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.
778 @xref{Blackfin Options}, for the options available when @value{AS} is
779 configured for the Blackfin processor family.
784 The following options are available when @value{AS} is configured for
785 the Blackfin processor family.
789 @c ended inside the included file
795 See the info pages for documentation of the CRIS-specific options.
799 The following options are available when @value{AS} is configured for
802 @cindex D10V optimization
803 @cindex optimization, D10V
805 Optimize output by parallelizing instructions.
810 The following options are available when @value{AS} is configured for a D30V
813 @cindex D30V optimization
814 @cindex optimization, D30V
816 Optimize output by parallelizing instructions.
820 Warn when nops are generated.
822 @cindex D30V nops after 32-bit multiply
824 Warn when a nop after a 32-bit multiply instruction is generated.
832 @xref{i386-Options}, for the options available when @value{AS} is
833 configured for an i386 processor.
838 The following options are available when @value{AS} is configured for
843 @c ended inside the included file
850 The following options are available when @value{AS} is configured for the
851 Intel 80960 processor.
854 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
855 Specify which variant of the 960 architecture is the target.
858 Add code to collect statistics about branches taken.
861 Do not alter compare-and-branch instructions for long displacements;
868 The following options are available when @value{AS} is configured for the
874 Specifies that the extended IP2022 instructions are allowed.
877 Restores the default behaviour, which restricts the permitted instructions to
878 just the basic IP2022 ones.
884 The following options are available when @value{AS} is configured for the
885 Renesas M32C and M16C processors.
890 Assemble M32C instructions.
893 Assemble M16C instructions (the default).
896 Enable support for link-time relaxations.
899 Support H'00 style hex constants in addition to 0x00 style.
905 The following options are available when @value{AS} is configured for the
906 Renesas M32R (formerly Mitsubishi M32R) series.
911 Specify which processor in the M32R family is the target. The default
912 is normally the M32R, but this option changes it to the M32RX.
914 @item --warn-explicit-parallel-conflicts or --Wp
915 Produce warning messages when questionable parallel constructs are
918 @item --no-warn-explicit-parallel-conflicts or --Wnp
919 Do not produce warning messages when questionable parallel constructs are
926 The following options are available when @value{AS} is configured for the
927 Motorola 68000 series.
932 Shorten references to undefined symbols, to one word instead of two.
934 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
935 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
936 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
937 Specify what processor in the 68000 family is the target. The default
938 is normally the 68020, but this can be changed at configuration time.
940 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
941 The target machine does (or does not) have a floating-point coprocessor.
942 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
943 the basic 68000 is not compatible with the 68881, a combination of the
944 two can be specified, since it's possible to do emulation of the
945 coprocessor instructions with the main processor.
947 @item -m68851 | -mno-68851
948 The target machine does (or does not) have a memory-management
949 unit coprocessor. The default is to assume an MMU for 68020 and up.
956 For details about the PDP-11 machine dependent features options,
957 see @ref{PDP-11-Options}.
960 @item -mpic | -mno-pic
961 Generate position-independent (or position-dependent) code. The
962 default is @option{-mpic}.
965 @itemx -mall-extensions
966 Enable all instruction set extensions. This is the default.
968 @item -mno-extensions
969 Disable all instruction set extensions.
971 @item -m@var{extension} | -mno-@var{extension}
972 Enable (or disable) a particular instruction set extension.
975 Enable the instruction set extensions supported by a particular CPU, and
976 disable all other extensions.
978 @item -m@var{machine}
979 Enable the instruction set extensions supported by a particular machine
980 model, and disable all other extensions.
986 The following options are available when @value{AS} is configured for
987 a picoJava processor.
991 @cindex PJ endianness
992 @cindex endianness, PJ
993 @cindex big endian output, PJ
995 Generate ``big endian'' format output.
997 @cindex little endian output, PJ
999 Generate ``little endian'' format output.
1005 The following options are available when @value{AS} is configured for the
1006 Motorola 68HC11 or 68HC12 series.
1010 @item -m68hc11 | -m68hc12 | -m68hcs12
1011 Specify what processor is the target. The default is
1012 defined by the configuration option when building the assembler.
1015 Specify to use the 16-bit integer ABI.
1018 Specify to use the 32-bit integer ABI.
1020 @item -mshort-double
1021 Specify to use the 32-bit double ABI.
1024 Specify to use the 64-bit double ABI.
1026 @item --force-long-branches
1027 Relative branches are turned into absolute ones. This concerns
1028 conditional branches, unconditional branches and branches to a
1031 @item -S | --short-branches
1032 Do not turn relative branches into absolute ones
1033 when the offset is out of range.
1035 @item --strict-direct-mode
1036 Do not turn the direct addressing mode into extended addressing mode
1037 when the instruction does not support direct addressing mode.
1039 @item --print-insn-syntax
1040 Print the syntax of instruction in case of error.
1042 @item --print-opcodes
1043 print the list of instructions with syntax and then exit.
1045 @item --generate-example
1046 print an example of instruction for each possible instruction and then exit.
1047 This option is only useful for testing @command{@value{AS}}.
1053 The following options are available when @command{@value{AS}} is configured
1054 for the SPARC architecture:
1057 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1058 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1059 Explicitly select a variant of the SPARC architecture.
1061 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1062 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1064 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1065 UltraSPARC extensions.
1067 @item -xarch=v8plus | -xarch=v8plusa
1068 For compatibility with the Solaris v9 assembler. These options are
1069 equivalent to -Av8plus and -Av8plusa, respectively.
1072 Warn when the assembler switches to another architecture.
1077 The following options are available when @value{AS} is configured for the 'c54x
1082 Enable extended addressing mode. All addresses and relocations will assume
1083 extended addressing (usually 23 bits).
1084 @item -mcpu=@var{CPU_VERSION}
1085 Sets the CPU version being compiled for.
1086 @item -merrors-to-file @var{FILENAME}
1087 Redirect error output to a file, for broken systems which don't support such
1088 behaviour in the shell.
1093 The following options are available when @value{AS} is configured for
1094 a @sc{mips} processor.
1098 This option sets the largest size of an object that can be referenced
1099 implicitly with the @code{gp} register. It is only accepted for targets that
1100 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1102 @cindex MIPS endianness
1103 @cindex endianness, MIPS
1104 @cindex big endian output, MIPS
1106 Generate ``big endian'' format output.
1108 @cindex little endian output, MIPS
1110 Generate ``little endian'' format output.
1122 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1123 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1124 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1125 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1126 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1128 correspond to generic
1129 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1130 and @samp{MIPS64 Release 2}
1131 ISA processors, respectively.
1133 @item -march=@var{CPU}
1134 Generate code for a particular @sc{mips} cpu.
1136 @item -mtune=@var{cpu}
1137 Schedule and tune for a particular @sc{mips} cpu.
1141 Cause nops to be inserted if the read of the destination register
1142 of an mfhi or mflo instruction occurs in the following two instructions.
1146 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1147 section instead of the standard ELF .stabs sections.
1151 Control generation of @code{.pdr} sections.
1155 The register sizes are normally inferred from the ISA and ABI, but these
1156 flags force a certain group of registers to be treated as 32 bits wide at
1157 all times. @samp{-mgp32} controls the size of general-purpose registers
1158 and @samp{-mfp32} controls the size of floating-point registers.
1162 Generate code for the MIPS 16 processor. This is equivalent to putting
1163 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1164 turns off this option.
1167 @itemx -mno-smartmips
1168 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1169 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1170 @samp{-mno-smartmips} turns off this option.
1174 Generate code for the MIPS-3D Application Specific Extension.
1175 This tells the assembler to accept MIPS-3D instructions.
1176 @samp{-no-mips3d} turns off this option.
1180 Generate code for the MDMX Application Specific Extension.
1181 This tells the assembler to accept MDMX instructions.
1182 @samp{-no-mdmx} turns off this option.
1186 Generate code for the DSP Release 1 Application Specific Extension.
1187 This tells the assembler to accept DSP Release 1 instructions.
1188 @samp{-mno-dsp} turns off this option.
1192 Generate code for the DSP Release 2 Application Specific Extension.
1193 This option implies -mdsp.
1194 This tells the assembler to accept DSP Release 2 instructions.
1195 @samp{-mno-dspr2} turns off this option.
1199 Generate code for the MT Application Specific Extension.
1200 This tells the assembler to accept MT instructions.
1201 @samp{-mno-mt} turns off this option.
1203 @item --construct-floats
1204 @itemx --no-construct-floats
1205 The @samp{--no-construct-floats} option disables the construction of
1206 double width floating point constants by loading the two halves of the
1207 value into the two single width floating point registers that make up
1208 the double width register. By default @samp{--construct-floats} is
1209 selected, allowing construction of these floating point constants.
1212 @item --emulation=@var{name}
1213 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1214 for some other target, in all respects, including output format (choosing
1215 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1216 debugging information or store symbol table information, and default
1217 endianness. The available configuration names are: @samp{mipsecoff},
1218 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1219 @samp{mipsbelf}. The first two do not alter the default endianness from that
1220 of the primary target for which the assembler was configured; the others change
1221 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1222 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1223 selection in any case.
1225 This option is currently supported only when the primary target
1226 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1227 Furthermore, the primary target or others specified with
1228 @samp{--enable-targets=@dots{}} at configuration time must include support for
1229 the other format, if both are to be available. For example, the Irix 5
1230 configuration includes support for both.
1232 Eventually, this option will support more configurations, with more
1233 fine-grained control over the assembler's behavior, and will be supported for
1237 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1244 Control how to deal with multiplication overflow and division by zero.
1245 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1246 (and only work for Instruction Set Architecture level 2 and higher);
1247 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1251 When this option is used, @command{@value{AS}} will issue a warning every
1252 time it generates a nop instruction from a macro.
1257 The following options are available when @value{AS} is configured for
1263 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1264 The command line option @samp{-nojsri2bsr} can be used to disable it.
1268 Enable or disable the silicon filter behaviour. By default this is disabled.
1269 The default can be overridden by the @samp{-sifilter} command line option.
1272 Alter jump instructions for long displacements.
1274 @item -mcpu=[210|340]
1275 Select the cpu type on the target hardware. This controls which instructions
1279 Assemble for a big endian target.
1282 Assemble for a little endian target.
1288 See the info pages for documentation of the MMIX-specific options.
1294 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1295 for a PowerPC processor.
1299 @c man begin OPTIONS
1300 The following options are available when @value{AS} is configured for a
1303 @c man begin INCLUDE
1305 @c ended inside the included file
1311 See the info pages for documentation of the RX-specific options.
1315 The following options are available when @value{AS} is configured for the s390
1321 Select the word size, either 31/32 bits or 64 bits.
1324 Select the architecture mode, either the Enterprise System
1325 Architecture (esa) or the z/Architecture mode (zarch).
1326 @item -march=@var{processor}
1327 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1328 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1330 @itemx -mno-regnames
1331 Allow or disallow symbolic names for registers.
1332 @item -mwarn-areg-zero
1333 Warn whenever the operand for a base or index register has been specified
1334 but evaluates to zero.
1342 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1343 for a TMS320C6000 processor.
1347 @c man begin OPTIONS
1348 The following options are available when @value{AS} is configured for a
1349 TMS320C6000 processor.
1351 @c man begin INCLUDE
1352 @include c-tic6x.texi
1353 @c ended inside the included file
1361 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1362 for an Xtensa processor.
1366 @c man begin OPTIONS
1367 The following options are available when @value{AS} is configured for an
1370 @c man begin INCLUDE
1371 @include c-xtensa.texi
1372 @c ended inside the included file
1377 @c man begin OPTIONS
1380 The following options are available when @value{AS} is configured for
1381 a Z80 family processor.
1384 Assemble for Z80 processor.
1386 Assemble for R800 processor.
1387 @item -ignore-undocumented-instructions
1389 Assemble undocumented Z80 instructions that also work on R800 without warning.
1390 @item -ignore-unportable-instructions
1392 Assemble all undocumented Z80 instructions without warning.
1393 @item -warn-undocumented-instructions
1395 Issue a warning for undocumented Z80 instructions that also work on R800.
1396 @item -warn-unportable-instructions
1398 Issue a warning for undocumented Z80 instructions that do not work on R800.
1399 @item -forbid-undocumented-instructions
1401 Treat all undocumented instructions as errors.
1402 @item -forbid-unportable-instructions
1404 Treat undocumented Z80 instructions that do not work on R800 as errors.
1411 * Manual:: Structure of this Manual
1412 * GNU Assembler:: The GNU Assembler
1413 * Object Formats:: Object File Formats
1414 * Command Line:: Command Line
1415 * Input Files:: Input Files
1416 * Object:: Output (Object) File
1417 * Errors:: Error and Warning Messages
1421 @section Structure of this Manual
1423 @cindex manual, structure and purpose
1424 This manual is intended to describe what you need to know to use
1425 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1426 notation for symbols, constants, and expressions; the directives that
1427 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1430 We also cover special features in the @value{TARGET}
1431 configuration of @command{@value{AS}}, including assembler directives.
1434 This manual also describes some of the machine-dependent features of
1435 various flavors of the assembler.
1438 @cindex machine instructions (not covered)
1439 On the other hand, this manual is @emph{not} intended as an introduction
1440 to programming in assembly language---let alone programming in general!
1441 In a similar vein, we make no attempt to introduce the machine
1442 architecture; we do @emph{not} describe the instruction set, standard
1443 mnemonics, registers or addressing modes that are standard to a
1444 particular architecture.
1446 You may want to consult the manufacturer's
1447 machine architecture manual for this information.
1451 For information on the H8/300 machine instruction set, see @cite{H8/300
1452 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1453 Programming Manual} (Renesas).
1456 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1457 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1458 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1459 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1462 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1466 @c I think this is premature---doc@cygnus.com, 17jan1991
1468 Throughout this manual, we assume that you are running @dfn{GNU},
1469 the portable operating system from the @dfn{Free Software
1470 Foundation, Inc.}. This restricts our attention to certain kinds of
1471 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1472 once this assumption is granted examples and definitions need less
1475 @command{@value{AS}} is part of a team of programs that turn a high-level
1476 human-readable series of instructions into a low-level
1477 computer-readable series of instructions. Different versions of
1478 @command{@value{AS}} are used for different kinds of computer.
1481 @c There used to be a section "Terminology" here, which defined
1482 @c "contents", "byte", "word", and "long". Defining "word" to any
1483 @c particular size is confusing when the .word directive may generate 16
1484 @c bits on one machine and 32 bits on another; in general, for the user
1485 @c version of this manual, none of these terms seem essential to define.
1486 @c They were used very little even in the former draft of the manual;
1487 @c this draft makes an effort to avoid them (except in names of
1491 @section The GNU Assembler
1493 @c man begin DESCRIPTION
1495 @sc{gnu} @command{as} is really a family of assemblers.
1497 This manual describes @command{@value{AS}}, a member of that family which is
1498 configured for the @value{TARGET} architectures.
1500 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1501 should find a fairly similar environment when you use it on another
1502 architecture. Each version has much in common with the others,
1503 including object file formats, most assembler directives (often called
1504 @dfn{pseudo-ops}) and assembler syntax.@refill
1506 @cindex purpose of @sc{gnu} assembler
1507 @command{@value{AS}} is primarily intended to assemble the output of the
1508 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1509 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1510 assemble correctly everything that other assemblers for the same
1511 machine would assemble.
1513 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1516 @c This remark should appear in generic version of manual; assumption
1517 @c here is that generic version sets M680x0.
1518 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1519 assembler for the same architecture; for example, we know of several
1520 incompatible versions of 680x0 assembly language syntax.
1525 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1526 program in one pass of the source file. This has a subtle impact on the
1527 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1529 @node Object Formats
1530 @section Object File Formats
1532 @cindex object file format
1533 The @sc{gnu} assembler can be configured to produce several alternative
1534 object file formats. For the most part, this does not affect how you
1535 write assembly language programs; but directives for debugging symbols
1536 are typically different in different file formats. @xref{Symbol
1537 Attributes,,Symbol Attributes}.
1540 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1541 @value{OBJ-NAME} format object files.
1543 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1545 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1546 @code{b.out} or COFF format object files.
1549 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1550 SOM or ELF format object files.
1555 @section Command Line
1557 @cindex command line conventions
1559 After the program name @command{@value{AS}}, the command line may contain
1560 options and file names. Options may appear in any order, and may be
1561 before, after, or between file names. The order of file names is
1564 @cindex standard input, as input file
1566 @file{--} (two hyphens) by itself names the standard input file
1567 explicitly, as one of the files for @command{@value{AS}} to assemble.
1569 @cindex options, command line
1570 Except for @samp{--} any command line argument that begins with a
1571 hyphen (@samp{-}) is an option. Each option changes the behavior of
1572 @command{@value{AS}}. No option changes the way another option works. An
1573 option is a @samp{-} followed by one or more letters; the case of
1574 the letter is important. All options are optional.
1576 Some options expect exactly one file name to follow them. The file
1577 name may either immediately follow the option's letter (compatible
1578 with older assemblers) or it may be the next command argument (@sc{gnu}
1579 standard). These two command lines are equivalent:
1582 @value{AS} -o my-object-file.o mumble.s
1583 @value{AS} -omy-object-file.o mumble.s
1587 @section Input Files
1590 @cindex source program
1591 @cindex files, input
1592 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1593 describe the program input to one run of @command{@value{AS}}. The program may
1594 be in one or more files; how the source is partitioned into files
1595 doesn't change the meaning of the source.
1597 @c I added "con" prefix to "catenation" just to prove I can overcome my
1598 @c APL training... doc@cygnus.com
1599 The source program is a concatenation of the text in all the files, in the
1602 @c man begin DESCRIPTION
1603 Each time you run @command{@value{AS}} it assembles exactly one source
1604 program. The source program is made up of one or more files.
1605 (The standard input is also a file.)
1607 You give @command{@value{AS}} a command line that has zero or more input file
1608 names. The input files are read (from left file name to right). A
1609 command line argument (in any position) that has no special meaning
1610 is taken to be an input file name.
1612 If you give @command{@value{AS}} no file names it attempts to read one input file
1613 from the @command{@value{AS}} standard input, which is normally your terminal. You
1614 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1617 Use @samp{--} if you need to explicitly name the standard input file
1618 in your command line.
1620 If the source is empty, @command{@value{AS}} produces a small, empty object
1625 @subheading Filenames and Line-numbers
1627 @cindex input file linenumbers
1628 @cindex line numbers, in input files
1629 There are two ways of locating a line in the input file (or files) and
1630 either may be used in reporting error messages. One way refers to a line
1631 number in a physical file; the other refers to a line number in a
1632 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1634 @dfn{Physical files} are those files named in the command line given
1635 to @command{@value{AS}}.
1637 @dfn{Logical files} are simply names declared explicitly by assembler
1638 directives; they bear no relation to physical files. Logical file names help
1639 error messages reflect the original source file, when @command{@value{AS}} source
1640 is itself synthesized from other files. @command{@value{AS}} understands the
1641 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1642 @ref{File,,@code{.file}}.
1645 @section Output (Object) File
1651 Every time you run @command{@value{AS}} it produces an output file, which is
1652 your assembly language program translated into numbers. This file
1653 is the object file. Its default name is
1661 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1663 You can give it another name by using the @option{-o} option. Conventionally,
1664 object file names end with @file{.o}. The default name is used for historical
1665 reasons: older assemblers were capable of assembling self-contained programs
1666 directly into a runnable program. (For some formats, this isn't currently
1667 possible, but it can be done for the @code{a.out} format.)
1671 The object file is meant for input to the linker @code{@value{LD}}. It contains
1672 assembled program code, information to help @code{@value{LD}} integrate
1673 the assembled program into a runnable file, and (optionally) symbolic
1674 information for the debugger.
1676 @c link above to some info file(s) like the description of a.out.
1677 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1680 @section Error and Warning Messages
1682 @c man begin DESCRIPTION
1684 @cindex error messages
1685 @cindex warning messages
1686 @cindex messages from assembler
1687 @command{@value{AS}} may write warnings and error messages to the standard error
1688 file (usually your terminal). This should not happen when a compiler
1689 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1690 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1691 grave problem that stops the assembly.
1695 @cindex format of warning messages
1696 Warning messages have the format
1699 file_name:@b{NNN}:Warning Message Text
1703 @cindex line numbers, in warnings/errors
1704 (where @b{NNN} is a line number). If a logical file name has been given
1705 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1706 the current input file is used. If a logical line number was given
1708 (@pxref{Line,,@code{.line}})
1710 then it is used to calculate the number printed,
1711 otherwise the actual line in the current source file is printed. The
1712 message text is intended to be self explanatory (in the grand Unix
1715 @cindex format of error messages
1716 Error messages have the format
1718 file_name:@b{NNN}:FATAL:Error Message Text
1720 The file name and line number are derived as for warning
1721 messages. The actual message text may be rather less explanatory
1722 because many of them aren't supposed to happen.
