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
24 @c Configure for the generation of man pages
55 @c common OR combinations of conditions
75 @set abnormal-separator
79 @settitle Using @value{AS}
82 @settitle Using @value{AS} (@value{TARGET})
84 @setchapternewpage odd
89 @c WARE! Some of the machine-dependent sections contain tables of machine
90 @c instructions. Except in multi-column format, these tables look silly.
91 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
92 @c the multi-col format is faked within @example sections.
94 @c Again unfortunately, the natural size that fits on a page, for these tables,
95 @c is different depending on whether or not smallbook is turned on.
96 @c This matters, because of order: text flow switches columns at each page
99 @c The format faked in this source works reasonably well for smallbook,
100 @c not well for the default large-page format. This manual expects that if you
101 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
102 @c tables in question. You can turn on one without the other at your
103 @c discretion, of course.
106 @c the insn tables look just as silly in info files regardless of smallbook,
107 @c might as well show 'em anyways.
113 * As: (as). The GNU assembler.
122 This file documents the GNU Assembler "@value{AS}".
124 @c man begin COPYRIGHT
125 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
127 Permission is granted to copy, distribute and/or modify this document
128 under the terms of the GNU Free Documentation License, Version 1.1
129 or any later version published by the Free Software Foundation;
130 with no Invariant Sections, with no Front-Cover Texts, and with no
131 Back-Cover Texts. A copy of the license is included in the
132 section entitled "GNU Free Documentation License".
137 Permission is granted to process this file through Tex and print the
138 results, provided the printed document carries copying permission
139 notice identical to this one except for the removal of this paragraph
140 (this paragraph not being relevant to the printed manual).
146 @title Using @value{AS}
147 @subtitle The @sc{gnu} Assembler
149 @subtitle for the @value{TARGET} family
152 @subtitle Version @value{VERSION}
155 The Free Software Foundation Inc. thanks The Nice Computer
156 Company of Australia for loaning Dean Elsner to write the
157 first (Vax) version of @code{as} for Project @sc{gnu}.
158 The proprietors, management and staff of TNCCA thank FSF for
159 distracting the boss while they got some work
162 @author Dean Elsner, Jay Fenlason & friends
166 \hfill {\it Using {\tt @value{AS}}}\par
167 \hfill Edited by Cygnus Support\par
169 %"boxit" macro for figures:
170 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
171 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
172 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
173 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
174 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
177 @vskip 0pt plus 1filll
178 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 Free Software Foundation, Inc.
180 Permission is granted to copy, distribute and/or modify this document
181 under the terms of the GNU Free Documentation License, Version 1.1
182 or any later version published by the Free Software Foundation;
183 with no Invariant Sections, with no Front-Cover Texts, and with no
184 Back-Cover Texts. A copy of the license is included in the
185 section entitled "GNU Free Documentation License".
191 @top Using @value{AS}
193 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}} version
196 This version of the file describes @code{@value{AS}} configured to generate
197 code for @value{TARGET} architectures.
200 This document is distributed under the terms of the GNU Free
201 Documentation License. A copy of the license is included in the
202 section entitled "GNU Free Documentation License".
205 * Overview:: Overview
206 * Invoking:: Command-Line Options
208 * Sections:: Sections and Relocation
210 * Expressions:: Expressions
211 * Pseudo Ops:: Assembler Directives
212 * Machine Dependencies:: Machine Dependent Features
213 * Reporting Bugs:: Reporting Bugs
214 * Acknowledgements:: Who Did What
215 * GNU Free Documentation License:: GNU Free Documentation License
223 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
225 This version of the manual describes @code{@value{AS}} configured to generate
226 code for @value{TARGET} architectures.
230 @cindex invocation summary
231 @cindex option summary
232 @cindex summary of options
233 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
234 @pxref{Invoking,,Comand-Line Options}.
236 @c man title AS the portable GNU assembler.
239 gcc(1), ld(1), and the Info entries for @file{binutils} and @file{ld}.
242 @c We don't use deffn and friends for the following because they seem
243 @c to be limited to one line for the header.
245 @c man begin SYNOPSIS
246 @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
247 [ -f ] [ --gstabs ] [ --gdwarf2 ] [ --help ] [ -I @var{dir} ]
249 [ --listing--lhs-width=NUM ][ --listing-lhs-width2=NUM ]
250 [ --listing-rhs-width=NUM ][ --listing-cont-lines=NUM ]
251 [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ]
252 [ -version ] [ --version ] [ -W ] [ --warn ] [ --fatal-warnings ]
253 [ -w ] [ -x ] [ -Z ] [ --target-help ]
255 @c am29k has no machine-dependent assembler options
262 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 |
263 -m[arm]6 | -m[arm]60 | -m[arm]600 | -m[arm]610 |
264 -m[arm]620 | -m[arm]7[t][[d]m[i]][fe] | -m[arm]70 |
265 -m[arm]700 | -m[arm]710[c] | -m[arm]7100 |
266 -m[arm]7500 | -m[arm]8 | -m[arm]810 | -m[arm]9 |
267 -m[arm]920 | -m[arm]920t | -m[arm]9tdmi |
268 -mstrongarm | -mstrongarm110 | -mstrongarm1100 ]
269 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m |
270 -m[arm]v4 | -m[arm]v4t | -m[arm]v5 | -[arm]v5t |
273 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
275 [ -mapcs-32 | -mapcs-26 | -mapcs-float |
277 [ -mthumb-interwork ] [ -moabi ] [ -k ]
286 @c Hitachi family chips have no machine-dependent assembler options
289 @c HPPA has no machine-dependent assembler options (yet).
295 @c The order here is important. See c-sparc.texi.
296 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
297 -Av8plus | -Av8plusa | -Av9 | -Av9a ]
298 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ]
302 [ -mcpu=54[123589] | -mcpu=54[56]lp ] [ -mfar-mode | -mf ]
303 [ -merrors-to-file <filename> | -me <filename> ]
306 @c Z8000 has no machine-dependent assembler options
309 @c see md_parse_option in tc-i960.c
310 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB |
315 [ --m32rx | --[no-]warn-explicit-parallel-conflicts |
319 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
322 [ -jsri2bsr ] [ -sifilter ] [ -relax ]
326 [ -m68hc11 | -m68hc12 ]
327 [ --force-long-branchs ] [ --short-branchs ]
328 [ --strict-direct-mode ] [ --print-insn-syntax ]
329 [ --print-opcodes ] [ --generate-example ]
332 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
333 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -mips4 ] [ -mips5 ]
334 [ -mips32 ] [ -mips64 ]
335 [ -m4650 ] [ -no-m4650 ]
336 [ --trap ] [ --break ] [ -n ]
337 [ --emulation=@var{name} ]
339 [ -- | @var{files} @dots{} ]
347 Turn on listings, in any of a variety of ways:
351 omit false conditionals
354 omit debugging directives
357 include high-level source
363 include macro expansions
366 omit forms processing
372 set the name of the listing file
375 You may combine these options; for example, use @samp{-aln} for assembly
376 listing without forms processing. The @samp{=file} option, if used, must be
377 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
380 Ignored. This option is accepted for script compatibility with calls to
383 @item --defsym @var{sym}=@var{value}
384 Define the symbol @var{sym} to be @var{value} before assembling the input file.
385 @var{value} must be an integer constant. As in C, a leading @samp{0x}
386 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
389 ``fast''---skip whitespace and comment preprocessing (assume source is
393 Generate stabs debugging information for each assembler line. This
394 may help debugging assembler code, if the debugger can handle it.
397 Generate DWARF2 debugging information for each assembler line. This
398 may help debugging assembler code, if the debugger can handle it. Note - this
399 option is only supported by some targets, not all of them.
402 Print a summary of the command line options and exit.
405 Print a summary of all target specific options and exit.
408 Add directory @var{dir} to the search list for @code{.include} directives.
411 Don't warn about signed overflow.
414 @ifclear DIFF-TBL-KLUGE
415 This option is accepted but has no effect on the @value{TARGET} family.
417 @ifset DIFF-TBL-KLUGE
418 Issue warnings when difference tables altered for long displacements.
423 Keep (in the symbol table) local symbols. On traditional a.out systems
424 these start with @samp{L}, but different systems have different local
427 @item --listing-lhs-width=@var{number}
428 Set the maximum width, in words, of the output data column for an assembler
429 listing to @var{number}.
431 @item --listing-lhs-width2=@var{number}
432 Set the maximum width, in words, of the output data column for continuation
433 lines in an assembler listing to @var{number}.
435 @item --listing-rhs-width=@var{number}
436 Set the maximum width of an input source line, as displayed in a listing, to
439 @item --listing-cont-lines=@var{number}
440 Set the maximum number of lines printed in a listing for a single line of input
443 @item -o @var{objfile}
444 Name the object-file output from @code{@value{AS}} @var{objfile}.
447 Fold the data section into the text section.
450 Print the maximum space (in bytes) and total time (in seconds) used by
453 @item --strip-local-absolute
454 Remove local absolute symbols from the outgoing symbol table.
458 Print the @code{as} version.
461 Print the @code{as} version and exit.
465 Suppress warning messages.
467 @item --fatal-warnings
468 Treat warnings as errors.
471 Don't suppress warning messages or treat them as errors.
480 Generate an object file even after errors.
482 @item -- | @var{files} @dots{}
483 Standard input, or source files to assemble.
488 The following options are available when @value{AS} is configured for
493 This option selects the core processor variant.
495 Select either big-endian (-EB) or little-endian (-EL) output.
500 The following options are available when @value{AS} is configured for the ARM
504 @item -m[arm][1|2|3|6|7|8|9][...]
505 Specify which ARM processor variant is the target.
506 @item -m[arm]v[2|2a|3|3m|4|4t|5|5t]
507 Specify which ARM architecture variant is used by the target.
508 @item -mthumb | -mall
509 Enable or disable Thumb only instruction decoding.
510 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
511 Select which Floating Point architecture is the target.
512 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
513 Select which procedure calling convention is in use.
515 Select either big-endian (-EB) or little-endian (-EL) output.
516 @item -mthumb-interwork
517 Specify that the code has been generated with interworking between Thumb and
520 Specify that PIC code has been generated.
525 The following options are available when @value{AS} is configured for
528 @cindex D10V optimization
529 @cindex optimization, D10V
531 Optimize output by parallelizing instructions.
536 The following options are available when @value{AS} is configured for a D30V
539 @cindex D30V optimization
540 @cindex optimization, D30V
542 Optimize output by parallelizing instructions.
546 Warn when nops are generated.
548 @cindex D30V nops after 32-bit multiply
550 Warn when a nop after a 32-bit multiply instruction is generated.
555 The following options are available when @value{AS} is configured for the
556 Intel 80960 processor.
559 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
560 Specify which variant of the 960 architecture is the target.
563 Add code to collect statistics about branches taken.
566 Do not alter compare-and-branch instructions for long displacements;
573 The following options are available when @value{AS} is configured for the
574 Mitsubishi M32R series.
579 Specify which processor in the M32R family is the target. The default
580 is normally the M32R, but this option changes it to the M32RX.
582 @item --warn-explicit-parallel-conflicts or --Wp
583 Produce warning messages when questionable parallel constructs are
586 @item --no-warn-explicit-parallel-conflicts or --Wnp
587 Do not produce warning messages when questionable parallel constructs are
594 The following options are available when @value{AS} is configured for the
595 Motorola 68000 series.
600 Shorten references to undefined symbols, to one word instead of two.
602 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030
603 @itemx | -m68040 | -m68060 | -m68302 | -m68331 | -m68332
604 @itemx | -m68333 | -m68340 | -mcpu32 | -m5200
605 Specify what processor in the 68000 family is the target. The default
606 is normally the 68020, but this can be changed at configuration time.
608 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
609 The target machine does (or does not) have a floating-point coprocessor.
610 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
611 the basic 68000 is not compatible with the 68881, a combination of the
612 two can be specified, since it's possible to do emulation of the
613 coprocessor instructions with the main processor.
615 @item -m68851 | -mno-68851
616 The target machine does (or does not) have a memory-management
617 unit coprocessor. The default is to assume an MMU for 68020 and up.
624 For details about the PDP-11 machine dependent features options,
625 see @ref{PDP-11-Options}.
628 @item -mpic | -mno-pic
629 Generate position-independent (or position-dependent) code. The
630 default is @code{-mpic}.
633 @itemx -mall-extensions
634 Enable all instruction set extensions. This is the default.
636 @item -mno-extensions
637 Disable all instruction set extensions.
639 @item -m@var{extension} | -mno-@var{extension}
640 Enable (or disable) a particular instruction set extension.
643 Enable the instruction set extensions supported by a particular CPU, and
644 disable all other extensions.
646 @item -m@var{machine}
647 Enable the instruction set extensions supported by a particular machine
648 model, and disable all other extensions.
654 The following options are available when @value{AS} is configured for
655 a picoJava processor.
659 @cindex PJ endianness
660 @cindex endianness, PJ
661 @cindex big endian output, PJ
663 Generate ``big endian'' format output.
665 @cindex little endian output, PJ
667 Generate ``little endian'' format output.
673 The following options are available when @value{AS} is configured for the
674 Motorola 68HC11 or 68HC12 series.
678 @item -m68hc11 | -m68hc12
679 Specify what processor is the target. The default is
680 defined by the configuration option when building the assembler.
682 @item --force-long-branchs
683 Relative branches are turned into absolute ones. This concerns
684 conditional branches, unconditional branches and branches to a
687 @item -S | --short-branchs
688 Do not turn relative branchs into absolute ones
689 when the offset is out of range.
691 @item --strict-direct-mode
692 Do not turn the direct addressing mode into extended addressing mode
693 when the instruction does not support direct addressing mode.
695 @item --print-insn-syntax
696 Print the syntax of instruction in case of error.
698 @item --print-opcodes
699 print the list of instructions with syntax and then exit.
701 @item --generate-example
702 print an example of instruction for each possible instruction and then exit.
703 This option is only useful for testing @code{@value{AS}}.
709 The following options are available when @code{@value{AS}} is configured
710 for the SPARC architecture:
713 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
714 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
715 Explicitly select a variant of the SPARC architecture.
717 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
718 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
720 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
721 UltraSPARC extensions.
723 @item -xarch=v8plus | -xarch=v8plusa
724 For compatibility with the Solaris v9 assembler. These options are
725 equivalent to -Av8plus and -Av8plusa, respectively.
728 Warn when the assembler switches to another architecture.
733 The following options are available when @value{AS} is configured for the 'c54x
738 Enable extended addressing mode. All addresses and relocations will assume
739 extended addressing (usually 23 bits).
740 @item -mcpu=@var{CPU_VERSION}
741 Sets the CPU version being compiled for.
742 @item -merrors-to-file @var{FILENAME}
743 Redirect error output to a file, for broken systems which don't support such
744 behaviour in the shell.
749 The following options are available when @value{AS} is configured for
754 This option sets the largest size of an object that can be referenced
755 implicitly with the @code{gp} register. It is only accepted for targets that
756 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
758 @cindex MIPS endianness
759 @cindex endianness, MIPS
760 @cindex big endian output, MIPS
762 Generate ``big endian'' format output.
764 @cindex little endian output, MIPS
766 Generate ``little endian'' format output.
774 Generate code for a particular MIPS Instruction Set Architecture level.
775 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
776 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
778 @samp{-mips5}, @samp{-mips32}, and @samp{-mips64} correspond
779 to generic @sc{MIPS V}, @sc{MIPS32}, and @sc{MIPS64} ISA
780 processors, respectively.
784 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
785 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
786 instructions around accesses to the @samp{HI} and @samp{LO} registers.
787 @samp{-no-m4650} turns off this option.
789 @item -mcpu=@var{CPU}
790 Generate code for a particular MIPS cpu. It is exactly equivalent to
791 @samp{-m@var{cpu}}, except that there are more value of @var{cpu}
795 @item --emulation=@var{name}
796 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
797 for some other target, in all respects, including output format (choosing
798 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
799 debugging information or store symbol table information, and default
800 endianness. The available configuration names are: @samp{mipsecoff},
801 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
802 @samp{mipsbelf}. The first two do not alter the default endianness from that
803 of the primary target for which the assembler was configured; the others change
804 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
805 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
806 selection in any case.
808 This option is currently supported only when the primary target
809 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
810 Furthermore, the primary target or others specified with
811 @samp{--enable-targets=@dots{}} at configuration time must include support for
812 the other format, if both are to be available. For example, the Irix 5
813 configuration includes support for both.
815 Eventually, this option will support more configurations, with more
816 fine-grained control over the assembler's behavior, and will be supported for
820 @code{@value{AS}} ignores this option. It is accepted for compatibility with
828 Control how to deal with multiplication overflow and division by zero.
829 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
830 (and only work for Instruction Set Architecture level 2 and higher);
831 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
835 When this option is used, @code{@value{AS}} will issue a warning every
836 time it generates a nop instruction from a macro.
841 The following options are available when @value{AS} is configured for
847 Enable or disable the JSRI to BSR transformation. By default this is enabled.
848 The command line option @samp{-nojsri2bsr} can be used to disable it.
852 Enable or disable the silicon filter behaviour. By default this is disabled.
853 The default can be overridden by the @samp{-sifilter} command line option.
856 Alter jump instructions for long displacements.
858 @item -mcpu=[210|340]
859 Select the cpu type on the target hardware. This controls which instructions
863 Assemble for a big endian target.
866 Assemble for a little endian target.
874 * Manual:: Structure of this Manual
875 * GNU Assembler:: The GNU Assembler
876 * Object Formats:: Object File Formats
877 * Command Line:: Command Line
878 * Input Files:: Input Files
879 * Object:: Output (Object) File
880 * Errors:: Error and Warning Messages
884 @section Structure of this Manual
886 @cindex manual, structure and purpose
887 This manual is intended to describe what you need to know to use
888 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
889 notation for symbols, constants, and expressions; the directives that
890 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
893 We also cover special features in the @value{TARGET}
894 configuration of @code{@value{AS}}, including assembler directives.
897 This manual also describes some of the machine-dependent features of
898 various flavors of the assembler.
901 @cindex machine instructions (not covered)
902 On the other hand, this manual is @emph{not} intended as an introduction
903 to programming in assembly language---let alone programming in general!
904 In a similar vein, we make no attempt to introduce the machine
905 architecture; we do @emph{not} describe the instruction set, standard
906 mnemonics, registers or addressing modes that are standard to a
907 particular architecture.
909 You may want to consult the manufacturer's
910 machine architecture manual for this information.
914 For information on the H8/300 machine instruction set, see @cite{H8/300
915 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
916 see @cite{H8/300H Series Programming Manual} (Hitachi).
919 For information on the H8/500 machine instruction set, see @cite{H8/500
920 Series Programming Manual} (Hitachi M21T001).
923 For information on the Hitachi SH machine instruction set, see
924 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
927 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
931 @c I think this is premature---doc@cygnus.com, 17jan1991
933 Throughout this manual, we assume that you are running @dfn{GNU},
934 the portable operating system from the @dfn{Free Software
935 Foundation, Inc.}. This restricts our attention to certain kinds of
936 computer (in particular, the kinds of computers that @sc{gnu} can run on);
937 once this assumption is granted examples and definitions need less
940 @code{@value{AS}} is part of a team of programs that turn a high-level
941 human-readable series of instructions into a low-level
942 computer-readable series of instructions. Different versions of
943 @code{@value{AS}} are used for different kinds of computer.
946 @c There used to be a section "Terminology" here, which defined
947 @c "contents", "byte", "word", and "long". Defining "word" to any
948 @c particular size is confusing when the .word directive may generate 16
949 @c bits on one machine and 32 bits on another; in general, for the user
950 @c version of this manual, none of these terms seem essential to define.
951 @c They were used very little even in the former draft of the manual;
952 @c this draft makes an effort to avoid them (except in names of
956 @section The GNU Assembler
958 @c man begin DESCRIPTION
960 @sc{gnu} @code{as} is really a family of assemblers.
962 This manual describes @code{@value{AS}}, a member of that family which is
963 configured for the @value{TARGET} architectures.
965 If you use (or have used) the @sc{gnu} assembler on one architecture, you
966 should find a fairly similar environment when you use it on another
967 architecture. Each version has much in common with the others,
968 including object file formats, most assembler directives (often called
969 @dfn{pseudo-ops}) and assembler syntax.@refill
971 @cindex purpose of @sc{gnu} assembler
972 @code{@value{AS}} is primarily intended to assemble the output of the
973 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
974 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
975 assemble correctly everything that other assemblers for the same
976 machine would assemble.
978 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
981 @c This remark should appear in generic version of manual; assumption
982 @c here is that generic version sets M680x0.
983 This doesn't mean @code{@value{AS}} always uses the same syntax as another
984 assembler for the same architecture; for example, we know of several
985 incompatible versions of 680x0 assembly language syntax.
