1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991-2013 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
254 @emph{Target Alpha options:}
256 [@b{-mdebug} | @b{-no-mdebug}]
257 [@b{-replace} | @b{-noreplace}]
258 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
259 [@b{-F}] [@b{-32addr}]
263 @emph{Target ARC options:}
269 @emph{Target ARM options:}
270 @c Don't document the deprecated options
271 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
272 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
273 [@b{-mfpu}=@var{floating-point-format}]
274 [@b{-mfloat-abi}=@var{abi}]
275 [@b{-meabi}=@var{ver}]
278 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
279 @b{-mapcs-reentrant}]
280 [@b{-mthumb-interwork}] [@b{-k}]
284 @emph{Target Blackfin options:}
285 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
292 @emph{Target CRIS options:}
293 [@b{--underscore} | @b{--no-underscore}]
295 [@b{--emulation=criself} | @b{--emulation=crisaout}]
296 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
297 @c Deprecated -- deliberately not documented.
302 @emph{Target D10V options:}
307 @emph{Target D30V options:}
308 [@b{-O}|@b{-n}|@b{-N}]
312 @emph{Target EPIPHANY options:}
313 [@b{-mepiphany}|@b{-mepiphany16}]
317 @emph{Target H8/300 options:}
321 @c HPPA has no machine-dependent assembler options (yet).
325 @emph{Target i386 options:}
326 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
327 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
331 @emph{Target i960 options:}
332 @c see md_parse_option in tc-i960.c
333 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
335 [@b{-b}] [@b{-no-relax}]
339 @emph{Target IA-64 options:}
340 [@b{-mconstant-gp}|@b{-mauto-pic}]
341 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
343 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
344 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
345 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
346 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
350 @emph{Target IP2K options:}
351 [@b{-mip2022}|@b{-mip2022ext}]
355 @emph{Target M32C options:}
356 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
360 @emph{Target M32R options:}
361 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
366 @emph{Target M680X0 options:}
367 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
371 @emph{Target M68HC11 options:}
372 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branches}] [@b{--short-branches}]
376 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
377 [@b{--print-opcodes}] [@b{--generate-example}]
381 @emph{Target MCORE options:}
382 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
383 [@b{-mcpu=[210|340]}]
387 @emph{Target Meta options:}
388 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
391 @emph{Target MICROBLAZE options:}
392 @c MicroBlaze has no machine-dependent assembler options.
396 @emph{Target MIPS options:}
397 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
398 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
399 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
400 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
401 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
402 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
403 [@b{-mips64}] [@b{-mips64r2}]
404 [@b{-construct-floats}] [@b{-no-construct-floats}]
405 [@b{-mnan=@var{encoding}}]
406 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
407 [@b{-mips16}] [@b{-no-mips16}]
408 [@b{-mmicromips}] [@b{-mno-micromips}]
409 [@b{-msmartmips}] [@b{-mno-smartmips}]
410 [@b{-mips3d}] [@b{-no-mips3d}]
411 [@b{-mdmx}] [@b{-no-mdmx}]
412 [@b{-mdsp}] [@b{-mno-dsp}]
413 [@b{-mdspr2}] [@b{-mno-dspr2}]
414 [@b{-mmt}] [@b{-mno-mt}]
415 [@b{-mmcu}] [@b{-mno-mcu}]
416 [@b{-minsn32}] [@b{-mno-insn32}]
417 [@b{-mfix7000}] [@b{-mno-fix7000}]
418 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
419 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
420 [@b{-mdebug}] [@b{-no-mdebug}]
421 [@b{-mpdr}] [@b{-mno-pdr}]
425 @emph{Target MMIX options:}
426 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
427 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
428 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
429 [@b{--linker-allocated-gregs}]
433 @emph{Target Nios II options:}
434 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
439 @emph{Target PDP11 options:}
440 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
441 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
442 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
446 @emph{Target picoJava options:}
451 @emph{Target PowerPC options:}
453 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
454 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
455 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
456 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
457 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
458 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
459 [@b{-mregnames}|@b{-mno-regnames}]
460 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
461 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
462 [@b{-msolaris}|@b{-mno-solaris}]
463 [@b{-nops=@var{count}}]
467 @emph{Target RX options:}
468 [@b{-mlittle-endian}|@b{-mbig-endian}]
469 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
470 [@b{-muse-conventional-section-names}]
471 [@b{-msmall-data-limit}]
474 [@b{-mint-register=@var{number}}]
475 [@b{-mgcc-abi}|@b{-mrx-abi}]
479 @emph{Target s390 options:}
480 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
481 [@b{-mregnames}|@b{-mno-regnames}]
482 [@b{-mwarn-areg-zero}]
486 @emph{Target SCORE options:}
487 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
488 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
489 [@b{-march=score7}][@b{-march=score3}]
490 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
494 @emph{Target SPARC options:}
495 @c The order here is important. See c-sparc.texi.
496 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
497 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
498 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
503 @emph{Target TIC54X options:}
504 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
505 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
510 @emph{Target TIC6X options:}
511 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
512 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
513 [@b{-mpic}|@b{-mno-pic}]
517 @emph{Target TILE-Gx options:}
518 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
521 @c TILEPro has no machine-dependent assembler options
526 @emph{Target Xtensa options:}
527 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
528 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
529 [@b{--[no-]transform}]
530 [@b{--rename-section} @var{oldname}=@var{newname}]
535 @emph{Target Z80 options:}
536 [@b{-z80}] [@b{-r800}]
537 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
538 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
539 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
540 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
541 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
542 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
546 @c Z8000 has no machine-dependent assembler options
555 @include at-file.texi
558 Turn on listings, in any of a variety of ways:
562 omit false conditionals
565 omit debugging directives
568 include general information, like @value{AS} version and options passed
571 include high-level source
577 include macro expansions
580 omit forms processing
586 set the name of the listing file
589 You may combine these options; for example, use @samp{-aln} for assembly
590 listing without forms processing. The @samp{=file} option, if used, must be
591 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
594 Begin in alternate macro mode.
596 @xref{Altmacro,,@code{.altmacro}}.
599 @item --compress-debug-sections
600 Compress DWARF debug sections using zlib. The debug sections are renamed
601 to begin with @samp{.zdebug}, and the resulting object file may not be
602 compatible with older linkers and object file utilities.
604 @item --nocompress-debug-sections
605 Do not compress DWARF debug sections. This is the default.
608 Ignored. This option is accepted for script compatibility with calls to
611 @item --debug-prefix-map @var{old}=@var{new}
612 When assembling files in directory @file{@var{old}}, record debugging
613 information describing them as in @file{@var{new}} instead.
615 @item --defsym @var{sym}=@var{value}
616 Define the symbol @var{sym} to be @var{value} before assembling the input file.
617 @var{value} must be an integer constant. As in C, a leading @samp{0x}
618 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
619 value. The value of the symbol can be overridden inside a source file via the
620 use of a @code{.set} pseudo-op.
623 ``fast''---skip whitespace and comment preprocessing (assume source is
628 Generate debugging information for each assembler source line using whichever
629 debug format is preferred by the target. This currently means either STABS,
633 Generate stabs debugging information for each assembler line. This
634 may help debugging assembler code, if the debugger can handle it.
637 Generate stabs debugging information for each assembler line, with GNU
638 extensions that probably only gdb can handle, and that could make other
639 debuggers crash or refuse to read your program. This
640 may help debugging assembler code. Currently the only GNU extension is
641 the location of the current working directory at assembling time.
644 Generate DWARF2 debugging information for each assembler line. This
645 may help debugging assembler code, if the debugger can handle it. Note---this
646 option is only supported by some targets, not all of them.
648 @item --gdwarf-sections
649 Instead of creating a .debug_line section, create a series of
650 .debug_line.@var{foo} sections where @var{foo} is the name of the
651 corresponding code section. For example a code section called @var{.text.func}
652 will have its dwarf line number information placed into a section called
653 @var{.debug_line.text.func}. If the code section is just called @var{.text}
654 then debug line section will still be called just @var{.debug_line} without any
657 @item --size-check=error
658 @itemx --size-check=warning
659 Issue an error or warning for invalid ELF .size directive.
662 Print a summary of the command line options and exit.
665 Print a summary of all target specific options and exit.
668 Add directory @var{dir} to the search list for @code{.include} directives.
671 Don't warn about signed overflow.
674 @ifclear DIFF-TBL-KLUGE
675 This option is accepted but has no effect on the @value{TARGET} family.
677 @ifset DIFF-TBL-KLUGE
678 Issue warnings when difference tables altered for long displacements.
683 Keep (in the symbol table) local symbols. These symbols start with
684 system-specific local label prefixes, typically @samp{.L} for ELF systems
685 or @samp{L} for traditional a.out systems.
690 @item --listing-lhs-width=@var{number}
691 Set the maximum width, in words, of the output data column for an assembler
692 listing to @var{number}.
694 @item --listing-lhs-width2=@var{number}
695 Set the maximum width, in words, of the output data column for continuation
696 lines in an assembler listing to @var{number}.
698 @item --listing-rhs-width=@var{number}
699 Set the maximum width of an input source line, as displayed in a listing, to
702 @item --listing-cont-lines=@var{number}
703 Set the maximum number of lines printed in a listing for a single line of input
706 @item -o @var{objfile}
707 Name the object-file output from @command{@value{AS}} @var{objfile}.
710 Fold the data section into the text section.
712 @kindex --hash-size=@var{number}
713 Set the default size of GAS's hash tables to a prime number close to
714 @var{number}. Increasing this value can reduce the length of time it takes the
715 assembler to perform its tasks, at the expense of increasing the assembler's
716 memory requirements. Similarly reducing this value can reduce the memory
717 requirements at the expense of speed.
719 @item --reduce-memory-overheads
720 This option reduces GAS's memory requirements, at the expense of making the
721 assembly processes slower. Currently this switch is a synonym for
722 @samp{--hash-size=4051}, but in the future it may have other effects as well.
725 Print the maximum space (in bytes) and total time (in seconds) used by
728 @item --strip-local-absolute
729 Remove local absolute symbols from the outgoing symbol table.
733 Print the @command{as} version.
736 Print the @command{as} version and exit.
740 Suppress warning messages.
742 @item --fatal-warnings
743 Treat warnings as errors.
746 Don't suppress warning messages or treat them as errors.
755 Generate an object file even after errors.
757 @item -- | @var{files} @dots{}
758 Standard input, or source files to assemble.
766 @xref{AArch64 Options}, for the options available when @value{AS} is configured
767 for the 64-bit mode of the ARM Architecture (AArch64).
772 The following options are available when @value{AS} is configured for the
773 64-bit mode of the ARM Architecture (AArch64).
776 @include c-aarch64.texi
777 @c ended inside the included file
785 @xref{Alpha Options}, for the options available when @value{AS} is configured
786 for an Alpha processor.
791 The following options are available when @value{AS} is configured for an Alpha
795 @include c-alpha.texi
796 @c ended inside the included file
803 The following options are available when @value{AS} is configured for
808 This option selects the core processor variant.
810 Select either big-endian (-EB) or little-endian (-EL) output.
815 The following options are available when @value{AS} is configured for the ARM
819 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
820 Specify which ARM processor variant is the target.
821 @item -march=@var{architecture}[+@var{extension}@dots{}]
822 Specify which ARM architecture variant is used by the target.
823 @item -mfpu=@var{floating-point-format}
824 Select which Floating Point architecture is the target.
825 @item -mfloat-abi=@var{abi}
826 Select which floating point ABI is in use.
828 Enable Thumb only instruction decoding.
829 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
830 Select which procedure calling convention is in use.
832 Select either big-endian (-EB) or little-endian (-EL) output.
833 @item -mthumb-interwork
834 Specify that the code has been generated with interworking between Thumb and
837 Specify that PIC code has been generated.
845 @xref{Blackfin Options}, for the options available when @value{AS} is
846 configured for the Blackfin processor family.
851 The following options are available when @value{AS} is configured for
852 the Blackfin processor family.
856 @c ended inside the included file
863 See the info pages for documentation of the CRIS-specific options.
867 The following options are available when @value{AS} is configured for
870 @cindex D10V optimization
871 @cindex optimization, D10V
873 Optimize output by parallelizing instructions.
878 The following options are available when @value{AS} is configured for a D30V
881 @cindex D30V optimization
882 @cindex optimization, D30V
884 Optimize output by parallelizing instructions.
888 Warn when nops are generated.
890 @cindex D30V nops after 32-bit multiply
892 Warn when a nop after a 32-bit multiply instruction is generated.
898 The following options are available when @value{AS} is configured for the
899 Adapteva EPIPHANY series.
902 @xref{Epiphany Options}, for the options available when @value{AS} is
903 configured for an Epiphany processor.
908 The following options are available when @value{AS} is configured for
909 an Epiphany processor.
912 @include c-epiphany.texi
913 @c ended inside the included file
921 @xref{H8/300 Options}, for the options available when @value{AS} is configured
922 for an H8/300 processor.
927 The following options are available when @value{AS} is configured for an H8/300
931 @include c-h8300.texi
932 @c ended inside the included file
940 @xref{i386-Options}, for the options available when @value{AS} is
941 configured for an i386 processor.
946 The following options are available when @value{AS} is configured for
951 @c ended inside the included file
958 The following options are available when @value{AS} is configured for the
959 Intel 80960 processor.
962 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
963 Specify which variant of the 960 architecture is the target.
966 Add code to collect statistics about branches taken.
969 Do not alter compare-and-branch instructions for long displacements;
976 The following options are available when @value{AS} is configured for the
982 Specifies that the extended IP2022 instructions are allowed.
985 Restores the default behaviour, which restricts the permitted instructions to
986 just the basic IP2022 ones.
992 The following options are available when @value{AS} is configured for the
993 Renesas M32C and M16C processors.
998 Assemble M32C instructions.
1001 Assemble M16C instructions (the default).
1004 Enable support for link-time relaxations.
1007 Support H'00 style hex constants in addition to 0x00 style.
1013 The following options are available when @value{AS} is configured for the
1014 Renesas M32R (formerly Mitsubishi M32R) series.
1019 Specify which processor in the M32R family is the target. The default
1020 is normally the M32R, but this option changes it to the M32RX.
1022 @item --warn-explicit-parallel-conflicts or --Wp
1023 Produce warning messages when questionable parallel constructs are
1026 @item --no-warn-explicit-parallel-conflicts or --Wnp
1027 Do not produce warning messages when questionable parallel constructs are
1034 The following options are available when @value{AS} is configured for the
1035 Motorola 68000 series.
1040 Shorten references to undefined symbols, to one word instead of two.
1042 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1043 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1044 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1045 Specify what processor in the 68000 family is the target. The default
1046 is normally the 68020, but this can be changed at configuration time.
1048 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1049 The target machine does (or does not) have a floating-point coprocessor.
1050 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1051 the basic 68000 is not compatible with the 68881, a combination of the
1052 two can be specified, since it's possible to do emulation of the
1053 coprocessor instructions with the main processor.
1055 @item -m68851 | -mno-68851
1056 The target machine does (or does not) have a memory-management
1057 unit coprocessor. The default is to assume an MMU for 68020 and up.
1065 @xref{Nios II Options}, for the options available when @value{AS} is configured
1066 for an Altera Nios II processor.
1070 @c man begin OPTIONS
1071 The following options are available when @value{AS} is configured for an
1072 Altera Nios II processor.
1074 @c man begin INCLUDE
1075 @include c-nios2.texi
1076 @c ended inside the included file
1082 For details about the PDP-11 machine dependent features options,
1083 see @ref{PDP-11-Options}.
1086 @item -mpic | -mno-pic
1087 Generate position-independent (or position-dependent) code. The
1088 default is @option{-mpic}.
1091 @itemx -mall-extensions
1092 Enable all instruction set extensions. This is the default.
1094 @item -mno-extensions
1095 Disable all instruction set extensions.
1097 @item -m@var{extension} | -mno-@var{extension}
1098 Enable (or disable) a particular instruction set extension.
1101 Enable the instruction set extensions supported by a particular CPU, and
1102 disable all other extensions.
1104 @item -m@var{machine}
1105 Enable the instruction set extensions supported by a particular machine
1106 model, and disable all other extensions.
1112 The following options are available when @value{AS} is configured for
1113 a picoJava processor.
1117 @cindex PJ endianness
1118 @cindex endianness, PJ
1119 @cindex big endian output, PJ
1121 Generate ``big endian'' format output.
1123 @cindex little endian output, PJ
1125 Generate ``little endian'' format output.
1131 The following options are available when @value{AS} is configured for the
1132 Motorola 68HC11 or 68HC12 series.
1136 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1137 Specify what processor is the target. The default is
1138 defined by the configuration option when building the assembler.
1140 @item --xgate-ramoffset
1141 Instruct the linker to offset RAM addresses from S12X address space into
1142 XGATE address space.
1145 Specify to use the 16-bit integer ABI.
1148 Specify to use the 32-bit integer ABI.
1150 @item -mshort-double
1151 Specify to use the 32-bit double ABI.
1154 Specify to use the 64-bit double ABI.
1156 @item --force-long-branches
1157 Relative branches are turned into absolute ones. This concerns
1158 conditional branches, unconditional branches and branches to a
1161 @item -S | --short-branches
1162 Do not turn relative branches into absolute ones
1163 when the offset is out of range.
1165 @item --strict-direct-mode
1166 Do not turn the direct addressing mode into extended addressing mode
1167 when the instruction does not support direct addressing mode.
1169 @item --print-insn-syntax
1170 Print the syntax of instruction in case of error.
1172 @item --print-opcodes
1173 Print the list of instructions with syntax and then exit.
1175 @item --generate-example
1176 Print an example of instruction for each possible instruction and then exit.
1177 This option is only useful for testing @command{@value{AS}}.
1183 The following options are available when @command{@value{AS}} is configured
1184 for the SPARC architecture:
1187 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1188 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1189 Explicitly select a variant of the SPARC architecture.
1191 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1192 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1194 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1195 UltraSPARC extensions.
1197 @item -xarch=v8plus | -xarch=v8plusa
1198 For compatibility with the Solaris v9 assembler. These options are
1199 equivalent to -Av8plus and -Av8plusa, respectively.
1202 Warn when the assembler switches to another architecture.
1207 The following options are available when @value{AS} is configured for the 'c54x
1212 Enable extended addressing mode. All addresses and relocations will assume
1213 extended addressing (usually 23 bits).
1214 @item -mcpu=@var{CPU_VERSION}
1215 Sets the CPU version being compiled for.
1216 @item -merrors-to-file @var{FILENAME}
1217 Redirect error output to a file, for broken systems which don't support such
1218 behaviour in the shell.
1223 The following options are available when @value{AS} is configured for
1228 This option sets the largest size of an object that can be referenced
1229 implicitly with the @code{gp} register. It is only accepted for targets that
1230 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1232 @cindex MIPS endianness
1233 @cindex endianness, MIPS
1234 @cindex big endian output, MIPS
1236 Generate ``big endian'' format output.
1238 @cindex little endian output, MIPS
1240 Generate ``little endian'' format output.
1252 Generate code for a particular MIPS Instruction Set Architecture level.
1253 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1254 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1255 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1256 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1257 @samp{-mips64r2} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1258 MIPS64, and MIPS64 Release 2 ISA processors, respectively.
1260 @item -march=@var{cpu}
1261 Generate code for a particular MIPS CPU.
1263 @item -mtune=@var{cpu}
1264 Schedule and tune for a particular MIPS CPU.
1268 Cause nops to be inserted if the read of the destination register
1269 of an mfhi or mflo instruction occurs in the following two instructions.
1273 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1274 section instead of the standard ELF .stabs sections.
1278 Control generation of @code{.pdr} sections.
1282 The register sizes are normally inferred from the ISA and ABI, but these
1283 flags force a certain group of registers to be treated as 32 bits wide at
1284 all times. @samp{-mgp32} controls the size of general-purpose registers
1285 and @samp{-mfp32} controls the size of floating-point registers.
1289 Generate code for the MIPS 16 processor. This is equivalent to putting
1290 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1291 turns off this option.
1294 @itemx -mno-micromips
1295 Generate code for the microMIPS processor. This is equivalent to putting
1296 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1297 turns off this option. This is equivalent to putting @code{.set nomicromips}
1298 at the start of the assembly file.
1301 @itemx -mno-smartmips
1302 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1303 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1304 @samp{-mno-smartmips} turns off this option.
1308 Generate code for the MIPS-3D Application Specific Extension.
1309 This tells the assembler to accept MIPS-3D instructions.
1310 @samp{-no-mips3d} turns off this option.
1314 Generate code for the MDMX Application Specific Extension.
1315 This tells the assembler to accept MDMX instructions.
1316 @samp{-no-mdmx} turns off this option.
1320 Generate code for the DSP Release 1 Application Specific Extension.
1321 This tells the assembler to accept DSP Release 1 instructions.
1322 @samp{-mno-dsp} turns off this option.
1326 Generate code for the DSP Release 2 Application Specific Extension.
1327 This option implies -mdsp.
1328 This tells the assembler to accept DSP Release 2 instructions.
1329 @samp{-mno-dspr2} turns off this option.
1333 Generate code for the MT Application Specific Extension.
1334 This tells the assembler to accept MT instructions.
1335 @samp{-mno-mt} turns off this option.
1339 Generate code for the MCU Application Specific Extension.
1340 This tells the assembler to accept MCU instructions.
1341 @samp{-mno-mcu} turns off this option.
1345 Only use 32-bit instruction encodings when generating code for the
1346 microMIPS processor. This option inhibits the use of any 16-bit
1347 instructions. This is equivalent to putting @code{.set insn32} at
1348 the start of the assembly file. @samp{-mno-insn32} turns off this
1349 option. This is equivalent to putting @code{.set noinsn32} at the
1350 start of the assembly file. By default @samp{-mno-insn32} is
1351 selected, allowing all instructions to be used.
1353 @item --construct-floats
1354 @itemx --no-construct-floats
1355 The @samp{--no-construct-floats} option disables the construction of
1356 double width floating point constants by loading the two halves of the
1357 value into the two single width floating point registers that make up
1358 the double width register. By default @samp{--construct-floats} is
1359 selected, allowing construction of these floating point constants.
1361 @item --relax-branch
1362 @itemx --no-relax-branch
1363 The @samp{--relax-branch} option enables the relaxation of out-of-range
1364 branches. By default @samp{--no-relax-branch} is selected, causing any
1365 out-of-range branches to produce an error.
1367 @item -mnan=@var{encoding}
1368 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1369 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1372 @item --emulation=@var{name}
1373 This option was formerly used to switch between ELF and ECOFF output
1374 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1375 removed in GAS 2.24, so the option now serves little purpose.
1376 It is retained for backwards compatibility.
1378 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1379 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1380 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1381 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1382 preferred options instead.
1385 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1392 Control how to deal with multiplication overflow and division by zero.
1393 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1394 (and only work for Instruction Set Architecture level 2 and higher);
1395 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1399 When this option is used, @command{@value{AS}} will issue a warning every
1400 time it generates a nop instruction from a macro.
1405 The following options are available when @value{AS} is configured for
1411 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1412 The command line option @samp{-nojsri2bsr} can be used to disable it.
1416 Enable or disable the silicon filter behaviour. By default this is disabled.
1417 The default can be overridden by the @samp{-sifilter} command line option.
1420 Alter jump instructions for long displacements.
1422 @item -mcpu=[210|340]
1423 Select the cpu type on the target hardware. This controls which instructions
1427 Assemble for a big endian target.
1430 Assemble for a little endian target.
1439 @xref{Meta Options}, for the options available when @value{AS} is configured
1440 for a Meta processor.
1444 @c man begin OPTIONS
1445 The following options are available when @value{AS} is configured for a
1448 @c man begin INCLUDE
1449 @include c-metag.texi
1450 @c ended inside the included file
1455 @c man begin OPTIONS
1457 See the info pages for documentation of the MMIX-specific options.
1464 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1465 for a PowerPC processor.
1469 @c man begin OPTIONS
1470 The following options are available when @value{AS} is configured for a
1473 @c man begin INCLUDE
1475 @c ended inside the included file
1480 @c man begin OPTIONS
1482 See the info pages for documentation of the RX-specific options.
1486 The following options are available when @value{AS} is configured for the s390
1492 Select the word size, either 31/32 bits or 64 bits.
1495 Select the architecture mode, either the Enterprise System
1496 Architecture (esa) or the z/Architecture mode (zarch).
1497 @item -march=@var{processor}
1498 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1499 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1500 @samp{z196}, or @samp{zEC12}.
1502 @itemx -mno-regnames
1503 Allow or disallow symbolic names for registers.
1504 @item -mwarn-areg-zero
1505 Warn whenever the operand for a base or index register has been specified
1506 but evaluates to zero.
1514 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1515 for a TMS320C6000 processor.
1519 @c man begin OPTIONS
1520 The following options are available when @value{AS} is configured for a
1521 TMS320C6000 processor.
1523 @c man begin INCLUDE
1524 @include c-tic6x.texi
1525 @c ended inside the included file
1533 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1534 for a TILE-Gx processor.
1538 @c man begin OPTIONS
1539 The following options are available when @value{AS} is configured for a TILE-Gx
1542 @c man begin INCLUDE
1543 @include c-tilegx.texi
1544 @c ended inside the included file
1552 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1553 for an Xtensa processor.
1557 @c man begin OPTIONS
1558 The following options are available when @value{AS} is configured for an
1561 @c man begin INCLUDE
1562 @include c-xtensa.texi
1563 @c ended inside the included file
1568 @c man begin OPTIONS
1571 The following options are available when @value{AS} is configured for
1572 a Z80 family processor.
1575 Assemble for Z80 processor.
1577 Assemble for R800 processor.
1578 @item -ignore-undocumented-instructions
1580 Assemble undocumented Z80 instructions that also work on R800 without warning.
1581 @item -ignore-unportable-instructions
1583 Assemble all undocumented Z80 instructions without warning.
1584 @item -warn-undocumented-instructions
1586 Issue a warning for undocumented Z80 instructions that also work on R800.
1587 @item -warn-unportable-instructions
1589 Issue a warning for undocumented Z80 instructions that do not work on R800.
1590 @item -forbid-undocumented-instructions
1592 Treat all undocumented instructions as errors.
1593 @item -forbid-unportable-instructions
1595 Treat undocumented Z80 instructions that do not work on R800 as errors.
1602 * Manual:: Structure of this Manual
1603 * GNU Assembler:: The GNU Assembler
1604 * Object Formats:: Object File Formats
1605 * Command Line:: Command Line
1606 * Input Files:: Input Files
1607 * Object:: Output (Object) File
1608 * Errors:: Error and Warning Messages
1612 @section Structure of this Manual
1614 @cindex manual, structure and purpose
1615 This manual is intended to describe what you need to know to use
1616 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1617 notation for symbols, constants, and expressions; the directives that
1618 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1621 We also cover special features in the @value{TARGET}
1622 configuration of @command{@value{AS}}, including assembler directives.
1625 This manual also describes some of the machine-dependent features of
1626 various flavors of the assembler.
1629 @cindex machine instructions (not covered)
1630 On the other hand, this manual is @emph{not} intended as an introduction
1631 to programming in assembly language---let alone programming in general!
1632 In a similar vein, we make no attempt to introduce the machine
1633 architecture; we do @emph{not} describe the instruction set, standard
1634 mnemonics, registers or addressing modes that are standard to a
1635 particular architecture.
1637 You may want to consult the manufacturer's
1638 machine architecture manual for this information.
1642 For information on the H8/300 machine instruction set, see @cite{H8/300
1643 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1644 Programming Manual} (Renesas).
1647 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1648 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1649 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1650 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1653 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1657 @c I think this is premature---doc@cygnus.com, 17jan1991
1659 Throughout this manual, we assume that you are running @dfn{GNU},
1660 the portable operating system from the @dfn{Free Software
1661 Foundation, Inc.}. This restricts our attention to certain kinds of
1662 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1663 once this assumption is granted examples and definitions need less
1666 @command{@value{AS}} is part of a team of programs that turn a high-level
1667 human-readable series of instructions into a low-level
1668 computer-readable series of instructions. Different versions of
1669 @command{@value{AS}} are used for different kinds of computer.
1672 @c There used to be a section "Terminology" here, which defined
1673 @c "contents", "byte", "word", and "long". Defining "word" to any
1674 @c particular size is confusing when the .word directive may generate 16
1675 @c bits on one machine and 32 bits on another; in general, for the user
1676 @c version of this manual, none of these terms seem essential to define.
1677 @c They were used very little even in the former draft of the manual;
1678 @c this draft makes an effort to avoid them (except in names of
1682 @section The GNU Assembler
1684 @c man begin DESCRIPTION
1686 @sc{gnu} @command{as} is really a family of assemblers.
1688 This manual describes @command{@value{AS}}, a member of that family which is
1689 configured for the @value{TARGET} architectures.
1691 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1692 should find a fairly similar environment when you use it on another
1693 architecture. Each version has much in common with the others,
1694 including object file formats, most assembler directives (often called
1695 @dfn{pseudo-ops}) and assembler syntax.@refill
1697 @cindex purpose of @sc{gnu} assembler
1698 @command{@value{AS}} is primarily intended to assemble the output of the
1699 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1700 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1701 assemble correctly everything that other assemblers for the same
1702 machine would assemble.
1704 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1707 @c This remark should appear in generic version of manual; assumption
1708 @c here is that generic version sets M680x0.
1709 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1710 assembler for the same architecture; for example, we know of several
1711 incompatible versions of 680x0 assembly language syntax.
1716 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1717 program in one pass of the source file. This has a subtle impact on the
1718 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1720 @node Object Formats
1721 @section Object File Formats
1723 @cindex object file format
1724 The @sc{gnu} assembler can be configured to produce several alternative
1725 object file formats. For the most part, this does not affect how you
1726 write assembly language programs; but directives for debugging symbols
1727 are typically different in different file formats. @xref{Symbol
1728 Attributes,,Symbol Attributes}.
1731 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1732 @value{OBJ-NAME} format object files.
1734 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1736 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1737 @code{b.out} or COFF format object files.
1740 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1741 SOM or ELF format object files.
1746 @section Command Line
1748 @cindex command line conventions
1750 After the program name @command{@value{AS}}, the command line may contain
1751 options and file names. Options may appear in any order, and may be
1752 before, after, or between file names. The order of file names is
1755 @cindex standard input, as input file
1757 @file{--} (two hyphens) by itself names the standard input file
1758 explicitly, as one of the files for @command{@value{AS}} to assemble.
1760 @cindex options, command line
1761 Except for @samp{--} any command line argument that begins with a
1762 hyphen (@samp{-}) is an option. Each option changes the behavior of
1763 @command{@value{AS}}. No option changes the way another option works. An
1764 option is a @samp{-} followed by one or more letters; the case of
1765 the letter is important. All options are optional.
1767 Some options expect exactly one file name to follow them. The file
1768 name may either immediately follow the option's letter (compatible
1769 with older assemblers) or it may be the next command argument (@sc{gnu}
1770 standard). These two command lines are equivalent:
1773 @value{AS} -o my-object-file.o mumble.s
1774 @value{AS} -omy-object-file.o mumble.s
1778 @section Input Files
1781 @cindex source program
1782 @cindex files, input
1783 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1784 describe the program input to one run of @command{@value{AS}}. The program may
1785 be in one or more files; how the source is partitioned into files
1786 doesn't change the meaning of the source.
1788 @c I added "con" prefix to "catenation" just to prove I can overcome my
1789 @c APL training... doc@cygnus.com
1790 The source program is a concatenation of the text in all the files, in the
1793 @c man begin DESCRIPTION
1794 Each time you run @command{@value{AS}} it assembles exactly one source
1795 program. The source program is made up of one or more files.
1796 (The standard input is also a file.)
1798 You give @command{@value{AS}} a command line that has zero or more input file
1799 names. The input files are read (from left file name to right). A
1800 command line argument (in any position) that has no special meaning
1801 is taken to be an input file name.
1803 If you give @command{@value{AS}} no file names it attempts to read one input file
1804 from the @command{@value{AS}} standard input, which is normally your terminal. You
1805 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1808 Use @samp{--} if you need to explicitly name the standard input file
1809 in your command line.
1811 If the source is empty, @command{@value{AS}} produces a small, empty object
1816 @subheading Filenames and Line-numbers
1818 @cindex input file linenumbers
1819 @cindex line numbers, in input files
1820 There are two ways of locating a line in the input file (or files) and
1821 either may be used in reporting error messages. One way refers to a line
1822 number in a physical file; the other refers to a line number in a
1823 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1825 @dfn{Physical files} are those files named in the command line given
1826 to @command{@value{AS}}.
1828 @dfn{Logical files} are simply names declared explicitly by assembler
1829 directives; they bear no relation to physical files. Logical file names help
1830 error messages reflect the original source file, when @command{@value{AS}} source
1831 is itself synthesized from other files. @command{@value{AS}} understands the
1832 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1833 @ref{File,,@code{.file}}.
1836 @section Output (Object) File
1842 Every time you run @command{@value{AS}} it produces an output file, which is
1843 your assembly language program translated into numbers. This file
1844 is the object file. Its default name is
1852 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1854 You can give it another name by using the @option{-o} option. Conventionally,
1855 object file names end with @file{.o}. The default name is used for historical
1856 reasons: older assemblers were capable of assembling self-contained programs
1857 directly into a runnable program. (For some formats, this isn't currently
1858 possible, but it can be done for the @code{a.out} format.)
1862 The object file is meant for input to the linker @code{@value{LD}}. It contains
1863 assembled program code, information to help @code{@value{LD}} integrate
1864 the assembled program into a runnable file, and (optionally) symbolic
1865 information for the debugger.
1867 @c link above to some info file(s) like the description of a.out.
1868 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1871 @section Error and Warning Messages
1873 @c man begin DESCRIPTION
1875 @cindex error messages
1876 @cindex warning messages
1877 @cindex messages from assembler
1878 @command{@value{AS}} may write warnings and error messages to the standard error
1879 file (usually your terminal). This should not happen when a compiler
1880 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1881 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1882 grave problem that stops the assembly.
1886 @cindex format of warning messages
1887 Warning messages have the format
1890 file_name:@b{NNN}:Warning Message Text
1894 @cindex line numbers, in warnings/errors
1895 (where @b{NNN} is a line number). If a logical file name has been given
1896 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1897 the current input file is used. If a logical line number was given
1899 (@pxref{Line,,@code{.line}})
1901 then it is used to calculate the number printed,
1902 otherwise the actual line in the current source file is printed. The
1903 message text is intended to be self explanatory (in the grand Unix
1906 @cindex format of error messages
1907 Error messages have the format
1909 file_name:@b{NNN}:FATAL:Error Message Text
1911 The file name and line number are derived as for warning
1912 messages. The actual message text may be rather less explanatory
1913 because many of them aren't supposed to happen.
1916 @chapter Command-Line Options
1918 @cindex options, all versions of assembler
1919 This chapter describes command-line options available in @emph{all}
1920 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1921 for options specific
1923 to the @value{TARGET} target.
1926 to particular machine architectures.
1929 @c man begin DESCRIPTION
1931 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1932 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1933 The assembler arguments must be separated from each other (and the @samp{-Wa})
1934 by commas. For example:
1937 gcc -c -g -O -Wa,-alh,-L file.c
1941 This passes two options to the assembler: @samp{-alh} (emit a listing to
1942 standard output with high-level and assembly source) and @samp{-L} (retain
1943 local symbols in the symbol table).
1945 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1946 command-line options are automatically passed to the assembler by the compiler.
1947 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1948 precisely what options it passes to each compilation pass, including the
1954 * a:: -a[cdghlns] enable listings
1955 * alternate:: --alternate enable alternate macro syntax
1956 * D:: -D for compatibility
1957 * f:: -f to work faster
1958 * I:: -I for .include search path
1959 @ifclear DIFF-TBL-KLUGE
1960 * K:: -K for compatibility
1962 @ifset DIFF-TBL-KLUGE
1963 * K:: -K for difference tables
1966 * L:: -L to retain local symbols
1967 * listing:: --listing-XXX to configure listing output
1968 * M:: -M or --mri to assemble in MRI compatibility mode
1969 * MD:: --MD for dependency tracking
1970 * o:: -o to name the object file
1971 * R:: -R to join data and text sections
1972 * statistics:: --statistics to see statistics about assembly
1973 * traditional-format:: --traditional-format for compatible output
1974 * v:: -v to announce version
1975 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1976 * Z:: -Z to make object file even after errors
1980 @section Enable Listings: @option{-a[cdghlns]}
1990 @cindex listings, enabling
1991 @cindex assembly listings, enabling
1993 These options enable listing output from the assembler. By itself,
1994 @samp{-a} requests high-level, assembly, and symbols listing.
1995 You can use other letters to select specific options for the list:
1996 @samp{-ah} requests a high-level language listing,
1997 @samp{-al} requests an output-program assembly listing, and
1998 @samp{-as} requests a symbol table listing.
1999 High-level listings require that a compiler debugging option like
2000 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2003 Use the @samp{-ag} option to print a first section with general assembly
2004 information, like @value{AS} version, switches passed, or time stamp.
2006 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2007 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2008 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2009 omitted from the listing.
2011 Use the @samp{-ad} option to omit debugging directives from the
2014 Once you have specified one of these options, you can further control
2015 listing output and its appearance using the directives @code{.list},
2016 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2018 The @samp{-an} option turns off all forms processing.
2019 If you do not request listing output with one of the @samp{-a} options, the
2020 listing-control directives have no effect.
2022 The letters after @samp{-a} may be combined into one option,
2023 @emph{e.g.}, @samp{-aln}.
2025 Note if the assembler source is coming from the standard input (e.g.,
2027 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2028 is being used) then the listing will not contain any comments or preprocessor
2029 directives. This is because the listing code buffers input source lines from
2030 stdin only after they have been preprocessed by the assembler. This reduces
2031 memory usage and makes the code more efficient.
2034 @section @option{--alternate}
2037 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2040 @section @option{-D}
2043 This option has no effect whatsoever, but it is accepted to make it more
2044 likely that scripts written for other assemblers also work with
2045 @command{@value{AS}}.
2048 @section Work Faster: @option{-f}
2051 @cindex trusted compiler
2052 @cindex faster processing (@option{-f})
2053 @samp{-f} should only be used when assembling programs written by a
2054 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2055 and comment preprocessing on
2056 the input file(s) before assembling them. @xref{Preprocessing,
2060 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2061 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2066 @section @code{.include} Search Path: @option{-I} @var{path}
2068 @kindex -I @var{path}
2069 @cindex paths for @code{.include}
2070 @cindex search path for @code{.include}
2071 @cindex @code{include} directive search path
2072 Use this option to add a @var{path} to the list of directories
2073 @command{@value{AS}} searches for files specified in @code{.include}
2074 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2075 many times as necessary to include a variety of paths. The current
2076 working directory is always searched first; after that, @command{@value{AS}}
2077 searches any @samp{-I} directories in the same order as they were
2078 specified (left to right) on the command line.
2081 @section Difference Tables: @option{-K}
2084 @ifclear DIFF-TBL-KLUGE
2085 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2086 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2087 where it can be used to warn when the assembler alters the machine code
2088 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2089 family does not have the addressing limitations that sometimes lead to this
2090 alteration on other platforms.
2093 @ifset DIFF-TBL-KLUGE
2094 @cindex difference tables, warning
2095 @cindex warning for altered difference tables
2096 @command{@value{AS}} sometimes alters the code emitted for directives of the
2097 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2098 You can use the @samp{-K} option if you want a warning issued when this
2103 @section Include Local Symbols: @option{-L}
2106 @cindex local symbols, retaining in output
2107 Symbols beginning with system-specific local label prefixes, typically
2108 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2109 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2110 such symbols when debugging, because they are intended for the use of
2111 programs (like compilers) that compose assembler programs, not for your
2112 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2113 such symbols, so you do not normally debug with them.
2115 This option tells @command{@value{AS}} to retain those local symbols
2116 in the object file. Usually if you do this you also tell the linker
2117 @code{@value{LD}} to preserve those symbols.
2120 @section Configuring listing output: @option{--listing}
2122 The listing feature of the assembler can be enabled via the command line switch
2123 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2124 hex dump of the corresponding locations in the output object file, and displays
2125 them as a listing file. The format of this listing can be controlled by
2126 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2127 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2128 @code{.psize} (@pxref{Psize}), and
2129 @code{.eject} (@pxref{Eject}) and also by the following switches:
2132 @item --listing-lhs-width=@samp{number}
2133 @kindex --listing-lhs-width
2134 @cindex Width of first line disassembly output
2135 Sets the maximum width, in words, of the first line of the hex byte dump. This
2136 dump appears on the left hand side of the listing output.
2138 @item --listing-lhs-width2=@samp{number}
2139 @kindex --listing-lhs-width2
2140 @cindex Width of continuation lines of disassembly output
2141 Sets the maximum width, in words, of any further lines of the hex byte dump for
2142 a given input source line. If this value is not specified, it defaults to being
2143 the same as the value specified for @samp{--listing-lhs-width}. If neither
2144 switch is used the default is to one.
2146 @item --listing-rhs-width=@samp{number}
2147 @kindex --listing-rhs-width
2148 @cindex Width of source line output
2149 Sets the maximum width, in characters, of the source line that is displayed
2150 alongside the hex dump. The default value for this parameter is 100. The
2151 source line is displayed on the right hand side of the listing output.
2153 @item --listing-cont-lines=@samp{number}
2154 @kindex --listing-cont-lines
2155 @cindex Maximum number of continuation lines
2156 Sets the maximum number of continuation lines of hex dump that will be
2157 displayed for a given single line of source input. The default value is 4.
2161 @section Assemble in MRI Compatibility Mode: @option{-M}
2164 @cindex MRI compatibility mode
2165 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2166 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2167 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2168 configured target) assembler from Microtec Research. The exact nature of the
2169 MRI syntax will not be documented here; see the MRI manuals for more
2170 information. Note in particular that the handling of macros and macro
2171 arguments is somewhat different. The purpose of this option is to permit
2172 assembling existing MRI assembler code using @command{@value{AS}}.
2174 The MRI compatibility is not complete. Certain operations of the MRI assembler
2175 depend upon its object file format, and can not be supported using other object
2176 file formats. Supporting these would require enhancing each object file format
2177 individually. These are:
2180 @item global symbols in common section
2182 The m68k MRI assembler supports common sections which are merged by the linker.
2183 Other object file formats do not support this. @command{@value{AS}} handles
2184 common sections by treating them as a single common symbol. It permits local
2185 symbols to be defined within a common section, but it can not support global
2186 symbols, since it has no way to describe them.
2188 @item complex relocations
2190 The MRI assemblers support relocations against a negated section address, and
2191 relocations which combine the start addresses of two or more sections. These
2192 are not support by other object file formats.
2194 @item @code{END} pseudo-op specifying start address
2196 The MRI @code{END} pseudo-op permits the specification of a start address.
2197 This is not supported by other object file formats. The start address may
2198 instead be specified using the @option{-e} option to the linker, or in a linker
2201 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2203 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2204 name to the output file. This is not supported by other object file formats.
2206 @item @code{ORG} pseudo-op
2208 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2209 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2210 which changes the location within the current section. Absolute sections are
2211 not supported by other object file formats. The address of a section may be
2212 assigned within a linker script.
2215 There are some other features of the MRI assembler which are not supported by
2216 @command{@value{AS}}, typically either because they are difficult or because they
2217 seem of little consequence. Some of these may be supported in future releases.
2221 @item EBCDIC strings
2223 EBCDIC strings are not supported.
2225 @item packed binary coded decimal
2227 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2228 and @code{DCB.P} pseudo-ops are not supported.
2230 @item @code{FEQU} pseudo-op
2232 The m68k @code{FEQU} pseudo-op is not supported.
2234 @item @code{NOOBJ} pseudo-op
2236 The m68k @code{NOOBJ} pseudo-op is not supported.
2238 @item @code{OPT} branch control options
2240 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2241 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2242 relaxes all branches, whether forward or backward, to an appropriate size, so
2243 these options serve no purpose.
2245 @item @code{OPT} list control options
2247 The following m68k @code{OPT} list control options are ignored: @code{C},
2248 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2249 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2251 @item other @code{OPT} options
2253 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2254 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2256 @item @code{OPT} @code{D} option is default
2258 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2259 @code{OPT NOD} may be used to turn it off.
2261 @item @code{XREF} pseudo-op.
2263 The m68k @code{XREF} pseudo-op is ignored.
2265 @item @code{.debug} pseudo-op
2267 The i960 @code{.debug} pseudo-op is not supported.
2269 @item @code{.extended} pseudo-op
2271 The i960 @code{.extended} pseudo-op is not supported.
2273 @item @code{.list} pseudo-op.
2275 The various options of the i960 @code{.list} pseudo-op are not supported.
2277 @item @code{.optimize} pseudo-op
2279 The i960 @code{.optimize} pseudo-op is not supported.
2281 @item @code{.output} pseudo-op
2283 The i960 @code{.output} pseudo-op is not supported.
2285 @item @code{.setreal} pseudo-op
2287 The i960 @code{.setreal} pseudo-op is not supported.
2292 @section Dependency Tracking: @option{--MD}
2295 @cindex dependency tracking
2298 @command{@value{AS}} can generate a dependency file for the file it creates. This
2299 file consists of a single rule suitable for @code{make} describing the
2300 dependencies of the main source file.
2302 The rule is written to the file named in its argument.
2304 This feature is used in the automatic updating of makefiles.
2307 @section Name the Object File: @option{-o}
2310 @cindex naming object file
2311 @cindex object file name
2312 There is always one object file output when you run @command{@value{AS}}. By
2313 default it has the name
2316 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2330 You use this option (which takes exactly one filename) to give the
2331 object file a different name.
2333 Whatever the object file is called, @command{@value{AS}} overwrites any
2334 existing file of the same name.
2337 @section Join Data and Text Sections: @option{-R}
2340 @cindex data and text sections, joining
2341 @cindex text and data sections, joining
2342 @cindex joining text and data sections
2343 @cindex merging text and data sections
2344 @option{-R} tells @command{@value{AS}} to write the object file as if all
2345 data-section data lives in the text section. This is only done at
2346 the very last moment: your binary data are the same, but data
2347 section parts are relocated differently. The data section part of
2348 your object file is zero bytes long because all its bytes are
2349 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2351 When you specify @option{-R} it would be possible to generate shorter
2352 address displacements (because we do not have to cross between text and
2353 data section). We refrain from doing this simply for compatibility with
2354 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2357 When @command{@value{AS}} is configured for COFF or ELF output,
2358 this option is only useful if you use sections named @samp{.text} and
2363 @option{-R} is not supported for any of the HPPA targets. Using
2364 @option{-R} generates a warning from @command{@value{AS}}.
2368 @section Display Assembly Statistics: @option{--statistics}
2370 @kindex --statistics
2371 @cindex statistics, about assembly
2372 @cindex time, total for assembly
2373 @cindex space used, maximum for assembly
2374 Use @samp{--statistics} to display two statistics about the resources used by
2375 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2376 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2379 @node traditional-format
2380 @section Compatible Output: @option{--traditional-format}
2382 @kindex --traditional-format
2383 For some targets, the output of @command{@value{AS}} is different in some ways
2384 from the output of some existing assembler. This switch requests
2385 @command{@value{AS}} to use the traditional format instead.
2387 For example, it disables the exception frame optimizations which
2388 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2391 @section Announce Version: @option{-v}
2395 @cindex assembler version
2396 @cindex version of assembler
2397 You can find out what version of as is running by including the
2398 option @samp{-v} (which you can also spell as @samp{-version}) on the
2402 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2404 @command{@value{AS}} should never give a warning or error message when
2405 assembling compiler output. But programs written by people often
2406 cause @command{@value{AS}} to give a warning that a particular assumption was
2407 made. All such warnings are directed to the standard error file.
2411 @cindex suppressing warnings
2412 @cindex warnings, suppressing
2413 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2414 This only affects the warning messages: it does not change any particular of
2415 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2418 @kindex --fatal-warnings
2419 @cindex errors, caused by warnings
2420 @cindex warnings, causing error
2421 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2422 files that generate warnings to be in error.
2425 @cindex warnings, switching on
2426 You can switch these options off again by specifying @option{--warn}, which
2427 causes warnings to be output as usual.
2430 @section Generate Object File in Spite of Errors: @option{-Z}
2431 @cindex object file, after errors
2432 @cindex errors, continuing after
2433 After an error message, @command{@value{AS}} normally produces no output. If for
2434 some reason you are interested in object file output even after
2435 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2436 option. If there are any errors, @command{@value{AS}} continues anyways, and
2437 writes an object file after a final warning message of the form @samp{@var{n}
2438 errors, @var{m} warnings, generating bad object file.}
2443 @cindex machine-independent syntax
2444 @cindex syntax, machine-independent
2445 This chapter describes the machine-independent syntax allowed in a
2446 source file. @command{@value{AS}} syntax is similar to what many other
2447 assemblers use; it is inspired by the BSD 4.2
2452 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2456 * Preprocessing:: Preprocessing
2457 * Whitespace:: Whitespace
2458 * Comments:: Comments
2459 * Symbol Intro:: Symbols
2460 * Statements:: Statements
2461 * Constants:: Constants
2465 @section Preprocessing
2467 @cindex preprocessing
2468 The @command{@value{AS}} internal preprocessor:
2470 @cindex whitespace, removed by preprocessor
2472 adjusts and removes extra whitespace. It leaves one space or tab before
2473 the keywords on a line, and turns any other whitespace on the line into
2476 @cindex comments, removed by preprocessor
2478 removes all comments, replacing them with a single space, or an
2479 appropriate number of newlines.
2481 @cindex constants, converted by preprocessor
2483 converts character constants into the appropriate numeric values.
2486 It does not do macro processing, include file handling, or
2487 anything else you may get from your C compiler's preprocessor. You can
2488 do include file processing with the @code{.include} directive
2489 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2490 to get other ``CPP'' style preprocessing by giving the input file a
2491 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2492 Output, gcc.info, Using GNU CC}.
2494 Excess whitespace, comments, and character constants
2495 cannot be used in the portions of the input text that are not
2498 @cindex turning preprocessing on and off
2499 @cindex preprocessing, turning on and off
2502 If the first line of an input file is @code{#NO_APP} or if you use the
2503 @samp{-f} option, whitespace and comments are not removed from the input file.
2504 Within an input file, you can ask for whitespace and comment removal in
2505 specific portions of the by putting a line that says @code{#APP} before the
2506 text that may contain whitespace or comments, and putting a line that says
2507 @code{#NO_APP} after this text. This feature is mainly intend to support
2508 @code{asm} statements in compilers whose output is otherwise free of comments
2515 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2516 Whitespace is used to separate symbols, and to make programs neater for
2517 people to read. Unless within character constants
2518 (@pxref{Characters,,Character Constants}), any whitespace means the same
2519 as exactly one space.
2525 There are two ways of rendering comments to @command{@value{AS}}. In both
2526 cases the comment is equivalent to one space.
2528 Anything from @samp{/*} through the next @samp{*/} is a comment.
2529 This means you may not nest these comments.
2533 The only way to include a newline ('\n') in a comment
2534 is to use this sort of comment.
2537 /* This sort of comment does not nest. */
2540 @cindex line comment character
2541 Anything from a @dfn{line comment} character up to the next newline is
2542 considered a comment and is ignored. The line comment character is target
2543 specific, and some targets multiple comment characters. Some targets also have
2544 line comment characters that only work if they are the first character on a
2545 line. Some targets use a sequence of two characters to introduce a line
2546 comment. Some targets can also change their line comment characters depending
2547 upon command line options that have been used. For more details see the
2548 @emph{Syntax} section in the documentation for individual targets.
2550 If the line comment character is the hash sign (@samp{#}) then it still has the
2551 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2552 to specify logical line numbers:
2555 @cindex lines starting with @code{#}
2556 @cindex logical line numbers
2557 To be compatible with past assemblers, lines that begin with @samp{#} have a
2558 special interpretation. Following the @samp{#} should be an absolute
2559 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2560 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2561 new logical file name. The rest of the line, if any, should be whitespace.
2563 If the first non-whitespace characters on the line are not numeric,
2564 the line is ignored. (Just like a comment.)
2567 # This is an ordinary comment.
2568 # 42-6 "new_file_name" # New logical file name
2569 # This is logical line # 36.
2571 This feature is deprecated, and may disappear from future versions
2572 of @command{@value{AS}}.
2577 @cindex characters used in symbols
2578 @ifclear SPECIAL-SYMS
2579 A @dfn{symbol} is one or more characters chosen from the set of all
2580 letters (both upper and lower case), digits and the three characters
2586 A @dfn{symbol} is one or more characters chosen from the set of all
2587 letters (both upper and lower case), digits and the three characters
2588 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2594 On most machines, you can also use @code{$} in symbol names; exceptions
2595 are noted in @ref{Machine Dependencies}.
2597 No symbol may begin with a digit. Case is significant.
2598 There is no length limit: all characters are significant. Multibyte characters
2599 are supported. Symbols are delimited by characters not in that set, or by the
2600 beginning of a file (since the source program must end with a newline, the end
2601 of a file is not a possible symbol delimiter). @xref{Symbols}.
2602 @cindex length of symbols
2607 @cindex statements, structure of
2608 @cindex line separator character
2609 @cindex statement separator character
2611 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2612 @dfn{line separator character}. The line separator character is target
2613 specific and described in the @emph{Syntax} section of each
2614 target's documentation. Not all targets support a line separator character.
2615 The newline or line separator character is considered to be part of the
2616 preceding statement. Newlines and separators within character constants are an
2617 exception: they do not end statements.
2619 @cindex newline, required at file end
2620 @cindex EOF, newline must precede
2621 It is an error to end any statement with end-of-file: the last
2622 character of any input file should be a newline.@refill
2624 An empty statement is allowed, and may include whitespace. It is ignored.
2626 @cindex instructions and directives
2627 @cindex directives and instructions
2628 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2629 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2631 A statement begins with zero or more labels, optionally followed by a
2632 key symbol which determines what kind of statement it is. The key
2633 symbol determines the syntax of the rest of the statement. If the
2634 symbol begins with a dot @samp{.} then the statement is an assembler
2635 directive: typically valid for any computer. If the symbol begins with
2636 a letter the statement is an assembly language @dfn{instruction}: it
2637 assembles into a machine language instruction.
2639 Different versions of @command{@value{AS}} for different computers
2640 recognize different instructions. In fact, the same symbol may
2641 represent a different instruction in a different computer's assembly
2645 @cindex @code{:} (label)
2646 @cindex label (@code{:})
2647 A label is a symbol immediately followed by a colon (@code{:}).
2648 Whitespace before a label or after a colon is permitted, but you may not
2649 have whitespace between a label's symbol and its colon. @xref{Labels}.
2652 For HPPA targets, labels need not be immediately followed by a colon, but
2653 the definition of a label must begin in column zero. This also implies that
2654 only one label may be defined on each line.
2658 label: .directive followed by something
2659 another_label: # This is an empty statement.
2660 instruction operand_1, operand_2, @dots{}
2667 A constant is a number, written so that its value is known by
2668 inspection, without knowing any context. Like this:
2671 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2672 .ascii "Ring the bell\7" # A string constant.
2673 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2674 .float 0f-314159265358979323846264338327\
2675 95028841971.693993751E-40 # - pi, a flonum.
2680 * Characters:: Character Constants
2681 * Numbers:: Number Constants
2685 @subsection Character Constants
2687 @cindex character constants
2688 @cindex constants, character
2689 There are two kinds of character constants. A @dfn{character} stands
2690 for one character in one byte and its value may be used in
2691 numeric expressions. String constants (properly called string
2692 @emph{literals}) are potentially many bytes and their values may not be
2693 used in arithmetic expressions.
2697 * Chars:: Characters
2701 @subsubsection Strings
2703 @cindex string constants
2704 @cindex constants, string
2705 A @dfn{string} is written between double-quotes. It may contain
2706 double-quotes or null characters. The way to get special characters
2707 into a string is to @dfn{escape} these characters: precede them with
2708 a backslash @samp{\} character. For example @samp{\\} represents
2709 one backslash: the first @code{\} is an escape which tells
2710 @command{@value{AS}} to interpret the second character literally as a backslash
2711 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2712 escape character). The complete list of escapes follows.
2714 @cindex escape codes, character
2715 @cindex character escape codes
2718 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2720 @cindex @code{\b} (backspace character)
2721 @cindex backspace (@code{\b})
2723 Mnemonic for backspace; for ASCII this is octal code 010.
2726 @c Mnemonic for EOText; for ASCII this is octal code 004.
2728 @cindex @code{\f} (formfeed character)
2729 @cindex formfeed (@code{\f})
2731 Mnemonic for FormFeed; for ASCII this is octal code 014.
2733 @cindex @code{\n} (newline character)
2734 @cindex newline (@code{\n})
2736 Mnemonic for newline; for ASCII this is octal code 012.
2739 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2741 @cindex @code{\r} (carriage return character)
2742 @cindex carriage return (@code{\r})
2744 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2747 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2748 @c other assemblers.
2750 @cindex @code{\t} (tab)
2751 @cindex tab (@code{\t})
2753 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2756 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2757 @c @item \x @var{digit} @var{digit} @var{digit}
2758 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2760 @cindex @code{\@var{ddd}} (octal character code)
2761 @cindex octal character code (@code{\@var{ddd}})
2762 @item \ @var{digit} @var{digit} @var{digit}
2763 An octal character code. The numeric code is 3 octal digits.
2764 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2765 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2767 @cindex @code{\@var{xd...}} (hex character code)
2768 @cindex hex character code (@code{\@var{xd...}})
2769 @item \@code{x} @var{hex-digits...}
2770 A hex character code. All trailing hex digits are combined. Either upper or
2771 lower case @code{x} works.
2773 @cindex @code{\\} (@samp{\} character)
2774 @cindex backslash (@code{\\})
2776 Represents one @samp{\} character.
2779 @c Represents one @samp{'} (accent acute) character.
2780 @c This is needed in single character literals
2781 @c (@xref{Characters,,Character Constants}.) to represent
2784 @cindex @code{\"} (doublequote character)
2785 @cindex doublequote (@code{\"})
2787 Represents one @samp{"} character. Needed in strings to represent
2788 this character, because an unescaped @samp{"} would end the string.
2790 @item \ @var{anything-else}
2791 Any other character when escaped by @kbd{\} gives a warning, but
2792 assembles as if the @samp{\} was not present. The idea is that if
2793 you used an escape sequence you clearly didn't want the literal
2794 interpretation of the following character. However @command{@value{AS}} has no
2795 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2796 code and warns you of the fact.
2799 Which characters are escapable, and what those escapes represent,
2800 varies widely among assemblers. The current set is what we think
2801 the BSD 4.2 assembler recognizes, and is a subset of what most C
2802 compilers recognize. If you are in doubt, do not use an escape
2806 @subsubsection Characters
2808 @cindex single character constant
2809 @cindex character, single
2810 @cindex constant, single character
2811 A single character may be written as a single quote immediately
2812 followed by that character. The same escapes apply to characters as
2813 to strings. So if you want to write the character backslash, you
2814 must write @kbd{'\\} where the first @code{\} escapes the second
2815 @code{\}. As you can see, the quote is an acute accent, not a
2816 grave accent. A newline
2818 @ifclear abnormal-separator
2819 (or semicolon @samp{;})
2821 @ifset abnormal-separator
2823 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2828 immediately following an acute accent is taken as a literal character
2829 and does not count as the end of a statement. The value of a character
2830 constant in a numeric expression is the machine's byte-wide code for
2831 that character. @command{@value{AS}} assumes your character code is ASCII:
2832 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2835 @subsection Number Constants
2837 @cindex constants, number
2838 @cindex number constants
2839 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2840 are stored in the target machine. @emph{Integers} are numbers that
2841 would fit into an @code{int} in the C language. @emph{Bignums} are
2842 integers, but they are stored in more than 32 bits. @emph{Flonums}
2843 are floating point numbers, described below.
2846 * Integers:: Integers
2851 * Bit Fields:: Bit Fields
2857 @subsubsection Integers
2859 @cindex constants, integer
2861 @cindex binary integers
2862 @cindex integers, binary
2863 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2864 the binary digits @samp{01}.
2866 @cindex octal integers
2867 @cindex integers, octal
2868 An octal integer is @samp{0} followed by zero or more of the octal
2869 digits (@samp{01234567}).
2871 @cindex decimal integers
2872 @cindex integers, decimal
2873 A decimal integer starts with a non-zero digit followed by zero or
2874 more digits (@samp{0123456789}).
2876 @cindex hexadecimal integers
2877 @cindex integers, hexadecimal
2878 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2879 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2881 Integers have the usual values. To denote a negative integer, use
2882 the prefix operator @samp{-} discussed under expressions
2883 (@pxref{Prefix Ops,,Prefix Operators}).
2886 @subsubsection Bignums
2889 @cindex constants, bignum
2890 A @dfn{bignum} has the same syntax and semantics as an integer
2891 except that the number (or its negative) takes more than 32 bits to
2892 represent in binary. The distinction is made because in some places
2893 integers are permitted while bignums are not.
2896 @subsubsection Flonums
2898 @cindex floating point numbers
2899 @cindex constants, floating point
2901 @cindex precision, floating point
2902 A @dfn{flonum} represents a floating point number. The translation is
2903 indirect: a decimal floating point number from the text is converted by
2904 @command{@value{AS}} to a generic binary floating point number of more than
2905 sufficient precision. This generic floating point number is converted
2906 to a particular computer's floating point format (or formats) by a
2907 portion of @command{@value{AS}} specialized to that computer.
2909 A flonum is written by writing (in order)
2914 (@samp{0} is optional on the HPPA.)
2918 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2920 @kbd{e} is recommended. Case is not important.
2922 @c FIXME: verify if flonum syntax really this vague for most cases
2923 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2924 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2927 On the H8/300, Renesas / SuperH SH,
2928 and AMD 29K architectures, the letter must be
2929 one of the letters @samp{DFPRSX} (in upper or lower case).
2931 On the ARC, the letter must be one of the letters @samp{DFRS}
2932 (in upper or lower case).
2934 On the Intel 960 architecture, the letter must be
2935 one of the letters @samp{DFT} (in upper or lower case).
2937 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2941 One of the letters @samp{DFRS} (in upper or lower case).
2944 One of the letters @samp{DFPRSX} (in upper or lower case).
2947 The letter @samp{E} (upper case only).
2950 One of the letters @samp{DFT} (in upper or lower case).
2955 An optional sign: either @samp{+} or @samp{-}.
2958 An optional @dfn{integer part}: zero or more decimal digits.
2961 An optional @dfn{fractional part}: @samp{.} followed by zero
2962 or more decimal digits.
2965 An optional exponent, consisting of:
2969 An @samp{E} or @samp{e}.
2970 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2971 @c principle this can perfectly well be different on different targets.
2973 Optional sign: either @samp{+} or @samp{-}.
2975 One or more decimal digits.
2980 At least one of the integer part or the fractional part must be
2981 present. The floating point number has the usual base-10 value.
2983 @command{@value{AS}} does all processing using integers. Flonums are computed
2984 independently of any floating point hardware in the computer running
2985 @command{@value{AS}}.
2989 @c Bit fields are written as a general facility but are also controlled
2990 @c by a conditional-compilation flag---which is as of now (21mar91)
2991 @c turned on only by the i960 config of GAS.
2993 @subsubsection Bit Fields
2996 @cindex constants, bit field
2997 You can also define numeric constants as @dfn{bit fields}.
2998 Specify two numbers separated by a colon---
3000 @var{mask}:@var{value}
3003 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3006 The resulting number is then packed
3008 @c this conditional paren in case bit fields turned on elsewhere than 960
3009 (in host-dependent byte order)
3011 into a field whose width depends on which assembler directive has the
3012 bit-field as its argument. Overflow (a result from the bitwise and
3013 requiring more binary digits to represent) is not an error; instead,
3014 more constants are generated, of the specified width, beginning with the
3015 least significant digits.@refill
3017 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3018 @code{.short}, and @code{.word} accept bit-field arguments.
3023 @chapter Sections and Relocation
3028 * Secs Background:: Background
3029 * Ld Sections:: Linker Sections
3030 * As Sections:: Assembler Internal Sections
3031 * Sub-Sections:: Sub-Sections
3035 @node Secs Background
3038 Roughly, a section is a range of addresses, with no gaps; all data
3039 ``in'' those addresses is treated the same for some particular purpose.
3040 For example there may be a ``read only'' section.
3042 @cindex linker, and assembler
3043 @cindex assembler, and linker
3044 The linker @code{@value{LD}} reads many object files (partial programs) and
3045 combines their contents to form a runnable program. When @command{@value{AS}}
3046 emits an object file, the partial program is assumed to start at address 0.
3047 @code{@value{LD}} assigns the final addresses for the partial program, so that
3048 different partial programs do not overlap. This is actually an
3049 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3052 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3053 addresses. These blocks slide to their run-time addresses as rigid
3054 units; their length does not change and neither does the order of bytes
3055 within them. Such a rigid unit is called a @emph{section}. Assigning
3056 run-time addresses to sections is called @dfn{relocation}. It includes
3057 the task of adjusting mentions of object-file addresses so they refer to
3058 the proper run-time addresses.
3060 For the H8/300, and for the Renesas / SuperH SH,
3061 @command{@value{AS}} pads sections if needed to
3062 ensure they end on a word (sixteen bit) boundary.
3065 @cindex standard assembler sections
3066 An object file written by @command{@value{AS}} has at least three sections, any
3067 of which may be empty. These are named @dfn{text}, @dfn{data} and
3072 When it generates COFF or ELF output,
3074 @command{@value{AS}} can also generate whatever other named sections you specify
3075 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3076 If you do not use any directives that place output in the @samp{.text}
3077 or @samp{.data} sections, these sections still exist, but are empty.
3082 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3084 @command{@value{AS}} can also generate whatever other named sections you
3085 specify using the @samp{.space} and @samp{.subspace} directives. See
3086 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3087 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3088 assembler directives.
3091 Additionally, @command{@value{AS}} uses different names for the standard
3092 text, data, and bss sections when generating SOM output. Program text
3093 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3094 BSS into @samp{$BSS$}.
3098 Within the object file, the text section starts at address @code{0}, the
3099 data section follows, and the bss section follows the data section.
3102 When generating either SOM or ELF output files on the HPPA, the text
3103 section starts at address @code{0}, the data section at address
3104 @code{0x4000000}, and the bss section follows the data section.
3107 To let @code{@value{LD}} know which data changes when the sections are
3108 relocated, and how to change that data, @command{@value{AS}} also writes to the
3109 object file details of the relocation needed. To perform relocation
3110 @code{@value{LD}} must know, each time an address in the object
3114 Where in the object file is the beginning of this reference to
3117 How long (in bytes) is this reference?
3119 Which section does the address refer to? What is the numeric value of
3121 (@var{address}) @minus{} (@var{start-address of section})?
3124 Is the reference to an address ``Program-Counter relative''?
3127 @cindex addresses, format of
3128 @cindex section-relative addressing
3129 In fact, every address @command{@value{AS}} ever uses is expressed as
3131 (@var{section}) + (@var{offset into section})
3134 Further, most expressions @command{@value{AS}} computes have this section-relative
3137 (For some object formats, such as SOM for the HPPA, some expressions are
3138 symbol-relative instead.)
3141 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3142 @var{N} into section @var{secname}.''
3144 Apart from text, data and bss sections you need to know about the
3145 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3146 addresses in the absolute section remain unchanged. For example, address
3147 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3148 @code{@value{LD}}. Although the linker never arranges two partial programs'
3149 data sections with overlapping addresses after linking, @emph{by definition}
3150 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3151 part of a program is always the same address when the program is running as
3152 address @code{@{absolute@ 239@}} in any other part of the program.
3154 The idea of sections is extended to the @dfn{undefined} section. Any
3155 address whose section is unknown at assembly time is by definition
3156 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3157 Since numbers are always defined, the only way to generate an undefined
3158 address is to mention an undefined symbol. A reference to a named
3159 common block would be such a symbol: its value is unknown at assembly
3160 time so it has section @emph{undefined}.
3162 By analogy the word @emph{section} is used to describe groups of sections in
3163 the linked program. @code{@value{LD}} puts all partial programs' text
3164 sections in contiguous addresses in the linked program. It is
3165 customary to refer to the @emph{text section} of a program, meaning all
3166 the addresses of all partial programs' text sections. Likewise for
3167 data and bss sections.
3169 Some sections are manipulated by @code{@value{LD}}; others are invented for
3170 use of @command{@value{AS}} and have no meaning except during assembly.
3173 @section Linker Sections
3174 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3179 @cindex named sections
3180 @cindex sections, named
3181 @item named sections
3184 @cindex text section
3185 @cindex data section
3189 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3190 separate but equal sections. Anything you can say of one section is
3193 When the program is running, however, it is
3194 customary for the text section to be unalterable. The
3195 text section is often shared among processes: it contains
3196 instructions, constants and the like. The data section of a running
3197 program is usually alterable: for example, C variables would be stored
3198 in the data section.
3203 This section contains zeroed bytes when your program begins running. It
3204 is used to hold uninitialized variables or common storage. The length of
3205 each partial program's bss section is important, but because it starts
3206 out containing zeroed bytes there is no need to store explicit zero
3207 bytes in the object file. The bss section was invented to eliminate
3208 those explicit zeros from object files.
3210 @cindex absolute section
3211 @item absolute section
3212 Address 0 of this section is always ``relocated'' to runtime address 0.
3213 This is useful if you want to refer to an address that @code{@value{LD}} must
3214 not change when relocating. In this sense we speak of absolute
3215 addresses being ``unrelocatable'': they do not change during relocation.
3217 @cindex undefined section
3218 @item undefined section
3219 This ``section'' is a catch-all for address references to objects not in
3220 the preceding sections.
3221 @c FIXME: ref to some other doc on obj-file formats could go here.
3224 @cindex relocation example
3225 An idealized example of three relocatable sections follows.
3227 The example uses the traditional section names @samp{.text} and @samp{.data}.
3229 Memory addresses are on the horizontal axis.
3233 @c END TEXI2ROFF-KILL
3236 partial program # 1: |ttttt|dddd|00|
3243 partial program # 2: |TTT|DDD|000|
3246 +--+---+-----+--+----+---+-----+~~
3247 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3248 +--+---+-----+--+----+---+-----+~~
3250 addresses: 0 @dots{}
3257 \line{\it Partial program \#1: \hfil}
3258 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3259 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3261 \line{\it Partial program \#2: \hfil}
3262 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3263 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3265 \line{\it linked program: \hfil}
3266 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3267 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3268 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3269 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3271 \line{\it addresses: \hfil}
3275 @c END TEXI2ROFF-KILL
3278 @section Assembler Internal Sections
3280 @cindex internal assembler sections
3281 @cindex sections in messages, internal
3282 These sections are meant only for the internal use of @command{@value{AS}}. They
3283 have no meaning at run-time. You do not really need to know about these
3284 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3285 warning messages, so it might be helpful to have an idea of their
3286 meanings to @command{@value{AS}}. These sections are used to permit the
3287 value of every expression in your assembly language program to be a
3288 section-relative address.
3291 @cindex assembler internal logic error
3292 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3293 An internal assembler logic error has been found. This means there is a
3294 bug in the assembler.
3296 @cindex expr (internal section)
3298 The assembler stores complex expression internally as combinations of
3299 symbols. When it needs to represent an expression as a symbol, it puts
3300 it in the expr section.
3302 @c FIXME item transfer[t] vector preload
3303 @c FIXME item transfer[t] vector postload
3304 @c FIXME item register
3308 @section Sub-Sections
3310 @cindex numbered subsections
3311 @cindex grouping data
3317 fall into two sections: text and data.
3319 You may have separate groups of
3321 data in named sections
3325 data in named sections
3331 that you want to end up near to each other in the object file, even though they
3332 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3333 use @dfn{subsections} for this purpose. Within each section, there can be
3334 numbered subsections with values from 0 to 8192. Objects assembled into the
3335 same subsection go into the object file together with other objects in the same
3336 subsection. For example, a compiler might want to store constants in the text
3337 section, but might not want to have them interspersed with the program being
3338 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3339 section of code being output, and a @samp{.text 1} before each group of
3340 constants being output.
3342 Subsections are optional. If you do not use subsections, everything
3343 goes in subsection number zero.
3346 Each subsection is zero-padded up to a multiple of four bytes.
3347 (Subsections may be padded a different amount on different flavors
3348 of @command{@value{AS}}.)
3352 On the H8/300 platform, each subsection is zero-padded to a word
3353 boundary (two bytes).
3354 The same is true on the Renesas SH.
3357 @c FIXME section padding (alignment)?
3358 @c Rich Pixley says padding here depends on target obj code format; that
3359 @c doesn't seem particularly useful to say without further elaboration,
3360 @c so for now I say nothing about it. If this is a generic BFD issue,
3361 @c these paragraphs might need to vanish from this manual, and be
3362 @c discussed in BFD chapter of binutils (or some such).
3366 Subsections appear in your object file in numeric order, lowest numbered
3367 to highest. (All this to be compatible with other people's assemblers.)
3368 The object file contains no representation of subsections; @code{@value{LD}} and
3369 other programs that manipulate object files see no trace of them.
3370 They just see all your text subsections as a text section, and all your
3371 data subsections as a data section.
3373 To specify which subsection you want subsequent statements assembled
3374 into, use a numeric argument to specify it, in a @samp{.text
3375 @var{expression}} or a @samp{.data @var{expression}} statement.
3378 When generating COFF output, you
3383 can also use an extra subsection
3384 argument with arbitrary named sections: @samp{.section @var{name},
3389 When generating ELF output, you
3394 can also use the @code{.subsection} directive (@pxref{SubSection})
3395 to specify a subsection: @samp{.subsection @var{expression}}.
3397 @var{Expression} should be an absolute expression
3398 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3399 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3400 begins in @code{text 0}. For instance:
3402 .text 0 # The default subsection is text 0 anyway.
3403 .ascii "This lives in the first text subsection. *"
3405 .ascii "But this lives in the second text subsection."
3407 .ascii "This lives in the data section,"
3408 .ascii "in the first data subsection."
3410 .ascii "This lives in the first text section,"
3411 .ascii "immediately following the asterisk (*)."
3414 Each section has a @dfn{location counter} incremented by one for every byte
3415 assembled into that section. Because subsections are merely a convenience
3416 restricted to @command{@value{AS}} there is no concept of a subsection location
3417 counter. There is no way to directly manipulate a location counter---but the
3418 @code{.align} directive changes it, and any label definition captures its
3419 current value. The location counter of the section where statements are being
3420 assembled is said to be the @dfn{active} location counter.
3423 @section bss Section
3426 @cindex common variable storage
3427 The bss section is used for local common variable storage.
3428 You may allocate address space in the bss section, but you may
3429 not dictate data to load into it before your program executes. When
3430 your program starts running, all the contents of the bss
3431 section are zeroed bytes.
3433 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3434 @ref{Lcomm,,@code{.lcomm}}.
3436 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3437 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3440 When assembling for a target which supports multiple sections, such as ELF or
3441 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3442 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3443 section. Typically the section will only contain symbol definitions and
3444 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3451 Symbols are a central concept: the programmer uses symbols to name
3452 things, the linker uses symbols to link, and the debugger uses symbols
3456 @cindex debuggers, and symbol order
3457 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3458 the same order they were declared. This may break some debuggers.
3463 * Setting Symbols:: Giving Symbols Other Values
3464 * Symbol Names:: Symbol Names
3465 * Dot:: The Special Dot Symbol
3466 * Symbol Attributes:: Symbol Attributes
3473 A @dfn{label} is written as a symbol immediately followed by a colon
3474 @samp{:}. The symbol then represents the current value of the
3475 active location counter, and is, for example, a suitable instruction
3476 operand. You are warned if you use the same symbol to represent two
3477 different locations: the first definition overrides any other
3481 On the HPPA, the usual form for a label need not be immediately followed by a
3482 colon, but instead must start in column zero. Only one label may be defined on
3483 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3484 provides a special directive @code{.label} for defining labels more flexibly.
3487 @node Setting Symbols
3488 @section Giving Symbols Other Values
3490 @cindex assigning values to symbols
3491 @cindex symbol values, assigning
3492 A symbol can be given an arbitrary value by writing a symbol, followed
3493 by an equals sign @samp{=}, followed by an expression
3494 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3495 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3496 equals sign @samp{=}@samp{=} here represents an equivalent of the
3497 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3500 Blackfin does not support symbol assignment with @samp{=}.
3504 @section Symbol Names
3506 @cindex symbol names
3507 @cindex names, symbol
3508 @ifclear SPECIAL-SYMS
3509 Symbol names begin with a letter or with one of @samp{._}. On most
3510 machines, you can also use @code{$} in symbol names; exceptions are
3511 noted in @ref{Machine Dependencies}. That character may be followed by any
3512 string of digits, letters, dollar signs (unless otherwise noted for a
3513 particular target machine), and underscores.
3517 Symbol names begin with a letter or with one of @samp{._}. On the
3518 Renesas SH you can also use @code{$} in symbol names. That
3519 character may be followed by any string of digits, letters, dollar signs (save
3520 on the H8/300), and underscores.
3524 Case of letters is significant: @code{foo} is a different symbol name
3527 Multibyte characters are supported. To generate a symbol name containing
3528 multibyte characters enclose it within double quotes and use escape codes. cf
3529 @xref{Strings}. Generating a multibyte symbol name from a label is not
3530 currently supported.
3532 Each symbol has exactly one name. Each name in an assembly language program
3533 refers to exactly one symbol. You may use that symbol name any number of times
3536 @subheading Local Symbol Names
3538 @cindex local symbol names
3539 @cindex symbol names, local
3540 A local symbol is any symbol beginning with certain local label prefixes.
3541 By default, the local label prefix is @samp{.L} for ELF systems or
3542 @samp{L} for traditional a.out systems, but each target may have its own
3543 set of local label prefixes.
3545 On the HPPA local symbols begin with @samp{L$}.
3548 Local symbols are defined and used within the assembler, but they are
3549 normally not saved in object files. Thus, they are not visible when debugging.
3550 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3551 @option{-L}}) to retain the local symbols in the object files.
3553 @subheading Local Labels
3555 @cindex local labels
3556 @cindex temporary symbol names
3557 @cindex symbol names, temporary
3558 Local labels help compilers and programmers use names temporarily.
3559 They create symbols which are guaranteed to be unique over the entire scope of
3560 the input source code and which can be referred to by a simple notation.
3561 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3562 represents any positive integer). To refer to the most recent previous
3563 definition of that label write @samp{@b{N}b}, using the same number as when
3564 you defined the label. To refer to the next definition of a local label, write
3565 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3568 There is no restriction on how you can use these labels, and you can reuse them
3569 too. So that it is possible to repeatedly define the same local label (using
3570 the same number @samp{@b{N}}), although you can only refer to the most recently
3571 defined local label of that number (for a backwards reference) or the next
3572 definition of a specific local label for a forward reference. It is also worth
3573 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3574 implemented in a slightly more efficient manner than the others.
3585 Which is the equivalent of:
3588 label_1: branch label_3
3589 label_2: branch label_1
3590 label_3: branch label_4
3591 label_4: branch label_3
3594 Local label names are only a notational device. They are immediately
3595 transformed into more conventional symbol names before the assembler uses them.
3596 The symbol names are stored in the symbol table, appear in error messages, and
3597 are optionally emitted to the object file. The names are constructed using
3601 @item @emph{local label prefix}
3602 All local symbols begin with the system-specific local label prefix.
3603 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3604 that start with the local label prefix. These labels are
3605 used for symbols you are never intended to see. If you use the
3606 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3607 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3608 you may use them in debugging.
3611 This is the number that was used in the local label definition. So if the
3612 label is written @samp{55:} then the number is @samp{55}.
3615 This unusual character is included so you do not accidentally invent a symbol
3616 of the same name. The character has ASCII value of @samp{\002} (control-B).
3618 @item @emph{ordinal number}
3619 This is a serial number to keep the labels distinct. The first definition of
3620 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3621 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3622 the number @samp{1} and its 15th definition gets @samp{15} as well.
3625 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3626 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3628 @subheading Dollar Local Labels
3629 @cindex dollar local symbols
3631 @code{@value{AS}} also supports an even more local form of local labels called
3632 dollar labels. These labels go out of scope (i.e., they become undefined) as
3633 soon as a non-local label is defined. Thus they remain valid for only a small
3634 region of the input source code. Normal local labels, by contrast, remain in
3635 scope for the entire file, or until they are redefined by another occurrence of
3636 the same local label.
3638 Dollar labels are defined in exactly the same way as ordinary local labels,
3639 except that they have a dollar sign suffix to their numeric value, e.g.,
3642 They can also be distinguished from ordinary local labels by their transformed
3643 names which use ASCII character @samp{\001} (control-A) as the magic character
3644 to distinguish them from ordinary labels. For example, the fifth definition of
3645 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3648 @section The Special Dot Symbol
3650 @cindex dot (symbol)
3651 @cindex @code{.} (symbol)
3652 @cindex current address
3653 @cindex location counter
3654 The special symbol @samp{.} refers to the current address that
3655 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3656 .long .} defines @code{melvin} to contain its own address.
3657 Assigning a value to @code{.} is treated the same as a @code{.org}
3659 @ifclear no-space-dir
3660 Thus, the expression @samp{.=.+4} is the same as saying
3664 @node Symbol Attributes
3665 @section Symbol Attributes
3667 @cindex symbol attributes
3668 @cindex attributes, symbol
3669 Every symbol has, as well as its name, the attributes ``Value'' and
3670 ``Type''. Depending on output format, symbols can also have auxiliary
3673 The detailed definitions are in @file{a.out.h}.
3676 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3677 all these attributes, and probably won't warn you. This makes the
3678 symbol an externally defined symbol, which is generally what you
3682 * Symbol Value:: Value
3683 * Symbol Type:: Type
3686 * a.out Symbols:: Symbol Attributes: @code{a.out}
3690 * a.out Symbols:: Symbol Attributes: @code{a.out}
3693 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3698 * COFF Symbols:: Symbol Attributes for COFF
3701 * SOM Symbols:: Symbol Attributes for SOM
3708 @cindex value of a symbol
3709 @cindex symbol value
3710 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3711 location in the text, data, bss or absolute sections the value is the
3712 number of addresses from the start of that section to the label.
3713 Naturally for text, data and bss sections the value of a symbol changes
3714 as @code{@value{LD}} changes section base addresses during linking. Absolute
3715 symbols' values do not change during linking: that is why they are
3718 The value of an undefined symbol is treated in a special way. If it is
3719 0 then the symbol is not defined in this assembler source file, and
3720 @code{@value{LD}} tries to determine its value from other files linked into the
3721 same program. You make this kind of symbol simply by mentioning a symbol
3722 name without defining it. A non-zero value represents a @code{.comm}
3723 common declaration. The value is how much common storage to reserve, in
3724 bytes (addresses). The symbol refers to the first address of the
3730 @cindex type of a symbol
3732 The type attribute of a symbol contains relocation (section)
3733 information, any flag settings indicating that a symbol is external, and
3734 (optionally), other information for linkers and debuggers. The exact
3735 format depends on the object-code output format in use.
3740 @c The following avoids a "widow" subsection title. @group would be
3741 @c better if it were available outside examples.
3744 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3746 @cindex @code{b.out} symbol attributes
3747 @cindex symbol attributes, @code{b.out}
3748 These symbol attributes appear only when @command{@value{AS}} is configured for
3749 one of the Berkeley-descended object output formats---@code{a.out} or
3755 @subsection Symbol Attributes: @code{a.out}
3757 @cindex @code{a.out} symbol attributes
3758 @cindex symbol attributes, @code{a.out}
3764 @subsection Symbol Attributes: @code{a.out}
3766 @cindex @code{a.out} symbol attributes
3767 @cindex symbol attributes, @code{a.out}
3771 * Symbol Desc:: Descriptor
3772 * Symbol Other:: Other
3776 @subsubsection Descriptor
3778 @cindex descriptor, of @code{a.out} symbol
3779 This is an arbitrary 16-bit value. You may establish a symbol's
3780 descriptor value by using a @code{.desc} statement
3781 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3782 @command{@value{AS}}.
3785 @subsubsection Other
3787 @cindex other attribute, of @code{a.out} symbol
3788 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3793 @subsection Symbol Attributes for COFF
3795 @cindex COFF symbol attributes
3796 @cindex symbol attributes, COFF
3798 The COFF format supports a multitude of auxiliary symbol attributes;
3799 like the primary symbol attributes, they are set between @code{.def} and
3800 @code{.endef} directives.
3802 @subsubsection Primary Attributes
3804 @cindex primary attributes, COFF symbols
3805 The symbol name is set with @code{.def}; the value and type,
3806 respectively, with @code{.val} and @code{.type}.
3808 @subsubsection Auxiliary Attributes
3810 @cindex auxiliary attributes, COFF symbols
3811 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3812 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3813 table information for COFF.
3818 @subsection Symbol Attributes for SOM
3820 @cindex SOM symbol attributes
3821 @cindex symbol attributes, SOM
3823 The SOM format for the HPPA supports a multitude of symbol attributes set with
3824 the @code{.EXPORT} and @code{.IMPORT} directives.
3826 The attributes are described in @cite{HP9000 Series 800 Assembly
3827 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3828 @code{EXPORT} assembler directive documentation.
3832 @chapter Expressions
3836 @cindex numeric values
3837 An @dfn{expression} specifies an address or numeric value.
3838 Whitespace may precede and/or follow an expression.
3840 The result of an expression must be an absolute number, or else an offset into
3841 a particular section. If an expression is not absolute, and there is not
3842 enough information when @command{@value{AS}} sees the expression to know its
3843 section, a second pass over the source program might be necessary to interpret
3844 the expression---but the second pass is currently not implemented.
3845 @command{@value{AS}} aborts with an error message in this situation.
3848 * Empty Exprs:: Empty Expressions
3849 * Integer Exprs:: Integer Expressions
3853 @section Empty Expressions
3855 @cindex empty expressions
3856 @cindex expressions, empty
3857 An empty expression has no value: it is just whitespace or null.
3858 Wherever an absolute expression is required, you may omit the
3859 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3860 is compatible with other assemblers.
3863 @section Integer Expressions
3865 @cindex integer expressions
3866 @cindex expressions, integer
3867 An @dfn{integer expression} is one or more @emph{arguments} delimited
3868 by @emph{operators}.
3871 * Arguments:: Arguments
3872 * Operators:: Operators
3873 * Prefix Ops:: Prefix Operators
3874 * Infix Ops:: Infix Operators
3878 @subsection Arguments
3880 @cindex expression arguments
3881 @cindex arguments in expressions
3882 @cindex operands in expressions
3883 @cindex arithmetic operands
3884 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3885 contexts arguments are sometimes called ``arithmetic operands''. In
3886 this manual, to avoid confusing them with the ``instruction operands'' of
3887 the machine language, we use the term ``argument'' to refer to parts of
3888 expressions only, reserving the word ``operand'' to refer only to machine
3889 instruction operands.
3891 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3892 @var{section} is one of text, data, bss, absolute,
3893 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3896 Numbers are usually integers.
3898 A number can be a flonum or bignum. In this case, you are warned
3899 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3900 these 32 bits are an integer. You may write integer-manipulating
3901 instructions that act on exotic constants, compatible with other
3904 @cindex subexpressions
3905 Subexpressions are a left parenthesis @samp{(} followed by an integer
3906 expression, followed by a right parenthesis @samp{)}; or a prefix
3907 operator followed by an argument.
3910 @subsection Operators
3912 @cindex operators, in expressions
3913 @cindex arithmetic functions
3914 @cindex functions, in expressions
3915 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3916 operators are followed by an argument. Infix operators appear
3917 between their arguments. Operators may be preceded and/or followed by
3921 @subsection Prefix Operator
3923 @cindex prefix operators
3924 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3925 one argument, which must be absolute.
3927 @c the tex/end tex stuff surrounding this small table is meant to make
3928 @c it align, on the printed page, with the similar table in the next
3929 @c section (which is inside an enumerate).
3931 \global\advance\leftskip by \itemindent
3936 @dfn{Negation}. Two's complement negation.
3938 @dfn{Complementation}. Bitwise not.
3942 \global\advance\leftskip by -\itemindent
3946 @subsection Infix Operators
3948 @cindex infix operators
3949 @cindex operators, permitted arguments
3950 @dfn{Infix operators} take two arguments, one on either side. Operators
3951 have precedence, but operations with equal precedence are performed left
3952 to right. Apart from @code{+} or @option{-}, both arguments must be
3953 absolute, and the result is absolute.
3956 @cindex operator precedence
3957 @cindex precedence of operators
3964 @dfn{Multiplication}.
3967 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3973 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3976 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3980 Intermediate precedence
3985 @dfn{Bitwise Inclusive Or}.
3991 @dfn{Bitwise Exclusive Or}.
3994 @dfn{Bitwise Or Not}.
4001 @cindex addition, permitted arguments
4002 @cindex plus, permitted arguments
4003 @cindex arguments for addition
4005 @dfn{Addition}. If either argument is absolute, the result has the section of
4006 the other argument. You may not add together arguments from different
4009 @cindex subtraction, permitted arguments
4010 @cindex minus, permitted arguments
4011 @cindex arguments for subtraction
4013 @dfn{Subtraction}. If the right argument is absolute, the
4014 result has the section of the left argument.
4015 If both arguments are in the same section, the result is absolute.
4016 You may not subtract arguments from different sections.
4017 @c FIXME is there still something useful to say about undefined - undefined ?
4019 @cindex comparison expressions
4020 @cindex expressions, comparison
4025 @dfn{Is Not Equal To}
4029 @dfn{Is Greater Than}
4031 @dfn{Is Greater Than Or Equal To}
4033 @dfn{Is Less Than Or Equal To}
4035 The comparison operators can be used as infix operators. A true results has a
4036 value of -1 whereas a false result has a value of 0. Note, these operators
4037 perform signed comparisons.
4040 @item Lowest Precedence
4049 These two logical operations can be used to combine the results of sub
4050 expressions. Note, unlike the comparison operators a true result returns a
4051 value of 1 but a false results does still return 0. Also note that the logical
4052 or operator has a slightly lower precedence than logical and.
4057 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4058 address; you can only have a defined section in one of the two arguments.
4061 @chapter Assembler Directives
4063 @cindex directives, machine independent
4064 @cindex pseudo-ops, machine independent
4065 @cindex machine independent directives
4066 All assembler directives have names that begin with a period (@samp{.}).
4067 The rest of the name is letters, usually in lower case.
4069 This chapter discusses directives that are available regardless of the
4070 target machine configuration for the @sc{gnu} assembler.
4072 Some machine configurations provide additional directives.
4073 @xref{Machine Dependencies}.
4076 @ifset machine-directives
4077 @xref{Machine Dependencies}, for additional directives.
4082 * Abort:: @code{.abort}
4084 * ABORT (COFF):: @code{.ABORT}
4087 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4088 * Altmacro:: @code{.altmacro}
4089 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4090 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4091 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4092 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4093 * Byte:: @code{.byte @var{expressions}}
4094 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4095 * Comm:: @code{.comm @var{symbol} , @var{length} }
4096 * Data:: @code{.data @var{subsection}}
4098 * Def:: @code{.def @var{name}}
4101 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4107 * Double:: @code{.double @var{flonums}}
4108 * Eject:: @code{.eject}
4109 * Else:: @code{.else}
4110 * Elseif:: @code{.elseif}
4113 * Endef:: @code{.endef}
4116 * Endfunc:: @code{.endfunc}
4117 * Endif:: @code{.endif}
4118 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4119 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4120 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4122 * Error:: @code{.error @var{string}}
4123 * Exitm:: @code{.exitm}
4124 * Extern:: @code{.extern}
4125 * Fail:: @code{.fail}
4126 * File:: @code{.file}
4127 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4128 * Float:: @code{.float @var{flonums}}
4129 * Func:: @code{.func}
4130 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4132 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4133 * Hidden:: @code{.hidden @var{names}}
4136 * hword:: @code{.hword @var{expressions}}
4137 * Ident:: @code{.ident}
4138 * If:: @code{.if @var{absolute expression}}
4139 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4140 * Include:: @code{.include "@var{file}"}
4141 * Int:: @code{.int @var{expressions}}
4143 * Internal:: @code{.internal @var{names}}
4146 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4147 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4148 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4149 * Lflags:: @code{.lflags}
4150 @ifclear no-line-dir
4151 * Line:: @code{.line @var{line-number}}
4154 * Linkonce:: @code{.linkonce [@var{type}]}
4155 * List:: @code{.list}
4156 * Ln:: @code{.ln @var{line-number}}
4157 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4158 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4160 * Local:: @code{.local @var{names}}
4163 * Long:: @code{.long @var{expressions}}
4165 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4168 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4169 * MRI:: @code{.mri @var{val}}
4170 * Noaltmacro:: @code{.noaltmacro}
4171 * Nolist:: @code{.nolist}
4172 * Octa:: @code{.octa @var{bignums}}
4173 * Offset:: @code{.offset @var{loc}}
4174 * Org:: @code{.org @var{new-lc}, @var{fill}}
4175 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4177 * PopSection:: @code{.popsection}
4178 * Previous:: @code{.previous}
4181 * Print:: @code{.print @var{string}}
4183 * Protected:: @code{.protected @var{names}}
4186 * Psize:: @code{.psize @var{lines}, @var{columns}}
4187 * Purgem:: @code{.purgem @var{name}}
4189 * PushSection:: @code{.pushsection @var{name}}
4192 * Quad:: @code{.quad @var{bignums}}
4193 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4194 * Rept:: @code{.rept @var{count}}
4195 * Sbttl:: @code{.sbttl "@var{subheading}"}
4197 * Scl:: @code{.scl @var{class}}
4200 * Section:: @code{.section @var{name}[, @var{flags}]}
4203 * Set:: @code{.set @var{symbol}, @var{expression}}
4204 * Short:: @code{.short @var{expressions}}
4205 * Single:: @code{.single @var{flonums}}
4207 * Size:: @code{.size [@var{name} , @var{expression}]}
4209 @ifclear no-space-dir
4210 * Skip:: @code{.skip @var{size} , @var{fill}}
4213 * Sleb128:: @code{.sleb128 @var{expressions}}
4214 @ifclear no-space-dir
4215 * Space:: @code{.space @var{size} , @var{fill}}
4218 * Stab:: @code{.stabd, .stabn, .stabs}
4221 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4222 * Struct:: @code{.struct @var{expression}}
4224 * SubSection:: @code{.subsection}
4225 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4229 * Tag:: @code{.tag @var{structname}}
4232 * Text:: @code{.text @var{subsection}}
4233 * Title:: @code{.title "@var{heading}"}
4235 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4238 * Uleb128:: @code{.uleb128 @var{expressions}}
4240 * Val:: @code{.val @var{addr}}
4244 * Version:: @code{.version "@var{string}"}
4245 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4246 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4249 * Warning:: @code{.warning @var{string}}
4250 * Weak:: @code{.weak @var{names}}
4251 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4252 * Word:: @code{.word @var{expressions}}
4253 * Deprecated:: Deprecated Directives
4257 @section @code{.abort}
4259 @cindex @code{abort} directive
4260 @cindex stopping the assembly
4261 This directive stops the assembly immediately. It is for
4262 compatibility with other assemblers. The original idea was that the
4263 assembly language source would be piped into the assembler. If the sender
4264 of the source quit, it could use this directive tells @command{@value{AS}} to
4265 quit also. One day @code{.abort} will not be supported.
4269 @section @code{.ABORT} (COFF)
4271 @cindex @code{ABORT} directive
4272 When producing COFF output, @command{@value{AS}} accepts this directive as a
4273 synonym for @samp{.abort}.
4276 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4282 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4284 @cindex padding the location counter
4285 @cindex @code{align} directive
4286 Pad the location counter (in the current subsection) to a particular storage
4287 boundary. The first expression (which must be absolute) is the alignment
4288 required, as described below.
4290 The second expression (also absolute) gives the fill value to be stored in the
4291 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4292 padding bytes are normally zero. However, on some systems, if the section is
4293 marked as containing code and the fill value is omitted, the space is filled
4294 with no-op instructions.
4296 The third expression is also absolute, and is also optional. If it is present,
4297 it is the maximum number of bytes that should be skipped by this alignment
4298 directive. If doing the alignment would require skipping more bytes than the
4299 specified maximum, then the alignment is not done at all. You can omit the
4300 fill value (the second argument) entirely by simply using two commas after the
4301 required alignment; this can be useful if you want the alignment to be filled
4302 with no-op instructions when appropriate.
4304 The way the required alignment is specified varies from system to system.
4305 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4306 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4307 alignment request in bytes. For example @samp{.align 8} advances
4308 the location counter until it is a multiple of 8. If the location counter
4309 is already a multiple of 8, no change is needed. For the tic54x, the
4310 first expression is the alignment request in words.
4312 For other systems, including ppc, i386 using a.out format, arm and
4313 strongarm, it is the
4314 number of low-order zero bits the location counter must have after
4315 advancement. For example @samp{.align 3} advances the location
4316 counter until it a multiple of 8. If the location counter is already a
4317 multiple of 8, no change is needed.
4319 This inconsistency is due to the different behaviors of the various
4320 native assemblers for these systems which GAS must emulate.
4321 GAS also provides @code{.balign} and @code{.p2align} directives,
4322 described later, which have a consistent behavior across all
4323 architectures (but are specific to GAS).
4326 @section @code{.altmacro}
4327 Enable alternate macro mode, enabling:
4330 @item LOCAL @var{name} [ , @dots{} ]
4331 One additional directive, @code{LOCAL}, is available. It is used to
4332 generate a string replacement for each of the @var{name} arguments, and
4333 replace any instances of @var{name} in each macro expansion. The
4334 replacement string is unique in the assembly, and different for each
4335 separate macro expansion. @code{LOCAL} allows you to write macros that
4336 define symbols, without fear of conflict between separate macro expansions.
4338 @item String delimiters
4339 You can write strings delimited in these other ways besides
4340 @code{"@var{string}"}:
4343 @item '@var{string}'
4344 You can delimit strings with single-quote characters.
4346 @item <@var{string}>
4347 You can delimit strings with matching angle brackets.
4350 @item single-character string escape
4351 To include any single character literally in a string (even if the
4352 character would otherwise have some special meaning), you can prefix the
4353 character with @samp{!} (an exclamation mark). For example, you can
4354 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4356 @item Expression results as strings
4357 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4358 and use the result as a string.
4362 @section @code{.ascii "@var{string}"}@dots{}
4364 @cindex @code{ascii} directive
4365 @cindex string literals
4366 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4367 separated by commas. It assembles each string (with no automatic
4368 trailing zero byte) into consecutive addresses.
4371 @section @code{.asciz "@var{string}"}@dots{}
4373 @cindex @code{asciz} directive
4374 @cindex zero-terminated strings
4375 @cindex null-terminated strings
4376 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4377 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4380 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4382 @cindex padding the location counter given number of bytes
4383 @cindex @code{balign} directive
4384 Pad the location counter (in the current subsection) to a particular
4385 storage boundary. The first expression (which must be absolute) is the
4386 alignment request in bytes. For example @samp{.balign 8} advances
4387 the location counter until it is a multiple of 8. If the location counter
4388 is already a multiple of 8, no change is needed.
4390 The second expression (also absolute) gives the fill value to be stored in the
4391 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4392 padding bytes are normally zero. However, on some systems, if the section is
4393 marked as containing code and the fill value is omitted, the space is filled
4394 with no-op instructions.
4396 The third expression is also absolute, and is also optional. If it is present,
4397 it is the maximum number of bytes that should be skipped by this alignment
4398 directive. If doing the alignment would require skipping more bytes than the
4399 specified maximum, then the alignment is not done at all. You can omit the
4400 fill value (the second argument) entirely by simply using two commas after the
4401 required alignment; this can be useful if you want the alignment to be filled
4402 with no-op instructions when appropriate.
4404 @cindex @code{balignw} directive
4405 @cindex @code{balignl} directive
4406 The @code{.balignw} and @code{.balignl} directives are variants of the
4407 @code{.balign} directive. The @code{.balignw} directive treats the fill
4408 pattern as a two byte word value. The @code{.balignl} directives treats the
4409 fill pattern as a four byte longword value. For example, @code{.balignw
4410 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4411 filled in with the value 0x368d (the exact placement of the bytes depends upon
4412 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4415 @node Bundle directives
4416 @section @code{.bundle_align_mode @var{abs-expr}}
4417 @cindex @code{bundle_align_mode} directive
4419 @cindex instruction bundle
4420 @cindex aligned instruction bundle
4421 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4422 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4423 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4424 disabled (which is the default state). If the argument it not zero, it
4425 gives the size of an instruction bundle as a power of two (as for the
4426 @code{.p2align} directive, @pxref{P2align}).
4428 For some targets, it's an ABI requirement that no instruction may span a
4429 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4430 instructions that starts on an aligned boundary. For example, if
4431 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4432 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4433 effect, no single instruction may span a boundary between bundles. If an
4434 instruction would start too close to the end of a bundle for the length of
4435 that particular instruction to fit within the bundle, then the space at the
4436 end of that bundle is filled with no-op instructions so the instruction
4437 starts in the next bundle. As a corollary, it's an error if any single
4438 instruction's encoding is longer than the bundle size.
4440 @section @code{.bundle_lock} and @code{.bundle_unlock}
4441 @cindex @code{bundle_lock} directive
4442 @cindex @code{bundle_unlock} directive
4443 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4444 allow explicit control over instruction bundle padding. These directives
4445 are only valid when @code{.bundle_align_mode} has been used to enable
4446 aligned instruction bundle mode. It's an error if they appear when
4447 @code{.bundle_align_mode} has not been used at all, or when the last
4448 directive was @w{@code{.bundle_align_mode 0}}.
4450 @cindex bundle-locked
4451 For some targets, it's an ABI requirement that certain instructions may
4452 appear only as part of specified permissible sequences of multiple
4453 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4454 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4455 instruction sequence. For purposes of aligned instruction bundle mode, a
4456 sequence starting with @code{.bundle_lock} and ending with
4457 @code{.bundle_unlock} is treated as a single instruction. That is, the
4458 entire sequence must fit into a single bundle and may not span a bundle
4459 boundary. If necessary, no-op instructions will be inserted before the
4460 first instruction of the sequence so that the whole sequence starts on an
4461 aligned bundle boundary. It's an error if the sequence is longer than the
4464 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4465 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4466 nested. That is, a second @code{.bundle_lock} directive before the next
4467 @code{.bundle_unlock} directive has no effect except that it must be
4468 matched by another closing @code{.bundle_unlock} so that there is the
4469 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4472 @section @code{.byte @var{expressions}}
4474 @cindex @code{byte} directive
4475 @cindex integers, one byte
4476 @code{.byte} expects zero or more expressions, separated by commas.
4477 Each expression is assembled into the next byte.
4479 @node CFI directives
4480 @section @code{.cfi_sections @var{section_list}}
4481 @cindex @code{cfi_sections} directive
4482 @code{.cfi_sections} may be used to specify whether CFI directives
4483 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4484 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4485 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4486 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4487 directive is not used is @code{.cfi_sections .eh_frame}.
4489 @section @code{.cfi_startproc [simple]}
4490 @cindex @code{cfi_startproc} directive
4491 @code{.cfi_startproc} is used at the beginning of each function that
4492 should have an entry in @code{.eh_frame}. It initializes some internal
4493 data structures. Don't forget to close the function by
4494 @code{.cfi_endproc}.
4496 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4497 it also emits some architecture dependent initial CFI instructions.
4499 @section @code{.cfi_endproc}
4500 @cindex @code{cfi_endproc} directive
4501 @code{.cfi_endproc} is used at the end of a function where it closes its
4502 unwind entry previously opened by
4503 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4505 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4506 @code{.cfi_personality} defines personality routine and its encoding.
4507 @var{encoding} must be a constant determining how the personality
4508 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4509 argument is not present, otherwise second argument should be
4510 a constant or a symbol name. When using indirect encodings,
4511 the symbol provided should be the location where personality
4512 can be loaded from, not the personality routine itself.
4513 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4514 no personality routine.
4516 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4517 @code{.cfi_lsda} defines LSDA and its encoding.
4518 @var{encoding} must be a constant determining how the LSDA
4519 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4520 argument is not present, otherwise second argument should be a constant
4521 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4524 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4525 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4526 address from @var{register} and add @var{offset} to it}.
4528 @section @code{.cfi_def_cfa_register @var{register}}
4529 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4530 now on @var{register} will be used instead of the old one. Offset
4533 @section @code{.cfi_def_cfa_offset @var{offset}}
4534 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4535 remains the same, but @var{offset} is new. Note that it is the
4536 absolute offset that will be added to a defined register to compute
4539 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4540 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4541 value that is added/substracted from the previous offset.
4543 @section @code{.cfi_offset @var{register}, @var{offset}}
4544 Previous value of @var{register} is saved at offset @var{offset} from
4547 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4548 Previous value of @var{register} is saved at offset @var{offset} from
4549 the current CFA register. This is transformed to @code{.cfi_offset}
4550 using the known displacement of the CFA register from the CFA.
4551 This is often easier to use, because the number will match the
4552 code it's annotating.
4554 @section @code{.cfi_register @var{register1}, @var{register2}}
4555 Previous value of @var{register1} is saved in register @var{register2}.
4557 @section @code{.cfi_restore @var{register}}
4558 @code{.cfi_restore} says that the rule for @var{register} is now the
4559 same as it was at the beginning of the function, after all initial
4560 instruction added by @code{.cfi_startproc} were executed.
4562 @section @code{.cfi_undefined @var{register}}
4563 From now on the previous value of @var{register} can't be restored anymore.
4565 @section @code{.cfi_same_value @var{register}}
4566 Current value of @var{register} is the same like in the previous frame,
4567 i.e. no restoration needed.
4569 @section @code{.cfi_remember_state},
4570 First save all current rules for all registers by @code{.cfi_remember_state},
4571 then totally screw them up by subsequent @code{.cfi_*} directives and when
4572 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4573 the previous saved state.
4575 @section @code{.cfi_return_column @var{register}}
4576 Change return column @var{register}, i.e. the return address is either
4577 directly in @var{register} or can be accessed by rules for @var{register}.
4579 @section @code{.cfi_signal_frame}
4580 Mark current function as signal trampoline.
4582 @section @code{.cfi_window_save}
4583 SPARC register window has been saved.
4585 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4586 Allows the user to add arbitrary bytes to the unwind info. One
4587 might use this to add OS-specific CFI opcodes, or generic CFI
4588 opcodes that GAS does not yet support.
4590 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4591 The current value of @var{register} is @var{label}. The value of @var{label}
4592 will be encoded in the output file according to @var{encoding}; see the
4593 description of @code{.cfi_personality} for details on this encoding.
4595 The usefulness of equating a register to a fixed label is probably
4596 limited to the return address register. Here, it can be useful to
4597 mark a code segment that has only one return address which is reached
4598 by a direct branch and no copy of the return address exists in memory
4599 or another register.
4602 @section @code{.comm @var{symbol} , @var{length} }
4604 @cindex @code{comm} directive
4605 @cindex symbol, common
4606 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4607 common symbol in one object file may be merged with a defined or common symbol
4608 of the same name in another object file. If @code{@value{LD}} does not see a
4609 definition for the symbol--just one or more common symbols--then it will
4610 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4611 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4612 the same name, and they do not all have the same size, it will allocate space
4613 using the largest size.
4616 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4617 an optional third argument. This is the desired alignment of the symbol,
4618 specified for ELF as a byte boundary (for example, an alignment of 16 means
4619 that the least significant 4 bits of the address should be zero), and for PE
4620 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4621 boundary). The alignment must be an absolute expression, and it must be a
4622 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4623 common symbol, it will use the alignment when placing the symbol. If no
4624 alignment is specified, @command{@value{AS}} will set the alignment to the
4625 largest power of two less than or equal to the size of the symbol, up to a
4626 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4627 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4628 @samp{--section-alignment} option; image file sections in PE are aligned to
4629 multiples of 4096, which is far too large an alignment for ordinary variables.
4630 It is rather the default alignment for (non-debug) sections within object
4631 (@samp{*.o}) files, which are less strictly aligned.}.
4635 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4636 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4640 @section @code{.data @var{subsection}}
4642 @cindex @code{data} directive
4643 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4644 end of the data subsection numbered @var{subsection} (which is an
4645 absolute expression). If @var{subsection} is omitted, it defaults
4650 @section @code{.def @var{name}}
4652 @cindex @code{def} directive
4653 @cindex COFF symbols, debugging
4654 @cindex debugging COFF symbols
4655 Begin defining debugging information for a symbol @var{name}; the
4656 definition extends until the @code{.endef} directive is encountered.
4659 This directive is only observed when @command{@value{AS}} is configured for COFF
4660 format output; when producing @code{b.out}, @samp{.def} is recognized,
4667 @section @code{.desc @var{symbol}, @var{abs-expression}}
4669 @cindex @code{desc} directive
4670 @cindex COFF symbol descriptor
4671 @cindex symbol descriptor, COFF
4672 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4673 to the low 16 bits of an absolute expression.
4676 The @samp{.desc} directive is not available when @command{@value{AS}} is
4677 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4678 object format. For the sake of compatibility, @command{@value{AS}} accepts
4679 it, but produces no output, when configured for COFF.
4685 @section @code{.dim}
4687 @cindex @code{dim} directive
4688 @cindex COFF auxiliary symbol information
4689 @cindex auxiliary symbol information, COFF
4690 This directive is generated by compilers to include auxiliary debugging
4691 information in the symbol table. It is only permitted inside
4692 @code{.def}/@code{.endef} pairs.
4695 @samp{.dim} is only meaningful when generating COFF format output; when
4696 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4702 @section @code{.double @var{flonums}}
4704 @cindex @code{double} directive
4705 @cindex floating point numbers (double)
4706 @code{.double} expects zero or more flonums, separated by commas. It
4707 assembles floating point numbers.
4709 The exact kind of floating point numbers emitted depends on how
4710 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4714 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4715 in @sc{ieee} format.
4720 @section @code{.eject}
4722 @cindex @code{eject} directive
4723 @cindex new page, in listings
4724 @cindex page, in listings
4725 @cindex listing control: new page
4726 Force a page break at this point, when generating assembly listings.
4729 @section @code{.else}
4731 @cindex @code{else} directive
4732 @code{.else} is part of the @command{@value{AS}} support for conditional
4733 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4734 of code to be assembled if the condition for the preceding @code{.if}
4738 @section @code{.elseif}
4740 @cindex @code{elseif} directive
4741 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4742 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4743 @code{.if} block that would otherwise fill the entire @code{.else} section.
4746 @section @code{.end}
4748 @cindex @code{end} directive
4749 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4750 process anything in the file past the @code{.end} directive.
4754 @section @code{.endef}
4756 @cindex @code{endef} directive
4757 This directive flags the end of a symbol definition begun with
4761 @samp{.endef} is only meaningful when generating COFF format output; if
4762 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4763 directive but ignores it.
4768 @section @code{.endfunc}
4769 @cindex @code{endfunc} directive
4770 @code{.endfunc} marks the end of a function specified with @code{.func}.
4773 @section @code{.endif}
4775 @cindex @code{endif} directive
4776 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4777 it marks the end of a block of code that is only assembled
4778 conditionally. @xref{If,,@code{.if}}.
4781 @section @code{.equ @var{symbol}, @var{expression}}
4783 @cindex @code{equ} directive
4784 @cindex assigning values to symbols
4785 @cindex symbols, assigning values to
4786 This directive sets the value of @var{symbol} to @var{expression}.
4787 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4790 The syntax for @code{equ} on the HPPA is
4791 @samp{@var{symbol} .equ @var{expression}}.
4795 The syntax for @code{equ} on the Z80 is
4796 @samp{@var{symbol} equ @var{expression}}.
4797 On the Z80 it is an eror if @var{symbol} is already defined,
4798 but the symbol is not protected from later redefinition.
4799 Compare @ref{Equiv}.
4803 @section @code{.equiv @var{symbol}, @var{expression}}
4804 @cindex @code{equiv} directive
4805 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4806 the assembler will signal an error if @var{symbol} is already defined. Note a
4807 symbol which has been referenced but not actually defined is considered to be
4810 Except for the contents of the error message, this is roughly equivalent to
4817 plus it protects the symbol from later redefinition.
4820 @section @code{.eqv @var{symbol}, @var{expression}}
4821 @cindex @code{eqv} directive
4822 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4823 evaluate the expression or any part of it immediately. Instead each time
4824 the resulting symbol is used in an expression, a snapshot of its current
4828 @section @code{.err}
4829 @cindex @code{err} directive
4830 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4831 message and, unless the @option{-Z} option was used, it will not generate an
4832 object file. This can be used to signal an error in conditionally compiled code.
4835 @section @code{.error "@var{string}"}
4836 @cindex error directive
4838 Similarly to @code{.err}, this directive emits an error, but you can specify a
4839 string that will be emitted as the error message. If you don't specify the
4840 message, it defaults to @code{".error directive invoked in source file"}.
4841 @xref{Errors, ,Error and Warning Messages}.
4844 .error "This code has not been assembled and tested."
4848 @section @code{.exitm}
4849 Exit early from the current macro definition. @xref{Macro}.
4852 @section @code{.extern}
4854 @cindex @code{extern} directive
4855 @code{.extern} is accepted in the source program---for compatibility
4856 with other assemblers---but it is ignored. @command{@value{AS}} treats
4857 all undefined symbols as external.
4860 @section @code{.fail @var{expression}}
4862 @cindex @code{fail} directive
4863 Generates an error or a warning. If the value of the @var{expression} is 500
4864 or more, @command{@value{AS}} will print a warning message. If the value is less
4865 than 500, @command{@value{AS}} will print an error message. The message will
4866 include the value of @var{expression}. This can occasionally be useful inside
4867 complex nested macros or conditional assembly.
4870 @section @code{.file}
4871 @cindex @code{file} directive
4873 @ifclear no-file-dir
4874 There are two different versions of the @code{.file} directive. Targets
4875 that support DWARF2 line number information use the DWARF2 version of
4876 @code{.file}. Other targets use the default version.
4878 @subheading Default Version
4880 @cindex logical file name
4881 @cindex file name, logical
4882 This version of the @code{.file} directive tells @command{@value{AS}} that we
4883 are about to start a new logical file. The syntax is:
4889 @var{string} is the new file name. In general, the filename is
4890 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4891 to specify an empty file name, you must give the quotes--@code{""}. This
4892 statement may go away in future: it is only recognized to be compatible with
4893 old @command{@value{AS}} programs.
4895 @subheading DWARF2 Version
4898 When emitting DWARF2 line number information, @code{.file} assigns filenames
4899 to the @code{.debug_line} file name table. The syntax is:
4902 .file @var{fileno} @var{filename}
4905 The @var{fileno} operand should be a unique positive integer to use as the
4906 index of the entry in the table. The @var{filename} operand is a C string
4909 The detail of filename indices is exposed to the user because the filename
4910 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4911 information, and thus the user must know the exact indices that table
4915 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4917 @cindex @code{fill} directive
4918 @cindex writing patterns in memory
4919 @cindex patterns, writing in memory
4920 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4921 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4922 may be zero or more. @var{Size} may be zero or more, but if it is
4923 more than 8, then it is deemed to have the value 8, compatible with
4924 other people's assemblers. The contents of each @var{repeat} bytes
4925 is taken from an 8-byte number. The highest order 4 bytes are
4926 zero. The lowest order 4 bytes are @var{value} rendered in the
4927 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4928 Each @var{size} bytes in a repetition is taken from the lowest order
4929 @var{size} bytes of this number. Again, this bizarre behavior is
4930 compatible with other people's assemblers.
4932 @var{size} and @var{value} are optional.
4933 If the second comma and @var{value} are absent, @var{value} is
4934 assumed zero. If the first comma and following tokens are absent,
4935 @var{size} is assumed to be 1.
4938 @section @code{.float @var{flonums}}
4940 @cindex floating point numbers (single)
4941 @cindex @code{float} directive
4942 This directive assembles zero or more flonums, separated by commas. It
4943 has the same effect as @code{.single}.
4945 The exact kind of floating point numbers emitted depends on how
4946 @command{@value{AS}} is configured.
4947 @xref{Machine Dependencies}.
4951 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4952 in @sc{ieee} format.
4957 @section @code{.func @var{name}[,@var{label}]}
4958 @cindex @code{func} directive
4959 @code{.func} emits debugging information to denote function @var{name}, and
4960 is ignored unless the file is assembled with debugging enabled.
4961 Only @samp{--gstabs[+]} is currently supported.
4962 @var{label} is the entry point of the function and if omitted @var{name}
4963 prepended with the @samp{leading char} is used.
4964 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4965 All functions are currently defined to have @code{void} return type.
4966 The function must be terminated with @code{.endfunc}.
4969 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4971 @cindex @code{global} directive
4972 @cindex symbol, making visible to linker
4973 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4974 @var{symbol} in your partial program, its value is made available to
4975 other partial programs that are linked with it. Otherwise,
4976 @var{symbol} takes its attributes from a symbol of the same name
4977 from another file linked into the same program.
4979 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4980 compatibility with other assemblers.
4983 On the HPPA, @code{.global} is not always enough to make it accessible to other
4984 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4985 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4990 @section @code{.gnu_attribute @var{tag},@var{value}}
4991 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4994 @section @code{.hidden @var{names}}
4996 @cindex @code{hidden} directive
4998 This is one of the ELF visibility directives. The other two are
4999 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5000 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5002 This directive overrides the named symbols default visibility (which is set by
5003 their binding: local, global or weak). The directive sets the visibility to
5004 @code{hidden} which means that the symbols are not visible to other components.
5005 Such symbols are always considered to be @code{protected} as well.
5009 @section @code{.hword @var{expressions}}
5011 @cindex @code{hword} directive
5012 @cindex integers, 16-bit
5013 @cindex numbers, 16-bit
5014 @cindex sixteen bit integers
5015 This expects zero or more @var{expressions}, and emits
5016 a 16 bit number for each.
5019 This directive is a synonym for @samp{.short}; depending on the target
5020 architecture, it may also be a synonym for @samp{.word}.
5024 This directive is a synonym for @samp{.short}.
5027 This directive is a synonym for both @samp{.short} and @samp{.word}.
5032 @section @code{.ident}
5034 @cindex @code{ident} directive
5036 This directive is used by some assemblers to place tags in object files. The
5037 behavior of this directive varies depending on the target. When using the
5038 a.out object file format, @command{@value{AS}} simply accepts the directive for
5039 source-file compatibility with existing assemblers, but does not emit anything
5040 for it. When using COFF, comments are emitted to the @code{.comment} or
5041 @code{.rdata} section, depending on the target. When using ELF, comments are
5042 emitted to the @code{.comment} section.
5045 @section @code{.if @var{absolute expression}}
5047 @cindex conditional assembly
5048 @cindex @code{if} directive
5049 @code{.if} marks the beginning of a section of code which is only
5050 considered part of the source program being assembled if the argument
5051 (which must be an @var{absolute expression}) is non-zero. The end of
5052 the conditional section of code must be marked by @code{.endif}
5053 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5054 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5055 If you have several conditions to check, @code{.elseif} may be used to avoid
5056 nesting blocks if/else within each subsequent @code{.else} block.
5058 The following variants of @code{.if} are also supported:
5060 @cindex @code{ifdef} directive
5061 @item .ifdef @var{symbol}
5062 Assembles the following section of code if the specified @var{symbol}
5063 has been defined. Note a symbol which has been referenced but not yet defined
5064 is considered to be undefined.
5066 @cindex @code{ifb} directive
5067 @item .ifb @var{text}
5068 Assembles the following section of code if the operand is blank (empty).
5070 @cindex @code{ifc} directive
5071 @item .ifc @var{string1},@var{string2}
5072 Assembles the following section of code if the two strings are the same. The
5073 strings may be optionally quoted with single quotes. If they are not quoted,
5074 the first string stops at the first comma, and the second string stops at the
5075 end of the line. Strings which contain whitespace should be quoted. The
5076 string comparison is case sensitive.
5078 @cindex @code{ifeq} directive
5079 @item .ifeq @var{absolute expression}
5080 Assembles the following section of code if the argument is zero.
5082 @cindex @code{ifeqs} directive
5083 @item .ifeqs @var{string1},@var{string2}
5084 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5086 @cindex @code{ifge} directive
5087 @item .ifge @var{absolute expression}
5088 Assembles the following section of code if the argument is greater than or
5091 @cindex @code{ifgt} directive
5092 @item .ifgt @var{absolute expression}
5093 Assembles the following section of code if the argument is greater than zero.
5095 @cindex @code{ifle} directive
5096 @item .ifle @var{absolute expression}
5097 Assembles the following section of code if the argument is less than or equal
5100 @cindex @code{iflt} directive
5101 @item .iflt @var{absolute expression}
5102 Assembles the following section of code if the argument is less than zero.
5104 @cindex @code{ifnb} directive
5105 @item .ifnb @var{text}
5106 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5107 following section of code if the operand is non-blank (non-empty).
5109 @cindex @code{ifnc} directive
5110 @item .ifnc @var{string1},@var{string2}.
5111 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5112 following section of code if the two strings are not the same.
5114 @cindex @code{ifndef} directive
5115 @cindex @code{ifnotdef} directive
5116 @item .ifndef @var{symbol}
5117 @itemx .ifnotdef @var{symbol}
5118 Assembles the following section of code if the specified @var{symbol}
5119 has not been defined. Both spelling variants are equivalent. Note a symbol
5120 which has been referenced but not yet defined is considered to be undefined.
5122 @cindex @code{ifne} directive
5123 @item .ifne @var{absolute expression}
5124 Assembles the following section of code if the argument is not equal to zero
5125 (in other words, this is equivalent to @code{.if}).
5127 @cindex @code{ifnes} directive
5128 @item .ifnes @var{string1},@var{string2}
5129 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5130 following section of code if the two strings are not the same.
5134 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5136 @cindex @code{incbin} directive
5137 @cindex binary files, including
5138 The @code{incbin} directive includes @var{file} verbatim at the current
5139 location. You can control the search paths used with the @samp{-I} command-line
5140 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5143 The @var{skip} argument skips a number of bytes from the start of the
5144 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5145 read. Note that the data is not aligned in any way, so it is the user's
5146 responsibility to make sure that proper alignment is provided both before and
5147 after the @code{incbin} directive.
5150 @section @code{.include "@var{file}"}
5152 @cindex @code{include} directive
5153 @cindex supporting files, including
5154 @cindex files, including
5155 This directive provides a way to include supporting files at specified
5156 points in your source program. The code from @var{file} is assembled as
5157 if it followed the point of the @code{.include}; when the end of the
5158 included file is reached, assembly of the original file continues. You
5159 can control the search paths used with the @samp{-I} command-line option
5160 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5164 @section @code{.int @var{expressions}}
5166 @cindex @code{int} directive
5167 @cindex integers, 32-bit
5168 Expect zero or more @var{expressions}, of any section, separated by commas.
5169 For each expression, emit a number that, at run time, is the value of that
5170 expression. The byte order and bit size of the number depends on what kind
5171 of target the assembly is for.
5175 On most forms of the H8/300, @code{.int} emits 16-bit
5176 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5183 @section @code{.internal @var{names}}
5185 @cindex @code{internal} directive
5187 This is one of the ELF visibility directives. The other two are
5188 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5189 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5191 This directive overrides the named symbols default visibility (which is set by
5192 their binding: local, global or weak). The directive sets the visibility to
5193 @code{internal} which means that the symbols are considered to be @code{hidden}
5194 (i.e., not visible to other components), and that some extra, processor specific
5195 processing must also be performed upon the symbols as well.
5199 @section @code{.irp @var{symbol},@var{values}}@dots{}
5201 @cindex @code{irp} directive
5202 Evaluate a sequence of statements assigning different values to @var{symbol}.
5203 The sequence of statements starts at the @code{.irp} directive, and is
5204 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5205 set to @var{value}, and the sequence of statements is assembled. If no
5206 @var{value} is listed, the sequence of statements is assembled once, with
5207 @var{symbol} set to the null string. To refer to @var{symbol} within the
5208 sequence of statements, use @var{\symbol}.
5210 For example, assembling
5218 is equivalent to assembling
5226 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5229 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5231 @cindex @code{irpc} directive
5232 Evaluate a sequence of statements assigning different values to @var{symbol}.
5233 The sequence of statements starts at the @code{.irpc} directive, and is
5234 terminated by an @code{.endr} directive. For each character in @var{value},
5235 @var{symbol} is set to the character, and the sequence of statements is
5236 assembled. If no @var{value} is listed, the sequence of statements is
5237 assembled once, with @var{symbol} set to the null string. To refer to
5238 @var{symbol} within the sequence of statements, use @var{\symbol}.
5240 For example, assembling
5248 is equivalent to assembling
5256 For some caveats with the spelling of @var{symbol}, see also the discussion
5260 @section @code{.lcomm @var{symbol} , @var{length}}
5262 @cindex @code{lcomm} directive
5263 @cindex local common symbols
5264 @cindex symbols, local common
5265 Reserve @var{length} (an absolute expression) bytes for a local common
5266 denoted by @var{symbol}. The section and value of @var{symbol} are
5267 those of the new local common. The addresses are allocated in the bss
5268 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5269 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5270 not visible to @code{@value{LD}}.
5273 Some targets permit a third argument to be used with @code{.lcomm}. This
5274 argument specifies the desired alignment of the symbol in the bss section.
5278 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5279 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5283 @section @code{.lflags}
5285 @cindex @code{lflags} directive (ignored)
5286 @command{@value{AS}} accepts this directive, for compatibility with other
5287 assemblers, but ignores it.
5289 @ifclear no-line-dir
5291 @section @code{.line @var{line-number}}
5293 @cindex @code{line} directive
5294 @cindex logical line number
5296 Change the logical line number. @var{line-number} must be an absolute
5297 expression. The next line has that logical line number. Therefore any other
5298 statements on the current line (after a statement separator character) are
5299 reported as on logical line number @var{line-number} @minus{} 1. One day
5300 @command{@value{AS}} will no longer support this directive: it is recognized only
5301 for compatibility with existing assembler programs.
5304 Even though this is a directive associated with the @code{a.out} or
5305 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5306 when producing COFF output, and treats @samp{.line} as though it
5307 were the COFF @samp{.ln} @emph{if} it is found outside a
5308 @code{.def}/@code{.endef} pair.
5310 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5311 used by compilers to generate auxiliary symbol information for
5316 @section @code{.linkonce [@var{type}]}
5318 @cindex @code{linkonce} directive
5319 @cindex common sections
5320 Mark the current section so that the linker only includes a single copy of it.
5321 This may be used to include the same section in several different object files,
5322 but ensure that the linker will only include it once in the final output file.
5323 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5324 Duplicate sections are detected based on the section name, so it should be
5327 This directive is only supported by a few object file formats; as of this
5328 writing, the only object file format which supports it is the Portable
5329 Executable format used on Windows NT.
5331 The @var{type} argument is optional. If specified, it must be one of the
5332 following strings. For example:
5336 Not all types may be supported on all object file formats.
5340 Silently discard duplicate sections. This is the default.
5343 Warn if there are duplicate sections, but still keep only one copy.
5346 Warn if any of the duplicates have different sizes.
5349 Warn if any of the duplicates do not have exactly the same contents.
5353 @section @code{.list}
5355 @cindex @code{list} directive
5356 @cindex listing control, turning on
5357 Control (in conjunction with the @code{.nolist} directive) whether or
5358 not assembly listings are generated. These two directives maintain an
5359 internal counter (which is zero initially). @code{.list} increments the
5360 counter, and @code{.nolist} decrements it. Assembly listings are
5361 generated whenever the counter is greater than zero.
5363 By default, listings are disabled. When you enable them (with the
5364 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5365 the initial value of the listing counter is one.
5368 @section @code{.ln @var{line-number}}
5370 @cindex @code{ln} directive
5371 @ifclear no-line-dir
5372 @samp{.ln} is a synonym for @samp{.line}.
5375 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5376 must be an absolute expression. The next line has that logical
5377 line number, so any other statements on the current line (after a
5378 statement separator character @code{;}) are reported as on logical
5379 line number @var{line-number} @minus{} 1.
5382 This directive is accepted, but ignored, when @command{@value{AS}} is
5383 configured for @code{b.out}; its effect is only associated with COFF
5389 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5390 @cindex @code{loc} directive
5391 When emitting DWARF2 line number information,
5392 the @code{.loc} directive will add a row to the @code{.debug_line} line
5393 number matrix corresponding to the immediately following assembly
5394 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5395 arguments will be applied to the @code{.debug_line} state machine before
5398 The @var{options} are a sequence of the following tokens in any order:
5402 This option will set the @code{basic_block} register in the
5403 @code{.debug_line} state machine to @code{true}.
5406 This option will set the @code{prologue_end} register in the
5407 @code{.debug_line} state machine to @code{true}.
5409 @item epilogue_begin
5410 This option will set the @code{epilogue_begin} register in the
5411 @code{.debug_line} state machine to @code{true}.
5413 @item is_stmt @var{value}
5414 This option will set the @code{is_stmt} register in the
5415 @code{.debug_line} state machine to @code{value}, which must be
5418 @item isa @var{value}
5419 This directive will set the @code{isa} register in the @code{.debug_line}
5420 state machine to @var{value}, which must be an unsigned integer.
5422 @item discriminator @var{value}
5423 This directive will set the @code{discriminator} register in the @code{.debug_line}
5424 state machine to @var{value}, which must be an unsigned integer.
5428 @node Loc_mark_labels
5429 @section @code{.loc_mark_labels @var{enable}}
5430 @cindex @code{loc_mark_labels} directive
5431 When emitting DWARF2 line number information,
5432 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5433 to the @code{.debug_line} line number matrix with the @code{basic_block}
5434 register in the state machine set whenever a code label is seen.
5435 The @var{enable} argument should be either 1 or 0, to enable or disable
5436 this function respectively.
5440 @section @code{.local @var{names}}
5442 @cindex @code{local} directive
5443 This directive, which is available for ELF targets, marks each symbol in
5444 the comma-separated list of @code{names} as a local symbol so that it
5445 will not be externally visible. If the symbols do not already exist,
5446 they will be created.
5448 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5449 accept an alignment argument, which is the case for most ELF targets,
5450 the @code{.local} directive can be used in combination with @code{.comm}
5451 (@pxref{Comm}) to define aligned local common data.
5455 @section @code{.long @var{expressions}}
5457 @cindex @code{long} directive
5458 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5461 @c no one seems to know what this is for or whether this description is
5462 @c what it really ought to do
5464 @section @code{.lsym @var{symbol}, @var{expression}}
5466 @cindex @code{lsym} directive
5467 @cindex symbol, not referenced in assembly
5468 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5469 the hash table, ensuring it cannot be referenced by name during the
5470 rest of the assembly. This sets the attributes of the symbol to be
5471 the same as the expression value:
5473 @var{other} = @var{descriptor} = 0
5474 @var{type} = @r{(section of @var{expression})}
5475 @var{value} = @var{expression}
5478 The new symbol is not flagged as external.
5482 @section @code{.macro}
5485 The commands @code{.macro} and @code{.endm} allow you to define macros that
5486 generate assembly output. For example, this definition specifies a macro
5487 @code{sum} that puts a sequence of numbers into memory:
5490 .macro sum from=0, to=5
5499 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5511 @item .macro @var{macname}
5512 @itemx .macro @var{macname} @var{macargs} @dots{}
5513 @cindex @code{macro} directive
5514 Begin the definition of a macro called @var{macname}. If your macro
5515 definition requires arguments, specify their names after the macro name,
5516 separated by commas or spaces. You can qualify the macro argument to
5517 indicate whether all invocations must specify a non-blank value (through
5518 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5519 (through @samp{:@code{vararg}}). You can supply a default value for any
5520 macro argument by following the name with @samp{=@var{deflt}}. You
5521 cannot define two macros with the same @var{macname} unless it has been
5522 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5523 definitions. For example, these are all valid @code{.macro} statements:
5527 Begin the definition of a macro called @code{comm}, which takes no
5530 @item .macro plus1 p, p1
5531 @itemx .macro plus1 p p1
5532 Either statement begins the definition of a macro called @code{plus1},
5533 which takes two arguments; within the macro definition, write
5534 @samp{\p} or @samp{\p1} to evaluate the arguments.
5536 @item .macro reserve_str p1=0 p2
5537 Begin the definition of a macro called @code{reserve_str}, with two
5538 arguments. The first argument has a default value, but not the second.
5539 After the definition is complete, you can call the macro either as
5540 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5541 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5542 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5543 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5545 @item .macro m p1:req, p2=0, p3:vararg
5546 Begin the definition of a macro called @code{m}, with at least three
5547 arguments. The first argument must always have a value specified, but
5548 not the second, which instead has a default value. The third formal
5549 will get assigned all remaining arguments specified at invocation time.
5551 When you call a macro, you can specify the argument values either by
5552 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5553 @samp{sum to=17, from=9}.
5557 Note that since each of the @var{macargs} can be an identifier exactly
5558 as any other one permitted by the target architecture, there may be
5559 occasional problems if the target hand-crafts special meanings to certain
5560 characters when they occur in a special position. For example, if the colon
5561 (@code{:}) is generally permitted to be part of a symbol name, but the
5562 architecture specific code special-cases it when occurring as the final
5563 character of a symbol (to denote a label), then the macro parameter
5564 replacement code will have no way of knowing that and consider the whole
5565 construct (including the colon) an identifier, and check only this
5566 identifier for being the subject to parameter substitution. So for example
5567 this macro definition:
5575 might not work as expected. Invoking @samp{label foo} might not create a label
5576 called @samp{foo} but instead just insert the text @samp{\l:} into the
5577 assembler source, probably generating an error about an unrecognised
5580 Similarly problems might occur with the period character (@samp{.})
5581 which is often allowed inside opcode names (and hence identifier names). So
5582 for example constructing a macro to build an opcode from a base name and a
5583 length specifier like this:
5586 .macro opcode base length
5591 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5592 instruction but instead generate some kind of error as the assembler tries to
5593 interpret the text @samp{\base.\length}.
5595 There are several possible ways around this problem:
5598 @item Insert white space
5599 If it is possible to use white space characters then this is the simplest
5608 @item Use @samp{\()}
5609 The string @samp{\()} can be used to separate the end of a macro argument from
5610 the following text. eg:
5613 .macro opcode base length
5618 @item Use the alternate macro syntax mode
5619 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5620 used as a separator. eg:
5630 Note: this problem of correctly identifying string parameters to pseudo ops
5631 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5632 and @code{.irpc} (@pxref{Irpc}) as well.
5635 @cindex @code{endm} directive
5636 Mark the end of a macro definition.
5639 @cindex @code{exitm} directive
5640 Exit early from the current macro definition.
5642 @cindex number of macros executed
5643 @cindex macros, count executed
5645 @command{@value{AS}} maintains a counter of how many macros it has
5646 executed in this pseudo-variable; you can copy that number to your
5647 output with @samp{\@@}, but @emph{only within a macro definition}.
5649 @item LOCAL @var{name} [ , @dots{} ]
5650 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5651 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5652 @xref{Altmacro,,@code{.altmacro}}.
5656 @section @code{.mri @var{val}}
5658 @cindex @code{mri} directive
5659 @cindex MRI mode, temporarily
5660 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5661 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5662 affects code assembled until the next @code{.mri} directive, or until the end
5663 of the file. @xref{M, MRI mode, MRI mode}.
5666 @section @code{.noaltmacro}
5667 Disable alternate macro mode. @xref{Altmacro}.
5670 @section @code{.nolist}
5672 @cindex @code{nolist} directive
5673 @cindex listing control, turning off
5674 Control (in conjunction with the @code{.list} directive) whether or
5675 not assembly listings are generated. These two directives maintain an
5676 internal counter (which is zero initially). @code{.list} increments the
5677 counter, and @code{.nolist} decrements it. Assembly listings are
5678 generated whenever the counter is greater than zero.
5681 @section @code{.octa @var{bignums}}
5683 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5684 @cindex @code{octa} directive
5685 @cindex integer, 16-byte
5686 @cindex sixteen byte integer
5687 This directive expects zero or more bignums, separated by commas. For each
5688 bignum, it emits a 16-byte integer.
5690 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5691 hence @emph{octa}-word for 16 bytes.
5694 @section @code{.offset @var{loc}}
5696 @cindex @code{offset} directive
5697 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5698 be an absolute expression. This directive may be useful for defining
5699 symbols with absolute values. Do not confuse it with the @code{.org}
5703 @section @code{.org @var{new-lc} , @var{fill}}
5705 @cindex @code{org} directive
5706 @cindex location counter, advancing
5707 @cindex advancing location counter
5708 @cindex current address, advancing
5709 Advance the location counter of the current section to
5710 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5711 expression with the same section as the current subsection. That is,
5712 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5713 wrong section, the @code{.org} directive is ignored. To be compatible
5714 with former assemblers, if the section of @var{new-lc} is absolute,
5715 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5716 is the same as the current subsection.
5718 @code{.org} may only increase the location counter, or leave it
5719 unchanged; you cannot use @code{.org} to move the location counter
5722 @c double negative used below "not undefined" because this is a specific
5723 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5724 @c section. doc@cygnus.com 18feb91
5725 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5726 may not be undefined. If you really detest this restriction we eagerly await
5727 a chance to share your improved assembler.
5729 Beware that the origin is relative to the start of the section, not
5730 to the start of the subsection. This is compatible with other
5731 people's assemblers.
5733 When the location counter (of the current subsection) is advanced, the
5734 intervening bytes are filled with @var{fill} which should be an
5735 absolute expression. If the comma and @var{fill} are omitted,
5736 @var{fill} defaults to zero.
5739 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5741 @cindex padding the location counter given a power of two
5742 @cindex @code{p2align} directive
5743 Pad the location counter (in the current subsection) to a particular
5744 storage boundary. The first expression (which must be absolute) is the
5745 number of low-order zero bits the location counter must have after
5746 advancement. For example @samp{.p2align 3} advances the location
5747 counter until it a multiple of 8. If the location counter is already a
5748 multiple of 8, no change is needed.
5750 The second expression (also absolute) gives the fill value to be stored in the
5751 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5752 padding bytes are normally zero. However, on some systems, if the section is
5753 marked as containing code and the fill value is omitted, the space is filled
5754 with no-op instructions.
5756 The third expression is also absolute, and is also optional. If it is present,
5757 it is the maximum number of bytes that should be skipped by this alignment
5758 directive. If doing the alignment would require skipping more bytes than the
5759 specified maximum, then the alignment is not done at all. You can omit the
5760 fill value (the second argument) entirely by simply using two commas after the
5761 required alignment; this can be useful if you want the alignment to be filled
5762 with no-op instructions when appropriate.
5764 @cindex @code{p2alignw} directive
5765 @cindex @code{p2alignl} directive
5766 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5767 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5768 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5769 fill pattern as a four byte longword value. For example, @code{.p2alignw
5770 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5771 filled in with the value 0x368d (the exact placement of the bytes depends upon
5772 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5777 @section @code{.popsection}
5779 @cindex @code{popsection} directive
5780 @cindex Section Stack
5781 This is one of the ELF section stack manipulation directives. The others are
5782 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5783 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5786 This directive replaces the current section (and subsection) with the top
5787 section (and subsection) on the section stack. This section is popped off the
5793 @section @code{.previous}
5795 @cindex @code{previous} directive
5796 @cindex Section Stack
5797 This is one of the ELF section stack manipulation directives. The others are
5798 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5799 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5800 (@pxref{PopSection}).
5802 This directive swaps the current section (and subsection) with most recently
5803 referenced section/subsection pair prior to this one. Multiple
5804 @code{.previous} directives in a row will flip between two sections (and their
5805 subsections). For example:
5817 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5823 # Now in section A subsection 1
5827 # Now in section B subsection 0
5830 # Now in section B subsection 1
5833 # Now in section B subsection 0
5837 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5838 section B and 0x9abc into subsection 1 of section B.
5840 In terms of the section stack, this directive swaps the current section with
5841 the top section on the section stack.
5845 @section @code{.print @var{string}}
5847 @cindex @code{print} directive
5848 @command{@value{AS}} will print @var{string} on the standard output during
5849 assembly. You must put @var{string} in double quotes.
5853 @section @code{.protected @var{names}}
5855 @cindex @code{protected} directive
5857 This is one of the ELF visibility directives. The other two are
5858 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5860 This directive overrides the named symbols default visibility (which is set by
5861 their binding: local, global or weak). The directive sets the visibility to
5862 @code{protected} which means that any references to the symbols from within the
5863 components that defines them must be resolved to the definition in that
5864 component, even if a definition in another component would normally preempt
5869 @section @code{.psize @var{lines} , @var{columns}}
5871 @cindex @code{psize} directive
5872 @cindex listing control: paper size
5873 @cindex paper size, for listings
5874 Use this directive to declare the number of lines---and, optionally, the
5875 number of columns---to use for each page, when generating listings.
5877 If you do not use @code{.psize}, listings use a default line-count
5878 of 60. You may omit the comma and @var{columns} specification; the
5879 default width is 200 columns.
5881 @command{@value{AS}} generates formfeeds whenever the specified number of
5882 lines is exceeded (or whenever you explicitly request one, using
5885 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5886 those explicitly specified with @code{.eject}.
5889 @section @code{.purgem @var{name}}
5891 @cindex @code{purgem} directive
5892 Undefine the macro @var{name}, so that later uses of the string will not be
5893 expanded. @xref{Macro}.
5897 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5899 @cindex @code{pushsection} directive
5900 @cindex Section Stack
5901 This is one of the ELF section stack manipulation directives. The others are
5902 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5903 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5906 This directive pushes the current section (and subsection) onto the
5907 top of the section stack, and then replaces the current section and
5908 subsection with @code{name} and @code{subsection}. The optional
5909 @code{flags}, @code{type} and @code{arguments} are treated the same
5910 as in the @code{.section} (@pxref{Section}) directive.
5914 @section @code{.quad @var{bignums}}
5916 @cindex @code{quad} directive
5917 @code{.quad} expects zero or more bignums, separated by commas. For
5918 each bignum, it emits
5920 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5921 warning message; and just takes the lowest order 8 bytes of the bignum.
5922 @cindex eight-byte integer
5923 @cindex integer, 8-byte
5925 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5926 hence @emph{quad}-word for 8 bytes.
5929 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5930 warning message; and just takes the lowest order 16 bytes of the bignum.
5931 @cindex sixteen-byte integer
5932 @cindex integer, 16-byte
5936 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5938 @cindex @code{reloc} directive
5939 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5940 @var{expression}. If @var{offset} is a number, the relocation is generated in
5941 the current section. If @var{offset} is an expression that resolves to a
5942 symbol plus offset, the relocation is generated in the given symbol's section.
5943 @var{expression}, if present, must resolve to a symbol plus addend or to an
5944 absolute value, but note that not all targets support an addend. e.g. ELF REL
5945 targets such as i386 store an addend in the section contents rather than in the
5946 relocation. This low level interface does not support addends stored in the
5950 @section @code{.rept @var{count}}
5952 @cindex @code{rept} directive
5953 Repeat the sequence of lines between the @code{.rept} directive and the next
5954 @code{.endr} directive @var{count} times.
5956 For example, assembling
5964 is equivalent to assembling
5973 @section @code{.sbttl "@var{subheading}"}
5975 @cindex @code{sbttl} directive
5976 @cindex subtitles for listings
5977 @cindex listing control: subtitle
5978 Use @var{subheading} as the title (third line, immediately after the
5979 title line) when generating assembly listings.
5981 This directive affects subsequent pages, as well as the current page if
5982 it appears within ten lines of the top of a page.
5986 @section @code{.scl @var{class}}
5988 @cindex @code{scl} directive
5989 @cindex symbol storage class (COFF)
5990 @cindex COFF symbol storage class
5991 Set the storage-class value for a symbol. This directive may only be
5992 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5993 whether a symbol is static or external, or it may record further
5994 symbolic debugging information.
5997 The @samp{.scl} directive is primarily associated with COFF output; when
5998 configured to generate @code{b.out} output format, @command{@value{AS}}
5999 accepts this directive but ignores it.
6005 @section @code{.section @var{name}}
6007 @cindex named section
6008 Use the @code{.section} directive to assemble the following code into a section
6011 This directive is only supported for targets that actually support arbitrarily
6012 named sections; on @code{a.out} targets, for example, it is not accepted, even
6013 with a standard @code{a.out} section name.
6017 @c only print the extra heading if both COFF and ELF are set
6018 @subheading COFF Version
6021 @cindex @code{section} directive (COFF version)
6022 For COFF targets, the @code{.section} directive is used in one of the following
6026 .section @var{name}[, "@var{flags}"]
6027 .section @var{name}[, @var{subsection}]
6030 If the optional argument is quoted, it is taken as flags to use for the
6031 section. Each flag is a single character. The following flags are recognized:
6034 bss section (uninitialized data)
6036 section is not loaded
6042 exclude section from linking
6048 shared section (meaningful for PE targets)
6050 ignored. (For compatibility with the ELF version)
6052 section is not readable (meaningful for PE targets)
6054 single-digit power-of-two section alignment (GNU extension)
6057 If no flags are specified, the default flags depend upon the section name. If
6058 the section name is not recognized, the default will be for the section to be
6059 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6060 from the section, rather than adding them, so if they are used on their own it
6061 will be as if no flags had been specified at all.
6063 If the optional argument to the @code{.section} directive is not quoted, it is
6064 taken as a subsection number (@pxref{Sub-Sections}).
6069 @c only print the extra heading if both COFF and ELF are set
6070 @subheading ELF Version
6073 @cindex Section Stack
6074 This is one of the ELF section stack manipulation directives. The others are
6075 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6076 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6077 @code{.previous} (@pxref{Previous}).
6079 @cindex @code{section} directive (ELF version)
6080 For ELF targets, the @code{.section} directive is used like this:
6083 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6086 The optional @var{flags} argument is a quoted string which may contain any
6087 combination of the following characters:
6090 section is allocatable
6092 section is excluded from executable and shared library.
6096 section is executable
6098 section is mergeable
6100 section contains zero terminated strings
6102 section is a member of a section group
6104 section is used for thread-local-storage
6106 section is a member of the previously-current section's group, if any
6109 The optional @var{type} argument may contain one of the following constants:
6112 section contains data
6114 section does not contain data (i.e., section only occupies space)
6116 section contains data which is used by things other than the program
6118 section contains an array of pointers to init functions
6120 section contains an array of pointers to finish functions
6121 @item @@preinit_array
6122 section contains an array of pointers to pre-init functions
6125 Many targets only support the first three section types.
6127 Note on targets where the @code{@@} character is the start of a comment (eg
6128 ARM) then another character is used instead. For example the ARM port uses the
6131 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6132 be specified as well as an extra argument---@var{entsize}---like this:
6135 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6138 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6139 constants, each @var{entsize} octets long. Sections with both @code{M} and
6140 @code{S} must contain zero terminated strings where each character is
6141 @var{entsize} bytes long. The linker may remove duplicates within sections with
6142 the same name, same entity size and same flags. @var{entsize} must be an
6143 absolute expression. For sections with both @code{M} and @code{S}, a string
6144 which is a suffix of a larger string is considered a duplicate. Thus
6145 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6146 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6148 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6149 be present along with an additional field like this:
6152 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6155 The @var{GroupName} field specifies the name of the section group to which this
6156 particular section belongs. The optional linkage field can contain:
6159 indicates that only one copy of this section should be retained
6164 Note: if both the @var{M} and @var{G} flags are present then the fields for
6165 the Merge flag should come first, like this:
6168 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6171 If @var{flags} contains the @code{?} symbol then it may not also contain the
6172 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6173 present. Instead, @code{?} says to consider the section that's current before
6174 this directive. If that section used @code{G}, then the new section will use
6175 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6176 If not, then the @code{?} symbol has no effect.
6178 If no flags are specified, the default flags depend upon the section name. If
6179 the section name is not recognized, the default will be for the section to have
6180 none of the above flags: it will not be allocated in memory, nor writable, nor
6181 executable. The section will contain data.
6183 For ELF targets, the assembler supports another type of @code{.section}
6184 directive for compatibility with the Solaris assembler:
6187 .section "@var{name}"[, @var{flags}...]
6190 Note that the section name is quoted. There may be a sequence of comma
6194 section is allocatable
6198 section is executable
6200 section is excluded from executable and shared library.
6202 section is used for thread local storage
6205 This directive replaces the current section and subsection. See the
6206 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6207 some examples of how this directive and the other section stack directives
6213 @section @code{.set @var{symbol}, @var{expression}}
6215 @cindex @code{set} directive
6216 @cindex symbol value, setting
6217 Set the value of @var{symbol} to @var{expression}. This
6218 changes @var{symbol}'s value and type to conform to
6219 @var{expression}. If @var{symbol} was flagged as external, it remains
6220 flagged (@pxref{Symbol Attributes}).
6222 You may @code{.set} a symbol many times in the same assembly.
6224 If you @code{.set} a global symbol, the value stored in the object
6225 file is the last value stored into it.
6228 On Z80 @code{set} is a real instruction, use
6229 @samp{@var{symbol} defl @var{expression}} instead.
6233 @section @code{.short @var{expressions}}
6235 @cindex @code{short} directive
6237 @code{.short} is normally the same as @samp{.word}.
6238 @xref{Word,,@code{.word}}.
6240 In some configurations, however, @code{.short} and @code{.word} generate
6241 numbers of different lengths. @xref{Machine Dependencies}.
6245 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6248 This expects zero or more @var{expressions}, and emits
6249 a 16 bit number for each.
6254 @section @code{.single @var{flonums}}
6256 @cindex @code{single} directive
6257 @cindex floating point numbers (single)
6258 This directive assembles zero or more flonums, separated by commas. It
6259 has the same effect as @code{.float}.
6261 The exact kind of floating point numbers emitted depends on how
6262 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6266 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6267 numbers in @sc{ieee} format.
6273 @section @code{.size}
6275 This directive is used to set the size associated with a symbol.
6279 @c only print the extra heading if both COFF and ELF are set
6280 @subheading COFF Version
6283 @cindex @code{size} directive (COFF version)
6284 For COFF targets, the @code{.size} directive is only permitted inside
6285 @code{.def}/@code{.endef} pairs. It is used like this:
6288 .size @var{expression}
6292 @samp{.size} is only meaningful when generating COFF format output; when
6293 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6300 @c only print the extra heading if both COFF and ELF are set
6301 @subheading ELF Version
6304 @cindex @code{size} directive (ELF version)
6305 For ELF targets, the @code{.size} directive is used like this:
6308 .size @var{name} , @var{expression}
6311 This directive sets the size associated with a symbol @var{name}.
6312 The size in bytes is computed from @var{expression} which can make use of label
6313 arithmetic. This directive is typically used to set the size of function
6318 @ifclear no-space-dir
6320 @section @code{.skip @var{size} , @var{fill}}
6322 @cindex @code{skip} directive
6323 @cindex filling memory
6324 This directive emits @var{size} bytes, each of value @var{fill}. Both
6325 @var{size} and @var{fill} are absolute expressions. If the comma and
6326 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6331 @section @code{.sleb128 @var{expressions}}
6333 @cindex @code{sleb128} directive
6334 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6335 compact, variable length representation of numbers used by the DWARF
6336 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6338 @ifclear no-space-dir
6340 @section @code{.space @var{size} , @var{fill}}
6342 @cindex @code{space} directive
6343 @cindex filling memory
6344 This directive emits @var{size} bytes, each of value @var{fill}. Both
6345 @var{size} and @var{fill} are absolute expressions. If the comma
6346 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6351 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6352 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6353 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6354 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6362 @section @code{.stabd, .stabn, .stabs}
6364 @cindex symbolic debuggers, information for
6365 @cindex @code{stab@var{x}} directives
6366 There are three directives that begin @samp{.stab}.
6367 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6368 The symbols are not entered in the @command{@value{AS}} hash table: they
6369 cannot be referenced elsewhere in the source file.
6370 Up to five fields are required:
6374 This is the symbol's name. It may contain any character except
6375 @samp{\000}, so is more general than ordinary symbol names. Some
6376 debuggers used to code arbitrarily complex structures into symbol names
6380 An absolute expression. The symbol's type is set to the low 8 bits of
6381 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6382 and debuggers choke on silly bit patterns.
6385 An absolute expression. The symbol's ``other'' attribute is set to the
6386 low 8 bits of this expression.
6389 An absolute expression. The symbol's descriptor is set to the low 16
6390 bits of this expression.
6393 An absolute expression which becomes the symbol's value.
6396 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6397 or @code{.stabs} statement, the symbol has probably already been created;
6398 you get a half-formed symbol in your object file. This is
6399 compatible with earlier assemblers!
6402 @cindex @code{stabd} directive
6403 @item .stabd @var{type} , @var{other} , @var{desc}
6405 The ``name'' of the symbol generated is not even an empty string.
6406 It is a null pointer, for compatibility. Older assemblers used a
6407 null pointer so they didn't waste space in object files with empty
6410 The symbol's value is set to the location counter,
6411 relocatably. When your program is linked, the value of this symbol
6412 is the address of the location counter when the @code{.stabd} was
6415 @cindex @code{stabn} directive
6416 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6417 The name of the symbol is set to the empty string @code{""}.
6419 @cindex @code{stabs} directive
6420 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6421 All five fields are specified.
6427 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6428 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6430 @cindex string, copying to object file
6431 @cindex string8, copying to object file
6432 @cindex string16, copying to object file
6433 @cindex string32, copying to object file
6434 @cindex string64, copying to object file
6435 @cindex @code{string} directive
6436 @cindex @code{string8} directive
6437 @cindex @code{string16} directive
6438 @cindex @code{string32} directive
6439 @cindex @code{string64} directive
6441 Copy the characters in @var{str} to the object file. You may specify more than
6442 one string to copy, separated by commas. Unless otherwise specified for a
6443 particular machine, the assembler marks the end of each string with a 0 byte.
6444 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6446 The variants @code{string16}, @code{string32} and @code{string64} differ from
6447 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6448 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6449 are stored in target endianness byte order.
6455 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6456 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6461 @section @code{.struct @var{expression}}
6463 @cindex @code{struct} directive
6464 Switch to the absolute section, and set the section offset to @var{expression},
6465 which must be an absolute expression. You might use this as follows:
6474 This would define the symbol @code{field1} to have the value 0, the symbol
6475 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6476 value 8. Assembly would be left in the absolute section, and you would need to
6477 use a @code{.section} directive of some sort to change to some other section
6478 before further assembly.
6482 @section @code{.subsection @var{name}}
6484 @cindex @code{subsection} directive
6485 @cindex Section Stack
6486 This is one of the ELF section stack manipulation directives. The others are
6487 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6488 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6491 This directive replaces the current subsection with @code{name}. The current
6492 section is not changed. The replaced subsection is put onto the section stack
6493 in place of the then current top of stack subsection.
6498 @section @code{.symver}
6499 @cindex @code{symver} directive
6500 @cindex symbol versioning
6501 @cindex versions of symbols
6502 Use the @code{.symver} directive to bind symbols to specific version nodes
6503 within a source file. This is only supported on ELF platforms, and is
6504 typically used when assembling files to be linked into a shared library.
6505 There are cases where it may make sense to use this in objects to be bound
6506 into an application itself so as to override a versioned symbol from a
6509 For ELF targets, the @code{.symver} directive can be used like this:
6511 .symver @var{name}, @var{name2@@nodename}
6513 If the symbol @var{name} is defined within the file
6514 being assembled, the @code{.symver} directive effectively creates a symbol
6515 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6516 just don't try and create a regular alias is that the @var{@@} character isn't
6517 permitted in symbol names. The @var{name2} part of the name is the actual name
6518 of the symbol by which it will be externally referenced. The name @var{name}
6519 itself is merely a name of convenience that is used so that it is possible to
6520 have definitions for multiple versions of a function within a single source
6521 file, and so that the compiler can unambiguously know which version of a
6522 function is being mentioned. The @var{nodename} portion of the alias should be
6523 the name of a node specified in the version script supplied to the linker when
6524 building a shared library. If you are attempting to override a versioned
6525 symbol from a shared library, then @var{nodename} should correspond to the
6526 nodename of the symbol you are trying to override.
6528 If the symbol @var{name} is not defined within the file being assembled, all
6529 references to @var{name} will be changed to @var{name2@@nodename}. If no
6530 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6533 Another usage of the @code{.symver} directive is:
6535 .symver @var{name}, @var{name2@@@@nodename}
6537 In this case, the symbol @var{name} must exist and be defined within
6538 the file being assembled. It is similar to @var{name2@@nodename}. The
6539 difference is @var{name2@@@@nodename} will also be used to resolve
6540 references to @var{name2} by the linker.
6542 The third usage of the @code{.symver} directive is:
6544 .symver @var{name}, @var{name2@@@@@@nodename}
6546 When @var{name} is not defined within the
6547 file being assembled, it is treated as @var{name2@@nodename}. When
6548 @var{name} is defined within the file being assembled, the symbol
6549 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6554 @section @code{.tag @var{structname}}
6556 @cindex COFF structure debugging
6557 @cindex structure debugging, COFF
6558 @cindex @code{tag} directive
6559 This directive is generated by compilers to include auxiliary debugging
6560 information in the symbol table. It is only permitted inside
6561 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6562 definitions in the symbol table with instances of those structures.
6565 @samp{.tag} is only used when generating COFF format output; when
6566 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6572 @section @code{.text @var{subsection}}
6574 @cindex @code{text} directive
6575 Tells @command{@value{AS}} to assemble the following statements onto the end of
6576 the text subsection numbered @var{subsection}, which is an absolute
6577 expression. If @var{subsection} is omitted, subsection number zero
6581 @section @code{.title "@var{heading}"}
6583 @cindex @code{title} directive
6584 @cindex listing control: title line
6585 Use @var{heading} as the title (second line, immediately after the
6586 source file name and pagenumber) when generating assembly listings.
6588 This directive affects subsequent pages, as well as the current page if
6589 it appears within ten lines of the top of a page.
6593 @section @code{.type}
6595 This directive is used to set the type of a symbol.
6599 @c only print the extra heading if both COFF and ELF are set
6600 @subheading COFF Version
6603 @cindex COFF symbol type
6604 @cindex symbol type, COFF
6605 @cindex @code{type} directive (COFF version)
6606 For COFF targets, this directive is permitted only within
6607 @code{.def}/@code{.endef} pairs. It is used like this:
6613 This records the integer @var{int} as the type attribute of a symbol table
6617 @samp{.type} is associated only with COFF format output; when
6618 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6619 directive but ignores it.
6625 @c only print the extra heading if both COFF and ELF are set
6626 @subheading ELF Version
6629 @cindex ELF symbol type
6630 @cindex symbol type, ELF
6631 @cindex @code{type} directive (ELF version)
6632 For ELF targets, the @code{.type} directive is used like this:
6635 .type @var{name} , @var{type description}
6638 This sets the type of symbol @var{name} to be either a
6639 function symbol or an object symbol. There are five different syntaxes
6640 supported for the @var{type description} field, in order to provide
6641 compatibility with various other assemblers.
6643 Because some of the characters used in these syntaxes (such as @samp{@@} and
6644 @samp{#}) are comment characters for some architectures, some of the syntaxes
6645 below do not work on all architectures. The first variant will be accepted by
6646 the GNU assembler on all architectures so that variant should be used for
6647 maximum portability, if you do not need to assemble your code with other
6650 The syntaxes supported are:
6653 .type <name> STT_<TYPE_IN_UPPER_CASE>
6654 .type <name>,#<type>
6655 .type <name>,@@<type>
6656 .type <name>,%<type>
6657 .type <name>,"<type>"
6660 The types supported are:
6665 Mark the symbol as being a function name.
6668 @itemx gnu_indirect_function
6669 Mark the symbol as an indirect function when evaluated during reloc
6670 processing. (This is only supported on assemblers targeting GNU systems).
6674 Mark the symbol as being a data object.
6678 Mark the symbol as being a thead-local data object.
6682 Mark the symbol as being a common data object.
6686 Does not mark the symbol in any way. It is supported just for completeness.
6688 @item gnu_unique_object
6689 Marks the symbol as being a globally unique data object. The dynamic linker
6690 will make sure that in the entire process there is just one symbol with this
6691 name and type in use. (This is only supported on assemblers targeting GNU
6696 Note: Some targets support extra types in addition to those listed above.
6702 @section @code{.uleb128 @var{expressions}}
6704 @cindex @code{uleb128} directive
6705 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6706 compact, variable length representation of numbers used by the DWARF
6707 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6711 @section @code{.val @var{addr}}
6713 @cindex @code{val} directive
6714 @cindex COFF value attribute
6715 @cindex value attribute, COFF
6716 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6717 records the address @var{addr} as the value attribute of a symbol table
6721 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6722 configured for @code{b.out}, it accepts this directive but ignores it.
6728 @section @code{.version "@var{string}"}
6730 @cindex @code{version} directive
6731 This directive creates a @code{.note} section and places into it an ELF
6732 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6737 @section @code{.vtable_entry @var{table}, @var{offset}}
6739 @cindex @code{vtable_entry} directive
6740 This directive finds or creates a symbol @code{table} and creates a
6741 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6744 @section @code{.vtable_inherit @var{child}, @var{parent}}
6746 @cindex @code{vtable_inherit} directive
6747 This directive finds the symbol @code{child} and finds or creates the symbol
6748 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6749 parent whose addend is the value of the child symbol. As a special case the
6750 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6754 @section @code{.warning "@var{string}"}
6755 @cindex warning directive
6756 Similar to the directive @code{.error}
6757 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6760 @section @code{.weak @var{names}}
6762 @cindex @code{weak} directive
6763 This directive sets the weak attribute on the comma separated list of symbol
6764 @code{names}. If the symbols do not already exist, they will be created.
6766 On COFF targets other than PE, weak symbols are a GNU extension. This
6767 directive sets the weak attribute on the comma separated list of symbol
6768 @code{names}. If the symbols do not already exist, they will be created.
6770 On the PE target, weak symbols are supported natively as weak aliases.
6771 When a weak symbol is created that is not an alias, GAS creates an
6772 alternate symbol to hold the default value.
6775 @section @code{.weakref @var{alias}, @var{target}}
6777 @cindex @code{weakref} directive
6778 This directive creates an alias to the target symbol that enables the symbol to
6779 be referenced with weak-symbol semantics, but without actually making it weak.
6780 If direct references or definitions of the symbol are present, then the symbol
6781 will not be weak, but if all references to it are through weak references, the
6782 symbol will be marked as weak in the symbol table.
6784 The effect is equivalent to moving all references to the alias to a separate
6785 assembly source file, renaming the alias to the symbol in it, declaring the
6786 symbol as weak there, and running a reloadable link to merge the object files
6787 resulting from the assembly of the new source file and the old source file that
6788 had the references to the alias removed.
6790 The alias itself never makes to the symbol table, and is entirely handled
6791 within the assembler.
6794 @section @code{.word @var{expressions}}
6796 @cindex @code{word} directive
6797 This directive expects zero or more @var{expressions}, of any section,
6798 separated by commas.
6801 For each expression, @command{@value{AS}} emits a 32-bit number.
6804 For each expression, @command{@value{AS}} emits a 16-bit number.
6809 The size of the number emitted, and its byte order,
6810 depend on what target computer the assembly is for.
6813 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6814 @c happen---32-bit addressability, period; no long/short jumps.
6815 @ifset DIFF-TBL-KLUGE
6816 @cindex difference tables altered
6817 @cindex altered difference tables
6819 @emph{Warning: Special Treatment to support Compilers}
6823 Machines with a 32-bit address space, but that do less than 32-bit
6824 addressing, require the following special treatment. If the machine of
6825 interest to you does 32-bit addressing (or doesn't require it;
6826 @pxref{Machine Dependencies}), you can ignore this issue.
6829 In order to assemble compiler output into something that works,
6830 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6831 Directives of the form @samp{.word sym1-sym2} are often emitted by
6832 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6833 directive of the form @samp{.word sym1-sym2}, and the difference between
6834 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6835 creates a @dfn{secondary jump table}, immediately before the next label.
6836 This secondary jump table is preceded by a short-jump to the
6837 first byte after the secondary table. This short-jump prevents the flow
6838 of control from accidentally falling into the new table. Inside the
6839 table is a long-jump to @code{sym2}. The original @samp{.word}
6840 contains @code{sym1} minus the address of the long-jump to
6843 If there were several occurrences of @samp{.word sym1-sym2} before the
6844 secondary jump table, all of them are adjusted. If there was a
6845 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6846 long-jump to @code{sym4} is included in the secondary jump table,
6847 and the @code{.word} directives are adjusted to contain @code{sym3}
6848 minus the address of the long-jump to @code{sym4}; and so on, for as many
6849 entries in the original jump table as necessary.
6852 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6853 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6854 assembly language programmers.
6857 @c end DIFF-TBL-KLUGE
6860 @section Deprecated Directives
6862 @cindex deprecated directives
6863 @cindex obsolescent directives
6864 One day these directives won't work.
6865 They are included for compatibility with older assemblers.
6872 @node Object Attributes
6873 @chapter Object Attributes
6874 @cindex object attributes
6876 @command{@value{AS}} assembles source files written for a specific architecture
6877 into object files for that architecture. But not all object files are alike.
6878 Many architectures support incompatible variations. For instance, floating
6879 point arguments might be passed in floating point registers if the object file
6880 requires hardware floating point support---or floating point arguments might be
6881 passed in integer registers if the object file supports processors with no
6882 hardware floating point unit. Or, if two objects are built for different
6883 generations of the same architecture, the combination may require the
6884 newer generation at run-time.
6886 This information is useful during and after linking. At link time,
6887 @command{@value{LD}} can warn about incompatible object files. After link
6888 time, tools like @command{gdb} can use it to process the linked file
6891 Compatibility information is recorded as a series of object attributes. Each
6892 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6893 string, and indicates who sets the meaning of the tag. The tag is an integer,
6894 and indicates what property the attribute describes. The value may be a string
6895 or an integer, and indicates how the property affects this object. Missing
6896 attributes are the same as attributes with a zero value or empty string value.
6898 Object attributes were developed as part of the ABI for the ARM Architecture.
6899 The file format is documented in @cite{ELF for the ARM Architecture}.
6902 * GNU Object Attributes:: @sc{gnu} Object Attributes
6903 * Defining New Object Attributes:: Defining New Object Attributes
6906 @node GNU Object Attributes
6907 @section @sc{gnu} Object Attributes
6909 The @code{.gnu_attribute} directive records an object attribute
6910 with vendor @samp{gnu}.
6912 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6913 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6914 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6915 2} is set for architecture-independent attributes and clear for
6916 architecture-dependent ones.
6918 @subsection Common @sc{gnu} attributes
6920 These attributes are valid on all architectures.
6923 @item Tag_compatibility (32)
6924 The compatibility attribute takes an integer flag value and a vendor name. If
6925 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6926 then the file is only compatible with the named toolchain. If it is greater
6927 than 1, the file can only be processed by other toolchains under some private
6928 arrangement indicated by the flag value and the vendor name.
6931 @subsection MIPS Attributes
6934 @item Tag_GNU_MIPS_ABI_FP (4)
6935 The floating-point ABI used by this object file. The value will be:
6939 0 for files not affected by the floating-point ABI.
6941 1 for files using the hardware floating-point with a standard double-precision
6944 2 for files using the hardware floating-point ABI with a single-precision FPU.
6946 3 for files using the software floating-point ABI.
6948 4 for files using the hardware floating-point ABI with 64-bit wide
6949 double-precision floating-point registers and 32-bit wide general
6954 @subsection PowerPC Attributes
6957 @item Tag_GNU_Power_ABI_FP (4)
6958 The floating-point ABI used by this object file. The value will be:
6962 0 for files not affected by the floating-point ABI.
6964 1 for files using double-precision hardware floating-point ABI.
6966 2 for files using the software floating-point ABI.
6968 3 for files using single-precision hardware floating-point ABI.
6971 @item Tag_GNU_Power_ABI_Vector (8)
6972 The vector ABI used by this object file. The value will be:
6976 0 for files not affected by the vector ABI.
6978 1 for files using general purpose registers to pass vectors.
6980 2 for files using AltiVec registers to pass vectors.
6982 3 for files using SPE registers to pass vectors.
6986 @node Defining New Object Attributes
6987 @section Defining New Object Attributes
6989 If you want to define a new @sc{gnu} object attribute, here are the places you
6990 will need to modify. New attributes should be discussed on the @samp{binutils}
6995 This manual, which is the official register of attributes.
6997 The header for your architecture @file{include/elf}, to define the tag.
6999 The @file{bfd} support file for your architecture, to merge the attribute
7000 and issue any appropriate link warnings.
7002 Test cases in @file{ld/testsuite} for merging and link warnings.
7004 @file{binutils/readelf.c} to display your attribute.
7006 GCC, if you want the compiler to mark the attribute automatically.
7012 @node Machine Dependencies
7013 @chapter Machine Dependent Features
7015 @cindex machine dependencies
7016 The machine instruction sets are (almost by definition) different on
7017 each machine where @command{@value{AS}} runs. Floating point representations
7018 vary as well, and @command{@value{AS}} often supports a few additional
7019 directives or command-line options for compatibility with other
7020 assemblers on a particular platform. Finally, some versions of
7021 @command{@value{AS}} support special pseudo-instructions for branch
7024 This chapter discusses most of these differences, though it does not
7025 include details on any machine's instruction set. For details on that
7026 subject, see the hardware manufacturer's manual.
7030 * AArch64-Dependent:: AArch64 Dependent Features
7033 * Alpha-Dependent:: Alpha Dependent Features
7036 * ARC-Dependent:: ARC Dependent Features
7039 * ARM-Dependent:: ARM Dependent Features
7042 * AVR-Dependent:: AVR Dependent Features
7045 * Blackfin-Dependent:: Blackfin Dependent Features
7048 * CR16-Dependent:: CR16 Dependent Features
7051 * CRIS-Dependent:: CRIS Dependent Features
7054 * D10V-Dependent:: D10V Dependent Features
7057 * D30V-Dependent:: D30V Dependent Features
7060 * Epiphany-Dependent:: EPIPHANY Dependent Features
7063 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7066 * HPPA-Dependent:: HPPA Dependent Features
7069 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7072 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7075 * i860-Dependent:: Intel 80860 Dependent Features
7078 * i960-Dependent:: Intel 80960 Dependent Features
7081 * IA-64-Dependent:: Intel IA-64 Dependent Features
7084 * IP2K-Dependent:: IP2K Dependent Features
7087 * LM32-Dependent:: LM32 Dependent Features
7090 * M32C-Dependent:: M32C Dependent Features
7093 * M32R-Dependent:: M32R Dependent Features
7096 * M68K-Dependent:: M680x0 Dependent Features
7099 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7102 * Meta-Dependent :: Meta Dependent Features
7105 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7108 * MIPS-Dependent:: MIPS Dependent Features
7111 * MMIX-Dependent:: MMIX Dependent Features
7114 * MSP430-Dependent:: MSP430 Dependent Features
7117 * NiosII-Dependent:: Altera Nios II Dependent Features
7120 * NS32K-Dependent:: NS32K Dependent Features
7123 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7124 * SH64-Dependent:: SuperH SH64 Dependent Features
7127 * PDP-11-Dependent:: PDP-11 Dependent Features
7130 * PJ-Dependent:: picoJava Dependent Features
7133 * PPC-Dependent:: PowerPC Dependent Features
7136 * RL78-Dependent:: RL78 Dependent Features
7139 * RX-Dependent:: RX Dependent Features
7142 * S/390-Dependent:: IBM S/390 Dependent Features
7145 * SCORE-Dependent:: SCORE Dependent Features
7148 * Sparc-Dependent:: SPARC Dependent Features
7151 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7154 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7157 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7160 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7163 * V850-Dependent:: V850 Dependent Features
7166 * XGATE-Dependent:: XGATE Features
7169 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7172 * Xtensa-Dependent:: Xtensa Dependent Features
7175 * Z80-Dependent:: Z80 Dependent Features
7178 * Z8000-Dependent:: Z8000 Dependent Features
7181 * Vax-Dependent:: VAX Dependent Features
7188 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7189 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7190 @c peculiarity: to preserve cross-references, there must be a node called
7191 @c "Machine Dependencies". Hence the conditional nodenames in each
7192 @c major node below. Node defaulting in makeinfo requires adjacency of
7193 @c node and sectioning commands; hence the repetition of @chapter BLAH
7194 @c in both conditional blocks.
7197 @include c-aarch64.texi
7201 @include c-alpha.texi
7217 @include c-bfin.texi
7221 @include c-cr16.texi
7225 @include c-cris.texi
7230 @node Machine Dependencies
7231 @chapter Machine Dependent Features
7233 The machine instruction sets are different on each Renesas chip family,
7234 and there are also some syntax differences among the families. This
7235 chapter describes the specific @command{@value{AS}} features for each
7239 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7240 * SH-Dependent:: Renesas SH Dependent Features
7247 @include c-d10v.texi
7251 @include c-d30v.texi
7255 @include c-epiphany.texi
7259 @include c-h8300.texi
7263 @include c-hppa.texi
7267 @include c-i370.texi
7271 @include c-i386.texi
7275 @include c-i860.texi
7279 @include c-i960.texi
7283 @include c-ia64.texi
7287 @include c-ip2k.texi
7291 @include c-lm32.texi
7295 @include c-m32c.texi
7299 @include c-m32r.texi
7303 @include c-m68k.texi
7307 @include c-m68hc11.texi
7311 @include c-metag.texi
7315 @include c-microblaze.texi
7319 @include c-mips.texi
7323 @include c-mmix.texi
7327 @include c-msp430.texi
7331 @include c-nios2.texi
7335 @include c-ns32k.texi
7339 @include c-pdp11.texi
7351 @include c-rl78.texi
7359 @include c-s390.texi
7363 @include c-score.texi
7368 @include c-sh64.texi
7372 @include c-sparc.texi
7376 @include c-tic54x.texi
7380 @include c-tic6x.texi
7384 @include c-tilegx.texi
7388 @include c-tilepro.texi
7404 @include c-v850.texi
7408 @include c-xgate.texi
7412 @include c-xstormy16.texi
7416 @include c-xtensa.texi
7420 @c reverse effect of @down at top of generic Machine-Dep chapter
7424 @node Reporting Bugs
7425 @chapter Reporting Bugs
7426 @cindex bugs in assembler
7427 @cindex reporting bugs in assembler
7429 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7431 Reporting a bug may help you by bringing a solution to your problem, or it may
7432 not. But in any case the principal function of a bug report is to help the
7433 entire community by making the next version of @command{@value{AS}} work better.
7434 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7436 In order for a bug report to serve its purpose, you must include the
7437 information that enables us to fix the bug.
7440 * Bug Criteria:: Have you found a bug?
7441 * Bug Reporting:: How to report bugs
7445 @section Have You Found a Bug?
7446 @cindex bug criteria
7448 If you are not sure whether you have found a bug, here are some guidelines:
7451 @cindex fatal signal
7452 @cindex assembler crash
7453 @cindex crash of assembler
7455 If the assembler gets a fatal signal, for any input whatever, that is a
7456 @command{@value{AS}} bug. Reliable assemblers never crash.
7458 @cindex error on valid input
7460 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7462 @cindex invalid input
7464 If @command{@value{AS}} does not produce an error message for invalid input, that
7465 is a bug. However, you should note that your idea of ``invalid input'' might
7466 be our idea of ``an extension'' or ``support for traditional practice''.
7469 If you are an experienced user of assemblers, your suggestions for improvement
7470 of @command{@value{AS}} are welcome in any case.
7474 @section How to Report Bugs
7476 @cindex assembler bugs, reporting
7478 A number of companies and individuals offer support for @sc{gnu} products. If
7479 you obtained @command{@value{AS}} from a support organization, we recommend you
7480 contact that organization first.
7482 You can find contact information for many support companies and
7483 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7487 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7491 The fundamental principle of reporting bugs usefully is this:
7492 @strong{report all the facts}. If you are not sure whether to state a
7493 fact or leave it out, state it!
7495 Often people omit facts because they think they know what causes the problem
7496 and assume that some details do not matter. Thus, you might assume that the
7497 name of a symbol you use in an example does not matter. Well, probably it does
7498 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7499 happens to fetch from the location where that name is stored in memory;
7500 perhaps, if the name were different, the contents of that location would fool
7501 the assembler into doing the right thing despite the bug. Play it safe and
7502 give a specific, complete example. That is the easiest thing for you to do,
7503 and the most helpful.
7505 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7506 it is new to us. Therefore, always write your bug reports on the assumption
7507 that the bug has not been reported previously.
7509 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7510 bell?'' This cannot help us fix a bug, so it is basically useless. We
7511 respond by asking for enough details to enable us to investigate.
7512 You might as well expedite matters by sending them to begin with.
7514 To enable us to fix the bug, you should include all these things:
7518 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7519 it with the @samp{--version} argument.
7521 Without this, we will not know whether there is any point in looking for
7522 the bug in the current version of @command{@value{AS}}.
7525 Any patches you may have applied to the @command{@value{AS}} source.
7528 The type of machine you are using, and the operating system name and
7532 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7536 The command arguments you gave the assembler to assemble your example and
7537 observe the bug. To guarantee you will not omit something important, list them
7538 all. A copy of the Makefile (or the output from make) is sufficient.
7540 If we were to try to guess the arguments, we would probably guess wrong
7541 and then we might not encounter the bug.
7544 A complete input file that will reproduce the bug. If the bug is observed when
7545 the assembler is invoked via a compiler, send the assembler source, not the
7546 high level language source. Most compilers will produce the assembler source
7547 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7548 the options @samp{-v --save-temps}; this will save the assembler source in a
7549 file with an extension of @file{.s}, and also show you exactly how
7550 @command{@value{AS}} is being run.
7553 A description of what behavior you observe that you believe is
7554 incorrect. For example, ``It gets a fatal signal.''
7556 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7557 will certainly notice it. But if the bug is incorrect output, we might not
7558 notice unless it is glaringly wrong. You might as well not give us a chance to
7561 Even if the problem you experience is a fatal signal, you should still say so
7562 explicitly. Suppose something strange is going on, such as, your copy of
7563 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7564 library on your system. (This has happened!) Your copy might crash and ours
7565 would not. If you told us to expect a crash, then when ours fails to crash, we
7566 would know that the bug was not happening for us. If you had not told us to
7567 expect a crash, then we would not be able to draw any conclusion from our
7571 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7572 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7573 option. Always send diffs from the old file to the new file. If you even
7574 discuss something in the @command{@value{AS}} source, refer to it by context, not
7577 The line numbers in our development sources will not match those in your
7578 sources. Your line numbers would convey no useful information to us.
7581 Here are some things that are not necessary:
7585 A description of the envelope of the bug.
7587 Often people who encounter a bug spend a lot of time investigating
7588 which changes to the input file will make the bug go away and which
7589 changes will not affect it.
7591 This is often time consuming and not very useful, because the way we
7592 will find the bug is by running a single example under the debugger
7593 with breakpoints, not by pure deduction from a series of examples.
7594 We recommend that you save your time for something else.
7596 Of course, if you can find a simpler example to report @emph{instead}
7597 of the original one, that is a convenience for us. Errors in the
7598 output will be easier to spot, running under the debugger will take
7599 less time, and so on.
7601 However, simplification is not vital; if you do not want to do this,
7602 report the bug anyway and send us the entire test case you used.
7605 A patch for the bug.
7607 A patch for the bug does help us if it is a good one. But do not omit
7608 the necessary information, such as the test case, on the assumption that
7609 a patch is all we need. We might see problems with your patch and decide
7610 to fix the problem another way, or we might not understand it at all.
7612 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7613 construct an example that will make the program follow a certain path through
7614 the code. If you do not send us the example, we will not be able to construct
7615 one, so we will not be able to verify that the bug is fixed.
7617 And if we cannot understand what bug you are trying to fix, or why your
7618 patch should be an improvement, we will not install it. A test case will
7619 help us to understand.
7622 A guess about what the bug is or what it depends on.
7624 Such guesses are usually wrong. Even we cannot guess right about such
7625 things without first using the debugger to find the facts.
7628 @node Acknowledgements
7629 @chapter Acknowledgements
7631 If you have contributed to GAS and your name isn't listed here,
7632 it is not meant as a slight. We just don't know about it. Send mail to the
7633 maintainer, and we'll correct the situation. Currently
7635 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7637 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7640 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7641 information and the 68k series machines, most of the preprocessing pass, and
7642 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7644 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7645 many bug fixes, including merging support for several processors, breaking GAS
7646 up to handle multiple object file format back ends (including heavy rewrite,
7647 testing, an integration of the coff and b.out back ends), adding configuration
7648 including heavy testing and verification of cross assemblers and file splits
7649 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7650 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7651 port (including considerable amounts of reverse engineering), a SPARC opcode
7652 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7653 assertions and made them work, much other reorganization, cleanup, and lint.
7655 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7656 in format-specific I/O modules.
7658 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7659 has done much work with it since.
7661 The Intel 80386 machine description was written by Eliot Dresselhaus.
7663 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7665 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7666 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7668 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7669 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7670 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7671 support a.out format.
7673 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7674 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7675 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7676 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7679 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7680 simplified the configuration of which versions accept which directives. He
7681 updated the 68k machine description so that Motorola's opcodes always produced
7682 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7683 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7684 cross-compilation support, and one bug in relaxation that took a week and
7685 required the proverbial one-bit fix.
7687 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7688 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7689 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7690 PowerPC assembler, and made a few other minor patches.
7692 Steve Chamberlain made GAS able to generate listings.
7694 Hewlett-Packard contributed support for the HP9000/300.
7696 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7697 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7698 formats). This work was supported by both the Center for Software Science at
7699 the University of Utah and Cygnus Support.
7701 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7702 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7703 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7704 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7705 and some initial 64-bit support).
7707 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7709 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7710 support for openVMS/Alpha.
7712 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7715 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7716 Inc.@: added support for Xtensa processors.
7718 Several engineers at Cygnus Support have also provided many small bug fixes and
7719 configuration enhancements.
7721 Jon Beniston added support for the Lattice Mico32 architecture.
7723 Many others have contributed large or small bugfixes and enhancements. If
7724 you have contributed significant work and are not mentioned on this list, and
7725 want to be, let us know. Some of the history has been lost; we are not
7726 intentionally leaving anyone out.
7728 @node GNU Free Documentation License
7729 @appendix GNU Free Documentation License
7733 @unnumbered AS Index