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{-mips64}] [@b{-mips64r2}]
407 [@b{-mips64r3}] [@b{-mips64r5}]
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.
1284 Generate code for a particular MIPS Instruction Set Architecture level.
1285 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1286 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1287 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1288 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips32r3},
1289 @samp{-mips32r5}, @samp{-mips64}, @samp{-mips64r2}, @samp{-mips64r3}, and
1290 @samp{-mips64r5} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1291 MIPS32 Release 3, MIPS32 Release 5, MIPS64, MIPS64 Release 2,
1292 MIPS64 Release 3, and MIPS64 Release 5 ISA processors, respectively.
1294 @item -march=@var{cpu}
1295 Generate code for a particular MIPS CPU.
1297 @item -mtune=@var{cpu}
1298 Schedule and tune for a particular MIPS CPU.
1302 Cause nops to be inserted if the read of the destination register
1303 of an mfhi or mflo instruction occurs in the following two instructions.
1306 @itemx -mno-fix-rm7000
1307 Cause nops to be inserted if a dmult or dmultu instruction is
1308 followed by a load instruction.
1312 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1313 section instead of the standard ELF .stabs sections.
1317 Control generation of @code{.pdr} sections.
1321 The register sizes are normally inferred from the ISA and ABI, but these
1322 flags force a certain group of registers to be treated as 32 bits wide at
1323 all times. @samp{-mgp32} controls the size of general-purpose registers
1324 and @samp{-mfp32} controls the size of floating-point registers.
1328 The register sizes are normally inferred from the ISA and ABI, but these
1329 flags force a certain group of registers to be treated as 64 bits wide at
1330 all times. @samp{-mgp64} controls the size of general-purpose registers
1331 and @samp{-mfp64} controls the size of floating-point registers.
1334 The register sizes are normally inferred from the ISA and ABI, but using
1335 this flag in combination with @samp{-mabi=32} enables an ABI variant
1336 which will operate correctly with floating-point registers which are
1340 @itemx -mno-odd-spreg
1341 Enable use of floating-point operations on odd-numbered single-precision
1342 registers when supported by the ISA. @samp{-mfpxx} implies
1343 @samp{-mno-odd-spreg}, otherwise the default is @samp{-modd-spreg}.
1347 Generate code for the MIPS 16 processor. This is equivalent to putting
1348 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1349 turns off this option.
1352 @itemx -mno-micromips
1353 Generate code for the microMIPS processor. This is equivalent to putting
1354 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1355 turns off this option. This is equivalent to putting @code{.set nomicromips}
1356 at the start of the assembly file.
1359 @itemx -mno-smartmips
1360 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1361 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1362 @samp{-mno-smartmips} turns off this option.
1366 Generate code for the MIPS-3D Application Specific Extension.
1367 This tells the assembler to accept MIPS-3D instructions.
1368 @samp{-no-mips3d} turns off this option.
1372 Generate code for the MDMX Application Specific Extension.
1373 This tells the assembler to accept MDMX instructions.
1374 @samp{-no-mdmx} turns off this option.
1378 Generate code for the DSP Release 1 Application Specific Extension.
1379 This tells the assembler to accept DSP Release 1 instructions.
1380 @samp{-mno-dsp} turns off this option.
1384 Generate code for the DSP Release 2 Application Specific Extension.
1385 This option implies -mdsp.
1386 This tells the assembler to accept DSP Release 2 instructions.
1387 @samp{-mno-dspr2} turns off this option.
1391 Generate code for the MIPS SIMD Architecture Extension.
1392 This tells the assembler to accept MSA instructions.
1393 @samp{-mno-msa} turns off this option.
1397 Generate code for the MIPS eXtended Physical Address (XPA) Extension.
1398 This tells the assembler to accept XPA instructions.
1399 @samp{-mno-xpa} turns off this option.
1403 Generate code for the MT Application Specific Extension.
1404 This tells the assembler to accept MT instructions.
1405 @samp{-mno-mt} turns off this option.
1409 Generate code for the MCU Application Specific Extension.
1410 This tells the assembler to accept MCU instructions.
1411 @samp{-mno-mcu} turns off this option.
1415 Only use 32-bit instruction encodings when generating code for the
1416 microMIPS processor. This option inhibits the use of any 16-bit
1417 instructions. This is equivalent to putting @code{.set insn32} at
1418 the start of the assembly file. @samp{-mno-insn32} turns off this
1419 option. This is equivalent to putting @code{.set noinsn32} at the
1420 start of the assembly file. By default @samp{-mno-insn32} is
1421 selected, allowing all instructions to be used.
1423 @item --construct-floats
1424 @itemx --no-construct-floats
1425 The @samp{--no-construct-floats} option disables the construction of
1426 double width floating point constants by loading the two halves of the
1427 value into the two single width floating point registers that make up
1428 the double width register. By default @samp{--construct-floats} is
1429 selected, allowing construction of these floating point constants.
1431 @item --relax-branch
1432 @itemx --no-relax-branch
1433 The @samp{--relax-branch} option enables the relaxation of out-of-range
1434 branches. By default @samp{--no-relax-branch} is selected, causing any
1435 out-of-range branches to produce an error.
1437 @item -mnan=@var{encoding}
1438 Select between the IEEE 754-2008 (@option{-mnan=2008}) or the legacy
1439 (@option{-mnan=legacy}) NaN encoding format. The latter is the default.
1442 @item --emulation=@var{name}
1443 This option was formerly used to switch between ELF and ECOFF output
1444 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1445 removed in GAS 2.24, so the option now serves little purpose.
1446 It is retained for backwards compatibility.
1448 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1449 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1450 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1451 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1452 preferred options instead.
1455 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1462 Control how to deal with multiplication overflow and division by zero.
1463 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1464 (and only work for Instruction Set Architecture level 2 and higher);
1465 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1469 When this option is used, @command{@value{AS}} will issue a warning every
1470 time it generates a nop instruction from a macro.
1475 The following options are available when @value{AS} is configured for
1481 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1482 The command line option @samp{-nojsri2bsr} can be used to disable it.
1486 Enable or disable the silicon filter behaviour. By default this is disabled.
1487 The default can be overridden by the @samp{-sifilter} command line option.
1490 Alter jump instructions for long displacements.
1492 @item -mcpu=[210|340]
1493 Select the cpu type on the target hardware. This controls which instructions
1497 Assemble for a big endian target.
1500 Assemble for a little endian target.
1509 @xref{Meta Options}, for the options available when @value{AS} is configured
1510 for a Meta processor.
1514 @c man begin OPTIONS
1515 The following options are available when @value{AS} is configured for a
1518 @c man begin INCLUDE
1519 @include c-metag.texi
1520 @c ended inside the included file
1525 @c man begin OPTIONS
1527 See the info pages for documentation of the MMIX-specific options.
1533 @xref{NDS32 Options}, for the options available when @value{AS} is configured
1534 for a NDS32 processor.
1536 @c ended inside the included file
1540 @c man begin OPTIONS
1541 The following options are available when @value{AS} is configured for a
1544 @c man begin INCLUDE
1545 @include c-nds32.texi
1546 @c ended inside the included file
1553 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1554 for a PowerPC processor.
1558 @c man begin OPTIONS
1559 The following options are available when @value{AS} is configured for a
1562 @c man begin INCLUDE
1564 @c ended inside the included file
1569 @c man begin OPTIONS
1571 See the info pages for documentation of the RX-specific options.
1575 The following options are available when @value{AS} is configured for the s390
1581 Select the word size, either 31/32 bits or 64 bits.
1584 Select the architecture mode, either the Enterprise System
1585 Architecture (esa) or the z/Architecture mode (zarch).
1586 @item -march=@var{processor}
1587 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1588 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1589 @samp{z196}, or @samp{zEC12}.
1591 @itemx -mno-regnames
1592 Allow or disallow symbolic names for registers.
1593 @item -mwarn-areg-zero
1594 Warn whenever the operand for a base or index register has been specified
1595 but evaluates to zero.
1603 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1604 for a TMS320C6000 processor.
1608 @c man begin OPTIONS
1609 The following options are available when @value{AS} is configured for a
1610 TMS320C6000 processor.
1612 @c man begin INCLUDE
1613 @include c-tic6x.texi
1614 @c ended inside the included file
1622 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1623 for a TILE-Gx processor.
1627 @c man begin OPTIONS
1628 The following options are available when @value{AS} is configured for a TILE-Gx
1631 @c man begin INCLUDE
1632 @include c-tilegx.texi
1633 @c ended inside the included file
1641 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1642 for an Xtensa processor.
1646 @c man begin OPTIONS
1647 The following options are available when @value{AS} is configured for an
1650 @c man begin INCLUDE
1651 @include c-xtensa.texi
1652 @c ended inside the included file
1657 @c man begin OPTIONS
1660 The following options are available when @value{AS} is configured for
1661 a Z80 family processor.
1664 Assemble for Z80 processor.
1666 Assemble for R800 processor.
1667 @item -ignore-undocumented-instructions
1669 Assemble undocumented Z80 instructions that also work on R800 without warning.
1670 @item -ignore-unportable-instructions
1672 Assemble all undocumented Z80 instructions without warning.
1673 @item -warn-undocumented-instructions
1675 Issue a warning for undocumented Z80 instructions that also work on R800.
1676 @item -warn-unportable-instructions
1678 Issue a warning for undocumented Z80 instructions that do not work on R800.
1679 @item -forbid-undocumented-instructions
1681 Treat all undocumented instructions as errors.
1682 @item -forbid-unportable-instructions
1684 Treat undocumented Z80 instructions that do not work on R800 as errors.
1691 * Manual:: Structure of this Manual
1692 * GNU Assembler:: The GNU Assembler
1693 * Object Formats:: Object File Formats
1694 * Command Line:: Command Line
1695 * Input Files:: Input Files
1696 * Object:: Output (Object) File
1697 * Errors:: Error and Warning Messages
1701 @section Structure of this Manual
1703 @cindex manual, structure and purpose
1704 This manual is intended to describe what you need to know to use
1705 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1706 notation for symbols, constants, and expressions; the directives that
1707 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1710 We also cover special features in the @value{TARGET}
1711 configuration of @command{@value{AS}}, including assembler directives.
1714 This manual also describes some of the machine-dependent features of
1715 various flavors of the assembler.
1718 @cindex machine instructions (not covered)
1719 On the other hand, this manual is @emph{not} intended as an introduction
1720 to programming in assembly language---let alone programming in general!
1721 In a similar vein, we make no attempt to introduce the machine
1722 architecture; we do @emph{not} describe the instruction set, standard
1723 mnemonics, registers or addressing modes that are standard to a
1724 particular architecture.
1726 You may want to consult the manufacturer's
1727 machine architecture manual for this information.
1731 For information on the H8/300 machine instruction set, see @cite{H8/300
1732 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1733 Programming Manual} (Renesas).
1736 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1737 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1738 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1739 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1742 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1746 @c I think this is premature---doc@cygnus.com, 17jan1991
1748 Throughout this manual, we assume that you are running @dfn{GNU},
1749 the portable operating system from the @dfn{Free Software
1750 Foundation, Inc.}. This restricts our attention to certain kinds of
1751 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1752 once this assumption is granted examples and definitions need less
1755 @command{@value{AS}} is part of a team of programs that turn a high-level
1756 human-readable series of instructions into a low-level
1757 computer-readable series of instructions. Different versions of
1758 @command{@value{AS}} are used for different kinds of computer.
1761 @c There used to be a section "Terminology" here, which defined
1762 @c "contents", "byte", "word", and "long". Defining "word" to any
1763 @c particular size is confusing when the .word directive may generate 16
1764 @c bits on one machine and 32 bits on another; in general, for the user
1765 @c version of this manual, none of these terms seem essential to define.
1766 @c They were used very little even in the former draft of the manual;
1767 @c this draft makes an effort to avoid them (except in names of
1771 @section The GNU Assembler
1773 @c man begin DESCRIPTION
1775 @sc{gnu} @command{as} is really a family of assemblers.
1777 This manual describes @command{@value{AS}}, a member of that family which is
1778 configured for the @value{TARGET} architectures.
1780 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1781 should find a fairly similar environment when you use it on another
1782 architecture. Each version has much in common with the others,
1783 including object file formats, most assembler directives (often called
1784 @dfn{pseudo-ops}) and assembler syntax.@refill
1786 @cindex purpose of @sc{gnu} assembler
1787 @command{@value{AS}} is primarily intended to assemble the output of the
1788 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1789 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1790 assemble correctly everything that other assemblers for the same
1791 machine would assemble.
1793 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1796 @c This remark should appear in generic version of manual; assumption
1797 @c here is that generic version sets M680x0.
1798 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1799 assembler for the same architecture; for example, we know of several
1800 incompatible versions of 680x0 assembly language syntax.
1805 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1806 program in one pass of the source file. This has a subtle impact on the
1807 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1809 @node Object Formats
1810 @section Object File Formats
1812 @cindex object file format
1813 The @sc{gnu} assembler can be configured to produce several alternative
1814 object file formats. For the most part, this does not affect how you
1815 write assembly language programs; but directives for debugging symbols
1816 are typically different in different file formats. @xref{Symbol
1817 Attributes,,Symbol Attributes}.
1820 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1821 @value{OBJ-NAME} format object files.
1823 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1825 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1826 @code{b.out} or COFF format object files.
1829 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1830 SOM or ELF format object files.
1835 @section Command Line
1837 @cindex command line conventions
1839 After the program name @command{@value{AS}}, the command line may contain
1840 options and file names. Options may appear in any order, and may be
1841 before, after, or between file names. The order of file names is
1844 @cindex standard input, as input file
1846 @file{--} (two hyphens) by itself names the standard input file
1847 explicitly, as one of the files for @command{@value{AS}} to assemble.
1849 @cindex options, command line
1850 Except for @samp{--} any command line argument that begins with a
1851 hyphen (@samp{-}) is an option. Each option changes the behavior of
1852 @command{@value{AS}}. No option changes the way another option works. An
1853 option is a @samp{-} followed by one or more letters; the case of
1854 the letter is important. All options are optional.
1856 Some options expect exactly one file name to follow them. The file
1857 name may either immediately follow the option's letter (compatible
1858 with older assemblers) or it may be the next command argument (@sc{gnu}
1859 standard). These two command lines are equivalent:
1862 @value{AS} -o my-object-file.o mumble.s
1863 @value{AS} -omy-object-file.o mumble.s
1867 @section Input Files
1870 @cindex source program
1871 @cindex files, input
1872 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1873 describe the program input to one run of @command{@value{AS}}. The program may
1874 be in one or more files; how the source is partitioned into files
1875 doesn't change the meaning of the source.
1877 @c I added "con" prefix to "catenation" just to prove I can overcome my
1878 @c APL training... doc@cygnus.com
1879 The source program is a concatenation of the text in all the files, in the
1882 @c man begin DESCRIPTION
1883 Each time you run @command{@value{AS}} it assembles exactly one source
1884 program. The source program is made up of one or more files.
1885 (The standard input is also a file.)
1887 You give @command{@value{AS}} a command line that has zero or more input file
1888 names. The input files are read (from left file name to right). A
1889 command line argument (in any position) that has no special meaning
1890 is taken to be an input file name.
1892 If you give @command{@value{AS}} no file names it attempts to read one input file
1893 from the @command{@value{AS}} standard input, which is normally your terminal. You
1894 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1897 Use @samp{--} if you need to explicitly name the standard input file
1898 in your command line.
1900 If the source is empty, @command{@value{AS}} produces a small, empty object
1905 @subheading Filenames and Line-numbers
1907 @cindex input file linenumbers
1908 @cindex line numbers, in input files
1909 There are two ways of locating a line in the input file (or files) and
1910 either may be used in reporting error messages. One way refers to a line
1911 number in a physical file; the other refers to a line number in a
1912 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1914 @dfn{Physical files} are those files named in the command line given
1915 to @command{@value{AS}}.
1917 @dfn{Logical files} are simply names declared explicitly by assembler
1918 directives; they bear no relation to physical files. Logical file names help
1919 error messages reflect the original source file, when @command{@value{AS}} source
1920 is itself synthesized from other files. @command{@value{AS}} understands the
1921 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1922 @ref{File,,@code{.file}}.
1925 @section Output (Object) File
1931 Every time you run @command{@value{AS}} it produces an output file, which is
1932 your assembly language program translated into numbers. This file
1933 is the object file. Its default name is
1941 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1943 You can give it another name by using the @option{-o} option. Conventionally,
1944 object file names end with @file{.o}. The default name is used for historical
1945 reasons: older assemblers were capable of assembling self-contained programs
1946 directly into a runnable program. (For some formats, this isn't currently
1947 possible, but it can be done for the @code{a.out} format.)
1951 The object file is meant for input to the linker @code{@value{LD}}. It contains
1952 assembled program code, information to help @code{@value{LD}} integrate
1953 the assembled program into a runnable file, and (optionally) symbolic
1954 information for the debugger.
1956 @c link above to some info file(s) like the description of a.out.
1957 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1960 @section Error and Warning Messages
1962 @c man begin DESCRIPTION
1964 @cindex error messages
1965 @cindex warning messages
1966 @cindex messages from assembler
1967 @command{@value{AS}} may write warnings and error messages to the standard error
1968 file (usually your terminal). This should not happen when a compiler
1969 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1970 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1971 grave problem that stops the assembly.
1975 @cindex format of warning messages
1976 Warning messages have the format
1979 file_name:@b{NNN}:Warning Message Text
1983 @cindex line numbers, in warnings/errors
1984 (where @b{NNN} is a line number). If a logical file name has been given
1985 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1986 the current input file is used. If a logical line number was given
1988 (@pxref{Line,,@code{.line}})
1990 then it is used to calculate the number printed,
1991 otherwise the actual line in the current source file is printed. The
1992 message text is intended to be self explanatory (in the grand Unix
1995 @cindex format of error messages
1996 Error messages have the format
1998 file_name:@b{NNN}:FATAL:Error Message Text
2000 The file name and line number are derived as for warning
2001 messages. The actual message text may be rather less explanatory
2002 because many of them aren't supposed to happen.
2005 @chapter Command-Line Options
2007 @cindex options, all versions of assembler
2008 This chapter describes command-line options available in @emph{all}
2009 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
2010 for options specific
2012 to the @value{TARGET} target.
2015 to particular machine architectures.
2018 @c man begin DESCRIPTION
2020 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
2021 you can use the @samp{-Wa} option to pass arguments through to the assembler.
2022 The assembler arguments must be separated from each other (and the @samp{-Wa})
2023 by commas. For example:
2026 gcc -c -g -O -Wa,-alh,-L file.c
2030 This passes two options to the assembler: @samp{-alh} (emit a listing to
2031 standard output with high-level and assembly source) and @samp{-L} (retain
2032 local symbols in the symbol table).
2034 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
2035 command-line options are automatically passed to the assembler by the compiler.
2036 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
2037 precisely what options it passes to each compilation pass, including the
2043 * a:: -a[cdghlns] enable listings
2044 * alternate:: --alternate enable alternate macro syntax
2045 * D:: -D for compatibility
2046 * f:: -f to work faster
2047 * I:: -I for .include search path
2048 @ifclear DIFF-TBL-KLUGE
2049 * K:: -K for compatibility
2051 @ifset DIFF-TBL-KLUGE
2052 * K:: -K for difference tables
2055 * L:: -L to retain local symbols
2056 * listing:: --listing-XXX to configure listing output
2057 * M:: -M or --mri to assemble in MRI compatibility mode
2058 * MD:: --MD for dependency tracking
2059 * o:: -o to name the object file
2060 * R:: -R to join data and text sections
2061 * statistics:: --statistics to see statistics about assembly
2062 * traditional-format:: --traditional-format for compatible output
2063 * v:: -v to announce version
2064 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
2065 * Z:: -Z to make object file even after errors
2069 @section Enable Listings: @option{-a[cdghlns]}
2079 @cindex listings, enabling
2080 @cindex assembly listings, enabling
2082 These options enable listing output from the assembler. By itself,
2083 @samp{-a} requests high-level, assembly, and symbols listing.
2084 You can use other letters to select specific options for the list:
2085 @samp{-ah} requests a high-level language listing,
2086 @samp{-al} requests an output-program assembly listing, and
2087 @samp{-as} requests a symbol table listing.
2088 High-level listings require that a compiler debugging option like
2089 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
2092 Use the @samp{-ag} option to print a first section with general assembly
2093 information, like @value{AS} version, switches passed, or time stamp.
2095 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2096 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2097 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2098 omitted from the listing.
2100 Use the @samp{-ad} option to omit debugging directives from the
2103 Once you have specified one of these options, you can further control
2104 listing output and its appearance using the directives @code{.list},
2105 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2107 The @samp{-an} option turns off all forms processing.
2108 If you do not request listing output with one of the @samp{-a} options, the
2109 listing-control directives have no effect.
2111 The letters after @samp{-a} may be combined into one option,
2112 @emph{e.g.}, @samp{-aln}.
2114 Note if the assembler source is coming from the standard input (e.g.,
2116 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2117 is being used) then the listing will not contain any comments or preprocessor
2118 directives. This is because the listing code buffers input source lines from
2119 stdin only after they have been preprocessed by the assembler. This reduces
2120 memory usage and makes the code more efficient.
