1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991-2013 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
254 @emph{Target Alpha options:}
256 [@b{-mdebug} | @b{-no-mdebug}]
257 [@b{-replace} | @b{-noreplace}]
258 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
259 [@b{-F}] [@b{-32addr}]
263 @emph{Target ARC options:}
269 @emph{Target ARM options:}
270 @c Don't document the deprecated options
271 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
272 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
273 [@b{-mfpu}=@var{floating-point-format}]
274 [@b{-mfloat-abi}=@var{abi}]
275 [@b{-meabi}=@var{ver}]
278 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
279 @b{-mapcs-reentrant}]
280 [@b{-mthumb-interwork}] [@b{-k}]
284 @emph{Target Blackfin options:}
285 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
292 @emph{Target CRIS options:}
293 [@b{--underscore} | @b{--no-underscore}]
295 [@b{--emulation=criself} | @b{--emulation=crisaout}]
296 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
297 @c Deprecated -- deliberately not documented.
302 @emph{Target D10V options:}
307 @emph{Target D30V options:}
308 [@b{-O}|@b{-n}|@b{-N}]
312 @emph{Target EPIPHANY options:}
313 [@b{-mepiphany}|@b{-mepiphany16}]
317 @emph{Target H8/300 options:}
321 @c HPPA has no machine-dependent assembler options (yet).
325 @emph{Target i386 options:}
326 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
327 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
331 @emph{Target i960 options:}
332 @c see md_parse_option in tc-i960.c
333 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
335 [@b{-b}] [@b{-no-relax}]
339 @emph{Target IA-64 options:}
340 [@b{-mconstant-gp}|@b{-mauto-pic}]
341 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
343 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
344 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
345 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
346 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
350 @emph{Target IP2K options:}
351 [@b{-mip2022}|@b{-mip2022ext}]
355 @emph{Target M32C options:}
356 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
360 @emph{Target M32R options:}
361 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
366 @emph{Target M680X0 options:}
367 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
371 @emph{Target M68HC11 options:}
372 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branches}] [@b{--short-branches}]
376 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
377 [@b{--print-opcodes}] [@b{--generate-example}]
381 @emph{Target MCORE options:}
382 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
383 [@b{-mcpu=[210|340]}]
387 @emph{Target Meta options:}
388 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
391 @emph{Target MICROBLAZE options:}
392 @c MicroBlaze has no machine-dependent assembler options.
396 @emph{Target MIPS options:}
397 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
398 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
399 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
400 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
401 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
402 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
403 [@b{-mips64}] [@b{-mips64r2}]
404 [@b{-construct-floats}] [@b{-no-construct-floats}]
405 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
406 [@b{-mips16}] [@b{-no-mips16}]
407 [@b{-mmicromips}] [@b{-mno-micromips}]
408 [@b{-msmartmips}] [@b{-mno-smartmips}]
409 [@b{-mips3d}] [@b{-no-mips3d}]
410 [@b{-mdmx}] [@b{-no-mdmx}]
411 [@b{-mdsp}] [@b{-mno-dsp}]
412 [@b{-mdspr2}] [@b{-mno-dspr2}]
413 [@b{-mmt}] [@b{-mno-mt}]
414 [@b{-mmcu}] [@b{-mno-mcu}]
415 [@b{-mfix7000}] [@b{-mno-fix7000}]
416 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
417 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
418 [@b{-mdebug}] [@b{-no-mdebug}]
419 [@b{-mpdr}] [@b{-mno-pdr}]
423 @emph{Target MMIX options:}
424 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
425 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
426 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
427 [@b{--linker-allocated-gregs}]
431 @emph{Target Nios II options:}
432 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
437 @emph{Target PDP11 options:}
438 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
439 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
440 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
444 @emph{Target picoJava options:}
449 @emph{Target PowerPC options:}
451 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
452 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
453 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
454 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
455 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
456 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
457 [@b{-mregnames}|@b{-mno-regnames}]
458 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
459 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
460 [@b{-msolaris}|@b{-mno-solaris}]
461 [@b{-nops=@var{count}}]
465 @emph{Target RX options:}
466 [@b{-mlittle-endian}|@b{-mbig-endian}]
467 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
468 [@b{-muse-conventional-section-names}]
469 [@b{-msmall-data-limit}]
472 [@b{-mint-register=@var{number}}]
473 [@b{-mgcc-abi}|@b{-mrx-abi}]
477 @emph{Target s390 options:}
478 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
479 [@b{-mregnames}|@b{-mno-regnames}]
480 [@b{-mwarn-areg-zero}]
484 @emph{Target SCORE options:}
485 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
486 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
487 [@b{-march=score7}][@b{-march=score3}]
488 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
492 @emph{Target SPARC options:}
493 @c The order here is important. See c-sparc.texi.
494 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
495 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
496 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
501 @emph{Target TIC54X options:}
502 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
503 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
508 @emph{Target TIC6X options:}
509 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
510 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
511 [@b{-mpic}|@b{-mno-pic}]
515 @emph{Target TILE-Gx options:}
516 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
519 @c TILEPro has no machine-dependent assembler options
524 @emph{Target Xtensa options:}
525 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
526 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
527 [@b{--[no-]transform}]
528 [@b{--rename-section} @var{oldname}=@var{newname}]
533 @emph{Target Z80 options:}
534 [@b{-z80}] [@b{-r800}]
535 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
536 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
537 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
538 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
539 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
540 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
544 @c Z8000 has no machine-dependent assembler options
553 @include at-file.texi
556 Turn on listings, in any of a variety of ways:
560 omit false conditionals
563 omit debugging directives
566 include general information, like @value{AS} version and options passed
569 include high-level source
575 include macro expansions
578 omit forms processing
584 set the name of the listing file
587 You may combine these options; for example, use @samp{-aln} for assembly
588 listing without forms processing. The @samp{=file} option, if used, must be
589 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
592 Begin in alternate macro mode.
594 @xref{Altmacro,,@code{.altmacro}}.
597 @item --compress-debug-sections
598 Compress DWARF debug sections using zlib. The debug sections are renamed
599 to begin with @samp{.zdebug}, and the resulting object file may not be
600 compatible with older linkers and object file utilities.
602 @item --nocompress-debug-sections
603 Do not compress DWARF debug sections. This is the default.
606 Ignored. This option is accepted for script compatibility with calls to
609 @item --debug-prefix-map @var{old}=@var{new}
610 When assembling files in directory @file{@var{old}}, record debugging
611 information describing them as in @file{@var{new}} instead.
613 @item --defsym @var{sym}=@var{value}
614 Define the symbol @var{sym} to be @var{value} before assembling the input file.
615 @var{value} must be an integer constant. As in C, a leading @samp{0x}
616 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
617 value. The value of the symbol can be overridden inside a source file via the
618 use of a @code{.set} pseudo-op.
621 ``fast''---skip whitespace and comment preprocessing (assume source is
626 Generate debugging information for each assembler source line using whichever
627 debug format is preferred by the target. This currently means either STABS,
631 Generate stabs debugging information for each assembler line. This
632 may help debugging assembler code, if the debugger can handle it.
635 Generate stabs debugging information for each assembler line, with GNU
636 extensions that probably only gdb can handle, and that could make other
637 debuggers crash or refuse to read your program. This
638 may help debugging assembler code. Currently the only GNU extension is
639 the location of the current working directory at assembling time.
642 Generate DWARF2 debugging information for each assembler line. This
643 may help debugging assembler code, if the debugger can handle it. Note---this
644 option is only supported by some targets, not all of them.
646 @item --gdwarf-sections
647 Instead of creating a .debug_line section, create a series of
648 .debug_line.@var{foo} sections where @var{foo} is the name of the
649 corresponding code section. For example a code section called @var{.text.func}
650 will have its dwarf line number information placed into a section called
651 @var{.debug_line.text.func}. If the code section is just called @var{.text}
652 then debug line section will still be called just @var{.debug_line} without any
655 @item --size-check=error
656 @itemx --size-check=warning
657 Issue an error or warning for invalid ELF .size directive.
660 Print a summary of the command line options and exit.
663 Print a summary of all target specific options and exit.
666 Add directory @var{dir} to the search list for @code{.include} directives.
669 Don't warn about signed overflow.
672 @ifclear DIFF-TBL-KLUGE
673 This option is accepted but has no effect on the @value{TARGET} family.
675 @ifset DIFF-TBL-KLUGE
676 Issue warnings when difference tables altered for long displacements.
681 Keep (in the symbol table) local symbols. These symbols start with
682 system-specific local label prefixes, typically @samp{.L} for ELF systems
683 or @samp{L} for traditional a.out systems.
688 @item --listing-lhs-width=@var{number}
689 Set the maximum width, in words, of the output data column for an assembler
690 listing to @var{number}.
692 @item --listing-lhs-width2=@var{number}
693 Set the maximum width, in words, of the output data column for continuation
694 lines in an assembler listing to @var{number}.
696 @item --listing-rhs-width=@var{number}
697 Set the maximum width of an input source line, as displayed in a listing, to
700 @item --listing-cont-lines=@var{number}
701 Set the maximum number of lines printed in a listing for a single line of input
704 @item -o @var{objfile}
705 Name the object-file output from @command{@value{AS}} @var{objfile}.
708 Fold the data section into the text section.
710 @kindex --hash-size=@var{number}
711 Set the default size of GAS's hash tables to a prime number close to
712 @var{number}. Increasing this value can reduce the length of time it takes the
713 assembler to perform its tasks, at the expense of increasing the assembler's
714 memory requirements. Similarly reducing this value can reduce the memory
715 requirements at the expense of speed.
717 @item --reduce-memory-overheads
718 This option reduces GAS's memory requirements, at the expense of making the
719 assembly processes slower. Currently this switch is a synonym for
720 @samp{--hash-size=4051}, but in the future it may have other effects as well.
723 Print the maximum space (in bytes) and total time (in seconds) used by
726 @item --strip-local-absolute
727 Remove local absolute symbols from the outgoing symbol table.
731 Print the @command{as} version.
734 Print the @command{as} version and exit.
738 Suppress warning messages.
740 @item --fatal-warnings
741 Treat warnings as errors.
744 Don't suppress warning messages or treat them as errors.
753 Generate an object file even after errors.
755 @item -- | @var{files} @dots{}
756 Standard input, or source files to assemble.
764 @xref{AArch64 Options}, for the options available when @value{AS} is configured
765 for the 64-bit mode of the ARM Architecture (AArch64).
770 The following options are available when @value{AS} is configured for the
771 64-bit mode of the ARM Architecture (AArch64).
774 @include c-aarch64.texi
775 @c ended inside the included file
783 @xref{Alpha Options}, for the options available when @value{AS} is configured
784 for an Alpha processor.
789 The following options are available when @value{AS} is configured for an Alpha
793 @include c-alpha.texi
794 @c ended inside the included file
801 The following options are available when @value{AS} is configured for
806 This option selects the core processor variant.
808 Select either big-endian (-EB) or little-endian (-EL) output.
813 The following options are available when @value{AS} is configured for the ARM
817 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
818 Specify which ARM processor variant is the target.
819 @item -march=@var{architecture}[+@var{extension}@dots{}]
820 Specify which ARM architecture variant is used by the target.
821 @item -mfpu=@var{floating-point-format}
822 Select which Floating Point architecture is the target.
823 @item -mfloat-abi=@var{abi}
824 Select which floating point ABI is in use.
826 Enable Thumb only instruction decoding.
827 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
828 Select which procedure calling convention is in use.
830 Select either big-endian (-EB) or little-endian (-EL) output.
831 @item -mthumb-interwork
832 Specify that the code has been generated with interworking between Thumb and
835 Specify that PIC code has been generated.
843 @xref{Blackfin Options}, for the options available when @value{AS} is
844 configured for the Blackfin processor family.
849 The following options are available when @value{AS} is configured for
850 the Blackfin processor family.
854 @c ended inside the included file
861 See the info pages for documentation of the CRIS-specific options.
865 The following options are available when @value{AS} is configured for
868 @cindex D10V optimization
869 @cindex optimization, D10V
871 Optimize output by parallelizing instructions.
876 The following options are available when @value{AS} is configured for a D30V
879 @cindex D30V optimization
880 @cindex optimization, D30V
882 Optimize output by parallelizing instructions.
886 Warn when nops are generated.
888 @cindex D30V nops after 32-bit multiply
890 Warn when a nop after a 32-bit multiply instruction is generated.
896 The following options are available when @value{AS} is configured for the
897 Adapteva EPIPHANY series.
900 @xref{Epiphany Options}, for the options available when @value{AS} is
901 configured for an Epiphany processor.
906 The following options are available when @value{AS} is configured for
907 an Epiphany processor.
910 @include c-epiphany.texi
911 @c ended inside the included file
919 @xref{H8/300 Options}, for the options available when @value{AS} is configured
920 for an H8/300 processor.
925 The following options are available when @value{AS} is configured for an H8/300
929 @include c-h8300.texi
930 @c ended inside the included file
938 @xref{i386-Options}, for the options available when @value{AS} is
939 configured for an i386 processor.
944 The following options are available when @value{AS} is configured for
949 @c ended inside the included file
956 The following options are available when @value{AS} is configured for the
957 Intel 80960 processor.
960 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
961 Specify which variant of the 960 architecture is the target.
964 Add code to collect statistics about branches taken.
967 Do not alter compare-and-branch instructions for long displacements;
974 The following options are available when @value{AS} is configured for the
980 Specifies that the extended IP2022 instructions are allowed.
983 Restores the default behaviour, which restricts the permitted instructions to
984 just the basic IP2022 ones.
990 The following options are available when @value{AS} is configured for the
991 Renesas M32C and M16C processors.
996 Assemble M32C instructions.
999 Assemble M16C instructions (the default).
1002 Enable support for link-time relaxations.
1005 Support H'00 style hex constants in addition to 0x00 style.
1011 The following options are available when @value{AS} is configured for the
1012 Renesas M32R (formerly Mitsubishi M32R) series.
1017 Specify which processor in the M32R family is the target. The default
1018 is normally the M32R, but this option changes it to the M32RX.
1020 @item --warn-explicit-parallel-conflicts or --Wp
1021 Produce warning messages when questionable parallel constructs are
1024 @item --no-warn-explicit-parallel-conflicts or --Wnp
1025 Do not produce warning messages when questionable parallel constructs are
1032 The following options are available when @value{AS} is configured for the
1033 Motorola 68000 series.
1038 Shorten references to undefined symbols, to one word instead of two.
1040 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1041 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1042 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1043 Specify what processor in the 68000 family is the target. The default
1044 is normally the 68020, but this can be changed at configuration time.
1046 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1047 The target machine does (or does not) have a floating-point coprocessor.
1048 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1049 the basic 68000 is not compatible with the 68881, a combination of the
1050 two can be specified, since it's possible to do emulation of the
1051 coprocessor instructions with the main processor.
1053 @item -m68851 | -mno-68851
1054 The target machine does (or does not) have a memory-management
1055 unit coprocessor. The default is to assume an MMU for 68020 and up.
1063 @xref{Nios II Options}, for the options available when @value{AS} is configured
1064 for an Altera Nios II processor.
1068 @c man begin OPTIONS
1069 The following options are available when @value{AS} is configured for an
1070 Altera Nios II processor.
1072 @c man begin INCLUDE
1073 @include c-nios2.texi
1074 @c ended inside the included file
1080 For details about the PDP-11 machine dependent features options,
1081 see @ref{PDP-11-Options}.
1084 @item -mpic | -mno-pic
1085 Generate position-independent (or position-dependent) code. The
1086 default is @option{-mpic}.
1089 @itemx -mall-extensions
1090 Enable all instruction set extensions. This is the default.
1092 @item -mno-extensions
1093 Disable all instruction set extensions.
1095 @item -m@var{extension} | -mno-@var{extension}
1096 Enable (or disable) a particular instruction set extension.
1099 Enable the instruction set extensions supported by a particular CPU, and
1100 disable all other extensions.
1102 @item -m@var{machine}
1103 Enable the instruction set extensions supported by a particular machine
1104 model, and disable all other extensions.
1110 The following options are available when @value{AS} is configured for
1111 a picoJava processor.
1115 @cindex PJ endianness
1116 @cindex endianness, PJ
1117 @cindex big endian output, PJ
1119 Generate ``big endian'' format output.
1121 @cindex little endian output, PJ
1123 Generate ``little endian'' format output.
1129 The following options are available when @value{AS} is configured for the
1130 Motorola 68HC11 or 68HC12 series.
1134 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1135 Specify what processor is the target. The default is
1136 defined by the configuration option when building the assembler.
1138 @item --xgate-ramoffset
1139 Instruct the linker to offset RAM addresses from S12X address space into
1140 XGATE address space.
1143 Specify to use the 16-bit integer ABI.
1146 Specify to use the 32-bit integer ABI.
1148 @item -mshort-double
1149 Specify to use the 32-bit double ABI.
1152 Specify to use the 64-bit double ABI.
1154 @item --force-long-branches
1155 Relative branches are turned into absolute ones. This concerns
1156 conditional branches, unconditional branches and branches to a
1159 @item -S | --short-branches
1160 Do not turn relative branches into absolute ones
1161 when the offset is out of range.
1163 @item --strict-direct-mode
1164 Do not turn the direct addressing mode into extended addressing mode
1165 when the instruction does not support direct addressing mode.
1167 @item --print-insn-syntax
1168 Print the syntax of instruction in case of error.
1170 @item --print-opcodes
1171 Print the list of instructions with syntax and then exit.
1173 @item --generate-example
1174 Print an example of instruction for each possible instruction and then exit.
1175 This option is only useful for testing @command{@value{AS}}.
1181 The following options are available when @command{@value{AS}} is configured
1182 for the SPARC architecture:
1185 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1186 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1187 Explicitly select a variant of the SPARC architecture.
1189 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1190 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1192 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1193 UltraSPARC extensions.
1195 @item -xarch=v8plus | -xarch=v8plusa
1196 For compatibility with the Solaris v9 assembler. These options are
1197 equivalent to -Av8plus and -Av8plusa, respectively.
1200 Warn when the assembler switches to another architecture.
1205 The following options are available when @value{AS} is configured for the 'c54x
1210 Enable extended addressing mode. All addresses and relocations will assume
1211 extended addressing (usually 23 bits).
1212 @item -mcpu=@var{CPU_VERSION}
1213 Sets the CPU version being compiled for.
1214 @item -merrors-to-file @var{FILENAME}
1215 Redirect error output to a file, for broken systems which don't support such
1216 behaviour in the shell.
1221 The following options are available when @value{AS} is configured for
1226 This option sets the largest size of an object that can be referenced
1227 implicitly with the @code{gp} register. It is only accepted for targets that
1228 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1230 @cindex MIPS endianness
1231 @cindex endianness, MIPS
1232 @cindex big endian output, MIPS
1234 Generate ``big endian'' format output.
1236 @cindex little endian output, MIPS
1238 Generate ``little endian'' format output.
1250 Generate code for a particular MIPS Instruction Set Architecture level.
1251 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1252 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1253 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1254 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1256 correspond to generic
1257 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, @samp{MIPS64},
1258 and @samp{MIPS64 Release 2}
1259 ISA processors, respectively.
1261 @item -march=@var{cpu}
1262 Generate code for a particular MIPS CPU.
1264 @item -mtune=@var{cpu}
1265 Schedule and tune for a particular MIPS CPU.
1269 Cause nops to be inserted if the read of the destination register
1270 of an mfhi or mflo instruction occurs in the following two instructions.
1274 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1275 section instead of the standard ELF .stabs sections.
1279 Control generation of @code{.pdr} sections.
1283 The register sizes are normally inferred from the ISA and ABI, but these
1284 flags force a certain group of registers to be treated as 32 bits wide at
1285 all times. @samp{-mgp32} controls the size of general-purpose registers
1286 and @samp{-mfp32} controls the size of floating-point registers.
1290 Generate code for the MIPS 16 processor. This is equivalent to putting
1291 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1292 turns off this option.
1295 @itemx -mno-micromips
1296 Generate code for the microMIPS processor. This is equivalent to putting
1297 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1298 turns off this option. This is equivalent to putting @code{.set nomicromips}
1299 at the start of the assembly file.
1302 @itemx -mno-smartmips
1303 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1304 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1305 @samp{-mno-smartmips} turns off this option.
1309 Generate code for the MIPS-3D Application Specific Extension.
1310 This tells the assembler to accept MIPS-3D instructions.
1311 @samp{-no-mips3d} turns off this option.
1315 Generate code for the MDMX Application Specific Extension.
1316 This tells the assembler to accept MDMX instructions.
1317 @samp{-no-mdmx} turns off this option.
1321 Generate code for the DSP Release 1 Application Specific Extension.
1322 This tells the assembler to accept DSP Release 1 instructions.
1323 @samp{-mno-dsp} turns off this option.
1327 Generate code for the DSP Release 2 Application Specific Extension.
1328 This option implies -mdsp.
1329 This tells the assembler to accept DSP Release 2 instructions.
1330 @samp{-mno-dspr2} turns off this option.
1334 Generate code for the MT Application Specific Extension.
1335 This tells the assembler to accept MT instructions.
1336 @samp{-mno-mt} turns off this option.
1340 Generate code for the MCU Application Specific Extension.
1341 This tells the assembler to accept MCU instructions.
1342 @samp{-mno-mcu} turns off this option.
1344 @item --construct-floats
1345 @itemx --no-construct-floats
1346 The @samp{--no-construct-floats} option disables the construction of
1347 double width floating point constants by loading the two halves of the
1348 value into the two single width floating point registers that make up
1349 the double width register. By default @samp{--construct-floats} is
1350 selected, allowing construction of these floating point constants.
1352 @item --relax-branch
1353 @itemx --no-relax-branch
1354 The @samp{--relax-branch} option enables the relaxation of out-of-range
1355 branches. By default @samp{--no-relax-branch} is selected, causing any
1356 out-of-range branches to produce an error.
1359 @item --emulation=@var{name}
1360 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
1361 for some other target, in all respects, including output format (choosing
1362 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
1363 debugging information or store symbol table information, and default
1364 endianness. The available configuration names are: @samp{mipsecoff},
1365 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
1366 @samp{mipsbelf}. The first two do not alter the default endianness from that
1367 of the primary target for which the assembler was configured; the others change
1368 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
1369 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1370 selection in any case.
1372 This option is currently supported only when the primary target
1373 @command{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
1374 Furthermore, the primary target or others specified with
1375 @samp{--enable-targets=@dots{}} at configuration time must include support for
1376 the other format, if both are to be available. For example, the Irix 5
1377 configuration includes support for both.
1379 Eventually, this option will support more configurations, with more
1380 fine-grained control over the assembler's behavior, and will be supported for
1384 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1391 Control how to deal with multiplication overflow and division by zero.
1392 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1393 (and only work for Instruction Set Architecture level 2 and higher);
1394 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1398 When this option is used, @command{@value{AS}} will issue a warning every
1399 time it generates a nop instruction from a macro.
1404 The following options are available when @value{AS} is configured for
1410 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1411 The command line option @samp{-nojsri2bsr} can be used to disable it.
