1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (C) 1991-2014 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{} 1991-2014 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{} 1991-2014 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
251 [@b{-mabi}=@var{ABI}]
255 @emph{Target Alpha options:}
257 [@b{-mdebug} | @b{-no-mdebug}]
258 [@b{-replace} | @b{-noreplace}]
259 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
260 [@b{-F}] [@b{-32addr}]
264 @emph{Target ARC options:}
270 @emph{Target ARM options:}
271 @c Don't document the deprecated options
272 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
273 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
274 [@b{-mfpu}=@var{floating-point-format}]
275 [@b{-mfloat-abi}=@var{abi}]
276 [@b{-meabi}=@var{ver}]
279 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
280 @b{-mapcs-reentrant}]
281 [@b{-mthumb-interwork}] [@b{-k}]
285 @emph{Target Blackfin options:}
286 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
293 @emph{Target CRIS options:}
294 [@b{--underscore} | @b{--no-underscore}]
296 [@b{--emulation=criself} | @b{--emulation=crisaout}]
297 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
298 @c Deprecated -- deliberately not documented.
303 @emph{Target D10V options:}
308 @emph{Target D30V options:}
309 [@b{-O}|@b{-n}|@b{-N}]
313 @emph{Target EPIPHANY options:}
314 [@b{-mepiphany}|@b{-mepiphany16}]
318 @emph{Target H8/300 options:}
322 @c HPPA has no machine-dependent assembler options (yet).
326 @emph{Target i386 options:}
327 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
328 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
332 @emph{Target i960 options:}
333 @c see md_parse_option in tc-i960.c
334 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
336 [@b{-b}] [@b{-no-relax}]
340 @emph{Target IA-64 options:}
341 [@b{-mconstant-gp}|@b{-mauto-pic}]
342 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
344 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
345 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
346 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
347 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
351 @emph{Target IP2K options:}
352 [@b{-mip2022}|@b{-mip2022ext}]
356 @emph{Target M32C options:}
357 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
361 @emph{Target M32R options:}
362 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
367 @emph{Target M680X0 options:}
368 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
372 @emph{Target M68HC11 options:}
373 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
374 [@b{-mshort}|@b{-mlong}]
375 [@b{-mshort-double}|@b{-mlong-double}]
376 [@b{--force-long-branches}] [@b{--short-branches}]
377 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
378 [@b{--print-opcodes}] [@b{--generate-example}]
382 @emph{Target MCORE options:}
383 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
384 [@b{-mcpu=[210|340]}]
388 @emph{Target Meta options:}
389 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
392 @emph{Target MICROBLAZE options:}
393 @c MicroBlaze has no machine-dependent assembler options.
397 @emph{Target MIPS options:}
398 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
399 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
400 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
401 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
402 [@b{-mfp64}] [@b{-mgp64}] [@b{-mfpxx}]
403 [@b{-modd-spreg}] [@b{-mno-odd-spreg}]
404 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
405 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
406 [@b{-mips32r3}] [@b{-mips32r5}] [@b{-mips32r6}] [@b{-mips64}] [@b{-mips64r2}]
407 [@b{-mips64r3}] [@b{-mips64r5}] [@b{-mips64r6}]
408 [@b{-construct-floats}] [@b{-no-construct-floats}]
409 [@b{-mnan=@var{encoding}}]
410 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
411 [@b{-mips16}] [@b{-no-mips16}]
412 [@b{-mmicromips}] [@b{-mno-micromips}]
413 [@b{-msmartmips}] [@b{-mno-smartmips}]
414 [@b{-mips3d}] [@b{-no-mips3d}]
415 [@b{-mdmx}] [@b{-no-mdmx}]
416 [@b{-mdsp}] [@b{-mno-dsp}]
417 [@b{-mdspr2}] [@b{-mno-dspr2}]
418 [@b{-mmsa}] [@b{-mno-msa}]
419 [@b{-mxpa}] [@b{-mno-xpa}]
420 [@b{-mmt}] [@b{-mno-mt}]
421 [@b{-mmcu}] [@b{-mno-mcu}]
422 [@b{-minsn32}] [@b{-mno-insn32}]
423 [@b{-mfix7000}] [@b{-mno-fix7000}]
424 [@b{-mfix-rm7000}] [@b{-mno-fix-rm7000}]
425 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
426 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
427 [@b{-mdebug}] [@b{-no-mdebug}]
428 [@b{-mpdr}] [@b{-mno-pdr}]
432 @emph{Target MMIX options:}
433 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
434 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
435 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
436 [@b{--linker-allocated-gregs}]
440 @emph{Target Nios II options:}
441 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
446 @emph{Target NDS32 options:}
447 [@b{-EL}] [@b{-EB}] [@b{-O}] [@b{-Os}] [@b{-mcpu=@var{cpu}}]
448 [@b{-misa=@var{isa}}] [@b{-mabi=@var{abi}}] [@b{-mall-ext}]
449 [@b{-m[no-]16-bit}] [@b{-m[no-]perf-ext}] [@b{-m[no-]perf2-ext}]
450 [@b{-m[no-]string-ext}] [@b{-m[no-]dsp-ext}] [@b{-m[no-]mac}] [@b{-m[no-]div}]
451 [@b{-m[no-]audio-isa-ext}] [@b{-m[no-]fpu-sp-ext}] [@b{-m[no-]fpu-dp-ext}]
452 [@b{-m[no-]fpu-fma}] [@b{-mfpu-freg=@var{FREG}}] [@b{-mreduced-regs}]
453 [@b{-mfull-regs}] [@b{-m[no-]dx-regs}] [@b{-mpic}] [@b{-mno-relax}]
458 @emph{Target PDP11 options:}
459 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
460 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
461 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
465 @emph{Target picoJava options:}
470 @emph{Target PowerPC options:}
472 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
473 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
474 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
475 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
476 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
477 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
478 [@b{-mregnames}|@b{-mno-regnames}]
479 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
480 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
481 [@b{-msolaris}|@b{-mno-solaris}]
482 [@b{-nops=@var{count}}]
486 @emph{Target RL78 options:}
488 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
492 @emph{Target RX options:}
493 [@b{-mlittle-endian}|@b{-mbig-endian}]
494 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
495 [@b{-muse-conventional-section-names}]
496 [@b{-msmall-data-limit}]
499 [@b{-mint-register=@var{number}}]
500 [@b{-mgcc-abi}|@b{-mrx-abi}]
504 @emph{Target s390 options:}
505 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
506 [@b{-mregnames}|@b{-mno-regnames}]
507 [@b{-mwarn-areg-zero}]
511 @emph{Target SCORE options:}
512 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
513 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
514 [@b{-march=score7}][@b{-march=score3}]
515 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
519 @emph{Target SPARC options:}
520 @c The order here is important. See c-sparc.texi.
521 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
522 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
523 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
528 @emph{Target TIC54X options:}
529 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
530 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
535 @emph{Target TIC6X options:}
536 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
537 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
538 [@b{-mpic}|@b{-mno-pic}]
542 @emph{Target TILE-Gx options:}
543 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
546 @c TILEPro has no machine-dependent assembler options
551 @emph{Target Xtensa options:}
552 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
553 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
554 [@b{--[no-]transform}]
555 [@b{--rename-section} @var{oldname}=@var{newname}]
556 [@b{--[no-]trampolines}]
561 @emph{Target Z80 options:}
562 [@b{-z80}] [@b{-r800}]
563 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
564 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
565 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
566 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
567 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
568 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
572 @c Z8000 has no machine-dependent assembler options
581 @include at-file.texi
584 Turn on listings, in any of a variety of ways:
588 omit false conditionals
591 omit debugging directives
594 include general information, like @value{AS} version and options passed
597 include high-level source
603 include macro expansions
606 omit forms processing
612 set the name of the listing file
615 You may combine these options; for example, use @samp{-aln} for assembly
616 listing without forms processing. The @samp{=file} option, if used, must be
617 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
620 Begin in alternate macro mode.
622 @xref{Altmacro,,@code{.altmacro}}.
625 @item --compress-debug-sections
626 Compress DWARF debug sections using zlib. The debug sections are renamed
627 to begin with @samp{.zdebug}, and the resulting object file may not be
628 compatible with older linkers and object file utilities.
630 @item --nocompress-debug-sections
631 Do not compress DWARF debug sections. This is the default.
634 Ignored. This option is accepted for script compatibility with calls to
637 @item --debug-prefix-map @var{old}=@var{new}
638 When assembling files in directory @file{@var{old}}, record debugging
639 information describing them as in @file{@var{new}} instead.
641 @item --defsym @var{sym}=@var{value}
642 Define the symbol @var{sym} to be @var{value} before assembling the input file.
643 @var{value} must be an integer constant. As in C, a leading @samp{0x}
644 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
645 value. The value of the symbol can be overridden inside a source file via the
646 use of a @code{.set} pseudo-op.
649 ``fast''---skip whitespace and comment preprocessing (assume source is
654 Generate debugging information for each assembler source line using whichever
655 debug format is preferred by the target. This currently means either STABS,
659 Generate stabs debugging information for each assembler line. This
660 may help debugging assembler code, if the debugger can handle it.
663 Generate stabs debugging information for each assembler line, with GNU
664 extensions that probably only gdb can handle, and that could make other
665 debuggers crash or refuse to read your program. This
666 may help debugging assembler code. Currently the only GNU extension is
667 the location of the current working directory at assembling time.
670 Generate DWARF2 debugging information for each assembler line. This
671 may help debugging assembler code, if the debugger can handle it. Note---this
672 option is only supported by some targets, not all of them.
674 @item --gdwarf-sections
675 Instead of creating a .debug_line section, create a series of
676 .debug_line.@var{foo} sections where @var{foo} is the name of the
677 corresponding code section. For example a code section called @var{.text.func}
678 will have its dwarf line number information placed into a section called
679 @var{.debug_line.text.func}. If the code section is just called @var{.text}
680 then debug line section will still be called just @var{.debug_line} without any
683 @item --size-check=error
684 @itemx --size-check=warning
685 Issue an error or warning for invalid ELF .size directive.
688 Print a summary of the command line options and exit.
691 Print a summary of all target specific options and exit.
694 Add directory @var{dir} to the search list for @code{.include} directives.
697 Don't warn about signed overflow.
700 @ifclear DIFF-TBL-KLUGE
701 This option is accepted but has no effect on the @value{TARGET} family.
703 @ifset DIFF-TBL-KLUGE
704 Issue warnings when difference tables altered for long displacements.
709 Keep (in the symbol table) local symbols. These symbols start with
710 system-specific local label prefixes, typically @samp{.L} for ELF systems
711 or @samp{L} for traditional a.out systems.
716 @item --listing-lhs-width=@var{number}
717 Set the maximum width, in words, of the output data column for an assembler
718 listing to @var{number}.
720 @item --listing-lhs-width2=@var{number}
721 Set the maximum width, in words, of the output data column for continuation
722 lines in an assembler listing to @var{number}.
724 @item --listing-rhs-width=@var{number}
725 Set the maximum width of an input source line, as displayed in a listing, to
728 @item --listing-cont-lines=@var{number}
729 Set the maximum number of lines printed in a listing for a single line of input
732 @item -o @var{objfile}
733 Name the object-file output from @command{@value{AS}} @var{objfile}.
736 Fold the data section into the text section.
738 @kindex --hash-size=@var{number}
739 Set the default size of GAS's hash tables to a prime number close to
740 @var{number}. Increasing this value can reduce the length of time it takes the
741 assembler to perform its tasks, at the expense of increasing the assembler's
742 memory requirements. Similarly reducing this value can reduce the memory
743 requirements at the expense of speed.
745 @item --reduce-memory-overheads
746 This option reduces GAS's memory requirements, at the expense of making the
747 assembly processes slower. Currently this switch is a synonym for
748 @samp{--hash-size=4051}, but in the future it may have other effects as well.
751 Print the maximum space (in bytes) and total time (in seconds) used by
754 @item --strip-local-absolute
755 Remove local absolute symbols from the outgoing symbol table.
759 Print the @command{as} version.
762 Print the @command{as} version and exit.
766 Suppress warning messages.
768 @item --fatal-warnings
769 Treat warnings as errors.
772 Don't suppress warning messages or treat them as errors.
781 Generate an object file even after errors.
783 @item -- | @var{files} @dots{}
784 Standard input, or source files to assemble.
792 @xref{AArch64 Options}, for the options available when @value{AS} is configured
793 for the 64-bit mode of the ARM Architecture (AArch64).
798 The following options are available when @value{AS} is configured for the
799 64-bit mode of the ARM Architecture (AArch64).
802 @include c-aarch64.texi
803 @c ended inside the included file
811 @xref{Alpha Options}, for the options available when @value{AS} is configured
812 for an Alpha processor.
817 The following options are available when @value{AS} is configured for an Alpha
821 @include c-alpha.texi
822 @c ended inside the included file
829 The following options are available when @value{AS} is configured for
834 This option selects the core processor variant.
836 Select either big-endian (-EB) or little-endian (-EL) output.
841 The following options are available when @value{AS} is configured for the ARM
845 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
846 Specify which ARM processor variant is the target.
847 @item -march=@var{architecture}[+@var{extension}@dots{}]
848 Specify which ARM architecture variant is used by the target.
849 @item -mfpu=@var{floating-point-format}
850 Select which Floating Point architecture is the target.
851 @item -mfloat-abi=@var{abi}
852 Select which floating point ABI is in use.
854 Enable Thumb only instruction decoding.
855 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
856 Select which procedure calling convention is in use.
858 Select either big-endian (-EB) or little-endian (-EL) output.
859 @item -mthumb-interwork
860 Specify that the code has been generated with interworking between Thumb and
863 Turns on CodeComposer Studio assembly syntax compatibility mode.
865 Specify that PIC code has been generated.
873 @xref{Blackfin Options}, for the options available when @value{AS} is
874 configured for the Blackfin processor family.
879 The following options are available when @value{AS} is configured for
880 the Blackfin processor family.
884 @c ended inside the included file
891 See the info pages for documentation of the CRIS-specific options.
895 The following options are available when @value{AS} is configured for
898 @cindex D10V optimization
899 @cindex optimization, D10V
901 Optimize output by parallelizing instructions.
906 The following options are available when @value{AS} is configured for a D30V
909 @cindex D30V optimization
910 @cindex optimization, D30V
912 Optimize output by parallelizing instructions.
916 Warn when nops are generated.
918 @cindex D30V nops after 32-bit multiply
920 Warn when a nop after a 32-bit multiply instruction is generated.
926 The following options are available when @value{AS} is configured for the
927 Adapteva EPIPHANY series.
930 @xref{Epiphany Options}, for the options available when @value{AS} is
931 configured for an Epiphany processor.
936 The following options are available when @value{AS} is configured for
937 an Epiphany processor.
940 @include c-epiphany.texi
941 @c ended inside the included file
949 @xref{H8/300 Options}, for the options available when @value{AS} is configured
950 for an H8/300 processor.
955 The following options are available when @value{AS} is configured for an H8/300
959 @include c-h8300.texi
960 @c ended inside the included file
968 @xref{i386-Options}, for the options available when @value{AS} is
969 configured for an i386 processor.
974 The following options are available when @value{AS} is configured for
979 @c ended inside the included file
986 The following options are available when @value{AS} is configured for the
987 Intel 80960 processor.
990 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
991 Specify which variant of the 960 architecture is the target.
994 Add code to collect statistics about branches taken.
997 Do not alter compare-and-branch instructions for long displacements;
1004 The following options are available when @value{AS} is configured for the
1010 Specifies that the extended IP2022 instructions are allowed.
1013 Restores the default behaviour, which restricts the permitted instructions to
1014 just the basic IP2022 ones.
1020 The following options are available when @value{AS} is configured for the
1021 Renesas M32C and M16C processors.
1026 Assemble M32C instructions.
1029 Assemble M16C instructions (the default).
1032 Enable support for link-time relaxations.
1035 Support H'00 style hex constants in addition to 0x00 style.
1041 The following options are available when @value{AS} is configured for the
1042 Renesas M32R (formerly Mitsubishi M32R) series.
1047 Specify which processor in the M32R family is the target. The default
1048 is normally the M32R, but this option changes it to the M32RX.
1050 @item --warn-explicit-parallel-conflicts or --Wp
1051 Produce warning messages when questionable parallel constructs are
1054 @item --no-warn-explicit-parallel-conflicts or --Wnp
1055 Do not produce warning messages when questionable parallel constructs are
1062 The following options are available when @value{AS} is configured for the
1063 Motorola 68000 series.
1068 Shorten references to undefined symbols, to one word instead of two.
1070 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1071 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1072 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1073 Specify what processor in the 68000 family is the target. The default
1074 is normally the 68020, but this can be changed at configuration time.
1076 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1077 The target machine does (or does not) have a floating-point coprocessor.
1078 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1079 the basic 68000 is not compatible with the 68881, a combination of the
1080 two can be specified, since it's possible to do emulation of the
1081 coprocessor instructions with the main processor.
1083 @item -m68851 | -mno-68851
1084 The target machine does (or does not) have a memory-management
1085 unit coprocessor. The default is to assume an MMU for 68020 and up.
1093 @xref{Nios II Options}, for the options available when @value{AS} is configured
1094 for an Altera Nios II processor.
1098 @c man begin OPTIONS
1099 The following options are available when @value{AS} is configured for an
1100 Altera Nios II processor.
1102 @c man begin INCLUDE
1103 @include c-nios2.texi
1104 @c ended inside the included file
1110 For details about the PDP-11 machine dependent features options,
1111 see @ref{PDP-11-Options}.
1114 @item -mpic | -mno-pic
1115 Generate position-independent (or position-dependent) code. The
1116 default is @option{-mpic}.
1119 @itemx -mall-extensions
1120 Enable all instruction set extensions. This is the default.
1122 @item -mno-extensions
1123 Disable all instruction set extensions.
1125 @item -m@var{extension} | -mno-@var{extension}
1126 Enable (or disable) a particular instruction set extension.
1129 Enable the instruction set extensions supported by a particular CPU, and
1130 disable all other extensions.
1132 @item -m@var{machine}
1133 Enable the instruction set extensions supported by a particular machine
1134 model, and disable all other extensions.
1140 The following options are available when @value{AS} is configured for
1141 a picoJava processor.
1145 @cindex PJ endianness
1146 @cindex endianness, PJ
1147 @cindex big endian output, PJ
1149 Generate ``big endian'' format output.
1151 @cindex little endian output, PJ
1153 Generate ``little endian'' format output.
1159 The following options are available when @value{AS} is configured for the
1160 Motorola 68HC11 or 68HC12 series.
1164 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1165 Specify what processor is the target. The default is
1166 defined by the configuration option when building the assembler.
1168 @item --xgate-ramoffset
1169 Instruct the linker to offset RAM addresses from S12X address space into
1170 XGATE address space.
1173 Specify to use the 16-bit integer ABI.
1176 Specify to use the 32-bit integer ABI.
1178 @item -mshort-double
1179 Specify to use the 32-bit double ABI.
1182 Specify to use the 64-bit double ABI.
1184 @item --force-long-branches
1185 Relative branches are turned into absolute ones. This concerns
1186 conditional branches, unconditional branches and branches to a
1189 @item -S | --short-branches
1190 Do not turn relative branches into absolute ones
1191 when the offset is out of range.
1193 @item --strict-direct-mode
1194 Do not turn the direct addressing mode into extended addressing mode
1195 when the instruction does not support direct addressing mode.
1197 @item --print-insn-syntax
1198 Print the syntax of instruction in case of error.
1200 @item --print-opcodes
1201 Print the list of instructions with syntax and then exit.
1203 @item --generate-example
1204 Print an example of instruction for each possible instruction and then exit.
1205 This option is only useful for testing @command{@value{AS}}.
1211 The following options are available when @command{@value{AS}} is configured
1212 for the SPARC architecture:
1215 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1216 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1217 Explicitly select a variant of the SPARC architecture.
1219 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1220 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1222 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1223 UltraSPARC extensions.
1225 @item -xarch=v8plus | -xarch=v8plusa
1226 For compatibility with the Solaris v9 assembler. These options are
1227 equivalent to -Av8plus and -Av8plusa, respectively.
1230 Warn when the assembler switches to another architecture.
1235 The following options are available when @value{AS} is configured for the 'c54x
1240 Enable extended addressing mode. All addresses and relocations will assume
1241 extended addressing (usually 23 bits).
1242 @item -mcpu=@var{CPU_VERSION}
1243 Sets the CPU version being compiled for.
1244 @item -merrors-to-file @var{FILENAME}
1245 Redirect error output to a file, for broken systems which don't support such
1246 behaviour in the shell.
1251 The following options are available when @value{AS} is configured for
1256 This option sets the largest size of an object that can be referenced
1257 implicitly with the @code{gp} register. It is only accepted for targets that
1258 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1260 @cindex MIPS endianness
1261 @cindex endianness, MIPS
1262 @cindex big endian output, MIPS
1264 Generate ``big endian'' format output.
1266 @cindex little endian output, MIPS
1268 Generate ``little endian'' format output.
1286 Generate code for a particular MIPS Instruction Set Architecture level.
1287 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1288 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1289 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1290 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1291 @samp{-mips32r5}, @samp{-mips32r6}, @samp{-mips64}, @samp{-mips64r2},
1292 @samp{-mips64r3}, @samp{-mips64r5}, and @samp{-mips64r6} correspond to generic
1293 MIPS V, MIPS32, MIPS32 Release 2, MIPS32 Release 3, MIPS32 Release 5, MIPS32
1294 Release 6, MIPS64, MIPS64 Release 2, MIPS64 Release 3, MIPS64 Release 5, and
1295 MIPS64 Release 6 ISA processors, respectively.
1297 @item -march=@var{cpu}
1298 Generate code for a particular MIPS CPU.
1300 @item -mtune=@var{cpu}
1301 Schedule and tune for a particular MIPS CPU.
1305 Cause nops to be inserted if the read of the destination register
1306 of an mfhi or mflo instruction occurs in the following two instructions.
1309 @itemx -mno-fix-rm7000
1310 Cause nops to be inserted if a dmult or dmultu instruction is
1311 followed by a load instruction.
1315 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1316 section instead of the standard ELF .stabs sections.
1320 Control generation of @code{.pdr} sections.
1324 The register sizes are normally inferred from the ISA and ABI, but these
1325 flags force a certain group of registers to be treated as 32 bits wide at
1326 all times. @samp{-mgp32} controls the size of general-purpose registers
1327 and @samp{-mfp32} controls the size of floating-point registers.
1331 The register sizes are normally inferred from the ISA and ABI, but these
1332 flags force a certain group of registers to be treated as 64 bits wide at
1333 all times. @samp{-mgp64} controls the size of general-purpose registers
1334 and @samp{-mfp64} controls the size of floating-point registers.
1337 The register sizes are normally inferred from the ISA and ABI, but using
1338 this flag in combination with @samp{-mabi=32} enables an ABI variant
1339 which will operate correctly with floating-point registers which are
1343 @itemx -mno-odd-spreg
1344 Enable use of floating-point operations on odd-numbered single-precision
1345 registers when supported by the ISA. @samp{-mfpxx} implies
1346 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1350 Generate code for the MIPS 16 processor. This is equivalent to putting
1351 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1352 turns off this option.
1355 @itemx -mno-micromips
1356 Generate code for the microMIPS processor. This is equivalent to putting
1357 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1358 turns off this option. This is equivalent to putting @code{.set nomicromips}
1359 at the start of the assembly file.
1362 @itemx -mno-smartmips
1363 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1364 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1365 @samp{-mno-smartmips} turns off this option.