1725 @chapter Command-Line Options
1727 @cindex options, all versions of assembler
1728 This chapter describes command-line options available in @emph{all}
1729 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1730 for options specific
1732 to the @value{TARGET} target.
1735 to particular machine architectures.
1738 @c man begin DESCRIPTION
1740 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1741 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1742 The assembler arguments must be separated from each other (and the @samp{-Wa})
1743 by commas. For example:
1746 gcc -c -g -O -Wa,-alh,-L file.c
1750 This passes two options to the assembler: @samp{-alh} (emit a listing to
1751 standard output with high-level and assembly source) and @samp{-L} (retain
1752 local symbols in the symbol table).
1754 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1755 command-line options are automatically passed to the assembler by the compiler.
1756 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1757 precisely what options it passes to each compilation pass, including the
1763 * a:: -a[cdghlns] enable listings
1764 * alternate:: --alternate enable alternate macro syntax
1765 * D:: -D for compatibility
1766 * f:: -f to work faster
1767 * I:: -I for .include search path
1768 @ifclear DIFF-TBL-KLUGE
1769 * K:: -K for compatibility
1771 @ifset DIFF-TBL-KLUGE
1772 * K:: -K for difference tables
1775 * L:: -L to retain local symbols
1776 * listing:: --listing-XXX to configure listing output
1777 * M:: -M or --mri to assemble in MRI compatibility mode
1778 * MD:: --MD for dependency tracking
1779 * o:: -o to name the object file
1780 * R:: -R to join data and text sections
1781 * statistics:: --statistics to see statistics about assembly
1782 * traditional-format:: --traditional-format for compatible output
1783 * v:: -v to announce version
1784 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1785 * Z:: -Z to make object file even after errors
1789 @section Enable Listings: @option{-a[cdghlns]}
1799 @cindex listings, enabling
1800 @cindex assembly listings, enabling
1802 These options enable listing output from the assembler. By itself,
1803 @samp{-a} requests high-level, assembly, and symbols listing.
1804 You can use other letters to select specific options for the list:
1805 @samp{-ah} requests a high-level language listing,
1806 @samp{-al} requests an output-program assembly listing, and
1807 @samp{-as} requests a symbol table listing.
1808 High-level listings require that a compiler debugging option like
1809 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1812 Use the @samp{-ag} option to print a first section with general assembly
1813 information, like @value{AS} version, switches passed, or time stamp.
1815 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1816 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1817 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1818 omitted from the listing.
1820 Use the @samp{-ad} option to omit debugging directives from the
1823 Once you have specified one of these options, you can further control
1824 listing output and its appearance using the directives @code{.list},
1825 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1827 The @samp{-an} option turns off all forms processing.
1828 If you do not request listing output with one of the @samp{-a} options, the
1829 listing-control directives have no effect.
1831 The letters after @samp{-a} may be combined into one option,
1832 @emph{e.g.}, @samp{-aln}.
1834 Note if the assembler source is coming from the standard input (e.g.,
1836 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1837 is being used) then the listing will not contain any comments or preprocessor
1838 directives. This is because the listing code buffers input source lines from
1839 stdin only after they have been preprocessed by the assembler. This reduces
1840 memory usage and makes the code more efficient.
1843 @section @option{--alternate}
1846 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1849 @section @option{-D}
1852 This option has no effect whatsoever, but it is accepted to make it more
1853 likely that scripts written for other assemblers also work with
1854 @command{@value{AS}}.
1857 @section Work Faster: @option{-f}
1860 @cindex trusted compiler
1861 @cindex faster processing (@option{-f})
1862 @samp{-f} should only be used when assembling programs written by a
1863 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1864 and comment preprocessing on
1865 the input file(s) before assembling them. @xref{Preprocessing,
1869 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1870 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1875 @section @code{.include} Search Path: @option{-I} @var{path}
1877 @kindex -I @var{path}
1878 @cindex paths for @code{.include}
1879 @cindex search path for @code{.include}
1880 @cindex @code{include} directive search path
1881 Use this option to add a @var{path} to the list of directories
1882 @command{@value{AS}} searches for files specified in @code{.include}
1883 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1884 many times as necessary to include a variety of paths. The current
1885 working directory is always searched first; after that, @command{@value{AS}}
1886 searches any @samp{-I} directories in the same order as they were
1887 specified (left to right) on the command line.
1890 @section Difference Tables: @option{-K}
1893 @ifclear DIFF-TBL-KLUGE
1894 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1895 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1896 where it can be used to warn when the assembler alters the machine code
1897 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1898 family does not have the addressing limitations that sometimes lead to this
1899 alteration on other platforms.
1902 @ifset DIFF-TBL-KLUGE
1903 @cindex difference tables, warning
1904 @cindex warning for altered difference tables
1905 @command{@value{AS}} sometimes alters the code emitted for directives of the
1906 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1907 You can use the @samp{-K} option if you want a warning issued when this
1912 @section Include Local Symbols: @option{-L}
1915 @cindex local symbols, retaining in output
1916 Symbols beginning with system-specific local label prefixes, typically
1917 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1918 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1919 such symbols when debugging, because they are intended for the use of
1920 programs (like compilers) that compose assembler programs, not for your
1921 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1922 such symbols, so you do not normally debug with them.
1924 This option tells @command{@value{AS}} to retain those local symbols
1925 in the object file. Usually if you do this you also tell the linker
1926 @code{@value{LD}} to preserve those symbols.
1929 @section Configuring listing output: @option{--listing}
1931 The listing feature of the assembler can be enabled via the command line switch
1932 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1933 hex dump of the corresponding locations in the output object file, and displays
1934 them as a listing file. The format of this listing can be controlled by
1935 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1936 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1937 @code{.psize} (@pxref{Psize}), and
1938 @code{.eject} (@pxref{Eject}) and also by the following switches:
1941 @item --listing-lhs-width=@samp{number}
1942 @kindex --listing-lhs-width
1943 @cindex Width of first line disassembly output
1944 Sets the maximum width, in words, of the first line of the hex byte dump. This
1945 dump appears on the left hand side of the listing output.
1947 @item --listing-lhs-width2=@samp{number}
1948 @kindex --listing-lhs-width2
1949 @cindex Width of continuation lines of disassembly output
1950 Sets the maximum width, in words, of any further lines of the hex byte dump for
1951 a given input source line. If this value is not specified, it defaults to being
1952 the same as the value specified for @samp{--listing-lhs-width}. If neither
1953 switch is used the default is to one.
1955 @item --listing-rhs-width=@samp{number}
1956 @kindex --listing-rhs-width
1957 @cindex Width of source line output
1958 Sets the maximum width, in characters, of the source line that is displayed
1959 alongside the hex dump. The default value for this parameter is 100. The
1960 source line is displayed on the right hand side of the listing output.
1962 @item --listing-cont-lines=@samp{number}
1963 @kindex --listing-cont-lines
1964 @cindex Maximum number of continuation lines
1965 Sets the maximum number of continuation lines of hex dump that will be
1966 displayed for a given single line of source input. The default value is 4.
1970 @section Assemble in MRI Compatibility Mode: @option{-M}
1973 @cindex MRI compatibility mode
1974 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1975 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1976 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1977 configured target) assembler from Microtec Research. The exact nature of the
1978 MRI syntax will not be documented here; see the MRI manuals for more
1979 information. Note in particular that the handling of macros and macro
1980 arguments is somewhat different. The purpose of this option is to permit
1981 assembling existing MRI assembler code using @command{@value{AS}}.
1983 The MRI compatibility is not complete. Certain operations of the MRI assembler
1984 depend upon its object file format, and can not be supported using other object
1985 file formats. Supporting these would require enhancing each object file format
1986 individually. These are:
1989 @item global symbols in common section
1991 The m68k MRI assembler supports common sections which are merged by the linker.
1992 Other object file formats do not support this. @command{@value{AS}} handles
1993 common sections by treating them as a single common symbol. It permits local
1994 symbols to be defined within a common section, but it can not support global
1995 symbols, since it has no way to describe them.
1997 @item complex relocations
1999 The MRI assemblers support relocations against a negated section address, and
2000 relocations which combine the start addresses of two or more sections. These
2001 are not support by other object file formats.
2003 @item @code{END} pseudo-op specifying start address
2005 The MRI @code{END} pseudo-op permits the specification of a start address.
2006 This is not supported by other object file formats. The start address may
2007 instead be specified using the @option{-e} option to the linker, or in a linker
2010 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2012 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2013 name to the output file. This is not supported by other object file formats.
2015 @item @code{ORG} pseudo-op
2017 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2018 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2019 which changes the location within the current section. Absolute sections are
2020 not supported by other object file formats. The address of a section may be
2021 assigned within a linker script.
2024 There are some other features of the MRI assembler which are not supported by
2025 @command{@value{AS}}, typically either because they are difficult or because they
2026 seem of little consequence. Some of these may be supported in future releases.
2030 @item EBCDIC strings
2032 EBCDIC strings are not supported.
2034 @item packed binary coded decimal
2036 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2037 and @code{DCB.P} pseudo-ops are not supported.
2039 @item @code{FEQU} pseudo-op
2041 The m68k @code{FEQU} pseudo-op is not supported.
2043 @item @code{NOOBJ} pseudo-op
2045 The m68k @code{NOOBJ} pseudo-op is not supported.
2047 @item @code{OPT} branch control options
2049 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2050 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2051 relaxes all branches, whether forward or backward, to an appropriate size, so
2052 these options serve no purpose.
2054 @item @code{OPT} list control options
2056 The following m68k @code{OPT} list control options are ignored: @code{C},
2057 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2058 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2060 @item other @code{OPT} options
2062 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2063 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2065 @item @code{OPT} @code{D} option is default
2067 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2068 @code{OPT NOD} may be used to turn it off.
2070 @item @code{XREF} pseudo-op.
2072 The m68k @code{XREF} pseudo-op is ignored.
2074 @item @code{.debug} pseudo-op
2076 The i960 @code{.debug} pseudo-op is not supported.
2078 @item @code{.extended} pseudo-op
2080 The i960 @code{.extended} pseudo-op is not supported.
2082 @item @code{.list} pseudo-op.
2084 The various options of the i960 @code{.list} pseudo-op are not supported.
2086 @item @code{.optimize} pseudo-op
2088 The i960 @code{.optimize} pseudo-op is not supported.
2090 @item @code{.output} pseudo-op
2092 The i960 @code{.output} pseudo-op is not supported.
2094 @item @code{.setreal} pseudo-op
2096 The i960 @code{.setreal} pseudo-op is not supported.
2101 @section Dependency Tracking: @option{--MD}
2104 @cindex dependency tracking
2107 @command{@value{AS}} can generate a dependency file for the file it creates. This
2108 file consists of a single rule suitable for @code{make} describing the
2109 dependencies of the main source file.
2111 The rule is written to the file named in its argument.
2113 This feature is used in the automatic updating of makefiles.
2116 @section Name the Object File: @option{-o}
2119 @cindex naming object file
2120 @cindex object file name
2121 There is always one object file output when you run @command{@value{AS}}. By
2122 default it has the name
2125 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2139 You use this option (which takes exactly one filename) to give the
2140 object file a different name.
2142 Whatever the object file is called, @command{@value{AS}} overwrites any
2143 existing file of the same name.
2146 @section Join Data and Text Sections: @option{-R}
2149 @cindex data and text sections, joining
2150 @cindex text and data sections, joining
2151 @cindex joining text and data sections
2152 @cindex merging text and data sections
2153 @option{-R} tells @command{@value{AS}} to write the object file as if all
2154 data-section data lives in the text section. This is only done at
2155 the very last moment: your binary data are the same, but data
2156 section parts are relocated differently. The data section part of
2157 your object file is zero bytes long because all its bytes are
2158 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2160 When you specify @option{-R} it would be possible to generate shorter
2161 address displacements (because we do not have to cross between text and
2162 data section). We refrain from doing this simply for compatibility with
2163 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2166 When @command{@value{AS}} is configured for COFF or ELF output,
2167 this option is only useful if you use sections named @samp{.text} and
2172 @option{-R} is not supported for any of the HPPA targets. Using
2173 @option{-R} generates a warning from @command{@value{AS}}.
2177 @section Display Assembly Statistics: @option{--statistics}
2179 @kindex --statistics
2180 @cindex statistics, about assembly
2181 @cindex time, total for assembly
2182 @cindex space used, maximum for assembly
2183 Use @samp{--statistics} to display two statistics about the resources used by
2184 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2185 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2188 @node traditional-format
2189 @section Compatible Output: @option{--traditional-format}
2191 @kindex --traditional-format
2192 For some targets, the output of @command{@value{AS}} is different in some ways
2193 from the output of some existing assembler. This switch requests
2194 @command{@value{AS}} to use the traditional format instead.
2196 For example, it disables the exception frame optimizations which
2197 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2200 @section Announce Version: @option{-v}
2204 @cindex assembler version
2205 @cindex version of assembler
2206 You can find out what version of as is running by including the
2207 option @samp{-v} (which you can also spell as @samp{-version}) on the
2211 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2213 @command{@value{AS}} should never give a warning or error message when
2214 assembling compiler output. But programs written by people often
2215 cause @command{@value{AS}} to give a warning that a particular assumption was
2216 made. All such warnings are directed to the standard error file.
2220 @cindex suppressing warnings
2221 @cindex warnings, suppressing
2222 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2223 This only affects the warning messages: it does not change any particular of
2224 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2227 @kindex --fatal-warnings
2228 @cindex errors, caused by warnings
2229 @cindex warnings, causing error
2230 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2231 files that generate warnings to be in error.
2234 @cindex warnings, switching on
2235 You can switch these options off again by specifying @option{--warn}, which
2236 causes warnings to be output as usual.
2239 @section Generate Object File in Spite of Errors: @option{-Z}
2240 @cindex object file, after errors
2241 @cindex errors, continuing after
2242 After an error message, @command{@value{AS}} normally produces no output. If for
2243 some reason you are interested in object file output even after
2244 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2245 option. If there are any errors, @command{@value{AS}} continues anyways, and
2246 writes an object file after a final warning message of the form @samp{@var{n}
2247 errors, @var{m} warnings, generating bad object file.}
2252 @cindex machine-independent syntax
2253 @cindex syntax, machine-independent
2254 This chapter describes the machine-independent syntax allowed in a
2255 source file. @command{@value{AS}} syntax is similar to what many other
2256 assemblers use; it is inspired by the BSD 4.2
2261 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2265 * Preprocessing:: Preprocessing
2266 * Whitespace:: Whitespace
2267 * Comments:: Comments
2268 * Symbol Intro:: Symbols
2269 * Statements:: Statements
2270 * Constants:: Constants
2274 @section Preprocessing
2276 @cindex preprocessing
2277 The @command{@value{AS}} internal preprocessor:
2279 @cindex whitespace, removed by preprocessor
2281 adjusts and removes extra whitespace. It leaves one space or tab before
2282 the keywords on a line, and turns any other whitespace on the line into
2285 @cindex comments, removed by preprocessor
2287 removes all comments, replacing them with a single space, or an
2288 appropriate number of newlines.
2290 @cindex constants, converted by preprocessor
2292 converts character constants into the appropriate numeric values.
2295 It does not do macro processing, include file handling, or
2296 anything else you may get from your C compiler's preprocessor. You can
2297 do include file processing with the @code{.include} directive
2298 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2299 to get other ``CPP'' style preprocessing by giving the input file a
2300 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2301 Output, gcc.info, Using GNU CC}.
2303 Excess whitespace, comments, and character constants
2304 cannot be used in the portions of the input text that are not
2307 @cindex turning preprocessing on and off
2308 @cindex preprocessing, turning on and off
2311 If the first line of an input file is @code{#NO_APP} or if you use the
2312 @samp{-f} option, whitespace and comments are not removed from the input file.
2313 Within an input file, you can ask for whitespace and comment removal in
2314 specific portions of the by putting a line that says @code{#APP} before the
2315 text that may contain whitespace or comments, and putting a line that says
2316 @code{#NO_APP} after this text. This feature is mainly intend to support
2317 @code{asm} statements in compilers whose output is otherwise free of comments
2324 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2325 Whitespace is used to separate symbols, and to make programs neater for
2326 people to read. Unless within character constants
2327 (@pxref{Characters,,Character Constants}), any whitespace means the same
2328 as exactly one space.
2334 There are two ways of rendering comments to @command{@value{AS}}. In both
2335 cases the comment is equivalent to one space.
2337 Anything from @samp{/*} through the next @samp{*/} is a comment.
2338 This means you may not nest these comments.
2342 The only way to include a newline ('\n') in a comment
2343 is to use this sort of comment.
2346 /* This sort of comment does not nest. */
2349 @cindex line comment character
2350 Anything from a @dfn{line comment} character up to the next newline is
2351 considered a comment and is ignored. The line comment character is target
2352 specific, and some targets multiple comment characters. Some targets also have
2353 line comment characters that only work if they are the first character on a
2354 line. Some targets use a sequence of two characters to introduce a line
2355 comment. Some targets can also change their line comment characters depending
2356 upon command line options that have been used. For more details see the
2357 @emph{Syntax} section in the documentation for individual targets.
2359 If the line comment character is the hash sign (@samp{#}) then it still has the
2360 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2361 to specify logical line numbers:
2364 @cindex lines starting with @code{#}
2365 @cindex logical line numbers
2366 To be compatible with past assemblers, lines that begin with @samp{#} have a
2367 special interpretation. Following the @samp{#} should be an absolute
2368 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2369 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2370 new logical file name. The rest of the line, if any, should be whitespace.
2372 If the first non-whitespace characters on the line are not numeric,
2373 the line is ignored. (Just like a comment.)
2376 # This is an ordinary comment.
2377 # 42-6 "new_file_name" # New logical file name
2378 # This is logical line # 36.
2380 This feature is deprecated, and may disappear from future versions
2381 of @command{@value{AS}}.
2386 @cindex characters used in symbols
2387 @ifclear SPECIAL-SYMS
2388 A @dfn{symbol} is one or more characters chosen from the set of all
2389 letters (both upper and lower case), digits and the three characters
2395 A @dfn{symbol} is one or more characters chosen from the set of all
2396 letters (both upper and lower case), digits and the three characters
2397 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2403 On most machines, you can also use @code{$} in symbol names; exceptions
2404 are noted in @ref{Machine Dependencies}.
2406 No symbol may begin with a digit. Case is significant.
2407 There is no length limit: all characters are significant. Symbols are
2408 delimited by characters not in that set, or by the beginning of a file
2409 (since the source program must end with a newline, the end of a file is
2410 not a possible symbol delimiter). @xref{Symbols}.
2411 @cindex length of symbols
2416 @cindex statements, structure of
2417 @cindex line separator character
2418 @cindex statement separator character
2420 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2421 @dfn{line separator character}. The line separator character is target
2422 specific and described in the @emph{Syntax} section of each
2423 target's documentation. Not all targets support a line separator character.
2424 The newline or line separator character is considered to be part of the
2425 preceding statement. Newlines and separators within character constants are an
2426 exception: they do not end statements.
2428 @cindex newline, required at file end
2429 @cindex EOF, newline must precede
2430 It is an error to end any statement with end-of-file: the last
2431 character of any input file should be a newline.@refill
2433 An empty statement is allowed, and may include whitespace. It is ignored.
2435 @cindex instructions and directives
2436 @cindex directives and instructions
2437 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2438 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2440 A statement begins with zero or more labels, optionally followed by a
2441 key symbol which determines what kind of statement it is. The key
2442 symbol determines the syntax of the rest of the statement. If the
2443 symbol begins with a dot @samp{.} then the statement is an assembler
2444 directive: typically valid for any computer. If the symbol begins with
2445 a letter the statement is an assembly language @dfn{instruction}: it
2446 assembles into a machine language instruction.
2448 Different versions of @command{@value{AS}} for different computers
2449 recognize different instructions. In fact, the same symbol may
2450 represent a different instruction in a different computer's assembly
2454 @cindex @code{:} (label)
2455 @cindex label (@code{:})
2456 A label is a symbol immediately followed by a colon (@code{:}).
2457 Whitespace before a label or after a colon is permitted, but you may not
2458 have whitespace between a label's symbol and its colon. @xref{Labels}.
2461 For HPPA targets, labels need not be immediately followed by a colon, but
2462 the definition of a label must begin in column zero. This also implies that
2463 only one label may be defined on each line.
2467 label: .directive followed by something
2468 another_label: # This is an empty statement.
2469 instruction operand_1, operand_2, @dots{}
2476 A constant is a number, written so that its value is known by
2477 inspection, without knowing any context. Like this:
2480 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2481 .ascii "Ring the bell\7" # A string constant.
2482 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2483 .float 0f-314159265358979323846264338327\
2484 95028841971.693993751E-40 # - pi, a flonum.