2123 @section @option{--alternate}
2126 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2129 @section @option{-D}
2132 This option has no effect whatsoever, but it is accepted to make it more
2133 likely that scripts written for other assemblers also work with
2134 @command{@value{AS}}.
2137 @section Work Faster: @option{-f}
2140 @cindex trusted compiler
2141 @cindex faster processing (@option{-f})
2142 @samp{-f} should only be used when assembling programs written by a
2143 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2144 and comment preprocessing on
2145 the input file(s) before assembling them. @xref{Preprocessing,
2149 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2150 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2155 @section @code{.include} Search Path: @option{-I} @var{path}
2157 @kindex -I @var{path}
2158 @cindex paths for @code{.include}
2159 @cindex search path for @code{.include}
2160 @cindex @code{include} directive search path
2161 Use this option to add a @var{path} to the list of directories
2162 @command{@value{AS}} searches for files specified in @code{.include}
2163 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2164 many times as necessary to include a variety of paths. The current
2165 working directory is always searched first; after that, @command{@value{AS}}
2166 searches any @samp{-I} directories in the same order as they were
2167 specified (left to right) on the command line.
2170 @section Difference Tables: @option{-K}
2173 @ifclear DIFF-TBL-KLUGE
2174 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2175 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2176 where it can be used to warn when the assembler alters the machine code
2177 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2178 family does not have the addressing limitations that sometimes lead to this
2179 alteration on other platforms.
2182 @ifset DIFF-TBL-KLUGE
2183 @cindex difference tables, warning
2184 @cindex warning for altered difference tables
2185 @command{@value{AS}} sometimes alters the code emitted for directives of the
2186 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2187 You can use the @samp{-K} option if you want a warning issued when this
2192 @section Include Local Symbols: @option{-L}
2195 @cindex local symbols, retaining in output
2196 Symbols beginning with system-specific local label prefixes, typically
2197 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2198 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2199 such symbols when debugging, because they are intended for the use of
2200 programs (like compilers) that compose assembler programs, not for your
2201 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2202 such symbols, so you do not normally debug with them.
2204 This option tells @command{@value{AS}} to retain those local symbols
2205 in the object file. Usually if you do this you also tell the linker
2206 @code{@value{LD}} to preserve those symbols.
2209 @section Configuring listing output: @option{--listing}
2211 The listing feature of the assembler can be enabled via the command line switch
2212 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2213 hex dump of the corresponding locations in the output object file, and displays
2214 them as a listing file. The format of this listing can be controlled by
2215 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2216 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2217 @code{.psize} (@pxref{Psize}), and
2218 @code{.eject} (@pxref{Eject}) and also by the following switches:
2221 @item --listing-lhs-width=@samp{number}
2222 @kindex --listing-lhs-width
2223 @cindex Width of first line disassembly output
2224 Sets the maximum width, in words, of the first line of the hex byte dump. This
2225 dump appears on the left hand side of the listing output.
2227 @item --listing-lhs-width2=@samp{number}
2228 @kindex --listing-lhs-width2
2229 @cindex Width of continuation lines of disassembly output
2230 Sets the maximum width, in words, of any further lines of the hex byte dump for
2231 a given input source line. If this value is not specified, it defaults to being
2232 the same as the value specified for @samp{--listing-lhs-width}. If neither
2233 switch is used the default is to one.
2235 @item --listing-rhs-width=@samp{number}
2236 @kindex --listing-rhs-width
2237 @cindex Width of source line output
2238 Sets the maximum width, in characters, of the source line that is displayed
2239 alongside the hex dump. The default value for this parameter is 100. The
2240 source line is displayed on the right hand side of the listing output.
2242 @item --listing-cont-lines=@samp{number}
2243 @kindex --listing-cont-lines
2244 @cindex Maximum number of continuation lines
2245 Sets the maximum number of continuation lines of hex dump that will be
2246 displayed for a given single line of source input. The default value is 4.
2250 @section Assemble in MRI Compatibility Mode: @option{-M}
2253 @cindex MRI compatibility mode
2254 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2255 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2256 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2257 configured target) assembler from Microtec Research. The exact nature of the
2258 MRI syntax will not be documented here; see the MRI manuals for more
2259 information. Note in particular that the handling of macros and macro
2260 arguments is somewhat different. The purpose of this option is to permit
2261 assembling existing MRI assembler code using @command{@value{AS}}.
2263 The MRI compatibility is not complete. Certain operations of the MRI assembler
2264 depend upon its object file format, and can not be supported using other object
2265 file formats. Supporting these would require enhancing each object file format
2266 individually. These are:
2269 @item global symbols in common section
2271 The m68k MRI assembler supports common sections which are merged by the linker.
2272 Other object file formats do not support this. @command{@value{AS}} handles
2273 common sections by treating them as a single common symbol. It permits local
2274 symbols to be defined within a common section, but it can not support global
2275 symbols, since it has no way to describe them.
2277 @item complex relocations
2279 The MRI assemblers support relocations against a negated section address, and
2280 relocations which combine the start addresses of two or more sections. These
2281 are not support by other object file formats.
2283 @item @code{END} pseudo-op specifying start address
2285 The MRI @code{END} pseudo-op permits the specification of a start address.
2286 This is not supported by other object file formats. The start address may
2287 instead be specified using the @option{-e} option to the linker, or in a linker
2290 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2292 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2293 name to the output file. This is not supported by other object file formats.
2295 @item @code{ORG} pseudo-op
2297 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2298 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2299 which changes the location within the current section. Absolute sections are
2300 not supported by other object file formats. The address of a section may be
2301 assigned within a linker script.
2304 There are some other features of the MRI assembler which are not supported by
2305 @command{@value{AS}}, typically either because they are difficult or because they
2306 seem of little consequence. Some of these may be supported in future releases.
2310 @item EBCDIC strings
2312 EBCDIC strings are not supported.
2314 @item packed binary coded decimal
2316 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2317 and @code{DCB.P} pseudo-ops are not supported.
2319 @item @code{FEQU} pseudo-op
2321 The m68k @code{FEQU} pseudo-op is not supported.
2323 @item @code{NOOBJ} pseudo-op
2325 The m68k @code{NOOBJ} pseudo-op is not supported.
2327 @item @code{OPT} branch control options
2329 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2330 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2331 relaxes all branches, whether forward or backward, to an appropriate size, so
2332 these options serve no purpose.
2334 @item @code{OPT} list control options
2336 The following m68k @code{OPT} list control options are ignored: @code{C},
2337 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2338 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2340 @item other @code{OPT} options
2342 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2343 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2345 @item @code{OPT} @code{D} option is default
2347 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2348 @code{OPT NOD} may be used to turn it off.
2350 @item @code{XREF} pseudo-op.
2352 The m68k @code{XREF} pseudo-op is ignored.
2354 @item @code{.debug} pseudo-op
2356 The i960 @code{.debug} pseudo-op is not supported.
2358 @item @code{.extended} pseudo-op
2360 The i960 @code{.extended} pseudo-op is not supported.
2362 @item @code{.list} pseudo-op.
2364 The various options of the i960 @code{.list} pseudo-op are not supported.
2366 @item @code{.optimize} pseudo-op
2368 The i960 @code{.optimize} pseudo-op is not supported.
2370 @item @code{.output} pseudo-op
2372 The i960 @code{.output} pseudo-op is not supported.
2374 @item @code{.setreal} pseudo-op
2376 The i960 @code{.setreal} pseudo-op is not supported.
2381 @section Dependency Tracking: @option{--MD}
2384 @cindex dependency tracking
2387 @command{@value{AS}} can generate a dependency file for the file it creates. This
2388 file consists of a single rule suitable for @code{make} describing the
2389 dependencies of the main source file.
2391 The rule is written to the file named in its argument.
2393 This feature is used in the automatic updating of makefiles.
2396 @section Name the Object File: @option{-o}
2399 @cindex naming object file
2400 @cindex object file name
2401 There is always one object file output when you run @command{@value{AS}}. By
2402 default it has the name
2405 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2419 You use this option (which takes exactly one filename) to give the
2420 object file a different name.
2422 Whatever the object file is called, @command{@value{AS}} overwrites any
2423 existing file of the same name.
2426 @section Join Data and Text Sections: @option{-R}
2429 @cindex data and text sections, joining
2430 @cindex text and data sections, joining
2431 @cindex joining text and data sections
2432 @cindex merging text and data sections
2433 @option{-R} tells @command{@value{AS}} to write the object file as if all
2434 data-section data lives in the text section. This is only done at
2435 the very last moment: your binary data are the same, but data
2436 section parts are relocated differently. The data section part of
2437 your object file is zero bytes long because all its bytes are
2438 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2440 When you specify @option{-R} it would be possible to generate shorter
2441 address displacements (because we do not have to cross between text and
2442 data section). We refrain from doing this simply for compatibility with
2443 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2446 When @command{@value{AS}} is configured for COFF or ELF output,
2447 this option is only useful if you use sections named @samp{.text} and
2452 @option{-R} is not supported for any of the HPPA targets. Using
2453 @option{-R} generates a warning from @command{@value{AS}}.
2457 @section Display Assembly Statistics: @option{--statistics}
2459 @kindex --statistics
2460 @cindex statistics, about assembly
2461 @cindex time, total for assembly
2462 @cindex space used, maximum for assembly
2463 Use @samp{--statistics} to display two statistics about the resources used by
2464 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2465 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2468 @node traditional-format
2469 @section Compatible Output: @option{--traditional-format}
2471 @kindex --traditional-format
2472 For some targets, the output of @command{@value{AS}} is different in some ways
2473 from the output of some existing assembler. This switch requests
2474 @command{@value{AS}} to use the traditional format instead.
2476 For example, it disables the exception frame optimizations which
2477 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2480 @section Announce Version: @option{-v}
2484 @cindex assembler version
2485 @cindex version of assembler
2486 You can find out what version of as is running by including the
2487 option @samp{-v} (which you can also spell as @samp{-version}) on the
2491 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2493 @command{@value{AS}} should never give a warning or error message when
2494 assembling compiler output. But programs written by people often
2495 cause @command{@value{AS}} to give a warning that a particular assumption was
2496 made. All such warnings are directed to the standard error file.
2500 @cindex suppressing warnings
2501 @cindex warnings, suppressing
2502 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2503 This only affects the warning messages: it does not change any particular of
2504 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2507 @kindex --fatal-warnings
2508 @cindex errors, caused by warnings
2509 @cindex warnings, causing error
2510 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2511 files that generate warnings to be in error.
2514 @cindex warnings, switching on
2515 You can switch these options off again by specifying @option{--warn}, which
2516 causes warnings to be output as usual.
2519 @section Generate Object File in Spite of Errors: @option{-Z}
2520 @cindex object file, after errors
2521 @cindex errors, continuing after
2522 After an error message, @command{@value{AS}} normally produces no output. If for
2523 some reason you are interested in object file output even after
2524 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2525 option. If there are any errors, @command{@value{AS}} continues anyways, and
2526 writes an object file after a final warning message of the form @samp{@var{n}
2527 errors, @var{m} warnings, generating bad object file.}
2532 @cindex machine-independent syntax
2533 @cindex syntax, machine-independent
2534 This chapter describes the machine-independent syntax allowed in a
2535 source file. @command{@value{AS}} syntax is similar to what many other
2536 assemblers use; it is inspired by the BSD 4.2
2541 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2545 * Preprocessing:: Preprocessing
2546 * Whitespace:: Whitespace
2547 * Comments:: Comments
2548 * Symbol Intro:: Symbols
2549 * Statements:: Statements
2550 * Constants:: Constants
2554 @section Preprocessing
2556 @cindex preprocessing
2557 The @command{@value{AS}} internal preprocessor:
2559 @cindex whitespace, removed by preprocessor
2561 adjusts and removes extra whitespace. It leaves one space or tab before
2562 the keywords on a line, and turns any other whitespace on the line into
2565 @cindex comments, removed by preprocessor
2567 removes all comments, replacing them with a single space, or an
2568 appropriate number of newlines.
2570 @cindex constants, converted by preprocessor
2572 converts character constants into the appropriate numeric values.
2575 It does not do macro processing, include file handling, or
2576 anything else you may get from your C compiler's preprocessor. You can
2577 do include file processing with the @code{.include} directive
2578 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2579 to get other ``CPP'' style preprocessing by giving the input file a
2580 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2581 Output, gcc.info, Using GNU CC}.
2583 Excess whitespace, comments, and character constants
2584 cannot be used in the portions of the input text that are not
2587 @cindex turning preprocessing on and off
2588 @cindex preprocessing, turning on and off
2591 If the first line of an input file is @code{#NO_APP} or if you use the
2592 @samp{-f} option, whitespace and comments are not removed from the input file.
2593 Within an input file, you can ask for whitespace and comment removal in
2594 specific portions of the by putting a line that says @code{#APP} before the
2595 text that may contain whitespace or comments, and putting a line that says
2596 @code{#NO_APP} after this text. This feature is mainly intend to support
2597 @code{asm} statements in compilers whose output is otherwise free of comments
2604 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2605 Whitespace is used to separate symbols, and to make programs neater for
2606 people to read. Unless within character constants
2607 (@pxref{Characters,,Character Constants}), any whitespace means the same
2608 as exactly one space.
2614 There are two ways of rendering comments to @command{@value{AS}}. In both
2615 cases the comment is equivalent to one space.
2617 Anything from @samp{/*} through the next @samp{*/} is a comment.
2618 This means you may not nest these comments.
2622 The only way to include a newline ('\n') in a comment
2623 is to use this sort of comment.
2626 /* This sort of comment does not nest. */
2629 @cindex line comment character
2630 Anything from a @dfn{line comment} character up to the next newline is
2631 considered a comment and is ignored. The line comment character is target
2632 specific, and some targets multiple comment characters. Some targets also have
2633 line comment characters that only work if they are the first character on a
2634 line. Some targets use a sequence of two characters to introduce a line
2635 comment. Some targets can also change their line comment characters depending
2636 upon command line options that have been used. For more details see the
2637 @emph{Syntax} section in the documentation for individual targets.
2639 If the line comment character is the hash sign (@samp{#}) then it still has the
2640 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2641 to specify logical line numbers:
2644 @cindex lines starting with @code{#}
2645 @cindex logical line numbers
2646 To be compatible with past assemblers, lines that begin with @samp{#} have a
2647 special interpretation. Following the @samp{#} should be an absolute
2648 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2649 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2650 new logical file name. The rest of the line, if any, should be whitespace.
2652 If the first non-whitespace characters on the line are not numeric,
2653 the line is ignored. (Just like a comment.)
2656 # This is an ordinary comment.
2657 # 42-6 "new_file_name" # New logical file name
2658 # This is logical line # 36.
2660 This feature is deprecated, and may disappear from future versions
2661 of @command{@value{AS}}.
2666 @cindex characters used in symbols
2667 @ifclear SPECIAL-SYMS
2668 A @dfn{symbol} is one or more characters chosen from the set of all
2669 letters (both upper and lower case), digits and the three characters
2675 A @dfn{symbol} is one or more characters chosen from the set of all
2676 letters (both upper and lower case), digits and the three characters
2677 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2683 On most machines, you can also use @code{$} in symbol names; exceptions
2684 are noted in @ref{Machine Dependencies}.
2686 No symbol may begin with a digit. Case is significant.
2687 There is no length limit: all characters are significant. Multibyte characters
2688 are supported. Symbols are delimited by characters not in that set, or by the
2689 beginning of a file (since the source program must end with a newline, the end
2690 of a file is not a possible symbol delimiter). @xref{Symbols}.
2691 @cindex length of symbols
2696 @cindex statements, structure of
2697 @cindex line separator character
2698 @cindex statement separator character
2700 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2701 @dfn{line separator character}. The line separator character is target
2702 specific and described in the @emph{Syntax} section of each
2703 target's documentation. Not all targets support a line separator character.
2704 The newline or line separator character is considered to be part of the
2705 preceding statement. Newlines and separators within character constants are an
2706 exception: they do not end statements.
2708 @cindex newline, required at file end
2709 @cindex EOF, newline must precede
2710 It is an error to end any statement with end-of-file: the last
2711 character of any input file should be a newline.@refill
2713 An empty statement is allowed, and may include whitespace. It is ignored.
2715 @cindex instructions and directives
2716 @cindex directives and instructions
2717 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2718 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2720 A statement begins with zero or more labels, optionally followed by a
2721 key symbol which determines what kind of statement it is. The key
2722 symbol determines the syntax of the rest of the statement. If the
2723 symbol begins with a dot @samp{.} then the statement is an assembler
2724 directive: typically valid for any computer. If the symbol begins with
2725 a letter the statement is an assembly language @dfn{instruction}: it
2726 assembles into a machine language instruction.
2728 Different versions of @command{@value{AS}} for different computers
2729 recognize different instructions. In fact, the same symbol may
2730 represent a different instruction in a different computer's assembly
2734 @cindex @code{:} (label)
2735 @cindex label (@code{:})
2736 A label is a symbol immediately followed by a colon (@code{:}).
2737 Whitespace before a label or after a colon is permitted, but you may not
2738 have whitespace between a label's symbol and its colon. @xref{Labels}.
2741 For HPPA targets, labels need not be immediately followed by a colon, but
2742 the definition of a label must begin in column zero. This also implies that
2743 only one label may be defined on each line.
2747 label: .directive followed by something
2748 another_label: # This is an empty statement.
2749 instruction operand_1, operand_2, @dots{}
2756 A constant is a number, written so that its value is known by
2757 inspection, without knowing any context. Like this:
2760 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2761 .ascii "Ring the bell\7" # A string constant.
2762 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2763 .float 0f-314159265358979323846264338327\
2764 95028841971.693993751E-40 # - pi, a flonum.
2769 * Characters:: Character Constants
2770 * Numbers:: Number Constants
2774 @subsection Character Constants
2776 @cindex character constants
2777 @cindex constants, character
2778 There are two kinds of character constants. A @dfn{character} stands
2779 for one character in one byte and its value may be used in
2780 numeric expressions. String constants (properly called string
2781 @emph{literals}) are potentially many bytes and their values may not be
2782 used in arithmetic expressions.
2786 * Chars:: Characters
2790 @subsubsection Strings
2792 @cindex string constants
2793 @cindex constants, string
2794 A @dfn{string} is written between double-quotes. It may contain
2795 double-quotes or null characters. The way to get special characters
2796 into a string is to @dfn{escape} these characters: precede them with
2797 a backslash @samp{\} character. For example @samp{\\} represents
2798 one backslash: the first @code{\} is an escape which tells
2799 @command{@value{AS}} to interpret the second character literally as a backslash
2800 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2801 escape character). The complete list of escapes follows.
2803 @cindex escape codes, character
2804 @cindex character escape codes
2807 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2809 @cindex @code{\b} (backspace character)
2810 @cindex backspace (@code{\b})
2812 Mnemonic for backspace; for ASCII this is octal code 010.
2815 @c Mnemonic for EOText; for ASCII this is octal code 004.
2817 @cindex @code{\f} (formfeed character)
2818 @cindex formfeed (@code{\f})
2820 Mnemonic for FormFeed; for ASCII this is octal code 014.
2822 @cindex @code{\n} (newline character)
2823 @cindex newline (@code{\n})
2825 Mnemonic for newline; for ASCII this is octal code 012.
2828 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2830 @cindex @code{\r} (carriage return character)
2831 @cindex carriage return (@code{\r})
2833 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2836 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2837 @c other assemblers.
2839 @cindex @code{\t} (tab)
2840 @cindex tab (@code{\t})
2842 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2845 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2846 @c @item \x @var{digit} @var{digit} @var{digit}
2847 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2849 @cindex @code{\@var{ddd}} (octal character code)
2850 @cindex octal character code (@code{\@var{ddd}})
2851 @item \ @var{digit} @var{digit} @var{digit}
2852 An octal character code. The numeric code is 3 octal digits.
2853 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2854 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2856 @cindex @code{\@var{xd...}} (hex character code)
2857 @cindex hex character code (@code{\@var{xd...}})
2858 @item \@code{x} @var{hex-digits...}
2859 A hex character code. All trailing hex digits are combined. Either upper or
2860 lower case @code{x} works.
2862 @cindex @code{\\} (@samp{\} character)
2863 @cindex backslash (@code{\\})
2865 Represents one @samp{\} character.
2868 @c Represents one @samp{'} (accent acute) character.
2869 @c This is needed in single character literals
2870 @c (@xref{Characters,,Character Constants}.) to represent
2873 @cindex @code{\"} (doublequote character)
2874 @cindex doublequote (@code{\"})
2876 Represents one @samp{"} character. Needed in strings to represent
2877 this character, because an unescaped @samp{"} would end the string.
2879 @item \ @var{anything-else}
2880 Any other character when escaped by @kbd{\} gives a warning, but
2881 assembles as if the @samp{\} was not present. The idea is that if
2882 you used an escape sequence you clearly didn't want the literal
2883 interpretation of the following character. However @command{@value{AS}} has no
2884 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2885 code and warns you of the fact.
