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
63 @c common OR combinations of conditions
83 @set abnormal-separator
87 @settitle Using @value{AS}
90 @settitle Using @value{AS} (@value{TARGET})
92 @setchapternewpage odd
97 @c WARE! Some of the machine-dependent sections contain tables of machine
98 @c instructions. Except in multi-column format, these tables look silly.
99 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
100 @c the multi-col format is faked within @example sections.
102 @c Again unfortunately, the natural size that fits on a page, for these tables,
103 @c is different depending on whether or not smallbook is turned on.
104 @c This matters, because of order: text flow switches columns at each page
107 @c The format faked in this source works reasonably well for smallbook,
108 @c not well for the default large-page format. This manual expects that if you
109 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
110 @c tables in question. You can turn on one without the other at your
111 @c discretion, of course.
114 @c the insn tables look just as silly in info files regardless of smallbook,
115 @c might as well show 'em anyways.
121 * As: (as). The GNU assembler.
122 * Gas: (as). The GNU assembler.
131 This file documents the GNU Assembler "@value{AS}".
133 @c man begin COPYRIGHT
134 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
136 Permission is granted to copy, distribute and/or modify this document
137 under the terms of the GNU Free Documentation License, Version 1.1
138 or any later version published by the Free Software Foundation;
139 with no Invariant Sections, with no Front-Cover Texts, and with no
140 Back-Cover Texts. A copy of the license is included in the
141 section entitled "GNU Free Documentation License".
146 Permission is granted to process this file through Tex and print the
147 results, provided the printed document carries copying permission
148 notice identical to this one except for the removal of this paragraph
149 (this paragraph not being relevant to the printed manual).
155 @title Using @value{AS}
156 @subtitle The @sc{gnu} Assembler
158 @subtitle for the @value{TARGET} family
161 @subtitle Version @value{VERSION}
164 The Free Software Foundation Inc. thanks The Nice Computer
165 Company of Australia for loaning Dean Elsner to write the
166 first (Vax) version of @command{as} for Project @sc{gnu}.
167 The proprietors, management and staff of TNCCA thank FSF for
168 distracting the boss while they got some work
171 @author Dean Elsner, Jay Fenlason & friends
175 \hfill {\it Using {\tt @value{AS}}}\par
176 \hfill Edited by Cygnus Support\par
178 %"boxit" macro for figures:
179 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
180 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
181 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
182 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
183 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
186 @vskip 0pt plus 1filll
187 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002 Free Software Foundation, Inc.
189 Permission is granted to copy, distribute and/or modify this document
190 under the terms of the GNU Free Documentation License, Version 1.1
191 or any later version published by the Free Software Foundation;
192 with no Invariant Sections, with no Front-Cover Texts, and with no
193 Back-Cover Texts. A copy of the license is included in the
194 section entitled "GNU Free Documentation License".
200 @top Using @value{AS}
202 This file is a user guide to the @sc{gnu} assembler @command{@value{AS}} version
205 This version of the file describes @command{@value{AS}} configured to generate
206 code for @value{TARGET} architectures.
209 This document is distributed under the terms of the GNU Free
210 Documentation License. A copy of the license is included in the
211 section entitled "GNU Free Documentation License".
214 * Overview:: Overview
215 * Invoking:: Command-Line Options
217 * Sections:: Sections and Relocation
219 * Expressions:: Expressions
220 * Pseudo Ops:: Assembler Directives
221 * Machine Dependencies:: Machine Dependent Features
222 * Reporting Bugs:: Reporting Bugs
223 * Acknowledgements:: Who Did What
224 * GNU Free Documentation License:: GNU Free Documentation License
232 This manual is a user guide to the @sc{gnu} assembler @command{@value{AS}}.
234 This version of the manual describes @command{@value{AS}} configured to generate
235 code for @value{TARGET} architectures.
239 @cindex invocation summary
240 @cindex option summary
241 @cindex summary of options
242 Here is a brief summary of how to invoke @command{@value{AS}}. For details,
243 @pxref{Invoking,,Comand-Line Options}.
245 @c man title AS the portable GNU assembler.
249 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
253 @c We don't use deffn and friends for the following because they seem
254 @c to be limited to one line for the header.
256 @c man begin SYNOPSIS
257 @value{AS} [@b{-a}[@b{cdhlns}][=@var{file}]] [@b{-D}] [@b{--defsym} @var{sym}=@var{val}]
258 [@b{-f}] [@b{--gstabs}] [@b{--gdwarf2}] [@b{--help}] [@b{-I} @var{dir}]
259 [@b{-J}] [@b{-K}] [@b{-L}]
260 [@b{--listing-lhs-width}=@var{NUM}] [@b{--listing-lhs-width2}=@var{NUM}]
261 [@b{--listing-rhs-width}=@var{NUM}] [@b{--listing-cont-lines}=@var{NUM}]
262 [@b{--keep-locals}] [@b{-o} @var{objfile}] [@b{-R}] [@b{--statistics}] [@b{-v}]
263 [@b{-version}] [@b{--version}] [@b{-W}] [@b{--warn}] [@b{--fatal-warnings}]
264 [@b{-w}] [@b{-x}] [@b{-Z}] [@b{--target-help}] [@var{target-options}]
265 [@b{--}|@var{files} @dots{}]
267 @c Target dependent options are listed below. Keep the list sorted.
268 @c Add an empty line for separation.
270 @c am29k has no machine-dependent assembler options
274 @emph{Target Alpha options:}
276 [@b{-mdebug} | @b{-no-mdebug}]
277 [@b{-relax}] [@b{-g}] [@b{-G@var{size}}]
278 [@b{-F}] [@b{-32addr}]
282 @emph{Target ARC options:}
288 @emph{Target ARM options:}
289 @c Don't document the deprecated options
290 [@b{-mcpu}=@var{processor}[+@var{extension}@dots{}]]
291 [@b{-march}=@var{architecture}[+@var{extension}@dots{}]]
292 [@b{-mfpu}=@var{floating-point-fromat}]
295 [@b{-mapcs-32}|@b{-mapcs-26}|@b{-mapcs-float}|
296 @b{-mapcs-reentrant}]
297 [@b{-mthumb-interwork}] [@b{-moabi}] [@b{-k}]
301 @emph{Target CRIS options:}
302 [@b{--underscore} | @b{--no-underscore}]
304 [@b{--emulation=criself} | @b{--emulation=crisaout}]
305 @c Deprecated -- deliberately not documented.
310 @emph{Target D10V options:}
315 @emph{Target D30V options:}
316 [@b{-O}|@b{-n}|@b{-N}]
319 @c Hitachi family chips have no machine-dependent assembler options
322 @c HPPA has no machine-dependent assembler options (yet).
326 @emph{Target i386 options:}
331 @emph{Target i960 options:}
332 @c see md_parse_option in tc-i960.c
333 [@b{-ACA}|@b{-ACA_A}|@b{-ACB}|@b{-ACC}|@b{-AKA}|@b{-AKB}|
335 [@b{-b}] [@b{-no-relax}]
339 @emph{Target IA-64 options:}
340 [@b{-mconstant-gp}|@b{-mauto-pic}]
341 [@b{-milp32}|@b{-milp64}|@b{-mlp64}|@b{-mp64}]
343 [@b{-x}|@b{-xexplicit}] [@b{-xauto}] [@b{-xdebug}]
347 @emph{Target M32R options:}
348 [@b{--m32rx}|@b{--[no-]warn-explicit-parallel-conflicts}|
353 @emph{Target M680X0 options:}
354 [@b{-l}] [@b{-m68000}|@b{-m68010}|@b{-m68020}|@dots{}]
358 @emph{Target M68HC11 options:}
359 [@b{-m68hc11}|@b{-m68hc12}]
360 [@b{--force-long-branchs}] [@b{--short-branchs}]
361 [@b{--strict-direct-mode}] [@b{--print-insn-syntax}]
362 [@b{--print-opcodes}] [@b{--generate-example}]
366 @emph{Target MCORE options:}
367 [@b{-jsri2bsr}] [@b{-sifilter}] [@b{-relax}]
368 [@b{-mcpu=[210|340]}]
372 @emph{Target MIPS options:}
373 [@b{-nocpp}] [@b{-EL}] [@b{-EB}] [@b{-n}] [@b{-O}[@var{optimization level}]]
374 [@b{-g}[@var{debug level}]] [@b{-G} @var{num}] [@b{-KPIC}] [@b{-call_shared}]
375 [@b{-non_shared}] [@b{-xgot}] [@b{--membedded-pic}]
376 [@b{-mabi}=@var{ABI}] [@b{-32}] [@b{-n32}] [@b{-64}] [@b{-mfp32}] [@b{-mgp32}]
377 [@b{-march}=@var{CPU}] [@b{-mtune}=@var{CPU}] [@b{-mips1}] [@b{-mips2}]
378 [@b{-mips3}] [@b{-mips4}] [@b{-mips5}] [@b{-mips32}] [@b{-mips64}]
379 [@b{-construct-floats}] [@b{-no-construct-floats}]
380 [@b{-trap}] [@b{-no-break}] [@b{-break}] [@b{-no-trap}]
381 [@b{-mfix7000}] [@b{-mno-fix7000}]
382 [@b{-mips16}] [@b{-no-mips16}]
383 [@b{-mips3d}] [@b{-no-mips3d}]
384 [@b{-mdmx}] [@b{-no-mdmx}]
388 @emph{Target MMIX options:}
389 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
390 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
391 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
392 [@b{--linker-allocated-gregs}]
396 @emph{Target PDP11 options:}
397 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
398 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
399 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
403 @emph{Target picoJava options:}
408 @emph{Target PowerPC options:}
409 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
410 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
411 @b{-mbooke32}|@b{-mbooke64}]
412 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
413 [@b{-mregnames}|@b{-mno-regnames}]
414 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
415 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
416 [@b{-msolaris}|@b{-mno-solaris}]
420 @emph{Target SPARC options:}
421 @c The order here is important. See c-sparc.texi.
422 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
423 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
424 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
429 @emph{Target TIC54X options:}
430 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
431 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
434 @c Z8000 has no machine-dependent assembler options
443 Turn on listings, in any of a variety of ways:
447 omit false conditionals
450 omit debugging directives
453 include high-level source
459 include macro expansions
462 omit forms processing
468 set the name of the listing file
471 You may combine these options; for example, use @samp{-aln} for assembly
472 listing without forms processing. The @samp{=file} option, if used, must be
473 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
476 Ignored. This option is accepted for script compatibility with calls to
479 @item --defsym @var{sym}=@var{value}
480 Define the symbol @var{sym} to be @var{value} before assembling the input file.
481 @var{value} must be an integer constant. As in C, a leading @samp{0x}
482 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
485 ``fast''---skip whitespace and comment preprocessing (assume source is
489 Generate stabs debugging information for each assembler line. This
490 may help debugging assembler code, if the debugger can handle it.
493 Generate DWARF2 debugging information for each assembler line. This
494 may help debugging assembler code, if the debugger can handle it. Note - this
495 option is only supported by some targets, not all of them.
498 Print a summary of the command line options and exit.
501 Print a summary of all target specific options and exit.
504 Add directory @var{dir} to the search list for @code{.include} directives.
507 Don't warn about signed overflow.
510 @ifclear DIFF-TBL-KLUGE
511 This option is accepted but has no effect on the @value{TARGET} family.
513 @ifset DIFF-TBL-KLUGE
514 Issue warnings when difference tables altered for long displacements.
519 Keep (in the symbol table) local symbols. On traditional a.out systems
520 these start with @samp{L}, but different systems have different local
523 @item --listing-lhs-width=@var{number}
524 Set the maximum width, in words, of the output data column for an assembler
525 listing to @var{number}.
527 @item --listing-lhs-width2=@var{number}
528 Set the maximum width, in words, of the output data column for continuation
529 lines in an assembler listing to @var{number}.
531 @item --listing-rhs-width=@var{number}
532 Set the maximum width of an input source line, as displayed in a listing, to
535 @item --listing-cont-lines=@var{number}
536 Set the maximum number of lines printed in a listing for a single line of input
539 @item -o @var{objfile}
540 Name the object-file output from @command{@value{AS}} @var{objfile}.
543 Fold the data section into the text section.
546 Print the maximum space (in bytes) and total time (in seconds) used by
549 @item --strip-local-absolute
550 Remove local absolute symbols from the outgoing symbol table.
554 Print the @command{as} version.
557 Print the @command{as} version and exit.
561 Suppress warning messages.
563 @item --fatal-warnings
564 Treat warnings as errors.
567 Don't suppress warning messages or treat them as errors.
576 Generate an object file even after errors.
578 @item -- | @var{files} @dots{}
579 Standard input, or source files to assemble.
584 The following options are available when @value{AS} is configured for
589 This option selects the core processor variant.
591 Select either big-endian (-EB) or little-endian (-EL) output.
596 The following options are available when @value{AS} is configured for the ARM
600 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
601 Specify which ARM processor variant is the target.
602 @item -march=@var{architecture}[+@var{extension}@dots{}]
603 Specify which ARM architecture variant is used by the target.
604 @item -mfpu=@var{floating-point-format}
605 Select which Floating Point architecture is the target.
607 Enable Thumb only instruction decoding.
608 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
609 Select which procedure calling convention is in use.
611 Select either big-endian (-EB) or little-endian (-EL) output.
612 @item -mthumb-interwork
613 Specify that the code has been generated with interworking between Thumb and
616 Specify that PIC code has been generated.
621 See the info pages for documentation of the CRIS-specific options.
625 The following options are available when @value{AS} is configured for
628 @cindex D10V optimization
629 @cindex optimization, D10V
631 Optimize output by parallelizing instructions.
636 The following options are available when @value{AS} is configured for a D30V
639 @cindex D30V optimization
640 @cindex optimization, D30V
642 Optimize output by parallelizing instructions.
646 Warn when nops are generated.
648 @cindex D30V nops after 32-bit multiply
650 Warn when a nop after a 32-bit multiply instruction is generated.
655 The following options are available when @value{AS} is configured for the
656 Intel 80960 processor.
659 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
660 Specify which variant of the 960 architecture is the target.
663 Add code to collect statistics about branches taken.
666 Do not alter compare-and-branch instructions for long displacements;
673 The following options are available when @value{AS} is configured for the
674 Mitsubishi M32R series.
679 Specify which processor in the M32R family is the target. The default
680 is normally the M32R, but this option changes it to the M32RX.
682 @item --warn-explicit-parallel-conflicts or --Wp
683 Produce warning messages when questionable parallel constructs are
686 @item --no-warn-explicit-parallel-conflicts or --Wnp
687 Do not produce warning messages when questionable parallel constructs are
694 The following options are available when @value{AS} is configured for the
695 Motorola 68000 series.
700 Shorten references to undefined symbols, to one word instead of two.
702 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
703 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
704 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
705 Specify what processor in the 68000 family is the target. The default
706 is normally the 68020, but this can be changed at configuration time.
708 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
709 The target machine does (or does not) have a floating-point coprocessor.
710 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
711 the basic 68000 is not compatible with the 68881, a combination of the
712 two can be specified, since it's possible to do emulation of the
713 coprocessor instructions with the main processor.
715 @item -m68851 | -mno-68851
716 The target machine does (or does not) have a memory-management
717 unit coprocessor. The default is to assume an MMU for 68020 and up.
724 For details about the PDP-11 machine dependent features options,
725 see @ref{PDP-11-Options}.
728 @item -mpic | -mno-pic
729 Generate position-independent (or position-dependent) code. The
730 default is @option{-mpic}.
733 @itemx -mall-extensions
734 Enable all instruction set extensions. This is the default.
736 @item -mno-extensions
737 Disable all instruction set extensions.
739 @item -m@var{extension} | -mno-@var{extension}
740 Enable (or disable) a particular instruction set extension.
743 Enable the instruction set extensions supported by a particular CPU, and
744 disable all other extensions.
746 @item -m@var{machine}
747 Enable the instruction set extensions supported by a particular machine
748 model, and disable all other extensions.
754 The following options are available when @value{AS} is configured for
755 a picoJava processor.
759 @cindex PJ endianness
760 @cindex endianness, PJ
761 @cindex big endian output, PJ
763 Generate ``big endian'' format output.
765 @cindex little endian output, PJ
767 Generate ``little endian'' format output.
773 The following options are available when @value{AS} is configured for the
774 Motorola 68HC11 or 68HC12 series.
778 @item -m68hc11 | -m68hc12
779 Specify what processor is the target. The default is
780 defined by the configuration option when building the assembler.
782 @item --force-long-branchs
783 Relative branches are turned into absolute ones. This concerns
784 conditional branches, unconditional branches and branches to a
787 @item -S | --short-branchs
788 Do not turn relative branchs into absolute ones
789 when the offset is out of range.
791 @item --strict-direct-mode
792 Do not turn the direct addressing mode into extended addressing mode
793 when the instruction does not support direct addressing mode.
795 @item --print-insn-syntax
796 Print the syntax of instruction in case of error.
798 @item --print-opcodes
799 print the list of instructions with syntax and then exit.
801 @item --generate-example
802 print an example of instruction for each possible instruction and then exit.
803 This option is only useful for testing @command{@value{AS}}.
809 The following options are available when @command{@value{AS}} is configured
810 for the SPARC architecture:
813 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
814 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
815 Explicitly select a variant of the SPARC architecture.
817 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
818 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
820 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
821 UltraSPARC extensions.
823 @item -xarch=v8plus | -xarch=v8plusa
824 For compatibility with the Solaris v9 assembler. These options are
825 equivalent to -Av8plus and -Av8plusa, respectively.
828 Warn when the assembler switches to another architecture.
833 The following options are available when @value{AS} is configured for the 'c54x
838 Enable extended addressing mode. All addresses and relocations will assume
839 extended addressing (usually 23 bits).
840 @item -mcpu=@var{CPU_VERSION}
841 Sets the CPU version being compiled for.
842 @item -merrors-to-file @var{FILENAME}
843 Redirect error output to a file, for broken systems which don't support such
844 behaviour in the shell.
849 The following options are available when @value{AS} is configured for
850 a @sc{mips} processor.
854 This option sets the largest size of an object that can be referenced
855 implicitly with the @code{gp} register. It is only accepted for targets that
856 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
858 @cindex MIPS endianness
859 @cindex endianness, MIPS
860 @cindex big endian output, MIPS
862 Generate ``big endian'' format output.
864 @cindex little endian output, MIPS
866 Generate ``little endian'' format output.
876 Generate code for a particular @sc{mips} Instruction Set Architecture level.
877 @samp{-mips1} is an alias for @samp{-march=r3000}, @samp{-mips2} is an
878 alias for @samp{-march=r6000}, @samp{-mips3} is an alias for
879 @samp{-march=r4000} and @samp{-mips4} is an alias for @samp{-march=r8000}.
880 @samp{-mips5}, @samp{-mips32}, and @samp{-mips64} correspond to generic
881 @samp{MIPS V}, @samp{MIPS32}, and @samp{MIPS64} ISA processors,
884 @item -march=@var{CPU}
885 Generate code for a particular @sc{mips} cpu.
887 @item -mtune=@var{cpu}
888 Schedule and tune for a particular @sc{mips} cpu.
892 Cause nops to be inserted if the read of the destination register
893 of an mfhi or mflo instruction occurs in the following two instructions.
897 The register sizes are normally inferred from the ISA and ABI, but these
898 flags force a certain group of registers to be treated as 32 bits wide at
899 all times. @samp{-mgp32} controls the size of general-purpose registers
900 and @samp{-mfp32} controls the size of floating-point registers.
904 Generate code for the MIPS 16 processor. This is equivalent to putting
905 @code{.set mips16} at the start of the assembly file. @samp{-no-mips16}
906 turns off this option.
910 Generate code for the MIPS-3D Application Specific Extension.
911 This tells the assembler to accept MIPS-3D instructions.
912 @samp{-no-mips3d} turns off this option.
916 Generate code for the MDMX Application Specific Extension.
917 This tells the assembler to accept MDMX instructions.
918 @samp{-no-mdmx} turns off this option.
920 @item --construct-floats
921 @itemx --no-construct-floats
922 The @samp{--no-construct-floats} option disables the construction of
923 double width floating point constants by loading the two halves of the
924 value into the two single width floating point registers that make up
925 the double width register. By default @samp{--construct-floats} is
926 selected, allowing construction of these floating point constants.