2489 * Characters:: Character Constants
2490 * Numbers:: Number Constants
2494 @subsection Character Constants
2496 @cindex character constants
2497 @cindex constants, character
2498 There are two kinds of character constants. A @dfn{character} stands
2499 for one character in one byte and its value may be used in
2500 numeric expressions. String constants (properly called string
2501 @emph{literals}) are potentially many bytes and their values may not be
2502 used in arithmetic expressions.
2506 * Chars:: Characters
2510 @subsubsection Strings
2512 @cindex string constants
2513 @cindex constants, string
2514 A @dfn{string} is written between double-quotes. It may contain
2515 double-quotes or null characters. The way to get special characters
2516 into a string is to @dfn{escape} these characters: precede them with
2517 a backslash @samp{\} character. For example @samp{\\} represents
2518 one backslash: the first @code{\} is an escape which tells
2519 @command{@value{AS}} to interpret the second character literally as a backslash
2520 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2521 escape character). The complete list of escapes follows.
2523 @cindex escape codes, character
2524 @cindex character escape codes
2527 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2529 @cindex @code{\b} (backspace character)
2530 @cindex backspace (@code{\b})
2532 Mnemonic for backspace; for ASCII this is octal code 010.
2535 @c Mnemonic for EOText; for ASCII this is octal code 004.
2537 @cindex @code{\f} (formfeed character)
2538 @cindex formfeed (@code{\f})
2540 Mnemonic for FormFeed; for ASCII this is octal code 014.
2542 @cindex @code{\n} (newline character)
2543 @cindex newline (@code{\n})
2545 Mnemonic for newline; for ASCII this is octal code 012.
2548 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2550 @cindex @code{\r} (carriage return character)
2551 @cindex carriage return (@code{\r})
2553 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2556 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2557 @c other assemblers.
2559 @cindex @code{\t} (tab)
2560 @cindex tab (@code{\t})
2562 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2565 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2566 @c @item \x @var{digit} @var{digit} @var{digit}
2567 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2569 @cindex @code{\@var{ddd}} (octal character code)
2570 @cindex octal character code (@code{\@var{ddd}})
2571 @item \ @var{digit} @var{digit} @var{digit}
2572 An octal character code. The numeric code is 3 octal digits.
2573 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2574 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2576 @cindex @code{\@var{xd...}} (hex character code)
2577 @cindex hex character code (@code{\@var{xd...}})
2578 @item \@code{x} @var{hex-digits...}
2579 A hex character code. All trailing hex digits are combined. Either upper or
2580 lower case @code{x} works.
2582 @cindex @code{\\} (@samp{\} character)
2583 @cindex backslash (@code{\\})
2585 Represents one @samp{\} character.
2588 @c Represents one @samp{'} (accent acute) character.
2589 @c This is needed in single character literals
2590 @c (@xref{Characters,,Character Constants}.) to represent
2593 @cindex @code{\"} (doublequote character)
2594 @cindex doublequote (@code{\"})
2596 Represents one @samp{"} character. Needed in strings to represent
2597 this character, because an unescaped @samp{"} would end the string.
2599 @item \ @var{anything-else}
2600 Any other character when escaped by @kbd{\} gives a warning, but
2601 assembles as if the @samp{\} was not present. The idea is that if
2602 you used an escape sequence you clearly didn't want the literal
2603 interpretation of the following character. However @command{@value{AS}} has no
2604 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2605 code and warns you of the fact.
2608 Which characters are escapable, and what those escapes represent,
2609 varies widely among assemblers. The current set is what we think
2610 the BSD 4.2 assembler recognizes, and is a subset of what most C
2611 compilers recognize. If you are in doubt, do not use an escape
2615 @subsubsection Characters
2617 @cindex single character constant
2618 @cindex character, single
2619 @cindex constant, single character
2620 A single character may be written as a single quote immediately
2621 followed by that character. The same escapes apply to characters as
2622 to strings. So if you want to write the character backslash, you
2623 must write @kbd{'\\} where the first @code{\} escapes the second
2624 @code{\}. As you can see, the quote is an acute accent, not a
2625 grave accent. A newline
2627 @ifclear abnormal-separator
2628 (or semicolon @samp{;})
2630 @ifset abnormal-separator
2632 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2637 immediately following an acute accent is taken as a literal character
2638 and does not count as the end of a statement. The value of a character
2639 constant in a numeric expression is the machine's byte-wide code for
2640 that character. @command{@value{AS}} assumes your character code is ASCII:
2641 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2644 @subsection Number Constants
2646 @cindex constants, number
2647 @cindex number constants
2648 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2649 are stored in the target machine. @emph{Integers} are numbers that
2650 would fit into an @code{int} in the C language. @emph{Bignums} are
2651 integers, but they are stored in more than 32 bits. @emph{Flonums}
2652 are floating point numbers, described below.
2655 * Integers:: Integers
2660 * Bit Fields:: Bit Fields
2666 @subsubsection Integers
2668 @cindex constants, integer
2670 @cindex binary integers
2671 @cindex integers, binary
2672 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2673 the binary digits @samp{01}.
2675 @cindex octal integers
2676 @cindex integers, octal
2677 An octal integer is @samp{0} followed by zero or more of the octal
2678 digits (@samp{01234567}).
2680 @cindex decimal integers
2681 @cindex integers, decimal
2682 A decimal integer starts with a non-zero digit followed by zero or
2683 more digits (@samp{0123456789}).
2685 @cindex hexadecimal integers
2686 @cindex integers, hexadecimal
2687 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2688 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2690 Integers have the usual values. To denote a negative integer, use
2691 the prefix operator @samp{-} discussed under expressions
2692 (@pxref{Prefix Ops,,Prefix Operators}).
2695 @subsubsection Bignums
2698 @cindex constants, bignum
2699 A @dfn{bignum} has the same syntax and semantics as an integer
2700 except that the number (or its negative) takes more than 32 bits to
2701 represent in binary. The distinction is made because in some places
2702 integers are permitted while bignums are not.
2705 @subsubsection Flonums
2707 @cindex floating point numbers
2708 @cindex constants, floating point
2710 @cindex precision, floating point
2711 A @dfn{flonum} represents a floating point number. The translation is
2712 indirect: a decimal floating point number from the text is converted by
2713 @command{@value{AS}} to a generic binary floating point number of more than
2714 sufficient precision. This generic floating point number is converted
2715 to a particular computer's floating point format (or formats) by a
2716 portion of @command{@value{AS}} specialized to that computer.
2718 A flonum is written by writing (in order)
2723 (@samp{0} is optional on the HPPA.)
2727 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2729 @kbd{e} is recommended. Case is not important.
2731 @c FIXME: verify if flonum syntax really this vague for most cases
2732 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2733 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2736 On the H8/300, Renesas / SuperH SH,
2737 and AMD 29K architectures, the letter must be
2738 one of the letters @samp{DFPRSX} (in upper or lower case).
2740 On the ARC, the letter must be one of the letters @samp{DFRS}
2741 (in upper or lower case).
2743 On the Intel 960 architecture, the letter must be
2744 one of the letters @samp{DFT} (in upper or lower case).
2746 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2750 One of the letters @samp{DFRS} (in upper or lower case).
2753 One of the letters @samp{DFPRSX} (in upper or lower case).
2756 The letter @samp{E} (upper case only).
2759 One of the letters @samp{DFT} (in upper or lower case).
2764 An optional sign: either @samp{+} or @samp{-}.
2767 An optional @dfn{integer part}: zero or more decimal digits.
2770 An optional @dfn{fractional part}: @samp{.} followed by zero
2771 or more decimal digits.
2774 An optional exponent, consisting of:
2778 An @samp{E} or @samp{e}.
2779 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2780 @c principle this can perfectly well be different on different targets.
2782 Optional sign: either @samp{+} or @samp{-}.
2784 One or more decimal digits.
2789 At least one of the integer part or the fractional part must be
2790 present. The floating point number has the usual base-10 value.
2792 @command{@value{AS}} does all processing using integers. Flonums are computed
2793 independently of any floating point hardware in the computer running
2794 @command{@value{AS}}.
2798 @c Bit fields are written as a general facility but are also controlled
2799 @c by a conditional-compilation flag---which is as of now (21mar91)
2800 @c turned on only by the i960 config of GAS.
2802 @subsubsection Bit Fields
2805 @cindex constants, bit field
2806 You can also define numeric constants as @dfn{bit fields}.
2807 Specify two numbers separated by a colon---
2809 @var{mask}:@var{value}
2812 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2815 The resulting number is then packed
2817 @c this conditional paren in case bit fields turned on elsewhere than 960
2818 (in host-dependent byte order)
2820 into a field whose width depends on which assembler directive has the
2821 bit-field as its argument. Overflow (a result from the bitwise and
2822 requiring more binary digits to represent) is not an error; instead,
2823 more constants are generated, of the specified width, beginning with the
2824 least significant digits.@refill
2826 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2827 @code{.short}, and @code{.word} accept bit-field arguments.
2832 @chapter Sections and Relocation
2837 * Secs Background:: Background
2838 * Ld Sections:: Linker Sections
2839 * As Sections:: Assembler Internal Sections
2840 * Sub-Sections:: Sub-Sections
2844 @node Secs Background
2847 Roughly, a section is a range of addresses, with no gaps; all data
2848 ``in'' those addresses is treated the same for some particular purpose.
2849 For example there may be a ``read only'' section.
2851 @cindex linker, and assembler
2852 @cindex assembler, and linker
2853 The linker @code{@value{LD}} reads many object files (partial programs) and
2854 combines their contents to form a runnable program. When @command{@value{AS}}
2855 emits an object file, the partial program is assumed to start at address 0.
2856 @code{@value{LD}} assigns the final addresses for the partial program, so that
2857 different partial programs do not overlap. This is actually an
2858 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2861 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2862 addresses. These blocks slide to their run-time addresses as rigid
2863 units; their length does not change and neither does the order of bytes
2864 within them. Such a rigid unit is called a @emph{section}. Assigning
2865 run-time addresses to sections is called @dfn{relocation}. It includes
2866 the task of adjusting mentions of object-file addresses so they refer to
2867 the proper run-time addresses.
2869 For the H8/300, and for the Renesas / SuperH SH,
2870 @command{@value{AS}} pads sections if needed to
2871 ensure they end on a word (sixteen bit) boundary.
2874 @cindex standard assembler sections
2875 An object file written by @command{@value{AS}} has at least three sections, any
2876 of which may be empty. These are named @dfn{text}, @dfn{data} and
2881 When it generates COFF or ELF output,
2883 @command{@value{AS}} can also generate whatever other named sections you specify
2884 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2885 If you do not use any directives that place output in the @samp{.text}
2886 or @samp{.data} sections, these sections still exist, but are empty.
2891 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2893 @command{@value{AS}} can also generate whatever other named sections you
2894 specify using the @samp{.space} and @samp{.subspace} directives. See
2895 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2896 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2897 assembler directives.
2900 Additionally, @command{@value{AS}} uses different names for the standard
2901 text, data, and bss sections when generating SOM output. Program text
2902 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2903 BSS into @samp{$BSS$}.
2907 Within the object file, the text section starts at address @code{0}, the
2908 data section follows, and the bss section follows the data section.
2911 When generating either SOM or ELF output files on the HPPA, the text
2912 section starts at address @code{0}, the data section at address
2913 @code{0x4000000}, and the bss section follows the data section.
2916 To let @code{@value{LD}} know which data changes when the sections are
2917 relocated, and how to change that data, @command{@value{AS}} also writes to the
2918 object file details of the relocation needed. To perform relocation
2919 @code{@value{LD}} must know, each time an address in the object
2923 Where in the object file is the beginning of this reference to
2926 How long (in bytes) is this reference?
2928 Which section does the address refer to? What is the numeric value of
2930 (@var{address}) @minus{} (@var{start-address of section})?
2933 Is the reference to an address ``Program-Counter relative''?
2936 @cindex addresses, format of
2937 @cindex section-relative addressing
2938 In fact, every address @command{@value{AS}} ever uses is expressed as
2940 (@var{section}) + (@var{offset into section})
2943 Further, most expressions @command{@value{AS}} computes have this section-relative
2946 (For some object formats, such as SOM for the HPPA, some expressions are
2947 symbol-relative instead.)
2950 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2951 @var{N} into section @var{secname}.''
2953 Apart from text, data and bss sections you need to know about the
2954 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2955 addresses in the absolute section remain unchanged. For example, address
2956 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2957 @code{@value{LD}}. Although the linker never arranges two partial programs'
2958 data sections with overlapping addresses after linking, @emph{by definition}
2959 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2960 part of a program is always the same address when the program is running as
2961 address @code{@{absolute@ 239@}} in any other part of the program.
2963 The idea of sections is extended to the @dfn{undefined} section. Any
2964 address whose section is unknown at assembly time is by definition
2965 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2966 Since numbers are always defined, the only way to generate an undefined
2967 address is to mention an undefined symbol. A reference to a named
2968 common block would be such a symbol: its value is unknown at assembly
2969 time so it has section @emph{undefined}.
2971 By analogy the word @emph{section} is used to describe groups of sections in
2972 the linked program. @code{@value{LD}} puts all partial programs' text
2973 sections in contiguous addresses in the linked program. It is
2974 customary to refer to the @emph{text section} of a program, meaning all
2975 the addresses of all partial programs' text sections. Likewise for
2976 data and bss sections.
2978 Some sections are manipulated by @code{@value{LD}}; others are invented for
2979 use of @command{@value{AS}} and have no meaning except during assembly.
2982 @section Linker Sections
2983 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2988 @cindex named sections
2989 @cindex sections, named
2990 @item named sections
2993 @cindex text section
2994 @cindex data section
2998 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2999 separate but equal sections. Anything you can say of one section is
3002 When the program is running, however, it is
3003 customary for the text section to be unalterable. The
3004 text section is often shared among processes: it contains
3005 instructions, constants and the like. The data section of a running
3006 program is usually alterable: for example, C variables would be stored
3007 in the data section.
3012 This section contains zeroed bytes when your program begins running. It
3013 is used to hold uninitialized variables or common storage. The length of
3014 each partial program's bss section is important, but because it starts
3015 out containing zeroed bytes there is no need to store explicit zero
3016 bytes in the object file. The bss section was invented to eliminate
3017 those explicit zeros from object files.
3019 @cindex absolute section
3020 @item absolute section
3021 Address 0 of this section is always ``relocated'' to runtime address 0.
3022 This is useful if you want to refer to an address that @code{@value{LD}} must
3023 not change when relocating. In this sense we speak of absolute
3024 addresses being ``unrelocatable'': they do not change during relocation.
3026 @cindex undefined section
3027 @item undefined section
3028 This ``section'' is a catch-all for address references to objects not in
3029 the preceding sections.
3030 @c FIXME: ref to some other doc on obj-file formats could go here.
3033 @cindex relocation example
3034 An idealized example of three relocatable sections follows.
3036 The example uses the traditional section names @samp{.text} and @samp{.data}.
3038 Memory addresses are on the horizontal axis.
3042 @c END TEXI2ROFF-KILL
3045 partial program # 1: |ttttt|dddd|00|
3052 partial program # 2: |TTT|DDD|000|
3055 +--+---+-----+--+----+---+-----+~~
3056 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3057 +--+---+-----+--+----+---+-----+~~
3059 addresses: 0 @dots{}
3066 \line{\it Partial program \#1: \hfil}
3067 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3068 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3070 \line{\it Partial program \#2: \hfil}
3071 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3072 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3074 \line{\it linked program: \hfil}
3075 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3076 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3077 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3078 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3080 \line{\it addresses: \hfil}
3084 @c END TEXI2ROFF-KILL
3087 @section Assembler Internal Sections
3089 @cindex internal assembler sections
3090 @cindex sections in messages, internal
3091 These sections are meant only for the internal use of @command{@value{AS}}. They
3092 have no meaning at run-time. You do not really need to know about these
3093 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3094 warning messages, so it might be helpful to have an idea of their
3095 meanings to @command{@value{AS}}. These sections are used to permit the
3096 value of every expression in your assembly language program to be a
3097 section-relative address.
3100 @cindex assembler internal logic error
3101 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3102 An internal assembler logic error has been found. This means there is a
3103 bug in the assembler.
3105 @cindex expr (internal section)
3107 The assembler stores complex expression internally as combinations of
3108 symbols. When it needs to represent an expression as a symbol, it puts
3109 it in the expr section.
3111 @c FIXME item transfer[t] vector preload
3112 @c FIXME item transfer[t] vector postload
3113 @c FIXME item register
3117 @section Sub-Sections
3119 @cindex numbered subsections
3120 @cindex grouping data
3126 fall into two sections: text and data.
3128 You may have separate groups of
3130 data in named sections
3134 data in named sections
3140 that you want to end up near to each other in the object file, even though they
3141 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3142 use @dfn{subsections} for this purpose. Within each section, there can be
3143 numbered subsections with values from 0 to 8192. Objects assembled into the
3144 same subsection go into the object file together with other objects in the same
3145 subsection. For example, a compiler might want to store constants in the text
3146 section, but might not want to have them interspersed with the program being
3147 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3148 section of code being output, and a @samp{.text 1} before each group of
3149 constants being output.
3151 Subsections are optional. If you do not use subsections, everything
3152 goes in subsection number zero.
3155 Each subsection is zero-padded up to a multiple of four bytes.
3156 (Subsections may be padded a different amount on different flavors
3157 of @command{@value{AS}}.)
3161 On the H8/300 platform, each subsection is zero-padded to a word
3162 boundary (two bytes).
3163 The same is true on the Renesas SH.
3166 @c FIXME section padding (alignment)?
3167 @c Rich Pixley says padding here depends on target obj code format; that
3168 @c doesn't seem particularly useful to say without further elaboration,
3169 @c so for now I say nothing about it. If this is a generic BFD issue,
3170 @c these paragraphs might need to vanish from this manual, and be
3171 @c discussed in BFD chapter of binutils (or some such).
3175 Subsections appear in your object file in numeric order, lowest numbered
3176 to highest. (All this to be compatible with other people's assemblers.)
3177 The object file contains no representation of subsections; @code{@value{LD}} and
3178 other programs that manipulate object files see no trace of them.
3179 They just see all your text subsections as a text section, and all your
3180 data subsections as a data section.
3182 To specify which subsection you want subsequent statements assembled
3183 into, use a numeric argument to specify it, in a @samp{.text
3184 @var{expression}} or a @samp{.data @var{expression}} statement.
3187 When generating COFF output, you
3192 can also use an extra subsection
3193 argument with arbitrary named sections: @samp{.section @var{name},
3198 When generating ELF output, you
3203 can also use the @code{.subsection} directive (@pxref{SubSection})
3204 to specify a subsection: @samp{.subsection @var{expression}}.
3206 @var{Expression} should be an absolute expression
3207 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3208 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3209 begins in @code{text 0}. For instance:
3211 .text 0 # The default subsection is text 0 anyway.
3212 .ascii "This lives in the first text subsection. *"
3214 .ascii "But this lives in the second text subsection."
3216 .ascii "This lives in the data section,"
3217 .ascii "in the first data subsection."
3219 .ascii "This lives in the first text section,"
3220 .ascii "immediately following the asterisk (*)."
3223 Each section has a @dfn{location counter} incremented by one for every byte
3224 assembled into that section. Because subsections are merely a convenience
3225 restricted to @command{@value{AS}} there is no concept of a subsection location
3226 counter. There is no way to directly manipulate a location counter---but the
3227 @code{.align} directive changes it, and any label definition captures its
3228 current value. The location counter of the section where statements are being
3229 assembled is said to be the @dfn{active} location counter.
3232 @section bss Section
3235 @cindex common variable storage
3236 The bss section is used for local common variable storage.
3237 You may allocate address space in the bss section, but you may
3238 not dictate data to load into it before your program executes. When
3239 your program starts running, all the contents of the bss
3240 section are zeroed bytes.
3242 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3243 @ref{Lcomm,,@code{.lcomm}}.
3245 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3246 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3249 When assembling for a target which supports multiple sections, such as ELF or
3250 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3251 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3252 section. Typically the section will only contain symbol definitions and
3253 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3260 Symbols are a central concept: the programmer uses symbols to name
3261 things, the linker uses symbols to link, and the debugger uses symbols
3265 @cindex debuggers, and symbol order
3266 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3267 the same order they were declared. This may break some debuggers.
3272 * Setting Symbols:: Giving Symbols Other Values
3273 * Symbol Names:: Symbol Names
3274 * Dot:: The Special Dot Symbol
3275 * Symbol Attributes:: Symbol Attributes
3282 A @dfn{label} is written as a symbol immediately followed by a colon
3283 @samp{:}. The symbol then represents the current value of the
3284 active location counter, and is, for example, a suitable instruction
3285 operand. You are warned if you use the same symbol to represent two
3286 different locations: the first definition overrides any other
3290 On the HPPA, the usual form for a label need not be immediately followed by a
3291 colon, but instead must start in column zero. Only one label may be defined on
3292 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3293 provides a special directive @code{.label} for defining labels more flexibly.