1369 Generate code for the MIPS-3D Application Specific Extension.
1370 This tells the assembler to accept MIPS-3D instructions.
1371 @samp{-no-mips3d} turns off this option.
1375 Generate code for the MDMX Application Specific Extension.
1376 This tells the assembler to accept MDMX instructions.
1377 @samp{-no-mdmx} turns off this option.
1381 Generate code for the DSP Release 1 Application Specific Extension.
1382 This tells the assembler to accept DSP Release 1 instructions.
1383 @samp{-mno-dsp} turns off this option.
1387 Generate code for the DSP Release 2 Application Specific Extension.
1388 This option implies -mdsp.
1389 This tells the assembler to accept DSP Release 2 instructions.
1390 @samp{-mno-dspr2} turns off this option.
1394 Generate code for the MIPS SIMD Architecture Extension.
1395 This tells the assembler to accept MSA instructions.
1396 @samp{-mno-msa} turns off this option.
1400 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1401 This tells the assembler to accept XPA instructions.
1402 @samp{-mno-xpa} turns off this option.
1406 Generate code for the MT Application Specific Extension.
1407 This tells the assembler to accept MT instructions.
1408 @samp{-mno-mt} turns off this option.
1412 Generate code for the MCU Application Specific Extension.
1413 This tells the assembler to accept MCU instructions.
1414 @samp{-mno-mcu} turns off this option.
1418 Only use 32-bit instruction encodings when generating code for the
1419 microMIPS processor. This option inhibits the use of any 16-bit
1420 instructions. This is equivalent to putting @code{.set insn32} at
1421 the start of the assembly file. @samp{-mno-insn32} turns off this
1422 option. This is equivalent to putting @code{.set noinsn32} at the
1423 start of the assembly file. By default @samp{-mno-insn32} is
1424 selected, allowing all instructions to be used.
1426 @item --construct-floats
1427 @itemx --no-construct-floats
1428 The @samp{--no-construct-floats} option disables the construction of
1429 double width floating point constants by loading the two halves of the
1430 value into the two single width floating point registers that make up
1431 the double width register. By default @samp{--construct-floats} is
1432 selected, allowing construction of these floating point constants.
1434 @item --relax-branch
1435 @itemx --no-relax-branch
1436 The @samp{--relax-branch} option enables the relaxation of out-of-range
1437 branches. By default @samp{--no-relax-branch} is selected, causing any
1438 out-of-range branches to produce an error.
1440 @item -mnan=@var{encoding}
1441 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1442 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1445 @item --emulation=@var{name}
1446 This option was formerly used to switch between ELF and ECOFF output
1447 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1448 removed in GAS 2.24, so the option now serves little purpose.
1449 It is retained for backwards compatibility.
1451 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1452 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1453 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1454 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1455 preferred options instead.
1458 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1465 Control how to deal with multiplication overflow and division by zero.
1466 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1467 (and only work for Instruction Set Architecture level 2 and higher);
1468 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1472 When this option is used, @command{@value{AS}} will issue a warning every
1473 time it generates a nop instruction from a macro.
1478 The following options are available when @value{AS} is configured for
1484 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1485 The command line option @samp{-nojsri2bsr} can be used to disable it.
1489 Enable or disable the silicon filter behaviour. By default this is disabled.
1490 The default can be overridden by the @samp{-sifilter} command line option.
1493 Alter jump instructions for long displacements.
1495 @item -mcpu=[210|340]
1496 Select the cpu type on the target hardware. This controls which instructions
1500 Assemble for a big endian target.
1503 Assemble for a little endian target.
1512 @xref{Meta Options}, for the options available when @value{AS} is configured
1513 for a Meta processor.
1517 @c man begin OPTIONS
1518 The following options are available when @value{AS} is configured for a
1521 @c man begin INCLUDE
1522 @include c-metag.texi
1523 @c ended inside the included file
1528 @c man begin OPTIONS
1530 See the info pages for documentation of the MMIX-specific options.
1536 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1537 for a NDS32 processor.
1539 @c ended inside the included file
1543 @c man begin OPTIONS
1544 The following options are available when @value{AS} is configured for a
1547 @c man begin INCLUDE
1548 @include c-nds32.texi
1549 @c ended inside the included file
1556 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1557 for a PowerPC processor.
1561 @c man begin OPTIONS
1562 The following options are available when @value{AS} is configured for a
1565 @c man begin INCLUDE
1567 @c ended inside the included file
1572 @c man begin OPTIONS
1574 See the info pages for documentation of the RX-specific options.
1578 The following options are available when @value{AS} is configured for the s390
1584 Select the word size, either 31/32 bits or 64 bits.
1587 Select the architecture mode, either the Enterprise System
1588 Architecture (esa) or the z/Architecture mode (zarch).
1589 @item -march=@var{processor}
1590 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1591 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1592 @samp{z196}, or @samp{zEC12}.
1594 @itemx -mno-regnames
1595 Allow or disallow symbolic names for registers.
1596 @item -mwarn-areg-zero
1597 Warn whenever the operand for a base or index register has been specified
1598 but evaluates to zero.
1606 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1607 for a TMS320C6000 processor.
1611 @c man begin OPTIONS
1612 The following options are available when @value{AS} is configured for a
1613 TMS320C6000 processor.
1615 @c man begin INCLUDE
1616 @include c-tic6x.texi
1617 @c ended inside the included file
1625 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1626 for a TILE-Gx processor.
1630 @c man begin OPTIONS
1631 The following options are available when @value{AS} is configured for a TILE-Gx
1634 @c man begin INCLUDE
1635 @include c-tilegx.texi
1636 @c ended inside the included file
1644 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1645 for an Xtensa processor.
1649 @c man begin OPTIONS
1650 The following options are available when @value{AS} is configured for an
1653 @c man begin INCLUDE
1654 @include c-xtensa.texi
1655 @c ended inside the included file
1660 @c man begin OPTIONS
1663 The following options are available when @value{AS} is configured for
1664 a Z80 family processor.
1667 Assemble for Z80 processor.
1669 Assemble for R800 processor.
1670 @item -ignore-undocumented-instructions
1672 Assemble undocumented Z80 instructions that also work on R800 without warning.
1673 @item -ignore-unportable-instructions
1675 Assemble all undocumented Z80 instructions without warning.
1676 @item -warn-undocumented-instructions
1678 Issue a warning for undocumented Z80 instructions that also work on R800.
1679 @item -warn-unportable-instructions
1681 Issue a warning for undocumented Z80 instructions that do not work on R800.
1682 @item -forbid-undocumented-instructions
1684 Treat all undocumented instructions as errors.
1685 @item -forbid-unportable-instructions
1687 Treat undocumented Z80 instructions that do not work on R800 as errors.
1694 * Manual:: Structure of this Manual
1695 * GNU Assembler:: The GNU Assembler
1696 * Object Formats:: Object File Formats
1697 * Command Line:: Command Line
1698 * Input Files:: Input Files
1699 * Object:: Output (Object) File
1700 * Errors:: Error and Warning Messages
1704 @section Structure of this Manual
1706 @cindex manual, structure and purpose
1707 This manual is intended to describe what you need to know to use
1708 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1709 notation for symbols, constants, and expressions; the directives that
1710 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1713 We also cover special features in the @value{TARGET}
1714 configuration of @command{@value{AS}}, including assembler directives.
1717 This manual also describes some of the machine-dependent features of
1718 various flavors of the assembler.
1721 @cindex machine instructions (not covered)
1722 On the other hand, this manual is @emph{not} intended as an introduction
1723 to programming in assembly language---let alone programming in general!
1724 In a similar vein, we make no attempt to introduce the machine
1725 architecture; we do @emph{not} describe the instruction set, standard
1726 mnemonics, registers or addressing modes that are standard to a
1727 particular architecture.
1729 You may want to consult the manufacturer's
1730 machine architecture manual for this information.
1734 For information on the H8/300 machine instruction set, see @cite{H8/300
1735 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1736 Programming Manual} (Renesas).
1739 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1740 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1741 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1742 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1745 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1749 @c I think this is premature---doc@cygnus.com, 17jan1991
1751 Throughout this manual, we assume that you are running @dfn{GNU},
1752 the portable operating system from the @dfn{Free Software
1753 Foundation, Inc.}. This restricts our attention to certain kinds of
1754 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1755 once this assumption is granted examples and definitions need less
1758 @command{@value{AS}} is part of a team of programs that turn a high-level
1759 human-readable series of instructions into a low-level
1760 computer-readable series of instructions. Different versions of
1761 @command{@value{AS}} are used for different kinds of computer.
1764 @c There used to be a section "Terminology" here, which defined
1765 @c "contents", "byte", "word", and "long". Defining "word" to any
1766 @c particular size is confusing when the .word directive may generate 16
1767 @c bits on one machine and 32 bits on another; in general, for the user
1768 @c version of this manual, none of these terms seem essential to define.
1769 @c They were used very little even in the former draft of the manual;
1770 @c this draft makes an effort to avoid them (except in names of
1774 @section The GNU Assembler
1776 @c man begin DESCRIPTION
1778 @sc{gnu} @command{as} is really a family of assemblers.
1780 This manual describes @command{@value{AS}}, a member of that family which is
1781 configured for the @value{TARGET} architectures.
1783 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1784 should find a fairly similar environment when you use it on another
1785 architecture. Each version has much in common with the others,
1786 including object file formats, most assembler directives (often called
1787 @dfn{pseudo-ops}) and assembler syntax.@refill
1789 @cindex purpose of @sc{gnu} assembler
1790 @command{@value{AS}} is primarily intended to assemble the output of the
1791 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1792 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1793 assemble correctly everything that other assemblers for the same
1794 machine would assemble.
1796 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1799 @c This remark should appear in generic version of manual; assumption
1800 @c here is that generic version sets M680x0.
1801 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1802 assembler for the same architecture; for example, we know of several
1803 incompatible versions of 680x0 assembly language syntax.
1808 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1809 program in one pass of the source file. This has a subtle impact on the
1810 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1812 @node Object Formats
1813 @section Object File Formats
1815 @cindex object file format
1816 The @sc{gnu} assembler can be configured to produce several alternative
1817 object file formats. For the most part, this does not affect how you
1818 write assembly language programs; but directives for debugging symbols
1819 are typically different in different file formats. @xref{Symbol
1820 Attributes,,Symbol Attributes}.
1823 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1824 @value{OBJ-NAME} format object files.
1826 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1828 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1829 @code{b.out} or COFF format object files.
1832 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1833 SOM or ELF format object files.
1838 @section Command Line
1840 @cindex command line conventions
1842 After the program name @command{@value{AS}}, the command line may contain
1843 options and file names. Options may appear in any order, and may be
1844 before, after, or between file names. The order of file names is
1847 @cindex standard input, as input file
1849 @file{--} (two hyphens) by itself names the standard input file
1850 explicitly, as one of the files for @command{@value{AS}} to assemble.
1852 @cindex options, command line
1853 Except for @samp{--} any command line argument that begins with a
1854 hyphen (@samp{-}) is an option. Each option changes the behavior of
1855 @command{@value{AS}}. No option changes the way another option works. An
1856 option is a @samp{-} followed by one or more letters; the case of
1857 the letter is important. All options are optional.
1859 Some options expect exactly one file name to follow them. The file
1860 name may either immediately follow the option's letter (compatible
1861 with older assemblers) or it may be the next command argument (@sc{gnu}
1862 standard). These two command lines are equivalent:
1865 @value{AS} -o my-object-file.o mumble.s
1866 @value{AS} -omy-object-file.o mumble.s
1870 @section Input Files
1873 @cindex source program
1874 @cindex files, input
1875 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1876 describe the program input to one run of @command{@value{AS}}. The program may
1877 be in one or more files; how the source is partitioned into files
1878 doesn't change the meaning of the source.
1880 @c I added "con" prefix to "catenation" just to prove I can overcome my
1881 @c APL training... doc@cygnus.com
1882 The source program is a concatenation of the text in all the files, in the
1885 @c man begin DESCRIPTION
1886 Each time you run @command{@value{AS}} it assembles exactly one source
1887 program. The source program is made up of one or more files.
1888 (The standard input is also a file.)
1890 You give @command{@value{AS}} a command line that has zero or more input file
1891 names. The input files are read (from left file name to right). A
1892 command line argument (in any position) that has no special meaning
1893 is taken to be an input file name.
1895 If you give @command{@value{AS}} no file names it attempts to read one input file
1896 from the @command{@value{AS}} standard input, which is normally your terminal. You
1897 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1900 Use @samp{--} if you need to explicitly name the standard input file
1901 in your command line.
1903 If the source is empty, @command{@value{AS}} produces a small, empty object
1908 @subheading Filenames and Line-numbers
1910 @cindex input file linenumbers
1911 @cindex line numbers, in input files
1912 There are two ways of locating a line in the input file (or files) and
1913 either may be used in reporting error messages. One way refers to a line
1914 number in a physical file; the other refers to a line number in a
1915 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1917 @dfn{Physical files} are those files named in the command line given
1918 to @command{@value{AS}}.
1920 @dfn{Logical files} are simply names declared explicitly by assembler
1921 directives; they bear no relation to physical files. Logical file names help
1922 error messages reflect the original source file, when @command{@value{AS}} source
1923 is itself synthesized from other files. @command{@value{AS}} understands the
1924 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1925 @ref{File,,@code{.file}}.
1928 @section Output (Object) File
1934 Every time you run @command{@value{AS}} it produces an output file, which is
1935 your assembly language program translated into numbers. This file
1936 is the object file. Its default name is
1944 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1946 You can give it another name by using the @option{-o} option. Conventionally,
1947 object file names end with @file{.o}. The default name is used for historical
1948 reasons: older assemblers were capable of assembling self-contained programs
1949 directly into a runnable program. (For some formats, this isn't currently
1950 possible, but it can be done for the @code{a.out} format.)
1954 The object file is meant for input to the linker @code{@value{LD}}. It contains
1955 assembled program code, information to help @code{@value{LD}} integrate
1956 the assembled program into a runnable file, and (optionally) symbolic
1957 information for the debugger.
1959 @c link above to some info file(s) like the description of a.out.
1960 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1963 @section Error and Warning Messages
1965 @c man begin DESCRIPTION
1967 @cindex error messages
1968 @cindex warning messages
1969 @cindex messages from assembler
1970 @command{@value{AS}} may write warnings and error messages to the standard error
1971 file (usually your terminal). This should not happen when a compiler
1972 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1973 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1974 grave problem that stops the assembly.
1978 @cindex format of warning messages
1979 Warning messages have the format
1982 file_name:@b{NNN}:Warning Message Text
1986 @cindex line numbers, in warnings/errors
1987 (where @b{NNN} is a line number). If a logical file name has been given
1988 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1989 the current input file is used. If a logical line number was given
1991 (@pxref{Line,,@code{.line}})
1993 then it is used to calculate the number printed,
1994 otherwise the actual line in the current source file is printed. The
1995 message text is intended to be self explanatory (in the grand Unix
1998 @cindex format of error messages
1999 Error messages have the format
2001 file_name:@b{NNN}:FATAL:Error Message Text
2003 The file name and line number are derived as for warning
2004 messages. The actual message text may be rather less explanatory
2005 because many of them aren't supposed to happen.
2008 @chapter Command-Line Options
2010 @cindex options, all versions of assembler
2011 This chapter describes command-line options available in @emph{all}
2012 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2013 for options specific
2015 to the @value{TARGET} target.
2018 to particular machine architectures.
2021 @c man begin DESCRIPTION
2023 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2024 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2025 The assembler arguments must be separated from each other (and the @samp{-Wa})
2026 by commas. For example:
2029 gcc -c -g -O -Wa,-alh,-L file.c
2033 This passes two options to the assembler: @samp{-alh} (emit a listing to
2034 standard output with high-level and assembly source) and @samp{-L} (retain
2035 local symbols in the symbol table).
2037 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2038 command-line options are automatically passed to the assembler by the compiler.
2039 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2040 precisely what options it passes to each compilation pass, including the
2046 * a:: -a[cdghlns] enable listings
2047 * alternate:: --alternate enable alternate macro syntax
2048 * D:: -D for compatibility
2049 * f:: -f to work faster
2050 * I:: -I for .include search path
2051 @ifclear DIFF-TBL-KLUGE
2052 * K:: -K for compatibility
2054 @ifset DIFF-TBL-KLUGE
2055 * K:: -K for difference tables
2058 * L:: -L to retain local symbols
2059 * listing:: --listing-XXX to configure listing output
2060 * M:: -M or --mri to assemble in MRI compatibility mode
2061 * MD:: --MD for dependency tracking
2062 * o:: -o to name the object file
2063 * R:: -R to join data and text sections
2064 * statistics:: --statistics to see statistics about assembly
2065 * traditional-format:: --traditional-format for compatible output
2066 * v:: -v to announce version
2067 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2068 * Z:: -Z to make object file even after errors
2072 @section Enable Listings: @option{-a[cdghlns]}
2082 @cindex listings, enabling
2083 @cindex assembly listings, enabling
2085 These options enable listing output from the assembler. By itself,
2086 @samp{-a} requests high-level, assembly, and symbols listing.
2087 You can use other letters to select specific options for the list:
2088 @samp{-ah} requests a high-level language listing,
2089 @samp{-al} requests an output-program assembly listing, and
2090 @samp{-as} requests a symbol table listing.
2091 High-level listings require that a compiler debugging option like
2092 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2095 Use the @samp{-ag} option to print a first section with general assembly
2096 information, like @value{AS} version, switches passed, or time stamp.
2098 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2099 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2100 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2101 omitted from the listing.
2103 Use the @samp{-ad} option to omit debugging directives from the
2106 Once you have specified one of these options, you can further control
2107 listing output and its appearance using the directives @code{.list},
2108 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2110 The @samp{-an} option turns off all forms processing.
2111 If you do not request listing output with one of the @samp{-a} options, the
2112 listing-control directives have no effect.
2114 The letters after @samp{-a} may be combined into one option,
2115 @emph{e.g.}, @samp{-aln}.
2117 Note if the assembler source is coming from the standard input (e.g.,
2119 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2120 is being used) then the listing will not contain any comments or preprocessor
2121 directives. This is because the listing code buffers input source lines from
2122 stdin only after they have been preprocessed by the assembler. This reduces
2123 memory usage and makes the code more efficient.
2126 @section @option{--alternate}
2129 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2132 @section @option{-D}
2135 This option has no effect whatsoever, but it is accepted to make it more
2136 likely that scripts written for other assemblers also work with
2137 @command{@value{AS}}.
2140 @section Work Faster: @option{-f}
2143 @cindex trusted compiler
2144 @cindex faster processing (@option{-f})
2145 @samp{-f} should only be used when assembling programs written by a
2146 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2147 and comment preprocessing on
2148 the input file(s) before assembling them. @xref{Preprocessing,
2152 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2153 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2158 @section @code{.include} Search Path: @option{-I} @var{path}
2160 @kindex -I @var{path}
2161 @cindex paths for @code{.include}
2162 @cindex search path for @code{.include}
2163 @cindex @code{include} directive search path
2164 Use this option to add a @var{path} to the list of directories
2165 @command{@value{AS}} searches for files specified in @code{.include}
2166 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2167 many times as necessary to include a variety of paths. The current
2168 working directory is always searched first; after that, @command{@value{AS}}
2169 searches any @samp{-I} directories in the same order as they were
2170 specified (left to right) on the command line.
2173 @section Difference Tables: @option{-K}
2176 @ifclear DIFF-TBL-KLUGE
2177 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2178 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2179 where it can be used to warn when the assembler alters the machine code
2180 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2181 family does not have the addressing limitations that sometimes lead to this
2182 alteration on other platforms.
2185 @ifset DIFF-TBL-KLUGE
2186 @cindex difference tables, warning
2187 @cindex warning for altered difference tables
2188 @command{@value{AS}} sometimes alters the code emitted for directives of the
2189 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2190 You can use the @samp{-K} option if you want a warning issued when this
2195 @section Include Local Symbols: @option{-L}
2198 @cindex local symbols, retaining in output
2199 Symbols beginning with system-specific local label prefixes, typically
2200 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2201 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2202 such symbols when debugging, because they are intended for the use of
2203 programs (like compilers) that compose assembler programs, not for your
2204 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2205 such symbols, so you do not normally debug with them.
2207 This option tells @command{@value{AS}} to retain those local symbols
2208 in the object file. Usually if you do this you also tell the linker
2209 @code{@value{LD}} to preserve those symbols.
2212 @section Configuring listing output: @option{--listing}
2214 The listing feature of the assembler can be enabled via the command line switch
2215 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2216 hex dump of the corresponding locations in the output object file, and displays
2217 them as a listing file. The format of this listing can be controlled by
2218 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2219 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2220 @code{.psize} (@pxref{Psize}), and
2221 @code{.eject} (@pxref{Eject}) and also by the following switches:
2224 @item --listing-lhs-width=@samp{number}
2225 @kindex --listing-lhs-width
2226 @cindex Width of first line disassembly output
2227 Sets the maximum width, in words, of the first line of the hex byte dump. This
2228 dump appears on the left hand side of the listing output.
2230 @item --listing-lhs-width2=@samp{number}
2231 @kindex --listing-lhs-width2
2232 @cindex Width of continuation lines of disassembly output
2233 Sets the maximum width, in words, of any further lines of the hex byte dump for
2234 a given input source line. If this value is not specified, it defaults to being
2235 the same as the value specified for @samp{--listing-lhs-width}. If neither
2236 switch is used the default is to one.
2238 @item --listing-rhs-width=@samp{number}
2239 @kindex --listing-rhs-width
2240 @cindex Width of source line output
2241 Sets the maximum width, in characters, of the source line that is displayed
2242 alongside the hex dump. The default value for this parameter is 100. The
2243 source line is displayed on the right hand side of the listing output.
2245 @item --listing-cont-lines=@samp{number}
2246 @kindex --listing-cont-lines
2247 @cindex Maximum number of continuation lines
2248 Sets the maximum number of continuation lines of hex dump that will be
2249 displayed for a given single line of source input. The default value is 4.
2253 @section Assemble in MRI Compatibility Mode: @option{-M}
2256 @cindex MRI compatibility mode
2257 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2258 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2259 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2260 configured target) assembler from Microtec Research. The exact nature of the
2261 MRI syntax will not be documented here; see the MRI manuals for more
2262 information. Note in particular that the handling of macros and macro
2263 arguments is somewhat different. The purpose of this option is to permit
2264 assembling existing MRI assembler code using @command{@value{AS}}.
2266 The MRI compatibility is not complete. Certain operations of the MRI assembler
2267 depend upon its object file format, and can not be supported using other object
2268 file formats. Supporting these would require enhancing each object file format
2269 individually. These are:
2272 @item global symbols in common section
2274 The m68k MRI assembler supports common sections which are merged by the linker.
2275 Other object file formats do not support this. @command{@value{AS}} handles
2276 common sections by treating them as a single common symbol. It permits local
2277 symbols to be defined within a common section, but it can not support global
2278 symbols, since it has no way to describe them.
2280 @item complex relocations
2282 The MRI assemblers support relocations against a negated section address, and
2283 relocations which combine the start addresses of two or more sections. These
2284 are not support by other object file formats.
2286 @item @code{END} pseudo-op specifying start address
2288 The MRI @code{END} pseudo-op permits the specification of a start address.
2289 This is not supported by other object file formats. The start address may
2290 instead be specified using the @option{-e} option to the linker, or in a linker
2293 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2295 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2296 name to the output file. This is not supported by other object file formats.
2298 @item @code{ORG} pseudo-op
2300 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2301 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2302 which changes the location within the current section. Absolute sections are
2303 not supported by other object file formats. The address of a section may be
2304 assigned within a linker script.
