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{-G} @var{num}] [@b{-mcpu}=@var{CPU} ]
374 [@b{-mips1}] [@b{-mips2}] [@b{-mips3}] [@b{-mips4}] [@b{-mips5}]
375 [@b{-mips32}] [@b{-mips64}]
376 [@b{-m4650}] [@b{-no-m4650}]
377 [@b{-mips3d}] [@b{-no-mips3d}]
378 [@b{--trap}] [@b{--break}] [@b{-n}]
379 [@b{--emulation}=@var{name} ]
383 @emph{Target MMIX options:}
384 [@b{--fixed-special-register-names}] [@b{--globalize-symbols}]
385 [@b{--gnu-syntax}] [@b{--relax}] [@b{--no-predefined-symbols}]
386 [@b{--no-expand}] [@b{--no-merge-gregs}] [@b{-x}]
387 [@b{--linker-allocated-gregs}]
391 @emph{Target PDP11 options:}
392 [@b{-mpic}|@b{-mno-pic}] [@b{-mall}] [@b{-mno-extensions}]
393 [@b{-m}@var{extension}|@b{-mno-}@var{extension}]
394 [@b{-m}@var{cpu}] [@b{-m}@var{machine}]
398 @emph{Target picoJava options:}
403 @emph{Target PowerPC options:}
404 [@b{-mpwrx}|@b{-mpwr2}|@b{-mpwr}|@b{-m601}|@b{-mppc}|@b{-mppc32}|@b{-m603}|@b{-m604}|
405 @b{-m403}|@b{-m405}|@b{-mppc64}|@b{-m620}|@b{-mppc64bridge}|@b{-mbooke}|
406 @b{-mbooke32}|@b{-mbooke64}]
407 [@b{-mcom}|@b{-many}|@b{-maltivec}] [@b{-memb}]
408 [@b{-mregnames}|@b{-mno-regnames}]
409 [@b{-mrelocatable}|@b{-mrelocatable-lib}]
410 [@b{-mlittle}|@b{-mlittle-endian}|@b{-mbig}|@b{-mbig-endian}]
411 [@b{-msolaris}|@b{-mno-solaris}]
415 @emph{Target SPARC options:}
416 @c The order here is important. See c-sparc.texi.
417 [@b{-Av6}|@b{-Av7}|@b{-Av8}|@b{-Asparclet}|@b{-Asparclite}
418 @b{-Av8plus}|@b{-Av8plusa}|@b{-Av9}|@b{-Av9a}]
419 [@b{-xarch=v8plus}|@b{-xarch=v8plusa}] [@b{-bump}]
424 @emph{Target TIC54X options:}
425 [@b{-mcpu=54[123589]}|@b{-mcpu=54[56]lp}] [@b{-mfar-mode}|@b{-mf}]
426 [@b{-merrors-to-file} @var{<filename>}|@b{-me} @var{<filename>}]
429 @c Z8000 has no machine-dependent assembler options
438 Turn on listings, in any of a variety of ways:
442 omit false conditionals
445 omit debugging directives
448 include high-level source
454 include macro expansions
457 omit forms processing
463 set the name of the listing file
466 You may combine these options; for example, use @samp{-aln} for assembly
467 listing without forms processing. The @samp{=file} option, if used, must be
468 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
471 Ignored. This option is accepted for script compatibility with calls to
474 @item --defsym @var{sym}=@var{value}
475 Define the symbol @var{sym} to be @var{value} before assembling the input file.
476 @var{value} must be an integer constant. As in C, a leading @samp{0x}
477 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
480 ``fast''---skip whitespace and comment preprocessing (assume source is
484 Generate stabs debugging information for each assembler line. This
485 may help debugging assembler code, if the debugger can handle it.
488 Generate DWARF2 debugging information for each assembler line. This
489 may help debugging assembler code, if the debugger can handle it. Note - this
490 option is only supported by some targets, not all of them.
493 Print a summary of the command line options and exit.
496 Print a summary of all target specific options and exit.
499 Add directory @var{dir} to the search list for @code{.include} directives.
502 Don't warn about signed overflow.
505 @ifclear DIFF-TBL-KLUGE
506 This option is accepted but has no effect on the @value{TARGET} family.
508 @ifset DIFF-TBL-KLUGE
509 Issue warnings when difference tables altered for long displacements.
514 Keep (in the symbol table) local symbols. On traditional a.out systems
515 these start with @samp{L}, but different systems have different local
518 @item --listing-lhs-width=@var{number}
519 Set the maximum width, in words, of the output data column for an assembler
520 listing to @var{number}.
522 @item --listing-lhs-width2=@var{number}
523 Set the maximum width, in words, of the output data column for continuation
524 lines in an assembler listing to @var{number}.
526 @item --listing-rhs-width=@var{number}
527 Set the maximum width of an input source line, as displayed in a listing, to
530 @item --listing-cont-lines=@var{number}
531 Set the maximum number of lines printed in a listing for a single line of input
534 @item -o @var{objfile}
535 Name the object-file output from @command{@value{AS}} @var{objfile}.
538 Fold the data section into the text section.
541 Print the maximum space (in bytes) and total time (in seconds) used by
544 @item --strip-local-absolute
545 Remove local absolute symbols from the outgoing symbol table.
549 Print the @command{as} version.
552 Print the @command{as} version and exit.
556 Suppress warning messages.
558 @item --fatal-warnings
559 Treat warnings as errors.
562 Don't suppress warning messages or treat them as errors.
571 Generate an object file even after errors.
573 @item -- | @var{files} @dots{}
574 Standard input, or source files to assemble.
579 The following options are available when @value{AS} is configured for
584 This option selects the core processor variant.
586 Select either big-endian (-EB) or little-endian (-EL) output.
591 The following options are available when @value{AS} is configured for the ARM
595 @item -mcpu=@var{processor}[+@var{extension}@dots{}]
596 Specify which ARM processor variant is the target.
597 @item -march=@var{architecture}[+@var{extension}@dots{}]
598 Specify which ARM architecture variant is used by the target.
599 @item -mfpu=@var{floating-point-format}
600 Select which Floating Point architecture is the target.
602 Enable Thumb only instruction decoding.
603 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
604 Select which procedure calling convention is in use.
606 Select either big-endian (-EB) or little-endian (-EL) output.
607 @item -mthumb-interwork
608 Specify that the code has been generated with interworking between Thumb and
611 Specify that PIC code has been generated.
616 See the info pages for documentation of the CRIS-specific options.
620 The following options are available when @value{AS} is configured for
623 @cindex D10V optimization
624 @cindex optimization, D10V
626 Optimize output by parallelizing instructions.
631 The following options are available when @value{AS} is configured for a D30V
634 @cindex D30V optimization
635 @cindex optimization, D30V
637 Optimize output by parallelizing instructions.
641 Warn when nops are generated.
643 @cindex D30V nops after 32-bit multiply
645 Warn when a nop after a 32-bit multiply instruction is generated.
650 The following options are available when @value{AS} is configured for the
651 Intel 80960 processor.
654 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
655 Specify which variant of the 960 architecture is the target.
658 Add code to collect statistics about branches taken.
661 Do not alter compare-and-branch instructions for long displacements;
668 The following options are available when @value{AS} is configured for the
669 Mitsubishi M32R series.
674 Specify which processor in the M32R family is the target. The default
675 is normally the M32R, but this option changes it to the M32RX.
677 @item --warn-explicit-parallel-conflicts or --Wp
678 Produce warning messages when questionable parallel constructs are
681 @item --no-warn-explicit-parallel-conflicts or --Wnp
682 Do not produce warning messages when questionable parallel constructs are
689 The following options are available when @value{AS} is configured for the
690 Motorola 68000 series.
695 Shorten references to undefined symbols, to one word instead of two.
697 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
698 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
699 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
700 Specify what processor in the 68000 family is the target. The default
701 is normally the 68020, but this can be changed at configuration time.
703 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
704 The target machine does (or does not) have a floating-point coprocessor.
705 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
706 the basic 68000 is not compatible with the 68881, a combination of the
707 two can be specified, since it's possible to do emulation of the
708 coprocessor instructions with the main processor.
710 @item -m68851 | -mno-68851
711 The target machine does (or does not) have a memory-management
712 unit coprocessor. The default is to assume an MMU for 68020 and up.
719 For details about the PDP-11 machine dependent features options,
720 see @ref{PDP-11-Options}.
723 @item -mpic | -mno-pic
724 Generate position-independent (or position-dependent) code. The
725 default is @option{-mpic}.
728 @itemx -mall-extensions
729 Enable all instruction set extensions. This is the default.
731 @item -mno-extensions
732 Disable all instruction set extensions.
734 @item -m@var{extension} | -mno-@var{extension}
735 Enable (or disable) a particular instruction set extension.
738 Enable the instruction set extensions supported by a particular CPU, and
739 disable all other extensions.
741 @item -m@var{machine}
742 Enable the instruction set extensions supported by a particular machine
743 model, and disable all other extensions.
749 The following options are available when @value{AS} is configured for
750 a picoJava processor.
754 @cindex PJ endianness
755 @cindex endianness, PJ
756 @cindex big endian output, PJ
758 Generate ``big endian'' format output.
760 @cindex little endian output, PJ
762 Generate ``little endian'' format output.
768 The following options are available when @value{AS} is configured for the
769 Motorola 68HC11 or 68HC12 series.
773 @item -m68hc11 | -m68hc12
774 Specify what processor is the target. The default is
775 defined by the configuration option when building the assembler.
777 @item --force-long-branchs
778 Relative branches are turned into absolute ones. This concerns
779 conditional branches, unconditional branches and branches to a
782 @item -S | --short-branchs
783 Do not turn relative branchs into absolute ones
784 when the offset is out of range.
786 @item --strict-direct-mode
787 Do not turn the direct addressing mode into extended addressing mode
788 when the instruction does not support direct addressing mode.
790 @item --print-insn-syntax
791 Print the syntax of instruction in case of error.
793 @item --print-opcodes
794 print the list of instructions with syntax and then exit.
796 @item --generate-example
797 print an example of instruction for each possible instruction and then exit.
798 This option is only useful for testing @command{@value{AS}}.
804 The following options are available when @command{@value{AS}} is configured
805 for the SPARC architecture:
808 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
809 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
810 Explicitly select a variant of the SPARC architecture.
812 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
813 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
815 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
816 UltraSPARC extensions.
818 @item -xarch=v8plus | -xarch=v8plusa
819 For compatibility with the Solaris v9 assembler. These options are
820 equivalent to -Av8plus and -Av8plusa, respectively.
823 Warn when the assembler switches to another architecture.
828 The following options are available when @value{AS} is configured for the 'c54x
833 Enable extended addressing mode. All addresses and relocations will assume
834 extended addressing (usually 23 bits).
835 @item -mcpu=@var{CPU_VERSION}
836 Sets the CPU version being compiled for.
837 @item -merrors-to-file @var{FILENAME}
838 Redirect error output to a file, for broken systems which don't support such
839 behaviour in the shell.
844 The following options are available when @value{AS} is configured for
849 This option sets the largest size of an object that can be referenced
850 implicitly with the @code{gp} register. It is only accepted for targets that
851 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
853 @cindex MIPS endianness
854 @cindex endianness, MIPS
855 @cindex big endian output, MIPS
857 Generate ``big endian'' format output.
859 @cindex little endian output, MIPS
861 Generate ``little endian'' format output.
870 Generate code for a particular MIPS Instruction Set Architecture level.
871 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
872 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
874 @samp{-mips5}, @samp{-mips32}, and @samp{-mips64} correspond
875 to generic @sc{MIPS V}, @sc{MIPS32}, and @sc{MIPS64} ISA
876 processors, respectively.
880 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
881 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
882 instructions around accesses to the @samp{HI} and @samp{LO} registers.
883 @samp{-no-m4650} turns off this option.
887 Generate code for the MIPS-3D Application Specific Extension.
888 This tells the assembler to accept MIPS-3D instructions.
889 @samp{-no-mips3d} turns off this option.
891 @item -mcpu=@var{CPU}
892 Generate code for a particular MIPS cpu. It is exactly equivalent to
893 @samp{-m@var{cpu}}, except that there are more value of @var{cpu}
897 @item --emulation=@var{name}
898 This option causes @command{@value{AS}} to emulate @command{@value{AS}} configured
899 for some other target, in all respects, including output format (choosing
900 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
901 debugging information or store symbol table information, and default
902 endianness. The available configuration names are: @samp{mipsecoff},
903 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
904 @samp{mipsbelf}. The first two do not alter the default endianness from that
905 of the primary target for which the assembler was configured; the others change
906 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
907 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
908 selection in any case.
910 This option is currently supported only when the primary target
911 @command{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
912 Furthermore, the primary target or others specified with
913 @samp{--enable-targets=@dots{}} at configuration time must include support for
914 the other format, if both are to be available. For example, the Irix 5
915 configuration includes support for both.
917 Eventually, this option will support more configurations, with more
918 fine-grained control over the assembler's behavior, and will be supported for
922 @command{@value{AS}} ignores this option. It is accepted for compatibility with
930 Control how to deal with multiplication overflow and division by zero.
931 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
932 (and only work for Instruction Set Architecture level 2 and higher);
933 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
937 When this option is used, @command{@value{AS}} will issue a warning every
938 time it generates a nop instruction from a macro.
943 The following options are available when @value{AS} is configured for
949 Enable or disable the JSRI to BSR transformation. By default this is enabled.
950 The command line option @samp{-nojsri2bsr} can be used to disable it.
954 Enable or disable the silicon filter behaviour. By default this is disabled.
955 The default can be overridden by the @samp{-sifilter} command line option.
958 Alter jump instructions for long displacements.
960 @item -mcpu=[210|340]
961 Select the cpu type on the target hardware. This controls which instructions
965 Assemble for a big endian target.
968 Assemble for a little endian target.
974 See the info pages for documentation of the MMIX-specific options.
980 * Manual:: Structure of this Manual
981 * GNU Assembler:: The GNU Assembler
982 * Object Formats:: Object File Formats
983 * Command Line:: Command Line
984 * Input Files:: Input Files
985 * Object:: Output (Object) File
986 * Errors:: Error and Warning Messages
990 @section Structure of this Manual
992 @cindex manual, structure and purpose
993 This manual is intended to describe what you need to know to use
994 @sc{gnu} @command{@value{AS}}. We cover the syntax expected in source files, including
995 notation for symbols, constants, and expressions; the directives that
996 @command{@value{AS}} understands; and of course how to invoke @command{@value{AS}}.
999 We also cover special features in the @value{TARGET}
1000 configuration of @command{@value{AS}}, including assembler directives.
1003 This manual also describes some of the machine-dependent features of
1004 various flavors of the assembler.
1007 @cindex machine instructions (not covered)
1008 On the other hand, this manual is @emph{not} intended as an introduction
1009 to programming in assembly language---let alone programming in general!
1010 In a similar vein, we make no attempt to introduce the machine
1011 architecture; we do @emph{not} describe the instruction set, standard
1012 mnemonics, registers or addressing modes that are standard to a
1013 particular architecture.
1015 You may want to consult the manufacturer's
1016 machine architecture manual for this information.
1020 For information on the H8/300 machine instruction set, see @cite{H8/300
1021 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
1022 see @cite{H8/300H Series Programming Manual} (Hitachi).
1025 For information on the H8/500 machine instruction set, see @cite{H8/500
1026 Series Programming Manual} (Hitachi M21T001).
1029 For information on the Hitachi SH machine instruction set, see
1030 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
1033 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
1037 @c I think this is premature---doc@cygnus.com, 17jan1991
1039 Throughout this manual, we assume that you are running @dfn{GNU},
1040 the portable operating system from the @dfn{Free Software
1041 Foundation, Inc.}. This restricts our attention to certain kinds of
1042 computer (in particular, the kinds of computers that @sc{gnu} can run on);
1043 once this assumption is granted examples and definitions need less
1046 @command{@value{AS}} is part of a team of programs that turn a high-level
1047 human-readable series of instructions into a low-level
1048 computer-readable series of instructions. Different versions of
1049 @command{@value{AS}} are used for different kinds of computer.
1052 @c There used to be a section "Terminology" here, which defined
1053 @c "contents", "byte", "word", and "long". Defining "word" to any
1054 @c particular size is confusing when the .word directive may generate 16
1055 @c bits on one machine and 32 bits on another; in general, for the user
1056 @c version of this manual, none of these terms seem essential to define.
1057 @c They were used very little even in the former draft of the manual;
1058 @c this draft makes an effort to avoid them (except in names of
1062 @section The GNU Assembler
1064 @c man begin DESCRIPTION
1066 @sc{gnu} @command{as} is really a family of assemblers.
1068 This manual describes @command{@value{AS}}, a member of that family which is
1069 configured for the @value{TARGET} architectures.
1071 If you use (or have used) the @sc{gnu} assembler on one architecture, you
1072 should find a fairly similar environment when you use it on another
1073 architecture. Each version has much in common with the others,
1074 including object file formats, most assembler directives (often called
1075 @dfn{pseudo-ops}) and assembler syntax.@refill
1077 @cindex purpose of @sc{gnu} assembler
1078 @command{@value{AS}} is primarily intended to assemble the output of the
1079 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
1080 @code{@value{LD}}. Nevertheless, we've tried to make @command{@value{AS}}
1081 assemble correctly everything that other assemblers for the same
1082 machine would assemble.
1084 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
1087 @c This remark should appear in generic version of manual; assumption
1088 @c here is that generic version sets M680x0.
1089 This doesn't mean @command{@value{AS}} always uses the same syntax as another
1090 assembler for the same architecture; for example, we know of several
1091 incompatible versions of 680x0 assembly language syntax.
1096 Unlike older assemblers, @command{@value{AS}} is designed to assemble a source
1097 program in one pass of the source file. This has a subtle impact on the
1098 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
1100 @node Object Formats
1101 @section Object File Formats
1103 @cindex object file format
1104 The @sc{gnu} assembler can be configured to produce several alternative
1105 object file formats. For the most part, this does not affect how you
1106 write assembly language programs; but directives for debugging symbols
1107 are typically different in different file formats. @xref{Symbol
1108 Attributes,,Symbol Attributes}.
1111 On the @value{TARGET}, @command{@value{AS}} is configured to produce
1112 @value{OBJ-NAME} format object files.
1114 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1116 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1117 @code{a.out} or COFF format object files.
1120 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1121 @code{b.out} or COFF format object files.
1124 On the @value{TARGET}, @command{@value{AS}} can be configured to produce either
1125 SOM or ELF format object files.
1130 @section Command Line
1132 @cindex command line conventions
1134 After the program name @command{@value{AS}}, the command line may contain
1135 options and file names. Options may appear in any order, and may be
1136 before, after, or between file names. The order of file names is
1139 @cindex standard input, as input file
1141 @file{--} (two hyphens) by itself names the standard input file
1142 explicitly, as one of the files for @command{@value{AS}} to assemble.
1144 @cindex options, command line
1145 Except for @samp{--} any command line argument that begins with a
1146 hyphen (@samp{-}) is an option. Each option changes the behavior of
1147 @command{@value{AS}}. No option changes the way another option works. An
1148 option is a @samp{-} followed by one or more letters; the case of
1149 the letter is important. All options are optional.
1151 Some options expect exactly one file name to follow them. The file
1152 name may either immediately follow the option's letter (compatible
1153 with older assemblers) or it may be the next command argument (@sc{gnu}
1154 standard). These two command lines are equivalent:
1157 @value{AS} -o my-object-file.o mumble.s
1158 @value{AS} -omy-object-file.o mumble.s
1162 @section Input Files
1165 @cindex source program
1166 @cindex files, input
1167 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1168 describe the program input to one run of @command{@value{AS}}. The program may
1169 be in one or more files; how the source is partitioned into files
1170 doesn't change the meaning of the source.
1172 @c I added "con" prefix to "catenation" just to prove I can overcome my
1173 @c APL training... doc@cygnus.com
1174 The source program is a concatenation of the text in all the files, in the
1177 @c man begin DESCRIPTION
1178 Each time you run @command{@value{AS}} it assembles exactly one source
1179 program. The source program is made up of one or more files.
1180 (The standard input is also a file.)
1182 You give @command{@value{AS}} a command line that has zero or more input file
1183 names. The input files are read (from left file name to right). A
1184 command line argument (in any position) that has no special meaning
1185 is taken to be an input file name.
1187 If you give @command{@value{AS}} no file names it attempts to read one input file
1188 from the @command{@value{AS}} standard input, which is normally your terminal. You
1189 may have to type @key{ctl-D} to tell @command{@value{AS}} there is no more program
1192 Use @samp{--} if you need to explicitly name the standard input file
1193 in your command line.
1195 If the source is empty, @command{@value{AS}} produces a small, empty object
1200 @subheading Filenames and Line-numbers
1202 @cindex input file linenumbers
1203 @cindex line numbers, in input files
1204 There are two ways of locating a line in the input file (or files) and
1205 either may be used in reporting error messages. One way refers to a line
1206 number in a physical file; the other refers to a line number in a
1207 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1209 @dfn{Physical files} are those files named in the command line given
1210 to @command{@value{AS}}.
1212 @dfn{Logical files} are simply names declared explicitly by assembler
1213 directives; they bear no relation to physical files. Logical file names help
1214 error messages reflect the original source file, when @command{@value{AS}} source
1215 is itself synthesized from other files. @command{@value{AS}} understands the
1216 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1217 @ref{File,,@code{.file}}.
1220 @section Output (Object) File
1226 Every time you run @command{@value{AS}} it produces an output file, which is
1227 your assembly language program translated into numbers. This file
1228 is the object file. Its default name is
1236 @code{b.out} when @command{@value{AS}} is configured for the Intel 80960.
1238 You can give it another name by using the @option{-o} option. Conventionally,
1239 object file names end with @file{.o}. The default name is used for historical
1240 reasons: older assemblers were capable of assembling self-contained programs
1241 directly into a runnable program. (For some formats, this isn't currently
1242 possible, but it can be done for the @code{a.out} format.)
1246 The object file is meant for input to the linker @code{@value{LD}}. It contains
1247 assembled program code, information to help @code{@value{LD}} integrate
1248 the assembled program into a runnable file, and (optionally) symbolic
1249 information for the debugger.
1251 @c link above to some info file(s) like the description of a.out.
1252 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1255 @section Error and Warning Messages
1257 @c man begin DESCRIPTION
1259 @cindex error messages
1260 @cindex warning messages
1261 @cindex messages from assembler
1262 @command{@value{AS}} may write warnings and error messages to the standard error
1263 file (usually your terminal). This should not happen when a compiler
1264 runs @command{@value{AS}} automatically. Warnings report an assumption made so
1265 that @command{@value{AS}} could keep assembling a flawed program; errors report a
1266 grave problem that stops the assembly.
1270 @cindex format of warning messages
1271 Warning messages have the format
1274 file_name:@b{NNN}:Warning Message Text
1278 @cindex line numbers, in warnings/errors
1279 (where @b{NNN} is a line number). If a logical file name has been given
1280 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1281 the current input file is used. If a logical line number was given
1283 (@pxref{Line,,@code{.line}})
1287 (@pxref{Line,,@code{.line}})
1290 (@pxref{Ln,,@code{.ln}})
1293 then it is used to calculate the number printed,
1294 otherwise the actual line in the current source file is printed. The
1295 message text is intended to be self explanatory (in the grand Unix
1298 @cindex format of error messages
1299 Error messages have the format
1301 file_name:@b{NNN}:FATAL:Error Message Text
1303 The file name and line number are derived as for warning
1304 messages. The actual message text may be rather less explanatory
1305 because many of them aren't supposed to happen.
1308 @chapter Command-Line Options
1310 @cindex options, all versions of assembler
1311 This chapter describes command-line options available in @emph{all}
1312 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1314 to the @value{TARGET}.
1317 to particular machine architectures.
1320 @c man begin DESCRIPTION
1322 If you are invoking @command{@value{AS}} via the @sc{gnu} C compiler (version 2),
1323 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1324 The assembler arguments must be separated from each other (and the @samp{-Wa})
1325 by commas. For example:
1328 gcc -c -g -O -Wa,-alh,-L file.c
1332 This passes two options to the assembler: @samp{-alh} (emit a listing to
1333 standard output with with high-level and assembly source) and @samp{-L} (retain
1334 local symbols in the symbol table).
1336 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1337 command-line options are automatically passed to the assembler by the compiler.
1338 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1339 precisely what options it passes to each compilation pass, including the
1345 * a:: -a[cdhlns] enable listings
1346 * D:: -D for compatibility
1347 * f:: -f to work faster
1348 * I:: -I for .include search path
1349 @ifclear DIFF-TBL-KLUGE
1350 * K:: -K for compatibility
1352 @ifset DIFF-TBL-KLUGE
1353 * K:: -K for difference tables
1356 * L:: -L to retain local labels
1357 * listing:: --listing-XXX to configure listing output
1358 * M:: -M or --mri to assemble in MRI compatibility mode
1359 * MD:: --MD for dependency tracking
1360 * o:: -o to name the object file
1361 * R:: -R to join data and text sections
1362 * statistics:: --statistics to see statistics about assembly
1363 * traditional-format:: --traditional-format for compatible output
1364 * v:: -v to announce version
1365 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1366 * Z:: -Z to make object file even after errors
1370 @section Enable Listings: @option{-a[cdhlns]}
1379 @cindex listings, enabling
1380 @cindex assembly listings, enabling
1382 These options enable listing output from the assembler. By itself,
1383 @samp{-a} requests high-level, assembly, and symbols listing.
1384 You can use other letters to select specific options for the list:
1385 @samp{-ah} requests a high-level language listing,
1386 @samp{-al} requests an output-program assembly listing, and
1387 @samp{-as} requests a symbol table listing.
1388 High-level listings require that a compiler debugging option like
1389 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1392 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1393 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1394 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1395 omitted from the listing.
1397 Use the @samp{-ad} option to omit debugging directives from the
1400 Once you have specified one of these options, you can further control
1401 listing output and its appearance using the directives @code{.list},
1402 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1404 The @samp{-an} option turns off all forms processing.
1405 If you do not request listing output with one of the @samp{-a} options, the
1406 listing-control directives have no effect.
1408 The letters after @samp{-a} may be combined into one option,
1409 @emph{e.g.}, @samp{-aln}.
1411 Note if the assembler source is coming from the standard input (eg because it
1412 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1413 is being used) then the listing will not contain any comments or preprocessor
1414 directives. This is because the listing code buffers input source lines from
1415 stdin only after they have been preprocessed by the assembler. This reduces
1416 memory usage and makes the code more efficient.
1419 @section @option{-D}
1422 This option has no effect whatsoever, but it is accepted to make it more
1423 likely that scripts written for other assemblers also work with
1424 @command{@value{AS}}.
1427 @section Work Faster: @option{-f}
1430 @cindex trusted compiler
1431 @cindex faster processing (@option{-f})
1432 @samp{-f} should only be used when assembling programs written by a
1433 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1434 and comment preprocessing on
1435 the input file(s) before assembling them. @xref{Preprocessing,
1439 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1440 preprocessed (if they contain comments, for example), @command{@value{AS}} does
1445 @section @code{.include} search path: @option{-I} @var{path}
1447 @kindex -I @var{path}
1448 @cindex paths for @code{.include}
1449 @cindex search path for @code{.include}
1450 @cindex @code{include} directive search path
1451 Use this option to add a @var{path} to the list of directories
1452 @command{@value{AS}} searches for files specified in @code{.include}
1453 directives (@pxref{Include,,@code{.include}}). You may use @option{-I} as
1454 many times as necessary to include a variety of paths. The current
1455 working directory is always searched first; after that, @command{@value{AS}}
1456 searches any @samp{-I} directories in the same order as they were
1457 specified (left to right) on the command line.
1460 @section Difference Tables: @option{-K}
1463 @ifclear DIFF-TBL-KLUGE
1464 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1465 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1466 where it can be used to warn when the assembler alters the machine code
1467 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1468 family does not have the addressing limitations that sometimes lead to this
1469 alteration on other platforms.
1472 @ifset DIFF-TBL-KLUGE
1473 @cindex difference tables, warning
1474 @cindex warning for altered difference tables
1475 @command{@value{AS}} sometimes alters the code emitted for directives of the form
1476 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1477 You can use the @samp{-K} option if you want a warning issued when this
1482 @section Include Local Labels: @option{-L}
1485 @cindex local labels, retaining in output
1486 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1487 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1488 debugging, because they are intended for the use of programs (like
1489 compilers) that compose assembler programs, not for your notice.
1490 Normally both @command{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1491 normally debug with them.
1493 This option tells @command{@value{AS}} to retain those @samp{L@dots{}} symbols
1494 in the object file. Usually if you do this you also tell the linker
1495 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1497 By default, a local label is any label beginning with @samp{L}, but each
1498 target is allowed to redefine the local label prefix.
1500 On the HPPA local labels begin with @samp{L$}.
1504 @section Configuring listing output: @option{--listing}
1506 The listing feature of the assembler can be enabled via the command line switch
1507 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1508 hex dump of the corresponding locations in the output object file, and displays
1509 them as a listing file. The format of this listing can be controlled by pseudo
1510 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1511 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1514 @item --listing-lhs-width=@samp{number}
1515 @kindex --listing-lhs-width
1516 @cindex Width of first line disassembly output
1517 Sets the maximum width, in words, of the first line of the hex byte dump. This
1518 dump appears on the left hand side of the listing output.
1520 @item --listing-lhs-width2=@samp{number}
1521 @kindex --listing-lhs-width2
1522 @cindex Width of continuation lines of disassembly output
1523 Sets the maximum width, in words, of any further lines of the hex byte dump for
1524 a given inut source line. If this value is not specified, it defaults to being
1525 the same as the value specified for @samp{--listing-lhs-width}. If neither
1526 switch is used the default is to one.
1528 @item --listing-rhs-width=@samp{number}
1529 @kindex --listing-rhs-width
1530 @cindex Width of source line output
1531 Sets the maximum width, in characters, of the source line that is displayed
1532 alongside the hex dump. The default value for this parameter is 100. The
1533 source line is displayed on the right hand side of the listing output.
1535 @item --listing-cont-lines=@samp{number}
1536 @kindex --listing-cont-lines
1537 @cindex Maximum number of continuation lines
1538 Sets the maximum number of continuation lines of hex dump that will be
1539 displayed for a given single line of source input. The default value is 4.
1543 @section Assemble in MRI Compatibility Mode: @option{-M}
1546 @cindex MRI compatibility mode
1547 The @option{-M} or @option{--mri} option selects MRI compatibility mode. This
1548 changes the syntax and pseudo-op handling of @command{@value{AS}} to make it
1549 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1550 configured target) assembler from Microtec Research. The exact nature of the
1551 MRI syntax will not be documented here; see the MRI manuals for more
1552 information. Note in particular that the handling of macros and macro
1553 arguments is somewhat different. The purpose of this option is to permit
1554 assembling existing MRI assembler code using @command{@value{AS}}.
1556 The MRI compatibility is not complete. Certain operations of the MRI assembler
1557 depend upon its object file format, and can not be supported using other object
1558 file formats. Supporting these would require enhancing each object file format
1559 individually. These are:
1562 @item global symbols in common section
1564 The m68k MRI assembler supports common sections which are merged by the linker.
1565 Other object file formats do not support this. @command{@value{AS}} handles
1566 common sections by treating them as a single common symbol. It permits local
1567 symbols to be defined within a common section, but it can not support global
1568 symbols, since it has no way to describe them.
1570 @item complex relocations
1572 The MRI assemblers support relocations against a negated section address, and
1573 relocations which combine the start addresses of two or more sections. These
1574 are not support by other object file formats.
1576 @item @code{END} pseudo-op specifying start address
1578 The MRI @code{END} pseudo-op permits the specification of a start address.
1579 This is not supported by other object file formats. The start address may
1580 instead be specified using the @option{-e} option to the linker, or in a linker
1583 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1585 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1586 name to the output file. This is not supported by other object file formats.
1588 @item @code{ORG} pseudo-op
1590 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1591 address. This differs from the usual @command{@value{AS}} @code{.org} pseudo-op,
1592 which changes the location within the current section. Absolute sections are
1593 not supported by other object file formats. The address of a section may be
1594 assigned within a linker script.
1597 There are some other features of the MRI assembler which are not supported by
1598 @command{@value{AS}}, typically either because they are difficult or because they
1599 seem of little consequence. Some of these may be supported in future releases.
1603 @item EBCDIC strings
1605 EBCDIC strings are not supported.
1607 @item packed binary coded decimal
1609 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1610 and @code{DCB.P} pseudo-ops are not supported.
1612 @item @code{FEQU} pseudo-op
1614 The m68k @code{FEQU} pseudo-op is not supported.
1616 @item @code{NOOBJ} pseudo-op
1618 The m68k @code{NOOBJ} pseudo-op is not supported.
1620 @item @code{OPT} branch control options
1622 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1623 @code{BRL}, and @code{BRW}---are ignored. @command{@value{AS}} automatically
1624 relaxes all branches, whether forward or backward, to an appropriate size, so
1625 these options serve no purpose.
1627 @item @code{OPT} list control options
1629 The following m68k @code{OPT} list control options are ignored: @code{C},
1630 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1631 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1633 @item other @code{OPT} options
1635 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1636 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1638 @item @code{OPT} @code{D} option is default
1640 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1641 @code{OPT NOD} may be used to turn it off.
1643 @item @code{XREF} pseudo-op.
1645 The m68k @code{XREF} pseudo-op is ignored.
1647 @item @code{.debug} pseudo-op
1649 The i960 @code{.debug} pseudo-op is not supported.
1651 @item @code{.extended} pseudo-op
1653 The i960 @code{.extended} pseudo-op is not supported.
1655 @item @code{.list} pseudo-op.
1657 The various options of the i960 @code{.list} pseudo-op are not supported.
1659 @item @code{.optimize} pseudo-op
1661 The i960 @code{.optimize} pseudo-op is not supported.
1663 @item @code{.output} pseudo-op
1665 The i960 @code{.output} pseudo-op is not supported.
1667 @item @code{.setreal} pseudo-op
1669 The i960 @code{.setreal} pseudo-op is not supported.
1674 @section Dependency tracking: @option{--MD}
1677 @cindex dependency tracking
1680 @command{@value{AS}} can generate a dependency file for the file it creates. This
1681 file consists of a single rule suitable for @code{make} describing the
1682 dependencies of the main source file.
1684 The rule is written to the file named in its argument.
1686 This feature is used in the automatic updating of makefiles.
1689 @section Name the Object File: @option{-o}
1692 @cindex naming object file
1693 @cindex object file name
1694 There is always one object file output when you run @command{@value{AS}}. By
1695 default it has the name
1698 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1712 You use this option (which takes exactly one filename) to give the
1713 object file a different name.
1715 Whatever the object file is called, @command{@value{AS}} overwrites any
1716 existing file of the same name.
1719 @section Join Data and Text Sections: @option{-R}
1722 @cindex data and text sections, joining
1723 @cindex text and data sections, joining
1724 @cindex joining text and data sections
1725 @cindex merging text and data sections
1726 @option{-R} tells @command{@value{AS}} to write the object file as if all
1727 data-section data lives in the text section. This is only done at
1728 the very last moment: your binary data are the same, but data
1729 section parts are relocated differently. The data section part of
1730 your object file is zero bytes long because all its bytes are
1731 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1733 When you specify @option{-R} it would be possible to generate shorter
1734 address displacements (because we do not have to cross between text and
1735 data section). We refrain from doing this simply for compatibility with
1736 older versions of @command{@value{AS}}. In future, @option{-R} may work this way.
1739 When @command{@value{AS}} is configured for COFF output,
1740 this option is only useful if you use sections named @samp{.text} and
1745 @option{-R} is not supported for any of the HPPA targets. Using
1746 @option{-R} generates a warning from @command{@value{AS}}.
1750 @section Display Assembly Statistics: @option{--statistics}
1752 @kindex --statistics
1753 @cindex statistics, about assembly
1754 @cindex time, total for assembly
1755 @cindex space used, maximum for assembly
1756 Use @samp{--statistics} to display two statistics about the resources used by
1757 @command{@value{AS}}: the maximum amount of space allocated during the assembly
1758 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1761 @node traditional-format
1762 @section Compatible output: @option{--traditional-format}
1764 @kindex --traditional-format
1765 For some targets, the output of @command{@value{AS}} is different in some ways
1766 from the output of some existing assembler. This switch requests
1767 @command{@value{AS}} to use the traditional format instead.
1769 For example, it disables the exception frame optimizations which
1770 @command{@value{AS}} normally does by default on @code{@value{GCC}} output.
1773 @section Announce Version: @option{-v}
1777 @cindex assembler version
1778 @cindex version of assembler
1779 You can find out what version of as is running by including the
1780 option @samp{-v} (which you can also spell as @samp{-version}) on the
1784 @section Control Warnings: @option{-W}, @option{--warn}, @option{--no-warn}, @option{--fatal-warnings}
1786 @command{@value{AS}} should never give a warning or error message when
1787 assembling compiler output. But programs written by people often
1788 cause @command{@value{AS}} to give a warning that a particular assumption was
1789 made. All such warnings are directed to the standard error file.
1792 @kindex @samp{--no-warn}
1793 @cindex suppressing warnings
1794 @cindex warnings, suppressing
1795 If you use the @option{-W} and @option{--no-warn} options, no warnings are issued.
1796 This only affects the warning messages: it does not change any particular of
1797 how @command{@value{AS}} assembles your file. Errors, which stop the assembly,
1800 @kindex @samp{--fatal-warnings}
1801 @cindex errors, caused by warnings
1802 @cindex warnings, causing error
1803 If you use the @option{--fatal-warnings} option, @command{@value{AS}} considers
1804 files that generate warnings to be in error.
1806 @kindex @samp{--warn}
1807 @cindex warnings, switching on
1808 You can switch these options off again by specifying @option{--warn}, which
1809 causes warnings to be output as usual.
1812 @section Generate Object File in Spite of Errors: @option{-Z}
1813 @cindex object file, after errors
1814 @cindex errors, continuing after
1815 After an error message, @command{@value{AS}} normally produces no output. If for
1816 some reason you are interested in object file output even after
1817 @command{@value{AS}} gives an error message on your program, use the @samp{-Z}
1818 option. If there are any errors, @command{@value{AS}} continues anyways, and
1819 writes an object file after a final warning message of the form @samp{@var{n}
1820 errors, @var{m} warnings, generating bad object file.}
1825 @cindex machine-independent syntax
1826 @cindex syntax, machine-independent
1827 This chapter describes the machine-independent syntax allowed in a
1828 source file. @command{@value{AS}} syntax is similar to what many other
1829 assemblers use; it is inspired by the BSD 4.2
1834 assembler, except that @command{@value{AS}} does not assemble Vax bit-fields.
1838 * Preprocessing:: Preprocessing
1839 * Whitespace:: Whitespace
1840 * Comments:: Comments
1841 * Symbol Intro:: Symbols
1842 * Statements:: Statements
1843 * Constants:: Constants
1847 @section Preprocessing
1849 @cindex preprocessing
1850 The @command{@value{AS}} internal preprocessor:
1852 @cindex whitespace, removed by preprocessor
1854 adjusts and removes extra whitespace. It leaves one space or tab before
1855 the keywords on a line, and turns any other whitespace on the line into
1858 @cindex comments, removed by preprocessor
1860 removes all comments, replacing them with a single space, or an
1861 appropriate number of newlines.
1863 @cindex constants, converted by preprocessor
1865 converts character constants into the appropriate numeric values.
1868 It does not do macro processing, include file handling, or
1869 anything else you may get from your C compiler's preprocessor. You can
1870 do include file processing with the @code{.include} directive
1871 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1872 to get other ``CPP'' style preprocessing, by giving the input file a
1873 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1874 Output, gcc.info, Using GNU CC}.
1876 Excess whitespace, comments, and character constants
1877 cannot be used in the portions of the input text that are not
1880 @cindex turning preprocessing on and off
1881 @cindex preprocessing, turning on and off
1884 If the first line of an input file is @code{#NO_APP} or if you use the
1885 @samp{-f} option, whitespace and comments are not removed from the input file.
1886 Within an input file, you can ask for whitespace and comment removal in
1887 specific portions of the by putting a line that says @code{#APP} before the
1888 text that may contain whitespace or comments, and putting a line that says
1889 @code{#NO_APP} after this text. This feature is mainly intend to support
1890 @code{asm} statements in compilers whose output is otherwise free of comments
1897 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1898 Whitespace is used to separate symbols, and to make programs neater for
1899 people to read. Unless within character constants
1900 (@pxref{Characters,,Character Constants}), any whitespace means the same
1901 as exactly one space.
1907 There are two ways of rendering comments to @command{@value{AS}}. In both
1908 cases the comment is equivalent to one space.
1910 Anything from @samp{/*} through the next @samp{*/} is a comment.
1911 This means you may not nest these comments.
1915 The only way to include a newline ('\n') in a comment
1916 is to use this sort of comment.
1919 /* This sort of comment does not nest. */
1922 @cindex line comment character
1923 Anything from the @dfn{line comment} character to the next newline
1924 is considered a comment and is ignored. The line comment character is
1926 @samp{;} for the AMD 29K family;
1929 @samp{;} on the ARC;
1932 @samp{@@} on the ARM;
1935 @samp{;} for the H8/300 family;
1938 @samp{!} for the H8/500 family;
1941 @samp{;} for the HPPA;
1944 @samp{#} on the i386 and x86-64;
1947 @samp{#} on the i960;
1950 @samp{;} for the PDP-11;
1953 @samp{;} for picoJava;
1956 @samp{;} for Motorola PowerPC;
1959 @samp{!} for the Hitachi SH;
1962 @samp{!} on the SPARC;
1965 @samp{#} on the m32r;
1968 @samp{|} on the 680x0;
1971 @samp{#} on the 68HC11 and 68HC12;
1974 @samp{;} on the M880x0;
1977 @samp{#} on the Vax;
1980 @samp{!} for the Z8000;
1983 @samp{#} on the V850;
1985 see @ref{Machine Dependencies}. @refill
1986 @c FIXME What about i860?
1989 On some machines there are two different line comment characters. One
1990 character only begins a comment if it is the first non-whitespace character on
1991 a line, while the other always begins a comment.
1995 The V850 assembler also supports a double dash as starting a comment that
1996 extends to the end of the line.
2002 @cindex lines starting with @code{#}
2003 @cindex logical line numbers
2004 To be compatible with past assemblers, lines that begin with @samp{#} have a
2005 special interpretation. Following the @samp{#} should be an absolute
2006 expression (@pxref{Expressions}): the logical line number of the @emph{next}
2007 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
2008 new logical file name. The rest of the line, if any, should be whitespace.
2010 If the first non-whitespace characters on the line are not numeric,
2011 the line is ignored. (Just like a comment.)
2014 # This is an ordinary comment.
2015 # 42-6 "new_file_name" # New logical file name
2016 # This is logical line # 36.
2018 This feature is deprecated, and may disappear from future versions
2019 of @command{@value{AS}}.
2024 @cindex characters used in symbols
2025 @ifclear SPECIAL-SYMS
2026 A @dfn{symbol} is one or more characters chosen from the set of all
2027 letters (both upper and lower case), digits and the three characters
2033 A @dfn{symbol} is one or more characters chosen from the set of all
2034 letters (both upper and lower case), digits and the three characters
2035 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
2041 On most machines, you can also use @code{$} in symbol names; exceptions
2042 are noted in @ref{Machine Dependencies}.
2044 No symbol may begin with a digit. Case is significant.
2045 There is no length limit: all characters are significant. Symbols are
2046 delimited by characters not in that set, or by the beginning of a file
2047 (since the source program must end with a newline, the end of a file is
2048 not a possible symbol delimiter). @xref{Symbols}.
2049 @cindex length of symbols
2054 @cindex statements, structure of
2055 @cindex line separator character
2056 @cindex statement separator character
2058 @ifclear abnormal-separator
2059 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
2060 semicolon (@samp{;}). The newline or semicolon is considered part of
2061 the preceding statement. Newlines and semicolons within character
2062 constants are an exception: they do not end statements.
2064 @ifset abnormal-separator
2066 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
2067 sign (@samp{@@}). The newline or at sign is considered part of the
2068 preceding statement. Newlines and at signs within character constants
2069 are an exception: they do not end statements.
2072 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
2073 point (@samp{!}). The newline or exclamation point is considered part of the
2074 preceding statement. Newlines and exclamation points within character
2075 constants are an exception: they do not end statements.
2078 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
2079 H8/300) a dollar sign (@samp{$}); or (for the
2082 (@samp{;}). The newline or separator character is considered part of
2083 the preceding statement. Newlines and separators within character
2084 constants are an exception: they do not end statements.
2089 A @dfn{statement} ends at a newline character (@samp{\n}) or line
2090 separator character. (The line separator is usually @samp{;}, unless
2091 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
2092 newline or separator character is considered part of the preceding
2093 statement. Newlines and separators within character constants are an
2094 exception: they do not end statements.
2097 @cindex newline, required at file end
2098 @cindex EOF, newline must precede
2099 It is an error to end any statement with end-of-file: the last
2100 character of any input file should be a newline.@refill
2102 An empty statement is allowed, and may include whitespace. It is ignored.
2104 @cindex instructions and directives
2105 @cindex directives and instructions
2106 @c "key symbol" is not used elsewhere in the document; seems pedantic to
2107 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2109 A statement begins with zero or more labels, optionally followed by a
2110 key symbol which determines what kind of statement it is. The key
2111 symbol determines the syntax of the rest of the statement. If the
2112 symbol begins with a dot @samp{.} then the statement is an assembler
2113 directive: typically valid for any computer. If the symbol begins with
2114 a letter the statement is an assembly language @dfn{instruction}: it
2115 assembles into a machine language instruction.
2117 Different versions of @command{@value{AS}} for different computers
2118 recognize different instructions. In fact, the same symbol may
2119 represent a different instruction in a different computer's assembly
2123 @cindex @code{:} (label)
2124 @cindex label (@code{:})
2125 A label is a symbol immediately followed by a colon (@code{:}).
2126 Whitespace before a label or after a colon is permitted, but you may not
2127 have whitespace between a label's symbol and its colon. @xref{Labels}.
2130 For HPPA targets, labels need not be immediately followed by a colon, but
2131 the definition of a label must begin in column zero. This also implies that
2132 only one label may be defined on each line.
2136 label: .directive followed by something
2137 another_label: # This is an empty statement.
2138 instruction operand_1, operand_2, @dots{}
2145 A constant is a number, written so that its value is known by
2146 inspection, without knowing any context. Like this:
2149 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2150 .ascii "Ring the bell\7" # A string constant.
2151 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2152 .float 0f-314159265358979323846264338327\
2153 95028841971.693993751E-40 # - pi, a flonum.
2158 * Characters:: Character Constants
2159 * Numbers:: Number Constants
2163 @subsection Character Constants
2165 @cindex character constants
2166 @cindex constants, character
2167 There are two kinds of character constants. A @dfn{character} stands
2168 for one character in one byte and its value may be used in
2169 numeric expressions. String constants (properly called string
2170 @emph{literals}) are potentially many bytes and their values may not be
2171 used in arithmetic expressions.
2175 * Chars:: Characters
2179 @subsubsection Strings
2181 @cindex string constants
2182 @cindex constants, string
2183 A @dfn{string} is written between double-quotes. It may contain
2184 double-quotes or null characters. The way to get special characters
2185 into a string is to @dfn{escape} these characters: precede them with
2186 a backslash @samp{\} character. For example @samp{\\} represents
2187 one backslash: the first @code{\} is an escape which tells
2188 @command{@value{AS}} to interpret the second character literally as a backslash
2189 (which prevents @command{@value{AS}} from recognizing the second @code{\} as an
2190 escape character). The complete list of escapes follows.
2192 @cindex escape codes, character
2193 @cindex character escape codes
2196 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2198 @cindex @code{\b} (backspace character)
2199 @cindex backspace (@code{\b})
2201 Mnemonic for backspace; for ASCII this is octal code 010.
2204 @c Mnemonic for EOText; for ASCII this is octal code 004.
2206 @cindex @code{\f} (formfeed character)
2207 @cindex formfeed (@code{\f})
2209 Mnemonic for FormFeed; for ASCII this is octal code 014.
2211 @cindex @code{\n} (newline character)
2212 @cindex newline (@code{\n})
2214 Mnemonic for newline; for ASCII this is octal code 012.
2217 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2219 @cindex @code{\r} (carriage return character)
2220 @cindex carriage return (@code{\r})
2222 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2225 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2226 @c other assemblers.
2228 @cindex @code{\t} (tab)
2229 @cindex tab (@code{\t})
2231 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2234 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2235 @c @item \x @var{digit} @var{digit} @var{digit}
2236 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2238 @cindex @code{\@var{ddd}} (octal character code)
2239 @cindex octal character code (@code{\@var{ddd}})
2240 @item \ @var{digit} @var{digit} @var{digit}
2241 An octal character code. The numeric code is 3 octal digits.
2242 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2243 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2245 @cindex @code{\@var{xd...}} (hex character code)
2246 @cindex hex character code (@code{\@var{xd...}})
2247 @item \@code{x} @var{hex-digits...}
2248 A hex character code. All trailing hex digits are combined. Either upper or
2249 lower case @code{x} works.
2251 @cindex @code{\\} (@samp{\} character)
2252 @cindex backslash (@code{\\})
2254 Represents one @samp{\} character.
2257 @c Represents one @samp{'} (accent acute) character.
2258 @c This is needed in single character literals
2259 @c (@xref{Characters,,Character Constants}.) to represent
2262 @cindex @code{\"} (doublequote character)
2263 @cindex doublequote (@code{\"})
2265 Represents one @samp{"} character. Needed in strings to represent
2266 this character, because an unescaped @samp{"} would end the string.
2268 @item \ @var{anything-else}
2269 Any other character when escaped by @kbd{\} gives a warning, but
2270 assembles as if the @samp{\} was not present. The idea is that if
2271 you used an escape sequence you clearly didn't want the literal
2272 interpretation of the following character. However @command{@value{AS}} has no
2273 other interpretation, so @command{@value{AS}} knows it is giving you the wrong
2274 code and warns you of the fact.
2277 Which characters are escapable, and what those escapes represent,
2278 varies widely among assemblers. The current set is what we think
2279 the BSD 4.2 assembler recognizes, and is a subset of what most C
2280 compilers recognize. If you are in doubt, do not use an escape
2284 @subsubsection Characters
2286 @cindex single character constant
2287 @cindex character, single
2288 @cindex constant, single character
2289 A single character may be written as a single quote immediately
2290 followed by that character. The same escapes apply to characters as
2291 to strings. So if you want to write the character backslash, you
2292 must write @kbd{'\\} where the first @code{\} escapes the second
2293 @code{\}. As you can see, the quote is an acute accent, not a
2294 grave accent. A newline
2296 @ifclear abnormal-separator
2297 (or semicolon @samp{;})
2299 @ifset abnormal-separator
2301 (or at sign @samp{@@})
2304 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2310 immediately following an acute accent is taken as a literal character
2311 and does not count as the end of a statement. The value of a character
2312 constant in a numeric expression is the machine's byte-wide code for
2313 that character. @command{@value{AS}} assumes your character code is ASCII:
2314 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2317 @subsection Number Constants
2319 @cindex constants, number
2320 @cindex number constants
2321 @command{@value{AS}} distinguishes three kinds of numbers according to how they
2322 are stored in the target machine. @emph{Integers} are numbers that
2323 would fit into an @code{int} in the C language. @emph{Bignums} are
2324 integers, but they are stored in more than 32 bits. @emph{Flonums}
2325 are floating point numbers, described below.
2328 * Integers:: Integers
2333 * Bit Fields:: Bit Fields
2339 @subsubsection Integers
2341 @cindex constants, integer
2343 @cindex binary integers
2344 @cindex integers, binary
2345 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2346 the binary digits @samp{01}.
2348 @cindex octal integers
2349 @cindex integers, octal
2350 An octal integer is @samp{0} followed by zero or more of the octal
2351 digits (@samp{01234567}).
2353 @cindex decimal integers
2354 @cindex integers, decimal
2355 A decimal integer starts with a non-zero digit followed by zero or
2356 more digits (@samp{0123456789}).
2358 @cindex hexadecimal integers
2359 @cindex integers, hexadecimal
2360 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2361 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2363 Integers have the usual values. To denote a negative integer, use
2364 the prefix operator @samp{-} discussed under expressions
2365 (@pxref{Prefix Ops,,Prefix Operators}).
2368 @subsubsection Bignums
2371 @cindex constants, bignum
2372 A @dfn{bignum} has the same syntax and semantics as an integer
2373 except that the number (or its negative) takes more than 32 bits to
2374 represent in binary. The distinction is made because in some places
2375 integers are permitted while bignums are not.
2378 @subsubsection Flonums
2380 @cindex floating point numbers
2381 @cindex constants, floating point
2383 @cindex precision, floating point
2384 A @dfn{flonum} represents a floating point number. The translation is
2385 indirect: a decimal floating point number from the text is converted by
2386 @command{@value{AS}} to a generic binary floating point number of more than
2387 sufficient precision. This generic floating point number is converted
2388 to a particular computer's floating point format (or formats) by a
2389 portion of @command{@value{AS}} specialized to that computer.
2391 A flonum is written by writing (in order)
2396 (@samp{0} is optional on the HPPA.)
2400 A letter, to tell @command{@value{AS}} the rest of the number is a flonum.
2402 @kbd{e} is recommended. Case is not important.
2404 @c FIXME: verify if flonum syntax really this vague for most cases
2405 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2406 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2409 On the H8/300, H8/500,
2411 and AMD 29K architectures, the letter must be
2412 one of the letters @samp{DFPRSX} (in upper or lower case).
2414 On the ARC, the letter must be one of the letters @samp{DFRS}
2415 (in upper or lower case).
2417 On the Intel 960 architecture, the letter must be
2418 one of the letters @samp{DFT} (in upper or lower case).
2420 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2424 One of the letters @samp{DFPRSX} (in upper or lower case).
2427 One of the letters @samp{DFRS} (in upper or lower case).
2430 One of the letters @samp{DFPRSX} (in upper or lower case).
2433 The letter @samp{E} (upper case only).
2436 One of the letters @samp{DFT} (in upper or lower case).
2441 An optional sign: either @samp{+} or @samp{-}.
2444 An optional @dfn{integer part}: zero or more decimal digits.
2447 An optional @dfn{fractional part}: @samp{.} followed by zero
2448 or more decimal digits.
2451 An optional exponent, consisting of:
2455 An @samp{E} or @samp{e}.
2456 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2457 @c principle this can perfectly well be different on different targets.
2459 Optional sign: either @samp{+} or @samp{-}.
2461 One or more decimal digits.
2466 At least one of the integer part or the fractional part must be
2467 present. The floating point number has the usual base-10 value.
2469 @command{@value{AS}} does all processing using integers. Flonums are computed
2470 independently of any floating point hardware in the computer running
2471 @command{@value{AS}}.
2475 @c Bit fields are written as a general facility but are also controlled
2476 @c by a conditional-compilation flag---which is as of now (21mar91)
2477 @c turned on only by the i960 config of GAS.
2479 @subsubsection Bit Fields
2482 @cindex constants, bit field
2483 You can also define numeric constants as @dfn{bit fields}.
2484 specify two numbers separated by a colon---
2486 @var{mask}:@var{value}
2489 @command{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2492 The resulting number is then packed
2494 @c this conditional paren in case bit fields turned on elsewhere than 960
2495 (in host-dependent byte order)
2497 into a field whose width depends on which assembler directive has the
2498 bit-field as its argument. Overflow (a result from the bitwise and
2499 requiring more binary digits to represent) is not an error; instead,
2500 more constants are generated, of the specified width, beginning with the
2501 least significant digits.@refill
2503 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2504 @code{.short}, and @code{.word} accept bit-field arguments.
2509 @chapter Sections and Relocation
2514 * Secs Background:: Background
2515 * Ld Sections:: Linker Sections
2516 * As Sections:: Assembler Internal Sections
2517 * Sub-Sections:: Sub-Sections
2521 @node Secs Background
2524 Roughly, a section is a range of addresses, with no gaps; all data
2525 ``in'' those addresses is treated the same for some particular purpose.
2526 For example there may be a ``read only'' section.
2528 @cindex linker, and assembler
2529 @cindex assembler, and linker
2530 The linker @code{@value{LD}} reads many object files (partial programs) and
2531 combines their contents to form a runnable program. When @command{@value{AS}}
2532 emits an object file, the partial program is assumed to start at address 0.
2533 @code{@value{LD}} assigns the final addresses for the partial program, so that
2534 different partial programs do not overlap. This is actually an
2535 oversimplification, but it suffices to explain how @command{@value{AS}} uses
2538 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2539 addresses. These blocks slide to their run-time addresses as rigid
2540 units; their length does not change and neither does the order of bytes
2541 within them. Such a rigid unit is called a @emph{section}. Assigning
2542 run-time addresses to sections is called @dfn{relocation}. It includes
2543 the task of adjusting mentions of object-file addresses so they refer to
2544 the proper run-time addresses.
2546 For the H8/300 and H8/500,
2547 and for the Hitachi SH,
2548 @command{@value{AS}} pads sections if needed to
2549 ensure they end on a word (sixteen bit) boundary.
2552 @cindex standard assembler sections
2553 An object file written by @command{@value{AS}} has at least three sections, any
2554 of which may be empty. These are named @dfn{text}, @dfn{data} and
2559 When it generates COFF output,
2561 @command{@value{AS}} can also generate whatever other named sections you specify
2562 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2563 If you do not use any directives that place output in the @samp{.text}
2564 or @samp{.data} sections, these sections still exist, but are empty.
2569 When @command{@value{AS}} generates SOM or ELF output for the HPPA,
2571 @command{@value{AS}} can also generate whatever other named sections you
2572 specify using the @samp{.space} and @samp{.subspace} directives. See
2573 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2574 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2575 assembler directives.
2578 Additionally, @command{@value{AS}} uses different names for the standard
2579 text, data, and bss sections when generating SOM output. Program text
2580 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2581 BSS into @samp{$BSS$}.
2585 Within the object file, the text section starts at address @code{0}, the
2586 data section follows, and the bss section follows the data section.
2589 When generating either SOM or ELF output files on the HPPA, the text
2590 section starts at address @code{0}, the data section at address
2591 @code{0x4000000}, and the bss section follows the data section.
2594 To let @code{@value{LD}} know which data changes when the sections are
2595 relocated, and how to change that data, @command{@value{AS}} also writes to the
2596 object file details of the relocation needed. To perform relocation
2597 @code{@value{LD}} must know, each time an address in the object
2601 Where in the object file is the beginning of this reference to
2604 How long (in bytes) is this reference?
2606 Which section does the address refer to? What is the numeric value of
2608 (@var{address}) @minus{} (@var{start-address of section})?
2611 Is the reference to an address ``Program-Counter relative''?
2614 @cindex addresses, format of
2615 @cindex section-relative addressing
2616 In fact, every address @command{@value{AS}} ever uses is expressed as
2618 (@var{section}) + (@var{offset into section})
2621 Further, most expressions @command{@value{AS}} computes have this section-relative
2624 (For some object formats, such as SOM for the HPPA, some expressions are
2625 symbol-relative instead.)
2628 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2629 @var{N} into section @var{secname}.''
2631 Apart from text, data and bss sections you need to know about the
2632 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2633 addresses in the absolute section remain unchanged. For example, address
2634 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2635 @code{@value{LD}}. Although the linker never arranges two partial programs'
2636 data sections with overlapping addresses after linking, @emph{by definition}
2637 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2638 part of a program is always the same address when the program is running as
2639 address @code{@{absolute@ 239@}} in any other part of the program.
2641 The idea of sections is extended to the @dfn{undefined} section. Any
2642 address whose section is unknown at assembly time is by definition
2643 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2644 Since numbers are always defined, the only way to generate an undefined
2645 address is to mention an undefined symbol. A reference to a named
2646 common block would be such a symbol: its value is unknown at assembly
2647 time so it has section @emph{undefined}.
2649 By analogy the word @emph{section} is used to describe groups of sections in
2650 the linked program. @code{@value{LD}} puts all partial programs' text
2651 sections in contiguous addresses in the linked program. It is
2652 customary to refer to the @emph{text section} of a program, meaning all
2653 the addresses of all partial programs' text sections. Likewise for
2654 data and bss sections.
2656 Some sections are manipulated by @code{@value{LD}}; others are invented for
2657 use of @command{@value{AS}} and have no meaning except during assembly.
2660 @section Linker Sections
2661 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2666 @cindex named sections
2667 @cindex sections, named
2668 @item named sections
2671 @cindex text section
2672 @cindex data section
2676 These sections hold your program. @command{@value{AS}} and @code{@value{LD}} treat them as
2677 separate but equal sections. Anything you can say of one section is
2680 When the program is running, however, it is
2681 customary for the text section to be unalterable. The
2682 text section is often shared among processes: it contains
2683 instructions, constants and the like. The data section of a running
2684 program is usually alterable: for example, C variables would be stored
2685 in the data section.
2690 This section contains zeroed bytes when your program begins running. It
2691 is used to hold uninitialized variables or common storage. The length of
2692 each partial program's bss section is important, but because it starts
2693 out containing zeroed bytes there is no need to store explicit zero
2694 bytes in the object file. The bss section was invented to eliminate
2695 those explicit zeros from object files.
2697 @cindex absolute section
2698 @item absolute section
2699 Address 0 of this section is always ``relocated'' to runtime address 0.
2700 This is useful if you want to refer to an address that @code{@value{LD}} must
2701 not change when relocating. In this sense we speak of absolute
2702 addresses being ``unrelocatable'': they do not change during relocation.
2704 @cindex undefined section
2705 @item undefined section
2706 This ``section'' is a catch-all for address references to objects not in
2707 the preceding sections.
2708 @c FIXME: ref to some other doc on obj-file formats could go here.
2711 @cindex relocation example
2712 An idealized example of three relocatable sections follows.
2714 The example uses the traditional section names @samp{.text} and @samp{.data}.
2716 Memory addresses are on the horizontal axis.
2720 @c END TEXI2ROFF-KILL
2723 partial program # 1: |ttttt|dddd|00|
2730 partial program # 2: |TTT|DDD|000|
2733 +--+---+-----+--+----+---+-----+~~
2734 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2735 +--+---+-----+--+----+---+-----+~~
2737 addresses: 0 @dots{}
2744 \line{\it Partial program \#1: \hfil}
2745 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2746 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2748 \line{\it Partial program \#2: \hfil}
2749 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2750 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2752 \line{\it linked program: \hfil}
2753 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2754 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2755 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2756 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2758 \line{\it addresses: \hfil}
2762 @c END TEXI2ROFF-KILL
2765 @section Assembler Internal Sections
2767 @cindex internal assembler sections
2768 @cindex sections in messages, internal
2769 These sections are meant only for the internal use of @command{@value{AS}}. They
2770 have no meaning at run-time. You do not really need to know about these
2771 sections for most purposes; but they can be mentioned in @command{@value{AS}}
2772 warning messages, so it might be helpful to have an idea of their
2773 meanings to @command{@value{AS}}. These sections are used to permit the
2774 value of every expression in your assembly language program to be a
2775 section-relative address.
2778 @cindex assembler internal logic error
2779 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2780 An internal assembler logic error has been found. This means there is a
2781 bug in the assembler.
2783 @cindex expr (internal section)
2785 The assembler stores complex expression internally as combinations of
2786 symbols. When it needs to represent an expression as a symbol, it puts
2787 it in the expr section.
2789 @c FIXME item transfer[t] vector preload
2790 @c FIXME item transfer[t] vector postload
2791 @c FIXME item register
2795 @section Sub-Sections
2797 @cindex numbered subsections
2798 @cindex grouping data
2804 fall into two sections: text and data.
2806 You may have separate groups of
2808 data in named sections
2812 data in named sections
2818 that you want to end up near to each other in the object file, even though they
2819 are not contiguous in the assembler source. @command{@value{AS}} allows you to
2820 use @dfn{subsections} for this purpose. Within each section, there can be
2821 numbered subsections with values from 0 to 8192. Objects assembled into the
2822 same subsection go into the object file together with other objects in the same
2823 subsection. For example, a compiler might want to store constants in the text
2824 section, but might not want to have them interspersed with the program being
2825 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2826 section of code being output, and a @samp{.text 1} before each group of
2827 constants being output.
2829 Subsections are optional. If you do not use subsections, everything
2830 goes in subsection number zero.
2833 Each subsection is zero-padded up to a multiple of four bytes.
2834 (Subsections may be padded a different amount on different flavors
2835 of @command{@value{AS}}.)
2839 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2840 boundary (two bytes).
2841 The same is true on the Hitachi SH.
2844 @c FIXME section padding (alignment)?
2845 @c Rich Pixley says padding here depends on target obj code format; that
2846 @c doesn't seem particularly useful to say without further elaboration,
2847 @c so for now I say nothing about it. If this is a generic BFD issue,
2848 @c these paragraphs might need to vanish from this manual, and be
2849 @c discussed in BFD chapter of binutils (or some such).
2852 On the AMD 29K family, no particular padding is added to section or
2853 subsection sizes; @value{AS} forces no alignment on this platform.
2857 Subsections appear in your object file in numeric order, lowest numbered
2858 to highest. (All this to be compatible with other people's assemblers.)
2859 The object file contains no representation of subsections; @code{@value{LD}} and
2860 other programs that manipulate object files see no trace of them.
2861 They just see all your text subsections as a text section, and all your
2862 data subsections as a data section.
2864 To specify which subsection you want subsequent statements assembled
2865 into, use a numeric argument to specify it, in a @samp{.text
2866 @var{expression}} or a @samp{.data @var{expression}} statement.
2869 When generating COFF output, you
2874 can also use an extra subsection
2875 argument with arbitrary named sections: @samp{.section @var{name},
2878 @var{Expression} should be an absolute expression.
2879 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2880 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2881 begins in @code{text 0}. For instance:
2883 .text 0 # The default subsection is text 0 anyway.
2884 .ascii "This lives in the first text subsection. *"
2886 .ascii "But this lives in the second text subsection."
2888 .ascii "This lives in the data section,"
2889 .ascii "in the first data subsection."
2891 .ascii "This lives in the first text section,"
2892 .ascii "immediately following the asterisk (*)."
2895 Each section has a @dfn{location counter} incremented by one for every byte
2896 assembled into that section. Because subsections are merely a convenience
2897 restricted to @command{@value{AS}} there is no concept of a subsection location
2898 counter. There is no way to directly manipulate a location counter---but the
2899 @code{.align} directive changes it, and any label definition captures its
2900 current value. The location counter of the section where statements are being
2901 assembled is said to be the @dfn{active} location counter.
2904 @section bss Section
2907 @cindex common variable storage
2908 The bss section is used for local common variable storage.
2909 You may allocate address space in the bss section, but you may
2910 not dictate data to load into it before your program executes. When
2911 your program starts running, all the contents of the bss
2912 section are zeroed bytes.
2914 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2915 @ref{Lcomm,,@code{.lcomm}}.
2917 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2918 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2921 When assembling for a target which supports multiple sections, such as ELF or
2922 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2923 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2924 section. Typically the section will only contain symbol definitions and
2925 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2932 Symbols are a central concept: the programmer uses symbols to name
2933 things, the linker uses symbols to link, and the debugger uses symbols
2937 @cindex debuggers, and symbol order
2938 @emph{Warning:} @command{@value{AS}} does not place symbols in the object file in
2939 the same order they were declared. This may break some debuggers.
2944 * Setting Symbols:: Giving Symbols Other Values
2945 * Symbol Names:: Symbol Names
2946 * Dot:: The Special Dot Symbol
2947 * Symbol Attributes:: Symbol Attributes
2954 A @dfn{label} is written as a symbol immediately followed by a colon
2955 @samp{:}. The symbol then represents the current value of the
2956 active location counter, and is, for example, a suitable instruction
2957 operand. You are warned if you use the same symbol to represent two
2958 different locations: the first definition overrides any other
2962 On the HPPA, the usual form for a label need not be immediately followed by a
2963 colon, but instead must start in column zero. Only one label may be defined on
2964 a single line. To work around this, the HPPA version of @command{@value{AS}} also
2965 provides a special directive @code{.label} for defining labels more flexibly.
2968 @node Setting Symbols
2969 @section Giving Symbols Other Values
2971 @cindex assigning values to symbols
2972 @cindex symbol values, assigning
2973 A symbol can be given an arbitrary value by writing a symbol, followed
2974 by an equals sign @samp{=}, followed by an expression
2975 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2976 directive. @xref{Set,,@code{.set}}.
2979 @section Symbol Names
2981 @cindex symbol names
2982 @cindex names, symbol
2983 @ifclear SPECIAL-SYMS
2984 Symbol names begin with a letter or with one of @samp{._}. On most
2985 machines, you can also use @code{$} in symbol names; exceptions are
2986 noted in @ref{Machine Dependencies}. That character may be followed by any
2987 string of digits, letters, dollar signs (unless otherwise noted in
2988 @ref{Machine Dependencies}), and underscores.
2991 For the AMD 29K family, @samp{?} is also allowed in the
2992 body of a symbol name, though not at its beginning.
2997 Symbol names begin with a letter or with one of @samp{._}. On the
2999 H8/500, you can also use @code{$} in symbol names. That character may
3000 be followed by any string of digits, letters, dollar signs (save on the
3001 H8/300), and underscores.
3005 Case of letters is significant: @code{foo} is a different symbol name
3008 Each symbol has exactly one name. Each name in an assembly language program
3009 refers to exactly one symbol. You may use that symbol name any number of times
3012 @subheading Local Symbol Names
3014 @cindex local symbol names
3015 @cindex symbol names, local
3016 @cindex temporary symbol names
3017 @cindex symbol names, temporary
3018 Local symbols help compilers and programmers use names temporarily.
3019 They create symbols which are guaranteed to be unique over the entire scope of
3020 the input source code and which can be referred to by a simple notation.
3021 To define a local symbol, write a label of the form @samp{@b{N}:} (where @b{N}
3022 represents any positive integer). To refer to the most recent previous
3023 definition of that symbol write @samp{@b{N}b}, using the same number as when
3024 you defined the label. To refer to the next definition of a local label, write
3025 @samp{@b{N}f}--- The @samp{b} stands for``backwards'' and the @samp{f} stands
3028 There is no restriction on how you can use these labels, and you can reuse them
3029 too. So that it is possible to repeatedly define the same local label (using
3030 the same number @samp{@b{N}}), although you can only refer to the most recently
3031 defined local label of that number (for a backwards reference) or the next
3032 definition of a specific local label for a forward reference. It is also worth
3033 noting that the first 10 local labels (@samp{@b{0:}}@dots{}@samp{@b{9:}}) are
3034 implemented in a slightly more efficient manner than the others.
3045 Which is the equivalent of:
3048 label_1: branch label_3
3049 label_2: branch label_1
3050 label_3: branch label_4
3051 label_4: branch label_3
3054 Local symbol names are only a notational device. They are immediately
3055 transformed into more conventional symbol names before the assembler uses them.
3056 The symbol names stored in the symbol table, appearing in error messages and
3057 optionally emitted to the object file. The names are constructed using these
3062 All local labels begin with @samp{L}. Normally both @command{@value{AS}} and
3063 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
3064 used for symbols you are never intended to see. If you use the
3065 @samp{-L} option then @command{@value{AS}} retains these symbols in the
3066 object file. If you also instruct @code{@value{LD}} to retain these symbols,
3067 you may use them in debugging.
3070 This is the number that was used in the local label definition. So if the
3071 label is written @samp{55:} then the number is @samp{55}.
3074 This unusual character is included so you do not accidentally invent a symbol
3075 of the same name. The character has ASCII value of @samp{\002} (control-B).
3077 @item @emph{ordinal number}
3078 This is a serial number to keep the labels distinct. The first definition of
3079 @samp{0:} gets the number @samp{1}. The 15th definition of @samp{0:} gets the
3080 number @samp{15}, and so on. Likewise the first definition of @samp{1:} gets
3081 the number @samp{1} and its 15th defintion gets @samp{15} as well.
3084 So for example, the first @code{1:} is named @code{L1@kbd{C-B}1}, the 44th
3085 @code{3:} is named @code{L3@kbd{C-B}44}.
3087 @subheading Dollar Local Labels
3088 @cindex dollar local symbols
3090 @code{@value{AS}} also supports an even more local form of local labels called
3091 dollar labels. These labels go out of scope (ie they become undefined) as soon
3092 as a non-local label is defined. Thus they remain valid for only a small
3093 region of the input source code. Normal local labels, by contrast, remain in
3094 scope for the entire file, or until they are redefined by another occurrence of
3095 the same local label.
3097 Dollar labels are defined in exactly the same way as ordinary local labels,
3098 except that instead of being terminated by a colon, they are terminated by a
3099 dollar sign. eg @samp{@b{55$}}.
3101 They can also be distinguished from ordinary local labels by their transformed
3102 name which uses ASCII character @samp{\001} (control-A) as the magic character
3103 to distinguish them from ordinary labels. Thus the 5th defintion of @samp{6$}
3104 is named @samp{L6@kbd{C-A}5}.
3107 @section The Special Dot Symbol
3109 @cindex dot (symbol)
3110 @cindex @code{.} (symbol)
3111 @cindex current address
3112 @cindex location counter
3113 The special symbol @samp{.} refers to the current address that
3114 @command{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
3115 .long .} defines @code{melvin} to contain its own address.
3116 Assigning a value to @code{.} is treated the same as a @code{.org}
3117 directive. Thus, the expression @samp{.=.+4} is the same as saying
3118 @ifclear no-space-dir
3127 @node Symbol Attributes
3128 @section Symbol Attributes
3130 @cindex symbol attributes
3131 @cindex attributes, symbol
3132 Every symbol has, as well as its name, the attributes ``Value'' and
3133 ``Type''. Depending on output format, symbols can also have auxiliary
3136 The detailed definitions are in @file{a.out.h}.
3139 If you use a symbol without defining it, @command{@value{AS}} assumes zero for
3140 all these attributes, and probably won't warn you. This makes the
3141 symbol an externally defined symbol, which is generally what you
3145 * Symbol Value:: Value
3146 * Symbol Type:: Type
3149 * a.out Symbols:: Symbol Attributes: @code{a.out}
3153 * a.out Symbols:: Symbol Attributes: @code{a.out}
3156 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3161 * COFF Symbols:: Symbol Attributes for COFF
3164 * SOM Symbols:: Symbol Attributes for SOM
3171 @cindex value of a symbol
3172 @cindex symbol value
3173 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3174 location in the text, data, bss or absolute sections the value is the
3175 number of addresses from the start of that section to the label.
3176 Naturally for text, data and bss sections the value of a symbol changes
3177 as @code{@value{LD}} changes section base addresses during linking. Absolute
3178 symbols' values do not change during linking: that is why they are
3181 The value of an undefined symbol is treated in a special way. If it is
3182 0 then the symbol is not defined in this assembler source file, and
3183 @code{@value{LD}} tries to determine its value from other files linked into the
3184 same program. You make this kind of symbol simply by mentioning a symbol
3185 name without defining it. A non-zero value represents a @code{.comm}
3186 common declaration. The value is how much common storage to reserve, in
3187 bytes (addresses). The symbol refers to the first address of the
3193 @cindex type of a symbol
3195 The type attribute of a symbol contains relocation (section)
3196 information, any flag settings indicating that a symbol is external, and
3197 (optionally), other information for linkers and debuggers. The exact
3198 format depends on the object-code output format in use.
3203 @c The following avoids a "widow" subsection title. @group would be
3204 @c better if it were available outside examples.
3207 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3209 @cindex @code{b.out} symbol attributes
3210 @cindex symbol attributes, @code{b.out}
3211 These symbol attributes appear only when @command{@value{AS}} is configured for
3212 one of the Berkeley-descended object output formats---@code{a.out} or
3218 @subsection Symbol Attributes: @code{a.out}
3220 @cindex @code{a.out} symbol attributes
3221 @cindex symbol attributes, @code{a.out}
3227 @subsection Symbol Attributes: @code{a.out}
3229 @cindex @code{a.out} symbol attributes
3230 @cindex symbol attributes, @code{a.out}
3234 * Symbol Desc:: Descriptor
3235 * Symbol Other:: Other
3239 @subsubsection Descriptor
3241 @cindex descriptor, of @code{a.out} symbol
3242 This is an arbitrary 16-bit value. You may establish a symbol's
3243 descriptor value by using a @code{.desc} statement
3244 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3245 @command{@value{AS}}.
3248 @subsubsection Other
3250 @cindex other attribute, of @code{a.out} symbol
3251 This is an arbitrary 8-bit value. It means nothing to @command{@value{AS}}.
3256 @subsection Symbol Attributes for COFF
3258 @cindex COFF symbol attributes
3259 @cindex symbol attributes, COFF
3261 The COFF format supports a multitude of auxiliary symbol attributes;
3262 like the primary symbol attributes, they are set between @code{.def} and
3263 @code{.endef} directives.
3265 @subsubsection Primary Attributes
3267 @cindex primary attributes, COFF symbols
3268 The symbol name is set with @code{.def}; the value and type,
3269 respectively, with @code{.val} and @code{.type}.
3271 @subsubsection Auxiliary Attributes
3273 @cindex auxiliary attributes, COFF symbols
3274 The @command{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3275 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3276 information for COFF.
3281 @subsection Symbol Attributes for SOM
3283 @cindex SOM symbol attributes
3284 @cindex symbol attributes, SOM
3286 The SOM format for the HPPA supports a multitude of symbol attributes set with
3287 the @code{.EXPORT} and @code{.IMPORT} directives.
3289 The attributes are described in @cite{HP9000 Series 800 Assembly
3290 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3291 @code{EXPORT} assembler directive documentation.
3295 @chapter Expressions
3299 @cindex numeric values
3300 An @dfn{expression} specifies an address or numeric value.
3301 Whitespace may precede and/or follow an expression.
3303 The result of an expression must be an absolute number, or else an offset into
3304 a particular section. If an expression is not absolute, and there is not
3305 enough information when @command{@value{AS}} sees the expression to know its
3306 section, a second pass over the source program might be necessary to interpret
3307 the expression---but the second pass is currently not implemented.
3308 @command{@value{AS}} aborts with an error message in this situation.
3311 * Empty Exprs:: Empty Expressions
3312 * Integer Exprs:: Integer Expressions
3316 @section Empty Expressions
3318 @cindex empty expressions
3319 @cindex expressions, empty
3320 An empty expression has no value: it is just whitespace or null.
3321 Wherever an absolute expression is required, you may omit the
3322 expression, and @command{@value{AS}} assumes a value of (absolute) 0. This
3323 is compatible with other assemblers.
3326 @section Integer Expressions
3328 @cindex integer expressions
3329 @cindex expressions, integer
3330 An @dfn{integer expression} is one or more @emph{arguments} delimited
3331 by @emph{operators}.
3334 * Arguments:: Arguments
3335 * Operators:: Operators
3336 * Prefix Ops:: Prefix Operators
3337 * Infix Ops:: Infix Operators
3341 @subsection Arguments
3343 @cindex expression arguments
3344 @cindex arguments in expressions
3345 @cindex operands in expressions
3346 @cindex arithmetic operands
3347 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3348 contexts arguments are sometimes called ``arithmetic operands''. In
3349 this manual, to avoid confusing them with the ``instruction operands'' of
3350 the machine language, we use the term ``argument'' to refer to parts of
3351 expressions only, reserving the word ``operand'' to refer only to machine
3352 instruction operands.
3354 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3355 @var{section} is one of text, data, bss, absolute,
3356 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3359 Numbers are usually integers.
3361 A number can be a flonum or bignum. In this case, you are warned
3362 that only the low order 32 bits are used, and @command{@value{AS}} pretends
3363 these 32 bits are an integer. You may write integer-manipulating
3364 instructions that act on exotic constants, compatible with other
3367 @cindex subexpressions
3368 Subexpressions are a left parenthesis @samp{(} followed by an integer
3369 expression, followed by a right parenthesis @samp{)}; or a prefix
3370 operator followed by an argument.
3373 @subsection Operators
3375 @cindex operators, in expressions
3376 @cindex arithmetic functions
3377 @cindex functions, in expressions
3378 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3379 operators are followed by an argument. Infix operators appear
3380 between their arguments. Operators may be preceded and/or followed by
3384 @subsection Prefix Operator
3386 @cindex prefix operators
3387 @command{@value{AS}} has the following @dfn{prefix operators}. They each take
3388 one argument, which must be absolute.
3390 @c the tex/end tex stuff surrounding this small table is meant to make
3391 @c it align, on the printed page, with the similar table in the next
3392 @c section (which is inside an enumerate).
3394 \global\advance\leftskip by \itemindent
3399 @dfn{Negation}. Two's complement negation.
3401 @dfn{Complementation}. Bitwise not.
3405 \global\advance\leftskip by -\itemindent
3409 @subsection Infix Operators
3411 @cindex infix operators
3412 @cindex operators, permitted arguments
3413 @dfn{Infix operators} take two arguments, one on either side. Operators
3414 have precedence, but operations with equal precedence are performed left
3415 to right. Apart from @code{+} or @option{-}, both arguments must be
3416 absolute, and the result is absolute.
3419 @cindex operator precedence
3420 @cindex precedence of operators
3427 @dfn{Multiplication}.
3430 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3437 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3441 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3445 Intermediate precedence
3450 @dfn{Bitwise Inclusive Or}.
3456 @dfn{Bitwise Exclusive Or}.
3459 @dfn{Bitwise Or Not}.
3466 @cindex addition, permitted arguments
3467 @cindex plus, permitted arguments
3468 @cindex arguments for addition
3470 @dfn{Addition}. If either argument is absolute, the result has the section of
3471 the other argument. You may not add together arguments from different
3474 @cindex subtraction, permitted arguments
3475 @cindex minus, permitted arguments
3476 @cindex arguments for subtraction
3478 @dfn{Subtraction}. If the right argument is absolute, the
3479 result has the section of the left argument.
3480 If both arguments are in the same section, the result is absolute.
3481 You may not subtract arguments from different sections.
3482 @c FIXME is there still something useful to say about undefined - undefined ?
3484 @cindex comparison expressions
3485 @cindex expressions, comparison
3489 @dfn{Is Not Equal To}
3493 @dfn{Is Greater Than}
3495 @dfn{Is Greater Than Or Equal To}
3497 @dfn{Is Less Than Or Equal To}
3499 The comparison operators can be used as infix operators. A true results has a
3500 value of -1 whereas a false result has a value of 0. Note, these operators
3501 perform signed comparisons.
3504 @item Lowest Precedence
3513 These two logical operations can be used to combine the results of sub
3514 expressions. Note, unlike the comparison operators a true result returns a
3515 value of 1 but a false results does still return 0. Also note that the logical
3516 or operator has a slightly lower precedence than logical and.
3521 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3522 address; you can only have a defined section in one of the two arguments.
3525 @chapter Assembler Directives
3527 @cindex directives, machine independent
3528 @cindex pseudo-ops, machine independent
3529 @cindex machine independent directives
3530 All assembler directives have names that begin with a period (@samp{.}).
3531 The rest of the name is letters, usually in lower case.
3533 This chapter discusses directives that are available regardless of the
3534 target machine configuration for the @sc{gnu} assembler.
3536 Some machine configurations provide additional directives.
3537 @xref{Machine Dependencies}.
3540 @ifset machine-directives
3541 @xref{Machine Dependencies} for additional directives.
3546 * Abort:: @code{.abort}
3548 * ABORT:: @code{.ABORT}
3551 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3552 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3553 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3554 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3555 * Byte:: @code{.byte @var{expressions}}
3556 * Comm:: @code{.comm @var{symbol} , @var{length} }
3557 * Data:: @code{.data @var{subsection}}
3559 * Def:: @code{.def @var{name}}
3562 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3568 * Double:: @code{.double @var{flonums}}
3569 * Eject:: @code{.eject}
3570 * Else:: @code{.else}
3571 * Elseif:: @code{.elseif}
3574 * Endef:: @code{.endef}
3577 * Endfunc:: @code{.endfunc}
3578 * Endif:: @code{.endif}
3579 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3580 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3582 * Exitm:: @code{.exitm}
3583 * Extern:: @code{.extern}
3584 * Fail:: @code{.fail}
3585 @ifclear no-file-dir
3586 * File:: @code{.file @var{string}}
3589 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3590 * Float:: @code{.float @var{flonums}}
3591 * Func:: @code{.func}
3592 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3594 * Hidden:: @code{.hidden @var{names}}
3597 * hword:: @code{.hword @var{expressions}}
3598 * Ident:: @code{.ident}
3599 * If:: @code{.if @var{absolute expression}}
3600 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3601 * Include:: @code{.include "@var{file}"}
3602 * Int:: @code{.int @var{expressions}}
3604 * Internal:: @code{.internal @var{names}}
3607 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3608 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3609 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3610 * Lflags:: @code{.lflags}
3611 @ifclear no-line-dir
3612 * Line:: @code{.line @var{line-number}}
3615 * Ln:: @code{.ln @var{line-number}}
3616 * Linkonce:: @code{.linkonce [@var{type}]}
3617 * List:: @code{.list}
3618 * Long:: @code{.long @var{expressions}}
3620 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3623 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3624 * MRI:: @code{.mri @var{val}}
3625 * Nolist:: @code{.nolist}
3626 * Octa:: @code{.octa @var{bignums}}
3627 * Org:: @code{.org @var{new-lc} , @var{fill}}
3628 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3630 * PopSection:: @code{.popsection}
3631 * Previous:: @code{.previous}
3634 * Print:: @code{.print @var{string}}
3636 * Protected:: @code{.protected @var{names}}
3639 * Psize:: @code{.psize @var{lines}, @var{columns}}
3640 * Purgem:: @code{.purgem @var{name}}
3642 * PushSection:: @code{.pushsection @var{name}}
3645 * Quad:: @code{.quad @var{bignums}}
3646 * Rept:: @code{.rept @var{count}}
3647 * Sbttl:: @code{.sbttl "@var{subheading}"}
3649 * Scl:: @code{.scl @var{class}}
3650 * Section:: @code{.section @var{name}, @var{subsection}}
3653 * Set:: @code{.set @var{symbol}, @var{expression}}
3654 * Short:: @code{.short @var{expressions}}
3655 * Single:: @code{.single @var{flonums}}
3656 * Size:: @code{.size [@var{name} , @var{expression}]}
3657 * Skip:: @code{.skip @var{size} , @var{fill}}
3658 * Sleb128:: @code{.sleb128 @var{expressions}}
3659 * Space:: @code{.space @var{size} , @var{fill}}
3661 * Stab:: @code{.stabd, .stabn, .stabs}
3664 * String:: @code{.string "@var{str}"}
3665 * Struct:: @code{.struct @var{expression}}
3667 * SubSection:: @code{.subsection}
3668 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3672 * Tag:: @code{.tag @var{structname}}
3675 * Text:: @code{.text @var{subsection}}
3676 * Title:: @code{.title "@var{heading}"}
3677 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3678 * Uleb128:: @code{.uleb128 @var{expressions}}
3680 * Val:: @code{.val @var{addr}}
3684 * Version:: @code{.version "@var{string}"}
3685 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3686 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3687 * Weak:: @code{.weak @var{names}}
3690 * Word:: @code{.word @var{expressions}}
3691 * Deprecated:: Deprecated Directives
3695 @section @code{.abort}
3697 @cindex @code{abort} directive
3698 @cindex stopping the assembly
3699 This directive stops the assembly immediately. It is for
3700 compatibility with other assemblers. The original idea was that the
3701 assembly language source would be piped into the assembler. If the sender
3702 of the source quit, it could use this directive tells @command{@value{AS}} to
3703 quit also. One day @code{.abort} will not be supported.
3707 @section @code{.ABORT}
3709 @cindex @code{ABORT} directive
3710 When producing COFF output, @command{@value{AS}} accepts this directive as a
3711 synonym for @samp{.abort}.
3714 When producing @code{b.out} output, @command{@value{AS}} accepts this directive,
3720 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3722 @cindex padding the location counter
3723 @cindex @code{align} directive
3724 Pad the location counter (in the current subsection) to a particular storage
3725 boundary. The first expression (which must be absolute) is the alignment
3726 required, as described below.
3728 The second expression (also absolute) gives the fill value to be stored in the
3729 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3730 padding bytes are normally zero. However, on some systems, if the section is
3731 marked as containing code and the fill value is omitted, the space is filled
3732 with no-op instructions.
3734 The third expression is also absolute, and is also optional. If it is present,
3735 it is the maximum number of bytes that should be skipped by this alignment
3736 directive. If doing the alignment would require skipping more bytes than the
3737 specified maximum, then the alignment is not done at all. You can omit the
3738 fill value (the second argument) entirely by simply using two commas after the
3739 required alignment; this can be useful if you want the alignment to be filled
3740 with no-op instructions when appropriate.
3742 The way the required alignment is specified varies from system to system.
3743 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3745 the first expression is the
3746 alignment request in bytes. For example @samp{.align 8} advances
3747 the location counter until it is a multiple of 8. If the location counter
3748 is already a multiple of 8, no change is needed.
3750 For other systems, including the i386 using a.out format, and the arm and
3751 strongarm, it is the
3752 number of low-order zero bits the location counter must have after
3753 advancement. For example @samp{.align 3} advances the location
3754 counter until it a multiple of 8. If the location counter is already a
3755 multiple of 8, no change is needed.
3757 This inconsistency is due to the different behaviors of the various
3758 native assemblers for these systems which GAS must emulate.
3759 GAS also provides @code{.balign} and @code{.p2align} directives,
3760 described later, which have a consistent behavior across all
3761 architectures (but are specific to GAS).
3764 @section @code{.ascii "@var{string}"}@dots{}
3766 @cindex @code{ascii} directive
3767 @cindex string literals
3768 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3769 separated by commas. It assembles each string (with no automatic
3770 trailing zero byte) into consecutive addresses.
3773 @section @code{.asciz "@var{string}"}@dots{}
3775 @cindex @code{asciz} directive
3776 @cindex zero-terminated strings
3777 @cindex null-terminated strings
3778 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3779 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3782 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3784 @cindex padding the location counter given number of bytes
3785 @cindex @code{balign} directive
3786 Pad the location counter (in the current subsection) to a particular
3787 storage boundary. The first expression (which must be absolute) is the
3788 alignment request in bytes. For example @samp{.balign 8} advances
3789 the location counter until it is a multiple of 8. If the location counter
3790 is already a multiple of 8, no change is needed.
3792 The second expression (also absolute) gives the fill value to be stored in the
3793 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3794 padding bytes are normally zero. However, on some systems, if the section is
3795 marked as containing code and the fill value is omitted, the space is filled
3796 with no-op instructions.
3798 The third expression is also absolute, and is also optional. If it is present,
3799 it is the maximum number of bytes that should be skipped by this alignment
3800 directive. If doing the alignment would require skipping more bytes than the
3801 specified maximum, then the alignment is not done at all. You can omit the
3802 fill value (the second argument) entirely by simply using two commas after the
3803 required alignment; this can be useful if you want the alignment to be filled
3804 with no-op instructions when appropriate.
3806 @cindex @code{balignw} directive
3807 @cindex @code{balignl} directive
3808 The @code{.balignw} and @code{.balignl} directives are variants of the
3809 @code{.balign} directive. The @code{.balignw} directive treats the fill
3810 pattern as a two byte word value. The @code{.balignl} directives treats the
3811 fill pattern as a four byte longword value. For example, @code{.balignw
3812 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3813 filled in with the value 0x368d (the exact placement of the bytes depends upon
3814 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3818 @section @code{.byte @var{expressions}}
3820 @cindex @code{byte} directive
3821 @cindex integers, one byte
3822 @code{.byte} expects zero or more expressions, separated by commas.
3823 Each expression is assembled into the next byte.
3826 @section @code{.comm @var{symbol} , @var{length} }
3828 @cindex @code{comm} directive
3829 @cindex symbol, common
3830 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3831 common symbol in one object file may be merged with a defined or common symbol
3832 of the same name in another object file. If @code{@value{LD}} does not see a
3833 definition for the symbol--just one or more common symbols--then it will
3834 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3835 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3836 the same name, and they do not all have the same size, it will allocate space
3837 using the largest size.
3840 When using ELF, the @code{.comm} directive takes an optional third argument.
3841 This is the desired alignment of the symbol, specified as a byte boundary (for
3842 example, an alignment of 16 means that the least significant 4 bits of the
3843 address should be zero). The alignment must be an absolute expression, and it
3844 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3845 for the common symbol, it will use the alignment when placing the symbol. If
3846 no alignment is specified, @command{@value{AS}} will set the alignment to the
3847 largest power of two less than or equal to the size of the symbol, up to a
3852 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3853 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3857 @section @code{.data @var{subsection}}
3859 @cindex @code{data} directive
3860 @code{.data} tells @command{@value{AS}} to assemble the following statements onto the
3861 end of the data subsection numbered @var{subsection} (which is an
3862 absolute expression). If @var{subsection} is omitted, it defaults
3867 @section @code{.def @var{name}}
3869 @cindex @code{def} directive
3870 @cindex COFF symbols, debugging
3871 @cindex debugging COFF symbols
3872 Begin defining debugging information for a symbol @var{name}; the
3873 definition extends until the @code{.endef} directive is encountered.
3876 This directive is only observed when @command{@value{AS}} is configured for COFF
3877 format output; when producing @code{b.out}, @samp{.def} is recognized,
3884 @section @code{.desc @var{symbol}, @var{abs-expression}}
3886 @cindex @code{desc} directive
3887 @cindex COFF symbol descriptor
3888 @cindex symbol descriptor, COFF
3889 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3890 to the low 16 bits of an absolute expression.
3893 The @samp{.desc} directive is not available when @command{@value{AS}} is
3894 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3895 object format. For the sake of compatibility, @command{@value{AS}} accepts
3896 it, but produces no output, when configured for COFF.
3902 @section @code{.dim}
3904 @cindex @code{dim} directive
3905 @cindex COFF auxiliary symbol information
3906 @cindex auxiliary symbol information, COFF
3907 This directive is generated by compilers to include auxiliary debugging
3908 information in the symbol table. It is only permitted inside
3909 @code{.def}/@code{.endef} pairs.
3912 @samp{.dim} is only meaningful when generating COFF format output; when
3913 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
3919 @section @code{.double @var{flonums}}
3921 @cindex @code{double} directive
3922 @cindex floating point numbers (double)
3923 @code{.double} expects zero or more flonums, separated by commas. It
3924 assembles floating point numbers.
3926 The exact kind of floating point numbers emitted depends on how
3927 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
3931 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3932 in @sc{ieee} format.
3937 @section @code{.eject}
3939 @cindex @code{eject} directive
3940 @cindex new page, in listings
3941 @cindex page, in listings
3942 @cindex listing control: new page
3943 Force a page break at this point, when generating assembly listings.
3946 @section @code{.else}
3948 @cindex @code{else} directive
3949 @code{.else} is part of the @command{@value{AS}} support for conditional
3950 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3951 of code to be assembled if the condition for the preceding @code{.if}
3955 @section @code{.elseif}
3957 @cindex @code{elseif} directive
3958 @code{.elseif} is part of the @command{@value{AS}} support for conditional
3959 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
3960 @code{.if} block that would otherwise fill the entire @code{.else} section.
3963 @section @code{.end}
3965 @cindex @code{end} directive
3966 @code{.end} marks the end of the assembly file. @command{@value{AS}} does not
3967 process anything in the file past the @code{.end} directive.
3971 @section @code{.endef}
3973 @cindex @code{endef} directive
3974 This directive flags the end of a symbol definition begun with
3978 @samp{.endef} is only meaningful when generating COFF format output; if
3979 @command{@value{AS}} is configured to generate @code{b.out}, it accepts this
3980 directive but ignores it.
3985 @section @code{.endfunc}
3986 @cindex @code{endfunc} directive
3987 @code{.endfunc} marks the end of a function specified with @code{.func}.
3990 @section @code{.endif}
3992 @cindex @code{endif} directive
3993 @code{.endif} is part of the @command{@value{AS}} support for conditional assembly;
3994 it marks the end of a block of code that is only assembled
3995 conditionally. @xref{If,,@code{.if}}.
3998 @section @code{.equ @var{symbol}, @var{expression}}
4000 @cindex @code{equ} directive
4001 @cindex assigning values to symbols
4002 @cindex symbols, assigning values to
4003 This directive sets the value of @var{symbol} to @var{expression}.
4004 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
4007 The syntax for @code{equ} on the HPPA is
4008 @samp{@var{symbol} .equ @var{expression}}.
4012 @section @code{.equiv @var{symbol}, @var{expression}}
4013 @cindex @code{equiv} directive
4014 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
4015 the assembler will signal an error if @var{symbol} is already defined.
4017 Except for the contents of the error message, this is roughly equivalent to
4026 @section @code{.err}
4027 @cindex @code{err} directive
4028 If @command{@value{AS}} assembles a @code{.err} directive, it will print an error
4029 message and, unless the @option{-Z} option was used, it will not generate an
4030 object file. This can be used to signal error an conditionally compiled code.
4033 @section @code{.exitm}
4034 Exit early from the current macro definition. @xref{Macro}.
4037 @section @code{.extern}
4039 @cindex @code{extern} directive
4040 @code{.extern} is accepted in the source program---for compatibility
4041 with other assemblers---but it is ignored. @command{@value{AS}} treats
4042 all undefined symbols as external.
4045 @section @code{.fail @var{expression}}
4047 @cindex @code{fail} directive
4048 Generates an error or a warning. If the value of the @var{expression} is 500
4049 or more, @command{@value{AS}} will print a warning message. If the value is less
4050 than 500, @command{@value{AS}} will print an error message. The message will
4051 include the value of @var{expression}. This can occasionally be useful inside
4052 complex nested macros or conditional assembly.
4054 @ifclear no-file-dir
4056 @section @code{.file @var{string}}
4058 @cindex @code{file} directive
4059 @cindex logical file name
4060 @cindex file name, logical
4061 @code{.file} tells @command{@value{AS}} that we are about to start a new logical
4062 file. @var{string} is the new file name. In general, the filename is
4063 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
4064 to specify an empty file name, you must give the quotes--@code{""}. This
4065 statement may go away in future: it is only recognized to be compatible with
4066 old @command{@value{AS}} programs.
4068 In some configurations of @command{@value{AS}}, @code{.file} has already been
4069 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
4074 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
4076 @cindex @code{fill} directive
4077 @cindex writing patterns in memory
4078 @cindex patterns, writing in memory
4079 @var{repeat}, @var{size} and @var{value} are absolute expressions.
4080 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
4081 may be zero or more. @var{Size} may be zero or more, but if it is
4082 more than 8, then it is deemed to have the value 8, compatible with
4083 other people's assemblers. The contents of each @var{repeat} bytes
4084 is taken from an 8-byte number. The highest order 4 bytes are
4085 zero. The lowest order 4 bytes are @var{value} rendered in the
4086 byte-order of an integer on the computer @command{@value{AS}} is assembling for.
4087 Each @var{size} bytes in a repetition is taken from the lowest order
4088 @var{size} bytes of this number. Again, this bizarre behavior is
4089 compatible with other people's assemblers.
4091 @var{size} and @var{value} are optional.
4092 If the second comma and @var{value} are absent, @var{value} is
4093 assumed zero. If the first comma and following tokens are absent,
4094 @var{size} is assumed to be 1.
4097 @section @code{.float @var{flonums}}
4099 @cindex floating point numbers (single)
4100 @cindex @code{float} directive
4101 This directive assembles zero or more flonums, separated by commas. It
4102 has the same effect as @code{.single}.
4104 The exact kind of floating point numbers emitted depends on how
4105 @command{@value{AS}} is configured.
4106 @xref{Machine Dependencies}.
4110 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
4111 in @sc{ieee} format.
4116 @section @code{.func @var{name}[,@var{label}]}
4117 @cindex @code{func} directive
4118 @code{.func} emits debugging information to denote function @var{name}, and
4119 is ignored unless the file is assembled with debugging enabled.
4120 Only @samp{--gstabs} is currently supported.
4121 @var{label} is the entry point of the function and if omitted @var{name}
4122 prepended with the @samp{leading char} is used.
4123 @samp{leading char} is usually @code{_} or nothing, depending on the target.
4124 All functions are currently defined to have @code{void} return type.
4125 The function must be terminated with @code{.endfunc}.
4128 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
4130 @cindex @code{global} directive
4131 @cindex symbol, making visible to linker
4132 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
4133 @var{symbol} in your partial program, its value is made available to
4134 other partial programs that are linked with it. Otherwise,
4135 @var{symbol} takes its attributes from a symbol of the same name
4136 from another file linked into the same program.
4138 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
4139 compatibility with other assemblers.
4142 On the HPPA, @code{.global} is not always enough to make it accessible to other
4143 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
4144 @xref{HPPA Directives,, HPPA Assembler Directives}.
4149 @section @code{.hidden @var{names}}
4151 @cindex @code{.hidden} directive
4153 This one of the ELF visibility directives. The other two are
4154 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4155 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4157 This directive overrides the named symbols default visibility (which is set by
4158 their binding: local, global or weak). The directive sets the visibility to
4159 @code{hidden} which means that the symbols are not visible to other components.
4160 Such symbols are always considered to be @code{protected} as well.
4164 @section @code{.hword @var{expressions}}
4166 @cindex @code{hword} directive
4167 @cindex integers, 16-bit
4168 @cindex numbers, 16-bit
4169 @cindex sixteen bit integers
4170 This expects zero or more @var{expressions}, and emits
4171 a 16 bit number for each.
4174 This directive is a synonym for @samp{.short}; depending on the target
4175 architecture, it may also be a synonym for @samp{.word}.
4179 This directive is a synonym for @samp{.short}.
4182 This directive is a synonym for both @samp{.short} and @samp{.word}.
4187 @section @code{.ident}
4189 @cindex @code{ident} directive
4190 This directive is used by some assemblers to place tags in object files.
4191 @command{@value{AS}} simply accepts the directive for source-file
4192 compatibility with such assemblers, but does not actually emit anything
4196 @section @code{.if @var{absolute expression}}
4198 @cindex conditional assembly
4199 @cindex @code{if} directive
4200 @code{.if} marks the beginning of a section of code which is only
4201 considered part of the source program being assembled if the argument
4202 (which must be an @var{absolute expression}) is non-zero. The end of
4203 the conditional section of code must be marked by @code{.endif}
4204 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4205 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4206 If you have several conditions to check, @code{.elseif} may be used to avoid
4207 nesting blocks if/else within each subsequent @code{.else} block.
4209 The following variants of @code{.if} are also supported:
4211 @cindex @code{ifdef} directive
4212 @item .ifdef @var{symbol}
4213 Assembles the following section of code if the specified @var{symbol}
4216 @cindex @code{ifc} directive
4217 @item .ifc @var{string1},@var{string2}
4218 Assembles the following section of code if the two strings are the same. The
4219 strings may be optionally quoted with single quotes. If they are not quoted,
4220 the first string stops at the first comma, and the second string stops at the
4221 end of the line. Strings which contain whitespace should be quoted. The
4222 string comparison is case sensitive.
4224 @cindex @code{ifeq} directive
4225 @item .ifeq @var{absolute expression}
4226 Assembles the following section of code if the argument is zero.
4228 @cindex @code{ifeqs} directive
4229 @item .ifeqs @var{string1},@var{string2}
4230 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4232 @cindex @code{ifge} directive
4233 @item .ifge @var{absolute expression}
4234 Assembles the following section of code if the argument is greater than or
4237 @cindex @code{ifgt} directive
4238 @item .ifgt @var{absolute expression}
4239 Assembles the following section of code if the argument is greater than zero.
4241 @cindex @code{ifle} directive
4242 @item .ifle @var{absolute expression}
4243 Assembles the following section of code if the argument is less than or equal
4246 @cindex @code{iflt} directive
4247 @item .iflt @var{absolute expression}
4248 Assembles the following section of code if the argument is less than zero.
4250 @cindex @code{ifnc} directive
4251 @item .ifnc @var{string1},@var{string2}.
4252 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4253 following section of code if the two strings are not the same.
4255 @cindex @code{ifndef} directive
4256 @cindex @code{ifnotdef} directive
4257 @item .ifndef @var{symbol}
4258 @itemx .ifnotdef @var{symbol}
4259 Assembles the following section of code if the specified @var{symbol}
4260 has not been defined. Both spelling variants are equivalent.
4262 @cindex @code{ifne} directive
4263 @item .ifne @var{absolute expression}
4264 Assembles the following section of code if the argument is not equal to zero
4265 (in other words, this is equivalent to @code{.if}).
4267 @cindex @code{ifnes} directive
4268 @item .ifnes @var{string1},@var{string2}
4269 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4270 following section of code if the two strings are not the same.
4274 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4276 @cindex @code{incbin} directive
4277 @cindex binary files, including
4278 The @code{incbin} directive includes @var{file} verbatim at the current
4279 location. You can control the search paths used with the @samp{-I} command-line
4280 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4283 The @var{skip} argument skips a number of bytes from the start of the
4284 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4285 read. Note that the data is not aligned in any way, so it is the user's
4286 responsibility to make sure that proper alignment is provided both before and
4287 after the @code{incbin} directive.
4290 @section @code{.include "@var{file}"}
4292 @cindex @code{include} directive
4293 @cindex supporting files, including
4294 @cindex files, including
4295 This directive provides a way to include supporting files at specified
4296 points in your source program. The code from @var{file} is assembled as
4297 if it followed the point of the @code{.include}; when the end of the
4298 included file is reached, assembly of the original file continues. You
4299 can control the search paths used with the @samp{-I} command-line option
4300 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4304 @section @code{.int @var{expressions}}
4306 @cindex @code{int} directive
4307 @cindex integers, 32-bit
4308 Expect zero or more @var{expressions}, of any section, separated by commas.
4309 For each expression, emit a number that, at run time, is the value of that
4310 expression. The byte order and bit size of the number depends on what kind
4311 of target the assembly is for.
4315 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4316 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
4323 @section @code{.internal @var{names}}
4325 @cindex @code{.internal} directive
4327 This one of the ELF visibility directives. The other two are
4328 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4329 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4331 This directive overrides the named symbols default visibility (which is set by
4332 their binding: local, global or weak). The directive sets the visibility to
4333 @code{internal} which means that the symbols are considered to be @code{hidden}
4334 (ie not visible to other components), and that some extra, processor specific
4335 processing must also be performed upon the symbols as well.
4339 @section @code{.irp @var{symbol},@var{values}}@dots{}
4341 @cindex @code{irp} directive
4342 Evaluate a sequence of statements assigning different values to @var{symbol}.
4343 The sequence of statements starts at the @code{.irp} directive, and is
4344 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4345 set to @var{value}, and the sequence of statements is assembled. If no
4346 @var{value} is listed, the sequence of statements is assembled once, with
4347 @var{symbol} set to the null string. To refer to @var{symbol} within the
4348 sequence of statements, use @var{\symbol}.
4350 For example, assembling
4358 is equivalent to assembling
4367 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4369 @cindex @code{irpc} directive
4370 Evaluate a sequence of statements assigning different values to @var{symbol}.
4371 The sequence of statements starts at the @code{.irpc} directive, and is
4372 terminated by an @code{.endr} directive. For each character in @var{value},
4373 @var{symbol} is set to the character, and the sequence of statements is
4374 assembled. If no @var{value} is listed, the sequence of statements is
4375 assembled once, with @var{symbol} set to the null string. To refer to
4376 @var{symbol} within the sequence of statements, use @var{\symbol}.
4378 For example, assembling
4386 is equivalent to assembling
4395 @section @code{.lcomm @var{symbol} , @var{length}}
4397 @cindex @code{lcomm} directive
4398 @cindex local common symbols
4399 @cindex symbols, local common
4400 Reserve @var{length} (an absolute expression) bytes for a local common
4401 denoted by @var{symbol}. The section and value of @var{symbol} are
4402 those of the new local common. The addresses are allocated in the bss
4403 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4404 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4405 not visible to @code{@value{LD}}.
4408 Some targets permit a third argument to be used with @code{.lcomm}. This
4409 argument specifies the desired alignment of the symbol in the bss section.
4413 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4414 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4418 @section @code{.lflags}
4420 @cindex @code{lflags} directive (ignored)
4421 @command{@value{AS}} accepts this directive, for compatibility with other
4422 assemblers, but ignores it.
4424 @ifclear no-line-dir
4426 @section @code{.line @var{line-number}}
4428 @cindex @code{line} directive
4432 @section @code{.ln @var{line-number}}
4434 @cindex @code{ln} directive
4436 @cindex logical line number
4438 Change the logical line number. @var{line-number} must be an absolute
4439 expression. The next line has that logical line number. Therefore any other
4440 statements on the current line (after a statement separator character) are
4441 reported as on logical line number @var{line-number} @minus{} 1. One day
4442 @command{@value{AS}} will no longer support this directive: it is recognized only
4443 for compatibility with existing assembler programs.
4447 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4448 not available; use the synonym @code{.ln} in that context.
4453 @ifclear no-line-dir
4454 Even though this is a directive associated with the @code{a.out} or
4455 @code{b.out} object-code formats, @command{@value{AS}} still recognizes it
4456 when producing COFF output, and treats @samp{.line} as though it
4457 were the COFF @samp{.ln} @emph{if} it is found outside a
4458 @code{.def}/@code{.endef} pair.
4460 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4461 used by compilers to generate auxiliary symbol information for
4466 @section @code{.linkonce [@var{type}]}
4468 @cindex @code{linkonce} directive
4469 @cindex common sections
4470 Mark the current section so that the linker only includes a single copy of it.
4471 This may be used to include the same section in several different object files,
4472 but ensure that the linker will only include it once in the final output file.
4473 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4474 Duplicate sections are detected based on the section name, so it should be
4477 This directive is only supported by a few object file formats; as of this
4478 writing, the only object file format which supports it is the Portable
4479 Executable format used on Windows NT.
4481 The @var{type} argument is optional. If specified, it must be one of the
4482 following strings. For example:
4486 Not all types may be supported on all object file formats.
4490 Silently discard duplicate sections. This is the default.
4493 Warn if there are duplicate sections, but still keep only one copy.
4496 Warn if any of the duplicates have different sizes.
4499 Warn if any of the duplicates do not have exactly the same contents.
4503 @section @code{.ln @var{line-number}}
4505 @cindex @code{ln} directive
4506 @ifclear no-line-dir
4507 @samp{.ln} is a synonym for @samp{.line}.
4510 Tell @command{@value{AS}} to change the logical line number. @var{line-number}
4511 must be an absolute expression. The next line has that logical
4512 line number, so any other statements on the current line (after a
4513 statement separator character @code{;}) are reported as on logical
4514 line number @var{line-number} @minus{} 1.
4517 This directive is accepted, but ignored, when @command{@value{AS}} is
4518 configured for @code{b.out}; its effect is only associated with COFF
4524 @section @code{.mri @var{val}}
4526 @cindex @code{mri} directive
4527 @cindex MRI mode, temporarily
4528 If @var{val} is non-zero, this tells @command{@value{AS}} to enter MRI mode. If
4529 @var{val} is zero, this tells @command{@value{AS}} to exit MRI mode. This change
4530 affects code assembled until the next @code{.mri} directive, or until the end
4531 of the file. @xref{M, MRI mode, MRI mode}.
4534 @section @code{.list}
4536 @cindex @code{list} directive
4537 @cindex listing control, turning on
4538 Control (in conjunction with the @code{.nolist} directive) whether or
4539 not assembly listings are generated. These two directives maintain an
4540 internal counter (which is zero initially). @code{.list} increments the
4541 counter, and @code{.nolist} decrements it. Assembly listings are
4542 generated whenever the counter is greater than zero.
4544 By default, listings are disabled. When you enable them (with the
4545 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4546 the initial value of the listing counter is one.
4549 @section @code{.long @var{expressions}}
4551 @cindex @code{long} directive
4552 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4555 @c no one seems to know what this is for or whether this description is
4556 @c what it really ought to do
4558 @section @code{.lsym @var{symbol}, @var{expression}}
4560 @cindex @code{lsym} directive
4561 @cindex symbol, not referenced in assembly
4562 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4563 the hash table, ensuring it cannot be referenced by name during the
4564 rest of the assembly. This sets the attributes of the symbol to be
4565 the same as the expression value:
4567 @var{other} = @var{descriptor} = 0
4568 @var{type} = @r{(section of @var{expression})}
4569 @var{value} = @var{expression}
4572 The new symbol is not flagged as external.
4576 @section @code{.macro}
4579 The commands @code{.macro} and @code{.endm} allow you to define macros that
4580 generate assembly output. For example, this definition specifies a macro
4581 @code{sum} that puts a sequence of numbers into memory:
4584 .macro sum from=0, to=5
4593 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4605 @item .macro @var{macname}
4606 @itemx .macro @var{macname} @var{macargs} @dots{}
4607 @cindex @code{macro} directive
4608 Begin the definition of a macro called @var{macname}. If your macro
4609 definition requires arguments, specify their names after the macro name,
4610 separated by commas or spaces. You can supply a default value for any
4611 macro argument by following the name with @samp{=@var{deflt}}. For
4612 example, these are all valid @code{.macro} statements:
4616 Begin the definition of a macro called @code{comm}, which takes no
4619 @item .macro plus1 p, p1
4620 @itemx .macro plus1 p p1
4621 Either statement begins the definition of a macro called @code{plus1},
4622 which takes two arguments; within the macro definition, write
4623 @samp{\p} or @samp{\p1} to evaluate the arguments.
4625 @item .macro reserve_str p1=0 p2
4626 Begin the definition of a macro called @code{reserve_str}, with two
4627 arguments. The first argument has a default value, but not the second.
4628 After the definition is complete, you can call the macro either as
4629 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4630 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4631 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4632 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4635 When you call a macro, you can specify the argument values either by
4636 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4637 @samp{sum to=17, from=9}.
4640 @cindex @code{endm} directive
4641 Mark the end of a macro definition.
4644 @cindex @code{exitm} directive
4645 Exit early from the current macro definition.
4647 @cindex number of macros executed
4648 @cindex macros, count executed
4650 @command{@value{AS}} maintains a counter of how many macros it has
4651 executed in this pseudo-variable; you can copy that number to your
4652 output with @samp{\@@}, but @emph{only within a macro definition}.
4655 @item LOCAL @var{name} [ , @dots{} ]
4656 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4657 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4658 Alternate macro syntax}.
4660 Generate a string replacement for each of the @var{name} arguments, and
4661 replace any instances of @var{name} in each macro expansion. The
4662 replacement string is unique in the assembly, and different for each
4663 separate macro expansion. @code{LOCAL} allows you to write macros that
4664 define symbols, without fear of conflict between separate macro expansions.
4669 @section @code{.nolist}
4671 @cindex @code{nolist} directive
4672 @cindex listing control, turning off
4673 Control (in conjunction with the @code{.list} directive) whether or
4674 not assembly listings are generated. These two directives maintain an
4675 internal counter (which is zero initially). @code{.list} increments the
4676 counter, and @code{.nolist} decrements it. Assembly listings are
4677 generated whenever the counter is greater than zero.
4680 @section @code{.octa @var{bignums}}
4682 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4683 @cindex @code{octa} directive
4684 @cindex integer, 16-byte
4685 @cindex sixteen byte integer
4686 This directive expects zero or more bignums, separated by commas. For each
4687 bignum, it emits a 16-byte integer.
4689 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4690 hence @emph{octa}-word for 16 bytes.
4693 @section @code{.org @var{new-lc} , @var{fill}}
4695 @cindex @code{org} directive
4696 @cindex location counter, advancing
4697 @cindex advancing location counter
4698 @cindex current address, advancing
4699 Advance the location counter of the current section to
4700 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4701 expression with the same section as the current subsection. That is,
4702 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4703 wrong section, the @code{.org} directive is ignored. To be compatible
4704 with former assemblers, if the section of @var{new-lc} is absolute,
4705 @command{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4706 is the same as the current subsection.
4708 @code{.org} may only increase the location counter, or leave it
4709 unchanged; you cannot use @code{.org} to move the location counter
4712 @c double negative used below "not undefined" because this is a specific
4713 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4714 @c section. doc@cygnus.com 18feb91
4715 Because @command{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4716 may not be undefined. If you really detest this restriction we eagerly await
4717 a chance to share your improved assembler.
4719 Beware that the origin is relative to the start of the section, not
4720 to the start of the subsection. This is compatible with other
4721 people's assemblers.
4723 When the location counter (of the current subsection) is advanced, the
4724 intervening bytes are filled with @var{fill} which should be an
4725 absolute expression. If the comma and @var{fill} are omitted,
4726 @var{fill} defaults to zero.
4729 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4731 @cindex padding the location counter given a power of two
4732 @cindex @code{p2align} directive
4733 Pad the location counter (in the current subsection) to a particular
4734 storage boundary. The first expression (which must be absolute) is the
4735 number of low-order zero bits the location counter must have after
4736 advancement. For example @samp{.p2align 3} advances the location
4737 counter until it a multiple of 8. If the location counter is already a
4738 multiple of 8, no change is needed.
4740 The second expression (also absolute) gives the fill value to be stored in the
4741 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4742 padding bytes are normally zero. However, on some systems, if the section is
4743 marked as containing code and the fill value is omitted, the space is filled
4744 with no-op instructions.
4746 The third expression is also absolute, and is also optional. If it is present,
4747 it is the maximum number of bytes that should be skipped by this alignment
4748 directive. If doing the alignment would require skipping more bytes than the
4749 specified maximum, then the alignment is not done at all. You can omit the
4750 fill value (the second argument) entirely by simply using two commas after the
4751 required alignment; this can be useful if you want the alignment to be filled
4752 with no-op instructions when appropriate.
4754 @cindex @code{p2alignw} directive
4755 @cindex @code{p2alignl} directive
4756 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4757 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4758 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4759 fill pattern as a four byte longword value. For example, @code{.p2alignw
4760 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4761 filled in with the value 0x368d (the exact placement of the bytes depends upon
4762 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4767 @section @code{.previous}
4769 @cindex @code{.previous} directive
4770 @cindex Section Stack
4771 This is one of the ELF section stack manipulation directives. The others are
4772 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4773 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4774 (@pxref{PopSection}).
4776 This directive swaps the current section (and subsection) with most recently
4777 referenced section (and subsection) prior to this one. Multiple
4778 @code{.previous} directives in a row will flip between two sections (and their
4781 In terms of the section stack, this directive swaps the current section with
4782 the top section on the section stack.
4787 @section @code{.popsection}
4789 @cindex @code{.popsection} directive
4790 @cindex Section Stack
4791 This is one of the ELF section stack manipulation directives. The others are
4792 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4793 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4796 This directive replaces the current section (and subsection) with the top
4797 section (and subsection) on the section stack. This section is popped off the
4802 @section @code{.print @var{string}}
4804 @cindex @code{print} directive
4805 @command{@value{AS}} will print @var{string} on the standard output during
4806 assembly. You must put @var{string} in double quotes.
4810 @section @code{.protected @var{names}}
4812 @cindex @code{.protected} directive
4814 This one of the ELF visibility directives. The other two are
4815 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
4817 This directive overrides the named symbols default visibility (which is set by
4818 their binding: local, global or weak). The directive sets the visibility to
4819 @code{protected} which means that any references to the symbols from within the
4820 components that defines them must be resolved to the definition in that
4821 component, even if a definition in another component would normally preempt
4826 @section @code{.psize @var{lines} , @var{columns}}
4828 @cindex @code{psize} directive
4829 @cindex listing control: paper size
4830 @cindex paper size, for listings
4831 Use this directive to declare the number of lines---and, optionally, the
4832 number of columns---to use for each page, when generating listings.
4834 If you do not use @code{.psize}, listings use a default line-count
4835 of 60. You may omit the comma and @var{columns} specification; the
4836 default width is 200 columns.
4838 @command{@value{AS}} generates formfeeds whenever the specified number of
4839 lines is exceeded (or whenever you explicitly request one, using
4842 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4843 those explicitly specified with @code{.eject}.
4846 @section @code{.purgem @var{name}}
4848 @cindex @code{purgem} directive
4849 Undefine the macro @var{name}, so that later uses of the string will not be
4850 expanded. @xref{Macro}.
4854 @section @code{.pushsection @var{name} , @var{subsection}}
4856 @cindex @code{.pushsection} directive
4857 @cindex Section Stack
4858 This is one of the ELF section stack manipulation directives. The others are
4859 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4860 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
4863 This directive is a synonym for @code{.section}. It pushes the current section
4864 (and subsection) onto the top of the section stack, and then replaces the
4865 current section and subsection with @code{name} and @code{subsection}.
4869 @section @code{.quad @var{bignums}}
4871 @cindex @code{quad} directive
4872 @code{.quad} expects zero or more bignums, separated by commas. For
4873 each bignum, it emits
4875 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4876 warning message; and just takes the lowest order 8 bytes of the bignum.
4877 @cindex eight-byte integer
4878 @cindex integer, 8-byte
4880 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4881 hence @emph{quad}-word for 8 bytes.
4884 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4885 warning message; and just takes the lowest order 16 bytes of the bignum.
4886 @cindex sixteen-byte integer
4887 @cindex integer, 16-byte
4891 @section @code{.rept @var{count}}
4893 @cindex @code{rept} directive
4894 Repeat the sequence of lines between the @code{.rept} directive and the next
4895 @code{.endr} directive @var{count} times.
4897 For example, assembling
4905 is equivalent to assembling
4914 @section @code{.sbttl "@var{subheading}"}
4916 @cindex @code{sbttl} directive
4917 @cindex subtitles for listings
4918 @cindex listing control: subtitle
4919 Use @var{subheading} as the title (third line, immediately after the
4920 title line) when generating assembly listings.
4922 This directive affects subsequent pages, as well as the current page if
4923 it appears within ten lines of the top of a page.
4927 @section @code{.scl @var{class}}
4929 @cindex @code{scl} directive
4930 @cindex symbol storage class (COFF)
4931 @cindex COFF symbol storage class
4932 Set the storage-class value for a symbol. This directive may only be
4933 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4934 whether a symbol is static or external, or it may record further
4935 symbolic debugging information.
4938 The @samp{.scl} directive is primarily associated with COFF output; when
4939 configured to generate @code{b.out} output format, @command{@value{AS}}
4940 accepts this directive but ignores it.
4945 @section @code{.section @var{name}} (COFF version)
4947 @cindex @code{section} directive
4948 @cindex named section
4949 Use the @code{.section} directive to assemble the following code into a section
4952 This directive is only supported for targets that actually support arbitrarily
4953 named sections; on @code{a.out} targets, for example, it is not accepted, even
4954 with a standard @code{a.out} section name.
4956 For COFF targets, the @code{.section} directive is used in one of the following
4960 .section @var{name}[, "@var{flags}"]
4961 .section @var{name}[, @var{subsegment}]
4964 If the optional argument is quoted, it is taken as flags to use for the
4965 section. Each flag is a single character. The following flags are recognized:
4968 bss section (uninitialized data)
4970 section is not loaded
4980 shared section (meaningful for PE targets)
4983 If no flags are specified, the default flags depend upon the section name. If
4984 the section name is not recognized, the default will be for the section to be
4985 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
4986 from the section, rather than adding them, so if they are used on their own it
4987 will be as if no flags had been specified at all.
4989 If the optional argument to the @code{.section} directive is not quoted, it is
4990 taken as a subsegment number (@pxref{Sub-Sections}).
4993 @section @code{.section @var{name}} (ELF version)
4995 @cindex @code{section} directive
4996 @cindex named section
4998 @cindex Section Stack
4999 This is one of the ELF section stack manipulation directives. The others are
5000 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
5001 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
5002 @code{.previous} (@pxref{Previous}).
5005 For ELF targets, the @code{.section} directive is used like this:
5008 .section @var{name} [, "@var{flags}"[, @@@var{type}[, @@@var{entsize}]]]
5011 The optional @var{flags} argument is a quoted string which may contain any
5012 combination of the following characters:
5015 section is allocatable
5019 section is executable
5021 section is mergeable
5023 section contains zero terminated strings
5026 The optional @var{type} argument may contain one of the following constants:
5029 section contains data
5031 section does not contain data (i.e., section only occupies space)
5034 If @var{flags} contains @code{M} flag, @var{type} argument must be specified
5035 as well as @var{entsize} argument. Sections with @code{M} flag but not
5036 @code{S} flag must contain fixed size constants, each @var{entsize} octets
5037 long. Sections with both @code{M} and @code{S} must contain zero terminated
5038 strings where each character is @var{entsize} bytes long. The linker may remove
5039 duplicates within sections with the same name, same entity size and same flags.
5041 If no flags are specified, the default flags depend upon the section name. If
5042 the section name is not recognized, the default will be for the section to have
5043 none of the above flags: it will not be allocated in memory, nor writable, nor
5044 executable. The section will contain data.
5046 For ELF targets, the assembler supports another type of @code{.section}
5047 directive for compatibility with the Solaris assembler:
5050 .section "@var{name}"[, @var{flags}...]
5053 Note that the section name is quoted. There may be a sequence of comma
5057 section is allocatable
5061 section is executable
5064 This directive replaces the current section and subsection. The replaced
5065 section and subsection are pushed onto the section stack. See the contents of
5066 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
5067 how this directive and the other section stack directives work.
5070 @section @code{.set @var{symbol}, @var{expression}}
5072 @cindex @code{set} directive
5073 @cindex symbol value, setting
5074 Set the value of @var{symbol} to @var{expression}. This
5075 changes @var{symbol}'s value and type to conform to
5076 @var{expression}. If @var{symbol} was flagged as external, it remains
5077 flagged (@pxref{Symbol Attributes}).
5079 You may @code{.set} a symbol many times in the same assembly.
5081 If you @code{.set} a global symbol, the value stored in the object
5082 file is the last value stored into it.
5085 The syntax for @code{set} on the HPPA is
5086 @samp{@var{symbol} .set @var{expression}}.
5090 @section @code{.short @var{expressions}}
5092 @cindex @code{short} directive
5094 @code{.short} is normally the same as @samp{.word}.
5095 @xref{Word,,@code{.word}}.
5097 In some configurations, however, @code{.short} and @code{.word} generate
5098 numbers of different lengths; @pxref{Machine Dependencies}.
5102 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
5105 This expects zero or more @var{expressions}, and emits
5106 a 16 bit number for each.
5111 @section @code{.single @var{flonums}}
5113 @cindex @code{single} directive
5114 @cindex floating point numbers (single)
5115 This directive assembles zero or more flonums, separated by commas. It
5116 has the same effect as @code{.float}.
5118 The exact kind of floating point numbers emitted depends on how
5119 @command{@value{AS}} is configured. @xref{Machine Dependencies}.
5123 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
5124 numbers in @sc{ieee} format.
5129 @section @code{.size} (COFF version)
5131 @cindex @code{size} directive
5132 This directive is generated by compilers to include auxiliary debugging
5133 information in the symbol table. It is only permitted inside
5134 @code{.def}/@code{.endef} pairs.
5137 @samp{.size} is only meaningful when generating COFF format output; when
5138 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5142 @section @code{.size @var{name} , @var{expression}} (ELF version)
5143 @cindex @code{size} directive
5145 This directive is used to set the size associated with a symbol @var{name}.
5146 The size in bytes is computed from @var{expression} which can make use of label
5147 arithmetic. This directive is typically used to set the size of function
5151 @section @code{.sleb128 @var{expressions}}
5153 @cindex @code{sleb128} directive
5154 @var{sleb128} stands for ``signed little endian base 128.'' This is a
5155 compact, variable length representation of numbers used by the DWARF
5156 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5158 @ifclear no-space-dir
5160 @section @code{.skip @var{size} , @var{fill}}
5162 @cindex @code{skip} directive
5163 @cindex filling memory
5164 This directive emits @var{size} bytes, each of value @var{fill}. Both
5165 @var{size} and @var{fill} are absolute expressions. If the comma and
5166 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5170 @section @code{.space @var{size} , @var{fill}}
5172 @cindex @code{space} directive
5173 @cindex filling memory
5174 This directive emits @var{size} bytes, each of value @var{fill}. Both
5175 @var{size} and @var{fill} are absolute expressions. If the comma
5176 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5181 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5182 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5183 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5184 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5193 @section @code{.space}
5194 @cindex @code{space} directive
5196 On the AMD 29K, this directive is ignored; it is accepted for
5197 compatibility with other AMD 29K assemblers.
5200 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5201 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5207 @section @code{.stabd, .stabn, .stabs}
5209 @cindex symbolic debuggers, information for
5210 @cindex @code{stab@var{x}} directives
5211 There are three directives that begin @samp{.stab}.
5212 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5213 The symbols are not entered in the @command{@value{AS}} hash table: they
5214 cannot be referenced elsewhere in the source file.
5215 Up to five fields are required:
5219 This is the symbol's name. It may contain any character except
5220 @samp{\000}, so is more general than ordinary symbol names. Some
5221 debuggers used to code arbitrarily complex structures into symbol names
5225 An absolute expression. The symbol's type is set to the low 8 bits of
5226 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5227 and debuggers choke on silly bit patterns.
5230 An absolute expression. The symbol's ``other'' attribute is set to the
5231 low 8 bits of this expression.
5234 An absolute expression. The symbol's descriptor is set to the low 16
5235 bits of this expression.
5238 An absolute expression which becomes the symbol's value.
5241 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5242 or @code{.stabs} statement, the symbol has probably already been created;
5243 you get a half-formed symbol in your object file. This is
5244 compatible with earlier assemblers!
5247 @cindex @code{stabd} directive
5248 @item .stabd @var{type} , @var{other} , @var{desc}
5250 The ``name'' of the symbol generated is not even an empty string.
5251 It is a null pointer, for compatibility. Older assemblers used a
5252 null pointer so they didn't waste space in object files with empty
5255 The symbol's value is set to the location counter,
5256 relocatably. When your program is linked, the value of this symbol
5257 is the address of the location counter when the @code{.stabd} was
5260 @cindex @code{stabn} directive
5261 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5262 The name of the symbol is set to the empty string @code{""}.
5264 @cindex @code{stabs} directive
5265 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5266 All five fields are specified.
5272 @section @code{.string} "@var{str}"
5274 @cindex string, copying to object file
5275 @cindex @code{string} directive
5277 Copy the characters in @var{str} to the object file. You may specify more than
5278 one string to copy, separated by commas. Unless otherwise specified for a
5279 particular machine, the assembler marks the end of each string with a 0 byte.
5280 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5283 @section @code{.struct @var{expression}}
5285 @cindex @code{struct} directive
5286 Switch to the absolute section, and set the section offset to @var{expression},
5287 which must be an absolute expression. You might use this as follows:
5296 This would define the symbol @code{field1} to have the value 0, the symbol
5297 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5298 value 8. Assembly would be left in the absolute section, and you would need to
5299 use a @code{.section} directive of some sort to change to some other section
5300 before further assembly.
5304 @section @code{.subsection @var{name}}
5306 @cindex @code{.subsection} directive
5307 @cindex Section Stack
5308 This is one of the ELF section stack manipulation directives. The others are
5309 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5310 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5313 This directive replaces the current subsection with @code{name}. The current
5314 section is not changed. The replaced subsection is put onto the section stack
5315 in place of the then current top of stack subsection.
5320 @section @code{.symver}
5321 @cindex @code{symver} directive
5322 @cindex symbol versioning
5323 @cindex versions of symbols
5324 Use the @code{.symver} directive to bind symbols to specific version nodes
5325 within a source file. This is only supported on ELF platforms, and is
5326 typically used when assembling files to be linked into a shared library.
5327 There are cases where it may make sense to use this in objects to be bound
5328 into an application itself so as to override a versioned symbol from a
5331 For ELF targets, the @code{.symver} directive can be used like this:
5333 .symver @var{name}, @var{name2@@nodename}
5335 If the symbol @var{name} is defined within the file
5336 being assembled, the @code{.symver} directive effectively creates a symbol
5337 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5338 just don't try and create a regular alias is that the @var{@@} character isn't
5339 permitted in symbol names. The @var{name2} part of the name is the actual name
5340 of the symbol by which it will be externally referenced. The name @var{name}
5341 itself is merely a name of convenience that is used so that it is possible to
5342 have definitions for multiple versions of a function within a single source
5343 file, and so that the compiler can unambiguously know which version of a
5344 function is being mentioned. The @var{nodename} portion of the alias should be
5345 the name of a node specified in the version script supplied to the linker when
5346 building a shared library. If you are attempting to override a versioned
5347 symbol from a shared library, then @var{nodename} should correspond to the
5348 nodename of the symbol you are trying to override.
5350 If the symbol @var{name} is not defined within the file being assembled, all
5351 references to @var{name} will be changed to @var{name2@@nodename}. If no
5352 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5355 Another usage of the @code{.symver} directive is:
5357 .symver @var{name}, @var{name2@@@@nodename}
5359 In this case, the symbol @var{name} must exist and be defined within
5360 the file being assembled. It is similar to @var{name2@@nodename}. The
5361 difference is @var{name2@@@@nodename} will also be used to resolve
5362 references to @var{name2} by the linker.
5364 The third usage of the @code{.symver} directive is:
5366 .symver @var{name}, @var{name2@@@@@@nodename}
5368 When @var{name} is not defined within the
5369 file being assembled, it is treated as @var{name2@@nodename}. When
5370 @var{name} is defined within the file being assembled, the symbol
5371 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5376 @section @code{.tag @var{structname}}
5378 @cindex COFF structure debugging
5379 @cindex structure debugging, COFF
5380 @cindex @code{tag} directive
5381 This directive is generated by compilers to include auxiliary debugging
5382 information in the symbol table. It is only permitted inside
5383 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5384 definitions in the symbol table with instances of those structures.
5387 @samp{.tag} is only used when generating COFF format output; when
5388 @command{@value{AS}} is generating @code{b.out}, it accepts this directive but
5394 @section @code{.text @var{subsection}}
5396 @cindex @code{text} directive
5397 Tells @command{@value{AS}} to assemble the following statements onto the end of
5398 the text subsection numbered @var{subsection}, which is an absolute
5399 expression. If @var{subsection} is omitted, subsection number zero
5403 @section @code{.title "@var{heading}"}
5405 @cindex @code{title} directive
5406 @cindex listing control: title line
5407 Use @var{heading} as the title (second line, immediately after the
5408 source file name and pagenumber) when generating assembly listings.
5410 This directive affects subsequent pages, as well as the current page if
5411 it appears within ten lines of the top of a page.
5414 @section @code{.type @var{int}} (COFF version)
5416 @cindex COFF symbol type
5417 @cindex symbol type, COFF
5418 @cindex @code{type} directive
5419 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5420 records the integer @var{int} as the type attribute of a symbol table entry.
5423 @samp{.type} is associated only with COFF format output; when
5424 @command{@value{AS}} is configured for @code{b.out} output, it accepts this
5425 directive but ignores it.
5428 @section @code{.type @var{name} , @var{type description}} (ELF version)
5430 @cindex ELF symbol type
5431 @cindex symbol type, ELF
5432 @cindex @code{type} directive
5433 This directive is used to set the type of symbol @var{name} to be either a
5434 function symbol or an object symbol. There are five different syntaxes
5435 supported for the @var{type description} field, in order to provide
5436 compatibility with various other assemblers. The syntaxes supported are:
5439 .type <name>,#function
5440 .type <name>,#object
5442 .type <name>,@@function
5443 .type <name>,@@object
5445 .type <name>,%function
5446 .type <name>,%object
5448 .type <name>,"function"
5449 .type <name>,"object"
5451 .type <name> STT_FUNCTION
5452 .type <name> STT_OBJECT
5456 @section @code{.uleb128 @var{expressions}}
5458 @cindex @code{uleb128} directive
5459 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5460 compact, variable length representation of numbers used by the DWARF
5461 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5465 @section @code{.val @var{addr}}
5467 @cindex @code{val} directive
5468 @cindex COFF value attribute
5469 @cindex value attribute, COFF
5470 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5471 records the address @var{addr} as the value attribute of a symbol table
5475 @samp{.val} is used only for COFF output; when @command{@value{AS}} is
5476 configured for @code{b.out}, it accepts this directive but ignores it.
5482 @section @code{.version "@var{string}"}
5484 @cindex @code{.version}
5485 This directive creates a @code{.note} section and places into it an ELF
5486 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5491 @section @code{.vtable_entry @var{table}, @var{offset}}
5493 @cindex @code{.vtable_entry}
5494 This directive finds or creates a symbol @code{table} and creates a
5495 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5498 @section @code{.vtable_inherit @var{child}, @var{parent}}
5500 @cindex @code{.vtable_inherit}
5501 This directive finds the symbol @code{child} and finds or creates the symbol
5502 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5503 parent whose addend is the value of the child symbol. As a special case the
5504 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5509 @section @code{.weak @var{names}}
5511 @cindex @code{.weak}
5512 This directive sets the weak attribute on the comma separated list of symbol
5513 @code{names}. If the symbols do not already exist, they will be created.
5517 @section @code{.word @var{expressions}}
5519 @cindex @code{word} directive
5520 This directive expects zero or more @var{expressions}, of any section,
5521 separated by commas.
5524 For each expression, @command{@value{AS}} emits a 32-bit number.
5527 For each expression, @command{@value{AS}} emits a 16-bit number.
5532 The size of the number emitted, and its byte order,
5533 depend on what target computer the assembly is for.
5536 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5537 @c happen---32-bit addressability, period; no long/short jumps.
5538 @ifset DIFF-TBL-KLUGE
5539 @cindex difference tables altered
5540 @cindex altered difference tables
5542 @emph{Warning: Special Treatment to support Compilers}
5546 Machines with a 32-bit address space, but that do less than 32-bit
5547 addressing, require the following special treatment. If the machine of
5548 interest to you does 32-bit addressing (or doesn't require it;
5549 @pxref{Machine Dependencies}), you can ignore this issue.
5552 In order to assemble compiler output into something that works,
5553 @command{@value{AS}} occasionally does strange things to @samp{.word} directives.
5554 Directives of the form @samp{.word sym1-sym2} are often emitted by
5555 compilers as part of jump tables. Therefore, when @command{@value{AS}} assembles a
5556 directive of the form @samp{.word sym1-sym2}, and the difference between
5557 @code{sym1} and @code{sym2} does not fit in 16 bits, @command{@value{AS}}
5558 creates a @dfn{secondary jump table}, immediately before the next label.
5559 This secondary jump table is preceded by a short-jump to the
5560 first byte after the secondary table. This short-jump prevents the flow
5561 of control from accidentally falling into the new table. Inside the
5562 table is a long-jump to @code{sym2}. The original @samp{.word}
5563 contains @code{sym1} minus the address of the long-jump to
5566 If there were several occurrences of @samp{.word sym1-sym2} before the
5567 secondary jump table, all of them are adjusted. If there was a
5568 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5569 long-jump to @code{sym4} is included in the secondary jump table,
5570 and the @code{.word} directives are adjusted to contain @code{sym3}
5571 minus the address of the long-jump to @code{sym4}; and so on, for as many
5572 entries in the original jump table as necessary.
5575 @emph{This feature may be disabled by compiling @command{@value{AS}} with the
5576 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5577 assembly language programmers.
5580 @c end DIFF-TBL-KLUGE
5583 @section Deprecated Directives
5585 @cindex deprecated directives
5586 @cindex obsolescent directives
5587 One day these directives won't work.
5588 They are included for compatibility with older assemblers.
5595 @node Machine Dependencies
5596 @chapter Machine Dependent Features
5598 @cindex machine dependencies
5599 The machine instruction sets are (almost by definition) different on
5600 each machine where @command{@value{AS}} runs. Floating point representations
5601 vary as well, and @command{@value{AS}} often supports a few additional
5602 directives or command-line options for compatibility with other
5603 assemblers on a particular platform. Finally, some versions of
5604 @command{@value{AS}} support special pseudo-instructions for branch
5607 This chapter discusses most of these differences, though it does not
5608 include details on any machine's instruction set. For details on that
5609 subject, see the hardware manufacturer's manual.
5613 * AMD29K-Dependent:: AMD 29K Dependent Features
5616 * Alpha-Dependent:: Alpha Dependent Features
5619 * ARC-Dependent:: ARC Dependent Features
5622 * ARM-Dependent:: ARM Dependent Features
5625 * CRIS-Dependent:: CRIS Dependent Features
5628 * D10V-Dependent:: D10V Dependent Features
5631 * D30V-Dependent:: D30V Dependent Features
5634 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5637 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5640 * HPPA-Dependent:: HPPA Dependent Features
5643 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5646 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5649 * i860-Dependent:: Intel 80860 Dependent Features
5652 * i960-Dependent:: Intel 80960 Dependent Features
5655 * M32R-Dependent:: M32R Dependent Features
5658 * M68K-Dependent:: M680x0 Dependent Features
5661 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5664 * M88K-Dependent:: M880x0 Dependent Features
5667 * MIPS-Dependent:: MIPS Dependent Features
5670 * MMIX-Dependent:: MMIX Dependent Features
5673 * SH-Dependent:: Hitachi SH Dependent Features
5674 * SH64-Dependent:: Hitachi SH64 Dependent Features
5677 * PDP-11-Dependent:: PDP-11 Dependent Features
5680 * PJ-Dependent:: picoJava Dependent Features
5683 * PPC-Dependent:: PowerPC Dependent Features
5686 * Sparc-Dependent:: SPARC Dependent Features
5689 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5692 * V850-Dependent:: V850 Dependent Features
5695 * Z8000-Dependent:: Z8000 Dependent Features
5698 * Vax-Dependent:: VAX Dependent Features
5705 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5706 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5707 @c peculiarity: to preserve cross-references, there must be a node called
5708 @c "Machine Dependencies". Hence the conditional nodenames in each
5709 @c major node below. Node defaulting in makeinfo requires adjacency of
5710 @c node and sectioning commands; hence the repetition of @chapter BLAH
5711 @c in both conditional blocks.
5714 @include c-a29k.texi
5718 @include c-alpha.texi
5730 @include c-cris.texi
5735 @node Machine Dependencies
5736 @chapter Machine Dependent Features
5738 The machine instruction sets are different on each Hitachi chip family,
5739 and there are also some syntax differences among the families. This
5740 chapter describes the specific @command{@value{AS}} features for each
5744 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5745 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5746 * SH-Dependent:: Hitachi SH Dependent Features
5753 @include c-d10v.texi
5757 @include c-d30v.texi
5761 @include c-h8300.texi
5765 @include c-h8500.texi
5769 @include c-hppa.texi
5773 @include c-i370.texi
5777 @include c-i386.texi
5781 @include c-i860.texi
5785 @include c-i960.texi
5789 @include c-ia64.texi
5793 @include c-m32r.texi
5797 @include c-m68k.texi
5801 @include c-m68hc11.texi
5805 @include c-m88k.texi
5809 @include c-mips.texi
5813 @include c-mmix.texi
5817 @include c-ns32k.texi
5821 @include c-pdp11.texi
5834 @include c-sh64.texi
5838 @include c-sparc.texi
5842 @include c-tic54x.texi
5854 @include c-v850.texi
5858 @c reverse effect of @down at top of generic Machine-Dep chapter
5862 @node Reporting Bugs
5863 @chapter Reporting Bugs
5864 @cindex bugs in assembler
5865 @cindex reporting bugs in assembler
5867 Your bug reports play an essential role in making @command{@value{AS}} reliable.
5869 Reporting a bug may help you by bringing a solution to your problem, or it may
5870 not. But in any case the principal function of a bug report is to help the
5871 entire community by making the next version of @command{@value{AS}} work better.
5872 Bug reports are your contribution to the maintenance of @command{@value{AS}}.
5874 In order for a bug report to serve its purpose, you must include the
5875 information that enables us to fix the bug.
5878 * Bug Criteria:: Have you found a bug?
5879 * Bug Reporting:: How to report bugs
5883 @section Have you found a bug?
5884 @cindex bug criteria
5886 If you are not sure whether you have found a bug, here are some guidelines:
5889 @cindex fatal signal
5890 @cindex assembler crash
5891 @cindex crash of assembler
5893 If the assembler gets a fatal signal, for any input whatever, that is a
5894 @command{@value{AS}} bug. Reliable assemblers never crash.
5896 @cindex error on valid input
5898 If @command{@value{AS}} produces an error message for valid input, that is a bug.
5900 @cindex invalid input
5902 If @command{@value{AS}} does not produce an error message for invalid input, that
5903 is a bug. However, you should note that your idea of ``invalid input'' might
5904 be our idea of ``an extension'' or ``support for traditional practice''.
5907 If you are an experienced user of assemblers, your suggestions for improvement
5908 of @command{@value{AS}} are welcome in any case.
5912 @section How to report bugs
5914 @cindex assembler bugs, reporting
5916 A number of companies and individuals offer support for @sc{gnu} products. If
5917 you obtained @command{@value{AS}} from a support organization, we recommend you
5918 contact that organization first.
5920 You can find contact information for many support companies and
5921 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5924 In any event, we also recommend that you send bug reports for @command{@value{AS}}
5925 to @samp{bug-binutils@@gnu.org}.
5927 The fundamental principle of reporting bugs usefully is this:
5928 @strong{report all the facts}. If you are not sure whether to state a
5929 fact or leave it out, state it!
5931 Often people omit facts because they think they know what causes the problem
5932 and assume that some details do not matter. Thus, you might assume that the
5933 name of a symbol you use in an example does not matter. Well, probably it does
5934 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5935 happens to fetch from the location where that name is stored in memory;
5936 perhaps, if the name were different, the contents of that location would fool
5937 the assembler into doing the right thing despite the bug. Play it safe and
5938 give a specific, complete example. That is the easiest thing for you to do,
5939 and the most helpful.
5941 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5942 it is new to us. Therefore, always write your bug reports on the assumption
5943 that the bug has not been reported previously.
5945 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5946 bell?'' Those bug reports are useless, and we urge everyone to
5947 @emph{refuse to respond to them} except to chide the sender to report
5950 To enable us to fix the bug, you should include all these things:
5954 The version of @command{@value{AS}}. @command{@value{AS}} announces it if you start
5955 it with the @samp{--version} argument.
5957 Without this, we will not know whether there is any point in looking for
5958 the bug in the current version of @command{@value{AS}}.
5961 Any patches you may have applied to the @command{@value{AS}} source.
5964 The type of machine you are using, and the operating system name and
5968 What compiler (and its version) was used to compile @command{@value{AS}}---e.g.
5972 The command arguments you gave the assembler to assemble your example and
5973 observe the bug. To guarantee you will not omit something important, list them
5974 all. A copy of the Makefile (or the output from make) is sufficient.
5976 If we were to try to guess the arguments, we would probably guess wrong
5977 and then we might not encounter the bug.
5980 A complete input file that will reproduce the bug. If the bug is observed when
5981 the assembler is invoked via a compiler, send the assembler source, not the
5982 high level language source. Most compilers will produce the assembler source
5983 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5984 the options @samp{-v --save-temps}; this will save the assembler source in a
5985 file with an extension of @file{.s}, and also show you exactly how
5986 @command{@value{AS}} is being run.
5989 A description of what behavior you observe that you believe is
5990 incorrect. For example, ``It gets a fatal signal.''
5992 Of course, if the bug is that @command{@value{AS}} gets a fatal signal, then we
5993 will certainly notice it. But if the bug is incorrect output, we might not
5994 notice unless it is glaringly wrong. You might as well not give us a chance to
5997 Even if the problem you experience is a fatal signal, you should still say so
5998 explicitly. Suppose something strange is going on, such as, your copy of
5999 @command{@value{AS}} is out of synch, or you have encountered a bug in the C
6000 library on your system. (This has happened!) Your copy might crash and ours
6001 would not. If you told us to expect a crash, then when ours fails to crash, we
6002 would know that the bug was not happening for us. If you had not told us to
6003 expect a crash, then we would not be able to draw any conclusion from our
6007 If you wish to suggest changes to the @command{@value{AS}} source, send us context
6008 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
6009 option. Always send diffs from the old file to the new file. If you even
6010 discuss something in the @command{@value{AS}} source, refer to it by context, not
6013 The line numbers in our development sources will not match those in your
6014 sources. Your line numbers would convey no useful information to us.
6017 Here are some things that are not necessary:
6021 A description of the envelope of the bug.
6023 Often people who encounter a bug spend a lot of time investigating
6024 which changes to the input file will make the bug go away and which
6025 changes will not affect it.
6027 This is often time consuming and not very useful, because the way we
6028 will find the bug is by running a single example under the debugger
6029 with breakpoints, not by pure deduction from a series of examples.
6030 We recommend that you save your time for something else.
6032 Of course, if you can find a simpler example to report @emph{instead}
6033 of the original one, that is a convenience for us. Errors in the
6034 output will be easier to spot, running under the debugger will take
6035 less time, and so on.
6037 However, simplification is not vital; if you do not want to do this,
6038 report the bug anyway and send us the entire test case you used.
6041 A patch for the bug.
6043 A patch for the bug does help us if it is a good one. But do not omit
6044 the necessary information, such as the test case, on the assumption that
6045 a patch is all we need. We might see problems with your patch and decide
6046 to fix the problem another way, or we might not understand it at all.
6048 Sometimes with a program as complicated as @command{@value{AS}} it is very hard to
6049 construct an example that will make the program follow a certain path through
6050 the code. If you do not send us the example, we will not be able to construct
6051 one, so we will not be able to verify that the bug is fixed.
6053 And if we cannot understand what bug you are trying to fix, or why your
6054 patch should be an improvement, we will not install it. A test case will
6055 help us to understand.
6058 A guess about what the bug is or what it depends on.
6060 Such guesses are usually wrong. Even we cannot guess right about such
6061 things without first using the debugger to find the facts.
6064 @node Acknowledgements
6065 @chapter Acknowledgements
6067 If you have contributed to @command{@value{AS}} and your name isn't listed here,
6068 it is not meant as a slight. We just don't know about it. Send mail to the
6069 maintainer, and we'll correct the situation. Currently
6071 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
6073 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
6076 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
6077 information and the 68k series machines, most of the preprocessing pass, and
6078 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
6080 K. Richard Pixley maintained GAS for a while, adding various enhancements and
6081 many bug fixes, including merging support for several processors, breaking GAS
6082 up to handle multiple object file format back ends (including heavy rewrite,
6083 testing, an integration of the coff and b.out back ends), adding configuration
6084 including heavy testing and verification of cross assemblers and file splits
6085 and renaming, converted GAS to strictly ANSI C including full prototypes, added
6086 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
6087 port (including considerable amounts of reverse engineering), a SPARC opcode
6088 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
6089 assertions and made them work, much other reorganization, cleanup, and lint.
6091 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
6092 in format-specific I/O modules.
6094 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
6095 has done much work with it since.
6097 The Intel 80386 machine description was written by Eliot Dresselhaus.
6099 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
6101 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
6102 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
6104 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
6105 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
6106 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
6107 support a.out format.
6109 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
6110 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
6111 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
6112 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
6115 John Gilmore built the AMD 29000 support, added @code{.include} support, and
6116 simplified the configuration of which versions accept which directives. He
6117 updated the 68k machine description so that Motorola's opcodes always produced
6118 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
6119 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
6120 cross-compilation support, and one bug in relaxation that took a week and
6121 required the proverbial one-bit fix.
6123 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
6124 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
6125 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
6126 PowerPC assembler, and made a few other minor patches.
6128 Steve Chamberlain made @command{@value{AS}} able to generate listings.
6130 Hewlett-Packard contributed support for the HP9000/300.
6132 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
6133 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
6134 formats). This work was supported by both the Center for Software Science at
6135 the University of Utah and Cygnus Support.
6137 Support for ELF format files has been worked on by Mark Eichin of Cygnus
6138 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
6139 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
6140 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
6141 and some initial 64-bit support).
6143 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
6145 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
6146 support for openVMS/Alpha.
6148 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
6151 Several engineers at Cygnus Support have also provided many small bug fixes and
6152 configuration enhancements.
6154 Many others have contributed large or small bugfixes and enhancements. If
6155 you have contributed significant work and are not mentioned on this list, and
6156 want to be, let us know. Some of the history has been lost; we are not
6157 intentionally leaving anyone out.
6159 @node GNU Free Documentation License
6160 @chapter GNU Free Documentation License
6162 GNU Free Documentation License
6164 Version 1.1, March 2000
6166 Copyright (C) 2000 Free Software Foundation, Inc.
6167 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
6169 Everyone is permitted to copy and distribute verbatim copies
6170 of this license document, but changing it is not allowed.
6175 The purpose of this License is to make a manual, textbook, or other
6176 written document "free" in the sense of freedom: to assure everyone
6177 the effective freedom to copy and redistribute it, with or without
6178 modifying it, either commercially or noncommercially. Secondarily,
6179 this License preserves for the author and publisher a way to get
6180 credit for their work, while not being considered responsible for
6181 modifications made by others.
6183 This License is a kind of "copyleft", which means that derivative
6184 works of the document must themselves be free in the same sense. It
6185 complements the GNU General Public License, which is a copyleft
6186 license designed for free software.
6188 We have designed this License in order to use it for manuals for free
6189 software, because free software needs free documentation: a free
6190 program should come with manuals providing the same freedoms that the
6191 software does. But this License is not limited to software manuals;
6192 it can be used for any textual work, regardless of subject matter or
6193 whether it is published as a printed book. We recommend this License
6194 principally for works whose purpose is instruction or reference.
6197 1. APPLICABILITY AND DEFINITIONS
6199 This License applies to any manual or other work that contains a
6200 notice placed by the copyright holder saying it can be distributed
6201 under the terms of this License. The "Document", below, refers to any
6202 such manual or work. Any member of the public is a licensee, and is
6205 A "Modified Version" of the Document means any work containing the
6206 Document or a portion of it, either copied verbatim, or with
6207 modifications and/or translated into another language.
6209 A "Secondary Section" is a named appendix or a front-matter section of
6210 the Document that deals exclusively with the relationship of the
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6220 The "Invariant Sections" are certain Secondary Sections whose titles
6221 are designated, as being those of Invariant Sections, in the notice
6222 that says that the Document is released under this License.
6224 The "Cover Texts" are certain short passages of text that are listed,
6225 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
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6247 machine-generated HTML produced by some word processors for output
6250 The "Title Page" means, for a printed book, the title page itself,
6251 plus such following pages as are needed to hold, legibly, the material
6252 this License requires to appear in the title page. For works in
6253 formats which do not have any title page as such, "Title Page" means
6254 the text near the most prominent appearance of the work's title,
6255 preceding the beginning of the body of the text.
6260 You may copy and distribute the Document in any medium, either
6261 commercially or noncommercially, provided that this License, the
6262 copyright notices, and the license notice saying this License applies
6263 to the Document are reproduced in all copies, and that you add no other
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6265 technical measures to obstruct or control the reading or further
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6267 compensation in exchange for copies. If you distribute a large enough
6268 number of copies you must also follow the conditions in section 3.
6270 You may also lend copies, under the same conditions stated above, and
6271 you may publicly display copies.
6274 3. COPYING IN QUANTITY
6276 If you publish printed copies of the Document numbering more than 100,
6277 and the Document's license notice requires Cover Texts, you must enclose
6278 the copies in covers that carry, clearly and legibly, all these Cover
6279 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
6280 the back cover. Both covers must also clearly and legibly identify
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6282 the full title with all words of the title equally prominent and
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6284 Copying with changes limited to the covers, as long as they preserve
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6286 as verbatim copying in other respects.
6288 If the required texts for either cover are too voluminous to fit
6289 legibly, you should put the first ones listed (as many as fit
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6293 If you publish or distribute Opaque copies of the Document numbering
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6296 a publicly-accessible computer-network location containing a complete
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6298 general network-using public has access to download anonymously at no
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6301 distribution of Opaque copies in quantity, to ensure that this
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6303 until at least one year after the last time you distribute an Opaque
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6307 It is requested, but not required, that you contact the authors of the
6308 Document well before redistributing any large number of copies, to give
6309 them a chance to provide you with an updated version of the Document.
6314 You may copy and distribute a Modified Version of the Document under
6315 the conditions of sections 2 and 3 above, provided that you release
6316 the Modified Version under precisely this License, with the Modified
6317 Version filling the role of the Document, thus licensing distribution
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6319 of it. In addition, you must do these things in the Modified Version:
6321 A. Use in the Title Page (and on the covers, if any) a title distinct
6322 from that of the Document, and from those of previous versions
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6326 B. List on the Title Page, as authors, one or more persons or entities
6327 responsible for authorship of the modifications in the Modified
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6329 Document (all of its principal authors, if it has less than five).
6330 C. State on the Title page the name of the publisher of the
6331 Modified Version, as the publisher.
6332 D. Preserve all the copyright notices of the Document.
6333 E. Add an appropriate copyright notice for your modifications
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6335 F. Include, immediately after the copyright notices, a license notice
6336 giving the public permission to use the Modified Version under the
6337 terms of this License, in the form shown in the Addendum below.
6338 G. Preserve in that license notice the full lists of Invariant Sections
6339 and required Cover Texts given in the Document's license notice.
6340 H. Include an unaltered copy of this License.
6341 I. Preserve the section entitled "History", and its title, and add to
6342 it an item stating at least the title, year, new authors, and
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6344 there is no section entitled "History" in the Document, create one
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6348 J. Preserve the network location, if any, given in the Document for
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6355 K. In any section entitled "Acknowledgements" or "Dedications",
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6357 substance and tone of each of the contributor acknowledgements
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6359 L. Preserve all the Invariant Sections of the Document,
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6362 M. Delete any section entitled "Endorsements". Such a section
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6364 N. Do not retitle any existing section as "Endorsements"
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6367 If the Modified Version includes new front-matter sections or
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6370 of these sections as invariant. To do this, add their titles to the
6371 list of Invariant Sections in the Modified Version's license notice.
6372 These titles must be distinct from any other section titles.
6374 You may add a section entitled "Endorsements", provided it contains
6375 nothing but endorsements of your Modified Version by various
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6395 5. COMBINING DOCUMENTS
6397 You may combine the Document with other documents released under this
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6400 Invariant Sections of all of the original documents, unmodified, and
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6410 Make the same adjustment to the section titles in the list of
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6413 In the combination, you must combine any sections entitled "History"
6414 in the various original documents, forming one section entitled
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6417 entitled "Endorsements."
6420 6. COLLECTIONS OF DOCUMENTS
6422 You may make a collection consisting of the Document and other documents
6423 released under this License, and replace the individual copies of this
6424 License in the various documents with a single copy that is included in
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6426 verbatim copying of each of the documents in all other respects.
6428 You may extract a single document from such a collection, and distribute
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6430 License into the extracted document, and follow this License in all
6431 other respects regarding verbatim copying of that document.
6434 7. AGGREGATION WITH INDEPENDENT WORKS
6436 A compilation of the Document or its derivatives with other separate
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6438 distribution medium, does not as a whole count as a Modified Version
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6440 compilation. Such a compilation is called an "aggregate", and this
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6443 are not themselves derivative works of the Document.
6445 If the Cover Text requirement of section 3 is applicable to these
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6459 original versions of these Invariant Sections. You may include a
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6468 You may not copy, modify, sublicense, or distribute the Document except
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6477 10. FUTURE REVISIONS OF THIS LICENSE
6479 The Free Software Foundation may publish new, revised versions
6480 of the GNU Free Documentation License from time to time. Such new
6481 versions will be similar in spirit to the present version, but may
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6483 http://www.gnu.org/copyleft/.
6485 Each version of the License is given a distinguishing version number.
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6490 Free Software Foundation. If the Document does not specify a version
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6495 ADDENDUM: How to use this License for your documents
6497 To use this License in a document you have written, include a copy of
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6502 Copyright (c) YEAR YOUR NAME.
6503 Permission is granted to copy, distribute and/or modify this document
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6506 with the Invariant Sections being LIST THEIR TITLES, with the
6507 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
6508 A copy of the license is included in the section entitled "GNU
6509 Free Documentation License".
6512 If you have no Invariant Sections, write "with no Invariant Sections"
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6517 If your document contains nontrivial examples of program code, we
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6520 to permit their use in free software.
projects / deliverable / binutils-gdb.git / blob