3296 @node Setting Symbols
3297 @section Giving Symbols Other Values
3299 @cindex assigning values to symbols
3300 @cindex symbol values, assigning
3301 A symbol can be given an arbitrary value by writing a symbol, followed
3302 by an equals sign @samp{=}, followed by an expression
3303 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3304 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3305 equals sign @samp{=}@samp{=} here represents an equivalent of the
3306 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3309 Blackfin does not support symbol assignment with @samp{=}.
3313 @section Symbol Names
3315 @cindex symbol names
3316 @cindex names, symbol
3317 @ifclear SPECIAL-SYMS
3318 Symbol names begin with a letter or with one of @samp{._}. On most
3319 machines, you can also use @code{$} in symbol names; exceptions are
3320 noted in @ref{Machine Dependencies}. That character may be followed by any
3321 string of digits, letters, dollar signs (unless otherwise noted for a
3322 particular target machine), and underscores.
3326 Symbol names begin with a letter or with one of @samp{._}. On the
3327 Renesas SH you can also use @code{$} in symbol names. That
3328 character may be followed by any string of digits, letters, dollar signs (save
3329 on the H8/300), and underscores.
3333 Case of letters is significant: @code{foo} is a different symbol name
3336 Each symbol has exactly one name. Each name in an assembly language program
3337 refers to exactly one symbol. You may use that symbol name any number of times
3340 @subheading Local Symbol Names
3342 @cindex local symbol names
3343 @cindex symbol names, local
3344 A local symbol is any symbol beginning with certain local label prefixes.
3345 By default, the local label prefix is @samp{.L} for ELF systems or
3346 @samp{L} for traditional a.out systems, but each target may have its own
3347 set of local label prefixes.
3349 On the HPPA local symbols begin with @samp{L$}.
3352 Local symbols are defined and used within the assembler, but they are
3353 normally not saved in object files. Thus, they are not visible when debugging.
3354 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3355 @option{-L}}) to retain the local symbols in the object files.
3357 @subheading Local Labels
3359 @cindex local labels
3360 @cindex temporary symbol names
3361 @cindex symbol names, temporary
3362 Local labels help compilers and programmers use names temporarily.
3363 They create symbols which are guaranteed to be unique over the entire scope of
3364 the input source code and which can be referred to by a simple notation.
3365 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3366 represents any positive integer). To refer to the most recent previous
3367 definition of that label write @samp{@b{N}b}, using the same number as when
3368 you defined the label. To refer to the next definition of a local label, write
3369 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3372 There is no restriction on how you can use these labels, and you can reuse them
3373 too. So that it is possible to repeatedly define the same local label (using
3374 the same number @samp{@b{N}}), although you can only refer to the most recently
3375 defined local label of that number (for a backwards reference) or the next
3376 definition of a specific local label for a forward reference. It is also worth
3377 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3378 implemented in a slightly more efficient manner than the others.
3389 Which is the equivalent of:
3392 label_1: branch label_3
3393 label_2: branch label_1
3394 label_3: branch label_4
3395 label_4: branch label_3
3398 Local label names are only a notational device. They are immediately
3399 transformed into more conventional symbol names before the assembler uses them.
3400 The symbol names are stored in the symbol table, appear in error messages, and
3401 are optionally emitted to the object file. The names are constructed using
3405 @item @emph{local label prefix}
3406 All local symbols begin with the system-specific local label prefix.
3407 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3408 that start with the local label prefix. These labels are
3409 used for symbols you are never intended to see. If you use the
3410 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3411 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3412 you may use them in debugging.
3415 This is the number that was used in the local label definition. So if the
3416 label is written @samp{55:} then the number is @samp{55}.
3419 This unusual character is included so you do not accidentally invent a symbol
3420 of the same name. The character has ASCII value of @samp{\002} (control-B).
3422 @item @emph{ordinal number}
3423 This is a serial number to keep the labels distinct. The first definition of
3424 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3425 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3426 the number @samp{1} and its 15th definition gets @samp{15} as well.
3429 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3430 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3432 @subheading Dollar Local Labels
3433 @cindex dollar local symbols
3435 @code{@value{AS}} also supports an even more local form of local labels called
3436 dollar labels. These labels go out of scope (i.e., they become undefined) as
3437 soon as a non-local label is defined. Thus they remain valid for only a small
3438 region of the input source code. Normal local labels, by contrast, remain in
3439 scope for the entire file, or until they are redefined by another occurrence of
3440 the same local label.
3442 Dollar labels are defined in exactly the same way as ordinary local labels,
3443 except that they have a dollar sign suffix to their numeric value, e.g.,
3446 They can also be distinguished from ordinary local labels by their transformed
3447 names which use ASCII character @samp{\001} (control-A) as the magic character
3448 to distinguish them from ordinary labels. For example, the fifth definition of
3449 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3452 @section The Special Dot Symbol
3454 @cindex dot (symbol)
3455 @cindex @code{.} (symbol)
3456 @cindex current address
3457 @cindex location counter
3458 The special symbol @samp{.} refers to the current address that
3459 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3460 .long .} defines @code{melvin} to contain its own address.
3461 Assigning a value to @code{.} is treated the same as a @code{.org}
3463 @ifclear no-space-dir
3464 Thus, the expression @samp{.=.+4} is the same as saying
3468 @node Symbol Attributes
3469 @section Symbol Attributes
3471 @cindex symbol attributes
3472 @cindex attributes, symbol
3473 Every symbol has, as well as its name, the attributes ``Value'' and
3474 ``Type''. Depending on output format, symbols can also have auxiliary
3477 The detailed definitions are in @file{a.out.h}.
3480 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3481 all these attributes, and probably won't warn you. This makes the
3482 symbol an externally defined symbol, which is generally what you
3486 * Symbol Value:: Value
3487 * Symbol Type:: Type
3490 * a.out Symbols:: Symbol Attributes: @code{a.out}
3494 * a.out Symbols:: Symbol Attributes: @code{a.out}
3497 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3502 * COFF Symbols:: Symbol Attributes for COFF
3505 * SOM Symbols:: Symbol Attributes for SOM
3512 @cindex value of a symbol
3513 @cindex symbol value
3514 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3515 location in the text, data, bss or absolute sections the value is the
3516 number of addresses from the start of that section to the label.
3517 Naturally for text, data and bss sections the value of a symbol changes
3518 as @code{@value{LD}} changes section base addresses during linking. Absolute
3519 symbols' values do not change during linking: that is why they are
3522 The value of an undefined symbol is treated in a special way. If it is
3523 0 then the symbol is not defined in this assembler source file, and
3524 @code{@value{LD}} tries to determine its value from other files linked into the
3525 same program. You make this kind of symbol simply by mentioning a symbol
3526 name without defining it. A non-zero value represents a @code{.comm}
3527 common declaration. The value is how much common storage to reserve, in
3528 bytes (addresses). The symbol refers to the first address of the
3534 @cindex type of a symbol
3536 The type attribute of a symbol contains relocation (section)
3537 information, any flag settings indicating that a symbol is external, and
3538 (optionally), other information for linkers and debuggers. The exact
3539 format depends on the object-code output format in use.
3544 @c The following avoids a "widow" subsection title. @group would be
3545 @c better if it were available outside examples.
3548 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3550 @cindex @code{b.out} symbol attributes
3551 @cindex symbol attributes, @code{b.out}
3552 These symbol attributes appear only when @command{@value{AS}} is configured for
3553 one of the Berkeley-descended object output formats---@code{a.out} or
3559 @subsection Symbol Attributes: @code{a.out}
3561 @cindex @code{a.out} symbol attributes
3562 @cindex symbol attributes, @code{a.out}
3568 @subsection Symbol Attributes: @code{a.out}
3570 @cindex @code{a.out} symbol attributes
3571 @cindex symbol attributes, @code{a.out}
3575 * Symbol Desc:: Descriptor
3576 * Symbol Other:: Other
3580 @subsubsection Descriptor
3582 @cindex descriptor, of @code{a.out} symbol
3583 This is an arbitrary 16-bit value. You may establish a symbol's
3584 descriptor value by using a @code{.desc} statement
3585 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3586 @command{@value{AS}}.
3589 @subsubsection Other
3591 @cindex other attribute, of @code{a.out} symbol
3592 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3597 @subsection Symbol Attributes for COFF
3599 @cindex COFF symbol attributes
3600 @cindex symbol attributes, COFF
3602 The COFF format supports a multitude of auxiliary symbol attributes;
3603 like the primary symbol attributes, they are set between @code{.def} and
3604 @code{.endef} directives.
3606 @subsubsection Primary Attributes
3608 @cindex primary attributes, COFF symbols
3609 The symbol name is set with @code{.def}; the value and type,
3610 respectively, with @code{.val} and @code{.type}.
3612 @subsubsection Auxiliary Attributes
3614 @cindex auxiliary attributes, COFF symbols
3615 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3616 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3617 table information for COFF.
3622 @subsection Symbol Attributes for SOM
3624 @cindex SOM symbol attributes
3625 @cindex symbol attributes, SOM
3627 The SOM format for the HPPA supports a multitude of symbol attributes set with
3628 the @code{.EXPORT} and @code{.IMPORT} directives.
3630 The attributes are described in @cite{HP9000 Series 800 Assembly
3631 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3632 @code{EXPORT} assembler directive documentation.
3636 @chapter Expressions
3640 @cindex numeric values
3641 An @dfn{expression} specifies an address or numeric value.
3642 Whitespace may precede and/or follow an expression.
3644 The result of an expression must be an absolute number, or else an offset into
3645 a particular section. If an expression is not absolute, and there is not
3646 enough information when @command{@value{AS}} sees the expression to know its
3647 section, a second pass over the source program might be necessary to interpret
3648 the expression---but the second pass is currently not implemented.
3649 @command{@value{AS}} aborts with an error message in this situation.
3652 * Empty Exprs:: Empty Expressions
3653 * Integer Exprs:: Integer Expressions
3657 @section Empty Expressions
3659 @cindex empty expressions
3660 @cindex expressions, empty
3661 An empty expression has no value: it is just whitespace or null.
3662 Wherever an absolute expression is required, you may omit the
3663 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3664 is compatible with other assemblers.
3667 @section Integer Expressions
3669 @cindex integer expressions
3670 @cindex expressions, integer
3671 An @dfn{integer expression} is one or more @emph{arguments} delimited
3672 by @emph{operators}.
3675 * Arguments:: Arguments
3676 * Operators:: Operators
3677 * Prefix Ops:: Prefix Operators
3678 * Infix Ops:: Infix Operators
3682 @subsection Arguments
3684 @cindex expression arguments
3685 @cindex arguments in expressions
3686 @cindex operands in expressions
3687 @cindex arithmetic operands
3688 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3689 contexts arguments are sometimes called ``arithmetic operands''. In
3690 this manual, to avoid confusing them with the ``instruction operands'' of
3691 the machine language, we use the term ``argument'' to refer to parts of
3692 expressions only, reserving the word ``operand'' to refer only to machine
3693 instruction operands.
3695 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3696 @var{section} is one of text, data, bss, absolute,
3697 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3700 Numbers are usually integers.
3702 A number can be a flonum or bignum. In this case, you are warned
3703 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3704 these 32 bits are an integer. You may write integer-manipulating
3705 instructions that act on exotic constants, compatible with other
3708 @cindex subexpressions
3709 Subexpressions are a left parenthesis @samp{(} followed by an integer
3710 expression, followed by a right parenthesis @samp{)}; or a prefix
3711 operator followed by an argument.
3714 @subsection Operators
3716 @cindex operators, in expressions
3717 @cindex arithmetic functions
3718 @cindex functions, in expressions
3719 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3720 operators are followed by an argument. Infix operators appear
3721 between their arguments. Operators may be preceded and/or followed by
3725 @subsection Prefix Operator
3727 @cindex prefix operators
3728 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3729 one argument, which must be absolute.
3731 @c the tex/end tex stuff surrounding this small table is meant to make
3732 @c it align, on the printed page, with the similar table in the next
3733 @c section (which is inside an enumerate).
3735 \global\advance\leftskip by \itemindent
3740 @dfn{Negation}. Two's complement negation.
3742 @dfn{Complementation}. Bitwise not.
3746 \global\advance\leftskip by -\itemindent
3750 @subsection Infix Operators
3752 @cindex infix operators
3753 @cindex operators, permitted arguments
3754 @dfn{Infix operators} take two arguments, one on either side. Operators
3755 have precedence, but operations with equal precedence are performed left
3756 to right. Apart from @code{+} or @option{-}, both arguments must be
3757 absolute, and the result is absolute.
3760 @cindex operator precedence
3761 @cindex precedence of operators
3768 @dfn{Multiplication}.
3771 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3777 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3780 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3784 Intermediate precedence
3789 @dfn{Bitwise Inclusive Or}.
3795 @dfn{Bitwise Exclusive Or}.
3798 @dfn{Bitwise Or Not}.
3805 @cindex addition, permitted arguments
3806 @cindex plus, permitted arguments
3807 @cindex arguments for addition
3809 @dfn{Addition}. If either argument is absolute, the result has the section of
3810 the other argument. You may not add together arguments from different
3813 @cindex subtraction, permitted arguments
3814 @cindex minus, permitted arguments
3815 @cindex arguments for subtraction
3817 @dfn{Subtraction}. If the right argument is absolute, the
3818 result has the section of the left argument.
3819 If both arguments are in the same section, the result is absolute.
3820 You may not subtract arguments from different sections.
3821 @c FIXME is there still something useful to say about undefined - undefined ?
3823 @cindex comparison expressions
3824 @cindex expressions, comparison
3829 @dfn{Is Not Equal To}
3833 @dfn{Is Greater Than}
3835 @dfn{Is Greater Than Or Equal To}
3837 @dfn{Is Less Than Or Equal To}
3839 The comparison operators can be used as infix operators. A true results has a
3840 value of -1 whereas a false result has a value of 0. Note, these operators
3841 perform signed comparisons.
3844 @item Lowest Precedence
3853 These two logical operations can be used to combine the results of sub
3854 expressions. Note, unlike the comparison operators a true result returns a
3855 value of 1 but a false results does still return 0. Also note that the logical
3856 or operator has a slightly lower precedence than logical and.
3861 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3862 address; you can only have a defined section in one of the two arguments.
3865 @chapter Assembler Directives
3867 @cindex directives, machine independent
3868 @cindex pseudo-ops, machine independent
3869 @cindex machine independent directives
3870 All assembler directives have names that begin with a period (@samp{.}).
3871 The rest of the name is letters, usually in lower case.
3873 This chapter discusses directives that are available regardless of the
3874 target machine configuration for the @sc{gnu} assembler.
3876 Some machine configurations provide additional directives.
3877 @xref{Machine Dependencies}.
3880 @ifset machine-directives
3881 @xref{Machine Dependencies}, for additional directives.
3886 * Abort:: @code{.abort}
3888 * ABORT (COFF):: @code{.ABORT}
3891 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3892 * Altmacro:: @code{.altmacro}
3893 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3894 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3895 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3896 * Byte:: @code{.byte @var{expressions}}
3897 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3898 * Comm:: @code{.comm @var{symbol} , @var{length} }
3899 * Data:: @code{.data @var{subsection}}
3901 * Def:: @code{.def @var{name}}
3904 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3910 * Double:: @code{.double @var{flonums}}
3911 * Eject:: @code{.eject}
3912 * Else:: @code{.else}
3913 * Elseif:: @code{.elseif}
3916 * Endef:: @code{.endef}
3919 * Endfunc:: @code{.endfunc}
3920 * Endif:: @code{.endif}
3921 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3922 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3923 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
3925 * Error:: @code{.error @var{string}}
3926 * Exitm:: @code{.exitm}
3927 * Extern:: @code{.extern}
3928 * Fail:: @code{.fail}
3929 * File:: @code{.file}
3930 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3931 * Float:: @code{.float @var{flonums}}
3932 * Func:: @code{.func}
3933 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3935 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
3936 * Hidden:: @code{.hidden @var{names}}
3939 * hword:: @code{.hword @var{expressions}}
3940 * Ident:: @code{.ident}
3941 * If:: @code{.if @var{absolute expression}}
3942 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3943 * Include:: @code{.include "@var{file}"}
3944 * Int:: @code{.int @var{expressions}}
3946 * Internal:: @code{.internal @var{names}}
3949 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3950 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3951 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3952 * Lflags:: @code{.lflags}
3953 @ifclear no-line-dir
3954 * Line:: @code{.line @var{line-number}}
3957 * Linkonce:: @code{.linkonce [@var{type}]}
3958 * List:: @code{.list}
3959 * Ln:: @code{.ln @var{line-number}}
3960 * Loc:: @code{.loc @var{fileno} @var{lineno}}
3961 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
3963 * Local:: @code{.local @var{names}}
3966 * Long:: @code{.long @var{expressions}}
3968 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3971 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3972 * MRI:: @code{.mri @var{val}}
3973 * Noaltmacro:: @code{.noaltmacro}
3974 * Nolist:: @code{.nolist}
3975 * Octa:: @code{.octa @var{bignums}}
3976 * Org:: @code{.org @var{new-lc}, @var{fill}}
3977 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3979 * PopSection:: @code{.popsection}
3980 * Previous:: @code{.previous}
3983 * Print:: @code{.print @var{string}}
3985 * Protected:: @code{.protected @var{names}}
3988 * Psize:: @code{.psize @var{lines}, @var{columns}}
3989 * Purgem:: @code{.purgem @var{name}}
3991 * PushSection:: @code{.pushsection @var{name}}
3994 * Quad:: @code{.quad @var{bignums}}
3995 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
3996 * Rept:: @code{.rept @var{count}}
3997 * Sbttl:: @code{.sbttl "@var{subheading}"}
3999 * Scl:: @code{.scl @var{class}}
4002 * Section:: @code{.section @var{name}[, @var{flags}]}
4005 * Set:: @code{.set @var{symbol}, @var{expression}}
4006 * Short:: @code{.short @var{expressions}}
4007 * Single:: @code{.single @var{flonums}}
4009 * Size:: @code{.size [@var{name} , @var{expression}]}
4011 @ifclear no-space-dir
4012 * Skip:: @code{.skip @var{size} , @var{fill}}
4015 * Sleb128:: @code{.sleb128 @var{expressions}}
4016 @ifclear no-space-dir
4017 * Space:: @code{.space @var{size} , @var{fill}}
4020 * Stab:: @code{.stabd, .stabn, .stabs}
4023 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4024 * Struct:: @code{.struct @var{expression}}
4026 * SubSection:: @code{.subsection}
4027 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4031 * Tag:: @code{.tag @var{structname}}
4034 * Text:: @code{.text @var{subsection}}
4035 * Title:: @code{.title "@var{heading}"}
4037 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4040 * Uleb128:: @code{.uleb128 @var{expressions}}
4042 * Val:: @code{.val @var{addr}}
4046 * Version:: @code{.version "@var{string}"}
4047 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4048 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4051 * Warning:: @code{.warning @var{string}}
4052 * Weak:: @code{.weak @var{names}}
4053 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4054 * Word:: @code{.word @var{expressions}}
4055 * Deprecated:: Deprecated Directives
4059 @section @code{.abort}
4061 @cindex @code{abort} directive
4062 @cindex stopping the assembly
4063 This directive stops the assembly immediately. It is for
4064 compatibility with other assemblers. The original idea was that the
4065 assembly language source would be piped into the assembler. If the sender
4066 of the source quit, it could use this directive tells @command{@value{AS}} to
4067 quit also. One day @code{.abort} will not be supported.
4071 @section @code{.ABORT} (COFF)
4073 @cindex @code{ABORT} directive
4074 When producing COFF output, @command{@value{AS}} accepts this directive as a
4075 synonym for @samp{.abort}.
4078 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4084 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4086 @cindex padding the location counter
4087 @cindex @code{align} directive
4088 Pad the location counter (in the current subsection) to a particular storage
4089 boundary. The first expression (which must be absolute) is the alignment
4090 required, as described below.
4092 The second expression (also absolute) gives the fill value to be stored in the
4093 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4094 padding bytes are normally zero. However, on some systems, if the section is
4095 marked as containing code and the fill value is omitted, the space is filled
4096 with no-op instructions.
4098 The third expression is also absolute, and is also optional. If it is present,
4099 it is the maximum number of bytes that should be skipped by this alignment
4100 directive. If doing the alignment would require skipping more bytes than the
4101 specified maximum, then the alignment is not done at all. You can omit the
4102 fill value (the second argument) entirely by simply using two commas after the
4103 required alignment; this can be useful if you want the alignment to be filled
4104 with no-op instructions when appropriate.
4106 The way the required alignment is specified varies from system to system.
4107 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4108 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4109 alignment request in bytes. For example @samp{.align 8} advances
4110 the location counter until it is a multiple of 8. If the location counter
4111 is already a multiple of 8, no change is needed. For the tic54x, the
4112 first expression is the alignment request in words.
