1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991-2013 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @macro gcctabopt{body}
17 @c defaults, config file may override:
22 @include asconfig.texi
27 @c common OR combinations of conditions
53 @set abnormal-separator
57 @settitle Using @value{AS}
60 @settitle Using @value{AS} (@value{TARGET})
62 @setchapternewpage odd
67 @c WARE! Some of the machine-dependent sections contain tables of machine
68 @c instructions. Except in multi-column format, these tables look silly.
69 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
70 @c the multi-col format is faked within @example sections.
72 @c Again unfortunately, the natural size that fits on a page, for these tables,
73 @c is different depending on whether or not smallbook is turned on.
74 @c This matters, because of order: text flow switches columns at each page
77 @c The format faked in this source works reasonably well for smallbook,
78 @c not well for the default large-page format. This manual expects that if you
79 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
80 @c tables in question. You can turn on one without the other at your
81 @c discretion, of course.
84 @c the insn tables look just as silly in info files regardless of smallbook,
85 @c might as well show 'em anyways.
89 @dircategory Software development
91 * As: (as). The GNU assembler.
92 * Gas: (as). The GNU assembler.
100 This file documents the GNU Assembler "@value{AS}".
102 @c man begin COPYRIGHT
103 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
105 Permission is granted to copy, distribute and/or modify this document
106 under the terms of the GNU Free Documentation License, Version 1.3
107 or any later version published by the Free Software Foundation;
108 with no Invariant Sections, with no Front-Cover Texts, and with no
109 Back-Cover Texts. A copy of the license is included in the
110 section entitled ``GNU Free Documentation License''.
116 @title Using @value{AS}
117 @subtitle The @sc{gnu} Assembler
119 @subtitle for the @value{TARGET} family
121 @ifset VERSION_PACKAGE
123 @subtitle @value{VERSION_PACKAGE}
126 @subtitle Version @value{VERSION}
129 The Free Software Foundation Inc.@: thanks The Nice Computer
130 Company of Australia for loaning Dean Elsner to write the
131 first (Vax) version of @command{as} for Project @sc{gnu}.
132 The proprietors, management and staff of TNCCA thank FSF for
133 distracting the boss while they got some work
136 @author Dean Elsner, Jay Fenlason & friends
140 \hfill {\it Using {\tt @value{AS}}}\par
141 \hfill Edited by Cygnus Support\par
143 %"boxit" macro for figures:
144 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
145 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
146 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
147 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
148 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
151 @vskip 0pt plus 1filll
152 Copyright @copyright{} 1991-2013 Free Software Foundation, Inc.
154 Permission is granted to copy, distribute and/or modify this document
155 under the terms of the GNU Free Documentation License, Version 1.3
156 or any later version published by the Free Software Foundation;
157 with no Invariant Sections, with no Front-Cover Texts, and with no
158 Back-Cover Texts. A copy of the license is included in the
159 section entitled ``GNU Free Documentation License''.
166 @top Using @value{AS}
168 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}}
169 @ifset VERSION_PACKAGE
170 @value{VERSION_PACKAGE}
172 version @value{VERSION}.
174 This version of the file describes @command{@value{AS}} configured to generate
175 code for @value{TARGET} architectures.
178 This document is distributed under the terms of the GNU Free
179 Documentation License. A copy of the license is included in the
180 section entitled ``GNU Free Documentation License''.
183 * Overview:: Overview
184 * Invoking:: Command-Line Options
186 * Sections:: Sections and Relocation
188 * Expressions:: Expressions
189 * Pseudo Ops:: Assembler Directives
191 * Object Attributes:: Object Attributes
193 * Machine Dependencies:: Machine Dependent Features
194 * Reporting Bugs:: Reporting Bugs
195 * Acknowledgements:: Who Did What
196 * GNU Free Documentation License:: GNU Free Documentation License
197 * AS Index:: AS Index
204 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
206 This version of the manual describes @command{@value{AS}} configured to generate
207 code for @value{TARGET} architectures.
211 @cindex invocation summary
212 @cindex option summary
213 @cindex summary of options
214 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
215 see @ref{Invoking,,Command-Line Options}.
217 @c man title AS the portable GNU assembler.
221 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
225 @c We don't use deffn and friends for the following because they seem
226 @c to be limited to one line for the header.
228 @c man begin SYNOPSIS
229 @value{AS} [@b{-a}[@b{cdghlns}][=@var{file}]] [@b{--alternate}] [@b{-D}]
230 [@b{--compress-debug-sections}] [@b{--nocompress-debug-sections}]
231 [@b{--debug-prefix-map} @var{old}=@var{new}]
232 [@b{--defsym} @var{sym}=@var{val}] [@b{-f}] [@b{-g}] [@b{--gstabs}]
233 [@b{--gstabs+}] [@b{--gdwarf-2}] [@b{--gdwarf-sections}]
234 [@b{--help}] [@b{-I} @var{dir}] [@b{-J}]
235 [@b{-K}] [@b{-L}] [@b{--listing-lhs-width}=@var{NUM}]
236 [@b{--listing-lhs-width2}=@var{NUM}] [@b{--listing-rhs-width}=@var{NUM}]
237 [@b{--listing-cont-lines}=@var{NUM}] [@b{--keep-locals}] [@b{-o}
238 @var{objfile}] [@b{-R}] [@b{--reduce-memory-overheads}] [@b{--statistics}]
239 [@b{-v}] [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}]
240 [@b{--fatal-warnings}] [@b{-w}] [@b{-x}] [@b{-Z}] [@b{@@@var{FILE}}]
241 [@b{--size-check=[error|warning]}]
242 [@b{--target-help}] [@var{target-options}]
243 [@b{--}|@var{files} @dots{}]
245 @c Target dependent options are listed below. Keep the list sorted.
246 @c Add an empty line for separation.
249 @emph{Target AArch64 options:}
254 @emph{Target Alpha options:}
256 [@b{-mdebug} | @b{-no-mdebug}]
257 [@b{-replace} | @b{-noreplace}]
258 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
259 [@b{-F}] [@b{-32addr}]
263 @emph{Target ARC options:}
269 @emph{Target ARM options:}
270 @c Don't document the deprecated options
271 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
272 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
273 [@b{-mfpu}=@var{floating-point-format}]
274 [@b{-mfloat-abi}=@var{abi}]
275 [@b{-meabi}=@var{ver}]
278 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
279 @b{-mapcs-reentrant}]
280 [@b{-mthumb-interwork}] [@b{-k}]
284 @emph{Target Blackfin options:}
285 [@b{-mcpu}=@var{processor}[-@var{sirevision}]]
292 @emph{Target CRIS options:}
293 [@b{--underscore} | @b{--no-underscore}]
295 [@b{--emulation=criself} | @b{--emulation=crisaout}]
296 [@b{--march=v0_v10} | @b{--march=v10} | @b{--march=v32} | @b{--march=common_v10_v32}]
297 @c Deprecated -- deliberately not documented.
302 @emph{Target D10V options:}
307 @emph{Target D30V options:}
308 [@b{-O}|@b{-n}|@b{-N}]
312 @emph{Target EPIPHANY options:}
313 [@b{-mepiphany}|@b{-mepiphany16}]
317 @emph{Target H8/300 options:}
321 @c HPPA has no machine-dependent assembler options (yet).
325 @emph{Target i386 options:}
326 [@b{--32}|@b{--x32}|@b{--64}] [@b{-n}]
327 [@b{-march}=@var{CPU}[+@var{EXTENSION}@dots{}]] [@b{-mtune}=@var{CPU}]
331 @emph{Target i960 options:}
332 @c see md_parse_option in tc-i960.c
333 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
335 [@b{-b}] [@b{-no-relax}]
339 @emph{Target IA-64 options:}
340 [@b{-mconstant-gp}|@b{-mauto-pic}]
341 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
343 [@b{-mtune=itanium1}|@b{-mtune=itanium2}]
344 [@b{-munwind-check=warning}|@b{-munwind-check=error}]
345 [@b{-mhint.b=ok}|@b{-mhint.b=warning}|@b{-mhint.b=error}]
346 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
350 @emph{Target IP2K options:}
351 [@b{-mip2022}|@b{-mip2022ext}]
355 @emph{Target M32C options:}
356 [@b{-m32c}|@b{-m16c}] [-relax] [-h-tick-hex]
360 @emph{Target M32R options:}
361 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
366 @emph{Target M680X0 options:}
367 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
371 @emph{Target M68HC11 options:}
372 [@b{-m68hc11}|@b{-m68hc12}|@b{-m68hcs12}|@b{-mm9s12x}|@b{-mm9s12xg}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branches}] [@b{--short-branches}]
376 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
377 [@b{--print-opcodes}] [@b{--generate-example}]
381 @emph{Target MCORE options:}
382 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
383 [@b{-mcpu=[210|340]}]
387 @emph{Target Meta options:}
388 [@b{-mcpu=@var{cpu}}] [@b{-mfpu=@var{cpu}}] [@b{-mdsp=@var{cpu}}]
391 @emph{Target MICROBLAZE options:}
392 @c MicroBlaze has no machine-dependent assembler options.
396 @emph{Target MIPS options:}
397 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-O}[@var{optimization level}]]
398 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
399 [@b{-non_shared}] [@b{-xgot} [@b{-mvxworks-pic}]
400 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
401 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
402 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
403 [@b{-mips64}] [@b{-mips64r2}]
404 [@b{-construct-floats}] [@b{-no-construct-floats}]
405 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
406 [@b{-mips16}] [@b{-no-mips16}]
407 [@b{-mmicromips}] [@b{-mno-micromips}]
408 [@b{-msmartmips}] [@b{-mno-smartmips}]
409 [@b{-mips3d}] [@b{-no-mips3d}]
410 [@b{-mdmx}] [@b{-no-mdmx}]
411 [@b{-mdsp}] [@b{-mno-dsp}]
412 [@b{-mdspr2}] [@b{-mno-dspr2}]
413 [@b{-mmt}] [@b{-mno-mt}]
414 [@b{-mmcu}] [@b{-mno-mcu}]
415 [@b{-minsn32}] [@b{-mno-insn32}]
416 [@b{-mfix7000}] [@b{-mno-fix7000}]
417 [@b{-mfix-vr4120}] [@b{-mno-fix-vr4120}]
418 [@b{-mfix-vr4130}] [@b{-mno-fix-vr4130}]
419 [@b{-mdebug}] [@b{-no-mdebug}]
420 [@b{-mpdr}] [@b{-mno-pdr}]
424 @emph{Target MMIX options:}
425 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
426 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
427 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
428 [@b{--linker-allocated-gregs}]
432 @emph{Target Nios II options:}
433 [@b{-relax-all}] [@b{-relax-section}] [@b{-no-relax}]
438 @emph{Target PDP11 options:}
439 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
440 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
441 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
445 @emph{Target picoJava options:}
450 @emph{Target PowerPC options:}
452 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|@b{-m403}|@b{-m405}|
453 @b{-m440}|@b{-m464}|@b{-m476}|@b{-m7400}|@b{-m7410}|@b{-m7450}|@b{-m7455}|@b{-m750cl}|@b{-mppc64}|
454 @b{-m620}|@b{-me500}|@b{-e500x2}|@b{-me500mc}|@b{-me500mc64}|@b{-me5500}|@b{-me6500}|@b{-mppc64bridge}|
455 @b{-mbooke}|@b{-mpower4}|@b{-mpwr4}|@b{-mpower5}|@b{-mpwr5}|@b{-mpwr5x}|@b{-mpower6}|@b{-mpwr6}|
456 @b{-mpower7}|@b{-mpwr7}|@b{-mpower8}|@b{-mpwr8}|@b{-ma2}|@b{-mcell}|@b{-mspe}|@b{-mtitan}|@b{-me300}|@b{-mcom}]
457 [@b{-many}] [@b{-maltivec}|@b{-mvsx}|@b{-mhtm}|@b{-mvle}]
458 [@b{-mregnames}|@b{-mno-regnames}]
459 [@b{-mrelocatable}|@b{-mrelocatable-lib}|@b{-K PIC}] [@b{-memb}]
460 [@b{-mlittle}|@b{-mlittle-endian}|@b{-le}|@b{-mbig}|@b{-mbig-endian}|@b{-be}]
461 [@b{-msolaris}|@b{-mno-solaris}]
462 [@b{-nops=@var{count}}]
466 @emph{Target RX options:}
467 [@b{-mlittle-endian}|@b{-mbig-endian}]
468 [@b{-m32bit-doubles}|@b{-m64bit-doubles}]
469 [@b{-muse-conventional-section-names}]
470 [@b{-msmall-data-limit}]
473 [@b{-mint-register=@var{number}}]
474 [@b{-mgcc-abi}|@b{-mrx-abi}]
478 @emph{Target s390 options:}
479 [@b{-m31}|@b{-m64}] [@b{-mesa}|@b{-mzarch}] [@b{-march}=@var{CPU}]
480 [@b{-mregnames}|@b{-mno-regnames}]
481 [@b{-mwarn-areg-zero}]
485 @emph{Target SCORE options:}
486 [@b{-EB}][@b{-EL}][@b{-FIXDD}][@b{-NWARN}]
487 [@b{-SCORE5}][@b{-SCORE5U}][@b{-SCORE7}][@b{-SCORE3}]
488 [@b{-march=score7}][@b{-march=score3}]
489 [@b{-USE_R1}][@b{-KPIC}][@b{-O0}][@b{-G} @var{num}][@b{-V}]
493 @emph{Target SPARC options:}
494 @c The order here is important. See c-sparc.texi.
495 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
496 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
497 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
502 @emph{Target TIC54X options:}
503 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
504 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
509 @emph{Target TIC6X options:}
510 [@b{-march=@var{arch}}] [@b{-mbig-endian}|@b{-mlittle-endian}]
511 [@b{-mdsbt}|@b{-mno-dsbt}] [@b{-mpid=no}|@b{-mpid=near}|@b{-mpid=far}]
512 [@b{-mpic}|@b{-mno-pic}]
516 @emph{Target TILE-Gx options:}
517 [@b{-m32}|@b{-m64}][@b{-EB}][@b{-EL}]
520 @c TILEPro has no machine-dependent assembler options
525 @emph{Target Xtensa options:}
526 [@b{--[no-]text-section-literals}] [@b{--[no-]absolute-literals}]
527 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
528 [@b{--[no-]transform}]
529 [@b{--rename-section} @var{oldname}=@var{newname}]
534 @emph{Target Z80 options:}
535 [@b{-z80}] [@b{-r800}]
536 [@b{ -ignore-undocumented-instructions}] [@b{-Wnud}]
537 [@b{ -ignore-unportable-instructions}] [@b{-Wnup}]
538 [@b{ -warn-undocumented-instructions}] [@b{-Wud}]
539 [@b{ -warn-unportable-instructions}] [@b{-Wup}]
540 [@b{ -forbid-undocumented-instructions}] [@b{-Fud}]
541 [@b{ -forbid-unportable-instructions}] [@b{-Fup}]
545 @c Z8000 has no machine-dependent assembler options
554 @include at-file.texi
557 Turn on listings, in any of a variety of ways:
561 omit false conditionals
564 omit debugging directives
567 include general information, like @value{AS} version and options passed
570 include high-level source
576 include macro expansions
579 omit forms processing
585 set the name of the listing file
588 You may combine these options; for example, use @samp{-aln} for assembly
589 listing without forms processing. The @samp{=file} option, if used, must be
590 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
593 Begin in alternate macro mode.
595 @xref{Altmacro,,@code{.altmacro}}.
598 @item --compress-debug-sections
599 Compress DWARF debug sections using zlib. The debug sections are renamed
600 to begin with @samp{.zdebug}, and the resulting object file may not be
601 compatible with older linkers and object file utilities.
603 @item --nocompress-debug-sections
604 Do not compress DWARF debug sections. This is the default.
607 Ignored. This option is accepted for script compatibility with calls to
610 @item --debug-prefix-map @var{old}=@var{new}
611 When assembling files in directory @file{@var{old}}, record debugging
612 information describing them as in @file{@var{new}} instead.
614 @item --defsym @var{sym}=@var{value}
615 Define the symbol @var{sym} to be @var{value} before assembling the input file.
616 @var{value} must be an integer constant. As in C, a leading @samp{0x}
617 indicates a hexadecimal value, and a leading @samp{0} indicates an octal
618 value. The value of the symbol can be overridden inside a source file via the
619 use of a @code{.set} pseudo-op.
622 ``fast''---skip whitespace and comment preprocessing (assume source is
627 Generate debugging information for each assembler source line using whichever
628 debug format is preferred by the target. This currently means either STABS,
632 Generate stabs debugging information for each assembler line. This
633 may help debugging assembler code, if the debugger can handle it.
636 Generate stabs debugging information for each assembler line, with GNU
637 extensions that probably only gdb can handle, and that could make other
638 debuggers crash or refuse to read your program. This
639 may help debugging assembler code. Currently the only GNU extension is
640 the location of the current working directory at assembling time.
643 Generate DWARF2 debugging information for each assembler line. This
644 may help debugging assembler code, if the debugger can handle it. Note---this
645 option is only supported by some targets, not all of them.
647 @item --gdwarf-sections
648 Instead of creating a .debug_line section, create a series of
649 .debug_line.@var{foo} sections where @var{foo} is the name of the
650 corresponding code section. For example a code section called @var{.text.func}
651 will have its dwarf line number information placed into a section called
652 @var{.debug_line.text.func}. If the code section is just called @var{.text}
653 then debug line section will still be called just @var{.debug_line} without any
656 @item --size-check=error
657 @itemx --size-check=warning
658 Issue an error or warning for invalid ELF .size directive.
661 Print a summary of the command line options and exit.
664 Print a summary of all target specific options and exit.
667 Add directory @var{dir} to the search list for @code{.include} directives.
670 Don't warn about signed overflow.
673 @ifclear DIFF-TBL-KLUGE
674 This option is accepted but has no effect on the @value{TARGET} family.
676 @ifset DIFF-TBL-KLUGE
677 Issue warnings when difference tables altered for long displacements.
682 Keep (in the symbol table) local symbols. These symbols start with
683 system-specific local label prefixes, typically @samp{.L} for ELF systems
684 or @samp{L} for traditional a.out systems.
689 @item --listing-lhs-width=@var{number}
690 Set the maximum width, in words, of the output data column for an assembler
691 listing to @var{number}.
693 @item --listing-lhs-width2=@var{number}
694 Set the maximum width, in words, of the output data column for continuation
695 lines in an assembler listing to @var{number}.
697 @item --listing-rhs-width=@var{number}
698 Set the maximum width of an input source line, as displayed in a listing, to
701 @item --listing-cont-lines=@var{number}
702 Set the maximum number of lines printed in a listing for a single line of input
705 @item -o @var{objfile}
706 Name the object-file output from @command{@value{AS}} @var{objfile}.
709 Fold the data section into the text section.
711 @kindex --hash-size=@var{number}
712 Set the default size of GAS's hash tables to a prime number close to
713 @var{number}. Increasing this value can reduce the length of time it takes the
714 assembler to perform its tasks, at the expense of increasing the assembler's
715 memory requirements. Similarly reducing this value can reduce the memory
716 requirements at the expense of speed.
718 @item --reduce-memory-overheads
719 This option reduces GAS's memory requirements, at the expense of making the
720 assembly processes slower. Currently this switch is a synonym for
721 @samp{--hash-size=4051}, but in the future it may have other effects as well.
724 Print the maximum space (in bytes) and total time (in seconds) used by
727 @item --strip-local-absolute
728 Remove local absolute symbols from the outgoing symbol table.
732 Print the @command{as} version.
735 Print the @command{as} version and exit.
739 Suppress warning messages.
741 @item --fatal-warnings
742 Treat warnings as errors.
745 Don't suppress warning messages or treat them as errors.
754 Generate an object file even after errors.
756 @item -- | @var{files} @dots{}
757 Standard input, or source files to assemble.
765 @xref{AArch64 Options}, for the options available when @value{AS} is configured
766 for the 64-bit mode of the ARM Architecture (AArch64).
771 The following options are available when @value{AS} is configured for the
772 64-bit mode of the ARM Architecture (AArch64).
775 @include c-aarch64.texi
776 @c ended inside the included file
784 @xref{Alpha Options}, for the options available when @value{AS} is configured
785 for an Alpha processor.
790 The following options are available when @value{AS} is configured for an Alpha
794 @include c-alpha.texi
795 @c ended inside the included file
802 The following options are available when @value{AS} is configured for
807 This option selects the core processor variant.
809 Select either big-endian (-EB) or little-endian (-EL) output.
814 The following options are available when @value{AS} is configured for the ARM
818 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
819 Specify which ARM processor variant is the target.
820 @item -march=@var{architecture}[+@var{extension}@dots{}]
821 Specify which ARM architecture variant is used by the target.
822 @item -mfpu=@var{floating-point-format}
823 Select which Floating Point architecture is the target.
824 @item -mfloat-abi=@var{abi}
825 Select which floating point ABI is in use.
827 Enable Thumb only instruction decoding.
828 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant
829 Select which procedure calling convention is in use.
831 Select either big-endian (-EB) or little-endian (-EL) output.
832 @item -mthumb-interwork
833 Specify that the code has been generated with interworking between Thumb and
836 Specify that PIC code has been generated.
844 @xref{Blackfin Options}, for the options available when @value{AS} is
845 configured for the Blackfin processor family.
850 The following options are available when @value{AS} is configured for
851 the Blackfin processor family.
855 @c ended inside the included file
862 See the info pages for documentation of the CRIS-specific options.
866 The following options are available when @value{AS} is configured for
869 @cindex D10V optimization
870 @cindex optimization, D10V
872 Optimize output by parallelizing instructions.
877 The following options are available when @value{AS} is configured for a D30V
880 @cindex D30V optimization
881 @cindex optimization, D30V
883 Optimize output by parallelizing instructions.
887 Warn when nops are generated.
889 @cindex D30V nops after 32-bit multiply
891 Warn when a nop after a 32-bit multiply instruction is generated.
897 The following options are available when @value{AS} is configured for the
898 Adapteva EPIPHANY series.
901 @xref{Epiphany Options}, for the options available when @value{AS} is
902 configured for an Epiphany processor.
907 The following options are available when @value{AS} is configured for
908 an Epiphany processor.
911 @include c-epiphany.texi
912 @c ended inside the included file
920 @xref{H8/300 Options}, for the options available when @value{AS} is configured
921 for an H8/300 processor.
926 The following options are available when @value{AS} is configured for an H8/300
930 @include c-h8300.texi
931 @c ended inside the included file
939 @xref{i386-Options}, for the options available when @value{AS} is
940 configured for an i386 processor.
945 The following options are available when @value{AS} is configured for
950 @c ended inside the included file
957 The following options are available when @value{AS} is configured for the
958 Intel 80960 processor.
961 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
962 Specify which variant of the 960 architecture is the target.
965 Add code to collect statistics about branches taken.
968 Do not alter compare-and-branch instructions for long displacements;
975 The following options are available when @value{AS} is configured for the
981 Specifies that the extended IP2022 instructions are allowed.
984 Restores the default behaviour, which restricts the permitted instructions to
985 just the basic IP2022 ones.
991 The following options are available when @value{AS} is configured for the
992 Renesas M32C and M16C processors.
997 Assemble M32C instructions.
1000 Assemble M16C instructions (the default).
1003 Enable support for link-time relaxations.
1006 Support H'00 style hex constants in addition to 0x00 style.
1012 The following options are available when @value{AS} is configured for the
1013 Renesas M32R (formerly Mitsubishi M32R) series.
1018 Specify which processor in the M32R family is the target. The default
1019 is normally the M32R, but this option changes it to the M32RX.
1021 @item --warn-explicit-parallel-conflicts or --Wp
1022 Produce warning messages when questionable parallel constructs are
1025 @item --no-warn-explicit-parallel-conflicts or --Wnp
1026 Do not produce warning messages when questionable parallel constructs are
1033 The following options are available when @value{AS} is configured for the
1034 Motorola 68000 series.
1039 Shorten references to undefined symbols, to one word instead of two.
1041 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
1042 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
1043 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
1044 Specify what processor in the 68000 family is the target. The default
1045 is normally the 68020, but this can be changed at configuration time.
1047 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
1048 The target machine does (or does not) have a floating-point coprocessor.
1049 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
1050 the basic 68000 is not compatible with the 68881, a combination of the
1051 two can be specified, since it's possible to do emulation of the
1052 coprocessor instructions with the main processor.
1054 @item -m68851 | -mno-68851
1055 The target machine does (or does not) have a memory-management
1056 unit coprocessor. The default is to assume an MMU for 68020 and up.
1064 @xref{Nios II Options}, for the options available when @value{AS} is configured
1065 for an Altera Nios II processor.
1069 @c man begin OPTIONS
1070 The following options are available when @value{AS} is configured for an
1071 Altera Nios II processor.
1073 @c man begin INCLUDE
1074 @include c-nios2.texi
1075 @c ended inside the included file
1081 For details about the PDP-11 machine dependent features options,
1082 see @ref{PDP-11-Options}.
1085 @item -mpic | -mno-pic
1086 Generate position-independent (or position-dependent) code. The
1087 default is @option{-mpic}.
1090 @itemx -mall-extensions
1091 Enable all instruction set extensions. This is the default.
1093 @item -mno-extensions
1094 Disable all instruction set extensions.
1096 @item -m@var{extension} | -mno-@var{extension}
1097 Enable (or disable) a particular instruction set extension.
1100 Enable the instruction set extensions supported by a particular CPU, and
1101 disable all other extensions.
1103 @item -m@var{machine}
1104 Enable the instruction set extensions supported by a particular machine
1105 model, and disable all other extensions.
1111 The following options are available when @value{AS} is configured for
1112 a picoJava processor.
1116 @cindex PJ endianness
1117 @cindex endianness, PJ
1118 @cindex big endian output, PJ
1120 Generate ``big endian'' format output.
1122 @cindex little endian output, PJ
1124 Generate ``little endian'' format output.
1130 The following options are available when @value{AS} is configured for the
1131 Motorola 68HC11 or 68HC12 series.
1135 @item -m68hc11 | -m68hc12 | -m68hcs12 | -mm9s12x | -mm9s12xg
1136 Specify what processor is the target. The default is
1137 defined by the configuration option when building the assembler.
1139 @item --xgate-ramoffset
1140 Instruct the linker to offset RAM addresses from S12X address space into
1141 XGATE address space.
1144 Specify to use the 16-bit integer ABI.
1147 Specify to use the 32-bit integer ABI.
1149 @item -mshort-double
1150 Specify to use the 32-bit double ABI.
1153 Specify to use the 64-bit double ABI.
1155 @item --force-long-branches
1156 Relative branches are turned into absolute ones. This concerns
1157 conditional branches, unconditional branches and branches to a
1160 @item -S | --short-branches
1161 Do not turn relative branches into absolute ones
1162 when the offset is out of range.
1164 @item --strict-direct-mode
1165 Do not turn the direct addressing mode into extended addressing mode
1166 when the instruction does not support direct addressing mode.
1168 @item --print-insn-syntax
1169 Print the syntax of instruction in case of error.
1171 @item --print-opcodes
1172 Print the list of instructions with syntax and then exit.
1174 @item --generate-example
1175 Print an example of instruction for each possible instruction and then exit.
1176 This option is only useful for testing @command{@value{AS}}.
1182 The following options are available when @command{@value{AS}} is configured
1183 for the SPARC architecture:
1186 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
1187 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
1188 Explicitly select a variant of the SPARC architecture.
1190 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
1191 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
1193 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
1194 UltraSPARC extensions.
1196 @item -xarch=v8plus | -xarch=v8plusa
1197 For compatibility with the Solaris v9 assembler. These options are
1198 equivalent to -Av8plus and -Av8plusa, respectively.
1201 Warn when the assembler switches to another architecture.
1206 The following options are available when @value{AS} is configured for the 'c54x
1211 Enable extended addressing mode. All addresses and relocations will assume
1212 extended addressing (usually 23 bits).
1213 @item -mcpu=@var{CPU_VERSION}
1214 Sets the CPU version being compiled for.
1215 @item -merrors-to-file @var{FILENAME}
1216 Redirect error output to a file, for broken systems which don't support such
1217 behaviour in the shell.
1222 The following options are available when @value{AS} is configured for
1227 This option sets the largest size of an object that can be referenced
1228 implicitly with the @code{gp} register. It is only accepted for targets that
1229 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
1231 @cindex MIPS endianness
1232 @cindex endianness, MIPS
1233 @cindex big endian output, MIPS
1235 Generate ``big endian'' format output.
1237 @cindex little endian output, MIPS
1239 Generate ``little endian'' format output.
1251 Generate code for a particular MIPS Instruction Set Architecture level.
1252 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
1253 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
1254 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
1255 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, @samp{-mips64}, and
1256 @samp{-mips64r2} correspond to generic MIPS V, MIPS32, MIPS32 Release 2,
1257 MIPS64, and MIPS64 Release 2 ISA processors, respectively.
1259 @item -march=@var{cpu}
1260 Generate code for a particular MIPS CPU.
1262 @item -mtune=@var{cpu}
1263 Schedule and tune for a particular MIPS CPU.
1267 Cause nops to be inserted if the read of the destination register
1268 of an mfhi or mflo instruction occurs in the following two instructions.
1272 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
1273 section instead of the standard ELF .stabs sections.
1277 Control generation of @code{.pdr} sections.
1281 The register sizes are normally inferred from the ISA and ABI, but these
1282 flags force a certain group of registers to be treated as 32 bits wide at
1283 all times. @samp{-mgp32} controls the size of general-purpose registers
1284 and @samp{-mfp32} controls the size of floating-point registers.
1288 Generate code for the MIPS 16 processor. This is equivalent to putting
1289 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
1290 turns off this option.
1293 @itemx -mno-micromips
1294 Generate code for the microMIPS processor. This is equivalent to putting
1295 @code{.set micromips} at the start of the assembly file. @samp{-mno-micromips}
1296 turns off this option. This is equivalent to putting @code{.set nomicromips}
1297 at the start of the assembly file.
1300 @itemx -mno-smartmips
1301 Enables the SmartMIPS extension to the MIPS32 instruction set. This is
1302 equivalent to putting @code{.set smartmips} at the start of the assembly file.
1303 @samp{-mno-smartmips} turns off this option.
1307 Generate code for the MIPS-3D Application Specific Extension.
1308 This tells the assembler to accept MIPS-3D instructions.
1309 @samp{-no-mips3d} turns off this option.
1313 Generate code for the MDMX Application Specific Extension.
1314 This tells the assembler to accept MDMX instructions.
1315 @samp{-no-mdmx} turns off this option.
1319 Generate code for the DSP Release 1 Application Specific Extension.
1320 This tells the assembler to accept DSP Release 1 instructions.
1321 @samp{-mno-dsp} turns off this option.
1325 Generate code for the DSP Release 2 Application Specific Extension.
1326 This option implies -mdsp.
1327 This tells the assembler to accept DSP Release 2 instructions.
1328 @samp{-mno-dspr2} turns off this option.
1332 Generate code for the MT Application Specific Extension.
1333 This tells the assembler to accept MT instructions.
1334 @samp{-mno-mt} turns off this option.
1338 Generate code for the MCU Application Specific Extension.
1339 This tells the assembler to accept MCU instructions.
1340 @samp{-mno-mcu} turns off this option.
1344 Only use 32-bit instruction encodings when generating code for the
1345 microMIPS processor. This option inhibits the use of any 16-bit
1346 instructions. This is equivalent to putting @code{.set insn32} at
1347 the start of the assembly file. @samp{-mno-insn32} turns off this
1348 option. This is equivalent to putting @code{.set noinsn32} at the
1349 start of the assembly file. By default @samp{-mno-insn32} is
1350 selected, allowing all instructions to be used.
1352 @item --construct-floats
1353 @itemx --no-construct-floats
1354 The @samp{--no-construct-floats} option disables the construction of
1355 double width floating point constants by loading the two halves of the
1356 value into the two single width floating point registers that make up
1357 the double width register. By default @samp{--construct-floats} is
1358 selected, allowing construction of these floating point constants.
1360 @item --relax-branch
1361 @itemx --no-relax-branch
1362 The @samp{--relax-branch} option enables the relaxation of out-of-range
1363 branches. By default @samp{--no-relax-branch} is selected, causing any
1364 out-of-range branches to produce an error.
1367 @item --emulation=@var{name}
1368 This option was formerly used to switch between ELF and ECOFF output
1369 on targets like IRIX 5 that supported both. MIPS ECOFF support was
1370 removed in GAS 2.24, so the option now serves little purpose.
1371 It is retained for backwards compatibility.
1373 The available configuration names are: @samp{mipself}, @samp{mipslelf} and
1374 @samp{mipsbelf}. Choosing @samp{mipself} now has no effect, since the output
1375 is always ELF. @samp{mipslelf} and @samp{mipsbelf} select little- and
1376 big-endian output respectively, but @samp{-EL} and @samp{-EB} are now the
1377 preferred options instead.
1380 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1387 Control how to deal with multiplication overflow and division by zero.
1388 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1389 (and only work for Instruction Set Architecture level 2 and higher);
1390 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1394 When this option is used, @command{@value{AS}} will issue a warning every
1395 time it generates a nop instruction from a macro.
1400 The following options are available when @value{AS} is configured for
1406 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1407 The command line option @samp{-nojsri2bsr} can be used to disable it.
1411 Enable or disable the silicon filter behaviour. By default this is disabled.
1412 The default can be overridden by the @samp{-sifilter} command line option.
1415 Alter jump instructions for long displacements.
1417 @item -mcpu=[210|340]
1418 Select the cpu type on the target hardware. This controls which instructions
1422 Assemble for a big endian target.
1425 Assemble for a little endian target.
1434 @xref{Meta Options}, for the options available when @value{AS} is configured
1435 for a Meta processor.
1439 @c man begin OPTIONS
1440 The following options are available when @value{AS} is configured for a
1443 @c man begin INCLUDE
1444 @include c-metag.texi
1445 @c ended inside the included file
1450 @c man begin OPTIONS
1452 See the info pages for documentation of the MMIX-specific options.
1459 @xref{PowerPC-Opts}, for the options available when @value{AS} is configured
1460 for a PowerPC processor.
1464 @c man begin OPTIONS
1465 The following options are available when @value{AS} is configured for a
1468 @c man begin INCLUDE
1470 @c ended inside the included file
1475 @c man begin OPTIONS
1477 See the info pages for documentation of the RX-specific options.
1481 The following options are available when @value{AS} is configured for the s390
1487 Select the word size, either 31/32 bits or 64 bits.
1490 Select the architecture mode, either the Enterprise System
1491 Architecture (esa) or the z/Architecture mode (zarch).
1492 @item -march=@var{processor}
1493 Specify which s390 processor variant is the target, @samp{g6}, @samp{g6},
1494 @samp{z900}, @samp{z990}, @samp{z9-109}, @samp{z9-ec}, @samp{z10},
1495 @samp{z196}, or @samp{zEC12}.
1497 @itemx -mno-regnames
1498 Allow or disallow symbolic names for registers.
1499 @item -mwarn-areg-zero
1500 Warn whenever the operand for a base or index register has been specified
1501 but evaluates to zero.
1509 @xref{TIC6X Options}, for the options available when @value{AS} is configured
1510 for a TMS320C6000 processor.
1514 @c man begin OPTIONS
1515 The following options are available when @value{AS} is configured for a
1516 TMS320C6000 processor.
1518 @c man begin INCLUDE
1519 @include c-tic6x.texi
1520 @c ended inside the included file
1528 @xref{TILE-Gx Options}, for the options available when @value{AS} is configured
1529 for a TILE-Gx processor.
1533 @c man begin OPTIONS
1534 The following options are available when @value{AS} is configured for a TILE-Gx
1537 @c man begin INCLUDE
1538 @include c-tilegx.texi
1539 @c ended inside the included file
1547 @xref{Xtensa Options}, for the options available when @value{AS} is configured
1548 for an Xtensa processor.
1552 @c man begin OPTIONS
1553 The following options are available when @value{AS} is configured for an
1556 @c man begin INCLUDE
1557 @include c-xtensa.texi
1558 @c ended inside the included file
1563 @c man begin OPTIONS
1566 The following options are available when @value{AS} is configured for
1567 a Z80 family processor.
1570 Assemble for Z80 processor.
1572 Assemble for R800 processor.
1573 @item -ignore-undocumented-instructions
1575 Assemble undocumented Z80 instructions that also work on R800 without warning.
1576 @item -ignore-unportable-instructions
1578 Assemble all undocumented Z80 instructions without warning.
1579 @item -warn-undocumented-instructions
1581 Issue a warning for undocumented Z80 instructions that also work on R800.
1582 @item -warn-unportable-instructions
1584 Issue a warning for undocumented Z80 instructions that do not work on R800.
1585 @item -forbid-undocumented-instructions
1587 Treat all undocumented instructions as errors.
1588 @item -forbid-unportable-instructions
1590 Treat undocumented Z80 instructions that do not work on R800 as errors.
1597 * Manual:: Structure of this Manual
1598 * GNU Assembler:: The GNU Assembler
1599 * Object Formats:: Object File Formats
1600 * Command Line:: Command Line
1601 * Input Files:: Input Files
1602 * Object:: Output (Object) File
1603 * Errors:: Error and Warning Messages
1607 @section Structure of this Manual
1609 @cindex manual, structure and purpose
1610 This manual is intended to describe what you need to know to use
1611 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1612 notation for symbols, constants, and expressions; the directives that
1613 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1616 We also cover special features in the @value{TARGET}
1617 configuration of @command{@value{AS}}, including assembler directives.
1620 This manual also describes some of the machine-dependent features of
1621 various flavors of the assembler.
1624 @cindex machine instructions (not covered)
1625 On the other hand, this manual is @emph{not} intended as an introduction
1626 to programming in assembly language---let alone programming in general!
1627 In a similar vein, we make no attempt to introduce the machine
1628 architecture; we do @emph{not} describe the instruction set, standard
1629 mnemonics, registers or addressing modes that are standard to a
1630 particular architecture.
1632 You may want to consult the manufacturer's
1633 machine architecture manual for this information.
1637 For information on the H8/300 machine instruction set, see @cite{H8/300
1638 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1639 Programming Manual} (Renesas).
1642 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1643 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1644 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1645 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1648 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1652 @c I think this is premature---doc@cygnus.com, 17jan1991
1654 Throughout this manual, we assume that you are running @dfn{GNU},
1655 the portable operating system from the @dfn{Free Software
1656 Foundation, Inc.}. This restricts our attention to certain kinds of
1657 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1658 once this assumption is granted examples and definitions need less
1661 @command{@value{AS}} is part of a team of programs that turn a high-level
1662 human-readable series of instructions into a low-level
1663 computer-readable series of instructions. Different versions of
1664 @command{@value{AS}} are used for different kinds of computer.
1667 @c There used to be a section "Terminology" here, which defined
1668 @c "contents", "byte", "word", and "long". Defining "word" to any
1669 @c particular size is confusing when the .word directive may generate 16
1670 @c bits on one machine and 32 bits on another; in general, for the user
1671 @c version of this manual, none of these terms seem essential to define.
1672 @c They were used very little even in the former draft of the manual;
1673 @c this draft makes an effort to avoid them (except in names of
1677 @section The GNU Assembler
1679 @c man begin DESCRIPTION
1681 @sc{gnu} @command{as} is really a family of assemblers.
1683 This manual describes @command{@value{AS}}, a member of that family which is
1684 configured for the @value{TARGET} architectures.
1686 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1687 should find a fairly similar environment when you use it on another
1688 architecture. Each version has much in common with the others,
1689 including object file formats, most assembler directives (often called
1690 @dfn{pseudo-ops}) and assembler syntax.@refill
1692 @cindex purpose of @sc{gnu} assembler
1693 @command{@value{AS}} is primarily intended to assemble the output of the
1694 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1695 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1696 assemble correctly everything that other assemblers for the same
1697 machine would assemble.
1699 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1702 @c This remark should appear in generic version of manual; assumption
1703 @c here is that generic version sets M680x0.
1704 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1705 assembler for the same architecture; for example, we know of several
1706 incompatible versions of 680x0 assembly language syntax.
1711 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1712 program in one pass of the source file. This has a subtle impact on the
1713 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1715 @node Object Formats
1716 @section Object File Formats
1718 @cindex object file format
1719 The @sc{gnu} assembler can be configured to produce several alternative
1720 object file formats. For the most part, this does not affect how you
1721 write assembly language programs; but directives for debugging symbols
1722 are typically different in different file formats. @xref{Symbol
1723 Attributes,,Symbol Attributes}.
1726 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1727 @value{OBJ-NAME} format object files.
1729 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1731 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1732 @code{b.out} or COFF format object files.
1735 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1736 SOM or ELF format object files.
1741 @section Command Line
1743 @cindex command line conventions
1745 After the program name @command{@value{AS}}, the command line may contain
1746 options and file names. Options may appear in any order, and may be
1747 before, after, or between file names. The order of file names is
1750 @cindex standard input, as input file
1752 @file{--} (two hyphens) by itself names the standard input file
1753 explicitly, as one of the files for @command{@value{AS}} to assemble.
1755 @cindex options, command line
1756 Except for @samp{--} any command line argument that begins with a
1757 hyphen (@samp{-}) is an option. Each option changes the behavior of
1758 @command{@value{AS}}. No option changes the way another option works. An
1759 option is a @samp{-} followed by one or more letters; the case of
1760 the letter is important. All options are optional.
1762 Some options expect exactly one file name to follow them. The file
1763 name may either immediately follow the option's letter (compatible
1764 with older assemblers) or it may be the next command argument (@sc{gnu}
1765 standard). These two command lines are equivalent:
1768 @value{AS} -o my-object-file.o mumble.s
1769 @value{AS} -omy-object-file.o mumble.s
1773 @section Input Files
1776 @cindex source program
1777 @cindex files, input
1778 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1779 describe the program input to one run of @command{@value{AS}}. The program may
1780 be in one or more files; how the source is partitioned into files
1781 doesn't change the meaning of the source.
1783 @c I added "con" prefix to "catenation" just to prove I can overcome my
1784 @c APL training... doc@cygnus.com
1785 The source program is a concatenation of the text in all the files, in the
1788 @c man begin DESCRIPTION
1789 Each time you run @command{@value{AS}} it assembles exactly one source
1790 program. The source program is made up of one or more files.
1791 (The standard input is also a file.)
1793 You give @command{@value{AS}} a command line that has zero or more input file
1794 names. The input files are read (from left file name to right). A
1795 command line argument (in any position) that has no special meaning
1796 is taken to be an input file name.
1798 If you give @command{@value{AS}} no file names it attempts to read one input file
1799 from the @command{@value{AS}} standard input, which is normally your terminal. You
1800 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1803 Use @samp{--} if you need to explicitly name the standard input file
1804 in your command line.
1806 If the source is empty, @command{@value{AS}} produces a small, empty object
1811 @subheading Filenames and Line-numbers
1813 @cindex input file linenumbers
1814 @cindex line numbers, in input files
1815 There are two ways of locating a line in the input file (or files) and
1816 either may be used in reporting error messages. One way refers to a line
1817 number in a physical file; the other refers to a line number in a
1818 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1820 @dfn{Physical files} are those files named in the command line given
1821 to @command{@value{AS}}.
1823 @dfn{Logical files} are simply names declared explicitly by assembler
1824 directives; they bear no relation to physical files. Logical file names help
1825 error messages reflect the original source file, when @command{@value{AS}} source
1826 is itself synthesized from other files. @command{@value{AS}} understands the
1827 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1828 @ref{File,,@code{.file}}.
1831 @section Output (Object) File
1837 Every time you run @command{@value{AS}} it produces an output file, which is
1838 your assembly language program translated into numbers. This file
1839 is the object file. Its default name is
1847 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1849 You can give it another name by using the @option{-o} option. Conventionally,
1850 object file names end with @file{.o}. The default name is used for historical
1851 reasons: older assemblers were capable of assembling self-contained programs
1852 directly into a runnable program. (For some formats, this isn't currently
1853 possible, but it can be done for the @code{a.out} format.)
1857 The object file is meant for input to the linker @code{@value{LD}}. It contains
1858 assembled program code, information to help @code{@value{LD}} integrate
1859 the assembled program into a runnable file, and (optionally) symbolic
1860 information for the debugger.
1862 @c link above to some info file(s) like the description of a.out.
1863 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1866 @section Error and Warning Messages
1868 @c man begin DESCRIPTION
1870 @cindex error messages
1871 @cindex warning messages
1872 @cindex messages from assembler
1873 @command{@value{AS}} may write warnings and error messages to the standard error
1874 file (usually your terminal). This should not happen when a compiler
1875 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1876 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1877 grave problem that stops the assembly.
1881 @cindex format of warning messages
1882 Warning messages have the format
1885 file_name:@b{NNN}:Warning Message Text
1889 @cindex line numbers, in warnings/errors
1890 (where @b{NNN} is a line number). If a logical file name has been given
1891 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1892 the current input file is used. If a logical line number was given
1894 (@pxref{Line,,@code{.line}})
1896 then it is used to calculate the number printed,
1897 otherwise the actual line in the current source file is printed. The
1898 message text is intended to be self explanatory (in the grand Unix
1901 @cindex format of error messages
1902 Error messages have the format
1904 file_name:@b{NNN}:FATAL:Error Message Text
1906 The file name and line number are derived as for warning
1907 messages. The actual message text may be rather less explanatory
1908 because many of them aren't supposed to happen.
1911 @chapter Command-Line Options
1913 @cindex options, all versions of assembler
1914 This chapter describes command-line options available in @emph{all}
1915 versions of the @sc{gnu} assembler; see @ref{Machine Dependencies},
1916 for options specific
1918 to the @value{TARGET} target.
1921 to particular machine architectures.
1924 @c man begin DESCRIPTION
1926 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1927 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1928 The assembler arguments must be separated from each other (and the @samp{-Wa})
1929 by commas. For example:
1932 gcc -c -g -O -Wa,-alh,-L file.c
1936 This passes two options to the assembler: @samp{-alh} (emit a listing to
1937 standard output with high-level and assembly source) and @samp{-L} (retain
1938 local symbols in the symbol table).
1940 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1941 command-line options are automatically passed to the assembler by the compiler.
1942 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1943 precisely what options it passes to each compilation pass, including the
1949 * a:: -a[cdghlns] enable listings
1950 * alternate:: --alternate enable alternate macro syntax
1951 * D:: -D for compatibility
1952 * f:: -f to work faster
1953 * I:: -I for .include search path
1954 @ifclear DIFF-TBL-KLUGE
1955 * K:: -K for compatibility
1957 @ifset DIFF-TBL-KLUGE
1958 * K:: -K for difference tables
1961 * L:: -L to retain local symbols
1962 * listing:: --listing-XXX to configure listing output
1963 * M:: -M or --mri to assemble in MRI compatibility mode
1964 * MD:: --MD for dependency tracking
1965 * o:: -o to name the object file
1966 * R:: -R to join data and text sections
1967 * statistics:: --statistics to see statistics about assembly
1968 * traditional-format:: --traditional-format for compatible output
1969 * v:: -v to announce version
1970 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1971 * Z:: -Z to make object file even after errors
1975 @section Enable Listings: @option{-a[cdghlns]}
1985 @cindex listings, enabling
1986 @cindex assembly listings, enabling
1988 These options enable listing output from the assembler. By itself,
1989 @samp{-a} requests high-level, assembly, and symbols listing.
1990 You can use other letters to select specific options for the list:
1991 @samp{-ah} requests a high-level language listing,
1992 @samp{-al} requests an output-program assembly listing, and
1993 @samp{-as} requests a symbol table listing.
1994 High-level listings require that a compiler debugging option like
1995 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1998 Use the @samp{-ag} option to print a first section with general assembly
1999 information, like @value{AS} version, switches passed, or time stamp.
2001 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
2002 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
2003 other conditional), or a true @code{.if} followed by an @code{.else}, will be
2004 omitted from the listing.
2006 Use the @samp{-ad} option to omit debugging directives from the
2009 Once you have specified one of these options, you can further control
2010 listing output and its appearance using the directives @code{.list},
2011 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
2013 The @samp{-an} option turns off all forms processing.
2014 If you do not request listing output with one of the @samp{-a} options, the
2015 listing-control directives have no effect.
2017 The letters after @samp{-a} may be combined into one option,
2018 @emph{e.g.}, @samp{-aln}.
2020 Note if the assembler source is coming from the standard input (e.g.,
2022 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
2023 is being used) then the listing will not contain any comments or preprocessor
2024 directives. This is because the listing code buffers input source lines from
2025 stdin only after they have been preprocessed by the assembler. This reduces
2026 memory usage and makes the code more efficient.
2029 @section @option{--alternate}
2032 Begin in alternate macro mode, see @ref{Altmacro,,@code{.altmacro}}.
2035 @section @option{-D}
2038 This option has no effect whatsoever, but it is accepted to make it more
2039 likely that scripts written for other assemblers also work with
2040 @command{@value{AS}}.
2043 @section Work Faster: @option{-f}
2046 @cindex trusted compiler
2047 @cindex faster processing (@option{-f})
2048 @samp{-f} should only be used when assembling programs written by a
2049 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
2050 and comment preprocessing on
2051 the input file(s) before assembling them. @xref{Preprocessing,
2055 @emph{Warning:} if you use @samp{-f} when the files actually need to be
2056 preprocessed (if they contain comments, for example), @command{@value{AS}} does
2061 @section @code{.include} Search Path: @option{-I} @var{path}
2063 @kindex -I @var{path}
2064 @cindex paths for @code{.include}
2065 @cindex search path for @code{.include}
2066 @cindex @code{include} directive search path
2067 Use this option to add a @var{path} to the list of directories
2068 @command{@value{AS}} searches for files specified in @code{.include}
2069 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
2070 many times as necessary to include a variety of paths. The current
2071 working directory is always searched first; after that, @command{@value{AS}}
2072 searches any @samp{-I} directories in the same order as they were
2073 specified (left to right) on the command line.
2076 @section Difference Tables: @option{-K}
2079 @ifclear DIFF-TBL-KLUGE
2080 On the @value{TARGET} family, this option is allowed, but has no effect. It is
2081 permitted for compatibility with the @sc{gnu} assembler on other platforms,
2082 where it can be used to warn when the assembler alters the machine code
2083 generated for @samp{.word} directives in difference tables. The @value{TARGET}
2084 family does not have the addressing limitations that sometimes lead to this
2085 alteration on other platforms.
2088 @ifset DIFF-TBL-KLUGE
2089 @cindex difference tables, warning
2090 @cindex warning for altered difference tables
2091 @command{@value{AS}} sometimes alters the code emitted for directives of the
2092 form @samp{.word @var{sym1}-@var{sym2}}. @xref{Word,,@code{.word}}.
2093 You can use the @samp{-K} option if you want a warning issued when this
2098 @section Include Local Symbols: @option{-L}
2101 @cindex local symbols, retaining in output
2102 Symbols beginning with system-specific local label prefixes, typically
2103 @samp{.L} for ELF systems or @samp{L} for traditional a.out systems, are
2104 called @dfn{local symbols}. @xref{Symbol Names}. Normally you do not see
2105 such symbols when debugging, because they are intended for the use of
2106 programs (like compilers) that compose assembler programs, not for your
2107 notice. Normally both @command{@value{AS}} and @code{@value{LD}} discard
2108 such symbols, so you do not normally debug with them.
2110 This option tells @command{@value{AS}} to retain those local symbols
2111 in the object file. Usually if you do this you also tell the linker
2112 @code{@value{LD}} to preserve those symbols.
2115 @section Configuring listing output: @option{--listing}
2117 The listing feature of the assembler can be enabled via the command line switch
2118 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
2119 hex dump of the corresponding locations in the output object file, and displays
2120 them as a listing file. The format of this listing can be controlled by
2121 directives inside the assembler source (i.e., @code{.list} (@pxref{List}),
2122 @code{.title} (@pxref{Title}), @code{.sbttl} (@pxref{Sbttl}),
2123 @code{.psize} (@pxref{Psize}), and
2124 @code{.eject} (@pxref{Eject}) and also by the following switches:
2127 @item --listing-lhs-width=@samp{number}
2128 @kindex --listing-lhs-width
2129 @cindex Width of first line disassembly output
2130 Sets the maximum width, in words, of the first line of the hex byte dump. This
2131 dump appears on the left hand side of the listing output.
2133 @item --listing-lhs-width2=@samp{number}
2134 @kindex --listing-lhs-width2
2135 @cindex Width of continuation lines of disassembly output
2136 Sets the maximum width, in words, of any further lines of the hex byte dump for
2137 a given input source line. If this value is not specified, it defaults to being
2138 the same as the value specified for @samp{--listing-lhs-width}. If neither
2139 switch is used the default is to one.
2141 @item --listing-rhs-width=@samp{number}
2142 @kindex --listing-rhs-width
2143 @cindex Width of source line output
2144 Sets the maximum width, in characters, of the source line that is displayed
2145 alongside the hex dump. The default value for this parameter is 100. The
2146 source line is displayed on the right hand side of the listing output.
2148 @item --listing-cont-lines=@samp{number}
2149 @kindex --listing-cont-lines
2150 @cindex Maximum number of continuation lines
2151 Sets the maximum number of continuation lines of hex dump that will be
2152 displayed for a given single line of source input. The default value is 4.
2156 @section Assemble in MRI Compatibility Mode: @option{-M}
2159 @cindex MRI compatibility mode
2160 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
2161 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
2162 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
2163 configured target) assembler from Microtec Research. The exact nature of the
2164 MRI syntax will not be documented here; see the MRI manuals for more
2165 information. Note in particular that the handling of macros and macro
2166 arguments is somewhat different. The purpose of this option is to permit
2167 assembling existing MRI assembler code using @command{@value{AS}}.
2169 The MRI compatibility is not complete. Certain operations of the MRI assembler
2170 depend upon its object file format, and can not be supported using other object
2171 file formats. Supporting these would require enhancing each object file format
2172 individually. These are:
2175 @item global symbols in common section
2177 The m68k MRI assembler supports common sections which are merged by the linker.
2178 Other object file formats do not support this. @command{@value{AS}} handles
2179 common sections by treating them as a single common symbol. It permits local
2180 symbols to be defined within a common section, but it can not support global
2181 symbols, since it has no way to describe them.
2183 @item complex relocations
2185 The MRI assemblers support relocations against a negated section address, and
2186 relocations which combine the start addresses of two or more sections. These
2187 are not support by other object file formats.
2189 @item @code{END} pseudo-op specifying start address
2191 The MRI @code{END} pseudo-op permits the specification of a start address.
2192 This is not supported by other object file formats. The start address may
2193 instead be specified using the @option{-e} option to the linker, or in a linker
2196 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
2198 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
2199 name to the output file. This is not supported by other object file formats.
2201 @item @code{ORG} pseudo-op
2203 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
2204 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
2205 which changes the location within the current section. Absolute sections are
2206 not supported by other object file formats. The address of a section may be
2207 assigned within a linker script.
2210 There are some other features of the MRI assembler which are not supported by
2211 @command{@value{AS}}, typically either because they are difficult or because they
2212 seem of little consequence. Some of these may be supported in future releases.
2216 @item EBCDIC strings
2218 EBCDIC strings are not supported.
2220 @item packed binary coded decimal
2222 Packed binary coded decimal is not supported. This means that the @code{DC.P}
2223 and @code{DCB.P} pseudo-ops are not supported.
2225 @item @code{FEQU} pseudo-op
2227 The m68k @code{FEQU} pseudo-op is not supported.
2229 @item @code{NOOBJ} pseudo-op
2231 The m68k @code{NOOBJ} pseudo-op is not supported.
2233 @item @code{OPT} branch control options
2235 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
2236 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
2237 relaxes all branches, whether forward or backward, to an appropriate size, so
2238 these options serve no purpose.
2240 @item @code{OPT} list control options
2242 The following m68k @code{OPT} list control options are ignored: @code{C},
2243 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
2244 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
2246 @item other @code{OPT} options
2248 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
2249 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
2251 @item @code{OPT} @code{D} option is default
2253 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
2254 @code{OPT NOD} may be used to turn it off.
2256 @item @code{XREF} pseudo-op.
2258 The m68k @code{XREF} pseudo-op is ignored.
2260 @item @code{.debug} pseudo-op
2262 The i960 @code{.debug} pseudo-op is not supported.
2264 @item @code{.extended} pseudo-op
2266 The i960 @code{.extended} pseudo-op is not supported.
2268 @item @code{.list} pseudo-op.
2270 The various options of the i960 @code{.list} pseudo-op are not supported.
2272 @item @code{.optimize} pseudo-op
2274 The i960 @code{.optimize} pseudo-op is not supported.
2276 @item @code{.output} pseudo-op
2278 The i960 @code{.output} pseudo-op is not supported.
2280 @item @code{.setreal} pseudo-op
2282 The i960 @code{.setreal} pseudo-op is not supported.
2287 @section Dependency Tracking: @option{--MD}
2290 @cindex dependency tracking
2293 @command{@value{AS}} can generate a dependency file for the file it creates. This
2294 file consists of a single rule suitable for @code{make} describing the
2295 dependencies of the main source file.
2297 The rule is written to the file named in its argument.
2299 This feature is used in the automatic updating of makefiles.
2302 @section Name the Object File: @option{-o}
2305 @cindex naming object file
2306 @cindex object file name
2307 There is always one object file output when you run @command{@value{AS}}. By
2308 default it has the name
2311 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
2325 You use this option (which takes exactly one filename) to give the
2326 object file a different name.
2328 Whatever the object file is called, @command{@value{AS}} overwrites any
2329 existing file of the same name.
2332 @section Join Data and Text Sections: @option{-R}
2335 @cindex data and text sections, joining
2336 @cindex text and data sections, joining
2337 @cindex joining text and data sections
2338 @cindex merging text and data sections
2339 @option{-R} tells @command{@value{AS}} to write the object file as if all
2340 data-section data lives in the text section. This is only done at
2341 the very last moment: your binary data are the same, but data
2342 section parts are relocated differently. The data section part of
2343 your object file is zero bytes long because all its bytes are
2344 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
2346 When you specify @option{-R} it would be possible to generate shorter
2347 address displacements (because we do not have to cross between text and
2348 data section). We refrain from doing this simply for compatibility with
2349 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
2352 When @command{@value{AS}} is configured for COFF or ELF output,
2353 this option is only useful if you use sections named @samp{.text} and
2358 @option{-R} is not supported for any of the HPPA targets. Using
2359 @option{-R} generates a warning from @command{@value{AS}}.
2363 @section Display Assembly Statistics: @option{--statistics}
2365 @kindex --statistics
2366 @cindex statistics, about assembly
2367 @cindex time, total for assembly
2368 @cindex space used, maximum for assembly
2369 Use @samp{--statistics} to display two statistics about the resources used by
2370 @command{@value{AS}}: the maximum amount of space allocated during the assembly
2371 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
2374 @node traditional-format
2375 @section Compatible Output: @option{--traditional-format}
2377 @kindex --traditional-format
2378 For some targets, the output of @command{@value{AS}} is different in some ways
2379 from the output of some existing assembler. This switch requests
2380 @command{@value{AS}} to use the traditional format instead.
2382 For example, it disables the exception frame optimizations which
2383 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
2386 @section Announce Version: @option{-v}
2390 @cindex assembler version
2391 @cindex version of assembler
2392 You can find out what version of as is running by including the
2393 option @samp{-v} (which you can also spell as @samp{-version}) on the
2397 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
2399 @command{@value{AS}} should never give a warning or error message when
2400 assembling compiler output. But programs written by people often
2401 cause @command{@value{AS}} to give a warning that a particular assumption was
2402 made. All such warnings are directed to the standard error file.
2406 @cindex suppressing warnings
2407 @cindex warnings, suppressing
2408 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
2409 This only affects the warning messages: it does not change any particular of
2410 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
2413 @kindex --fatal-warnings
2414 @cindex errors, caused by warnings
2415 @cindex warnings, causing error
2416 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
2417 files that generate warnings to be in error.
2420 @cindex warnings, switching on
2421 You can switch these options off again by specifying @option{--warn}, which
2422 causes warnings to be output as usual.
2425 @section Generate Object File in Spite of Errors: @option{-Z}
2426 @cindex object file, after errors
2427 @cindex errors, continuing after
2428 After an error message, @command{@value{AS}} normally produces no output. If for
2429 some reason you are interested in object file output even after
2430 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
2431 option. If there are any errors, @command{@value{AS}} continues anyways, and
2432 writes an object file after a final warning message of the form @samp{@var{n}
2433 errors, @var{m} warnings, generating bad object file.}
2438 @cindex machine-independent syntax
2439 @cindex syntax, machine-independent
2440 This chapter describes the machine-independent syntax allowed in a
2441 source file. @command{@value{AS}} syntax is similar to what many other
2442 assemblers use; it is inspired by the BSD 4.2
2447 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
2451 * Preprocessing:: Preprocessing
2452 * Whitespace:: Whitespace
2453 * Comments:: Comments
2454 * Symbol Intro:: Symbols
2455 * Statements:: Statements
2456 * Constants:: Constants
2460 @section Preprocessing
2462 @cindex preprocessing
2463 The @command{@value{AS}} internal preprocessor:
2465 @cindex whitespace, removed by preprocessor
2467 adjusts and removes extra whitespace. It leaves one space or tab before
2468 the keywords on a line, and turns any other whitespace on the line into
2471 @cindex comments, removed by preprocessor
2473 removes all comments, replacing them with a single space, or an
2474 appropriate number of newlines.
2476 @cindex constants, converted by preprocessor
2478 converts character constants into the appropriate numeric values.
2481 It does not do macro processing, include file handling, or
2482 anything else you may get from your C compiler's preprocessor. You can
2483 do include file processing with the @code{.include} directive
2484 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2485 to get other ``CPP'' style preprocessing by giving the input file a
2486 @samp{.S} suffix. @xref{Overall Options, ,Options Controlling the Kind of
2487 Output, gcc.info, Using GNU CC}.
2489 Excess whitespace, comments, and character constants
2490 cannot be used in the portions of the input text that are not
2493 @cindex turning preprocessing on and off
2494 @cindex preprocessing, turning on and off
2497 If the first line of an input file is @code{#NO_APP} or if you use the
2498 @samp{-f} option, whitespace and comments are not removed from the input file.
2499 Within an input file, you can ask for whitespace and comment removal in
2500 specific portions of the by putting a line that says @code{#APP} before the
2501 text that may contain whitespace or comments, and putting a line that says
2502 @code{#NO_APP} after this text. This feature is mainly intend to support
2503 @code{asm} statements in compilers whose output is otherwise free of comments
2510 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2511 Whitespace is used to separate symbols, and to make programs neater for
2512 people to read. Unless within character constants
2513 (@pxref{Characters,,Character Constants}), any whitespace means the same
2514 as exactly one space.
2520 There are two ways of rendering comments to @command{@value{AS}}. In both
2521 cases the comment is equivalent to one space.
2523 Anything from @samp{/*} through the next @samp{*/} is a comment.
2524 This means you may not nest these comments.
2528 The only way to include a newline ('\n') in a comment
2529 is to use this sort of comment.
2532 /* This sort of comment does not nest. */
2535 @cindex line comment character
2536 Anything from a @dfn{line comment} character up to the next newline is
2537 considered a comment and is ignored. The line comment character is target
2538 specific, and some targets multiple comment characters. Some targets also have
2539 line comment characters that only work if they are the first character on a
2540 line. Some targets use a sequence of two characters to introduce a line
2541 comment. Some targets can also change their line comment characters depending
2542 upon command line options that have been used. For more details see the
2543 @emph{Syntax} section in the documentation for individual targets.
2545 If the line comment character is the hash sign (@samp{#}) then it still has the
2546 special ability to enable and disable preprocessing (@pxref{Preprocessing}) and
2547 to specify logical line numbers:
2550 @cindex lines starting with @code{#}
2551 @cindex logical line numbers
2552 To be compatible with past assemblers, lines that begin with @samp{#} have a
2553 special interpretation. Following the @samp{#} should be an absolute
2554 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2555 line. Then a string (@pxref{Strings, ,Strings}) is allowed: if present it is a
2556 new logical file name. The rest of the line, if any, should be whitespace.
2558 If the first non-whitespace characters on the line are not numeric,
2559 the line is ignored. (Just like a comment.)
2562 # This is an ordinary comment.
2563 # 42-6 "new_file_name" # New logical file name
2564 # This is logical line # 36.
2566 This feature is deprecated, and may disappear from future versions
2567 of @command{@value{AS}}.
2572 @cindex characters used in symbols
2573 @ifclear SPECIAL-SYMS
2574 A @dfn{symbol} is one or more characters chosen from the set of all
2575 letters (both upper and lower case), digits and the three characters
2581 A @dfn{symbol} is one or more characters chosen from the set of all
2582 letters (both upper and lower case), digits and the three characters
2583 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2589 On most machines, you can also use @code{$} in symbol names; exceptions
2590 are noted in @ref{Machine Dependencies}.
2592 No symbol may begin with a digit. Case is significant.
2593 There is no length limit: all characters are significant. Multibyte characters
2594 are supported. Symbols are delimited by characters not in that set, or by the
2595 beginning of a file (since the source program must end with a newline, the end
2596 of a file is not a possible symbol delimiter). @xref{Symbols}.
2597 @cindex length of symbols
2602 @cindex statements, structure of
2603 @cindex line separator character
2604 @cindex statement separator character
2606 A @dfn{statement} ends at a newline character (@samp{\n}) or a
2607 @dfn{line separator character}. The line separator character is target
2608 specific and described in the @emph{Syntax} section of each
2609 target's documentation. Not all targets support a line separator character.
2610 The newline or line separator character is considered to be part of the
2611 preceding statement. Newlines and separators within character constants are an
2612 exception: they do not end statements.
2614 @cindex newline, required at file end
2615 @cindex EOF, newline must precede
2616 It is an error to end any statement with end-of-file: the last
2617 character of any input file should be a newline.@refill
2619 An empty statement is allowed, and may include whitespace. It is ignored.
2621 @cindex instructions and directives
2622 @cindex directives and instructions
2623 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2624 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2626 A statement begins with zero or more labels, optionally followed by a
2627 key symbol which determines what kind of statement it is. The key
2628 symbol determines the syntax of the rest of the statement. If the
2629 symbol begins with a dot @samp{.} then the statement is an assembler
2630 directive: typically valid for any computer. If the symbol begins with
2631 a letter the statement is an assembly language @dfn{instruction}: it
2632 assembles into a machine language instruction.
2634 Different versions of @command{@value{AS}} for different computers
2635 recognize different instructions. In fact, the same symbol may
2636 represent a different instruction in a different computer's assembly
2640 @cindex @code{:} (label)
2641 @cindex label (@code{:})
2642 A label is a symbol immediately followed by a colon (@code{:}).
2643 Whitespace before a label or after a colon is permitted, but you may not
2644 have whitespace between a label's symbol and its colon. @xref{Labels}.
2647 For HPPA targets, labels need not be immediately followed by a colon, but
2648 the definition of a label must begin in column zero. This also implies that
2649 only one label may be defined on each line.
2653 label: .directive followed by something
2654 another_label: # This is an empty statement.
2655 instruction operand_1, operand_2, @dots{}
2662 A constant is a number, written so that its value is known by
2663 inspection, without knowing any context. Like this:
2666 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2667 .ascii "Ring the bell\7" # A string constant.
2668 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2669 .float 0f-314159265358979323846264338327\
2670 95028841971.693993751E-40 # - pi, a flonum.
2675 * Characters:: Character Constants
2676 * Numbers:: Number Constants
2680 @subsection Character Constants
2682 @cindex character constants
2683 @cindex constants, character
2684 There are two kinds of character constants. A @dfn{character} stands
2685 for one character in one byte and its value may be used in
2686 numeric expressions. String constants (properly called string
2687 @emph{literals}) are potentially many bytes and their values may not be
2688 used in arithmetic expressions.
2692 * Chars:: Characters
2696 @subsubsection Strings
2698 @cindex string constants
2699 @cindex constants, string
2700 A @dfn{string} is written between double-quotes. It may contain
2701 double-quotes or null characters. The way to get special characters
2702 into a string is to @dfn{escape} these characters: precede them with
2703 a backslash @samp{\} character. For example @samp{\\} represents
2704 one backslash: the first @code{\} is an escape which tells
2705 @command{@value{AS}} to interpret the second character literally as a backslash
2706 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2707 escape character). The complete list of escapes follows.
2709 @cindex escape codes, character
2710 @cindex character escape codes
2713 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2715 @cindex @code{\b} (backspace character)
2716 @cindex backspace (@code{\b})
2718 Mnemonic for backspace; for ASCII this is octal code 010.
2721 @c Mnemonic for EOText; for ASCII this is octal code 004.
2723 @cindex @code{\f} (formfeed character)
2724 @cindex formfeed (@code{\f})
2726 Mnemonic for FormFeed; for ASCII this is octal code 014.
2728 @cindex @code{\n} (newline character)
2729 @cindex newline (@code{\n})
2731 Mnemonic for newline; for ASCII this is octal code 012.
2734 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2736 @cindex @code{\r} (carriage return character)
2737 @cindex carriage return (@code{\r})
2739 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2742 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2743 @c other assemblers.
2745 @cindex @code{\t} (tab)
2746 @cindex tab (@code{\t})
2748 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2751 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2752 @c @item \x @var{digit} @var{digit} @var{digit}
2753 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2755 @cindex @code{\@var{ddd}} (octal character code)
2756 @cindex octal character code (@code{\@var{ddd}})
2757 @item \ @var{digit} @var{digit} @var{digit}
2758 An octal character code. The numeric code is 3 octal digits.
2759 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2760 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2762 @cindex @code{\@var{xd...}} (hex character code)
2763 @cindex hex character code (@code{\@var{xd...}})
2764 @item \@code{x} @var{hex-digits...}
2765 A hex character code. All trailing hex digits are combined. Either upper or
2766 lower case @code{x} works.
2768 @cindex @code{\\} (@samp{\} character)
2769 @cindex backslash (@code{\\})
2771 Represents one @samp{\} character.
2774 @c Represents one @samp{'} (accent acute) character.
2775 @c This is needed in single character literals
2776 @c (@xref{Characters,,Character Constants}.) to represent
2779 @cindex @code{\"} (doublequote character)
2780 @cindex doublequote (@code{\"})
2782 Represents one @samp{"} character. Needed in strings to represent
2783 this character, because an unescaped @samp{"} would end the string.
2785 @item \ @var{anything-else}
2786 Any other character when escaped by @kbd{\} gives a warning, but
2787 assembles as if the @samp{\} was not present. The idea is that if
2788 you used an escape sequence you clearly didn't want the literal
2789 interpretation of the following character. However @command{@value{AS}} has no
2790 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2791 code and warns you of the fact.
2794 Which characters are escapable, and what those escapes represent,
2795 varies widely among assemblers. The current set is what we think
2796 the BSD 4.2 assembler recognizes, and is a subset of what most C
2797 compilers recognize. If you are in doubt, do not use an escape
2801 @subsubsection Characters
2803 @cindex single character constant
2804 @cindex character, single
2805 @cindex constant, single character
2806 A single character may be written as a single quote immediately
2807 followed by that character. The same escapes apply to characters as
2808 to strings. So if you want to write the character backslash, you
2809 must write @kbd{'\\} where the first @code{\} escapes the second
2810 @code{\}. As you can see, the quote is an acute accent, not a
2811 grave accent. A newline
2813 @ifclear abnormal-separator
2814 (or semicolon @samp{;})
2816 @ifset abnormal-separator
2818 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2823 immediately following an acute accent is taken as a literal character
2824 and does not count as the end of a statement. The value of a character
2825 constant in a numeric expression is the machine's byte-wide code for
2826 that character. @command{@value{AS}} assumes your character code is ASCII:
2827 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2830 @subsection Number Constants
2832 @cindex constants, number
2833 @cindex number constants
2834 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2835 are stored in the target machine. @emph{Integers} are numbers that
2836 would fit into an @code{int} in the C language. @emph{Bignums} are
2837 integers, but they are stored in more than 32 bits. @emph{Flonums}
2838 are floating point numbers, described below.
2841 * Integers:: Integers
2846 * Bit Fields:: Bit Fields
2852 @subsubsection Integers
2854 @cindex constants, integer
2856 @cindex binary integers
2857 @cindex integers, binary
2858 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2859 the binary digits @samp{01}.
2861 @cindex octal integers
2862 @cindex integers, octal
2863 An octal integer is @samp{0} followed by zero or more of the octal
2864 digits (@samp{01234567}).
2866 @cindex decimal integers
2867 @cindex integers, decimal
2868 A decimal integer starts with a non-zero digit followed by zero or
2869 more digits (@samp{0123456789}).
2871 @cindex hexadecimal integers
2872 @cindex integers, hexadecimal
2873 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2874 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2876 Integers have the usual values. To denote a negative integer, use
2877 the prefix operator @samp{-} discussed under expressions
2878 (@pxref{Prefix Ops,,Prefix Operators}).
2881 @subsubsection Bignums
2884 @cindex constants, bignum
2885 A @dfn{bignum} has the same syntax and semantics as an integer
2886 except that the number (or its negative) takes more than 32 bits to
2887 represent in binary. The distinction is made because in some places
2888 integers are permitted while bignums are not.
2891 @subsubsection Flonums
2893 @cindex floating point numbers
2894 @cindex constants, floating point
2896 @cindex precision, floating point
2897 A @dfn{flonum} represents a floating point number. The translation is
2898 indirect: a decimal floating point number from the text is converted by
2899 @command{@value{AS}} to a generic binary floating point number of more than
2900 sufficient precision. This generic floating point number is converted
2901 to a particular computer's floating point format (or formats) by a
2902 portion of @command{@value{AS}} specialized to that computer.
2904 A flonum is written by writing (in order)
2909 (@samp{0} is optional on the HPPA.)
2913 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2915 @kbd{e} is recommended. Case is not important.
2917 @c FIXME: verify if flonum syntax really this vague for most cases
2918 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2919 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2922 On the H8/300, Renesas / SuperH SH,
2923 and AMD 29K architectures, the letter must be
2924 one of the letters @samp{DFPRSX} (in upper or lower case).
2926 On the ARC, the letter must be one of the letters @samp{DFRS}
2927 (in upper or lower case).
2929 On the Intel 960 architecture, the letter must be
2930 one of the letters @samp{DFT} (in upper or lower case).
2932 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2936 One of the letters @samp{DFRS} (in upper or lower case).
2939 One of the letters @samp{DFPRSX} (in upper or lower case).
2942 The letter @samp{E} (upper case only).
2945 One of the letters @samp{DFT} (in upper or lower case).
2950 An optional sign: either @samp{+} or @samp{-}.
2953 An optional @dfn{integer part}: zero or more decimal digits.
2956 An optional @dfn{fractional part}: @samp{.} followed by zero
2957 or more decimal digits.
2960 An optional exponent, consisting of:
2964 An @samp{E} or @samp{e}.
2965 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2966 @c principle this can perfectly well be different on different targets.
2968 Optional sign: either @samp{+} or @samp{-}.
2970 One or more decimal digits.
2975 At least one of the integer part or the fractional part must be
2976 present. The floating point number has the usual base-10 value.
2978 @command{@value{AS}} does all processing using integers. Flonums are computed
2979 independently of any floating point hardware in the computer running
2980 @command{@value{AS}}.
2984 @c Bit fields are written as a general facility but are also controlled
2985 @c by a conditional-compilation flag---which is as of now (21mar91)
2986 @c turned on only by the i960 config of GAS.
2988 @subsubsection Bit Fields
2991 @cindex constants, bit field
2992 You can also define numeric constants as @dfn{bit fields}.
2993 Specify two numbers separated by a colon---
2995 @var{mask}:@var{value}
2998 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
3001 The resulting number is then packed
3003 @c this conditional paren in case bit fields turned on elsewhere than 960
3004 (in host-dependent byte order)
3006 into a field whose width depends on which assembler directive has the
3007 bit-field as its argument. Overflow (a result from the bitwise and
3008 requiring more binary digits to represent) is not an error; instead,
3009 more constants are generated, of the specified width, beginning with the
3010 least significant digits.@refill
3012 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
3013 @code{.short}, and @code{.word} accept bit-field arguments.
3018 @chapter Sections and Relocation
3023 * Secs Background:: Background
3024 * Ld Sections:: Linker Sections
3025 * As Sections:: Assembler Internal Sections
3026 * Sub-Sections:: Sub-Sections
3030 @node Secs Background
3033 Roughly, a section is a range of addresses, with no gaps; all data
3034 ``in'' those addresses is treated the same for some particular purpose.
3035 For example there may be a ``read only'' section.
3037 @cindex linker, and assembler
3038 @cindex assembler, and linker
3039 The linker @code{@value{LD}} reads many object files (partial programs) and
3040 combines their contents to form a runnable program. When @command{@value{AS}}
3041 emits an object file, the partial program is assumed to start at address 0.
3042 @code{@value{LD}} assigns the final addresses for the partial program, so that
3043 different partial programs do not overlap. This is actually an
3044 oversimplification, but it suffices to explain how @command{@value{AS}} uses
3047 @code{@value{LD}} moves blocks of bytes of your program to their run-time
3048 addresses. These blocks slide to their run-time addresses as rigid
3049 units; their length does not change and neither does the order of bytes
3050 within them. Such a rigid unit is called a @emph{section}. Assigning
3051 run-time addresses to sections is called @dfn{relocation}. It includes
3052 the task of adjusting mentions of object-file addresses so they refer to
3053 the proper run-time addresses.
3055 For the H8/300, and for the Renesas / SuperH SH,
3056 @command{@value{AS}} pads sections if needed to
3057 ensure they end on a word (sixteen bit) boundary.
3060 @cindex standard assembler sections
3061 An object file written by @command{@value{AS}} has at least three sections, any
3062 of which may be empty. These are named @dfn{text}, @dfn{data} and
3067 When it generates COFF or ELF output,
3069 @command{@value{AS}} can also generate whatever other named sections you specify
3070 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
3071 If you do not use any directives that place output in the @samp{.text}
3072 or @samp{.data} sections, these sections still exist, but are empty.
3077 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
3079 @command{@value{AS}} can also generate whatever other named sections you
3080 specify using the @samp{.space} and @samp{.subspace} directives. See
3081 @cite{HP9000 Series 800 Assembly Language Reference Manual}
3082 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
3083 assembler directives.
3086 Additionally, @command{@value{AS}} uses different names for the standard
3087 text, data, and bss sections when generating SOM output. Program text
3088 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
3089 BSS into @samp{$BSS$}.
3093 Within the object file, the text section starts at address @code{0}, the
3094 data section follows, and the bss section follows the data section.
3097 When generating either SOM or ELF output files on the HPPA, the text
3098 section starts at address @code{0}, the data section at address
3099 @code{0x4000000}, and the bss section follows the data section.
3102 To let @code{@value{LD}} know which data changes when the sections are
3103 relocated, and how to change that data, @command{@value{AS}} also writes to the
3104 object file details of the relocation needed. To perform relocation
3105 @code{@value{LD}} must know, each time an address in the object
3109 Where in the object file is the beginning of this reference to
3112 How long (in bytes) is this reference?
3114 Which section does the address refer to? What is the numeric value of
3116 (@var{address}) @minus{} (@var{start-address of section})?
3119 Is the reference to an address ``Program-Counter relative''?
3122 @cindex addresses, format of
3123 @cindex section-relative addressing
3124 In fact, every address @command{@value{AS}} ever uses is expressed as
3126 (@var{section}) + (@var{offset into section})
3129 Further, most expressions @command{@value{AS}} computes have this section-relative
3132 (For some object formats, such as SOM for the HPPA, some expressions are
3133 symbol-relative instead.)
3136 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
3137 @var{N} into section @var{secname}.''
3139 Apart from text, data and bss sections you need to know about the
3140 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
3141 addresses in the absolute section remain unchanged. For example, address
3142 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
3143 @code{@value{LD}}. Although the linker never arranges two partial programs'
3144 data sections with overlapping addresses after linking, @emph{by definition}
3145 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
3146 part of a program is always the same address when the program is running as
3147 address @code{@{absolute@ 239@}} in any other part of the program.
3149 The idea of sections is extended to the @dfn{undefined} section. Any
3150 address whose section is unknown at assembly time is by definition
3151 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
3152 Since numbers are always defined, the only way to generate an undefined
3153 address is to mention an undefined symbol. A reference to a named
3154 common block would be such a symbol: its value is unknown at assembly
3155 time so it has section @emph{undefined}.
3157 By analogy the word @emph{section} is used to describe groups of sections in
3158 the linked program. @code{@value{LD}} puts all partial programs' text
3159 sections in contiguous addresses in the linked program. It is
3160 customary to refer to the @emph{text section} of a program, meaning all
3161 the addresses of all partial programs' text sections. Likewise for
3162 data and bss sections.
3164 Some sections are manipulated by @code{@value{LD}}; others are invented for
3165 use of @command{@value{AS}} and have no meaning except during assembly.
3168 @section Linker Sections
3169 @code{@value{LD}} deals with just four kinds of sections, summarized below.
3174 @cindex named sections
3175 @cindex sections, named
3176 @item named sections
3179 @cindex text section
3180 @cindex data section
3184 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
3185 separate but equal sections. Anything you can say of one section is
3188 When the program is running, however, it is
3189 customary for the text section to be unalterable. The
3190 text section is often shared among processes: it contains
3191 instructions, constants and the like. The data section of a running
3192 program is usually alterable: for example, C variables would be stored
3193 in the data section.
3198 This section contains zeroed bytes when your program begins running. It
3199 is used to hold uninitialized variables or common storage. The length of
3200 each partial program's bss section is important, but because it starts
3201 out containing zeroed bytes there is no need to store explicit zero
3202 bytes in the object file. The bss section was invented to eliminate
3203 those explicit zeros from object files.
3205 @cindex absolute section
3206 @item absolute section
3207 Address 0 of this section is always ``relocated'' to runtime address 0.
3208 This is useful if you want to refer to an address that @code{@value{LD}} must
3209 not change when relocating. In this sense we speak of absolute
3210 addresses being ``unrelocatable'': they do not change during relocation.
3212 @cindex undefined section
3213 @item undefined section
3214 This ``section'' is a catch-all for address references to objects not in
3215 the preceding sections.
3216 @c FIXME: ref to some other doc on obj-file formats could go here.
3219 @cindex relocation example
3220 An idealized example of three relocatable sections follows.
3222 The example uses the traditional section names @samp{.text} and @samp{.data}.
3224 Memory addresses are on the horizontal axis.
3228 @c END TEXI2ROFF-KILL
3231 partial program # 1: |ttttt|dddd|00|
3238 partial program # 2: |TTT|DDD|000|
3241 +--+---+-----+--+----+---+-----+~~
3242 linked program: | |TTT|ttttt| |dddd|DDD|00000|
3243 +--+---+-----+--+----+---+-----+~~
3245 addresses: 0 @dots{}
3252 \line{\it Partial program \#1: \hfil}
3253 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3254 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
3256 \line{\it Partial program \#2: \hfil}
3257 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
3258 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
3260 \line{\it linked program: \hfil}
3261 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
3262 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
3263 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
3264 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
3266 \line{\it addresses: \hfil}
3270 @c END TEXI2ROFF-KILL
3273 @section Assembler Internal Sections
3275 @cindex internal assembler sections
3276 @cindex sections in messages, internal
3277 These sections are meant only for the internal use of @command{@value{AS}}. They
3278 have no meaning at run-time. You do not really need to know about these
3279 sections for most purposes; but they can be mentioned in @command{@value{AS}}
3280 warning messages, so it might be helpful to have an idea of their
3281 meanings to @command{@value{AS}}. These sections are used to permit the
3282 value of every expression in your assembly language program to be a
3283 section-relative address.
3286 @cindex assembler internal logic error
3287 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
3288 An internal assembler logic error has been found. This means there is a
3289 bug in the assembler.
3291 @cindex expr (internal section)
3293 The assembler stores complex expression internally as combinations of
3294 symbols. When it needs to represent an expression as a symbol, it puts
3295 it in the expr section.
3297 @c FIXME item transfer[t] vector preload
3298 @c FIXME item transfer[t] vector postload
3299 @c FIXME item register
3303 @section Sub-Sections
3305 @cindex numbered subsections
3306 @cindex grouping data
3312 fall into two sections: text and data.
3314 You may have separate groups of
3316 data in named sections
3320 data in named sections
3326 that you want to end up near to each other in the object file, even though they
3327 are not contiguous in the assembler source. @command{@value{AS}} allows you to
3328 use @dfn{subsections} for this purpose. Within each section, there can be
3329 numbered subsections with values from 0 to 8192. Objects assembled into the
3330 same subsection go into the object file together with other objects in the same
3331 subsection. For example, a compiler might want to store constants in the text
3332 section, but might not want to have them interspersed with the program being
3333 assembled. In this case, the compiler could issue a @samp{.text 0} before each
3334 section of code being output, and a @samp{.text 1} before each group of
3335 constants being output.
3337 Subsections are optional. If you do not use subsections, everything
3338 goes in subsection number zero.
3341 Each subsection is zero-padded up to a multiple of four bytes.
3342 (Subsections may be padded a different amount on different flavors
3343 of @command{@value{AS}}.)
3347 On the H8/300 platform, each subsection is zero-padded to a word
3348 boundary (two bytes).
3349 The same is true on the Renesas SH.
3352 @c FIXME section padding (alignment)?
3353 @c Rich Pixley says padding here depends on target obj code format; that
3354 @c doesn't seem particularly useful to say without further elaboration,
3355 @c so for now I say nothing about it. If this is a generic BFD issue,
3356 @c these paragraphs might need to vanish from this manual, and be
3357 @c discussed in BFD chapter of binutils (or some such).
3361 Subsections appear in your object file in numeric order, lowest numbered
3362 to highest. (All this to be compatible with other people's assemblers.)
3363 The object file contains no representation of subsections; @code{@value{LD}} and
3364 other programs that manipulate object files see no trace of them.
3365 They just see all your text subsections as a text section, and all your
3366 data subsections as a data section.
3368 To specify which subsection you want subsequent statements assembled
3369 into, use a numeric argument to specify it, in a @samp{.text
3370 @var{expression}} or a @samp{.data @var{expression}} statement.
3373 When generating COFF output, you
3378 can also use an extra subsection
3379 argument with arbitrary named sections: @samp{.section @var{name},
3384 When generating ELF output, you
3389 can also use the @code{.subsection} directive (@pxref{SubSection})
3390 to specify a subsection: @samp{.subsection @var{expression}}.
3392 @var{Expression} should be an absolute expression
3393 (@pxref{Expressions}). If you just say @samp{.text} then @samp{.text 0}
3394 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3395 begins in @code{text 0}. For instance:
3397 .text 0 # The default subsection is text 0 anyway.
3398 .ascii "This lives in the first text subsection. *"
3400 .ascii "But this lives in the second text subsection."
3402 .ascii "This lives in the data section,"
3403 .ascii "in the first data subsection."
3405 .ascii "This lives in the first text section,"
3406 .ascii "immediately following the asterisk (*)."
3409 Each section has a @dfn{location counter} incremented by one for every byte
3410 assembled into that section. Because subsections are merely a convenience
3411 restricted to @command{@value{AS}} there is no concept of a subsection location
3412 counter. There is no way to directly manipulate a location counter---but the
3413 @code{.align} directive changes it, and any label definition captures its
3414 current value. The location counter of the section where statements are being
3415 assembled is said to be the @dfn{active} location counter.
3418 @section bss Section
3421 @cindex common variable storage
3422 The bss section is used for local common variable storage.
3423 You may allocate address space in the bss section, but you may
3424 not dictate data to load into it before your program executes. When
3425 your program starts running, all the contents of the bss
3426 section are zeroed bytes.
3428 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3429 @ref{Lcomm,,@code{.lcomm}}.
3431 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3432 another form of uninitialized symbol; see @ref{Comm,,@code{.comm}}.
3435 When assembling for a target which supports multiple sections, such as ELF or
3436 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3437 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3438 section. Typically the section will only contain symbol definitions and
3439 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3446 Symbols are a central concept: the programmer uses symbols to name
3447 things, the linker uses symbols to link, and the debugger uses symbols
3451 @cindex debuggers, and symbol order
3452 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3453 the same order they were declared. This may break some debuggers.
3458 * Setting Symbols:: Giving Symbols Other Values
3459 * Symbol Names:: Symbol Names
3460 * Dot:: The Special Dot Symbol
3461 * Symbol Attributes:: Symbol Attributes
3468 A @dfn{label} is written as a symbol immediately followed by a colon
3469 @samp{:}. The symbol then represents the current value of the
3470 active location counter, and is, for example, a suitable instruction
3471 operand. You are warned if you use the same symbol to represent two
3472 different locations: the first definition overrides any other
3476 On the HPPA, the usual form for a label need not be immediately followed by a
3477 colon, but instead must start in column zero. Only one label may be defined on
3478 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3479 provides a special directive @code{.label} for defining labels more flexibly.
3482 @node Setting Symbols
3483 @section Giving Symbols Other Values
3485 @cindex assigning values to symbols
3486 @cindex symbol values, assigning
3487 A symbol can be given an arbitrary value by writing a symbol, followed
3488 by an equals sign @samp{=}, followed by an expression
3489 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3490 directive. @xref{Set,,@code{.set}}. In the same way, using a double
3491 equals sign @samp{=}@samp{=} here represents an equivalent of the
3492 @code{.eqv} directive. @xref{Eqv,,@code{.eqv}}.
3495 Blackfin does not support symbol assignment with @samp{=}.
3499 @section Symbol Names
3501 @cindex symbol names
3502 @cindex names, symbol
3503 @ifclear SPECIAL-SYMS
3504 Symbol names begin with a letter or with one of @samp{._}. On most
3505 machines, you can also use @code{$} in symbol names; exceptions are
3506 noted in @ref{Machine Dependencies}. That character may be followed by any
3507 string of digits, letters, dollar signs (unless otherwise noted for a
3508 particular target machine), and underscores.
3512 Symbol names begin with a letter or with one of @samp{._}. On the
3513 Renesas SH you can also use @code{$} in symbol names. That
3514 character may be followed by any string of digits, letters, dollar signs (save
3515 on the H8/300), and underscores.
3519 Case of letters is significant: @code{foo} is a different symbol name
3522 Multibyte characters are supported. To generate a symbol name containing
3523 multibyte characters enclose it within double quotes and use escape codes. cf
3524 @xref{Strings}. Generating a multibyte symbol name from a label is not
3525 currently supported.
3527 Each symbol has exactly one name. Each name in an assembly language program
3528 refers to exactly one symbol. You may use that symbol name any number of times
3531 @subheading Local Symbol Names
3533 @cindex local symbol names
3534 @cindex symbol names, local
3535 A local symbol is any symbol beginning with certain local label prefixes.
3536 By default, the local label prefix is @samp{.L} for ELF systems or
3537 @samp{L} for traditional a.out systems, but each target may have its own
3538 set of local label prefixes.
3540 On the HPPA local symbols begin with @samp{L$}.
3543 Local symbols are defined and used within the assembler, but they are
3544 normally not saved in object files. Thus, they are not visible when debugging.
3545 You may use the @samp{-L} option (@pxref{L, ,Include Local Symbols:
3546 @option{-L}}) to retain the local symbols in the object files.
3548 @subheading Local Labels
3550 @cindex local labels
3551 @cindex temporary symbol names
3552 @cindex symbol names, temporary
3553 Local labels help compilers and programmers use names temporarily.
3554 They create symbols which are guaranteed to be unique over the entire scope of
3555 the input source code and which can be referred to by a simple notation.
3556 To define a local label, write a label of the form @samp{@b{N}:} (where @b{N}
3557 represents any positive integer). To refer to the most recent previous
3558 definition of that label write @samp{@b{N}b}, using the same number as when
3559 you defined the label. To refer to the next definition of a local label, write
3560 @samp{@b{N}f}---the @samp{b} stands for ``backwards'' and the @samp{f} stands
3563 There is no restriction on how you can use these labels, and you can reuse them
3564 too. So that it is possible to repeatedly define the same local label (using
3565 the same number @samp{@b{N}}), although you can only refer to the most recently
3566 defined local label of that number (for a backwards reference) or the next
3567 definition of a specific local label for a forward reference. It is also worth
3568 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3569 implemented in a slightly more efficient manner than the others.
3580 Which is the equivalent of:
3583 label_1: branch label_3
3584 label_2: branch label_1
3585 label_3: branch label_4
3586 label_4: branch label_3
3589 Local label names are only a notational device. They are immediately
3590 transformed into more conventional symbol names before the assembler uses them.
3591 The symbol names are stored in the symbol table, appear in error messages, and
3592 are optionally emitted to the object file. The names are constructed using
3596 @item @emph{local label prefix}
3597 All local symbols begin with the system-specific local label prefix.
3598 Normally both @command{@value{AS}} and @code{@value{LD}} forget symbols
3599 that start with the local label prefix. These labels are
3600 used for symbols you are never intended to see. If you use the
3601 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3602 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3603 you may use them in debugging.
3606 This is the number that was used in the local label definition. So if the
3607 label is written @samp{55:} then the number is @samp{55}.
3610 This unusual character is included so you do not accidentally invent a symbol
3611 of the same name. The character has ASCII value of @samp{\002} (control-B).
3613 @item @emph{ordinal number}
3614 This is a serial number to keep the labels distinct. The first definition of
3615 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3616 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3617 the number @samp{1} and its 15th definition gets @samp{15} as well.
3620 So for example, the first @code{1:} may be named @code{.L1@kbd{C-B}1}, and
3621 the 44th @code{3:} may be named @code{.L3@kbd{C-B}44}.
3623 @subheading Dollar Local Labels
3624 @cindex dollar local symbols
3626 @code{@value{AS}} also supports an even more local form of local labels called
3627 dollar labels. These labels go out of scope (i.e., they become undefined) as
3628 soon as a non-local label is defined. Thus they remain valid for only a small
3629 region of the input source code. Normal local labels, by contrast, remain in
3630 scope for the entire file, or until they are redefined by another occurrence of
3631 the same local label.
3633 Dollar labels are defined in exactly the same way as ordinary local labels,
3634 except that they have a dollar sign suffix to their numeric value, e.g.,
3637 They can also be distinguished from ordinary local labels by their transformed
3638 names which use ASCII character @samp{\001} (control-A) as the magic character
3639 to distinguish them from ordinary labels. For example, the fifth definition of
3640 @samp{6$} may be named @samp{.L6@kbd{C-A}5}.
3643 @section The Special Dot Symbol
3645 @cindex dot (symbol)
3646 @cindex @code{.} (symbol)
3647 @cindex current address
3648 @cindex location counter
3649 The special symbol @samp{.} refers to the current address that
3650 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3651 .long .} defines @code{melvin} to contain its own address.
3652 Assigning a value to @code{.} is treated the same as a @code{.org}
3654 @ifclear no-space-dir
3655 Thus, the expression @samp{.=.+4} is the same as saying
3659 @node Symbol Attributes
3660 @section Symbol Attributes
3662 @cindex symbol attributes
3663 @cindex attributes, symbol
3664 Every symbol has, as well as its name, the attributes ``Value'' and
3665 ``Type''. Depending on output format, symbols can also have auxiliary
3668 The detailed definitions are in @file{a.out.h}.
3671 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3672 all these attributes, and probably won't warn you. This makes the
3673 symbol an externally defined symbol, which is generally what you
3677 * Symbol Value:: Value
3678 * Symbol Type:: Type
3681 * a.out Symbols:: Symbol Attributes: @code{a.out}
3685 * a.out Symbols:: Symbol Attributes: @code{a.out}
3688 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3693 * COFF Symbols:: Symbol Attributes for COFF
3696 * SOM Symbols:: Symbol Attributes for SOM
3703 @cindex value of a symbol
3704 @cindex symbol value
3705 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3706 location in the text, data, bss or absolute sections the value is the
3707 number of addresses from the start of that section to the label.
3708 Naturally for text, data and bss sections the value of a symbol changes
3709 as @code{@value{LD}} changes section base addresses during linking. Absolute
3710 symbols' values do not change during linking: that is why they are
3713 The value of an undefined symbol is treated in a special way. If it is
3714 0 then the symbol is not defined in this assembler source file, and
3715 @code{@value{LD}} tries to determine its value from other files linked into the
3716 same program. You make this kind of symbol simply by mentioning a symbol
3717 name without defining it. A non-zero value represents a @code{.comm}
3718 common declaration. The value is how much common storage to reserve, in
3719 bytes (addresses). The symbol refers to the first address of the
3725 @cindex type of a symbol
3727 The type attribute of a symbol contains relocation (section)
3728 information, any flag settings indicating that a symbol is external, and
3729 (optionally), other information for linkers and debuggers. The exact
3730 format depends on the object-code output format in use.
3735 @c The following avoids a "widow" subsection title. @group would be
3736 @c better if it were available outside examples.
3739 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3741 @cindex @code{b.out} symbol attributes
3742 @cindex symbol attributes, @code{b.out}
3743 These symbol attributes appear only when @command{@value{AS}} is configured for
3744 one of the Berkeley-descended object output formats---@code{a.out} or
3750 @subsection Symbol Attributes: @code{a.out}
3752 @cindex @code{a.out} symbol attributes
3753 @cindex symbol attributes, @code{a.out}
3759 @subsection Symbol Attributes: @code{a.out}
3761 @cindex @code{a.out} symbol attributes
3762 @cindex symbol attributes, @code{a.out}
3766 * Symbol Desc:: Descriptor
3767 * Symbol Other:: Other
3771 @subsubsection Descriptor
3773 @cindex descriptor, of @code{a.out} symbol
3774 This is an arbitrary 16-bit value. You may establish a symbol's
3775 descriptor value by using a @code{.desc} statement
3776 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3777 @command{@value{AS}}.
3780 @subsubsection Other
3782 @cindex other attribute, of @code{a.out} symbol
3783 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3788 @subsection Symbol Attributes for COFF
3790 @cindex COFF symbol attributes
3791 @cindex symbol attributes, COFF
3793 The COFF format supports a multitude of auxiliary symbol attributes;
3794 like the primary symbol attributes, they are set between @code{.def} and
3795 @code{.endef} directives.
3797 @subsubsection Primary Attributes
3799 @cindex primary attributes, COFF symbols
3800 The symbol name is set with @code{.def}; the value and type,
3801 respectively, with @code{.val} and @code{.type}.
3803 @subsubsection Auxiliary Attributes
3805 @cindex auxiliary attributes, COFF symbols
3806 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3807 @code{.size}, @code{.tag}, and @code{.weak} can generate auxiliary symbol
3808 table information for COFF.
3813 @subsection Symbol Attributes for SOM
3815 @cindex SOM symbol attributes
3816 @cindex symbol attributes, SOM
3818 The SOM format for the HPPA supports a multitude of symbol attributes set with
3819 the @code{.EXPORT} and @code{.IMPORT} directives.
3821 The attributes are described in @cite{HP9000 Series 800 Assembly
3822 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3823 @code{EXPORT} assembler directive documentation.
3827 @chapter Expressions
3831 @cindex numeric values
3832 An @dfn{expression} specifies an address or numeric value.
3833 Whitespace may precede and/or follow an expression.
3835 The result of an expression must be an absolute number, or else an offset into
3836 a particular section. If an expression is not absolute, and there is not
3837 enough information when @command{@value{AS}} sees the expression to know its
3838 section, a second pass over the source program might be necessary to interpret
3839 the expression---but the second pass is currently not implemented.
3840 @command{@value{AS}} aborts with an error message in this situation.
3843 * Empty Exprs:: Empty Expressions
3844 * Integer Exprs:: Integer Expressions
3848 @section Empty Expressions
3850 @cindex empty expressions
3851 @cindex expressions, empty
3852 An empty expression has no value: it is just whitespace or null.
3853 Wherever an absolute expression is required, you may omit the
3854 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3855 is compatible with other assemblers.
3858 @section Integer Expressions
3860 @cindex integer expressions
3861 @cindex expressions, integer
3862 An @dfn{integer expression} is one or more @emph{arguments} delimited
3863 by @emph{operators}.
3866 * Arguments:: Arguments
3867 * Operators:: Operators
3868 * Prefix Ops:: Prefix Operators
3869 * Infix Ops:: Infix Operators
3873 @subsection Arguments
3875 @cindex expression arguments
3876 @cindex arguments in expressions
3877 @cindex operands in expressions
3878 @cindex arithmetic operands
3879 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3880 contexts arguments are sometimes called ``arithmetic operands''. In
3881 this manual, to avoid confusing them with the ``instruction operands'' of
3882 the machine language, we use the term ``argument'' to refer to parts of
3883 expressions only, reserving the word ``operand'' to refer only to machine
3884 instruction operands.
3886 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3887 @var{section} is one of text, data, bss, absolute,
3888 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3891 Numbers are usually integers.
3893 A number can be a flonum or bignum. In this case, you are warned
3894 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3895 these 32 bits are an integer. You may write integer-manipulating
3896 instructions that act on exotic constants, compatible with other
3899 @cindex subexpressions
3900 Subexpressions are a left parenthesis @samp{(} followed by an integer
3901 expression, followed by a right parenthesis @samp{)}; or a prefix
3902 operator followed by an argument.
3905 @subsection Operators
3907 @cindex operators, in expressions
3908 @cindex arithmetic functions
3909 @cindex functions, in expressions
3910 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3911 operators are followed by an argument. Infix operators appear
3912 between their arguments. Operators may be preceded and/or followed by
3916 @subsection Prefix Operator
3918 @cindex prefix operators
3919 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3920 one argument, which must be absolute.
3922 @c the tex/end tex stuff surrounding this small table is meant to make
3923 @c it align, on the printed page, with the similar table in the next
3924 @c section (which is inside an enumerate).
3926 \global\advance\leftskip by \itemindent
3931 @dfn{Negation}. Two's complement negation.
3933 @dfn{Complementation}. Bitwise not.
3937 \global\advance\leftskip by -\itemindent
3941 @subsection Infix Operators
3943 @cindex infix operators
3944 @cindex operators, permitted arguments
3945 @dfn{Infix operators} take two arguments, one on either side. Operators
3946 have precedence, but operations with equal precedence are performed left
3947 to right. Apart from @code{+} or @option{-}, both arguments must be
3948 absolute, and the result is absolute.
3951 @cindex operator precedence
3952 @cindex precedence of operators
3959 @dfn{Multiplication}.
3962 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3968 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3971 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3975 Intermediate precedence
3980 @dfn{Bitwise Inclusive Or}.
3986 @dfn{Bitwise Exclusive Or}.
3989 @dfn{Bitwise Or Not}.
3996 @cindex addition, permitted arguments
3997 @cindex plus, permitted arguments
3998 @cindex arguments for addition
4000 @dfn{Addition}. If either argument is absolute, the result has the section of
4001 the other argument. You may not add together arguments from different
4004 @cindex subtraction, permitted arguments
4005 @cindex minus, permitted arguments
4006 @cindex arguments for subtraction
4008 @dfn{Subtraction}. If the right argument is absolute, the
4009 result has the section of the left argument.
4010 If both arguments are in the same section, the result is absolute.
4011 You may not subtract arguments from different sections.
4012 @c FIXME is there still something useful to say about undefined - undefined ?
4014 @cindex comparison expressions
4015 @cindex expressions, comparison
4020 @dfn{Is Not Equal To}
4024 @dfn{Is Greater Than}
4026 @dfn{Is Greater Than Or Equal To}
4028 @dfn{Is Less Than Or Equal To}
4030 The comparison operators can be used as infix operators. A true results has a
4031 value of -1 whereas a false result has a value of 0. Note, these operators
4032 perform signed comparisons.
4035 @item Lowest Precedence
4044 These two logical operations can be used to combine the results of sub
4045 expressions. Note, unlike the comparison operators a true result returns a
4046 value of 1 but a false results does still return 0. Also note that the logical
4047 or operator has a slightly lower precedence than logical and.
4052 In short, it's only meaningful to add or subtract the @emph{offsets} in an
4053 address; you can only have a defined section in one of the two arguments.
4056 @chapter Assembler Directives
4058 @cindex directives, machine independent
4059 @cindex pseudo-ops, machine independent
4060 @cindex machine independent directives
4061 All assembler directives have names that begin with a period (@samp{.}).
4062 The rest of the name is letters, usually in lower case.
4064 This chapter discusses directives that are available regardless of the
4065 target machine configuration for the @sc{gnu} assembler.
4067 Some machine configurations provide additional directives.
4068 @xref{Machine Dependencies}.
4071 @ifset machine-directives
4072 @xref{Machine Dependencies}, for additional directives.
4077 * Abort:: @code{.abort}
4079 * ABORT (COFF):: @code{.ABORT}
4082 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
4083 * Altmacro:: @code{.altmacro}
4084 * Ascii:: @code{.ascii "@var{string}"}@dots{}
4085 * Asciz:: @code{.asciz "@var{string}"}@dots{}
4086 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
4087 * Bundle directives:: @code{.bundle_align_mode @var{abs-expr}}, @code{.bundle_lock}, @code{.bundle_unlock}
4088 * Byte:: @code{.byte @var{expressions}}
4089 * CFI directives:: @code{.cfi_startproc [simple]}, @code{.cfi_endproc}, etc.
4090 * Comm:: @code{.comm @var{symbol} , @var{length} }
4091 * Data:: @code{.data @var{subsection}}
4093 * Def:: @code{.def @var{name}}
4096 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
4102 * Double:: @code{.double @var{flonums}}
4103 * Eject:: @code{.eject}
4104 * Else:: @code{.else}
4105 * Elseif:: @code{.elseif}
4108 * Endef:: @code{.endef}
4111 * Endfunc:: @code{.endfunc}
4112 * Endif:: @code{.endif}
4113 * Equ:: @code{.equ @var{symbol}, @var{expression}}
4114 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
4115 * Eqv:: @code{.eqv @var{symbol}, @var{expression}}
4117 * Error:: @code{.error @var{string}}
4118 * Exitm:: @code{.exitm}
4119 * Extern:: @code{.extern}
4120 * Fail:: @code{.fail}
4121 * File:: @code{.file}
4122 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
4123 * Float:: @code{.float @var{flonums}}
4124 * Func:: @code{.func}
4125 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4127 * Gnu_attribute:: @code{.gnu_attribute @var{tag},@var{value}}
4128 * Hidden:: @code{.hidden @var{names}}
4131 * hword:: @code{.hword @var{expressions}}
4132 * Ident:: @code{.ident}
4133 * If:: @code{.if @var{absolute expression}}
4134 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4135 * Include:: @code{.include "@var{file}"}
4136 * Int:: @code{.int @var{expressions}}
4138 * Internal:: @code{.internal @var{names}}
4141 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
4142 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
4143 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
4144 * Lflags:: @code{.lflags}
4145 @ifclear no-line-dir
4146 * Line:: @code{.line @var{line-number}}
4149 * Linkonce:: @code{.linkonce [@var{type}]}
4150 * List:: @code{.list}
4151 * Ln:: @code{.ln @var{line-number}}
4152 * Loc:: @code{.loc @var{fileno} @var{lineno}}
4153 * Loc_mark_labels:: @code{.loc_mark_labels @var{enable}}
4155 * Local:: @code{.local @var{names}}
4158 * Long:: @code{.long @var{expressions}}
4160 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
4163 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
4164 * MRI:: @code{.mri @var{val}}
4165 * Noaltmacro:: @code{.noaltmacro}
4166 * Nolist:: @code{.nolist}
4167 * Octa:: @code{.octa @var{bignums}}
4168 * Offset:: @code{.offset @var{loc}}
4169 * Org:: @code{.org @var{new-lc}, @var{fill}}
4170 * P2align:: @code{.p2align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4172 * PopSection:: @code{.popsection}
4173 * Previous:: @code{.previous}
4176 * Print:: @code{.print @var{string}}
4178 * Protected:: @code{.protected @var{names}}
4181 * Psize:: @code{.psize @var{lines}, @var{columns}}
4182 * Purgem:: @code{.purgem @var{name}}
4184 * PushSection:: @code{.pushsection @var{name}}
4187 * Quad:: @code{.quad @var{bignums}}
4188 * Reloc:: @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
4189 * Rept:: @code{.rept @var{count}}
4190 * Sbttl:: @code{.sbttl "@var{subheading}"}
4192 * Scl:: @code{.scl @var{class}}
4195 * Section:: @code{.section @var{name}[, @var{flags}]}
4198 * Set:: @code{.set @var{symbol}, @var{expression}}
4199 * Short:: @code{.short @var{expressions}}
4200 * Single:: @code{.single @var{flonums}}
4202 * Size:: @code{.size [@var{name} , @var{expression}]}
4204 @ifclear no-space-dir
4205 * Skip:: @code{.skip @var{size} , @var{fill}}
4208 * Sleb128:: @code{.sleb128 @var{expressions}}
4209 @ifclear no-space-dir
4210 * Space:: @code{.space @var{size} , @var{fill}}
4213 * Stab:: @code{.stabd, .stabn, .stabs}
4216 * String:: @code{.string "@var{str}"}, @code{.string8 "@var{str}"}, @code{.string16 "@var{str}"}, @code{.string32 "@var{str}"}, @code{.string64 "@var{str}"}
4217 * Struct:: @code{.struct @var{expression}}
4219 * SubSection:: @code{.subsection}
4220 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
4224 * Tag:: @code{.tag @var{structname}}
4227 * Text:: @code{.text @var{subsection}}
4228 * Title:: @code{.title "@var{heading}"}
4230 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
4233 * Uleb128:: @code{.uleb128 @var{expressions}}
4235 * Val:: @code{.val @var{addr}}
4239 * Version:: @code{.version "@var{string}"}
4240 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
4241 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
4244 * Warning:: @code{.warning @var{string}}
4245 * Weak:: @code{.weak @var{names}}
4246 * Weakref:: @code{.weakref @var{alias}, @var{symbol}}
4247 * Word:: @code{.word @var{expressions}}
4248 * Deprecated:: Deprecated Directives
4252 @section @code{.abort}
4254 @cindex @code{abort} directive
4255 @cindex stopping the assembly
4256 This directive stops the assembly immediately. It is for
4257 compatibility with other assemblers. The original idea was that the
4258 assembly language source would be piped into the assembler. If the sender
4259 of the source quit, it could use this directive tells @command{@value{AS}} to
4260 quit also. One day @code{.abort} will not be supported.
4264 @section @code{.ABORT} (COFF)
4266 @cindex @code{ABORT} directive
4267 When producing COFF output, @command{@value{AS}} accepts this directive as a
4268 synonym for @samp{.abort}.
4271 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
4277 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4279 @cindex padding the location counter
4280 @cindex @code{align} directive
4281 Pad the location counter (in the current subsection) to a particular storage
4282 boundary. The first expression (which must be absolute) is the alignment
4283 required, as described below.
4285 The second expression (also absolute) gives the fill value to be stored in the
4286 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4287 padding bytes are normally zero. However, on some systems, if the section is
4288 marked as containing code and the fill value is omitted, the space is filled
4289 with no-op instructions.
4291 The third expression is also absolute, and is also optional. If it is present,
4292 it is the maximum number of bytes that should be skipped by this alignment
4293 directive. If doing the alignment would require skipping more bytes than the
4294 specified maximum, then the alignment is not done at all. You can omit the
4295 fill value (the second argument) entirely by simply using two commas after the
4296 required alignment; this can be useful if you want the alignment to be filled
4297 with no-op instructions when appropriate.
4299 The way the required alignment is specified varies from system to system.
4300 For the arc, hppa, i386 using ELF, i860, iq2000, m68k, or32,
4301 s390, sparc, tic4x, tic80 and xtensa, the first expression is the
4302 alignment request in bytes. For example @samp{.align 8} advances
4303 the location counter until it is a multiple of 8. If the location counter
4304 is already a multiple of 8, no change is needed. For the tic54x, the
4305 first expression is the alignment request in words.
4307 For other systems, including ppc, i386 using a.out format, arm and
4308 strongarm, it is the
4309 number of low-order zero bits the location counter must have after
4310 advancement. For example @samp{.align 3} advances the location
4311 counter until it a multiple of 8. If the location counter is already a
4312 multiple of 8, no change is needed.
4314 This inconsistency is due to the different behaviors of the various
4315 native assemblers for these systems which GAS must emulate.
4316 GAS also provides @code{.balign} and @code{.p2align} directives,
4317 described later, which have a consistent behavior across all
4318 architectures (but are specific to GAS).
4321 @section @code{.altmacro}
4322 Enable alternate macro mode, enabling:
4325 @item LOCAL @var{name} [ , @dots{} ]
4326 One additional directive, @code{LOCAL}, is available. It is used to
4327 generate a string replacement for each of the @var{name} arguments, and
4328 replace any instances of @var{name} in each macro expansion. The
4329 replacement string is unique in the assembly, and different for each
4330 separate macro expansion. @code{LOCAL} allows you to write macros that
4331 define symbols, without fear of conflict between separate macro expansions.
4333 @item String delimiters
4334 You can write strings delimited in these other ways besides
4335 @code{"@var{string}"}:
4338 @item '@var{string}'
4339 You can delimit strings with single-quote characters.
4341 @item <@var{string}>
4342 You can delimit strings with matching angle brackets.
4345 @item single-character string escape
4346 To include any single character literally in a string (even if the
4347 character would otherwise have some special meaning), you can prefix the
4348 character with @samp{!} (an exclamation mark). For example, you can
4349 write @samp{<4.3 !> 5.4!!>} to get the literal text @samp{4.3 > 5.4!}.
4351 @item Expression results as strings
4352 You can write @samp{%@var{expr}} to evaluate the expression @var{expr}
4353 and use the result as a string.
4357 @section @code{.ascii "@var{string}"}@dots{}
4359 @cindex @code{ascii} directive
4360 @cindex string literals
4361 @code{.ascii} expects zero or more string literals (@pxref{Strings})
4362 separated by commas. It assembles each string (with no automatic
4363 trailing zero byte) into consecutive addresses.
4366 @section @code{.asciz "@var{string}"}@dots{}
4368 @cindex @code{asciz} directive
4369 @cindex zero-terminated strings
4370 @cindex null-terminated strings
4371 @code{.asciz} is just like @code{.ascii}, but each string is followed by
4372 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
4375 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4377 @cindex padding the location counter given number of bytes
4378 @cindex @code{balign} directive
4379 Pad the location counter (in the current subsection) to a particular
4380 storage boundary. The first expression (which must be absolute) is the
4381 alignment request in bytes. For example @samp{.balign 8} advances
4382 the location counter until it is a multiple of 8. If the location counter
4383 is already a multiple of 8, no change is needed.
4385 The second expression (also absolute) gives the fill value to be stored in the
4386 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4387 padding bytes are normally zero. However, on some systems, if the section is
4388 marked as containing code and the fill value is omitted, the space is filled
4389 with no-op instructions.
4391 The third expression is also absolute, and is also optional. If it is present,
4392 it is the maximum number of bytes that should be skipped by this alignment
4393 directive. If doing the alignment would require skipping more bytes than the
4394 specified maximum, then the alignment is not done at all. You can omit the
4395 fill value (the second argument) entirely by simply using two commas after the
4396 required alignment; this can be useful if you want the alignment to be filled
4397 with no-op instructions when appropriate.
4399 @cindex @code{balignw} directive
4400 @cindex @code{balignl} directive
4401 The @code{.balignw} and @code{.balignl} directives are variants of the
4402 @code{.balign} directive. The @code{.balignw} directive treats the fill
4403 pattern as a two byte word value. The @code{.balignl} directives treats the
4404 fill pattern as a four byte longword value. For example, @code{.balignw
4405 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4406 filled in with the value 0x368d (the exact placement of the bytes depends upon
4407 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4410 @node Bundle directives
4411 @section @code{.bundle_align_mode @var{abs-expr}}
4412 @cindex @code{bundle_align_mode} directive
4414 @cindex instruction bundle
4415 @cindex aligned instruction bundle
4416 @code{.bundle_align_mode} enables or disables @dfn{aligned instruction
4417 bundle} mode. In this mode, sequences of adjacent instructions are grouped
4418 into fixed-sized @dfn{bundles}. If the argument is zero, this mode is
4419 disabled (which is the default state). If the argument it not zero, it
4420 gives the size of an instruction bundle as a power of two (as for the
4421 @code{.p2align} directive, @pxref{P2align}).
4423 For some targets, it's an ABI requirement that no instruction may span a
4424 certain aligned boundary. A @dfn{bundle} is simply a sequence of
4425 instructions that starts on an aligned boundary. For example, if
4426 @var{abs-expr} is @code{5} then the bundle size is 32, so each aligned
4427 chunk of 32 bytes is a bundle. When aligned instruction bundle mode is in
4428 effect, no single instruction may span a boundary between bundles. If an
4429 instruction would start too close to the end of a bundle for the length of
4430 that particular instruction to fit within the bundle, then the space at the
4431 end of that bundle is filled with no-op instructions so the instruction
4432 starts in the next bundle. As a corollary, it's an error if any single
4433 instruction's encoding is longer than the bundle size.
4435 @section @code{.bundle_lock} and @code{.bundle_unlock}
4436 @cindex @code{bundle_lock} directive
4437 @cindex @code{bundle_unlock} directive
4438 The @code{.bundle_lock} and directive @code{.bundle_unlock} directives
4439 allow explicit control over instruction bundle padding. These directives
4440 are only valid when @code{.bundle_align_mode} has been used to enable
4441 aligned instruction bundle mode. It's an error if they appear when
4442 @code{.bundle_align_mode} has not been used at all, or when the last
4443 directive was @w{@code{.bundle_align_mode 0}}.
4445 @cindex bundle-locked
4446 For some targets, it's an ABI requirement that certain instructions may
4447 appear only as part of specified permissible sequences of multiple
4448 instructions, all within the same bundle. A pair of @code{.bundle_lock}
4449 and @code{.bundle_unlock} directives define a @dfn{bundle-locked}
4450 instruction sequence. For purposes of aligned instruction bundle mode, a
4451 sequence starting with @code{.bundle_lock} and ending with
4452 @code{.bundle_unlock} is treated as a single instruction. That is, the
4453 entire sequence must fit into a single bundle and may not span a bundle
4454 boundary. If necessary, no-op instructions will be inserted before the
4455 first instruction of the sequence so that the whole sequence starts on an
4456 aligned bundle boundary. It's an error if the sequence is longer than the
4459 For convenience when using @code{.bundle_lock} and @code{.bundle_unlock}
4460 inside assembler macros (@pxref{Macro}), bundle-locked sequences may be
4461 nested. That is, a second @code{.bundle_lock} directive before the next
4462 @code{.bundle_unlock} directive has no effect except that it must be
4463 matched by another closing @code{.bundle_unlock} so that there is the
4464 same number of @code{.bundle_lock} and @code{.bundle_unlock} directives.
4467 @section @code{.byte @var{expressions}}
4469 @cindex @code{byte} directive
4470 @cindex integers, one byte
4471 @code{.byte} expects zero or more expressions, separated by commas.
4472 Each expression is assembled into the next byte.
4474 @node CFI directives
4475 @section @code{.cfi_sections @var{section_list}}
4476 @cindex @code{cfi_sections} directive
4477 @code{.cfi_sections} may be used to specify whether CFI directives
4478 should emit @code{.eh_frame} section and/or @code{.debug_frame} section.
4479 If @var{section_list} is @code{.eh_frame}, @code{.eh_frame} is emitted,
4480 if @var{section_list} is @code{.debug_frame}, @code{.debug_frame} is emitted.
4481 To emit both use @code{.eh_frame, .debug_frame}. The default if this
4482 directive is not used is @code{.cfi_sections .eh_frame}.
4484 @section @code{.cfi_startproc [simple]}
4485 @cindex @code{cfi_startproc} directive
4486 @code{.cfi_startproc} is used at the beginning of each function that
4487 should have an entry in @code{.eh_frame}. It initializes some internal
4488 data structures. Don't forget to close the function by
4489 @code{.cfi_endproc}.
4491 Unless @code{.cfi_startproc} is used along with parameter @code{simple}
4492 it also emits some architecture dependent initial CFI instructions.
4494 @section @code{.cfi_endproc}
4495 @cindex @code{cfi_endproc} directive
4496 @code{.cfi_endproc} is used at the end of a function where it closes its
4497 unwind entry previously opened by
4498 @code{.cfi_startproc}, and emits it to @code{.eh_frame}.
4500 @section @code{.cfi_personality @var{encoding} [, @var{exp}]}
4501 @code{.cfi_personality} defines personality routine and its encoding.
4502 @var{encoding} must be a constant determining how the personality
4503 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4504 argument is not present, otherwise second argument should be
4505 a constant or a symbol name. When using indirect encodings,
4506 the symbol provided should be the location where personality
4507 can be loaded from, not the personality routine itself.
4508 The default after @code{.cfi_startproc} is @code{.cfi_personality 0xff},
4509 no personality routine.
4511 @section @code{.cfi_lsda @var{encoding} [, @var{exp}]}
4512 @code{.cfi_lsda} defines LSDA and its encoding.
4513 @var{encoding} must be a constant determining how the LSDA
4514 should be encoded. If it is 255 (@code{DW_EH_PE_omit}), second
4515 argument is not present, otherwise second argument should be a constant
4516 or a symbol name. The default after @code{.cfi_startproc} is @code{.cfi_lsda 0xff},
4519 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
4520 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
4521 address from @var{register} and add @var{offset} to it}.
4523 @section @code{.cfi_def_cfa_register @var{register}}
4524 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
4525 now on @var{register} will be used instead of the old one. Offset
4528 @section @code{.cfi_def_cfa_offset @var{offset}}
4529 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4530 remains the same, but @var{offset} is new. Note that it is the
4531 absolute offset that will be added to a defined register to compute
4534 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4535 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4536 value that is added/substracted from the previous offset.
4538 @section @code{.cfi_offset @var{register}, @var{offset}}
4539 Previous value of @var{register} is saved at offset @var{offset} from
4542 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4543 Previous value of @var{register} is saved at offset @var{offset} from
4544 the current CFA register. This is transformed to @code{.cfi_offset}
4545 using the known displacement of the CFA register from the CFA.
4546 This is often easier to use, because the number will match the
4547 code it's annotating.
4549 @section @code{.cfi_register @var{register1}, @var{register2}}
4550 Previous value of @var{register1} is saved in register @var{register2}.
4552 @section @code{.cfi_restore @var{register}}
4553 @code{.cfi_restore} says that the rule for @var{register} is now the
4554 same as it was at the beginning of the function, after all initial
4555 instruction added by @code{.cfi_startproc} were executed.
4557 @section @code{.cfi_undefined @var{register}}
4558 From now on the previous value of @var{register} can't be restored anymore.
4560 @section @code{.cfi_same_value @var{register}}
4561 Current value of @var{register} is the same like in the previous frame,
4562 i.e. no restoration needed.
4564 @section @code{.cfi_remember_state},
4565 First save all current rules for all registers by @code{.cfi_remember_state},
4566 then totally screw them up by subsequent @code{.cfi_*} directives and when
4567 everything is hopelessly bad, use @code{.cfi_restore_state} to restore
4568 the previous saved state.
4570 @section @code{.cfi_return_column @var{register}}
4571 Change return column @var{register}, i.e. the return address is either
4572 directly in @var{register} or can be accessed by rules for @var{register}.
4574 @section @code{.cfi_signal_frame}
4575 Mark current function as signal trampoline.
4577 @section @code{.cfi_window_save}
4578 SPARC register window has been saved.
4580 @section @code{.cfi_escape} @var{expression}[, @dots{}]
4581 Allows the user to add arbitrary bytes to the unwind info. One
4582 might use this to add OS-specific CFI opcodes, or generic CFI
4583 opcodes that GAS does not yet support.
4585 @section @code{.cfi_val_encoded_addr @var{register}, @var{encoding}, @var{label}}
4586 The current value of @var{register} is @var{label}. The value of @var{label}
4587 will be encoded in the output file according to @var{encoding}; see the
4588 description of @code{.cfi_personality} for details on this encoding.
4590 The usefulness of equating a register to a fixed label is probably
4591 limited to the return address register. Here, it can be useful to
4592 mark a code segment that has only one return address which is reached
4593 by a direct branch and no copy of the return address exists in memory
4594 or another register.
4597 @section @code{.comm @var{symbol} , @var{length} }
4599 @cindex @code{comm} directive
4600 @cindex symbol, common
4601 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4602 common symbol in one object file may be merged with a defined or common symbol
4603 of the same name in another object file. If @code{@value{LD}} does not see a
4604 definition for the symbol--just one or more common symbols--then it will
4605 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4606 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4607 the same name, and they do not all have the same size, it will allocate space
4608 using the largest size.
4611 When using ELF or (as a GNU extension) PE, the @code{.comm} directive takes
4612 an optional third argument. This is the desired alignment of the symbol,
4613 specified for ELF as a byte boundary (for example, an alignment of 16 means
4614 that the least significant 4 bits of the address should be zero), and for PE
4615 as a power of two (for example, an alignment of 5 means aligned to a 32-byte
4616 boundary). The alignment must be an absolute expression, and it must be a
4617 power of two. If @code{@value{LD}} allocates uninitialized memory for the
4618 common symbol, it will use the alignment when placing the symbol. If no
4619 alignment is specified, @command{@value{AS}} will set the alignment to the
4620 largest power of two less than or equal to the size of the symbol, up to a
4621 maximum of 16 on ELF, or the default section alignment of 4 on PE@footnote{This
4622 is not the same as the executable image file alignment controlled by @code{@value{LD}}'s
4623 @samp{--section-alignment} option; image file sections in PE are aligned to
4624 multiples of 4096, which is far too large an alignment for ordinary variables.
4625 It is rather the default alignment for (non-debug) sections within object
4626 (@samp{*.o}) files, which are less strictly aligned.}.
4630 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4631 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4635 @section @code{.data @var{subsection}}
4637 @cindex @code{data} directive
4638 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4639 end of the data subsection numbered @var{subsection} (which is an
4640 absolute expression). If @var{subsection} is omitted, it defaults
4645 @section @code{.def @var{name}}
4647 @cindex @code{def} directive
4648 @cindex COFF symbols, debugging
4649 @cindex debugging COFF symbols
4650 Begin defining debugging information for a symbol @var{name}; the
4651 definition extends until the @code{.endef} directive is encountered.
4654 This directive is only observed when @command{@value{AS}} is configured for COFF
4655 format output; when producing @code{b.out}, @samp{.def} is recognized,
4662 @section @code{.desc @var{symbol}, @var{abs-expression}}
4664 @cindex @code{desc} directive
4665 @cindex COFF symbol descriptor
4666 @cindex symbol descriptor, COFF
4667 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4668 to the low 16 bits of an absolute expression.
4671 The @samp{.desc} directive is not available when @command{@value{AS}} is
4672 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4673 object format. For the sake of compatibility, @command{@value{AS}} accepts
4674 it, but produces no output, when configured for COFF.
4680 @section @code{.dim}
4682 @cindex @code{dim} directive
4683 @cindex COFF auxiliary symbol information
4684 @cindex auxiliary symbol information, COFF
4685 This directive is generated by compilers to include auxiliary debugging
4686 information in the symbol table. It is only permitted inside
4687 @code{.def}/@code{.endef} pairs.
4690 @samp{.dim} is only meaningful when generating COFF format output; when
4691 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4697 @section @code{.double @var{flonums}}
4699 @cindex @code{double} directive
4700 @cindex floating point numbers (double)
4701 @code{.double} expects zero or more flonums, separated by commas. It
4702 assembles floating point numbers.
4704 The exact kind of floating point numbers emitted depends on how
4705 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4709 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4710 in @sc{ieee} format.
4715 @section @code{.eject}
4717 @cindex @code{eject} directive
4718 @cindex new page, in listings
4719 @cindex page, in listings
4720 @cindex listing control: new page
4721 Force a page break at this point, when generating assembly listings.
4724 @section @code{.else}
4726 @cindex @code{else} directive
4727 @code{.else} is part of the @command{@value{AS}} support for conditional
4728 assembly; see @ref{If,,@code{.if}}. It marks the beginning of a section
4729 of code to be assembled if the condition for the preceding @code{.if}
4733 @section @code{.elseif}
4735 @cindex @code{elseif} directive
4736 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4737 assembly; see @ref{If,,@code{.if}}. It is shorthand for beginning a new
4738 @code{.if} block that would otherwise fill the entire @code{.else} section.
4741 @section @code{.end}
4743 @cindex @code{end} directive
4744 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4745 process anything in the file past the @code{.end} directive.
4749 @section @code{.endef}
4751 @cindex @code{endef} directive
4752 This directive flags the end of a symbol definition begun with
4756 @samp{.endef} is only meaningful when generating COFF format output; if
4757 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4758 directive but ignores it.
4763 @section @code{.endfunc}
4764 @cindex @code{endfunc} directive
4765 @code{.endfunc} marks the end of a function specified with @code{.func}.
4768 @section @code{.endif}
4770 @cindex @code{endif} directive
4771 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4772 it marks the end of a block of code that is only assembled
4773 conditionally. @xref{If,,@code{.if}}.
4776 @section @code{.equ @var{symbol}, @var{expression}}
4778 @cindex @code{equ} directive
4779 @cindex assigning values to symbols
4780 @cindex symbols, assigning values to
4781 This directive sets the value of @var{symbol} to @var{expression}.
4782 It is synonymous with @samp{.set}; see @ref{Set,,@code{.set}}.
4785 The syntax for @code{equ} on the HPPA is
4786 @samp{@var{symbol} .equ @var{expression}}.
4790 The syntax for @code{equ} on the Z80 is
4791 @samp{@var{symbol} equ @var{expression}}.
4792 On the Z80 it is an eror if @var{symbol} is already defined,
4793 but the symbol is not protected from later redefinition.
4794 Compare @ref{Equiv}.
4798 @section @code{.equiv @var{symbol}, @var{expression}}
4799 @cindex @code{equiv} directive
4800 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4801 the assembler will signal an error if @var{symbol} is already defined. Note a
4802 symbol which has been referenced but not actually defined is considered to be
4805 Except for the contents of the error message, this is roughly equivalent to
4812 plus it protects the symbol from later redefinition.
4815 @section @code{.eqv @var{symbol}, @var{expression}}
4816 @cindex @code{eqv} directive
4817 The @code{.eqv} directive is like @code{.equiv}, but no attempt is made to
4818 evaluate the expression or any part of it immediately. Instead each time
4819 the resulting symbol is used in an expression, a snapshot of its current
4823 @section @code{.err}
4824 @cindex @code{err} directive
4825 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4826 message and, unless the @option{-Z} option was used, it will not generate an
4827 object file. This can be used to signal an error in conditionally compiled code.
4830 @section @code{.error "@var{string}"}
4831 @cindex error directive
4833 Similarly to @code{.err}, this directive emits an error, but you can specify a
4834 string that will be emitted as the error message. If you don't specify the
4835 message, it defaults to @code{".error directive invoked in source file"}.
4836 @xref{Errors, ,Error and Warning Messages}.
4839 .error "This code has not been assembled and tested."
4843 @section @code{.exitm}
4844 Exit early from the current macro definition. @xref{Macro}.
4847 @section @code{.extern}
4849 @cindex @code{extern} directive
4850 @code{.extern} is accepted in the source program---for compatibility
4851 with other assemblers---but it is ignored. @command{@value{AS}} treats
4852 all undefined symbols as external.
4855 @section @code{.fail @var{expression}}
4857 @cindex @code{fail} directive
4858 Generates an error or a warning. If the value of the @var{expression} is 500
4859 or more, @command{@value{AS}} will print a warning message. If the value is less
4860 than 500, @command{@value{AS}} will print an error message. The message will
4861 include the value of @var{expression}. This can occasionally be useful inside
4862 complex nested macros or conditional assembly.
4865 @section @code{.file}
4866 @cindex @code{file} directive
4868 @ifclear no-file-dir
4869 There are two different versions of the @code{.file} directive. Targets
4870 that support DWARF2 line number information use the DWARF2 version of
4871 @code{.file}. Other targets use the default version.
4873 @subheading Default Version
4875 @cindex logical file name
4876 @cindex file name, logical
4877 This version of the @code{.file} directive tells @command{@value{AS}} that we
4878 are about to start a new logical file. The syntax is:
4884 @var{string} is the new file name. In general, the filename is
4885 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4886 to specify an empty file name, you must give the quotes--@code{""}. This
4887 statement may go away in future: it is only recognized to be compatible with
4888 old @command{@value{AS}} programs.
4890 @subheading DWARF2 Version
4893 When emitting DWARF2 line number information, @code{.file} assigns filenames
4894 to the @code{.debug_line} file name table. The syntax is:
4897 .file @var{fileno} @var{filename}
4900 The @var{fileno} operand should be a unique positive integer to use as the
4901 index of the entry in the table. The @var{filename} operand is a C string
4904 The detail of filename indices is exposed to the user because the filename
4905 table is shared with the @code{.debug_info} section of the DWARF2 debugging
4906 information, and thus the user must know the exact indices that table
4910 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4912 @cindex @code{fill} directive
4913 @cindex writing patterns in memory
4914 @cindex patterns, writing in memory
4915 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4916 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4917 may be zero or more. @var{Size} may be zero or more, but if it is
4918 more than 8, then it is deemed to have the value 8, compatible with
4919 other people's assemblers. The contents of each @var{repeat} bytes
4920 is taken from an 8-byte number. The highest order 4 bytes are
4921 zero. The lowest order 4 bytes are @var{value} rendered in the
4922 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4923 Each @var{size} bytes in a repetition is taken from the lowest order
4924 @var{size} bytes of this number. Again, this bizarre behavior is
4925 compatible with other people's assemblers.
4927 @var{size} and @var{value} are optional.
4928 If the second comma and @var{value} are absent, @var{value} is
4929 assumed zero. If the first comma and following tokens are absent,
4930 @var{size} is assumed to be 1.
4933 @section @code{.float @var{flonums}}
4935 @cindex floating point numbers (single)
4936 @cindex @code{float} directive
4937 This directive assembles zero or more flonums, separated by commas. It
4938 has the same effect as @code{.single}.
4940 The exact kind of floating point numbers emitted depends on how
4941 @command{@value{AS}} is configured.
4942 @xref{Machine Dependencies}.
4946 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4947 in @sc{ieee} format.
4952 @section @code{.func @var{name}[,@var{label}]}
4953 @cindex @code{func} directive
4954 @code{.func} emits debugging information to denote function @var{name}, and
4955 is ignored unless the file is assembled with debugging enabled.
4956 Only @samp{--gstabs[+]} is currently supported.
4957 @var{label} is the entry point of the function and if omitted @var{name}
4958 prepended with the @samp{leading char} is used.
4959 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4960 All functions are currently defined to have @code{void} return type.
4961 The function must be terminated with @code{.endfunc}.
4964 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4966 @cindex @code{global} directive
4967 @cindex symbol, making visible to linker
4968 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4969 @var{symbol} in your partial program, its value is made available to
4970 other partial programs that are linked with it. Otherwise,
4971 @var{symbol} takes its attributes from a symbol of the same name
4972 from another file linked into the same program.
4974 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4975 compatibility with other assemblers.
4978 On the HPPA, @code{.global} is not always enough to make it accessible to other
4979 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4980 @xref{HPPA Directives, ,HPPA Assembler Directives}.
4985 @section @code{.gnu_attribute @var{tag},@var{value}}
4986 Record a @sc{gnu} object attribute for this file. @xref{Object Attributes}.
4989 @section @code{.hidden @var{names}}
4991 @cindex @code{hidden} directive
4993 This is one of the ELF visibility directives. The other two are
4994 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4995 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4997 This directive overrides the named symbols default visibility (which is set by
4998 their binding: local, global or weak). The directive sets the visibility to
4999 @code{hidden} which means that the symbols are not visible to other components.
5000 Such symbols are always considered to be @code{protected} as well.
5004 @section @code{.hword @var{expressions}}
5006 @cindex @code{hword} directive
5007 @cindex integers, 16-bit
5008 @cindex numbers, 16-bit
5009 @cindex sixteen bit integers
5010 This expects zero or more @var{expressions}, and emits
5011 a 16 bit number for each.
5014 This directive is a synonym for @samp{.short}; depending on the target
5015 architecture, it may also be a synonym for @samp{.word}.
5019 This directive is a synonym for @samp{.short}.
5022 This directive is a synonym for both @samp{.short} and @samp{.word}.
5027 @section @code{.ident}
5029 @cindex @code{ident} directive
5031 This directive is used by some assemblers to place tags in object files. The
5032 behavior of this directive varies depending on the target. When using the
5033 a.out object file format, @command{@value{AS}} simply accepts the directive for
5034 source-file compatibility with existing assemblers, but does not emit anything
5035 for it. When using COFF, comments are emitted to the @code{.comment} or
5036 @code{.rdata} section, depending on the target. When using ELF, comments are
5037 emitted to the @code{.comment} section.
5040 @section @code{.if @var{absolute expression}}
5042 @cindex conditional assembly
5043 @cindex @code{if} directive
5044 @code{.if} marks the beginning of a section of code which is only
5045 considered part of the source program being assembled if the argument
5046 (which must be an @var{absolute expression}) is non-zero. The end of
5047 the conditional section of code must be marked by @code{.endif}
5048 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
5049 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
5050 If you have several conditions to check, @code{.elseif} may be used to avoid
5051 nesting blocks if/else within each subsequent @code{.else} block.
5053 The following variants of @code{.if} are also supported:
5055 @cindex @code{ifdef} directive
5056 @item .ifdef @var{symbol}
5057 Assembles the following section of code if the specified @var{symbol}
5058 has been defined. Note a symbol which has been referenced but not yet defined
5059 is considered to be undefined.
5061 @cindex @code{ifb} directive
5062 @item .ifb @var{text}
5063 Assembles the following section of code if the operand is blank (empty).
5065 @cindex @code{ifc} directive
5066 @item .ifc @var{string1},@var{string2}
5067 Assembles the following section of code if the two strings are the same. The
5068 strings may be optionally quoted with single quotes. If they are not quoted,
5069 the first string stops at the first comma, and the second string stops at the
5070 end of the line. Strings which contain whitespace should be quoted. The
5071 string comparison is case sensitive.
5073 @cindex @code{ifeq} directive
5074 @item .ifeq @var{absolute expression}
5075 Assembles the following section of code if the argument is zero.
5077 @cindex @code{ifeqs} directive
5078 @item .ifeqs @var{string1},@var{string2}
5079 Another form of @code{.ifc}. The strings must be quoted using double quotes.
5081 @cindex @code{ifge} directive
5082 @item .ifge @var{absolute expression}
5083 Assembles the following section of code if the argument is greater than or
5086 @cindex @code{ifgt} directive
5087 @item .ifgt @var{absolute expression}
5088 Assembles the following section of code if the argument is greater than zero.
5090 @cindex @code{ifle} directive
5091 @item .ifle @var{absolute expression}
5092 Assembles the following section of code if the argument is less than or equal
5095 @cindex @code{iflt} directive
5096 @item .iflt @var{absolute expression}
5097 Assembles the following section of code if the argument is less than zero.
5099 @cindex @code{ifnb} directive
5100 @item .ifnb @var{text}
5101 Like @code{.ifb}, but the sense of the test is reversed: this assembles the
5102 following section of code if the operand is non-blank (non-empty).
5104 @cindex @code{ifnc} directive
5105 @item .ifnc @var{string1},@var{string2}.
5106 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
5107 following section of code if the two strings are not the same.
5109 @cindex @code{ifndef} directive
5110 @cindex @code{ifnotdef} directive
5111 @item .ifndef @var{symbol}
5112 @itemx .ifnotdef @var{symbol}
5113 Assembles the following section of code if the specified @var{symbol}
5114 has not been defined. Both spelling variants are equivalent. Note a symbol
5115 which has been referenced but not yet defined is considered to be undefined.
5117 @cindex @code{ifne} directive
5118 @item .ifne @var{absolute expression}
5119 Assembles the following section of code if the argument is not equal to zero
5120 (in other words, this is equivalent to @code{.if}).
5122 @cindex @code{ifnes} directive
5123 @item .ifnes @var{string1},@var{string2}
5124 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
5125 following section of code if the two strings are not the same.
5129 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
5131 @cindex @code{incbin} directive
5132 @cindex binary files, including
5133 The @code{incbin} directive includes @var{file} verbatim at the current
5134 location. You can control the search paths used with the @samp{-I} command-line
5135 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5138 The @var{skip} argument skips a number of bytes from the start of the
5139 @var{file}. The @var{count} argument indicates the maximum number of bytes to
5140 read. Note that the data is not aligned in any way, so it is the user's
5141 responsibility to make sure that proper alignment is provided both before and
5142 after the @code{incbin} directive.
5145 @section @code{.include "@var{file}"}
5147 @cindex @code{include} directive
5148 @cindex supporting files, including
5149 @cindex files, including
5150 This directive provides a way to include supporting files at specified
5151 points in your source program. The code from @var{file} is assembled as
5152 if it followed the point of the @code{.include}; when the end of the
5153 included file is reached, assembly of the original file continues. You
5154 can control the search paths used with the @samp{-I} command-line option
5155 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
5159 @section @code{.int @var{expressions}}
5161 @cindex @code{int} directive
5162 @cindex integers, 32-bit
5163 Expect zero or more @var{expressions}, of any section, separated by commas.
5164 For each expression, emit a number that, at run time, is the value of that
5165 expression. The byte order and bit size of the number depends on what kind
5166 of target the assembly is for.
5170 On most forms of the H8/300, @code{.int} emits 16-bit
5171 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
5178 @section @code{.internal @var{names}}
5180 @cindex @code{internal} directive
5182 This is one of the ELF visibility directives. The other two are
5183 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
5184 @code{.protected} (@pxref{Protected,,@code{.protected}}).
5186 This directive overrides the named symbols default visibility (which is set by
5187 their binding: local, global or weak). The directive sets the visibility to
5188 @code{internal} which means that the symbols are considered to be @code{hidden}
5189 (i.e., not visible to other components), and that some extra, processor specific
5190 processing must also be performed upon the symbols as well.
5194 @section @code{.irp @var{symbol},@var{values}}@dots{}
5196 @cindex @code{irp} directive
5197 Evaluate a sequence of statements assigning different values to @var{symbol}.
5198 The sequence of statements starts at the @code{.irp} directive, and is
5199 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
5200 set to @var{value}, and the sequence of statements is assembled. If no
5201 @var{value} is listed, the sequence of statements is assembled once, with
5202 @var{symbol} set to the null string. To refer to @var{symbol} within the
5203 sequence of statements, use @var{\symbol}.
5205 For example, assembling
5213 is equivalent to assembling
5221 For some caveats with the spelling of @var{symbol}, see also @ref{Macro}.
5224 @section @code{.irpc @var{symbol},@var{values}}@dots{}
5226 @cindex @code{irpc} directive
5227 Evaluate a sequence of statements assigning different values to @var{symbol}.
5228 The sequence of statements starts at the @code{.irpc} directive, and is
5229 terminated by an @code{.endr} directive. For each character in @var{value},
5230 @var{symbol} is set to the character, and the sequence of statements is
5231 assembled. If no @var{value} is listed, the sequence of statements is
5232 assembled once, with @var{symbol} set to the null string. To refer to
5233 @var{symbol} within the sequence of statements, use @var{\symbol}.
5235 For example, assembling
5243 is equivalent to assembling
5251 For some caveats with the spelling of @var{symbol}, see also the discussion
5255 @section @code{.lcomm @var{symbol} , @var{length}}
5257 @cindex @code{lcomm} directive
5258 @cindex local common symbols
5259 @cindex symbols, local common
5260 Reserve @var{length} (an absolute expression) bytes for a local common
5261 denoted by @var{symbol}. The section and value of @var{symbol} are
5262 those of the new local common. The addresses are allocated in the bss
5263 section, so that at run-time the bytes start off zeroed. @var{Symbol}
5264 is not declared global (@pxref{Global,,@code{.global}}), so is normally
5265 not visible to @code{@value{LD}}.
5268 Some targets permit a third argument to be used with @code{.lcomm}. This
5269 argument specifies the desired alignment of the symbol in the bss section.
5273 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
5274 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
5278 @section @code{.lflags}
5280 @cindex @code{lflags} directive (ignored)
5281 @command{@value{AS}} accepts this directive, for compatibility with other
5282 assemblers, but ignores it.
5284 @ifclear no-line-dir
5286 @section @code{.line @var{line-number}}
5288 @cindex @code{line} directive
5289 @cindex logical line number
5291 Change the logical line number. @var{line-number} must be an absolute
5292 expression. The next line has that logical line number. Therefore any other
5293 statements on the current line (after a statement separator character) are
5294 reported as on logical line number @var{line-number} @minus{} 1. One day
5295 @command{@value{AS}} will no longer support this directive: it is recognized only
5296 for compatibility with existing assembler programs.
5299 Even though this is a directive associated with the @code{a.out} or
5300 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
5301 when producing COFF output, and treats @samp{.line} as though it
5302 were the COFF @samp{.ln} @emph{if} it is found outside a
5303 @code{.def}/@code{.endef} pair.
5305 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
5306 used by compilers to generate auxiliary symbol information for
5311 @section @code{.linkonce [@var{type}]}
5313 @cindex @code{linkonce} directive
5314 @cindex common sections
5315 Mark the current section so that the linker only includes a single copy of it.
5316 This may be used to include the same section in several different object files,
5317 but ensure that the linker will only include it once in the final output file.
5318 The @code{.linkonce} pseudo-op must be used for each instance of the section.
5319 Duplicate sections are detected based on the section name, so it should be
5322 This directive is only supported by a few object file formats; as of this
5323 writing, the only object file format which supports it is the Portable
5324 Executable format used on Windows NT.
5326 The @var{type} argument is optional. If specified, it must be one of the
5327 following strings. For example:
5331 Not all types may be supported on all object file formats.
5335 Silently discard duplicate sections. This is the default.
5338 Warn if there are duplicate sections, but still keep only one copy.
5341 Warn if any of the duplicates have different sizes.
5344 Warn if any of the duplicates do not have exactly the same contents.
5348 @section @code{.list}
5350 @cindex @code{list} directive
5351 @cindex listing control, turning on
5352 Control (in conjunction with the @code{.nolist} directive) whether or
5353 not assembly listings are generated. These two directives maintain an
5354 internal counter (which is zero initially). @code{.list} increments the
5355 counter, and @code{.nolist} decrements it. Assembly listings are
5356 generated whenever the counter is greater than zero.
5358 By default, listings are disabled. When you enable them (with the
5359 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
5360 the initial value of the listing counter is one.
5363 @section @code{.ln @var{line-number}}
5365 @cindex @code{ln} directive
5366 @ifclear no-line-dir
5367 @samp{.ln} is a synonym for @samp{.line}.
5370 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
5371 must be an absolute expression. The next line has that logical
5372 line number, so any other statements on the current line (after a
5373 statement separator character @code{;}) are reported as on logical
5374 line number @var{line-number} @minus{} 1.
5377 This directive is accepted, but ignored, when @command{@value{AS}} is
5378 configured for @code{b.out}; its effect is only associated with COFF
5384 @section @code{.loc @var{fileno} @var{lineno} [@var{column}] [@var{options}]}
5385 @cindex @code{loc} directive
5386 When emitting DWARF2 line number information,
5387 the @code{.loc} directive will add a row to the @code{.debug_line} line
5388 number matrix corresponding to the immediately following assembly
5389 instruction. The @var{fileno}, @var{lineno}, and optional @var{column}
5390 arguments will be applied to the @code{.debug_line} state machine before
5393 The @var{options} are a sequence of the following tokens in any order:
5397 This option will set the @code{basic_block} register in the
5398 @code{.debug_line} state machine to @code{true}.
5401 This option will set the @code{prologue_end} register in the
5402 @code{.debug_line} state machine to @code{true}.
5404 @item epilogue_begin
5405 This option will set the @code{epilogue_begin} register in the
5406 @code{.debug_line} state machine to @code{true}.
5408 @item is_stmt @var{value}
5409 This option will set the @code{is_stmt} register in the
5410 @code{.debug_line} state machine to @code{value}, which must be
5413 @item isa @var{value}
5414 This directive will set the @code{isa} register in the @code{.debug_line}
5415 state machine to @var{value}, which must be an unsigned integer.
5417 @item discriminator @var{value}
5418 This directive will set the @code{discriminator} register in the @code{.debug_line}
5419 state machine to @var{value}, which must be an unsigned integer.
5423 @node Loc_mark_labels
5424 @section @code{.loc_mark_labels @var{enable}}
5425 @cindex @code{loc_mark_labels} directive
5426 When emitting DWARF2 line number information,
5427 the @code{.loc_mark_labels} directive makes the assembler emit an entry
5428 to the @code{.debug_line} line number matrix with the @code{basic_block}
5429 register in the state machine set whenever a code label is seen.
5430 The @var{enable} argument should be either 1 or 0, to enable or disable
5431 this function respectively.
5435 @section @code{.local @var{names}}
5437 @cindex @code{local} directive
5438 This directive, which is available for ELF targets, marks each symbol in
5439 the comma-separated list of @code{names} as a local symbol so that it
5440 will not be externally visible. If the symbols do not already exist,
5441 they will be created.
5443 For targets where the @code{.lcomm} directive (@pxref{Lcomm}) does not
5444 accept an alignment argument, which is the case for most ELF targets,
5445 the @code{.local} directive can be used in combination with @code{.comm}
5446 (@pxref{Comm}) to define aligned local common data.
5450 @section @code{.long @var{expressions}}
5452 @cindex @code{long} directive
5453 @code{.long} is the same as @samp{.int}. @xref{Int,,@code{.int}}.
5456 @c no one seems to know what this is for or whether this description is
5457 @c what it really ought to do
5459 @section @code{.lsym @var{symbol}, @var{expression}}
5461 @cindex @code{lsym} directive
5462 @cindex symbol, not referenced in assembly
5463 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
5464 the hash table, ensuring it cannot be referenced by name during the
5465 rest of the assembly. This sets the attributes of the symbol to be
5466 the same as the expression value:
5468 @var{other} = @var{descriptor} = 0
5469 @var{type} = @r{(section of @var{expression})}
5470 @var{value} = @var{expression}
5473 The new symbol is not flagged as external.
5477 @section @code{.macro}
5480 The commands @code{.macro} and @code{.endm} allow you to define macros that
5481 generate assembly output. For example, this definition specifies a macro
5482 @code{sum} that puts a sequence of numbers into memory:
5485 .macro sum from=0, to=5
5494 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
5506 @item .macro @var{macname}
5507 @itemx .macro @var{macname} @var{macargs} @dots{}
5508 @cindex @code{macro} directive
5509 Begin the definition of a macro called @var{macname}. If your macro
5510 definition requires arguments, specify their names after the macro name,
5511 separated by commas or spaces. You can qualify the macro argument to
5512 indicate whether all invocations must specify a non-blank value (through
5513 @samp{:@code{req}}), or whether it takes all of the remaining arguments
5514 (through @samp{:@code{vararg}}). You can supply a default value for any
5515 macro argument by following the name with @samp{=@var{deflt}}. You
5516 cannot define two macros with the same @var{macname} unless it has been
5517 subject to the @code{.purgem} directive (@pxref{Purgem}) between the two
5518 definitions. For example, these are all valid @code{.macro} statements:
5522 Begin the definition of a macro called @code{comm}, which takes no
5525 @item .macro plus1 p, p1
5526 @itemx .macro plus1 p p1
5527 Either statement begins the definition of a macro called @code{plus1},
5528 which takes two arguments; within the macro definition, write
5529 @samp{\p} or @samp{\p1} to evaluate the arguments.
5531 @item .macro reserve_str p1=0 p2
5532 Begin the definition of a macro called @code{reserve_str}, with two
5533 arguments. The first argument has a default value, but not the second.
5534 After the definition is complete, you can call the macro either as
5535 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
5536 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
5537 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
5538 @samp{0}, and @samp{\p2} evaluating to @var{b}).
5540 @item .macro m p1:req, p2=0, p3:vararg
5541 Begin the definition of a macro called @code{m}, with at least three
5542 arguments. The first argument must always have a value specified, but
5543 not the second, which instead has a default value. The third formal
5544 will get assigned all remaining arguments specified at invocation time.
5546 When you call a macro, you can specify the argument values either by
5547 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
5548 @samp{sum to=17, from=9}.
5552 Note that since each of the @var{macargs} can be an identifier exactly
5553 as any other one permitted by the target architecture, there may be
5554 occasional problems if the target hand-crafts special meanings to certain
5555 characters when they occur in a special position. For example, if the colon
5556 (@code{:}) is generally permitted to be part of a symbol name, but the
5557 architecture specific code special-cases it when occurring as the final
5558 character of a symbol (to denote a label), then the macro parameter
5559 replacement code will have no way of knowing that and consider the whole
5560 construct (including the colon) an identifier, and check only this
5561 identifier for being the subject to parameter substitution. So for example
5562 this macro definition:
5570 might not work as expected. Invoking @samp{label foo} might not create a label
5571 called @samp{foo} but instead just insert the text @samp{\l:} into the
5572 assembler source, probably generating an error about an unrecognised
5575 Similarly problems might occur with the period character (@samp{.})
5576 which is often allowed inside opcode names (and hence identifier names). So
5577 for example constructing a macro to build an opcode from a base name and a
5578 length specifier like this:
5581 .macro opcode base length
5586 and invoking it as @samp{opcode store l} will not create a @samp{store.l}
5587 instruction but instead generate some kind of error as the assembler tries to
5588 interpret the text @samp{\base.\length}.
5590 There are several possible ways around this problem:
5593 @item Insert white space
5594 If it is possible to use white space characters then this is the simplest
5603 @item Use @samp{\()}
5604 The string @samp{\()} can be used to separate the end of a macro argument from
5605 the following text. eg:
5608 .macro opcode base length
5613 @item Use the alternate macro syntax mode
5614 In the alternative macro syntax mode the ampersand character (@samp{&}) can be
5615 used as a separator. eg:
5625 Note: this problem of correctly identifying string parameters to pseudo ops
5626 also applies to the identifiers used in @code{.irp} (@pxref{Irp})
5627 and @code{.irpc} (@pxref{Irpc}) as well.
5630 @cindex @code{endm} directive
5631 Mark the end of a macro definition.
5634 @cindex @code{exitm} directive
5635 Exit early from the current macro definition.
5637 @cindex number of macros executed
5638 @cindex macros, count executed
5640 @command{@value{AS}} maintains a counter of how many macros it has
5641 executed in this pseudo-variable; you can copy that number to your
5642 output with @samp{\@@}, but @emph{only within a macro definition}.
5644 @item LOCAL @var{name} [ , @dots{} ]
5645 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
5646 macro syntax'' with @samp{--alternate} or @code{.altmacro}.}
5647 @xref{Altmacro,,@code{.altmacro}}.
5651 @section @code{.mri @var{val}}
5653 @cindex @code{mri} directive
5654 @cindex MRI mode, temporarily
5655 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
5656 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
5657 affects code assembled until the next @code{.mri} directive, or until the end
5658 of the file. @xref{M, MRI mode, MRI mode}.
5661 @section @code{.noaltmacro}
5662 Disable alternate macro mode. @xref{Altmacro}.
5665 @section @code{.nolist}
5667 @cindex @code{nolist} directive
5668 @cindex listing control, turning off
5669 Control (in conjunction with the @code{.list} directive) whether or
5670 not assembly listings are generated. These two directives maintain an
5671 internal counter (which is zero initially). @code{.list} increments the
5672 counter, and @code{.nolist} decrements it. Assembly listings are
5673 generated whenever the counter is greater than zero.
5676 @section @code{.octa @var{bignums}}
5678 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
5679 @cindex @code{octa} directive
5680 @cindex integer, 16-byte
5681 @cindex sixteen byte integer
5682 This directive expects zero or more bignums, separated by commas. For each
5683 bignum, it emits a 16-byte integer.
5685 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
5686 hence @emph{octa}-word for 16 bytes.
5689 @section @code{.offset @var{loc}}
5691 @cindex @code{offset} directive
5692 Set the location counter to @var{loc} in the absolute section. @var{loc} must
5693 be an absolute expression. This directive may be useful for defining
5694 symbols with absolute values. Do not confuse it with the @code{.org}
5698 @section @code{.org @var{new-lc} , @var{fill}}
5700 @cindex @code{org} directive
5701 @cindex location counter, advancing
5702 @cindex advancing location counter
5703 @cindex current address, advancing
5704 Advance the location counter of the current section to
5705 @var{new-lc}. @var{new-lc} is either an absolute expression or an
5706 expression with the same section as the current subsection. That is,
5707 you can't use @code{.org} to cross sections: if @var{new-lc} has the
5708 wrong section, the @code{.org} directive is ignored. To be compatible
5709 with former assemblers, if the section of @var{new-lc} is absolute,
5710 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
5711 is the same as the current subsection.
5713 @code{.org} may only increase the location counter, or leave it
5714 unchanged; you cannot use @code{.org} to move the location counter
5717 @c double negative used below "not undefined" because this is a specific
5718 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
5719 @c section. doc@cygnus.com 18feb91
5720 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
5721 may not be undefined. If you really detest this restriction we eagerly await
5722 a chance to share your improved assembler.
5724 Beware that the origin is relative to the start of the section, not
5725 to the start of the subsection. This is compatible with other
5726 people's assemblers.
5728 When the location counter (of the current subsection) is advanced, the
5729 intervening bytes are filled with @var{fill} which should be an
5730 absolute expression. If the comma and @var{fill} are omitted,
5731 @var{fill} defaults to zero.
5734 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
5736 @cindex padding the location counter given a power of two
5737 @cindex @code{p2align} directive
5738 Pad the location counter (in the current subsection) to a particular
5739 storage boundary. The first expression (which must be absolute) is the
5740 number of low-order zero bits the location counter must have after
5741 advancement. For example @samp{.p2align 3} advances the location
5742 counter until it a multiple of 8. If the location counter is already a
5743 multiple of 8, no change is needed.
5745 The second expression (also absolute) gives the fill value to be stored in the
5746 padding bytes. It (and the comma) may be omitted. If it is omitted, the
5747 padding bytes are normally zero. However, on some systems, if the section is
5748 marked as containing code and the fill value is omitted, the space is filled
5749 with no-op instructions.
5751 The third expression is also absolute, and is also optional. If it is present,
5752 it is the maximum number of bytes that should be skipped by this alignment
5753 directive. If doing the alignment would require skipping more bytes than the
5754 specified maximum, then the alignment is not done at all. You can omit the
5755 fill value (the second argument) entirely by simply using two commas after the
5756 required alignment; this can be useful if you want the alignment to be filled
5757 with no-op instructions when appropriate.
5759 @cindex @code{p2alignw} directive
5760 @cindex @code{p2alignl} directive
5761 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
5762 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
5763 pattern as a two byte word value. The @code{.p2alignl} directives treats the
5764 fill pattern as a four byte longword value. For example, @code{.p2alignw
5765 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
5766 filled in with the value 0x368d (the exact placement of the bytes depends upon
5767 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
5772 @section @code{.popsection}
5774 @cindex @code{popsection} directive
5775 @cindex Section Stack
5776 This is one of the ELF section stack manipulation directives. The others are
5777 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5778 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
5781 This directive replaces the current section (and subsection) with the top
5782 section (and subsection) on the section stack. This section is popped off the
5788 @section @code{.previous}
5790 @cindex @code{previous} directive
5791 @cindex Section Stack
5792 This is one of the ELF section stack manipulation directives. The others are
5793 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5794 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
5795 (@pxref{PopSection}).
5797 This directive swaps the current section (and subsection) with most recently
5798 referenced section/subsection pair prior to this one. Multiple
5799 @code{.previous} directives in a row will flip between two sections (and their
5800 subsections). For example:
5812 Will place 0x1234 and 0x9abc into subsection 1 and 0x5678 into subsection 2 of
5818 # Now in section A subsection 1
5822 # Now in section B subsection 0
5825 # Now in section B subsection 1
5828 # Now in section B subsection 0
5832 Will place 0x1234 into section A, 0x5678 and 0xdef0 into subsection 0 of
5833 section B and 0x9abc into subsection 1 of section B.
5835 In terms of the section stack, this directive swaps the current section with
5836 the top section on the section stack.
5840 @section @code{.print @var{string}}
5842 @cindex @code{print} directive
5843 @command{@value{AS}} will print @var{string} on the standard output during
5844 assembly. You must put @var{string} in double quotes.
5848 @section @code{.protected @var{names}}
5850 @cindex @code{protected} directive
5852 This is one of the ELF visibility directives. The other two are
5853 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5855 This directive overrides the named symbols default visibility (which is set by
5856 their binding: local, global or weak). The directive sets the visibility to
5857 @code{protected} which means that any references to the symbols from within the
5858 components that defines them must be resolved to the definition in that
5859 component, even if a definition in another component would normally preempt
5864 @section @code{.psize @var{lines} , @var{columns}}
5866 @cindex @code{psize} directive
5867 @cindex listing control: paper size
5868 @cindex paper size, for listings
5869 Use this directive to declare the number of lines---and, optionally, the
5870 number of columns---to use for each page, when generating listings.
5872 If you do not use @code{.psize}, listings use a default line-count
5873 of 60. You may omit the comma and @var{columns} specification; the
5874 default width is 200 columns.
5876 @command{@value{AS}} generates formfeeds whenever the specified number of
5877 lines is exceeded (or whenever you explicitly request one, using
5880 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5881 those explicitly specified with @code{.eject}.
5884 @section @code{.purgem @var{name}}
5886 @cindex @code{purgem} directive
5887 Undefine the macro @var{name}, so that later uses of the string will not be
5888 expanded. @xref{Macro}.
5892 @section @code{.pushsection @var{name} [, @var{subsection}] [, "@var{flags}"[, @@@var{type}[,@var{arguments}]]]}
5894 @cindex @code{pushsection} directive
5895 @cindex Section Stack
5896 This is one of the ELF section stack manipulation directives. The others are
5897 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5898 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5901 This directive pushes the current section (and subsection) onto the
5902 top of the section stack, and then replaces the current section and
5903 subsection with @code{name} and @code{subsection}. The optional
5904 @code{flags}, @code{type} and @code{arguments} are treated the same
5905 as in the @code{.section} (@pxref{Section}) directive.
5909 @section @code{.quad @var{bignums}}
5911 @cindex @code{quad} directive
5912 @code{.quad} expects zero or more bignums, separated by commas. For
5913 each bignum, it emits
5915 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5916 warning message; and just takes the lowest order 8 bytes of the bignum.
5917 @cindex eight-byte integer
5918 @cindex integer, 8-byte
5920 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5921 hence @emph{quad}-word for 8 bytes.
5924 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5925 warning message; and just takes the lowest order 16 bytes of the bignum.
5926 @cindex sixteen-byte integer
5927 @cindex integer, 16-byte
5931 @section @code{.reloc @var{offset}, @var{reloc_name}[, @var{expression}]}
5933 @cindex @code{reloc} directive
5934 Generate a relocation at @var{offset} of type @var{reloc_name} with value
5935 @var{expression}. If @var{offset} is a number, the relocation is generated in
5936 the current section. If @var{offset} is an expression that resolves to a
5937 symbol plus offset, the relocation is generated in the given symbol's section.
5938 @var{expression}, if present, must resolve to a symbol plus addend or to an
5939 absolute value, but note that not all targets support an addend. e.g. ELF REL
5940 targets such as i386 store an addend in the section contents rather than in the
5941 relocation. This low level interface does not support addends stored in the
5945 @section @code{.rept @var{count}}
5947 @cindex @code{rept} directive
5948 Repeat the sequence of lines between the @code{.rept} directive and the next
5949 @code{.endr} directive @var{count} times.
5951 For example, assembling
5959 is equivalent to assembling
5968 @section @code{.sbttl "@var{subheading}"}
5970 @cindex @code{sbttl} directive
5971 @cindex subtitles for listings
5972 @cindex listing control: subtitle
5973 Use @var{subheading} as the title (third line, immediately after the
5974 title line) when generating assembly listings.
5976 This directive affects subsequent pages, as well as the current page if
5977 it appears within ten lines of the top of a page.
5981 @section @code{.scl @var{class}}
5983 @cindex @code{scl} directive
5984 @cindex symbol storage class (COFF)
5985 @cindex COFF symbol storage class
5986 Set the storage-class value for a symbol. This directive may only be
5987 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5988 whether a symbol is static or external, or it may record further
5989 symbolic debugging information.
5992 The @samp{.scl} directive is primarily associated with COFF output; when
5993 configured to generate @code{b.out} output format, @command{@value{AS}}
5994 accepts this directive but ignores it.
6000 @section @code{.section @var{name}}
6002 @cindex named section
6003 Use the @code{.section} directive to assemble the following code into a section
6006 This directive is only supported for targets that actually support arbitrarily
6007 named sections; on @code{a.out} targets, for example, it is not accepted, even
6008 with a standard @code{a.out} section name.
6012 @c only print the extra heading if both COFF and ELF are set
6013 @subheading COFF Version
6016 @cindex @code{section} directive (COFF version)
6017 For COFF targets, the @code{.section} directive is used in one of the following
6021 .section @var{name}[, "@var{flags}"]
6022 .section @var{name}[, @var{subsection}]
6025 If the optional argument is quoted, it is taken as flags to use for the
6026 section. Each flag is a single character. The following flags are recognized:
6029 bss section (uninitialized data)
6031 section is not loaded
6037 exclude section from linking
6043 shared section (meaningful for PE targets)
6045 ignored. (For compatibility with the ELF version)
6047 section is not readable (meaningful for PE targets)
6049 single-digit power-of-two section alignment (GNU extension)
6052 If no flags are specified, the default flags depend upon the section name. If
6053 the section name is not recognized, the default will be for the section to be
6054 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
6055 from the section, rather than adding them, so if they are used on their own it
6056 will be as if no flags had been specified at all.
6058 If the optional argument to the @code{.section} directive is not quoted, it is
6059 taken as a subsection number (@pxref{Sub-Sections}).
6064 @c only print the extra heading if both COFF and ELF are set
6065 @subheading ELF Version
6068 @cindex Section Stack
6069 This is one of the ELF section stack manipulation directives. The others are
6070 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
6071 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
6072 @code{.previous} (@pxref{Previous}).
6074 @cindex @code{section} directive (ELF version)
6075 For ELF targets, the @code{.section} directive is used like this:
6078 .section @var{name} [, "@var{flags}"[, @@@var{type}[,@var{flag_specific_arguments}]]]
6081 The optional @var{flags} argument is a quoted string which may contain any
6082 combination of the following characters:
6085 section is allocatable
6087 section is excluded from executable and shared library.
6091 section is executable
6093 section is mergeable
6095 section contains zero terminated strings
6097 section is a member of a section group
6099 section is used for thread-local-storage
6101 section is a member of the previously-current section's group, if any
6104 The optional @var{type} argument may contain one of the following constants:
6107 section contains data
6109 section does not contain data (i.e., section only occupies space)
6111 section contains data which is used by things other than the program
6113 section contains an array of pointers to init functions
6115 section contains an array of pointers to finish functions
6116 @item @@preinit_array
6117 section contains an array of pointers to pre-init functions
6120 Many targets only support the first three section types.
6122 Note on targets where the @code{@@} character is the start of a comment (eg
6123 ARM) then another character is used instead. For example the ARM port uses the
6126 If @var{flags} contains the @code{M} symbol then the @var{type} argument must
6127 be specified as well as an extra argument---@var{entsize}---like this:
6130 .section @var{name} , "@var{flags}"M, @@@var{type}, @var{entsize}
6133 Sections with the @code{M} flag but not @code{S} flag must contain fixed size
6134 constants, each @var{entsize} octets long. Sections with both @code{M} and
6135 @code{S} must contain zero terminated strings where each character is
6136 @var{entsize} bytes long. The linker may remove duplicates within sections with
6137 the same name, same entity size and same flags. @var{entsize} must be an
6138 absolute expression. For sections with both @code{M} and @code{S}, a string
6139 which is a suffix of a larger string is considered a duplicate. Thus
6140 @code{"def"} will be merged with @code{"abcdef"}; A reference to the first
6141 @code{"def"} will be changed to a reference to @code{"abcdef"+3}.
6143 If @var{flags} contains the @code{G} symbol then the @var{type} argument must
6144 be present along with an additional field like this:
6147 .section @var{name} , "@var{flags}"G, @@@var{type}, @var{GroupName}[, @var{linkage}]
6150 The @var{GroupName} field specifies the name of the section group to which this
6151 particular section belongs. The optional linkage field can contain:
6154 indicates that only one copy of this section should be retained
6159 Note: if both the @var{M} and @var{G} flags are present then the fields for
6160 the Merge flag should come first, like this:
6163 .section @var{name} , "@var{flags}"MG, @@@var{type}, @var{entsize}, @var{GroupName}[, @var{linkage}]
6166 If @var{flags} contains the @code{?} symbol then it may not also contain the
6167 @code{G} symbol and the @var{GroupName} or @var{linkage} fields should not be
6168 present. Instead, @code{?} says to consider the section that's current before
6169 this directive. If that section used @code{G}, then the new section will use
6170 @code{G} with those same @var{GroupName} and @var{linkage} fields implicitly.
6171 If not, then the @code{?} symbol has no effect.
6173 If no flags are specified, the default flags depend upon the section name. If
6174 the section name is not recognized, the default will be for the section to have
6175 none of the above flags: it will not be allocated in memory, nor writable, nor
6176 executable. The section will contain data.
6178 For ELF targets, the assembler supports another type of @code{.section}
6179 directive for compatibility with the Solaris assembler:
6182 .section "@var{name}"[, @var{flags}...]
6185 Note that the section name is quoted. There may be a sequence of comma
6189 section is allocatable
6193 section is executable
6195 section is excluded from executable and shared library.
6197 section is used for thread local storage
6200 This directive replaces the current section and subsection. See the
6201 contents of the gas testsuite directory @code{gas/testsuite/gas/elf} for
6202 some examples of how this directive and the other section stack directives
6208 @section @code{.set @var{symbol}, @var{expression}}
6210 @cindex @code{set} directive
6211 @cindex symbol value, setting
6212 Set the value of @var{symbol} to @var{expression}. This
6213 changes @var{symbol}'s value and type to conform to
6214 @var{expression}. If @var{symbol} was flagged as external, it remains
6215 flagged (@pxref{Symbol Attributes}).
6217 You may @code{.set} a symbol many times in the same assembly.
6219 If you @code{.set} a global symbol, the value stored in the object
6220 file is the last value stored into it.
6223 On Z80 @code{set} is a real instruction, use
6224 @samp{@var{symbol} defl @var{expression}} instead.
6228 @section @code{.short @var{expressions}}
6230 @cindex @code{short} directive
6232 @code{.short} is normally the same as @samp{.word}.
6233 @xref{Word,,@code{.word}}.
6235 In some configurations, however, @code{.short} and @code{.word} generate
6236 numbers of different lengths. @xref{Machine Dependencies}.
6240 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
6243 This expects zero or more @var{expressions}, and emits
6244 a 16 bit number for each.
6249 @section @code{.single @var{flonums}}
6251 @cindex @code{single} directive
6252 @cindex floating point numbers (single)
6253 This directive assembles zero or more flonums, separated by commas. It
6254 has the same effect as @code{.float}.
6256 The exact kind of floating point numbers emitted depends on how
6257 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
6261 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
6262 numbers in @sc{ieee} format.
6268 @section @code{.size}
6270 This directive is used to set the size associated with a symbol.
6274 @c only print the extra heading if both COFF and ELF are set
6275 @subheading COFF Version
6278 @cindex @code{size} directive (COFF version)
6279 For COFF targets, the @code{.size} directive is only permitted inside
6280 @code{.def}/@code{.endef} pairs. It is used like this:
6283 .size @var{expression}
6287 @samp{.size} is only meaningful when generating COFF format output; when
6288 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6295 @c only print the extra heading if both COFF and ELF are set
6296 @subheading ELF Version
6299 @cindex @code{size} directive (ELF version)
6300 For ELF targets, the @code{.size} directive is used like this:
6303 .size @var{name} , @var{expression}
6306 This directive sets the size associated with a symbol @var{name}.
6307 The size in bytes is computed from @var{expression} which can make use of label
6308 arithmetic. This directive is typically used to set the size of function
6313 @ifclear no-space-dir
6315 @section @code{.skip @var{size} , @var{fill}}
6317 @cindex @code{skip} directive
6318 @cindex filling memory
6319 This directive emits @var{size} bytes, each of value @var{fill}. Both
6320 @var{size} and @var{fill} are absolute expressions. If the comma and
6321 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
6326 @section @code{.sleb128 @var{expressions}}
6328 @cindex @code{sleb128} directive
6329 @var{sleb128} stands for ``signed little endian base 128.'' This is a
6330 compact, variable length representation of numbers used by the DWARF
6331 symbolic debugging format. @xref{Uleb128, ,@code{.uleb128}}.
6333 @ifclear no-space-dir
6335 @section @code{.space @var{size} , @var{fill}}
6337 @cindex @code{space} directive
6338 @cindex filling memory
6339 This directive emits @var{size} bytes, each of value @var{fill}. Both
6340 @var{size} and @var{fill} are absolute expressions. If the comma
6341 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
6346 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
6347 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
6348 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
6349 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
6357 @section @code{.stabd, .stabn, .stabs}
6359 @cindex symbolic debuggers, information for
6360 @cindex @code{stab@var{x}} directives
6361 There are three directives that begin @samp{.stab}.
6362 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
6363 The symbols are not entered in the @command{@value{AS}} hash table: they
6364 cannot be referenced elsewhere in the source file.
6365 Up to five fields are required:
6369 This is the symbol's name. It may contain any character except
6370 @samp{\000}, so is more general than ordinary symbol names. Some
6371 debuggers used to code arbitrarily complex structures into symbol names
6375 An absolute expression. The symbol's type is set to the low 8 bits of
6376 this expression. Any bit pattern is permitted, but @code{@value{LD}}
6377 and debuggers choke on silly bit patterns.
6380 An absolute expression. The symbol's ``other'' attribute is set to the
6381 low 8 bits of this expression.
6384 An absolute expression. The symbol's descriptor is set to the low 16
6385 bits of this expression.
6388 An absolute expression which becomes the symbol's value.
6391 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
6392 or @code{.stabs} statement, the symbol has probably already been created;
6393 you get a half-formed symbol in your object file. This is
6394 compatible with earlier assemblers!
6397 @cindex @code{stabd} directive
6398 @item .stabd @var{type} , @var{other} , @var{desc}
6400 The ``name'' of the symbol generated is not even an empty string.
6401 It is a null pointer, for compatibility. Older assemblers used a
6402 null pointer so they didn't waste space in object files with empty
6405 The symbol's value is set to the location counter,
6406 relocatably. When your program is linked, the value of this symbol
6407 is the address of the location counter when the @code{.stabd} was
6410 @cindex @code{stabn} directive
6411 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
6412 The name of the symbol is set to the empty string @code{""}.
6414 @cindex @code{stabs} directive
6415 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
6416 All five fields are specified.
6422 @section @code{.string} "@var{str}", @code{.string8} "@var{str}", @code{.string16}
6423 "@var{str}", @code{.string32} "@var{str}", @code{.string64} "@var{str}"
6425 @cindex string, copying to object file
6426 @cindex string8, copying to object file
6427 @cindex string16, copying to object file
6428 @cindex string32, copying to object file
6429 @cindex string64, copying to object file
6430 @cindex @code{string} directive
6431 @cindex @code{string8} directive
6432 @cindex @code{string16} directive
6433 @cindex @code{string32} directive
6434 @cindex @code{string64} directive
6436 Copy the characters in @var{str} to the object file. You may specify more than
6437 one string to copy, separated by commas. Unless otherwise specified for a
6438 particular machine, the assembler marks the end of each string with a 0 byte.
6439 You can use any of the escape sequences described in @ref{Strings,,Strings}.
6441 The variants @code{string16}, @code{string32} and @code{string64} differ from
6442 the @code{string} pseudo opcode in that each 8-bit character from @var{str} is
6443 copied and expanded to 16, 32 or 64 bits respectively. The expanded characters
6444 are stored in target endianness byte order.
6450 .string "B\0\0\0Y\0\0\0E\0\0\0" /* On little endian targets. */
6451 .string "\0\0\0B\0\0\0Y\0\0\0E" /* On big endian targets. */
6456 @section @code{.struct @var{expression}}
6458 @cindex @code{struct} directive
6459 Switch to the absolute section, and set the section offset to @var{expression},
6460 which must be an absolute expression. You might use this as follows:
6469 This would define the symbol @code{field1} to have the value 0, the symbol
6470 @code{field2} to have the value 4, and the symbol @code{field3} to have the
6471 value 8. Assembly would be left in the absolute section, and you would need to
6472 use a @code{.section} directive of some sort to change to some other section
6473 before further assembly.
6477 @section @code{.subsection @var{name}}
6479 @cindex @code{subsection} directive
6480 @cindex Section Stack
6481 This is one of the ELF section stack manipulation directives. The others are
6482 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
6483 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
6486 This directive replaces the current subsection with @code{name}. The current
6487 section is not changed. The replaced subsection is put onto the section stack
6488 in place of the then current top of stack subsection.
6493 @section @code{.symver}
6494 @cindex @code{symver} directive
6495 @cindex symbol versioning
6496 @cindex versions of symbols
6497 Use the @code{.symver} directive to bind symbols to specific version nodes
6498 within a source file. This is only supported on ELF platforms, and is
6499 typically used when assembling files to be linked into a shared library.
6500 There are cases where it may make sense to use this in objects to be bound
6501 into an application itself so as to override a versioned symbol from a
6504 For ELF targets, the @code{.symver} directive can be used like this:
6506 .symver @var{name}, @var{name2@@nodename}
6508 If the symbol @var{name} is defined within the file
6509 being assembled, the @code{.symver} directive effectively creates a symbol
6510 alias with the name @var{name2@@nodename}, and in fact the main reason that we
6511 just don't try and create a regular alias is that the @var{@@} character isn't
6512 permitted in symbol names. The @var{name2} part of the name is the actual name
6513 of the symbol by which it will be externally referenced. The name @var{name}
6514 itself is merely a name of convenience that is used so that it is possible to
6515 have definitions for multiple versions of a function within a single source
6516 file, and so that the compiler can unambiguously know which version of a
6517 function is being mentioned. The @var{nodename} portion of the alias should be
6518 the name of a node specified in the version script supplied to the linker when
6519 building a shared library. If you are attempting to override a versioned
6520 symbol from a shared library, then @var{nodename} should correspond to the
6521 nodename of the symbol you are trying to override.
6523 If the symbol @var{name} is not defined within the file being assembled, all
6524 references to @var{name} will be changed to @var{name2@@nodename}. If no
6525 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
6528 Another usage of the @code{.symver} directive is:
6530 .symver @var{name}, @var{name2@@@@nodename}
6532 In this case, the symbol @var{name} must exist and be defined within
6533 the file being assembled. It is similar to @var{name2@@nodename}. The
6534 difference is @var{name2@@@@nodename} will also be used to resolve
6535 references to @var{name2} by the linker.
6537 The third usage of the @code{.symver} directive is:
6539 .symver @var{name}, @var{name2@@@@@@nodename}
6541 When @var{name} is not defined within the
6542 file being assembled, it is treated as @var{name2@@nodename}. When
6543 @var{name} is defined within the file being assembled, the symbol
6544 name, @var{name}, will be changed to @var{name2@@@@nodename}.
6549 @section @code{.tag @var{structname}}
6551 @cindex COFF structure debugging
6552 @cindex structure debugging, COFF
6553 @cindex @code{tag} directive
6554 This directive is generated by compilers to include auxiliary debugging
6555 information in the symbol table. It is only permitted inside
6556 @code{.def}/@code{.endef} pairs. Tags are used to link structure
6557 definitions in the symbol table with instances of those structures.
6560 @samp{.tag} is only used when generating COFF format output; when
6561 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
6567 @section @code{.text @var{subsection}}
6569 @cindex @code{text} directive
6570 Tells @command{@value{AS}} to assemble the following statements onto the end of
6571 the text subsection numbered @var{subsection}, which is an absolute
6572 expression. If @var{subsection} is omitted, subsection number zero
6576 @section @code{.title "@var{heading}"}
6578 @cindex @code{title} directive
6579 @cindex listing control: title line
6580 Use @var{heading} as the title (second line, immediately after the
6581 source file name and pagenumber) when generating assembly listings.
6583 This directive affects subsequent pages, as well as the current page if
6584 it appears within ten lines of the top of a page.
6588 @section @code{.type}
6590 This directive is used to set the type of a symbol.
6594 @c only print the extra heading if both COFF and ELF are set
6595 @subheading COFF Version
6598 @cindex COFF symbol type
6599 @cindex symbol type, COFF
6600 @cindex @code{type} directive (COFF version)
6601 For COFF targets, this directive is permitted only within
6602 @code{.def}/@code{.endef} pairs. It is used like this:
6608 This records the integer @var{int} as the type attribute of a symbol table
6612 @samp{.type} is associated only with COFF format output; when
6613 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
6614 directive but ignores it.
6620 @c only print the extra heading if both COFF and ELF are set
6621 @subheading ELF Version
6624 @cindex ELF symbol type
6625 @cindex symbol type, ELF
6626 @cindex @code{type} directive (ELF version)
6627 For ELF targets, the @code{.type} directive is used like this:
6630 .type @var{name} , @var{type description}
6633 This sets the type of symbol @var{name} to be either a
6634 function symbol or an object symbol. There are five different syntaxes
6635 supported for the @var{type description} field, in order to provide
6636 compatibility with various other assemblers.
6638 Because some of the characters used in these syntaxes (such as @samp{@@} and
6639 @samp{#}) are comment characters for some architectures, some of the syntaxes
6640 below do not work on all architectures. The first variant will be accepted by
6641 the GNU assembler on all architectures so that variant should be used for
6642 maximum portability, if you do not need to assemble your code with other
6645 The syntaxes supported are:
6648 .type <name> STT_<TYPE_IN_UPPER_CASE>
6649 .type <name>,#<type>
6650 .type <name>,@@<type>
6651 .type <name>,%<type>
6652 .type <name>,"<type>"
6655 The types supported are:
6660 Mark the symbol as being a function name.
6663 @itemx gnu_indirect_function
6664 Mark the symbol as an indirect function when evaluated during reloc
6665 processing. (This is only supported on assemblers targeting GNU systems).
6669 Mark the symbol as being a data object.
6673 Mark the symbol as being a thead-local data object.
6677 Mark the symbol as being a common data object.
6681 Does not mark the symbol in any way. It is supported just for completeness.
6683 @item gnu_unique_object
6684 Marks the symbol as being a globally unique data object. The dynamic linker
6685 will make sure that in the entire process there is just one symbol with this
6686 name and type in use. (This is only supported on assemblers targeting GNU
6691 Note: Some targets support extra types in addition to those listed above.
6697 @section @code{.uleb128 @var{expressions}}
6699 @cindex @code{uleb128} directive
6700 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
6701 compact, variable length representation of numbers used by the DWARF
6702 symbolic debugging format. @xref{Sleb128, ,@code{.sleb128}}.
6706 @section @code{.val @var{addr}}
6708 @cindex @code{val} directive
6709 @cindex COFF value attribute
6710 @cindex value attribute, COFF
6711 This directive, permitted only within @code{.def}/@code{.endef} pairs,
6712 records the address @var{addr} as the value attribute of a symbol table
6716 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
6717 configured for @code{b.out}, it accepts this directive but ignores it.
6723 @section @code{.version "@var{string}"}
6725 @cindex @code{version} directive
6726 This directive creates a @code{.note} section and places into it an ELF
6727 formatted note of type NT_VERSION. The note's name is set to @code{string}.
6732 @section @code{.vtable_entry @var{table}, @var{offset}}
6734 @cindex @code{vtable_entry} directive
6735 This directive finds or creates a symbol @code{table} and creates a
6736 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
6739 @section @code{.vtable_inherit @var{child}, @var{parent}}
6741 @cindex @code{vtable_inherit} directive
6742 This directive finds the symbol @code{child} and finds or creates the symbol
6743 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
6744 parent whose addend is the value of the child symbol. As a special case the
6745 parent name of @code{0} is treated as referring to the @code{*ABS*} section.
6749 @section @code{.warning "@var{string}"}
6750 @cindex warning directive
6751 Similar to the directive @code{.error}
6752 (@pxref{Error,,@code{.error "@var{string}"}}), but just emits a warning.
6755 @section @code{.weak @var{names}}
6757 @cindex @code{weak} directive
6758 This directive sets the weak attribute on the comma separated list of symbol
6759 @code{names}. If the symbols do not already exist, they will be created.
6761 On COFF targets other than PE, weak symbols are a GNU extension. This
6762 directive sets the weak attribute on the comma separated list of symbol
6763 @code{names}. If the symbols do not already exist, they will be created.
6765 On the PE target, weak symbols are supported natively as weak aliases.
6766 When a weak symbol is created that is not an alias, GAS creates an
6767 alternate symbol to hold the default value.
6770 @section @code{.weakref @var{alias}, @var{target}}
6772 @cindex @code{weakref} directive
6773 This directive creates an alias to the target symbol that enables the symbol to
6774 be referenced with weak-symbol semantics, but without actually making it weak.
6775 If direct references or definitions of the symbol are present, then the symbol
6776 will not be weak, but if all references to it are through weak references, the
6777 symbol will be marked as weak in the symbol table.
6779 The effect is equivalent to moving all references to the alias to a separate
6780 assembly source file, renaming the alias to the symbol in it, declaring the
6781 symbol as weak there, and running a reloadable link to merge the object files
6782 resulting from the assembly of the new source file and the old source file that
6783 had the references to the alias removed.
6785 The alias itself never makes to the symbol table, and is entirely handled
6786 within the assembler.
6789 @section @code{.word @var{expressions}}
6791 @cindex @code{word} directive
6792 This directive expects zero or more @var{expressions}, of any section,
6793 separated by commas.
6796 For each expression, @command{@value{AS}} emits a 32-bit number.
6799 For each expression, @command{@value{AS}} emits a 16-bit number.
6804 The size of the number emitted, and its byte order,
6805 depend on what target computer the assembly is for.
6808 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
6809 @c happen---32-bit addressability, period; no long/short jumps.
6810 @ifset DIFF-TBL-KLUGE
6811 @cindex difference tables altered
6812 @cindex altered difference tables
6814 @emph{Warning: Special Treatment to support Compilers}
6818 Machines with a 32-bit address space, but that do less than 32-bit
6819 addressing, require the following special treatment. If the machine of
6820 interest to you does 32-bit addressing (or doesn't require it;
6821 @pxref{Machine Dependencies}), you can ignore this issue.
6824 In order to assemble compiler output into something that works,
6825 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
6826 Directives of the form @samp{.word sym1-sym2} are often emitted by
6827 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
6828 directive of the form @samp{.word sym1-sym2}, and the difference between
6829 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
6830 creates a @dfn{secondary jump table}, immediately before the next label.
6831 This secondary jump table is preceded by a short-jump to the
6832 first byte after the secondary table. This short-jump prevents the flow
6833 of control from accidentally falling into the new table. Inside the
6834 table is a long-jump to @code{sym2}. The original @samp{.word}
6835 contains @code{sym1} minus the address of the long-jump to
6838 If there were several occurrences of @samp{.word sym1-sym2} before the
6839 secondary jump table, all of them are adjusted. If there was a
6840 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
6841 long-jump to @code{sym4} is included in the secondary jump table,
6842 and the @code{.word} directives are adjusted to contain @code{sym3}
6843 minus the address of the long-jump to @code{sym4}; and so on, for as many
6844 entries in the original jump table as necessary.
6847 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
6848 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
6849 assembly language programmers.
6852 @c end DIFF-TBL-KLUGE
6855 @section Deprecated Directives
6857 @cindex deprecated directives
6858 @cindex obsolescent directives
6859 One day these directives won't work.
6860 They are included for compatibility with older assemblers.
6867 @node Object Attributes
6868 @chapter Object Attributes
6869 @cindex object attributes
6871 @command{@value{AS}} assembles source files written for a specific architecture
6872 into object files for that architecture. But not all object files are alike.
6873 Many architectures support incompatible variations. For instance, floating
6874 point arguments might be passed in floating point registers if the object file
6875 requires hardware floating point support---or floating point arguments might be
6876 passed in integer registers if the object file supports processors with no
6877 hardware floating point unit. Or, if two objects are built for different
6878 generations of the same architecture, the combination may require the
6879 newer generation at run-time.
6881 This information is useful during and after linking. At link time,
6882 @command{@value{LD}} can warn about incompatible object files. After link
6883 time, tools like @command{gdb} can use it to process the linked file
6886 Compatibility information is recorded as a series of object attributes. Each
6887 attribute has a @dfn{vendor}, @dfn{tag}, and @dfn{value}. The vendor is a
6888 string, and indicates who sets the meaning of the tag. The tag is an integer,
6889 and indicates what property the attribute describes. The value may be a string
6890 or an integer, and indicates how the property affects this object. Missing
6891 attributes are the same as attributes with a zero value or empty string value.
6893 Object attributes were developed as part of the ABI for the ARM Architecture.
6894 The file format is documented in @cite{ELF for the ARM Architecture}.
6897 * GNU Object Attributes:: @sc{gnu} Object Attributes
6898 * Defining New Object Attributes:: Defining New Object Attributes
6901 @node GNU Object Attributes
6902 @section @sc{gnu} Object Attributes
6904 The @code{.gnu_attribute} directive records an object attribute
6905 with vendor @samp{gnu}.
6907 Except for @samp{Tag_compatibility}, which has both an integer and a string for
6908 its value, @sc{gnu} attributes have a string value if the tag number is odd and
6909 an integer value if the tag number is even. The second bit (@code{@var{tag} &
6910 2} is set for architecture-independent attributes and clear for
6911 architecture-dependent ones.
6913 @subsection Common @sc{gnu} attributes
6915 These attributes are valid on all architectures.
6918 @item Tag_compatibility (32)
6919 The compatibility attribute takes an integer flag value and a vendor name. If
6920 the flag value is 0, the file is compatible with other toolchains. If it is 1,
6921 then the file is only compatible with the named toolchain. If it is greater
6922 than 1, the file can only be processed by other toolchains under some private
6923 arrangement indicated by the flag value and the vendor name.
6926 @subsection MIPS Attributes
6929 @item Tag_GNU_MIPS_ABI_FP (4)
6930 The floating-point ABI used by this object file. The value will be:
6934 0 for files not affected by the floating-point ABI.
6936 1 for files using the hardware floating-point with a standard double-precision
6939 2 for files using the hardware floating-point ABI with a single-precision FPU.
6941 3 for files using the software floating-point ABI.
6943 4 for files using the hardware floating-point ABI with 64-bit wide
6944 double-precision floating-point registers and 32-bit wide general
6949 @subsection PowerPC Attributes
6952 @item Tag_GNU_Power_ABI_FP (4)
6953 The floating-point ABI used by this object file. The value will be:
6957 0 for files not affected by the floating-point ABI.
6959 1 for files using double-precision hardware floating-point ABI.
6961 2 for files using the software floating-point ABI.
6963 3 for files using single-precision hardware floating-point ABI.
6966 @item Tag_GNU_Power_ABI_Vector (8)
6967 The vector ABI used by this object file. The value will be:
6971 0 for files not affected by the vector ABI.
6973 1 for files using general purpose registers to pass vectors.
6975 2 for files using AltiVec registers to pass vectors.
6977 3 for files using SPE registers to pass vectors.
6981 @node Defining New Object Attributes
6982 @section Defining New Object Attributes
6984 If you want to define a new @sc{gnu} object attribute, here are the places you
6985 will need to modify. New attributes should be discussed on the @samp{binutils}
6990 This manual, which is the official register of attributes.
6992 The header for your architecture @file{include/elf}, to define the tag.
6994 The @file{bfd} support file for your architecture, to merge the attribute
6995 and issue any appropriate link warnings.
6997 Test cases in @file{ld/testsuite} for merging and link warnings.
6999 @file{binutils/readelf.c} to display your attribute.
7001 GCC, if you want the compiler to mark the attribute automatically.
7007 @node Machine Dependencies
7008 @chapter Machine Dependent Features
7010 @cindex machine dependencies
7011 The machine instruction sets are (almost by definition) different on
7012 each machine where @command{@value{AS}} runs. Floating point representations
7013 vary as well, and @command{@value{AS}} often supports a few additional
7014 directives or command-line options for compatibility with other
7015 assemblers on a particular platform. Finally, some versions of
7016 @command{@value{AS}} support special pseudo-instructions for branch
7019 This chapter discusses most of these differences, though it does not
7020 include details on any machine's instruction set. For details on that
7021 subject, see the hardware manufacturer's manual.
7025 * AArch64-Dependent:: AArch64 Dependent Features
7028 * Alpha-Dependent:: Alpha Dependent Features
7031 * ARC-Dependent:: ARC Dependent Features
7034 * ARM-Dependent:: ARM Dependent Features
7037 * AVR-Dependent:: AVR Dependent Features
7040 * Blackfin-Dependent:: Blackfin Dependent Features
7043 * CR16-Dependent:: CR16 Dependent Features
7046 * CRIS-Dependent:: CRIS Dependent Features
7049 * D10V-Dependent:: D10V Dependent Features
7052 * D30V-Dependent:: D30V Dependent Features
7055 * Epiphany-Dependent:: EPIPHANY Dependent Features
7058 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7061 * HPPA-Dependent:: HPPA Dependent Features
7064 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
7067 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
7070 * i860-Dependent:: Intel 80860 Dependent Features
7073 * i960-Dependent:: Intel 80960 Dependent Features
7076 * IA-64-Dependent:: Intel IA-64 Dependent Features
7079 * IP2K-Dependent:: IP2K Dependent Features
7082 * LM32-Dependent:: LM32 Dependent Features
7085 * M32C-Dependent:: M32C Dependent Features
7088 * M32R-Dependent:: M32R Dependent Features
7091 * M68K-Dependent:: M680x0 Dependent Features
7094 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
7097 * Meta-Dependent :: Meta Dependent Features
7100 * MicroBlaze-Dependent:: MICROBLAZE Dependent Features
7103 * MIPS-Dependent:: MIPS Dependent Features
7106 * MMIX-Dependent:: MMIX Dependent Features
7109 * MSP430-Dependent:: MSP430 Dependent Features
7112 * NiosII-Dependent:: Altera Nios II Dependent Features
7115 * NS32K-Dependent:: NS32K Dependent Features
7118 * SH-Dependent:: Renesas / SuperH SH Dependent Features
7119 * SH64-Dependent:: SuperH SH64 Dependent Features
7122 * PDP-11-Dependent:: PDP-11 Dependent Features
7125 * PJ-Dependent:: picoJava Dependent Features
7128 * PPC-Dependent:: PowerPC Dependent Features
7131 * RL78-Dependent:: RL78 Dependent Features
7134 * RX-Dependent:: RX Dependent Features
7137 * S/390-Dependent:: IBM S/390 Dependent Features
7140 * SCORE-Dependent:: SCORE Dependent Features
7143 * Sparc-Dependent:: SPARC Dependent Features
7146 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
7149 * TIC6X-Dependent :: TI TMS320C6x Dependent Features
7152 * TILE-Gx-Dependent :: Tilera TILE-Gx Dependent Features
7155 * TILEPro-Dependent :: Tilera TILEPro Dependent Features
7158 * V850-Dependent:: V850 Dependent Features
7161 * XGATE-Dependent:: XGATE Features
7164 * XSTORMY16-Dependent:: XStormy16 Dependent Features
7167 * Xtensa-Dependent:: Xtensa Dependent Features
7170 * Z80-Dependent:: Z80 Dependent Features
7173 * Z8000-Dependent:: Z8000 Dependent Features
7176 * Vax-Dependent:: VAX Dependent Features
7183 @c The following major nodes are *sections* in the GENERIC version, *chapters*
7184 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
7185 @c peculiarity: to preserve cross-references, there must be a node called
7186 @c "Machine Dependencies". Hence the conditional nodenames in each
7187 @c major node below. Node defaulting in makeinfo requires adjacency of
7188 @c node and sectioning commands; hence the repetition of @chapter BLAH
7189 @c in both conditional blocks.
7192 @include c-aarch64.texi
7196 @include c-alpha.texi
7212 @include c-bfin.texi
7216 @include c-cr16.texi
7220 @include c-cris.texi
7225 @node Machine Dependencies
7226 @chapter Machine Dependent Features
7228 The machine instruction sets are different on each Renesas chip family,
7229 and there are also some syntax differences among the families. This
7230 chapter describes the specific @command{@value{AS}} features for each
7234 * H8/300-Dependent:: Renesas H8/300 Dependent Features
7235 * SH-Dependent:: Renesas SH Dependent Features
7242 @include c-d10v.texi
7246 @include c-d30v.texi
7250 @include c-epiphany.texi
7254 @include c-h8300.texi
7258 @include c-hppa.texi
7262 @include c-i370.texi
7266 @include c-i386.texi
7270 @include c-i860.texi
7274 @include c-i960.texi
7278 @include c-ia64.texi
7282 @include c-ip2k.texi
7286 @include c-lm32.texi
7290 @include c-m32c.texi
7294 @include c-m32r.texi
7298 @include c-m68k.texi
7302 @include c-m68hc11.texi
7306 @include c-metag.texi
7310 @include c-microblaze.texi
7314 @include c-mips.texi
7318 @include c-mmix.texi
7322 @include c-msp430.texi
7326 @include c-nios2.texi
7330 @include c-ns32k.texi
7334 @include c-pdp11.texi
7346 @include c-rl78.texi
7354 @include c-s390.texi
7358 @include c-score.texi
7363 @include c-sh64.texi
7367 @include c-sparc.texi
7371 @include c-tic54x.texi
7375 @include c-tic6x.texi
7379 @include c-tilegx.texi
7383 @include c-tilepro.texi
7399 @include c-v850.texi
7403 @include c-xgate.texi
7407 @include c-xstormy16.texi
7411 @include c-xtensa.texi
7415 @c reverse effect of @down at top of generic Machine-Dep chapter
7419 @node Reporting Bugs
7420 @chapter Reporting Bugs
7421 @cindex bugs in assembler
7422 @cindex reporting bugs in assembler
7424 Your bug reports play an essential role in making @command{@value{AS}} reliable.
7426 Reporting a bug may help you by bringing a solution to your problem, or it may
7427 not. But in any case the principal function of a bug report is to help the
7428 entire community by making the next version of @command{@value{AS}} work better.
7429 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
7431 In order for a bug report to serve its purpose, you must include the
7432 information that enables us to fix the bug.
7435 * Bug Criteria:: Have you found a bug?
7436 * Bug Reporting:: How to report bugs
7440 @section Have You Found a Bug?
7441 @cindex bug criteria
7443 If you are not sure whether you have found a bug, here are some guidelines:
7446 @cindex fatal signal
7447 @cindex assembler crash
7448 @cindex crash of assembler
7450 If the assembler gets a fatal signal, for any input whatever, that is a
7451 @command{@value{AS}} bug. Reliable assemblers never crash.
7453 @cindex error on valid input
7455 If @command{@value{AS}} produces an error message for valid input, that is a bug.
7457 @cindex invalid input
7459 If @command{@value{AS}} does not produce an error message for invalid input, that
7460 is a bug. However, you should note that your idea of ``invalid input'' might
7461 be our idea of ``an extension'' or ``support for traditional practice''.
7464 If you are an experienced user of assemblers, your suggestions for improvement
7465 of @command{@value{AS}} are welcome in any case.
7469 @section How to Report Bugs
7471 @cindex assembler bugs, reporting
7473 A number of companies and individuals offer support for @sc{gnu} products. If
7474 you obtained @command{@value{AS}} from a support organization, we recommend you
7475 contact that organization first.
7477 You can find contact information for many support companies and
7478 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
7482 In any event, we also recommend that you send bug reports for @command{@value{AS}}
7486 The fundamental principle of reporting bugs usefully is this:
7487 @strong{report all the facts}. If you are not sure whether to state a
7488 fact or leave it out, state it!
7490 Often people omit facts because they think they know what causes the problem
7491 and assume that some details do not matter. Thus, you might assume that the
7492 name of a symbol you use in an example does not matter. Well, probably it does
7493 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
7494 happens to fetch from the location where that name is stored in memory;
7495 perhaps, if the name were different, the contents of that location would fool
7496 the assembler into doing the right thing despite the bug. Play it safe and
7497 give a specific, complete example. That is the easiest thing for you to do,
7498 and the most helpful.
7500 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
7501 it is new to us. Therefore, always write your bug reports on the assumption
7502 that the bug has not been reported previously.
7504 Sometimes people give a few sketchy facts and ask, ``Does this ring a
7505 bell?'' This cannot help us fix a bug, so it is basically useless. We
7506 respond by asking for enough details to enable us to investigate.
7507 You might as well expedite matters by sending them to begin with.
7509 To enable us to fix the bug, you should include all these things:
7513 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
7514 it with the @samp{--version} argument.
7516 Without this, we will not know whether there is any point in looking for
7517 the bug in the current version of @command{@value{AS}}.
7520 Any patches you may have applied to the @command{@value{AS}} source.
7523 The type of machine you are using, and the operating system name and
7527 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
7531 The command arguments you gave the assembler to assemble your example and
7532 observe the bug. To guarantee you will not omit something important, list them
7533 all. A copy of the Makefile (or the output from make) is sufficient.
7535 If we were to try to guess the arguments, we would probably guess wrong
7536 and then we might not encounter the bug.
7539 A complete input file that will reproduce the bug. If the bug is observed when
7540 the assembler is invoked via a compiler, send the assembler source, not the
7541 high level language source. Most compilers will produce the assembler source
7542 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
7543 the options @samp{-v --save-temps}; this will save the assembler source in a
7544 file with an extension of @file{.s}, and also show you exactly how
7545 @command{@value{AS}} is being run.
7548 A description of what behavior you observe that you believe is
7549 incorrect. For example, ``It gets a fatal signal.''
7551 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
7552 will certainly notice it. But if the bug is incorrect output, we might not
7553 notice unless it is glaringly wrong. You might as well not give us a chance to
7556 Even if the problem you experience is a fatal signal, you should still say so
7557 explicitly. Suppose something strange is going on, such as, your copy of
7558 @command{@value{AS}} is out of sync, or you have encountered a bug in the C
7559 library on your system. (This has happened!) Your copy might crash and ours
7560 would not. If you told us to expect a crash, then when ours fails to crash, we
7561 would know that the bug was not happening for us. If you had not told us to
7562 expect a crash, then we would not be able to draw any conclusion from our
7566 If you wish to suggest changes to the @command{@value{AS}} source, send us context
7567 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
7568 option. Always send diffs from the old file to the new file. If you even
7569 discuss something in the @command{@value{AS}} source, refer to it by context, not
7572 The line numbers in our development sources will not match those in your
7573 sources. Your line numbers would convey no useful information to us.
7576 Here are some things that are not necessary:
7580 A description of the envelope of the bug.
7582 Often people who encounter a bug spend a lot of time investigating
7583 which changes to the input file will make the bug go away and which
7584 changes will not affect it.
7586 This is often time consuming and not very useful, because the way we
7587 will find the bug is by running a single example under the debugger
7588 with breakpoints, not by pure deduction from a series of examples.
7589 We recommend that you save your time for something else.
7591 Of course, if you can find a simpler example to report @emph{instead}
7592 of the original one, that is a convenience for us. Errors in the
7593 output will be easier to spot, running under the debugger will take
7594 less time, and so on.
7596 However, simplification is not vital; if you do not want to do this,
7597 report the bug anyway and send us the entire test case you used.
7600 A patch for the bug.
7602 A patch for the bug does help us if it is a good one. But do not omit
7603 the necessary information, such as the test case, on the assumption that
7604 a patch is all we need. We might see problems with your patch and decide
7605 to fix the problem another way, or we might not understand it at all.
7607 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
7608 construct an example that will make the program follow a certain path through
7609 the code. If you do not send us the example, we will not be able to construct
7610 one, so we will not be able to verify that the bug is fixed.
7612 And if we cannot understand what bug you are trying to fix, or why your
7613 patch should be an improvement, we will not install it. A test case will
7614 help us to understand.
7617 A guess about what the bug is or what it depends on.
7619 Such guesses are usually wrong. Even we cannot guess right about such
7620 things without first using the debugger to find the facts.
7623 @node Acknowledgements
7624 @chapter Acknowledgements
7626 If you have contributed to GAS and your name isn't listed here,
7627 it is not meant as a slight. We just don't know about it. Send mail to the
7628 maintainer, and we'll correct the situation. Currently
7630 the maintainer is Nick Clifton (email address @code{nickc@@redhat.com}).
7632 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
7635 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
7636 information and the 68k series machines, most of the preprocessing pass, and
7637 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
7639 K. Richard Pixley maintained GAS for a while, adding various enhancements and
7640 many bug fixes, including merging support for several processors, breaking GAS
7641 up to handle multiple object file format back ends (including heavy rewrite,
7642 testing, an integration of the coff and b.out back ends), adding configuration
7643 including heavy testing and verification of cross assemblers and file splits
7644 and renaming, converted GAS to strictly ANSI C including full prototypes, added
7645 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
7646 port (including considerable amounts of reverse engineering), a SPARC opcode
7647 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
7648 assertions and made them work, much other reorganization, cleanup, and lint.
7650 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
7651 in format-specific I/O modules.
7653 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
7654 has done much work with it since.
7656 The Intel 80386 machine description was written by Eliot Dresselhaus.
7658 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
7660 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
7661 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
7663 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
7664 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
7665 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
7666 support a.out format.
7668 Support for the Zilog Z8k and Renesas H8/300 processors (tc-z8k,
7669 tc-h8300), and IEEE 695 object file format (obj-ieee), was written by
7670 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
7671 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
7674 John Gilmore built the AMD 29000 support, added @code{.include} support, and
7675 simplified the configuration of which versions accept which directives. He
7676 updated the 68k machine description so that Motorola's opcodes always produced
7677 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
7678 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
7679 cross-compilation support, and one bug in relaxation that took a week and
7680 required the proverbial one-bit fix.
7682 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
7683 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
7684 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
7685 PowerPC assembler, and made a few other minor patches.
7687 Steve Chamberlain made GAS able to generate listings.
7689 Hewlett-Packard contributed support for the HP9000/300.
7691 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
7692 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
7693 formats). This work was supported by both the Center for Software Science at
7694 the University of Utah and Cygnus Support.
7696 Support for ELF format files has been worked on by Mark Eichin of Cygnus
7697 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
7698 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
7699 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
7700 and some initial 64-bit support).
7702 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
7704 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
7705 support for openVMS/Alpha.
7707 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
7710 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
7711 Inc.@: added support for Xtensa processors.
7713 Several engineers at Cygnus Support have also provided many small bug fixes and
7714 configuration enhancements.
7716 Jon Beniston added support for the Lattice Mico32 architecture.
7718 Many others have contributed large or small bugfixes and enhancements. If
7719 you have contributed significant work and are not mentioned on this list, and
7720 want to be, let us know. Some of the history has been lost; we are not
7721 intentionally leaving anyone out.
7723 @node GNU Free Documentation License
7724 @appendix GNU Free Documentation License
7728 @unnumbered AS Index
projects / deliverable / binutils-gdb.git / blob