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 was formerly used to switch between ELF and ECOFF output
1361 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1362 removed in GAS 2.24, so the option now serves little purpose.
1363 It is retained for backwards compatibility.
1365 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1366 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1367 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1368 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1369 preferred options instead.
1372 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1379 Control how to deal with multiplication overflow and division by zero.
1380 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1381 (and only work for Instruction Set Architecture level 2 and higher);
1382 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1386 When this option is used, @command{@value{AS}} will issue a warning every
1387 time it generates a nop instruction from a macro.
1392 The following options are available when @value{AS} is configured for
1398 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1399 The command line option @samp{-nojsri2bsr} can be used to disable it.
1403 Enable or disable the silicon filter behaviour. By default this is disabled.
1404 The default can be overridden by the @samp{-sifilter} command line option.
1407 Alter jump instructions for long displacements.
1409 @item -mcpu=[210|340]
1410 Select the cpu type on the target hardware. This controls which instructions
1414 Assemble for a big endian target.
1417 Assemble for a little endian target.
1426 @xref{Meta Options}, for the options available when @value{AS} is configured
1427 for a Meta processor.
1431 @c man begin OPTIONS
1432 The following options are available when @value{AS} is configured for a
1435 @c man begin INCLUDE
1436 @include c-metag.texi
1437 @c ended inside the included file
1442 @c man begin OPTIONS
1444 See the info pages for documentation of the MMIX-specific options.
1451 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1452 for a PowerPC processor.
1456 @c man begin OPTIONS
1457 The following options are available when @value{AS} is configured for a
1460 @c man begin INCLUDE
1462 @c ended inside the included file
1467 @c man begin OPTIONS
1469 See the info pages for documentation of the RX-specific options.
1473 The following options are available when @value{AS} is configured for the s390
1479 Select the word size, either 31/32 bits or 64 bits.
1482 Select the architecture mode, either the Enterprise System
1483 Architecture (esa) or the z/Architecture mode (zarch).
1484 @item -march=@var{processor}
1485 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1486 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1487 @samp{z196}, or @samp{zEC12}.
1489 @itemx -mno-regnames
1490 Allow or disallow symbolic names for registers.
1491 @item -mwarn-areg-zero
1492 Warn whenever the operand for a base or index register has been specified
1493 but evaluates to zero.
1501 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1502 for a TMS320C6000 processor.
1506 @c man begin OPTIONS
1507 The following options are available when @value{AS} is configured for a
1508 TMS320C6000 processor.
1510 @c man begin INCLUDE
1511 @include c-tic6x.texi
1512 @c ended inside the included file
1520 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1521 for a TILE-Gx processor.
1525 @c man begin OPTIONS
1526 The following options are available when @value{AS} is configured for a TILE-Gx
1529 @c man begin INCLUDE
1530 @include c-tilegx.texi
1531 @c ended inside the included file
1539 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1540 for an Xtensa processor.
1544 @c man begin OPTIONS
1545 The following options are available when @value{AS} is configured for an
1548 @c man begin INCLUDE
1549 @include c-xtensa.texi
1550 @c ended inside the included file
1555 @c man begin OPTIONS
1558 The following options are available when @value{AS} is configured for
1559 a Z80 family processor.
1562 Assemble for Z80 processor.
1564 Assemble for R800 processor.
1565 @item -ignore-undocumented-instructions
1567 Assemble undocumented Z80 instructions that also work on R800 without warning.
1568 @item -ignore-unportable-instructions
1570 Assemble all undocumented Z80 instructions without warning.
1571 @item -warn-undocumented-instructions
1573 Issue a warning for undocumented Z80 instructions that also work on R800.
1574 @item -warn-unportable-instructions
1576 Issue a warning for undocumented Z80 instructions that do not work on R800.
1577 @item -forbid-undocumented-instructions
1579 Treat all undocumented instructions as errors.
1580 @item -forbid-unportable-instructions
1582 Treat undocumented Z80 instructions that do not work on R800 as errors.
1589 * Manual:: Structure of this Manual
1590 * GNU Assembler:: The GNU Assembler
1591 * Object Formats:: Object File Formats
1592 * Command Line:: Command Line
1593 * Input Files:: Input Files
1594 * Object:: Output (Object) File
1595 * Errors:: Error and Warning Messages
1599 @section Structure of this Manual
1601 @cindex manual, structure and purpose
1602 This manual is intended to describe what you need to know to use
1603 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1604 notation for symbols, constants, and expressions; the directives that
1605 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1608 We also cover special features in the @value{TARGET}
1609 configuration of @command{@value{AS}}, including assembler directives.
1612 This manual also describes some of the machine-dependent features of
1613 various flavors of the assembler.
1616 @cindex machine instructions (not covered)
1617 On the other hand, this manual is @emph{not} intended as an introduction
1618 to programming in assembly language---let alone programming in general!
1619 In a similar vein, we make no attempt to introduce the machine
1620 architecture; we do @emph{not} describe the instruction set, standard
1621 mnemonics, registers or addressing modes that are standard to a
1622 particular architecture.
1624 You may want to consult the manufacturer's
1625 machine architecture manual for this information.
1629 For information on the H8/300 machine instruction set, see @cite{H8/300
1630 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1631 Programming Manual} (Renesas).
1634 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1635 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1636 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1637 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1640 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1644 @c I think this is premature---doc@cygnus.com, 17jan1991
1646 Throughout this manual, we assume that you are running @dfn{GNU},
1647 the portable operating system from the @dfn{Free Software
1648 Foundation, Inc.}. This restricts our attention to certain kinds of
1649 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1650 once this assumption is granted examples and definitions need less
1653 @command{@value{AS}} is part of a team of programs that turn a high-level
1654 human-readable series of instructions into a low-level
1655 computer-readable series of instructions. Different versions of
1656 @command{@value{AS}} are used for different kinds of computer.
1659 @c There used to be a section "Terminology" here, which defined
1660 @c "contents", "byte", "word", and "long". Defining "word" to any
1661 @c particular size is confusing when the .word directive may generate 16
1662 @c bits on one machine and 32 bits on another; in general, for the user
1663 @c version of this manual, none of these terms seem essential to define.
1664 @c They were used very little even in the former draft of the manual;
1665 @c this draft makes an effort to avoid them (except in names of
1669 @section The GNU Assembler
1671 @c man begin DESCRIPTION
1673 @sc{gnu} @command{as} is really a family of assemblers.
1675 This manual describes @command{@value{AS}}, a member of that family which is
1676 configured for the @value{TARGET} architectures.
1678 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1679 should find a fairly similar environment when you use it on another
1680 architecture. Each version has much in common with the others,
1681 including object file formats, most assembler directives (often called
1682 @dfn{pseudo-ops}) and assembler syntax.@refill
1684 @cindex purpose of @sc{gnu} assembler
1685 @command{@value{AS}} is primarily intended to assemble the output of the
1686 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1687 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1688 assemble correctly everything that other assemblers for the same
1689 machine would assemble.
1691 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1694 @c This remark should appear in generic version of manual; assumption
1695 @c here is that generic version sets M680x0.
1696 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1697 assembler for the same architecture; for example, we know of several
1698 incompatible versions of 680x0 assembly language syntax.
1703 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1704 program in one pass of the source file. This has a subtle impact on the
1705 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1707 @node Object Formats
1708 @section Object File Formats
1710 @cindex object file format
1711 The @sc{gnu} assembler can be configured to produce several alternative
1712 object file formats. For the most part, this does not affect how you
1713 write assembly language programs; but directives for debugging symbols
1714 are typically different in different file formats. @xref{Symbol
1715 Attributes,,Symbol Attributes}.
1718 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1719 @value{OBJ-NAME} format object files.
1721 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1723 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1724 @code{b.out} or COFF format object files.
1727 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1728 SOM or ELF format object files.
1733 @section Command Line
1735 @cindex command line conventions
1737 After the program name @command{@value{AS}}, the command line may contain
1738 options and file names. Options may appear in any order, and may be
1739 before, after, or between file names. The order of file names is
1742 @cindex standard input, as input file
1744 @file{--} (two hyphens) by itself names the standard input file
1745 explicitly, as one of the files for @command{@value{AS}} to assemble.
1747 @cindex options, command line
1748 Except for @samp{--} any command line argument that begins with a
1749 hyphen (@samp{-}) is an option. Each option changes the behavior of
1750 @command{@value{AS}}. No option changes the way another option works. An
1751 option is a @samp{-} followed by one or more letters; the case of
1752 the letter is important. All options are optional.
1754 Some options expect exactly one file name to follow them. The file
1755 name may either immediately follow the option's letter (compatible
1756 with older assemblers) or it may be the next command argument (@sc{gnu}
1757 standard). These two command lines are equivalent:
1760 @value{AS} -o my-object-file.o mumble.s
1761 @value{AS} -omy-object-file.o mumble.s
1765 @section Input Files
1768 @cindex source program
1769 @cindex files, input
1770 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1771 describe the program input to one run of @command{@value{AS}}. The program may
1772 be in one or more files; how the source is partitioned into files
1773 doesn't change the meaning of the source.
1775 @c I added "con" prefix to "catenation" just to prove I can overcome my
1776 @c APL training... doc@cygnus.com
1777 The source program is a concatenation of the text in all the files, in the
1780 @c man begin DESCRIPTION
1781 Each time you run @command{@value{AS}} it assembles exactly one source
1782 program. The source program is made up of one or more files.
1783 (The standard input is also a file.)
1785 You give @command{@value{AS}} a command line that has zero or more input file
1786 names. The input files are read (from left file name to right). A
1787 command line argument (in any position) that has no special meaning
1788 is taken to be an input file name.
1790 If you give @command{@value{AS}} no file names it attempts to read one input file
1791 from the @command{@value{AS}} standard input, which is normally your terminal. You
1792 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1795 Use @samp{--} if you need to explicitly name the standard input file
1796 in your command line.
1798 If the source is empty, @command{@value{AS}} produces a small, empty object
1803 @subheading Filenames and Line-numbers
1805 @cindex input file linenumbers
1806 @cindex line numbers, in input files
1807 There are two ways of locating a line in the input file (or files) and
1808 either may be used in reporting error messages. One way refers to a line
1809 number in a physical file; the other refers to a line number in a
1810 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1812 @dfn{Physical files} are those files named in the command line given
1813 to @command{@value{AS}}.
1815 @dfn{Logical files} are simply names declared explicitly by assembler
1816 directives; they bear no relation to physical files. Logical file names help
1817 error messages reflect the original source file, when @command{@value{AS}} source
1818 is itself synthesized from other files. @command{@value{AS}} understands the
1819 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1820 @ref{File,,@code{.file}}.
1823 @section Output (Object) File
1829 Every time you run @command{@value{AS}} it produces an output file, which is
1830 your assembly language program translated into numbers. This file
1831 is the object file. Its default name is
1839 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1841 You can give it another name by using the @option{-o} option. Conventionally,
1842 object file names end with @file{.o}. The default name is used for historical
1843 reasons: older assemblers were capable of assembling self-contained programs
1844 directly into a runnable program. (For some formats, this isn't currently
1845 possible, but it can be done for the @code{a.out} format.)
1849 The object file is meant for input to the linker @code{@value{LD}}. It contains
1850 assembled program code, information to help @code{@value{LD}} integrate
1851 the assembled program into a runnable file, and (optionally) symbolic
1852 information for the debugger.
1854 @c link above to some info file(s) like the description of a.out.
1855 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1858 @section Error and Warning Messages
1860 @c man begin DESCRIPTION
1862 @cindex error messages
1863 @cindex warning messages
1864 @cindex messages from assembler
1865 @command{@value{AS}} may write warnings and error messages to the standard error
1866 file (usually your terminal). This should not happen when a compiler
1867 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1868 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1869 grave problem that stops the assembly.
1873 @cindex format of warning messages
1874 Warning messages have the format
1877 file_name:@b{NNN}:Warning Message Text
1881 @cindex line numbers, in warnings/errors
1882 (where @b{NNN} is a line number). If a logical file name has been given
1883 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1884 the current input file is used. If a logical line number was given
1886 (@pxref{Line,,@code{.line}})
1888 then it is used to calculate the number printed,
1889 otherwise the actual line in the current source file is printed. The
1890 message text is intended to be self explanatory (in the grand Unix
1893 @cindex format of error messages
1894 Error messages have the format
1896 file_name:@b{NNN}:FATAL:Error Message Text
1898 The file name and line number are derived as for warning
1899 messages. The actual message text may be rather less explanatory
1900 because many of them aren't supposed to happen.
1903 @chapter Command-Line Options
1905 @cindex options, all versions of assembler
1906 This chapter describes command-line options available in @emph{all}
1907 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1908 for options specific
1910 to the @value{TARGET} target.
1913 to particular machine architectures.
1916 @c man begin DESCRIPTION
1918 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1919 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1920 The assembler arguments must be separated from each other (and the @samp{-Wa})
1921 by commas. For example:
1924 gcc -c -g -O -Wa,-alh,-L file.c
1928 This passes two options to the assembler: @samp{-alh} (emit a listing to
1929 standard output with high-level and assembly source) and @samp{-L} (retain
1930 local symbols in the symbol table).
1932 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1933 command-line options are automatically passed to the assembler by the compiler.
1934 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1935 precisely what options it passes to each compilation pass, including the
1941 * a:: -a[cdghlns] enable listings
1942 * alternate:: --alternate enable alternate macro syntax
1943 * D:: -D for compatibility
1944 * f:: -f to work faster
1945 * I:: -I for .include search path
1946 @ifclear DIFF-TBL-KLUGE
1947 * K:: -K for compatibility
1949 @ifset DIFF-TBL-KLUGE
1950 * K:: -K for difference tables
1953 * L:: -L to retain local symbols
1954 * listing:: --listing-XXX to configure listing output
1955 * M:: -M or --mri to assemble in MRI compatibility mode
1956 * MD:: --MD for dependency tracking
1957 * o:: -o to name the object file
1958 * R:: -R to join data and text sections
1959 * statistics:: --statistics to see statistics about assembly
1960 * traditional-format:: --traditional-format for compatible output
1961 * v:: -v to announce version
1962 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1963 * Z:: -Z to make object file even after errors
1967 @section Enable Listings: @option{-a[cdghlns]}
1977 @cindex listings, enabling
1978 @cindex assembly listings, enabling
1980 These options enable listing output from the assembler. By itself,
1981 @samp{-a} requests high-level, assembly, and symbols listing.
1982 You can use other letters to select specific options for the list:
1983 @samp{-ah} requests a high-level language listing,
1984 @samp{-al} requests an output-program assembly listing, and
1985 @samp{-as} requests a symbol table listing.
1986 High-level listings require that a compiler debugging option like
1987 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1990 Use the @samp{-ag} option to print a first section with general assembly
1991 information, like @value{AS} version, switches passed, or time stamp.
1993 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1994 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1995 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1996 omitted from the listing.
1998 Use the @samp{-ad} option to omit debugging directives from the
2001 Once you have specified one of these options, you can further control
2002 listing output and its appearance using the directives @code{.list},
2003 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2005 The @samp{-an} option turns off all forms processing.
2006 If you do not request listing output with one of the @samp{-a} options, the
2007 listing-control directives have no effect.
2009 The letters after @samp{-a} may be combined into one option,
2010 @emph{e.g.}, @samp{-aln}.
2012 Note if the assembler source is coming from the standard input (e.g.,
2014 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2015 is being used) then the listing will not contain any comments or preprocessor
2016 directives. This is because the listing code buffers input source lines from
2017 stdin only after they have been preprocessed by the assembler. This reduces
2018 memory usage and makes the code more efficient.
2021 @section @option{--alternate}
2024 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2027 @section @option{-D}
2030 This option has no effect whatsoever, but it is accepted to make it more
2031 likely that scripts written for other assemblers also work with
2032 @command{@value{AS}}.
2035 @section Work Faster: @option{-f}
2038 @cindex trusted compiler
2039 @cindex faster processing (@option{-f})
2040 @samp{-f} should only be used when assembling programs written by a
2041 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2042 and comment preprocessing on
2043 the input file(s) before assembling them. @xref{Preprocessing,
2047 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2048 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2053 @section @code{.include} Search Path: @option{-I} @var{path}
2055 @kindex -I @var{path}
2056 @cindex paths for @code{.include}
2057 @cindex search path for @code{.include}
2058 @cindex @code{include} directive search path
2059 Use this option to add a @var{path} to the list of directories
2060 @command{@value{AS}} searches for files specified in @code{.include}
2061 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2062 many times as necessary to include a variety of paths. The current
2063 working directory is always searched first; after that, @command{@value{AS}}
2064 searches any @samp{-I} directories in the same order as they were
2065 specified (left to right) on the command line.
2068 @section Difference Tables: @option{-K}
2071 @ifclear DIFF-TBL-KLUGE
2072 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2073 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2074 where it can be used to warn when the assembler alters the machine code
2075 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2076 family does not have the addressing limitations that sometimes lead to this
2077 alteration on other platforms.
2080 @ifset DIFF-TBL-KLUGE
2081 @cindex difference tables, warning
2082 @cindex warning for altered difference tables
2083 @command{@value{AS}} sometimes alters the code emitted for directives of the
2084 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2085 You can use the @samp{-K} option if you want a warning issued when this
2090 @section Include Local Symbols: @option{-L}
2093 @cindex local symbols, retaining in output
2094 Symbols beginning with system-specific local label prefixes, typically
2095 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2096 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2097 such symbols when debugging, because they are intended for the use of
2098 programs (like compilers) that compose assembler programs, not for your
2099 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2100 such symbols, so you do not normally debug with them.
2102 This option tells @command{@value{AS}} to retain those local symbols
2103 in the object file. Usually if you do this you also tell the linker
2104 @code{@value{LD}} to preserve those symbols.
2107 @section Configuring listing output: @option{--listing}
2109 The listing feature of the assembler can be enabled via the command line switch
2110 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2111 hex dump of the corresponding locations in the output object file, and displays
2112 them as a listing file. The format of this listing can be controlled by
2113 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2114 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2115 @code{.psize} (@pxref{Psize}), and
2116 @code{.eject} (@pxref{Eject}) and also by the following switches:
2119 @item --listing-lhs-width=@samp{number}
2120 @kindex --listing-lhs-width
2121 @cindex Width of first line disassembly output
2122 Sets the maximum width, in words, of the first line of the hex byte dump. This
2123 dump appears on the left hand side of the listing output.
2125 @item --listing-lhs-width2=@samp{number}
2126 @kindex --listing-lhs-width2
2127 @cindex Width of continuation lines of disassembly output
2128 Sets the maximum width, in words, of any further lines of the hex byte dump for
2129 a given input source line. If this value is not specified, it defaults to being
2130 the same as the value specified for @samp{--listing-lhs-width}. If neither
2131 switch is used the default is to one.
2133 @item --listing-rhs-width=@samp{number}
2134 @kindex --listing-rhs-width
2135 @cindex Width of source line output
2136 Sets the maximum width, in characters, of the source line that is displayed
2137 alongside the hex dump. The default value for this parameter is 100. The
2138 source line is displayed on the right hand side of the listing output.
2140 @item --listing-cont-lines=@samp{number}
2141 @kindex --listing-cont-lines
2142 @cindex Maximum number of continuation lines
2143 Sets the maximum number of continuation lines of hex dump that will be
2144 displayed for a given single line of source input. The default value is 4.
2148 @section Assemble in MRI Compatibility Mode: @option{-M}
2151 @cindex MRI compatibility mode
2152 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2153 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2154 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2155 configured target) assembler from Microtec Research. The exact nature of the
2156 MRI syntax will not be documented here; see the MRI manuals for more
2157 information. Note in particular that the handling of macros and macro
2158 arguments is somewhat different. The purpose of this option is to permit
2159 assembling existing MRI assembler code using @command{@value{AS}}.
2161 The MRI compatibility is not complete. Certain operations of the MRI assembler
2162 depend upon its object file format, and can not be supported using other object
2163 file formats. Supporting these would require enhancing each object file format
2164 individually. These are:
2167 @item global symbols in common section
2169 The m68k MRI assembler supports common sections which are merged by the linker.
2170 Other object file formats do not support this. @command{@value{AS}} handles
2171 common sections by treating them as a single common symbol. It permits local
2172 symbols to be defined within a common section, but it can not support global
2173 symbols, since it has no way to describe them.
2175 @item complex relocations
2177 The MRI assemblers support relocations against a negated section address, and
2178 relocations which combine the start addresses of two or more sections. These
2179 are not support by other object file formats.
2181 @item @code{END} pseudo-op specifying start address
2183 The MRI @code{END} pseudo-op permits the specification of a start address.
2184 This is not supported by other object file formats. The start address may
2185 instead be specified using the @option{-e} option to the linker, or in a linker
2188 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2190 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2191 name to the output file. This is not supported by other object file formats.
2193 @item @code{ORG} pseudo-op
2195 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2196 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2197 which changes the location within the current section. Absolute sections are
2198 not supported by other object file formats. The address of a section may be
2199 assigned within a linker script.
2202 There are some other features of the MRI assembler which are not supported by
2203 @command{@value{AS}}, typically either because they are difficult or because they
2204 seem of little consequence. Some of these may be supported in future releases.
2208 @item EBCDIC strings
2210 EBCDIC strings are not supported.
2212 @item packed binary coded decimal
2214 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2215 and @code{DCB.P} pseudo-ops are not supported.
2217 @item @code{FEQU} pseudo-op
2219 The m68k @code{FEQU} pseudo-op is not supported.
2221 @item @code{NOOBJ} pseudo-op
2223 The m68k @code{NOOBJ} pseudo-op is not supported.
2225 @item @code{OPT} branch control options
2227 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2228 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2229 relaxes all branches, whether forward or backward, to an appropriate size, so
2230 these options serve no purpose.
2232 @item @code{OPT} list control options
2234 The following m68k @code{OPT} list control options are ignored: @code{C},
2235 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2236 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2238 @item other @code{OPT} options
2240 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2241 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2243 @item @code{OPT} @code{D} option is default
2245 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2246 @code{OPT NOD} may be used to turn it off.
2248 @item @code{XREF} pseudo-op.
2250 The m68k @code{XREF} pseudo-op is ignored.
2252 @item @code{.debug} pseudo-op
2254 The i960 @code{.debug} pseudo-op is not supported.
2256 @item @code{.extended} pseudo-op
2258 The i960 @code{.extended} pseudo-op is not supported.
2260 @item @code{.list} pseudo-op.
2262 The various options of the i960 @code{.list} pseudo-op are not supported.
2264 @item @code{.optimize} pseudo-op
2266 The i960 @code{.optimize} pseudo-op is not supported.
2268 @item @code{.output} pseudo-op
2270 The i960 @code{.output} pseudo-op is not supported.
2272 @item @code{.setreal} pseudo-op
2274 The i960 @code{.setreal} pseudo-op is not supported.
2279 @section Dependency Tracking: @option{--MD}
2282 @cindex dependency tracking
2285 @command{@value{AS}} can generate a dependency file for the file it creates. This
2286 file consists of a single rule suitable for @code{make} describing the
2287 dependencies of the main source file.
2289 The rule is written to the file named in its argument.
2291 This feature is used in the automatic updating of makefiles.
2294 @section Name the Object File: @option{-o}
2297 @cindex naming object file
2298 @cindex object file name
2299 There is always one object file output when you run @command{@value{AS}}. By
2300 default it has the name
2303 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2317 You use this option (which takes exactly one filename) to give the
2318 object file a different name.
2320 Whatever the object file is called, @command{@value{AS}} overwrites any
2321 existing file of the same name.
2324 @section Join Data and Text Sections: @option{-R}
2327 @cindex data and text sections, joining
2328 @cindex text and data sections, joining
2329 @cindex joining text and data sections
2330 @cindex merging text and data sections
2331 @option{-R} tells @command{@value{AS}} to write the object file as if all
2332 data-section data lives in the text section. This is only done at
2333 the very last moment: your binary data are the same, but data
2334 section parts are relocated differently. The data section part of
2335 your object file is zero bytes long because all its bytes are
2336 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2338 When you specify @option{-R} it would be possible to generate shorter
2339 address displacements (because we do not have to cross between text and
2340 data section). We refrain from doing this simply for compatibility with
2341 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2344 When @command{@value{AS}} is configured for COFF or ELF output,
2345 this option is only useful if you use sections named @samp{.text} and
2350 @option{-R} is not supported for any of the HPPA targets. Using
2351 @option{-R} generates a warning from @command{@value{AS}}.
2355 @section Display Assembly Statistics: @option{--statistics}
2357 @kindex --statistics
2358 @cindex statistics, about assembly
2359 @cindex time, total for assembly
2360 @cindex space used, maximum for assembly
2361 Use @samp{--statistics} to display two statistics about the resources used by
2362 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2363 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2366 @node traditional-format
2367 @section Compatible Output: @option{--traditional-format}
2369 @kindex --traditional-format
2370 For some targets, the output of @command{@value{AS}} is different in some ways
2371 from the output of some existing assembler. This switch requests
2372 @command{@value{AS}} to use the traditional format instead.
2374 For example, it disables the exception frame optimizations which
2375 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2378 @section Announce Version: @option{-v}
2382 @cindex assembler version
2383 @cindex version of assembler
2384 You can find out what version of as is running by including the
2385 option @samp{-v} (which you can also spell as @samp{-version}) on the
2389 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2391 @command{@value{AS}} should never give a warning or error message when
2392 assembling compiler output. But programs written by people often
2393 cause @command{@value{AS}} to give a warning that a particular assumption was
2394 made. All such warnings are directed to the standard error file.
2398 @cindex suppressing warnings
2399 @cindex warnings, suppressing
2400 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2401 This only affects the warning messages: it does not change any particular of
2402 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2405 @kindex --fatal-warnings
2406 @cindex errors, caused by warnings
2407 @cindex warnings, causing error
2408 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2409 files that generate warnings to be in error.
2412 @cindex warnings, switching on
2413 You can switch these options off again by specifying @option{--warn}, which
2414 causes warnings to be output as usual.
2417 @section Generate Object File in Spite of Errors: @option{-Z}
2418 @cindex object file, after errors
2419 @cindex errors, continuing after
2420 After an error message, @command{@value{AS}} normally produces no output. If for
2421 some reason you are interested in object file output even after
2422 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2423 option. If there are any errors, @command{@value{AS}} continues anyways, and
2424 writes an object file after a final warning message of the form @samp{@var{n}
2425 errors, @var{m} warnings, generating bad object file.}
2430 @cindex machine-independent syntax
2431 @cindex syntax, machine-independent
2432 This chapter describes the machine-independent syntax allowed in a
2433 source file. @command{@value{AS}} syntax is similar to what many other
2434 assemblers use; it is inspired by the BSD 4.2
2439 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2443 * Preprocessing:: Preprocessing
2444 * Whitespace:: Whitespace
2445 * Comments:: Comments
2446 * Symbol Intro:: Symbols
2447 * Statements:: Statements
2448 * Constants:: Constants
2452 @section Preprocessing
2454 @cindex preprocessing
2455 The @command{@value{AS}} internal preprocessor:
2457 @cindex whitespace, removed by preprocessor
2459 adjusts and removes extra whitespace. It leaves one space or tab before
2460 the keywords on a line, and turns any other whitespace on the line into
2463 @cindex comments, removed by preprocessor
2465 removes all comments, replacing them with a single space, or an
2466 appropriate number of newlines.
2468 @cindex constants, converted by preprocessor
2470 converts character constants into the appropriate numeric values.
2473 It does not do macro processing, include file handling, or
2474 anything else you may get from your C compiler's preprocessor. You can
2475 do include file processing with the @code{.include} directive
2476 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2477 to get other ``CPP'' style preprocessing by giving the input file a
2478 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2479 Output, gcc.info, Using GNU CC}.
2481 Excess whitespace, comments, and character constants
2482 cannot be used in the portions of the input text that are not
2485 @cindex turning preprocessing on and off
2486 @cindex preprocessing, turning on and off
2489 If the first line of an input file is @code{#NO_APP} or if you use the
2490 @samp{-f} option, whitespace and comments are not removed from the input file.
2491 Within an input file, you can ask for whitespace and comment removal in
2492 specific portions of the by putting a line that says @code{#APP} before the
2493 text that may contain whitespace or comments, and putting a line that says
2494 @code{#NO_APP} after this text. This feature is mainly intend to support
2495 @code{asm} statements in compilers whose output is otherwise free of comments
2502 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2503 Whitespace is used to separate symbols, and to make programs neater for
2504 people to read. Unless within character constants
2505 (@pxref{Characters,,Character Constants}), any whitespace means the same
2506 as exactly one space.
2512 There are two ways of rendering comments to @command{@value{AS}}. In both
2513 cases the comment is equivalent to one space.
2515 Anything from @samp{/*} through the next @samp{*/} is a comment.
2516 This means you may not nest these comments.
2520 The only way to include a newline ('\n') in a comment
2521 is to use this sort of comment.
2524 /* This sort of comment does not nest. */
2527 @cindex line comment character
2528 Anything from a @dfn{line comment} character up to the next newline is
2529 considered a comment and is ignored. The line comment character is target
2530 specific, and some targets multiple comment characters. Some targets also have
2531 line comment characters that only work if they are the first character on a
2532 line. Some targets use a sequence of two characters to introduce a line
2533 comment. Some targets can also change their line comment characters depending
2534 upon command line options that have been used. For more details see the
2535 @emph{Syntax} section in the documentation for individual targets.
2537 If the line comment character is the hash sign (@samp{#}) then it still has the
2538 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2539 to specify logical line numbers:
2542 @cindex lines starting with @code{#}
2543 @cindex logical line numbers
2544 To be compatible with past assemblers, lines that begin with @samp{#} have a
2545 special interpretation. Following the @samp{#} should be an absolute
2546 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2547 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2548 new logical file name. The rest of the line, if any, should be whitespace.
2550 If the first non-whitespace characters on the line are not numeric,
2551 the line is ignored. (Just like a comment.)
2554 # This is an ordinary comment.
2555 # 42-6 "new_file_name" # New logical file name
2556 # This is logical line # 36.
2558 This feature is deprecated, and may disappear from future versions
2559 of @command{@value{AS}}.
2564 @cindex characters used in symbols
2565 @ifclear SPECIAL-SYMS
2566 A @dfn{symbol} is one or more characters chosen from the set of all
2567 letters (both upper and lower case), digits and the three characters
2573 A @dfn{symbol} is one or more characters chosen from the set of all
2574 letters (both upper and lower case), digits and the three characters
2575 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2581 On most machines, you can also use @code{$} in symbol names; exceptions
2582 are noted in @ref{Machine Dependencies}.
2584 No symbol may begin with a digit. Case is significant.
2585 There is no length limit: all characters are significant. Multibyte characters
2586 are supported. Symbols are delimited by characters not in that set, or by the
2587 beginning of a file (since the source program must end with a newline, the end
2588 of a file is not a possible symbol delimiter). @xref{Symbols}.
2589 @cindex length of symbols
2594 @cindex statements, structure of
2595 @cindex line separator character
2596 @cindex statement separator character
2598 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2599 @dfn{line separator character}. The line separator character is target
2600 specific and described in the @emph{Syntax} section of each
2601 target's documentation. Not all targets support a line separator character.
2602 The newline or line separator character is considered to be part of the
2603 preceding statement. Newlines and separators within character constants are an
2604 exception: they do not end statements.
2606 @cindex newline, required at file end
2607 @cindex EOF, newline must precede
2608 It is an error to end any statement with end-of-file: the last
2609 character of any input file should be a newline.@refill
2611 An empty statement is allowed, and may include whitespace. It is ignored.
2613 @cindex instructions and directives
2614 @cindex directives and instructions
2615 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2616 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2618 A statement begins with zero or more labels, optionally followed by a
2619 key symbol which determines what kind of statement it is. The key
2620 symbol determines the syntax of the rest of the statement. If the
2621 symbol begins with a dot @samp{.} then the statement is an assembler
2622 directive: typically valid for any computer. If the symbol begins with
2623 a letter the statement is an assembly language @dfn{instruction}: it
2624 assembles into a machine language instruction.
2626 Different versions of @command{@value{AS}} for different computers
2627 recognize different instructions. In fact, the same symbol may
2628 represent a different instruction in a different computer's assembly
2632 @cindex @code{:} (label)
2633 @cindex label (@code{:})
2634 A label is a symbol immediately followed by a colon (@code{:}).
2635 Whitespace before a label or after a colon is permitted, but you may not
2636 have whitespace between a label's symbol and its colon. @xref{Labels}.
2639 For HPPA targets, labels need not be immediately followed by a colon, but
2640 the definition of a label must begin in column zero. This also implies that
2641 only one label may be defined on each line.
2645 label: .directive followed by something
2646 another_label: # This is an empty statement.
2647 instruction operand_1, operand_2, @dots{}
2654 A constant is a number, written so that its value is known by
2655 inspection, without knowing any context. Like this:
2658 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2659 .ascii "Ring the bell\7" # A string constant.
2660 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2661 .float 0f-314159265358979323846264338327\
2662 95028841971.693993751E-40 # - pi, a flonum.
2667 * Characters:: Character Constants
2668 * Numbers:: Number Constants
2672 @subsection Character Constants
2674 @cindex character constants
2675 @cindex constants, character
2676 There are two kinds of character constants. A @dfn{character} stands
2677 for one character in one byte and its value may be used in
2678 numeric expressions. String constants (properly called string
2679 @emph{literals}) are potentially many bytes and their values may not be
2680 used in arithmetic expressions.
2684 * Chars:: Characters
2688 @subsubsection Strings
2690 @cindex string constants
2691 @cindex constants, string
2692 A @dfn{string} is written between double-quotes. It may contain
2693 double-quotes or null characters. The way to get special characters
2694 into a string is to @dfn{escape} these characters: precede them with
2695 a backslash @samp{\} character. For example @samp{\\} represents
2696 one backslash: the first @code{\} is an escape which tells
2697 @command{@value{AS}} to interpret the second character literally as a backslash
2698 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2699 escape character). The complete list of escapes follows.
2701 @cindex escape codes, character
2702 @cindex character escape codes
2705 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2707 @cindex @code{\b} (backspace character)
2708 @cindex backspace (@code{\b})
2710 Mnemonic for backspace; for ASCII this is octal code 010.
2713 @c Mnemonic for EOText; for ASCII this is octal code 004.
2715 @cindex @code{\f} (formfeed character)
2716 @cindex formfeed (@code{\f})
2718 Mnemonic for FormFeed; for ASCII this is octal code 014.
2720 @cindex @code{\n} (newline character)
2721 @cindex newline (@code{\n})
2723 Mnemonic for newline; for ASCII this is octal code 012.
2726 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2728 @cindex @code{\r} (carriage return character)
2729 @cindex carriage return (@code{\r})
2731 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2734 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2735 @c other assemblers.
2737 @cindex @code{\t} (tab)
2738 @cindex tab (@code{\t})
2740 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2743 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2744 @c @item \x @var{digit} @var{digit} @var{digit}
2745 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2747 @cindex @code{\@var{ddd}} (octal character code)
2748 @cindex octal character code (@code{\@var{ddd}})
2749 @item \ @var{digit} @var{digit} @var{digit}
2750 An octal character code. The numeric code is 3 octal digits.
2751 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2752 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2754 @cindex @code{\@var{xd...}} (hex character code)
2755 @cindex hex character code (@code{\@var{xd...}})
2756 @item \@code{x} @var{hex-digits...}
2757 A hex character code. All trailing hex digits are combined. Either upper or
2758 lower case @code{x} works.
2760 @cindex @code{\\} (@samp{\} character)
2761 @cindex backslash (@code{\\})
2763 Represents one @samp{\} character.
2766 @c Represents one @samp{'} (accent acute) character.
2767 @c This is needed in single character literals
2768 @c (@xref{Characters,,Character Constants}.) to represent
2771 @cindex @code{\"} (doublequote character)
2772 @cindex doublequote (@code{\"})
2774 Represents one @samp{"} character. Needed in strings to represent
2775 this character, because an unescaped @samp{"} would end the string.
2777 @item \ @var{anything-else}
2778 Any other character when escaped by @kbd{\} gives a warning, but
2779 assembles as if the @samp{\} was not present. The idea is that if
2780 you used an escape sequence you clearly didn't want the literal
2781 interpretation of the following character. However @command{@value{AS}} has no
2782 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2783 code and warns you of the fact.
2786 Which characters are escapable, and what those escapes represent,
2787 varies widely among assemblers. The current set is what we think
2788 the BSD 4.2 assembler recognizes, and is a subset of what most C
2789 compilers recognize. If you are in doubt, do not use an escape
2793 @subsubsection Characters
2795 @cindex single character constant
2796 @cindex character, single
2797 @cindex constant, single character
2798 A single character may be written as a single quote immediately
2799 followed by that character. The same escapes apply to characters as
2800 to strings. So if you want to write the character backslash, you
2801 must write @kbd{'\\} where the first @code{\} escapes the second
2802 @code{\}. As you can see, the quote is an acute accent, not a
2803 grave accent. A newline
2805 @ifclear abnormal-separator
2806 (or semicolon @samp{;})
2808 @ifset abnormal-separator
2810 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2815 immediately following an acute accent is taken as a literal character
2816 and does not count as the end of a statement. The value of a character
2817 constant in a numeric expression is the machine's byte-wide code for
2818 that character. @command{@value{AS}} assumes your character code is ASCII:
2819 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2822 @subsection Number Constants
2824 @cindex constants, number
2825 @cindex number constants
2826 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2827 are stored in the target machine. @emph{Integers} are numbers that
2828 would fit into an @code{int} in the C language. @emph{Bignums} are
2829 integers, but they are stored in more than 32 bits. @emph{Flonums}
2830 are floating point numbers, described below.
2833 * Integers:: Integers
2838 * Bit Fields:: Bit Fields
2844 @subsubsection Integers
2846 @cindex constants, integer
2848 @cindex binary integers
2849 @cindex integers, binary
2850 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2851 the binary digits @samp{01}.
2853 @cindex octal integers
2854 @cindex integers, octal
2855 An octal integer is @samp{0} followed by zero or more of the octal
2856 digits (@samp{01234567}).
2858 @cindex decimal integers
2859 @cindex integers, decimal
2860 A decimal integer starts with a non-zero digit followed by zero or
2861 more digits (@samp{0123456789}).
2863 @cindex hexadecimal integers
2864 @cindex integers, hexadecimal
2865 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2866 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2868 Integers have the usual values. To denote a negative integer, use
2869 the prefix operator @samp{-} discussed under expressions
2870 (@pxref{Prefix Ops,,Prefix Operators}).
2873 @subsubsection Bignums
2876 @cindex constants, bignum
2877 A @dfn{bignum} has the same syntax and semantics as an integer
2878 except that the number (or its negative) takes more than 32 bits to
2879 represent in binary. The distinction is made because in some places
2880 integers are permitted while bignums are not.
2883 @subsubsection Flonums
2885 @cindex floating point numbers
2886 @cindex constants, floating point
2888 @cindex precision, floating point
2889 A @dfn{flonum} represents a floating point number. The translation is
2890 indirect: a decimal floating point number from the text is converted by
2891 @command{@value{AS}} to a generic binary floating point number of more than
2892 sufficient precision. This generic floating point number is converted
2893 to a particular computer's floating point format (or formats) by a
2894 portion of @command{@value{AS}} specialized to that computer.
2896 A flonum is written by writing (in order)
2901 (@samp{0} is optional on the HPPA.)
2905 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2907 @kbd{e} is recommended. Case is not important.
2909 @c FIXME: verify if flonum syntax really this vague for most cases
2910 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2911 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2914 On the H8/300, Renesas / SuperH SH,
2915 and AMD 29K architectures, the letter must be
2916 one of the letters @samp{DFPRSX} (in upper or lower case).
2918 On the ARC, the letter must be one of the letters @samp{DFRS}
2919 (in upper or lower case).
2921 On the Intel 960 architecture, the letter must be
2922 one of the letters @samp{DFT} (in upper or lower case).
2924 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2928 One of the letters @samp{DFRS} (in upper or lower case).
2931 One of the letters @samp{DFPRSX} (in upper or lower case).
2934 The letter @samp{E} (upper case only).
2937 One of the letters @samp{DFT} (in upper or lower case).
2942 An optional sign: either @samp{+} or @samp{-}.
2945 An optional @dfn{integer part}: zero or more decimal digits.
2948 An optional @dfn{fractional part}: @samp{.} followed by zero
2949 or more decimal digits.
2952 An optional exponent, consisting of:
2956 An @samp{E} or @samp{e}.
2957 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2958 @c principle this can perfectly well be different on different targets.
2960 Optional sign: either @samp{+} or @samp{-}.
2962 One or more decimal digits.
2967 At least one of the integer part or the fractional part must be
2968 present. The floating point number has the usual base-10 value.
2970 @command{@value{AS}} does all processing using integers. Flonums are computed
2971 independently of any floating point hardware in the computer running
2972 @command{@value{AS}}.
2976 @c Bit fields are written as a general facility but are also controlled
2977 @c by a conditional-compilation flag---which is as of now (21mar91)
2978 @c turned on only by the i960 config of GAS.
2980 @subsubsection Bit Fields
2983 @cindex constants, bit field
2984 You can also define numeric constants as @dfn{bit fields}.
2985 Specify two numbers separated by a colon---
2987 @var{mask}:@var{value}
2990 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2993 The resulting number is then packed
2995 @c this conditional paren in case bit fields turned on elsewhere than 960
2996 (in host-dependent byte order)
2998 into a field whose width depends on which assembler directive has the
2999 bit-field as its argument. Overflow (a result from the bitwise and
3000 requiring more binary digits to represent) is not an error; instead,
3001 more constants are generated, of the specified width, beginning with the
3002 least significant digits.@refill
3004 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3005 @code{.short}, and @code{.word} accept bit-field arguments.
3010 @chapter Sections and Relocation
3015 * Secs Background:: Background
3016 * Ld Sections:: Linker Sections
3017 * As Sections:: Assembler Internal Sections
3018 * Sub-Sections:: Sub-Sections
3022 @node Secs Background
3025 Roughly, a section is a range of addresses, with no gaps; all data
3026 ``in'' those addresses is treated the same for some particular purpose.
3027 For example there may be a ``read only'' section.
3029 @cindex linker, and assembler
3030 @cindex assembler, and linker
3031 The linker @code{@value{LD}} reads many object files (partial programs) and
3032 combines their contents to form a runnable program. When @command{@value{AS}}
3033 emits an object file, the partial program is assumed to start at address 0.
3034 @code{@value{LD}} assigns the final addresses for the partial program, so that
3035 different partial programs do not overlap. This is actually an
3036 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3039 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3040 addresses. These blocks slide to their run-time addresses as rigid
3041 units; their length does not change and neither does the order of bytes
3042 within them. Such a rigid unit is called a @emph{section}. Assigning
3043 run-time addresses to sections is called @dfn{relocation}. It includes
3044 the task of adjusting mentions of object-file addresses so they refer to
3045 the proper run-time addresses.
3047 For the H8/300, and for the Renesas / SuperH SH,
3048 @command{@value{AS}} pads sections if needed to
3049 ensure they end on a word (sixteen bit) boundary.
3052 @cindex standard assembler sections
3053 An object file written by @command{@value{AS}} has at least three sections, any
3054 of which may be empty. These are named @dfn{text}, @dfn{data} and
3059 When it generates COFF or ELF output,
3061 @command{@value{AS}} can also generate whatever other named sections you specify
3062 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3063 If you do not use any directives that place output in the @samp{.text}
3064 or @samp{.data} sections, these sections still exist, but are empty.
3069 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3071 @command{@value{AS}} can also generate whatever other named sections you
3072 specify using the @samp{.space} and @samp{.subspace} directives. See
3073 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3074 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3075 assembler directives.
3078 Additionally, @command{@value{AS}} uses different names for the standard
3079 text, data, and bss sections when generating SOM output. Program text
3080 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3081 BSS into @samp{$BSS$}.
3085 Within the object file, the text section starts at address @code{0}, the
3086 data section follows, and the bss section follows the data section.
3089 When generating either SOM or ELF output files on the HPPA, the text
3090 section starts at address @code{0}, the data section at address
3091 @code{0x4000000}, and the bss section follows the data section.
3094 To let @code{@value{LD}} know which data changes when the sections are
3095 relocated, and how to change that data, @command{@value{AS}} also writes to the
3096 object file details of the relocation needed. To perform relocation
3097 @code{@value{LD}} must know, each time an address in the object
3101 Where in the object file is the beginning of this reference to
3104 How long (in bytes) is this reference?
3106 Which section does the address refer to? What is the numeric value of
3108 (@var{address}) @minus{} (@var{start-address of section})?
3111 Is the reference to an address ``Program-Counter relative''?
3114 @cindex addresses, format of
3115 @cindex section-relative addressing
3116 In fact, every address @command{@value{AS}} ever uses is expressed as
3118 (@var{section}) + (@var{offset into section})
3121 Further, most expressions @command{@value{AS}} computes have this section-relative
3124 (For some object formats, such as SOM for the HPPA, some expressions are
3125 symbol-relative instead.)
3128 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3129 @var{N} into section @var{secname}.''
3131 Apart from text, data and bss sections you need to know about the
3132 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3133 addresses in the absolute section remain unchanged. For example, address
3134 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3135 @code{@value{LD}}. Although the linker never arranges two partial programs'
3136 data sections with overlapping addresses after linking, @emph{by definition}
3137 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3138 part of a program is always the same address when the program is running as
3139 address @code{@{absolute@ 239@}} in any other part of the program.
3141 The idea of sections is extended to the @dfn{undefined} section. Any
3142 address whose section is unknown at assembly time is by definition
3143 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3144 Since numbers are always defined, the only way to generate an undefined
3145 address is to mention an undefined symbol. A reference to a named
3146 common block would be such a symbol: its value is unknown at assembly
3147 time so it has section @emph{undefined}.
3149 By analogy the word @emph{section} is used to describe groups of sections in
3150 the linked program. @code{@value{LD}} puts all partial programs' text
3151 sections in contiguous addresses in the linked program. It is
3152 customary to refer to the @emph{text section} of a program, meaning all
3153 the addresses of all partial programs' text sections. Likewise for
3154 data and bss sections.
3156 Some sections are manipulated by @code{@value{LD}}; others are invented for
3157 use of @command{@value{AS}} and have no meaning except during assembly.
3160 @section Linker Sections
3161 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3166 @cindex named sections
3167 @cindex sections, named
3168 @item named sections
3171 @cindex text section
3172 @cindex data section
3176 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3177 separate but equal sections. Anything you can say of one section is
3180 When the program is running, however, it is
3181 customary for the text section to be unalterable. The
3182 text section is often shared among processes: it contains
3183 instructions, constants and the like. The data section of a running
3184 program is usually alterable: for example, C variables would be stored
3185 in the data section.
3190 This section contains zeroed bytes when your program begins running. It
3191 is used to hold uninitialized variables or common storage. The length of
3192 each partial program's bss section is important, but because it starts
3193 out containing zeroed bytes there is no need to store explicit zero
3194 bytes in the object file. The bss section was invented to eliminate
3195 those explicit zeros from object files.
3197 @cindex absolute section
3198 @item absolute section
3199 Address 0 of this section is always ``relocated'' to runtime address 0.
3200 This is useful if you want to refer to an address that @code{@value{LD}} must
3201 not change when relocating. In this sense we speak of absolute
3202 addresses being ``unrelocatable'': they do not change during relocation.
3204 @cindex undefined section
3205 @item undefined section
3206 This ``section'' is a catch-all for address references to objects not in
3207 the preceding sections.
3208 @c FIXME: ref to some other doc on obj-file formats could go here.
3211 @cindex relocation example
3212 An idealized example of three relocatable sections follows.
3214 The example uses the traditional section names @samp{.text} and @samp{.data}.
3216 Memory addresses are on the horizontal axis.
3220 @c END TEXI2ROFF-KILL
3223 partial program # 1: |ttttt|dddd|00|
3230 partial program # 2: |TTT|DDD|000|
3233 +--+---+-----+--+----+---+-----+~~
3234 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3235 +--+---+-----+--+----+---+-----+~~
3237 addresses: 0 @dots{}
3244 \line{\it Partial program \#1: \hfil}
3245 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3246 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3248 \line{\it Partial program \#2: \hfil}
3249 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3250 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3252 \line{\it linked program: \hfil}
3253 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3254 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3255 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3256 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3258 \line{\it addresses: \hfil}
3262 @c END TEXI2ROFF-KILL
3265 @section Assembler Internal Sections
3267 @cindex internal assembler sections
3268 @cindex sections in messages, internal
3269 These sections are meant only for the internal use of @command{@value{AS}}. They
3270 have no meaning at run-time. You do not really need to know about these
3271 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3272 warning messages, so it might be helpful to have an idea of their
3273 meanings to @command{@value{AS}}. These sections are used to permit the
3274 value of every expression in your assembly language program to be a
3275 section-relative address.
3278 @cindex assembler internal logic error
3279 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3280 An internal assembler logic error has been found. This means there is a
3281 bug in the assembler.
3283 @cindex expr (internal section)
3285 The assembler stores complex expression internally as combinations of
3286 symbols. When it needs to represent an expression as a symbol, it puts
3287 it in the expr section.
3289 @c FIXME item transfer[t] vector preload
3290 @c FIXME item transfer[t] vector postload
3291 @c FIXME item register
3295 @section Sub-Sections
3297 @cindex numbered subsections
3298 @cindex grouping data
3304 fall into two sections: text and data.
3306 You may have separate groups of
3308 data in named sections
3312 data in named sections
3318 that you want to end up near to each other in the object file, even though they
3319 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3320 use @dfn{subsections} for this purpose. Within each section, there can be
3321 numbered subsections with values from 0 to 8192. Objects assembled into the
3322 same subsection go into the object file together with other objects in the same
3323 subsection. For example, a compiler might want to store constants in the text
3324 section, but might not want to have them interspersed with the program being
3325 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3326 section of code being output, and a @samp{.text 1} before each group of
3327 constants being output.
3329 Subsections are optional. If you do not use subsections, everything
3330 goes in subsection number zero.
3333 Each subsection is zero-padded up to a multiple of four bytes.
3334 (Subsections may be padded a different amount on different flavors
3335 of @command{@value{AS}}.)
3339 On the H8/300 platform, each subsection is zero-padded to a word
3340 boundary (two bytes).
3341 The same is true on the Renesas SH.
3344 @c FIXME section padding (alignment)?
3345 @c Rich Pixley says padding here depends on target obj code format; that
3346 @c doesn't seem particularly useful to say without further elaboration,
3347 @c so for now I say nothing about it. If this is a generic BFD issue,
3348 @c these paragraphs might need to vanish from this manual, and be
3349 @c discussed in BFD chapter of binutils (or some such).
3353 Subsections appear in your object file in numeric order, lowest numbered
3354 to highest. (All this to be compatible with other people's assemblers.)
3355 The object file contains no representation of subsections; @code{@value{LD}} and
3356 other programs that manipulate object files see no trace of them.
3357 They just see all your text subsections as a text section, and all your
3358 data subsections as a data section.
3360 To specify which subsection you want subsequent statements assembled
3361 into, use a numeric argument to specify it, in a @samp{.text
3362 @var{expression}} or a @samp{.data @var{expression}} statement.
3365 When generating COFF output, you
3370 can also use an extra subsection
3371 argument with arbitrary named sections: @samp{.section @var{name},
3376 When generating ELF output, you
3381 can also use the @code{.subsection} directive (@pxref{SubSection})
3382 to specify a subsection: @samp{.subsection @var{expression}}.
3384 @var{Expression} should be an absolute expression
3385 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3386 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3387 begins in @code{text 0}. For instance:
3389 .text 0 # The default subsection is text 0 anyway.
3390 .ascii "This lives in the first text subsection. *"
3392 .ascii "But this lives in the second text subsection."
3394 .ascii "This lives in the data section,"
3395 .ascii "in the first data subsection."
3397 .ascii "This lives in the first text section,"
3398 .ascii "immediately following the asterisk (*)."
3401 Each section has a @dfn{location counter} incremented by one for every byte
3402 assembled into that section. Because subsections are merely a convenience
3403 restricted to @command{@value{AS}} there is no concept of a subsection location
3404 counter. There is no way to directly manipulate a location counter---but the
3405 @code{.align} directive changes it, and any label definition captures its
3406 current value. The location counter of the section where statements are being
3407 assembled is said to be the @dfn{active} location counter.
3410 @section bss Section
3413 @cindex common variable storage
3414 The bss section is used for local common variable storage.
3415 You may allocate address space in the bss section, but you may
3416 not dictate data to load into it before your program executes. When
3417 your program starts running, all the contents of the bss
3418 section are zeroed bytes.
3420 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3421 @ref{Lcomm,,@code{.lcomm}}.
3423 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3424 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3427 When assembling for a target which supports multiple sections, such as ELF or
3428 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3429 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3430 section. Typically the section will only contain symbol definitions and
3431 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3438 Symbols are a central concept: the programmer uses symbols to name
3439 things, the linker uses symbols to link, and the debugger uses symbols
3443 @cindex debuggers, and symbol order
3444 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3445 the same order they were declared. This may break some debuggers.
3450 * Setting Symbols:: Giving Symbols Other Values
3451 * Symbol Names:: Symbol Names
3452 * Dot:: The Special Dot Symbol
3453 * Symbol Attributes:: Symbol Attributes
3460 A @dfn{label} is written as a symbol immediately followed by a colon
3461 @samp{:}. The symbol then represents the current value of the
3462 active location counter, and is, for example, a suitable instruction
3463 operand. You are warned if you use the same symbol to represent two
3464 different locations: the first definition overrides any other
3468 On the HPPA, the usual form for a label need not be immediately followed by a
3469 colon, but instead must start in column zero. Only one label may be defined on
3470 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3471 provides a special directive @code{.label} for defining labels more flexibly.
3474 @node Setting Symbols
3475 @section Giving Symbols Other Values
3477 @cindex assigning values to symbols
3478 @cindex symbol values, assigning
3479 A symbol can be given an arbitrary value by writing a symbol, followed
3480 by an equals sign @samp{=}, followed by an expression
3481 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3482 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3483 equals sign @samp{=}@samp{=} here represents an equivalent of the
3484 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3487 Blackfin does not support symbol assignment with @samp{=}.
3491 @section Symbol Names
3493 @cindex symbol names
3494 @cindex names, symbol
3495 @ifclear SPECIAL-SYMS
3496 Symbol names begin with a letter or with one of @samp{._}. On most
3497 machines, you can also use @code{$} in symbol names; exceptions are
3498 noted in @ref{Machine Dependencies}. That character may be followed by any
3499 string of digits, letters, dollar signs (unless otherwise noted for a
3500 particular target machine), and underscores.
3504 Symbol names begin with a letter or with one of @samp{._}. On the
3505 Renesas SH you can also use @code{$} in symbol names. That
3506 character may be followed by any string of digits, letters, dollar signs (save
3507 on the H8/300), and underscores.
3511 Case of letters is significant: @code{foo} is a different symbol name
3514 Multibyte characters are supported. To generate a symbol name containing
3515 multibyte characters enclose it within double quotes and use escape codes. cf
3516 @xref{Strings}. Generating a multibyte symbol name from a label is not
3517 currently supported.
3519 Each symbol has exactly one name. Each name in an assembly language program
3520 refers to exactly one symbol. You may use that symbol name any number of times
3523 @subheading Local Symbol Names
3525 @cindex local symbol names
3526 @cindex symbol names, local
3527 A local symbol is any symbol beginning with certain local label prefixes.
3528 By default, the local label prefix is @samp{.L} for ELF systems or
3529 @samp{L} for traditional a.out systems, but each target may have its own
3530 set of local label prefixes.
3532 On the HPPA local symbols begin with @samp{L$}.
3535 Local symbols are defined and used within the assembler, but they are
3536 normally not saved in object files. Thus, they are not visible when debugging.
3537 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3538 @option{-L}}) to retain the local symbols in the object files.
3540 @subheading Local Labels
3542 @cindex local labels
3543 @cindex temporary symbol names
3544 @cindex symbol names, temporary
3545 Local labels help compilers and programmers use names temporarily.
3546 They create symbols which are guaranteed to be unique over the entire scope of
3547 the input source code and which can be referred to by a simple notation.
3548 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3549 represents any positive integer). To refer to the most recent previous
3550 definition of that label write @samp{@b{N}b}, using the same number as when
3551 you defined the label. To refer to the next definition of a local label, write
3552 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3555 There is no restriction on how you can use these labels, and you can reuse them
3556 too. So that it is possible to repeatedly define the same local label (using
3557 the same number @samp{@b{N}}), although you can only refer to the most recently
3558 defined local label of that number (for a backwards reference) or the next
3559 definition of a specific local label for a forward reference. It is also worth
3560 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3561 implemented in a slightly more efficient manner than the others.
3572 Which is the equivalent of:
3575 label_1: branch label_3
3576 label_2: branch label_1
3577 label_3: branch label_4
3578 label_4: branch label_3
3581 Local label names are only a notational device. They are immediately
3582 transformed into more conventional symbol names before the assembler uses them.
3583 The symbol names are stored in the symbol table, appear in error messages, and
3584 are optionally emitted to the object file. The names are constructed using
3588 @item @emph{local label prefix}
3589 All local symbols begin with the system-specific local label prefix.
3590 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3591 that start with the local label prefix. These labels are
3592 used for symbols you are never intended to see. If you use the
3593 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3594 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3595 you may use them in debugging.
3598 This is the number that was used in the local label definition. So if the
3599 label is written @samp{55:} then the number is @samp{55}.
3602 This unusual character is included so you do not accidentally invent a symbol
3603 of the same name. The character has ASCII value of @samp{\002} (control-B).
3605 @item @emph{ordinal number}
3606 This is a serial number to keep the labels distinct. The first definition of
3607 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3608 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3609 the number @samp{1} and its 15th definition gets @samp{15} as well.
3612 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3613 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3615 @subheading Dollar Local Labels
3616 @cindex dollar local symbols
3618 @code{@value{AS}} also supports an even more local form of local labels called
3619 dollar labels. These labels go out of scope (i.e., they become undefined) as
3620 soon as a non-local label is defined. Thus they remain valid for only a small
3621 region of the input source code. Normal local labels, by contrast, remain in
3622 scope for the entire file, or until they are redefined by another occurrence of
3623 the same local label.
3625 Dollar labels are defined in exactly the same way as ordinary local labels,
3626 except that they have a dollar sign suffix to their numeric value, e.g.,
3629 They can also be distinguished from ordinary local labels by their transformed
3630 names which use ASCII character @samp{\001} (control-A) as the magic character
3631 to distinguish them from ordinary labels. For example, the fifth definition of
3632 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3635 @section The Special Dot Symbol
3637 @cindex dot (symbol)
3638 @cindex @code{.} (symbol)
3639 @cindex current address
3640 @cindex location counter
3641 The special symbol @samp{.} refers to the current address that
3642 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3643 .long .} defines @code{melvin} to contain its own address.
3644 Assigning a value to @code{.} is treated the same as a @code{.org}
3646 @ifclear no-space-dir
3647 Thus, the expression @samp{.=.+4} is the same as saying
3651 @node Symbol Attributes
3652 @section Symbol Attributes
3654 @cindex symbol attributes
3655 @cindex attributes, symbol
3656 Every symbol has, as well as its name, the attributes ``Value'' and
3657 ``Type''. Depending on output format, symbols can also have auxiliary
3660 The detailed definitions are in @file{a.out.h}.
3663 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3664 all these attributes, and probably won't warn you. This makes the
3665 symbol an externally defined symbol, which is generally what you
3669 * Symbol Value:: Value
3670 * Symbol Type:: Type
3673 * a.out Symbols:: Symbol Attributes: @code{a.out}
3677 * a.out Symbols:: Symbol Attributes: @code{a.out}
3680 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3685 * COFF Symbols:: Symbol Attributes for COFF
3688 * SOM Symbols:: Symbol Attributes for SOM
3695 @cindex value of a symbol
3696 @cindex symbol value
3697 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3698 location in the text, data, bss or absolute sections the value is the
3699 number of addresses from the start of that section to the label.
3700 Naturally for text, data and bss sections the value of a symbol changes
3701 as @code{@value{LD}} changes section base addresses during linking. Absolute
3702 symbols' values do not change during linking: that is why they are
3705 The value of an undefined symbol is treated in a special way. If it is
3706 0 then the symbol is not defined in this assembler source file, and
3707 @code{@value{LD}} tries to determine its value from other files linked into the
3708 same program. You make this kind of symbol simply by mentioning a symbol
3709 name without defining it. A non-zero value represents a @code{.comm}
3710 common declaration. The value is how much common storage to reserve, in
3711 bytes (addresses). The symbol refers to the first address of the
3717 @cindex type of a symbol
3719 The type attribute of a symbol contains relocation (section)
3720 information, any flag settings indicating that a symbol is external, and
3721 (optionally), other information for linkers and debuggers. The exact
3722 format depends on the object-code output format in use.
3727 @c The following avoids a "widow" subsection title. @group would be
3728 @c better if it were available outside examples.
3731 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3733 @cindex @code{b.out} symbol attributes
3734 @cindex symbol attributes, @code{b.out}
3735 These symbol attributes appear only when @command{@value{AS}} is configured for
3736 one of the Berkeley-descended object output formats---@code{a.out} or
3742 @subsection Symbol Attributes: @code{a.out}
3744 @cindex @code{a.out} symbol attributes
3745 @cindex symbol attributes, @code{a.out}
3751 @subsection Symbol Attributes: @code{a.out}
3753 @cindex @code{a.out} symbol attributes
3754 @cindex symbol attributes, @code{a.out}
3758 * Symbol Desc:: Descriptor
3759 * Symbol Other:: Other
3763 @subsubsection Descriptor
3765 @cindex descriptor, of @code{a.out} symbol
3766 This is an arbitrary 16-bit value. You may establish a symbol's
3767 descriptor value by using a @code{.desc} statement
3768 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3769 @command{@value{AS}}.
3772 @subsubsection Other
3774 @cindex other attribute, of @code{a.out} symbol
3775 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3780 @subsection Symbol Attributes for COFF
3782 @cindex COFF symbol attributes
3783 @cindex symbol attributes, COFF
3785 The COFF format supports a multitude of auxiliary symbol attributes;
3786 like the primary symbol attributes, they are set between @code{.def} and
3787 @code{.endef} directives.
3789 @subsubsection Primary Attributes
3791 @cindex primary attributes, COFF symbols
3792 The symbol name is set with @code{.def}; the value and type,
3793 respectively, with @code{.val} and @code{.type}.
3795 @subsubsection Auxiliary Attributes
3797 @cindex auxiliary attributes, COFF symbols
3798 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3799 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3800 table information for COFF.
3805 @subsection Symbol Attributes for SOM
3807 @cindex SOM symbol attributes
3808 @cindex symbol attributes, SOM
3810 The SOM format for the HPPA supports a multitude of symbol attributes set with
3811 the @code{.EXPORT} and @code{.IMPORT} directives.
3813 The attributes are described in @cite{HP9000 Series 800 Assembly
3814 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3815 @code{EXPORT} assembler directive documentation.
3819 @chapter Expressions
3823 @cindex numeric values
3824 An @dfn{expression} specifies an address or numeric value.
3825 Whitespace may precede and/or follow an expression.
3827 The result of an expression must be an absolute number, or else an offset into
3828 a particular section. If an expression is not absolute, and there is not
3829 enough information when @command{@value{AS}} sees the expression to know its
3830 section, a second pass over the source program might be necessary to interpret
3831 the expression---but the second pass is currently not implemented.
3832 @command{@value{AS}} aborts with an error message in this situation.
3835 * Empty Exprs:: Empty Expressions
3836 * Integer Exprs:: Integer Expressions
3840 @section Empty Expressions
3842 @cindex empty expressions
3843 @cindex expressions, empty
3844 An empty expression has no value: it is just whitespace or null.
3845 Wherever an absolute expression is required, you may omit the
3846 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3847 is compatible with other assemblers.
3850 @section Integer Expressions
3852 @cindex integer expressions
3853 @cindex expressions, integer
3854 An @dfn{integer expression} is one or more @emph{arguments} delimited
3855 by @emph{operators}.
3858 * Arguments:: Arguments
3859 * Operators:: Operators
3860 * Prefix Ops:: Prefix Operators
3861 * Infix Ops:: Infix Operators
3865 @subsection Arguments
3867 @cindex expression arguments
3868 @cindex arguments in expressions
3869 @cindex operands in expressions
3870 @cindex arithmetic operands
3871 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3872 contexts arguments are sometimes called ``arithmetic operands''. In
3873 this manual, to avoid confusing them with the ``instruction operands'' of
3874 the machine language, we use the term ``argument'' to refer to parts of
3875 expressions only, reserving the word ``operand'' to refer only to machine
3876 instruction operands.
3878 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3879 @var{section} is one of text, data, bss, absolute,
3880 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3883 Numbers are usually integers.
3885 A number can be a flonum or bignum. In this case, you are warned
3886 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3887 these 32 bits are an integer. You may write integer-manipulating
3888 instructions that act on exotic constants, compatible with other
3891 @cindex subexpressions
3892 Subexpressions are a left parenthesis @samp{(} followed by an integer
3893 expression, followed by a right parenthesis @samp{)}; or a prefix
3894 operator followed by an argument.
3897 @subsection Operators
3899 @cindex operators, in expressions
3900 @cindex arithmetic functions
3901 @cindex functions, in expressions
3902 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3903 operators are followed by an argument. Infix operators appear
3904 between their arguments. Operators may be preceded and/or followed by
3908 @subsection Prefix Operator
3910 @cindex prefix operators
3911 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3912 one argument, which must be absolute.
3914 @c the tex/end tex stuff surrounding this small table is meant to make
3915 @c it align, on the printed page, with the similar table in the next
3916 @c section (which is inside an enumerate).
3918 \global\advance\leftskip by \itemindent
3923 @dfn{Negation}. Two's complement negation.
3925 @dfn{Complementation}. Bitwise not.
3929 \global\advance\leftskip by -\itemindent
3933 @subsection Infix Operators
3935 @cindex infix operators
3936 @cindex operators, permitted arguments
3937 @dfn{Infix operators} take two arguments, one on either side. Operators
3938 have precedence, but operations with equal precedence are performed left
3939 to right. Apart from @code{+} or @option{-}, both arguments must be
3940 absolute, and the result is absolute.
3943 @cindex operator precedence
3944 @cindex precedence of operators
3951 @dfn{Multiplication}.
3954 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3960 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3963 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3967 Intermediate precedence
3972 @dfn{Bitwise Inclusive Or}.
3978 @dfn{Bitwise Exclusive Or}.
3981 @dfn{Bitwise Or Not}.
3988 @cindex addition, permitted arguments
3989 @cindex plus, permitted arguments
3990 @cindex arguments for addition
3992 @dfn{Addition}. If either argument is absolute, the result has the section of
3993 the other argument. You may not add together arguments from different
3996 @cindex subtraction, permitted arguments
3997 @cindex minus, permitted arguments
3998 @cindex arguments for subtraction
4000 @dfn{Subtraction}. If the right argument is absolute, the
4001 result has the section of the left argument.
4002 If both arguments are in the same section, the result is absolute.
4003 You may not subtract arguments from different sections.
4004 @c FIXME is there still something useful to say about undefined - undefined ?
4006 @cindex comparison expressions
4007 @cindex expressions, comparison
4012 @dfn{Is Not Equal To}
4016 @dfn{Is Greater Than}
4018 @dfn{Is Greater Than Or Equal To}
4020 @dfn{Is Less Than Or Equal To}
4022 The comparison operators can be used as infix operators. A true results has a
4023 value of -1 whereas a false result has a value of 0. Note, these operators
4024 perform signed comparisons.
4027 @item Lowest Precedence
4036 These two logical operations can be used to combine the results of sub
4037 expressions. Note, unlike the comparison operators a true result returns a
4038 value of 1 but a false results does still return 0. Also note that the logical
4039 or operator has a slightly lower precedence than logical and.
4044 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4045 address; you can only have a defined section in one of the two arguments.
4048 @chapter Assembler Directives
4050 @cindex directives, machine independent
4051 @cindex pseudo-ops, machine independent
4052 @cindex machine independent directives
4053 All assembler directives have names that begin with a period (@samp{.}).
4054 The rest of the name is letters, usually in lower case.
4056 This chapter discusses directives that are available regardless of the
4057 target machine configuration for the @sc{gnu} assembler.
4059 Some machine configurations provide additional directives.
4060 @xref{Machine Dependencies}.
4063 @ifset machine-directives
4064 @xref{Machine Dependencies}, for additional directives.
4069 * Abort:: @code{.abort}
4071 * ABORT (COFF):: @code{.ABORT}
4074 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4075 * Altmacro:: @code{.altmacro}
4076 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4077 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4078 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4079 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4080 * Byte:: @code{.byte @var{expressions}}
4081 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4082 * Comm:: @code{.comm @var{symbol} , @var{length} }
4083 * Data:: @code{.data @var{subsection}}
4085 * Def:: @code{.def @var{name}}
4088 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4094 * Double:: @code{.double @var{flonums}}
4095 * Eject:: @code{.eject}
4096 * Else:: @code{.else}
4097 * Elseif:: @code{.elseif}
4100 * Endef:: @code{.endef}
4103 * Endfunc:: @code{.endfunc}
4104 * Endif:: @code{.endif}
4105 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4106 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4107 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4109 * Error:: @code{.error @var{string}}
4110 * Exitm:: @code{.exitm}
4111 * Extern:: @code{.extern}
4112 * Fail:: @code{.fail}
4113 * File:: @code{.file}
4114 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4115 * Float:: @code{.float @var{flonums}}
4116 * Func:: @code{.func}
4117 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4119 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4120 * Hidden:: @code{.hidden @var{names}}
4123 * hword:: @code{.hword @var{expressions}}
4124 * Ident:: @code{.ident}
4125 * If:: @code{.if @var{absolute expression}}
4126 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4127 * Include:: @code{.include "@var{file}"}
4128 * Int:: @code{.int @var{expressions}}
4130 * Internal:: @code{.internal @var{names}}
4133 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4134 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4135 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4136 * Lflags:: @code{.lflags}
4137 @ifclear no-line-dir
4138 * Line:: @code{.line @var{line-number}}
4141 * Linkonce:: @code{.linkonce [@var{type}]}
4142 * List:: @code{.list}
4143 * Ln:: @code{.ln @var{line-number}}
4144 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4145 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4147 * Local:: @code{.local @var{names}}
4150 * Long:: @code{.long @var{expressions}}
4152 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4155 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4156 * MRI:: @code{.mri @var{val}}
4157 * Noaltmacro:: @code{.noaltmacro}
4158 * Nolist:: @code{.nolist}
4159 * Octa:: @code{.octa @var{bignums}}
4160 * Offset:: @code{.offset @var{loc}}
4161 * Org:: @code{.org @var{new-lc}, @var{fill}}
4162 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4164 * PopSection:: @code{.popsection}
4165 * Previous:: @code{.previous}
4168 * Print:: @code{.print @var{string}}
4170 * Protected:: @code{.protected @var{names}}
4173 * Psize:: @code{.psize @var{lines}, @var{columns}}
4174 * Purgem:: @code{.purgem @var{name}}
4176 * PushSection:: @code{.pushsection @var{name}}
4179 * Quad:: @code{.quad @var{bignums}}
4180 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4181 * Rept:: @code{.rept @var{count}}
4182 * Sbttl:: @code{.sbttl "@var{subheading}"}
4184 * Scl:: @code{.scl @var{class}}
4187 * Section:: @code{.section @var{name}[, @var{flags}]}
4190 * Set:: @code{.set @var{symbol}, @var{expression}}
4191 * Short:: @code{.short @var{expressions}}
4192 * Single:: @code{.single @var{flonums}}
4194 * Size:: @code{.size [@var{name} , @var{expression}]}
4196 @ifclear no-space-dir
4197 * Skip:: @code{.skip @var{size} , @var{fill}}
4200 * Sleb128:: @code{.sleb128 @var{expressions}}
4201 @ifclear no-space-dir
4202 * Space:: @code{.space @var{size} , @var{fill}}
4205 * Stab:: @code{.stabd, .stabn, .stabs}
4208 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4209 * Struct:: @code{.struct @var{expression}}
4211 * SubSection:: @code{.subsection}
4212 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4216 * Tag:: @code{.tag @var{structname}}
4219 * Text:: @code{.text @var{subsection}}
4220 * Title:: @code{.title "@var{heading}"}
4222 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4225 * Uleb128:: @code{.uleb128 @var{expressions}}
4227 * Val:: @code{.val @var{addr}}
4231 * Version:: @code{.version "@var{string}"}
4232 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4233 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4236 * Warning:: @code{.warning @var{string}}
4237 * Weak:: @code{.weak @var{names}}
4238 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4239 * Word:: @code{.word @var{expressions}}
4240 * Deprecated:: Deprecated Directives
4244 @section @code{.abort}
4246 @cindex @code{abort} directive
4247 @cindex stopping the assembly
4248 This directive stops the assembly immediately. It is for
4249 compatibility with other assemblers. The original idea was that the
4250 assembly language source would be piped into the assembler. If the sender
4251 of the source quit, it could use this directive tells @command{@value{AS}} to
4252 quit also. One day @code{.abort} will not be supported.
4256 @section @code{.ABORT} (COFF)
4258 @cindex @code{ABORT} directive
4259 When producing COFF output, @command{@value{AS}} accepts this directive as a
4260 synonym for @samp{.abort}.
4263 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4269 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4271 @cindex padding the location counter
4272 @cindex @code{align} directive
4273 Pad the location counter (in the current subsection) to a particular storage
4274 boundary. The first expression (which must be absolute) is the alignment
4275 required, as described below.
4277 The second expression (also absolute) gives the fill value to be stored in the
4278 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4279 padding bytes are normally zero. However, on some systems, if the section is
4280 marked as containing code and the fill value is omitted, the space is filled
4281 with no-op instructions.
4283 The third expression is also absolute, and is also optional. If it is present,
4284 it is the maximum number of bytes that should be skipped by this alignment
4285 directive. If doing the alignment would require skipping more bytes than the
4286 specified maximum, then the alignment is not done at all. You can omit the
4287 fill value (the second argument) entirely by simply using two commas after the
4288 required alignment; this can be useful if you want the alignment to be filled
4289 with no-op instructions when appropriate.
4291 The way the required alignment is specified varies from system to system.
4292 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4293 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4294 alignment request in bytes. For example @samp{.align 8} advances
4295 the location counter until it is a multiple of 8. If the location counter
4296 is already a multiple of 8, no change is needed. For the tic54x, the
4297 first expression is the alignment request in words.
4299 For other systems, including ppc, i386 using a.out format, arm and
4300 strongarm, it is the
4301 number of low-order zero bits the location counter must have after
4302 advancement. For example @samp{.align 3} advances the location
4303 counter until it a multiple of 8. If the location counter is already a
4304 multiple of 8, no change is needed.
4306 This inconsistency is due to the different behaviors of the various
4307 native assemblers for these systems which GAS must emulate.
4308 GAS also provides @code{.balign} and @code{.p2align} directives,
4309 described later, which have a consistent behavior across all
4310 architectures (but are specific to GAS).
4313 @section @code{.altmacro}
4314 Enable alternate macro mode, enabling:
4317 @item LOCAL @var{name} [ , @dots{} ]
4318 One additional directive, @code{LOCAL}, is available. It is used to
4319 generate a string replacement for each of the @var{name} arguments, and
4320 replace any instances of @var{name} in each macro expansion. The
4321 replacement string is unique in the assembly, and different for each
4322 separate macro expansion. @code{LOCAL} allows you to write macros that
4323 define symbols, without fear of conflict between separate macro expansions.
4325 @item String delimiters
4326 You can write strings delimited in these other ways besides
4327 @code{"@var{string}"}:
4330 @item '@var{string}'
4331 You can delimit strings with single-quote characters.
4333 @item <@var{string}>
4334 You can delimit strings with matching angle brackets.
4337 @item single-character string escape
4338 To include any single character literally in a string (even if the
4339 character would otherwise have some special meaning), you can prefix the
4340 character with @samp{!} (an exclamation mark). For example, you can
4341 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4343 @item Expression results as strings
4344 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4345 and use the result as a string.
4349 @section @code{.ascii "@var{string}"}@dots{}
4351 @cindex @code{ascii} directive
4352 @cindex string literals
4353 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4354 separated by commas. It assembles each string (with no automatic
4355 trailing zero byte) into consecutive addresses.
4358 @section @code{.asciz "@var{string}"}@dots{}
4360 @cindex @code{asciz} directive
4361 @cindex zero-terminated strings
4362 @cindex null-terminated strings
4363 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4364 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4367 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4369 @cindex padding the location counter given number of bytes
4370 @cindex @code{balign} directive
4371 Pad the location counter (in the current subsection) to a particular
4372 storage boundary. The first expression (which must be absolute) is the
4373 alignment request in bytes. For example @samp{.balign 8} advances
4374 the location counter until it is a multiple of 8. If the location counter
4375 is already a multiple of 8, no change is needed.
4377 The second expression (also absolute) gives the fill value to be stored in the
4378 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4379 padding bytes are normally zero. However, on some systems, if the section is
4380 marked as containing code and the fill value is omitted, the space is filled
4381 with no-op instructions.
4383 The third expression is also absolute, and is also optional. If it is present,
4384 it is the maximum number of bytes that should be skipped by this alignment
4385 directive. If doing the alignment would require skipping more bytes than the
4386 specified maximum, then the alignment is not done at all. You can omit the
4387 fill value (the second argument) entirely by simply using two commas after the
4388 required alignment; this can be useful if you want the alignment to be filled
4389 with no-op instructions when appropriate.
4391 @cindex @code{balignw} directive
4392 @cindex @code{balignl} directive
4393 The @code{.balignw} and @code{.balignl} directives are variants of the
4394 @code{.balign} directive. The @code{.balignw} directive treats the fill
4395 pattern as a two byte word value. The @code{.balignl} directives treats the
4396 fill pattern as a four byte longword value. For example, @code{.balignw
4397 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4398 filled in with the value 0x368d (the exact placement of the bytes depends upon
4399 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4402 @node Bundle directives
4403 @section @code{.bundle_align_mode @var{abs-expr}}
4404 @cindex @code{bundle_align_mode} directive
4406 @cindex instruction bundle
4407 @cindex aligned instruction bundle
4408 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4409 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4410 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4411 disabled (which is the default state). If the argument it not zero, it
4412 gives the size of an instruction bundle as a power of two (as for the
4413 @code{.p2align} directive, @pxref{P2align}).
4415 For some targets, it's an ABI requirement that no instruction may span a
4416 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4417 instructions that starts on an aligned boundary. For example, if
4418 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4419 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4420 effect, no single instruction may span a boundary between bundles. If an
4421 instruction would start too close to the end of a bundle for the length of
4422 that particular instruction to fit within the bundle, then the space at the
4423 end of that bundle is filled with no-op instructions so the instruction
4424 starts in the next bundle. As a corollary, it's an error if any single
4425 instruction's encoding is longer than the bundle size.
4427 @section @code{.bundle_lock} and @code{.bundle_unlock}
4428 @cindex @code{bundle_lock} directive
4429 @cindex @code{bundle_unlock} directive
4430 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4431 allow explicit control over instruction bundle padding. These directives
4432 are only valid when @code{.bundle_align_mode} has been used to enable
4433 aligned instruction bundle mode. It's an error if they appear when
4434 @code{.bundle_align_mode} has not been used at all, or when the last
4435 directive was @w{@code{.bundle_align_mode 0}}.
4437 @cindex bundle-locked
4438 For some targets, it's an ABI requirement that certain instructions may
4439 appear only as part of specified permissible sequences of multiple
4440 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4441 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4442 instruction sequence. For purposes of aligned instruction bundle mode, a
4443 sequence starting with @code{.bundle_lock} and ending with
4444 @code{.bundle_unlock} is treated as a single instruction. That is, the
4445 entire sequence must fit into a single bundle and may not span a bundle
4446 boundary. If necessary, no-op instructions will be inserted before the
4447 first instruction of the sequence so that the whole sequence starts on an
4448 aligned bundle boundary. It's an error if the sequence is longer than the
4451 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4452 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4453 nested. That is, a second @code{.bundle_lock} directive before the next
4454 @code{.bundle_unlock} directive has no effect except that it must be
4455 matched by another closing @code{.bundle_unlock} so that there is the
4456 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4459 @section @code{.byte @var{expressions}}
4461 @cindex @code{byte} directive
4462 @cindex integers, one byte
4463 @code{.byte} expects zero or more expressions, separated by commas.
4464 Each expression is assembled into the next byte.
4466 @node CFI directives
4467 @section @code{.cfi_sections @var{section_list}}
4468 @cindex @code{cfi_sections} directive
4469 @code{.cfi_sections} may be used to specify whether CFI directives
4470 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4471 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4472 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4473 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4474 directive is not used is @code{.cfi_sections .eh_frame}.
4476 @section @code{.cfi_startproc [simple]}
4477 @cindex @code{cfi_startproc} directive
4478 @code{.cfi_startproc} is used at the beginning of each function that
4479 should have an entry in @code{.eh_frame}. It initializes some internal
4480 data structures. Don't forget to close the function by
4481 @code{.cfi_endproc}.
4483 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4484 it also emits some architecture dependent initial CFI instructions.
4486 @section @code{.cfi_endproc}
4487 @cindex @code{cfi_endproc} directive
4488 @code{.cfi_endproc} is used at the end of a function where it closes its
4489 unwind entry previously opened by
4490 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4492 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4493 @code{.cfi_personality} defines personality routine and its encoding.
4494 @var{encoding} must be a constant determining how the personality
4495 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4496 argument is not present, otherwise second argument should be
4497 a constant or a symbol name. When using indirect encodings,
4498 the symbol provided should be the location where personality
4499 can be loaded from, not the personality routine itself.
4500 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4501 no personality routine.
4503 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4504 @code{.cfi_lsda} defines LSDA and its encoding.
4505 @var{encoding} must be a constant determining how the LSDA
4506 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4507 argument is not present, otherwise second argument should be a constant
4508 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4511 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4512 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4513 address from @var{register} and add @var{offset} to it}.
4515 @section @code{.cfi_def_cfa_register @var{register}}
4516 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4517 now on @var{register} will be used instead of the old one. Offset
4520 @section @code{.cfi_def_cfa_offset @var{offset}}
4521 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4522 remains the same, but @var{offset} is new. Note that it is the
4523 absolute offset that will be added to a defined register to compute
4526 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4527 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4528 value that is added/substracted from the previous offset.
4530 @section @code{.cfi_offset @var{register}, @var{offset}}
4531 Previous value of @var{register} is saved at offset @var{offset} from
4534 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4535 Previous value of @var{register} is saved at offset @var{offset} from
4536 the current CFA register. This is transformed to @code{.cfi_offset}
4537 using the known displacement of the CFA register from the CFA.
4538 This is often easier to use, because the number will match the
4539 code it's annotating.
4541 @section @code{.cfi_register @var{register1}, @var{register2}}
4542 Previous value of @var{register1} is saved in register @var{register2}.
4544 @section @code{.cfi_restore @var{register}}
4545 @code{.cfi_restore} says that the rule for @var{register} is now the
4546 same as it was at the beginning of the function, after all initial
4547 instruction added by @code{.cfi_startproc} were executed.
4549 @section @code{.cfi_undefined @var{register}}
4550 From now on the previous value of @var{register} can't be restored anymore.
4552 @section @code{.cfi_same_value @var{register}}
4553 Current value of @var{register} is the same like in the previous frame,
4554 i.e. no restoration needed.
4556 @section @code{.cfi_remember_state},
4557 First save all current rules for all registers by @code{.cfi_remember_state},
4558 then totally screw them up by subsequent @code{.cfi_*} directives and when
4559 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4560 the previous saved state.
4562 @section @code{.cfi_return_column @var{register}}
4563 Change return column @var{register}, i.e. the return address is either
4564 directly in @var{register} or can be accessed by rules for @var{register}.
4566 @section @code{.cfi_signal_frame}
4567 Mark current function as signal trampoline.
4569 @section @code{.cfi_window_save}
4570 SPARC register window has been saved.
4572 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4573 Allows the user to add arbitrary bytes to the unwind info. One
4574 might use this to add OS-specific CFI opcodes, or generic CFI
4575 opcodes that GAS does not yet support.
4577 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4578 The current value of @var{register} is @var{label}. The value of @var{label}
4579 will be encoded in the output file according to @var{encoding}; see the
4580 description of @code{.cfi_personality} for details on this encoding.
4582 The usefulness of equating a register to a fixed label is probably
4583 limited to the return address register. Here, it can be useful to
4584 mark a code segment that has only one return address which is reached
4585 by a direct branch and no copy of the return address exists in memory
4586 or another register.
4589 @section @code{.comm @var{symbol} , @var{length} }
4591 @cindex @code{comm} directive
4592 @cindex symbol, common
4593 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4594 common symbol in one object file may be merged with a defined or common symbol
4595 of the same name in another object file. If @code{@value{LD}} does not see a
4596 definition for the symbol--just one or more common symbols--then it will
4597 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4598 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4599 the same name, and they do not all have the same size, it will allocate space
4600 using the largest size.
4603 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4604 an optional third argument. This is the desired alignment of the symbol,
4605 specified for ELF as a byte boundary (for example, an alignment of 16 means
4606 that the least significant 4 bits of the address should be zero), and for PE
4607 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4608 boundary). The alignment must be an absolute expression, and it must be a
4609 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4610 common symbol, it will use the alignment when placing the symbol. If no
4611 alignment is specified, @command{@value{AS}} will set the alignment to the
4612 largest power of two less than or equal to the size of the symbol, up to a
4613 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4614 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4615 @samp{--section-alignment} option; image file sections in PE are aligned to
4616 multiples of 4096, which is far too large an alignment for ordinary variables.
4617 It is rather the default alignment for (non-debug) sections within object
4618 (@samp{*.o}) files, which are less strictly aligned.}.
4622 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4623 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4627 @section @code{.data @var{subsection}}
4629 @cindex @code{data} directive
4630 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4631 end of the data subsection numbered @var{subsection} (which is an
4632 absolute expression). If @var{subsection} is omitted, it defaults
4637 @section @code{.def @var{name}}
4639 @cindex @code{def} directive
4640 @cindex COFF symbols, debugging
4641 @cindex debugging COFF symbols
4642 Begin defining debugging information for a symbol @var{name}; the
4643 definition extends until the @code{.endef} directive is encountered.
4646 This directive is only observed when @command{@value{AS}} is configured for COFF
4647 format output; when producing @code{b.out}, @samp{.def} is recognized,
4654 @section @code{.desc @var{symbol}, @var{abs-expression}}
4656 @cindex @code{desc} directive
4657 @cindex COFF symbol descriptor
4658 @cindex symbol descriptor, COFF
4659 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4660 to the low 16 bits of an absolute expression.
4663 The @samp{.desc} directive is not available when @command{@value{AS}} is
4664 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4665 object format. For the sake of compatibility, @command{@value{AS}} accepts
4666 it, but produces no output, when configured for COFF.
4672 @section @code{.dim}
4674 @cindex @code{dim} directive
4675 @cindex COFF auxiliary symbol information
4676 @cindex auxiliary symbol information, COFF
4677 This directive is generated by compilers to include auxiliary debugging
4678 information in the symbol table. It is only permitted inside
4679 @code{.def}/@code{.endef} pairs.
4682 @samp{.dim} is only meaningful when generating COFF format output; when
4683 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4689 @section @code{.double @var{flonums}}
4691 @cindex @code{double} directive
4692 @cindex floating point numbers (double)
4693 @code{.double} expects zero or more flonums, separated by commas. It
4694 assembles floating point numbers.
4696 The exact kind of floating point numbers emitted depends on how
4697 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4701 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4702 in @sc{ieee} format.
4707 @section @code{.eject}
4709 @cindex @code{eject} directive
4710 @cindex new page, in listings
4711 @cindex page, in listings
4712 @cindex listing control: new page
4713 Force a page break at this point, when generating assembly listings.
4716 @section @code{.else}
4718 @cindex @code{else} directive
4719 @code{.else} is part of the @command{@value{AS}} support for conditional
4720 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4721 of code to be assembled if the condition for the preceding @code{.if}
4725 @section @code{.elseif}
4727 @cindex @code{elseif} directive
4728 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4729 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4730 @code{.if} block that would otherwise fill the entire @code{.else} section.
4733 @section @code{.end}
4735 @cindex @code{end} directive
4736 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4737 process anything in the file past the @code{.end} directive.
4741 @section @code{.endef}
4743 @cindex @code{endef} directive
4744 This directive flags the end of a symbol definition begun with
4748 @samp{.endef} is only meaningful when generating COFF format output; if
4749 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4750 directive but ignores it.
4755 @section @code{.endfunc}
4756 @cindex @code{endfunc} directive
4757 @code{.endfunc} marks the end of a function specified with @code{.func}.
4760 @section @code{.endif}
4762 @cindex @code{endif} directive
4763 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4764 it marks the end of a block of code that is only assembled
4765 conditionally. @xref{If,,@code{.if}}.
4768 @section @code{.equ @var{symbol}, @var{expression}}
4770 @cindex @code{equ} directive
4771 @cindex assigning values to symbols
4772 @cindex symbols, assigning values to
4773 This directive sets the value of @var{symbol} to @var{expression}.
4774 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4777 The syntax for @code{equ} on the HPPA is
4778 @samp{@var{symbol} .equ @var{expression}}.
4782 The syntax for @code{equ} on the Z80 is
4783 @samp{@var{symbol} equ @var{expression}}.
4784 On the Z80 it is an eror if @var{symbol} is already defined,
4785 but the symbol is not protected from later redefinition.
4786 Compare @ref{Equiv}.
4790 @section @code{.equiv @var{symbol}, @var{expression}}
4791 @cindex @code{equiv} directive
4792 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4793 the assembler will signal an error if @var{symbol} is already defined. Note a
4794 symbol which has been referenced but not actually defined is considered to be
4797 Except for the contents of the error message, this is roughly equivalent to
4804 plus it protects the symbol from later redefinition.
4807 @section @code{.eqv @var{symbol}, @var{expression}}
4808 @cindex @code{eqv} directive
4809 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4810 evaluate the expression or any part of it immediately. Instead each time
4811 the resulting symbol is used in an expression, a snapshot of its current
4815 @section @code{.err}
4816 @cindex @code{err} directive
4817 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4818 message and, unless the @option{-Z} option was used, it will not generate an
4819 object file. This can be used to signal an error in conditionally compiled code.
4822 @section @code{.error "@var{string}"}
4823 @cindex error directive
4825 Similarly to @code{.err}, this directive emits an error, but you can specify a
4826 string that will be emitted as the error message. If you don't specify the
4827 message, it defaults to @code{".error directive invoked in source file"}.
4828 @xref{Errors, ,Error and Warning Messages}.
4831 .error "This code has not been assembled and tested."
4835 @section @code{.exitm}
4836 Exit early from the current macro definition. @xref{Macro}.
4839 @section @code{.extern}
4841 @cindex @code{extern} directive
4842 @code{.extern} is accepted in the source program---for compatibility
4843 with other assemblers---but it is ignored. @command{@value{AS}} treats
4844 all undefined symbols as external.
4847 @section @code{.fail @var{expression}}
4849 @cindex @code{fail} directive
4850 Generates an error or a warning. If the value of the @var{expression} is 500
4851 or more, @command{@value{AS}} will print a warning message. If the value is less
4852 than 500, @command{@value{AS}} will print an error message. The message will
4853 include the value of @var{expression}. This can occasionally be useful inside
4854 complex nested macros or conditional assembly.
4857 @section @code{.file}
4858 @cindex @code{file} directive
4860 @ifclear no-file-dir
4861 There are two different versions of the @code{.file} directive. Targets
4862 that support DWARF2 line number information use the DWARF2 version of
4863 @code{.file}. Other targets use the default version.
4865 @subheading Default Version
4867 @cindex logical file name
4868 @cindex file name, logical
4869 This version of the @code{.file} directive tells @command{@value{AS}} that we
4870 are about to start a new logical file. The syntax is:
4876 @var{string} is the new file name. In general, the filename is
4877 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4878 to specify an empty file name, you must give the quotes--@code{""}. This
4879 statement may go away in future: it is only recognized to be compatible with
4880 old @command{@value{AS}} programs.
4882 @subheading DWARF2 Version
4885 When emitting DWARF2 line number information, @code{.file} assigns filenames
4886 to the @code{.debug_line} file name table. The syntax is:
4889 .file @var{fileno} @var{filename}
4892 The @var{fileno} operand should be a unique positive integer to use as the
4893 index of the entry in the table. The @var{filename} operand is a C string
4896 The detail of filename indices is exposed to the user because the filename
4897 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4898 information, and thus the user must know the exact indices that table
4902 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4904 @cindex @code{fill} directive
4905 @cindex writing patterns in memory
4906 @cindex patterns, writing in memory
4907 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4908 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4909 may be zero or more. @var{Size} may be zero or more, but if it is
4910 more than 8, then it is deemed to have the value 8, compatible with
4911 other people's assemblers. The contents of each @var{repeat} bytes
4912 is taken from an 8-byte number. The highest order 4 bytes are
4913 zero. The lowest order 4 bytes are @var{value} rendered in the
4914 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4915 Each @var{size} bytes in a repetition is taken from the lowest order
4916 @var{size} bytes of this number. Again, this bizarre behavior is
4917 compatible with other people's assemblers.
4919 @var{size} and @var{value} are optional.
4920 If the second comma and @var{value} are absent, @var{value} is
4921 assumed zero. If the first comma and following tokens are absent,
4922 @var{size} is assumed to be 1.
4925 @section @code{.float @var{flonums}}
4927 @cindex floating point numbers (single)
4928 @cindex @code{float} directive
4929 This directive assembles zero or more flonums, separated by commas. It
4930 has the same effect as @code{.single}.
4932 The exact kind of floating point numbers emitted depends on how
4933 @command{@value{AS}} is configured.
4934 @xref{Machine Dependencies}.
4938 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4939 in @sc{ieee} format.
4944 @section @code{.func @var{name}[,@var{label}]}
4945 @cindex @code{func} directive
4946 @code{.func} emits debugging information to denote function @var{name}, and
4947 is ignored unless the file is assembled with debugging enabled.
4948 Only @samp{--gstabs[+]} is currently supported.
4949 @var{label} is the entry point of the function and if omitted @var{name}
4950 prepended with the @samp{leading char} is used.
4951 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4952 All functions are currently defined to have @code{void} return type.
4953 The function must be terminated with @code{.endfunc}.
4956 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4958 @cindex @code{global} directive
4959 @cindex symbol, making visible to linker
4960 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4961 @var{symbol} in your partial program, its value is made available to
4962 other partial programs that are linked with it. Otherwise,
4963 @var{symbol} takes its attributes from a symbol of the same name
4964 from another file linked into the same program.
4966 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4967 compatibility with other assemblers.
4970 On the HPPA, @code{.global} is not always enough to make it accessible to other
4971 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4972 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4977 @section @code{.gnu_attribute @var{tag},@var{value}}
4978 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4981 @section @code{.hidden @var{names}}
4983 @cindex @code{hidden} directive
4985 This is one of the ELF visibility directives. The other two are
4986 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4987 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4989 This directive overrides the named symbols default visibility (which is set by
4990 their binding: local, global or weak). The directive sets the visibility to
4991 @code{hidden} which means that the symbols are not visible to other components.
4992 Such symbols are always considered to be @code{protected} as well.
4996 @section @code{.hword @var{expressions}}
4998 @cindex @code{hword} directive
4999 @cindex integers, 16-bit
5000 @cindex numbers, 16-bit
5001 @cindex sixteen bit integers
5002 This expects zero or more @var{expressions}, and emits
5003 a 16 bit number for each.
5006 This directive is a synonym for @samp{.short}; depending on the target
5007 architecture, it may also be a synonym for @samp{.word}.
5011 This directive is a synonym for @samp{.short}.
5014 This directive is a synonym for both @samp{.short} and @samp{.word}.
5019 @section @code{.ident}
5021 @cindex @code{ident} directive
5023 This directive is used by some assemblers to place tags in object files. The
5024 behavior of this directive varies depending on the target. When using the
5025 a.out object file format, @command{@value{AS}} simply accepts the directive for
5026 source-file compatibility with existing assemblers, but does not emit anything
5027 for it. When using COFF, comments are emitted to the @code{.comment} or
5028 @code{.rdata} section, depending on the target. When using ELF, comments are
5029 emitted to the @code{.comment} section.
5032 @section @code{.if @var{absolute expression}}
5034 @cindex conditional assembly
5035 @cindex @code{if} directive
5036 @code{.if} marks the beginning of a section of code which is only
5037 considered part of the source program being assembled if the argument
5038 (which must be an @var{absolute expression}) is non-zero. The end of
5039 the conditional section of code must be marked by @code{.endif}
5040 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5041 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5042 If you have several conditions to check, @code{.elseif} may be used to avoid
5043 nesting blocks if/else within each subsequent @code{.else} block.
5045 The following variants of @code{.if} are also supported:
5047 @cindex @code{ifdef} directive
5048 @item .ifdef @var{symbol}
5049 Assembles the following section of code if the specified @var{symbol}
5050 has been defined. Note a symbol which has been referenced but not yet defined
5051 is considered to be undefined.
5053 @cindex @code{ifb} directive
5054 @item .ifb @var{text}
5055 Assembles the following section of code if the operand is blank (empty).
5057 @cindex @code{ifc} directive
5058 @item .ifc @var{string1},@var{string2}
5059 Assembles the following section of code if the two strings are the same. The
5060 strings may be optionally quoted with single quotes. If they are not quoted,
5061 the first string stops at the first comma, and the second string stops at the
5062 end of the line. Strings which contain whitespace should be quoted. The
5063 string comparison is case sensitive.
5065 @cindex @code{ifeq} directive
5066 @item .ifeq @var{absolute expression}
5067 Assembles the following section of code if the argument is zero.
5069 @cindex @code{ifeqs} directive
5070 @item .ifeqs @var{string1},@var{string2}
5071 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5073 @cindex @code{ifge} directive
5074 @item .ifge @var{absolute expression}
5075 Assembles the following section of code if the argument is greater than or
5078 @cindex @code{ifgt} directive
5079 @item .ifgt @var{absolute expression}
5080 Assembles the following section of code if the argument is greater than zero.
5082 @cindex @code{ifle} directive
5083 @item .ifle @var{absolute expression}
5084 Assembles the following section of code if the argument is less than or equal
5087 @cindex @code{iflt} directive
5088 @item .iflt @var{absolute expression}
5089 Assembles the following section of code if the argument is less than zero.
5091 @cindex @code{ifnb} directive
5092 @item .ifnb @var{text}
5093 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5094 following section of code if the operand is non-blank (non-empty).
5096 @cindex @code{ifnc} directive
5097 @item .ifnc @var{string1},@var{string2}.
5098 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5099 following section of code if the two strings are not the same.
5101 @cindex @code{ifndef} directive
5102 @cindex @code{ifnotdef} directive
5103 @item .ifndef @var{symbol}
5104 @itemx .ifnotdef @var{symbol}
5105 Assembles the following section of code if the specified @var{symbol}
5106 has not been defined. Both spelling variants are equivalent. Note a symbol
5107 which has been referenced but not yet defined is considered to be undefined.
5109 @cindex @code{ifne} directive
5110 @item .ifne @var{absolute expression}
5111 Assembles the following section of code if the argument is not equal to zero
5112 (in other words, this is equivalent to @code{.if}).
5114 @cindex @code{ifnes} directive
5115 @item .ifnes @var{string1},@var{string2}
5116 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5117 following section of code if the two strings are not the same.
5121 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5123 @cindex @code{incbin} directive
5124 @cindex binary files, including
5125 The @code{incbin} directive includes @var{file} verbatim at the current
5126 location. You can control the search paths used with the @samp{-I} command-line
5127 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5130 The @var{skip} argument skips a number of bytes from the start of the
5131 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5132 read. Note that the data is not aligned in any way, so it is the user's
5133 responsibility to make sure that proper alignment is provided both before and
5134 after the @code{incbin} directive.
5137 @section @code{.include "@var{file}"}
5139 @cindex @code{include} directive
5140 @cindex supporting files, including
5141 @cindex files, including
5142 This directive provides a way to include supporting files at specified
5143 points in your source program. The code from @var{file} is assembled as
5144 if it followed the point of the @code{.include}; when the end of the
5145 included file is reached, assembly of the original file continues. You
5146 can control the search paths used with the @samp{-I} command-line option
5147 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5151 @section @code{.int @var{expressions}}
5153 @cindex @code{int} directive
5154 @cindex integers, 32-bit
5155 Expect zero or more @var{expressions}, of any section, separated by commas.
5156 For each expression, emit a number that, at run time, is the value of that
5157 expression. The byte order and bit size of the number depends on what kind
5158 of target the assembly is for.
5162 On most forms of the H8/300, @code{.int} emits 16-bit
5163 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5170 @section @code{.internal @var{names}}
5172 @cindex @code{internal} directive
5174 This is one of the ELF visibility directives. The other two are
5175 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5176 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5178 This directive overrides the named symbols default visibility (which is set by
5179 their binding: local, global or weak). The directive sets the visibility to
5180 @code{internal} which means that the symbols are considered to be @code{hidden}
5181 (i.e., not visible to other components), and that some extra, processor specific
5182 processing must also be performed upon the symbols as well.
5186 @section @code{.irp @var{symbol},@var{values}}@dots{}
5188 @cindex @code{irp} directive
5189 Evaluate a sequence of statements assigning different values to @var{symbol}.
5190 The sequence of statements starts at the @code{.irp} directive, and is
5191 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5192 set to @var{value}, and the sequence of statements is assembled. If no
5193 @var{value} is listed, the sequence of statements is assembled once, with
5194 @var{symbol} set to the null string. To refer to @var{symbol} within the
5195 sequence of statements, use @var{\symbol}.
5197 For example, assembling
5205 is equivalent to assembling
5213 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5216 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5218 @cindex @code{irpc} directive
5219 Evaluate a sequence of statements assigning different values to @var{symbol}.
5220 The sequence of statements starts at the @code{.irpc} directive, and is
5221 terminated by an @code{.endr} directive. For each character in @var{value},
5222 @var{symbol} is set to the character, and the sequence of statements is
5223 assembled. If no @var{value} is listed, the sequence of statements is
5224 assembled once, with @var{symbol} set to the null string. To refer to
5225 @var{symbol} within the sequence of statements, use @var{\symbol}.
5227 For example, assembling
5235 is equivalent to assembling
5243 For some caveats with the spelling of @var{symbol}, see also the discussion
5247 @section @code{.lcomm @var{symbol} , @var{length}}
5249 @cindex @code{lcomm} directive
5250 @cindex local common symbols
5251 @cindex symbols, local common
5252 Reserve @var{length} (an absolute expression) bytes for a local common
5253 denoted by @var{symbol}. The section and value of @var{symbol} are
5254 those of the new local common. The addresses are allocated in the bss
5255 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5256 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5257 not visible to @code{@value{LD}}.
5260 Some targets permit a third argument to be used with @code{.lcomm}. This
5261 argument specifies the desired alignment of the symbol in the bss section.
5265 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5266 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5270 @section @code{.lflags}
5272 @cindex @code{lflags} directive (ignored)
5273 @command{@value{AS}} accepts this directive, for compatibility with other
5274 assemblers, but ignores it.
5276 @ifclear no-line-dir
5278 @section @code{.line @var{line-number}}
5280 @cindex @code{line} directive
5281 @cindex logical line number
5283 Change the logical line number. @var{line-number} must be an absolute
5284 expression. The next line has that logical line number. Therefore any other
5285 statements on the current line (after a statement separator character) are
5286 reported as on logical line number @var{line-number} @minus{} 1. One day
5287 @command{@value{AS}} will no longer support this directive: it is recognized only
5288 for compatibility with existing assembler programs.
5291 Even though this is a directive associated with the @code{a.out} or
5292 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5293 when producing COFF output, and treats @samp{.line} as though it
5294 were the COFF @samp{.ln} @emph{if} it is found outside a
5295 @code{.def}/@code{.endef} pair.
5297 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5298 used by compilers to generate auxiliary symbol information for
5303 @section @code{.linkonce [@var{type}]}
5305 @cindex @code{linkonce} directive
5306 @cindex common sections
5307 Mark the current section so that the linker only includes a single copy of it.
5308 This may be used to include the same section in several different object files,
5309 but ensure that the linker will only include it once in the final output file.
5310 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5311 Duplicate sections are detected based on the section name, so it should be
5314 This directive is only supported by a few object file formats; as of this
5315 writing, the only object file format which supports it is the Portable
5316 Executable format used on Windows NT.
5318 The @var{type} argument is optional. If specified, it must be one of the
5319 following strings. For example:
5323 Not all types may be supported on all object file formats.
5327 Silently discard duplicate sections. This is the default.
5330 Warn if there are duplicate sections, but still keep only one copy.
5333 Warn if any of the duplicates have different sizes.
5336 Warn if any of the duplicates do not have exactly the same contents.
5340 @section @code{.list}
5342 @cindex @code{list} directive
5343 @cindex listing control, turning on
5344 Control (in conjunction with the @code{.nolist} directive) whether or
5345 not assembly listings are generated. These two directives maintain an
5346 internal counter (which is zero initially). @code{.list} increments the
5347 counter, and @code{.nolist} decrements it. Assembly listings are
5348 generated whenever the counter is greater than zero.
5350 By default, listings are disabled. When you enable them (with the
5351 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5352 the initial value of the listing counter is one.
5355 @section @code{.ln @var{line-number}}
5357 @cindex @code{ln} directive
5358 @ifclear no-line-dir
5359 @samp{.ln} is a synonym for @samp{.line}.
5362 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5363 must be an absolute expression. The next line has that logical
5364 line number, so any other statements on the current line (after a
5365 statement separator character @code{;}) are reported as on logical
5366 line number @var{line-number} @minus{} 1.
5369 This directive is accepted, but ignored, when @command{@value{AS}} is
5370 configured for @code{b.out}; its effect is only associated with COFF
5376 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5377 @cindex @code{loc} directive
5378 When emitting DWARF2 line number information,
5379 the @code{.loc} directive will add a row to the @code{.debug_line} line
5380 number matrix corresponding to the immediately following assembly
5381 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5382 arguments will be applied to the @code{.debug_line} state machine before
5385 The @var{options} are a sequence of the following tokens in any order:
5389 This option will set the @code{basic_block} register in the
5390 @code{.debug_line} state machine to @code{true}.
5393 This option will set the @code{prologue_end} register in the
5394 @code{.debug_line} state machine to @code{true}.
5396 @item epilogue_begin
5397 This option will set the @code{epilogue_begin} register in the
5398 @code{.debug_line} state machine to @code{true}.
5400 @item is_stmt @var{value}
5401 This option will set the @code{is_stmt} register in the
5402 @code{.debug_line} state machine to @code{value}, which must be
5405 @item isa @var{value}
5406 This directive will set the @code{isa} register in the @code{.debug_line}
5407 state machine to @var{value}, which must be an unsigned integer.
5409 @item discriminator @var{value}
5410 This directive will set the @code{discriminator} register in the @code{.debug_line}
5411 state machine to @var{value}, which must be an unsigned integer.
5415 @node Loc_mark_labels
5416 @section @code{.loc_mark_labels @var{enable}}
5417 @cindex @code{loc_mark_labels} directive
5418 When emitting DWARF2 line number information,
5419 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5420 to the @code{.debug_line} line number matrix with the @code{basic_block}
5421 register in the state machine set whenever a code label is seen.
5422 The @var{enable} argument should be either 1 or 0, to enable or disable
5423 this function respectively.
5427 @section @code{.local @var{names}}
5429 @cindex @code{local} directive
5430 This directive, which is available for ELF targets, marks each symbol in
5431 the comma-separated list of @code{names} as a local symbol so that it
5432 will not be externally visible. If the symbols do not already exist,
5433 they will be created.
5435 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5436 accept an alignment argument, which is the case for most ELF targets,
5437 the @code{.local} directive can be used in combination with @code{.comm}
5438 (@pxref{Comm}) to define aligned local common data.
5442 @section @code{.long @var{expressions}}
5444 @cindex @code{long} directive
5445 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5448 @c no one seems to know what this is for or whether this description is
5449 @c what it really ought to do
5451 @section @code{.lsym @var{symbol}, @var{expression}}
5453 @cindex @code{lsym} directive
5454 @cindex symbol, not referenced in assembly
5455 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5456 the hash table, ensuring it cannot be referenced by name during the
5457 rest of the assembly. This sets the attributes of the symbol to be
5458 the same as the expression value:
5460 @var{other} = @var{descriptor} = 0
5461 @var{type} = @r{(section of @var{expression})}
5462 @var{value} = @var{expression}
5465 The new symbol is not flagged as external.
5469 @section @code{.macro}
5472 The commands @code{.macro} and @code{.endm} allow you to define macros that
5473 generate assembly output. For example, this definition specifies a macro
5474 @code{sum} that puts a sequence of numbers into memory:
5477 .macro sum from=0, to=5
5486 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5498 @item .macro @var{macname}
5499 @itemx .macro @var{macname} @var{macargs} @dots{}
5500 @cindex @code{macro} directive
5501 Begin the definition of a macro called @var{macname}. If your macro
5502 definition requires arguments, specify their names after the macro name,
5503 separated by commas or spaces. You can qualify the macro argument to
5504 indicate whether all invocations must specify a non-blank value (through
5505 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5506 (through @samp{:@code{vararg}}). You can supply a default value for any
5507 macro argument by following the name with @samp{=@var{deflt}}. You
5508 cannot define two macros with the same @var{macname} unless it has been
5509 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5510 definitions. For example, these are all valid @code{.macro} statements:
5514 Begin the definition of a macro called @code{comm}, which takes no
5517 @item .macro plus1 p, p1
5518 @itemx .macro plus1 p p1
5519 Either statement begins the definition of a macro called @code{plus1},
5520 which takes two arguments; within the macro definition, write
5521 @samp{\p} or @samp{\p1} to evaluate the arguments.
5523 @item .macro reserve_str p1=0 p2
5524 Begin the definition of a macro called @code{reserve_str}, with two
5525 arguments. The first argument has a default value, but not the second.
5526 After the definition is complete, you can call the macro either as
5527 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5528 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5529 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5530 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5532 @item .macro m p1:req, p2=0, p3:vararg
5533 Begin the definition of a macro called @code{m}, with at least three
5534 arguments. The first argument must always have a value specified, but
5535 not the second, which instead has a default value. The third formal
5536 will get assigned all remaining arguments specified at invocation time.
5538 When you call a macro, you can specify the argument values either by
5539 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5540 @samp{sum to=17, from=9}.
5544 Note that since each of the @var{macargs} can be an identifier exactly
5545 as any other one permitted by the target architecture, there may be
5546 occasional problems if the target hand-crafts special meanings to certain
5547 characters when they occur in a special position. For example, if the colon
5548 (@code{:}) is generally permitted to be part of a symbol name, but the
5549 architecture specific code special-cases it when occurring as the final
5550 character of a symbol (to denote a label), then the macro parameter
5551 replacement code will have no way of knowing that and consider the whole
5552 construct (including the colon) an identifier, and check only this
5553 identifier for being the subject to parameter substitution. So for example
5554 this macro definition:
5562 might not work as expected. Invoking @samp{label foo} might not create a label
5563 called @samp{foo} but instead just insert the text @samp{\l:} into the
5564 assembler source, probably generating an error about an unrecognised
5567 Similarly problems might occur with the period character (@samp{.})
5568 which is often allowed inside opcode names (and hence identifier names). So
5569 for example constructing a macro to build an opcode from a base name and a
5570 length specifier like this:
5573 .macro opcode base length
5578 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5579 instruction but instead generate some kind of error as the assembler tries to
5580 interpret the text @samp{\base.\length}.
5582 There are several possible ways around this problem:
5585 @item Insert white space
5586 If it is possible to use white space characters then this is the simplest
5595 @item Use @samp{\()}
5596 The string @samp{\()} can be used to separate the end of a macro argument from
5597 the following text. eg:
5600 .macro opcode base length
5605 @item Use the alternate macro syntax mode
5606 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5607 used as a separator. eg:
5617 Note: this problem of correctly identifying string parameters to pseudo ops
5618 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5619 and @code{.irpc} (@pxref{Irpc}) as well.
5622 @cindex @code{endm} directive
5623 Mark the end of a macro definition.
5626 @cindex @code{exitm} directive
5627 Exit early from the current macro definition.
5629 @cindex number of macros executed
5630 @cindex macros, count executed
5632 @command{@value{AS}} maintains a counter of how many macros it has
5633 executed in this pseudo-variable; you can copy that number to your
5634 output with @samp{\@@}, but @emph{only within a macro definition}.
5636 @item LOCAL @var{name} [ , @dots{} ]
5637 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5638 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5639 @xref{Altmacro,,@code{.altmacro}}.
5643 @section @code{.mri @var{val}}
5645 @cindex @code{mri} directive
5646 @cindex MRI mode, temporarily
5647 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5648 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5649 affects code assembled until the next @code{.mri} directive, or until the end
5650 of the file. @xref{M, MRI mode, MRI mode}.
5653 @section @code{.noaltmacro}
5654 Disable alternate macro mode. @xref{Altmacro}.
5657 @section @code{.nolist}
5659 @cindex @code{nolist} directive
5660 @cindex listing control, turning off
5661 Control (in conjunction with the @code{.list} directive) whether or
5662 not assembly listings are generated. These two directives maintain an
5663 internal counter (which is zero initially). @code{.list} increments the
5664 counter, and @code{.nolist} decrements it. Assembly listings are
5665 generated whenever the counter is greater than zero.
5668 @section @code{.octa @var{bignums}}
5670 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5671 @cindex @code{octa} directive
5672 @cindex integer, 16-byte
5673 @cindex sixteen byte integer
5674 This directive expects zero or more bignums, separated by commas. For each
5675 bignum, it emits a 16-byte integer.
5677 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5678 hence @emph{octa}-word for 16 bytes.
5681 @section @code{.offset @var{loc}}
5683 @cindex @code{offset} directive
5684 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5685 be an absolute expression. This directive may be useful for defining
5686 symbols with absolute values. Do not confuse it with the @code{.org}
5690 @section @code{.org @var{new-lc} , @var{fill}}
5692 @cindex @code{org} directive
5693 @cindex location counter, advancing
5694 @cindex advancing location counter
5695 @cindex current address, advancing
5696 Advance the location counter of the current section to
5697 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5698 expression with the same section as the current subsection. That is,
5699 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5700 wrong section, the @code{.org} directive is ignored. To be compatible
5701 with former assemblers, if the section of @var{new-lc} is absolute,
5702 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5703 is the same as the current subsection.
5705 @code{.org} may only increase the location counter, or leave it
5706 unchanged; you cannot use @code{.org} to move the location counter
5709 @c double negative used below "not undefined" because this is a specific
5710 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5711 @c section. doc@cygnus.com 18feb91
5712 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5713 may not be undefined. If you really detest this restriction we eagerly await
5714 a chance to share your improved assembler.
5716 Beware that the origin is relative to the start of the section, not
5717 to the start of the subsection. This is compatible with other
5718 people's assemblers.
5720 When the location counter (of the current subsection) is advanced, the
5721 intervening bytes are filled with @var{fill} which should be an
5722 absolute expression. If the comma and @var{fill} are omitted,
5723 @var{fill} defaults to zero.
5726 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5728 @cindex padding the location counter given a power of two
5729 @cindex @code{p2align} directive
5730 Pad the location counter (in the current subsection) to a particular
5731 storage boundary. The first expression (which must be absolute) is the
5732 number of low-order zero bits the location counter must have after
5733 advancement. For example @samp{.p2align 3} advances the location
5734 counter until it a multiple of 8. If the location counter is already a
5735 multiple of 8, no change is needed.
5737 The second expression (also absolute) gives the fill value to be stored in the
5738 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5739 padding bytes are normally zero. However, on some systems, if the section is
5740 marked as containing code and the fill value is omitted, the space is filled
5741 with no-op instructions.
5743 The third expression is also absolute, and is also optional. If it is present,
5744 it is the maximum number of bytes that should be skipped by this alignment
5745 directive. If doing the alignment would require skipping more bytes than the
5746 specified maximum, then the alignment is not done at all. You can omit the
5747 fill value (the second argument) entirely by simply using two commas after the
5748 required alignment; this can be useful if you want the alignment to be filled
5749 with no-op instructions when appropriate.
5751 @cindex @code{p2alignw} directive
5752 @cindex @code{p2alignl} directive
5753 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5754 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5755 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5756 fill pattern as a four byte longword value. For example, @code{.p2alignw
5757 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5758 filled in with the value 0x368d (the exact placement of the bytes depends upon
5759 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5764 @section @code{.popsection}
5766 @cindex @code{popsection} directive
5767 @cindex Section Stack
5768 This is one of the ELF section stack manipulation directives. The others are
5769 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5770 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5773 This directive replaces the current section (and subsection) with the top
5774 section (and subsection) on the section stack. This section is popped off the
5780 @section @code{.previous}
5782 @cindex @code{previous} directive
5783 @cindex Section Stack
5784 This is one of the ELF section stack manipulation directives. The others are
5785 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5786 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5787 (@pxref{PopSection}).
5789 This directive swaps the current section (and subsection) with most recently
5790 referenced section/subsection pair prior to this one. Multiple
5791 @code{.previous} directives in a row will flip between two sections (and their
5792 subsections). For example:
5804 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5810 # Now in section A subsection 1
5814 # Now in section B subsection 0
5817 # Now in section B subsection 1
5820 # Now in section B subsection 0
5824 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5825 section B and 0x9abc into subsection 1 of section B.
5827 In terms of the section stack, this directive swaps the current section with
5828 the top section on the section stack.
5832 @section @code{.print @var{string}}
5834 @cindex @code{print} directive
5835 @command{@value{AS}} will print @var{string} on the standard output during
5836 assembly. You must put @var{string} in double quotes.
5840 @section @code{.protected @var{names}}
5842 @cindex @code{protected} directive
5844 This is one of the ELF visibility directives. The other two are
5845 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5847 This directive overrides the named symbols default visibility (which is set by
5848 their binding: local, global or weak). The directive sets the visibility to
5849 @code{protected} which means that any references to the symbols from within the
5850 components that defines them must be resolved to the definition in that
5851 component, even if a definition in another component would normally preempt
5856 @section @code{.psize @var{lines} , @var{columns}}
5858 @cindex @code{psize} directive
5859 @cindex listing control: paper size
5860 @cindex paper size, for listings
5861 Use this directive to declare the number of lines---and, optionally, the
5862 number of columns---to use for each page, when generating listings.
5864 If you do not use @code{.psize}, listings use a default line-count
5865 of 60. You may omit the comma and @var{columns} specification; the
5866 default width is 200 columns.
5868 @command{@value{AS}} generates formfeeds whenever the specified number of
5869 lines is exceeded (or whenever you explicitly request one, using
5872 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5873 those explicitly specified with @code{.eject}.
5876 @section @code{.purgem @var{name}}
5878 @cindex @code{purgem} directive
5879 Undefine the macro @var{name}, so that later uses of the string will not be
5880 expanded. @xref{Macro}.
5884 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5886 @cindex @code{pushsection} directive
5887 @cindex Section Stack
5888 This is one of the ELF section stack manipulation directives. The others are
5889 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5890 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5893 This directive pushes the current section (and subsection) onto the
5894 top of the section stack, and then replaces the current section and
5895 subsection with @code{name} and @code{subsection}. The optional
5896 @code{flags}, @code{type} and @code{arguments} are treated the same
5897 as in the @code{.section} (@pxref{Section}) directive.
5901 @section @code{.quad @var{bignums}}
5903 @cindex @code{quad} directive
5904 @code{.quad} expects zero or more bignums, separated by commas. For
5905 each bignum, it emits
5907 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5908 warning message; and just takes the lowest order 8 bytes of the bignum.
5909 @cindex eight-byte integer
5910 @cindex integer, 8-byte
5912 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5913 hence @emph{quad}-word for 8 bytes.
5916 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5917 warning message; and just takes the lowest order 16 bytes of the bignum.
5918 @cindex sixteen-byte integer
5919 @cindex integer, 16-byte
5923 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5925 @cindex @code{reloc} directive
5926 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5927 @var{expression}. If @var{offset} is a number, the relocation is generated in
5928 the current section. If @var{offset} is an expression that resolves to a
5929 symbol plus offset, the relocation is generated in the given symbol's section.
5930 @var{expression}, if present, must resolve to a symbol plus addend or to an
5931 absolute value, but note that not all targets support an addend. e.g. ELF REL
5932 targets such as i386 store an addend in the section contents rather than in the
5933 relocation. This low level interface does not support addends stored in the
5937 @section @code{.rept @var{count}}
5939 @cindex @code{rept} directive
5940 Repeat the sequence of lines between the @code{.rept} directive and the next
5941 @code{.endr} directive @var{count} times.
5943 For example, assembling
5951 is equivalent to assembling
5960 @section @code{.sbttl "@var{subheading}"}
5962 @cindex @code{sbttl} directive
5963 @cindex subtitles for listings
5964 @cindex listing control: subtitle
5965 Use @var{subheading} as the title (third line, immediately after the
5966 title line) when generating assembly listings.
5968 This directive affects subsequent pages, as well as the current page if
5969 it appears within ten lines of the top of a page.
5973 @section @code{.scl @var{class}}
5975 @cindex @code{scl} directive
5976 @cindex symbol storage class (COFF)
5977 @cindex COFF symbol storage class
5978 Set the storage-class value for a symbol. This directive may only be
5979 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5980 whether a symbol is static or external, or it may record further
5981 symbolic debugging information.
5984 The @samp{.scl} directive is primarily associated with COFF output; when
5985 configured to generate @code{b.out} output format, @command{@value{AS}}
5986 accepts this directive but ignores it.
5992 @section @code{.section @var{name}}
5994 @cindex named section
5995 Use the @code{.section} directive to assemble the following code into a section
5998 This directive is only supported for targets that actually support arbitrarily
5999 named sections; on @code{a.out} targets, for example, it is not accepted, even
6000 with a standard @code{a.out} section name.
6004 @c only print the extra heading if both COFF and ELF are set
6005 @subheading COFF Version
6008 @cindex @code{section} directive (COFF version)
6009 For COFF targets, the @code{.section} directive is used in one of the following
6013 .section @var{name}[, "@var{flags}"]
6014 .section @var{name}[, @var{subsection}]
6017 If the optional argument is quoted, it is taken as flags to use for the
6018 section. Each flag is a single character. The following flags are recognized:
6021 bss section (uninitialized data)
6023 section is not loaded
6029 exclude section from linking
6035 shared section (meaningful for PE targets)
6037 ignored. (For compatibility with the ELF version)
6039 section is not readable (meaningful for PE targets)
6041 single-digit power-of-two section alignment (GNU extension)
6044 If no flags are specified, the default flags depend upon the section name. If
6045 the section name is not recognized, the default will be for the section to be
6046 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6047 from the section, rather than adding them, so if they are used on their own it
6048 will be as if no flags had been specified at all.
6050 If the optional argument to the @code{.section} directive is not quoted, it is
6051 taken as a subsection number (@pxref{Sub-Sections}).
6056 @c only print the extra heading if both COFF and ELF are set
6057 @subheading ELF Version
6060 @cindex Section Stack
6061 This is one of the ELF section stack manipulation directives. The others are
6062 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6063 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6064 @code{.previous} (@pxref{Previous}).
6066 @cindex @code{section} directive (ELF version)
6067 For ELF targets, the @code{.section} directive is used like this:
6070 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6073 The optional @var{flags} argument is a quoted string which may contain any
6074 combination of the following characters:
6077 section is allocatable
6079 section is excluded from executable and shared library.
6083 section is executable
6085 section is mergeable
6087 section contains zero terminated strings
6089 section is a member of a section group
6091 section is used for thread-local-storage
6093 section is a member of the previously-current section's group, if any
6096 The optional @var{type} argument may contain one of the following constants:
6099 section contains data
6101 section does not contain data (i.e., section only occupies space)
6103 section contains data which is used by things other than the program
6105 section contains an array of pointers to init functions
6107 section contains an array of pointers to finish functions
6108 @item @@preinit_array
6109 section contains an array of pointers to pre-init functions
6112 Many targets only support the first three section types.
6114 Note on targets where the @code{@@} character is the start of a comment (eg
6115 ARM) then another character is used instead. For example the ARM port uses the
6118 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6119 be specified as well as an extra argument---@var{entsize}---like this:
6122 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6125 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6126 constants, each @var{entsize} octets long. Sections with both @code{M} and
6127 @code{S} must contain zero terminated strings where each character is
6128 @var{entsize} bytes long. The linker may remove duplicates within sections with
6129 the same name, same entity size and same flags. @var{entsize} must be an
6130 absolute expression. For sections with both @code{M} and @code{S}, a string
6131 which is a suffix of a larger string is considered a duplicate. Thus
6132 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6133 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6135 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6136 be present along with an additional field like this:
6139 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6142 The @var{GroupName} field specifies the name of the section group to which this
6143 particular section belongs. The optional linkage field can contain:
6146 indicates that only one copy of this section should be retained
6151 Note: if both the @var{M} and @var{G} flags are present then the fields for
6152 the Merge flag should come first, like this:
6155 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6158 If @var{flags} contains the @code{?} symbol then it may not also contain the
6159 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6160 present. Instead, @code{?} says to consider the section that's current before
6161 this directive. If that section used @code{G}, then the new section will use
6162 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6163 If not, then the @code{?} symbol has no effect.
6165 If no flags are specified, the default flags depend upon the section name. If
6166 the section name is not recognized, the default will be for the section to have
6167 none of the above flags: it will not be allocated in memory, nor writable, nor
6168 executable. The section will contain data.
6170 For ELF targets, the assembler supports another type of @code{.section}
6171 directive for compatibility with the Solaris assembler:
6174 .section "@var{name}"[, @var{flags}...]
6177 Note that the section name is quoted. There may be a sequence of comma
6181 section is allocatable
6185 section is executable
6187 section is excluded from executable and shared library.
6189 section is used for thread local storage
6192 This directive replaces the current section and subsection. See the
6193 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6194 some examples of how this directive and the other section stack directives
6200 @section @code{.set @var{symbol}, @var{expression}}
6202 @cindex @code{set} directive
6203 @cindex symbol value, setting
6204 Set the value of @var{symbol} to @var{expression}. This
6205 changes @var{symbol}'s value and type to conform to
6206 @var{expression}. If @var{symbol} was flagged as external, it remains
6207 flagged (@pxref{Symbol Attributes}).
6209 You may @code{.set} a symbol many times in the same assembly.
6211 If you @code{.set} a global symbol, the value stored in the object
6212 file is the last value stored into it.
6215 On Z80 @code{set} is a real instruction, use
6216 @samp{@var{symbol} defl @var{expression}} instead.
6220 @section @code{.short @var{expressions}}
6222 @cindex @code{short} directive
6224 @code{.short} is normally the same as @samp{.word}.
6225 @xref{Word,,@code{.word}}.
6227 In some configurations, however, @code{.short} and @code{.word} generate
6228 numbers of different lengths. @xref{Machine Dependencies}.
6232 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6235 This expects zero or more @var{expressions}, and emits
6236 a 16 bit number for each.
6241 @section @code{.single @var{flonums}}
6243 @cindex @code{single} directive
6244 @cindex floating point numbers (single)
6245 This directive assembles zero or more flonums, separated by commas. It
6246 has the same effect as @code{.float}.
6248 The exact kind of floating point numbers emitted depends on how
6249 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6253 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6254 numbers in @sc{ieee} format.
6260 @section @code{.size}
6262 This directive is used to set the size associated with a symbol.
6266 @c only print the extra heading if both COFF and ELF are set
6267 @subheading COFF Version
6270 @cindex @code{size} directive (COFF version)
6271 For COFF targets, the @code{.size} directive is only permitted inside
6272 @code{.def}/@code{.endef} pairs. It is used like this:
6275 .size @var{expression}
6279 @samp{.size} is only meaningful when generating COFF format output; when
6280 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6287 @c only print the extra heading if both COFF and ELF are set
6288 @subheading ELF Version
6291 @cindex @code{size} directive (ELF version)
6292 For ELF targets, the @code{.size} directive is used like this:
6295 .size @var{name} , @var{expression}
6298 This directive sets the size associated with a symbol @var{name}.
6299 The size in bytes is computed from @var{expression} which can make use of label
6300 arithmetic. This directive is typically used to set the size of function
6305 @ifclear no-space-dir
6307 @section @code{.skip @var{size} , @var{fill}}
6309 @cindex @code{skip} directive
6310 @cindex filling memory
6311 This directive emits @var{size} bytes, each of value @var{fill}. Both
6312 @var{size} and @var{fill} are absolute expressions. If the comma and
6313 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6318 @section @code{.sleb128 @var{expressions}}
6320 @cindex @code{sleb128} directive
6321 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6322 compact, variable length representation of numbers used by the DWARF
6323 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6325 @ifclear no-space-dir
6327 @section @code{.space @var{size} , @var{fill}}
6329 @cindex @code{space} directive
6330 @cindex filling memory
6331 This directive emits @var{size} bytes, each of value @var{fill}. Both
6332 @var{size} and @var{fill} are absolute expressions. If the comma
6333 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6338 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6339 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6340 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6341 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6349 @section @code{.stabd, .stabn, .stabs}
6351 @cindex symbolic debuggers, information for
6352 @cindex @code{stab@var{x}} directives
6353 There are three directives that begin @samp{.stab}.
6354 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6355 The symbols are not entered in the @command{@value{AS}} hash table: they
6356 cannot be referenced elsewhere in the source file.
6357 Up to five fields are required:
6361 This is the symbol's name. It may contain any character except
6362 @samp{\000}, so is more general than ordinary symbol names. Some
6363 debuggers used to code arbitrarily complex structures into symbol names
6367 An absolute expression. The symbol's type is set to the low 8 bits of
6368 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6369 and debuggers choke on silly bit patterns.
6372 An absolute expression. The symbol's ``other'' attribute is set to the
6373 low 8 bits of this expression.
6376 An absolute expression. The symbol's descriptor is set to the low 16
6377 bits of this expression.
6380 An absolute expression which becomes the symbol's value.
6383 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6384 or @code{.stabs} statement, the symbol has probably already been created;
6385 you get a half-formed symbol in your object file. This is
6386 compatible with earlier assemblers!
6389 @cindex @code{stabd} directive
6390 @item .stabd @var{type} , @var{other} , @var{desc}
6392 The ``name'' of the symbol generated is not even an empty string.
6393 It is a null pointer, for compatibility. Older assemblers used a
6394 null pointer so they didn't waste space in object files with empty
6397 The symbol's value is set to the location counter,
6398 relocatably. When your program is linked, the value of this symbol
6399 is the address of the location counter when the @code{.stabd} was
6402 @cindex @code{stabn} directive
6403 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6404 The name of the symbol is set to the empty string @code{""}.
6406 @cindex @code{stabs} directive
6407 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6408 All five fields are specified.
6414 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6415 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6417 @cindex string, copying to object file
6418 @cindex string8, copying to object file
6419 @cindex string16, copying to object file
6420 @cindex string32, copying to object file
6421 @cindex string64, copying to object file
6422 @cindex @code{string} directive
6423 @cindex @code{string8} directive
6424 @cindex @code{string16} directive
6425 @cindex @code{string32} directive
6426 @cindex @code{string64} directive
6428 Copy the characters in @var{str} to the object file. You may specify more than
6429 one string to copy, separated by commas. Unless otherwise specified for a
6430 particular machine, the assembler marks the end of each string with a 0 byte.
6431 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6433 The variants @code{string16}, @code{string32} and @code{string64} differ from
6434 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6435 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6436 are stored in target endianness byte order.
6442 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6443 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6448 @section @code{.struct @var{expression}}
6450 @cindex @code{struct} directive
6451 Switch to the absolute section, and set the section offset to @var{expression},
6452 which must be an absolute expression. You might use this as follows:
6461 This would define the symbol @code{field1} to have the value 0, the symbol
6462 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6463 value 8. Assembly would be left in the absolute section, and you would need to
6464 use a @code{.section} directive of some sort to change to some other section
6465 before further assembly.
6469 @section @code{.subsection @var{name}}
6471 @cindex @code{subsection} directive
6472 @cindex Section Stack
6473 This is one of the ELF section stack manipulation directives. The others are
6474 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6475 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6478 This directive replaces the current subsection with @code{name}. The current
6479 section is not changed. The replaced subsection is put onto the section stack
6480 in place of the then current top of stack subsection.
6485 @section @code{.symver}
6486 @cindex @code{symver} directive
6487 @cindex symbol versioning
6488 @cindex versions of symbols
6489 Use the @code{.symver} directive to bind symbols to specific version nodes
6490 within a source file. This is only supported on ELF platforms, and is
6491 typically used when assembling files to be linked into a shared library.
6492 There are cases where it may make sense to use this in objects to be bound
6493 into an application itself so as to override a versioned symbol from a
6496 For ELF targets, the @code{.symver} directive can be used like this:
6498 .symver @var{name}, @var{name2@@nodename}
6500 If the symbol @var{name} is defined within the file
6501 being assembled, the @code{.symver} directive effectively creates a symbol
6502 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6503 just don't try and create a regular alias is that the @var{@@} character isn't
6504 permitted in symbol names. The @var{name2} part of the name is the actual name
6505 of the symbol by which it will be externally referenced. The name @var{name}
6506 itself is merely a name of convenience that is used so that it is possible to
6507 have definitions for multiple versions of a function within a single source
6508 file, and so that the compiler can unambiguously know which version of a
6509 function is being mentioned. The @var{nodename} portion of the alias should be
6510 the name of a node specified in the version script supplied to the linker when
6511 building a shared library. If you are attempting to override a versioned
6512 symbol from a shared library, then @var{nodename} should correspond to the
6513 nodename of the symbol you are trying to override.
6515 If the symbol @var{name} is not defined within the file being assembled, all
6516 references to @var{name} will be changed to @var{name2@@nodename}. If no
6517 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6520 Another usage of the @code{.symver} directive is:
6522 .symver @var{name}, @var{name2@@@@nodename}
6524 In this case, the symbol @var{name} must exist and be defined within
6525 the file being assembled. It is similar to @var{name2@@nodename}. The
6526 difference is @var{name2@@@@nodename} will also be used to resolve
6527 references to @var{name2} by the linker.
6529 The third usage of the @code{.symver} directive is:
6531 .symver @var{name}, @var{name2@@@@@@nodename}
6533 When @var{name} is not defined within the
6534 file being assembled, it is treated as @var{name2@@nodename}. When
6535 @var{name} is defined within the file being assembled, the symbol
6536 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6541 @section @code{.tag @var{structname}}
6543 @cindex COFF structure debugging
6544 @cindex structure debugging, COFF
6545 @cindex @code{tag} directive
6546 This directive is generated by compilers to include auxiliary debugging
6547 information in the symbol table. It is only permitted inside
6548 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6549 definitions in the symbol table with instances of those structures.
6552 @samp{.tag} is only used when generating COFF format output; when
6553 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6559 @section @code{.text @var{subsection}}
6561 @cindex @code{text} directive
6562 Tells @command{@value{AS}} to assemble the following statements onto the end of
6563 the text subsection numbered @var{subsection}, which is an absolute
6564 expression. If @var{subsection} is omitted, subsection number zero
6568 @section @code{.title "@var{heading}"}
6570 @cindex @code{title} directive
6571 @cindex listing control: title line
6572 Use @var{heading} as the title (second line, immediately after the
6573 source file name and pagenumber) when generating assembly listings.
6575 This directive affects subsequent pages, as well as the current page if
6576 it appears within ten lines of the top of a page.
6580 @section @code{.type}
6582 This directive is used to set the type of a symbol.
6586 @c only print the extra heading if both COFF and ELF are set
6587 @subheading COFF Version
6590 @cindex COFF symbol type
6591 @cindex symbol type, COFF
6592 @cindex @code{type} directive (COFF version)
6593 For COFF targets, this directive is permitted only within
6594 @code{.def}/@code{.endef} pairs. It is used like this:
6600 This records the integer @var{int} as the type attribute of a symbol table
6604 @samp{.type} is associated only with COFF format output; when
6605 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6606 directive but ignores it.
6612 @c only print the extra heading if both COFF and ELF are set
6613 @subheading ELF Version
6616 @cindex ELF symbol type
6617 @cindex symbol type, ELF
6618 @cindex @code{type} directive (ELF version)
6619 For ELF targets, the @code{.type} directive is used like this:
6622 .type @var{name} , @var{type description}
6625 This sets the type of symbol @var{name} to be either a
6626 function symbol or an object symbol. There are five different syntaxes
6627 supported for the @var{type description} field, in order to provide
6628 compatibility with various other assemblers.
6630 Because some of the characters used in these syntaxes (such as @samp{@@} and
6631 @samp{#}) are comment characters for some architectures, some of the syntaxes
6632 below do not work on all architectures. The first variant will be accepted by
6633 the GNU assembler on all architectures so that variant should be used for
6634 maximum portability, if you do not need to assemble your code with other
6637 The syntaxes supported are:
6640 .type <name> STT_<TYPE_IN_UPPER_CASE>
6641 .type <name>,#<type>
6642 .type <name>,@@<type>
6643 .type <name>,%<type>
6644 .type <name>,"<type>"
6647 The types supported are:
6652 Mark the symbol as being a function name.
6655 @itemx gnu_indirect_function
6656 Mark the symbol as an indirect function when evaluated during reloc
6657 processing. (This is only supported on assemblers targeting GNU systems).
6661 Mark the symbol as being a data object.
6665 Mark the symbol as being a thead-local data object.
6669 Mark the symbol as being a common data object.
6673 Does not mark the symbol in any way. It is supported just for completeness.
6675 @item gnu_unique_object
6676 Marks the symbol as being a globally unique data object. The dynamic linker
6677 will make sure that in the entire process there is just one symbol with this
6678 name and type in use. (This is only supported on assemblers targeting GNU
6683 Note: Some targets support extra types in addition to those listed above.
6689 @section @code{.uleb128 @var{expressions}}
6691 @cindex @code{uleb128} directive
6692 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6693 compact, variable length representation of numbers used by the DWARF
6694 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6698 @section @code{.val @var{addr}}
6700 @cindex @code{val} directive
6701 @cindex COFF value attribute
6702 @cindex value attribute, COFF
6703 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6704 records the address @var{addr} as the value attribute of a symbol table
6708 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6709 configured for @code{b.out}, it accepts this directive but ignores it.
6715 @section @code{.version "@var{string}"}
6717 @cindex @code{version} directive
6718 This directive creates a @code{.note} section and places into it an ELF
6719 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6724 @section @code{.vtable_entry @var{table}, @var{offset}}
6726 @cindex @code{vtable_entry} directive
6727 This directive finds or creates a symbol @code{table} and creates a
6728 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6731 @section @code{.vtable_inherit @var{child}, @var{parent}}
6733 @cindex @code{vtable_inherit} directive
6734 This directive finds the symbol @code{child} and finds or creates the symbol
6735 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6736 parent whose addend is the value of the child symbol. As a special case the
6737 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6741 @section @code{.warning "@var{string}"}
6742 @cindex warning directive
6743 Similar to the directive @code{.error}
6744 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6747 @section @code{.weak @var{names}}
6749 @cindex @code{weak} directive
6750 This directive sets the weak attribute on the comma separated list of symbol
6751 @code{names}. If the symbols do not already exist, they will be created.
6753 On COFF targets other than PE, weak symbols are a GNU extension. This
6754 directive sets the weak attribute on the comma separated list of symbol
6755 @code{names}. If the symbols do not already exist, they will be created.
6757 On the PE target, weak symbols are supported natively as weak aliases.
6758 When a weak symbol is created that is not an alias, GAS creates an
6759 alternate symbol to hold the default value.
6762 @section @code{.weakref @var{alias}, @var{target}}
6764 @cindex @code{weakref} directive
6765 This directive creates an alias to the target symbol that enables the symbol to
6766 be referenced with weak-symbol semantics, but without actually making it weak.
6767 If direct references or definitions of the symbol are present, then the symbol
6768 will not be weak, but if all references to it are through weak references, the
6769 symbol will be marked as weak in the symbol table.
6771 The effect is equivalent to moving all references to the alias to a separate
6772 assembly source file, renaming the alias to the symbol in it, declaring the
6773 symbol as weak there, and running a reloadable link to merge the object files
6774 resulting from the assembly of the new source file and the old source file that
6775 had the references to the alias removed.
6777 The alias itself never makes to the symbol table, and is entirely handled
6778 within the assembler.
6781 @section @code{.word @var{expressions}}
6783 @cindex @code{word} directive
6784 This directive expects zero or more @var{expressions}, of any section,
6785 separated by commas.
6788 For each expression, @command{@value{AS}} emits a 32-bit number.
6791 For each expression, @command{@value{AS}} emits a 16-bit number.
6796 The size of the number emitted, and its byte order,
6797 depend on what target computer the assembly is for.
6800 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6801 @c happen---32-bit addressability, period; no long/short jumps.
6802 @ifset DIFF-TBL-KLUGE
6803 @cindex difference tables altered
6804 @cindex altered difference tables
6806 @emph{Warning: Special Treatment to support Compilers}
6810 Machines with a 32-bit address space, but that do less than 32-bit
6811 addressing, require the following special treatment. If the machine of
6812 interest to you does 32-bit addressing (or doesn't require it;
6813 @pxref{Machine Dependencies}), you can ignore this issue.
6816 In order to assemble compiler output into something that works,
6817 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6818 Directives of the form @samp{.word sym1-sym2} are often emitted by
6819 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6820 directive of the form @samp{.word sym1-sym2}, and the difference between
6821 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6822 creates a @dfn{secondary jump table}, immediately before the next label.
6823 This secondary jump table is preceded by a short-jump to the
6824 first byte after the secondary table. This short-jump prevents the flow
6825 of control from accidentally falling into the new table. Inside the
6826 table is a long-jump to @code{sym2}. The original @samp{.word}
6827 contains @code{sym1} minus the address of the long-jump to
6830 If there were several occurrences of @samp{.word sym1-sym2} before the
6831 secondary jump table, all of them are adjusted. If there was a
6832 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6833 long-jump to @code{sym4} is included in the secondary jump table,
6834 and the @code{.word} directives are adjusted to contain @code{sym3}
6835 minus the address of the long-jump to @code{sym4}; and so on, for as many
6836 entries in the original jump table as necessary.
6839 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6840 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6841 assembly language programmers.
6844 @c end DIFF-TBL-KLUGE
6847 @section Deprecated Directives
6849 @cindex deprecated directives
6850 @cindex obsolescent directives
6851 One day these directives won't work.
6852 They are included for compatibility with older assemblers.
6859 @node Object Attributes
6860 @chapter Object Attributes
6861 @cindex object attributes
6863 @command{@value{AS}} assembles source files written for a specific architecture
6864 into object files for that architecture. But not all object files are alike.
6865 Many architectures support incompatible variations. For instance, floating
6866 point arguments might be passed in floating point registers if the object file
6867 requires hardware floating point support---or floating point arguments might be
6868 passed in integer registers if the object file supports processors with no
6869 hardware floating point unit. Or, if two objects are built for different
6870 generations of the same architecture, the combination may require the
6871 newer generation at run-time.
6873 This information is useful during and after linking. At link time,
6874 @command{@value{LD}} can warn about incompatible object files. After link
6875 time, tools like @command{gdb} can use it to process the linked file
6878 Compatibility information is recorded as a series of object attributes. Each
6879 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6880 string, and indicates who sets the meaning of the tag. The tag is an integer,
6881 and indicates what property the attribute describes. The value may be a string
6882 or an integer, and indicates how the property affects this object. Missing
6883 attributes are the same as attributes with a zero value or empty string value.
6885 Object attributes were developed as part of the ABI for the ARM Architecture.
6886 The file format is documented in @cite{ELF for the ARM Architecture}.
6889 * GNU Object Attributes:: @sc{gnu} Object Attributes
6890 * Defining New Object Attributes:: Defining New Object Attributes
6893 @node GNU Object Attributes
6894 @section @sc{gnu} Object Attributes
6896 The @code{.gnu_attribute} directive records an object attribute
6897 with vendor @samp{gnu}.
6899 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6900 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6901 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6902 2} is set for architecture-independent attributes and clear for
6903 architecture-dependent ones.
6905 @subsection Common @sc{gnu} attributes
6907 These attributes are valid on all architectures.
6910 @item Tag_compatibility (32)
6911 The compatibility attribute takes an integer flag value and a vendor name. If
6912 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6913 then the file is only compatible with the named toolchain. If it is greater
6914 than 1, the file can only be processed by other toolchains under some private
6915 arrangement indicated by the flag value and the vendor name.
6918 @subsection MIPS Attributes
6921 @item Tag_GNU_MIPS_ABI_FP (4)
6922 The floating-point ABI used by this object file. The value will be:
6926 0 for files not affected by the floating-point ABI.
6928 1 for files using the hardware floating-point with a standard double-precision
6931 2 for files using the hardware floating-point ABI with a single-precision FPU.
6933 3 for files using the software floating-point ABI.
6935 4 for files using the hardware floating-point ABI with 64-bit wide
6936 double-precision floating-point registers and 32-bit wide general
6941 @subsection PowerPC Attributes
6944 @item Tag_GNU_Power_ABI_FP (4)
6945 The floating-point ABI used by this object file. The value will be:
6949 0 for files not affected by the floating-point ABI.
6951 1 for files using double-precision hardware floating-point ABI.
6953 2 for files using the software floating-point ABI.
6955 3 for files using single-precision hardware floating-point ABI.
6958 @item Tag_GNU_Power_ABI_Vector (8)
6959 The vector ABI used by this object file. The value will be:
6963 0 for files not affected by the vector ABI.
6965 1 for files using general purpose registers to pass vectors.
6967 2 for files using AltiVec registers to pass vectors.
6969 3 for files using SPE registers to pass vectors.
6973 @node Defining New Object Attributes
6974 @section Defining New Object Attributes
6976 If you want to define a new @sc{gnu} object attribute, here are the places you
6977 will need to modify. New attributes should be discussed on the @samp{binutils}
6982 This manual, which is the official register of attributes.
6984 The header for your architecture @file{include/elf}, to define the tag.
6986 The @file{bfd} support file for your architecture, to merge the attribute
6987 and issue any appropriate link warnings.
6989 Test cases in @file{ld/testsuite} for merging and link warnings.
6991 @file{binutils/readelf.c} to display your attribute.
6993 GCC, if you want the compiler to mark the attribute automatically.
6999 @node Machine Dependencies
7000 @chapter Machine Dependent Features
7002 @cindex machine dependencies
7003 The machine instruction sets are (almost by definition) different on
7004 each machine where @command{@value{AS}} runs. Floating point representations
7005 vary as well, and @command{@value{AS}} often supports a few additional
7006 directives or command-line options for compatibility with other
7007 assemblers on a particular platform. Finally, some versions of
7008 @command{@value{AS}} support special pseudo-instructions for branch
7011 This chapter discusses most of these differences, though it does not
7012 include details on any machine's instruction set. For details on that
7013 subject, see the hardware manufacturer's manual.
7017 * AArch64-Dependent:: AArch64 Dependent Features
7020 * Alpha-Dependent:: Alpha Dependent Features
7023 * ARC-Dependent:: ARC Dependent Features
7026 * ARM-Dependent:: ARM Dependent Features
7029 * AVR-Dependent:: AVR Dependent Features
7032 * Blackfin-Dependent:: Blackfin Dependent Features
7035 * CR16-Dependent:: CR16 Dependent Features
7038 * CRIS-Dependent:: CRIS Dependent Features
7041 * D10V-Dependent:: D10V Dependent Features
7044 * D30V-Dependent:: D30V Dependent Features
7047 * Epiphany-Dependent:: EPIPHANY Dependent Features
7050 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7053 * HPPA-Dependent:: HPPA Dependent Features
7056 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7059 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7062 * i860-Dependent:: Intel 80860 Dependent Features
7065 * i960-Dependent:: Intel 80960 Dependent Features
7068 * IA-64-Dependent:: Intel IA-64 Dependent Features
7071 * IP2K-Dependent:: IP2K Dependent Features
7074 * LM32-Dependent:: LM32 Dependent Features
7077 * M32C-Dependent:: M32C Dependent Features
7080 * M32R-Dependent:: M32R Dependent Features
7083 * M68K-Dependent:: M680x0 Dependent Features
7086 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7089 * Meta-Dependent :: Meta Dependent Features
7092 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7095 * MIPS-Dependent:: MIPS Dependent Features
7098 * MMIX-Dependent:: MMIX Dependent Features
7101 * MSP430-Dependent:: MSP430 Dependent Features
7104 * NiosII-Dependent:: Altera Nios II Dependent Features
7107 * NS32K-Dependent:: NS32K Dependent Features
7110 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7111 * SH64-Dependent:: SuperH SH64 Dependent Features
7114 * PDP-11-Dependent:: PDP-11 Dependent Features
7117 * PJ-Dependent:: picoJava Dependent Features
7120 * PPC-Dependent:: PowerPC Dependent Features
7123 * RL78-Dependent:: RL78 Dependent Features
7126 * RX-Dependent:: RX Dependent Features
7129 * S/390-Dependent:: IBM S/390 Dependent Features
7132 * SCORE-Dependent:: SCORE Dependent Features
7135 * Sparc-Dependent:: SPARC Dependent Features
7138 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7141 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7144 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7147 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7150 * V850-Dependent:: V850 Dependent Features
7153 * XGATE-Dependent:: XGATE Features
7156 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7159 * Xtensa-Dependent:: Xtensa Dependent Features
7162 * Z80-Dependent:: Z80 Dependent Features
7165 * Z8000-Dependent:: Z8000 Dependent Features
7168 * Vax-Dependent:: VAX Dependent Features
7175 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7176 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7177 @c peculiarity: to preserve cross-references, there must be a node called
7178 @c "Machine Dependencies". Hence the conditional nodenames in each
7179 @c major node below. Node defaulting in makeinfo requires adjacency of
7180 @c node and sectioning commands; hence the repetition of @chapter BLAH
7181 @c in both conditional blocks.
7184 @include c-aarch64.texi
7188 @include c-alpha.texi
7204 @include c-bfin.texi
7208 @include c-cr16.texi
7212 @include c-cris.texi
7217 @node Machine Dependencies
7218 @chapter Machine Dependent Features
7220 The machine instruction sets are different on each Renesas chip family,
7221 and there are also some syntax differences among the families. This
7222 chapter describes the specific @command{@value{AS}} features for each
7226 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7227 * SH-Dependent:: Renesas SH Dependent Features
7234 @include c-d10v.texi
7238 @include c-d30v.texi
7242 @include c-epiphany.texi
7246 @include c-h8300.texi
7250 @include c-hppa.texi
7254 @include c-i370.texi
7258 @include c-i386.texi
7262 @include c-i860.texi
7266 @include c-i960.texi
7270 @include c-ia64.texi
7274 @include c-ip2k.texi
7278 @include c-lm32.texi
7282 @include c-m32c.texi
7286 @include c-m32r.texi
7290 @include c-m68k.texi
7294 @include c-m68hc11.texi
7298 @include c-metag.texi
7302 @include c-microblaze.texi
7306 @include c-mips.texi
7310 @include c-mmix.texi
7314 @include c-msp430.texi
7318 @include c-nios2.texi
7322 @include c-ns32k.texi
7326 @include c-pdp11.texi
7338 @include c-rl78.texi
7346 @include c-s390.texi
7350 @include c-score.texi
7355 @include c-sh64.texi
7359 @include c-sparc.texi
7363 @include c-tic54x.texi
7367 @include c-tic6x.texi
7371 @include c-tilegx.texi
7375 @include c-tilepro.texi
7391 @include c-v850.texi
7395 @include c-xgate.texi
7399 @include c-xstormy16.texi
7403 @include c-xtensa.texi
7407 @c reverse effect of @down at top of generic Machine-Dep chapter
7411 @node Reporting Bugs
7412 @chapter Reporting Bugs
7413 @cindex bugs in assembler
7414 @cindex reporting bugs in assembler
7416 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7418 Reporting a bug may help you by bringing a solution to your problem, or it may
7419 not. But in any case the principal function of a bug report is to help the
7420 entire community by making the next version of @command{@value{AS}} work better.
7421 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7423 In order for a bug report to serve its purpose, you must include the
7424 information that enables us to fix the bug.
7427 * Bug Criteria:: Have you found a bug?
7428 * Bug Reporting:: How to report bugs
7432 @section Have You Found a Bug?
7433 @cindex bug criteria
7435 If you are not sure whether you have found a bug, here are some guidelines:
7438 @cindex fatal signal
7439 @cindex assembler crash
7440 @cindex crash of assembler
7442 If the assembler gets a fatal signal, for any input whatever, that is a
7443 @command{@value{AS}} bug. Reliable assemblers never crash.
7445 @cindex error on valid input
7447 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7449 @cindex invalid input
7451 If @command{@value{AS}} does not produce an error message for invalid input, that
7452 is a bug. However, you should note that your idea of ``invalid input'' might
7453 be our idea of ``an extension'' or ``support for traditional practice''.
7456 If you are an experienced user of assemblers, your suggestions for improvement
7457 of @command{@value{AS}} are welcome in any case.
7461 @section How to Report Bugs
7463 @cindex assembler bugs, reporting
7465 A number of companies and individuals offer support for @sc{gnu} products. If
7466 you obtained @command{@value{AS}} from a support organization, we recommend you
7467 contact that organization first.
7469 You can find contact information for many support companies and
7470 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7474 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7478 The fundamental principle of reporting bugs usefully is this:
7479 @strong{report all the facts}. If you are not sure whether to state a
7480 fact or leave it out, state it!
7482 Often people omit facts because they think they know what causes the problem
7483 and assume that some details do not matter. Thus, you might assume that the
7484 name of a symbol you use in an example does not matter. Well, probably it does
7485 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7486 happens to fetch from the location where that name is stored in memory;
7487 perhaps, if the name were different, the contents of that location would fool
7488 the assembler into doing the right thing despite the bug. Play it safe and
7489 give a specific, complete example. That is the easiest thing for you to do,
7490 and the most helpful.
7492 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7493 it is new to us. Therefore, always write your bug reports on the assumption
7494 that the bug has not been reported previously.
7496 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7497 bell?'' This cannot help us fix a bug, so it is basically useless. We
7498 respond by asking for enough details to enable us to investigate.
7499 You might as well expedite matters by sending them to begin with.
7501 To enable us to fix the bug, you should include all these things:
7505 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7506 it with the @samp{--version} argument.
7508 Without this, we will not know whether there is any point in looking for
7509 the bug in the current version of @command{@value{AS}}.
7512 Any patches you may have applied to the @command{@value{AS}} source.
7515 The type of machine you are using, and the operating system name and
7519 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7523 The command arguments you gave the assembler to assemble your example and
7524 observe the bug. To guarantee you will not omit something important, list them
7525 all. A copy of the Makefile (or the output from make) is sufficient.
7527 If we were to try to guess the arguments, we would probably guess wrong
7528 and then we might not encounter the bug.
7531 A complete input file that will reproduce the bug. If the bug is observed when
7532 the assembler is invoked via a compiler, send the assembler source, not the
7533 high level language source. Most compilers will produce the assembler source
7534 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7535 the options @samp{-v --save-temps}; this will save the assembler source in a
7536 file with an extension of @file{.s}, and also show you exactly how
7537 @command{@value{AS}} is being run.
7540 A description of what behavior you observe that you believe is
7541 incorrect. For example, ``It gets a fatal signal.''
7543 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7544 will certainly notice it. But if the bug is incorrect output, we might not
7545 notice unless it is glaringly wrong. You might as well not give us a chance to
7548 Even if the problem you experience is a fatal signal, you should still say so
7549 explicitly. Suppose something strange is going on, such as, your copy of
7550 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7551 library on your system. (This has happened!) Your copy might crash and ours
7552 would not. If you told us to expect a crash, then when ours fails to crash, we
7553 would know that the bug was not happening for us. If you had not told us to
7554 expect a crash, then we would not be able to draw any conclusion from our
7558 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7559 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7560 option. Always send diffs from the old file to the new file. If you even
7561 discuss something in the @command{@value{AS}} source, refer to it by context, not
7564 The line numbers in our development sources will not match those in your
7565 sources. Your line numbers would convey no useful information to us.
7568 Here are some things that are not necessary:
7572 A description of the envelope of the bug.
7574 Often people who encounter a bug spend a lot of time investigating
7575 which changes to the input file will make the bug go away and which
7576 changes will not affect it.
7578 This is often time consuming and not very useful, because the way we
7579 will find the bug is by running a single example under the debugger
7580 with breakpoints, not by pure deduction from a series of examples.
7581 We recommend that you save your time for something else.
7583 Of course, if you can find a simpler example to report @emph{instead}
7584 of the original one, that is a convenience for us. Errors in the
7585 output will be easier to spot, running under the debugger will take
7586 less time, and so on.
7588 However, simplification is not vital; if you do not want to do this,
7589 report the bug anyway and send us the entire test case you used.
7592 A patch for the bug.
7594 A patch for the bug does help us if it is a good one. But do not omit
7595 the necessary information, such as the test case, on the assumption that
7596 a patch is all we need. We might see problems with your patch and decide
7597 to fix the problem another way, or we might not understand it at all.
7599 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7600 construct an example that will make the program follow a certain path through
7601 the code. If you do not send us the example, we will not be able to construct
7602 one, so we will not be able to verify that the bug is fixed.
7604 And if we cannot understand what bug you are trying to fix, or why your
7605 patch should be an improvement, we will not install it. A test case will
7606 help us to understand.
7609 A guess about what the bug is or what it depends on.
7611 Such guesses are usually wrong. Even we cannot guess right about such
7612 things without first using the debugger to find the facts.
7615 @node Acknowledgements
7616 @chapter Acknowledgements
7618 If you have contributed to GAS and your name isn't listed here,
7619 it is not meant as a slight. We just don't know about it. Send mail to the
7620 maintainer, and we'll correct the situation. Currently
7622 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7624 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7627 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7628 information and the 68k series machines, most of the preprocessing pass, and
7629 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7631 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7632 many bug fixes, including merging support for several processors, breaking GAS
7633 up to handle multiple object file format back ends (including heavy rewrite,
7634 testing, an integration of the coff and b.out back ends), adding configuration
7635 including heavy testing and verification of cross assemblers and file splits
7636 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7637 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7638 port (including considerable amounts of reverse engineering), a SPARC opcode
7639 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7640 assertions and made them work, much other reorganization, cleanup, and lint.
7642 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7643 in format-specific I/O modules.
7645 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7646 has done much work with it since.
7648 The Intel 80386 machine description was written by Eliot Dresselhaus.
7650 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7652 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7653 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7655 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7656 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7657 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7658 support a.out format.
7660 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7661 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7662 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7663 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7666 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7667 simplified the configuration of which versions accept which directives. He
7668 updated the 68k machine description so that Motorola's opcodes always produced
7669 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7670 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7671 cross-compilation support, and one bug in relaxation that took a week and
7672 required the proverbial one-bit fix.
7674 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7675 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7676 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7677 PowerPC assembler, and made a few other minor patches.
7679 Steve Chamberlain made GAS able to generate listings.
7681 Hewlett-Packard contributed support for the HP9000/300.
7683 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7684 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7685 formats). This work was supported by both the Center for Software Science at
7686 the University of Utah and Cygnus Support.
7688 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7689 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7690 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7691 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7692 and some initial 64-bit support).
7694 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7696 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7697 support for openVMS/Alpha.
7699 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7702 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7703 Inc.@: added support for Xtensa processors.
7705 Several engineers at Cygnus Support have also provided many small bug fixes and
7706 configuration enhancements.
7708 Jon Beniston added support for the Lattice Mico32 architecture.
7710 Many others have contributed large or small bugfixes and enhancements. If
7711 you have contributed significant work and are not mentioned on this list, and
7712 want to be, let us know. Some of the history has been lost; we are not
7713 intentionally leaving anyone out.
7715 @node GNU Free Documentation License
7716 @appendix GNU Free Documentation License
7720 @unnumbered AS Index
projects / platform / upstream / binutils.git / blob