4114 For other systems, including ppc, i386 using a.out format, arm and
4115 strongarm, it is the
4116 number of low-order zero bits the location counter must have after
4117 advancement. For example @samp{.align 3} advances the location
4118 counter until it a multiple of 8. If the location counter is already a
4119 multiple of 8, no change is needed.
4121 This inconsistency is due to the different behaviors of the various
4122 native assemblers for these systems which GAS must emulate.
4123 GAS also provides @code{.balign} and @code{.p2align} directives,
4124 described later, which have a consistent behavior across all
4125 architectures (but are specific to GAS).
4128 @section @code{.altmacro}
4129 Enable alternate macro mode, enabling:
4132 @item LOCAL @var{name} [ , @dots{} ]
4133 One additional directive, @code{LOCAL}, is available. It is used to
4134 generate a string replacement for each of the @var{name} arguments, and
4135 replace any instances of @var{name} in each macro expansion. The
4136 replacement string is unique in the assembly, and different for each
4137 separate macro expansion. @code{LOCAL} allows you to write macros that
4138 define symbols, without fear of conflict between separate macro expansions.
4140 @item String delimiters
4141 You can write strings delimited in these other ways besides
4142 @code{"@var{string}"}:
4145 @item '@var{string}'
4146 You can delimit strings with single-quote characters.
4148 @item <@var{string}>
4149 You can delimit strings with matching angle brackets.
4152 @item single-character string escape
4153 To include any single character literally in a string (even if the
4154 character would otherwise have some special meaning), you can prefix the
4155 character with @samp{!} (an exclamation mark). For example, you can
4156 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4158 @item Expression results as strings
4159 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4160 and use the result as a string.
4164 @section @code{.ascii "@var{string}"}@dots{}
4166 @cindex @code{ascii} directive
4167 @cindex string literals
4168 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4169 separated by commas. It assembles each string (with no automatic
4170 trailing zero byte) into consecutive addresses.
4173 @section @code{.asciz "@var{string}"}@dots{}
4175 @cindex @code{asciz} directive
4176 @cindex zero-terminated strings
4177 @cindex null-terminated strings
4178 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4179 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4182 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4184 @cindex padding the location counter given number of bytes
4185 @cindex @code{balign} directive
4186 Pad the location counter (in the current subsection) to a particular
4187 storage boundary. The first expression (which must be absolute) is the
4188 alignment request in bytes. For example @samp{.balign 8} advances
4189 the location counter until it is a multiple of 8. If the location counter
4190 is already a multiple of 8, no change is needed.
4192 The second expression (also absolute) gives the fill value to be stored in the
4193 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4194 padding bytes are normally zero. However, on some systems, if the section is
4195 marked as containing code and the fill value is omitted, the space is filled
4196 with no-op instructions.
4198 The third expression is also absolute, and is also optional. If it is present,
4199 it is the maximum number of bytes that should be skipped by this alignment
4200 directive. If doing the alignment would require skipping more bytes than the
4201 specified maximum, then the alignment is not done at all. You can omit the
4202 fill value (the second argument) entirely by simply using two commas after the
4203 required alignment; this can be useful if you want the alignment to be filled
4204 with no-op instructions when appropriate.
4206 @cindex @code{balignw} directive
4207 @cindex @code{balignl} directive
4208 The @code{.balignw} and @code{.balignl} directives are variants of the
4209 @code{.balign} directive. The @code{.balignw} directive treats the fill
4210 pattern as a two byte word value. The @code{.balignl} directives treats the
4211 fill pattern as a four byte longword value. For example, @code{.balignw
4212 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4213 filled in with the value 0x368d (the exact placement of the bytes depends upon
4214 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4218 @section @code{.byte @var{expressions}}
4220 @cindex @code{byte} directive
4221 @cindex integers, one byte
4222 @code{.byte} expects zero or more expressions, separated by commas.
4223 Each expression is assembled into the next byte.
4225 @node CFI directives
4226 @section @code{.cfi_sections @var{section_list}}
4227 @cindex @code{cfi_sections} directive
4228 @code{.cfi_sections} may be used to specify whether CFI directives
4229 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4230 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4231 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4232 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4233 directive is not used is @code{.cfi_sections .eh_frame}.
4235 @section @code{.cfi_startproc [simple]}
4236 @cindex @code{cfi_startproc} directive
4237 @code{.cfi_startproc} is used at the beginning of each function that
4238 should have an entry in @code{.eh_frame}. It initializes some internal
4239 data structures. Don't forget to close the function by
4240 @code{.cfi_endproc}.
4242 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4243 it also emits some architecture dependent initial CFI instructions.
4245 @section @code{.cfi_endproc}
4246 @cindex @code{cfi_endproc} directive
4247 @code{.cfi_endproc} is used at the end of a function where it closes its
4248 unwind entry previously opened by
4249 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4251 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4252 @code{.cfi_personality} defines personality routine and its encoding.
4253 @var{encoding} must be a constant determining how the personality
4254 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4255 argument is not present, otherwise second argument should be
4256 a constant or a symbol name. When using indirect encodings,
4257 the symbol provided should be the location where personality
4258 can be loaded from, not the personality routine itself.
4259 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4260 no personality routine.
4262 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4263 @code{.cfi_lsda} defines LSDA and its encoding.
4264 @var{encoding} must be a constant determining how the LSDA
4265 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4266 argument is not present, otherwise second argument should be a constant
4267 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4270 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4271 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4272 address from @var{register} and add @var{offset} to it}.
4274 @section @code{.cfi_def_cfa_register @var{register}}
4275 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4276 now on @var{register} will be used instead of the old one. Offset
4279 @section @code{.cfi_def_cfa_offset @var{offset}}
4280 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4281 remains the same, but @var{offset} is new. Note that it is the
4282 absolute offset that will be added to a defined register to compute
4285 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4286 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4287 value that is added/substracted from the previous offset.
4289 @section @code{.cfi_offset @var{register}, @var{offset}}
4290 Previous value of @var{register} is saved at offset @var{offset} from
4293 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4294 Previous value of @var{register} is saved at offset @var{offset} from
4295 the current CFA register. This is transformed to @code{.cfi_offset}
4296 using the known displacement of the CFA register from the CFA.
4297 This is often easier to use, because the number will match the
4298 code it's annotating.
4300 @section @code{.cfi_register @var{register1}, @var{register2}}
4301 Previous value of @var{register1} is saved in register @var{register2}.
4303 @section @code{.cfi_restore @var{register}}
4304 @code{.cfi_restore} says that the rule for @var{register} is now the
4305 same as it was at the beginning of the function, after all initial
4306 instruction added by @code{.cfi_startproc} were executed.
4308 @section @code{.cfi_undefined @var{register}}
4309 From now on the previous value of @var{register} can't be restored anymore.
4311 @section @code{.cfi_same_value @var{register}}
4312 Current value of @var{register} is the same like in the previous frame,
4313 i.e. no restoration needed.
4315 @section @code{.cfi_remember_state},
4316 First save all current rules for all registers by @code{.cfi_remember_state},
4317 then totally screw them up by subsequent @code{.cfi_*} directives and when
4318 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4319 the previous saved state.
4321 @section @code{.cfi_return_column @var{register}}
4322 Change return column @var{register}, i.e. the return address is either
4323 directly in @var{register} or can be accessed by rules for @var{register}.
4325 @section @code{.cfi_signal_frame}
4326 Mark current function as signal trampoline.
4328 @section @code{.cfi_window_save}
4329 SPARC register window has been saved.
4331 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4332 Allows the user to add arbitrary bytes to the unwind info. One
4333 might use this to add OS-specific CFI opcodes, or generic CFI
4334 opcodes that GAS does not yet support.
4336 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4337 The current value of @var{register} is @var{label}. The value of @var{label}
4338 will be encoded in the output file according to @var{encoding}; see the
4339 description of @code{.cfi_personality} for details on this encoding.
4341 The usefulness of equating a register to a fixed label is probably
4342 limited to the return address register. Here, it can be useful to
4343 mark a code segment that has only one return address which is reached
4344 by a direct branch and no copy of the return address exists in memory
4345 or another register.
4348 @section @code{.comm @var{symbol} , @var{length} }
4350 @cindex @code{comm} directive
4351 @cindex symbol, common
4352 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4353 common symbol in one object file may be merged with a defined or common symbol
4354 of the same name in another object file. If @code{@value{LD}} does not see a
4355 definition for the symbol--just one or more common symbols--then it will
4356 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4357 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4358 the same name, and they do not all have the same size, it will allocate space
4359 using the largest size.
4362 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4363 an optional third argument. This is the desired alignment of the symbol,
4364 specified for ELF as a byte boundary (for example, an alignment of 16 means
4365 that the least significant 4 bits of the address should be zero), and for PE
4366 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4367 boundary). The alignment must be an absolute expression, and it must be a
4368 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4369 common symbol, it will use the alignment when placing the symbol. If no
4370 alignment is specified, @command{@value{AS}} will set the alignment to the
4371 largest power of two less than or equal to the size of the symbol, up to a
4372 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4373 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4374 @samp{--section-alignment} option; image file sections in PE are aligned to
4375 multiples of 4096, which is far too large an alignment for ordinary variables.
4376 It is rather the default alignment for (non-debug) sections within object
4377 (@samp{*.o}) files, which are less strictly aligned.}.
4381 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4382 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4386 @section @code{.data @var{subsection}}
4388 @cindex @code{data} directive
4389 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4390 end of the data subsection numbered @var{subsection} (which is an
4391 absolute expression). If @var{subsection} is omitted, it defaults
4396 @section @code{.def @var{name}}
4398 @cindex @code{def} directive
4399 @cindex COFF symbols, debugging
4400 @cindex debugging COFF symbols
4401 Begin defining debugging information for a symbol @var{name}; the
4402 definition extends until the @code{.endef} directive is encountered.
4405 This directive is only observed when @command{@value{AS}} is configured for COFF
4406 format output; when producing @code{b.out}, @samp{.def} is recognized,
4413 @section @code{.desc @var{symbol}, @var{abs-expression}}
4415 @cindex @code{desc} directive
4416 @cindex COFF symbol descriptor
4417 @cindex symbol descriptor, COFF
4418 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4419 to the low 16 bits of an absolute expression.
4422 The @samp{.desc} directive is not available when @command{@value{AS}} is
4423 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4424 object format. For the sake of compatibility, @command{@value{AS}} accepts
4425 it, but produces no output, when configured for COFF.
4431 @section @code{.dim}
4433 @cindex @code{dim} directive
4434 @cindex COFF auxiliary symbol information
4435 @cindex auxiliary symbol information, COFF
4436 This directive is generated by compilers to include auxiliary debugging
4437 information in the symbol table. It is only permitted inside
4438 @code{.def}/@code{.endef} pairs.
4441 @samp{.dim} is only meaningful when generating COFF format output; when
4442 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4448 @section @code{.double @var{flonums}}
4450 @cindex @code{double} directive
4451 @cindex floating point numbers (double)
4452 @code{.double} expects zero or more flonums, separated by commas. It
4453 assembles floating point numbers.
4455 The exact kind of floating point numbers emitted depends on how
4456 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4460 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4461 in @sc{ieee} format.
4466 @section @code{.eject}
4468 @cindex @code{eject} directive
4469 @cindex new page, in listings
4470 @cindex page, in listings
4471 @cindex listing control: new page
4472 Force a page break at this point, when generating assembly listings.
4475 @section @code{.else}
4477 @cindex @code{else} directive
4478 @code{.else} is part of the @command{@value{AS}} support for conditional
4479 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4480 of code to be assembled if the condition for the preceding @code{.if}
4484 @section @code{.elseif}
4486 @cindex @code{elseif} directive
4487 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4488 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4489 @code{.if} block that would otherwise fill the entire @code{.else} section.
4492 @section @code{.end}
4494 @cindex @code{end} directive
4495 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4496 process anything in the file past the @code{.end} directive.
4500 @section @code{.endef}
4502 @cindex @code{endef} directive
4503 This directive flags the end of a symbol definition begun with
4507 @samp{.endef} is only meaningful when generating COFF format output; if
4508 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4509 directive but ignores it.
4514 @section @code{.endfunc}
4515 @cindex @code{endfunc} directive
4516 @code{.endfunc} marks the end of a function specified with @code{.func}.
4519 @section @code{.endif}
4521 @cindex @code{endif} directive
4522 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4523 it marks the end of a block of code that is only assembled
4524 conditionally. @xref{If,,@code{.if}}.
4527 @section @code{.equ @var{symbol}, @var{expression}}
4529 @cindex @code{equ} directive
4530 @cindex assigning values to symbols
4531 @cindex symbols, assigning values to
4532 This directive sets the value of @var{symbol} to @var{expression}.
4533 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4536 The syntax for @code{equ} on the HPPA is
4537 @samp{@var{symbol} .equ @var{expression}}.
4541 The syntax for @code{equ} on the Z80 is
4542 @samp{@var{symbol} equ @var{expression}}.
4543 On the Z80 it is an eror if @var{symbol} is already defined,
4544 but the symbol is not protected from later redefinition.
4545 Compare @ref{Equiv}.
4549 @section @code{.equiv @var{symbol}, @var{expression}}
4550 @cindex @code{equiv} directive
4551 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4552 the assembler will signal an error if @var{symbol} is already defined. Note a
4553 symbol which has been referenced but not actually defined is considered to be
4556 Except for the contents of the error message, this is roughly equivalent to
4563 plus it protects the symbol from later redefinition.
4566 @section @code{.eqv @var{symbol}, @var{expression}}
4567 @cindex @code{eqv} directive
4568 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4569 evaluate the expression or any part of it immediately. Instead each time
4570 the resulting symbol is used in an expression, a snapshot of its current
4574 @section @code{.err}
4575 @cindex @code{err} directive
4576 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4577 message and, unless the @option{-Z} option was used, it will not generate an
4578 object file. This can be used to signal an error in conditionally compiled code.
4581 @section @code{.error "@var{string}"}
4582 @cindex error directive
4584 Similarly to @code{.err}, this directive emits an error, but you can specify a
4585 string that will be emitted as the error message. If you don't specify the
4586 message, it defaults to @code{".error directive invoked in source file"}.
4587 @xref{Errors, ,Error and Warning Messages}.
4590 .error "This code has not been assembled and tested."
4594 @section @code{.exitm}
4595 Exit early from the current macro definition. @xref{Macro}.
4598 @section @code{.extern}
4600 @cindex @code{extern} directive
4601 @code{.extern} is accepted in the source program---for compatibility
4602 with other assemblers---but it is ignored. @command{@value{AS}} treats
4603 all undefined symbols as external.
4606 @section @code{.fail @var{expression}}
4608 @cindex @code{fail} directive
4609 Generates an error or a warning. If the value of the @var{expression} is 500
4610 or more, @command{@value{AS}} will print a warning message. If the value is less
4611 than 500, @command{@value{AS}} will print an error message. The message will
4612 include the value of @var{expression}. This can occasionally be useful inside
4613 complex nested macros or conditional assembly.
4616 @section @code{.file}
4617 @cindex @code{file} directive
4619 @ifclear no-file-dir
4620 There are two different versions of the @code{.file} directive. Targets
4621 that support DWARF2 line number information use the DWARF2 version of
4622 @code{.file}. Other targets use the default version.
4624 @subheading Default Version
4626 @cindex logical file name
4627 @cindex file name, logical
4628 This version of the @code{.file} directive tells @command{@value{AS}} that we
4629 are about to start a new logical file. The syntax is:
4635 @var{string} is the new file name. In general, the filename is
4636 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4637 to specify an empty file name, you must give the quotes--@code{""}. This
4638 statement may go away in future: it is only recognized to be compatible with
4639 old @command{@value{AS}} programs.
4641 @subheading DWARF2 Version
4644 When emitting DWARF2 line number information, @code{.file} assigns filenames
4645 to the @code{.debug_line} file name table. The syntax is:
4648 .file @var{fileno} @var{filename}
4651 The @var{fileno} operand should be a unique positive integer to use as the
4652 index of the entry in the table. The @var{filename} operand is a C string
4655 The detail of filename indices is exposed to the user because the filename
4656 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4657 information, and thus the user must know the exact indices that table
4661 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4663 @cindex @code{fill} directive
4664 @cindex writing patterns in memory
4665 @cindex patterns, writing in memory
4666 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4667 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4668 may be zero or more. @var{Size} may be zero or more, but if it is
4669 more than 8, then it is deemed to have the value 8, compatible with
4670 other people's assemblers. The contents of each @var{repeat} bytes
4671 is taken from an 8-byte number. The highest order 4 bytes are
4672 zero. The lowest order 4 bytes are @var{value} rendered in the
4673 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4674 Each @var{size} bytes in a repetition is taken from the lowest order
4675 @var{size} bytes of this number. Again, this bizarre behavior is
4676 compatible with other people's assemblers.
4678 @var{size} and @var{value} are optional.
4679 If the second comma and @var{value} are absent, @var{value} is
4680 assumed zero. If the first comma and following tokens are absent,
4681 @var{size} is assumed to be 1.
4684 @section @code{.float @var{flonums}}
4686 @cindex floating point numbers (single)
4687 @cindex @code{float} directive
4688 This directive assembles zero or more flonums, separated by commas. It
4689 has the same effect as @code{.single}.
4691 The exact kind of floating point numbers emitted depends on how
4692 @command{@value{AS}} is configured.
4693 @xref{Machine Dependencies}.
4697 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4698 in @sc{ieee} format.
4703 @section @code{.func @var{name}[,@var{label}]}
4704 @cindex @code{func} directive
4705 @code{.func} emits debugging information to denote function @var{name}, and
4706 is ignored unless the file is assembled with debugging enabled.
4707 Only @samp{--gstabs[+]} is currently supported.
4708 @var{label} is the entry point of the function and if omitted @var{name}
4709 prepended with the @samp{leading char} is used.
4710 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4711 All functions are currently defined to have @code{void} return type.
4712 The function must be terminated with @code{.endfunc}.
4715 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4717 @cindex @code{global} directive
4718 @cindex symbol, making visible to linker
4719 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4720 @var{symbol} in your partial program, its value is made available to
4721 other partial programs that are linked with it. Otherwise,
4722 @var{symbol} takes its attributes from a symbol of the same name
4723 from another file linked into the same program.
4725 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4726 compatibility with other assemblers.
4729 On the HPPA, @code{.global} is not always enough to make it accessible to other
4730 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4731 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4736 @section @code{.gnu_attribute @var{tag},@var{value}}
4737 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4740 @section @code{.hidden @var{names}}
4742 @cindex @code{hidden} directive
4744 This is one of the ELF visibility directives. The other two are
4745 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4746 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4748 This directive overrides the named symbols default visibility (which is set by
4749 their binding: local, global or weak). The directive sets the visibility to
4750 @code{hidden} which means that the symbols are not visible to other components.
4751 Such symbols are always considered to be @code{protected} as well.
4755 @section @code{.hword @var{expressions}}
4757 @cindex @code{hword} directive
4758 @cindex integers, 16-bit
4759 @cindex numbers, 16-bit
4760 @cindex sixteen bit integers
4761 This expects zero or more @var{expressions}, and emits
4762 a 16 bit number for each.
4765 This directive is a synonym for @samp{.short}; depending on the target
4766 architecture, it may also be a synonym for @samp{.word}.
4770 This directive is a synonym for @samp{.short}.
4773 This directive is a synonym for both @samp{.short} and @samp{.word}.
4778 @section @code{.ident}
4780 @cindex @code{ident} directive
4782 This directive is used by some assemblers to place tags in object files. The
4783 behavior of this directive varies depending on the target. When using the
4784 a.out object file format, @command{@value{AS}} simply accepts the directive for
4785 source-file compatibility with existing assemblers, but does not emit anything
4786 for it. When using COFF, comments are emitted to the @code{.comment} or
4787 @code{.rdata} section, depending on the target. When using ELF, comments are
4788 emitted to the @code{.comment} section.
4791 @section @code{.if @var{absolute expression}}
4793 @cindex conditional assembly
4794 @cindex @code{if} directive
4795 @code{.if} marks the beginning of a section of code which is only
4796 considered part of the source program being assembled if the argument
4797 (which must be an @var{absolute expression}) is non-zero. The end of
4798 the conditional section of code must be marked by @code{.endif}
4799 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4800 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4801 If you have several conditions to check, @code{.elseif} may be used to avoid
4802 nesting blocks if/else within each subsequent @code{.else} block.
4804 The following variants of @code{.if} are also supported:
4806 @cindex @code{ifdef} directive
4807 @item .ifdef @var{symbol}
4808 Assembles the following section of code if the specified @var{symbol}
4809 has been defined. Note a symbol which has been referenced but not yet defined
4810 is considered to be undefined.
