1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (c) 1991, 92, 93, 94, 95, 96, 1997 Free Software Foundation, Inc.
3 @c UPDATE!! On future updates--
4 @c (1) check for new machine-dep cmdline options in
5 @c md_parse_option definitions in config/tc-*.c
6 @c (2) for platform-specific directives, examine md_pseudo_op
8 @c (3) for object-format specific directives, examine obj_pseudo_op
10 @c (4) portable directives in potable[] in read.c
14 @c defaults, config file may override:
17 @include asconfig.texi
19 @c common OR combinations of conditions
36 @set abnormal-separator
40 @settitle Using @value{AS}
43 @settitle Using @value{AS} (@value{TARGET})
45 @setchapternewpage odd
50 @c WARE! Some of the machine-dependent sections contain tables of machine
51 @c instructions. Except in multi-column format, these tables look silly.
52 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
53 @c the multi-col format is faked within @example sections.
55 @c Again unfortunately, the natural size that fits on a page, for these tables,
56 @c is different depending on whether or not smallbook is turned on.
57 @c This matters, because of order: text flow switches columns at each page
60 @c The format faked in this source works reasonably well for smallbook,
61 @c not well for the default large-page format. This manual expects that if you
62 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
63 @c tables in question. You can turn on one without the other at your
64 @c discretion, of course.
67 @c the insn tables look just as silly in info files regardless of smallbook,
68 @c might as well show 'em anyways.
74 * As: (as). The GNU assembler.
83 This file documents the GNU Assembler "@value{AS}".
85 Copyright (C) 1991, 92, 93, 94, 95, 96, 1997 Free Software Foundation, Inc.
87 Permission is granted to make and distribute verbatim copies of
88 this manual provided the copyright notice and this permission notice
89 are preserved on all copies.
92 Permission is granted to process this file through Tex and print the
93 results, provided the printed document carries copying permission
94 notice identical to this one except for the removal of this paragraph
95 (this paragraph not being relevant to the printed manual).
98 Permission is granted to copy and distribute modified versions of this manual
99 under the conditions for verbatim copying, provided that the entire resulting
100 derived work is distributed under the terms of a permission notice identical to
103 Permission is granted to copy and distribute translations of this manual
104 into another language, under the above conditions for modified versions.
108 @title Using @value{AS}
109 @subtitle The @sc{gnu} Assembler
111 @subtitle for the @value{TARGET} family
114 @subtitle January 1994
117 The Free Software Foundation Inc. thanks The Nice Computer
118 Company of Australia for loaning Dean Elsner to write the
119 first (Vax) version of @code{as} for Project @sc{gnu}.
120 The proprietors, management and staff of TNCCA thank FSF for
121 distracting the boss while they got some work
124 @author Dean Elsner, Jay Fenlason & friends
128 \hfill {\it Using {\tt @value{AS}}}\par
129 \hfill Edited by Cygnus Support\par
131 %"boxit" macro for figures:
132 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
133 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
134 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
135 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
136 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
139 @vskip 0pt plus 1filll
140 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 1997 Free Software Foundation, Inc.
142 Permission is granted to make and distribute verbatim copies of
143 this manual provided the copyright notice and this permission notice
144 are preserved on all copies.
146 Permission is granted to copy and distribute modified versions of this manual
147 under the conditions for verbatim copying, provided that the entire resulting
148 derived work is distributed under the terms of a permission notice identical to
151 Permission is granted to copy and distribute translations of this manual
152 into another language, under the above conditions for modified versions.
157 @top Using @value{AS}
159 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
161 This version of the file describes @code{@value{AS}} configured to generate
162 code for @value{TARGET} architectures.
165 * Overview:: Overview
166 * Invoking:: Command-Line Options
168 * Sections:: Sections and Relocation
170 * Expressions:: Expressions
171 * Pseudo Ops:: Assembler Directives
172 * Machine Dependencies:: Machine Dependent Features
173 * Reporting Bugs:: Reporting Bugs
174 * Acknowledgements:: Who Did What
182 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
184 This version of the manual describes @code{@value{AS}} configured to generate
185 code for @value{TARGET} architectures.
189 @cindex invocation summary
190 @cindex option summary
191 @cindex summary of options
192 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
193 @pxref{Invoking,,Comand-Line Options}.
195 @c We don't use deffn and friends for the following because they seem
196 @c to be limited to one line for the header.
198 @value{AS} [ -a[dhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
199 [ -f ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
200 [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ] [ -version ]
201 [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ]
203 @c am29k has no machine-dependent assembler options
205 @c start-sanitize-arc
207 [ -mbig-endian | -mlittle-endian ]
215 @c Hitachi family chips have no machine-dependent assembler options
218 @c HPPA has no machine-dependent assembler options (yet).
221 @c The order here is important. See c-sparc.texi.
222 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite | -Av9 | -Av9a ]
223 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ]
226 @c Z8000 has no machine-dependent assembler options
229 @c see md_parse_option in tc-i960.c
230 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
234 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
237 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
238 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
239 [ --trap ] [ --break ]
240 [ --emulation=@var{name} ]
242 [ -- | @var{files} @dots{} ]
247 Turn on listings, in any of a variety of ways:
251 omit debugging directives
254 include high-level source
260 omit forms processing
266 set the name of the listing file
269 You may combine these options; for example, use @samp{-aln} for assembly
270 listing without forms processing. The @samp{=file} option, if used, must be
271 the last one. By itself, @samp{-a} defaults to @samp{-ahls}---that is, all
275 Ignored. This option is accepted for script compatibility with calls to
278 @item --defsym @var{sym}=@var{value}
279 Define the symbol @var{sym} to be @var{value} before assembling the input file.
280 @var{value} must be an integer constant. As in C, a leading @samp{0x}
281 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
284 ``fast''---skip whitespace and comment preprocessing (assume source is
288 Print a summary of the command line options and exit.
291 Add directory @var{dir} to the search list for @code{.include} directives.
294 Don't warn about signed overflow.
297 @ifclear DIFF-TBL-KLUGE
298 This option is accepted but has no effect on the @value{TARGET} family.
300 @ifset DIFF-TBL-KLUGE
301 Issue warnings when difference tables altered for long displacements.
305 Keep (in the symbol table) local symbols, starting with @samp{L}.
307 @item -o @var{objfile}
308 Name the object-file output from @code{@value{AS}} @var{objfile}.
311 Fold the data section into the text section.
314 Print the maximum space (in bytes) and total time (in seconds) used by
319 Print the @code{as} version.
322 Print the @code{as} version and exit.
325 Suppress warning messages.
334 Generate an object file even after errors.
336 @item -- | @var{files} @dots{}
337 Standard input, or source files to assemble.
342 The following options are available when @value{AS} is configured for
347 @cindex ARC endianness
348 @cindex endianness, ARC
349 @cindex big endian output, ARC
351 Generate ``big endian'' format output.
353 @cindex little endian output, ARC
354 @item -mlittle-endian
355 Generate ``little endian'' format output.
361 The following options are available when @value{AS} is configured for
364 @cindex D10V optimization
365 @cindex optimization, D10V
367 Optimize output by parallelizing instructions.
372 The following options are available when @value{AS} is configured for the
373 Intel 80960 processor.
376 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
377 Specify which variant of the 960 architecture is the target.
380 Add code to collect statistics about branches taken.
383 Do not alter compare-and-branch instructions for long displacements;
390 The following options are available when @value{AS} is configured for the
391 Motorola 68000 series.
396 Shorten references to undefined symbols, to one word instead of two.
398 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
399 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
400 Specify what processor in the 68000 family is the target. The default
401 is normally the 68020, but this can be changed at configuration time.
403 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
404 The target machine does (or does not) have a floating-point coprocessor.
405 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
406 the basic 68000 is not compatible with the 68881, a combination of the
407 two can be specified, since it's possible to do emulation of the
408 coprocessor instructions with the main processor.
410 @item -m68851 | -mno-68851
411 The target machine does (or does not) have a memory-management
412 unit coprocessor. The default is to assume an MMU for 68020 and up.
418 The following options are available when @code{@value{AS}} is configured
419 for the SPARC architecture:
422 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite | -Av9 | -Av9a
423 Explicitly select a variant of the SPARC architecture.
425 @item -xarch=v8plus | -xarch=v8plusa
426 For compatibility with the Solaris v9 assembler. These options are
427 equivalent to -Av9 and -Av9a, respectively.
430 Warn when the assembler switches to another architecture.
435 The following options are available when @value{AS} is configured for
440 This option sets the largest size of an object that can be referenced
441 implicitly with the @code{gp} register. It is only accepted for targets that
442 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
444 @cindex MIPS endianness
445 @cindex endianness, MIPS
446 @cindex big endian output, MIPS
448 Generate ``big endian'' format output.
450 @cindex little endian output, MIPS
452 Generate ``little endian'' format output.
458 Generate code for a particular MIPS Instruction Set Architecture level.
459 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
460 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
465 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
466 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
467 instructions around accesses to the @samp{HI} and @samp{LO} registers.
468 @samp{-no-m4650} turns off this option.
470 @item -mcpu=@var{CPU}
471 Generate code for a particular MIPS cpu. This has little effect on the
472 assembler, but it is passed by @code{@value{GCC}}.
475 @item --emulation=@var{name}
476 This option causes @code{@value{AS}} to emulated @code{@value{AS}} configured
477 for some other target, in all respects, including output format (choosing
478 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
479 debugging information or store symbol table information, and default
480 endianness. The available configuration names are: @samp{mipsecoff},
481 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
482 @samp{mipsbelf}. The first two do not alter the default endianness from that
483 of the primary target for which the assembler was configured; the others change
484 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
485 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
486 selection in any case.
488 This option is currently supported only when the primary target
489 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
490 Furthermore, the primary target or others specified with
491 @samp{--enable-targets=@dots{}} at configuration time must include support for
492 the other format, if both are to be available. For example, the Irix 5
493 configuration includes support for both.
495 Eventually, this option will support more configurations, with more
496 fine-grained control over the assembler's behavior, and will be supported for
500 @code{@value{AS}} ignores this option. It is accepted for compatibility with
508 Control how to deal with multiplication overflow and division by zero.
509 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
510 (and only work for Instruction Set Architecture level 2 and higher);
511 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
517 * Manual:: Structure of this Manual
518 * GNU Assembler:: @value{AS}, the GNU Assembler
519 * Object Formats:: Object File Formats
520 * Command Line:: Command Line
521 * Input Files:: Input Files
522 * Object:: Output (Object) File
523 * Errors:: Error and Warning Messages
527 @section Structure of this Manual
529 @cindex manual, structure and purpose
530 This manual is intended to describe what you need to know to use
531 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
532 notation for symbols, constants, and expressions; the directives that
533 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
536 We also cover special features in the @value{TARGET}
537 configuration of @code{@value{AS}}, including assembler directives.
540 This manual also describes some of the machine-dependent features of
541 various flavors of the assembler.
544 @cindex machine instructions (not covered)
545 On the other hand, this manual is @emph{not} intended as an introduction
546 to programming in assembly language---let alone programming in general!
547 In a similar vein, we make no attempt to introduce the machine
548 architecture; we do @emph{not} describe the instruction set, standard
549 mnemonics, registers or addressing modes that are standard to a
550 particular architecture.
552 You may want to consult the manufacturer's
553 machine architecture manual for this information.
557 For information on the H8/300 machine instruction set, see @cite{H8/300
558 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
559 see @cite{H8/300H Series Programming Manual} (Hitachi).
562 For information on the H8/500 machine instruction set, see @cite{H8/500
563 Series Programming Manual} (Hitachi M21T001).
566 For information on the Hitachi SH machine instruction set, see
567 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
570 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
574 @c I think this is premature---doc@cygnus.com, 17jan1991
576 Throughout this manual, we assume that you are running @dfn{GNU},
577 the portable operating system from the @dfn{Free Software
578 Foundation, Inc.}. This restricts our attention to certain kinds of
579 computer (in particular, the kinds of computers that @sc{gnu} can run on);
580 once this assumption is granted examples and definitions need less
583 @code{@value{AS}} is part of a team of programs that turn a high-level
584 human-readable series of instructions into a low-level
585 computer-readable series of instructions. Different versions of
586 @code{@value{AS}} are used for different kinds of computer.
589 @c There used to be a section "Terminology" here, which defined
590 @c "contents", "byte", "word", and "long". Defining "word" to any
591 @c particular size is confusing when the .word directive may generate 16
592 @c bits on one machine and 32 bits on another; in general, for the user
593 @c version of this manual, none of these terms seem essential to define.
594 @c They were used very little even in the former draft of the manual;
595 @c this draft makes an effort to avoid them (except in names of
599 @section @value{AS}, the GNU Assembler
601 @sc{gnu} @code{as} is really a family of assemblers.
603 This manual describes @code{@value{AS}}, a member of that family which is
604 configured for the @value{TARGET} architectures.
606 If you use (or have used) the @sc{gnu} assembler on one architecture, you
607 should find a fairly similar environment when you use it on another
608 architecture. Each version has much in common with the others,
609 including object file formats, most assembler directives (often called
610 @dfn{pseudo-ops}) and assembler syntax.@refill
612 @cindex purpose of @sc{gnu} @code{@value{AS}}
613 @code{@value{AS}} is primarily intended to assemble the output of the
614 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
615 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
616 assemble correctly everything that other assemblers for the same
617 machine would assemble.
619 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
622 @c This remark should appear in generic version of manual; assumption
623 @c here is that generic version sets M680x0.
624 This doesn't mean @code{@value{AS}} always uses the same syntax as another
625 assembler for the same architecture; for example, we know of several
626 incompatible versions of 680x0 assembly language syntax.
629 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
630 program in one pass of the source file. This has a subtle impact on the
631 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
634 @section Object File Formats
636 @cindex object file format
637 The @sc{gnu} assembler can be configured to produce several alternative
638 object file formats. For the most part, this does not affect how you
639 write assembly language programs; but directives for debugging symbols
640 are typically different in different file formats. @xref{Symbol
641 Attributes,,Symbol Attributes}.
644 On the @value{TARGET}, @code{@value{AS}} is configured to produce
645 @value{OBJ-NAME} format object files.
647 @c The following should exhaust all configs that set MULTI-OBJ, ideally
649 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
650 @code{a.out} or COFF format object files.
653 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
654 @code{b.out} or COFF format object files.
657 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
658 SOM or ELF format object files.
663 @section Command Line
665 @cindex command line conventions
666 After the program name @code{@value{AS}}, the command line may contain
667 options and file names. Options may appear in any order, and may be
668 before, after, or between file names. The order of file names is
671 @cindex standard input, as input file
673 @file{--} (two hyphens) by itself names the standard input file
674 explicitly, as one of the files for @code{@value{AS}} to assemble.
676 @cindex options, command line
677 Except for @samp{--} any command line argument that begins with a
678 hyphen (@samp{-}) is an option. Each option changes the behavior of
679 @code{@value{AS}}. No option changes the way another option works. An
680 option is a @samp{-} followed by one or more letters; the case of
681 the letter is important. All options are optional.
683 Some options expect exactly one file name to follow them. The file
684 name may either immediately follow the option's letter (compatible
685 with older assemblers) or it may be the next command argument (@sc{gnu}
686 standard). These two command lines are equivalent:
689 @value{AS} -o my-object-file.o mumble.s
690 @value{AS} -omy-object-file.o mumble.s
697 @cindex source program
699 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
700 describe the program input to one run of @code{@value{AS}}. The program may
701 be in one or more files; how the source is partitioned into files
702 doesn't change the meaning of the source.
704 @c I added "con" prefix to "catenation" just to prove I can overcome my
705 @c APL training... doc@cygnus.com
706 The source program is a concatenation of the text in all the files, in the
709 Each time you run @code{@value{AS}} it assembles exactly one source
710 program. The source program is made up of one or more files.
711 (The standard input is also a file.)
713 You give @code{@value{AS}} a command line that has zero or more input file
714 names. The input files are read (from left file name to right). A
715 command line argument (in any position) that has no special meaning
716 is taken to be an input file name.
718 If you give @code{@value{AS}} no file names it attempts to read one input file
719 from the @code{@value{AS}} standard input, which is normally your terminal. You
720 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
723 Use @samp{--} if you need to explicitly name the standard input file
724 in your command line.
726 If the source is empty, @code{@value{AS}} produces a small, empty object
729 @subheading Filenames and Line-numbers
731 @cindex input file linenumbers
732 @cindex line numbers, in input files
733 There are two ways of locating a line in the input file (or files) and
734 either may be used in reporting error messages. One way refers to a line
735 number in a physical file; the other refers to a line number in a
736 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
738 @dfn{Physical files} are those files named in the command line given
739 to @code{@value{AS}}.
741 @dfn{Logical files} are simply names declared explicitly by assembler
742 directives; they bear no relation to physical files. Logical file names
743 help error messages reflect the original source file, when @code{@value{AS}}
744 source is itself synthesized from other files.
745 @xref{App-File,,@code{.app-file}}.
748 @section Output (Object) File
754 Every time you run @code{@value{AS}} it produces an output file, which is
755 your assembly language program translated into numbers. This file
756 is the object file. Its default name is
764 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
766 You can give it another name by using the @code{-o} option. Conventionally,
767 object file names end with @file{.o}. The default name is used for historical
768 reasons: older assemblers were capable of assembling self-contained programs
769 directly into a runnable program. (For some formats, this isn't currently
770 possible, but it can be done for the @code{a.out} format.)
774 The object file is meant for input to the linker @code{@value{LD}}. It contains
775 assembled program code, information to help @code{@value{LD}} integrate
776 the assembled program into a runnable file, and (optionally) symbolic
777 information for the debugger.
779 @c link above to some info file(s) like the description of a.out.
780 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
783 @section Error and Warning Messages
785 @cindex error messsages
786 @cindex warning messages
787 @cindex messages from @code{@value{AS}}
788 @code{@value{AS}} may write warnings and error messages to the standard error
789 file (usually your terminal). This should not happen when a compiler
790 runs @code{@value{AS}} automatically. Warnings report an assumption made so
791 that @code{@value{AS}} could keep assembling a flawed program; errors report a
792 grave problem that stops the assembly.
794 @cindex format of warning messages
795 Warning messages have the format
798 file_name:@b{NNN}:Warning Message Text
802 @cindex line numbers, in warnings/errors
803 (where @b{NNN} is a line number). If a logical file name has been given
804 (@pxref{App-File,,@code{.app-file}}) it is used for the filename,
805 otherwise the name of the current input file is used. If a logical line
808 (@pxref{Line,,@code{.line}})
812 (@pxref{Line,,@code{.line}})
815 (@pxref{Ln,,@code{.ln}})
818 then it is used to calculate the number printed,
819 otherwise the actual line in the current source file is printed. The
820 message text is intended to be self explanatory (in the grand Unix
823 @cindex format of error messages
824 Error messages have the format
826 file_name:@b{NNN}:FATAL:Error Message Text
828 The file name and line number are derived as for warning
829 messages. The actual message text may be rather less explanatory
830 because many of them aren't supposed to happen.
833 @chapter Command-Line Options
835 @cindex options, all versions of @code{@value{AS}}
836 This chapter describes command-line options available in @emph{all}
837 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
839 to the @value{TARGET}.
842 to particular machine architectures.
845 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2), you
846 can use the @samp{-Wa} option to pass arguments through to the
847 assembler. The assembler arguments must be separated from each other
848 (and the @samp{-Wa}) by commas. For example:
851 gcc -c -g -O -Wa,-alh,-L file.c
855 emits a listing to standard output with high-level
858 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
859 command-line options are automatically passed to the assembler by the compiler.
860 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
861 precisely what options it passes to each compilation pass, including the
865 * a:: -a[dhlns] enable listings
866 * D:: -D for compatibility
867 * f:: -f to work faster
868 * I:: -I for .include search path
869 @ifclear DIFF-TBL-KLUGE
870 * K:: -K for compatibility
872 @ifset DIFF-TBL-KLUGE
873 * K:: -K for difference tables
876 * L:: -L to retain local labels
877 * M:: -M or --mri to assemble in MRI compatibility mode
878 * o:: -o to name the object file
879 * R:: -R to join data and text sections
880 * statistics:: --statistics to see statistics about assembly
881 * v:: -v to announce version
882 * W:: -W to suppress warnings
883 * Z:: -Z to make object file even after errors
887 @section Enable Listings: @code{-a[dhlns]}
895 @cindex listings, enabling
896 @cindex assembly listings, enabling
898 These options enable listing output from the assembler. By itself,
899 @samp{-a} requests high-level, assembly, and symbols listing.
900 You can use other letters to select specific options for the list:
901 @samp{-ah} requests a high-level language listing,
902 @samp{-al} requests an output-program assembly listing, and
903 @samp{-as} requests a symbol table listing.
904 High-level listings require that a compiler debugging option like
905 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
908 Use the @samp{-ad} option to omit debugging directives from the
911 Once you have specified one of these options, you can further control
912 listing output and its appearance using the directives @code{.list},
913 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
915 The @samp{-an} option turns off all forms processing.
916 If you do not request listing output with one of the @samp{-a} options, the
917 listing-control directives have no effect.
919 The letters after @samp{-a} may be combined into one option,
920 @emph{e.g.}, @samp{-aln}.
926 This option has no effect whatsoever, but it is accepted to make it more
927 likely that scripts written for other assemblers also work with
931 @section Work Faster: @code{-f}
934 @cindex trusted compiler
935 @cindex faster processing (@code{-f})
936 @samp{-f} should only be used when assembling programs written by a
937 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
938 and comment preprocessing on
939 the input file(s) before assembling them. @xref{Preprocessing,
943 @emph{Warning:} if you use @samp{-f} when the files actually need to be
944 preprocessed (if they contain comments, for example), @code{@value{AS}} does
949 @section @code{.include} search path: @code{-I} @var{path}
951 @kindex -I @var{path}
952 @cindex paths for @code{.include}
953 @cindex search path for @code{.include}
954 @cindex @code{include} directive search path
955 Use this option to add a @var{path} to the list of directories
956 @code{@value{AS}} searches for files specified in @code{.include}
957 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
958 many times as necessary to include a variety of paths. The current
959 working directory is always searched first; after that, @code{@value{AS}}
960 searches any @samp{-I} directories in the same order as they were
961 specified (left to right) on the command line.
964 @section Difference Tables: @code{-K}
967 @ifclear DIFF-TBL-KLUGE
968 On the @value{TARGET} family, this option is allowed, but has no effect. It is
969 permitted for compatibility with the @sc{gnu} assembler on other platforms,
970 where it can be used to warn when the assembler alters the machine code
971 generated for @samp{.word} directives in difference tables. The @value{TARGET}
972 family does not have the addressing limitations that sometimes lead to this
973 alteration on other platforms.
976 @ifset DIFF-TBL-KLUGE
977 @cindex difference tables, warning
978 @cindex warning for altered difference tables
979 @code{@value{AS}} sometimes alters the code emitted for directives of the form
980 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
981 You can use the @samp{-K} option if you want a warning issued when this
986 @section Include Local Labels: @code{-L}
989 @cindex local labels, retaining in output
990 Labels beginning with @samp{L} (upper case only) are called @dfn{local
991 labels}. @xref{Symbol Names}. Normally you do not see such labels when
992 debugging, because they are intended for the use of programs (like
993 compilers) that compose assembler programs, not for your notice.
994 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
995 normally debug with them.
997 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
998 in the object file. Usually if you do this you also tell the linker
999 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1001 By default, a local label is any label beginning with @samp{L}, but each
1002 target is allowed to redefine the local label prefix.
1004 On the HPPA local labels begin with @samp{L$}.
1006 @c start-sanitize-arc
1008 On the ARC local labels begin with @samp{.L}.
1013 @section Assemble in MRI Compatibility Mode: @code{-M}
1016 @cindex MRI compatibility mode
1017 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1018 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1019 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1020 configured target) assembler from Microtec Research. The exact nature of the
1021 MRI syntax will not be documented here; see the MRI manuals for more
1022 information. Note in particular that the handling of macros and macro
1023 arguments is somewhat different. The purpose of this option is to permit
1024 assembling existing MRI assembler code using @code{@value{AS}}.
1026 The MRI compatibility is not complete. Certain operations of the MRI assembler
1027 depend upon its object file format, and can not be supported using other object
1028 file formats. Supporting these would require enhancing each object file format
1029 individually. These are:
1032 @item global symbols in common section
1034 The m68k MRI assembler supports common sections which are merged by the linker.
1035 Other object file formats do not support this. @code{@value{AS}} handles
1036 common sections by treating them as a single common symbol. It permits local
1037 symbols to be defined within a common section, but it can not support global
1038 symbols, since it has no way to describe them.
1040 @item complex relocations
1042 The MRI assemblers support relocations against a negated section address, and
1043 relocations which combine the start addresses of two or more sections. These
1044 are not support by other object file formats.
1046 @item @code{END} pseudo-op specifying start address
1048 The MRI @code{END} pseudo-op permits the specification of a start address.
1049 This is not supported by other object file formats. The start address may
1050 instead be specified using the @code{-e} option to the linker, or in a linker
1053 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1055 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1056 name to the output file. This is not supported by other object file formats.
1058 @item @code{ORG} pseudo-op
1060 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1061 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1062 which changes the location within the current section. Absolute sections are
1063 not supported by other object file formats. The address of a section may be
1064 assigned within a linker script.
1067 There are some other features of the MRI assembler which are not supported by
1068 @code{@value{AS}}, typically either because they are difficult or because they
1069 seem of little consequence. Some of these may be supported in future releases.
1073 @item EBCDIC strings
1075 EBCDIC strings are not supported.
1077 @item packed binary coded decimal
1079 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1080 and @code{DCB.P} pseudo-ops are not supported.
1082 @item @code{FEQU} pseudo-op
1084 The m68k @code{FEQU} pseudo-op is not supported.
1086 @item @code{NOOBJ} pseudo-op
1088 The m68k @code{NOOBJ} pseudo-op is not supported.
1090 @item @code{OPT} branch control options
1092 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1093 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1094 relaxes all branches, whether forward or backward, to an appropriate size, so
1095 these options serve no purpose.
1097 @item @code{OPT} list control options
1099 The following m68k @code{OPT} list control options are ignored: @code{C},
1100 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1101 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1103 @item other @code{OPT} options
1105 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1106 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1108 @item @code{OPT} @code{D} option is default
1110 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1111 @code{OPT NOD} may be used to turn it off.
1113 @item @code{XREF} pseudo-op.
1115 The m68k @code{XREF} pseudo-op is ignored.
1117 @item @code{.debug} pseudo-op
1119 The i960 @code{.debug} pseudo-op is not supported.
1121 @item @code{.extended} pseudo-op
1123 The i960 @code{.extended} pseudo-op is not supported.
1125 @item @code{.list} pseudo-op.
1127 The various options of the i960 @code{.list} pseudo-op are not supported.
1129 @item @code{.optimize} pseudo-op
1131 The i960 @code{.optimize} pseudo-op is not supported.
1133 @item @code{.output} pseudo-op
1135 The i960 @code{.output} pseudo-op is not supported.
1137 @item @code{.setreal} pseudo-op
1139 The i960 @code{.setreal} pseudo-op is not supported.
1144 @section Name the Object File: @code{-o}
1147 @cindex naming object file
1148 @cindex object file name
1149 There is always one object file output when you run @code{@value{AS}}. By
1150 default it has the name
1153 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1167 You use this option (which takes exactly one filename) to give the
1168 object file a different name.
1170 Whatever the object file is called, @code{@value{AS}} overwrites any
1171 existing file of the same name.
1174 @section Join Data and Text Sections: @code{-R}
1177 @cindex data and text sections, joining
1178 @cindex text and data sections, joining
1179 @cindex joining text and data sections
1180 @cindex merging text and data sections
1181 @code{-R} tells @code{@value{AS}} to write the object file as if all
1182 data-section data lives in the text section. This is only done at
1183 the very last moment: your binary data are the same, but data
1184 section parts are relocated differently. The data section part of
1185 your object file is zero bytes long because all its bytes are
1186 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1188 When you specify @code{-R} it would be possible to generate shorter
1189 address displacements (because we do not have to cross between text and
1190 data section). We refrain from doing this simply for compatibility with
1191 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1194 When @code{@value{AS}} is configured for COFF output,
1195 this option is only useful if you use sections named @samp{.text} and
1200 @code{-R} is not supported for any of the HPPA targets. Using
1201 @code{-R} generates a warning from @code{@value{AS}}.
1205 @section Display Assembly Statistics: @code{--statistics}
1207 @kindex --statistics
1208 @cindex statistics, about assembly
1209 @cindex time, total for assembly
1210 @cindex space used, maximum for assembly
1211 Use @samp{--statistics} to display two statistics about the resources used by
1212 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1213 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1217 @section Announce Version: @code{-v}
1221 @cindex @code{@value{AS}} version
1222 @cindex version of @code{@value{AS}}
1223 You can find out what version of as is running by including the
1224 option @samp{-v} (which you can also spell as @samp{-version}) on the
1228 @section Suppress Warnings: @code{-W}
1231 @cindex suppressing warnings
1232 @cindex warnings, suppressing
1233 @code{@value{AS}} should never give a warning or error message when
1234 assembling compiler output. But programs written by people often
1235 cause @code{@value{AS}} to give a warning that a particular assumption was
1236 made. All such warnings are directed to the standard error file.
1237 If you use this option, no warnings are issued. This option only
1238 affects the warning messages: it does not change any particular of how
1239 @code{@value{AS}} assembles your file. Errors, which stop the assembly, are
1243 @section Generate Object File in Spite of Errors: @code{-Z}
1244 @cindex object file, after errors
1245 @cindex errors, continuing after
1246 After an error message, @code{@value{AS}} normally produces no output. If for
1247 some reason you are interested in object file output even after
1248 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1249 option. If there are any errors, @code{@value{AS}} continues anyways, and
1250 writes an object file after a final warning message of the form @samp{@var{n}
1251 errors, @var{m} warnings, generating bad object file.}
1256 @cindex machine-independent syntax
1257 @cindex syntax, machine-independent
1258 This chapter describes the machine-independent syntax allowed in a
1259 source file. @code{@value{AS}} syntax is similar to what many other
1260 assemblers use; it is inspired by the BSD 4.2
1265 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1269 * Preprocessing:: Preprocessing
1270 * Whitespace:: Whitespace
1271 * Comments:: Comments
1272 * Symbol Intro:: Symbols
1273 * Statements:: Statements
1274 * Constants:: Constants
1278 @section Preprocessing
1280 @cindex preprocessing
1281 The @code{@value{AS}} internal preprocessor:
1283 @cindex whitespace, removed by preprocessor
1285 adjusts and removes extra whitespace. It leaves one space or tab before
1286 the keywords on a line, and turns any other whitespace on the line into
1289 @cindex comments, removed by preprocessor
1291 removes all comments, replacing them with a single space, or an
1292 appropriate number of newlines.
1294 @cindex constants, converted by preprocessor
1296 converts character constants into the appropriate numeric values.
1299 It does not do macro processing, include file handling, or
1300 anything else you may get from your C compiler's preprocessor. You can
1301 do include file processing with the @code{.include} directive
1302 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1303 to get other ``CPP'' style preprocessing, by giving the input file a
1304 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1305 Output, gcc.info, Using GNU CC}.
1307 Excess whitespace, comments, and character constants
1308 cannot be used in the portions of the input text that are not
1311 @cindex turning preprocessing on and off
1312 @cindex preprocessing, turning on and off
1315 If the first line of an input file is @code{#NO_APP} or if you use the
1316 @samp{-f} option, whitespace and comments are not removed from the input file.
1317 Within an input file, you can ask for whitespace and comment removal in
1318 specific portions of the by putting a line that says @code{#APP} before the
1319 text that may contain whitespace or comments, and putting a line that says
1320 @code{#NO_APP} after this text. This feature is mainly intend to support
1321 @code{asm} statements in compilers whose output is otherwise free of comments
1328 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1329 Whitespace is used to separate symbols, and to make programs neater for
1330 people to read. Unless within character constants
1331 (@pxref{Characters,,Character Constants}), any whitespace means the same
1332 as exactly one space.
1338 There are two ways of rendering comments to @code{@value{AS}}. In both
1339 cases the comment is equivalent to one space.
1341 Anything from @samp{/*} through the next @samp{*/} is a comment.
1342 This means you may not nest these comments.
1346 The only way to include a newline ('\n') in a comment
1347 is to use this sort of comment.
1350 /* This sort of comment does not nest. */
1353 @cindex line comment character
1354 Anything from the @dfn{line comment} character to the next newline
1355 is considered a comment and is ignored. The line comment character is
1357 @samp{;} for the AMD 29K family;
1359 @c start-sanitize-arc
1361 @samp{;} on the ARC;
1365 @samp{;} for the H8/300 family;
1368 @samp{!} for the H8/500 family;
1371 @samp{;} for the HPPA;
1374 @samp{#} on the i960;
1377 @samp{!} for the Hitachi SH;
1380 @samp{!} on the SPARC;
1383 @samp{|} on the 680x0;
1386 @samp{#} on the Vax;
1389 @samp{!} for the Z8000;
1391 see @ref{Machine Dependencies}. @refill
1392 @c FIXME What about i386, m88k, i860?
1395 On some machines there are two different line comment characters. One
1396 character only begins a comment if it is the first non-whitespace character on
1397 a line, while the other always begins a comment.
1401 @cindex lines starting with @code{#}
1402 @cindex logical line numbers
1403 To be compatible with past assemblers, lines that begin with @samp{#} have a
1404 special interpretation. Following the @samp{#} should be an absolute
1405 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1406 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1407 new logical file name. The rest of the line, if any, should be whitespace.
1409 If the first non-whitespace characters on the line are not numeric,
1410 the line is ignored. (Just like a comment.)
1413 # This is an ordinary comment.
1414 # 42-6 "new_file_name" # New logical file name
1415 # This is logical line # 36.
1417 This feature is deprecated, and may disappear from future versions
1418 of @code{@value{AS}}.
1423 @cindex characters used in symbols
1424 @ifclear SPECIAL-SYMS
1425 A @dfn{symbol} is one or more characters chosen from the set of all
1426 letters (both upper and lower case), digits and the three characters
1432 A @dfn{symbol} is one or more characters chosen from the set of all
1433 letters (both upper and lower case), digits and the three characters
1434 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1440 On most machines, you can also use @code{$} in symbol names; exceptions
1441 are noted in @ref{Machine Dependencies}.
1443 No symbol may begin with a digit. Case is significant.
1444 There is no length limit: all characters are significant. Symbols are
1445 delimited by characters not in that set, or by the beginning of a file
1446 (since the source program must end with a newline, the end of a file is
1447 not a possible symbol delimiter). @xref{Symbols}.
1448 @cindex length of symbols
1453 @cindex statements, structure of
1454 @cindex line separator character
1455 @cindex statement separator character
1457 @ifclear abnormal-separator
1458 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1459 semicolon (@samp{;}). The newline or semicolon is considered part of
1460 the preceding statement. Newlines and semicolons within character
1461 constants are an exception: they do not end statements.
1463 @ifset abnormal-separator
1465 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1466 sign (@samp{@@}). The newline or at sign is considered part of the
1467 preceding statement. Newlines and at signs within character constants
1468 are an exception: they do not end statements.
1471 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1472 point (@samp{!}). The newline or exclamation point is considered part of the
1473 preceding statement. Newlines and exclamation points within character
1474 constants are an exception: they do not end statements.
1477 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1478 H8/300) a dollar sign (@samp{$}); or (for the
1481 (@samp{;}). The newline or separator character is considered part of
1482 the preceding statement. Newlines and separators within character
1483 constants are an exception: they do not end statements.
1488 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1489 separator character. (The line separator is usually @samp{;}, unless
1490 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1491 newline or separator character is considered part of the preceding
1492 statement. Newlines and separators within character constants are an
1493 exception: they do not end statements.
1496 @cindex newline, required at file end
1497 @cindex EOF, newline must precede
1498 It is an error to end any statement with end-of-file: the last
1499 character of any input file should be a newline.@refill
1501 @cindex continuing statements
1502 @cindex multi-line statements
1503 @cindex statement on multiple lines
1504 You may write a statement on more than one line if you put a
1505 backslash (@kbd{\}) immediately in front of any newlines within the
1506 statement. When @code{@value{AS}} reads a backslashed newline both
1507 characters are ignored. You can even put backslashed newlines in
1508 the middle of symbol names without changing the meaning of your
1511 An empty statement is allowed, and may include whitespace. It is ignored.
1513 @cindex instructions and directives
1514 @cindex directives and instructions
1515 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1516 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1518 A statement begins with zero or more labels, optionally followed by a
1519 key symbol which determines what kind of statement it is. The key
1520 symbol determines the syntax of the rest of the statement. If the
1521 symbol begins with a dot @samp{.} then the statement is an assembler
1522 directive: typically valid for any computer. If the symbol begins with
1523 a letter the statement is an assembly language @dfn{instruction}: it
1524 assembles into a machine language instruction.
1526 Different versions of @code{@value{AS}} for different computers
1527 recognize different instructions. In fact, the same symbol may
1528 represent a different instruction in a different computer's assembly
1532 @cindex @code{:} (label)
1533 @cindex label (@code{:})
1534 A label is a symbol immediately followed by a colon (@code{:}).
1535 Whitespace before a label or after a colon is permitted, but you may not
1536 have whitespace between a label's symbol and its colon. @xref{Labels}.
1539 For HPPA targets, labels need not be immediately followed by a colon, but
1540 the definition of a label must begin in column zero. This also implies that
1541 only one label may be defined on each line.
1545 label: .directive followed by something
1546 another_label: # This is an empty statement.
1547 instruction operand_1, operand_2, @dots{}
1554 A constant is a number, written so that its value is known by
1555 inspection, without knowing any context. Like this:
1558 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1559 .ascii "Ring the bell\7" # A string constant.
1560 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1561 .float 0f-314159265358979323846264338327\
1562 95028841971.693993751E-40 # - pi, a flonum.
1567 * Characters:: Character Constants
1568 * Numbers:: Number Constants
1572 @subsection Character Constants
1574 @cindex character constants
1575 @cindex constants, character
1576 There are two kinds of character constants. A @dfn{character} stands
1577 for one character in one byte and its value may be used in
1578 numeric expressions. String constants (properly called string
1579 @emph{literals}) are potentially many bytes and their values may not be
1580 used in arithmetic expressions.
1584 * Chars:: Characters
1588 @subsubsection Strings
1590 @cindex string constants
1591 @cindex constants, string
1592 A @dfn{string} is written between double-quotes. It may contain
1593 double-quotes or null characters. The way to get special characters
1594 into a string is to @dfn{escape} these characters: precede them with
1595 a backslash @samp{\} character. For example @samp{\\} represents
1596 one backslash: the first @code{\} is an escape which tells
1597 @code{@value{AS}} to interpret the second character literally as a backslash
1598 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1599 escape character). The complete list of escapes follows.
1601 @cindex escape codes, character
1602 @cindex character escape codes
1605 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1607 @cindex @code{\b} (backspace character)
1608 @cindex backspace (@code{\b})
1610 Mnemonic for backspace; for ASCII this is octal code 010.
1613 @c Mnemonic for EOText; for ASCII this is octal code 004.
1615 @cindex @code{\f} (formfeed character)
1616 @cindex formfeed (@code{\f})
1618 Mnemonic for FormFeed; for ASCII this is octal code 014.
1620 @cindex @code{\n} (newline character)
1621 @cindex newline (@code{\n})
1623 Mnemonic for newline; for ASCII this is octal code 012.
1626 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1628 @cindex @code{\r} (carriage return character)
1629 @cindex carriage return (@code{\r})
1631 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1634 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1635 @c other assemblers.
1637 @cindex @code{\t} (tab)
1638 @cindex tab (@code{\t})
1640 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1643 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1644 @c @item \x @var{digit} @var{digit} @var{digit}
1645 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1647 @cindex @code{\@var{ddd}} (octal character code)
1648 @cindex octal character code (@code{\@var{ddd}})
1649 @item \ @var{digit} @var{digit} @var{digit}
1650 An octal character code. The numeric code is 3 octal digits.
1651 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1652 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1654 @cindex @code{\@var{xd...}} (hex character code)
1655 @cindex hex character code (@code{\@var{xd...}})
1656 @item \@code{x} @var{hex-digits...}
1657 A hex character code. All trailing hex digits are combined. Either upper or
1658 lower case @code{x} works.
1660 @cindex @code{\\} (@samp{\} character)
1661 @cindex backslash (@code{\\})
1663 Represents one @samp{\} character.
1666 @c Represents one @samp{'} (accent acute) character.
1667 @c This is needed in single character literals
1668 @c (@xref{Characters,,Character Constants}.) to represent
1671 @cindex @code{\"} (doublequote character)
1672 @cindex doublequote (@code{\"})
1674 Represents one @samp{"} character. Needed in strings to represent
1675 this character, because an unescaped @samp{"} would end the string.
1677 @item \ @var{anything-else}
1678 Any other character when escaped by @kbd{\} gives a warning, but
1679 assembles as if the @samp{\} was not present. The idea is that if
1680 you used an escape sequence you clearly didn't want the literal
1681 interpretation of the following character. However @code{@value{AS}} has no
1682 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1683 code and warns you of the fact.
1686 Which characters are escapable, and what those escapes represent,
1687 varies widely among assemblers. The current set is what we think
1688 the BSD 4.2 assembler recognizes, and is a subset of what most C
1689 compilers recognize. If you are in doubt, do not use an escape
1693 @subsubsection Characters
1695 @cindex single character constant
1696 @cindex character, single
1697 @cindex constant, single character
1698 A single character may be written as a single quote immediately
1699 followed by that character. The same escapes apply to characters as
1700 to strings. So if you want to write the character backslash, you
1701 must write @kbd{'\\} where the first @code{\} escapes the second
1702 @code{\}. As you can see, the quote is an acute accent, not a
1703 grave accent. A newline
1705 @ifclear abnormal-separator
1706 (or semicolon @samp{;})
1708 @ifset abnormal-separator
1710 (or at sign @samp{@@})
1713 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1719 immediately following an acute accent is taken as a literal character
1720 and does not count as the end of a statement. The value of a character
1721 constant in a numeric expression is the machine's byte-wide code for
1722 that character. @code{@value{AS}} assumes your character code is ASCII:
1723 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1726 @subsection Number Constants
1728 @cindex constants, number
1729 @cindex number constants
1730 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1731 are stored in the target machine. @emph{Integers} are numbers that
1732 would fit into an @code{int} in the C language. @emph{Bignums} are
1733 integers, but they are stored in more than 32 bits. @emph{Flonums}
1734 are floating point numbers, described below.
1737 * Integers:: Integers
1742 * Bit Fields:: Bit Fields
1748 @subsubsection Integers
1750 @cindex constants, integer
1752 @cindex binary integers
1753 @cindex integers, binary
1754 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1755 the binary digits @samp{01}.
1757 @cindex octal integers
1758 @cindex integers, octal
1759 An octal integer is @samp{0} followed by zero or more of the octal
1760 digits (@samp{01234567}).
1762 @cindex decimal integers
1763 @cindex integers, decimal
1764 A decimal integer starts with a non-zero digit followed by zero or
1765 more digits (@samp{0123456789}).
1767 @cindex hexadecimal integers
1768 @cindex integers, hexadecimal
1769 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
1770 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
1772 Integers have the usual values. To denote a negative integer, use
1773 the prefix operator @samp{-} discussed under expressions
1774 (@pxref{Prefix Ops,,Prefix Operators}).
1777 @subsubsection Bignums
1780 @cindex constants, bignum
1781 A @dfn{bignum} has the same syntax and semantics as an integer
1782 except that the number (or its negative) takes more than 32 bits to
1783 represent in binary. The distinction is made because in some places
1784 integers are permitted while bignums are not.
1787 @subsubsection Flonums
1789 @cindex floating point numbers
1790 @cindex constants, floating point
1792 @cindex precision, floating point
1793 A @dfn{flonum} represents a floating point number. The translation is
1794 indirect: a decimal floating point number from the text is converted by
1795 @code{@value{AS}} to a generic binary floating point number of more than
1796 sufficient precision. This generic floating point number is converted
1797 to a particular computer's floating point format (or formats) by a
1798 portion of @code{@value{AS}} specialized to that computer.
1800 A flonum is written by writing (in order)
1805 (@samp{0} is optional on the HPPA.)
1809 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
1811 @kbd{e} is recommended. Case is not important.
1813 @c FIXME: verify if flonum syntax really this vague for most cases
1814 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
1815 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
1818 On the H8/300, H8/500,
1820 and AMD 29K architectures, the letter must be
1821 one of the letters @samp{DFPRSX} (in upper or lower case).
1823 @c start-sanitize-arc
1824 On the ARC, the letter one of the letters @samp{DFRS}
1825 (in upper or lower case).
1828 On the Intel 960 architecture, the letter must be
1829 one of the letters @samp{DFT} (in upper or lower case).
1831 On the HPPA architecture, the letter must be @samp{E} (upper case only).
1835 One of the letters @samp{DFPRSX} (in upper or lower case).
1837 @c start-sanitize-arc
1839 One of the letters @samp{DFRS} (in upper or lower case).
1843 One of the letters @samp{DFPRSX} (in upper or lower case).
1846 The letter @samp{E} (upper case only).
1849 One of the letters @samp{DFT} (in upper or lower case).
1854 An optional sign: either @samp{+} or @samp{-}.
1857 An optional @dfn{integer part}: zero or more decimal digits.
1860 An optional @dfn{fractional part}: @samp{.} followed by zero
1861 or more decimal digits.
1864 An optional exponent, consisting of:
1868 An @samp{E} or @samp{e}.
1869 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
1870 @c principle this can perfectly well be different on different targets.
1872 Optional sign: either @samp{+} or @samp{-}.
1874 One or more decimal digits.
1879 At least one of the integer part or the fractional part must be
1880 present. The floating point number has the usual base-10 value.
1882 @code{@value{AS}} does all processing using integers. Flonums are computed
1883 independently of any floating point hardware in the computer running
1888 @c Bit fields are written as a general facility but are also controlled
1889 @c by a conditional-compilation flag---which is as of now (21mar91)
1890 @c turned on only by the i960 config of GAS.
1892 @subsubsection Bit Fields
1895 @cindex constants, bit field
1896 You can also define numeric constants as @dfn{bit fields}.
1897 specify two numbers separated by a colon---
1899 @var{mask}:@var{value}
1902 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
1905 The resulting number is then packed
1907 @c this conditional paren in case bit fields turned on elsewhere than 960
1908 (in host-dependent byte order)
1910 into a field whose width depends on which assembler directive has the
1911 bit-field as its argument. Overflow (a result from the bitwise and
1912 requiring more binary digits to represent) is not an error; instead,
1913 more constants are generated, of the specified width, beginning with the
1914 least significant digits.@refill
1916 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
1917 @code{.short}, and @code{.word} accept bit-field arguments.
1922 @chapter Sections and Relocation
1927 * Secs Background:: Background
1928 * Ld Sections:: @value{LD} Sections
1929 * As Sections:: @value{AS} Internal Sections
1930 * Sub-Sections:: Sub-Sections
1934 @node Secs Background
1937 Roughly, a section is a range of addresses, with no gaps; all data
1938 ``in'' those addresses is treated the same for some particular purpose.
1939 For example there may be a ``read only'' section.
1941 @cindex linker, and assembler
1942 @cindex assembler, and linker
1943 The linker @code{@value{LD}} reads many object files (partial programs) and
1944 combines their contents to form a runnable program. When @code{@value{AS}}
1945 emits an object file, the partial program is assumed to start at address 0.
1946 @code{@value{LD}} assigns the final addresses for the partial program, so that
1947 different partial programs do not overlap. This is actually an
1948 oversimplification, but it suffices to explain how @code{@value{AS}} uses
1951 @code{@value{LD}} moves blocks of bytes of your program to their run-time
1952 addresses. These blocks slide to their run-time addresses as rigid
1953 units; their length does not change and neither does the order of bytes
1954 within them. Such a rigid unit is called a @emph{section}. Assigning
1955 run-time addresses to sections is called @dfn{relocation}. It includes
1956 the task of adjusting mentions of object-file addresses so they refer to
1957 the proper run-time addresses.
1959 For the H8/300 and H8/500,
1960 and for the Hitachi SH,
1961 @code{@value{AS}} pads sections if needed to
1962 ensure they end on a word (sixteen bit) boundary.
1965 @cindex standard @code{@value{AS}} sections
1966 An object file written by @code{@value{AS}} has at least three sections, any
1967 of which may be empty. These are named @dfn{text}, @dfn{data} and
1972 When it generates COFF output,
1974 @code{@value{AS}} can also generate whatever other named sections you specify
1975 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
1976 If you do not use any directives that place output in the @samp{.text}
1977 or @samp{.data} sections, these sections still exist, but are empty.
1982 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
1984 @code{@value{AS}} can also generate whatever other named sections you
1985 specify using the @samp{.space} and @samp{.subspace} directives. See
1986 @cite{HP9000 Series 800 Assembly Language Reference Manual}
1987 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
1988 assembler directives.
1991 Additionally, @code{@value{AS}} uses different names for the standard
1992 text, data, and bss sections when generating SOM output. Program text
1993 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
1994 BSS into @samp{$BSS$}.
1998 Within the object file, the text section starts at address @code{0}, the
1999 data section follows, and the bss section follows the data section.
2002 When generating either SOM or ELF output files on the HPPA, the text
2003 section starts at address @code{0}, the data section at address
2004 @code{0x4000000}, and the bss section follows the data section.
2007 To let @code{@value{LD}} know which data changes when the sections are
2008 relocated, and how to change that data, @code{@value{AS}} also writes to the
2009 object file details of the relocation needed. To perform relocation
2010 @code{@value{LD}} must know, each time an address in the object
2014 Where in the object file is the beginning of this reference to
2017 How long (in bytes) is this reference?
2019 Which section does the address refer to? What is the numeric value of
2021 (@var{address}) @minus{} (@var{start-address of section})?
2024 Is the reference to an address ``Program-Counter relative''?
2027 @cindex addresses, format of
2028 @cindex section-relative addressing
2029 In fact, every address @code{@value{AS}} ever uses is expressed as
2031 (@var{section}) + (@var{offset into section})
2034 Further, most expressions @code{@value{AS}} computes have this section-relative
2037 (For some object formats, such as SOM for the HPPA, some expressions are
2038 symbol-relative instead.)
2041 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2042 @var{N} into section @var{secname}.''
2044 Apart from text, data and bss sections you need to know about the
2045 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2046 addresses in the absolute section remain unchanged. For example, address
2047 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2048 @code{@value{LD}}. Although the linker never arranges two partial programs'
2049 data sections with overlapping addresses after linking, @emph{by definition}
2050 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2051 part of a program is always the same address when the program is running as
2052 address @code{@{absolute@ 239@}} in any other part of the program.
2054 The idea of sections is extended to the @dfn{undefined} section. Any
2055 address whose section is unknown at assembly time is by definition
2056 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2057 Since numbers are always defined, the only way to generate an undefined
2058 address is to mention an undefined symbol. A reference to a named
2059 common block would be such a symbol: its value is unknown at assembly
2060 time so it has section @emph{undefined}.
2062 By analogy the word @emph{section} is used to describe groups of sections in
2063 the linked program. @code{@value{LD}} puts all partial programs' text
2064 sections in contiguous addresses in the linked program. It is
2065 customary to refer to the @emph{text section} of a program, meaning all
2066 the addresses of all partial programs' text sections. Likewise for
2067 data and bss sections.
2069 Some sections are manipulated by @code{@value{LD}}; others are invented for
2070 use of @code{@value{AS}} and have no meaning except during assembly.
2073 @section @value{LD} Sections
2074 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2079 @cindex named sections
2080 @cindex sections, named
2081 @item named sections
2084 @cindex text section
2085 @cindex data section
2089 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2090 separate but equal sections. Anything you can say of one section is
2093 When the program is running, however, it is
2094 customary for the text section to be unalterable. The
2095 text section is often shared among processes: it contains
2096 instructions, constants and the like. The data section of a running
2097 program is usually alterable: for example, C variables would be stored
2098 in the data section.
2103 This section contains zeroed bytes when your program begins running. It
2104 is used to hold unitialized variables or common storage. The length of
2105 each partial program's bss section is important, but because it starts
2106 out containing zeroed bytes there is no need to store explicit zero
2107 bytes in the object file. The bss section was invented to eliminate
2108 those explicit zeros from object files.
2110 @cindex absolute section
2111 @item absolute section
2112 Address 0 of this section is always ``relocated'' to runtime address 0.
2113 This is useful if you want to refer to an address that @code{@value{LD}} must
2114 not change when relocating. In this sense we speak of absolute
2115 addresses being ``unrelocatable'': they do not change during relocation.
2117 @cindex undefined section
2118 @item undefined section
2119 This ``section'' is a catch-all for address references to objects not in
2120 the preceding sections.
2121 @c FIXME: ref to some other doc on obj-file formats could go here.
2124 @cindex relocation example
2125 An idealized example of three relocatable sections follows.
2127 The example uses the traditional section names @samp{.text} and @samp{.data}.
2129 Memory addresses are on the horizontal axis.
2133 @c END TEXI2ROFF-KILL
2136 partial program # 1: |ttttt|dddd|00|
2143 partial program # 2: |TTT|DDD|000|
2146 +--+---+-----+--+----+---+-----+~~
2147 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2148 +--+---+-----+--+----+---+-----+~~
2150 addresses: 0 @dots{}
2157 \line{\it Partial program \#1: \hfil}
2158 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2159 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2161 \line{\it Partial program \#2: \hfil}
2162 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2163 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2165 \line{\it linked program: \hfil}
2166 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2167 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2168 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2169 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2171 \line{\it addresses: \hfil}
2175 @c END TEXI2ROFF-KILL
2178 @section @value{AS} Internal Sections
2180 @cindex internal @code{@value{AS}} sections
2181 @cindex sections in messages, internal
2182 These sections are meant only for the internal use of @code{@value{AS}}. They
2183 have no meaning at run-time. You do not really need to know about these
2184 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2185 warning messages, so it might be helpful to have an idea of their
2186 meanings to @code{@value{AS}}. These sections are used to permit the
2187 value of every expression in your assembly language program to be a
2188 section-relative address.
2191 @cindex assembler internal logic error
2192 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2193 An internal assembler logic error has been found. This means there is a
2194 bug in the assembler.
2196 @cindex expr (internal section)
2198 The assembler stores complex expression internally as combinations of
2199 symbols. When it needs to represent an expression as a symbol, it puts
2200 it in the expr section.
2202 @c FIXME item transfer[t] vector preload
2203 @c FIXME item transfer[t] vector postload
2204 @c FIXME item register
2208 @section Sub-Sections
2210 @cindex numbered subsections
2211 @cindex grouping data
2217 fall into two sections: text and data.
2219 You may have separate groups of
2221 data in named sections
2225 data in named sections
2231 that you want to end up near to each other in the object file, even though they
2232 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2233 use @dfn{subsections} for this purpose. Within each section, there can be
2234 numbered subsections with values from 0 to 8192. Objects assembled into the
2235 same subsection go into the object file together with other objects in the same
2236 subsection. For example, a compiler might want to store constants in the text
2237 section, but might not want to have them interspersed with the program being
2238 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2239 section of code being output, and a @samp{.text 1} before each group of
2240 constants being output.
2242 Subsections are optional. If you do not use subsections, everything
2243 goes in subsection number zero.
2246 Each subsection is zero-padded up to a multiple of four bytes.
2247 (Subsections may be padded a different amount on different flavors
2248 of @code{@value{AS}}.)
2252 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2253 boundary (two bytes).
2254 The same is true on the Hitachi SH.
2257 @c FIXME section padding (alignment)?
2258 @c Rich Pixley says padding here depends on target obj code format; that
2259 @c doesn't seem particularly useful to say without further elaboration,
2260 @c so for now I say nothing about it. If this is a generic BFD issue,
2261 @c these paragraphs might need to vanish from this manual, and be
2262 @c discussed in BFD chapter of binutils (or some such).
2265 On the AMD 29K family, no particular padding is added to section or
2266 subsection sizes; @value{AS} forces no alignment on this platform.
2270 Subsections appear in your object file in numeric order, lowest numbered
2271 to highest. (All this to be compatible with other people's assemblers.)
2272 The object file contains no representation of subsections; @code{@value{LD}} and
2273 other programs that manipulate object files see no trace of them.
2274 They just see all your text subsections as a text section, and all your
2275 data subsections as a data section.
2277 To specify which subsection you want subsequent statements assembled
2278 into, use a numeric argument to specify it, in a @samp{.text
2279 @var{expression}} or a @samp{.data @var{expression}} statement.
2282 When generating COFF output, you
2287 can also use an extra subsection
2288 argument with arbitrary named sections: @samp{.section @var{name},
2291 @var{Expression} should be an absolute expression.
2292 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2293 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2294 begins in @code{text 0}. For instance:
2296 .text 0 # The default subsection is text 0 anyway.
2297 .ascii "This lives in the first text subsection. *"
2299 .ascii "But this lives in the second text subsection."
2301 .ascii "This lives in the data section,"
2302 .ascii "in the first data subsection."
2304 .ascii "This lives in the first text section,"
2305 .ascii "immediately following the asterisk (*)."
2308 Each section has a @dfn{location counter} incremented by one for every byte
2309 assembled into that section. Because subsections are merely a convenience
2310 restricted to @code{@value{AS}} there is no concept of a subsection location
2311 counter. There is no way to directly manipulate a location counter---but the
2312 @code{.align} directive changes it, and any label definition captures its
2313 current value. The location counter of the section where statements are being
2314 assembled is said to be the @dfn{active} location counter.
2317 @section bss Section
2320 @cindex common variable storage
2321 The bss section is used for local common variable storage.
2322 You may allocate address space in the bss section, but you may
2323 not dictate data to load into it before your program executes. When
2324 your program starts running, all the contents of the bss
2325 section are zeroed bytes.
2327 Addresses in the bss section are allocated with special directives; you
2328 may not assemble anything directly into the bss section. Hence there
2329 are no bss subsections. @xref{Comm,,@code{.comm}},
2330 @pxref{Lcomm,,@code{.lcomm}}.
2336 Symbols are a central concept: the programmer uses symbols to name
2337 things, the linker uses symbols to link, and the debugger uses symbols
2341 @cindex debuggers, and symbol order
2342 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2343 the same order they were declared. This may break some debuggers.
2348 * Setting Symbols:: Giving Symbols Other Values
2349 * Symbol Names:: Symbol Names
2350 * Dot:: The Special Dot Symbol
2351 * Symbol Attributes:: Symbol Attributes
2358 A @dfn{label} is written as a symbol immediately followed by a colon
2359 @samp{:}. The symbol then represents the current value of the
2360 active location counter, and is, for example, a suitable instruction
2361 operand. You are warned if you use the same symbol to represent two
2362 different locations: the first definition overrides any other
2366 On the HPPA, the usual form for a label need not be immediately followed by a
2367 colon, but instead must start in column zero. Only one label may be defined on
2368 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2369 provides a special directive @code{.label} for defining labels more flexibly.
2372 @node Setting Symbols
2373 @section Giving Symbols Other Values
2375 @cindex assigning values to symbols
2376 @cindex symbol values, assigning
2377 A symbol can be given an arbitrary value by writing a symbol, followed
2378 by an equals sign @samp{=}, followed by an expression
2379 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2380 directive. @xref{Set,,@code{.set}}.
2383 @section Symbol Names
2385 @cindex symbol names
2386 @cindex names, symbol
2387 @ifclear SPECIAL-SYMS
2388 Symbol names begin with a letter or with one of @samp{._}. On most
2389 machines, you can also use @code{$} in symbol names; exceptions are
2390 noted in @ref{Machine Dependencies}. That character may be followed by any
2391 string of digits, letters, dollar signs (unless otherwise noted in
2392 @ref{Machine Dependencies}), and underscores.
2395 For the AMD 29K family, @samp{?} is also allowed in the
2396 body of a symbol name, though not at its beginning.
2401 Symbol names begin with a letter or with one of @samp{._}. On the
2403 H8/500, you can also use @code{$} in symbol names. That character may
2404 be followed by any string of digits, letters, dollar signs (save on the
2405 H8/300), and underscores.
2409 Case of letters is significant: @code{foo} is a different symbol name
2412 Each symbol has exactly one name. Each name in an assembly language program
2413 refers to exactly one symbol. You may use that symbol name any number of times
2416 @subheading Local Symbol Names
2418 @cindex local symbol names
2419 @cindex symbol names, local
2420 @cindex temporary symbol names
2421 @cindex symbol names, temporary
2422 Local symbols help compilers and programmers use names temporarily.
2423 There are ten local symbol names, which are re-used throughout the
2424 program. You may refer to them using the names @samp{0} @samp{1}
2425 @dots{} @samp{9}. To define a local symbol, write a label of the form
2426 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2427 recent previous definition of that symbol write @samp{@b{N}b}, using the
2428 same digit as when you defined the label. To refer to the next
2429 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2430 a choice of 10 forward references. The @samp{b} stands for
2431 ``backwards'' and the @samp{f} stands for ``forwards''.
2433 Local symbols are not emitted by the current @sc{gnu} C compiler.
2435 There is no restriction on how you can use these labels, but
2436 remember that at any point in the assembly you can refer to at most
2437 10 prior local labels and to at most 10 forward local labels.
2439 Local symbol names are only a notation device. They are immediately
2440 transformed into more conventional symbol names before the assembler
2441 uses them. The symbol names stored in the symbol table, appearing in
2442 error messages and optionally emitted to the object file have these
2447 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2448 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2449 used for symbols you are never intended to see. If you use the
2450 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2451 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2452 you may use them in debugging.
2455 If the label is written @samp{0:} then the digit is @samp{0}.
2456 If the label is written @samp{1:} then the digit is @samp{1}.
2457 And so on up through @samp{9:}.
2460 This unusual character is included so you do not accidentally invent
2461 a symbol of the same name. The character has ASCII value
2464 @item @emph{ordinal number}
2465 This is a serial number to keep the labels distinct. The first
2466 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2467 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2471 For instance, the first @code{1:} is named @code{L1@ctrl{A}1}, the 44th
2472 @code{3:} is named @code{L3@ctrl{A}44}.
2475 @section The Special Dot Symbol
2477 @cindex dot (symbol)
2478 @cindex @code{.} (symbol)
2479 @cindex current address
2480 @cindex location counter
2481 The special symbol @samp{.} refers to the current address that
2482 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2483 .long .} defines @code{melvin} to contain its own address.
2484 Assigning a value to @code{.} is treated the same as a @code{.org}
2485 directive. Thus, the expression @samp{.=.+4} is the same as saying
2486 @ifclear no-space-dir
2495 @node Symbol Attributes
2496 @section Symbol Attributes
2498 @cindex symbol attributes
2499 @cindex attributes, symbol
2500 Every symbol has, as well as its name, the attributes ``Value'' and
2501 ``Type''. Depending on output format, symbols can also have auxiliary
2504 The detailed definitions are in @file{a.out.h}.
2507 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2508 all these attributes, and probably won't warn you. This makes the
2509 symbol an externally defined symbol, which is generally what you
2513 * Symbol Value:: Value
2514 * Symbol Type:: Type
2517 * a.out Symbols:: Symbol Attributes: @code{a.out}
2521 * a.out Symbols:: Symbol Attributes: @code{a.out}
2524 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2529 * COFF Symbols:: Symbol Attributes for COFF
2532 * SOM Symbols:: Symbol Attributes for SOM
2539 @cindex value of a symbol
2540 @cindex symbol value
2541 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2542 location in the text, data, bss or absolute sections the value is the
2543 number of addresses from the start of that section to the label.
2544 Naturally for text, data and bss sections the value of a symbol changes
2545 as @code{@value{LD}} changes section base addresses during linking. Absolute
2546 symbols' values do not change during linking: that is why they are
2549 The value of an undefined symbol is treated in a special way. If it is
2550 0 then the symbol is not defined in this assembler source file, and
2551 @code{@value{LD}} tries to determine its value from other files linked into the
2552 same program. You make this kind of symbol simply by mentioning a symbol
2553 name without defining it. A non-zero value represents a @code{.comm}
2554 common declaration. The value is how much common storage to reserve, in
2555 bytes (addresses). The symbol refers to the first address of the
2561 @cindex type of a symbol
2563 The type attribute of a symbol contains relocation (section)
2564 information, any flag settings indicating that a symbol is external, and
2565 (optionally), other information for linkers and debuggers. The exact
2566 format depends on the object-code output format in use.
2571 @c The following avoids a "widow" subsection title. @group would be
2572 @c better if it were available outside examples.
2575 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2577 @cindex @code{b.out} symbol attributes
2578 @cindex symbol attributes, @code{b.out}
2579 These symbol attributes appear only when @code{@value{AS}} is configured for
2580 one of the Berkeley-descended object output formats---@code{a.out} or
2586 @subsection Symbol Attributes: @code{a.out}
2588 @cindex @code{a.out} symbol attributes
2589 @cindex symbol attributes, @code{a.out}
2595 @subsection Symbol Attributes: @code{a.out}
2597 @cindex @code{a.out} symbol attributes
2598 @cindex symbol attributes, @code{a.out}
2602 * Symbol Desc:: Descriptor
2603 * Symbol Other:: Other
2607 @subsubsection Descriptor
2609 @cindex descriptor, of @code{a.out} symbol
2610 This is an arbitrary 16-bit value. You may establish a symbol's
2611 descriptor value by using a @code{.desc} statement
2612 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2616 @subsubsection Other
2618 @cindex other attribute, of @code{a.out} symbol
2619 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2624 @subsection Symbol Attributes for COFF
2626 @cindex COFF symbol attributes
2627 @cindex symbol attributes, COFF
2629 The COFF format supports a multitude of auxiliary symbol attributes;
2630 like the primary symbol attributes, they are set between @code{.def} and
2631 @code{.endef} directives.
2633 @subsubsection Primary Attributes
2635 @cindex primary attributes, COFF symbols
2636 The symbol name is set with @code{.def}; the value and type,
2637 respectively, with @code{.val} and @code{.type}.
2639 @subsubsection Auxiliary Attributes
2641 @cindex auxiliary attributes, COFF symbols
2642 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2643 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2644 information for COFF.
2649 @subsection Symbol Attributes for SOM
2651 @cindex SOM symbol attributes
2652 @cindex symbol attributes, SOM
2654 The SOM format for the HPPA supports a multitude of symbol attributes set with
2655 the @code{.EXPORT} and @code{.IMPORT} directives.
2657 The attributes are described in @cite{HP9000 Series 800 Assembly
2658 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2659 @code{EXPORT} assembler directive documentation.
2663 @chapter Expressions
2667 @cindex numeric values
2668 An @dfn{expression} specifies an address or numeric value.
2669 Whitespace may precede and/or follow an expression.
2671 The result of an expression must be an absolute number, or else an offset into
2672 a particular section. If an expression is not absolute, and there is not
2673 enough information when @code{@value{AS}} sees the expression to know its
2674 section, a second pass over the source program might be necessary to interpret
2675 the expression---but the second pass is currently not implemented.
2676 @code{@value{AS}} aborts with an error message in this situation.
2679 * Empty Exprs:: Empty Expressions
2680 * Integer Exprs:: Integer Expressions
2684 @section Empty Expressions
2686 @cindex empty expressions
2687 @cindex expressions, empty
2688 An empty expression has no value: it is just whitespace or null.
2689 Wherever an absolute expression is required, you may omit the
2690 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2691 is compatible with other assemblers.
2694 @section Integer Expressions
2696 @cindex integer expressions
2697 @cindex expressions, integer
2698 An @dfn{integer expression} is one or more @emph{arguments} delimited
2699 by @emph{operators}.
2702 * Arguments:: Arguments
2703 * Operators:: Operators
2704 * Prefix Ops:: Prefix Operators
2705 * Infix Ops:: Infix Operators
2709 @subsection Arguments
2711 @cindex expression arguments
2712 @cindex arguments in expressions
2713 @cindex operands in expressions
2714 @cindex arithmetic operands
2715 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2716 contexts arguments are sometimes called ``arithmetic operands''. In
2717 this manual, to avoid confusing them with the ``instruction operands'' of
2718 the machine language, we use the term ``argument'' to refer to parts of
2719 expressions only, reserving the word ``operand'' to refer only to machine
2720 instruction operands.
2722 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2723 @var{section} is one of text, data, bss, absolute,
2724 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2727 Numbers are usually integers.
2729 A number can be a flonum or bignum. In this case, you are warned
2730 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2731 these 32 bits are an integer. You may write integer-manipulating
2732 instructions that act on exotic constants, compatible with other
2735 @cindex subexpressions
2736 Subexpressions are a left parenthesis @samp{(} followed by an integer
2737 expression, followed by a right parenthesis @samp{)}; or a prefix
2738 operator followed by an argument.
2741 @subsection Operators
2743 @cindex operators, in expressions
2744 @cindex arithmetic functions
2745 @cindex functions, in expressions
2746 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2747 operators are followed by an argument. Infix operators appear
2748 between their arguments. Operators may be preceded and/or followed by
2752 @subsection Prefix Operator
2754 @cindex prefix operators
2755 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2756 one argument, which must be absolute.
2758 @c the tex/end tex stuff surrounding this small table is meant to make
2759 @c it align, on the printed page, with the similar table in the next
2760 @c section (which is inside an enumerate).
2762 \global\advance\leftskip by \itemindent
2767 @dfn{Negation}. Two's complement negation.
2769 @dfn{Complementation}. Bitwise not.
2773 \global\advance\leftskip by -\itemindent
2777 @subsection Infix Operators
2779 @cindex infix operators
2780 @cindex operators, permitted arguments
2781 @dfn{Infix operators} take two arguments, one on either side. Operators
2782 have precedence, but operations with equal precedence are performed left
2783 to right. Apart from @code{+} or @code{-}, both arguments must be
2784 absolute, and the result is absolute.
2787 @cindex operator precedence
2788 @cindex precedence of operators
2795 @dfn{Multiplication}.
2798 @dfn{Division}. Truncation is the same as the C operator @samp{/}
2805 @dfn{Shift Left}. Same as the C operator @samp{<<}.
2809 @dfn{Shift Right}. Same as the C operator @samp{>>}.
2813 Intermediate precedence
2818 @dfn{Bitwise Inclusive Or}.
2824 @dfn{Bitwise Exclusive Or}.
2827 @dfn{Bitwise Or Not}.
2834 @cindex addition, permitted arguments
2835 @cindex plus, permitted arguments
2836 @cindex arguments for addition
2838 @dfn{Addition}. If either argument is absolute, the result has the section of
2839 the other argument. You may not add together arguments from different
2842 @cindex subtraction, permitted arguments
2843 @cindex minus, permitted arguments
2844 @cindex arguments for subtraction
2846 @dfn{Subtraction}. If the right argument is absolute, the
2847 result has the section of the left argument.
2848 If both arguments are in the same section, the result is absolute.
2849 You may not subtract arguments from different sections.
2850 @c FIXME is there still something useful to say about undefined - undefined ?
2854 In short, it's only meaningful to add or subtract the @emph{offsets} in an
2855 address; you can only have a defined section in one of the two arguments.
2858 @chapter Assembler Directives
2860 @cindex directives, machine independent
2861 @cindex pseudo-ops, machine independent
2862 @cindex machine independent directives
2863 All assembler directives have names that begin with a period (@samp{.}).
2864 The rest of the name is letters, usually in lower case.
2866 This chapter discusses directives that are available regardless of the
2867 target machine configuration for the @sc{gnu} assembler.
2869 Some machine configurations provide additional directives.
2870 @xref{Machine Dependencies}.
2873 @ifset machine-directives
2874 @xref{Machine Dependencies} for additional directives.
2879 * Abort:: @code{.abort}
2881 * ABORT:: @code{.ABORT}
2884 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
2885 * App-File:: @code{.app-file @var{string}}
2886 * Ascii:: @code{.ascii "@var{string}"}@dots{}
2887 * Asciz:: @code{.asciz "@var{string}"}@dots{}
2888 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
2889 * Byte:: @code{.byte @var{expressions}}
2890 * Comm:: @code{.comm @var{symbol} , @var{length} }
2891 * Data:: @code{.data @var{subsection}}
2893 * Def:: @code{.def @var{name}}
2896 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
2902 * Double:: @code{.double @var{flonums}}
2903 * Eject:: @code{.eject}
2904 * Else:: @code{.else}
2906 * Endef:: @code{.endef}
2909 * Endif:: @code{.endif}
2910 * Equ:: @code{.equ @var{symbol}, @var{expression}}
2911 * Extern:: @code{.extern}
2912 @ifclear no-file-dir
2913 * File:: @code{.file @var{string}}
2916 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
2917 * Float:: @code{.float @var{flonums}}
2918 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
2919 * hword:: @code{.hword @var{expressions}}
2920 * Ident:: @code{.ident}
2921 * If:: @code{.if @var{absolute expression}}
2922 * Include:: @code{.include "@var{file}"}
2923 * Int:: @code{.int @var{expressions}}
2924 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
2925 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
2926 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
2927 * Lflags:: @code{.lflags}
2928 @ifclear no-line-dir
2929 * Line:: @code{.line @var{line-number}}
2932 * Ln:: @code{.ln @var{line-number}}
2933 * Linkonce:: @code{.linkonce [@var{type}]}
2934 * List:: @code{.list}
2935 * Long:: @code{.long @var{expressions}}
2937 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
2940 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
2941 * MRI:: @code{.mri @var{val}}
2943 * Nolist:: @code{.nolist}
2944 * Octa:: @code{.octa @var{bignums}}
2945 * Org:: @code{.org @var{new-lc} , @var{fill}}
2946 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
2947 * Psize:: @code{.psize @var{lines}, @var{columns}}
2948 * Quad:: @code{.quad @var{bignums}}
2949 * Rept:: @code{.rept @var{count}}
2950 * Sbttl:: @code{.sbttl "@var{subheading}"}
2952 * Scl:: @code{.scl @var{class}}
2955 * Section:: @code{.section @var{name}, @var{subsection}}
2958 * Set:: @code{.set @var{symbol}, @var{expression}}
2959 * Short:: @code{.short @var{expressions}}
2960 * Single:: @code{.single @var{flonums}}
2962 * Size:: @code{.size}
2965 * Skip:: @code{.skip @var{size} , @var{fill}}
2966 * Space:: @code{.space @var{size} , @var{fill}}
2968 * Stab:: @code{.stabd, .stabn, .stabs}
2971 * String:: @code{.string "@var{str}"}
2973 * Tag:: @code{.tag @var{structname}}
2976 * Text:: @code{.text @var{subsection}}
2977 * Title:: @code{.title "@var{heading}"}
2979 * Type:: @code{.type @var{int}}
2980 * Val:: @code{.val @var{addr}}
2983 * Word:: @code{.word @var{expressions}}
2984 * Deprecated:: Deprecated Directives
2988 @section @code{.abort}
2990 @cindex @code{abort} directive
2991 @cindex stopping the assembly
2992 This directive stops the assembly immediately. It is for
2993 compatibility with other assemblers. The original idea was that the
2994 assembly language source would be piped into the assembler. If the sender
2995 of the source quit, it could use this directive tells @code{@value{AS}} to
2996 quit also. One day @code{.abort} will not be supported.
3000 @section @code{.ABORT}
3002 @cindex @code{ABORT} directive
3003 When producing COFF output, @code{@value{AS}} accepts this directive as a
3004 synonym for @samp{.abort}.
3007 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3013 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3015 @cindex padding the location counter
3016 @cindex @code{align} directive
3017 Pad the location counter (in the current subsection) to a particular storage
3018 boundary. The first expression (which must be absolute) is the alignment
3019 required, as described below.
3021 The second expression (also absolute) gives the fill value to be stored in the
3022 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3023 padding bytes are normally zero. However, on some systems, if the section is
3024 marked as containing code and the fill value is omitted, the space is filled
3025 with no-op instructions.
3027 The third expression is also absolute, and is also optional. If it is present,
3028 it is the maximum number of bytes that should be skipped by this alignment
3029 directive. If doing the alignment would require skipping more bytes than the
3030 specified maximum, then the alignment is not done at all. You can omit the
3031 fill value (the second argument) entirely by simply using two commas after the
3032 required alignment; this can be useful if you want the alignment to be filled
3033 with no-op instructions when appropriate.
3035 The way the required alignment is specified varies from system to system.
3036 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3038 the first expression is the
3039 alignment request in bytes. For example @samp{.align 8} advances
3040 the location counter until it is a multiple of 8. If the location counter
3041 is already a multiple of 8, no change is needed.
3043 For other systems, including the i386 using a.out format, it is the
3044 number of low-order zero bits the location counter must have after
3045 advancement. For example @samp{.align 3} advances the location
3046 counter until it a multiple of 8. If the location counter is already a
3047 multiple of 8, no change is needed.
3049 This inconsistency is due to the different behaviors of the various
3050 native assemblers for these systems which GAS must emulate.
3051 GAS also provides @code{.balign} and @code{.p2align} directives,
3052 described later, which have a consistent behavior across all
3053 architectures (but are specific to GAS).
3056 @section @code{.app-file @var{string}}
3058 @cindex logical file name
3059 @cindex file name, logical
3060 @cindex @code{app-file} directive
3062 @ifclear no-file-dir
3063 (which may also be spelled @samp{.file})
3065 tells @code{@value{AS}} that we are about to start a new
3066 logical file. @var{string} is the new file name. In general, the
3067 filename is recognized whether or not it is surrounded by quotes @samp{"};
3068 but if you wish to specify an empty file name is permitted,
3069 you must give the quotes--@code{""}. This statement may go away in
3070 future: it is only recognized to be compatible with old @code{@value{AS}}
3074 @section @code{.ascii "@var{string}"}@dots{}
3076 @cindex @code{ascii} directive
3077 @cindex string literals
3078 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3079 separated by commas. It assembles each string (with no automatic
3080 trailing zero byte) into consecutive addresses.
3083 @section @code{.asciz "@var{string}"}@dots{}
3085 @cindex @code{asciz} directive
3086 @cindex zero-terminated strings
3087 @cindex null-terminated strings
3088 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3089 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3092 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3094 @cindex padding the location counter given number of bytes
3095 @cindex @code{balign} directive
3096 Pad the location counter (in the current subsection) to a particular
3097 storage boundary. The first expression (which must be absolute) is the
3098 alignment request in bytes. For example @samp{.balign 8} advances
3099 the location counter until it is a multiple of 8. If the location counter
3100 is already a multiple of 8, no change is needed.
3102 The second expression (also absolute) gives the fill value to be stored in the
3103 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3104 padding bytes are normally zero. However, on some systems, if the section is
3105 marked as containing code and the fill value is omitted, the space is filled
3106 with no-op instructions.
3108 The third expression is also absolute, and is also optional. If it is present,
3109 it is the maximum number of bytes that should be skipped by this alignment
3110 directive. If doing the alignment would require skipping more bytes than the
3111 specified maximum, then the alignment is not done at all. You can omit the
3112 fill value (the second argument) entirely by simply using two commas after the
3113 required alignment; this can be useful if you want the alignment to be filled
3114 with no-op instructions when appropriate.
3116 @cindex @code{balignw} directive
3117 @cindex @code{balignl} directive
3118 The @code{.balignw} and @code{.balignl} directives are variants of the
3119 @code{.balign} directive. The @code{.balignw} directive treats the fill
3120 pattern as a two byte word value. The @code{.balignl} directives treats the
3121 fill pattern as a four byte longword value. For example, @code{.balignw
3122 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3123 filled in with the value 0x368d (the exact placement of the bytes depends upon
3124 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3128 @section @code{.byte @var{expressions}}
3130 @cindex @code{byte} directive
3131 @cindex integers, one byte
3132 @code{.byte} expects zero or more expressions, separated by commas.
3133 Each expression is assembled into the next byte.
3136 @section @code{.comm @var{symbol} , @var{length} }
3138 @cindex @code{comm} directive
3139 @cindex symbol, common
3140 @code{.comm} declares a named common area in the bss section. Normally
3141 @code{@value{LD}} reserves memory addresses for it during linking, so no partial
3142 program defines the location of the symbol. Use @code{.comm} to tell
3143 @code{@value{LD}} that it must be at least @var{length} bytes long. @code{@value{LD}}
3144 allocates space for each @code{.comm} symbol that is at least as
3145 long as the longest @code{.comm} request in any of the partial programs
3146 linked. @var{length} is an absolute expression.
3149 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3150 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3154 @section @code{.data @var{subsection}}
3156 @cindex @code{data} directive
3157 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3158 end of the data subsection numbered @var{subsection} (which is an
3159 absolute expression). If @var{subsection} is omitted, it defaults
3164 @section @code{.def @var{name}}
3166 @cindex @code{def} directive
3167 @cindex COFF symbols, debugging
3168 @cindex debugging COFF symbols
3169 Begin defining debugging information for a symbol @var{name}; the
3170 definition extends until the @code{.endef} directive is encountered.
3173 This directive is only observed when @code{@value{AS}} is configured for COFF
3174 format output; when producing @code{b.out}, @samp{.def} is recognized,
3181 @section @code{.desc @var{symbol}, @var{abs-expression}}
3183 @cindex @code{desc} directive
3184 @cindex COFF symbol descriptor
3185 @cindex symbol descriptor, COFF
3186 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3187 to the low 16 bits of an absolute expression.
3190 The @samp{.desc} directive is not available when @code{@value{AS}} is
3191 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3192 object format. For the sake of compatibility, @code{@value{AS}} accepts
3193 it, but produces no output, when configured for COFF.
3199 @section @code{.dim}
3201 @cindex @code{dim} directive
3202 @cindex COFF auxiliary symbol information
3203 @cindex auxiliary symbol information, COFF
3204 This directive is generated by compilers to include auxiliary debugging
3205 information in the symbol table. It is only permitted inside
3206 @code{.def}/@code{.endef} pairs.
3209 @samp{.dim} is only meaningful when generating COFF format output; when
3210 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3216 @section @code{.double @var{flonums}}
3218 @cindex @code{double} directive
3219 @cindex floating point numbers (double)
3220 @code{.double} expects zero or more flonums, separated by commas. It
3221 assembles floating point numbers.
3223 The exact kind of floating point numbers emitted depends on how
3224 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3228 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3229 in @sc{ieee} format.
3234 @section @code{.eject}
3236 @cindex @code{eject} directive
3237 @cindex new page, in listings
3238 @cindex page, in listings
3239 @cindex listing control: new page
3240 Force a page break at this point, when generating assembly listings.
3243 @section @code{.else}
3245 @cindex @code{else} directive
3246 @code{.else} is part of the @code{@value{AS}} support for conditional
3247 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3248 of code to be assembled if the condition for the preceding @code{.if}
3252 @node End, Endef, Else, Pseudo Ops
3253 @section @code{.end}
3255 @cindex @code{end} directive
3256 This doesn't do anything---but isn't an s_ignore, so I suspect it's
3257 meant to do something eventually (which is why it isn't documented here
3258 as "for compatibility with blah").
3263 @section @code{.endef}
3265 @cindex @code{endef} directive
3266 This directive flags the end of a symbol definition begun with
3270 @samp{.endef} is only meaningful when generating COFF format output; if
3271 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3272 directive but ignores it.
3277 @section @code{.endif}
3279 @cindex @code{endif} directive
3280 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3281 it marks the end of a block of code that is only assembled
3282 conditionally. @xref{If,,@code{.if}}.
3285 @section @code{.equ @var{symbol}, @var{expression}}
3287 @cindex @code{equ} directive
3288 @cindex assigning values to symbols
3289 @cindex symbols, assigning values to
3290 This directive sets the value of @var{symbol} to @var{expression}.
3291 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3294 The syntax for @code{equ} on the HPPA is
3295 @samp{@var{symbol} .equ @var{expression}}.
3299 @section @code{.extern}
3301 @cindex @code{extern} directive
3302 @code{.extern} is accepted in the source program---for compatibility
3303 with other assemblers---but it is ignored. @code{@value{AS}} treats
3304 all undefined symbols as external.
3306 @ifclear no-file-dir
3308 @section @code{.file @var{string}}
3310 @cindex @code{file} directive
3311 @cindex logical file name
3312 @cindex file name, logical
3313 @code{.file} (which may also be spelled @samp{.app-file}) tells
3314 @code{@value{AS}} that we are about to start a new logical file.
3315 @var{string} is the new file name. In general, the filename is
3316 recognized whether or not it is surrounded by quotes @samp{"}; but if
3317 you wish to specify an empty file name, you must give the
3318 quotes--@code{""}. This statement may go away in future: it is only
3319 recognized to be compatible with old @code{@value{AS}} programs.
3321 In some configurations of @code{@value{AS}}, @code{.file} has already been
3322 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3327 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3329 @cindex @code{fill} directive
3330 @cindex writing patterns in memory
3331 @cindex patterns, writing in memory
3332 @var{result}, @var{size} and @var{value} are absolute expressions.
3333 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3334 may be zero or more. @var{Size} may be zero or more, but if it is
3335 more than 8, then it is deemed to have the value 8, compatible with
3336 other people's assemblers. The contents of each @var{repeat} bytes
3337 is taken from an 8-byte number. The highest order 4 bytes are
3338 zero. The lowest order 4 bytes are @var{value} rendered in the
3339 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3340 Each @var{size} bytes in a repetition is taken from the lowest order
3341 @var{size} bytes of this number. Again, this bizarre behavior is
3342 compatible with other people's assemblers.
3344 @var{size} and @var{value} are optional.
3345 If the second comma and @var{value} are absent, @var{value} is
3346 assumed zero. If the first comma and following tokens are absent,
3347 @var{size} is assumed to be 1.
3350 @section @code{.float @var{flonums}}
3352 @cindex floating point numbers (single)
3353 @cindex @code{float} directive
3354 This directive assembles zero or more flonums, separated by commas. It
3355 has the same effect as @code{.single}.
3357 The exact kind of floating point numbers emitted depends on how
3358 @code{@value{AS}} is configured.
3359 @xref{Machine Dependencies}.
3363 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3364 in @sc{ieee} format.
3369 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3371 @cindex @code{global} directive
3372 @cindex symbol, making visible to linker
3373 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3374 @var{symbol} in your partial program, its value is made available to
3375 other partial programs that are linked with it. Otherwise,
3376 @var{symbol} takes its attributes from a symbol of the same name
3377 from another file linked into the same program.
3379 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3380 compatibility with other assemblers.
3383 On the HPPA, @code{.global} is not always enough to make it accessible to other
3384 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3385 @xref{HPPA Directives,, HPPA Assembler Directives}.
3389 @section @code{.hword @var{expressions}}
3391 @cindex @code{hword} directive
3392 @cindex integers, 16-bit
3393 @cindex numbers, 16-bit
3394 @cindex sixteen bit integers
3395 This expects zero or more @var{expressions}, and emits
3396 a 16 bit number for each.
3399 This directive is a synonym for @samp{.short}; depending on the target
3400 architecture, it may also be a synonym for @samp{.word}.
3404 This directive is a synonym for @samp{.short}.
3407 This directive is a synonym for both @samp{.short} and @samp{.word}.
3412 @section @code{.ident}
3414 @cindex @code{ident} directive
3415 This directive is used by some assemblers to place tags in object files.
3416 @code{@value{AS}} simply accepts the directive for source-file
3417 compatibility with such assemblers, but does not actually emit anything
3421 @section @code{.if @var{absolute expression}}
3423 @cindex conditional assembly
3424 @cindex @code{if} directive
3425 @code{.if} marks the beginning of a section of code which is only
3426 considered part of the source program being assembled if the argument
3427 (which must be an @var{absolute expression}) is non-zero. The end of
3428 the conditional section of code must be marked by @code{.endif}
3429 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3430 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3432 The following variants of @code{.if} are also supported:
3434 @cindex @code{ifdef} directive
3435 @item .ifdef @var{symbol}
3436 Assembles the following section of code if the specified @var{symbol}
3440 @cindex @code{ifeqs} directive
3442 Not yet implemented.
3445 @cindex @code{ifndef} directive
3446 @cindex @code{ifnotdef} directive
3447 @item .ifndef @var{symbol}
3448 @itemx .ifnotdef @var{symbol}
3449 Assembles the following section of code if the specified @var{symbol}
3450 has not been defined. Both spelling variants are equivalent.
3454 Not yet implemented.
3459 @section @code{.include "@var{file}"}
3461 @cindex @code{include} directive
3462 @cindex supporting files, including
3463 @cindex files, including
3464 This directive provides a way to include supporting files at specified
3465 points in your source program. The code from @var{file} is assembled as
3466 if it followed the point of the @code{.include}; when the end of the
3467 included file is reached, assembly of the original file continues. You
3468 can control the search paths used with the @samp{-I} command-line option
3469 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3473 @section @code{.int @var{expressions}}
3475 @cindex @code{int} directive
3476 @cindex integers, 32-bit
3477 Expect zero or more @var{expressions}, of any section, separated by commas.
3478 For each expression, emit a number that, at run time, is the value of that
3479 expression. The byte order and bit size of the number depends on what kind
3480 of target the assembly is for.
3484 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3485 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3491 @section @code{.irp @var{symbol},@var{values}}@dots{}
3493 @cindex @code{irp} directive
3494 Evaluate a sequence of statements assigning different values to @var{symbol}.
3495 The sequence of statements starts at the @code{.irp} directive, and is
3496 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3497 set to @var{value}, and the sequence of statements is assembled. If no
3498 @var{value} is listed, the sequence of statements is assembled once, with
3499 @var{symbol} set to the null string. To refer to @var{symbol} within the
3500 sequence of statements, use @var{\symbol}.
3502 For example, assembling
3510 is equivalent to assembling
3519 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3521 @cindex @code{irpc} directive
3522 Evaluate a sequence of statements assigning different values to @var{symbol}.
3523 The sequence of statements starts at the @code{.irpc} directive, and is
3524 terminated by an @code{.endr} directive. For each character in @var{value},
3525 @var{symbol} is set to the character, and the sequence of statements is
3526 assembled. If no @var{value} is listed, the sequence of statements is
3527 assembled once, with @var{symbol} set to the null string. To refer to
3528 @var{symbol} within the sequence of statements, use @var{\symbol}.
3530 For example, assembling
3538 is equivalent to assembling
3547 @section @code{.lcomm @var{symbol} , @var{length}}
3549 @cindex @code{lcomm} directive
3550 @cindex local common symbols
3551 @cindex symbols, local common
3552 Reserve @var{length} (an absolute expression) bytes for a local common
3553 denoted by @var{symbol}. The section and value of @var{symbol} are
3554 those of the new local common. The addresses are allocated in the bss
3555 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3556 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3557 not visible to @code{@value{LD}}.
3560 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3561 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3565 @section @code{.lflags}
3567 @cindex @code{lflags} directive (ignored)
3568 @code{@value{AS}} accepts this directive, for compatibility with other
3569 assemblers, but ignores it.
3571 @ifclear no-line-dir
3573 @section @code{.line @var{line-number}}
3575 @cindex @code{line} directive
3579 @section @code{.ln @var{line-number}}
3581 @cindex @code{ln} directive
3583 @cindex logical line number
3585 Change the logical line number. @var{line-number} must be an absolute
3586 expression. The next line has that logical line number. Therefore any other
3587 statements on the current line (after a statement separator character) are
3588 reported as on logical line number @var{line-number} @minus{} 1. One day
3589 @code{@value{AS}} will no longer support this directive: it is recognized only
3590 for compatibility with existing assembler programs.
3594 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3595 not available; use the synonym @code{.ln} in that context.
3600 @ifclear no-line-dir
3601 Even though this is a directive associated with the @code{a.out} or
3602 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3603 when producing COFF output, and treats @samp{.line} as though it
3604 were the COFF @samp{.ln} @emph{if} it is found outside a
3605 @code{.def}/@code{.endef} pair.
3607 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3608 used by compilers to generate auxiliary symbol information for
3613 @section @code{.linkonce [@var{type}]}
3615 @cindex @code{linkonce} directive
3616 @cindex common sections
3617 Mark the current section so that the linker only includes a single copy of it.
3618 This may be used to include the same section in several different object files,
3619 but ensure that the linker will only include it once in the final output file.
3620 The @code{.linkonce} pseudo-op must be used for each instance of the section.
3621 Duplicate sections are detected based on the section name, so it should be
3624 This directive is only supported by a few object file formats; as of this
3625 writing, the only object file format which supports it is the Portable
3626 Executable format used on Windows NT.
3628 The @var{type} argument is optional. If specified, it must be one of the
3629 following strings. For example:
3633 Not all types may be supported on all object file formats.
3637 Silently discard duplicate sections. This is the default.
3640 Warn if there are duplicate sections, but still keep only one copy.
3643 Warn if any of the duplicates have different sizes.
3646 Warn if any of the duplicates do not have exactly the same contents.
3650 @section @code{.ln @var{line-number}}
3652 @cindex @code{ln} directive
3653 @ifclear no-line-dir
3654 @samp{.ln} is a synonym for @samp{.line}.
3657 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
3658 must be an absolute expression. The next line has that logical
3659 line number, so any other statements on the current line (after a
3660 statement separator character @code{;}) are reported as on logical
3661 line number @var{line-number} @minus{} 1.
3664 This directive is accepted, but ignored, when @code{@value{AS}} is
3665 configured for @code{b.out}; its effect is only associated with COFF
3671 @section @code{.mri @var{val}}
3673 @cindex @code{mri} directive
3674 @cindex MRI mode, temporarily
3675 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
3676 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
3677 affects code assembled until the next @code{.mri} directive, or until the end
3678 of the file. @xref{M, MRI mode, MRI mode}.
3681 @section @code{.list}
3683 @cindex @code{list} directive
3684 @cindex listing control, turning on
3685 Control (in conjunction with the @code{.nolist} directive) whether or
3686 not assembly listings are generated. These two directives maintain an
3687 internal counter (which is zero initially). @code{.list} increments the
3688 counter, and @code{.nolist} decrements it. Assembly listings are
3689 generated whenever the counter is greater than zero.
3691 By default, listings are disabled. When you enable them (with the
3692 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
3693 the initial value of the listing counter is one.
3696 @section @code{.long @var{expressions}}
3698 @cindex @code{long} directive
3699 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
3702 @c no one seems to know what this is for or whether this description is
3703 @c what it really ought to do
3705 @section @code{.lsym @var{symbol}, @var{expression}}
3707 @cindex @code{lsym} directive
3708 @cindex symbol, not referenced in assembly
3709 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
3710 the hash table, ensuring it cannot be referenced by name during the
3711 rest of the assembly. This sets the attributes of the symbol to be
3712 the same as the expression value:
3714 @var{other} = @var{descriptor} = 0
3715 @var{type} = @r{(section of @var{expression})}
3716 @var{value} = @var{expression}
3719 The new symbol is not flagged as external.
3723 @section @code{.macro}
3726 The commands @code{.macro} and @code{.endm} allow you to define macros that
3727 generate assembly output. For example, this definition specifies a macro
3728 @code{sum} that puts a sequence of numbers into memory:
3731 .macro sum from=0, to=5
3740 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
3752 @item .macro @var{macname}
3753 @itemx .macro @var{macname} @var{macargs} @dots{}
3754 @cindex @code{macro} directive
3755 Begin the definition of a macro called @var{macname}. If your macro
3756 definition requires arguments, specify their names after the macro name,
3757 separated by commas or spaces. You can supply a default value for any
3758 macro argument by following the name with @samp{=@var{deflt}}. For
3759 example, these are all valid @code{.macro} statements:
3763 Begin the definition of a macro called @code{comm}, which takes no
3766 @item .macro plus1 p, p1
3767 @itemx .macro plus1 p p1
3768 Either statement begins the definition of a macro called @code{plus1},
3769 which takes two arguments; within the macro definition, write
3770 @samp{\p} or @samp{\p1} to evaluate the arguments.
3772 @item .macro reserve_str p1=0 p2
3773 Begin the definition of a macro called @code{reserve_str}, with two
3774 arguments. The first argument has a default value, but not the second.
3775 After the definition is complete, you can call the macro either as
3776 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
3777 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
3778 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
3779 @samp{0}, and @samp{\p2} evaluating to @var{b}).
3782 When you call a macro, you can specify the argument values either by
3783 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
3784 @samp{sum to=17, from=9}.
3787 @cindex @code{endm} directive
3788 Mark the end of a macro definition.
3791 @cindex @code{exitm} directive
3792 Exit early from the current macro definition.
3794 @cindex number of macros executed
3795 @cindex macros, count executed
3797 @code{@value{AS}} maintains a counter of how many macros it has
3798 executed in this pseudo-variable; you can copy that number to your
3799 output with @samp{\@@}, but @emph{only within a macro definition}.
3802 @item LOCAL @var{name} [ , @dots{} ]
3803 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
3804 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
3805 Alternate macro syntax}.
3807 Generate a string replacement for each of the @var{name} arguments, and
3808 replace any instances of @var{name} in each macro expansion. The
3809 replacement string is unique in the assembly, and different for each
3810 separate macro expansion. @code{LOCAL} allows you to write macros that
3811 define symbols, without fear of conflict between separate macro expansions.
3816 @section @code{.nolist}
3818 @cindex @code{nolist} directive
3819 @cindex listing control, turning off
3820 Control (in conjunction with the @code{.list} directive) whether or
3821 not assembly listings are generated. These two directives maintain an
3822 internal counter (which is zero initially). @code{.list} increments the
3823 counter, and @code{.nolist} decrements it. Assembly listings are
3824 generated whenever the counter is greater than zero.
3827 @section @code{.octa @var{bignums}}
3829 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
3830 @cindex @code{octa} directive
3831 @cindex integer, 16-byte
3832 @cindex sixteen byte integer
3833 This directive expects zero or more bignums, separated by commas. For each
3834 bignum, it emits a 16-byte integer.
3836 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
3837 hence @emph{octa}-word for 16 bytes.
3840 @section @code{.org @var{new-lc} , @var{fill}}
3842 @cindex @code{org} directive
3843 @cindex location counter, advancing
3844 @cindex advancing location counter
3845 @cindex current address, advancing
3846 Advance the location counter of the current section to
3847 @var{new-lc}. @var{new-lc} is either an absolute expression or an
3848 expression with the same section as the current subsection. That is,
3849 you can't use @code{.org} to cross sections: if @var{new-lc} has the
3850 wrong section, the @code{.org} directive is ignored. To be compatible
3851 with former assemblers, if the section of @var{new-lc} is absolute,
3852 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
3853 is the same as the current subsection.
3855 @code{.org} may only increase the location counter, or leave it
3856 unchanged; you cannot use @code{.org} to move the location counter
3859 @c double negative used below "not undefined" because this is a specific
3860 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
3861 @c section. doc@cygnus.com 18feb91
3862 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
3863 may not be undefined. If you really detest this restriction we eagerly await
3864 a chance to share your improved assembler.
3866 Beware that the origin is relative to the start of the section, not
3867 to the start of the subsection. This is compatible with other
3868 people's assemblers.
3870 When the location counter (of the current subsection) is advanced, the
3871 intervening bytes are filled with @var{fill} which should be an
3872 absolute expression. If the comma and @var{fill} are omitted,
3873 @var{fill} defaults to zero.
3876 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3878 @cindex padding the location counter given a power of two
3879 @cindex @code{p2align} directive
3880 Pad the location counter (in the current subsection) to a particular
3881 storage boundary. The first expression (which must be absolute) is the
3882 number of low-order zero bits the location counter must have after
3883 advancement. For example @samp{.p2align 3} advances the location
3884 counter until it a multiple of 8. If the location counter is already a
3885 multiple of 8, no change is needed.
3887 The second expression (also absolute) gives the fill value to be stored in the
3888 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3889 padding bytes are normally zero. However, on some systems, if the section is
3890 marked as containing code and the fill value is omitted, the space is filled
3891 with no-op instructions.
3893 The third expression is also absolute, and is also optional. If it is present,
3894 it is the maximum number of bytes that should be skipped by this alignment
3895 directive. If doing the alignment would require skipping more bytes than the
3896 specified maximum, then the alignment is not done at all. You can omit the
3897 fill value (the second argument) entirely by simply using two commas after the
3898 required alignment; this can be useful if you want the alignment to be filled
3899 with no-op instructions when appropriate.
3901 @cindex @code{p2alignw} directive
3902 @cindex @code{p2alignl} directive
3903 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
3904 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
3905 pattern as a two byte word value. The @code{.p2alignl} directives treats the
3906 fill pattern as a four byte longword value. For example, @code{.p2alignw
3907 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3908 filled in with the value 0x368d (the exact placement of the bytes depends upon
3909 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3913 @section @code{.psize @var{lines} , @var{columns}}
3915 @cindex @code{psize} directive
3916 @cindex listing control: paper size
3917 @cindex paper size, for listings
3918 Use this directive to declare the number of lines---and, optionally, the
3919 number of columns---to use for each page, when generating listings.
3921 If you do not use @code{.psize}, listings use a default line-count
3922 of 60. You may omit the comma and @var{columns} specification; the
3923 default width is 200 columns.
3925 @code{@value{AS}} generates formfeeds whenever the specified number of
3926 lines is exceeded (or whenever you explicitly request one, using
3929 If you specify @var{lines} as @code{0}, no formfeeds are generated save
3930 those explicitly specified with @code{.eject}.
3933 @section @code{.quad @var{bignums}}
3935 @cindex @code{quad} directive
3936 @code{.quad} expects zero or more bignums, separated by commas. For
3937 each bignum, it emits
3939 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
3940 warning message; and just takes the lowest order 8 bytes of the bignum.
3941 @cindex eight-byte integer
3942 @cindex integer, 8-byte
3944 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
3945 hence @emph{quad}-word for 8 bytes.
3948 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
3949 warning message; and just takes the lowest order 16 bytes of the bignum.
3950 @cindex sixteen-byte integer
3951 @cindex integer, 16-byte
3955 @section @code{.rept @var{count}}
3957 @cindex @code{rept} directive
3958 Repeat the sequence of lines between the @code{.rept} directive and the next
3959 @code{.endr} directive @var{count} times.
3961 For example, assembling
3969 is equivalent to assembling
3978 @section @code{.sbttl "@var{subheading}"}
3980 @cindex @code{sbttl} directive
3981 @cindex subtitles for listings
3982 @cindex listing control: subtitle
3983 Use @var{subheading} as the title (third line, immediately after the
3984 title line) when generating assembly listings.
3986 This directive affects subsequent pages, as well as the current page if
3987 it appears within ten lines of the top of a page.
3991 @section @code{.scl @var{class}}
3993 @cindex @code{scl} directive
3994 @cindex symbol storage class (COFF)
3995 @cindex COFF symbol storage class
3996 Set the storage-class value for a symbol. This directive may only be
3997 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
3998 whether a symbol is static or external, or it may record further
3999 symbolic debugging information.
4002 The @samp{.scl} directive is primarily associated with COFF output; when
4003 configured to generate @code{b.out} output format, @code{@value{AS}}
4004 accepts this directive but ignores it.
4009 @section @code{.section @var{name}}
4011 @cindex @code{section} directive
4012 @cindex named section
4013 Use the @code{.section} directive to assemble the following code into a section
4016 This directive is only supported for targets that actually support arbitrarily
4017 named sections; on @code{a.out} targets, for example, it is not accepted, even
4018 with a standard @code{a.out} section name.
4021 For COFF targets, the @code{.section} directive is used in one of the following
4024 .section @var{name}[, "@var{flags}"]
4025 .section @var{name}[, @var{subsegment}]
4028 If the optional argument is quoted, it is taken as flags to use for the
4029 section. Each flag is a single character. The following flags are recognized:
4032 bss section (uninitialized data)
4034 section is not loaded
4043 If no flags are specified, the default flags depend upon the section name. If
4044 the section name is not recognized, the default will be for the section to be
4045 loaded and writable.
4047 If the optional argument to the @code{.section} directive is not quoted, it is
4048 taken as a subsegment number (@pxref{Sub-Sections}).
4052 For ELF targets, the @code{.section} directive is used like this:
4054 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4056 The optional @var{flags} argument is a quoted string which may contain any
4057 combintion of the following characters:
4060 section is allocatable
4064 section is executable
4067 The optional @var{type} argument may contain one of the following constants:
4070 section contains data
4072 section does not contain data (i.e., section only occupies space)
4075 If no flags are specified, the default flags depend upon the section name. If
4076 the section name is not recognized, the default will be for the section to have
4077 none of the above flags: it will not be allocated in memory, nor writable, nor
4078 executable. The section will contain data.
4080 For ELF targets, the assembler supports another type of @code{.section}
4081 directive for compatibility with the Solaris assembler:
4083 .section "@var{name}"[, @var{flags}...]
4085 Note that the section name is quoted. There may be a sequence of comma
4089 section is allocatable
4093 section is executable
4098 @section @code{.set @var{symbol}, @var{expression}}
4100 @cindex @code{set} directive
4101 @cindex symbol value, setting
4102 Set the value of @var{symbol} to @var{expression}. This
4103 changes @var{symbol}'s value and type to conform to
4104 @var{expression}. If @var{symbol} was flagged as external, it remains
4105 flagged (@pxref{Symbol Attributes}).
4107 You may @code{.set} a symbol many times in the same assembly.
4109 If you @code{.set} a global symbol, the value stored in the object
4110 file is the last value stored into it.
4113 The syntax for @code{set} on the HPPA is
4114 @samp{@var{symbol} .set @var{expression}}.
4118 @section @code{.short @var{expressions}}
4120 @cindex @code{short} directive
4122 @code{.short} is normally the same as @samp{.word}.
4123 @xref{Word,,@code{.word}}.
4125 In some configurations, however, @code{.short} and @code{.word} generate
4126 numbers of different lengths; @pxref{Machine Dependencies}.
4130 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4133 This expects zero or more @var{expressions}, and emits
4134 a 16 bit number for each.
4139 @section @code{.single @var{flonums}}
4141 @cindex @code{single} directive
4142 @cindex floating point numbers (single)
4143 This directive assembles zero or more flonums, separated by commas. It
4144 has the same effect as @code{.float}.
4146 The exact kind of floating point numbers emitted depends on how
4147 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4151 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4152 numbers in @sc{ieee} format.
4158 @section @code{.size}
4160 @cindex @code{size} directive
4161 This directive is generated by compilers to include auxiliary debugging
4162 information in the symbol table. It is only permitted inside
4163 @code{.def}/@code{.endef} pairs.
4166 @samp{.size} is only meaningful when generating COFF format output; when
4167 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4172 @ifclear no-space-dir
4174 @section @code{.skip @var{size} , @var{fill}}
4176 @cindex @code{skip} directive
4177 @cindex filling memory
4178 This directive emits @var{size} bytes, each of value @var{fill}. Both
4179 @var{size} and @var{fill} are absolute expressions. If the comma and
4180 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4184 @section @code{.space @var{size} , @var{fill}}
4186 @cindex @code{space} directive
4187 @cindex filling memory
4188 This directive emits @var{size} bytes, each of value @var{fill}. Both
4189 @var{size} and @var{fill} are absolute expressions. If the comma
4190 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4195 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4196 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4197 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4198 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4207 @section @code{.space}
4208 @cindex @code{space} directive
4210 On the AMD 29K, this directive is ignored; it is accepted for
4211 compatibility with other AMD 29K assemblers.
4214 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4215 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4221 @section @code{.stabd, .stabn, .stabs}
4223 @cindex symbolic debuggers, information for
4224 @cindex @code{stab@var{x}} directives
4225 There are three directives that begin @samp{.stab}.
4226 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4227 The symbols are not entered in the @code{@value{AS}} hash table: they
4228 cannot be referenced elsewhere in the source file.
4229 Up to five fields are required:
4233 This is the symbol's name. It may contain any character except
4234 @samp{\000}, so is more general than ordinary symbol names. Some
4235 debuggers used to code arbitrarily complex structures into symbol names
4239 An absolute expression. The symbol's type is set to the low 8 bits of
4240 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4241 and debuggers choke on silly bit patterns.
4244 An absolute expression. The symbol's ``other'' attribute is set to the
4245 low 8 bits of this expression.
4248 An absolute expression. The symbol's descriptor is set to the low 16
4249 bits of this expression.
4252 An absolute expression which becomes the symbol's value.
4255 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4256 or @code{.stabs} statement, the symbol has probably already been created;
4257 you get a half-formed symbol in your object file. This is
4258 compatible with earlier assemblers!
4261 @cindex @code{stabd} directive
4262 @item .stabd @var{type} , @var{other} , @var{desc}
4264 The ``name'' of the symbol generated is not even an empty string.
4265 It is a null pointer, for compatibility. Older assemblers used a
4266 null pointer so they didn't waste space in object files with empty
4269 The symbol's value is set to the location counter,
4270 relocatably. When your program is linked, the value of this symbol
4271 is the address of the location counter when the @code{.stabd} was
4274 @cindex @code{stabn} directive
4275 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4276 The name of the symbol is set to the empty string @code{""}.
4278 @cindex @code{stabs} directive
4279 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4280 All five fields are specified.
4286 @section @code{.string} "@var{str}"
4288 @cindex string, copying to object file
4289 @cindex @code{string} directive
4291 Copy the characters in @var{str} to the object file. You may specify more than
4292 one string to copy, separated by commas. Unless otherwise specified for a
4293 particular machine, the assembler marks the end of each string with a 0 byte.
4294 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4298 @section @code{.tag @var{structname}}
4300 @cindex COFF structure debugging
4301 @cindex structure debugging, COFF
4302 @cindex @code{tag} directive
4303 This directive is generated by compilers to include auxiliary debugging
4304 information in the symbol table. It is only permitted inside
4305 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4306 definitions in the symbol table with instances of those structures.
4309 @samp{.tag} is only used when generating COFF format output; when
4310 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4316 @section @code{.text @var{subsection}}
4318 @cindex @code{text} directive
4319 Tells @code{@value{AS}} to assemble the following statements onto the end of
4320 the text subsection numbered @var{subsection}, which is an absolute
4321 expression. If @var{subsection} is omitted, subsection number zero
4325 @section @code{.title "@var{heading}"}
4327 @cindex @code{title} directive
4328 @cindex listing control: title line
4329 Use @var{heading} as the title (second line, immediately after the
4330 source file name and pagenumber) when generating assembly listings.
4332 This directive affects subsequent pages, as well as the current page if
4333 it appears within ten lines of the top of a page.
4337 @section @code{.type @var{int}}
4339 @cindex COFF symbol type
4340 @cindex symbol type, COFF
4341 @cindex @code{type} directive
4342 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4343 records the integer @var{int} as the type attribute of a symbol table entry.
4346 @samp{.type} is associated only with COFF format output; when
4347 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4348 directive but ignores it.
4354 @section @code{.val @var{addr}}
4356 @cindex @code{val} directive
4357 @cindex COFF value attribute
4358 @cindex value attribute, COFF
4359 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4360 records the address @var{addr} as the value attribute of a symbol table
4364 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4365 configured for @code{b.out}, it accepts this directive but ignores it.
4370 @section @code{.word @var{expressions}}
4372 @cindex @code{word} directive
4373 This directive expects zero or more @var{expressions}, of any section,
4374 separated by commas.
4377 For each expression, @code{@value{AS}} emits a 32-bit number.
4380 For each expression, @code{@value{AS}} emits a 16-bit number.
4385 The size of the number emitted, and its byte order,
4386 depend on what target computer the assembly is for.
4389 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4390 @c happen---32-bit addressability, period; no long/short jumps.
4391 @ifset DIFF-TBL-KLUGE
4392 @cindex difference tables altered
4393 @cindex altered difference tables
4395 @emph{Warning: Special Treatment to support Compilers}
4399 Machines with a 32-bit address space, but that do less than 32-bit
4400 addressing, require the following special treatment. If the machine of
4401 interest to you does 32-bit addressing (or doesn't require it;
4402 @pxref{Machine Dependencies}), you can ignore this issue.
4405 In order to assemble compiler output into something that works,
4406 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4407 Directives of the form @samp{.word sym1-sym2} are often emitted by
4408 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4409 directive of the form @samp{.word sym1-sym2}, and the difference between
4410 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4411 creates a @dfn{secondary jump table}, immediately before the next label.
4412 This secondary jump table is preceded by a short-jump to the
4413 first byte after the secondary table. This short-jump prevents the flow
4414 of control from accidentally falling into the new table. Inside the
4415 table is a long-jump to @code{sym2}. The original @samp{.word}
4416 contains @code{sym1} minus the address of the long-jump to
4419 If there were several occurrences of @samp{.word sym1-sym2} before the
4420 secondary jump table, all of them are adjusted. If there was a
4421 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4422 long-jump to @code{sym4} is included in the secondary jump table,
4423 and the @code{.word} directives are adjusted to contain @code{sym3}
4424 minus the address of the long-jump to @code{sym4}; and so on, for as many
4425 entries in the original jump table as necessary.
4428 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4429 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4430 assembly language programmers.
4433 @c end DIFF-TBL-KLUGE
4436 @section Deprecated Directives
4438 @cindex deprecated directives
4439 @cindex obsolescent directives
4440 One day these directives won't work.
4441 They are included for compatibility with older assemblers.
4449 @node Machine Dependencies
4450 @chapter Machine Dependent Features
4452 @cindex machine dependencies
4453 The machine instruction sets are (almost by definition) different on
4454 each machine where @code{@value{AS}} runs. Floating point representations
4455 vary as well, and @code{@value{AS}} often supports a few additional
4456 directives or command-line options for compatibility with other
4457 assemblers on a particular platform. Finally, some versions of
4458 @code{@value{AS}} support special pseudo-instructions for branch
4461 This chapter discusses most of these differences, though it does not
4462 include details on any machine's instruction set. For details on that
4463 subject, see the hardware manufacturer's manual.
4467 * AMD29K-Dependent:: AMD 29K Dependent Features
4469 @c start-sanitize-arc
4471 * ARC-Dependent:: ARC Dependent Features
4475 * D10V-Dependent:: D10V Dependent Features
4478 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4481 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4484 * HPPA-Dependent:: HPPA Dependent Features
4487 * i386-Dependent:: Intel 80386 Dependent Features
4490 * i960-Dependent:: Intel 80960 Dependent Features
4493 * M68K-Dependent:: M680x0 Dependent Features
4496 * MIPS-Dependent:: MIPS Dependent Features
4499 * SH-Dependent:: Hitachi SH Dependent Features
4502 * Sparc-Dependent:: SPARC Dependent Features
4505 * Z8000-Dependent:: Z8000 Dependent Features
4508 * Vax-Dependent:: VAX Dependent Features
4515 @c The following major nodes are *sections* in the GENERIC version, *chapters*
4516 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
4517 @c peculiarity: to preserve cross-references, there must be a node called
4518 @c "Machine Dependencies". Hence the conditional nodenames in each
4519 @c major node below. Node defaulting in makeinfo requires adjacency of
4520 @c node and sectioning commands; hence the repetition of @chapter BLAH
4521 @c in both conditional blocks.
4523 @c start-sanitize-arc
4528 @chapter ARC Dependent Features
4531 @node Machine Dependencies
4532 @chapter ARC Dependent Features
4537 * ARC-Opts:: Options
4538 * ARC-Float:: Floating Point
4539 * ARC-Directives:: Sparc Machine Directives
4545 @cindex options for ARC
4547 @cindex architectures, ARC
4548 @cindex ARC architectures
4549 The ARC chip family includes several successive levels (or other
4550 variants) of chip, using the same core instruction set, but including
4551 a few additional instructions at each level.
4553 By default, @code{@value{AS}} assumes the core instruction set (ARC
4554 base). The @code{.cpu} pseudo-op is used to select a different variant.
4557 @cindex @code{-mbig-endian} option (ARC)
4558 @cindex @code{-mlittle-endian} option (ARC)
4559 @cindex ARC big-endian output
4560 @cindex ARC little-endian output
4561 @cindex big-endian output, ARC
4562 @cindex little-endian output, ARC
4564 @itemx -mlittle-endian
4565 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
4566 little-endian output at run time (unlike most other @sc{gnu} development
4567 tools, which must be configured for one or the other). Use
4568 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
4573 @section Floating Point
4575 @cindex floating point, ARC (@sc{ieee})
4576 @cindex ARC floating point (@sc{ieee})
4577 The ARC cpu family currently does not have hardware floating point
4578 support. Software floating point support is provided by @code{GCC}
4579 and uses @sc{ieee} floating-point numbers.
4581 @node ARC-Directives
4582 @section ARC Machine Directives
4584 @cindex ARC machine directives
4585 @cindex machine directives, ARC
4586 The ARC version of @code{@value{AS}} supports the following additional
4591 @cindex @code{cpu} directive, SPARC
4592 This must be followed by the desired cpu. It must be one of
4593 @code{base}, @code{host}, @code{graphics}, or @code{audio}.
4601 @include c-a29k.texi
4606 @node Machine Dependencies
4607 @chapter Machine Dependent Features
4609 The machine instruction sets are different on each Hitachi chip family,
4610 and there are also some syntax differences among the families. This
4611 chapter describes the specific @code{@value{AS}} features for each
4615 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4616 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4617 * SH-Dependent:: Hitachi SH Dependent Features
4624 @include c-d10v.texi
4628 @include c-h8300.texi
4632 @include c-h8500.texi
4636 @include c-hppa.texi
4640 @include c-i386.texi
4644 @include c-i960.texi
4648 @include c-m68k.texi
4652 @include c-mips.texi
4656 @include c-ns32k.texi
4664 @include c-sparc.texi
4676 @c reverse effect of @down at top of generic Machine-Dep chapter
4680 @node Reporting Bugs
4681 @chapter Reporting Bugs
4682 @cindex bugs in @code{@value{AS}}
4683 @cindex reporting bugs in @code{@value{AS}}
4685 Your bug reports play an essential role in making @code{@value{AS}} reliable.
4687 Reporting a bug may help you by bringing a solution to your problem, or it may
4688 not. But in any case the principal function of a bug report is to help the
4689 entire community by making the next version of @code{@value{AS}} work better.
4690 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
4692 In order for a bug report to serve its purpose, you must include the
4693 information that enables us to fix the bug.
4696 * Bug Criteria:: Have you found a bug?
4697 * Bug Reporting:: How to report bugs
4701 @section Have you found a bug?
4702 @cindex bug criteria
4704 If you are not sure whether you have found a bug, here are some guidelines:
4707 @cindex fatal signal
4708 @cindex assembler crash
4709 @cindex crash of assembler
4711 If the assembler gets a fatal signal, for any input whatever, that is a
4712 @code{@value{AS}} bug. Reliable assemblers never crash.
4714 @cindex error on valid input
4716 If @code{@value{AS}} produces an error message for valid input, that is a bug.
4718 @cindex invalid input
4720 If @code{@value{AS}} does not produce an error message for invalid input, that
4721 is a bug. However, you should note that your idea of ``invalid input'' might
4722 be our idea of ``an extension'' or ``support for traditional practice''.
4725 If you are an experienced user of assemblers, your suggestions for improvement
4726 of @code{@value{AS}} are welcome in any case.
4730 @section How to report bugs
4732 @cindex @code{@value{AS}} bugs, reporting
4734 A number of companies and individuals offer support for @sc{gnu} products. If
4735 you obtained @code{@value{AS}} from a support organization, we recommend you
4736 contact that organization first.
4738 You can find contact information for many support companies and
4739 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
4742 In any event, we also recommend that you send bug reports for @code{@value{AS}}
4743 to @samp{bug-gnu-utils@@prep.ai.mit.edu}.
4745 The fundamental principle of reporting bugs usefully is this:
4746 @strong{report all the facts}. If you are not sure whether to state a
4747 fact or leave it out, state it!
4749 Often people omit facts because they think they know what causes the problem
4750 and assume that some details do not matter. Thus, you might assume that the
4751 name of a symbol you use in an example does not matter. Well, probably it does
4752 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
4753 happens to fetch from the location where that name is stored in memory;
4754 perhaps, if the name were different, the contents of that location would fool
4755 the assembler into doing the right thing despite the bug. Play it safe and
4756 give a specific, complete example. That is the easiest thing for you to do,
4757 and the most helpful.
4759 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
4760 it is new to us. Therefore, always write your bug reports on the assumption
4761 that the bug has not been reported previously.
4763 Sometimes people give a few sketchy facts and ask, ``Does this ring a
4764 bell?'' Those bug reports are useless, and we urge everyone to
4765 @emph{refuse to respond to them} except to chide the sender to report
4768 To enable us to fix the bug, you should include all these things:
4772 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
4773 it with the @samp{--version} argument.
4775 Without this, we will not know whether there is any point in looking for
4776 the bug in the current version of @code{@value{AS}}.
4779 Any patches you may have applied to the @code{@value{AS}} source.
4782 The type of machine you are using, and the operating system name and
4786 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
4790 The command arguments you gave the assembler to assemble your example and
4791 observe the bug. To guarantee you will not omit something important, list them
4792 all. A copy of the Makefile (or the output from make) is sufficient.
4794 If we were to try to guess the arguments, we would probably guess wrong
4795 and then we might not encounter the bug.
4798 A complete input file that will reproduce the bug. If the bug is observed when
4799 the assembler is invoked via a compiler, send the assembler source, not the
4800 high level language source. Most compilers will produce the assembler source
4801 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
4802 the options @samp{-v --save-temps}; this will save the assembler source in a
4803 file with an extension of @file{.s}, and also show you exactly how
4804 @code{@value{AS}} is being run.
4807 A description of what behavior you observe that you believe is
4808 incorrect. For example, ``It gets a fatal signal.''
4810 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
4811 will certainly notice it. But if the bug is incorrect output, we might not
4812 notice unless it is glaringly wrong. You might as well not give us a chance to
4815 Even if the problem you experience is a fatal signal, you should still say so
4816 explicitly. Suppose something strange is going on, such as, your copy of
4817 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
4818 library on your system. (This has happened!) Your copy might crash and ours
4819 would not. If you told us to expect a crash, then when ours fails to crash, we
4820 would know that the bug was not happening for us. If you had not told us to
4821 expect a crash, then we would not be able to draw any conclusion from our
4825 If you wish to suggest changes to the @code{@value{AS}} source, send us context
4826 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
4827 option. Always send diffs from the old file to the new file. If you even
4828 discuss something in the @code{@value{AS}} source, refer to it by context, not
4831 The line numbers in our development sources will not match those in your
4832 sources. Your line numbers would convey no useful information to us.
4835 Here are some things that are not necessary:
4839 A description of the envelope of the bug.
4841 Often people who encounter a bug spend a lot of time investigating
4842 which changes to the input file will make the bug go away and which
4843 changes will not affect it.
4845 This is often time consuming and not very useful, because the way we
4846 will find the bug is by running a single example under the debugger
4847 with breakpoints, not by pure deduction from a series of examples.
4848 We recommend that you save your time for something else.
4850 Of course, if you can find a simpler example to report @emph{instead}
4851 of the original one, that is a convenience for us. Errors in the
4852 output will be easier to spot, running under the debugger will take
4853 less time, and so on.
4855 However, simplification is not vital; if you do not want to do this,
4856 report the bug anyway and send us the entire test case you used.
4859 A patch for the bug.
4861 A patch for the bug does help us if it is a good one. But do not omit
4862 the necessary information, such as the test case, on the assumption that
4863 a patch is all we need. We might see problems with your patch and decide
4864 to fix the problem another way, or we might not understand it at all.
4866 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
4867 construct an example that will make the program follow a certain path through
4868 the code. If you do not send us the example, we will not be able to construct
4869 one, so we will not be able to verify that the bug is fixed.
4871 And if we cannot understand what bug you are trying to fix, or why your
4872 patch should be an improvement, we will not install it. A test case will
4873 help us to understand.
4876 A guess about what the bug is or what it depends on.
4878 Such guesses are usually wrong. Even we cannot guess right about such
4879 things without first using the debugger to find the facts.
4882 @node Acknowledgements
4883 @chapter Acknowledgements
4885 If you have contributed to @code{@value{AS}} and your name isn't listed here,
4886 it is not meant as a slight. We just don't know about it. Send mail to the
4887 maintainer, and we'll correct the situation. Currently
4889 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
4891 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
4894 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
4895 information and the 68k series machines, most of the preprocessing pass, and
4896 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
4898 K. Richard Pixley maintained GAS for a while, adding various enhancements and
4899 many bug fixes, including merging support for several processors, breaking GAS
4900 up to handle multiple object file format back ends (including heavy rewrite,
4901 testing, an integration of the coff and b.out back ends), adding configuration
4902 including heavy testing and verification of cross assemblers and file splits
4903 and renaming, converted GAS to strictly ANSI C including full prototypes, added
4904 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
4905 port (including considerable amounts of reverse engineering), a SPARC opcode
4906 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
4907 assertions and made them work, much other reorganization, cleanup, and lint.
4909 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
4910 in format-specific I/O modules.
4912 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
4913 has done much work with it since.
4915 The Intel 80386 machine description was written by Eliot Dresselhaus.
4917 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
4919 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
4920 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
4922 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
4923 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
4924 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
4925 support a.out format.
4927 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
4928 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
4929 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
4930 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
4933 John Gilmore built the AMD 29000 support, added @code{.include} support, and
4934 simplified the configuration of which versions accept which directives. He
4935 updated the 68k machine description so that Motorola's opcodes always produced
4936 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
4937 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
4938 cross-compilation support, and one bug in relaxation that took a week and
4939 required the proverbial one-bit fix.
4941 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
4942 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
4943 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
4944 PowerPC assembler, and made a few other minor patches.
4946 Steve Chamberlain made @code{@value{AS}} able to generate listings.
4948 Hewlett-Packard contributed support for the HP9000/300.
4950 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
4951 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
4952 formats). This work was supported by both the Center for Software Science at
4953 the University of Utah and Cygnus Support.
4955 Support for ELF format files has been worked on by Mark Eichin of Cygnus
4956 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
4957 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
4958 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
4959 and some initial 64-bit support).
4961 Richard Henderson rewrote the Alpha assembler.
4963 Several engineers at Cygnus Support have also provided many small bug fixes and
4964 configuration enhancements.
4966 Many others have contributed large or small bugfixes and enhancements. If
4967 you have contributed significant work and are not mentioned on this list, and
4968 want to be, let us know. Some of the history has been lost; we are not
4969 intentionally leaving anyone out.