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 @c defaults, config file may override:
19 @include asconfig.texi
22 @c common OR combinations of conditions
42 @set abnormal-separator
46 @settitle Using @value{AS}
49 @settitle Using @value{AS} (@value{TARGET})
51 @setchapternewpage odd
56 @c WARE! Some of the machine-dependent sections contain tables of machine
57 @c instructions. Except in multi-column format, these tables look silly.
58 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
59 @c the multi-col format is faked within @example sections.
61 @c Again unfortunately, the natural size that fits on a page, for these tables,
62 @c is different depending on whether or not smallbook is turned on.
63 @c This matters, because of order: text flow switches columns at each page
66 @c The format faked in this source works reasonably well for smallbook,
67 @c not well for the default large-page format. This manual expects that if you
68 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
69 @c tables in question. You can turn on one without the other at your
70 @c discretion, of course.
73 @c the insn tables look just as silly in info files regardless of smallbook,
74 @c might as well show 'em anyways.
80 * As: (as). The GNU assembler.
89 This file documents the GNU Assembler "@value{AS}".
91 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
93 Permission is granted to copy, distribute and/or modify this document
94 under the terms of the GNU Free Documentation License, Version 1.1
95 or any later version published by the Free Software Foundation;
96 with no Invariant Sections, with no Front-Cover Texts, and with no
97 Back-Cover Texts. A copy of the license is included in the
98 section entitled "GNU Free Documentation License".
101 Permission is granted to process this file through Tex and print the
102 results, provided the printed document carries copying permission
103 notice identical to this one except for the removal of this paragraph
104 (this paragraph not being relevant to the printed manual).
110 @title Using @value{AS}
111 @subtitle The @sc{gnu} Assembler
113 @subtitle for the @value{TARGET} family
116 @subtitle Version @value{VERSION}
119 The Free Software Foundation Inc. thanks The Nice Computer
120 Company of Australia for loaning Dean Elsner to write the
121 first (Vax) version of @code{as} for Project @sc{gnu}.
122 The proprietors, management and staff of TNCCA thank FSF for
123 distracting the boss while they got some work
126 @author Dean Elsner, Jay Fenlason & friends
130 \hfill {\it Using {\tt @value{AS}}}\par
131 \hfill Edited by Cygnus Support\par
133 %"boxit" macro for figures:
134 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
135 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
136 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
137 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
138 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
141 @vskip 0pt plus 1filll
142 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
144 Permission is granted to copy, distribute and/or modify this document
145 under the terms of the GNU Free Documentation License, Version 1.1
146 or any later version published by the Free Software Foundation;
147 with no Invariant Sections, with no Front-Cover Texts, and with no
148 Back-Cover Texts. A copy of the license is included in the
149 section entitled "GNU Free Documentation License".
155 @top Using @value{AS}
157 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}} version
160 This version of the file describes @code{@value{AS}} configured to generate
161 code for @value{TARGET} architectures.
164 This document is distributed under the terms of the GNU Free
165 Documentation License. A copy of the license is included in the
166 section entitled "GNU Free Documentation License".
169 * Overview:: Overview
170 * Invoking:: Command-Line Options
172 * Sections:: Sections and Relocation
174 * Expressions:: Expressions
175 * Pseudo Ops:: Assembler Directives
176 * Machine Dependencies:: Machine Dependent Features
177 * Reporting Bugs:: Reporting Bugs
178 * Acknowledgements:: Who Did What
179 * GNU Free Documentation License:: GNU Free Documentation License
187 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
189 This version of the manual describes @code{@value{AS}} configured to generate
190 code for @value{TARGET} architectures.
194 @cindex invocation summary
195 @cindex option summary
196 @cindex summary of options
197 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
198 @pxref{Invoking,,Comand-Line Options}.
200 @c We don't use deffn and friends for the following because they seem
201 @c to be limited to one line for the header.
203 @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
204 [ -f ] [ --gstabs ] [ --gdwarf2 ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
205 [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ]
206 [ -version ] [ --version ] [ -W ] [ --warn ] [ --fatal-warnings ]
207 [ -w ] [ -x ] [ -Z ] [ --target-help ]
209 @c am29k has no machine-dependent assembler options
216 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]60 |
217 -m[arm]600 | -m[arm]610 | -m[arm]620 | -m[arm]7[t][[d]m[i]][fe] | -m[arm]70 |
218 -m[arm]700 | -m[arm]710[c] | -m[arm]7100 | -m[arm]7500 | -m[arm]8 |
219 -m[arm]810 | -m[arm]9 | -m[arm]920 | -m[arm]920t | -m[arm]9tdmi |
220 -mstrongarm | -mstrongarm110 | -mstrongarm1100 ]
221 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t |
222 -m[arm]v5 | -[arm]v5t | -[arm]v5te ]
224 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
226 [ -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant ]
227 [ -mthumb-interwork ]
238 @c Hitachi family chips have no machine-dependent assembler options
241 @c HPPA has no machine-dependent assembler options (yet).
247 @c The order here is important. See c-sparc.texi.
248 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
249 -Av8plus | -Av8plusa | -Av9 | -Av9a ]
250 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
253 [ -mcpu=54[123589] | -mcpu=54[56]lp ] [ -mfar-mode | -mf ]
254 [ -merrors-to-file <filename> | -me <filename> ]
257 @c Z8000 has no machine-dependent assembler options
260 @c see md_parse_option in tc-i960.c
261 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
265 [ --m32rx | --[no-]warn-explicit-parallel-conflicts | --W[n]p ]
268 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
271 [ -jsri2bsr ] [ -sifilter ] [ -relax ]
275 [ -m68hc11 | -m68hc12 ]
276 [ --force-long-branchs ] [ --short-branchs ] [ --strict-direct-mode ]
277 [ --print-insn-syntax ] [ --print-opcodes ] [ --generate-example ]
280 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
281 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -mips4 ] [ -mips5 ]
282 [ -mips32 ] [ -mips64 ]
283 [ -m4650 ] [ -no-m4650 ]
284 [ --trap ] [ --break ]
285 [ --emulation=@var{name} ]
287 [ -- | @var{files} @dots{} ]
292 Turn on listings, in any of a variety of ways:
296 omit false conditionals
299 omit debugging directives
302 include high-level source
308 include macro expansions
311 omit forms processing
317 set the name of the listing file
320 You may combine these options; for example, use @samp{-aln} for assembly
321 listing without forms processing. The @samp{=file} option, if used, must be
322 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
325 Ignored. This option is accepted for script compatibility with calls to
328 @item --defsym @var{sym}=@var{value}
329 Define the symbol @var{sym} to be @var{value} before assembling the input file.
330 @var{value} must be an integer constant. As in C, a leading @samp{0x}
331 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
334 ``fast''---skip whitespace and comment preprocessing (assume source is
338 Generate stabs debugging information for each assembler line. This
339 may help debugging assembler code, if the debugger can handle it.
342 Generate DWARF2 debugging information for each assembler line. This
343 may help debugging assembler code, if the debugger can handle it. Note - this
344 option is only supported by some targets, not all of them.
347 Print a summary of the command line options and exit.
350 Print a summary of all target specific options and exit.
353 Add directory @var{dir} to the search list for @code{.include} directives.
356 Don't warn about signed overflow.
359 @ifclear DIFF-TBL-KLUGE
360 This option is accepted but has no effect on the @value{TARGET} family.
362 @ifset DIFF-TBL-KLUGE
363 Issue warnings when difference tables altered for long displacements.
368 Keep (in the symbol table) local symbols. On traditional a.out systems
369 these start with @samp{L}, but different systems have different local
372 @item -o @var{objfile}
373 Name the object-file output from @code{@value{AS}} @var{objfile}.
376 Fold the data section into the text section.
379 Print the maximum space (in bytes) and total time (in seconds) used by
382 @item --strip-local-absolute
383 Remove local absolute symbols from the outgoing symbol table.
387 Print the @code{as} version.
390 Print the @code{as} version and exit.
394 Suppress warning messages.
396 @item --fatal-warnings
397 Treat warnings as errors.
400 Don't suppress warning messages or treat them as errors.
409 Generate an object file even after errors.
411 @item -- | @var{files} @dots{}
412 Standard input, or source files to assemble.
417 The following options are available when @value{AS} is configured for
422 This option selects the core processor variant.
424 Select either big-endian (-EB) or little-endian (-EL) output.
429 The following options are available when @value{AS} is configured for the ARM
433 @item -m[arm][1|2|3|6|7|8|9][...]
434 Specify which ARM processor variant is the target.
435 @item -m[arm]v[2|2a|3|3m|4|4t|5|5t]
436 Specify which ARM architecture variant is used by the target.
437 @item -mthumb | -mall
438 Enable or disable Thumb only instruction decoding.
439 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
440 Select which Floating Point architecture is the target.
441 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
442 Select which procedure calling convention is in use.
444 Select either big-endian (-EB) or little-endian (-EL) output.
445 @item -mthumb-interwork
446 Specify that the code has been generated with interworking between Thumb and
449 Specify that PIC code has been generated.
454 The following options are available when @value{AS} is configured for
457 @cindex D10V optimization
458 @cindex optimization, D10V
460 Optimize output by parallelizing instructions.
465 The following options are available when @value{AS} is configured for a D30V
468 @cindex D30V optimization
469 @cindex optimization, D30V
471 Optimize output by parallelizing instructions.
475 Warn when nops are generated.
477 @cindex D30V nops after 32-bit multiply
479 Warn when a nop after a 32-bit multiply instruction is generated.
484 The following options are available when @value{AS} is configured for the
485 Intel 80960 processor.
488 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
489 Specify which variant of the 960 architecture is the target.
492 Add code to collect statistics about branches taken.
495 Do not alter compare-and-branch instructions for long displacements;
502 The following options are available when @value{AS} is configured for the
503 Mitsubishi M32R series.
508 Specify which processor in the M32R family is the target. The default
509 is normally the M32R, but this option changes it to the M32RX.
511 @item --warn-explicit-parallel-conflicts or --Wp
512 Produce warning messages when questionable parallel constructs are
515 @item --no-warn-explicit-parallel-conflicts or --Wnp
516 Do not produce warning messages when questionable parallel constructs are
523 The following options are available when @value{AS} is configured for the
524 Motorola 68000 series.
529 Shorten references to undefined symbols, to one word instead of two.
531 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
532 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
533 Specify what processor in the 68000 family is the target. The default
534 is normally the 68020, but this can be changed at configuration time.
536 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
537 The target machine does (or does not) have a floating-point coprocessor.
538 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
539 the basic 68000 is not compatible with the 68881, a combination of the
540 two can be specified, since it's possible to do emulation of the
541 coprocessor instructions with the main processor.
543 @item -m68851 | -mno-68851
544 The target machine does (or does not) have a memory-management
545 unit coprocessor. The default is to assume an MMU for 68020 and up.
552 For details about the PDP-11 machine dependent features options,
553 see @ref{PDP-11-Options}.
556 @item -mpic | -mno-pic
557 Generate position-independent (or position-dependent) code. The
558 default is @code{-mpic}.
561 @itemx -mall-extensions
562 Enable all instruction set extensions. This is the default.
564 @item -mno-extensions
565 Disable all instruction set extensions.
567 @item -m@var{extension} | -mno-@var{extension}
568 Enable (or disable) a particular instruction set extension.
571 Enable the instruction set extensions supported by a particular CPU, and
572 disable all other extensions.
574 @item -m@var{machine}
575 Enable the instruction set extensions supported by a particular machine
576 model, and disable all other extensions.
582 The following options are available when @value{AS} is configured for
583 a picoJava processor.
587 @cindex PJ endianness
588 @cindex endianness, PJ
589 @cindex big endian output, PJ
591 Generate ``big endian'' format output.
593 @cindex little endian output, PJ
595 Generate ``little endian'' format output.
601 The following options are available when @value{AS} is configured for the
602 Motorola 68HC11 or 68HC12 series.
606 @item -m68hc11 | -m68hc12
607 Specify what processor is the target. The default is
608 defined by the configuration option when building the assembler.
610 @item --force-long-branchs
611 Relative branches are turned into absolute ones. This concerns
612 conditional branches, unconditional branches and branches to a
615 @item -S | --short-branchs
616 Do not turn relative branchs into absolute ones
617 when the offset is out of range.
619 @item --strict-direct-mode
620 Do not turn the direct addressing mode into extended addressing mode
621 when the instruction does not support direct addressing mode.
623 @item --print-insn-syntax
624 Print the syntax of instruction in case of error.
626 @item --print-opcodes
627 print the list of instructions with syntax and then exit.
629 @item --generate-example
630 print an example of instruction for each possible instruction and then exit.
631 This option is only useful for testing @code{@value{AS}}.
637 The following options are available when @code{@value{AS}} is configured
638 for the SPARC architecture:
641 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
642 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
643 Explicitly select a variant of the SPARC architecture.
645 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
646 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
648 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
649 UltraSPARC extensions.
651 @item -xarch=v8plus | -xarch=v8plusa
652 For compatibility with the Solaris v9 assembler. These options are
653 equivalent to -Av8plus and -Av8plusa, respectively.
656 Warn when the assembler switches to another architecture.
661 The following options are available when @value{AS} is configured for the 'c54x
666 Enable extended addressing mode. All addresses and relocations will assume
667 extended addressing (usually 23 bits).
668 @item -mcpu=@var{CPU_VERSION}
669 Sets the CPU version being compiled for.
670 @item -merrors-to-file @var{FILENAME}
671 Redirect error output to a file, for broken systems which don't support such
672 behaviour in the shell.
677 The following options are available when @value{AS} is configured for
682 This option sets the largest size of an object that can be referenced
683 implicitly with the @code{gp} register. It is only accepted for targets that
684 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
686 @cindex MIPS endianness
687 @cindex endianness, MIPS
688 @cindex big endian output, MIPS
690 Generate ``big endian'' format output.
692 @cindex little endian output, MIPS
694 Generate ``little endian'' format output.
702 Generate code for a particular MIPS Instruction Set Architecture level.
703 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
704 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
706 @samp{-mips5}, @samp{-mips32}, and @samp{-mips64} correspond
707 to generic @sc{MIPS V}, @sc{MIPS32}, and @sc{MIPS64} ISA
708 processors, respectively.
712 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
713 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
714 instructions around accesses to the @samp{HI} and @samp{LO} registers.
715 @samp{-no-m4650} turns off this option.
717 @item -mcpu=@var{CPU}
718 Generate code for a particular MIPS cpu. It is exactly equivalent to
719 @samp{-m@var{cpu}}, except that there are more value of @var{cpu}
723 @item --emulation=@var{name}
724 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
725 for some other target, in all respects, including output format (choosing
726 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
727 debugging information or store symbol table information, and default
728 endianness. The available configuration names are: @samp{mipsecoff},
729 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
730 @samp{mipsbelf}. The first two do not alter the default endianness from that
731 of the primary target for which the assembler was configured; the others change
732 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
733 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
734 selection in any case.
736 This option is currently supported only when the primary target
737 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
738 Furthermore, the primary target or others specified with
739 @samp{--enable-targets=@dots{}} at configuration time must include support for
740 the other format, if both are to be available. For example, the Irix 5
741 configuration includes support for both.
743 Eventually, this option will support more configurations, with more
744 fine-grained control over the assembler's behavior, and will be supported for
748 @code{@value{AS}} ignores this option. It is accepted for compatibility with
756 Control how to deal with multiplication overflow and division by zero.
757 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
758 (and only work for Instruction Set Architecture level 2 and higher);
759 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
765 The following options are available when @value{AS} is configured for
771 Enable or disable the JSRI to BSR transformation. By default this is enabled.
772 The command line option @samp{-nojsri2bsr} can be used to disable it.
776 Enable or disable the silicon filter behaviour. By default this is disabled.
777 The default can be overridden by the @samp{-sifilter} command line option.
780 Alter jump instructions for long displacements.
782 @item -mcpu=[210|340]
783 Select the cpu type on the target hardware. This controls which instructions
787 Assemble for a big endian target.
790 Assemble for a little endian target.
796 * Manual:: Structure of this Manual
797 * GNU Assembler:: The GNU Assembler
798 * Object Formats:: Object File Formats
799 * Command Line:: Command Line
800 * Input Files:: Input Files
801 * Object:: Output (Object) File
802 * Errors:: Error and Warning Messages
806 @section Structure of this Manual
808 @cindex manual, structure and purpose
809 This manual is intended to describe what you need to know to use
810 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
811 notation for symbols, constants, and expressions; the directives that
812 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
815 We also cover special features in the @value{TARGET}
816 configuration of @code{@value{AS}}, including assembler directives.
819 This manual also describes some of the machine-dependent features of
820 various flavors of the assembler.
823 @cindex machine instructions (not covered)
824 On the other hand, this manual is @emph{not} intended as an introduction
825 to programming in assembly language---let alone programming in general!
826 In a similar vein, we make no attempt to introduce the machine
827 architecture; we do @emph{not} describe the instruction set, standard
828 mnemonics, registers or addressing modes that are standard to a
829 particular architecture.
831 You may want to consult the manufacturer's
832 machine architecture manual for this information.
836 For information on the H8/300 machine instruction set, see @cite{H8/300
837 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
838 see @cite{H8/300H Series Programming Manual} (Hitachi).
841 For information on the H8/500 machine instruction set, see @cite{H8/500
842 Series Programming Manual} (Hitachi M21T001).
845 For information on the Hitachi SH machine instruction set, see
846 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
849 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
853 @c I think this is premature---doc@cygnus.com, 17jan1991
855 Throughout this manual, we assume that you are running @dfn{GNU},
856 the portable operating system from the @dfn{Free Software
857 Foundation, Inc.}. This restricts our attention to certain kinds of
858 computer (in particular, the kinds of computers that @sc{gnu} can run on);
859 once this assumption is granted examples and definitions need less
862 @code{@value{AS}} is part of a team of programs that turn a high-level
863 human-readable series of instructions into a low-level
864 computer-readable series of instructions. Different versions of
865 @code{@value{AS}} are used for different kinds of computer.
868 @c There used to be a section "Terminology" here, which defined
869 @c "contents", "byte", "word", and "long". Defining "word" to any
870 @c particular size is confusing when the .word directive may generate 16
871 @c bits on one machine and 32 bits on another; in general, for the user
872 @c version of this manual, none of these terms seem essential to define.
873 @c They were used very little even in the former draft of the manual;
874 @c this draft makes an effort to avoid them (except in names of
878 @section The GNU Assembler
880 @sc{gnu} @code{as} is really a family of assemblers.
882 This manual describes @code{@value{AS}}, a member of that family which is
883 configured for the @value{TARGET} architectures.
885 If you use (or have used) the @sc{gnu} assembler on one architecture, you
886 should find a fairly similar environment when you use it on another
887 architecture. Each version has much in common with the others,
888 including object file formats, most assembler directives (often called
889 @dfn{pseudo-ops}) and assembler syntax.@refill
891 @cindex purpose of @sc{gnu} assembler
892 @code{@value{AS}} is primarily intended to assemble the output of the
893 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
894 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
895 assemble correctly everything that other assemblers for the same
896 machine would assemble.
898 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
901 @c This remark should appear in generic version of manual; assumption
902 @c here is that generic version sets M680x0.
903 This doesn't mean @code{@value{AS}} always uses the same syntax as another
904 assembler for the same architecture; for example, we know of several
905 incompatible versions of 680x0 assembly language syntax.
908 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
909 program in one pass of the source file. This has a subtle impact on the
910 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
913 @section Object File Formats
915 @cindex object file format
916 The @sc{gnu} assembler can be configured to produce several alternative
917 object file formats. For the most part, this does not affect how you
918 write assembly language programs; but directives for debugging symbols
919 are typically different in different file formats. @xref{Symbol
920 Attributes,,Symbol Attributes}.
923 On the @value{TARGET}, @code{@value{AS}} is configured to produce
924 @value{OBJ-NAME} format object files.
