1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright 1991, 1992, 1993, 1994, 1995, 1996, 1997, 1998, 1999, 2000,
4 @c Free Software Foundation, Inc.
5 @c UPDATE!! On future updates--
6 @c (1) check for new machine-dep cmdline options in
7 @c md_parse_option definitions in config/tc-*.c
8 @c (2) for platform-specific directives, examine md_pseudo_op
10 @c (3) for object-format specific directives, examine obj_pseudo_op
12 @c (4) portable directives in potable[] in read.c
16 @macro gcctabopt{body}
19 @c defaults, config file may override:
22 @include asconfig.texi
27 @c Configure for the generation of man pages
65 @c common OR combinations of conditions
91 @set abnormal-separator
95 @settitle Using @value{AS}
98 @settitle Using @value{AS} (@value{TARGET})
100 @setchapternewpage odd
105 @c WARE! Some of the machine-dependent sections contain tables of machine
106 @c instructions. Except in multi-column format, these tables look silly.
107 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
108 @c the multi-col format is faked within @example sections.
110 @c Again unfortunately, the natural size that fits on a page, for these tables,
111 @c is different depending on whether or not smallbook is turned on.
112 @c This matters, because of order: text flow switches columns at each page
115 @c The format faked in this source works reasonably well for smallbook,
116 @c not well for the default large-page format. This manual expects that if you
117 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
118 @c tables in question. You can turn on one without the other at your
119 @c discretion, of course.
122 @c the insn tables look just as silly in info files regardless of smallbook,
123 @c might as well show 'em anyways.
129 * As: (as). The GNU assembler.
130 * Gas: (as). The GNU assembler.
139 This file documents the GNU Assembler "@value{AS}".
141 @c man begin COPYRIGHT
142 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
144 Permission is granted to copy, distribute and/or modify this document
145 under the terms of the GNU Free Documentation License, Version 1.1
146 or any later version published by the Free Software Foundation;
147 with no Invariant Sections, with no Front-Cover Texts, and with no
148 Back-Cover Texts. A copy of the license is included in the
149 section entitled ``GNU Free Documentation License''.
154 Permission is granted to process this file through Tex and print the
155 results, provided the printed document carries copying permission
156 notice identical to this one except for the removal of this paragraph
157 (this paragraph not being relevant to the printed manual).
163 @title Using @value{AS}
164 @subtitle The @sc{gnu} Assembler
166 @subtitle for the @value{TARGET} family
169 @subtitle Version @value{VERSION}
172 The Free Software Foundation Inc. thanks The Nice Computer
173 Company of Australia for loaning Dean Elsner to write the
174 first (Vax) version of @command{as} for Project @sc{gnu}.
175 The proprietors, management and staff of TNCCA thank FSF for
176 distracting the boss while they got some work
179 @author Dean Elsner, Jay Fenlason & friends
183 \hfill {\it Using {\tt @value{AS}}}\par
184 \hfill Edited by Cygnus Support\par
186 %"boxit" macro for figures:
187 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
188 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
189 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
190 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
191 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
194 @vskip 0pt plus 1filll
195 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
197 Permission is granted to copy, distribute and/or modify this document
198 under the terms of the GNU Free Documentation License, Version 1.1
199 or any later version published by the Free Software Foundation;
200 with no Invariant Sections, with no Front-Cover Texts, and with no
201 Back-Cover Texts. A copy of the license is included in the
202 section entitled ``GNU Free Documentation License''.
208 @top Using @value{AS}
210 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
213 This version of the file describes @command{@value{AS}} configured to generate
214 code for @value{TARGET} architectures.
217 This document is distributed under the terms of the GNU Free
218 Documentation License. A copy of the license is included in the
219 section entitled ``GNU Free Documentation License''.
222 * Overview:: Overview
223 * Invoking:: Command-Line Options
225 * Sections:: Sections and Relocation
227 * Expressions:: Expressions
228 * Pseudo Ops:: Assembler Directives
229 * Machine Dependencies:: Machine Dependent Features
230 * Reporting Bugs:: Reporting Bugs
231 * Acknowledgements:: Who Did What
232 * GNU Free Documentation License:: GNU Free Documentation License
240 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
242 This version of the manual describes @command{@value{AS}} configured to generate
243 code for @value{TARGET} architectures.
247 @cindex invocation summary
248 @cindex option summary
249 @cindex summary of options
250 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
251 @pxref{Invoking,,Command-Line Options}.
253 @c man title AS the portable GNU assembler.
257 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
261 @c We don't use deffn and friends for the following because they seem
262 @c to be limited to one line for the header.
264 @c man begin SYNOPSIS
265 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{-D}] [@b{--defsym} @var{sym}=@var{val}]
266 [@b{-f}] [@b{--gstabs}] [@b{--gdwarf2}] [@b{--help}] [@b{-I} @var{dir}]
267 [@b{-J}] [@b{-K}] [@b{-L}]
268 [@b{--listing-lhs-width}=@var{NUM}] [@b{--listing-lhs-width2}=@var{NUM}]
269 [@b{--listing-rhs-width}=@var{NUM}] [@b{--listing-cont-lines}=@var{NUM}]
270 [@b{--keep-locals}] [@b{-o} @var{objfile}] [@b{-R}] [@b{--statistics}] [@b{-v}]
271 [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}]
272 [@b{-w}] [@b{-x}] [@b{-Z}] [@b{--target-help}] [@var{target-options}]
273 [@b{--}|@var{files} @dots{}]
275 @c Target dependent options are listed below. Keep the list sorted.
276 @c Add an empty line for separation.
278 @c am29k has no machine-dependent assembler options
282 @emph{Target Alpha options:}
284 [@b{-mdebug} | @b{-no-mdebug}]
285 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
286 [@b{-F}] [@b{-32addr}]
290 @emph{Target ARC options:}
296 @emph{Target ARM options:}
297 @c Don't document the deprecated options
298 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
299 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
300 [@b{-mfpu}=@var{floating-point-fromat}]
303 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
304 @b{-mapcs-reentrant}]
305 [@b{-mthumb-interwork}] [@b{-moabi}] [@b{-k}]
309 @emph{Target CRIS options:}
310 [@b{--underscore} | @b{--no-underscore}]
312 [@b{--emulation=criself} | @b{--emulation=crisaout}]
313 @c Deprecated -- deliberately not documented.
318 @emph{Target D10V options:}
323 @emph{Target D30V options:}
324 [@b{-O}|@b{-n}|@b{-N}]
327 @c Renesas family chips have no machine-dependent assembler options
330 @c HPPA has no machine-dependent assembler options (yet).
334 @emph{Target i386 options:}
335 [@b{--32}|@b{--64}] [@b{-n}]
339 @emph{Target i960 options:}
340 @c see md_parse_option in tc-i960.c
341 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
343 [@b{-b}] [@b{-no-relax}]
347 @emph{Target IA-64 options:}
348 [@b{-mconstant-gp}|@b{-mauto-pic}]
349 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
351 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
355 @emph{Target IP2K options:}
356 [@b{-mip2022}|@b{-mip2022ext}]
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}]
373 [@b{-mshort}|@b{-mlong}]
374 [@b{-mshort-double}|@b{-mlong-double}]
375 [@b{--force-long-branchs}] [@b{--short-branchs}]
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 MIPS options:}
388 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-n}] [@b{-O}[@var{optimization level}]]
389 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
390 [@b{-non_shared}] [@b{-xgot}] [@b{--membedded-pic}]
391 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
392 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
393 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips32r2}]
395 [@b{-construct-floats}] [@b{-no-construct-floats}]
396 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
397 [@b{-mfix7000}] [@b{-mno-fix7000}]
398 [@b{-mips16}] [@b{-no-mips16}]
399 [@b{-mips3d}] [@b{-no-mips3d}]
400 [@b{-mdmx}] [@b{-no-mdmx}]
401 [@b{-mdebug}] [@b{-no-mdebug}]
405 @emph{Target MMIX options:}
406 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
407 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
408 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
409 [@b{--linker-allocated-gregs}]
413 @emph{Target PDP11 options:}
414 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
415 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
416 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
420 @emph{Target picoJava options:}
425 @emph{Target PowerPC options:}
426 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
427 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
428 @b{-mbooke32}|@b{-mbooke64}]
429 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
430 [@b{-mregnames}|@b{-mno-regnames}]
431 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
432 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
433 [@b{-msolaris}|@b{-mno-solaris}]
437 @emph{Target SPARC options:}
438 @c The order here is important. See c-sparc.texi.
439 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
440 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
441 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
446 @emph{Target TIC54X options:}
447 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
448 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
451 @c Z8000 has no machine-dependent assembler options
455 @emph{Target Xtensa options:}
456 [@b{--[no-]density}] [@b{--[no-]relax}] [@b{--[no-]generics}]
457 [@b{--[no-]text-section-literals}]
458 [@b{--[no-]target-align}] [@b{--[no-]longcalls}]
467 Turn on listings, in any of a variety of ways:
471 omit false conditionals
474 omit debugging directives
477 include high-level source
483 include macro expansions
486 omit forms processing
492 set the name of the listing file
495 You may combine these options; for example, use @samp{-aln} for assembly
496 listing without forms processing. The @samp{=file} option, if used, must be
497 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
500 Ignored. This option is accepted for script compatibility with calls to
503 @item --defsym @var{sym}=@var{value}
504 Define the symbol @var{sym} to be @var{value} before assembling the input file.
505 @var{value} must be an integer constant. As in C, a leading @samp{0x}
506 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
509 ``fast''---skip whitespace and comment preprocessing (assume source is
513 Generate stabs debugging information for each assembler line. This
514 may help debugging assembler code, if the debugger can handle it.
517 Generate DWARF2 debugging information for each assembler line. This
518 may help debugging assembler code, if the debugger can handle it. Note---this
519 option is only supported by some targets, not all of them.
522 Print a summary of the command line options and exit.
525 Print a summary of all target specific options and exit.
528 Add directory @var{dir} to the search list for @code{.include} directives.
531 Don't warn about signed overflow.
534 @ifclear DIFF-TBL-KLUGE
535 This option is accepted but has no effect on the @value{TARGET} family.
537 @ifset DIFF-TBL-KLUGE
538 Issue warnings when difference tables altered for long displacements.
543 Keep (in the symbol table) local symbols. On traditional a.out systems
544 these start with @samp{L}, but different systems have different local
547 @item --listing-lhs-width=@var{number}
548 Set the maximum width, in words, of the output data column for an assembler
549 listing to @var{number}.
551 @item --listing-lhs-width2=@var{number}
552 Set the maximum width, in words, of the output data column for continuation
553 lines in an assembler listing to @var{number}.
555 @item --listing-rhs-width=@var{number}
556 Set the maximum width of an input source line, as displayed in a listing, to
559 @item --listing-cont-lines=@var{number}
560 Set the maximum number of lines printed in a listing for a single line of input
563 @item -o @var{objfile}
564 Name the object-file output from @command{@value{AS}} @var{objfile}.
567 Fold the data section into the text section.
570 Print the maximum space (in bytes) and total time (in seconds) used by
573 @item --strip-local-absolute
574 Remove local absolute symbols from the outgoing symbol table.
578 Print the @command{as} version.
581 Print the @command{as} version and exit.
585 Suppress warning messages.
587 @item --fatal-warnings
588 Treat warnings as errors.
591 Don't suppress warning messages or treat them as errors.
600 Generate an object file even after errors.
602 @item -- | @var{files} @dots{}
603 Standard input, or source files to assemble.
608 The following options are available when @value{AS} is configured for
613 This option selects the core processor variant.
615 Select either big-endian (-EB) or little-endian (-EL) output.
620 The following options are available when @value{AS} is configured for the ARM
624 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
625 Specify which ARM processor variant is the target.
626 @item -march=@var{architecture}[+@var{extension}@dots{}]
627 Specify which ARM architecture variant is used by the target.
628 @item -mfpu=@var{floating-point-format}
629 Select which Floating Point architecture is the target.
631 Enable Thumb only instruction decoding.
632 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
633 Select which procedure calling convention is in use.
635 Select either big-endian (-EB) or little-endian (-EL) output.
636 @item -mthumb-interwork
637 Specify that the code has been generated with interworking between Thumb and
640 Specify that PIC code has been generated.
645 See the info pages for documentation of the CRIS-specific options.
649 The following options are available when @value{AS} is configured for
652 @cindex D10V optimization
653 @cindex optimization, D10V
655 Optimize output by parallelizing instructions.
660 The following options are available when @value{AS} is configured for a D30V
663 @cindex D30V optimization
664 @cindex optimization, D30V
666 Optimize output by parallelizing instructions.
670 Warn when nops are generated.
672 @cindex D30V nops after 32-bit multiply
674 Warn when a nop after a 32-bit multiply instruction is generated.
679 The following options are available when @value{AS} is configured for the
680 Intel 80960 processor.
683 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
684 Specify which variant of the 960 architecture is the target.
687 Add code to collect statistics about branches taken.
690 Do not alter compare-and-branch instructions for long displacements;
697 The following options are available when @value{AS} is configured for the
703 Specifies that the extended IP2022 instructions are allowed.
706 Restores the default behaviour, which restricts the permitted instructions to
707 just the basic IP2022 ones.
713 The following options are available when @value{AS} is configured for the
714 Renesas M32R (formerly Mitsubishi M32R) series.
719 Specify which processor in the M32R family is the target. The default
720 is normally the M32R, but this option changes it to the M32RX.
722 @item --warn-explicit-parallel-conflicts or --Wp
723 Produce warning messages when questionable parallel constructs are
726 @item --no-warn-explicit-parallel-conflicts or --Wnp
727 Do not produce warning messages when questionable parallel constructs are
734 The following options are available when @value{AS} is configured for the
735 Motorola 68000 series.
740 Shorten references to undefined symbols, to one word instead of two.
742 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
743 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
744 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
745 Specify what processor in the 68000 family is the target. The default
746 is normally the 68020, but this can be changed at configuration time.
748 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
749 The target machine does (or does not) have a floating-point coprocessor.
750 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
751 the basic 68000 is not compatible with the 68881, a combination of the
752 two can be specified, since it's possible to do emulation of the
753 coprocessor instructions with the main processor.
755 @item -m68851 | -mno-68851
756 The target machine does (or does not) have a memory-management
757 unit coprocessor. The default is to assume an MMU for 68020 and up.
764 For details about the PDP-11 machine dependent features options,
765 see @ref{PDP-11-Options}.
768 @item -mpic | -mno-pic
769 Generate position-independent (or position-dependent) code. The
770 default is @option{-mpic}.
773 @itemx -mall-extensions
774 Enable all instruction set extensions. This is the default.
776 @item -mno-extensions
777 Disable all instruction set extensions.
779 @item -m@var{extension} | -mno-@var{extension}
780 Enable (or disable) a particular instruction set extension.
783 Enable the instruction set extensions supported by a particular CPU, and
784 disable all other extensions.
786 @item -m@var{machine}
787 Enable the instruction set extensions supported by a particular machine
788 model, and disable all other extensions.
794 The following options are available when @value{AS} is configured for
795 a picoJava processor.
799 @cindex PJ endianness
800 @cindex endianness, PJ
801 @cindex big endian output, PJ
803 Generate ``big endian'' format output.
805 @cindex little endian output, PJ
807 Generate ``little endian'' format output.
813 The following options are available when @value{AS} is configured for the
814 Motorola 68HC11 or 68HC12 series.
818 @item -m68hc11 | -m68hc12 | -m68hcs12
819 Specify what processor is the target. The default is
820 defined by the configuration option when building the assembler.
823 Specify to use the 16-bit integer ABI.
826 Specify to use the 32-bit integer ABI.
829 Specify to use the 32-bit double ABI.
832 Specify to use the 64-bit double ABI.
834 @item --force-long-branchs
835 Relative branches are turned into absolute ones. This concerns
836 conditional branches, unconditional branches and branches to a
839 @item -S | --short-branchs
840 Do not turn relative branchs into absolute ones
841 when the offset is out of range.
843 @item --strict-direct-mode
844 Do not turn the direct addressing mode into extended addressing mode
845 when the instruction does not support direct addressing mode.
847 @item --print-insn-syntax
848 Print the syntax of instruction in case of error.
850 @item --print-opcodes
851 print the list of instructions with syntax and then exit.
853 @item --generate-example
854 print an example of instruction for each possible instruction and then exit.
855 This option is only useful for testing @command{@value{AS}}.
861 The following options are available when @command{@value{AS}} is configured
862 for the SPARC architecture:
865 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
866 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
867 Explicitly select a variant of the SPARC architecture.
869 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
870 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
872 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
873 UltraSPARC extensions.
875 @item -xarch=v8plus | -xarch=v8plusa
876 For compatibility with the Solaris v9 assembler. These options are
877 equivalent to -Av8plus and -Av8plusa, respectively.
880 Warn when the assembler switches to another architecture.
885 The following options are available when @value{AS} is configured for the 'c54x
890 Enable extended addressing mode. All addresses and relocations will assume
891 extended addressing (usually 23 bits).
892 @item -mcpu=@var{CPU_VERSION}
893 Sets the CPU version being compiled for.
894 @item -merrors-to-file @var{FILENAME}
895 Redirect error output to a file, for broken systems which don't support such
896 behaviour in the shell.
901 The following options are available when @value{AS} is configured for
902 a @sc{mips} processor.
906 This option sets the largest size of an object that can be referenced
907 implicitly with the @code{gp} register. It is only accepted for targets that
908 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
910 @cindex MIPS endianness
911 @cindex endianness, MIPS
912 @cindex big endian output, MIPS
914 Generate ``big endian'' format output.
916 @cindex little endian output, MIPS
918 Generate ``little endian'' format output.
929 Generate code for a particular @sc{mips} Instruction Set Architecture level.
930 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
931 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
932 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
933 @samp{-mips5}, @samp{-mips32}, @samp{-mips32r2}, and @samp{-mips64}
934 correspond to generic
935 @samp{MIPS V}, @samp{MIPS32}, @samp{MIPS32 Release 2}, and
936 @samp{MIPS64} ISA processors,
939 @item -march=@var{CPU}
940 Generate code for a particular @sc{mips} cpu.
942 @item -mtune=@var{cpu}
943 Schedule and tune for a particular @sc{mips} cpu.
947 Cause nops to be inserted if the read of the destination register
948 of an mfhi or mflo instruction occurs in the following two instructions.
952 Cause stabs-style debugging output to go into an ECOFF-style .mdebug
953 section instead of the standard ELF .stabs sections.
957 The register sizes are normally inferred from the ISA and ABI, but these
958 flags force a certain group of registers to be treated as 32 bits wide at
959 all times. @samp{-mgp32} controls the size of general-purpose registers
960 and @samp{-mfp32} controls the size of floating-point registers.
964 Generate code for the MIPS 16 processor. This is equivalent to putting
965 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
966 turns off this option.
970 Generate code for the MIPS-3D Application Specific Extension.
971 This tells the assembler to accept MIPS-3D instructions.
972 @samp{-no-mips3d} turns off this option.
976 Generate code for the MDMX Application Specific Extension.
977 This tells the assembler to accept MDMX instructions.
978 @samp{-no-mdmx} turns off this option.
980 @item --construct-floats
981 @itemx --no-construct-floats
982 The @samp{--no-construct-floats} option disables the construction of
983 double width floating point constants by loading the two halves of the
984 value into the two single width floating point registers that make up
985 the double width register. By default @samp{--construct-floats} is
986 selected, allowing construction of these floating point constants.
989 @item --emulation=@var{name}
990 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
991 for some other target, in all respects, including output format (choosing
992 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
993 debugging information or store symbol table information, and default
994 endianness. The available configuration names are: @samp{mipsecoff},
995 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
996 @samp{mipsbelf}. The first two do not alter the default endianness from that
997 of the primary target for which the assembler was configured; the others change
998 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
999 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
1000 selection in any case.
1002 This option is currently supported only when the primary target
1003 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
1004 Furthermore, the primary target or others specified with
1005 @samp{--enable-targets=@dots{}} at configuration time must include support for
1006 the other format, if both are to be available. For example, the Irix 5
1007 configuration includes support for both.
1009 Eventually, this option will support more configurations, with more
1010 fine-grained control over the assembler's behavior, and will be supported for
1014 @command{@value{AS}} ignores this option. It is accepted for compatibility with
1021 Control how to deal with multiplication overflow and division by zero.
1022 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
1023 (and only work for Instruction Set Architecture level 2 and higher);
1024 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
1028 When this option is used, @command{@value{AS}} will issue a warning every
1029 time it generates a nop instruction from a macro.
1034 The following options are available when @value{AS} is configured for
1040 Enable or disable the JSRI to BSR transformation. By default this is enabled.
1041 The command line option @samp{-nojsri2bsr} can be used to disable it.
1045 Enable or disable the silicon filter behaviour. By default this is disabled.
1046 The default can be overridden by the @samp{-sifilter} command line option.
1049 Alter jump instructions for long displacements.
1051 @item -mcpu=[210|340]
1052 Select the cpu type on the target hardware. This controls which instructions
1056 Assemble for a big endian target.
1059 Assemble for a little endian target.
1065 See the info pages for documentation of the MMIX-specific options.
1069 The following options are available when @value{AS} is configured for
1070 an Xtensa processor.
1073 @item --density | --no-density
1074 Enable or disable use of instructions from the Xtensa code density
1075 option. This is enabled by default when the Xtensa processor supports
1076 the code density option.
1078 @item --relax | --no-relax
1079 Enable or disable instruction relaxation. This is enabled by default.
1080 Note: In the current implementation, these options also control whether
1081 assembler optimizations are performed, making these options equivalent
1082 to @option{--generics} and @option{--no-generics}.
1084 @item --generics | --no-generics
1085 Enable or disable all assembler transformations of Xtensa instructions.
1086 The default is @option{--generics};
1087 @option{--no-generics} should be used only in the rare cases when the
1088 instructions must be exactly as specified in the assembly source.
1090 @item --text-section-literals | --no-text-section-literals
1091 With @option{--text-@-section-@-literals}, literal pools are interspersed
1092 in the text section. The default is
1093 @option{--no-@-text-@-section-@-literals}, which places literals in a
1094 separate section in the output file.
1096 @item --target-align | --no-target-align
1097 Enable or disable automatic alignment to reduce branch penalties at the
1098 expense of some code density. The default is @option{--target-@-align}.
1100 @item --longcalls | --no-longcalls
1101 Enable or disable transformation of call instructions to allow calls
1102 across a greater range of addresses. The default is
1103 @option{--no-@-longcalls}.
1110 * Manual:: Structure of this Manual
1111 * GNU Assembler:: The GNU Assembler
1112 * Object Formats:: Object File Formats
1113 * Command Line:: Command Line
1114 * Input Files:: Input Files
1115 * Object:: Output (Object) File
1116 * Errors:: Error and Warning Messages
1120 @section Structure of this Manual
1122 @cindex manual, structure and purpose
1123 This manual is intended to describe what you need to know to use
1124 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1125 notation for symbols, constants, and expressions; the directives that
1126 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1129 We also cover special features in the @value{TARGET}
1130 configuration of @command{@value{AS}}, including assembler directives.
1133 This manual also describes some of the machine-dependent features of
1134 various flavors of the assembler.
1137 @cindex machine instructions (not covered)
1138 On the other hand, this manual is @emph{not} intended as an introduction
1139 to programming in assembly language---let alone programming in general!
1140 In a similar vein, we make no attempt to introduce the machine
1141 architecture; we do @emph{not} describe the instruction set, standard
1142 mnemonics, registers or addressing modes that are standard to a
1143 particular architecture.
1145 You may want to consult the manufacturer's
1146 machine architecture manual for this information.
1150 For information on the H8/300 machine instruction set, see @cite{H8/300
1151 Series Programming Manual}. For the H8/300H, see @cite{H8/300H Series
1152 Programming Manual} (Renesas).
1155 For information on the H8/500 machine instruction set, see @cite{H8/500
1156 Series Programming Manual} (Renesas M21T001).
1159 For information on the Renesas (formerly Hitachi) / SuperH SH machine instruction set,
1160 see @cite{SH-Microcomputer User's Manual} (Renesas) or
1161 @cite{SH-4 32-bit CPU Core Architecture} (SuperH) and
1162 @cite{SuperH (SH) 64-Bit RISC Series} (SuperH).
1165 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1169 @c I think this is premature---doc@cygnus.com, 17jan1991
1171 Throughout this manual, we assume that you are running @dfn{GNU},
1172 the portable operating system from the @dfn{Free Software
1173 Foundation, Inc.}. This restricts our attention to certain kinds of
1174 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1175 once this assumption is granted examples and definitions need less
1178 @command{@value{AS}} is part of a team of programs that turn a high-level
1179 human-readable series of instructions into a low-level
1180 computer-readable series of instructions. Different versions of
1181 @command{@value{AS}} are used for different kinds of computer.
1184 @c There used to be a section "Terminology" here, which defined
1185 @c "contents", "byte", "word", and "long". Defining "word" to any
1186 @c particular size is confusing when the .word directive may generate 16
1187 @c bits on one machine and 32 bits on another; in general, for the user
1188 @c version of this manual, none of these terms seem essential to define.
1189 @c They were used very little even in the former draft of the manual;
1190 @c this draft makes an effort to avoid them (except in names of
1194 @section The GNU Assembler
1196 @c man begin DESCRIPTION
1198 @sc{gnu} @command{as} is really a family of assemblers.
1200 This manual describes @command{@value{AS}}, a member of that family which is
1201 configured for the @value{TARGET} architectures.
1203 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1204 should find a fairly similar environment when you use it on another
1205 architecture. Each version has much in common with the others,
1206 including object file formats, most assembler directives (often called
1207 @dfn{pseudo-ops}) and assembler syntax.@refill
1209 @cindex purpose of @sc{gnu} assembler
1210 @command{@value{AS}} is primarily intended to assemble the output of the
1211 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1212 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1213 assemble correctly everything that other assemblers for the same
1214 machine would assemble.
1216 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1219 @c This remark should appear in generic version of manual; assumption
1220 @c here is that generic version sets M680x0.
1221 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1222 assembler for the same architecture; for example, we know of several
1223 incompatible versions of 680x0 assembly language syntax.
1228 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1229 program in one pass of the source file. This has a subtle impact on the
1230 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1232 @node Object Formats
1233 @section Object File Formats
1235 @cindex object file format
1236 The @sc{gnu} assembler can be configured to produce several alternative
1237 object file formats. For the most part, this does not affect how you
1238 write assembly language programs; but directives for debugging symbols
1239 are typically different in different file formats. @xref{Symbol
1240 Attributes,,Symbol Attributes}.
1243 For the @value{TARGET} target, @command{@value{AS}} is configured to produce
1244 @value{OBJ-NAME} format object files.
1246 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1248 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1249 @code{a.out} or COFF format object files.
1252 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1253 @code{b.out} or COFF format object files.
1256 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1257 SOM or ELF format object files.
1262 @section Command Line
1264 @cindex command line conventions
1266 After the program name @command{@value{AS}}, the command line may contain
1267 options and file names. Options may appear in any order, and may be
1268 before, after, or between file names. The order of file names is
1271 @cindex standard input, as input file
1273 @file{--} (two hyphens) by itself names the standard input file
1274 explicitly, as one of the files for @command{@value{AS}} to assemble.
1276 @cindex options, command line
1277 Except for @samp{--} any command line argument that begins with a
1278 hyphen (@samp{-}) is an option. Each option changes the behavior of
1279 @command{@value{AS}}. No option changes the way another option works. An
1280 option is a @samp{-} followed by one or more letters; the case of
1281 the letter is important. All options are optional.
1283 Some options expect exactly one file name to follow them. The file
1284 name may either immediately follow the option's letter (compatible
1285 with older assemblers) or it may be the next command argument (@sc{gnu}
1286 standard). These two command lines are equivalent:
1289 @value{AS} -o my-object-file.o mumble.s
1290 @value{AS} -omy-object-file.o mumble.s
1294 @section Input Files
1297 @cindex source program
1298 @cindex files, input
1299 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1300 describe the program input to one run of @command{@value{AS}}. The program may
1301 be in one or more files; how the source is partitioned into files
1302 doesn't change the meaning of the source.
1304 @c I added "con" prefix to "catenation" just to prove I can overcome my
1305 @c APL training... doc@cygnus.com
1306 The source program is a concatenation of the text in all the files, in the
1309 @c man begin DESCRIPTION
1310 Each time you run @command{@value{AS}} it assembles exactly one source
1311 program. The source program is made up of one or more files.
1312 (The standard input is also a file.)
1314 You give @command{@value{AS}} a command line that has zero or more input file
1315 names. The input files are read (from left file name to right). A
1316 command line argument (in any position) that has no special meaning
1317 is taken to be an input file name.
1319 If you give @command{@value{AS}} no file names it attempts to read one input file
1320 from the @command{@value{AS}} standard input, which is normally your terminal. You
1321 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1324 Use @samp{--} if you need to explicitly name the standard input file
1325 in your command line.
1327 If the source is empty, @command{@value{AS}} produces a small, empty object
1332 @subheading Filenames and Line-numbers
1334 @cindex input file linenumbers
1335 @cindex line numbers, in input files
1336 There are two ways of locating a line in the input file (or files) and
1337 either may be used in reporting error messages. One way refers to a line
1338 number in a physical file; the other refers to a line number in a
1339 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1341 @dfn{Physical files} are those files named in the command line given
1342 to @command{@value{AS}}.
1344 @dfn{Logical files} are simply names declared explicitly by assembler
1345 directives; they bear no relation to physical files. Logical file names help
1346 error messages reflect the original source file, when @command{@value{AS}} source
1347 is itself synthesized from other files. @command{@value{AS}} understands the
1348 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1349 @ref{File,,@code{.file}}.
1352 @section Output (Object) File
1358 Every time you run @command{@value{AS}} it produces an output file, which is
1359 your assembly language program translated into numbers. This file
1360 is the object file. Its default name is
1368 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1370 You can give it another name by using the @option{-o} option. Conventionally,
1371 object file names end with @file{.o}. The default name is used for historical
1372 reasons: older assemblers were capable of assembling self-contained programs
1373 directly into a runnable program. (For some formats, this isn't currently
1374 possible, but it can be done for the @code{a.out} format.)
1378 The object file is meant for input to the linker @code{@value{LD}}. It contains
1379 assembled program code, information to help @code{@value{LD}} integrate
1380 the assembled program into a runnable file, and (optionally) symbolic
1381 information for the debugger.
1383 @c link above to some info file(s) like the description of a.out.
1384 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1387 @section Error and Warning Messages
1389 @c man begin DESCRIPTION
1391 @cindex error messages
1392 @cindex warning messages
1393 @cindex messages from assembler
1394 @command{@value{AS}} may write warnings and error messages to the standard error
1395 file (usually your terminal). This should not happen when a compiler
1396 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1397 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1398 grave problem that stops the assembly.
1402 @cindex format of warning messages
1403 Warning messages have the format
1406 file_name:@b{NNN}:Warning Message Text
1410 @cindex line numbers, in warnings/errors
1411 (where @b{NNN} is a line number). If a logical file name has been given
1412 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1413 the current input file is used. If a logical line number was given
1415 (@pxref{Line,,@code{.line}})
1419 (@pxref{Line,,@code{.line}})
1422 (@pxref{Ln,,@code{.ln}})
1425 then it is used to calculate the number printed,
1426 otherwise the actual line in the current source file is printed. The
1427 message text is intended to be self explanatory (in the grand Unix
1430 @cindex format of error messages
1431 Error messages have the format
1433 file_name:@b{NNN}:FATAL:Error Message Text
1435 The file name and line number are derived as for warning
1436 messages. The actual message text may be rather less explanatory
1437 because many of them aren't supposed to happen.
1440 @chapter Command-Line Options
1442 @cindex options, all versions of assembler
1443 This chapter describes command-line options available in @emph{all}
1444 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1446 to the @value{TARGET} target.
1449 to particular machine architectures.
1452 @c man begin DESCRIPTION
1454 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler,
1455 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1456 The assembler arguments must be separated from each other (and the @samp{-Wa})
1457 by commas. For example:
1460 gcc -c -g -O -Wa,-alh,-L file.c
1464 This passes two options to the assembler: @samp{-alh} (emit a listing to
1465 standard output with high-level and assembly source) and @samp{-L} (retain
1466 local symbols in the symbol table).
1468 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1469 command-line options are automatically passed to the assembler by the compiler.
1470 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1471 precisely what options it passes to each compilation pass, including the
1477 * a:: -a[cdhlns] enable listings
1478 * D:: -D for compatibility
1479 * f:: -f to work faster
1480 * I:: -I for .include search path
1481 @ifclear DIFF-TBL-KLUGE
1482 * K:: -K for compatibility
1484 @ifset DIFF-TBL-KLUGE
1485 * K:: -K for difference tables
1488 * L:: -L to retain local labels
1489 * listing:: --listing-XXX to configure listing output
1490 * M:: -M or --mri to assemble in MRI compatibility mode
1491 * MD:: --MD for dependency tracking
1492 * o:: -o to name the object file
1493 * R:: -R to join data and text sections
1494 * statistics:: --statistics to see statistics about assembly
1495 * traditional-format:: --traditional-format for compatible output
1496 * v:: -v to announce version
1497 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1498 * Z:: -Z to make object file even after errors
1502 @section Enable Listings: @option{-a[cdhlns]}
1511 @cindex listings, enabling
1512 @cindex assembly listings, enabling
1514 These options enable listing output from the assembler. By itself,
1515 @samp{-a} requests high-level, assembly, and symbols listing.
1516 You can use other letters to select specific options for the list:
1517 @samp{-ah} requests a high-level language listing,
1518 @samp{-al} requests an output-program assembly listing, and
1519 @samp{-as} requests a symbol table listing.
1520 High-level listings require that a compiler debugging option like
1521 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1524 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1525 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1526 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1527 omitted from the listing.
1529 Use the @samp{-ad} option to omit debugging directives from the
1532 Once you have specified one of these options, you can further control
1533 listing output and its appearance using the directives @code{.list},
1534 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1536 The @samp{-an} option turns off all forms processing.
1537 If you do not request listing output with one of the @samp{-a} options, the
1538 listing-control directives have no effect.
1540 The letters after @samp{-a} may be combined into one option,
1541 @emph{e.g.}, @samp{-aln}.
1543 Note if the assembler source is coming from the standard input (eg because it
1544 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1545 is being used) then the listing will not contain any comments or preprocessor
1546 directives. This is because the listing code buffers input source lines from
1547 stdin only after they have been preprocessed by the assembler. This reduces
1548 memory usage and makes the code more efficient.
1551 @section @option{-D}
1554 This option has no effect whatsoever, but it is accepted to make it more
1555 likely that scripts written for other assemblers also work with
1556 @command{@value{AS}}.
1559 @section Work Faster: @option{-f}
1562 @cindex trusted compiler
1563 @cindex faster processing (@option{-f})
1564 @samp{-f} should only be used when assembling programs written by a
1565 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1566 and comment preprocessing on
1567 the input file(s) before assembling them. @xref{Preprocessing,
1571 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1572 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1577 @section @code{.include} Search Path: @option{-I} @var{path}
1579 @kindex -I @var{path}
1580 @cindex paths for @code{.include}
1581 @cindex search path for @code{.include}
1582 @cindex @code{include} directive search path
1583 Use this option to add a @var{path} to the list of directories
1584 @command{@value{AS}} searches for files specified in @code{.include}
1585 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1586 many times as necessary to include a variety of paths. The current
1587 working directory is always searched first; after that, @command{@value{AS}}
1588 searches any @samp{-I} directories in the same order as they were
1589 specified (left to right) on the command line.
1592 @section Difference Tables: @option{-K}
1595 @ifclear DIFF-TBL-KLUGE
1596 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1597 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1598 where it can be used to warn when the assembler alters the machine code
1599 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1600 family does not have the addressing limitations that sometimes lead to this
1601 alteration on other platforms.
1604 @ifset DIFF-TBL-KLUGE
1605 @cindex difference tables, warning
1606 @cindex warning for altered difference tables
1607 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1608 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1609 You can use the @samp{-K} option if you want a warning issued when this
1614 @section Include Local Labels: @option{-L}
1617 @cindex local labels, retaining in output
1618 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1619 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1620 debugging, because they are intended for the use of programs (like
1621 compilers) that compose assembler programs, not for your notice.
1622 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1623 normally debug with them.
1625 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1626 in the object file. Usually if you do this you also tell the linker
1627 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1629 By default, a local label is any label beginning with @samp{L}, but each
1630 target is allowed to redefine the local label prefix.
1632 On the HPPA local labels begin with @samp{L$}.
1636 @section Configuring listing output: @option{--listing}
1638 The listing feature of the assembler can be enabled via the command line switch
1639 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1640 hex dump of the corresponding locations in the output object file, and displays
1641 them as a listing file. The format of this listing can be controlled by pseudo
1642 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1643 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1646 @item --listing-lhs-width=@samp{number}
1647 @kindex --listing-lhs-width
1648 @cindex Width of first line disassembly output
1649 Sets the maximum width, in words, of the first line of the hex byte dump. This
1650 dump appears on the left hand side of the listing output.
1652 @item --listing-lhs-width2=@samp{number}
1653 @kindex --listing-lhs-width2
1654 @cindex Width of continuation lines of disassembly output
1655 Sets the maximum width, in words, of any further lines of the hex byte dump for
1656 a given input source line. If this value is not specified, it defaults to being
1657 the same as the value specified for @samp{--listing-lhs-width}. If neither
1658 switch is used the default is to one.
1660 @item --listing-rhs-width=@samp{number}
1661 @kindex --listing-rhs-width
1662 @cindex Width of source line output
1663 Sets the maximum width, in characters, of the source line that is displayed
1664 alongside the hex dump. The default value for this parameter is 100. The
1665 source line is displayed on the right hand side of the listing output.
1667 @item --listing-cont-lines=@samp{number}
1668 @kindex --listing-cont-lines
1669 @cindex Maximum number of continuation lines
1670 Sets the maximum number of continuation lines of hex dump that will be
1671 displayed for a given single line of source input. The default value is 4.
1675 @section Assemble in MRI Compatibility Mode: @option{-M}
1678 @cindex MRI compatibility mode
1679 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1680 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1681 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1682 configured target) assembler from Microtec Research. The exact nature of the
1683 MRI syntax will not be documented here; see the MRI manuals for more
1684 information. Note in particular that the handling of macros and macro
1685 arguments is somewhat different. The purpose of this option is to permit
1686 assembling existing MRI assembler code using @command{@value{AS}}.
1688 The MRI compatibility is not complete. Certain operations of the MRI assembler
1689 depend upon its object file format, and can not be supported using other object
1690 file formats. Supporting these would require enhancing each object file format
1691 individually. These are:
1694 @item global symbols in common section
1696 The m68k MRI assembler supports common sections which are merged by the linker.
1697 Other object file formats do not support this. @command{@value{AS}} handles
1698 common sections by treating them as a single common symbol. It permits local
1699 symbols to be defined within a common section, but it can not support global
1700 symbols, since it has no way to describe them.
1702 @item complex relocations
1704 The MRI assemblers support relocations against a negated section address, and
1705 relocations which combine the start addresses of two or more sections. These
1706 are not support by other object file formats.
1708 @item @code{END} pseudo-op specifying start address
1710 The MRI @code{END} pseudo-op permits the specification of a start address.
1711 This is not supported by other object file formats. The start address may
1712 instead be specified using the @option{-e} option to the linker, or in a linker
1715 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1717 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1718 name to the output file. This is not supported by other object file formats.
1720 @item @code{ORG} pseudo-op
1722 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1723 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1724 which changes the location within the current section. Absolute sections are
1725 not supported by other object file formats. The address of a section may be
1726 assigned within a linker script.
1729 There are some other features of the MRI assembler which are not supported by
1730 @command{@value{AS}}, typically either because they are difficult or because they
1731 seem of little consequence. Some of these may be supported in future releases.
1735 @item EBCDIC strings
1737 EBCDIC strings are not supported.
1739 @item packed binary coded decimal
1741 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1742 and @code{DCB.P} pseudo-ops are not supported.
1744 @item @code{FEQU} pseudo-op
1746 The m68k @code{FEQU} pseudo-op is not supported.
1748 @item @code{NOOBJ} pseudo-op
1750 The m68k @code{NOOBJ} pseudo-op is not supported.
1752 @item @code{OPT} branch control options
1754 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1755 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1756 relaxes all branches, whether forward or backward, to an appropriate size, so
1757 these options serve no purpose.
1759 @item @code{OPT} list control options
1761 The following m68k @code{OPT} list control options are ignored: @code{C},
1762 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1763 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1765 @item other @code{OPT} options
1767 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1768 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1770 @item @code{OPT} @code{D} option is default
1772 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1773 @code{OPT NOD} may be used to turn it off.
1775 @item @code{XREF} pseudo-op.
1777 The m68k @code{XREF} pseudo-op is ignored.
1779 @item @code{.debug} pseudo-op
1781 The i960 @code{.debug} pseudo-op is not supported.
1783 @item @code{.extended} pseudo-op
1785 The i960 @code{.extended} pseudo-op is not supported.
1787 @item @code{.list} pseudo-op.
1789 The various options of the i960 @code{.list} pseudo-op are not supported.
1791 @item @code{.optimize} pseudo-op
1793 The i960 @code{.optimize} pseudo-op is not supported.
1795 @item @code{.output} pseudo-op
1797 The i960 @code{.output} pseudo-op is not supported.
1799 @item @code{.setreal} pseudo-op
1801 The i960 @code{.setreal} pseudo-op is not supported.
1806 @section Dependency Tracking: @option{--MD}
1809 @cindex dependency tracking
1812 @command{@value{AS}} can generate a dependency file for the file it creates. This
1813 file consists of a single rule suitable for @code{make} describing the
1814 dependencies of the main source file.
1816 The rule is written to the file named in its argument.
1818 This feature is used in the automatic updating of makefiles.
1821 @section Name the Object File: @option{-o}
1824 @cindex naming object file
1825 @cindex object file name
1826 There is always one object file output when you run @command{@value{AS}}. By
1827 default it has the name
1830 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1844 You use this option (which takes exactly one filename) to give the
1845 object file a different name.
1847 Whatever the object file is called, @command{@value{AS}} overwrites any
1848 existing file of the same name.
1851 @section Join Data and Text Sections: @option{-R}
1854 @cindex data and text sections, joining
1855 @cindex text and data sections, joining
1856 @cindex joining text and data sections
1857 @cindex merging text and data sections
1858 @option{-R} tells @command{@value{AS}} to write the object file as if all
1859 data-section data lives in the text section. This is only done at
1860 the very last moment: your binary data are the same, but data
1861 section parts are relocated differently. The data section part of
1862 your object file is zero bytes long because all its bytes are
1863 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1865 When you specify @option{-R} it would be possible to generate shorter
1866 address displacements (because we do not have to cross between text and
1867 data section). We refrain from doing this simply for compatibility with
1868 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1871 When @command{@value{AS}} is configured for COFF or ELF output,
1872 this option is only useful if you use sections named @samp{.text} and
1877 @option{-R} is not supported for any of the HPPA targets. Using
1878 @option{-R} generates a warning from @command{@value{AS}}.
1882 @section Display Assembly Statistics: @option{--statistics}
1884 @kindex --statistics
1885 @cindex statistics, about assembly
1886 @cindex time, total for assembly
1887 @cindex space used, maximum for assembly
1888 Use @samp{--statistics} to display two statistics about the resources used by
1889 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1890 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1893 @node traditional-format
1894 @section Compatible Output: @option{--traditional-format}
1896 @kindex --traditional-format
1897 For some targets, the output of @command{@value{AS}} is different in some ways
1898 from the output of some existing assembler. This switch requests
1899 @command{@value{AS}} to use the traditional format instead.
1901 For example, it disables the exception frame optimizations which
1902 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1905 @section Announce Version: @option{-v}
1909 @cindex assembler version
1910 @cindex version of assembler
1911 You can find out what version of as is running by including the
1912 option @samp{-v} (which you can also spell as @samp{-version}) on the
1916 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1918 @command{@value{AS}} should never give a warning or error message when
1919 assembling compiler output. But programs written by people often
1920 cause @command{@value{AS}} to give a warning that a particular assumption was
1921 made. All such warnings are directed to the standard error file.
1925 @cindex suppressing warnings
1926 @cindex warnings, suppressing
1927 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1928 This only affects the warning messages: it does not change any particular of
1929 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1932 @kindex --fatal-warnings
1933 @cindex errors, caused by warnings
1934 @cindex warnings, causing error
1935 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1936 files that generate warnings to be in error.
1939 @cindex warnings, switching on
1940 You can switch these options off again by specifying @option{--warn}, which
1941 causes warnings to be output as usual.
1944 @section Generate Object File in Spite of Errors: @option{-Z}
1945 @cindex object file, after errors
1946 @cindex errors, continuing after
1947 After an error message, @command{@value{AS}} normally produces no output. If for
1948 some reason you are interested in object file output even after
1949 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1950 option. If there are any errors, @command{@value{AS}} continues anyways, and
1951 writes an object file after a final warning message of the form @samp{@var{n}
1952 errors, @var{m} warnings, generating bad object file.}
1957 @cindex machine-independent syntax
1958 @cindex syntax, machine-independent
1959 This chapter describes the machine-independent syntax allowed in a
1960 source file. @command{@value{AS}} syntax is similar to what many other
1961 assemblers use; it is inspired by the BSD 4.2
1966 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1970 * Preprocessing:: Preprocessing
1971 * Whitespace:: Whitespace
1972 * Comments:: Comments
1973 * Symbol Intro:: Symbols
1974 * Statements:: Statements
1975 * Constants:: Constants
1979 @section Preprocessing
1981 @cindex preprocessing
1982 The @command{@value{AS}} internal preprocessor:
1984 @cindex whitespace, removed by preprocessor
1986 adjusts and removes extra whitespace. It leaves one space or tab before
1987 the keywords on a line, and turns any other whitespace on the line into
1990 @cindex comments, removed by preprocessor
1992 removes all comments, replacing them with a single space, or an
1993 appropriate number of newlines.
1995 @cindex constants, converted by preprocessor
1997 converts character constants into the appropriate numeric values.
2000 It does not do macro processing, include file handling, or
2001 anything else you may get from your C compiler's preprocessor. You can
2002 do include file processing with the @code{.include} directive
2003 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
2004 to get other ``CPP'' style preprocessing by giving the input file a
2005 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
2006 Output, gcc.info, Using GNU CC}.
2008 Excess whitespace, comments, and character constants
2009 cannot be used in the portions of the input text that are not
2012 @cindex turning preprocessing on and off
2013 @cindex preprocessing, turning on and off
2016 If the first line of an input file is @code{#NO_APP} or if you use the
2017 @samp{-f} option, whitespace and comments are not removed from the input file.
2018 Within an input file, you can ask for whitespace and comment removal in
2019 specific portions of the by putting a line that says @code{#APP} before the
2020 text that may contain whitespace or comments, and putting a line that says
2021 @code{#NO_APP} after this text. This feature is mainly intend to support
2022 @code{asm} statements in compilers whose output is otherwise free of comments
2029 @dfn{Whitespace} is one or more blanks or tabs, in any order.
2030 Whitespace is used to separate symbols, and to make programs neater for
2031 people to read. Unless within character constants
2032 (@pxref{Characters,,Character Constants}), any whitespace means the same
2033 as exactly one space.
2039 There are two ways of rendering comments to @command{@value{AS}}. In both
2040 cases the comment is equivalent to one space.
2042 Anything from @samp{/*} through the next @samp{*/} is a comment.
2043 This means you may not nest these comments.
2047 The only way to include a newline ('\n') in a comment
2048 is to use this sort of comment.
2051 /* This sort of comment does not nest. */
2054 @cindex line comment character
2055 Anything from the @dfn{line comment} character to the next newline
2056 is considered a comment and is ignored. The line comment character is
2058 @samp{;} for the AMD 29K family;
2061 @samp{;} on the ARC;
2064 @samp{@@} on the ARM;
2067 @samp{;} for the H8/300 family;
2070 @samp{!} for the H8/500 family;
2073 @samp{;} for the HPPA;
2076 @samp{#} on the i386 and x86-64;
2079 @samp{#} on the i960;
2082 @samp{;} for the PDP-11;
2085 @samp{;} for picoJava;
2088 @samp{;} for Motorola PowerPC;
2091 @samp{!} for the Renesas / SuperH SH;
2094 @samp{!} on the SPARC;
2097 @samp{#} on the ip2k;
2100 @samp{#} on the m32r;
2103 @samp{|} on the 680x0;
2106 @samp{#} on the 68HC11 and 68HC12;
2109 @samp{;} on the M880x0;
2112 @samp{#} on the Vax;
2115 @samp{!} for the Z8000;
2118 @samp{#} on the V850;
2121 @samp{#} for Xtensa systems;
2123 see @ref{Machine Dependencies}. @refill
2124 @c FIXME What about i860?
2127 On some machines there are two different line comment characters. One
2128 character only begins a comment if it is the first non-whitespace character on
2129 a line, while the other always begins a comment.
2133 The V850 assembler also supports a double dash as starting a comment that
2134 extends to the end of the line.
2140 @cindex lines starting with @code{#}
2141 @cindex logical line numbers
2142 To be compatible with past assemblers, lines that begin with @samp{#} have a
2143 special interpretation. Following the @samp{#} should be an absolute
2144 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2145 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2146 new logical file name. The rest of the line, if any, should be whitespace.
2148 If the first non-whitespace characters on the line are not numeric,
2149 the line is ignored. (Just like a comment.)
2152 # This is an ordinary comment.
2153 # 42-6 "new_file_name" # New logical file name
2154 # This is logical line # 36.
2156 This feature is deprecated, and may disappear from future versions
2157 of @command{@value{AS}}.
2162 @cindex characters used in symbols
2163 @ifclear SPECIAL-SYMS
2164 A @dfn{symbol} is one or more characters chosen from the set of all
2165 letters (both upper and lower case), digits and the three characters
2171 A @dfn{symbol} is one or more characters chosen from the set of all
2172 letters (both upper and lower case), digits and the three characters
2173 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2179 On most machines, you can also use @code{$} in symbol names; exceptions
2180 are noted in @ref{Machine Dependencies}.
2182 No symbol may begin with a digit. Case is significant.
2183 There is no length limit: all characters are significant. Symbols are
2184 delimited by characters not in that set, or by the beginning of a file
2185 (since the source program must end with a newline, the end of a file is
2186 not a possible symbol delimiter). @xref{Symbols}.
2187 @cindex length of symbols
2192 @cindex statements, structure of
2193 @cindex line separator character
2194 @cindex statement separator character
2196 @ifclear abnormal-separator
2197 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2198 semicolon (@samp{;}). The newline or semicolon is considered part of
2199 the preceding statement. Newlines and semicolons within character
2200 constants are an exception: they do not end statements.
2202 @ifset abnormal-separator
2204 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
2205 sign (@samp{@@}). The newline or at sign is considered part of the
2206 preceding statement. Newlines and at signs within character constants
2207 are an exception: they do not end statements.
2210 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2211 point (@samp{!}). The newline or exclamation point is considered part of the
2212 preceding statement. Newlines and exclamation points within character
2213 constants are an exception: they do not end statements.
2216 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2217 H8/300) a dollar sign (@samp{$}); or (for the
2220 (@samp{;}). The newline or separator character is considered part of
2221 the preceding statement. Newlines and separators within character
2222 constants are an exception: they do not end statements.
2227 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2228 separator character. (The line separator is usually @samp{;}, unless
2229 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2230 newline or separator character is considered part of the preceding
2231 statement. Newlines and separators within character constants are an
2232 exception: they do not end statements.
2235 @cindex newline, required at file end
2236 @cindex EOF, newline must precede
2237 It is an error to end any statement with end-of-file: the last
2238 character of any input file should be a newline.@refill
2240 An empty statement is allowed, and may include whitespace. It is ignored.
2242 @cindex instructions and directives
2243 @cindex directives and instructions
2244 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2245 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2247 A statement begins with zero or more labels, optionally followed by a
2248 key symbol which determines what kind of statement it is. The key
2249 symbol determines the syntax of the rest of the statement. If the
2250 symbol begins with a dot @samp{.} then the statement is an assembler
2251 directive: typically valid for any computer. If the symbol begins with
2252 a letter the statement is an assembly language @dfn{instruction}: it
2253 assembles into a machine language instruction.
2255 Different versions of @command{@value{AS}} for different computers
2256 recognize different instructions. In fact, the same symbol may
2257 represent a different instruction in a different computer's assembly
2261 @cindex @code{:} (label)
2262 @cindex label (@code{:})
2263 A label is a symbol immediately followed by a colon (@code{:}).
2264 Whitespace before a label or after a colon is permitted, but you may not
2265 have whitespace between a label's symbol and its colon. @xref{Labels}.
2268 For HPPA targets, labels need not be immediately followed by a colon, but
2269 the definition of a label must begin in column zero. This also implies that
2270 only one label may be defined on each line.
2274 label: .directive followed by something
2275 another_label: # This is an empty statement.
2276 instruction operand_1, operand_2, @dots{}
2283 A constant is a number, written so that its value is known by
2284 inspection, without knowing any context. Like this:
2287 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2288 .ascii "Ring the bell\7" # A string constant.
2289 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2290 .float 0f-314159265358979323846264338327\
2291 95028841971.693993751E-40 # - pi, a flonum.
2296 * Characters:: Character Constants
2297 * Numbers:: Number Constants
2301 @subsection Character Constants
2303 @cindex character constants
2304 @cindex constants, character
2305 There are two kinds of character constants. A @dfn{character} stands
2306 for one character in one byte and its value may be used in
2307 numeric expressions. String constants (properly called string
2308 @emph{literals}) are potentially many bytes and their values may not be
2309 used in arithmetic expressions.
2313 * Chars:: Characters
2317 @subsubsection Strings
2319 @cindex string constants
2320 @cindex constants, string
2321 A @dfn{string} is written between double-quotes. It may contain
2322 double-quotes or null characters. The way to get special characters
2323 into a string is to @dfn{escape} these characters: precede them with
2324 a backslash @samp{\} character. For example @samp{\\} represents
2325 one backslash: the first @code{\} is an escape which tells
2326 @command{@value{AS}} to interpret the second character literally as a backslash
2327 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2328 escape character). The complete list of escapes follows.
2330 @cindex escape codes, character
2331 @cindex character escape codes
2334 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2336 @cindex @code{\b} (backspace character)
2337 @cindex backspace (@code{\b})
2339 Mnemonic for backspace; for ASCII this is octal code 010.
2342 @c Mnemonic for EOText; for ASCII this is octal code 004.
2344 @cindex @code{\f} (formfeed character)
2345 @cindex formfeed (@code{\f})
2347 Mnemonic for FormFeed; for ASCII this is octal code 014.
2349 @cindex @code{\n} (newline character)
2350 @cindex newline (@code{\n})
2352 Mnemonic for newline; for ASCII this is octal code 012.
2355 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2357 @cindex @code{\r} (carriage return character)
2358 @cindex carriage return (@code{\r})
2360 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2363 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2364 @c other assemblers.
2366 @cindex @code{\t} (tab)
2367 @cindex tab (@code{\t})
2369 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2372 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2373 @c @item \x @var{digit} @var{digit} @var{digit}
2374 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2376 @cindex @code{\@var{ddd}} (octal character code)
2377 @cindex octal character code (@code{\@var{ddd}})
2378 @item \ @var{digit} @var{digit} @var{digit}
2379 An octal character code. The numeric code is 3 octal digits.
2380 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2381 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2383 @cindex @code{\@var{xd...}} (hex character code)
2384 @cindex hex character code (@code{\@var{xd...}})
2385 @item \@code{x} @var{hex-digits...}
2386 A hex character code. All trailing hex digits are combined. Either upper or
2387 lower case @code{x} works.
2389 @cindex @code{\\} (@samp{\} character)
2390 @cindex backslash (@code{\\})
2392 Represents one @samp{\} character.
2395 @c Represents one @samp{'} (accent acute) character.
2396 @c This is needed in single character literals
2397 @c (@xref{Characters,,Character Constants}.) to represent
2400 @cindex @code{\"} (doublequote character)
2401 @cindex doublequote (@code{\"})
2403 Represents one @samp{"} character. Needed in strings to represent
2404 this character, because an unescaped @samp{"} would end the string.
2406 @item \ @var{anything-else}
2407 Any other character when escaped by @kbd{\} gives a warning, but
2408 assembles as if the @samp{\} was not present. The idea is that if
2409 you used an escape sequence you clearly didn't want the literal
2410 interpretation of the following character. However @command{@value{AS}} has no
2411 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2412 code and warns you of the fact.
2415 Which characters are escapable, and what those escapes represent,
2416 varies widely among assemblers. The current set is what we think
2417 the BSD 4.2 assembler recognizes, and is a subset of what most C
2418 compilers recognize. If you are in doubt, do not use an escape
2422 @subsubsection Characters
2424 @cindex single character constant
2425 @cindex character, single
2426 @cindex constant, single character
2427 A single character may be written as a single quote immediately
2428 followed by that character. The same escapes apply to characters as
2429 to strings. So if you want to write the character backslash, you
2430 must write @kbd{'\\} where the first @code{\} escapes the second
2431 @code{\}. As you can see, the quote is an acute accent, not a
2432 grave accent. A newline
2434 @ifclear abnormal-separator
2435 (or semicolon @samp{;})
2437 @ifset abnormal-separator
2439 (or at sign @samp{@@})
2442 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2443 Renesas SH or H8/500)
2447 immediately following an acute accent is taken as a literal character
2448 and does not count as the end of a statement. The value of a character
2449 constant in a numeric expression is the machine's byte-wide code for
2450 that character. @command{@value{AS}} assumes your character code is ASCII:
2451 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2454 @subsection Number Constants
2456 @cindex constants, number
2457 @cindex number constants
2458 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2459 are stored in the target machine. @emph{Integers} are numbers that
2460 would fit into an @code{int} in the C language. @emph{Bignums} are
2461 integers, but they are stored in more than 32 bits. @emph{Flonums}
2462 are floating point numbers, described below.
2465 * Integers:: Integers
2470 * Bit Fields:: Bit Fields
2476 @subsubsection Integers
2478 @cindex constants, integer
2480 @cindex binary integers
2481 @cindex integers, binary
2482 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2483 the binary digits @samp{01}.
2485 @cindex octal integers
2486 @cindex integers, octal
2487 An octal integer is @samp{0} followed by zero or more of the octal
2488 digits (@samp{01234567}).
2490 @cindex decimal integers
2491 @cindex integers, decimal
2492 A decimal integer starts with a non-zero digit followed by zero or
2493 more digits (@samp{0123456789}).
2495 @cindex hexadecimal integers
2496 @cindex integers, hexadecimal
2497 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2498 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2500 Integers have the usual values. To denote a negative integer, use
2501 the prefix operator @samp{-} discussed under expressions
2502 (@pxref{Prefix Ops,,Prefix Operators}).
2505 @subsubsection Bignums
2508 @cindex constants, bignum
2509 A @dfn{bignum} has the same syntax and semantics as an integer
2510 except that the number (or its negative) takes more than 32 bits to
2511 represent in binary. The distinction is made because in some places
2512 integers are permitted while bignums are not.
2515 @subsubsection Flonums
2517 @cindex floating point numbers
2518 @cindex constants, floating point
2520 @cindex precision, floating point
2521 A @dfn{flonum} represents a floating point number. The translation is
2522 indirect: a decimal floating point number from the text is converted by
2523 @command{@value{AS}} to a generic binary floating point number of more than
2524 sufficient precision. This generic floating point number is converted
2525 to a particular computer's floating point format (or formats) by a
2526 portion of @command{@value{AS}} specialized to that computer.
2528 A flonum is written by writing (in order)
2533 (@samp{0} is optional on the HPPA.)
2537 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2539 @kbd{e} is recommended. Case is not important.
2541 @c FIXME: verify if flonum syntax really this vague for most cases
2542 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2543 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2546 On the H8/300, H8/500,
2547 Renesas / SuperH SH,
2548 and AMD 29K architectures, the letter must be
2549 one of the letters @samp{DFPRSX} (in upper or lower case).
2551 On the ARC, the letter must be one of the letters @samp{DFRS}
2552 (in upper or lower case).
2554 On the Intel 960 architecture, the letter must be
2555 one of the letters @samp{DFT} (in upper or lower case).
2557 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2561 One of the letters @samp{DFPRSX} (in upper or lower case).
2564 One of the letters @samp{DFRS} (in upper or lower case).
2567 One of the letters @samp{DFPRSX} (in upper or lower case).
2570 The letter @samp{E} (upper case only).
2573 One of the letters @samp{DFT} (in upper or lower case).
2578 An optional sign: either @samp{+} or @samp{-}.
2581 An optional @dfn{integer part}: zero or more decimal digits.
2584 An optional @dfn{fractional part}: @samp{.} followed by zero
2585 or more decimal digits.
2588 An optional exponent, consisting of:
2592 An @samp{E} or @samp{e}.
2593 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2594 @c principle this can perfectly well be different on different targets.
2596 Optional sign: either @samp{+} or @samp{-}.
2598 One or more decimal digits.
2603 At least one of the integer part or the fractional part must be
2604 present. The floating point number has the usual base-10 value.
2606 @command{@value{AS}} does all processing using integers. Flonums are computed
2607 independently of any floating point hardware in the computer running
2608 @command{@value{AS}}.
2612 @c Bit fields are written as a general facility but are also controlled
2613 @c by a conditional-compilation flag---which is as of now (21mar91)
2614 @c turned on only by the i960 config of GAS.
2616 @subsubsection Bit Fields
2619 @cindex constants, bit field
2620 You can also define numeric constants as @dfn{bit fields}.
2621 specify two numbers separated by a colon---
2623 @var{mask}:@var{value}
2626 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2629 The resulting number is then packed
2631 @c this conditional paren in case bit fields turned on elsewhere than 960
2632 (in host-dependent byte order)
2634 into a field whose width depends on which assembler directive has the
2635 bit-field as its argument. Overflow (a result from the bitwise and
2636 requiring more binary digits to represent) is not an error; instead,
2637 more constants are generated, of the specified width, beginning with the
2638 least significant digits.@refill
2640 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2641 @code{.short}, and @code{.word} accept bit-field arguments.
2646 @chapter Sections and Relocation
2651 * Secs Background:: Background
2652 * Ld Sections:: Linker Sections
2653 * As Sections:: Assembler Internal Sections
2654 * Sub-Sections:: Sub-Sections
2658 @node Secs Background
2661 Roughly, a section is a range of addresses, with no gaps; all data
2662 ``in'' those addresses is treated the same for some particular purpose.
2663 For example there may be a ``read only'' section.
2665 @cindex linker, and assembler
2666 @cindex assembler, and linker
2667 The linker @code{@value{LD}} reads many object files (partial programs) and
2668 combines their contents to form a runnable program. When @command{@value{AS}}
2669 emits an object file, the partial program is assumed to start at address 0.
2670 @code{@value{LD}} assigns the final addresses for the partial program, so that
2671 different partial programs do not overlap. This is actually an
2672 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2675 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2676 addresses. These blocks slide to their run-time addresses as rigid
2677 units; their length does not change and neither does the order of bytes
2678 within them. Such a rigid unit is called a @emph{section}. Assigning
2679 run-time addresses to sections is called @dfn{relocation}. It includes
2680 the task of adjusting mentions of object-file addresses so they refer to
2681 the proper run-time addresses.
2683 For the H8/300 and H8/500,
2684 and for the Renesas / SuperH SH,
2685 @command{@value{AS}} pads sections if needed to
2686 ensure they end on a word (sixteen bit) boundary.
2689 @cindex standard assembler sections
2690 An object file written by @command{@value{AS}} has at least three sections, any
2691 of which may be empty. These are named @dfn{text}, @dfn{data} and
2696 When it generates COFF or ELF output,
2698 @command{@value{AS}} can also generate whatever other named sections you specify
2699 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2700 If you do not use any directives that place output in the @samp{.text}
2701 or @samp{.data} sections, these sections still exist, but are empty.
2706 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2708 @command{@value{AS}} can also generate whatever other named sections you
2709 specify using the @samp{.space} and @samp{.subspace} directives. See
2710 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2711 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2712 assembler directives.
2715 Additionally, @command{@value{AS}} uses different names for the standard
2716 text, data, and bss sections when generating SOM output. Program text
2717 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2718 BSS into @samp{$BSS$}.
2722 Within the object file, the text section starts at address @code{0}, the
2723 data section follows, and the bss section follows the data section.
2726 When generating either SOM or ELF output files on the HPPA, the text
2727 section starts at address @code{0}, the data section at address
2728 @code{0x4000000}, and the bss section follows the data section.
2731 To let @code{@value{LD}} know which data changes when the sections are
2732 relocated, and how to change that data, @command{@value{AS}} also writes to the
2733 object file details of the relocation needed. To perform relocation
2734 @code{@value{LD}} must know, each time an address in the object
2738 Where in the object file is the beginning of this reference to
2741 How long (in bytes) is this reference?
2743 Which section does the address refer to? What is the numeric value of
2745 (@var{address}) @minus{} (@var{start-address of section})?
2748 Is the reference to an address ``Program-Counter relative''?
2751 @cindex addresses, format of
2752 @cindex section-relative addressing
2753 In fact, every address @command{@value{AS}} ever uses is expressed as
2755 (@var{section}) + (@var{offset into section})
2758 Further, most expressions @command{@value{AS}} computes have this section-relative
2761 (For some object formats, such as SOM for the HPPA, some expressions are
2762 symbol-relative instead.)
2765 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2766 @var{N} into section @var{secname}.''
2768 Apart from text, data and bss sections you need to know about the
2769 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2770 addresses in the absolute section remain unchanged. For example, address
2771 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2772 @code{@value{LD}}. Although the linker never arranges two partial programs'
2773 data sections with overlapping addresses after linking, @emph{by definition}
2774 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2775 part of a program is always the same address when the program is running as
2776 address @code{@{absolute@ 239@}} in any other part of the program.
2778 The idea of sections is extended to the @dfn{undefined} section. Any
2779 address whose section is unknown at assembly time is by definition
2780 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2781 Since numbers are always defined, the only way to generate an undefined
2782 address is to mention an undefined symbol. A reference to a named
2783 common block would be such a symbol: its value is unknown at assembly
2784 time so it has section @emph{undefined}.
2786 By analogy the word @emph{section} is used to describe groups of sections in
2787 the linked program. @code{@value{LD}} puts all partial programs' text
2788 sections in contiguous addresses in the linked program. It is
2789 customary to refer to the @emph{text section} of a program, meaning all
2790 the addresses of all partial programs' text sections. Likewise for
2791 data and bss sections.
2793 Some sections are manipulated by @code{@value{LD}}; others are invented for
2794 use of @command{@value{AS}} and have no meaning except during assembly.
2797 @section Linker Sections
2798 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2803 @cindex named sections
2804 @cindex sections, named
2805 @item named sections
2808 @cindex text section
2809 @cindex data section
2813 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2814 separate but equal sections. Anything you can say of one section is
2817 When the program is running, however, it is
2818 customary for the text section to be unalterable. The
2819 text section is often shared among processes: it contains
2820 instructions, constants and the like. The data section of a running
2821 program is usually alterable: for example, C variables would be stored
2822 in the data section.
2827 This section contains zeroed bytes when your program begins running. It
2828 is used to hold uninitialized variables or common storage. The length of
2829 each partial program's bss section is important, but because it starts
2830 out containing zeroed bytes there is no need to store explicit zero
2831 bytes in the object file. The bss section was invented to eliminate
2832 those explicit zeros from object files.
2834 @cindex absolute section
2835 @item absolute section
2836 Address 0 of this section is always ``relocated'' to runtime address 0.
2837 This is useful if you want to refer to an address that @code{@value{LD}} must
2838 not change when relocating. In this sense we speak of absolute
2839 addresses being ``unrelocatable'': they do not change during relocation.
2841 @cindex undefined section
2842 @item undefined section
2843 This ``section'' is a catch-all for address references to objects not in
2844 the preceding sections.
2845 @c FIXME: ref to some other doc on obj-file formats could go here.
2848 @cindex relocation example
2849 An idealized example of three relocatable sections follows.
2851 The example uses the traditional section names @samp{.text} and @samp{.data}.
2853 Memory addresses are on the horizontal axis.
2857 @c END TEXI2ROFF-KILL
2860 partial program # 1: |ttttt|dddd|00|
2867 partial program # 2: |TTT|DDD|000|
2870 +--+---+-----+--+----+---+-----+~~
2871 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2872 +--+---+-----+--+----+---+-----+~~
2874 addresses: 0 @dots{}
2881 \line{\it Partial program \#1: \hfil}
2882 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2883 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2885 \line{\it Partial program \#2: \hfil}
2886 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2887 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2889 \line{\it linked program: \hfil}
2890 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2891 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2892 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2893 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2895 \line{\it addresses: \hfil}
2899 @c END TEXI2ROFF-KILL
2902 @section Assembler Internal Sections
2904 @cindex internal assembler sections
2905 @cindex sections in messages, internal
2906 These sections are meant only for the internal use of @command{@value{AS}}. They
2907 have no meaning at run-time. You do not really need to know about these
2908 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2909 warning messages, so it might be helpful to have an idea of their
2910 meanings to @command{@value{AS}}. These sections are used to permit the
2911 value of every expression in your assembly language program to be a
2912 section-relative address.
2915 @cindex assembler internal logic error
2916 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2917 An internal assembler logic error has been found. This means there is a
2918 bug in the assembler.
2920 @cindex expr (internal section)
2922 The assembler stores complex expression internally as combinations of
2923 symbols. When it needs to represent an expression as a symbol, it puts
2924 it in the expr section.
2926 @c FIXME item transfer[t] vector preload
2927 @c FIXME item transfer[t] vector postload
2928 @c FIXME item register
2932 @section Sub-Sections
2934 @cindex numbered subsections
2935 @cindex grouping data
2941 fall into two sections: text and data.
2943 You may have separate groups of
2945 data in named sections
2949 data in named sections
2955 that you want to end up near to each other in the object file, even though they
2956 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2957 use @dfn{subsections} for this purpose. Within each section, there can be
2958 numbered subsections with values from 0 to 8192. Objects assembled into the
2959 same subsection go into the object file together with other objects in the same
2960 subsection. For example, a compiler might want to store constants in the text
2961 section, but might not want to have them interspersed with the program being
2962 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2963 section of code being output, and a @samp{.text 1} before each group of
2964 constants being output.
2966 Subsections are optional. If you do not use subsections, everything
2967 goes in subsection number zero.
2970 Each subsection is zero-padded up to a multiple of four bytes.
2971 (Subsections may be padded a different amount on different flavors
2972 of @command{@value{AS}}.)
2976 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2977 boundary (two bytes).
2978 The same is true on the Renesas SH.
2981 @c FIXME section padding (alignment)?
2982 @c Rich Pixley says padding here depends on target obj code format; that
2983 @c doesn't seem particularly useful to say without further elaboration,
2984 @c so for now I say nothing about it. If this is a generic BFD issue,
2985 @c these paragraphs might need to vanish from this manual, and be
2986 @c discussed in BFD chapter of binutils (or some such).
2989 On the AMD 29K family, no particular padding is added to section or
2990 subsection sizes; @value{AS} forces no alignment on this platform.
2994 Subsections appear in your object file in numeric order, lowest numbered
2995 to highest. (All this to be compatible with other people's assemblers.)
2996 The object file contains no representation of subsections; @code{@value{LD}} and
2997 other programs that manipulate object files see no trace of them.
2998 They just see all your text subsections as a text section, and all your
2999 data subsections as a data section.
3001 To specify which subsection you want subsequent statements assembled
3002 into, use a numeric argument to specify it, in a @samp{.text
3003 @var{expression}} or a @samp{.data @var{expression}} statement.
3006 When generating COFF or ELF output, you
3011 can also use an extra subsection
3012 argument with arbitrary named sections: @samp{.section @var{name},
3015 @var{Expression} should be an absolute expression.
3016 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
3017 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
3018 begins in @code{text 0}. For instance:
3020 .text 0 # The default subsection is text 0 anyway.
3021 .ascii "This lives in the first text subsection. *"
3023 .ascii "But this lives in the second text subsection."
3025 .ascii "This lives in the data section,"
3026 .ascii "in the first data subsection."
3028 .ascii "This lives in the first text section,"
3029 .ascii "immediately following the asterisk (*)."
3032 Each section has a @dfn{location counter} incremented by one for every byte
3033 assembled into that section. Because subsections are merely a convenience
3034 restricted to @command{@value{AS}} there is no concept of a subsection location
3035 counter. There is no way to directly manipulate a location counter---but the
3036 @code{.align} directive changes it, and any label definition captures its
3037 current value. The location counter of the section where statements are being
3038 assembled is said to be the @dfn{active} location counter.
3041 @section bss Section
3044 @cindex common variable storage
3045 The bss section is used for local common variable storage.
3046 You may allocate address space in the bss section, but you may
3047 not dictate data to load into it before your program executes. When
3048 your program starts running, all the contents of the bss
3049 section are zeroed bytes.
3051 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
3052 @ref{Lcomm,,@code{.lcomm}}.
3054 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
3055 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
3058 When assembling for a target which supports multiple sections, such as ELF or
3059 COFF, you may switch into the @code{.bss} section and define symbols as usual;
3060 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
3061 section. Typically the section will only contain symbol definitions and
3062 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
3069 Symbols are a central concept: the programmer uses symbols to name
3070 things, the linker uses symbols to link, and the debugger uses symbols
3074 @cindex debuggers, and symbol order
3075 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
3076 the same order they were declared. This may break some debuggers.
3081 * Setting Symbols:: Giving Symbols Other Values
3082 * Symbol Names:: Symbol Names
3083 * Dot:: The Special Dot Symbol
3084 * Symbol Attributes:: Symbol Attributes
3091 A @dfn{label} is written as a symbol immediately followed by a colon
3092 @samp{:}. The symbol then represents the current value of the
3093 active location counter, and is, for example, a suitable instruction
3094 operand. You are warned if you use the same symbol to represent two
3095 different locations: the first definition overrides any other
3099 On the HPPA, the usual form for a label need not be immediately followed by a
3100 colon, but instead must start in column zero. Only one label may be defined on
3101 a single line. To work around this, the HPPA version of @command{@value{AS}} also
3102 provides a special directive @code{.label} for defining labels more flexibly.
3105 @node Setting Symbols
3106 @section Giving Symbols Other Values
3108 @cindex assigning values to symbols
3109 @cindex symbol values, assigning
3110 A symbol can be given an arbitrary value by writing a symbol, followed
3111 by an equals sign @samp{=}, followed by an expression
3112 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3113 directive. @xref{Set,,@code{.set}}.
3116 @section Symbol Names
3118 @cindex symbol names
3119 @cindex names, symbol
3120 @ifclear SPECIAL-SYMS
3121 Symbol names begin with a letter or with one of @samp{._}. On most
3122 machines, you can also use @code{$} in symbol names; exceptions are
3123 noted in @ref{Machine Dependencies}. That character may be followed by any
3124 string of digits, letters, dollar signs (unless otherwise noted in
3125 @ref{Machine Dependencies}), and underscores.
3128 For the AMD 29K family, @samp{?} is also allowed in the
3129 body of a symbol name, though not at its beginning.
3134 Symbol names begin with a letter or with one of @samp{._}. On the
3135 Renesas SH or the H8/500, you can also use @code{$} in symbol names. That
3136 character may be followed by any string of digits, letters, dollar signs (save
3137 on the H8/300), and underscores.
3141 Case of letters is significant: @code{foo} is a different symbol name
3144 Each symbol has exactly one name. Each name in an assembly language program
3145 refers to exactly one symbol. You may use that symbol name any number of times
3148 @subheading Local Symbol Names
3150 @cindex local symbol names
3151 @cindex symbol names, local
3152 @cindex temporary symbol names
3153 @cindex symbol names, temporary
3154 Local symbols help compilers and programmers use names temporarily.
3155 They create symbols which are guaranteed to be unique over the entire scope of
3156 the input source code and which can be referred to by a simple notation.
3157 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3158 represents any positive integer). To refer to the most recent previous
3159 definition of that symbol write @samp{@b{N}b}, using the same number as when
3160 you defined the label. To refer to the next definition of a local label, write
3161 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3164 There is no restriction on how you can use these labels, and you can reuse them
3165 too. So that it is possible to repeatedly define the same local label (using
3166 the same number @samp{@b{N}}), although you can only refer to the most recently
3167 defined local label of that number (for a backwards reference) or the next
3168 definition of a specific local label for a forward reference. It is also worth
3169 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3170 implemented in a slightly more efficient manner than the others.
3181 Which is the equivalent of:
3184 label_1: branch label_3
3185 label_2: branch label_1
3186 label_3: branch label_4
3187 label_4: branch label_3
3190 Local symbol names are only a notational device. They are immediately
3191 transformed into more conventional symbol names before the assembler uses them.
3192 The symbol names stored in the symbol table, appearing in error messages and
3193 optionally emitted to the object file. The names are constructed using these
3198 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3199 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3200 used for symbols you are never intended to see. If you use the
3201 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3202 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3203 you may use them in debugging.
3206 This is the number that was used in the local label definition. So if the
3207 label is written @samp{55:} then the number is @samp{55}.
3210 This unusual character is included so you do not accidentally invent a symbol
3211 of the same name. The character has ASCII value of @samp{\002} (control-B).
3213 @item @emph{ordinal number}
3214 This is a serial number to keep the labels distinct. The first definition of
3215 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3216 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3217 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3220 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3221 @code{3:} is named @code{L3@kbd{C-B}44}.
3223 @subheading Dollar Local Labels
3224 @cindex dollar local symbols
3226 @code{@value{AS}} also supports an even more local form of local labels called
3227 dollar labels. These labels go out of scope (ie they become undefined) as soon
3228 as a non-local label is defined. Thus they remain valid for only a small
3229 region of the input source code. Normal local labels, by contrast, remain in
3230 scope for the entire file, or until they are redefined by another occurrence of
3231 the same local label.
3233 Dollar labels are defined in exactly the same way as ordinary local labels,
3234 except that instead of being terminated by a colon, they are terminated by a
3235 dollar sign. eg @samp{@b{55$}}.
3237 They can also be distinguished from ordinary local labels by their transformed
3238 name which uses ASCII character @samp{\001} (control-A) as the magic character
3239 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3240 is named @samp{L6@kbd{C-A}5}.
3243 @section The Special Dot Symbol
3245 @cindex dot (symbol)
3246 @cindex @code{.} (symbol)
3247 @cindex current address
3248 @cindex location counter
3249 The special symbol @samp{.} refers to the current address that
3250 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3251 .long .} defines @code{melvin} to contain its own address.
3252 Assigning a value to @code{.} is treated the same as a @code{.org}
3253 directive. Thus, the expression @samp{.=.+4} is the same as saying
3254 @ifclear no-space-dir
3263 @node Symbol Attributes
3264 @section Symbol Attributes
3266 @cindex symbol attributes
3267 @cindex attributes, symbol
3268 Every symbol has, as well as its name, the attributes ``Value'' and
3269 ``Type''. Depending on output format, symbols can also have auxiliary
3272 The detailed definitions are in @file{a.out.h}.
3275 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3276 all these attributes, and probably won't warn you. This makes the
3277 symbol an externally defined symbol, which is generally what you
3281 * Symbol Value:: Value
3282 * Symbol Type:: Type
3285 * a.out Symbols:: Symbol Attributes: @code{a.out}
3289 * a.out Symbols:: Symbol Attributes: @code{a.out}
3292 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3297 * COFF Symbols:: Symbol Attributes for COFF
3300 * SOM Symbols:: Symbol Attributes for SOM
3307 @cindex value of a symbol
3308 @cindex symbol value
3309 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3310 location in the text, data, bss or absolute sections the value is the
3311 number of addresses from the start of that section to the label.
3312 Naturally for text, data and bss sections the value of a symbol changes
3313 as @code{@value{LD}} changes section base addresses during linking. Absolute
3314 symbols' values do not change during linking: that is why they are
3317 The value of an undefined symbol is treated in a special way. If it is
3318 0 then the symbol is not defined in this assembler source file, and
3319 @code{@value{LD}} tries to determine its value from other files linked into the
3320 same program. You make this kind of symbol simply by mentioning a symbol
3321 name without defining it. A non-zero value represents a @code{.comm}
3322 common declaration. The value is how much common storage to reserve, in
3323 bytes (addresses). The symbol refers to the first address of the
3329 @cindex type of a symbol
3331 The type attribute of a symbol contains relocation (section)
3332 information, any flag settings indicating that a symbol is external, and
3333 (optionally), other information for linkers and debuggers. The exact
3334 format depends on the object-code output format in use.
3339 @c The following avoids a "widow" subsection title. @group would be
3340 @c better if it were available outside examples.
3343 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3345 @cindex @code{b.out} symbol attributes
3346 @cindex symbol attributes, @code{b.out}
3347 These symbol attributes appear only when @command{@value{AS}} is configured for
3348 one of the Berkeley-descended object output formats---@code{a.out} or
3354 @subsection Symbol Attributes: @code{a.out}
3356 @cindex @code{a.out} symbol attributes
3357 @cindex symbol attributes, @code{a.out}
3363 @subsection Symbol Attributes: @code{a.out}
3365 @cindex @code{a.out} symbol attributes
3366 @cindex symbol attributes, @code{a.out}
3370 * Symbol Desc:: Descriptor
3371 * Symbol Other:: Other
3375 @subsubsection Descriptor
3377 @cindex descriptor, of @code{a.out} symbol
3378 This is an arbitrary 16-bit value. You may establish a symbol's
3379 descriptor value by using a @code{.desc} statement
3380 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3381 @command{@value{AS}}.
3384 @subsubsection Other
3386 @cindex other attribute, of @code{a.out} symbol
3387 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3392 @subsection Symbol Attributes for COFF
3394 @cindex COFF symbol attributes
3395 @cindex symbol attributes, COFF
3397 The COFF format supports a multitude of auxiliary symbol attributes;
3398 like the primary symbol attributes, they are set between @code{.def} and
3399 @code{.endef} directives.
3401 @subsubsection Primary Attributes
3403 @cindex primary attributes, COFF symbols
3404 The symbol name is set with @code{.def}; the value and type,
3405 respectively, with @code{.val} and @code{.type}.
3407 @subsubsection Auxiliary Attributes
3409 @cindex auxiliary attributes, COFF symbols
3410 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3411 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3412 information for COFF.
3417 @subsection Symbol Attributes for SOM
3419 @cindex SOM symbol attributes
3420 @cindex symbol attributes, SOM
3422 The SOM format for the HPPA supports a multitude of symbol attributes set with
3423 the @code{.EXPORT} and @code{.IMPORT} directives.
3425 The attributes are described in @cite{HP9000 Series 800 Assembly
3426 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3427 @code{EXPORT} assembler directive documentation.
3431 @chapter Expressions
3435 @cindex numeric values
3436 An @dfn{expression} specifies an address or numeric value.
3437 Whitespace may precede and/or follow an expression.
3439 The result of an expression must be an absolute number, or else an offset into
3440 a particular section. If an expression is not absolute, and there is not
3441 enough information when @command{@value{AS}} sees the expression to know its
3442 section, a second pass over the source program might be necessary to interpret
3443 the expression---but the second pass is currently not implemented.
3444 @command{@value{AS}} aborts with an error message in this situation.
3447 * Empty Exprs:: Empty Expressions
3448 * Integer Exprs:: Integer Expressions
3452 @section Empty Expressions
3454 @cindex empty expressions
3455 @cindex expressions, empty
3456 An empty expression has no value: it is just whitespace or null.
3457 Wherever an absolute expression is required, you may omit the
3458 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3459 is compatible with other assemblers.
3462 @section Integer Expressions
3464 @cindex integer expressions
3465 @cindex expressions, integer
3466 An @dfn{integer expression} is one or more @emph{arguments} delimited
3467 by @emph{operators}.
3470 * Arguments:: Arguments
3471 * Operators:: Operators
3472 * Prefix Ops:: Prefix Operators
3473 * Infix Ops:: Infix Operators
3477 @subsection Arguments
3479 @cindex expression arguments
3480 @cindex arguments in expressions
3481 @cindex operands in expressions
3482 @cindex arithmetic operands
3483 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3484 contexts arguments are sometimes called ``arithmetic operands''. In
3485 this manual, to avoid confusing them with the ``instruction operands'' of
3486 the machine language, we use the term ``argument'' to refer to parts of
3487 expressions only, reserving the word ``operand'' to refer only to machine
3488 instruction operands.
3490 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3491 @var{section} is one of text, data, bss, absolute,
3492 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3495 Numbers are usually integers.
3497 A number can be a flonum or bignum. In this case, you are warned
3498 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3499 these 32 bits are an integer. You may write integer-manipulating
3500 instructions that act on exotic constants, compatible with other
3503 @cindex subexpressions
3504 Subexpressions are a left parenthesis @samp{(} followed by an integer
3505 expression, followed by a right parenthesis @samp{)}; or a prefix
3506 operator followed by an argument.
3509 @subsection Operators
3511 @cindex operators, in expressions
3512 @cindex arithmetic functions
3513 @cindex functions, in expressions
3514 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3515 operators are followed by an argument. Infix operators appear
3516 between their arguments. Operators may be preceded and/or followed by
3520 @subsection Prefix Operator
3522 @cindex prefix operators
3523 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3524 one argument, which must be absolute.
3526 @c the tex/end tex stuff surrounding this small table is meant to make
3527 @c it align, on the printed page, with the similar table in the next
3528 @c section (which is inside an enumerate).
3530 \global\advance\leftskip by \itemindent
3535 @dfn{Negation}. Two's complement negation.
3537 @dfn{Complementation}. Bitwise not.
3541 \global\advance\leftskip by -\itemindent
3545 @subsection Infix Operators
3547 @cindex infix operators
3548 @cindex operators, permitted arguments
3549 @dfn{Infix operators} take two arguments, one on either side. Operators
3550 have precedence, but operations with equal precedence are performed left
3551 to right. Apart from @code{+} or @option{-}, both arguments must be
3552 absolute, and the result is absolute.
3555 @cindex operator precedence
3556 @cindex precedence of operators
3563 @dfn{Multiplication}.
3566 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3573 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3577 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3581 Intermediate precedence
3586 @dfn{Bitwise Inclusive Or}.
3592 @dfn{Bitwise Exclusive Or}.
3595 @dfn{Bitwise Or Not}.
3602 @cindex addition, permitted arguments
3603 @cindex plus, permitted arguments
3604 @cindex arguments for addition
3606 @dfn{Addition}. If either argument is absolute, the result has the section of
3607 the other argument. You may not add together arguments from different
3610 @cindex subtraction, permitted arguments
3611 @cindex minus, permitted arguments
3612 @cindex arguments for subtraction
3614 @dfn{Subtraction}. If the right argument is absolute, the
3615 result has the section of the left argument.
3616 If both arguments are in the same section, the result is absolute.
3617 You may not subtract arguments from different sections.
3618 @c FIXME is there still something useful to say about undefined - undefined ?
3620 @cindex comparison expressions
3621 @cindex expressions, comparison
3625 @dfn{Is Not Equal To}
3629 @dfn{Is Greater Than}
3631 @dfn{Is Greater Than Or Equal To}
3633 @dfn{Is Less Than Or Equal To}
3635 The comparison operators can be used as infix operators. A true results has a
3636 value of -1 whereas a false result has a value of 0. Note, these operators
3637 perform signed comparisons.
3640 @item Lowest Precedence
3649 These two logical operations can be used to combine the results of sub
3650 expressions. Note, unlike the comparison operators a true result returns a
3651 value of 1 but a false results does still return 0. Also note that the logical
3652 or operator has a slightly lower precedence than logical and.
3657 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3658 address; you can only have a defined section in one of the two arguments.
3661 @chapter Assembler Directives
3663 @cindex directives, machine independent
3664 @cindex pseudo-ops, machine independent
3665 @cindex machine independent directives
3666 All assembler directives have names that begin with a period (@samp{.}).
3667 The rest of the name is letters, usually in lower case.
3669 This chapter discusses directives that are available regardless of the
3670 target machine configuration for the @sc{gnu} assembler.
3672 Some machine configurations provide additional directives.
3673 @xref{Machine Dependencies}.
3676 @ifset machine-directives
3677 @xref{Machine Dependencies} for additional directives.
3682 * Abort:: @code{.abort}
3684 * ABORT:: @code{.ABORT}
3687 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3688 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3689 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3690 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3691 * Byte:: @code{.byte @var{expressions}}
3692 * Comm:: @code{.comm @var{symbol} , @var{length} }
3694 * CFI directives:: @code{.cfi_startproc}
3696 @code{.cfi_def_cfa @var{register}, @var{offset}}
3697 @code{.cfi_def_cfa_register @var{register}}
3698 @code{.cfi_def_cfa_offset @var{offset}}
3699 @code{.cfi_adjust_cfa_offset @var{offset}}
3700 @code{.cfi_offset @var{register}, @var{offset}}
3702 * Data:: @code{.data @var{subsection}}
3704 * Def:: @code{.def @var{name}}
3707 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3713 * Double:: @code{.double @var{flonums}}
3714 * Eject:: @code{.eject}
3715 * Else:: @code{.else}
3716 * Elseif:: @code{.elseif}
3719 * Endef:: @code{.endef}
3722 * Endfunc:: @code{.endfunc}
3723 * Endif:: @code{.endif}
3724 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3725 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3727 * Exitm:: @code{.exitm}
3728 * Extern:: @code{.extern}
3729 * Fail:: @code{.fail}
3730 @ifclear no-file-dir
3731 * File:: @code{.file @var{string}}
3734 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3735 * Float:: @code{.float @var{flonums}}
3736 * Func:: @code{.func}
3737 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3739 * Hidden:: @code{.hidden @var{names}}
3742 * hword:: @code{.hword @var{expressions}}
3743 * Ident:: @code{.ident}
3744 * If:: @code{.if @var{absolute expression}}
3745 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3746 * Include:: @code{.include "@var{file}"}
3747 * Int:: @code{.int @var{expressions}}
3749 * Internal:: @code{.internal @var{names}}
3752 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3753 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3754 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3755 * Lflags:: @code{.lflags}
3756 @ifclear no-line-dir
3757 * Line:: @code{.line @var{line-number}}
3760 * Ln:: @code{.ln @var{line-number}}
3761 * Linkonce:: @code{.linkonce [@var{type}]}
3762 * List:: @code{.list}
3763 * Long:: @code{.long @var{expressions}}
3765 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3768 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3769 * MRI:: @code{.mri @var{val}}
3770 * Nolist:: @code{.nolist}
3771 * Octa:: @code{.octa @var{bignums}}
3772 * Org:: @code{.org @var{new-lc} , @var{fill}}
3773 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3775 * PopSection:: @code{.popsection}
3776 * Previous:: @code{.previous}
3779 * Print:: @code{.print @var{string}}
3781 * Protected:: @code{.protected @var{names}}
3784 * Psize:: @code{.psize @var{lines}, @var{columns}}
3785 * Purgem:: @code{.purgem @var{name}}
3787 * PushSection:: @code{.pushsection @var{name}}
3790 * Quad:: @code{.quad @var{bignums}}
3791 * Rept:: @code{.rept @var{count}}
3792 * Sbttl:: @code{.sbttl "@var{subheading}"}
3794 * Scl:: @code{.scl @var{class}}
3797 * Section:: @code{.section @var{name}}
3800 * Set:: @code{.set @var{symbol}, @var{expression}}
3801 * Short:: @code{.short @var{expressions}}
3802 * Single:: @code{.single @var{flonums}}
3804 * Size:: @code{.size [@var{name} , @var{expression}]}
3807 * Skip:: @code{.skip @var{size} , @var{fill}}
3808 * Sleb128:: @code{.sleb128 @var{expressions}}
3809 * Space:: @code{.space @var{size} , @var{fill}}
3811 * Stab:: @code{.stabd, .stabn, .stabs}
3814 * String:: @code{.string "@var{str}"}
3815 * Struct:: @code{.struct @var{expression}}
3817 * SubSection:: @code{.subsection}
3818 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3822 * Tag:: @code{.tag @var{structname}}
3825 * Text:: @code{.text @var{subsection}}
3826 * Title:: @code{.title "@var{heading}"}
3828 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3831 * Uleb128:: @code{.uleb128 @var{expressions}}
3833 * Val:: @code{.val @var{addr}}
3837 * Version:: @code{.version "@var{string}"}
3838 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3839 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3840 * Weak:: @code{.weak @var{names}}
3843 * Word:: @code{.word @var{expressions}}
3844 * Deprecated:: Deprecated Directives
3848 @section @code{.abort}
3850 @cindex @code{abort} directive
3851 @cindex stopping the assembly
3852 This directive stops the assembly immediately. It is for
3853 compatibility with other assemblers. The original idea was that the
3854 assembly language source would be piped into the assembler. If the sender
3855 of the source quit, it could use this directive tells @command{@value{AS}} to
3856 quit also. One day @code{.abort} will not be supported.
3860 @section @code{.ABORT}
3862 @cindex @code{ABORT} directive
3863 When producing COFF output, @command{@value{AS}} accepts this directive as a
3864 synonym for @samp{.abort}.
3867 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3873 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3875 @cindex padding the location counter
3876 @cindex @code{align} directive
3877 Pad the location counter (in the current subsection) to a particular storage
3878 boundary. The first expression (which must be absolute) is the alignment
3879 required, as described below.
3881 The second expression (also absolute) gives the fill value to be stored in the
3882 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3883 padding bytes are normally zero. However, on some systems, if the section is
3884 marked as containing code and the fill value is omitted, the space is filled
3885 with no-op instructions.
3887 The third expression is also absolute, and is also optional. If it is present,
3888 it is the maximum number of bytes that should be skipped by this alignment
3889 directive. If doing the alignment would require skipping more bytes than the
3890 specified maximum, then the alignment is not done at all. You can omit the
3891 fill value (the second argument) entirely by simply using two commas after the
3892 required alignment; this can be useful if you want the alignment to be filled
3893 with no-op instructions when appropriate.
3895 The way the required alignment is specified varies from system to system.
3896 For the a29k, hppa, m68k, m88k, w65, sparc, Xtensa, and Renesas / SuperH SH,
3897 and i386 using ELF format,
3898 the first expression is the
3899 alignment request in bytes. For example @samp{.align 8} advances
3900 the location counter until it is a multiple of 8. If the location counter
3901 is already a multiple of 8, no change is needed.
3903 For other systems, including the i386 using a.out format, and the arm and
3904 strongarm, it is the
3905 number of low-order zero bits the location counter must have after
3906 advancement. For example @samp{.align 3} advances the location
3907 counter until it a multiple of 8. If the location counter is already a
3908 multiple of 8, no change is needed.
3910 This inconsistency is due to the different behaviors of the various
3911 native assemblers for these systems which GAS must emulate.
3912 GAS also provides @code{.balign} and @code{.p2align} directives,
3913 described later, which have a consistent behavior across all
3914 architectures (but are specific to GAS).
3917 @section @code{.ascii "@var{string}"}@dots{}
3919 @cindex @code{ascii} directive
3920 @cindex string literals
3921 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3922 separated by commas. It assembles each string (with no automatic
3923 trailing zero byte) into consecutive addresses.
3926 @section @code{.asciz "@var{string}"}@dots{}
3928 @cindex @code{asciz} directive
3929 @cindex zero-terminated strings
3930 @cindex null-terminated strings
3931 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3932 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3935 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3937 @cindex padding the location counter given number of bytes
3938 @cindex @code{balign} directive
3939 Pad the location counter (in the current subsection) to a particular
3940 storage boundary. The first expression (which must be absolute) is the
3941 alignment request in bytes. For example @samp{.balign 8} advances
3942 the location counter until it is a multiple of 8. If the location counter
3943 is already a multiple of 8, no change is needed.
3945 The second expression (also absolute) gives the fill value to be stored in the
3946 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3947 padding bytes are normally zero. However, on some systems, if the section is
3948 marked as containing code and the fill value is omitted, the space is filled
3949 with no-op instructions.
3951 The third expression is also absolute, and is also optional. If it is present,
3952 it is the maximum number of bytes that should be skipped by this alignment
3953 directive. If doing the alignment would require skipping more bytes than the
3954 specified maximum, then the alignment is not done at all. You can omit the
3955 fill value (the second argument) entirely by simply using two commas after the
3956 required alignment; this can be useful if you want the alignment to be filled
3957 with no-op instructions when appropriate.
3959 @cindex @code{balignw} directive
3960 @cindex @code{balignl} directive
3961 The @code{.balignw} and @code{.balignl} directives are variants of the
3962 @code{.balign} directive. The @code{.balignw} directive treats the fill
3963 pattern as a two byte word value. The @code{.balignl} directives treats the
3964 fill pattern as a four byte longword value. For example, @code{.balignw
3965 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3966 filled in with the value 0x368d (the exact placement of the bytes depends upon
3967 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3971 @section @code{.byte @var{expressions}}
3973 @cindex @code{byte} directive
3974 @cindex integers, one byte
3975 @code{.byte} expects zero or more expressions, separated by commas.
3976 Each expression is assembled into the next byte.
3978 @node CFI directives
3979 @section @code{.cfi_startproc}
3980 @cindex @code{cfi_startproc} directive
3981 @code{.cfi_startproc} is used at the beginning of each function that
3982 should have an entry in @code{.eh_frame}. It initializes some internal
3983 data structures and emits architecture dependent initial CFI instructions.
3984 Don't forget to close the function by
3985 @code{.cfi_endproc}.
3987 @section @code{.cfi_endproc}
3988 @cindex @code{cfi_endproc} directive
3989 @code{.cfi_endproc} is used at the end of a function where it closes its
3990 unwind entry previously opened by
3991 @code{.cfi_startproc}. and emits it to @code{.eh_frame}.
3993 @section @code{.cfi_def_cfa @var{register}, @var{offset}}
3994 @code{.cfi_def_cfa} defines a rule for computing CFA as: @i{take
3995 address from @var{register} and add @var{offset} to it}.
3997 @section @code{.cfi_def_cfa_register @var{register}}
3998 @code{.cfi_def_cfa_register} modifies a rule for computing CFA. From
3999 now on @var{register} will be used instead of the old one. Offset
4002 @section @code{.cfi_def_cfa_offset @var{offset}}
4003 @code{.cfi_def_cfa_offset} modifies a rule for computing CFA. Register
4004 remains the same, but @var{offset} is new. Note that it is the
4005 absolute offset that will be added to a defined register to compute
4008 @section @code{.cfi_adjust_cfa_offset @var{offset}}
4009 Same as @code{.cfi_def_cfa_offset} but @var{offset} is a relative
4010 value that is added/substracted from the previous offset.
4012 @section @code{.cfi_offset @var{register}, @var{offset}}
4013 Previous value of @var{register} is saved at offset @var{offset} from
4016 @section @code{.cfi_rel_offset @var{register}, @var{offset}}
4017 Previous value of @var{register} is saved at offset @var{offset} from
4018 the current CFA register. This is transformed to @code{.cfi_offset}
4019 using the known displacement of the CFA register from the CFA.
4020 This is often easier to use, because the number will match the
4021 code it's annotating.
4024 @section @code{.comm @var{symbol} , @var{length} }
4026 @cindex @code{comm} directive
4027 @cindex symbol, common
4028 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
4029 common symbol in one object file may be merged with a defined or common symbol
4030 of the same name in another object file. If @code{@value{LD}} does not see a
4031 definition for the symbol--just one or more common symbols--then it will
4032 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
4033 absolute expression. If @code{@value{LD}} sees multiple common symbols with
4034 the same name, and they do not all have the same size, it will allocate space
4035 using the largest size.
4038 When using ELF, the @code{.comm} directive takes an optional third argument.
4039 This is the desired alignment of the symbol, specified as a byte boundary (for
4040 example, an alignment of 16 means that the least significant 4 bits of the
4041 address should be zero). The alignment must be an absolute expression, and it
4042 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
4043 for the common symbol, it will use the alignment when placing the symbol. If
4044 no alignment is specified, @command{@value{AS}} will set the alignment to the
4045 largest power of two less than or equal to the size of the symbol, up to a
4050 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
4051 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
4055 @section @code{.data @var{subsection}}
4057 @cindex @code{data} directive
4058 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
4059 end of the data subsection numbered @var{subsection} (which is an
4060 absolute expression). If @var{subsection} is omitted, it defaults
4065 @section @code{.def @var{name}}
4067 @cindex @code{def} directive
4068 @cindex COFF symbols, debugging
4069 @cindex debugging COFF symbols
4070 Begin defining debugging information for a symbol @var{name}; the
4071 definition extends until the @code{.endef} directive is encountered.
4074 This directive is only observed when @command{@value{AS}} is configured for COFF
4075 format output; when producing @code{b.out}, @samp{.def} is recognized,
4082 @section @code{.desc @var{symbol}, @var{abs-expression}}
4084 @cindex @code{desc} directive
4085 @cindex COFF symbol descriptor
4086 @cindex symbol descriptor, COFF
4087 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
4088 to the low 16 bits of an absolute expression.
4091 The @samp{.desc} directive is not available when @command{@value{AS}} is
4092 configured for COFF output; it is only for @code{a.out} or @code{b.out}
4093 object format. For the sake of compatibility, @command{@value{AS}} accepts
4094 it, but produces no output, when configured for COFF.
4100 @section @code{.dim}
4102 @cindex @code{dim} directive
4103 @cindex COFF auxiliary symbol information
4104 @cindex auxiliary symbol information, COFF
4105 This directive is generated by compilers to include auxiliary debugging
4106 information in the symbol table. It is only permitted inside
4107 @code{.def}/@code{.endef} pairs.
4110 @samp{.dim} is only meaningful when generating COFF format output; when
4111 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
4117 @section @code{.double @var{flonums}}
4119 @cindex @code{double} directive
4120 @cindex floating point numbers (double)
4121 @code{.double} expects zero or more flonums, separated by commas. It
4122 assembles floating point numbers.
4124 The exact kind of floating point numbers emitted depends on how
4125 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
4129 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
4130 in @sc{ieee} format.
4135 @section @code{.eject}
4137 @cindex @code{eject} directive
4138 @cindex new page, in listings
4139 @cindex page, in listings
4140 @cindex listing control: new page
4141 Force a page break at this point, when generating assembly listings.
4144 @section @code{.else}
4146 @cindex @code{else} directive
4147 @code{.else} is part of the @command{@value{AS}} support for conditional
4148 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
4149 of code to be assembled if the condition for the preceding @code{.if}
4153 @section @code{.elseif}
4155 @cindex @code{elseif} directive
4156 @code{.elseif} is part of the @command{@value{AS}} support for conditional
4157 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
4158 @code{.if} block that would otherwise fill the entire @code{.else} section.
4161 @section @code{.end}
4163 @cindex @code{end} directive
4164 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
4165 process anything in the file past the @code{.end} directive.
4169 @section @code{.endef}
4171 @cindex @code{endef} directive
4172 This directive flags the end of a symbol definition begun with
4176 @samp{.endef} is only meaningful when generating COFF format output; if
4177 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4178 directive but ignores it.
4183 @section @code{.endfunc}
4184 @cindex @code{endfunc} directive
4185 @code{.endfunc} marks the end of a function specified with @code{.func}.
4188 @section @code{.endif}
4190 @cindex @code{endif} directive
4191 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4192 it marks the end of a block of code that is only assembled
4193 conditionally. @xref{If,,@code{.if}}.
4196 @section @code{.equ @var{symbol}, @var{expression}}
4198 @cindex @code{equ} directive
4199 @cindex assigning values to symbols
4200 @cindex symbols, assigning values to
4201 This directive sets the value of @var{symbol} to @var{expression}.
4202 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4205 The syntax for @code{equ} on the HPPA is
4206 @samp{@var{symbol} .equ @var{expression}}.
4210 @section @code{.equiv @var{symbol}, @var{expression}}
4211 @cindex @code{equiv} directive
4212 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4213 the assembler will signal an error if @var{symbol} is already defined. Note a
4214 symbol which has been referenced but not actually defined is considered to be
4217 Except for the contents of the error message, this is roughly equivalent to
4226 @section @code{.err}
4227 @cindex @code{err} directive
4228 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4229 message and, unless the @option{-Z} option was used, it will not generate an
4230 object file. This can be used to signal error an conditionally compiled code.
4233 @section @code{.exitm}
4234 Exit early from the current macro definition. @xref{Macro}.
4237 @section @code{.extern}
4239 @cindex @code{extern} directive
4240 @code{.extern} is accepted in the source program---for compatibility
4241 with other assemblers---but it is ignored. @command{@value{AS}} treats
4242 all undefined symbols as external.
4245 @section @code{.fail @var{expression}}
4247 @cindex @code{fail} directive
4248 Generates an error or a warning. If the value of the @var{expression} is 500
4249 or more, @command{@value{AS}} will print a warning message. If the value is less
4250 than 500, @command{@value{AS}} will print an error message. The message will
4251 include the value of @var{expression}. This can occasionally be useful inside
4252 complex nested macros or conditional assembly.
4254 @ifclear no-file-dir
4256 @section @code{.file @var{string}}
4258 @cindex @code{file} directive
4259 @cindex logical file name
4260 @cindex file name, logical
4261 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4262 file. @var{string} is the new file name. In general, the filename is
4263 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4264 to specify an empty file name, you must give the quotes--@code{""}. This
4265 statement may go away in future: it is only recognized to be compatible with
4266 old @command{@value{AS}} programs.
4268 In some configurations of @command{@value{AS}}, @code{.file} has already been
4269 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
4274 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4276 @cindex @code{fill} directive
4277 @cindex writing patterns in memory
4278 @cindex patterns, writing in memory
4279 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4280 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4281 may be zero or more. @var{Size} may be zero or more, but if it is
4282 more than 8, then it is deemed to have the value 8, compatible with
4283 other people's assemblers. The contents of each @var{repeat} bytes
4284 is taken from an 8-byte number. The highest order 4 bytes are
4285 zero. The lowest order 4 bytes are @var{value} rendered in the
4286 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4287 Each @var{size} bytes in a repetition is taken from the lowest order
4288 @var{size} bytes of this number. Again, this bizarre behavior is
4289 compatible with other people's assemblers.
4291 @var{size} and @var{value} are optional.
4292 If the second comma and @var{value} are absent, @var{value} is
4293 assumed zero. If the first comma and following tokens are absent,
4294 @var{size} is assumed to be 1.
4297 @section @code{.float @var{flonums}}
4299 @cindex floating point numbers (single)
4300 @cindex @code{float} directive
4301 This directive assembles zero or more flonums, separated by commas. It
4302 has the same effect as @code{.single}.
4304 The exact kind of floating point numbers emitted depends on how
4305 @command{@value{AS}} is configured.
4306 @xref{Machine Dependencies}.
4310 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4311 in @sc{ieee} format.
4316 @section @code{.func @var{name}[,@var{label}]}
4317 @cindex @code{func} directive
4318 @code{.func} emits debugging information to denote function @var{name}, and
4319 is ignored unless the file is assembled with debugging enabled.
4320 Only @samp{--gstabs} is currently supported.
4321 @var{label} is the entry point of the function and if omitted @var{name}
4322 prepended with the @samp{leading char} is used.
4323 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4324 All functions are currently defined to have @code{void} return type.
4325 The function must be terminated with @code{.endfunc}.
4328 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4330 @cindex @code{global} directive
4331 @cindex symbol, making visible to linker
4332 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4333 @var{symbol} in your partial program, its value is made available to
4334 other partial programs that are linked with it. Otherwise,
4335 @var{symbol} takes its attributes from a symbol of the same name
4336 from another file linked into the same program.
4338 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4339 compatibility with other assemblers.
4342 On the HPPA, @code{.global} is not always enough to make it accessible to other
4343 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4344 @xref{HPPA Directives,, HPPA Assembler Directives}.
4349 @section @code{.hidden @var{names}}
4351 @cindex @code{hidden} directive
4353 This one of the ELF visibility directives. The other two are
4354 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4355 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4357 This directive overrides the named symbols default visibility (which is set by
4358 their binding: local, global or weak). The directive sets the visibility to
4359 @code{hidden} which means that the symbols are not visible to other components.
4360 Such symbols are always considered to be @code{protected} as well.
4364 @section @code{.hword @var{expressions}}
4366 @cindex @code{hword} directive
4367 @cindex integers, 16-bit
4368 @cindex numbers, 16-bit
4369 @cindex sixteen bit integers
4370 This expects zero or more @var{expressions}, and emits
4371 a 16 bit number for each.
4374 This directive is a synonym for @samp{.short}; depending on the target
4375 architecture, it may also be a synonym for @samp{.word}.
4379 This directive is a synonym for @samp{.short}.
4382 This directive is a synonym for both @samp{.short} and @samp{.word}.
4387 @section @code{.ident}
4389 @cindex @code{ident} directive
4390 This directive is used by some assemblers to place tags in object files.
4391 @command{@value{AS}} simply accepts the directive for source-file
4392 compatibility with such assemblers, but does not actually emit anything
4396 @section @code{.if @var{absolute expression}}
4398 @cindex conditional assembly
4399 @cindex @code{if} directive
4400 @code{.if} marks the beginning of a section of code which is only
4401 considered part of the source program being assembled if the argument
4402 (which must be an @var{absolute expression}) is non-zero. The end of
4403 the conditional section of code must be marked by @code{.endif}
4404 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4405 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4406 If you have several conditions to check, @code{.elseif} may be used to avoid
4407 nesting blocks if/else within each subsequent @code{.else} block.
4409 The following variants of @code{.if} are also supported:
4411 @cindex @code{ifdef} directive
4412 @item .ifdef @var{symbol}
4413 Assembles the following section of code if the specified @var{symbol}
4414 has been defined. Note a symbol which has been referenced but not yet defined
4415 is considered to be undefined.
4417 @cindex @code{ifc} directive
4418 @item .ifc @var{string1},@var{string2}
4419 Assembles the following section of code if the two strings are the same. The
4420 strings may be optionally quoted with single quotes. If they are not quoted,
4421 the first string stops at the first comma, and the second string stops at the
4422 end of the line. Strings which contain whitespace should be quoted. The
4423 string comparison is case sensitive.
4425 @cindex @code{ifeq} directive
4426 @item .ifeq @var{absolute expression}
4427 Assembles the following section of code if the argument is zero.
4429 @cindex @code{ifeqs} directive
4430 @item .ifeqs @var{string1},@var{string2}
4431 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4433 @cindex @code{ifge} directive
4434 @item .ifge @var{absolute expression}
4435 Assembles the following section of code if the argument is greater than or
4438 @cindex @code{ifgt} directive
4439 @item .ifgt @var{absolute expression}
4440 Assembles the following section of code if the argument is greater than zero.
4442 @cindex @code{ifle} directive
4443 @item .ifle @var{absolute expression}
4444 Assembles the following section of code if the argument is less than or equal
4447 @cindex @code{iflt} directive
4448 @item .iflt @var{absolute expression}
4449 Assembles the following section of code if the argument is less than zero.
4451 @cindex @code{ifnc} directive
4452 @item .ifnc @var{string1},@var{string2}.
4453 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4454 following section of code if the two strings are not the same.
4456 @cindex @code{ifndef} directive
4457 @cindex @code{ifnotdef} directive
4458 @item .ifndef @var{symbol}
4459 @itemx .ifnotdef @var{symbol}
4460 Assembles the following section of code if the specified @var{symbol}
4461 has not been defined. Both spelling variants are equivalent. Note a symbol
4462 which has been referenced but not yet defined is considered to be undefined.
4464 @cindex @code{ifne} directive
4465 @item .ifne @var{absolute expression}
4466 Assembles the following section of code if the argument is not equal to zero
4467 (in other words, this is equivalent to @code{.if}).
4469 @cindex @code{ifnes} directive
4470 @item .ifnes @var{string1},@var{string2}
4471 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4472 following section of code if the two strings are not the same.
4476 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4478 @cindex @code{incbin} directive
4479 @cindex binary files, including
4480 The @code{incbin} directive includes @var{file} verbatim at the current
4481 location. You can control the search paths used with the @samp{-I} command-line
4482 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4485 The @var{skip} argument skips a number of bytes from the start of the
4486 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4487 read. Note that the data is not aligned in any way, so it is the user's
4488 responsibility to make sure that proper alignment is provided both before and
4489 after the @code{incbin} directive.
4492 @section @code{.include "@var{file}"}
4494 @cindex @code{include} directive
4495 @cindex supporting files, including
4496 @cindex files, including
4497 This directive provides a way to include supporting files at specified
4498 points in your source program. The code from @var{file} is assembled as
4499 if it followed the point of the @code{.include}; when the end of the
4500 included file is reached, assembly of the original file continues. You
4501 can control the search paths used with the @samp{-I} command-line option
4502 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4506 @section @code{.int @var{expressions}}
4508 @cindex @code{int} directive
4509 @cindex integers, 32-bit
4510 Expect zero or more @var{expressions}, of any section, separated by commas.
4511 For each expression, emit a number that, at run time, is the value of that
4512 expression. The byte order and bit size of the number depends on what kind
4513 of target the assembly is for.
4517 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4518 integers. On the H8/300H and the Renesas SH, however, @code{.int} emits
4525 @section @code{.internal @var{names}}
4527 @cindex @code{internal} directive
4529 This one of the ELF visibility directives. The other two are
4530 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4531 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4533 This directive overrides the named symbols default visibility (which is set by
4534 their binding: local, global or weak). The directive sets the visibility to
4535 @code{internal} which means that the symbols are considered to be @code{hidden}
4536 (i.e., not visible to other components), and that some extra, processor specific
4537 processing must also be performed upon the symbols as well.
4541 @section @code{.irp @var{symbol},@var{values}}@dots{}
4543 @cindex @code{irp} directive
4544 Evaluate a sequence of statements assigning different values to @var{symbol}.
4545 The sequence of statements starts at the @code{.irp} directive, and is
4546 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4547 set to @var{value}, and the sequence of statements is assembled. If no
4548 @var{value} is listed, the sequence of statements is assembled once, with
4549 @var{symbol} set to the null string. To refer to @var{symbol} within the
4550 sequence of statements, use @var{\symbol}.
4552 For example, assembling
4560 is equivalent to assembling
4569 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4571 @cindex @code{irpc} directive
4572 Evaluate a sequence of statements assigning different values to @var{symbol}.
4573 The sequence of statements starts at the @code{.irpc} directive, and is
4574 terminated by an @code{.endr} directive. For each character in @var{value},
4575 @var{symbol} is set to the character, and the sequence of statements is
4576 assembled. If no @var{value} is listed, the sequence of statements is
4577 assembled once, with @var{symbol} set to the null string. To refer to
4578 @var{symbol} within the sequence of statements, use @var{\symbol}.
4580 For example, assembling
4588 is equivalent to assembling
4597 @section @code{.lcomm @var{symbol} , @var{length}}
4599 @cindex @code{lcomm} directive
4600 @cindex local common symbols
4601 @cindex symbols, local common
4602 Reserve @var{length} (an absolute expression) bytes for a local common
4603 denoted by @var{symbol}. The section and value of @var{symbol} are
4604 those of the new local common. The addresses are allocated in the bss
4605 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4606 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4607 not visible to @code{@value{LD}}.
4610 Some targets permit a third argument to be used with @code{.lcomm}. This
4611 argument specifies the desired alignment of the symbol in the bss section.
4615 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4616 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4620 @section @code{.lflags}
4622 @cindex @code{lflags} directive (ignored)
4623 @command{@value{AS}} accepts this directive, for compatibility with other
4624 assemblers, but ignores it.
4626 @ifclear no-line-dir
4628 @section @code{.line @var{line-number}}
4630 @cindex @code{line} directive
4634 @section @code{.ln @var{line-number}}
4636 @cindex @code{ln} directive
4638 @cindex logical line number
4640 Change the logical line number. @var{line-number} must be an absolute
4641 expression. The next line has that logical line number. Therefore any other
4642 statements on the current line (after a statement separator character) are
4643 reported as on logical line number @var{line-number} @minus{} 1. One day
4644 @command{@value{AS}} will no longer support this directive: it is recognized only
4645 for compatibility with existing assembler programs.
4649 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4650 not available; use the synonym @code{.ln} in that context.
4655 @ifclear no-line-dir
4656 Even though this is a directive associated with the @code{a.out} or
4657 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4658 when producing COFF output, and treats @samp{.line} as though it
4659 were the COFF @samp{.ln} @emph{if} it is found outside a
4660 @code{.def}/@code{.endef} pair.
4662 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4663 used by compilers to generate auxiliary symbol information for
4668 @section @code{.linkonce [@var{type}]}
4670 @cindex @code{linkonce} directive
4671 @cindex common sections
4672 Mark the current section so that the linker only includes a single copy of it.
4673 This may be used to include the same section in several different object files,
4674 but ensure that the linker will only include it once in the final output file.
4675 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4676 Duplicate sections are detected based on the section name, so it should be
4679 This directive is only supported by a few object file formats; as of this
4680 writing, the only object file format which supports it is the Portable
4681 Executable format used on Windows NT.
4683 The @var{type} argument is optional. If specified, it must be one of the
4684 following strings. For example:
4688 Not all types may be supported on all object file formats.
4692 Silently discard duplicate sections. This is the default.
4695 Warn if there are duplicate sections, but still keep only one copy.
4698 Warn if any of the duplicates have different sizes.
4701 Warn if any of the duplicates do not have exactly the same contents.
4705 @section @code{.ln @var{line-number}}
4707 @cindex @code{ln} directive
4708 @ifclear no-line-dir
4709 @samp{.ln} is a synonym for @samp{.line}.
4712 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4713 must be an absolute expression. The next line has that logical
4714 line number, so any other statements on the current line (after a
4715 statement separator character @code{;}) are reported as on logical
4716 line number @var{line-number} @minus{} 1.
4719 This directive is accepted, but ignored, when @command{@value{AS}} is
4720 configured for @code{b.out}; its effect is only associated with COFF
4726 @section @code{.mri @var{val}}
4728 @cindex @code{mri} directive
4729 @cindex MRI mode, temporarily
4730 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4731 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4732 affects code assembled until the next @code{.mri} directive, or until the end
4733 of the file. @xref{M, MRI mode, MRI mode}.
4736 @section @code{.list}
4738 @cindex @code{list} directive
4739 @cindex listing control, turning on
4740 Control (in conjunction with the @code{.nolist} directive) whether or
4741 not assembly listings are generated. These two directives maintain an
4742 internal counter (which is zero initially). @code{.list} increments the
4743 counter, and @code{.nolist} decrements it. Assembly listings are
4744 generated whenever the counter is greater than zero.
4746 By default, listings are disabled. When you enable them (with the
4747 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4748 the initial value of the listing counter is one.
4751 @section @code{.long @var{expressions}}
4753 @cindex @code{long} directive
4754 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4757 @c no one seems to know what this is for or whether this description is
4758 @c what it really ought to do
4760 @section @code{.lsym @var{symbol}, @var{expression}}
4762 @cindex @code{lsym} directive
4763 @cindex symbol, not referenced in assembly
4764 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4765 the hash table, ensuring it cannot be referenced by name during the
4766 rest of the assembly. This sets the attributes of the symbol to be
4767 the same as the expression value:
4769 @var{other} = @var{descriptor} = 0
4770 @var{type} = @r{(section of @var{expression})}
4771 @var{value} = @var{expression}
4774 The new symbol is not flagged as external.
4778 @section @code{.macro}
4781 The commands @code{.macro} and @code{.endm} allow you to define macros that
4782 generate assembly output. For example, this definition specifies a macro
4783 @code{sum} that puts a sequence of numbers into memory:
4786 .macro sum from=0, to=5
4795 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4807 @item .macro @var{macname}
4808 @itemx .macro @var{macname} @var{macargs} @dots{}
4809 @cindex @code{macro} directive
4810 Begin the definition of a macro called @var{macname}. If your macro
4811 definition requires arguments, specify their names after the macro name,
4812 separated by commas or spaces. You can supply a default value for any
4813 macro argument by following the name with @samp{=@var{deflt}}. For
4814 example, these are all valid @code{.macro} statements:
4818 Begin the definition of a macro called @code{comm}, which takes no
4821 @item .macro plus1 p, p1
4822 @itemx .macro plus1 p p1
4823 Either statement begins the definition of a macro called @code{plus1},
4824 which takes two arguments; within the macro definition, write
4825 @samp{\p} or @samp{\p1} to evaluate the arguments.
4827 @item .macro reserve_str p1=0 p2
4828 Begin the definition of a macro called @code{reserve_str}, with two
4829 arguments. The first argument has a default value, but not the second.
4830 After the definition is complete, you can call the macro either as
4831 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4832 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4833 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4834 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4837 When you call a macro, you can specify the argument values either by
4838 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4839 @samp{sum to=17, from=9}.
4842 @cindex @code{endm} directive
4843 Mark the end of a macro definition.
4846 @cindex @code{exitm} directive
4847 Exit early from the current macro definition.
4849 @cindex number of macros executed
4850 @cindex macros, count executed
4852 @command{@value{AS}} maintains a counter of how many macros it has
4853 executed in this pseudo-variable; you can copy that number to your
4854 output with @samp{\@@}, but @emph{only within a macro definition}.
4857 @item LOCAL @var{name} [ , @dots{} ]
4858 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4859 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4860 Alternate macro syntax}.
4862 Generate a string replacement for each of the @var{name} arguments, and
4863 replace any instances of @var{name} in each macro expansion. The
4864 replacement string is unique in the assembly, and different for each
4865 separate macro expansion. @code{LOCAL} allows you to write macros that
4866 define symbols, without fear of conflict between separate macro expansions.
4871 @section @code{.nolist}
4873 @cindex @code{nolist} directive
4874 @cindex listing control, turning off
4875 Control (in conjunction with the @code{.list} directive) whether or
4876 not assembly listings are generated. These two directives maintain an
4877 internal counter (which is zero initially). @code{.list} increments the
4878 counter, and @code{.nolist} decrements it. Assembly listings are
4879 generated whenever the counter is greater than zero.
4882 @section @code{.octa @var{bignums}}
4884 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4885 @cindex @code{octa} directive
4886 @cindex integer, 16-byte
4887 @cindex sixteen byte integer
4888 This directive expects zero or more bignums, separated by commas. For each
4889 bignum, it emits a 16-byte integer.
4891 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4892 hence @emph{octa}-word for 16 bytes.
4895 @section @code{.org @var{new-lc} , @var{fill}}
4897 @cindex @code{org} directive
4898 @cindex location counter, advancing
4899 @cindex advancing location counter
4900 @cindex current address, advancing
4901 Advance the location counter of the current section to
4902 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4903 expression with the same section as the current subsection. That is,
4904 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4905 wrong section, the @code{.org} directive is ignored. To be compatible
4906 with former assemblers, if the section of @var{new-lc} is absolute,
4907 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4908 is the same as the current subsection.
4910 @code{.org} may only increase the location counter, or leave it
4911 unchanged; you cannot use @code{.org} to move the location counter
4914 @c double negative used below "not undefined" because this is a specific
4915 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4916 @c section. doc@cygnus.com 18feb91
4917 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4918 may not be undefined. If you really detest this restriction we eagerly await
4919 a chance to share your improved assembler.
4921 Beware that the origin is relative to the start of the section, not
4922 to the start of the subsection. This is compatible with other
4923 people's assemblers.
4925 When the location counter (of the current subsection) is advanced, the
4926 intervening bytes are filled with @var{fill} which should be an
4927 absolute expression. If the comma and @var{fill} are omitted,
4928 @var{fill} defaults to zero.
4931 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4933 @cindex padding the location counter given a power of two
4934 @cindex @code{p2align} directive
4935 Pad the location counter (in the current subsection) to a particular
4936 storage boundary. The first expression (which must be absolute) is the
4937 number of low-order zero bits the location counter must have after
4938 advancement. For example @samp{.p2align 3} advances the location
4939 counter until it a multiple of 8. If the location counter is already a
4940 multiple of 8, no change is needed.
4942 The second expression (also absolute) gives the fill value to be stored in the
4943 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4944 padding bytes are normally zero. However, on some systems, if the section is
4945 marked as containing code and the fill value is omitted, the space is filled
4946 with no-op instructions.
4948 The third expression is also absolute, and is also optional. If it is present,
4949 it is the maximum number of bytes that should be skipped by this alignment
4950 directive. If doing the alignment would require skipping more bytes than the
4951 specified maximum, then the alignment is not done at all. You can omit the
4952 fill value (the second argument) entirely by simply using two commas after the
4953 required alignment; this can be useful if you want the alignment to be filled
4954 with no-op instructions when appropriate.
4956 @cindex @code{p2alignw} directive
4957 @cindex @code{p2alignl} directive
4958 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4959 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4960 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4961 fill pattern as a four byte longword value. For example, @code{.p2alignw
4962 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4963 filled in with the value 0x368d (the exact placement of the bytes depends upon
4964 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4969 @section @code{.previous}
4971 @cindex @code{previous} directive
4972 @cindex Section Stack
4973 This is one of the ELF section stack manipulation directives. The others are
4974 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4975 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4976 (@pxref{PopSection}).
4978 This directive swaps the current section (and subsection) with most recently
4979 referenced section (and subsection) prior to this one. Multiple
4980 @code{.previous} directives in a row will flip between two sections (and their
4983 In terms of the section stack, this directive swaps the current section with
4984 the top section on the section stack.
4989 @section @code{.popsection}
4991 @cindex @code{popsection} directive
4992 @cindex Section Stack
4993 This is one of the ELF section stack manipulation directives. The others are
4994 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4995 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4998 This directive replaces the current section (and subsection) with the top
4999 section (and subsection) on the section stack. This section is popped off the
5004 @section @code{.print @var{string}}
5006 @cindex @code{print} directive
5007 @command{@value{AS}} will print @var{string} on the standard output during
5008 assembly. You must put @var{string} in double quotes.
5012 @section @code{.protected @var{names}}
5014 @cindex @code{protected} directive
5016 This one of the ELF visibility directives. The other two are
5017 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
5019 This directive overrides the named symbols default visibility (which is set by
5020 their binding: local, global or weak). The directive sets the visibility to
5021 @code{protected} which means that any references to the symbols from within the
5022 components that defines them must be resolved to the definition in that
5023 component, even if a definition in another component would normally preempt
5028 @section @code{.psize @var{lines} , @var{columns}}
5030 @cindex @code{psize} directive
5031 @cindex listing control: paper size
5032 @cindex paper size, for listings
5033 Use this directive to declare the number of lines---and, optionally, the
5034 number of columns---to use for each page, when generating listings.
5036 If you do not use @code{.psize}, listings use a default line-count
5037 of 60. You may omit the comma and @var{columns} specification; the
5038 default width is 200 columns.
5040 @command{@value{AS}} generates formfeeds whenever the specified number of
5041 lines is exceeded (or whenever you explicitly request one, using
5044 If you specify @var{lines} as @code{0}, no formfeeds are generated save
5045 those explicitly specified with @code{.eject}.
5048 @section @code{.purgem @var{name}}
5050 @cindex @code{purgem} directive
5051 Undefine the macro @var{name}, so that later uses of the string will not be
5052 expanded. @xref{Macro}.
5056 @section @code{.pushsection @var{name} , @var{subsection}}
5058 @cindex @code{pushsection} directive
5059 @cindex Section Stack
5060 This is one of the ELF section stack manipulation directives. The others are
5061 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
5062 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5065 This directive is a synonym for @code{.section}. It pushes the current section
5066 (and subsection) onto the top of the section stack, and then replaces the
5067 current section and subsection with @code{name} and @code{subsection}.
5071 @section @code{.quad @var{bignums}}
5073 @cindex @code{quad} directive
5074 @code{.quad} expects zero or more bignums, separated by commas. For
5075 each bignum, it emits
5077 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
5078 warning message; and just takes the lowest order 8 bytes of the bignum.
5079 @cindex eight-byte integer
5080 @cindex integer, 8-byte
5082 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
5083 hence @emph{quad}-word for 8 bytes.
5086 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
5087 warning message; and just takes the lowest order 16 bytes of the bignum.
5088 @cindex sixteen-byte integer
5089 @cindex integer, 16-byte
5093 @section @code{.rept @var{count}}
5095 @cindex @code{rept} directive
5096 Repeat the sequence of lines between the @code{.rept} directive and the next
5097 @code{.endr} directive @var{count} times.
5099 For example, assembling
5107 is equivalent to assembling
5116 @section @code{.sbttl "@var{subheading}"}
5118 @cindex @code{sbttl} directive
5119 @cindex subtitles for listings
5120 @cindex listing control: subtitle
5121 Use @var{subheading} as the title (third line, immediately after the
5122 title line) when generating assembly listings.
5124 This directive affects subsequent pages, as well as the current page if
5125 it appears within ten lines of the top of a page.
5129 @section @code{.scl @var{class}}
5131 @cindex @code{scl} directive
5132 @cindex symbol storage class (COFF)
5133 @cindex COFF symbol storage class
5134 Set the storage-class value for a symbol. This directive may only be
5135 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
5136 whether a symbol is static or external, or it may record further
5137 symbolic debugging information.
5140 The @samp{.scl} directive is primarily associated with COFF output; when
5141 configured to generate @code{b.out} output format, @command{@value{AS}}
5142 accepts this directive but ignores it.
5148 @section @code{.section @var{name}}
5150 @cindex named section
5151 Use the @code{.section} directive to assemble the following code into a section
5154 This directive is only supported for targets that actually support arbitrarily
5155 named sections; on @code{a.out} targets, for example, it is not accepted, even
5156 with a standard @code{a.out} section name.
5160 @c only print the extra heading if both COFF and ELF are set
5161 @subheading COFF Version
5164 @cindex @code{section} directive (COFF version)
5165 For COFF targets, the @code{.section} directive is used in one of the following
5169 .section @var{name}[, "@var{flags}"]
5170 .section @var{name}[, @var{subsegment}]
5173 If the optional argument is quoted, it is taken as flags to use for the
5174 section. Each flag is a single character. The following flags are recognized:
5177 bss section (uninitialized data)
5179 section is not loaded
5189 shared section (meaningful for PE targets)
5191 ignored. (For compatibility with the ELF version)
5194 If no flags are specified, the default flags depend upon the section name. If
5195 the section name is not recognized, the default will be for the section to be
5196 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5197 from the section, rather than adding them, so if they are used on their own it
5198 will be as if no flags had been specified at all.
5200 If the optional argument to the @code{.section} directive is not quoted, it is
5201 taken as a subsegment number (@pxref{Sub-Sections}).
5206 @c only print the extra heading if both COFF and ELF are set
5207 @subheading ELF Version
5210 @cindex Section Stack
5211 This is one of the ELF section stack manipulation directives. The others are
5212 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5213 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5214 @code{.previous} (@pxref{Previous}).
5216 @cindex @code{section} directive (ELF version)
5217 For ELF targets, the @code{.section} directive is used like this:
5220 .section @var{name} [, "@var{flags}"[, @@@var{type}[, @@@var{entsize}]]]
5223 The optional @var{flags} argument is a quoted string which may contain any
5224 combination of the following characters:
5227 section is allocatable
5231 section is executable
5233 section is mergeable
5235 section contains zero terminated strings
5238 The optional @var{type} argument may contain one of the following constants:
5241 section contains data
5243 section does not contain data (i.e., section only occupies space)
5246 Note on targets where the @code{@@} character is the start of a comment (eg
5247 ARM) then another character is used instead. For example the ARM port uses the
5250 If @var{flags} contains @code{M} flag, @var{type} argument must be specified
5251 as well as @var{entsize} argument. Sections with @code{M} flag but not
5252 @code{S} flag must contain fixed size constants, each @var{entsize} octets
5253 long. Sections with both @code{M} and @code{S} must contain zero terminated
5254 strings where each character is @var{entsize} bytes long. The linker may remove
5255 duplicates within sections with the same name, same entity size and same flags.
5257 If no flags are specified, the default flags depend upon the section name. If
5258 the section name is not recognized, the default will be for the section to have
5259 none of the above flags: it will not be allocated in memory, nor writable, nor
5260 executable. The section will contain data.
5262 For ELF targets, the assembler supports another type of @code{.section}
5263 directive for compatibility with the Solaris assembler:
5266 .section "@var{name}"[, @var{flags}...]
5269 Note that the section name is quoted. There may be a sequence of comma
5273 section is allocatable
5277 section is executable
5280 This directive replaces the current section and subsection. The replaced
5281 section and subsection are pushed onto the section stack. See the contents of
5282 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
5283 how this directive and the other section stack directives work.
5288 @section @code{.set @var{symbol}, @var{expression}}
5290 @cindex @code{set} directive
5291 @cindex symbol value, setting
5292 Set the value of @var{symbol} to @var{expression}. This
5293 changes @var{symbol}'s value and type to conform to
5294 @var{expression}. If @var{symbol} was flagged as external, it remains
5295 flagged (@pxref{Symbol Attributes}).
5297 You may @code{.set} a symbol many times in the same assembly.
5299 If you @code{.set} a global symbol, the value stored in the object
5300 file is the last value stored into it.
5303 The syntax for @code{set} on the HPPA is
5304 @samp{@var{symbol} .set @var{expression}}.
5308 @section @code{.short @var{expressions}}
5310 @cindex @code{short} directive
5312 @code{.short} is normally the same as @samp{.word}.
5313 @xref{Word,,@code{.word}}.
5315 In some configurations, however, @code{.short} and @code{.word} generate
5316 numbers of different lengths; @pxref{Machine Dependencies}.
5320 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5323 This expects zero or more @var{expressions}, and emits
5324 a 16 bit number for each.
5329 @section @code{.single @var{flonums}}
5331 @cindex @code{single} directive
5332 @cindex floating point numbers (single)
5333 This directive assembles zero or more flonums, separated by commas. It
5334 has the same effect as @code{.float}.
5336 The exact kind of floating point numbers emitted depends on how
5337 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5341 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5342 numbers in @sc{ieee} format.
5348 @section @code{.size}
5350 This directive is used to set the size associated with a symbol.
5354 @c only print the extra heading if both COFF and ELF are set
5355 @subheading COFF Version
5358 @cindex @code{size} directive (COFF version)
5359 For COFF targets, the @code{.size} directive is only permitted inside
5360 @code{.def}/@code{.endef} pairs. It is used like this:
5363 .size @var{expression}
5367 @samp{.size} is only meaningful when generating COFF format output; when
5368 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5375 @c only print the extra heading if both COFF and ELF are set
5376 @subheading ELF Version
5379 @cindex @code{size} directive (ELF version)
5380 For ELF targets, the @code{.size} directive is used like this:
5383 .size @var{name} , @var{expression}
5386 This directive sets the size associated with a symbol @var{name}.
5387 The size in bytes is computed from @var{expression} which can make use of label
5388 arithmetic. This directive is typically used to set the size of function
5394 @section @code{.sleb128 @var{expressions}}
5396 @cindex @code{sleb128} directive
5397 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5398 compact, variable length representation of numbers used by the DWARF
5399 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5401 @ifclear no-space-dir
5403 @section @code{.skip @var{size} , @var{fill}}
5405 @cindex @code{skip} directive
5406 @cindex filling memory
5407 This directive emits @var{size} bytes, each of value @var{fill}. Both
5408 @var{size} and @var{fill} are absolute expressions. If the comma and
5409 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5413 @section @code{.space @var{size} , @var{fill}}
5415 @cindex @code{space} directive
5416 @cindex filling memory
5417 This directive emits @var{size} bytes, each of value @var{fill}. Both
5418 @var{size} and @var{fill} are absolute expressions. If the comma
5419 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5424 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5425 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5426 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5427 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5436 @section @code{.space}
5437 @cindex @code{space} directive
5439 On the AMD 29K, this directive is ignored; it is accepted for
5440 compatibility with other AMD 29K assemblers.
5443 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5444 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5450 @section @code{.stabd, .stabn, .stabs}
5452 @cindex symbolic debuggers, information for
5453 @cindex @code{stab@var{x}} directives
5454 There are three directives that begin @samp{.stab}.
5455 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5456 The symbols are not entered in the @command{@value{AS}} hash table: they
5457 cannot be referenced elsewhere in the source file.
5458 Up to five fields are required:
5462 This is the symbol's name. It may contain any character except
5463 @samp{\000}, so is more general than ordinary symbol names. Some
5464 debuggers used to code arbitrarily complex structures into symbol names
5468 An absolute expression. The symbol's type is set to the low 8 bits of
5469 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5470 and debuggers choke on silly bit patterns.
5473 An absolute expression. The symbol's ``other'' attribute is set to the
5474 low 8 bits of this expression.
5477 An absolute expression. The symbol's descriptor is set to the low 16
5478 bits of this expression.
5481 An absolute expression which becomes the symbol's value.
5484 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5485 or @code{.stabs} statement, the symbol has probably already been created;
5486 you get a half-formed symbol in your object file. This is
5487 compatible with earlier assemblers!
5490 @cindex @code{stabd} directive
5491 @item .stabd @var{type} , @var{other} , @var{desc}
5493 The ``name'' of the symbol generated is not even an empty string.
5494 It is a null pointer, for compatibility. Older assemblers used a
5495 null pointer so they didn't waste space in object files with empty
5498 The symbol's value is set to the location counter,
5499 relocatably. When your program is linked, the value of this symbol
5500 is the address of the location counter when the @code{.stabd} was
5503 @cindex @code{stabn} directive
5504 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5505 The name of the symbol is set to the empty string @code{""}.
5507 @cindex @code{stabs} directive
5508 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5509 All five fields are specified.
5515 @section @code{.string} "@var{str}"
5517 @cindex string, copying to object file
5518 @cindex @code{string} directive
5520 Copy the characters in @var{str} to the object file. You may specify more than
5521 one string to copy, separated by commas. Unless otherwise specified for a
5522 particular machine, the assembler marks the end of each string with a 0 byte.
5523 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5526 @section @code{.struct @var{expression}}
5528 @cindex @code{struct} directive
5529 Switch to the absolute section, and set the section offset to @var{expression},
5530 which must be an absolute expression. You might use this as follows:
5539 This would define the symbol @code{field1} to have the value 0, the symbol
5540 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5541 value 8. Assembly would be left in the absolute section, and you would need to
5542 use a @code{.section} directive of some sort to change to some other section
5543 before further assembly.
5547 @section @code{.subsection @var{name}}
5549 @cindex @code{subsection} directive
5550 @cindex Section Stack
5551 This is one of the ELF section stack manipulation directives. The others are
5552 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5553 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5556 This directive replaces the current subsection with @code{name}. The current
5557 section is not changed. The replaced subsection is put onto the section stack
5558 in place of the then current top of stack subsection.
5563 @section @code{.symver}
5564 @cindex @code{symver} directive
5565 @cindex symbol versioning
5566 @cindex versions of symbols
5567 Use the @code{.symver} directive to bind symbols to specific version nodes
5568 within a source file. This is only supported on ELF platforms, and is
5569 typically used when assembling files to be linked into a shared library.
5570 There are cases where it may make sense to use this in objects to be bound
5571 into an application itself so as to override a versioned symbol from a
5574 For ELF targets, the @code{.symver} directive can be used like this:
5576 .symver @var{name}, @var{name2@@nodename}
5578 If the symbol @var{name} is defined within the file
5579 being assembled, the @code{.symver} directive effectively creates a symbol
5580 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5581 just don't try and create a regular alias is that the @var{@@} character isn't
5582 permitted in symbol names. The @var{name2} part of the name is the actual name
5583 of the symbol by which it will be externally referenced. The name @var{name}
5584 itself is merely a name of convenience that is used so that it is possible to
5585 have definitions for multiple versions of a function within a single source
5586 file, and so that the compiler can unambiguously know which version of a
5587 function is being mentioned. The @var{nodename} portion of the alias should be
5588 the name of a node specified in the version script supplied to the linker when
5589 building a shared library. If you are attempting to override a versioned
5590 symbol from a shared library, then @var{nodename} should correspond to the
5591 nodename of the symbol you are trying to override.
5593 If the symbol @var{name} is not defined within the file being assembled, all
5594 references to @var{name} will be changed to @var{name2@@nodename}. If no
5595 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5598 Another usage of the @code{.symver} directive is:
5600 .symver @var{name}, @var{name2@@@@nodename}
5602 In this case, the symbol @var{name} must exist and be defined within
5603 the file being assembled. It is similar to @var{name2@@nodename}. The
5604 difference is @var{name2@@@@nodename} will also be used to resolve
5605 references to @var{name2} by the linker.
5607 The third usage of the @code{.symver} directive is:
5609 .symver @var{name}, @var{name2@@@@@@nodename}
5611 When @var{name} is not defined within the
5612 file being assembled, it is treated as @var{name2@@nodename}. When
5613 @var{name} is defined within the file being assembled, the symbol
5614 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5619 @section @code{.tag @var{structname}}
5621 @cindex COFF structure debugging
5622 @cindex structure debugging, COFF
5623 @cindex @code{tag} directive
5624 This directive is generated by compilers to include auxiliary debugging
5625 information in the symbol table. It is only permitted inside
5626 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5627 definitions in the symbol table with instances of those structures.
5630 @samp{.tag} is only used when generating COFF format output; when
5631 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5637 @section @code{.text @var{subsection}}
5639 @cindex @code{text} directive
5640 Tells @command{@value{AS}} to assemble the following statements onto the end of
5641 the text subsection numbered @var{subsection}, which is an absolute
5642 expression. If @var{subsection} is omitted, subsection number zero
5646 @section @code{.title "@var{heading}"}
5648 @cindex @code{title} directive
5649 @cindex listing control: title line
5650 Use @var{heading} as the title (second line, immediately after the
5651 source file name and pagenumber) when generating assembly listings.
5653 This directive affects subsequent pages, as well as the current page if
5654 it appears within ten lines of the top of a page.
5658 @section @code{.type}
5660 This directive is used to set the type of a symbol.
5664 @c only print the extra heading if both COFF and ELF are set
5665 @subheading COFF Version
5668 @cindex COFF symbol type
5669 @cindex symbol type, COFF
5670 @cindex @code{type} directive (COFF version)
5671 For COFF targets, this directive is permitted only within
5672 @code{.def}/@code{.endef} pairs. It is used like this:
5678 This records the integer @var{int} as the type attribute of a symbol table
5682 @samp{.type} is associated only with COFF format output; when
5683 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5684 directive but ignores it.
5690 @c only print the extra heading if both COFF and ELF are set
5691 @subheading ELF Version
5694 @cindex ELF symbol type
5695 @cindex symbol type, ELF
5696 @cindex @code{type} directive (ELF version)
5697 For ELF targets, the @code{.type} directive is used like this:
5700 .type @var{name} , @var{type description}
5703 This sets the type of symbol @var{name} to be either a
5704 function symbol or an object symbol. There are five different syntaxes
5705 supported for the @var{type description} field, in order to provide
5706 compatibility with various other assemblers. The syntaxes supported are:
5709 .type <name>,#function
5710 .type <name>,#object
5712 .type <name>,@@function
5713 .type <name>,@@object
5715 .type <name>,%function
5716 .type <name>,%object
5718 .type <name>,"function"
5719 .type <name>,"object"
5721 .type <name> STT_FUNCTION
5722 .type <name> STT_OBJECT
5728 @section @code{.uleb128 @var{expressions}}
5730 @cindex @code{uleb128} directive
5731 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5732 compact, variable length representation of numbers used by the DWARF
5733 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5737 @section @code{.val @var{addr}}
5739 @cindex @code{val} directive
5740 @cindex COFF value attribute
5741 @cindex value attribute, COFF
5742 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5743 records the address @var{addr} as the value attribute of a symbol table
5747 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5748 configured for @code{b.out}, it accepts this directive but ignores it.
5754 @section @code{.version "@var{string}"}
5756 @cindex @code{version} directive
5757 This directive creates a @code{.note} section and places into it an ELF
5758 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5763 @section @code{.vtable_entry @var{table}, @var{offset}}
5765 @cindex @code{vtable_entry}
5766 This directive finds or creates a symbol @code{table} and creates a
5767 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5770 @section @code{.vtable_inherit @var{child}, @var{parent}}
5772 @cindex @code{vtable_inherit}
5773 This directive finds the symbol @code{child} and finds or creates the symbol
5774 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5775 parent whose addend is the value of the child symbol. As a special case the
5776 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5781 @section @code{.weak @var{names}}
5783 @cindex @code{weak} directive
5784 This directive sets the weak attribute on the comma separated list of symbol
5785 @code{names}. If the symbols do not already exist, they will be created.
5789 @section @code{.word @var{expressions}}
5791 @cindex @code{word} directive
5792 This directive expects zero or more @var{expressions}, of any section,
5793 separated by commas.
5796 For each expression, @command{@value{AS}} emits a 32-bit number.
5799 For each expression, @command{@value{AS}} emits a 16-bit number.
5804 The size of the number emitted, and its byte order,
5805 depend on what target computer the assembly is for.
5808 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5809 @c happen---32-bit addressability, period; no long/short jumps.
5810 @ifset DIFF-TBL-KLUGE
5811 @cindex difference tables altered
5812 @cindex altered difference tables
5814 @emph{Warning: Special Treatment to support Compilers}
5818 Machines with a 32-bit address space, but that do less than 32-bit
5819 addressing, require the following special treatment. If the machine of
5820 interest to you does 32-bit addressing (or doesn't require it;
5821 @pxref{Machine Dependencies}), you can ignore this issue.
5824 In order to assemble compiler output into something that works,
5825 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5826 Directives of the form @samp{.word sym1-sym2} are often emitted by
5827 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
5828 directive of the form @samp{.word sym1-sym2}, and the difference between
5829 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
5830 creates a @dfn{secondary jump table}, immediately before the next label.
5831 This secondary jump table is preceded by a short-jump to the
5832 first byte after the secondary table. This short-jump prevents the flow
5833 of control from accidentally falling into the new table. Inside the
5834 table is a long-jump to @code{sym2}. The original @samp{.word}
5835 contains @code{sym1} minus the address of the long-jump to
5838 If there were several occurrences of @samp{.word sym1-sym2} before the
5839 secondary jump table, all of them are adjusted. If there was a
5840 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5841 long-jump to @code{sym4} is included in the secondary jump table,
5842 and the @code{.word} directives are adjusted to contain @code{sym3}
5843 minus the address of the long-jump to @code{sym4}; and so on, for as many
5844 entries in the original jump table as necessary.
5847 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
5848 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5849 assembly language programmers.
5852 @c end DIFF-TBL-KLUGE
5855 @section Deprecated Directives
5857 @cindex deprecated directives
5858 @cindex obsolescent directives
5859 One day these directives won't work.
5860 They are included for compatibility with older assemblers.
5867 @node Machine Dependencies
5868 @chapter Machine Dependent Features
5870 @cindex machine dependencies
5871 The machine instruction sets are (almost by definition) different on
5872 each machine where @command{@value{AS}} runs. Floating point representations
5873 vary as well, and @command{@value{AS}} often supports a few additional
5874 directives or command-line options for compatibility with other
5875 assemblers on a particular platform. Finally, some versions of
5876 @command{@value{AS}} support special pseudo-instructions for branch
5879 This chapter discusses most of these differences, though it does not
5880 include details on any machine's instruction set. For details on that
5881 subject, see the hardware manufacturer's manual.
5885 * AMD29K-Dependent:: AMD 29K Dependent Features
5888 * Alpha-Dependent:: Alpha Dependent Features
5891 * ARC-Dependent:: ARC Dependent Features
5894 * ARM-Dependent:: ARM Dependent Features
5897 * CRIS-Dependent:: CRIS Dependent Features
5900 * D10V-Dependent:: D10V Dependent Features
5903 * D30V-Dependent:: D30V Dependent Features
5906 * H8/300-Dependent:: Renesas H8/300 Dependent Features
5909 * H8/500-Dependent:: Renesas H8/500 Dependent Features
5912 * HPPA-Dependent:: HPPA Dependent Features
5915 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5918 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5921 * i860-Dependent:: Intel 80860 Dependent Features
5924 * i960-Dependent:: Intel 80960 Dependent Features
5927 * IP2K-Dependent:: IP2K Dependent Features
5930 * M32R-Dependent:: M32R Dependent Features
5933 * M68K-Dependent:: M680x0 Dependent Features
5936 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5939 * M88K-Dependent:: M880x0 Dependent Features
5942 * MIPS-Dependent:: MIPS Dependent Features
5945 * MMIX-Dependent:: MMIX Dependent Features
5948 * MSP430-Dependent:: MSP430 Dependent Features
5951 * SH-Dependent:: Renesas / SuperH SH Dependent Features
5952 * SH64-Dependent:: SuperH SH64 Dependent Features
5955 * PDP-11-Dependent:: PDP-11 Dependent Features
5958 * PJ-Dependent:: picoJava Dependent Features
5961 * PPC-Dependent:: PowerPC Dependent Features
5964 * Sparc-Dependent:: SPARC Dependent Features
5967 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5970 * V850-Dependent:: V850 Dependent Features
5973 * Xtensa-Dependent:: Xtensa Dependent Features
5976 * Z8000-Dependent:: Z8000 Dependent Features
5979 * Vax-Dependent:: VAX Dependent Features
5986 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5987 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5988 @c peculiarity: to preserve cross-references, there must be a node called
5989 @c "Machine Dependencies". Hence the conditional nodenames in each
5990 @c major node below. Node defaulting in makeinfo requires adjacency of
5991 @c node and sectioning commands; hence the repetition of @chapter BLAH
5992 @c in both conditional blocks.
5995 @include c-a29k.texi
5999 @include c-alpha.texi
6011 @include c-cris.texi
6016 @node Machine Dependencies
6017 @chapter Machine Dependent Features
6019 The machine instruction sets are different on each Renesas chip family,
6020 and there are also some syntax differences among the families. This
6021 chapter describes the specific @command{@value{AS}} features for each
6025 * H8/300-Dependent:: Renesas H8/300 Dependent Features
6026 * H8/500-Dependent:: Renesas H8/500 Dependent Features
6027 * SH-Dependent:: Renesas SH Dependent Features
6034 @include c-d10v.texi
6038 @include c-d30v.texi
6042 @include c-h8300.texi
6046 @include c-h8500.texi
6050 @include c-hppa.texi
6054 @include c-i370.texi
6058 @include c-i386.texi
6062 @include c-i860.texi
6066 @include c-i960.texi
6070 @include c-ia64.texi
6074 @include c-ip2k.texi
6078 @include c-m32r.texi
6082 @include c-m68k.texi
6086 @include c-m68hc11.texi
6090 @include c-m88k.texi
6094 @include c-mips.texi
6098 @include c-mmix.texi
6102 @include c-msp430.texi
6106 @include c-ns32k.texi
6110 @include c-pdp11.texi
6123 @include c-sh64.texi
6127 @include c-sparc.texi
6131 @include c-tic54x.texi
6143 @include c-v850.texi
6147 @include c-xtensa.texi
6151 @c reverse effect of @down at top of generic Machine-Dep chapter
6155 @node Reporting Bugs
6156 @chapter Reporting Bugs
6157 @cindex bugs in assembler
6158 @cindex reporting bugs in assembler
6160 Your bug reports play an essential role in making @command{@value{AS}} reliable.
6162 Reporting a bug may help you by bringing a solution to your problem, or it may
6163 not. But in any case the principal function of a bug report is to help the
6164 entire community by making the next version of @command{@value{AS}} work better.
6165 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
6167 In order for a bug report to serve its purpose, you must include the
6168 information that enables us to fix the bug.
6171 * Bug Criteria:: Have you found a bug?
6172 * Bug Reporting:: How to report bugs
6176 @section Have You Found a Bug?
6177 @cindex bug criteria
6179 If you are not sure whether you have found a bug, here are some guidelines:
6182 @cindex fatal signal
6183 @cindex assembler crash
6184 @cindex crash of assembler
6186 If the assembler gets a fatal signal, for any input whatever, that is a
6187 @command{@value{AS}} bug. Reliable assemblers never crash.
6189 @cindex error on valid input
6191 If @command{@value{AS}} produces an error message for valid input, that is a bug.
6193 @cindex invalid input
6195 If @command{@value{AS}} does not produce an error message for invalid input, that
6196 is a bug. However, you should note that your idea of ``invalid input'' might
6197 be our idea of ``an extension'' or ``support for traditional practice''.
6200 If you are an experienced user of assemblers, your suggestions for improvement
6201 of @command{@value{AS}} are welcome in any case.
6205 @section How to Report Bugs
6207 @cindex assembler bugs, reporting
6209 A number of companies and individuals offer support for @sc{gnu} products. If
6210 you obtained @command{@value{AS}} from a support organization, we recommend you
6211 contact that organization first.
6213 You can find contact information for many support companies and
6214 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
6217 In any event, we also recommend that you send bug reports for @command{@value{AS}}
6218 to @samp{bug-binutils@@gnu.org}.
6220 The fundamental principle of reporting bugs usefully is this:
6221 @strong{report all the facts}. If you are not sure whether to state a
6222 fact or leave it out, state it!
6224 Often people omit facts because they think they know what causes the problem
6225 and assume that some details do not matter. Thus, you might assume that the
6226 name of a symbol you use in an example does not matter. Well, probably it does
6227 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
6228 happens to fetch from the location where that name is stored in memory;
6229 perhaps, if the name were different, the contents of that location would fool
6230 the assembler into doing the right thing despite the bug. Play it safe and
6231 give a specific, complete example. That is the easiest thing for you to do,
6232 and the most helpful.
6234 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
6235 it is new to us. Therefore, always write your bug reports on the assumption
6236 that the bug has not been reported previously.
6238 Sometimes people give a few sketchy facts and ask, ``Does this ring a
6239 bell?'' This cannot help us fix a bug, so it is basically useless. We
6240 respond by asking for enough details to enable us to investigate.
6241 You might as well expedite matters by sending them to begin with.
6243 To enable us to fix the bug, you should include all these things:
6247 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
6248 it with the @samp{--version} argument.
6250 Without this, we will not know whether there is any point in looking for
6251 the bug in the current version of @command{@value{AS}}.
6254 Any patches you may have applied to the @command{@value{AS}} source.
6257 The type of machine you are using, and the operating system name and
6261 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6265 The command arguments you gave the assembler to assemble your example and
6266 observe the bug. To guarantee you will not omit something important, list them
6267 all. A copy of the Makefile (or the output from make) is sufficient.
6269 If we were to try to guess the arguments, we would probably guess wrong
6270 and then we might not encounter the bug.
6273 A complete input file that will reproduce the bug. If the bug is observed when
6274 the assembler is invoked via a compiler, send the assembler source, not the
6275 high level language source. Most compilers will produce the assembler source
6276 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6277 the options @samp{-v --save-temps}; this will save the assembler source in a
6278 file with an extension of @file{.s}, and also show you exactly how
6279 @command{@value{AS}} is being run.
6282 A description of what behavior you observe that you believe is
6283 incorrect. For example, ``It gets a fatal signal.''
6285 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6286 will certainly notice it. But if the bug is incorrect output, we might not
6287 notice unless it is glaringly wrong. You might as well not give us a chance to
6290 Even if the problem you experience is a fatal signal, you should still say so
6291 explicitly. Suppose something strange is going on, such as, your copy of
6292 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6293 library on your system. (This has happened!) Your copy might crash and ours
6294 would not. If you told us to expect a crash, then when ours fails to crash, we
6295 would know that the bug was not happening for us. If you had not told us to
6296 expect a crash, then we would not be able to draw any conclusion from our
6300 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6301 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6302 option. Always send diffs from the old file to the new file. If you even
6303 discuss something in the @command{@value{AS}} source, refer to it by context, not
6306 The line numbers in our development sources will not match those in your
6307 sources. Your line numbers would convey no useful information to us.
6310 Here are some things that are not necessary:
6314 A description of the envelope of the bug.
6316 Often people who encounter a bug spend a lot of time investigating
6317 which changes to the input file will make the bug go away and which
6318 changes will not affect it.
6320 This is often time consuming and not very useful, because the way we
6321 will find the bug is by running a single example under the debugger
6322 with breakpoints, not by pure deduction from a series of examples.
6323 We recommend that you save your time for something else.
6325 Of course, if you can find a simpler example to report @emph{instead}
6326 of the original one, that is a convenience for us. Errors in the
6327 output will be easier to spot, running under the debugger will take
6328 less time, and so on.
6330 However, simplification is not vital; if you do not want to do this,
6331 report the bug anyway and send us the entire test case you used.
6334 A patch for the bug.
6336 A patch for the bug does help us if it is a good one. But do not omit
6337 the necessary information, such as the test case, on the assumption that
6338 a patch is all we need. We might see problems with your patch and decide
6339 to fix the problem another way, or we might not understand it at all.
6341 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6342 construct an example that will make the program follow a certain path through
6343 the code. If you do not send us the example, we will not be able to construct
6344 one, so we will not be able to verify that the bug is fixed.
6346 And if we cannot understand what bug you are trying to fix, or why your
6347 patch should be an improvement, we will not install it. A test case will
6348 help us to understand.
6351 A guess about what the bug is or what it depends on.
6353 Such guesses are usually wrong. Even we cannot guess right about such
6354 things without first using the debugger to find the facts.
6357 @node Acknowledgements
6358 @chapter Acknowledgements
6360 If you have contributed to @command{@value{AS}} and your name isn't listed here,
6361 it is not meant as a slight. We just don't know about it. Send mail to the
6362 maintainer, and we'll correct the situation. Currently
6364 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6366 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6369 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6370 information and the 68k series machines, most of the preprocessing pass, and
6371 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6373 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6374 many bug fixes, including merging support for several processors, breaking GAS
6375 up to handle multiple object file format back ends (including heavy rewrite,
6376 testing, an integration of the coff and b.out back ends), adding configuration
6377 including heavy testing and verification of cross assemblers and file splits
6378 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6379 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6380 port (including considerable amounts of reverse engineering), a SPARC opcode
6381 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6382 assertions and made them work, much other reorganization, cleanup, and lint.
6384 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6385 in format-specific I/O modules.
6387 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6388 has done much work with it since.
6390 The Intel 80386 machine description was written by Eliot Dresselhaus.
6392 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6394 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6395 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6397 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6398 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6399 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6400 support a.out format.
6402 Support for the Zilog Z8k and Renesas H8/300 and H8/500 processors (tc-z8k,
6403 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
6404 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6405 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6408 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6409 simplified the configuration of which versions accept which directives. He
6410 updated the 68k machine description so that Motorola's opcodes always produced
6411 fixed-size instructions (e.g., @code{jsr}), while synthetic instructions
6412 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6413 cross-compilation support, and one bug in relaxation that took a week and
6414 required the proverbial one-bit fix.
6416 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6417 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6418 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6419 PowerPC assembler, and made a few other minor patches.
6421 Steve Chamberlain made @command{@value{AS}} able to generate listings.
6423 Hewlett-Packard contributed support for the HP9000/300.
6425 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6426 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6427 formats). This work was supported by both the Center for Software Science at
6428 the University of Utah and Cygnus Support.
6430 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6431 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6432 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6433 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6434 and some initial 64-bit support).
6436 Linas Vepstas added GAS support for the ESA/390 ``IBM 370'' architecture.
6438 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6439 support for openVMS/Alpha.
6441 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6444 David Heine, Sterling Augustine, Bob Wilson and John Ruttenberg from Tensilica,
6445 Inc. added support for Xtensa processors.
6447 Several engineers at Cygnus Support have also provided many small bug fixes and
6448 configuration enhancements.
6450 Many others have contributed large or small bugfixes and enhancements. If
6451 you have contributed significant work and are not mentioned on this list, and
6452 want to be, let us know. Some of the history has been lost; we are not
6453 intentionally leaving anyone out.
projects / binutils-gdb.git / blob