4812 @cindex @code{ifb} directive
4813 @item .ifb @var{text}
4814 Assembles the following section of code if the operand is blank (empty).
4816 @cindex @code{ifc} directive
4817 @item .ifc @var{string1},@var{string2}
4818 Assembles the following section of code if the two strings are the same. The
4819 strings may be optionally quoted with single quotes. If they are not quoted,
4820 the first string stops at the first comma, and the second string stops at the
4821 end of the line. Strings which contain whitespace should be quoted. The
4822 string comparison is case sensitive.
4824 @cindex @code{ifeq} directive
4825 @item .ifeq @var{absolute expression}
4826 Assembles the following section of code if the argument is zero.
4828 @cindex @code{ifeqs} directive
4829 @item .ifeqs @var{string1},@var{string2}
4830 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4832 @cindex @code{ifge} directive
4833 @item .ifge @var{absolute expression}
4834 Assembles the following section of code if the argument is greater than or
4837 @cindex @code{ifgt} directive
4838 @item .ifgt @var{absolute expression}
4839 Assembles the following section of code if the argument is greater than zero.
4841 @cindex @code{ifle} directive
4842 @item .ifle @var{absolute expression}
4843 Assembles the following section of code if the argument is less than or equal
4846 @cindex @code{iflt} directive
4847 @item .iflt @var{absolute expression}
4848 Assembles the following section of code if the argument is less than zero.
4850 @cindex @code{ifnb} directive
4851 @item .ifnb @var{text}
4852 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4853 following section of code if the operand is non-blank (non-empty).
4855 @cindex @code{ifnc} directive
4856 @item .ifnc @var{string1},@var{string2}.
4857 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4858 following section of code if the two strings are not the same.
4860 @cindex @code{ifndef} directive
4861 @cindex @code{ifnotdef} directive
4862 @item .ifndef @var{symbol}
4863 @itemx .ifnotdef @var{symbol}
4864 Assembles the following section of code if the specified @var{symbol}
4865 has not been defined. Both spelling variants are equivalent. Note a symbol
4866 which has been referenced but not yet defined is considered to be undefined.
4868 @cindex @code{ifne} directive
4869 @item .ifne @var{absolute expression}
4870 Assembles the following section of code if the argument is not equal to zero
4871 (in other words, this is equivalent to @code{.if}).
4873 @cindex @code{ifnes} directive
4874 @item .ifnes @var{string1},@var{string2}
4875 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4876 following section of code if the two strings are not the same.
4880 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4882 @cindex @code{incbin} directive
4883 @cindex binary files, including
4884 The @code{incbin} directive includes @var{file} verbatim at the current
4885 location. You can control the search paths used with the @samp{-I} command-line
4886 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4889 The @var{skip} argument skips a number of bytes from the start of the
4890 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4891 read. Note that the data is not aligned in any way, so it is the user's
4892 responsibility to make sure that proper alignment is provided both before and
4893 after the @code{incbin} directive.
4896 @section @code{.include "@var{file}"}
4898 @cindex @code{include} directive
4899 @cindex supporting files, including
4900 @cindex files, including
4901 This directive provides a way to include supporting files at specified
4902 points in your source program. The code from @var{file} is assembled as
4903 if it followed the point of the @code{.include}; when the end of the
4904 included file is reached, assembly of the original file continues. You
4905 can control the search paths used with the @samp{-I} command-line option
4906 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4910 @section @code{.int @var{expressions}}
4912 @cindex @code{int} directive
4913 @cindex integers, 32-bit
4914 Expect zero or more @var{expressions}, of any section, separated by commas.
4915 For each expression, emit a number that, at run time, is the value of that
4916 expression. The byte order and bit size of the number depends on what kind
4917 of target the assembly is for.
4921 On most forms of the H8/300, @code{.int} emits 16-bit
4922 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4929 @section @code{.internal @var{names}}
4931 @cindex @code{internal} directive
4933 This is one of the ELF visibility directives. The other two are
4934 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4935 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4937 This directive overrides the named symbols default visibility (which is set by
4938 their binding: local, global or weak). The directive sets the visibility to
4939 @code{internal} which means that the symbols are considered to be @code{hidden}
4940 (i.e., not visible to other components), and that some extra, processor specific
4941 processing must also be performed upon the symbols as well.
4945 @section @code{.irp @var{symbol},@var{values}}@dots{}
4947 @cindex @code{irp} directive
4948 Evaluate a sequence of statements assigning different values to @var{symbol}.
4949 The sequence of statements starts at the @code{.irp} directive, and is
4950 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4951 set to @var{value}, and the sequence of statements is assembled. If no
4952 @var{value} is listed, the sequence of statements is assembled once, with
4953 @var{symbol} set to the null string. To refer to @var{symbol} within the
4954 sequence of statements, use @var{\symbol}.
4956 For example, assembling
4964 is equivalent to assembling
4972 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
4975 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4977 @cindex @code{irpc} directive
4978 Evaluate a sequence of statements assigning different values to @var{symbol}.
4979 The sequence of statements starts at the @code{.irpc} directive, and is
4980 terminated by an @code{.endr} directive. For each character in @var{value},
4981 @var{symbol} is set to the character, and the sequence of statements is
4982 assembled. If no @var{value} is listed, the sequence of statements is
4983 assembled once, with @var{symbol} set to the null string. To refer to
4984 @var{symbol} within the sequence of statements, use @var{\symbol}.
4986 For example, assembling
4994 is equivalent to assembling
5002 For some caveats with the spelling of @var{symbol}, see also the discussion
5006 @section @code{.lcomm @var{symbol} , @var{length}}
5008 @cindex @code{lcomm} directive
5009 @cindex local common symbols
5010 @cindex symbols, local common
5011 Reserve @var{length} (an absolute expression) bytes for a local common
5012 denoted by @var{symbol}. The section and value of @var{symbol} are
5013 those of the new local common. The addresses are allocated in the bss
5014 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5015 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5016 not visible to @code{@value{LD}}.
5019 Some targets permit a third argument to be used with @code{.lcomm}. This
5020 argument specifies the desired alignment of the symbol in the bss section.
5024 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5025 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5029 @section @code{.lflags}
5031 @cindex @code{lflags} directive (ignored)
5032 @command{@value{AS}} accepts this directive, for compatibility with other
5033 assemblers, but ignores it.
5035 @ifclear no-line-dir
5037 @section @code{.line @var{line-number}}
5039 @cindex @code{line} directive
5040 @cindex logical line number
5042 Change the logical line number. @var{line-number} must be an absolute
5043 expression. The next line has that logical line number. Therefore any other
5044 statements on the current line (after a statement separator character) are
5045 reported as on logical line number @var{line-number} @minus{} 1. One day
5046 @command{@value{AS}} will no longer support this directive: it is recognized only
5047 for compatibility with existing assembler programs.
5050 Even though this is a directive associated with the @code{a.out} or
5051 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5052 when producing COFF output, and treats @samp{.line} as though it
5053 were the COFF @samp{.ln} @emph{if} it is found outside a
5054 @code{.def}/@code{.endef} pair.
5056 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5057 used by compilers to generate auxiliary symbol information for
5062 @section @code{.linkonce [@var{type}]}
5064 @cindex @code{linkonce} directive
5065 @cindex common sections
5066 Mark the current section so that the linker only includes a single copy of it.
5067 This may be used to include the same section in several different object files,
5068 but ensure that the linker will only include it once in the final output file.
5069 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5070 Duplicate sections are detected based on the section name, so it should be
5073 This directive is only supported by a few object file formats; as of this
5074 writing, the only object file format which supports it is the Portable
5075 Executable format used on Windows NT.
5077 The @var{type} argument is optional. If specified, it must be one of the
5078 following strings. For example:
5082 Not all types may be supported on all object file formats.
5086 Silently discard duplicate sections. This is the default.
5089 Warn if there are duplicate sections, but still keep only one copy.
5092 Warn if any of the duplicates have different sizes.
5095 Warn if any of the duplicates do not have exactly the same contents.
5099 @section @code{.list}
5101 @cindex @code{list} directive
5102 @cindex listing control, turning on
5103 Control (in conjunction with the @code{.nolist} directive) whether or
5104 not assembly listings are generated. These two directives maintain an
5105 internal counter (which is zero initially). @code{.list} increments the
5106 counter, and @code{.nolist} decrements it. Assembly listings are
5107 generated whenever the counter is greater than zero.
5109 By default, listings are disabled. When you enable them (with the
5110 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5111 the initial value of the listing counter is one.
5114 @section @code{.ln @var{line-number}}
5116 @cindex @code{ln} directive
5117 @ifclear no-line-dir
5118 @samp{.ln} is a synonym for @samp{.line}.
5121 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5122 must be an absolute expression. The next line has that logical
5123 line number, so any other statements on the current line (after a
5124 statement separator character @code{;}) are reported as on logical
5125 line number @var{line-number} @minus{} 1.
5128 This directive is accepted, but ignored, when @command{@value{AS}} is
5129 configured for @code{b.out}; its effect is only associated with COFF
5135 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5136 @cindex @code{loc} directive
5137 When emitting DWARF2 line number information,
5138 the @code{.loc} directive will add a row to the @code{.debug_line} line
5139 number matrix corresponding to the immediately following assembly
5140 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5141 arguments will be applied to the @code{.debug_line} state machine before
5144 The @var{options} are a sequence of the following tokens in any order:
5148 This option will set the @code{basic_block} register in the
5149 @code{.debug_line} state machine to @code{true}.
5152 This option will set the @code{prologue_end} register in the
5153 @code{.debug_line} state machine to @code{true}.
5155 @item epilogue_begin
5156 This option will set the @code{epilogue_begin} register in the
5157 @code{.debug_line} state machine to @code{true}.
5159 @item is_stmt @var{value}
5160 This option will set the @code{is_stmt} register in the
5161 @code{.debug_line} state machine to @code{value}, which must be
5164 @item isa @var{value}
5165 This directive will set the @code{isa} register in the @code{.debug_line}
5166 state machine to @var{value}, which must be an unsigned integer.
5168 @item discriminator @var{value}
5169 This directive will set the @code{discriminator} register in the @code{.debug_line}
5170 state machine to @var{value}, which must be an unsigned integer.
5174 @node Loc_mark_labels
5175 @section @code{.loc_mark_labels @var{enable}}
5176 @cindex @code{loc_mark_labels} directive
5177 When emitting DWARF2 line number information,
5178 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5179 to the @code{.debug_line} line number matrix with the @code{basic_block}
5180 register in the state machine set whenever a code label is seen.
5181 The @var{enable} argument should be either 1 or 0, to enable or disable
5182 this function respectively.
5186 @section @code{.local @var{names}}
5188 @cindex @code{local} directive
5189 This directive, which is available for ELF targets, marks each symbol in
5190 the comma-separated list of @code{names} as a local symbol so that it
5191 will not be externally visible. If the symbols do not already exist,
5192 they will be created.
5194 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5195 accept an alignment argument, which is the case for most ELF targets,
5196 the @code{.local} directive can be used in combination with @code{.comm}
5197 (@pxref{Comm}) to define aligned local common data.
5201 @section @code{.long @var{expressions}}
5203 @cindex @code{long} directive
5204 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5207 @c no one seems to know what this is for or whether this description is
5208 @c what it really ought to do
5210 @section @code{.lsym @var{symbol}, @var{expression}}
5212 @cindex @code{lsym} directive
5213 @cindex symbol, not referenced in assembly
5214 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5215 the hash table, ensuring it cannot be referenced by name during the
5216 rest of the assembly. This sets the attributes of the symbol to be
5217 the same as the expression value:
5219 @var{other} = @var{descriptor} = 0
5220 @var{type} = @r{(section of @var{expression})}
5221 @var{value} = @var{expression}
5224 The new symbol is not flagged as external.
5228 @section @code{.macro}
5231 The commands @code{.macro} and @code{.endm} allow you to define macros that
5232 generate assembly output. For example, this definition specifies a macro
5233 @code{sum} that puts a sequence of numbers into memory:
5236 .macro sum from=0, to=5
5245 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5257 @item .macro @var{macname}
5258 @itemx .macro @var{macname} @var{macargs} @dots{}
5259 @cindex @code{macro} directive
5260 Begin the definition of a macro called @var{macname}. If your macro
5261 definition requires arguments, specify their names after the macro name,
5262 separated by commas or spaces. You can qualify the macro argument to
5263 indicate whether all invocations must specify a non-blank value (through
5264 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5265 (through @samp{:@code{vararg}}). You can supply a default value for any
5266 macro argument by following the name with @samp{=@var{deflt}}. You
5267 cannot define two macros with the same @var{macname} unless it has been
5268 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5269 definitions. For example, these are all valid @code{.macro} statements:
5273 Begin the definition of a macro called @code{comm}, which takes no
5276 @item .macro plus1 p, p1
5277 @itemx .macro plus1 p p1
5278 Either statement begins the definition of a macro called @code{plus1},
5279 which takes two arguments; within the macro definition, write
5280 @samp{\p} or @samp{\p1} to evaluate the arguments.
5282 @item .macro reserve_str p1=0 p2
5283 Begin the definition of a macro called @code{reserve_str}, with two
5284 arguments. The first argument has a default value, but not the second.
5285 After the definition is complete, you can call the macro either as
5286 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5287 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5288 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5289 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5291 @item .macro m p1:req, p2=0, p3:vararg
5292 Begin the definition of a macro called @code{m}, with at least three
5293 arguments. The first argument must always have a value specified, but
5294 not the second, which instead has a default value. The third formal
5295 will get assigned all remaining arguments specified at invocation time.
5297 When you call a macro, you can specify the argument values either by
5298 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5299 @samp{sum to=17, from=9}.
5303 Note that since each of the @var{macargs} can be an identifier exactly
5304 as any other one permitted by the target architecture, there may be
5305 occasional problems if the target hand-crafts special meanings to certain
5306 characters when they occur in a special position. For example, if the colon
5307 (@code{:}) is generally permitted to be part of a symbol name, but the
5308 architecture specific code special-cases it when occurring as the final
5309 character of a symbol (to denote a label), then the macro parameter
5310 replacement code will have no way of knowing that and consider the whole
5311 construct (including the colon) an identifier, and check only this
5312 identifier for being the subject to parameter substitution. So for example
5313 this macro definition:
5321 might not work as expected. Invoking @samp{label foo} might not create a label
5322 called @samp{foo} but instead just insert the text @samp{\l:} into the
5323 assembler source, probably generating an error about an unrecognised
5326 Similarly problems might occur with the period character (@samp{.})
5327 which is often allowed inside opcode names (and hence identifier names). So
5328 for example constructing a macro to build an opcode from a base name and a
5329 length specifier like this:
5332 .macro opcode base length
5337 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5338 instruction but instead generate some kind of error as the assembler tries to
5339 interpret the text @samp{\base.\length}.
5341 There are several possible ways around this problem:
5344 @item Insert white space
5345 If it is possible to use white space characters then this is the simplest
5354 @item Use @samp{\()}
5355 The string @samp{\()} can be used to separate the end of a macro argument from
5356 the following text. eg:
5359 .macro opcode base length
5364 @item Use the alternate macro syntax mode
5365 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5366 used as a separator. eg:
5376 Note: this problem of correctly identifying string parameters to pseudo ops
5377 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5378 and @code{.irpc} (@pxref{Irpc}) as well.
5381 @cindex @code{endm} directive
5382 Mark the end of a macro definition.
5385 @cindex @code{exitm} directive
5386 Exit early from the current macro definition.
5388 @cindex number of macros executed
5389 @cindex macros, count executed
5391 @command{@value{AS}} maintains a counter of how many macros it has
5392 executed in this pseudo-variable; you can copy that number to your
5393 output with @samp{\@@}, but @emph{only within a macro definition}.
5395 @item LOCAL @var{name} [ , @dots{} ]
5396 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5397 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5398 @xref{Altmacro,,@code{.altmacro}}.
5402 @section @code{.mri @var{val}}
5404 @cindex @code{mri} directive
5405 @cindex MRI mode, temporarily
5406 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5407 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5408 affects code assembled until the next @code{.mri} directive, or until the end
5409 of the file. @xref{M, MRI mode, MRI mode}.
5412 @section @code{.noaltmacro}
5413 Disable alternate macro mode. @xref{Altmacro}.
5416 @section @code{.nolist}
5418 @cindex @code{nolist} directive
5419 @cindex listing control, turning off
5420 Control (in conjunction with the @code{.list} directive) whether or
5421 not assembly listings are generated. These two directives maintain an
5422 internal counter (which is zero initially). @code{.list} increments the
5423 counter, and @code{.nolist} decrements it. Assembly listings are
5424 generated whenever the counter is greater than zero.
5427 @section @code{.octa @var{bignums}}
5429 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5430 @cindex @code{octa} directive
5431 @cindex integer, 16-byte
5432 @cindex sixteen byte integer
5433 This directive expects zero or more bignums, separated by commas. For each
5434 bignum, it emits a 16-byte integer.
5436 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5437 hence @emph{octa}-word for 16 bytes.
5440 @section @code{.org @var{new-lc} , @var{fill}}
5442 @cindex @code{org} directive
5443 @cindex location counter, advancing
5444 @cindex advancing location counter
5445 @cindex current address, advancing
5446 Advance the location counter of the current section to
5447 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5448 expression with the same section as the current subsection. That is,
5449 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5450 wrong section, the @code{.org} directive is ignored. To be compatible
5451 with former assemblers, if the section of @var{new-lc} is absolute,
5452 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5453 is the same as the current subsection.
5455 @code{.org} may only increase the location counter, or leave it
5456 unchanged; you cannot use @code{.org} to move the location counter
5459 @c double negative used below "not undefined" because this is a specific
5460 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5461 @c section. doc@cygnus.com 18feb91
5462 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5463 may not be undefined. If you really detest this restriction we eagerly await
5464 a chance to share your improved assembler.
5466 Beware that the origin is relative to the start of the section, not
5467 to the start of the subsection. This is compatible with other
5468 people's assemblers.
5470 When the location counter (of the current subsection) is advanced, the
5471 intervening bytes are filled with @var{fill} which should be an
5472 absolute expression. If the comma and @var{fill} are omitted,
5473 @var{fill} defaults to zero.
5476 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5478 @cindex padding the location counter given a power of two
5479 @cindex @code{p2align} directive
5480 Pad the location counter (in the current subsection) to a particular
5481 storage boundary. The first expression (which must be absolute) is the
5482 number of low-order zero bits the location counter must have after
5483 advancement. For example @samp{.p2align 3} advances the location
5484 counter until it a multiple of 8. If the location counter is already a
5485 multiple of 8, no change is needed.
5487 The second expression (also absolute) gives the fill value to be stored in the
5488 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5489 padding bytes are normally zero. However, on some systems, if the section is
5490 marked as containing code and the fill value is omitted, the space is filled
5491 with no-op instructions.
5493 The third expression is also absolute, and is also optional. If it is present,
5494 it is the maximum number of bytes that should be skipped by this alignment
5495 directive. If doing the alignment would require skipping more bytes than the
5496 specified maximum, then the alignment is not done at all. You can omit the
5497 fill value (the second argument) entirely by simply using two commas after the
5498 required alignment; this can be useful if you want the alignment to be filled
5499 with no-op instructions when appropriate.
5501 @cindex @code{p2alignw} directive
5502 @cindex @code{p2alignl} directive
5503 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5504 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5505 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5506 fill pattern as a four byte longword value. For example, @code{.p2alignw
5507 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5508 filled in with the value 0x368d (the exact placement of the bytes depends upon
5509 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5514 @section @code{.popsection}
5516 @cindex @code{popsection} directive
5517 @cindex Section Stack
5518 This is one of the ELF section stack manipulation directives. The others are
5519 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5520 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5523 This directive replaces the current section (and subsection) with the top
5524 section (and subsection) on the section stack. This section is popped off the
5530 @section @code{.previous}
5532 @cindex @code{previous} directive
5533 @cindex Section Stack
5534 This is one of the ELF section stack manipulation directives. The others are
5535 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5536 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5537 (@pxref{PopSection}).
5539 This directive swaps the current section (and subsection) with most recently
5540 referenced section/subsection pair prior to this one. Multiple
5541 @code{.previous} directives in a row will flip between two sections (and their
5542 subsections). For example:
5554 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5560 # Now in section A subsection 1
5564 # Now in section B subsection 0
5567 # Now in section B subsection 1
5570 # Now in section B subsection 0
5574 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5575 section B and 0x9abc into subsection 1 of section B.
5577 In terms of the section stack, this directive swaps the current section with
5578 the top section on the section stack.
5582 @section @code{.print @var{string}}
5584 @cindex @code{print} directive
5585 @command{@value{AS}} will print @var{string} on the standard output during
5586 assembly. You must put @var{string} in double quotes.
