject:: @code{.eject}
3916 * Else:: @code{.else}
3917 * Elseif:: @code{.elseif}
3920 * Endef:: @code{.endef}
3923 * Endfunc:: @code{.endfunc}
3924 * Endif:: @code{.endif}
3925 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3926 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3927 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3929 * Error:: @code{.error @var{string}}
3930 * Exitm:: @code{.exitm}
3931 * Extern:: @code{.extern}
3932 * Fail:: @code{.fail}
3933 * File:: @code{.file}
3934 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3935 * Float:: @code{.float @var{flonums}}
3936 * Func:: @code{.func}
3937 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3939 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3940 * Hidden:: @code{.hidden @var{names}}
3943 * hword:: @code{.hword @var{expressions}}
3944 * Ident:: @code{.ident}
3945 * If:: @code{.if @var{absolute expression}}
3946 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3947 * Include:: @code{.include "@var{file}"}
3948 * Int:: @code{.int @var{expressions}}
3950 * Internal:: @code{.internal @var{names}}
3953 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3954 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3955 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3956 * Lflags:: @code{.lflags}
3957 @ifclear no-line-dir
3958 * Line:: @code{.line @var{line-number}}
3961 * Linkonce:: @code{.linkonce [@var{type}]}
3962 * List:: @code{.list}
3963 * Ln:: @code{.ln @var{line-number}}
3964 * Loc:: @code{.loc @var{fileno} @var{lineno}}
3965 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
3967 * Local:: @code{.local @var{names}}
3970 * Long:: @code{.long @var{expressions}}
3972 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3975 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3976 * MRI:: @code{.mri @var{val}}
3977 * Noaltmacro:: @code{.noaltmacro}
3978 * Nolist:: @code{.nolist}
3979 * Octa:: @code{.octa @var{bignums}}
3980 * Org:: @code{.org @var{new-lc}, @var{fill}}
3981 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3983 * PopSection:: @code{.popsection}
3984 * Previous:: @code{.previous}
3987 * Print:: @code{.print @var{string}}
3989 * Protected:: @code{.protected @var{names}}
3992 * Psize:: @code{.psize @var{lines}, @var{columns}}
3993 * Purgem:: @code{.purgem @var{name}}
3995 * PushSection:: @code{.pushsection @var{name}}
3998 * Quad:: @code{.quad @var{bignums}}
3999 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4000 * Rept:: @code{.rept @var{count}}
4001 * Sbttl:: @code{.sbttl "@var{subheading}"}
4003 * Scl:: @code{.scl @var{class}}
4006 * Section:: @code{.section @var{name}[, @var{flags}]}
4009 * Set:: @code{.set @var{symbol}, @var{expression}}
4010 * Short:: @code{.short @var{expressions}}
4011 * Single:: @code{.single @var{flonums}}
4013 * Size:: @code{.size [@var{name} , @var{expression}]}
4015 @ifclear no-space-dir
4016 * Skip:: @code{.skip @var{size} , @var{fill}}
4019 * Sleb128:: @code{.sleb128 @var{expressions}}
4020 @ifclear no-space-dir
4021 * Space:: @code{.space @var{size} , @var{fill}}
4024 * Stab:: @code{.stabd, .stabn, .stabs}
4027 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4028 * Struct:: @code{.struct @var{expression}}
4030 * SubSection:: @code{.subsection}
4031 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4035 * Tag:: @code{.tag @var{structname}}
4038 * Text:: @code{.text @var{subsection}}
4039 * Title:: @code{.title "@var{heading}"}
4041 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4044 * Uleb128:: @code{.uleb128 @var{expressions}}
4046 * Val:: @code{.val @var{addr}}
4050 * Version:: @code{.version "@var{string}"}
4051 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4052 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4055 * Warning:: @code{.warning @var{string}}
4056 * Weak:: @code{.weak @var{names}}
4057 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4058 * Word:: @code{.word @var{expressions}}
4059 * Deprecated:: Deprecated Directives
4063 @section @code{.abort}
4065 @cindex @code{abort} directive
4066 @cindex stopping the assembly
4067 This directive stops the assembly immediately. It is for
4068 compatibility with other assemblers. The original idea was that the
4069 assembly language source would be piped into the assembler. If the sender
4070 of the source quit, it could use this directive tells @command{@value{AS}} to
4071 quit also. One day @code{.abort} will not be supported.
4075 @section @code{.ABORT} (COFF)
4077 @cindex @code{ABORT} directive
4078 When producing COFF output, @command{@value{AS}} accepts this directive as a
4079 synonym for @samp{.abort}.
4082 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4088 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4090 @cindex padding the location counter
4091 @cindex @code{align} directive
4092 Pad the location counter (in the current subsection) to a particular storage
4093 boundary. The first expression (which must be absolute) is the alignment
4094 required, as described below.
4096 The second expression (also absolute) gives the fill value to be stored in the
4097 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4098 padding bytes are normally zero. However, on some systems, if the section is
4099 marked as containing code and the fill value is omitted, the space is filled
4100 with no-op instructions.
4102 The third expression is also absolute, and is also optional. If it is present,
4103 it is the maximum number of bytes that should be skipped by this alignment
4104 directive. If doing the alignment would require skipping more bytes than the
4105 specified maximum, then the alignment is not done at all. You can omit the
4106 fill value (the second argument) entirely by simply using two commas after the
4107 required alignment; this can be useful if you want the alignment to be filled
4108 with no-op instructions when appropriate.
4110 The way the required alignment is specified varies from system to system.
4111 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4112 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4113 alignment request in bytes. For example @samp{.align 8} advances
4114 the location counter until it is a multiple of 8. If the location counter
4115 is already a multiple of 8, no change is needed. For the tic54x, the
4116 first expression is the alignment request in words.
4118 For other systems, including ppc, i386 using a.out format, arm and
4119 strongarm, it is the
4120 number of low-order zero bits the location counter must have after
4121 advancement. For example @samp{.align 3} advances the location
4122 counter until it a multiple of 8. If the location counter is already a
4123 multiple of 8, no change is needed.
4125 This inconsistency is due to the different behaviors of the various
4126 native assemblers for these systems which GAS must emulate.
4127 GAS also provides @code{.balign} and @code{.p2align} directives,
4128 described later, which have a consistent behavior across all
4129 architectures (but are specific to GAS).
4132 @section @code{.altmacro}
4133 Enable alternate macro mode, enabling:
4136 @item LOCAL @var{name} [ , @dots{} ]
4137 One additional directive, @code{LOCAL}, is available. It is used to
4138 generate a string replacement for each of the @var{name} arguments, and
4139 replace any instances of @var{name} in each macro expansion. The
4140 replacement string is unique in the assembly, and different for each
4141 separate macro expansion. @code{LOCAL} allows you to write macros that
4142 define symbols, without fear of conflict between separate macro expansions.
4144 @item String delimiters
4145 You can write strings delimited in these other ways besides
4146 @code{"@var{string}"}:
4149 @item '@var{string}'
4150 You can delimit strings with single-quote characters.
4152 @item <@var{string}>
4153 You can delimit strings with matching angle brackets.
4156 @item single-character string escape
4157 To include any single character literally in a string (even if the
4158 character would otherwise have some special meaning), you can prefix the
4159 character with @samp{!} (an exclamation mark). For example, you can
4160 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4162 @item Expression results as strings
4163 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4164 and use the result as a string.
4168 @section @code{.ascii "@var{string}"}@dots{}
4170 @cindex @code{ascii} directive
4171 @cindex string literals
4172 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4173 separated by commas. It assembles each string (with no automatic
4174 trailing zero byte) into consecutive addresses.
4177 @section @code{.asciz "@var{string}"}@dots{}
4179 @cindex @code{asciz} directive
4180 @cindex zero-terminated strings
4181 @cindex null-terminated strings
4182 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4183 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4186 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4188 @cindex padding the location counter given number of bytes
4189 @cindex @code{balign} directive
4190 Pad the location counter (in the current subsection) to a particular
4191 storage boundary. The first expression (which must be absolute) is the
4192 alignment request in bytes. For example @samp{.balign 8} advances
4193 the location counter until it is a multiple of 8. If the location counter
4194 is already a multiple of 8, no change is needed.
4196 The second expression (also absolute) gives the fill value to be stored in the
4197 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4198 padding bytes are normally zero. However, on some systems, if the section is
4199 marked as containing code and the fill value is omitted, the space is filled
4200 with no-op instructions.
4202 The third expression is also absolute, and is also optional. If it is present,
4203 it is the maximum number of bytes that should be skipped by this alignment
4204 directive. If doing the alignment would require skipping more bytes than the
4205 specified maximum, then the alignment is not done at all. You can omit the
4206 fill value (the second argument) entirely by simply using two commas after the
4207 required alignment; this can be useful if you want the alignment to be filled
4208 with no-op instructions when appropriate.
4210 @cindex @code{balignw} directive
4211 @cindex @code{balignl} directive
4212 The @code{.balignw} and @code{.balignl} directives are variants of the
4213 @code{.balign} directive. The @code{.balignw} directive treats the fill
4214 pattern as a two byte word value. The @code{.balignl} directives treats the
4215 fill pattern as a four byte longword value. For example, @code{.balignw
4216 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4217 filled in with the value 0x368d (the exact placement of the bytes depends upon
4218 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4222 @section @code{.byte @var{expressions}}
4224 @cindex @code{byte} directive
4225 @cindex integers, one byte
4226 @code{.byte} expects zero or more expressions, separated by commas.
4227 Each expression is assembled into the next byte.
4229 @node CFI directives
4230 @section @code{.cfi_sections @var{section_list}}
4231 @cindex @code{cfi_sections} directive
4232 @code{.cfi_sections} may be used to specify whether CFI directives
4233 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4234 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4235 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4236 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4237 directive is not used is @code{.cfi_sections .eh_frame}.
4239 @section @code{.cfi_startproc [simple]}
4240 @cindex @code{cfi_startproc} directive
4241 @code{.cfi_startproc} is used at the beginning of each function that
4242 should have an entry in @code{.eh_frame}. It initializes some internal
4243 data structures. Don't forget to close the function by
4244 @code{.cfi_endproc}.
4246 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4247 it also emits some architecture dependent initial CFI instructions.
4249 @section @code{.cfi_endproc}
4250 @cindex @code{cfi_endproc} directive
4251 @code{.cfi_endproc} is used at the end of a function where it closes its
4252 unwind entry previously opened by
4253 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4255 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4256 @code{.cfi_personality} defines personality routine and its encoding.
4257 @var{encoding} must be a constant determining how the personality
4258 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4259 argument is not present, otherwise second argument should be
4260 a constant or a symbol name. When using indirect encodings,
4261 the symbol provided should be the location where personality
4262 can be loaded from, not the personality routine itself.
4263 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4264 no personality routine.
4266 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4267 @code{.cfi_lsda} defines LSDA and its encoding.
4268 @var{encoding} must be a constant determining how the LSDA
4269 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4270 argument is not present, otherwise second argument should be a constant
4271 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4274 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4275 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4276 address from @var{register} and add @var{offset} to it}.
4278 @section @code{.cfi_def_cfa_register @var{register}}
4279 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4280 now on @var{register} will be used instead of the old one. Offset
4283 @section @code{.cfi_def_cfa_offset @var{offset}}
4284 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4285 remains the same, but @var{offset} is new. Note that it is the
4286 absolute offset that will be added to a defined register to compute
4289 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4290 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4291 value that is added/substracted from the previous offset.
4293 @section @code{.cfi_offset @var{register}, @var{offset}}
4294 Previous value of @var{register} is saved at offset @var{offset} from
4297 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4298 Previous value of @var{register} is saved at offset @var{offset} from
4299 the current CFA register. This is transformed to @code{.cfi_offset}
4300 using the known displacement of the CFA register from the CFA.
4301 This is often easier to use, because the number will match the
4302 code it's annotating.
4304 @section @code{.cfi_register @var{register1}, @var{register2}}
4305 Previous value of @var{register1} is saved in register @var{register2}.
4307 @section @code{.cfi_restore @var{register}}
4308 @code{.cfi_restore} says that the rule for @var{register} is now the
4309 same as it was at the beginning of the function, after all initial
4310 instruction added by @code{.cfi_startproc} were executed.
4312 @section @code{.cfi_undefined @var{register}}
4313 From now on the previous value of @var{register} can't be restored anymore.
4315 @section @code{.cfi_same_value @var{register}}
4316 Current value of @var{register} is the same like in the previous frame,
4317 i.e. no restoration needed.
4319 @section @code{.cfi_remember_state},
4320 First save all current rules for all registers by @code{.cfi_remember_state},
4321 then totally screw them up by subsequent @code{.cfi_*} directives and when
4322 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4323 the previous saved state.
4325 @section @code{.cfi_return_column @var{register}}
4326 Change return column @var{register}, i.e. the return address is either
4327 directly in @var{register} or can be accessed by rules for @var{register}.
4329 @section @code{.cfi_signal_frame}
4330 Mark current function as signal trampoline.
4332 @section @code{.cfi_window_save}
4333 SPARC register window has been saved.
4335 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4336 Allows the user to add arbitrary bytes to the unwind info. One
4337 might use this to add OS-specific CFI opcodes, or generic CFI
4338 opcodes that GAS does not yet support.
4340 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4341 The current value of @var{register} is @var{label}. The value of @var{label}
4342 will be encoded in the output file according to @var{encoding}; see the
4343 description of @code{.cfi_personality} for details on this encoding.
4345 The usefulness of equating a register to a fixed label is probably
4346 limited to the return address register. Here, it can be useful to
4347 mark a code segment that has only one return address which is reached
4348 by a direct branch and no copy of the return address exists in memory
4349 or another register.
4352 @section @code{.comm @var{symbol} , @var{length} }
4354 @cindex @code{comm} directive
4355 @cindex symbol, common
4356 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4357 common symbol in one object file may be merged with a defined or common symbol
4358 of the same name in another object file. If @code{@value{LD}} does not see a
4359 definition for the symbol--just one or more common symbols--then it will
4360 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4361 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4362 the same name, and they do not all have the same size, it will allocate space
4363 using the largest size.
4366 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4367 an optional third argument. This is the desired alignment of the symbol,
4368 specified for ELF as a byte boundary (for example, an alignment of 16 means
4369 that the least significant 4 bits of the address should be zero), and for PE
4370 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4371 boundary). The alignment must be an absolute expression, and it must be a
4372 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4373 common symbol, it will use the alignment when placing the symbol. If no
4374 alignment is specified, @command{@value{AS}} will set the alignment to the
4375 largest power of two less than or equal to the size of the symbol, up to a
4376 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4377 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4378 @samp{--section-alignment} option; image file sections in PE are aligned to
4379 multiples of 4096, which is far too large an alignment for ordinary variables.
4380 It is rather the default alignment for (non-debug) sections within object
4381 (@samp{*.o}) files, which are less strictly aligned.}.
4385 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4386 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4390 @section @code{.data @var{subsection}}
4392 @cindex @code{data} directive
4393 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4394 end of the data subsection numbered @var{subsection} (which is an
4395 absolute expression). If @var{subsection} is omitted, it defaults
4400 @section @code{.def @var{name}}
4402 @cindex @code{def} directive
4403 @cindex COFF symbols, debugging
4404 @cindex debugging COFF symbols
4405 Begin defining debugging information for a symbol @var{name}; the
4406 definition extends until the @code{.endef} directive is encountered.
4409 This directive is only observed when @command{@value{AS}} is configured for COFF
4410 format output; when producing @code{b.out}, @samp{.def} is recognized,
4417 @section @code{.desc @var{symbol}, @var{abs-expression}}
4419 @cindex @code{desc} directive
4420 @cindex COFF symbol descriptor
4421 @cindex symbol descriptor, COFF
4422 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4423 to the low 16 bits of an absolute expression.
4426 The @samp{.desc} directive is not available when @command{@value{AS}} is
4427 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4428 object format. For the sake of compatibility, @command{@value{AS}} accepts
4429 it, but produces no output, when configured for COFF.
4435 @section @code{.dim}
4437 @cindex @code{dim} directive
4438 @cindex COFF auxiliary symbol information
4439 @cindex auxiliary symbol information, COFF
4440 This directive is generated by compilers to include auxiliary debugging
4441 information in the symbol table. It is only permitted inside
4442 @code{.def}/@code{.endef} pairs.
4445 @samp{.dim} is only meaningful when generating COFF format output; when
4446 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4452 @section @code{.double @var{flonums}}
4454 @cindex @code{double} directive
4455 @cindex floating point numbers (double)
4456 @code{.double} expects zero or more flonums, separated by commas. It
4457 assembles floating point numbers.
4459 The exact kind of floating point numbers emitted depends on how
4460 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4464 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4465 in @sc{ieee} format.
4470 @section @code{.eject}
4472 @cindex @code{eject} directive
4473 @cindex new page, in listings
4474 @cindex page, in listings
4475 @cindex listing control: new page
4476 Force a page break at this point, when generating assembly listings.
4479 @section @code{.else}
4481 @cindex @code{else} directive
4482 @code{.else} is part of the @command{@value{AS}} support for conditional
4483 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4484 of code to be assembled if the condition for the preceding @code{.if}
4488 @section @code{.elseif}
4490 @cindex @code{elseif} directive
4491 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4492 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4493 @code{.if} block that would otherwise fill the entire @code{.else} section.
4496 @section @code{.end}
4498 @cindex @code{end} directive
4499 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4500 process anything in the file past the @code{.end} directive.
4504 @section @code{.endef}
4506 @cindex @code{endef} directive
4507 This directive flags the end of a symbol definition begun with
4511 @samp{.endef} is only meaningful when generating COFF format output; if
4512 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4513 directive but ignores it.
4518 @section @code{.endfunc}
4519 @cindex @code{endfunc} directive
4520 @code{.endfunc} marks the end of a function specified with @code{.func}.
4523 @section @code{.endif}
4525 @cindex @code{endif} directive
4526 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4527 it marks the end of a block of code that is only assembled
4528 conditionally. @xref{If,,@code{.if}}.
4531 @section @code{.equ @var{symbol}, @var{expression}}
4533 @cindex @code{equ} directive
4534 @cindex assigning values to symbols
4535 @cindex symbols, assigning values to
4536 This directive sets the value of @var{symbol} to @var{expression}.
4537 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4540 The syntax for @code{equ} on the HPPA is
4541 @samp{@var{symbol} .equ @var{expression}}.
4545 The syntax for @code{equ} on the Z80 is
4546 @samp{@var{symbol} equ @var{expression}}.
4547 On the Z80 it is an eror if @var{symbol} is already defined,
4548 but the symbol is not protected from later redefinition.
4549 Compare @ref{Equiv}.
4553 @section @code{.equiv @var{symbol}, @var{expression}}
4554 @cindex @code{equiv} directive
4555 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4556 the assembler will signal an error if @var{symbol} is already defined. Note a
4557 symbol which has been referenced but not actually defined is considered to be
4560 Except for the contents of the error message, this is roughly equivalent to
4567 plus it protects the symbol from later redefinition.
4570 @section @code{.eqv @var{symbol}, @var{expression}}
4571 @cindex @code{eqv} directive
4572 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4573 evaluate the expression or any part of it immediately. Instead each time
4574 the resulting symbol is used in an expression, a snapshot of its current
4578 @section @code{.err}
4579 @cindex @code{err} directive
4580 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4581 message and, unless the @option{-Z} option was used, it will not generate an
4582 object file. This can be used to signal an error in conditionally compiled code.
4585 @section @code{.error "@var{string}"}
4586 @cindex error directive
4588 Similarly to @code{.err}, this directive emits an error, but you can specify a
4589 string that will be emitted as the error message. If you don't specify the
4590 message, it defaults to @code{".error directive invoked in source file"}.
4591 @xref{Errors, ,Error and Warning Messages}.
4594 .error "This code has not been assembled and tested."
4598 @section @code{.exitm}
4599 Exit early from the current macro definition. @xref{Macro}.
4602 @section @code{.extern}
4604 @cindex @code{extern} directive
4605 @code{.extern} is accepted in the source program---for compatibility
4606 with other assemblers---but it is ignored. @command{@value{AS}} treats
4607 all undefined symbols as external.
4610 @section @code{.fail @var{expression}}
4612 @cindex @code{fail} directive
4613 Generates an error or a warning. If the value of the @var{expression} is 500
4614 or more, @command{@value{AS}} will print a warning message. If the value is less
4615 than 500, @command{@value{AS}} will print an error message. The message will
4616 include the value of @var{expression}. This can occasionally be useful inside
4617 complex nested macros or conditional assembly.
4620 @section @code{.file}
4621 @cindex @code{file} directive
4623 @ifclear no-file-dir
4624 There are two different versions of the @code{.file} directive. Targets
4625 that support DWARF2 line number information use the DWARF2 version of
4626 @code{.file}. Other targets use the default version.
4628 @subheading Default Version
4630 @cindex logical file name
4631 @cindex file name, logical
4632 This version of the @code{.file} directive tells @command{@value{AS}} that we
4633 are about to start a new logical file. The syntax is:
4639 @var{string} is the new file name. In general, the filename is
4640 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4641 to specify an empty file name, you must give the quotes--@code{""}. This
4642 statement may go away in future: it is only recognized to be compatible with
4643 old @command{@value{AS}} programs.
4645 @subheading DWARF2 Version
4648 When emitting DWARF2 line number information, @code{.file} assigns filenames
4649 to the @code{.debug_line} file name table. The syntax is:
4652 .file @var{fileno} @var{filename}
4655 The @var{fileno} operand should be a unique positive integer to use as the
4656 index of the entry in the table. The @var{filename} operand is a C string
4659 The detail of filename indices is exposed to the user because the filename
4660 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4661 information, and thus the user must know the exact indices that table
4665 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4667 @cindex @code{fill} directive
4668 @cindex writing patterns in memory
4669 @cindex patterns, writing in memory
4670 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4671 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4672 may be zero or more. @var{Size} may be zero or more, but if it is
4673 more than 8, then it is deemed to have the value 8, compatible with
4674 other people's assemblers. The contents of each @var{repeat} bytes
4675 is taken from an 8-byte number. The highest order 4 bytes are
4676 zero. The lowest order 4 bytes are @var{value} rendered in the
4677 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4678 Each @var{size} bytes in a repetition is taken from the lowest order
4679 @var{size} bytes of this number. Again, this bizarre behavior is
4680 compatible with other people's assemblers.
4682 @var{size} and @var{value} are optional.
4683 If the second comma and @var{value} are absent, @var{value} is
4684 assumed zero. If the first comma and following tokens are absent,
4685 @var{size} is assumed to be 1.
4688 @section @code{.float @var{flonums}}
4690 @cindex floating point numbers (single)
4691 @cindex @code{float} directive
4692 This directive assembles zero or more flonums, separated by commas. It
4693 has the same effect as @code{.single}.
4695 The exact kind of floating point numbers emitted depends on how
4696 @command{@value{AS}} is configured.
4697 @xref{Machine Dependencies}.
4701 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4702 in @sc{ieee} format.
4707 @section @code{.func @var{name}[,@var{label}]}
4708 @cindex @code{func} directive
4709 @code{.func} emits debugging information to denote function @var{name}, and
4710 is ignored unless the file is assembled with debugging enabled.
4711 Only @samp{--gstabs[+]} is currently supported.
4712 @var{label} is the entry point of the function and if omitted @var{name}
4713 prepended with the @samp{leading char} is used.
4714 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4715 All functions are currently defined to have @code{void} return type.
4716 The function must be terminated with @code{.endfunc}.
4719 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4721 @cindex @code{global} directive
4722 @cindex symbol, making visible to linker
4723 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4724 @var{symbol} in your partial program, its value is made available to
4725 other partial programs that are linked with it. Otherwise,
4726 @var{symbol} takes its attributes from a symbol of the same name
4727 from another file linked into the same program.
4729 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4730 compatibility with other assemblers.
4733 On the HPPA, @code{.global} is not always enough to make it accessible to other
4734 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4735 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4740 @section @code{.gnu_attribute @var{tag},@var{value}}
4741 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4744 @section @code{.hidden @var{names}}
4746 @cindex @code{hidden} directive
4748 This is one of the ELF visibility directives. The other two are
4749 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4750 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4752 This directive overrides the named symbols default visibility (which is set by
4753 their binding: local, global or weak). The directive sets the visibility to
4754 @code{hidden} which means that the symbols are not visible to other components.
4755 Such symbols are always considered to be @code{protected} as well.
4759 @section @code{.hword @var{expressions}}
4761 @cindex @code{hword} directive
4762 @cindex integers, 16-bit
4763 @cindex numbers, 16-bit
4764 @cindex sixteen bit integers
4765 This expects zero or more @var{expressions}, and emits
4766 a 16 bit number for each.
4769 This directive is a synonym for @samp{.short}; depending on the target
4770 architecture, it may also be a synonym for @samp{.word}.
4774 This directive is a synonym for @samp{.short}.
4777 This directive is a synonym for both @samp{.short} and @samp{.word}.
4782 @section @code{.ident}
4784 @cindex @code{ident} directive
4786 This directive is used by some assemblers to place tags in object files. The
4787 behavior of this directive varies depending on the target. When using the
4788 a.out object file format, @command{@value{AS}} simply accepts the directive for
4789 source-file compatibility with existing assemblers, but does not emit anything
4790 for it. When using COFF, comments are emitted to the @code{.comment} or
4791 @code{.rdata} section, depending on the target. When using ELF, comments are
4792 emitted to the @code{.comment} section.
4795 @section @code{.if @var{absolute expression}}
4797 @cindex conditional assembly
4798 @cindex @code{if} directive
4799 @code{.if} marks the beginning of a section of code which is only
4800 considered part of the source program being assembled if the argument
4801 (which must be an @var{absolute expression}) is non-zero. The end of
4802 the conditional section of code must be marked by @code{.endif}
4803 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4804 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4805 If you have several conditions to check, @code{.elseif} may be used to avoid
4806 nesting blocks if/else within each subsequent @code{.else} block.
4808 The following variants of @code{.if} are also supported:
4810 @cindex @code{ifdef} directive
4811 @item .ifdef @var{symbol}
4812 Assembles the following section of code if the specified @var{symbol}
4813 has been defined. Note a symbol which has been referenced but not yet defined
4814 is considered to be undefined.
4816 @cindex @code{ifb} directive
4817 @item .ifb @var{text}
4818 Assembles the following section of code if the operand is blank (empty).
4820 @cindex @code{ifc} directive
4821 @item .ifc @var{string1},@var{string2}
4822 Assembles the following section of code if the two strings are the same. The
4823 strings may be optionally quoted with single quotes. If they are not quoted,
4824 the first string stops at the first comma, and the second string stops at the
4825 end of the line. Strings which contain whitespace should be quoted. The
4826 string comparison is case sensitive.
4828 @cindex @code{ifeq} directive
4829 @item .ifeq @var{absolute expression}
4830 Assembles the following section of code if the argument is zero.
4832 @cindex @code{ifeqs} directive
4833 @item .ifeqs @var{string1},@var{string2}
4834 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4836 @cindex @code{ifge} directive
4837 @item .ifge @var{absolute expression}
4838 Assembles the following section of code if the argument is greater than or
4841 @cindex @code{ifgt} directive
4842 @item .ifgt @var{absolute expression}
4843 Assembles the following section of code if the argument is greater than zero.
4845 @cindex @code{ifle} directive
4846 @item .ifle @var{absolute expression}
4847 Assembles the following section of code if the argument is less than or equal
4850 @cindex @code{iflt} directive
4851 @item .iflt @var{absolute expression}
4852 Assembles the following section of code if the argument is less than zero.
4854 @cindex @code{ifnb} directive
4855 @item .ifnb @var{text}
4856 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4857 following section of code if the operand is non-blank (non-empty).
4859 @cindex @code{ifnc} directive
4860 @item .ifnc @var{string1},@var{string2}.
4861 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4862 following section of code if the two strings are not the same.
4864 @cindex @code{ifndef} directive
4865 @cindex @code{ifnotdef} directive
4866 @item .ifndef @var{symbol}
4867 @itemx .ifnotdef @var{symbol}
4868 Assembles the following section of code if the specified @var{symbol}
4869 has not been defined. Both spelling variants are equivalent. Note a symbol
4870 which has been referenced but not yet defined is considered to be undefined.
4872 @cindex @code{ifne} directive
4873 @item .ifne @var{absolute expression}
4874 Assembles the following section of code if the argument is not equal to zero
4875 (in other words, this is equivalent to @code{.if}).
4877 @cindex @code{ifnes} directive
4878 @item .ifnes @var{string1},@var{string2}
4879 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4880 following section of code if the two strings are not the same.
4884 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4886 @cindex @code{incbin} directive
4887 @cindex binary files, including
4888 The @code{incbin} directive includes @var{file} verbatim at the current
4889 location. You can control the search paths used with the @samp{-I} command-line
4890 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4893 The @var{skip} argument skips a number of bytes from the start of the
4894 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4895 read. Note that the data is not aligned in any way, so it is the user's
4896 responsibility to make sure that proper alignment is provided both before and
4897 after the @code{incbin} directive.
4900 @section @code{.include "@var{file}"}
4902 @cindex @code{include} directive
4903 @cindex supporting files, including
4904 @cindex files, including
4905 This directive provides a way to include supporting files at specified
4906 points in your source program. The code from @var{file} is assembled as
4907 if it followed the point of the @code{.include}; when the end of the
4908 included file is reached, assembly of the original file continues. You
4909 can control the search paths used with the @samp{-I} command-line option
4910 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4914 @section @code{.int @var{expressions}}
4916 @cindex @code{int} directive
4917 @cindex integers, 32-bit
4918 Expect zero or more @var{expressions}, of any section, separated by commas.
4919 For each expression, emit a number that, at run time, is the value of that
4920 expression. The byte order and bit size of the number depends on what kind
4921 of target the assembly is for.
4925 On most forms of the H8/300, @code{.int} emits 16-bit
4926 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4933 @section @code{.internal @var{names}}
4935 @cindex @code{internal} directive
4937 This is one of the ELF visibility directives. The other two are
4938 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4939 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4941 This directive overrides the named symbols default visibility (which is set by
4942 their binding: local, global or weak). The directive sets the visibility to
4943 @code{internal} which means that the symbols are considered to be @code{hidden}
4944 (i.e., not visible to other components), and that some extra, processor specific
4945 processing must also be performed upon the symbols as well.
4949 @section @code{.irp @var{symbol},@var{values}}@dots{}
4951 @cindex @code{irp} directive
4952 Evaluate a sequence of statements assigning different values to @var{symbol}.
4953 The sequence of statements starts at the @code{.irp} directive, and is
4954 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4955 set to @var{value}, and the sequence of statements is assembled. If no
4956 @var{value} is listed, the sequence of statements is assembled once, with
4957 @var{symbol} set to the null string. To refer to @var{symbol} within the
4958 sequence of statements, use @var{\symbol}.
4960 For example, assembling
4968 is equivalent to assembling
4976 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4979 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4981 @cindex @code{irpc} directive
4982 Evaluate a sequence of statements assigning different values to @var{symbol}.
4983 The sequence of statements starts at the @code{.irpc} directive, and is
4984 terminated by an @code{.endr} directive. For each character in @var{value},
4985 @var{symbol} is set to the character, and the sequence of statements is
4986 assembled. If no @var{value} is listed, the sequence of statements is
4987 assembled once, with @var{symbol} set to the null string. To refer to
4988 @var{symbol} within the sequence of statements, use @var{\symbol}.
4990 For example, assembling
4998 is equivalent to assembling
5006 For some caveats with the spelling of @var{symbol}, see also the discussion
5010 @section @code{.lcomm @var{symbol} , @var{length}}
5012 @cindex @code{lcomm} directive
5013 @cindex local common symbols
5014 @cindex symbols, local common
5015 Reserve @var{length} (an absolute expression) bytes for a local common
5016 denoted by @var{symbol}. The section and value of @var{symbol} are
5017 those of the new local common. The addresses are allocated in the bss
5018 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5019 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5020 not visible to @code{@value{LD}}.
5023 Some targets permit a third argument to be used with @code{.lcomm}. This
5024 argument specifies the desired alignment of the symbol in the bss section.
5028 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5029 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5033 @section @code{.lflags}
5035 @cindex @code{lflags} directive (ignored)
5036 @command{@value{AS}} accepts this directive, for compatibility with other
5037 assemblers, but ignores it.
5039 @ifclear no-line-dir
5041 @section @code{.line @var{line-number}}
5043 @cindex @code{line} directive
5044 @cindex logical line number
5046 Change the logical line number. @var{line-number} must be an absolute
5047 expression. The next line has that logical line number. Therefore any other
5048 statements on the current line (after a statement separator character) are
5049 reported as on logical line number @var{line-number} @minus{} 1. One day
5050 @command{@value{AS}} will no longer support this directive: it is recognized only
5051 for compatibility with existing assembler programs.
5054 Even though this is a directive associated with the @code{a.out} or
5055 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5056 when producing COFF output, and treats @samp{.line} as though it
5057 were the COFF @samp{.ln} @emph{if} it is found outside a
5058 @code{.def}/@code{.endef} pair.