1415 Enable or disable the silicon filter behaviour. By default this is disabled.
1416 The default can be overridden by the @samp{-sifilter} command line option.
1419 Alter jump instructions for long displacements.
1421 @item -mcpu=[210|340]
1422 Select the cpu type on the target hardware. This controls which instructions
1426 Assemble for a big endian target.
1429 Assemble for a little endian target.
1438 @xref{Meta Options}, for the options available when @value{AS} is configured
1439 for a Meta processor.
1443 @c man begin OPTIONS
1444 The following options are available when @value{AS} is configured for a
1447 @c man begin INCLUDE
1448 @include c-metag.texi
1449 @c ended inside the included file
1454 @c man begin OPTIONS
1456 See the info pages for documentation of the MMIX-specific options.
1463 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1464 for a PowerPC processor.
1468 @c man begin OPTIONS
1469 The following options are available when @value{AS} is configured for a
1472 @c man begin INCLUDE
1474 @c ended inside the included file
1479 @c man begin OPTIONS
1481 See the info pages for documentation of the RX-specific options.
1485 The following options are available when @value{AS} is configured for the s390
1491 Select the word size, either 31/32 bits or 64 bits.
1494 Select the architecture mode, either the Enterprise System
1495 Architecture (esa) or the z/Architecture mode (zarch).
1496 @item -march=@var{processor}
1497 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1498 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1499 @samp{z196}, or @samp{zEC12}.
1501 @itemx -mno-regnames
1502 Allow or disallow symbolic names for registers.
1503 @item -mwarn-areg-zero
1504 Warn whenever the operand for a base or index register has been specified
1505 but evaluates to zero.
1513 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1514 for a TMS320C6000 processor.
1518 @c man begin OPTIONS
1519 The following options are available when @value{AS} is configured for a
1520 TMS320C6000 processor.
1522 @c man begin INCLUDE
1523 @include c-tic6x.texi
1524 @c ended inside the included file
1532 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1533 for a TILE-Gx processor.
1537 @c man begin OPTIONS
1538 The following options are available when @value{AS} is configured for a TILE-Gx
1541 @c man begin INCLUDE
1542 @include c-tilegx.texi
1543 @c ended inside the included file
1551 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1552 for an Xtensa processor.
1556 @c man begin OPTIONS
1557 The following options are available when @value{AS} is configured for an
1560 @c man begin INCLUDE
1561 @include c-xtensa.texi
1562 @c ended inside the included file
1567 @c man begin OPTIONS
1570 The following options are available when @value{AS} is configured for
1571 a Z80 family processor.
1574 Assemble for Z80 processor.
1576 Assemble for R800 processor.
1577 @item -ignore-undocumented-instructions
1579 Assemble undocumented Z80 instructions that also work on R800 without warning.
1580 @item -ignore-unportable-instructions
1582 Assemble all undocumented Z80 instructions without warning.
1583 @item -warn-undocumented-instructions
1585 Issue a warning for undocumented Z80 instructions that also work on R800.
1586 @item -warn-unportable-instructions
1588 Issue a warning for undocumented Z80 instructions that do not work on R800.
1589 @item -forbid-undocumented-instructions
1591 Treat all undocumented instructions as errors.
1592 @item -forbid-unportable-instructions
1594 Treat undocumented Z80 instructions that do not work on R800 as errors.
1601 * Manual:: Structure of this Manual
1602 * GNU Assembler:: The GNU Assembler
1603 * Object Formats:: Object File Formats
1604 * Command Line:: Command Line
1605 * Input Files:: Input Files
1606 * Object:: Output (Object) File
1607 * Errors:: Error and Warning Messages
1611 @section Structure of this Manual
1613 @cindex manual, structure and purpose
1614 This manual is intended to describe what you need to know to use
1615 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1616 notation for symbols, constants, and expressions; the directives that
1617 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1620 We also cover special features in the @value{TARGET}
1621 configuration of @command{@value{AS}}, including assembler directives.
1624 This manual also describes some of the machine-dependent features of
1625 various flavors of the assembler.
1628 @cindex machine instructions (not covered)
1629 On the other hand, this manual is @emph{not} intended as an introduction
1630 to programming in assembly language---let alone programming in general!
1631 In a similar vein, we make no attempt to introduce the machine
1632 architecture; we do @emph{not} describe the instruction set, standard
1633 mnemonics, registers or addressing modes that are standard to a
1634 particular architecture.
1636 You may want to consult the manufacturer's
1637 machine architecture manual for this information.
1641 For information on the H8/300 machine instruction set, see @cite{H8/300
1642 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1643 Programming Manual} (Renesas).
1646 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1647 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1648 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1649 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1652 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1656 @c I think this is premature---doc@cygnus.com, 17jan1991
1658 Throughout this manual, we assume that you are running @dfn{GNU},
1659 the portable operating system from the @dfn{Free Software
1660 Foundation, Inc.}. This restricts our attention to certain kinds of
1661 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1662 once this assumption is granted examples and definitions need less
1665 @command{@value{AS}} is part of a team of programs that turn a high-level
1666 human-readable series of instructions into a low-level
1667 computer-readable series of instructions. Different versions of
1668 @command{@value{AS}} are used for different kinds of computer.
1671 @c There used to be a section "Terminology" here, which defined
1672 @c "contents", "byte", "word", and "long". Defining "word" to any
1673 @c particular size is confusing when the .word directive may generate 16
1674 @c bits on one machine and 32 bits on another; in general, for the user
1675 @c version of this manual, none of these terms seem essential to define.
1676 @c They were used very little even in the former draft of the manual;
1677 @c this draft makes an effort to avoid them (except in names of
1681 @section The GNU Assembler
1683 @c man begin DESCRIPTION
1685 @sc{gnu} @command{as} is really a family of assemblers.
1687 This manual describes @command{@value{AS}}, a member of that family which is
1688 configured for the @value{TARGET} architectures.
1690 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1691 should find a fairly similar environment when you use it on another
1692 architecture. Each version has much in common with the others,
1693 including object file formats, most assembler directives (often called
1694 @dfn{pseudo-ops}) and assembler syntax.@refill
1696 @cindex purpose of @sc{gnu} assembler
1697 @command{@value{AS}} is primarily intended to assemble the output of the
1698 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1699 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1700 assemble correctly everything that other assemblers for the same
1701 machine would assemble.
1703 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1706 @c This remark should appear in generic version of manual; assumption
1707 @c here is that generic version sets M680x0.
1708 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1709 assembler for the same architecture; for example, we know of several
1710 incompatible versions of 680x0 assembly language syntax.
1715 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1716 program in one pass of the source file. This has a subtle impact on the
1717 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1719 @node Object Formats
1720 @section Object File Formats
1722 @cindex object file format
1723 The @sc{gnu} assembler can be configured to produce several alternative
1724 object file formats. For the most part, this does not affect how you
1725 write assembly language programs; but directives for debugging symbols
1726 are typically different in different file formats. @xref{Symbol
1727 Attributes,,Symbol Attributes}.
1730 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1731 @value{OBJ-NAME} format object files.
1733 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1735 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1736 @code{b.out} or COFF format object files.
1739 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1740 SOM or ELF format object files.
1745 @section Command Line
1747 @cindex command line conventions
1749 After the program name @command{@value{AS}}, the command line may contain
1750 options and file names. Options may appear in any order, and may be
1751 before, after, or between file names. The order of file names is
1754 @cindex standard input, as input file
1756 @file{--} (two hyphens) by itself names the standard input file
1757 explicitly, as one of the files for @command{@value{AS}} to assemble.
1759 @cindex options, command line
1760 Except for @samp{--} any command line argument that begins with a
1761 hyphen (@samp{-}) is an option. Each option changes the behavior of
1762 @command{@value{AS}}. No option changes the way another option works. An
1763 option is a @samp{-} followed by one or more letters; the case of
1764 the letter is important. All options are optional.
1766 Some options expect exactly one file name to follow them. The file
1767 name may either immediately follow the option's letter (compatible
1768 with older assemblers) or it may be the next command argument (@sc{gnu}
1769 standard). These two command lines are equivalent:
1772 @value{AS} -o my-object-file.o mumble.s
1773 @value{AS} -omy-object-file.o mumble.s
1777 @section Input Files
1780 @cindex source program
1781 @cindex files, input
1782 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1783 describe the program input to one run of @command{@value{AS}}. The program may
1784 be in one or more files; how the source is partitioned into files
1785 doesn't change the meaning of the source.
1787 @c I added "con" prefix to "catenation" just to prove I can overcome my
1788 @c APL training... doc@cygnus.com
1789 The source program is a concatenation of the text in all the files, in the
1792 @c man begin DESCRIPTION
1793 Each time you run @command{@value{AS}} it assembles exactly one source
1794 program. The source program is made up of one or more files.
1795 (The standard input is also a file.)
1797 You give @command{@value{AS}} a command line that has zero or more input file
1798 names. The input files are read (from left file name to right). A
1799 command line argument (in any position) that has no special meaning
1800 is taken to be an input file name.
1802 If you give @command{@value{AS}} no file names it attempts to read one input file
1803 from the @command{@value{AS}} standard input, which is normally your terminal. You
1804 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1807 Use @samp{--} if you need to explicitly name the standard input file
1808 in your command line.
1810 If the source is empty, @command{@value{AS}} produces a small, empty object
1815 @subheading Filenames and Line-numbers
1817 @cindex input file linenumbers
1818 @cindex line numbers, in input files
1819 There are two ways of locating a line in the input file (or files) and
1820 either may be used in reporting error messages. One way refers to a line
1821 number in a physical file; the other refers to a line number in a
1822 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1824 @dfn{Physical files} are those files named in the command line given
1825 to @command{@value{AS}}.
1827 @dfn{Logical files} are simply names declared explicitly by assembler
1828 directives; they bear no relation to physical files. Logical file names help
1829 error messages reflect the original source file, when @command{@value{AS}} source
1830 is itself synthesized from other files. @command{@value{AS}} understands the
1831 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1832 @ref{File,,@code{.file}}.
1835 @section Output (Object) File
1841 Every time you run @command{@value{AS}} it produces an output file, which is
1842 your assembly language program translated into numbers. This file
1843 is the object file. Its default name is
1851 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1853 You can give it another name by using the @option{-o} option. Conventionally,
1854 object file names end with @file{.o}. The default name is used for historical
1855 reasons: older assemblers were capable of assembling self-contained programs
1856 directly into a runnable program. (For some formats, this isn't currently
1857 possible, but it can be done for the @code{a.out} format.)
1861 The object file is meant for input to the linker @code{@value{LD}}. It contains
1862 assembled program code, information to help @code{@value{LD}} integrate
1863 the assembled program into a runnable file, and (optionally) symbolic
1864 information for the debugger.
1866 @c link above to some info file(s) like the description of a.out.
1867 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1870 @section Error and Warning Messages
1872 @c man begin DESCRIPTION
1874 @cindex error messages
1875 @cindex warning messages
1876 @cindex messages from assembler
1877 @command{@value{AS}} may write warnings and error messages to the standard error
1878 file (usually your terminal). This should not happen when a compiler
1879 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1880 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1881 grave problem that stops the assembly.
1885 @cindex format of warning messages
1886 Warning messages have the format
1889 file_name:@b{NNN}:Warning Message Text
1893 @cindex line numbers, in warnings/errors
1894 (where @b{NNN} is a line number). If a logical file name has been given
1895 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1896 the current input file is used. If a logical line number was given
1898 (@pxref{Line,,@code{.line}})
1900 then it is used to calculate the number printed,
1901 otherwise the actual line in the current source file is printed. The
1902 message text is intended to be self explanatory (in the grand Unix
1905 @cindex format of error messages
1906 Error messages have the format
1908 file_name:@b{NNN}:FATAL:Error Message Text
1910 The file name and line number are derived as for warning
1911 messages. The actual message text may be rather less explanatory
1912 because many of them aren't supposed to happen.
1915 @chapter Command-Line Options
1917 @cindex options, all versions of assembler
1918 This chapter describes command-line options available in @emph{all}
1919 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1920 for options specific
1922 to the @value{TARGET} target.
1925 to particular machine architectures.
1928 @c man begin DESCRIPTION
1930 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1931 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1932 The assembler arguments must be separated from each other (and the @samp{-Wa})
1933 by commas. For example:
1936 gcc -c -g -O -Wa,-alh,-L file.c
1940 This passes two options to the assembler: @samp{-alh} (emit a listing to
1941 standard output with high-level and assembly source) and @samp{-L} (retain
1942 local symbols in the symbol table).
1944 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1945 command-line options are automatically passed to the assembler by the compiler.
1946 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1947 precisely what options it passes to each compilation pass, including the
1953 * a:: -a[cdghlns] enable listings
1954 * alternate:: --alternate enable alternate macro syntax
1955 * D:: -D for compatibility
1956 * f:: -f to work faster
1957 * I:: -I for .include search path
1958 @ifclear DIFF-TBL-KLUGE
1959 * K:: -K for compatibility
1961 @ifset DIFF-TBL-KLUGE
1962 * K:: -K for difference tables
1965 * L:: -L to retain local symbols
1966 * listing:: --listing-XXX to configure listing output
1967 * M:: -M or --mri to assemble in MRI compatibility mode
1968 * MD:: --MD for dependency tracking
1969 * o:: -o to name the object file
1970 * R:: -R to join data and text sections
1971 * statistics:: --statistics to see statistics about assembly
1972 * traditional-format:: --traditional-format for compatible output
1973 * v:: -v to announce version
1974 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1975 * Z:: -Z to make object file even after errors
1979 @section Enable Listings: @option{-a[cdghlns]}
1989 @cindex listings, enabling
1990 @cindex assembly listings, enabling
1992 These options enable listing output from the assembler. By itself,
1993 @samp{-a} requests high-level, assembly, and symbols listing.
1994 You can use other letters to select specific options for the list:
1995 @samp{-ah} requests a high-level language listing,
1996 @samp{-al} requests an output-program assembly listing, and
1997 @samp{-as} requests a symbol table listing.
1998 High-level listings require that a compiler debugging option like
1999 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2002 Use the @samp{-ag} option to print a first section with general assembly
2003 information, like @value{AS} version, switches passed, or time stamp.
2005 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2006 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2007 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2008 omitted from the listing.
2010 Use the @samp{-ad} option to omit debugging directives from the
2013 Once you have specified one of these options, you can further control
2014 listing output and its appearance using the directives @code{.list},
2015 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2017 The @samp{-an} option turns off all forms processing.
2018 If you do not request listing output with one of the @samp{-a} options, the
2019 listing-control directives have no effect.
2021 The letters after @samp{-a} may be combined into one option,
2022 @emph{e.g.}, @samp{-aln}.
2024 Note if the assembler source is coming from the standard input (e.g.,
2026 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2027 is being used) then the listing will not contain any comments or preprocessor
2028 directives. This is because the listing code buffers input source lines from
2029 stdin only after they have been preprocessed by the assembler. This reduces
2030 memory usage and makes the code more efficient.
2033 @section @option{--alternate}
2036 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2039 @section @option{-D}
2042 This option has no effect whatsoever, but it is accepted to make it more
2043 likely that scripts written for other assemblers also work with
2044 @command{@value{AS}}.
2047 @section Work Faster: @option{-f}
2050 @cindex trusted compiler
2051 @cindex faster processing (@option{-f})
2052 @samp{-f} should only be used when assembling programs written by a
2053 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2054 and comment preprocessing on
2055 the input file(s) before assembling them. @xref{Preprocessing,
2059 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2060 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2065 @section @code{.include} Search Path: @option{-I} @var{path}
2067 @kindex -I @var{path}
2068 @cindex paths for @code{.include}
2069 @cindex search path for @code{.include}
2070 @cindex @code{include} directive search path
2071 Use this option to add a @var{path} to the list of directories
2072 @command{@value{AS}} searches for files specified in @code{.include}
2073 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2074 many times as necessary to include a variety of paths. The current
2075 working directory is always searched first; after that, @command{@value{AS}}
2076 searches any @samp{-I} directories in the same order as they were
2077 specified (left to right) on the command line.
2080 @section Difference Tables: @option{-K}
2083 @ifclear DIFF-TBL-KLUGE
2084 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2085 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2086 where it can be used to warn when the assembler alters the machine code
2087 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2088 family does not have the addressing limitations that sometimes lead to this
2089 alteration on other platforms.
2092 @ifset DIFF-TBL-KLUGE
2093 @cindex difference tables, warning
2094 @cindex warning for altered difference tables
2095 @command{@value{AS}} sometimes alters the code emitted for directives of the
2096 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2097 You can use the @samp{-K} option if you want a warning issued when this
2102 @section Include Local Symbols: @option{-L}
2105 @cindex local symbols, retaining in output
2106 Symbols beginning with system-specific local label prefixes, typically
2107 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2108 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2109 such symbols when debugging, because they are intended for the use of
2110 programs (like compilers) that compose assembler programs, not for your
2111 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2112 such symbols, so you do not normally debug with them.
2114 This option tells @command{@value{AS}} to retain those local symbols
2115 in the object file. Usually if you do this you also tell the linker
2116 @code{@value{LD}} to preserve those symbols.
2119 @section Configuring listing output: @option{--listing}
2121 The listing feature of the assembler can be enabled via the command line switch
2122 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2123 hex dump of the corresponding locations in the output object file, and displays
2124 them as a listing file. The format of this listing can be controlled by
2125 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2126 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2127 @code{.psize} (@pxref{Psize}), and
2128 @code{.eject} (@pxref{Eject}) and also by the following switches:
2131 @item --listing-lhs-width=@samp{number}
2132 @kindex --listing-lhs-width
2133 @cindex Width of first line disassembly output
2134 Sets the maximum width, in words, of the first line of the hex byte dump. This
2135 dump appears on the left hand side of the listing output.
2137 @item --listing-lhs-width2=@samp{number}
2138 @kindex --listing-lhs-width2
2139 @cindex Width of continuation lines of disassembly output
2140 Sets the maximum width, in words, of any further lines of the hex byte dump for
2141 a given input source line. If this value is not specified, it defaults to being
2142 the same as the value specified for @samp{--listing-lhs-width}. If neither
2143 switch is used the default is to one.
2145 @item --listing-rhs-width=@samp{number}
2146 @kindex --listing-rhs-width
2147 @cindex Width of source line output
2148 Sets the maximum width, in characters, of the source line that is displayed
2149 alongside the hex dump. The default value for this parameter is 100. The
2150 source line is displayed on the right hand side of the listing output.
2152 @item --listing-cont-lines=@samp{number}
2153 @kindex --listing-cont-lines
2154 @cindex Maximum number of continuation lines
2155 Sets the maximum number of continuation lines of hex dump that will be
2156 displayed for a given single line of source input. The default value is 4.
2160 @section Assemble in MRI Compatibility Mode: @option{-M}
2163 @cindex MRI compatibility mode
2164 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2165 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2166 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2167 configured target) assembler from Microtec Research. The exact nature of the
2168 MRI syntax will not be documented here; see the MRI manuals for more
2169 information. Note in particular that the handling of macros and macro
2170 arguments is somewhat different. The purpose of this option is to permit
2171 assembling existing MRI assembler code using @command{@value{AS}}.
2173 The MRI compatibility is not complete. Certain operations of the MRI assembler
2174 depend upon its object file format, and can not be supported using other object
2175 file formats. Supporting these would require enhancing each object file format
2176 individually. These are:
2179 @item global symbols in common section
2181 The m68k MRI assembler supports common sections which are merged by the linker.
2182 Other object file formats do not support this. @command{@value{AS}} handles
2183 common sections by treating them as a single common symbol. It permits local
2184 symbols to be defined within a common section, but it can not support global
2185 symbols, since it has no way to describe them.
2187 @item complex relocations
2189 The MRI assemblers support relocations against a negated section address, and
2190 relocations which combine the start addresses of two or more sections. These
2191 are not support by other object file formats.
2193 @item @code{END} pseudo-op specifying start address
2195 The MRI @code{END} pseudo-op permits the specification of a start address.
2196 This is not supported by other object file formats. The start address may
2197 instead be specified using the @option{-e} option to the linker, or in a linker
2200 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2202 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2203 name to the output file. This is not supported by other object file formats.
2205 @item @code{ORG} pseudo-op
2207 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2208 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2209 which changes the location within the current section. Absolute sections are
2210 not supported by other object file formats. The address of a section may be
2211 assigned within a linker script.
2214 There are some other features of the MRI assembler which are not supported by
2215 @command{@value{AS}}, typically either because they are difficult or because they
2216 seem of little consequence. Some of these may be supported in future releases.
2220 @item EBCDIC strings
2222 EBCDIC strings are not supported.
2224 @item packed binary coded decimal
2226 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2227 and @code{DCB.P} pseudo-ops are not supported.
2229 @item @code{FEQU} pseudo-op
2231 The m68k @code{FEQU} pseudo-op is not supported.
2233 @item @code{NOOBJ} pseudo-op
2235 The m68k @code{NOOBJ} pseudo-op is not supported.
2237 @item @code{OPT} branch control options
2239 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2240 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2241 relaxes all branches, whether forward or backward, to an appropriate size, so
2242 these options serve no purpose.
2244 @item @code{OPT} list control options
2246 The following m68k @code{OPT} list control options are ignored: @code{C},
2247 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2248 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2250 @item other @code{OPT} options
2252 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2253 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2255 @item @code{OPT} @code{D} option is default
2257 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2258 @code{OPT NOD} may be used to turn it off.
2260 @item @code{XREF} pseudo-op.
2262 The m68k @code{XREF} pseudo-op is ignored.
2264 @item @code{.debug} pseudo-op
2266 The i960 @code{.debug} pseudo-op is not supported.
2268 @item @code{.extended} pseudo-op
2270 The i960 @code{.extended} pseudo-op is not supported.
2272 @item @code{.list} pseudo-op.
2274 The various options of the i960 @code{.list} pseudo-op are not supported.
2276 @item @code{.optimize} pseudo-op
2278 The i960 @code{.optimize} pseudo-op is not supported.
2280 @item @code{.output} pseudo-op
2282 The i960 @code{.output} pseudo-op is not supported.
2284 @item @code{.setreal} pseudo-op
2286 The i960 @code{.setreal} pseudo-op is not supported.
2291 @section Dependency Tracking: @option{--MD}
2294 @cindex dependency tracking
2297 @command{@value{AS}} can generate a dependency file for the file it creates. This
2298 file consists of a single rule suitable for @code{make} describing the
2299 dependencies of the main source file.
2301 The rule is written to the file named in its argument.
2303 This feature is used in the automatic updating of makefiles.
2306 @section Name the Object File: @option{-o}
2309 @cindex naming object file
2310 @cindex object file name
2311 There is always one object file output when you run @command{@value{AS}}. By
2312 default it has the name
2315 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2329 You use this option (which takes exactly one filename) to give the
2330 object file a different name.
2332 Whatever the object file is called, @command{@value{AS}} overwrites any
2333 existing file of the same name.