2888 Which characters are escapable, and what those escapes represent,
2889 varies widely among assemblers. The current set is what we think
2890 the BSD 4.2 assembler recognizes, and is a subset of what most C
2891 compilers recognize. If you are in doubt, do not use an escape
2895 @subsubsection Characters
2897 @cindex single character constant
2898 @cindex character, single
2899 @cindex constant, single character
2900 A single character may be written as a single quote immediately
2901 followed by that character. The same escapes apply to characters as
2902 to strings. So if you want to write the character backslash, you
2903 must write @kbd{'\\} where the first @code{\} escapes the second
2904 @code{\}. As you can see, the quote is an acute accent, not a
2905 grave accent. A newline
2907 @ifclear abnormal-separator
2908 (or semicolon @samp{;})
2910 @ifset abnormal-separator
2912 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2917 immediately following an acute accent is taken as a literal character
2918 and does not count as the end of a statement. The value of a character
2919 constant in a numeric expression is the machine's byte-wide code for
2920 that character. @command{@value{AS}} assumes your character code is ASCII:
2921 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2924 @subsection Number Constants
2926 @cindex constants, number
2927 @cindex number constants
2928 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2929 are stored in the target machine. @emph{Integers} are numbers that
2930 would fit into an @code{int} in the C language. @emph{Bignums} are
2931 integers, but they are stored in more than 32 bits. @emph{Flonums}
2932 are floating point numbers, described below.
2935 * Integers:: Integers
2940 * Bit Fields:: Bit Fields
2946 @subsubsection Integers
2948 @cindex constants, integer
2950 @cindex binary integers
2951 @cindex integers, binary
2952 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2953 the binary digits @samp{01}.
2955 @cindex octal integers
2956 @cindex integers, octal
2957 An octal integer is @samp{0} followed by zero or more of the octal
2958 digits (@samp{01234567}).
2960 @cindex decimal integers
2961 @cindex integers, decimal
2962 A decimal integer starts with a non-zero digit followed by zero or
2963 more digits (@samp{0123456789}).
2965 @cindex hexadecimal integers
2966 @cindex integers, hexadecimal
2967 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2968 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2970 Integers have the usual values. To denote a negative integer, use
2971 the prefix operator @samp{-} discussed under expressions
2972 (@pxref{Prefix Ops,,Prefix Operators}).
2975 @subsubsection Bignums
2978 @cindex constants, bignum
2979 A @dfn{bignum} has the same syntax and semantics as an integer
2980 except that the number (or its negative) takes more than 32 bits to
2981 represent in binary. The distinction is made because in some places
2982 integers are permitted while bignums are not.
2985 @subsubsection Flonums
2987 @cindex floating point numbers
2988 @cindex constants, floating point
2990 @cindex precision, floating point
2991 A @dfn{flonum} represents a floating point number. The translation is
2992 indirect: a decimal floating point number from the text is converted by
2993 @command{@value{AS}} to a generic binary floating point number of more than
2994 sufficient precision. This generic floating point number is converted
2995 to a particular computer's floating point format (or formats) by a
2996 portion of @command{@value{AS}} specialized to that computer.
2998 A flonum is written by writing (in order)
3003 (@samp{0} is optional on the HPPA.)
3007 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
3009 @kbd{e} is recommended. Case is not important.
3011 @c FIXME: verify if flonum syntax really this vague for most cases
3012 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
3013 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
3016 On the H8/300, Renesas / SuperH SH,
3017 and AMD 29K architectures, the letter must be
3018 one of the letters @samp{DFPRSX} (in upper or lower case).
3020 On the ARC, the letter must be one of the letters @samp{DFRS}
3021 (in upper or lower case).
3023 On the Intel 960 architecture, the letter must be
3024 one of the letters @samp{DFT} (in upper or lower case).
3026 On the HPPA architecture, the letter must be @samp{E} (upper case only).
3030 One of the letters @samp{DFRS} (in upper or lower case).
3033 One of the letters @samp{DFPRSX} (in upper or lower case).
3036 The letter @samp{E} (upper case only).
3039 One of the letters @samp{DFT} (in upper or lower case).
3044 An optional sign: either @samp{+} or @samp{-}.
3047 An optional @dfn{integer part}: zero or more decimal digits.
3050 An optional @dfn{fractional part}: @samp{.} followed by zero
3051 or more decimal digits.
3054 An optional exponent, consisting of:
3058 An @samp{E} or @samp{e}.
3059 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
3060 @c principle this can perfectly well be different on different targets.
3062 Optional sign: either @samp{+} or @samp{-}.
3064 One or more decimal digits.
3069 At least one of the integer part or the fractional part must be
3070 present. The floating point number has the usual base-10 value.
3072 @command{@value{AS}} does all processing using integers. Flonums are computed
3073 independently of any floating point hardware in the computer running
3074 @command{@value{AS}}.
3078 @c Bit fields are written as a general facility but are also controlled
3079 @c by a conditional-compilation flag---which is as of now (21mar91)
3080 @c turned on only by the i960 config of GAS.
3082 @subsubsection Bit Fields
3085 @cindex constants, bit field
3086 You can also define numeric constants as @dfn{bit fields}.
3087 Specify two numbers separated by a colon---
3089 @var{mask}:@var{value}
3092 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3095 The resulting number is then packed
3097 @c this conditional paren in case bit fields turned on elsewhere than 960
3098 (in host-dependent byte order)
3100 into a field whose width depends on which assembler directive has the
3101 bit-field as its argument. Overflow (a result from the bitwise and
3102 requiring more binary digits to represent) is not an error; instead,
3103 more constants are generated, of the specified width, beginning with the
3104 least significant digits.@refill
3106 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3107 @code{.short}, and @code{.word} accept bit-field arguments.
3112 @chapter Sections and Relocation
3117 * Secs Background:: Background
3118 * Ld Sections:: Linker Sections
3119 * As Sections:: Assembler Internal Sections
3120 * Sub-Sections:: Sub-Sections
3124 @node Secs Background
3127 Roughly, a section is a range of addresses, with no gaps; all data
3128 ``in'' those addresses is treated the same for some particular purpose.
3129 For example there may be a ``read only'' section.
3131 @cindex linker, and assembler
3132 @cindex assembler, and linker
3133 The linker @code{@value{LD}} reads many object files (partial programs) and
3134 combines their contents to form a runnable program. When @command{@value{AS}}
3135 emits an object file, the partial program is assumed to start at address 0.
3136 @code{@value{LD}} assigns the final addresses for the partial program, so that
3137 different partial programs do not overlap. This is actually an
3138 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3141 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3142 addresses. These blocks slide to their run-time addresses as rigid
3143 units; their length does not change and neither does the order of bytes
3144 within them. Such a rigid unit is called a @emph{section}. Assigning
3145 run-time addresses to sections is called @dfn{relocation}. It includes
3146 the task of adjusting mentions of object-file addresses so they refer to
3147 the proper run-time addresses.
3149 For the H8/300, and for the Renesas / SuperH SH,
3150 @command{@value{AS}} pads sections if needed to
3151 ensure they end on a word (sixteen bit) boundary.
3154 @cindex standard assembler sections
3155 An object file written by @command{@value{AS}} has at least three sections, any
3156 of which may be empty. These are named @dfn{text}, @dfn{data} and
3161 When it generates COFF or ELF output,
3163 @command{@value{AS}} can also generate whatever other named sections you specify
3164 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3165 If you do not use any directives that place output in the @samp{.text}
3166 or @samp{.data} sections, these sections still exist, but are empty.
3171 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3173 @command{@value{AS}} can also generate whatever other named sections you
3174 specify using the @samp{.space} and @samp{.subspace} directives. See
3175 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3176 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3177 assembler directives.
3180 Additionally, @command{@value{AS}} uses different names for the standard
3181 text, data, and bss sections when generating SOM output. Program text
3182 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3183 BSS into @samp{$BSS$}.
3187 Within the object file, the text section starts at address @code{0}, the
3188 data section follows, and the bss section follows the data section.
3191 When generating either SOM or ELF output files on the HPPA, the text
3192 section starts at address @code{0}, the data section at address
3193 @code{0x4000000}, and the bss section follows the data section.
3196 To let @code{@value{LD}} know which data changes when the sections are
3197 relocated, and how to change that data, @command{@value{AS}} also writes to the
3198 object file details of the relocation needed. To perform relocation
3199 @code{@value{LD}} must know, each time an address in the object
3203 Where in the object file is the beginning of this reference to
3206 How long (in bytes) is this reference?
3208 Which section does the address refer to? What is the numeric value of
3210 (@var{address}) @minus{} (@var{start-address of section})?
3213 Is the reference to an address ``Program-Counter relative''?
3216 @cindex addresses, format of
3217 @cindex section-relative addressing
3218 In fact, every address @command{@value{AS}} ever uses is expressed as
3220 (@var{section}) + (@var{offset into section})
3223 Further, most expressions @command{@value{AS}} computes have this section-relative
3226 (For some object formats, such as SOM for the HPPA, some expressions are
3227 symbol-relative instead.)
3230 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3231 @var{N} into section @var{secname}.''
3233 Apart from text, data and bss sections you need to know about the
3234 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3235 addresses in the absolute section remain unchanged. For example, address
3236 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3237 @code{@value{LD}}. Although the linker never arranges two partial programs'
3238 data sections with overlapping addresses after linking, @emph{by definition}
3239 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3240 part of a program is always the same address when the program is running as
3241 address @code{@{absolute@ 239@}} in any other part of the program.
3243 The idea of sections is extended to the @dfn{undefined} section. Any
3244 address whose section is unknown at assembly time is by definition
3245 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3246 Since numbers are always defined, the only way to generate an undefined
3247 address is to mention an undefined symbol. A reference to a named
3248 common block would be such a symbol: its value is unknown at assembly
3249 time so it has section @emph{undefined}.
3251 By analogy the word @emph{section} is used to describe groups of sections in
3252 the linked program. @code{@value{LD}} puts all partial programs' text
3253 sections in contiguous addresses in the linked program. It is
3254 customary to refer to the @emph{text section} of a program, meaning all
3255 the addresses of all partial programs' text sections. Likewise for
3256 data and bss sections.
3258 Some sections are manipulated by @code{@value{LD}}; others are invented for
3259 use of @command{@value{AS}} and have no meaning except during assembly.
3262 @section Linker Sections
3263 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3268 @cindex named sections
3269 @cindex sections, named
3270 @item named sections
3273 @cindex text section
3274 @cindex data section
3278 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3279 separate but equal sections. Anything you can say of one section is
3282 When the program is running, however, it is
3283 customary for the text section to be unalterable. The
3284 text section is often shared among processes: it contains
3285 instructions, constants and the like. The data section of a running
3286 program is usually alterable: for example, C variables would be stored
3287 in the data section.
3292 This section contains zeroed bytes when your program begins running. It
3293 is used to hold uninitialized variables or common storage. The length of
3294 each partial program's bss section is important, but because it starts
3295 out containing zeroed bytes there is no need to store explicit zero
3296 bytes in the object file. The bss section was invented to eliminate
3297 those explicit zeros from object files.
3299 @cindex absolute section
3300 @item absolute section
3301 Address 0 of this section is always ``relocated'' to runtime address 0.
3302 This is useful if you want to refer to an address that @code{@value{LD}} must
3303 not change when relocating. In this sense we speak of absolute
3304 addresses being ``unrelocatable'': they do not change during relocation.
3306 @cindex undefined section
3307 @item undefined section
3308 This ``section'' is a catch-all for address references to objects not in
3309 the preceding sections.
3310 @c FIXME: ref to some other doc on obj-file formats could go here.
3313 @cindex relocation example
3314 An idealized example of three relocatable sections follows.
3316 The example uses the traditional section names @samp{.text} and @samp{.data}.
3318 Memory addresses are on the horizontal axis.
3322 @c END TEXI2ROFF-KILL
3325 partial program # 1: |ttttt|dddd|00|
3332 partial program # 2: |TTT|DDD|000|
3335 +--+---+-----+--+----+---+-----+~~
3336 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3337 +--+---+-----+--+----+---+-----+~~
3339 addresses: 0 @dots{}
3346 \line{\it Partial program \#1: \hfil}
3347 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3348 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3350 \line{\it Partial program \#2: \hfil}
3351 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3352 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3354 \line{\it linked program: \hfil}
3355 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3356 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3357 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3358 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3360 \line{\it addresses: \hfil}
3364 @c END TEXI2ROFF-KILL
3367 @section Assembler Internal Sections
3369 @cindex internal assembler sections
3370 @cindex sections in messages, internal
3371 These sections are meant only for the internal use of @command{@value{AS}}. They
3372 have no meaning at run-time. You do not really need to know about these
3373 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3374 warning messages, so it might be helpful to have an idea of their
3375 meanings to @command{@value{AS}}. These sections are used to permit the
3376 value of every expression in your assembly language program to be a
3377 section-relative address.
3380 @cindex assembler internal logic error
3381 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3382 An internal assembler logic error has been found. This means there is a
3383 bug in the assembler.
3385 @cindex expr (internal section)
3387 The assembler stores complex expression internally as combinations of
3388 symbols. When it needs to represent an expression as a symbol, it puts
3389 it in the expr section.
3391 @c FIXME item transfer[t] vector preload
3392 @c FIXME item transfer[t] vector postload
3393 @c FIXME item register
3397 @section Sub-Sections
3399 @cindex numbered subsections
3400 @cindex grouping data
3406 fall into two sections: text and data.
3408 You may have separate groups of
3410 data in named sections
3414 data in named sections
3420 that you want to end up near to each other in the object file, even though they
3421 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3422 use @dfn{subsections} for this purpose. Within each section, there can be
3423 numbered subsections with values from 0 to 8192. Objects assembled into the
3424 same subsection go into the object file together with other objects in the same
3425 subsection. For example, a compiler might want to store constants in the text
3426 section, but might not want to have them interspersed with the program being
3427 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3428 section of code being output, and a @samp{.text 1} before each group of
3429 constants being output.
3431 Subsections are optional. If you do not use subsections, everything
3432 goes in subsection number zero.
3435 Each subsection is zero-padded up to a multiple of four bytes.
3436 (Subsections may be padded a different amount on different flavors
3437 of @command{@value{AS}}.)
3441 On the H8/300 platform, each subsection is zero-padded to a word
3442 boundary (two bytes).
3443 The same is true on the Renesas SH.
3446 @c FIXME section padding (alignment)?
3447 @c Rich Pixley says padding here depends on target obj code format; that
3448 @c doesn't seem particularly useful to say without further elaboration,
3449 @c so for now I say nothing about it. If this is a generic BFD issue,
3450 @c these paragraphs might need to vanish from this manual, and be
3451 @c discussed in BFD chapter of binutils (or some such).
3455 Subsections appear in your object file in numeric order, lowest numbered
3456 to highest. (All this to be compatible with other people's assemblers.)
3457 The object file contains no representation of subsections; @code{@value{LD}} and
3458 other programs that manipulate object files see no trace of them.
3459 They just see all your text subsections as a text section, and all your
3460 data subsections as a data section.
3462 To specify which subsection you want subsequent statements assembled
3463 into, use a numeric argument to specify it, in a @samp{.text
3464 @var{expression}} or a @samp{.data @var{expression}} statement.
3467 When generating COFF output, you
3472 can also use an extra subsection
3473 argument with arbitrary named sections: @samp{.section @var{name},
3478 When generating ELF output, you
3483 can also use the @code{.subsection} directive (@pxref{SubSection})
3484 to specify a subsection: @samp{.subsection @var{expression}}.
3486 @var{Expression} should be an absolute expression
3487 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3488 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3489 begins in @code{text 0}. For instance:
3491 .text 0 # The default subsection is text 0 anyway.
3492 .ascii "This lives in the first text subsection. *"
3494 .ascii "But this lives in the second text subsection."
3496 .ascii "This lives in the data section,"
3497 .ascii "in the first data subsection."
3499 .ascii "This lives in the first text section,"
3500 .ascii "immediately following the asterisk (*)."
3503 Each section has a @dfn{location counter} incremented by one for every byte
3504 assembled into that section. Because subsections are merely a convenience
3505 restricted to @command{@value{AS}} there is no concept of a subsection location
3506 counter. There is no way to directly manipulate a location counter---but the
3507 @code{.align} directive changes it, and any label definition captures its
3508 current value. The location counter of the section where statements are being
3509 assembled is said to be the @dfn{active} location counter.
3512 @section bss Section
3515 @cindex common variable storage
3516 The bss section is used for local common variable storage.
3517 You may allocate address space in the bss section, but you may
3518 not dictate data to load into it before your program executes. When
3519 your program starts running, all the contents of the bss
3520 section are zeroed bytes.
3522 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3523 @ref{Lcomm,,@code{.lcomm}}.
3525 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3526 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3529 When assembling for a target which supports multiple sections, such as ELF or
3530 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3531 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3532 section. Typically the section will only contain symbol definitions and
3533 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3540 Symbols are a central concept: the programmer uses symbols to name
3541 things, the linker uses symbols to link, and the debugger uses symbols
3545 @cindex debuggers, and symbol order
3546 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3547 the same order they were declared. This may break some debuggers.
3552 * Setting Symbols:: Giving Symbols Other Values
3553 * Symbol Names:: Symbol Names
3554 * Dot:: The Special Dot Symbol
3555 * Symbol Attributes:: Symbol Attributes
3562 A @dfn{label} is written as a symbol immediately followed by a colon
3563 @samp{:}. The symbol then represents the current value of the
3564 active location counter, and is, for example, a suitable instruction
3565 operand. You are warned if you use the same symbol to represent two
3566 different locations: the first definition overrides any other
3570 On the HPPA, the usual form for a label need not be immediately followed by a
3571 colon, but instead must start in column zero. Only one label may be defined on
3572 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3573 provides a special directive @code{.label} for defining labels more flexibly.
3576 @node Setting Symbols
3577 @section Giving Symbols Other Values
3579 @cindex assigning values to symbols
3580 @cindex symbol values, assigning
3581 A symbol can be given an arbitrary value by writing a symbol, followed
3582 by an equals sign @samp{=}, followed by an expression
3583 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3584 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3585 equals sign @samp{=}@samp{=} here represents an equivalent of the
3586 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3589 Blackfin does not support symbol assignment with @samp{=}.
3593 @section Symbol Names
3595 @cindex symbol names
3596 @cindex names, symbol
3597 @ifclear SPECIAL-SYMS
3598 Symbol names begin with a letter or with one of @samp{._}. On most
3599 machines, you can also use @code{$} in symbol names; exceptions are
3600 noted in @ref{Machine Dependencies}. That character may be followed by any
3601 string of digits, letters, dollar signs (unless otherwise noted for a
3602 particular target machine), and underscores.
3606 Symbol names begin with a letter or with one of @samp{._}. On the
3607 Renesas SH you can also use @code{$} in symbol names. That
3608 character may be followed by any string of digits, letters, dollar signs (save
3609 on the H8/300), and underscores.
3613 Case of letters is significant: @code{foo} is a different symbol name
3616 Multibyte characters are supported. To generate a symbol name containing
3617 multibyte characters enclose it within double quotes and use escape codes. cf
3618 @xref{Strings}. Generating a multibyte symbol name from a label is not
3619 currently supported.
3621 Each symbol has exactly one name. Each name in an assembly language program
3622 refers to exactly one symbol. You may use that symbol name any number of times
3625 @subheading Local Symbol Names
3627 @cindex local symbol names
3628 @cindex symbol names, local
3629 A local symbol is any symbol beginning with certain local label prefixes.
3630 By default, the local label prefix is @samp{.L} for ELF systems or
3631 @samp{L} for traditional a.out systems, but each target may have its own
3632 set of local label prefixes.
3634 On the HPPA local symbols begin with @samp{L$}.
3637 Local symbols are defined and used within the assembler, but they are
3638 normally not saved in object files. Thus, they are not visible when debugging.
3639 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3640 @option{-L}}) to retain the local symbols in the object files.
3642 @subheading Local Labels
3644 @cindex local labels
3645 @cindex temporary symbol names
3646 @cindex symbol names, temporary
3647 Local labels help compilers and programmers use names temporarily.
3648 They create symbols which are guaranteed to be unique over the entire scope of
3649 the input source code and which can be referred to by a simple notation.
3650 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3651 represents any positive integer). To refer to the most recent previous
3652 definition of that label write @samp{@b{N}b}, using the same number as when
3653 you defined the label. To refer to the next definition of a local label, write
3654 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3657 There is no restriction on how you can use these labels, and you can reuse them
3658 too. So that it is possible to repeatedly define the same local label (using
3659 the same number @samp{@b{N}}), although you can only refer to the most recently
3660 defined local label of that number (for a backwards reference) or the next
3661 definition of a specific local label for a forward reference. It is also worth
3662 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3663 implemented in a slightly more efficient manner than the others.
3674 Which is the equivalent of:
3677 label_1: branch label_3
3678 label_2: branch label_1
3679 label_3: branch label_4
3680 label_4: branch label_3
3683 Local label names are only a notational device. They are immediately
3684 transformed into more conventional symbol names before the assembler uses them.