990 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
991 program in one pass of the source file. This has a subtle impact on the
992 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
995 @section Object File Formats
997 @cindex object file format
998 The @sc{gnu} assembler can be configured to produce several alternative
999 object file formats. For the most part, this does not affect how you
1000 write assembly language programs; but directives for debugging symbols
1001 are typically different in different file formats. @xref{Symbol
1002 Attributes,,Symbol Attributes}.
1005 On the @value{TARGET}, @code{@value{AS}} is configured to produce
1006 @value{OBJ-NAME} format object files.
1008 @c The following should exhaust all configs that set MULTI-OBJ, ideally
1010 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
1011 @code{a.out} or COFF format object files.
1014 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
1015 @code{b.out} or COFF format object files.
1018 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
1019 SOM or ELF format object files.
1024 @section Command Line
1026 @cindex command line conventions
1028 After the program name @code{@value{AS}}, the command line may contain
1029 options and file names. Options may appear in any order, and may be
1030 before, after, or between file names. The order of file names is
1033 @cindex standard input, as input file
1035 @file{--} (two hyphens) by itself names the standard input file
1036 explicitly, as one of the files for @code{@value{AS}} to assemble.
1038 @cindex options, command line
1039 Except for @samp{--} any command line argument that begins with a
1040 hyphen (@samp{-}) is an option. Each option changes the behavior of
1041 @code{@value{AS}}. No option changes the way another option works. An
1042 option is a @samp{-} followed by one or more letters; the case of
1043 the letter is important. All options are optional.
1045 Some options expect exactly one file name to follow them. The file
1046 name may either immediately follow the option's letter (compatible
1047 with older assemblers) or it may be the next command argument (@sc{gnu}
1048 standard). These two command lines are equivalent:
1051 @value{AS} -o my-object-file.o mumble.s
1052 @value{AS} -omy-object-file.o mumble.s
1056 @section Input Files
1059 @cindex source program
1060 @cindex files, input
1061 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
1062 describe the program input to one run of @code{@value{AS}}. The program may
1063 be in one or more files; how the source is partitioned into files
1064 doesn't change the meaning of the source.
1066 @c I added "con" prefix to "catenation" just to prove I can overcome my
1067 @c APL training... doc@cygnus.com
1068 The source program is a concatenation of the text in all the files, in the
1071 @c man begin DESCRIPTION
1072 Each time you run @code{@value{AS}} it assembles exactly one source
1073 program. The source program is made up of one or more files.
1074 (The standard input is also a file.)
1076 You give @code{@value{AS}} a command line that has zero or more input file
1077 names. The input files are read (from left file name to right). A
1078 command line argument (in any position) that has no special meaning
1079 is taken to be an input file name.
1081 If you give @code{@value{AS}} no file names it attempts to read one input file
1082 from the @code{@value{AS}} standard input, which is normally your terminal. You
1083 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
1086 Use @samp{--} if you need to explicitly name the standard input file
1087 in your command line.
1089 If the source is empty, @code{@value{AS}} produces a small, empty object
1094 @subheading Filenames and Line-numbers
1096 @cindex input file linenumbers
1097 @cindex line numbers, in input files
1098 There are two ways of locating a line in the input file (or files) and
1099 either may be used in reporting error messages. One way refers to a line
1100 number in a physical file; the other refers to a line number in a
1101 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
1103 @dfn{Physical files} are those files named in the command line given
1104 to @code{@value{AS}}.
1106 @dfn{Logical files} are simply names declared explicitly by assembler
1107 directives; they bear no relation to physical files. Logical file names help
1108 error messages reflect the original source file, when @code{@value{AS}} source
1109 is itself synthesized from other files. @code{@value{AS}} understands the
1110 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
1111 @ref{File,,@code{.file}}.
1114 @section Output (Object) File
1120 Every time you run @code{@value{AS}} it produces an output file, which is
1121 your assembly language program translated into numbers. This file
1122 is the object file. Its default name is
1130 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
1132 You can give it another name by using the @code{-o} option. Conventionally,
1133 object file names end with @file{.o}. The default name is used for historical
1134 reasons: older assemblers were capable of assembling self-contained programs
1135 directly into a runnable program. (For some formats, this isn't currently
1136 possible, but it can be done for the @code{a.out} format.)
1140 The object file is meant for input to the linker @code{@value{LD}}. It contains
1141 assembled program code, information to help @code{@value{LD}} integrate
1142 the assembled program into a runnable file, and (optionally) symbolic
1143 information for the debugger.
1145 @c link above to some info file(s) like the description of a.out.
1146 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1149 @section Error and Warning Messages
1151 @c man begin DESCRIPTION
1153 @cindex error messages
1154 @cindex warning messages
1155 @cindex messages from assembler
1156 @code{@value{AS}} may write warnings and error messages to the standard error
1157 file (usually your terminal). This should not happen when a compiler
1158 runs @code{@value{AS}} automatically. Warnings report an assumption made so
1159 that @code{@value{AS}} could keep assembling a flawed program; errors report a
1160 grave problem that stops the assembly.
1164 @cindex format of warning messages
1165 Warning messages have the format
1168 file_name:@b{NNN}:Warning Message Text
1172 @cindex line numbers, in warnings/errors
1173 (where @b{NNN} is a line number). If a logical file name has been given
1174 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1175 the current input file is used. If a logical line number was given
1177 (@pxref{Line,,@code{.line}})
1181 (@pxref{Line,,@code{.line}})
1184 (@pxref{Ln,,@code{.ln}})
1187 then it is used to calculate the number printed,
1188 otherwise the actual line in the current source file is printed. The
1189 message text is intended to be self explanatory (in the grand Unix
1192 @cindex format of error messages
1193 Error messages have the format
1195 file_name:@b{NNN}:FATAL:Error Message Text
1197 The file name and line number are derived as for warning
1198 messages. The actual message text may be rather less explanatory
1199 because many of them aren't supposed to happen.
1202 @chapter Command-Line Options
1204 @cindex options, all versions of assembler
1205 This chapter describes command-line options available in @emph{all}
1206 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1208 to the @value{TARGET}.
1211 to particular machine architectures.
1214 @c man begin DESCRIPTION
1216 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
1217 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1218 The assembler arguments must be separated from each other (and the @samp{-Wa})
1219 by commas. For example:
1222 gcc -c -g -O -Wa,-alh,-L file.c
1226 This passes two options to the assembler: @samp{-alh} (emit a listing to
1227 standard output with with high-level and assembly source) and @samp{-L} (retain
1228 local symbols in the symbol table).
1230 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1231 command-line options are automatically passed to the assembler by the compiler.
1232 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1233 precisely what options it passes to each compilation pass, including the
1239 * a:: -a[cdhlns] enable listings
1240 * D:: -D for compatibility
1241 * f:: -f to work faster
1242 * I:: -I for .include search path
1243 @ifclear DIFF-TBL-KLUGE
1244 * K:: -K for compatibility
1246 @ifset DIFF-TBL-KLUGE
1247 * K:: -K for difference tables
1250 * L:: -L to retain local labels
1251 * listing:: --listing-XXX to configure listing output
1252 * M:: -M or --mri to assemble in MRI compatibility mode
1253 * MD:: --MD for dependency tracking
1254 * o:: -o to name the object file
1255 * R:: -R to join data and text sections
1256 * statistics:: --statistics to see statistics about assembly
1257 * traditional-format:: --traditional-format for compatible output
1258 * v:: -v to announce version
1259 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1260 * Z:: -Z to make object file even after errors
1264 @section Enable Listings: @code{-a[cdhlns]}
1273 @cindex listings, enabling
1274 @cindex assembly listings, enabling
1276 These options enable listing output from the assembler. By itself,
1277 @samp{-a} requests high-level, assembly, and symbols listing.
1278 You can use other letters to select specific options for the list:
1279 @samp{-ah} requests a high-level language listing,
1280 @samp{-al} requests an output-program assembly listing, and
1281 @samp{-as} requests a symbol table listing.
1282 High-level listings require that a compiler debugging option like
1283 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1286 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1287 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1288 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1289 omitted from the listing.
1291 Use the @samp{-ad} option to omit debugging directives from the
1294 Once you have specified one of these options, you can further control
1295 listing output and its appearance using the directives @code{.list},
1296 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1298 The @samp{-an} option turns off all forms processing.
1299 If you do not request listing output with one of the @samp{-a} options, the
1300 listing-control directives have no effect.
1302 The letters after @samp{-a} may be combined into one option,
1303 @emph{e.g.}, @samp{-aln}.
1305 Note if the assembler source is coming from the standard input (eg because it
1306 is being created by @code{@value{GCC}} and the @samp{-pipe} command line switch
1307 is being used) then the listing will not contain any comments or preprocessor
1308 directives. This is because the listing code buffers input source lines from
1309 stdin only after they have been preprocessed by the assembler. This reduces
1310 memory usage and makes the code more efficient.
1316 This option has no effect whatsoever, but it is accepted to make it more
1317 likely that scripts written for other assemblers also work with
1321 @section Work Faster: @code{-f}
1324 @cindex trusted compiler
1325 @cindex faster processing (@code{-f})
1326 @samp{-f} should only be used when assembling programs written by a
1327 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1328 and comment preprocessing on
1329 the input file(s) before assembling them. @xref{Preprocessing,
1333 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1334 preprocessed (if they contain comments, for example), @code{@value{AS}} does
1339 @section @code{.include} search path: @code{-I} @var{path}
1341 @kindex -I @var{path}
1342 @cindex paths for @code{.include}
1343 @cindex search path for @code{.include}
1344 @cindex @code{include} directive search path
1345 Use this option to add a @var{path} to the list of directories
1346 @code{@value{AS}} searches for files specified in @code{.include}
1347 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
1348 many times as necessary to include a variety of paths. The current
1349 working directory is always searched first; after that, @code{@value{AS}}
1350 searches any @samp{-I} directories in the same order as they were
1351 specified (left to right) on the command line.
1354 @section Difference Tables: @code{-K}
1357 @ifclear DIFF-TBL-KLUGE
1358 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1359 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1360 where it can be used to warn when the assembler alters the machine code
1361 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1362 family does not have the addressing limitations that sometimes lead to this
1363 alteration on other platforms.
1366 @ifset DIFF-TBL-KLUGE
1367 @cindex difference tables, warning
1368 @cindex warning for altered difference tables
1369 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1370 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1371 You can use the @samp{-K} option if you want a warning issued when this
1376 @section Include Local Labels: @code{-L}
1379 @cindex local labels, retaining in output
1380 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1381 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1382 debugging, because they are intended for the use of programs (like
1383 compilers) that compose assembler programs, not for your notice.
1384 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1385 normally debug with them.
1387 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1388 in the object file. Usually if you do this you also tell the linker
1389 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1391 By default, a local label is any label beginning with @samp{L}, but each
1392 target is allowed to redefine the local label prefix.
1394 On the HPPA local labels begin with @samp{L$}.
1398 @section Configuringh listing output: @code{--listing}
1400 The listing feature of the assembler can be enabled via the command line switch
1401 @samp{-a} (@pxref{a}). This feature combines the input source file(s) with a
1402 hex dump of the corresponding locations in the output object file, and displays
1403 them as a listing file. The format of this listing can be controlled by pseudo
1404 ops inside the assembler source (@pxref{List} @pxref{Title} @pxref{Sbttl}
1405 @pxref{Psize} @pxref{Eject}) and also by the following switches:
1408 @item --listing-lhs-width=@samp{number}
1409 @kindex --listing-lhs-width
1410 @cindex Width of first line disassembly output
1411 Sets the maximum width, in words, of the first line of the hex byte dump. This
1412 dump appears on the left hand side of the listing output.
1414 @item --listing-lhs-width2=@samp{number}
1415 @kindex --listing-lhs-width2
1416 @cindex Width of continuation lines of disassembly output
1417 Sets the maximum width, in words, of any further lines of the hex byte dump for
1418 a given inut source line. If this value is not specified, it defaults to being
1419 the same as the value specified for @samp{--listing-lhs-width}. If neither
1420 switch is used the default is to one.
1422 @item --listing-rhs-width=@samp{number}
1423 @kindex --listing-rhs-width
1424 @cindex Width of source line output
1425 Sets the maximum width, in characters, of the source line that is displayed
1426 alongside the hex dump. The default value for this parameter is 100. The
1427 source line is displayed on the right hand side of the listing output.
1429 @item --listing-cont-lines=@samp{number}
1430 @kindex --listing-cont-lines
1431 @cindex Maximum number of continuation lines
1432 Sets the maximum number of continuation lines of hex dump that will be
1433 displayed for a given single line of source input. The default value is 4.
1437 @section Assemble in MRI Compatibility Mode: @code{-M}
1440 @cindex MRI compatibility mode
1441 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1442 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1443 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1444 configured target) assembler from Microtec Research. The exact nature of the
1445 MRI syntax will not be documented here; see the MRI manuals for more
1446 information. Note in particular that the handling of macros and macro
1447 arguments is somewhat different. The purpose of this option is to permit
1448 assembling existing MRI assembler code using @code{@value{AS}}.
1450 The MRI compatibility is not complete. Certain operations of the MRI assembler
1451 depend upon its object file format, and can not be supported using other object
1452 file formats. Supporting these would require enhancing each object file format
1453 individually. These are:
1456 @item global symbols in common section
1458 The m68k MRI assembler supports common sections which are merged by the linker.
1459 Other object file formats do not support this. @code{@value{AS}} handles
1460 common sections by treating them as a single common symbol. It permits local
1461 symbols to be defined within a common section, but it can not support global
1462 symbols, since it has no way to describe them.
1464 @item complex relocations
1466 The MRI assemblers support relocations against a negated section address, and
1467 relocations which combine the start addresses of two or more sections. These
1468 are not support by other object file formats.
1470 @item @code{END} pseudo-op specifying start address
1472 The MRI @code{END} pseudo-op permits the specification of a start address.
1473 This is not supported by other object file formats. The start address may
1474 instead be specified using the @code{-e} option to the linker, or in a linker
1477 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1479 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1480 name to the output file. This is not supported by other object file formats.
1482 @item @code{ORG} pseudo-op
1484 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1485 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1486 which changes the location within the current section. Absolute sections are
1487 not supported by other object file formats. The address of a section may be
1488 assigned within a linker script.
1491 There are some other features of the MRI assembler which are not supported by
1492 @code{@value{AS}}, typically either because they are difficult or because they
1493 seem of little consequence. Some of these may be supported in future releases.
1497 @item EBCDIC strings
1499 EBCDIC strings are not supported.
1501 @item packed binary coded decimal
1503 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1504 and @code{DCB.P} pseudo-ops are not supported.
1506 @item @code{FEQU} pseudo-op
1508 The m68k @code{FEQU} pseudo-op is not supported.
1510 @item @code{NOOBJ} pseudo-op
1512 The m68k @code{NOOBJ} pseudo-op is not supported.
1514 @item @code{OPT} branch control options
1516 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1517 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1518 relaxes all branches, whether forward or backward, to an appropriate size, so
1519 these options serve no purpose.
1521 @item @code{OPT} list control options
1523 The following m68k @code{OPT} list control options are ignored: @code{C},
1524 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1525 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1527 @item other @code{OPT} options
1529 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1530 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1532 @item @code{OPT} @code{D} option is default
1534 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1535 @code{OPT NOD} may be used to turn it off.
1537 @item @code{XREF} pseudo-op.
1539 The m68k @code{XREF} pseudo-op is ignored.
1541 @item @code{.debug} pseudo-op
1543 The i960 @code{.debug} pseudo-op is not supported.
1545 @item @code{.extended} pseudo-op
1547 The i960 @code{.extended} pseudo-op is not supported.
1549 @item @code{.list} pseudo-op.
1551 The various options of the i960 @code{.list} pseudo-op are not supported.
1553 @item @code{.optimize} pseudo-op
1555 The i960 @code{.optimize} pseudo-op is not supported.
1557 @item @code{.output} pseudo-op
1559 The i960 @code{.output} pseudo-op is not supported.
1561 @item @code{.setreal} pseudo-op
1563 The i960 @code{.setreal} pseudo-op is not supported.
1568 @section Dependency tracking: @code{--MD}
1571 @cindex dependency tracking
1574 @code{@value{AS}} can generate a dependency file for the file it creates. This
1575 file consists of a single rule suitable for @code{make} describing the
1576 dependencies of the main source file.
1578 The rule is written to the file named in its argument.
1580 This feature is used in the automatic updating of makefiles.
1583 @section Name the Object File: @code{-o}
1586 @cindex naming object file
1587 @cindex object file name
1588 There is always one object file output when you run @code{@value{AS}}. By
1589 default it has the name
1592 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1606 You use this option (which takes exactly one filename) to give the
1607 object file a different name.
1609 Whatever the object file is called, @code{@value{AS}} overwrites any
1610 existing file of the same name.
1613 @section Join Data and Text Sections: @code{-R}
1616 @cindex data and text sections, joining
1617 @cindex text and data sections, joining
1618 @cindex joining text and data sections
1619 @cindex merging text and data sections
1620 @code{-R} tells @code{@value{AS}} to write the object file as if all
1621 data-section data lives in the text section. This is only done at
1622 the very last moment: your binary data are the same, but data
1623 section parts are relocated differently. The data section part of
1624 your object file is zero bytes long because all its bytes are
1625 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1627 When you specify @code{-R} it would be possible to generate shorter
1628 address displacements (because we do not have to cross between text and
1629 data section). We refrain from doing this simply for compatibility with
1630 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1633 When @code{@value{AS}} is configured for COFF output,
1634 this option is only useful if you use sections named @samp{.text} and
1639 @code{-R} is not supported for any of the HPPA targets. Using
1640 @code{-R} generates a warning from @code{@value{AS}}.
1644 @section Display Assembly Statistics: @code{--statistics}
1646 @kindex --statistics
1647 @cindex statistics, about assembly
1648 @cindex time, total for assembly
1649 @cindex space used, maximum for assembly
1650 Use @samp{--statistics} to display two statistics about the resources used by
1651 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1652 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1655 @node traditional-format
1656 @section Compatible output: @code{--traditional-format}
1658 @kindex --traditional-format
1659 For some targets, the output of @code{@value{AS}} is different in some ways
1660 from the output of some existing assembler. This switch requests
1661 @code{@value{AS}} to use the traditional format instead.
1663 For example, it disables the exception frame optimizations which
1664 @code{@value{AS}} normally does by default on @code{@value{GCC}} output.
1667 @section Announce Version: @code{-v}
1671 @cindex assembler version
1672 @cindex version of assembler
1673 You can find out what version of as is running by including the
1674 option @samp{-v} (which you can also spell as @samp{-version}) on the
1678 @section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings}
1680 @code{@value{AS}} should never give a warning or error message when
1681 assembling compiler output. But programs written by people often
1682 cause @code{@value{AS}} to give a warning that a particular assumption was
1683 made. All such warnings are directed to the standard error file.
1686 @kindex @samp{--no-warn}
1687 @cindex suppressing warnings
1688 @cindex warnings, suppressing
1689 If you use the @code{-W} and @code{--no-warn} options, no warnings are issued.
1690 This only affects the warning messages: it does not change any particular of
1691 how @code{@value{AS}} assembles your file. Errors, which stop the assembly,
1694 @kindex @samp{--fatal-warnings}
1695 @cindex errors, caused by warnings
1696 @cindex warnings, causing error
1697 If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers
1698 files that generate warnings to be in error.
1700 @kindex @samp{--warn}
1701 @cindex warnings, switching on
1702 You can switch these options off again by specifying @code{--warn}, which
1703 causes warnings to be output as usual.
1706 @section Generate Object File in Spite of Errors: @code{-Z}
1707 @cindex object file, after errors
1708 @cindex errors, continuing after
1709 After an error message, @code{@value{AS}} normally produces no output. If for
1710 some reason you are interested in object file output even after
1711 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1712 option. If there are any errors, @code{@value{AS}} continues anyways, and
1713 writes an object file after a final warning message of the form @samp{@var{n}
1714 errors, @var{m} warnings, generating bad object file.}
1719 @cindex machine-independent syntax
1720 @cindex syntax, machine-independent
1721 This chapter describes the machine-independent syntax allowed in a
1722 source file. @code{@value{AS}} syntax is similar to what many other
1723 assemblers use; it is inspired by the BSD 4.2
1728 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1732 * Preprocessing:: Preprocessing
1733 * Whitespace:: Whitespace
1734 * Comments:: Comments
1735 * Symbol Intro:: Symbols
1736 * Statements:: Statements
1737 * Constants:: Constants
1741 @section Preprocessing
1743 @cindex preprocessing
1744 The @code{@value{AS}} internal preprocessor:
1746 @cindex whitespace, removed by preprocessor
1748 adjusts and removes extra whitespace. It leaves one space or tab before
1749 the keywords on a line, and turns any other whitespace on the line into
1752 @cindex comments, removed by preprocessor
1754 removes all comments, replacing them with a single space, or an
1755 appropriate number of newlines.
1757 @cindex constants, converted by preprocessor
1759 converts character constants into the appropriate numeric values.
1762 It does not do macro processing, include file handling, or
1763 anything else you may get from your C compiler's preprocessor. You can
1764 do include file processing with the @code{.include} directive
1765 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1766 to get other ``CPP'' style preprocessing, by giving the input file a
1767 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1768 Output, gcc.info, Using GNU CC}.
1770 Excess whitespace, comments, and character constants
1771 cannot be used in the portions of the input text that are not
1774 @cindex turning preprocessing on and off
1775 @cindex preprocessing, turning on and off
1778 If the first line of an input file is @code{#NO_APP} or if you use the
1779 @samp{-f} option, whitespace and comments are not removed from the input file.
1780 Within an input file, you can ask for whitespace and comment removal in
1781 specific portions of the by putting a line that says @code{#APP} before the
1782 text that may contain whitespace or comments, and putting a line that says
1783 @code{#NO_APP} after this text. This feature is mainly intend to support
1784 @code{asm} statements in compilers whose output is otherwise free of comments
1791 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1792 Whitespace is used to separate symbols, and to make programs neater for
1793 people to read. Unless within character constants
1794 (@pxref{Characters,,Character Constants}), any whitespace means the same
1795 as exactly one space.
1801 There are two ways of rendering comments to @code{@value{AS}}. In both
1802 cases the comment is equivalent to one space.
1804 Anything from @samp{/*} through the next @samp{*/} is a comment.
1805 This means you may not nest these comments.
1809 The only way to include a newline ('\n') in a comment
1810 is to use this sort of comment.
1813 /* This sort of comment does not nest. */
1816 @cindex line comment character
1817 Anything from the @dfn{line comment} character to the next newline
1818 is considered a comment and is ignored. The line comment character is
1820 @samp{;} for the AMD 29K family;
1823 @samp{;} on the ARC;
1826 @samp{@@} on the ARM;
1829 @samp{;} for the H8/300 family;
1832 @samp{!} for the H8/500 family;
1835 @samp{;} for the HPPA;
1838 @samp{#} on the i386 and x86-64;
1841 @samp{#} on the i960;
1844 @samp{;} for the PDP-11;
1847 @samp{;} for picoJava;
1850 @samp{!} for the Hitachi SH;
1853 @samp{!} on the SPARC;
1856 @samp{#} on the m32r;
1859 @samp{|} on the 680x0;
1862 @samp{#} on the 68HC11 and 68HC12;
1865 @samp{;} on the M880x0;
1868 @samp{#} on the Vax;
1871 @samp{!} for the Z8000;
1874 @samp{#} on the V850;
1876 see @ref{Machine Dependencies}. @refill
1877 @c FIXME What about i860?
1880 On some machines there are two different line comment characters. One
1881 character only begins a comment if it is the first non-whitespace character on
1882 a line, while the other always begins a comment.
1886 The V850 assembler also supports a double dash as starting a comment that
1887 extends to the end of the line.
1893 @cindex lines starting with @code{#}
1894 @cindex logical line numbers
1895 To be compatible with past assemblers, lines that begin with @samp{#} have a
1896 special interpretation. Following the @samp{#} should be an absolute
1897 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1898 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1899 new logical file name. The rest of the line, if any, should be whitespace.
1901 If the first non-whitespace characters on the line are not numeric,
1902 the line is ignored. (Just like a comment.)
1905 # This is an ordinary comment.
1906 # 42-6 "new_file_name" # New logical file name
1907 # This is logical line # 36.
1909 This feature is deprecated, and may disappear from future versions
1910 of @code{@value{AS}}.
1915 @cindex characters used in symbols
1916 @ifclear SPECIAL-SYMS
1917 A @dfn{symbol} is one or more characters chosen from the set of all
1918 letters (both upper and lower case), digits and the three characters
1924 A @dfn{symbol} is one or more characters chosen from the set of all
1925 letters (both upper and lower case), digits and the three characters
1926 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1932 On most machines, you can also use @code{$} in symbol names; exceptions
1933 are noted in @ref{Machine Dependencies}.
1935 No symbol may begin with a digit. Case is significant.
1936 There is no length limit: all characters are significant. Symbols are
1937 delimited by characters not in that set, or by the beginning of a file
1938 (since the source program must end with a newline, the end of a file is
1939 not a possible symbol delimiter). @xref{Symbols}.
1940 @cindex length of symbols
1945 @cindex statements, structure of
1946 @cindex line separator character
1947 @cindex statement separator character
1949 @ifclear abnormal-separator
1950 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1951 semicolon (@samp{;}). The newline or semicolon is considered part of
1952 the preceding statement. Newlines and semicolons within character
1953 constants are an exception: they do not end statements.
1955 @ifset abnormal-separator
1957 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1958 sign (@samp{@@}). The newline or at sign is considered part of the
1959 preceding statement. Newlines and at signs within character constants
1960 are an exception: they do not end statements.
1963 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1964 point (@samp{!}). The newline or exclamation point is considered part of the
1965 preceding statement. Newlines and exclamation points within character
1966 constants are an exception: they do not end statements.
1969 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1970 H8/300) a dollar sign (@samp{$}); or (for the
1973 (@samp{;}). The newline or separator character is considered part of
1974 the preceding statement. Newlines and separators within character
1975 constants are an exception: they do not end statements.
1980 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1981 separator character. (The line separator is usually @samp{;}, unless
1982 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1983 newline or separator character is considered part of the preceding
1984 statement. Newlines and separators within character constants are an
1985 exception: they do not end statements.
1988 @cindex newline, required at file end
1989 @cindex EOF, newline must precede
1990 It is an error to end any statement with end-of-file: the last
1991 character of any input file should be a newline.@refill
1993 An empty statement is allowed, and may include whitespace. It is ignored.
1995 @cindex instructions and directives
1996 @cindex directives and instructions
1997 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1998 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
2000 A statement begins with zero or more labels, optionally followed by a
2001 key symbol which determines what kind of statement it is. The key
2002 symbol determines the syntax of the rest of the statement. If the
2003 symbol begins with a dot @samp{.} then the statement is an assembler
2004 directive: typically valid for any computer. If the symbol begins with
2005 a letter the statement is an assembly language @dfn{instruction}: it
2006 assembles into a machine language instruction.
2008 Different versions of @code{@value{AS}} for different computers
2009 recognize different instructions. In fact, the same symbol may
2010 represent a different instruction in a different computer's assembly
2014 @cindex @code{:} (label)
2015 @cindex label (@code{:})
2016 A label is a symbol immediately followed by a colon (@code{:}).
2017 Whitespace before a label or after a colon is permitted, but you may not
2018 have whitespace between a label's symbol and its colon. @xref{Labels}.
2021 For HPPA targets, labels need not be immediately followed by a colon, but
2022 the definition of a label must begin in column zero. This also implies that
2023 only one label may be defined on each line.
2027 label: .directive followed by something
2028 another_label: # This is an empty statement.
2029 instruction operand_1, operand_2, @dots{}
2036 A constant is a number, written so that its value is known by
2037 inspection, without knowing any context. Like this:
2040 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
2041 .ascii "Ring the bell\7" # A string constant.
2042 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
2043 .float 0f-314159265358979323846264338327\
2044 95028841971.693993751E-40 # - pi, a flonum.
2049 * Characters:: Character Constants
2050 * Numbers:: Number Constants
2054 @subsection Character Constants
2056 @cindex character constants
2057 @cindex constants, character
2058 There are two kinds of character constants. A @dfn{character} stands
2059 for one character in one byte and its value may be used in
2060 numeric expressions. String constants (properly called string
2061 @emph{literals}) are potentially many bytes and their values may not be
2062 used in arithmetic expressions.
2066 * Chars:: Characters
2070 @subsubsection Strings
2072 @cindex string constants
2073 @cindex constants, string
2074 A @dfn{string} is written between double-quotes. It may contain
2075 double-quotes or null characters. The way to get special characters
2076 into a string is to @dfn{escape} these characters: precede them with
2077 a backslash @samp{\} character. For example @samp{\\} represents
2078 one backslash: the first @code{\} is an escape which tells
2079 @code{@value{AS}} to interpret the second character literally as a backslash
2080 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
2081 escape character). The complete list of escapes follows.
2083 @cindex escape codes, character
2084 @cindex character escape codes
2087 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
2089 @cindex @code{\b} (backspace character)
2090 @cindex backspace (@code{\b})
2092 Mnemonic for backspace; for ASCII this is octal code 010.
2095 @c Mnemonic for EOText; for ASCII this is octal code 004.
2097 @cindex @code{\f} (formfeed character)
2098 @cindex formfeed (@code{\f})
2100 Mnemonic for FormFeed; for ASCII this is octal code 014.
2102 @cindex @code{\n} (newline character)
2103 @cindex newline (@code{\n})
2105 Mnemonic for newline; for ASCII this is octal code 012.
2108 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
2110 @cindex @code{\r} (carriage return character)
2111 @cindex carriage return (@code{\r})
2113 Mnemonic for carriage-Return; for ASCII this is octal code 015.
2116 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
2117 @c other assemblers.
2119 @cindex @code{\t} (tab)
2120 @cindex tab (@code{\t})
2122 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
2125 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
2126 @c @item \x @var{digit} @var{digit} @var{digit}
2127 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
2129 @cindex @code{\@var{ddd}} (octal character code)
2130 @cindex octal character code (@code{\@var{ddd}})
2131 @item \ @var{digit} @var{digit} @var{digit}
2132 An octal character code. The numeric code is 3 octal digits.
2133 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
2134 for example, @code{\008} has the value 010, and @code{\009} the value 011.
2136 @cindex @code{\@var{xd...}} (hex character code)
2137 @cindex hex character code (@code{\@var{xd...}})
2138 @item \@code{x} @var{hex-digits...}
2139 A hex character code. All trailing hex digits are combined. Either upper or
2140 lower case @code{x} works.
2142 @cindex @code{\\} (@samp{\} character)
2143 @cindex backslash (@code{\\})
2145 Represents one @samp{\} character.
2148 @c Represents one @samp{'} (accent acute) character.
2149 @c This is needed in single character literals
2150 @c (@xref{Characters,,Character Constants}.) to represent
2153 @cindex @code{\"} (doublequote character)
2154 @cindex doublequote (@code{\"})
2156 Represents one @samp{"} character. Needed in strings to represent
2157 this character, because an unescaped @samp{"} would end the string.
2159 @item \ @var{anything-else}
2160 Any other character when escaped by @kbd{\} gives a warning, but
2161 assembles as if the @samp{\} was not present. The idea is that if
2162 you used an escape sequence you clearly didn't want the literal
2163 interpretation of the following character. However @code{@value{AS}} has no
2164 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
2165 code and warns you of the fact.
2168 Which characters are escapable, and what those escapes represent,
2169 varies widely among assemblers. The current set is what we think
2170 the BSD 4.2 assembler recognizes, and is a subset of what most C
2171 compilers recognize. If you are in doubt, do not use an escape
2175 @subsubsection Characters
2177 @cindex single character constant
2178 @cindex character, single
2179 @cindex constant, single character
2180 A single character may be written as a single quote immediately
2181 followed by that character. The same escapes apply to characters as
2182 to strings. So if you want to write the character backslash, you
2183 must write @kbd{'\\} where the first @code{\} escapes the second
2184 @code{\}. As you can see, the quote is an acute accent, not a
2185 grave accent. A newline
2187 @ifclear abnormal-separator
2188 (or semicolon @samp{;})
2190 @ifset abnormal-separator
2192 (or at sign @samp{@@})
2195 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
2201 immediately following an acute accent is taken as a literal character
2202 and does not count as the end of a statement. The value of a character
2203 constant in a numeric expression is the machine's byte-wide code for
2204 that character. @code{@value{AS}} assumes your character code is ASCII:
2205 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2208 @subsection Number Constants
2210 @cindex constants, number
2211 @cindex number constants
2212 @code{@value{AS}} distinguishes three kinds of numbers according to how they
2213 are stored in the target machine. @emph{Integers} are numbers that
2214 would fit into an @code{int} in the C language. @emph{Bignums} are
2215 integers, but they are stored in more than 32 bits. @emph{Flonums}
2216 are floating point numbers, described below.
2219 * Integers:: Integers
2224 * Bit Fields:: Bit Fields
2230 @subsubsection Integers
2232 @cindex constants, integer
2234 @cindex binary integers
2235 @cindex integers, binary
2236 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2237 the binary digits @samp{01}.
2239 @cindex octal integers
2240 @cindex integers, octal
2241 An octal integer is @samp{0} followed by zero or more of the octal
2242 digits (@samp{01234567}).
2244 @cindex decimal integers
2245 @cindex integers, decimal
2246 A decimal integer starts with a non-zero digit followed by zero or
2247 more digits (@samp{0123456789}).
2249 @cindex hexadecimal integers
2250 @cindex integers, hexadecimal
2251 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2252 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2254 Integers have the usual values. To denote a negative integer, use
2255 the prefix operator @samp{-} discussed under expressions
2256 (@pxref{Prefix Ops,,Prefix Operators}).
2259 @subsubsection Bignums
2262 @cindex constants, bignum
2263 A @dfn{bignum} has the same syntax and semantics as an integer
2264 except that the number (or its negative) takes more than 32 bits to
2265 represent in binary. The distinction is made because in some places
2266 integers are permitted while bignums are not.
2269 @subsubsection Flonums
2271 @cindex floating point numbers
2272 @cindex constants, floating point
2274 @cindex precision, floating point
2275 A @dfn{flonum} represents a floating point number. The translation is
2276 indirect: a decimal floating point number from the text is converted by
2277 @code{@value{AS}} to a generic binary floating point number of more than
2278 sufficient precision. This generic floating point number is converted
2279 to a particular computer's floating point format (or formats) by a
2280 portion of @code{@value{AS}} specialized to that computer.
2282 A flonum is written by writing (in order)
2287 (@samp{0} is optional on the HPPA.)
2291 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
2293 @kbd{e} is recommended. Case is not important.
2295 @c FIXME: verify if flonum syntax really this vague for most cases
2296 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2297 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2300 On the H8/300, H8/500,
2302 and AMD 29K architectures, the letter must be
2303 one of the letters @samp{DFPRSX} (in upper or lower case).
2305 On the ARC, the letter must be one of the letters @samp{DFRS}
2306 (in upper or lower case).
2308 On the Intel 960 architecture, the letter must be
2309 one of the letters @samp{DFT} (in upper or lower case).
2311 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2315 One of the letters @samp{DFPRSX} (in upper or lower case).
2318 One of the letters @samp{DFRS} (in upper or lower case).
2321 One of the letters @samp{DFPRSX} (in upper or lower case).
2324 The letter @samp{E} (upper case only).
2327 One of the letters @samp{DFT} (in upper or lower case).
2332 An optional sign: either @samp{+} or @samp{-}.
2335 An optional @dfn{integer part}: zero or more decimal digits.
2338 An optional @dfn{fractional part}: @samp{.} followed by zero
2339 or more decimal digits.
2342 An optional exponent, consisting of:
2346 An @samp{E} or @samp{e}.
2347 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2348 @c principle this can perfectly well be different on different targets.
2350 Optional sign: either @samp{+} or @samp{-}.
2352 One or more decimal digits.
2357 At least one of the integer part or the fractional part must be
2358 present. The floating point number has the usual base-10 value.
2360 @code{@value{AS}} does all processing using integers. Flonums are computed
2361 independently of any floating point hardware in the computer running
2366 @c Bit fields are written as a general facility but are also controlled
2367 @c by a conditional-compilation flag---which is as of now (21mar91)
2368 @c turned on only by the i960 config of GAS.
2370 @subsubsection Bit Fields
2373 @cindex constants, bit field
2374 You can also define numeric constants as @dfn{bit fields}.
2375 specify two numbers separated by a colon---
2377 @var{mask}:@var{value}
2380 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2383 The resulting number is then packed
2385 @c this conditional paren in case bit fields turned on elsewhere than 960
2386 (in host-dependent byte order)
2388 into a field whose width depends on which assembler directive has the
2389 bit-field as its argument. Overflow (a result from the bitwise and
2390 requiring more binary digits to represent) is not an error; instead,
2391 more constants are generated, of the specified width, beginning with the
2392 least significant digits.@refill
2394 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2395 @code{.short}, and @code{.word} accept bit-field arguments.
2400 @chapter Sections and Relocation
2405 * Secs Background:: Background
2406 * Ld Sections:: Linker Sections
2407 * As Sections:: Assembler Internal Sections
2408 * Sub-Sections:: Sub-Sections
2412 @node Secs Background
2415 Roughly, a section is a range of addresses, with no gaps; all data
2416 ``in'' those addresses is treated the same for some particular purpose.
2417 For example there may be a ``read only'' section.
2419 @cindex linker, and assembler
2420 @cindex assembler, and linker
2421 The linker @code{@value{LD}} reads many object files (partial programs) and
2422 combines their contents to form a runnable program. When @code{@value{AS}}
2423 emits an object file, the partial program is assumed to start at address 0.
2424 @code{@value{LD}} assigns the final addresses for the partial program, so that
2425 different partial programs do not overlap. This is actually an
2426 oversimplification, but it suffices to explain how @code{@value{AS}} uses
2429 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2430 addresses. These blocks slide to their run-time addresses as rigid
2431 units; their length does not change and neither does the order of bytes
2432 within them. Such a rigid unit is called a @emph{section}. Assigning
2433 run-time addresses to sections is called @dfn{relocation}. It includes
2434 the task of adjusting mentions of object-file addresses so they refer to
2435 the proper run-time addresses.
2437 For the H8/300 and H8/500,
2438 and for the Hitachi SH,
2439 @code{@value{AS}} pads sections if needed to
2440 ensure they end on a word (sixteen bit) boundary.
2443 @cindex standard assembler sections
2444 An object file written by @code{@value{AS}} has at least three sections, any
2445 of which may be empty. These are named @dfn{text}, @dfn{data} and
2450 When it generates COFF output,
2452 @code{@value{AS}} can also generate whatever other named sections you specify
2453 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2454 If you do not use any directives that place output in the @samp{.text}
2455 or @samp{.data} sections, these sections still exist, but are empty.
2460 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2462 @code{@value{AS}} can also generate whatever other named sections you
2463 specify using the @samp{.space} and @samp{.subspace} directives. See
2464 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2465 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2466 assembler directives.
2469 Additionally, @code{@value{AS}} uses different names for the standard
2470 text, data, and bss sections when generating SOM output. Program text
2471 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2472 BSS into @samp{$BSS$}.
2476 Within the object file, the text section starts at address @code{0}, the
2477 data section follows, and the bss section follows the data section.
2480 When generating either SOM or ELF output files on the HPPA, the text
2481 section starts at address @code{0}, the data section at address
2482 @code{0x4000000}, and the bss section follows the data section.
2485 To let @code{@value{LD}} know which data changes when the sections are
2486 relocated, and how to change that data, @code{@value{AS}} also writes to the
2487 object file details of the relocation needed. To perform relocation
2488 @code{@value{LD}} must know, each time an address in the object
2492 Where in the object file is the beginning of this reference to
2495 How long (in bytes) is this reference?
2497 Which section does the address refer to? What is the numeric value of
2499 (@var{address}) @minus{} (@var{start-address of section})?
2502 Is the reference to an address ``Program-Counter relative''?
2505 @cindex addresses, format of
2506 @cindex section-relative addressing
2507 In fact, every address @code{@value{AS}} ever uses is expressed as
2509 (@var{section}) + (@var{offset into section})
2512 Further, most expressions @code{@value{AS}} computes have this section-relative
2515 (For some object formats, such as SOM for the HPPA, some expressions are
2516 symbol-relative instead.)
2519 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2520 @var{N} into section @var{secname}.''
2522 Apart from text, data and bss sections you need to know about the
2523 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2524 addresses in the absolute section remain unchanged. For example, address
2525 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2526 @code{@value{LD}}. Although the linker never arranges two partial programs'
2527 data sections with overlapping addresses after linking, @emph{by definition}
2528 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2529 part of a program is always the same address when the program is running as
2530 address @code{@{absolute@ 239@}} in any other part of the program.
2532 The idea of sections is extended to the @dfn{undefined} section. Any
2533 address whose section is unknown at assembly time is by definition
2534 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2535 Since numbers are always defined, the only way to generate an undefined
2536 address is to mention an undefined symbol. A reference to a named
2537 common block would be such a symbol: its value is unknown at assembly
2538 time so it has section @emph{undefined}.
2540 By analogy the word @emph{section} is used to describe groups of sections in
2541 the linked program. @code{@value{LD}} puts all partial programs' text
2542 sections in contiguous addresses in the linked program. It is
2543 customary to refer to the @emph{text section} of a program, meaning all
2544 the addresses of all partial programs' text sections. Likewise for
2545 data and bss sections.
2547 Some sections are manipulated by @code{@value{LD}}; others are invented for
2548 use of @code{@value{AS}} and have no meaning except during assembly.
2551 @section Linker Sections
2552 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2557 @cindex named sections
2558 @cindex sections, named
2559 @item named sections
2562 @cindex text section
2563 @cindex data section
2567 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2568 separate but equal sections. Anything you can say of one section is
2571 When the program is running, however, it is
2572 customary for the text section to be unalterable. The
2573 text section is often shared among processes: it contains
2574 instructions, constants and the like. The data section of a running
2575 program is usually alterable: for example, C variables would be stored
2576 in the data section.
2581 This section contains zeroed bytes when your program begins running. It
2582 is used to hold uninitialized variables or common storage. The length of
2583 each partial program's bss section is important, but because it starts
2584 out containing zeroed bytes there is no need to store explicit zero
2585 bytes in the object file. The bss section was invented to eliminate
2586 those explicit zeros from object files.
2588 @cindex absolute section
2589 @item absolute section
2590 Address 0 of this section is always ``relocated'' to runtime address 0.
2591 This is useful if you want to refer to an address that @code{@value{LD}} must
2592 not change when relocating. In this sense we speak of absolute
2593 addresses being ``unrelocatable'': they do not change during relocation.
2595 @cindex undefined section
2596 @item undefined section
2597 This ``section'' is a catch-all for address references to objects not in
2598 the preceding sections.
2599 @c FIXME: ref to some other doc on obj-file formats could go here.
2602 @cindex relocation example
2603 An idealized example of three relocatable sections follows.
2605 The example uses the traditional section names @samp{.text} and @samp{.data}.
2607 Memory addresses are on the horizontal axis.
2611 @c END TEXI2ROFF-KILL
2614 partial program # 1: |ttttt|dddd|00|
2621 partial program # 2: |TTT|DDD|000|
2624 +--+---+-----+--+----+---+-----+~~
2625 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2626 +--+---+-----+--+----+---+-----+~~
2628 addresses: 0 @dots{}
2635 \line{\it Partial program \#1: \hfil}
2636 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2637 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2639 \line{\it Partial program \#2: \hfil}
2640 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2641 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2643 \line{\it linked program: \hfil}
2644 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2645 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2646 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2647 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2649 \line{\it addresses: \hfil}
2653 @c END TEXI2ROFF-KILL
2656 @section Assembler Internal Sections
2658 @cindex internal assembler sections
2659 @cindex sections in messages, internal
2660 These sections are meant only for the internal use of @code{@value{AS}}. They
2661 have no meaning at run-time. You do not really need to know about these
2662 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2663 warning messages, so it might be helpful to have an idea of their
2664 meanings to @code{@value{AS}}. These sections are used to permit the
2665 value of every expression in your assembly language program to be a
2666 section-relative address.
2669 @cindex assembler internal logic error
2670 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2671 An internal assembler logic error has been found. This means there is a
2672 bug in the assembler.
2674 @cindex expr (internal section)
2676 The assembler stores complex expression internally as combinations of
2677 symbols. When it needs to represent an expression as a symbol, it puts
2678 it in the expr section.
2680 @c FIXME item transfer[t] vector preload
2681 @c FIXME item transfer[t] vector postload
2682 @c FIXME item register
2686 @section Sub-Sections
2688 @cindex numbered subsections
2689 @cindex grouping data
2695 fall into two sections: text and data.
2697 You may have separate groups of
2699 data in named sections
2703 data in named sections
2709 that you want to end up near to each other in the object file, even though they
2710 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2711 use @dfn{subsections} for this purpose. Within each section, there can be
2712 numbered subsections with values from 0 to 8192. Objects assembled into the
2713 same subsection go into the object file together with other objects in the same
2714 subsection. For example, a compiler might want to store constants in the text
2715 section, but might not want to have them interspersed with the program being
2716 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2717 section of code being output, and a @samp{.text 1} before each group of
2718 constants being output.
2720 Subsections are optional. If you do not use subsections, everything
2721 goes in subsection number zero.
2724 Each subsection is zero-padded up to a multiple of four bytes.
2725 (Subsections may be padded a different amount on different flavors
2726 of @code{@value{AS}}.)
2730 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2731 boundary (two bytes).
2732 The same is true on the Hitachi SH.
2735 @c FIXME section padding (alignment)?
2736 @c Rich Pixley says padding here depends on target obj code format; that
2737 @c doesn't seem particularly useful to say without further elaboration,
2738 @c so for now I say nothing about it. If this is a generic BFD issue,
2739 @c these paragraphs might need to vanish from this manual, and be
2740 @c discussed in BFD chapter of binutils (or some such).
2743 On the AMD 29K family, no particular padding is added to section or
2744 subsection sizes; @value{AS} forces no alignment on this platform.
2748 Subsections appear in your object file in numeric order, lowest numbered
2749 to highest. (All this to be compatible with other people's assemblers.)
2750 The object file contains no representation of subsections; @code{@value{LD}} and
2751 other programs that manipulate object files see no trace of them.
2752 They just see all your text subsections as a text section, and all your
2753 data subsections as a data section.
2755 To specify which subsection you want subsequent statements assembled
2756 into, use a numeric argument to specify it, in a @samp{.text
2757 @var{expression}} or a @samp{.data @var{expression}} statement.
2760 When generating COFF output, you
2765 can also use an extra subsection
2766 argument with arbitrary named sections: @samp{.section @var{name},
2769 @var{Expression} should be an absolute expression.
2770 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2771 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2772 begins in @code{text 0}. For instance:
2774 .text 0 # The default subsection is text 0 anyway.
2775 .ascii "This lives in the first text subsection. *"
2777 .ascii "But this lives in the second text subsection."
2779 .ascii "This lives in the data section,"
2780 .ascii "in the first data subsection."
2782 .ascii "This lives in the first text section,"
2783 .ascii "immediately following the asterisk (*)."
2786 Each section has a @dfn{location counter} incremented by one for every byte
2787 assembled into that section. Because subsections are merely a convenience
2788 restricted to @code{@value{AS}} there is no concept of a subsection location
2789 counter. There is no way to directly manipulate a location counter---but the
2790 @code{.align} directive changes it, and any label definition captures its
2791 current value. The location counter of the section where statements are being
2792 assembled is said to be the @dfn{active} location counter.
2795 @section bss Section
2798 @cindex common variable storage
2799 The bss section is used for local common variable storage.
2800 You may allocate address space in the bss section, but you may
2801 not dictate data to load into it before your program executes. When
2802 your program starts running, all the contents of the bss
2803 section are zeroed bytes.
2805 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2806 @ref{Lcomm,,@code{.lcomm}}.
2808 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2809 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2812 When assembling for a target which supports multiple sections, such as ELF or
2813 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2814 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2815 section. Typically the section will only contain symbol definitions and
2816 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2823 Symbols are a central concept: the programmer uses symbols to name
2824 things, the linker uses symbols to link, and the debugger uses symbols
2828 @cindex debuggers, and symbol order
2829 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2830 the same order they were declared. This may break some debuggers.
2835 * Setting Symbols:: Giving Symbols Other Values
2836 * Symbol Names:: Symbol Names
2837 * Dot:: The Special Dot Symbol
2838 * Symbol Attributes:: Symbol Attributes
2845 A @dfn{label} is written as a symbol immediately followed by a colon
2846 @samp{:}. The symbol then represents the current value of the
2847 active location counter, and is, for example, a suitable instruction
2848 operand. You are warned if you use the same symbol to represent two
2849 different locations: the first definition overrides any other
2853 On the HPPA, the usual form for a label need not be immediately followed by a
2854 colon, but instead must start in column zero. Only one label may be defined on
2855 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2856 provides a special directive @code{.label} for defining labels more flexibly.
2859 @node Setting Symbols
2860 @section Giving Symbols Other Values
2862 @cindex assigning values to symbols
2863 @cindex symbol values, assigning
2864 A symbol can be given an arbitrary value by writing a symbol, followed
2865 by an equals sign @samp{=}, followed by an expression
2866 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2867 directive. @xref{Set,,@code{.set}}.
2870 @section Symbol Names
2872 @cindex symbol names
2873 @cindex names, symbol
2874 @ifclear SPECIAL-SYMS
2875 Symbol names begin with a letter or with one of @samp{._}. On most
2876 machines, you can also use @code{$} in symbol names; exceptions are
2877 noted in @ref{Machine Dependencies}. That character may be followed by any
2878 string of digits, letters, dollar signs (unless otherwise noted in
2879 @ref{Machine Dependencies}), and underscores.
2882 For the AMD 29K family, @samp{?} is also allowed in the
2883 body of a symbol name, though not at its beginning.
2888 Symbol names begin with a letter or with one of @samp{._}. On the
2890 H8/500, you can also use @code{$} in symbol names. That character may
2891 be followed by any string of digits, letters, dollar signs (save on the
2892 H8/300), and underscores.
2896 Case of letters is significant: @code{foo} is a different symbol name
2899 Each symbol has exactly one name. Each name in an assembly language program
2900 refers to exactly one symbol. You may use that symbol name any number of times
2903 @subheading Local Symbol Names
2905 @cindex local symbol names
2906 @cindex symbol names, local
2907 @cindex temporary symbol names
2908 @cindex symbol names, temporary
2909 Local symbols help compilers and programmers use names temporarily.
2910 There are ten local symbol names, which are re-used throughout the
2911 program. You may refer to them using the names @samp{0} @samp{1}
2912 @dots{} @samp{9}. To define a local symbol, write a label of the form
2913 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2914 recent previous definition of that symbol write @samp{@b{N}b}, using the
2915 same digit as when you defined the label. To refer to the next
2916 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2917 a choice of 10 forward references. The @samp{b} stands for
2918 ``backwards'' and the @samp{f} stands for ``forwards''.
2920 Local symbols are not emitted by the current @sc{gnu} C compiler.
2922 There is no restriction on how you can use these labels, but
2923 remember that at any point in the assembly you can refer to at most
2924 10 prior local labels and to at most 10 forward local labels.
2926 Local symbol names are only a notation device. They are immediately
2927 transformed into more conventional symbol names before the assembler
2928 uses them. The symbol names stored in the symbol table, appearing in
2929 error messages and optionally emitted to the object file have these
2934 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2935 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2936 used for symbols you are never intended to see. If you use the
2937 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2938 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2939 you may use them in debugging.
2942 If the label is written @samp{0:} then the digit is @samp{0}.
2943 If the label is written @samp{1:} then the digit is @samp{1}.
2944 And so on up through @samp{9:}.
2947 This unusual character is included so you do not accidentally invent
2948 a symbol of the same name. The character has ASCII value
2951 @item @emph{ordinal number}
2952 This is a serial number to keep the labels distinct. The first
2953 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2954 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2958 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2959 @code{3:} is named @code{L3@kbd{C-A}44}.
2962 @section The Special Dot Symbol
2964 @cindex dot (symbol)
2965 @cindex @code{.} (symbol)
2966 @cindex current address
2967 @cindex location counter
2968 The special symbol @samp{.} refers to the current address that
2969 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2970 .long .} defines @code{melvin} to contain its own address.
2971 Assigning a value to @code{.} is treated the same as a @code{.org}
2972 directive. Thus, the expression @samp{.=.+4} is the same as saying
2973 @ifclear no-space-dir
2982 @node Symbol Attributes
2983 @section Symbol Attributes
2985 @cindex symbol attributes
2986 @cindex attributes, symbol
2987 Every symbol has, as well as its name, the attributes ``Value'' and
2988 ``Type''. Depending on output format, symbols can also have auxiliary
2991 The detailed definitions are in @file{a.out.h}.
2994 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2995 all these attributes, and probably won't warn you. This makes the
2996 symbol an externally defined symbol, which is generally what you
3000 * Symbol Value:: Value
3001 * Symbol Type:: Type
3004 * a.out Symbols:: Symbol Attributes: @code{a.out}
3008 * a.out Symbols:: Symbol Attributes: @code{a.out}
3011 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
3016 * COFF Symbols:: Symbol Attributes for COFF
3019 * SOM Symbols:: Symbol Attributes for SOM
3026 @cindex value of a symbol
3027 @cindex symbol value
3028 The value of a symbol is (usually) 32 bits. For a symbol which labels a
3029 location in the text, data, bss or absolute sections the value is the
3030 number of addresses from the start of that section to the label.
3031 Naturally for text, data and bss sections the value of a symbol changes
3032 as @code{@value{LD}} changes section base addresses during linking. Absolute
3033 symbols' values do not change during linking: that is why they are
3036 The value of an undefined symbol is treated in a special way. If it is
3037 0 then the symbol is not defined in this assembler source file, and
3038 @code{@value{LD}} tries to determine its value from other files linked into the
3039 same program. You make this kind of symbol simply by mentioning a symbol
3040 name without defining it. A non-zero value represents a @code{.comm}
3041 common declaration. The value is how much common storage to reserve, in
3042 bytes (addresses). The symbol refers to the first address of the
3048 @cindex type of a symbol
3050 The type attribute of a symbol contains relocation (section)
3051 information, any flag settings indicating that a symbol is external, and
3052 (optionally), other information for linkers and debuggers. The exact
3053 format depends on the object-code output format in use.
3058 @c The following avoids a "widow" subsection title. @group would be
3059 @c better if it were available outside examples.
3062 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
3064 @cindex @code{b.out} symbol attributes
3065 @cindex symbol attributes, @code{b.out}
3066 These symbol attributes appear only when @code{@value{AS}} is configured for
3067 one of the Berkeley-descended object output formats---@code{a.out} or
3073 @subsection Symbol Attributes: @code{a.out}
3075 @cindex @code{a.out} symbol attributes
3076 @cindex symbol attributes, @code{a.out}
3082 @subsection Symbol Attributes: @code{a.out}
3084 @cindex @code{a.out} symbol attributes
3085 @cindex symbol attributes, @code{a.out}
3089 * Symbol Desc:: Descriptor
3090 * Symbol Other:: Other
3094 @subsubsection Descriptor
3096 @cindex descriptor, of @code{a.out} symbol
3097 This is an arbitrary 16-bit value. You may establish a symbol's
3098 descriptor value by using a @code{.desc} statement
3099 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
3103 @subsubsection Other
3105 @cindex other attribute, of @code{a.out} symbol
3106 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
3111 @subsection Symbol Attributes for COFF
3113 @cindex COFF symbol attributes
3114 @cindex symbol attributes, COFF
3116 The COFF format supports a multitude of auxiliary symbol attributes;
3117 like the primary symbol attributes, they are set between @code{.def} and
3118 @code{.endef} directives.
3120 @subsubsection Primary Attributes
3122 @cindex primary attributes, COFF symbols
3123 The symbol name is set with @code{.def}; the value and type,
3124 respectively, with @code{.val} and @code{.type}.
3126 @subsubsection Auxiliary Attributes
3128 @cindex auxiliary attributes, COFF symbols
3129 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
3130 @code{.size}, and @code{.tag} can generate auxiliary symbol table
3131 information for COFF.
3136 @subsection Symbol Attributes for SOM
3138 @cindex SOM symbol attributes
3139 @cindex symbol attributes, SOM
3141 The SOM format for the HPPA supports a multitude of symbol attributes set with
3142 the @code{.EXPORT} and @code{.IMPORT} directives.
3144 The attributes are described in @cite{HP9000 Series 800 Assembly
3145 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
3146 @code{EXPORT} assembler directive documentation.
3150 @chapter Expressions
3154 @cindex numeric values
3155 An @dfn{expression} specifies an address or numeric value.
3156 Whitespace may precede and/or follow an expression.
3158 The result of an expression must be an absolute number, or else an offset into
3159 a particular section. If an expression is not absolute, and there is not
3160 enough information when @code{@value{AS}} sees the expression to know its
3161 section, a second pass over the source program might be necessary to interpret
3162 the expression---but the second pass is currently not implemented.
3163 @code{@value{AS}} aborts with an error message in this situation.
3166 * Empty Exprs:: Empty Expressions
3167 * Integer Exprs:: Integer Expressions
3171 @section Empty Expressions
3173 @cindex empty expressions
3174 @cindex expressions, empty
3175 An empty expression has no value: it is just whitespace or null.
3176 Wherever an absolute expression is required, you may omit the
3177 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
3178 is compatible with other assemblers.
3181 @section Integer Expressions
3183 @cindex integer expressions
3184 @cindex expressions, integer
3185 An @dfn{integer expression} is one or more @emph{arguments} delimited
3186 by @emph{operators}.
3189 * Arguments:: Arguments
3190 * Operators:: Operators
3191 * Prefix Ops:: Prefix Operators
3192 * Infix Ops:: Infix Operators
3196 @subsection Arguments
3198 @cindex expression arguments
3199 @cindex arguments in expressions
3200 @cindex operands in expressions
3201 @cindex arithmetic operands
3202 @dfn{Arguments} are symbols, numbers or subexpressions. In other
3203 contexts arguments are sometimes called ``arithmetic operands''. In
3204 this manual, to avoid confusing them with the ``instruction operands'' of
3205 the machine language, we use the term ``argument'' to refer to parts of
3206 expressions only, reserving the word ``operand'' to refer only to machine
3207 instruction operands.
3209 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3210 @var{section} is one of text, data, bss, absolute,
3211 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3214 Numbers are usually integers.
3216 A number can be a flonum or bignum. In this case, you are warned
3217 that only the low order 32 bits are used, and @code{@value{AS}} pretends
3218 these 32 bits are an integer. You may write integer-manipulating
3219 instructions that act on exotic constants, compatible with other
3222 @cindex subexpressions
3223 Subexpressions are a left parenthesis @samp{(} followed by an integer
3224 expression, followed by a right parenthesis @samp{)}; or a prefix
3225 operator followed by an argument.
3228 @subsection Operators
3230 @cindex operators, in expressions
3231 @cindex arithmetic functions
3232 @cindex functions, in expressions
3233 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3234 operators are followed by an argument. Infix operators appear
3235 between their arguments. Operators may be preceded and/or followed by
3239 @subsection Prefix Operator
3241 @cindex prefix operators
3242 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
3243 one argument, which must be absolute.
3245 @c the tex/end tex stuff surrounding this small table is meant to make
3246 @c it align, on the printed page, with the similar table in the next
3247 @c section (which is inside an enumerate).
3249 \global\advance\leftskip by \itemindent
3254 @dfn{Negation}. Two's complement negation.
3256 @dfn{Complementation}. Bitwise not.
3260 \global\advance\leftskip by -\itemindent
3264 @subsection Infix Operators
3266 @cindex infix operators
3267 @cindex operators, permitted arguments
3268 @dfn{Infix operators} take two arguments, one on either side. Operators
3269 have precedence, but operations with equal precedence are performed left
3270 to right. Apart from @code{+} or @code{-}, both arguments must be
3271 absolute, and the result is absolute.
3274 @cindex operator precedence
3275 @cindex precedence of operators
3282 @dfn{Multiplication}.
3285 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3292 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3296 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3300 Intermediate precedence
3305 @dfn{Bitwise Inclusive Or}.
3311 @dfn{Bitwise Exclusive Or}.
3314 @dfn{Bitwise Or Not}.
3321 @cindex addition, permitted arguments
3322 @cindex plus, permitted arguments
3323 @cindex arguments for addition
3325 @dfn{Addition}. If either argument is absolute, the result has the section of
3326 the other argument. You may not add together arguments from different
3329 @cindex subtraction, permitted arguments
3330 @cindex minus, permitted arguments
3331 @cindex arguments for subtraction
3333 @dfn{Subtraction}. If the right argument is absolute, the
3334 result has the section of the left argument.
3335 If both arguments are in the same section, the result is absolute.
3336 You may not subtract arguments from different sections.
3337 @c FIXME is there still something useful to say about undefined - undefined ?
3339 @cindex comparison expressions
3340 @cindex expressions, comparison
3344 @dfn{Is Not Equal To}
3348 @dfn{Is Greater Than}
3350 @dfn{Is Greater Than Or Equal To}
3352 @dfn{Is Less Than Or Equal To}
3354 The comparison operators can be used as infix operators. A true results has a
3355 value of -1 whereas a false result has a value of 0. Note, these operators
3356 perform signed comparisons.
3359 @item Lowest Precedence
3368 These two logical operations can be used to combine the results of sub
3369 expressions. Note, unlike the comparison operators a true result returns a
3370 value of 1 but a false results does still return 0. Also note that the logical
3371 or operator has a slightly lower precedence than logical and.
3376 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3377 address; you can only have a defined section in one of the two arguments.
3380 @chapter Assembler Directives
3382 @cindex directives, machine independent
3383 @cindex pseudo-ops, machine independent
3384 @cindex machine independent directives
3385 All assembler directives have names that begin with a period (@samp{.}).
3386 The rest of the name is letters, usually in lower case.
3388 This chapter discusses directives that are available regardless of the
3389 target machine configuration for the @sc{gnu} assembler.
3391 Some machine configurations provide additional directives.
3392 @xref{Machine Dependencies}.
3395 @ifset machine-directives
3396 @xref{Machine Dependencies} for additional directives.
3401 * Abort:: @code{.abort}
3403 * ABORT:: @code{.ABORT}
3406 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3407 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3408 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3409 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3410 * Byte:: @code{.byte @var{expressions}}
3411 * Comm:: @code{.comm @var{symbol} , @var{length} }
3412 * Data:: @code{.data @var{subsection}}
3414 * Def:: @code{.def @var{name}}
3417 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3423 * Double:: @code{.double @var{flonums}}
3424 * Eject:: @code{.eject}
3425 * Else:: @code{.else}
3426 * Elseif:: @code{.elseif}
3429 * Endef:: @code{.endef}
3432 * Endfunc:: @code{.endfunc}
3433 * Endif:: @code{.endif}
3434 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3435 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3437 * Exitm:: @code{.exitm}
3438 * Extern:: @code{.extern}
3439 * Fail:: @code{.fail}
3440 @ifclear no-file-dir
3441 * File:: @code{.file @var{string}}
3444 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3445 * Float:: @code{.float @var{flonums}}
3446 * Func:: @code{.func}
3447 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3449 * Hidden:: @code{.hidden @var{names}}
3452 * hword:: @code{.hword @var{expressions}}
3453 * Ident:: @code{.ident}
3454 * If:: @code{.if @var{absolute expression}}
3455 * Incbin:: @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
3456 * Include:: @code{.include "@var{file}"}
3457 * Int:: @code{.int @var{expressions}}
3459 * Internal:: @code{.internal @var{names}}
3462 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3463 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3464 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3465 * Lflags:: @code{.lflags}
3466 @ifclear no-line-dir
3467 * Line:: @code{.line @var{line-number}}
3470 * Ln:: @code{.ln @var{line-number}}
3471 * Linkonce:: @code{.linkonce [@var{type}]}
3472 * List:: @code{.list}
3473 * Long:: @code{.long @var{expressions}}
3475 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3478 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3479 * MRI:: @code{.mri @var{val}}
3480 * Nolist:: @code{.nolist}
3481 * Octa:: @code{.octa @var{bignums}}
3482 * Org:: @code{.org @var{new-lc} , @var{fill}}
3483 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3485 * PopSection:: @code{.popsection}
3486 * Previous:: @code{.previous}
3489 * Print:: @code{.print @var{string}}
3491 * Protected:: @code{.protected @var{names}}
3494 * Psize:: @code{.psize @var{lines}, @var{columns}}
3495 * Purgem:: @code{.purgem @var{name}}
3497 * PushSection:: @code{.pushsection @var{name}}
3500 * Quad:: @code{.quad @var{bignums}}
3501 * Rept:: @code{.rept @var{count}}
3502 * Sbttl:: @code{.sbttl "@var{subheading}"}
3504 * Scl:: @code{.scl @var{class}}
3505 * Section:: @code{.section @var{name}, @var{subsection}}
3508 * Set:: @code{.set @var{symbol}, @var{expression}}
3509 * Short:: @code{.short @var{expressions}}
3510 * Single:: @code{.single @var{flonums}}
3511 * Size:: @code{.size [@var{name} , @var{expression}]}
3512 * Skip:: @code{.skip @var{size} , @var{fill}}
3513 * Sleb128:: @code{.sleb128 @var{expressions}}
3514 * Space:: @code{.space @var{size} , @var{fill}}
3516 * Stab:: @code{.stabd, .stabn, .stabs}
3519 * String:: @code{.string "@var{str}"}
3520 * Struct:: @code{.struct @var{expression}}
3522 * SubSection:: @code{.subsection}
3523 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3527 * Tag:: @code{.tag @var{structname}}
3530 * Text:: @code{.text @var{subsection}}
3531 * Title:: @code{.title "@var{heading}"}
3532 * Type:: @code{.type <@var{int} | @var{name} , @var{type description}>}
3533 * Uleb128:: @code{.uleb128 @var{expressions}}
3535 * Val:: @code{.val @var{addr}}
3539 * Version:: @code{.version "@var{string}"}
3540 * VTableEntry:: @code{.vtable_entry @var{table}, @var{offset}}
3541 * VTableInherit:: @code{.vtable_inherit @var{child}, @var{parent}}
3542 * Weak:: @code{.weak @var{names}}
3545 * Word:: @code{.word @var{expressions}}
3546 * Deprecated:: Deprecated Directives
3550 @section @code{.abort}
3552 @cindex @code{abort} directive
3553 @cindex stopping the assembly
3554 This directive stops the assembly immediately. It is for
3555 compatibility with other assemblers. The original idea was that the
3556 assembly language source would be piped into the assembler. If the sender
3557 of the source quit, it could use this directive tells @code{@value{AS}} to
3558 quit also. One day @code{.abort} will not be supported.
3562 @section @code{.ABORT}
3564 @cindex @code{ABORT} directive
3565 When producing COFF output, @code{@value{AS}} accepts this directive as a
3566 synonym for @samp{.abort}.
3569 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3575 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3577 @cindex padding the location counter
3578 @cindex @code{align} directive
3579 Pad the location counter (in the current subsection) to a particular storage
3580 boundary. The first expression (which must be absolute) is the alignment
3581 required, as described below.
3583 The second expression (also absolute) gives the fill value to be stored in the
3584 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3585 padding bytes are normally zero. However, on some systems, if the section is
3586 marked as containing code and the fill value is omitted, the space is filled
3587 with no-op instructions.
3589 The third expression is also absolute, and is also optional. If it is present,
3590 it is the maximum number of bytes that should be skipped by this alignment
3591 directive. If doing the alignment would require skipping more bytes than the
3592 specified maximum, then the alignment is not done at all. You can omit the
3593 fill value (the second argument) entirely by simply using two commas after the
3594 required alignment; this can be useful if you want the alignment to be filled
3595 with no-op instructions when appropriate.
3597 The way the required alignment is specified varies from system to system.
3598 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3600 the first expression is the
3601 alignment request in bytes. For example @samp{.align 8} advances
3602 the location counter until it is a multiple of 8. If the location counter
3603 is already a multiple of 8, no change is needed.
3605 For other systems, including the i386 using a.out format, and the arm and
3606 strongarm, it is the
3607 number of low-order zero bits the location counter must have after
3608 advancement. For example @samp{.align 3} advances the location
3609 counter until it a multiple of 8. If the location counter is already a
3610 multiple of 8, no change is needed.
3612 This inconsistency is due to the different behaviors of the various
3613 native assemblers for these systems which GAS must emulate.
3614 GAS also provides @code{.balign} and @code{.p2align} directives,
3615 described later, which have a consistent behavior across all
3616 architectures (but are specific to GAS).
3619 @section @code{.ascii "@var{string}"}@dots{}
3621 @cindex @code{ascii} directive
3622 @cindex string literals
3623 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3624 separated by commas. It assembles each string (with no automatic
3625 trailing zero byte) into consecutive addresses.
3628 @section @code{.asciz "@var{string}"}@dots{}
3630 @cindex @code{asciz} directive
3631 @cindex zero-terminated strings
3632 @cindex null-terminated strings
3633 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3634 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3637 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3639 @cindex padding the location counter given number of bytes
3640 @cindex @code{balign} directive
3641 Pad the location counter (in the current subsection) to a particular
3642 storage boundary. The first expression (which must be absolute) is the
3643 alignment request in bytes. For example @samp{.balign 8} advances
3644 the location counter until it is a multiple of 8. If the location counter
3645 is already a multiple of 8, no change is needed.
3647 The second expression (also absolute) gives the fill value to be stored in the
3648 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3649 padding bytes are normally zero. However, on some systems, if the section is
3650 marked as containing code and the fill value is omitted, the space is filled
3651 with no-op instructions.
3653 The third expression is also absolute, and is also optional. If it is present,
3654 it is the maximum number of bytes that should be skipped by this alignment
3655 directive. If doing the alignment would require skipping more bytes than the
3656 specified maximum, then the alignment is not done at all. You can omit the
3657 fill value (the second argument) entirely by simply using two commas after the
3658 required alignment; this can be useful if you want the alignment to be filled
3659 with no-op instructions when appropriate.
3661 @cindex @code{balignw} directive
3662 @cindex @code{balignl} directive
3663 The @code{.balignw} and @code{.balignl} directives are variants of the
3664 @code{.balign} directive. The @code{.balignw} directive treats the fill
3665 pattern as a two byte word value. The @code{.balignl} directives treats the
3666 fill pattern as a four byte longword value. For example, @code{.balignw
3667 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3668 filled in with the value 0x368d (the exact placement of the bytes depends upon
3669 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3673 @section @code{.byte @var{expressions}}
3675 @cindex @code{byte} directive
3676 @cindex integers, one byte
3677 @code{.byte} expects zero or more expressions, separated by commas.
3678 Each expression is assembled into the next byte.
3681 @section @code{.comm @var{symbol} , @var{length} }
3683 @cindex @code{comm} directive
3684 @cindex symbol, common
3685 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3686 common symbol in one object file may be merged with a defined or common symbol
3687 of the same name in another object file. If @code{@value{LD}} does not see a
3688 definition for the symbol--just one or more common symbols--then it will
3689 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3690 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3691 the same name, and they do not all have the same size, it will allocate space
3692 using the largest size.
3695 When using ELF, the @code{.comm} directive takes an optional third argument.
3696 This is the desired alignment of the symbol, specified as a byte boundary (for
3697 example, an alignment of 16 means that the least significant 4 bits of the
3698 address should be zero). The alignment must be an absolute expression, and it
3699 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3700 for the common symbol, it will use the alignment when placing the symbol. If
3701 no alignment is specified, @code{@value{AS}} will set the alignment to the
3702 largest power of two less than or equal to the size of the symbol, up to a
3707 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3708 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3712 @section @code{.data @var{subsection}}
3714 @cindex @code{data} directive
3715 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3716 end of the data subsection numbered @var{subsection} (which is an
3717 absolute expression). If @var{subsection} is omitted, it defaults
3722 @section @code{.def @var{name}}
3724 @cindex @code{def} directive
3725 @cindex COFF symbols, debugging
3726 @cindex debugging COFF symbols
3727 Begin defining debugging information for a symbol @var{name}; the
3728 definition extends until the @code{.endef} directive is encountered.
3731 This directive is only observed when @code{@value{AS}} is configured for COFF
3732 format output; when producing @code{b.out}, @samp{.def} is recognized,
3739 @section @code{.desc @var{symbol}, @var{abs-expression}}
3741 @cindex @code{desc} directive
3742 @cindex COFF symbol descriptor
3743 @cindex symbol descriptor, COFF
3744 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3745 to the low 16 bits of an absolute expression.
3748 The @samp{.desc} directive is not available when @code{@value{AS}} is
3749 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3750 object format. For the sake of compatibility, @code{@value{AS}} accepts
3751 it, but produces no output, when configured for COFF.
3757 @section @code{.dim}
3759 @cindex @code{dim} directive
3760 @cindex COFF auxiliary symbol information
3761 @cindex auxiliary symbol information, COFF
3762 This directive is generated by compilers to include auxiliary debugging
3763 information in the symbol table. It is only permitted inside
3764 @code{.def}/@code{.endef} pairs.
3767 @samp{.dim} is only meaningful when generating COFF format output; when
3768 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3774 @section @code{.double @var{flonums}}
3776 @cindex @code{double} directive
3777 @cindex floating point numbers (double)
3778 @code{.double} expects zero or more flonums, separated by commas. It
3779 assembles floating point numbers.
3781 The exact kind of floating point numbers emitted depends on how
3782 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3786 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3787 in @sc{ieee} format.
3792 @section @code{.eject}
3794 @cindex @code{eject} directive
3795 @cindex new page, in listings
3796 @cindex page, in listings
3797 @cindex listing control: new page
3798 Force a page break at this point, when generating assembly listings.
3801 @section @code{.else}
3803 @cindex @code{else} directive
3804 @code{.else} is part of the @code{@value{AS}} support for conditional
3805 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3806 of code to be assembled if the condition for the preceding @code{.if}
3810 @section @code{.elseif}
3812 @cindex @code{elseif} directive
3813 @code{.elseif} is part of the @code{@value{AS}} support for conditional
3814 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
3815 @code{.if} block that would otherwise fill the entire @code{.else} section.
3818 @section @code{.end}
3820 @cindex @code{end} directive
3821 @code{.end} marks the end of the assembly file. @code{@value{AS}} does not
3822 process anything in the file past the @code{.end} directive.
3826 @section @code{.endef}
3828 @cindex @code{endef} directive
3829 This directive flags the end of a symbol definition begun with
3833 @samp{.endef} is only meaningful when generating COFF format output; if
3834 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3835 directive but ignores it.
3840 @section @code{.endfunc}
3841 @cindex @code{endfunc} directive
3842 @code{.endfunc} marks the end of a function specified with @code{.func}.
3845 @section @code{.endif}
3847 @cindex @code{endif} directive
3848 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3849 it marks the end of a block of code that is only assembled
3850 conditionally. @xref{If,,@code{.if}}.
3853 @section @code{.equ @var{symbol}, @var{expression}}
3855 @cindex @code{equ} directive
3856 @cindex assigning values to symbols
3857 @cindex symbols, assigning values to
3858 This directive sets the value of @var{symbol} to @var{expression}.
3859 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3862 The syntax for @code{equ} on the HPPA is
3863 @samp{@var{symbol} .equ @var{expression}}.
3867 @section @code{.equiv @var{symbol}, @var{expression}}
3868 @cindex @code{equiv} directive
3869 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3870 the assembler will signal an error if @var{symbol} is already defined.
3872 Except for the contents of the error message, this is roughly equivalent to
3881 @section @code{.err}
3882 @cindex @code{err} directive
3883 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3884 message and, unless the @code{-Z} option was used, it will not generate an
3885 object file. This can be used to signal error an conditionally compiled code.
3888 @section @code{.exitm}
3889 Exit early from the current macro definition. @xref{Macro}.
3892 @section @code{.extern}
3894 @cindex @code{extern} directive
3895 @code{.extern} is accepted in the source program---for compatibility
3896 with other assemblers---but it is ignored. @code{@value{AS}} treats
3897 all undefined symbols as external.
3900 @section @code{.fail @var{expression}}
3902 @cindex @code{fail} directive
3903 Generates an error or a warning. If the value of the @var{expression} is 500
3904 or more, @code{@value{AS}} will print a warning message. If the value is less
3905 than 500, @code{@value{AS}} will print an error message. The message will
3906 include the value of @var{expression}. This can occasionally be useful inside
3907 complex nested macros or conditional assembly.
3909 @ifclear no-file-dir
3911 @section @code{.file @var{string}}
3913 @cindex @code{file} directive
3914 @cindex logical file name
3915 @cindex file name, logical
3916 @code{.file} tells @code{@value{AS}} that we are about to start a new logical
3917 file. @var{string} is the new file name. In general, the filename is
3918 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
3919 to specify an empty file name, you must give the quotes--@code{""}. This
3920 statement may go away in future: it is only recognized to be compatible with
3921 old @code{@value{AS}} programs.
3923 In some configurations of @code{@value{AS}}, @code{.file} has already been
3924 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3929 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3931 @cindex @code{fill} directive
3932 @cindex writing patterns in memory
3933 @cindex patterns, writing in memory
3934 @var{repeat}, @var{size} and @var{value} are absolute expressions.
3935 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3936 may be zero or more. @var{Size} may be zero or more, but if it is
3937 more than 8, then it is deemed to have the value 8, compatible with
3938 other people's assemblers. The contents of each @var{repeat} bytes
3939 is taken from an 8-byte number. The highest order 4 bytes are
3940 zero. The lowest order 4 bytes are @var{value} rendered in the
3941 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3942 Each @var{size} bytes in a repetition is taken from the lowest order
3943 @var{size} bytes of this number. Again, this bizarre behavior is
3944 compatible with other people's assemblers.
3946 @var{size} and @var{value} are optional.
3947 If the second comma and @var{value} are absent, @var{value} is
3948 assumed zero. If the first comma and following tokens are absent,
3949 @var{size} is assumed to be 1.
3952 @section @code{.float @var{flonums}}
3954 @cindex floating point numbers (single)
3955 @cindex @code{float} directive
3956 This directive assembles zero or more flonums, separated by commas. It
3957 has the same effect as @code{.single}.
3959 The exact kind of floating point numbers emitted depends on how
3960 @code{@value{AS}} is configured.
3961 @xref{Machine Dependencies}.
3965 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3966 in @sc{ieee} format.
3971 @section @code{.func @var{name}[,@var{label}]}
3972 @cindex @code{func} directive
3973 @code{.func} emits debugging information to denote function @var{name}, and
3974 is ignored unless the file is assembled with debugging enabled.
3975 Only @samp{--gstabs} is currently supported.
3976 @var{label} is the entry point of the function and if omitted @var{name}
3977 prepended with the @samp{leading char} is used.
3978 @samp{leading char} is usually @code{_} or nothing, depending on the target.
3979 All functions are currently defined to have @code{void} return type.
3980 The function must be terminated with @code{.endfunc}.
3983 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3985 @cindex @code{global} directive
3986 @cindex symbol, making visible to linker
3987 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3988 @var{symbol} in your partial program, its value is made available to
3989 other partial programs that are linked with it. Otherwise,
3990 @var{symbol} takes its attributes from a symbol of the same name
3991 from another file linked into the same program.
3993 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3994 compatibility with other assemblers.
3997 On the HPPA, @code{.global} is not always enough to make it accessible to other
3998 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3999 @xref{HPPA Directives,, HPPA Assembler Directives}.
4004 @section @code{.hidden @var{names}}
4006 @cindex @code{.hidden} directive
4008 This one of the ELF visibility directives. The other two are
4009 @code{.internal} (@pxref{Internal,,@code{.internal}}) and
4010 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4012 This directive overrides the named symbols default visibility (which is set by
4013 their binding: local, global or weak). The directive sets the visibility to
4014 @code{hidden} which means that the symbols are not visible to other components.
4015 Such symbols are always considered to be @code{protected} as well.
4019 @section @code{.hword @var{expressions}}
4021 @cindex @code{hword} directive
4022 @cindex integers, 16-bit
4023 @cindex numbers, 16-bit
4024 @cindex sixteen bit integers
4025 This expects zero or more @var{expressions}, and emits
4026 a 16 bit number for each.
4029 This directive is a synonym for @samp{.short}; depending on the target
4030 architecture, it may also be a synonym for @samp{.word}.
4034 This directive is a synonym for @samp{.short}.
4037 This directive is a synonym for both @samp{.short} and @samp{.word}.
4042 @section @code{.ident}
4044 @cindex @code{ident} directive
4045 This directive is used by some assemblers to place tags in object files.
4046 @code{@value{AS}} simply accepts the directive for source-file
4047 compatibility with such assemblers, but does not actually emit anything
4051 @section @code{.if @var{absolute expression}}
4053 @cindex conditional assembly
4054 @cindex @code{if} directive
4055 @code{.if} marks the beginning of a section of code which is only
4056 considered part of the source program being assembled if the argument
4057 (which must be an @var{absolute expression}) is non-zero. The end of
4058 the conditional section of code must be marked by @code{.endif}
4059 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
4060 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
4061 If you have several conditions to check, @code{.elseif} may be used to avoid
4062 nesting blocks if/else within each subsequent @code{.else} block.
4064 The following variants of @code{.if} are also supported:
4066 @cindex @code{ifdef} directive
4067 @item .ifdef @var{symbol}
4068 Assembles the following section of code if the specified @var{symbol}
4071 @cindex @code{ifc} directive
4072 @item .ifc @var{string1},@var{string2}
4073 Assembles the following section of code if the two strings are the same. The
4074 strings may be optionally quoted with single quotes. If they are not quoted,
4075 the first string stops at the first comma, and the second string stops at the
4076 end of the line. Strings which contain whitespace should be quoted. The
4077 string comparison is case sensitive.
4079 @cindex @code{ifeq} directive
4080 @item .ifeq @var{absolute expression}
4081 Assembles the following section of code if the argument is zero.
4083 @cindex @code{ifeqs} directive
4084 @item .ifeqs @var{string1},@var{string2}
4085 Another form of @code{.ifc}. The strings must be quoted using double quotes.
4087 @cindex @code{ifge} directive
4088 @item .ifge @var{absolute expression}
4089 Assembles the following section of code if the argument is greater than or
4092 @cindex @code{ifgt} directive
4093 @item .ifgt @var{absolute expression}
4094 Assembles the following section of code if the argument is greater than zero.
4096 @cindex @code{ifle} directive
4097 @item .ifle @var{absolute expression}
4098 Assembles the following section of code if the argument is less than or equal
4101 @cindex @code{iflt} directive
4102 @item .iflt @var{absolute expression}
4103 Assembles the following section of code if the argument is less than zero.
4105 @cindex @code{ifnc} directive
4106 @item .ifnc @var{string1},@var{string2}.
4107 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
4108 following section of code if the two strings are not the same.
4110 @cindex @code{ifndef} directive
4111 @cindex @code{ifnotdef} directive
4112 @item .ifndef @var{symbol}
4113 @itemx .ifnotdef @var{symbol}
4114 Assembles the following section of code if the specified @var{symbol}
4115 has not been defined. Both spelling variants are equivalent.
4117 @cindex @code{ifne} directive
4118 @item .ifne @var{absolute expression}
4119 Assembles the following section of code if the argument is not equal to zero
4120 (in other words, this is equivalent to @code{.if}).
4122 @cindex @code{ifnes} directive
4123 @item .ifnes @var{string1},@var{string2}
4124 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
4125 following section of code if the two strings are not the same.
4129 @section @code{.incbin "@var{file}"[,@var{skip}[,@var{count}]]}
4131 @cindex @code{incbin} directive
4132 @cindex binary files, including
4133 The @code{incbin} directive includes @var{file} verbatim at the current
4134 location. You can control the search paths used with the @samp{-I} command-line
4135 option (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4138 The @var{skip} argument skips a number of bytes from the start of the
4139 @var{file}. The @var{count} argument indicates the maximum number of bytes to
4140 read. Note that the data from is not aligned in any way, make sure to proper
4141 alignment is provided before and after the @code{incbin} directive.
4144 @section @code{.include "@var{file}"}
4146 @cindex @code{include} directive
4147 @cindex supporting files, including
4148 @cindex files, including
4149 This directive provides a way to include supporting files at specified
4150 points in your source program. The code from @var{file} is assembled as
4151 if it followed the point of the @code{.include}; when the end of the
4152 included file is reached, assembly of the original file continues. You
4153 can control the search paths used with the @samp{-I} command-line option
4154 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
4158 @section @code{.int @var{expressions}}
4160 @cindex @code{int} directive
4161 @cindex integers, 32-bit
4162 Expect zero or more @var{expressions}, of any section, separated by commas.
4163 For each expression, emit a number that, at run time, is the value of that
4164 expression. The byte order and bit size of the number depends on what kind
4165 of target the assembly is for.
4169 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
4170 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
4177 @section @code{.internal @var{names}}
4179 @cindex @code{.internal} directive
4181 This one of the ELF visibility directives. The other two are
4182 @code{.hidden} (@pxref{Hidden,,@code{.hidden}}) and
4183 @code{.protected} (@pxref{Protected,,@code{.protected}}).
4185 This directive overrides the named symbols default visibility (which is set by
4186 their binding: local, global or weak). The directive sets the visibility to
4187 @code{internal} which means that the symbols are considered to be @code{hidden}
4188 (ie not visible to other components), and that some extra, processor specific
4189 processing must also be performed upon the symbols as well.
4193 @section @code{.irp @var{symbol},@var{values}}@dots{}
4195 @cindex @code{irp} directive
4196 Evaluate a sequence of statements assigning different values to @var{symbol}.
4197 The sequence of statements starts at the @code{.irp} directive, and is
4198 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
4199 set to @var{value}, and the sequence of statements is assembled. If no
4200 @var{value} is listed, the sequence of statements is assembled once, with
4201 @var{symbol} set to the null string. To refer to @var{symbol} within the
4202 sequence of statements, use @var{\symbol}.
4204 For example, assembling
4212 is equivalent to assembling
4221 @section @code{.irpc @var{symbol},@var{values}}@dots{}
4223 @cindex @code{irpc} directive
4224 Evaluate a sequence of statements assigning different values to @var{symbol}.
4225 The sequence of statements starts at the @code{.irpc} directive, and is
4226 terminated by an @code{.endr} directive. For each character in @var{value},
4227 @var{symbol} is set to the character, and the sequence of statements is
4228 assembled. If no @var{value} is listed, the sequence of statements is
4229 assembled once, with @var{symbol} set to the null string. To refer to
4230 @var{symbol} within the sequence of statements, use @var{\symbol}.
4232 For example, assembling
4240 is equivalent to assembling
4249 @section @code{.lcomm @var{symbol} , @var{length}}
4251 @cindex @code{lcomm} directive
4252 @cindex local common symbols
4253 @cindex symbols, local common
4254 Reserve @var{length} (an absolute expression) bytes for a local common
4255 denoted by @var{symbol}. The section and value of @var{symbol} are
4256 those of the new local common. The addresses are allocated in the bss
4257 section, so that at run-time the bytes start off zeroed. @var{Symbol}
4258 is not declared global (@pxref{Global,,@code{.global}}), so is normally
4259 not visible to @code{@value{LD}}.
4262 Some targets permit a third argument to be used with @code{.lcomm}. This
4263 argument specifies the desired alignment of the symbol in the bss section.
4267 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
4268 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
4272 @section @code{.lflags}
4274 @cindex @code{lflags} directive (ignored)
4275 @code{@value{AS}} accepts this directive, for compatibility with other
4276 assemblers, but ignores it.
4278 @ifclear no-line-dir
4280 @section @code{.line @var{line-number}}
4282 @cindex @code{line} directive
4286 @section @code{.ln @var{line-number}}
4288 @cindex @code{ln} directive
4290 @cindex logical line number
4292 Change the logical line number. @var{line-number} must be an absolute
4293 expression. The next line has that logical line number. Therefore any other
4294 statements on the current line (after a statement separator character) are
4295 reported as on logical line number @var{line-number} @minus{} 1. One day
4296 @code{@value{AS}} will no longer support this directive: it is recognized only
4297 for compatibility with existing assembler programs.
4301 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
4302 not available; use the synonym @code{.ln} in that context.
4307 @ifclear no-line-dir
4308 Even though this is a directive associated with the @code{a.out} or
4309 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
4310 when producing COFF output, and treats @samp{.line} as though it
4311 were the COFF @samp{.ln} @emph{if} it is found outside a
4312 @code{.def}/@code{.endef} pair.
4314 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4315 used by compilers to generate auxiliary symbol information for
4320 @section @code{.linkonce [@var{type}]}
4322 @cindex @code{linkonce} directive
4323 @cindex common sections
4324 Mark the current section so that the linker only includes a single copy of it.
4325 This may be used to include the same section in several different object files,
4326 but ensure that the linker will only include it once in the final output file.
4327 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4328 Duplicate sections are detected based on the section name, so it should be
4331 This directive is only supported by a few object file formats; as of this
4332 writing, the only object file format which supports it is the Portable
4333 Executable format used on Windows NT.
4335 The @var{type} argument is optional. If specified, it must be one of the
4336 following strings. For example:
4340 Not all types may be supported on all object file formats.
4344 Silently discard duplicate sections. This is the default.
4347 Warn if there are duplicate sections, but still keep only one copy.
4350 Warn if any of the duplicates have different sizes.
4353 Warn if any of the duplicates do not have exactly the same contents.
4357 @section @code{.ln @var{line-number}}
4359 @cindex @code{ln} directive
4360 @ifclear no-line-dir
4361 @samp{.ln} is a synonym for @samp{.line}.
4364 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
4365 must be an absolute expression. The next line has that logical
4366 line number, so any other statements on the current line (after a
4367 statement separator character @code{;}) are reported as on logical
4368 line number @var{line-number} @minus{} 1.
4371 This directive is accepted, but ignored, when @code{@value{AS}} is
4372 configured for @code{b.out}; its effect is only associated with COFF
4378 @section @code{.mri @var{val}}
4380 @cindex @code{mri} directive
4381 @cindex MRI mode, temporarily
4382 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
4383 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
4384 affects code assembled until the next @code{.mri} directive, or until the end
4385 of the file. @xref{M, MRI mode, MRI mode}.
4388 @section @code{.list}
4390 @cindex @code{list} directive
4391 @cindex listing control, turning on
4392 Control (in conjunction with the @code{.nolist} directive) whether or
4393 not assembly listings are generated. These two directives maintain an
4394 internal counter (which is zero initially). @code{.list} increments the
4395 counter, and @code{.nolist} decrements it. Assembly listings are
4396 generated whenever the counter is greater than zero.
4398 By default, listings are disabled. When you enable them (with the
4399 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4400 the initial value of the listing counter is one.
4403 @section @code{.long @var{expressions}}
4405 @cindex @code{long} directive
4406 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4409 @c no one seems to know what this is for or whether this description is
4410 @c what it really ought to do
4412 @section @code{.lsym @var{symbol}, @var{expression}}
4414 @cindex @code{lsym} directive
4415 @cindex symbol, not referenced in assembly
4416 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4417 the hash table, ensuring it cannot be referenced by name during the
4418 rest of the assembly. This sets the attributes of the symbol to be
4419 the same as the expression value:
4421 @var{other} = @var{descriptor} = 0
4422 @var{type} = @r{(section of @var{expression})}
4423 @var{value} = @var{expression}
4426 The new symbol is not flagged as external.
4430 @section @code{.macro}
4433 The commands @code{.macro} and @code{.endm} allow you to define macros that
4434 generate assembly output. For example, this definition specifies a macro
4435 @code{sum} that puts a sequence of numbers into memory:
4438 .macro sum from=0, to=5
4447 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4459 @item .macro @var{macname}
4460 @itemx .macro @var{macname} @var{macargs} @dots{}
4461 @cindex @code{macro} directive
4462 Begin the definition of a macro called @var{macname}. If your macro
4463 definition requires arguments, specify their names after the macro name,
4464 separated by commas or spaces. You can supply a default value for any
4465 macro argument by following the name with @samp{=@var{deflt}}. For
4466 example, these are all valid @code{.macro} statements:
4470 Begin the definition of a macro called @code{comm}, which takes no
4473 @item .macro plus1 p, p1
4474 @itemx .macro plus1 p p1
4475 Either statement begins the definition of a macro called @code{plus1},
4476 which takes two arguments; within the macro definition, write
4477 @samp{\p} or @samp{\p1} to evaluate the arguments.
4479 @item .macro reserve_str p1=0 p2
4480 Begin the definition of a macro called @code{reserve_str}, with two
4481 arguments. The first argument has a default value, but not the second.
4482 After the definition is complete, you can call the macro either as
4483 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4484 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4485 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4486 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4489 When you call a macro, you can specify the argument values either by
4490 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4491 @samp{sum to=17, from=9}.
4494 @cindex @code{endm} directive
4495 Mark the end of a macro definition.
4498 @cindex @code{exitm} directive
4499 Exit early from the current macro definition.
4501 @cindex number of macros executed
4502 @cindex macros, count executed
4504 @code{@value{AS}} maintains a counter of how many macros it has
4505 executed in this pseudo-variable; you can copy that number to your
4506 output with @samp{\@@}, but @emph{only within a macro definition}.
4509 @item LOCAL @var{name} [ , @dots{} ]
4510 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4511 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4512 Alternate macro syntax}.
4514 Generate a string replacement for each of the @var{name} arguments, and
4515 replace any instances of @var{name} in each macro expansion. The
4516 replacement string is unique in the assembly, and different for each
4517 separate macro expansion. @code{LOCAL} allows you to write macros that
4518 define symbols, without fear of conflict between separate macro expansions.
4523 @section @code{.nolist}
4525 @cindex @code{nolist} directive
4526 @cindex listing control, turning off
4527 Control (in conjunction with the @code{.list} directive) whether or
4528 not assembly listings are generated. These two directives maintain an
4529 internal counter (which is zero initially). @code{.list} increments the
4530 counter, and @code{.nolist} decrements it. Assembly listings are
4531 generated whenever the counter is greater than zero.
4534 @section @code{.octa @var{bignums}}
4536 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4537 @cindex @code{octa} directive
4538 @cindex integer, 16-byte
4539 @cindex sixteen byte integer
4540 This directive expects zero or more bignums, separated by commas. For each
4541 bignum, it emits a 16-byte integer.
4543 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4544 hence @emph{octa}-word for 16 bytes.
4547 @section @code{.org @var{new-lc} , @var{fill}}
4549 @cindex @code{org} directive
4550 @cindex location counter, advancing
4551 @cindex advancing location counter
4552 @cindex current address, advancing
4553 Advance the location counter of the current section to
4554 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4555 expression with the same section as the current subsection. That is,
4556 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4557 wrong section, the @code{.org} directive is ignored. To be compatible
4558 with former assemblers, if the section of @var{new-lc} is absolute,
4559 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4560 is the same as the current subsection.
4562 @code{.org} may only increase the location counter, or leave it
4563 unchanged; you cannot use @code{.org} to move the location counter
4566 @c double negative used below "not undefined" because this is a specific
4567 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4568 @c section. doc@cygnus.com 18feb91
4569 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4570 may not be undefined. If you really detest this restriction we eagerly await
4571 a chance to share your improved assembler.
4573 Beware that the origin is relative to the start of the section, not
4574 to the start of the subsection. This is compatible with other
4575 people's assemblers.
4577 When the location counter (of the current subsection) is advanced, the
4578 intervening bytes are filled with @var{fill} which should be an
4579 absolute expression. If the comma and @var{fill} are omitted,
4580 @var{fill} defaults to zero.
4583 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4585 @cindex padding the location counter given a power of two
4586 @cindex @code{p2align} directive
4587 Pad the location counter (in the current subsection) to a particular
4588 storage boundary. The first expression (which must be absolute) is the
4589 number of low-order zero bits the location counter must have after
4590 advancement. For example @samp{.p2align 3} advances the location
4591 counter until it a multiple of 8. If the location counter is already a
4592 multiple of 8, no change is needed.
4594 The second expression (also absolute) gives the fill value to be stored in the
4595 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4596 padding bytes are normally zero. However, on some systems, if the section is
4597 marked as containing code and the fill value is omitted, the space is filled
4598 with no-op instructions.
4600 The third expression is also absolute, and is also optional. If it is present,
4601 it is the maximum number of bytes that should be skipped by this alignment
4602 directive. If doing the alignment would require skipping more bytes than the
4603 specified maximum, then the alignment is not done at all. You can omit the
4604 fill value (the second argument) entirely by simply using two commas after the
4605 required alignment; this can be useful if you want the alignment to be filled
4606 with no-op instructions when appropriate.
4608 @cindex @code{p2alignw} directive
4609 @cindex @code{p2alignl} directive
4610 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4611 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4612 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4613 fill pattern as a four byte longword value. For example, @code{.p2alignw
4614 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4615 filled in with the value 0x368d (the exact placement of the bytes depends upon
4616 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4621 @section @code{.previous}
4623 @cindex @code{.previous} directive
4624 @cindex Section Stack
4625 This is one of the ELF section stack manipulation directives. The others are
4626 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4627 @code{.pushsection} (@pxref{PushSection}), and @code{.popsection}
4628 (@pxref{PopSection}).
4630 This directive swaps the current section (and subsection) with most recently
4631 referenced section (and subsection) prior to this one. Multiple
4632 @code{.previous} directives in a row will flip between two sections (and their
4635 In terms of the section stack, this directive swaps the current section with
4636 the top section on the section stack.
4641 @section @code{.popsection}
4643 @cindex @code{.popsection} directive
4644 @cindex Section Stack
4645 This is one of the ELF section stack manipulation directives. The others are
4646 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4647 @code{.pushsection} (@pxref{PushSection}), and @code{.previous}
4650 This directive replaces the current section (and subsection) with the top
4651 section (and subsection) on the section stack. This section is popped off the
4656 @section @code{.print @var{string}}
4658 @cindex @code{print} directive
4659 @code{@value{AS}} will print @var{string} on the standard output during
4660 assembly. You must put @var{string} in double quotes.
4664 @section @code{.protected @var{names}}
4666 @cindex @code{.protected} directive
4668 This one of the ELF visibility directives. The other two are
4669 @code{.hidden} (@pxref{Hidden}) and @code{.internal} (@pxref{Internal}).
4671 This directive overrides the named symbols default visibility (which is set by
4672 their binding: local, global or weak). The directive sets the visibility to
4673 @code{protected} which means that any references to the symbols from within the
4674 components that defines them must be resolved to the definition in that
4675 component, even if a definition in another component would normally preempt
4680 @section @code{.psize @var{lines} , @var{columns}}
4682 @cindex @code{psize} directive
4683 @cindex listing control: paper size
4684 @cindex paper size, for listings
4685 Use this directive to declare the number of lines---and, optionally, the
4686 number of columns---to use for each page, when generating listings.
4688 If you do not use @code{.psize}, listings use a default line-count
4689 of 60. You may omit the comma and @var{columns} specification; the
4690 default width is 200 columns.
4692 @code{@value{AS}} generates formfeeds whenever the specified number of
4693 lines is exceeded (or whenever you explicitly request one, using
4696 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4697 those explicitly specified with @code{.eject}.
4700 @section @code{.purgem @var{name}}
4702 @cindex @code{purgem} directive
4703 Undefine the macro @var{name}, so that later uses of the string will not be
4704 expanded. @xref{Macro}.
4708 @section @code{.pushsection @var{name} , @var{subsection}}
4710 @cindex @code{.pushsection} directive
4711 @cindex Section Stack
4712 This is one of the ELF section stack manipulation directives. The others are
4713 @code{.section} (@pxref{Section}), @code{.subsection} (@pxref{SubSection}),
4714 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
4717 This directive is a synonym for @code{.section}. It pushes the current section
4718 (and subsection) onto the top of the section stack, and then replaces the
4719 current section and subsection with @code{name} and @code{subsection}.
4723 @section @code{.quad @var{bignums}}
4725 @cindex @code{quad} directive
4726 @code{.quad} expects zero or more bignums, separated by commas. For
4727 each bignum, it emits
4729 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4730 warning message; and just takes the lowest order 8 bytes of the bignum.
4731 @cindex eight-byte integer
4732 @cindex integer, 8-byte
4734 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4735 hence @emph{quad}-word for 8 bytes.
4738 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4739 warning message; and just takes the lowest order 16 bytes of the bignum.
4740 @cindex sixteen-byte integer
4741 @cindex integer, 16-byte
4745 @section @code{.rept @var{count}}
4747 @cindex @code{rept} directive
4748 Repeat the sequence of lines between the @code{.rept} directive and the next
4749 @code{.endr} directive @var{count} times.
4751 For example, assembling
4759 is equivalent to assembling
4768 @section @code{.sbttl "@var{subheading}"}
4770 @cindex @code{sbttl} directive
4771 @cindex subtitles for listings
4772 @cindex listing control: subtitle
4773 Use @var{subheading} as the title (third line, immediately after the
4774 title line) when generating assembly listings.
4776 This directive affects subsequent pages, as well as the current page if
4777 it appears within ten lines of the top of a page.
4781 @section @code{.scl @var{class}}
4783 @cindex @code{scl} directive
4784 @cindex symbol storage class (COFF)
4785 @cindex COFF symbol storage class
4786 Set the storage-class value for a symbol. This directive may only be
4787 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4788 whether a symbol is static or external, or it may record further
4789 symbolic debugging information.
4792 The @samp{.scl} directive is primarily associated with COFF output; when
4793 configured to generate @code{b.out} output format, @code{@value{AS}}
4794 accepts this directive but ignores it.
4799 @section @code{.section @var{name}} (COFF version)
4801 @cindex @code{section} directive
4802 @cindex named section
4803 Use the @code{.section} directive to assemble the following code into a section
4806 This directive is only supported for targets that actually support arbitrarily
4807 named sections; on @code{a.out} targets, for example, it is not accepted, even
4808 with a standard @code{a.out} section name.
4810 For COFF targets, the @code{.section} directive is used in one of the following
4814 .section @var{name}[, "@var{flags}"]
4815 .section @var{name}[, @var{subsegment}]
4818 If the optional argument is quoted, it is taken as flags to use for the
4819 section. Each flag is a single character. The following flags are recognized:
4822 bss section (uninitialized data)
4824 section is not loaded
4834 shared section (meaningful for PE targets)
4837 If no flags are specified, the default flags depend upon the section name. If
4838 the section name is not recognized, the default will be for the section to be
4839 loaded and writable. Note the @code{n} and @code{w} flags remove attributes
4840 from the section, rather than adding them, so if they are used on their own it
4841 will be as if no flags had been specified at all.
4843 If the optional argument to the @code{.section} directive is not quoted, it is
4844 taken as a subsegment number (@pxref{Sub-Sections}).
4847 @section @code{.section @var{name}} (ELF version)
4849 @cindex @code{section} directive
4850 @cindex named section
4852 @cindex Section Stack
4853 This is one of the ELF section stack manipulation directives. The others are
4854 @code{.subsection} (@pxref{SubSection}), @code{.pushsection}
4855 (@pxref{PushSection}), @code{.popsection} (@pxref{PopSection}), and
4856 @code{.previous} (@pxref{Previous}).
4859 For ELF targets, the @code{.section} directive is used like this:
4862 .section @var{name} [, "@var{flags}"[, @@@var{type}]]
4865 The optional @var{flags} argument is a quoted string which may contain any
4866 combination of the following characters:
4869 section is allocatable
4873 section is executable
4876 The optional @var{type} argument may contain one of the following constants:
4879 section contains data
4881 section does not contain data (i.e., section only occupies space)
4884 If no flags are specified, the default flags depend upon the section name. If
4885 the section name is not recognized, the default will be for the section to have
4886 none of the above flags: it will not be allocated in memory, nor writable, nor
4887 executable. The section will contain data.
4889 For ELF targets, the assembler supports another type of @code{.section}
4890 directive for compatibility with the Solaris assembler:
4893 .section "@var{name}"[, @var{flags}...]
4896 Note that the section name is quoted. There may be a sequence of comma
4900 section is allocatable
4904 section is executable
4907 This directive replaces the current section and subsection. The replaced
4908 section and subsection are pushed onto the section stack. See the contents of
4909 the gas testsuite directory @code{gas/testsuite/gas/elf} for some examples of
4910 how this directive and the other section stack directives work.
4913 @section @code{.set @var{symbol}, @var{expression}}
4915 @cindex @code{set} directive
4916 @cindex symbol value, setting
4917 Set the value of @var{symbol} to @var{expression}. This
4918 changes @var{symbol}'s value and type to conform to
4919 @var{expression}. If @var{symbol} was flagged as external, it remains
4920 flagged (@pxref{Symbol Attributes}).
4922 You may @code{.set} a symbol many times in the same assembly.
4924 If you @code{.set} a global symbol, the value stored in the object
4925 file is the last value stored into it.
4928 The syntax for @code{set} on the HPPA is
4929 @samp{@var{symbol} .set @var{expression}}.
4933 @section @code{.short @var{expressions}}
4935 @cindex @code{short} directive
4937 @code{.short} is normally the same as @samp{.word}.
4938 @xref{Word,,@code{.word}}.
4940 In some configurations, however, @code{.short} and @code{.word} generate
4941 numbers of different lengths; @pxref{Machine Dependencies}.
4945 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4948 This expects zero or more @var{expressions}, and emits
4949 a 16 bit number for each.
4954 @section @code{.single @var{flonums}}
4956 @cindex @code{single} directive
4957 @cindex floating point numbers (single)
4958 This directive assembles zero or more flonums, separated by commas. It
4959 has the same effect as @code{.float}.
4961 The exact kind of floating point numbers emitted depends on how
4962 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4966 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4967 numbers in @sc{ieee} format.
4972 @section @code{.size} (COFF version)
4974 @cindex @code{size} directive
4975 This directive is generated by compilers to include auxiliary debugging
4976 information in the symbol table. It is only permitted inside
4977 @code{.def}/@code{.endef} pairs.
4980 @samp{.size} is only meaningful when generating COFF format output; when
4981 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4985 @section @code{.size @var{name} , @var{expression}} (ELF version)
4986 @cindex @code{size} directive
4988 This directive is used to set the size associated with a symbol @var{name}.
4989 The size in bytes is computed from @var{expression} which can make use of label
4990 arithmetic. This directive is typically used to set the size of function
4994 @section @code{.sleb128 @var{expressions}}
4996 @cindex @code{sleb128} directive
4997 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4998 compact, variable length representation of numbers used by the DWARF
4999 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
5001 @ifclear no-space-dir
5003 @section @code{.skip @var{size} , @var{fill}}
5005 @cindex @code{skip} directive
5006 @cindex filling memory
5007 This directive emits @var{size} bytes, each of value @var{fill}. Both
5008 @var{size} and @var{fill} are absolute expressions. If the comma and
5009 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
5013 @section @code{.space @var{size} , @var{fill}}
5015 @cindex @code{space} directive
5016 @cindex filling memory
5017 This directive emits @var{size} bytes, each of value @var{fill}. Both
5018 @var{size} and @var{fill} are absolute expressions. If the comma
5019 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
5024 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
5025 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
5026 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
5027 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
5036 @section @code{.space}
5037 @cindex @code{space} directive
5039 On the AMD 29K, this directive is ignored; it is accepted for
5040 compatibility with other AMD 29K assemblers.
5043 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
5044 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
5050 @section @code{.stabd, .stabn, .stabs}
5052 @cindex symbolic debuggers, information for
5053 @cindex @code{stab@var{x}} directives
5054 There are three directives that begin @samp{.stab}.
5055 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
5056 The symbols are not entered in the @code{@value{AS}} hash table: they
5057 cannot be referenced elsewhere in the source file.
5058 Up to five fields are required:
5062 This is the symbol's name. It may contain any character except
5063 @samp{\000}, so is more general than ordinary symbol names. Some
5064 debuggers used to code arbitrarily complex structures into symbol names
5068 An absolute expression. The symbol's type is set to the low 8 bits of
5069 this expression. Any bit pattern is permitted, but @code{@value{LD}}
5070 and debuggers choke on silly bit patterns.
5073 An absolute expression. The symbol's ``other'' attribute is set to the
5074 low 8 bits of this expression.
5077 An absolute expression. The symbol's descriptor is set to the low 16
5078 bits of this expression.
5081 An absolute expression which becomes the symbol's value.
5084 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
5085 or @code{.stabs} statement, the symbol has probably already been created;
5086 you get a half-formed symbol in your object file. This is
5087 compatible with earlier assemblers!
5090 @cindex @code{stabd} directive
5091 @item .stabd @var{type} , @var{other} , @var{desc}
5093 The ``name'' of the symbol generated is not even an empty string.
5094 It is a null pointer, for compatibility. Older assemblers used a
5095 null pointer so they didn't waste space in object files with empty
5098 The symbol's value is set to the location counter,
5099 relocatably. When your program is linked, the value of this symbol
5100 is the address of the location counter when the @code{.stabd} was
5103 @cindex @code{stabn} directive
5104 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
5105 The name of the symbol is set to the empty string @code{""}.
5107 @cindex @code{stabs} directive
5108 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
5109 All five fields are specified.
5115 @section @code{.string} "@var{str}"
5117 @cindex string, copying to object file
5118 @cindex @code{string} directive
5120 Copy the characters in @var{str} to the object file. You may specify more than
5121 one string to copy, separated by commas. Unless otherwise specified for a
5122 particular machine, the assembler marks the end of each string with a 0 byte.
5123 You can use any of the escape sequences described in @ref{Strings,,Strings}.
5126 @section @code{.struct @var{expression}}
5128 @cindex @code{struct} directive
5129 Switch to the absolute section, and set the section offset to @var{expression},
5130 which must be an absolute expression. You might use this as follows:
5139 This would define the symbol @code{field1} to have the value 0, the symbol
5140 @code{field2} to have the value 4, and the symbol @code{field3} to have the
5141 value 8. Assembly would be left in the absolute section, and you would need to
5142 use a @code{.section} directive of some sort to change to some other section
5143 before further assembly.
5147 @section @code{.subsection @var{name}}
5149 @cindex @code{.subsection} directive
5150 @cindex Section Stack
5151 This is one of the ELF section stack manipulation directives. The others are
5152 @code{.section} (@pxref{Section}), @code{.pushsection} (@pxref{PushSection}),
5153 @code{.popsection} (@pxref{PopSection}), and @code{.previous}
5156 This directive replaces the current subsection with @code{name}. The current
5157 section is not changed. The replaced subsection is put onto the section stack
5158 in place of the then current top of stack subsection.
5163 @section @code{.symver}
5164 @cindex @code{symver} directive
5165 @cindex symbol versioning
5166 @cindex versions of symbols
5167 Use the @code{.symver} directive to bind symbols to specific version nodes
5168 within a source file. This is only supported on ELF platforms, and is
5169 typically used when assembling files to be linked into a shared library.
5170 There are cases where it may make sense to use this in objects to be bound
5171 into an application itself so as to override a versioned symbol from a
5174 For ELF targets, the @code{.symver} directive can be used like this:
5176 .symver @var{name}, @var{name2@@nodename}
5178 If the symbol @var{name} is defined within the file
5179 being assembled, the @code{.symver} directive effectively creates a symbol
5180 alias with the name @var{name2@@nodename}, and in fact the main reason that we
5181 just don't try and create a regular alias is that the @var{@@} character isn't
5182 permitted in symbol names. The @var{name2} part of the name is the actual name
5183 of the symbol by which it will be externally referenced. The name @var{name}
5184 itself is merely a name of convenience that is used so that it is possible to
5185 have definitions for multiple versions of a function within a single source
5186 file, and so that the compiler can unambiguously know which version of a
5187 function is being mentioned. The @var{nodename} portion of the alias should be
5188 the name of a node specified in the version script supplied to the linker when
5189 building a shared library. If you are attempting to override a versioned
5190 symbol from a shared library, then @var{nodename} should correspond to the
5191 nodename of the symbol you are trying to override.
5193 If the symbol @var{name} is not defined within the file being assembled, all
5194 references to @var{name} will be changed to @var{name2@@nodename}. If no
5195 reference to @var{name} is made, @var{name2@@nodename} will be removed from the
5198 Another usage of the @code{.symver} directive is:
5200 .symver @var{name}, @var{name2@@@@nodename}
5202 In this case, the symbol @var{name} must exist and be defined within
5203 the file being assembled. It is similar to @var{name2@@nodename}. The
5204 difference is @var{name2@@@@nodename} will also be used to resolve
5205 references to @var{name2} by the linker.
5207 The third usage of the @code{.symver} directive is:
5209 .symver @var{name}, @var{name2@@@@@@nodename}
5211 When @var{name} is not defined within the
5212 file being assembled, it is treated as @var{name2@@nodename}. When
5213 @var{name} is defined within the file being assembled, the symbol
5214 name, @var{name}, will be changed to @var{name2@@@@nodename}.
5219 @section @code{.tag @var{structname}}
5221 @cindex COFF structure debugging
5222 @cindex structure debugging, COFF
5223 @cindex @code{tag} directive
5224 This directive is generated by compilers to include auxiliary debugging
5225 information in the symbol table. It is only permitted inside
5226 @code{.def}/@code{.endef} pairs. Tags are used to link structure
5227 definitions in the symbol table with instances of those structures.
5230 @samp{.tag} is only used when generating COFF format output; when
5231 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
5237 @section @code{.text @var{subsection}}
5239 @cindex @code{text} directive
5240 Tells @code{@value{AS}} to assemble the following statements onto the end of
5241 the text subsection numbered @var{subsection}, which is an absolute
5242 expression. If @var{subsection} is omitted, subsection number zero
5246 @section @code{.title "@var{heading}"}
5248 @cindex @code{title} directive
5249 @cindex listing control: title line
5250 Use @var{heading} as the title (second line, immediately after the
5251 source file name and pagenumber) when generating assembly listings.
5253 This directive affects subsequent pages, as well as the current page if
5254 it appears within ten lines of the top of a page.
5257 @section @code{.type @var{int}} (COFF version)
5259 @cindex COFF symbol type
5260 @cindex symbol type, COFF
5261 @cindex @code{type} directive
5262 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5263 records the integer @var{int} as the type attribute of a symbol table entry.
5266 @samp{.type} is associated only with COFF format output; when
5267 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
5268 directive but ignores it.
5271 @section @code{.type @var{name} , @var{type description}} (ELF version)
5273 @cindex ELF symbol type
5274 @cindex symbol type, ELF
5275 @cindex @code{type} directive
5276 This directive is used to set the type of symbol @var{name} to be either a
5277 function symbol or an object symbol. There are five different syntaxes
5278 supported for the @var{type description} field, in order to provide
5279 compatibility with various other assemblers. The syntaxes supported are:
5282 .type <name>,#function
5283 .type <name>,#object
5285 .type <name>,@@function
5286 .type <name>,@@object
5288 .type <name>,%function
5289 .type <name>,%object
5291 .type <name>,"function"
5292 .type <name>,"object"
5294 .type <name> STT_FUNCTION
5295 .type <name> STT_OBJECT
5299 @section @code{.uleb128 @var{expressions}}
5301 @cindex @code{uleb128} directive
5302 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
5303 compact, variable length representation of numbers used by the DWARF
5304 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
5308 @section @code{.val @var{addr}}
5310 @cindex @code{val} directive
5311 @cindex COFF value attribute
5312 @cindex value attribute, COFF
5313 This directive, permitted only within @code{.def}/@code{.endef} pairs,
5314 records the address @var{addr} as the value attribute of a symbol table
5318 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
5319 configured for @code{b.out}, it accepts this directive but ignores it.
5325 @section @code{.version "@var{string}"}
5327 @cindex @code{.version}
5328 This directive creates a @code{.note} section and places into it an ELF
5329 formatted note of type NT_VERSION. The note's name is set to @code{string}.
5334 @section @code{.vtable_entry @var{table}, @var{offset}}
5336 @cindex @code{.vtable_entry}
5337 This directive finds or creates a symbol @code{table} and creates a
5338 @code{VTABLE_ENTRY} relocation for it with an addend of @code{offset}.
5341 @section @code{.vtable_inherit @var{child}, @var{parent}}
5343 @cindex @code{.vtable_inherit}
5344 This directive finds the symbol @code{child} and finds or creates the symbol
5345 @code{parent} and then creates a @code{VTABLE_INHERIT} relocation for the
5346 parent whose addend is the value of the child symbol. As a special case the
5347 parent name of @code{0} is treated as refering the @code{*ABS*} section.
5352 @section @code{.weak @var{names}}
5354 @cindex @code{.weak}
5355 This directive sets the weak attribute on the comma separated list of symbol
5356 @code{names}. If the symbols do not already exist, they will be created.
5360 @section @code{.word @var{expressions}}
5362 @cindex @code{word} directive
5363 This directive expects zero or more @var{expressions}, of any section,
5364 separated by commas.
5367 For each expression, @code{@value{AS}} emits a 32-bit number.
5370 For each expression, @code{@value{AS}} emits a 16-bit number.
5375 The size of the number emitted, and its byte order,
5376 depend on what target computer the assembly is for.
5379 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
5380 @c happen---32-bit addressability, period; no long/short jumps.
5381 @ifset DIFF-TBL-KLUGE
5382 @cindex difference tables altered
5383 @cindex altered difference tables
5385 @emph{Warning: Special Treatment to support Compilers}
5389 Machines with a 32-bit address space, but that do less than 32-bit
5390 addressing, require the following special treatment. If the machine of
5391 interest to you does 32-bit addressing (or doesn't require it;
5392 @pxref{Machine Dependencies}), you can ignore this issue.
5395 In order to assemble compiler output into something that works,
5396 @code{@value{AS}} occasionally does strange things to @samp{.word} directives.
5397 Directives of the form @samp{.word sym1-sym2} are often emitted by
5398 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
5399 directive of the form @samp{.word sym1-sym2}, and the difference between
5400 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
5401 creates a @dfn{secondary jump table}, immediately before the next label.
5402 This secondary jump table is preceded by a short-jump to the
5403 first byte after the secondary table. This short-jump prevents the flow
5404 of control from accidentally falling into the new table. Inside the
5405 table is a long-jump to @code{sym2}. The original @samp{.word}
5406 contains @code{sym1} minus the address of the long-jump to
5409 If there were several occurrences of @samp{.word sym1-sym2} before the
5410 secondary jump table, all of them are adjusted. If there was a
5411 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
5412 long-jump to @code{sym4} is included in the secondary jump table,
5413 and the @code{.word} directives are adjusted to contain @code{sym3}
5414 minus the address of the long-jump to @code{sym4}; and so on, for as many
5415 entries in the original jump table as necessary.
5418 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
5419 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
5420 assembly language programmers.
5423 @c end DIFF-TBL-KLUGE
5426 @section Deprecated Directives
5428 @cindex deprecated directives
5429 @cindex obsolescent directives
5430 One day these directives won't work.
5431 They are included for compatibility with older assemblers.
5438 @node Machine Dependencies
5439 @chapter Machine Dependent Features
5441 @cindex machine dependencies
5442 The machine instruction sets are (almost by definition) different on
5443 each machine where @code{@value{AS}} runs. Floating point representations
5444 vary as well, and @code{@value{AS}} often supports a few additional
5445 directives or command-line options for compatibility with other
5446 assemblers on a particular platform. Finally, some versions of
5447 @code{@value{AS}} support special pseudo-instructions for branch
5450 This chapter discusses most of these differences, though it does not
5451 include details on any machine's instruction set. For details on that
5452 subject, see the hardware manufacturer's manual.
5456 * AMD29K-Dependent:: AMD 29K Dependent Features
5459 * ARC-Dependent:: ARC Dependent Features
5462 * ARM-Dependent:: ARM Dependent Features
5465 * D10V-Dependent:: D10V Dependent Features
5468 * D30V-Dependent:: D30V Dependent Features
5471 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5474 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5477 * HPPA-Dependent:: HPPA Dependent Features
5480 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5483 * i386-Dependent:: Intel 80386 and AMD x86-64 Dependent Features
5486 * i860-Dependent:: Intel 80860 Dependent Features
5489 * i960-Dependent:: Intel 80960 Dependent Features
5492 * M32R-Dependent:: M32R Dependent Features
5495 * M68K-Dependent:: M680x0 Dependent Features
5498 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5501 * M88K-Dependent:: M880x0 Dependent Features
5504 * MIPS-Dependent:: MIPS Dependent Features
5507 * SH-Dependent:: Hitachi SH Dependent Features
5510 * PDP-11-Dependent:: PDP-11 Dependent Features
5513 * PJ-Dependent:: picoJava Dependent Features
5516 * Sparc-Dependent:: SPARC Dependent Features
5519 * TIC54X-Dependent:: TI TMS320C54x Dependent Features
5522 * V850-Dependent:: V850 Dependent Features
5525 * Z8000-Dependent:: Z8000 Dependent Features
5528 * Vax-Dependent:: VAX Dependent Features
5535 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5536 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5537 @c peculiarity: to preserve cross-references, there must be a node called
5538 @c "Machine Dependencies". Hence the conditional nodenames in each
5539 @c major node below. Node defaulting in makeinfo requires adjacency of
5540 @c node and sectioning commands; hence the repetition of @chapter BLAH
5541 @c in both conditional blocks.
5548 @include c-a29k.texi
5557 @node Machine Dependencies
5558 @chapter Machine Dependent Features
5560 The machine instruction sets are different on each Hitachi chip family,
5561 and there are also some syntax differences among the families. This
5562 chapter describes the specific @code{@value{AS}} features for each
5566 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5567 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5568 * SH-Dependent:: Hitachi SH Dependent Features
5575 @include c-d10v.texi
5579 @include c-d30v.texi
5583 @include c-h8300.texi
5587 @include c-h8500.texi
5591 @include c-hppa.texi
5595 @include c-i370.texi
5599 @include c-i386.texi
5603 @include c-i860.texi
5607 @include c-i960.texi
5611 @include c-m32r.texi
5615 @include c-m68k.texi
5619 @include c-m68hc11.texi
5623 @include c-m88k.texi
5627 @include c-mips.texi
5631 @include c-ns32k.texi
5635 @include c-pdp11.texi
5647 @include c-sparc.texi
5651 @include c-tic54x.texi
5663 @include c-v850.texi
5667 @c reverse effect of @down at top of generic Machine-Dep chapter
5671 @node Reporting Bugs
5672 @chapter Reporting Bugs
5673 @cindex bugs in assembler
5674 @cindex reporting bugs in assembler
5676 Your bug reports play an essential role in making @code{@value{AS}} reliable.
5678 Reporting a bug may help you by bringing a solution to your problem, or it may
5679 not. But in any case the principal function of a bug report is to help the
5680 entire community by making the next version of @code{@value{AS}} work better.
5681 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
5683 In order for a bug report to serve its purpose, you must include the
5684 information that enables us to fix the bug.
5687 * Bug Criteria:: Have you found a bug?
5688 * Bug Reporting:: How to report bugs
5692 @section Have you found a bug?
5693 @cindex bug criteria
5695 If you are not sure whether you have found a bug, here are some guidelines:
5698 @cindex fatal signal
5699 @cindex assembler crash
5700 @cindex crash of assembler
5702 If the assembler gets a fatal signal, for any input whatever, that is a
5703 @code{@value{AS}} bug. Reliable assemblers never crash.
5705 @cindex error on valid input
5707 If @code{@value{AS}} produces an error message for valid input, that is a bug.
5709 @cindex invalid input
5711 If @code{@value{AS}} does not produce an error message for invalid input, that
5712 is a bug. However, you should note that your idea of ``invalid input'' might
5713 be our idea of ``an extension'' or ``support for traditional practice''.
5716 If you are an experienced user of assemblers, your suggestions for improvement
5717 of @code{@value{AS}} are welcome in any case.
5721 @section How to report bugs
5723 @cindex assembler bugs, reporting
5725 A number of companies and individuals offer support for @sc{gnu} products. If
5726 you obtained @code{@value{AS}} from a support organization, we recommend you
5727 contact that organization first.
5729 You can find contact information for many support companies and
5730 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5733 In any event, we also recommend that you send bug reports for @code{@value{AS}}
5734 to @samp{bug-binutils@@gnu.org}.
5736 The fundamental principle of reporting bugs usefully is this:
5737 @strong{report all the facts}. If you are not sure whether to state a
5738 fact or leave it out, state it!
5740 Often people omit facts because they think they know what causes the problem
5741 and assume that some details do not matter. Thus, you might assume that the
5742 name of a symbol you use in an example does not matter. Well, probably it does
5743 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5744 happens to fetch from the location where that name is stored in memory;
5745 perhaps, if the name were different, the contents of that location would fool
5746 the assembler into doing the right thing despite the bug. Play it safe and
5747 give a specific, complete example. That is the easiest thing for you to do,
5748 and the most helpful.
5750 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5751 it is new to us. Therefore, always write your bug reports on the assumption
5752 that the bug has not been reported previously.
5754 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5755 bell?'' Those bug reports are useless, and we urge everyone to
5756 @emph{refuse to respond to them} except to chide the sender to report
5759 To enable us to fix the bug, you should include all these things:
5763 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
5764 it with the @samp{--version} argument.
5766 Without this, we will not know whether there is any point in looking for
5767 the bug in the current version of @code{@value{AS}}.
5770 Any patches you may have applied to the @code{@value{AS}} source.
5773 The type of machine you are using, and the operating system name and
5777 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
5781 The command arguments you gave the assembler to assemble your example and
5782 observe the bug. To guarantee you will not omit something important, list them
5783 all. A copy of the Makefile (or the output from make) is sufficient.
5785 If we were to try to guess the arguments, we would probably guess wrong
5786 and then we might not encounter the bug.
5789 A complete input file that will reproduce the bug. If the bug is observed when
5790 the assembler is invoked via a compiler, send the assembler source, not the
5791 high level language source. Most compilers will produce the assembler source
5792 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5793 the options @samp{-v --save-temps}; this will save the assembler source in a
5794 file with an extension of @file{.s}, and also show you exactly how
5795 @code{@value{AS}} is being run.
5798 A description of what behavior you observe that you believe is
5799 incorrect. For example, ``It gets a fatal signal.''
5801 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
5802 will certainly notice it. But if the bug is incorrect output, we might not
5803 notice unless it is glaringly wrong. You might as well not give us a chance to
5806 Even if the problem you experience is a fatal signal, you should still say so
5807 explicitly. Suppose something strange is going on, such as, your copy of
5808 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
5809 library on your system. (This has happened!) Your copy might crash and ours
5810 would not. If you told us to expect a crash, then when ours fails to crash, we
5811 would know that the bug was not happening for us. If you had not told us to
5812 expect a crash, then we would not be able to draw any conclusion from our
5816 If you wish to suggest changes to the @code{@value{AS}} source, send us context
5817 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
5818 option. Always send diffs from the old file to the new file. If you even
5819 discuss something in the @code{@value{AS}} source, refer to it by context, not
5822 The line numbers in our development sources will not match those in your
5823 sources. Your line numbers would convey no useful information to us.
5826 Here are some things that are not necessary:
5830 A description of the envelope of the bug.
5832 Often people who encounter a bug spend a lot of time investigating
5833 which changes to the input file will make the bug go away and which
5834 changes will not affect it.
5836 This is often time consuming and not very useful, because the way we
5837 will find the bug is by running a single example under the debugger
5838 with breakpoints, not by pure deduction from a series of examples.
5839 We recommend that you save your time for something else.
5841 Of course, if you can find a simpler example to report @emph{instead}
5842 of the original one, that is a convenience for us. Errors in the
5843 output will be easier to spot, running under the debugger will take
5844 less time, and so on.
5846 However, simplification is not vital; if you do not want to do this,
5847 report the bug anyway and send us the entire test case you used.
5850 A patch for the bug.
5852 A patch for the bug does help us if it is a good one. But do not omit
5853 the necessary information, such as the test case, on the assumption that
5854 a patch is all we need. We might see problems with your patch and decide
5855 to fix the problem another way, or we might not understand it at all.
5857 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5858 construct an example that will make the program follow a certain path through
5859 the code. If you do not send us the example, we will not be able to construct
5860 one, so we will not be able to verify that the bug is fixed.
5862 And if we cannot understand what bug you are trying to fix, or why your
5863 patch should be an improvement, we will not install it. A test case will
5864 help us to understand.
5867 A guess about what the bug is or what it depends on.
5869 Such guesses are usually wrong. Even we cannot guess right about such
5870 things without first using the debugger to find the facts.
5873 @node Acknowledgements
5874 @chapter Acknowledgements
5876 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5877 it is not meant as a slight. We just don't know about it. Send mail to the
5878 maintainer, and we'll correct the situation. Currently
5880 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5882 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5885 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5886 information and the 68k series machines, most of the preprocessing pass, and
5887 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5889 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5890 many bug fixes, including merging support for several processors, breaking GAS
5891 up to handle multiple object file format back ends (including heavy rewrite,
5892 testing, an integration of the coff and b.out back ends), adding configuration
5893 including heavy testing and verification of cross assemblers and file splits
5894 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5895 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5896 port (including considerable amounts of reverse engineering), a SPARC opcode
5897 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5898 assertions and made them work, much other reorganization, cleanup, and lint.
5900 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5901 in format-specific I/O modules.
5903 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5904 has done much work with it since.
5906 The Intel 80386 machine description was written by Eliot Dresselhaus.
5908 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5910 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5911 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5913 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5914 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5915 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5916 support a.out format.
5918 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5919 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5920 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5921 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5924 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5925 simplified the configuration of which versions accept which directives. He
5926 updated the 68k machine description so that Motorola's opcodes always produced
5927 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5928 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5929 cross-compilation support, and one bug in relaxation that took a week and
5930 required the proverbial one-bit fix.
5932 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5933 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5934 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5935 PowerPC assembler, and made a few other minor patches.
5937 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5939 Hewlett-Packard contributed support for the HP9000/300.
5941 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5942 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5943 formats). This work was supported by both the Center for Software Science at
5944 the University of Utah and Cygnus Support.
5946 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5947 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5948 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5949 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5950 and some initial 64-bit support).
5952 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
5954 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5955 support for openVMS/Alpha.
5957 Timothy Wall, Michael Hayes, and Greg Smart contributed to the various tic*
5960 Several engineers at Cygnus Support have also provided many small bug fixes and
5961 configuration enhancements.
5963 Many others have contributed large or small bugfixes and enhancements. If
5964 you have contributed significant work and are not mentioned on this list, and
5965 want to be, let us know. Some of the history has been lost; we are not
5966 intentionally leaving anyone out.
5968 @node GNU Free Documentation License
5969 @chapter GNU Free Documentation License
5971 GNU Free Documentation License
5973 Version 1.1, March 2000
5975 Copyright (C) 2000 Free Software Foundation, Inc.
5976 59 Temple Place, Suite 330, Boston, MA 02111-1307 USA
5978 Everyone is permitted to copy and distribute verbatim copies
5979 of this license document, but changing it is not allowed.
5984 The purpose of this License is to make a manual, textbook, or other
5985 written document "free" in the sense of freedom: to assure everyone
5986 the effective freedom to copy and redistribute it, with or without
5987 modifying it, either commercially or noncommercially. Secondarily,
5988 this License preserves for the author and publisher a way to get
5989 credit for their work, while not being considered responsible for
5990 modifications made by others.
5992 This License is a kind of "copyleft", which means that derivative
5993 works of the document must themselves be free in the same sense. It
5994 complements the GNU General Public License, which is a copyleft
5995 license designed for free software.
5997 We have designed this License in order to use it for manuals for free
5998 software, because free software needs free documentation: a free
5999 program should come with manuals providing the same freedoms that the
6000 software does. But this License is not limited to software manuals;
6001 it can be used for any textual work, regardless of subject matter or
6002 whether it is published as a printed book. We recommend this License
6003 principally for works whose purpose is instruction or reference.
6006 1. APPLICABILITY AND DEFINITIONS
6008 This License applies to any manual or other work that contains a
6009 notice placed by the copyright holder saying it can be distributed
6010 under the terms of this License. The "Document", below, refers to any
6011 such manual or work. Any member of the public is a licensee, and is
6014 A "Modified Version" of the Document means any work containing the
6015 Document or a portion of it, either copied verbatim, or with
6016 modifications and/or translated into another language.
6018 A "Secondary Section" is a named appendix or a front-matter section of
6019 the Document that deals exclusively with the relationship of the
6020 publishers or authors of the Document to the Document's overall subject
6021 (or to related matters) and contains nothing that could fall directly
6022 within that overall subject. (For example, if the Document is in part a
6023 textbook of mathematics, a Secondary Section may not explain any
6024 mathematics.) The relationship could be a matter of historical
6025 connection with the subject or with related matters, or of legal,
6026 commercial, philosophical, ethical or political position regarding
6029 The "Invariant Sections" are certain Secondary Sections whose titles
6030 are designated, as being those of Invariant Sections, in the notice
6031 that says that the Document is released under this License.
6033 The "Cover Texts" are certain short passages of text that are listed,
6034 as Front-Cover Texts or Back-Cover Texts, in the notice that says that
6035 the Document is released under this License.
6037 A "Transparent" copy of the Document means a machine-readable copy,
6038 represented in a format whose specification is available to the
6039 general public, whose contents can be viewed and edited directly and
6040 straightforwardly with generic text editors or (for images composed of
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6042 drawing editor, and that is suitable for input to text formatters or
6043 for automatic translation to a variety of formats suitable for input
6044 to text formatters. A copy made in an otherwise Transparent file
6045 format whose markup has been designed to thwart or discourage
6046 subsequent modification by readers is not Transparent. A copy that is
6047 not "Transparent" is called "Opaque".
6049 Examples of suitable formats for Transparent copies include plain
6050 ASCII without markup, Texinfo input format, LaTeX input format, SGML
6051 or XML using a publicly available DTD, and standard-conforming simple
6052 HTML designed for human modification. Opaque formats include
6053 PostScript, PDF, proprietary formats that can be read and edited only
6054 by proprietary word processors, SGML or XML for which the DTD and/or
6055 processing tools are not generally available, and the
6056 machine-generated HTML produced by some word processors for output
6059 The "Title Page" means, for a printed book, the title page itself,
6060 plus such following pages as are needed to hold, legibly, the material
6061 this License requires to appear in the title page. For works in
6062 formats which do not have any title page as such, "Title Page" means
6063 the text near the most prominent appearance of the work's title,
6064 preceding the beginning of the body of the text.
6069 You may copy and distribute the Document in any medium, either
6070 commercially or noncommercially, provided that this License, the
6071 copyright notices, and the license notice saying this License applies
6072 to the Document are reproduced in all copies, and that you add no other
6073 conditions whatsoever to those of this License. You may not use
6074 technical measures to obstruct or control the reading or further
6075 copying of the copies you make or distribute. However, you may accept
6076 compensation in exchange for copies. If you distribute a large enough
6077 number of copies you must also follow the conditions in section 3.
6079 You may also lend copies, under the same conditions stated above, and
6080 you may publicly display copies.
6083 3. COPYING IN QUANTITY
6085 If you publish printed copies of the Document numbering more than 100,
6086 and the Document's license notice requires Cover Texts, you must enclose
6087 the copies in covers that carry, clearly and legibly, all these Cover
6088 Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
6089 the back cover. Both covers must also clearly and legibly identify
6090 you as the publisher of these copies. The front cover must present
6091 the full title with all words of the title equally prominent and
6092 visible. You may add other material on the covers in addition.
6093 Copying with changes limited to the covers, as long as they preserve
6094 the title of the Document and satisfy these conditions, can be treated
6095 as verbatim copying in other respects.
6097 If the required texts for either cover are too voluminous to fit
6098 legibly, you should put the first ones listed (as many as fit
6099 reasonably) on the actual cover, and continue the rest onto adjacent
6102 If you publish or distribute Opaque copies of the Document numbering
6103 more than 100, you must either include a machine-readable Transparent
6104 copy along with each Opaque copy, or state in or with each Opaque copy
6105 a publicly-accessible computer-network location containing a complete
6106 Transparent copy of the Document, free of added material, which the
6107 general network-using public has access to download anonymously at no
6108 charge using public-standard network protocols. If you use the latter
6109 option, you must take reasonably prudent steps, when you begin
6110 distribution of Opaque copies in quantity, to ensure that this
6111 Transparent copy will remain thus accessible at the stated location
6112 until at least one year after the last time you distribute an Opaque
6113 copy (directly or through your agents or retailers) of that edition to
6116 It is requested, but not required, that you contact the authors of the
6117 Document well before redistributing any large number of copies, to give
6118 them a chance to provide you with an updated version of the Document.
6123 You may copy and distribute a Modified Version of the Document under
6124 the conditions of sections 2 and 3 above, provided that you release
6125 the Modified Version under precisely this License, with the Modified
6126 Version filling the role of the Document, thus licensing distribution
6127 and modification of the Modified Version to whoever possesses a copy
6128 of it. In addition, you must do these things in the Modified Version:
6130 A. Use in the Title Page (and on the covers, if any) a title distinct
6131 from that of the Document, and from those of previous versions
6132 (which should, if there were any, be listed in the History section
6133 of the Document). You may use the same title as a previous version
6134 if the original publisher of that version gives permission.
6135 B. List on the Title Page, as authors, one or more persons or entities
6136 responsible for authorship of the modifications in the Modified
6137 Version, together with at least five of the principal authors of the
6138 Document (all of its principal authors, if it has less than five).
6139 C. State on the Title page the name of the publisher of the
6140 Modified Version, as the publisher.
6141 D. Preserve all the copyright notices of the Document.
6142 E. Add an appropriate copyright notice for your modifications
6143 adjacent to the other copyright notices.
6144 F. Include, immediately after the copyright notices, a license notice
6145 giving the public permission to use the Modified Version under the
6146 terms of this License, in the form shown in the Addendum below.
6147 G. Preserve in that license notice the full lists of Invariant Sections
6148 and required Cover Texts given in the Document's license notice.
6149 H. Include an unaltered copy of this License.
6150 I. Preserve the section entitled "History", and its title, and add to
6151 it an item stating at least the title, year, new authors, and
6152 publisher of the Modified Version as given on the Title Page. If
6153 there is no section entitled "History" in the Document, create one
6154 stating the title, year, authors, and publisher of the Document as
6155 given on its Title Page, then add an item describing the Modified
6156 Version as stated in the previous sentence.
6157 J. Preserve the network location, if any, given in the Document for
6158 public access to a Transparent copy of the Document, and likewise
6159 the network locations given in the Document for previous versions
6160 it was based on. These may be placed in the "History" section.
6161 You may omit a network location for a work that was published at
6162 least four years before the Document itself, or if the original
6163 publisher of the version it refers to gives permission.
6164 K. In any section entitled "Acknowledgements" or "Dedications",
6165 preserve the section's title, and preserve in the section all the
6166 substance and tone of each of the contributor acknowledgements
6167 and/or dedications given therein.
6168 L. Preserve all the Invariant Sections of the Document,
6169 unaltered in their text and in their titles. Section numbers
6170 or the equivalent are not considered part of the section titles.
6171 M. Delete any section entitled "Endorsements". Such a section
6172 may not be included in the Modified Version.
6173 N. Do not retitle any existing section as "Endorsements"
6174 or to conflict in title with any Invariant Section.
6176 If the Modified Version includes new front-matter sections or
6177 appendices that qualify as Secondary Sections and contain no material
6178 copied from the Document, you may at your option designate some or all
6179 of these sections as invariant. To do this, add their titles to the
6180 list of Invariant Sections in the Modified Version's license notice.
6181 These titles must be distinct from any other section titles.
6183 You may add a section entitled "Endorsements", provided it contains
6184 nothing but endorsements of your Modified Version by various
6185 parties--for example, statements of peer review or that the text has
6186 been approved by an organization as the authoritative definition of a
6189 You may add a passage of up to five words as a Front-Cover Text, and a
6190 passage of up to 25 words as a Back-Cover Text, to the end of the list
6191 of Cover Texts in the Modified Version. Only one passage of
6192 Front-Cover Text and one of Back-Cover Text may be added by (or
6193 through arrangements made by) any one entity. If the Document already
6194 includes a cover text for the same cover, previously added by you or
6195 by arrangement made by the same entity you are acting on behalf of,
6196 you may not add another; but you may replace the old one, on explicit
6197 permission from the previous publisher that added the old one.
6199 The author(s) and publisher(s) of the Document do not by this License
6200 give permission to use their names for publicity for or to assert or
6201 imply endorsement of any Modified Version.
6204 5. COMBINING DOCUMENTS
6206 You may combine the Document with other documents released under this
6207 License, under the terms defined in section 4 above for modified
6208 versions, provided that you include in the combination all of the
6209 Invariant Sections of all of the original documents, unmodified, and
6210 list them all as Invariant Sections of your combined work in its
6213 The combined work need only contain one copy of this License, and
6214 multiple identical Invariant Sections may be replaced with a single
6215 copy. If there are multiple Invariant Sections with the same name but
6216 different contents, make the title of each such section unique by
6217 adding at the end of it, in parentheses, the name of the original
6218 author or publisher of that section if known, or else a unique number.
6219 Make the same adjustment to the section titles in the list of
6220 Invariant Sections in the license notice of the combined work.
6222 In the combination, you must combine any sections entitled "History"
6223 in the various original documents, forming one section entitled
6224 "History"; likewise combine any sections entitled "Acknowledgements",
6225 and any sections entitled "Dedications". You must delete all sections
6226 entitled "Endorsements."
6229 6. COLLECTIONS OF DOCUMENTS
6231 You may make a collection consisting of the Document and other documents
6232 released under this License, and replace the individual copies of this
6233 License in the various documents with a single copy that is included in
6234 the collection, provided that you follow the rules of this License for
6235 verbatim copying of each of the documents in all other respects.
6237 You may extract a single document from such a collection, and distribute
6238 it individually under this License, provided you insert a copy of this
6239 License into the extracted document, and follow this License in all
6240 other respects regarding verbatim copying of that document.
6243 7. AGGREGATION WITH INDEPENDENT WORKS
6245 A compilation of the Document or its derivatives with other separate
6246 and independent documents or works, in or on a volume of a storage or
6247 distribution medium, does not as a whole count as a Modified Version
6248 of the Document, provided no compilation copyright is claimed for the
6249 compilation. Such a compilation is called an "aggregate", and this
6250 License does not apply to the other self-contained works thus compiled
6251 with the Document, on account of their being thus compiled, if they
6252 are not themselves derivative works of the Document.
6254 If the Cover Text requirement of section 3 is applicable to these
6255 copies of the Document, then if the Document is less than one quarter
6256 of the entire aggregate, the Document's Cover Texts may be placed on
6257 covers that surround only the Document within the aggregate.
6258 Otherwise they must appear on covers around the whole aggregate.
6263 Translation is considered a kind of modification, so you may
6264 distribute translations of the Document under the terms of section 4.
6265 Replacing Invariant Sections with translations requires special
6266 permission from their copyright holders, but you may include
6267 translations of some or all Invariant Sections in addition to the
6268 original versions of these Invariant Sections. You may include a
6269 translation of this License provided that you also include the
6270 original English version of this License. In case of a disagreement
6271 between the translation and the original English version of this
6272 License, the original English version will prevail.
6277 You may not copy, modify, sublicense, or distribute the Document except
6278 as expressly provided for under this License. Any other attempt to
6279 copy, modify, sublicense or distribute the Document is void, and will
6280 automatically terminate your rights under this License. However,
6281 parties who have received copies, or rights, from you under this
6282 License will not have their licenses terminated so long as such
6283 parties remain in full compliance.
6286 10. FUTURE REVISIONS OF THIS LICENSE
6288 The Free Software Foundation may publish new, revised versions
6289 of the GNU Free Documentation License from time to time. Such new
6290 versions will be similar in spirit to the present version, but may
6291 differ in detail to address new problems or concerns. See
6292 http://www.gnu.org/copyleft/.
6294 Each version of the License is given a distinguishing version number.
6295 If the Document specifies that a particular numbered version of this
6296 License "or any later version" applies to it, you have the option of
6297 following the terms and conditions either of that specified version or
6298 of any later version that has been published (not as a draft) by the
6299 Free Software Foundation. If the Document does not specify a version
6300 number of this License, you may choose any version ever published (not
6301 as a draft) by the Free Software Foundation.
6304 ADDENDUM: How to use this License for your documents
6306 To use this License in a document you have written, include a copy of
6307 the License in the document and put the following copyright and
6308 license notices just after the title page:
6311 Copyright (c) YEAR YOUR NAME.
6312 Permission is granted to copy, distribute and/or modify this document
6313 under the terms of the GNU Free Documentation License, Version 1.1
6314 or any later version published by the Free Software Foundation;
6315 with the Invariant Sections being LIST THEIR TITLES, with the
6316 Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.
6317 A copy of the license is included in the section entitled "GNU
6318 Free Documentation License".
6321 If you have no Invariant Sections, write "with no Invariant Sections"
6322 instead of saying which ones are invariant. If you have no
6323 Front-Cover Texts, write "no Front-Cover Texts" instead of
6324 "Front-Cover Texts being LIST"; likewise for Back-Cover Texts.
6326 If your document contains nontrivial examples of program code, we
6327 recommend releasing these examples in parallel under your choice of
6328 free software license, such as the GNU General Public License,
6329 to permit their use in free software.
projects / deliverable / binutils-gdb.git / blob