2336 @section Join Data and Text Sections: @option{-R}
2339 @cindex data and text sections, joining
2340 @cindex text and data sections, joining
2341 @cindex joining text and data sections
2342 @cindex merging text and data sections
2343 @option{-R} tells @command{@value{AS}} to write the object file as if all
2344 data-section data lives in the text section. This is only done at
2345 the very last moment: your binary data are the same, but data
2346 section parts are relocated differently. The data section part of
2347 your object file is zero bytes long because all its bytes are
2348 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2350 When you specify @option{-R} it would be possible to generate shorter
2351 address displacements (because we do not have to cross between text and
2352 data section). We refrain from doing this simply for compatibility with
2353 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2356 When @command{@value{AS}} is configured for COFF or ELF output,
2357 this option is only useful if you use sections named @samp{.text} and
2362 @option{-R} is not supported for any of the HPPA targets. Using
2363 @option{-R} generates a warning from @command{@value{AS}}.
2367 @section Display Assembly Statistics: @option{--statistics}
2369 @kindex --statistics
2370 @cindex statistics, about assembly
2371 @cindex time, total for assembly
2372 @cindex space used, maximum for assembly
2373 Use @samp{--statistics} to display two statistics about the resources used by
2374 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2375 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2378 @node traditional-format
2379 @section Compatible Output: @option{--traditional-format}
2381 @kindex --traditional-format
2382 For some targets, the output of @command{@value{AS}} is different in some ways
2383 from the output of some existing assembler. This switch requests
2384 @command{@value{AS}} to use the traditional format instead.
2386 For example, it disables the exception frame optimizations which
2387 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2390 @section Announce Version: @option{-v}
2394 @cindex assembler version
2395 @cindex version of assembler
2396 You can find out what version of as is running by including the
2397 option @samp{-v} (which you can also spell as @samp{-version}) on the
2401 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2403 @command{@value{AS}} should never give a warning or error message when
2404 assembling compiler output. But programs written by people often
2405 cause @command{@value{AS}} to give a warning that a particular assumption was
2406 made. All such warnings are directed to the standard error file.
2410 @cindex suppressing warnings
2411 @cindex warnings, suppressing
2412 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2413 This only affects the warning messages: it does not change any particular of
2414 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2417 @kindex --fatal-warnings
2418 @cindex errors, caused by warnings
2419 @cindex warnings, causing error
2420 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2421 files that generate warnings to be in error.
2424 @cindex warnings, switching on
2425 You can switch these options off again by specifying @option{--warn}, which
2426 causes warnings to be output as usual.
2429 @section Generate Object File in Spite of Errors: @option{-Z}
2430 @cindex object file, after errors
2431 @cindex errors, continuing after
2432 After an error message, @command{@value{AS}} normally produces no output. If for
2433 some reason you are interested in object file output even after
2434 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2435 option. If there are any errors, @command{@value{AS}} continues anyways, and
2436 writes an object file after a final warning message of the form @samp{@var{n}
2437 errors, @var{m} warnings, generating bad object file.}
2442 @cindex machine-independent syntax
2443 @cindex syntax, machine-independent
2444 This chapter describes the machine-independent syntax allowed in a
2445 source file. @command{@value{AS}} syntax is similar to what many other
2446 assemblers use; it is inspired by the BSD 4.2
2451 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2455 * Preprocessing:: Preprocessing
2456 * Whitespace:: Whitespace
2457 * Comments:: Comments
2458 * Symbol Intro:: Symbols
2459 * Statements:: Statements
2460 * Constants:: Constants
2464 @section Preprocessing
2466 @cindex preprocessing
2467 The @command{@value{AS}} internal preprocessor:
2469 @cindex whitespace, removed by preprocessor
2471 adjusts and removes extra whitespace. It leaves one space or tab before
2472 the keywords on a line, and turns any other whitespace on the line into
2475 @cindex comments, removed by preprocessor
2477 removes all comments, replacing them with a single space, or an
2478 appropriate number of newlines.
2480 @cindex constants, converted by preprocessor
2482 converts character constants into the appropriate numeric values.
2485 It does not do macro processing, include file handling, or
2486 anything else you may get from your C compiler's preprocessor. You can
2487 do include file processing with the @code{.include} directive
2488 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2489 to get other ``CPP'' style preprocessing by giving the input file a
2490 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2491 Output, gcc.info, Using GNU CC}.
2493 Excess whitespace, comments, and character constants
2494 cannot be used in the portions of the input text that are not
2497 @cindex turning preprocessing on and off
2498 @cindex preprocessing, turning on and off
2501 If the first line of an input file is @code{#NO_APP} or if you use the
2502 @samp{-f} option, whitespace and comments are not removed from the input file.
2503 Within an input file, you can ask for whitespace and comment removal in
2504 specific portions of the by putting a line that says @code{#APP} before the
2505 text that may contain whitespace or comments, and putting a line that says
2506 @code{#NO_APP} after this text. This feature is mainly intend to support
2507 @code{asm} statements in compilers whose output is otherwise free of comments
2514 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2515 Whitespace is used to separate symbols, and to make programs neater for
2516 people to read. Unless within character constants
2517 (@pxref{Characters,,Character Constants}), any whitespace means the same
2518 as exactly one space.
2524 There are two ways of rendering comments to @command{@value{AS}}. In both
2525 cases the comment is equivalent to one space.
2527 Anything from @samp{/*} through the next @samp{*/} is a comment.
2528 This means you may not nest these comments.
2532 The only way to include a newline ('\n') in a comment
2533 is to use this sort of comment.
2536 /* This sort of comment does not nest. */
2539 @cindex line comment character
2540 Anything from a @dfn{line comment} character up to the next newline is
2541 considered a comment and is ignored. The line comment character is target
2542 specific, and some targets multiple comment characters. Some targets also have
2543 line comment characters that only work if they are the first character on a
2544 line. Some targets use a sequence of two characters to introduce a line
2545 comment. Some targets can also change their line comment characters depending
2546 upon command line options that have been used. For more details see the
2547 @emph{Syntax} section in the documentation for individual targets.
2549 If the line comment character is the hash sign (@samp{#}) then it still has the
2550 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2551 to specify logical line numbers:
2554 @cindex lines starting with @code{#}
2555 @cindex logical line numbers
2556 To be compatible with past assemblers, lines that begin with @samp{#} have a
2557 special interpretation. Following the @samp{#} should be an absolute
2558 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2559 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2560 new logical file name. The rest of the line, if any, should be whitespace.
2562 If the first non-whitespace characters on the line are not numeric,
2563 the line is ignored. (Just like a comment.)
2566 # This is an ordinary comment.
2567 # 42-6 "new_file_name" # New logical file name
2568 # This is logical line # 36.
2570 This feature is deprecated, and may disappear from future versions
2571 of @command{@value{AS}}.
2576 @cindex characters used in symbols
2577 @ifclear SPECIAL-SYMS
2578 A @dfn{symbol} is one or more characters chosen from the set of all
2579 letters (both upper and lower case), digits and the three characters
2585 A @dfn{symbol} is one or more characters chosen from the set of all
2586 letters (both upper and lower case), digits and the three characters
2587 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2593 On most machines, you can also use @code{$} in symbol names; exceptions
2594 are noted in @ref{Machine Dependencies}.
2596 No symbol may begin with a digit. Case is significant.
2597 There is no length limit: all characters are significant. Multibyte characters
2598 are supported. Symbols are delimited by characters not in that set, or by the
2599 beginning of a file (since the source program must end with a newline, the end
2600 of a file is not a possible symbol delimiter). @xref{Symbols}.
2601 @cindex length of symbols
2606 @cindex statements, structure of
2607 @cindex line separator character
2608 @cindex statement separator character
2610 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2611 @dfn{line separator character}. The line separator character is target
2612 specific and described in the @emph{Syntax} section of each
2613 target's documentation. Not all targets support a line separator character.
2614 The newline or line separator character is considered to be part of the
2615 preceding statement. Newlines and separators within character constants are an
2616 exception: they do not end statements.
2618 @cindex newline, required at file end
2619 @cindex EOF, newline must precede
2620 It is an error to end any statement with end-of-file: the last
2621 character of any input file should be a newline.@refill
2623 An empty statement is allowed, and may include whitespace. It is ignored.
2625 @cindex instructions and directives
2626 @cindex directives and instructions
2627 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2628 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2630 A statement begins with zero or more labels, optionally followed by a
2631 key symbol which determines what kind of statement it is. The key
2632 symbol determines the syntax of the rest of the statement. If the
2633 symbol begins with a dot @samp{.} then the statement is an assembler
2634 directive: typically valid for any computer. If the symbol begins with
2635 a letter the statement is an assembly language @dfn{instruction}: it
2636 assembles into a machine language instruction.
2638 Different versions of @command{@value{AS}} for different computers
2639 recognize different instructions. In fact, the same symbol may
2640 represent a different instruction in a different computer's assembly
2644 @cindex @code{:} (label)
2645 @cindex label (@code{:})
2646 A label is a symbol immediately followed by a colon (@code{:}).
2647 Whitespace before a label or after a colon is permitted, but you may not
2648 have whitespace between a label's symbol and its colon. @xref{Labels}.
2651 For HPPA targets, labels need not be immediately followed by a colon, but
2652 the definition of a label must begin in column zero. This also implies that
2653 only one label may be defined on each line.
2657 label: .directive followed by something
2658 another_label: # This is an empty statement.
2659 instruction operand_1, operand_2, @dots{}
2666 A constant is a number, written so that its value is known by
2667 inspection, without knowing any context. Like this:
2670 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2671 .ascii "Ring the bell\7" # A string constant.
2672 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2673 .float 0f-314159265358979323846264338327\
2674 95028841971.693993751E-40 # - pi, a flonum.
2679 * Characters:: Character Constants
2680 * Numbers:: Number Constants
2684 @subsection Character Constants
2686 @cindex character constants
2687 @cindex constants, character
2688 There are two kinds of character constants. A @dfn{character} stands
2689 for one character in one byte and its value may be used in
2690 numeric expressions. String constants (properly called string
2691 @emph{literals}) are potentially many bytes and their values may not be
2692 used in arithmetic expressions.
2696 * Chars:: Characters
2700 @subsubsection Strings
2702 @cindex string constants
2703 @cindex constants, string
2704 A @dfn{string} is written between double-quotes. It may contain
2705 double-quotes or null characters. The way to get special characters
2706 into a string is to @dfn{escape} these characters: precede them with
2707 a backslash @samp{\} character. For example @samp{\\} represents
2708 one backslash: the first @code{\} is an escape which tells
2709 @command{@value{AS}} to interpret the second character literally as a backslash
2710 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2711 escape character). The complete list of escapes follows.
2713 @cindex escape codes, character
2714 @cindex character escape codes
2717 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2719 @cindex @code{\b} (backspace character)
2720 @cindex backspace (@code{\b})
2722 Mnemonic for backspace; for ASCII this is octal code 010.
2725 @c Mnemonic for EOText; for ASCII this is octal code 004.
2727 @cindex @code{\f} (formfeed character)
2728 @cindex formfeed (@code{\f})
2730 Mnemonic for FormFeed; for ASCII this is octal code 014.
2732 @cindex @code{\n} (newline character)
2733 @cindex newline (@code{\n})
2735 Mnemonic for newline; for ASCII this is octal code 012.
2738 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2740 @cindex @code{\r} (carriage return character)
2741 @cindex carriage return (@code{\r})
2743 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2746 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2747 @c other assemblers.
2749 @cindex @code{\t} (tab)
2750 @cindex tab (@code{\t})
2752 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2755 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2756 @c @item \x @var{digit} @var{digit} @var{digit}
2757 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2759 @cindex @code{\@var{ddd}} (octal character code)
2760 @cindex octal character code (@code{\@var{ddd}})
2761 @item \ @var{digit} @var{digit} @var{digit}
2762 An octal character code. The numeric code is 3 octal digits.
2763 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2764 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2766 @cindex @code{\@var{xd...}} (hex character code)
2767 @cindex hex character code (@code{\@var{xd...}})
2768 @item \@code{x} @var{hex-digits...}
2769 A hex character code. All trailing hex digits are combined. Either upper or
2770 lower case @code{x} works.
2772 @cindex @code{\\} (@samp{\} character)
2773 @cindex backslash (@code{\\})
2775 Represents one @samp{\} character.
2778 @c Represents one @samp{'} (accent acute) character.
2779 @c This is needed in single character literals
2780 @c (@xref{Characters,,Character Constants}.) to represent
2783 @cindex @code{\"} (doublequote character)
2784 @cindex doublequote (@code{\"})
2786 Represents one @samp{"} character. Needed in strings to represent
2787 this character, because an unescaped @samp{"} would end the string.
2789 @item \ @var{anything-else}
2790 Any other character when escaped by @kbd{\} gives a warning, but
2791 assembles as if the @samp{\} was not present. The idea is that if
2792 you used an escape sequence you clearly didn't want the literal
2793 interpretation of the following character. However @command{@value{AS}} has no
2794 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2795 code and warns you of the fact.
2798 Which characters are escapable, and what those escapes represent,
2799 varies widely among assemblers. The current set is what we think
2800 the BSD 4.2 assembler recognizes, and is a subset of what most C
2801 compilers recognize. If you are in doubt, do not use an escape
2805 @subsubsection Characters
2807 @cindex single character constant
2808 @cindex character, single
2809 @cindex constant, single character
2810 A single character may be written as a single quote immediately
2811 followed by that character. The same escapes apply to characters as
2812 to strings. So if you want to write the character backslash, you
2813 must write @kbd{'\\} where the first @code{\} escapes the second
2814 @code{\}. As you can see, the quote is an acute accent, not a
2815 grave accent. A newline
2817 @ifclear abnormal-separator
2818 (or semicolon @samp{;})
2820 @ifset abnormal-separator
2822 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2827 immediately following an acute accent is taken as a literal character
2828 and does not count as the end of a statement. The value of a character
2829 constant in a numeric expression is the machine's byte-wide code for
2830 that character. @command{@value{AS}} assumes your character code is ASCII:
2831 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2834 @subsection Number Constants
2836 @cindex constants, number
2837 @cindex number constants
2838 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2839 are stored in the target machine. @emph{Integers} are numbers that
2840 would fit into an @code{int} in the C language. @emph{Bignums} are
2841 integers, but they are stored in more than 32 bits. @emph{Flonums}
2842 are floating point numbers, described below.
2845 * Integers:: Integers
2850 * Bit Fields:: Bit Fields
2856 @subsubsection Integers
2858 @cindex constants, integer
2860 @cindex binary integers
2861 @cindex integers, binary
2862 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2863 the binary digits @samp{01}.
2865 @cindex octal integers
2866 @cindex integers, octal
2867 An octal integer is @samp{0} followed by zero or more of the octal
2868 digits (@samp{01234567}).
2870 @cindex decimal integers
2871 @cindex integers, decimal
2872 A decimal integer starts with a non-zero digit followed by zero or
2873 more digits (@samp{0123456789}).
2875 @cindex hexadecimal integers
2876 @cindex integers, hexadecimal
2877 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2878 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2880 Integers have the usual values. To denote a negative integer, use
2881 the prefix operator @samp{-} discussed under expressions
2882 (@pxref{Prefix Ops,,Prefix Operators}).
2885 @subsubsection Bignums
2888 @cindex constants, bignum
2889 A @dfn{bignum} has the same syntax and semantics as an integer
2890 except that the number (or its negative) takes more than 32 bits to
2891 represent in binary. The distinction is made because in some places
2892 integers are permitted while bignums are not.
2895 @subsubsection Flonums
2897 @cindex floating point numbers
2898 @cindex constants, floating point
2900 @cindex precision, floating point
2901 A @dfn{flonum} represents a floating point number. The translation is
2902 indirect: a decimal floating point number from the text is converted by
2903 @command{@value{AS}} to a generic binary floating point number of more than
2904 sufficient precision. This generic floating point number is converted
2905 to a particular computer's floating point format (or formats) by a
2906 portion of @command{@value{AS}} specialized to that computer.
2908 A flonum is written by writing (in order)
2913 (@samp{0} is optional on the HPPA.)
2917 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2919 @kbd{e} is recommended. Case is not important.
2921 @c FIXME: verify if flonum syntax really this vague for most cases
2922 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2923 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2926 On the H8/300, Renesas / SuperH SH,
2927 and AMD 29K architectures, the letter must be
2928 one of the letters @samp{DFPRSX} (in upper or lower case).
2930 On the ARC, the letter must be one of the letters @samp{DFRS}
2931 (in upper or lower case).
2933 On the Intel 960 architecture, the letter must be
2934 one of the letters @samp{DFT} (in upper or lower case).
2936 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2940 One of the letters @samp{DFRS} (in upper or lower case).
2943 One of the letters @samp{DFPRSX} (in upper or lower case).
2946 The letter @samp{E} (upper case only).
2949 One of the letters @samp{DFT} (in upper or lower case).
2954 An optional sign: either @samp{+} or @samp{-}.
2957 An optional @dfn{integer part}: zero or more decimal digits.
2960 An optional @dfn{fractional part}: @samp{.} followed by zero
2961 or more decimal digits.
2964 An optional exponent, consisting of:
2968 An @samp{E} or @samp{e}.
2969 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2970 @c principle this can perfectly well be different on different targets.
2972 Optional sign: either @samp{+} or @samp{-}.
2974 One or more decimal digits.
2979 At least one of the integer part or the fractional part must be
2980 present. The floating point number has the usual base-10 value.
2982 @command{@value{AS}} does all processing using integers. Flonums are computed
2983 independently of any floating point hardware in the computer running
2984 @command{@value{AS}}.
2988 @c Bit fields are written as a general facility but are also controlled
2989 @c by a conditional-compilation flag---which is as of now (21mar91)
2990 @c turned on only by the i960 config of GAS.
2992 @subsubsection Bit Fields
2995 @cindex constants, bit field
2996 You can also define numeric constants as @dfn{bit fields}.
2997 Specify two numbers separated by a colon---
2999 @var{mask}:@var{value}
3002 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3005 The resulting number is then packed
3007 @c this conditional paren in case bit fields turned on elsewhere than 960
3008 (in host-dependent byte order)
3010 into a field whose width depends on which assembler directive has the
3011 bit-field as its argument. Overflow (a result from the bitwise and
3012 requiring more binary digits to represent) is not an error; instead,
3013 more constants are generated, of the specified width, beginning with the
3014 least significant digits.@refill
3016 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3017 @code{.short}, and @code{.word} accept bit-field arguments.
3022 @chapter Sections and Relocation
3027 * Secs Background:: Background
3028 * Ld Sections:: Linker Sections
3029 * As Sections:: Assembler Internal Sections
3030 * Sub-Sections:: Sub-Sections
3034 @node Secs Background
3037 Roughly, a section is a range of addresses, with no gaps; all data
3038 ``in'' those addresses is treated the same for some particular purpose.
3039 For example there may be a ``read only'' section.
3041 @cindex linker, and assembler
3042 @cindex assembler, and linker
3043 The linker @code{@value{LD}} reads many object files (partial programs) and
3044 combines their contents to form a runnable program. When @command{@value{AS}}
3045 emits an object file, the partial program is assumed to start at address 0.
3046 @code{@value{LD}} assigns the final addresses for the partial program, so that
3047 different partial programs do not overlap. This is actually an
3048 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3051 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3052 addresses. These blocks slide to their run-time addresses as rigid
3053 units; their length does not change and neither does the order of bytes
3054 within them. Such a rigid unit is called a @emph{section}. Assigning
3055 run-time addresses to sections is called @dfn{relocation}. It includes
3056 the task of adjusting mentions of object-file addresses so they refer to
3057 the proper run-time addresses.
3059 For the H8/300, and for the Renesas / SuperH SH,
3060 @command{@value{AS}} pads sections if needed to
3061 ensure they end on a word (sixteen bit) boundary.
3064 @cindex standard assembler sections
3065 An object file written by @command{@value{AS}} has at least three sections, any
3066 of which may be empty. These are named @dfn{text}, @dfn{data} and
3071 When it generates COFF or ELF output,
3073 @command{@value{AS}} can also generate whatever other named sections you specify
3074 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3075 If you do not use any directives that place output in the @samp{.text}
3076 or @samp{.data} sections, these sections still exist, but are empty.
3081 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3083 @command{@value{AS}} can also generate whatever other named sections you
3084 specify using the @samp{.space} and @samp{.subspace} directives. See
3085 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3086 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3087 assembler directives.
3090 Additionally, @command{@value{AS}} uses different names for the standard
3091 text, data, and bss sections when generating SOM output. Program text
3092 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3093 BSS into @samp{$BSS$}.
3097 Within the object file, the text section starts at address @code{0}, the
3098 data section follows, and the bss section follows the data section.
3101 When generating either SOM or ELF output files on the HPPA, the text
3102 section starts at address @code{0}, the data section at address
3103 @code{0x4000000}, and the bss section follows the data section.
3106 To let @code{@value{LD}} know which data changes when the sections are
3107 relocated, and how to change that data, @command{@value{AS}} also writes to the
3108 object file details of the relocation needed. To perform relocation
3109 @code{@value{LD}} must know, each time an address in the object
3113 Where in the object file is the beginning of this reference to
3116 How long (in bytes) is this reference?
3118 Which section does the address refer to? What is the numeric value of
3120 (@var{address}) @minus{} (@var{start-address of section})?
3123 Is the reference to an address ``Program-Counter relative''?
3126 @cindex addresses, format of
3127 @cindex section-relative addressing
3128 In fact, every address @command{@value{AS}} ever uses is expressed as
3130 (@var{section}) + (@var{offset into section})
3133 Further, most expressions @command{@value{AS}} computes have this section-relative
3136 (For some object formats, such as SOM for the HPPA, some expressions are
3137 symbol-relative instead.)
3140 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3141 @var{N} into section @var{secname}.''
3143 Apart from text, data and bss sections you need to know about the
3144 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3145 addresses in the absolute section remain unchanged. For example, address
3146 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3147 @code{@value{LD}}. Although the linker never arranges two partial programs'
3148 data sections with overlapping addresses after linking, @emph{by definition}
3149 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3150 part of a program is always the same address when the program is running as
3151 address @code{@{absolute@ 239@}} in any other part of the program.
3153 The idea of sections is extended to the @dfn{undefined} section. Any
3154 address whose section is unknown at assembly time is by definition
3155 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3156 Since numbers are always defined, the only way to generate an undefined
3157 address is to mention an undefined symbol. A reference to a named
3158 common block would be such a symbol: its value is unknown at assembly
3159 time so it has section @emph{undefined}.
3161 By analogy the word @emph{section} is used to describe groups of sections in
3162 the linked program. @code{@value{LD}} puts all partial programs' text
3163 sections in contiguous addresses in the linked program. It is
3164 customary to refer to the @emph{text section} of a program, meaning all
3165 the addresses of all partial programs' text sections. Likewise for
3166 data and bss sections.
3168 Some sections are manipulated by @code{@value{LD}}; others are invented for
3169 use of @command{@value{AS}} and have no meaning except during assembly.
3172 @section Linker Sections
3173 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3178 @cindex named sections
3179 @cindex sections, named
3180 @item named sections
3183 @cindex text section
3184 @cindex data section
3188 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3189 separate but equal sections. Anything you can say of one section is
3192 When the program is running, however, it is
3193 customary for the text section to be unalterable. The
3194 text section is often shared among processes: it contains
3195 instructions, constants and the like. The data section of a running
3196 program is usually alterable: for example, C variables would be stored
3197 in the data section.
3202 This section contains zeroed bytes when your program begins running. It
3203 is used to hold uninitialized variables or common storage. The length of
3204 each partial program's bss section is important, but because it starts
3205 out containing zeroed bytes there is no need to store explicit zero
3206 bytes in the object file. The bss section was invented to eliminate
3207 those explicit zeros from object files.
3209 @cindex absolute section
3210 @item absolute section
3211 Address 0 of this section is always ``relocated'' to runtime address 0.
3212 This is useful if you want to refer to an address that @code{@value{LD}} must
3213 not change when relocating. In this sense we speak of absolute
3214 addresses being ``unrelocatable'': they do not change during relocation.
3216 @cindex undefined section
3217 @item undefined section
3218 This ``section'' is a catch-all for address references to objects not in
3219 the preceding sections.
3220 @c FIXME: ref to some other doc on obj-file formats could go here.
3223 @cindex relocation example
3224 An idealized example of three relocatable sections follows.
3226 The example uses the traditional section names @samp{.text} and @samp{.data}.
3228 Memory addresses are on the horizontal axis.
3232 @c END TEXI2ROFF-KILL
3235 partial program # 1: |ttttt|dddd|00|
3242 partial program # 2: |TTT|DDD|000|
3245 +--+---+-----+--+----+---+-----+~~
3246 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3247 +--+---+-----+--+----+---+-----+~~
3249 addresses: 0 @dots{}
3256 \line{\it Partial program \#1: \hfil}
3257 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3258 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3260 \line{\it Partial program \#2: \hfil}
3261 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3262 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3264 \line{\it linked program: \hfil}
3265 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3266 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3267 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3268 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3270 \line{\it addresses: \hfil}
3274 @c END TEXI2ROFF-KILL
3277 @section Assembler Internal Sections
3279 @cindex internal assembler sections
3280 @cindex sections in messages, internal
3281 These sections are meant only for the internal use of @command{@value{AS}}. They
3282 have no meaning at run-time. You do not really need to know about these
3283 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3284 warning messages, so it might be helpful to have an idea of their
3285 meanings to @command{@value{AS}}. These sections are used to permit the
3286 value of every expression in your assembly language program to be a
3287 section-relative address.
3290 @cindex assembler internal logic error
3291 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3292 An internal assembler logic error has been found. This means there is a
3293 bug in the assembler.
3295 @cindex expr (internal section)
3297 The assembler stores complex expression internally as combinations of
3298 symbols. When it needs to represent an expression as a symbol, it puts
3299 it in the expr section.
3301 @c FIXME item transfer[t] vector preload
3302 @c FIXME item transfer[t] vector postload
3303 @c FIXME item register
3307 @section Sub-Sections
3309 @cindex numbered subsections
3310 @cindex grouping data
3316 fall into two sections: text and data.
3318 You may have separate groups of
3320 data in named sections
3324 data in named sections
3330 that you want to end up near to each other in the object file, even though they
3331 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3332 use @dfn{subsections} for this purpose. Within each section, there can be
3333 numbered subsections with values from 0 to 8192. Objects assembled into the
3334 same subsection go into the object file together with other objects in the same
3335 subsection. For example, a compiler might want to store constants in the text
3336 section, but might not want to have them interspersed with the program being
3337 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3338 section of code being output, and a @samp{.text 1} before each group of
3339 constants being output.
3341 Subsections are optional. If you do not use subsections, everything
3342 goes in subsection number zero.
3345 Each subsection is zero-padded up to a multiple of four bytes.
3346 (Subsections may be padded a different amount on different flavors
3347 of @command{@value{AS}}.)
3351 On the H8/300 platform, each subsection is zero-padded to a word
3352 boundary (two bytes).
3353 The same is true on the Renesas SH.
3356 @c FIXME section padding (alignment)?
3357 @c Rich Pixley says padding here depends on target obj code format; that
3358 @c doesn't seem particularly useful to say without further elaboration,
3359 @c so for now I say nothing about it. If this is a generic BFD issue,
3360 @c these paragraphs might need to vanish from this manual, and be
3361 @c discussed in BFD chapter of binutils (or some such).
3365 Subsections appear in your object file in numeric order, lowest numbered
3366 to highest. (All this to be compatible with other people's assemblers.)
3367 The object file contains no representation of subsections; @code{@value{LD}} and
3368 other programs that manipulate object files see no trace of them.
3369 They just see all your text subsections as a text section, and all your
3370 data subsections as a data section.
3372 To specify which subsection you want subsequent statements assembled
3373 into, use a numeric argument to specify it, in a @samp{.text
3374 @var{expression}} or a @samp{.data @var{expression}} statement.
3377 When generating COFF output, you
3382 can also use an extra subsection
3383 argument with arbitrary named sections: @samp{.section @var{name},
3388 When generating ELF output, you
3393 can also use the @code{.subsection} directive (@pxref{SubSection})
3394 to specify a subsection: @samp{.subsection @var{expression}}.
3396 @var{Expression} should be an absolute expression
3397 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3398 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3399 begins in @code{text 0}. For instance:
3401 .text 0 # The default subsection is text 0 anyway.
3402 .ascii "This lives in the first text subsection. *"
3404 .ascii "But this lives in the second text subsection."
3406 .ascii "This lives in the data section,"
3407 .ascii "in the first data subsection."
3409 .ascii "This lives in the first text section,"
3410 .ascii "immediately following the asterisk (*)."
3413 Each section has a @dfn{location counter} incremented by one for every byte
3414 assembled into that section. Because subsections are merely a convenience
3415 restricted to @command{@value{AS}} there is no concept of a subsection location
3416 counter. There is no way to directly manipulate a location counter---but the
3417 @code{.align} directive changes it, and any label definition captures its
3418 current value. The location counter of the section where statements are being
3419 assembled is said to be the @dfn{active} location counter.
3422 @section bss Section
3425 @cindex common variable storage
3426 The bss section is used for local common variable storage.
3427 You may allocate address space in the bss section, but you may
3428 not dictate data to load into it before your program executes. When
3429 your program starts running, all the contents of the bss
3430 section are zeroed bytes.
3432 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3433 @ref{Lcomm,,@code{.lcomm}}.
3435 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3436 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3439 When assembling for a target which supports multiple sections, such as ELF or
3440 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3441 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3442 section. Typically the section will only contain symbol definitions and
3443 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3450 Symbols are a central concept: the programmer uses symbols to name
3451 things, the linker uses symbols to link, and the debugger uses symbols
3455 @cindex debuggers, and symbol order
3456 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3457 the same order they were declared. This may break some debuggers.
3462 * Setting Symbols:: Giving Symbols Other Values
3463 * Symbol Names:: Symbol Names
3464 * Dot:: The Special Dot Symbol
3465 * Symbol Attributes:: Symbol Attributes
3472 A @dfn{label} is written as a symbol immediately followed by a colon
3473 @samp{:}. The symbol then represents the current value of the
3474 active location counter, and is, for example, a suitable instruction
3475 operand. You are warned if you use the same symbol to represent two
3476 different locations: the first definition overrides any other
3480 On the HPPA, the usual form for a label need not be immediately followed by a
3481 colon, but instead must start in column zero. Only one label may be defined on
3482 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3483 provides a special directive @code{.label} for defining labels more flexibly.
3486 @node Setting Symbols
3487 @section Giving Symbols Other Values
3489 @cindex assigning values to symbols
3490 @cindex symbol values, assigning
3491 A symbol can be given an arbitrary value by writing a symbol, followed
3492 by an equals sign @samp{=}, followed by an expression
3493 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3494 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3495 equals sign @samp{=}@samp{=} here represents an equivalent of the
3496 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3499 Blackfin does not support symbol assignment with @samp{=}.
3503 @section Symbol Names
3505 @cindex symbol names
3506 @cindex names, symbol
3507 @ifclear SPECIAL-SYMS
3508 Symbol names begin with a letter or with one of @samp{._}. On most
3509 machines, you can also use @code{$} in symbol names; exceptions are
3510 noted in @ref{Machine Dependencies}. That character may be followed by any
3511 string of digits, letters, dollar signs (unless otherwise noted for a
3512 particular target machine), and underscores.
3516 Symbol names begin with a letter or with one of @samp{._}. On the
3517 Renesas SH you can also use @code{$} in symbol names. That
3518 character may be followed by any string of digits, letters, dollar signs (save
3519 on the H8/300), and underscores.
3523 Case of letters is significant: @code{foo} is a different symbol name
3526 Multibyte characters are supported. To generate a symbol name containing
3527 multibyte characters enclose it within double quotes and use escape codes. cf
3528 @xref{Strings}. Generating a multibyte symbol name from a label is not
3529 currently supported.
3531 Each symbol has exactly one name. Each name in an assembly language program
3532 refers to exactly one symbol. You may use that symbol name any number of times
3535 @subheading Local Symbol Names
3537 @cindex local symbol names
3538 @cindex symbol names, local
3539 A local symbol is any symbol beginning with certain local label prefixes.
3540 By default, the local label prefix is @samp{.L} for ELF systems or
3541 @samp{L} for traditional a.out systems, but each target may have its own
3542 set of local label prefixes.
3544 On the HPPA local symbols begin with @samp{L$}.
3547 Local symbols are defined and used within the assembler, but they are
3548 normally not saved in object files. Thus, they are not visible when debugging.
3549 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3550 @option{-L}}) to retain the local symbols in the object files.
3552 @subheading Local Labels
3554 @cindex local labels
3555 @cindex temporary symbol names
3556 @cindex symbol names, temporary
3557 Local labels help compilers and programmers use names temporarily.
3558 They create symbols which are guaranteed to be unique over the entire scope of
3559 the input source code and which can be referred to by a simple notation.
3560 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3561 represents any positive integer). To refer to the most recent previous
3562 definition of that label write @samp{@b{N}b}, using the same number as when
3563 you defined the label. To refer to the next definition of a local label, write
3564 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3567 There is no restriction on how you can use these labels, and you can reuse them
3568 too. So that it is possible to repeatedly define the same local label (using
3569 the same number @samp{@b{N}}), although you can only refer to the most recently
3570 defined local label of that number (for a backwards reference) or the next
3571 definition of a specific local label for a forward reference. It is also worth
3572 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3573 implemented in a slightly more efficient manner than the others.
3584 Which is the equivalent of:
3587 label_1: branch label_3
3588 label_2: branch label_1
3589 label_3: branch label_4
3590 label_4: branch label_3
3593 Local label names are only a notational device. They are immediately
3594 transformed into more conventional symbol names before the assembler uses them.
3595 The symbol names are stored in the symbol table, appear in error messages, and
3596 are optionally emitted to the object file. The names are constructed using
3600 @item @emph{local label prefix}
3601 All local symbols begin with the system-specific local label prefix.
3602 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3603 that start with the local label prefix. These labels are
3604 used for symbols you are never intended to see. If you use the
3605 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3606 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3607 you may use them in debugging.
3610 This is the number that was used in the local label definition. So if the
3611 label is written @samp{55:} then the number is @samp{55}.
3614 This unusual character is included so you do not accidentally invent a symbol
3615 of the same name. The character has ASCII value of @samp{\002} (control-B).
3617 @item @emph{ordinal number}
3618 This is a serial number to keep the labels distinct. The first definition of
3619 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3620 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3621 the number @samp{1} and its 15th definition gets @samp{15} as well.
3624 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3625 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3627 @subheading Dollar Local Labels
3628 @cindex dollar local symbols
3630 @code{@value{AS}} also supports an even more local form of local labels called
3631 dollar labels. These labels go out of scope (i.e., they become undefined) as
3632 soon as a non-local label is defined. Thus they remain valid for only a small
3633 region of the input source code. Normal local labels, by contrast, remain in
3634 scope for the entire file, or until they are redefined by another occurrence of
3635 the same local label.
3637 Dollar labels are defined in exactly the same way as ordinary local labels,
3638 except that they have a dollar sign suffix to their numeric value, e.g.,
3641 They can also be distinguished from ordinary local labels by their transformed
3642 names which use ASCII character @samp{\001} (control-A) as the magic character
3643 to distinguish them from ordinary labels. For example, the fifth definition of
3644 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3647 @section The Special Dot Symbol
3649 @cindex dot (symbol)
3650 @cindex @code{.} (symbol)
3651 @cindex current address
3652 @cindex location counter
3653 The special symbol @samp{.} refers to the current address that
3654 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3655 .long .} defines @code{melvin} to contain its own address.
3656 Assigning a value to @code{.} is treated the same as a @code{.org}
3658 @ifclear no-space-dir
3659 Thus, the expression @samp{.=.+4} is the same as saying
3663 @node Symbol Attributes
3664 @section Symbol Attributes
3666 @cindex symbol attributes
3667 @cindex attributes, symbol
3668 Every symbol has, as well as its name, the attributes ``Value'' and
3669 ``Type''. Depending on output format, symbols can also have auxiliary
3672 The detailed definitions are in @file{a.out.h}.
3675 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3676 all these attributes, and probably won't warn you. This makes the
3677 symbol an externally defined symbol, which is generally what you
3681 * Symbol Value:: Value
3682 * Symbol Type:: Type
3685 * a.out Symbols:: Symbol Attributes: @code{a.out}
3689 * a.out Symbols:: Symbol Attributes: @code{a.out}
3692 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3697 * COFF Symbols:: Symbol Attributes for COFF
3700 * SOM Symbols:: Symbol Attributes for SOM
3707 @cindex value of a symbol
3708 @cindex symbol value
3709 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3710 location in the text, data, bss or absolute sections the value is the
3711 number of addresses from the start of that section to the label.
3712 Naturally for text, data and bss sections the value of a symbol changes
3713 as @code{@value{LD}} changes section base addresses during linking. Absolute
3714 symbols' values do not change during linking: that is why they are
3717 The value of an undefined symbol is treated in a special way. If it is
3718 0 then the symbol is not defined in this assembler source file, and
3719 @code{@value{LD}} tries to determine its value from other files linked into the
3720 same program. You make this kind of symbol simply by mentioning a symbol
3721 name without defining it. A non-zero value represents a @code{.comm}
3722 common declaration. The value is how much common storage to reserve, in
3723 bytes (addresses). The symbol refers to the first address of the
3729 @cindex type of a symbol
3731 The type attribute of a symbol contains relocation (section)
3732 information, any flag settings indicating that a symbol is external, and
3733 (optionally), other information for linkers and debuggers. The exact
3734 format depends on the object-code output format in use.
3739 @c The following avoids a "widow" subsection title. @group would be
3740 @c better if it were available outside examples.
3743 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3745 @cindex @code{b.out} symbol attributes
3746 @cindex symbol attributes, @code{b.out}
3747 These symbol attributes appear only when @command{@value{AS}} is configured for
3748 one of the Berkeley-descended object output formats---@code{a.out} or
3754 @subsection Symbol Attributes: @code{a.out}
3756 @cindex @code{a.out} symbol attributes
3757 @cindex symbol attributes, @code{a.out}
3763 @subsection Symbol Attributes: @code{a.out}
3765 @cindex @code{a.out} symbol attributes
3766 @cindex symbol attributes, @code{a.out}
3770 * Symbol Desc:: Descriptor
3771 * Symbol Other:: Other
3775 @subsubsection Descriptor
3777 @cindex descriptor, of @code{a.out} symbol
3778 This is an arbitrary 16-bit value. You may establish a symbol's
3779 descriptor value by using a @code{.desc} statement
3780 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3781 @command{@value{AS}}.
3784 @subsubsection Other
3786 @cindex other attribute, of @code{a.out} symbol
3787 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3792 @subsection Symbol Attributes for COFF
3794 @cindex COFF symbol attributes
3795 @cindex symbol attributes, COFF
3797 The COFF format supports a multitude of auxiliary symbol attributes;
3798 like the primary symbol attributes, they are set between @code{.def} and
3799 @code{.endef} directives.
3801 @subsubsection Primary Attributes
3803 @cindex primary attributes, COFF symbols
3804 The symbol name is set with @code{.def}; the value and type,
3805 respectively, with @code{.val} and @code{.type}.
3807 @subsubsection Auxiliary Attributes
3809 @cindex auxiliary attributes, COFF symbols
3810 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3811 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3812 table information for COFF.
3817 @subsection Symbol Attributes for SOM
3819 @cindex SOM symbol attributes
3820 @cindex symbol attributes, SOM
3822 The SOM format for the HPPA supports a multitude of symbol attributes set with
3823 the @code{.EXPORT} and @code{.IMPORT} directives.
3825 The attributes are described in @cite{HP9000 Series 800 Assembly
3826 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3827 @code{EXPORT} assembler directive documentation.
3831 @chapter Expressions
3835 @cindex numeric values
3836 An @dfn{expression} specifies an address or numeric value.
3837 Whitespace may precede and/or follow an expression.
3839 The result of an expression must be an absolute number, or else an offset into
3840 a particular section. If an expression is not absolute, and there is not
3841 enough information when @command{@value{AS}} sees the expression to know its
3842 section, a second pass over the source program might be necessary to interpret
3843 the expression---but the second pass is currently not implemented.
3844 @command{@value{AS}} aborts with an error message in this situation.
3847 * Empty Exprs:: Empty Expressions
3848 * Integer Exprs:: Integer Expressions
3852 @section Empty Expressions
3854 @cindex empty expressions
3855 @cindex expressions, empty
3856 An empty expression has no value: it is just whitespace or null.
3857 Wherever an absolute expression is required, you may omit the
3858 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3859 is compatible with other assemblers.
3862 @section Integer Expressions
3864 @cindex integer expressions
3865 @cindex expressions, integer
3866 An @dfn{integer expression} is one or more @emph{arguments} delimited
3867 by @emph{operators}.
3870 * Arguments:: Arguments
3871 * Operators:: Operators
3872 * Prefix Ops:: Prefix Operators
3873 * Infix Ops:: Infix Operators
3877 @subsection Arguments
3879 @cindex expression arguments
3880 @cindex arguments in expressions
3881 @cindex operands in expressions
3882 @cindex arithmetic operands
3883 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3884 contexts arguments are sometimes called ``arithmetic operands''. In
3885 this manual, to avoid confusing them with the ``instruction operands'' of
3886 the machine language, we use the term ``argument'' to refer to parts of
3887 expressions only, reserving the word ``operand'' to refer only to machine
3888 instruction operands.
3890 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3891 @var{section} is one of text, data, bss, absolute,
3892 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3895 Numbers are usually integers.
3897 A number can be a flonum or bignum. In this case, you are warned
3898 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3899 these 32 bits are an integer. You may write integer-manipulating
3900 instructions that act on exotic constants, compatible with other
3903 @cindex subexpressions
3904 Subexpressions are a left parenthesis @samp{(} followed by an integer
3905 expression, followed by a right parenthesis @samp{)}; or a prefix
3906 operator followed by an argument.
3909 @subsection Operators
3911 @cindex operators, in expressions
3912 @cindex arithmetic functions
3913 @cindex functions, in expressions
3914 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3915 operators are followed by an argument. Infix operators appear
3916 between their arguments. Operators may be preceded and/or followed by
3920 @subsection Prefix Operator
3922 @cindex prefix operators
3923 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3924 one argument, which must be absolute.
3926 @c the tex/end tex stuff surrounding this small table is meant to make
3927 @c it align, on the printed page, with the similar table in the next
3928 @c section (which is inside an enumerate).
3930 \global\advance\leftskip by \itemindent
3935 @dfn{Negation}. Two's complement negation.
3937 @dfn{Complementation}. Bitwise not.
3941 \global\advance\leftskip by -\itemindent
3945 @subsection Infix Operators
3947 @cindex infix operators
3948 @cindex operators, permitted arguments
3949 @dfn{Infix operators} take two arguments, one on either side. Operators
3950 have precedence, but operations with equal precedence are performed left
3951 to right. Apart from @code{+} or @option{-}, both arguments must be
3952 absolute, and the result is absolute.
3955 @cindex operator precedence
3956 @cindex precedence of operators
3963 @dfn{Multiplication}.
3966 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3972 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3975 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3979 Intermediate precedence
3984 @dfn{Bitwise Inclusive Or}.
3990 @dfn{Bitwise Exclusive Or}.
3993 @dfn{Bitwise Or Not}.
4000 @cindex addition, permitted arguments
4001 @cindex plus, permitted arguments
4002 @cindex arguments for addition
4004 @dfn{Addition}. If either argument is absolute, the result has the section of
4005 the other argument. You may not add together arguments from different
4008 @cindex subtraction, permitted arguments
4009 @cindex minus, permitted arguments
4010 @cindex arguments for subtraction
4012 @dfn{Subtraction}. If the right argument is absolute, the
4013 result has the section of the left argument.
4014 If both arguments are in the same section, the result is absolute.
4015 You may not subtract arguments from different sections.
4016 @c FIXME is there still something useful to say about undefined - undefined ?
4018 @cindex comparison expressions
4019 @cindex expressions, comparison
4024 @dfn{Is Not Equal To}
4028 @dfn{Is Greater Than}
4030 @dfn{Is Greater Than Or Equal To}
4032 @dfn{Is Less Than Or Equal To}
4034 The comparison operators can be used as infix operators. A true results has a
4035 value of -1 whereas a false result has a value of 0. Note, these operators
4036 perform signed comparisons.
4039 @item Lowest Precedence
4048 These two logical operations can be used to combine the results of sub
4049 expressions. Note, unlike the comparison operators a true result returns a
4050 value of 1 but a false results does still return 0. Also note that the logical
4051 or operator has a slightly lower precedence than logical and.
4056 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4057 address; you can only have a defined section in one of the two arguments.
4060 @chapter Assembler Directives
4062 @cindex directives, machine independent
4063 @cindex pseudo-ops, machine independent
4064 @cindex machine independent directives
4065 All assembler directives have names that begin with a period (@samp{.}).
4066 The rest of the name is letters, usually in lower case.
4068 This chapter discusses directives that are available regardless of the
4069 target machine configuration for the @sc{gnu} assembler.
4071 Some machine configurations provide additional directives.
4072 @xref{Machine Dependencies}.
4075 @ifset machine-directives
4076 @xref{Machine Dependencies}, for additional directives.
4081 * Abort:: @code{.abort}
4083 * ABORT (COFF):: @code{.ABORT}
4086 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4087 * Altmacro:: @code{.altmacro}
4088 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4089 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4090 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4091 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4092 * Byte:: @code{.byte @var{expressions}}
4093 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4094 * Comm:: @code{.comm @var{symbol} , @var{length} }
4095 * Data:: @code{.data @var{subsection}}
4097 * Def:: @code{.def @var{name}}
4100 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4106 * Double:: @code{.double @var{flonums}}
4107 * Eject:: @code{.eject}
4108 * Else:: @code{.else}
4109 * Elseif:: @code{.elseif}
4112 * Endef:: @code{.endef}
4115 * Endfunc:: @code{.endfunc}
4116 * Endif:: @code{.endif}
4117 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4118 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4119 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4121 * Error:: @code{.error @var{string}}
4122 * Exitm:: @code{.exitm}
4123 * Extern:: @code{.extern}
4124 * Fail:: @code{.fail}
4125 * File:: @code{.file}
4126 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4127 * Float:: @code{.float @var{flonums}}
4128 * Func:: @code{.func}
4129 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4131 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4132 * Hidden:: @code{.hidden @var{names}}
4135 * hword:: @code{.hword @var{expressions}}
4136 * Ident:: @code{.ident}
4137 * If:: @code{.if @var{absolute expression}}
4138 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4139 * Include:: @code{.include "@var{file}"}
4140 * Int:: @code{.int @var{expressions}}
4142 * Internal:: @code{.internal @var{names}}
4145 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4146 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4147 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4148 * Lflags:: @code{.lflags}
4149 @ifclear no-line-dir
4150 * Line:: @code{.line @var{line-number}}
4153 * Linkonce:: @code{.linkonce [@var{type}]}
4154 * List:: @code{.list}
4155 * Ln:: @code{.ln @var{line-number}}
4156 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4157 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4159 * Local:: @code{.local @var{names}}
4162 * Long:: @code{.long @var{expressions}}
4164 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4167 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4168 * MRI:: @code{.mri @var{val}}
4169 * Noaltmacro:: @code{.noaltmacro}
4170 * Nolist:: @code{.nolist}
4171 * Octa:: @code{.octa @var{bignums}}
4172 * Offset:: @code{.offset @var{loc}}
4173 * Org:: @code{.org @var{new-lc}, @var{fill}}
4174 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4176 * PopSection:: @code{.popsection}
4177 * Previous:: @code{.previous}
4180 * Print:: @code{.print @var{string}}
4182 * Protected:: @code{.protected @var{names}}
4185 * Psize:: @code{.psize @var{lines}, @var{columns}}
4186 * Purgem:: @code{.purgem @var{name}}
4188 * PushSection:: @code{.pushsection @var{name}}
4191 * Quad:: @code{.quad @var{bignums}}
4192 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4193 * Rept:: @code{.rept @var{count}}
4194 * Sbttl:: @code{.sbttl "@var{subheading}"}
4196 * Scl:: @code{.scl @var{class}}
4199 * Section:: @code{.section @var{name}[, @var{flags}]}
4202 * Set:: @code{.set @var{symbol}, @var{expression}}
4203 * Short:: @code{.short @var{expressions}}
4204 * Single:: @code{.single @var{flonums}}
4206 * Size:: @code{.size [@var{name} , @var{expression}]}
4208 @ifclear no-space-dir
4209 * Skip:: @code{.skip @var{size} , @var{fill}}
4212 * Sleb128:: @code{.sleb128 @var{expressions}}
4213 @ifclear no-space-dir
4214 * Space:: @code{.space @var{size} , @var{fill}}
4217 * Stab:: @code{.stabd, .stabn, .stabs}
4220 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4221 * Struct:: @code{.struct @var{expression}}
4223 * SubSection:: @code{.subsection}
4224 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4228 * Tag:: @code{.tag @var{structname}}
4231 * Text:: @code{.text @var{subsection}}
4232 * Title:: @code{.title "@var{heading}"}
4234 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4237 * Uleb128:: @code{.uleb128 @var{expressions}}
4239 * Val:: @code{.val @var{addr}}
4243 * Version:: @code{.version "@var{string}"}
4244 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4245 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4248 * Warning:: @code{.warning @var{string}}
4249 * Weak:: @code{.weak @var{names}}
4250 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4251 * Word:: @code{.word @var{expressions}}
4252 * Deprecated:: Deprecated Directives
4256 @section @code{.abort}
4258 @cindex @code{abort} directive
4259 @cindex stopping the assembly
4260 This directive stops the assembly immediately. It is for
4261 compatibility with other assemblers. The original idea was that the
4262 assembly language source would be piped into the assembler. If the sender
4263 of the source quit, it could use this directive tells @command{@value{AS}} to
4264 quit also. One day @code{.abort} will not be supported.
4268 @section @code{.ABORT} (COFF)
4270 @cindex @code{ABORT} directive
4271 When producing COFF output, @command{@value{AS}} accepts this directive as a
4272 synonym for @samp{.abort}.
4275 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4281 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4283 @cindex padding the location counter
4284 @cindex @code{align} directive
4285 Pad the location counter (in the current subsection) to a particular storage
4286 boundary. The first expression (which must be absolute) is the alignment
4287 required, as described below.
4289 The second expression (also absolute) gives the fill value to be stored in the
4290 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4291 padding bytes are normally zero. However, on some systems, if the section is
4292 marked as containing code and the fill value is omitted, the space is filled
4293 with no-op instructions.
4295 The third expression is also absolute, and is also optional. If it is present,
4296 it is the maximum number of bytes that should be skipped by this alignment
4297 directive. If doing the alignment would require skipping more bytes than the
4298 specified maximum, then the alignment is not done at all. You can omit the
4299 fill value (the second argument) entirely by simply using two commas after the
4300 required alignment; this can be useful if you want the alignment to be filled
4301 with no-op instructions when appropriate.
4303 The way the required alignment is specified varies from system to system.
4304 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4305 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4306 alignment request in bytes. For example @samp{.align 8} advances
4307 the location counter until it is a multiple of 8. If the location counter
4308 is already a multiple of 8, no change is needed. For the tic54x, the
4309 first expression is the alignment request in words.
4311 For other systems, including ppc, i386 using a.out format, arm and
4312 strongarm, it is the
4313 number of low-order zero bits the location counter must have after
4314 advancement. For example @samp{.align 3} advances the location
4315 counter until it a multiple of 8. If the location counter is already a
4316 multiple of 8, no change is needed.
4318 This inconsistency is due to the different behaviors of the various
4319 native assemblers for these systems which GAS must emulate.
4320 GAS also provides @code{.balign} and @code{.p2align} directives,
4321 described later, which have a consistent behavior across all
4322 architectures (but are specific to GAS).
4325 @section @code{.altmacro}
4326 Enable alternate macro mode, enabling:
4329 @item LOCAL @var{name} [ , @dots{} ]
4330 One additional directive, @code{LOCAL}, is available. It is used to
4331 generate a string replacement for each of the @var{name} arguments, and
4332 replace any instances of @var{name} in each macro expansion. The
4333 replacement string is unique in the assembly, and different for each
4334 separate macro expansion. @code{LOCAL} allows you to write macros that
4335 define symbols, without fear of conflict between separate macro expansions.
4337 @item String delimiters
4338 You can write strings delimited in these other ways besides
4339 @code{"@var{string}"}:
4342 @item '@var{string}'
4343 You can delimit strings with single-quote characters.
4345 @item <@var{string}>
4346 You can delimit strings with matching angle brackets.
4349 @item single-character string escape
4350 To include any single character literally in a string (even if the
4351 character would otherwise have some special meaning), you can prefix the
4352 character with @samp{!} (an exclamation mark). For example, you can
4353 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4355 @item Expression results as strings
4356 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4357 and use the result as a string.
4361 @section @code{.ascii "@var{string}"}@dots{}
4363 @cindex @code{ascii} directive
4364 @cindex string literals
4365 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4366 separated by commas. It assembles each string (with no automatic
4367 trailing zero byte) into consecutive addresses.
4370 @section @code{.asciz "@var{string}"}@dots{}
4372 @cindex @code{asciz} directive
4373 @cindex zero-terminated strings
4374 @cindex null-terminated strings
4375 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4376 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4379 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4381 @cindex padding the location counter given number of bytes
4382 @cindex @code{balign} directive
4383 Pad the location counter (in the current subsection) to a particular
4384 storage boundary. The first expression (which must be absolute) is the
4385 alignment request in bytes. For example @samp{.balign 8} advances
4386 the location counter until it is a multiple of 8. If the location counter
4387 is already a multiple of 8, no change is needed.
4389 The second expression (also absolute) gives the fill value to be stored in the
4390 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4391 padding bytes are normally zero. However, on some systems, if the section is
4392 marked as containing code and the fill value is omitted, the space is filled
4393 with no-op instructions.
4395 The third expression is also absolute, and is also optional. If it is present,
4396 it is the maximum number of bytes that should be skipped by this alignment
4397 directive. If doing the alignment would require skipping more bytes than the
4398 specified maximum, then the alignment is not done at all. You can omit the
4399 fill value (the second argument) entirely by simply using two commas after the
4400 required alignment; this can be useful if you want the alignment to be filled
4401 with no-op instructions when appropriate.
4403 @cindex @code{balignw} directive
4404 @cindex @code{balignl} directive
4405 The @code{.balignw} and @code{.balignl} directives are variants of the
4406 @code{.balign} directive. The @code{.balignw} directive treats the fill
4407 pattern as a two byte word value. The @code{.balignl} directives treats the
4408 fill pattern as a four byte longword value. For example, @code{.balignw
4409 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4410 filled in with the value 0x368d (the exact placement of the bytes depends upon
4411 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4414 @node Bundle directives
4415 @section @code{.bundle_align_mode @var{abs-expr}}
4416 @cindex @code{bundle_align_mode} directive
4418 @cindex instruction bundle
4419 @cindex aligned instruction bundle
4420 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4421 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4422 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4423 disabled (which is the default state). If the argument it not zero, it
4424 gives the size of an instruction bundle as a power of two (as for the
4425 @code{.p2align} directive, @pxref{P2align}).
4427 For some targets, it's an ABI requirement that no instruction may span a
4428 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4429 instructions that starts on an aligned boundary. For example, if
4430 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4431 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4432 effect, no single instruction may span a boundary between bundles. If an
4433 instruction would start too close to the end of a bundle for the length of
4434 that particular instruction to fit within the bundle, then the space at the
4435 end of that bundle is filled with no-op instructions so the instruction
4436 starts in the next bundle. As a corollary, it's an error if any single
4437 instruction's encoding is longer than the bundle size.
4439 @section @code{.bundle_lock} and @code{.bundle_unlock}
4440 @cindex @code{bundle_lock} directive
4441 @cindex @code{bundle_unlock} directive
4442 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4443 allow explicit control over instruction bundle padding. These directives
4444 are only valid when @code{.bundle_align_mode} has been used to enable
4445 aligned instruction bundle mode. It's an error if they appear when
4446 @code{.bundle_align_mode} has not been used at all, or when the last
4447 directive was @w{@code{.bundle_align_mode 0}}.
4449 @cindex bundle-locked
4450 For some targets, it's an ABI requirement that certain instructions may
4451 appear only as part of specified permissible sequences of multiple
4452 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4453 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4454 instruction sequence. For purposes of aligned instruction bundle mode, a
4455 sequence starting with @code{.bundle_lock} and ending with
4456 @code{.bundle_unlock} is treated as a single instruction. That is, the
4457 entire sequence must fit into a single bundle and may not span a bundle
4458 boundary. If necessary, no-op instructions will be inserted before the
4459 first instruction of the sequence so that the whole sequence starts on an
4460 aligned bundle boundary. It's an error if the sequence is longer than the
4463 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4464 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4465 nested. That is, a second @code{.bundle_lock} directive before the next
4466 @code{.bundle_unlock} directive has no effect except that it must be
4467 matched by another closing @code{.bundle_unlock} so that there is the
4468 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4471 @section @code{.byte @var{expressions}}
4473 @cindex @code{byte} directive
4474 @cindex integers, one byte
4475 @code{.byte} expects zero or more expressions, separated by commas.
4476 Each expression is assembled into the next byte.
4478 @node CFI directives
4479 @section @code{.cfi_sections @var{section_list}}
4480 @cindex @code{cfi_sections} directive
4481 @code{.cfi_sections} may be used to specify whether CFI directives
4482 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4483 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4484 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4485 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4486 directive is not used is @code{.cfi_sections .eh_frame}.
4488 @section @code{.cfi_startproc [simple]}
4489 @cindex @code{cfi_startproc} directive
4490 @code{.cfi_startproc} is used at the beginning of each function that
4491 should have an entry in @code{.eh_frame}. It initializes some internal
4492 data structures. Don't forget to close the function by
4493 @code{.cfi_endproc}.
4495 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4496 it also emits some architecture dependent initial CFI instructions.
4498 @section @code{.cfi_endproc}
4499 @cindex @code{cfi_endproc} directive
4500 @code{.cfi_endproc} is used at the end of a function where it closes its
4501 unwind entry previously opened by
4502 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4504 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4505 @code{.cfi_personality} defines personality routine and its encoding.
4506 @var{encoding} must be a constant determining how the personality
4507 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4508 argument is not present, otherwise second argument should be
4509 a constant or a symbol name. When using indirect encodings,
4510 the symbol provided should be the location where personality
4511 can be loaded from, not the personality routine itself.
4512 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4513 no personality routine.
4515 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4516 @code{.cfi_lsda} defines LSDA and its encoding.
4517 @var{encoding} must be a constant determining how the LSDA
4518 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4519 argument is not present, otherwise second argument should be a constant
4520 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4523 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4524 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4525 address from @var{register} and add @var{offset} to it}.
4527 @section @code{.cfi_def_cfa_register @var{register}}
4528 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4529 now on @var{register} will be used instead of the old one. Offset
4532 @section @code{.cfi_def_cfa_offset @var{offset}}
4533 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4534 remains the same, but @var{offset} is new. Note that it is the
4535 absolute offset that will be added to a defined register to compute
4538 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4539 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4540 value that is added/substracted from the previous offset.
4542 @section @code{.cfi_offset @var{register}, @var{offset}}
4543 Previous value of @var{register} is saved at offset @var{offset} from
4546 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4547 Previous value of @var{register} is saved at offset @var{offset} from
4548 the current CFA register. This is transformed to @code{.cfi_offset}
4549 using the known displacement of the CFA register from the CFA.
4550 This is often easier to use, because the number will match the
4551 code it's annotating.
4553 @section @code{.cfi_register @var{register1}, @var{register2}}
4554 Previous value of @var{register1} is saved in register @var{register2}.
4556 @section @code{.cfi_restore @var{register}}
4557 @code{.cfi_restore} says that the rule for @var{register} is now the
4558 same as it was at the beginning of the function, after all initial
4559 instruction added by @code{.cfi_startproc} were executed.
4561 @section @code{.cfi_undefined @var{register}}
4562 From now on the previous value of @var{register} can't be restored anymore.
4564 @section @code{.cfi_same_value @var{register}}
4565 Current value of @var{register} is the same like in the previous frame,
4566 i.e. no restoration needed.
4568 @section @code{.cfi_remember_state},
4569 First save all current rules for all registers by @code{.cfi_remember_state},
4570 then totally screw them up by subsequent @code{.cfi_*} directives and when
4571 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4572 the previous saved state.
4574 @section @code{.cfi_return_column @var{register}}
4575 Change return column @var{register}, i.e. the return address is either
4576 directly in @var{register} or can be accessed by rules for @var{register}.
4578 @section @code{.cfi_signal_frame}
4579 Mark current function as signal trampoline.
4581 @section @code{.cfi_window_save}
4582 SPARC register window has been saved.
4584 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4585 Allows the user to add arbitrary bytes to the unwind info. One
4586 might use this to add OS-specific CFI opcodes, or generic CFI
4587 opcodes that GAS does not yet support.
4589 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4590 The current value of @var{register} is @var{label}. The value of @var{label}
4591 will be encoded in the output file according to @var{encoding}; see the
4592 description of @code{.cfi_personality} for details on this encoding.
4594 The usefulness of equating a register to a fixed label is probably
4595 limited to the return address register. Here, it can be useful to
4596 mark a code segment that has only one return address which is reached
4597 by a direct branch and no copy of the return address exists in memory
4598 or another register.
4601 @section @code{.comm @var{symbol} , @var{length} }
4603 @cindex @code{comm} directive
4604 @cindex symbol, common
4605 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4606 common symbol in one object file may be merged with a defined or common symbol
4607 of the same name in another object file. If @code{@value{LD}} does not see a
4608 definition for the symbol--just one or more common symbols--then it will
4609 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4610 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4611 the same name, and they do not all have the same size, it will allocate space
4612 using the largest size.
4615 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4616 an optional third argument. This is the desired alignment of the symbol,
4617 specified for ELF as a byte boundary (for example, an alignment of 16 means
4618 that the least significant 4 bits of the address should be zero), and for PE
4619 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4620 boundary). The alignment must be an absolute expression, and it must be a
4621 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4622 common symbol, it will use the alignment when placing the symbol. If no
4623 alignment is specified, @command{@value{AS}} will set the alignment to the
4624 largest power of two less than or equal to the size of the symbol, up to a
4625 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4626 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4627 @samp{--section-alignment} option; image file sections in PE are aligned to
4628 multiples of 4096, which is far too large an alignment for ordinary variables.
4629 It is rather the default alignment for (non-debug) sections within object
4630 (@samp{*.o}) files, which are less strictly aligned.}.
4634 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4635 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4639 @section @code{.data @var{subsection}}
4641 @cindex @code{data} directive
4642 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4643 end of the data subsection numbered @var{subsection} (which is an
4644 absolute expression). If @var{subsection} is omitted, it defaults
4649 @section @code{.def @var{name}}
4651 @cindex @code{def} directive
4652 @cindex COFF symbols, debugging
4653 @cindex debugging COFF symbols
4654 Begin defining debugging information for a symbol @var{name}; the
4655 definition extends until the @code{.endef} directive is encountered.
4658 This directive is only observed when @command{@value{AS}} is configured for COFF
4659 format output; when producing @code{b.out}, @samp{.def} is recognized,
4666 @section @code{.desc @var{symbol}, @var{abs-expression}}
4668 @cindex @code{desc} directive
4669 @cindex COFF symbol descriptor
4670 @cindex symbol descriptor, COFF
4671 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4672 to the low 16 bits of an absolute expression.
4675 The @samp{.desc} directive is not available when @command{@value{AS}} is
4676 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4677 object format. For the sake of compatibility, @command{@value{AS}} accepts
4678 it, but produces no output, when configured for COFF.
4684 @section @code{.dim}
4686 @cindex @code{dim} directive
4687 @cindex COFF auxiliary symbol information
4688 @cindex auxiliary symbol information, COFF
4689 This directive is generated by compilers to include auxiliary debugging
4690 information in the symbol table. It is only permitted inside
4691 @code{.def}/@code{.endef} pairs.
4694 @samp{.dim} is only meaningful when generating COFF format output; when
4695 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4701 @section @code{.double @var{flonums}}
4703 @cindex @code{double} directive
4704 @cindex floating point numbers (double)
4705 @code{.double} expects zero or more flonums, separated by commas. It
4706 assembles floating point numbers.
4708 The exact kind of floating point numbers emitted depends on how
4709 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4713 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4714 in @sc{ieee} format.
4719 @section @code{.eject}
4721 @cindex @code{eject} directive
4722 @cindex new page, in listings
4723 @cindex page, in listings
4724 @cindex listing control: new page
4725 Force a page break at this point, when generating assembly listings.
4728 @section @code{.else}
4730 @cindex @code{else} directive
4731 @code{.else} is part of the @command{@value{AS}} support for conditional
4732 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4733 of code to be assembled if the condition for the preceding @code{.if}
4737 @section @code{.elseif}
4739 @cindex @code{elseif} directive
4740 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4741 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4742 @code{.if} block that would otherwise fill the entire @code{.else} section.
4745 @section @code{.end}
4747 @cindex @code{end} directive
4748 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4749 process anything in the file past the @code{.end} directive.
4753 @section @code{.endef}
4755 @cindex @code{endef} directive
4756 This directive flags the end of a symbol definition begun with
4760 @samp{.endef} is only meaningful when generating COFF format output; if
4761 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4762 directive but ignores it.
4767 @section @code{.endfunc}
4768 @cindex @code{endfunc} directive
4769 @code{.endfunc} marks the end of a function specified with @code{.func}.
4772 @section @code{.endif}
4774 @cindex @code{endif} directive
4775 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4776 it marks the end of a block of code that is only assembled
4777 conditionally. @xref{If,,@code{.if}}.
4780 @section @code{.equ @var{symbol}, @var{expression}}
4782 @cindex @code{equ} directive
4783 @cindex assigning values to symbols
4784 @cindex symbols, assigning values to
4785 This directive sets the value of @var{symbol} to @var{expression}.
4786 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4789 The syntax for @code{equ} on the HPPA is
4790 @samp{@var{symbol} .equ @var{expression}}.
4794 The syntax for @code{equ} on the Z80 is
4795 @samp{@var{symbol} equ @var{expression}}.
4796 On the Z80 it is an eror if @var{symbol} is already defined,
4797 but the symbol is not protected from later redefinition.
4798 Compare @ref{Equiv}.
4802 @section @code{.equiv @var{symbol}, @var{expression}}
4803 @cindex @code{equiv} directive
4804 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4805 the assembler will signal an error if @var{symbol} is already defined. Note a
4806 symbol which has been referenced but not actually defined is considered to be
4809 Except for the contents of the error message, this is roughly equivalent to
4816 plus it protects the symbol from later redefinition.
4819 @section @code{.eqv @var{symbol}, @var{expression}}
4820 @cindex @code{eqv} directive
4821 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4822 evaluate the expression or any part of it immediately. Instead each time
4823 the resulting symbol is used in an expression, a snapshot of its current
4827 @section @code{.err}
4828 @cindex @code{err} directive
4829 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4830 message and, unless the @option{-Z} option was used, it will not generate an
4831 object file. This can be used to signal an error in conditionally compiled code.
4834 @section @code{.error "@var{string}"}
4835 @cindex error directive
4837 Similarly to @code{.err}, this directive emits an error, but you can specify a
4838 string that will be emitted as the error message. If you don't specify the
4839 message, it defaults to @code{".error directive invoked in source file"}.
4840 @xref{Errors, ,Error and Warning Messages}.
4843 .error "This code has not been assembled and tested."
4847 @section @code{.exitm}
4848 Exit early from the current macro definition. @xref{Macro}.
4851 @section @code{.extern}
4853 @cindex @code{extern} directive
4854 @code{.extern} is accepted in the source program---for compatibility
4855 with other assemblers---but it is ignored. @command{@value{AS}} treats
4856 all undefined symbols as external.
4859 @section @code{.fail @var{expression}}
4861 @cindex @code{fail} directive
4862 Generates an error or a warning. If the value of the @var{expression} is 500
4863 or more, @command{@value{AS}} will print a warning message. If the value is less
4864 than 500, @command{@value{AS}} will print an error message. The message will
4865 include the value of @var{expression}. This can occasionally be useful inside
4866 complex nested macros or conditional assembly.
4869 @section @code{.file}
4870 @cindex @code{file} directive
4872 @ifclear no-file-dir
4873 There are two different versions of the @code{.file} directive. Targets
4874 that support DWARF2 line number information use the DWARF2 version of
4875 @code{.file}. Other targets use the default version.
4877 @subheading Default Version
4879 @cindex logical file name
4880 @cindex file name, logical
4881 This version of the @code{.file} directive tells @command{@value{AS}} that we
4882 are about to start a new logical file. The syntax is:
4888 @var{string} is the new file name. In general, the filename is
4889 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4890 to specify an empty file name, you must give the quotes--@code{""}. This
4891 statement may go away in future: it is only recognized to be compatible with
4892 old @command{@value{AS}} programs.
4894 @subheading DWARF2 Version
4897 When emitting DWARF2 line number information, @code{.file} assigns filenames
4898 to the @code{.debug_line} file name table. The syntax is:
4901 .file @var{fileno} @var{filename}
4904 The @var{fileno} operand should be a unique positive integer to use as the
4905 index of the entry in the table. The @var{filename} operand is a C string
4908 The detail of filename indices is exposed to the user because the filename
4909 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4910 information, and thus the user must know the exact indices that table
4914 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4916 @cindex @code{fill} directive
4917 @cindex writing patterns in memory
4918 @cindex patterns, writing in memory
4919 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4920 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4921 may be zero or more. @var{Size} may be zero or more, but if it is
4922 more than 8, then it is deemed to have the value 8, compatible with
4923 other people's assemblers. The contents of each @var{repeat} bytes
4924 is taken from an 8-byte number. The highest order 4 bytes are
4925 zero. The lowest order 4 bytes are @var{value} rendered in the
4926 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4927 Each @var{size} bytes in a repetition is taken from the lowest order
4928 @var{size} bytes of this number. Again, this bizarre behavior is
4929 compatible with other people's assemblers.
4931 @var{size} and @var{value} are optional.
4932 If the second comma and @var{value} are absent, @var{value} is
4933 assumed zero. If the first comma and following tokens are absent,
4934 @var{size} is assumed to be 1.
4937 @section @code{.float @var{flonums}}
4939 @cindex floating point numbers (single)
4940 @cindex @code{float} directive
4941 This directive assembles zero or more flonums, separated by commas. It
4942 has the same effect as @code{.single}.
4944 The exact kind of floating point numbers emitted depends on how
4945 @command{@value{AS}} is configured.
4946 @xref{Machine Dependencies}.
4950 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4951 in @sc{ieee} format.
4956 @section @code{.func @var{name}[,@var{label}]}
4957 @cindex @code{func} directive
4958 @code{.func} emits debugging information to denote function @var{name}, and
4959 is ignored unless the file is assembled with debugging enabled.
4960 Only @samp{--gstabs[+]} is currently supported.
4961 @var{label} is the entry point of the function and if omitted @var{name}
4962 prepended with the @samp{leading char} is used.
4963 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4964 All functions are currently defined to have @code{void} return type.
4965 The function must be terminated with @code{.endfunc}.
4968 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4970 @cindex @code{global} directive
4971 @cindex symbol, making visible to linker
4972 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4973 @var{symbol} in your partial program, its value is made available to
4974 other partial programs that are linked with it. Otherwise,
4975 @var{symbol} takes its attributes from a symbol of the same name
4976 from another file linked into the same program.
4978 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4979 compatibility with other assemblers.
4982 On the HPPA, @code{.global} is not always enough to make it accessible to other
4983 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4984 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4989 @section @code{.gnu_attribute @var{tag},@var{value}}
4990 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4993 @section @code{.hidden @var{names}}
4995 @cindex @code{hidden} directive
4997 This is one of the ELF visibility directives. The other two are
4998 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4999 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5001 This directive overrides the named symbols default visibility (which is set by
5002 their binding: local, global or weak). The directive sets the visibility to
5003 @code{hidden} which means that the symbols are not visible to other components.
5004 Such symbols are always considered to be @code{protected} as well.
5008 @section @code{.hword @var{expressions}}
5010 @cindex @code{hword} directive
5011 @cindex integers, 16-bit
5012 @cindex numbers, 16-bit
5013 @cindex sixteen bit integers
5014 This expects zero or more @var{expressions}, and emits
5015 a 16 bit number for each.
5018 This directive is a synonym for @samp{.short}; depending on the target
5019 architecture, it may also be a synonym for @samp{.word}.
5023 This directive is a synonym for @samp{.short}.
5026 This directive is a synonym for both @samp{.short} and @samp{.word}.
5031 @section @code{.ident}
5033 @cindex @code{ident} directive
5035 This directive is used by some assemblers to place tags in object files. The
5036 behavior of this directive varies depending on the target. When using the
5037 a.out object file format, @command{@value{AS}} simply accepts the directive for
5038 source-file compatibility with existing assemblers, but does not emit anything
5039 for it. When using COFF, comments are emitted to the @code{.comment} or
5040 @code{.rdata} section, depending on the target. When using ELF, comments are
5041 emitted to the @code{.comment} section.
5044 @section @code{.if @var{absolute expression}}
5046 @cindex conditional assembly
5047 @cindex @code{if} directive
5048 @code{.if} marks the beginning of a section of code which is only
5049 considered part of the source program being assembled if the argument
5050 (which must be an @var{absolute expression}) is non-zero. The end of
5051 the conditional section of code must be marked by @code{.endif}
5052 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5053 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5054 If you have several conditions to check, @code{.elseif} may be used to avoid
5055 nesting blocks if/else within each subsequent @code{.else} block.
5057 The following variants of @code{.if} are also supported:
5059 @cindex @code{ifdef} directive
5060 @item .ifdef @var{symbol}
5061 Assembles the following section of code if the specified @var{symbol}
5062 has been defined. Note a symbol which has been referenced but not yet defined
5063 is considered to be undefined.
5065 @cindex @code{ifb} directive
5066 @item .ifb @var{text}
5067 Assembles the following section of code if the operand is blank (empty).
5069 @cindex @code{ifc} directive
5070 @item .ifc @var{string1},@var{string2}
5071 Assembles the following section of code if the two strings are the same. The
5072 strings may be optionally quoted with single quotes. If they are not quoted,
5073 the first string stops at the first comma, and the second string stops at the
5074 end of the line. Strings which contain whitespace should be quoted. The
5075 string comparison is case sensitive.
5077 @cindex @code{ifeq} directive
5078 @item .ifeq @var{absolute expression}
5079 Assembles the following section of code if the argument is zero.
5081 @cindex @code{ifeqs} directive
5082 @item .ifeqs @var{string1},@var{string2}
5083 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5085 @cindex @code{ifge} directive
5086 @item .ifge @var{absolute expression}
5087 Assembles the following section of code if the argument is greater than or
5090 @cindex @code{ifgt} directive
5091 @item .ifgt @var{absolute expression}
5092 Assembles the following section of code if the argument is greater than zero.
5094 @cindex @code{ifle} directive
5095 @item .ifle @var{absolute expression}
5096 Assembles the following section of code if the argument is less than or equal
5099 @cindex @code{iflt} directive
5100 @item .iflt @var{absolute expression}
5101 Assembles the following section of code if the argument is less than zero.
5103 @cindex @code{ifnb} directive
5104 @item .ifnb @var{text}
5105 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5106 following section of code if the operand is non-blank (non-empty).
5108 @cindex @code{ifnc} directive
5109 @item .ifnc @var{string1},@var{string2}.
5110 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5111 following section of code if the two strings are not the same.
5113 @cindex @code{ifndef} directive
5114 @cindex @code{ifnotdef} directive
5115 @item .ifndef @var{symbol}
5116 @itemx .ifnotdef @var{symbol}
5117 Assembles the following section of code if the specified @var{symbol}
5118 has not been defined. Both spelling variants are equivalent. Note a symbol
5119 which has been referenced but not yet defined is considered to be undefined.
5121 @cindex @code{ifne} directive
5122 @item .ifne @var{absolute expression}
5123 Assembles the following section of code if the argument is not equal to zero
5124 (in other words, this is equivalent to @code{.if}).
5126 @cindex @code{ifnes} directive
5127 @item .ifnes @var{string1},@var{string2}
5128 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5129 following section of code if the two strings are not the same.
5133 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5135 @cindex @code{incbin} directive
5136 @cindex binary files, including
5137 The @code{incbin} directive includes @var{file} verbatim at the current
5138 location. You can control the search paths used with the @samp{-I} command-line
5139 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5142 The @var{skip} argument skips a number of bytes from the start of the
5143 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5144 read. Note that the data is not aligned in any way, so it is the user's
5145 responsibility to make sure that proper alignment is provided both before and
5146 after the @code{incbin} directive.
5149 @section @code{.include "@var{file}"}
5151 @cindex @code{include} directive
5152 @cindex supporting files, including
5153 @cindex files, including
5154 This directive provides a way to include supporting files at specified
5155 points in your source program. The code from @var{file} is assembled as
5156 if it followed the point of the @code{.include}; when the end of the
5157 included file is reached, assembly of the original file continues. You
5158 can control the search paths used with the @samp{-I} command-line option
5159 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5163 @section @code{.int @var{expressions}}
5165 @cindex @code{int} directive
5166 @cindex integers, 32-bit
5167 Expect zero or more @var{expressions}, of any section, separated by commas.
5168 For each expression, emit a number that, at run time, is the value of that
5169 expression. The byte order and bit size of the number depends on what kind
5170 of target the assembly is for.
5174 On most forms of the H8/300, @code{.int} emits 16-bit
5175 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5182 @section @code{.internal @var{names}}
5184 @cindex @code{internal} directive
5186 This is one of the ELF visibility directives. The other two are
5187 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5188 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5190 This directive overrides the named symbols default visibility (which is set by
5191 their binding: local, global or weak). The directive sets the visibility to
5192 @code{internal} which means that the symbols are considered to be @code{hidden}
5193 (i.e., not visible to other components), and that some extra, processor specific
5194 processing must also be performed upon the symbols as well.
5198 @section @code{.irp @var{symbol},@var{values}}@dots{}
5200 @cindex @code{irp} directive
5201 Evaluate a sequence of statements assigning different values to @var{symbol}.
5202 The sequence of statements starts at the @code{.irp} directive, and is
5203 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5204 set to @var{value}, and the sequence of statements is assembled. If no
5205 @var{value} is listed, the sequence of statements is assembled once, with
5206 @var{symbol} set to the null string. To refer to @var{symbol} within the
5207 sequence of statements, use @var{\symbol}.
5209 For example, assembling
5217 is equivalent to assembling
5225 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5228 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5230 @cindex @code{irpc} directive
5231 Evaluate a sequence of statements assigning different values to @var{symbol}.
5232 The sequence of statements starts at the @code{.irpc} directive, and is
5233 terminated by an @code{.endr} directive. For each character in @var{value},
5234 @var{symbol} is set to the character, and the sequence of statements is
5235 assembled. If no @var{value} is listed, the sequence of statements is
5236 assembled once, with @var{symbol} set to the null string. To refer to
5237 @var{symbol} within the sequence of statements, use @var{\symbol}.
5239 For example, assembling
5247 is equivalent to assembling
5255 For some caveats with the spelling of @var{symbol}, see also the discussion
5259 @section @code{.lcomm @var{symbol} , @var{length}}
5261 @cindex @code{lcomm} directive
5262 @cindex local common symbols
5263 @cindex symbols, local common
5264 Reserve @var{length} (an absolute expression) bytes for a local common
5265 denoted by @var{symbol}. The section and value of @var{symbol} are
5266 those of the new local common. The addresses are allocated in the bss
5267 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5268 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5269 not visible to @code{@value{LD}}.
5272 Some targets permit a third argument to be used with @code{.lcomm}. This
5273 argument specifies the desired alignment of the symbol in the bss section.
5277 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5278 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5282 @section @code{.lflags}
5284 @cindex @code{lflags} directive (ignored)
5285 @command{@value{AS}} accepts this directive, for compatibility with other
5286 assemblers, but ignores it.
5288 @ifclear no-line-dir
5290 @section @code{.line @var{line-number}}
5292 @cindex @code{line} directive
5293 @cindex logical line number
5295 Change the logical line number. @var{line-number} must be an absolute
5296 expression. The next line has that logical line number. Therefore any other
5297 statements on the current line (after a statement separator character) are
5298 reported as on logical line number @var{line-number} @minus{} 1. One day
5299 @command{@value{AS}} will no longer support this directive: it is recognized only
5300 for compatibility with existing assembler programs.
5303 Even though this is a directive associated with the @code{a.out} or
5304 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5305 when producing COFF output, and treats @samp{.line} as though it
5306 were the COFF @samp{.ln} @emph{if} it is found outside a
5307 @code{.def}/@code{.endef} pair.
5309 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5310 used by compilers to generate auxiliary symbol information for
5315 @section @code{.linkonce [@var{type}]}
5317 @cindex @code{linkonce} directive
5318 @cindex common sections
5319 Mark the current section so that the linker only includes a single copy of it.
5320 This may be used to include the same section in several different object files,
5321 but ensure that the linker will only include it once in the final output file.
5322 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5323 Duplicate sections are detected based on the section name, so it should be
5326 This directive is only supported by a few object file formats; as of this
5327 writing, the only object file format which supports it is the Portable
5328 Executable format used on Windows NT.
5330 The @var{type} argument is optional. If specified, it must be one of the
5331 following strings. For example:
5335 Not all types may be supported on all object file formats.
5339 Silently discard duplicate sections. This is the default.
5342 Warn if there are duplicate sections, but still keep only one copy.
5345 Warn if any of the duplicates have different sizes.
5348 Warn if any of the duplicates do not have exactly the same contents.
5352 @section @code{.list}
5354 @cindex @code{list} directive
5355 @cindex listing control, turning on
5356 Control (in conjunction with the @code{.nolist} directive) whether or
5357 not assembly listings are generated. These two directives maintain an
5358 internal counter (which is zero initially). @code{.list} increments the
5359 counter, and @code{.nolist} decrements it. Assembly listings are
5360 generated whenever the counter is greater than zero.
5362 By default, listings are disabled. When you enable them (with the
5363 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5364 the initial value of the listing counter is one.
5367 @section @code{.ln @var{line-number}}
5369 @cindex @code{ln} directive
5370 @ifclear no-line-dir
5371 @samp{.ln} is a synonym for @samp{.line}.
5374 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5375 must be an absolute expression. The next line has that logical
5376 line number, so any other statements on the current line (after a
5377 statement separator character @code{;}) are reported as on logical
5378 line number @var{line-number} @minus{} 1.
5381 This directive is accepted, but ignored, when @command{@value{AS}} is
5382 configured for @code{b.out}; its effect is only associated with COFF
5388 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5389 @cindex @code{loc} directive
5390 When emitting DWARF2 line number information,
5391 the @code{.loc} directive will add a row to the @code{.debug_line} line
5392 number matrix corresponding to the immediately following assembly
5393 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5394 arguments will be applied to the @code{.debug_line} state machine before
5397 The @var{options} are a sequence of the following tokens in any order:
5401 This option will set the @code{basic_block} register in the
5402 @code{.debug_line} state machine to @code{true}.
5405 This option will set the @code{prologue_end} register in the
5406 @code{.debug_line} state machine to @code{true}.
5408 @item epilogue_begin
5409 This option will set the @code{epilogue_begin} register in the
5410 @code{.debug_line} state machine to @code{true}.
5412 @item is_stmt @var{value}
5413 This option will set the @code{is_stmt} register in the
5414 @code{.debug_line} state machine to @code{value}, which must be
5417 @item isa @var{value}
5418 This directive will set the @code{isa} register in the @code{.debug_line}
5419 state machine to @var{value}, which must be an unsigned integer.
5421 @item discriminator @var{value}
5422 This directive will set the @code{discriminator} register in the @code{.debug_line}
5423 state machine to @var{value}, which must be an unsigned integer.
5427 @node Loc_mark_labels
5428 @section @code{.loc_mark_labels @var{enable}}
5429 @cindex @code{loc_mark_labels} directive
5430 When emitting DWARF2 line number information,
5431 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5432 to the @code{.debug_line} line number matrix with the @code{basic_block}
5433 register in the state machine set whenever a code label is seen.
5434 The @var{enable} argument should be either 1 or 0, to enable or disable
5435 this function respectively.
5439 @section @code{.local @var{names}}
5441 @cindex @code{local} directive
5442 This directive, which is available for ELF targets, marks each symbol in
5443 the comma-separated list of @code{names} as a local symbol so that it
5444 will not be externally visible. If the symbols do not already exist,
5445 they will be created.
5447 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5448 accept an alignment argument, which is the case for most ELF targets,
5449 the @code{.local} directive can be used in combination with @code{.comm}
5450 (@pxref{Comm}) to define aligned local common data.
5454 @section @code{.long @var{expressions}}
5456 @cindex @code{long} directive
5457 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5460 @c no one seems to know what this is for or whether this description is
5461 @c what it really ought to do
5463 @section @code{.lsym @var{symbol}, @var{expression}}
5465 @cindex @code{lsym} directive
5466 @cindex symbol, not referenced in assembly
5467 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5468 the hash table, ensuring it cannot be referenced by name during the
5469 rest of the assembly. This sets the attributes of the symbol to be
5470 the same as the expression value:
5472 @var{other} = @var{descriptor} = 0
5473 @var{type} = @r{(section of @var{expression})}
5474 @var{value} = @var{expression}
5477 The new symbol is not flagged as external.
5481 @section @code{.macro}
5484 The commands @code{.macro} and @code{.endm} allow you to define macros that
5485 generate assembly output. For example, this definition specifies a macro
5486 @code{sum} that puts a sequence of numbers into memory:
5489 .macro sum from=0, to=5
5498 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5510 @item .macro @var{macname}
5511 @itemx .macro @var{macname} @var{macargs} @dots{}
5512 @cindex @code{macro} directive
5513 Begin the definition of a macro called @var{macname}. If your macro
5514 definition requires arguments, specify their names after the macro name,
5515 separated by commas or spaces. You can qualify the macro argument to
5516 indicate whether all invocations must specify a non-blank value (through
5517 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5518 (through @samp{:@code{vararg}}). You can supply a default value for any
5519 macro argument by following the name with @samp{=@var{deflt}}. You
5520 cannot define two macros with the same @var{macname} unless it has been
5521 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5522 definitions. For example, these are all valid @code{.macro} statements:
5526 Begin the definition of a macro called @code{comm}, which takes no
5529 @item .macro plus1 p, p1
5530 @itemx .macro plus1 p p1
5531 Either statement begins the definition of a macro called @code{plus1},
5532 which takes two arguments; within the macro definition, write
5533 @samp{\p} or @samp{\p1} to evaluate the arguments.
5535 @item .macro reserve_str p1=0 p2
5536 Begin the definition of a macro called @code{reserve_str}, with two
5537 arguments. The first argument has a default value, but not the second.
5538 After the definition is complete, you can call the macro either as
5539 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5540 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5541 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5542 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5544 @item .macro m p1:req, p2=0, p3:vararg
5545 Begin the definition of a macro called @code{m}, with at least three
5546 arguments. The first argument must always have a value specified, but
5547 not the second, which instead has a default value. The third formal
5548 will get assigned all remaining arguments specified at invocation time.
5550 When you call a macro, you can specify the argument values either by
5551 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5552 @samp{sum to=17, from=9}.
5556 Note that since each of the @var{macargs} can be an identifier exactly
5557 as any other one permitted by the target architecture, there may be
5558 occasional problems if the target hand-crafts special meanings to certain
5559 characters when they occur in a special position. For example, if the colon
5560 (@code{:}) is generally permitted to be part of a symbol name, but the
5561 architecture specific code special-cases it when occurring as the final
5562 character of a symbol (to denote a label), then the macro parameter
5563 replacement code will have no way of knowing that and consider the whole
5564 construct (including the colon) an identifier, and check only this
5565 identifier for being the subject to parameter substitution. So for example
5566 this macro definition:
5574 might not work as expected. Invoking @samp{label foo} might not create a label
5575 called @samp{foo} but instead just insert the text @samp{\l:} into the
5576 assembler source, probably generating an error about an unrecognised
5579 Similarly problems might occur with the period character (@samp{.})
5580 which is often allowed inside opcode names (and hence identifier names). So
5581 for example constructing a macro to build an opcode from a base name and a
5582 length specifier like this:
5585 .macro opcode base length
5590 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5591 instruction but instead generate some kind of error as the assembler tries to
5592 interpret the text @samp{\base.\length}.
5594 There are several possible ways around this problem:
5597 @item Insert white space
5598 If it is possible to use white space characters then this is the simplest
5607 @item Use @samp{\()}
5608 The string @samp{\()} can be used to separate the end of a macro argument from
5609 the following text. eg:
5612 .macro opcode base length
5617 @item Use the alternate macro syntax mode
5618 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5619 used as a separator. eg:
5629 Note: this problem of correctly identifying string parameters to pseudo ops
5630 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5631 and @code{.irpc} (@pxref{Irpc}) as well.
5634 @cindex @code{endm} directive
5635 Mark the end of a macro definition.
5638 @cindex @code{exitm} directive
5639 Exit early from the current macro definition.
5641 @cindex number of macros executed
5642 @cindex macros, count executed
5644 @command{@value{AS}} maintains a counter of how many macros it has
5645 executed in this pseudo-variable; you can copy that number to your
5646 output with @samp{\@@}, but @emph{only within a macro definition}.
5648 @item LOCAL @var{name} [ , @dots{} ]
5649 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5650 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5651 @xref{Altmacro,,@code{.altmacro}}.
5655 @section @code{.mri @var{val}}
5657 @cindex @code{mri} directive
5658 @cindex MRI mode, temporarily
5659 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5660 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5661 affects code assembled until the next @code{.mri} directive, or until the end
5662 of the file. @xref{M, MRI mode, MRI mode}.
5665 @section @code{.noaltmacro}
5666 Disable alternate macro mode. @xref{Altmacro}.
5669 @section @code{.nolist}
5671 @cindex @code{nolist} directive
5672 @cindex listing control, turning off
5673 Control (in conjunction with the @code{.list} directive) whether or
5674 not assembly listings are generated. These two directives maintain an
5675 internal counter (which is zero initially). @code{.list} increments the
5676 counter, and @code{.nolist} decrements it. Assembly listings are
5677 generated whenever the counter is greater than zero.
5680 @section @code{.octa @var{bignums}}
5682 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5683 @cindex @code{octa} directive
5684 @cindex integer, 16-byte
5685 @cindex sixteen byte integer
5686 This directive expects zero or more bignums, separated by commas. For each
5687 bignum, it emits a 16-byte integer.
5689 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5690 hence @emph{octa}-word for 16 bytes.
5693 @section @code{.offset @var{loc}}
5695 @cindex @code{offset} directive
5696 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5697 be an absolute expression. This directive may be useful for defining
5698 symbols with absolute values. Do not confuse it with the @code{.org}
5702 @section @code{.org @var{new-lc} , @var{fill}}
5704 @cindex @code{org} directive
5705 @cindex location counter, advancing
5706 @cindex advancing location counter
5707 @cindex current address, advancing
5708 Advance the location counter of the current section to
5709 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5710 expression with the same section as the current subsection. That is,
5711 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5712 wrong section, the @code{.org} directive is ignored. To be compatible
5713 with former assemblers, if the section of @var{new-lc} is absolute,
5714 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5715 is the same as the current subsection.