3685 The symbol names are stored in the symbol table, appear in error messages, and
3686 are optionally emitted to the object file. The names are constructed using
3690 @item @emph{local label prefix}
3691 All local symbols begin with the system-specific local label prefix.
3692 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3693 that start with the local label prefix. These labels are
3694 used for symbols you are never intended to see. If you use the
3695 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3696 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3697 you may use them in debugging.
3700 This is the number that was used in the local label definition. So if the
3701 label is written @samp{55:} then the number is @samp{55}.
3704 This unusual character is included so you do not accidentally invent a symbol
3705 of the same name. The character has ASCII value of @samp{\002} (control-B).
3707 @item @emph{ordinal number}
3708 This is a serial number to keep the labels distinct. The first definition of
3709 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3710 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3711 the number @samp{1} and its 15th definition gets @samp{15} as well.
3714 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3715 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3717 @subheading Dollar Local Labels
3718 @cindex dollar local symbols
3720 @code{@value{AS}} also supports an even more local form of local labels called
3721 dollar labels. These labels go out of scope (i.e., they become undefined) as
3722 soon as a non-local label is defined. Thus they remain valid for only a small
3723 region of the input source code. Normal local labels, by contrast, remain in
3724 scope for the entire file, or until they are redefined by another occurrence of
3725 the same local label.
3727 Dollar labels are defined in exactly the same way as ordinary local labels,
3728 except that they have a dollar sign suffix to their numeric value, e.g.,
3731 They can also be distinguished from ordinary local labels by their transformed
3732 names which use ASCII character @samp{\001} (control-A) as the magic character
3733 to distinguish them from ordinary labels. For example, the fifth definition of
3734 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3737 @section The Special Dot Symbol
3739 @cindex dot (symbol)
3740 @cindex @code{.} (symbol)
3741 @cindex current address
3742 @cindex location counter
3743 The special symbol @samp{.} refers to the current address that
3744 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3745 .long .} defines @code{melvin} to contain its own address.
3746 Assigning a value to @code{.} is treated the same as a @code{.org}
3748 @ifclear no-space-dir
3749 Thus, the expression @samp{.=.+4} is the same as saying
3753 @node Symbol Attributes
3754 @section Symbol Attributes
3756 @cindex symbol attributes
3757 @cindex attributes, symbol
3758 Every symbol has, as well as its name, the attributes ``Value'' and
3759 ``Type''. Depending on output format, symbols can also have auxiliary
3762 The detailed definitions are in @file{a.out.h}.
3765 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3766 all these attributes, and probably won't warn you. This makes the
3767 symbol an externally defined symbol, which is generally what you
3771 * Symbol Value:: Value
3772 * Symbol Type:: Type
3775 * a.out Symbols:: Symbol Attributes: @code{a.out}
3779 * a.out Symbols:: Symbol Attributes: @code{a.out}
3782 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3787 * COFF Symbols:: Symbol Attributes for COFF
3790 * SOM Symbols:: Symbol Attributes for SOM
3797 @cindex value of a symbol
3798 @cindex symbol value
3799 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3800 location in the text, data, bss or absolute sections the value is the
3801 number of addresses from the start of that section to the label.
3802 Naturally for text, data and bss sections the value of a symbol changes
3803 as @code{@value{LD}} changes section base addresses during linking. Absolute
3804 symbols' values do not change during linking: that is why they are
3807 The value of an undefined symbol is treated in a special way. If it is
3808 0 then the symbol is not defined in this assembler source file, and
3809 @code{@value{LD}} tries to determine its value from other files linked into the
3810 same program. You make this kind of symbol simply by mentioning a symbol
3811 name without defining it. A non-zero value represents a @code{.comm}
3812 common declaration. The value is how much common storage to reserve, in
3813 bytes (addresses). The symbol refers to the first address of the
3819 @cindex type of a symbol
3821 The type attribute of a symbol contains relocation (section)
3822 information, any flag settings indicating that a symbol is external, and
3823 (optionally), other information for linkers and debuggers. The exact
3824 format depends on the object-code output format in use.
3829 @c The following avoids a "widow" subsection title. @group would be
3830 @c better if it were available outside examples.
3833 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3835 @cindex @code{b.out} symbol attributes
3836 @cindex symbol attributes, @code{b.out}
3837 These symbol attributes appear only when @command{@value{AS}} is configured for
3838 one of the Berkeley-descended object output formats---@code{a.out} or
3844 @subsection Symbol Attributes: @code{a.out}
3846 @cindex @code{a.out} symbol attributes
3847 @cindex symbol attributes, @code{a.out}
3853 @subsection Symbol Attributes: @code{a.out}
3855 @cindex @code{a.out} symbol attributes
3856 @cindex symbol attributes, @code{a.out}
3860 * Symbol Desc:: Descriptor
3861 * Symbol Other:: Other
3865 @subsubsection Descriptor
3867 @cindex descriptor, of @code{a.out} symbol
3868 This is an arbitrary 16-bit value. You may establish a symbol's
3869 descriptor value by using a @code{.desc} statement
3870 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3871 @command{@value{AS}}.
3874 @subsubsection Other
3876 @cindex other attribute, of @code{a.out} symbol
3877 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3882 @subsection Symbol Attributes for COFF
3884 @cindex COFF symbol attributes
3885 @cindex symbol attributes, COFF
3887 The COFF format supports a multitude of auxiliary symbol attributes;
3888 like the primary symbol attributes, they are set between @code{.def} and
3889 @code{.endef} directives.
3891 @subsubsection Primary Attributes
3893 @cindex primary attributes, COFF symbols
3894 The symbol name is set with @code{.def}; the value and type,
3895 respectively, with @code{.val} and @code{.type}.
3897 @subsubsection Auxiliary Attributes
3899 @cindex auxiliary attributes, COFF symbols
3900 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3901 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3902 table information for COFF.
3907 @subsection Symbol Attributes for SOM
3909 @cindex SOM symbol attributes
3910 @cindex symbol attributes, SOM
3912 The SOM format for the HPPA supports a multitude of symbol attributes set with
3913 the @code{.EXPORT} and @code{.IMPORT} directives.
3915 The attributes are described in @cite{HP9000 Series 800 Assembly
3916 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3917 @code{EXPORT} assembler directive documentation.
3921 @chapter Expressions
3925 @cindex numeric values
3926 An @dfn{expression} specifies an address or numeric value.
3927 Whitespace may precede and/or follow an expression.
3929 The result of an expression must be an absolute number, or else an offset into
3930 a particular section. If an expression is not absolute, and there is not
3931 enough information when @command{@value{AS}} sees the expression to know its
3932 section, a second pass over the source program might be necessary to interpret
3933 the expression---but the second pass is currently not implemented.
3934 @command{@value{AS}} aborts with an error message in this situation.
3937 * Empty Exprs:: Empty Expressions
3938 * Integer Exprs:: Integer Expressions
3942 @section Empty Expressions
3944 @cindex empty expressions
3945 @cindex expressions, empty
3946 An empty expression has no value: it is just whitespace or null.
3947 Wherever an absolute expression is required, you may omit the
3948 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3949 is compatible with other assemblers.
3952 @section Integer Expressions
3954 @cindex integer expressions
3955 @cindex expressions, integer
3956 An @dfn{integer expression} is one or more @emph{arguments} delimited
3957 by @emph{operators}.
3960 * Arguments:: Arguments
3961 * Operators:: Operators
3962 * Prefix Ops:: Prefix Operators
3963 * Infix Ops:: Infix Operators
3967 @subsection Arguments
3969 @cindex expression arguments
3970 @cindex arguments in expressions
3971 @cindex operands in expressions
3972 @cindex arithmetic operands
3973 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3974 contexts arguments are sometimes called ``arithmetic operands''. In
3975 this manual, to avoid confusing them with the ``instruction operands'' of
3976 the machine language, we use the term ``argument'' to refer to parts of
3977 expressions only, reserving the word ``operand'' to refer only to machine
3978 instruction operands.
3980 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3981 @var{section} is one of text, data, bss, absolute,
3982 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3985 Numbers are usually integers.
3987 A number can be a flonum or bignum. In this case, you are warned
3988 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3989 these 32 bits are an integer. You may write integer-manipulating
3990 instructions that act on exotic constants, compatible with other
3993 @cindex subexpressions
3994 Subexpressions are a left parenthesis @samp{(} followed by an integer
3995 expression, followed by a right parenthesis @samp{)}; or a prefix
3996 operator followed by an argument.
3999 @subsection Operators
4001 @cindex operators, in expressions
4002 @cindex arithmetic functions
4003 @cindex functions, in expressions
4004 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
4005 operators are followed by an argument. Infix operators appear
4006 between their arguments. Operators may be preceded and/or followed by
4010 @subsection Prefix Operator
4012 @cindex prefix operators
4013 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
4014 one argument, which must be absolute.
4016 @c the tex/end tex stuff surrounding this small table is meant to make
4017 @c it align, on the printed page, with the similar table in the next
4018 @c section (which is inside an enumerate).
4020 \global\advance\leftskip by \itemindent
4025 @dfn{Negation}. Two's complement negation.
4027 @dfn{Complementation}. Bitwise not.
4031 \global\advance\leftskip by -\itemindent
4035 @subsection Infix Operators
4037 @cindex infix operators
4038 @cindex operators, permitted arguments
4039 @dfn{Infix operators} take two arguments, one on either side. Operators
4040 have precedence, but operations with equal precedence are performed left
4041 to right. Apart from @code{+} or @option{-}, both arguments must be
4042 absolute, and the result is absolute.
4045 @cindex operator precedence
4046 @cindex precedence of operators
4053 @dfn{Multiplication}.
4056 @dfn{Division}. Truncation is the same as the C operator @samp{/}
4062 @dfn{Shift Left}. Same as the C operator @samp{<<}.
4065 @dfn{Shift Right}. Same as the C operator @samp{>>}.
4069 Intermediate precedence
4074 @dfn{Bitwise Inclusive Or}.
4080 @dfn{Bitwise Exclusive Or}.
4083 @dfn{Bitwise Or Not}.
4090 @cindex addition, permitted arguments
4091 @cindex plus, permitted arguments
4092 @cindex arguments for addition
4094 @dfn{Addition}. If either argument is absolute, the result has the section of
4095 the other argument. You may not add together arguments from different
4098 @cindex subtraction, permitted arguments
4099 @cindex minus, permitted arguments
4100 @cindex arguments for subtraction
4102 @dfn{Subtraction}. If the right argument is absolute, the
4103 result has the section of the left argument.
4104 If both arguments are in the same section, the result is absolute.
4105 You may not subtract arguments from different sections.
4106 @c FIXME is there still something useful to say about undefined - undefined ?
4108 @cindex comparison expressions
4109 @cindex expressions, comparison
4114 @dfn{Is Not Equal To}
4118 @dfn{Is Greater Than}
4120 @dfn{Is Greater Than Or Equal To}
4122 @dfn{Is Less Than Or Equal To}
4124 The comparison operators can be used as infix operators. A true results has a
4125 value of -1 whereas a false result has a value of 0. Note, these operators
4126 perform signed comparisons.
4129 @item Lowest Precedence
4138 These two logical operations can be used to combine the results of sub
4139 expressions. Note, unlike the comparison operators a true result returns a
4140 value of 1 but a false results does still return 0. Also note that the logical
4141 or operator has a slightly lower precedence than logical and.
4146 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4147 address; you can only have a defined section in one of the two arguments.
4150 @chapter Assembler Directives
4152 @cindex directives, machine independent
4153 @cindex pseudo-ops, machine independent
4154 @cindex machine independent directives
4155 All assembler directives have names that begin with a period (@samp{.}).
4156 The rest of the name is letters, usually in lower case.
4158 This chapter discusses directives that are available regardless of the
4159 target machine configuration for the @sc{gnu} assembler.
4161 Some machine configurations provide additional directives.
4162 @xref{Machine Dependencies}.
4165 @ifset machine-directives
4166 @xref{Machine Dependencies}, for additional directives.
4171 * Abort:: @code{.abort}
4173 * ABORT (COFF):: @code{.ABORT}
4176 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4177 * Altmacro:: @code{.altmacro}
4178 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4179 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4180 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4181 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4182 * Byte:: @code{.byte @var{expressions}}
4183 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4184 * Comm:: @code{.comm @var{symbol} , @var{length} }
4185 * Data:: @code{.data @var{subsection}}
4187 * Def:: @code{.def @var{name}}
4190 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4196 * Double:: @code{.double @var{flonums}}
4197 * Eject:: @code{.eject}
4198 * Else:: @code{.else}
4199 * Elseif:: @code{.elseif}
4202 * Endef:: @code{.endef}
4205 * Endfunc:: @code{.endfunc}
4206 * Endif:: @code{.endif}
4207 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4208 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4209 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4211 * Error:: @code{.error @var{string}}
4212 * Exitm:: @code{.exitm}
4213 * Extern:: @code{.extern}
4214 * Fail:: @code{.fail}
4215 * File:: @code{.file}
4216 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4217 * Float:: @code{.float @var{flonums}}
4218 * Func:: @code{.func}
4219 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4221 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4222 * Hidden:: @code{.hidden @var{names}}
4225 * hword:: @code{.hword @var{expressions}}
4226 * Ident:: @code{.ident}
4227 * If:: @code{.if @var{absolute expression}}
4228 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4229 * Include:: @code{.include "@var{file}"}
4230 * Int:: @code{.int @var{expressions}}
4232 * Internal:: @code{.internal @var{names}}
4235 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4236 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4237 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4238 * Lflags:: @code{.lflags}
4239 @ifclear no-line-dir
4240 * Line:: @code{.line @var{line-number}}
4243 * Linkonce:: @code{.linkonce [@var{type}]}
4244 * List:: @code{.list}
4245 * Ln:: @code{.ln @var{line-number}}
4246 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4247 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4249 * Local:: @code{.local @var{names}}
4252 * Long:: @code{.long @var{expressions}}
4254 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4257 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4258 * MRI:: @code{.mri @var{val}}
4259 * Noaltmacro:: @code{.noaltmacro}
4260 * Nolist:: @code{.nolist}
4261 * Octa:: @code{.octa @var{bignums}}
4262 * Offset:: @code{.offset @var{loc}}
4263 * Org:: @code{.org @var{new-lc}, @var{fill}}
4264 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4266 * PopSection:: @code{.popsection}
4267 * Previous:: @code{.previous}
4270 * Print:: @code{.print @var{string}}
4272 * Protected:: @code{.protected @var{names}}
4275 * Psize:: @code{.psize @var{lines}, @var{columns}}
4276 * Purgem:: @code{.purgem @var{name}}
4278 * PushSection:: @code{.pushsection @var{name}}
4281 * Quad:: @code{.quad @var{bignums}}
4282 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4283 * Rept:: @code{.rept @var{count}}
4284 * Sbttl:: @code{.sbttl "@var{subheading}"}
4286 * Scl:: @code{.scl @var{class}}
4289 * Section:: @code{.section @var{name}[, @var{flags}]}
4292 * Set:: @code{.set @var{symbol}, @var{expression}}
4293 * Short:: @code{.short @var{expressions}}
4294 * Single:: @code{.single @var{flonums}}
4296 * Size:: @code{.size [@var{name} , @var{expression}]}
4298 @ifclear no-space-dir
4299 * Skip:: @code{.skip @var{size} , @var{fill}}
4302 * Sleb128:: @code{.sleb128 @var{expressions}}
4303 @ifclear no-space-dir
4304 * Space:: @code{.space @var{size} , @var{fill}}
4307 * Stab:: @code{.stabd, .stabn, .stabs}
4310 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4311 * Struct:: @code{.struct @var{expression}}
4313 * SubSection:: @code{.subsection}
4314 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4318 * Tag:: @code{.tag @var{structname}}
4321 * Text:: @code{.text @var{subsection}}
4322 * Title:: @code{.title "@var{heading}"}
4324 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4327 * Uleb128:: @code{.uleb128 @var{expressions}}
4329 * Val:: @code{.val @var{addr}}
4333 * Version:: @code{.version "@var{string}"}
4334 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4335 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4338 * Warning:: @code{.warning @var{string}}
4339 * Weak:: @code{.weak @var{names}}
4340 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4341 * Word:: @code{.word @var{expressions}}
4342 * Deprecated:: Deprecated Directives
4346 @section @code{.abort}
4348 @cindex @code{abort} directive
4349 @cindex stopping the assembly
4350 This directive stops the assembly immediately. It is for
4351 compatibility with other assemblers. The original idea was that the
4352 assembly language source would be piped into the assembler. If the sender
4353 of the source quit, it could use this directive tells @command{@value{AS}} to
4354 quit also. One day @code{.abort} will not be supported.
4358 @section @code{.ABORT} (COFF)
4360 @cindex @code{ABORT} directive
4361 When producing COFF output, @command{@value{AS}} accepts this directive as a
4362 synonym for @samp{.abort}.
4365 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4371 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4373 @cindex padding the location counter
4374 @cindex @code{align} directive
4375 Pad the location counter (in the current subsection) to a particular storage
4376 boundary. The first expression (which must be absolute) is the alignment
4377 required, as described below.
4379 The second expression (also absolute) gives the fill value to be stored in the
4380 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4381 padding bytes are normally zero. However, on some systems, if the section is
4382 marked as containing code and the fill value is omitted, the space is filled
4383 with no-op instructions.
4385 The third expression is also absolute, and is also optional. If it is present,
4386 it is the maximum number of bytes that should be skipped by this alignment
4387 directive. If doing the alignment would require skipping more bytes than the
4388 specified maximum, then the alignment is not done at all. You can omit the
4389 fill value (the second argument) entirely by simply using two commas after the
4390 required alignment; this can be useful if you want the alignment to be filled
4391 with no-op instructions when appropriate.
4393 The way the required alignment is specified varies from system to system.
4394 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or1k,
4395 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4396 alignment request in bytes. For example @samp{.align 8} advances
4397 the location counter until it is a multiple of 8. If the location counter
4398 is already a multiple of 8, no change is needed. For the tic54x, the
4399 first expression is the alignment request in words.
4401 For other systems, including ppc, i386 using a.out format, arm and
4402 strongarm, it is the
4403 number of low-order zero bits the location counter must have after
4404 advancement. For example @samp{.align 3} advances the location
4405 counter until it a multiple of 8. If the location counter is already a
4406 multiple of 8, no change is needed.
4408 This inconsistency is due to the different behaviors of the various
4409 native assemblers for these systems which GAS must emulate.
4410 GAS also provides @code{.balign} and @code{.p2align} directives,
4411 described later, which have a consistent behavior across all
4412 architectures (but are specific to GAS).
4415 @section @code{.altmacro}
4416 Enable alternate macro mode, enabling:
4419 @item LOCAL @var{name} [ , @dots{} ]
4420 One additional directive, @code{LOCAL}, is available. It is used to
4421 generate a string replacement for each of the @var{name} arguments, and
4422 replace any instances of @var{name} in each macro expansion. The
4423 replacement string is unique in the assembly, and different for each
4424 separate macro expansion. @code{LOCAL} allows you to write macros that
4425 define symbols, without fear of conflict between separate macro expansions.
4427 @item String delimiters
4428 You can write strings delimited in these other ways besides
4429 @code{"@var{string}"}:
4432 @item '@var{string}'
4433 You can delimit strings with single-quote characters.
4435 @item <@var{string}>
4436 You can delimit strings with matching angle brackets.
4439 @item single-character string escape
4440 To include any single character literally in a string (even if the
4441 character would otherwise have some special meaning), you can prefix the
4442 character with @samp{!} (an exclamation mark). For example, you can
4443 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4445 @item Expression results as strings
4446 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4447 and use the result as a string.
4451 @section @code{.ascii "@var{string}"}@dots{}
4453 @cindex @code{ascii} directive
4454 @cindex string literals
4455 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4456 separated by commas. It assembles each string (with no automatic
4457 trailing zero byte) into consecutive addresses.
4460 @section @code{.asciz "@var{string}"}@dots{}
4462 @cindex @code{asciz} directive
4463 @cindex zero-terminated strings
4464 @cindex null-terminated strings
4465 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4466 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4469 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4471 @cindex padding the location counter given number of bytes
4472 @cindex @code{balign} directive
4473 Pad the location counter (in the current subsection) to a particular
4474 storage boundary. The first expression (which must be absolute) is the
4475 alignment request in bytes. For example @samp{.balign 8} advances
4476 the location counter until it is a multiple of 8. If the location counter
4477 is already a multiple of 8, no change is needed.
4479 The second expression (also absolute) gives the fill value to be stored in the
4480 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4481 padding bytes are normally zero. However, on some systems, if the section is
4482 marked as containing code and the fill value is omitted, the space is filled
4483 with no-op instructions.
4485 The third expression is also absolute, and is also optional. If it is present,
4486 it is the maximum number of bytes that should be skipped by this alignment
4487 directive. If doing the alignment would require skipping more bytes than the
4488 specified maximum, then the alignment is not done at all. You can omit the
4489 fill value (the second argument) entirely by simply using two commas after the
4490 required alignment; this can be useful if you want the alignment to be filled
4491 with no-op instructions when appropriate.
4493 @cindex @code{balignw} directive
4494 @cindex @code{balignl} directive
4495 The @code{.balignw} and @code{.balignl} directives are variants of the
4496 @code{.balign} directive. The @code{.balignw} directive treats the fill
4497 pattern as a two byte word value. The @code{.balignl} directives treats the
4498 fill pattern as a four byte longword value. For example, @code{.balignw
4499 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4500 filled in with the value 0x368d (the exact placement of the bytes depends upon
4501 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4504 @node Bundle directives
4505 @section @code{.bundle_align_mode @var{abs-expr}}
4506 @cindex @code{bundle_align_mode} directive
4508 @cindex instruction bundle
4509 @cindex aligned instruction bundle
4510 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4511 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4512 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4513 disabled (which is the default state). If the argument it not zero, it
4514 gives the size of an instruction bundle as a power of two (as for the
4515 @code{.p2align} directive, @pxref{P2align}).
4517 For some targets, it's an ABI requirement that no instruction may span a
4518 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4519 instructions that starts on an aligned boundary. For example, if
4520 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4521 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4522 effect, no single instruction may span a boundary between bundles. If an
4523 instruction would start too close to the end of a bundle for the length of
4524 that particular instruction to fit within the bundle, then the space at the
4525 end of that bundle is filled with no-op instructions so the instruction
4526 starts in the next bundle. As a corollary, it's an error if any single
4527 instruction's encoding is longer than the bundle size.
4529 @section @code{.bundle_lock} and @code{.bundle_unlock}
4530 @cindex @code{bundle_lock} directive
4531 @cindex @code{bundle_unlock} directive
4532 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4533 allow explicit control over instruction bundle padding. These directives
4534 are only valid when @code{.bundle_align_mode} has been used to enable
4535 aligned instruction bundle mode. It's an error if they appear when
4536 @code{.bundle_align_mode} has not been used at all, or when the last
4537 directive was @w{@code{.bundle_align_mode 0}}.
4539 @cindex bundle-locked
4540 For some targets, it's an ABI requirement that certain instructions may
4541 appear only as part of specified permissible sequences of multiple
4542 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4543 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4544 instruction sequence. For purposes of aligned instruction bundle mode, a
4545 sequence starting with @code{.bundle_lock} and ending with
4546 @code{.bundle_unlock} is treated as a single instruction. That is, the
4547 entire sequence must fit into a single bundle and may not span a bundle
4548 boundary. If necessary, no-op instructions will be inserted before the
4549 first instruction of the sequence so that the whole sequence starts on an
4550 aligned bundle boundary. It's an error if the sequence is longer than the
4553 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4554 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4555 nested. That is, a second @code{.bundle_lock} directive before the next
4556 @code{.bundle_unlock} directive has no effect except that it must be
4557 matched by another closing @code{.bundle_unlock} so that there is the
4558 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4561 @section @code{.byte @var{expressions}}
4563 @cindex @code{byte} directive
4564 @cindex integers, one byte
4565 @code{.byte} expects zero or more expressions, separated by commas.
4566 Each expression is assembled into the next byte.
4568 @node CFI directives
4569 @section @code{.cfi_sections @var{section_list}}
4570 @cindex @code{cfi_sections} directive
4571 @code{.cfi_sections} may be used to specify whether CFI directives
4572 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4573 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4574 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4575 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4576 directive is not used is @code{.cfi_sections .eh_frame}.
4578 @section @code{.cfi_startproc [simple]}
4579 @cindex @code{cfi_startproc} directive
4580 @code{.cfi_startproc} is used at the beginning of each function that
4581 should have an entry in @code{.eh_frame}. It initializes some internal
4582 data structures. Don't forget to close the function by
4583 @code{.cfi_endproc}.
4585 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4586 it also emits some architecture dependent initial CFI instructions.
4588 @section @code{.cfi_endproc}
4589 @cindex @code{cfi_endproc} directive
4590 @code{.cfi_endproc} is used at the end of a function where it closes its
4591 unwind entry previously opened by
4592 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4594 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4595 @code{.cfi_personality} defines personality routine and its encoding.
4596 @var{encoding} must be a constant determining how the personality
4597 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4598 argument is not present, otherwise second argument should be
4599 a constant or a symbol name. When using indirect encodings,
4600 the symbol provided should be the location where personality
4601 can be loaded from, not the personality routine itself.
4602 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4603 no personality routine.
4605 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4606 @code{.cfi_lsda} defines LSDA and its encoding.
4607 @var{encoding} must be a constant determining how the LSDA
4608 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4609 argument is not present, otherwise second argument should be a constant
4610 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4613 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4614 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4615 address from @var{register} and add @var{offset} to it}.
4617 @section @code{.cfi_def_cfa_register @var{register}}
4618 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4619 now on @var{register} will be used instead of the old one. Offset
4622 @section @code{.cfi_def_cfa_offset @var{offset}}
4623 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4624 remains the same, but @var{offset} is new. Note that it is the
4625 absolute offset that will be added to a defined register to compute
4628 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4629 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4630 value that is added/substracted from the previous offset.
4632 @section @code{.cfi_offset @var{register}, @var{offset}}
4633 Previous value of @var{register} is saved at offset @var{offset} from
4636 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4637 Previous value of @var{register} is saved at offset @var{offset} from
4638 the current CFA register. This is transformed to @code{.cfi_offset}
4639 using the known displacement of the CFA register from the CFA.
4640 This is often easier to use, because the number will match the
4641 code it's annotating.
4643 @section @code{.cfi_register @var{register1}, @var{register2}}
4644 Previous value of @var{register1} is saved in register @var{register2}.
4646 @section @code{.cfi_restore @var{register}}
4647 @code{.cfi_restore} says that the rule for @var{register} is now the
4648 same as it was at the beginning of the function, after all initial
4649 instruction added by @code{.cfi_startproc} were executed.
4651 @section @code{.cfi_undefined @var{register}}
4652 From now on the previous value of @var{register} can't be restored anymore.
4654 @section @code{.cfi_same_value @var{register}}
4655 Current value of @var{register} is the same like in the previous frame,
4656 i.e. no restoration needed.
4658 @section @code{.cfi_remember_state},
4659 First save all current rules for all registers by @code{.cfi_remember_state},
4660 then totally screw them up by subsequent @code{.cfi_*} directives and when
4661 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4662 the previous saved state.
4664 @section @code{.cfi_return_column @var{register}}
4665 Change return column @var{register}, i.e. the return address is either
4666 directly in @var{register} or can be accessed by rules for @var{register}.
4668 @section @code{.cfi_signal_frame}
4669 Mark current function as signal trampoline.
4671 @section @code{.cfi_window_save}
4672 SPARC register window has been saved.
4674 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4675 Allows the user to add arbitrary bytes to the unwind info. One
4676 might use this to add OS-specific CFI opcodes, or generic CFI
4677 opcodes that GAS does not yet support.
4679 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4680 The current value of @var{register} is @var{label}. The value of @var{label}
4681 will be encoded in the output file according to @var{encoding}; see the
4682 description of @code{.cfi_personality} for details on this encoding.
4684 The usefulness of equating a register to a fixed label is probably
4685 limited to the return address register. Here, it can be useful to
4686 mark a code segment that has only one return address which is reached
4687 by a direct branch and no copy of the return address exists in memory
4688 or another register.
4691 @section @code{.comm @var{symbol} , @var{length} }
4693 @cindex @code{comm} directive
4694 @cindex symbol, common
4695 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4696 common symbol in one object file may be merged with a defined or common symbol
4697 of the same name in another object file. If @code{@value{LD}} does not see a
4698 definition for the symbol--just one or more common symbols--then it will
4699 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4700 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4701 the same name, and they do not all have the same size, it will allocate space
4702 using the largest size.
4705 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4706 an optional third argument. This is the desired alignment of the symbol,
4707 specified for ELF as a byte boundary (for example, an alignment of 16 means
4708 that the least significant 4 bits of the address should be zero), and for PE
4709 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4710 boundary). The alignment must be an absolute expression, and it must be a
4711 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4712 common symbol, it will use the alignment when placing the symbol. If no
4713 alignment is specified, @command{@value{AS}} will set the alignment to the
4714 largest power of two less than or equal to the size of the symbol, up to a
4715 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4716 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4717 @samp{--section-alignment} option; image file sections in PE are aligned to
4718 multiples of 4096, which is far too large an alignment for ordinary variables.
4719 It is rather the default alignment for (non-debug) sections within object
4720 (@samp{*.o}) files, which are less strictly aligned.}.
4724 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4725 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4729 @section @code{.data @var{subsection}}
4731 @cindex @code{data} directive
4732 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4733 end of the data subsection numbered @var{subsection} (which is an
4734 absolute expression). If @var{subsection} is omitted, it defaults
4739 @section @code{.def @var{name}}
4741 @cindex @code{def} directive
4742 @cindex COFF symbols, debugging
4743 @cindex debugging COFF symbols
4744 Begin defining debugging information for a symbol @var{name}; the
4745 definition extends until the @code{.endef} directive is encountered.
4748 This directive is only observed when @command{@value{AS}} is configured for COFF
4749 format output; when producing @code{b.out}, @samp{.def} is recognized,
4756 @section @code{.desc @var{symbol}, @var{abs-expression}}
4758 @cindex @code{desc} directive
4759 @cindex COFF symbol descriptor
4760 @cindex symbol descriptor, COFF
4761 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4762 to the low 16 bits of an absolute expression.
4765 The @samp{.desc} directive is not available when @command{@value{AS}} is
4766 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4767 object format. For the sake of compatibility, @command{@value{AS}} accepts
4768 it, but produces no output, when configured for COFF.
4774 @section @code{.dim}
4776 @cindex @code{dim} directive
4777 @cindex COFF auxiliary symbol information
4778 @cindex auxiliary symbol information, COFF
4779 This directive is generated by compilers to include auxiliary debugging
4780 information in the symbol table. It is only permitted inside
4781 @code{.def}/@code{.endef} pairs.
4784 @samp{.dim} is only meaningful when generating COFF format output; when
4785 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4791 @section @code{.double @var{flonums}}
4793 @cindex @code{double} directive
4794 @cindex floating point numbers (double)
4795 @code{.double} expects zero or more flonums, separated by commas. It
4796 assembles floating point numbers.
4798 The exact kind of floating point numbers emitted depends on how
4799 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4803 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4804 in @sc{ieee} format.
4809 @section @code{.eject}
4811 @cindex @code{eject} directive
4812 @cindex new page, in listings
4813 @cindex page, in listings
4814 @cindex listing control: new page
4815 Force a page break at this point, when generating assembly listings.
4818 @section @code{.else}
4820 @cindex @code{else} directive
4821 @code{.else} is part of the @command{@value{AS}} support for conditional
4822 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4823 of code to be assembled if the condition for the preceding @code{.if}
4827 @section @code{.elseif}
4829 @cindex @code{elseif} directive
4830 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4831 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4832 @code{.if} block that would otherwise fill the entire @code{.else} section.
4835 @section @code{.end}
4837 @cindex @code{end} directive
4838 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4839 process anything in the file past the @code{.end} directive.
4843 @section @code{.endef}
4845 @cindex @code{endef} directive
4846 This directive flags the end of a symbol definition begun with
4850 @samp{.endef} is only meaningful when generating COFF format output; if
4851 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4852 directive but ignores it.
4857 @section @code{.endfunc}
4858 @cindex @code{endfunc} directive
4859 @code{.endfunc} marks the end of a function specified with @code{.func}.
4862 @section @code{.endif}
4864 @cindex @code{endif} directive
4865 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4866 it marks the end of a block of code that is only assembled
4867 conditionally. @xref{If,,@code{.if}}.
4870 @section @code{.equ @var{symbol}, @var{expression}}
4872 @cindex @code{equ} directive
4873 @cindex assigning values to symbols
4874 @cindex symbols, assigning values to
4875 This directive sets the value of @var{symbol} to @var{expression}.
4876 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4879 The syntax for @code{equ} on the HPPA is
4880 @samp{@var{symbol} .equ @var{expression}}.
4884 The syntax for @code{equ} on the Z80 is
4885 @samp{@var{symbol} equ @var{expression}}.
4886 On the Z80 it is an eror if @var{symbol} is already defined,
4887 but the symbol is not protected from later redefinition.
4888 Compare @ref{Equiv}.
4892 @section @code{.equiv @var{symbol}, @var{expression}}
4893 @cindex @code{equiv} directive
4894 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4895 the assembler will signal an error if @var{symbol} is already defined. Note a
4896 symbol which has been referenced but not actually defined is considered to be
4899 Except for the contents of the error message, this is roughly equivalent to
4906 plus it protects the symbol from later redefinition.
4909 @section @code{.eqv @var{symbol}, @var{expression}}
4910 @cindex @code{eqv} directive
4911 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4912 evaluate the expression or any part of it immediately. Instead each time
4913 the resulting symbol is used in an expression, a snapshot of its current
4917 @section @code{.err}
4918 @cindex @code{err} directive
4919 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4920 message and, unless the @option{-Z} option was used, it will not generate an
4921 object file. This can be used to signal an error in conditionally compiled code.
4924 @section @code{.error "@var{string}"}
4925 @cindex error directive
4927 Similarly to @code{.err}, this directive emits an error, but you can specify a
4928 string that will be emitted as the error message. If you don't specify the
4929 message, it defaults to @code{".error directive invoked in source file"}.
4930 @xref{Errors, ,Error and Warning Messages}.
4933 .error "This code has not been assembled and tested."
4937 @section @code{.exitm}
4938 Exit early from the current macro definition. @xref{Macro}.
4941 @section @code{.extern}
4943 @cindex @code{extern} directive
4944 @code{.extern} is accepted in the source program---for compatibility
4945 with other assemblers---but it is ignored. @command{@value{AS}} treats
4946 all undefined symbols as external.
4949 @section @code{.fail @var{expression}}
4951 @cindex @code{fail} directive
4952 Generates an error or a warning. If the value of the @var{expression} is 500
4953 or more, @command{@value{AS}} will print a warning message. If the value is less
4954 than 500, @command{@value{AS}} will print an error message. The message will
4955 include the value of @var{expression}. This can occasionally be useful inside
4956 complex nested macros or conditional assembly.
4959 @section @code{.file}
4960 @cindex @code{file} directive
4962 @ifclear no-file-dir
4963 There are two different versions of the @code{.file} directive. Targets
4964 that support DWARF2 line number information use the DWARF2 version of
4965 @code{.file}. Other targets use the default version.
4967 @subheading Default Version
4969 @cindex logical file name
4970 @cindex file name, logical
4971 This version of the @code{.file} directive tells @command{@value{AS}} that we
4972 are about to start a new logical file. The syntax is:
4978 @var{string} is the new file name. In general, the filename is
4979 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4980 to specify an empty file name, you must give the quotes--@code{""}. This
4981 statement may go away in future: it is only recognized to be compatible with
4982 old @command{@value{AS}} programs.
4984 @subheading DWARF2 Version
4987 When emitting DWARF2 line number information, @code{.file} assigns filenames
4988 to the @code{.debug_line} file name table. The syntax is:
4991 .file @var{fileno} @var{filename}
4994 The @var{fileno} operand should be a unique positive integer to use as the
4995 index of the entry in the table. The @var{filename} operand is a C string
4998 The detail of filename indices is exposed to the user because the filename
4999 table is shared with the @code{.debug_info} section of the DWARF2 debugging
5000 information, and thus the user must know the exact indices that table
5004 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
5006 @cindex @code{fill} directive
5007 @cindex writing patterns in memory
5008 @cindex patterns, writing in memory
5009 @var{repeat}, @var{size} and @var{value} are absolute expressions.
5010 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
5011 may be zero or more. @var{Size} may be zero or more, but if it is
5012 more than 8, then it is deemed to have the value 8, compatible with
5013 other people's assemblers. The contents of each @var{repeat} bytes
5014 is taken from an 8-byte number. The highest order 4 bytes are
5015 zero. The lowest order 4 bytes are @var{value} rendered in the
5016 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
5017 Each @var{size} bytes in a repetition is taken from the lowest order
5018 @var{size} bytes of this number. Again, this bizarre behavior is
5019 compatible with other people's assemblers.
5021 @var{size} and @var{value} are optional.
5022 If the second comma and @var{value} are absent, @var{value} is
5023 assumed zero. If the first comma and following tokens are absent,
5024 @var{size} is assumed to be 1.
5027 @section @code{.float @var{flonums}}
5029 @cindex floating point numbers (single)
5030 @cindex @code{float} directive
5031 This directive assembles zero or more flonums, separated by commas. It
5032 has the same effect as @code{.single}.
5034 The exact kind of floating point numbers emitted depends on how
5035 @command{@value{AS}} is configured.
5036 @xref{Machine Dependencies}.
5040 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
5041 in @sc{ieee} format.
5046 @section @code{.func @var{name}[,@var{label}]}
5047 @cindex @code{func} directive
5048 @code{.func} emits debugging information to denote function @var{name}, and
5049 is ignored unless the file is assembled with debugging enabled.
5050 Only @samp{--gstabs[+]} is currently supported.
5051 @var{label} is the entry point of the function and if omitted @var{name}
5052 prepended with the @samp{leading char} is used.
5053 @samp{leading char} is usually @code{_} or nothing, depending on the target.
5054 All functions are currently defined to have @code{void} return type.
5055 The function must be terminated with @code{.endfunc}.
5058 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
5060 @cindex @code{global} directive
5061 @cindex symbol, making visible to linker
5062 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
5063 @var{symbol} in your partial program, its value is made available to
5064 other partial programs that are linked with it. Otherwise,
5065 @var{symbol} takes its attributes from a symbol of the same name
5066 from another file linked into the same program.
5068 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
5069 compatibility with other assemblers.
5072 On the HPPA, @code{.global} is not always enough to make it accessible to other
5073 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
5074 @xref{HPPA Directives, ,HPPA Assembler Directives}.
5079 @section @code{.gnu_attribute @var{tag},@var{value}}
5080 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
5083 @section @code{.hidden @var{names}}
5085 @cindex @code{hidden} directive
5087 This is one of the ELF visibility directives. The other two are
5088 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
5089 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5091 This directive overrides the named symbols default visibility (which is set by
5092 their binding: local, global or weak). The directive sets the visibility to
5093 @code{hidden} which means that the symbols are not visible to other components.
5094 Such symbols are always considered to be @code{protected} as well.
5098 @section @code{.hword @var{expressions}}
5100 @cindex @code{hword} directive
5101 @cindex integers, 16-bit
5102 @cindex numbers, 16-bit
5103 @cindex sixteen bit integers
5104 This expects zero or more @var{expressions}, and emits
5105 a 16 bit number for each.
5108 This directive is a synonym for @samp{.short}; depending on the target
5109 architecture, it may also be a synonym for @samp{.word}.
5113 This directive is a synonym for @samp{.short}.
5116 This directive is a synonym for both @samp{.short} and @samp{.word}.
5121 @section @code{.ident}
5123 @cindex @code{ident} directive
5125 This directive is used by some assemblers to place tags in object files. The
5126 behavior of this directive varies depending on the target. When using the
5127 a.out object file format, @command{@value{AS}} simply accepts the directive for
5128 source-file compatibility with existing assemblers, but does not emit anything
5129 for it. When using COFF, comments are emitted to the @code{.comment} or
5130 @code{.rdata} section, depending on the target. When using ELF, comments are
5131 emitted to the @code{.comment} section.
5134 @section @code{.if @var{absolute expression}}
5136 @cindex conditional assembly
5137 @cindex @code{if} directive
5138 @code{.if} marks the beginning of a section of code which is only
5139 considered part of the source program being assembled if the argument
5140 (which must be an @var{absolute expression}) is non-zero. The end of
5141 the conditional section of code must be marked by @code{.endif}
5142 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5143 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5144 If you have several conditions to check, @code{.elseif} may be used to avoid
5145 nesting blocks if/else within each subsequent @code{.else} block.
5147 The following variants of @code{.if} are also supported:
5149 @cindex @code{ifdef} directive
5150 @item .ifdef @var{symbol}
5151 Assembles the following section of code if the specified @var{symbol}
5152 has been defined. Note a symbol which has been referenced but not yet defined
5153 is considered to be undefined.
5155 @cindex @code{ifb} directive
5156 @item .ifb @var{text}
5157 Assembles the following section of code if the operand is blank (empty).
5159 @cindex @code{ifc} directive
5160 @item .ifc @var{string1},@var{string2}
5161 Assembles the following section of code if the two strings are the same. The
5162 strings may be optionally quoted with single quotes. If they are not quoted,
5163 the first string stops at the first comma, and the second string stops at the
5164 end of the line. Strings which contain whitespace should be quoted. The
5165 string comparison is case sensitive.