2307 There are some other features of the MRI assembler which are not supported by
2308 @command{@value{AS}}, typically either because they are difficult or because they
2309 seem of little consequence. Some of these may be supported in future releases.
2313 @item EBCDIC strings
2315 EBCDIC strings are not supported.
2317 @item packed binary coded decimal
2319 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2320 and @code{DCB.P} pseudo-ops are not supported.
2322 @item @code{FEQU} pseudo-op
2324 The m68k @code{FEQU} pseudo-op is not supported.
2326 @item @code{NOOBJ} pseudo-op
2328 The m68k @code{NOOBJ} pseudo-op is not supported.
2330 @item @code{OPT} branch control options
2332 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2333 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2334 relaxes all branches, whether forward or backward, to an appropriate size, so
2335 these options serve no purpose.
2337 @item @code{OPT} list control options
2339 The following m68k @code{OPT} list control options are ignored: @code{C},
2340 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2341 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2343 @item other @code{OPT} options
2345 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2346 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2348 @item @code{OPT} @code{D} option is default
2350 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2351 @code{OPT NOD} may be used to turn it off.
2353 @item @code{XREF} pseudo-op.
2355 The m68k @code{XREF} pseudo-op is ignored.
2357 @item @code{.debug} pseudo-op
2359 The i960 @code{.debug} pseudo-op is not supported.
2361 @item @code{.extended} pseudo-op
2363 The i960 @code{.extended} pseudo-op is not supported.
2365 @item @code{.list} pseudo-op.
2367 The various options of the i960 @code{.list} pseudo-op are not supported.
2369 @item @code{.optimize} pseudo-op
2371 The i960 @code{.optimize} pseudo-op is not supported.
2373 @item @code{.output} pseudo-op
2375 The i960 @code{.output} pseudo-op is not supported.
2377 @item @code{.setreal} pseudo-op
2379 The i960 @code{.setreal} pseudo-op is not supported.
2384 @section Dependency Tracking: @option{--MD}
2387 @cindex dependency tracking
2390 @command{@value{AS}} can generate a dependency file for the file it creates. This
2391 file consists of a single rule suitable for @code{make} describing the
2392 dependencies of the main source file.
2394 The rule is written to the file named in its argument.
2396 This feature is used in the automatic updating of makefiles.
2399 @section Name the Object File: @option{-o}
2402 @cindex naming object file
2403 @cindex object file name
2404 There is always one object file output when you run @command{@value{AS}}. By
2405 default it has the name
2408 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2422 You use this option (which takes exactly one filename) to give the
2423 object file a different name.
2425 Whatever the object file is called, @command{@value{AS}} overwrites any
2426 existing file of the same name.
2429 @section Join Data and Text Sections: @option{-R}
2432 @cindex data and text sections, joining
2433 @cindex text and data sections, joining
2434 @cindex joining text and data sections
2435 @cindex merging text and data sections
2436 @option{-R} tells @command{@value{AS}} to write the object file as if all
2437 data-section data lives in the text section. This is only done at
2438 the very last moment: your binary data are the same, but data
2439 section parts are relocated differently. The data section part of
2440 your object file is zero bytes long because all its bytes are
2441 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2443 When you specify @option{-R} it would be possible to generate shorter
2444 address displacements (because we do not have to cross between text and
2445 data section). We refrain from doing this simply for compatibility with
2446 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2449 When @command{@value{AS}} is configured for COFF or ELF output,
2450 this option is only useful if you use sections named @samp{.text} and
2455 @option{-R} is not supported for any of the HPPA targets. Using
2456 @option{-R} generates a warning from @command{@value{AS}}.
2460 @section Display Assembly Statistics: @option{--statistics}
2462 @kindex --statistics
2463 @cindex statistics, about assembly
2464 @cindex time, total for assembly
2465 @cindex space used, maximum for assembly
2466 Use @samp{--statistics} to display two statistics about the resources used by
2467 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2468 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2471 @node traditional-format
2472 @section Compatible Output: @option{--traditional-format}
2474 @kindex --traditional-format
2475 For some targets, the output of @command{@value{AS}} is different in some ways
2476 from the output of some existing assembler. This switch requests
2477 @command{@value{AS}} to use the traditional format instead.
2479 For example, it disables the exception frame optimizations which
2480 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2483 @section Announce Version: @option{-v}
2487 @cindex assembler version
2488 @cindex version of assembler
2489 You can find out what version of as is running by including the
2490 option @samp{-v} (which you can also spell as @samp{-version}) on the
2494 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2496 @command{@value{AS}} should never give a warning or error message when
2497 assembling compiler output. But programs written by people often
2498 cause @command{@value{AS}} to give a warning that a particular assumption was
2499 made. All such warnings are directed to the standard error file.
2503 @cindex suppressing warnings
2504 @cindex warnings, suppressing
2505 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2506 This only affects the warning messages: it does not change any particular of
2507 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2510 @kindex --fatal-warnings
2511 @cindex errors, caused by warnings
2512 @cindex warnings, causing error
2513 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2514 files that generate warnings to be in error.
2517 @cindex warnings, switching on
2518 You can switch these options off again by specifying @option{--warn}, which
2519 causes warnings to be output as usual.
2522 @section Generate Object File in Spite of Errors: @option{-Z}
2523 @cindex object file, after errors
2524 @cindex errors, continuing after
2525 After an error message, @command{@value{AS}} normally produces no output. If for
2526 some reason you are interested in object file output even after
2527 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2528 option. If there are any errors, @command{@value{AS}} continues anyways, and
2529 writes an object file after a final warning message of the form @samp{@var{n}
2530 errors, @var{m} warnings, generating bad object file.}
2535 @cindex machine-independent syntax
2536 @cindex syntax, machine-independent
2537 This chapter describes the machine-independent syntax allowed in a
2538 source file. @command{@value{AS}} syntax is similar to what many other
2539 assemblers use; it is inspired by the BSD 4.2
2544 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2548 * Preprocessing:: Preprocessing
2549 * Whitespace:: Whitespace
2550 * Comments:: Comments
2551 * Symbol Intro:: Symbols
2552 * Statements:: Statements
2553 * Constants:: Constants
2557 @section Preprocessing
2559 @cindex preprocessing
2560 The @command{@value{AS}} internal preprocessor:
2562 @cindex whitespace, removed by preprocessor
2564 adjusts and removes extra whitespace. It leaves one space or tab before
2565 the keywords on a line, and turns any other whitespace on the line into
2568 @cindex comments, removed by preprocessor
2570 removes all comments, replacing them with a single space, or an
2571 appropriate number of newlines.
2573 @cindex constants, converted by preprocessor
2575 converts character constants into the appropriate numeric values.
2578 It does not do macro processing, include file handling, or
2579 anything else you may get from your C compiler's preprocessor. You can
2580 do include file processing with the @code{.include} directive
2581 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2582 to get other ``CPP'' style preprocessing by giving the input file a
2583 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2584 Output, gcc.info, Using GNU CC}.
2586 Excess whitespace, comments, and character constants
2587 cannot be used in the portions of the input text that are not
2590 @cindex turning preprocessing on and off
2591 @cindex preprocessing, turning on and off
2594 If the first line of an input file is @code{#NO_APP} or if you use the
2595 @samp{-f} option, whitespace and comments are not removed from the input file.
2596 Within an input file, you can ask for whitespace and comment removal in
2597 specific portions of the by putting a line that says @code{#APP} before the
2598 text that may contain whitespace or comments, and putting a line that says
2599 @code{#NO_APP} after this text. This feature is mainly intend to support
2600 @code{asm} statements in compilers whose output is otherwise free of comments
2607 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2608 Whitespace is used to separate symbols, and to make programs neater for
2609 people to read. Unless within character constants
2610 (@pxref{Characters,,Character Constants}), any whitespace means the same
2611 as exactly one space.
2617 There are two ways of rendering comments to @command{@value{AS}}. In both
2618 cases the comment is equivalent to one space.
2620 Anything from @samp{/*} through the next @samp{*/} is a comment.
2621 This means you may not nest these comments.
2625 The only way to include a newline ('\n') in a comment
2626 is to use this sort of comment.
2629 /* This sort of comment does not nest. */
2632 @cindex line comment character
2633 Anything from a @dfn{line comment} character up to the next newline is
2634 considered a comment and is ignored. The line comment character is target
2635 specific, and some targets multiple comment characters. Some targets also have
2636 line comment characters that only work if they are the first character on a
2637 line. Some targets use a sequence of two characters to introduce a line
2638 comment. Some targets can also change their line comment characters depending
2639 upon command line options that have been used. For more details see the
2640 @emph{Syntax} section in the documentation for individual targets.
2642 If the line comment character is the hash sign (@samp{#}) then it still has the
2643 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2644 to specify logical line numbers:
2647 @cindex lines starting with @code{#}
2648 @cindex logical line numbers
2649 To be compatible with past assemblers, lines that begin with @samp{#} have a
2650 special interpretation. Following the @samp{#} should be an absolute
2651 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2652 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2653 new logical file name. The rest of the line, if any, should be whitespace.
2655 If the first non-whitespace characters on the line are not numeric,
2656 the line is ignored. (Just like a comment.)
2659 # This is an ordinary comment.
2660 # 42-6 "new_file_name" # New logical file name
2661 # This is logical line # 36.
2663 This feature is deprecated, and may disappear from future versions
2664 of @command{@value{AS}}.
2669 @cindex characters used in symbols
2670 @ifclear SPECIAL-SYMS
2671 A @dfn{symbol} is one or more characters chosen from the set of all
2672 letters (both upper and lower case), digits and the three characters
2678 A @dfn{symbol} is one or more characters chosen from the set of all
2679 letters (both upper and lower case), digits and the three characters
2680 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2686 On most machines, you can also use @code{$} in symbol names; exceptions
2687 are noted in @ref{Machine Dependencies}.
2689 No symbol may begin with a digit. Case is significant.
2690 There is no length limit: all characters are significant. Multibyte characters
2691 are supported. Symbols are delimited by characters not in that set, or by the
2692 beginning of a file (since the source program must end with a newline, the end
2693 of a file is not a possible symbol delimiter). @xref{Symbols}.
2694 @cindex length of symbols
2699 @cindex statements, structure of
2700 @cindex line separator character
2701 @cindex statement separator character
2703 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2704 @dfn{line separator character}. The line separator character is target
2705 specific and described in the @emph{Syntax} section of each
2706 target's documentation. Not all targets support a line separator character.
2707 The newline or line separator character is considered to be part of the
2708 preceding statement. Newlines and separators within character constants are an
2709 exception: they do not end statements.
2711 @cindex newline, required at file end
2712 @cindex EOF, newline must precede
2713 It is an error to end any statement with end-of-file: the last
2714 character of any input file should be a newline.@refill
2716 An empty statement is allowed, and may include whitespace. It is ignored.
2718 @cindex instructions and directives
2719 @cindex directives and instructions
2720 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2721 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2723 A statement begins with zero or more labels, optionally followed by a
2724 key symbol which determines what kind of statement it is. The key
2725 symbol determines the syntax of the rest of the statement. If the
2726 symbol begins with a dot @samp{.} then the statement is an assembler
2727 directive: typically valid for any computer. If the symbol begins with
2728 a letter the statement is an assembly language @dfn{instruction}: it
2729 assembles into a machine language instruction.
2731 Different versions of @command{@value{AS}} for different computers
2732 recognize different instructions. In fact, the same symbol may
2733 represent a different instruction in a different computer's assembly
2737 @cindex @code{:} (label)
2738 @cindex label (@code{:})
2739 A label is a symbol immediately followed by a colon (@code{:}).
2740 Whitespace before a label or after a colon is permitted, but you may not
2741 have whitespace between a label's symbol and its colon. @xref{Labels}.
2744 For HPPA targets, labels need not be immediately followed by a colon, but
2745 the definition of a label must begin in column zero. This also implies that
2746 only one label may be defined on each line.
2750 label: .directive followed by something
2751 another_label: # This is an empty statement.
2752 instruction operand_1, operand_2, @dots{}
2759 A constant is a number, written so that its value is known by
2760 inspection, without knowing any context. Like this:
2763 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2764 .ascii "Ring the bell\7" # A string constant.
2765 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2766 .float 0f-314159265358979323846264338327\
2767 95028841971.693993751E-40 # - pi, a flonum.
2772 * Characters:: Character Constants
2773 * Numbers:: Number Constants
2777 @subsection Character Constants
2779 @cindex character constants
2780 @cindex constants, character
2781 There are two kinds of character constants. A @dfn{character} stands
2782 for one character in one byte and its value may be used in
2783 numeric expressions. String constants (properly called string
2784 @emph{literals}) are potentially many bytes and their values may not be
2785 used in arithmetic expressions.
2789 * Chars:: Characters
2793 @subsubsection Strings
2795 @cindex string constants
2796 @cindex constants, string
2797 A @dfn{string} is written between double-quotes. It may contain
2798 double-quotes or null characters. The way to get special characters
2799 into a string is to @dfn{escape} these characters: precede them with
2800 a backslash @samp{\} character. For example @samp{\\} represents
2801 one backslash: the first @code{\} is an escape which tells
2802 @command{@value{AS}} to interpret the second character literally as a backslash
2803 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2804 escape character). The complete list of escapes follows.
2806 @cindex escape codes, character
2807 @cindex character escape codes
2810 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2812 @cindex @code{\b} (backspace character)
2813 @cindex backspace (@code{\b})
2815 Mnemonic for backspace; for ASCII this is octal code 010.
2818 @c Mnemonic for EOText; for ASCII this is octal code 004.
2820 @cindex @code{\f} (formfeed character)
2821 @cindex formfeed (@code{\f})
2823 Mnemonic for FormFeed; for ASCII this is octal code 014.
2825 @cindex @code{\n} (newline character)
2826 @cindex newline (@code{\n})
2828 Mnemonic for newline; for ASCII this is octal code 012.
2831 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2833 @cindex @code{\r} (carriage return character)
2834 @cindex carriage return (@code{\r})
2836 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2839 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2840 @c other assemblers.
2842 @cindex @code{\t} (tab)
2843 @cindex tab (@code{\t})
2845 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2848 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2849 @c @item \x @var{digit} @var{digit} @var{digit}
2850 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2852 @cindex @code{\@var{ddd}} (octal character code)
2853 @cindex octal character code (@code{\@var{ddd}})
2854 @item \ @var{digit} @var{digit} @var{digit}
2855 An octal character code. The numeric code is 3 octal digits.
2856 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2857 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2859 @cindex @code{\@var{xd...}} (hex character code)
2860 @cindex hex character code (@code{\@var{xd...}})
2861 @item \@code{x} @var{hex-digits...}
2862 A hex character code. All trailing hex digits are combined. Either upper or
2863 lower case @code{x} works.
2865 @cindex @code{\\} (@samp{\} character)
2866 @cindex backslash (@code{\\})
2868 Represents one @samp{\} character.
2871 @c Represents one @samp{'} (accent acute) character.
2872 @c This is needed in single character literals
2873 @c (@xref{Characters,,Character Constants}.) to represent
2876 @cindex @code{\"} (doublequote character)
2877 @cindex doublequote (@code{\"})
2879 Represents one @samp{"} character. Needed in strings to represent
2880 this character, because an unescaped @samp{"} would end the string.
2882 @item \ @var{anything-else}
2883 Any other character when escaped by @kbd{\} gives a warning, but
2884 assembles as if the @samp{\} was not present. The idea is that if
2885 you used an escape sequence you clearly didn't want the literal
2886 interpretation of the following character. However @command{@value{AS}} has no
2887 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2888 code and warns you of the fact.
2891 Which characters are escapable, and what those escapes represent,
2892 varies widely among assemblers. The current set is what we think
2893 the BSD 4.2 assembler recognizes, and is a subset of what most C
2894 compilers recognize. If you are in doubt, do not use an escape
2898 @subsubsection Characters
2900 @cindex single character constant
2901 @cindex character, single
2902 @cindex constant, single character
2903 A single character may be written as a single quote immediately
2904 followed by that character. The same escapes apply to characters as
2905 to strings. So if you want to write the character backslash, you
2906 must write @kbd{'\\} where the first @code{\} escapes the second
2907 @code{\}. As you can see, the quote is an acute accent, not a
2908 grave accent. A newline
2910 @ifclear abnormal-separator
2911 (or semicolon @samp{;})
2913 @ifset abnormal-separator
2915 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2920 immediately following an acute accent is taken as a literal character
2921 and does not count as the end of a statement. The value of a character
2922 constant in a numeric expression is the machine's byte-wide code for
2923 that character. @command{@value{AS}} assumes your character code is ASCII:
2924 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2927 @subsection Number Constants
2929 @cindex constants, number
2930 @cindex number constants
2931 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2932 are stored in the target machine. @emph{Integers} are numbers that
2933 would fit into an @code{int} in the C language. @emph{Bignums} are
2934 integers, but they are stored in more than 32 bits. @emph{Flonums}
2935 are floating point numbers, described below.
2938 * Integers:: Integers
2943 * Bit Fields:: Bit Fields
2949 @subsubsection Integers
2951 @cindex constants, integer
2953 @cindex binary integers
2954 @cindex integers, binary
2955 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2956 the binary digits @samp{01}.
2958 @cindex octal integers
2959 @cindex integers, octal
2960 An octal integer is @samp{0} followed by zero or more of the octal
2961 digits (@samp{01234567}).
2963 @cindex decimal integers
2964 @cindex integers, decimal
2965 A decimal integer starts with a non-zero digit followed by zero or
2966 more digits (@samp{0123456789}).
2968 @cindex hexadecimal integers
2969 @cindex integers, hexadecimal
2970 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2971 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2973 Integers have the usual values. To denote a negative integer, use
2974 the prefix operator @samp{-} discussed under expressions
2975 (@pxref{Prefix Ops,,Prefix Operators}).
2978 @subsubsection Bignums
2981 @cindex constants, bignum
2982 A @dfn{bignum} has the same syntax and semantics as an integer
2983 except that the number (or its negative) takes more than 32 bits to
2984 represent in binary. The distinction is made because in some places
2985 integers are permitted while bignums are not.
2988 @subsubsection Flonums
2990 @cindex floating point numbers
2991 @cindex constants, floating point
2993 @cindex precision, floating point
2994 A @dfn{flonum} represents a floating point number. The translation is
2995 indirect: a decimal floating point number from the text is converted by
2996 @command{@value{AS}} to a generic binary floating point number of more than
2997 sufficient precision. This generic floating point number is converted
2998 to a particular computer's floating point format (or formats) by a
2999 portion of @command{@value{AS}} specialized to that computer.
3001 A flonum is written by writing (in order)
3006 (@samp{0} is optional on the HPPA.)
3010 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3012 @kbd{e} is recommended. Case is not important.
3014 @c FIXME: verify if flonum syntax really this vague for most cases
3015 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3016 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3019 On the H8/300, Renesas / SuperH SH,
3020 and AMD 29K architectures, the letter must be
3021 one of the letters @samp{DFPRSX} (in upper or lower case).
3023 On the ARC, the letter must be one of the letters @samp{DFRS}
3024 (in upper or lower case).
3026 On the Intel 960 architecture, the letter must be
3027 one of the letters @samp{DFT} (in upper or lower case).
3029 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3033 One of the letters @samp{DFRS} (in upper or lower case).
3036 One of the letters @samp{DFPRSX} (in upper or lower case).
3039 The letter @samp{E} (upper case only).
3042 One of the letters @samp{DFT} (in upper or lower case).
3047 An optional sign: either @samp{+} or @samp{-}.
3050 An optional @dfn{integer part}: zero or more decimal digits.
3053 An optional @dfn{fractional part}: @samp{.} followed by zero
3054 or more decimal digits.
3057 An optional exponent, consisting of:
3061 An @samp{E} or @samp{e}.
3062 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3063 @c principle this can perfectly well be different on different targets.
3065 Optional sign: either @samp{+} or @samp{-}.
3067 One or more decimal digits.
3072 At least one of the integer part or the fractional part must be
3073 present. The floating point number has the usual base-10 value.
3075 @command{@value{AS}} does all processing using integers. Flonums are computed
3076 independently of any floating point hardware in the computer running
3077 @command{@value{AS}}.
3081 @c Bit fields are written as a general facility but are also controlled
3082 @c by a conditional-compilation flag---which is as of now (21mar91)
3083 @c turned on only by the i960 config of GAS.
3085 @subsubsection Bit Fields
3088 @cindex constants, bit field
3089 You can also define numeric constants as @dfn{bit fields}.
3090 Specify two numbers separated by a colon---
3092 @var{mask}:@var{value}
3095 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3098 The resulting number is then packed
3100 @c this conditional paren in case bit fields turned on elsewhere than 960
3101 (in host-dependent byte order)
3103 into a field whose width depends on which assembler directive has the
3104 bit-field as its argument. Overflow (a result from the bitwise and
3105 requiring more binary digits to represent) is not an error; instead,
3106 more constants are generated, of the specified width, beginning with the
3107 least significant digits.@refill
3109 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3110 @code{.short}, and @code{.word} accept bit-field arguments.
3115 @chapter Sections and Relocation
3120 * Secs Background:: Background
3121 * Ld Sections:: Linker Sections
3122 * As Sections:: Assembler Internal Sections
3123 * Sub-Sections:: Sub-Sections
3127 @node Secs Background
3130 Roughly, a section is a range of addresses, with no gaps; all data
3131 ``in'' those addresses is treated the same for some particular purpose.
3132 For example there may be a ``read only'' section.
3134 @cindex linker, and assembler
3135 @cindex assembler, and linker
3136 The linker @code{@value{LD}} reads many object files (partial programs) and
3137 combines their contents to form a runnable program. When @command{@value{AS}}
3138 emits an object file, the partial program is assumed to start at address 0.
3139 @code{@value{LD}} assigns the final addresses for the partial program, so that
3140 different partial programs do not overlap. This is actually an
3141 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3144 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3145 addresses. These blocks slide to their run-time addresses as rigid
3146 units; their length does not change and neither does the order of bytes
3147 within them. Such a rigid unit is called a @emph{section}. Assigning
3148 run-time addresses to sections is called @dfn{relocation}. It includes
3149 the task of adjusting mentions of object-file addresses so they refer to
3150 the proper run-time addresses.
3152 For the H8/300, and for the Renesas / SuperH SH,
3153 @command{@value{AS}} pads sections if needed to
3154 ensure they end on a word (sixteen bit) boundary.
3157 @cindex standard assembler sections
3158 An object file written by @command{@value{AS}} has at least three sections, any
3159 of which may be empty. These are named @dfn{text}, @dfn{data} and
3164 When it generates COFF or ELF output,
3166 @command{@value{AS}} can also generate whatever other named sections you specify
3167 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3168 If you do not use any directives that place output in the @samp{.text}
3169 or @samp{.data} sections, these sections still exist, but are empty.
3174 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3176 @command{@value{AS}} can also generate whatever other named sections you
3177 specify using the @samp{.space} and @samp{.subspace} directives. See
3178 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3179 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3180 assembler directives.
3183 Additionally, @command{@value{AS}} uses different names for the standard
3184 text, data, and bss sections when generating SOM output. Program text
3185 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3186 BSS into @samp{$BSS$}.
3190 Within the object file, the text section starts at address @code{0}, the
3191 data section follows, and the bss section follows the data section.
3194 When generating either SOM or ELF output files on the HPPA, the text
3195 section starts at address @code{0}, the data section at address
3196 @code{0x4000000}, and the bss section follows the data section.
3199 To let @code{@value{LD}} know which data changes when the sections are
3200 relocated, and how to change that data, @command{@value{AS}} also writes to the
3201 object file details of the relocation needed. To perform relocation
3202 @code{@value{LD}} must know, each time an address in the object
3206 Where in the object file is the beginning of this reference to
3209 How long (in bytes) is this reference?
3211 Which section does the address refer to? What is the numeric value of
3213 (@var{address}) @minus{} (@var{start-address of section})?
3216 Is the reference to an address ``Program-Counter relative''?
3219 @cindex addresses, format of
3220 @cindex section-relative addressing
3221 In fact, every address @command{@value{AS}} ever uses is expressed as
3223 (@var{section}) + (@var{offset into section})
3226 Further, most expressions @command{@value{AS}} computes have this section-relative
3229 (For some object formats, such as SOM for the HPPA, some expressions are
3230 symbol-relative instead.)
3233 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3234 @var{N} into section @var{secname}.''
3236 Apart from text, data and bss sections you need to know about the
3237 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3238 addresses in the absolute section remain unchanged. For example, address
3239 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3240 @code{@value{LD}}. Although the linker never arranges two partial programs'
3241 data sections with overlapping addresses after linking, @emph{by definition}
3242 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3243 part of a program is always the same address when the program is running as
3244 address @code{@{absolute@ 239@}} in any other part of the program.
3246 The idea of sections is extended to the @dfn{undefined} section. Any
3247 address whose section is unknown at assembly time is by definition
3248 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3249 Since numbers are always defined, the only way to generate an undefined
3250 address is to mention an undefined symbol. A reference to a named
3251 common block would be such a symbol: its value is unknown at assembly
3252 time so it has section @emph{undefined}.
3254 By analogy the word @emph{section} is used to describe groups of sections in
3255 the linked program. @code{@value{LD}} puts all partial programs' text
3256 sections in contiguous addresses in the linked program. It is
3257 customary to refer to the @emph{text section} of a program, meaning all
3258 the addresses of all partial programs' text sections. Likewise for
3259 data and bss sections.
3261 Some sections are manipulated by @code{@value{LD}}; others are invented for
3262 use of @command{@value{AS}} and have no meaning except during assembly.
3265 @section Linker Sections
3266 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3271 @cindex named sections
3272 @cindex sections, named
3273 @item named sections
3276 @cindex text section
3277 @cindex data section
3281 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3282 separate but equal sections. Anything you can say of one section is
3285 When the program is running, however, it is
3286 customary for the text section to be unalterable. The
3287 text section is often shared among processes: it contains
3288 instructions, constants and the like. The data section of a running
3289 program is usually alterable: for example, C variables would be stored
3290 in the data section.
3295 This section contains zeroed bytes when your program begins running. It
3296 is used to hold uninitialized variables or common storage. The length of
3297 each partial program's bss section is important, but because it starts
3298 out containing zeroed bytes there is no need to store explicit zero
3299 bytes in the object file. The bss section was invented to eliminate
3300 those explicit zeros from object files.
3302 @cindex absolute section
3303 @item absolute section
3304 Address 0 of this section is always ``relocated'' to runtime address 0.
3305 This is useful if you want to refer to an address that @code{@value{LD}} must
3306 not change when relocating. In this sense we speak of absolute
3307 addresses being ``unrelocatable'': they do not change during relocation.
3309 @cindex undefined section
3310 @item undefined section
3311 This ``section'' is a catch-all for address references to objects not in
3312 the preceding sections.
3313 @c FIXME: ref to some other doc on obj-file formats could go here.
3316 @cindex relocation example
3317 An idealized example of three relocatable sections follows.
3319 The example uses the traditional section names @samp{.text} and @samp{.data}.
3321 Memory addresses are on the horizontal axis.
3325 @c END TEXI2ROFF-KILL
3328 partial program # 1: |ttttt|dddd|00|
3335 partial program # 2: |TTT|DDD|000|
3338 +--+---+-----+--+----+---+-----+~~
3339 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3340 +--+---+-----+--+----+---+-----+~~
3342 addresses: 0 @dots{}
3349 \line{\it Partial program \#1: \hfil}
3350 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3351 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3353 \line{\it Partial program \#2: \hfil}
3354 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3355 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3357 \line{\it linked program: \hfil}
3358 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3359 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3360 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3361 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3363 \line{\it addresses: \hfil}
3367 @c END TEXI2ROFF-KILL
3370 @section Assembler Internal Sections
3372 @cindex internal assembler sections
3373 @cindex sections in messages, internal
3374 These sections are meant only for the internal use of @command{@value{AS}}. They
3375 have no meaning at run-time. You do not really need to know about these
3376 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3377 warning messages, so it might be helpful to have an idea of their
3378 meanings to @command{@value{AS}}. These sections are used to permit the
3379 value of every expression in your assembly language program to be a
3380 section-relative address.
3383 @cindex assembler internal logic error
3384 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3385 An internal assembler logic error has been found. This means there is a
3386 bug in the assembler.
3388 @cindex expr (internal section)
3390 The assembler stores complex expression internally as combinations of
3391 symbols. When it needs to represent an expression as a symbol, it puts
3392 it in the expr section.
3394 @c FIXME item transfer[t] vector preload
3395 @c FIXME item transfer[t] vector postload
3396 @c FIXME item register
3400 @section Sub-Sections
3402 @cindex numbered subsections
3403 @cindex grouping data
3409 fall into two sections: text and data.
3411 You may have separate groups of
3413 data in named sections
3417 data in named sections
3423 that you want to end up near to each other in the object file, even though they
3424 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3425 use @dfn{subsections} for this purpose. Within each section, there can be
3426 numbered subsections with values from 0 to 8192. Objects assembled into the
3427 same subsection go into the object file together with other objects in the same
3428 subsection. For example, a compiler might want to store constants in the text
3429 section, but might not want to have them interspersed with the program being
3430 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3431 section of code being output, and a @samp{.text 1} before each group of
3432 constants being output.
3434 Subsections are optional. If you do not use subsections, everything
3435 goes in subsection number zero.
3438 Each subsection is zero-padded up to a multiple of four bytes.
3439 (Subsections may be padded a different amount on different flavors
3440 of @command{@value{AS}}.)
3444 On the H8/300 platform, each subsection is zero-padded to a word
3445 boundary (two bytes).
3446 The same is true on the Renesas SH.
3449 @c FIXME section padding (alignment)?
3450 @c Rich Pixley says padding here depends on target obj code format; that
3451 @c doesn't seem particularly useful to say without further elaboration,
3452 @c so for now I say nothing about it. If this is a generic BFD issue,
3453 @c these paragraphs might need to vanish from this manual, and be
3454 @c discussed in BFD chapter of binutils (or some such).
3458 Subsections appear in your object file in numeric order, lowest numbered
3459 to highest. (All this to be compatible with other people's assemblers.)
3460 The object file contains no representation of subsections; @code{@value{LD}} and
3461 other programs that manipulate object files see no trace of them.
3462 They just see all your text subsections as a text section, and all your
3463 data subsections as a data section.
3465 To specify which subsection you want subsequent statements assembled
3466 into, use a numeric argument to specify it, in a @samp{.text
3467 @var{expression}} or a @samp{.data @var{expression}} statement.
3470 When generating COFF output, you
3475 can also use an extra subsection
3476 argument with arbitrary named sections: @samp{.section @var{name},
3481 When generating ELF output, you
3486 can also use the @code{.subsection} directive (@pxref{SubSection})
3487 to specify a subsection: @samp{.subsection @var{expression}}.
3489 @var{Expression} should be an absolute expression
3490 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3491 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3492 begins in @code{text 0}. For instance:
3494 .text 0 # The default subsection is text 0 anyway.
3495 .ascii "This lives in the first text subsection. *"
3497 .ascii "But this lives in the second text subsection."
3499 .ascii "This lives in the data section,"
3500 .ascii "in the first data subsection."
3502 .ascii "This lives in the first text section,"
3503 .ascii "immediately following the asterisk (*)."
3506 Each section has a @dfn{location counter} incremented by one for every byte
3507 assembled into that section. Because subsections are merely a convenience
3508 restricted to @command{@value{AS}} there is no concept of a subsection location
3509 counter. There is no way to directly manipulate a location counter---but the
3510 @code{.align} directive changes it, and any label definition captures its
3511 current value. The location counter of the section where statements are being
3512 assembled is said to be the @dfn{active} location counter.
3515 @section bss Section
3518 @cindex common variable storage
3519 The bss section is used for local common variable storage.
3520 You may allocate address space in the bss section, but you may
3521 not dictate data to load into it before your program executes. When
3522 your program starts running, all the contents of the bss
3523 section are zeroed bytes.
3525 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3526 @ref{Lcomm,,@code{.lcomm}}.
3528 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3529 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3532 When assembling for a target which supports multiple sections, such as ELF or
3533 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3534 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3535 section. Typically the section will only contain symbol definitions and
3536 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3543 Symbols are a central concept: the programmer uses symbols to name
3544 things, the linker uses symbols to link, and the debugger uses symbols
3548 @cindex debuggers, and symbol order
3549 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3550 the same order they were declared. This may break some debuggers.
3555 * Setting Symbols:: Giving Symbols Other Values
3556 * Symbol Names:: Symbol Names
3557 * Dot:: The Special Dot Symbol
3558 * Symbol Attributes:: Symbol Attributes
3565 A @dfn{label} is written as a symbol immediately followed by a colon
3566 @samp{:}. The symbol then represents the current value of the
3567 active location counter, and is, for example, a suitable instruction
3568 operand. You are warned if you use the same symbol to represent two
3569 different locations: the first definition overrides any other
3573 On the HPPA, the usual form for a label need not be immediately followed by a
3574 colon, but instead must start in column zero. Only one label may be defined on
3575 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3576 provides a special directive @code{.label} for defining labels more flexibly.
3579 @node Setting Symbols
3580 @section Giving Symbols Other Values
3582 @cindex assigning values to symbols
3583 @cindex symbol values, assigning
3584 A symbol can be given an arbitrary value by writing a symbol, followed
3585 by an equals sign @samp{=}, followed by an expression
3586 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3587 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3588 equals sign @samp{=}@samp{=} here represents an equivalent of the
3589 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3592 Blackfin does not support symbol assignment with @samp{=}.
3596 @section Symbol Names
3598 @cindex symbol names
3599 @cindex names, symbol
3600 @ifclear SPECIAL-SYMS
3601 Symbol names begin with a letter or with one of @samp{._}. On most
3602 machines, you can also use @code{$} in symbol names; exceptions are
3603 noted in @ref{Machine Dependencies}. That character may be followed by any
3604 string of digits, letters, dollar signs (unless otherwise noted for a
3605 particular target machine), and underscores.
3609 Symbol names begin with a letter or with one of @samp{._}. On the
3610 Renesas SH you can also use @code{$} in symbol names. That
3611 character may be followed by any string of digits, letters, dollar signs (save
3612 on the H8/300), and underscores.
3616 Case of letters is significant: @code{foo} is a different symbol name
3619 Multibyte characters are supported. To generate a symbol name containing
3620 multibyte characters enclose it within double quotes and use escape codes. cf
3621 @xref{Strings}. Generating a multibyte symbol name from a label is not
3622 currently supported.
3624 Each symbol has exactly one name. Each name in an assembly language program
3625 refers to exactly one symbol. You may use that symbol name any number of times
3628 @subheading Local Symbol Names
3630 @cindex local symbol names
3631 @cindex symbol names, local
3632 A local symbol is any symbol beginning with certain local label prefixes.
3633 By default, the local label prefix is @samp{.L} for ELF systems or
3634 @samp{L} for traditional a.out systems, but each target may have its own
3635 set of local label prefixes.
3637 On the HPPA local symbols begin with @samp{L$}.
3640 Local symbols are defined and used within the assembler, but they are
3641 normally not saved in object files. Thus, they are not visible when debugging.
3642 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3643 @option{-L}}) to retain the local symbols in the object files.
3645 @subheading Local Labels
3647 @cindex local labels
3648 @cindex temporary symbol names
3649 @cindex symbol names, temporary
3650 Local labels help compilers and programmers use names temporarily.
3651 They create symbols which are guaranteed to be unique over the entire scope of
3652 the input source code and which can be referred to by a simple notation.
3653 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3654 represents any positive integer). To refer to the most recent previous
3655 definition of that label write @samp{@b{N}b}, using the same number as when
3656 you defined the label. To refer to the next definition of a local label, write
3657 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3660 There is no restriction on how you can use these labels, and you can reuse them
3661 too. So that it is possible to repeatedly define the same local label (using
3662 the same number @samp{@b{N}}), although you can only refer to the most recently
3663 defined local label of that number (for a backwards reference) or the next
3664 definition of a specific local label for a forward reference. It is also worth
3665 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3666 implemented in a slightly more efficient manner than the others.
3677 Which is the equivalent of:
3680 label_1: branch label_3
3681 label_2: branch label_1
3682 label_3: branch label_4
3683 label_4: branch label_3
3686 Local label names are only a notational device. They are immediately
3687 transformed into more conventional symbol names before the assembler uses them.
3688 The symbol names are stored in the symbol table, appear in error messages, and
3689 are optionally emitted to the object file. The names are constructed using
3693 @item @emph{local label prefix}
3694 All local symbols begin with the system-specific local label prefix.
3695 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3696 that start with the local label prefix. These labels are
3697 used for symbols you are never intended to see. If you use the
3698 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3699 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3700 you may use them in debugging.
3703 This is the number that was used in the local label definition. So if the
3704 label is written @samp{55:} then the number is @samp{55}.
3707 This unusual character is included so you do not accidentally invent a symbol
3708 of the same name. The character has ASCII value of @samp{\002} (control-B).
3710 @item @emph{ordinal number}
3711 This is a serial number to keep the labels distinct. The first definition of
3712 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3713 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3714 the number @samp{1} and its 15th definition gets @samp{15} as well.
3717 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3718 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3720 @subheading Dollar Local Labels
3721 @cindex dollar local symbols
3723 @code{@value{AS}} also supports an even more local form of local labels called
3724 dollar labels. These labels go out of scope (i.e., they become undefined) as
3725 soon as a non-local label is defined. Thus they remain valid for only a small
3726 region of the input source code. Normal local labels, by contrast, remain in
3727 scope for the entire file, or until they are redefined by another occurrence of
3728 the same local label.
3730 Dollar labels are defined in exactly the same way as ordinary local labels,
3731 except that they have a dollar sign suffix to their numeric value, e.g.,
3734 They can also be distinguished from ordinary local labels by their transformed
3735 names which use ASCII character @samp{\001} (control-A) as the magic character
3736 to distinguish them from ordinary labels. For example, the fifth definition of
3737 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3740 @section The Special Dot Symbol
3742 @cindex dot (symbol)
3743 @cindex @code{.} (symbol)
3744 @cindex current address
3745 @cindex location counter
3746 The special symbol @samp{.} refers to the current address that
3747 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3748 .long .} defines @code{melvin} to contain its own address.
3749 Assigning a value to @code{.} is treated the same as a @code{.org}
3751 @ifclear no-space-dir
3752 Thus, the expression @samp{.=.+4} is the same as saying
3756 @node Symbol Attributes
3757 @section Symbol Attributes
3759 @cindex symbol attributes
3760 @cindex attributes, symbol
3761 Every symbol has, as well as its name, the attributes ``Value'' and
3762 ``Type''. Depending on output format, symbols can also have auxiliary
3765 The detailed definitions are in @file{a.out.h}.
3768 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3769 all these attributes, and probably won't warn you. This makes the
3770 symbol an externally defined symbol, which is generally what you
3774 * Symbol Value:: Value
3775 * Symbol Type:: Type
3778 * a.out Symbols:: Symbol Attributes: @code{a.out}
3782 * a.out Symbols:: Symbol Attributes: @code{a.out}
3785 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3790 * COFF Symbols:: Symbol Attributes for COFF
3793 * SOM Symbols:: Symbol Attributes for SOM
3800 @cindex value of a symbol
3801 @cindex symbol value
3802 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3803 location in the text, data, bss or absolute sections the value is the
3804 number of addresses from the start of that section to the label.
3805 Naturally for text, data and bss sections the value of a symbol changes
3806 as @code{@value{LD}} changes section base addresses during linking. Absolute
3807 symbols' values do not change during linking: that is why they are
3810 The value of an undefined symbol is treated in a special way. If it is
3811 0 then the symbol is not defined in this assembler source file, and
3812 @code{@value{LD}} tries to determine its value from other files linked into the
3813 same program. You make this kind of symbol simply by mentioning a symbol
3814 name without defining it. A non-zero value represents a @code{.comm}
3815 common declaration. The value is how much common storage to reserve, in
3816 bytes (addresses). The symbol refers to the first address of the
3822 @cindex type of a symbol
3824 The type attribute of a symbol contains relocation (section)
3825 information, any flag settings indicating that a symbol is external, and
3826 (optionally), other information for linkers and debuggers. The exact
3827 format depends on the object-code output format in use.
3832 @c The following avoids a "widow" subsection title. @group would be
3833 @c better if it were available outside examples.
3836 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3838 @cindex @code{b.out} symbol attributes
3839 @cindex symbol attributes, @code{b.out}
3840 These symbol attributes appear only when @command{@value{AS}} is configured for
3841 one of the Berkeley-descended object output formats---@code{a.out} or
3847 @subsection Symbol Attributes: @code{a.out}
3849 @cindex @code{a.out} symbol attributes
3850 @cindex symbol attributes, @code{a.out}
3856 @subsection Symbol Attributes: @code{a.out}
3858 @cindex @code{a.out} symbol attributes
3859 @cindex symbol attributes, @code{a.out}
3863 * Symbol Desc:: Descriptor
3864 * Symbol Other:: Other
3868 @subsubsection Descriptor
3870 @cindex descriptor, of @code{a.out} symbol
3871 This is an arbitrary 16-bit value. You may establish a symbol's
3872 descriptor value by using a @code{.desc} statement
3873 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3874 @command{@value{AS}}.
3877 @subsubsection Other
3879 @cindex other attribute, of @code{a.out} symbol
3880 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3885 @subsection Symbol Attributes for COFF
3887 @cindex COFF symbol attributes
3888 @cindex symbol attributes, COFF
3890 The COFF format supports a multitude of auxiliary symbol attributes;
3891 like the primary symbol attributes, they are set between @code{.def} and
3892 @code{.endef} directives.
3894 @subsubsection Primary Attributes
3896 @cindex primary attributes, COFF symbols
3897 The symbol name is set with @code{.def}; the value and type,
3898 respectively, with @code{.val} and @code{.type}.
3900 @subsubsection Auxiliary Attributes
3902 @cindex auxiliary attributes, COFF symbols
3903 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3904 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3905 table information for COFF.
3910 @subsection Symbol Attributes for SOM
3912 @cindex SOM symbol attributes
3913 @cindex symbol attributes, SOM
3915 The SOM format for the HPPA supports a multitude of symbol attributes set with
3916 the @code{.EXPORT} and @code{.IMPORT} directives.
3918 The attributes are described in @cite{HP9000 Series 800 Assembly
3919 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3920 @code{EXPORT} assembler directive documentation.
3924 @chapter Expressions
3928 @cindex numeric values
3929 An @dfn{expression} specifies an address or numeric value.
3930 Whitespace may precede and/or follow an expression.
3932 The result of an expression must be an absolute number, or else an offset into
3933 a particular section. If an expression is not absolute, and there is not
3934 enough information when @command{@value{AS}} sees the expression to know its
3935 section, a second pass over the source program might be necessary to interpret
3936 the expression---but the second pass is currently not implemented.
3937 @command{@value{AS}} aborts with an error message in this situation.
3940 * Empty Exprs:: Empty Expressions
3941 * Integer Exprs:: Integer Expressions
3945 @section Empty Expressions
3947 @cindex empty expressions
3948 @cindex expressions, empty
3949 An empty expression has no value: it is just whitespace or null.
3950 Wherever an absolute expression is required, you may omit the
3951 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3952 is compatible with other assemblers.
3955 @section Integer Expressions
3957 @cindex integer expressions
3958 @cindex expressions, integer
3959 An @dfn{integer expression} is one or more @emph{arguments} delimited
3960 by @emph{operators}.
3963 * Arguments:: Arguments
3964 * Operators:: Operators
3965 * Prefix Ops:: Prefix Operators
3966 * Infix Ops:: Infix Operators
3970 @subsection Arguments
3972 @cindex expression arguments
3973 @cindex arguments in expressions
3974 @cindex operands in expressions
3975 @cindex arithmetic operands
3976 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3977 contexts arguments are sometimes called ``arithmetic operands''. In
3978 this manual, to avoid confusing them with the ``instruction operands'' of
3979 the machine language, we use the term ``argument'' to refer to parts of
3980 expressions only, reserving the word ``operand'' to refer only to machine
3981 instruction operands.
3983 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3984 @var{section} is one of text, data, bss, absolute,
3985 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3988 Numbers are usually integers.
3990 A number can be a flonum or bignum. In this case, you are warned
3991 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3992 these 32 bits are an integer. You may write integer-manipulating
3993 instructions that act on exotic constants, compatible with other
3996 @cindex subexpressions
3997 Subexpressions are a left parenthesis @samp{(} followed by an integer
3998 expression, followed by a right parenthesis @samp{)}; or a prefix
3999 operator followed by an argument.
4002 @subsection Operators
4004 @cindex operators, in expressions
4005 @cindex arithmetic functions
4006 @cindex functions, in expressions
4007 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4008 operators are followed by an argument. Infix operators appear
4009 between their arguments. Operators may be preceded and/or followed by
4013 @subsection Prefix Operator
4015 @cindex prefix operators
4016 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4017 one argument, which must be absolute.
4019 @c the tex/end tex stuff surrounding this small table is meant to make
4020 @c it align, on the printed page, with the similar table in the next
4021 @c section (which is inside an enumerate).
4023 \global\advance\leftskip by \itemindent
4028 @dfn{Negation}. Two's complement negation.
4030 @dfn{Complementation}. Bitwise not.
4034 \global\advance\leftskip by -\itemindent
4038 @subsection Infix Operators
4040 @cindex infix operators
4041 @cindex operators, permitted arguments
4042 @dfn{Infix operators} take two arguments, one on either side. Operators
4043 have precedence, but operations with equal precedence are performed left
4044 to right. Apart from @code{+} or @option{-}, both arguments must be
4045 absolute, and the result is absolute.
4048 @cindex operator precedence
4049 @cindex precedence of operators
4056 @dfn{Multiplication}.
4059 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4065 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4068 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4072 Intermediate precedence
4077 @dfn{Bitwise Inclusive Or}.
4083 @dfn{Bitwise Exclusive Or}.
4086 @dfn{Bitwise Or Not}.
4093 @cindex addition, permitted arguments
4094 @cindex plus, permitted arguments
4095 @cindex arguments for addition
4097 @dfn{Addition}. If either argument is absolute, the result has the section of
4098 the other argument. You may not add together arguments from different
4101 @cindex subtraction, permitted arguments
4102 @cindex minus, permitted arguments
4103 @cindex arguments for subtraction
4105 @dfn{Subtraction}. If the right argument is absolute, the
4106 result has the section of the left argument.
4107 If both arguments are in the same section, the result is absolute.
4108 You may not subtract arguments from different sections.
4109 @c FIXME is there still something useful to say about undefined - undefined ?
4111 @cindex comparison expressions
4112 @cindex expressions, comparison
4117 @dfn{Is Not Equal To}
4121 @dfn{Is Greater Than}
4123 @dfn{Is Greater Than Or Equal To}
4125 @dfn{Is Less Than Or Equal To}
4127 The comparison operators can be used as infix operators. A true results has a
4128 value of -1 whereas a false result has a value of 0. Note, these operators
4129 perform signed comparisons.
4132 @item Lowest Precedence
4141 These two logical operations can be used to combine the results of sub
4142 expressions. Note, unlike the comparison operators a true result returns a
4143 value of 1 but a false results does still return 0. Also note that the logical
4144 or operator has a slightly lower precedence than logical and.
4149 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4150 address; you can only have a defined section in one of the two arguments.
4153 @chapter Assembler Directives
4155 @cindex directives, machine independent
4156 @cindex pseudo-ops, machine independent
4157 @cindex machine independent directives
4158 All assembler directives have names that begin with a period (@samp{.}).
4159 The rest of the name is letters, usually in lower case.
4161 This chapter discusses directives that are available regardless of the
4162 target machine configuration for the @sc{gnu} assembler.
4164 Some machine configurations provide additional directives.
4165 @xref{Machine Dependencies}.
4168 @ifset machine-directives
4169 @xref{Machine Dependencies}, for additional directives.
4174 * Abort:: @code{.abort}
4176 * ABORT (COFF):: @code{.ABORT}
4179 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4180 * Altmacro:: @code{.altmacro}
4181 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4182 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4183 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4184 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4185 * Byte:: @code{.byte @var{expressions}}
4186 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4187 * Comm:: @code{.comm @var{symbol} , @var{length} }
4188 * Data:: @code{.data @var{subsection}}
4190 * Def:: @code{.def @var{name}}
4193 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4199 * Double:: @code{.double @var{flonums}}
4200 * Eject:: @code{.eject}
4201 * Else:: @code{.else}
4202 * Elseif:: @code{.elseif}
4205 * Endef:: @code{.endef}
4208 * Endfunc:: @code{.endfunc}
4209 * Endif:: @code{.endif}
4210 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4211 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4212 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4214 * Error:: @code{.error @var{string}}
4215 * Exitm:: @code{.exitm}
4216 * Extern:: @code{.extern}
4217 * Fail:: @code{.fail}
4218 * File:: @code{.file}
4219 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4220 * Float:: @code{.float @var{flonums}}
4221 * Func:: @code{.func}
4222 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4224 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4225 * Hidden:: @code{.hidden @var{names}}
4228 * hword:: @code{.hword @var{expressions}}
4229 * Ident:: @code{.ident}
4230 * If:: @code{.if @var{absolute expression}}
4231 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4232 * Include:: @code{.include "@var{file}"}
4233 * Int:: @code{.int @var{expressions}}
4235 * Internal:: @code{.internal @var{names}}
4238 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4239 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4240 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4241 * Lflags:: @code{.lflags}
4242 @ifclear no-line-dir
4243 * Line:: @code{.line @var{line-number}}
4246 * Linkonce:: @code{.linkonce [@var{type}]}
4247 * List:: @code{.list}
4248 * Ln:: @code{.ln @var{line-number}}
4249 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4250 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4252 * Local:: @code{.local @var{names}}
4255 * Long:: @code{.long @var{expressions}}
4257 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4260 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4261 * MRI:: @code{.mri @var{val}}
4262 * Noaltmacro:: @code{.noaltmacro}
4263 * Nolist:: @code{.nolist}
4264 * Octa:: @code{.octa @var{bignums}}
4265 * Offset:: @code{.offset @var{loc}}
4266 * Org:: @code{.org @var{new-lc}, @var{fill}}
4267 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4269 * PopSection:: @code{.popsection}
4270 * Previous:: @code{.previous}
4273 * Print:: @code{.print @var{string}}
4275 * Protected:: @code{.protected @var{names}}
4278 * Psize:: @code{.psize @var{lines}, @var{columns}}
4279 * Purgem:: @code{.purgem @var{name}}
4281 * PushSection:: @code{.pushsection @var{name}}
4284 * Quad:: @code{.quad @var{bignums}}
4285 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4286 * Rept:: @code{.rept @var{count}}
4287 * Sbttl:: @code{.sbttl "@var{subheading}"}
4289 * Scl:: @code{.scl @var{class}}
4292 * Section:: @code{.section @var{name}[, @var{flags}]}
4295 * Set:: @code{.set @var{symbol}, @var{expression}}
4296 * Short:: @code{.short @var{expressions}}
4297 * Single:: @code{.single @var{flonums}}
4299 * Size:: @code{.size [@var{name} , @var{expression}]}
4301 @ifclear no-space-dir
4302 * Skip:: @code{.skip @var{size} , @var{fill}}
4305 * Sleb128:: @code{.sleb128 @var{expressions}}
4306 @ifclear no-space-dir
4307 * Space:: @code{.space @var{size} , @var{fill}}
4310 * Stab:: @code{.stabd, .stabn, .stabs}
4313 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4314 * Struct:: @code{.struct @var{expression}}
4316 * SubSection:: @code{.subsection}
4317 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4321 * Tag:: @code{.tag @var{structname}}
4324 * Text:: @code{.text @var{subsection}}
4325 * Title:: @code{.title "@var{heading}"}
4327 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4330 * Uleb128:: @code{.uleb128 @var{expressions}}
4332 * Val:: @code{.val @var{addr}}
4336 * Version:: @code{.version "@var{string}"}
4337 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4338 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4341 * Warning:: @code{.warning @var{string}}
4342 * Weak:: @code{.weak @var{names}}
4343 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4344 * Word:: @code{.word @var{expressions}}
4345 * Deprecated:: Deprecated Directives
4349 @section @code{.abort}
4351 @cindex @code{abort} directive
4352 @cindex stopping the assembly
4353 This directive stops the assembly immediately. It is for
4354 compatibility with other assemblers. The original idea was that the
4355 assembly language source would be piped into the assembler. If the sender
4356 of the source quit, it could use this directive tells @command{@value{AS}} to
4357 quit also. One day @code{.abort} will not be supported.
4361 @section @code{.ABORT} (COFF)
4363 @cindex @code{ABORT} directive
4364 When producing COFF output, @command{@value{AS}} accepts this directive as a
4365 synonym for @samp{.abort}.
4368 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4374 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4376 @cindex padding the location counter
4377 @cindex @code{align} directive
4378 Pad the location counter (in the current subsection) to a particular storage
4379 boundary. The first expression (which must be absolute) is the alignment
4380 required, as described below.
4382 The second expression (also absolute) gives the fill value to be stored in the
4383 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4384 padding bytes are normally zero. However, on some systems, if the section is
4385 marked as containing code and the fill value is omitted, the space is filled
4386 with no-op instructions.
4388 The third expression is also absolute, and is also optional. If it is present,
4389 it is the maximum number of bytes that should be skipped by this alignment
4390 directive. If doing the alignment would require skipping more bytes than the
4391 specified maximum, then the alignment is not done at all. You can omit the
4392 fill value (the second argument) entirely by simply using two commas after the
4393 required alignment; this can be useful if you want the alignment to be filled
4394 with no-op instructions when appropriate.
4396 The way the required alignment is specified varies from system to system.
4397 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4398 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4399 alignment request in bytes. For example @samp{.align 8} advances
4400 the location counter until it is a multiple of 8. If the location counter
4401 is already a multiple of 8, no change is needed. For the tic54x, the
4402 first expression is the alignment request in words.
4404 For other systems, including ppc, i386 using a.out format, arm and
4405 strongarm, it is the
4406 number of low-order zero bits the location counter must have after
4407 advancement. For example @samp{.align 3} advances the location
4408 counter until it a multiple of 8. If the location counter is already a
4409 multiple of 8, no change is needed.
4411 This inconsistency is due to the different behaviors of the various
4412 native assemblers for these systems which GAS must emulate.
4413 GAS also provides @code{.balign} and @code{.p2align} directives,
4414 described later, which have a consistent behavior across all
4415 architectures (but are specific to GAS).
4418 @section @code{.altmacro}
4419 Enable alternate macro mode, enabling:
4422 @item LOCAL @var{name} [ , @dots{} ]
4423 One additional directive, @code{LOCAL}, is available. It is used to
4424 generate a string replacement for each of the @var{name} arguments, and
4425 replace any instances of @var{name} in each macro expansion. The
4426 replacement string is unique in the assembly, and different for each
4427 separate macro expansion. @code{LOCAL} allows you to write macros that
4428 define symbols, without fear of conflict between separate macro expansions.
4430 @item String delimiters
4431 You can write strings delimited in these other ways besides
4432 @code{"@var{string}"}:
4435 @item '@var{string}'
4436 You can delimit strings with single-quote characters.
4438 @item <@var{string}>
4439 You can delimit strings with matching angle brackets.
4442 @item single-character string escape
4443 To include any single character literally in a string (even if the
4444 character would otherwise have some special meaning), you can prefix the
4445 character with @samp{!} (an exclamation mark). For example, you can
4446 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4448 @item Expression results as strings
4449 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4450 and use the result as a string.
4454 @section @code{.ascii "@var{string}"}@dots{}
4456 @cindex @code{ascii} directive
4457 @cindex string literals
4458 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4459 separated by commas. It assembles each string (with no automatic
4460 trailing zero byte) into consecutive addresses.
4463 @section @code{.asciz "@var{string}"}@dots{}
4465 @cindex @code{asciz} directive
4466 @cindex zero-terminated strings
4467 @cindex null-terminated strings
4468 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4469 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4472 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4474 @cindex padding the location counter given number of bytes
4475 @cindex @code{balign} directive
4476 Pad the location counter (in the current subsection) to a particular
4477 storage boundary. The first expression (which must be absolute) is the
4478 alignment request in bytes. For example @samp{.balign 8} advances
4479 the location counter until it is a multiple of 8. If the location counter
4480 is already a multiple of 8, no change is needed.
4482 The second expression (also absolute) gives the fill value to be stored in the
4483 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4484 padding bytes are normally zero. However, on some systems, if the section is
4485 marked as containing code and the fill value is omitted, the space is filled
4486 with no-op instructions.
4488 The third expression is also absolute, and is also optional. If it is present,
4489 it is the maximum number of bytes that should be skipped by this alignment
4490 directive. If doing the alignment would require skipping more bytes than the
4491 specified maximum, then the alignment is not done at all. You can omit the
4492 fill value (the second argument) entirely by simply using two commas after the
4493 required alignment; this can be useful if you want the alignment to be filled
4494 with no-op instructions when appropriate.
4496 @cindex @code{balignw} directive
4497 @cindex @code{balignl} directive
4498 The @code{.balignw} and @code{.balignl} directives are variants of the
4499 @code{.balign} directive. The @code{.balignw} directive treats the fill
4500 pattern as a two byte word value. The @code{.balignl} directives treats the
4501 fill pattern as a four byte longword value. For example, @code{.balignw
4502 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4503 filled in with the value 0x368d (the exact placement of the bytes depends upon
4504 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4507 @node Bundle directives
4508 @section @code{.bundle_align_mode @var{abs-expr}}
4509 @cindex @code{bundle_align_mode} directive
4511 @cindex instruction bundle
4512 @cindex aligned instruction bundle
4513 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4514 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4515 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4516 disabled (which is the default state). If the argument it not zero, it
4517 gives the size of an instruction bundle as a power of two (as for the
4518 @code{.p2align} directive, @pxref{P2align}).
4520 For some targets, it's an ABI requirement that no instruction may span a
4521 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4522 instructions that starts on an aligned boundary. For example, if
4523 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4524 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4525 effect, no single instruction may span a boundary between bundles. If an
4526 instruction would start too close to the end of a bundle for the length of
4527 that particular instruction to fit within the bundle, then the space at the
4528 end of that bundle is filled with no-op instructions so the instruction
4529 starts in the next bundle. As a corollary, it's an error if any single
4530 instruction's encoding is longer than the bundle size.
4532 @section @code{.bundle_lock} and @code{.bundle_unlock}
4533 @cindex @code{bundle_lock} directive
4534 @cindex @code{bundle_unlock} directive
4535 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4536 allow explicit control over instruction bundle padding. These directives
4537 are only valid when @code{.bundle_align_mode} has been used to enable
4538 aligned instruction bundle mode. It's an error if they appear when
4539 @code{.bundle_align_mode} has not been used at all, or when the last
4540 directive was @w{@code{.bundle_align_mode 0}}.
4542 @cindex bundle-locked
4543 For some targets, it's an ABI requirement that certain instructions may
4544 appear only as part of specified permissible sequences of multiple
4545 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4546 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4547 instruction sequence. For purposes of aligned instruction bundle mode, a
4548 sequence starting with @code{.bundle_lock} and ending with
4549 @code{.bundle_unlock} is treated as a single instruction. That is, the
4550 entire sequence must fit into a single bundle and may not span a bundle
4551 boundary. If necessary, no-op instructions will be inserted before the
4552 first instruction of the sequence so that the whole sequence starts on an
4553 aligned bundle boundary. It's an error if the sequence is longer than the
4556 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4557 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4558 nested. That is, a second @code{.bundle_lock} directive before the next
4559 @code{.bundle_unlock} directive has no effect except that it must be
4560 matched by another closing @code{.bundle_unlock} so that there is the
4561 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4564 @section @code{.byte @var{expressions}}
4566 @cindex @code{byte} directive
4567 @cindex integers, one byte
4568 @code{.byte} expects zero or more expressions, separated by commas.
4569 Each expression is assembled into the next byte.
4571 @node CFI directives
4572 @section @code{.cfi_sections @var{section_list}}
4573 @cindex @code{cfi_sections} directive
4574 @code{.cfi_sections} may be used to specify whether CFI directives
4575 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4576 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4577 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4578 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4579 directive is not used is @code{.cfi_sections .eh_frame}.
4581 @section @code{.cfi_startproc [simple]}
4582 @cindex @code{cfi_startproc} directive
4583 @code{.cfi_startproc} is used at the beginning of each function that
4584 should have an entry in @code{.eh_frame}. It initializes some internal
4585 data structures. Don't forget to close the function by
4586 @code{.cfi_endproc}.
4588 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4589 it also emits some architecture dependent initial CFI instructions.
4591 @section @code{.cfi_endproc}
4592 @cindex @code{cfi_endproc} directive
4593 @code{.cfi_endproc} is used at the end of a function where it closes its
4594 unwind entry previously opened by
4595 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4597 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4598 @code{.cfi_personality} defines personality routine and its encoding.
4599 @var{encoding} must be a constant determining how the personality
4600 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4601 argument is not present, otherwise second argument should be
4602 a constant or a symbol name. When using indirect encodings,
4603 the symbol provided should be the location where personality
4604 can be loaded from, not the personality routine itself.
4605 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4606 no personality routine.
4608 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4609 @code{.cfi_lsda} defines LSDA and its encoding.
4610 @var{encoding} must be a constant determining how the LSDA
4611 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4612 argument is not present, otherwise second argument should be a constant
4613 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4616 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4617 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4618 address from @var{register} and add @var{offset} to it}.
4620 @section @code{.cfi_def_cfa_register @var{register}}
4621 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4622 now on @var{register} will be used instead of the old one. Offset
4625 @section @code{.cfi_def_cfa_offset @var{offset}}
4626 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4627 remains the same, but @var{offset} is new. Note that it is the
4628 absolute offset that will be added to a defined register to compute
4631 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4632 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4633 value that is added/substracted from the previous offset.
4635 @section @code{.cfi_offset @var{register}, @var{offset}}
4636 Previous value of @var{register} is saved at offset @var{offset} from
4639 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4640 Previous value of @var{register} is saved at offset @var{offset} from
4641 the current CFA register. This is transformed to @code{.cfi_offset}
4642 using the known displacement of the CFA register from the CFA.
4643 This is often easier to use, because the number will match the
4644 code it's annotating.
4646 @section @code{.cfi_register @var{register1}, @var{register2}}
4647 Previous value of @var{register1} is saved in register @var{register2}.
4649 @section @code{.cfi_restore @var{register}}
4650 @code{.cfi_restore} says that the rule for @var{register} is now the
4651 same as it was at the beginning of the function, after all initial
4652 instruction added by @code{.cfi_startproc} were executed.
4654 @section @code{.cfi_undefined @var{register}}
4655 From now on the previous value of @var{register} can't be restored anymore.
4657 @section @code{.cfi_same_value @var{register}}
4658 Current value of @var{register} is the same like in the previous frame,
4659 i.e. no restoration needed.
4661 @section @code{.cfi_remember_state},
4662 First save all current rules for all registers by @code{.cfi_remember_state},
4663 then totally screw them up by subsequent @code{.cfi_*} directives and when
4664 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4665 the previous saved state.
4667 @section @code{.cfi_return_column @var{register}}
4668 Change return column @var{register}, i.e. the return address is either
4669 directly in @var{register} or can be accessed by rules for @var{register}.
4671 @section @code{.cfi_signal_frame}
4672 Mark current function as signal trampoline.
4674 @section @code{.cfi_window_save}
4675 SPARC register window has been saved.
4677 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4678 Allows the user to add arbitrary bytes to the unwind info. One
4679 might use this to add OS-specific CFI opcodes, or generic CFI
4680 opcodes that GAS does not yet support.
4682 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4683 The current value of @var{register} is @var{label}. The value of @var{label}
4684 will be encoded in the output file according to @var{encoding}; see the
4685 description of @code{.cfi_personality} for details on this encoding.
4687 The usefulness of equating a register to a fixed label is probably
4688 limited to the return address register. Here, it can be useful to
4689 mark a code segment that has only one return address which is reached
4690 by a direct branch and no copy of the return address exists in memory
4691 or another register.
4694 @section @code{.comm @var{symbol} , @var{length} }
4696 @cindex @code{comm} directive
4697 @cindex symbol, common
4698 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4699 common symbol in one object file may be merged with a defined or common symbol
4700 of the same name in another object file. If @code{@value{LD}} does not see a
4701 definition for the symbol--just one or more common symbols--then it will
4702 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4703 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4704 the same name, and they do not all have the same size, it will allocate space
4705 using the largest size.
4708 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4709 an optional third argument. This is the desired alignment of the symbol,
4710 specified for ELF as a byte boundary (for example, an alignment of 16 means
4711 that the least significant 4 bits of the address should be zero), and for PE
4712 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4713 boundary). The alignment must be an absolute expression, and it must be a
4714 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4715 common symbol, it will use the alignment when placing the symbol. If no
4716 alignment is specified, @command{@value{AS}} will set the alignment to the
4717 largest power of two less than or equal to the size of the symbol, up to a
4718 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4719 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4720 @samp{--section-alignment} option; image file sections in PE are aligned to
4721 multiples of 4096, which is far too large an alignment for ordinary variables.
4722 It is rather the default alignment for (non-debug) sections within object
4723 (@samp{*.o}) files, which are less strictly aligned.}.
4727 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4728 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4732 @section @code{.data @var{subsection}}
4734 @cindex @code{data} directive
4735 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4736 end of the data subsection numbered @var{subsection} (which is an
4737 absolute expression). If @var{subsection} is omitted, it defaults
4742 @section @code{.def @var{name}}
4744 @cindex @code{def} directive
4745 @cindex COFF symbols, debugging
4746 @cindex debugging COFF symbols
4747 Begin defining debugging information for a symbol @var{name}; the
4748 definition extends until the @code{.endef} directive is encountered.
4751 This directive is only observed when @command{@value{AS}} is configured for COFF
4752 format output; when producing @code{b.out}, @samp{.def} is recognized,
4759 @section @code{.desc @var{symbol}, @var{abs-expression}}
4761 @cindex @code{desc} directive
4762 @cindex COFF symbol descriptor
4763 @cindex symbol descriptor, COFF
4764 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4765 to the low 16 bits of an absolute expression.
4768 The @samp{.desc} directive is not available when @command{@value{AS}} is
4769 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4770 object format. For the sake of compatibility, @command{@value{AS}} accepts
4771 it, but produces no output, when configured for COFF.
4777 @section @code{.dim}
4779 @cindex @code{dim} directive
4780 @cindex COFF auxiliary symbol information
4781 @cindex auxiliary symbol information, COFF
4782 This directive is generated by compilers to include auxiliary debugging
4783 information in the symbol table. It is only permitted inside
4784 @code{.def}/@code{.endef} pairs.
4787 @samp{.dim} is only meaningful when generating COFF format output; when
4788 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4794 @section @code{.double @var{flonums}}
4796 @cindex @code{double} directive
4797 @cindex floating point numbers (double)
4798 @code{.double} expects zero or more flonums, separated by commas. It
4799 assembles floating point numbers.
4801 The exact kind of floating point numbers emitted depends on how
4802 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4806 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4807 in @sc{ieee} format.
4812 @section @code{.eject}
4814 @cindex @code{eject} directive
4815 @cindex new page, in listings
4816 @cindex page, in listings
4817 @cindex listing control: new page
4818 Force a page break at this point, when generating assembly listings.
4821 @section @code{.else}
4823 @cindex @code{else} directive
4824 @code{.else} is part of the @command{@value{AS}} support for conditional
4825 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4826 of code to be assembled if the condition for the preceding @code{.if}
4830 @section @code{.elseif}
4832 @cindex @code{elseif} directive
4833 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4834 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4835 @code{.if} block that would otherwise fill the entire @code{.else} section.
4838 @section @code{.end}
4840 @cindex @code{end} directive
4841 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4842 process anything in the file past the @code{.end} directive.
4846 @section @code{.endef}
4848 @cindex @code{endef} directive
4849 This directive flags the end of a symbol definition begun with
4853 @samp{.endef} is only meaningful when generating COFF format output; if
4854 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4855 directive but ignores it.
4860 @section @code{.endfunc}
4861 @cindex @code{endfunc} directive
4862 @code{.endfunc} marks the end of a function specified with @code{.func}.
4865 @section @code{.endif}
4867 @cindex @code{endif} directive
4868 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4869 it marks the end of a block of code that is only assembled
4870 conditionally. @xref{If,,@code{.if}}.
4873 @section @code{.equ @var{symbol}, @var{expression}}
4875 @cindex @code{equ} directive
4876 @cindex assigning values to symbols
4877 @cindex symbols, assigning values to
4878 This directive sets the value of @var{symbol} to @var{expression}.
4879 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4882 The syntax for @code{equ} on the HPPA is
4883 @samp{@var{symbol} .equ @var{expression}}.
4887 The syntax for @code{equ} on the Z80 is
4888 @samp{@var{symbol} equ @var{expression}}.
4889 On the Z80 it is an eror if @var{symbol} is already defined,
4890 but the symbol is not protected from later redefinition.
4891 Compare @ref{Equiv}.
4895 @section @code{.equiv @var{symbol}, @var{expression}}
4896 @cindex @code{equiv} directive
4897 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4898 the assembler will signal an error if @var{symbol} is already defined. Note a
4899 symbol which has been referenced but not actually defined is considered to be
4902 Except for the contents of the error message, this is roughly equivalent to
4909 plus it protects the symbol from later redefinition.
4912 @section @code{.eqv @var{symbol}, @var{expression}}
4913 @cindex @code{eqv} directive
4914 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4915 evaluate the expression or any part of it immediately. Instead each time
4916 the resulting symbol is used in an expression, a snapshot of its current
4920 @section @code{.err}
4921 @cindex @code{err} directive
4922 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4923 message and, unless the @option{-Z} option was used, it will not generate an
4924 object file. This can be used to signal an error in conditionally compiled code.
4927 @section @code{.error "@var{string}"}
4928 @cindex error directive
4930 Similarly to @code{.err}, this directive emits an error, but you can specify a
4931 string that will be emitted as the error message. If you don't specify the
4932 message, it defaults to @code{".error directive invoked in source file"}.
4933 @xref{Errors, ,Error and Warning Messages}.
4936 .error "This code has not been assembled and tested."
4940 @section @code{.exitm}
4941 Exit early from the current macro definition. @xref{Macro}.
4944 @section @code{.extern}
4946 @cindex @code{extern} directive
4947 @code{.extern} is accepted in the source program---for compatibility
4948 with other assemblers---but it is ignored. @command{@value{AS}} treats
4949 all undefined symbols as external.
4952 @section @code{.fail @var{expression}}
4954 @cindex @code{fail} directive
4955 Generates an error or a warning. If the value of the @var{expression} is 500
4956 or more, @command{@value{AS}} will print a warning message. If the value is less
4957 than 500, @command{@value{AS}} will print an error message. The message will
4958 include the value of @var{expression}. This can occasionally be useful inside
4959 complex nested macros or conditional assembly.
4962 @section @code{.file}
4963 @cindex @code{file} directive
4965 @ifclear no-file-dir
4966 There are two different versions of the @code{.file} directive. Targets
4967 that support DWARF2 line number information use the DWARF2 version of
4968 @code{.file}. Other targets use the default version.
4970 @subheading Default Version
4972 @cindex logical file name
4973 @cindex file name, logical
4974 This version of the @code{.file} directive tells @command{@value{AS}} that we
4975 are about to start a new logical file. The syntax is:
4981 @var{string} is the new file name. In general, the filename is
4982 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4983 to specify an empty file name, you must give the quotes--@code{""}. This
4984 statement may go away in future: it is only recognized to be compatible with
4985 old @command{@value{AS}} programs.
4987 @subheading DWARF2 Version
4990 When emitting DWARF2 line number information, @code{.file} assigns filenames
4991 to the @code{.debug_line} file name table. The syntax is:
4994 .file @var{fileno} @var{filename}
4997 The @var{fileno} operand should be a unique positive integer to use as the
4998 index of the entry in the table. The @var{filename} operand is a C string
5001 The detail of filename indices is exposed to the user because the filename
5002 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5003 information, and thus the user must know the exact indices that table
5007 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5009 @cindex @code{fill} directive
5010 @cindex writing patterns in memory
5011 @cindex patterns, writing in memory
5012 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5013 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5014 may be zero or more. @var{Size} may be zero or more, but if it is
5015 more than 8, then it is deemed to have the value 8, compatible with
5016 other people's assemblers. The contents of each @var{repeat} bytes
5017 is taken from an 8-byte number. The highest order 4 bytes are
5018 zero. The lowest order 4 bytes are @var{value} rendered in the
5019 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5020 Each @var{size} bytes in a repetition is taken from the lowest order
5021 @var{size} bytes of this number. Again, this bizarre behavior is
5022 compatible with other people's assemblers.
5024 @var{size} and @var{value} are optional.
5025 If the second comma and @var{value} are absent, @var{value} is
5026 assumed zero. If the first comma and following tokens are absent,
5027 @var{size} is assumed to be 1.
5030 @section @code{.float @var{flonums}}
5032 @cindex floating point numbers (single)
5033 @cindex @code{float} directive
5034 This directive assembles zero or more flonums, separated by commas. It
5035 has the same effect as @code{.single}.
5037 The exact kind of floating point numbers emitted depends on how
5038 @command{@value{AS}} is configured.
5039 @xref{Machine Dependencies}.
5043 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5044 in @sc{ieee} format.
5049 @section @code{.func @var{name}[,@var{label}]}
5050 @cindex @code{func} directive
5051 @code{.func} emits debugging information to denote function @var{name}, and
5052 is ignored unless the file is assembled with debugging enabled.
5053 Only @samp{--gstabs[+]} is currently supported.
5054 @var{label} is the entry point of the function and if omitted @var{name}
5055 prepended with the @samp{leading char} is used.
5056 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5057 All functions are currently defined to have @code{void} return type.
5058 The function must be terminated with @code{.endfunc}.
5061 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5063 @cindex @code{global} directive
5064 @cindex symbol, making visible to linker
5065 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5066 @var{symbol} in your partial program, its value is made available to
5067 other partial programs that are linked with it. Otherwise,
5068 @var{symbol} takes its attributes from a symbol of the same name
5069 from another file linked into the same program.
5071 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5072 compatibility with other assemblers.
5075 On the HPPA, @code{.global} is not always enough to make it accessible to other
5076 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5077 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5082 @section @code{.gnu_attribute @var{tag},@var{value}}
5083 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5086 @section @code{.hidden @var{names}}
5088 @cindex @code{hidden} directive
5090 This is one of the ELF visibility directives. The other two are
5091 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5092 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5094 This directive overrides the named symbols default visibility (which is set by
5095 their binding: local, global or weak). The directive sets the visibility to
5096 @code{hidden} which means that the symbols are not visible to other components.
5097 Such symbols are always considered to be @code{protected} as well.
5101 @section @code{.hword @var{expressions}}
5103 @cindex @code{hword} directive
5104 @cindex integers, 16-bit
5105 @cindex numbers, 16-bit
5106 @cindex sixteen bit integers
5107 This expects zero or more @var{expressions}, and emits
5108 a 16 bit number for each.
5111 This directive is a synonym for @samp{.short}; depending on the target
5112 architecture, it may also be a synonym for @samp{.word}.
5116 This directive is a synonym for @samp{.short}.
5119 This directive is a synonym for both @samp{.short} and @samp{.word}.
5124 @section @code{.ident}
5126 @cindex @code{ident} directive
5128 This directive is used by some assemblers to place tags in object files. The
5129 behavior of this directive varies depending on the target. When using the
5130 a.out object file format, @command{@value{AS}} simply accepts the directive for
5131 source-file compatibility with existing assemblers, but does not emit anything
5132 for it. When using COFF, comments are emitted to the @code{.comment} or
5133 @code{.rdata} section, depending on the target. When using ELF, comments are
5134 emitted to the @code{.comment} section.
5137 @section @code{.if @var{absolute expression}}
5139 @cindex conditional assembly
5140 @cindex @code{if} directive
5141 @code{.if} marks the beginning of a section of code which is only
5142 considered part of the source program being assembled if the argument
5143 (which must be an @var{absolute expression}) is non-zero. The end of
5144 the conditional section of code must be marked by @code{.endif}
5145 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5146 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5147 If you have several conditions to check, @code{.elseif} may be used to avoid
5148 nesting blocks if/else within each subsequent @code{.else} block.
5150 The following variants of @code{.if} are also supported:
5152 @cindex @code{ifdef} directive
5153 @item .ifdef @var{symbol}
5154 Assembles the following section of code if the specified @var{symbol}
5155 has been defined. Note a symbol which has been referenced but not yet defined
5156 is considered to be undefined.
5158 @cindex @code{ifb} directive
5159 @item .ifb @var{text}
5160 Assembles the following section of code if the operand is blank (empty).
5162 @cindex @code{ifc} directive
5163 @item .ifc @var{string1},@var{string2}
5164 Assembles the following section of code if the two strings are the same. The
5165 strings may be optionally quoted with single quotes. If they are not quoted,
5166 the first string stops at the first comma, and the second string stops at the
5167 end of the line. Strings which contain whitespace should be quoted. The
5168 string comparison is case sensitive.
5170 @cindex @code{ifeq} directive
5171 @item .ifeq @var{absolute expression}
5172 Assembles the following section of code if the argument is zero.
5174 @cindex @code{ifeqs} directive
5175 @item .ifeqs @var{string1},@var{string2}
5176 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5178 @cindex @code{ifge} directive
5179 @item .ifge @var{absolute expression}
5180 Assembles the following section of code if the argument is greater than or
5183 @cindex @code{ifgt} directive
5184 @item .ifgt @var{absolute expression}
5185 Assembles the following section of code if the argument is greater than zero.
5187 @cindex @code{ifle} directive
5188 @item .ifle @var{absolute expression}
5189 Assembles the following section of code if the argument is less than or equal
5192 @cindex @code{iflt} directive
5193 @item .iflt @var{absolute expression}
5194 Assembles the following section of code if the argument is less than zero.
5196 @cindex @code{ifnb} directive
5197 @item .ifnb @var{text}
5198 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5199 following section of code if the operand is non-blank (non-empty).
5201 @cindex @code{ifnc} directive
5202 @item .ifnc @var{string1},@var{string2}.
5203 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5204 following section of code if the two strings are not the same.
5206 @cindex @code{ifndef} directive
5207 @cindex @code{ifnotdef} directive
5208 @item .ifndef @var{symbol}
5209 @itemx .ifnotdef @var{symbol}
5210 Assembles the following section of code if the specified @var{symbol}
5211 has not been defined. Both spelling variants are equivalent. Note a symbol
5212 which has been referenced but not yet defined is considered to be undefined.
5214 @cindex @code{ifne} directive
5215 @item .ifne @var{absolute expression}
5216 Assembles the following section of code if the argument is not equal to zero
5217 (in other words, this is equivalent to @code{.if}).
5219 @cindex @code{ifnes} directive
5220 @item .ifnes @var{string1},@var{string2}
5221 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5222 following section of code if the two strings are not the same.
5226 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5228 @cindex @code{incbin} directive
5229 @cindex binary files, including
5230 The @code{incbin} directive includes @var{file} verbatim at the current
5231 location. You can control the search paths used with the @samp{-I} command-line
5232 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5235 The @var{skip} argument skips a number of bytes from the start of the
5236 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5237 read. Note that the data is not aligned in any way, so it is the user's
5238 responsibility to make sure that proper alignment is provided both before and
5239 after the @code{incbin} directive.
5242 @section @code{.include "@var{file}"}
5244 @cindex @code{include} directive
5245 @cindex supporting files, including
5246 @cindex files, including
5247 This directive provides a way to include supporting files at specified
5248 points in your source program. The code from @var{file} is assembled as
5249 if it followed the point of the @code{.include}; when the end of the
5250 included file is reached, assembly of the original file continues. You
5251 can control the search paths used with the @samp{-I} command-line option
5252 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5256 @section @code{.int @var{expressions}}
5258 @cindex @code{int} directive
5259 @cindex integers, 32-bit
5260 Expect zero or more @var{expressions}, of any section, separated by commas.
5261 For each expression, emit a number that, at run time, is the value of that
5262 expression. The byte order and bit size of the number depends on what kind
5263 of target the assembly is for.
5267 On most forms of the H8/300, @code{.int} emits 16-bit
5268 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5275 @section @code{.internal @var{names}}
5277 @cindex @code{internal} directive
5279 This is one of the ELF visibility directives. The other two are
5280 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5281 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5283 This directive overrides the named symbols default visibility (which is set by
5284 their binding: local, global or weak). The directive sets the visibility to
5285 @code{internal} which means that the symbols are considered to be @code{hidden}
5286 (i.e., not visible to other components), and that some extra, processor specific
5287 processing must also be performed upon the symbols as well.
5291 @section @code{.irp @var{symbol},@var{values}}@dots{}
5293 @cindex @code{irp} directive
5294 Evaluate a sequence of statements assigning different values to @var{symbol}.
5295 The sequence of statements starts at the @code{.irp} directive, and is
5296 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5297 set to @var{value}, and the sequence of statements is assembled. If no
5298 @var{value} is listed, the sequence of statements is assembled once, with
5299 @var{symbol} set to the null string. To refer to @var{symbol} within the
5300 sequence of statements, use @var{\symbol}.
5302 For example, assembling
5310 is equivalent to assembling
5318 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5321 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5323 @cindex @code{irpc} directive
5324 Evaluate a sequence of statements assigning different values to @var{symbol}.
5325 The sequence of statements starts at the @code{.irpc} directive, and is
5326 terminated by an @code{.endr} directive. For each character in @var{value},
5327 @var{symbol} is set to the character, and the sequence of statements is
5328 assembled. If no @var{value} is listed, the sequence of statements is
5329 assembled once, with @var{symbol} set to the null string. To refer to
5330 @var{symbol} within the sequence of statements, use @var{\symbol}.
5332 For example, assembling
5340 is equivalent to assembling
5348 For some caveats with the spelling of @var{symbol}, see also the discussion
5352 @section @code{.lcomm @var{symbol} , @var{length}}
5354 @cindex @code{lcomm} directive
5355 @cindex local common symbols
5356 @cindex symbols, local common
5357 Reserve @var{length} (an absolute expression) bytes for a local common
5358 denoted by @var{symbol}. The section and value of @var{symbol} are
5359 those of the new local common. The addresses are allocated in the bss
5360 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5361 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5362 not visible to @code{@value{LD}}.
5365 Some targets permit a third argument to be used with @code{.lcomm}. This
5366 argument specifies the desired alignment of the symbol in the bss section.
5370 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5371 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5375 @section @code{.lflags}
5377 @cindex @code{lflags} directive (ignored)
5378 @command{@value{AS}} accepts this directive, for compatibility with other
5379 assemblers, but ignores it.
5381 @ifclear no-line-dir
5383 @section @code{.line @var{line-number}}
5385 @cindex @code{line} directive
5386 @cindex logical line number
5388 Change the logical line number. @var{line-number} must be an absolute
5389 expression. The next line has that logical line number. Therefore any other
5390 statements on the current line (after a statement separator character) are
5391 reported as on logical line number @var{line-number} @minus{} 1. One day
5392 @command{@value{AS}} will no longer support this directive: it is recognized only
5393 for compatibility with existing assembler programs.
5396 Even though this is a directive associated with the @code{a.out} or
5397 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5398 when producing COFF output, and treats @samp{.line} as though it
5399 were the COFF @samp{.ln} @emph{if} it is found outside a
5400 @code{.def}/@code{.endef} pair.
5402 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5403 used by compilers to generate auxiliary symbol information for
5408 @section @code{.linkonce [@var{type}]}
5410 @cindex @code{linkonce} directive
5411 @cindex common sections
5412 Mark the current section so that the linker only includes a single copy of it.
5413 This may be used to include the same section in several different object files,
5414 but ensure that the linker will only include it once in the final output file.
5415 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5416 Duplicate sections are detected based on the section name, so it should be
5419 This directive is only supported by a few object file formats; as of this
5420 writing, the only object file format which supports it is the Portable
5421 Executable format used on Windows NT.
5423 The @var{type} argument is optional. If specified, it must be one of the
5424 following strings. For example:
5428 Not all types may be supported on all object file formats.
5432 Silently discard duplicate sections. This is the default.
5435 Warn if there are duplicate sections, but still keep only one copy.
5438 Warn if any of the duplicates have different sizes.
5441 Warn if any of the duplicates do not have exactly the same contents.
5445 @section @code{.list}
5447 @cindex @code{list} directive
5448 @cindex listing control, turning on
5449 Control (in conjunction with the @code{.nolist} directive) whether or
5450 not assembly listings are generated. These two directives maintain an
5451 internal counter (which is zero initially). @code{.list} increments the
5452 counter, and @code{.nolist} decrements it. Assembly listings are
5453 generated whenever the counter is greater than zero.
5455 By default, listings are disabled. When you enable them (with the
5456 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5457 the initial value of the listing counter is one.
5460 @section @code{.ln @var{line-number}}
5462 @cindex @code{ln} directive
5463 @ifclear no-line-dir
5464 @samp{.ln} is a synonym for @samp{.line}.
5467 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5468 must be an absolute expression. The next line has that logical
5469 line number, so any other statements on the current line (after a
5470 statement separator character @code{;}) are reported as on logical
5471 line number @var{line-number} @minus{} 1.
5474 This directive is accepted, but ignored, when @command{@value{AS}} is
5475 configured for @code{b.out}; its effect is only associated with COFF
5481 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5482 @cindex @code{loc} directive
5483 When emitting DWARF2 line number information,
5484 the @code{.loc} directive will add a row to the @code{.debug_line} line
5485 number matrix corresponding to the immediately following assembly
5486 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5487 arguments will be applied to the @code{.debug_line} state machine before
5490 The @var{options} are a sequence of the following tokens in any order:
5494 This option will set the @code{basic_block} register in the
5495 @code{.debug_line} state machine to @code{true}.
5498 This option will set the @code{prologue_end} register in the
5499 @code{.debug_line} state machine to @code{true}.
5501 @item epilogue_begin
5502 This option will set the @code{epilogue_begin} register in the
5503 @code{.debug_line} state machine to @code{true}.
5505 @item is_stmt @var{value}
5506 This option will set the @code{is_stmt} register in the
5507 @code{.debug_line} state machine to @code{value}, which must be
5510 @item isa @var{value}
5511 This directive will set the @code{isa} register in the @code{.debug_line}
5512 state machine to @var{value}, which must be an unsigned integer.
5514 @item discriminator @var{value}
5515 This directive will set the @code{discriminator} register in the @code{.debug_line}
5516 state machine to @var{value}, which must be an unsigned integer.
5520 @node Loc_mark_labels
5521 @section @code{.loc_mark_labels @var{enable}}
5522 @cindex @code{loc_mark_labels} directive
5523 When emitting DWARF2 line number information,
5524 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5525 to the @code{.debug_line} line number matrix with the @code{basic_block}
5526 register in the state machine set whenever a code label is seen.
5527 The @var{enable} argument should be either 1 or 0, to enable or disable
5528 this function respectively.
5532 @section @code{.local @var{names}}
5534 @cindex @code{local} directive
5535 This directive, which is available for ELF targets, marks each symbol in
5536 the comma-separated list of @code{names} as a local symbol so that it
5537 will not be externally visible. If the symbols do not already exist,
5538 they will be created.
5540 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5541 accept an alignment argument, which is the case for most ELF targets,
5542 the @code{.local} directive can be used in combination with @code{.comm}
5543 (@pxref{Comm}) to define aligned local common data.
5547 @section @code{.long @var{expressions}}
5549 @cindex @code{long} directive
5550 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5553 @c no one seems to know what this is for or whether this description is
5554 @c what it really ought to do
5556 @section @code{.lsym @var{symbol}, @var{expression}}
5558 @cindex @code{lsym} directive
5559 @cindex symbol, not referenced in assembly
5560 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5561 the hash table, ensuring it cannot be referenced by name during the
5562 rest of the assembly. This sets the attributes of the symbol to be
5563 the same as the expression value:
5565 @var{other} = @var{descriptor} = 0
5566 @var{type} = @r{(section of @var{expression})}
5567 @var{value} = @var{expression}
5570 The new symbol is not flagged as external.
5574 @section @code{.macro}
5577 The commands @code{.macro} and @code{.endm} allow you to define macros that
5578 generate assembly output. For example, this definition specifies a macro
5579 @code{sum} that puts a sequence of numbers into memory:
5582 .macro sum from=0, to=5
5591 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5603 @item .macro @var{macname}
5604 @itemx .macro @var{macname} @var{macargs} @dots{}
5605 @cindex @code{macro} directive
5606 Begin the definition of a macro called @var{macname}. If your macro
5607 definition requires arguments, specify their names after the macro name,
5608 separated by commas or spaces. You can qualify the macro argument to
5609 indicate whether all invocations must specify a non-blank value (through
5610 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5611 (through @samp{:@code{vararg}}). You can supply a default value for any
5612 macro argument by following the name with @samp{=@var{deflt}}. You
5613 cannot define two macros with the same @var{macname} unless it has been
5614 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5615 definitions. For example, these are all valid @code{.macro} statements:
5619 Begin the definition of a macro called @code{comm}, which takes no
5622 @item .macro plus1 p, p1
5623 @itemx .macro plus1 p p1
5624 Either statement begins the definition of a macro called @code{plus1},
5625 which takes two arguments; within the macro definition, write
5626 @samp{\p} or @samp{\p1} to evaluate the arguments.
5628 @item .macro reserve_str p1=0 p2
5629 Begin the definition of a macro called @code{reserve_str}, with two
5630 arguments. The first argument has a default value, but not the second.
5631 After the definition is complete, you can call the macro either as
5632 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5633 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5634 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5635 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5637 @item .macro m p1:req, p2=0, p3:vararg
5638 Begin the definition of a macro called @code{m}, with at least three
5639 arguments. The first argument must always have a value specified, but
5640 not the second, which instead has a default value. The third formal
5641 will get assigned all remaining arguments specified at invocation time.
5643 When you call a macro, you can specify the argument values either by
5644 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5645 @samp{sum to=17, from=9}.
5649 Note that since each of the @var{macargs} can be an identifier exactly
5650 as any other one permitted by the target architecture, there may be
5651 occasional problems if the target hand-crafts special meanings to certain
5652 characters when they occur in a special position. For example, if the colon
5653 (@code{:}) is generally permitted to be part of a symbol name, but the
5654 architecture specific code special-cases it when occurring as the final
5655 character of a symbol (to denote a label), then the macro parameter
5656 replacement code will have no way of knowing that and consider the whole
5657 construct (including the colon) an identifier, and check only this
5658 identifier for being the subject to parameter substitution. So for example
5659 this macro definition:
5667 might not work as expected. Invoking @samp{label foo} might not create a label
5668 called @samp{foo} but instead just insert the text @samp{\l:} into the
5669 assembler source, probably generating an error about an unrecognised
5672 Similarly problems might occur with the period character (@samp{.})
5673 which is often allowed inside opcode names (and hence identifier names). So
5674 for example constructing a macro to build an opcode from a base name and a
5675 length specifier like this:
5678 .macro opcode base length
5683 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5684 instruction but instead generate some kind of error as the assembler tries to
5685 interpret the text @samp{\base.\length}.
5687 There are several possible ways around this problem:
5690 @item Insert white space
5691 If it is possible to use white space characters then this is the simplest
5700 @item Use @samp{\()}
5701 The string @samp{\()} can be used to separate the end of a macro argument from
5702 the following text. eg:
5705 .macro opcode base length
5710 @item Use the alternate macro syntax mode
5711 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5712 used as a separator. eg:
5722 Note: this problem of correctly identifying string parameters to pseudo ops
5723 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5724 and @code{.irpc} (@pxref{Irpc}) as well.
5727 @cindex @code{endm} directive
5728 Mark the end of a macro definition.
5731 @cindex @code{exitm} directive
5732 Exit early from the current macro definition.
5734 @cindex number of macros executed
5735 @cindex macros, count executed
5737 @command{@value{AS}} maintains a counter of how many macros it has
5738 executed in this pseudo-variable; you can copy that number to your
5739 output with @samp{\@@}, but @emph{only within a macro definition}.
5741 @item LOCAL @var{name} [ , @dots{} ]
5742 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5743 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5744 @xref{Altmacro,,@code{.altmacro}}.
5748 @section @code{.mri @var{val}}
5750 @cindex @code{mri} directive
5751 @cindex MRI mode, temporarily
5752 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5753 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5754 affects code assembled until the next @code{.mri} directive, or until the end
5755 of the file. @xref{M, MRI mode, MRI mode}.
5758 @section @code{.noaltmacro}
5759 Disable alternate macro mode. @xref{Altmacro}.
5762 @section @code{.nolist}
5764 @cindex @code{nolist} directive
5765 @cindex listing control, turning off
5766 Control (in conjunction with the @code{.list} directive) whether or
5767 not assembly listings are generated. These two directives maintain an
5768 internal counter (which is zero initially). @code{.list} increments the
5769 counter, and @code{.nolist} decrements it. Assembly listings are
5770 generated whenever the counter is greater than zero.
5773 @section @code{.octa @var{bignums}}
5775 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5776 @cindex @code{octa} directive
5777 @cindex integer, 16-byte
5778 @cindex sixteen byte integer
5779 This directive expects zero or more bignums, separated by commas. For each
5780 bignum, it emits a 16-byte integer.
5782 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5783 hence @emph{octa}-word for 16 bytes.