929 @item --emulation=@var{name}
930 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
931 for some other target, in all respects, including output format (choosing
932 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
933 debugging information or store symbol table information, and default
934 endianness. The available configuration names are: @samp{mipsecoff},
935 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
936 @samp{mipsbelf}. The first two do not alter the default endianness from that
937 of the primary target for which the assembler was configured; the others change
938 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
939 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
940 selection in any case.
942 This option is currently supported only when the primary target
943 @command{@value{AS}} is configured for is a @sc{mips} ELF or ECOFF target.
944 Furthermore, the primary target or others specified with
945 @samp{--enable-targets=@dots{}} at configuration time must include support for
946 the other format, if both are to be available. For example, the Irix 5
947 configuration includes support for both.
949 Eventually, this option will support more configurations, with more
950 fine-grained control over the assembler's behavior, and will be supported for
954 @command{@value{AS}} ignores this option. It is accepted for compatibility with
961 Control how to deal with multiplication overflow and division by zero.
962 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
963 (and only work for Instruction Set Architecture level 2 and higher);
964 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
968 When this option is used, @command{@value{AS}} will issue a warning every
969 time it generates a nop instruction from a macro.
974 The following options are available when @value{AS} is configured for
980 Enable or disable the JSRI to BSR transformation. By default this is enabled.
981 The command line option @samp{-nojsri2bsr} can be used to disable it.
985 Enable or disable the silicon filter behaviour. By default this is disabled.
986 The default can be overridden by the @samp{-sifilter} command line option.
989 Alter jump instructions for long displacements.
991 @item -mcpu=[210|340]
992 Select the cpu type on the target hardware. This controls which instructions
996 Assemble for a big endian target.
999 Assemble for a little endian target.
1005 See the info pages for documentation of the MMIX-specific options.
1011 * Manual:: Structure of this Manual
1012 * GNU Assembler:: The GNU Assembler
1013 * Object Formats:: Object File Formats
1014 * Command Line:: Command Line
1015 * Input Files:: Input Files
1016 * Object:: Output (Object) File
1017 * Errors:: Error and Warning Messages
1021 @section Structure of this Manual
1023 @cindex manual, structure and purpose
1024 This manual is intended to describe what you need to know to use
1025 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
1026 notation for symbols, constants, and expressions; the directives that
1027 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
1030 We also cover special features in the @value{TARGET}
1031 configuration of @command{@value{AS}}, including assembler directives.
1034 This manual also describes some of the machine-dependent features of
1035 various flavors of the assembler.
1038 @cindex machine instructions (not covered)
1039 On the other hand, this manual is @emph{not} intended as an introduction
1040 to programming in assembly language---let alone programming in general!
1041 In a similar vein, we make no attempt to introduce the machine
1042 architecture; we do @emph{not} describe the instruction set, standard
1043 mnemonics, registers or addressing modes that are standard to a
1044 particular architecture.
1046 You may want to consult the manufacturer's
1047 machine architecture manual for this information.
1051 For information on the H8/300 machine instruction set, see @cite{H8/300
1052 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
1053 see @cite{H8/300H Series Programming Manual} (Hitachi).
1056 For information on the H8/500 machine instruction set, see @cite{H8/500
1057 Series Programming Manual} (Hitachi M21T001).
1060 For information on the Hitachi SH machine instruction set, see
1061 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
1064 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1068 @c I think this is premature---doc@cygnus.com, 17jan1991
1070 Throughout this manual, we assume that you are running @dfn{GNU},
1071 the portable operating system from the @dfn{Free Software
1072 Foundation, Inc.}. This restricts our attention to certain kinds of
1073 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1074 once this assumption is granted examples and definitions need less
1077 @command{@value{AS}} is part of a team of programs that turn a high-level
1078 human-readable series of instructions into a low-level
1079 computer-readable series of instructions. Different versions of
1080 @command{@value{AS}} are used for different kinds of computer.
1083 @c There used to be a section "Terminology" here, which defined
1084 @c "contents", "byte", "word", and "long". Defining "word" to any
1085 @c particular size is confusing when the .word directive may generate 16
1086 @c bits on one machine and 32 bits on another; in general, for the user
1087 @c version of this manual, none of these terms seem essential to define.
1088 @c They were used very little even in the former draft of the manual;
1089 @c this draft makes an effort to avoid them (except in names of
1093 @section The GNU Assembler
1095 @c man begin DESCRIPTION
1097 @sc{gnu} @command{as} is really a family of assemblers.
1099 This manual describes @command{@value{AS}}, a member of that family which is
1100 configured for the @value{TARGET} architectures.
1102 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1103 should find a fairly similar environment when you use it on another
1104 architecture. Each version has much in common with the others,
1105 including object file formats, most assembler directives (often called
1106 @dfn{pseudo-ops}) and assembler syntax.@refill
1108 @cindex purpose of @sc{gnu} assembler
1109 @command{@value{AS}} is primarily intended to assemble the output of the
1110 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1111 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1112 assemble correctly everything that other assemblers for the same
1113 machine would assemble.
1115 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1118 @c This remark should appear in generic version of manual; assumption
1119 @c here is that generic version sets M680x0.
1120 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1121 assembler for the same architecture; for example, we know of several
1122 incompatible versions of 680x0 assembly language syntax.
1127 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1128 program in one pass of the source file. This has a subtle impact on the
1129 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1131 @node Object Formats
1132 @section Object File Formats
1134 @cindex object file format
1135 The @sc{gnu} assembler can be configured to produce several alternative
1136 object file formats. For the most part, this does not affect how you
1137 write assembly language programs; but directives for debugging symbols
1138 are typically different in different file formats. @xref{Symbol
1139 Attributes,,Symbol Attributes}.
1142 On the @value{TARGET}, @command{@value{AS}} is configured to produce
1143 @value{OBJ-NAME} format object files.
1145 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1147 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1148 @code{a.out} or COFF format object files.
1151 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1152 @code{b.out} or COFF format object files.
1155 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1156 SOM or ELF format object files.
1161 @section Command Line
1163 @cindex command line conventions
1165 After the program name @command{@value{AS}}, the command line may contain
1166 options and file names. Options may appear in any order, and may be
1167 before, after, or between file names. The order of file names is
1170 @cindex standard input, as input file
1172 @file{--} (two hyphens) by itself names the standard input file
1173 explicitly, as one of the files for @command{@value{AS}} to assemble.
1175 @cindex options, command line
1176 Except for @samp{--} any command line argument that begins with a
1177 hyphen (@samp{-}) is an option. Each option changes the behavior of
1178 @command{@value{AS}}. No option changes the way another option works. An
1179 option is a @samp{-} followed by one or more letters; the case of
1180 the letter is important. All options are optional.
1182 Some options expect exactly one file name to follow them. The file
1183 name may either immediately follow the option's letter (compatible
1184 with older assemblers) or it may be the next command argument (@sc{gnu}
1185 standard). These two command lines are equivalent:
1188 @value{AS} -o my-object-file.o mumble.s
1189 @value{AS} -omy-object-file.o mumble.s
1193 @section Input Files
1196 @cindex source program
1197 @cindex files, input
1198 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1199 describe the program input to one run of @command{@value{AS}}. The program may
1200 be in one or more files; how the source is partitioned into files
1201 doesn't change the meaning of the source.
1203 @c I added "con" prefix to "catenation" just to prove I can overcome my
1204 @c APL training... doc@cygnus.com
1205 The source program is a concatenation of the text in all the files, in the
1208 @c man begin DESCRIPTION
1209 Each time you run @command{@value{AS}} it assembles exactly one source
1210 program. The source program is made up of one or more files.
1211 (The standard input is also a file.)
1213 You give @command{@value{AS}} a command line that has zero or more input file
1214 names. The input files are read (from left file name to right). A
1215 command line argument (in any position) that has no special meaning
1216 is taken to be an input file name.
1218 If you give @command{@value{AS}} no file names it attempts to read one input file
1219 from the @command{@value{AS}} standard input, which is normally your terminal. You
1220 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1223 Use @samp{--} if you need to explicitly name the standard input file
1224 in your command line.
1226 If the source is empty, @command{@value{AS}} produces a small, empty object
1231 @subheading Filenames and Line-numbers
1233 @cindex input file linenumbers
1234 @cindex line numbers, in input files
1235 There are two ways of locating a line in the input file (or files) and
1236 either may be used in reporting error messages. One way refers to a line
1237 number in a physical file; the other refers to a line number in a
1238 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1240 @dfn{Physical files} are those files named in the command line given
1241 to @command{@value{AS}}.
1243 @dfn{Logical files} are simply names declared explicitly by assembler
1244 directives; they bear no relation to physical files. Logical file names help
1245 error messages reflect the original source file, when @command{@value{AS}} source
1246 is itself synthesized from other files. @command{@value{AS}} understands the
1247 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1248 @ref{File,,@code{.file}}.
1251 @section Output (Object) File
1257 Every time you run @command{@value{AS}} it produces an output file, which is
1258 your assembly language program translated into numbers. This file
1259 is the object file. Its default name is
1267 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1269 You can give it another name by using the @option{-o} option. Conventionally,
1270 object file names end with @file{.o}. The default name is used for historical
1271 reasons: older assemblers were capable of assembling self-contained programs
1272 directly into a runnable program. (For some formats, this isn't currently
1273 possible, but it can be done for the @code{a.out} format.)
1277 The object file is meant for input to the linker @code{@value{LD}}. It contains
1278 assembled program code, information to help @code{@value{LD}} integrate
1279 the assembled program into a runnable file, and (optionally) symbolic
1280 information for the debugger.
1282 @c link above to some info file(s) like the description of a.out.
1283 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1286 @section Error and Warning Messages
1288 @c man begin DESCRIPTION
1290 @cindex error messages
1291 @cindex warning messages
1292 @cindex messages from assembler
1293 @command{@value{AS}} may write warnings and error messages to the standard error
1294 file (usually your terminal). This should not happen when a compiler
1295 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1296 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1297 grave problem that stops the assembly.
1301 @cindex format of warning messages
1302 Warning messages have the format
1305 file_name:@b{NNN}:Warning Message Text
1309 @cindex line numbers, in warnings/errors
1310 (where @b{NNN} is a line number). If a logical file name has been given
1311 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1312 the current input file is used. If a logical line number was given
1314 (@pxref{Line,,@code{.line}})
1318 (@pxref{Line,,@code{.line}})
1321 (@pxref{Ln,,@code{.ln}})
1324 then it is used to calculate the number printed,
1325 otherwise the actual line in the current source file is printed. The
1326 message text is intended to be self explanatory (in the grand Unix
1329 @cindex format of error messages
1330 Error messages have the format
1332 file_name:@b{NNN}:FATAL:Error Message Text
1334 The file name and line number are derived as for warning
1335 messages. The actual message text may be rather less explanatory
1336 because many of them aren't supposed to happen.
1339 @chapter Command-Line Options
1341 @cindex options, all versions of assembler
1342 This chapter describes command-line options available in @emph{all}
1343 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1345 to the @value{TARGET}.
1348 to particular machine architectures.
1351 @c man begin DESCRIPTION
1353 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler (version 2),
1354 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1355 The assembler arguments must be separated from each other (and the @samp{-Wa})
1356 by commas. For example:
1359 gcc -c -g -O -Wa,-alh,-L file.c
1363 This passes two options to the assembler: @samp{-alh} (emit a listing to
1364 standard output with with high-level and assembly source) and @samp{-L} (retain
1365 local symbols in the symbol table).
1367 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1368 command-line options are automatically passed to the assembler by the compiler.
1369 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1370 precisely what options it passes to each compilation pass, including the
1376 * a:: -a[cdhlns] enable listings
1377 * D:: -D for compatibility
1378 * f:: -f to work faster
1379 * I:: -I for .include search path
1380 @ifclear DIFF-TBL-KLUGE
1381 * K:: -K for compatibility
1383 @ifset DIFF-TBL-KLUGE
1384 * K:: -K for difference tables
1387 * L:: -L to retain local labels
1388 * listing:: --listing-XXX to configure listing output
1389 * M:: -M or --mri to assemble in MRI compatibility mode
1390 * MD:: --MD for dependency tracking
1391 * o:: -o to name the object file
1392 * R:: -R to join data and text sections
1393 * statistics:: --statistics to see statistics about assembly
1394 * traditional-format:: --traditional-format for compatible output
1395 * v:: -v to announce version
1396 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1397 * Z:: -Z to make object file even after errors
1401 @section Enable Listings: @option{-a[cdhlns]}
1410 @cindex listings, enabling
1411 @cindex assembly listings, enabling
1413 These options enable listing output from the assembler. By itself,
1414 @samp{-a} requests high-level, assembly, and symbols listing.
1415 You can use other letters to select specific options for the list:
1416 @samp{-ah} requests a high-level language listing,
1417 @samp{-al} requests an output-program assembly listing, and
1418 @samp{-as} requests a symbol table listing.
1419 High-level listings require that a compiler debugging option like
1420 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1423 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1424 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1425 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1426 omitted from the listing.
1428 Use the @samp{-ad} option to omit debugging directives from the
1431 Once you have specified one of these options, you can further control
1432 listing output and its appearance using the directives @code{.list},
1433 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1435 The @samp{-an} option turns off all forms processing.
1436 If you do not request listing output with one of the @samp{-a} options, the
1437 listing-control directives have no effect.
1439 The letters after @samp{-a} may be combined into one option,
1440 @emph{e.g.}, @samp{-aln}.
1442 Note if the assembler source is coming from the standard input (eg because it
1443 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1444 is being used) then the listing will not contain any comments or preprocessor
1445 directives. This is because the listing code buffers input source lines from
1446 stdin only after they have been preprocessed by the assembler. This reduces
1447 memory usage and makes the code more efficient.
1450 @section @option{-D}
1453 This option has no effect whatsoever, but it is accepted to make it more
1454 likely that scripts written for other assemblers also work with
1455 @command{@value{AS}}.
1458 @section Work Faster: @option{-f}
1461 @cindex trusted compiler
1462 @cindex faster processing (@option{-f})
1463 @samp{-f} should only be used when assembling programs written by a
1464 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1465 and comment preprocessing on
1466 the input file(s) before assembling them. @xref{Preprocessing,
1470 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1471 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1476 @section @code{.include} search path: @option{-I} @var{path}
1478 @kindex -I @var{path}
1479 @cindex paths for @code{.include}
1480 @cindex search path for @code{.include}
1481 @cindex @code{include} directive search path
1482 Use this option to add a @var{path} to the list of directories
1483 @command{@value{AS}} searches for files specified in @code{.include}
1484 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1485 many times as necessary to include a variety of paths. The current
1486 working directory is always searched first; after that, @command{@value{AS}}
1487 searches any @samp{-I} directories in the same order as they were
1488 specified (left to right) on the command line.
1491 @section Difference Tables: @option{-K}
1494 @ifclear DIFF-TBL-KLUGE
1495 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1496 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1497 where it can be used to warn when the assembler alters the machine code
1498 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1499 family does not have the addressing limitations that sometimes lead to this
1500 alteration on other platforms.
1503 @ifset DIFF-TBL-KLUGE
1504 @cindex difference tables, warning
1505 @cindex warning for altered difference tables
1506 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1507 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1508 You can use the @samp{-K} option if you want a warning issued when this
1513 @section Include Local Labels: @option{-L}
1516 @cindex local labels, retaining in output
1517 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1518 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1519 debugging, because they are intended for the use of programs (like
1520 compilers) that compose assembler programs, not for your notice.
1521 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1522 normally debug with them.
1524 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1525 in the object file. Usually if you do this you also tell the linker
1526 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1528 By default, a local label is any label beginning with @samp{L}, but each
1529 target is allowed to redefine the local label prefix.
1531 On the HPPA local labels begin with @samp{L$}.
1535 @section Configuring listing output: @option{--listing}
1537 The listing feature of the assembler can be enabled via the command line switch
1538 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1539 hex dump of the corresponding locations in the output object file, and displays
1540 them as a listing file. The format of this listing can be controlled by pseudo
1541 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1542 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1545 @item --listing-lhs-width=@samp{number}
1546 @kindex --listing-lhs-width
1547 @cindex Width of first line disassembly output
1548 Sets the maximum width, in words, of the first line of the hex byte dump. This
1549 dump appears on the left hand side of the listing output.
1551 @item --listing-lhs-width2=@samp{number}
1552 @kindex --listing-lhs-width2
1553 @cindex Width of continuation lines of disassembly output
1554 Sets the maximum width, in words, of any further lines of the hex byte dump for
1555 a given inut source line. If this value is not specified, it defaults to being
1556 the same as the value specified for @samp{--listing-lhs-width}. If neither
1557 switch is used the default is to one.
1559 @item --listing-rhs-width=@samp{number}
1560 @kindex --listing-rhs-width
1561 @cindex Width of source line output
1562 Sets the maximum width, in characters, of the source line that is displayed
1563 alongside the hex dump. The default value for this parameter is 100. The
1564 source line is displayed on the right hand side of the listing output.
1566 @item --listing-cont-lines=@samp{number}
1567 @kindex --listing-cont-lines
1568 @cindex Maximum number of continuation lines
1569 Sets the maximum number of continuation lines of hex dump that will be
1570 displayed for a given single line of source input. The default value is 4.
1574 @section Assemble in MRI Compatibility Mode: @option{-M}
1577 @cindex MRI compatibility mode
1578 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1579 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1580 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1581 configured target) assembler from Microtec Research. The exact nature of the
1582 MRI syntax will not be documented here; see the MRI manuals for more
1583 information. Note in particular that the handling of macros and macro
1584 arguments is somewhat different. The purpose of this option is to permit
1585 assembling existing MRI assembler code using @command{@value{AS}}.
1587 The MRI compatibility is not complete. Certain operations of the MRI assembler
1588 depend upon its object file format, and can not be supported using other object
1589 file formats. Supporting these would require enhancing each object file format
1590 individually. These are:
1593 @item global symbols in common section
1595 The m68k MRI assembler supports common sections which are merged by the linker.
1596 Other object file formats do not support this. @command{@value{AS}} handles
1597 common sections by treating them as a single common symbol. It permits local
1598 symbols to be defined within a common section, but it can not support global
1599 symbols, since it has no way to describe them.
1601 @item complex relocations
1603 The MRI assemblers support relocations against a negated section address, and
1604 relocations which combine the start addresses of two or more sections. These
1605 are not support by other object file formats.
1607 @item @code{END} pseudo-op specifying start address
1609 The MRI @code{END} pseudo-op permits the specification of a start address.
1610 This is not supported by other object file formats. The start address may
1611 instead be specified using the @option{-e} option to the linker, or in a linker
1614 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1616 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1617 name to the output file. This is not supported by other object file formats.
1619 @item @code{ORG} pseudo-op
1621 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1622 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1623 which changes the location within the current section. Absolute sections are
1624 not supported by other object file formats. The address of a section may be
1625 assigned within a linker script.
1628 There are some other features of the MRI assembler which are not supported by
1629 @command{@value{AS}}, typically either because they are difficult or because they
1630 seem of little consequence. Some of these may be supported in future releases.
1634 @item EBCDIC strings
1636 EBCDIC strings are not supported.
1638 @item packed binary coded decimal
1640 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1641 and @code{DCB.P} pseudo-ops are not supported.
1643 @item @code{FEQU} pseudo-op
1645 The m68k @code{FEQU} pseudo-op is not supported.
1647 @item @code{NOOBJ} pseudo-op
1649 The m68k @code{NOOBJ} pseudo-op is not supported.
1651 @item @code{OPT} branch control options
1653 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1654 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1655 relaxes all branches, whether forward or backward, to an appropriate size, so
1656 these options serve no purpose.
1658 @item @code{OPT} list control options
1660 The following m68k @code{OPT} list control options are ignored: @code{C},
1661 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1662 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1664 @item other @code{OPT} options
1666 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1667 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1669 @item @code{OPT} @code{D} option is default
1671 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1672 @code{OPT NOD} may be used to turn it off.
1674 @item @code{XREF} pseudo-op.
1676 The m68k @code{XREF} pseudo-op is ignored.
1678 @item @code{.debug} pseudo-op
1680 The i960 @code{.debug} pseudo-op is not supported.
1682 @item @code{.extended} pseudo-op
1684 The i960 @code{.extended} pseudo-op is not supported.
1686 @item @code{.list} pseudo-op.
1688 The various options of the i960 @code{.list} pseudo-op are not supported.
1690 @item @code{.optimize} pseudo-op
1692 The i960 @code{.optimize} pseudo-op is not supported.
1694 @item @code{.output} pseudo-op
1696 The i960 @code{.output} pseudo-op is not supported.
1698 @item @code{.setreal} pseudo-op
1700 The i960 @code{.setreal} pseudo-op is not supported.
1705 @section Dependency tracking: @option{--MD}
1708 @cindex dependency tracking
1711 @command{@value{AS}} can generate a dependency file for the file it creates. This
1712 file consists of a single rule suitable for @code{make} describing the
1713 dependencies of the main source file.
1715 The rule is written to the file named in its argument.
1717 This feature is used in the automatic updating of makefiles.
1720 @section Name the Object File: @option{-o}
1723 @cindex naming object file
1724 @cindex object file name
1725 There is always one object file output when you run @command{@value{AS}}. By
1726 default it has the name
1729 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1743 You use this option (which takes exactly one filename) to give the
1744 object file a different name.
1746 Whatever the object file is called, @command{@value{AS}} overwrites any
1747 existing file of the same name.
1750 @section Join Data and Text Sections: @option{-R}
1753 @cindex data and text sections, joining
1754 @cindex text and data sections, joining
1755 @cindex joining text and data sections
1756 @cindex merging text and data sections
1757 @option{-R} tells @command{@value{AS}} to write the object file as if all
1758 data-section data lives in the text section. This is only done at
1759 the very last moment: your binary data are the same, but data
1760 section parts are relocated differently. The data section part of
1761 your object file is zero bytes long because all its bytes are
1762 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1764 When you specify @option{-R} it would be possible to generate shorter
1765 address displacements (because we do not have to cross between text and
1766 data section). We refrain from doing this simply for compatibility with
1767 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1770 When @command{@value{AS}} is configured for COFF output,
1771 this option is only useful if you use sections named @samp{.text} and
1776 @option{-R} is not supported for any of the HPPA targets. Using
1777 @option{-R} generates a warning from @command{@value{AS}}.
1781 @section Display Assembly Statistics: @option{--statistics}
1783 @kindex --statistics
1784 @cindex statistics, about assembly
1785 @cindex time, total for assembly
1786 @cindex space used, maximum for assembly
1787 Use @samp{--statistics} to display two statistics about the resources used by
1788 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1789 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1792 @node traditional-format
1793 @section Compatible output: @option{--traditional-format}
1795 @kindex --traditional-format
1796 For some targets, the output of @command{@value{AS}} is different in some ways
1797 from the output of some existing assembler. This switch requests
1798 @command{@value{AS}} to use the traditional format instead.
1800 For example, it disables the exception frame optimizations which
1801 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1804 @section Announce Version: @option{-v}
1808 @cindex assembler version
1809 @cindex version of assembler
1810 You can find out what version of as is running by including the
1811 option @samp{-v} (which you can also spell as @samp{-version}) on the
1815 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1817 @command{@value{AS}} should never give a warning or error message when
1818 assembling compiler output. But programs written by people often
1819 cause @command{@value{AS}} to give a warning that a particular assumption was
1820 made. All such warnings are directed to the standard error file.
1823 @kindex @samp{--no-warn}
1824 @cindex suppressing warnings
1825 @cindex warnings, suppressing
1826 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1827 This only affects the warning messages: it does not change any particular of
1828 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1831 @kindex @samp{--fatal-warnings}
1832 @cindex errors, caused by warnings
1833 @cindex warnings, causing error
1834 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1835 files that generate warnings to be in error.
1837 @kindex @samp{--warn}
1838 @cindex warnings, switching on
1839 You can switch these options off again by specifying @option{--warn}, which
1840 causes warnings to be output as usual.
1843 @section Generate Object File in Spite of Errors: @option{-Z}
1844 @cindex object file, after errors
1845 @cindex errors, continuing after
1846 After an error message, @command{@value{AS}} normally produces no output. If for
1847 some reason you are interested in object file output even after
1848 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1849 option. If there are any errors, @command{@value{AS}} continues anyways, and
1850 writes an object file after a final warning message of the form @samp{@var{n}
1851 errors, @var{m} warnings, generating bad object file.}
1856 @cindex machine-independent syntax
1857 @cindex syntax, machine-independent
1858 This chapter describes the machine-independent syntax allowed in a
1859 source file. @command{@value{AS}} syntax is similar to what many other
1860 assemblers use; it is inspired by the BSD 4.2
1865 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1869 * Preprocessing:: Preprocessing
1870 * Whitespace:: Whitespace
1871 * Comments:: Comments
1872 * Symbol Intro:: Symbols
1873 * Statements:: Statements
1874 * Constants:: Constants
1878 @section Preprocessing
1880 @cindex preprocessing
1881 The @command{@value{AS}} internal preprocessor:
1883 @cindex whitespace, removed by preprocessor
1885 adjusts and removes extra whitespace. It leaves one space or tab before
1886 the keywords on a line, and turns any other whitespace on the line into
1889 @cindex comments, removed by preprocessor
1891 removes all comments, replacing them with a single space, or an
1892 appropriate number of newlines.
1894 @cindex constants, converted by preprocessor
1896 converts character constants into the appropriate numeric values.
1899 It does not do macro processing, include file handling, or
1900 anything else you may get from your C compiler's preprocessor. You can
1901 do include file processing with the @code{.include} directive
1902 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1903 to get other ``CPP'' style preprocessing, by giving the input file a
1904 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1905 Output, gcc.info, Using GNU CC}.
1907 Excess whitespace, comments, and character constants
1908 cannot be used in the portions of the input text that are not
1911 @cindex turning preprocessing on and off
1912 @cindex preprocessing, turning on and off
1915 If the first line of an input file is @code{#NO_APP} or if you use the
1916 @samp{-f} option, whitespace and comments are not removed from the input file.
1917 Within an input file, you can ask for whitespace and comment removal in
1918 specific portions of the by putting a line that says @code{#APP} before the
1919 text that may contain whitespace or comments, and putting a line that says
1920 @code{#NO_APP} after this text. This feature is mainly intend to support
1921 @code{asm} statements in compilers whose output is otherwise free of comments
1928 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1929 Whitespace is used to separate symbols, and to make programs neater for
1930 people to read. Unless within character constants
1931 (@pxref{Characters,,Character Constants}), any whitespace means the same
1932 as exactly one space.
1938 There are two ways of rendering comments to @command{@value{AS}}. In both
1939 cases the comment is equivalent to one space.
1941 Anything from @samp{/*} through the next @samp{*/} is a comment.
1942 This means you may not nest these comments.
1946 The only way to include a newline ('\n') in a comment
1947 is to use this sort of comment.
1950 /* This sort of comment does not nest. */
1953 @cindex line comment character
1954 Anything from the @dfn{line comment} character to the next newline
1955 is considered a comment and is ignored. The line comment character is
1957 @samp{;} for the AMD 29K family;
1960 @samp{;} on the ARC;
1963 @samp{@@} on the ARM;
1966 @samp{;} for the H8/300 family;
1969 @samp{!} for the H8/500 family;
1972 @samp{;} for the HPPA;
1975 @samp{#} on the i386 and x86-64;
1978 @samp{#} on the i960;
1981 @samp{;} for the PDP-11;
1984 @samp{;} for picoJava;
1987 @samp{;} for Motorola PowerPC;
1990 @samp{!} for the Hitachi SH;
1993 @samp{!} on the SPARC;
1996 @samp{#} on the m32r;
1999 @samp{|} on the 680x0;
2002 @samp{#} on the 68HC11 and 68HC12;
2005 @samp{;} on the M880x0;
2008 @samp{#} on the Vax;
2011 @samp{!} for the Z8000;
2014 @samp{#} on the V850;
2016 see @ref{Machine Dependencies}. @refill
2017 @c FIXME What about i860?
2020 On some machines there are two different line comment characters. One
2021 character only begins a comment if it is the first non-whitespace character on
2022 a line, while the other always begins a comment.
2026 The V850 assembler also supports a double dash as starting a comment that
2027 extends to the end of the line.
2033 @cindex lines starting with @code{#}
2034 @cindex logical line numbers
2035 To be compatible with past assemblers, lines that begin with @samp{#} have a
2036 special interpretation. Following the @samp{#} should be an absolute
2037 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2038 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2039 new logical file name. The rest of the line, if any, should be whitespace.
2041 If the first non-whitespace characters on the line are not numeric,
2042 the line is ignored. (Just like a comment.)
2045 # This is an ordinary comment.
2046 # 42-6 "new_file_name" # New logical file name
2047 # This is logical line # 36.
2049 This feature is deprecated, and may disappear from future versions
2050 of @command{@value{AS}}.
2055 @cindex characters used in symbols
2056 @ifclear SPECIAL-SYMS
2057 A @dfn{symbol} is one or more characters chosen from the set of all
2058 letters (both upper and lower case), digits and the three characters
2064 A @dfn{symbol} is one or more characters chosen from the set of all
2065 letters (both upper and lower case), digits and the three characters
2066 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2072 On most machines, you can also use @code{$} in symbol names; exceptions
2073 are noted in @ref{Machine Dependencies}.
2075 No symbol may begin with a digit. Case is significant.
2076 There is no length limit: all characters are significant. Symbols are
2077 delimited by characters not in that set, or by the beginning of a file
2078 (since the source program must end with a newline, the end of a file is
2079 not a possible symbol delimiter). @xref{Symbols}.
2080 @cindex length of symbols
2085 @cindex statements, structure of
2086 @cindex line separator character
2087 @cindex statement separator character
2089 @ifclear abnormal-separator
2090 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2091 semicolon (@samp{;}). The newline or semicolon is considered part of
2092 the preceding statement. Newlines and semicolons within character
2093 constants are an exception: they do not end statements.
2095 @ifset abnormal-separator
2097 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
2098 sign (@samp{@@}). The newline or at sign is considered part of the
2099 preceding statement. Newlines and at signs within character constants
2100 are an exception: they do not end statements.
2103 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2104 point (@samp{!}). The newline or exclamation point is considered part of the
2105 preceding statement. Newlines and exclamation points within character
2106 constants are an exception: they do not end statements.
2109 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2110 H8/300) a dollar sign (@samp{$}); or (for the
2113 (@samp{;}). The newline or separator character is considered part of
2114 the preceding statement. Newlines and separators within character
2115 constants are an exception: they do not end statements.
2120 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2121 separator character. (The line separator is usually @samp{;}, unless
2122 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2123 newline or separator character is considered part of the preceding
2124 statement. Newlines and separators within character constants are an
2125 exception: they do not end statements.
2128 @cindex newline, required at file end
2129 @cindex EOF, newline must precede
2130 It is an error to end any statement with end-of-file: the last
2131 character of any input file should be a newline.@refill
2133 An empty statement is allowed, and may include whitespace. It is ignored.
2135 @cindex instructions and directives
2136 @cindex directives and instructions
2137 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2138 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2140 A statement begins with zero or more labels, optionally followed by a
2141 key symbol which determines what kind of statement it is. The key
2142 symbol determines the syntax of the rest of the statement. If the
2143 symbol begins with a dot @samp{.} then the statement is an assembler
2144 directive: typically valid for any computer. If the symbol begins with
2145 a letter the statement is an assembly language @dfn{instruction}: it
2146 assembles into a machine language instruction.
2148 Different versions of @command{@value{AS}} for different computers
2149 recognize different instructions. In fact, the same symbol may
2150 represent a different instruction in a different computer's assembly
2154 @cindex @code{:} (label)
2155 @cindex label (@code{:})
2156 A label is a symbol immediately followed by a colon (@code{:}).
2157 Whitespace before a label or after a colon is permitted, but you may not
2158 have whitespace between a label's symbol and its colon. @xref{Labels}.
2161 For HPPA targets, labels need not be immediately followed by a colon, but
2162 the definition of a label must begin in column zero. This also implies that
2163 only one label may be defined on each line.
2167 label: .directive followed by something
2168 another_label: # This is an empty statement.
2169 instruction operand_1, operand_2, @dots{}
2176 A constant is a number, written so that its value is known by
2177 inspection, without knowing any context. Like this:
2180 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2181 .ascii "Ring the bell\7" # A string constant.
2182 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2183 .float 0f-314159265358979323846264338327\
2184 95028841971.693993751E-40 # - pi, a flonum.
2189 * Characters:: Character Constants
2190 * Numbers:: Number Constants
2194 @subsection Character Constants
2196 @cindex character constants
2197 @cindex constants, character
2198 There are two kinds of character constants. A @dfn{character} stands
2199 for one character in one byte and its value may be used in
2200 numeric expressions. String constants (properly called string
2201 @emph{literals}) are potentially many bytes and their values may not be
2202 used in arithmetic expressions.
2206 * Chars:: Characters
2210 @subsubsection Strings
2212 @cindex string constants
2213 @cindex constants, string
2214 A @dfn{string} is written between double-quotes. It may contain
2215 double-quotes or null characters. The way to get special characters
2216 into a string is to @dfn{escape} these characters: precede them with
2217 a backslash @samp{\} character. For example @samp{\\} represents
2218 one backslash: the first @code{\} is an escape which tells
2219 @command{@value{AS}} to interpret the second character literally as a backslash
2220 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2221 escape character). The complete list of escapes follows.
2223 @cindex escape codes, character
2224 @cindex character escape codes
2227 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2229 @cindex @code{\b} (backspace character)
2230 @cindex backspace (@code{\b})
2232 Mnemonic for backspace; for ASCII this is octal code 010.
2235 @c Mnemonic for EOText; for ASCII this is octal code 004.
2237 @cindex @code{\f} (formfeed character)
2238 @cindex formfeed (@code{\f})
2240 Mnemonic for FormFeed; for ASCII this is octal code 014.
2242 @cindex @code{\n} (newline character)
2243 @cindex newline (@code{\n})
2245 Mnemonic for newline; for ASCII this is octal code 012.
2248 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2250 @cindex @code{\r} (carriage return character)
2251 @cindex carriage return (@code{\r})
2253 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2256 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2257 @c other assemblers.
2259 @cindex @code{\t} (tab)
2260 @cindex tab (@code{\t})
2262 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2265 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2266 @c @item \x @var{digit} @var{digit} @var{digit}
2267 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2269 @cindex @code{\@var{ddd}} (octal character code)
2270 @cindex octal character code (@code{\@var{ddd}})
2271 @item \ @var{digit} @var{digit} @var{digit}
2272 An octal character code. The numeric code is 3 octal digits.
2273 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2274 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2276 @cindex @code{\@var{xd...}} (hex character code)
2277 @cindex hex character code (@code{\@var{xd...}})
2278 @item \@code{x} @var{hex-digits...}
2279 A hex character code. All trailing hex digits are combined. Either upper or
2280 lower case @code{x} works.
2282 @cindex @code{\\} (@samp{\} character)
2283 @cindex backslash (@code{\\})
2285 Represents one @samp{\} character.
2288 @c Represents one @samp{'} (accent acute) character.
2289 @c This is needed in single character literals
2290 @c (@xref{Characters,,Character Constants}.) to represent
2293 @cindex @code{\"} (doublequote character)
2294 @cindex doublequote (@code{\"})
2296 Represents one @samp{"} character. Needed in strings to represent
2297 this character, because an unescaped @samp{"} would end the string.
2299 @item \ @var{anything-else}
2300 Any other character when escaped by @kbd{\} gives a warning, but
2301 assembles as if the @samp{\} was not present. The idea is that if
2302 you used an escape sequence you clearly didn't want the literal
2303 interpretation of the following character. However @command{@value{AS}} has no
2304 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2305 code and warns you of the fact.
2308 Which characters are escapable, and what those escapes represent,
2309 varies widely among assemblers. The current set is what we think
2310 the BSD 4.2 assembler recognizes, and is a subset of what most C
2311 compilers recognize. If you are in doubt, do not use an escape
2315 @subsubsection Characters
2317 @cindex single character constant
2318 @cindex character, single
2319 @cindex constant, single character
2320 A single character may be written as a single quote immediately
2321 followed by that character. The same escapes apply to characters as
2322 to strings. So if you want to write the character backslash, you
2323 must write @kbd{'\\} where the first @code{\} escapes the second
2324 @code{\}. As you can see, the quote is an acute accent, not a
2325 grave accent. A newline
2327 @ifclear abnormal-separator
2328 (or semicolon @samp{;})
2330 @ifset abnormal-separator
2332 (or at sign @samp{@@})
2335 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2341 immediately following an acute accent is taken as a literal character
2342 and does not count as the end of a statement. The value of a character
2343 constant in a numeric expression is the machine's byte-wide code for
2344 that character. @command{@value{AS}} assumes your character code is ASCII:
2345 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2348 @subsection Number Constants
2350 @cindex constants, number
2351 @cindex number constants
2352 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2353 are stored in the target machine. @emph{Integers} are numbers that
2354 would fit into an @code{int} in the C language. @emph{Bignums} are
2355 integers, but they are stored in more than 32 bits. @emph{Flonums}
2356 are floating point numbers, described below.
2359 * Integers:: Integers
2364 * Bit Fields:: Bit Fields
2370 @subsubsection Integers
2372 @cindex constants, integer
2374 @cindex binary integers
2375 @cindex integers, binary
2376 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2377 the binary digits @samp{01}.
2379 @cindex octal integers
2380 @cindex integers, octal
2381 An octal integer is @samp{0} followed by zero or more of the octal
2382 digits (@samp{01234567}).
2384 @cindex decimal integers
2385 @cindex integers, decimal
2386 A decimal integer starts with a non-zero digit followed by zero or
2387 more digits (@samp{0123456789}).
2389 @cindex hexadecimal integers
2390 @cindex integers, hexadecimal
2391 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2392 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2394 Integers have the usual values. To denote a negative integer, use
2395 the prefix operator @samp{-} discussed under expressions
2396 (@pxref{Prefix Ops,,Prefix Operators}).
2399 @subsubsection Bignums
2402 @cindex constants, bignum
2403 A @dfn{bignum} has the same syntax and semantics as an integer
2404 except that the number (or its negative) takes more than 32 bits to
2405 represent in binary. The distinction is made because in some places
2406 integers are permitted while bignums are not.
2409 @subsubsection Flonums
2411 @cindex floating point numbers
2412 @cindex constants, floating point
2414 @cindex precision, floating point
2415 A @dfn{flonum} represents a floating point number. The translation is
2416 indirect: a decimal floating point number from the text is converted by
2417 @command{@value{AS}} to a generic binary floating point number of more than
2418 sufficient precision. This generic floating point number is converted
2419 to a particular computer's floating point format (or formats) by a
2420 portion of @command{@value{AS}} specialized to that computer.
2422 A flonum is written by writing (in order)
2427 (@samp{0} is optional on the HPPA.)
2431 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2433 @kbd{e} is recommended. Case is not important.
2435 @c FIXME: verify if flonum syntax really this vague for most cases
2436 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2437 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2440 On the H8/300, H8/500,
2442 and AMD 29K architectures, the letter must be
2443 one of the letters @samp{DFPRSX} (in upper or lower case).
2445 On the ARC, the letter must be one of the letters @samp{DFRS}
2446 (in upper or lower case).
2448 On the Intel 960 architecture, the letter must be
2449 one of the letters @samp{DFT} (in upper or lower case).
2451 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2455 One of the letters @samp{DFPRSX} (in upper or lower case).
2458 One of the letters @samp{DFRS} (in upper or lower case).
2461 One of the letters @samp{DFPRSX} (in upper or lower case).
2464 The letter @samp{E} (upper case only).
2467 One of the letters @samp{DFT} (in upper or lower case).
2472 An optional sign: either @samp{+} or @samp{-}.
2475 An optional @dfn{integer part}: zero or more decimal digits.
2478 An optional @dfn{fractional part}: @samp{.} followed by zero
2479 or more decimal digits.
2482 An optional exponent, consisting of:
2486 An @samp{E} or @samp{e}.
2487 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2488 @c principle this can perfectly well be different on different targets.
2490 Optional sign: either @samp{+} or @samp{-}.
2492 One or more decimal digits.
2497 At least one of the integer part or the fractional part must be
2498 present. The floating point number has the usual base-10 value.
2500 @command{@value{AS}} does all processing using integers. Flonums are computed
2501 independently of any floating point hardware in the computer running
2502 @command{@value{AS}}.
2506 @c Bit fields are written as a general facility but are also controlled
2507 @c by a conditional-compilation flag---which is as of now (21mar91)
2508 @c turned on only by the i960 config of GAS.
2510 @subsubsection Bit Fields
2513 @cindex constants, bit field
2514 You can also define numeric constants as @dfn{bit fields}.
2515 specify two numbers separated by a colon---
2517 @var{mask}:@var{value}
2520 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2523 The resulting number is then packed
2525 @c this conditional paren in case bit fields turned on elsewhere than 960
2526 (in host-dependent byte order)
2528 into a field whose width depends on which assembler directive has the
2529 bit-field as its argument. Overflow (a result from the bitwise and
2530 requiring more binary digits to represent) is not an error; instead,
2531 more constants are generated, of the specified width, beginning with the
2532 least significant digits.@refill
2534 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2535 @code{.short}, and @code{.word} accept bit-field arguments.
2540 @chapter Sections and Relocation
2545 * Secs Background:: Background
2546 * Ld Sections:: Linker Sections
2547 * As Sections:: Assembler Internal Sections
2548 * Sub-Sections:: Sub-Sections
2552 @node Secs Background
2555 Roughly, a section is a range of addresses, with no gaps; all data
2556 ``in'' those addresses is treated the same for some particular purpose.
2557 For example there may be a ``read only'' section.
2559 @cindex linker, and assembler
2560 @cindex assembler, and linker
2561 The linker @code{@value{LD}} reads many object files (partial programs) and
2562 combines their contents to form a runnable program. When @command{@value{AS}}
2563 emits an object file, the partial program is assumed to start at address 0.
2564 @code{@value{LD}} assigns the final addresses for the partial program, so that
2565 different partial programs do not overlap. This is actually an
2566 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2569 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2570 addresses. These blocks slide to their run-time addresses as rigid
2571 units; their length does not change and neither does the order of bytes
2572 within them. Such a rigid unit is called a @emph{section}. Assigning
2573 run-time addresses to sections is called @dfn{relocation}. It includes
2574 the task of adjusting mentions of object-file addresses so they refer to
2575 the proper run-time addresses.
2577 For the H8/300 and H8/500,
2578 and for the Hitachi SH,
2579 @command{@value{AS}} pads sections if needed to
2580 ensure they end on a word (sixteen bit) boundary.
2583 @cindex standard assembler sections
2584 An object file written by @command{@value{AS}} has at least three sections, any
2585 of which may be empty. These are named @dfn{text}, @dfn{data} and
2590 When it generates COFF output,
2592 @command{@value{AS}} can also generate whatever other named sections you specify
2593 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2594 If you do not use any directives that place output in the @samp{.text}
2595 or @samp{.data} sections, these sections still exist, but are empty.
2600 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2602 @command{@value{AS}} can also generate whatever other named sections you
2603 specify using the @samp{.space} and @samp{.subspace} directives. See
2604 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2605 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2606 assembler directives.
2609 Additionally, @command{@value{AS}} uses different names for the standard
2610 text, data, and bss sections when generating SOM output. Program text
2611 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2612 BSS into @samp{$BSS$}.
2616 Within the object file, the text section starts at address @code{0}, the
2617 data section follows, and the bss section follows the data section.
2620 When generating either SOM or ELF output files on the HPPA, the text
2621 section starts at address @code{0}, the data section at address
2622 @code{0x4000000}, and the bss section follows the data section.
2625 To let @code{@value{LD}} know which data changes when the sections are
2626 relocated, and how to change that data, @command{@value{AS}} also writes to the
2627 object file details of the relocation needed. To perform relocation
2628 @code{@value{LD}} must know, each time an address in the object
2632 Where in the object file is the beginning of this reference to
2635 How long (in bytes) is this reference?
2637 Which section does the address refer to? What is the numeric value of
2639 (@var{address}) @minus{} (@var{start-address of section})?
2642 Is the reference to an address ``Program-Counter relative''?
2645 @cindex addresses, format of
2646 @cindex section-relative addressing
2647 In fact, every address @command{@value{AS}} ever uses is expressed as
2649 (@var{section}) + (@var{offset into section})
2652 Further, most expressions @command{@value{AS}} computes have this section-relative
2655 (For some object formats, such as SOM for the HPPA, some expressions are
2656 symbol-relative instead.)
2659 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2660 @var{N} into section @var{secname}.''
2662 Apart from text, data and bss sections you need to know about the
2663 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2664 addresses in the absolute section remain unchanged. For example, address
2665 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2666 @code{@value{LD}}. Although the linker never arranges two partial programs'
2667 data sections with overlapping addresses after linking, @emph{by definition}
2668 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2669 part of a program is always the same address when the program is running as
2670 address @code{@{absolute@ 239@}} in any other part of the program.
2672 The idea of sections is extended to the @dfn{undefined} section. Any
2673 address whose section is unknown at assembly time is by definition
2674 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2675 Since numbers are always defined, the only way to generate an undefined
2676 address is to mention an undefined symbol. A reference to a named
2677 common block would be such a symbol: its value is unknown at assembly
2678 time so it has section @emph{undefined}.
2680 By analogy the word @emph{section} is used to describe groups of sections in
2681 the linked program. @code{@value{LD}} puts all partial programs' text
2682 sections in contiguous addresses in the linked program. It is
2683 customary to refer to the @emph{text section} of a program, meaning all
2684 the addresses of all partial programs' text sections. Likewise for
2685 data and bss sections.
2687 Some sections are manipulated by @code{@value{LD}}; others are invented for
2688 use of @command{@value{AS}} and have no meaning except during assembly.
2691 @section Linker Sections
2692 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2697 @cindex named sections
2698 @cindex sections, named
2699 @item named sections
2702 @cindex text section
2703 @cindex data section
2707 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2708 separate but equal sections. Anything you can say of one section is
2711 When the program is running, however, it is
2712 customary for the text section to be unalterable. The
2713 text section is often shared among processes: it contains
2714 instructions, constants and the like. The data section of a running
2715 program is usually alterable: for example, C variables would be stored
2716 in the data section.
2721 This section contains zeroed bytes when your program begins running. It
2722 is used to hold uninitialized variables or common storage. The length of
2723 each partial program's bss section is important, but because it starts
2724 out containing zeroed bytes there is no need to store explicit zero
2725 bytes in the object file. The bss section was invented to eliminate
2726 those explicit zeros from object files.
2728 @cindex absolute section
2729 @item absolute section
2730 Address 0 of this section is always ``relocated'' to runtime address 0.
2731 This is useful if you want to refer to an address that @code{@value{LD}} must
2732 not change when relocating. In this sense we speak of absolute
2733 addresses being ``unrelocatable'': they do not change during relocation.
2735 @cindex undefined section
2736 @item undefined section
2737 This ``section'' is a catch-all for address references to objects not in
2738 the preceding sections.
2739 @c FIXME: ref to some other doc on obj-file formats could go here.
2742 @cindex relocation example
2743 An idealized example of three relocatable sections follows.
2745 The example uses the traditional section names @samp{.text} and @samp{.data}.
2747 Memory addresses are on the horizontal axis.
2751 @c END TEXI2ROFF-KILL
2754 partial program # 1: |ttttt|dddd|00|
2761 partial program # 2: |TTT|DDD|000|
2764 +--+---+-----+--+----+---+-----+~~
2765 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2766 +--+---+-----+--+----+---+-----+~~
2768 addresses: 0 @dots{}
2775 \line{\it Partial program \#1: \hfil}
2776 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2777 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2779 \line{\it Partial program \#2: \hfil}
2780 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2781 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2783 \line{\it linked program: \hfil}
2784 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2785 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2786 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2787 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2789 \line{\it addresses: \hfil}
2793 @c END TEXI2ROFF-KILL
2796 @section Assembler Internal Sections
2798 @cindex internal assembler sections
2799 @cindex sections in messages, internal
2800 These sections are meant only for the internal use of @command{@value{AS}}. They
2801 have no meaning at run-time. You do not really need to know about these
2802 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2803 warning messages, so it might be helpful to have an idea of their
2804 meanings to @command{@value{AS}}. These sections are used to permit the
2805 value of every expression in your assembly language program to be a
2806 section-relative address.
2809 @cindex assembler internal logic error
2810 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2811 An internal assembler logic error has been found. This means there is a
2812 bug in the assembler.
2814 @cindex expr (internal section)
2816 The assembler stores complex expression internally as combinations of
2817 symbols. When it needs to represent an expression as a symbol, it puts
2818 it in the expr section.
2820 @c FIXME item transfer[t] vector preload
2821 @c FIXME item transfer[t] vector postload
2822 @c FIXME item register
2826 @section Sub-Sections
2828 @cindex numbered subsections
2829 @cindex grouping data
2835 fall into two sections: text and data.
2837 You may have separate groups of
2839 data in named sections
2843 data in named sections
2849 that you want to end up near to each other in the object file, even though they
2850 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2851 use @dfn{subsections} for this purpose. Within each section, there can be
2852 numbered subsections with values from 0 to 8192. Objects assembled into the
2853 same subsection go into the object file together with other objects in the same
2854 subsection. For example, a compiler might want to store constants in the text
2855 section, but might not want to have them interspersed with the program being
2856 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2857 section of code being output, and a @samp{.text 1} before each group of
2858 constants being output.
2860 Subsections are optional. If you do not use subsections, everything
2861 goes in subsection number zero.
2864 Each subsection is zero-padded up to a multiple of four bytes.
2865 (Subsections may be padded a different amount on different flavors
2866 of @command{@value{AS}}.)
2870 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2871 boundary (two bytes).
2872 The same is true on the Hitachi SH.
2875 @c FIXME section padding (alignment)?
2876 @c Rich Pixley says padding here depends on target obj code format; that
2877 @c doesn't seem particularly useful to say without further elaboration,
2878 @c so for now I say nothing about it. If this is a generic BFD issue,
2879 @c these paragraphs might need to vanish from this manual, and be
2880 @c discussed in BFD chapter of binutils (or some such).
2883 On the AMD 29K family, no particular padding is added to section or
2884 subsection sizes; @value{AS} forces no alignment on this platform.
2888 Subsections appear in your object file in numeric order, lowest numbered
2889 to highest. (All this to be compatible with other people's assemblers.)
2890 The object file contains no representation of subsections; @code{@value{LD}} and
2891 other programs that manipulate object files see no trace of them.
2892 They just see all your text subsections as a text section, and all your
2893 data subsections as a data section.
2895 To specify which subsection you want subsequent statements assembled
2896 into, use a numeric argument to specify it, in a @samp{.text
2897 @var{expression}} or a @samp{.data @var{expression}} statement.
2900 When generating COFF output, you
2905 can also use an extra subsection
2906 argument with arbitrary named sections: @samp{.section @var{name},
2909 @var{Expression} should be an absolute expression.
2910 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2911 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2912 begins in @code{text 0}. For instance:
2914 .text 0 # The default subsection is text 0 anyway.
2915 .ascii "This lives in the first text subsection. *"
2917 .ascii "But this lives in the second text subsection."
2919 .ascii "This lives in the data section,"
2920 .ascii "in the first data subsection."
2922 .ascii "This lives in the first text section,"
2923 .ascii "immediately following the asterisk (*)."
2926 Each section has a @dfn{location counter} incremented by one for every byte
2927 assembled into that section. Because subsections are merely a convenience
2928 restricted to @command{@value{AS}} there is no concept of a subsection location
2929 counter. There is no way to directly manipulate a location counter---but the
2930 @code{.align} directive changes it, and any label definition captures its
2931 current value. The location counter of the section where statements are being
2932 assembled is said to be the @dfn{active} location counter.
2935 @section bss Section
2938 @cindex common variable storage
2939 The bss section is used for local common variable storage.
2940 You may allocate address space in the bss section, but you may
2941 not dictate data to load into it before your program executes. When
2942 your program starts running, all the contents of the bss
2943 section are zeroed bytes.
2945 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2946 @ref{Lcomm,,@code{.lcomm}}.
2948 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2949 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2952 When assembling for a target which supports multiple sections, such as ELF or
2953 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2954 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2955 section. Typically the section will only contain symbol definitions and
2956 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2963 Symbols are a central concept: the programmer uses symbols to name
2964 things, the linker uses symbols to link, and the debugger uses symbols
2968 @cindex debuggers, and symbol order
2969 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
2970 the same order they were declared. This may break some debuggers.
2975 * Setting Symbols:: Giving Symbols Other Values
2976 * Symbol Names:: Symbol Names
2977 * Dot:: The Special Dot Symbol
2978 * Symbol Attributes:: Symbol Attributes
2985 A @dfn{label} is written as a symbol immediately followed by a colon
2986 @samp{:}. The symbol then represents the current value of the
2987 active location counter, and is, for example, a suitable instruction
2988 operand. You are warned if you use the same symbol to represent two
2989 different locations: the first definition overrides any other
2993 On the HPPA, the usual form for a label need not be immediately followed by a
2994 colon, but instead must start in column zero. Only one label may be defined on
2995 a single line. To work around this, the HPPA version of @command{@value{AS}} also
2996 provides a special directive @code{.label} for defining labels more flexibly.
2999 @node Setting Symbols
3000 @section Giving Symbols Other Values
3002 @cindex assigning values to symbols
3003 @cindex symbol values, assigning
3004 A symbol can be given an arbitrary value by writing a symbol, followed
3005 by an equals sign @samp{=}, followed by an expression
3006 (@pxref{Expressions}). This is equivalent to using the @code{.set}
3007 directive. @xref{Set,,@code{.set}}.
3010 @section Symbol Names
3012 @cindex symbol names
3013 @cindex names, symbol
3014 @ifclear SPECIAL-SYMS
3015 Symbol names begin with a letter or with one of @samp{._}. On most
3016 machines, you can also use @code{$} in symbol names; exceptions are
3017 noted in @ref{Machine Dependencies}. That character may be followed by any
3018 string of digits, letters, dollar signs (unless otherwise noted in
3019 @ref{Machine Dependencies}), and underscores.
3022 For the AMD 29K family, @samp{?} is also allowed in the
3023 body of a symbol name, though not at its beginning.
3028 Symbol names begin with a letter or with one of @samp{._}. On the
3030 H8/500, you can also use @code{$} in symbol names. That character may
3031 be followed by any string of digits, letters, dollar signs (save on the
3032 H8/300), and underscores.
3036 Case of letters is significant: @code{foo} is a different symbol name
3039 Each symbol has exactly one name. Each name in an assembly language program
3040 refers to exactly one symbol. You may use that symbol name any number of times
3043 @subheading Local Symbol Names
3045 @cindex local symbol names
3046 @cindex symbol names, local
3047 @cindex temporary symbol names
3048 @cindex symbol names, temporary
3049 Local symbols help compilers and programmers use names temporarily.
3050 They create symbols which are guaranteed to be unique over the entire scope of
3051 the input source code and which can be referred to by a simple notation.
3052 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3053 represents any positive integer). To refer to the most recent previous
3054 definition of that symbol write @samp{@b{N}b}, using the same number as when
3055 you defined the label. To refer to the next definition of a local label, write
3056 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3059 There is no restriction on how you can use these labels, and you can reuse them
3060 too. So that it is possible to repeatedly define the same local label (using
3061 the same number @samp{@b{N}}), although you can only refer to the most recently
3062 defined local label of that number (for a backwards reference) or the next
3063 definition of a specific local label for a forward reference. It is also worth
3064 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3065 implemented in a slightly more efficient manner than the others.
3076 Which is the equivalent of:
3079 label_1: branch label_3
3080 label_2: branch label_1
3081 label_3: branch label_4
3082 label_4: branch label_3
3085 Local symbol names are only a notational device. They are immediately
3086 transformed into more conventional symbol names before the assembler uses them.
3087 The symbol names stored in the symbol table, appearing in error messages and
3088 optionally emitted to the object file. The names are constructed using these
3093 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3094 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3095 used for symbols you are never intended to see. If you use the
3096 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3097 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3098 you may use them in debugging.
3101 This is the number that was used in the local label definition. So if the
3102 label is written @samp{55:} then the number is @samp{55}.
3105 This unusual character is included so you do not accidentally invent a symbol
3106 of the same name. The character has ASCII value of @samp{\002} (control-B).
3108 @item @emph{ordinal number}
3109 This is a serial number to keep the labels distinct. The first definition of
3110 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3111 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3112 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3115 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3116 @code{3:} is named @code{L3@kbd{C-B}44}.
3118 @subheading Dollar Local Labels
3119 @cindex dollar local symbols
3121 @code{@value{AS}} also supports an even more local form of local labels called
3122 dollar labels. These labels go out of scope (ie they become undefined) as soon
3123 as a non-local label is defined. Thus they remain valid for only a small
3124 region of the input source code. Normal local labels, by contrast, remain in
3125 scope for the entire file, or until they are redefined by another occurrence of
3126 the same local label.
3128 Dollar labels are defined in exactly the same way as ordinary local labels,
3129 except that instead of being terminated by a colon, they are terminated by a
3130 dollar sign. eg @samp{@b{55$}}.
3132 They can also be distinguished from ordinary local labels by their transformed
3133 name which uses ASCII character @samp{\001} (control-A) as the magic character
3134 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3135 is named @samp{L6@kbd{C-A}5}.
3138 @section The Special Dot Symbol
3140 @cindex dot (symbol)
3141 @cindex @code{.} (symbol)
3142 @cindex current address
3143 @cindex location counter
3144 The special symbol @samp{.} refers to the current address that
3145 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3146 .long .} defines @code{melvin} to contain its own address.
3147 Assigning a value to @code{.} is treated the same as a @code{.org}
3148 directive. Thus, the expression @samp{.=.+4} is the same as saying
3149 @ifclear no-space-dir
3158 @node Symbol Attributes
3159 @section Symbol Attributes
3161 @cindex symbol attributes
3162 @cindex attributes, symbol
3163 Every symbol has, as well as its name, the attributes ``Value'' and
3164 ``Type''. Depending on output format, symbols can also have auxiliary
3167 The detailed definitions are in @file{a.out.h}.
3170 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3171 all these attributes, and probably won't warn you. This makes the
3172 symbol an externally defined symbol, which is generally what you
3176 * Symbol Value:: Value
3177 * Symbol Type:: Type
3180 * a.out Symbols:: Symbol Attributes: @code{a.out}
3184 * a.out Symbols:: Symbol Attributes: @code{a.out}
3187 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3192 * COFF Symbols:: Symbol Attributes for COFF
3195 * SOM Symbols:: Symbol Attributes for SOM
3202 @cindex value of a symbol
3203 @cindex symbol value
3204 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3205 location in the text, data, bss or absolute sections the value is the
3206 number of addresses from the start of that section to the label.
3207 Naturally for text, data and bss sections the value of a symbol changes
3208 as @code{@value{LD}} changes section base addresses during linking. Absolute
3209 symbols' values do not change during linking: that is why they are
3212 The value of an undefined symbol is treated in a special way. If it is
3213 0 then the symbol is not defined in this assembler source file, and
3214 @code{@value{LD}} tries to determine its value from other files linked into the
3215 same program. You make this kind of symbol simply by mentioning a symbol
3216 name without defining it. A non-zero value represents a @code{.comm}
3217 common declaration. The value is how much common storage to reserve, in
3218 bytes (addresses). The symbol refers to the first address of the
3224 @cindex type of a symbol
3226 The type attribute of a symbol contains relocation (section)
3227 information, any flag settings indicating that a symbol is external, and
3228 (optionally), other information for linkers and debuggers. The exact
3229 format depends on the object-code output format in use.
3234 @c The following avoids a "widow" subsection title. @group would be
3235 @c better if it were available outside examples.
3238 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3240 @cindex @code{b.out} symbol attributes
3241 @cindex symbol attributes, @code{b.out}
3242 These symbol attributes appear only when @command{@value{AS}} is configured for
3243 one of the Berkeley-descended object output formats---@code{a.out} or
3249 @subsection Symbol Attributes: @code{a.out}
3251 @cindex @code{a.out} symbol attributes
3252 @cindex symbol attributes, @code{a.out}
3258 @subsection Symbol Attributes: @code{a.out}
3260 @cindex @code{a.out} symbol attributes
3261 @cindex symbol attributes, @code{a.out}
3265 * Symbol Desc:: Descriptor
3266 * Symbol Other:: Other
3270 @subsubsection Descriptor
3272 @cindex descriptor, of @code{a.out} symbol
3273 This is an arbitrary 16-bit value. You may establish a symbol's
3274 descriptor value by using a @code{.desc} statement
3275 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3276 @command{@value{AS}}.
3279 @subsubsection Other
3281 @cindex other attribute, of @code{a.out} symbol
3282 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3287 @subsection Symbol Attributes for COFF
3289 @cindex COFF symbol attributes
3290 @cindex symbol attributes, COFF
3292 The COFF format supports a multitude of auxiliary symbol attributes;
3293 like the primary symbol attributes, they are set between @code{.def} and
3294 @code{.endef} directives.
3296 @subsubsection Primary Attributes
3298 @cindex primary attributes, COFF symbols
3299 The symbol name is set with @code{.def}; the value and type,
3300 respectively, with @code{.val} and @code{.type}.
3302 @subsubsection Auxiliary Attributes
3304 @cindex auxiliary attributes, COFF symbols
3305 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3306 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3307 information for COFF.
3312 @subsection Symbol Attributes for SOM
3314 @cindex SOM symbol attributes
3315 @cindex symbol attributes, SOM
3317 The SOM format for the HPPA supports a multitude of symbol attributes set with
3318 the @code{.EXPORT} and @code{.IMPORT} directives.
3320 The attributes are described in @cite{HP9000 Series 800 Assembly
3321 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3322 @code{EXPORT} assembler directive documentation.
3326 @chapter Expressions
3330 @cindex numeric values
3331 An @dfn{expression} specifies an address or numeric value.
3332 Whitespace may precede and/or follow an expression.
3334 The result of an expression must be an absolute number, or else an offset into
3335 a particular section. If an expression is not absolute, and there is not
3336 enough information when @command{@value{AS}} sees the expression to know its
3337 section, a second pass over the source program might be necessary to interpret
3338 the expression---but the second pass is currently not implemented.
3339 @command{@value{AS}} aborts with an error message in this situation.
3342 * Empty Exprs:: Empty Expressions
3343 * Integer Exprs:: Integer Expressions
3347 @section Empty Expressions
3349 @cindex empty expressions
3350 @cindex expressions, empty
3351 An empty expression has no value: it is just whitespace or null.
3352 Wherever an absolute expression is required, you may omit the
3353 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3354 is compatible with other assemblers.
3357 @section Integer Expressions
3359 @cindex integer expressions
3360 @cindex expressions, integer
3361 An @dfn{integer expression} is one or more @emph{arguments} delimited
3362 by @emph{operators}.
3365 * Arguments:: Arguments
3366 * Operators:: Operators
3367 * Prefix Ops:: Prefix Operators
3368 * Infix Ops:: Infix Operators
3372 @subsection Arguments
3374 @cindex expression arguments
3375 @cindex arguments in expressions
3376 @cindex operands in expressions
3377 @cindex arithmetic operands
3378 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3379 contexts arguments are sometimes called ``arithmetic operands''. In
3380 this manual, to avoid confusing them with the ``instruction operands'' of
3381 the machine language, we use the term ``argument'' to refer to parts of
3382 expressions only, reserving the word ``operand'' to refer only to machine
3383 instruction operands.
3385 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3386 @var{section} is one of text, data, bss, absolute,
3387 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3390 Numbers are usually integers.
3392 A number can be a flonum or bignum. In this case, you are warned
3393 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3394 these 32 bits are an integer. You may write integer-manipulating
3395 instructions that act on exotic constants, compatible with other
3398 @cindex subexpressions
3399 Subexpressions are a left parenthesis @samp{(} followed by an integer
3400 expression, followed by a right parenthesis @samp{)}; or a prefix
3401 operator followed by an argument.
3404 @subsection Operators
3406 @cindex operators, in expressions
3407 @cindex arithmetic functions
3408 @cindex functions, in expressions
3409 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3410 operators are followed by an argument. Infix operators appear
3411 between their arguments. Operators may be preceded and/or followed by
3415 @subsection Prefix Operator
3417 @cindex prefix operators
3418 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3419 one argument, which must be absolute.
3421 @c the tex/end tex stuff surrounding this small table is meant to make
3422 @c it align, on the printed page, with the similar table in the next
3423 @c section (which is inside an enumerate).
3425 \global\advance\leftskip by \itemindent
3430 @dfn{Negation}. Two's complement negation.
3432 @dfn{Complementation}. Bitwise not.
3436 \global\advance\leftskip by -\itemindent
3440 @subsection Infix Operators
3442 @cindex infix operators
3443 @cindex operators, permitted arguments
3444 @dfn{Infix operators} take two arguments, one on either side. Operators
3445 have precedence, but operations with equal precedence are performed left
3446 to right. Apart from @code{+} or @option{-}, both arguments must be
3447 absolute, and the result is absolute.
3450 @cindex operator precedence
3451 @cindex precedence of operators
3458 @dfn{Multiplication}.
3461 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3468 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3472 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3476 Intermediate precedence
3481 @dfn{Bitwise Inclusive Or}.
3487 @dfn{Bitwise Exclusive Or}.
3490 @dfn{Bitwise Or Not}.
3497 @cindex addition, permitted arguments
3498 @cindex plus, permitted arguments
3499 @cindex arguments for addition
3501 @dfn{Addition}. If either argument is absolute, the result has the section of
3502 the other argument. You may not add together arguments from different
3505 @cindex subtraction, permitted arguments
3506 @cindex minus, permitted arguments
3507 @cindex arguments for subtraction
3509 @dfn{Subtraction}. If the right argument is absolute, the
3510 result has the section of the left argument.
3511 If both arguments are in the same section, the result is absolute.
3512 You may not subtract arguments from different sections.
3513 @c FIXME is there still something useful to say about undefined - undefined ?
3515 @cindex comparison expressions
3516 @cindex expressions, comparison
3520 @dfn{Is Not Equal To}
3524 @dfn{Is Greater Than}
3526 @dfn{Is Greater Than Or Equal To}
3528 @dfn{Is Less Than Or Equal To}
3530 The comparison operators can be used as infix operators. A true results has a
3531 value of -1 whereas a false result has a value of 0. Note, these operators
3532 perform signed comparisons.
3535 @item Lowest Precedence
3544 These two logical operations can be used to combine the results of sub
3545 expressions. Note, unlike the comparison operators a true result returns a
3546 value of 1 but a false results does still return 0. Also note that the logical
3547 or operator has a slightly lower precedence than logical and.
3552 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3553 address; you can only have a defined section in one of the two arguments.
3556 @chapter Assembler Directives
3558 @cindex directives, machine independent
3559 @cindex pseudo-ops, machine independent
3560 @cindex machine independent directives
3561 All assembler directives have names that begin with a period (@samp{.}).
3562 The rest of the name is letters, usually in lower case.
3564 This chapter discusses directives that are available regardless of the
3565 target machine configuration for the @sc{gnu} assembler.
3567 Some machine configurations provide additional directives.
3568 @xref{Machine Dependencies}.
3571 @ifset machine-directives
3572 @xref{Machine Dependencies} for additional directives.
3577 * Abort:: @code{.abort}
3579 * ABORT:: @code{.ABORT}
3582 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3583 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3584 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3585 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3586 * Byte:: @code{.byte @var{expressions}}
3587 * Comm:: @code{.comm @var{symbol} , @var{length} }
3588 * Data:: @code{.data @var{subsection}}
3590 * Def:: @code{.def @var{name}}
3593 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3599 * Double:: @code{.double @var{flonums}}
3600 * Eject:: @code{.eject}
3601 * Else:: @code{.else}
3602 * Elseif:: @code{.elseif}
3605 * Endef:: @code{.endef}
3608 * Endfunc:: @code{.endfunc}
3609 * Endif:: @code{.endif}
3610 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3611 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3613 * Exitm:: @code{.exitm}
3614 * Extern:: @code{.extern}
3615 * Fail:: @code{.fail}
3616 @ifclear no-file-dir
3617 * File:: @code{.file @var{string}}
3620 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3621 * Float:: @code{.float @var{flonums}}
3622 * Func:: @code{.func}
3623 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3625 * Hidden:: @code{.hidden @var{names}}
3628 * hword:: @code{.hword @var{expressions}}
3629 * Ident:: @code{.ident}
3630 * If:: @code{.if @var{absolute expression}}
3631 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3632 * Include:: @code{.include "@var{file}"}
3633 * Int:: @code{.int @var{expressions}}
3635 * Internal:: @code{.internal @var{names}}
3638 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3639 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3640 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3641 * Lflags:: @code{.lflags}
3642 @ifclear no-line-dir
3643 * Line:: @code{.line @var{line-number}}
3646 * Ln:: @code{.ln @var{line-number}}
3647 * Linkonce:: @code{.linkonce [@var{type}]}
3648 * List:: @code{.list}
3649 * Long:: @code{.long @var{expressions}}
3651 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3654 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3655 * MRI:: @code{.mri @var{val}}
3656 * Nolist:: @code{.nolist}
3657 * Octa:: @code{.octa @var{bignums}}
3658 * Org:: @code{.org @var{new-lc} , @var{fill}}
3659 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3661 * PopSection:: @code{.popsection}
3662 * Previous:: @code{.previous}
3665 * Print:: @code{.print @var{string}}
3667 * Protected:: @code{.protected @var{names}}
3670 * Psize:: @code{.psize @var{lines}, @var{columns}}
3671 * Purgem:: @code{.purgem @var{name}}
3673 * PushSection:: @code{.pushsection @var{name}}
3676 * Quad:: @code{.quad @var{bignums}}
3677 * Rept:: @code{.rept @var{count}}
3678 * Sbttl:: @code{.sbttl "@var{subheading}"}
3680 * Scl:: @code{.scl @var{class}}
3681 * Section:: @code{.section @var{name}, @var{subsection}}
3684 * Set:: @code{.set @var{symbol}, @var{expression}}
3685 * Short:: @code{.short @var{expressions}}
3686 * Single:: @code{.single @var{flonums}}
3687 * Size:: @code{.size [@var{name} , @var{expression}]}
3688 * Skip:: @code{.skip @var{size} , @var{fill}}
3689 * Sleb128:: @code{.sleb128 @var{expressions}}
3690 * Space:: @code{.space @var{size} , @var{fill}}
3692 * Stab:: @code{.stabd, .stabn, .stabs}
3695 * String:: @code{.string "@var{str}"}
3696 * Struct:: @code{.struct @var{expression}}
3698 * SubSection:: @code{.subsection}
3699 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3703 * Tag:: @code{.tag @var{structname}}
3706 * Text:: @code{.text @var{subsection}}
3707 * Title:: @code{.title "@var{heading}"}
3708 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3709 * Uleb128:: @code{.uleb128 @var{expressions}}
3711 * Val:: @code{.val @var{addr}}
3715 * Version:: @code{.version "@var{string}"}
3716 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3717 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3718 * Weak:: @code{.weak @var{names}}
3721 * Word:: @code{.word @var{expressions}}
3722 * Deprecated:: Deprecated Directives
3726 @section @code{.abort}
3728 @cindex @code{abort} directive
3729 @cindex stopping the assembly
3730 This directive stops the assembly immediately. It is for
3731 compatibility with other assemblers. The original idea was that the
3732 assembly language source would be piped into the assembler. If the sender
3733 of the source quit, it could use this directive tells @command{@value{AS}} to
3734 quit also. One day @code{.abort} will not be supported.
3738 @section @code{.ABORT}
3740 @cindex @code{ABORT} directive
3741 When producing COFF output, @command{@value{AS}} accepts this directive as a
3742 synonym for @samp{.abort}.
3745 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3751 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3753 @cindex padding the location counter
3754 @cindex @code{align} directive
3755 Pad the location counter (in the current subsection) to a particular storage
3756 boundary. The first expression (which must be absolute) is the alignment
3757 required, as described below.
3759 The second expression (also absolute) gives the fill value to be stored in the
3760 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3761 padding bytes are normally zero. However, on some systems, if the section is
3762 marked as containing code and the fill value is omitted, the space is filled
3763 with no-op instructions.
3765 The third expression is also absolute, and is also optional. If it is present,
3766 it is the maximum number of bytes that should be skipped by this alignment
3767 directive. If doing the alignment would require skipping more bytes than the
3768 specified maximum, then the alignment is not done at all. You can omit the
3769 fill value (the second argument) entirely by simply using two commas after the
3770 required alignment; this can be useful if you want the alignment to be filled
3771 with no-op instructions when appropriate.
3773 The way the required alignment is specified varies from system to system.
3774 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3776 the first expression is the
3777 alignment request in bytes. For example @samp{.align 8} advances
3778 the location counter until it is a multiple of 8. If the location counter
3779 is already a multiple of 8, no change is needed.
3781 For other systems, including the i386 using a.out format, and the arm and
3782 strongarm, it is the
3783 number of low-order zero bits the location counter must have after
3784 advancement. For example @samp{.align 3} advances the location
3785 counter until it a multiple of 8. If the location counter is already a
3786 multiple of 8, no change is needed.
3788 This inconsistency is due to the different behaviors of the various
3789 native assemblers for these systems which GAS must emulate.
3790 GAS also provides @code{.balign} and @code{.p2align} directives,
3791 described later, which have a consistent behavior across all
3792 architectures (but are specific to GAS).
3795 @section @code{.ascii "@var{string}"}@dots{}
3797 @cindex @code{ascii} directive
3798 @cindex string literals
3799 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3800 separated by commas. It assembles each string (with no automatic
3801 trailing zero byte) into consecutive addresses.
3804 @section @code{.asciz "@var{string}"}@dots{}
3806 @cindex @code{asciz} directive
3807 @cindex zero-terminated strings
3808 @cindex null-terminated strings
3809 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3810 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3813 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3815 @cindex padding the location counter given number of bytes
3816 @cindex @code{balign} directive
3817 Pad the location counter (in the current subsection) to a particular
3818 storage boundary. The first expression (which must be absolute) is the
3819 alignment request in bytes. For example @samp{.balign 8} advances
3820 the location counter until it is a multiple of 8. If the location counter
3821 is already a multiple of 8, no change is needed.
3823 The second expression (also absolute) gives the fill value to be stored in the
3824 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3825 padding bytes are normally zero. However, on some systems, if the section is
3826 marked as containing code and the fill value is omitted, the space is filled
3827 with no-op instructions.
3829 The third expression is also absolute, and is also optional. If it is present,
3830 it is the maximum number of bytes that should be skipped by this alignment
3831 directive. If doing the alignment would require skipping more bytes than the
3832 specified maximum, then the alignment is not done at all. You can omit the
3833 fill value (the second argument) entirely by simply using two commas after the
3834 required alignment; this can be useful if you want the alignment to be filled
3835 with no-op instructions when appropriate.
3837 @cindex @code{balignw} directive
3838 @cindex @code{balignl} directive
3839 The @code{.balignw} and @code{.balignl} directives are variants of the
3840 @code{.balign} directive. The @code{.balignw} directive treats the fill
3841 pattern as a two byte word value. The @code{.balignl} directives treats the
3842 fill pattern as a four byte longword value. For example, @code{.balignw
3843 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3844 filled in with the value 0x368d (the exact placement of the bytes depends upon
3845 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3849 @section @code{.byte @var{expressions}}
3851 @cindex @code{byte} directive
3852 @cindex integers, one byte
3853 @code{.byte} expects zero or more expressions, separated by commas.
3854 Each expression is assembled into the next byte.
3857 @section @code{.comm @var{symbol} , @var{length} }
3859 @cindex @code{comm} directive
3860 @cindex symbol, common
3861 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3862 common symbol in one object file may be merged with a defined or common symbol
3863 of the same name in another object file. If @code{@value{LD}} does not see a
3864 definition for the symbol--just one or more common symbols--then it will
3865 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3866 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3867 the same name, and they do not all have the same size, it will allocate space
3868 using the largest size.
3871 When using ELF, the @code{.comm} directive takes an optional third argument.
3872 This is the desired alignment of the symbol, specified as a byte boundary (for
3873 example, an alignment of 16 means that the least significant 4 bits of the
3874 address should be zero). The alignment must be an absolute expression, and it
3875 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3876 for the common symbol, it will use the alignment when placing the symbol. If
3877 no alignment is specified, @command{@value{AS}} will set the alignment to the
3878 largest power of two less than or equal to the size of the symbol, up to a
3883 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3884 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3888 @section @code{.data @var{subsection}}
3890 @cindex @code{data} directive
3891 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
3892 end of the data subsection numbered @var{subsection} (which is an
3893 absolute expression). If @var{subsection} is omitted, it defaults
3898 @section @code{.def @var{name}}
3900 @cindex @code{def} directive
3901 @cindex COFF symbols, debugging
3902 @cindex debugging COFF symbols
3903 Begin defining debugging information for a symbol @var{name}; the
3904 definition extends until the @code{.endef} directive is encountered.
3907 This directive is only observed when @command{@value{AS}} is configured for COFF
3908 format output; when producing @code{b.out}, @samp{.def} is recognized,
3915 @section @code{.desc @var{symbol}, @var{abs-expression}}
3917 @cindex @code{desc} directive
3918 @cindex COFF symbol descriptor
3919 @cindex symbol descriptor, COFF
3920 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3921 to the low 16 bits of an absolute expression.
3924 The @samp{.desc} directive is not available when @command{@value{AS}} is
3925 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3926 object format. For the sake of compatibility, @command{@value{AS}} accepts
3927 it, but produces no output, when configured for COFF.
3933 @section @code{.dim}
3935 @cindex @code{dim} directive
3936 @cindex COFF auxiliary symbol information
3937 @cindex auxiliary symbol information, COFF
3938 This directive is generated by compilers to include auxiliary debugging
3939 information in the symbol table. It is only permitted inside
3940 @code{.def}/@code{.endef} pairs.
3943 @samp{.dim} is only meaningful when generating COFF format output; when
3944 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
3950 @section @code{.double @var{flonums}}
3952 @cindex @code{double} directive
3953 @cindex floating point numbers (double)
3954 @code{.double} expects zero or more flonums, separated by commas. It
3955 assembles floating point numbers.
3957 The exact kind of floating point numbers emitted depends on how
3958 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
3962 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3963 in @sc{ieee} format.
3968 @section @code{.eject}
3970 @cindex @code{eject} directive
3971 @cindex new page, in listings
3972 @cindex page, in listings
3973 @cindex listing control: new page
3974 Force a page break at this point, when generating assembly listings.
3977 @section @code{.else}
3979 @cindex @code{else} directive
3980 @code{.else} is part of the @command{@value{AS}} support for conditional
3981 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3982 of code to be assembled if the condition for the preceding @code{.if}
3986 @section @code{.elseif}
3988 @cindex @code{elseif} directive
3989 @code{.elseif} is part of the @command{@value{AS}} support for conditional
3990 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
3991 @code{.if} block that would otherwise fill the entire @code{.else} section.
3994 @section @code{.end}
3996 @cindex @code{end} directive
3997 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
3998 process anything in the file past the @code{.end} directive.
4002 @section @code{.endef}
4004 @cindex @code{endef} directive
4005 This directive flags the end of a symbol definition begun with
4009 @samp{.endef} is only meaningful when generating COFF format output; if
4010 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
4011 directive but ignores it.
4016 @section @code{.endfunc}
4017 @cindex @code{endfunc} directive
4018 @code{.endfunc} marks the end of a function specified with @code{.func}.
4021 @section @code{.endif}
4023 @cindex @code{endif} directive
4024 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
4025 it marks the end of a block of code that is only assembled
4026 conditionally. @xref{If,,@code{.if}}.
4029 @section @code{.equ @var{symbol}, @var{expression}}
4031 @cindex @code{equ} directive
4032 @cindex assigning values to symbols
4033 @cindex symbols, assigning values to
4034 This directive sets the value of @var{symbol} to @var{expression}.
4035 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4038 The syntax for @code{equ} on the HPPA is
4039 @samp{@var{symbol} .equ @var{expression}}.
4043 @section @code{.equiv @var{symbol}, @var{expression}}
4044 @cindex @code{equiv} directive
4045 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4046 the assembler will signal an error if @var{symbol} is already defined.
4048 Except for the contents of the error message, this is roughly equivalent to
4057 @section @code{.err}
4058 @cindex @code{err} directive
4059 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4060 message and, unless the @option{-Z} option was used, it will not generate an
4061 object file. This can be used to signal error an conditionally compiled code.
4064 @section @code{.exitm}
4065 Exit early from the current macro definition. @xref{Macro}.
4068 @section @code{.extern}
4070 @cindex @code{extern} directive
4071 @code{.extern} is accepted in the source program---for compatibility
4072 with other assemblers---but it is ignored. @command{@value{AS}} treats
4073 all undefined symbols as external.
4076 @section @code{.fail @var{expression}}
4078 @cindex @code{fail} directive
4079 Generates an error or a warning. If the value of the @var{expression} is 500
4080 or more, @command{@value{AS}} will print a warning message. If the value is less
4081 than 500, @command{@value{AS}} will print an error message. The message will
4082 include the value of @var{expression}. This can occasionally be useful inside
4083 complex nested macros or conditional assembly.
4085 @ifclear no-file-dir
4087 @section @code{.file @var{string}}
4089 @cindex @code{file} directive
4090 @cindex logical file name
4091 @cindex file name, logical
4092 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4093 file. @var{string} is the new file name. In general, the filename is
4094 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4095 to specify an empty file name, you must give the quotes--@code{""}. This
4096 statement may go away in future: it is only recognized to be compatible with
4097 old @command{@value{AS}} programs.
4099 In some configurations of @command{@value{AS}}, @code{.file} has already been
4100 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
4105 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4107 @cindex @code{fill} directive
4108 @cindex writing patterns in memory
4109 @cindex patterns, writing in memory
4110 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4111 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4112 may be zero or more. @var{Size} may be zero or more, but if it is
4113 more than 8, then it is deemed to have the value 8, compatible with
4114 other people's assemblers. The contents of each @var{repeat} bytes
4115 is taken from an 8-byte number. The highest order 4 bytes are
4116 zero. The lowest order 4 bytes are @var{value} rendered in the
4117 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4118 Each @var{size} bytes in a repetition is taken from the lowest order
4119 @var{size} bytes of this number. Again, this bizarre behavior is
4120 compatible with other people's assemblers.
4122 @var{size} and @var{value} are optional.
4123 If the second comma and @var{value} are absent, @var{value} is
4124 assumed zero. If the first comma and following tokens are absent,
4125 @var{size} is assumed to be 1.
4128 @section @code{.float @var{flonums}}
4130 @cindex floating point numbers (single)
4131 @cindex @code{float} directive
4132 This directive assembles zero or more flonums, separated by commas. It
4133 has the same effect as @code{.single}.
4135 The exact kind of floating point numbers emitted depends on how
4136 @command{@value{AS}} is configured.
4137 @xref{Machine Dependencies}.
4141 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4142 in @sc{ieee} format.
4147 @section @code{.func @var{name}[,@var{label}]}
4148 @cindex @code{func} directive
4149 @code{.func} emits debugging information to denote function @var{name}, and
4150 is ignored unless the file is assembled with debugging enabled.
4151 Only @samp{--gstabs} is currently supported.
4152 @var{label} is the entry point of the function and if omitted @var{name}
4153 prepended with the @samp{leading char} is used.
4154 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4155 All functions are currently defined to have @code{void} return type.
4156 The function must be terminated with @code{.endfunc}.
4159 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4161 @cindex @code{global} directive
4162 @cindex symbol, making visible to linker
4163 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4164 @var{symbol} in your partial program, its value is made available to
4165 other partial programs that are linked with it. Otherwise,
4166 @var{symbol} takes its attributes from a symbol of the same name
4167 from another file linked into the same program.
4169 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4170 compatibility with other assemblers.
4173 On the HPPA, @code{.global} is not always enough to make it accessible to other
4174 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4175 @xref{HPPA Directives,, HPPA Assembler Directives}.
4180 @section @code{.hidden @var{names}}
4182 @cindex @code{.hidden} directive
4184 This one of the ELF visibility directives. The other two are
4185 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4186 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4188 This directive overrides the named symbols default visibility (which is set by
4189 their binding: local, global or weak). The directive sets the visibility to
4190 @code{hidden} which means that the symbols are not visible to other components.
4191 Such symbols are always considered to be @code{protected} as well.
4195 @section @code{.hword @var{expressions}}
4197 @cindex @code{hword} directive
4198 @cindex integers, 16-bit
4199 @cindex numbers, 16-bit
4200 @cindex sixteen bit integers
4201 This expects zero or more @var{expressions}, and emits
4202 a 16 bit number for each.
4205 This directive is a synonym for @samp{.short}; depending on the target
4206 architecture, it may also be a synonym for @samp{.word}.
4210 This directive is a synonym for @samp{.short}.
4213 This directive is a synonym for both @samp{.short} and @samp{.word}.
4218 @section @code{.ident}
4220 @cindex @code{ident} directive
4221 This directive is used by some assemblers to place tags in object files.
4222 @command{@value{AS}} simply accepts the directive for source-file
4223 compatibility with such assemblers, but does not actually emit anything
4227 @section @code{.if @var{absolute expression}}
4229 @cindex conditional assembly
4230 @cindex @code{if} directive
4231 @code{.if} marks the beginning of a section of code which is only
4232 considered part of the source program being assembled if the argument
4233 (which must be an @var{absolute expression}) is non-zero. The end of
4234 the conditional section of code must be marked by @code{.endif}
4235 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4236 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4237 If you have several conditions to check, @code{.elseif} may be used to avoid
4238 nesting blocks if/else within each subsequent @code{.else} block.
4240 The following variants of @code{.if} are also supported:
4242 @cindex @code{ifdef} directive
4243 @item .ifdef @var{symbol}
4244 Assembles the following section of code if the specified @var{symbol}
4247 @cindex @code{ifc} directive
4248 @item .ifc @var{string1},@var{string2}
4249 Assembles the following section of code if the two strings are the same. The
4250 strings may be optionally quoted with single quotes. If they are not quoted,
4251 the first string stops at the first comma, and the second string stops at the
4252 end of the line. Strings which contain whitespace should be quoted. The
4253 string comparison is case sensitive.
4255 @cindex @code{ifeq} directive
4256 @item .ifeq @var{absolute expression}
4257 Assembles the following section of code if the argument is zero.
4259 @cindex @code{ifeqs} directive
4260 @item .ifeqs @var{string1},@var{string2}
4261 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4263 @cindex @code{ifge} directive
4264 @item .ifge @var{absolute expression}
4265 Assembles the following section of code if the argument is greater than or
4268 @cindex @code{ifgt} directive
4269 @item .ifgt @var{absolute expression}
4270 Assembles the following section of code if the argument is greater than zero.
4272 @cindex @code{ifle} directive
4273 @item .ifle @var{absolute expression}
4274 Assembles the following section of code if the argument is less than or equal
4277 @cindex @code{iflt} directive
4278 @item .iflt @var{absolute expression}
4279 Assembles the following section of code if the argument is less than zero.
4281 @cindex @code{ifnc} directive
4282 @item .ifnc @var{string1},@var{string2}.
4283 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4284 following section of code if the two strings are not the same.
4286 @cindex @code{ifndef} directive
4287 @cindex @code{ifnotdef} directive
4288 @item .ifndef @var{symbol}
4289 @itemx .ifnotdef @var{symbol}
4290 Assembles the following section of code if the specified @var{symbol}
4291 has not been defined. Both spelling variants are equivalent.
4293 @cindex @code{ifne} directive
4294 @item .ifne @var{absolute expression}
4295 Assembles the following section of code if the argument is not equal to zero
4296 (in other words, this is equivalent to @code{.if}).
4298 @cindex @code{ifnes} directive
4299 @item .ifnes @var{string1},@var{string2}
4300 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4301 following section of code if the two strings are not the same.
4305 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4307 @cindex @code{incbin} directive
4308 @cindex binary files, including
4309 The @code{incbin} directive includes @var{file} verbatim at the current
4310 location. You can control the search paths used with the @samp{-I} command-line
4311 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4314 The @var{skip} argument skips a number of bytes from the start of the
4315 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4316 read. Note that the data is not aligned in any way, so it is the user's
4317 responsibility to make sure that proper alignment is provided both before and
4318 after the @code{incbin} directive.
4321 @section @code{.include "@var{file}"}
4323 @cindex @code{include} directive
4324 @cindex supporting files, including
4325 @cindex files, including
4326 This directive provides a way to include supporting files at specified
4327 points in your source program. The code from @var{file} is assembled as
4328 if it followed the point of the @code{.include}; when the end of the
4329 included file is reached, assembly of the original file continues. You
4330 can control the search paths used with the @samp{-I} command-line option
4331 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4335 @section @code{.int @var{expressions}}
4337 @cindex @code{int} directive
4338 @cindex integers, 32-bit
4339 Expect zero or more @var{expressions}, of any section, separated by commas.
4340 For each expression, emit a number that, at run time, is the value of that
4341 expression. The byte order and bit size of the number depends on what kind
4342 of target the assembly is for.
4346 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4347 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
4354 @section @code{.internal @var{names}}
4356 @cindex @code{.internal} directive
4358 This one of the ELF visibility directives. The other two are
4359 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4360 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4362 This directive overrides the named symbols default visibility (which is set by
4363 their binding: local, global or weak). The directive sets the visibility to
4364 @code{internal} which means that the symbols are considered to be @code{hidden}
4365 (ie not visible to other components), and that some extra, processor specific
4366 processing must also be performed upon the symbols as well.
4370 @section @code{.irp @var{symbol},@var{values}}@dots{}
4372 @cindex @code{irp} directive
4373 Evaluate a sequence of statements assigning different values to @var{symbol}.
4374 The sequence of statements starts at the @code{.irp} directive, and is
4375 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4376 set to @var{value}, and the sequence of statements is assembled. If no
4377 @var{value} is listed, the sequence of statements is assembled once, with
4378 @var{symbol} set to the null string. To refer to @var{symbol} within the
4379 sequence of statements, use @var{\symbol}.
4381 For example, assembling
4389 is equivalent to assembling
4398 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4400 @cindex @code{irpc} directive
4401 Evaluate a sequence of statements assigning different values to @var{symbol}.
4402 The sequence of statements starts at the @code{.irpc} directive, and is
4403 terminated by an @code{.endr} directive. For each character in @var{value},
4404 @var{symbol} is set to the character, and the sequence of statements is
4405 assembled. If no @var{value} is listed, the sequence of statements is
4406 assembled once, with @var{symbol} set to the null string. To refer to
4407 @var{symbol} within the sequence of statements, use @var{\symbol}.
4409 For example, assembling
4417 is equivalent to assembling
4426 @section @code{.lcomm @var{symbol} , @var{length}}
4428 @cindex @code{lcomm} directive
4429 @cindex local common symbols
4430 @cindex symbols, local common
4431 Reserve @var{length} (an absolute expression) bytes for a local common
4432 denoted by @var{symbol}. The section and value of @var{symbol} are
4433 those of the new local common. The addresses are allocated in the bss
4434 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4435 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4436 not visible to @code{@value{LD}}.
4439 Some targets permit a third argument to be used with @code{.lcomm}. This
4440 argument specifies the desired alignment of the symbol in the bss section.
4444 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4445 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4449 @section @code{.lflags}
4451 @cindex @code{lflags} directive (ignored)
4452 @command{@value{AS}} accepts this directive, for compatibility with other
4453 assemblers, but ignores it.
4455 @ifclear no-line-dir
4457 @section @code{.line @var{line-number}}
4459 @cindex @code{line} directive
4463 @section @code{.ln @var{line-number}}
4465 @cindex @code{ln} directive
4467 @cindex logical line number
4469 Change the logical line number. @var{line-number} must be an absolute
4470 expression. The next line has that logical line number. Therefore any other
4471 statements on the current line (after a statement separator character) are
4472 reported as on logical line number @var{line-number} @minus{} 1. One day
4473 @command{@value{AS}} will no longer support this directive: it is recognized only
4474 for compatibility with existing assembler programs.
4478 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4479 not available; use the synonym @code{.ln} in that context.
4484 @ifclear no-line-dir
4485 Even though this is a directive associated with the @code{a.out} or
4486 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4487 when producing COFF output, and treats @samp{.line} as though it
4488 were the COFF @samp{.ln} @emph{if} it is found outside a
4489 @code{.def}/@code{.endef} pair.
4491 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4492 used by compilers to generate auxiliary symbol information for
4497 @section @code{.linkonce [@var{type}]}
4499 @cindex @code{linkonce} directive
4500 @cindex common sections
4501 Mark the current section so that the linker only includes a single copy of it.
4502 This may be used to include the same section in several different object files,
4503 but ensure that the linker will only include it once in the final output file.
4504 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4505 Duplicate sections are detected based on the section name, so it should be
4508 This directive is only supported by a few object file formats; as of this
4509 writing, the only object file format which supports it is the Portable
4510 Executable format used on Windows NT.
4512 The @var{type} argument is optional. If specified, it must be one of the
4513 following strings. For example:
4517 Not all types may be supported on all object file formats.
4521 Silently discard duplicate sections. This is the default.
4524 Warn if there are duplicate sections, but still keep only one copy.
4527 Warn if any of the duplicates have different sizes.
4530 Warn if any of the duplicates do not have exactly the same contents.
4534 @section @code{.ln @var{line-number}}
4536 @cindex @code{ln} directive
4537 @ifclear no-line-dir
4538 @samp{.ln} is a synonym for @samp{.line}.
4541 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4542 must be an absolute expression. The next line has that logical
4543 line number, so any other statements on the current line (after a
4544 statement separator character @code{;}) are reported as on logical
4545 line number @var{line-number} @minus{} 1.
4548 This directive is accepted, but ignored, when @command{@value{AS}} is
4549 configured for @code{b.out}; its effect is only associated with COFF
4555 @section @code{.mri @var{val}}
4557 @cindex @code{mri} directive
4558 @cindex MRI mode, temporarily
4559 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4560 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4561 affects code assembled until the next @code{.mri} directive, or until the end
4562 of the file. @xref{M, MRI mode, MRI mode}.
4565 @section @code{.list}
4567 @cindex @code{list} directive
4568 @cindex listing control, turning on
4569 Control (in conjunction with the @code{.nolist} directive) whether or
4570 not assembly listings are generated. These two directives maintain an
4571 internal counter (which is zero initially). @code{.list} increments the
4572 counter, and @code{.nolist} decrements it. Assembly listings are
4573 generated whenever the counter is greater than zero.
4575 By default, listings are disabled. When you enable them (with the
4576 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4577 the initial value of the listing counter is one.
4580 @section @code{.long @var{expressions}}
4582 @cindex @code{long} directive
4583 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4586 @c no one seems to know what this is for or whether this description is
4587 @c what it really ought to do
4589 @section @code{.lsym @var{symbol}, @var{expression}}
4591 @cindex @code{lsym} directive
4592 @cindex symbol, not referenced in assembly
4593 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4594 the hash table, ensuring it cannot be referenced by name during the
4595 rest of the assembly. This sets the attributes of the symbol to be
4596 the same as the expression value:
4598 @var{other} = @var{descriptor} = 0
4599 @var{type} = @r{(section of @var{expression})}
4600 @var{value} = @var{expression}
4603 The new symbol is not flagged as external.
4607 @section @code{.macro}
4610 The commands @code{.macro} and @code{.endm} allow you to define macros that
4611 generate assembly output. For example, this definition specifies a macro
4612 @code{sum} that puts a sequence of numbers into memory:
4615 .macro sum from=0, to=5
4624 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4636 @item .macro @var{macname}
4637 @itemx .macro @var{macname} @var{macargs} @dots{}
4638 @cindex @code{macro} directive
4639 Begin the definition of a macro called @var{macname}. If your macro
4640 definition requires arguments, specify their names after the macro name,
4641 separated by commas or spaces. You can supply a default value for any
4642 macro argument by following the name with @samp{=@var{deflt}}. For
4643 example, these are all valid @code{.macro} statements:
4647 Begin the definition of a macro called @code{comm}, which takes no
4650 @item .macro plus1 p, p1
4651 @itemx .macro plus1 p p1
4652 Either statement begins the definition of a macro called @code{plus1},
4653 which takes two arguments; within the macro definition, write
4654 @samp{\p} or @samp{\p1} to evaluate the arguments.
4656 @item .macro reserve_str p1=0 p2
4657 Begin the definition of a macro called @code{reserve_str}, with two
4658 arguments. The first argument has a default value, but not the second.
4659 After the definition is complete, you can call the macro either as
4660 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4661 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4662 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4663 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4666 When you call a macro, you can specify the argument values either by
4667 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4668 @samp{sum to=17, from=9}.
4671 @cindex @code{endm} directive
4672 Mark the end of a macro definition.
4675 @cindex @code{exitm} directive
4676 Exit early from the current macro definition.
4678 @cindex number of macros executed
4679 @cindex macros, count executed
4681 @command{@value{AS}} maintains a counter of how many macros it has
4682 executed in this pseudo-variable; you can copy that number to your
4683 output with @samp{\@@}, but @emph{only within a macro definition}.
4686 @item LOCAL @var{name} [ , @dots{} ]
4687 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4688 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4689 Alternate macro syntax}.
4691 Generate a string replacement for each of the @var{name} arguments, and
4692 replace any instances of @var{name} in each macro expansion. The
4693 replacement string is unique in the assembly, and different for each
4694 separate macro expansion. @code{LOCAL} allows you to write macros that
4695 define symbols, without fear of conflict between separate macro expansions.
4700 @section @code{.nolist}
4702 @cindex @code{nolist} directive
4703 @cindex listing control, turning off
4704 Control (in conjunction with the @code{.list} directive) whether or
4705 not assembly listings are generated. These two directives maintain an
4706 internal counter (which is zero initially). @code{.list} increments the
4707 counter, and @code{.nolist} decrements it. Assembly listings are
4708 generated whenever the counter is greater than zero.
4711 @section @code{.octa @var{bignums}}
4713 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4714 @cindex @code{octa} directive
4715 @cindex integer, 16-byte
4716 @cindex sixteen byte integer
4717 This directive expects zero or more bignums, separated by commas. For each
4718 bignum, it emits a 16-byte integer.
4720 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4721 hence @emph{octa}-word for 16 bytes.
4724 @section @code{.org @var{new-lc} , @var{fill}}
4726 @cindex @code{org} directive
4727 @cindex location counter, advancing
4728 @cindex advancing location counter
4729 @cindex current address, advancing
4730 Advance the location counter of the current section to
4731 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4732 expression with the same section as the current subsection. That is,
4733 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4734 wrong section, the @code{.org} directive is ignored. To be compatible
4735 with former assemblers, if the section of @var{new-lc} is absolute,
4736 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4737 is the same as the current subsection.
4739 @code{.org} may only increase the location counter, or leave it
4740 unchanged; you cannot use @code{.org} to move the location counter
4743 @c double negative used below "not undefined" because this is a specific
4744 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4745 @c section. doc@cygnus.com 18feb91
4746 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4747 may not be undefined. If you really detest this restriction we eagerly await
4748 a chance to share your improved assembler.
4750 Beware that the origin is relative to the start of the section, not
4751 to the start of the subsection. This is compatible with other
4752 people's assemblers.
4754 When the location counter (of the current subsection) is advanced, the
4755 intervening bytes are filled with @var{fill} which should be an
4756 absolute expression. If the comma and @var{fill} are omitted,
4757 @var{fill} defaults to zero.
4760 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4762 @cindex padding the location counter given a power of two
4763 @cindex @code{p2align} directive
4764 Pad the location counter (in the current subsection) to a particular
4765 storage boundary. The first expression (which must be absolute) is the
4766 number of low-order zero bits the location counter must have after
4767 advancement. For example @samp{.p2align 3} advances the location
4768 counter until it a multiple of 8. If the location counter is already a
4769 multiple of 8, no change is needed.
4771 The second expression (also absolute) gives the fill value to be stored in the
4772 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4773 padding bytes are normally zero. However, on some systems, if the section is
4774 marked as containing code and the fill value is omitted, the space is filled
4775 with no-op instructions.
4777 The third expression is also absolute, and is also optional. If it is present,
4778 it is the maximum number of bytes that should be skipped by this alignment
4779 directive. If doing the alignment would require skipping more bytes than the
4780 specified maximum, then the alignment is not done at all. You can omit the
4781 fill value (the second argument) entirely by simply using two commas after the
4782 required alignment; this can be useful if you want the alignment to be filled
4783 with no-op instructions when appropriate.
4785 @cindex @code{p2alignw} directive
4786 @cindex @code{p2alignl} directive
4787 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4788 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4789 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4790 fill pattern as a four byte longword value. For example, @code{.p2alignw
4791 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4792 filled in with the value 0x368d (the exact placement of the bytes depends upon
4793 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4798 @section @code{.previous}
4800 @cindex @code{.previous} directive
4801 @cindex Section Stack
4802 This is one of the ELF section stack manipulation directives. The others are
4803 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4804 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4805 (@pxref{PopSection}).
4807 This directive swaps the current section (and subsection) with most recently
4808 referenced section (and subsection) prior to this one. Multiple
4809 @code{.previous} directives in a row will flip between two sections (and their
4812 In terms of the section stack, this directive swaps the current section with
4813 the top section on the section stack.
4818 @section @code{.popsection}
4820 @cindex @code{.popsection} directive
4821 @cindex Section Stack
4822 This is one of the ELF section stack manipulation directives. The others are
4823 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4824 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4827 This directive replaces the current section (and subsection) with the top
4828 section (and subsection) on the section stack. This section is popped off the
4833 @section @code{.print @var{string}}
4835 @cindex @code{print} directive
4836 @command{@value{AS}} will print @var{string} on the standard output during
4837 assembly. You must put @var{string} in double quotes.
4841 @section @code{.protected @var{names}}
4843 @cindex @code{.protected} directive
4845 This one of the ELF visibility directives. The other two are
4846 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
4848 This directive overrides the named symbols default visibility (which is set by
4849 their binding: local, global or weak). The directive sets the visibility to
4850 @code{protected} which means that any references to the symbols from within the
4851 components that defines them must be resolved to the definition in that
4852 component, even if a definition in another component would normally preempt
4857 @section @code{.psize @var{lines} , @var{columns}}
4859 @cindex @code{psize} directive
4860 @cindex listing control: paper size
4861 @cindex paper size, for listings
4862 Use this directive to declare the number of lines---and, optionally, the
4863 number of columns---to use for each page, when generating listings.
4865 If you do not use @code{.psize}, listings use a default line-count
4866 of 60. You may omit the comma and @var{columns} specification; the
4867 default width is 200 columns.
4869 @command{@value{AS}} generates formfeeds whenever the specified number of
4870 lines is exceeded (or whenever you explicitly request one, using
4873 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4874 those explicitly specified with @code{.eject}.
4877 @section @code{.purgem @var{name}}
4879 @cindex @code{purgem} directive
4880 Undefine the macro @var{name}, so that later uses of the string will not be
4881 expanded. @xref{Macro}.
4885 @section @code{.pushsection @var{name} , @var{subsection}}
4887 @cindex @code{.pushsection} directive
4888 @cindex Section Stack
4889 This is one of the ELF section stack manipulation directives. The others are
4890 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4891 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
4894 This directive is a synonym for @code{.section}. It pushes the current section
4895 (and subsection) onto the top of the section stack, and then replaces the
4896 current section and subsection with @code{name} and @code{subsection}.
4900 @section @code{.quad @var{bignums}}
4902 @cindex @code{quad} directive
4903 @code{.quad} expects zero or more bignums, separated by commas. For
4904 each bignum, it emits
4906 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4907 warning message; and just takes the lowest order 8 bytes of the bignum.
4908 @cindex eight-byte integer
4909 @cindex integer, 8-byte
4911 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4912 hence @emph{quad}-word for 8 bytes.
4915 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4916 warning message; and just takes the lowest order 16 bytes of the bignum.
4917 @cindex sixteen-byte integer
4918 @cindex integer, 16-byte
4922 @section @code{.rept @var{count}}
4924 @cindex @code{rept} directive
4925 Repeat the sequence of lines between the @code{.rept} directive and the next
4926 @code{.endr} directive @var{count} times.
4928 For example, assembling
4936 is equivalent to assembling
4945 @section @code{.sbttl "@var{subheading}"}
4947 @cindex @code{sbttl} directive
4948 @cindex subtitles for listings
4949 @cindex listing control: subtitle
4950 Use @var{subheading} as the title (third line, immediately after the
4951 title line) when generating assembly listings.
4953 This directive affects subsequent pages, as well as the current page if
4954 it appears within ten lines of the top of a page.
4958 @section @code{.scl @var{class}}
4960 @cindex @code{scl} directive
4961 @cindex symbol storage class (COFF)
4962 @cindex COFF symbol storage class
4963 Set the storage-class value for a symbol. This directive may only be
4964 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4965 whether a symbol is static or external, or it may record further
4966 symbolic debugging information.
4969 The @samp{.scl} directive is primarily associated with COFF output; when
4970 configured to generate @code{b.out} output format, @command{@value{AS}}
4971 accepts this directive but ignores it.
4976 @section @code{.section @var{name}} (COFF version)
4978 @cindex @code{section} directive
4979 @cindex named section
4980 Use the @code{.section} directive to assemble the following code into a section
4983 This directive is only supported for targets that actually support arbitrarily
4984 named sections; on @code{a.out} targets, for example, it is not accepted, even
4985 with a standard @code{a.out} section name.
4987 For COFF targets, the @code{.section} directive is used in one of the following
4991 .section @var{name}[, "@var{flags}"]
4992 .section @var{name}[, @var{subsegment}]
4995 If the optional argument is quoted, it is taken as flags to use for the
4996 section. Each flag is a single character. The following flags are recognized:
4999 bss section (uninitialized data)
5001 section is not loaded
5011 shared section (meaningful for PE targets)
5013 ignored. (For compatibility with the ELF version)
5016 If no flags are specified, the default flags depend upon the section name. If
5017 the section name is not recognized, the default will be for the section to be
5018 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
5019 from the section, rather than adding them, so if they are used on their own it
5020 will be as if no flags had been specified at all.
5022 If the optional argument to the @code{.section} directive is not quoted, it is
5023 taken as a subsegment number (@pxref{Sub-Sections}).
5026 @section @code{.section @var{name}} (ELF version)
5028 @cindex @code{section} directive
5029 @cindex named section
5031 @cindex Section Stack
5032 This is one of the ELF section stack manipulation directives. The others are
5033 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5034 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5035 @code{.previous} (@pxref{Previous}).
5038 For ELF targets, the @code{.section} directive is used like this:
5041 .section @var{name} [, "@var{flags}"[, @@@var{type}[, @@@var{entsize}]]]
5044 The optional @var{flags} argument is a quoted string which may contain any
5045 combination of the following characters:
5048 section is allocatable
5052 section is executable
5054 section is mergeable
5056 section contains zero terminated strings
5059 The optional @var{type} argument may contain one of the following constants:
5062 section contains data
5064 section does not contain data (i.e., section only occupies space)
5067 If @var{flags} contains @code{M} flag, @var{type} argument must be specified
5068 as well as @var{entsize} argument. Sections with @code{M} flag but not
5069 @code{S} flag must contain fixed size constants, each @var{entsize} octets
5070 long. Sections with both @code{M} and @code{S} must contain zero terminated
5071 strings where each character is @var{entsize} bytes long. The linker may remove
5072 duplicates within sections with the same name, same entity size and same flags.
5074 If no flags are specified, the default flags depend upon the section name. If
5075 the section name is not recognized, the default will be for the section to have
5076 none of the above flags: it will not be allocated in memory, nor writable, nor
5077 executable. The section will contain data.
5079 For ELF targets, the assembler supports another type of @code{.section}
5080 directive for compatibility with the Solaris assembler:
5083 .section "@var{name}"[, @var{flags}...]
5086 Note that the section name is quoted. There may be a sequence of comma
5090 section is allocatable
5094 section is executable
5097 This directive replaces the current section and subsection. The replaced
5098 section and subsection are pushed onto the section stack. See the contents of
5099 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
5100 how this directive and the other section stack directives work.
5103 @section @code{.set @var{symbol}, @var{expression}}
5105 @cindex @code{set} directive
5106 @cindex symbol value, setting
5107 Set the value of @var{symbol} to @var{expression}. This
5108 changes @var{symbol}'s value and type to conform to
5109 @var{expression}. If @var{symbol} was flagged as external, it remains
5110 flagged (@pxref{Symbol Attributes}).
5112 You may @code{.set} a symbol many times in the same assembly.
5114 If you @code{.set} a global symbol, the value stored in the object
5115 file is the last value stored into it.
5118 The syntax for @code{set} on the HPPA is
5119 @samp{@var{symbol} .set @var{expression}}.
5123 @section @code{.short @var{expressions}}
5125 @cindex @code{short} directive
5127 @code{.short} is normally the same as @samp{.word}.
5128 @xref{Word,,@code{.word}}.
5130 In some configurations, however, @code{.short} and @code{.word} generate
5131 numbers of different lengths; @pxref{Machine Dependencies}.
5135 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5138 This expects zero or more @var{expressions}, and emits
5139 a 16 bit number for each.
5144 @section @code{.single @var{flonums}}
5146 @cindex @code{single} directive
5147 @cindex floating point numbers (single)
5148 This directive assembles zero or more flonums, separated by commas. It
5149 has the same effect as @code{.float}.
5151 The exact kind of floating point numbers emitted depends on how
5152 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5156 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5157 numbers in @sc{ieee} format.
5162 @section @code{.size} (COFF version)
5164 @cindex @code{size} directive
5165 This directive is generated by compilers to include auxiliary debugging
5166 information in the symbol table. It is only permitted inside
5167 @code{.def}/@code{.endef} pairs.
5170 @samp{.size} is only meaningful when generating COFF format output; when
5171 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5175 @section @code{.size @var{name} , @var{expression}} (ELF version)
5176 @cindex @code{size} directive
5178 This directive is used to set the size associated with a symbol @var{name}.
5179 The size in bytes is computed from @var{expression} which can make use of label
5180 arithmetic. This directive is typically used to set the size of function
5184 @section @code{.sleb128 @var{expressions}}
5186 @cindex @code{sleb128} directive
5187 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5188 compact, variable length representation of numbers used by the DWARF
5189 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5191 @ifclear no-space-dir
5193 @section @code{.skip @var{size} , @var{fill}}
5195 @cindex @code{skip} directive
5196 @cindex filling memory
5197 This directive emits @var{size} bytes, each of value @var{fill}. Both
5198 @var{size} and @var{fill} are absolute expressions. If the comma and
5199 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5203 @section @code{.space @var{size} , @var{fill}}
5205 @cindex @code{space} directive
5206 @cindex filling memory
5207 This directive emits @var{size} bytes, each of value @var{fill}. Both
5208 @var{size} and @var{fill} are absolute expressions. If the comma
5209 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5214 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5215 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5216 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5217 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5226 @section @code{.space}
5227 @cindex @code{space} directive
5229 On the AMD 29K, this directive is ignored; it is accepted for
5230 compatibility with other AMD 29K assemblers.
5233 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5234 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5240 @section @code{.stabd, .stabn, .stabs}
5242 @cindex symbolic debuggers, information for
5243 @cindex @code{stab@var{x}} directives
5244 There are three directives that begin @samp{.stab}.
5245 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5246 The symbols are not entered in the @command{@value{AS}} hash table: they
5247 cannot be referenced elsewhere in the source file.
5248 Up to five fields are required:
5252 This is the symbol's name. It may contain any character except
5253 @samp{\000}, so is more general than ordinary symbol names. Some
5254 debuggers used to code arbitrarily complex structures into symbol names
5258 An absolute expression. The symbol's type is set to the low 8 bits of
5259 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5260 and debuggers choke on silly bit patterns.
5263 An absolute expression. The symbol's ``other'' attribute is set to the
5264 low 8 bits of this expression.
5267 An absolute expression. The symbol's descriptor is set to the low 16
5268 bits of this expression.
5271 An absolute expression which becomes the symbol's value.
5274 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5275 or @code{.stabs} statement, the symbol has probably already been created;
5276 you get a half-formed symbol in your object file. This is
5277 compatible with earlier assemblers!
5280 @cindex @code{stabd} directive
5281 @item .stabd @var{type} , @var{other} , @var{desc}
5283 The ``name'' of the symbol generated is not even an empty string.
5284 It is a null pointer, for compatibility. Older assemblers used a
5285 null pointer so they didn't waste space in object files with empty
5288 The symbol's value is set to the location counter,
5289 relocatably. When your program is linked, the value of this symbol
5290 is the address of the location counter when the @code{.stabd} was
5293 @cindex @code{stabn} directive
5294 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5295 The name of the symbol is set to the empty string @code{""}.
5297 @cindex @code{stabs} directive
5298 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5299 All five fields are specified.
5305 @section @code{.string} "@var{str}"
5307 @cindex string, copying to object file
5308 @cindex @code{string} directive
5310 Copy the characters in @var{str} to the object file. You may specify more than
5311 one string to copy, separated by commas. Unless otherwise specified for a
5312 particular machine, the assembler marks the end of each string with a 0 byte.
5313 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5316 @section @code{.struct @var{expression}}
5318 @cindex @code{struct} directive
5319 Switch to the absolute section, and set the section offset to @var{expression},
5320 which must be an absolute expression. You might use this as follows:
5329 This would define the symbol @code{field1} to have the value 0, the symbol
5330 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5331 value 8. Assembly would be left in the absolute section, and you would need to
5332 use a @code{.section} directive of some sort to change to some other section
5333 before further assembly.
5337 @section @code{.subsection @var{name}}
5339 @cindex @code{.subsection} directive
5340 @cindex Section Stack
5341 This is one of the ELF section stack manipulation directives. The others are
5342 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5343 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5346 This directive replaces the current subsection with @code{name}. The current
5347 section is not changed. The replaced subsection is put onto the section stack
5348 in place of the then current top of stack subsection.
5353 @section @code{.symver}
5354 @cindex @code{symver} directive
5355 @cindex symbol versioning
5356 @cindex versions of symbols
5357 Use the @code{.symver} directive to bind symbols to specific version nodes
5358 within a source file. This is only supported on ELF platforms, and is
5359 typically used when assembling files to be linked into a shared library.
5360 There are cases where it may make sense to use this in objects to be bound
5361 into an application itself so as to override a versioned symbol from a
5364 For ELF targets, the @code{.symver} directive can be used like this:
5366 .symver @var{name}, @var{name2@@nodename}
5368 If the symbol @var{name} is defined within the file
5369 being assembled, the @code{.symver} directive effectively creates a symbol
5370 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5371 just don't try and create a regular alias is that the @var{@@} character isn't
5372 permitted in symbol names. The @var{name2} part of the name is the actual name
5373 of the symbol by which it will be externally referenced. The name @var{name}
5374 itself is merely a name of convenience that is used so that it is possible to
5375 have definitions for multiple versions of a function within a single source
5376 file, and so that the compiler can unambiguously know which version of a
5377 function is being mentioned. The @var{nodename} portion of the alias should be
5378 the name of a node specified in the version script supplied to the linker when
5379 building a shared library. If you are attempting to override a versioned
5380 symbol from a shared library, then @var{nodename} should correspond to the
5381 nodename of the symbol you are trying to override.
5383 If the symbol @var{name} is not defined within the file being assembled, all
5384 references to @var{name} will be changed to @var{name2@@nodename}. If no
5385 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5388 Another usage of the @code{.symver} directive is:
5390 .symver @var{name}, @var{name2@@@@nodename}
5392 In this case, the symbol @var{name} must exist and be defined within
5393 the file being assembled. It is similar to @var{name2@@nodename}. The
5394 difference is @var{name2@@@@nodename} will also be used to resolve
5395 references to @var{name2} by the linker.
5397 The third usage of the @code{.symver} directive is:
5399 .symver @var{name}, @var{name2@@@@@@nodename}
5401 When @var{name} is not defined within the
5402 file being assembled, it is treated as @var{name2@@nodename}. When
5403 @var{name} is defined within the file being assembled, the symbol
5404 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5409 @section @code{.tag @var{structname}}
5411 @cindex COFF structure debugging
5412 @cindex structure debugging, COFF
5413 @cindex @code{tag} directive
5414 This directive is generated by compilers to include auxiliary debugging
5415 information in the symbol table. It is only permitted inside
5416 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5417 definitions in the symbol table with instances of those structures.
5420 @samp{.tag} is only used when generating COFF format output; when
5421 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5427 @section @code{.text @var{subsection}}
5429 @cindex @code{text} directive
5430 Tells @command{@value{AS}} to assemble the following statements onto the end of
5431 the text subsection numbered @var{subsection}, which is an absolute
5432 expression. If @var{subsection} is omitted, subsection number zero
5436 @section @code{.title "@var{heading}"}
5438 @cindex @code{title} directive
5439 @cindex listing control: title line
5440 Use @var{heading} as the title (second line, immediately after the
5441 source file name and pagenumber) when generating assembly listings.
5443 This directive affects subsequent pages, as well as the current page if
5444 it appears within ten lines of the top of a page.
5447 @section @code{.type @var{int}} (COFF version)
5449 @cindex COFF symbol type
5450 @cindex symbol type, COFF
5451 @cindex @code{type} directive
5452 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5453 records the integer @var{int} as the type attribute of a symbol table entry.
5456 @samp{.type} is associated only with COFF format output; when
5457 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5458 directive but ignores it.
5461 @section @code{.type @var{name} , @var{type description}} (ELF version)
5463 @cindex ELF symbol type
5464 @cindex symbol type, ELF
5465 @cindex @code{type} directive
5466 This directive is used to set the type of symbol @var{name} to be either a
5467 function symbol or an object symbol. There are five different syntaxes
5468 supported for the @var{type description} field, in order to provide
5469 compatibility with various other assemblers. The syntaxes supported are:
5472 .type <name>,#function
5473 .type <name>,#object
5475 .type <name>,@@function
5476 .type <name>,@@object
5478 .type <name>,%function
5479 .type <name>,%object
5481 .type <name>,"function"
5482 .type <name>,"object"
5484 .type <name> STT_FUNCTION
5485 .type <name> STT_OBJECT
5489 @section @code{.uleb128 @var{expressions}}
5491 @cindex @code{uleb128} directive
5492 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5493 compact, variable length representation of numbers used by the DWARF
5494 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5498 @section @code{.val @var{addr}}
5500 @cindex @code{val} directive
5501 @cindex COFF value attribute
5502 @cindex value attribute, COFF
5503 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5504 records the address @var{addr} as the value attribute of a symbol table
5508 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5509 configured for @code{b.out}, it accepts this directive but ignores it.
5515 @section @code{.version "@var{string}"}
5517 @cindex @code{.version}
5518 This directive creates a @code{.note} section and places into it an ELF
5519 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5524 @section @code{.vtable_entry @var{table}, @var{offset}}
5526 @cindex @code{.vtable_entry}
5527 This directive finds or creates a symbol @code{table} and creates a
5528 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5531 @section @code{.vtable_inherit @var{child}, @var{parent}}
5533 @cindex @code{.vtable_inherit}
5534 This directive finds the symbol @code{child} and finds or creates the symbol
5535 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5536 parent whose addend is the value of the child symbol. As a special case the
5537 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5542 @section @code{.weak @var{names}}
5544 @cindex @code{.weak}
5545 This directive sets the weak attribute on the comma separated list of symbol
5546 @code{names}. If the symbols do not already exist, they will be created.
5550 @section @code{.word @var{expressions}}
5552 @cindex @code{word} directive
5553 This directive expects zero or more @var{expressions}, of any section,
5554 separated by commas.
5557 For each expression, @command{@value{AS}} emits a 32-bit number.
5560 For each expression, @command{@value{AS}} emits a 16-bit number.
5565 The size of the number emitted, and its byte order,
5566 depend on what target computer the assembly is for.
5569 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5570 @c happen---32-bit addressability, period; no long/short jumps.
5571 @ifset DIFF-TBL-KLUGE
5572 @cindex difference tables altered
5573 @cindex altered difference tables
5575 @emph{Warning: Special Treatment to support Compilers}
5579 Machines with a 32-bit address space, but that do less than 32-bit
5580 addressing, require the following special treatment. If the machine of
5581 interest to you does 32-bit addressing (or doesn't require it;
5582 @pxref{Machine Dependencies}), you can ignore this issue.
5585 In order to assemble compiler output into something that works,
5586 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5587 Directives of the form @samp{.word sym1-sym2} are often emitted by
5588 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
5589 directive of the form @samp{.word sym1-sym2}, and the difference between
5590 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
5591 creates a @dfn{secondary jump table}, immediately before the next label.
5592 This secondary jump table is preceded by a short-jump to the
5593 first byte after the secondary table. This short-jump prevents the flow
5594 of control from accidentally falling into the new table. Inside the
5595 table is a long-jump to @code{sym2}. The original @samp{.word}
5596 contains @code{sym1} minus the address of the long-jump to
5599 If there were several occurrences of @samp{.word sym1-sym2} before the
5600 secondary jump table, all of them are adjusted. If there was a
5601 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5602 long-jump to @code{sym4} is included in the secondary jump table,
5603 and the @code{.word} directives are adjusted to contain @code{sym3}
5604 minus the address of the long-jump to @code{sym4}; and so on, for as many
5605 entries in the original jump table as necessary.
5608 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
5609 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5610 assembly language programmers.
5613 @c end DIFF-TBL-KLUGE
5616 @section Deprecated Directives
5618 @cindex deprecated directives
5619 @cindex obsolescent directives
5620 One day these directives won't work.
5621 They are included for compatibility with older assemblers.
5628 @node Machine Dependencies
5629 @chapter Machine Dependent Features
5631 @cindex machine dependencies
5632 The machine instruction sets are (almost by definition) different on
5633 each machine where @command{@value{AS}} runs. Floating point representations
5634 vary as well, and @command{@value{AS}} often supports a few additional
5635 directives or command-line options for compatibility with other
5636 assemblers on a particular platform. Finally, some versions of
5637 @command{@value{AS}} support special pseudo-instructions for branch
5640 This chapter discusses most of these differences, though it does not
5641 include details on any machine's instruction set. For details on that
5642 subject, see the hardware manufacturer's manual.
5646 * AMD29K-Dependent:: AMD 29K Dependent Features
5649 * Alpha-Dependent:: Alpha Dependent Features
5652 * ARC-Dependent:: ARC Dependent Features
5655 * ARM-Dependent:: ARM Dependent Features
5658 * CRIS-Dependent:: CRIS Dependent Features
5661 * D10V-Dependent:: D10V Dependent Features
5664 * D30V-Dependent:: D30V Dependent Features
5667 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5670 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5673 * HPPA-Dependent:: HPPA Dependent Features
5676 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5679 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5682 * i860-Dependent:: Intel 80860 Dependent Features
5685 * i960-Dependent:: Intel 80960 Dependent Features
5688 * M32R-Dependent:: M32R Dependent Features
5691 * M68K-Dependent:: M680x0 Dependent Features
5694 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5697 * M88K-Dependent:: M880x0 Dependent Features
5700 * MIPS-Dependent:: MIPS Dependent Features
5703 * MMIX-Dependent:: MMIX Dependent Features
5706 * SH-Dependent:: Hitachi SH Dependent Features
5707 * SH64-Dependent:: Hitachi SH64 Dependent Features
5710 * PDP-11-Dependent:: PDP-11 Dependent Features
5713 * PJ-Dependent:: picoJava Dependent Features
5716 * PPC-Dependent:: PowerPC Dependent Features
5719 * Sparc-Dependent:: SPARC Dependent Features
5722 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5725 * V850-Dependent:: V850 Dependent Features
5728 * Z8000-Dependent:: Z8000 Dependent Features
5731 * Vax-Dependent:: VAX Dependent Features
5738 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5739 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5740 @c peculiarity: to preserve cross-references, there must be a node called
5741 @c "Machine Dependencies". Hence the conditional nodenames in each
5742 @c major node below. Node defaulting in makeinfo requires adjacency of
5743 @c node and sectioning commands; hence the repetition of @chapter BLAH
5744 @c in both conditional blocks.
5747 @include c-a29k.texi
5751 @include c-alpha.texi
5763 @include c-cris.texi
5768 @node Machine Dependencies
5769 @chapter Machine Dependent Features
5771 The machine instruction sets are different on each Hitachi chip family,
5772 and there are also some syntax differences among the families. This
5773 chapter describes the specific @command{@value{AS}} features for each
5777 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5778 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5779 * SH-Dependent:: Hitachi SH Dependent Features
5786 @include c-d10v.texi
5790 @include c-d30v.texi
5794 @include c-h8300.texi
5798 @include c-h8500.texi
5802 @include c-hppa.texi
5806 @include c-i370.texi
5810 @include c-i386.texi
5814 @include c-i860.texi
5818 @include c-i960.texi
5822 @include c-ia64.texi
5826 @include c-m32r.texi
5830 @include c-m68k.texi
5834 @include c-m68hc11.texi
5838 @include c-m88k.texi
5842 @include c-mips.texi
5846 @include c-mmix.texi
5850 @include c-ns32k.texi
5854 @include c-pdp11.texi
5867 @include c-sh64.texi
5871 @include c-sparc.texi
5875 @include c-tic54x.texi
5887 @include c-v850.texi
5891 @c reverse effect of @down at top of generic Machine-Dep chapter
5895 @node Reporting Bugs
5896 @chapter Reporting Bugs
5897 @cindex bugs in assembler
5898 @cindex reporting bugs in assembler
5900 Your bug reports play an essential role in making @command{@value{AS}} reliable.
5902 Reporting a bug may help you by bringing a solution to your problem, or it may
5903 not. But in any case the principal function of a bug report is to help the
5904 entire community by making the next version of @command{@value{AS}} work better.
5905 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
5907 In order for a bug report to serve its purpose, you must include the
5908 information that enables us to fix the bug.
5911 * Bug Criteria:: Have you found a bug?
5912 * Bug Reporting:: How to report bugs
5916 @section Have you found a bug?
5917 @cindex bug criteria
5919 If you are not sure whether you have found a bug, here are some guidelines:
5922 @cindex fatal signal
5923 @cindex assembler crash
5924 @cindex crash of assembler
5926 If the assembler gets a fatal signal, for any input whatever, that is a
5927 @command{@value{AS}} bug. Reliable assemblers never crash.
5929 @cindex error on valid input
5931 If @command{@value{AS}} produces an error message for valid input, that is a bug.
5933 @cindex invalid input
5935 If @command{@value{AS}} does not produce an error message for invalid input, that
5936 is a bug. However, you should note that your idea of ``invalid input'' might
5937 be our idea of ``an extension'' or ``support for traditional practice''.
5940 If you are an experienced user of assemblers, your suggestions for improvement
5941 of @command{@value{AS}} are welcome in any case.
5945 @section How to report bugs
5947 @cindex assembler bugs, reporting
5949 A number of companies and individuals offer support for @sc{gnu} products. If
5950 you obtained @command{@value{AS}} from a support organization, we recommend you
5951 contact that organization first.
5953 You can find contact information for many support companies and
5954 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5957 In any event, we also recommend that you send bug reports for @command{@value{AS}}
5958 to @samp{bug-binutils@@gnu.org}.
5960 The fundamental principle of reporting bugs usefully is this:
5961 @strong{report all the facts}. If you are not sure whether to state a
5962 fact or leave it out, state it!
5964 Often people omit facts because they think they know what causes the problem
5965 and assume that some details do not matter. Thus, you might assume that the
5966 name of a symbol you use in an example does not matter. Well, probably it does
5967 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5968 happens to fetch from the location where that name is stored in memory;
5969 perhaps, if the name were different, the contents of that location would fool
5970 the assembler into doing the right thing despite the bug. Play it safe and
5971 give a specific, complete example. That is the easiest thing for you to do,
5972 and the most helpful.
5974 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5975 it is new to us. Therefore, always write your bug reports on the assumption
5976 that the bug has not been reported previously.
5978 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5979 bell?'' Those bug reports are useless, and we urge everyone to
5980 @emph{refuse to respond to them} except to chide the sender to report
5983 To enable us to fix the bug, you should include all these things:
5987 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
5988 it with the @samp{--version} argument.
5990 Without this, we will not know whether there is any point in looking for
5991 the bug in the current version of @command{@value{AS}}.
5994 Any patches you may have applied to the @command{@value{AS}} source.
5997 The type of machine you are using, and the operating system name and
6001 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
6005 The command arguments you gave the assembler to assemble your example and
6006 observe the bug. To guarantee you will not omit something important, list them
6007 all. A copy of the Makefile (or the output from make) is sufficient.
6009 If we were to try to guess the arguments, we would probably guess wrong
6010 and then we might not encounter the bug.
6013 A complete input file that will reproduce the bug. If the bug is observed when
6014 the assembler is invoked via a compiler, send the assembler source, not the
6015 high level language source. Most compilers will produce the assembler source
6016 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
6017 the options @samp{-v --save-temps}; this will save the assembler source in a
6018 file with an extension of @file{.s}, and also show you exactly how
6019 @command{@value{AS}} is being run.
6022 A description of what behavior you observe that you believe is
6023 incorrect. For example, ``It gets a fatal signal.''
6025 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
6026 will certainly notice it. But if the bug is incorrect output, we might not
6027 notice unless it is glaringly wrong. You might as well not give us a chance to
6030 Even if the problem you experience is a fatal signal, you should still say so
6031 explicitly. Suppose something strange is going on, such as, your copy of
6032 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6033 library on your system. (This has happened!) Your copy might crash and ours
6034 would not. If you told us to expect a crash, then when ours fails to crash, we
6035 would know that the bug was not happening for us. If you had not told us to
6036 expect a crash, then we would not be able to draw any conclusion from our
6040 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6041 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6042 option. Always send diffs from the old file to the new file. If you even
6043 discuss something in the @command{@value{AS}} source, refer to it by context, not
6046 The line numbers in our development sources will not match those in your
6047 sources. Your line numbers would convey no useful information to us.
6050 Here are some things that are not necessary:
6054 A description of the envelope of the bug.
6056 Often people who encounter a bug spend a lot of time investigating
6057 which changes to the input file will make the bug go away and which
6058 changes will not affect it.
6060 This is often time consuming and not very useful, because the way we
6061 will find the bug is by running a single example under the debugger
6062 with breakpoints, not by pure deduction from a series of examples.
6063 We recommend that you save your time for something else.
6065 Of course, if you can find a simpler example to report @emph{instead}
6066 of the original one, that is a convenience for us. Errors in the
6067 output will be easier to spot, running under the debugger will take
6068 less time, and so on.
6070 However, simplification is not vital; if you do not want to do this,
6071 report the bug anyway and send us the entire test case you used.
6074 A patch for the bug.
6076 A patch for the bug does help us if it is a good one. But do not omit
6077 the necessary information, such as the test case, on the assumption that
6078 a patch is all we need. We might see problems with your patch and decide
6079 to fix the problem another way, or we might not understand it at all.
6081 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6082 construct an example that will make the program follow a certain path through
6083 the code. If you do not send us the example, we will not be able to construct
6084 one, so we will not be able to verify that the bug is fixed.
6086 And if we cannot understand what bug you are trying to fix, or why your
6087 patch should be an improvement, we will not install it. A test case will
6088 help us to understand.
6091 A guess about what the bug is or what it depends on.
6093 Such guesses are usually wrong. Even we cannot guess right about such
6094 things without first using the debugger to find the facts.
6097 @node Acknowledgements
6098 @chapter Acknowledgements
6100 If you have contributed to @command{@value{AS}} and your name isn't listed here,
6101 it is not meant as a slight. We just don't know about it. Send mail to the
6102 maintainer, and we'll correct the situation. Currently
6104 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6106 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6109 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6110 information and the 68k series machines, most of the preprocessing pass, and
6111 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6113 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6114 many bug fixes, including merging support for several processors, breaking GAS
6115 up to handle multiple object file format back ends (including heavy rewrite,
6116 testing, an integration of the coff and b.out back ends), adding configuration
6117 including heavy testing and verification of cross assemblers and file splits
6118 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6119 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6120 port (including considerable amounts of reverse engineering), a SPARC opcode
6121 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6122 assertions and made them work, much other reorganization, cleanup, and lint.
6124 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6125 in format-specific I/O modules.
6127 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6128 has done much work with it since.
6130 The Intel 80386 machine description was written by Eliot Dresselhaus.
6132 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6134 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6135 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6137 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6138 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6139 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6140 support a.out format.
6142 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
6143 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
6144 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6145 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6148 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6149 simplified the configuration of which versions accept which directives. He
6150 updated the 68k machine description so that Motorola's opcodes always produced
6151 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
6152 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6153 cross-compilation support, and one bug in relaxation that took a week and
6154 required the proverbial one-bit fix.
6156 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6157 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6158 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6159 PowerPC assembler, and made a few other minor patches.
6161 Steve Chamberlain made @command{@value{AS}} able to generate listings.
6163 Hewlett-Packard contributed support for the HP9000/300.
6165 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6166 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6167 formats). This work was supported by both the Center for Software Science at
6168 the University of Utah and Cygnus Support.
6170 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6171 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6172 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6173 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6174 and some initial 64-bit support).
6176 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
6178 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6179 support for openVMS/Alpha.
6181 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6184 Several engineers at Cygnus Support have also provided many small bug fixes and
6185 configuration enhancements.
6187 Many others have contributed large or small bugfixes and enhancements. If
6188 you have contributed significant work and are not mentioned on this list, and
6189 want to be, let us know. Some of the history has been lost; we are not
6190 intentionally leaving anyone out.
6192 @node GNU Free Documentation License
6193 @chapter GNU Free Documentation License
6195 GNU Free Documentation License
6197 Version 1.1, March 2000
6199 Copyright (C) 2000 Free Software Foundation, Inc.
6200 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
6202 Everyone is permitted to copy and distribute verbatim copies
6203 of this license document, but changing it is not allowed.
6208 The purpose of this License is to make a manual, textbook, or other
6209 written document "free" in the sense of freedom: to assure everyone
6210 the effective freedom to copy and redistribute it, with or without
6211 modifying it, either commercially or noncommercially. Secondarily,
6212 this License preserves for the author and publisher a way to get
6213 credit for their work, while not being considered responsible for
6214 modifications made by others.
6216 This License is a kind of "copyleft", which means that derivative
6217 works of the document must themselves be free in the same sense. It
6218 complements the GNU General Public License, which is a copyleft
6219 license designed for free software.
6221 We have designed this License in order to use it for manuals for free
6222 software, because free software needs free documentation: a free
6223 program should come with manuals providing the same freedoms that the
6224 software does. But this License is not limited to software manuals;
6225 it can be used for any textual work, regardless of subject matter or
6226 whether it is published as a printed book. We recommend this License
6227 principally for works whose purpose is instruction or reference.
6230 1. APPLICABILITY AND DEFINITIONS
6232 This License applies to any manual or other work that contains a
6233 notice placed by the copyright holder saying it can be distributed
6234 under the terms of this License. The "Document", below, refers to any
6235 such manual or work. Any member of the public is a licensee, and is
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6242 A "Secondary Section" is a named appendix or a front-matter section of
6243 the Document that deals exclusively with the relationship of the
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6254 are designated, as being those of Invariant Sections, in the notice
6255 that says that the Document is released under this License.
6257 The "Cover Texts" are certain short passages of text that are listed,
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6261 A "Transparent" copy of the Document means a machine-readable copy,
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6273 Examples of suitable formats for Transparent copies include plain
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6280 machine-generated HTML produced by some word processors for output
6283 The "Title Page" means, for a printed book, the title page itself,
6284 plus such following pages as are needed to hold, legibly, the material
6285 this License requires to appear in the title page. For works in
6286 formats which do not have any title page as such, "Title Page" means
6287 the text near the most prominent appearance of the work's title,
6288 preceding the beginning of the body of the text.
6293 You may copy and distribute the Document in any medium, either
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6295 copyright notices, and the license notice saying this License applies
6296 to the Document are reproduced in all copies, and that you add no other
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6300 compensation in exchange for copies. If you distribute a large enough
6301 number of copies you must also follow the conditions in section 3.
6303 You may also lend copies, under the same conditions stated above, and
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6307 3. COPYING IN QUANTITY
6309 If you publish printed copies of the Document numbering more than 100,
6310 and the Document's license notice requires Cover Texts, you must enclose
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6317 Copying with changes limited to the covers, as long as they preserve
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6321 If the required texts for either cover are too voluminous to fit
6322 legibly, you should put the first ones listed (as many as fit
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6326 If you publish or distribute Opaque copies of the Document numbering
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6329 a publicly-accessible computer-network location containing a complete
6330 Transparent copy of the Document, free of added material, which the
6331 general network-using public has access to download anonymously at no
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6340 It is requested, but not required, that you contact the authors of the
6341 Document well before redistributing any large number of copies, to give
6342 them a chance to provide you with an updated version of the Document.
6347 You may copy and distribute a Modified Version of the Document under
6348 the conditions of sections 2 and 3 above, provided that you release
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6354 A. Use in the Title Page (and on the covers, if any) a title distinct
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6359 B. List on the Title Page, as authors, one or more persons or entities
6360 responsible for authorship of the modifications in the Modified
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6362 Document (all of its principal authors, if it has less than five).
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6365 D. Preserve all the copyright notices of the Document.
6366 E. Add an appropriate copyright notice for your modifications
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6368 F. Include, immediately after the copyright notices, a license notice
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6371 G. Preserve in that license notice the full lists of Invariant Sections
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6375 it an item stating at least the title, year, new authors, and
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6381 J. Preserve the network location, if any, given in the Document for
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6388 K. In any section entitled "Acknowledgements" or "Dedications",
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6390 substance and tone of each of the contributor acknowledgements
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6392 L. Preserve all the Invariant Sections of the Document,
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6395 M. Delete any section entitled "Endorsements". Such a section
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6400 If the Modified Version includes new front-matter sections or
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6405 These titles must be distinct from any other section titles.
6407 You may add a section entitled "Endorsements", provided it contains
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6428 5. COMBINING DOCUMENTS
6430 You may combine the Document with other documents released under this
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6447 in the various original documents, forming one section entitled
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6453 6. COLLECTIONS OF DOCUMENTS
6455 You may make a collection consisting of the Document and other documents
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6467 7. AGGREGATION WITH INDEPENDENT WORKS
6469 A compilation of the Document or its derivatives with other separate
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6492 original versions of these Invariant Sections. You may include a
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6501 You may not copy, modify, sublicense, or distribute the Document except
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6507 parties remain in full compliance.
6510 10. FUTURE REVISIONS OF THIS LICENSE
6512 The Free Software Foundation may publish new, revised versions
6513 of the GNU Free Documentation License from time to time. Such new
6514 versions will be similar in spirit to the present version, but may
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6516 http://www.gnu.org/copyleft/.
6518 Each version of the License is given a distinguishing version number.
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6528 ADDENDUM: How to use this License for your documents
6530 To use this License in a document you have written, include a copy of
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6535 Copyright (c) YEAR YOUR NAME.
6536 Permission is granted to copy, distribute and/or modify this document
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6538 or any later version published by the Free Software Foundation;
6539 with the Invariant Sections being LIST THEIR TITLES, with the
6540 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
6541 A copy of the license is included in the section entitled "GNU
6542 Free Documentation License".
6545 If you have no Invariant Sections, write "with no Invariant Sections"
6546 instead of saying which ones are invariant. If you have no
6547 Front-Cover Texts, write "no Front-Cover Texts" instead of
6548 "Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
6550 If your document contains nontrivial examples of program code, we
6551 recommend releasing these examples in parallel under your choice of
6552 free software license, such as the GNU General Public License,
6553 to permit their use in free software.
projects / external / binutils.git / blob