1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 1998
3 @c Free Software Foundation, Inc.
4 @c UPDATE!! On future updates--
5 @c (1) check for new machine-dep cmdline options in
6 @c md_parse_option definitions in config/tc-*.c
7 @c (2) for platform-specific directives, examine md_pseudo_op
9 @c (3) for object-format specific directives, examine obj_pseudo_op
11 @c (4) portable directives in potable[] in read.c
15 @c defaults, config file may override:
18 @include asconfig.texi
20 @c common OR combinations of conditions
40 @set abnormal-separator
44 @settitle Using @value{AS}
47 @settitle Using @value{AS} (@value{TARGET})
49 @setchapternewpage odd
54 @c WARE! Some of the machine-dependent sections contain tables of machine
55 @c instructions. Except in multi-column format, these tables look silly.
56 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
57 @c the multi-col format is faked within @example sections.
59 @c Again unfortunately, the natural size that fits on a page, for these tables,
60 @c is different depending on whether or not smallbook is turned on.
61 @c This matters, because of order: text flow switches columns at each page
64 @c The format faked in this source works reasonably well for smallbook,
65 @c not well for the default large-page format. This manual expects that if you
66 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
67 @c tables in question. You can turn on one without the other at your
68 @c discretion, of course.
71 @c the insn tables look just as silly in info files regardless of smallbook,
72 @c might as well show 'em anyways.
78 * As: (as). The GNU assembler.
87 This file documents the GNU Assembler "@value{AS}".
89 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc.
91 Permission is granted to make and distribute verbatim copies of
92 this manual provided the copyright notice and this permission notice
93 are preserved on all copies.
96 Permission is granted to process this file through Tex and print the
97 results, provided the printed document carries copying permission
98 notice identical to this one except for the removal of this paragraph
99 (this paragraph not being relevant to the printed manual).
102 Permission is granted to copy and distribute modified versions of this manual
103 under the conditions for verbatim copying, provided that the entire resulting
104 derived work is distributed under the terms of a permission notice identical to
107 Permission is granted to copy and distribute translations of this manual
108 into another language, under the above conditions for modified versions.
112 @title Using @value{AS}
113 @subtitle The @sc{gnu} Assembler
115 @subtitle for the @value{TARGET} family
118 @subtitle January 1994
121 The Free Software Foundation Inc. thanks The Nice Computer
122 Company of Australia for loaning Dean Elsner to write the
123 first (Vax) version of @code{as} for Project @sc{gnu}.
124 The proprietors, management and staff of TNCCA thank FSF for
125 distracting the boss while they got some work
128 @author Dean Elsner, Jay Fenlason & friends
132 \hfill {\it Using {\tt @value{AS}}}\par
133 \hfill Edited by Cygnus Support\par
135 %"boxit" macro for figures:
136 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
137 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
138 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
139 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
140 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
143 @vskip 0pt plus 1filll
144 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 1998 Free Software Foundation, Inc.
146 Permission is granted to make and distribute verbatim copies of
147 this manual provided the copyright notice and this permission notice
148 are preserved on all copies.
150 Permission is granted to copy and distribute modified versions of this manual
151 under the conditions for verbatim copying, provided that the entire resulting
152 derived work is distributed under the terms of a permission notice identical to
155 Permission is granted to copy and distribute translations of this manual
156 into another language, under the above conditions for modified versions.
161 @top Using @value{AS}
163 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
165 This version of the file describes @code{@value{AS}} configured to generate
166 code for @value{TARGET} architectures.
169 * Overview:: Overview
170 * Invoking:: Command-Line Options
172 * Sections:: Sections and Relocation
174 * Expressions:: Expressions
175 * Pseudo Ops:: Assembler Directives
176 * Machine Dependencies:: Machine Dependent Features
177 * Reporting Bugs:: Reporting Bugs
178 * Acknowledgements:: Who Did What
186 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
188 This version of the manual describes @code{@value{AS}} configured to generate
189 code for @value{TARGET} architectures.
193 @cindex invocation summary
194 @cindex option summary
195 @cindex summary of options
196 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
197 @pxref{Invoking,,Comand-Line Options}.
199 @c We don't use deffn and friends for the following because they seem
200 @c to be limited to one line for the header.
202 @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
203 [ -f ] [ --gstabs ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
204 [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ]
205 [ -version ] [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ]
207 @c am29k has no machine-dependent assembler options
210 [ -mbig-endian | -mlittle-endian ]
213 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m[i]] ]
214 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t ]
216 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
218 [ -mapcs-32 | -mapcs-26 ]
223 @c start-sanitize-d30v
229 @c Hitachi family chips have no machine-dependent assembler options
232 @c HPPA has no machine-dependent assembler options (yet).
235 @c The order here is important. See c-sparc.texi.
236 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
237 -Av8plus | -Av8plusa | -Av9 | -Av9a ]
238 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
241 @c Z8000 has no machine-dependent assembler options
244 @c see md_parse_option in tc-i960.c
245 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
248 @c start-sanitize-m32rx
250 [ --m32rx | --[no-]warn-explicit-parallel-conflicts | --W[n]p ]
252 @c end-sanitize-m32rx
254 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
257 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
258 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
259 [ --trap ] [ --break ]
260 [ --emulation=@var{name} ]
262 [ -- | @var{files} @dots{} ]
267 Turn on listings, in any of a variety of ways:
271 omit false conditionals
274 omit debugging directives
277 include high-level source
283 include macro expansions
286 omit forms processing
292 set the name of the listing file
295 You may combine these options; for example, use @samp{-aln} for assembly
296 listing without forms processing. The @samp{=file} option, if used, must be
297 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
300 Ignored. This option is accepted for script compatibility with calls to
303 @item --defsym @var{sym}=@var{value}
304 Define the symbol @var{sym} to be @var{value} before assembling the input file.
305 @var{value} must be an integer constant. As in C, a leading @samp{0x}
306 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
309 ``fast''---skip whitespace and comment preprocessing (assume source is
313 Generate stabs debugging information for each assembler line. This
314 may help debugging assembler code, if the debugger can handle it.
317 Print a summary of the command line options and exit.
320 Add directory @var{dir} to the search list for @code{.include} directives.
323 Don't warn about signed overflow.
326 @ifclear DIFF-TBL-KLUGE
327 This option is accepted but has no effect on the @value{TARGET} family.
329 @ifset DIFF-TBL-KLUGE
330 Issue warnings when difference tables altered for long displacements.
335 Keep (in the symbol table) local symbols. On traditional a.out systems
336 these start with @samp{L}, but different systems have different local
339 @item -o @var{objfile}
340 Name the object-file output from @code{@value{AS}} @var{objfile}.
343 Fold the data section into the text section.
346 Print the maximum space (in bytes) and total time (in seconds) used by
349 @item --strip-local-absolute
350 Remove local absolute symbols from the outgoing symbol table.
354 Print the @code{as} version.
357 Print the @code{as} version and exit.
360 Suppress warning messages.
369 Generate an object file even after errors.
371 @item -- | @var{files} @dots{}
372 Standard input, or source files to assemble.
377 The following options are available when @value{AS} is configured for
382 @cindex ARC endianness
383 @cindex endianness, ARC
384 @cindex big endian output, ARC
386 Generate ``big endian'' format output.
388 @cindex little endian output, ARC
389 @item -mlittle-endian
390 Generate ``little endian'' format output.
396 The following options are available when @value{AS} is configured for the ARM
400 @item -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m] | -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t
401 Specify which variant of the ARM architecture is the target.
402 @item -mthumb | -mall
403 Enable or disable Thumb only instruction decoding.
404 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
405 Select which Floating Point architcture is the target.
406 @item -mapcs-32 | -mapcs-26
407 Select which procedure calling convention is in use.
409 Select either big-endian (-EB) or little-endian (-EL) output.
414 The following options are available when @value{AS} is configured for
417 @cindex D10V optimization
418 @cindex optimization, D10V
420 Optimize output by parallelizing instructions.
424 @c start-sanitize-d30v
426 The following options are available when @value{AS} is configured for a D30V
429 @cindex D30V optimization
430 @cindex optimization, D30V
432 Optimize output by parallelizing instructions.
436 Warn when nops are generated.
438 @cindex D30V nops after 32-bit multiply
440 Warn when a nop after a 32-bit multiply instruction is generated.
446 The following options are available when @value{AS} is configured for the
447 Intel 80960 processor.
450 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
451 Specify which variant of the 960 architecture is the target.
454 Add code to collect statistics about branches taken.
457 Do not alter compare-and-branch instructions for long displacements;
463 @c start-sanitize-m32rx
465 The following options are available when @value{AS} is configured for the
466 Mitsubishi M32R series.
471 Specify which processor in the M32R family is the target. The default
472 is normally the M32R, but this option changes it to the M32RX.
474 @item --warn-explicit-parallel-conflicts or --Wp
475 Produce warning messages when questionable parallel constructs are
478 @item --no-warn-explicit-parallel-conflicts or --Wnp
479 Do not produce warning messages when questionable parallel constructs are
484 @c end-sanitize-m32rx
487 The following options are available when @value{AS} is configured for the
488 Motorola 68000 series.
493 Shorten references to undefined symbols, to one word instead of two.
495 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
496 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
497 Specify what processor in the 68000 family is the target. The default
498 is normally the 68020, but this can be changed at configuration time.
500 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
501 The target machine does (or does not) have a floating-point coprocessor.
502 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
503 the basic 68000 is not compatible with the 68881, a combination of the
504 two can be specified, since it's possible to do emulation of the
505 coprocessor instructions with the main processor.
507 @item -m68851 | -mno-68851
508 The target machine does (or does not) have a memory-management
509 unit coprocessor. The default is to assume an MMU for 68020 and up.
515 The following options are available when @code{@value{AS}} is configured
516 for the SPARC architecture:
519 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
520 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
521 Explicitly select a variant of the SPARC architecture.
523 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
524 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
526 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
527 UltraSPARC extensions.
529 @item -xarch=v8plus | -xarch=v8plusa
530 For compatibility with the Solaris v9 assembler. These options are
531 equivalent to -Av8plus and -Av8plusa, respectively.
534 Warn when the assembler switches to another architecture.
539 The following options are available when @value{AS} is configured for
544 This option sets the largest size of an object that can be referenced
545 implicitly with the @code{gp} register. It is only accepted for targets that
546 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
548 @cindex MIPS endianness
549 @cindex endianness, MIPS
550 @cindex big endian output, MIPS
552 Generate ``big endian'' format output.
554 @cindex little endian output, MIPS
556 Generate ``little endian'' format output.
562 Generate code for a particular MIPS Instruction Set Architecture level.
563 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
564 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
569 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
570 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
571 instructions around accesses to the @samp{HI} and @samp{LO} registers.
572 @samp{-no-m4650} turns off this option.
574 @item -mcpu=@var{CPU}
575 Generate code for a particular MIPS cpu. This has little effect on the
576 assembler, but it is passed by @code{@value{GCC}}.
579 @item --emulation=@var{name}
580 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
581 for some other target, in all respects, including output format (choosing
582 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
583 debugging information or store symbol table information, and default
584 endianness. The available configuration names are: @samp{mipsecoff},
585 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
586 @samp{mipsbelf}. The first two do not alter the default endianness from that
587 of the primary target for which the assembler was configured; the others change
588 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
589 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
590 selection in any case.
592 This option is currently supported only when the primary target
593 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
594 Furthermore, the primary target or others specified with
595 @samp{--enable-targets=@dots{}} at configuration time must include support for
596 the other format, if both are to be available. For example, the Irix 5
597 configuration includes support for both.
599 Eventually, this option will support more configurations, with more
600 fine-grained control over the assembler's behavior, and will be supported for
604 @code{@value{AS}} ignores this option. It is accepted for compatibility with
612 Control how to deal with multiplication overflow and division by zero.
613 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
614 (and only work for Instruction Set Architecture level 2 and higher);
615 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
621 * Manual:: Structure of this Manual
622 * GNU Assembler:: The GNU Assembler
623 * Object Formats:: Object File Formats
624 * Command Line:: Command Line
625 * Input Files:: Input Files
626 * Object:: Output (Object) File
627 * Errors:: Error and Warning Messages
631 @section Structure of this Manual
633 @cindex manual, structure and purpose
634 This manual is intended to describe what you need to know to use
635 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
636 notation for symbols, constants, and expressions; the directives that
637 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
640 We also cover special features in the @value{TARGET}
641 configuration of @code{@value{AS}}, including assembler directives.
644 This manual also describes some of the machine-dependent features of
645 various flavors of the assembler.
648 @cindex machine instructions (not covered)
649 On the other hand, this manual is @emph{not} intended as an introduction
650 to programming in assembly language---let alone programming in general!
651 In a similar vein, we make no attempt to introduce the machine
652 architecture; we do @emph{not} describe the instruction set, standard
653 mnemonics, registers or addressing modes that are standard to a
654 particular architecture.
656 You may want to consult the manufacturer's
657 machine architecture manual for this information.
661 For information on the H8/300 machine instruction set, see @cite{H8/300
662 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
663 see @cite{H8/300H Series Programming Manual} (Hitachi).
666 For information on the H8/500 machine instruction set, see @cite{H8/500
667 Series Programming Manual} (Hitachi M21T001).
670 For information on the Hitachi SH machine instruction set, see
671 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
674 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
678 @c I think this is premature---doc@cygnus.com, 17jan1991
680 Throughout this manual, we assume that you are running @dfn{GNU},
681 the portable operating system from the @dfn{Free Software
682 Foundation, Inc.}. This restricts our attention to certain kinds of
683 computer (in particular, the kinds of computers that @sc{gnu} can run on);
684 once this assumption is granted examples and definitions need less
687 @code{@value{AS}} is part of a team of programs that turn a high-level
688 human-readable series of instructions into a low-level
689 computer-readable series of instructions. Different versions of
690 @code{@value{AS}} are used for different kinds of computer.
693 @c There used to be a section "Terminology" here, which defined
694 @c "contents", "byte", "word", and "long". Defining "word" to any
695 @c particular size is confusing when the .word directive may generate 16
696 @c bits on one machine and 32 bits on another; in general, for the user
697 @c version of this manual, none of these terms seem essential to define.
698 @c They were used very little even in the former draft of the manual;
699 @c this draft makes an effort to avoid them (except in names of
703 @section The GNU Assembler
705 @sc{gnu} @code{as} is really a family of assemblers.
707 This manual describes @code{@value{AS}}, a member of that family which is
708 configured for the @value{TARGET} architectures.
710 If you use (or have used) the @sc{gnu} assembler on one architecture, you
711 should find a fairly similar environment when you use it on another
712 architecture. Each version has much in common with the others,
713 including object file formats, most assembler directives (often called
714 @dfn{pseudo-ops}) and assembler syntax.@refill
716 @cindex purpose of @sc{gnu} assembler
717 @code{@value{AS}} is primarily intended to assemble the output of the
718 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
719 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
720 assemble correctly everything that other assemblers for the same
721 machine would assemble.
723 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
726 @c This remark should appear in generic version of manual; assumption
727 @c here is that generic version sets M680x0.
728 This doesn't mean @code{@value{AS}} always uses the same syntax as another
729 assembler for the same architecture; for example, we know of several
730 incompatible versions of 680x0 assembly language syntax.
733 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
734 program in one pass of the source file. This has a subtle impact on the
735 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
738 @section Object File Formats
740 @cindex object file format
741 The @sc{gnu} assembler can be configured to produce several alternative
742 object file formats. For the most part, this does not affect how you
743 write assembly language programs; but directives for debugging symbols
744 are typically different in different file formats. @xref{Symbol
745 Attributes,,Symbol Attributes}.
748 On the @value{TARGET}, @code{@value{AS}} is configured to produce
749 @value{OBJ-NAME} format object files.
751 @c The following should exhaust all configs that set MULTI-OBJ, ideally
753 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
754 @code{a.out} or COFF format object files.
757 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
758 @code{b.out} or COFF format object files.
761 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
762 SOM or ELF format object files.
767 @section Command Line
769 @cindex command line conventions
770 After the program name @code{@value{AS}}, the command line may contain
771 options and file names. Options may appear in any order, and may be
772 before, after, or between file names. The order of file names is
775 @cindex standard input, as input file
777 @file{--} (two hyphens) by itself names the standard input file
778 explicitly, as one of the files for @code{@value{AS}} to assemble.
780 @cindex options, command line
781 Except for @samp{--} any command line argument that begins with a
782 hyphen (@samp{-}) is an option. Each option changes the behavior of
783 @code{@value{AS}}. No option changes the way another option works. An
784 option is a @samp{-} followed by one or more letters; the case of
785 the letter is important. All options are optional.
787 Some options expect exactly one file name to follow them. The file
788 name may either immediately follow the option's letter (compatible
789 with older assemblers) or it may be the next command argument (@sc{gnu}
790 standard). These two command lines are equivalent:
793 @value{AS} -o my-object-file.o mumble.s
794 @value{AS} -omy-object-file.o mumble.s
801 @cindex source program
803 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
804 describe the program input to one run of @code{@value{AS}}. The program may
805 be in one or more files; how the source is partitioned into files
806 doesn't change the meaning of the source.
808 @c I added "con" prefix to "catenation" just to prove I can overcome my
809 @c APL training... doc@cygnus.com
810 The source program is a concatenation of the text in all the files, in the
813 Each time you run @code{@value{AS}} it assembles exactly one source
814 program. The source program is made up of one or more files.
815 (The standard input is also a file.)
817 You give @code{@value{AS}} a command line that has zero or more input file
818 names. The input files are read (from left file name to right). A
819 command line argument (in any position) that has no special meaning
820 is taken to be an input file name.
822 If you give @code{@value{AS}} no file names it attempts to read one input file
823 from the @code{@value{AS}} standard input, which is normally your terminal. You
824 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
827 Use @samp{--} if you need to explicitly name the standard input file
828 in your command line.
830 If the source is empty, @code{@value{AS}} produces a small, empty object
833 @subheading Filenames and Line-numbers
835 @cindex input file linenumbers
836 @cindex line numbers, in input files
837 There are two ways of locating a line in the input file (or files) and
838 either may be used in reporting error messages. One way refers to a line
839 number in a physical file; the other refers to a line number in a
840 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
842 @dfn{Physical files} are those files named in the command line given
843 to @code{@value{AS}}.
845 @dfn{Logical files} are simply names declared explicitly by assembler
846 directives; they bear no relation to physical files. Logical file names
847 help error messages reflect the original source file, when @code{@value{AS}}
848 source is itself synthesized from other files.
849 @xref{App-File,,@code{.app-file}}.
852 @section Output (Object) File
858 Every time you run @code{@value{AS}} it produces an output file, which is
859 your assembly language program translated into numbers. This file
860 is the object file. Its default name is
868 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
870 You can give it another name by using the @code{-o} option. Conventionally,
871 object file names end with @file{.o}. The default name is used for historical
872 reasons: older assemblers were capable of assembling self-contained programs
873 directly into a runnable program. (For some formats, this isn't currently
874 possible, but it can be done for the @code{a.out} format.)
878 The object file is meant for input to the linker @code{@value{LD}}. It contains
879 assembled program code, information to help @code{@value{LD}} integrate
880 the assembled program into a runnable file, and (optionally) symbolic
881 information for the debugger.
883 @c link above to some info file(s) like the description of a.out.
884 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
887 @section Error and Warning Messages
889 @cindex error messsages
890 @cindex warning messages
891 @cindex messages from assembler
892 @code{@value{AS}} may write warnings and error messages to the standard error
893 file (usually your terminal). This should not happen when a compiler
894 runs @code{@value{AS}} automatically. Warnings report an assumption made so
895 that @code{@value{AS}} could keep assembling a flawed program; errors report a
896 grave problem that stops the assembly.
898 @cindex format of warning messages
899 Warning messages have the format
902 file_name:@b{NNN}:Warning Message Text
906 @cindex line numbers, in warnings/errors
907 (where @b{NNN} is a line number). If a logical file name has been given
908 (@pxref{App-File,,@code{.app-file}}) it is used for the filename,
909 otherwise the name of the current input file is used. If a logical line
912 (@pxref{Line,,@code{.line}})
916 (@pxref{Line,,@code{.line}})
919 (@pxref{Ln,,@code{.ln}})
922 then it is used to calculate the number printed,
923 otherwise the actual line in the current source file is printed. The
924 message text is intended to be self explanatory (in the grand Unix
927 @cindex format of error messages
928 Error messages have the format
930 file_name:@b{NNN}:FATAL:Error Message Text
932 The file name and line number are derived as for warning
933 messages. The actual message text may be rather less explanatory
934 because many of them aren't supposed to happen.
937 @chapter Command-Line Options
939 @cindex options, all versions of assembler
940 This chapter describes command-line options available in @emph{all}
941 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
943 to the @value{TARGET}.
946 to particular machine architectures.
949 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
950 you can use the @samp{-Wa} option to pass arguments through to the assembler.
951 The assembler arguments must be separated from each other (and the @samp{-Wa})
952 by commas. For example:
955 gcc -c -g -O -Wa,-alh,-L file.c
959 This passes two options to the assembler: @samp{-alh} (emit a listing to
960 standard output with with high-level and assembly source) and @samp{-L} (retain
961 local symbols in the symbol table).
963 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
964 command-line options are automatically passed to the assembler by the compiler.
965 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
966 precisely what options it passes to each compilation pass, including the
970 * a:: -a[cdhlns] enable listings
971 * D:: -D for compatibility
972 * f:: -f to work faster
973 * I:: -I for .include search path
974 @ifclear DIFF-TBL-KLUGE
975 * K:: -K for compatibility
977 @ifset DIFF-TBL-KLUGE
978 * K:: -K for difference tables
981 * L:: -L to retain local labels
982 * M:: -M or --mri to assemble in MRI compatibility mode
983 * MD:: --MD for dependency tracking
984 * o:: -o to name the object file
985 * R:: -R to join data and text sections
986 * statistics:: --statistics to see statistics about assembly
987 * traditional-format:: --traditional-format for compatible output
988 * v:: -v to announce version
989 * W:: -W to suppress warnings
990 * Z:: -Z to make object file even after errors
994 @section Enable Listings: @code{-a[cdhlns]}
1003 @cindex listings, enabling
1004 @cindex assembly listings, enabling
1006 These options enable listing output from the assembler. By itself,
1007 @samp{-a} requests high-level, assembly, and symbols listing.
1008 You can use other letters to select specific options for the list:
1009 @samp{-ah} requests a high-level language listing,
1010 @samp{-al} requests an output-program assembly listing, and
1011 @samp{-as} requests a symbol table listing.
1012 High-level listings require that a compiler debugging option like
1013 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1016 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1017 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1018 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1019 omitted from the listing.
1021 Use the @samp{-ad} option to omit debugging directives from the
1024 Once you have specified one of these options, you can further control
1025 listing output and its appearance using the directives @code{.list},
1026 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1028 The @samp{-an} option turns off all forms processing.
1029 If you do not request listing output with one of the @samp{-a} options, the
1030 listing-control directives have no effect.
1032 The letters after @samp{-a} may be combined into one option,
1033 @emph{e.g.}, @samp{-aln}.
1039 This option has no effect whatsoever, but it is accepted to make it more
1040 likely that scripts written for other assemblers also work with
1044 @section Work Faster: @code{-f}
1047 @cindex trusted compiler
1048 @cindex faster processing (@code{-f})
1049 @samp{-f} should only be used when assembling programs written by a
1050 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1051 and comment preprocessing on
1052 the input file(s) before assembling them. @xref{Preprocessing,
1056 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1057 preprocessed (if they contain comments, for example), @code{@value{AS}} does
1062 @section @code{.include} search path: @code{-I} @var{path}
1064 @kindex -I @var{path}
1065 @cindex paths for @code{.include}
1066 @cindex search path for @code{.include}
1067 @cindex @code{include} directive search path
1068 Use this option to add a @var{path} to the list of directories
1069 @code{@value{AS}} searches for files specified in @code{.include}
1070 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
1071 many times as necessary to include a variety of paths. The current
1072 working directory is always searched first; after that, @code{@value{AS}}
1073 searches any @samp{-I} directories in the same order as they were
1074 specified (left to right) on the command line.
1077 @section Difference Tables: @code{-K}
1080 @ifclear DIFF-TBL-KLUGE
1081 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1082 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1083 where it can be used to warn when the assembler alters the machine code
1084 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1085 family does not have the addressing limitations that sometimes lead to this
1086 alteration on other platforms.
1089 @ifset DIFF-TBL-KLUGE
1090 @cindex difference tables, warning
1091 @cindex warning for altered difference tables
1092 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1093 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1094 You can use the @samp{-K} option if you want a warning issued when this
1099 @section Include Local Labels: @code{-L}
1102 @cindex local labels, retaining in output
1103 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1104 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1105 debugging, because they are intended for the use of programs (like
1106 compilers) that compose assembler programs, not for your notice.
1107 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1108 normally debug with them.
1110 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1111 in the object file. Usually if you do this you also tell the linker
1112 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1114 By default, a local label is any label beginning with @samp{L}, but each
1115 target is allowed to redefine the local label prefix.
1117 On the HPPA local labels begin with @samp{L$}.
1120 @samp{;} for the ARM family;
1124 @section Assemble in MRI Compatibility Mode: @code{-M}
1127 @cindex MRI compatibility mode
1128 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1129 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1130 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1131 configured target) assembler from Microtec Research. The exact nature of the
1132 MRI syntax will not be documented here; see the MRI manuals for more
1133 information. Note in particular that the handling of macros and macro
1134 arguments is somewhat different. The purpose of this option is to permit
1135 assembling existing MRI assembler code using @code{@value{AS}}.
1137 The MRI compatibility is not complete. Certain operations of the MRI assembler
1138 depend upon its object file format, and can not be supported using other object
1139 file formats. Supporting these would require enhancing each object file format
1140 individually. These are:
1143 @item global symbols in common section
1145 The m68k MRI assembler supports common sections which are merged by the linker.
1146 Other object file formats do not support this. @code{@value{AS}} handles
1147 common sections by treating them as a single common symbol. It permits local
1148 symbols to be defined within a common section, but it can not support global
1149 symbols, since it has no way to describe them.
1151 @item complex relocations
1153 The MRI assemblers support relocations against a negated section address, and
1154 relocations which combine the start addresses of two or more sections. These
1155 are not support by other object file formats.
1157 @item @code{END} pseudo-op specifying start address
1159 The MRI @code{END} pseudo-op permits the specification of a start address.
1160 This is not supported by other object file formats. The start address may
1161 instead be specified using the @code{-e} option to the linker, or in a linker
1164 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1166 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1167 name to the output file. This is not supported by other object file formats.
1169 @item @code{ORG} pseudo-op
1171 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1172 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1173 which changes the location within the current section. Absolute sections are
1174 not supported by other object file formats. The address of a section may be
1175 assigned within a linker script.
1178 There are some other features of the MRI assembler which are not supported by
1179 @code{@value{AS}}, typically either because they are difficult or because they
1180 seem of little consequence. Some of these may be supported in future releases.
1184 @item EBCDIC strings
1186 EBCDIC strings are not supported.
1188 @item packed binary coded decimal
1190 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1191 and @code{DCB.P} pseudo-ops are not supported.
1193 @item @code{FEQU} pseudo-op
1195 The m68k @code{FEQU} pseudo-op is not supported.
1197 @item @code{NOOBJ} pseudo-op
1199 The m68k @code{NOOBJ} pseudo-op is not supported.
1201 @item @code{OPT} branch control options
1203 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1204 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1205 relaxes all branches, whether forward or backward, to an appropriate size, so
1206 these options serve no purpose.
1208 @item @code{OPT} list control options
1210 The following m68k @code{OPT} list control options are ignored: @code{C},
1211 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1212 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1214 @item other @code{OPT} options
1216 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1217 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1219 @item @code{OPT} @code{D} option is default
1221 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1222 @code{OPT NOD} may be used to turn it off.
1224 @item @code{XREF} pseudo-op.
1226 The m68k @code{XREF} pseudo-op is ignored.
1228 @item @code{.debug} pseudo-op
1230 The i960 @code{.debug} pseudo-op is not supported.
1232 @item @code{.extended} pseudo-op
1234 The i960 @code{.extended} pseudo-op is not supported.
1236 @item @code{.list} pseudo-op.
1238 The various options of the i960 @code{.list} pseudo-op are not supported.
1240 @item @code{.optimize} pseudo-op
1242 The i960 @code{.optimize} pseudo-op is not supported.
1244 @item @code{.output} pseudo-op
1246 The i960 @code{.output} pseudo-op is not supported.
1248 @item @code{.setreal} pseudo-op
1250 The i960 @code{.setreal} pseudo-op is not supported.
1255 @section Dependency tracking: @code{--MD}
1258 @cindex dependency tracking
1261 @code{@value{AS}} can generate a dependency file for the file it creates. This
1262 file consists of a single rule suitable for @code{make} describing the
1263 dependencies of the main source file.
1265 The rule is written to the file named in its argument.
1267 This feature is used in the automatic updating of makefiles.
1270 @section Name the Object File: @code{-o}
1273 @cindex naming object file
1274 @cindex object file name
1275 There is always one object file output when you run @code{@value{AS}}. By
1276 default it has the name
1279 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1293 You use this option (which takes exactly one filename) to give the
1294 object file a different name.
1296 Whatever the object file is called, @code{@value{AS}} overwrites any
1297 existing file of the same name.
1300 @section Join Data and Text Sections: @code{-R}
1303 @cindex data and text sections, joining
1304 @cindex text and data sections, joining
1305 @cindex joining text and data sections
1306 @cindex merging text and data sections
1307 @code{-R} tells @code{@value{AS}} to write the object file as if all
1308 data-section data lives in the text section. This is only done at
1309 the very last moment: your binary data are the same, but data
1310 section parts are relocated differently. The data section part of
1311 your object file is zero bytes long because all its bytes are
1312 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1314 When you specify @code{-R} it would be possible to generate shorter
1315 address displacements (because we do not have to cross between text and
1316 data section). We refrain from doing this simply for compatibility with
1317 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1320 When @code{@value{AS}} is configured for COFF output,
1321 this option is only useful if you use sections named @samp{.text} and
1326 @code{-R} is not supported for any of the HPPA targets. Using
1327 @code{-R} generates a warning from @code{@value{AS}}.
1331 @section Display Assembly Statistics: @code{--statistics}
1333 @kindex --statistics
1334 @cindex statistics, about assembly
1335 @cindex time, total for assembly
1336 @cindex space used, maximum for assembly
1337 Use @samp{--statistics} to display two statistics about the resources used by
1338 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1339 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1342 @node traditional-format
1343 @section Compatible output: @code{--traditional-format}
1345 @kindex --traditional-format
1346 For some targets, the output of @code{@value{AS}} is different in some ways
1347 from the output of some existing assembler. This switch requests
1348 @code{@value{AS}} to use the traditional format instead.
1350 For example, it disables the exception frame optimizations which
1351 @code{@value{AS}} normally does by default on @code{@value{GCC}} output.
1354 @section Announce Version: @code{-v}
1358 @cindex assembler version
1359 @cindex version of assembler
1360 You can find out what version of as is running by including the
1361 option @samp{-v} (which you can also spell as @samp{-version}) on the
1365 @section Suppress Warnings: @code{-W}
1368 @cindex suppressing warnings
1369 @cindex warnings, suppressing
1370 @code{@value{AS}} should never give a warning or error message when
1371 assembling compiler output. But programs written by people often
1372 cause @code{@value{AS}} to give a warning that a particular assumption was
1373 made. All such warnings are directed to the standard error file.
1374 If you use this option, no warnings are issued. This option only
1375 affects the warning messages: it does not change any particular of how
1376 @code{@value{AS}} assembles your file. Errors, which stop the assembly, are
1380 @section Generate Object File in Spite of Errors: @code{-Z}
1381 @cindex object file, after errors
1382 @cindex errors, continuing after
1383 After an error message, @code{@value{AS}} normally produces no output. If for
1384 some reason you are interested in object file output even after
1385 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1386 option. If there are any errors, @code{@value{AS}} continues anyways, and
1387 writes an object file after a final warning message of the form @samp{@var{n}
1388 errors, @var{m} warnings, generating bad object file.}
1393 @cindex machine-independent syntax
1394 @cindex syntax, machine-independent
1395 This chapter describes the machine-independent syntax allowed in a
1396 source file. @code{@value{AS}} syntax is similar to what many other
1397 assemblers use; it is inspired by the BSD 4.2
1402 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1406 * Preprocessing:: Preprocessing
1407 * Whitespace:: Whitespace
1408 * Comments:: Comments
1409 * Symbol Intro:: Symbols
1410 * Statements:: Statements
1411 * Constants:: Constants
1415 @section Preprocessing
1417 @cindex preprocessing
1418 The @code{@value{AS}} internal preprocessor:
1420 @cindex whitespace, removed by preprocessor
1422 adjusts and removes extra whitespace. It leaves one space or tab before
1423 the keywords on a line, and turns any other whitespace on the line into
1426 @cindex comments, removed by preprocessor
1428 removes all comments, replacing them with a single space, or an
1429 appropriate number of newlines.
1431 @cindex constants, converted by preprocessor
1433 converts character constants into the appropriate numeric values.
1436 It does not do macro processing, include file handling, or
1437 anything else you may get from your C compiler's preprocessor. You can
1438 do include file processing with the @code{.include} directive
1439 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1440 to get other ``CPP'' style preprocessing, by giving the input file a
1441 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1442 Output, gcc.info, Using GNU CC}.
1444 Excess whitespace, comments, and character constants
1445 cannot be used in the portions of the input text that are not
1448 @cindex turning preprocessing on and off
1449 @cindex preprocessing, turning on and off
1452 If the first line of an input file is @code{#NO_APP} or if you use the
1453 @samp{-f} option, whitespace and comments are not removed from the input file.
1454 Within an input file, you can ask for whitespace and comment removal in
1455 specific portions of the by putting a line that says @code{#APP} before the
1456 text that may contain whitespace or comments, and putting a line that says
1457 @code{#NO_APP} after this text. This feature is mainly intend to support
1458 @code{asm} statements in compilers whose output is otherwise free of comments
1465 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1466 Whitespace is used to separate symbols, and to make programs neater for
1467 people to read. Unless within character constants
1468 (@pxref{Characters,,Character Constants}), any whitespace means the same
1469 as exactly one space.
1475 There are two ways of rendering comments to @code{@value{AS}}. In both
1476 cases the comment is equivalent to one space.
1478 Anything from @samp{/*} through the next @samp{*/} is a comment.
1479 This means you may not nest these comments.
1483 The only way to include a newline ('\n') in a comment
1484 is to use this sort of comment.
1487 /* This sort of comment does not nest. */
1490 @cindex line comment character
1491 Anything from the @dfn{line comment} character to the next newline
1492 is considered a comment and is ignored. The line comment character is
1494 @samp{;} for the AMD 29K family;
1497 @samp{;} on the ARC;
1500 @samp{;} for the H8/300 family;
1503 @samp{!} for the H8/500 family;
1506 @samp{;} for the HPPA;
1509 @samp{#} on the i960;
1512 @samp{!} for the Hitachi SH;
1515 @samp{!} on the SPARC;
1518 @samp{#} on the m32r;
1521 @samp{|} on the 680x0;
1524 @samp{#} on the Vax;
1527 @samp{!} for the Z8000;
1530 @samp{#} on the V850;
1532 see @ref{Machine Dependencies}. @refill
1533 @c FIXME What about i386, m88k, i860?
1536 On some machines there are two different line comment characters. One
1537 character only begins a comment if it is the first non-whitespace character on
1538 a line, while the other always begins a comment.
1542 The V850 assembler also supports a double dash as starting a comment that
1543 extends to the end of the line.
1549 @cindex lines starting with @code{#}
1550 @cindex logical line numbers
1551 To be compatible with past assemblers, lines that begin with @samp{#} have a
1552 special interpretation. Following the @samp{#} should be an absolute
1553 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1554 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1555 new logical file name. The rest of the line, if any, should be whitespace.
1557 If the first non-whitespace characters on the line are not numeric,
1558 the line is ignored. (Just like a comment.)
1561 # This is an ordinary comment.
1562 # 42-6 "new_file_name" # New logical file name
1563 # This is logical line # 36.
1565 This feature is deprecated, and may disappear from future versions
1566 of @code{@value{AS}}.
1571 @cindex characters used in symbols
1572 @ifclear SPECIAL-SYMS
1573 A @dfn{symbol} is one or more characters chosen from the set of all
1574 letters (both upper and lower case), digits and the three characters
1580 A @dfn{symbol} is one or more characters chosen from the set of all
1581 letters (both upper and lower case), digits and the three characters
1582 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1588 On most machines, you can also use @code{$} in symbol names; exceptions
1589 are noted in @ref{Machine Dependencies}.
1591 No symbol may begin with a digit. Case is significant.
1592 There is no length limit: all characters are significant. Symbols are
1593 delimited by characters not in that set, or by the beginning of a file
1594 (since the source program must end with a newline, the end of a file is
1595 not a possible symbol delimiter). @xref{Symbols}.
1596 @cindex length of symbols
1601 @cindex statements, structure of
1602 @cindex line separator character
1603 @cindex statement separator character
1605 @ifclear abnormal-separator
1606 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1607 semicolon (@samp{;}). The newline or semicolon is considered part of
1608 the preceding statement. Newlines and semicolons within character
1609 constants are an exception: they do not end statements.
1611 @ifset abnormal-separator
1613 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1614 sign (@samp{@@}). The newline or at sign is considered part of the
1615 preceding statement. Newlines and at signs within character constants
1616 are an exception: they do not end statements.
1619 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1620 point (@samp{!}). The newline or exclamation point is considered part of the
1621 preceding statement. Newlines and exclamation points within character
1622 constants are an exception: they do not end statements.
1625 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1626 H8/300) a dollar sign (@samp{$}); or (for the
1629 (@samp{;}). The newline or separator character is considered part of
1630 the preceding statement. Newlines and separators within character
1631 constants are an exception: they do not end statements.
1636 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1637 separator character. (The line separator is usually @samp{;}, unless
1638 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1639 newline or separator character is considered part of the preceding
1640 statement. Newlines and separators within character constants are an
1641 exception: they do not end statements.
1644 @cindex newline, required at file end
1645 @cindex EOF, newline must precede
1646 It is an error to end any statement with end-of-file: the last
1647 character of any input file should be a newline.@refill
1649 @cindex continuing statements
1650 @cindex multi-line statements
1651 @cindex statement on multiple lines
1652 You may write a statement on more than one line if you put a
1653 backslash (@kbd{\}) immediately in front of any newlines within the
1654 statement. When @code{@value{AS}} reads a backslashed newline both
1655 characters are ignored. You can even put backslashed newlines in
1656 the middle of symbol names without changing the meaning of your
1659 An empty statement is allowed, and may include whitespace. It is ignored.
1661 @cindex instructions and directives
1662 @cindex directives and instructions
1663 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1664 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1666 A statement begins with zero or more labels, optionally followed by a
1667 key symbol which determines what kind of statement it is. The key
1668 symbol determines the syntax of the rest of the statement. If the
1669 symbol begins with a dot @samp{.} then the statement is an assembler
1670 directive: typically valid for any computer. If the symbol begins with
1671 a letter the statement is an assembly language @dfn{instruction}: it
1672 assembles into a machine language instruction.
1674 Different versions of @code{@value{AS}} for different computers
1675 recognize different instructions. In fact, the same symbol may
1676 represent a different instruction in a different computer's assembly
1680 @cindex @code{:} (label)
1681 @cindex label (@code{:})
1682 A label is a symbol immediately followed by a colon (@code{:}).
1683 Whitespace before a label or after a colon is permitted, but you may not
1684 have whitespace between a label's symbol and its colon. @xref{Labels}.
1687 For HPPA targets, labels need not be immediately followed by a colon, but
1688 the definition of a label must begin in column zero. This also implies that
1689 only one label may be defined on each line.
1693 label: .directive followed by something
1694 another_label: # This is an empty statement.
1695 instruction operand_1, operand_2, @dots{}
1702 A constant is a number, written so that its value is known by
1703 inspection, without knowing any context. Like this:
1706 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1707 .ascii "Ring the bell\7" # A string constant.
1708 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1709 .float 0f-314159265358979323846264338327\
1710 95028841971.693993751E-40 # - pi, a flonum.
1715 * Characters:: Character Constants
1716 * Numbers:: Number Constants
1720 @subsection Character Constants
1722 @cindex character constants
1723 @cindex constants, character
1724 There are two kinds of character constants. A @dfn{character} stands
1725 for one character in one byte and its value may be used in
1726 numeric expressions. String constants (properly called string
1727 @emph{literals}) are potentially many bytes and their values may not be
1728 used in arithmetic expressions.
1732 * Chars:: Characters
1736 @subsubsection Strings
1738 @cindex string constants
1739 @cindex constants, string
1740 A @dfn{string} is written between double-quotes. It may contain
1741 double-quotes or null characters. The way to get special characters
1742 into a string is to @dfn{escape} these characters: precede them with
1743 a backslash @samp{\} character. For example @samp{\\} represents
1744 one backslash: the first @code{\} is an escape which tells
1745 @code{@value{AS}} to interpret the second character literally as a backslash
1746 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1747 escape character). The complete list of escapes follows.
1749 @cindex escape codes, character
1750 @cindex character escape codes
1753 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1755 @cindex @code{\b} (backspace character)
1756 @cindex backspace (@code{\b})
1758 Mnemonic for backspace; for ASCII this is octal code 010.
1761 @c Mnemonic for EOText; for ASCII this is octal code 004.
1763 @cindex @code{\f} (formfeed character)
1764 @cindex formfeed (@code{\f})
1766 Mnemonic for FormFeed; for ASCII this is octal code 014.
1768 @cindex @code{\n} (newline character)
1769 @cindex newline (@code{\n})
1771 Mnemonic for newline; for ASCII this is octal code 012.
1774 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1776 @cindex @code{\r} (carriage return character)
1777 @cindex carriage return (@code{\r})
1779 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1782 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1783 @c other assemblers.
1785 @cindex @code{\t} (tab)
1786 @cindex tab (@code{\t})
1788 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1791 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1792 @c @item \x @var{digit} @var{digit} @var{digit}
1793 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1795 @cindex @code{\@var{ddd}} (octal character code)
1796 @cindex octal character code (@code{\@var{ddd}})
1797 @item \ @var{digit} @var{digit} @var{digit}
1798 An octal character code. The numeric code is 3 octal digits.
1799 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1800 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1802 @cindex @code{\@var{xd...}} (hex character code)
1803 @cindex hex character code (@code{\@var{xd...}})
1804 @item \@code{x} @var{hex-digits...}
1805 A hex character code. All trailing hex digits are combined. Either upper or
1806 lower case @code{x} works.
1808 @cindex @code{\\} (@samp{\} character)
1809 @cindex backslash (@code{\\})
1811 Represents one @samp{\} character.
1814 @c Represents one @samp{'} (accent acute) character.
1815 @c This is needed in single character literals
1816 @c (@xref{Characters,,Character Constants}.) to represent
1819 @cindex @code{\"} (doublequote character)
1820 @cindex doublequote (@code{\"})
1822 Represents one @samp{"} character. Needed in strings to represent
1823 this character, because an unescaped @samp{"} would end the string.
1825 @item \ @var{anything-else}
1826 Any other character when escaped by @kbd{\} gives a warning, but
1827 assembles as if the @samp{\} was not present. The idea is that if
1828 you used an escape sequence you clearly didn't want the literal
1829 interpretation of the following character. However @code{@value{AS}} has no
1830 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1831 code and warns you of the fact.
1834 Which characters are escapable, and what those escapes represent,
1835 varies widely among assemblers. The current set is what we think
1836 the BSD 4.2 assembler recognizes, and is a subset of what most C
1837 compilers recognize. If you are in doubt, do not use an escape
1841 @subsubsection Characters
1843 @cindex single character constant
1844 @cindex character, single
1845 @cindex constant, single character
1846 A single character may be written as a single quote immediately
1847 followed by that character. The same escapes apply to characters as
1848 to strings. So if you want to write the character backslash, you
1849 must write @kbd{'\\} where the first @code{\} escapes the second
1850 @code{\}. As you can see, the quote is an acute accent, not a
1851 grave accent. A newline
1853 @ifclear abnormal-separator
1854 (or semicolon @samp{;})
1856 @ifset abnormal-separator
1858 (or at sign @samp{@@})
1861 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1867 immediately following an acute accent is taken as a literal character
1868 and does not count as the end of a statement. The value of a character
1869 constant in a numeric expression is the machine's byte-wide code for
1870 that character. @code{@value{AS}} assumes your character code is ASCII:
1871 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1874 @subsection Number Constants
1876 @cindex constants, number
1877 @cindex number constants
1878 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1879 are stored in the target machine. @emph{Integers} are numbers that
1880 would fit into an @code{int} in the C language. @emph{Bignums} are
1881 integers, but they are stored in more than 32 bits. @emph{Flonums}
1882 are floating point numbers, described below.
1885 * Integers:: Integers
1890 * Bit Fields:: Bit Fields
1896 @subsubsection Integers
1898 @cindex constants, integer
1900 @cindex binary integers
1901 @cindex integers, binary
1902 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1903 the binary digits @samp{01}.
1905 @cindex octal integers
1906 @cindex integers, octal
1907 An octal integer is @samp{0} followed by zero or more of the octal
1908 digits (@samp{01234567}).
1910 @cindex decimal integers
1911 @cindex integers, decimal
1912 A decimal integer starts with a non-zero digit followed by zero or
1913 more digits (@samp{0123456789}).
1915 @cindex hexadecimal integers
1916 @cindex integers, hexadecimal
1917 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
1918 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
1920 Integers have the usual values. To denote a negative integer, use
1921 the prefix operator @samp{-} discussed under expressions
1922 (@pxref{Prefix Ops,,Prefix Operators}).
1925 @subsubsection Bignums
1928 @cindex constants, bignum
1929 A @dfn{bignum} has the same syntax and semantics as an integer
1930 except that the number (or its negative) takes more than 32 bits to
1931 represent in binary. The distinction is made because in some places
1932 integers are permitted while bignums are not.
1935 @subsubsection Flonums
1937 @cindex floating point numbers
1938 @cindex constants, floating point
1940 @cindex precision, floating point
1941 A @dfn{flonum} represents a floating point number. The translation is
1942 indirect: a decimal floating point number from the text is converted by
1943 @code{@value{AS}} to a generic binary floating point number of more than
1944 sufficient precision. This generic floating point number is converted
1945 to a particular computer's floating point format (or formats) by a
1946 portion of @code{@value{AS}} specialized to that computer.
1948 A flonum is written by writing (in order)
1953 (@samp{0} is optional on the HPPA.)
1957 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
1959 @kbd{e} is recommended. Case is not important.
1961 @c FIXME: verify if flonum syntax really this vague for most cases
1962 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
1963 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
1966 On the H8/300, H8/500,
1968 and AMD 29K architectures, the letter must be
1969 one of the letters @samp{DFPRSX} (in upper or lower case).
1971 On the ARC, the letter must be one of the letters @samp{DFRS}
1972 (in upper or lower case).
1974 On the Intel 960 architecture, the letter must be
1975 one of the letters @samp{DFT} (in upper or lower case).
1977 On the HPPA architecture, the letter must be @samp{E} (upper case only).
1981 One of the letters @samp{DFPRSX} (in upper or lower case).
1984 One of the letters @samp{DFRS} (in upper or lower case).
1987 One of the letters @samp{DFPRSX} (in upper or lower case).
1990 The letter @samp{E} (upper case only).
1993 One of the letters @samp{DFT} (in upper or lower case).
1998 An optional sign: either @samp{+} or @samp{-}.
2001 An optional @dfn{integer part}: zero or more decimal digits.
2004 An optional @dfn{fractional part}: @samp{.} followed by zero
2005 or more decimal digits.
2008 An optional exponent, consisting of:
2012 An @samp{E} or @samp{e}.
2013 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2014 @c principle this can perfectly well be different on different targets.
2016 Optional sign: either @samp{+} or @samp{-}.
2018 One or more decimal digits.
2023 At least one of the integer part or the fractional part must be
2024 present. The floating point number has the usual base-10 value.
2026 @code{@value{AS}} does all processing using integers. Flonums are computed
2027 independently of any floating point hardware in the computer running
2032 @c Bit fields are written as a general facility but are also controlled
2033 @c by a conditional-compilation flag---which is as of now (21mar91)
2034 @c turned on only by the i960 config of GAS.
2036 @subsubsection Bit Fields
2039 @cindex constants, bit field
2040 You can also define numeric constants as @dfn{bit fields}.
2041 specify two numbers separated by a colon---
2043 @var{mask}:@var{value}
2046 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2049 The resulting number is then packed
2051 @c this conditional paren in case bit fields turned on elsewhere than 960
2052 (in host-dependent byte order)
2054 into a field whose width depends on which assembler directive has the
2055 bit-field as its argument. Overflow (a result from the bitwise and
2056 requiring more binary digits to represent) is not an error; instead,
2057 more constants are generated, of the specified width, beginning with the
2058 least significant digits.@refill
2060 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2061 @code{.short}, and @code{.word} accept bit-field arguments.
2066 @chapter Sections and Relocation
2071 * Secs Background:: Background
2072 * Ld Sections:: Linker Sections
2073 * As Sections:: Assembler Internal Sections
2074 * Sub-Sections:: Sub-Sections
2078 @node Secs Background
2081 Roughly, a section is a range of addresses, with no gaps; all data
2082 ``in'' those addresses is treated the same for some particular purpose.
2083 For example there may be a ``read only'' section.
2085 @cindex linker, and assembler
2086 @cindex assembler, and linker
2087 The linker @code{@value{LD}} reads many object files (partial programs) and
2088 combines their contents to form a runnable program. When @code{@value{AS}}
2089 emits an object file, the partial program is assumed to start at address 0.
2090 @code{@value{LD}} assigns the final addresses for the partial program, so that
2091 different partial programs do not overlap. This is actually an
2092 oversimplification, but it suffices to explain how @code{@value{AS}} uses
2095 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2096 addresses. These blocks slide to their run-time addresses as rigid
2097 units; their length does not change and neither does the order of bytes
2098 within them. Such a rigid unit is called a @emph{section}. Assigning
2099 run-time addresses to sections is called @dfn{relocation}. It includes
2100 the task of adjusting mentions of object-file addresses so they refer to
2101 the proper run-time addresses.
2103 For the H8/300 and H8/500,
2104 and for the Hitachi SH,
2105 @code{@value{AS}} pads sections if needed to
2106 ensure they end on a word (sixteen bit) boundary.
2109 @cindex standard assembler sections
2110 An object file written by @code{@value{AS}} has at least three sections, any
2111 of which may be empty. These are named @dfn{text}, @dfn{data} and
2116 When it generates COFF output,
2118 @code{@value{AS}} can also generate whatever other named sections you specify
2119 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2120 If you do not use any directives that place output in the @samp{.text}
2121 or @samp{.data} sections, these sections still exist, but are empty.
2126 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2128 @code{@value{AS}} can also generate whatever other named sections you
2129 specify using the @samp{.space} and @samp{.subspace} directives. See
2130 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2131 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2132 assembler directives.
2135 Additionally, @code{@value{AS}} uses different names for the standard
2136 text, data, and bss sections when generating SOM output. Program text
2137 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2138 BSS into @samp{$BSS$}.
2142 Within the object file, the text section starts at address @code{0}, the
2143 data section follows, and the bss section follows the data section.
2146 When generating either SOM or ELF output files on the HPPA, the text
2147 section starts at address @code{0}, the data section at address
2148 @code{0x4000000}, and the bss section follows the data section.
2151 To let @code{@value{LD}} know which data changes when the sections are
2152 relocated, and how to change that data, @code{@value{AS}} also writes to the
2153 object file details of the relocation needed. To perform relocation
2154 @code{@value{LD}} must know, each time an address in the object
2158 Where in the object file is the beginning of this reference to
2161 How long (in bytes) is this reference?
2163 Which section does the address refer to? What is the numeric value of
2165 (@var{address}) @minus{} (@var{start-address of section})?
2168 Is the reference to an address ``Program-Counter relative''?
2171 @cindex addresses, format of
2172 @cindex section-relative addressing
2173 In fact, every address @code{@value{AS}} ever uses is expressed as
2175 (@var{section}) + (@var{offset into section})
2178 Further, most expressions @code{@value{AS}} computes have this section-relative
2181 (For some object formats, such as SOM for the HPPA, some expressions are
2182 symbol-relative instead.)
2185 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2186 @var{N} into section @var{secname}.''
2188 Apart from text, data and bss sections you need to know about the
2189 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2190 addresses in the absolute section remain unchanged. For example, address
2191 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2192 @code{@value{LD}}. Although the linker never arranges two partial programs'
2193 data sections with overlapping addresses after linking, @emph{by definition}
2194 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2195 part of a program is always the same address when the program is running as
2196 address @code{@{absolute@ 239@}} in any other part of the program.
2198 The idea of sections is extended to the @dfn{undefined} section. Any
2199 address whose section is unknown at assembly time is by definition
2200 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2201 Since numbers are always defined, the only way to generate an undefined
2202 address is to mention an undefined symbol. A reference to a named
2203 common block would be such a symbol: its value is unknown at assembly
2204 time so it has section @emph{undefined}.
2206 By analogy the word @emph{section} is used to describe groups of sections in
2207 the linked program. @code{@value{LD}} puts all partial programs' text
2208 sections in contiguous addresses in the linked program. It is
2209 customary to refer to the @emph{text section} of a program, meaning all
2210 the addresses of all partial programs' text sections. Likewise for
2211 data and bss sections.
2213 Some sections are manipulated by @code{@value{LD}}; others are invented for
2214 use of @code{@value{AS}} and have no meaning except during assembly.
2217 @section Linker Sections
2218 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2223 @cindex named sections
2224 @cindex sections, named
2225 @item named sections
2228 @cindex text section
2229 @cindex data section
2233 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2234 separate but equal sections. Anything you can say of one section is
2237 When the program is running, however, it is
2238 customary for the text section to be unalterable. The
2239 text section is often shared among processes: it contains
2240 instructions, constants and the like. The data section of a running
2241 program is usually alterable: for example, C variables would be stored
2242 in the data section.
2247 This section contains zeroed bytes when your program begins running. It
2248 is used to hold unitialized variables or common storage. The length of
2249 each partial program's bss section is important, but because it starts
2250 out containing zeroed bytes there is no need to store explicit zero
2251 bytes in the object file. The bss section was invented to eliminate
2252 those explicit zeros from object files.
2254 @cindex absolute section
2255 @item absolute section
2256 Address 0 of this section is always ``relocated'' to runtime address 0.
2257 This is useful if you want to refer to an address that @code{@value{LD}} must
2258 not change when relocating. In this sense we speak of absolute
2259 addresses being ``unrelocatable'': they do not change during relocation.
2261 @cindex undefined section
2262 @item undefined section
2263 This ``section'' is a catch-all for address references to objects not in
2264 the preceding sections.
2265 @c FIXME: ref to some other doc on obj-file formats could go here.
2268 @cindex relocation example
2269 An idealized example of three relocatable sections follows.
2271 The example uses the traditional section names @samp{.text} and @samp{.data}.
2273 Memory addresses are on the horizontal axis.
2277 @c END TEXI2ROFF-KILL
2280 partial program # 1: |ttttt|dddd|00|
2287 partial program # 2: |TTT|DDD|000|
2290 +--+---+-----+--+----+---+-----+~~
2291 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2292 +--+---+-----+--+----+---+-----+~~
2294 addresses: 0 @dots{}
2301 \line{\it Partial program \#1: \hfil}
2302 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2303 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2305 \line{\it Partial program \#2: \hfil}
2306 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2307 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2309 \line{\it linked program: \hfil}
2310 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2311 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2312 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2313 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2315 \line{\it addresses: \hfil}
2319 @c END TEXI2ROFF-KILL
2322 @section Assembler Internal Sections
2324 @cindex internal assembler sections
2325 @cindex sections in messages, internal
2326 These sections are meant only for the internal use of @code{@value{AS}}. They
2327 have no meaning at run-time. You do not really need to know about these
2328 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2329 warning messages, so it might be helpful to have an idea of their
2330 meanings to @code{@value{AS}}. These sections are used to permit the
2331 value of every expression in your assembly language program to be a
2332 section-relative address.
2335 @cindex assembler internal logic error
2336 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2337 An internal assembler logic error has been found. This means there is a
2338 bug in the assembler.
2340 @cindex expr (internal section)
2342 The assembler stores complex expression internally as combinations of
2343 symbols. When it needs to represent an expression as a symbol, it puts
2344 it in the expr section.
2346 @c FIXME item transfer[t] vector preload
2347 @c FIXME item transfer[t] vector postload
2348 @c FIXME item register
2352 @section Sub-Sections
2354 @cindex numbered subsections
2355 @cindex grouping data
2361 fall into two sections: text and data.
2363 You may have separate groups of
2365 data in named sections
2369 data in named sections
2375 that you want to end up near to each other in the object file, even though they
2376 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2377 use @dfn{subsections} for this purpose. Within each section, there can be
2378 numbered subsections with values from 0 to 8192. Objects assembled into the
2379 same subsection go into the object file together with other objects in the same
2380 subsection. For example, a compiler might want to store constants in the text
2381 section, but might not want to have them interspersed with the program being
2382 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2383 section of code being output, and a @samp{.text 1} before each group of
2384 constants being output.
2386 Subsections are optional. If you do not use subsections, everything
2387 goes in subsection number zero.
2390 Each subsection is zero-padded up to a multiple of four bytes.
2391 (Subsections may be padded a different amount on different flavors
2392 of @code{@value{AS}}.)
2396 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2397 boundary (two bytes).
2398 The same is true on the Hitachi SH.
2401 @c FIXME section padding (alignment)?
2402 @c Rich Pixley says padding here depends on target obj code format; that
2403 @c doesn't seem particularly useful to say without further elaboration,
2404 @c so for now I say nothing about it. If this is a generic BFD issue,
2405 @c these paragraphs might need to vanish from this manual, and be
2406 @c discussed in BFD chapter of binutils (or some such).
2409 On the AMD 29K family, no particular padding is added to section or
2410 subsection sizes; @value{AS} forces no alignment on this platform.
2414 Subsections appear in your object file in numeric order, lowest numbered
2415 to highest. (All this to be compatible with other people's assemblers.)
2416 The object file contains no representation of subsections; @code{@value{LD}} and
2417 other programs that manipulate object files see no trace of them.
2418 They just see all your text subsections as a text section, and all your
2419 data subsections as a data section.
2421 To specify which subsection you want subsequent statements assembled
2422 into, use a numeric argument to specify it, in a @samp{.text
2423 @var{expression}} or a @samp{.data @var{expression}} statement.
2426 When generating COFF output, you
2431 can also use an extra subsection
2432 argument with arbitrary named sections: @samp{.section @var{name},
2435 @var{Expression} should be an absolute expression.
2436 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2437 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2438 begins in @code{text 0}. For instance:
2440 .text 0 # The default subsection is text 0 anyway.
2441 .ascii "This lives in the first text subsection. *"
2443 .ascii "But this lives in the second text subsection."
2445 .ascii "This lives in the data section,"
2446 .ascii "in the first data subsection."
2448 .ascii "This lives in the first text section,"
2449 .ascii "immediately following the asterisk (*)."
2452 Each section has a @dfn{location counter} incremented by one for every byte
2453 assembled into that section. Because subsections are merely a convenience
2454 restricted to @code{@value{AS}} there is no concept of a subsection location
2455 counter. There is no way to directly manipulate a location counter---but the
2456 @code{.align} directive changes it, and any label definition captures its
2457 current value. The location counter of the section where statements are being
2458 assembled is said to be the @dfn{active} location counter.
2461 @section bss Section
2464 @cindex common variable storage
2465 The bss section is used for local common variable storage.
2466 You may allocate address space in the bss section, but you may
2467 not dictate data to load into it before your program executes. When
2468 your program starts running, all the contents of the bss
2469 section are zeroed bytes.
2471 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2472 @ref{Lcomm,,@code{.lcomm}}.
2474 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2475 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2478 When assembling for a target which supports multiple sections, such as ELF or
2479 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2480 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2481 section. Typically the section will only contain symbol definitions and
2482 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2489 Symbols are a central concept: the programmer uses symbols to name
2490 things, the linker uses symbols to link, and the debugger uses symbols
2494 @cindex debuggers, and symbol order
2495 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2496 the same order they were declared. This may break some debuggers.
2501 * Setting Symbols:: Giving Symbols Other Values
2502 * Symbol Names:: Symbol Names
2503 * Dot:: The Special Dot Symbol
2504 * Symbol Attributes:: Symbol Attributes
2511 A @dfn{label} is written as a symbol immediately followed by a colon
2512 @samp{:}. The symbol then represents the current value of the
2513 active location counter, and is, for example, a suitable instruction
2514 operand. You are warned if you use the same symbol to represent two
2515 different locations: the first definition overrides any other
2519 On the HPPA, the usual form for a label need not be immediately followed by a
2520 colon, but instead must start in column zero. Only one label may be defined on
2521 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2522 provides a special directive @code{.label} for defining labels more flexibly.
2525 @node Setting Symbols
2526 @section Giving Symbols Other Values
2528 @cindex assigning values to symbols
2529 @cindex symbol values, assigning
2530 A symbol can be given an arbitrary value by writing a symbol, followed
2531 by an equals sign @samp{=}, followed by an expression
2532 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2533 directive. @xref{Set,,@code{.set}}.
2536 @section Symbol Names
2538 @cindex symbol names
2539 @cindex names, symbol
2540 @ifclear SPECIAL-SYMS
2541 Symbol names begin with a letter or with one of @samp{._}. On most
2542 machines, you can also use @code{$} in symbol names; exceptions are
2543 noted in @ref{Machine Dependencies}. That character may be followed by any
2544 string of digits, letters, dollar signs (unless otherwise noted in
2545 @ref{Machine Dependencies}), and underscores.
2548 For the AMD 29K family, @samp{?} is also allowed in the
2549 body of a symbol name, though not at its beginning.
2554 Symbol names begin with a letter or with one of @samp{._}. On the
2556 H8/500, you can also use @code{$} in symbol names. That character may
2557 be followed by any string of digits, letters, dollar signs (save on the
2558 H8/300), and underscores.
2562 Case of letters is significant: @code{foo} is a different symbol name
2565 Each symbol has exactly one name. Each name in an assembly language program
2566 refers to exactly one symbol. You may use that symbol name any number of times
2569 @subheading Local Symbol Names
2571 @cindex local symbol names
2572 @cindex symbol names, local
2573 @cindex temporary symbol names
2574 @cindex symbol names, temporary
2575 Local symbols help compilers and programmers use names temporarily.
2576 There are ten local symbol names, which are re-used throughout the
2577 program. You may refer to them using the names @samp{0} @samp{1}
2578 @dots{} @samp{9}. To define a local symbol, write a label of the form
2579 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2580 recent previous definition of that symbol write @samp{@b{N}b}, using the
2581 same digit as when you defined the label. To refer to the next
2582 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2583 a choice of 10 forward references. The @samp{b} stands for
2584 ``backwards'' and the @samp{f} stands for ``forwards''.
2586 Local symbols are not emitted by the current @sc{gnu} C compiler.
2588 There is no restriction on how you can use these labels, but
2589 remember that at any point in the assembly you can refer to at most
2590 10 prior local labels and to at most 10 forward local labels.
2592 Local symbol names are only a notation device. They are immediately
2593 transformed into more conventional symbol names before the assembler
2594 uses them. The symbol names stored in the symbol table, appearing in
2595 error messages and optionally emitted to the object file have these
2600 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2601 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2602 used for symbols you are never intended to see. If you use the
2603 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2604 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2605 you may use them in debugging.
2608 If the label is written @samp{0:} then the digit is @samp{0}.
2609 If the label is written @samp{1:} then the digit is @samp{1}.
2610 And so on up through @samp{9:}.
2613 This unusual character is included so you do not accidentally invent
2614 a symbol of the same name. The character has ASCII value
2617 @item @emph{ordinal number}
2618 This is a serial number to keep the labels distinct. The first
2619 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2620 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2624 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2625 @code{3:} is named @code{L3@kbd{C-A}44}.
2628 @section The Special Dot Symbol
2630 @cindex dot (symbol)
2631 @cindex @code{.} (symbol)
2632 @cindex current address
2633 @cindex location counter
2634 The special symbol @samp{.} refers to the current address that
2635 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2636 .long .} defines @code{melvin} to contain its own address.
2637 Assigning a value to @code{.} is treated the same as a @code{.org}
2638 directive. Thus, the expression @samp{.=.+4} is the same as saying
2639 @ifclear no-space-dir
2648 @node Symbol Attributes
2649 @section Symbol Attributes
2651 @cindex symbol attributes
2652 @cindex attributes, symbol
2653 Every symbol has, as well as its name, the attributes ``Value'' and
2654 ``Type''. Depending on output format, symbols can also have auxiliary
2657 The detailed definitions are in @file{a.out.h}.
2660 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2661 all these attributes, and probably won't warn you. This makes the
2662 symbol an externally defined symbol, which is generally what you
2666 * Symbol Value:: Value
2667 * Symbol Type:: Type
2670 * a.out Symbols:: Symbol Attributes: @code{a.out}
2674 * a.out Symbols:: Symbol Attributes: @code{a.out}
2677 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2682 * COFF Symbols:: Symbol Attributes for COFF
2685 * SOM Symbols:: Symbol Attributes for SOM
2692 @cindex value of a symbol
2693 @cindex symbol value
2694 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2695 location in the text, data, bss or absolute sections the value is the
2696 number of addresses from the start of that section to the label.
2697 Naturally for text, data and bss sections the value of a symbol changes
2698 as @code{@value{LD}} changes section base addresses during linking. Absolute
2699 symbols' values do not change during linking: that is why they are
2702 The value of an undefined symbol is treated in a special way. If it is
2703 0 then the symbol is not defined in this assembler source file, and
2704 @code{@value{LD}} tries to determine its value from other files linked into the
2705 same program. You make this kind of symbol simply by mentioning a symbol
2706 name without defining it. A non-zero value represents a @code{.comm}
2707 common declaration. The value is how much common storage to reserve, in
2708 bytes (addresses). The symbol refers to the first address of the
2714 @cindex type of a symbol
2716 The type attribute of a symbol contains relocation (section)
2717 information, any flag settings indicating that a symbol is external, and
2718 (optionally), other information for linkers and debuggers. The exact
2719 format depends on the object-code output format in use.
2724 @c The following avoids a "widow" subsection title. @group would be
2725 @c better if it were available outside examples.
2728 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2730 @cindex @code{b.out} symbol attributes
2731 @cindex symbol attributes, @code{b.out}
2732 These symbol attributes appear only when @code{@value{AS}} is configured for
2733 one of the Berkeley-descended object output formats---@code{a.out} or
2739 @subsection Symbol Attributes: @code{a.out}
2741 @cindex @code{a.out} symbol attributes
2742 @cindex symbol attributes, @code{a.out}
2748 @subsection Symbol Attributes: @code{a.out}
2750 @cindex @code{a.out} symbol attributes
2751 @cindex symbol attributes, @code{a.out}
2755 * Symbol Desc:: Descriptor
2756 * Symbol Other:: Other
2760 @subsubsection Descriptor
2762 @cindex descriptor, of @code{a.out} symbol
2763 This is an arbitrary 16-bit value. You may establish a symbol's
2764 descriptor value by using a @code{.desc} statement
2765 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2769 @subsubsection Other
2771 @cindex other attribute, of @code{a.out} symbol
2772 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2777 @subsection Symbol Attributes for COFF
2779 @cindex COFF symbol attributes
2780 @cindex symbol attributes, COFF
2782 The COFF format supports a multitude of auxiliary symbol attributes;
2783 like the primary symbol attributes, they are set between @code{.def} and
2784 @code{.endef} directives.
2786 @subsubsection Primary Attributes
2788 @cindex primary attributes, COFF symbols
2789 The symbol name is set with @code{.def}; the value and type,
2790 respectively, with @code{.val} and @code{.type}.
2792 @subsubsection Auxiliary Attributes
2794 @cindex auxiliary attributes, COFF symbols
2795 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2796 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2797 information for COFF.
2802 @subsection Symbol Attributes for SOM
2804 @cindex SOM symbol attributes
2805 @cindex symbol attributes, SOM
2807 The SOM format for the HPPA supports a multitude of symbol attributes set with
2808 the @code{.EXPORT} and @code{.IMPORT} directives.
2810 The attributes are described in @cite{HP9000 Series 800 Assembly
2811 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2812 @code{EXPORT} assembler directive documentation.
2816 @chapter Expressions
2820 @cindex numeric values
2821 An @dfn{expression} specifies an address or numeric value.
2822 Whitespace may precede and/or follow an expression.
2824 The result of an expression must be an absolute number, or else an offset into
2825 a particular section. If an expression is not absolute, and there is not
2826 enough information when @code{@value{AS}} sees the expression to know its
2827 section, a second pass over the source program might be necessary to interpret
2828 the expression---but the second pass is currently not implemented.
2829 @code{@value{AS}} aborts with an error message in this situation.
2832 * Empty Exprs:: Empty Expressions
2833 * Integer Exprs:: Integer Expressions
2837 @section Empty Expressions
2839 @cindex empty expressions
2840 @cindex expressions, empty
2841 An empty expression has no value: it is just whitespace or null.
2842 Wherever an absolute expression is required, you may omit the
2843 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2844 is compatible with other assemblers.
2847 @section Integer Expressions
2849 @cindex integer expressions
2850 @cindex expressions, integer
2851 An @dfn{integer expression} is one or more @emph{arguments} delimited
2852 by @emph{operators}.
2855 * Arguments:: Arguments
2856 * Operators:: Operators
2857 * Prefix Ops:: Prefix Operators
2858 * Infix Ops:: Infix Operators
2862 @subsection Arguments
2864 @cindex expression arguments
2865 @cindex arguments in expressions
2866 @cindex operands in expressions
2867 @cindex arithmetic operands
2868 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2869 contexts arguments are sometimes called ``arithmetic operands''. In
2870 this manual, to avoid confusing them with the ``instruction operands'' of
2871 the machine language, we use the term ``argument'' to refer to parts of
2872 expressions only, reserving the word ``operand'' to refer only to machine
2873 instruction operands.
2875 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2876 @var{section} is one of text, data, bss, absolute,
2877 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2880 Numbers are usually integers.
2882 A number can be a flonum or bignum. In this case, you are warned
2883 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2884 these 32 bits are an integer. You may write integer-manipulating
2885 instructions that act on exotic constants, compatible with other
2888 @cindex subexpressions
2889 Subexpressions are a left parenthesis @samp{(} followed by an integer
2890 expression, followed by a right parenthesis @samp{)}; or a prefix
2891 operator followed by an argument.
2894 @subsection Operators
2896 @cindex operators, in expressions
2897 @cindex arithmetic functions
2898 @cindex functions, in expressions
2899 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2900 operators are followed by an argument. Infix operators appear
2901 between their arguments. Operators may be preceded and/or followed by
2905 @subsection Prefix Operator
2907 @cindex prefix operators
2908 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2909 one argument, which must be absolute.
2911 @c the tex/end tex stuff surrounding this small table is meant to make
2912 @c it align, on the printed page, with the similar table in the next
2913 @c section (which is inside an enumerate).
2915 \global\advance\leftskip by \itemindent
2920 @dfn{Negation}. Two's complement negation.
2922 @dfn{Complementation}. Bitwise not.
2926 \global\advance\leftskip by -\itemindent
2930 @subsection Infix Operators
2932 @cindex infix operators
2933 @cindex operators, permitted arguments
2934 @dfn{Infix operators} take two arguments, one on either side. Operators
2935 have precedence, but operations with equal precedence are performed left
2936 to right. Apart from @code{+} or @code{-}, both arguments must be
2937 absolute, and the result is absolute.
2940 @cindex operator precedence
2941 @cindex precedence of operators
2948 @dfn{Multiplication}.
2951 @dfn{Division}. Truncation is the same as the C operator @samp{/}
2958 @dfn{Shift Left}. Same as the C operator @samp{<<}.
2962 @dfn{Shift Right}. Same as the C operator @samp{>>}.
2966 Intermediate precedence
2971 @dfn{Bitwise Inclusive Or}.
2977 @dfn{Bitwise Exclusive Or}.
2980 @dfn{Bitwise Or Not}.
2987 @cindex addition, permitted arguments
2988 @cindex plus, permitted arguments
2989 @cindex arguments for addition
2991 @dfn{Addition}. If either argument is absolute, the result has the section of
2992 the other argument. You may not add together arguments from different
2995 @cindex subtraction, permitted arguments
2996 @cindex minus, permitted arguments
2997 @cindex arguments for subtraction
2999 @dfn{Subtraction}. If the right argument is absolute, the
3000 result has the section of the left argument.
3001 If both arguments are in the same section, the result is absolute.
3002 You may not subtract arguments from different sections.
3003 @c FIXME is there still something useful to say about undefined - undefined ?
3007 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3008 address; you can only have a defined section in one of the two arguments.
3011 @chapter Assembler Directives
3013 @cindex directives, machine independent
3014 @cindex pseudo-ops, machine independent
3015 @cindex machine independent directives
3016 All assembler directives have names that begin with a period (@samp{.}).
3017 The rest of the name is letters, usually in lower case.
3019 This chapter discusses directives that are available regardless of the
3020 target machine configuration for the @sc{gnu} assembler.
3022 Some machine configurations provide additional directives.
3023 @xref{Machine Dependencies}.
3026 @ifset machine-directives
3027 @xref{Machine Dependencies} for additional directives.
3032 * Abort:: @code{.abort}
3034 * ABORT:: @code{.ABORT}
3037 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3038 * App-File:: @code{.app-file @var{string}}
3039 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3040 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3041 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3042 * Byte:: @code{.byte @var{expressions}}
3043 * Comm:: @code{.comm @var{symbol} , @var{length} }
3044 * Data:: @code{.data @var{subsection}}
3046 * Def:: @code{.def @var{name}}
3049 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3055 * Double:: @code{.double @var{flonums}}
3056 * Eject:: @code{.eject}
3057 * Else:: @code{.else}
3059 * Endef:: @code{.endef}
3062 * Endfunc:: @code{.endfunc}
3063 * Endif:: @code{.endif}
3064 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3065 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3067 * Extern:: @code{.extern}
3068 @ifclear no-file-dir
3069 * File:: @code{.file @var{string}}
3072 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3073 * Float:: @code{.float @var{flonums}}
3074 * Func:: @code{.func}
3075 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3076 * hword:: @code{.hword @var{expressions}}
3077 * Ident:: @code{.ident}
3078 * If:: @code{.if @var{absolute expression}}
3079 * Include:: @code{.include "@var{file}"}
3080 * Int:: @code{.int @var{expressions}}
3081 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3082 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3083 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3084 * Lflags:: @code{.lflags}
3085 @ifclear no-line-dir
3086 * Line:: @code{.line @var{line-number}}
3089 * Ln:: @code{.ln @var{line-number}}
3090 * Linkonce:: @code{.linkonce [@var{type}]}
3091 * List:: @code{.list}
3092 * Long:: @code{.long @var{expressions}}
3094 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3097 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3098 * MRI:: @code{.mri @var{val}}
3100 * Nolist:: @code{.nolist}
3101 * Octa:: @code{.octa @var{bignums}}
3102 * Org:: @code{.org @var{new-lc} , @var{fill}}
3103 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3104 * Psize:: @code{.psize @var{lines}, @var{columns}}
3105 * Quad:: @code{.quad @var{bignums}}
3106 * Rept:: @code{.rept @var{count}}
3107 * Sbttl:: @code{.sbttl "@var{subheading}"}
3109 * Scl:: @code{.scl @var{class}}
3110 * Section:: @code{.section @var{name}, @var{subsection}}
3113 * Set:: @code{.set @var{symbol}, @var{expression}}
3114 * Short:: @code{.short @var{expressions}}
3115 * Single:: @code{.single @var{flonums}}
3117 * Size:: @code{.size}
3120 * Skip:: @code{.skip @var{size} , @var{fill}}
3121 * Sleb128:: @code{.sleb128 @var{expressions}}
3122 * Space:: @code{.space @var{size} , @var{fill}}
3124 * Stab:: @code{.stabd, .stabn, .stabs}
3127 * String:: @code{.string "@var{str}"}
3129 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3132 * Tag:: @code{.tag @var{structname}}
3135 * Text:: @code{.text @var{subsection}}
3136 * Title:: @code{.title "@var{heading}"}
3138 * Type:: @code{.type @var{int}}
3139 * Val:: @code{.val @var{addr}}
3142 * Uleb128:: @code{.uleb128 @var{expressions}}
3143 * Word:: @code{.word @var{expressions}}
3144 * Deprecated:: Deprecated Directives
3148 @section @code{.abort}
3150 @cindex @code{abort} directive
3151 @cindex stopping the assembly
3152 This directive stops the assembly immediately. It is for
3153 compatibility with other assemblers. The original idea was that the
3154 assembly language source would be piped into the assembler. If the sender
3155 of the source quit, it could use this directive tells @code{@value{AS}} to
3156 quit also. One day @code{.abort} will not be supported.
3160 @section @code{.ABORT}
3162 @cindex @code{ABORT} directive
3163 When producing COFF output, @code{@value{AS}} accepts this directive as a
3164 synonym for @samp{.abort}.
3167 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3173 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3175 @cindex padding the location counter
3176 @cindex @code{align} directive
3177 Pad the location counter (in the current subsection) to a particular storage
3178 boundary. The first expression (which must be absolute) is the alignment
3179 required, as described below.
3181 The second expression (also absolute) gives the fill value to be stored in the
3182 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3183 padding bytes are normally zero. However, on some systems, if the section is
3184 marked as containing code and the fill value is omitted, the space is filled
3185 with no-op instructions.
3187 The third expression is also absolute, and is also optional. If it is present,
3188 it is the maximum number of bytes that should be skipped by this alignment
3189 directive. If doing the alignment would require skipping more bytes than the
3190 specified maximum, then the alignment is not done at all. You can omit the
3191 fill value (the second argument) entirely by simply using two commas after the
3192 required alignment; this can be useful if you want the alignment to be filled
3193 with no-op instructions when appropriate.
3195 The way the required alignment is specified varies from system to system.
3196 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3198 the first expression is the
3199 alignment request in bytes. For example @samp{.align 8} advances
3200 the location counter until it is a multiple of 8. If the location counter
3201 is already a multiple of 8, no change is needed.
3203 For other systems, including the i386 using a.out format, it is the
3204 number of low-order zero bits the location counter must have after
3205 advancement. For example @samp{.align 3} advances the location
3206 counter until it a multiple of 8. If the location counter is already a
3207 multiple of 8, no change is needed.
3209 This inconsistency is due to the different behaviors of the various
3210 native assemblers for these systems which GAS must emulate.
3211 GAS also provides @code{.balign} and @code{.p2align} directives,
3212 described later, which have a consistent behavior across all
3213 architectures (but are specific to GAS).
3216 @section @code{.app-file @var{string}}
3218 @cindex logical file name
3219 @cindex file name, logical
3220 @cindex @code{app-file} directive
3222 @ifclear no-file-dir
3223 (which may also be spelled @samp{.file})
3225 tells @code{@value{AS}} that we are about to start a new
3226 logical file. @var{string} is the new file name. In general, the
3227 filename is recognized whether or not it is surrounded by quotes @samp{"};
3228 but if you wish to specify an empty file name is permitted,
3229 you must give the quotes--@code{""}. This statement may go away in
3230 future: it is only recognized to be compatible with old @code{@value{AS}}
3234 @section @code{.ascii "@var{string}"}@dots{}
3236 @cindex @code{ascii} directive
3237 @cindex string literals
3238 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3239 separated by commas. It assembles each string (with no automatic
3240 trailing zero byte) into consecutive addresses.
3243 @section @code{.asciz "@var{string}"}@dots{}
3245 @cindex @code{asciz} directive
3246 @cindex zero-terminated strings
3247 @cindex null-terminated strings
3248 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3249 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3252 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3254 @cindex padding the location counter given number of bytes
3255 @cindex @code{balign} directive
3256 Pad the location counter (in the current subsection) to a particular
3257 storage boundary. The first expression (which must be absolute) is the
3258 alignment request in bytes. For example @samp{.balign 8} advances
3259 the location counter until it is a multiple of 8. If the location counter
3260 is already a multiple of 8, no change is needed.
3262 The second expression (also absolute) gives the fill value to be stored in the
3263 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3264 padding bytes are normally zero. However, on some systems, if the section is
3265 marked as containing code and the fill value is omitted, the space is filled
3266 with no-op instructions.
3268 The third expression is also absolute, and is also optional. If it is present,
3269 it is the maximum number of bytes that should be skipped by this alignment
3270 directive. If doing the alignment would require skipping more bytes than the
3271 specified maximum, then the alignment is not done at all. You can omit the
3272 fill value (the second argument) entirely by simply using two commas after the
3273 required alignment; this can be useful if you want the alignment to be filled
3274 with no-op instructions when appropriate.
3276 @cindex @code{balignw} directive
3277 @cindex @code{balignl} directive
3278 The @code{.balignw} and @code{.balignl} directives are variants of the
3279 @code{.balign} directive. The @code{.balignw} directive treats the fill
3280 pattern as a two byte word value. The @code{.balignl} directives treats the
3281 fill pattern as a four byte longword value. For example, @code{.balignw
3282 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3283 filled in with the value 0x368d (the exact placement of the bytes depends upon
3284 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3288 @section @code{.byte @var{expressions}}
3290 @cindex @code{byte} directive
3291 @cindex integers, one byte
3292 @code{.byte} expects zero or more expressions, separated by commas.
3293 Each expression is assembled into the next byte.
3296 @section @code{.comm @var{symbol} , @var{length} }
3298 @cindex @code{comm} directive
3299 @cindex symbol, common
3300 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3301 common symbol in one object file may be merged with a defined or common symbol
3302 of the same name in another object file. If @code{@value{LD}} does not see a
3303 definition for the symbol--just one or more common symbols--then it will
3304 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3305 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3306 the same name, and they do not all have the same size, it will allocate space
3307 using the largest size.
3310 When using ELF, the @code{.comm} directive takes an optional third argument.
3311 This is the desired alignment of the symbol, specified as a byte boundary (for
3312 example, an alignment of 16 means that the least significant 4 bits of the
3313 address should be zero). The alignment must be an absolute expression, and it
3314 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3315 for the common symbol, it will use the alignment when placing the symbol. If
3316 no alignment is specified, @code{@value{AS}} will set the alignment to the
3317 largest power of two less than or equal to the size of the symbol, up to a
3322 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3323 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3327 @section @code{.data @var{subsection}}
3329 @cindex @code{data} directive
3330 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3331 end of the data subsection numbered @var{subsection} (which is an
3332 absolute expression). If @var{subsection} is omitted, it defaults
3337 @section @code{.def @var{name}}
3339 @cindex @code{def} directive
3340 @cindex COFF symbols, debugging
3341 @cindex debugging COFF symbols
3342 Begin defining debugging information for a symbol @var{name}; the
3343 definition extends until the @code{.endef} directive is encountered.
3346 This directive is only observed when @code{@value{AS}} is configured for COFF
3347 format output; when producing @code{b.out}, @samp{.def} is recognized,
3354 @section @code{.desc @var{symbol}, @var{abs-expression}}
3356 @cindex @code{desc} directive
3357 @cindex COFF symbol descriptor
3358 @cindex symbol descriptor, COFF
3359 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3360 to the low 16 bits of an absolute expression.
3363 The @samp{.desc} directive is not available when @code{@value{AS}} is
3364 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3365 object format. For the sake of compatibility, @code{@value{AS}} accepts
3366 it, but produces no output, when configured for COFF.
3372 @section @code{.dim}
3374 @cindex @code{dim} directive
3375 @cindex COFF auxiliary symbol information
3376 @cindex auxiliary symbol information, COFF
3377 This directive is generated by compilers to include auxiliary debugging
3378 information in the symbol table. It is only permitted inside
3379 @code{.def}/@code{.endef} pairs.
3382 @samp{.dim} is only meaningful when generating COFF format output; when
3383 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3389 @section @code{.double @var{flonums}}
3391 @cindex @code{double} directive
3392 @cindex floating point numbers (double)
3393 @code{.double} expects zero or more flonums, separated by commas. It
3394 assembles floating point numbers.
3396 The exact kind of floating point numbers emitted depends on how
3397 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3401 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3402 in @sc{ieee} format.
3407 @section @code{.eject}
3409 @cindex @code{eject} directive
3410 @cindex new page, in listings
3411 @cindex page, in listings
3412 @cindex listing control: new page
3413 Force a page break at this point, when generating assembly listings.
3416 @section @code{.else}
3418 @cindex @code{else} directive
3419 @code{.else} is part of the @code{@value{AS}} support for conditional
3420 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3421 of code to be assembled if the condition for the preceding @code{.if}
3425 @node End, Endef, Else, Pseudo Ops
3426 @section @code{.end}
3428 @cindex @code{end} directive
3429 This doesn't do anything---but isn't an s_ignore, so I suspect it's
3430 meant to do something eventually (which is why it isn't documented here
3431 as "for compatibility with blah").
3436 @section @code{.endef}
3438 @cindex @code{endef} directive
3439 This directive flags the end of a symbol definition begun with
3443 @samp{.endef} is only meaningful when generating COFF format output; if
3444 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3445 directive but ignores it.
3450 @section @code{.endfunc}
3451 @cindex @code{endfunc} directive
3452 @code{.endfunc} marks the end of a function specified with @code{.func}.
3455 @section @code{.endif}
3457 @cindex @code{endif} directive
3458 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3459 it marks the end of a block of code that is only assembled
3460 conditionally. @xref{If,,@code{.if}}.
3463 @section @code{.equ @var{symbol}, @var{expression}}
3465 @cindex @code{equ} directive
3466 @cindex assigning values to symbols
3467 @cindex symbols, assigning values to
3468 This directive sets the value of @var{symbol} to @var{expression}.
3469 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3472 The syntax for @code{equ} on the HPPA is
3473 @samp{@var{symbol} .equ @var{expression}}.
3477 @section @code{.equiv @var{symbol}, @var{expression}}
3478 @cindex @code{equiv} directive
3479 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3480 the assembler will signal an error if @var{symbol} is already defined.
3482 Except for the contents of the error message, this is roughly equivalent to
3491 @section @code{.err}
3492 @cindex @code{err} directive
3493 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3494 message and, unless the @code{-Z} option was used, it will not generate an
3495 object file. This can be used to signal error an conditionally compiled code.
3498 @section @code{.extern}
3500 @cindex @code{extern} directive
3501 @code{.extern} is accepted in the source program---for compatibility
3502 with other assemblers---but it is ignored. @code{@value{AS}} treats
3503 all undefined symbols as external.
3505 @ifclear no-file-dir
3507 @section @code{.file @var{string}}
3509 @cindex @code{file} directive
3510 @cindex logical file name
3511 @cindex file name, logical
3512 @code{.file} (which may also be spelled @samp{.app-file}) tells
3513 @code{@value{AS}} that we are about to start a new logical file.
3514 @var{string} is the new file name. In general, the filename is
3515 recognized whether or not it is surrounded by quotes @samp{"}; but if
3516 you wish to specify an empty file name, you must give the
3517 quotes--@code{""}. This statement may go away in future: it is only
3518 recognized to be compatible with old @code{@value{AS}} programs.
3520 In some configurations of @code{@value{AS}}, @code{.file} has already been
3521 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3526 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3528 @cindex @code{fill} directive
3529 @cindex writing patterns in memory
3530 @cindex patterns, writing in memory
3531 @var{result}, @var{size} and @var{value} are absolute expressions.
3532 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3533 may be zero or more. @var{Size} may be zero or more, but if it is
3534 more than 8, then it is deemed to have the value 8, compatible with
3535 other people's assemblers. The contents of each @var{repeat} bytes
3536 is taken from an 8-byte number. The highest order 4 bytes are
3537 zero. The lowest order 4 bytes are @var{value} rendered in the
3538 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3539 Each @var{size} bytes in a repetition is taken from the lowest order
3540 @var{size} bytes of this number. Again, this bizarre behavior is
3541 compatible with other people's assemblers.
3543 @var{size} and @var{value} are optional.
3544 If the second comma and @var{value} are absent, @var{value} is
3545 assumed zero. If the first comma and following tokens are absent,
3546 @var{size} is assumed to be 1.
3549 @section @code{.float @var{flonums}}
3551 @cindex floating point numbers (single)
3552 @cindex @code{float} directive
3553 This directive assembles zero or more flonums, separated by commas. It
3554 has the same effect as @code{.single}.
3556 The exact kind of floating point numbers emitted depends on how
3557 @code{@value{AS}} is configured.
3558 @xref{Machine Dependencies}.
3562 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3563 in @sc{ieee} format.
3568 @section @code{.func @var{name}[,@var{label}]}
3569 @cindex @code{func} directive
3570 @code{.func} emits debugging information to denote function @var{name}, and
3571 is ignored unless the file is assembled with debugging enabled.
3572 Only @samp{--gstabs} is currently supported.
3573 @var{label} is the entry point of the function and if omitted @var{name}
3575 All functions are currently defined to have @code{void} return type.
3576 The function must be terminated with @code{.endfunc}.
3579 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3581 @cindex @code{global} directive
3582 @cindex symbol, making visible to linker
3583 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3584 @var{symbol} in your partial program, its value is made available to
3585 other partial programs that are linked with it. Otherwise,
3586 @var{symbol} takes its attributes from a symbol of the same name
3587 from another file linked into the same program.
3589 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3590 compatibility with other assemblers.
3593 On the HPPA, @code{.global} is not always enough to make it accessible to other
3594 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3595 @xref{HPPA Directives,, HPPA Assembler Directives}.
3599 @section @code{.hword @var{expressions}}
3601 @cindex @code{hword} directive
3602 @cindex integers, 16-bit
3603 @cindex numbers, 16-bit
3604 @cindex sixteen bit integers
3605 This expects zero or more @var{expressions}, and emits
3606 a 16 bit number for each.
3609 This directive is a synonym for @samp{.short}; depending on the target
3610 architecture, it may also be a synonym for @samp{.word}.
3614 This directive is a synonym for @samp{.short}.
3617 This directive is a synonym for both @samp{.short} and @samp{.word}.
3622 @section @code{.ident}
3624 @cindex @code{ident} directive
3625 This directive is used by some assemblers to place tags in object files.
3626 @code{@value{AS}} simply accepts the directive for source-file
3627 compatibility with such assemblers, but does not actually emit anything
3631 @section @code{.if @var{absolute expression}}
3633 @cindex conditional assembly
3634 @cindex @code{if} directive
3635 @code{.if} marks the beginning of a section of code which is only
3636 considered part of the source program being assembled if the argument
3637 (which must be an @var{absolute expression}) is non-zero. The end of
3638 the conditional section of code must be marked by @code{.endif}
3639 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3640 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3642 The following variants of @code{.if} are also supported:
3644 @cindex @code{ifdef} directive
3645 @item .ifdef @var{symbol}
3646 Assembles the following section of code if the specified @var{symbol}
3650 @cindex @code{ifeqs} directive
3652 Not yet implemented.
3655 @cindex @code{ifndef} directive
3656 @cindex @code{ifnotdef} directive
3657 @item .ifndef @var{symbol}
3658 @itemx .ifnotdef @var{symbol}
3659 Assembles the following section of code if the specified @var{symbol}
3660 has not been defined. Both spelling variants are equivalent.
3664 Not yet implemented.
3669 @section @code{.include "@var{file}"}
3671 @cindex @code{include} directive
3672 @cindex supporting files, including
3673 @cindex files, including
3674 This directive provides a way to include supporting files at specified
3675 points in your source program. The code from @var{file} is assembled as
3676 if it followed the point of the @code{.include}; when the end of the
3677 included file is reached, assembly of the original file continues. You
3678 can control the search paths used with the @samp{-I} command-line option
3679 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3683 @section @code{.int @var{expressions}}
3685 @cindex @code{int} directive
3686 @cindex integers, 32-bit
3687 Expect zero or more @var{expressions}, of any section, separated by commas.
3688 For each expression, emit a number that, at run time, is the value of that
3689 expression. The byte order and bit size of the number depends on what kind
3690 of target the assembly is for.
3694 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3695 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3701 @section @code{.irp @var{symbol},@var{values}}@dots{}
3703 @cindex @code{irp} directive
3704 Evaluate a sequence of statements assigning different values to @var{symbol}.
3705 The sequence of statements starts at the @code{.irp} directive, and is
3706 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3707 set to @var{value}, and the sequence of statements is assembled. If no
3708 @var{value} is listed, the sequence of statements is assembled once, with
3709 @var{symbol} set to the null string. To refer to @var{symbol} within the
3710 sequence of statements, use @var{\symbol}.
3712 For example, assembling
3720 is equivalent to assembling
3729 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3731 @cindex @code{irpc} directive
3732 Evaluate a sequence of statements assigning different values to @var{symbol}.
3733 The sequence of statements starts at the @code{.irpc} directive, and is
3734 terminated by an @code{.endr} directive. For each character in @var{value},
3735 @var{symbol} is set to the character, and the sequence of statements is
3736 assembled. If no @var{value} is listed, the sequence of statements is
3737 assembled once, with @var{symbol} set to the null string. To refer to
3738 @var{symbol} within the sequence of statements, use @var{\symbol}.
3740 For example, assembling
3748 is equivalent to assembling
3757 @section @code{.lcomm @var{symbol} , @var{length}}
3759 @cindex @code{lcomm} directive
3760 @cindex local common symbols
3761 @cindex symbols, local common
3762 Reserve @var{length} (an absolute expression) bytes for a local common
3763 denoted by @var{symbol}. The section and value of @var{symbol} are
3764 those of the new local common. The addresses are allocated in the bss
3765 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3766 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3767 not visible to @code{@value{LD}}.
3770 Some targets permit a third argument to be used with @code{.lcomm}. This
3771 argument specifies the desired alignment of the symbol in the bss section.
3775 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3776 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3780 @section @code{.lflags}
3782 @cindex @code{lflags} directive (ignored)
3783 @code{@value{AS}} accepts this directive, for compatibility with other
3784 assemblers, but ignores it.
3786 @ifclear no-line-dir
3788 @section @code{.line @var{line-number}}
3790 @cindex @code{line} directive
3794 @section @code{.ln @var{line-number}}
3796 @cindex @code{ln} directive
3798 @cindex logical line number
3800 Change the logical line number. @var{line-number} must be an absolute
3801 expression. The next line has that logical line number. Therefore any other
3802 statements on the current line (after a statement separator character) are
3803 reported as on logical line number @var{line-number} @minus{} 1. One day
3804 @code{@value{AS}} will no longer support this directive: it is recognized only
3805 for compatibility with existing assembler programs.
3809 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3810 not available; use the synonym @code{.ln} in that context.
3815 @ifclear no-line-dir
3816 Even though this is a directive associated with the @code{a.out} or
3817 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3818 when producing COFF output, and treats @samp{.line} as though it
3819 were the COFF @samp{.ln} @emph{if} it is found outside a
3820 @code{.def}/@code{.endef} pair.
3822 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3823 used by compilers to generate auxiliary symbol information for
3828 @section @code{.linkonce [@var{type}]}
3830 @cindex @code{linkonce} directive
3831 @cindex common sections
3832 Mark the current section so that the linker only includes a single copy of it.
3833 This may be used to include the same section in several different object files,
3834 but ensure that the linker will only include it once in the final output file.
3835 The @code{.linkonce} pseudo-op must be used for each instance of the section.
3836 Duplicate sections are detected based on the section name, so it should be
3839 This directive is only supported by a few object file formats; as of this
3840 writing, the only object file format which supports it is the Portable
3841 Executable format used on Windows NT.
3843 The @var{type} argument is optional. If specified, it must be one of the
3844 following strings. For example:
3848 Not all types may be supported on all object file formats.
3852 Silently discard duplicate sections. This is the default.
3855 Warn if there are duplicate sections, but still keep only one copy.
3858 Warn if any of the duplicates have different sizes.
3861 Warn if any of the duplicates do not have exactly the same contents.
3865 @section @code{.ln @var{line-number}}
3867 @cindex @code{ln} directive
3868 @ifclear no-line-dir
3869 @samp{.ln} is a synonym for @samp{.line}.
3872 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
3873 must be an absolute expression. The next line has that logical
3874 line number, so any other statements on the current line (after a
3875 statement separator character @code{;}) are reported as on logical
3876 line number @var{line-number} @minus{} 1.
3879 This directive is accepted, but ignored, when @code{@value{AS}} is
3880 configured for @code{b.out}; its effect is only associated with COFF
3886 @section @code{.mri @var{val}}
3888 @cindex @code{mri} directive
3889 @cindex MRI mode, temporarily
3890 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
3891 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
3892 affects code assembled until the next @code{.mri} directive, or until the end
3893 of the file. @xref{M, MRI mode, MRI mode}.
3896 @section @code{.list}
3898 @cindex @code{list} directive
3899 @cindex listing control, turning on
3900 Control (in conjunction with the @code{.nolist} directive) whether or
3901 not assembly listings are generated. These two directives maintain an
3902 internal counter (which is zero initially). @code{.list} increments the
3903 counter, and @code{.nolist} decrements it. Assembly listings are
3904 generated whenever the counter is greater than zero.
3906 By default, listings are disabled. When you enable them (with the
3907 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
3908 the initial value of the listing counter is one.
3911 @section @code{.long @var{expressions}}
3913 @cindex @code{long} directive
3914 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
3917 @c no one seems to know what this is for or whether this description is
3918 @c what it really ought to do
3920 @section @code{.lsym @var{symbol}, @var{expression}}
3922 @cindex @code{lsym} directive
3923 @cindex symbol, not referenced in assembly
3924 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
3925 the hash table, ensuring it cannot be referenced by name during the
3926 rest of the assembly. This sets the attributes of the symbol to be
3927 the same as the expression value:
3929 @var{other} = @var{descriptor} = 0
3930 @var{type} = @r{(section of @var{expression})}
3931 @var{value} = @var{expression}
3934 The new symbol is not flagged as external.
3938 @section @code{.macro}
3941 The commands @code{.macro} and @code{.endm} allow you to define macros that
3942 generate assembly output. For example, this definition specifies a macro
3943 @code{sum} that puts a sequence of numbers into memory:
3946 .macro sum from=0, to=5
3955 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
3967 @item .macro @var{macname}
3968 @itemx .macro @var{macname} @var{macargs} @dots{}
3969 @cindex @code{macro} directive
3970 Begin the definition of a macro called @var{macname}. If your macro
3971 definition requires arguments, specify their names after the macro name,
3972 separated by commas or spaces. You can supply a default value for any
3973 macro argument by following the name with @samp{=@var{deflt}}. For
3974 example, these are all valid @code{.macro} statements:
3978 Begin the definition of a macro called @code{comm}, which takes no
3981 @item .macro plus1 p, p1
3982 @itemx .macro plus1 p p1
3983 Either statement begins the definition of a macro called @code{plus1},
3984 which takes two arguments; within the macro definition, write
3985 @samp{\p} or @samp{\p1} to evaluate the arguments.
3987 @item .macro reserve_str p1=0 p2
3988 Begin the definition of a macro called @code{reserve_str}, with two
3989 arguments. The first argument has a default value, but not the second.
3990 After the definition is complete, you can call the macro either as
3991 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
3992 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
3993 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
3994 @samp{0}, and @samp{\p2} evaluating to @var{b}).
3997 When you call a macro, you can specify the argument values either by
3998 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
3999 @samp{sum to=17, from=9}.
4002 @cindex @code{endm} directive
4003 Mark the end of a macro definition.
4006 @cindex @code{exitm} directive
4007 Exit early from the current macro definition.
4009 @cindex number of macros executed
4010 @cindex macros, count executed
4012 @code{@value{AS}} maintains a counter of how many macros it has
4013 executed in this pseudo-variable; you can copy that number to your
4014 output with @samp{\@@}, but @emph{only within a macro definition}.
4017 @item LOCAL @var{name} [ , @dots{} ]
4018 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4019 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4020 Alternate macro syntax}.
4022 Generate a string replacement for each of the @var{name} arguments, and
4023 replace any instances of @var{name} in each macro expansion. The
4024 replacement string is unique in the assembly, and different for each
4025 separate macro expansion. @code{LOCAL} allows you to write macros that
4026 define symbols, without fear of conflict between separate macro expansions.
4031 @section @code{.nolist}
4033 @cindex @code{nolist} directive
4034 @cindex listing control, turning off
4035 Control (in conjunction with the @code{.list} directive) whether or
4036 not assembly listings are generated. These two directives maintain an
4037 internal counter (which is zero initially). @code{.list} increments the
4038 counter, and @code{.nolist} decrements it. Assembly listings are
4039 generated whenever the counter is greater than zero.
4042 @section @code{.octa @var{bignums}}
4044 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4045 @cindex @code{octa} directive
4046 @cindex integer, 16-byte
4047 @cindex sixteen byte integer
4048 This directive expects zero or more bignums, separated by commas. For each
4049 bignum, it emits a 16-byte integer.
4051 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4052 hence @emph{octa}-word for 16 bytes.
4055 @section @code{.org @var{new-lc} , @var{fill}}
4057 @cindex @code{org} directive
4058 @cindex location counter, advancing
4059 @cindex advancing location counter
4060 @cindex current address, advancing
4061 Advance the location counter of the current section to
4062 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4063 expression with the same section as the current subsection. That is,
4064 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4065 wrong section, the @code{.org} directive is ignored. To be compatible
4066 with former assemblers, if the section of @var{new-lc} is absolute,
4067 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4068 is the same as the current subsection.
4070 @code{.org} may only increase the location counter, or leave it
4071 unchanged; you cannot use @code{.org} to move the location counter
4074 @c double negative used below "not undefined" because this is a specific
4075 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4076 @c section. doc@cygnus.com 18feb91
4077 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4078 may not be undefined. If you really detest this restriction we eagerly await
4079 a chance to share your improved assembler.
4081 Beware that the origin is relative to the start of the section, not
4082 to the start of the subsection. This is compatible with other
4083 people's assemblers.
4085 When the location counter (of the current subsection) is advanced, the
4086 intervening bytes are filled with @var{fill} which should be an
4087 absolute expression. If the comma and @var{fill} are omitted,
4088 @var{fill} defaults to zero.
4091 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4093 @cindex padding the location counter given a power of two
4094 @cindex @code{p2align} directive
4095 Pad the location counter (in the current subsection) to a particular
4096 storage boundary. The first expression (which must be absolute) is the
4097 number of low-order zero bits the location counter must have after
4098 advancement. For example @samp{.p2align 3} advances the location
4099 counter until it a multiple of 8. If the location counter is already a
4100 multiple of 8, no change is needed.
4102 The second expression (also absolute) gives the fill value to be stored in the
4103 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4104 padding bytes are normally zero. However, on some systems, if the section is
4105 marked as containing code and the fill value is omitted, the space is filled
4106 with no-op instructions.
4108 The third expression is also absolute, and is also optional. If it is present,
4109 it is the maximum number of bytes that should be skipped by this alignment
4110 directive. If doing the alignment would require skipping more bytes than the
4111 specified maximum, then the alignment is not done at all. You can omit the
4112 fill value (the second argument) entirely by simply using two commas after the
4113 required alignment; this can be useful if you want the alignment to be filled
4114 with no-op instructions when appropriate.
4116 @cindex @code{p2alignw} directive
4117 @cindex @code{p2alignl} directive
4118 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4119 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4120 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4121 fill pattern as a four byte longword value. For example, @code{.p2alignw
4122 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4123 filled in with the value 0x368d (the exact placement of the bytes depends upon
4124 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4128 @section @code{.psize @var{lines} , @var{columns}}
4130 @cindex @code{psize} directive
4131 @cindex listing control: paper size
4132 @cindex paper size, for listings
4133 Use this directive to declare the number of lines---and, optionally, the
4134 number of columns---to use for each page, when generating listings.
4136 If you do not use @code{.psize}, listings use a default line-count
4137 of 60. You may omit the comma and @var{columns} specification; the
4138 default width is 200 columns.
4140 @code{@value{AS}} generates formfeeds whenever the specified number of
4141 lines is exceeded (or whenever you explicitly request one, using
4144 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4145 those explicitly specified with @code{.eject}.
4148 @section @code{.quad @var{bignums}}
4150 @cindex @code{quad} directive
4151 @code{.quad} expects zero or more bignums, separated by commas. For
4152 each bignum, it emits
4154 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4155 warning message; and just takes the lowest order 8 bytes of the bignum.
4156 @cindex eight-byte integer
4157 @cindex integer, 8-byte
4159 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4160 hence @emph{quad}-word for 8 bytes.
4163 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4164 warning message; and just takes the lowest order 16 bytes of the bignum.
4165 @cindex sixteen-byte integer
4166 @cindex integer, 16-byte
4170 @section @code{.rept @var{count}}
4172 @cindex @code{rept} directive
4173 Repeat the sequence of lines between the @code{.rept} directive and the next
4174 @code{.endr} directive @var{count} times.
4176 For example, assembling
4184 is equivalent to assembling
4193 @section @code{.sbttl "@var{subheading}"}
4195 @cindex @code{sbttl} directive
4196 @cindex subtitles for listings
4197 @cindex listing control: subtitle
4198 Use @var{subheading} as the title (third line, immediately after the
4199 title line) when generating assembly listings.
4201 This directive affects subsequent pages, as well as the current page if
4202 it appears within ten lines of the top of a page.
4206 @section @code{.scl @var{class}}
4208 @cindex @code{scl} directive
4209 @cindex symbol storage class (COFF)
4210 @cindex COFF symbol storage class
4211 Set the storage-class value for a symbol. This directive may only be
4212 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4213 whether a symbol is static or external, or it may record further
4214 symbolic debugging information.
4217 The @samp{.scl} directive is primarily associated with COFF output; when
4218 configured to generate @code{b.out} output format, @code{@value{AS}}
4219 accepts this directive but ignores it.
4224 @section @code{.section @var{name}}
4226 @cindex @code{section} directive
4227 @cindex named section
4228 Use the @code{.section} directive to assemble the following code into a section
4231 This directive is only supported for targets that actually support arbitrarily
4232 named sections; on @code{a.out} targets, for example, it is not accepted, even
4233 with a standard @code{a.out} section name.
4236 For COFF targets, the @code{.section} directive is used in one of the following
4239 .section @var{name}[, "@var{flags}"]
4240 .section @var{name}[, @var{subsegment}]
4243 If the optional argument is quoted, it is taken as flags to use for the
4244 section. Each flag is a single character. The following flags are recognized:
4247 bss section (uninitialized data)
4249 section is not loaded
4260 If no flags are specified, the default flags depend upon the section name. If
4261 the section name is not recognized, the default will be for the section to be
4262 loaded and writable.
4264 If the optional argument to the @code{.section} directive is not quoted, it is
4265 taken as a subsegment number (@pxref{Sub-Sections}).
4269 For ELF targets, the @code{.section} directive is used like this:
4271 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4273 The optional @var{flags} argument is a quoted string which may contain any
4274 combintion of the following characters:
4277 section is allocatable
4281 section is executable
4284 The optional @var{type} argument may contain one of the following constants:
4287 section contains data
4289 section does not contain data (i.e., section only occupies space)
4292 If no flags are specified, the default flags depend upon the section name. If
4293 the section name is not recognized, the default will be for the section to have
4294 none of the above flags: it will not be allocated in memory, nor writable, nor
4295 executable. The section will contain data.
4297 For ELF targets, the assembler supports another type of @code{.section}
4298 directive for compatibility with the Solaris assembler:
4300 .section "@var{name}"[, @var{flags}...]
4302 Note that the section name is quoted. There may be a sequence of comma
4306 section is allocatable
4310 section is executable
4315 @section @code{.set @var{symbol}, @var{expression}}
4317 @cindex @code{set} directive
4318 @cindex symbol value, setting
4319 Set the value of @var{symbol} to @var{expression}. This
4320 changes @var{symbol}'s value and type to conform to
4321 @var{expression}. If @var{symbol} was flagged as external, it remains
4322 flagged (@pxref{Symbol Attributes}).
4324 You may @code{.set} a symbol many times in the same assembly.
4326 If you @code{.set} a global symbol, the value stored in the object
4327 file is the last value stored into it.
4330 The syntax for @code{set} on the HPPA is
4331 @samp{@var{symbol} .set @var{expression}}.
4335 @section @code{.short @var{expressions}}
4337 @cindex @code{short} directive
4339 @code{.short} is normally the same as @samp{.word}.
4340 @xref{Word,,@code{.word}}.
4342 In some configurations, however, @code{.short} and @code{.word} generate
4343 numbers of different lengths; @pxref{Machine Dependencies}.
4347 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4350 This expects zero or more @var{expressions}, and emits
4351 a 16 bit number for each.
4356 @section @code{.single @var{flonums}}
4358 @cindex @code{single} directive
4359 @cindex floating point numbers (single)
4360 This directive assembles zero or more flonums, separated by commas. It
4361 has the same effect as @code{.float}.
4363 The exact kind of floating point numbers emitted depends on how
4364 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4368 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4369 numbers in @sc{ieee} format.
4375 @section @code{.size}
4377 @cindex @code{size} directive
4378 This directive is generated by compilers to include auxiliary debugging
4379 information in the symbol table. It is only permitted inside
4380 @code{.def}/@code{.endef} pairs.
4383 @samp{.size} is only meaningful when generating COFF format output; when
4384 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4390 @section @code{.sleb128 @var{expressions}}
4392 @cindex @code{sleb128} directive
4393 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4394 compact, variable length representation of numbers used by the DWARF
4395 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
4397 @ifclear no-space-dir
4399 @section @code{.skip @var{size} , @var{fill}}
4401 @cindex @code{skip} directive
4402 @cindex filling memory
4403 This directive emits @var{size} bytes, each of value @var{fill}. Both
4404 @var{size} and @var{fill} are absolute expressions. If the comma and
4405 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4409 @section @code{.space @var{size} , @var{fill}}
4411 @cindex @code{space} directive
4412 @cindex filling memory
4413 This directive emits @var{size} bytes, each of value @var{fill}. Both
4414 @var{size} and @var{fill} are absolute expressions. If the comma
4415 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4420 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4421 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4422 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4423 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4432 @section @code{.space}
4433 @cindex @code{space} directive
4435 On the AMD 29K, this directive is ignored; it is accepted for
4436 compatibility with other AMD 29K assemblers.
4439 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4440 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4446 @section @code{.stabd, .stabn, .stabs}
4448 @cindex symbolic debuggers, information for
4449 @cindex @code{stab@var{x}} directives
4450 There are three directives that begin @samp{.stab}.
4451 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4452 The symbols are not entered in the @code{@value{AS}} hash table: they
4453 cannot be referenced elsewhere in the source file.
4454 Up to five fields are required:
4458 This is the symbol's name. It may contain any character except
4459 @samp{\000}, so is more general than ordinary symbol names. Some
4460 debuggers used to code arbitrarily complex structures into symbol names
4464 An absolute expression. The symbol's type is set to the low 8 bits of
4465 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4466 and debuggers choke on silly bit patterns.
4469 An absolute expression. The symbol's ``other'' attribute is set to the
4470 low 8 bits of this expression.
4473 An absolute expression. The symbol's descriptor is set to the low 16
4474 bits of this expression.
4477 An absolute expression which becomes the symbol's value.
4480 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4481 or @code{.stabs} statement, the symbol has probably already been created;
4482 you get a half-formed symbol in your object file. This is
4483 compatible with earlier assemblers!
4486 @cindex @code{stabd} directive
4487 @item .stabd @var{type} , @var{other} , @var{desc}
4489 The ``name'' of the symbol generated is not even an empty string.
4490 It is a null pointer, for compatibility. Older assemblers used a
4491 null pointer so they didn't waste space in object files with empty
4494 The symbol's value is set to the location counter,
4495 relocatably. When your program is linked, the value of this symbol
4496 is the address of the location counter when the @code{.stabd} was
4499 @cindex @code{stabn} directive
4500 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4501 The name of the symbol is set to the empty string @code{""}.
4503 @cindex @code{stabs} directive
4504 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4505 All five fields are specified.
4511 @section @code{.string} "@var{str}"
4513 @cindex string, copying to object file
4514 @cindex @code{string} directive
4516 Copy the characters in @var{str} to the object file. You may specify more than
4517 one string to copy, separated by commas. Unless otherwise specified for a
4518 particular machine, the assembler marks the end of each string with a 0 byte.
4519 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4523 @section @code{.symver}
4524 @cindex @code{symver} directive
4525 @cindex symbol versioning
4526 @cindex versions of symbols
4527 Use the @code{.symver} directive to bind symbols to specific version nodes
4528 within a source file. This is only supported on ELF platforms, and is
4529 typically used when assembling files to be linked into a shared library.
4530 There are cases where it may make sense to use this in objects to be bound
4531 into an application itself so as to override a versioned symbol from a
4534 For ELF targets, the @code{.symver} directive is used like this:
4536 .symver @var{name}, @var{name2@@nodename}
4538 In this case, the symbol @var{name} must exist and be defined within the file
4539 being assembled. The @code{.versym} directive effectively creates a symbol
4540 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4541 just don't try and create a regular alias is that the @var{@@} character isn't
4542 permitted in symbol names. The @var{name2} part of the name is the actual name
4543 of the symbol by which it will be externally referenced. The name @var{name}
4544 itself is merely a name of convenience that is used so that it is possible to
4545 have definitions for multiple versions of a function within a single source
4546 file, and so that the compiler can unambiguously know which version of a
4547 function is being mentioned. The @var{nodename} portion of the alias should be
4548 the name of a node specified in the version script supplied to the linker when
4549 building a shared library. If you are attempting to override a versioned
4550 symbol from a shared library, then @var{nodename} should correspond to the
4551 nodename of the symbol you are trying to override.
4556 @section @code{.tag @var{structname}}
4558 @cindex COFF structure debugging
4559 @cindex structure debugging, COFF
4560 @cindex @code{tag} directive
4561 This directive is generated by compilers to include auxiliary debugging
4562 information in the symbol table. It is only permitted inside
4563 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4564 definitions in the symbol table with instances of those structures.
4567 @samp{.tag} is only used when generating COFF format output; when
4568 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4574 @section @code{.text @var{subsection}}
4576 @cindex @code{text} directive
4577 Tells @code{@value{AS}} to assemble the following statements onto the end of
4578 the text subsection numbered @var{subsection}, which is an absolute
4579 expression. If @var{subsection} is omitted, subsection number zero
4583 @section @code{.title "@var{heading}"}
4585 @cindex @code{title} directive
4586 @cindex listing control: title line
4587 Use @var{heading} as the title (second line, immediately after the
4588 source file name and pagenumber) when generating assembly listings.
4590 This directive affects subsequent pages, as well as the current page if
4591 it appears within ten lines of the top of a page.
4595 @section @code{.type @var{int}}
4597 @cindex COFF symbol type
4598 @cindex symbol type, COFF
4599 @cindex @code{type} directive
4600 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4601 records the integer @var{int} as the type attribute of a symbol table entry.
4604 @samp{.type} is associated only with COFF format output; when
4605 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4606 directive but ignores it.
4612 @section @code{.val @var{addr}}
4614 @cindex @code{val} directive
4615 @cindex COFF value attribute
4616 @cindex value attribute, COFF
4617 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4618 records the address @var{addr} as the value attribute of a symbol table
4622 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4623 configured for @code{b.out}, it accepts this directive but ignores it.
4628 @section @code{.uleb128 @var{expressions}}
4630 @cindex @code{uleb128} directive
4631 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
4632 compact, variable length representation of numbers used by the DWARF
4633 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
4636 @section @code{.word @var{expressions}}
4638 @cindex @code{word} directive
4639 This directive expects zero or more @var{expressions}, of any section,
4640 separated by commas.
4643 For each expression, @code{@value{AS}} emits a 32-bit number.
4646 For each expression, @code{@value{AS}} emits a 16-bit number.
4651 The size of the number emitted, and its byte order,
4652 depend on what target computer the assembly is for.
4655 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4656 @c happen---32-bit addressability, period; no long/short jumps.
4657 @ifset DIFF-TBL-KLUGE
4658 @cindex difference tables altered
4659 @cindex altered difference tables
4661 @emph{Warning: Special Treatment to support Compilers}
4665 Machines with a 32-bit address space, but that do less than 32-bit
4666 addressing, require the following special treatment. If the machine of
4667 interest to you does 32-bit addressing (or doesn't require it;
4668 @pxref{Machine Dependencies}), you can ignore this issue.
4671 In order to assemble compiler output into something that works,
4672 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4673 Directives of the form @samp{.word sym1-sym2} are often emitted by
4674 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4675 directive of the form @samp{.word sym1-sym2}, and the difference between
4676 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4677 creates a @dfn{secondary jump table}, immediately before the next label.
4678 This secondary jump table is preceded by a short-jump to the
4679 first byte after the secondary table. This short-jump prevents the flow
4680 of control from accidentally falling into the new table. Inside the
4681 table is a long-jump to @code{sym2}. The original @samp{.word}
4682 contains @code{sym1} minus the address of the long-jump to
4685 If there were several occurrences of @samp{.word sym1-sym2} before the
4686 secondary jump table, all of them are adjusted. If there was a
4687 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4688 long-jump to @code{sym4} is included in the secondary jump table,
4689 and the @code{.word} directives are adjusted to contain @code{sym3}
4690 minus the address of the long-jump to @code{sym4}; and so on, for as many
4691 entries in the original jump table as necessary.
4694 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4695 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4696 assembly language programmers.
4699 @c end DIFF-TBL-KLUGE
4702 @section Deprecated Directives
4704 @cindex deprecated directives
4705 @cindex obsolescent directives
4706 One day these directives won't work.
4707 They are included for compatibility with older assemblers.
4715 @node Machine Dependencies
4716 @chapter Machine Dependent Features
4718 @cindex machine dependencies
4719 The machine instruction sets are (almost by definition) different on
4720 each machine where @code{@value{AS}} runs. Floating point representations
4721 vary as well, and @code{@value{AS}} often supports a few additional
4722 directives or command-line options for compatibility with other
4723 assemblers on a particular platform. Finally, some versions of
4724 @code{@value{AS}} support special pseudo-instructions for branch
4727 This chapter discusses most of these differences, though it does not
4728 include details on any machine's instruction set. For details on that
4729 subject, see the hardware manufacturer's manual.
4733 * AMD29K-Dependent:: AMD 29K Dependent Features
4736 * ARC-Dependent:: ARC Dependent Features
4739 * ARM-Dependent:: ARM Dependent Features
4742 * D10V-Dependent:: D10V Dependent Features
4744 @c start-sanitize-d30v
4746 * D30V-Dependent:: D30V Dependent Features
4748 @c end-sanitize-d30v
4750 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4753 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4756 * HPPA-Dependent:: HPPA Dependent Features
4759 * i386-Dependent:: Intel 80386 Dependent Features
4762 * i960-Dependent:: Intel 80960 Dependent Features
4764 @c start-sanitize-m32rx
4766 * M32R-Dependent:: M32R Dependent Features
4768 @c end-sanitize-m32rx
4770 * M68K-Dependent:: M680x0 Dependent Features
4773 * MIPS-Dependent:: MIPS Dependent Features
4776 * SH-Dependent:: Hitachi SH Dependent Features
4779 * Sparc-Dependent:: SPARC Dependent Features
4782 * V850-Dependent:: V850 Dependent Features
4785 * Z8000-Dependent:: Z8000 Dependent Features
4788 * Vax-Dependent:: VAX Dependent Features
4795 @c The following major nodes are *sections* in the GENERIC version, *chapters*
4796 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
4797 @c peculiarity: to preserve cross-references, there must be a node called
4798 @c "Machine Dependencies". Hence the conditional nodenames in each
4799 @c major node below. Node defaulting in makeinfo requires adjacency of
4800 @c node and sectioning commands; hence the repetition of @chapter BLAH
4801 @c in both conditional blocks.
4807 @chapter ARC Dependent Features
4810 @node Machine Dependencies
4811 @chapter ARC Dependent Features
4816 * ARC-Opts:: Options
4817 * ARC-Float:: Floating Point
4818 * ARC-Directives:: Sparc Machine Directives
4824 @cindex options for ARC
4826 @cindex architectures, ARC
4827 @cindex ARC architectures
4828 The ARC chip family includes several successive levels (or other
4829 variants) of chip, using the same core instruction set, but including
4830 a few additional instructions at each level.
4832 By default, @code{@value{AS}} assumes the core instruction set (ARC
4833 base). The @code{.cpu} pseudo-op is intended to be used to select
4837 @cindex @code{-mbig-endian} option (ARC)
4838 @cindex @code{-mlittle-endian} option (ARC)
4839 @cindex ARC big-endian output
4840 @cindex ARC little-endian output
4841 @cindex big-endian output, ARC
4842 @cindex little-endian output, ARC
4844 @itemx -mlittle-endian
4845 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
4846 little-endian output at run time (unlike most other @sc{gnu} development
4847 tools, which must be configured for one or the other). Use
4848 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
4853 @section Floating Point
4855 @cindex floating point, ARC (@sc{ieee})
4856 @cindex ARC floating point (@sc{ieee})
4857 The ARC cpu family currently does not have hardware floating point
4858 support. Software floating point support is provided by @code{GCC}
4859 and uses @sc{ieee} floating-point numbers.
4861 @node ARC-Directives
4862 @section ARC Machine Directives
4864 @cindex ARC machine directives
4865 @cindex machine directives, ARC
4866 The ARC version of @code{@value{AS}} supports the following additional
4871 @cindex @code{cpu} directive, SPARC
4872 This must be followed by the desired cpu.
4873 The ARC is intended to be customizable, @code{.cpu} is used to
4874 select the desired variant [though currently there are none].
4881 @include c-a29k.texi
4890 @node Machine Dependencies
4891 @chapter Machine Dependent Features
4893 The machine instruction sets are different on each Hitachi chip family,
4894 and there are also some syntax differences among the families. This
4895 chapter describes the specific @code{@value{AS}} features for each
4899 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4900 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4901 * SH-Dependent:: Hitachi SH Dependent Features
4908 @include c-d10v.texi
4911 @c start-sanitize-d30v
4913 @include c-d30v.texi
4915 @c end-sanitize-d30v
4918 @include c-h8300.texi
4922 @include c-h8500.texi
4926 @include c-hppa.texi
4930 @include c-i386.texi
4934 @include c-i960.texi
4937 @c start-sanitize-m32rx
4939 @include c-m32r.texi
4941 @c end-sanitize-m32rx
4944 @include c-m68k.texi
4948 @include c-mips.texi
4952 @include c-ns32k.texi
4960 @include c-sparc.texi
4972 @include c-v850.texi
4976 @c reverse effect of @down at top of generic Machine-Dep chapter
4980 @node Reporting Bugs
4981 @chapter Reporting Bugs
4982 @cindex bugs in assembler
4983 @cindex reporting bugs in assembler
4985 Your bug reports play an essential role in making @code{@value{AS}} reliable.
4987 Reporting a bug may help you by bringing a solution to your problem, or it may
4988 not. But in any case the principal function of a bug report is to help the
4989 entire community by making the next version of @code{@value{AS}} work better.
4990 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
4992 In order for a bug report to serve its purpose, you must include the
4993 information that enables us to fix the bug.
4996 * Bug Criteria:: Have you found a bug?
4997 * Bug Reporting:: How to report bugs
5001 @section Have you found a bug?
5002 @cindex bug criteria
5004 If you are not sure whether you have found a bug, here are some guidelines:
5007 @cindex fatal signal
5008 @cindex assembler crash
5009 @cindex crash of assembler
5011 If the assembler gets a fatal signal, for any input whatever, that is a
5012 @code{@value{AS}} bug. Reliable assemblers never crash.
5014 @cindex error on valid input
5016 If @code{@value{AS}} produces an error message for valid input, that is a bug.
5018 @cindex invalid input
5020 If @code{@value{AS}} does not produce an error message for invalid input, that
5021 is a bug. However, you should note that your idea of ``invalid input'' might
5022 be our idea of ``an extension'' or ``support for traditional practice''.
5025 If you are an experienced user of assemblers, your suggestions for improvement
5026 of @code{@value{AS}} are welcome in any case.
5030 @section How to report bugs
5032 @cindex assembler bugs, reporting
5034 A number of companies and individuals offer support for @sc{gnu} products. If
5035 you obtained @code{@value{AS}} from a support organization, we recommend you
5036 contact that organization first.
5038 You can find contact information for many support companies and
5039 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5042 In any event, we also recommend that you send bug reports for @code{@value{AS}}
5043 to @samp{bug-gnu-utils@@gnu.org}.
5045 The fundamental principle of reporting bugs usefully is this:
5046 @strong{report all the facts}. If you are not sure whether to state a
5047 fact or leave it out, state it!
5049 Often people omit facts because they think they know what causes the problem
5050 and assume that some details do not matter. Thus, you might assume that the
5051 name of a symbol you use in an example does not matter. Well, probably it does
5052 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5053 happens to fetch from the location where that name is stored in memory;
5054 perhaps, if the name were different, the contents of that location would fool
5055 the assembler into doing the right thing despite the bug. Play it safe and
5056 give a specific, complete example. That is the easiest thing for you to do,
5057 and the most helpful.
5059 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5060 it is new to us. Therefore, always write your bug reports on the assumption
5061 that the bug has not been reported previously.
5063 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5064 bell?'' Those bug reports are useless, and we urge everyone to
5065 @emph{refuse to respond to them} except to chide the sender to report
5068 To enable us to fix the bug, you should include all these things:
5072 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
5073 it with the @samp{--version} argument.
5075 Without this, we will not know whether there is any point in looking for
5076 the bug in the current version of @code{@value{AS}}.
5079 Any patches you may have applied to the @code{@value{AS}} source.
5082 The type of machine you are using, and the operating system name and
5086 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
5090 The command arguments you gave the assembler to assemble your example and
5091 observe the bug. To guarantee you will not omit something important, list them
5092 all. A copy of the Makefile (or the output from make) is sufficient.
5094 If we were to try to guess the arguments, we would probably guess wrong
5095 and then we might not encounter the bug.
5098 A complete input file that will reproduce the bug. If the bug is observed when
5099 the assembler is invoked via a compiler, send the assembler source, not the
5100 high level language source. Most compilers will produce the assembler source
5101 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5102 the options @samp{-v --save-temps}; this will save the assembler source in a
5103 file with an extension of @file{.s}, and also show you exactly how
5104 @code{@value{AS}} is being run.
5107 A description of what behavior you observe that you believe is
5108 incorrect. For example, ``It gets a fatal signal.''
5110 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
5111 will certainly notice it. But if the bug is incorrect output, we might not
5112 notice unless it is glaringly wrong. You might as well not give us a chance to
5115 Even if the problem you experience is a fatal signal, you should still say so
5116 explicitly. Suppose something strange is going on, such as, your copy of
5117 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
5118 library on your system. (This has happened!) Your copy might crash and ours
5119 would not. If you told us to expect a crash, then when ours fails to crash, we
5120 would know that the bug was not happening for us. If you had not told us to
5121 expect a crash, then we would not be able to draw any conclusion from our
5125 If you wish to suggest changes to the @code{@value{AS}} source, send us context
5126 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
5127 option. Always send diffs from the old file to the new file. If you even
5128 discuss something in the @code{@value{AS}} source, refer to it by context, not
5131 The line numbers in our development sources will not match those in your
5132 sources. Your line numbers would convey no useful information to us.
5135 Here are some things that are not necessary:
5139 A description of the envelope of the bug.
5141 Often people who encounter a bug spend a lot of time investigating
5142 which changes to the input file will make the bug go away and which
5143 changes will not affect it.
5145 This is often time consuming and not very useful, because the way we
5146 will find the bug is by running a single example under the debugger
5147 with breakpoints, not by pure deduction from a series of examples.
5148 We recommend that you save your time for something else.
5150 Of course, if you can find a simpler example to report @emph{instead}
5151 of the original one, that is a convenience for us. Errors in the
5152 output will be easier to spot, running under the debugger will take
5153 less time, and so on.
5155 However, simplification is not vital; if you do not want to do this,
5156 report the bug anyway and send us the entire test case you used.
5159 A patch for the bug.
5161 A patch for the bug does help us if it is a good one. But do not omit
5162 the necessary information, such as the test case, on the assumption that
5163 a patch is all we need. We might see problems with your patch and decide
5164 to fix the problem another way, or we might not understand it at all.
5166 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5167 construct an example that will make the program follow a certain path through
5168 the code. If you do not send us the example, we will not be able to construct
5169 one, so we will not be able to verify that the bug is fixed.
5171 And if we cannot understand what bug you are trying to fix, or why your
5172 patch should be an improvement, we will not install it. A test case will
5173 help us to understand.
5176 A guess about what the bug is or what it depends on.
5178 Such guesses are usually wrong. Even we cannot guess right about such
5179 things without first using the debugger to find the facts.
5182 @node Acknowledgements
5183 @chapter Acknowledgements
5185 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5186 it is not meant as a slight. We just don't know about it. Send mail to the
5187 maintainer, and we'll correct the situation. Currently
5189 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5191 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5194 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5195 information and the 68k series machines, most of the preprocessing pass, and
5196 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5198 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5199 many bug fixes, including merging support for several processors, breaking GAS
5200 up to handle multiple object file format back ends (including heavy rewrite,
5201 testing, an integration of the coff and b.out back ends), adding configuration
5202 including heavy testing and verification of cross assemblers and file splits
5203 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5204 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5205 port (including considerable amounts of reverse engineering), a SPARC opcode
5206 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5207 assertions and made them work, much other reorganization, cleanup, and lint.
5209 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5210 in format-specific I/O modules.
5212 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5213 has done much work with it since.
5215 The Intel 80386 machine description was written by Eliot Dresselhaus.
5217 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5219 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5220 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5222 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5223 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5224 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5225 support a.out format.
5227 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5228 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5229 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5230 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5233 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5234 simplified the configuration of which versions accept which directives. He
5235 updated the 68k machine description so that Motorola's opcodes always produced
5236 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5237 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5238 cross-compilation support, and one bug in relaxation that took a week and
5239 required the proverbial one-bit fix.
5241 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5242 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5243 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5244 PowerPC assembler, and made a few other minor patches.
5246 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5248 Hewlett-Packard contributed support for the HP9000/300.
5250 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5251 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5252 formats). This work was supported by both the Center for Software Science at
5253 the University of Utah and Cygnus Support.
5255 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5256 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5257 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5258 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5259 and some initial 64-bit support).
5261 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5262 support for openVMS/Alpha.
5264 Several engineers at Cygnus Support have also provided many small bug fixes and
5265 configuration enhancements.
5267 Many others have contributed large or small bugfixes and enhancements. If
5268 you have contributed significant work and are not mentioned on this list, and
5269 want to be, let us know. Some of the history has been lost; we are not
5270 intentionally leaving anyone out.