5167 @cindex @code{ifeq} directive
5168 @item .ifeq @var{absolute expression}
5169 Assembles the following section of code if the argument is zero.
5171 @cindex @code{ifeqs} directive
5172 @item .ifeqs @var{string1},@var{string2}
5173 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5175 @cindex @code{ifge} directive
5176 @item .ifge @var{absolute expression}
5177 Assembles the following section of code if the argument is greater than or
5180 @cindex @code{ifgt} directive
5181 @item .ifgt @var{absolute expression}
5182 Assembles the following section of code if the argument is greater than zero.
5184 @cindex @code{ifle} directive
5185 @item .ifle @var{absolute expression}
5186 Assembles the following section of code if the argument is less than or equal
5189 @cindex @code{iflt} directive
5190 @item .iflt @var{absolute expression}
5191 Assembles the following section of code if the argument is less than zero.
5193 @cindex @code{ifnb} directive
5194 @item .ifnb @var{text}
5195 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5196 following section of code if the operand is non-blank (non-empty).
5198 @cindex @code{ifnc} directive
5199 @item .ifnc @var{string1},@var{string2}.
5200 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5201 following section of code if the two strings are not the same.
5203 @cindex @code{ifndef} directive
5204 @cindex @code{ifnotdef} directive
5205 @item .ifndef @var{symbol}
5206 @itemx .ifnotdef @var{symbol}
5207 Assembles the following section of code if the specified @var{symbol}
5208 has not been defined. Both spelling variants are equivalent. Note a symbol
5209 which has been referenced but not yet defined is considered to be undefined.
5211 @cindex @code{ifne} directive
5212 @item .ifne @var{absolute expression}
5213 Assembles the following section of code if the argument is not equal to zero
5214 (in other words, this is equivalent to @code{.if}).
5216 @cindex @code{ifnes} directive
5217 @item .ifnes @var{string1},@var{string2}
5218 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5219 following section of code if the two strings are not the same.
5223 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5225 @cindex @code{incbin} directive
5226 @cindex binary files, including
5227 The @code{incbin} directive includes @var{file} verbatim at the current
5228 location. You can control the search paths used with the @samp{-I} command-line
5229 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5232 The @var{skip} argument skips a number of bytes from the start of the
5233 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5234 read. Note that the data is not aligned in any way, so it is the user's
5235 responsibility to make sure that proper alignment is provided both before and
5236 after the @code{incbin} directive.
5239 @section @code{.include "@var{file}"}
5241 @cindex @code{include} directive
5242 @cindex supporting files, including
5243 @cindex files, including
5244 This directive provides a way to include supporting files at specified
5245 points in your source program. The code from @var{file} is assembled as
5246 if it followed the point of the @code{.include}; when the end of the
5247 included file is reached, assembly of the original file continues. You
5248 can control the search paths used with the @samp{-I} command-line option
5249 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5253 @section @code{.int @var{expressions}}
5255 @cindex @code{int} directive
5256 @cindex integers, 32-bit
5257 Expect zero or more @var{expressions}, of any section, separated by commas.
5258 For each expression, emit a number that, at run time, is the value of that
5259 expression. The byte order and bit size of the number depends on what kind
5260 of target the assembly is for.
5264 On most forms of the H8/300, @code{.int} emits 16-bit
5265 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5272 @section @code{.internal @var{names}}
5274 @cindex @code{internal} directive
5276 This is one of the ELF visibility directives. The other two are
5277 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5278 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5280 This directive overrides the named symbols default visibility (which is set by
5281 their binding: local, global or weak). The directive sets the visibility to
5282 @code{internal} which means that the symbols are considered to be @code{hidden}
5283 (i.e., not visible to other components), and that some extra, processor specific
5284 processing must also be performed upon the symbols as well.
5288 @section @code{.irp @var{symbol},@var{values}}@dots{}
5290 @cindex @code{irp} directive
5291 Evaluate a sequence of statements assigning different values to @var{symbol}.
5292 The sequence of statements starts at the @code{.irp} directive, and is
5293 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5294 set to @var{value}, and the sequence of statements is assembled. If no
5295 @var{value} is listed, the sequence of statements is assembled once, with
5296 @var{symbol} set to the null string. To refer to @var{symbol} within the
5297 sequence of statements, use @var{\symbol}.
5299 For example, assembling
5307 is equivalent to assembling
5315 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5318 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5320 @cindex @code{irpc} directive
5321 Evaluate a sequence of statements assigning different values to @var{symbol}.
5322 The sequence of statements starts at the @code{.irpc} directive, and is
5323 terminated by an @code{.endr} directive. For each character in @var{value},
5324 @var{symbol} is set to the character, and the sequence of statements is
5325 assembled. If no @var{value} is listed, the sequence of statements is
5326 assembled once, with @var{symbol} set to the null string. To refer to
5327 @var{symbol} within the sequence of statements, use @var{\symbol}.
5329 For example, assembling
5337 is equivalent to assembling
5345 For some caveats with the spelling of @var{symbol}, see also the discussion
5349 @section @code{.lcomm @var{symbol} , @var{length}}
5351 @cindex @code{lcomm} directive
5352 @cindex local common symbols
5353 @cindex symbols, local common
5354 Reserve @var{length} (an absolute expression) bytes for a local common
5355 denoted by @var{symbol}. The section and value of @var{symbol} are
5356 those of the new local common. The addresses are allocated in the bss
5357 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5358 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5359 not visible to @code{@value{LD}}.
5362 Some targets permit a third argument to be used with @code{.lcomm}. This
5363 argument specifies the desired alignment of the symbol in the bss section.
5367 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5368 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5372 @section @code{.lflags}
5374 @cindex @code{lflags} directive (ignored)
5375 @command{@value{AS}} accepts this directive, for compatibility with other
5376 assemblers, but ignores it.
5378 @ifclear no-line-dir
5380 @section @code{.line @var{line-number}}
5382 @cindex @code{line} directive
5383 @cindex logical line number
5385 Change the logical line number. @var{line-number} must be an absolute
5386 expression. The next line has that logical line number. Therefore any other
5387 statements on the current line (after a statement separator character) are
5388 reported as on logical line number @var{line-number} @minus{} 1. One day
5389 @command{@value{AS}} will no longer support this directive: it is recognized only
5390 for compatibility with existing assembler programs.
5393 Even though this is a directive associated with the @code{a.out} or
5394 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5395 when producing COFF output, and treats @samp{.line} as though it
5396 were the COFF @samp{.ln} @emph{if} it is found outside a
5397 @code{.def}/@code{.endef} pair.
5399 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5400 used by compilers to generate auxiliary symbol information for
5405 @section @code{.linkonce [@var{type}]}
5407 @cindex @code{linkonce} directive
5408 @cindex common sections
5409 Mark the current section so that the linker only includes a single copy of it.
5410 This may be used to include the same section in several different object files,
5411 but ensure that the linker will only include it once in the final output file.
5412 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5413 Duplicate sections are detected based on the section name, so it should be
5416 This directive is only supported by a few object file formats; as of this
5417 writing, the only object file format which supports it is the Portable
5418 Executable format used on Windows NT.
5420 The @var{type} argument is optional. If specified, it must be one of the
5421 following strings. For example:
5425 Not all types may be supported on all object file formats.
5429 Silently discard duplicate sections. This is the default.
5432 Warn if there are duplicate sections, but still keep only one copy.
5435 Warn if any of the duplicates have different sizes.
5438 Warn if any of the duplicates do not have exactly the same contents.
5442 @section @code{.list}
5444 @cindex @code{list} directive
5445 @cindex listing control, turning on
5446 Control (in conjunction with the @code{.nolist} directive) whether or
5447 not assembly listings are generated. These two directives maintain an
5448 internal counter (which is zero initially). @code{.list} increments the
5449 counter, and @code{.nolist} decrements it. Assembly listings are
5450 generated whenever the counter is greater than zero.
5452 By default, listings are disabled. When you enable them (with the
5453 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5454 the initial value of the listing counter is one.
5457 @section @code{.ln @var{line-number}}
5459 @cindex @code{ln} directive
5460 @ifclear no-line-dir
5461 @samp{.ln} is a synonym for @samp{.line}.
5464 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5465 must be an absolute expression. The next line has that logical
5466 line number, so any other statements on the current line (after a
5467 statement separator character @code{;}) are reported as on logical
5468 line number @var{line-number} @minus{} 1.
5471 This directive is accepted, but ignored, when @command{@value{AS}} is
5472 configured for @code{b.out}; its effect is only associated with COFF
5478 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5479 @cindex @code{loc} directive
5480 When emitting DWARF2 line number information,
5481 the @code{.loc} directive will add a row to the @code{.debug_line} line
5482 number matrix corresponding to the immediately following assembly
5483 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5484 arguments will be applied to the @code{.debug_line} state machine before
5487 The @var{options} are a sequence of the following tokens in any order:
5491 This option will set the @code{basic_block} register in the
5492 @code{.debug_line} state machine to @code{true}.
5495 This option will set the @code{prologue_end} register in the
5496 @code{.debug_line} state machine to @code{true}.
5498 @item epilogue_begin
5499 This option will set the @code{epilogue_begin} register in the
5500 @code{.debug_line} state machine to @code{true}.
5502 @item is_stmt @var{value}
5503 This option will set the @code{is_stmt} register in the
5504 @code{.debug_line} state machine to @code{value}, which must be
5507 @item isa @var{value}
5508 This directive will set the @code{isa} register in the @code{.debug_line}
5509 state machine to @var{value}, which must be an unsigned integer.
5511 @item discriminator @var{value}
5512 This directive will set the @code{discriminator} register in the @code{.debug_line}
5513 state machine to @var{value}, which must be an unsigned integer.
5517 @node Loc_mark_labels
5518 @section @code{.loc_mark_labels @var{enable}}
5519 @cindex @code{loc_mark_labels} directive
5520 When emitting DWARF2 line number information,
5521 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5522 to the @code{.debug_line} line number matrix with the @code{basic_block}
5523 register in the state machine set whenever a code label is seen.
5524 The @var{enable} argument should be either 1 or 0, to enable or disable
5525 this function respectively.
5529 @section @code{.local @var{names}}
5531 @cindex @code{local} directive
5532 This directive, which is available for ELF targets, marks each symbol in
5533 the comma-separated list of @code{names} as a local symbol so that it
5534 will not be externally visible. If the symbols do not already exist,
5535 they will be created.
5537 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5538 accept an alignment argument, which is the case for most ELF targets,
5539 the @code{.local} directive can be used in combination with @code{.comm}
5540 (@pxref{Comm}) to define aligned local common data.
5544 @section @code{.long @var{expressions}}
5546 @cindex @code{long} directive
5547 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5550 @c no one seems to know what this is for or whether this description is
5551 @c what it really ought to do
5553 @section @code{.lsym @var{symbol}, @var{expression}}
5555 @cindex @code{lsym} directive
5556 @cindex symbol, not referenced in assembly
5557 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5558 the hash table, ensuring it cannot be referenced by name during the
5559 rest of the assembly. This sets the attributes of the symbol to be
5560 the same as the expression value:
5562 @var{other} = @var{descriptor} = 0
5563 @var{type} = @r{(section of @var{expression})}
5564 @var{value} = @var{expression}
5567 The new symbol is not flagged as external.
5571 @section @code{.macro}
5574 The commands @code{.macro} and @code{.endm} allow you to define macros that
5575 generate assembly output. For example, this definition specifies a macro
5576 @code{sum} that puts a sequence of numbers into memory:
5579 .macro sum from=0, to=5
5588 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5600 @item .macro @var{macname}
5601 @itemx .macro @var{macname} @var{macargs} @dots{}
5602 @cindex @code{macro} directive
5603 Begin the definition of a macro called @var{macname}. If your macro
5604 definition requires arguments, specify their names after the macro name,
5605 separated by commas or spaces. You can qualify the macro argument to
5606 indicate whether all invocations must specify a non-blank value (through
5607 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5608 (through @samp{:@code{vararg}}). You can supply a default value for any
5609 macro argument by following the name with @samp{=@var{deflt}}. You
5610 cannot define two macros with the same @var{macname} unless it has been
5611 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5612 definitions. For example, these are all valid @code{.macro} statements:
5616 Begin the definition of a macro called @code{comm}, which takes no
5619 @item .macro plus1 p, p1
5620 @itemx .macro plus1 p p1
5621 Either statement begins the definition of a macro called @code{plus1},
5622 which takes two arguments; within the macro definition, write
5623 @samp{\p} or @samp{\p1} to evaluate the arguments.
5625 @item .macro reserve_str p1=0 p2
5626 Begin the definition of a macro called @code{reserve_str}, with two
5627 arguments. The first argument has a default value, but not the second.
5628 After the definition is complete, you can call the macro either as
5629 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5630 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5631 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5632 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5634 @item .macro m p1:req, p2=0, p3:vararg
5635 Begin the definition of a macro called @code{m}, with at least three
5636 arguments. The first argument must always have a value specified, but
5637 not the second, which instead has a default value. The third formal
5638 will get assigned all remaining arguments specified at invocation time.
5640 When you call a macro, you can specify the argument values either by
5641 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5642 @samp{sum to=17, from=9}.
5646 Note that since each of the @var{macargs} can be an identifier exactly
5647 as any other one permitted by the target architecture, there may be
5648 occasional problems if the target hand-crafts special meanings to certain
5649 characters when they occur in a special position. For example, if the colon
5650 (@code{:}) is generally permitted to be part of a symbol name, but the
5651 architecture specific code special-cases it when occurring as the final
5652 character of a symbol (to denote a label), then the macro parameter
5653 replacement code will have no way of knowing that and consider the whole
5654 construct (including the colon) an identifier, and check only this
5655 identifier for being the subject to parameter substitution. So for example
5656 this macro definition:
5664 might not work as expected. Invoking @samp{label foo} might not create a label
5665 called @samp{foo} but instead just insert the text @samp{\l:} into the
5666 assembler source, probably generating an error about an unrecognised
5669 Similarly problems might occur with the period character (@samp{.})
5670 which is often allowed inside opcode names (and hence identifier names). So
5671 for example constructing a macro to build an opcode from a base name and a
5672 length specifier like this:
5675 .macro opcode base length
5680 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5681 instruction but instead generate some kind of error as the assembler tries to
5682 interpret the text @samp{\base.\length}.
5684 There are several possible ways around this problem:
5687 @item Insert white space
5688 If it is possible to use white space characters then this is the simplest
5697 @item Use @samp{\()}
5698 The string @samp{\()} can be used to separate the end of a macro argument from
5699 the following text. eg:
5702 .macro opcode base length
5707 @item Use the alternate macro syntax mode
5708 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5709 used as a separator. eg:
5719 Note: this problem of correctly identifying string parameters to pseudo ops
5720 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5721 and @code{.irpc} (@pxref{Irpc}) as well.
5724 @cindex @code{endm} directive
5725 Mark the end of a macro definition.
5728 @cindex @code{exitm} directive
5729 Exit early from the current macro definition.
5731 @cindex number of macros executed
5732 @cindex macros, count executed
5734 @command{@value{AS}} maintains a counter of how many macros it has
5735 executed in this pseudo-variable; you can copy that number to your
5736 output with @samp{\@@}, but @emph{only within a macro definition}.
5738 @item LOCAL @var{name} [ , @dots{} ]
5739 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5740 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5741 @xref{Altmacro,,@code{.altmacro}}.
5745 @section @code{.mri @var{val}}
5747 @cindex @code{mri} directive
5748 @cindex MRI mode, temporarily
5749 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5750 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5751 affects code assembled until the next @code{.mri} directive, or until the end
5752 of the file. @xref{M, MRI mode, MRI mode}.
5755 @section @code{.noaltmacro}
5756 Disable alternate macro mode. @xref{Altmacro}.
5759 @section @code{.nolist}
5761 @cindex @code{nolist} directive
5762 @cindex listing control, turning off
5763 Control (in conjunction with the @code{.list} directive) whether or
5764 not assembly listings are generated. These two directives maintain an
5765 internal counter (which is zero initially). @code{.list} increments the
5766 counter, and @code{.nolist} decrements it. Assembly listings are
5767 generated whenever the counter is greater than zero.
5770 @section @code{.octa @var{bignums}}
5772 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5773 @cindex @code{octa} directive
5774 @cindex integer, 16-byte
5775 @cindex sixteen byte integer
5776 This directive expects zero or more bignums, separated by commas. For each
5777 bignum, it emits a 16-byte integer.
5779 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5780 hence @emph{octa}-word for 16 bytes.
5783 @section @code{.offset @var{loc}}
5785 @cindex @code{offset} directive
5786 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5787 be an absolute expression. This directive may be useful for defining
5788 symbols with absolute values. Do not confuse it with the @code{.org}
5792 @section @code{.org @var{new-lc} , @var{fill}}
5794 @cindex @code{org} directive
5795 @cindex location counter, advancing
5796 @cindex advancing location counter
5797 @cindex current address, advancing
5798 Advance the location counter of the current section to
5799 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5800 expression with the same section as the current subsection. That is,
5801 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5802 wrong section, the @code{.org} directive is ignored. To be compatible
5803 with former assemblers, if the section of @var{new-lc} is absolute,
5804 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5805 is the same as the current subsection.
5807 @code{.org} may only increase the location counter, or leave it
5808 unchanged; you cannot use @code{.org} to move the location counter
5811 @c double negative used below "not undefined" because this is a specific
5812 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5813 @c section. doc@cygnus.com 18feb91
5814 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5815 may not be undefined. If you really detest this restriction we eagerly await
5816 a chance to share your improved assembler.
5818 Beware that the origin is relative to the start of the section, not
5819 to the start of the subsection. This is compatible with other
5820 people's assemblers.
5822 When the location counter (of the current subsection) is advanced, the
5823 intervening bytes are filled with @var{fill} which should be an
5824 absolute expression. If the comma and @var{fill} are omitted,
5825 @var{fill} defaults to zero.
5828 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5830 @cindex padding the location counter given a power of two
5831 @cindex @code{p2align} directive
5832 Pad the location counter (in the current subsection) to a particular
5833 storage boundary. The first expression (which must be absolute) is the
5834 number of low-order zero bits the location counter must have after
5835 advancement. For example @samp{.p2align 3} advances the location
5836 counter until it a multiple of 8. If the location counter is already a
5837 multiple of 8, no change is needed.
5839 The second expression (also absolute) gives the fill value to be stored in the
5840 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5841 padding bytes are normally zero. However, on some systems, if the section is
5842 marked as containing code and the fill value is omitted, the space is filled
5843 with no-op instructions.
5845 The third expression is also absolute, and is also optional. If it is present,
5846 it is the maximum number of bytes that should be skipped by this alignment
5847 directive. If doing the alignment would require skipping more bytes than the
5848 specified maximum, then the alignment is not done at all. You can omit the
5849 fill value (the second argument) entirely by simply using two commas after the
5850 required alignment; this can be useful if you want the alignment to be filled
5851 with no-op instructions when appropriate.
5853 @cindex @code{p2alignw} directive
5854 @cindex @code{p2alignl} directive
5855 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5856 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5857 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5858 fill pattern as a four byte longword value. For example, @code{.p2alignw
5859 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5860 filled in with the value 0x368d (the exact placement of the bytes depends upon
5861 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5866 @section @code{.popsection}
5868 @cindex @code{popsection} directive
5869 @cindex Section Stack
5870 This is one of the ELF section stack manipulation directives. The others are
5871 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5872 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5875 This directive replaces the current section (and subsection) with the top
5876 section (and subsection) on the section stack. This section is popped off the
5882 @section @code{.previous}
5884 @cindex @code{previous} directive
5885 @cindex Section Stack
5886 This is one of the ELF section stack manipulation directives. The others are
5887 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5888 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5889 (@pxref{PopSection}).
5891 This directive swaps the current section (and subsection) with most recently
5892 referenced section/subsection pair prior to this one. Multiple
5893 @code{.previous} directives in a row will flip between two sections (and their
5894 subsections). For example:
5906 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5912 # Now in section A subsection 1
5916 # Now in section B subsection 0
5919 # Now in section B subsection 1
5922 # Now in section B subsection 0
5926 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5927 section B and 0x9abc into subsection 1 of section B.
5929 In terms of the section stack, this directive swaps the current section with
5930 the top section on the section stack.
5934 @section @code{.print @var{string}}
5936 @cindex @code{print} directive
5937 @command{@value{AS}} will print @var{string} on the standard output during
5938 assembly. You must put @var{string} in double quotes.
5942 @section @code{.protected @var{names}}
5944 @cindex @code{protected} directive
5946 This is one of the ELF visibility directives. The other two are
5947 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5949 This directive overrides the named symbols default visibility (which is set by
5950 their binding: local, global or weak). The directive sets the visibility to
5951 @code{protected} which means that any references to the symbols from within the
5952 components that defines them must be resolved to the definition in that
5953 component, even if a definition in another component would normally preempt
5958 @section @code{.psize @var{lines} , @var{columns}}
5960 @cindex @code{psize} directive
5961 @cindex listing control: paper size
5962 @cindex paper size, for listings
5963 Use this directive to declare the number of lines---and, optionally, the
5964 number of columns---to use for each page, when generating listings.
5966 If you do not use @code{.psize}, listings use a default line-count
5967 of 60. You may omit the comma and @var{columns} specification; the
5968 default width is 200 columns.
5970 @command{@value{AS}} generates formfeeds whenever the specified number of
5971 lines is exceeded (or whenever you explicitly request one, using
5974 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5975 those explicitly specified with @code{.eject}.
5978 @section @code{.purgem @var{name}}
5980 @cindex @code{purgem} directive
5981 Undefine the macro @var{name}, so that later uses of the string will not be
5982 expanded. @xref{Macro}.
5986 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5988 @cindex @code{pushsection} directive
5989 @cindex Section Stack
5990 This is one of the ELF section stack manipulation directives. The others are
5991 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5992 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5995 This directive pushes the current section (and subsection) onto the
5996 top of the section stack, and then replaces the current section and
5997 subsection with @code{name} and @code{subsection}. The optional
5998 @code{flags}, @code{type} and @code{arguments} are treated the same
5999 as in the @code{.section} (@pxref{Section}) directive.
6003 @section @code{.quad @var{bignums}}
6005 @cindex @code{quad} directive
6006 @code{.quad} expects zero or more bignums, separated by commas. For
6007 each bignum, it emits
6009 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
6010 warning message; and just takes the lowest order 8 bytes of the bignum.
6011 @cindex eight-byte integer
6012 @cindex integer, 8-byte
6014 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
6015 hence @emph{quad}-word for 8 bytes.
6018 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
6019 warning message; and just takes the lowest order 16 bytes of the bignum.
6020 @cindex sixteen-byte integer
6021 @cindex integer, 16-byte
6025 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
6027 @cindex @code{reloc} directive
6028 Generate a relocation at @var{offset} of type @var{reloc_name} with value
6029 @var{expression}. If @var{offset} is a number, the relocation is generated in
6030 the current section. If @var{offset} is an expression that resolves to a
6031 symbol plus offset, the relocation is generated in the given symbol's section.
6032 @var{expression}, if present, must resolve to a symbol plus addend or to an
6033 absolute value, but note that not all targets support an addend. e.g. ELF REL
6034 targets such as i386 store an addend in the section contents rather than in the
6035 relocation. This low level interface does not support addends stored in the
6039 @section @code{.rept @var{count}}
6041 @cindex @code{rept} directive
6042 Repeat the sequence of lines between the @code{.rept} directive and the next
6043 @code{.endr} directive @var{count} times.
6045 For example, assembling
6053 is equivalent to assembling
6062 @section @code{.sbttl "@var{subheading}"}
6064 @cindex @code{sbttl} directive
6065 @cindex subtitles for listings
6066 @cindex listing control: subtitle
6067 Use @var{subheading} as the title (third line, immediately after the
6068 title line) when generating assembly listings.
6070 This directive affects subsequent pages, as well as the current page if
6071 it appears within ten lines of the top of a page.
6075 @section @code{.scl @var{class}}
6077 @cindex @code{scl} directive
6078 @cindex symbol storage class (COFF)
6079 @cindex COFF symbol storage class
6080 Set the storage-class value for a symbol. This directive may only be
6081 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
6082 whether a symbol is static or external, or it may record further
6083 symbolic debugging information.
6086 The @samp{.scl} directive is primarily associated with COFF output; when
6087 configured to generate @code{b.out} output format, @command{@value{AS}}
6088 accepts this directive but ignores it.
6094 @section @code{.section @var{name}}
6096 @cindex named section
6097 Use the @code{.section} directive to assemble the following code into a section
6100 This directive is only supported for targets that actually support arbitrarily
6101 named sections; on @code{a.out} targets, for example, it is not accepted, even
6102 with a standard @code{a.out} section name.
6106 @c only print the extra heading if both COFF and ELF are set
6107 @subheading COFF Version
6110 @cindex @code{section} directive (COFF version)
6111 For COFF targets, the @code{.section} directive is used in one of the following
6115 .section @var{name}[, "@var{flags}"]
6116 .section @var{name}[, @var{subsection}]
6119 If the optional argument is quoted, it is taken as flags to use for the
6120 section. Each flag is a single character. The following flags are recognized:
6123 bss section (uninitialized data)
6125 section is not loaded
6131 exclude section from linking
6137 shared section (meaningful for PE targets)
6139 ignored. (For compatibility with the ELF version)
6141 section is not readable (meaningful for PE targets)
6143 single-digit power-of-two section alignment (GNU extension)
6146 If no flags are specified, the default flags depend upon the section name. If
6147 the section name is not recognized, the default will be for the section to be
6148 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6149 from the section, rather than adding them, so if they are used on their own it
6150 will be as if no flags had been specified at all.
6152 If the optional argument to the @code{.section} directive is not quoted, it is
6153 taken as a subsection number (@pxref{Sub-Sections}).
6158 @c only print the extra heading if both COFF and ELF are set
6159 @subheading ELF Version
6162 @cindex Section Stack
6163 This is one of the ELF section stack manipulation directives. The others are
6164 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6165 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6166 @code{.previous} (@pxref{Previous}).
6168 @cindex @code{section} directive (ELF version)
6169 For ELF targets, the @code{.section} directive is used like this:
6172 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6175 The optional @var{flags} argument is a quoted string which may contain any
6176 combination of the following characters:
6179 section is allocatable
6181 section is excluded from executable and shared library.
6185 section is executable
6187 section is mergeable
6189 section contains zero terminated strings
6191 section is a member of a section group
6193 section is used for thread-local-storage
6195 section is a member of the previously-current section's group, if any
6198 The optional @var{type} argument may contain one of the following constants:
6201 section contains data
6203 section does not contain data (i.e., section only occupies space)
6205 section contains data which is used by things other than the program
6207 section contains an array of pointers to init functions
6209 section contains an array of pointers to finish functions
6210 @item @@preinit_array
6211 section contains an array of pointers to pre-init functions
6214 Many targets only support the first three section types.
6216 Note on targets where the @code{@@} character is the start of a comment (eg
6217 ARM) then another character is used instead. For example the ARM port uses the
6220 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6221 be specified as well as an extra argument---@var{entsize}---like this:
6224 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6227 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6228 constants, each @var{entsize} octets long. Sections with both @code{M} and
6229 @code{S} must contain zero terminated strings where each character is
6230 @var{entsize} bytes long. The linker may remove duplicates within sections with
6231 the same name, same entity size and same flags. @var{entsize} must be an
6232 absolute expression. For sections with both @code{M} and @code{S}, a string
6233 which is a suffix of a larger string is considered a duplicate. Thus
6234 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6235 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6237 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6238 be present along with an additional field like this:
6241 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6244 The @var{GroupName} field specifies the name of the section group to which this
6245 particular section belongs. The optional linkage field can contain:
6248 indicates that only one copy of this section should be retained
6253 Note: if both the @var{M} and @var{G} flags are present then the fields for
6254 the Merge flag should come first, like this:
6257 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6260 If @var{flags} contains the @code{?} symbol then it may not also contain the
6261 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6262 present. Instead, @code{?} says to consider the section that's current before
6263 this directive. If that section used @code{G}, then the new section will use
6264 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6265 If not, then the @code{?} symbol has no effect.
6267 If no flags are specified, the default flags depend upon the section name. If
6268 the section name is not recognized, the default will be for the section to have
6269 none of the above flags: it will not be allocated in memory, nor writable, nor
6270 executable. The section will contain data.
6272 For ELF targets, the assembler supports another type of @code{.section}
6273 directive for compatibility with the Solaris assembler:
6276 .section "@var{name}"[, @var{flags}...]
6279 Note that the section name is quoted. There may be a sequence of comma
6283 section is allocatable
6287 section is executable
6289 section is excluded from executable and shared library.
6291 section is used for thread local storage
6294 This directive replaces the current section and subsection. See the
6295 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6296 some examples of how this directive and the other section stack directives
6302 @section @code{.set @var{symbol}, @var{expression}}
6304 @cindex @code{set} directive
6305 @cindex symbol value, setting
6306 Set the value of @var{symbol} to @var{expression}. This
6307 changes @var{symbol}'s value and type to conform to
6308 @var{expression}. If @var{symbol} was flagged as external, it remains
6309 flagged (@pxref{Symbol Attributes}).
6311 You may @code{.set} a symbol many times in the same assembly.
6313 If you @code{.set} a global symbol, the value stored in the object
6314 file is the last value stored into it.
6317 On Z80 @code{set} is a real instruction, use
6318 @samp{@var{symbol} defl @var{expression}} instead.
6322 @section @code{.short @var{expressions}}
6324 @cindex @code{short} directive
6326 @code{.short} is normally the same as @samp{.word}.
6327 @xref{Word,,@code{.word}}.
6329 In some configurations, however, @code{.short} and @code{.word} generate
6330 numbers of different lengths. @xref{Machine Dependencies}.
6334 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6337 This expects zero or more @var{expressions}, and emits
6338 a 16 bit number for each.
6343 @section @code{.single @var{flonums}}
6345 @cindex @code{single} directive
6346 @cindex floating point numbers (single)
6347 This directive assembles zero or more flonums, separated by commas. It
6348 has the same effect as @code{.float}.
6350 The exact kind of floating point numbers emitted depends on how
6351 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6355 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6356 numbers in @sc{ieee} format.
6362 @section @code{.size}
6364 This directive is used to set the size associated with a symbol.
6368 @c only print the extra heading if both COFF and ELF are set
6369 @subheading COFF Version
6372 @cindex @code{size} directive (COFF version)
6373 For COFF targets, the @code{.size} directive is only permitted inside
6374 @code{.def}/@code{.endef} pairs. It is used like this:
6377 .size @var{expression}
6381 @samp{.size} is only meaningful when generating COFF format output; when
6382 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6389 @c only print the extra heading if both COFF and ELF are set
6390 @subheading ELF Version
6393 @cindex @code{size} directive (ELF version)
6394 For ELF targets, the @code{.size} directive is used like this:
6397 .size @var{name} , @var{expression}
6400 This directive sets the size associated with a symbol @var{name}.
6401 The size in bytes is computed from @var{expression} which can make use of label
6402 arithmetic. This directive is typically used to set the size of function
6407 @ifclear no-space-dir
6409 @section @code{.skip @var{size} , @var{fill}}
6411 @cindex @code{skip} directive
6412 @cindex filling memory
6413 This directive emits @var{size} bytes, each of value @var{fill}. Both
6414 @var{size} and @var{fill} are absolute expressions. If the comma and
6415 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6420 @section @code{.sleb128 @var{expressions}}
6422 @cindex @code{sleb128} directive
6423 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6424 compact, variable length representation of numbers used by the DWARF
6425 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6427 @ifclear no-space-dir
6429 @section @code{.space @var{size} , @var{fill}}
6431 @cindex @code{space} directive
6432 @cindex filling memory
6433 This directive emits @var{size} bytes, each of value @var{fill}. Both
6434 @var{size} and @var{fill} are absolute expressions. If the comma
6435 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6440 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6441 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6442 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6443 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6451 @section @code{.stabd, .stabn, .stabs}
6453 @cindex symbolic debuggers, information for
6454 @cindex @code{stab@var{x}} directives
6455 There are three directives that begin @samp{.stab}.
6456 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6457 The symbols are not entered in the @command{@value{AS}} hash table: they
6458 cannot be referenced elsewhere in the source file.
6459 Up to five fields are required:
6463 This is the symbol's name. It may contain any character except
6464 @samp{\000}, so is more general than ordinary symbol names. Some
6465 debuggers used to code arbitrarily complex structures into symbol names
6469 An absolute expression. The symbol's type is set to the low 8 bits of
6470 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6471 and debuggers choke on silly bit patterns.
6474 An absolute expression. The symbol's ``other'' attribute is set to the
6475 low 8 bits of this expression.
6478 An absolute expression. The symbol's descriptor is set to the low 16
6479 bits of this expression.
6482 An absolute expression which becomes the symbol's value.
6485 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6486 or @code{.stabs} statement, the symbol has probably already been created;
6487 you get a half-formed symbol in your object file. This is
6488 compatible with earlier assemblers!
6491 @cindex @code{stabd} directive
6492 @item .stabd @var{type} , @var{other} , @var{desc}
6494 The ``name'' of the symbol generated is not even an empty string.
6495 It is a null pointer, for compatibility. Older assemblers used a
6496 null pointer so they didn't waste space in object files with empty
6499 The symbol's value is set to the location counter,
6500 relocatably. When your program is linked, the value of this symbol
6501 is the address of the location counter when the @code{.stabd} was
6504 @cindex @code{stabn} directive
6505 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6506 The name of the symbol is set to the empty string @code{""}.
6508 @cindex @code{stabs} directive
6509 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6510 All five fields are specified.
6516 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6517 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6519 @cindex string, copying to object file
6520 @cindex string8, copying to object file
6521 @cindex string16, copying to object file
6522 @cindex string32, copying to object file
6523 @cindex string64, copying to object file
6524 @cindex @code{string} directive
6525 @cindex @code{string8} directive
6526 @cindex @code{string16} directive
6527 @cindex @code{string32} directive
6528 @cindex @code{string64} directive
6530 Copy the characters in @var{str} to the object file. You may specify more than
6531 one string to copy, separated by commas. Unless otherwise specified for a
6532 particular machine, the assembler marks the end of each string with a 0 byte.
6533 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6535 The variants @code{string16}, @code{string32} and @code{string64} differ from
6536 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6537 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6538 are stored in target endianness byte order.
6544 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6545 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6550 @section @code{.struct @var{expression}}
6552 @cindex @code{struct} directive
6553 Switch to the absolute section, and set the section offset to @var{expression},
6554 which must be an absolute expression. You might use this as follows:
6563 This would define the symbol @code{field1} to have the value 0, the symbol
6564 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6565 value 8. Assembly would be left in the absolute section, and you would need to
6566 use a @code{.section} directive of some sort to change to some other section
6567 before further assembly.
6571 @section @code{.subsection @var{name}}
6573 @cindex @code{subsection} directive
6574 @cindex Section Stack
6575 This is one of the ELF section stack manipulation directives. The others are
6576 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6577 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6580 This directive replaces the current subsection with @code{name}. The current
6581 section is not changed. The replaced subsection is put onto the section stack
6582 in place of the then current top of stack subsection.
6587 @section @code{.symver}
6588 @cindex @code{symver} directive
6589 @cindex symbol versioning
6590 @cindex versions of symbols
6591 Use the @code{.symver} directive to bind symbols to specific version nodes
6592 within a source file. This is only supported on ELF platforms, and is
6593 typically used when assembling files to be linked into a shared library.
6594 There are cases where it may make sense to use this in objects to be bound
6595 into an application itself so as to override a versioned symbol from a
6598 For ELF targets, the @code{.symver} directive can be used like this:
6600 .symver @var{name}, @var{name2@@nodename}
6602 If the symbol @var{name} is defined within the file
6603 being assembled, the @code{.symver} directive effectively creates a symbol
6604 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6605 just don't try and create a regular alias is that the @var{@@} character isn't
6606 permitted in symbol names. The @var{name2} part of the name is the actual name
6607 of the symbol by which it will be externally referenced. The name @var{name}
6608 itself is merely a name of convenience that is used so that it is possible to
6609 have definitions for multiple versions of a function within a single source
6610 file, and so that the compiler can unambiguously know which version of a
6611 function is being mentioned. The @var{nodename} portion of the alias should be
6612 the name of a node specified in the version script supplied to the linker when
6613 building a shared library. If you are attempting to override a versioned
6614 symbol from a shared library, then @var{nodename} should correspond to the
6615 nodename of the symbol you are trying to override.
6617 If the symbol @var{name} is not defined within the file being assembled, all
6618 references to @var{name} will be changed to @var{name2@@nodename}. If no
6619 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6622 Another usage of the @code{.symver} directive is:
6624 .symver @var{name}, @var{name2@@@@nodename}
6626 In this case, the symbol @var{name} must exist and be defined within
6627 the file being assembled. It is similar to @var{name2@@nodename}. The
6628 difference is @var{name2@@@@nodename} will also be used to resolve
6629 references to @var{name2} by the linker.
6631 The third usage of the @code{.symver} directive is:
6633 .symver @var{name}, @var{name2@@@@@@nodename}
6635 When @var{name} is not defined within the
6636 file being assembled, it is treated as @var{name2@@nodename}. When
6637 @var{name} is defined within the file being assembled, the symbol
6638 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6643 @section @code{.tag @var{structname}}
6645 @cindex COFF structure debugging
6646 @cindex structure debugging, COFF
6647 @cindex @code{tag} directive
6648 This directive is generated by compilers to include auxiliary debugging
6649 information in the symbol table. It is only permitted inside
6650 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6651 definitions in the symbol table with instances of those structures.
6654 @samp{.tag} is only used when generating COFF format output; when
6655 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6661 @section @code{.text @var{subsection}}
6663 @cindex @code{text} directive
6664 Tells @command{@value{AS}} to assemble the following statements onto the end of
6665 the text subsection numbered @var{subsection}, which is an absolute
6666 expression. If @var{subsection} is omitted, subsection number zero
6670 @section @code{.title "@var{heading}"}
6672 @cindex @code{title} directive
6673 @cindex listing control: title line
6674 Use @var{heading} as the title (second line, immediately after the
6675 source file name and pagenumber) when generating assembly listings.
6677 This directive affects subsequent pages, as well as the current page if
6678 it appears within ten lines of the top of a page.
6682 @section @code{.type}
6684 This directive is used to set the type of a symbol.
6688 @c only print the extra heading if both COFF and ELF are set
6689 @subheading COFF Version
6692 @cindex COFF symbol type
6693 @cindex symbol type, COFF
6694 @cindex @code{type} directive (COFF version)
6695 For COFF targets, this directive is permitted only within
6696 @code{.def}/@code{.endef} pairs. It is used like this:
6702 This records the integer @var{int} as the type attribute of a symbol table
6706 @samp{.type} is associated only with COFF format output; when
6707 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6708 directive but ignores it.
6714 @c only print the extra heading if both COFF and ELF are set
6715 @subheading ELF Version
6718 @cindex ELF symbol type
6719 @cindex symbol type, ELF
6720 @cindex @code{type} directive (ELF version)
6721 For ELF targets, the @code{.type} directive is used like this:
6724 .type @var{name} , @var{type description}
6727 This sets the type of symbol @var{name} to be either a
6728 function symbol or an object symbol. There are five different syntaxes
6729 supported for the @var{type description} field, in order to provide
6730 compatibility with various other assemblers.
6732 Because some of the characters used in these syntaxes (such as @samp{@@} and
6733 @samp{#}) are comment characters for some architectures, some of the syntaxes
6734 below do not work on all architectures. The first variant will be accepted by
6735 the GNU assembler on all architectures so that variant should be used for
6736 maximum portability, if you do not need to assemble your code with other
6739 The syntaxes supported are:
6742 .type <name> STT_<TYPE_IN_UPPER_CASE>
6743 .type <name>,#<type>
6744 .type <name>,@@<type>
6745 .type <name>,%<type>
6746 .type <name>,"<type>"
6749 The types supported are:
6754 Mark the symbol as being a function name.
6757 @itemx gnu_indirect_function
6758 Mark the symbol as an indirect function when evaluated during reloc
6759 processing. (This is only supported on assemblers targeting GNU systems).
6763 Mark the symbol as being a data object.
6767 Mark the symbol as being a thead-local data object.
6771 Mark the symbol as being a common data object.
6775 Does not mark the symbol in any way. It is supported just for completeness.
6777 @item gnu_unique_object
6778 Marks the symbol as being a globally unique data object. The dynamic linker
6779 will make sure that in the entire process there is just one symbol with this
6780 name and type in use. (This is only supported on assemblers targeting GNU
6785 Note: Some targets support extra types in addition to those listed above.
6791 @section @code{.uleb128 @var{expressions}}
6793 @cindex @code{uleb128} directive
6794 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6795 compact, variable length representation of numbers used by the DWARF
6796 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6800 @section @code{.val @var{addr}}
6802 @cindex @code{val} directive
6803 @cindex COFF value attribute
6804 @cindex value attribute, COFF
6805 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6806 records the address @var{addr} as the value attribute of a symbol table
6810 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6811 configured for @code{b.out}, it accepts this directive but ignores it.
6817 @section @code{.version "@var{string}"}
6819 @cindex @code{version} directive
6820 This directive creates a @code{.note} section and places into it an ELF
6821 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6826 @section @code{.vtable_entry @var{table}, @var{offset}}
6828 @cindex @code{vtable_entry} directive
6829 This directive finds or creates a symbol @code{table} and creates a
6830 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6833 @section @code{.vtable_inherit @var{child}, @var{parent}}
6835 @cindex @code{vtable_inherit} directive
6836 This directive finds the symbol @code{child} and finds or creates the symbol
6837 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6838 parent whose addend is the value of the child symbol. As a special case the
6839 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6843 @section @code{.warning "@var{string}"}
6844 @cindex warning directive
6845 Similar to the directive @code{.error}
6846 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6849 @section @code{.weak @var{names}}
6851 @cindex @code{weak} directive
6852 This directive sets the weak attribute on the comma separated list of symbol
6853 @code{names}. If the symbols do not already exist, they will be created.
6855 On COFF targets other than PE, weak symbols are a GNU extension. This
6856 directive sets the weak attribute on the comma separated list of symbol
6857 @code{names}. If the symbols do not already exist, they will be created.
