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
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 Free Software Foundation, Inc.
108 Permission is granted to copy, distribute and/or modify this document
109 under the terms of the GNU Free Documentation License, Version 1.3
110 or any later version published by the Free Software Foundation;
111 with no Invariant Sections, with no Front-Cover Texts, and with no
112 Back-Cover Texts. A copy of the license is included in the
113 section entitled ``GNU Free Documentation License''.
119 @title Using @value{AS}
120 @subtitle The @sc{gnu} Assembler
122 @subtitle for the @value{TARGET} family
124 @ifset VERSION_PACKAGE
126 @subtitle @value{VERSION_PACKAGE}
129 @subtitle Version @value{VERSION}
132 The Free Software Foundation Inc.@: thanks The Nice Computer
133 Company of Australia for loaning Dean Elsner to write the
134 first (Vax) version of @command{as} for Project @sc{gnu}.
135 The proprietors, management and staff of TNCCA thank FSF for
136 distracting the boss while they got some work
139 @author Dean Elsner, Jay Fenlason & friends
143 \hfill {\it Using {\tt @value{AS}}}\par
144 \hfill Edited by Cygnus Support\par
146 %"boxit" macro for figures:
147 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
148 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
149 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
150 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
151 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
154 @vskip 0pt plus 1filll
155 Copyright @copyright{} 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999,
156 2000, 2001, 2002, 2006, 2007, 2008, 2009, 2010 Free Software Foundation, Inc.
158 Permission is granted to copy, distribute and/or modify this document
159 under the terms of the GNU Free Documentation License, Version 1.3
160 or any later version published by the Free Software Foundation;
161 with no Invariant Sections, with no Front-Cover Texts, and with no
162 Back-Cover Texts. A copy of the license is included in the
163 section entitled ``GNU Free Documentation License''.
170 @top Using @value{AS}
172 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
173 @ifset VERSION_PACKAGE
174 @value{VERSION_PACKAGE}
176 version @value{VERSION}.
178 This version of the file describes @command{@value{AS}} configured to generate
179 code for @value{TARGET} architectures.
182 This document is distributed under the terms of the GNU Free
183 Documentation License. A copy of the license is included in the
184 section entitled ``GNU Free Documentation License''.
187 * Overview:: Overview
188 * Invoking:: Command-Line Options
190 * Sections:: Sections and Relocation
192 * Expressions:: Expressions
193 * Pseudo Ops:: Assembler Directives
195 * Object Attributes:: Object Attributes
197 * Machine Dependencies:: Machine Dependent Features
198 * Reporting Bugs:: Reporting Bugs
199 * Acknowledgements:: Who Did What
200 * GNU Free Documentation License:: GNU Free Documentation License
201 * AS Index:: AS Index
208 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
210 This version of the manual describes @command{@value{AS}} configured to generate
211 code for @value{TARGET} architectures.
215 @cindex invocation summary
216 @cindex option summary
217 @cindex summary of options
218 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
219 see @ref{Invoking,,Command-Line Options}.
221 @c man title AS the portable GNU assembler.
225 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
229 @c We don't use deffn and friends for the following because they seem
230 @c to be limited to one line for the header.
232 @c man begin SYNOPSIS
233 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
234 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
235 [@b{--debug-prefix-map} @var{old}=@var{new}]
236 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
237 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
238 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
239 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
240 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
241 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
242 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
243 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
244 [@b{--target-help}] [@var{target-options}]
245 [@b{--}|@var{files} @dots{}]
247 @c Target dependent options are listed below. Keep the list sorted.
248 @c Add an empty line for separation.
251 @emph{Target Alpha options:}
253 [@b{-mdebug} | @b{-no-mdebug}]
254 [@b{-replace} | @b{-noreplace}]
255 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
256 [@b{-F}] [@b{-32addr}]
260 @emph{Target ARC options:}
266 @emph{Target ARM options:}
267 @c Don't document the deprecated options
268 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
269 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
270 [@b{-mfpu}=@var{floating-point-format}]
271 [@b{-mfloat-abi}=@var{abi}]
272 [@b{-meabi}=@var{ver}]
275 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
276 @b{-mapcs-reentrant}]
277 [@b{-mthumb-interwork}] [@b{-k}]
281 @emph{Target Blackfin options:}
282 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
289 @emph{Target CRIS options:}
290 [@b{--underscore} | @b{--no-underscore}]
292 [@b{--emulation=criself} | @b{--emulation=crisaout}]
293 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
294 @c Deprecated -- deliberately not documented.
299 @emph{Target D10V options:}
304 @emph{Target D30V options:}
305 [@b{-O}|@b{-n}|@b{-N}]
309 @emph{Target H8/300 options:}
313 @c HPPA has no machine-dependent assembler options (yet).
317 @emph{Target i386 options:}
318 [@b{--32}|@b{--64}] [@b{-n}]
319 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
323 @emph{Target i960 options:}
324 @c see md_parse_option in tc-i960.c
325 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
327 [@b{-b}] [@b{-no-relax}]
331 @emph{Target IA-64 options:}
332 [@b{-mconstant-gp}|@b{-mauto-pic}]
333 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
335 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
336 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
337 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
338 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
342 @emph{Target IP2K options:}
343 [@b{-mip2022}|@b{-mip2022ext}]
347 @emph{Target M32C options:}
348 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
352 @emph{Target M32R options:}
353 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
358 @emph{Target M680X0 options:}
359 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
363 @emph{Target M68HC11 options:}
364 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}]
365 [@b{-mshort}|@b{-mlong}]
366 [@b{-mshort-double}|@b{-mlong-double}]
367 [@b{--force-long-branches}] [@b{--short-branches}]
368 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
369 [@b{--print-opcodes}] [@b{--generate-example}]
373 @emph{Target MCORE options:}
374 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
375 [@b{-mcpu=[210|340]}]
378 @emph{Target MICROBLAZE options:}
379 @c MicroBlaze has no machine-dependent assembler options.
383 @emph{Target MIPS options:}
384 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
385 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
386 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
387 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
388 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
389 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
390 [@b{-mips64}] [@b{-mips64r2}]
391 [@b{-construct-floats}] [@b{-no-construct-floats}]
392 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
393 [@b{-mips16}] [@b{-no-mips16}]
394 [@b{-msmartmips}] [@b{-mno-smartmips}]
395 [@b{-mips3d}] [@b{-no-mips3d}]
396 [@b{-mdmx}] [@b{-no-mdmx}]
397 [@b{-mdsp}] [@b{-mno-dsp}]
398 [@b{-mdspr2}] [@b{-mno-dspr2}]
399 [@b{-mmt}] [@b{-mno-mt}]
400 [@b{-mfix7000}] [@b{-mno-fix7000}]
401 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
402 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
403 [@b{-mdebug}] [@b{-no-mdebug}]
404 [@b{-mpdr}] [@b{-mno-pdr}]
408 @emph{Target MMIX options:}
409 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
410 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
411 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
412 [@b{--linker-allocated-gregs}]
416 @emph{Target PDP11 options:}
417 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
418 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
419 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
423 @emph{Target picoJava options:}
428 @emph{Target PowerPC options:}
429 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
430 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}]
431 [@b{-mcom}|@b{-many}|@b{-maltivec}|@b{-mvsx}] [@b{-memb}]
432 [@b{-mregnames}|@b{-mno-regnames}]
433 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
434 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
435 [@b{-msolaris}|@b{-mno-solaris}]
439 @emph{Target RX options:}
440 [@b{-mlittle-endian}|@b{-mbig-endian}]
441 [@b{-m32bit-ints}|@b{-m16bit-ints}]
442 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
446 @emph{Target s390 options:}
447 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
448 [@b{-mregnames}|@b{-mno-regnames}]
449 [@b{-mwarn-areg-zero}]
453 @emph{Target SCORE options:}
454 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
455 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
456 [@b{-march=score7}][@b{-march=score3}]
457 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
461 @emph{Target SPARC options:}
462 @c The order here is important. See c-sparc.texi.
463 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
464 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
465 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
470 @emph{Target TIC54X options:}
471 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
472 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
477 @emph{Target TIC6X options:}
478 [@b{-march=@var{arch}}] [@b{-matomic}|@b{-mno-atomic}]
479 [@b{-mbig-endian}|@b{-mlittle-endian}] [@b{-mdsbt}|@b{-mno-dsbt}]
480 [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}] [@b{-mpic}|@b{-mno-pic}]
485 @emph{Target Z80 options:}
486 [@b{-z80}] [@b{-r800}]
487 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
488 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
489 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
490 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
491 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
492 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
496 @c Z8000 has no machine-dependent assembler options
500 @emph{Target Xtensa options:}
501 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
502 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
503 [@b{--[no-]transform}]
504 [@b{--rename-section} @var{oldname}=@var{newname}]
512 @include at-file.texi
515 Turn on listings, in any of a variety of ways:
519 omit false conditionals
522 omit debugging directives
525 include general information, like @value{AS} version and options passed
528 include high-level source
534 include macro expansions
537 omit forms processing
543 set the name of the listing file
546 You may combine these options; for example, use @samp{-aln} for assembly
547 listing without forms processing. The @samp{=file} option, if used, must be
548 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
551 Begin in alternate macro mode.
553 @xref{Altmacro,,@code{.altmacro}}.
556 @item --compress-debug-sections
557 Compress DWARF debug sections using zlib. The debug sections are renamed
558 to begin with @samp{.zdebug}, and the resulting object file may not be
559 compatible with older linkers and object file utilities.
561 @item --nocompress-debug-sections
562 Do not compress DWARF debug sections. This is the default.
565 Ignored. This option is accepted for script compatibility with calls to
568 @item --debug-prefix-map @var{old}=@var{new}
569 When assembling files in directory @file{@var{old}}, record debugging
570 information describing them as in @file{@var{new}} instead.
572 @item --defsym @var{sym}=@var{value}
573 Define the symbol @var{sym} to be @var{value} before assembling the input file.
574 @var{value} must be an integer constant. As in C, a leading @samp{0x}
575 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
576 value. The value of the symbol can be overridden inside a source file via the
577 use of a @code{.set} pseudo-op.
580 ``fast''---skip whitespace and comment preprocessing (assume source is
585 Generate debugging information for each assembler source line using whichever
586 debug format is preferred by the target. This currently means either STABS,
590 Generate stabs debugging information for each assembler line. This
591 may help debugging assembler code, if the debugger can handle it.
594 Generate stabs debugging information for each assembler line, with GNU
595 extensions that probably only gdb can handle, and that could make other
596 debuggers crash or refuse to read your program. This
597 may help debugging assembler code. Currently the only GNU extension is
598 the location of the current working directory at assembling time.
601 Generate DWARF2 debugging information for each assembler line. This
602 may help debugging assembler code, if the debugger can handle it. Note---this
603 option is only supported by some targets, not all of them.
606 Print a summary of the command line options and exit.
609 Print a summary of all target specific options and exit.
612 Add directory @var{dir} to the search list for @code{.include} directives.
615 Don't warn about signed overflow.
618 @ifclear DIFF-TBL-KLUGE
619 This option is accepted but has no effect on the @value{TARGET} family.
621 @ifset DIFF-TBL-KLUGE
622 Issue warnings when difference tables altered for long displacements.
627 Keep (in the symbol table) local symbols. These symbols start with
628 system-specific local label prefixes, typically @samp{.L} for ELF systems
629 or @samp{L} for traditional a.out systems.
634 @item --listing-lhs-width=@var{number}
635 Set the maximum width, in words, of the output data column for an assembler
636 listing to @var{number}.
638 @item --listing-lhs-width2=@var{number}
639 Set the maximum width, in words, of the output data column for continuation
640 lines in an assembler listing to @var{number}.
642 @item --listing-rhs-width=@var{number}
643 Set the maximum width of an input source line, as displayed in a listing, to
646 @item --listing-cont-lines=@var{number}
647 Set the maximum number of lines printed in a listing for a single line of input
650 @item -o @var{objfile}
651 Name the object-file output from @command{@value{AS}} @var{objfile}.
654 Fold the data section into the text section.
656 @kindex --hash-size=@var{number}
657 Set the default size of GAS's hash tables to a prime number close to
658 @var{number}. Increasing this value can reduce the length of time it takes the
659 assembler to perform its tasks, at the expense of increasing the assembler's
660 memory requirements. Similarly reducing this value can reduce the memory
661 requirements at the expense of speed.
663 @item --reduce-memory-overheads
664 This option reduces GAS's memory requirements, at the expense of making the
665 assembly processes slower. Currently this switch is a synonym for
666 @samp{--hash-size=4051}, but in the future it may have other effects as well.
669 Print the maximum space (in bytes) and total time (in seconds) used by
672 @item --strip-local-absolute
673 Remove local absolute symbols from the outgoing symbol table.
677 Print the @command{as} version.
680 Print the @command{as} version and exit.
684 Suppress warning messages.
686 @item --fatal-warnings
687 Treat warnings as errors.
690 Don't suppress warning messages or treat them as errors.
699 Generate an object file even after errors.
701 @item -- | @var{files} @dots{}
702 Standard input, or source files to assemble.
707 The following options are available when @value{AS} is configured for
712 This option selects the core processor variant.
714 Select either big-endian (-EB) or little-endian (-EL) output.
719 The following options are available when @value{AS} is configured for the ARM
723 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
724 Specify which ARM processor variant is the target.
725 @item -march=@var{architecture}[+@var{extension}@dots{}]
726 Specify which ARM architecture variant is used by the target.
727 @item -mfpu=@var{floating-point-format}
728 Select which Floating Point architecture is the target.
729 @item -mfloat-abi=@var{abi}
730 Select which floating point ABI is in use.
732 Enable Thumb only instruction decoding.
733 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
734 Select which procedure calling convention is in use.
736 Select either big-endian (-EB) or little-endian (-EL) output.
737 @item -mthumb-interwork
738 Specify that the code has been generated with interworking between Thumb and
741 Specify that PIC code has been generated.
746 The following options are available when @value{AS} is configured for
747 the Blackfin processor family.
750 @item -mcpu=@var{processor}@r{[}-@var{sirevision}@r{]}
751 This option specifies the target processor. The optional @var{sirevision}
752 is not used in assembler.
754 Assemble for the FDPIC ABI.
762 See the info pages for documentation of the CRIS-specific options.
766 The following options are available when @value{AS} is configured for
769 @cindex D10V optimization
770 @cindex optimization, D10V
772 Optimize output by parallelizing instructions.
777 The following options are available when @value{AS} is configured for a D30V
780 @cindex D30V optimization
781 @cindex optimization, D30V
783 Optimize output by parallelizing instructions.
787 Warn when nops are generated.
789 @cindex D30V nops after 32-bit multiply
791 Warn when a nop after a 32-bit multiply instruction is generated.
796 The following options are available when @value{AS} is configured for the
797 Intel 80960 processor.
800 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
801 Specify which variant of the 960 architecture is the target.
804 Add code to collect statistics about branches taken.
807 Do not alter compare-and-branch instructions for long displacements;
814 The following options are available when @value{AS} is configured for the
820 Specifies that the extended IP2022 instructions are allowed.
823 Restores the default behaviour, which restricts the permitted instructions to
824 just the basic IP2022 ones.
830 The following options are available when @value{AS} is configured for the
831 Renesas M32C and M16C processors.
836 Assemble M32C instructions.
839 Assemble M16C instructions (the default).
842 Enable support for link-time relaxations.
845 Support H'00 style hex constants in addition to 0x00 style.
851 The following options are available when @value{AS} is configured for the
852 Renesas M32R (formerly Mitsubishi M32R) series.
857 Specify which processor in the M32R family is the target. The default
858 is normally the M32R, but this option changes it to the M32RX.
860 @item --warn-explicit-parallel-conflicts or --Wp
861 Produce warning messages when questionable parallel constructs are
864 @item --no-warn-explicit-parallel-conflicts or --Wnp
865 Do not produce warning messages when questionable parallel constructs are
872 The following options are available when @value{AS} is configured for the
873 Motorola 68000 series.
878 Shorten references to undefined symbols, to one word instead of two.
880 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
881 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
882 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
883 Specify what processor in the 68000 family is the target. The default
884 is normally the 68020, but this can be changed at configuration time.
886 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
887 The target machine does (or does not) have a floating-point coprocessor.
888 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
889 the basic 68000 is not compatible with the 68881, a combination of the
890 two can be specified, since it's possible to do emulation of the
891 coprocessor instructions with the main processor.
893 @item -m68851 | -mno-68851
894 The target machine does (or does not) have a memory-management
895 unit coprocessor. The default is to assume an MMU for 68020 and up.
902 For details about the PDP-11 machine dependent features options,
903 see @ref{PDP-11-Options}.
906 @item -mpic | -mno-pic
907 Generate position-independent (or position-dependent) code. The
908 default is @option{-mpic}.
911 @itemx -mall-extensions
912 Enable all instruction set extensions. This is the default.
914 @item -mno-extensions
915 Disable all instruction set extensions.
917 @item -m@var{extension} | -mno-@var{extension}
918 Enable (or disable) a particular instruction set extension.
921 Enable the instruction set extensions supported by a particular CPU, and
922 disable all other extensions.
924 @item -m@var{machine}
925 Enable the instruction set extensions supported by a particular machine
926 model, and disable all other extensions.
932 The following options are available when @value{AS} is configured for
933 a picoJava processor.
937 @cindex PJ endianness
938 @cindex endianness, PJ
939 @cindex big endian output, PJ
941 Generate ``big endian'' format output.
943 @cindex little endian output, PJ
945 Generate ``little endian'' format output.
951 The following options are available when @value{AS} is configured for the
952 Motorola 68HC11 or 68HC12 series.
956 @item -m68hc11 | -m68hc12 | -m68hcs12
957 Specify what processor is the target. The default is
958 defined by the configuration option when building the assembler.
961 Specify to use the 16-bit integer ABI.
964 Specify to use the 32-bit integer ABI.
967 Specify to use the 32-bit double ABI.
970 Specify to use the 64-bit double ABI.
972 @item --force-long-branches
973 Relative branches are turned into absolute ones. This concerns
974 conditional branches, unconditional branches and branches to a
977 @item -S | --short-branches
978 Do not turn relative branches into absolute ones
979 when the offset is out of range.
981 @item --strict-direct-mode
982 Do not turn the direct addressing mode into extended addressing mode
983 when the instruction does not support direct addressing mode.
985 @item --print-insn-syntax
986 Print the syntax of instruction in case of error.
988 @item --print-opcodes
989 print the list of instructions with syntax and then exit.
991 @item --generate-example
992 print an example of instruction for each possible instruction and then exit.
993 This option is only useful for testing @command{@value{AS}}.
999 The following options are available when @command{@value{AS}} is configured
1000 for the SPARC architecture:
1003 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1004 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1005 Explicitly select a variant of the SPARC architecture.
1007 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1008 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1010 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1011 UltraSPARC extensions.
1013 @item -xarch=v8plus | -xarch=v8plusa
1014 For compatibility with the Solaris v9 assembler. These options are
1015 equivalent to -Av8plus and -Av8plusa, respectively.
1018 Warn when the assembler switches to another architecture.
1023 The following options are available when @value{AS} is configured for the 'c54x
1028 Enable extended addressing mode. All addresses and relocations will assume
1029 extended addressing (usually 23 bits).
1030 @item -mcpu=@var{CPU_VERSION}
1031 Sets the CPU version being compiled for.
1032 @item -merrors-to-file @var{FILENAME}
1033 Redirect error output to a file, for broken systems which don't support such
1034 behaviour in the shell.
1039 The following options are available when @value{AS} is configured for
1040 a @sc{mips} processor.
1044 This option sets the largest size of an object that can be referenced
1045 implicitly with the @code{gp} register. It is only accepted for targets that
1046 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1048 @cindex MIPS endianness
1049 @cindex endianness, MIPS
1050 @cindex big endian output, MIPS
1052 Generate ``big endian'' format output.
1054 @cindex little endian output, MIPS
1056 Generate ``little endian'' format output.
1068 Generate code for a particular @sc{mips} Instruction Set Architecture level.
1069 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1070 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1071 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1072 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1074 correspond to generic
1075 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1076 and @samp{MIPS64 Release 2}
1077 ISA processors, respectively.
1079 @item -march=@var{CPU}
1080 Generate code for a particular @sc{mips} cpu.
1082 @item -mtune=@var{cpu}
1083 Schedule and tune for a particular @sc{mips} cpu.
1087 Cause nops to be inserted if the read of the destination register
1088 of an mfhi or mflo instruction occurs in the following two instructions.
1092 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1093 section instead of the standard ELF .stabs sections.
1097 Control generation of @code{.pdr} sections.
1101 The register sizes are normally inferred from the ISA and ABI, but these
1102 flags force a certain group of registers to be treated as 32 bits wide at
1103 all times. @samp{-mgp32} controls the size of general-purpose registers
1104 and @samp{-mfp32} controls the size of floating-point registers.
1108 Generate code for the MIPS 16 processor. This is equivalent to putting
1109 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1110 turns off this option.
1113 @itemx -mno-smartmips
1114 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1115 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1116 @samp{-mno-smartmips} turns off this option.
1120 Generate code for the MIPS-3D Application Specific Extension.
1121 This tells the assembler to accept MIPS-3D instructions.
1122 @samp{-no-mips3d} turns off this option.
1126 Generate code for the MDMX Application Specific Extension.
1127 This tells the assembler to accept MDMX instructions.
1128 @samp{-no-mdmx} turns off this option.
1132 Generate code for the DSP Release 1 Application Specific Extension.
1133 This tells the assembler to accept DSP Release 1 instructions.
1134 @samp{-mno-dsp} turns off this option.
1138 Generate code for the DSP Release 2 Application Specific Extension.
1139 This option implies -mdsp.
1140 This tells the assembler to accept DSP Release 2 instructions.
1141 @samp{-mno-dspr2} turns off this option.
1145 Generate code for the MT Application Specific Extension.
1146 This tells the assembler to accept MT instructions.
1147 @samp{-mno-mt} turns off this option.
1149 @item --construct-floats
1150 @itemx --no-construct-floats
1151 The @samp{--no-construct-floats} option disables the construction of
1152 double width floating point constants by loading the two halves of the
1153 value into the two single width floating point registers that make up
1154 the double width register. By default @samp{--construct-floats} is
1155 selected, allowing construction of these floating point constants.
1158 @item --emulation=@var{name}
1159 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1160 for some other target, in all respects, including output format (choosing
1161 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1162 debugging information or store symbol table information, and default
1163 endianness. The available configuration names are: @samp{mipsecoff},
1164 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1165 @samp{mipsbelf}. The first two do not alter the default endianness from that
1166 of the primary target for which the assembler was configured; the others change
1167 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1168 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1169 selection in any case.
1171 This option is currently supported only when the primary target
1172 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1173 Furthermore, the primary target or others specified with
1174 @samp{--enable-targets=@dots{}} at configuration time must include support for
1175 the other format, if both are to be available. For example, the Irix 5
1176 configuration includes support for both.
1178 Eventually, this option will support more configurations, with more
1179 fine-grained control over the assembler's behavior, and will be supported for
1183 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1190 Control how to deal with multiplication overflow and division by zero.
1191 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1192 (and only work for Instruction Set Architecture level 2 and higher);
1193 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1197 When this option is used, @command{@value{AS}} will issue a warning every
1198 time it generates a nop instruction from a macro.
1203 The following options are available when @value{AS} is configured for
1209 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1210 The command line option @samp{-nojsri2bsr} can be used to disable it.
1214 Enable or disable the silicon filter behaviour. By default this is disabled.
1215 The default can be overridden by the @samp{-sifilter} command line option.
1218 Alter jump instructions for long displacements.
1220 @item -mcpu=[210|340]
1221 Select the cpu type on the target hardware. This controls which instructions
1225 Assemble for a big endian target.
1228 Assemble for a little endian target.
1234 See the info pages for documentation of the MMIX-specific options.
1238 See the info pages for documentation of the RX-specific options.
1242 The following options are available when @value{AS} is configured for the s390
1248 Select the word size, either 31/32 bits or 64 bits.
1251 Select the architecture mode, either the Enterprise System
1252 Architecture (esa) or the z/Architecture mode (zarch).
1253 @item -march=@var{processor}
1254 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1255 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, or @samp{z10}.
1257 @itemx -mno-regnames
1258 Allow or disallow symbolic names for registers.
1259 @item -mwarn-areg-zero
1260 Warn whenever the operand for a base or index register has been specified
1261 but evaluates to zero.
1266 The following options are available when @value{AS} is configured for a
1267 TMS320C6000 processor.
1270 @item -march=@var{arch}
1271 Enable (only) instructions from architecture @var{arch}. By default,
1272 all instructions are permitted.
1274 The following values of @var{arch} are accepted: @code{c62x},
1275 @code{c64x}, @code{c64x+}, @code{c67x}, @code{c67x+}, @code{c674x}.
1279 Enable or disable the optional C64x+ atomic operation instructions.
1280 By default, they are enabled if no @option{-march} option is given, or
1281 if an architecture is specified with @option{-march} that implies
1282 these instructions are present (currently, there are no such
1283 architectures); they are disabled if an architecture is specified with
1284 @option{-march} on which the instructions are optional or not
1285 present. This option overrides such a default from the architecture,
1286 independent of the order in which the @option{-march} or
1287 @option{-matomic} or @option{-mno-atomic} options are passed.
1291 The @option{-mdsbt} option causes the assembler to generate the
1292 @code{Tag_ABI_DSBT} attribute with a value of 1, indicating that the
1293 code is using DSBT addressing. The @option{-mno-dsbt} option, the
1294 default, causes the tag to have a value of 0, indicating that the code
1295 does not use DSBT addressing. The linker will emit a warning if
1296 objects of different type (DSBT and non-DSBT) are linked together.
1301 The @option{-mpid=} option causes the assembler to generate the
1302 @code{Tag_ABI_PID} attribute with a value indicating the form of data
1303 addressing used by the code. @option{-mpid=no}, the default,
1304 indicates position-dependent data addressing, @option{-mpid=near}
1305 indicates position-independent addressing with GOT accesses using near
1306 DP addressing, and @option{-mpid=far} indicates position-independent
1307 addressing with GOT accesses using far DP addressing. The linker will
1308 emit a warning if objects built with different settings of this option
1309 are linked together.
1313 The @option{-mpic} option causes the assembler to generate the
1314 @code{Tag_ABI_PIC} attribute with a value of 1, indicating that the
1315 code is using position-independent code addressing, The
1316 @code{-mno-pic} option, the default, causes the tag to have a value of
1317 0, indicating position-dependent code addressing. The linker will
1318 emit a warning if objects of different type (position-dependent and
1319 position-independent) are linked together.
1322 @itemx -mlittle-endian
1323 Generate code for the specified endianness. The default is
1330 The following options are available when @value{AS} is configured for
1331 an Xtensa processor.
1334 @item --text-section-literals | --no-text-section-literals
1335 With @option{--text-@-section-@-literals}, literal pools are interspersed
1336 in the text section. The default is
1337 @option{--no-@-text-@-section-@-literals}, which places literals in a
1338 separate section in the output file. These options only affect literals
1339 referenced via PC-relative @code{L32R} instructions; literals for
1340 absolute mode @code{L32R} instructions are handled separately.
1342 @item --absolute-literals | --no-absolute-literals
1343 Indicate to the assembler whether @code{L32R} instructions use absolute
1344 or PC-relative addressing. The default is to assume absolute addressing
1345 if the Xtensa processor includes the absolute @code{L32R} addressing
1346 option. Otherwise, only the PC-relative @code{L32R} mode can be used.
1348 @item --target-align | --no-target-align
1349 Enable or disable automatic alignment to reduce branch penalties at the
1350 expense of some code density. The default is @option{--target-@-align}.
1352 @item --longcalls | --no-longcalls
1353 Enable or disable transformation of call instructions to allow calls
1354 across a greater range of addresses. The default is
1355 @option{--no-@-longcalls}.
1357 @item --transform | --no-transform
1358 Enable or disable all assembler transformations of Xtensa instructions.
1359 The default is @option{--transform};
1360 @option{--no-transform} should be used only in the rare cases when the
1361 instructions must be exactly as specified in the assembly source.
1363 @item --rename-section @var{oldname}=@var{newname}
1364 When generating output sections, rename the @var{oldname} section to
1370 The following options are available when @value{AS} is configured for
1371 a Z80 family processor.
1374 Assemble for Z80 processor.
1376 Assemble for R800 processor.
1377 @item -ignore-undocumented-instructions
1379 Assemble undocumented Z80 instructions that also work on R800 without warning.
1380 @item -ignore-unportable-instructions
1382 Assemble all undocumented Z80 instructions without warning.
1383 @item -warn-undocumented-instructions
1385 Issue a warning for undocumented Z80 instructions that also work on R800.
1386 @item -warn-unportable-instructions
1388 Issue a warning for undocumented Z80 instructions that do not work on R800.
1389 @item -forbid-undocumented-instructions
1391 Treat all undocumented instructions as errors.
1392 @item -forbid-unportable-instructions
1394 Treat undocumented Z80 instructions that do not work on R800 as errors.
1401 * Manual:: Structure of this Manual
1402 * GNU Assembler:: The GNU Assembler
1403 * Object Formats:: Object File Formats
1404 * Command Line:: Command Line
1405 * Input Files:: Input Files
1406 * Object:: Output (Object) File
1407 * Errors:: Error and Warning Messages
1411 @section Structure of this Manual
1413 @cindex manual, structure and purpose
1414 This manual is intended to describe what you need to know to use
1415 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1416 notation for symbols, constants, and expressions; the directives that
1417 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1420 We also cover special features in the @value{TARGET}
1421 configuration of @command{@value{AS}}, including assembler directives.
1424 This manual also describes some of the machine-dependent features of
1425 various flavors of the assembler.
1428 @cindex machine instructions (not covered)
1429 On the other hand, this manual is @emph{not} intended as an introduction
1430 to programming in assembly language---let alone programming in general!
1431 In a similar vein, we make no attempt to introduce the machine
1432 architecture; we do @emph{not} describe the instruction set, standard
1433 mnemonics, registers or addressing modes that are standard to a
1434 particular architecture.
1436 You may want to consult the manufacturer's
1437 machine architecture manual for this information.
1441 For information on the H8/300 machine instruction set, see @cite{H8/300
1442 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1443 Programming Manual} (Renesas).
1446 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1447 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1448 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1449 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1452 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1456 @c I think this is premature---doc@cygnus.com, 17jan1991
1458 Throughout this manual, we assume that you are running @dfn{GNU},
1459 the portable operating system from the @dfn{Free Software
1460 Foundation, Inc.}. This restricts our attention to certain kinds of
1461 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1462 once this assumption is granted examples and definitions need less
1465 @command{@value{AS}} is part of a team of programs that turn a high-level
1466 human-readable series of instructions into a low-level
1467 computer-readable series of instructions. Different versions of
1468 @command{@value{AS}} are used for different kinds of computer.
1471 @c There used to be a section "Terminology" here, which defined
1472 @c "contents", "byte", "word", and "long". Defining "word" to any
1473 @c particular size is confusing when the .word directive may generate 16
1474 @c bits on one machine and 32 bits on another; in general, for the user
1475 @c version of this manual, none of these terms seem essential to define.
1476 @c They were used very little even in the former draft of the manual;
1477 @c this draft makes an effort to avoid them (except in names of
1481 @section The GNU Assembler
1483 @c man begin DESCRIPTION
1485 @sc{gnu} @command{as} is really a family of assemblers.
1487 This manual describes @command{@value{AS}}, a member of that family which is
1488 configured for the @value{TARGET} architectures.
1490 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1491 should find a fairly similar environment when you use it on another
1492 architecture. Each version has much in common with the others,
1493 including object file formats, most assembler directives (often called
1494 @dfn{pseudo-ops}) and assembler syntax.@refill
1496 @cindex purpose of @sc{gnu} assembler
1497 @command{@value{AS}} is primarily intended to assemble the output of the
1498 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1499 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1500 assemble correctly everything that other assemblers for the same
1501 machine would assemble.
1503 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1506 @c This remark should appear in generic version of manual; assumption
1507 @c here is that generic version sets M680x0.
1508 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1509 assembler for the same architecture; for example, we know of several
1510 incompatible versions of 680x0 assembly language syntax.
1515 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1516 program in one pass of the source file. This has a subtle impact on the
1517 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1519 @node Object Formats
1520 @section Object File Formats
1522 @cindex object file format
1523 The @sc{gnu} assembler can be configured to produce several alternative
1524 object file formats. For the most part, this does not affect how you
1525 write assembly language programs; but directives for debugging symbols
1526 are typically different in different file formats. @xref{Symbol
1527 Attributes,,Symbol Attributes}.
1530 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1531 @value{OBJ-NAME} format object files.
1533 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1535 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1536 @code{b.out} or COFF format object files.
1539 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1540 SOM or ELF format object files.
1545 @section Command Line
1547 @cindex command line conventions
1549 After the program name @command{@value{AS}}, the command line may contain
1550 options and file names. Options may appear in any order, and may be
1551 before, after, or between file names. The order of file names is
1554 @cindex standard input, as input file
1556 @file{--} (two hyphens) by itself names the standard input file
1557 explicitly, as one of the files for @command{@value{AS}} to assemble.
1559 @cindex options, command line
1560 Except for @samp{--} any command line argument that begins with a
1561 hyphen (@samp{-}) is an option. Each option changes the behavior of
1562 @command{@value{AS}}. No option changes the way another option works. An
1563 option is a @samp{-} followed by one or more letters; the case of
1564 the letter is important. All options are optional.
1566 Some options expect exactly one file name to follow them. The file
1567 name may either immediately follow the option's letter (compatible
1568 with older assemblers) or it may be the next command argument (@sc{gnu}
1569 standard). These two command lines are equivalent:
1572 @value{AS} -o my-object-file.o mumble.s
1573 @value{AS} -omy-object-file.o mumble.s
1577 @section Input Files
1580 @cindex source program
1581 @cindex files, input
1582 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1583 describe the program input to one run of @command{@value{AS}}. The program may
1584 be in one or more files; how the source is partitioned into files
1585 doesn't change the meaning of the source.
1587 @c I added "con" prefix to "catenation" just to prove I can overcome my
1588 @c APL training... doc@cygnus.com
1589 The source program is a concatenation of the text in all the files, in the
1592 @c man begin DESCRIPTION
1593 Each time you run @command{@value{AS}} it assembles exactly one source
1594 program. The source program is made up of one or more files.
1595 (The standard input is also a file.)
1597 You give @command{@value{AS}} a command line that has zero or more input file
1598 names. The input files are read (from left file name to right). A
1599 command line argument (in any position) that has no special meaning
1600 is taken to be an input file name.
1602 If you give @command{@value{AS}} no file names it attempts to read one input file
1603 from the @command{@value{AS}} standard input, which is normally your terminal. You
1604 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1607 Use @samp{--} if you need to explicitly name the standard input file
1608 in your command line.
1610 If the source is empty, @command{@value{AS}} produces a small, empty object
1615 @subheading Filenames and Line-numbers
1617 @cindex input file linenumbers
1618 @cindex line numbers, in input files
1619 There are two ways of locating a line in the input file (or files) and
1620 either may be used in reporting error messages. One way refers to a line
1621 number in a physical file; the other refers to a line number in a
1622 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1624 @dfn{Physical files} are those files named in the command line given
1625 to @command{@value{AS}}.
1627 @dfn{Logical files} are simply names declared explicitly by assembler
1628 directives; they bear no relation to physical files. Logical file names help
1629 error messages reflect the original source file, when @command{@value{AS}} source
1630 is itself synthesized from other files. @command{@value{AS}} understands the
1631 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1632 @ref{File,,@code{.file}}.
1635 @section Output (Object) File
1641 Every time you run @command{@value{AS}} it produces an output file, which is
1642 your assembly language program translated into numbers. This file
1643 is the object file. Its default name is
1651 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1653 You can give it another name by using the @option{-o} option. Conventionally,
1654 object file names end with @file{.o}. The default name is used for historical
1655 reasons: older assemblers were capable of assembling self-contained programs
1656 directly into a runnable program. (For some formats, this isn't currently
1657 possible, but it can be done for the @code{a.out} format.)
1661 The object file is meant for input to the linker @code{@value{LD}}. It contains
1662 assembled program code, information to help @code{@value{LD}} integrate
1663 the assembled program into a runnable file, and (optionally) symbolic
1664 information for the debugger.
1666 @c link above to some info file(s) like the description of a.out.
1667 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1670 @section Error and Warning Messages
1672 @c man begin DESCRIPTION
1674 @cindex error messages
1675 @cindex warning messages
1676 @cindex messages from assembler
1677 @command{@value{AS}} may write warnings and error messages to the standard error
1678 file (usually your terminal). This should not happen when a compiler
1679 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1680 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1681 grave problem that stops the assembly.
1685 @cindex format of warning messages
1686 Warning messages have the format
1689 file_name:@b{NNN}:Warning Message Text
1693 @cindex line numbers, in warnings/errors
1694 (where @b{NNN} is a line number). If a logical file name has been given
1695 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1696 the current input file is used. If a logical line number was given
1698 (@pxref{Line,,@code{.line}})
1700 then it is used to calculate the number printed,
1701 otherwise the actual line in the current source file is printed. The
1702 message text is intended to be self explanatory (in the grand Unix
1705 @cindex format of error messages
1706 Error messages have the format
1708 file_name:@b{NNN}:FATAL:Error Message Text
1710 The file name and line number are derived as for warning
1711 messages. The actual message text may be rather less explanatory
1712 because many of them aren't supposed to happen.
1715 @chapter Command-Line Options
1717 @cindex options, all versions of assembler
1718 This chapter describes command-line options available in @emph{all}
1719 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1720 for options specific
1722 to the @value{TARGET} target.
1725 to particular machine architectures.
1728 @c man begin DESCRIPTION
1730 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1731 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1732 The assembler arguments must be separated from each other (and the @samp{-Wa})
1733 by commas. For example:
1736 gcc -c -g -O -Wa,-alh,-L file.c
1740 This passes two options to the assembler: @samp{-alh} (emit a listing to
1741 standard output with high-level and assembly source) and @samp{-L} (retain
1742 local symbols in the symbol table).
1744 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1745 command-line options are automatically passed to the assembler by the compiler.
1746 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1747 precisely what options it passes to each compilation pass, including the
1753 * a:: -a[cdghlns] enable listings
1754 * alternate:: --alternate enable alternate macro syntax
1755 * D:: -D for compatibility
1756 * f:: -f to work faster
1757 * I:: -I for .include search path
1758 @ifclear DIFF-TBL-KLUGE
1759 * K:: -K for compatibility
1761 @ifset DIFF-TBL-KLUGE
1762 * K:: -K for difference tables
1765 * L:: -L to retain local symbols
1766 * listing:: --listing-XXX to configure listing output
1767 * M:: -M or --mri to assemble in MRI compatibility mode
1768 * MD:: --MD for dependency tracking
1769 * o:: -o to name the object file
1770 * R:: -R to join data and text sections
1771 * statistics:: --statistics to see statistics about assembly
1772 * traditional-format:: --traditional-format for compatible output
1773 * v:: -v to announce version
1774 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1775 * Z:: -Z to make object file even after errors
1779 @section Enable Listings: @option{-a[cdghlns]}
1789 @cindex listings, enabling
1790 @cindex assembly listings, enabling
1792 These options enable listing output from the assembler. By itself,
1793 @samp{-a} requests high-level, assembly, and symbols listing.
1794 You can use other letters to select specific options for the list:
1795 @samp{-ah} requests a high-level language listing,
1796 @samp{-al} requests an output-program assembly listing, and
1797 @samp{-as} requests a symbol table listing.
1798 High-level listings require that a compiler debugging option like
1799 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1802 Use the @samp{-ag} option to print a first section with general assembly
1803 information, like @value{AS} version, switches passed, or time stamp.
1805 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1806 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1807 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1808 omitted from the listing.
1810 Use the @samp{-ad} option to omit debugging directives from the
1813 Once you have specified one of these options, you can further control
1814 listing output and its appearance using the directives @code{.list},
1815 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1817 The @samp{-an} option turns off all forms processing.
1818 If you do not request listing output with one of the @samp{-a} options, the
1819 listing-control directives have no effect.
1821 The letters after @samp{-a} may be combined into one option,
1822 @emph{e.g.}, @samp{-aln}.
1824 Note if the assembler source is coming from the standard input (e.g.,
1826 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1827 is being used) then the listing will not contain any comments or preprocessor
1828 directives. This is because the listing code buffers input source lines from
1829 stdin only after they have been preprocessed by the assembler. This reduces
1830 memory usage and makes the code more efficient.
1833 @section @option{--alternate}
1836 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
1839 @section @option{-D}
1842 This option has no effect whatsoever, but it is accepted to make it more
1843 likely that scripts written for other assemblers also work with
1844 @command{@value{AS}}.
1847 @section Work Faster: @option{-f}
1850 @cindex trusted compiler
1851 @cindex faster processing (@option{-f})
1852 @samp{-f} should only be used when assembling programs written by a
1853 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1854 and comment preprocessing on
1855 the input file(s) before assembling them. @xref{Preprocessing,
1859 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1860 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1865 @section @code{.include} Search Path: @option{-I} @var{path}
1867 @kindex -I @var{path}
1868 @cindex paths for @code{.include}
1869 @cindex search path for @code{.include}
1870 @cindex @code{include} directive search path
1871 Use this option to add a @var{path} to the list of directories
1872 @command{@value{AS}} searches for files specified in @code{.include}
1873 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1874 many times as necessary to include a variety of paths. The current
1875 working directory is always searched first; after that, @command{@value{AS}}
1876 searches any @samp{-I} directories in the same order as they were
1877 specified (left to right) on the command line.
1880 @section Difference Tables: @option{-K}
1883 @ifclear DIFF-TBL-KLUGE
1884 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1885 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1886 where it can be used to warn when the assembler alters the machine code
1887 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1888 family does not have the addressing limitations that sometimes lead to this
1889 alteration on other platforms.
1892 @ifset DIFF-TBL-KLUGE
1893 @cindex difference tables, warning
1894 @cindex warning for altered difference tables
1895 @command{@value{AS}} sometimes alters the code emitted for directives of the
1896 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
1897 You can use the @samp{-K} option if you want a warning issued when this
1902 @section Include Local Symbols: @option{-L}
1905 @cindex local symbols, retaining in output
1906 Symbols beginning with system-specific local label prefixes, typically
1907 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
1908 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
1909 such symbols when debugging, because they are intended for the use of
1910 programs (like compilers) that compose assembler programs, not for your
1911 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
1912 such symbols, so you do not normally debug with them.
1914 This option tells @command{@value{AS}} to retain those local symbols
1915 in the object file. Usually if you do this you also tell the linker
1916 @code{@value{LD}} to preserve those symbols.
1919 @section Configuring listing output: @option{--listing}
1921 The listing feature of the assembler can be enabled via the command line switch
1922 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1923 hex dump of the corresponding locations in the output object file, and displays
1924 them as a listing file. The format of this listing can be controlled by
1925 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
1926 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
1927 @code{.psize} (@pxref{Psize}), and
1928 @code{.eject} (@pxref{Eject}) and also by the following switches:
1931 @item --listing-lhs-width=@samp{number}
1932 @kindex --listing-lhs-width
1933 @cindex Width of first line disassembly output
1934 Sets the maximum width, in words, of the first line of the hex byte dump. This
1935 dump appears on the left hand side of the listing output.
1937 @item --listing-lhs-width2=@samp{number}
1938 @kindex --listing-lhs-width2
1939 @cindex Width of continuation lines of disassembly output
1940 Sets the maximum width, in words, of any further lines of the hex byte dump for
1941 a given input source line. If this value is not specified, it defaults to being
1942 the same as the value specified for @samp{--listing-lhs-width}. If neither
1943 switch is used the default is to one.
1945 @item --listing-rhs-width=@samp{number}
1946 @kindex --listing-rhs-width
1947 @cindex Width of source line output
1948 Sets the maximum width, in characters, of the source line that is displayed
1949 alongside the hex dump. The default value for this parameter is 100. The
1950 source line is displayed on the right hand side of the listing output.
1952 @item --listing-cont-lines=@samp{number}
1953 @kindex --listing-cont-lines
1954 @cindex Maximum number of continuation lines
1955 Sets the maximum number of continuation lines of hex dump that will be
1956 displayed for a given single line of source input. The default value is 4.
1960 @section Assemble in MRI Compatibility Mode: @option{-M}
1963 @cindex MRI compatibility mode
1964 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1965 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1966 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1967 configured target) assembler from Microtec Research. The exact nature of the
1968 MRI syntax will not be documented here; see the MRI manuals for more
1969 information. Note in particular that the handling of macros and macro
1970 arguments is somewhat different. The purpose of this option is to permit
1971 assembling existing MRI assembler code using @command{@value{AS}}.
1973 The MRI compatibility is not complete. Certain operations of the MRI assembler
1974 depend upon its object file format, and can not be supported using other object
1975 file formats. Supporting these would require enhancing each object file format
1976 individually. These are:
1979 @item global symbols in common section
1981 The m68k MRI assembler supports common sections which are merged by the linker.
1982 Other object file formats do not support this. @command{@value{AS}} handles
1983 common sections by treating them as a single common symbol. It permits local
1984 symbols to be defined within a common section, but it can not support global
1985 symbols, since it has no way to describe them.
1987 @item complex relocations
1989 The MRI assemblers support relocations against a negated section address, and
1990 relocations which combine the start addresses of two or more sections. These
1991 are not support by other object file formats.
1993 @item @code{END} pseudo-op specifying start address
1995 The MRI @code{END} pseudo-op permits the specification of a start address.
1996 This is not supported by other object file formats. The start address may
1997 instead be specified using the @option{-e} option to the linker, or in a linker
2000 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2002 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2003 name to the output file. This is not supported by other object file formats.
2005 @item @code{ORG} pseudo-op
2007 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2008 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2009 which changes the location within the current section. Absolute sections are
2010 not supported by other object file formats. The address of a section may be
2011 assigned within a linker script.
2014 There are some other features of the MRI assembler which are not supported by
2015 @command{@value{AS}}, typically either because they are difficult or because they
2016 seem of little consequence. Some of these may be supported in future releases.
2020 @item EBCDIC strings
2022 EBCDIC strings are not supported.
2024 @item packed binary coded decimal
2026 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2027 and @code{DCB.P} pseudo-ops are not supported.
2029 @item @code{FEQU} pseudo-op
2031 The m68k @code{FEQU} pseudo-op is not supported.
2033 @item @code{NOOBJ} pseudo-op
2035 The m68k @code{NOOBJ} pseudo-op is not supported.
2037 @item @code{OPT} branch control options
2039 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2040 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2041 relaxes all branches, whether forward or backward, to an appropriate size, so
2042 these options serve no purpose.
2044 @item @code{OPT} list control options
2046 The following m68k @code{OPT} list control options are ignored: @code{C},
2047 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2048 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2050 @item other @code{OPT} options
2052 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2053 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2055 @item @code{OPT} @code{D} option is default
2057 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2058 @code{OPT NOD} may be used to turn it off.
2060 @item @code{XREF} pseudo-op.
2062 The m68k @code{XREF} pseudo-op is ignored.
2064 @item @code{.debug} pseudo-op
2066 The i960 @code{.debug} pseudo-op is not supported.
2068 @item @code{.extended} pseudo-op
2070 The i960 @code{.extended} pseudo-op is not supported.
2072 @item @code{.list} pseudo-op.
2074 The various options of the i960 @code{.list} pseudo-op are not supported.
2076 @item @code{.optimize} pseudo-op
2078 The i960 @code{.optimize} pseudo-op is not supported.
2080 @item @code{.output} pseudo-op
2082 The i960 @code{.output} pseudo-op is not supported.
2084 @item @code{.setreal} pseudo-op
2086 The i960 @code{.setreal} pseudo-op is not supported.
2091 @section Dependency Tracking: @option{--MD}
2094 @cindex dependency tracking
2097 @command{@value{AS}} can generate a dependency file for the file it creates. This
2098 file consists of a single rule suitable for @code{make} describing the
2099 dependencies of the main source file.
2101 The rule is written to the file named in its argument.
2103 This feature is used in the automatic updating of makefiles.
2106 @section Name the Object File: @option{-o}
2109 @cindex naming object file
2110 @cindex object file name
2111 There is always one object file output when you run @command{@value{AS}}. By
2112 default it has the name
2115 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2129 You use this option (which takes exactly one filename) to give the
2130 object file a different name.
2132 Whatever the object file is called, @command{@value{AS}} overwrites any
2133 existing file of the same name.
2136 @section Join Data and Text Sections: @option{-R}
2139 @cindex data and text sections, joining
2140 @cindex text and data sections, joining
2141 @cindex joining text and data sections
2142 @cindex merging text and data sections
2143 @option{-R} tells @command{@value{AS}} to write the object file as if all
2144 data-section data lives in the text section. This is only done at
2145 the very last moment: your binary data are the same, but data
2146 section parts are relocated differently. The data section part of
2147 your object file is zero bytes long because all its bytes are
2148 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2150 When you specify @option{-R} it would be possible to generate shorter
2151 address displacements (because we do not have to cross between text and
2152 data section). We refrain from doing this simply for compatibility with
2153 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2156 When @command{@value{AS}} is configured for COFF or ELF output,
2157 this option is only useful if you use sections named @samp{.text} and
2162 @option{-R} is not supported for any of the HPPA targets. Using
2163 @option{-R} generates a warning from @command{@value{AS}}.
2167 @section Display Assembly Statistics: @option{--statistics}
2169 @kindex --statistics
2170 @cindex statistics, about assembly
2171 @cindex time, total for assembly
2172 @cindex space used, maximum for assembly
2173 Use @samp{--statistics} to display two statistics about the resources used by
2174 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2175 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2178 @node traditional-format
2179 @section Compatible Output: @option{--traditional-format}
2181 @kindex --traditional-format
2182 For some targets, the output of @command{@value{AS}} is different in some ways
2183 from the output of some existing assembler. This switch requests
2184 @command{@value{AS}} to use the traditional format instead.
2186 For example, it disables the exception frame optimizations which
2187 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2190 @section Announce Version: @option{-v}
2194 @cindex assembler version
2195 @cindex version of assembler
2196 You can find out what version of as is running by including the
2197 option @samp{-v} (which you can also spell as @samp{-version}) on the
2201 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2203 @command{@value{AS}} should never give a warning or error message when
2204 assembling compiler output. But programs written by people often
2205 cause @command{@value{AS}} to give a warning that a particular assumption was
2206 made. All such warnings are directed to the standard error file.
2210 @cindex suppressing warnings
2211 @cindex warnings, suppressing
2212 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2213 This only affects the warning messages: it does not change any particular of
2214 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2217 @kindex --fatal-warnings
2218 @cindex errors, caused by warnings
2219 @cindex warnings, causing error
2220 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2221 files that generate warnings to be in error.
2224 @cindex warnings, switching on
2225 You can switch these options off again by specifying @option{--warn}, which
2226 causes warnings to be output as usual.
2229 @section Generate Object File in Spite of Errors: @option{-Z}
2230 @cindex object file, after errors
2231 @cindex errors, continuing after
2232 After an error message, @command{@value{AS}} normally produces no output. If for
2233 some reason you are interested in object file output even after
2234 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2235 option. If there are any errors, @command{@value{AS}} continues anyways, and
2236 writes an object file after a final warning message of the form @samp{@var{n}
2237 errors, @var{m} warnings, generating bad object file.}
2242 @cindex machine-independent syntax
2243 @cindex syntax, machine-independent
2244 This chapter describes the machine-independent syntax allowed in a
2245 source file. @command{@value{AS}} syntax is similar to what many other
2246 assemblers use; it is inspired by the BSD 4.2
2251 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2255 * Preprocessing:: Preprocessing
2256 * Whitespace:: Whitespace
2257 * Comments:: Comments
2258 * Symbol Intro:: Symbols
2259 * Statements:: Statements
2260 * Constants:: Constants
2264 @section Preprocessing
2266 @cindex preprocessing
2267 The @command{@value{AS}} internal preprocessor:
2269 @cindex whitespace, removed by preprocessor
2271 adjusts and removes extra whitespace. It leaves one space or tab before
2272 the keywords on a line, and turns any other whitespace on the line into
2275 @cindex comments, removed by preprocessor
2277 removes all comments, replacing them with a single space, or an
2278 appropriate number of newlines.
2280 @cindex constants, converted by preprocessor
2282 converts character constants into the appropriate numeric values.
2285 It does not do macro processing, include file handling, or
2286 anything else you may get from your C compiler's preprocessor. You can
2287 do include file processing with the @code{.include} directive
2288 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2289 to get other ``CPP'' style preprocessing by giving the input file a
2290 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2291 Output, gcc.info, Using GNU CC}.
2293 Excess whitespace, comments, and character constants
2294 cannot be used in the portions of the input text that are not
2297 @cindex turning preprocessing on and off
2298 @cindex preprocessing, turning on and off
2301 If the first line of an input file is @code{#NO_APP} or if you use the
2302 @samp{-f} option, whitespace and comments are not removed from the input file.
2303 Within an input file, you can ask for whitespace and comment removal in
2304 specific portions of the by putting a line that says @code{#APP} before the
2305 text that may contain whitespace or comments, and putting a line that says
2306 @code{#NO_APP} after this text. This feature is mainly intend to support
2307 @code{asm} statements in compilers whose output is otherwise free of comments
2314 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2315 Whitespace is used to separate symbols, and to make programs neater for
2316 people to read. Unless within character constants
2317 (@pxref{Characters,,Character Constants}), any whitespace means the same
2318 as exactly one space.
2324 There are two ways of rendering comments to @command{@value{AS}}. In both
2325 cases the comment is equivalent to one space.
2327 Anything from @samp{/*} through the next @samp{*/} is a comment.
2328 This means you may not nest these comments.
2332 The only way to include a newline ('\n') in a comment
2333 is to use this sort of comment.
2336 /* This sort of comment does not nest. */
2339 @cindex line comment character
2340 Anything from the @dfn{line comment} character to the next newline
2341 is considered a comment and is ignored. The line comment character is
2343 @samp{;} on the ARC;
2346 @samp{@@} on the ARM;
2349 @samp{;} for the H8/300 family;
2352 @samp{;} for the HPPA;
2355 @samp{#} on the i386 and x86-64;
2358 @samp{#} on the i960;
2361 @samp{;} for the PDP-11;
2364 @samp{;} for picoJava;
2367 @samp{#} for Motorola PowerPC;
2370 @samp{#} for IBM S/390;
2373 @samp{#} for the Sunplus SCORE;
2376 @samp{!} for the Renesas / SuperH SH;
2379 @samp{!} on the SPARC;
2382 @samp{#} on the ip2k;
2385 @samp{#} on the m32c;
2388 @samp{#} on the m32r;
2391 @samp{|} on the 680x0;
2394 @samp{#} on the 68HC11 and 68HC12;
2400 @samp{;} on the TMS320C6X;
2403 @samp{#} on the Vax;
2406 @samp{;} for the Z80;
2409 @samp{!} for the Z8000;
2412 @samp{#} on the V850;
2415 @samp{#} for Xtensa systems;
2417 see @ref{Machine Dependencies}. @refill
2418 @c FIXME What about i860?
2421 On some machines there are two different line comment characters. One
2422 character only begins a comment if it is the first non-whitespace character on
2423 a line, while the other always begins a comment.
2427 The V850 assembler also supports a double dash as starting a comment that
2428 extends to the end of the line.
2434 @cindex lines starting with @code{#}
2435 @cindex logical line numbers
2436 To be compatible with past assemblers, lines that begin with @samp{#} have a
2437 special interpretation. Following the @samp{#} should be an absolute
2438 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2439 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2440 new logical file name. The rest of the line, if any, should be whitespace.
2442 If the first non-whitespace characters on the line are not numeric,
2443 the line is ignored. (Just like a comment.)
2446 # This is an ordinary comment.
2447 # 42-6 "new_file_name" # New logical file name
2448 # This is logical line # 36.
2450 This feature is deprecated, and may disappear from future versions
2451 of @command{@value{AS}}.
2456 @cindex characters used in symbols
2457 @ifclear SPECIAL-SYMS
2458 A @dfn{symbol} is one or more characters chosen from the set of all
2459 letters (both upper and lower case), digits and the three characters
2465 A @dfn{symbol} is one or more characters chosen from the set of all
2466 letters (both upper and lower case), digits and the three characters
2467 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2473 On most machines, you can also use @code{$} in symbol names; exceptions
2474 are noted in @ref{Machine Dependencies}.
2476 No symbol may begin with a digit. Case is significant.
2477 There is no length limit: all characters are significant. Symbols are
2478 delimited by characters not in that set, or by the beginning of a file
2479 (since the source program must end with a newline, the end of a file is
2480 not a possible symbol delimiter). @xref{Symbols}.
2481 @cindex length of symbols
2486 @cindex statements, structure of
2487 @cindex line separator character
2488 @cindex statement separator character
2490 @ifclear abnormal-separator
2491 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2492 semicolon (@samp{;}). The newline or semicolon is considered part of
2493 the preceding statement. Newlines and semicolons within character
2494 constants are an exception: they do not end statements.
2496 @ifset abnormal-separator
2498 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2499 point (@samp{!}). The newline or exclamation point is considered part of the
2500 preceding statement. Newlines and exclamation points within character
2501 constants are an exception: they do not end statements.
2504 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2505 H8/300) a dollar sign (@samp{$}); or (for the Renesas-SH) a semicolon
2506 (@samp{;}). The newline or separator character is considered part of
2507 the preceding statement. Newlines and separators within character
2508 constants are an exception: they do not end statements.
2513 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2514 separator character. (The line separator is usually @samp{;}, unless this
2515 conflicts with the comment character; see @ref{Machine Dependencies}.) The
2516 newline or separator character is considered part of the preceding
2517 statement. Newlines and separators within character constants are an
2518 exception: they do not end statements.
2521 @cindex newline, required at file end
2522 @cindex EOF, newline must precede
2523 It is an error to end any statement with end-of-file: the last
2524 character of any input file should be a newline.@refill
2526 An empty statement is allowed, and may include whitespace. It is ignored.
2528 @cindex instructions and directives
2529 @cindex directives and instructions
2530 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2531 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2533 A statement begins with zero or more labels, optionally followed by a
2534 key symbol which determines what kind of statement it is. The key
2535 symbol determines the syntax of the rest of the statement. If the
2536 symbol begins with a dot @samp{.} then the statement is an assembler
2537 directive: typically valid for any computer. If the symbol begins with
2538 a letter the statement is an assembly language @dfn{instruction}: it
2539 assembles into a machine language instruction.
2541 Different versions of @command{@value{AS}} for different computers
2542 recognize different instructions. In fact, the same symbol may
2543 represent a different instruction in a different computer's assembly
2547 @cindex @code{:} (label)
2548 @cindex label (@code{:})
2549 A label is a symbol immediately followed by a colon (@code{:}).
2550 Whitespace before a label or after a colon is permitted, but you may not
2551 have whitespace between a label's symbol and its colon. @xref{Labels}.
2554 For HPPA targets, labels need not be immediately followed by a colon, but
2555 the definition of a label must begin in column zero. This also implies that
2556 only one label may be defined on each line.
2560 label: .directive followed by something
2561 another_label: # This is an empty statement.
2562 instruction operand_1, operand_2, @dots{}
2569 A constant is a number, written so that its value is known by
2570 inspection, without knowing any context. Like this:
2573 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2574 .ascii "Ring the bell\7" # A string constant.
2575 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2576 .float 0f-314159265358979323846264338327\
2577 95028841971.693993751E-40 # - pi, a flonum.
2582 * Characters:: Character Constants
2583 * Numbers:: Number Constants
2587 @subsection Character Constants
2589 @cindex character constants
2590 @cindex constants, character
2591 There are two kinds of character constants. A @dfn{character} stands
2592 for one character in one byte and its value may be used in
2593 numeric expressions. String constants (properly called string
2594 @emph{literals}) are potentially many bytes and their values may not be
2595 used in arithmetic expressions.
2599 * Chars:: Characters
2603 @subsubsection Strings
2605 @cindex string constants
2606 @cindex constants, string
2607 A @dfn{string} is written between double-quotes. It may contain
2608 double-quotes or null characters. The way to get special characters
2609 into a string is to @dfn{escape} these characters: precede them with
2610 a backslash @samp{\} character. For example @samp{\\} represents
2611 one backslash: the first @code{\} is an escape which tells
2612 @command{@value{AS}} to interpret the second character literally as a backslash
2613 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2614 escape character). The complete list of escapes follows.
2616 @cindex escape codes, character
2617 @cindex character escape codes
2620 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2622 @cindex @code{\b} (backspace character)
2623 @cindex backspace (@code{\b})
2625 Mnemonic for backspace; for ASCII this is octal code 010.
2628 @c Mnemonic for EOText; for ASCII this is octal code 004.
2630 @cindex @code{\f} (formfeed character)
2631 @cindex formfeed (@code{\f})
2633 Mnemonic for FormFeed; for ASCII this is octal code 014.
2635 @cindex @code{\n} (newline character)
2636 @cindex newline (@code{\n})
2638 Mnemonic for newline; for ASCII this is octal code 012.
2641 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2643 @cindex @code{\r} (carriage return character)
2644 @cindex carriage return (@code{\r})
2646 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2649 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2650 @c other assemblers.
2652 @cindex @code{\t} (tab)
2653 @cindex tab (@code{\t})
2655 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2658 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2659 @c @item \x @var{digit} @var{digit} @var{digit}
2660 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2662 @cindex @code{\@var{ddd}} (octal character code)
2663 @cindex octal character code (@code{\@var{ddd}})
2664 @item \ @var{digit} @var{digit} @var{digit}
2665 An octal character code. The numeric code is 3 octal digits.
2666 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2667 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2669 @cindex @code{\@var{xd...}} (hex character code)
2670 @cindex hex character code (@code{\@var{xd...}})
2671 @item \@code{x} @var{hex-digits...}
2672 A hex character code. All trailing hex digits are combined. Either upper or
2673 lower case @code{x} works.
2675 @cindex @code{\\} (@samp{\} character)
2676 @cindex backslash (@code{\\})
2678 Represents one @samp{\} character.
2681 @c Represents one @samp{'} (accent acute) character.
2682 @c This is needed in single character literals
2683 @c (@xref{Characters,,Character Constants}.) to represent
2686 @cindex @code{\"} (doublequote character)
2687 @cindex doublequote (@code{\"})
2689 Represents one @samp{"} character. Needed in strings to represent
2690 this character, because an unescaped @samp{"} would end the string.
2692 @item \ @var{anything-else}
2693 Any other character when escaped by @kbd{\} gives a warning, but
2694 assembles as if the @samp{\} was not present. The idea is that if
2695 you used an escape sequence you clearly didn't want the literal
2696 interpretation of the following character. However @command{@value{AS}} has no
2697 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2698 code and warns you of the fact.
2701 Which characters are escapable, and what those escapes represent,
2702 varies widely among assemblers. The current set is what we think
2703 the BSD 4.2 assembler recognizes, and is a subset of what most C
2704 compilers recognize. If you are in doubt, do not use an escape
2708 @subsubsection Characters
2710 @cindex single character constant
2711 @cindex character, single
2712 @cindex constant, single character
2713 A single character may be written as a single quote immediately
2714 followed by that character. The same escapes apply to characters as
2715 to strings. So if you want to write the character backslash, you
2716 must write @kbd{'\\} where the first @code{\} escapes the second
2717 @code{\}. As you can see, the quote is an acute accent, not a
2718 grave accent. A newline
2720 @ifclear abnormal-separator
2721 (or semicolon @samp{;})
2723 @ifset abnormal-separator
2725 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2730 immediately following an acute accent is taken as a literal character
2731 and does not count as the end of a statement. The value of a character
2732 constant in a numeric expression is the machine's byte-wide code for
2733 that character. @command{@value{AS}} assumes your character code is ASCII:
2734 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2737 @subsection Number Constants
2739 @cindex constants, number
2740 @cindex number constants
2741 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2742 are stored in the target machine. @emph{Integers} are numbers that
2743 would fit into an @code{int} in the C language. @emph{Bignums} are
2744 integers, but they are stored in more than 32 bits. @emph{Flonums}
2745 are floating point numbers, described below.
2748 * Integers:: Integers
2753 * Bit Fields:: Bit Fields
2759 @subsubsection Integers
2761 @cindex constants, integer
2763 @cindex binary integers
2764 @cindex integers, binary
2765 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2766 the binary digits @samp{01}.
2768 @cindex octal integers
2769 @cindex integers, octal
2770 An octal integer is @samp{0} followed by zero or more of the octal
2771 digits (@samp{01234567}).
2773 @cindex decimal integers
2774 @cindex integers, decimal
2775 A decimal integer starts with a non-zero digit followed by zero or
2776 more digits (@samp{0123456789}).
2778 @cindex hexadecimal integers
2779 @cindex integers, hexadecimal
2780 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2781 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2783 Integers have the usual values. To denote a negative integer, use
2784 the prefix operator @samp{-} discussed under expressions
2785 (@pxref{Prefix Ops,,Prefix Operators}).
2788 @subsubsection Bignums
2791 @cindex constants, bignum
2792 A @dfn{bignum} has the same syntax and semantics as an integer
2793 except that the number (or its negative) takes more than 32 bits to
2794 represent in binary. The distinction is made because in some places
2795 integers are permitted while bignums are not.
2798 @subsubsection Flonums
2800 @cindex floating point numbers
2801 @cindex constants, floating point
2803 @cindex precision, floating point
2804 A @dfn{flonum} represents a floating point number. The translation is
2805 indirect: a decimal floating point number from the text is converted by
2806 @command{@value{AS}} to a generic binary floating point number of more than
2807 sufficient precision. This generic floating point number is converted
2808 to a particular computer's floating point format (or formats) by a
2809 portion of @command{@value{AS}} specialized to that computer.
2811 A flonum is written by writing (in order)
2816 (@samp{0} is optional on the HPPA.)
2820 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2822 @kbd{e} is recommended. Case is not important.
2824 @c FIXME: verify if flonum syntax really this vague for most cases
2825 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2826 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2829 On the H8/300, Renesas / SuperH SH,
2830 and AMD 29K architectures, the letter must be
2831 one of the letters @samp{DFPRSX} (in upper or lower case).
2833 On the ARC, the letter must be one of the letters @samp{DFRS}
2834 (in upper or lower case).
2836 On the Intel 960 architecture, the letter must be
2837 one of the letters @samp{DFT} (in upper or lower case).
2839 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2843 One of the letters @samp{DFRS} (in upper or lower case).
2846 One of the letters @samp{DFPRSX} (in upper or lower case).
2849 The letter @samp{E} (upper case only).
2852 One of the letters @samp{DFT} (in upper or lower case).
2857 An optional sign: either @samp{+} or @samp{-}.
2860 An optional @dfn{integer part}: zero or more decimal digits.
2863 An optional @dfn{fractional part}: @samp{.} followed by zero
2864 or more decimal digits.
2867 An optional exponent, consisting of:
2871 An @samp{E} or @samp{e}.
2872 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2873 @c principle this can perfectly well be different on different targets.
2875 Optional sign: either @samp{+} or @samp{-}.
2877 One or more decimal digits.
2882 At least one of the integer part or the fractional part must be
2883 present. The floating point number has the usual base-10 value.
2885 @command{@value{AS}} does all processing using integers. Flonums are computed
2886 independently of any floating point hardware in the computer running
2887 @command{@value{AS}}.
2891 @c Bit fields are written as a general facility but are also controlled
2892 @c by a conditional-compilation flag---which is as of now (21mar91)
2893 @c turned on only by the i960 config of GAS.
2895 @subsubsection Bit Fields
2898 @cindex constants, bit field
2899 You can also define numeric constants as @dfn{bit fields}.
2900 Specify two numbers separated by a colon---
2902 @var{mask}:@var{value}
2905 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2908 The resulting number is then packed
2910 @c this conditional paren in case bit fields turned on elsewhere than 960
2911 (in host-dependent byte order)
2913 into a field whose width depends on which assembler directive has the
2914 bit-field as its argument. Overflow (a result from the bitwise and
2915 requiring more binary digits to represent) is not an error; instead,
2916 more constants are generated, of the specified width, beginning with the
2917 least significant digits.@refill
2919 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2920 @code{.short}, and @code{.word} accept bit-field arguments.
2925 @chapter Sections and Relocation
2930 * Secs Background:: Background
2931 * Ld Sections:: Linker Sections
2932 * As Sections:: Assembler Internal Sections
2933 * Sub-Sections:: Sub-Sections
2937 @node Secs Background
2940 Roughly, a section is a range of addresses, with no gaps; all data
2941 ``in'' those addresses is treated the same for some particular purpose.
2942 For example there may be a ``read only'' section.
2944 @cindex linker, and assembler
2945 @cindex assembler, and linker
2946 The linker @code{@value{LD}} reads many object files (partial programs) and
2947 combines their contents to form a runnable program. When @command{@value{AS}}
2948 emits an object file, the partial program is assumed to start at address 0.
2949 @code{@value{LD}} assigns the final addresses for the partial program, so that
2950 different partial programs do not overlap. This is actually an
2951 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2954 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2955 addresses. These blocks slide to their run-time addresses as rigid
2956 units; their length does not change and neither does the order of bytes
2957 within them. Such a rigid unit is called a @emph{section}. Assigning
2958 run-time addresses to sections is called @dfn{relocation}. It includes
2959 the task of adjusting mentions of object-file addresses so they refer to
2960 the proper run-time addresses.
2962 For the H8/300, and for the Renesas / SuperH SH,
2963 @command{@value{AS}} pads sections if needed to
2964 ensure they end on a word (sixteen bit) boundary.
2967 @cindex standard assembler sections
2968 An object file written by @command{@value{AS}} has at least three sections, any
2969 of which may be empty. These are named @dfn{text}, @dfn{data} and
2974 When it generates COFF or ELF output,
2976 @command{@value{AS}} can also generate whatever other named sections you specify
2977 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2978 If you do not use any directives that place output in the @samp{.text}
2979 or @samp{.data} sections, these sections still exist, but are empty.
2984 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2986 @command{@value{AS}} can also generate whatever other named sections you
2987 specify using the @samp{.space} and @samp{.subspace} directives. See
2988 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2989 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2990 assembler directives.
2993 Additionally, @command{@value{AS}} uses different names for the standard
2994 text, data, and bss sections when generating SOM output. Program text
2995 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2996 BSS into @samp{$BSS$}.
3000 Within the object file, the text section starts at address @code{0}, the
3001 data section follows, and the bss section follows the data section.
3004 When generating either SOM or ELF output files on the HPPA, the text
3005 section starts at address @code{0}, the data section at address
3006 @code{0x4000000}, and the bss section follows the data section.
3009 To let @code{@value{LD}} know which data changes when the sections are
3010 relocated, and how to change that data, @command{@value{AS}} also writes to the
3011 object file details of the relocation needed. To perform relocation
3012 @code{@value{LD}} must know, each time an address in the object
3016 Where in the object file is the beginning of this reference to
3019 How long (in bytes) is this reference?
3021 Which section does the address refer to? What is the numeric value of
3023 (@var{address}) @minus{} (@var{start-address of section})?
3026 Is the reference to an address ``Program-Counter relative''?
3029 @cindex addresses, format of
3030 @cindex section-relative addressing
3031 In fact, every address @command{@value{AS}} ever uses is expressed as
3033 (@var{section}) + (@var{offset into section})
3036 Further, most expressions @command{@value{AS}} computes have this section-relative
3039 (For some object formats, such as SOM for the HPPA, some expressions are
3040 symbol-relative instead.)
3043 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3044 @var{N} into section @var{secname}.''
3046 Apart from text, data and bss sections you need to know about the
3047 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3048 addresses in the absolute section remain unchanged. For example, address
3049 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3050 @code{@value{LD}}. Although the linker never arranges two partial programs'
3051 data sections with overlapping addresses after linking, @emph{by definition}
3052 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3053 part of a program is always the same address when the program is running as
3054 address @code{@{absolute@ 239@}} in any other part of the program.
3056 The idea of sections is extended to the @dfn{undefined} section. Any
3057 address whose section is unknown at assembly time is by definition
3058 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3059 Since numbers are always defined, the only way to generate an undefined
3060 address is to mention an undefined symbol. A reference to a named
3061 common block would be such a symbol: its value is unknown at assembly
3062 time so it has section @emph{undefined}.
3064 By analogy the word @emph{section} is used to describe groups of sections in
3065 the linked program. @code{@value{LD}} puts all partial programs' text
3066 sections in contiguous addresses in the linked program. It is
3067 customary to refer to the @emph{text section} of a program, meaning all
3068 the addresses of all partial programs' text sections. Likewise for
3069 data and bss sections.
3071 Some sections are manipulated by @code{@value{LD}}; others are invented for
3072 use of @command{@value{AS}} and have no meaning except during assembly.
3075 @section Linker Sections
3076 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3081 @cindex named sections
3082 @cindex sections, named
3083 @item named sections
3086 @cindex text section
3087 @cindex data section
3091 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3092 separate but equal sections. Anything you can say of one section is
3095 When the program is running, however, it is
3096 customary for the text section to be unalterable. The
3097 text section is often shared among processes: it contains
3098 instructions, constants and the like. The data section of a running
3099 program is usually alterable: for example, C variables would be stored
3100 in the data section.
3105 This section contains zeroed bytes when your program begins running. It
3106 is used to hold uninitialized variables or common storage. The length of
3107 each partial program's bss section is important, but because it starts
3108 out containing zeroed bytes there is no need to store explicit zero
3109 bytes in the object file. The bss section was invented to eliminate
3110 those explicit zeros from object files.
3112 @cindex absolute section
3113 @item absolute section
3114 Address 0 of this section is always ``relocated'' to runtime address 0.
3115 This is useful if you want to refer to an address that @code{@value{LD}} must
3116 not change when relocating. In this sense we speak of absolute
3117 addresses being ``unrelocatable'': they do not change during relocation.
3119 @cindex undefined section
3120 @item undefined section
3121 This ``section'' is a catch-all for address references to objects not in
3122 the preceding sections.
3123 @c FIXME: ref to some other doc on obj-file formats could go here.
3126 @cindex relocation example
3127 An idealized example of three relocatable sections follows.
3129 The example uses the traditional section names @samp{.text} and @samp{.data}.
3131 Memory addresses are on the horizontal axis.
3135 @c END TEXI2ROFF-KILL
3138 partial program # 1: |ttttt|dddd|00|
3145 partial program # 2: |TTT|DDD|000|
3148 +--+---+-----+--+----+---+-----+~~
3149 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3150 +--+---+-----+--+----+---+-----+~~
3152 addresses: 0 @dots{}
3159 \line{\it Partial program \#1: \hfil}
3160 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3161 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3163 \line{\it Partial program \#2: \hfil}
3164 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3165 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3167 \line{\it linked program: \hfil}
3168 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3169 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3170 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3171 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3173 \line{\it addresses: \hfil}
3177 @c END TEXI2ROFF-KILL
3180 @section Assembler Internal Sections
3182 @cindex internal assembler sections
3183 @cindex sections in messages, internal
3184 These sections are meant only for the internal use of @command{@value{AS}}. They
3185 have no meaning at run-time. You do not really need to know about these
3186 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3187 warning messages, so it might be helpful to have an idea of their
3188 meanings to @command{@value{AS}}. These sections are used to permit the
3189 value of every expression in your assembly language program to be a
3190 section-relative address.
3193 @cindex assembler internal logic error
3194 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3195 An internal assembler logic error has been found. This means there is a
3196 bug in the assembler.
3198 @cindex expr (internal section)
3200 The assembler stores complex expression internally as combinations of
3201 symbols. When it needs to represent an expression as a symbol, it puts
3202 it in the expr section.
3204 @c FIXME item transfer[t] vector preload
3205 @c FIXME item transfer[t] vector postload
3206 @c FIXME item register
3210 @section Sub-Sections
3212 @cindex numbered subsections
3213 @cindex grouping data
3219 fall into two sections: text and data.
3221 You may have separate groups of
3223 data in named sections
3227 data in named sections
3233 that you want to end up near to each other in the object file, even though they
3234 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3235 use @dfn{subsections} for this purpose. Within each section, there can be
3236 numbered subsections with values from 0 to 8192. Objects assembled into the
3237 same subsection go into the object file together with other objects in the same
3238 subsection. For example, a compiler might want to store constants in the text
3239 section, but might not want to have them interspersed with the program being
3240 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3241 section of code being output, and a @samp{.text 1} before each group of
3242 constants being output.
3244 Subsections are optional. If you do not use subsections, everything
3245 goes in subsection number zero.
3248 Each subsection is zero-padded up to a multiple of four bytes.
3249 (Subsections may be padded a different amount on different flavors
3250 of @command{@value{AS}}.)
3254 On the H8/300 platform, each subsection is zero-padded to a word
3255 boundary (two bytes).
3256 The same is true on the Renesas SH.
3259 @c FIXME section padding (alignment)?
3260 @c Rich Pixley says padding here depends on target obj code format; that
3261 @c doesn't seem particularly useful to say without further elaboration,
3262 @c so for now I say nothing about it. If this is a generic BFD issue,
3263 @c these paragraphs might need to vanish from this manual, and be
3264 @c discussed in BFD chapter of binutils (or some such).
3268 Subsections appear in your object file in numeric order, lowest numbered
3269 to highest. (All this to be compatible with other people's assemblers.)
3270 The object file contains no representation of subsections; @code{@value{LD}} and
3271 other programs that manipulate object files see no trace of them.
3272 They just see all your text subsections as a text section, and all your
3273 data subsections as a data section.
3275 To specify which subsection you want subsequent statements assembled
3276 into, use a numeric argument to specify it, in a @samp{.text
3277 @var{expression}} or a @samp{.data @var{expression}} statement.
3280 When generating COFF output, you
3285 can also use an extra subsection
3286 argument with arbitrary named sections: @samp{.section @var{name},
3291 When generating ELF output, you
3296 can also use the @code{.subsection} directive (@pxref{SubSection})
3297 to specify a subsection: @samp{.subsection @var{expression}}.
3299 @var{Expression} should be an absolute expression
3300 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3301 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3302 begins in @code{text 0}. For instance:
3304 .text 0 # The default subsection is text 0 anyway.
3305 .ascii "This lives in the first text subsection. *"
3307 .ascii "But this lives in the second text subsection."
3309 .ascii "This lives in the data section,"
3310 .ascii "in the first data subsection."
3312 .ascii "This lives in the first text section,"
3313 .ascii "immediately following the asterisk (*)."
3316 Each section has a @dfn{location counter} incremented by one for every byte
3317 assembled into that section. Because subsections are merely a convenience
3318 restricted to @command{@value{AS}} there is no concept of a subsection location
3319 counter. There is no way to directly manipulate a location counter---but the
3320 @code{.align} directive changes it, and any label definition captures its
3321 current value. The location counter of the section where statements are being
3322 assembled is said to be the @dfn{active} location counter.
3325 @section bss Section
3328 @cindex common variable storage
3329 The bss section is used for local common variable storage.
3330 You may allocate address space in the bss section, but you may
3331 not dictate data to load into it before your program executes. When
3332 your program starts running, all the contents of the bss
3333 section are zeroed bytes.
3335 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3336 @ref{Lcomm,,@code{.lcomm}}.
3338 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3339 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3342 When assembling for a target which supports multiple sections, such as ELF or
3343 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3344 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3345 section. Typically the section will only contain symbol definitions and
3346 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3353 Symbols are a central concept: the programmer uses symbols to name
3354 things, the linker uses symbols to link, and the debugger uses symbols
3358 @cindex debuggers, and symbol order
3359 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3360 the same order they were declared. This may break some debuggers.
3365 * Setting Symbols:: Giving Symbols Other Values
3366 * Symbol Names:: Symbol Names
3367 * Dot:: The Special Dot Symbol
3368 * Symbol Attributes:: Symbol Attributes
3375 A @dfn{label} is written as a symbol immediately followed by a colon
3376 @samp{:}. The symbol then represents the current value of the
3377 active location counter, and is, for example, a suitable instruction
3378 operand. You are warned if you use the same symbol to represent two
3379 different locations: the first definition overrides any other
3383 On the HPPA, the usual form for a label need not be immediately followed by a
3384 colon, but instead must start in column zero. Only one label may be defined on
3385 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3386 provides a special directive @code{.label} for defining labels more flexibly.
3389 @node Setting Symbols
3390 @section Giving Symbols Other Values
3392 @cindex assigning values to symbols
3393 @cindex symbol values, assigning
3394 A symbol can be given an arbitrary value by writing a symbol, followed
3395 by an equals sign @samp{=}, followed by an expression
3396 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3397 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3398 equals sign @samp{=}@samp{=} here represents an equivalent of the
3399 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3402 Blackfin does not support symbol assignment with @samp{=}.
3406 @section Symbol Names
3408 @cindex symbol names
3409 @cindex names, symbol
3410 @ifclear SPECIAL-SYMS
3411 Symbol names begin with a letter or with one of @samp{._}. On most
3412 machines, you can also use @code{$} in symbol names; exceptions are
3413 noted in @ref{Machine Dependencies}. That character may be followed by any
3414 string of digits, letters, dollar signs (unless otherwise noted for a
3415 particular target machine), and underscores.
3419 Symbol names begin with a letter or with one of @samp{._}. On the
3420 Renesas SH you can also use @code{$} in symbol names. That
3421 character may be followed by any string of digits, letters, dollar signs (save
3422 on the H8/300), and underscores.
3426 Case of letters is significant: @code{foo} is a different symbol name
3429 Each symbol has exactly one name. Each name in an assembly language program
3430 refers to exactly one symbol. You may use that symbol name any number of times
3433 @subheading Local Symbol Names
3435 @cindex local symbol names
3436 @cindex symbol names, local
3437 A local symbol is any symbol beginning with certain local label prefixes.
3438 By default, the local label prefix is @samp{.L} for ELF systems or
3439 @samp{L} for traditional a.out systems, but each target may have its own
3440 set of local label prefixes.
3442 On the HPPA local symbols begin with @samp{L$}.
3445 Local symbols are defined and used within the assembler, but they are
3446 normally not saved in object files. Thus, they are not visible when debugging.
3447 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3448 @option{-L}}) to retain the local symbols in the object files.
3450 @subheading Local Labels
3452 @cindex local labels
3453 @cindex temporary symbol names
3454 @cindex symbol names, temporary
3455 Local labels help compilers and programmers use names temporarily.
3456 They create symbols which are guaranteed to be unique over the entire scope of
3457 the input source code and which can be referred to by a simple notation.
3458 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3459 represents any positive integer). To refer to the most recent previous
3460 definition of that label write @samp{@b{N}b}, using the same number as when
3461 you defined the label. To refer to the next definition of a local label, write
3462 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3465 There is no restriction on how you can use these labels, and you can reuse them
3466 too. So that it is possible to repeatedly define the same local label (using
3467 the same number @samp{@b{N}}), although you can only refer to the most recently
3468 defined local label of that number (for a backwards reference) or the next
3469 definition of a specific local label for a forward reference. It is also worth
3470 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3471 implemented in a slightly more efficient manner than the others.
3482 Which is the equivalent of:
3485 label_1: branch label_3
3486 label_2: branch label_1
3487 label_3: branch label_4
3488 label_4: branch label_3
3491 Local label names are only a notational device. They are immediately
3492 transformed into more conventional symbol names before the assembler uses them.
3493 The symbol names are stored in the symbol table, appear in error messages, and
3494 are optionally emitted to the object file. The names are constructed using
3498 @item @emph{local label prefix}
3499 All local symbols begin with the system-specific local label prefix.
3500 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3501 that start with the local label prefix. These labels are
3502 used for symbols you are never intended to see. If you use the
3503 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3504 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3505 you may use them in debugging.
3508 This is the number that was used in the local label definition. So if the
3509 label is written @samp{55:} then the number is @samp{55}.
3512 This unusual character is included so you do not accidentally invent a symbol
3513 of the same name. The character has ASCII value of @samp{\002} (control-B).
3515 @item @emph{ordinal number}
3516 This is a serial number to keep the labels distinct. The first definition of
3517 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3518 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3519 the number @samp{1} and its 15th definition gets @samp{15} as well.
3522 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3523 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3525 @subheading Dollar Local Labels
3526 @cindex dollar local symbols
3528 @code{@value{AS}} also supports an even more local form of local labels called
3529 dollar labels. These labels go out of scope (i.e., they become undefined) as
3530 soon as a non-local label is defined. Thus they remain valid for only a small
3531 region of the input source code. Normal local labels, by contrast, remain in
3532 scope for the entire file, or until they are redefined by another occurrence of
3533 the same local label.
3535 Dollar labels are defined in exactly the same way as ordinary local labels,
3536 except that they have a dollar sign suffix to their numeric value, e.g.,
3539 They can also be distinguished from ordinary local labels by their transformed
3540 names which use ASCII character @samp{\001} (control-A) as the magic character
3541 to distinguish them from ordinary labels. For example, the fifth definition of
3542 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3545 @section The Special Dot Symbol
3547 @cindex dot (symbol)
3548 @cindex @code{.} (symbol)
3549 @cindex current address
3550 @cindex location counter
3551 The special symbol @samp{.} refers to the current address that
3552 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3553 .long .} defines @code{melvin} to contain its own address.
3554 Assigning a value to @code{.} is treated the same as a @code{.org}
3556 @ifclear no-space-dir
3557 Thus, the expression @samp{.=.+4} is the same as saying
3561 @node Symbol Attributes
3562 @section Symbol Attributes
3564 @cindex symbol attributes
3565 @cindex attributes, symbol
3566 Every symbol has, as well as its name, the attributes ``Value'' and
3567 ``Type''. Depending on output format, symbols can also have auxiliary
3570 The detailed definitions are in @file{a.out.h}.
3573 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3574 all these attributes, and probably won't warn you. This makes the
3575 symbol an externally defined symbol, which is generally what you
3579 * Symbol Value:: Value
3580 * Symbol Type:: Type
3583 * a.out Symbols:: Symbol Attributes: @code{a.out}
3587 * a.out Symbols:: Symbol Attributes: @code{a.out}
3590 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3595 * COFF Symbols:: Symbol Attributes for COFF
3598 * SOM Symbols:: Symbol Attributes for SOM
3605 @cindex value of a symbol
3606 @cindex symbol value
3607 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3608 location in the text, data, bss or absolute sections the value is the
3609 number of addresses from the start of that section to the label.
3610 Naturally for text, data and bss sections the value of a symbol changes
3611 as @code{@value{LD}} changes section base addresses during linking. Absolute
3612 symbols' values do not change during linking: that is why they are
3615 The value of an undefined symbol is treated in a special way. If it is
3616 0 then the symbol is not defined in this assembler source file, and
3617 @code{@value{LD}} tries to determine its value from other files linked into the
3618 same program. You make this kind of symbol simply by mentioning a symbol
3619 name without defining it. A non-zero value represents a @code{.comm}
3620 common declaration. The value is how much common storage to reserve, in
3621 bytes (addresses). The symbol refers to the first address of the
3627 @cindex type of a symbol
3629 The type attribute of a symbol contains relocation (section)
3630 information, any flag settings indicating that a symbol is external, and
3631 (optionally), other information for linkers and debuggers. The exact
3632 format depends on the object-code output format in use.
3637 @c The following avoids a "widow" subsection title. @group would be
3638 @c better if it were available outside examples.
3641 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3643 @cindex @code{b.out} symbol attributes
3644 @cindex symbol attributes, @code{b.out}
3645 These symbol attributes appear only when @command{@value{AS}} is configured for
3646 one of the Berkeley-descended object output formats---@code{a.out} or
3652 @subsection Symbol Attributes: @code{a.out}
3654 @cindex @code{a.out} symbol attributes
3655 @cindex symbol attributes, @code{a.out}
3661 @subsection Symbol Attributes: @code{a.out}
3663 @cindex @code{a.out} symbol attributes
3664 @cindex symbol attributes, @code{a.out}
3668 * Symbol Desc:: Descriptor
3669 * Symbol Other:: Other
3673 @subsubsection Descriptor
3675 @cindex descriptor, of @code{a.out} symbol
3676 This is an arbitrary 16-bit value. You may establish a symbol's
3677 descriptor value by using a @code{.desc} statement
3678 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3679 @command{@value{AS}}.
3682 @subsubsection Other
3684 @cindex other attribute, of @code{a.out} symbol
3685 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3690 @subsection Symbol Attributes for COFF
3692 @cindex COFF symbol attributes
3693 @cindex symbol attributes, COFF
3695 The COFF format supports a multitude of auxiliary symbol attributes;
3696 like the primary symbol attributes, they are set between @code{.def} and
3697 @code{.endef} directives.
3699 @subsubsection Primary Attributes
3701 @cindex primary attributes, COFF symbols
3702 The symbol name is set with @code{.def}; the value and type,
3703 respectively, with @code{.val} and @code{.type}.
3705 @subsubsection Auxiliary Attributes
3707 @cindex auxiliary attributes, COFF symbols
3708 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3709 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3710 table information for COFF.
3715 @subsection Symbol Attributes for SOM
3717 @cindex SOM symbol attributes
3718 @cindex symbol attributes, SOM
3720 The SOM format for the HPPA supports a multitude of symbol attributes set with
3721 the @code{.EXPORT} and @code{.IMPORT} directives.
3723 The attributes are described in @cite{HP9000 Series 800 Assembly
3724 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3725 @code{EXPORT} assembler directive documentation.
3729 @chapter Expressions
3733 @cindex numeric values
3734 An @dfn{expression} specifies an address or numeric value.
3735 Whitespace may precede and/or follow an expression.
3737 The result of an expression must be an absolute number, or else an offset into
3738 a particular section. If an expression is not absolute, and there is not
3739 enough information when @command{@value{AS}} sees the expression to know its
3740 section, a second pass over the source program might be necessary to interpret
3741 the expression---but the second pass is currently not implemented.
3742 @command{@value{AS}} aborts with an error message in this situation.
3745 * Empty Exprs:: Empty Expressions
3746 * Integer Exprs:: Integer Expressions
3750 @section Empty Expressions
3752 @cindex empty expressions
3753 @cindex expressions, empty
3754 An empty expression has no value: it is just whitespace or null.
3755 Wherever an absolute expression is required, you may omit the
3756 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3757 is compatible with other assemblers.
3760 @section Integer Expressions
3762 @cindex integer expressions
3763 @cindex expressions, integer
3764 An @dfn{integer expression} is one or more @emph{arguments} delimited
3765 by @emph{operators}.
3768 * Arguments:: Arguments
3769 * Operators:: Operators
3770 * Prefix Ops:: Prefix Operators
3771 * Infix Ops:: Infix Operators
3775 @subsection Arguments
3777 @cindex expression arguments
3778 @cindex arguments in expressions
3779 @cindex operands in expressions
3780 @cindex arithmetic operands
3781 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3782 contexts arguments are sometimes called ``arithmetic operands''. In
3783 this manual, to avoid confusing them with the ``instruction operands'' of
3784 the machine language, we use the term ``argument'' to refer to parts of
3785 expressions only, reserving the word ``operand'' to refer only to machine
3786 instruction operands.
3788 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3789 @var{section} is one of text, data, bss, absolute,
3790 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3793 Numbers are usually integers.
3795 A number can be a flonum or bignum. In this case, you are warned
3796 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3797 these 32 bits are an integer. You may write integer-manipulating
3798 instructions that act on exotic constants, compatible with other
3801 @cindex subexpressions
3802 Subexpressions are a left parenthesis @samp{(} followed by an integer
3803 expression, followed by a right parenthesis @samp{)}; or a prefix
3804 operator followed by an argument.
3807 @subsection Operators
3809 @cindex operators, in expressions
3810 @cindex arithmetic functions
3811 @cindex functions, in expressions
3812 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3813 operators are followed by an argument. Infix operators appear
3814 between their arguments. Operators may be preceded and/or followed by
3818 @subsection Prefix Operator
3820 @cindex prefix operators
3821 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3822 one argument, which must be absolute.
3824 @c the tex/end tex stuff surrounding this small table is meant to make
3825 @c it align, on the printed page, with the similar table in the next
3826 @c section (which is inside an enumerate).
3828 \global\advance\leftskip by \itemindent
3833 @dfn{Negation}. Two's complement negation.
3835 @dfn{Complementation}. Bitwise not.
3839 \global\advance\leftskip by -\itemindent
3843 @subsection Infix Operators
3845 @cindex infix operators
3846 @cindex operators, permitted arguments
3847 @dfn{Infix operators} take two arguments, one on either side. Operators
3848 have precedence, but operations with equal precedence are performed left
3849 to right. Apart from @code{+} or @option{-}, both arguments must be
3850 absolute, and the result is absolute.
3853 @cindex operator precedence
3854 @cindex precedence of operators
3861 @dfn{Multiplication}.
3864 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3870 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3873 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3877 Intermediate precedence
3882 @dfn{Bitwise Inclusive Or}.
3888 @dfn{Bitwise Exclusive Or}.
3891 @dfn{Bitwise Or Not}.
3898 @cindex addition, permitted arguments
3899 @cindex plus, permitted arguments
3900 @cindex arguments for addition
3902 @dfn{Addition}. If either argument is absolute, the result has the section of
3903 the other argument. You may not add together arguments from different
3906 @cindex subtraction, permitted arguments
3907 @cindex minus, permitted arguments
3908 @cindex arguments for subtraction
3910 @dfn{Subtraction}. If the right argument is absolute, the
3911 result has the section of the left argument.
3912 If both arguments are in the same section, the result is absolute.
3913 You may not subtract arguments from different sections.
3914 @c FIXME is there still something useful to say about undefined - undefined ?
3916 @cindex comparison expressions
3917 @cindex expressions, comparison
3922 @dfn{Is Not Equal To}
3926 @dfn{Is Greater Than}
3928 @dfn{Is Greater Than Or Equal To}
3930 @dfn{Is Less Than Or Equal To}
3932 The comparison operators can be used as infix operators. A true results has a
3933 value of -1 whereas a false result has a value of 0. Note, these operators
3934 perform signed comparisons.
3937 @item Lowest Precedence
3946 These two logical operations can be used to combine the results of sub
3947 expressions. Note, unlike the comparison operators a true result returns a
3948 value of 1 but a false results does still return 0. Also note that the logical
3949 or operator has a slightly lower precedence than logical and.
3954 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3955 address; you can only have a defined section in one of the two arguments.
3958 @chapter Assembler Directives
3960 @cindex directives, machine independent
3961 @cindex pseudo-ops, machine independent
3962 @cindex machine independent directives
3963 All assembler directives have names that begin with a period (@samp{.}).
3964 The rest of the name is letters, usually in lower case.
3966 This chapter discusses directives that are available regardless of the
3967 target machine configuration for the @sc{gnu} assembler.
3969 Some machine configurations provide additional directives.
3970 @xref{Machine Dependencies}.
3973 @ifset machine-directives
3974 @xref{Machine Dependencies}, for additional directives.
3979 * Abort:: @code{.abort}
3981 * ABORT (COFF):: @code{.ABORT}
3984 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3985 * Altmacro:: @code{.altmacro}
3986 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3987 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3988 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3989 * Byte:: @code{.byte @var{expressions}}
3990 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
3991 * Comm:: @code{.comm @var{symbol} , @var{length} }
3992 * Data:: @code{.data @var{subsection}}
3994 * Def:: @code{.def @var{name}}
3997 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4003 * Double:: @code{.double @var{flonums}}
4004 * Eject:: @code{.eject}
4005 * Else:: @code{.else}
4006 * Elseif:: @code{.elseif}
4009 * Endef:: @code{.endef}
4012 * Endfunc:: @code{.endfunc}
4013 * Endif:: @code{.endif}
4014 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4015 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4016 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4018 * Error:: @code{.error @var{string}}
4019 * Exitm:: @code{.exitm}
4020 * Extern:: @code{.extern}
4021 * Fail:: @code{.fail}
4022 * File:: @code{.file}
4023 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4024 * Float:: @code{.float @var{flonums}}
4025 * Func:: @code{.func}
4026 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4028 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4029 * Hidden:: @code{.hidden @var{names}}
4032 * hword:: @code{.hword @var{expressions}}
4033 * Ident:: @code{.ident}
4034 * If:: @code{.if @var{absolute expression}}
4035 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4036 * Include:: @code{.include "@var{file}"}
4037 * Int:: @code{.int @var{expressions}}
4039 * Internal:: @code{.internal @var{names}}
4042 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4043 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4044 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4045 * Lflags:: @code{.lflags}
4046 @ifclear no-line-dir
4047 * Line:: @code{.line @var{line-number}}
4050 * Linkonce:: @code{.linkonce [@var{type}]}
4051 * List:: @code{.list}
4052 * Ln:: @code{.ln @var{line-number}}
4053 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4054 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4056 * Local:: @code{.local @var{names}}
4059 * Long:: @code{.long @var{expressions}}
4061 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4064 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4065 * MRI:: @code{.mri @var{val}}
4066 * Noaltmacro:: @code{.noaltmacro}
4067 * Nolist:: @code{.nolist}
4068 * Octa:: @code{.octa @var{bignums}}
4069 * Org:: @code{.org @var{new-lc}, @var{fill}}
4070 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4072 * PopSection:: @code{.popsection}
4073 * Previous:: @code{.previous}
4076 * Print:: @code{.print @var{string}}
4078 * Protected:: @code{.protected @var{names}}
4081 * Psize:: @code{.psize @var{lines}, @var{columns}}
4082 * Purgem:: @code{.purgem @var{name}}
4084 * PushSection:: @code{.pushsection @var{name}}
4087 * Quad:: @code{.quad @var{bignums}}
4088 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4089 * Rept:: @code{.rept @var{count}}
4090 * Sbttl:: @code{.sbttl "@var{subheading}"}
4092 * Scl:: @code{.scl @var{class}}
4095 * Section:: @code{.section @var{name}[, @var{flags}]}
4098 * Set:: @code{.set @var{symbol}, @var{expression}}
4099 * Short:: @code{.short @var{expressions}}
4100 * Single:: @code{.single @var{flonums}}
4102 * Size:: @code{.size [@var{name} , @var{expression}]}
4104 @ifclear no-space-dir
4105 * Skip:: @code{.skip @var{size} , @var{fill}}
4108 * Sleb128:: @code{.sleb128 @var{expressions}}
4109 @ifclear no-space-dir
4110 * Space:: @code{.space @var{size} , @var{fill}}
4113 * Stab:: @code{.stabd, .stabn, .stabs}
4116 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4117 * Struct:: @code{.struct @var{expression}}
4119 * SubSection:: @code{.subsection}
4120 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4124 * Tag:: @code{.tag @var{structname}}
4127 * Text:: @code{.text @var{subsection}}
4128 * Title:: @code{.title "@var{heading}"}
4130 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4133 * Uleb128:: @code{.uleb128 @var{expressions}}
4135 * Val:: @code{.val @var{addr}}
4139 * Version:: @code{.version "@var{string}"}
4140 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4141 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4144 * Warning:: @code{.warning @var{string}}
4145 * Weak:: @code{.weak @var{names}}
4146 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4147 * Word:: @code{.word @var{expressions}}
4148 * Deprecated:: Deprecated Directives
4152 @section @code{.abort}
4154 @cindex @code{abort} directive
4155 @cindex stopping the assembly
4156 This directive stops the assembly immediately. It is for
4157 compatibility with other assemblers. The original idea was that the
4158 assembly language source would be piped into the assembler. If the sender
4159 of the source quit, it could use this directive tells @command{@value{AS}} to
4160 quit also. One day @code{.abort} will not be supported.
4164 @section @code{.ABORT} (COFF)
4166 @cindex @code{ABORT} directive
4167 When producing COFF output, @command{@value{AS}} accepts this directive as a
4168 synonym for @samp{.abort}.
4171 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4177 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4179 @cindex padding the location counter
4180 @cindex @code{align} directive
4181 Pad the location counter (in the current subsection) to a particular storage
4182 boundary. The first expression (which must be absolute) is the alignment
4183 required, as described below.
4185 The second expression (also absolute) gives the fill value to be stored in the
4186 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4187 padding bytes are normally zero. However, on some systems, if the section is
4188 marked as containing code and the fill value is omitted, the space is filled
4189 with no-op instructions.
4191 The third expression is also absolute, and is also optional. If it is present,
4192 it is the maximum number of bytes that should be skipped by this alignment
4193 directive. If doing the alignment would require skipping more bytes than the
4194 specified maximum, then the alignment is not done at all. You can omit the
4195 fill value (the second argument) entirely by simply using two commas after the
4196 required alignment; this can be useful if you want the alignment to be filled
4197 with no-op instructions when appropriate.
4199 The way the required alignment is specified varies from system to system.
4200 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4201 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4202 alignment request in bytes. For example @samp{.align 8} advances
4203 the location counter until it is a multiple of 8. If the location counter
4204 is already a multiple of 8, no change is needed. For the tic54x, the
4205 first expression is the alignment request in words.
4207 For other systems, including ppc, i386 using a.out format, arm and
4208 strongarm, it is the
4209 number of low-order zero bits the location counter must have after
4210 advancement. For example @samp{.align 3} advances the location
4211 counter until it a multiple of 8. If the location counter is already a
4212 multiple of 8, no change is needed.
4214 This inconsistency is due to the different behaviors of the various
4215 native assemblers for these systems which GAS must emulate.
4216 GAS also provides @code{.balign} and @code{.p2align} directives,
4217 described later, which have a consistent behavior across all
4218 architectures (but are specific to GAS).
4221 @section @code{.altmacro}
4222 Enable alternate macro mode, enabling:
4225 @item LOCAL @var{name} [ , @dots{} ]
4226 One additional directive, @code{LOCAL}, is available. It is used to
4227 generate a string replacement for each of the @var{name} arguments, and
4228 replace any instances of @var{name} in each macro expansion. The
4229 replacement string is unique in the assembly, and different for each
4230 separate macro expansion. @code{LOCAL} allows you to write macros that
4231 define symbols, without fear of conflict between separate macro expansions.
4233 @item String delimiters
4234 You can write strings delimited in these other ways besides
4235 @code{"@var{string}"}:
4238 @item '@var{string}'
4239 You can delimit strings with single-quote characters.
4241 @item <@var{string}>
4242 You can delimit strings with matching angle brackets.
4245 @item single-character string escape
4246 To include any single character literally in a string (even if the
4247 character would otherwise have some special meaning), you can prefix the
4248 character with @samp{!} (an exclamation mark). For example, you can
4249 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4251 @item Expression results as strings
4252 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4253 and use the result as a string.
4257 @section @code{.ascii "@var{string}"}@dots{}
4259 @cindex @code{ascii} directive
4260 @cindex string literals
4261 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4262 separated by commas. It assembles each string (with no automatic
4263 trailing zero byte) into consecutive addresses.
4266 @section @code{.asciz "@var{string}"}@dots{}
4268 @cindex @code{asciz} directive
4269 @cindex zero-terminated strings
4270 @cindex null-terminated strings
4271 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4272 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4275 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4277 @cindex padding the location counter given number of bytes
4278 @cindex @code{balign} directive
4279 Pad the location counter (in the current subsection) to a particular
4280 storage boundary. The first expression (which must be absolute) is the
4281 alignment request in bytes. For example @samp{.balign 8} advances
4282 the location counter until it is a multiple of 8. If the location counter
4283 is already a multiple of 8, no change is needed.
4285 The second expression (also absolute) gives the fill value to be stored in the
4286 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4287 padding bytes are normally zero. However, on some systems, if the section is
4288 marked as containing code and the fill value is omitted, the space is filled
4289 with no-op instructions.
4291 The third expression is also absolute, and is also optional. If it is present,
4292 it is the maximum number of bytes that should be skipped by this alignment
4293 directive. If doing the alignment would require skipping more bytes than the
4294 specified maximum, then the alignment is not done at all. You can omit the
4295 fill value (the second argument) entirely by simply using two commas after the
4296 required alignment; this can be useful if you want the alignment to be filled
4297 with no-op instructions when appropriate.
4299 @cindex @code{balignw} directive
4300 @cindex @code{balignl} directive
4301 The @code{.balignw} and @code{.balignl} directives are variants of the
4302 @code{.balign} directive. The @code{.balignw} directive treats the fill
4303 pattern as a two byte word value. The @code{.balignl} directives treats the
4304 fill pattern as a four byte longword value. For example, @code{.balignw
4305 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4306 filled in with the value 0x368d (the exact placement of the bytes depends upon
4307 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4311 @section @code{.byte @var{expressions}}
4313 @cindex @code{byte} directive
4314 @cindex integers, one byte
4315 @code{.byte} expects zero or more expressions, separated by commas.
4316 Each expression is assembled into the next byte.
4318 @node CFI directives
4319 @section @code{.cfi_sections @var{section_list}}
4320 @cindex @code{cfi_sections} directive
4321 @code{.cfi_sections} may be used to specify whether CFI directives
4322 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4323 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4324 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4325 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4326 directive is not used is @code{.cfi_sections .eh_frame}.
4328 @section @code{.cfi_startproc [simple]}
4329 @cindex @code{cfi_startproc} directive
4330 @code{.cfi_startproc} is used at the beginning of each function that
4331 should have an entry in @code{.eh_frame}. It initializes some internal
4332 data structures. Don't forget to close the function by
4333 @code{.cfi_endproc}.
4335 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4336 it also emits some architecture dependent initial CFI instructions.
4338 @section @code{.cfi_endproc}
4339 @cindex @code{cfi_endproc} directive
4340 @code{.cfi_endproc} is used at the end of a function where it closes its
4341 unwind entry previously opened by
4342 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4344 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4345 @code{.cfi_personality} defines personality routine and its encoding.
4346 @var{encoding} must be a constant determining how the personality
4347 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4348 argument is not present, otherwise second argument should be
4349 a constant or a symbol name. When using indirect encodings,
4350 the symbol provided should be the location where personality
4351 can be loaded from, not the personality routine itself.
4352 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4353 no personality routine.
4355 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4356 @code{.cfi_lsda} defines LSDA and its encoding.
4357 @var{encoding} must be a constant determining how the LSDA
4358 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4359 argument is not present, otherwise second argument should be a constant
4360 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4363 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4364 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4365 address from @var{register} and add @var{offset} to it}.
4367 @section @code{.cfi_def_cfa_register @var{register}}
4368 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4369 now on @var{register} will be used instead of the old one. Offset
4372 @section @code{.cfi_def_cfa_offset @var{offset}}
4373 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4374 remains the same, but @var{offset} is new. Note that it is the
4375 absolute offset that will be added to a defined register to compute
4378 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4379 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4380 value that is added/substracted from the previous offset.
4382 @section @code{.cfi_offset @var{register}, @var{offset}}
4383 Previous value of @var{register} is saved at offset @var{offset} from
4386 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4387 Previous value of @var{register} is saved at offset @var{offset} from
4388 the current CFA register. This is transformed to @code{.cfi_offset}
4389 using the known displacement of the CFA register from the CFA.
4390 This is often easier to use, because the number will match the
4391 code it's annotating.
4393 @section @code{.cfi_register @var{register1}, @var{register2}}
4394 Previous value of @var{register1} is saved in register @var{register2}.
4396 @section @code{.cfi_restore @var{register}}
4397 @code{.cfi_restore} says that the rule for @var{register} is now the
4398 same as it was at the beginning of the function, after all initial
4399 instruction added by @code{.cfi_startproc} were executed.
4401 @section @code{.cfi_undefined @var{register}}
4402 From now on the previous value of @var{register} can't be restored anymore.
4404 @section @code{.cfi_same_value @var{register}}
4405 Current value of @var{register} is the same like in the previous frame,
4406 i.e. no restoration needed.
4408 @section @code{.cfi_remember_state},
4409 First save all current rules for all registers by @code{.cfi_remember_state},
4410 then totally screw them up by subsequent @code{.cfi_*} directives and when
4411 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4412 the previous saved state.
4414 @section @code{.cfi_return_column @var{register}}
4415 Change return column @var{register}, i.e. the return address is either
4416 directly in @var{register} or can be accessed by rules for @var{register}.
4418 @section @code{.cfi_signal_frame}
4419 Mark current function as signal trampoline.
4421 @section @code{.cfi_window_save}
4422 SPARC register window has been saved.
4424 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4425 Allows the user to add arbitrary bytes to the unwind info. One
4426 might use this to add OS-specific CFI opcodes, or generic CFI
4427 opcodes that GAS does not yet support.
4429 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4430 The current value of @var{register} is @var{label}. The value of @var{label}
4431 will be encoded in the output file according to @var{encoding}; see the
4432 description of @code{.cfi_personality} for details on this encoding.
4434 The usefulness of equating a register to a fixed label is probably
4435 limited to the return address register. Here, it can be useful to
4436 mark a code segment that has only one return address which is reached
4437 by a direct branch and no copy of the return address exists in memory
4438 or another register.
4441 @section @code{.comm @var{symbol} , @var{length} }
4443 @cindex @code{comm} directive
4444 @cindex symbol, common
4445 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4446 common symbol in one object file may be merged with a defined or common symbol
4447 of the same name in another object file. If @code{@value{LD}} does not see a
4448 definition for the symbol--just one or more common symbols--then it will
4449 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4450 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4451 the same name, and they do not all have the same size, it will allocate space
4452 using the largest size.
4455 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4456 an optional third argument. This is the desired alignment of the symbol,
4457 specified for ELF as a byte boundary (for example, an alignment of 16 means
4458 that the least significant 4 bits of the address should be zero), and for PE
4459 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4460 boundary). The alignment must be an absolute expression, and it must be a
4461 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4462 common symbol, it will use the alignment when placing the symbol. If no
4463 alignment is specified, @command{@value{AS}} will set the alignment to the
4464 largest power of two less than or equal to the size of the symbol, up to a
4465 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4466 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4467 @samp{--section-alignment} option; image file sections in PE are aligned to
4468 multiples of 4096, which is far too large an alignment for ordinary variables.
4469 It is rather the default alignment for (non-debug) sections within object
4470 (@samp{*.o}) files, which are less strictly aligned.}.
4474 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4475 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4479 @section @code{.data @var{subsection}}
4481 @cindex @code{data} directive
4482 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4483 end of the data subsection numbered @var{subsection} (which is an
4484 absolute expression). If @var{subsection} is omitted, it defaults
4489 @section @code{.def @var{name}}
4491 @cindex @code{def} directive
4492 @cindex COFF symbols, debugging
4493 @cindex debugging COFF symbols
4494 Begin defining debugging information for a symbol @var{name}; the
4495 definition extends until the @code{.endef} directive is encountered.
4498 This directive is only observed when @command{@value{AS}} is configured for COFF
4499 format output; when producing @code{b.out}, @samp{.def} is recognized,
4506 @section @code{.desc @var{symbol}, @var{abs-expression}}
4508 @cindex @code{desc} directive
4509 @cindex COFF symbol descriptor
4510 @cindex symbol descriptor, COFF
4511 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4512 to the low 16 bits of an absolute expression.
4515 The @samp{.desc} directive is not available when @command{@value{AS}} is
4516 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4517 object format. For the sake of compatibility, @command{@value{AS}} accepts
4518 it, but produces no output, when configured for COFF.
4524 @section @code{.dim}
4526 @cindex @code{dim} directive
4527 @cindex COFF auxiliary symbol information
4528 @cindex auxiliary symbol information, COFF
4529 This directive is generated by compilers to include auxiliary debugging
4530 information in the symbol table. It is only permitted inside
4531 @code{.def}/@code{.endef} pairs.
4534 @samp{.dim} is only meaningful when generating COFF format output; when
4535 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4541 @section @code{.double @var{flonums}}
4543 @cindex @code{double} directive
4544 @cindex floating point numbers (double)
4545 @code{.double} expects zero or more flonums, separated by commas. It
4546 assembles floating point numbers.
4548 The exact kind of floating point numbers emitted depends on how
4549 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4553 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4554 in @sc{ieee} format.
4559 @section @code{.eject}
4561 @cindex @code{eject} directive
4562 @cindex new page, in listings
4563 @cindex page, in listings
4564 @cindex listing control: new page
4565 Force a page break at this point, when generating assembly listings.
4568 @section @code{.else}
4570 @cindex @code{else} directive
4571 @code{.else} is part of the @command{@value{AS}} support for conditional
4572 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4573 of code to be assembled if the condition for the preceding @code{.if}
4577 @section @code{.elseif}
4579 @cindex @code{elseif} directive
4580 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4581 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4582 @code{.if} block that would otherwise fill the entire @code{.else} section.
4585 @section @code{.end}
4587 @cindex @code{end} directive
4588 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4589 process anything in the file past the @code{.end} directive.
4593 @section @code{.endef}
4595 @cindex @code{endef} directive
4596 This directive flags the end of a symbol definition begun with
4600 @samp{.endef} is only meaningful when generating COFF format output; if
4601 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4602 directive but ignores it.
4607 @section @code{.endfunc}
4608 @cindex @code{endfunc} directive
4609 @code{.endfunc} marks the end of a function specified with @code{.func}.
4612 @section @code{.endif}
4614 @cindex @code{endif} directive
4615 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4616 it marks the end of a block of code that is only assembled
4617 conditionally. @xref{If,,@code{.if}}.
4620 @section @code{.equ @var{symbol}, @var{expression}}
4622 @cindex @code{equ} directive
4623 @cindex assigning values to symbols
4624 @cindex symbols, assigning values to
4625 This directive sets the value of @var{symbol} to @var{expression}.
4626 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4629 The syntax for @code{equ} on the HPPA is
4630 @samp{@var{symbol} .equ @var{expression}}.
4634 The syntax for @code{equ} on the Z80 is
4635 @samp{@var{symbol} equ @var{expression}}.
4636 On the Z80 it is an eror if @var{symbol} is already defined,
4637 but the symbol is not protected from later redefinition.
4638 Compare @ref{Equiv}.
4642 @section @code{.equiv @var{symbol}, @var{expression}}
4643 @cindex @code{equiv} directive
4644 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4645 the assembler will signal an error if @var{symbol} is already defined. Note a
4646 symbol which has been referenced but not actually defined is considered to be
4649 Except for the contents of the error message, this is roughly equivalent to
4656 plus it protects the symbol from later redefinition.
4659 @section @code{.eqv @var{symbol}, @var{expression}}
4660 @cindex @code{eqv} directive
4661 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4662 evaluate the expression or any part of it immediately. Instead each time
4663 the resulting symbol is used in an expression, a snapshot of its current
4667 @section @code{.err}
4668 @cindex @code{err} directive
4669 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4670 message and, unless the @option{-Z} option was used, it will not generate an
4671 object file. This can be used to signal an error in conditionally compiled code.
4674 @section @code{.error "@var{string}"}
4675 @cindex error directive
4677 Similarly to @code{.err}, this directive emits an error, but you can specify a
4678 string that will be emitted as the error message. If you don't specify the
4679 message, it defaults to @code{".error directive invoked in source file"}.
4680 @xref{Errors, ,Error and Warning Messages}.
4683 .error "This code has not been assembled and tested."
4687 @section @code{.exitm}
4688 Exit early from the current macro definition. @xref{Macro}.
4691 @section @code{.extern}
4693 @cindex @code{extern} directive
4694 @code{.extern} is accepted in the source program---for compatibility
4695 with other assemblers---but it is ignored. @command{@value{AS}} treats
4696 all undefined symbols as external.
4699 @section @code{.fail @var{expression}}
4701 @cindex @code{fail} directive
4702 Generates an error or a warning. If the value of the @var{expression} is 500
4703 or more, @command{@value{AS}} will print a warning message. If the value is less
4704 than 500, @command{@value{AS}} will print an error message. The message will
4705 include the value of @var{expression}. This can occasionally be useful inside
4706 complex nested macros or conditional assembly.
4709 @section @code{.file}
4710 @cindex @code{file} directive
4712 @ifclear no-file-dir
4713 There are two different versions of the @code{.file} directive. Targets
4714 that support DWARF2 line number information use the DWARF2 version of
4715 @code{.file}. Other targets use the default version.
4717 @subheading Default Version
4719 @cindex logical file name
4720 @cindex file name, logical
4721 This version of the @code{.file} directive tells @command{@value{AS}} that we
4722 are about to start a new logical file. The syntax is:
4728 @var{string} is the new file name. In general, the filename is
4729 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4730 to specify an empty file name, you must give the quotes--@code{""}. This
4731 statement may go away in future: it is only recognized to be compatible with
4732 old @command{@value{AS}} programs.
4734 @subheading DWARF2 Version
4737 When emitting DWARF2 line number information, @code{.file} assigns filenames
4738 to the @code{.debug_line} file name table. The syntax is:
4741 .file @var{fileno} @var{filename}
4744 The @var{fileno} operand should be a unique positive integer to use as the
4745 index of the entry in the table. The @var{filename} operand is a C string
4748 The detail of filename indices is exposed to the user because the filename
4749 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4750 information, and thus the user must know the exact indices that table
4754 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4756 @cindex @code{fill} directive
4757 @cindex writing patterns in memory
4758 @cindex patterns, writing in memory
4759 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4760 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4761 may be zero or more. @var{Size} may be zero or more, but if it is
4762 more than 8, then it is deemed to have the value 8, compatible with
4763 other people's assemblers. The contents of each @var{repeat} bytes
4764 is taken from an 8-byte number. The highest order 4 bytes are
4765 zero. The lowest order 4 bytes are @var{value} rendered in the
4766 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4767 Each @var{size} bytes in a repetition is taken from the lowest order
4768 @var{size} bytes of this number. Again, this bizarre behavior is
4769 compatible with other people's assemblers.
4771 @var{size} and @var{value} are optional.
4772 If the second comma and @var{value} are absent, @var{value} is
4773 assumed zero. If the first comma and following tokens are absent,
4774 @var{size} is assumed to be 1.
4777 @section @code{.float @var{flonums}}
4779 @cindex floating point numbers (single)
4780 @cindex @code{float} directive
4781 This directive assembles zero or more flonums, separated by commas. It
4782 has the same effect as @code{.single}.
4784 The exact kind of floating point numbers emitted depends on how
4785 @command{@value{AS}} is configured.
4786 @xref{Machine Dependencies}.
4790 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4791 in @sc{ieee} format.
4796 @section @code{.func @var{name}[,@var{label}]}
4797 @cindex @code{func} directive
4798 @code{.func} emits debugging information to denote function @var{name}, and
4799 is ignored unless the file is assembled with debugging enabled.
4800 Only @samp{--gstabs[+]} is currently supported.
4801 @var{label} is the entry point of the function and if omitted @var{name}
4802 prepended with the @samp{leading char} is used.
4803 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4804 All functions are currently defined to have @code{void} return type.
4805 The function must be terminated with @code{.endfunc}.
4808 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4810 @cindex @code{global} directive
4811 @cindex symbol, making visible to linker
4812 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4813 @var{symbol} in your partial program, its value is made available to
4814 other partial programs that are linked with it. Otherwise,
4815 @var{symbol} takes its attributes from a symbol of the same name
4816 from another file linked into the same program.
4818 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4819 compatibility with other assemblers.
4822 On the HPPA, @code{.global} is not always enough to make it accessible to other
4823 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4824 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4829 @section @code{.gnu_attribute @var{tag},@var{value}}
4830 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4833 @section @code{.hidden @var{names}}
4835 @cindex @code{hidden} directive
4837 This is one of the ELF visibility directives. The other two are
4838 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4839 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4841 This directive overrides the named symbols default visibility (which is set by
4842 their binding: local, global or weak). The directive sets the visibility to
4843 @code{hidden} which means that the symbols are not visible to other components.
4844 Such symbols are always considered to be @code{protected} as well.
4848 @section @code{.hword @var{expressions}}
4850 @cindex @code{hword} directive
4851 @cindex integers, 16-bit
4852 @cindex numbers, 16-bit
4853 @cindex sixteen bit integers
4854 This expects zero or more @var{expressions}, and emits
4855 a 16 bit number for each.
4858 This directive is a synonym for @samp{.short}; depending on the target
4859 architecture, it may also be a synonym for @samp{.word}.
4863 This directive is a synonym for @samp{.short}.
4866 This directive is a synonym for both @samp{.short} and @samp{.word}.
4871 @section @code{.ident}
4873 @cindex @code{ident} directive
4875 This directive is used by some assemblers to place tags in object files. The
4876 behavior of this directive varies depending on the target. When using the
4877 a.out object file format, @command{@value{AS}} simply accepts the directive for
4878 source-file compatibility with existing assemblers, but does not emit anything
4879 for it. When using COFF, comments are emitted to the @code{.comment} or
4880 @code{.rdata} section, depending on the target. When using ELF, comments are
4881 emitted to the @code{.comment} section.
4884 @section @code{.if @var{absolute expression}}
4886 @cindex conditional assembly
4887 @cindex @code{if} directive
4888 @code{.if} marks the beginning of a section of code which is only
4889 considered part of the source program being assembled if the argument
4890 (which must be an @var{absolute expression}) is non-zero. The end of
4891 the conditional section of code must be marked by @code{.endif}
4892 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4893 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4894 If you have several conditions to check, @code{.elseif} may be used to avoid
4895 nesting blocks if/else within each subsequent @code{.else} block.
4897 The following variants of @code{.if} are also supported:
4899 @cindex @code{ifdef} directive
4900 @item .ifdef @var{symbol}
4901 Assembles the following section of code if the specified @var{symbol}
4902 has been defined. Note a symbol which has been referenced but not yet defined
4903 is considered to be undefined.
4905 @cindex @code{ifb} directive
4906 @item .ifb @var{text}
4907 Assembles the following section of code if the operand is blank (empty).
4909 @cindex @code{ifc} directive
4910 @item .ifc @var{string1},@var{string2}
4911 Assembles the following section of code if the two strings are the same. The
4912 strings may be optionally quoted with single quotes. If they are not quoted,
4913 the first string stops at the first comma, and the second string stops at the
4914 end of the line. Strings which contain whitespace should be quoted. The
4915 string comparison is case sensitive.
4917 @cindex @code{ifeq} directive
4918 @item .ifeq @var{absolute expression}
4919 Assembles the following section of code if the argument is zero.
4921 @cindex @code{ifeqs} directive
4922 @item .ifeqs @var{string1},@var{string2}
4923 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4925 @cindex @code{ifge} directive
4926 @item .ifge @var{absolute expression}
4927 Assembles the following section of code if the argument is greater than or
4930 @cindex @code{ifgt} directive
4931 @item .ifgt @var{absolute expression}
4932 Assembles the following section of code if the argument is greater than zero.
4934 @cindex @code{ifle} directive
4935 @item .ifle @var{absolute expression}
4936 Assembles the following section of code if the argument is less than or equal
4939 @cindex @code{iflt} directive
4940 @item .iflt @var{absolute expression}
4941 Assembles the following section of code if the argument is less than zero.
4943 @cindex @code{ifnb} directive
4944 @item .ifnb @var{text}
4945 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
4946 following section of code if the operand is non-blank (non-empty).
4948 @cindex @code{ifnc} directive
4949 @item .ifnc @var{string1},@var{string2}.
4950 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4951 following section of code if the two strings are not the same.
4953 @cindex @code{ifndef} directive
4954 @cindex @code{ifnotdef} directive
4955 @item .ifndef @var{symbol}
4956 @itemx .ifnotdef @var{symbol}
4957 Assembles the following section of code if the specified @var{symbol}
4958 has not been defined. Both spelling variants are equivalent. Note a symbol
4959 which has been referenced but not yet defined is considered to be undefined.
4961 @cindex @code{ifne} directive
4962 @item .ifne @var{absolute expression}
4963 Assembles the following section of code if the argument is not equal to zero
4964 (in other words, this is equivalent to @code{.if}).
4966 @cindex @code{ifnes} directive
4967 @item .ifnes @var{string1},@var{string2}
4968 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4969 following section of code if the two strings are not the same.
4973 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4975 @cindex @code{incbin} directive
4976 @cindex binary files, including
4977 The @code{incbin} directive includes @var{file} verbatim at the current
4978 location. You can control the search paths used with the @samp{-I} command-line
4979 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4982 The @var{skip} argument skips a number of bytes from the start of the
4983 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4984 read. Note that the data is not aligned in any way, so it is the user's
4985 responsibility to make sure that proper alignment is provided both before and
4986 after the @code{incbin} directive.
4989 @section @code{.include "@var{file}"}
4991 @cindex @code{include} directive
4992 @cindex supporting files, including
4993 @cindex files, including
4994 This directive provides a way to include supporting files at specified
4995 points in your source program. The code from @var{file} is assembled as
4996 if it followed the point of the @code{.include}; when the end of the
4997 included file is reached, assembly of the original file continues. You
4998 can control the search paths used with the @samp{-I} command-line option
4999 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5003 @section @code{.int @var{expressions}}
5005 @cindex @code{int} directive
5006 @cindex integers, 32-bit
5007 Expect zero or more @var{expressions}, of any section, separated by commas.
5008 For each expression, emit a number that, at run time, is the value of that
5009 expression. The byte order and bit size of the number depends on what kind
5010 of target the assembly is for.
5014 On most forms of the H8/300, @code{.int} emits 16-bit
5015 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5022 @section @code{.internal @var{names}}
5024 @cindex @code{internal} directive
5026 This is one of the ELF visibility directives. The other two are
5027 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5028 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5030 This directive overrides the named symbols default visibility (which is set by
5031 their binding: local, global or weak). The directive sets the visibility to
5032 @code{internal} which means that the symbols are considered to be @code{hidden}
5033 (i.e., not visible to other components), and that some extra, processor specific
5034 processing must also be performed upon the symbols as well.
5038 @section @code{.irp @var{symbol},@var{values}}@dots{}
5040 @cindex @code{irp} directive
5041 Evaluate a sequence of statements assigning different values to @var{symbol}.
5042 The sequence of statements starts at the @code{.irp} directive, and is
5043 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5044 set to @var{value}, and the sequence of statements is assembled. If no
5045 @var{value} is listed, the sequence of statements is assembled once, with
5046 @var{symbol} set to the null string. To refer to @var{symbol} within the
5047 sequence of statements, use @var{\symbol}.
5049 For example, assembling
5057 is equivalent to assembling
5065 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5068 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5070 @cindex @code{irpc} directive
5071 Evaluate a sequence of statements assigning different values to @var{symbol}.
5072 The sequence of statements starts at the @code{.irpc} directive, and is
5073 terminated by an @code{.endr} directive. For each character in @var{value},
5074 @var{symbol} is set to the character, and the sequence of statements is
5075 assembled. If no @var{value} is listed, the sequence of statements is
5076 assembled once, with @var{symbol} set to the null string. To refer to
5077 @var{symbol} within the sequence of statements, use @var{\symbol}.
5079 For example, assembling
5087 is equivalent to assembling
5095 For some caveats with the spelling of @var{symbol}, see also the discussion
5099 @section @code{.lcomm @var{symbol} , @var{length}}
5101 @cindex @code{lcomm} directive
5102 @cindex local common symbols
5103 @cindex symbols, local common
5104 Reserve @var{length} (an absolute expression) bytes for a local common
5105 denoted by @var{symbol}. The section and value of @var{symbol} are
5106 those of the new local common. The addresses are allocated in the bss
5107 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5108 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5109 not visible to @code{@value{LD}}.
5112 Some targets permit a third argument to be used with @code{.lcomm}. This
5113 argument specifies the desired alignment of the symbol in the bss section.
5117 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5118 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5122 @section @code{.lflags}
5124 @cindex @code{lflags} directive (ignored)
5125 @command{@value{AS}} accepts this directive, for compatibility with other
5126 assemblers, but ignores it.
5128 @ifclear no-line-dir
5130 @section @code{.line @var{line-number}}
5132 @cindex @code{line} directive
5133 @cindex logical line number
5135 Change the logical line number. @var{line-number} must be an absolute
5136 expression. The next line has that logical line number. Therefore any other
5137 statements on the current line (after a statement separator character) are
5138 reported as on logical line number @var{line-number} @minus{} 1. One day
5139 @command{@value{AS}} will no longer support this directive: it is recognized only
5140 for compatibility with existing assembler programs.
5143 Even though this is a directive associated with the @code{a.out} or
5144 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5145 when producing COFF output, and treats @samp{.line} as though it
5146 were the COFF @samp{.ln} @emph{if} it is found outside a
5147 @code{.def}/@code{.endef} pair.
5149 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5150 used by compilers to generate auxiliary symbol information for
5155 @section @code{.linkonce [@var{type}]}
5157 @cindex @code{linkonce} directive
5158 @cindex common sections
5159 Mark the current section so that the linker only includes a single copy of it.
5160 This may be used to include the same section in several different object files,
5161 but ensure that the linker will only include it once in the final output file.
5162 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5163 Duplicate sections are detected based on the section name, so it should be
5166 This directive is only supported by a few object file formats; as of this
5167 writing, the only object file format which supports it is the Portable
5168 Executable format used on Windows NT.
5170 The @var{type} argument is optional. If specified, it must be one of the
5171 following strings. For example:
5175 Not all types may be supported on all object file formats.
5179 Silently discard duplicate sections. This is the default.
5182 Warn if there are duplicate sections, but still keep only one copy.
5185 Warn if any of the duplicates have different sizes.
5188 Warn if any of the duplicates do not have exactly the same contents.
5192 @section @code{.list}
5194 @cindex @code{list} directive
5195 @cindex listing control, turning on
5196 Control (in conjunction with the @code{.nolist} directive) whether or
5197 not assembly listings are generated. These two directives maintain an
5198 internal counter (which is zero initially). @code{.list} increments the
5199 counter, and @code{.nolist} decrements it. Assembly listings are
5200 generated whenever the counter is greater than zero.
5202 By default, listings are disabled. When you enable them (with the
5203 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5204 the initial value of the listing counter is one.
5207 @section @code{.ln @var{line-number}}
5209 @cindex @code{ln} directive
5210 @ifclear no-line-dir
5211 @samp{.ln} is a synonym for @samp{.line}.
5214 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5215 must be an absolute expression. The next line has that logical
5216 line number, so any other statements on the current line (after a
5217 statement separator character @code{;}) are reported as on logical
5218 line number @var{line-number} @minus{} 1.
5221 This directive is accepted, but ignored, when @command{@value{AS}} is
5222 configured for @code{b.out}; its effect is only associated with COFF
5228 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5229 @cindex @code{loc} directive
5230 When emitting DWARF2 line number information,
5231 the @code{.loc} directive will add a row to the @code{.debug_line} line
5232 number matrix corresponding to the immediately following assembly
5233 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5234 arguments will be applied to the @code{.debug_line} state machine before
5237 The @var{options} are a sequence of the following tokens in any order:
5241 This option will set the @code{basic_block} register in the
5242 @code{.debug_line} state machine to @code{true}.
5245 This option will set the @code{prologue_end} register in the
5246 @code{.debug_line} state machine to @code{true}.
5248 @item epilogue_begin
5249 This option will set the @code{epilogue_begin} register in the
5250 @code{.debug_line} state machine to @code{true}.
5252 @item is_stmt @var{value}
5253 This option will set the @code{is_stmt} register in the
5254 @code{.debug_line} state machine to @code{value}, which must be
5257 @item isa @var{value}
5258 This directive will set the @code{isa} register in the @code{.debug_line}
5259 state machine to @var{value}, which must be an unsigned integer.
5261 @item discriminator @var{value}
5262 This directive will set the @code{discriminator} register in the @code{.debug_line}
5263 state machine to @var{value}, which must be an unsigned integer.
5267 @node Loc_mark_labels
5268 @section @code{.loc_mark_labels @var{enable}}
5269 @cindex @code{loc_mark_labels} directive
5270 When emitting DWARF2 line number information,
5271 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5272 to the @code{.debug_line} line number matrix with the @code{basic_block}
5273 register in the state machine set whenever a code label is seen.
5274 The @var{enable} argument should be either 1 or 0, to enable or disable
5275 this function respectively.
5279 @section @code{.local @var{names}}
5281 @cindex @code{local} directive
5282 This directive, which is available for ELF targets, marks each symbol in
5283 the comma-separated list of @code{names} as a local symbol so that it
5284 will not be externally visible. If the symbols do not already exist,
5285 they will be created.
5287 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5288 accept an alignment argument, which is the case for most ELF targets,
5289 the @code{.local} directive can be used in combination with @code{.comm}
5290 (@pxref{Comm}) to define aligned local common data.
5294 @section @code{.long @var{expressions}}
5296 @cindex @code{long} directive
5297 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5300 @c no one seems to know what this is for or whether this description is
5301 @c what it really ought to do
5303 @section @code{.lsym @var{symbol}, @var{expression}}
5305 @cindex @code{lsym} directive
5306 @cindex symbol, not referenced in assembly
5307 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5308 the hash table, ensuring it cannot be referenced by name during the
5309 rest of the assembly. This sets the attributes of the symbol to be
5310 the same as the expression value:
5312 @var{other} = @var{descriptor} = 0
5313 @var{type} = @r{(section of @var{expression})}
5314 @var{value} = @var{expression}
5317 The new symbol is not flagged as external.
5321 @section @code{.macro}
5324 The commands @code{.macro} and @code{.endm} allow you to define macros that
5325 generate assembly output. For example, this definition specifies a macro
5326 @code{sum} that puts a sequence of numbers into memory:
5329 .macro sum from=0, to=5
5338 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5350 @item .macro @var{macname}
5351 @itemx .macro @var{macname} @var{macargs} @dots{}
5352 @cindex @code{macro} directive
5353 Begin the definition of a macro called @var{macname}. If your macro
5354 definition requires arguments, specify their names after the macro name,
5355 separated by commas or spaces. You can qualify the macro argument to
5356 indicate whether all invocations must specify a non-blank value (through
5357 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5358 (through @samp{:@code{vararg}}). You can supply a default value for any
5359 macro argument by following the name with @samp{=@var{deflt}}. You
5360 cannot define two macros with the same @var{macname} unless it has been
5361 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5362 definitions. For example, these are all valid @code{.macro} statements:
5366 Begin the definition of a macro called @code{comm}, which takes no
5369 @item .macro plus1 p, p1
5370 @itemx .macro plus1 p p1
5371 Either statement begins the definition of a macro called @code{plus1},
5372 which takes two arguments; within the macro definition, write
5373 @samp{\p} or @samp{\p1} to evaluate the arguments.
5375 @item .macro reserve_str p1=0 p2
5376 Begin the definition of a macro called @code{reserve_str}, with two
5377 arguments. The first argument has a default value, but not the second.
5378 After the definition is complete, you can call the macro either as
5379 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5380 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5381 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5382 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5384 @item .macro m p1:req, p2=0, p3:vararg
5385 Begin the definition of a macro called @code{m}, with at least three
5386 arguments. The first argument must always have a value specified, but
5387 not the second, which instead has a default value. The third formal
5388 will get assigned all remaining arguments specified at invocation time.
5390 When you call a macro, you can specify the argument values either by
5391 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5392 @samp{sum to=17, from=9}.
5396 Note that since each of the @var{macargs} can be an identifier exactly
5397 as any other one permitted by the target architecture, there may be
5398 occasional problems if the target hand-crafts special meanings to certain
5399 characters when they occur in a special position. For example, if the colon
5400 (@code{:}) is generally permitted to be part of a symbol name, but the
5401 architecture specific code special-cases it when occurring as the final
5402 character of a symbol (to denote a label), then the macro parameter
5403 replacement code will have no way of knowing that and consider the whole
5404 construct (including the colon) an identifier, and check only this
5405 identifier for being the subject to parameter substitution. So for example
5406 this macro definition:
5414 might not work as expected. Invoking @samp{label foo} might not create a label
5415 called @samp{foo} but instead just insert the text @samp{\l:} into the
5416 assembler source, probably generating an error about an unrecognised
5419 Similarly problems might occur with the period character (@samp{.})
5420 which is often allowed inside opcode names (and hence identifier names). So
5421 for example constructing a macro to build an opcode from a base name and a
5422 length specifier like this:
5425 .macro opcode base length
5430 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5431 instruction but instead generate some kind of error as the assembler tries to
5432 interpret the text @samp{\base.\length}.
5434 There are several possible ways around this problem:
5437 @item Insert white space
5438 If it is possible to use white space characters then this is the simplest
5447 @item Use @samp{\()}
5448 The string @samp{\()} can be used to separate the end of a macro argument from
5449 the following text. eg:
5452 .macro opcode base length
5457 @item Use the alternate macro syntax mode
5458 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5459 used as a separator. eg:
5469 Note: this problem of correctly identifying string parameters to pseudo ops
5470 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5471 and @code{.irpc} (@pxref{Irpc}) as well.
5474 @cindex @code{endm} directive
5475 Mark the end of a macro definition.
5478 @cindex @code{exitm} directive
5479 Exit early from the current macro definition.
5481 @cindex number of macros executed
5482 @cindex macros, count executed
5484 @command{@value{AS}} maintains a counter of how many macros it has
5485 executed in this pseudo-variable; you can copy that number to your
5486 output with @samp{\@@}, but @emph{only within a macro definition}.
5488 @item LOCAL @var{name} [ , @dots{} ]
5489 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5490 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5491 @xref{Altmacro,,@code{.altmacro}}.
5495 @section @code{.mri @var{val}}
5497 @cindex @code{mri} directive
5498 @cindex MRI mode, temporarily
5499 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5500 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5501 affects code assembled until the next @code{.mri} directive, or until the end
5502 of the file. @xref{M, MRI mode, MRI mode}.
5505 @section @code{.noaltmacro}
5506 Disable alternate macro mode. @xref{Altmacro}.
5509 @section @code{.nolist}
5511 @cindex @code{nolist} directive
5512 @cindex listing control, turning off
5513 Control (in conjunction with the @code{.list} directive) whether or
5514 not assembly listings are generated. These two directives maintain an
5515 internal counter (which is zero initially). @code{.list} increments the
5516 counter, and @code{.nolist} decrements it. Assembly listings are
5517 generated whenever the counter is greater than zero.
5520 @section @code{.octa @var{bignums}}
5522 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5523 @cindex @code{octa} directive
5524 @cindex integer, 16-byte
5525 @cindex sixteen byte integer
5526 This directive expects zero or more bignums, separated by commas. For each
5527 bignum, it emits a 16-byte integer.
5529 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5530 hence @emph{octa}-word for 16 bytes.
5533 @section @code{.org @var{new-lc} , @var{fill}}
5535 @cindex @code{org} directive
5536 @cindex location counter, advancing
5537 @cindex advancing location counter
5538 @cindex current address, advancing
5539 Advance the location counter of the current section to
5540 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5541 expression with the same section as the current subsection. That is,
5542 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5543 wrong section, the @code{.org} directive is ignored. To be compatible
5544 with former assemblers, if the section of @var{new-lc} is absolute,
5545 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5546 is the same as the current subsection.
5548 @code{.org} may only increase the location counter, or leave it
5549 unchanged; you cannot use @code{.org} to move the location counter
5552 @c double negative used below "not undefined" because this is a specific
5553 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5554 @c section. doc@cygnus.com 18feb91
5555 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5556 may not be undefined. If you really detest this restriction we eagerly await
5557 a chance to share your improved assembler.
5559 Beware that the origin is relative to the start of the section, not
5560 to the start of the subsection. This is compatible with other
5561 people's assemblers.
5563 When the location counter (of the current subsection) is advanced, the
5564 intervening bytes are filled with @var{fill} which should be an
5565 absolute expression. If the comma and @var{fill} are omitted,
5566 @var{fill} defaults to zero.
5569 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5571 @cindex padding the location counter given a power of two
5572 @cindex @code{p2align} directive
5573 Pad the location counter (in the current subsection) to a particular
5574 storage boundary. The first expression (which must be absolute) is the
5575 number of low-order zero bits the location counter must have after
5576 advancement. For example @samp{.p2align 3} advances the location
5577 counter until it a multiple of 8. If the location counter is already a
5578 multiple of 8, no change is needed.
5580 The second expression (also absolute) gives the fill value to be stored in the
5581 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5582 padding bytes are normally zero. However, on some systems, if the section is
5583 marked as containing code and the fill value is omitted, the space is filled
5584 with no-op instructions.
5586 The third expression is also absolute, and is also optional. If it is present,
5587 it is the maximum number of bytes that should be skipped by this alignment
5588 directive. If doing the alignment would require skipping more bytes than the
5589 specified maximum, then the alignment is not done at all. You can omit the
5590 fill value (the second argument) entirely by simply using two commas after the
5591 required alignment; this can be useful if you want the alignment to be filled
5592 with no-op instructions when appropriate.
5594 @cindex @code{p2alignw} directive
5595 @cindex @code{p2alignl} directive
5596 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5597 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5598 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5599 fill pattern as a four byte longword value. For example, @code{.p2alignw
5600 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5601 filled in with the value 0x368d (the exact placement of the bytes depends upon
5602 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5607 @section @code{.popsection}
5609 @cindex @code{popsection} directive
5610 @cindex Section Stack
5611 This is one of the ELF section stack manipulation directives. The others are
5612 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5613 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5616 This directive replaces the current section (and subsection) with the top
5617 section (and subsection) on the section stack. This section is popped off the
5623 @section @code{.previous}
5625 @cindex @code{previous} directive
5626 @cindex Section Stack
5627 This is one of the ELF section stack manipulation directives. The others are
5628 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5629 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5630 (@pxref{PopSection}).
5632 This directive swaps the current section (and subsection) with most recently
5633 referenced section/subsection pair prior to this one. Multiple
5634 @code{.previous} directives in a row will flip between two sections (and their
5635 subsections). For example:
5647 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5653 # Now in section A subsection 1
5657 # Now in section B subsection 0
5660 # Now in section B subsection 1
5663 # Now in section B subsection 0
5667 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5668 section B and 0x9abc into subsection 1 of section B.
5670 In terms of the section stack, this directive swaps the current section with
5671 the top section on the section stack.
5675 @section @code{.print @var{string}}
5677 @cindex @code{print} directive
5678 @command{@value{AS}} will print @var{string} on the standard output during
5679 assembly. You must put @var{string} in double quotes.
5683 @section @code{.protected @var{names}}
5685 @cindex @code{protected} directive
5687 This is one of the ELF visibility directives. The other two are
5688 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5690 This directive overrides the named symbols default visibility (which is set by
5691 their binding: local, global or weak). The directive sets the visibility to
5692 @code{protected} which means that any references to the symbols from within the
5693 components that defines them must be resolved to the definition in that
5694 component, even if a definition in another component would normally preempt
5699 @section @code{.psize @var{lines} , @var{columns}}
5701 @cindex @code{psize} directive
5702 @cindex listing control: paper size
5703 @cindex paper size, for listings
5704 Use this directive to declare the number of lines---and, optionally, the
5705 number of columns---to use for each page, when generating listings.
5707 If you do not use @code{.psize}, listings use a default line-count
5708 of 60. You may omit the comma and @var{columns} specification; the
5709 default width is 200 columns.
5711 @command{@value{AS}} generates formfeeds whenever the specified number of
5712 lines is exceeded (or whenever you explicitly request one, using
5715 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5716 those explicitly specified with @code{.eject}.
5719 @section @code{.purgem @var{name}}
5721 @cindex @code{purgem} directive
5722 Undefine the macro @var{name}, so that later uses of the string will not be
5723 expanded. @xref{Macro}.
5727 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5729 @cindex @code{pushsection} directive
5730 @cindex Section Stack
5731 This is one of the ELF section stack manipulation directives. The others are
5732 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5733 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5736 This directive pushes the current section (and subsection) onto the
5737 top of the section stack, and then replaces the current section and
5738 subsection with @code{name} and @code{subsection}. The optional
5739 @code{flags}, @code{type} and @code{arguments} are treated the same
5740 as in the @code{.section} (@pxref{Section}) directive.
5744 @section @code{.quad @var{bignums}}
5746 @cindex @code{quad} directive
5747 @code{.quad} expects zero or more bignums, separated by commas. For
5748 each bignum, it emits
5750 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5751 warning message; and just takes the lowest order 8 bytes of the bignum.
5752 @cindex eight-byte integer
5753 @cindex integer, 8-byte
5755 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5756 hence @emph{quad}-word for 8 bytes.
5759 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5760 warning message; and just takes the lowest order 16 bytes of the bignum.
5761 @cindex sixteen-byte integer
5762 @cindex integer, 16-byte
5766 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5768 @cindex @code{reloc} directive
5769 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5770 @var{expression}. If @var{offset} is a number, the relocation is generated in
5771 the current section. If @var{offset} is an expression that resolves to a
5772 symbol plus offset, the relocation is generated in the given symbol's section.
5773 @var{expression}, if present, must resolve to a symbol plus addend or to an
5774 absolute value, but note that not all targets support an addend. e.g. ELF REL
5775 targets such as i386 store an addend in the section contents rather than in the
5776 relocation. This low level interface does not support addends stored in the
5780 @section @code{.rept @var{count}}
5782 @cindex @code{rept} directive
5783 Repeat the sequence of lines between the @code{.rept} directive and the next
5784 @code{.endr} directive @var{count} times.
5786 For example, assembling
5794 is equivalent to assembling
5803 @section @code{.sbttl "@var{subheading}"}
5805 @cindex @code{sbttl} directive
5806 @cindex subtitles for listings
5807 @cindex listing control: subtitle
5808 Use @var{subheading} as the title (third line, immediately after the
5809 title line) when generating assembly listings.
5811 This directive affects subsequent pages, as well as the current page if
5812 it appears within ten lines of the top of a page.
5816 @section @code{.scl @var{class}}
5818 @cindex @code{scl} directive
5819 @cindex symbol storage class (COFF)
5820 @cindex COFF symbol storage class
5821 Set the storage-class value for a symbol. This directive may only be
5822 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5823 whether a symbol is static or external, or it may record further
5824 symbolic debugging information.
5827 The @samp{.scl} directive is primarily associated with COFF output; when
5828 configured to generate @code{b.out} output format, @command{@value{AS}}
5829 accepts this directive but ignores it.
5835 @section @code{.section @var{name}}
5837 @cindex named section
5838 Use the @code{.section} directive to assemble the following code into a section
5841 This directive is only supported for targets that actually support arbitrarily
5842 named sections; on @code{a.out} targets, for example, it is not accepted, even
5843 with a standard @code{a.out} section name.
5847 @c only print the extra heading if both COFF and ELF are set
5848 @subheading COFF Version
5851 @cindex @code{section} directive (COFF version)
5852 For COFF targets, the @code{.section} directive is used in one of the following
5856 .section @var{name}[, "@var{flags}"]
5857 .section @var{name}[, @var{subsection}]
5860 If the optional argument is quoted, it is taken as flags to use for the
5861 section. Each flag is a single character. The following flags are recognized:
5864 bss section (uninitialized data)
5866 section is not loaded
5876 shared section (meaningful for PE targets)
5878 ignored. (For compatibility with the ELF version)
5880 section is not readable (meaningful for PE targets)
5882 single-digit power-of-two section alignment (GNU extension)
5885 If no flags are specified, the default flags depend upon the section name. If
5886 the section name is not recognized, the default will be for the section to be
5887 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5888 from the section, rather than adding them, so if they are used on their own it
5889 will be as if no flags had been specified at all.
5891 If the optional argument to the @code{.section} directive is not quoted, it is
5892 taken as a subsection number (@pxref{Sub-Sections}).
5897 @c only print the extra heading if both COFF and ELF are set
5898 @subheading ELF Version
5901 @cindex Section Stack
5902 This is one of the ELF section stack manipulation directives. The others are
5903 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5904 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5905 @code{.previous} (@pxref{Previous}).
5907 @cindex @code{section} directive (ELF version)
5908 For ELF targets, the @code{.section} directive is used like this:
5911 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
5914 The optional @var{flags} argument is a quoted string which may contain any
5915 combination of the following characters:
5918 section is allocatable
5920 section is excluded from executable and shared library.
5924 section is executable
5926 section is mergeable
5928 section contains zero terminated strings
5930 section is a member of a section group
5932 section is used for thread-local-storage
5934 section is a member of the previously-current section's group, if any
5937 The optional @var{type} argument may contain one of the following constants:
5940 section contains data
5942 section does not contain data (i.e., section only occupies space)
5944 section contains data which is used by things other than the program
5946 section contains an array of pointers to init functions
5948 section contains an array of pointers to finish functions
5949 @item @@preinit_array
5950 section contains an array of pointers to pre-init functions
5953 Many targets only support the first three section types.
5955 Note on targets where the @code{@@} character is the start of a comment (eg
5956 ARM) then another character is used instead. For example the ARM port uses the
5959 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
5960 be specified as well as an extra argument---@var{entsize}---like this:
5963 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
5966 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
5967 constants, each @var{entsize} octets long. Sections with both @code{M} and
5968 @code{S} must contain zero terminated strings where each character is
5969 @var{entsize} bytes long. The linker may remove duplicates within sections with
5970 the same name, same entity size and same flags. @var{entsize} must be an
5971 absolute expression. For sections with both @code{M} and @code{S}, a string
5972 which is a suffix of a larger string is considered a duplicate. Thus
5973 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
5974 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
5976 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
5977 be present along with an additional field like this:
5980 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
5983 The @var{GroupName} field specifies the name of the section group to which this
5984 particular section belongs. The optional linkage field can contain:
5987 indicates that only one copy of this section should be retained
5992 Note: if both the @var{M} and @var{G} flags are present then the fields for
5993 the Merge flag should come first, like this:
5996 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
5999 If @var{flags} contains the @code{?} symbol then it may not also contain the
6000 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6001 present. Instead, @code{?} says to consider the section that's current before
6002 this directive. If that section used @code{G}, then the new section will use
6003 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6004 If not, then the @code{?} symbol has no effect.
6006 If no flags are specified, the default flags depend upon the section name. If
6007 the section name is not recognized, the default will be for the section to have
6008 none of the above flags: it will not be allocated in memory, nor writable, nor
6009 executable. The section will contain data.
6011 For ELF targets, the assembler supports another type of @code{.section}
6012 directive for compatibility with the Solaris assembler:
6015 .section "@var{name}"[, @var{flags}...]
6018 Note that the section name is quoted. There may be a sequence of comma
6022 section is allocatable
6026 section is executable
6028 section is excluded from executable and shared library.
6030 section is used for thread local storage
6033 This directive replaces the current section and subsection. See the
6034 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6035 some examples of how this directive and the other section stack directives
6041 @section @code{.set @var{symbol}, @var{expression}}
6043 @cindex @code{set} directive
6044 @cindex symbol value, setting
6045 Set the value of @var{symbol} to @var{expression}. This
6046 changes @var{symbol}'s value and type to conform to
6047 @var{expression}. If @var{symbol} was flagged as external, it remains
6048 flagged (@pxref{Symbol Attributes}).
6050 You may @code{.set} a symbol many times in the same assembly.
6052 If you @code{.set} a global symbol, the value stored in the object
6053 file is the last value stored into it.
6056 On Z80 @code{set} is a real instruction, use
6057 @samp{@var{symbol} defl @var{expression}} instead.
6061 @section @code{.short @var{expressions}}
6063 @cindex @code{short} directive
6065 @code{.short} is normally the same as @samp{.word}.
6066 @xref{Word,,@code{.word}}.
6068 In some configurations, however, @code{.short} and @code{.word} generate
6069 numbers of different lengths. @xref{Machine Dependencies}.
6073 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6076 This expects zero or more @var{expressions}, and emits
6077 a 16 bit number for each.
6082 @section @code{.single @var{flonums}}
6084 @cindex @code{single} directive
6085 @cindex floating point numbers (single)
6086 This directive assembles zero or more flonums, separated by commas. It
6087 has the same effect as @code{.float}.
6089 The exact kind of floating point numbers emitted depends on how
6090 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6094 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6095 numbers in @sc{ieee} format.
6101 @section @code{.size}
6103 This directive is used to set the size associated with a symbol.
6107 @c only print the extra heading if both COFF and ELF are set
6108 @subheading COFF Version
6111 @cindex @code{size} directive (COFF version)
6112 For COFF targets, the @code{.size} directive is only permitted inside
6113 @code{.def}/@code{.endef} pairs. It is used like this:
6116 .size @var{expression}
6120 @samp{.size} is only meaningful when generating COFF format output; when
6121 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6128 @c only print the extra heading if both COFF and ELF are set
6129 @subheading ELF Version
6132 @cindex @code{size} directive (ELF version)
6133 For ELF targets, the @code{.size} directive is used like this:
6136 .size @var{name} , @var{expression}
6139 This directive sets the size associated with a symbol @var{name}.
6140 The size in bytes is computed from @var{expression} which can make use of label
6141 arithmetic. This directive is typically used to set the size of function
6146 @ifclear no-space-dir
6148 @section @code{.skip @var{size} , @var{fill}}
6150 @cindex @code{skip} directive
6151 @cindex filling memory
6152 This directive emits @var{size} bytes, each of value @var{fill}. Both
6153 @var{size} and @var{fill} are absolute expressions. If the comma and
6154 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6159 @section @code{.sleb128 @var{expressions}}
6161 @cindex @code{sleb128} directive
6162 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6163 compact, variable length representation of numbers used by the DWARF
6164 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6166 @ifclear no-space-dir
6168 @section @code{.space @var{size} , @var{fill}}
6170 @cindex @code{space} directive
6171 @cindex filling memory
6172 This directive emits @var{size} bytes, each of value @var{fill}. Both
6173 @var{size} and @var{fill} are absolute expressions. If the comma
6174 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6179 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6180 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6181 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6182 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6190 @section @code{.stabd, .stabn, .stabs}
6192 @cindex symbolic debuggers, information for
6193 @cindex @code{stab@var{x}} directives
6194 There are three directives that begin @samp{.stab}.
6195 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6196 The symbols are not entered in the @command{@value{AS}} hash table: they
6197 cannot be referenced elsewhere in the source file.
6198 Up to five fields are required:
6202 This is the symbol's name. It may contain any character except
6203 @samp{\000}, so is more general than ordinary symbol names. Some
6204 debuggers used to code arbitrarily complex structures into symbol names
6208 An absolute expression. The symbol's type is set to the low 8 bits of
6209 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6210 and debuggers choke on silly bit patterns.
6213 An absolute expression. The symbol's ``other'' attribute is set to the
6214 low 8 bits of this expression.
6217 An absolute expression. The symbol's descriptor is set to the low 16
6218 bits of this expression.
6221 An absolute expression which becomes the symbol's value.
6224 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6225 or @code{.stabs} statement, the symbol has probably already been created;
6226 you get a half-formed symbol in your object file. This is
6227 compatible with earlier assemblers!
6230 @cindex @code{stabd} directive
6231 @item .stabd @var{type} , @var{other} , @var{desc}
6233 The ``name'' of the symbol generated is not even an empty string.
6234 It is a null pointer, for compatibility. Older assemblers used a
6235 null pointer so they didn't waste space in object files with empty
6238 The symbol's value is set to the location counter,
6239 relocatably. When your program is linked, the value of this symbol
6240 is the address of the location counter when the @code{.stabd} was
6243 @cindex @code{stabn} directive
6244 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6245 The name of the symbol is set to the empty string @code{""}.
6247 @cindex @code{stabs} directive
6248 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6249 All five fields are specified.
6255 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6256 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6258 @cindex string, copying to object file
6259 @cindex string8, copying to object file
6260 @cindex string16, copying to object file
6261 @cindex string32, copying to object file
6262 @cindex string64, copying to object file
6263 @cindex @code{string} directive
6264 @cindex @code{string8} directive
6265 @cindex @code{string16} directive
6266 @cindex @code{string32} directive
6267 @cindex @code{string64} directive
6269 Copy the characters in @var{str} to the object file. You may specify more than
6270 one string to copy, separated by commas. Unless otherwise specified for a
6271 particular machine, the assembler marks the end of each string with a 0 byte.
6272 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6274 The variants @code{string16}, @code{string32} and @code{string64} differ from
6275 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6276 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6277 are stored in target endianness byte order.
6283 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6284 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6289 @section @code{.struct @var{expression}}
6291 @cindex @code{struct} directive
6292 Switch to the absolute section, and set the section offset to @var{expression},
6293 which must be an absolute expression. You might use this as follows:
6302 This would define the symbol @code{field1} to have the value 0, the symbol
6303 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6304 value 8. Assembly would be left in the absolute section, and you would need to
6305 use a @code{.section} directive of some sort to change to some other section
6306 before further assembly.
6310 @section @code{.subsection @var{name}}
6312 @cindex @code{subsection} directive
6313 @cindex Section Stack
6314 This is one of the ELF section stack manipulation directives. The others are
6315 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6316 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6319 This directive replaces the current subsection with @code{name}. The current
6320 section is not changed. The replaced subsection is put onto the section stack
6321 in place of the then current top of stack subsection.
6326 @section @code{.symver}
6327 @cindex @code{symver} directive
6328 @cindex symbol versioning
6329 @cindex versions of symbols
6330 Use the @code{.symver} directive to bind symbols to specific version nodes
6331 within a source file. This is only supported on ELF platforms, and is
6332 typically used when assembling files to be linked into a shared library.
6333 There are cases where it may make sense to use this in objects to be bound
6334 into an application itself so as to override a versioned symbol from a
6337 For ELF targets, the @code{.symver} directive can be used like this:
6339 .symver @var{name}, @var{name2@@nodename}
6341 If the symbol @var{name} is defined within the file
6342 being assembled, the @code{.symver} directive effectively creates a symbol
6343 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6344 just don't try and create a regular alias is that the @var{@@} character isn't
6345 permitted in symbol names. The @var{name2} part of the name is the actual name
6346 of the symbol by which it will be externally referenced. The name @var{name}
6347 itself is merely a name of convenience that is used so that it is possible to
6348 have definitions for multiple versions of a function within a single source
6349 file, and so that the compiler can unambiguously know which version of a
6350 function is being mentioned. The @var{nodename} portion of the alias should be
6351 the name of a node specified in the version script supplied to the linker when
6352 building a shared library. If you are attempting to override a versioned
6353 symbol from a shared library, then @var{nodename} should correspond to the
6354 nodename of the symbol you are trying to override.
6356 If the symbol @var{name} is not defined within the file being assembled, all
6357 references to @var{name} will be changed to @var{name2@@nodename}. If no
6358 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6361 Another usage of the @code{.symver} directive is:
6363 .symver @var{name}, @var{name2@@@@nodename}
6365 In this case, the symbol @var{name} must exist and be defined within
6366 the file being assembled. It is similar to @var{name2@@nodename}. The
6367 difference is @var{name2@@@@nodename} will also be used to resolve
6368 references to @var{name2} by the linker.
6370 The third usage of the @code{.symver} directive is:
6372 .symver @var{name}, @var{name2@@@@@@nodename}
6374 When @var{name} is not defined within the
6375 file being assembled, it is treated as @var{name2@@nodename}. When
6376 @var{name} is defined within the file being assembled, the symbol
6377 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6382 @section @code{.tag @var{structname}}
6384 @cindex COFF structure debugging
6385 @cindex structure debugging, COFF
6386 @cindex @code{tag} directive
6387 This directive is generated by compilers to include auxiliary debugging
6388 information in the symbol table. It is only permitted inside
6389 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6390 definitions in the symbol table with instances of those structures.
6393 @samp{.tag} is only used when generating COFF format output; when
6394 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6400 @section @code{.text @var{subsection}}
6402 @cindex @code{text} directive
6403 Tells @command{@value{AS}} to assemble the following statements onto the end of
6404 the text subsection numbered @var{subsection}, which is an absolute
6405 expression. If @var{subsection} is omitted, subsection number zero
6409 @section @code{.title "@var{heading}"}
6411 @cindex @code{title} directive
6412 @cindex listing control: title line
6413 Use @var{heading} as the title (second line, immediately after the
6414 source file name and pagenumber) when generating assembly listings.
6416 This directive affects subsequent pages, as well as the current page if
6417 it appears within ten lines of the top of a page.
6421 @section @code{.type}
6423 This directive is used to set the type of a symbol.
6427 @c only print the extra heading if both COFF and ELF are set
6428 @subheading COFF Version
6431 @cindex COFF symbol type
6432 @cindex symbol type, COFF
6433 @cindex @code{type} directive (COFF version)
6434 For COFF targets, this directive is permitted only within
6435 @code{.def}/@code{.endef} pairs. It is used like this:
6441 This records the integer @var{int} as the type attribute of a symbol table
6445 @samp{.type} is associated only with COFF format output; when
6446 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6447 directive but ignores it.
6453 @c only print the extra heading if both COFF and ELF are set
6454 @subheading ELF Version
6457 @cindex ELF symbol type
6458 @cindex symbol type, ELF
6459 @cindex @code{type} directive (ELF version)
6460 For ELF targets, the @code{.type} directive is used like this:
6463 .type @var{name} , @var{type description}
6466 This sets the type of symbol @var{name} to be either a
6467 function symbol or an object symbol. There are five different syntaxes
6468 supported for the @var{type description} field, in order to provide
6469 compatibility with various other assemblers.
6471 Because some of the characters used in these syntaxes (such as @samp{@@} and
6472 @samp{#}) are comment characters for some architectures, some of the syntaxes
6473 below do not work on all architectures. The first variant will be accepted by
6474 the GNU assembler on all architectures so that variant should be used for
6475 maximum portability, if you do not need to assemble your code with other
6478 The syntaxes supported are:
6481 .type <name> STT_<TYPE_IN_UPPER_CASE>
6482 .type <name>,#<type>
6483 .type <name>,@@<type>
6484 .type <name>,%<type>
6485 .type <name>,"<type>"
6488 The types supported are:
6493 Mark the symbol as being a function name.
6496 @itemx gnu_indirect_function
6497 Mark the symbol as an indirect function when evaluated during reloc
6498 processing. (This is only supported on Linux targeted assemblers).
6502 Mark the symbol as being a data object.
6506 Mark the symbol as being a thead-local data object.
6510 Mark the symbol as being a common data object.
6514 Does not mark the symbol in any way. It is supported just for completeness.
6516 @item gnu_unique_object
6517 Marks the symbol as being a globally unique data object. The dynamic linker
6518 will make sure that in the entire process there is just one symbol with this
6519 name and type in use. (This is only supported on Linux targeted assemblers).
6523 Note: Some targets support extra types in addition to those listed above.
6529 @section @code{.uleb128 @var{expressions}}
6531 @cindex @code{uleb128} directive
6532 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6533 compact, variable length representation of numbers used by the DWARF
6534 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6538 @section @code{.val @var{addr}}
6540 @cindex @code{val} directive
6541 @cindex COFF value attribute
6542 @cindex value attribute, COFF
6543 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6544 records the address @var{addr} as the value attribute of a symbol table
6548 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6549 configured for @code{b.out}, it accepts this directive but ignores it.
6555 @section @code{.version "@var{string}"}
6557 @cindex @code{version} directive
6558 This directive creates a @code{.note} section and places into it an ELF
6559 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6564 @section @code{.vtable_entry @var{table}, @var{offset}}
6566 @cindex @code{vtable_entry} directive
6567 This directive finds or creates a symbol @code{table} and creates a
6568 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6571 @section @code{.vtable_inherit @var{child}, @var{parent}}
6573 @cindex @code{vtable_inherit} directive
6574 This directive finds the symbol @code{child} and finds or creates the symbol
6575 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6576 parent whose addend is the value of the child symbol. As a special case the
6577 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6581 @section @code{.warning "@var{string}"}
6582 @cindex warning directive
6583 Similar to the directive @code{.error}
6584 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6587 @section @code{.weak @var{names}}
6589 @cindex @code{weak} directive
6590 This directive sets the weak attribute on the comma separated list of symbol
6591 @code{names}. If the symbols do not already exist, they will be created.
6593 On COFF targets other than PE, weak symbols are a GNU extension. This
6594 directive sets the weak attribute on the comma separated list of symbol
6595 @code{names}. If the symbols do not already exist, they will be created.
6597 On the PE target, weak symbols are supported natively as weak aliases.
6598 When a weak symbol is created that is not an alias, GAS creates an
6599 alternate symbol to hold the default value.
6602 @section @code{.weakref @var{alias}, @var{target}}
6604 @cindex @code{weakref} directive
6605 This directive creates an alias to the target symbol that enables the symbol to
6606 be referenced with weak-symbol semantics, but without actually making it weak.
6607 If direct references or definitions of the symbol are present, then the symbol
6608 will not be weak, but if all references to it are through weak references, the
6609 symbol will be marked as weak in the symbol table.
6611 The effect is equivalent to moving all references to the alias to a separate
6612 assembly source file, renaming the alias to the symbol in it, declaring the
6613 symbol as weak there, and running a reloadable link to merge the object files
6614 resulting from the assembly of the new source file and the old source file that
6615 had the references to the alias removed.
6617 The alias itself never makes to the symbol table, and is entirely handled
6618 within the assembler.
6621 @section @code{.word @var{expressions}}
6623 @cindex @code{word} directive
6624 This directive expects zero or more @var{expressions}, of any section,
6625 separated by commas.
6628 For each expression, @command{@value{AS}} emits a 32-bit number.
6631 For each expression, @command{@value{AS}} emits a 16-bit number.
6636 The size of the number emitted, and its byte order,
6637 depend on what target computer the assembly is for.
6640 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6641 @c happen---32-bit addressability, period; no long/short jumps.
6642 @ifset DIFF-TBL-KLUGE
6643 @cindex difference tables altered
6644 @cindex altered difference tables
6646 @emph{Warning: Special Treatment to support Compilers}
6650 Machines with a 32-bit address space, but that do less than 32-bit
6651 addressing, require the following special treatment. If the machine of
6652 interest to you does 32-bit addressing (or doesn't require it;
6653 @pxref{Machine Dependencies}), you can ignore this issue.
6656 In order to assemble compiler output into something that works,
6657 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6658 Directives of the form @samp{.word sym1-sym2} are often emitted by
6659 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6660 directive of the form @samp{.word sym1-sym2}, and the difference between
6661 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6662 creates a @dfn{secondary jump table}, immediately before the next label.
6663 This secondary jump table is preceded by a short-jump to the
6664 first byte after the secondary table. This short-jump prevents the flow
6665 of control from accidentally falling into the new table. Inside the
6666 table is a long-jump to @code{sym2}. The original @samp{.word}
6667 contains @code{sym1} minus the address of the long-jump to
6670 If there were several occurrences of @samp{.word sym1-sym2} before the
6671 secondary jump table, all of them are adjusted. If there was a
6672 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6673 long-jump to @code{sym4} is included in the secondary jump table,
6674 and the @code{.word} directives are adjusted to contain @code{sym3}
6675 minus the address of the long-jump to @code{sym4}; and so on, for as many
6676 entries in the original jump table as necessary.
6679 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6680 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6681 assembly language programmers.
6684 @c end DIFF-TBL-KLUGE
6687 @section Deprecated Directives
6689 @cindex deprecated directives
6690 @cindex obsolescent directives
6691 One day these directives won't work.
6692 They are included for compatibility with older assemblers.
6699 @node Object Attributes
6700 @chapter Object Attributes
6701 @cindex object attributes
6703 @command{@value{AS}} assembles source files written for a specific architecture
6704 into object files for that architecture. But not all object files are alike.
6705 Many architectures support incompatible variations. For instance, floating
6706 point arguments might be passed in floating point registers if the object file
6707 requires hardware floating point support---or floating point arguments might be
6708 passed in integer registers if the object file supports processors with no
6709 hardware floating point unit. Or, if two objects are built for different
6710 generations of the same architecture, the combination may require the
6711 newer generation at run-time.
6713 This information is useful during and after linking. At link time,
6714 @command{@value{LD}} can warn about incompatible object files. After link
6715 time, tools like @command{gdb} can use it to process the linked file
6718 Compatibility information is recorded as a series of object attributes. Each
6719 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6720 string, and indicates who sets the meaning of the tag. The tag is an integer,
6721 and indicates what property the attribute describes. The value may be a string
6722 or an integer, and indicates how the property affects this object. Missing
6723 attributes are the same as attributes with a zero value or empty string value.
6725 Object attributes were developed as part of the ABI for the ARM Architecture.
6726 The file format is documented in @cite{ELF for the ARM Architecture}.
6729 * GNU Object Attributes:: @sc{gnu} Object Attributes
6730 * Defining New Object Attributes:: Defining New Object Attributes
6733 @node GNU Object Attributes
6734 @section @sc{gnu} Object Attributes
6736 The @code{.gnu_attribute} directive records an object attribute
6737 with vendor @samp{gnu}.
6739 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6740 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6741 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6742 2} is set for architecture-independent attributes and clear for
6743 architecture-dependent ones.
6745 @subsection Common @sc{gnu} attributes
6747 These attributes are valid on all architectures.
6750 @item Tag_compatibility (32)
6751 The compatibility attribute takes an integer flag value and a vendor name. If
6752 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6753 then the file is only compatible with the named toolchain. If it is greater
6754 than 1, the file can only be processed by other toolchains under some private
6755 arrangement indicated by the flag value and the vendor name.
6758 @subsection MIPS Attributes
6761 @item Tag_GNU_MIPS_ABI_FP (4)
6762 The floating-point ABI used by this object file. The value will be:
6766 0 for files not affected by the floating-point ABI.
6768 1 for files using the hardware floating-point with a standard double-precision
6771 2 for files using the hardware floating-point ABI with a single-precision FPU.
6773 3 for files using the software floating-point ABI.
6775 4 for files using the hardware floating-point ABI with 64-bit wide
6776 double-precision floating-point registers and 32-bit wide general
6781 @subsection PowerPC Attributes
6784 @item Tag_GNU_Power_ABI_FP (4)
6785 The floating-point ABI used by this object file. The value will be:
6789 0 for files not affected by the floating-point ABI.
6791 1 for files using double-precision hardware floating-point ABI.
6793 2 for files using the software floating-point ABI.
6795 3 for files using single-precision hardware floating-point ABI.
6798 @item Tag_GNU_Power_ABI_Vector (8)
6799 The vector ABI used by this object file. The value will be:
6803 0 for files not affected by the vector ABI.
6805 1 for files using general purpose registers to pass vectors.
6807 2 for files using AltiVec registers to pass vectors.
6809 3 for files using SPE registers to pass vectors.
6813 @node Defining New Object Attributes
6814 @section Defining New Object Attributes
6816 If you want to define a new @sc{gnu} object attribute, here are the places you
6817 will need to modify. New attributes should be discussed on the @samp{binutils}
6822 This manual, which is the official register of attributes.
6824 The header for your architecture @file{include/elf}, to define the tag.
6826 The @file{bfd} support file for your architecture, to merge the attribute
6827 and issue any appropriate link warnings.
6829 Test cases in @file{ld/testsuite} for merging and link warnings.
6831 @file{binutils/readelf.c} to display your attribute.
6833 GCC, if you want the compiler to mark the attribute automatically.
6839 @node Machine Dependencies
6840 @chapter Machine Dependent Features
6842 @cindex machine dependencies
6843 The machine instruction sets are (almost by definition) different on
6844 each machine where @command{@value{AS}} runs. Floating point representations
6845 vary as well, and @command{@value{AS}} often supports a few additional
6846 directives or command-line options for compatibility with other
6847 assemblers on a particular platform. Finally, some versions of
6848 @command{@value{AS}} support special pseudo-instructions for branch
6851 This chapter discusses most of these differences, though it does not
6852 include details on any machine's instruction set. For details on that
6853 subject, see the hardware manufacturer's manual.
6857 * Alpha-Dependent:: Alpha Dependent Features
6860 * ARC-Dependent:: ARC Dependent Features
6863 * ARM-Dependent:: ARM Dependent Features
6866 * AVR-Dependent:: AVR Dependent Features
6869 * Blackfin-Dependent:: Blackfin Dependent Features
6872 * CR16-Dependent:: CR16 Dependent Features
6875 * CRIS-Dependent:: CRIS Dependent Features
6878 * D10V-Dependent:: D10V Dependent Features
6881 * D30V-Dependent:: D30V Dependent Features
6884 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6887 * HPPA-Dependent:: HPPA Dependent Features
6890 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
6893 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
6896 * i860-Dependent:: Intel 80860 Dependent Features
6899 * i960-Dependent:: Intel 80960 Dependent Features
6902 * IA-64-Dependent:: Intel IA-64 Dependent Features
6905 * IP2K-Dependent:: IP2K Dependent Features
6908 * LM32-Dependent:: LM32 Dependent Features
6911 * M32C-Dependent:: M32C Dependent Features
6914 * M32R-Dependent:: M32R Dependent Features
6917 * M68K-Dependent:: M680x0 Dependent Features
6920 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
6923 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
6926 * MIPS-Dependent:: MIPS Dependent Features
6929 * MMIX-Dependent:: MMIX Dependent Features
6932 * MSP430-Dependent:: MSP430 Dependent Features
6935 * SH-Dependent:: Renesas / SuperH SH Dependent Features
6936 * SH64-Dependent:: SuperH SH64 Dependent Features
6939 * PDP-11-Dependent:: PDP-11 Dependent Features
6942 * PJ-Dependent:: picoJava Dependent Features
6945 * PPC-Dependent:: PowerPC Dependent Features
6948 * RX-Dependent:: RX Dependent Features
6951 * S/390-Dependent:: IBM S/390 Dependent Features
6954 * SCORE-Dependent:: SCORE Dependent Features
6957 * Sparc-Dependent:: SPARC Dependent Features
6960 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
6963 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
6966 * V850-Dependent:: V850 Dependent Features
6969 * Xtensa-Dependent:: Xtensa Dependent Features
6972 * Z80-Dependent:: Z80 Dependent Features
6975 * Z8000-Dependent:: Z8000 Dependent Features
6978 * Vax-Dependent:: VAX Dependent Features
6985 @c The following major nodes are *sections* in the GENERIC version, *chapters*
6986 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
6987 @c peculiarity: to preserve cross-references, there must be a node called
6988 @c "Machine Dependencies". Hence the conditional nodenames in each
6989 @c major node below. Node defaulting in makeinfo requires adjacency of
6990 @c node and sectioning commands; hence the repetition of @chapter BLAH
6991 @c in both conditional blocks.
6994 @include c-alpha.texi
7010 @include c-bfin.texi
7014 @include c-cr16.texi
7018 @include c-cris.texi
7023 @node Machine Dependencies
7024 @chapter Machine Dependent Features
7026 The machine instruction sets are different on each Renesas chip family,
7027 and there are also some syntax differences among the families. This
7028 chapter describes the specific @command{@value{AS}} features for each
7032 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7033 * SH-Dependent:: Renesas SH Dependent Features
7040 @include c-d10v.texi
7044 @include c-d30v.texi
7048 @include c-h8300.texi
7052 @include c-hppa.texi
7056 @include c-i370.texi
7060 @include c-i386.texi
7064 @include c-i860.texi
7068 @include c-i960.texi
7072 @include c-ia64.texi
7076 @include c-ip2k.texi
7080 @include c-lm32.texi
7084 @include c-m32c.texi
7088 @include c-m32r.texi
7092 @include c-m68k.texi
7096 @include c-m68hc11.texi
7100 @include c-microblaze.texi
7104 @include c-mips.texi
7108 @include c-mmix.texi
7112 @include c-msp430.texi
7116 @include c-ns32k.texi
7120 @include c-pdp11.texi
7136 @include c-s390.texi
7140 @include c-score.texi
7145 @include c-sh64.texi
7149 @include c-sparc.texi
7153 @include c-tic54x.texi
7157 @include c-tic6x.texi
7173 @include c-v850.texi
7177 @include c-xtensa.texi
7181 @c reverse effect of @down at top of generic Machine-Dep chapter
7185 @node Reporting Bugs
7186 @chapter Reporting Bugs
7187 @cindex bugs in assembler
7188 @cindex reporting bugs in assembler
7190 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7192 Reporting a bug may help you by bringing a solution to your problem, or it may
7193 not. But in any case the principal function of a bug report is to help the
7194 entire community by making the next version of @command{@value{AS}} work better.
7195 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7197 In order for a bug report to serve its purpose, you must include the
7198 information that enables us to fix the bug.
7201 * Bug Criteria:: Have you found a bug?
7202 * Bug Reporting:: How to report bugs
7206 @section Have You Found a Bug?
7207 @cindex bug criteria
7209 If you are not sure whether you have found a bug, here are some guidelines:
7212 @cindex fatal signal
7213 @cindex assembler crash
7214 @cindex crash of assembler
7216 If the assembler gets a fatal signal, for any input whatever, that is a
7217 @command{@value{AS}} bug. Reliable assemblers never crash.
7219 @cindex error on valid input
7221 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7223 @cindex invalid input
7225 If @command{@value{AS}} does not produce an error message for invalid input, that
7226 is a bug. However, you should note that your idea of ``invalid input'' might
7227 be our idea of ``an extension'' or ``support for traditional practice''.
7230 If you are an experienced user of assemblers, your suggestions for improvement
7231 of @command{@value{AS}} are welcome in any case.
7235 @section How to Report Bugs
7237 @cindex assembler bugs, reporting
7239 A number of companies and individuals offer support for @sc{gnu} products. If
7240 you obtained @command{@value{AS}} from a support organization, we recommend you
7241 contact that organization first.
7243 You can find contact information for many support companies and
7244 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7248 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7252 The fundamental principle of reporting bugs usefully is this:
7253 @strong{report all the facts}. If you are not sure whether to state a
7254 fact or leave it out, state it!
7256 Often people omit facts because they think they know what causes the problem
7257 and assume that some details do not matter. Thus, you might assume that the
7258 name of a symbol you use in an example does not matter. Well, probably it does
7259 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7260 happens to fetch from the location where that name is stored in memory;
7261 perhaps, if the name were different, the contents of that location would fool
7262 the assembler into doing the right thing despite the bug. Play it safe and
7263 give a specific, complete example. That is the easiest thing for you to do,
7264 and the most helpful.
7266 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7267 it is new to us. Therefore, always write your bug reports on the assumption
7268 that the bug has not been reported previously.
7270 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7271 bell?'' This cannot help us fix a bug, so it is basically useless. We
7272 respond by asking for enough details to enable us to investigate.
7273 You might as well expedite matters by sending them to begin with.
7275 To enable us to fix the bug, you should include all these things:
7279 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7280 it with the @samp{--version} argument.
7282 Without this, we will not know whether there is any point in looking for
7283 the bug in the current version of @command{@value{AS}}.
7286 Any patches you may have applied to the @command{@value{AS}} source.
7289 The type of machine you are using, and the operating system name and
7293 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7297 The command arguments you gave the assembler to assemble your example and
7298 observe the bug. To guarantee you will not omit something important, list them
7299 all. A copy of the Makefile (or the output from make) is sufficient.
7301 If we were to try to guess the arguments, we would probably guess wrong
7302 and then we might not encounter the bug.
7305 A complete input file that will reproduce the bug. If the bug is observed when
7306 the assembler is invoked via a compiler, send the assembler source, not the
7307 high level language source. Most compilers will produce the assembler source
7308 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7309 the options @samp{-v --save-temps}; this will save the assembler source in a
7310 file with an extension of @file{.s}, and also show you exactly how
7311 @command{@value{AS}} is being run.
7314 A description of what behavior you observe that you believe is
7315 incorrect. For example, ``It gets a fatal signal.''
7317 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7318 will certainly notice it. But if the bug is incorrect output, we might not
7319 notice unless it is glaringly wrong. You might as well not give us a chance to
7322 Even if the problem you experience is a fatal signal, you should still say so
7323 explicitly. Suppose something strange is going on, such as, your copy of
7324 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7325 library on your system. (This has happened!) Your copy might crash and ours
7326 would not. If you told us to expect a crash, then when ours fails to crash, we
7327 would know that the bug was not happening for us. If you had not told us to
7328 expect a crash, then we would not be able to draw any conclusion from our
7332 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7333 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7334 option. Always send diffs from the old file to the new file. If you even
7335 discuss something in the @command{@value{AS}} source, refer to it by context, not
7338 The line numbers in our development sources will not match those in your
7339 sources. Your line numbers would convey no useful information to us.
7342 Here are some things that are not necessary:
7346 A description of the envelope of the bug.
7348 Often people who encounter a bug spend a lot of time investigating
7349 which changes to the input file will make the bug go away and which
7350 changes will not affect it.
7352 This is often time consuming and not very useful, because the way we
7353 will find the bug is by running a single example under the debugger
7354 with breakpoints, not by pure deduction from a series of examples.
7355 We recommend that you save your time for something else.
7357 Of course, if you can find a simpler example to report @emph{instead}
7358 of the original one, that is a convenience for us. Errors in the
7359 output will be easier to spot, running under the debugger will take
7360 less time, and so on.
7362 However, simplification is not vital; if you do not want to do this,
7363 report the bug anyway and send us the entire test case you used.
7366 A patch for the bug.
7368 A patch for the bug does help us if it is a good one. But do not omit
7369 the necessary information, such as the test case, on the assumption that
7370 a patch is all we need. We might see problems with your patch and decide
7371 to fix the problem another way, or we might not understand it at all.
7373 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7374 construct an example that will make the program follow a certain path through
7375 the code. If you do not send us the example, we will not be able to construct
7376 one, so we will not be able to verify that the bug is fixed.
7378 And if we cannot understand what bug you are trying to fix, or why your
7379 patch should be an improvement, we will not install it. A test case will
7380 help us to understand.
7383 A guess about what the bug is or what it depends on.
7385 Such guesses are usually wrong. Even we cannot guess right about such
7386 things without first using the debugger to find the facts.
7389 @node Acknowledgements
7390 @chapter Acknowledgements
7392 If you have contributed to GAS and your name isn't listed here,
7393 it is not meant as a slight. We just don't know about it. Send mail to the
7394 maintainer, and we'll correct the situation. Currently
7396 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
7398 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7401 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7402 information and the 68k series machines, most of the preprocessing pass, and
7403 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7405 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7406 many bug fixes, including merging support for several processors, breaking GAS
7407 up to handle multiple object file format back ends (including heavy rewrite,
7408 testing, an integration of the coff and b.out back ends), adding configuration
7409 including heavy testing and verification of cross assemblers and file splits
7410 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7411 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7412 port (including considerable amounts of reverse engineering), a SPARC opcode
7413 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7414 assertions and made them work, much other reorganization, cleanup, and lint.
7416 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7417 in format-specific I/O modules.
7419 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7420 has done much work with it since.
7422 The Intel 80386 machine description was written by Eliot Dresselhaus.
7424 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7426 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7427 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7429 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7430 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7431 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7432 support a.out format.
7434 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7435 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7436 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7437 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7440 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7441 simplified the configuration of which versions accept which directives. He
7442 updated the 68k machine description so that Motorola's opcodes always produced
7443 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7444 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7445 cross-compilation support, and one bug in relaxation that took a week and
7446 required the proverbial one-bit fix.
7448 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7449 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7450 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7451 PowerPC assembler, and made a few other minor patches.
7453 Steve Chamberlain made GAS able to generate listings.
7455 Hewlett-Packard contributed support for the HP9000/300.
7457 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7458 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7459 formats). This work was supported by both the Center for Software Science at
7460 the University of Utah and Cygnus Support.
7462 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7463 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7464 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7465 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7466 and some initial 64-bit support).
7468 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7470 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7471 support for openVMS/Alpha.
7473 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7476 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7477 Inc.@: added support for Xtensa processors.
7479 Several engineers at Cygnus Support have also provided many small bug fixes and
7480 configuration enhancements.
7482 Jon Beniston added support for the Lattice Mico32 architecture.
7484 Many others have contributed large or small bugfixes and enhancements. If
7485 you have contributed significant work and are not mentioned on this list, and
7486 want to be, let us know. Some of the history has been lost; we are not
7487 intentionally leaving anyone out.
7489 @node GNU Free Documentation License
7490 @appendix GNU Free Documentation License
7494 @unnumbered AS Index
projects / dragonfly.git / blob