5590 @section @code{.protected @var{names}}
5592 @cindex @code{protected} directive
5594 This is one of the ELF visibility directives. The other two are
5595 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5597 This directive overrides the named symbols default visibility (which is set by
5598 their binding: local, global or weak). The directive sets the visibility to
5599 @code{protected} which means that any references to the symbols from within the
5600 components that defines them must be resolved to the definition in that
5601 component, even if a definition in another component would normally preempt
5606 @section @code{.psize @var{lines} , @var{columns}}
5608 @cindex @code{psize} directive
5609 @cindex listing control: paper size
5610 @cindex paper size, for listings
5611 Use this directive to declare the number of lines---and, optionally, the
5612 number of columns---to use for each page, when generating listings.
5614 If you do not use @code{.psize}, listings use a default line-count
5615 of 60. You may omit the comma and @var{columns} specification; the
5616 default width is 200 columns.
5618 @command{@value{AS}} generates formfeeds whenever the specified number of
5619 lines is exceeded (or whenever you explicitly request one, using
5622 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5623 those explicitly specified with @code{.eject}.
5626 @section @code{.purgem @var{name}}
5628 @cindex @code{purgem} directive
5629 Undefine the macro @var{name}, so that later uses of the string will not be
5630 expanded. @xref{Macro}.
5634 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5636 @cindex @code{pushsection} directive
5637 @cindex Section Stack
5638 This is one of the ELF section stack manipulation directives. The others are
5639 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5640 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5643 This directive pushes the current section (and subsection) onto the
5644 top of the section stack, and then replaces the current section and
5645 subsection with @code{name} and @code{subsection}. The optional
5646 @code{flags}, @code{type} and @code{arguments} are treated the same
5647 as in the @code{.section} (@pxref{Section}) directive.
5651 @section @code{.quad @var{bignums}}
5653 @cindex @code{quad} directive
5654 @code{.quad} expects zero or more bignums, separated by commas. For
5655 each bignum, it emits
5657 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5658 warning message; and just takes the lowest order 8 bytes of the bignum.
5659 @cindex eight-byte integer
5660 @cindex integer, 8-byte
5662 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5663 hence @emph{quad}-word for 8 bytes.
5666 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5667 warning message; and just takes the lowest order 16 bytes of the bignum.
5668 @cindex sixteen-byte integer
5669 @cindex integer, 16-byte
5673 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5675 @cindex @code{reloc} directive
5676 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5677 @var{expression}. If @var{offset} is a number, the relocation is generated in
5678 the current section. If @var{offset} is an expression that resolves to a
5679 symbol plus offset, the relocation is generated in the given symbol's section.
5680 @var{expression}, if present, must resolve to a symbol plus addend or to an
5681 absolute value, but note that not all targets support an addend. e.g. ELF REL
5682 targets such as i386 store an addend in the section contents rather than in the
5683 relocation. This low level interface does not support addends stored in the
5687 @section @code{.rept @var{count}}
5689 @cindex @code{rept} directive
5690 Repeat the sequence of lines between the @code{.rept} directive and the next
5691 @code{.endr} directive @var{count} times.
5693 For example, assembling
5701 is equivalent to assembling
5710 @section @code{.sbttl "@var{subheading}"}
5712 @cindex @code{sbttl} directive
5713 @cindex subtitles for listings
5714 @cindex listing control: subtitle
5715 Use @var{subheading} as the title (third line, immediately after the
5716 title line) when generating assembly listings.
5718 This directive affects subsequent pages, as well as the current page if
5719 it appears within ten lines of the top of a page.
5723 @section @code{.scl @var{class}}
5725 @cindex @code{scl} directive
5726 @cindex symbol storage class (COFF)
5727 @cindex COFF symbol storage class
5728 Set the storage-class value for a symbol. This directive may only be
5729 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5730 whether a symbol is static or external, or it may record further
5731 symbolic debugging information.
5734 The @samp{.scl} directive is primarily associated with COFF output; when
5735 configured to generate @code{b.out} output format, @command{@value{AS}}
5736 accepts this directive but ignores it.
5742 @section @code{.section @var{name}}
5744 @cindex named section
5745 Use the @code{.section} directive to assemble the following code into a section
5748 This directive is only supported for targets that actually support arbitrarily
5749 named sections; on @code{a.out} targets, for example, it is not accepted, even
5750 with a standard @code{a.out} section name.
5754 @c only print the extra heading if both COFF and ELF are set
5755 @subheading COFF Version
5758 @cindex @code{section} directive (COFF version)
5759 For COFF targets, the @code{.section} directive is used in one of the following
5763 .section @var{name}[, "@var{flags}"]
5764 .section @var{name}[, @var{subsection}]
5767 If the optional argument is quoted, it is taken as flags to use for the
5768 section. Each flag is a single character. The following flags are recognized:
5771 bss section (uninitialized data)
5773 section is not loaded
5783 shared section (meaningful for PE targets)
5785 ignored. (For compatibility with the ELF version)
5787 section is not readable (meaningful for PE targets)
5789 single-digit power-of-two section alignment (GNU extension)
5792 If no flags are specified, the default flags depend upon the section name. If
5793 the section name is not recognized, the default will be for the section to be
5794 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5795 from the section, rather than adding them, so if they are used on their own it
5796 will be as if no flags had been specified at all.
5798 If the optional argument to the @code{.section} directive is not quoted, it is
5799 taken as a subsection number (@pxref{Sub-Sections}).
5804 @c only print the extra heading if both COFF and ELF are set
5805 @subheading ELF Version
5808 @cindex Section Stack
5809 This is one of the ELF section stack manipulation directives. The others are
5810 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5811 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5812 @code{.previous} (@pxref{Previous}).
5814 @cindex @code{section} directive (ELF version)
5815 For ELF targets, the @code{.section} directive is used like this:
5818 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5821 The optional @var{flags} argument is a quoted string which may contain any
5822 combination of the following characters:
5825 section is allocatable
5827 section is excluded from executable and shared library.
5831 section is executable
5833 section is mergeable
5835 section contains zero terminated strings
5837 section is a member of a section group
5839 section is used for thread-local-storage
5841 section is a member of the previously-current section's group, if any
5844 The optional @var{type} argument may contain one of the following constants:
5847 section contains data
5849 section does not contain data (i.e., section only occupies space)
5851 section contains data which is used by things other than the program
5853 section contains an array of pointers to init functions
5855 section contains an array of pointers to finish functions
5856 @item @@preinit_array
5857 section contains an array of pointers to pre-init functions
5860 Many targets only support the first three section types.
5862 Note on targets where the @code{@@} character is the start of a comment (eg
5863 ARM) then another character is used instead. For example the ARM port uses the
5866 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5867 be specified as well as an extra argument---@var{entsize}---like this:
5870 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5873 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5874 constants, each @var{entsize} octets long. Sections with both @code{M} and
5875 @code{S} must contain zero terminated strings where each character is
5876 @var{entsize} bytes long. The linker may remove duplicates within sections with
5877 the same name, same entity size and same flags. @var{entsize} must be an
5878 absolute expression. For sections with both @code{M} and @code{S}, a string
5879 which is a suffix of a larger string is considered a duplicate. Thus
5880 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5881 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5883 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5884 be present along with an additional field like this:
5887 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5890 The @var{GroupName} field specifies the name of the section group to which this
5891 particular section belongs. The optional linkage field can contain:
5894 indicates that only one copy of this section should be retained
5899 Note: if both the @var{M} and @var{G} flags are present then the fields for
5900 the Merge flag should come first, like this:
5903 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5906 If @var{flags} contains the @code{?} symbol then it may not also contain the
5907 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
5908 present. Instead, @code{?} says to consider the section that's current before
5909 this directive. If that section used @code{G}, then the new section will use
5910 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
5911 If not, then the @code{?} symbol has no effect.
5913 If no flags are specified, the default flags depend upon the section name. If
5914 the section name is not recognized, the default will be for the section to have
5915 none of the above flags: it will not be allocated in memory, nor writable, nor
5916 executable. The section will contain data.
5918 For ELF targets, the assembler supports another type of @code{.section}
5919 directive for compatibility with the Solaris assembler:
5922 .section "@var{name}"[, @var{flags}...]
5925 Note that the section name is quoted. There may be a sequence of comma
5929 section is allocatable
5933 section is executable
5935 section is excluded from executable and shared library.
5937 section is used for thread local storage
5940 This directive replaces the current section and subsection. See the
5941 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
5942 some examples of how this directive and the other section stack directives
5948 @section @code{.set @var{symbol}, @var{expression}}
5950 @cindex @code{set} directive
5951 @cindex symbol value, setting
5952 Set the value of @var{symbol} to @var{expression}. This
5953 changes @var{symbol}'s value and type to conform to
5954 @var{expression}. If @var{symbol} was flagged as external, it remains
5955 flagged (@pxref{Symbol Attributes}).
5957 You may @code{.set} a symbol many times in the same assembly.
5959 If you @code{.set} a global symbol, the value stored in the object
5960 file is the last value stored into it.
5963 On Z80 @code{set} is a real instruction, use
5964 @samp{@var{symbol} defl @var{expression}} instead.
5968 @section @code{.short @var{expressions}}
5970 @cindex @code{short} directive
5972 @code{.short} is normally the same as @samp{.word}.
5973 @xref{Word,,@code{.word}}.
5975 In some configurations, however, @code{.short} and @code{.word} generate
5976 numbers of different lengths. @xref{Machine Dependencies}.
5980 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5983 This expects zero or more @var{expressions}, and emits
5984 a 16 bit number for each.
5989 @section @code{.single @var{flonums}}
5991 @cindex @code{single} directive
5992 @cindex floating point numbers (single)
5993 This directive assembles zero or more flonums, separated by commas. It
5994 has the same effect as @code{.float}.
5996 The exact kind of floating point numbers emitted depends on how
5997 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6001 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6002 numbers in @sc{ieee} format.
6008 @section @code{.size}
6010 This directive is used to set the size associated with a symbol.
6014 @c only print the extra heading if both COFF and ELF are set
6015 @subheading COFF Version
6018 @cindex @code{size} directive (COFF version)
6019 For COFF targets, the @code{.size} directive is only permitted inside
6020 @code{.def}/@code{.endef} pairs. It is used like this:
6023 .size @var{expression}
6027 @samp{.size} is only meaningful when generating COFF format output; when
6028 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6035 @c only print the extra heading if both COFF and ELF are set
6036 @subheading ELF Version
6039 @cindex @code{size} directive (ELF version)
6040 For ELF targets, the @code{.size} directive is used like this:
6043 .size @var{name} , @var{expression}
6046 This directive sets the size associated with a symbol @var{name}.
6047 The size in bytes is computed from @var{expression} which can make use of label
6048 arithmetic. This directive is typically used to set the size of function
6053 @ifclear no-space-dir
6055 @section @code{.skip @var{size} , @var{fill}}
6057 @cindex @code{skip} directive
6058 @cindex filling memory
6059 This directive emits @var{size} bytes, each of value @var{fill}. Both
6060 @var{size} and @var{fill} are absolute expressions. If the comma and
6061 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6066 @section @code{.sleb128 @var{expressions}}
6068 @cindex @code{sleb128} directive
6069 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6070 compact, variable length representation of numbers used by the DWARF
6071 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6073 @ifclear no-space-dir
6075 @section @code{.space @var{size} , @var{fill}}
6077 @cindex @code{space} directive
6078 @cindex filling memory
6079 This directive emits @var{size} bytes, each of value @var{fill}. Both
6080 @var{size} and @var{fill} are absolute expressions. If the comma
6081 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6086 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6087 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6088 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6089 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6097 @section @code{.stabd, .stabn, .stabs}
6099 @cindex symbolic debuggers, information for
6100 @cindex @code{stab@var{x}} directives
6101 There are three directives that begin @samp{.stab}.
6102 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6103 The symbols are not entered in the @command{@value{AS}} hash table: they
6104 cannot be referenced elsewhere in the source file.
6105 Up to five fields are required:
6109 This is the symbol's name. It may contain any character except
6110 @samp{\000}, so is more general than ordinary symbol names. Some
6111 debuggers used to code arbitrarily complex structures into symbol names
6115 An absolute expression. The symbol's type is set to the low 8 bits of
6116 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6117 and debuggers choke on silly bit patterns.
6120 An absolute expression. The symbol's ``other'' attribute is set to the
6121 low 8 bits of this expression.
6124 An absolute expression. The symbol's descriptor is set to the low 16
6125 bits of this expression.
6128 An absolute expression which becomes the symbol's value.
6131 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6132 or @code{.stabs} statement, the symbol has probably already been created;
6133 you get a half-formed symbol in your object file. This is
6134 compatible with earlier assemblers!
6137 @cindex @code{stabd} directive
6138 @item .stabd @var{type} , @var{other} , @var{desc}
6140 The ``name'' of the symbol generated is not even an empty string.
6141 It is a null pointer, for compatibility. Older assemblers used a
6142 null pointer so they didn't waste space in object files with empty
6145 The symbol's value is set to the location counter,
6146 relocatably. When your program is linked, the value of this symbol
6147 is the address of the location counter when the @code{.stabd} was
6150 @cindex @code{stabn} directive
6151 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6152 The name of the symbol is set to the empty string @code{""}.
6154 @cindex @code{stabs} directive
6155 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6156 All five fields are specified.
6162 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6163 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6165 @cindex string, copying to object file
6166 @cindex string8, copying to object file
6167 @cindex string16, copying to object file
6168 @cindex string32, copying to object file
6169 @cindex string64, copying to object file
6170 @cindex @code{string} directive
6171 @cindex @code{string8} directive
6172 @cindex @code{string16} directive
6173 @cindex @code{string32} directive
6174 @cindex @code{string64} directive
6176 Copy the characters in @var{str} to the object file. You may specify more than
6177 one string to copy, separated by commas. Unless otherwise specified for a
6178 particular machine, the assembler marks the end of each string with a 0 byte.
6179 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6181 The variants @code{string16}, @code{string32} and @code{string64} differ from
6182 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6183 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6184 are stored in target endianness byte order.
6190 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6191 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6196 @section @code{.struct @var{expression}}
6198 @cindex @code{struct} directive
6199 Switch to the absolute section, and set the section offset to @var{expression},
6200 which must be an absolute expression. You might use this as follows:
6209 This would define the symbol @code{field1} to have the value 0, the symbol
6210 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6211 value 8. Assembly would be left in the absolute section, and you would need to
6212 use a @code{.section} directive of some sort to change to some other section
6213 before further assembly.
6217 @section @code{.subsection @var{name}}
6219 @cindex @code{subsection} directive
6220 @cindex Section Stack
6221 This is one of the ELF section stack manipulation directives. The others are
6222 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6223 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6226 This directive replaces the current subsection with @code{name}. The current
6227 section is not changed. The replaced subsection is put onto the section stack
6228 in place of the then current top of stack subsection.
6233 @section @code{.symver}
6234 @cindex @code{symver} directive
6235 @cindex symbol versioning
6236 @cindex versions of symbols
6237 Use the @code{.symver} directive to bind symbols to specific version nodes
6238 within a source file. This is only supported on ELF platforms, and is
6239 typically used when assembling files to be linked into a shared library.
6240 There are cases where it may make sense to use this in objects to be bound
6241 into an application itself so as to override a versioned symbol from a
6244 For ELF targets, the @code{.symver} directive can be used like this:
6246 .symver @var{name}, @var{name2@@nodename}
6248 If the symbol @var{name} is defined within the file
6249 being assembled, the @code{.symver} directive effectively creates a symbol
6250 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6251 just don't try and create a regular alias is that the @var{@@} character isn't
6252 permitted in symbol names. The @var{name2} part of the name is the actual name
6253 of the symbol by which it will be externally referenced. The name @var{name}
6254 itself is merely a name of convenience that is used so that it is possible to
6255 have definitions for multiple versions of a function within a single source
6256 file, and so that the compiler can unambiguously know which version of a
6257 function is being mentioned. The @var{nodename} portion of the alias should be
6258 the name of a node specified in the version script supplied to the linker when
6259 building a shared library. If you are attempting to override a versioned
6260 symbol from a shared library, then @var{nodename} should correspond to the
6261 nodename of the symbol you are trying to override.
6263 If the symbol @var{name} is not defined within the file being assembled, all
6264 references to @var{name} will be changed to @var{name2@@nodename}. If no
6265 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6268 Another usage of the @code{.symver} directive is:
6270 .symver @var{name}, @var{name2@@@@nodename}
6272 In this case, the symbol @var{name} must exist and be defined within
6273 the file being assembled. It is similar to @var{name2@@nodename}. The
6274 difference is @var{name2@@@@nodename} will also be used to resolve
6275 references to @var{name2} by the linker.
6277 The third usage of the @code{.symver} directive is:
6279 .symver @var{name}, @var{name2@@@@@@nodename}
6281 When @var{name} is not defined within the
6282 file being assembled, it is treated as @var{name2@@nodename}. When
6283 @var{name} is defined within the file being assembled, the symbol
6284 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6289 @section @code{.tag @var{structname}}
6291 @cindex COFF structure debugging
6292 @cindex structure debugging, COFF
6293 @cindex @code{tag} directive
6294 This directive is generated by compilers to include auxiliary debugging
6295 information in the symbol table. It is only permitted inside
6296 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6297 definitions in the symbol table with instances of those structures.
6300 @samp{.tag} is only used when generating COFF format output; when
6301 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6307 @section @code{.text @var{subsection}}
6309 @cindex @code{text} directive
6310 Tells @command{@value{AS}} to assemble the following statements onto the end of
6311 the text subsection numbered @var{subsection}, which is an absolute
6312 expression. If @var{subsection} is omitted, subsection number zero
6316 @section @code{.title "@var{heading}"}
6318 @cindex @code{title} directive
6319 @cindex listing control: title line
6320 Use @var{heading} as the title (second line, immediately after the
6321 source file name and pagenumber) when generating assembly listings.
6323 This directive affects subsequent pages, as well as the current page if
6324 it appears within ten lines of the top of a page.
6328 @section @code{.type}
6330 This directive is used to set the type of a symbol.
6334 @c only print the extra heading if both COFF and ELF are set
6335 @subheading COFF Version
6338 @cindex COFF symbol type
6339 @cindex symbol type, COFF
6340 @cindex @code{type} directive (COFF version)
6341 For COFF targets, this directive is permitted only within
6342 @code{.def}/@code{.endef} pairs. It is used like this:
6348 This records the integer @var{int} as the type attribute of a symbol table
6352 @samp{.type} is associated only with COFF format output; when
6353 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6354 directive but ignores it.
6360 @c only print the extra heading if both COFF and ELF are set
6361 @subheading ELF Version
6364 @cindex ELF symbol type
6365 @cindex symbol type, ELF
6366 @cindex @code{type} directive (ELF version)
6367 For ELF targets, the @code{.type} directive is used like this:
6370 .type @var{name} , @var{type description}
6373 This sets the type of symbol @var{name} to be either a
6374 function symbol or an object symbol. There are five different syntaxes
6375 supported for the @var{type description} field, in order to provide
6376 compatibility with various other assemblers.
6378 Because some of the characters used in these syntaxes (such as @samp{@@} and
6379 @samp{#}) are comment characters for some architectures, some of the syntaxes
6380 below do not work on all architectures. The first variant will be accepted by
6381 the GNU assembler on all architectures so that variant should be used for
6382 maximum portability, if you do not need to assemble your code with other
6385 The syntaxes supported are:
6388 .type <name> STT_<TYPE_IN_UPPER_CASE>
6389 .type <name>,#<type>
6390 .type <name>,@@<type>
6391 .type <name>,%<type>
6392 .type <name>,"<type>"
6395 The types supported are:
6400 Mark the symbol as being a function name.
6403 @itemx gnu_indirect_function
6404 Mark the symbol as an indirect function when evaluated during reloc
6405 processing. (This is only supported on Linux targeted assemblers).
6409 Mark the symbol as being a data object.
6413 Mark the symbol as being a thead-local data object.
6417 Mark the symbol as being a common data object.
6421 Does not mark the symbol in any way. It is supported just for completeness.
6423 @item gnu_unique_object
6424 Marks the symbol as being a globally unique data object. The dynamic linker
6425 will make sure that in the entire process there is just one symbol with this
6426 name and type in use. (This is only supported on Linux targeted assemblers).
6430 Note: Some targets support extra types in addition to those listed above.
6436 @section @code{.uleb128 @var{expressions}}
6438 @cindex @code{uleb128} directive
6439 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6440 compact, variable length representation of numbers used by the DWARF
6441 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6445 @section @code{.val @var{addr}}
6447 @cindex @code{val} directive
6448 @cindex COFF value attribute
6449 @cindex value attribute, COFF
6450 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6451 records the address @var{addr} as the value attribute of a symbol table
6455 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6456 configured for @code{b.out}, it accepts this directive but ignores it.