5717 @code{.org} may only increase the location counter, or leave it
5718 unchanged; you cannot use @code{.org} to move the location counter
5721 @c double negative used below "not undefined" because this is a specific
5722 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5723 @c section. doc@cygnus.com 18feb91
5724 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5725 may not be undefined. If you really detest this restriction we eagerly await
5726 a chance to share your improved assembler.
5728 Beware that the origin is relative to the start of the section, not
5729 to the start of the subsection. This is compatible with other
5730 people's assemblers.
5732 When the location counter (of the current subsection) is advanced, the
5733 intervening bytes are filled with @var{fill} which should be an
5734 absolute expression. If the comma and @var{fill} are omitted,
5735 @var{fill} defaults to zero.
5738 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5740 @cindex padding the location counter given a power of two
5741 @cindex @code{p2align} directive
5742 Pad the location counter (in the current subsection) to a particular
5743 storage boundary. The first expression (which must be absolute) is the
5744 number of low-order zero bits the location counter must have after
5745 advancement. For example @samp{.p2align 3} advances the location
5746 counter until it a multiple of 8. If the location counter is already a
5747 multiple of 8, no change is needed.
5749 The second expression (also absolute) gives the fill value to be stored in the
5750 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5751 padding bytes are normally zero. However, on some systems, if the section is
5752 marked as containing code and the fill value is omitted, the space is filled
5753 with no-op instructions.
5755 The third expression is also absolute, and is also optional. If it is present,
5756 it is the maximum number of bytes that should be skipped by this alignment
5757 directive. If doing the alignment would require skipping more bytes than the
5758 specified maximum, then the alignment is not done at all. You can omit the
5759 fill value (the second argument) entirely by simply using two commas after the
5760 required alignment; this can be useful if you want the alignment to be filled
5761 with no-op instructions when appropriate.
5763 @cindex @code{p2alignw} directive
5764 @cindex @code{p2alignl} directive
5765 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5766 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5767 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5768 fill pattern as a four byte longword value. For example, @code{.p2alignw
5769 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5770 filled in with the value 0x368d (the exact placement of the bytes depends upon
5771 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5776 @section @code{.popsection}
5778 @cindex @code{popsection} directive
5779 @cindex Section Stack
5780 This is one of the ELF section stack manipulation directives. The others are
5781 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5782 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5785 This directive replaces the current section (and subsection) with the top
5786 section (and subsection) on the section stack. This section is popped off the
5792 @section @code{.previous}
5794 @cindex @code{previous} directive
5795 @cindex Section Stack
5796 This is one of the ELF section stack manipulation directives. The others are
5797 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5798 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5799 (@pxref{PopSection}).
5801 This directive swaps the current section (and subsection) with most recently
5802 referenced section/subsection pair prior to this one. Multiple
5803 @code{.previous} directives in a row will flip between two sections (and their
5804 subsections). For example:
5816 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5822 # Now in section A subsection 1
5826 # Now in section B subsection 0
5829 # Now in section B subsection 1
5832 # Now in section B subsection 0
5836 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5837 section B and 0x9abc into subsection 1 of section B.
5839 In terms of the section stack, this directive swaps the current section with
5840 the top section on the section stack.
5844 @section @code{.print @var{string}}
5846 @cindex @code{print} directive
5847 @command{@value{AS}} will print @var{string} on the standard output during
5848 assembly. You must put @var{string} in double quotes.
5852 @section @code{.protected @var{names}}
5854 @cindex @code{protected} directive
5856 This is one of the ELF visibility directives. The other two are
5857 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5859 This directive overrides the named symbols default visibility (which is set by
5860 their binding: local, global or weak). The directive sets the visibility to
5861 @code{protected} which means that any references to the symbols from within the
5862 components that defines them must be resolved to the definition in that
5863 component, even if a definition in another component would normally preempt
5868 @section @code{.psize @var{lines} , @var{columns}}
5870 @cindex @code{psize} directive
5871 @cindex listing control: paper size
5872 @cindex paper size, for listings
5873 Use this directive to declare the number of lines---and, optionally, the
5874 number of columns---to use for each page, when generating listings.
5876 If you do not use @code{.psize}, listings use a default line-count
5877 of 60. You may omit the comma and @var{columns} specification; the
5878 default width is 200 columns.
5880 @command{@value{AS}} generates formfeeds whenever the specified number of
5881 lines is exceeded (or whenever you explicitly request one, using
5884 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5885 those explicitly specified with @code{.eject}.
5888 @section @code{.purgem @var{name}}
5890 @cindex @code{purgem} directive
5891 Undefine the macro @var{name}, so that later uses of the string will not be
5892 expanded. @xref{Macro}.
5896 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5898 @cindex @code{pushsection} directive
5899 @cindex Section Stack
5900 This is one of the ELF section stack manipulation directives. The others are
5901 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5902 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5905 This directive pushes the current section (and subsection) onto the
5906 top of the section stack, and then replaces the current section and
5907 subsection with @code{name} and @code{subsection}. The optional
5908 @code{flags}, @code{type} and @code{arguments} are treated the same
5909 as in the @code{.section} (@pxref{Section}) directive.
5913 @section @code{.quad @var{bignums}}
5915 @cindex @code{quad} directive
5916 @code{.quad} expects zero or more bignums, separated by commas. For
5917 each bignum, it emits
5919 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5920 warning message; and just takes the lowest order 8 bytes of the bignum.
5921 @cindex eight-byte integer
5922 @cindex integer, 8-byte
5924 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5925 hence @emph{quad}-word for 8 bytes.
5928 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5929 warning message; and just takes the lowest order 16 bytes of the bignum.
5930 @cindex sixteen-byte integer
5931 @cindex integer, 16-byte
5935 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5937 @cindex @code{reloc} directive
5938 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5939 @var{expression}. If @var{offset} is a number, the relocation is generated in
5940 the current section. If @var{offset} is an expression that resolves to a
5941 symbol plus offset, the relocation is generated in the given symbol's section.
5942 @var{expression}, if present, must resolve to a symbol plus addend or to an
5943 absolute value, but note that not all targets support an addend. e.g. ELF REL
5944 targets such as i386 store an addend in the section contents rather than in the
5945 relocation. This low level interface does not support addends stored in the
5949 @section @code{.rept @var{count}}
5951 @cindex @code{rept} directive
5952 Repeat the sequence of lines between the @code{.rept} directive and the next
5953 @code{.endr} directive @var{count} times.
5955 For example, assembling
5963 is equivalent to assembling
5972 @section @code{.sbttl "@var{subheading}"}
5974 @cindex @code{sbttl} directive
5975 @cindex subtitles for listings
5976 @cindex listing control: subtitle
5977 Use @var{subheading} as the title (third line, immediately after the
5978 title line) when generating assembly listings.
5980 This directive affects subsequent pages, as well as the current page if
5981 it appears within ten lines of the top of a page.
5985 @section @code{.scl @var{class}}
5987 @cindex @code{scl} directive
5988 @cindex symbol storage class (COFF)
5989 @cindex COFF symbol storage class
5990 Set the storage-class value for a symbol. This directive may only be
5991 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5992 whether a symbol is static or external, or it may record further
5993 symbolic debugging information.
5996 The @samp{.scl} directive is primarily associated with COFF output; when
5997 configured to generate @code{b.out} output format, @command{@value{AS}}
5998 accepts this directive but ignores it.
6004 @section @code{.section @var{name}}
6006 @cindex named section
6007 Use the @code{.section} directive to assemble the following code into a section
6010 This directive is only supported for targets that actually support arbitrarily
6011 named sections; on @code{a.out} targets, for example, it is not accepted, even
6012 with a standard @code{a.out} section name.
6016 @c only print the extra heading if both COFF and ELF are set
6017 @subheading COFF Version
6020 @cindex @code{section} directive (COFF version)
6021 For COFF targets, the @code{.section} directive is used in one of the following
6025 .section @var{name}[, "@var{flags}"]
6026 .section @var{name}[, @var{subsection}]
6029 If the optional argument is quoted, it is taken as flags to use for the
6030 section. Each flag is a single character. The following flags are recognized:
6033 bss section (uninitialized data)
6035 section is not loaded
6041 exclude section from linking
6047 shared section (meaningful for PE targets)
6049 ignored. (For compatibility with the ELF version)
6051 section is not readable (meaningful for PE targets)
6053 single-digit power-of-two section alignment (GNU extension)
6056 If no flags are specified, the default flags depend upon the section name. If
6057 the section name is not recognized, the default will be for the section to be
6058 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6059 from the section, rather than adding them, so if they are used on their own it
6060 will be as if no flags had been specified at all.
6062 If the optional argument to the @code{.section} directive is not quoted, it is
6063 taken as a subsection number (@pxref{Sub-Sections}).
6068 @c only print the extra heading if both COFF and ELF are set
6069 @subheading ELF Version
6072 @cindex Section Stack
6073 This is one of the ELF section stack manipulation directives. The others are
6074 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6075 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6076 @code{.previous} (@pxref{Previous}).
6078 @cindex @code{section} directive (ELF version)
6079 For ELF targets, the @code{.section} directive is used like this:
6082 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6085 The optional @var{flags} argument is a quoted string which may contain any
6086 combination of the following characters:
6089 section is allocatable
6091 section is excluded from executable and shared library.
6095 section is executable
6097 section is mergeable
6099 section contains zero terminated strings
6101 section is a member of a section group
6103 section is used for thread-local-storage
6105 section is a member of the previously-current section's group, if any
6108 The optional @var{type} argument may contain one of the following constants:
6111 section contains data
6113 section does not contain data (i.e., section only occupies space)
6115 section contains data which is used by things other than the program
6117 section contains an array of pointers to init functions
6119 section contains an array of pointers to finish functions
6120 @item @@preinit_array
6121 section contains an array of pointers to pre-init functions
6124 Many targets only support the first three section types.
6126 Note on targets where the @code{@@} character is the start of a comment (eg
6127 ARM) then another character is used instead. For example the ARM port uses the
6130 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6131 be specified as well as an extra argument---@var{entsize}---like this:
6134 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6137 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6138 constants, each @var{entsize} octets long. Sections with both @code{M} and
6139 @code{S} must contain zero terminated strings where each character is
6140 @var{entsize} bytes long. The linker may remove duplicates within sections with
6141 the same name, same entity size and same flags. @var{entsize} must be an
6142 absolute expression. For sections with both @code{M} and @code{S}, a string
6143 which is a suffix of a larger string is considered a duplicate. Thus
6144 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6145 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6147 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6148 be present along with an additional field like this:
6151 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6154 The @var{GroupName} field specifies the name of the section group to which this
6155 particular section belongs. The optional linkage field can contain:
6158 indicates that only one copy of this section should be retained
6163 Note: if both the @var{M} and @var{G} flags are present then the fields for
6164 the Merge flag should come first, like this:
6167 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6170 If @var{flags} contains the @code{?} symbol then it may not also contain the
6171 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6172 present. Instead, @code{?} says to consider the section that's current before
6173 this directive. If that section used @code{G}, then the new section will use
6174 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6175 If not, then the @code{?} symbol has no effect.
6177 If no flags are specified, the default flags depend upon the section name. If
6178 the section name is not recognized, the default will be for the section to have
6179 none of the above flags: it will not be allocated in memory, nor writable, nor
6180 executable. The section will contain data.
6182 For ELF targets, the assembler supports another type of @code{.section}
6183 directive for compatibility with the Solaris assembler:
6186 .section "@var{name}"[, @var{flags}...]
6189 Note that the section name is quoted. There may be a sequence of comma
6193 section is allocatable
6197 section is executable
6199 section is excluded from executable and shared library.
6201 section is used for thread local storage
6204 This directive replaces the current section and subsection. See the
6205 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6206 some examples of how this directive and the other section stack directives
6212 @section @code{.set @var{symbol}, @var{expression}}
6214 @cindex @code{set} directive
6215 @cindex symbol value, setting
6216 Set the value of @var{symbol} to @var{expression}. This
6217 changes @var{symbol}'s value and type to conform to
6218 @var{expression}. If @var{symbol} was flagged as external, it remains
6219 flagged (@pxref{Symbol Attributes}).
6221 You may @code{.set} a symbol many times in the same assembly.
6223 If you @code{.set} a global symbol, the value stored in the object
6224 file is the last value stored into it.
6227 On Z80 @code{set} is a real instruction, use
6228 @samp{@var{symbol} defl @var{expression}} instead.
6232 @section @code{.short @var{expressions}}
6234 @cindex @code{short} directive
6236 @code{.short} is normally the same as @samp{.word}.
6237 @xref{Word,,@code{.word}}.
6239 In some configurations, however, @code{.short} and @code{.word} generate
6240 numbers of different lengths. @xref{Machine Dependencies}.
6244 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6247 This expects zero or more @var{expressions}, and emits
6248 a 16 bit number for each.
6253 @section @code{.single @var{flonums}}
6255 @cindex @code{single} directive
6256 @cindex floating point numbers (single)
6257 This directive assembles zero or more flonums, separated by commas. It
6258 has the same effect as @code{.float}.
6260 The exact kind of floating point numbers emitted depends on how
6261 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6265 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6266 numbers in @sc{ieee} format.
6272 @section @code{.size}
6274 This directive is used to set the size associated with a symbol.
6278 @c only print the extra heading if both COFF and ELF are set
6279 @subheading COFF Version
6282 @cindex @code{size} directive (COFF version)
6283 For COFF targets, the @code{.size} directive is only permitted inside
6284 @code{.def}/@code{.endef} pairs. It is used like this:
6287 .size @var{expression}
6291 @samp{.size} is only meaningful when generating COFF format output; when
6292 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6299 @c only print the extra heading if both COFF and ELF are set
6300 @subheading ELF Version
6303 @cindex @code{size} directive (ELF version)
6304 For ELF targets, the @code{.size} directive is used like this:
6307 .size @var{name} , @var{expression}
6310 This directive sets the size associated with a symbol @var{name}.
6311 The size in bytes is computed from @var{expression} which can make use of label
6312 arithmetic. This directive is typically used to set the size of function
6317 @ifclear no-space-dir
6319 @section @code{.skip @var{size} , @var{fill}}
6321 @cindex @code{skip} directive
6322 @cindex filling memory
6323 This directive emits @var{size} bytes, each of value @var{fill}. Both
6324 @var{size} and @var{fill} are absolute expressions. If the comma and
6325 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6330 @section @code{.sleb128 @var{expressions}}
6332 @cindex @code{sleb128} directive
6333 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6334 compact, variable length representation of numbers used by the DWARF
6335 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6337 @ifclear no-space-dir
6339 @section @code{.space @var{size} , @var{fill}}
6341 @cindex @code{space} directive
6342 @cindex filling memory
6343 This directive emits @var{size} bytes, each of value @var{fill}. Both
6344 @var{size} and @var{fill} are absolute expressions. If the comma
6345 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6350 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6351 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6352 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6353 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6361 @section @code{.stabd, .stabn, .stabs}
6363 @cindex symbolic debuggers, information for
6364 @cindex @code{stab@var{x}} directives
6365 There are three directives that begin @samp{.stab}.
6366 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6367 The symbols are not entered in the @command{@value{AS}} hash table: they
6368 cannot be referenced elsewhere in the source file.
6369 Up to five fields are required:
6373 This is the symbol's name. It may contain any character except
6374 @samp{\000}, so is more general than ordinary symbol names. Some
6375 debuggers used to code arbitrarily complex structures into symbol names
6379 An absolute expression. The symbol's type is set to the low 8 bits of
6380 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6381 and debuggers choke on silly bit patterns.
6384 An absolute expression. The symbol's ``other'' attribute is set to the
6385 low 8 bits of this expression.
6388 An absolute expression. The symbol's descriptor is set to the low 16
6389 bits of this expression.
6392 An absolute expression which becomes the symbol's value.
6395 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6396 or @code{.stabs} statement, the symbol has probably already been created;
6397 you get a half-formed symbol in your object file. This is
6398 compatible with earlier assemblers!
6401 @cindex @code{stabd} directive
6402 @item .stabd @var{type} , @var{other} , @var{desc}
6404 The ``name'' of the symbol generated is not even an empty string.
6405 It is a null pointer, for compatibility. Older assemblers used a
6406 null pointer so they didn't waste space in object files with empty
6409 The symbol's value is set to the location counter,
6410 relocatably. When your program is linked, the value of this symbol
6411 is the address of the location counter when the @code{.stabd} was
6414 @cindex @code{stabn} directive
6415 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6416 The name of the symbol is set to the empty string @code{""}.
6418 @cindex @code{stabs} directive
6419 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6420 All five fields are specified.
6426 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6427 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6429 @cindex string, copying to object file
6430 @cindex string8, copying to object file
6431 @cindex string16, copying to object file
6432 @cindex string32, copying to object file
6433 @cindex string64, copying to object file
6434 @cindex @code{string} directive
6435 @cindex @code{string8} directive
6436 @cindex @code{string16} directive
6437 @cindex @code{string32} directive
6438 @cindex @code{string64} directive
6440 Copy the characters in @var{str} to the object file. You may specify more than
6441 one string to copy, separated by commas. Unless otherwise specified for a
6442 particular machine, the assembler marks the end of each string with a 0 byte.
6443 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6445 The variants @code{string16}, @code{string32} and @code{string64} differ from
6446 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6447 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6448 are stored in target endianness byte order.
6454 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6455 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6460 @section @code{.struct @var{expression}}
6462 @cindex @code{struct} directive
6463 Switch to the absolute section, and set the section offset to @var{expression},
6464 which must be an absolute expression. You might use this as follows:
6473 This would define the symbol @code{field1} to have the value 0, the symbol
6474 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6475 value 8. Assembly would be left in the absolute section, and you would need to
6476 use a @code{.section} directive of some sort to change to some other section
6477 before further assembly.
6481 @section @code{.subsection @var{name}}
6483 @cindex @code{subsection} directive
6484 @cindex Section Stack
6485 This is one of the ELF section stack manipulation directives. The others are
6486 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6487 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6490 This directive replaces the current subsection with @code{name}. The current
6491 section is not changed. The replaced subsection is put onto the section stack
6492 in place of the then current top of stack subsection.
6497 @section @code{.symver}
6498 @cindex @code{symver} directive
6499 @cindex symbol versioning
6500 @cindex versions of symbols
6501 Use the @code{.symver} directive to bind symbols to specific version nodes
6502 within a source file. This is only supported on ELF platforms, and is
6503 typically used when assembling files to be linked into a shared library.
6504 There are cases where it may make sense to use this in objects to be bound
6505 into an application itself so as to override a versioned symbol from a
6508 For ELF targets, the @code{.symver} directive can be used like this:
6510 .symver @var{name}, @var{name2@@nodename}
6512 If the symbol @var{name} is defined within the file
6513 being assembled, the @code{.symver} directive effectively creates a symbol
6514 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6515 just don't try and create a regular alias is that the @var{@@} character isn't
6516 permitted in symbol names. The @var{name2} part of the name is the actual name
6517 of the symbol by which it will be externally referenced. The name @var{name}
6518 itself is merely a name of convenience that is used so that it is possible to
6519 have definitions for multiple versions of a function within a single source
6520 file, and so that the compiler can unambiguously know which version of a
6521 function is being mentioned. The @var{nodename} portion of the alias should be
6522 the name of a node specified in the version script supplied to the linker when
6523 building a shared library. If you are attempting to override a versioned
6524 symbol from a shared library, then @var{nodename} should correspond to the
6525 nodename of the symbol you are trying to override.
6527 If the symbol @var{name} is not defined within the file being assembled, all
6528 references to @var{name} will be changed to @var{name2@@nodename}. If no
6529 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6532 Another usage of the @code{.symver} directive is:
6534 .symver @var{name}, @var{name2@@@@nodename}
6536 In this case, the symbol @var{name} must exist and be defined within
6537 the file being assembled. It is similar to @var{name2@@nodename}. The
6538 difference is @var{name2@@@@nodename} will also be used to resolve
6539 references to @var{name2} by the linker.
6541 The third usage of the @code{.symver} directive is:
6543 .symver @var{name}, @var{name2@@@@@@nodename}
6545 When @var{name} is not defined within the
6546 file being assembled, it is treated as @var{name2@@nodename}. When
6547 @var{name} is defined within the file being assembled, the symbol
6548 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6553 @section @code{.tag @var{structname}}
6555 @cindex COFF structure debugging
6556 @cindex structure debugging, COFF
6557 @cindex @code{tag} directive
6558 This directive is generated by compilers to include auxiliary debugging
6559 information in the symbol table. It is only permitted inside
6560 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6561 definitions in the symbol table with instances of those structures.
6564 @samp{.tag} is only used when generating COFF format output; when
6565 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6571 @section @code{.text @var{subsection}}
6573 @cindex @code{text} directive
6574 Tells @command{@value{AS}} to assemble the following statements onto the end of
6575 the text subsection numbered @var{subsection}, which is an absolute
6576 expression. If @var{subsection} is omitted, subsection number zero
6580 @section @code{.title "@var{heading}"}
6582 @cindex @code{title} directive
6583 @cindex listing control: title line
6584 Use @var{heading} as the title (second line, immediately after the
6585 source file name and pagenumber) when generating assembly listings.
6587 This directive affects subsequent pages, as well as the current page if
6588 it appears within ten lines of the top of a page.
6592 @section @code{.type}
6594 This directive is used to set the type of a symbol.
6598 @c only print the extra heading if both COFF and ELF are set
6599 @subheading COFF Version
6602 @cindex COFF symbol type
6603 @cindex symbol type, COFF
6604 @cindex @code{type} directive (COFF version)
6605 For COFF targets, this directive is permitted only within
6606 @code{.def}/@code{.endef} pairs. It is used like this:
6612 This records the integer @var{int} as the type attribute of a symbol table
6616 @samp{.type} is associated only with COFF format output; when
6617 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6618 directive but ignores it.
6624 @c only print the extra heading if both COFF and ELF are set
6625 @subheading ELF Version
6628 @cindex ELF symbol type
6629 @cindex symbol type, ELF
6630 @cindex @code{type} directive (ELF version)
6631 For ELF targets, the @code{.type} directive is used like this:
6634 .type @var{name} , @var{type description}
6637 This sets the type of symbol @var{name} to be either a
6638 function symbol or an object symbol. There are five different syntaxes
6639 supported for the @var{type description} field, in order to provide
6640 compatibility with various other assemblers.
6642 Because some of the characters used in these syntaxes (such as @samp{@@} and
6643 @samp{#}) are comment characters for some architectures, some of the syntaxes
6644 below do not work on all architectures. The first variant will be accepted by
6645 the GNU assembler on all architectures so that variant should be used for
6646 maximum portability, if you do not need to assemble your code with other
6649 The syntaxes supported are:
6652 .type <name> STT_<TYPE_IN_UPPER_CASE>
6653 .type <name>,#<type>
6654 .type <name>,@@<type>
6655 .type <name>,%<type>
6656 .type <name>,"<type>"
6659 The types supported are:
6664 Mark the symbol as being a function name.
6667 @itemx gnu_indirect_function
6668 Mark the symbol as an indirect function when evaluated during reloc
6669 processing. (This is only supported on assemblers targeting GNU systems).
6673 Mark the symbol as being a data object.
6677 Mark the symbol as being a thead-local data object.
6681 Mark the symbol as being a common data object.
6685 Does not mark the symbol in any way. It is supported just for completeness.
6687 @item gnu_unique_object
6688 Marks the symbol as being a globally unique data object. The dynamic linker
6689 will make sure that in the entire process there is just one symbol with this
6690 name and type in use. (This is only supported on assemblers targeting GNU
6695 Note: Some targets support extra types in addition to those listed above.
6701 @section @code{.uleb128 @var{expressions}}
6703 @cindex @code{uleb128} directive
6704 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6705 compact, variable length representation of numbers used by the DWARF
6706 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6710 @section @code{.val @var{addr}}
6712 @cindex @code{val} directive
6713 @cindex COFF value attribute
6714 @cindex value attribute, COFF
6715 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6716 records the address @var{addr} as the value attribute of a symbol table
6720 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6721 configured for @code{b.out}, it accepts this directive but ignores it.
6727 @section @code{.version "@var{string}"}
6729 @cindex @code{version} directive
6730 This directive creates a @code{.note} section and places into it an ELF
6731 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6736 @section @code{.vtable_entry @var{table}, @var{offset}}
6738 @cindex @code{vtable_entry} directive
6739 This directive finds or creates a symbol @code{table} and creates a
6740 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6743 @section @code{.vtable_inherit @var{child}, @var{parent}}
6745 @cindex @code{vtable_inherit} directive
6746 This directive finds the symbol @code{child} and finds or creates the symbol
6747 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6748 parent whose addend is the value of the child symbol. As a special case the
6749 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6753 @section @code{.warning "@var{string}"}
6754 @cindex warning directive
6755 Similar to the directive @code{.error}
6756 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6759 @section @code{.weak @var{names}}
6761 @cindex @code{weak} directive
6762 This directive sets the weak attribute on the comma separated list of symbol
6763 @code{names}. If the symbols do not already exist, they will be created.
6765 On COFF targets other than PE, weak symbols are a GNU extension. This
6766 directive sets the weak attribute on the comma separated list of symbol
6767 @code{names}. If the symbols do not already exist, they will be created.
6769 On the PE target, weak symbols are supported natively as weak aliases.
6770 When a weak symbol is created that is not an alias, GAS creates an
6771 alternate symbol to hold the default value.
6774 @section @code{.weakref @var{alias}, @var{target}}
6776 @cindex @code{weakref} directive
6777 This directive creates an alias to the target symbol that enables the symbol to
6778 be referenced with weak-symbol semantics, but without actually making it weak.
6779 If direct references or definitions of the symbol are present, then the symbol
6780 will not be weak, but if all references to it are through weak references, the
6781 symbol will be marked as weak in the symbol table.
6783 The effect is equivalent to moving all references to the alias to a separate
6784 assembly source file, renaming the alias to the symbol in it, declaring the
6785 symbol as weak there, and running a reloadable link to merge the object files
6786 resulting from the assembly of the new source file and the old source file that
6787 had the references to the alias removed.
6789 The alias itself never makes to the symbol table, and is entirely handled
6790 within the assembler.
6793 @section @code{.word @var{expressions}}
6795 @cindex @code{word} directive
6796 This directive expects zero or more @var{expressions}, of any section,
6797 separated by commas.
6800 For each expression, @command{@value{AS}} emits a 32-bit number.
6803 For each expression, @command{@value{AS}} emits a 16-bit number.
6808 The size of the number emitted, and its byte order,
6809 depend on what target computer the assembly is for.
6812 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6813 @c happen---32-bit addressability, period; no long/short jumps.
6814 @ifset DIFF-TBL-KLUGE
6815 @cindex difference tables altered
6816 @cindex altered difference tables
6818 @emph{Warning: Special Treatment to support Compilers}
6822 Machines with a 32-bit address space, but that do less than 32-bit
6823 addressing, require the following special treatment. If the machine of
6824 interest to you does 32-bit addressing (or doesn't require it;
6825 @pxref{Machine Dependencies}), you can ignore this issue.
6828 In order to assemble compiler output into something that works,
6829 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6830 Directives of the form @samp{.word sym1-sym2} are often emitted by
6831 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6832 directive of the form @samp{.word sym1-sym2}, and the difference between
6833 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6834 creates a @dfn{secondary jump table}, immediately before the next label.
6835 This secondary jump table is preceded by a short-jump to the
6836 first byte after the secondary table. This short-jump prevents the flow
6837 of control from accidentally falling into the new table. Inside the
6838 table is a long-jump to @code{sym2}. The original @samp{.word}
6839 contains @code{sym1} minus the address of the long-jump to
6842 If there were several occurrences of @samp{.word sym1-sym2} before the
6843 secondary jump table, all of them are adjusted. If there was a
6844 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6845 long-jump to @code{sym4} is included in the secondary jump table,
6846 and the @code{.word} directives are adjusted to contain @code{sym3}
6847 minus the address of the long-jump to @code{sym4}; and so on, for as many
6848 entries in the original jump table as necessary.
6851 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6852 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6853 assembly language programmers.
6856 @c end DIFF-TBL-KLUGE
6859 @section Deprecated Directives
6861 @cindex deprecated directives
6862 @cindex obsolescent directives
6863 One day these directives won't work.
6864 They are included for compatibility with older assemblers.
6871 @node Object Attributes
6872 @chapter Object Attributes
6873 @cindex object attributes
6875 @command{@value{AS}} assembles source files written for a specific architecture
6876 into object files for that architecture. But not all object files are alike.
6877 Many architectures support incompatible variations. For instance, floating
6878 point arguments might be passed in floating point registers if the object file
6879 requires hardware floating point support---or floating point arguments might be
6880 passed in integer registers if the object file supports processors with no
6881 hardware floating point unit. Or, if two objects are built for different
6882 generations of the same architecture, the combination may require the
6883 newer generation at run-time.
6885 This information is useful during and after linking. At link time,
6886 @command{@value{LD}} can warn about incompatible object files. After link
6887 time, tools like @command{gdb} can use it to process the linked file
6890 Compatibility information is recorded as a series of object attributes. Each
6891 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6892 string, and indicates who sets the meaning of the tag. The tag is an integer,
6893 and indicates what property the attribute describes. The value may be a string
6894 or an integer, and indicates how the property affects this object. Missing
6895 attributes are the same as attributes with a zero value or empty string value.
6897 Object attributes were developed as part of the ABI for the ARM Architecture.
6898 The file format is documented in @cite{ELF for the ARM Architecture}.
6901 * GNU Object Attributes:: @sc{gnu} Object Attributes
6902 * Defining New Object Attributes:: Defining New Object Attributes
6905 @node GNU Object Attributes
6906 @section @sc{gnu} Object Attributes
6908 The @code{.gnu_attribute} directive records an object attribute
6909 with vendor @samp{gnu}.
6911 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6912 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6913 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6914 2} is set for architecture-independent attributes and clear for
6915 architecture-dependent ones.
6917 @subsection Common @sc{gnu} attributes
6919 These attributes are valid on all architectures.
6922 @item Tag_compatibility (32)
6923 The compatibility attribute takes an integer flag value and a vendor name. If
6924 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6925 then the file is only compatible with the named toolchain. If it is greater
6926 than 1, the file can only be processed by other toolchains under some private
6927 arrangement indicated by the flag value and the vendor name.
6930 @subsection MIPS Attributes
6933 @item Tag_GNU_MIPS_ABI_FP (4)
6934 The floating-point ABI used by this object file. The value will be:
6938 0 for files not affected by the floating-point ABI.
6940 1 for files using the hardware floating-point with a standard double-precision
6943 2 for files using the hardware floating-point ABI with a single-precision FPU.
6945 3 for files using the software floating-point ABI.
6947 4 for files using the hardware floating-point ABI with 64-bit wide
6948 double-precision floating-point registers and 32-bit wide general
6953 @subsection PowerPC Attributes
6956 @item Tag_GNU_Power_ABI_FP (4)
6957 The floating-point ABI used by this object file. The value will be:
6961 0 for files not affected by the floating-point ABI.
6963 1 for files using double-precision hardware floating-point ABI.
6965 2 for files using the software floating-point ABI.
6967 3 for files using single-precision hardware floating-point ABI.
6970 @item Tag_GNU_Power_ABI_Vector (8)
6971 The vector ABI used by this object file. The value will be:
6975 0 for files not affected by the vector ABI.
6977 1 for files using general purpose registers to pass vectors.
6979 2 for files using AltiVec registers to pass vectors.
6981 3 for files using SPE registers to pass vectors.
6985 @node Defining New Object Attributes
6986 @section Defining New Object Attributes
6988 If you want to define a new @sc{gnu} object attribute, here are the places you
6989 will need to modify. New attributes should be discussed on the @samp{binutils}
6994 This manual, which is the official register of attributes.
6996 The header for your architecture @file{include/elf}, to define the tag.
6998 The @file{bfd} support file for your architecture, to merge the attribute
6999 and issue any appropriate link warnings.
7001 Test cases in @file{ld/testsuite} for merging and link warnings.
7003 @file{binutils/readelf.c} to display your attribute.
7005 GCC, if you want the compiler to mark the attribute automatically.
7011 @node Machine Dependencies
7012 @chapter Machine Dependent Features
7014 @cindex machine dependencies
7015 The machine instruction sets are (almost by definition) different on
7016 each machine where @command{@value{AS}} runs. Floating point representations
7017 vary as well, and @command{@value{AS}} often supports a few additional
7018 directives or command-line options for compatibility with other
7019 assemblers on a particular platform. Finally, some versions of
7020 @command{@value{AS}} support special pseudo-instructions for branch
7023 This chapter discusses most of these differences, though it does not
7024 include details on any machine's instruction set. For details on that
7025 subject, see the hardware manufacturer's manual.
7029 * AArch64-Dependent:: AArch64 Dependent Features
7032 * Alpha-Dependent:: Alpha Dependent Features
7035 * ARC-Dependent:: ARC Dependent Features
7038 * ARM-Dependent:: ARM Dependent Features
7041 * AVR-Dependent:: AVR Dependent Features
7044 * Blackfin-Dependent:: Blackfin Dependent Features
7047 * CR16-Dependent:: CR16 Dependent Features
7050 * CRIS-Dependent:: CRIS Dependent Features
7053 * D10V-Dependent:: D10V Dependent Features
7056 * D30V-Dependent:: D30V Dependent Features
7059 * Epiphany-Dependent:: EPIPHANY Dependent Features
7062 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7065 * HPPA-Dependent:: HPPA Dependent Features
7068 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7071 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7074 * i860-Dependent:: Intel 80860 Dependent Features
7077 * i960-Dependent:: Intel 80960 Dependent Features
7080 * IA-64-Dependent:: Intel IA-64 Dependent Features
7083 * IP2K-Dependent:: IP2K Dependent Features
7086 * LM32-Dependent:: LM32 Dependent Features
7089 * M32C-Dependent:: M32C Dependent Features
7092 * M32R-Dependent:: M32R Dependent Features
7095 * M68K-Dependent:: M680x0 Dependent Features
7098 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7101 * Meta-Dependent :: Meta Dependent Features
7104 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7107 * MIPS-Dependent:: MIPS Dependent Features
7110 * MMIX-Dependent:: MMIX Dependent Features
7113 * MSP430-Dependent:: MSP430 Dependent Features
7116 * NiosII-Dependent:: Altera Nios II Dependent Features
7119 * NS32K-Dependent:: NS32K Dependent Features
7122 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7123 * SH64-Dependent:: SuperH SH64 Dependent Features
7126 * PDP-11-Dependent:: PDP-11 Dependent Features
7129 * PJ-Dependent:: picoJava Dependent Features
7132 * PPC-Dependent:: PowerPC Dependent Features
7135 * RL78-Dependent:: RL78 Dependent Features
7138 * RX-Dependent:: RX Dependent Features
7141 * S/390-Dependent:: IBM S/390 Dependent Features
7144 * SCORE-Dependent:: SCORE Dependent Features
7147 * Sparc-Dependent:: SPARC Dependent Features
7150 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7153 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7156 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7159 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7162 * V850-Dependent:: V850 Dependent Features
7165 * XGATE-Dependent:: XGATE Features
7168 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7171 * Xtensa-Dependent:: Xtensa Dependent Features
7174 * Z80-Dependent:: Z80 Dependent Features
7177 * Z8000-Dependent:: Z8000 Dependent Features
7180 * Vax-Dependent:: VAX Dependent Features
7187 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7188 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7189 @c peculiarity: to preserve cross-references, there must be a node called
7190 @c "Machine Dependencies". Hence the conditional nodenames in each
7191 @c major node below. Node defaulting in makeinfo requires adjacency of
7192 @c node and sectioning commands; hence the repetition of @chapter BLAH
7193 @c in both conditional blocks.
7196 @include c-aarch64.texi
7200 @include c-alpha.texi
7216 @include c-bfin.texi
7220 @include c-cr16.texi
7224 @include c-cris.texi
7229 @node Machine Dependencies
7230 @chapter Machine Dependent Features
7232 The machine instruction sets are different on each Renesas chip family,
7233 and there are also some syntax differences among the families. This
7234 chapter describes the specific @command{@value{AS}} features for each
7238 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7239 * SH-Dependent:: Renesas SH Dependent Features
7246 @include c-d10v.texi
7250 @include c-d30v.texi
7254 @include c-epiphany.texi
7258 @include c-h8300.texi
7262 @include c-hppa.texi
7266 @include c-i370.texi
7270 @include c-i386.texi
7274 @include c-i860.texi
7278 @include c-i960.texi
7282 @include c-ia64.texi
7286 @include c-ip2k.texi
7290 @include c-lm32.texi
7294 @include c-m32c.texi
7298 @include c-m32r.texi
7302 @include c-m68k.texi
7306 @include c-m68hc11.texi
7310 @include c-metag.texi
7314 @include c-microblaze.texi
7318 @include c-mips.texi
7322 @include c-mmix.texi
7326 @include c-msp430.texi
7330 @include c-nios2.texi
7334 @include c-ns32k.texi
7338 @include c-pdp11.texi
7350 @include c-rl78.texi
7358 @include c-s390.texi
7362 @include c-score.texi
7367 @include c-sh64.texi
7371 @include c-sparc.texi
7375 @include c-tic54x.texi
7379 @include c-tic6x.texi
7383 @include c-tilegx.texi
7387 @include c-tilepro.texi
7403 @include c-v850.texi
7407 @include c-xgate.texi
7411 @include c-xstormy16.texi
7415 @include c-xtensa.texi
7419 @c reverse effect of @down at top of generic Machine-Dep chapter
7423 @node Reporting Bugs
7424 @chapter Reporting Bugs
7425 @cindex bugs in assembler
7426 @cindex reporting bugs in assembler
7428 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7430 Reporting a bug may help you by bringing a solution to your problem, or it may
7431 not. But in any case the principal function of a bug report is to help the
7432 entire community by making the next version of @command{@value{AS}} work better.
7433 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7435 In order for a bug report to serve its purpose, you must include the
7436 information that enables us to fix the bug.
7439 * Bug Criteria:: Have you found a bug?
7440 * Bug Reporting:: How to report bugs
7444 @section Have You Found a Bug?
7445 @cindex bug criteria
7447 If you are not sure whether you have found a bug, here are some guidelines:
7450 @cindex fatal signal
7451 @cindex assembler crash
7452 @cindex crash of assembler
7454 If the assembler gets a fatal signal, for any input whatever, that is a
7455 @command{@value{AS}} bug. Reliable assemblers never crash.
7457 @cindex error on valid input
7459 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7461 @cindex invalid input
7463 If @command{@value{AS}} does not produce an error message for invalid input, that
7464 is a bug. However, you should note that your idea of ``invalid input'' might
7465 be our idea of ``an extension'' or ``support for traditional practice''.
7468 If you are an experienced user of assemblers, your suggestions for improvement
7469 of @command{@value{AS}} are welcome in any case.
7473 @section How to Report Bugs
7475 @cindex assembler bugs, reporting
7477 A number of companies and individuals offer support for @sc{gnu} products. If
7478 you obtained @command{@value{AS}} from a support organization, we recommend you
7479 contact that organization first.
7481 You can find contact information for many support companies and
7482 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7486 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7490 The fundamental principle of reporting bugs usefully is this:
7491 @strong{report all the facts}. If you are not sure whether to state a
7492 fact or leave it out, state it!
7494 Often people omit facts because they think they know what causes the problem
7495 and assume that some details do not matter. Thus, you might assume that the
7496 name of a symbol you use in an example does not matter. Well, probably it does
7497 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7498 happens to fetch from the location where that name is stored in memory;
7499 perhaps, if the name were different, the contents of that location would fool
7500 the assembler into doing the right thing despite the bug. Play it safe and
7501 give a specific, complete example. That is the easiest thing for you to do,
7502 and the most helpful.
7504 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7505 it is new to us. Therefore, always write your bug reports on the assumption
7506 that the bug has not been reported previously.
7508 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7509 bell?'' This cannot help us fix a bug, so it is basically useless. We
7510 respond by asking for enough details to enable us to investigate.
7511 You might as well expedite matters by sending them to begin with.
7513 To enable us to fix the bug, you should include all these things:
7517 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7518 it with the @samp{--version} argument.
7520 Without this, we will not know whether there is any point in looking for
7521 the bug in the current version of @command{@value{AS}}.
7524 Any patches you may have applied to the @command{@value{AS}} source.
7527 The type of machine you are using, and the operating system name and
7531 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7535 The command arguments you gave the assembler to assemble your example and
7536 observe the bug. To guarantee you will not omit something important, list them
7537 all. A copy of the Makefile (or the output from make) is sufficient.
7539 If we were to try to guess the arguments, we would probably guess wrong
7540 and then we might not encounter the bug.
7543 A complete input file that will reproduce the bug. If the bug is observed when
7544 the assembler is invoked via a compiler, send the assembler source, not the
7545 high level language source. Most compilers will produce the assembler source
7546 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7547 the options @samp{-v --save-temps}; this will save the assembler source in a
7548 file with an extension of @file{.s}, and also show you exactly how
7549 @command{@value{AS}} is being run.
7552 A description of what behavior you observe that you believe is
7553 incorrect. For example, ``It gets a fatal signal.''
7555 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7556 will certainly notice it. But if the bug is incorrect output, we might not
7557 notice unless it is glaringly wrong. You might as well not give us a chance to
7560 Even if the problem you experience is a fatal signal, you should still say so
7561 explicitly. Suppose something strange is going on, such as, your copy of
7562 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7563 library on your system. (This has happened!) Your copy might crash and ours
7564 would not. If you told us to expect a crash, then when ours fails to crash, we
7565 would know that the bug was not happening for us. If you had not told us to
7566 expect a crash, then we would not be able to draw any conclusion from our
7570 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7571 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7572 option. Always send diffs from the old file to the new file. If you even
7573 discuss something in the @command{@value{AS}} source, refer to it by context, not
7576 The line numbers in our development sources will not match those in your
7577 sources. Your line numbers would convey no useful information to us.
7580 Here are some things that are not necessary:
7584 A description of the envelope of the bug.
7586 Often people who encounter a bug spend a lot of time investigating
7587 which changes to the input file will make the bug go away and which
7588 changes will not affect it.
7590 This is often time consuming and not very useful, because the way we
7591 will find the bug is by running a single example under the debugger
7592 with breakpoints, not by pure deduction from a series of examples.
7593 We recommend that you save your time for something else.
7595 Of course, if you can find a simpler example to report @emph{instead}
7596 of the original one, that is a convenience for us. Errors in the
7597 output will be easier to spot, running under the debugger will take
7598 less time, and so on.
7600 However, simplification is not vital; if you do not want to do this,
7601 report the bug anyway and send us the entire test case you used.
7604 A patch for the bug.
7606 A patch for the bug does help us if it is a good one. But do not omit
7607 the necessary information, such as the test case, on the assumption that
7608 a patch is all we need. We might see problems with your patch and decide
7609 to fix the problem another way, or we might not understand it at all.
7611 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7612 construct an example that will make the program follow a certain path through
7613 the code. If you do not send us the example, we will not be able to construct
7614 one, so we will not be able to verify that the bug is fixed.
7616 And if we cannot understand what bug you are trying to fix, or why your
7617 patch should be an improvement, we will not install it. A test case will
7618 help us to understand.
7621 A guess about what the bug is or what it depends on.
7623 Such guesses are usually wrong. Even we cannot guess right about such
7624 things without first using the debugger to find the facts.
7627 @node Acknowledgements
7628 @chapter Acknowledgements
7630 If you have contributed to GAS and your name isn't listed here,
7631 it is not meant as a slight. We just don't know about it. Send mail to the
7632 maintainer, and we'll correct the situation. Currently
7634 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7636 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7639 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7640 information and the 68k series machines, most of the preprocessing pass, and
7641 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7643 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7644 many bug fixes, including merging support for several processors, breaking GAS
7645 up to handle multiple object file format back ends (including heavy rewrite,
7646 testing, an integration of the coff and b.out back ends), adding configuration
7647 including heavy testing and verification of cross assemblers and file splits
7648 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7649 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7650 port (including considerable amounts of reverse engineering), a SPARC opcode
7651 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7652 assertions and made them work, much other reorganization, cleanup, and lint.
7654 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7655 in format-specific I/O modules.
7657 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7658 has done much work with it since.
7660 The Intel 80386 machine description was written by Eliot Dresselhaus.
7662 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7664 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7665 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7667 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7668 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7669 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7670 support a.out format.
7672 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7673 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7674 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7675 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7678 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7679 simplified the configuration of which versions accept which directives. He
7680 updated the 68k machine description so that Motorola's opcodes always produced
7681 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7682 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7683 cross-compilation support, and one bug in relaxation that took a week and
7684 required the proverbial one-bit fix.
7686 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7687 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7688 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7689 PowerPC assembler, and made a few other minor patches.
7691 Steve Chamberlain made GAS able to generate listings.
7693 Hewlett-Packard contributed support for the HP9000/300.
7695 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7696 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7697 formats). This work was supported by both the Center for Software Science at
7698 the University of Utah and Cygnus Support.
7700 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7701 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7702 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7703 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7704 and some initial 64-bit support).
7706 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7708 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7709 support for openVMS/Alpha.
7711 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7714 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7715 Inc.@: added support for Xtensa processors.
7717 Several engineers at Cygnus Support have also provided many small bug fixes and
7718 configuration enhancements.
7720 Jon Beniston added support for the Lattice Mico32 architecture.
7722 Many others have contributed large or small bugfixes and enhancements. If
7723 you have contributed significant work and are not mentioned on this list, and
7724 want to be, let us know. Some of the history has been lost; we are not
7725 intentionally leaving anyone out.
7727 @node GNU Free Documentation License
7728 @appendix GNU Free Documentation License
7732 @unnumbered AS Index