926 @c The following should exhaust all configs that set MULTI-OBJ, ideally
928 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
929 @code{a.out} or COFF format object files.
932 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
933 @code{b.out} or COFF format object files.
936 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
937 SOM or ELF format object files.
942 @section Command Line
944 @cindex command line conventions
945 After the program name @code{@value{AS}}, the command line may contain
946 options and file names. Options may appear in any order, and may be
947 before, after, or between file names. The order of file names is
950 @cindex standard input, as input file
952 @file{--} (two hyphens) by itself names the standard input file
953 explicitly, as one of the files for @code{@value{AS}} to assemble.
955 @cindex options, command line
956 Except for @samp{--} any command line argument that begins with a
957 hyphen (@samp{-}) is an option. Each option changes the behavior of
958 @code{@value{AS}}. No option changes the way another option works. An
959 option is a @samp{-} followed by one or more letters; the case of
960 the letter is important. All options are optional.
962 Some options expect exactly one file name to follow them. The file
963 name may either immediately follow the option's letter (compatible
964 with older assemblers) or it may be the next command argument (@sc{gnu}
965 standard). These two command lines are equivalent:
968 @value{AS} -o my-object-file.o mumble.s
969 @value{AS} -omy-object-file.o mumble.s
976 @cindex source program
978 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
979 describe the program input to one run of @code{@value{AS}}. The program may
980 be in one or more files; how the source is partitioned into files
981 doesn't change the meaning of the source.
983 @c I added "con" prefix to "catenation" just to prove I can overcome my
984 @c APL training... doc@cygnus.com
985 The source program is a concatenation of the text in all the files, in the
988 Each time you run @code{@value{AS}} it assembles exactly one source
989 program. The source program is made up of one or more files.
990 (The standard input is also a file.)
992 You give @code{@value{AS}} a command line that has zero or more input file
993 names. The input files are read (from left file name to right). A
994 command line argument (in any position) that has no special meaning
995 is taken to be an input file name.
997 If you give @code{@value{AS}} no file names it attempts to read one input file
998 from the @code{@value{AS}} standard input, which is normally your terminal. You
999 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
1002 Use @samp{--} if you need to explicitly name the standard input file
1003 in your command line.
1005 If the source is empty, @code{@value{AS}} produces a small, empty object
1008 @subheading Filenames and Line-numbers
1010 @cindex input file linenumbers
1011 @cindex line numbers, in input files
1012 There are two ways of locating a line in the input file (or files) and
1013 either may be used in reporting error messages. One way refers to a line
1014 number in a physical file; the other refers to a line number in a
1015 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1017 @dfn{Physical files} are those files named in the command line given
1018 to @code{@value{AS}}.
1020 @dfn{Logical files} are simply names declared explicitly by assembler
1021 directives; they bear no relation to physical files. Logical file names help
1022 error messages reflect the original source file, when @code{@value{AS}} source
1023 is itself synthesized from other files. @code{@value{AS}} understands the
1024 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1025 @ref{File,,@code{.file}}.
1028 @section Output (Object) File
1034 Every time you run @code{@value{AS}} it produces an output file, which is
1035 your assembly language program translated into numbers. This file
1036 is the object file. Its default name is
1044 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
1046 You can give it another name by using the @code{-o} option. Conventionally,
1047 object file names end with @file{.o}. The default name is used for historical
1048 reasons: older assemblers were capable of assembling self-contained programs
1049 directly into a runnable program. (For some formats, this isn't currently
1050 possible, but it can be done for the @code{a.out} format.)
1054 The object file is meant for input to the linker @code{@value{LD}}. It contains
1055 assembled program code, information to help @code{@value{LD}} integrate
1056 the assembled program into a runnable file, and (optionally) symbolic
1057 information for the debugger.
1059 @c link above to some info file(s) like the description of a.out.
1060 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1063 @section Error and Warning Messages
1065 @cindex error messages
1066 @cindex warning messages
1067 @cindex messages from assembler
1068 @code{@value{AS}} may write warnings and error messages to the standard error
1069 file (usually your terminal). This should not happen when a compiler
1070 runs @code{@value{AS}} automatically. Warnings report an assumption made so
1071 that @code{@value{AS}} could keep assembling a flawed program; errors report a
1072 grave problem that stops the assembly.
1074 @cindex format of warning messages
1075 Warning messages have the format
1078 file_name:@b{NNN}:Warning Message Text
1082 @cindex line numbers, in warnings/errors
1083 (where @b{NNN} is a line number). If a logical file name has been given
1084 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1085 the current input file is used. If a logical line number was given
1087 (@pxref{Line,,@code{.line}})
1091 (@pxref{Line,,@code{.line}})
1094 (@pxref{Ln,,@code{.ln}})
1097 then it is used to calculate the number printed,
1098 otherwise the actual line in the current source file is printed. The
1099 message text is intended to be self explanatory (in the grand Unix
1102 @cindex format of error messages
1103 Error messages have the format
1105 file_name:@b{NNN}:FATAL:Error Message Text
1107 The file name and line number are derived as for warning
1108 messages. The actual message text may be rather less explanatory
1109 because many of them aren't supposed to happen.
1112 @chapter Command-Line Options
1114 @cindex options, all versions of assembler
1115 This chapter describes command-line options available in @emph{all}
1116 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1118 to the @value{TARGET}.
1121 to particular machine architectures.
1124 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
1125 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1126 The assembler arguments must be separated from each other (and the @samp{-Wa})
1127 by commas. For example:
1130 gcc -c -g -O -Wa,-alh,-L file.c
1134 This passes two options to the assembler: @samp{-alh} (emit a listing to
1135 standard output with with high-level and assembly source) and @samp{-L} (retain
1136 local symbols in the symbol table).
1138 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1139 command-line options are automatically passed to the assembler by the compiler.
1140 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1141 precisely what options it passes to each compilation pass, including the
1145 * a:: -a[cdhlns] enable listings
1146 * D:: -D for compatibility
1147 * f:: -f to work faster
1148 * I:: -I for .include search path
1149 @ifclear DIFF-TBL-KLUGE
1150 * K:: -K for compatibility
1152 @ifset DIFF-TBL-KLUGE
1153 * K:: -K for difference tables
1156 * L:: -L to retain local labels
1157 * M:: -M or --mri to assemble in MRI compatibility mode
1158 * MD:: --MD for dependency tracking
1159 * o:: -o to name the object file
1160 * R:: -R to join data and text sections
1161 * statistics:: --statistics to see statistics about assembly
1162 * traditional-format:: --traditional-format for compatible output
1163 * v:: -v to announce version
1164 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1165 * Z:: -Z to make object file even after errors
1169 @section Enable Listings: @code{-a[cdhlns]}
1178 @cindex listings, enabling
1179 @cindex assembly listings, enabling
1181 These options enable listing output from the assembler. By itself,
1182 @samp{-a} requests high-level, assembly, and symbols listing.
1183 You can use other letters to select specific options for the list:
1184 @samp{-ah} requests a high-level language listing,
1185 @samp{-al} requests an output-program assembly listing, and
1186 @samp{-as} requests a symbol table listing.
1187 High-level listings require that a compiler debugging option like
1188 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1191 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1192 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1193 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1194 omitted from the listing.
1196 Use the @samp{-ad} option to omit debugging directives from the
1199 Once you have specified one of these options, you can further control
1200 listing output and its appearance using the directives @code{.list},
1201 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1203 The @samp{-an} option turns off all forms processing.
1204 If you do not request listing output with one of the @samp{-a} options, the
1205 listing-control directives have no effect.
1207 The letters after @samp{-a} may be combined into one option,
1208 @emph{e.g.}, @samp{-aln}.
1214 This option has no effect whatsoever, but it is accepted to make it more
1215 likely that scripts written for other assemblers also work with
1219 @section Work Faster: @code{-f}
1222 @cindex trusted compiler
1223 @cindex faster processing (@code{-f})
1224 @samp{-f} should only be used when assembling programs written by a
1225 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1226 and comment preprocessing on
1227 the input file(s) before assembling them. @xref{Preprocessing,
1231 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1232 preprocessed (if they contain comments, for example), @code{@value{AS}} does
1237 @section @code{.include} search path: @code{-I} @var{path}
1239 @kindex -I @var{path}
1240 @cindex paths for @code{.include}
1241 @cindex search path for @code{.include}
1242 @cindex @code{include} directive search path
1243 Use this option to add a @var{path} to the list of directories
1244 @code{@value{AS}} searches for files specified in @code{.include}
1245 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
1246 many times as necessary to include a variety of paths. The current
1247 working directory is always searched first; after that, @code{@value{AS}}
1248 searches any @samp{-I} directories in the same order as they were
1249 specified (left to right) on the command line.
1252 @section Difference Tables: @code{-K}
1255 @ifclear DIFF-TBL-KLUGE
1256 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1257 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1258 where it can be used to warn when the assembler alters the machine code
1259 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1260 family does not have the addressing limitations that sometimes lead to this
1261 alteration on other platforms.
1264 @ifset DIFF-TBL-KLUGE
1265 @cindex difference tables, warning
1266 @cindex warning for altered difference tables
1267 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1268 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1269 You can use the @samp{-K} option if you want a warning issued when this
1274 @section Include Local Labels: @code{-L}
1277 @cindex local labels, retaining in output
1278 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1279 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1280 debugging, because they are intended for the use of programs (like
1281 compilers) that compose assembler programs, not for your notice.
1282 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1283 normally debug with them.
1285 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1286 in the object file. Usually if you do this you also tell the linker
1287 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1289 By default, a local label is any label beginning with @samp{L}, but each
1290 target is allowed to redefine the local label prefix.
1292 On the HPPA local labels begin with @samp{L$}.
1296 @section Assemble in MRI Compatibility Mode: @code{-M}
1299 @cindex MRI compatibility mode
1300 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1301 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1302 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1303 configured target) assembler from Microtec Research. The exact nature of the
1304 MRI syntax will not be documented here; see the MRI manuals for more
1305 information. Note in particular that the handling of macros and macro
1306 arguments is somewhat different. The purpose of this option is to permit
1307 assembling existing MRI assembler code using @code{@value{AS}}.
1309 The MRI compatibility is not complete. Certain operations of the MRI assembler
1310 depend upon its object file format, and can not be supported using other object
1311 file formats. Supporting these would require enhancing each object file format
1312 individually. These are:
1315 @item global symbols in common section
1317 The m68k MRI assembler supports common sections which are merged by the linker.
1318 Other object file formats do not support this. @code{@value{AS}} handles
1319 common sections by treating them as a single common symbol. It permits local
1320 symbols to be defined within a common section, but it can not support global
1321 symbols, since it has no way to describe them.
1323 @item complex relocations
1325 The MRI assemblers support relocations against a negated section address, and
1326 relocations which combine the start addresses of two or more sections. These
1327 are not support by other object file formats.
1329 @item @code{END} pseudo-op specifying start address
1331 The MRI @code{END} pseudo-op permits the specification of a start address.
1332 This is not supported by other object file formats. The start address may
1333 instead be specified using the @code{-e} option to the linker, or in a linker
1336 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1338 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1339 name to the output file. This is not supported by other object file formats.
1341 @item @code{ORG} pseudo-op
1343 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1344 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1345 which changes the location within the current section. Absolute sections are
1346 not supported by other object file formats. The address of a section may be
1347 assigned within a linker script.
1350 There are some other features of the MRI assembler which are not supported by
1351 @code{@value{AS}}, typically either because they are difficult or because they
1352 seem of little consequence. Some of these may be supported in future releases.
1356 @item EBCDIC strings
1358 EBCDIC strings are not supported.
1360 @item packed binary coded decimal
1362 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1363 and @code{DCB.P} pseudo-ops are not supported.
1365 @item @code{FEQU} pseudo-op
1367 The m68k @code{FEQU} pseudo-op is not supported.
1369 @item @code{NOOBJ} pseudo-op
1371 The m68k @code{NOOBJ} pseudo-op is not supported.
1373 @item @code{OPT} branch control options
1375 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1376 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1377 relaxes all branches, whether forward or backward, to an appropriate size, so
1378 these options serve no purpose.
1380 @item @code{OPT} list control options
1382 The following m68k @code{OPT} list control options are ignored: @code{C},
1383 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1384 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1386 @item other @code{OPT} options
1388 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1389 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1391 @item @code{OPT} @code{D} option is default
1393 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1394 @code{OPT NOD} may be used to turn it off.
1396 @item @code{XREF} pseudo-op.
1398 The m68k @code{XREF} pseudo-op is ignored.
1400 @item @code{.debug} pseudo-op
1402 The i960 @code{.debug} pseudo-op is not supported.
1404 @item @code{.extended} pseudo-op
1406 The i960 @code{.extended} pseudo-op is not supported.
1408 @item @code{.list} pseudo-op.
1410 The various options of the i960 @code{.list} pseudo-op are not supported.
1412 @item @code{.optimize} pseudo-op
1414 The i960 @code{.optimize} pseudo-op is not supported.
1416 @item @code{.output} pseudo-op
1418 The i960 @code{.output} pseudo-op is not supported.
1420 @item @code{.setreal} pseudo-op
1422 The i960 @code{.setreal} pseudo-op is not supported.
1427 @section Dependency tracking: @code{--MD}
1430 @cindex dependency tracking
1433 @code{@value{AS}} can generate a dependency file for the file it creates. This
1434 file consists of a single rule suitable for @code{make} describing the
1435 dependencies of the main source file.
1437 The rule is written to the file named in its argument.
1439 This feature is used in the automatic updating of makefiles.
1442 @section Name the Object File: @code{-o}
1445 @cindex naming object file
1446 @cindex object file name
1447 There is always one object file output when you run @code{@value{AS}}. By
1448 default it has the name
1451 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1465 You use this option (which takes exactly one filename) to give the
1466 object file a different name.
1468 Whatever the object file is called, @code{@value{AS}} overwrites any
1469 existing file of the same name.
1472 @section Join Data and Text Sections: @code{-R}
1475 @cindex data and text sections, joining
1476 @cindex text and data sections, joining
1477 @cindex joining text and data sections
1478 @cindex merging text and data sections
1479 @code{-R} tells @code{@value{AS}} to write the object file as if all
1480 data-section data lives in the text section. This is only done at
1481 the very last moment: your binary data are the same, but data
1482 section parts are relocated differently. The data section part of
1483 your object file is zero bytes long because all its bytes are
1484 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1486 When you specify @code{-R} it would be possible to generate shorter
1487 address displacements (because we do not have to cross between text and
1488 data section). We refrain from doing this simply for compatibility with
1489 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1492 When @code{@value{AS}} is configured for COFF output,
1493 this option is only useful if you use sections named @samp{.text} and
1498 @code{-R} is not supported for any of the HPPA targets. Using
1499 @code{-R} generates a warning from @code{@value{AS}}.
1503 @section Display Assembly Statistics: @code{--statistics}
1505 @kindex --statistics
1506 @cindex statistics, about assembly
1507 @cindex time, total for assembly
1508 @cindex space used, maximum for assembly
1509 Use @samp{--statistics} to display two statistics about the resources used by
1510 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1511 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1514 @node traditional-format
1515 @section Compatible output: @code{--traditional-format}
1517 @kindex --traditional-format
1518 For some targets, the output of @code{@value{AS}} is different in some ways
1519 from the output of some existing assembler. This switch requests
1520 @code{@value{AS}} to use the traditional format instead.
1522 For example, it disables the exception frame optimizations which
1523 @code{@value{AS}} normally does by default on @code{@value{GCC}} output.
1526 @section Announce Version: @code{-v}
1530 @cindex assembler version
1531 @cindex version of assembler
1532 You can find out what version of as is running by including the
1533 option @samp{-v} (which you can also spell as @samp{-version}) on the
1537 @section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings}
1539 @code{@value{AS}} should never give a warning or error message when
1540 assembling compiler output. But programs written by people often
1541 cause @code{@value{AS}} to give a warning that a particular assumption was
1542 made. All such warnings are directed to the standard error file.
1545 @kindex @samp{--no-warn}
1546 @cindex suppressing warnings
1547 @cindex warnings, suppressing
1548 If you use the @code{-W} and @code{--no-warn} options, no warnings are issued.
1549 This only affects the warning messages: it does not change any particular of
1550 how @code{@value{AS}} assembles your file. Errors, which stop the assembly,
1553 @kindex @samp{--fatal-warnings}
1554 @cindex errors, caused by warnings
1555 @cindex warnings, causing error
1556 If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers
1557 files that generate warnings to be in error.
1559 @kindex @samp{--warn}
1560 @cindex warnings, switching on
1561 You can switch these options off again by specifying @code{--warn}, which
1562 causes warnings to be output as usual.
1565 @section Generate Object File in Spite of Errors: @code{-Z}
1566 @cindex object file, after errors
1567 @cindex errors, continuing after
1568 After an error message, @code{@value{AS}} normally produces no output. If for
1569 some reason you are interested in object file output even after
1570 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1571 option. If there are any errors, @code{@value{AS}} continues anyways, and
1572 writes an object file after a final warning message of the form @samp{@var{n}
1573 errors, @var{m} warnings, generating bad object file.}
1578 @cindex machine-independent syntax
1579 @cindex syntax, machine-independent
1580 This chapter describes the machine-independent syntax allowed in a
1581 source file. @code{@value{AS}} syntax is similar to what many other
1582 assemblers use; it is inspired by the BSD 4.2
1587 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1591 * Preprocessing:: Preprocessing
1592 * Whitespace:: Whitespace
1593 * Comments:: Comments
1594 * Symbol Intro:: Symbols
1595 * Statements:: Statements
1596 * Constants:: Constants
1600 @section Preprocessing
1602 @cindex preprocessing
1603 The @code{@value{AS}} internal preprocessor:
1605 @cindex whitespace, removed by preprocessor
1607 adjusts and removes extra whitespace. It leaves one space or tab before
1608 the keywords on a line, and turns any other whitespace on the line into
1611 @cindex comments, removed by preprocessor
1613 removes all comments, replacing them with a single space, or an
1614 appropriate number of newlines.
1616 @cindex constants, converted by preprocessor
1618 converts character constants into the appropriate numeric values.
1621 It does not do macro processing, include file handling, or
1622 anything else you may get from your C compiler's preprocessor. You can
1623 do include file processing with the @code{.include} directive
1624 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1625 to get other ``CPP'' style preprocessing, by giving the input file a
1626 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1627 Output, gcc.info, Using GNU CC}.
1629 Excess whitespace, comments, and character constants
1630 cannot be used in the portions of the input text that are not
1633 @cindex turning preprocessing on and off
1634 @cindex preprocessing, turning on and off
1637 If the first line of an input file is @code{#NO_APP} or if you use the
1638 @samp{-f} option, whitespace and comments are not removed from the input file.
1639 Within an input file, you can ask for whitespace and comment removal in
1640 specific portions of the by putting a line that says @code{#APP} before the
1641 text that may contain whitespace or comments, and putting a line that says
1642 @code{#NO_APP} after this text. This feature is mainly intend to support
1643 @code{asm} statements in compilers whose output is otherwise free of comments
1650 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1651 Whitespace is used to separate symbols, and to make programs neater for
1652 people to read. Unless within character constants
1653 (@pxref{Characters,,Character Constants}), any whitespace means the same
1654 as exactly one space.
1660 There are two ways of rendering comments to @code{@value{AS}}. In both
1661 cases the comment is equivalent to one space.
1663 Anything from @samp{/*} through the next @samp{*/} is a comment.
1664 This means you may not nest these comments.
1668 The only way to include a newline ('\n') in a comment
1669 is to use this sort of comment.