6462 @section @code{.version "@var{string}"}
6464 @cindex @code{version} directive
6465 This directive creates a @code{.note} section and places into it an ELF
6466 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6471 @section @code{.vtable_entry @var{table}, @var{offset}}
6473 @cindex @code{vtable_entry} directive
6474 This directive finds or creates a symbol @code{table} and creates a
6475 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6478 @section @code{.vtable_inherit @var{child}, @var{parent}}
6480 @cindex @code{vtable_inherit} directive
6481 This directive finds the symbol @code{child} and finds or creates the symbol
6482 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6483 parent whose addend is the value of the child symbol. As a special case the
6484 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6488 @section @code{.warning "@var{string}"}
6489 @cindex warning directive
6490 Similar to the directive @code{.error}
6491 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6494 @section @code{.weak @var{names}}
6496 @cindex @code{weak} directive
6497 This directive sets the weak attribute on the comma separated list of symbol
6498 @code{names}. If the symbols do not already exist, they will be created.
6500 On COFF targets other than PE, weak symbols are a GNU extension. This
6501 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 the PE target, weak symbols are supported natively as weak aliases.
6505 When a weak symbol is created that is not an alias, GAS creates an
6506 alternate symbol to hold the default value.
6509 @section @code{.weakref @var{alias}, @var{target}}
6511 @cindex @code{weakref} directive
6512 This directive creates an alias to the target symbol that enables the symbol to
6513 be referenced with weak-symbol semantics, but without actually making it weak.
6514 If direct references or definitions of the symbol are present, then the symbol
6515 will not be weak, but if all references to it are through weak references, the
6516 symbol will be marked as weak in the symbol table.
6518 The effect is equivalent to moving all references to the alias to a separate
6519 assembly source file, renaming the alias to the symbol in it, declaring the
6520 symbol as weak there, and running a reloadable link to merge the object files
6521 resulting from the assembly of the new source file and the old source file that
6522 had the references to the alias removed.
6524 The alias itself never makes to the symbol table, and is entirely handled
6525 within the assembler.
6528 @section @code{.word @var{expressions}}
6530 @cindex @code{word} directive
6531 This directive expects zero or more @var{expressions}, of any section,
6532 separated by commas.
6535 For each expression, @command{@value{AS}} emits a 32-bit number.
6538 For each expression, @command{@value{AS}} emits a 16-bit number.
6543 The size of the number emitted, and its byte order,
6544 depend on what target computer the assembly is for.
6547 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6548 @c happen---32-bit addressability, period; no long/short jumps.
6549 @ifset DIFF-TBL-KLUGE
6550 @cindex difference tables altered
6551 @cindex altered difference tables
6553 @emph{Warning: Special Treatment to support Compilers}
6557 Machines with a 32-bit address space, but that do less than 32-bit
6558 addressing, require the following special treatment. If the machine of
6559 interest to you does 32-bit addressing (or doesn't require it;
6560 @pxref{Machine Dependencies}), you can ignore this issue.
6563 In order to assemble compiler output into something that works,
6564 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6565 Directives of the form @samp{.word sym1-sym2} are often emitted by
6566 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6567 directive of the form @samp{.word sym1-sym2}, and the difference between
6568 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6569 creates a @dfn{secondary jump table}, immediately before the next label.
6570 This secondary jump table is preceded by a short-jump to the
6571 first byte after the secondary table. This short-jump prevents the flow
6572 of control from accidentally falling into the new table. Inside the
6573 table is a long-jump to @code{sym2}. The original @samp{.word}
6574 contains @code{sym1} minus the address of the long-jump to
6577 If there were several occurrences of @samp{.word sym1-sym2} before the
6578 secondary jump table, all of them are adjusted. If there was a
6579 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6580 long-jump to @code{sym4} is included in the secondary jump table,
6581 and the @code{.word} directives are adjusted to contain @code{sym3}
6582 minus the address of the long-jump to @code{sym4}; and so on, for as many
6583 entries in the original jump table as necessary.
6586 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6587 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6588 assembly language programmers.
6591 @c end DIFF-TBL-KLUGE
6594 @section Deprecated Directives
6596 @cindex deprecated directives
6597 @cindex obsolescent directives
6598 One day these directives won't work.
6599 They are included for compatibility with older assemblers.
6606 @node Object Attributes
6607 @chapter Object Attributes
6608 @cindex object attributes
6610 @command{@value{AS}} assembles source files written for a specific architecture
6611 into object files for that architecture. But not all object files are alike.
6612 Many architectures support incompatible variations. For instance, floating
6613 point arguments might be passed in floating point registers if the object file
6614 requires hardware floating point support---or floating point arguments might be
6615 passed in integer registers if the object file supports processors with no
6616 hardware floating point unit. Or, if two objects are built for different
6617 generations of the same architecture, the combination may require the
6618 newer generation at run-time.
6620 This information is useful during and after linking. At link time,
6621 @command{@value{LD}} can warn about incompatible object files. After link
6622 time, tools like @command{gdb} can use it to process the linked file
6625 Compatibility information is recorded as a series of object attributes. Each
6626 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6627 string, and indicates who sets the meaning of the tag. The tag is an integer,
6628 and indicates what property the attribute describes. The value may be a string
6629 or an integer, and indicates how the property affects this object. Missing
6630 attributes are the same as attributes with a zero value or empty string value.
6632 Object attributes were developed as part of the ABI for the ARM Architecture.
6633 The file format is documented in @cite{ELF for the ARM Architecture}.
6636 * GNU Object Attributes:: @sc{gnu} Object Attributes
6637 * Defining New Object Attributes:: Defining New Object Attributes
6640 @node GNU Object Attributes
6641 @section @sc{gnu} Object Attributes
6643 The @code{.gnu_attribute} directive records an object attribute
6644 with vendor @samp{gnu}.
6646 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6647 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6648 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6649 2} is set for architecture-independent attributes and clear for
6650 architecture-dependent ones.
6652 @subsection Common @sc{gnu} attributes
6654 These attributes are valid on all architectures.
6657 @item Tag_compatibility (32)
6658 The compatibility attribute takes an integer flag value and a vendor name. If
6659 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6660 then the file is only compatible with the named toolchain. If it is greater
6661 than 1, the file can only be processed by other toolchains under some private
6662 arrangement indicated by the flag value and the vendor name.
6665 @subsection MIPS Attributes
6668 @item Tag_GNU_MIPS_ABI_FP (4)
6669 The floating-point ABI used by this object file. The value will be:
6673 0 for files not affected by the floating-point ABI.
6675 1 for files using the hardware floating-point with a standard double-precision
6678 2 for files using the hardware floating-point ABI with a single-precision FPU.
6680 3 for files using the software floating-point ABI.
6682 4 for files using the hardware floating-point ABI with 64-bit wide
6683 double-precision floating-point registers and 32-bit wide general
6688 @subsection PowerPC Attributes
6691 @item Tag_GNU_Power_ABI_FP (4)
6692 The floating-point ABI used by this object file. The value will be:
6696 0 for files not affected by the floating-point ABI.
6698 1 for files using double-precision hardware floating-point ABI.
6700 2 for files using the software floating-point ABI.
6702 3 for files using single-precision hardware floating-point ABI.
6705 @item Tag_GNU_Power_ABI_Vector (8)
6706 The vector ABI used by this object file. The value will be:
6710 0 for files not affected by the vector ABI.
6712 1 for files using general purpose registers to pass vectors.
6714 2 for files using AltiVec registers to pass vectors.
6716 3 for files using SPE registers to pass vectors.
6720 @node Defining New Object Attributes
6721 @section Defining New Object Attributes
6723 If you want to define a new @sc{gnu} object attribute, here are the places you
6724 will need to modify. New attributes should be discussed on the @samp{binutils}
6729 This manual, which is the official register of attributes.
6731 The header for your architecture @file{include/elf}, to define the tag.
6733 The @file{bfd} support file for your architecture, to merge the attribute
6734 and issue any appropriate link warnings.
6736 Test cases in @file{ld/testsuite} for merging and link warnings.
6738 @file{binutils/readelf.c} to display your attribute.
6740 GCC, if you want the compiler to mark the attribute automatically.
6746 @node Machine Dependencies
6747 @chapter Machine Dependent Features
6749 @cindex machine dependencies
6750 The machine instruction sets are (almost by definition) different on
6751 each machine where @command{@value{AS}} runs. Floating point representations
6752 vary as well, and @command{@value{AS}} often supports a few additional
6753 directives or command-line options for compatibility with other
6754 assemblers on a particular platform. Finally, some versions of
6755 @command{@value{AS}} support special pseudo-instructions for branch
6758 This chapter discusses most of these differences, though it does not
6759 include details on any machine's instruction set. For details on that
6760 subject, see the hardware manufacturer's manual.
6764 * Alpha-Dependent:: Alpha Dependent Features
6767 * ARC-Dependent:: ARC Dependent Features
6770 * ARM-Dependent:: ARM Dependent Features
6773 * AVR-Dependent:: AVR Dependent Features
6776 * Blackfin-Dependent:: Blackfin Dependent Features
6779 * CR16-Dependent:: CR16 Dependent Features
6782 * CRIS-Dependent:: CRIS Dependent Features
6785 * D10V-Dependent:: D10V Dependent Features
6788 * D30V-Dependent:: D30V Dependent Features
6791 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6794 * HPPA-Dependent:: HPPA Dependent Features
6797 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6800 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6803 * i860-Dependent:: Intel 80860 Dependent Features
6806 * i960-Dependent:: Intel 80960 Dependent Features
6809 * IA-64-Dependent:: Intel IA-64 Dependent Features
6812 * IP2K-Dependent:: IP2K Dependent Features
6815 * LM32-Dependent:: LM32 Dependent Features
6818 * M32C-Dependent:: M32C Dependent Features
6821 * M32R-Dependent:: M32R Dependent Features
6824 * M68K-Dependent:: M680x0 Dependent Features
6827 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6830 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6833 * MIPS-Dependent:: MIPS Dependent Features
6836 * MMIX-Dependent:: MMIX Dependent Features
6839 * MSP430-Dependent:: MSP430 Dependent Features
6842 * NS32K-Dependent:: NS32K Dependent Features
6845 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6846 * SH64-Dependent:: SuperH SH64 Dependent Features
6849 * PDP-11-Dependent:: PDP-11 Dependent Features
6852 * PJ-Dependent:: picoJava Dependent Features
6855 * PPC-Dependent:: PowerPC Dependent Features
6858 * RX-Dependent:: RX Dependent Features
6861 * S/390-Dependent:: IBM S/390 Dependent Features
6864 * SCORE-Dependent:: SCORE Dependent Features
6867 * Sparc-Dependent:: SPARC Dependent Features
6870 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6873 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6876 * V850-Dependent:: V850 Dependent Features
6879 * Xtensa-Dependent:: Xtensa Dependent Features
6882 * Z80-Dependent:: Z80 Dependent Features
6885 * Z8000-Dependent:: Z8000 Dependent Features
6888 * Vax-Dependent:: VAX Dependent Features
6895 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6896 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6897 @c peculiarity: to preserve cross-references, there must be a node called
6898 @c "Machine Dependencies". Hence the conditional nodenames in each
6899 @c major node below. Node defaulting in makeinfo requires adjacency of
6900 @c node and sectioning commands; hence the repetition of @chapter BLAH
6901 @c in both conditional blocks.
6904 @include c-alpha.texi
6920 @include c-bfin.texi
6924 @include c-cr16.texi
6928 @include c-cris.texi
6933 @node Machine Dependencies
6934 @chapter Machine Dependent Features
6936 The machine instruction sets are different on each Renesas chip family,
6937 and there are also some syntax differences among the families. This
6938 chapter describes the specific @command{@value{AS}} features for each
6942 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6943 * SH-Dependent:: Renesas SH Dependent Features
6950 @include c-d10v.texi
6954 @include c-d30v.texi
6958 @include c-h8300.texi
6962 @include c-hppa.texi
6966 @include c-i370.texi
6970 @include c-i386.texi
6974 @include c-i860.texi
6978 @include c-i960.texi
6982 @include c-ia64.texi
6986 @include c-ip2k.texi
6990 @include c-lm32.texi
6994 @include c-m32c.texi
6998 @include c-m32r.texi
7002 @include c-m68k.texi
7006 @include c-m68hc11.texi
7010 @include c-microblaze.texi
7014 @include c-mips.texi
7018 @include c-mmix.texi
7022 @include c-msp430.texi
7026 @include c-ns32k.texi
7030 @include c-pdp11.texi
7046 @include c-s390.texi
7050 @include c-score.texi
7055 @include c-sh64.texi
7059 @include c-sparc.texi
7063 @include c-tic54x.texi
7067 @include c-tic6x.texi
7083 @include c-v850.texi
7087 @include c-xtensa.texi
7091 @c reverse effect of @down at top of generic Machine-Dep chapter
7095 @node Reporting Bugs
7096 @chapter Reporting Bugs
7097 @cindex bugs in assembler
7098 @cindex reporting bugs in assembler
7100 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7102 Reporting a bug may help you by bringing a solution to your problem, or it may
7103 not. But in any case the principal function of a bug report is to help the
7104 entire community by making the next version of @command{@value{AS}} work better.
7105 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7107 In order for a bug report to serve its purpose, you must include the
7108 information that enables us to fix the bug.
7111 * Bug Criteria:: Have you found a bug?
7112 * Bug Reporting:: How to report bugs
7116 @section Have You Found a Bug?
7117 @cindex bug criteria
7119 If you are not sure whether you have found a bug, here are some guidelines:
7122 @cindex fatal signal
7123 @cindex assembler crash
7124 @cindex crash of assembler
7126 If the assembler gets a fatal signal, for any input whatever, that is a
7127 @command{@value{AS}} bug. Reliable assemblers never crash.
7129 @cindex error on valid input
7131 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7133 @cindex invalid input
7135 If @command{@value{AS}} does not produce an error message for invalid input, that
7136 is a bug. However, you should note that your idea of ``invalid input'' might
7137 be our idea of ``an extension'' or ``support for traditional practice''.
7140 If you are an experienced user of assemblers, your suggestions for improvement
7141 of @command{@value{AS}} are welcome in any case.
7145 @section How to Report Bugs
7147 @cindex assembler bugs, reporting
7149 A number of companies and individuals offer support for @sc{gnu} products. If
7150 you obtained @command{@value{AS}} from a support organization, we recommend you
7151 contact that organization first.
7153 You can find contact information for many support companies and
7154 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7158 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7162 The fundamental principle of reporting bugs usefully is this:
7163 @strong{report all the facts}. If you are not sure whether to state a
7164 fact or leave it out, state it!
7166 Often people omit facts because they think they know what causes the problem
7167 and assume that some details do not matter. Thus, you might assume that the
7168 name of a symbol you use in an example does not matter. Well, probably it does
7169 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7170 happens to fetch from the location where that name is stored in memory;
7171 perhaps, if the name were different, the contents of that location would fool
7172 the assembler into doing the right thing despite the bug. Play it safe and
7173 give a specific, complete example. That is the easiest thing for you to do,
7174 and the most helpful.
7176 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7177 it is new to us. Therefore, always write your bug reports on the assumption
7178 that the bug has not been reported previously.
7180 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7181 bell?'' This cannot help us fix a bug, so it is basically useless. We
7182 respond by asking for enough details to enable us to investigate.
7183 You might as well expedite matters by sending them to begin with.
7185 To enable us to fix the bug, you should include all these things:
7189 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7190 it with the @samp{--version} argument.
7192 Without this, we will not know whether there is any point in looking for
7193 the bug in the current version of @command{@value{AS}}.
7196 Any patches you may have applied to the @command{@value{AS}} source.
7199 The type of machine you are using, and the operating system name and
7203 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7207 The command arguments you gave the assembler to assemble your example and
7208 observe the bug. To guarantee you will not omit something important, list them
7209 all. A copy of the Makefile (or the output from make) is sufficient.
7211 If we were to try to guess the arguments, we would probably guess wrong
7212 and then we might not encounter the bug.
7215 A complete input file that will reproduce the bug. If the bug is observed when
7216 the assembler is invoked via a compiler, send the assembler source, not the
7217 high level language source. Most compilers will produce the assembler source
7218 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7219 the options @samp{-v --save-temps}; this will save the assembler source in a
7220 file with an extension of @file{.s}, and also show you exactly how
7221 @command{@value{AS}} is being run.
7224 A description of what behavior you observe that you believe is
7225 incorrect. For example, ``It gets a fatal signal.''
7227 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7228 will certainly notice it. But if the bug is incorrect output, we might not
7229 notice unless it is glaringly wrong. You might as well not give us a chance to
7232 Even if the problem you experience is a fatal signal, you should still say so
7233 explicitly. Suppose something strange is going on, such as, your copy of
7234 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7235 library on your system. (This has happened!) Your copy might crash and ours
7236 would not. If you told us to expect a crash, then when ours fails to crash, we
7237 would know that the bug was not happening for us. If you had not told us to
7238 expect a crash, then we would not be able to draw any conclusion from our
7242 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7243 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7244 option. Always send diffs from the old file to the new file. If you even
7245 discuss something in the @command{@value{AS}} source, refer to it by context, not
7248 The line numbers in our development sources will not match those in your
7249 sources. Your line numbers would convey no useful information to us.
7252 Here are some things that are not necessary:
7256 A description of the envelope of the bug.
7258 Often people who encounter a bug spend a lot of time investigating
7259 which changes to the input file will make the bug go away and which
7260 changes will not affect it.
7262 This is often time consuming and not very useful, because the way we
7263 will find the bug is by running a single example under the debugger
7264 with breakpoints, not by pure deduction from a series of examples.
7265 We recommend that you save your time for something else.
7267 Of course, if you can find a simpler example to report @emph{instead}
7268 of the original one, that is a convenience for us. Errors in the
7269 output will be easier to spot, running under the debugger will take
7270 less time, and so on.
7272 However, simplification is not vital; if you do not want to do this,
7273 report the bug anyway and send us the entire test case you used.
7276 A patch for the bug.
7278 A patch for the bug does help us if it is a good one. But do not omit
7279 the necessary information, such as the test case, on the assumption that
7280 a patch is all we need. We might see problems with your patch and decide
7281 to fix the problem another way, or we might not understand it at all.
7283 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7284 construct an example that will make the program follow a certain path through
7285 the code. If you do not send us the example, we will not be able to construct
7286 one, so we will not be able to verify that the bug is fixed.
7288 And if we cannot understand what bug you are trying to fix, or why your
7289 patch should be an improvement, we will not install it. A test case will
7290 help us to understand.
7293 A guess about what the bug is or what it depends on.
7295 Such guesses are usually wrong. Even we cannot guess right about such
7296 things without first using the debugger to find the facts.
7299 @node Acknowledgements
7300 @chapter Acknowledgements
7302 If you have contributed to GAS and your name isn't listed here,
7303 it is not meant as a slight. We just don't know about it. Send mail to the
7304 maintainer, and we'll correct the situation. Currently
7306 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7308 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7311 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7312 information and the 68k series machines, most of the preprocessing pass, and
7313 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7315 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7316 many bug fixes, including merging support for several processors, breaking GAS
7317 up to handle multiple object file format back ends (including heavy rewrite,
7318 testing, an integration of the coff and b.out back ends), adding configuration
7319 including heavy testing and verification of cross assemblers and file splits
7320 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7321 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7322 port (including considerable amounts of reverse engineering), a SPARC opcode
7323 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7324 assertions and made them work, much other reorganization, cleanup, and lint.
7326 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7327 in format-specific I/O modules.
7329 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7330 has done much work with it since.
7332 The Intel 80386 machine description was written by Eliot Dresselhaus.
7334 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7336 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7337 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7339 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7340 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7341 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7342 support a.out format.
7344 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7345 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7346 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7347 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7350 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7351 simplified the configuration of which versions accept which directives. He
7352 updated the 68k machine description so that Motorola's opcodes always produced
7353 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7354 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7355 cross-compilation support, and one bug in relaxation that took a week and
7356 required the proverbial one-bit fix.
7358 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7359 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7360 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7361 PowerPC assembler, and made a few other minor patches.
7363 Steve Chamberlain made GAS able to generate listings.
7365 Hewlett-Packard contributed support for the HP9000/300.
7367 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7368 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7369 formats). This work was supported by both the Center for Software Science at
7370 the University of Utah and Cygnus Support.
7372 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7373 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7374 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7375 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7376 and some initial 64-bit support).
7378 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7380 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7381 support for openVMS/Alpha.
7383 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7386 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7387 Inc.@: added support for Xtensa processors.
7389 Several engineers at Cygnus Support have also provided many small bug fixes and
7390 configuration enhancements.
7392 Jon Beniston added support for the Lattice Mico32 architecture.
7394 Many others have contributed large or small bugfixes and enhancements. If
7395 you have contributed significant work and are not mentioned on this list, and
7396 want to be, let us know. Some of the history has been lost; we are not
7397 intentionally leaving anyone out.
7399 @node GNU Free Documentation License
7400 @appendix GNU Free Documentation License
7404 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob