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:}
251 [@b{-mabi}=@var{ABI}]
255 @emph{Target Alpha options:}
257 [@b{-mdebug} | @b{-no-mdebug}]
258 [@b{-replace} | @b{-noreplace}]
259 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
260 [@b{-F}] [@b{-32addr}]
264 @emph{Target ARC options:}
270 @emph{Target ARM options:}
271 @c Don't document the deprecated options
272 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
273 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
274 [@b{-mfpu}=@var{floating-point-format}]
275 [@b{-mfloat-abi}=@var{abi}]
276 [@b{-meabi}=@var{ver}]
279 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
280 @b{-mapcs-reentrant}]
281 [@b{-mthumb-interwork}] [@b{-k}]
285 @emph{Target Blackfin options:}
286 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
293 @emph{Target CRIS options:}
294 [@b{--underscore} | @b{--no-underscore}]
296 [@b{--emulation=criself} | @b{--emulation=crisaout}]
297 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
298 @c Deprecated -- deliberately not documented.
303 @emph{Target D10V options:}
308 @emph{Target D30V options:}
309 [@b{-O}|@b{-n}|@b{-N}]
313 @emph{Target EPIPHANY options:}
314 [@b{-mepiphany}|@b{-mepiphany16}]
318 @emph{Target H8/300 options:}
322 @c HPPA has no machine-dependent assembler options (yet).
326 @emph{Target i386 options:}
327 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
328 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
332 @emph{Target i960 options:}
333 @c see md_parse_option in tc-i960.c
334 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
336 [@b{-b}] [@b{-no-relax}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
345 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
346 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
347 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
351 @emph{Target IP2K options:}
352 [@b{-mip2022}|@b{-mip2022ext}]
356 @emph{Target M32C options:}
357 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
361 @emph{Target M32R options:}
362 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
367 @emph{Target M680X0 options:}
368 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
372 @emph{Target M68HC11 options:}
373 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
374 [@b{-mshort}|@b{-mlong}]
375 [@b{-mshort-double}|@b{-mlong-double}]
376 [@b{--force-long-branches}] [@b{--short-branches}]
377 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
378 [@b{--print-opcodes}] [@b{--generate-example}]
382 @emph{Target MCORE options:}
383 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
384 [@b{-mcpu=[210|340]}]
388 @emph{Target Meta options:}
389 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
392 @emph{Target MICROBLAZE options:}
393 @c MicroBlaze has no machine-dependent assembler options.
397 @emph{Target MIPS options:}
398 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
399 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
400 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
401 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
402 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
403 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
404 [@b{-mips64}] [@b{-mips64r2}]
405 [@b{-construct-floats}] [@b{-no-construct-floats}]
406 [@b{-mnan=@var{encoding}}]
407 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
408 [@b{-mips16}] [@b{-no-mips16}]
409 [@b{-mmicromips}] [@b{-mno-micromips}]
410 [@b{-msmartmips}] [@b{-mno-smartmips}]
411 [@b{-mips3d}] [@b{-no-mips3d}]
412 [@b{-mdmx}] [@b{-no-mdmx}]
413 [@b{-mdsp}] [@b{-mno-dsp}]
414 [@b{-mdspr2}] [@b{-mno-dspr2}]
415 [@b{-mmt}] [@b{-mno-mt}]
416 [@b{-mmcu}] [@b{-mno-mcu}]
417 [@b{-minsn32}] [@b{-mno-insn32}]
418 [@b{-mfix7000}] [@b{-mno-fix7000}]
419 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
420 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
421 [@b{-mdebug}] [@b{-no-mdebug}]
422 [@b{-mpdr}] [@b{-mno-pdr}]
426 @emph{Target MMIX options:}
427 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
428 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
429 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
430 [@b{--linker-allocated-gregs}]
434 @emph{Target Nios II options:}
435 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
440 @emph{Target PDP11 options:}
441 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
442 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
443 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
447 @emph{Target picoJava options:}
452 @emph{Target PowerPC options:}
454 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
455 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
456 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
457 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
458 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
459 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
460 [@b{-mregnames}|@b{-mno-regnames}]
461 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
462 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
463 [@b{-msolaris}|@b{-mno-solaris}]
464 [@b{-nops=@var{count}}]
468 @emph{Target RX options:}
469 [@b{-mlittle-endian}|@b{-mbig-endian}]
470 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
471 [@b{-muse-conventional-section-names}]
472 [@b{-msmall-data-limit}]
475 [@b{-mint-register=@var{number}}]
476 [@b{-mgcc-abi}|@b{-mrx-abi}]
480 @emph{Target s390 options:}
481 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
482 [@b{-mregnames}|@b{-mno-regnames}]
483 [@b{-mwarn-areg-zero}]
487 @emph{Target SCORE options:}
488 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
489 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
490 [@b{-march=score7}][@b{-march=score3}]
491 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
495 @emph{Target SPARC options:}
496 @c The order here is important. See c-sparc.texi.
497 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
498 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
499 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
504 @emph{Target TIC54X options:}
505 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
506 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
511 @emph{Target TIC6X options:}
512 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
513 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
514 [@b{-mpic}|@b{-mno-pic}]
518 @emph{Target TILE-Gx options:}
519 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
522 @c TILEPro has no machine-dependent assembler options
527 @emph{Target Xtensa options:}
528 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
529 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
530 [@b{--[no-]transform}]
531 [@b{--rename-section} @var{oldname}=@var{newname}]
536 @emph{Target Z80 options:}
537 [@b{-z80}] [@b{-r800}]
538 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
539 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
540 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
541 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
542 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
543 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
547 @c Z8000 has no machine-dependent assembler options
556 @include at-file.texi
559 Turn on listings, in any of a variety of ways:
563 omit false conditionals
566 omit debugging directives
569 include general information, like @value{AS} version and options passed
572 include high-level source
578 include macro expansions
581 omit forms processing
587 set the name of the listing file
590 You may combine these options; for example, use @samp{-aln} for assembly
591 listing without forms processing. The @samp{=file} option, if used, must be
592 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
595 Begin in alternate macro mode.
597 @xref{Altmacro,,@code{.altmacro}}.
600 @item --compress-debug-sections
601 Compress DWARF debug sections using zlib. The debug sections are renamed
602 to begin with @samp{.zdebug}, and the resulting object file may not be
603 compatible with older linkers and object file utilities.
605 @item --nocompress-debug-sections
606 Do not compress DWARF debug sections. This is the default.
609 Ignored. This option is accepted for script compatibility with calls to
612 @item --debug-prefix-map @var{old}=@var{new}
613 When assembling files in directory @file{@var{old}}, record debugging
614 information describing them as in @file{@var{new}} instead.
616 @item --defsym @var{sym}=@var{value}
617 Define the symbol @var{sym} to be @var{value} before assembling the input file.
618 @var{value} must be an integer constant. As in C, a leading @samp{0x}
619 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
620 value. The value of the symbol can be overridden inside a source file via the
621 use of a @code{.set} pseudo-op.
624 ``fast''---skip whitespace and comment preprocessing (assume source is
629 Generate debugging information for each assembler source line using whichever
630 debug format is preferred by the target. This currently means either STABS,
634 Generate stabs debugging information for each assembler line. This
635 may help debugging assembler code, if the debugger can handle it.
638 Generate stabs debugging information for each assembler line, with GNU
639 extensions that probably only gdb can handle, and that could make other
640 debuggers crash or refuse to read your program. This
641 may help debugging assembler code. Currently the only GNU extension is
642 the location of the current working directory at assembling time.
645 Generate DWARF2 debugging information for each assembler line. This
646 may help debugging assembler code, if the debugger can handle it. Note---this
647 option is only supported by some targets, not all of them.
649 @item --gdwarf-sections
650 Instead of creating a .debug_line section, create a series of
651 .debug_line.@var{foo} sections where @var{foo} is the name of the
652 corresponding code section. For example a code section called @var{.text.func}
653 will have its dwarf line number information placed into a section called
654 @var{.debug_line.text.func}. If the code section is just called @var{.text}
655 then debug line section will still be called just @var{.debug_line} without any
658 @item --size-check=error
659 @itemx --size-check=warning
660 Issue an error or warning for invalid ELF .size directive.
663 Print a summary of the command line options and exit.
666 Print a summary of all target specific options and exit.
669 Add directory @var{dir} to the search list for @code{.include} directives.
672 Don't warn about signed overflow.
675 @ifclear DIFF-TBL-KLUGE
676 This option is accepted but has no effect on the @value{TARGET} family.
678 @ifset DIFF-TBL-KLUGE
679 Issue warnings when difference tables altered for long displacements.
684 Keep (in the symbol table) local symbols. These symbols start with
685 system-specific local label prefixes, typically @samp{.L} for ELF systems
686 or @samp{L} for traditional a.out systems.
691 @item --listing-lhs-width=@var{number}
692 Set the maximum width, in words, of the output data column for an assembler
693 listing to @var{number}.
695 @item --listing-lhs-width2=@var{number}
696 Set the maximum width, in words, of the output data column for continuation
697 lines in an assembler listing to @var{number}.
699 @item --listing-rhs-width=@var{number}
700 Set the maximum width of an input source line, as displayed in a listing, to
703 @item --listing-cont-lines=@var{number}
704 Set the maximum number of lines printed in a listing for a single line of input
707 @item -o @var{objfile}
708 Name the object-file output from @command{@value{AS}} @var{objfile}.
711 Fold the data section into the text section.
713 @kindex --hash-size=@var{number}
714 Set the default size of GAS's hash tables to a prime number close to
715 @var{number}. Increasing this value can reduce the length of time it takes the
716 assembler to perform its tasks, at the expense of increasing the assembler's
717 memory requirements. Similarly reducing this value can reduce the memory
718 requirements at the expense of speed.
720 @item --reduce-memory-overheads
721 This option reduces GAS's memory requirements, at the expense of making the
722 assembly processes slower. Currently this switch is a synonym for
723 @samp{--hash-size=4051}, but in the future it may have other effects as well.
726 Print the maximum space (in bytes) and total time (in seconds) used by
729 @item --strip-local-absolute
730 Remove local absolute symbols from the outgoing symbol table.
734 Print the @command{as} version.
737 Print the @command{as} version and exit.
741 Suppress warning messages.
743 @item --fatal-warnings
744 Treat warnings as errors.
747 Don't suppress warning messages or treat them as errors.
756 Generate an object file even after errors.
758 @item -- | @var{files} @dots{}
759 Standard input, or source files to assemble.
767 @xref{AArch64 Options}, for the options available when @value{AS} is configured
768 for the 64-bit mode of the ARM Architecture (AArch64).
773 The following options are available when @value{AS} is configured for the
774 64-bit mode of the ARM Architecture (AArch64).
777 @include c-aarch64.texi
778 @c ended inside the included file
786 @xref{Alpha Options}, for the options available when @value{AS} is configured
787 for an Alpha processor.
792 The following options are available when @value{AS} is configured for an Alpha
796 @include c-alpha.texi
797 @c ended inside the included file
804 The following options are available when @value{AS} is configured for
809 This option selects the core processor variant.
811 Select either big-endian (-EB) or little-endian (-EL) output.
816 The following options are available when @value{AS} is configured for the ARM
820 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
821 Specify which ARM processor variant is the target.
822 @item -march=@var{architecture}[+@var{extension}@dots{}]
823 Specify which ARM architecture variant is used by the target.
824 @item -mfpu=@var{floating-point-format}
825 Select which Floating Point architecture is the target.
826 @item -mfloat-abi=@var{abi}
827 Select which floating point ABI is in use.
829 Enable Thumb only instruction decoding.
830 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
831 Select which procedure calling convention is in use.
833 Select either big-endian (-EB) or little-endian (-EL) output.
834 @item -mthumb-interwork
835 Specify that the code has been generated with interworking between Thumb and
838 Specify that PIC code has been generated.
846 @xref{Blackfin Options}, for the options available when @value{AS} is
847 configured for the Blackfin processor family.
852 The following options are available when @value{AS} is configured for
853 the Blackfin processor family.
857 @c ended inside the included file
864 See the info pages for documentation of the CRIS-specific options.
868 The following options are available when @value{AS} is configured for
871 @cindex D10V optimization
872 @cindex optimization, D10V
874 Optimize output by parallelizing instructions.
879 The following options are available when @value{AS} is configured for a D30V
882 @cindex D30V optimization
883 @cindex optimization, D30V
885 Optimize output by parallelizing instructions.
889 Warn when nops are generated.
891 @cindex D30V nops after 32-bit multiply
893 Warn when a nop after a 32-bit multiply instruction is generated.
899 The following options are available when @value{AS} is configured for the
900 Adapteva EPIPHANY series.
903 @xref{Epiphany Options}, for the options available when @value{AS} is
904 configured for an Epiphany processor.
909 The following options are available when @value{AS} is configured for
910 an Epiphany processor.
913 @include c-epiphany.texi
914 @c ended inside the included file
922 @xref{H8/300 Options}, for the options available when @value{AS} is configured
923 for an H8/300 processor.
928 The following options are available when @value{AS} is configured for an H8/300
932 @include c-h8300.texi
933 @c ended inside the included file
941 @xref{i386-Options}, for the options available when @value{AS} is
942 configured for an i386 processor.
947 The following options are available when @value{AS} is configured for
952 @c ended inside the included file
959 The following options are available when @value{AS} is configured for the
960 Intel 80960 processor.
963 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
964 Specify which variant of the 960 architecture is the target.
967 Add code to collect statistics about branches taken.
970 Do not alter compare-and-branch instructions for long displacements;
977 The following options are available when @value{AS} is configured for the
983 Specifies that the extended IP2022 instructions are allowed.
986 Restores the default behaviour, which restricts the permitted instructions to
987 just the basic IP2022 ones.
993 The following options are available when @value{AS} is configured for the
994 Renesas M32C and M16C processors.
999 Assemble M32C instructions.
1002 Assemble M16C instructions (the default).
1005 Enable support for link-time relaxations.
1008 Support H'00 style hex constants in addition to 0x00 style.
1014 The following options are available when @value{AS} is configured for the
1015 Renesas M32R (formerly Mitsubishi M32R) series.
1020 Specify which processor in the M32R family is the target. The default
1021 is normally the M32R, but this option changes it to the M32RX.
1023 @item --warn-explicit-parallel-conflicts or --Wp
1024 Produce warning messages when questionable parallel constructs are
1027 @item --no-warn-explicit-parallel-conflicts or --Wnp
1028 Do not produce warning messages when questionable parallel constructs are
1035 The following options are available when @value{AS} is configured for the
1036 Motorola 68000 series.
1041 Shorten references to undefined symbols, to one word instead of two.
1043 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1044 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1045 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1046 Specify what processor in the 68000 family is the target. The default
1047 is normally the 68020, but this can be changed at configuration time.
1049 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1050 The target machine does (or does not) have a floating-point coprocessor.
1051 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1052 the basic 68000 is not compatible with the 68881, a combination of the
1053 two can be specified, since it's possible to do emulation of the
1054 coprocessor instructions with the main processor.
1056 @item -m68851 | -mno-68851
1057 The target machine does (or does not) have a memory-management
1058 unit coprocessor. The default is to assume an MMU for 68020 and up.
1066 @xref{Nios II Options}, for the options available when @value{AS} is configured
1067 for an Altera Nios II processor.
1071 @c man begin OPTIONS
1072 The following options are available when @value{AS} is configured for an
1073 Altera Nios II processor.
1075 @c man begin INCLUDE
1076 @include c-nios2.texi
1077 @c ended inside the included file
1083 For details about the PDP-11 machine dependent features options,
1084 see @ref{PDP-11-Options}.
1087 @item -mpic | -mno-pic
1088 Generate position-independent (or position-dependent) code. The
1089 default is @option{-mpic}.
1092 @itemx -mall-extensions
1093 Enable all instruction set extensions. This is the default.
1095 @item -mno-extensions
1096 Disable all instruction set extensions.
1098 @item -m@var{extension} | -mno-@var{extension}
1099 Enable (or disable) a particular instruction set extension.
1102 Enable the instruction set extensions supported by a particular CPU, and
1103 disable all other extensions.
1105 @item -m@var{machine}
1106 Enable the instruction set extensions supported by a particular machine
1107 model, and disable all other extensions.
1113 The following options are available when @value{AS} is configured for
1114 a picoJava processor.
1118 @cindex PJ endianness
1119 @cindex endianness, PJ
1120 @cindex big endian output, PJ
1122 Generate ``big endian'' format output.
1124 @cindex little endian output, PJ
1126 Generate ``little endian'' format output.
1132 The following options are available when @value{AS} is configured for the
1133 Motorola 68HC11 or 68HC12 series.
1137 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1138 Specify what processor is the target. The default is
1139 defined by the configuration option when building the assembler.
1141 @item --xgate-ramoffset
1142 Instruct the linker to offset RAM addresses from S12X address space into
1143 XGATE address space.
1146 Specify to use the 16-bit integer ABI.
1149 Specify to use the 32-bit integer ABI.
1151 @item -mshort-double
1152 Specify to use the 32-bit double ABI.
1155 Specify to use the 64-bit double ABI.
1157 @item --force-long-branches
1158 Relative branches are turned into absolute ones. This concerns
1159 conditional branches, unconditional branches and branches to a
1162 @item -S | --short-branches
1163 Do not turn relative branches into absolute ones
1164 when the offset is out of range.
1166 @item --strict-direct-mode
1167 Do not turn the direct addressing mode into extended addressing mode
1168 when the instruction does not support direct addressing mode.
1170 @item --print-insn-syntax
1171 Print the syntax of instruction in case of error.
1173 @item --print-opcodes
1174 Print the list of instructions with syntax and then exit.
1176 @item --generate-example
1177 Print an example of instruction for each possible instruction and then exit.
1178 This option is only useful for testing @command{@value{AS}}.
1184 The following options are available when @command{@value{AS}} is configured
1185 for the SPARC architecture:
1188 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1189 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1190 Explicitly select a variant of the SPARC architecture.
1192 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1193 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1195 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1196 UltraSPARC extensions.
1198 @item -xarch=v8plus | -xarch=v8plusa
1199 For compatibility with the Solaris v9 assembler. These options are
1200 equivalent to -Av8plus and -Av8plusa, respectively.
1203 Warn when the assembler switches to another architecture.
1208 The following options are available when @value{AS} is configured for the 'c54x
1213 Enable extended addressing mode. All addresses and relocations will assume
1214 extended addressing (usually 23 bits).
1215 @item -mcpu=@var{CPU_VERSION}
1216 Sets the CPU version being compiled for.
1217 @item -merrors-to-file @var{FILENAME}
1218 Redirect error output to a file, for broken systems which don't support such
1219 behaviour in the shell.
1224 The following options are available when @value{AS} is configured for
1229 This option sets the largest size of an object that can be referenced
1230 implicitly with the @code{gp} register. It is only accepted for targets that
1231 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1233 @cindex MIPS endianness
1234 @cindex endianness, MIPS
1235 @cindex big endian output, MIPS
1237 Generate ``big endian'' format output.
1239 @cindex little endian output, MIPS
1241 Generate ``little endian'' format output.
1253 Generate code for a particular MIPS Instruction Set Architecture level.
1254 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1255 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1256 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1257 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1258 @samp{-mips64r2} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1259 MIPS64, and MIPS64 Release 2 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.
1346 Only use 32-bit instruction encodings when generating code for the
1347 microMIPS processor. This option inhibits the use of any 16-bit
1348 instructions. This is equivalent to putting @code{.set insn32} at
1349 the start of the assembly file. @samp{-mno-insn32} turns off this
1350 option. This is equivalent to putting @code{.set noinsn32} at the
1351 start of the assembly file. By default @samp{-mno-insn32} is
1352 selected, allowing all instructions to be used.
1354 @item --construct-floats
1355 @itemx --no-construct-floats
1356 The @samp{--no-construct-floats} option disables the construction of
1357 double width floating point constants by loading the two halves of the
1358 value into the two single width floating point registers that make up
1359 the double width register. By default @samp{--construct-floats} is
1360 selected, allowing construction of these floating point constants.
1362 @item --relax-branch
1363 @itemx --no-relax-branch
1364 The @samp{--relax-branch} option enables the relaxation of out-of-range
1365 branches. By default @samp{--no-relax-branch} is selected, causing any
1366 out-of-range branches to produce an error.
1368 @item -mnan=@var{encoding}
1369 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1370 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1373 @item --emulation=@var{name}
1374 This option was formerly used to switch between ELF and ECOFF output
1375 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1376 removed in GAS 2.24, so the option now serves little purpose.
1377 It is retained for backwards compatibility.
1379 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1380 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1381 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1382 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1383 preferred options instead.
1386 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1393 Control how to deal with multiplication overflow and division by zero.
1394 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1395 (and only work for Instruction Set Architecture level 2 and higher);
1396 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1400 When this option is used, @command{@value{AS}} will issue a warning every
1401 time it generates a nop instruction from a macro.
1406 The following options are available when @value{AS} is configured for
1412 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1413 The command line option @samp{-nojsri2bsr} can be used to disable it.
1417 Enable or disable the silicon filter behaviour. By default this is disabled.
1418 The default can be overridden by the @samp{-sifilter} command line option.
1421 Alter jump instructions for long displacements.
1423 @item -mcpu=[210|340]
1424 Select the cpu type on the target hardware. This controls which instructions
1428 Assemble for a big endian target.
1431 Assemble for a little endian target.
1440 @xref{Meta Options}, for the options available when @value{AS} is configured
1441 for a Meta processor.
1445 @c man begin OPTIONS
1446 The following options are available when @value{AS} is configured for a
1449 @c man begin INCLUDE
1450 @include c-metag.texi
1451 @c ended inside the included file
1456 @c man begin OPTIONS
1458 See the info pages for documentation of the MMIX-specific options.
1465 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1466 for a PowerPC processor.
1470 @c man begin OPTIONS
1471 The following options are available when @value{AS} is configured for a
1474 @c man begin INCLUDE
1476 @c ended inside the included file
1481 @c man begin OPTIONS
1483 See the info pages for documentation of the RX-specific options.
1487 The following options are available when @value{AS} is configured for the s390
1493 Select the word size, either 31/32 bits or 64 bits.
1496 Select the architecture mode, either the Enterprise System
1497 Architecture (esa) or the z/Architecture mode (zarch).
1498 @item -march=@var{processor}
1499 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1500 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1501 @samp{z196}, or @samp{zEC12}.
1503 @itemx -mno-regnames
1504 Allow or disallow symbolic names for registers.
1505 @item -mwarn-areg-zero
1506 Warn whenever the operand for a base or index register has been specified
1507 but evaluates to zero.
1515 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1516 for a TMS320C6000 processor.
1520 @c man begin OPTIONS
1521 The following options are available when @value{AS} is configured for a
1522 TMS320C6000 processor.
1524 @c man begin INCLUDE
1525 @include c-tic6x.texi
1526 @c ended inside the included file
1534 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1535 for a TILE-Gx processor.
1539 @c man begin OPTIONS
1540 The following options are available when @value{AS} is configured for a TILE-Gx
1543 @c man begin INCLUDE
1544 @include c-tilegx.texi
1545 @c ended inside the included file
1553 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1554 for an Xtensa processor.
1558 @c man begin OPTIONS
1559 The following options are available when @value{AS} is configured for an
1562 @c man begin INCLUDE
1563 @include c-xtensa.texi
1564 @c ended inside the included file
1569 @c man begin OPTIONS
1572 The following options are available when @value{AS} is configured for
1573 a Z80 family processor.
1576 Assemble for Z80 processor.
1578 Assemble for R800 processor.
1579 @item -ignore-undocumented-instructions
1581 Assemble undocumented Z80 instructions that also work on R800 without warning.
1582 @item -ignore-unportable-instructions
1584 Assemble all undocumented Z80 instructions without warning.
1585 @item -warn-undocumented-instructions
1587 Issue a warning for undocumented Z80 instructions that also work on R800.
1588 @item -warn-unportable-instructions
1590 Issue a warning for undocumented Z80 instructions that do not work on R800.
1591 @item -forbid-undocumented-instructions
1593 Treat all undocumented instructions as errors.
1594 @item -forbid-unportable-instructions
1596 Treat undocumented Z80 instructions that do not work on R800 as errors.
1603 * Manual:: Structure of this Manual
1604 * GNU Assembler:: The GNU Assembler
1605 * Object Formats:: Object File Formats
1606 * Command Line:: Command Line
1607 * Input Files:: Input Files
1608 * Object:: Output (Object) File
1609 * Errors:: Error and Warning Messages
1613 @section Structure of this Manual
1615 @cindex manual, structure and purpose
1616 This manual is intended to describe what you need to know to use
1617 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1618 notation for symbols, constants, and expressions; the directives that
1619 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1622 We also cover special features in the @value{TARGET}
1623 configuration of @command{@value{AS}}, including assembler directives.
1626 This manual also describes some of the machine-dependent features of
1627 various flavors of the assembler.
1630 @cindex machine instructions (not covered)
1631 On the other hand, this manual is @emph{not} intended as an introduction
1632 to programming in assembly language---let alone programming in general!
1633 In a similar vein, we make no attempt to introduce the machine
1634 architecture; we do @emph{not} describe the instruction set, standard
1635 mnemonics, registers or addressing modes that are standard to a
1636 particular architecture.
1638 You may want to consult the manufacturer's
1639 machine architecture manual for this information.
1643 For information on the H8/300 machine instruction set, see @cite{H8/300
1644 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1645 Programming Manual} (Renesas).
1648 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1649 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1650 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1651 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1654 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1658 @c I think this is premature---doc@cygnus.com, 17jan1991
1660 Throughout this manual, we assume that you are running @dfn{GNU},
1661 the portable operating system from the @dfn{Free Software
1662 Foundation, Inc.}. This restricts our attention to certain kinds of
1663 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1664 once this assumption is granted examples and definitions need less
1667 @command{@value{AS}} is part of a team of programs that turn a high-level
1668 human-readable series of instructions into a low-level
1669 computer-readable series of instructions. Different versions of
1670 @command{@value{AS}} are used for different kinds of computer.
1673 @c There used to be a section "Terminology" here, which defined
1674 @c "contents", "byte", "word", and "long". Defining "word" to any
1675 @c particular size is confusing when the .word directive may generate 16
1676 @c bits on one machine and 32 bits on another; in general, for the user
1677 @c version of this manual, none of these terms seem essential to define.
1678 @c They were used very little even in the former draft of the manual;
1679 @c this draft makes an effort to avoid them (except in names of
1683 @section The GNU Assembler
1685 @c man begin DESCRIPTION
1687 @sc{gnu} @command{as} is really a family of assemblers.
1689 This manual describes @command{@value{AS}}, a member of that family which is
1690 configured for the @value{TARGET} architectures.
1692 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1693 should find a fairly similar environment when you use it on another
1694 architecture. Each version has much in common with the others,
1695 including object file formats, most assembler directives (often called
1696 @dfn{pseudo-ops}) and assembler syntax.@refill
1698 @cindex purpose of @sc{gnu} assembler
1699 @command{@value{AS}} is primarily intended to assemble the output of the
1700 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1701 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1702 assemble correctly everything that other assemblers for the same
1703 machine would assemble.
1705 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1708 @c This remark should appear in generic version of manual; assumption
1709 @c here is that generic version sets M680x0.
1710 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1711 assembler for the same architecture; for example, we know of several
1712 incompatible versions of 680x0 assembly language syntax.
1717 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1718 program in one pass of the source file. This has a subtle impact on the
1719 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1721 @node Object Formats
1722 @section Object File Formats
1724 @cindex object file format
1725 The @sc{gnu} assembler can be configured to produce several alternative
1726 object file formats. For the most part, this does not affect how you
1727 write assembly language programs; but directives for debugging symbols
1728 are typically different in different file formats. @xref{Symbol
1729 Attributes,,Symbol Attributes}.
1732 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1733 @value{OBJ-NAME} format object files.
1735 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1737 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1738 @code{b.out} or COFF format object files.
1741 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1742 SOM or ELF format object files.
1747 @section Command Line
1749 @cindex command line conventions
1751 After the program name @command{@value{AS}}, the command line may contain
1752 options and file names. Options may appear in any order, and may be
1753 before, after, or between file names. The order of file names is
1756 @cindex standard input, as input file
1758 @file{--} (two hyphens) by itself names the standard input file
1759 explicitly, as one of the files for @command{@value{AS}} to assemble.
1761 @cindex options, command line
1762 Except for @samp{--} any command line argument that begins with a
1763 hyphen (@samp{-}) is an option. Each option changes the behavior of
1764 @command{@value{AS}}. No option changes the way another option works. An
1765 option is a @samp{-} followed by one or more letters; the case of
1766 the letter is important. All options are optional.
1768 Some options expect exactly one file name to follow them. The file
1769 name may either immediately follow the option's letter (compatible
1770 with older assemblers) or it may be the next command argument (@sc{gnu}
1771 standard). These two command lines are equivalent:
1774 @value{AS} -o my-object-file.o mumble.s
1775 @value{AS} -omy-object-file.o mumble.s
1779 @section Input Files
1782 @cindex source program
1783 @cindex files, input
1784 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1785 describe the program input to one run of @command{@value{AS}}. The program may
1786 be in one or more files; how the source is partitioned into files
1787 doesn't change the meaning of the source.
1789 @c I added "con" prefix to "catenation" just to prove I can overcome my
1790 @c APL training... doc@cygnus.com
1791 The source program is a concatenation of the text in all the files, in the
1794 @c man begin DESCRIPTION
1795 Each time you run @command{@value{AS}} it assembles exactly one source
1796 program. The source program is made up of one or more files.
1797 (The standard input is also a file.)
1799 You give @command{@value{AS}} a command line that has zero or more input file
1800 names. The input files are read (from left file name to right). A
1801 command line argument (in any position) that has no special meaning
1802 is taken to be an input file name.
1804 If you give @command{@value{AS}} no file names it attempts to read one input file
1805 from the @command{@value{AS}} standard input, which is normally your terminal. You
1806 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1809 Use @samp{--} if you need to explicitly name the standard input file
1810 in your command line.
1812 If the source is empty, @command{@value{AS}} produces a small, empty object
1817 @subheading Filenames and Line-numbers
1819 @cindex input file linenumbers
1820 @cindex line numbers, in input files
1821 There are two ways of locating a line in the input file (or files) and
1822 either may be used in reporting error messages. One way refers to a line
1823 number in a physical file; the other refers to a line number in a
1824 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1826 @dfn{Physical files} are those files named in the command line given
1827 to @command{@value{AS}}.
1829 @dfn{Logical files} are simply names declared explicitly by assembler
1830 directives; they bear no relation to physical files. Logical file names help
1831 error messages reflect the original source file, when @command{@value{AS}} source
1832 is itself synthesized from other files. @command{@value{AS}} understands the
1833 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1834 @ref{File,,@code{.file}}.
1837 @section Output (Object) File
1843 Every time you run @command{@value{AS}} it produces an output file, which is
1844 your assembly language program translated into numbers. This file
1845 is the object file. Its default name is
1853 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1855 You can give it another name by using the @option{-o} option. Conventionally,
1856 object file names end with @file{.o}. The default name is used for historical
1857 reasons: older assemblers were capable of assembling self-contained programs
1858 directly into a runnable program. (For some formats, this isn't currently
1859 possible, but it can be done for the @code{a.out} format.)
1863 The object file is meant for input to the linker @code{@value{LD}}. It contains
1864 assembled program code, information to help @code{@value{LD}} integrate
1865 the assembled program into a runnable file, and (optionally) symbolic
1866 information for the debugger.
1868 @c link above to some info file(s) like the description of a.out.
1869 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1872 @section Error and Warning Messages
1874 @c man begin DESCRIPTION
1876 @cindex error messages
1877 @cindex warning messages
1878 @cindex messages from assembler
1879 @command{@value{AS}} may write warnings and error messages to the standard error
1880 file (usually your terminal). This should not happen when a compiler
1881 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1882 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1883 grave problem that stops the assembly.
1887 @cindex format of warning messages
1888 Warning messages have the format
1891 file_name:@b{NNN}:Warning Message Text
1895 @cindex line numbers, in warnings/errors
1896 (where @b{NNN} is a line number). If a logical file name has been given
1897 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1898 the current input file is used. If a logical line number was given
1900 (@pxref{Line,,@code{.line}})
1902 then it is used to calculate the number printed,
1903 otherwise the actual line in the current source file is printed. The
1904 message text is intended to be self explanatory (in the grand Unix
1907 @cindex format of error messages
1908 Error messages have the format
1910 file_name:@b{NNN}:FATAL:Error Message Text
1912 The file name and line number are derived as for warning
1913 messages. The actual message text may be rather less explanatory
1914 because many of them aren't supposed to happen.
1917 @chapter Command-Line Options
1919 @cindex options, all versions of assembler
1920 This chapter describes command-line options available in @emph{all}
1921 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1922 for options specific
1924 to the @value{TARGET} target.
1927 to particular machine architectures.
1930 @c man begin DESCRIPTION
1932 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1933 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1934 The assembler arguments must be separated from each other (and the @samp{-Wa})
1935 by commas. For example:
1938 gcc -c -g -O -Wa,-alh,-L file.c
1942 This passes two options to the assembler: @samp{-alh} (emit a listing to
1943 standard output with high-level and assembly source) and @samp{-L} (retain
1944 local symbols in the symbol table).
1946 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1947 command-line options are automatically passed to the assembler by the compiler.
1948 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1949 precisely what options it passes to each compilation pass, including the
1955 * a:: -a[cdghlns] enable listings
1956 * alternate:: --alternate enable alternate macro syntax
1957 * D:: -D for compatibility
1958 * f:: -f to work faster
1959 * I:: -I for .include search path
1960 @ifclear DIFF-TBL-KLUGE
1961 * K:: -K for compatibility
1963 @ifset DIFF-TBL-KLUGE
1964 * K:: -K for difference tables
1967 * L:: -L to retain local symbols
1968 * listing:: --listing-XXX to configure listing output
1969 * M:: -M or --mri to assemble in MRI compatibility mode
1970 * MD:: --MD for dependency tracking
1971 * o:: -o to name the object file
1972 * R:: -R to join data and text sections
1973 * statistics:: --statistics to see statistics about assembly
1974 * traditional-format:: --traditional-format for compatible output
1975 * v:: -v to announce version
1976 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1977 * Z:: -Z to make object file even after errors
1981 @section Enable Listings: @option{-a[cdghlns]}
1991 @cindex listings, enabling
1992 @cindex assembly listings, enabling
1994 These options enable listing output from the assembler. By itself,
1995 @samp{-a} requests high-level, assembly, and symbols listing.
1996 You can use other letters to select specific options for the list:
1997 @samp{-ah} requests a high-level language listing,
1998 @samp{-al} requests an output-program assembly listing, and
1999 @samp{-as} requests a symbol table listing.
2000 High-level listings require that a compiler debugging option like
2001 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2004 Use the @samp{-ag} option to print a first section with general assembly
2005 information, like @value{AS} version, switches passed, or time stamp.
2007 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2008 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2009 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2010 omitted from the listing.
2012 Use the @samp{-ad} option to omit debugging directives from the
2015 Once you have specified one of these options, you can further control
2016 listing output and its appearance using the directives @code{.list},
2017 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2019 The @samp{-an} option turns off all forms processing.
2020 If you do not request listing output with one of the @samp{-a} options, the
2021 listing-control directives have no effect.
2023 The letters after @samp{-a} may be combined into one option,
2024 @emph{e.g.}, @samp{-aln}.
2026 Note if the assembler source is coming from the standard input (e.g.,
2028 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2029 is being used) then the listing will not contain any comments or preprocessor
2030 directives. This is because the listing code buffers input source lines from
2031 stdin only after they have been preprocessed by the assembler. This reduces
2032 memory usage and makes the code more efficient.
2035 @section @option{--alternate}
2038 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2041 @section @option{-D}
2044 This option has no effect whatsoever, but it is accepted to make it more
2045 likely that scripts written for other assemblers also work with
2046 @command{@value{AS}}.
2049 @section Work Faster: @option{-f}
2052 @cindex trusted compiler
2053 @cindex faster processing (@option{-f})
2054 @samp{-f} should only be used when assembling programs written by a
2055 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2056 and comment preprocessing on
2057 the input file(s) before assembling them. @xref{Preprocessing,
2061 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2062 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2067 @section @code{.include} Search Path: @option{-I} @var{path}
2069 @kindex -I @var{path}
2070 @cindex paths for @code{.include}
2071 @cindex search path for @code{.include}
2072 @cindex @code{include} directive search path
2073 Use this option to add a @var{path} to the list of directories
2074 @command{@value{AS}} searches for files specified in @code{.include}
2075 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2076 many times as necessary to include a variety of paths. The current
2077 working directory is always searched first; after that, @command{@value{AS}}
2078 searches any @samp{-I} directories in the same order as they were
2079 specified (left to right) on the command line.
2082 @section Difference Tables: @option{-K}
2085 @ifclear DIFF-TBL-KLUGE
2086 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2087 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2088 where it can be used to warn when the assembler alters the machine code
2089 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2090 family does not have the addressing limitations that sometimes lead to this
2091 alteration on other platforms.
2094 @ifset DIFF-TBL-KLUGE
2095 @cindex difference tables, warning
2096 @cindex warning for altered difference tables
2097 @command{@value{AS}} sometimes alters the code emitted for directives of the
2098 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2099 You can use the @samp{-K} option if you want a warning issued when this
2104 @section Include Local Symbols: @option{-L}
2107 @cindex local symbols, retaining in output
2108 Symbols beginning with system-specific local label prefixes, typically
2109 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2110 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2111 such symbols when debugging, because they are intended for the use of
2112 programs (like compilers) that compose assembler programs, not for your
2113 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2114 such symbols, so you do not normally debug with them.
2116 This option tells @command{@value{AS}} to retain those local symbols
2117 in the object file. Usually if you do this you also tell the linker
2118 @code{@value{LD}} to preserve those symbols.
2121 @section Configuring listing output: @option{--listing}
2123 The listing feature of the assembler can be enabled via the command line switch
2124 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2125 hex dump of the corresponding locations in the output object file, and displays
2126 them as a listing file. The format of this listing can be controlled by
2127 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2128 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2129 @code{.psize} (@pxref{Psize}), and
2130 @code{.eject} (@pxref{Eject}) and also by the following switches:
2133 @item --listing-lhs-width=@samp{number}
2134 @kindex --listing-lhs-width
2135 @cindex Width of first line disassembly output
2136 Sets the maximum width, in words, of the first line of the hex byte dump. This
2137 dump appears on the left hand side of the listing output.
2139 @item --listing-lhs-width2=@samp{number}
2140 @kindex --listing-lhs-width2
2141 @cindex Width of continuation lines of disassembly output
2142 Sets the maximum width, in words, of any further lines of the hex byte dump for
2143 a given input source line. If this value is not specified, it defaults to being
2144 the same as the value specified for @samp{--listing-lhs-width}. If neither
2145 switch is used the default is to one.
2147 @item --listing-rhs-width=@samp{number}
2148 @kindex --listing-rhs-width
2149 @cindex Width of source line output
2150 Sets the maximum width, in characters, of the source line that is displayed
2151 alongside the hex dump. The default value for this parameter is 100. The
2152 source line is displayed on the right hand side of the listing output.
2154 @item --listing-cont-lines=@samp{number}
2155 @kindex --listing-cont-lines
2156 @cindex Maximum number of continuation lines
2157 Sets the maximum number of continuation lines of hex dump that will be
2158 displayed for a given single line of source input. The default value is 4.
2162 @section Assemble in MRI Compatibility Mode: @option{-M}
2165 @cindex MRI compatibility mode
2166 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2167 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2168 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2169 configured target) assembler from Microtec Research. The exact nature of the
2170 MRI syntax will not be documented here; see the MRI manuals for more
2171 information. Note in particular that the handling of macros and macro
2172 arguments is somewhat different. The purpose of this option is to permit
2173 assembling existing MRI assembler code using @command{@value{AS}}.
2175 The MRI compatibility is not complete. Certain operations of the MRI assembler
2176 depend upon its object file format, and can not be supported using other object
2177 file formats. Supporting these would require enhancing each object file format
2178 individually. These are:
2181 @item global symbols in common section
2183 The m68k MRI assembler supports common sections which are merged by the linker.
2184 Other object file formats do not support this. @command{@value{AS}} handles
2185 common sections by treating them as a single common symbol. It permits local
2186 symbols to be defined within a common section, but it can not support global
2187 symbols, since it has no way to describe them.
2189 @item complex relocations
2191 The MRI assemblers support relocations against a negated section address, and
2192 relocations which combine the start addresses of two or more sections. These
2193 are not support by other object file formats.
2195 @item @code{END} pseudo-op specifying start address
2197 The MRI @code{END} pseudo-op permits the specification of a start address.
2198 This is not supported by other object file formats. The start address may
2199 instead be specified using the @option{-e} option to the linker, or in a linker
2202 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2204 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2205 name to the output file. This is not supported by other object file formats.
2207 @item @code{ORG} pseudo-op
2209 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2210 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2211 which changes the location within the current section. Absolute sections are
2212 not supported by other object file formats. The address of a section may be
2213 assigned within a linker script.
2216 There are some other features of the MRI assembler which are not supported by
2217 @command{@value{AS}}, typically either because they are difficult or because they
2218 seem of little consequence. Some of these may be supported in future releases.
2222 @item EBCDIC strings
2224 EBCDIC strings are not supported.
2226 @item packed binary coded decimal
2228 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2229 and @code{DCB.P} pseudo-ops are not supported.
2231 @item @code{FEQU} pseudo-op
2233 The m68k @code{FEQU} pseudo-op is not supported.
2235 @item @code{NOOBJ} pseudo-op
2237 The m68k @code{NOOBJ} pseudo-op is not supported.
2239 @item @code{OPT} branch control options
2241 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2242 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2243 relaxes all branches, whether forward or backward, to an appropriate size, so
2244 these options serve no purpose.
2246 @item @code{OPT} list control options
2248 The following m68k @code{OPT} list control options are ignored: @code{C},
2249 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2250 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2252 @item other @code{OPT} options
2254 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2255 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2257 @item @code{OPT} @code{D} option is default
2259 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2260 @code{OPT NOD} may be used to turn it off.
2262 @item @code{XREF} pseudo-op.
2264 The m68k @code{XREF} pseudo-op is ignored.
2266 @item @code{.debug} pseudo-op
2268 The i960 @code{.debug} pseudo-op is not supported.
2270 @item @code{.extended} pseudo-op
2272 The i960 @code{.extended} pseudo-op is not supported.
2274 @item @code{.list} pseudo-op.
2276 The various options of the i960 @code{.list} pseudo-op are not supported.
2278 @item @code{.optimize} pseudo-op
2280 The i960 @code{.optimize} pseudo-op is not supported.
2282 @item @code{.output} pseudo-op
2284 The i960 @code{.output} pseudo-op is not supported.
2286 @item @code{.setreal} pseudo-op
2288 The i960 @code{.setreal} pseudo-op is not supported.
2293 @section Dependency Tracking: @option{--MD}
2296 @cindex dependency tracking
2299 @command{@value{AS}} can generate a dependency file for the file it creates. This
2300 file consists of a single rule suitable for @code{make} describing the
2301 dependencies of the main source file.
2303 The rule is written to the file named in its argument.
2305 This feature is used in the automatic updating of makefiles.
2308 @section Name the Object File: @option{-o}
2311 @cindex naming object file
2312 @cindex object file name
2313 There is always one object file output when you run @command{@value{AS}}. By
2314 default it has the name
2317 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2331 You use this option (which takes exactly one filename) to give the
2332 object file a different name.
2334 Whatever the object file is called, @command{@value{AS}} overwrites any
2335 existing file of the same name.
2338 @section Join Data and Text Sections: @option{-R}
2341 @cindex data and text sections, joining
2342 @cindex text and data sections, joining
2343 @cindex joining text and data sections
2344 @cindex merging text and data sections
2345 @option{-R} tells @command{@value{AS}} to write the object file as if all
2346 data-section data lives in the text section. This is only done at
2347 the very last moment: your binary data are the same, but data
2348 section parts are relocated differently. The data section part of
2349 your object file is zero bytes long because all its bytes are
2350 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2352 When you specify @option{-R} it would be possible to generate shorter
2353 address displacements (because we do not have to cross between text and
2354 data section). We refrain from doing this simply for compatibility with
2355 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2358 When @command{@value{AS}} is configured for COFF or ELF output,
2359 this option is only useful if you use sections named @samp{.text} and
2364 @option{-R} is not supported for any of the HPPA targets. Using
2365 @option{-R} generates a warning from @command{@value{AS}}.
2369 @section Display Assembly Statistics: @option{--statistics}
2371 @kindex --statistics
2372 @cindex statistics, about assembly
2373 @cindex time, total for assembly
2374 @cindex space used, maximum for assembly
2375 Use @samp{--statistics} to display two statistics about the resources used by
2376 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2377 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2380 @node traditional-format
2381 @section Compatible Output: @option{--traditional-format}
2383 @kindex --traditional-format
2384 For some targets, the output of @command{@value{AS}} is different in some ways
2385 from the output of some existing assembler. This switch requests
2386 @command{@value{AS}} to use the traditional format instead.
2388 For example, it disables the exception frame optimizations which
2389 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2392 @section Announce Version: @option{-v}
2396 @cindex assembler version
2397 @cindex version of assembler
2398 You can find out what version of as is running by including the
2399 option @samp{-v} (which you can also spell as @samp{-version}) on the
2403 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2405 @command{@value{AS}} should never give a warning or error message when
2406 assembling compiler output. But programs written by people often
2407 cause @command{@value{AS}} to give a warning that a particular assumption was
2408 made. All such warnings are directed to the standard error file.
2412 @cindex suppressing warnings
2413 @cindex warnings, suppressing
2414 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2415 This only affects the warning messages: it does not change any particular of
2416 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2419 @kindex --fatal-warnings
2420 @cindex errors, caused by warnings
2421 @cindex warnings, causing error
2422 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2423 files that generate warnings to be in error.
2426 @cindex warnings, switching on
2427 You can switch these options off again by specifying @option{--warn}, which
2428 causes warnings to be output as usual.
2431 @section Generate Object File in Spite of Errors: @option{-Z}
2432 @cindex object file, after errors
2433 @cindex errors, continuing after
2434 After an error message, @command{@value{AS}} normally produces no output. If for
2435 some reason you are interested in object file output even after
2436 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2437 option. If there are any errors, @command{@value{AS}} continues anyways, and
2438 writes an object file after a final warning message of the form @samp{@var{n}
2439 errors, @var{m} warnings, generating bad object file.}
2444 @cindex machine-independent syntax
2445 @cindex syntax, machine-independent
2446 This chapter describes the machine-independent syntax allowed in a
2447 source file. @command{@value{AS}} syntax is similar to what many other
2448 assemblers use; it is inspired by the BSD 4.2
2453 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2457 * Preprocessing:: Preprocessing
2458 * Whitespace:: Whitespace
2459 * Comments:: Comments
2460 * Symbol Intro:: Symbols
2461 * Statements:: Statements
2462 * Constants:: Constants
2466 @section Preprocessing
2468 @cindex preprocessing
2469 The @command{@value{AS}} internal preprocessor:
2471 @cindex whitespace, removed by preprocessor
2473 adjusts and removes extra whitespace. It leaves one space or tab before
2474 the keywords on a line, and turns any other whitespace on the line into
2477 @cindex comments, removed by preprocessor
2479 removes all comments, replacing them with a single space, or an
2480 appropriate number of newlines.
2482 @cindex constants, converted by preprocessor
2484 converts character constants into the appropriate numeric values.
2487 It does not do macro processing, include file handling, or
2488 anything else you may get from your C compiler's preprocessor. You can
2489 do include file processing with the @code{.include} directive
2490 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2491 to get other ``CPP'' style preprocessing by giving the input file a
2492 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2493 Output, gcc.info, Using GNU CC}.
2495 Excess whitespace, comments, and character constants
2496 cannot be used in the portions of the input text that are not
2499 @cindex turning preprocessing on and off
2500 @cindex preprocessing, turning on and off
2503 If the first line of an input file is @code{#NO_APP} or if you use the
2504 @samp{-f} option, whitespace and comments are not removed from the input file.
2505 Within an input file, you can ask for whitespace and comment removal in
2506 specific portions of the by putting a line that says @code{#APP} before the
2507 text that may contain whitespace or comments, and putting a line that says
2508 @code{#NO_APP} after this text. This feature is mainly intend to support
2509 @code{asm} statements in compilers whose output is otherwise free of comments
2516 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2517 Whitespace is used to separate symbols, and to make programs neater for
2518 people to read. Unless within character constants
2519 (@pxref{Characters,,Character Constants}), any whitespace means the same
2520 as exactly one space.
2526 There are two ways of rendering comments to @command{@value{AS}}. In both
2527 cases the comment is equivalent to one space.
2529 Anything from @samp{/*} through the next @samp{*/} is a comment.
2530 This means you may not nest these comments.
2534 The only way to include a newline ('\n') in a comment
2535 is to use this sort of comment.
2538 /* This sort of comment does not nest. */
2541 @cindex line comment character
2542 Anything from a @dfn{line comment} character up to the next newline is
2543 considered a comment and is ignored. The line comment character is target
2544 specific, and some targets multiple comment characters. Some targets also have
2545 line comment characters that only work if they are the first character on a
2546 line. Some targets use a sequence of two characters to introduce a line
2547 comment. Some targets can also change their line comment characters depending
2548 upon command line options that have been used. For more details see the
2549 @emph{Syntax} section in the documentation for individual targets.
2551 If the line comment character is the hash sign (@samp{#}) then it still has the
2552 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2553 to specify logical line numbers:
2556 @cindex lines starting with @code{#}
2557 @cindex logical line numbers
2558 To be compatible with past assemblers, lines that begin with @samp{#} have a
2559 special interpretation. Following the @samp{#} should be an absolute
2560 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2561 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2562 new logical file name. The rest of the line, if any, should be whitespace.
2564 If the first non-whitespace characters on the line are not numeric,
2565 the line is ignored. (Just like a comment.)
2568 # This is an ordinary comment.
2569 # 42-6 "new_file_name" # New logical file name
2570 # This is logical line # 36.
2572 This feature is deprecated, and may disappear from future versions
2573 of @command{@value{AS}}.
2578 @cindex characters used in symbols
2579 @ifclear SPECIAL-SYMS
2580 A @dfn{symbol} is one or more characters chosen from the set of all
2581 letters (both upper and lower case), digits and the three characters
2587 A @dfn{symbol} is one or more characters chosen from the set of all
2588 letters (both upper and lower case), digits and the three characters
2589 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2595 On most machines, you can also use @code{$} in symbol names; exceptions
2596 are noted in @ref{Machine Dependencies}.
2598 No symbol may begin with a digit. Case is significant.
2599 There is no length limit: all characters are significant. Multibyte characters
2600 are supported. Symbols are delimited by characters not in that set, or by the
2601 beginning of a file (since the source program must end with a newline, the end
2602 of a file is not a possible symbol delimiter). @xref{Symbols}.
2603 @cindex length of symbols
2608 @cindex statements, structure of
2609 @cindex line separator character
2610 @cindex statement separator character
2612 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2613 @dfn{line separator character}. The line separator character is target
2614 specific and described in the @emph{Syntax} section of each
2615 target's documentation. Not all targets support a line separator character.
2616 The newline or line separator character is considered to be part of the
2617 preceding statement. Newlines and separators within character constants are an
2618 exception: they do not end statements.
2620 @cindex newline, required at file end
2621 @cindex EOF, newline must precede
2622 It is an error to end any statement with end-of-file: the last
2623 character of any input file should be a newline.@refill
2625 An empty statement is allowed, and may include whitespace. It is ignored.
2627 @cindex instructions and directives
2628 @cindex directives and instructions
2629 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2630 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2632 A statement begins with zero or more labels, optionally followed by a
2633 key symbol which determines what kind of statement it is. The key
2634 symbol determines the syntax of the rest of the statement. If the
2635 symbol begins with a dot @samp{.} then the statement is an assembler
2636 directive: typically valid for any computer. If the symbol begins with
2637 a letter the statement is an assembly language @dfn{instruction}: it
2638 assembles into a machine language instruction.
2640 Different versions of @command{@value{AS}} for different computers
2641 recognize different instructions. In fact, the same symbol may
2642 represent a different instruction in a different computer's assembly
2646 @cindex @code{:} (label)
2647 @cindex label (@code{:})
2648 A label is a symbol immediately followed by a colon (@code{:}).
2649 Whitespace before a label or after a colon is permitted, but you may not
2650 have whitespace between a label's symbol and its colon. @xref{Labels}.
2653 For HPPA targets, labels need not be immediately followed by a colon, but
2654 the definition of a label must begin in column zero. This also implies that
2655 only one label may be defined on each line.
2659 label: .directive followed by something
2660 another_label: # This is an empty statement.
2661 instruction operand_1, operand_2, @dots{}
2668 A constant is a number, written so that its value is known by
2669 inspection, without knowing any context. Like this:
2672 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2673 .ascii "Ring the bell\7" # A string constant.
2674 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2675 .float 0f-314159265358979323846264338327\
2676 95028841971.693993751E-40 # - pi, a flonum.
2681 * Characters:: Character Constants
2682 * Numbers:: Number Constants
2686 @subsection Character Constants
2688 @cindex character constants
2689 @cindex constants, character
2690 There are two kinds of character constants. A @dfn{character} stands
2691 for one character in one byte and its value may be used in
2692 numeric expressions. String constants (properly called string
2693 @emph{literals}) are potentially many bytes and their values may not be
2694 used in arithmetic expressions.
2698 * Chars:: Characters
2702 @subsubsection Strings
2704 @cindex string constants
2705 @cindex constants, string
2706 A @dfn{string} is written between double-quotes. It may contain
2707 double-quotes or null characters. The way to get special characters
2708 into a string is to @dfn{escape} these characters: precede them with
2709 a backslash @samp{\} character. For example @samp{\\} represents
2710 one backslash: the first @code{\} is an escape which tells
2711 @command{@value{AS}} to interpret the second character literally as a backslash
2712 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2713 escape character). The complete list of escapes follows.
2715 @cindex escape codes, character
2716 @cindex character escape codes
2719 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2721 @cindex @code{\b} (backspace character)
2722 @cindex backspace (@code{\b})
2724 Mnemonic for backspace; for ASCII this is octal code 010.
2727 @c Mnemonic for EOText; for ASCII this is octal code 004.
2729 @cindex @code{\f} (formfeed character)
2730 @cindex formfeed (@code{\f})
2732 Mnemonic for FormFeed; for ASCII this is octal code 014.
2734 @cindex @code{\n} (newline character)
2735 @cindex newline (@code{\n})
2737 Mnemonic for newline; for ASCII this is octal code 012.
2740 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2742 @cindex @code{\r} (carriage return character)
2743 @cindex carriage return (@code{\r})
2745 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2748 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2749 @c other assemblers.
2751 @cindex @code{\t} (tab)
2752 @cindex tab (@code{\t})
2754 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2757 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2758 @c @item \x @var{digit} @var{digit} @var{digit}
2759 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2761 @cindex @code{\@var{ddd}} (octal character code)
2762 @cindex octal character code (@code{\@var{ddd}})
2763 @item \ @var{digit} @var{digit} @var{digit}
2764 An octal character code. The numeric code is 3 octal digits.
2765 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2766 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2768 @cindex @code{\@var{xd...}} (hex character code)
2769 @cindex hex character code (@code{\@var{xd...}})
2770 @item \@code{x} @var{hex-digits...}
2771 A hex character code. All trailing hex digits are combined. Either upper or
2772 lower case @code{x} works.
2774 @cindex @code{\\} (@samp{\} character)
2775 @cindex backslash (@code{\\})
2777 Represents one @samp{\} character.
2780 @c Represents one @samp{'} (accent acute) character.
2781 @c This is needed in single character literals
2782 @c (@xref{Characters,,Character Constants}.) to represent
2785 @cindex @code{\"} (doublequote character)
2786 @cindex doublequote (@code{\"})
2788 Represents one @samp{"} character. Needed in strings to represent
2789 this character, because an unescaped @samp{"} would end the string.
2791 @item \ @var{anything-else}
2792 Any other character when escaped by @kbd{\} gives a warning, but
2793 assembles as if the @samp{\} was not present. The idea is that if
2794 you used an escape sequence you clearly didn't want the literal
2795 interpretation of the following character. However @command{@value{AS}} has no
2796 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2797 code and warns you of the fact.
2800 Which characters are escapable, and what those escapes represent,
2801 varies widely among assemblers. The current set is what we think
2802 the BSD 4.2 assembler recognizes, and is a subset of what most C
2803 compilers recognize. If you are in doubt, do not use an escape
2807 @subsubsection Characters
2809 @cindex single character constant
2810 @cindex character, single
2811 @cindex constant, single character
2812 A single character may be written as a single quote immediately
2813 followed by that character. The same escapes apply to characters as
2814 to strings. So if you want to write the character backslash, you
2815 must write @kbd{'\\} where the first @code{\} escapes the second
2816 @code{\}. As you can see, the quote is an acute accent, not a
2817 grave accent. A newline
2819 @ifclear abnormal-separator
2820 (or semicolon @samp{;})
2822 @ifset abnormal-separator
2824 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2829 immediately following an acute accent is taken as a literal character
2830 and does not count as the end of a statement. The value of a character
2831 constant in a numeric expression is the machine's byte-wide code for
2832 that character. @command{@value{AS}} assumes your character code is ASCII:
2833 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2836 @subsection Number Constants
2838 @cindex constants, number
2839 @cindex number constants
2840 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2841 are stored in the target machine. @emph{Integers} are numbers that
2842 would fit into an @code{int} in the C language. @emph{Bignums} are
2843 integers, but they are stored in more than 32 bits. @emph{Flonums}
2844 are floating point numbers, described below.
2847 * Integers:: Integers
2852 * Bit Fields:: Bit Fields
2858 @subsubsection Integers
2860 @cindex constants, integer
2862 @cindex binary integers
2863 @cindex integers, binary
2864 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2865 the binary digits @samp{01}.
2867 @cindex octal integers
2868 @cindex integers, octal
2869 An octal integer is @samp{0} followed by zero or more of the octal
2870 digits (@samp{01234567}).
2872 @cindex decimal integers
2873 @cindex integers, decimal
2874 A decimal integer starts with a non-zero digit followed by zero or
2875 more digits (@samp{0123456789}).
2877 @cindex hexadecimal integers
2878 @cindex integers, hexadecimal
2879 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2880 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2882 Integers have the usual values. To denote a negative integer, use
2883 the prefix operator @samp{-} discussed under expressions
2884 (@pxref{Prefix Ops,,Prefix Operators}).
2887 @subsubsection Bignums
2890 @cindex constants, bignum
2891 A @dfn{bignum} has the same syntax and semantics as an integer
2892 except that the number (or its negative) takes more than 32 bits to
2893 represent in binary. The distinction is made because in some places
2894 integers are permitted while bignums are not.
2897 @subsubsection Flonums
2899 @cindex floating point numbers
2900 @cindex constants, floating point
2902 @cindex precision, floating point
2903 A @dfn{flonum} represents a floating point number. The translation is
2904 indirect: a decimal floating point number from the text is converted by
2905 @command{@value{AS}} to a generic binary floating point number of more than
2906 sufficient precision. This generic floating point number is converted
2907 to a particular computer's floating point format (or formats) by a
2908 portion of @command{@value{AS}} specialized to that computer.
2910 A flonum is written by writing (in order)
2915 (@samp{0} is optional on the HPPA.)
2919 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2921 @kbd{e} is recommended. Case is not important.
2923 @c FIXME: verify if flonum syntax really this vague for most cases
2924 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2925 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2928 On the H8/300, Renesas / SuperH SH,
2929 and AMD 29K architectures, the letter must be
2930 one of the letters @samp{DFPRSX} (in upper or lower case).
2932 On the ARC, the letter must be one of the letters @samp{DFRS}
2933 (in upper or lower case).
2935 On the Intel 960 architecture, the letter must be
2936 one of the letters @samp{DFT} (in upper or lower case).
2938 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2942 One of the letters @samp{DFRS} (in upper or lower case).
2945 One of the letters @samp{DFPRSX} (in upper or lower case).
2948 The letter @samp{E} (upper case only).
2951 One of the letters @samp{DFT} (in upper or lower case).
2956 An optional sign: either @samp{+} or @samp{-}.
2959 An optional @dfn{integer part}: zero or more decimal digits.
2962 An optional @dfn{fractional part}: @samp{.} followed by zero
2963 or more decimal digits.
2966 An optional exponent, consisting of:
2970 An @samp{E} or @samp{e}.
2971 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2972 @c principle this can perfectly well be different on different targets.
2974 Optional sign: either @samp{+} or @samp{-}.
2976 One or more decimal digits.
2981 At least one of the integer part or the fractional part must be
2982 present. The floating point number has the usual base-10 value.
2984 @command{@value{AS}} does all processing using integers. Flonums are computed
2985 independently of any floating point hardware in the computer running
2986 @command{@value{AS}}.
2990 @c Bit fields are written as a general facility but are also controlled
2991 @c by a conditional-compilation flag---which is as of now (21mar91)
2992 @c turned on only by the i960 config of GAS.
2994 @subsubsection Bit Fields
2997 @cindex constants, bit field
2998 You can also define numeric constants as @dfn{bit fields}.
2999 Specify two numbers separated by a colon---
3001 @var{mask}:@var{value}
3004 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3007 The resulting number is then packed
3009 @c this conditional paren in case bit fields turned on elsewhere than 960
3010 (in host-dependent byte order)
3012 into a field whose width depends on which assembler directive has the
3013 bit-field as its argument. Overflow (a result from the bitwise and
3014 requiring more binary digits to represent) is not an error; instead,
3015 more constants are generated, of the specified width, beginning with the
3016 least significant digits.@refill
3018 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3019 @code{.short}, and @code{.word} accept bit-field arguments.
3024 @chapter Sections and Relocation
3029 * Secs Background:: Background
3030 * Ld Sections:: Linker Sections
3031 * As Sections:: Assembler Internal Sections
3032 * Sub-Sections:: Sub-Sections
3036 @node Secs Background
3039 Roughly, a section is a range of addresses, with no gaps; all data
3040 ``in'' those addresses is treated the same for some particular purpose.
3041 For example there may be a ``read only'' section.
3043 @cindex linker, and assembler
3044 @cindex assembler, and linker
3045 The linker @code{@value{LD}} reads many object files (partial programs) and
3046 combines their contents to form a runnable program. When @command{@value{AS}}
3047 emits an object file, the partial program is assumed to start at address 0.
3048 @code{@value{LD}} assigns the final addresses for the partial program, so that
3049 different partial programs do not overlap. This is actually an
3050 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3053 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3054 addresses. These blocks slide to their run-time addresses as rigid
3055 units; their length does not change and neither does the order of bytes
3056 within them. Such a rigid unit is called a @emph{section}. Assigning
3057 run-time addresses to sections is called @dfn{relocation}. It includes
3058 the task of adjusting mentions of object-file addresses so they refer to
3059 the proper run-time addresses.
3061 For the H8/300, and for the Renesas / SuperH SH,
3062 @command{@value{AS}} pads sections if needed to
3063 ensure they end on a word (sixteen bit) boundary.
3066 @cindex standard assembler sections
3067 An object file written by @command{@value{AS}} has at least three sections, any
3068 of which may be empty. These are named @dfn{text}, @dfn{data} and
3073 When it generates COFF or ELF output,
3075 @command{@value{AS}} can also generate whatever other named sections you specify
3076 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3077 If you do not use any directives that place output in the @samp{.text}
3078 or @samp{.data} sections, these sections still exist, but are empty.
3083 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3085 @command{@value{AS}} can also generate whatever other named sections you
3086 specify using the @samp{.space} and @samp{.subspace} directives. See
3087 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3088 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3089 assembler directives.
3092 Additionally, @command{@value{AS}} uses different names for the standard
3093 text, data, and bss sections when generating SOM output. Program text
3094 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3095 BSS into @samp{$BSS$}.
3099 Within the object file, the text section starts at address @code{0}, the
3100 data section follows, and the bss section follows the data section.
3103 When generating either SOM or ELF output files on the HPPA, the text
3104 section starts at address @code{0}, the data section at address
3105 @code{0x4000000}, and the bss section follows the data section.
3108 To let @code{@value{LD}} know which data changes when the sections are
3109 relocated, and how to change that data, @command{@value{AS}} also writes to the
3110 object file details of the relocation needed. To perform relocation
3111 @code{@value{LD}} must know, each time an address in the object
3115 Where in the object file is the beginning of this reference to
3118 How long (in bytes) is this reference?
3120 Which section does the address refer to? What is the numeric value of
3122 (@var{address}) @minus{} (@var{start-address of section})?
3125 Is the reference to an address ``Program-Counter relative''?
3128 @cindex addresses, format of
3129 @cindex section-relative addressing
3130 In fact, every address @command{@value{AS}} ever uses is expressed as
3132 (@var{section}) + (@var{offset into section})
3135 Further, most expressions @command{@value{AS}} computes have this section-relative
3138 (For some object formats, such as SOM for the HPPA, some expressions are
3139 symbol-relative instead.)
3142 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3143 @var{N} into section @var{secname}.''
3145 Apart from text, data and bss sections you need to know about the
3146 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3147 addresses in the absolute section remain unchanged. For example, address
3148 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3149 @code{@value{LD}}. Although the linker never arranges two partial programs'
3150 data sections with overlapping addresses after linking, @emph{by definition}
3151 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3152 part of a program is always the same address when the program is running as
3153 address @code{@{absolute@ 239@}} in any other part of the program.
3155 The idea of sections is extended to the @dfn{undefined} section. Any
3156 address whose section is unknown at assembly time is by definition
3157 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3158 Since numbers are always defined, the only way to generate an undefined
3159 address is to mention an undefined symbol. A reference to a named
3160 common block would be such a symbol: its value is unknown at assembly
3161 time so it has section @emph{undefined}.
3163 By analogy the word @emph{section} is used to describe groups of sections in
3164 the linked program. @code{@value{LD}} puts all partial programs' text
3165 sections in contiguous addresses in the linked program. It is
3166 customary to refer to the @emph{text section} of a program, meaning all
3167 the addresses of all partial programs' text sections. Likewise for
3168 data and bss sections.
3170 Some sections are manipulated by @code{@value{LD}}; others are invented for
3171 use of @command{@value{AS}} and have no meaning except during assembly.
3174 @section Linker Sections
3175 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3180 @cindex named sections
3181 @cindex sections, named
3182 @item named sections
3185 @cindex text section
3186 @cindex data section
3190 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3191 separate but equal sections. Anything you can say of one section is
3194 When the program is running, however, it is
3195 customary for the text section to be unalterable. The
3196 text section is often shared among processes: it contains
3197 instructions, constants and the like. The data section of a running
3198 program is usually alterable: for example, C variables would be stored
3199 in the data section.
3204 This section contains zeroed bytes when your program begins running. It
3205 is used to hold uninitialized variables or common storage. The length of
3206 each partial program's bss section is important, but because it starts
3207 out containing zeroed bytes there is no need to store explicit zero
3208 bytes in the object file. The bss section was invented to eliminate
3209 those explicit zeros from object files.
3211 @cindex absolute section
3212 @item absolute section
3213 Address 0 of this section is always ``relocated'' to runtime address 0.
3214 This is useful if you want to refer to an address that @code{@value{LD}} must
3215 not change when relocating. In this sense we speak of absolute
3216 addresses being ``unrelocatable'': they do not change during relocation.
3218 @cindex undefined section
3219 @item undefined section
3220 This ``section'' is a catch-all for address references to objects not in
3221 the preceding sections.
3222 @c FIXME: ref to some other doc on obj-file formats could go here.
3225 @cindex relocation example
3226 An idealized example of three relocatable sections follows.
3228 The example uses the traditional section names @samp{.text} and @samp{.data}.
3230 Memory addresses are on the horizontal axis.
3234 @c END TEXI2ROFF-KILL
3237 partial program # 1: |ttttt|dddd|00|
3244 partial program # 2: |TTT|DDD|000|
3247 +--+---+-----+--+----+---+-----+~~
3248 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3249 +--+---+-----+--+----+---+-----+~~
3251 addresses: 0 @dots{}
3258 \line{\it Partial program \#1: \hfil}
3259 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3260 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3262 \line{\it Partial program \#2: \hfil}
3263 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3264 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3266 \line{\it linked program: \hfil}
3267 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3268 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3269 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3270 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3272 \line{\it addresses: \hfil}
3276 @c END TEXI2ROFF-KILL
3279 @section Assembler Internal Sections
3281 @cindex internal assembler sections
3282 @cindex sections in messages, internal
3283 These sections are meant only for the internal use of @command{@value{AS}}. They
3284 have no meaning at run-time. You do not really need to know about these
3285 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3286 warning messages, so it might be helpful to have an idea of their
3287 meanings to @command{@value{AS}}. These sections are used to permit the
3288 value of every expression in your assembly language program to be a
3289 section-relative address.
3292 @cindex assembler internal logic error
3293 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3294 An internal assembler logic error has been found. This means there is a
3295 bug in the assembler.
3297 @cindex expr (internal section)
3299 The assembler stores complex expression internally as combinations of
3300 symbols. When it needs to represent an expression as a symbol, it puts
3301 it in the expr section.
3303 @c FIXME item transfer[t] vector preload
3304 @c FIXME item transfer[t] vector postload
3305 @c FIXME item register
3309 @section Sub-Sections
3311 @cindex numbered subsections
3312 @cindex grouping data
3318 fall into two sections: text and data.
3320 You may have separate groups of
3322 data in named sections
3326 data in named sections
3332 that you want to end up near to each other in the object file, even though they
3333 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3334 use @dfn{subsections} for this purpose. Within each section, there can be
3335 numbered subsections with values from 0 to 8192. Objects assembled into the
3336 same subsection go into the object file together with other objects in the same
3337 subsection. For example, a compiler might want to store constants in the text
3338 section, but might not want to have them interspersed with the program being
3339 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3340 section of code being output, and a @samp{.text 1} before each group of
3341 constants being output.
3343 Subsections are optional. If you do not use subsections, everything
3344 goes in subsection number zero.
3347 Each subsection is zero-padded up to a multiple of four bytes.
3348 (Subsections may be padded a different amount on different flavors
3349 of @command{@value{AS}}.)
3353 On the H8/300 platform, each subsection is zero-padded to a word
3354 boundary (two bytes).
3355 The same is true on the Renesas SH.
3358 @c FIXME section padding (alignment)?
3359 @c Rich Pixley says padding here depends on target obj code format; that
3360 @c doesn't seem particularly useful to say without further elaboration,
3361 @c so for now I say nothing about it. If this is a generic BFD issue,
3362 @c these paragraphs might need to vanish from this manual, and be
3363 @c discussed in BFD chapter of binutils (or some such).
3367 Subsections appear in your object file in numeric order, lowest numbered
3368 to highest. (All this to be compatible with other people's assemblers.)
3369 The object file contains no representation of subsections; @code{@value{LD}} and
3370 other programs that manipulate object files see no trace of them.
3371 They just see all your text subsections as a text section, and all your
3372 data subsections as a data section.
3374 To specify which subsection you want subsequent statements assembled
3375 into, use a numeric argument to specify it, in a @samp{.text
3376 @var{expression}} or a @samp{.data @var{expression}} statement.
3379 When generating COFF output, you
3384 can also use an extra subsection
3385 argument with arbitrary named sections: @samp{.section @var{name},
3390 When generating ELF output, you
3395 can also use the @code{.subsection} directive (@pxref{SubSection})
3396 to specify a subsection: @samp{.subsection @var{expression}}.
3398 @var{Expression} should be an absolute expression
3399 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3400 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3401 begins in @code{text 0}. For instance:
3403 .text 0 # The default subsection is text 0 anyway.
3404 .ascii "This lives in the first text subsection. *"
3406 .ascii "But this lives in the second text subsection."
3408 .ascii "This lives in the data section,"
3409 .ascii "in the first data subsection."
3411 .ascii "This lives in the first text section,"
3412 .ascii "immediately following the asterisk (*)."
3415 Each section has a @dfn{location counter} incremented by one for every byte
3416 assembled into that section. Because subsections are merely a convenience
3417 restricted to @command{@value{AS}} there is no concept of a subsection location
3418 counter. There is no way to directly manipulate a location counter---but the
3419 @code{.align} directive changes it, and any label definition captures its
3420 current value. The location counter of the section where statements are being
3421 assembled is said to be the @dfn{active} location counter.
3424 @section bss Section
3427 @cindex common variable storage
3428 The bss section is used for local common variable storage.
3429 You may allocate address space in the bss section, but you may
3430 not dictate data to load into it before your program executes. When
3431 your program starts running, all the contents of the bss
3432 section are zeroed bytes.
3434 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3435 @ref{Lcomm,,@code{.lcomm}}.
3437 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3438 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3441 When assembling for a target which supports multiple sections, such as ELF or
3442 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3443 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3444 section. Typically the section will only contain symbol definitions and
3445 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3452 Symbols are a central concept: the programmer uses symbols to name
3453 things, the linker uses symbols to link, and the debugger uses symbols
3457 @cindex debuggers, and symbol order
3458 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3459 the same order they were declared. This may break some debuggers.
3464 * Setting Symbols:: Giving Symbols Other Values
3465 * Symbol Names:: Symbol Names
3466 * Dot:: The Special Dot Symbol
3467 * Symbol Attributes:: Symbol Attributes
3474 A @dfn{label} is written as a symbol immediately followed by a colon
3475 @samp{:}. The symbol then represents the current value of the
3476 active location counter, and is, for example, a suitable instruction
3477 operand. You are warned if you use the same symbol to represent two
3478 different locations: the first definition overrides any other
3482 On the HPPA, the usual form for a label need not be immediately followed by a
3483 colon, but instead must start in column zero. Only one label may be defined on
3484 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3485 provides a special directive @code{.label} for defining labels more flexibly.
3488 @node Setting Symbols
3489 @section Giving Symbols Other Values
3491 @cindex assigning values to symbols
3492 @cindex symbol values, assigning
3493 A symbol can be given an arbitrary value by writing a symbol, followed
3494 by an equals sign @samp{=}, followed by an expression
3495 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3496 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3497 equals sign @samp{=}@samp{=} here represents an equivalent of the
3498 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3501 Blackfin does not support symbol assignment with @samp{=}.
3505 @section Symbol Names
3507 @cindex symbol names
3508 @cindex names, symbol
3509 @ifclear SPECIAL-SYMS
3510 Symbol names begin with a letter or with one of @samp{._}. On most
3511 machines, you can also use @code{$} in symbol names; exceptions are
3512 noted in @ref{Machine Dependencies}. That character may be followed by any
3513 string of digits, letters, dollar signs (unless otherwise noted for a
3514 particular target machine), and underscores.
3518 Symbol names begin with a letter or with one of @samp{._}. On the
3519 Renesas SH you can also use @code{$} in symbol names. That
3520 character may be followed by any string of digits, letters, dollar signs (save
3521 on the H8/300), and underscores.
3525 Case of letters is significant: @code{foo} is a different symbol name
3528 Multibyte characters are supported. To generate a symbol name containing
3529 multibyte characters enclose it within double quotes and use escape codes. cf
3530 @xref{Strings}. Generating a multibyte symbol name from a label is not
3531 currently supported.
3533 Each symbol has exactly one name. Each name in an assembly language program
3534 refers to exactly one symbol. You may use that symbol name any number of times
3537 @subheading Local Symbol Names
3539 @cindex local symbol names
3540 @cindex symbol names, local
3541 A local symbol is any symbol beginning with certain local label prefixes.
3542 By default, the local label prefix is @samp{.L} for ELF systems or
3543 @samp{L} for traditional a.out systems, but each target may have its own
3544 set of local label prefixes.
3546 On the HPPA local symbols begin with @samp{L$}.
3549 Local symbols are defined and used within the assembler, but they are
3550 normally not saved in object files. Thus, they are not visible when debugging.
3551 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3552 @option{-L}}) to retain the local symbols in the object files.
3554 @subheading Local Labels
3556 @cindex local labels
3557 @cindex temporary symbol names
3558 @cindex symbol names, temporary
3559 Local labels help compilers and programmers use names temporarily.
3560 They create symbols which are guaranteed to be unique over the entire scope of
3561 the input source code and which can be referred to by a simple notation.
3562 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3563 represents any positive integer). To refer to the most recent previous
3564 definition of that label write @samp{@b{N}b}, using the same number as when
3565 you defined the label. To refer to the next definition of a local label, write
3566 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3569 There is no restriction on how you can use these labels, and you can reuse them
3570 too. So that it is possible to repeatedly define the same local label (using
3571 the same number @samp{@b{N}}), although you can only refer to the most recently
3572 defined local label of that number (for a backwards reference) or the next
3573 definition of a specific local label for a forward reference. It is also worth
3574 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3575 implemented in a slightly more efficient manner than the others.
3586 Which is the equivalent of:
3589 label_1: branch label_3
3590 label_2: branch label_1
3591 label_3: branch label_4
3592 label_4: branch label_3
3595 Local label names are only a notational device. They are immediately
3596 transformed into more conventional symbol names before the assembler uses them.
3597 The symbol names are stored in the symbol table, appear in error messages, and
3598 are optionally emitted to the object file. The names are constructed using
3602 @item @emph{local label prefix}
3603 All local symbols begin with the system-specific local label prefix.
3604 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3605 that start with the local label prefix. These labels are
3606 used for symbols you are never intended to see. If you use the
3607 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3608 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3609 you may use them in debugging.
3612 This is the number that was used in the local label definition. So if the
3613 label is written @samp{55:} then the number is @samp{55}.
3616 This unusual character is included so you do not accidentally invent a symbol
3617 of the same name. The character has ASCII value of @samp{\002} (control-B).
3619 @item @emph{ordinal number}
3620 This is a serial number to keep the labels distinct. The first definition of
3621 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3622 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3623 the number @samp{1} and its 15th definition gets @samp{15} as well.
3626 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3627 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3629 @subheading Dollar Local Labels
3630 @cindex dollar local symbols
3632 @code{@value{AS}} also supports an even more local form of local labels called
3633 dollar labels. These labels go out of scope (i.e., they become undefined) as
3634 soon as a non-local label is defined. Thus they remain valid for only a small
3635 region of the input source code. Normal local labels, by contrast, remain in
3636 scope for the entire file, or until they are redefined by another occurrence of
3637 the same local label.
3639 Dollar labels are defined in exactly the same way as ordinary local labels,
3640 except that they have a dollar sign suffix to their numeric value, e.g.,
3643 They can also be distinguished from ordinary local labels by their transformed
3644 names which use ASCII character @samp{\001} (control-A) as the magic character
3645 to distinguish them from ordinary labels. For example, the fifth definition of
3646 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3649 @section The Special Dot Symbol
3651 @cindex dot (symbol)
3652 @cindex @code{.} (symbol)
3653 @cindex current address
3654 @cindex location counter
3655 The special symbol @samp{.} refers to the current address that
3656 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3657 .long .} defines @code{melvin} to contain its own address.
3658 Assigning a value to @code{.} is treated the same as a @code{.org}
3660 @ifclear no-space-dir
3661 Thus, the expression @samp{.=.+4} is the same as saying
3665 @node Symbol Attributes
3666 @section Symbol Attributes
3668 @cindex symbol attributes
3669 @cindex attributes, symbol
3670 Every symbol has, as well as its name, the attributes ``Value'' and
3671 ``Type''. Depending on output format, symbols can also have auxiliary
3674 The detailed definitions are in @file{a.out.h}.
3677 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3678 all these attributes, and probably won't warn you. This makes the
3679 symbol an externally defined symbol, which is generally what you
3683 * Symbol Value:: Value
3684 * Symbol Type:: Type
3687 * a.out Symbols:: Symbol Attributes: @code{a.out}
3691 * a.out Symbols:: Symbol Attributes: @code{a.out}
3694 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3699 * COFF Symbols:: Symbol Attributes for COFF
3702 * SOM Symbols:: Symbol Attributes for SOM
3709 @cindex value of a symbol
3710 @cindex symbol value
3711 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3712 location in the text, data, bss or absolute sections the value is the
3713 number of addresses from the start of that section to the label.
3714 Naturally for text, data and bss sections the value of a symbol changes
3715 as @code{@value{LD}} changes section base addresses during linking. Absolute
3716 symbols' values do not change during linking: that is why they are
3719 The value of an undefined symbol is treated in a special way. If it is
3720 0 then the symbol is not defined in this assembler source file, and
3721 @code{@value{LD}} tries to determine its value from other files linked into the
3722 same program. You make this kind of symbol simply by mentioning a symbol
3723 name without defining it. A non-zero value represents a @code{.comm}
3724 common declaration. The value is how much common storage to reserve, in
3725 bytes (addresses). The symbol refers to the first address of the
3731 @cindex type of a symbol
3733 The type attribute of a symbol contains relocation (section)
3734 information, any flag settings indicating that a symbol is external, and
3735 (optionally), other information for linkers and debuggers. The exact
3736 format depends on the object-code output format in use.
3741 @c The following avoids a "widow" subsection title. @group would be
3742 @c better if it were available outside examples.
3745 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3747 @cindex @code{b.out} symbol attributes
3748 @cindex symbol attributes, @code{b.out}
3749 These symbol attributes appear only when @command{@value{AS}} is configured for
3750 one of the Berkeley-descended object output formats---@code{a.out} or
3756 @subsection Symbol Attributes: @code{a.out}
3758 @cindex @code{a.out} symbol attributes
3759 @cindex symbol attributes, @code{a.out}
3765 @subsection Symbol Attributes: @code{a.out}
3767 @cindex @code{a.out} symbol attributes
3768 @cindex symbol attributes, @code{a.out}
3772 * Symbol Desc:: Descriptor
3773 * Symbol Other:: Other
3777 @subsubsection Descriptor
3779 @cindex descriptor, of @code{a.out} symbol
3780 This is an arbitrary 16-bit value. You may establish a symbol's
3781 descriptor value by using a @code{.desc} statement
3782 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3783 @command{@value{AS}}.
3786 @subsubsection Other
3788 @cindex other attribute, of @code{a.out} symbol
3789 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3794 @subsection Symbol Attributes for COFF
3796 @cindex COFF symbol attributes
3797 @cindex symbol attributes, COFF
3799 The COFF format supports a multitude of auxiliary symbol attributes;
3800 like the primary symbol attributes, they are set between @code{.def} and
3801 @code{.endef} directives.
3803 @subsubsection Primary Attributes
3805 @cindex primary attributes, COFF symbols
3806 The symbol name is set with @code{.def}; the value and type,
3807 respectively, with @code{.val} and @code{.type}.
3809 @subsubsection Auxiliary Attributes
3811 @cindex auxiliary attributes, COFF symbols
3812 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3813 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3814 table information for COFF.
3819 @subsection Symbol Attributes for SOM
3821 @cindex SOM symbol attributes
3822 @cindex symbol attributes, SOM
3824 The SOM format for the HPPA supports a multitude of symbol attributes set with
3825 the @code{.EXPORT} and @code{.IMPORT} directives.
3827 The attributes are described in @cite{HP9000 Series 800 Assembly
3828 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3829 @code{EXPORT} assembler directive documentation.
3833 @chapter Expressions
3837 @cindex numeric values
3838 An @dfn{expression} specifies an address or numeric value.
3839 Whitespace may precede and/or follow an expression.
3841 The result of an expression must be an absolute number, or else an offset into
3842 a particular section. If an expression is not absolute, and there is not
3843 enough information when @command{@value{AS}} sees the expression to know its
3844 section, a second pass over the source program might be necessary to interpret
3845 the expression---but the second pass is currently not implemented.
3846 @command{@value{AS}} aborts with an error message in this situation.
3849 * Empty Exprs:: Empty Expressions
3850 * Integer Exprs:: Integer Expressions
3854 @section Empty Expressions
3856 @cindex empty expressions
3857 @cindex expressions, empty
3858 An empty expression has no value: it is just whitespace or null.
3859 Wherever an absolute expression is required, you may omit the
3860 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3861 is compatible with other assemblers.
3864 @section Integer Expressions
3866 @cindex integer expressions
3867 @cindex expressions, integer
3868 An @dfn{integer expression} is one or more @emph{arguments} delimited
3869 by @emph{operators}.
3872 * Arguments:: Arguments
3873 * Operators:: Operators
3874 * Prefix Ops:: Prefix Operators
3875 * Infix Ops:: Infix Operators
3879 @subsection Arguments
3881 @cindex expression arguments
3882 @cindex arguments in expressions
3883 @cindex operands in expressions
3884 @cindex arithmetic operands
3885 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3886 contexts arguments are sometimes called ``arithmetic operands''. In
3887 this manual, to avoid confusing them with the ``instruction operands'' of
3888 the machine language, we use the term ``argument'' to refer to parts of
3889 expressions only, reserving the word ``operand'' to refer only to machine
3890 instruction operands.
3892 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3893 @var{section} is one of text, data, bss, absolute,
3894 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3897 Numbers are usually integers.
3899 A number can be a flonum or bignum. In this case, you are warned
3900 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3901 these 32 bits are an integer. You may write integer-manipulating
3902 instructions that act on exotic constants, compatible with other
3905 @cindex subexpressions
3906 Subexpressions are a left parenthesis @samp{(} followed by an integer
3907 expression, followed by a right parenthesis @samp{)}; or a prefix
3908 operator followed by an argument.
3911 @subsection Operators
3913 @cindex operators, in expressions
3914 @cindex arithmetic functions
3915 @cindex functions, in expressions
3916 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3917 operators are followed by an argument. Infix operators appear
3918 between their arguments. Operators may be preceded and/or followed by
3922 @subsection Prefix Operator
3924 @cindex prefix operators
3925 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3926 one argument, which must be absolute.
3928 @c the tex/end tex stuff surrounding this small table is meant to make
3929 @c it align, on the printed page, with the similar table in the next
3930 @c section (which is inside an enumerate).
3932 \global\advance\leftskip by \itemindent
3937 @dfn{Negation}. Two's complement negation.
3939 @dfn{Complementation}. Bitwise not.
3943 \global\advance\leftskip by -\itemindent
3947 @subsection Infix Operators
3949 @cindex infix operators
3950 @cindex operators, permitted arguments
3951 @dfn{Infix operators} take two arguments, one on either side. Operators
3952 have precedence, but operations with equal precedence are performed left
3953 to right. Apart from @code{+} or @option{-}, both arguments must be
3954 absolute, and the result is absolute.
3957 @cindex operator precedence
3958 @cindex precedence of operators
3965 @dfn{Multiplication}.
3968 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3974 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3977 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3981 Intermediate precedence
3986 @dfn{Bitwise Inclusive Or}.
3992 @dfn{Bitwise Exclusive Or}.
3995 @dfn{Bitwise Or Not}.
4002 @cindex addition, permitted arguments
4003 @cindex plus, permitted arguments
4004 @cindex arguments for addition
4006 @dfn{Addition}. If either argument is absolute, the result has the section of
4007 the other argument. You may not add together arguments from different
4010 @cindex subtraction, permitted arguments
4011 @cindex minus, permitted arguments
4012 @cindex arguments for subtraction
4014 @dfn{Subtraction}. If the right argument is absolute, the
4015 result has the section of the left argument.
4016 If both arguments are in the same section, the result is absolute.
4017 You may not subtract arguments from different sections.
4018 @c FIXME is there still something useful to say about undefined - undefined ?
4020 @cindex comparison expressions
4021 @cindex expressions, comparison
4026 @dfn{Is Not Equal To}
4030 @dfn{Is Greater Than}
4032 @dfn{Is Greater Than Or Equal To}
4034 @dfn{Is Less Than Or Equal To}
4036 The comparison operators can be used as infix operators. A true results has a
4037 value of -1 whereas a false result has a value of 0. Note, these operators
4038 perform signed comparisons.
4041 @item Lowest Precedence
4050 These two logical operations can be used to combine the results of sub
4051 expressions. Note, unlike the comparison operators a true result returns a
4052 value of 1 but a false results does still return 0. Also note that the logical
4053 or operator has a slightly lower precedence than logical and.
4058 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4059 address; you can only have a defined section in one of the two arguments.
4062 @chapter Assembler Directives
4064 @cindex directives, machine independent
4065 @cindex pseudo-ops, machine independent
4066 @cindex machine independent directives
4067 All assembler directives have names that begin with a period (@samp{.}).
4068 The rest of the name is letters, usually in lower case.
4070 This chapter discusses directives that are available regardless of the
4071 target machine configuration for the @sc{gnu} assembler.
4073 Some machine configurations provide additional directives.
4074 @xref{Machine Dependencies}.
4077 @ifset machine-directives
4078 @xref{Machine Dependencies}, for additional directives.
4083 * Abort:: @code{.abort}
4085 * ABORT (COFF):: @code{.ABORT}
4088 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4089 * Altmacro:: @code{.altmacro}
4090 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4091 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4092 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4093 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4094 * Byte:: @code{.byte @var{expressions}}
4095 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4096 * Comm:: @code{.comm @var{symbol} , @var{length} }
4097 * Data:: @code{.data @var{subsection}}
4099 * Def:: @code{.def @var{name}}
4102 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4108 * Double:: @code{.double @var{flonums}}
4109 * Eject:: @code{.eject}
4110 * Else:: @code{.else}
4111 * Elseif:: @code{.elseif}
4114 * Endef:: @code{.endef}
4117 * Endfunc:: @code{.endfunc}
4118 * Endif:: @code{.endif}
4119 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4120 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4121 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4123 * Error:: @code{.error @var{string}}
4124 * Exitm:: @code{.exitm}
4125 * Extern:: @code{.extern}
4126 * Fail:: @code{.fail}
4127 * File:: @code{.file}
4128 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4129 * Float:: @code{.float @var{flonums}}
4130 * Func:: @code{.func}
4131 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4133 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4134 * Hidden:: @code{.hidden @var{names}}
4137 * hword:: @code{.hword @var{expressions}}
4138 * Ident:: @code{.ident}
4139 * If:: @code{.if @var{absolute expression}}
4140 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4141 * Include:: @code{.include "@var{file}"}
4142 * Int:: @code{.int @var{expressions}}
4144 * Internal:: @code{.internal @var{names}}
4147 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4148 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4149 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4150 * Lflags:: @code{.lflags}
4151 @ifclear no-line-dir
4152 * Line:: @code{.line @var{line-number}}
4155 * Linkonce:: @code{.linkonce [@var{type}]}
4156 * List:: @code{.list}
4157 * Ln:: @code{.ln @var{line-number}}
4158 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4159 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4161 * Local:: @code{.local @var{names}}
4164 * Long:: @code{.long @var{expressions}}
4166 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4169 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4170 * MRI:: @code{.mri @var{val}}
4171 * Noaltmacro:: @code{.noaltmacro}
4172 * Nolist:: @code{.nolist}
4173 * Octa:: @code{.octa @var{bignums}}
4174 * Offset:: @code{.offset @var{loc}}
4175 * Org:: @code{.org @var{new-lc}, @var{fill}}
4176 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4178 * PopSection:: @code{.popsection}
4179 * Previous:: @code{.previous}
4182 * Print:: @code{.print @var{string}}
4184 * Protected:: @code{.protected @var{names}}
4187 * Psize:: @code{.psize @var{lines}, @var{columns}}
4188 * Purgem:: @code{.purgem @var{name}}
4190 * PushSection:: @code{.pushsection @var{name}}
4193 * Quad:: @code{.quad @var{bignums}}
4194 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4195 * Rept:: @code{.rept @var{count}}
4196 * Sbttl:: @code{.sbttl "@var{subheading}"}
4198 * Scl:: @code{.scl @var{class}}
4201 * Section:: @code{.section @var{name}[, @var{flags}]}
4204 * Set:: @code{.set @var{symbol}, @var{expression}}
4205 * Short:: @code{.short @var{expressions}}
4206 * Single:: @code{.single @var{flonums}}
4208 * Size:: @code{.size [@var{name} , @var{expression}]}
4210 @ifclear no-space-dir
4211 * Skip:: @code{.skip @var{size} , @var{fill}}
4214 * Sleb128:: @code{.sleb128 @var{expressions}}
4215 @ifclear no-space-dir
4216 * Space:: @code{.space @var{size} , @var{fill}}
4219 * Stab:: @code{.stabd, .stabn, .stabs}
4222 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4223 * Struct:: @code{.struct @var{expression}}
4225 * SubSection:: @code{.subsection}
4226 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4230 * Tag:: @code{.tag @var{structname}}
4233 * Text:: @code{.text @var{subsection}}
4234 * Title:: @code{.title "@var{heading}"}
4236 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4239 * Uleb128:: @code{.uleb128 @var{expressions}}
4241 * Val:: @code{.val @var{addr}}
4245 * Version:: @code{.version "@var{string}"}
4246 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4247 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4250 * Warning:: @code{.warning @var{string}}
4251 * Weak:: @code{.weak @var{names}}
4252 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4253 * Word:: @code{.word @var{expressions}}
4254 * Deprecated:: Deprecated Directives
4258 @section @code{.abort}
4260 @cindex @code{abort} directive
4261 @cindex stopping the assembly
4262 This directive stops the assembly immediately. It is for
4263 compatibility with other assemblers. The original idea was that the
4264 assembly language source would be piped into the assembler. If the sender
4265 of the source quit, it could use this directive tells @command{@value{AS}} to
4266 quit also. One day @code{.abort} will not be supported.
4270 @section @code{.ABORT} (COFF)
4272 @cindex @code{ABORT} directive
4273 When producing COFF output, @command{@value{AS}} accepts this directive as a
4274 synonym for @samp{.abort}.
4277 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4283 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4285 @cindex padding the location counter
4286 @cindex @code{align} directive
4287 Pad the location counter (in the current subsection) to a particular storage
4288 boundary. The first expression (which must be absolute) is the alignment
4289 required, as described below.
4291 The second expression (also absolute) gives the fill value to be stored in the
4292 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4293 padding bytes are normally zero. However, on some systems, if the section is
4294 marked as containing code and the fill value is omitted, the space is filled
4295 with no-op instructions.
4297 The third expression is also absolute, and is also optional. If it is present,
4298 it is the maximum number of bytes that should be skipped by this alignment
4299 directive. If doing the alignment would require skipping more bytes than the
4300 specified maximum, then the alignment is not done at all. You can omit the
4301 fill value (the second argument) entirely by simply using two commas after the
4302 required alignment; this can be useful if you want the alignment to be filled
4303 with no-op instructions when appropriate.
4305 The way the required alignment is specified varies from system to system.
4306 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4307 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4308 alignment request in bytes. For example @samp{.align 8} advances
4309 the location counter until it is a multiple of 8. If the location counter
4310 is already a multiple of 8, no change is needed. For the tic54x, the
4311 first expression is the alignment request in words.
4313 For other systems, including ppc, i386 using a.out format, arm and
4314 strongarm, it is the
4315 number of low-order zero bits the location counter must have after
4316 advancement. For example @samp{.align 3} advances the location
4317 counter until it a multiple of 8. If the location counter is already a
4318 multiple of 8, no change is needed.
4320 This inconsistency is due to the different behaviors of the various
4321 native assemblers for these systems which GAS must emulate.
4322 GAS also provides @code{.balign} and @code{.p2align} directives,
4323 described later, which have a consistent behavior across all
4324 architectures (but are specific to GAS).
4327 @section @code{.altmacro}
4328 Enable alternate macro mode, enabling:
4331 @item LOCAL @var{name} [ , @dots{} ]
4332 One additional directive, @code{LOCAL}, is available. It is used to
4333 generate a string replacement for each of the @var{name} arguments, and
4334 replace any instances of @var{name} in each macro expansion. The
4335 replacement string is unique in the assembly, and different for each
4336 separate macro expansion. @code{LOCAL} allows you to write macros that
4337 define symbols, without fear of conflict between separate macro expansions.
4339 @item String delimiters
4340 You can write strings delimited in these other ways besides
4341 @code{"@var{string}"}:
4344 @item '@var{string}'
4345 You can delimit strings with single-quote characters.
4347 @item <@var{string}>
4348 You can delimit strings with matching angle brackets.
4351 @item single-character string escape
4352 To include any single character literally in a string (even if the
4353 character would otherwise have some special meaning), you can prefix the
4354 character with @samp{!} (an exclamation mark). For example, you can
4355 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4357 @item Expression results as strings
4358 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4359 and use the result as a string.
4363 @section @code{.ascii "@var{string}"}@dots{}
4365 @cindex @code{ascii} directive
4366 @cindex string literals
4367 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4368 separated by commas. It assembles each string (with no automatic
4369 trailing zero byte) into consecutive addresses.
4372 @section @code{.asciz "@var{string}"}@dots{}
4374 @cindex @code{asciz} directive
4375 @cindex zero-terminated strings
4376 @cindex null-terminated strings
4377 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4378 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4381 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4383 @cindex padding the location counter given number of bytes
4384 @cindex @code{balign} directive
4385 Pad the location counter (in the current subsection) to a particular
4386 storage boundary. The first expression (which must be absolute) is the
4387 alignment request in bytes. For example @samp{.balign 8} advances
4388 the location counter until it is a multiple of 8. If the location counter
4389 is already a multiple of 8, no change is needed.
4391 The second expression (also absolute) gives the fill value to be stored in the
4392 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4393 padding bytes are normally zero. However, on some systems, if the section is
4394 marked as containing code and the fill value is omitted, the space is filled
4395 with no-op instructions.
4397 The third expression is also absolute, and is also optional. If it is present,
4398 it is the maximum number of bytes that should be skipped by this alignment
4399 directive. If doing the alignment would require skipping more bytes than the
4400 specified maximum, then the alignment is not done at all. You can omit the
4401 fill value (the second argument) entirely by simply using two commas after the
4402 required alignment; this can be useful if you want the alignment to be filled
4403 with no-op instructions when appropriate.
4405 @cindex @code{balignw} directive
4406 @cindex @code{balignl} directive
4407 The @code{.balignw} and @code{.balignl} directives are variants of the
4408 @code{.balign} directive. The @code{.balignw} directive treats the fill
4409 pattern as a two byte word value. The @code{.balignl} directives treats the
4410 fill pattern as a four byte longword value. For example, @code{.balignw
4411 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4412 filled in with the value 0x368d (the exact placement of the bytes depends upon
4413 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4416 @node Bundle directives
4417 @section @code{.bundle_align_mode @var{abs-expr}}
4418 @cindex @code{bundle_align_mode} directive
4420 @cindex instruction bundle
4421 @cindex aligned instruction bundle
4422 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4423 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4424 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4425 disabled (which is the default state). If the argument it not zero, it
4426 gives the size of an instruction bundle as a power of two (as for the
4427 @code{.p2align} directive, @pxref{P2align}).
4429 For some targets, it's an ABI requirement that no instruction may span a
4430 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4431 instructions that starts on an aligned boundary. For example, if
4432 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4433 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4434 effect, no single instruction may span a boundary between bundles. If an
4435 instruction would start too close to the end of a bundle for the length of
4436 that particular instruction to fit within the bundle, then the space at the
4437 end of that bundle is filled with no-op instructions so the instruction
4438 starts in the next bundle. As a corollary, it's an error if any single
4439 instruction's encoding is longer than the bundle size.
4441 @section @code{.bundle_lock} and @code{.bundle_unlock}
4442 @cindex @code{bundle_lock} directive
4443 @cindex @code{bundle_unlock} directive
4444 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4445 allow explicit control over instruction bundle padding. These directives
4446 are only valid when @code{.bundle_align_mode} has been used to enable
4447 aligned instruction bundle mode. It's an error if they appear when
4448 @code{.bundle_align_mode} has not been used at all, or when the last
4449 directive was @w{@code{.bundle_align_mode 0}}.
4451 @cindex bundle-locked
4452 For some targets, it's an ABI requirement that certain instructions may
4453 appear only as part of specified permissible sequences of multiple
4454 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4455 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4456 instruction sequence. For purposes of aligned instruction bundle mode, a
4457 sequence starting with @code{.bundle_lock} and ending with
4458 @code{.bundle_unlock} is treated as a single instruction. That is, the
4459 entire sequence must fit into a single bundle and may not span a bundle
4460 boundary. If necessary, no-op instructions will be inserted before the
4461 first instruction of the sequence so that the whole sequence starts on an
4462 aligned bundle boundary. It's an error if the sequence is longer than the
4465 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4466 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4467 nested. That is, a second @code{.bundle_lock} directive before the next
4468 @code{.bundle_unlock} directive has no effect except that it must be
4469 matched by another closing @code{.bundle_unlock} so that there is the
4470 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4473 @section @code{.byte @var{expressions}}
4475 @cindex @code{byte} directive
4476 @cindex integers, one byte
4477 @code{.byte} expects zero or more expressions, separated by commas.
4478 Each expression is assembled into the next byte.
4480 @node CFI directives
4481 @section @code{.cfi_sections @var{section_list}}
4482 @cindex @code{cfi_sections} directive
4483 @code{.cfi_sections} may be used to specify whether CFI directives
4484 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4485 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4486 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4487 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4488 directive is not used is @code{.cfi_sections .eh_frame}.
4490 @section @code{.cfi_startproc [simple]}
4491 @cindex @code{cfi_startproc} directive
4492 @code{.cfi_startproc} is used at the beginning of each function that
4493 should have an entry in @code{.eh_frame}. It initializes some internal
4494 data structures. Don't forget to close the function by
4495 @code{.cfi_endproc}.
4497 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4498 it also emits some architecture dependent initial CFI instructions.
4500 @section @code{.cfi_endproc}
4501 @cindex @code{cfi_endproc} directive
4502 @code{.cfi_endproc} is used at the end of a function where it closes its
4503 unwind entry previously opened by
4504 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4506 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4507 @code{.cfi_personality} defines personality routine and its encoding.
4508 @var{encoding} must be a constant determining how the personality
4509 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4510 argument is not present, otherwise second argument should be
4511 a constant or a symbol name. When using indirect encodings,
4512 the symbol provided should be the location where personality
4513 can be loaded from, not the personality routine itself.
4514 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4515 no personality routine.
4517 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4518 @code{.cfi_lsda} defines LSDA and its encoding.
4519 @var{encoding} must be a constant determining how the LSDA
4520 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4521 argument is not present, otherwise second argument should be a constant
4522 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4525 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4526 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4527 address from @var{register} and add @var{offset} to it}.
4529 @section @code{.cfi_def_cfa_register @var{register}}
4530 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4531 now on @var{register} will be used instead of the old one. Offset
4534 @section @code{.cfi_def_cfa_offset @var{offset}}
4535 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4536 remains the same, but @var{offset} is new. Note that it is the
4537 absolute offset that will be added to a defined register to compute
4540 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4541 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4542 value that is added/substracted from the previous offset.
4544 @section @code{.cfi_offset @var{register}, @var{offset}}
4545 Previous value of @var{register} is saved at offset @var{offset} from
4548 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4549 Previous value of @var{register} is saved at offset @var{offset} from
4550 the current CFA register. This is transformed to @code{.cfi_offset}
4551 using the known displacement of the CFA register from the CFA.
4552 This is often easier to use, because the number will match the
4553 code it's annotating.
4555 @section @code{.cfi_register @var{register1}, @var{register2}}
4556 Previous value of @var{register1} is saved in register @var{register2}.
4558 @section @code{.cfi_restore @var{register}}
4559 @code{.cfi_restore} says that the rule for @var{register} is now the
4560 same as it was at the beginning of the function, after all initial
4561 instruction added by @code{.cfi_startproc} were executed.
4563 @section @code{.cfi_undefined @var{register}}
4564 From now on the previous value of @var{register} can't be restored anymore.
4566 @section @code{.cfi_same_value @var{register}}
4567 Current value of @var{register} is the same like in the previous frame,
4568 i.e. no restoration needed.
4570 @section @code{.cfi_remember_state},
4571 First save all current rules for all registers by @code{.cfi_remember_state},
4572 then totally screw them up by subsequent @code{.cfi_*} directives and when
4573 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4574 the previous saved state.
4576 @section @code{.cfi_return_column @var{register}}
4577 Change return column @var{register}, i.e. the return address is either
4578 directly in @var{register} or can be accessed by rules for @var{register}.
4580 @section @code{.cfi_signal_frame}
4581 Mark current function as signal trampoline.
4583 @section @code{.cfi_window_save}
4584 SPARC register window has been saved.
4586 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4587 Allows the user to add arbitrary bytes to the unwind info. One
4588 might use this to add OS-specific CFI opcodes, or generic CFI
4589 opcodes that GAS does not yet support.
4591 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4592 The current value of @var{register} is @var{label}. The value of @var{label}
4593 will be encoded in the output file according to @var{encoding}; see the
4594 description of @code{.cfi_personality} for details on this encoding.
4596 The usefulness of equating a register to a fixed label is probably
4597 limited to the return address register. Here, it can be useful to
4598 mark a code segment that has only one return address which is reached
4599 by a direct branch and no copy of the return address exists in memory
4600 or another register.
4603 @section @code{.comm @var{symbol} , @var{length} }
4605 @cindex @code{comm} directive
4606 @cindex symbol, common
4607 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4608 common symbol in one object file may be merged with a defined or common symbol
4609 of the same name in another object file. If @code{@value{LD}} does not see a
4610 definition for the symbol--just one or more common symbols--then it will
4611 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4612 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4613 the same name, and they do not all have the same size, it will allocate space
4614 using the largest size.
4617 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4618 an optional third argument. This is the desired alignment of the symbol,
4619 specified for ELF as a byte boundary (for example, an alignment of 16 means
4620 that the least significant 4 bits of the address should be zero), and for PE
4621 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4622 boundary). The alignment must be an absolute expression, and it must be a
4623 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4624 common symbol, it will use the alignment when placing the symbol. If no
4625 alignment is specified, @command{@value{AS}} will set the alignment to the
4626 largest power of two less than or equal to the size of the symbol, up to a
4627 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4628 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4629 @samp{--section-alignment} option; image file sections in PE are aligned to
4630 multiples of 4096, which is far too large an alignment for ordinary variables.
4631 It is rather the default alignment for (non-debug) sections within object
4632 (@samp{*.o}) files, which are less strictly aligned.}.
4636 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4637 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4641 @section @code{.data @var{subsection}}
4643 @cindex @code{data} directive
4644 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4645 end of the data subsection numbered @var{subsection} (which is an
4646 absolute expression). If @var{subsection} is omitted, it defaults
4651 @section @code{.def @var{name}}
4653 @cindex @code{def} directive
4654 @cindex COFF symbols, debugging
4655 @cindex debugging COFF symbols
4656 Begin defining debugging information for a symbol @var{name}; the
4657 definition extends until the @code{.endef} directive is encountered.
4660 This directive is only observed when @command{@value{AS}} is configured for COFF
4661 format output; when producing @code{b.out}, @samp{.def} is recognized,
4668 @section @code{.desc @var{symbol}, @var{abs-expression}}
4670 @cindex @code{desc} directive
4671 @cindex COFF symbol descriptor
4672 @cindex symbol descriptor, COFF
4673 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4674 to the low 16 bits of an absolute expression.
4677 The @samp{.desc} directive is not available when @command{@value{AS}} is
4678 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4679 object format. For the sake of compatibility, @command{@value{AS}} accepts
4680 it, but produces no output, when configured for COFF.
4686 @section @code{.dim}
4688 @cindex @code{dim} directive
4689 @cindex COFF auxiliary symbol information
4690 @cindex auxiliary symbol information, COFF
4691 This directive is generated by compilers to include auxiliary debugging
4692 information in the symbol table. It is only permitted inside
4693 @code{.def}/@code{.endef} pairs.
4696 @samp{.dim} is only meaningful when generating COFF format output; when
4697 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4703 @section @code{.double @var{flonums}}
4705 @cindex @code{double} directive
4706 @cindex floating point numbers (double)
4707 @code{.double} expects zero or more flonums, separated by commas. It
4708 assembles floating point numbers.
4710 The exact kind of floating point numbers emitted depends on how
4711 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4715 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4716 in @sc{ieee} format.
4721 @section @code{.eject}
4723 @cindex @code{eject} directive
4724 @cindex new page, in listings
4725 @cindex page, in listings
4726 @cindex listing control: new page
4727 Force a page break at this point, when generating assembly listings.
4730 @section @code{.else}
4732 @cindex @code{else} directive
4733 @code{.else} is part of the @command{@value{AS}} support for conditional
4734 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4735 of code to be assembled if the condition for the preceding @code{.if}
4739 @section @code{.elseif}
4741 @cindex @code{elseif} directive
4742 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4743 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4744 @code{.if} block that would otherwise fill the entire @code{.else} section.
4747 @section @code{.end}
4749 @cindex @code{end} directive
4750 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4751 process anything in the file past the @code{.end} directive.
4755 @section @code{.endef}
4757 @cindex @code{endef} directive
4758 This directive flags the end of a symbol definition begun with
4762 @samp{.endef} is only meaningful when generating COFF format output; if
4763 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4764 directive but ignores it.
4769 @section @code{.endfunc}
4770 @cindex @code{endfunc} directive
4771 @code{.endfunc} marks the end of a function specified with @code{.func}.
4774 @section @code{.endif}
4776 @cindex @code{endif} directive
4777 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4778 it marks the end of a block of code that is only assembled
4779 conditionally. @xref{If,,@code{.if}}.
4782 @section @code{.equ @var{symbol}, @var{expression}}
4784 @cindex @code{equ} directive
4785 @cindex assigning values to symbols
4786 @cindex symbols, assigning values to
4787 This directive sets the value of @var{symbol} to @var{expression}.
4788 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4791 The syntax for @code{equ} on the HPPA is
4792 @samp{@var{symbol} .equ @var{expression}}.
4796 The syntax for @code{equ} on the Z80 is
4797 @samp{@var{symbol} equ @var{expression}}.
4798 On the Z80 it is an eror if @var{symbol} is already defined,
4799 but the symbol is not protected from later redefinition.
4800 Compare @ref{Equiv}.
4804 @section @code{.equiv @var{symbol}, @var{expression}}
4805 @cindex @code{equiv} directive
4806 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4807 the assembler will signal an error if @var{symbol} is already defined. Note a
4808 symbol which has been referenced but not actually defined is considered to be
4811 Except for the contents of the error message, this is roughly equivalent to
4818 plus it protects the symbol from later redefinition.
4821 @section @code{.eqv @var{symbol}, @var{expression}}
4822 @cindex @code{eqv} directive
4823 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4824 evaluate the expression or any part of it immediately. Instead each time
4825 the resulting symbol is used in an expression, a snapshot of its current
4829 @section @code{.err}
4830 @cindex @code{err} directive
4831 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4832 message and, unless the @option{-Z} option was used, it will not generate an
4833 object file. This can be used to signal an error in conditionally compiled code.
4836 @section @code{.error "@var{string}"}
4837 @cindex error directive
4839 Similarly to @code{.err}, this directive emits an error, but you can specify a
4840 string that will be emitted as the error message. If you don't specify the
4841 message, it defaults to @code{".error directive invoked in source file"}.
4842 @xref{Errors, ,Error and Warning Messages}.
4845 .error "This code has not been assembled and tested."
4849 @section @code{.exitm}
4850 Exit early from the current macro definition. @xref{Macro}.
4853 @section @code{.extern}
4855 @cindex @code{extern} directive
4856 @code{.extern} is accepted in the source program---for compatibility
4857 with other assemblers---but it is ignored. @command{@value{AS}} treats
4858 all undefined symbols as external.
4861 @section @code{.fail @var{expression}}
4863 @cindex @code{fail} directive
4864 Generates an error or a warning. If the value of the @var{expression} is 500
4865 or more, @command{@value{AS}} will print a warning message. If the value is less
4866 than 500, @command{@value{AS}} will print an error message. The message will
4867 include the value of @var{expression}. This can occasionally be useful inside
4868 complex nested macros or conditional assembly.
4871 @section @code{.file}
4872 @cindex @code{file} directive
4874 @ifclear no-file-dir
4875 There are two different versions of the @code{.file} directive. Targets
4876 that support DWARF2 line number information use the DWARF2 version of
4877 @code{.file}. Other targets use the default version.
4879 @subheading Default Version
4881 @cindex logical file name
4882 @cindex file name, logical
4883 This version of the @code{.file} directive tells @command{@value{AS}} that we
4884 are about to start a new logical file. The syntax is:
4890 @var{string} is the new file name. In general, the filename is
4891 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4892 to specify an empty file name, you must give the quotes--@code{""}. This
4893 statement may go away in future: it is only recognized to be compatible with
4894 old @command{@value{AS}} programs.
4896 @subheading DWARF2 Version
4899 When emitting DWARF2 line number information, @code{.file} assigns filenames
4900 to the @code{.debug_line} file name table. The syntax is:
4903 .file @var{fileno} @var{filename}
4906 The @var{fileno} operand should be a unique positive integer to use as the
4907 index of the entry in the table. The @var{filename} operand is a C string
4910 The detail of filename indices is exposed to the user because the filename
4911 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4912 information, and thus the user must know the exact indices that table
4916 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4918 @cindex @code{fill} directive
4919 @cindex writing patterns in memory
4920 @cindex patterns, writing in memory
4921 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4922 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4923 may be zero or more. @var{Size} may be zero or more, but if it is
4924 more than 8, then it is deemed to have the value 8, compatible with
4925 other people's assemblers. The contents of each @var{repeat} bytes
4926 is taken from an 8-byte number. The highest order 4 bytes are
4927 zero. The lowest order 4 bytes are @var{value} rendered in the
4928 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4929 Each @var{size} bytes in a repetition is taken from the lowest order
4930 @var{size} bytes of this number. Again, this bizarre behavior is
4931 compatible with other people's assemblers.
4933 @var{size} and @var{value} are optional.
4934 If the second comma and @var{value} are absent, @var{value} is
4935 assumed zero. If the first comma and following tokens are absent,
4936 @var{size} is assumed to be 1.
4939 @section @code{.float @var{flonums}}
4941 @cindex floating point numbers (single)
4942 @cindex @code{float} directive
4943 This directive assembles zero or more flonums, separated by commas. It
4944 has the same effect as @code{.single}.
4946 The exact kind of floating point numbers emitted depends on how
4947 @command{@value{AS}} is configured.
4948 @xref{Machine Dependencies}.
4952 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4953 in @sc{ieee} format.
4958 @section @code{.func @var{name}[,@var{label}]}
4959 @cindex @code{func} directive
4960 @code{.func} emits debugging information to denote function @var{name}, and
4961 is ignored unless the file is assembled with debugging enabled.
4962 Only @samp{--gstabs[+]} is currently supported.
4963 @var{label} is the entry point of the function and if omitted @var{name}
4964 prepended with the @samp{leading char} is used.
4965 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4966 All functions are currently defined to have @code{void} return type.
4967 The function must be terminated with @code{.endfunc}.
4970 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4972 @cindex @code{global} directive
4973 @cindex symbol, making visible to linker
4974 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4975 @var{symbol} in your partial program, its value is made available to
4976 other partial programs that are linked with it. Otherwise,
4977 @var{symbol} takes its attributes from a symbol of the same name
4978 from another file linked into the same program.
4980 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4981 compatibility with other assemblers.
4984 On the HPPA, @code{.global} is not always enough to make it accessible to other
4985 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4986 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4991 @section @code{.gnu_attribute @var{tag},@var{value}}
4992 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4995 @section @code{.hidden @var{names}}
4997 @cindex @code{hidden} directive
4999 This is one of the ELF visibility directives. The other two are
5000 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5001 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5003 This directive overrides the named symbols default visibility (which is set by
5004 their binding: local, global or weak). The directive sets the visibility to
5005 @code{hidden} which means that the symbols are not visible to other components.
5006 Such symbols are always considered to be @code{protected} as well.
5010 @section @code{.hword @var{expressions}}
5012 @cindex @code{hword} directive
5013 @cindex integers, 16-bit
5014 @cindex numbers, 16-bit
5015 @cindex sixteen bit integers
5016 This expects zero or more @var{expressions}, and emits
5017 a 16 bit number for each.
5020 This directive is a synonym for @samp{.short}; depending on the target
5021 architecture, it may also be a synonym for @samp{.word}.
5025 This directive is a synonym for @samp{.short}.
5028 This directive is a synonym for both @samp{.short} and @samp{.word}.
5033 @section @code{.ident}
5035 @cindex @code{ident} directive
5037 This directive is used by some assemblers to place tags in object files. The
5038 behavior of this directive varies depending on the target. When using the
5039 a.out object file format, @command{@value{AS}} simply accepts the directive for
5040 source-file compatibility with existing assemblers, but does not emit anything
5041 for it. When using COFF, comments are emitted to the @code{.comment} or
5042 @code{.rdata} section, depending on the target. When using ELF, comments are
5043 emitted to the @code{.comment} section.
5046 @section @code{.if @var{absolute expression}}
5048 @cindex conditional assembly
5049 @cindex @code{if} directive
5050 @code{.if} marks the beginning of a section of code which is only
5051 considered part of the source program being assembled if the argument
5052 (which must be an @var{absolute expression}) is non-zero. The end of
5053 the conditional section of code must be marked by @code{.endif}
5054 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5055 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5056 If you have several conditions to check, @code{.elseif} may be used to avoid
5057 nesting blocks if/else within each subsequent @code{.else} block.
5059 The following variants of @code{.if} are also supported:
5061 @cindex @code{ifdef} directive
5062 @item .ifdef @var{symbol}
5063 Assembles the following section of code if the specified @var{symbol}
5064 has been defined. Note a symbol which has been referenced but not yet defined
5065 is considered to be undefined.
5067 @cindex @code{ifb} directive
5068 @item .ifb @var{text}
5069 Assembles the following section of code if the operand is blank (empty).
5071 @cindex @code{ifc} directive
5072 @item .ifc @var{string1},@var{string2}
5073 Assembles the following section of code if the two strings are the same. The
5074 strings may be optionally quoted with single quotes. If they are not quoted,
5075 the first string stops at the first comma, and the second string stops at the
5076 end of the line. Strings which contain whitespace should be quoted. The
5077 string comparison is case sensitive.
5079 @cindex @code{ifeq} directive
5080 @item .ifeq @var{absolute expression}
5081 Assembles the following section of code if the argument is zero.
5083 @cindex @code{ifeqs} directive
5084 @item .ifeqs @var{string1},@var{string2}
5085 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5087 @cindex @code{ifge} directive
5088 @item .ifge @var{absolute expression}
5089 Assembles the following section of code if the argument is greater than or
5092 @cindex @code{ifgt} directive
5093 @item .ifgt @var{absolute expression}
5094 Assembles the following section of code if the argument is greater than zero.
5096 @cindex @code{ifle} directive
5097 @item .ifle @var{absolute expression}
5098 Assembles the following section of code if the argument is less than or equal
5101 @cindex @code{iflt} directive
5102 @item .iflt @var{absolute expression}
5103 Assembles the following section of code if the argument is less than zero.
5105 @cindex @code{ifnb} directive
5106 @item .ifnb @var{text}
5107 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5108 following section of code if the operand is non-blank (non-empty).
5110 @cindex @code{ifnc} directive
5111 @item .ifnc @var{string1},@var{string2}.
5112 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5113 following section of code if the two strings are not the same.
5115 @cindex @code{ifndef} directive
5116 @cindex @code{ifnotdef} directive
5117 @item .ifndef @var{symbol}
5118 @itemx .ifnotdef @var{symbol}
5119 Assembles the following section of code if the specified @var{symbol}
5120 has not been defined. Both spelling variants are equivalent. Note a symbol
5121 which has been referenced but not yet defined is considered to be undefined.
5123 @cindex @code{ifne} directive
5124 @item .ifne @var{absolute expression}
5125 Assembles the following section of code if the argument is not equal to zero
5126 (in other words, this is equivalent to @code{.if}).
5128 @cindex @code{ifnes} directive
5129 @item .ifnes @var{string1},@var{string2}
5130 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5131 following section of code if the two strings are not the same.
5135 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5137 @cindex @code{incbin} directive
5138 @cindex binary files, including
5139 The @code{incbin} directive includes @var{file} verbatim at the current
5140 location. You can control the search paths used with the @samp{-I} command-line
5141 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5144 The @var{skip} argument skips a number of bytes from the start of the
5145 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5146 read. Note that the data is not aligned in any way, so it is the user's
5147 responsibility to make sure that proper alignment is provided both before and
5148 after the @code{incbin} directive.
5151 @section @code{.include "@var{file}"}
5153 @cindex @code{include} directive
5154 @cindex supporting files, including
5155 @cindex files, including
5156 This directive provides a way to include supporting files at specified
5157 points in your source program. The code from @var{file} is assembled as
5158 if it followed the point of the @code{.include}; when the end of the
5159 included file is reached, assembly of the original file continues. You
5160 can control the search paths used with the @samp{-I} command-line option
5161 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5165 @section @code{.int @var{expressions}}
5167 @cindex @code{int} directive
5168 @cindex integers, 32-bit
5169 Expect zero or more @var{expressions}, of any section, separated by commas.
5170 For each expression, emit a number that, at run time, is the value of that
5171 expression. The byte order and bit size of the number depends on what kind
5172 of target the assembly is for.
5176 On most forms of the H8/300, @code{.int} emits 16-bit
5177 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5184 @section @code{.internal @var{names}}
5186 @cindex @code{internal} directive
5188 This is one of the ELF visibility directives. The other two are
5189 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5190 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5192 This directive overrides the named symbols default visibility (which is set by
5193 their binding: local, global or weak). The directive sets the visibility to
5194 @code{internal} which means that the symbols are considered to be @code{hidden}
5195 (i.e., not visible to other components), and that some extra, processor specific
5196 processing must also be performed upon the symbols as well.
5200 @section @code{.irp @var{symbol},@var{values}}@dots{}
5202 @cindex @code{irp} directive
5203 Evaluate a sequence of statements assigning different values to @var{symbol}.
5204 The sequence of statements starts at the @code{.irp} directive, and is
5205 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5206 set to @var{value}, and the sequence of statements is assembled. If no
5207 @var{value} is listed, the sequence of statements is assembled once, with
5208 @var{symbol} set to the null string. To refer to @var{symbol} within the
5209 sequence of statements, use @var{\symbol}.
5211 For example, assembling
5219 is equivalent to assembling
5227 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5230 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5232 @cindex @code{irpc} directive
5233 Evaluate a sequence of statements assigning different values to @var{symbol}.
5234 The sequence of statements starts at the @code{.irpc} directive, and is
5235 terminated by an @code{.endr} directive. For each character in @var{value},
5236 @var{symbol} is set to the character, and the sequence of statements is
5237 assembled. If no @var{value} is listed, the sequence of statements is
5238 assembled once, with @var{symbol} set to the null string. To refer to
5239 @var{symbol} within the sequence of statements, use @var{\symbol}.
5241 For example, assembling
5249 is equivalent to assembling
5257 For some caveats with the spelling of @var{symbol}, see also the discussion
5261 @section @code{.lcomm @var{symbol} , @var{length}}
5263 @cindex @code{lcomm} directive
5264 @cindex local common symbols
5265 @cindex symbols, local common
5266 Reserve @var{length} (an absolute expression) bytes for a local common
5267 denoted by @var{symbol}. The section and value of @var{symbol} are
5268 those of the new local common. The addresses are allocated in the bss
5269 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5270 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5271 not visible to @code{@value{LD}}.
5274 Some targets permit a third argument to be used with @code{.lcomm}. This
5275 argument specifies the desired alignment of the symbol in the bss section.
5279 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5280 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5284 @section @code{.lflags}
5286 @cindex @code{lflags} directive (ignored)
5287 @command{@value{AS}} accepts this directive, for compatibility with other
5288 assemblers, but ignores it.
5290 @ifclear no-line-dir
5292 @section @code{.line @var{line-number}}
5294 @cindex @code{line} directive
5295 @cindex logical line number
5297 Change the logical line number. @var{line-number} must be an absolute
5298 expression. The next line has that logical line number. Therefore any other
5299 statements on the current line (after a statement separator character) are
5300 reported as on logical line number @var{line-number} @minus{} 1. One day
5301 @command{@value{AS}} will no longer support this directive: it is recognized only
5302 for compatibility with existing assembler programs.
5305 Even though this is a directive associated with the @code{a.out} or
5306 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5307 when producing COFF output, and treats @samp{.line} as though it
5308 were the COFF @samp{.ln} @emph{if} it is found outside a
5309 @code{.def}/@code{.endef} pair.
5311 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5312 used by compilers to generate auxiliary symbol information for
5317 @section @code{.linkonce [@var{type}]}
5319 @cindex @code{linkonce} directive
5320 @cindex common sections
5321 Mark the current section so that the linker only includes a single copy of it.
5322 This may be used to include the same section in several different object files,
5323 but ensure that the linker will only include it once in the final output file.
5324 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5325 Duplicate sections are detected based on the section name, so it should be
5328 This directive is only supported by a few object file formats; as of this
5329 writing, the only object file format which supports it is the Portable
5330 Executable format used on Windows NT.
5332 The @var{type} argument is optional. If specified, it must be one of the
5333 following strings. For example:
5337 Not all types may be supported on all object file formats.
5341 Silently discard duplicate sections. This is the default.
5344 Warn if there are duplicate sections, but still keep only one copy.
5347 Warn if any of the duplicates have different sizes.
5350 Warn if any of the duplicates do not have exactly the same contents.
5354 @section @code{.list}
5356 @cindex @code{list} directive
5357 @cindex listing control, turning on
5358 Control (in conjunction with the @code{.nolist} directive) whether or
5359 not assembly listings are generated. These two directives maintain an
5360 internal counter (which is zero initially). @code{.list} increments the
5361 counter, and @code{.nolist} decrements it. Assembly listings are
5362 generated whenever the counter is greater than zero.
5364 By default, listings are disabled. When you enable them (with the
5365 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5366 the initial value of the listing counter is one.
5369 @section @code{.ln @var{line-number}}
5371 @cindex @code{ln} directive
5372 @ifclear no-line-dir
5373 @samp{.ln} is a synonym for @samp{.line}.
5376 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5377 must be an absolute expression. The next line has that logical
5378 line number, so any other statements on the current line (after a
5379 statement separator character @code{;}) are reported as on logical
5380 line number @var{line-number} @minus{} 1.
5383 This directive is accepted, but ignored, when @command{@value{AS}} is
5384 configured for @code{b.out}; its effect is only associated with COFF
5390 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5391 @cindex @code{loc} directive
5392 When emitting DWARF2 line number information,
5393 the @code{.loc} directive will add a row to the @code{.debug_line} line
5394 number matrix corresponding to the immediately following assembly
5395 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5396 arguments will be applied to the @code{.debug_line} state machine before
5399 The @var{options} are a sequence of the following tokens in any order:
5403 This option will set the @code{basic_block} register in the
5404 @code{.debug_line} state machine to @code{true}.
5407 This option will set the @code{prologue_end} register in the
5408 @code{.debug_line} state machine to @code{true}.
5410 @item epilogue_begin
5411 This option will set the @code{epilogue_begin} register in the
5412 @code{.debug_line} state machine to @code{true}.
5414 @item is_stmt @var{value}
5415 This option will set the @code{is_stmt} register in the
5416 @code{.debug_line} state machine to @code{value}, which must be
5419 @item isa @var{value}
5420 This directive will set the @code{isa} register in the @code{.debug_line}
5421 state machine to @var{value}, which must be an unsigned integer.
5423 @item discriminator @var{value}
5424 This directive will set the @code{discriminator} register in the @code{.debug_line}
5425 state machine to @var{value}, which must be an unsigned integer.
5429 @node Loc_mark_labels
5430 @section @code{.loc_mark_labels @var{enable}}
5431 @cindex @code{loc_mark_labels} directive
5432 When emitting DWARF2 line number information,
5433 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5434 to the @code{.debug_line} line number matrix with the @code{basic_block}
5435 register in the state machine set whenever a code label is seen.
5436 The @var{enable} argument should be either 1 or 0, to enable or disable
5437 this function respectively.
5441 @section @code{.local @var{names}}
5443 @cindex @code{local} directive
5444 This directive, which is available for ELF targets, marks each symbol in
5445 the comma-separated list of @code{names} as a local symbol so that it
5446 will not be externally visible. If the symbols do not already exist,
5447 they will be created.
5449 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5450 accept an alignment argument, which is the case for most ELF targets,
5451 the @code{.local} directive can be used in combination with @code{.comm}
5452 (@pxref{Comm}) to define aligned local common data.
5456 @section @code{.long @var{expressions}}
5458 @cindex @code{long} directive
5459 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5462 @c no one seems to know what this is for or whether this description is
5463 @c what it really ought to do
5465 @section @code{.lsym @var{symbol}, @var{expression}}
5467 @cindex @code{lsym} directive
5468 @cindex symbol, not referenced in assembly
5469 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5470 the hash table, ensuring it cannot be referenced by name during the
5471 rest of the assembly. This sets the attributes of the symbol to be
5472 the same as the expression value:
5474 @var{other} = @var{descriptor} = 0
5475 @var{type} = @r{(section of @var{expression})}
5476 @var{value} = @var{expression}
5479 The new symbol is not flagged as external.
5483 @section @code{.macro}
5486 The commands @code{.macro} and @code{.endm} allow you to define macros that
5487 generate assembly output. For example, this definition specifies a macro
5488 @code{sum} that puts a sequence of numbers into memory:
5491 .macro sum from=0, to=5
5500 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5512 @item .macro @var{macname}
5513 @itemx .macro @var{macname} @var{macargs} @dots{}
5514 @cindex @code{macro} directive
5515 Begin the definition of a macro called @var{macname}. If your macro
5516 definition requires arguments, specify their names after the macro name,
5517 separated by commas or spaces. You can qualify the macro argument to
5518 indicate whether all invocations must specify a non-blank value (through
5519 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5520 (through @samp{:@code{vararg}}). You can supply a default value for any
5521 macro argument by following the name with @samp{=@var{deflt}}. You
5522 cannot define two macros with the same @var{macname} unless it has been
5523 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5524 definitions. For example, these are all valid @code{.macro} statements:
5528 Begin the definition of a macro called @code{comm}, which takes no
5531 @item .macro plus1 p, p1
5532 @itemx .macro plus1 p p1
5533 Either statement begins the definition of a macro called @code{plus1},
5534 which takes two arguments; within the macro definition, write
5535 @samp{\p} or @samp{\p1} to evaluate the arguments.
5537 @item .macro reserve_str p1=0 p2
5538 Begin the definition of a macro called @code{reserve_str}, with two
5539 arguments. The first argument has a default value, but not the second.
5540 After the definition is complete, you can call the macro either as
5541 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5542 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5543 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5544 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5546 @item .macro m p1:req, p2=0, p3:vararg
5547 Begin the definition of a macro called @code{m}, with at least three
5548 arguments. The first argument must always have a value specified, but
5549 not the second, which instead has a default value. The third formal
5550 will get assigned all remaining arguments specified at invocation time.
5552 When you call a macro, you can specify the argument values either by
5553 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5554 @samp{sum to=17, from=9}.
5558 Note that since each of the @var{macargs} can be an identifier exactly
5559 as any other one permitted by the target architecture, there may be
5560 occasional problems if the target hand-crafts special meanings to certain
5561 characters when they occur in a special position. For example, if the colon
5562 (@code{:}) is generally permitted to be part of a symbol name, but the
5563 architecture specific code special-cases it when occurring as the final
5564 character of a symbol (to denote a label), then the macro parameter
5565 replacement code will have no way of knowing that and consider the whole
5566 construct (including the colon) an identifier, and check only this
5567 identifier for being the subject to parameter substitution. So for example
5568 this macro definition:
5576 might not work as expected. Invoking @samp{label foo} might not create a label
5577 called @samp{foo} but instead just insert the text @samp{\l:} into the
5578 assembler source, probably generating an error about an unrecognised
5581 Similarly problems might occur with the period character (@samp{.})
5582 which is often allowed inside opcode names (and hence identifier names). So
5583 for example constructing a macro to build an opcode from a base name and a
5584 length specifier like this:
5587 .macro opcode base length
5592 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5593 instruction but instead generate some kind of error as the assembler tries to
5594 interpret the text @samp{\base.\length}.
5596 There are several possible ways around this problem:
5599 @item Insert white space
5600 If it is possible to use white space characters then this is the simplest
5609 @item Use @samp{\()}
5610 The string @samp{\()} can be used to separate the end of a macro argument from
5611 the following text. eg:
5614 .macro opcode base length
5619 @item Use the alternate macro syntax mode
5620 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5621 used as a separator. eg:
5631 Note: this problem of correctly identifying string parameters to pseudo ops
5632 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5633 and @code{.irpc} (@pxref{Irpc}) as well.
5636 @cindex @code{endm} directive
5637 Mark the end of a macro definition.
5640 @cindex @code{exitm} directive
5641 Exit early from the current macro definition.
5643 @cindex number of macros executed
5644 @cindex macros, count executed
5646 @command{@value{AS}} maintains a counter of how many macros it has
5647 executed in this pseudo-variable; you can copy that number to your
5648 output with @samp{\@@}, but @emph{only within a macro definition}.
5650 @item LOCAL @var{name} [ , @dots{} ]
5651 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5652 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5653 @xref{Altmacro,,@code{.altmacro}}.
5657 @section @code{.mri @var{val}}
5659 @cindex @code{mri} directive
5660 @cindex MRI mode, temporarily
5661 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5662 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5663 affects code assembled until the next @code{.mri} directive, or until the end
5664 of the file. @xref{M, MRI mode, MRI mode}.
5667 @section @code{.noaltmacro}
5668 Disable alternate macro mode. @xref{Altmacro}.
5671 @section @code{.nolist}
5673 @cindex @code{nolist} directive
5674 @cindex listing control, turning off
5675 Control (in conjunction with the @code{.list} directive) whether or
5676 not assembly listings are generated. These two directives maintain an
5677 internal counter (which is zero initially). @code{.list} increments the
5678 counter, and @code{.nolist} decrements it. Assembly listings are
5679 generated whenever the counter is greater than zero.
5682 @section @code{.octa @var{bignums}}
5684 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5685 @cindex @code{octa} directive
5686 @cindex integer, 16-byte
5687 @cindex sixteen byte integer
5688 This directive expects zero or more bignums, separated by commas. For each
5689 bignum, it emits a 16-byte integer.
5691 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5692 hence @emph{octa}-word for 16 bytes.
5695 @section @code{.offset @var{loc}}
5697 @cindex @code{offset} directive
5698 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5699 be an absolute expression. This directive may be useful for defining
5700 symbols with absolute values. Do not confuse it with the @code{.org}
5704 @section @code{.org @var{new-lc} , @var{fill}}
5706 @cindex @code{org} directive
5707 @cindex location counter, advancing
5708 @cindex advancing location counter
5709 @cindex current address, advancing
5710 Advance the location counter of the current section to
5711 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5712 expression with the same section as the current subsection. That is,
5713 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5714 wrong section, the @code{.org} directive is ignored. To be compatible
5715 with former assemblers, if the section of @var{new-lc} is absolute,
5716 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5717 is the same as the current subsection.
5719 @code{.org} may only increase the location counter, or leave it
5720 unchanged; you cannot use @code{.org} to move the location counter
5723 @c double negative used below "not undefined" because this is a specific
5724 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5725 @c section. doc@cygnus.com 18feb91
5726 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5727 may not be undefined. If you really detest this restriction we eagerly await
5728 a chance to share your improved assembler.
5730 Beware that the origin is relative to the start of the section, not
5731 to the start of the subsection. This is compatible with other
5732 people's assemblers.
5734 When the location counter (of the current subsection) is advanced, the
5735 intervening bytes are filled with @var{fill} which should be an
5736 absolute expression. If the comma and @var{fill} are omitted,
5737 @var{fill} defaults to zero.
5740 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5742 @cindex padding the location counter given a power of two
5743 @cindex @code{p2align} directive
5744 Pad the location counter (in the current subsection) to a particular
5745 storage boundary. The first expression (which must be absolute) is the
5746 number of low-order zero bits the location counter must have after
5747 advancement. For example @samp{.p2align 3} advances the location
5748 counter until it a multiple of 8. If the location counter is already a
5749 multiple of 8, no change is needed.
5751 The second expression (also absolute) gives the fill value to be stored in the
5752 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5753 padding bytes are normally zero. However, on some systems, if the section is
5754 marked as containing code and the fill value is omitted, the space is filled
5755 with no-op instructions.
5757 The third expression is also absolute, and is also optional. If it is present,
5758 it is the maximum number of bytes that should be skipped by this alignment
5759 directive. If doing the alignment would require skipping more bytes than the
5760 specified maximum, then the alignment is not done at all. You can omit the
5761 fill value (the second argument) entirely by simply using two commas after the
5762 required alignment; this can be useful if you want the alignment to be filled
5763 with no-op instructions when appropriate.
5765 @cindex @code{p2alignw} directive
5766 @cindex @code{p2alignl} directive
5767 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5768 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5769 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5770 fill pattern as a four byte longword value. For example, @code{.p2alignw
5771 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5772 filled in with the value 0x368d (the exact placement of the bytes depends upon
5773 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5778 @section @code{.popsection}
5780 @cindex @code{popsection} directive
5781 @cindex Section Stack
5782 This is one of the ELF section stack manipulation directives. The others are
5783 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5784 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5787 This directive replaces the current section (and subsection) with the top
5788 section (and subsection) on the section stack. This section is popped off the
5794 @section @code{.previous}
5796 @cindex @code{previous} directive
5797 @cindex Section Stack
5798 This is one of the ELF section stack manipulation directives. The others are
5799 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5800 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5801 (@pxref{PopSection}).
5803 This directive swaps the current section (and subsection) with most recently
5804 referenced section/subsection pair prior to this one. Multiple
5805 @code{.previous} directives in a row will flip between two sections (and their
5806 subsections). For example:
5818 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5824 # Now in section A subsection 1
5828 # Now in section B subsection 0
5831 # Now in section B subsection 1
5834 # Now in section B subsection 0
5838 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5839 section B and 0x9abc into subsection 1 of section B.
5841 In terms of the section stack, this directive swaps the current section with
5842 the top section on the section stack.
5846 @section @code{.print @var{string}}
5848 @cindex @code{print} directive
5849 @command{@value{AS}} will print @var{string} on the standard output during
5850 assembly. You must put @var{string} in double quotes.
5854 @section @code{.protected @var{names}}
5856 @cindex @code{protected} directive
5858 This is one of the ELF visibility directives. The other two are
5859 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5861 This directive overrides the named symbols default visibility (which is set by
5862 their binding: local, global or weak). The directive sets the visibility to
5863 @code{protected} which means that any references to the symbols from within the
5864 components that defines them must be resolved to the definition in that
5865 component, even if a definition in another component would normally preempt
5870 @section @code{.psize @var{lines} , @var{columns}}
5872 @cindex @code{psize} directive
5873 @cindex listing control: paper size
5874 @cindex paper size, for listings
5875 Use this directive to declare the number of lines---and, optionally, the
5876 number of columns---to use for each page, when generating listings.
5878 If you do not use @code{.psize}, listings use a default line-count
5879 of 60. You may omit the comma and @var{columns} specification; the
5880 default width is 200 columns.
5882 @command{@value{AS}} generates formfeeds whenever the specified number of
5883 lines is exceeded (or whenever you explicitly request one, using
5886 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5887 those explicitly specified with @code{.eject}.
5890 @section @code{.purgem @var{name}}
5892 @cindex @code{purgem} directive
5893 Undefine the macro @var{name}, so that later uses of the string will not be
5894 expanded. @xref{Macro}.
5898 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5900 @cindex @code{pushsection} directive
5901 @cindex Section Stack
5902 This is one of the ELF section stack manipulation directives. The others are
5903 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5904 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5907 This directive pushes the current section (and subsection) onto the
5908 top of the section stack, and then replaces the current section and
5909 subsection with @code{name} and @code{subsection}. The optional
5910 @code{flags}, @code{type} and @code{arguments} are treated the same
5911 as in the @code{.section} (@pxref{Section}) directive.
5915 @section @code{.quad @var{bignums}}
5917 @cindex @code{quad} directive
5918 @code{.quad} expects zero or more bignums, separated by commas. For
5919 each bignum, it emits
5921 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5922 warning message; and just takes the lowest order 8 bytes of the bignum.
5923 @cindex eight-byte integer
5924 @cindex integer, 8-byte
5926 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5927 hence @emph{quad}-word for 8 bytes.
5930 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5931 warning message; and just takes the lowest order 16 bytes of the bignum.
5932 @cindex sixteen-byte integer
5933 @cindex integer, 16-byte
5937 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5939 @cindex @code{reloc} directive
5940 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5941 @var{expression}. If @var{offset} is a number, the relocation is generated in
5942 the current section. If @var{offset} is an expression that resolves to a
5943 symbol plus offset, the relocation is generated in the given symbol's section.
5944 @var{expression}, if present, must resolve to a symbol plus addend or to an
5945 absolute value, but note that not all targets support an addend. e.g. ELF REL
5946 targets such as i386 store an addend in the section contents rather than in the
5947 relocation. This low level interface does not support addends stored in the
5951 @section @code{.rept @var{count}}
5953 @cindex @code{rept} directive
5954 Repeat the sequence of lines between the @code{.rept} directive and the next
5955 @code{.endr} directive @var{count} times.
5957 For example, assembling
5965 is equivalent to assembling
5974 @section @code{.sbttl "@var{subheading}"}
5976 @cindex @code{sbttl} directive
5977 @cindex subtitles for listings
5978 @cindex listing control: subtitle
5979 Use @var{subheading} as the title (third line, immediately after the
5980 title line) when generating assembly listings.
5982 This directive affects subsequent pages, as well as the current page if
5983 it appears within ten lines of the top of a page.
5987 @section @code{.scl @var{class}}
5989 @cindex @code{scl} directive
5990 @cindex symbol storage class (COFF)
5991 @cindex COFF symbol storage class
5992 Set the storage-class value for a symbol. This directive may only be
5993 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5994 whether a symbol is static or external, or it may record further
5995 symbolic debugging information.
5998 The @samp{.scl} directive is primarily associated with COFF output; when
5999 configured to generate @code{b.out} output format, @command{@value{AS}}
6000 accepts this directive but ignores it.
6006 @section @code{.section @var{name}}
6008 @cindex named section
6009 Use the @code{.section} directive to assemble the following code into a section
6012 This directive is only supported for targets that actually support arbitrarily
6013 named sections; on @code{a.out} targets, for example, it is not accepted, even
6014 with a standard @code{a.out} section name.
6018 @c only print the extra heading if both COFF and ELF are set
6019 @subheading COFF Version
6022 @cindex @code{section} directive (COFF version)
6023 For COFF targets, the @code{.section} directive is used in one of the following
6027 .section @var{name}[, "@var{flags}"]
6028 .section @var{name}[, @var{subsection}]
6031 If the optional argument is quoted, it is taken as flags to use for the
6032 section. Each flag is a single character. The following flags are recognized:
6035 bss section (uninitialized data)
6037 section is not loaded
6043 exclude section from linking
6049 shared section (meaningful for PE targets)
6051 ignored. (For compatibility with the ELF version)
6053 section is not readable (meaningful for PE targets)
6055 single-digit power-of-two section alignment (GNU extension)
6058 If no flags are specified, the default flags depend upon the section name. If
6059 the section name is not recognized, the default will be for the section to be
6060 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6061 from the section, rather than adding them, so if they are used on their own it
6062 will be as if no flags had been specified at all.
6064 If the optional argument to the @code{.section} directive is not quoted, it is
6065 taken as a subsection number (@pxref{Sub-Sections}).
6070 @c only print the extra heading if both COFF and ELF are set
6071 @subheading ELF Version
6074 @cindex Section Stack
6075 This is one of the ELF section stack manipulation directives. The others are
6076 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6077 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6078 @code{.previous} (@pxref{Previous}).
6080 @cindex @code{section} directive (ELF version)
6081 For ELF targets, the @code{.section} directive is used like this:
6084 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6087 The optional @var{flags} argument is a quoted string which may contain any
6088 combination of the following characters:
6091 section is allocatable
6093 section is excluded from executable and shared library.
6097 section is executable
6099 section is mergeable
6101 section contains zero terminated strings
6103 section is a member of a section group
6105 section is used for thread-local-storage
6107 section is a member of the previously-current section's group, if any
6110 The optional @var{type} argument may contain one of the following constants:
6113 section contains data
6115 section does not contain data (i.e., section only occupies space)
6117 section contains data which is used by things other than the program
6119 section contains an array of pointers to init functions
6121 section contains an array of pointers to finish functions
6122 @item @@preinit_array
6123 section contains an array of pointers to pre-init functions
6126 Many targets only support the first three section types.
6128 Note on targets where the @code{@@} character is the start of a comment (eg
6129 ARM) then another character is used instead. For example the ARM port uses the
6132 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6133 be specified as well as an extra argument---@var{entsize}---like this:
6136 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6139 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6140 constants, each @var{entsize} octets long. Sections with both @code{M} and
6141 @code{S} must contain zero terminated strings where each character is
6142 @var{entsize} bytes long. The linker may remove duplicates within sections with
6143 the same name, same entity size and same flags. @var{entsize} must be an
6144 absolute expression. For sections with both @code{M} and @code{S}, a string
6145 which is a suffix of a larger string is considered a duplicate. Thus
6146 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6147 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6149 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6150 be present along with an additional field like this:
6153 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6156 The @var{GroupName} field specifies the name of the section group to which this
6157 particular section belongs. The optional linkage field can contain:
6160 indicates that only one copy of this section should be retained
6165 Note: if both the @var{M} and @var{G} flags are present then the fields for
6166 the Merge flag should come first, like this:
6169 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6172 If @var{flags} contains the @code{?} symbol then it may not also contain the
6173 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6174 present. Instead, @code{?} says to consider the section that's current before
6175 this directive. If that section used @code{G}, then the new section will use
6176 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6177 If not, then the @code{?} symbol has no effect.
6179 If no flags are specified, the default flags depend upon the section name. If
6180 the section name is not recognized, the default will be for the section to have
6181 none of the above flags: it will not be allocated in memory, nor writable, nor
6182 executable. The section will contain data.
6184 For ELF targets, the assembler supports another type of @code{.section}
6185 directive for compatibility with the Solaris assembler:
6188 .section "@var{name}"[, @var{flags}...]
6191 Note that the section name is quoted. There may be a sequence of comma
6195 section is allocatable
6199 section is executable
6201 section is excluded from executable and shared library.
6203 section is used for thread local storage
6206 This directive replaces the current section and subsection. See the
6207 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6208 some examples of how this directive and the other section stack directives
6214 @section @code{.set @var{symbol}, @var{expression}}
6216 @cindex @code{set} directive
6217 @cindex symbol value, setting
6218 Set the value of @var{symbol} to @var{expression}. This
6219 changes @var{symbol}'s value and type to conform to
6220 @var{expression}. If @var{symbol} was flagged as external, it remains
6221 flagged (@pxref{Symbol Attributes}).
6223 You may @code{.set} a symbol many times in the same assembly.
6225 If you @code{.set} a global symbol, the value stored in the object
6226 file is the last value stored into it.
6229 On Z80 @code{set} is a real instruction, use
6230 @samp{@var{symbol} defl @var{expression}} instead.
6234 @section @code{.short @var{expressions}}
6236 @cindex @code{short} directive
6238 @code{.short} is normally the same as @samp{.word}.
6239 @xref{Word,,@code{.word}}.
6241 In some configurations, however, @code{.short} and @code{.word} generate
6242 numbers of different lengths. @xref{Machine Dependencies}.
6246 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6249 This expects zero or more @var{expressions}, and emits
6250 a 16 bit number for each.
6255 @section @code{.single @var{flonums}}
6257 @cindex @code{single} directive
6258 @cindex floating point numbers (single)
6259 This directive assembles zero or more flonums, separated by commas. It
6260 has the same effect as @code{.float}.
6262 The exact kind of floating point numbers emitted depends on how
6263 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6267 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6268 numbers in @sc{ieee} format.
6274 @section @code{.size}
6276 This directive is used to set the size associated with a symbol.
6280 @c only print the extra heading if both COFF and ELF are set
6281 @subheading COFF Version
6284 @cindex @code{size} directive (COFF version)
6285 For COFF targets, the @code{.size} directive is only permitted inside
6286 @code{.def}/@code{.endef} pairs. It is used like this:
6289 .size @var{expression}
6293 @samp{.size} is only meaningful when generating COFF format output; when
6294 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6301 @c only print the extra heading if both COFF and ELF are set
6302 @subheading ELF Version
6305 @cindex @code{size} directive (ELF version)
6306 For ELF targets, the @code{.size} directive is used like this:
6309 .size @var{name} , @var{expression}
6312 This directive sets the size associated with a symbol @var{name}.
6313 The size in bytes is computed from @var{expression} which can make use of label
6314 arithmetic. This directive is typically used to set the size of function
6319 @ifclear no-space-dir
6321 @section @code{.skip @var{size} , @var{fill}}
6323 @cindex @code{skip} directive
6324 @cindex filling memory
6325 This directive emits @var{size} bytes, each of value @var{fill}. Both
6326 @var{size} and @var{fill} are absolute expressions. If the comma and
6327 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6332 @section @code{.sleb128 @var{expressions}}
6334 @cindex @code{sleb128} directive
6335 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6336 compact, variable length representation of numbers used by the DWARF
6337 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6339 @ifclear no-space-dir
6341 @section @code{.space @var{size} , @var{fill}}
6343 @cindex @code{space} directive
6344 @cindex filling memory
6345 This directive emits @var{size} bytes, each of value @var{fill}. Both
6346 @var{size} and @var{fill} are absolute expressions. If the comma
6347 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6352 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6353 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6354 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6355 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6363 @section @code{.stabd, .stabn, .stabs}
6365 @cindex symbolic debuggers, information for
6366 @cindex @code{stab@var{x}} directives
6367 There are three directives that begin @samp{.stab}.
6368 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6369 The symbols are not entered in the @command{@value{AS}} hash table: they
6370 cannot be referenced elsewhere in the source file.
6371 Up to five fields are required:
6375 This is the symbol's name. It may contain any character except
6376 @samp{\000}, so is more general than ordinary symbol names. Some
6377 debuggers used to code arbitrarily complex structures into symbol names
6381 An absolute expression. The symbol's type is set to the low 8 bits of
6382 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6383 and debuggers choke on silly bit patterns.
6386 An absolute expression. The symbol's ``other'' attribute is set to the
6387 low 8 bits of this expression.
6390 An absolute expression. The symbol's descriptor is set to the low 16
6391 bits of this expression.
6394 An absolute expression which becomes the symbol's value.
6397 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6398 or @code{.stabs} statement, the symbol has probably already been created;
6399 you get a half-formed symbol in your object file. This is
6400 compatible with earlier assemblers!
6403 @cindex @code{stabd} directive
6404 @item .stabd @var{type} , @var{other} , @var{desc}
6406 The ``name'' of the symbol generated is not even an empty string.
6407 It is a null pointer, for compatibility. Older assemblers used a
6408 null pointer so they didn't waste space in object files with empty
6411 The symbol's value is set to the location counter,
6412 relocatably. When your program is linked, the value of this symbol
6413 is the address of the location counter when the @code{.stabd} was
6416 @cindex @code{stabn} directive
6417 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6418 The name of the symbol is set to the empty string @code{""}.
6420 @cindex @code{stabs} directive
6421 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6422 All five fields are specified.
6428 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6429 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6431 @cindex string, copying to object file
6432 @cindex string8, copying to object file
6433 @cindex string16, copying to object file
6434 @cindex string32, copying to object file
6435 @cindex string64, copying to object file
6436 @cindex @code{string} directive
6437 @cindex @code{string8} directive
6438 @cindex @code{string16} directive
6439 @cindex @code{string32} directive
6440 @cindex @code{string64} directive
6442 Copy the characters in @var{str} to the object file. You may specify more than
6443 one string to copy, separated by commas. Unless otherwise specified for a
6444 particular machine, the assembler marks the end of each string with a 0 byte.
6445 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6447 The variants @code{string16}, @code{string32} and @code{string64} differ from
6448 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6449 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6450 are stored in target endianness byte order.
6456 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6457 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6462 @section @code{.struct @var{expression}}
6464 @cindex @code{struct} directive
6465 Switch to the absolute section, and set the section offset to @var{expression},
6466 which must be an absolute expression. You might use this as follows:
6475 This would define the symbol @code{field1} to have the value 0, the symbol
6476 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6477 value 8. Assembly would be left in the absolute section, and you would need to
6478 use a @code{.section} directive of some sort to change to some other section
6479 before further assembly.
6483 @section @code{.subsection @var{name}}
6485 @cindex @code{subsection} directive
6486 @cindex Section Stack
6487 This is one of the ELF section stack manipulation directives. The others are
6488 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6489 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6492 This directive replaces the current subsection with @code{name}. The current
6493 section is not changed. The replaced subsection is put onto the section stack
6494 in place of the then current top of stack subsection.
6499 @section @code{.symver}
6500 @cindex @code{symver} directive
6501 @cindex symbol versioning
6502 @cindex versions of symbols
6503 Use the @code{.symver} directive to bind symbols to specific version nodes
6504 within a source file. This is only supported on ELF platforms, and is
6505 typically used when assembling files to be linked into a shared library.
6506 There are cases where it may make sense to use this in objects to be bound
6507 into an application itself so as to override a versioned symbol from a
6510 For ELF targets, the @code{.symver} directive can be used like this:
6512 .symver @var{name}, @var{name2@@nodename}
6514 If the symbol @var{name} is defined within the file
6515 being assembled, the @code{.symver} directive effectively creates a symbol
6516 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6517 just don't try and create a regular alias is that the @var{@@} character isn't
6518 permitted in symbol names. The @var{name2} part of the name is the actual name
6519 of the symbol by which it will be externally referenced. The name @var{name}
6520 itself is merely a name of convenience that is used so that it is possible to
6521 have definitions for multiple versions of a function within a single source
6522 file, and so that the compiler can unambiguously know which version of a
6523 function is being mentioned. The @var{nodename} portion of the alias should be
6524 the name of a node specified in the version script supplied to the linker when
6525 building a shared library. If you are attempting to override a versioned
6526 symbol from a shared library, then @var{nodename} should correspond to the
6527 nodename of the symbol you are trying to override.
6529 If the symbol @var{name} is not defined within the file being assembled, all
6530 references to @var{name} will be changed to @var{name2@@nodename}. If no
6531 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6534 Another usage of the @code{.symver} directive is:
6536 .symver @var{name}, @var{name2@@@@nodename}
6538 In this case, the symbol @var{name} must exist and be defined within
6539 the file being assembled. It is similar to @var{name2@@nodename}. The
6540 difference is @var{name2@@@@nodename} will also be used to resolve
6541 references to @var{name2} by the linker.
6543 The third usage of the @code{.symver} directive is:
6545 .symver @var{name}, @var{name2@@@@@@nodename}
6547 When @var{name} is not defined within the
6548 file being assembled, it is treated as @var{name2@@nodename}. When
6549 @var{name} is defined within the file being assembled, the symbol
6550 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6555 @section @code{.tag @var{structname}}
6557 @cindex COFF structure debugging
6558 @cindex structure debugging, COFF
6559 @cindex @code{tag} directive
6560 This directive is generated by compilers to include auxiliary debugging
6561 information in the symbol table. It is only permitted inside
6562 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6563 definitions in the symbol table with instances of those structures.
6566 @samp{.tag} is only used when generating COFF format output; when
6567 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6573 @section @code{.text @var{subsection}}
6575 @cindex @code{text} directive
6576 Tells @command{@value{AS}} to assemble the following statements onto the end of
6577 the text subsection numbered @var{subsection}, which is an absolute
6578 expression. If @var{subsection} is omitted, subsection number zero
6582 @section @code{.title "@var{heading}"}
6584 @cindex @code{title} directive
6585 @cindex listing control: title line
6586 Use @var{heading} as the title (second line, immediately after the
6587 source file name and pagenumber) when generating assembly listings.
6589 This directive affects subsequent pages, as well as the current page if
6590 it appears within ten lines of the top of a page.
6594 @section @code{.type}
6596 This directive is used to set the type of a symbol.
6600 @c only print the extra heading if both COFF and ELF are set
6601 @subheading COFF Version
6604 @cindex COFF symbol type
6605 @cindex symbol type, COFF
6606 @cindex @code{type} directive (COFF version)
6607 For COFF targets, this directive is permitted only within
6608 @code{.def}/@code{.endef} pairs. It is used like this:
6614 This records the integer @var{int} as the type attribute of a symbol table
6618 @samp{.type} is associated only with COFF format output; when
6619 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6620 directive but ignores it.
6626 @c only print the extra heading if both COFF and ELF are set
6627 @subheading ELF Version
6630 @cindex ELF symbol type
6631 @cindex symbol type, ELF
6632 @cindex @code{type} directive (ELF version)
6633 For ELF targets, the @code{.type} directive is used like this:
6636 .type @var{name} , @var{type description}
6639 This sets the type of symbol @var{name} to be either a
6640 function symbol or an object symbol. There are five different syntaxes
6641 supported for the @var{type description} field, in order to provide
6642 compatibility with various other assemblers.
6644 Because some of the characters used in these syntaxes (such as @samp{@@} and
6645 @samp{#}) are comment characters for some architectures, some of the syntaxes
6646 below do not work on all architectures. The first variant will be accepted by
6647 the GNU assembler on all architectures so that variant should be used for
6648 maximum portability, if you do not need to assemble your code with other
6651 The syntaxes supported are:
6654 .type <name> STT_<TYPE_IN_UPPER_CASE>
6655 .type <name>,#<type>
6656 .type <name>,@@<type>
6657 .type <name>,%<type>
6658 .type <name>,"<type>"
6661 The types supported are:
6666 Mark the symbol as being a function name.
6669 @itemx gnu_indirect_function
6670 Mark the symbol as an indirect function when evaluated during reloc
6671 processing. (This is only supported on assemblers targeting GNU systems).
6675 Mark the symbol as being a data object.
6679 Mark the symbol as being a thead-local data object.
6683 Mark the symbol as being a common data object.
6687 Does not mark the symbol in any way. It is supported just for completeness.
6689 @item gnu_unique_object
6690 Marks the symbol as being a globally unique data object. The dynamic linker
6691 will make sure that in the entire process there is just one symbol with this
6692 name and type in use. (This is only supported on assemblers targeting GNU
6697 Note: Some targets support extra types in addition to those listed above.
6703 @section @code{.uleb128 @var{expressions}}
6705 @cindex @code{uleb128} directive
6706 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6707 compact, variable length representation of numbers used by the DWARF
6708 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6712 @section @code{.val @var{addr}}
6714 @cindex @code{val} directive
6715 @cindex COFF value attribute
6716 @cindex value attribute, COFF
6717 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6718 records the address @var{addr} as the value attribute of a symbol table
6722 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6723 configured for @code{b.out}, it accepts this directive but ignores it.
6729 @section @code{.version "@var{string}"}
6731 @cindex @code{version} directive
6732 This directive creates a @code{.note} section and places into it an ELF
6733 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6738 @section @code{.vtable_entry @var{table}, @var{offset}}
6740 @cindex @code{vtable_entry} directive
6741 This directive finds or creates a symbol @code{table} and creates a
6742 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6745 @section @code{.vtable_inherit @var{child}, @var{parent}}
6747 @cindex @code{vtable_inherit} directive
6748 This directive finds the symbol @code{child} and finds or creates the symbol
6749 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6750 parent whose addend is the value of the child symbol. As a special case the
6751 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6755 @section @code{.warning "@var{string}"}
6756 @cindex warning directive
6757 Similar to the directive @code{.error}
6758 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6761 @section @code{.weak @var{names}}
6763 @cindex @code{weak} directive
6764 This directive sets the weak attribute on the comma separated list of symbol
6765 @code{names}. If the symbols do not already exist, they will be created.
6767 On COFF targets other than PE, weak symbols are a GNU extension. This
6768 directive sets the weak attribute on the comma separated list of symbol
6769 @code{names}. If the symbols do not already exist, they will be created.
6771 On the PE target, weak symbols are supported natively as weak aliases.
6772 When a weak symbol is created that is not an alias, GAS creates an
6773 alternate symbol to hold the default value.
6776 @section @code{.weakref @var{alias}, @var{target}}
6778 @cindex @code{weakref} directive
6779 This directive creates an alias to the target symbol that enables the symbol to
6780 be referenced with weak-symbol semantics, but without actually making it weak.
6781 If direct references or definitions of the symbol are present, then the symbol
6782 will not be weak, but if all references to it are through weak references, the
6783 symbol will be marked as weak in the symbol table.
6785 The effect is equivalent to moving all references to the alias to a separate
6786 assembly source file, renaming the alias to the symbol in it, declaring the
6787 symbol as weak there, and running a reloadable link to merge the object files
6788 resulting from the assembly of the new source file and the old source file that
6789 had the references to the alias removed.
6791 The alias itself never makes to the symbol table, and is entirely handled
6792 within the assembler.
6795 @section @code{.word @var{expressions}}
6797 @cindex @code{word} directive
6798 This directive expects zero or more @var{expressions}, of any section,
6799 separated by commas.
6802 For each expression, @command{@value{AS}} emits a 32-bit number.
6805 For each expression, @command{@value{AS}} emits a 16-bit number.
6810 The size of the number emitted, and its byte order,
6811 depend on what target computer the assembly is for.
6814 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6815 @c happen---32-bit addressability, period; no long/short jumps.
6816 @ifset DIFF-TBL-KLUGE
6817 @cindex difference tables altered
6818 @cindex altered difference tables
6820 @emph{Warning: Special Treatment to support Compilers}
6824 Machines with a 32-bit address space, but that do less than 32-bit
6825 addressing, require the following special treatment. If the machine of
6826 interest to you does 32-bit addressing (or doesn't require it;
6827 @pxref{Machine Dependencies}), you can ignore this issue.
6830 In order to assemble compiler output into something that works,
6831 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6832 Directives of the form @samp{.word sym1-sym2} are often emitted by
6833 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6834 directive of the form @samp{.word sym1-sym2}, and the difference between
6835 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6836 creates a @dfn{secondary jump table}, immediately before the next label.
6837 This secondary jump table is preceded by a short-jump to the
6838 first byte after the secondary table. This short-jump prevents the flow
6839 of control from accidentally falling into the new table. Inside the
6840 table is a long-jump to @code{sym2}. The original @samp{.word}
6841 contains @code{sym1} minus the address of the long-jump to
6844 If there were several occurrences of @samp{.word sym1-sym2} before the
6845 secondary jump table, all of them are adjusted. If there was a
6846 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6847 long-jump to @code{sym4} is included in the secondary jump table,
6848 and the @code{.word} directives are adjusted to contain @code{sym3}
6849 minus the address of the long-jump to @code{sym4}; and so on, for as many
6850 entries in the original jump table as necessary.
6853 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6854 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6855 assembly language programmers.
6858 @c end DIFF-TBL-KLUGE
6861 @section Deprecated Directives
6863 @cindex deprecated directives
6864 @cindex obsolescent directives
6865 One day these directives won't work.
6866 They are included for compatibility with older assemblers.
6873 @node Object Attributes
6874 @chapter Object Attributes
6875 @cindex object attributes
6877 @command{@value{AS}} assembles source files written for a specific architecture
6878 into object files for that architecture. But not all object files are alike.
6879 Many architectures support incompatible variations. For instance, floating
6880 point arguments might be passed in floating point registers if the object file
6881 requires hardware floating point support---or floating point arguments might be
6882 passed in integer registers if the object file supports processors with no
6883 hardware floating point unit. Or, if two objects are built for different
6884 generations of the same architecture, the combination may require the
6885 newer generation at run-time.
6887 This information is useful during and after linking. At link time,
6888 @command{@value{LD}} can warn about incompatible object files. After link
6889 time, tools like @command{gdb} can use it to process the linked file
6892 Compatibility information is recorded as a series of object attributes. Each
6893 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6894 string, and indicates who sets the meaning of the tag. The tag is an integer,
6895 and indicates what property the attribute describes. The value may be a string
6896 or an integer, and indicates how the property affects this object. Missing
6897 attributes are the same as attributes with a zero value or empty string value.
6899 Object attributes were developed as part of the ABI for the ARM Architecture.
6900 The file format is documented in @cite{ELF for the ARM Architecture}.
6903 * GNU Object Attributes:: @sc{gnu} Object Attributes
6904 * Defining New Object Attributes:: Defining New Object Attributes
6907 @node GNU Object Attributes
6908 @section @sc{gnu} Object Attributes
6910 The @code{.gnu_attribute} directive records an object attribute
6911 with vendor @samp{gnu}.
6913 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6914 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6915 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6916 2} is set for architecture-independent attributes and clear for
6917 architecture-dependent ones.
6919 @subsection Common @sc{gnu} attributes
6921 These attributes are valid on all architectures.
6924 @item Tag_compatibility (32)
6925 The compatibility attribute takes an integer flag value and a vendor name. If
6926 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6927 then the file is only compatible with the named toolchain. If it is greater
6928 than 1, the file can only be processed by other toolchains under some private
6929 arrangement indicated by the flag value and the vendor name.
6932 @subsection MIPS Attributes
6935 @item Tag_GNU_MIPS_ABI_FP (4)
6936 The floating-point ABI used by this object file. The value will be:
6940 0 for files not affected by the floating-point ABI.
6942 1 for files using the hardware floating-point with a standard double-precision
6945 2 for files using the hardware floating-point ABI with a single-precision FPU.
6947 3 for files using the software floating-point ABI.
6949 4 for files using the hardware floating-point ABI with 64-bit wide
6950 double-precision floating-point registers and 32-bit wide general
6955 @subsection PowerPC Attributes
6958 @item Tag_GNU_Power_ABI_FP (4)
6959 The floating-point ABI used by this object file. The value will be:
6963 0 for files not affected by the floating-point ABI.
6965 1 for files using double-precision hardware floating-point ABI.
6967 2 for files using the software floating-point ABI.
6969 3 for files using single-precision hardware floating-point ABI.
6972 @item Tag_GNU_Power_ABI_Vector (8)
6973 The vector ABI used by this object file. The value will be:
6977 0 for files not affected by the vector ABI.
6979 1 for files using general purpose registers to pass vectors.
6981 2 for files using AltiVec registers to pass vectors.
6983 3 for files using SPE registers to pass vectors.
6987 @node Defining New Object Attributes
6988 @section Defining New Object Attributes
6990 If you want to define a new @sc{gnu} object attribute, here are the places you
6991 will need to modify. New attributes should be discussed on the @samp{binutils}
6996 This manual, which is the official register of attributes.
6998 The header for your architecture @file{include/elf}, to define the tag.
7000 The @file{bfd} support file for your architecture, to merge the attribute
7001 and issue any appropriate link warnings.
7003 Test cases in @file{ld/testsuite} for merging and link warnings.
7005 @file{binutils/readelf.c} to display your attribute.
7007 GCC, if you want the compiler to mark the attribute automatically.
7013 @node Machine Dependencies
7014 @chapter Machine Dependent Features
7016 @cindex machine dependencies
7017 The machine instruction sets are (almost by definition) different on
7018 each machine where @command{@value{AS}} runs. Floating point representations
7019 vary as well, and @command{@value{AS}} often supports a few additional
7020 directives or command-line options for compatibility with other
7021 assemblers on a particular platform. Finally, some versions of
7022 @command{@value{AS}} support special pseudo-instructions for branch
7025 This chapter discusses most of these differences, though it does not
7026 include details on any machine's instruction set. For details on that
7027 subject, see the hardware manufacturer's manual.
7031 * AArch64-Dependent:: AArch64 Dependent Features
7034 * Alpha-Dependent:: Alpha Dependent Features
7037 * ARC-Dependent:: ARC Dependent Features
7040 * ARM-Dependent:: ARM Dependent Features
7043 * AVR-Dependent:: AVR Dependent Features
7046 * Blackfin-Dependent:: Blackfin Dependent Features
7049 * CR16-Dependent:: CR16 Dependent Features
7052 * CRIS-Dependent:: CRIS Dependent Features
7055 * D10V-Dependent:: D10V Dependent Features
7058 * D30V-Dependent:: D30V Dependent Features
7061 * Epiphany-Dependent:: EPIPHANY Dependent Features
7064 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7067 * HPPA-Dependent:: HPPA Dependent Features
7070 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7073 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7076 * i860-Dependent:: Intel 80860 Dependent Features
7079 * i960-Dependent:: Intel 80960 Dependent Features
7082 * IA-64-Dependent:: Intel IA-64 Dependent Features
7085 * IP2K-Dependent:: IP2K Dependent Features
7088 * LM32-Dependent:: LM32 Dependent Features
7091 * M32C-Dependent:: M32C Dependent Features
7094 * M32R-Dependent:: M32R Dependent Features
7097 * M68K-Dependent:: M680x0 Dependent Features
7100 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7103 * Meta-Dependent :: Meta Dependent Features
7106 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7109 * MIPS-Dependent:: MIPS Dependent Features
7112 * MMIX-Dependent:: MMIX Dependent Features
7115 * MSP430-Dependent:: MSP430 Dependent Features
7118 * NiosII-Dependent:: Altera Nios II Dependent Features
7121 * NS32K-Dependent:: NS32K Dependent Features
7124 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7125 * SH64-Dependent:: SuperH SH64 Dependent Features
7128 * PDP-11-Dependent:: PDP-11 Dependent Features
7131 * PJ-Dependent:: picoJava Dependent Features
7134 * PPC-Dependent:: PowerPC Dependent Features
7137 * RL78-Dependent:: RL78 Dependent Features
7140 * RX-Dependent:: RX Dependent Features
7143 * S/390-Dependent:: IBM S/390 Dependent Features
7146 * SCORE-Dependent:: SCORE Dependent Features
7149 * Sparc-Dependent:: SPARC Dependent Features
7152 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7155 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7158 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7161 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7164 * V850-Dependent:: V850 Dependent Features
7167 * XGATE-Dependent:: XGATE Features
7170 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7173 * Xtensa-Dependent:: Xtensa Dependent Features
7176 * Z80-Dependent:: Z80 Dependent Features
7179 * Z8000-Dependent:: Z8000 Dependent Features
7182 * Vax-Dependent:: VAX Dependent Features
7189 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7190 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7191 @c peculiarity: to preserve cross-references, there must be a node called
7192 @c "Machine Dependencies". Hence the conditional nodenames in each
7193 @c major node below. Node defaulting in makeinfo requires adjacency of
7194 @c node and sectioning commands; hence the repetition of @chapter BLAH
7195 @c in both conditional blocks.
7198 @include c-aarch64.texi
7202 @include c-alpha.texi
7218 @include c-bfin.texi
7222 @include c-cr16.texi
7226 @include c-cris.texi
7231 @node Machine Dependencies
7232 @chapter Machine Dependent Features
7234 The machine instruction sets are different on each Renesas chip family,
7235 and there are also some syntax differences among the families. This
7236 chapter describes the specific @command{@value{AS}} features for each
7240 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7241 * SH-Dependent:: Renesas SH Dependent Features
7248 @include c-d10v.texi
7252 @include c-d30v.texi
7256 @include c-epiphany.texi
7260 @include c-h8300.texi
7264 @include c-hppa.texi
7268 @include c-i370.texi
7272 @include c-i386.texi
7276 @include c-i860.texi
7280 @include c-i960.texi
7284 @include c-ia64.texi
7288 @include c-ip2k.texi
7292 @include c-lm32.texi
7296 @include c-m32c.texi
7300 @include c-m32r.texi
7304 @include c-m68k.texi
7308 @include c-m68hc11.texi
7312 @include c-metag.texi
7316 @include c-microblaze.texi
7320 @include c-mips.texi
7324 @include c-mmix.texi
7328 @include c-msp430.texi
7332 @include c-nios2.texi
7336 @include c-ns32k.texi
7340 @include c-pdp11.texi
7352 @include c-rl78.texi
7360 @include c-s390.texi
7364 @include c-score.texi
7369 @include c-sh64.texi
7373 @include c-sparc.texi
7377 @include c-tic54x.texi
7381 @include c-tic6x.texi
7385 @include c-tilegx.texi
7389 @include c-tilepro.texi
7405 @include c-v850.texi
7409 @include c-xgate.texi
7413 @include c-xstormy16.texi
7417 @include c-xtensa.texi
7421 @c reverse effect of @down at top of generic Machine-Dep chapter
7425 @node Reporting Bugs
7426 @chapter Reporting Bugs
7427 @cindex bugs in assembler
7428 @cindex reporting bugs in assembler
7430 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7432 Reporting a bug may help you by bringing a solution to your problem, or it may
7433 not. But in any case the principal function of a bug report is to help the
7434 entire community by making the next version of @command{@value{AS}} work better.
7435 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7437 In order for a bug report to serve its purpose, you must include the
7438 information that enables us to fix the bug.
7441 * Bug Criteria:: Have you found a bug?
7442 * Bug Reporting:: How to report bugs
7446 @section Have You Found a Bug?
7447 @cindex bug criteria
7449 If you are not sure whether you have found a bug, here are some guidelines:
7452 @cindex fatal signal
7453 @cindex assembler crash
7454 @cindex crash of assembler
7456 If the assembler gets a fatal signal, for any input whatever, that is a
7457 @command{@value{AS}} bug. Reliable assemblers never crash.
7459 @cindex error on valid input
7461 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7463 @cindex invalid input
7465 If @command{@value{AS}} does not produce an error message for invalid input, that
7466 is a bug. However, you should note that your idea of ``invalid input'' might
7467 be our idea of ``an extension'' or ``support for traditional practice''.
7470 If you are an experienced user of assemblers, your suggestions for improvement
7471 of @command{@value{AS}} are welcome in any case.
7475 @section How to Report Bugs
7477 @cindex assembler bugs, reporting
7479 A number of companies and individuals offer support for @sc{gnu} products. If
7480 you obtained @command{@value{AS}} from a support organization, we recommend you
7481 contact that organization first.
7483 You can find contact information for many support companies and
7484 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7488 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7492 The fundamental principle of reporting bugs usefully is this:
7493 @strong{report all the facts}. If you are not sure whether to state a
7494 fact or leave it out, state it!
7496 Often people omit facts because they think they know what causes the problem
7497 and assume that some details do not matter. Thus, you might assume that the
7498 name of a symbol you use in an example does not matter. Well, probably it does
7499 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7500 happens to fetch from the location where that name is stored in memory;
7501 perhaps, if the name were different, the contents of that location would fool
7502 the assembler into doing the right thing despite the bug. Play it safe and
7503 give a specific, complete example. That is the easiest thing for you to do,
7504 and the most helpful.
7506 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7507 it is new to us. Therefore, always write your bug reports on the assumption
7508 that the bug has not been reported previously.
7510 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7511 bell?'' This cannot help us fix a bug, so it is basically useless. We
7512 respond by asking for enough details to enable us to investigate.
7513 You might as well expedite matters by sending them to begin with.
7515 To enable us to fix the bug, you should include all these things:
7519 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7520 it with the @samp{--version} argument.
7522 Without this, we will not know whether there is any point in looking for
7523 the bug in the current version of @command{@value{AS}}.
7526 Any patches you may have applied to the @command{@value{AS}} source.
7529 The type of machine you are using, and the operating system name and
7533 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7537 The command arguments you gave the assembler to assemble your example and
7538 observe the bug. To guarantee you will not omit something important, list them
7539 all. A copy of the Makefile (or the output from make) is sufficient.
7541 If we were to try to guess the arguments, we would probably guess wrong
7542 and then we might not encounter the bug.
7545 A complete input file that will reproduce the bug. If the bug is observed when
7546 the assembler is invoked via a compiler, send the assembler source, not the
7547 high level language source. Most compilers will produce the assembler source
7548 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7549 the options @samp{-v --save-temps}; this will save the assembler source in a
7550 file with an extension of @file{.s}, and also show you exactly how
7551 @command{@value{AS}} is being run.
7554 A description of what behavior you observe that you believe is
7555 incorrect. For example, ``It gets a fatal signal.''
7557 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7558 will certainly notice it. But if the bug is incorrect output, we might not
7559 notice unless it is glaringly wrong. You might as well not give us a chance to
7562 Even if the problem you experience is a fatal signal, you should still say so
7563 explicitly. Suppose something strange is going on, such as, your copy of
7564 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7565 library on your system. (This has happened!) Your copy might crash and ours
7566 would not. If you told us to expect a crash, then when ours fails to crash, we
7567 would know that the bug was not happening for us. If you had not told us to
7568 expect a crash, then we would not be able to draw any conclusion from our
7572 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7573 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7574 option. Always send diffs from the old file to the new file. If you even
7575 discuss something in the @command{@value{AS}} source, refer to it by context, not
7578 The line numbers in our development sources will not match those in your
7579 sources. Your line numbers would convey no useful information to us.
7582 Here are some things that are not necessary:
7586 A description of the envelope of the bug.
7588 Often people who encounter a bug spend a lot of time investigating
7589 which changes to the input file will make the bug go away and which
7590 changes will not affect it.
7592 This is often time consuming and not very useful, because the way we
7593 will find the bug is by running a single example under the debugger
7594 with breakpoints, not by pure deduction from a series of examples.
7595 We recommend that you save your time for something else.
7597 Of course, if you can find a simpler example to report @emph{instead}
7598 of the original one, that is a convenience for us. Errors in the
7599 output will be easier to spot, running under the debugger will take
7600 less time, and so on.
7602 However, simplification is not vital; if you do not want to do this,
7603 report the bug anyway and send us the entire test case you used.
7606 A patch for the bug.
7608 A patch for the bug does help us if it is a good one. But do not omit
7609 the necessary information, such as the test case, on the assumption that
7610 a patch is all we need. We might see problems with your patch and decide
7611 to fix the problem another way, or we might not understand it at all.
7613 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7614 construct an example that will make the program follow a certain path through
7615 the code. If you do not send us the example, we will not be able to construct
7616 one, so we will not be able to verify that the bug is fixed.
7618 And if we cannot understand what bug you are trying to fix, or why your
7619 patch should be an improvement, we will not install it. A test case will
7620 help us to understand.
7623 A guess about what the bug is or what it depends on.
7625 Such guesses are usually wrong. Even we cannot guess right about such
7626 things without first using the debugger to find the facts.
7629 @node Acknowledgements
7630 @chapter Acknowledgements
7632 If you have contributed to GAS and your name isn't listed here,
7633 it is not meant as a slight. We just don't know about it. Send mail to the
7634 maintainer, and we'll correct the situation. Currently
7636 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7638 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7641 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7642 information and the 68k series machines, most of the preprocessing pass, and
7643 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7645 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7646 many bug fixes, including merging support for several processors, breaking GAS
7647 up to handle multiple object file format back ends (including heavy rewrite,
7648 testing, an integration of the coff and b.out back ends), adding configuration
7649 including heavy testing and verification of cross assemblers and file splits
7650 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7651 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7652 port (including considerable amounts of reverse engineering), a SPARC opcode
7653 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7654 assertions and made them work, much other reorganization, cleanup, and lint.
7656 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7657 in format-specific I/O modules.
7659 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7660 has done much work with it since.
7662 The Intel 80386 machine description was written by Eliot Dresselhaus.
7664 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7666 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7667 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7669 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7670 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7671 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7672 support a.out format.
7674 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7675 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7676 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7677 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7680 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7681 simplified the configuration of which versions accept which directives. He
7682 updated the 68k machine description so that Motorola's opcodes always produced
7683 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7684 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7685 cross-compilation support, and one bug in relaxation that took a week and
7686 required the proverbial one-bit fix.
7688 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7689 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7690 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7691 PowerPC assembler, and made a few other minor patches.
7693 Steve Chamberlain made GAS able to generate listings.
7695 Hewlett-Packard contributed support for the HP9000/300.
7697 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7698 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7699 formats). This work was supported by both the Center for Software Science at
7700 the University of Utah and Cygnus Support.
7702 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7703 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7704 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7705 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7706 and some initial 64-bit support).
7708 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7710 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7711 support for openVMS/Alpha.
7713 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7716 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7717 Inc.@: added support for Xtensa processors.
7719 Several engineers at Cygnus Support have also provided many small bug fixes and
7720 configuration enhancements.
7722 Jon Beniston added support for the Lattice Mico32 architecture.
7724 Many others have contributed large or small bugfixes and enhancements. If
7725 you have contributed significant work and are not mentioned on this list, and
7726 want to be, let us know. Some of the history has been lost; we are not
7727 intentionally leaving anyone out.
7729 @node GNU Free Documentation License
7730 @appendix GNU Free Documentation License
7734 @unnumbered AS Index
projects / dragonfly.git / blob