1672 /* This sort of comment does not nest. */
1675 @cindex line comment character
1676 Anything from the @dfn{line comment} character to the next newline
1677 is considered a comment and is ignored. The line comment character is
1679 @samp{;} for the AMD 29K family;
1682 @samp{;} on the ARC;
1685 @samp{@@} on the ARM;
1688 @samp{;} for the H8/300 family;
1691 @samp{!} for the H8/500 family;
1694 @samp{;} for the HPPA;
1697 @samp{#} on the i386 and x86-64;
1700 @samp{#} on the i960;
1703 @samp{;} for the PDP-11;
1706 @samp{;} for picoJava;
1709 @samp{!} for the Hitachi SH;
1712 @samp{!} on the SPARC;
1715 @samp{#} on the m32r;
1718 @samp{|} on the 680x0;
1721 @samp{#} on the 68HC11 and 68HC12;
1724 @samp{#} on the Vax;
1727 @samp{!} for the Z8000;
1730 @samp{#} on the V850;
1732 see @ref{Machine Dependencies}. @refill
1733 @c FIXME What about m88k, i860?
1736 On some machines there are two different line comment characters. One
1737 character only begins a comment if it is the first non-whitespace character on
1738 a line, while the other always begins a comment.
1742 The V850 assembler also supports a double dash as starting a comment that
1743 extends to the end of the line.
1749 @cindex lines starting with @code{#}
1750 @cindex logical line numbers
1751 To be compatible with past assemblers, lines that begin with @samp{#} have a
1752 special interpretation. Following the @samp{#} should be an absolute
1753 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1754 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1755 new logical file name. The rest of the line, if any, should be whitespace.
1757 If the first non-whitespace characters on the line are not numeric,
1758 the line is ignored. (Just like a comment.)
1761 # This is an ordinary comment.
1762 # 42-6 "new_file_name" # New logical file name
1763 # This is logical line # 36.
1765 This feature is deprecated, and may disappear from future versions
1766 of @code{@value{AS}}.
1771 @cindex characters used in symbols
1772 @ifclear SPECIAL-SYMS
1773 A @dfn{symbol} is one or more characters chosen from the set of all
1774 letters (both upper and lower case), digits and the three characters
1780 A @dfn{symbol} is one or more characters chosen from the set of all
1781 letters (both upper and lower case), digits and the three characters
1782 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1788 On most machines, you can also use @code{$} in symbol names; exceptions
1789 are noted in @ref{Machine Dependencies}.
1791 No symbol may begin with a digit. Case is significant.
1792 There is no length limit: all characters are significant. Symbols are
1793 delimited by characters not in that set, or by the beginning of a file
1794 (since the source program must end with a newline, the end of a file is
1795 not a possible symbol delimiter). @xref{Symbols}.
1796 @cindex length of symbols
1801 @cindex statements, structure of
1802 @cindex line separator character
1803 @cindex statement separator character
1805 @ifclear abnormal-separator
1806 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1807 semicolon (@samp{;}). The newline or semicolon is considered part of
1808 the preceding statement. Newlines and semicolons within character
1809 constants are an exception: they do not end statements.
1811 @ifset abnormal-separator
1813 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1814 sign (@samp{@@}). The newline or at sign is considered part of the
1815 preceding statement. Newlines and at signs within character constants
1816 are an exception: they do not end statements.
1819 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1820 point (@samp{!}). The newline or exclamation point is considered part of the
1821 preceding statement. Newlines and exclamation points within character
1822 constants are an exception: they do not end statements.
1825 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1826 H8/300) a dollar sign (@samp{$}); or (for the
1829 (@samp{;}). The newline or separator character is considered part of
1830 the preceding statement. Newlines and separators within character
1831 constants are an exception: they do not end statements.
1836 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1837 separator character. (The line separator is usually @samp{;}, unless
1838 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1839 newline or separator character is considered part of the preceding
1840 statement. Newlines and separators within character constants are an
1841 exception: they do not end statements.
1844 @cindex newline, required at file end
1845 @cindex EOF, newline must precede
1846 It is an error to end any statement with end-of-file: the last
1847 character of any input file should be a newline.@refill
1849 An empty statement is allowed, and may include whitespace. It is ignored.
1851 @cindex instructions and directives
1852 @cindex directives and instructions
1853 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1854 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1856 A statement begins with zero or more labels, optionally followed by a
1857 key symbol which determines what kind of statement it is. The key
1858 symbol determines the syntax of the rest of the statement. If the
1859 symbol begins with a dot @samp{.} then the statement is an assembler
1860 directive: typically valid for any computer. If the symbol begins with
1861 a letter the statement is an assembly language @dfn{instruction}: it
1862 assembles into a machine language instruction.
1864 Different versions of @code{@value{AS}} for different computers
1865 recognize different instructions. In fact, the same symbol may
1866 represent a different instruction in a different computer's assembly
1870 @cindex @code{:} (label)
1871 @cindex label (@code{:})
1872 A label is a symbol immediately followed by a colon (@code{:}).
1873 Whitespace before a label or after a colon is permitted, but you may not
1874 have whitespace between a label's symbol and its colon. @xref{Labels}.
1877 For HPPA targets, labels need not be immediately followed by a colon, but
1878 the definition of a label must begin in column zero. This also implies that
1879 only one label may be defined on each line.
1883 label: .directive followed by something
1884 another_label: # This is an empty statement.
1885 instruction operand_1, operand_2, @dots{}
1892 A constant is a number, written so that its value is known by
1893 inspection, without knowing any context. Like this:
1896 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1897 .ascii "Ring the bell\7" # A string constant.
1898 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1899 .float 0f-314159265358979323846264338327\
1900 95028841971.693993751E-40 # - pi, a flonum.
1905 * Characters:: Character Constants
1906 * Numbers:: Number Constants
1910 @subsection Character Constants
1912 @cindex character constants
1913 @cindex constants, character
1914 There are two kinds of character constants. A @dfn{character} stands
1915 for one character in one byte and its value may be used in
1916 numeric expressions. String constants (properly called string
1917 @emph{literals}) are potentially many bytes and their values may not be
1918 used in arithmetic expressions.
1922 * Chars:: Characters
1926 @subsubsection Strings
1928 @cindex string constants
1929 @cindex constants, string
1930 A @dfn{string} is written between double-quotes. It may contain
1931 double-quotes or null characters. The way to get special characters
1932 into a string is to @dfn{escape} these characters: precede them with
1933 a backslash @samp{\} character. For example @samp{\\} represents
1934 one backslash: the first @code{\} is an escape which tells
1935 @code{@value{AS}} to interpret the second character literally as a backslash
1936 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1937 escape character). The complete list of escapes follows.
1939 @cindex escape codes, character
1940 @cindex character escape codes
1943 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1945 @cindex @code{\b} (backspace character)
1946 @cindex backspace (@code{\b})
1948 Mnemonic for backspace; for ASCII this is octal code 010.
1951 @c Mnemonic for EOText; for ASCII this is octal code 004.
1953 @cindex @code{\f} (formfeed character)
1954 @cindex formfeed (@code{\f})
1956 Mnemonic for FormFeed; for ASCII this is octal code 014.
1958 @cindex @code{\n} (newline character)
1959 @cindex newline (@code{\n})
1961 Mnemonic for newline; for ASCII this is octal code 012.
1964 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1966 @cindex @code{\r} (carriage return character)
1967 @cindex carriage return (@code{\r})
1969 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1972 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1973 @c other assemblers.
1975 @cindex @code{\t} (tab)
1976 @cindex tab (@code{\t})
1978 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1981 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1982 @c @item \x @var{digit} @var{digit} @var{digit}
1983 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1985 @cindex @code{\@var{ddd}} (octal character code)
1986 @cindex octal character code (@code{\@var{ddd}})
1987 @item \ @var{digit} @var{digit} @var{digit}
1988 An octal character code. The numeric code is 3 octal digits.
1989 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1990 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1992 @cindex @code{\@var{xd...}} (hex character code)
1993 @cindex hex character code (@code{\@var{xd...}})
1994 @item \@code{x} @var{hex-digits...}
1995 A hex character code. All trailing hex digits are combined. Either upper or
1996 lower case @code{x} works.
1998 @cindex @code{\\} (@samp{\} character)
1999 @cindex backslash (@code{\\})
2001 Represents one @samp{\} character.
2004 @c Represents one @samp{'} (accent acute) character.
2005 @c This is needed in single character literals
2006 @c (@xref{Characters,,Character Constants}.) to represent
2009 @cindex @code{\"} (doublequote character)
2010 @cindex doublequote (@code{\"})
2012 Represents one @samp{"} character. Needed in strings to represent
2013 this character, because an unescaped @samp{"} would end the string.
2015 @item \ @var{anything-else}
2016 Any other character when escaped by @kbd{\} gives a warning, but
2017 assembles as if the @samp{\} was not present. The idea is that if
2018 you used an escape sequence you clearly didn't want the literal
2019 interpretation of the following character. However @code{@value{AS}} has no
2020 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
2021 code and warns you of the fact.
2024 Which characters are escapable, and what those escapes represent,
2025 varies widely among assemblers. The current set is what we think
2026 the BSD 4.2 assembler recognizes, and is a subset of what most C
2027 compilers recognize. If you are in doubt, do not use an escape
2031 @subsubsection Characters
2033 @cindex single character constant
2034 @cindex character, single
2035 @cindex constant, single character
2036 A single character may be written as a single quote immediately
2037 followed by that character. The same escapes apply to characters as
2038 to strings. So if you want to write the character backslash, you
2039 must write @kbd{'\\} where the first @code{\} escapes the second
2040 @code{\}. As you can see, the quote is an acute accent, not a
2041 grave accent. A newline
2043 @ifclear abnormal-separator
2044 (or semicolon @samp{;})
2046 @ifset abnormal-separator
2048 (or at sign @samp{@@})
2051 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2057 immediately following an acute accent is taken as a literal character
2058 and does not count as the end of a statement. The value of a character
2059 constant in a numeric expression is the machine's byte-wide code for
2060 that character. @code{@value{AS}} assumes your character code is ASCII:
2061 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2064 @subsection Number Constants
2066 @cindex constants, number
2067 @cindex number constants
2068 @code{@value{AS}} distinguishes three kinds of numbers according to how they
2069 are stored in the target machine. @emph{Integers} are numbers that
2070 would fit into an @code{int} in the C language. @emph{Bignums} are
2071 integers, but they are stored in more than 32 bits. @emph{Flonums}
2072 are floating point numbers, described below.
2075 * Integers:: Integers
2080 * Bit Fields:: Bit Fields
2086 @subsubsection Integers
2088 @cindex constants, integer
2090 @cindex binary integers
2091 @cindex integers, binary
2092 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2093 the binary digits @samp{01}.
2095 @cindex octal integers
2096 @cindex integers, octal
2097 An octal integer is @samp{0} followed by zero or more of the octal
2098 digits (@samp{01234567}).
2100 @cindex decimal integers
2101 @cindex integers, decimal
2102 A decimal integer starts with a non-zero digit followed by zero or
2103 more digits (@samp{0123456789}).
2105 @cindex hexadecimal integers
2106 @cindex integers, hexadecimal
2107 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2108 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2110 Integers have the usual values. To denote a negative integer, use
2111 the prefix operator @samp{-} discussed under expressions
2112 (@pxref{Prefix Ops,,Prefix Operators}).
2115 @subsubsection Bignums
2118 @cindex constants, bignum
2119 A @dfn{bignum} has the same syntax and semantics as an integer
2120 except that the number (or its negative) takes more than 32 bits to
2121 represent in binary. The distinction is made because in some places
2122 integers are permitted while bignums are not.
2125 @subsubsection Flonums
2127 @cindex floating point numbers
2128 @cindex constants, floating point
2130 @cindex precision, floating point
2131 A @dfn{flonum} represents a floating point number. The translation is
2132 indirect: a decimal floating point number from the text is converted by
2133 @code{@value{AS}} to a generic binary floating point number of more than
2134 sufficient precision. This generic floating point number is converted
2135 to a particular computer's floating point format (or formats) by a
2136 portion of @code{@value{AS}} specialized to that computer.
2138 A flonum is written by writing (in order)
2143 (@samp{0} is optional on the HPPA.)
2147 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
2149 @kbd{e} is recommended. Case is not important.
2151 @c FIXME: verify if flonum syntax really this vague for most cases
2152 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2153 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2156 On the H8/300, H8/500,
2158 and AMD 29K architectures, the letter must be
2159 one of the letters @samp{DFPRSX} (in upper or lower case).
2161 On the ARC, the letter must be one of the letters @samp{DFRS}
2162 (in upper or lower case).
2164 On the Intel 960 architecture, the letter must be
2165 one of the letters @samp{DFT} (in upper or lower case).
2167 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2171 One of the letters @samp{DFPRSX} (in upper or lower case).
2174 One of the letters @samp{DFRS} (in upper or lower case).
2177 One of the letters @samp{DFPRSX} (in upper or lower case).
2180 The letter @samp{E} (upper case only).
2183 One of the letters @samp{DFT} (in upper or lower case).
2188 An optional sign: either @samp{+} or @samp{-}.
2191 An optional @dfn{integer part}: zero or more decimal digits.
2194 An optional @dfn{fractional part}: @samp{.} followed by zero
2195 or more decimal digits.
2198 An optional exponent, consisting of:
2202 An @samp{E} or @samp{e}.
2203 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2204 @c principle this can perfectly well be different on different targets.
2206 Optional sign: either @samp{+} or @samp{-}.
2208 One or more decimal digits.
2213 At least one of the integer part or the fractional part must be
2214 present. The floating point number has the usual base-10 value.
2216 @code{@value{AS}} does all processing using integers. Flonums are computed
2217 independently of any floating point hardware in the computer running
2222 @c Bit fields are written as a general facility but are also controlled
2223 @c by a conditional-compilation flag---which is as of now (21mar91)
2224 @c turned on only by the i960 config of GAS.
2226 @subsubsection Bit Fields
2229 @cindex constants, bit field
2230 You can also define numeric constants as @dfn{bit fields}.
2231 specify two numbers separated by a colon---
2233 @var{mask}:@var{value}
2236 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2239 The resulting number is then packed
2241 @c this conditional paren in case bit fields turned on elsewhere than 960
2242 (in host-dependent byte order)
2244 into a field whose width depends on which assembler directive has the
2245 bit-field as its argument. Overflow (a result from the bitwise and
2246 requiring more binary digits to represent) is not an error; instead,
2247 more constants are generated, of the specified width, beginning with the
2248 least significant digits.@refill
2250 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2251 @code{.short}, and @code{.word} accept bit-field arguments.
2256 @chapter Sections and Relocation
2261 * Secs Background:: Background
2262 * Ld Sections:: Linker Sections
2263 * As Sections:: Assembler Internal Sections
2264 * Sub-Sections:: Sub-Sections
2268 @node Secs Background
2271 Roughly, a section is a range of addresses, with no gaps; all data
2272 ``in'' those addresses is treated the same for some particular purpose.
2273 For example there may be a ``read only'' section.
2275 @cindex linker, and assembler
2276 @cindex assembler, and linker
2277 The linker @code{@value{LD}} reads many object files (partial programs) and
2278 combines their contents to form a runnable program. When @code{@value{AS}}
2279 emits an object file, the partial program is assumed to start at address 0.
2280 @code{@value{LD}} assigns the final addresses for the partial program, so that
2281 different partial programs do not overlap. This is actually an
2282 oversimplification, but it suffices to explain how @code{@value{AS}} uses
2285 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2286 addresses. These blocks slide to their run-time addresses as rigid
2287 units; their length does not change and neither does the order of bytes
2288 within them. Such a rigid unit is called a @emph{section}. Assigning
2289 run-time addresses to sections is called @dfn{relocation}. It includes
2290 the task of adjusting mentions of object-file addresses so they refer to
2291 the proper run-time addresses.
2293 For the H8/300 and H8/500,
2294 and for the Hitachi SH,
2295 @code{@value{AS}} pads sections if needed to
2296 ensure they end on a word (sixteen bit) boundary.
2299 @cindex standard assembler sections
2300 An object file written by @code{@value{AS}} has at least three sections, any
2301 of which may be empty. These are named @dfn{text}, @dfn{data} and
2306 When it generates COFF output,
2308 @code{@value{AS}} can also generate whatever other named sections you specify
2309 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2310 If you do not use any directives that place output in the @samp{.text}
2311 or @samp{.data} sections, these sections still exist, but are empty.
2316 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2318 @code{@value{AS}} can also generate whatever other named sections you
2319 specify using the @samp{.space} and @samp{.subspace} directives. See
2320 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2321 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2322 assembler directives.
2325 Additionally, @code{@value{AS}} uses different names for the standard
2326 text, data, and bss sections when generating SOM output. Program text
2327 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2328 BSS into @samp{$BSS$}.
2332 Within the object file, the text section starts at address @code{0}, the
2333 data section follows, and the bss section follows the data section.
2336 When generating either SOM or ELF output files on the HPPA, the text
2337 section starts at address @code{0}, the data section at address
2338 @code{0x4000000}, and the bss section follows the data section.
2341 To let @code{@value{LD}} know which data changes when the sections are
2342 relocated, and how to change that data, @code{@value{AS}} also writes to the
2343 object file details of the relocation needed. To perform relocation
2344 @code{@value{LD}} must know, each time an address in the object
2348 Where in the object file is the beginning of this reference to
2351 How long (in bytes) is this reference?
2353 Which section does the address refer to? What is the numeric value of
2355 (@var{address}) @minus{} (@var{start-address of section})?
2358 Is the reference to an address ``Program-Counter relative''?
2361 @cindex addresses, format of
2362 @cindex section-relative addressing
2363 In fact, every address @code{@value{AS}} ever uses is expressed as
2365 (@var{section}) + (@var{offset into section})
2368 Further, most expressions @code{@value{AS}} computes have this section-relative
2371 (For some object formats, such as SOM for the HPPA, some expressions are
2372 symbol-relative instead.)
2375 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2376 @var{N} into section @var{secname}.''
2378 Apart from text, data and bss sections you need to know about the
2379 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2380 addresses in the absolute section remain unchanged. For example, address
2381 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2382 @code{@value{LD}}. Although the linker never arranges two partial programs'
2383 data sections with overlapping addresses after linking, @emph{by definition}
2384 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2385 part of a program is always the same address when the program is running as
2386 address @code{@{absolute@ 239@}} in any other part of the program.
2388 The idea of sections is extended to the @dfn{undefined} section. Any
2389 address whose section is unknown at assembly time is by definition
2390 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2391 Since numbers are always defined, the only way to generate an undefined
2392 address is to mention an undefined symbol. A reference to a named
2393 common block would be such a symbol: its value is unknown at assembly
2394 time so it has section @emph{undefined}.
2396 By analogy the word @emph{section} is used to describe groups of sections in
2397 the linked program. @code{@value{LD}} puts all partial programs' text
2398 sections in contiguous addresses in the linked program. It is
2399 customary to refer to the @emph{text section} of a program, meaning all
2400 the addresses of all partial programs' text sections. Likewise for
2401 data and bss sections.
2403 Some sections are manipulated by @code{@value{LD}}; others are invented for
2404 use of @code{@value{AS}} and have no meaning except during assembly.
2407 @section Linker Sections
2408 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2413 @cindex named sections
2414 @cindex sections, named
2415 @item named sections
2418 @cindex text section
2419 @cindex data section
2423 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2424 separate but equal sections. Anything you can say of one section is
2427 When the program is running, however, it is
2428 customary for the text section to be unalterable. The
2429 text section is often shared among processes: it contains
2430 instructions, constants and the like. The data section of a running
2431 program is usually alterable: for example, C variables would be stored
2432 in the data section.
2437 This section contains zeroed bytes when your program begins running. It
2438 is used to hold uninitialized variables or common storage. The length of
2439 each partial program's bss section is important, but because it starts
2440 out containing zeroed bytes there is no need to store explicit zero
2441 bytes in the object file. The bss section was invented to eliminate
2442 those explicit zeros from object files.
2444 @cindex absolute section
2445 @item absolute section
2446 Address 0 of this section is always ``relocated'' to runtime address 0.
2447 This is useful if you want to refer to an address that @code{@value{LD}} must
2448 not change when relocating. In this sense we speak of absolute
2449 addresses being ``unrelocatable'': they do not change during relocation.
2451 @cindex undefined section
2452 @item undefined section
2453 This ``section'' is a catch-all for address references to objects not in
2454 the preceding sections.
2455 @c FIXME: ref to some other doc on obj-file formats could go here.
2458 @cindex relocation example
2459 An idealized example of three relocatable sections follows.
2461 The example uses the traditional section names @samp{.text} and @samp{.data}.
2463 Memory addresses are on the horizontal axis.
2467 @c END TEXI2ROFF-KILL
2470 partial program # 1: |ttttt|dddd|00|
2477 partial program # 2: |TTT|DDD|000|
2480 +--+---+-----+--+----+---+-----+~~
2481 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2482 +--+---+-----+--+----+---+-----+~~
2484 addresses: 0 @dots{}
2491 \line{\it Partial program \#1: \hfil}
2492 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2493 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2495 \line{\it Partial program \#2: \hfil}
2496 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2497 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2499 \line{\it linked program: \hfil}
2500 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2501 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2502 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2503 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2505 \line{\it addresses: \hfil}
2509 @c END TEXI2ROFF-KILL
2512 @section Assembler Internal Sections
2514 @cindex internal assembler sections
2515 @cindex sections in messages, internal
2516 These sections are meant only for the internal use of @code{@value{AS}}. They
2517 have no meaning at run-time. You do not really need to know about these
2518 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2519 warning messages, so it might be helpful to have an idea of their
2520 meanings to @code{@value{AS}}. These sections are used to permit the
2521 value of every expression in your assembly language program to be a
2522 section-relative address.
2525 @cindex assembler internal logic error
2526 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2527 An internal assembler logic error has been found. This means there is a
2528 bug in the assembler.
2530 @cindex expr (internal section)
2532 The assembler stores complex expression internally as combinations of
2533 symbols. When it needs to represent an expression as a symbol, it puts
2534 it in the expr section.
2536 @c FIXME item transfer[t] vector preload
2537 @c FIXME item transfer[t] vector postload
2538 @c FIXME item register
2542 @section Sub-Sections
2544 @cindex numbered subsections
2545 @cindex grouping data
2551 fall into two sections: text and data.
2553 You may have separate groups of
2555 data in named sections
2559 data in named sections
2565 that you want to end up near to each other in the object file, even though they
2566 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2567 use @dfn{subsections} for this purpose. Within each section, there can be
2568 numbered subsections with values from 0 to 8192. Objects assembled into the
2569 same subsection go into the object file together with other objects in the same
2570 subsection. For example, a compiler might want to store constants in the text
2571 section, but might not want to have them interspersed with the program being
2572 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2573 section of code being output, and a @samp{.text 1} before each group of
2574 constants being output.
2576 Subsections are optional. If you do not use subsections, everything
2577 goes in subsection number zero.
2580 Each subsection is zero-padded up to a multiple of four bytes.
2581 (Subsections may be padded a different amount on different flavors
2582 of @code{@value{AS}}.)
2586 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2587 boundary (two bytes).
2588 The same is true on the Hitachi SH.
2591 @c FIXME section padding (alignment)?
2592 @c Rich Pixley says padding here depends on target obj code format; that
2593 @c doesn't seem particularly useful to say without further elaboration,
2594 @c so for now I say nothing about it. If this is a generic BFD issue,
2595 @c these paragraphs might need to vanish from this manual, and be
2596 @c discussed in BFD chapter of binutils (or some such).
2599 On the AMD 29K family, no particular padding is added to section or
2600 subsection sizes; @value{AS} forces no alignment on this platform.
2604 Subsections appear in your object file in numeric order, lowest numbered
2605 to highest. (All this to be compatible with other people's assemblers.)
2606 The object file contains no representation of subsections; @code{@value{LD}} and
2607 other programs that manipulate object files see no trace of them.
2608 They just see all your text subsections as a text section, and all your
2609 data subsections as a data section.
2611 To specify which subsection you want subsequent statements assembled
2612 into, use a numeric argument to specify it, in a @samp{.text
2613 @var{expression}} or a @samp{.data @var{expression}} statement.
2616 When generating COFF output, you
2621 can also use an extra subsection
2622 argument with arbitrary named sections: @samp{.section @var{name},
2625 @var{Expression} should be an absolute expression.
2626 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2627 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2628 begins in @code{text 0}. For instance:
2630 .text 0 # The default subsection is text 0 anyway.
2631 .ascii "This lives in the first text subsection. *"
2633 .ascii "But this lives in the second text subsection."
2635 .ascii "This lives in the data section,"
2636 .ascii "in the first data subsection."
2638 .ascii "This lives in the first text section,"
2639 .ascii "immediately following the asterisk (*)."
2642 Each section has a @dfn{location counter} incremented by one for every byte
2643 assembled into that section. Because subsections are merely a convenience
2644 restricted to @code{@value{AS}} there is no concept of a subsection location
2645 counter. There is no way to directly manipulate a location counter---but the
2646 @code{.align} directive changes it, and any label definition captures its
2647 current value. The location counter of the section where statements are being
2648 assembled is said to be the @dfn{active} location counter.
2651 @section bss Section
2654 @cindex common variable storage
2655 The bss section is used for local common variable storage.
2656 You may allocate address space in the bss section, but you may
2657 not dictate data to load into it before your program executes. When
2658 your program starts running, all the contents of the bss
2659 section are zeroed bytes.
2661 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2662 @ref{Lcomm,,@code{.lcomm}}.
2664 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2665 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2668 When assembling for a target which supports multiple sections, such as ELF or
2669 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2670 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2671 section. Typically the section will only contain symbol definitions and
2672 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2679 Symbols are a central concept: the programmer uses symbols to name
2680 things, the linker uses symbols to link, and the debugger uses symbols
2684 @cindex debuggers, and symbol order
2685 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2686 the same order they were declared. This may break some debuggers.
2691 * Setting Symbols:: Giving Symbols Other Values
2692 * Symbol Names:: Symbol Names
2693 * Dot:: The Special Dot Symbol
2694 * Symbol Attributes:: Symbol Attributes
2701 A @dfn{label} is written as a symbol immediately followed by a colon
2702 @samp{:}. The symbol then represents the current value of the
2703 active location counter, and is, for example, a suitable instruction
2704 operand. You are warned if you use the same symbol to represent two
2705 different locations: the first definition overrides any other
2709 On the HPPA, the usual form for a label need not be immediately followed by a
2710 colon, but instead must start in column zero. Only one label may be defined on
2711 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2712 provides a special directive @code{.label} for defining labels more flexibly.
2715 @node Setting Symbols
2716 @section Giving Symbols Other Values
2718 @cindex assigning values to symbols
2719 @cindex symbol values, assigning
2720 A symbol can be given an arbitrary value by writing a symbol, followed
2721 by an equals sign @samp{=}, followed by an expression
2722 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2723 directive. @xref{Set,,@code{.set}}.
2726 @section Symbol Names
2728 @cindex symbol names
2729 @cindex names, symbol
2730 @ifclear SPECIAL-SYMS
2731 Symbol names begin with a letter or with one of @samp{._}. On most
2732 machines, you can also use @code{$} in symbol names; exceptions are
2733 noted in @ref{Machine Dependencies}. That character may be followed by any
2734 string of digits, letters, dollar signs (unless otherwise noted in
2735 @ref{Machine Dependencies}), and underscores.
2738 For the AMD 29K family, @samp{?} is also allowed in the
2739 body of a symbol name, though not at its beginning.
2744 Symbol names begin with a letter or with one of @samp{._}. On the
2746 H8/500, you can also use @code{$} in symbol names. That character may
2747 be followed by any string of digits, letters, dollar signs (save on the
2748 H8/300), and underscores.
2752 Case of letters is significant: @code{foo} is a different symbol name
2755 Each symbol has exactly one name. Each name in an assembly language program
2756 refers to exactly one symbol. You may use that symbol name any number of times
2759 @subheading Local Symbol Names
2761 @cindex local symbol names
2762 @cindex symbol names, local
2763 @cindex temporary symbol names
2764 @cindex symbol names, temporary
2765 Local symbols help compilers and programmers use names temporarily.
2766 There are ten local symbol names, which are re-used throughout the
2767 program. You may refer to them using the names @samp{0} @samp{1}
2768 @dots{} @samp{9}. To define a local symbol, write a label of the form
2769 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2770 recent previous definition of that symbol write @samp{@b{N}b}, using the
2771 same digit as when you defined the label. To refer to the next
2772 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2773 a choice of 10 forward references. The @samp{b} stands for
2774 ``backwards'' and the @samp{f} stands for ``forwards''.
2776 Local symbols are not emitted by the current @sc{gnu} C compiler.
2778 There is no restriction on how you can use these labels, but
2779 remember that at any point in the assembly you can refer to at most
2780 10 prior local labels and to at most 10 forward local labels.
2782 Local symbol names are only a notation device. They are immediately
2783 transformed into more conventional symbol names before the assembler
2784 uses them. The symbol names stored in the symbol table, appearing in
2785 error messages and optionally emitted to the object file have these
2790 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2791 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2792 used for symbols you are never intended to see. If you use the
2793 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2794 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2795 you may use them in debugging.
2798 If the label is written @samp{0:} then the digit is @samp{0}.
2799 If the label is written @samp{1:} then the digit is @samp{1}.
2800 And so on up through @samp{9:}.
2803 This unusual character is included so you do not accidentally invent
2804 a symbol of the same name. The character has ASCII value
2807 @item @emph{ordinal number}
2808 This is a serial number to keep the labels distinct. The first
2809 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2810 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2814 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2815 @code{3:} is named @code{L3@kbd{C-A}44}.
2818 @section The Special Dot Symbol
2820 @cindex dot (symbol)
2821 @cindex @code{.} (symbol)
2822 @cindex current address
2823 @cindex location counter
2824 The special symbol @samp{.} refers to the current address that
2825 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2826 .long .} defines @code{melvin} to contain its own address.
2827 Assigning a value to @code{.} is treated the same as a @code{.org}
2828 directive. Thus, the expression @samp{.=.+4} is the same as saying
2829 @ifclear no-space-dir
2838 @node Symbol Attributes
2839 @section Symbol Attributes
2841 @cindex symbol attributes
2842 @cindex attributes, symbol
2843 Every symbol has, as well as its name, the attributes ``Value'' and
2844 ``Type''. Depending on output format, symbols can also have auxiliary
2847 The detailed definitions are in @file{a.out.h}.
2850 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2851 all these attributes, and probably won't warn you. This makes the
2852 symbol an externally defined symbol, which is generally what you
2856 * Symbol Value:: Value
2857 * Symbol Type:: Type
2860 * a.out Symbols:: Symbol Attributes: @code{a.out}
2864 * a.out Symbols:: Symbol Attributes: @code{a.out}
2867 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2872 * COFF Symbols:: Symbol Attributes for COFF
2875 * SOM Symbols:: Symbol Attributes for SOM
2882 @cindex value of a symbol
2883 @cindex symbol value
2884 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2885 location in the text, data, bss or absolute sections the value is the
2886 number of addresses from the start of that section to the label.
2887 Naturally for text, data and bss sections the value of a symbol changes
2888 as @code{@value{LD}} changes section base addresses during linking. Absolute
2889 symbols' values do not change during linking: that is why they are
2892 The value of an undefined symbol is treated in a special way. If it is
2893 0 then the symbol is not defined in this assembler source file, and
2894 @code{@value{LD}} tries to determine its value from other files linked into the
2895 same program. You make this kind of symbol simply by mentioning a symbol
2896 name without defining it. A non-zero value represents a @code{.comm}
2897 common declaration. The value is how much common storage to reserve, in
2898 bytes (addresses). The symbol refers to the first address of the
2904 @cindex type of a symbol
2906 The type attribute of a symbol contains relocation (section)
2907 information, any flag settings indicating that a symbol is external, and
2908 (optionally), other information for linkers and debuggers. The exact
2909 format depends on the object-code output format in use.
2914 @c The following avoids a "widow" subsection title. @group would be
2915 @c better if it were available outside examples.
2918 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2920 @cindex @code{b.out} symbol attributes
2921 @cindex symbol attributes, @code{b.out}
2922 These symbol attributes appear only when @code{@value{AS}} is configured for
2923 one of the Berkeley-descended object output formats---@code{a.out} or
2929 @subsection Symbol Attributes: @code{a.out}
2931 @cindex @code{a.out} symbol attributes
2932 @cindex symbol attributes, @code{a.out}
2938 @subsection Symbol Attributes: @code{a.out}
2940 @cindex @code{a.out} symbol attributes
2941 @cindex symbol attributes, @code{a.out}
2945 * Symbol Desc:: Descriptor
2946 * Symbol Other:: Other
2950 @subsubsection Descriptor
2952 @cindex descriptor, of @code{a.out} symbol
2953 This is an arbitrary 16-bit value. You may establish a symbol's
2954 descriptor value by using a @code{.desc} statement
2955 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2959 @subsubsection Other
2961 @cindex other attribute, of @code{a.out} symbol
2962 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2967 @subsection Symbol Attributes for COFF
2969 @cindex COFF symbol attributes
2970 @cindex symbol attributes, COFF
2972 The COFF format supports a multitude of auxiliary symbol attributes;
2973 like the primary symbol attributes, they are set between @code{.def} and
2974 @code{.endef} directives.
2976 @subsubsection Primary Attributes
2978 @cindex primary attributes, COFF symbols
2979 The symbol name is set with @code{.def}; the value and type,
2980 respectively, with @code{.val} and @code{.type}.
2982 @subsubsection Auxiliary Attributes
2984 @cindex auxiliary attributes, COFF symbols
2985 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2986 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2987 information for COFF.
2992 @subsection Symbol Attributes for SOM
2994 @cindex SOM symbol attributes
2995 @cindex symbol attributes, SOM
2997 The SOM format for the HPPA supports a multitude of symbol attributes set with
2998 the @code{.EXPORT} and @code{.IMPORT} directives.
3000 The attributes are described in @cite{HP9000 Series 800 Assembly
3001 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3002 @code{EXPORT} assembler directive documentation.
3006 @chapter Expressions
3010 @cindex numeric values
3011 An @dfn{expression} specifies an address or numeric value.
3012 Whitespace may precede and/or follow an expression.
3014 The result of an expression must be an absolute number, or else an offset into
3015 a particular section. If an expression is not absolute, and there is not
3016 enough information when @code{@value{AS}} sees the expression to know its
3017 section, a second pass over the source program might be necessary to interpret
3018 the expression---but the second pass is currently not implemented.
3019 @code{@value{AS}} aborts with an error message in this situation.
3022 * Empty Exprs:: Empty Expressions
3023 * Integer Exprs:: Integer Expressions
3027 @section Empty Expressions
3029 @cindex empty expressions
3030 @cindex expressions, empty
3031 An empty expression has no value: it is just whitespace or null.
3032 Wherever an absolute expression is required, you may omit the
3033 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
3034 is compatible with other assemblers.
3037 @section Integer Expressions
3039 @cindex integer expressions
3040 @cindex expressions, integer
3041 An @dfn{integer expression} is one or more @emph{arguments} delimited
3042 by @emph{operators}.
3045 * Arguments:: Arguments
3046 * Operators:: Operators
3047 * Prefix Ops:: Prefix Operators
3048 * Infix Ops:: Infix Operators
3052 @subsection Arguments
3054 @cindex expression arguments
3055 @cindex arguments in expressions
3056 @cindex operands in expressions
3057 @cindex arithmetic operands
3058 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3059 contexts arguments are sometimes called ``arithmetic operands''. In
3060 this manual, to avoid confusing them with the ``instruction operands'' of
3061 the machine language, we use the term ``argument'' to refer to parts of
3062 expressions only, reserving the word ``operand'' to refer only to machine
3063 instruction operands.
3065 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3066 @var{section} is one of text, data, bss, absolute,
3067 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3070 Numbers are usually integers.
3072 A number can be a flonum or bignum. In this case, you are warned
3073 that only the low order 32 bits are used, and @code{@value{AS}} pretends
3074 these 32 bits are an integer. You may write integer-manipulating
3075 instructions that act on exotic constants, compatible with other
3078 @cindex subexpressions
3079 Subexpressions are a left parenthesis @samp{(} followed by an integer
3080 expression, followed by a right parenthesis @samp{)}; or a prefix
3081 operator followed by an argument.
3084 @subsection Operators
3086 @cindex operators, in expressions
3087 @cindex arithmetic functions
3088 @cindex functions, in expressions
3089 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3090 operators are followed by an argument. Infix operators appear
3091 between their arguments. Operators may be preceded and/or followed by
3095 @subsection Prefix Operator
3097 @cindex prefix operators
3098 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
3099 one argument, which must be absolute.
3101 @c the tex/end tex stuff surrounding this small table is meant to make
3102 @c it align, on the printed page, with the similar table in the next
3103 @c section (which is inside an enumerate).
3105 \global\advance\leftskip by \itemindent
3110 @dfn{Negation}. Two's complement negation.
3112 @dfn{Complementation}. Bitwise not.
3116 \global\advance\leftskip by -\itemindent
3120 @subsection Infix Operators
3122 @cindex infix operators
3123 @cindex operators, permitted arguments
3124 @dfn{Infix operators} take two arguments, one on either side. Operators
3125 have precedence, but operations with equal precedence are performed left
3126 to right. Apart from @code{+} or @code{-}, both arguments must be
3127 absolute, and the result is absolute.
3130 @cindex operator precedence
3131 @cindex precedence of operators
3138 @dfn{Multiplication}.
3141 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3148 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3152 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3156 Intermediate precedence
3161 @dfn{Bitwise Inclusive Or}.
3167 @dfn{Bitwise Exclusive Or}.
3170 @dfn{Bitwise Or Not}.
3177 @cindex addition, permitted arguments
3178 @cindex plus, permitted arguments
3179 @cindex arguments for addition
3181 @dfn{Addition}. If either argument is absolute, the result has the section of
3182 the other argument. You may not add together arguments from different
3185 @cindex subtraction, permitted arguments
3186 @cindex minus, permitted arguments
3187 @cindex arguments for subtraction
3189 @dfn{Subtraction}. If the right argument is absolute, the
3190 result has the section of the left argument.
3191 If both arguments are in the same section, the result is absolute.
3192 You may not subtract arguments from different sections.
3193 @c FIXME is there still something useful to say about undefined - undefined ?
3197 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3198 address; you can only have a defined section in one of the two arguments.
3201 @chapter Assembler Directives
3203 @cindex directives, machine independent
3204 @cindex pseudo-ops, machine independent
3205 @cindex machine independent directives
3206 All assembler directives have names that begin with a period (@samp{.}).
3207 The rest of the name is letters, usually in lower case.
3209 This chapter discusses directives that are available regardless of the
3210 target machine configuration for the @sc{gnu} assembler.
3212 Some machine configurations provide additional directives.
3213 @xref{Machine Dependencies}.
3216 @ifset machine-directives
3217 @xref{Machine Dependencies} for additional directives.
3222 * Abort:: @code{.abort}
3224 * ABORT:: @code{.ABORT}
3227 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3228 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3229 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3230 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3231 * Byte:: @code{.byte @var{expressions}}
3232 * Comm:: @code{.comm @var{symbol} , @var{length} }
3233 * Data:: @code{.data @var{subsection}}
3235 * Def:: @code{.def @var{name}}
3238 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3244 * Double:: @code{.double @var{flonums}}
3245 * Eject:: @code{.eject}
3246 * Else:: @code{.else}
3247 * Elseif:: @code{.elseif}
3250 * Endef:: @code{.endef}
3253 * Endfunc:: @code{.endfunc}
3254 * Endif:: @code{.endif}
3255 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3256 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3258 * Exitm:: @code{.exitm}
3259 * Extern:: @code{.extern}
3260 * Fail:: @code{.fail}
3261 @ifclear no-file-dir
3262 * File:: @code{.file @var{string}}
3265 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3266 * Float:: @code{.float @var{flonums}}
3267 * Func:: @code{.func}
3268 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3270 * Hidden:: @code{.hidden @var{names}}
3273 * hword:: @code{.hword @var{expressions}}
3274 * Ident:: @code{.ident}
3275 * If:: @code{.if @var{absolute expression}}
3276 * Include:: @code{.include "@var{file}"}
3277 * Int:: @code{.int @var{expressions}}
3279 * Internal:: @code{.internal @var{names}}
3282 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3283 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3284 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3285 * Lflags:: @code{.lflags}
3286 @ifclear no-line-dir
3287 * Line:: @code{.line @var{line-number}}
3290 * Ln:: @code{.ln @var{line-number}}
3291 * Linkonce:: @code{.linkonce [@var{type}]}
3292 * List:: @code{.list}
3293 * Long:: @code{.long @var{expressions}}
3295 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3298 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3299 * MRI:: @code{.mri @var{val}}
3300 * Nolist:: @code{.nolist}
3301 * Octa:: @code{.octa @var{bignums}}
3302 * Org:: @code{.org @var{new-lc} , @var{fill}}
3303 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3305 * PopSection:: @code{.popsection}
3306 * Previous:: @code{.previous}
3309 * Print:: @code{.print @var{string}}
3311 * Protected:: @code{.protected @var{names}}
3314 * Psize:: @code{.psize @var{lines}, @var{columns}}
3315 * Purgem:: @code{.purgem @var{name}}
3317 * PushSection:: @code{.pushsection @var{name}}
3320 * Quad:: @code{.quad @var{bignums}}
3321 * Rept:: @code{.rept @var{count}}
3322 * Sbttl:: @code{.sbttl "@var{subheading}"}
3324 * Scl:: @code{.scl @var{class}}
3325 * Section:: @code{.section @var{name}, @var{subsection}}
3328 * Set:: @code{.set @var{symbol}, @var{expression}}
3329 * Short:: @code{.short @var{expressions}}
3330 * Single:: @code{.single @var{flonums}}
3331 * Size:: @code{.size [@var{name} , @var{expression}]}
3332 * Skip:: @code{.skip @var{size} , @var{fill}}
3333 * Sleb128:: @code{.sleb128 @var{expressions}}
3334 * Space:: @code{.space @var{size} , @var{fill}}
3336 * Stab:: @code{.stabd, .stabn, .stabs}
3339 * String:: @code{.string "@var{str}"}
3340 * Struct:: @code{.struct @var{expression}}
3342 * SubSection:: @code{.subsection}
3343 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3347 * Tag:: @code{.tag @var{structname}}
3350 * Text:: @code{.text @var{subsection}}
3351 * Title:: @code{.title "@var{heading}"}
3352 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3353 * Uleb128:: @code{.uleb128 @var{expressions}}
3355 * Val:: @code{.val @var{addr}}
3359 * Version:: @code{.version "@var{string}"}
3360 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3361 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3362 * Weak:: @code{.weak @var{names}}
3365 * Word:: @code{.word @var{expressions}}
3366 * Deprecated:: Deprecated Directives
3370 @section @code{.abort}
3372 @cindex @code{abort} directive
3373 @cindex stopping the assembly
3374 This directive stops the assembly immediately. It is for
3375 compatibility with other assemblers. The original idea was that the
3376 assembly language source would be piped into the assembler. If the sender
3377 of the source quit, it could use this directive tells @code{@value{AS}} to
3378 quit also. One day @code{.abort} will not be supported.
3382 @section @code{.ABORT}
3384 @cindex @code{ABORT} directive
3385 When producing COFF output, @code{@value{AS}} accepts this directive as a
3386 synonym for @samp{.abort}.
3389 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3395 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3397 @cindex padding the location counter
3398 @cindex @code{align} directive
3399 Pad the location counter (in the current subsection) to a particular storage
3400 boundary. The first expression (which must be absolute) is the alignment
3401 required, as described below.
3403 The second expression (also absolute) gives the fill value to be stored in the
3404 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3405 padding bytes are normally zero. However, on some systems, if the section is
3406 marked as containing code and the fill value is omitted, the space is filled
3407 with no-op instructions.
3409 The third expression is also absolute, and is also optional. If it is present,
3410 it is the maximum number of bytes that should be skipped by this alignment
3411 directive. If doing the alignment would require skipping more bytes than the
3412 specified maximum, then the alignment is not done at all. You can omit the
3413 fill value (the second argument) entirely by simply using two commas after the
3414 required alignment; this can be useful if you want the alignment to be filled
3415 with no-op instructions when appropriate.
3417 The way the required alignment is specified varies from system to system.
3418 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3420 the first expression is the
3421 alignment request in bytes. For example @samp{.align 8} advances
3422 the location counter until it is a multiple of 8. If the location counter
3423 is already a multiple of 8, no change is needed.
3425 For other systems, including the i386 using a.out format, and the arm and
3426 strongarm, it is the
3427 number of low-order zero bits the location counter must have after
3428 advancement. For example @samp{.align 3} advances the location
3429 counter until it a multiple of 8. If the location counter is already a
3430 multiple of 8, no change is needed.
3432 This inconsistency is due to the different behaviors of the various
3433 native assemblers for these systems which GAS must emulate.
3434 GAS also provides @code{.balign} and @code{.p2align} directives,
3435 described later, which have a consistent behavior across all
3436 architectures (but are specific to GAS).
3439 @section @code{.ascii "@var{string}"}@dots{}
3441 @cindex @code{ascii} directive
3442 @cindex string literals
3443 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3444 separated by commas. It assembles each string (with no automatic
3445 trailing zero byte) into consecutive addresses.
3448 @section @code{.asciz "@var{string}"}@dots{}
3450 @cindex @code{asciz} directive
3451 @cindex zero-terminated strings
3452 @cindex null-terminated strings
3453 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3454 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3457 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3459 @cindex padding the location counter given number of bytes
3460 @cindex @code{balign} directive
3461 Pad the location counter (in the current subsection) to a particular
3462 storage boundary. The first expression (which must be absolute) is the
3463 alignment request in bytes. For example @samp{.balign 8} advances
3464 the location counter until it is a multiple of 8. If the location counter
3465 is already a multiple of 8, no change is needed.
3467 The second expression (also absolute) gives the fill value to be stored in the
3468 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3469 padding bytes are normally zero. However, on some systems, if the section is
3470 marked as containing code and the fill value is omitted, the space is filled
3471 with no-op instructions.
3473 The third expression is also absolute, and is also optional. If it is present,
3474 it is the maximum number of bytes that should be skipped by this alignment
3475 directive. If doing the alignment would require skipping more bytes than the
3476 specified maximum, then the alignment is not done at all. You can omit the
3477 fill value (the second argument) entirely by simply using two commas after the
3478 required alignment; this can be useful if you want the alignment to be filled
3479 with no-op instructions when appropriate.
3481 @cindex @code{balignw} directive
3482 @cindex @code{balignl} directive
3483 The @code{.balignw} and @code{.balignl} directives are variants of the
3484 @code{.balign} directive. The @code{.balignw} directive treats the fill
3485 pattern as a two byte word value. The @code{.balignl} directives treats the
3486 fill pattern as a four byte longword value. For example, @code{.balignw
3487 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3488 filled in with the value 0x368d (the exact placement of the bytes depends upon
3489 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3493 @section @code{.byte @var{expressions}}
3495 @cindex @code{byte} directive
3496 @cindex integers, one byte
3497 @code{.byte} expects zero or more expressions, separated by commas.
3498 Each expression is assembled into the next byte.
3501 @section @code{.comm @var{symbol} , @var{length} }
3503 @cindex @code{comm} directive
3504 @cindex symbol, common
3505 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3506 common symbol in one object file may be merged with a defined or common symbol
3507 of the same name in another object file. If @code{@value{LD}} does not see a
3508 definition for the symbol--just one or more common symbols--then it will
3509 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3510 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3511 the same name, and they do not all have the same size, it will allocate space
3512 using the largest size.
3515 When using ELF, the @code{.comm} directive takes an optional third argument.
3516 This is the desired alignment of the symbol, specified as a byte boundary (for
3517 example, an alignment of 16 means that the least significant 4 bits of the
3518 address should be zero). The alignment must be an absolute expression, and it
3519 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3520 for the common symbol, it will use the alignment when placing the symbol. If
3521 no alignment is specified, @code{@value{AS}} will set the alignment to the
3522 largest power of two less than or equal to the size of the symbol, up to a
3527 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3528 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3532 @section @code{.data @var{subsection}}
3534 @cindex @code{data} directive
3535 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3536 end of the data subsection numbered @var{subsection} (which is an
3537 absolute expression). If @var{subsection} is omitted, it defaults
3542 @section @code{.def @var{name}}
3544 @cindex @code{def} directive
3545 @cindex COFF symbols, debugging
3546 @cindex debugging COFF symbols
3547 Begin defining debugging information for a symbol @var{name}; the
3548 definition extends until the @code{.endef} directive is encountered.
3551 This directive is only observed when @code{@value{AS}} is configured for COFF
3552 format output; when producing @code{b.out}, @samp{.def} is recognized,
3559 @section @code{.desc @var{symbol}, @var{abs-expression}}
3561 @cindex @code{desc} directive
3562 @cindex COFF symbol descriptor
3563 @cindex symbol descriptor, COFF
3564 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3565 to the low 16 bits of an absolute expression.
3568 The @samp{.desc} directive is not available when @code{@value{AS}} is
3569 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3570 object format. For the sake of compatibility, @code{@value{AS}} accepts
3571 it, but produces no output, when configured for COFF.
3577 @section @code{.dim}
3579 @cindex @code{dim} directive
3580 @cindex COFF auxiliary symbol information
3581 @cindex auxiliary symbol information, COFF
3582 This directive is generated by compilers to include auxiliary debugging
3583 information in the symbol table. It is only permitted inside
3584 @code{.def}/@code{.endef} pairs.
3587 @samp{.dim} is only meaningful when generating COFF format output; when
3588 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3594 @section @code{.double @var{flonums}}
3596 @cindex @code{double} directive
3597 @cindex floating point numbers (double)
3598 @code{.double} expects zero or more flonums, separated by commas. It
3599 assembles floating point numbers.
3601 The exact kind of floating point numbers emitted depends on how
3602 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3606 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3607 in @sc{ieee} format.
3612 @section @code{.eject}
3614 @cindex @code{eject} directive
3615 @cindex new page, in listings
3616 @cindex page, in listings
3617 @cindex listing control: new page
3618 Force a page break at this point, when generating assembly listings.
3621 @section @code{.else}
3623 @cindex @code{else} directive
3624 @code{.else} is part of the @code{@value{AS}} support for conditional
3625 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3626 of code to be assembled if the condition for the preceding @code{.if}
3630 @section @code{.elseif}
3632 @cindex @code{elseif} directive
3633 @code{.elseif} is part of the @code{@value{AS}} support for conditional
3634 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
3635 @code{.if} block that would otherwise fill the entire @code{.else} section.
3638 @section @code{.end}
3640 @cindex @code{end} directive
3641 @code{.end} marks the end of the assembly file. @code{@value{AS}} does not
3642 process anything in the file past the @code{.end} directive.
3646 @section @code{.endef}
3648 @cindex @code{endef} directive
3649 This directive flags the end of a symbol definition begun with
3653 @samp{.endef} is only meaningful when generating COFF format output; if
3654 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3655 directive but ignores it.
3660 @section @code{.endfunc}
3661 @cindex @code{endfunc} directive
3662 @code{.endfunc} marks the end of a function specified with @code{.func}.
3665 @section @code{.endif}
3667 @cindex @code{endif} directive
3668 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3669 it marks the end of a block of code that is only assembled
3670 conditionally. @xref{If,,@code{.if}}.
3673 @section @code{.equ @var{symbol}, @var{expression}}
3675 @cindex @code{equ} directive
3676 @cindex assigning values to symbols
3677 @cindex symbols, assigning values to
3678 This directive sets the value of @var{symbol} to @var{expression}.
3679 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3682 The syntax for @code{equ} on the HPPA is
3683 @samp{@var{symbol} .equ @var{expression}}.
3687 @section @code{.equiv @var{symbol}, @var{expression}}
3688 @cindex @code{equiv} directive
3689 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3690 the assembler will signal an error if @var{symbol} is already defined.
3692 Except for the contents of the error message, this is roughly equivalent to
3701 @section @code{.err}
3702 @cindex @code{err} directive
3703 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3704 message and, unless the @code{-Z} option was used, it will not generate an
3705 object file. This can be used to signal error an conditionally compiled code.
3708 @section @code{.exitm}
3709 Exit early from the current macro definition. @xref{Macro}.
3712 @section @code{.extern}
3714 @cindex @code{extern} directive
3715 @code{.extern} is accepted in the source program---for compatibility
3716 with other assemblers---but it is ignored. @code{@value{AS}} treats
3717 all undefined symbols as external.
3720 @section @code{.fail @var{expression}}
3722 @cindex @code{fail} directive
3723 Generates an error or a warning. If the value of the @var{expression} is 500
3724 or more, @code{@value{AS}} will print a warning message. If the value is less
3725 than 500, @code{@value{AS}} will print an error message. The message will
3726 include the value of @var{expression}. This can occasionally be useful inside
3727 complex nested macros or conditional assembly.
3729 @ifclear no-file-dir
3731 @section @code{.file @var{string}}
3733 @cindex @code{file} directive
3734 @cindex logical file name
3735 @cindex file name, logical
3736 @code{.file} tells @code{@value{AS}} that we are about to start a new logical
3737 file. @var{string} is the new file name. In general, the filename is
3738 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
3739 to specify an empty file name, you must give the quotes--@code{""}. This
3740 statement may go away in future: it is only recognized to be compatible with
3741 old @code{@value{AS}} programs.
3743 In some configurations of @code{@value{AS}}, @code{.file} has already been
3744 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3749 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3751 @cindex @code{fill} directive
3752 @cindex writing patterns in memory
3753 @cindex patterns, writing in memory
3754 @var{result}, @var{size} and @var{value} are absolute expressions.
3755 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3756 may be zero or more. @var{Size} may be zero or more, but if it is
3757 more than 8, then it is deemed to have the value 8, compatible with
3758 other people's assemblers. The contents of each @var{repeat} bytes
3759 is taken from an 8-byte number. The highest order 4 bytes are
3760 zero. The lowest order 4 bytes are @var{value} rendered in the
3761 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3762 Each @var{size} bytes in a repetition is taken from the lowest order
3763 @var{size} bytes of this number. Again, this bizarre behavior is
3764 compatible with other people's assemblers.
3766 @var{size} and @var{value} are optional.
3767 If the second comma and @var{value} are absent, @var{value} is
3768 assumed zero. If the first comma and following tokens are absent,
3769 @var{size} is assumed to be 1.
3772 @section @code{.float @var{flonums}}
3774 @cindex floating point numbers (single)
3775 @cindex @code{float} directive
3776 This directive assembles zero or more flonums, separated by commas. It
3777 has the same effect as @code{.single}.
3779 The exact kind of floating point numbers emitted depends on how
3780 @code{@value{AS}} is configured.
3781 @xref{Machine Dependencies}.
3785 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3786 in @sc{ieee} format.
3791 @section @code{.func @var{name}[,@var{label}]}
3792 @cindex @code{func} directive
3793 @code{.func} emits debugging information to denote function @var{name}, and
3794 is ignored unless the file is assembled with debugging enabled.
3795 Only @samp{--gstabs} is currently supported.
3796 @var{label} is the entry point of the function and if omitted @var{name}
3797 prepended with the @samp{leading char} is used.
3798 @samp{leading char} is usually @code{_} or nothing, depending on the target.
3799 All functions are currently defined to have @code{void} return type.
3800 The function must be terminated with @code{.endfunc}.
3803 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3805 @cindex @code{global} directive
3806 @cindex symbol, making visible to linker
3807 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3808 @var{symbol} in your partial program, its value is made available to
3809 other partial programs that are linked with it. Otherwise,
3810 @var{symbol} takes its attributes from a symbol of the same name
3811 from another file linked into the same program.
3813 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3814 compatibility with other assemblers.
3817 On the HPPA, @code{.global} is not always enough to make it accessible to other
3818 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3819 @xref{HPPA Directives,, HPPA Assembler Directives}.
3824 @section @code{.hidden @var{names}}
3826 @cindex @code{.hidden} directive
3828 This one of the ELF visibility directives. The other two are
3829 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
3830 @code{.protected} (@pxref{Protected,,@code{.protected}}).
3832 This directive overrides the named symbols default visibility (which is set by
3833 their binding: local, global or weak). The directive sets the visibility to
3834 @code{hidden} which means that the symbols are not visible to other components.
3835 Such symbols are always considered to be @code{protected} as well.
3839 @section @code{.hword @var{expressions}}
3841 @cindex @code{hword} directive
3842 @cindex integers, 16-bit
3843 @cindex numbers, 16-bit
3844 @cindex sixteen bit integers
3845 This expects zero or more @var{expressions}, and emits
3846 a 16 bit number for each.
3849 This directive is a synonym for @samp{.short}; depending on the target
3850 architecture, it may also be a synonym for @samp{.word}.
3854 This directive is a synonym for @samp{.short}.
3857 This directive is a synonym for both @samp{.short} and @samp{.word}.
3862 @section @code{.ident}
3864 @cindex @code{ident} directive
3865 This directive is used by some assemblers to place tags in object files.
3866 @code{@value{AS}} simply accepts the directive for source-file
3867 compatibility with such assemblers, but does not actually emit anything
3871 @section @code{.if @var{absolute expression}}
3873 @cindex conditional assembly
3874 @cindex @code{if} directive
3875 @code{.if} marks the beginning of a section of code which is only
3876 considered part of the source program being assembled if the argument
3877 (which must be an @var{absolute expression}) is non-zero. The end of
3878 the conditional section of code must be marked by @code{.endif}
3879 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3880 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3881 If you have several conditions to check, @code{.elseif} may be used to avoid
3882 nesting blocks if/else within each subsequent @code{.else} block.
3884 The following variants of @code{.if} are also supported:
3886 @cindex @code{ifdef} directive
3887 @item .ifdef @var{symbol}
3888 Assembles the following section of code if the specified @var{symbol}
3891 @cindex @code{ifc} directive
3892 @item .ifc @var{string1},@var{string2}
3893 Assembles the following section of code if the two strings are the same. The
3894 strings may be optionally quoted with single quotes. If they are not quoted,
3895 the first string stops at the first comma, and the second string stops at the
3896 end of the line. Strings which contain whitespace should be quoted. The
3897 string comparison is case sensitive.
3899 @cindex @code{ifeq} directive
3900 @item .ifeq @var{absolute expression}
3901 Assembles the following section of code if the argument is zero.
3903 @cindex @code{ifeqs} directive
3904 @item .ifeqs @var{string1},@var{string2}
3905 Another form of @code{.ifc}. The strings must be quoted using double quotes.
3907 @cindex @code{ifge} directive
3908 @item .ifge @var{absolute expression}
3909 Assembles the following section of code if the argument is greater than or
3912 @cindex @code{ifgt} directive
3913 @item .ifgt @var{absolute expression}
3914 Assembles the following section of code if the argument is greater than zero.
3916 @cindex @code{ifle} directive
3917 @item .ifle @var{absolute expression}
3918 Assembles the following section of code if the argument is less than or equal
3921 @cindex @code{iflt} directive
3922 @item .iflt @var{absolute expression}
3923 Assembles the following section of code if the argument is less than zero.
3925 @cindex @code{ifnc} directive
3926 @item .ifnc @var{string1},@var{string2}.
3927 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
3928 following section of code if the two strings are not the same.
3930 @cindex @code{ifndef} directive
3931 @cindex @code{ifnotdef} directive
3932 @item .ifndef @var{symbol}
3933 @itemx .ifnotdef @var{symbol}
3934 Assembles the following section of code if the specified @var{symbol}
3935 has not been defined. Both spelling variants are equivalent.
3937 @cindex @code{ifne} directive
3938 @item .ifne @var{absolute expression}
3939 Assembles the following section of code if the argument is not equal to zero
3940 (in other words, this is equivalent to @code{.if}).
3942 @cindex @code{ifnes} directive
3943 @item .ifnes @var{string1},@var{string2}
3944 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
3945 following section of code if the two strings are not the same.
3949 @section @code{.include "@var{file}"}
3951 @cindex @code{include} directive
3952 @cindex supporting files, including
3953 @cindex files, including
3954 This directive provides a way to include supporting files at specified
3955 points in your source program. The code from @var{file} is assembled as
3956 if it followed the point of the @code{.include}; when the end of the
3957 included file is reached, assembly of the original file continues. You
3958 can control the search paths used with the @samp{-I} command-line option
3959 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3963 @section @code{.int @var{expressions}}
3965 @cindex @code{int} directive
3966 @cindex integers, 32-bit
3967 Expect zero or more @var{expressions}, of any section, separated by commas.
3968 For each expression, emit a number that, at run time, is the value of that
3969 expression. The byte order and bit size of the number depends on what kind
3970 of target the assembly is for.
3974 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3975 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3982 @section @code{.internal @var{names}}
3984 @cindex @code{.internal} directive
3986 This one of the ELF visibility directives. The other two are
3987 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
3988 @code{.protected} (@pxref{Protected,,@code{.protected}}).
3990 This directive overrides the named symbols default visibility (which is set by
3991 their binding: local, global or weak). The directive sets the visibility to
3992 @code{internal} which means that the symbols are considered to be @code{hidden}
3993 (ie not visible to other components), and that some extra, processor specific
3994 processing must also be performed upon the symbols as well.
3998 @section @code{.irp @var{symbol},@var{values}}@dots{}
4000 @cindex @code{irp} directive
4001 Evaluate a sequence of statements assigning different values to @var{symbol}.
4002 The sequence of statements starts at the @code{.irp} directive, and is
4003 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4004 set to @var{value}, and the sequence of statements is assembled. If no
4005 @var{value} is listed, the sequence of statements is assembled once, with
4006 @var{symbol} set to the null string. To refer to @var{symbol} within the
4007 sequence of statements, use @var{\symbol}.
4009 For example, assembling
4017 is equivalent to assembling
4026 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4028 @cindex @code{irpc} directive
4029 Evaluate a sequence of statements assigning different values to @var{symbol}.
4030 The sequence of statements starts at the @code{.irpc} directive, and is
4031 terminated by an @code{.endr} directive. For each character in @var{value},
4032 @var{symbol} is set to the character, and the sequence of statements is
4033 assembled. If no @var{value} is listed, the sequence of statements is
4034 assembled once, with @var{symbol} set to the null string. To refer to
4035 @var{symbol} within the sequence of statements, use @var{\symbol}.
4037 For example, assembling
4045 is equivalent to assembling
4054 @section @code{.lcomm @var{symbol} , @var{length}}
4056 @cindex @code{lcomm} directive
4057 @cindex local common symbols
4058 @cindex symbols, local common
4059 Reserve @var{length} (an absolute expression) bytes for a local common
4060 denoted by @var{symbol}. The section and value of @var{symbol} are
4061 those of the new local common. The addresses are allocated in the bss
4062 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4063 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4064 not visible to @code{@value{LD}}.
4067 Some targets permit a third argument to be used with @code{.lcomm}. This
4068 argument specifies the desired alignment of the symbol in the bss section.
4072 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4073 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4077 @section @code{.lflags}
4079 @cindex @code{lflags} directive (ignored)
4080 @code{@value{AS}} accepts this directive, for compatibility with other
4081 assemblers, but ignores it.
4083 @ifclear no-line-dir
4085 @section @code{.line @var{line-number}}
4087 @cindex @code{line} directive
4091 @section @code{.ln @var{line-number}}
4093 @cindex @code{ln} directive
4095 @cindex logical line number
4097 Change the logical line number. @var{line-number} must be an absolute
4098 expression. The next line has that logical line number. Therefore any other
4099 statements on the current line (after a statement separator character) are
4100 reported as on logical line number @var{line-number} @minus{} 1. One day
4101 @code{@value{AS}} will no longer support this directive: it is recognized only
4102 for compatibility with existing assembler programs.
4106 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4107 not available; use the synonym @code{.ln} in that context.
4112 @ifclear no-line-dir
4113 Even though this is a directive associated with the @code{a.out} or
4114 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
4115 when producing COFF output, and treats @samp{.line} as though it
4116 were the COFF @samp{.ln} @emph{if} it is found outside a
4117 @code{.def}/@code{.endef} pair.
4119 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4120 used by compilers to generate auxiliary symbol information for
4125 @section @code{.linkonce [@var{type}]}
4127 @cindex @code{linkonce} directive
4128 @cindex common sections
4129 Mark the current section so that the linker only includes a single copy of it.
4130 This may be used to include the same section in several different object files,
4131 but ensure that the linker will only include it once in the final output file.
4132 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4133 Duplicate sections are detected based on the section name, so it should be
4136 This directive is only supported by a few object file formats; as of this
4137 writing, the only object file format which supports it is the Portable
4138 Executable format used on Windows NT.
4140 The @var{type} argument is optional. If specified, it must be one of the
4141 following strings. For example:
4145 Not all types may be supported on all object file formats.
4149 Silently discard duplicate sections. This is the default.
4152 Warn if there are duplicate sections, but still keep only one copy.
4155 Warn if any of the duplicates have different sizes.
4158 Warn if any of the duplicates do not have exactly the same contents.
4162 @section @code{.ln @var{line-number}}
4164 @cindex @code{ln} directive
4165 @ifclear no-line-dir
4166 @samp{.ln} is a synonym for @samp{.line}.
4169 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
4170 must be an absolute expression. The next line has that logical
4171 line number, so any other statements on the current line (after a
4172 statement separator character @code{;}) are reported as on logical
4173 line number @var{line-number} @minus{} 1.
4176 This directive is accepted, but ignored, when @code{@value{AS}} is
4177 configured for @code{b.out}; its effect is only associated with COFF
4183 @section @code{.mri @var{val}}
4185 @cindex @code{mri} directive
4186 @cindex MRI mode, temporarily
4187 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
4188 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
4189 affects code assembled until the next @code{.mri} directive, or until the end
4190 of the file. @xref{M, MRI mode, MRI mode}.
4193 @section @code{.list}
4195 @cindex @code{list} directive
4196 @cindex listing control, turning on
4197 Control (in conjunction with the @code{.nolist} directive) whether or
4198 not assembly listings are generated. These two directives maintain an
4199 internal counter (which is zero initially). @code{.list} increments the
4200 counter, and @code{.nolist} decrements it. Assembly listings are
4201 generated whenever the counter is greater than zero.
4203 By default, listings are disabled. When you enable them (with the
4204 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4205 the initial value of the listing counter is one.
4208 @section @code{.long @var{expressions}}
4210 @cindex @code{long} directive
4211 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4214 @c no one seems to know what this is for or whether this description is
4215 @c what it really ought to do
4217 @section @code{.lsym @var{symbol}, @var{expression}}
4219 @cindex @code{lsym} directive
4220 @cindex symbol, not referenced in assembly
4221 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4222 the hash table, ensuring it cannot be referenced by name during the
4223 rest of the assembly. This sets the attributes of the symbol to be
4224 the same as the expression value:
4226 @var{other} = @var{descriptor} = 0
4227 @var{type} = @r{(section of @var{expression})}
4228 @var{value} = @var{expression}
4231 The new symbol is not flagged as external.
4235 @section @code{.macro}
4238 The commands @code{.macro} and @code{.endm} allow you to define macros that
4239 generate assembly output. For example, this definition specifies a macro
4240 @code{sum} that puts a sequence of numbers into memory:
4243 .macro sum from=0, to=5
4252 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4264 @item .macro @var{macname}
4265 @itemx .macro @var{macname} @var{macargs} @dots{}
4266 @cindex @code{macro} directive
4267 Begin the definition of a macro called @var{macname}. If your macro
4268 definition requires arguments, specify their names after the macro name,
4269 separated by commas or spaces. You can supply a default value for any
4270 macro argument by following the name with @samp{=@var{deflt}}. For
4271 example, these are all valid @code{.macro} statements:
4275 Begin the definition of a macro called @code{comm}, which takes no
4278 @item .macro plus1 p, p1
4279 @itemx .macro plus1 p p1
4280 Either statement begins the definition of a macro called @code{plus1},
4281 which takes two arguments; within the macro definition, write
4282 @samp{\p} or @samp{\p1} to evaluate the arguments.
4284 @item .macro reserve_str p1=0 p2
4285 Begin the definition of a macro called @code{reserve_str}, with two
4286 arguments. The first argument has a default value, but not the second.
4287 After the definition is complete, you can call the macro either as
4288 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4289 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4290 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4291 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4294 When you call a macro, you can specify the argument values either by
4295 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4296 @samp{sum to=17, from=9}.
4299 @cindex @code{endm} directive
4300 Mark the end of a macro definition.
4303 @cindex @code{exitm} directive
4304 Exit early from the current macro definition.
4306 @cindex number of macros executed
4307 @cindex macros, count executed
4309 @code{@value{AS}} maintains a counter of how many macros it has
4310 executed in this pseudo-variable; you can copy that number to your
4311 output with @samp{\@@}, but @emph{only within a macro definition}.
4314 @item LOCAL @var{name} [ , @dots{} ]
4315 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4316 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4317 Alternate macro syntax}.
4319 Generate a string replacement for each of the @var{name} arguments, and
4320 replace any instances of @var{name} in each macro expansion. The
4321 replacement string is unique in the assembly, and different for each
4322 separate macro expansion. @code{LOCAL} allows you to write macros that
4323 define symbols, without fear of conflict between separate macro expansions.
4328 @section @code{.nolist}
4330 @cindex @code{nolist} directive
4331 @cindex listing control, turning off
4332 Control (in conjunction with the @code{.list} directive) whether or
4333 not assembly listings are generated. These two directives maintain an
4334 internal counter (which is zero initially). @code{.list} increments the
4335 counter, and @code{.nolist} decrements it. Assembly listings are
4336 generated whenever the counter is greater than zero.
4339 @section @code{.octa @var{bignums}}
4341 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4342 @cindex @code{octa} directive
4343 @cindex integer, 16-byte
4344 @cindex sixteen byte integer
4345 This directive expects zero or more bignums, separated by commas. For each
4346 bignum, it emits a 16-byte integer.
4348 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4349 hence @emph{octa}-word for 16 bytes.
4352 @section @code{.org @var{new-lc} , @var{fill}}
4354 @cindex @code{org} directive
4355 @cindex location counter, advancing
4356 @cindex advancing location counter
4357 @cindex current address, advancing
4358 Advance the location counter of the current section to
4359 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4360 expression with the same section as the current subsection. That is,
4361 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4362 wrong section, the @code{.org} directive is ignored. To be compatible
4363 with former assemblers, if the section of @var{new-lc} is absolute,
4364 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4365 is the same as the current subsection.
4367 @code{.org} may only increase the location counter, or leave it
4368 unchanged; you cannot use @code{.org} to move the location counter
4371 @c double negative used below "not undefined" because this is a specific
4372 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4373 @c section. doc@cygnus.com 18feb91
4374 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4375 may not be undefined. If you really detest this restriction we eagerly await
4376 a chance to share your improved assembler.
4378 Beware that the origin is relative to the start of the section, not
4379 to the start of the subsection. This is compatible with other
4380 people's assemblers.
4382 When the location counter (of the current subsection) is advanced, the
4383 intervening bytes are filled with @var{fill} which should be an
4384 absolute expression. If the comma and @var{fill} are omitted,
4385 @var{fill} defaults to zero.
4388 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4390 @cindex padding the location counter given a power of two
4391 @cindex @code{p2align} directive
4392 Pad the location counter (in the current subsection) to a particular
4393 storage boundary. The first expression (which must be absolute) is the
4394 number of low-order zero bits the location counter must have after
4395 advancement. For example @samp{.p2align 3} advances the location
4396 counter until it a multiple of 8. If the location counter is already a
4397 multiple of 8, no change is needed.
4399 The second expression (also absolute) gives the fill value to be stored in the
4400 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4401 padding bytes are normally zero. However, on some systems, if the section is
4402 marked as containing code and the fill value is omitted, the space is filled
4403 with no-op instructions.
4405 The third expression is also absolute, and is also optional. If it is present,
4406 it is the maximum number of bytes that should be skipped by this alignment
4407 directive. If doing the alignment would require skipping more bytes than the
4408 specified maximum, then the alignment is not done at all. You can omit the
4409 fill value (the second argument) entirely by simply using two commas after the
4410 required alignment; this can be useful if you want the alignment to be filled
4411 with no-op instructions when appropriate.
4413 @cindex @code{p2alignw} directive
4414 @cindex @code{p2alignl} directive
4415 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4416 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4417 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4418 fill pattern as a four byte longword value. For example, @code{.p2alignw
4419 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4420 filled in with the value 0x368d (the exact placement of the bytes depends upon
4421 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4426 @section @code{.previous}
4428 @cindex @code{.previous} directive
4429 @cindex Section Stack
4430 This is one of the ELF section stack manipulation directives. The others are
4431 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4432 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4433 (@pxref{PopSection}).
4435 This directive swaps the current section (and subsection) with most recently
4436 referenced section (and subsection) prior to this one. Multiple
4437 @code{.previous} directives in a row will flip between two sections (and their
4440 In terms of the section stack, this directive swaps the current section with
4441 the top section on the section stack.
4446 @section @code{.popsection}
4448 @cindex @code{.popsection} directive
4449 @cindex Section Stack
4450 This is one of the ELF section stack manipulation directives. The others are
4451 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4452 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4455 This directive replaces the current section (and subsection) with the top
4456 section (and subsection) on the section stack. This section is popped off the
4461 @section @code{.print @var{string}}
4463 @cindex @code{print} directive
4464 @code{@value{AS}} will print @var{string} on the standard output during
4465 assembly. You must put @var{string} in double quotes.
4469 @section @code{.protected @var{names}}
4471 @cindex @code{.protected} directive
4473 This one of the ELF visibility directives. The other two are
4474 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
4476 This directive overrides the named symbols default visibility (which is set by
4477 their binding: local, global or weak). The directive sets the visibility to
4478 @code{protected} which means that any references to the symbols from within the
4479 components that defines them must be resolved to the definition in that
4480 component, even if a definition in another component would normally preempt
4485 @section @code{.psize @var{lines} , @var{columns}}
4487 @cindex @code{psize} directive
4488 @cindex listing control: paper size
4489 @cindex paper size, for listings
4490 Use this directive to declare the number of lines---and, optionally, the
4491 number of columns---to use for each page, when generating listings.
4493 If you do not use @code{.psize}, listings use a default line-count
4494 of 60. You may omit the comma and @var{columns} specification; the
4495 default width is 200 columns.
4497 @code{@value{AS}} generates formfeeds whenever the specified number of
4498 lines is exceeded (or whenever you explicitly request one, using
4501 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4502 those explicitly specified with @code{.eject}.
4505 @section @code{.purgem @var{name}}
4507 @cindex @code{purgem} directive
4508 Undefine the macro @var{name}, so that later uses of the string will not be
4509 expanded. @xref{Macro}.
4513 @section @code{.pushsection @var{name} , @var{subsection}}
4515 @cindex @code{.pushsection} directive
4516 @cindex Section Stack
4517 This is one of the ELF section stack manipulation directives. The others are
4518 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4519 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
4522 This directive is a synonym for @code{.section}. It pushes the current section
4523 (and subsection) onto the top of the section stack, and then replaces the
4524 current section and subsection with @code{name} and @code{subsection}.
4528 @section @code{.quad @var{bignums}}
4530 @cindex @code{quad} directive
4531 @code{.quad} expects zero or more bignums, separated by commas. For
4532 each bignum, it emits
4534 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4535 warning message; and just takes the lowest order 8 bytes of the bignum.
4536 @cindex eight-byte integer
4537 @cindex integer, 8-byte
4539 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4540 hence @emph{quad}-word for 8 bytes.
4543 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4544 warning message; and just takes the lowest order 16 bytes of the bignum.
4545 @cindex sixteen-byte integer
4546 @cindex integer, 16-byte
4550 @section @code{.rept @var{count}}
4552 @cindex @code{rept} directive
4553 Repeat the sequence of lines between the @code{.rept} directive and the next
4554 @code{.endr} directive @var{count} times.
4556 For example, assembling
4564 is equivalent to assembling
4573 @section @code{.sbttl "@var{subheading}"}
4575 @cindex @code{sbttl} directive
4576 @cindex subtitles for listings
4577 @cindex listing control: subtitle
4578 Use @var{subheading} as the title (third line, immediately after the
4579 title line) when generating assembly listings.
4581 This directive affects subsequent pages, as well as the current page if
4582 it appears within ten lines of the top of a page.
4586 @section @code{.scl @var{class}}
4588 @cindex @code{scl} directive
4589 @cindex symbol storage class (COFF)
4590 @cindex COFF symbol storage class
4591 Set the storage-class value for a symbol. This directive may only be
4592 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4593 whether a symbol is static or external, or it may record further
4594 symbolic debugging information.
4597 The @samp{.scl} directive is primarily associated with COFF output; when
4598 configured to generate @code{b.out} output format, @code{@value{AS}}
4599 accepts this directive but ignores it.
4604 @section @code{.section @var{name}} (COFF version)
4606 @cindex @code{section} directive
4607 @cindex named section
4608 Use the @code{.section} directive to assemble the following code into a section
4611 This directive is only supported for targets that actually support arbitrarily
4612 named sections; on @code{a.out} targets, for example, it is not accepted, even
4613 with a standard @code{a.out} section name.
4615 For COFF targets, the @code{.section} directive is used in one of the following
4619 .section @var{name}[, "@var{flags}"]
4620 .section @var{name}[, @var{subsegment}]
4623 If the optional argument is quoted, it is taken as flags to use for the
4624 section. Each flag is a single character. The following flags are recognized:
4627 bss section (uninitialized data)
4629 section is not loaded
4639 shared section (meaningful for PE targets)
4642 If no flags are specified, the default flags depend upon the section name. If
4643 the section name is not recognized, the default will be for the section to be
4644 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
4645 from the section, rather than adding them, so if they are used on their own it
4646 will be as if no flags had been specified at all.
4648 If the optional argument to the @code{.section} directive is not quoted, it is
4649 taken as a subsegment number (@pxref{Sub-Sections}).
4652 @section @code{.section @var{name}} (ELF version)
4654 @cindex @code{section} directive
4655 @cindex named section
4657 @cindex Section Stack
4658 This is one of the ELF section stack manipulation directives. The others are
4659 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
4660 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
4661 @code{.previous} (@pxref{Previous}).
4664 For ELF targets, the @code{.section} directive is used like this:
4667 .section @var{name} [, "@var{flags}"[, @@@var{type}]]
4670 The optional @var{flags} argument is a quoted string which may contain any
4671 combination of the following characters:
4674 section is allocatable
4678 section is executable
4681 The optional @var{type} argument may contain one of the following constants:
4684 section contains data
4686 section does not contain data (i.e., section only occupies space)
4689 If no flags are specified, the default flags depend upon the section name. If
4690 the section name is not recognized, the default will be for the section to have
4691 none of the above flags: it will not be allocated in memory, nor writable, nor
4692 executable. The section will contain data.
4694 For ELF targets, the assembler supports another type of @code{.section}
4695 directive for compatibility with the Solaris assembler:
4698 .section "@var{name}"[, @var{flags}...]
4701 Note that the section name is quoted. There may be a sequence of comma
4705 section is allocatable
4709 section is executable
4712 This directive replaces the current section and subsection. The replaced
4713 section and subsection are pushed onto the section stack. See the contents of
4714 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
4715 how this directive and the other section stack directives work.
4718 @section @code{.set @var{symbol}, @var{expression}}
4720 @cindex @code{set} directive
4721 @cindex symbol value, setting
4722 Set the value of @var{symbol} to @var{expression}. This
4723 changes @var{symbol}'s value and type to conform to
4724 @var{expression}. If @var{symbol} was flagged as external, it remains
4725 flagged (@pxref{Symbol Attributes}).
4727 You may @code{.set} a symbol many times in the same assembly.
4729 If you @code{.set} a global symbol, the value stored in the object
4730 file is the last value stored into it.
4733 The syntax for @code{set} on the HPPA is
4734 @samp{@var{symbol} .set @var{expression}}.
4738 @section @code{.short @var{expressions}}
4740 @cindex @code{short} directive
4742 @code{.short} is normally the same as @samp{.word}.
4743 @xref{Word,,@code{.word}}.
4745 In some configurations, however, @code{.short} and @code{.word} generate
4746 numbers of different lengths; @pxref{Machine Dependencies}.
4750 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4753 This expects zero or more @var{expressions}, and emits
4754 a 16 bit number for each.
4759 @section @code{.single @var{flonums}}
4761 @cindex @code{single} directive
4762 @cindex floating point numbers (single)
4763 This directive assembles zero or more flonums, separated by commas. It
4764 has the same effect as @code{.float}.
4766 The exact kind of floating point numbers emitted depends on how
4767 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4771 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4772 numbers in @sc{ieee} format.
4777 @section @code{.size} (COFF version)
4779 @cindex @code{size} directive
4780 This directive is generated by compilers to include auxiliary debugging
4781 information in the symbol table. It is only permitted inside
4782 @code{.def}/@code{.endef} pairs.
4785 @samp{.size} is only meaningful when generating COFF format output; when
4786 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4790 @section @code{.size @var{name} , @var{expression}} (ELF version)
4791 @cindex @code{size} directive
4793 This directive is used to set the size associated with a symbol @var{name}.
4794 The size in bytes is computed from @var{expression} which can make use of label
4795 arithmetic. This directive is typically used to set the size of function
4799 @section @code{.sleb128 @var{expressions}}
4801 @cindex @code{sleb128} directive
4802 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4803 compact, variable length representation of numbers used by the DWARF
4804 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
4806 @ifclear no-space-dir
4808 @section @code{.skip @var{size} , @var{fill}}
4810 @cindex @code{skip} directive
4811 @cindex filling memory
4812 This directive emits @var{size} bytes, each of value @var{fill}. Both
4813 @var{size} and @var{fill} are absolute expressions. If the comma and
4814 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4818 @section @code{.space @var{size} , @var{fill}}
4820 @cindex @code{space} directive
4821 @cindex filling memory
4822 This directive emits @var{size} bytes, each of value @var{fill}. Both
4823 @var{size} and @var{fill} are absolute expressions. If the comma
4824 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4829 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4830 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4831 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4832 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4841 @section @code{.space}
4842 @cindex @code{space} directive
4844 On the AMD 29K, this directive is ignored; it is accepted for
4845 compatibility with other AMD 29K assemblers.
4848 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4849 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4855 @section @code{.stabd, .stabn, .stabs}
4857 @cindex symbolic debuggers, information for
4858 @cindex @code{stab@var{x}} directives
4859 There are three directives that begin @samp{.stab}.
4860 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4861 The symbols are not entered in the @code{@value{AS}} hash table: they
4862 cannot be referenced elsewhere in the source file.
4863 Up to five fields are required:
4867 This is the symbol's name. It may contain any character except
4868 @samp{\000}, so is more general than ordinary symbol names. Some
4869 debuggers used to code arbitrarily complex structures into symbol names
4873 An absolute expression. The symbol's type is set to the low 8 bits of
4874 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4875 and debuggers choke on silly bit patterns.
4878 An absolute expression. The symbol's ``other'' attribute is set to the
4879 low 8 bits of this expression.
4882 An absolute expression. The symbol's descriptor is set to the low 16
4883 bits of this expression.
4886 An absolute expression which becomes the symbol's value.
4889 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4890 or @code{.stabs} statement, the symbol has probably already been created;
4891 you get a half-formed symbol in your object file. This is
4892 compatible with earlier assemblers!
4895 @cindex @code{stabd} directive
4896 @item .stabd @var{type} , @var{other} , @var{desc}
4898 The ``name'' of the symbol generated is not even an empty string.
4899 It is a null pointer, for compatibility. Older assemblers used a
4900 null pointer so they didn't waste space in object files with empty
4903 The symbol's value is set to the location counter,
4904 relocatably. When your program is linked, the value of this symbol
4905 is the address of the location counter when the @code{.stabd} was
4908 @cindex @code{stabn} directive
4909 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4910 The name of the symbol is set to the empty string @code{""}.
4912 @cindex @code{stabs} directive
4913 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4914 All five fields are specified.
4920 @section @code{.string} "@var{str}"
4922 @cindex string, copying to object file
4923 @cindex @code{string} directive
4925 Copy the characters in @var{str} to the object file. You may specify more than
4926 one string to copy, separated by commas. Unless otherwise specified for a
4927 particular machine, the assembler marks the end of each string with a 0 byte.
4928 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4931 @section @code{.struct @var{expression}}
4933 @cindex @code{struct} directive
4934 Switch to the absolute section, and set the section offset to @var{expression},
4935 which must be an absolute expression. You might use this as follows:
4944 This would define the symbol @code{field1} to have the value 0, the symbol
4945 @code{field2} to have the value 4, and the symbol @code{field3} to have the
4946 value 8. Assembly would be left in the absolute section, and you would need to
4947 use a @code{.section} directive of some sort to change to some other section
4948 before further assembly.
4952 @section @code{.subsection @var{name}}
4954 @cindex @code{.subsection} directive
4955 @cindex Section Stack
4956 This is one of the ELF section stack manipulation directives. The others are
4957 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
4958 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
4961 This directive replaces the current subsection with @code{name}. The current
4962 section is not changed. The replaced subsection is put onto the section stack
4963 in place of the then current top of stack subsection.
4968 @section @code{.symver}
4969 @cindex @code{symver} directive
4970 @cindex symbol versioning
4971 @cindex versions of symbols
4972 Use the @code{.symver} directive to bind symbols to specific version nodes
4973 within a source file. This is only supported on ELF platforms, and is
4974 typically used when assembling files to be linked into a shared library.
4975 There are cases where it may make sense to use this in objects to be bound
4976 into an application itself so as to override a versioned symbol from a
4979 For ELF targets, the @code{.symver} directive can be used like this:
4981 .symver @var{name}, @var{name2@@nodename}
4983 If the symbol @var{name} is defined within the file
4984 being assembled, the @code{.symver} directive effectively creates a symbol
4985 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4986 just don't try and create a regular alias is that the @var{@@} character isn't
4987 permitted in symbol names. The @var{name2} part of the name is the actual name
4988 of the symbol by which it will be externally referenced. The name @var{name}
4989 itself is merely a name of convenience that is used so that it is possible to
4990 have definitions for multiple versions of a function within a single source
4991 file, and so that the compiler can unambiguously know which version of a
4992 function is being mentioned. The @var{nodename} portion of the alias should be
4993 the name of a node specified in the version script supplied to the linker when
4994 building a shared library. If you are attempting to override a versioned
4995 symbol from a shared library, then @var{nodename} should correspond to the
4996 nodename of the symbol you are trying to override.
4998 If the symbol @var{name} is not defined within the file being assembled, all
4999 references to @var{name} will be changed to @var{name2@@nodename}. If no
5000 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5003 Another usage of the @code{.symver} directive is:
5005 .symver @var{name}, @var{name2@@@@nodename}
5007 In this case, the symbol @var{name} must exist and be defined within
5008 the file being assembled. It is similar to @var{name2@@nodename}. The
5009 difference is @var{name2@@@@nodename} will also be used to resolve
5010 references to @var{name2} by the linker.
5012 The third usage of the @code{.symver} directive is:
5014 .symver @var{name}, @var{name2@@@@@@nodename}
5016 When @var{name} is not defined within the
5017 file being assembled, it is treated as @var{name2@@nodename}. When
5018 @var{name} is defined within the file being assembled, the symbol
5019 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5024 @section @code{.tag @var{structname}}
5026 @cindex COFF structure debugging
5027 @cindex structure debugging, COFF
5028 @cindex @code{tag} directive
5029 This directive is generated by compilers to include auxiliary debugging
5030 information in the symbol table. It is only permitted inside
5031 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5032 definitions in the symbol table with instances of those structures.
5035 @samp{.tag} is only used when generating COFF format output; when
5036 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
5042 @section @code{.text @var{subsection}}
5044 @cindex @code{text} directive
5045 Tells @code{@value{AS}} to assemble the following statements onto the end of
5046 the text subsection numbered @var{subsection}, which is an absolute
5047 expression. If @var{subsection} is omitted, subsection number zero
5051 @section @code{.title "@var{heading}"}
5053 @cindex @code{title} directive
5054 @cindex listing control: title line
5055 Use @var{heading} as the title (second line, immediately after the
5056 source file name and pagenumber) when generating assembly listings.
5058 This directive affects subsequent pages, as well as the current page if
5059 it appears within ten lines of the top of a page.
5062 @section @code{.type @var{int}} (COFF version)
5064 @cindex COFF symbol type
5065 @cindex symbol type, COFF
5066 @cindex @code{type} directive
5067 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5068 records the integer @var{int} as the type attribute of a symbol table entry.
5071 @samp{.type} is associated only with COFF format output; when
5072 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
5073 directive but ignores it.
5076 @section @code{.type @var{name} , @var{type description}} (ELF version)
5078 @cindex ELF symbol type
5079 @cindex symbol type, ELF
5080 @cindex @code{type} directive
5081 This directive is used to set the type of symbol @var{name} to be either a
5082 function symbol or an object symbol. There are five different syntaxes
5083 supported for the @var{type description} field, in order to provide
5084 compatibility with various other assemblers. The syntaxes supported are:
5087 .type <name>,#function
5088 .type <name>,#object
5090 .type <name>,@@function
5091 .type <name>,@@object
5093 .type <name>,%function
5094 .type <name>,%object
5096 .type <name>,"function"
5097 .type <name>,"object"
5099 .type <name> STT_FUNCTION
5100 .type <name> STT_OBJECT
5104 @section @code{.uleb128 @var{expressions}}
5106 @cindex @code{uleb128} directive
5107 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5108 compact, variable length representation of numbers used by the DWARF
5109 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5113 @section @code{.val @var{addr}}
5115 @cindex @code{val} directive
5116 @cindex COFF value attribute
5117 @cindex value attribute, COFF
5118 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5119 records the address @var{addr} as the value attribute of a symbol table
5123 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
5124 configured for @code{b.out}, it accepts this directive but ignores it.
5130 @section @code{.version "@var{string}"}
5132 @cindex @code{.version}
5133 This directive creates a @code{.note} section and places into it an ELF
5134 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5139 @section @code{.vtable_entry @var{table}, @var{offset}}
5141 @cindex @code{.vtable_entry}
5142 This directive finds or creates a symbol @code{table} and creates a
5143 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5146 @section @code{.vtable_inherit @var{child}, @var{parent}}
5148 @cindex @code{.vtable_inherit}
5149 This directive finds the symbol @code{child} and finds or creates the symbol
5150 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5151 parent whose addend is the value of the child symbol. As a special case the
5152 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5157 @section @code{.weak @var{names}}
5159 @cindex @code{.weak}
5160 This directive sets the weak attribute on the comma separated list of symbol
5161 @code{names}. If the symbols do not already exist, they will be created.
5165 @section @code{.word @var{expressions}}
5167 @cindex @code{word} directive
5168 This directive expects zero or more @var{expressions}, of any section,
5169 separated by commas.
5172 For each expression, @code{@value{AS}} emits a 32-bit number.
5175 For each expression, @code{@value{AS}} emits a 16-bit number.
5180 The size of the number emitted, and its byte order,
5181 depend on what target computer the assembly is for.
5184 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5185 @c happen---32-bit addressability, period; no long/short jumps.
5186 @ifset DIFF-TBL-KLUGE
5187 @cindex difference tables altered
5188 @cindex altered difference tables
5190 @emph{Warning: Special Treatment to support Compilers}
5194 Machines with a 32-bit address space, but that do less than 32-bit
5195 addressing, require the following special treatment. If the machine of
5196 interest to you does 32-bit addressing (or doesn't require it;
5197 @pxref{Machine Dependencies}), you can ignore this issue.
5200 In order to assemble compiler output into something that works,
5201 @code{@value{AS}} occasionally does strange things to @samp{.word} directives.
5202 Directives of the form @samp{.word sym1-sym2} are often emitted by
5203 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
5204 directive of the form @samp{.word sym1-sym2}, and the difference between
5205 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
5206 creates a @dfn{secondary jump table}, immediately before the next label.
5207 This secondary jump table is preceded by a short-jump to the
5208 first byte after the secondary table. This short-jump prevents the flow
5209 of control from accidentally falling into the new table. Inside the
5210 table is a long-jump to @code{sym2}. The original @samp{.word}
5211 contains @code{sym1} minus the address of the long-jump to
5214 If there were several occurrences of @samp{.word sym1-sym2} before the
5215 secondary jump table, all of them are adjusted. If there was a
5216 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5217 long-jump to @code{sym4} is included in the secondary jump table,
5218 and the @code{.word} directives are adjusted to contain @code{sym3}
5219 minus the address of the long-jump to @code{sym4}; and so on, for as many
5220 entries in the original jump table as necessary.
5223 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
5224 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5225 assembly language programmers.
5228 @c end DIFF-TBL-KLUGE
5231 @section Deprecated Directives
5233 @cindex deprecated directives
5234 @cindex obsolescent directives
5235 One day these directives won't work.
5236 They are included for compatibility with older assemblers.
5243 @node Machine Dependencies
5244 @chapter Machine Dependent Features
5246 @cindex machine dependencies
5247 The machine instruction sets are (almost by definition) different on
5248 each machine where @code{@value{AS}} runs. Floating point representations
5249 vary as well, and @code{@value{AS}} often supports a few additional
5250 directives or command-line options for compatibility with other
5251 assemblers on a particular platform. Finally, some versions of
5252 @code{@value{AS}} support special pseudo-instructions for branch
5255 This chapter discusses most of these differences, though it does not
5256 include details on any machine's instruction set. For details on that
5257 subject, see the hardware manufacturer's manual.
5261 * AMD29K-Dependent:: AMD 29K Dependent Features
5264 * ARC-Dependent:: ARC Dependent Features
5267 * ARM-Dependent:: ARM Dependent Features
5270 * D10V-Dependent:: D10V Dependent Features
5273 * D30V-Dependent:: D30V Dependent Features
5276 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5279 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5282 * HPPA-Dependent:: HPPA Dependent Features
5285 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5288 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5291 * i860-Dependent:: Intel 80860 Dependent Features
5294 * i960-Dependent:: Intel 80960 Dependent Features
5297 * M32R-Dependent:: M32R Dependent Features
5300 * M68K-Dependent:: M680x0 Dependent Features
5303 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5306 * MIPS-Dependent:: MIPS Dependent Features
5309 * SH-Dependent:: Hitachi SH Dependent Features
5312 * PDP-11-Dependent:: PDP-11 Dependent Features
5315 * PJ-Dependent:: picoJava Dependent Features
5318 * Sparc-Dependent:: SPARC Dependent Features
5321 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5324 * V850-Dependent:: V850 Dependent Features
5327 * Z8000-Dependent:: Z8000 Dependent Features
5330 * Vax-Dependent:: VAX Dependent Features
5337 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5338 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5339 @c peculiarity: to preserve cross-references, there must be a node called
5340 @c "Machine Dependencies". Hence the conditional nodenames in each
5341 @c major node below. Node defaulting in makeinfo requires adjacency of
5342 @c node and sectioning commands; hence the repetition of @chapter BLAH
5343 @c in both conditional blocks.
5350 @include c-a29k.texi
5359 @node Machine Dependencies
5360 @chapter Machine Dependent Features
5362 The machine instruction sets are different on each Hitachi chip family,
5363 and there are also some syntax differences among the families. This
5364 chapter describes the specific @code{@value{AS}} features for each
5368 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5369 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5370 * SH-Dependent:: Hitachi SH Dependent Features
5377 @include c-d10v.texi
5381 @include c-d30v.texi
5385 @include c-h8300.texi
5389 @include c-h8500.texi
5393 @include c-hppa.texi
5397 @include c-i370.texi
5401 @include c-i386.texi
5405 @include c-i860.texi
5409 @include c-i960.texi
5413 @include c-m32r.texi
5417 @include c-m68k.texi
5421 @include c-m68hc11.texi
5425 @include c-mips.texi
5429 @include c-ns32k.texi
5433 @include c-pdp11.texi
5445 @include c-sparc.texi
5449 @include c-tic54x.texi
5461 @include c-v850.texi
5465 @c reverse effect of @down at top of generic Machine-Dep chapter
5469 @node Reporting Bugs
5470 @chapter Reporting Bugs
5471 @cindex bugs in assembler
5472 @cindex reporting bugs in assembler
5474 Your bug reports play an essential role in making @code{@value{AS}} reliable.
5476 Reporting a bug may help you by bringing a solution to your problem, or it may
5477 not. But in any case the principal function of a bug report is to help the
5478 entire community by making the next version of @code{@value{AS}} work better.
5479 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
5481 In order for a bug report to serve its purpose, you must include the
5482 information that enables us to fix the bug.
5485 * Bug Criteria:: Have you found a bug?
5486 * Bug Reporting:: How to report bugs
5490 @section Have you found a bug?
5491 @cindex bug criteria
5493 If you are not sure whether you have found a bug, here are some guidelines:
5496 @cindex fatal signal
5497 @cindex assembler crash
5498 @cindex crash of assembler
5500 If the assembler gets a fatal signal, for any input whatever, that is a
5501 @code{@value{AS}} bug. Reliable assemblers never crash.
5503 @cindex error on valid input
5505 If @code{@value{AS}} produces an error message for valid input, that is a bug.
5507 @cindex invalid input
5509 If @code{@value{AS}} does not produce an error message for invalid input, that
5510 is a bug. However, you should note that your idea of ``invalid input'' might
5511 be our idea of ``an extension'' or ``support for traditional practice''.
5514 If you are an experienced user of assemblers, your suggestions for improvement
5515 of @code{@value{AS}} are welcome in any case.
5519 @section How to report bugs
5521 @cindex assembler bugs, reporting
5523 A number of companies and individuals offer support for @sc{gnu} products. If
5524 you obtained @code{@value{AS}} from a support organization, we recommend you
5525 contact that organization first.
5527 You can find contact information for many support companies and
5528 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5531 In any event, we also recommend that you send bug reports for @code{@value{AS}}
5532 to @samp{bug-binutils@@gnu.org}.
5534 The fundamental principle of reporting bugs usefully is this:
5535 @strong{report all the facts}. If you are not sure whether to state a
5536 fact or leave it out, state it!
5538 Often people omit facts because they think they know what causes the problem
5539 and assume that some details do not matter. Thus, you might assume that the
5540 name of a symbol you use in an example does not matter. Well, probably it does
5541 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5542 happens to fetch from the location where that name is stored in memory;
5543 perhaps, if the name were different, the contents of that location would fool
5544 the assembler into doing the right thing despite the bug. Play it safe and
5545 give a specific, complete example. That is the easiest thing for you to do,
5546 and the most helpful.
5548 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5549 it is new to us. Therefore, always write your bug reports on the assumption
5550 that the bug has not been reported previously.
5552 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5553 bell?'' Those bug reports are useless, and we urge everyone to
5554 @emph{refuse to respond to them} except to chide the sender to report
5557 To enable us to fix the bug, you should include all these things:
5561 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
5562 it with the @samp{--version} argument.
5564 Without this, we will not know whether there is any point in looking for
5565 the bug in the current version of @code{@value{AS}}.
5568 Any patches you may have applied to the @code{@value{AS}} source.
5571 The type of machine you are using, and the operating system name and
5575 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
5579 The command arguments you gave the assembler to assemble your example and
5580 observe the bug. To guarantee you will not omit something important, list them
5581 all. A copy of the Makefile (or the output from make) is sufficient.
5583 If we were to try to guess the arguments, we would probably guess wrong
5584 and then we might not encounter the bug.
5587 A complete input file that will reproduce the bug. If the bug is observed when
5588 the assembler is invoked via a compiler, send the assembler source, not the
5589 high level language source. Most compilers will produce the assembler source
5590 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5591 the options @samp{-v --save-temps}; this will save the assembler source in a
5592 file with an extension of @file{.s}, and also show you exactly how
5593 @code{@value{AS}} is being run.
5596 A description of what behavior you observe that you believe is
5597 incorrect. For example, ``It gets a fatal signal.''
5599 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
5600 will certainly notice it. But if the bug is incorrect output, we might not
5601 notice unless it is glaringly wrong. You might as well not give us a chance to
5604 Even if the problem you experience is a fatal signal, you should still say so
5605 explicitly. Suppose something strange is going on, such as, your copy of
5606 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
5607 library on your system. (This has happened!) Your copy might crash and ours
5608 would not. If you told us to expect a crash, then when ours fails to crash, we
5609 would know that the bug was not happening for us. If you had not told us to
5610 expect a crash, then we would not be able to draw any conclusion from our
5614 If you wish to suggest changes to the @code{@value{AS}} source, send us context
5615 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
5616 option. Always send diffs from the old file to the new file. If you even
5617 discuss something in the @code{@value{AS}} source, refer to it by context, not
5620 The line numbers in our development sources will not match those in your
5621 sources. Your line numbers would convey no useful information to us.
5624 Here are some things that are not necessary:
5628 A description of the envelope of the bug.
5630 Often people who encounter a bug spend a lot of time investigating
5631 which changes to the input file will make the bug go away and which
5632 changes will not affect it.
5634 This is often time consuming and not very useful, because the way we
5635 will find the bug is by running a single example under the debugger
5636 with breakpoints, not by pure deduction from a series of examples.
5637 We recommend that you save your time for something else.
5639 Of course, if you can find a simpler example to report @emph{instead}
5640 of the original one, that is a convenience for us. Errors in the
5641 output will be easier to spot, running under the debugger will take
5642 less time, and so on.
5644 However, simplification is not vital; if you do not want to do this,
5645 report the bug anyway and send us the entire test case you used.
5648 A patch for the bug.
5650 A patch for the bug does help us if it is a good one. But do not omit
5651 the necessary information, such as the test case, on the assumption that
5652 a patch is all we need. We might see problems with your patch and decide
5653 to fix the problem another way, or we might not understand it at all.
5655 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5656 construct an example that will make the program follow a certain path through
5657 the code. If you do not send us the example, we will not be able to construct
5658 one, so we will not be able to verify that the bug is fixed.
5660 And if we cannot understand what bug you are trying to fix, or why your
5661 patch should be an improvement, we will not install it. A test case will
5662 help us to understand.
5665 A guess about what the bug is or what it depends on.
5667 Such guesses are usually wrong. Even we cannot guess right about such
5668 things without first using the debugger to find the facts.
5671 @node Acknowledgements
5672 @chapter Acknowledgements
5674 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5675 it is not meant as a slight. We just don't know about it. Send mail to the
5676 maintainer, and we'll correct the situation. Currently
5678 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5680 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5683 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5684 information and the 68k series machines, most of the preprocessing pass, and
5685 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5687 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5688 many bug fixes, including merging support for several processors, breaking GAS
5689 up to handle multiple object file format back ends (including heavy rewrite,
5690 testing, an integration of the coff and b.out back ends), adding configuration
5691 including heavy testing and verification of cross assemblers and file splits
5692 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5693 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5694 port (including considerable amounts of reverse engineering), a SPARC opcode
5695 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5696 assertions and made them work, much other reorganization, cleanup, and lint.
5698 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5699 in format-specific I/O modules.
5701 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5702 has done much work with it since.
5704 The Intel 80386 machine description was written by Eliot Dresselhaus.
5706 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5708 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5709 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5711 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5712 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5713 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5714 support a.out format.
5716 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5717 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5718 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5719 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5722 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5723 simplified the configuration of which versions accept which directives. He
5724 updated the 68k machine description so that Motorola's opcodes always produced
5725 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5726 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5727 cross-compilation support, and one bug in relaxation that took a week and
5728 required the proverbial one-bit fix.
5730 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5731 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5732 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5733 PowerPC assembler, and made a few other minor patches.
5735 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5737 Hewlett-Packard contributed support for the HP9000/300.
5739 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5740 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5741 formats). This work was supported by both the Center for Software Science at
5742 the University of Utah and Cygnus Support.
5744 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5745 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5746 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5747 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5748 and some initial 64-bit support).
5750 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
5752 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5753 support for openVMS/Alpha.
5755 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
5758 Several engineers at Cygnus Support have also provided many small bug fixes and
5759 configuration enhancements.
5761 Many others have contributed large or small bugfixes and enhancements. If
5762 you have contributed significant work and are not mentioned on this list, and
5763 want to be, let us know. Some of the history has been lost; we are not
5764 intentionally leaving anyone out.
5766 @node GNU Free Documentation License
5767 @chapter GNU Free Documentation License
5769 GNU Free Documentation License
5771 Version 1.1, March 2000
5773 Copyright (C) 2000 Free Software Foundation, Inc.
5774 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
5776 Everyone is permitted to copy and distribute verbatim copies
5777 of this license document, but changing it is not allowed.
5782 The purpose of this License is to make a manual, textbook, or other
5783 written document "free" in the sense of freedom: to assure everyone
5784 the effective freedom to copy and redistribute it, with or without
5785 modifying it, either commercially or noncommercially. Secondarily,
5786 this License preserves for the author and publisher a way to get
5787 credit for their work, while not being considered responsible for
5788 modifications made by others.
5790 This License is a kind of "copyleft", which means that derivative
5791 works of the document must themselves be free in the same sense. It
5792 complements the GNU General Public License, which is a copyleft
5793 license designed for free software.
5795 We have designed this License in order to use it for manuals for free
5796 software, because free software needs free documentation: a free
5797 program should come with manuals providing the same freedoms that the
5798 software does. But this License is not limited to software manuals;
5799 it can be used for any textual work, regardless of subject matter or
5800 whether it is published as a printed book. We recommend this License
5801 principally for works whose purpose is instruction or reference.
5804 1. APPLICABILITY AND DEFINITIONS
5806 This License applies to any manual or other work that contains a
5807 notice placed by the copyright holder saying it can be distributed
5808 under the terms of this License. The "Document", below, refers to any
5809 such manual or work. Any member of the public is a licensee, and is
5812 A "Modified Version" of the Document means any work containing the
5813 Document or a portion of it, either copied verbatim, or with
5814 modifications and/or translated into another language.
5816 A "Secondary Section" is a named appendix or a front-matter section of
5817 the Document that deals exclusively with the relationship of the
5818 publishers or authors of the Document to the Document's overall subject
5819 (or to related matters) and contains nothing that could fall directly
5820 within that overall subject. (For example, if the Document is in part a
5821 textbook of mathematics, a Secondary Section may not explain any
5822 mathematics.) The relationship could be a matter of historical
5823 connection with the subject or with related matters, or of legal,
5824 commercial, philosophical, ethical or political position regarding
5827 The "Invariant Sections" are certain Secondary Sections whose titles
5828 are designated, as being those of Invariant Sections, in the notice
5829 that says that the Document is released under this License.
5831 The "Cover Texts" are certain short passages of text that are listed,
5832 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
5833 the Document is released under this License.
5835 A "Transparent" copy of the Document means a machine-readable copy,
5836 represented in a format whose specification is available to the
5837 general public, whose contents can be viewed and edited directly and
5838 straightforwardly with generic text editors or (for images composed of
5839 pixels) generic paint programs or (for drawings) some widely available
5840 drawing editor, and that is suitable for input to text formatters or
5841 for automatic translation to a variety of formats suitable for input
5842 to text formatters. A copy made in an otherwise Transparent file
5843 format whose markup has been designed to thwart or discourage
5844 subsequent modification by readers is not Transparent. A copy that is
5845 not "Transparent" is called "Opaque".
5847 Examples of suitable formats for Transparent copies include plain
5848 ASCII without markup, Texinfo input format, LaTeX input format, SGML
5849 or XML using a publicly available DTD, and standard-conforming simple
5850 HTML designed for human modification. Opaque formats include
5851 PostScript, PDF, proprietary formats that can be read and edited only
5852 by proprietary word processors, SGML or XML for which the DTD and/or
5853 processing tools are not generally available, and the
5854 machine-generated HTML produced by some word processors for output
5857 The "Title Page" means, for a printed book, the title page itself,
5858 plus such following pages as are needed to hold, legibly, the material
5859 this License requires to appear in the title page. For works in
5860 formats which do not have any title page as such, "Title Page" means
5861 the text near the most prominent appearance of the work's title,
5862 preceding the beginning of the body of the text.
5867 You may copy and distribute the Document in any medium, either
5868 commercially or noncommercially, provided that this License, the
5869 copyright notices, and the license notice saying this License applies
5870 to the Document are reproduced in all copies, and that you add no other
5871 conditions whatsoever to those of this License. You may not use
5872 technical measures to obstruct or control the reading or further
5873 copying of the copies you make or distribute. However, you may accept
5874 compensation in exchange for copies. If you distribute a large enough
5875 number of copies you must also follow the conditions in section 3.
5877 You may also lend copies, under the same conditions stated above, and
5878 you may publicly display copies.
5881 3. COPYING IN QUANTITY
5883 If you publish printed copies of the Document numbering more than 100,
5884 and the Document's license notice requires Cover Texts, you must enclose
5885 the copies in covers that carry, clearly and legibly, all these Cover
5886 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
5887 the back cover. Both covers must also clearly and legibly identify
5888 you as the publisher of these copies. The front cover must present
5889 the full title with all words of the title equally prominent and
5890 visible. You may add other material on the covers in addition.
5891 Copying with changes limited to the covers, as long as they preserve
5892 the title of the Document and satisfy these conditions, can be treated
5893 as verbatim copying in other respects.
5895 If the required texts for either cover are too voluminous to fit
5896 legibly, you should put the first ones listed (as many as fit
5897 reasonably) on the actual cover, and continue the rest onto adjacent
5900 If you publish or distribute Opaque copies of the Document numbering
5901 more than 100, you must either include a machine-readable Transparent
5902 copy along with each Opaque copy, or state in or with each Opaque copy
5903 a publicly-accessible computer-network location containing a complete
5904 Transparent copy of the Document, free of added material, which the
5905 general network-using public has access to download anonymously at no
5906 charge using public-standard network protocols. If you use the latter
5907 option, you must take reasonably prudent steps, when you begin
5908 distribution of Opaque copies in quantity, to ensure that this
5909 Transparent copy will remain thus accessible at the stated location
5910 until at least one year after the last time you distribute an Opaque
5911 copy (directly or through your agents or retailers) of that edition to
5914 It is requested, but not required, that you contact the authors of the
5915 Document well before redistributing any large number of copies, to give
5916 them a chance to provide you with an updated version of the Document.
5921 You may copy and distribute a Modified Version of the Document under
5922 the conditions of sections 2 and 3 above, provided that you release
5923 the Modified Version under precisely this License, with the Modified
5924 Version filling the role of the Document, thus licensing distribution
5925 and modification of the Modified Version to whoever possesses a copy
5926 of it. In addition, you must do these things in the Modified Version:
5928 A. Use in the Title Page (and on the covers, if any) a title distinct
5929 from that of the Document, and from those of previous versions
5930 (which should, if there were any, be listed in the History section
5931 of the Document). You may use the same title as a previous version
5932 if the original publisher of that version gives permission.
5933 B. List on the Title Page, as authors, one or more persons or entities
5934 responsible for authorship of the modifications in the Modified
5935 Version, together with at least five of the principal authors of the
5936 Document (all of its principal authors, if it has less than five).
5937 C. State on the Title page the name of the publisher of the
5938 Modified Version, as the publisher.
5939 D. Preserve all the copyright notices of the Document.
5940 E. Add an appropriate copyright notice for your modifications
5941 adjacent to the other copyright notices.
5942 F. Include, immediately after the copyright notices, a license notice
5943 giving the public permission to use the Modified Version under the
5944 terms of this License, in the form shown in the Addendum below.
5945 G. Preserve in that license notice the full lists of Invariant Sections
5946 and required Cover Texts given in the Document's license notice.
5947 H. Include an unaltered copy of this License.
5948 I. Preserve the section entitled "History", and its title, and add to
5949 it an item stating at least the title, year, new authors, and
5950 publisher of the Modified Version as given on the Title Page. If
5951 there is no section entitled "History" in the Document, create one
5952 stating the title, year, authors, and publisher of the Document as
5953 given on its Title Page, then add an item describing the Modified
5954 Version as stated in the previous sentence.
5955 J. Preserve the network location, if any, given in the Document for
5956 public access to a Transparent copy of the Document, and likewise
5957 the network locations given in the Document for previous versions
5958 it was based on. These may be placed in the "History" section.
5959 You may omit a network location for a work that was published at
5960 least four years before the Document itself, or if the original
5961 publisher of the version it refers to gives permission.
5962 K. In any section entitled "Acknowledgements" or "Dedications",
5963 preserve the section's title, and preserve in the section all the
5964 substance and tone of each of the contributor acknowledgements
5965 and/or dedications given therein.
5966 L. Preserve all the Invariant Sections of the Document,
5967 unaltered in their text and in their titles. Section numbers
5968 or the equivalent are not considered part of the section titles.
5969 M. Delete any section entitled "Endorsements". Such a section
5970 may not be included in the Modified Version.
5971 N. Do not retitle any existing section as "Endorsements"
5972 or to conflict in title with any Invariant Section.
5974 If the Modified Version includes new front-matter sections or
5975 appendices that qualify as Secondary Sections and contain no material
5976 copied from the Document, you may at your option designate some or all
5977 of these sections as invariant. To do this, add their titles to the
5978 list of Invariant Sections in the Modified Version's license notice.
5979 These titles must be distinct from any other section titles.
5981 You may add a section entitled "Endorsements", provided it contains
5982 nothing but endorsements of your Modified Version by various
5983 parties--for example, statements of peer review or that the text has
5984 been approved by an organization as the authoritative definition of a
5987 You may add a passage of up to five words as a Front-Cover Text, and a
5988 passage of up to 25 words as a Back-Cover Text, to the end of the list
5989 of Cover Texts in the Modified Version. Only one passage of
5990 Front-Cover Text and one of Back-Cover Text may be added by (or
5991 through arrangements made by) any one entity. If the Document already
5992 includes a cover text for the same cover, previously added by you or
5993 by arrangement made by the same entity you are acting on behalf of,
5994 you may not add another; but you may replace the old one, on explicit
5995 permission from the previous publisher that added the old one.
5997 The author(s) and publisher(s) of the Document do not by this License
5998 give permission to use their names for publicity for or to assert or
5999 imply endorsement of any Modified Version.
6002 5. COMBINING DOCUMENTS
6004 You may combine the Document with other documents released under this
6005 License, under the terms defined in section 4 above for modified
6006 versions, provided that you include in the combination all of the
6007 Invariant Sections of all of the original documents, unmodified, and
6008 list them all as Invariant Sections of your combined work in its
6011 The combined work need only contain one copy of this License, and
6012 multiple identical Invariant Sections may be replaced with a single
6013 copy. If there are multiple Invariant Sections with the same name but
6014 different contents, make the title of each such section unique by
6015 adding at the end of it, in parentheses, the name of the original
6016 author or publisher of that section if known, or else a unique number.
6017 Make the same adjustment to the section titles in the list of
6018 Invariant Sections in the license notice of the combined work.
6020 In the combination, you must combine any sections entitled "History"
6021 in the various original documents, forming one section entitled
6022 "History"; likewise combine any sections entitled "Acknowledgements",
6023 and any sections entitled "Dedications". You must delete all sections
6024 entitled "Endorsements."
6027 6. COLLECTIONS OF DOCUMENTS
6029 You may make a collection consisting of the Document and other documents
6030 released under this License, and replace the individual copies of this
6031 License in the various documents with a single copy that is included in
6032 the collection, provided that you follow the rules of this License for
6033 verbatim copying of each of the documents in all other respects.
6035 You may extract a single document from such a collection, and distribute
6036 it individually under this License, provided you insert a copy of this
6037 License into the extracted document, and follow this License in all
6038 other respects regarding verbatim copying of that document.
6041 7. AGGREGATION WITH INDEPENDENT WORKS
6043 A compilation of the Document or its derivatives with other separate
6044 and independent documents or works, in or on a volume of a storage or
6045 distribution medium, does not as a whole count as a Modified Version
6046 of the Document, provided no compilation copyright is claimed for the
6047 compilation. Such a compilation is called an "aggregate", and this
6048 License does not apply to the other self-contained works thus compiled
6049 with the Document, on account of their being thus compiled, if they
6050 are not themselves derivative works of the Document.
6052 If the Cover Text requirement of section 3 is applicable to these
6053 copies of the Document, then if the Document is less than one quarter
6054 of the entire aggregate, the Document's Cover Texts may be placed on
6055 covers that surround only the Document within the aggregate.
6056 Otherwise they must appear on covers around the whole aggregate.
6061 Translation is considered a kind of modification, so you may
6062 distribute translations of the Document under the terms of section 4.
6063 Replacing Invariant Sections with translations requires special
6064 permission from their copyright holders, but you may include
6065 translations of some or all Invariant Sections in addition to the
6066 original versions of these Invariant Sections. You may include a
6067 translation of this License provided that you also include the
6068 original English version of this License. In case of a disagreement
6069 between the translation and the original English version of this
6070 License, the original English version will prevail.
6075 You may not copy, modify, sublicense, or distribute the Document except
6076 as expressly provided for under this License. Any other attempt to
6077 copy, modify, sublicense or distribute the Document is void, and will
6078 automatically terminate your rights under this License. However,
6079 parties who have received copies, or rights, from you under this
6080 License will not have their licenses terminated so long as such
6081 parties remain in full compliance.
6084 10. FUTURE REVISIONS OF THIS LICENSE
6086 The Free Software Foundation may publish new, revised versions
6087 of the GNU Free Documentation License from time to time. Such new
6088 versions will be similar in spirit to the present version, but may
6089 differ in detail to address new problems or concerns. See
6090 http://www.gnu.org/copyleft/.
6092 Each version of the License is given a distinguishing version number.
6093 If the Document specifies that a particular numbered version of this
6094 License "or any later version" applies to it, you have the option of
6095 following the terms and conditions either of that specified version or
6096 of any later version that has been published (not as a draft) by the
6097 Free Software Foundation. If the Document does not specify a version
6098 number of this License, you may choose any version ever published (not
6099 as a draft) by the Free Software Foundation.
6102 ADDENDUM: How to use this License for your documents
6104 To use this License in a document you have written, include a copy of
6105 the License in the document and put the following copyright and
6106 license notices just after the title page:
6109 Copyright (c) YEAR YOUR NAME.
6110 Permission is granted to copy, distribute and/or modify this document
6111 under the terms of the GNU Free Documentation License, Version 1.1
6112 or any later version published by the Free Software Foundation;
6113 with the Invariant Sections being LIST THEIR TITLES, with the
6114 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
6115 A copy of the license is included in the section entitled "GNU
6116 Free Documentation License".
6119 If you have no Invariant Sections, write "with no Invariant Sections"
6120 instead of saying which ones are invariant. If you have no
6121 Front-Cover Texts, write "no Front-Cover Texts" instead of
6122 "Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
6124 If your document contains nontrivial examples of program code, we
6125 recommend releasing these examples in parallel under your choice of
6126 free software license, such as the GNU General Public License,
6127 to permit their use in free software.