5060 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5061 used by compilers to generate auxiliary symbol information for
5066 @section @code{.linkonce [@var{type}]}
5068 @cindex @code{linkonce} directive
5069 @cindex common sections
5070 Mark the current section so that the linker only includes a single copy of it.
5071 This may be used to include the same section in several different object files,
5072 but ensure that the linker will only include it once in the final output file.
5073 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5074 Duplicate sections are detected based on the section name, so it should be
5077 This directive is only supported by a few object file formats; as of this
5078 writing, the only object file format which supports it is the Portable
5079 Executable format used on Windows NT.
5081 The @var{type} argument is optional. If specified, it must be one of the
5082 following strings. For example:
5086 Not all types may be supported on all object file formats.
5090 Silently discard duplicate sections. This is the default.
5093 Warn if there are duplicate sections, but still keep only one copy.
5096 Warn if any of the duplicates have different sizes.
5099 Warn if any of the duplicates do not have exactly the same contents.
5103 @section @code{.list}
5105 @cindex @code{list} directive
5106 @cindex listing control, turning on
5107 Control (in conjunction with the @code{.nolist} directive) whether or
5108 not assembly listings are generated. These two directives maintain an
5109 internal counter (which is zero initially). @code{.list} increments the
5110 counter, and @code{.nolist} decrements it. Assembly listings are
5111 generated whenever the counter is greater than zero.
5113 By default, listings are disabled. When you enable them (with the
5114 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5115 the initial value of the listing counter is one.
5118 @section @code{.ln @var{line-number}}
5120 @cindex @code{ln} directive
5121 @ifclear no-line-dir
5122 @samp{.ln} is a synonym for @samp{.line}.
5125 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5126 must be an absolute expression. The next line has that logical
5127 line number, so any other statements on the current line (after a
5128 statement separator character @code{;}) are reported as on logical
5129 line number @var{line-number} @minus{} 1.
5132 This directive is accepted, but ignored, when @command{@value{AS}} is
5133 configured for @code{b.out}; its effect is only associated with COFF
5139 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5140 @cindex @code{loc} directive
5141 When emitting DWARF2 line number information,
5142 the @code{.loc} directive will add a row to the @code{.debug_line} line
5143 number matrix corresponding to the immediately following assembly
5144 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5145 arguments will be applied to the @code{.debug_line} state machine before
5148 The @var{options} are a sequence of the following tokens in any order:
5152 This option will set the @code{basic_block} register in the
5153 @code{.debug_line} state machine to @code{true}.
5156 This option will set the @code{prologue_end} register in the
5157 @code{.debug_line} state machine to @code{true}.
5159 @item epilogue_begin
5160 This option will set the @code{epilogue_begin} register in the
5161 @code{.debug_line} state machine to @code{true}.
5163 @item is_stmt @var{value}
5164 This option will set the @code{is_stmt} register in the
5165 @code{.debug_line} state machine to @code{value}, which must be
5168 @item isa @var{value}
5169 This directive will set the @code{isa} register in the @code{.debug_line}
5170 state machine to @var{value}, which must be an unsigned integer.
5172 @item discriminator @var{value}
5173 This directive will set the @code{discriminator} register in the @code{.debug_line}
5174 state machine to @var{value}, which must be an unsigned integer.
5178 @node Loc_mark_labels
5179 @section @code{.loc_mark_labels @var{enable}}
5180 @cindex @code{loc_mark_labels} directive
5181 When emitting DWARF2 line number information,
5182 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5183 to the @code{.debug_line} line number matrix with the @code{basic_block}
5184 register in the state machine set whenever a code label is seen.
5185 The @var{enable} argument should be either 1 or 0, to enable or disable
5186 this function respectively.
5190 @section @code{.local @var{names}}
5192 @cindex @code{local} directive
5193 This directive, which is available for ELF targets, marks each symbol in
5194 the comma-separated list of @code{names} as a local symbol so that it
5195 will not be externally visible. If the symbols do not already exist,
5196 they will be created.
5198 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5199 accept an alignment argument, which is the case for most ELF targets,
5200 the @code{.local} directive can be used in combination with @code{.comm}
5201 (@pxref{Comm}) to define aligned local common data.
5205 @section @code{.long @var{expressions}}
5207 @cindex @code{long} directive
5208 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5211 @c no one seems to know what this is for or whether this description is
5212 @c what it really ought to do
5214 @section @code{.lsym @var{symbol}, @var{expression}}
5216 @cindex @code{lsym} directive
5217 @cindex symbol, not referenced in assembly
5218 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5219 the hash table, ensuring it cannot be referenced by name during the
5220 rest of the assembly. This sets the attributes of the symbol to be
5221 the same as the expression value:
5223 @var{other} = @var{descriptor} = 0
5224 @var{type} = @r{(section of @var{expression})}
5225 @var{value} = @var{expression}
5228 The new symbol is not flagged as external.
5232 @section @code{.macro}
5235 The commands @code{.macro} and @code{.endm} allow you to define macros that
5236 generate assembly output. For example, this definition specifies a macro
5237 @code{sum} that puts a sequence of numbers into memory:
5240 .macro sum from=0, to=5
5249 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5261 @item .macro @var{macname}
5262 @itemx .macro @var{macname} @var{macargs} @dots{}
5263 @cindex @code{macro} directive
5264 Begin the definition of a macro called @var{macname}. If your macro
5265 definition requires arguments, specify their names after the macro name,
5266 separated by commas or spaces. You can qualify the macro argument to
5267 indicate whether all invocations must specify a non-blank value (through
5268 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5269 (through @samp{:@code{vararg}}). You can supply a default value for any
5270 macro argument by following the name with @samp{=@var{deflt}}. You
5271 cannot define two macros with the same @var{macname} unless it has been
5272 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5273 definitions. For example, these are all valid @code{.macro} statements:
5277 Begin the definition of a macro called @code{comm}, which takes no
5280 @item .macro plus1 p, p1
5281 @itemx .macro plus1 p p1
5282 Either statement begins the definition of a macro called @code{plus1},
5283 which takes two arguments; within the macro definition, write
5284 @samp{\p} or @samp{\p1} to evaluate the arguments.
5286 @item .macro reserve_str p1=0 p2
5287 Begin the definition of a macro called @code{reserve_str}, with two
5288 arguments. The first argument has a default value, but not the second.
5289 After the definition is complete, you can call the macro either as
5290 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5291 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5292 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5293 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5295 @item .macro m p1:req, p2=0, p3:vararg
5296 Begin the definition of a macro called @code{m}, with at least three
5297 arguments. The first argument must always have a value specified, but
5298 not the second, which instead has a default value. The third formal
5299 will get assigned all remaining arguments specified at invocation time.
5301 When you call a macro, you can specify the argument values either by
5302 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5303 @samp{sum to=17, from=9}.
5307 Note that since each of the @var{macargs} can be an identifier exactly
5308 as any other one permitted by the target architecture, there may be
5309 occasional problems if the target hand-crafts special meanings to certain
5310 characters when they occur in a special position. For example, if the colon
5311 (@code{:}) is generally permitted to be part of a symbol name, but the
5312 architecture specific code special-cases it when occurring as the final
5313 character of a symbol (to denote a label), then the macro parameter
5314 replacement code will have no way of knowing that and consider the whole
5315 construct (including the colon) an identifier, and check only this
5316 identifier for being the subject to parameter substitution. So for example
5317 this macro definition:
5325 might not work as expected. Invoking @samp{label foo} might not create a label
5326 called @samp{foo} but instead just insert the text @samp{\l:} into the
5327 assembler source, probably generating an error about an unrecognised
5330 Similarly problems might occur with the period character (@samp{.})
5331 which is often allowed inside opcode names (and hence identifier names). So
5332 for example constructing a macro to build an opcode from a base name and a
5333 length specifier like this:
5336 .macro opcode base length
5341 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5342 instruction but instead generate some kind of error as the assembler tries to
5343 interpret the text @samp{\base.\length}.
5345 There are several possible ways around this problem:
5348 @item Insert white space
5349 If it is possible to use white space characters then this is the simplest
5358 @item Use @samp{\()}
5359 The string @samp{\()} can be used to separate the end of a macro argument from
5360 the following text. eg:
5363 .macro opcode base length
5368 @item Use the alternate macro syntax mode
5369 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5370 used as a separator. eg:
5380 Note: this problem of correctly identifying string parameters to pseudo ops
5381 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5382 and @code{.irpc} (@pxref{Irpc}) as well.
5385 @cindex @code{endm} directive
5386 Mark the end of a macro definition.
5389 @cindex @code{exitm} directive
5390 Exit early from the current macro definition.
5392 @cindex number of macros executed
5393 @cindex macros, count executed
5395 @command{@value{AS}} maintains a counter of how many macros it has
5396 executed in this pseudo-variable; you can copy that number to your
5397 output with @samp{\@@}, but @emph{only within a macro definition}.
5399 @item LOCAL @var{name} [ , @dots{} ]
5400 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5401 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5402 @xref{Altmacro,,@code{.altmacro}}.
5406 @section @code{.mri @var{val}}
5408 @cindex @code{mri} directive
5409 @cindex MRI mode, temporarily
5410 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5411 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5412 affects code assembled until the next @code{.mri} directive, or until the end
5413 of the file. @xref{M, MRI mode, MRI mode}.
5416 @section @code{.noaltmacro}
5417 Disable alternate macro mode. @xref{Altmacro}.
5420 @section @code{.nolist}
5422 @cindex @code{nolist} directive
5423 @cindex listing control, turning off
5424 Control (in conjunction with the @code{.list} directive) whether or
5425 not assembly listings are generated. These two directives maintain an
5426 internal counter (which is zero initially). @code{.list} increments the
5427 counter, and @code{.nolist} decrements it. Assembly listings are
5428 generated whenever the counter is greater than zero.
5431 @section @code{.octa @var{bignums}}
5433 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5434 @cindex @code{octa} directive
5435 @cindex integer, 16-byte
5436 @cindex sixteen byte integer
5437 This directive expects zero or more bignums, separated by commas. For each
5438 bignum, it emits a 16-byte integer.
5440 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5441 hence @emph{octa}-word for 16 bytes.
5444 @section @code{.org @var{new-lc} , @var{fill}}
5446 @cindex @code{org} directive
5447 @cindex location counter, advancing
5448 @cindex advancing location counter
5449 @cindex current address, advancing
5450 Advance the location counter of the current section to
5451 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5452 expression with the same section as the current subsection. That is,
5453 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5454 wrong section, the @code{.org} directive is ignored. To be compatible
5455 with former assemblers, if the section of @var{new-lc} is absolute,
5456 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5457 is the same as the current subsection.
5459 @code{.org} may only increase the location counter, or leave it
5460 unchanged; you cannot use @code{.org} to move the location counter
5463 @c double negative used below "not undefined" because this is a specific
5464 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5465 @c section. doc@cygnus.com 18feb91
5466 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5467 may not be undefined. If you really detest this restriction we eagerly await
5468 a chance to share your improved assembler.
5470 Beware that the origin is relative to the start of the section, not
5471 to the start of the subsection. This is compatible with other
5472 people's assemblers.
5474 When the location counter (of the current subsection) is advanced, the
5475 intervening bytes are filled with @var{fill} which should be an
5476 absolute expression. If the comma and @var{fill} are omitted,
5477 @var{fill} defaults to zero.
5480 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5482 @cindex padding the location counter given a power of two
5483 @cindex @code{p2align} directive
5484 Pad the location counter (in the current subsection) to a particular
5485 storage boundary. The first expression (which must be absolute) is the
5486 number of low-order zero bits the location counter must have after
5487 advancement. For example @samp{.p2align 3} advances the location
5488 counter until it a multiple of 8. If the location counter is already a
5489 multiple of 8, no change is needed.
5491 The second expression (also absolute) gives the fill value to be stored in the
5492 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5493 padding bytes are normally zero. However, on some systems, if the section is
5494 marked as containing code and the fill value is omitted, the space is filled
5495 with no-op instructions.
5497 The third expression is also absolute, and is also optional. If it is present,
5498 it is the maximum number of bytes that should be skipped by this alignment
5499 directive. If doing the alignment would require skipping more bytes than the
5500 specified maximum, then the alignment is not done at all. You can omit the
5501 fill value (the second argument) entirely by simply using two commas after the
5502 required alignment; this can be useful if you want the alignment to be filled
5503 with no-op instructions when appropriate.
5505 @cindex @code{p2alignw} directive
5506 @cindex @code{p2alignl} directive
5507 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5508 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5509 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5510 fill pattern as a four byte longword value. For example, @code{.p2alignw
5511 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5512 filled in with the value 0x368d (the exact placement of the bytes depends upon
5513 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5518 @section @code{.popsection}
5520 @cindex @code{popsection} directive
5521 @cindex Section Stack
5522 This is one of the ELF section stack manipulation directives. The others are
5523 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5524 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5527 This directive replaces the current section (and subsection) with the top
5528 section (and subsection) on the section stack. This section is popped off the
5534 @section @code{.previous}
5536 @cindex @code{previous} directive
5537 @cindex Section Stack
5538 This is one of the ELF section stack manipulation directives. The others are
5539 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5540 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5541 (@pxref{PopSection}).
5543 This directive swaps the current section (and subsection) with most recently
5544 referenced section/subsection pair prior to this one. Multiple
5545 @code{.previous} directives in a row will flip between two sections (and their
5546 subsections). For example:
5558 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5564 # Now in section A subsection 1
5568 # Now in section B subsection 0
5571 # Now in section B subsection 1
5574 # Now in section B subsection 0
5578 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5579 section B and 0x9abc into subsection 1 of section B.
5581 In terms of the section stack, this directive swaps the current section with
5582 the top section on the section stack.
5586 @section @code{.print @var{string}}
5588 @cindex @code{print} directive
5589 @command{@value{AS}} will print @var{string} on the standard output during
5590 assembly. You must put @var{string} in double quotes.
5594 @section @code{.protected @var{names}}
5596 @cindex @code{protected} directive
5598 This is one of the ELF visibility directives. The other two are
5599 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5601 This directive overrides the named symbols default visibility (which is set by
5602 their binding: local, global or weak). The directive sets the visibility to
5603 @code{protected} which means that any references to the symbols from within the
5604 components that defines them must be resolved to the definition in that
5605 component, even if a definition in another component would normally preempt
5610 @section @code{.psize @var{lines} , @var{columns}}
5612 @cindex @code{psize} directive
5613 @cindex listing control: paper size
5614 @cindex paper size, for listings
5615 Use this directive to declare the number of lines---and, optionally, the
5616 number of columns---to use for each page, when generating listings.
5618 If you do not use @code{.psize}, listings use a default line-count
5619 of 60. You may omit the comma and @var{columns} specification; the
5620 default width is 200 columns.
5622 @command{@value{AS}} generates formfeeds whenever the specified number of
5623 lines is exceeded (or whenever you explicitly request one, using
5626 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5627 those explicitly specified with @code{.eject}.
5630 @section @code{.purgem @var{name}}
5632 @cindex @code{purgem} directive
5633 Undefine the macro @var{name}, so that later uses of the string will not be
5634 expanded. @xref{Macro}.
5638 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5640 @cindex @code{pushsection} directive
5641 @cindex Section Stack
5642 This is one of the ELF section stack manipulation directives. The others are
5643 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5644 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5647 This directive pushes the current section (and subsection) onto the
5648 top of the section stack, and then replaces the current section and
5649 subsection with @code{name} and @code{subsection}. The optional
5650 @code{flags}, @code{type} and @code{arguments} are treated the same
5651 as in the @code{.section} (@pxref{Section}) directive.
5655 @section @code{.quad @var{bignums}}
5657 @cindex @code{quad} directive
5658 @code{.quad} expects zero or more bignums, separated by commas. For
5659 each bignum, it emits
5661 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5662 warning message; and just takes the lowest order 8 bytes of the bignum.
5663 @cindex eight-byte integer
5664 @cindex integer, 8-byte
5666 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5667 hence @emph{quad}-word for 8 bytes.
5670 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5671 warning message; and just takes the lowest order 16 bytes of the bignum.
5672 @cindex sixteen-byte integer
5673 @cindex integer, 16-byte
5677 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5679 @cindex @code{reloc} directive
5680 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5681 @var{expression}. If @var{offset} is a number, the relocation is generated in
5682 the current section. If @var{offset} is an expression that resolves to a
5683 symbol plus offset, the relocation is generated in the given symbol's section.
5684 @var{expression}, if present, must resolve to a symbol plus addend or to an
5685 absolute value, but note that not all targets support an addend. e.g. ELF REL
5686 targets such as i386 store an addend in the section contents rather than in the
5687 relocation. This low level interface does not support addends stored in the
5691 @section @code{.rept @var{count}}
5693 @cindex @code{rept} directive
5694 Repeat the sequence of lines between the @code{.rept} directive and the next
5695 @code{.endr} directive @var{count} times.
5697 For example, assembling
5705 is equivalent to assembling
5714 @section @code{.sbttl "@var{subheading}"}
5716 @cindex @code{sbttl} directive
5717 @cindex subtitles for listings
5718 @cindex listing control: subtitle
5719 Use @var{subheading} as the title (third line, immediately after the
5720 title line) when generating assembly listings.
5722 This directive affects subsequent pages, as well as the current page if
5723 it appears within ten lines of the top of a page.
5727 @section @code{.scl @var{class}}
5729 @cindex @code{scl} directive
5730 @cindex symbol storage class (COFF)
5731 @cindex COFF symbol storage class
5732 Set the storage-class value for a symbol. This directive may only be
5733 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5734 whether a symbol is static or external, or it may record further
5735 symbolic debugging information.
5738 The @samp{.scl} directive is primarily associated with COFF output; when
5739 configured to generate @code{b.out} output format, @command{@value{AS}}
5740 accepts this directive but ignores it.
5746 @section @code{.section @var{name}}
5748 @cindex named section
5749 Use the @code{.section} directive to assemble the following code into a section
5752 This directive is only supported for targets that actually support arbitrarily
5753 named sections; on @code{a.out} targets, for example, it is not accepted, even
5754 with a standard @code{a.out} section name.
5758 @c only print the extra heading if both COFF and ELF are set
5759 @subheading COFF Version
5762 @cindex @code{section} directive (COFF version)
5763 For COFF targets, the @code{.section} directive is used in one of the following
5767 .section @var{name}[, "@var{flags}"]
5768 .section @var{name}[, @var{subsection}]
5771 If the optional argument is quoted, it is taken as flags to use for the
5772 section. Each flag is a single character. The following flags are recognized:
5775 bss section (uninitialized data)
5777 section is not loaded
5787 shared section (meaningful for PE targets)
5789 ignored. (For compatibility with the ELF version)
5791 section is not readable (meaningful for PE targets)
5793 single-digit power-of-two section alignment (GNU extension)
5796 If no flags are specified, the default flags depend upon the section name. If
5797 the section name is not recognized, the default will be for the section to be
5798 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5799 from the section, rather than adding them, so if they are used on their own it
5800 will be as if no flags had been specified at all.
5802 If the optional argument to the @code{.section} directive is not quoted, it is
5803 taken as a subsection number (@pxref{Sub-Sections}).
5808 @c only print the extra heading if both COFF and ELF are set
5809 @subheading ELF Version
5812 @cindex Section Stack
5813 This is one of the ELF section stack manipulation directives. The others are
5814 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5815 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5816 @code{.previous} (@pxref{Previous}).
5818 @cindex @code{section} directive (ELF version)
5819 For ELF targets, the @code{.section} directive is used like this:
5822 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5825 The optional @var{flags} argument is a quoted string which may contain any
5826 combination of the following characters:
5829 section is allocatable
5831 section is excluded from executable and shared library.
5835 section is executable
5837 section is mergeable
5839 section contains zero terminated strings
5841 section is a member of a section group
5843 section is used for thread-local-storage
5845 section is a member of the previously-current section's group, if any
5848 The optional @var{type} argument may contain one of the following constants:
5851 section contains data
5853 section does not contain data (i.e., section only occupies space)
5855 section contains data which is used by things other than the program
5857 section contains an array of pointers to init functions
5859 section contains an array of pointers to finish functions
5860 @item @@preinit_array
5861 section contains an array of pointers to pre-init functions
5864 Many targets only support the first three section types.
5866 Note on targets where the @code{@@} character is the start of a comment (eg
5867 ARM) then another character is used instead. For example the ARM port uses the
5870 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5871 be specified as well as an extra argument---@var{entsize}---like this:
5874 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5877 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5878 constants, each @var{entsize} octets long. Sections with both @code{M} and
5879 @code{S} must contain zero terminated strings where each character is
5880 @var{entsize} bytes long. The linker may remove duplicates within sections with
5881 the same name, same entity size and same flags. @var{entsize} must be an
5882 absolute expression. For sections with both @code{M} and @code{S}, a string
5883 which is a suffix of a larger string is considered a duplicate. Thus
5884 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5885 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5887 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5888 be present along with an additional field like this:
5891 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5894 The @var{GroupName} field specifies the name of the section group to which this
5895 particular section belongs. The optional linkage field can contain:
5898 indicates that only one copy of this section should be retained
5903 Note: if both the @var{M} and @var{G} flags are present then the fields for
5904 the Merge flag should come first, like this:
5907 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5910 If @var{flags} contains the @code{?} symbol then it may not also contain the
5911 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
5912 present. Instead, @code{?} says to consider the section that's current before
5913 this directive. If that section used @code{G}, then the new section will use
5914 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
5915 If not, then the @code{?} symbol has no effect.
5917 If no flags are specified, the default flags depend upon the section name. If
5918 the section name is not recognized, the default will be for the section to have
5919 none of the above flags: it will not be allocated in memory, nor writable, nor
5920 executable. The section will contain data.
5922 For ELF targets, the assembler supports another type of @code{.section}
5923 directive for compatibility with the Solaris assembler:
5926 .section "@var{name}"[, @var{flags}...]
5929 Note that the section name is quoted. There may be a sequence of comma
5933 section is allocatable
5937 section is executable
5939 section is excluded from executable and shared library.
5941 section is used for thread local storage
5944 This directive replaces the current section and subsection. See the
5945 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5946 some examples of how this directive and the other section stack directives
5952 @section @code{.set @var{symbol}, @var{expression}}
5954 @cindex @code{set} directive
5955 @cindex symbol value, setting
5956 Set the value of @var{symbol} to @var{expression}. This
5957 changes @var{symbol}'s value and type to conform to
5958 @var{expression}. If @var{symbol} was flagged as external, it remains
5959 flagged (@pxref{Symbol Attributes}).
5961 You may @code{.set} a symbol many times in the same assembly.
5963 If you @code{.set} a global symbol, the value stored in the object
5964 file is the last value stored into it.
5967 On Z80 @code{set} is a real instruction, use
5968 @samp{@var{symbol} defl @var{expression}} instead.
5972 @section @code{.short @var{expressions}}
5974 @cindex @code{short} directive
5976 @code{.short} is normally the same as @samp{.word}.
5977 @xref{Word,,@code{.word}}.
5979 In some configurations, however, @code{.short} and @code{.word} generate
5980 numbers of different lengths. @xref{Machine Dependencies}.
5984 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5987 This expects zero or more @var{expressions}, and emits
5988 a 16 bit number for each.
5993 @section @code{.single @var{flonums}}
5995 @cindex @code{single} directive
5996 @cindex floating point numbers (single)
5997 This directive assembles zero or more flonums, separated by commas. It
5998 has the same effect as @code{.float}.
6000 The exact kind of floating point numbers emitted depends on how
6001 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6005 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6006 numbers in @sc{ieee} format.
6012 @section @code{.size}
6014 This directive is used to set the size associated with a symbol.
6018 @c only print the extra heading if both COFF and ELF are set
6019 @subheading COFF Version
6022 @cindex @code{size} directive (COFF version)
6023 For COFF targets, the @code{.size} directive is only permitted inside
6024 @code{.def}/@code{.endef} pairs. It is used like this:
6027 .size @var{expression}
6031 @samp{.size} is only meaningful when generating COFF format output; when
6032 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6039 @c only print the extra heading if both COFF and ELF are set
6040 @subheading ELF Version
6043 @cindex @code{size} directive (ELF version)
6044 For ELF targets, the @code{.size} directive is used like this:
6047 .size @var{name} , @var{expression}
6050 This directive sets the size associated with a symbol @var{name}.
6051 The size in bytes is computed from @var{expression} which can make use of label
6052 arithmetic. This directive is typically used to set the size of function
6057 @ifclear no-space-dir
6059 @section @code{.skip @var{size} , @var{fill}}
6061 @cindex @code{skip} directive
6062 @cindex filling memory
6063 This directive emits @var{size} bytes, each of value @var{fill}. Both
6064 @var{size} and @var{fill} are absolute expressions. If the comma and
6065 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6070 @section @code{.sleb128 @var{expressions}}
6072 @cindex @code{sleb128} directive
6073 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6074 compact, variable length representation of numbers used by the DWARF
6075 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6077 @ifclear no-space-dir
6079 @section @code{.space @var{size} , @var{fill}}
6081 @cindex @code{space} directive
6082 @cindex filling memory
6083 This directive emits @var{size} bytes, each of value @var{fill}. Both
6084 @var{size} and @var{fill} are absolute expressions. If the comma
6085 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6090 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6091 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6092 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6093 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6101 @section @code{.stabd, .stabn, .stabs}
6103 @cindex symbolic debuggers, information for
6104 @cindex @code{stab@var{x}} directives
6105 There are three directives that begin @samp{.stab}.
6106 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6107 The symbols are not entered in the @command{@value{AS}} hash table: they
6108 cannot be referenced elsewhere in the source file.
6109 Up to five fields are required:
6113 This is the symbol's name. It may contain any character except
6114 @samp{\000}, so is more general than ordinary symbol names. Some
6115 debuggers used to code arbitrarily complex structures into symbol names
6119 An absolute expression. The symbol's type is set to the low 8 bits of
6120 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6121 and debuggers choke on silly bit patterns.
6124 An absolute expression. The symbol's ``other'' attribute is set to the
6125 low 8 bits of this expression.
6128 An absolute expression. The symbol's descriptor is set to the low 16
6129 bits of this expression.
6132 An absolute expression which becomes the symbol's value.
6135 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6136 or @code{.stabs} statement, the symbol has probably already been created;
6137 you get a half-formed symbol in your object file. This is
6138 compatible with earlier assemblers!
6141 @cindex @code{stabd} directive
6142 @item .stabd @var{type} , @var{other} , @var{desc}
6144 The ``name'' of the symbol generated is not even an empty string.
6145 It is a null pointer, for compatibility. Older assemblers used a
6146 null pointer so they didn't waste space in object files with empty
6149 The symbol's value is set to the location counter,
6150 relocatably. When your program is linked, the value of this symbol
6151 is the address of the location counter when the @code{.stabd} was
6154 @cindex @code{stabn} directive
6155 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6156 The name of the symbol is set to the empty string @code{""}.
6158 @cindex @code{stabs} directive
6159 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6160 All five fields are specified.
6166 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6167 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6169 @cindex string, copying to object file
6170 @cindex string8, copying to object file
6171 @cindex string16, copying to object file
6172 @cindex string32, copying to object file
6173 @cindex string64, copying to object file
6174 @cindex @code{string} directive
6175 @cindex @code{string8} directive
6176 @cindex @code{string16} directive
6177 @cindex @code{string32} directive
6178 @cindex @code{string64} directive
6180 Copy the characters in @var{str} to the object file. You may specify more than
6181 one string to copy, separated by commas. Unless otherwise specified for a
6182 particular machine, the assembler marks the end of each string with a 0 byte.
6183 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6185 The variants @code{string16}, @code{string32} and @code{string64} differ from
6186 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6187 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6188 are stored in target endianness byte order.
6194 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6195 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6200 @section @code{.struct @var{expression}}
6202 @cindex @code{struct} directive
6203 Switch to the absolute section, and set the section offset to @var{expression},
6204 which must be an absolute expression. You might use this as follows:
6213 This would define the symbol @code{field1} to have the value 0, the symbol
6214 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6215 value 8. Assembly would be left in the absolute section, and you would need to
6216 use a @code{.section} directive of some sort to change to some other section
6217 before further assembly.
6221 @section @code{.subsection @var{name}}
6223 @cindex @code{subsection} directive
6224 @cindex Section Stack
6225 This is one of the ELF section stack manipulation directives. The others are
6226 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6227 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6230 This directive replaces the current subsection with @code{name}. The current
6231 section is not changed. The replaced subsection is put onto the section stack
6232 in place of the then current top of stack subsection.
6237 @section @code{.symver}
6238 @cindex @code{symver} directive
6239 @cindex symbol versioning
6240 @cindex versions of symbols
6241 Use the @code{.symver} directive to bind symbols to specific version nodes
6242 within a source file. This is only supported on ELF platforms, and is
6243 typically used when assembling files to be linked into a shared library.
6244 There are cases where it may make sense to use this in objects to be bound
6245 into an application itself so as to override a versioned symbol from a
6248 For ELF targets, the @code{.symver} directive can be used like this:
6250 .symver @var{name}, @var{name2@@nodename}
6252 If the symbol @var{name} is defined within the file
6253 being assembled, the @code{.symver} directive effectively creates a symbol
6254 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6255 just don't try and create a regular alias is that the @var{@@} character isn't
6256 permitted in symbol names. The @var{name2} part of the name is the actual name
6257 of the symbol by which it will be externally referenced. The name @var{name}
6258 itself is merely a name of convenience that is used so that it is possible to
6259 have definitions for multiple versions of a function within a single source
6260 file, and so that the compiler can unambiguously know which version of a
6261 function is being mentioned. The @var{nodename} portion of the alias should be
6262 the name of a node specified in the version script supplied to the linker when
6263 building a shared library. If you are attempting to override a versioned
6264 symbol from a shared library, then @var{nodename} should correspond to the
6265 nodename of the symbol you are trying to override.
6267 If the symbol @var{name} is not defined within the file being assembled, all
6268 references to @var{name} will be changed to @var{name2@@nodename}. If no
6269 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6272 Another usage of the @code{.symver} directive is:
6274 .symver @var{name}, @var{name2@@@@nodename}
6276 In this case, the symbol @var{name} must exist and be defined within
6277 the file being assembled. It is similar to @var{name2@@nodename}. The
6278 difference is @var{name2@@@@nodename} will also be used to resolve
6279 references to @var{name2} by the linker.
6281 The third usage of the @code{.symver} directive is:
6283 .symver @var{name}, @var{name2@@@@@@nodename}
6285 When @var{name} is not defined within the
6286 file being assembled, it is treated as @var{name2@@nodename}. When
6287 @var{name} is defined within the file being assembled, the symbol
6288 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6293 @section @code{.tag @var{structname}}
6295 @cindex COFF structure debugging
6296 @cindex structure debugging, COFF
6297 @cindex @code{tag} directive
6298 This directive is generated by compilers to include auxiliary debugging
6299 information in the symbol table. It is only permitted inside
6300 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6301 definitions in the symbol table with instances of those structures.
6304 @samp{.tag} is only used when generating COFF format output; when
6305 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6311 @section @code{.text @var{subsection}}
6313 @cindex @code{text} directive
6314 Tells @command{@value{AS}} to assemble the following statements onto the end of
6315 the text subsection numbered @var{subsection}, which is an absolute
6316 expression. If @var{subsection} is omitted, subsection number zero
6320 @section @code{.title "@var{heading}"}
6322 @cindex @code{title} directive
6323 @cindex listing control: title line
6324 Use @var{heading} as the title (second line, immediately after the
6325 source file name and pagenumber) when generating assembly listings.
6327 This directive affects subsequent pages, as well as the current page if
6328 it appears within ten lines of the top of a page.
6332 @section @code{.type}
6334 This directive is used to set the type of a symbol.
6338 @c only print the extra heading if both COFF and ELF are set
6339 @subheading COFF Version
6342 @cindex COFF symbol type
6343 @cindex symbol type, COFF
6344 @cindex @code{type} directive (COFF version)
6345 For COFF targets, this directive is permitted only within
6346 @code{.def}/@code{.endef} pairs. It is used like this:
6352 This records the integer @var{int} as the type attribute of a symbol table
6356 @samp{.type} is associated only with COFF format output; when
6357 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6358 directive but ignores it.
6364 @c only print the extra heading if both COFF and ELF are set
6365 @subheading ELF Version
6368 @cindex ELF symbol type
6369 @cindex symbol type, ELF
6370 @cindex @code{type} directive (ELF version)
6371 For ELF targets, the @code{.type} directive is used like this:
6374 .type @var{name} , @var{type description}
6377 This sets the type of symbol @var{name} to be either a
6378 function symbol or an object symbol. There are five different syntaxes
6379 supported for the @var{type description} field, in order to provide
6380 compatibility with various other assemblers.
6382 Because some of the characters used in these syntaxes (such as @samp{@@} and
6383 @samp{#}) are comment characters for some architectures, some of the syntaxes
6384 below do not work on all architectures. The first variant will be accepted by
6385 the GNU assembler on all architectures so that variant should be used for
6386 maximum portability, if you do not need to assemble your code with other
6389 The syntaxes supported are:
6392 .type <name> STT_<TYPE_IN_UPPER_CASE>
6393 .type <name>,#<type>
6394 .type <name>,@@<type>
6395 .type <name>,%<type>
6396 .type <name>,"<type>"
6399 The types supported are:
6404 Mark the symbol as being a function name.
6407 @itemx gnu_indirect_function
6408 Mark the symbol as an indirect function when evaluated during reloc
6409 processing. (This is only supported on Linux targeted assemblers).
6413 Mark the symbol as being a data object.
6417 Mark the symbol as being a thead-local data object.
6421 Mark the symbol as being a common data object.
6425 Does not mark the symbol in any way. It is supported just for completeness.
6427 @item gnu_unique_object
6428 Marks the symbol as being a globally unique data object. The dynamic linker
6429 will make sure that in the entire process there is just one symbol with this
6430 name and type in use. (This is only supported on Linux targeted assemblers).
6434 Note: Some targets support extra types in addition to those listed above.
6440 @section @code{.uleb128 @var{expressions}}
6442 @cindex @code{uleb128} directive
6443 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6444 compact, variable length representation of numbers used by the DWARF
6445 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6449 @section @code{.val @var{addr}}
6451 @cindex @code{val} directive
6452 @cindex COFF value attribute
6453 @cindex value attribute, COFF
6454 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6455 records the address @var{addr} as the value attribute of a symbol table
6459 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6460 configured for @code{b.out}, it accepts this directive but ignores it.
6466 @section @code{.version "@var{string}"}
6468 @cindex @code{version} directive
6469 This directive creates a @code{.note} section and places into it an ELF
6470 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6475 @section @code{.vtable_entry @var{table}, @var{offset}}
6477 @cindex @code{vtable_entry} directive
6478 This directive finds or creates a symbol @code{table} and creates a
6479 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6482 @section @code{.vtable_inherit @var{child}, @var{parent}}
6484 @cindex @code{vtable_inherit} directive
6485 This directive finds the symbol @code{child} and finds or creates the symbol
6486 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6487 parent whose addend is the value of the child symbol. As a special case the
6488 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6492 @section @code{.warning "@var{string}"}
6493 @cindex warning directive
6494 Similar to the directive @code{.error}
6495 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6498 @section @code{.weak @var{names}}
6500 @cindex @code{weak} directive
6501 This directive sets the weak attribute on the comma separated list of symbol
6502 @code{names}. If the symbols do not already exist, they will be created.
6504 On COFF targets other than PE, weak symbols are a GNU extension. This
6505 directive sets the weak attribute on the comma separated list of symbol
6506 @code{names}. If the symbols do not already exist, they will be created.
6508 On the PE target, weak symbols are supported natively as weak aliases.
6509 When a weak symbol is created that is not an alias, GAS creates an
6510 alternate symbol to hold the default value.
6513 @section @code{.weakref @var{alias}, @var{target}}
6515 @cindex @code{weakref} directive
6516 This directive creates an alias to the target symbol that enables the symbol to
6517 be referenced with weak-symbol semantics, but without actually making it weak.
6518 If direct references or definitions of the symbol are present, then the symbol
6519 will not be weak, but if all references to it are through weak references, the
6520 symbol will be marked as weak in the symbol table.
6522 The effect is equivalent to moving all references to the alias to a separate
6523 assembly source file, renaming the alias to the symbol in it, declaring the
6524 symbol as weak there, and running a reloadable link to merge the object files
6525 resulting from the assembly of the new source file and the old source file that
6526 had the references to the alias removed.
6528 The alias itself never makes to the symbol table, and is entirely handled
6529 within the assembler.
6532 @section @code{.word @var{expressions}}
6534 @cindex @code{word} directive
6535 This directive expects zero or more @var{expressions}, of any section,
6536 separated by commas.
6539 For each expression, @command{@value{AS}} emits a 32-bit number.
6542 For each expression, @command{@value{AS}} emits a 16-bit number.
6547 The size of the number emitted, and its byte order,
6548 depend on what target computer the assembly is for.
6551 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6552 @c happen---32-bit addressability, period; no long/short jumps.
6553 @ifset DIFF-TBL-KLUGE
6554 @cindex difference tables altered
6555 @cindex altered difference tables
6557 @emph{Warning: Special Treatment to support Compilers}
6561 Machines with a 32-bit address space, but that do less than 32-bit
6562 addressing, require the following special treatment. If the machine of
6563 interest to you does 32-bit addressing (or doesn't require it;
6564 @pxref{Machine Dependencies}), you can ignore this issue.
6567 In order to assemble compiler output into something that works,
6568 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6569 Directives of the form @samp{.word sym1-sym2} are often emitted by
6570 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6571 directive of the form @samp{.word sym1-sym2}, and the difference between
6572 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6573 creates a @dfn{secondary jump table}, immediately before the next label.
6574 This secondary jump table is preceded by a short-jump to the
6575 first byte after the secondary table. This short-jump prevents the flow
6576 of control from accidentally falling into the new table. Inside the
6577 table is a long-jump to @code{sym2}. The original @samp{.word}
6578 contains @code{sym1} minus the address of the long-jump to
6581 If there were several occurrences of @samp{.word sym1-sym2} before the
6582 secondary jump table, all of them are adjusted. If there was a
6583 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6584 long-jump to @code{sym4} is included in the secondary jump table,
6585 and the @code{.word} directives are adjusted to contain @code{sym3}
6586 minus the address of the long-jump to @code{sym4}; and so on, for as many
6587 entries in the original jump table as necessary.
6590 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6591 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6592 assembly language programmers.
6595 @c end DIFF-TBL-KLUGE
6598 @section Deprecated Directives
6600 @cindex deprecated directives
6601 @cindex obsolescent directives
6602 One day these directives won't work.
6603 They are included for compatibility with older assemblers.
6610 @node Object Attributes
6611 @chapter Object Attributes
6612 @cindex object attributes
6614 @command{@value{AS}} assembles source files written for a specific architecture
6615 into object files for that architecture. But not all object files are alike.
6616 Many architectures support incompatible variations. For instance, floating
6617 point arguments might be passed in floating point registers if the object file
6618 requires hardware floating point support---or floating point arguments might be
6619 passed in integer registers if the object file supports processors with no
6620 hardware floating point unit. Or, if two objects are built for different
6621 generations of the same architecture, the combination may require the
6622 newer generation at run-time.
6624 This information is useful during and after linking. At link time,
6625 @command{@value{LD}} can warn about incompatible object files. After link
6626 time, tools like @command{gdb} can use it to process the linked file
6629 Compatibility information is recorded as a series of object attributes. Each
6630 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6631 string, and indicates who sets the meaning of the tag. The tag is an integer,
6632 and indicates what property the attribute describes. The value may be a string
6633 or an integer, and indicates how the property affects this object. Missing
6634 attributes are the same as attributes with a zero value or empty string value.
6636 Object attributes were developed as part of the ABI for the ARM Architecture.
6637 The file format is documented in @cite{ELF for the ARM Architecture}.
6640 * GNU Object Attributes:: @sc{gnu} Object Attributes
6641 * Defining New Object Attributes:: Defining New Object Attributes
6644 @node GNU Object Attributes
6645 @section @sc{gnu} Object Attributes
6647 The @code{.gnu_attribute} directive records an object attribute
6648 with vendor @samp{gnu}.
6650 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6651 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6652 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6653 2} is set for architecture-independent attributes and clear for
6654 architecture-dependent ones.
6656 @subsection Common @sc{gnu} attributes
6658 These attributes are valid on all architectures.
6661 @item Tag_compatibility (32)
6662 The compatibility attribute takes an integer flag value and a vendor name. If
6663 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6664 then the file is only compatible with the named toolchain. If it is greater
6665 than 1, the file can only be processed by other toolchains under some private
6666 arrangement indicated by the flag value and the vendor name.
6669 @subsection MIPS Attributes
6672 @item Tag_GNU_MIPS_ABI_FP (4)
6673 The floating-point ABI used by this object file. The value will be:
6677 0 for files not affected by the floating-point ABI.
6679 1 for files using the hardware floating-point with a standard double-precision
6682 2 for files using the hardware floating-point ABI with a single-precision FPU.
6684 3 for files using the software floating-point ABI.
6686 4 for files using the hardware floating-point ABI with 64-bit wide
6687 double-precision floating-point registers and 32-bit wide general
6692 @subsection PowerPC Attributes
6695 @item Tag_GNU_Power_ABI_FP (4)
6696 The floating-point ABI used by this object file. The value will be:
6700 0 for files not affected by the floating-point ABI.
6702 1 for files using double-precision hardware floating-point ABI.
6704 2 for files using the software floating-point ABI.
6706 3 for files using single-precision hardware floating-point ABI.
6709 @item Tag_GNU_Power_ABI_Vector (8)
6710 The vector ABI used by this object file. The value will be:
6714 0 for files not affected by the vector ABI.
6716 1 for files using general purpose registers to pass vectors.
6718 2 for files using AltiVec registers to pass vectors.
6720 3 for files using SPE registers to pass vectors.
6724 @node Defining New Object Attributes
6725 @section Defining New Object Attributes
6727 If you want to define a new @sc{gnu} object attribute, here are the places you
6728 will need to modify. New attributes should be discussed on the @samp{binutils}
6733 This manual, which is the official register of attributes.
6735 The header for your architecture @file{include/elf}, to define the tag.
6737 The @file{bfd} support file for your architecture, to merge the attribute
6738 and issue any appropriate link warnings.
6740 Test cases in @file{ld/testsuite} for merging and link warnings.
6742 @file{binutils/readelf.c} to display your attribute.
6744 GCC, if you want the compiler to mark the attribute automatically.
6750 @node Machine Dependencies
6751 @chapter Machine Dependent Features
6753 @cindex machine dependencies
6754 The machine instruction sets are (almost by definition) different on
6755 each machine where @command{@value{AS}} runs. Floating point representations
6756 vary as well, and @command{@value{AS}} often supports a few additional
6757 directives or command-line options for compatibility with other
6758 assemblers on a particular platform. Finally, some versions of
6759 @command{@value{AS}} support special pseudo-instructions for branch
6762 This chapter discusses most of these differences, though it does not
6763 include details on any machine's instruction set. For details on that
6764 subject, see the hardware manufacturer's manual.
6768 * Alpha-Dependent:: Alpha Dependent Features
6771 * ARC-Dependent:: ARC Dependent Features
6774 * ARM-Dependent:: ARM Dependent Features
6777 * AVR-Dependent:: AVR Dependent Features
6780 * Blackfin-Dependent:: Blackfin Dependent Features
6783 * CR16-Dependent:: CR16 Dependent Features
6786 * CRIS-Dependent:: CRIS Dependent Features
6789 * D10V-Dependent:: D10V Dependent Features
6792 * D30V-Dependent:: D30V Dependent Features
6795 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6798 * HPPA-Dependent:: HPPA Dependent Features
6801 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6804 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6807 * i860-Dependent:: Intel 80860 Dependent Features
6810 * i960-Dependent:: Intel 80960 Dependent Features
6813 * IA-64-Dependent:: Intel IA-64 Dependent Features
6816 * IP2K-Dependent:: IP2K Dependent Features
6819 * LM32-Dependent:: LM32 Dependent Features
6822 * M32C-Dependent:: M32C Dependent Features
6825 * M32R-Dependent:: M32R Dependent Features
6828 * M68K-Dependent:: M680x0 Dependent Features
6831 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6834 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6837 * MIPS-Dependent:: MIPS Dependent Features
6840 * MMIX-Dependent:: MMIX Dependent Features
6843 * MSP430-Dependent:: MSP430 Dependent Features
6846 * NS32K-Dependent:: NS32K Dependent Features
6849 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6850 * SH64-Dependent:: SuperH SH64 Dependent Features
6853 * PDP-11-Dependent:: PDP-11 Dependent Features
6856 * PJ-Dependent:: picoJava Dependent Features
6859 * PPC-Dependent:: PowerPC Dependent Features
6862 * RX-Dependent:: RX Dependent Features
6865 * S/390-Dependent:: IBM S/390 Dependent Features
6868 * SCORE-Dependent:: SCORE Dependent Features
6871 * Sparc-Dependent:: SPARC Dependent Features
6874 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6877 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6880 * V850-Dependent:: V850 Dependent Features
6883 * Xtensa-Dependent:: Xtensa Dependent Features
6886 * Z80-Dependent:: Z80 Dependent Features
6889 * Z8000-Dependent:: Z8000 Dependent Features
6892 * Vax-Dependent:: VAX Dependent Features
6899 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6900 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6901 @c peculiarity: to preserve cross-references, there must be a node called
6902 @c "Machine Dependencies". Hence the conditional nodenames in each
6903 @c major node below. Node defaulting in makeinfo requires adjacency of
6904 @c node and sectioning commands; hence the repetition of @chapter BLAH
6905 @c in both conditional blocks.
6908 @include c-alpha.texi
6924 @include c-bfin.texi
6928 @include c-cr16.texi
6932 @include c-cris.texi
6937 @node Machine Dependencies
6938 @chapter Machine Dependent Features
6940 The machine instruction sets are different on each Renesas chip family,
6941 and there are also some syntax differences among the families. This
6942 chapter describes the specific @command{@value{AS}} features for each
6946 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6947 * SH-Dependent:: Renesas SH Dependent Features
6954 @include c-d10v.texi
6958 @include c-d30v.texi
6962 @include c-h8300.texi
6966 @include c-hppa.texi
6970 @include c-i370.texi
6974 @include c-i386.texi
6978 @include c-i860.texi
6982 @include c-i960.texi
6986 @include c-ia64.texi
6990 @include c-ip2k.texi
6994 @include c-lm32.texi
6998 @include c-m32c.texi
7002 @include c-m32r.texi
7006 @include c-m68k.texi
7010 @include c-m68hc11.texi
7014 @include c-microblaze.texi
7018 @include c-mips.texi
7022 @include c-mmix.texi
7026 @include c-msp430.texi
7030 @include c-ns32k.texi
7034 @include c-pdp11.texi
7050 @include c-s390.texi
7054 @include c-score.texi
7059 @include c-sh64.texi
7063 @include c-sparc.texi
7067 @include c-tic54x.texi
7071 @include c-tic6x.texi
7087 @include c-v850.texi
7091 @include c-xtensa.texi
7095 @c reverse effect of @down at top of generic Machine-Dep chapter
7099 @node Reporting Bugs
7100 @chapter Reporting Bugs
7101 @cindex bugs in assembler
7102 @cindex reporting bugs in assembler
7104 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7106 Reporting a bug may help you by bringing a solution to your problem, or it may
7107 not. But in any case the principal function of a bug report is to help the
7108 entire community by making the next version of @command{@value{AS}} work better.
7109 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7111 In order for a bug report to serve its purpose, you must include the
7112 information that enables us to fix the bug.
7115 * Bug Criteria:: Have you found a bug?
7116 * Bug Reporting:: How to report bugs
7120 @section Have You Found a Bug?
7121 @cindex bug criteria
7123 If you are not sure whether you have found a bug, here are some guidelines:
7126 @cindex fatal signal
7127 @cindex assembler crash
7128 @cindex crash of assembler
7130 If the assembler gets a fatal signal, for any input whatever, that is a
7131 @command{@value{AS}} bug. Reliable assemblers never crash.
7133 @cindex error on valid input
7135 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7137 @cindex invalid input
7139 If @command{@value{AS}} does not produce an error message for invalid input, that
7140 is a bug. However, you should note that your idea of ``invalid input'' might
7141 be our idea of ``an extension'' or ``support for traditional practice''.
7144 If you are an experienced user of assemblers, your suggestions for improvement
7145 of @command{@value{AS}} are welcome in any case.
7149 @section How to Report Bugs
7151 @cindex assembler bugs, reporting
7153 A number of companies and individuals offer support for @sc{gnu} products. If
7154 you obtained @command{@value{AS}} from a support organization, we recommend you
7155 contact that organization first.
7157 You can find contact information for many support companies and
7158 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7162 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7166 The fundamental principle of reporting bugs usefully is this:
7167 @strong{report all the facts}. If you are not sure whether to state a
7168 fact or leave it out, state it!
7170 Often people omit facts because they think they know what causes the problem
7171 and assume that some details do not matter. Thus, you might assume that the
7172 name of a symbol you use in an example does not matter. Well, probably it does
7173 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7174 happens to fetch from the location where that name is stored in memory;
7175 perhaps, if the name were different, the contents of that location would fool
7176 the assembler into doing the right thing despite the bug. Play it safe and
7177 give a specific, complete example. That is the easiest thing for you to do,
7178 and the most helpful.
7180 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7181 it is new to us. Therefore, always write your bug reports on the assumption
7182 that the bug has not been reported previously.
7184 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7185 bell?'' This cannot help us fix a bug, so it is basically useless. We
7186 respond by asking for enough details to enable us to investigate.
7187 You might as well expedite matters by sending them to begin with.
7189 To enable us to fix the bug, you should include all these things:
7193 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7194 it with the @samp{--version} argument.
7196 Without this, we will not know whether there is any point in looking for
7197 the bug in the current version of @command{@value{AS}}.
7200 Any patches you may have applied to the @command{@value{AS}} source.
7203 The type of machine you are using, and the operating system name and
7207 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7211 The command arguments you gave the assembler to assemble your example and
7212 observe the bug. To guarantee you will not omit something important, list them
7213 all. A copy of the Makefile (or the output from make) is sufficient.
7215 If we were to try to guess the arguments, we would probably guess wrong
7216 and then we might not encounter the bug.
7219 A complete input file that will reproduce the bug. If the bug is observed when
7220 the assembler is invoked via a compiler, send the assembler source, not the
7221 high level language source. Most compilers will produce the assembler source
7222 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7223 the options @samp{-v --save-temps}; this will save the assembler source in a
7224 file with an extension of @file{.s}, and also show you exactly how
7225 @command{@value{AS}} is being run.
7228 A description of what behavior you observe that you believe is
7229 incorrect. For example, ``It gets a fatal signal.''
7231 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7232 will certainly notice it. But if the bug is incorrect output, we might not
7233 notice unless it is glaringly wrong. You might as well not give us a chance to
7236 Even if the problem you experience is a fatal signal, you should still say so
7237 explicitly. Suppose something strange is going on, such as, your copy of
7238 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7239 library on your system. (This has happened!) Your copy might crash and ours
7240 would not. If you told us to expect a crash, then when ours fails to crash, we
7241 would know that the bug was not happening for us. If you had not told us to
7242 expect a crash, then we would not be able to draw any conclusion from our
7246 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7247 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7248 option. Always send diffs from the old file to the new file. If you even
7249 discuss something in the @command{@value{AS}} source, refer to it by context, not
7252 The line numbers in our development sources will not match those in your
7253 sources. Your line numbers would convey no useful information to us.
7256 Here are some things that are not necessary:
7260 A description of the envelope of the bug.
7262 Often people who encounter a bug spend a lot of time investigating
7263 which changes to the input file will make the bug go away and which
7264 changes will not affect it.
7266 This is often time consuming and not very useful, because the way we
7267 will find the bug is by running a single example under the debugger
7268 with breakpoints, not by pure deduction from a series of examples.
7269 We recommend that you save your time for something else.
7271 Of course, if you can find a simpler example to report @emph{instead}
7272 of the original one, that is a convenience for us. Errors in the
7273 output will be easier to spot, running under the debugger will take
7274 less time, and so on.
7276 However, simplification is not vital; if you do not want to do this,
7277 report the bug anyway and send us the entire test case you used.
7280 A patch for the bug.
7282 A patch for the bug does help us if it is a good one. But do not omit
7283 the necessary information, such as the test case, on the assumption that
7284 a patch is all we need. We might see problems with your patch and decide
7285 to fix the problem another way, or we might not understand it at all.
7287 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7288 construct an example that will make the program follow a certain path through
7289 the code. If you do not send us the example, we will not be able to construct
7290 one, so we will not be able to verify that the bug is fixed.
7292 And if we cannot understand what bug you are trying to fix, or why your
7293 patch should be an improvement, we will not install it. A test case will
7294 help us to understand.
7297 A guess about what the bug is or what it depends on.
7299 Such guesses are usually wrong. Even we cannot guess right about such
7300 things without first using the debugger to find the facts.
7303 @node Acknowledgements
7304 @chapter Acknowledgements
7306 If you have contributed to GAS and your name isn't listed here,
7307 it is not meant as a slight. We just don't know about it. Send mail to the
7308 maintainer, and we'll correct the situation. Currently
7310 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7312 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7315 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7316 information and the 68k series machines, most of the preprocessing pass, and
7317 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7319 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7320 many bug fixes, including merging support for several processors, breaking GAS
7321 up to handle multiple object file format back ends (including heavy rewrite,
7322 testing, an integration of the coff and b.out back ends), adding configuration
7323 including heavy testing and verification of cross assemblers and file splits
7324 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7325 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7326 port (including considerable amounts of reverse engineering), a SPARC opcode
7327 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7328 assertions and made them work, much other reorganization, cleanup, and lint.
7330 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7331 in format-specific I/O modules.
7333 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7334 has done much work with it since.
7336 The Intel 80386 machine description was written by Eliot Dresselhaus.
7338 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7340 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7341 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7343 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7344 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7345 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7346 support a.out format.
7348 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7349 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7350 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7351 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7354 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7355 simplified the configuration of which versions accept which directives. He
7356 updated the 68k machine description so that Motorola's opcodes always produced
7357 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7358 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7359 cross-compilation support, and one bug in relaxation that took a week and
7360 required the proverbial one-bit fix.
7362 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7363 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7364 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7365 PowerPC assembler, and made a few other minor patches.
7367 Steve Chamberlain made GAS able to generate listings.
7369 Hewlett-Packard contributed support for the HP9000/300.
7371 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7372 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7373 formats). This work was supported by both the Center for Software Science at
7374 the University of Utah and Cygnus Support.
7376 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7377 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7378 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7379 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7380 and some initial 64-bit support).
7382 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7384 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7385 support for openVMS/Alpha.
7387 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7390 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7391 Inc.@: added support for Xtensa processors.
7393 Several engineers at Cygnus Support have also provided many small bug fixes and
7394 configuration enhancements.
7396 Jon Beniston added support for the Lattice Mico32 architecture.
7398 Many others have contributed large or small bugfixes and enhancements. If
7399 you have contributed significant work and are not mentioned on this list, and
7400 want to be, let us know. Some of the history has been lost; we are not
7401 intentionally leaving anyone out.
7403 @node GNU Free Documentation License
7404 @appendix GNU Free Documentation License
7408 @unnumbered AS Index