5786 @section @code{.offset @var{loc}}
5788 @cindex @code{offset} directive
5789 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5790 be an absolute expression. This directive may be useful for defining
5791 symbols with absolute values. Do not confuse it with the @code{.org}
5795 @section @code{.org @var{new-lc} , @var{fill}}
5797 @cindex @code{org} directive
5798 @cindex location counter, advancing
5799 @cindex advancing location counter
5800 @cindex current address, advancing
5801 Advance the location counter of the current section to
5802 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5803 expression with the same section as the current subsection. That is,
5804 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5805 wrong section, the @code{.org} directive is ignored. To be compatible
5806 with former assemblers, if the section of @var{new-lc} is absolute,
5807 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5808 is the same as the current subsection.
5810 @code{.org} may only increase the location counter, or leave it
5811 unchanged; you cannot use @code{.org} to move the location counter
5814 @c double negative used below "not undefined" because this is a specific
5815 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5816 @c section. doc@cygnus.com 18feb91
5817 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5818 may not be undefined. If you really detest this restriction we eagerly await
5819 a chance to share your improved assembler.
5821 Beware that the origin is relative to the start of the section, not
5822 to the start of the subsection. This is compatible with other
5823 people's assemblers.
5825 When the location counter (of the current subsection) is advanced, the
5826 intervening bytes are filled with @var{fill} which should be an
5827 absolute expression. If the comma and @var{fill} are omitted,
5828 @var{fill} defaults to zero.
5831 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5833 @cindex padding the location counter given a power of two
5834 @cindex @code{p2align} directive
5835 Pad the location counter (in the current subsection) to a particular
5836 storage boundary. The first expression (which must be absolute) is the
5837 number of low-order zero bits the location counter must have after
5838 advancement. For example @samp{.p2align 3} advances the location
5839 counter until it a multiple of 8. If the location counter is already a
5840 multiple of 8, no change is needed.
5842 The second expression (also absolute) gives the fill value to be stored in the
5843 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5844 padding bytes are normally zero. However, on some systems, if the section is
5845 marked as containing code and the fill value is omitted, the space is filled
5846 with no-op instructions.
5848 The third expression is also absolute, and is also optional. If it is present,
5849 it is the maximum number of bytes that should be skipped by this alignment
5850 directive. If doing the alignment would require skipping more bytes than the
5851 specified maximum, then the alignment is not done at all. You can omit the
5852 fill value (the second argument) entirely by simply using two commas after the
5853 required alignment; this can be useful if you want the alignment to be filled
5854 with no-op instructions when appropriate.
5856 @cindex @code{p2alignw} directive
5857 @cindex @code{p2alignl} directive
5858 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5859 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5860 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5861 fill pattern as a four byte longword value. For example, @code{.p2alignw
5862 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5863 filled in with the value 0x368d (the exact placement of the bytes depends upon
5864 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5869 @section @code{.popsection}
5871 @cindex @code{popsection} directive
5872 @cindex Section Stack
5873 This is one of the ELF section stack manipulation directives. The others are
5874 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5875 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5878 This directive replaces the current section (and subsection) with the top
5879 section (and subsection) on the section stack. This section is popped off the
5885 @section @code{.previous}
5887 @cindex @code{previous} directive
5888 @cindex Section Stack
5889 This is one of the ELF section stack manipulation directives. The others are
5890 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5891 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5892 (@pxref{PopSection}).
5894 This directive swaps the current section (and subsection) with most recently
5895 referenced section/subsection pair prior to this one. Multiple
5896 @code{.previous} directives in a row will flip between two sections (and their
5897 subsections). For example:
5909 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5915 # Now in section A subsection 1
5919 # Now in section B subsection 0
5922 # Now in section B subsection 1
5925 # Now in section B subsection 0
5929 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5930 section B and 0x9abc into subsection 1 of section B.
5932 In terms of the section stack, this directive swaps the current section with
5933 the top section on the section stack.
5937 @section @code{.print @var{string}}
5939 @cindex @code{print} directive
5940 @command{@value{AS}} will print @var{string} on the standard output during
5941 assembly. You must put @var{string} in double quotes.
5945 @section @code{.protected @var{names}}
5947 @cindex @code{protected} directive
5949 This is one of the ELF visibility directives. The other two are
5950 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5952 This directive overrides the named symbols default visibility (which is set by
5953 their binding: local, global or weak). The directive sets the visibility to
5954 @code{protected} which means that any references to the symbols from within the
5955 components that defines them must be resolved to the definition in that
5956 component, even if a definition in another component would normally preempt
5961 @section @code{.psize @var{lines} , @var{columns}}
5963 @cindex @code{psize} directive
5964 @cindex listing control: paper size
5965 @cindex paper size, for listings
5966 Use this directive to declare the number of lines---and, optionally, the
5967 number of columns---to use for each page, when generating listings.
5969 If you do not use @code{.psize}, listings use a default line-count
5970 of 60. You may omit the comma and @var{columns} specification; the
5971 default width is 200 columns.
5973 @command{@value{AS}} generates formfeeds whenever the specified number of
5974 lines is exceeded (or whenever you explicitly request one, using
5977 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5978 those explicitly specified with @code{.eject}.
5981 @section @code{.purgem @var{name}}
5983 @cindex @code{purgem} directive
5984 Undefine the macro @var{name}, so that later uses of the string will not be
5985 expanded. @xref{Macro}.
5989 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5991 @cindex @code{pushsection} directive
5992 @cindex Section Stack
5993 This is one of the ELF section stack manipulation directives. The others are
5994 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5995 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5998 This directive pushes the current section (and subsection) onto the
5999 top of the section stack, and then replaces the current section and
6000 subsection with @code{name} and @code{subsection}. The optional
6001 @code{flags}, @code{type} and @code{arguments} are treated the same
6002 as in the @code{.section} (@pxref{Section}) directive.
6006 @section @code{.quad @var{bignums}}
6008 @cindex @code{quad} directive
6009 @code{.quad} expects zero or more bignums, separated by commas. For
6010 each bignum, it emits
6012 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6013 warning message; and just takes the lowest order 8 bytes of the bignum.
6014 @cindex eight-byte integer
6015 @cindex integer, 8-byte
6017 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6018 hence @emph{quad}-word for 8 bytes.
6021 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6022 warning message; and just takes the lowest order 16 bytes of the bignum.
6023 @cindex sixteen-byte integer
6024 @cindex integer, 16-byte
6028 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6030 @cindex @code{reloc} directive
6031 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6032 @var{expression}. If @var{offset} is a number, the relocation is generated in
6033 the current section. If @var{offset} is an expression that resolves to a
6034 symbol plus offset, the relocation is generated in the given symbol's section.
6035 @var{expression}, if present, must resolve to a symbol plus addend or to an
6036 absolute value, but note that not all targets support an addend. e.g. ELF REL
6037 targets such as i386 store an addend in the section contents rather than in the
6038 relocation. This low level interface does not support addends stored in the
6042 @section @code{.rept @var{count}}
6044 @cindex @code{rept} directive
6045 Repeat the sequence of lines between the @code{.rept} directive and the next
6046 @code{.endr} directive @var{count} times.
6048 For example, assembling
6056 is equivalent to assembling
6065 @section @code{.sbttl "@var{subheading}"}
6067 @cindex @code{sbttl} directive
6068 @cindex subtitles for listings
6069 @cindex listing control: subtitle
6070 Use @var{subheading} as the title (third line, immediately after the
6071 title line) when generating assembly listings.
6073 This directive affects subsequent pages, as well as the current page if
6074 it appears within ten lines of the top of a page.
6078 @section @code{.scl @var{class}}
6080 @cindex @code{scl} directive
6081 @cindex symbol storage class (COFF)
6082 @cindex COFF symbol storage class
6083 Set the storage-class value for a symbol. This directive may only be
6084 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6085 whether a symbol is static or external, or it may record further
6086 symbolic debugging information.
6089 The @samp{.scl} directive is primarily associated with COFF output; when
6090 configured to generate @code{b.out} output format, @command{@value{AS}}
6091 accepts this directive but ignores it.
6097 @section @code{.section @var{name}}
6099 @cindex named section
6100 Use the @code{.section} directive to assemble the following code into a section
6103 This directive is only supported for targets that actually support arbitrarily
6104 named sections; on @code{a.out} targets, for example, it is not accepted, even
6105 with a standard @code{a.out} section name.
6109 @c only print the extra heading if both COFF and ELF are set
6110 @subheading COFF Version
6113 @cindex @code{section} directive (COFF version)
6114 For COFF targets, the @code{.section} directive is used in one of the following
6118 .section @var{name}[, "@var{flags}"]
6119 .section @var{name}[, @var{subsection}]
6122 If the optional argument is quoted, it is taken as flags to use for the
6123 section. Each flag is a single character. The following flags are recognized:
6126 bss section (uninitialized data)
6128 section is not loaded
6134 exclude section from linking
6140 shared section (meaningful for PE targets)
6142 ignored. (For compatibility with the ELF version)
6144 section is not readable (meaningful for PE targets)
6146 single-digit power-of-two section alignment (GNU extension)
6149 If no flags are specified, the default flags depend upon the section name. If
6150 the section name is not recognized, the default will be for the section to be
6151 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6152 from the section, rather than adding them, so if they are used on their own it
6153 will be as if no flags had been specified at all.
6155 If the optional argument to the @code{.section} directive is not quoted, it is
6156 taken as a subsection number (@pxref{Sub-Sections}).
6161 @c only print the extra heading if both COFF and ELF are set
6162 @subheading ELF Version
6165 @cindex Section Stack
6166 This is one of the ELF section stack manipulation directives. The others are
6167 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6168 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6169 @code{.previous} (@pxref{Previous}).
6171 @cindex @code{section} directive (ELF version)
6172 For ELF targets, the @code{.section} directive is used like this:
6175 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6178 The optional @var{flags} argument is a quoted string which may contain any
6179 combination of the following characters:
6182 section is allocatable
6184 section is excluded from executable and shared library.
6188 section is executable
6190 section is mergeable
6192 section contains zero terminated strings
6194 section is a member of a section group
6196 section is used for thread-local-storage
6198 section is a member of the previously-current section's group, if any
6201 The optional @var{type} argument may contain one of the following constants:
6204 section contains data
6206 section does not contain data (i.e., section only occupies space)
6208 section contains data which is used by things other than the program
6210 section contains an array of pointers to init functions
6212 section contains an array of pointers to finish functions
6213 @item @@preinit_array
6214 section contains an array of pointers to pre-init functions
6217 Many targets only support the first three section types.
6219 Note on targets where the @code{@@} character is the start of a comment (eg
6220 ARM) then another character is used instead. For example the ARM port uses the
6223 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6224 be specified as well as an extra argument---@var{entsize}---like this:
6227 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6230 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6231 constants, each @var{entsize} octets long. Sections with both @code{M} and
6232 @code{S} must contain zero terminated strings where each character is
6233 @var{entsize} bytes long. The linker may remove duplicates within sections with
6234 the same name, same entity size and same flags. @var{entsize} must be an
6235 absolute expression. For sections with both @code{M} and @code{S}, a string
6236 which is a suffix of a larger string is considered a duplicate. Thus
6237 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6238 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6240 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6241 be present along with an additional field like this:
6244 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6247 The @var{GroupName} field specifies the name of the section group to which this
6248 particular section belongs. The optional linkage field can contain:
6251 indicates that only one copy of this section should be retained
6256 Note: if both the @var{M} and @var{G} flags are present then the fields for
6257 the Merge flag should come first, like this:
6260 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6263 If @var{flags} contains the @code{?} symbol then it may not also contain the
6264 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6265 present. Instead, @code{?} says to consider the section that's current before
6266 this directive. If that section used @code{G}, then the new section will use
6267 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6268 If not, then the @code{?} symbol has no effect.
6270 If no flags are specified, the default flags depend upon the section name. If
6271 the section name is not recognized, the default will be for the section to have
6272 none of the above flags: it will not be allocated in memory, nor writable, nor
6273 executable. The section will contain data.
6275 For ELF targets, the assembler supports another type of @code{.section}
6276 directive for compatibility with the Solaris assembler:
6279 .section "@var{name}"[, @var{flags}...]
6282 Note that the section name is quoted. There may be a sequence of comma
6286 section is allocatable
6290 section is executable
6292 section is excluded from executable and shared library.
6294 section is used for thread local storage
6297 This directive replaces the current section and subsection. See the
6298 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6299 some examples of how this directive and the other section stack directives
6305 @section @code{.set @var{symbol}, @var{expression}}
6307 @cindex @code{set} directive
6308 @cindex symbol value, setting
6309 Set the value of @var{symbol} to @var{expression}. This
6310 changes @var{symbol}'s value and type to conform to
6311 @var{expression}. If @var{symbol} was flagged as external, it remains
6312 flagged (@pxref{Symbol Attributes}).
6314 You may @code{.set} a symbol many times in the same assembly.
6316 If you @code{.set} a global symbol, the value stored in the object
6317 file is the last value stored into it.
6320 On Z80 @code{set} is a real instruction, use
6321 @samp{@var{symbol} defl @var{expression}} instead.
6325 @section @code{.short @var{expressions}}
6327 @cindex @code{short} directive
6329 @code{.short} is normally the same as @samp{.word}.
6330 @xref{Word,,@code{.word}}.
6332 In some configurations, however, @code{.short} and @code{.word} generate
6333 numbers of different lengths. @xref{Machine Dependencies}.
6337 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6340 This expects zero or more @var{expressions}, and emits
6341 a 16 bit number for each.
6346 @section @code{.single @var{flonums}}
6348 @cindex @code{single} directive
6349 @cindex floating point numbers (single)
6350 This directive assembles zero or more flonums, separated by commas. It
6351 has the same effect as @code{.float}.
6353 The exact kind of floating point numbers emitted depends on how
6354 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6358 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6359 numbers in @sc{ieee} format.
6365 @section @code{.size}
6367 This directive is used to set the size associated with a symbol.
6371 @c only print the extra heading if both COFF and ELF are set
6372 @subheading COFF Version
6375 @cindex @code{size} directive (COFF version)
6376 For COFF targets, the @code{.size} directive is only permitted inside
6377 @code{.def}/@code{.endef} pairs. It is used like this:
6380 .size @var{expression}
6384 @samp{.size} is only meaningful when generating COFF format output; when
6385 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6392 @c only print the extra heading if both COFF and ELF are set
6393 @subheading ELF Version
6396 @cindex @code{size} directive (ELF version)
6397 For ELF targets, the @code{.size} directive is used like this:
6400 .size @var{name} , @var{expression}
6403 This directive sets the size associated with a symbol @var{name}.
6404 The size in bytes is computed from @var{expression} which can make use of label
6405 arithmetic. This directive is typically used to set the size of function
6410 @ifclear no-space-dir
6412 @section @code{.skip @var{size} , @var{fill}}
6414 @cindex @code{skip} directive
6415 @cindex filling memory
6416 This directive emits @var{size} bytes, each of value @var{fill}. Both
6417 @var{size} and @var{fill} are absolute expressions. If the comma and
6418 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6423 @section @code{.sleb128 @var{expressions}}
6425 @cindex @code{sleb128} directive
6426 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6427 compact, variable length representation of numbers used by the DWARF
6428 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6430 @ifclear no-space-dir
6432 @section @code{.space @var{size} , @var{fill}}
6434 @cindex @code{space} directive
6435 @cindex filling memory
6436 This directive emits @var{size} bytes, each of value @var{fill}. Both
6437 @var{size} and @var{fill} are absolute expressions. If the comma
6438 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6443 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6444 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6445 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6446 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6454 @section @code{.stabd, .stabn, .stabs}
6456 @cindex symbolic debuggers, information for
6457 @cindex @code{stab@var{x}} directives
6458 There are three directives that begin @samp{.stab}.
6459 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6460 The symbols are not entered in the @command{@value{AS}} hash table: they
6461 cannot be referenced elsewhere in the source file.
6462 Up to five fields are required:
6466 This is the symbol's name. It may contain any character except
6467 @samp{\000}, so is more general than ordinary symbol names. Some
6468 debuggers used to code arbitrarily complex structures into symbol names
6472 An absolute expression. The symbol's type is set to the low 8 bits of
6473 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6474 and debuggers choke on silly bit patterns.
6477 An absolute expression. The symbol's ``other'' attribute is set to the
6478 low 8 bits of this expression.
6481 An absolute expression. The symbol's descriptor is set to the low 16
6482 bits of this expression.
6485 An absolute expression which becomes the symbol's value.
6488 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6489 or @code{.stabs} statement, the symbol has probably already been created;
6490 you get a half-formed symbol in your object file. This is
6491 compatible with earlier assemblers!
6494 @cindex @code{stabd} directive
6495 @item .stabd @var{type} , @var{other} , @var{desc}
6497 The ``name'' of the symbol generated is not even an empty string.
6498 It is a null pointer, for compatibility. Older assemblers used a
6499 null pointer so they didn't waste space in object files with empty
6502 The symbol's value is set to the location counter,
6503 relocatably. When your program is linked, the value of this symbol
6504 is the address of the location counter when the @code{.stabd} was
6507 @cindex @code{stabn} directive
6508 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6509 The name of the symbol is set to the empty string @code{""}.
6511 @cindex @code{stabs} directive
6512 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6513 All five fields are specified.
6519 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6520 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6522 @cindex string, copying to object file
6523 @cindex string8, copying to object file
6524 @cindex string16, copying to object file
6525 @cindex string32, copying to object file
6526 @cindex string64, copying to object file
6527 @cindex @code{string} directive
6528 @cindex @code{string8} directive
6529 @cindex @code{string16} directive
6530 @cindex @code{string32} directive
6531 @cindex @code{string64} directive
6533 Copy the characters in @var{str} to the object file. You may specify more than
6534 one string to copy, separated by commas. Unless otherwise specified for a
6535 particular machine, the assembler marks the end of each string with a 0 byte.
6536 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6538 The variants @code{string16}, @code{string32} and @code{string64} differ from
6539 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6540 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6541 are stored in target endianness byte order.
6547 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6548 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6553 @section @code{.struct @var{expression}}
6555 @cindex @code{struct} directive
6556 Switch to the absolute section, and set the section offset to @var{expression},
6557 which must be an absolute expression. You might use this as follows:
6566 This would define the symbol @code{field1} to have the value 0, the symbol
6567 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6568 value 8. Assembly would be left in the absolute section, and you would need to
6569 use a @code{.section} directive of some sort to change to some other section
6570 before further assembly.
6574 @section @code{.subsection @var{name}}
6576 @cindex @code{subsection} directive
6577 @cindex Section Stack
6578 This is one of the ELF section stack manipulation directives. The others are
6579 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6580 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6583 This directive replaces the current subsection with @code{name}. The current
6584 section is not changed. The replaced subsection is put onto the section stack
6585 in place of the then current top of stack subsection.
6590 @section @code{.symver}
6591 @cindex @code{symver} directive
6592 @cindex symbol versioning
6593 @cindex versions of symbols
6594 Use the @code{.symver} directive to bind symbols to specific version nodes
6595 within a source file. This is only supported on ELF platforms, and is
6596 typically used when assembling files to be linked into a shared library.
6597 There are cases where it may make sense to use this in objects to be bound
6598 into an application itself so as to override a versioned symbol from a
6601 For ELF targets, the @code{.symver} directive can be used like this:
6603 .symver @var{name}, @var{name2@@nodename}
6605 If the symbol @var{name} is defined within the file
6606 being assembled, the @code{.symver} directive effectively creates a symbol
6607 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6608 just don't try and create a regular alias is that the @var{@@} character isn't
6609 permitted in symbol names. The @var{name2} part of the name is the actual name
6610 of the symbol by which it will be externally referenced. The name @var{name}
6611 itself is merely a name of convenience that is used so that it is possible to
6612 have definitions for multiple versions of a function within a single source
6613 file, and so that the compiler can unambiguously know which version of a
6614 function is being mentioned. The @var{nodename} portion of the alias should be
6615 the name of a node specified in the version script supplied to the linker when
6616 building a shared library. If you are attempting to override a versioned
6617 symbol from a shared library, then @var{nodename} should correspond to the
6618 nodename of the symbol you are trying to override.
6620 If the symbol @var{name} is not defined within the file being assembled, all
6621 references to @var{name} will be changed to @var{name2@@nodename}. If no
6622 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6625 Another usage of the @code{.symver} directive is:
6627 .symver @var{name}, @var{name2@@@@nodename}
6629 In this case, the symbol @var{name} must exist and be defined within
6630 the file being assembled. It is similar to @var{name2@@nodename}. The
6631 difference is @var{name2@@@@nodename} will also be used to resolve
6632 references to @var{name2} by the linker.
6634 The third usage of the @code{.symver} directive is:
6636 .symver @var{name}, @var{name2@@@@@@nodename}
6638 When @var{name} is not defined within the
6639 file being assembled, it is treated as @var{name2@@nodename}. When
6640 @var{name} is defined within the file being assembled, the symbol
6641 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6646 @section @code{.tag @var{structname}}
6648 @cindex COFF structure debugging
6649 @cindex structure debugging, COFF
6650 @cindex @code{tag} directive
6651 This directive is generated by compilers to include auxiliary debugging
6652 information in the symbol table. It is only permitted inside
6653 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6654 definitions in the symbol table with instances of those structures.
6657 @samp{.tag} is only used when generating COFF format output; when
6658 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6664 @section @code{.text @var{subsection}}
6666 @cindex @code{text} directive
6667 Tells @command{@value{AS}} to assemble the following statements onto the end of
6668 the text subsection numbered @var{subsection}, which is an absolute
6669 expression. If @var{subsection} is omitted, subsection number zero
6673 @section @code{.title "@var{heading}"}
6675 @cindex @code{title} directive
6676 @cindex listing control: title line
6677 Use @var{heading} as the title (second line, immediately after the
6678 source file name and pagenumber) when generating assembly listings.
6680 This directive affects subsequent pages, as well as the current page if
6681 it appears within ten lines of the top of a page.
6685 @section @code{.type}
6687 This directive is used to set the type of a symbol.
6691 @c only print the extra heading if both COFF and ELF are set
6692 @subheading COFF Version
6695 @cindex COFF symbol type
6696 @cindex symbol type, COFF
6697 @cindex @code{type} directive (COFF version)
6698 For COFF targets, this directive is permitted only within
6699 @code{.def}/@code{.endef} pairs. It is used like this:
6705 This records the integer @var{int} as the type attribute of a symbol table
6709 @samp{.type} is associated only with COFF format output; when
6710 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6711 directive but ignores it.
6717 @c only print the extra heading if both COFF and ELF are set
6718 @subheading ELF Version
6721 @cindex ELF symbol type
6722 @cindex symbol type, ELF
6723 @cindex @code{type} directive (ELF version)
6724 For ELF targets, the @code{.type} directive is used like this:
6727 .type @var{name} , @var{type description}
6730 This sets the type of symbol @var{name} to be either a
6731 function symbol or an object symbol. There are five different syntaxes
6732 supported for the @var{type description} field, in order to provide
6733 compatibility with various other assemblers.
6735 Because some of the characters used in these syntaxes (such as @samp{@@} and
6736 @samp{#}) are comment characters for some architectures, some of the syntaxes
6737 below do not work on all architectures. The first variant will be accepted by
6738 the GNU assembler on all architectures so that variant should be used for
6739 maximum portability, if you do not need to assemble your code with other
6742 The syntaxes supported are:
6745 .type <name> STT_<TYPE_IN_UPPER_CASE>
6746 .type <name>,#<type>
6747 .type <name>,@@<type>
6748 .type <name>,%<type>
6749 .type <name>,"<type>"
6752 The types supported are:
6757 Mark the symbol as being a function name.
6760 @itemx gnu_indirect_function
6761 Mark the symbol as an indirect function when evaluated during reloc
6762 processing. (This is only supported on assemblers targeting GNU systems).
6766 Mark the symbol as being a data object.
6770 Mark the symbol as being a thead-local data object.
6774 Mark the symbol as being a common data object.
6778 Does not mark the symbol in any way. It is supported just for completeness.
6780 @item gnu_unique_object
6781 Marks the symbol as being a globally unique data object. The dynamic linker
6782 will make sure that in the entire process there is just one symbol with this
6783 name and type in use. (This is only supported on assemblers targeting GNU
6788 Note: Some targets support extra types in addition to those listed above.
6794 @section @code{.uleb128 @var{expressions}}
6796 @cindex @code{uleb128} directive
6797 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6798 compact, variable length representation of numbers used by the DWARF
6799 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6803 @section @code{.val @var{addr}}
6805 @cindex @code{val} directive
6806 @cindex COFF value attribute
6807 @cindex value attribute, COFF
6808 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6809 records the address @var{addr} as the value attribute of a symbol table
6813 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6814 configured for @code{b.out}, it accepts this directive but ignores it.
6820 @section @code{.version "@var{string}"}
6822 @cindex @code{version} directive
6823 This directive creates a @code{.note} section and places into it an ELF
6824 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6829 @section @code{.vtable_entry @var{table}, @var{offset}}
6831 @cindex @code{vtable_entry} directive
6832 This directive finds or creates a symbol @code{table} and creates a
6833 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6836 @section @code{.vtable_inherit @var{child}, @var{parent}}
6838 @cindex @code{vtable_inherit} directive
6839 This directive finds the symbol @code{child} and finds or creates the symbol
6840 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6841 parent whose addend is the value of the child symbol. As a special case the
6842 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6846 @section @code{.warning "@var{string}"}
6847 @cindex warning directive
6848 Similar to the directive @code{.error}
6849 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6852 @section @code{.weak @var{names}}
6854 @cindex @code{weak} directive
6855 This directive sets the weak attribute on the comma separated list of symbol
6856 @code{names}. If the symbols do not already exist, they will be created.
6858 On COFF targets other than PE, weak symbols are a GNU extension. This
6859 directive sets the weak attribute on the comma separated list of symbol
6860 @code{names}. If the symbols do not already exist, they will be created.
6862 On the PE target, weak symbols are supported natively as weak aliases.
6863 When a weak symbol is created that is not an alias, GAS creates an
6864 alternate symbol to hold the default value.
6867 @section @code{.weakref @var{alias}, @var{target}}
6869 @cindex @code{weakref} directive
6870 This directive creates an alias to the target symbol that enables the symbol to
6871 be referenced with weak-symbol semantics, but without actually making it weak.
6872 If direct references or definitions of the symbol are present, then the symbol
6873 will not be weak, but if all references to it are through weak references, the
6874 symbol will be marked as weak in the symbol table.
6876 The effect is equivalent to moving all references to the alias to a separate
6877 assembly source file, renaming the alias to the symbol in it, declaring the
6878 symbol as weak there, and running a reloadable link to merge the object files
6879 resulting from the assembly of the new source file and the old source file that
6880 had the references to the alias removed.
6882 The alias itself never makes to the symbol table, and is entirely handled
6883 within the assembler.
6886 @section @code{.word @var{expressions}}
6888 @cindex @code{word} directive
6889 This directive expects zero or more @var{expressions}, of any section,
6890 separated by commas.
6893 For each expression, @command{@value{AS}} emits a 32-bit number.
6896 For each expression, @command{@value{AS}} emits a 16-bit number.
6901 The size of the number emitted, and its byte order,
6902 depend on what target computer the assembly is for.
6905 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6906 @c happen---32-bit addressability, period; no long/short jumps.
6907 @ifset DIFF-TBL-KLUGE
6908 @cindex difference tables altered
6909 @cindex altered difference tables
6911 @emph{Warning: Special Treatment to support Compilers}
6915 Machines with a 32-bit address space, but that do less than 32-bit
6916 addressing, require the following special treatment. If the machine of
6917 interest to you does 32-bit addressing (or doesn't require it;
6918 @pxref{Machine Dependencies}), you can ignore this issue.
6921 In order to assemble compiler output into something that works,
6922 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6923 Directives of the form @samp{.word sym1-sym2} are often emitted by
6924 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6925 directive of the form @samp{.word sym1-sym2}, and the difference between
6926 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6927 creates a @dfn{secondary jump table}, immediately before the next label.
6928 This secondary jump table is preceded by a short-jump to the
6929 first byte after the secondary table. This short-jump prevents the flow
6930 of control from accidentally falling into the new table. Inside the
6931 table is a long-jump to @code{sym2}. The original @samp{.word}
6932 contains @code{sym1} minus the address of the long-jump to
6935 If there were several occurrences of @samp{.word sym1-sym2} before the
6936 secondary jump table, all of them are adjusted. If there was a
6937 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6938 long-jump to @code{sym4} is included in the secondary jump table,
6939 and the @code{.word} directives are adjusted to contain @code{sym3}
6940 minus the address of the long-jump to @code{sym4}; and so on, for as many
6941 entries in the original jump table as necessary.
6944 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6945 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6946 assembly language programmers.
6949 @c end DIFF-TBL-KLUGE
6952 @section Deprecated Directives
6954 @cindex deprecated directives
6955 @cindex obsolescent directives
6956 One day these directives won't work.
6957 They are included for compatibility with older assemblers.
6964 @node Object Attributes
6965 @chapter Object Attributes
6966 @cindex object attributes
6968 @command{@value{AS}} assembles source files written for a specific architecture
6969 into object files for that architecture. But not all object files are alike.
6970 Many architectures support incompatible variations. For instance, floating
6971 point arguments might be passed in floating point registers if the object file
6972 requires hardware floating point support---or floating point arguments might be
6973 passed in integer registers if the object file supports processors with no
6974 hardware floating point unit. Or, if two objects are built for different
6975 generations of the same architecture, the combination may require the
6976 newer generation at run-time.
6978 This information is useful during and after linking. At link time,
6979 @command{@value{LD}} can warn about incompatible object files. After link
6980 time, tools like @command{gdb} can use it to process the linked file
6983 Compatibility information is recorded as a series of object attributes. Each
6984 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6985 string, and indicates who sets the meaning of the tag. The tag is an integer,
6986 and indicates what property the attribute describes. The value may be a string
6987 or an integer, and indicates how the property affects this object. Missing
6988 attributes are the same as attributes with a zero value or empty string value.
6990 Object attributes were developed as part of the ABI for the ARM Architecture.
6991 The file format is documented in @cite{ELF for the ARM Architecture}.
6994 * GNU Object Attributes:: @sc{gnu} Object Attributes
6995 * Defining New Object Attributes:: Defining New Object Attributes
6998 @node GNU Object Attributes
6999 @section @sc{gnu} Object Attributes
7001 The @code{.gnu_attribute} directive records an object attribute
7002 with vendor @samp{gnu}.
7004 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7005 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7006 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7007 2} is set for architecture-independent attributes and clear for
7008 architecture-dependent ones.
7010 @subsection Common @sc{gnu} attributes
7012 These attributes are valid on all architectures.
7015 @item Tag_compatibility (32)
7016 The compatibility attribute takes an integer flag value and a vendor name. If
7017 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7018 then the file is only compatible with the named toolchain. If it is greater
7019 than 1, the file can only be processed by other toolchains under some private
7020 arrangement indicated by the flag value and the vendor name.
7023 @subsection MIPS Attributes
7026 @item Tag_GNU_MIPS_ABI_FP (4)
7027 The floating-point ABI used by this object file. The value will be:
7031 0 for files not affected by the floating-point ABI.
7033 1 for files using the hardware floating-point ABI with a standard
7034 double-precision FPU.
7036 2 for files using the hardware floating-point ABI with a single-precision FPU.
7038 3 for files using the software floating-point ABI.
7040 4 for files using the deprecated hardware floating-point ABI which used 64-bit
7041 floating-point registers, 32-bit general-purpose registers and increased the
7042 number of callee-saved floating-point registers.
7044 5 for files using the hardware floating-point ABI with a double-precision FPU
7045 with either 32-bit or 64-bit floating-point registers and 32-bit
7046 general-purpose registers.
7048 6 for files using the hardware floating-point ABI with 64-bit floating-point
7049 registers and 32-bit general-purpose registers.
7051 7 for files using the hardware floating-point ABI with 64-bit floating-point
7052 registers, 32-bit general-purpose registers and a rule that forbids the
7053 direct use of odd-numbered single-precision floating-point registers.
7057 @subsection PowerPC Attributes
7060 @item Tag_GNU_Power_ABI_FP (4)
7061 The floating-point ABI used by this object file. The value will be:
7065 0 for files not affected by the floating-point ABI.
7067 1 for files using double-precision hardware floating-point ABI.
7069 2 for files using the software floating-point ABI.
7071 3 for files using single-precision hardware floating-point ABI.
7074 @item Tag_GNU_Power_ABI_Vector (8)
7075 The vector ABI used by this object file. The value will be:
7079 0 for files not affected by the vector ABI.
7081 1 for files using general purpose registers to pass vectors.
7083 2 for files using AltiVec registers to pass vectors.
7085 3 for files using SPE registers to pass vectors.
7089 @node Defining New Object Attributes
7090 @section Defining New Object Attributes
7092 If you want to define a new @sc{gnu} object attribute, here are the places you
7093 will need to modify. New attributes should be discussed on the @samp{binutils}
7098 This manual, which is the official register of attributes.
7100 The header for your architecture @file{include/elf}, to define the tag.
7102 The @file{bfd} support file for your architecture, to merge the attribute
7103 and issue any appropriate link warnings.
7105 Test cases in @file{ld/testsuite} for merging and link warnings.
7107 @file{binutils/readelf.c} to display your attribute.
7109 GCC, if you want the compiler to mark the attribute automatically.
7115 @node Machine Dependencies
7116 @chapter Machine Dependent Features
7118 @cindex machine dependencies
7119 The machine instruction sets are (almost by definition) different on
7120 each machine where @command{@value{AS}} runs. Floating point representations
7121 vary as well, and @command{@value{AS}} often supports a few additional
7122 directives or command-line options for compatibility with other
7123 assemblers on a particular platform. Finally, some versions of
7124 @command{@value{AS}} support special pseudo-instructions for branch
7127 This chapter discusses most of these differences, though it does not
7128 include details on any machine's instruction set. For details on that
7129 subject, see the hardware manufacturer's manual.
7133 * AArch64-Dependent:: AArch64 Dependent Features
7136 * Alpha-Dependent:: Alpha Dependent Features
7139 * ARC-Dependent:: ARC Dependent Features
7142 * ARM-Dependent:: ARM Dependent Features
7145 * AVR-Dependent:: AVR Dependent Features
7148 * Blackfin-Dependent:: Blackfin Dependent Features
7151 * CR16-Dependent:: CR16 Dependent Features
7154 * CRIS-Dependent:: CRIS Dependent Features
7157 * D10V-Dependent:: D10V Dependent Features
7160 * D30V-Dependent:: D30V Dependent Features
7163 * Epiphany-Dependent:: EPIPHANY Dependent Features
7166 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7169 * HPPA-Dependent:: HPPA Dependent Features
7172 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7175 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7178 * i860-Dependent:: Intel 80860 Dependent Features
7181 * i960-Dependent:: Intel 80960 Dependent Features
7184 * IA-64-Dependent:: Intel IA-64 Dependent Features
7187 * IP2K-Dependent:: IP2K Dependent Features
7190 * LM32-Dependent:: LM32 Dependent Features
7193 * M32C-Dependent:: M32C Dependent Features
7196 * M32R-Dependent:: M32R Dependent Features
7199 * M68K-Dependent:: M680x0 Dependent Features
7202 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7205 * Meta-Dependent :: Meta Dependent Features
7208 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7211 * MIPS-Dependent:: MIPS Dependent Features
7214 * MMIX-Dependent:: MMIX Dependent Features
7217 * MSP430-Dependent:: MSP430 Dependent Features
7220 * NDS32-Dependent:: Andes NDS32 Dependent Features
7223 * NiosII-Dependent:: Altera Nios II Dependent Features
7226 * NS32K-Dependent:: NS32K Dependent Features
7229 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7230 * SH64-Dependent:: SuperH SH64 Dependent Features
7233 * PDP-11-Dependent:: PDP-11 Dependent Features
7236 * PJ-Dependent:: picoJava Dependent Features
7239 * PPC-Dependent:: PowerPC Dependent Features
7242 * RL78-Dependent:: RL78 Dependent Features
7245 * RX-Dependent:: RX Dependent Features
7248 * S/390-Dependent:: IBM S/390 Dependent Features
7251 * SCORE-Dependent:: SCORE Dependent Features
7254 * Sparc-Dependent:: SPARC Dependent Features
7257 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7260 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7263 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7266 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7269 * V850-Dependent:: V850 Dependent Features
7272 * XGATE-Dependent:: XGATE Features
7275 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7278 * Xtensa-Dependent:: Xtensa Dependent Features
7281 * Z80-Dependent:: Z80 Dependent Features
7284 * Z8000-Dependent:: Z8000 Dependent Features
7287 * Vax-Dependent:: VAX Dependent Features
7294 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7295 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7296 @c peculiarity: to preserve cross-references, there must be a node called
7297 @c "Machine Dependencies". Hence the conditional nodenames in each
7298 @c major node below. Node defaulting in makeinfo requires adjacency of
7299 @c node and sectioning commands; hence the repetition of @chapter BLAH
7300 @c in both conditional blocks.
7303 @include c-aarch64.texi
7307 @include c-alpha.texi
7323 @include c-bfin.texi
7327 @include c-cr16.texi
7331 @include c-cris.texi
7336 @node Machine Dependencies
7337 @chapter Machine Dependent Features
7339 The machine instruction sets are different on each Renesas chip family,
7340 and there are also some syntax differences among the families. This
7341 chapter describes the specific @command{@value{AS}} features for each
7345 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7346 * SH-Dependent:: Renesas SH Dependent Features
7353 @include c-d10v.texi
7357 @include c-d30v.texi
7361 @include c-epiphany.texi
7365 @include c-h8300.texi
7369 @include c-hppa.texi
7373 @include c-i370.texi
7377 @include c-i386.texi
7381 @include c-i860.texi
7385 @include c-i960.texi
7389 @include c-ia64.texi
7393 @include c-ip2k.texi
7397 @include c-lm32.texi
7401 @include c-m32c.texi
7405 @include c-m32r.texi
7409 @include c-m68k.texi
7413 @include c-m68hc11.texi
7417 @include c-metag.texi
7421 @include c-microblaze.texi
7425 @include c-mips.texi
7429 @include c-mmix.texi
7433 @include c-msp430.texi
7437 @include c-nds32.texi
7441 @include c-nios2.texi
7445 @include c-ns32k.texi
7449 @include c-pdp11.texi
7461 @include c-rl78.texi
7469 @include c-s390.texi
7473 @include c-score.texi
7478 @include c-sh64.texi
7482 @include c-sparc.texi
7486 @include c-tic54x.texi
7490 @include c-tic6x.texi
7494 @include c-tilegx.texi
7498 @include c-tilepro.texi
7514 @include c-v850.texi
7518 @include c-xgate.texi
7522 @include c-xstormy16.texi
7526 @include c-xtensa.texi
7530 @c reverse effect of @down at top of generic Machine-Dep chapter
7534 @node Reporting Bugs
7535 @chapter Reporting Bugs
7536 @cindex bugs in assembler
7537 @cindex reporting bugs in assembler
7539 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7541 Reporting a bug may help you by bringing a solution to your problem, or it may
7542 not. But in any case the principal function of a bug report is to help the
7543 entire community by making the next version of @command{@value{AS}} work better.
7544 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7546 In order for a bug report to serve its purpose, you must include the
7547 information that enables us to fix the bug.
7550 * Bug Criteria:: Have you found a bug?
7551 * Bug Reporting:: How to report bugs
7555 @section Have You Found a Bug?
7556 @cindex bug criteria
7558 If you are not sure whether you have found a bug, here are some guidelines:
7561 @cindex fatal signal
7562 @cindex assembler crash
7563 @cindex crash of assembler
7565 If the assembler gets a fatal signal, for any input whatever, that is a
7566 @command{@value{AS}} bug. Reliable assemblers never crash.
7568 @cindex error on valid input
7570 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7572 @cindex invalid input
7574 If @command{@value{AS}} does not produce an error message for invalid input, that
7575 is a bug. However, you should note that your idea of ``invalid input'' might
7576 be our idea of ``an extension'' or ``support for traditional practice''.
7579 If you are an experienced user of assemblers, your suggestions for improvement
7580 of @command{@value{AS}} are welcome in any case.
7584 @section How to Report Bugs
7586 @cindex assembler bugs, reporting
7588 A number of companies and individuals offer support for @sc{gnu} products. If
7589 you obtained @command{@value{AS}} from a support organization, we recommend you
7590 contact that organization first.
7592 You can find contact information for many support companies and
7593 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7597 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7601 The fundamental principle of reporting bugs usefully is this:
7602 @strong{report all the facts}. If you are not sure whether to state a
7603 fact or leave it out, state it!
7605 Often people omit facts because they think they know what causes the problem
7606 and assume that some details do not matter. Thus, you might assume that the
7607 name of a symbol you use in an example does not matter. Well, probably it does
7608 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7609 happens to fetch from the location where that name is stored in memory;
7610 perhaps, if the name were different, the contents of that location would fool
7611 the assembler into doing the right thing despite the bug. Play it safe and
7612 give a specific, complete example. That is the easiest thing for you to do,
7613 and the most helpful.
7615 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7616 it is new to us. Therefore, always write your bug reports on the assumption
7617 that the bug has not been reported previously.
7619 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7620 bell?'' This cannot help us fix a bug, so it is basically useless. We
7621 respond by asking for enough details to enable us to investigate.
7622 You might as well expedite matters by sending them to begin with.
7624 To enable us to fix the bug, you should include all these things:
7628 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7629 it with the @samp{--version} argument.
7631 Without this, we will not know whether there is any point in looking for
7632 the bug in the current version of @command{@value{AS}}.
7635 Any patches you may have applied to the @command{@value{AS}} source.
7638 The type of machine you are using, and the operating system name and
7642 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7646 The command arguments you gave the assembler to assemble your example and
7647 observe the bug. To guarantee you will not omit something important, list them
7648 all. A copy of the Makefile (or the output from make) is sufficient.
7650 If we were to try to guess the arguments, we would probably guess wrong
7651 and then we might not encounter the bug.
7654 A complete input file that will reproduce the bug. If the bug is observed when
7655 the assembler is invoked via a compiler, send the assembler source, not the
7656 high level language source. Most compilers will produce the assembler source
7657 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7658 the options @samp{-v --save-temps}; this will save the assembler source in a
7659 file with an extension of @file{.s}, and also show you exactly how
7660 @command{@value{AS}} is being run.
7663 A description of what behavior you observe that you believe is
7664 incorrect. For example, ``It gets a fatal signal.''
7666 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7667 will certainly notice it. But if the bug is incorrect output, we might not
7668 notice unless it is glaringly wrong. You might as well not give us a chance to
7671 Even if the problem you experience is a fatal signal, you should still say so
7672 explicitly. Suppose something strange is going on, such as, your copy of
7673 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7674 library on your system. (This has happened!) Your copy might crash and ours
7675 would not. If you told us to expect a crash, then when ours fails to crash, we
7676 would know that the bug was not happening for us. If you had not told us to
7677 expect a crash, then we would not be able to draw any conclusion from our
7681 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7682 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7683 option. Always send diffs from the old file to the new file. If you even
7684 discuss something in the @command{@value{AS}} source, refer to it by context, not
7687 The line numbers in our development sources will not match those in your
7688 sources. Your line numbers would convey no useful information to us.
7691 Here are some things that are not necessary:
7695 A description of the envelope of the bug.
7697 Often people who encounter a bug spend a lot of time investigating
7698 which changes to the input file will make the bug go away and which
7699 changes will not affect it.
7701 This is often time consuming and not very useful, because the way we
7702 will find the bug is by running a single example under the debugger
7703 with breakpoints, not by pure deduction from a series of examples.
7704 We recommend that you save your time for something else.
7706 Of course, if you can find a simpler example to report @emph{instead}
7707 of the original one, that is a convenience for us. Errors in the
7708 output will be easier to spot, running under the debugger will take
7709 less time, and so on.
7711 However, simplification is not vital; if you do not want to do this,
7712 report the bug anyway and send us the entire test case you used.
7715 A patch for the bug.
7717 A patch for the bug does help us if it is a good one. But do not omit
7718 the necessary information, such as the test case, on the assumption that
7719 a patch is all we need. We might see problems with your patch and decide
7720 to fix the problem another way, or we might not understand it at all.
7722 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7723 construct an example that will make the program follow a certain path through
7724 the code. If you do not send us the example, we will not be able to construct
7725 one, so we will not be able to verify that the bug is fixed.
7727 And if we cannot understand what bug you are trying to fix, or why your
7728 patch should be an improvement, we will not install it. A test case will
7729 help us to understand.
7732 A guess about what the bug is or what it depends on.
7734 Such guesses are usually wrong. Even we cannot guess right about such
7735 things without first using the debugger to find the facts.
7738 @node Acknowledgements
7739 @chapter Acknowledgements
7741 If you have contributed to GAS and your name isn't listed here,
7742 it is not meant as a slight. We just don't know about it. Send mail to the
7743 maintainer, and we'll correct the situation. Currently
7745 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7747 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7750 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7751 information and the 68k series machines, most of the preprocessing pass, and
7752 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7754 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7755 many bug fixes, including merging support for several processors, breaking GAS
7756 up to handle multiple object file format back ends (including heavy rewrite,
7757 testing, an integration of the coff and b.out back ends), adding configuration
7758 including heavy testing and verification of cross assemblers and file splits
7759 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7760 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7761 port (including considerable amounts of reverse engineering), a SPARC opcode
7762 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7763 assertions and made them work, much other reorganization, cleanup, and lint.
7765 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7766 in format-specific I/O modules.
7768 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7769 has done much work with it since.
7771 The Intel 80386 machine description was written by Eliot Dresselhaus.
7773 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7775 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7776 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7778 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7779 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7780 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7781 support a.out format.
7783 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7784 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7785 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7786 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7789 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7790 simplified the configuration of which versions accept which directives. He
7791 updated the 68k machine description so that Motorola's opcodes always produced
7792 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7793 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7794 cross-compilation support, and one bug in relaxation that took a week and
7795 required the proverbial one-bit fix.
7797 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7798 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7799 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7800 PowerPC assembler, and made a few other minor patches.
7802 Steve Chamberlain made GAS able to generate listings.
7804 Hewlett-Packard contributed support for the HP9000/300.
7806 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7807 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7808 formats). This work was supported by both the Center for Software Science at
7809 the University of Utah and Cygnus Support.
7811 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7812 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7813 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7814 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7815 and some initial 64-bit support).
7817 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7819 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7820 support for openVMS/Alpha.
7822 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7825 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7826 Inc.@: added support for Xtensa processors.
7828 Several engineers at Cygnus Support have also provided many small bug fixes and
7829 configuration enhancements.
7831 Jon Beniston added support for the Lattice Mico32 architecture.
7833 Many others have contributed large or small bugfixes and enhancements. If
7834 you have contributed significant work and are not mentioned on this list, and
7835 want to be, let us know. Some of the history has been lost; we are not
7836 intentionally leaving anyone out.
7838 @node GNU Free Documentation License
7839 @appendix GNU Free Documentation License
7843 @unnumbered AS Index
projects / dragonfly.git / blob