6859 On the PE target, weak symbols are supported natively as weak aliases.
6860 When a weak symbol is created that is not an alias, GAS creates an
6861 alternate symbol to hold the default value.
6864 @section @code{.weakref @var{alias}, @var{target}}
6866 @cindex @code{weakref} directive
6867 This directive creates an alias to the target symbol that enables the symbol to
6868 be referenced with weak-symbol semantics, but without actually making it weak.
6869 If direct references or definitions of the symbol are present, then the symbol
6870 will not be weak, but if all references to it are through weak references, the
6871 symbol will be marked as weak in the symbol table.
6873 The effect is equivalent to moving all references to the alias to a separate
6874 assembly source file, renaming the alias to the symbol in it, declaring the
6875 symbol as weak there, and running a reloadable link to merge the object files
6876 resulting from the assembly of the new source file and the old source file that
6877 had the references to the alias removed.
6879 The alias itself never makes to the symbol table, and is entirely handled
6880 within the assembler.
6883 @section @code{.word @var{expressions}}
6885 @cindex @code{word} directive
6886 This directive expects zero or more @var{expressions}, of any section,
6887 separated by commas.
6890 For each expression, @command{@value{AS}} emits a 32-bit number.
6893 For each expression, @command{@value{AS}} emits a 16-bit number.
6898 The size of the number emitted, and its byte order,
6899 depend on what target computer the assembly is for.
6902 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6903 @c happen---32-bit addressability, period; no long/short jumps.
6904 @ifset DIFF-TBL-KLUGE
6905 @cindex difference tables altered
6906 @cindex altered difference tables
6908 @emph{Warning: Special Treatment to support Compilers}
6912 Machines with a 32-bit address space, but that do less than 32-bit
6913 addressing, require the following special treatment. If the machine of
6914 interest to you does 32-bit addressing (or doesn't require it;
6915 @pxref{Machine Dependencies}), you can ignore this issue.
6918 In order to assemble compiler output into something that works,
6919 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6920 Directives of the form @samp{.word sym1-sym2} are often emitted by
6921 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6922 directive of the form @samp{.word sym1-sym2}, and the difference between
6923 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6924 creates a @dfn{secondary jump table}, immediately before the next label.
6925 This secondary jump table is preceded by a short-jump to the
6926 first byte after the secondary table. This short-jump prevents the flow
6927 of control from accidentally falling into the new table. Inside the
6928 table is a long-jump to @code{sym2}. The original @samp{.word}
6929 contains @code{sym1} minus the address of the long-jump to
6932 If there were several occurrences of @samp{.word sym1-sym2} before the
6933 secondary jump table, all of them are adjusted. If there was a
6934 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6935 long-jump to @code{sym4} is included in the secondary jump table,
6936 and the @code{.word} directives are adjusted to contain @code{sym3}
6937 minus the address of the long-jump to @code{sym4}; and so on, for as many
6938 entries in the original jump table as necessary.
6941 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6942 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6943 assembly language programmers.
6946 @c end DIFF-TBL-KLUGE
6949 @section Deprecated Directives
6951 @cindex deprecated directives
6952 @cindex obsolescent directives
6953 One day these directives won't work.
6954 They are included for compatibility with older assemblers.
6961 @node Object Attributes
6962 @chapter Object Attributes
6963 @cindex object attributes
6965 @command{@value{AS}} assembles source files written for a specific architecture
6966 into object files for that architecture. But not all object files are alike.
6967 Many architectures support incompatible variations. For instance, floating
6968 point arguments might be passed in floating point registers if the object file
6969 requires hardware floating point support---or floating point arguments might be
6970 passed in integer registers if the object file supports processors with no
6971 hardware floating point unit. Or, if two objects are built for different
6972 generations of the same architecture, the combination may require the
6973 newer generation at run-time.
6975 This information is useful during and after linking. At link time,
6976 @command{@value{LD}} can warn about incompatible object files. After link
6977 time, tools like @command{gdb} can use it to process the linked file
6980 Compatibility information is recorded as a series of object attributes. Each
6981 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6982 string, and indicates who sets the meaning of the tag. The tag is an integer,
6983 and indicates what property the attribute describes. The value may be a string
6984 or an integer, and indicates how the property affects this object. Missing
6985 attributes are the same as attributes with a zero value or empty string value.
6987 Object attributes were developed as part of the ABI for the ARM Architecture.
6988 The file format is documented in @cite{ELF for the ARM Architecture}.
6991 * GNU Object Attributes:: @sc{gnu} Object Attributes
6992 * Defining New Object Attributes:: Defining New Object Attributes
6995 @node GNU Object Attributes
6996 @section @sc{gnu} Object Attributes
6998 The @code{.gnu_attribute} directive records an object attribute
6999 with vendor @samp{gnu}.
7001 Except for @samp{Tag_compatibility}, which has both an integer and a string for
7002 its value, @sc{gnu} attributes have a string value if the tag number is odd and
7003 an integer value if the tag number is even. The second bit (@code{@var{tag} &
7004 2} is set for architecture-independent attributes and clear for
7005 architecture-dependent ones.
7007 @subsection Common @sc{gnu} attributes
7009 These attributes are valid on all architectures.
7012 @item Tag_compatibility (32)
7013 The compatibility attribute takes an integer flag value and a vendor name. If
7014 the flag value is 0, the file is compatible with other toolchains. If it is 1,
7015 then the file is only compatible with the named toolchain. If it is greater
7016 than 1, the file can only be processed by other toolchains under some private
7017 arrangement indicated by the flag value and the vendor name.
7020 @subsection MIPS Attributes
7023 @item Tag_GNU_MIPS_ABI_FP (4)
7024 The floating-point ABI used by this object file. The value will be:
7028 0 for files not affected by the floating-point ABI.
7030 1 for files using the hardware floating-point with a standard double-precision
7033 2 for files using the hardware floating-point ABI with a single-precision FPU.
7035 3 for files using the software floating-point ABI.
7037 4 for files using the hardware floating-point ABI with 64-bit wide
7038 double-precision floating-point registers and 32-bit wide general
7043 @subsection PowerPC Attributes
7046 @item Tag_GNU_Power_ABI_FP (4)
7047 The floating-point ABI used by this object file. The value will be:
7051 0 for files not affected by the floating-point ABI.
7053 1 for files using double-precision hardware floating-point ABI.
7055 2 for files using the software floating-point ABI.
7057 3 for files using single-precision hardware floating-point ABI.
7060 @item Tag_GNU_Power_ABI_Vector (8)
7061 The vector ABI used by this object file. The value will be:
7065 0 for files not affected by the vector ABI.
7067 1 for files using general purpose registers to pass vectors.
7069 2 for files using AltiVec registers to pass vectors.
7071 3 for files using SPE registers to pass vectors.
7075 @node Defining New Object Attributes
7076 @section Defining New Object Attributes
7078 If you want to define a new @sc{gnu} object attribute, here are the places you
7079 will need to modify. New attributes should be discussed on the @samp{binutils}
7084 This manual, which is the official register of attributes.
7086 The header for your architecture @file{include/elf}, to define the tag.
7088 The @file{bfd} support file for your architecture, to merge the attribute
7089 and issue any appropriate link warnings.
7091 Test cases in @file{ld/testsuite} for merging and link warnings.
7093 @file{binutils/readelf.c} to display your attribute.
7095 GCC, if you want the compiler to mark the attribute automatically.
7101 @node Machine Dependencies
7102 @chapter Machine Dependent Features
7104 @cindex machine dependencies
7105 The machine instruction sets are (almost by definition) different on
7106 each machine where @command{@value{AS}} runs. Floating point representations
7107 vary as well, and @command{@value{AS}} often supports a few additional
7108 directives or command-line options for compatibility with other
7109 assemblers on a particular platform. Finally, some versions of
7110 @command{@value{AS}} support special pseudo-instructions for branch
7113 This chapter discusses most of these differences, though it does not
7114 include details on any machine's instruction set. For details on that
7115 subject, see the hardware manufacturer's manual.
7119 * AArch64-Dependent:: AArch64 Dependent Features
7122 * Alpha-Dependent:: Alpha Dependent Features
7125 * ARC-Dependent:: ARC Dependent Features
7128 * ARM-Dependent:: ARM Dependent Features
7131 * AVR-Dependent:: AVR Dependent Features
7134 * Blackfin-Dependent:: Blackfin Dependent Features
7137 * CR16-Dependent:: CR16 Dependent Features
7140 * CRIS-Dependent:: CRIS Dependent Features
7143 * D10V-Dependent:: D10V Dependent Features
7146 * D30V-Dependent:: D30V Dependent Features
7149 * Epiphany-Dependent:: EPIPHANY Dependent Features
7152 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7155 * HPPA-Dependent:: HPPA Dependent Features
7158 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7161 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7164 * i860-Dependent:: Intel 80860 Dependent Features
7167 * i960-Dependent:: Intel 80960 Dependent Features
7170 * IA-64-Dependent:: Intel IA-64 Dependent Features
7173 * IP2K-Dependent:: IP2K Dependent Features
7176 * LM32-Dependent:: LM32 Dependent Features
7179 * M32C-Dependent:: M32C Dependent Features
7182 * M32R-Dependent:: M32R Dependent Features
7185 * M68K-Dependent:: M680x0 Dependent Features
7188 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7191 * Meta-Dependent :: Meta Dependent Features
7194 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7197 * MIPS-Dependent:: MIPS Dependent Features
7200 * MMIX-Dependent:: MMIX Dependent Features
7203 * MSP430-Dependent:: MSP430 Dependent Features
7206 * NDS32-Dependent:: Andes NDS32 Dependent Features
7209 * NiosII-Dependent:: Altera Nios II Dependent Features
7212 * NS32K-Dependent:: NS32K Dependent Features
7215 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7216 * SH64-Dependent:: SuperH SH64 Dependent Features
7219 * PDP-11-Dependent:: PDP-11 Dependent Features
7222 * PJ-Dependent:: picoJava Dependent Features
7225 * PPC-Dependent:: PowerPC Dependent Features
7228 * RL78-Dependent:: RL78 Dependent Features
7231 * RX-Dependent:: RX Dependent Features
7234 * S/390-Dependent:: IBM S/390 Dependent Features
7237 * SCORE-Dependent:: SCORE Dependent Features
7240 * Sparc-Dependent:: SPARC Dependent Features
7243 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7246 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7249 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7252 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7255 * V850-Dependent:: V850 Dependent Features
7258 * XGATE-Dependent:: XGATE Features
7261 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7264 * Xtensa-Dependent:: Xtensa Dependent Features
7267 * Z80-Dependent:: Z80 Dependent Features
7270 * Z8000-Dependent:: Z8000 Dependent Features
7273 * Vax-Dependent:: VAX Dependent Features
7280 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7281 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7282 @c peculiarity: to preserve cross-references, there must be a node called
7283 @c "Machine Dependencies". Hence the conditional nodenames in each
7284 @c major node below. Node defaulting in makeinfo requires adjacency of
7285 @c node and sectioning commands; hence the repetition of @chapter BLAH
7286 @c in both conditional blocks.
7289 @include c-aarch64.texi
7293 @include c-alpha.texi
7309 @include c-bfin.texi
7313 @include c-cr16.texi
7317 @include c-cris.texi
7322 @node Machine Dependencies
7323 @chapter Machine Dependent Features
7325 The machine instruction sets are different on each Renesas chip family,
7326 and there are also some syntax differences among the families. This
7327 chapter describes the specific @command{@value{AS}} features for each
7331 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7332 * SH-Dependent:: Renesas SH Dependent Features
7339 @include c-d10v.texi
7343 @include c-d30v.texi
7347 @include c-epiphany.texi
7351 @include c-h8300.texi
7355 @include c-hppa.texi
7359 @include c-i370.texi
7363 @include c-i386.texi
7367 @include c-i860.texi
7371 @include c-i960.texi
7375 @include c-ia64.texi
7379 @include c-ip2k.texi
7383 @include c-lm32.texi
7387 @include c-m32c.texi
7391 @include c-m32r.texi
7395 @include c-m68k.texi
7399 @include c-m68hc11.texi
7403 @include c-metag.texi
7407 @include c-microblaze.texi
7411 @include c-mips.texi
7415 @include c-mmix.texi
7419 @include c-msp430.texi
7423 @include c-nds32.texi
7427 @include c-nios2.texi
7431 @include c-ns32k.texi
7435 @include c-pdp11.texi
7447 @include c-rl78.texi
7455 @include c-s390.texi
7459 @include c-score.texi
7464 @include c-sh64.texi
7468 @include c-sparc.texi
7472 @include c-tic54x.texi
7476 @include c-tic6x.texi
7480 @include c-tilegx.texi
7484 @include c-tilepro.texi
7500 @include c-v850.texi
7504 @include c-xgate.texi
7508 @include c-xstormy16.texi
7512 @include c-xtensa.texi
7516 @c reverse effect of @down at top of generic Machine-Dep chapter
7520 @node Reporting Bugs
7521 @chapter Reporting Bugs
7522 @cindex bugs in assembler
7523 @cindex reporting bugs in assembler
7525 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7527 Reporting a bug may help you by bringing a solution to your problem, or it may
7528 not. But in any case the principal function of a bug report is to help the
7529 entire community by making the next version of @command{@value{AS}} work better.
7530 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7532 In order for a bug report to serve its purpose, you must include the
7533 information that enables us to fix the bug.
7536 * Bug Criteria:: Have you found a bug?
7537 * Bug Reporting:: How to report bugs
7541 @section Have You Found a Bug?
7542 @cindex bug criteria
7544 If you are not sure whether you have found a bug, here are some guidelines:
7547 @cindex fatal signal
7548 @cindex assembler crash
7549 @cindex crash of assembler
7551 If the assembler gets a fatal signal, for any input whatever, that is a
7552 @command{@value{AS}} bug. Reliable assemblers never crash.
7554 @cindex error on valid input
7556 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7558 @cindex invalid input
7560 If @command{@value{AS}} does not produce an error message for invalid input, that
7561 is a bug. However, you should note that your idea of ``invalid input'' might
7562 be our idea of ``an extension'' or ``support for traditional practice''.
7565 If you are an experienced user of assemblers, your suggestions for improvement
7566 of @command{@value{AS}} are welcome in any case.
7570 @section How to Report Bugs
7572 @cindex assembler bugs, reporting
7574 A number of companies and individuals offer support for @sc{gnu} products. If
7575 you obtained @command{@value{AS}} from a support organization, we recommend you
7576 contact that organization first.
7578 You can find contact information for many support companies and
7579 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7583 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7587 The fundamental principle of reporting bugs usefully is this:
7588 @strong{report all the facts}. If you are not sure whether to state a
7589 fact or leave it out, state it!
7591 Often people omit facts because they think they know what causes the problem
7592 and assume that some details do not matter. Thus, you might assume that the
7593 name of a symbol you use in an example does not matter. Well, probably it does
7594 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7595 happens to fetch from the location where that name is stored in memory;
7596 perhaps, if the name were different, the contents of that location would fool
7597 the assembler into doing the right thing despite the bug. Play it safe and
7598 give a specific, complete example. That is the easiest thing for you to do,
7599 and the most helpful.
7601 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7602 it is new to us. Therefore, always write your bug reports on the assumption
7603 that the bug has not been reported previously.
7605 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7606 bell?'' This cannot help us fix a bug, so it is basically useless. We
7607 respond by asking for enough details to enable us to investigate.
7608 You might as well expedite matters by sending them to begin with.
7610 To enable us to fix the bug, you should include all these things:
7614 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7615 it with the @samp{--version} argument.
7617 Without this, we will not know whether there is any point in looking for
7618 the bug in the current version of @command{@value{AS}}.
7621 Any patches you may have applied to the @command{@value{AS}} source.
7624 The type of machine you are using, and the operating system name and
7628 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7632 The command arguments you gave the assembler to assemble your example and
7633 observe the bug. To guarantee you will not omit something important, list them
7634 all. A copy of the Makefile (or the output from make) is sufficient.
7636 If we were to try to guess the arguments, we would probably guess wrong
7637 and then we might not encounter the bug.
7640 A complete input file that will reproduce the bug. If the bug is observed when
7641 the assembler is invoked via a compiler, send the assembler source, not the
7642 high level language source. Most compilers will produce the assembler source
7643 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7644 the options @samp{-v --save-temps}; this will save the assembler source in a
7645 file with an extension of @file{.s}, and also show you exactly how
7646 @command{@value{AS}} is being run.
7649 A description of what behavior you observe that you believe is
7650 incorrect. For example, ``It gets a fatal signal.''
7652 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7653 will certainly notice it. But if the bug is incorrect output, we might not
7654 notice unless it is glaringly wrong. You might as well not give us a chance to
7657 Even if the problem you experience is a fatal signal, you should still say so
7658 explicitly. Suppose something strange is going on, such as, your copy of
7659 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7660 library on your system. (This has happened!) Your copy might crash and ours
7661 would not. If you told us to expect a crash, then when ours fails to crash, we
7662 would know that the bug was not happening for us. If you had not told us to
7663 expect a crash, then we would not be able to draw any conclusion from our
7667 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7668 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7669 option. Always send diffs from the old file to the new file. If you even
7670 discuss something in the @command{@value{AS}} source, refer to it by context, not
7673 The line numbers in our development sources will not match those in your
7674 sources. Your line numbers would convey no useful information to us.
7677 Here are some things that are not necessary:
7681 A description of the envelope of the bug.
7683 Often people who encounter a bug spend a lot of time investigating
7684 which changes to the input file will make the bug go away and which
7685 changes will not affect it.
7687 This is often time consuming and not very useful, because the way we
7688 will find the bug is by running a single example under the debugger
7689 with breakpoints, not by pure deduction from a series of examples.
7690 We recommend that you save your time for something else.
7692 Of course, if you can find a simpler example to report @emph{instead}
7693 of the original one, that is a convenience for us. Errors in the
7694 output will be easier to spot, running under the debugger will take
7695 less time, and so on.
7697 However, simplification is not vital; if you do not want to do this,
7698 report the bug anyway and send us the entire test case you used.
7701 A patch for the bug.
7703 A patch for the bug does help us if it is a good one. But do not omit
7704 the necessary information, such as the test case, on the assumption that
7705 a patch is all we need. We might see problems with your patch and decide
7706 to fix the problem another way, or we might not understand it at all.
7708 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7709 construct an example that will make the program follow a certain path through
7710 the code. If you do not send us the example, we will not be able to construct
7711 one, so we will not be able to verify that the bug is fixed.
7713 And if we cannot understand what bug you are trying to fix, or why your
7714 patch should be an improvement, we will not install it. A test case will
7715 help us to understand.
7718 A guess about what the bug is or what it depends on.
7720 Such guesses are usually wrong. Even we cannot guess right about such
7721 things without first using the debugger to find the facts.
7724 @node Acknowledgements
7725 @chapter Acknowledgements
7727 If you have contributed to GAS and your name isn't listed here,
7728 it is not meant as a slight. We just don't know about it. Send mail to the
7729 maintainer, and we'll correct the situation. Currently
7731 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7733 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7736 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7737 information and the 68k series machines, most of the preprocessing pass, and
7738 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7740 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7741 many bug fixes, including merging support for several processors, breaking GAS
7742 up to handle multiple object file format back ends (including heavy rewrite,
7743 testing, an integration of the coff and b.out back ends), adding configuration
7744 including heavy testing and verification of cross assemblers and file splits
7745 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7746 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7747 port (including considerable amounts of reverse engineering), a SPARC opcode
7748 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7749 assertions and made them work, much other reorganization, cleanup, and lint.
7751 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7752 in format-specific I/O modules.
7754 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7755 has done much work with it since.
7757 The Intel 80386 machine description was written by Eliot Dresselhaus.
7759 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7761 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7762 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7764 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7765 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7766 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7767 support a.out format.
7769 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7770 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7771 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7772 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7775 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7776 simplified the configuration of which versions accept which directives. He
7777 updated the 68k machine description so that Motorola's opcodes always produced
7778 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7779 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7780 cross-compilation support, and one bug in relaxation that took a week and
7781 required the proverbial one-bit fix.
7783 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7784 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7785 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7786 PowerPC assembler, and made a few other minor patches.
7788 Steve Chamberlain made GAS able to generate listings.
7790 Hewlett-Packard contributed support for the HP9000/300.
7792 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7793 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7794 formats). This work was supported by both the Center for Software Science at
7795 the University of Utah and Cygnus Support.
7797 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7798 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7799 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7800 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7801 and some initial 64-bit support).
7803 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7805 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7806 support for openVMS/Alpha.
7808 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7811 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7812 Inc.@: added support for Xtensa processors.
7814 Several engineers at Cygnus Support have also provided many small bug fixes and
7815 configuration enhancements.
7817 Jon Beniston added support for the Lattice Mico32 architecture.
7819 Many others have contributed large or small bugfixes and enhancements. If
7820 you have contributed significant work and are not mentioned on this list, and
7821 want to be, let us know. Some of the history has been lost; we are not
7822 intentionally leaving anyone out.
7824 @node GNU Free Documentation License
7825 @appendix GNU Free Documentation License
7829 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob