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[cdhlns][=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[cdhlns] 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[cdhlns]}
896 @cindex listings, enabling
897 @cindex assembly listings, enabling
899 These options enable listing output from the assembler. By itself,
900 @samp{-a} requests high-level, assembly, and symbols listing.
901 You can use other letters to select specific options for the list:
902 @samp{-ah} requests a high-level language listing,
903 @samp{-al} requests an output-program assembly listing, and
904 @samp{-as} requests a symbol table listing.
905 High-level listings require that a compiler debugging option like
906 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
909 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
910 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
911 other conditional), or a true @code{.if} followed by an @code{.else}, will be
912 omitted from the listing.
914 Use the @samp{-ad} option to omit debugging directives from the
917 Once you have specified one of these options, you can further control
918 listing output and its appearance using the directives @code{.list},
919 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
921 The @samp{-an} option turns off all forms processing.
922 If you do not request listing output with one of the @samp{-a} options, the
923 listing-control directives have no effect.
925 The letters after @samp{-a} may be combined into one option,
926 @emph{e.g.}, @samp{-aln}.
932 This option has no effect whatsoever, but it is accepted to make it more
933 likely that scripts written for other assemblers also work with
937 @section Work Faster: @code{-f}
940 @cindex trusted compiler
941 @cindex faster processing (@code{-f})
942 @samp{-f} should only be used when assembling programs written by a
943 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
944 and comment preprocessing on
945 the input file(s) before assembling them. @xref{Preprocessing,
949 @emph{Warning:} if you use @samp{-f} when the files actually need to be
950 preprocessed (if they contain comments, for example), @code{@value{AS}} does
955 @section @code{.include} search path: @code{-I} @var{path}
957 @kindex -I @var{path}
958 @cindex paths for @code{.include}
959 @cindex search path for @code{.include}
960 @cindex @code{include} directive search path
961 Use this option to add a @var{path} to the list of directories
962 @code{@value{AS}} searches for files specified in @code{.include}
963 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
964 many times as necessary to include a variety of paths. The current
965 working directory is always searched first; after that, @code{@value{AS}}
966 searches any @samp{-I} directories in the same order as they were
967 specified (left to right) on the command line.
970 @section Difference Tables: @code{-K}
973 @ifclear DIFF-TBL-KLUGE
974 On the @value{TARGET} family, this option is allowed, but has no effect. It is
975 permitted for compatibility with the @sc{gnu} assembler on other platforms,
976 where it can be used to warn when the assembler alters the machine code
977 generated for @samp{.word} directives in difference tables. The @value{TARGET}
978 family does not have the addressing limitations that sometimes lead to this
979 alteration on other platforms.
982 @ifset DIFF-TBL-KLUGE
983 @cindex difference tables, warning
984 @cindex warning for altered difference tables
985 @code{@value{AS}} sometimes alters the code emitted for directives of the form
986 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
987 You can use the @samp{-K} option if you want a warning issued when this
992 @section Include Local Labels: @code{-L}
995 @cindex local labels, retaining in output
996 Labels beginning with @samp{L} (upper case only) are called @dfn{local
997 labels}. @xref{Symbol Names}. Normally you do not see such labels when
998 debugging, because they are intended for the use of programs (like
999 compilers) that compose assembler programs, not for your notice.
1000 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1001 normally debug with them.
1003 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1004 in the object file. Usually if you do this you also tell the linker
1005 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1007 By default, a local label is any label beginning with @samp{L}, but each
1008 target is allowed to redefine the local label prefix.
1010 On the HPPA local labels begin with @samp{L$}.
1012 @c start-sanitize-arc
1014 On the ARC local labels begin with @samp{.L}.
1019 @section Assemble in MRI Compatibility Mode: @code{-M}
1022 @cindex MRI compatibility mode
1023 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1024 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1025 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1026 configured target) assembler from Microtec Research. The exact nature of the
1027 MRI syntax will not be documented here; see the MRI manuals for more
1028 information. Note in particular that the handling of macros and macro
1029 arguments is somewhat different. The purpose of this option is to permit
1030 assembling existing MRI assembler code using @code{@value{AS}}.
1032 The MRI compatibility is not complete. Certain operations of the MRI assembler
1033 depend upon its object file format, and can not be supported using other object
1034 file formats. Supporting these would require enhancing each object file format
1035 individually. These are:
1038 @item global symbols in common section
1040 The m68k MRI assembler supports common sections which are merged by the linker.
1041 Other object file formats do not support this. @code{@value{AS}} handles
1042 common sections by treating them as a single common symbol. It permits local
1043 symbols to be defined within a common section, but it can not support global
1044 symbols, since it has no way to describe them.
1046 @item complex relocations
1048 The MRI assemblers support relocations against a negated section address, and
1049 relocations which combine the start addresses of two or more sections. These
1050 are not support by other object file formats.
1052 @item @code{END} pseudo-op specifying start address
1054 The MRI @code{END} pseudo-op permits the specification of a start address.
1055 This is not supported by other object file formats. The start address may
1056 instead be specified using the @code{-e} option to the linker, or in a linker
1059 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1061 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1062 name to the output file. This is not supported by other object file formats.
1064 @item @code{ORG} pseudo-op
1066 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1067 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1068 which changes the location within the current section. Absolute sections are
1069 not supported by other object file formats. The address of a section may be
1070 assigned within a linker script.
1073 There are some other features of the MRI assembler which are not supported by
1074 @code{@value{AS}}, typically either because they are difficult or because they
1075 seem of little consequence. Some of these may be supported in future releases.
1079 @item EBCDIC strings
1081 EBCDIC strings are not supported.
1083 @item packed binary coded decimal
1085 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1086 and @code{DCB.P} pseudo-ops are not supported.
1088 @item @code{FEQU} pseudo-op
1090 The m68k @code{FEQU} pseudo-op is not supported.
1092 @item @code{NOOBJ} pseudo-op
1094 The m68k @code{NOOBJ} pseudo-op is not supported.
1096 @item @code{OPT} branch control options
1098 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1099 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1100 relaxes all branches, whether forward or backward, to an appropriate size, so
1101 these options serve no purpose.
1103 @item @code{OPT} list control options
1105 The following m68k @code{OPT} list control options are ignored: @code{C},
1106 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1107 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1109 @item other @code{OPT} options
1111 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1112 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1114 @item @code{OPT} @code{D} option is default
1116 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1117 @code{OPT NOD} may be used to turn it off.
1119 @item @code{XREF} pseudo-op.
1121 The m68k @code{XREF} pseudo-op is ignored.
1123 @item @code{.debug} pseudo-op
1125 The i960 @code{.debug} pseudo-op is not supported.
1127 @item @code{.extended} pseudo-op
1129 The i960 @code{.extended} pseudo-op is not supported.
1131 @item @code{.list} pseudo-op.
1133 The various options of the i960 @code{.list} pseudo-op are not supported.
1135 @item @code{.optimize} pseudo-op
1137 The i960 @code{.optimize} pseudo-op is not supported.
1139 @item @code{.output} pseudo-op
1141 The i960 @code{.output} pseudo-op is not supported.
1143 @item @code{.setreal} pseudo-op
1145 The i960 @code{.setreal} pseudo-op is not supported.
1150 @section Name the Object File: @code{-o}
1153 @cindex naming object file
1154 @cindex object file name
1155 There is always one object file output when you run @code{@value{AS}}. By
1156 default it has the name
1159 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1173 You use this option (which takes exactly one filename) to give the
1174 object file a different name.
1176 Whatever the object file is called, @code{@value{AS}} overwrites any
1177 existing file of the same name.
1180 @section Join Data and Text Sections: @code{-R}
1183 @cindex data and text sections, joining
1184 @cindex text and data sections, joining
1185 @cindex joining text and data sections
1186 @cindex merging text and data sections
1187 @code{-R} tells @code{@value{AS}} to write the object file as if all
1188 data-section data lives in the text section. This is only done at
1189 the very last moment: your binary data are the same, but data
1190 section parts are relocated differently. The data section part of
1191 your object file is zero bytes long because all its bytes are
1192 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1194 When you specify @code{-R} it would be possible to generate shorter
1195 address displacements (because we do not have to cross between text and
1196 data section). We refrain from doing this simply for compatibility with
1197 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1200 When @code{@value{AS}} is configured for COFF output,
1201 this option is only useful if you use sections named @samp{.text} and
1206 @code{-R} is not supported for any of the HPPA targets. Using
1207 @code{-R} generates a warning from @code{@value{AS}}.
1211 @section Display Assembly Statistics: @code{--statistics}
1213 @kindex --statistics
1214 @cindex statistics, about assembly
1215 @cindex time, total for assembly
1216 @cindex space used, maximum for assembly
1217 Use @samp{--statistics} to display two statistics about the resources used by
1218 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1219 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1223 @section Announce Version: @code{-v}
1227 @cindex @code{@value{AS}} version
1228 @cindex version of @code{@value{AS}}
1229 You can find out what version of as is running by including the
1230 option @samp{-v} (which you can also spell as @samp{-version}) on the
1234 @section Suppress Warnings: @code{-W}
1237 @cindex suppressing warnings
1238 @cindex warnings, suppressing
1239 @code{@value{AS}} should never give a warning or error message when
1240 assembling compiler output. But programs written by people often
1241 cause @code{@value{AS}} to give a warning that a particular assumption was
1242 made. All such warnings are directed to the standard error file.
1243 If you use this option, no warnings are issued. This option only
1244 affects the warning messages: it does not change any particular of how
1245 @code{@value{AS}} assembles your file. Errors, which stop the assembly, are
1249 @section Generate Object File in Spite of Errors: @code{-Z}
1250 @cindex object file, after errors
1251 @cindex errors, continuing after
1252 After an error message, @code{@value{AS}} normally produces no output. If for
1253 some reason you are interested in object file output even after
1254 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1255 option. If there are any errors, @code{@value{AS}} continues anyways, and
1256 writes an object file after a final warning message of the form @samp{@var{n}
1257 errors, @var{m} warnings, generating bad object file.}
1262 @cindex machine-independent syntax
1263 @cindex syntax, machine-independent
1264 This chapter describes the machine-independent syntax allowed in a
1265 source file. @code{@value{AS}} syntax is similar to what many other
1266 assemblers use; it is inspired by the BSD 4.2
1271 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1275 * Preprocessing:: Preprocessing
1276 * Whitespace:: Whitespace
1277 * Comments:: Comments
1278 * Symbol Intro:: Symbols
1279 * Statements:: Statements
1280 * Constants:: Constants
1284 @section Preprocessing
1286 @cindex preprocessing
1287 The @code{@value{AS}} internal preprocessor:
1289 @cindex whitespace, removed by preprocessor
1291 adjusts and removes extra whitespace. It leaves one space or tab before
1292 the keywords on a line, and turns any other whitespace on the line into
1295 @cindex comments, removed by preprocessor
1297 removes all comments, replacing them with a single space, or an
1298 appropriate number of newlines.
1300 @cindex constants, converted by preprocessor
1302 converts character constants into the appropriate numeric values.
1305 It does not do macro processing, include file handling, or
1306 anything else you may get from your C compiler's preprocessor. You can
1307 do include file processing with the @code{.include} directive
1308 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1309 to get other ``CPP'' style preprocessing, by giving the input file a
1310 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1311 Output, gcc.info, Using GNU CC}.
1313 Excess whitespace, comments, and character constants
1314 cannot be used in the portions of the input text that are not
1317 @cindex turning preprocessing on and off
1318 @cindex preprocessing, turning on and off
1321 If the first line of an input file is @code{#NO_APP} or if you use the
1322 @samp{-f} option, whitespace and comments are not removed from the input file.
1323 Within an input file, you can ask for whitespace and comment removal in
1324 specific portions of the by putting a line that says @code{#APP} before the
1325 text that may contain whitespace or comments, and putting a line that says
1326 @code{#NO_APP} after this text. This feature is mainly intend to support
1327 @code{asm} statements in compilers whose output is otherwise free of comments
1334 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1335 Whitespace is used to separate symbols, and to make programs neater for
1336 people to read. Unless within character constants
1337 (@pxref{Characters,,Character Constants}), any whitespace means the same
1338 as exactly one space.
1344 There are two ways of rendering comments to @code{@value{AS}}. In both
1345 cases the comment is equivalent to one space.
1347 Anything from @samp{/*} through the next @samp{*/} is a comment.
1348 This means you may not nest these comments.
1352 The only way to include a newline ('\n') in a comment
1353 is to use this sort of comment.
1356 /* This sort of comment does not nest. */
1359 @cindex line comment character
1360 Anything from the @dfn{line comment} character to the next newline
1361 is considered a comment and is ignored. The line comment character is
1363 @samp{;} for the AMD 29K family;
1365 @c start-sanitize-arc
1367 @samp{;} on the ARC;
1371 @samp{;} for the H8/300 family;
1374 @samp{!} for the H8/500 family;
1377 @samp{;} for the HPPA;
1380 @samp{#} on the i960;
1383 @samp{!} for the Hitachi SH;
1386 @samp{!} on the SPARC;
1389 @samp{|} on the 680x0;
1392 @samp{#} on the Vax;
1395 @samp{!} for the Z8000;
1397 see @ref{Machine Dependencies}. @refill
1398 @c FIXME What about i386, m88k, i860?
1401 On some machines there are two different line comment characters. One
1402 character only begins a comment if it is the first non-whitespace character on
1403 a line, while the other always begins a comment.
1407 @cindex lines starting with @code{#}
1408 @cindex logical line numbers
1409 To be compatible with past assemblers, lines that begin with @samp{#} have a
1410 special interpretation. Following the @samp{#} should be an absolute
1411 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1412 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1413 new logical file name. The rest of the line, if any, should be whitespace.
1415 If the first non-whitespace characters on the line are not numeric,
1416 the line is ignored. (Just like a comment.)
1419 # This is an ordinary comment.
1420 # 42-6 "new_file_name" # New logical file name
1421 # This is logical line # 36.
1423 This feature is deprecated, and may disappear from future versions
1424 of @code{@value{AS}}.
1429 @cindex characters used in symbols
1430 @ifclear SPECIAL-SYMS
1431 A @dfn{symbol} is one or more characters chosen from the set of all
1432 letters (both upper and lower case), digits and the three characters
1438 A @dfn{symbol} is one or more characters chosen from the set of all
1439 letters (both upper and lower case), digits and the three characters
1440 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1446 On most machines, you can also use @code{$} in symbol names; exceptions
1447 are noted in @ref{Machine Dependencies}.
1449 No symbol may begin with a digit. Case is significant.
1450 There is no length limit: all characters are significant. Symbols are
1451 delimited by characters not in that set, or by the beginning of a file
1452 (since the source program must end with a newline, the end of a file is
1453 not a possible symbol delimiter). @xref{Symbols}.
1454 @cindex length of symbols
1459 @cindex statements, structure of
1460 @cindex line separator character
1461 @cindex statement separator character
1463 @ifclear abnormal-separator
1464 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1465 semicolon (@samp{;}). The newline or semicolon is considered part of
1466 the preceding statement. Newlines and semicolons within character
1467 constants are an exception: they do not end statements.
1469 @ifset abnormal-separator
1471 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1472 sign (@samp{@@}). The newline or at sign is considered part of the
1473 preceding statement. Newlines and at signs within character constants
1474 are an exception: they do not end statements.
1477 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1478 point (@samp{!}). The newline or exclamation point is considered part of the
1479 preceding statement. Newlines and exclamation points within character
1480 constants are an exception: they do not end statements.
1483 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1484 H8/300) a dollar sign (@samp{$}); or (for the
1487 (@samp{;}). The newline or separator character is considered part of
1488 the preceding statement. Newlines and separators within character
1489 constants are an exception: they do not end statements.
1494 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1495 separator character. (The line separator is usually @samp{;}, unless
1496 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1497 newline or separator character is considered part of the preceding
1498 statement. Newlines and separators within character constants are an
1499 exception: they do not end statements.
1502 @cindex newline, required at file end
1503 @cindex EOF, newline must precede
1504 It is an error to end any statement with end-of-file: the last
1505 character of any input file should be a newline.@refill
1507 @cindex continuing statements
1508 @cindex multi-line statements
1509 @cindex statement on multiple lines
1510 You may write a statement on more than one line if you put a
1511 backslash (@kbd{\}) immediately in front of any newlines within the
1512 statement. When @code{@value{AS}} reads a backslashed newline both
1513 characters are ignored. You can even put backslashed newlines in
1514 the middle of symbol names without changing the meaning of your
1517 An empty statement is allowed, and may include whitespace. It is ignored.
1519 @cindex instructions and directives
1520 @cindex directives and instructions
1521 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1522 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1524 A statement begins with zero or more labels, optionally followed by a
1525 key symbol which determines what kind of statement it is. The key
1526 symbol determines the syntax of the rest of the statement. If the
1527 symbol begins with a dot @samp{.} then the statement is an assembler
1528 directive: typically valid for any computer. If the symbol begins with
1529 a letter the statement is an assembly language @dfn{instruction}: it
1530 assembles into a machine language instruction.
1532 Different versions of @code{@value{AS}} for different computers
1533 recognize different instructions. In fact, the same symbol may
1534 represent a different instruction in a different computer's assembly
1538 @cindex @code{:} (label)
1539 @cindex label (@code{:})
1540 A label is a symbol immediately followed by a colon (@code{:}).
1541 Whitespace before a label or after a colon is permitted, but you may not
1542 have whitespace between a label's symbol and its colon. @xref{Labels}.
1545 For HPPA targets, labels need not be immediately followed by a colon, but
1546 the definition of a label must begin in column zero. This also implies that
1547 only one label may be defined on each line.
1551 label: .directive followed by something
1552 another_label: # This is an empty statement.
1553 instruction operand_1, operand_2, @dots{}
1560 A constant is a number, written so that its value is known by
1561 inspection, without knowing any context. Like this:
1564 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1565 .ascii "Ring the bell\7" # A string constant.
1566 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1567 .float 0f-314159265358979323846264338327\
1568 95028841971.693993751E-40 # - pi, a flonum.
1573 * Characters:: Character Constants
1574 * Numbers:: Number Constants
1578 @subsection Character Constants
1580 @cindex character constants
1581 @cindex constants, character
1582 There are two kinds of character constants. A @dfn{character} stands
1583 for one character in one byte and its value may be used in
1584 numeric expressions. String constants (properly called string
1585 @emph{literals}) are potentially many bytes and their values may not be
1586 used in arithmetic expressions.
1590 * Chars:: Characters
1594 @subsubsection Strings
1596 @cindex string constants
1597 @cindex constants, string
1598 A @dfn{string} is written between double-quotes. It may contain
1599 double-quotes or null characters. The way to get special characters
1600 into a string is to @dfn{escape} these characters: precede them with
1601 a backslash @samp{\} character. For example @samp{\\} represents
1602 one backslash: the first @code{\} is an escape which tells
1603 @code{@value{AS}} to interpret the second character literally as a backslash
1604 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1605 escape character). The complete list of escapes follows.
1607 @cindex escape codes, character
1608 @cindex character escape codes
1611 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1613 @cindex @code{\b} (backspace character)
1614 @cindex backspace (@code{\b})
1616 Mnemonic for backspace; for ASCII this is octal code 010.
1619 @c Mnemonic for EOText; for ASCII this is octal code 004.
1621 @cindex @code{\f} (formfeed character)
1622 @cindex formfeed (@code{\f})
1624 Mnemonic for FormFeed; for ASCII this is octal code 014.
1626 @cindex @code{\n} (newline character)
1627 @cindex newline (@code{\n})
1629 Mnemonic for newline; for ASCII this is octal code 012.
1632 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1634 @cindex @code{\r} (carriage return character)
1635 @cindex carriage return (@code{\r})
1637 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1640 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1641 @c other assemblers.
1643 @cindex @code{\t} (tab)
1644 @cindex tab (@code{\t})
1646 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1649 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1650 @c @item \x @var{digit} @var{digit} @var{digit}
1651 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1653 @cindex @code{\@var{ddd}} (octal character code)
1654 @cindex octal character code (@code{\@var{ddd}})
1655 @item \ @var{digit} @var{digit} @var{digit}
1656 An octal character code. The numeric code is 3 octal digits.
1657 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1658 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1660 @cindex @code{\@var{xd...}} (hex character code)
1661 @cindex hex character code (@code{\@var{xd...}})
1662 @item \@code{x} @var{hex-digits...}
1663 A hex character code. All trailing hex digits are combined. Either upper or
1664 lower case @code{x} works.
1666 @cindex @code{\\} (@samp{\} character)
1667 @cindex backslash (@code{\\})
1669 Represents one @samp{\} character.
1672 @c Represents one @samp{'} (accent acute) character.
1673 @c This is needed in single character literals
1674 @c (@xref{Characters,,Character Constants}.) to represent
1677 @cindex @code{\"} (doublequote character)
1678 @cindex doublequote (@code{\"})
1680 Represents one @samp{"} character. Needed in strings to represent
1681 this character, because an unescaped @samp{"} would end the string.
1683 @item \ @var{anything-else}
1684 Any other character when escaped by @kbd{\} gives a warning, but
1685 assembles as if the @samp{\} was not present. The idea is that if
1686 you used an escape sequence you clearly didn't want the literal
1687 interpretation of the following character. However @code{@value{AS}} has no
1688 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1689 code and warns you of the fact.
1692 Which characters are escapable, and what those escapes represent,
1693 varies widely among assemblers. The current set is what we think
1694 the BSD 4.2 assembler recognizes, and is a subset of what most C
1695 compilers recognize. If you are in doubt, do not use an escape
1699 @subsubsection Characters
1701 @cindex single character constant
1702 @cindex character, single
1703 @cindex constant, single character
1704 A single character may be written as a single quote immediately
1705 followed by that character. The same escapes apply to characters as
1706 to strings. So if you want to write the character backslash, you
1707 must write @kbd{'\\} where the first @code{\} escapes the second
1708 @code{\}. As you can see, the quote is an acute accent, not a
1709 grave accent. A newline
1711 @ifclear abnormal-separator
1712 (or semicolon @samp{;})
1714 @ifset abnormal-separator
1716 (or at sign @samp{@@})
1719 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1725 immediately following an acute accent is taken as a literal character
1726 and does not count as the end of a statement. The value of a character
1727 constant in a numeric expression is the machine's byte-wide code for
1728 that character. @code{@value{AS}} assumes your character code is ASCII:
1729 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1732 @subsection Number Constants
1734 @cindex constants, number
1735 @cindex number constants
1736 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1737 are stored in the target machine. @emph{Integers} are numbers that
1738 would fit into an @code{int} in the C language. @emph{Bignums} are
1739 integers, but they are stored in more than 32 bits. @emph{Flonums}
1740 are floating point numbers, described below.
1743 * Integers:: Integers
1748 * Bit Fields:: Bit Fields
1754 @subsubsection Integers
1756 @cindex constants, integer
1758 @cindex binary integers
1759 @cindex integers, binary
1760 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1761 the binary digits @samp{01}.
1763 @cindex octal integers
1764 @cindex integers, octal
1765 An octal integer is @samp{0} followed by zero or more of the octal
1766 digits (@samp{01234567}).
1768 @cindex decimal integers
1769 @cindex integers, decimal
1770 A decimal integer starts with a non-zero digit followed by zero or
1771 more digits (@samp{0123456789}).
1773 @cindex hexadecimal integers
1774 @cindex integers, hexadecimal
1775 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
1776 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
1778 Integers have the usual values. To denote a negative integer, use
1779 the prefix operator @samp{-} discussed under expressions
1780 (@pxref{Prefix Ops,,Prefix Operators}).
1783 @subsubsection Bignums
1786 @cindex constants, bignum
1787 A @dfn{bignum} has the same syntax and semantics as an integer
1788 except that the number (or its negative) takes more than 32 bits to
1789 represent in binary. The distinction is made because in some places
1790 integers are permitted while bignums are not.
1793 @subsubsection Flonums
1795 @cindex floating point numbers
1796 @cindex constants, floating point
1798 @cindex precision, floating point
1799 A @dfn{flonum} represents a floating point number. The translation is
1800 indirect: a decimal floating point number from the text is converted by
1801 @code{@value{AS}} to a generic binary floating point number of more than
1802 sufficient precision. This generic floating point number is converted
1803 to a particular computer's floating point format (or formats) by a
1804 portion of @code{@value{AS}} specialized to that computer.
1806 A flonum is written by writing (in order)
1811 (@samp{0} is optional on the HPPA.)
1815 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
1817 @kbd{e} is recommended. Case is not important.
1819 @c FIXME: verify if flonum syntax really this vague for most cases
1820 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
1821 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
1824 On the H8/300, H8/500,
1826 and AMD 29K architectures, the letter must be
1827 one of the letters @samp{DFPRSX} (in upper or lower case).
1829 @c start-sanitize-arc
1830 On the ARC, the letter one of the letters @samp{DFRS}
1831 (in upper or lower case).
1834 On the Intel 960 architecture, the letter must be
1835 one of the letters @samp{DFT} (in upper or lower case).
1837 On the HPPA architecture, the letter must be @samp{E} (upper case only).
1841 One of the letters @samp{DFPRSX} (in upper or lower case).
1843 @c start-sanitize-arc
1845 One of the letters @samp{DFRS} (in upper or lower case).
1849 One of the letters @samp{DFPRSX} (in upper or lower case).
1852 The letter @samp{E} (upper case only).
1855 One of the letters @samp{DFT} (in upper or lower case).
1860 An optional sign: either @samp{+} or @samp{-}.
1863 An optional @dfn{integer part}: zero or more decimal digits.
1866 An optional @dfn{fractional part}: @samp{.} followed by zero
1867 or more decimal digits.
1870 An optional exponent, consisting of:
1874 An @samp{E} or @samp{e}.
1875 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
1876 @c principle this can perfectly well be different on different targets.
1878 Optional sign: either @samp{+} or @samp{-}.
1880 One or more decimal digits.
1885 At least one of the integer part or the fractional part must be
1886 present. The floating point number has the usual base-10 value.
1888 @code{@value{AS}} does all processing using integers. Flonums are computed
1889 independently of any floating point hardware in the computer running
1894 @c Bit fields are written as a general facility but are also controlled
1895 @c by a conditional-compilation flag---which is as of now (21mar91)
1896 @c turned on only by the i960 config of GAS.
1898 @subsubsection Bit Fields
1901 @cindex constants, bit field
1902 You can also define numeric constants as @dfn{bit fields}.
1903 specify two numbers separated by a colon---
1905 @var{mask}:@var{value}
1908 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
1911 The resulting number is then packed
1913 @c this conditional paren in case bit fields turned on elsewhere than 960
1914 (in host-dependent byte order)
1916 into a field whose width depends on which assembler directive has the
1917 bit-field as its argument. Overflow (a result from the bitwise and
1918 requiring more binary digits to represent) is not an error; instead,
1919 more constants are generated, of the specified width, beginning with the
1920 least significant digits.@refill
1922 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
1923 @code{.short}, and @code{.word} accept bit-field arguments.
1928 @chapter Sections and Relocation
1933 * Secs Background:: Background
1934 * Ld Sections:: @value{LD} Sections
1935 * As Sections:: @value{AS} Internal Sections
1936 * Sub-Sections:: Sub-Sections
1940 @node Secs Background
1943 Roughly, a section is a range of addresses, with no gaps; all data
1944 ``in'' those addresses is treated the same for some particular purpose.
1945 For example there may be a ``read only'' section.
1947 @cindex linker, and assembler
1948 @cindex assembler, and linker
1949 The linker @code{@value{LD}} reads many object files (partial programs) and
1950 combines their contents to form a runnable program. When @code{@value{AS}}
1951 emits an object file, the partial program is assumed to start at address 0.
1952 @code{@value{LD}} assigns the final addresses for the partial program, so that
1953 different partial programs do not overlap. This is actually an
1954 oversimplification, but it suffices to explain how @code{@value{AS}} uses
1957 @code{@value{LD}} moves blocks of bytes of your program to their run-time
1958 addresses. These blocks slide to their run-time addresses as rigid
1959 units; their length does not change and neither does the order of bytes
1960 within them. Such a rigid unit is called a @emph{section}. Assigning
1961 run-time addresses to sections is called @dfn{relocation}. It includes
1962 the task of adjusting mentions of object-file addresses so they refer to
1963 the proper run-time addresses.
1965 For the H8/300 and H8/500,
1966 and for the Hitachi SH,
1967 @code{@value{AS}} pads sections if needed to
1968 ensure they end on a word (sixteen bit) boundary.
1971 @cindex standard @code{@value{AS}} sections
1972 An object file written by @code{@value{AS}} has at least three sections, any
1973 of which may be empty. These are named @dfn{text}, @dfn{data} and
1978 When it generates COFF output,
1980 @code{@value{AS}} can also generate whatever other named sections you specify
1981 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
1982 If you do not use any directives that place output in the @samp{.text}
1983 or @samp{.data} sections, these sections still exist, but are empty.
1988 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
1990 @code{@value{AS}} can also generate whatever other named sections you
1991 specify using the @samp{.space} and @samp{.subspace} directives. See
1992 @cite{HP9000 Series 800 Assembly Language Reference Manual}
1993 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
1994 assembler directives.
1997 Additionally, @code{@value{AS}} uses different names for the standard
1998 text, data, and bss sections when generating SOM output. Program text
1999 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2000 BSS into @samp{$BSS$}.
2004 Within the object file, the text section starts at address @code{0}, the
2005 data section follows, and the bss section follows the data section.
2008 When generating either SOM or ELF output files on the HPPA, the text
2009 section starts at address @code{0}, the data section at address
2010 @code{0x4000000}, and the bss section follows the data section.
2013 To let @code{@value{LD}} know which data changes when the sections are
2014 relocated, and how to change that data, @code{@value{AS}} also writes to the
2015 object file details of the relocation needed. To perform relocation
2016 @code{@value{LD}} must know, each time an address in the object
2020 Where in the object file is the beginning of this reference to
2023 How long (in bytes) is this reference?
2025 Which section does the address refer to? What is the numeric value of
2027 (@var{address}) @minus{} (@var{start-address of section})?
2030 Is the reference to an address ``Program-Counter relative''?
2033 @cindex addresses, format of
2034 @cindex section-relative addressing
2035 In fact, every address @code{@value{AS}} ever uses is expressed as
2037 (@var{section}) + (@var{offset into section})
2040 Further, most expressions @code{@value{AS}} computes have this section-relative
2043 (For some object formats, such as SOM for the HPPA, some expressions are
2044 symbol-relative instead.)
2047 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2048 @var{N} into section @var{secname}.''
2050 Apart from text, data and bss sections you need to know about the
2051 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2052 addresses in the absolute section remain unchanged. For example, address
2053 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2054 @code{@value{LD}}. Although the linker never arranges two partial programs'
2055 data sections with overlapping addresses after linking, @emph{by definition}
2056 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2057 part of a program is always the same address when the program is running as
2058 address @code{@{absolute@ 239@}} in any other part of the program.
2060 The idea of sections is extended to the @dfn{undefined} section. Any
2061 address whose section is unknown at assembly time is by definition
2062 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2063 Since numbers are always defined, the only way to generate an undefined
2064 address is to mention an undefined symbol. A reference to a named
2065 common block would be such a symbol: its value is unknown at assembly
2066 time so it has section @emph{undefined}.
2068 By analogy the word @emph{section} is used to describe groups of sections in
2069 the linked program. @code{@value{LD}} puts all partial programs' text
2070 sections in contiguous addresses in the linked program. It is
2071 customary to refer to the @emph{text section} of a program, meaning all
2072 the addresses of all partial programs' text sections. Likewise for
2073 data and bss sections.
2075 Some sections are manipulated by @code{@value{LD}}; others are invented for
2076 use of @code{@value{AS}} and have no meaning except during assembly.
2079 @section @value{LD} Sections
2080 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2085 @cindex named sections
2086 @cindex sections, named
2087 @item named sections
2090 @cindex text section
2091 @cindex data section
2095 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2096 separate but equal sections. Anything you can say of one section is
2099 When the program is running, however, it is
2100 customary for the text section to be unalterable. The
2101 text section is often shared among processes: it contains
2102 instructions, constants and the like. The data section of a running
2103 program is usually alterable: for example, C variables would be stored
2104 in the data section.
2109 This section contains zeroed bytes when your program begins running. It
2110 is used to hold unitialized variables or common storage. The length of
2111 each partial program's bss section is important, but because it starts
2112 out containing zeroed bytes there is no need to store explicit zero
2113 bytes in the object file. The bss section was invented to eliminate
2114 those explicit zeros from object files.
2116 @cindex absolute section
2117 @item absolute section
2118 Address 0 of this section is always ``relocated'' to runtime address 0.
2119 This is useful if you want to refer to an address that @code{@value{LD}} must
2120 not change when relocating. In this sense we speak of absolute
2121 addresses being ``unrelocatable'': they do not change during relocation.
2123 @cindex undefined section
2124 @item undefined section
2125 This ``section'' is a catch-all for address references to objects not in
2126 the preceding sections.
2127 @c FIXME: ref to some other doc on obj-file formats could go here.
2130 @cindex relocation example
2131 An idealized example of three relocatable sections follows.
2133 The example uses the traditional section names @samp{.text} and @samp{.data}.
2135 Memory addresses are on the horizontal axis.
2139 @c END TEXI2ROFF-KILL
2142 partial program # 1: |ttttt|dddd|00|
2149 partial program # 2: |TTT|DDD|000|
2152 +--+---+-----+--+----+---+-----+~~
2153 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2154 +--+---+-----+--+----+---+-----+~~
2156 addresses: 0 @dots{}
2163 \line{\it Partial program \#1: \hfil}
2164 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2165 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2167 \line{\it Partial program \#2: \hfil}
2168 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2169 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2171 \line{\it linked program: \hfil}
2172 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2173 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2174 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2175 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2177 \line{\it addresses: \hfil}
2181 @c END TEXI2ROFF-KILL
2184 @section @value{AS} Internal Sections
2186 @cindex internal @code{@value{AS}} sections
2187 @cindex sections in messages, internal
2188 These sections are meant only for the internal use of @code{@value{AS}}. They
2189 have no meaning at run-time. You do not really need to know about these
2190 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2191 warning messages, so it might be helpful to have an idea of their
2192 meanings to @code{@value{AS}}. These sections are used to permit the
2193 value of every expression in your assembly language program to be a
2194 section-relative address.
2197 @cindex assembler internal logic error
2198 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2199 An internal assembler logic error has been found. This means there is a
2200 bug in the assembler.
2202 @cindex expr (internal section)
2204 The assembler stores complex expression internally as combinations of
2205 symbols. When it needs to represent an expression as a symbol, it puts
2206 it in the expr section.
2208 @c FIXME item transfer[t] vector preload
2209 @c FIXME item transfer[t] vector postload
2210 @c FIXME item register
2214 @section Sub-Sections
2216 @cindex numbered subsections
2217 @cindex grouping data
2223 fall into two sections: text and data.
2225 You may have separate groups of
2227 data in named sections
2231 data in named sections
2237 that you want to end up near to each other in the object file, even though they
2238 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2239 use @dfn{subsections} for this purpose. Within each section, there can be
2240 numbered subsections with values from 0 to 8192. Objects assembled into the
2241 same subsection go into the object file together with other objects in the same
2242 subsection. For example, a compiler might want to store constants in the text
2243 section, but might not want to have them interspersed with the program being
2244 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2245 section of code being output, and a @samp{.text 1} before each group of
2246 constants being output.
2248 Subsections are optional. If you do not use subsections, everything
2249 goes in subsection number zero.
2252 Each subsection is zero-padded up to a multiple of four bytes.
2253 (Subsections may be padded a different amount on different flavors
2254 of @code{@value{AS}}.)
2258 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2259 boundary (two bytes).
2260 The same is true on the Hitachi SH.
2263 @c FIXME section padding (alignment)?
2264 @c Rich Pixley says padding here depends on target obj code format; that
2265 @c doesn't seem particularly useful to say without further elaboration,
2266 @c so for now I say nothing about it. If this is a generic BFD issue,
2267 @c these paragraphs might need to vanish from this manual, and be
2268 @c discussed in BFD chapter of binutils (or some such).
2271 On the AMD 29K family, no particular padding is added to section or
2272 subsection sizes; @value{AS} forces no alignment on this platform.
2276 Subsections appear in your object file in numeric order, lowest numbered
2277 to highest. (All this to be compatible with other people's assemblers.)
2278 The object file contains no representation of subsections; @code{@value{LD}} and
2279 other programs that manipulate object files see no trace of them.
2280 They just see all your text subsections as a text section, and all your
2281 data subsections as a data section.
2283 To specify which subsection you want subsequent statements assembled
2284 into, use a numeric argument to specify it, in a @samp{.text
2285 @var{expression}} or a @samp{.data @var{expression}} statement.
2288 When generating COFF output, you
2293 can also use an extra subsection
2294 argument with arbitrary named sections: @samp{.section @var{name},
2297 @var{Expression} should be an absolute expression.
2298 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2299 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2300 begins in @code{text 0}. For instance:
2302 .text 0 # The default subsection is text 0 anyway.
2303 .ascii "This lives in the first text subsection. *"
2305 .ascii "But this lives in the second text subsection."
2307 .ascii "This lives in the data section,"
2308 .ascii "in the first data subsection."
2310 .ascii "This lives in the first text section,"
2311 .ascii "immediately following the asterisk (*)."
2314 Each section has a @dfn{location counter} incremented by one for every byte
2315 assembled into that section. Because subsections are merely a convenience
2316 restricted to @code{@value{AS}} there is no concept of a subsection location
2317 counter. There is no way to directly manipulate a location counter---but the
2318 @code{.align} directive changes it, and any label definition captures its
2319 current value. The location counter of the section where statements are being
2320 assembled is said to be the @dfn{active} location counter.
2323 @section bss Section
2326 @cindex common variable storage
2327 The bss section is used for local common variable storage.
2328 You may allocate address space in the bss section, but you may
2329 not dictate data to load into it before your program executes. When
2330 your program starts running, all the contents of the bss
2331 section are zeroed bytes.
2333 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2334 @ref{Lcomm,,@code{.lcomm}}.
2336 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2337 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2340 When assembling for a target which supports multiple sections, such as ELF or
2341 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2342 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2343 section. Typically the section will only contain symbol definitions and
2344 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2351 Symbols are a central concept: the programmer uses symbols to name
2352 things, the linker uses symbols to link, and the debugger uses symbols
2356 @cindex debuggers, and symbol order
2357 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2358 the same order they were declared. This may break some debuggers.
2363 * Setting Symbols:: Giving Symbols Other Values
2364 * Symbol Names:: Symbol Names
2365 * Dot:: The Special Dot Symbol
2366 * Symbol Attributes:: Symbol Attributes
2373 A @dfn{label} is written as a symbol immediately followed by a colon
2374 @samp{:}. The symbol then represents the current value of the
2375 active location counter, and is, for example, a suitable instruction
2376 operand. You are warned if you use the same symbol to represent two
2377 different locations: the first definition overrides any other
2381 On the HPPA, the usual form for a label need not be immediately followed by a
2382 colon, but instead must start in column zero. Only one label may be defined on
2383 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2384 provides a special directive @code{.label} for defining labels more flexibly.
2387 @node Setting Symbols
2388 @section Giving Symbols Other Values
2390 @cindex assigning values to symbols
2391 @cindex symbol values, assigning
2392 A symbol can be given an arbitrary value by writing a symbol, followed
2393 by an equals sign @samp{=}, followed by an expression
2394 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2395 directive. @xref{Set,,@code{.set}}.
2398 @section Symbol Names
2400 @cindex symbol names
2401 @cindex names, symbol
2402 @ifclear SPECIAL-SYMS
2403 Symbol names begin with a letter or with one of @samp{._}. On most
2404 machines, you can also use @code{$} in symbol names; exceptions are
2405 noted in @ref{Machine Dependencies}. That character may be followed by any
2406 string of digits, letters, dollar signs (unless otherwise noted in
2407 @ref{Machine Dependencies}), and underscores.
2410 For the AMD 29K family, @samp{?} is also allowed in the
2411 body of a symbol name, though not at its beginning.
2416 Symbol names begin with a letter or with one of @samp{._}. On the
2418 H8/500, you can also use @code{$} in symbol names. That character may
2419 be followed by any string of digits, letters, dollar signs (save on the
2420 H8/300), and underscores.
2424 Case of letters is significant: @code{foo} is a different symbol name
2427 Each symbol has exactly one name. Each name in an assembly language program
2428 refers to exactly one symbol. You may use that symbol name any number of times
2431 @subheading Local Symbol Names
2433 @cindex local symbol names
2434 @cindex symbol names, local
2435 @cindex temporary symbol names
2436 @cindex symbol names, temporary
2437 Local symbols help compilers and programmers use names temporarily.
2438 There are ten local symbol names, which are re-used throughout the
2439 program. You may refer to them using the names @samp{0} @samp{1}
2440 @dots{} @samp{9}. To define a local symbol, write a label of the form
2441 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2442 recent previous definition of that symbol write @samp{@b{N}b}, using the
2443 same digit as when you defined the label. To refer to the next
2444 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2445 a choice of 10 forward references. The @samp{b} stands for
2446 ``backwards'' and the @samp{f} stands for ``forwards''.
2448 Local symbols are not emitted by the current @sc{gnu} C compiler.
2450 There is no restriction on how you can use these labels, but
2451 remember that at any point in the assembly you can refer to at most
2452 10 prior local labels and to at most 10 forward local labels.
2454 Local symbol names are only a notation device. They are immediately
2455 transformed into more conventional symbol names before the assembler
2456 uses them. The symbol names stored in the symbol table, appearing in
2457 error messages and optionally emitted to the object file have these
2462 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2463 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2464 used for symbols you are never intended to see. If you use the
2465 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2466 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2467 you may use them in debugging.
2470 If the label is written @samp{0:} then the digit is @samp{0}.
2471 If the label is written @samp{1:} then the digit is @samp{1}.
2472 And so on up through @samp{9:}.
2475 This unusual character is included so you do not accidentally invent
2476 a symbol of the same name. The character has ASCII value
2479 @item @emph{ordinal number}
2480 This is a serial number to keep the labels distinct. The first
2481 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2482 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2486 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2487 @code{3:} is named @code{L3@kbd{C-A}44}.
2490 @section The Special Dot Symbol
2492 @cindex dot (symbol)
2493 @cindex @code{.} (symbol)
2494 @cindex current address
2495 @cindex location counter
2496 The special symbol @samp{.} refers to the current address that
2497 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2498 .long .} defines @code{melvin} to contain its own address.
2499 Assigning a value to @code{.} is treated the same as a @code{.org}
2500 directive. Thus, the expression @samp{.=.+4} is the same as saying
2501 @ifclear no-space-dir
2510 @node Symbol Attributes
2511 @section Symbol Attributes
2513 @cindex symbol attributes
2514 @cindex attributes, symbol
2515 Every symbol has, as well as its name, the attributes ``Value'' and
2516 ``Type''. Depending on output format, symbols can also have auxiliary
2519 The detailed definitions are in @file{a.out.h}.
2522 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2523 all these attributes, and probably won't warn you. This makes the
2524 symbol an externally defined symbol, which is generally what you
2528 * Symbol Value:: Value
2529 * Symbol Type:: Type
2532 * a.out Symbols:: Symbol Attributes: @code{a.out}
2536 * a.out Symbols:: Symbol Attributes: @code{a.out}
2539 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2544 * COFF Symbols:: Symbol Attributes for COFF
2547 * SOM Symbols:: Symbol Attributes for SOM
2554 @cindex value of a symbol
2555 @cindex symbol value
2556 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2557 location in the text, data, bss or absolute sections the value is the
2558 number of addresses from the start of that section to the label.
2559 Naturally for text, data and bss sections the value of a symbol changes
2560 as @code{@value{LD}} changes section base addresses during linking. Absolute
2561 symbols' values do not change during linking: that is why they are
2564 The value of an undefined symbol is treated in a special way. If it is
2565 0 then the symbol is not defined in this assembler source file, and
2566 @code{@value{LD}} tries to determine its value from other files linked into the
2567 same program. You make this kind of symbol simply by mentioning a symbol
2568 name without defining it. A non-zero value represents a @code{.comm}
2569 common declaration. The value is how much common storage to reserve, in
2570 bytes (addresses). The symbol refers to the first address of the
2576 @cindex type of a symbol
2578 The type attribute of a symbol contains relocation (section)
2579 information, any flag settings indicating that a symbol is external, and
2580 (optionally), other information for linkers and debuggers. The exact
2581 format depends on the object-code output format in use.
2586 @c The following avoids a "widow" subsection title. @group would be
2587 @c better if it were available outside examples.
2590 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2592 @cindex @code{b.out} symbol attributes
2593 @cindex symbol attributes, @code{b.out}
2594 These symbol attributes appear only when @code{@value{AS}} is configured for
2595 one of the Berkeley-descended object output formats---@code{a.out} or
2601 @subsection Symbol Attributes: @code{a.out}
2603 @cindex @code{a.out} symbol attributes
2604 @cindex symbol attributes, @code{a.out}
2610 @subsection Symbol Attributes: @code{a.out}
2612 @cindex @code{a.out} symbol attributes
2613 @cindex symbol attributes, @code{a.out}
2617 * Symbol Desc:: Descriptor
2618 * Symbol Other:: Other
2622 @subsubsection Descriptor
2624 @cindex descriptor, of @code{a.out} symbol
2625 This is an arbitrary 16-bit value. You may establish a symbol's
2626 descriptor value by using a @code{.desc} statement
2627 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2631 @subsubsection Other
2633 @cindex other attribute, of @code{a.out} symbol
2634 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2639 @subsection Symbol Attributes for COFF
2641 @cindex COFF symbol attributes
2642 @cindex symbol attributes, COFF
2644 The COFF format supports a multitude of auxiliary symbol attributes;
2645 like the primary symbol attributes, they are set between @code{.def} and
2646 @code{.endef} directives.
2648 @subsubsection Primary Attributes
2650 @cindex primary attributes, COFF symbols
2651 The symbol name is set with @code{.def}; the value and type,
2652 respectively, with @code{.val} and @code{.type}.
2654 @subsubsection Auxiliary Attributes
2656 @cindex auxiliary attributes, COFF symbols
2657 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2658 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2659 information for COFF.
2664 @subsection Symbol Attributes for SOM
2666 @cindex SOM symbol attributes
2667 @cindex symbol attributes, SOM
2669 The SOM format for the HPPA supports a multitude of symbol attributes set with
2670 the @code{.EXPORT} and @code{.IMPORT} directives.
2672 The attributes are described in @cite{HP9000 Series 800 Assembly
2673 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2674 @code{EXPORT} assembler directive documentation.
2678 @chapter Expressions
2682 @cindex numeric values
2683 An @dfn{expression} specifies an address or numeric value.
2684 Whitespace may precede and/or follow an expression.
2686 The result of an expression must be an absolute number, or else an offset into
2687 a particular section. If an expression is not absolute, and there is not
2688 enough information when @code{@value{AS}} sees the expression to know its
2689 section, a second pass over the source program might be necessary to interpret
2690 the expression---but the second pass is currently not implemented.
2691 @code{@value{AS}} aborts with an error message in this situation.
2694 * Empty Exprs:: Empty Expressions
2695 * Integer Exprs:: Integer Expressions
2699 @section Empty Expressions
2701 @cindex empty expressions
2702 @cindex expressions, empty
2703 An empty expression has no value: it is just whitespace or null.
2704 Wherever an absolute expression is required, you may omit the
2705 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2706 is compatible with other assemblers.
2709 @section Integer Expressions
2711 @cindex integer expressions
2712 @cindex expressions, integer
2713 An @dfn{integer expression} is one or more @emph{arguments} delimited
2714 by @emph{operators}.
2717 * Arguments:: Arguments
2718 * Operators:: Operators
2719 * Prefix Ops:: Prefix Operators
2720 * Infix Ops:: Infix Operators
2724 @subsection Arguments
2726 @cindex expression arguments
2727 @cindex arguments in expressions
2728 @cindex operands in expressions
2729 @cindex arithmetic operands
2730 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2731 contexts arguments are sometimes called ``arithmetic operands''. In
2732 this manual, to avoid confusing them with the ``instruction operands'' of
2733 the machine language, we use the term ``argument'' to refer to parts of
2734 expressions only, reserving the word ``operand'' to refer only to machine
2735 instruction operands.
2737 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2738 @var{section} is one of text, data, bss, absolute,
2739 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2742 Numbers are usually integers.
2744 A number can be a flonum or bignum. In this case, you are warned
2745 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2746 these 32 bits are an integer. You may write integer-manipulating
2747 instructions that act on exotic constants, compatible with other
2750 @cindex subexpressions
2751 Subexpressions are a left parenthesis @samp{(} followed by an integer
2752 expression, followed by a right parenthesis @samp{)}; or a prefix
2753 operator followed by an argument.
2756 @subsection Operators
2758 @cindex operators, in expressions
2759 @cindex arithmetic functions
2760 @cindex functions, in expressions
2761 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2762 operators are followed by an argument. Infix operators appear
2763 between their arguments. Operators may be preceded and/or followed by
2767 @subsection Prefix Operator
2769 @cindex prefix operators
2770 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2771 one argument, which must be absolute.
2773 @c the tex/end tex stuff surrounding this small table is meant to make
2774 @c it align, on the printed page, with the similar table in the next
2775 @c section (which is inside an enumerate).
2777 \global\advance\leftskip by \itemindent
2782 @dfn{Negation}. Two's complement negation.
2784 @dfn{Complementation}. Bitwise not.
2788 \global\advance\leftskip by -\itemindent
2792 @subsection Infix Operators
2794 @cindex infix operators
2795 @cindex operators, permitted arguments
2796 @dfn{Infix operators} take two arguments, one on either side. Operators
2797 have precedence, but operations with equal precedence are performed left
2798 to right. Apart from @code{+} or @code{-}, both arguments must be
2799 absolute, and the result is absolute.
2802 @cindex operator precedence
2803 @cindex precedence of operators
2810 @dfn{Multiplication}.
2813 @dfn{Division}. Truncation is the same as the C operator @samp{/}
2820 @dfn{Shift Left}. Same as the C operator @samp{<<}.
2824 @dfn{Shift Right}. Same as the C operator @samp{>>}.
2828 Intermediate precedence
2833 @dfn{Bitwise Inclusive Or}.
2839 @dfn{Bitwise Exclusive Or}.
2842 @dfn{Bitwise Or Not}.
2849 @cindex addition, permitted arguments
2850 @cindex plus, permitted arguments
2851 @cindex arguments for addition
2853 @dfn{Addition}. If either argument is absolute, the result has the section of
2854 the other argument. You may not add together arguments from different
2857 @cindex subtraction, permitted arguments
2858 @cindex minus, permitted arguments
2859 @cindex arguments for subtraction
2861 @dfn{Subtraction}. If the right argument is absolute, the
2862 result has the section of the left argument.
2863 If both arguments are in the same section, the result is absolute.
2864 You may not subtract arguments from different sections.
2865 @c FIXME is there still something useful to say about undefined - undefined ?
2869 In short, it's only meaningful to add or subtract the @emph{offsets} in an
2870 address; you can only have a defined section in one of the two arguments.
2873 @chapter Assembler Directives
2875 @cindex directives, machine independent
2876 @cindex pseudo-ops, machine independent
2877 @cindex machine independent directives
2878 All assembler directives have names that begin with a period (@samp{.}).
2879 The rest of the name is letters, usually in lower case.
2881 This chapter discusses directives that are available regardless of the
2882 target machine configuration for the @sc{gnu} assembler.
2884 Some machine configurations provide additional directives.
2885 @xref{Machine Dependencies}.
2888 @ifset machine-directives
2889 @xref{Machine Dependencies} for additional directives.
2894 * Abort:: @code{.abort}
2896 * ABORT:: @code{.ABORT}
2899 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
2900 * App-File:: @code{.app-file @var{string}}
2901 * Ascii:: @code{.ascii "@var{string}"}@dots{}
2902 * Asciz:: @code{.asciz "@var{string}"}@dots{}
2903 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
2904 * Byte:: @code{.byte @var{expressions}}
2905 * Comm:: @code{.comm @var{symbol} , @var{length} }
2906 * Data:: @code{.data @var{subsection}}
2908 * Def:: @code{.def @var{name}}
2911 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
2917 * Double:: @code{.double @var{flonums}}
2918 * Eject:: @code{.eject}
2919 * Else:: @code{.else}
2921 * Endef:: @code{.endef}
2924 * Endif:: @code{.endif}
2925 * Equ:: @code{.equ @var{symbol}, @var{expression}}
2926 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
2928 * Extern:: @code{.extern}
2929 @ifclear no-file-dir
2930 * File:: @code{.file @var{string}}
2933 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
2934 * Float:: @code{.float @var{flonums}}
2935 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
2936 * hword:: @code{.hword @var{expressions}}
2937 * Ident:: @code{.ident}
2938 * If:: @code{.if @var{absolute expression}}
2939 * Include:: @code{.include "@var{file}"}
2940 * Int:: @code{.int @var{expressions}}
2941 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
2942 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
2943 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
2944 * Lflags:: @code{.lflags}
2945 @ifclear no-line-dir
2946 * Line:: @code{.line @var{line-number}}
2949 * Ln:: @code{.ln @var{line-number}}
2950 * Linkonce:: @code{.linkonce [@var{type}]}
2951 * List:: @code{.list}
2952 * Long:: @code{.long @var{expressions}}
2954 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
2957 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
2958 * MRI:: @code{.mri @var{val}}
2960 * Nolist:: @code{.nolist}
2961 * Octa:: @code{.octa @var{bignums}}
2962 * Org:: @code{.org @var{new-lc} , @var{fill}}
2963 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
2964 * Psize:: @code{.psize @var{lines}, @var{columns}}
2965 * Quad:: @code{.quad @var{bignums}}
2966 * Rept:: @code{.rept @var{count}}
2967 * Sbttl:: @code{.sbttl "@var{subheading}"}
2969 * Scl:: @code{.scl @var{class}}
2972 * Section:: @code{.section @var{name}, @var{subsection}}
2975 * Set:: @code{.set @var{symbol}, @var{expression}}
2976 * Short:: @code{.short @var{expressions}}
2977 * Single:: @code{.single @var{flonums}}
2979 * Size:: @code{.size}
2982 * Skip:: @code{.skip @var{size} , @var{fill}}
2983 * Space:: @code{.space @var{size} , @var{fill}}
2985 * Stab:: @code{.stabd, .stabn, .stabs}
2988 * String:: @code{.string "@var{str}"}
2990 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
2993 * Tag:: @code{.tag @var{structname}}
2996 * Text:: @code{.text @var{subsection}}
2997 * Title:: @code{.title "@var{heading}"}
2999 * Type:: @code{.type @var{int}}
3000 * Val:: @code{.val @var{addr}}
3003 * Word:: @code{.word @var{expressions}}
3004 * Deprecated:: Deprecated Directives
3008 @section @code{.abort}
3010 @cindex @code{abort} directive
3011 @cindex stopping the assembly
3012 This directive stops the assembly immediately. It is for
3013 compatibility with other assemblers. The original idea was that the
3014 assembly language source would be piped into the assembler. If the sender
3015 of the source quit, it could use this directive tells @code{@value{AS}} to
3016 quit also. One day @code{.abort} will not be supported.
3020 @section @code{.ABORT}
3022 @cindex @code{ABORT} directive
3023 When producing COFF output, @code{@value{AS}} accepts this directive as a
3024 synonym for @samp{.abort}.
3027 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3033 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3035 @cindex padding the location counter
3036 @cindex @code{align} directive
3037 Pad the location counter (in the current subsection) to a particular storage
3038 boundary. The first expression (which must be absolute) is the alignment
3039 required, as described below.
3041 The second expression (also absolute) gives the fill value to be stored in the
3042 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3043 padding bytes are normally zero. However, on some systems, if the section is
3044 marked as containing code and the fill value is omitted, the space is filled
3045 with no-op instructions.
3047 The third expression is also absolute, and is also optional. If it is present,
3048 it is the maximum number of bytes that should be skipped by this alignment
3049 directive. If doing the alignment would require skipping more bytes than the
3050 specified maximum, then the alignment is not done at all. You can omit the
3051 fill value (the second argument) entirely by simply using two commas after the
3052 required alignment; this can be useful if you want the alignment to be filled
3053 with no-op instructions when appropriate.
3055 The way the required alignment is specified varies from system to system.
3056 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3058 the first expression is the
3059 alignment request in bytes. For example @samp{.align 8} advances
3060 the location counter until it is a multiple of 8. If the location counter
3061 is already a multiple of 8, no change is needed.
3063 For other systems, including the i386 using a.out format, it is the
3064 number of low-order zero bits the location counter must have after
3065 advancement. For example @samp{.align 3} advances the location
3066 counter until it a multiple of 8. If the location counter is already a
3067 multiple of 8, no change is needed.
3069 This inconsistency is due to the different behaviors of the various
3070 native assemblers for these systems which GAS must emulate.
3071 GAS also provides @code{.balign} and @code{.p2align} directives,
3072 described later, which have a consistent behavior across all
3073 architectures (but are specific to GAS).
3076 @section @code{.app-file @var{string}}
3078 @cindex logical file name
3079 @cindex file name, logical
3080 @cindex @code{app-file} directive
3082 @ifclear no-file-dir
3083 (which may also be spelled @samp{.file})
3085 tells @code{@value{AS}} that we are about to start a new
3086 logical file. @var{string} is the new file name. In general, the
3087 filename is recognized whether or not it is surrounded by quotes @samp{"};
3088 but if you wish to specify an empty file name is permitted,
3089 you must give the quotes--@code{""}. This statement may go away in
3090 future: it is only recognized to be compatible with old @code{@value{AS}}
3094 @section @code{.ascii "@var{string}"}@dots{}
3096 @cindex @code{ascii} directive
3097 @cindex string literals
3098 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3099 separated by commas. It assembles each string (with no automatic
3100 trailing zero byte) into consecutive addresses.
3103 @section @code{.asciz "@var{string}"}@dots{}
3105 @cindex @code{asciz} directive
3106 @cindex zero-terminated strings
3107 @cindex null-terminated strings
3108 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3109 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3112 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3114 @cindex padding the location counter given number of bytes
3115 @cindex @code{balign} directive
3116 Pad the location counter (in the current subsection) to a particular
3117 storage boundary. The first expression (which must be absolute) is the
3118 alignment request in bytes. For example @samp{.balign 8} advances
3119 the location counter until it is a multiple of 8. If the location counter
3120 is already a multiple of 8, no change is needed.
3122 The second expression (also absolute) gives the fill value to be stored in the
3123 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3124 padding bytes are normally zero. However, on some systems, if the section is
3125 marked as containing code and the fill value is omitted, the space is filled
3126 with no-op instructions.
3128 The third expression is also absolute, and is also optional. If it is present,
3129 it is the maximum number of bytes that should be skipped by this alignment
3130 directive. If doing the alignment would require skipping more bytes than the
3131 specified maximum, then the alignment is not done at all. You can omit the
3132 fill value (the second argument) entirely by simply using two commas after the
3133 required alignment; this can be useful if you want the alignment to be filled
3134 with no-op instructions when appropriate.
3136 @cindex @code{balignw} directive
3137 @cindex @code{balignl} directive
3138 The @code{.balignw} and @code{.balignl} directives are variants of the
3139 @code{.balign} directive. The @code{.balignw} directive treats the fill
3140 pattern as a two byte word value. The @code{.balignl} directives treats the
3141 fill pattern as a four byte longword value. For example, @code{.balignw
3142 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3143 filled in with the value 0x368d (the exact placement of the bytes depends upon
3144 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3148 @section @code{.byte @var{expressions}}
3150 @cindex @code{byte} directive
3151 @cindex integers, one byte
3152 @code{.byte} expects zero or more expressions, separated by commas.
3153 Each expression is assembled into the next byte.
3156 @section @code{.comm @var{symbol} , @var{length} }
3158 @cindex @code{comm} directive
3159 @cindex symbol, common
3160 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3161 common symbol in one object file may be merged with a defined or common symbol
3162 of the same name in another object file. If @code{@value{LD}} does not see a
3163 definition for the symbol--just one or more common symbols--then it will
3164 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3165 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3166 the same name, and they do not all have the same size, it will allocate space
3167 using the largest size.
3170 When using ELF, the @code{.comm} directive takes an optional third argument.
3171 This is the desired alignment of the symbol, specified as a byte boundary (for
3172 example, an alignment of 16 means that the least significant 4 bits of the
3173 address should be zero). The alignment must be an absolute expression, and it
3174 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3175 for the common symbol, it will use the alignment when placing the symbol. If
3176 no alignment is specified, @code{@value{AS}} will set the alignment to the
3177 largest power of two less than or equal to the size of the symbol, up to a
3182 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3183 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3187 @section @code{.data @var{subsection}}
3189 @cindex @code{data} directive
3190 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3191 end of the data subsection numbered @var{subsection} (which is an
3192 absolute expression). If @var{subsection} is omitted, it defaults
3197 @section @code{.def @var{name}}
3199 @cindex @code{def} directive
3200 @cindex COFF symbols, debugging
3201 @cindex debugging COFF symbols
3202 Begin defining debugging information for a symbol @var{name}; the
3203 definition extends until the @code{.endef} directive is encountered.
3206 This directive is only observed when @code{@value{AS}} is configured for COFF
3207 format output; when producing @code{b.out}, @samp{.def} is recognized,
3214 @section @code{.desc @var{symbol}, @var{abs-expression}}
3216 @cindex @code{desc} directive
3217 @cindex COFF symbol descriptor
3218 @cindex symbol descriptor, COFF
3219 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3220 to the low 16 bits of an absolute expression.
3223 The @samp{.desc} directive is not available when @code{@value{AS}} is
3224 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3225 object format. For the sake of compatibility, @code{@value{AS}} accepts
3226 it, but produces no output, when configured for COFF.
3232 @section @code{.dim}
3234 @cindex @code{dim} directive
3235 @cindex COFF auxiliary symbol information
3236 @cindex auxiliary symbol information, COFF
3237 This directive is generated by compilers to include auxiliary debugging
3238 information in the symbol table. It is only permitted inside
3239 @code{.def}/@code{.endef} pairs.
3242 @samp{.dim} is only meaningful when generating COFF format output; when
3243 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3249 @section @code{.double @var{flonums}}
3251 @cindex @code{double} directive
3252 @cindex floating point numbers (double)
3253 @code{.double} expects zero or more flonums, separated by commas. It
3254 assembles floating point numbers.
3256 The exact kind of floating point numbers emitted depends on how
3257 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3261 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3262 in @sc{ieee} format.
3267 @section @code{.eject}
3269 @cindex @code{eject} directive
3270 @cindex new page, in listings
3271 @cindex page, in listings
3272 @cindex listing control: new page
3273 Force a page break at this point, when generating assembly listings.
3276 @section @code{.else}
3278 @cindex @code{else} directive
3279 @code{.else} is part of the @code{@value{AS}} support for conditional
3280 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3281 of code to be assembled if the condition for the preceding @code{.if}
3285 @node End, Endef, Else, Pseudo Ops
3286 @section @code{.end}
3288 @cindex @code{end} directive
3289 This doesn't do anything---but isn't an s_ignore, so I suspect it's
3290 meant to do something eventually (which is why it isn't documented here
3291 as "for compatibility with blah").
3296 @section @code{.endef}
3298 @cindex @code{endef} directive
3299 This directive flags the end of a symbol definition begun with
3303 @samp{.endef} is only meaningful when generating COFF format output; if
3304 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3305 directive but ignores it.
3310 @section @code{.endif}
3312 @cindex @code{endif} directive
3313 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3314 it marks the end of a block of code that is only assembled
3315 conditionally. @xref{If,,@code{.if}}.
3318 @section @code{.equ @var{symbol}, @var{expression}}
3320 @cindex @code{equ} directive
3321 @cindex assigning values to symbols
3322 @cindex symbols, assigning values to
3323 This directive sets the value of @var{symbol} to @var{expression}.
3324 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3327 The syntax for @code{equ} on the HPPA is
3328 @samp{@var{symbol} .equ @var{expression}}.
3332 @section @code{.equiv @var{symbol}, @var{expression}}
3333 @cindex @code{equiv} directive
3334 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3335 the assembler will signal an error if @var{symbol} is already defined.
3337 Except for the contents of the error message, this is roughly equivalent to
3346 @section @code{.err}
3347 @cindex @code{err} directive
3348 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3349 message and, unless the @code{-Z} option was used, it will not generate an
3350 object file. This can be used to signal error an conditionally compiled code.
3353 @section @code{.extern}
3355 @cindex @code{extern} directive
3356 @code{.extern} is accepted in the source program---for compatibility
3357 with other assemblers---but it is ignored. @code{@value{AS}} treats
3358 all undefined symbols as external.
3360 @ifclear no-file-dir
3362 @section @code{.file @var{string}}
3364 @cindex @code{file} directive
3365 @cindex logical file name
3366 @cindex file name, logical
3367 @code{.file} (which may also be spelled @samp{.app-file}) tells
3368 @code{@value{AS}} that we are about to start a new logical file.
3369 @var{string} is the new file name. In general, the filename is
3370 recognized whether or not it is surrounded by quotes @samp{"}; but if
3371 you wish to specify an empty file name, you must give the
3372 quotes--@code{""}. This statement may go away in future: it is only
3373 recognized to be compatible with old @code{@value{AS}} programs.
3375 In some configurations of @code{@value{AS}}, @code{.file} has already been
3376 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3381 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3383 @cindex @code{fill} directive
3384 @cindex writing patterns in memory
3385 @cindex patterns, writing in memory
3386 @var{result}, @var{size} and @var{value} are absolute expressions.
3387 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3388 may be zero or more. @var{Size} may be zero or more, but if it is
3389 more than 8, then it is deemed to have the value 8, compatible with
3390 other people's assemblers. The contents of each @var{repeat} bytes
3391 is taken from an 8-byte number. The highest order 4 bytes are
3392 zero. The lowest order 4 bytes are @var{value} rendered in the
3393 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3394 Each @var{size} bytes in a repetition is taken from the lowest order
3395 @var{size} bytes of this number. Again, this bizarre behavior is
3396 compatible with other people's assemblers.
3398 @var{size} and @var{value} are optional.
3399 If the second comma and @var{value} are absent, @var{value} is
3400 assumed zero. If the first comma and following tokens are absent,
3401 @var{size} is assumed to be 1.
3404 @section @code{.float @var{flonums}}
3406 @cindex floating point numbers (single)
3407 @cindex @code{float} directive
3408 This directive assembles zero or more flonums, separated by commas. It
3409 has the same effect as @code{.single}.
3411 The exact kind of floating point numbers emitted depends on how
3412 @code{@value{AS}} is configured.
3413 @xref{Machine Dependencies}.
3417 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3418 in @sc{ieee} format.
3423 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3425 @cindex @code{global} directive
3426 @cindex symbol, making visible to linker
3427 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3428 @var{symbol} in your partial program, its value is made available to
3429 other partial programs that are linked with it. Otherwise,
3430 @var{symbol} takes its attributes from a symbol of the same name
3431 from another file linked into the same program.
3433 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3434 compatibility with other assemblers.
3437 On the HPPA, @code{.global} is not always enough to make it accessible to other
3438 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3439 @xref{HPPA Directives,, HPPA Assembler Directives}.
3443 @section @code{.hword @var{expressions}}
3445 @cindex @code{hword} directive
3446 @cindex integers, 16-bit
3447 @cindex numbers, 16-bit
3448 @cindex sixteen bit integers
3449 This expects zero or more @var{expressions}, and emits
3450 a 16 bit number for each.
3453 This directive is a synonym for @samp{.short}; depending on the target
3454 architecture, it may also be a synonym for @samp{.word}.
3458 This directive is a synonym for @samp{.short}.
3461 This directive is a synonym for both @samp{.short} and @samp{.word}.
3466 @section @code{.ident}
3468 @cindex @code{ident} directive
3469 This directive is used by some assemblers to place tags in object files.
3470 @code{@value{AS}} simply accepts the directive for source-file
3471 compatibility with such assemblers, but does not actually emit anything
3475 @section @code{.if @var{absolute expression}}
3477 @cindex conditional assembly
3478 @cindex @code{if} directive
3479 @code{.if} marks the beginning of a section of code which is only
3480 considered part of the source program being assembled if the argument
3481 (which must be an @var{absolute expression}) is non-zero. The end of
3482 the conditional section of code must be marked by @code{.endif}
3483 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3484 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3486 The following variants of @code{.if} are also supported:
3488 @cindex @code{ifdef} directive
3489 @item .ifdef @var{symbol}
3490 Assembles the following section of code if the specified @var{symbol}
3494 @cindex @code{ifeqs} directive
3496 Not yet implemented.
3499 @cindex @code{ifndef} directive
3500 @cindex @code{ifnotdef} directive
3501 @item .ifndef @var{symbol}
3502 @itemx .ifnotdef @var{symbol}
3503 Assembles the following section of code if the specified @var{symbol}
3504 has not been defined. Both spelling variants are equivalent.
3508 Not yet implemented.
3513 @section @code{.include "@var{file}"}
3515 @cindex @code{include} directive
3516 @cindex supporting files, including
3517 @cindex files, including
3518 This directive provides a way to include supporting files at specified
3519 points in your source program. The code from @var{file} is assembled as
3520 if it followed the point of the @code{.include}; when the end of the
3521 included file is reached, assembly of the original file continues. You
3522 can control the search paths used with the @samp{-I} command-line option
3523 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3527 @section @code{.int @var{expressions}}
3529 @cindex @code{int} directive
3530 @cindex integers, 32-bit
3531 Expect zero or more @var{expressions}, of any section, separated by commas.
3532 For each expression, emit a number that, at run time, is the value of that
3533 expression. The byte order and bit size of the number depends on what kind
3534 of target the assembly is for.
3538 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3539 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3545 @section @code{.irp @var{symbol},@var{values}}@dots{}
3547 @cindex @code{irp} directive
3548 Evaluate a sequence of statements assigning different values to @var{symbol}.
3549 The sequence of statements starts at the @code{.irp} directive, and is
3550 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3551 set to @var{value}, and the sequence of statements is assembled. If no
3552 @var{value} is listed, the sequence of statements is assembled once, with
3553 @var{symbol} set to the null string. To refer to @var{symbol} within the
3554 sequence of statements, use @var{\symbol}.
3556 For example, assembling
3564 is equivalent to assembling
3573 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3575 @cindex @code{irpc} directive
3576 Evaluate a sequence of statements assigning different values to @var{symbol}.
3577 The sequence of statements starts at the @code{.irpc} directive, and is
3578 terminated by an @code{.endr} directive. For each character in @var{value},
3579 @var{symbol} is set to the character, and the sequence of statements is
3580 assembled. If no @var{value} is listed, the sequence of statements is
3581 assembled once, with @var{symbol} set to the null string. To refer to
3582 @var{symbol} within the sequence of statements, use @var{\symbol}.
3584 For example, assembling
3592 is equivalent to assembling
3601 @section @code{.lcomm @var{symbol} , @var{length}}
3603 @cindex @code{lcomm} directive
3604 @cindex local common symbols
3605 @cindex symbols, local common
3606 Reserve @var{length} (an absolute expression) bytes for a local common
3607 denoted by @var{symbol}. The section and value of @var{symbol} are
3608 those of the new local common. The addresses are allocated in the bss
3609 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3610 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3611 not visible to @code{@value{LD}}.
3614 Some targets permit a third argument to be used with @code{.lcomm}. This
3615 argument specifies the desired alignment of the symbol in the bss section.
3619 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3620 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3624 @section @code{.lflags}
3626 @cindex @code{lflags} directive (ignored)
3627 @code{@value{AS}} accepts this directive, for compatibility with other
3628 assemblers, but ignores it.
3630 @ifclear no-line-dir
3632 @section @code{.line @var{line-number}}
3634 @cindex @code{line} directive
3638 @section @code{.ln @var{line-number}}
3640 @cindex @code{ln} directive
3642 @cindex logical line number
3644 Change the logical line number. @var{line-number} must be an absolute
3645 expression. The next line has that logical line number. Therefore any other
3646 statements on the current line (after a statement separator character) are
3647 reported as on logical line number @var{line-number} @minus{} 1. One day
3648 @code{@value{AS}} will no longer support this directive: it is recognized only
3649 for compatibility with existing assembler programs.
3653 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3654 not available; use the synonym @code{.ln} in that context.
3659 @ifclear no-line-dir
3660 Even though this is a directive associated with the @code{a.out} or
3661 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3662 when producing COFF output, and treats @samp{.line} as though it
3663 were the COFF @samp{.ln} @emph{if} it is found outside a
3664 @code{.def}/@code{.endef} pair.
3666 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3667 used by compilers to generate auxiliary symbol information for
3672 @section @code{.linkonce [@var{type}]}
3674 @cindex @code{linkonce} directive
3675 @cindex common sections
3676 Mark the current section so that the linker only includes a single copy of it.
3677 This may be used to include the same section in several different object files,
3678 but ensure that the linker will only include it once in the final output file.
3679 The @code{.linkonce} pseudo-op must be used for each instance of the section.
3680 Duplicate sections are detected based on the section name, so it should be
3683 This directive is only supported by a few object file formats; as of this
3684 writing, the only object file format which supports it is the Portable
3685 Executable format used on Windows NT.
3687 The @var{type} argument is optional. If specified, it must be one of the
3688 following strings. For example:
3692 Not all types may be supported on all object file formats.
3696 Silently discard duplicate sections. This is the default.
3699 Warn if there are duplicate sections, but still keep only one copy.
3702 Warn if any of the duplicates have different sizes.
3705 Warn if any of the duplicates do not have exactly the same contents.
3709 @section @code{.ln @var{line-number}}
3711 @cindex @code{ln} directive
3712 @ifclear no-line-dir
3713 @samp{.ln} is a synonym for @samp{.line}.
3716 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
3717 must be an absolute expression. The next line has that logical
3718 line number, so any other statements on the current line (after a
3719 statement separator character @code{;}) are reported as on logical
3720 line number @var{line-number} @minus{} 1.
3723 This directive is accepted, but ignored, when @code{@value{AS}} is
3724 configured for @code{b.out}; its effect is only associated with COFF
3730 @section @code{.mri @var{val}}
3732 @cindex @code{mri} directive
3733 @cindex MRI mode, temporarily
3734 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
3735 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
3736 affects code assembled until the next @code{.mri} directive, or until the end
3737 of the file. @xref{M, MRI mode, MRI mode}.
3740 @section @code{.list}
3742 @cindex @code{list} directive
3743 @cindex listing control, turning on
3744 Control (in conjunction with the @code{.nolist} directive) whether or
3745 not assembly listings are generated. These two directives maintain an
3746 internal counter (which is zero initially). @code{.list} increments the
3747 counter, and @code{.nolist} decrements it. Assembly listings are
3748 generated whenever the counter is greater than zero.
3750 By default, listings are disabled. When you enable them (with the
3751 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
3752 the initial value of the listing counter is one.
3755 @section @code{.long @var{expressions}}
3757 @cindex @code{long} directive
3758 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
3761 @c no one seems to know what this is for or whether this description is
3762 @c what it really ought to do
3764 @section @code{.lsym @var{symbol}, @var{expression}}
3766 @cindex @code{lsym} directive
3767 @cindex symbol, not referenced in assembly
3768 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
3769 the hash table, ensuring it cannot be referenced by name during the
3770 rest of the assembly. This sets the attributes of the symbol to be
3771 the same as the expression value:
3773 @var{other} = @var{descriptor} = 0
3774 @var{type} = @r{(section of @var{expression})}
3775 @var{value} = @var{expression}
3778 The new symbol is not flagged as external.
3782 @section @code{.macro}
3785 The commands @code{.macro} and @code{.endm} allow you to define macros that
3786 generate assembly output. For example, this definition specifies a macro
3787 @code{sum} that puts a sequence of numbers into memory:
3790 .macro sum from=0, to=5
3799 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
3811 @item .macro @var{macname}
3812 @itemx .macro @var{macname} @var{macargs} @dots{}
3813 @cindex @code{macro} directive
3814 Begin the definition of a macro called @var{macname}. If your macro
3815 definition requires arguments, specify their names after the macro name,
3816 separated by commas or spaces. You can supply a default value for any
3817 macro argument by following the name with @samp{=@var{deflt}}. For
3818 example, these are all valid @code{.macro} statements:
3822 Begin the definition of a macro called @code{comm}, which takes no
3825 @item .macro plus1 p, p1
3826 @itemx .macro plus1 p p1
3827 Either statement begins the definition of a macro called @code{plus1},
3828 which takes two arguments; within the macro definition, write
3829 @samp{\p} or @samp{\p1} to evaluate the arguments.
3831 @item .macro reserve_str p1=0 p2
3832 Begin the definition of a macro called @code{reserve_str}, with two
3833 arguments. The first argument has a default value, but not the second.
3834 After the definition is complete, you can call the macro either as
3835 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
3836 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
3837 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
3838 @samp{0}, and @samp{\p2} evaluating to @var{b}).
3841 When you call a macro, you can specify the argument values either by
3842 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
3843 @samp{sum to=17, from=9}.
3846 @cindex @code{endm} directive
3847 Mark the end of a macro definition.
3850 @cindex @code{exitm} directive
3851 Exit early from the current macro definition.
3853 @cindex number of macros executed
3854 @cindex macros, count executed
3856 @code{@value{AS}} maintains a counter of how many macros it has
3857 executed in this pseudo-variable; you can copy that number to your
3858 output with @samp{\@@}, but @emph{only within a macro definition}.
3861 @item LOCAL @var{name} [ , @dots{} ]
3862 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
3863 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
3864 Alternate macro syntax}.
3866 Generate a string replacement for each of the @var{name} arguments, and
3867 replace any instances of @var{name} in each macro expansion. The
3868 replacement string is unique in the assembly, and different for each
3869 separate macro expansion. @code{LOCAL} allows you to write macros that
3870 define symbols, without fear of conflict between separate macro expansions.
3875 @section @code{.nolist}
3877 @cindex @code{nolist} directive
3878 @cindex listing control, turning off
3879 Control (in conjunction with the @code{.list} directive) whether or
3880 not assembly listings are generated. These two directives maintain an
3881 internal counter (which is zero initially). @code{.list} increments the
3882 counter, and @code{.nolist} decrements it. Assembly listings are
3883 generated whenever the counter is greater than zero.
3886 @section @code{.octa @var{bignums}}
3888 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
3889 @cindex @code{octa} directive
3890 @cindex integer, 16-byte
3891 @cindex sixteen byte integer
3892 This directive expects zero or more bignums, separated by commas. For each
3893 bignum, it emits a 16-byte integer.
3895 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
3896 hence @emph{octa}-word for 16 bytes.
3899 @section @code{.org @var{new-lc} , @var{fill}}
3901 @cindex @code{org} directive
3902 @cindex location counter, advancing
3903 @cindex advancing location counter
3904 @cindex current address, advancing
3905 Advance the location counter of the current section to
3906 @var{new-lc}. @var{new-lc} is either an absolute expression or an
3907 expression with the same section as the current subsection. That is,
3908 you can't use @code{.org} to cross sections: if @var{new-lc} has the
3909 wrong section, the @code{.org} directive is ignored. To be compatible
3910 with former assemblers, if the section of @var{new-lc} is absolute,
3911 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
3912 is the same as the current subsection.
3914 @code{.org} may only increase the location counter, or leave it
3915 unchanged; you cannot use @code{.org} to move the location counter
3918 @c double negative used below "not undefined" because this is a specific
3919 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
3920 @c section. doc@cygnus.com 18feb91
3921 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
3922 may not be undefined. If you really detest this restriction we eagerly await
3923 a chance to share your improved assembler.
3925 Beware that the origin is relative to the start of the section, not
3926 to the start of the subsection. This is compatible with other
3927 people's assemblers.
3929 When the location counter (of the current subsection) is advanced, the
3930 intervening bytes are filled with @var{fill} which should be an
3931 absolute expression. If the comma and @var{fill} are omitted,
3932 @var{fill} defaults to zero.
3935 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3937 @cindex padding the location counter given a power of two
3938 @cindex @code{p2align} directive
3939 Pad the location counter (in the current subsection) to a particular
3940 storage boundary. The first expression (which must be absolute) is the
3941 number of low-order zero bits the location counter must have after
3942 advancement. For example @samp{.p2align 3} advances the location
3943 counter until it a multiple of 8. If the location counter is already a
3944 multiple of 8, no change is needed.
3946 The second expression (also absolute) gives the fill value to be stored in the
3947 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3948 padding bytes are normally zero. However, on some systems, if the section is
3949 marked as containing code and the fill value is omitted, the space is filled
3950 with no-op instructions.
3952 The third expression is also absolute, and is also optional. If it is present,
3953 it is the maximum number of bytes that should be skipped by this alignment
3954 directive. If doing the alignment would require skipping more bytes than the
3955 specified maximum, then the alignment is not done at all. You can omit the
3956 fill value (the second argument) entirely by simply using two commas after the
3957 required alignment; this can be useful if you want the alignment to be filled
3958 with no-op instructions when appropriate.
3960 @cindex @code{p2alignw} directive
3961 @cindex @code{p2alignl} directive
3962 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
3963 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
3964 pattern as a two byte word value. The @code{.p2alignl} directives treats the
3965 fill pattern as a four byte longword value. For example, @code{.p2alignw
3966 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3967 filled in with the value 0x368d (the exact placement of the bytes depends upon
3968 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3972 @section @code{.psize @var{lines} , @var{columns}}
3974 @cindex @code{psize} directive
3975 @cindex listing control: paper size
3976 @cindex paper size, for listings
3977 Use this directive to declare the number of lines---and, optionally, the
3978 number of columns---to use for each page, when generating listings.
3980 If you do not use @code{.psize}, listings use a default line-count
3981 of 60. You may omit the comma and @var{columns} specification; the
3982 default width is 200 columns.
3984 @code{@value{AS}} generates formfeeds whenever the specified number of
3985 lines is exceeded (or whenever you explicitly request one, using
3988 If you specify @var{lines} as @code{0}, no formfeeds are generated save
3989 those explicitly specified with @code{.eject}.
3992 @section @code{.quad @var{bignums}}
3994 @cindex @code{quad} directive
3995 @code{.quad} expects zero or more bignums, separated by commas. For
3996 each bignum, it emits
3998 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
3999 warning message; and just takes the lowest order 8 bytes of the bignum.
4000 @cindex eight-byte integer
4001 @cindex integer, 8-byte
4003 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4004 hence @emph{quad}-word for 8 bytes.
4007 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4008 warning message; and just takes the lowest order 16 bytes of the bignum.
4009 @cindex sixteen-byte integer
4010 @cindex integer, 16-byte
4014 @section @code{.rept @var{count}}
4016 @cindex @code{rept} directive
4017 Repeat the sequence of lines between the @code{.rept} directive and the next
4018 @code{.endr} directive @var{count} times.
4020 For example, assembling
4028 is equivalent to assembling
4037 @section @code{.sbttl "@var{subheading}"}
4039 @cindex @code{sbttl} directive
4040 @cindex subtitles for listings
4041 @cindex listing control: subtitle
4042 Use @var{subheading} as the title (third line, immediately after the
4043 title line) when generating assembly listings.
4045 This directive affects subsequent pages, as well as the current page if
4046 it appears within ten lines of the top of a page.
4050 @section @code{.scl @var{class}}
4052 @cindex @code{scl} directive
4053 @cindex symbol storage class (COFF)
4054 @cindex COFF symbol storage class
4055 Set the storage-class value for a symbol. This directive may only be
4056 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4057 whether a symbol is static or external, or it may record further
4058 symbolic debugging information.
4061 The @samp{.scl} directive is primarily associated with COFF output; when
4062 configured to generate @code{b.out} output format, @code{@value{AS}}
4063 accepts this directive but ignores it.
4068 @section @code{.section @var{name}}
4070 @cindex @code{section} directive
4071 @cindex named section
4072 Use the @code{.section} directive to assemble the following code into a section
4075 This directive is only supported for targets that actually support arbitrarily
4076 named sections; on @code{a.out} targets, for example, it is not accepted, even
4077 with a standard @code{a.out} section name.
4080 For COFF targets, the @code{.section} directive is used in one of the following
4083 .section @var{name}[, "@var{flags}"]
4084 .section @var{name}[, @var{subsegment}]
4087 If the optional argument is quoted, it is taken as flags to use for the
4088 section. Each flag is a single character. The following flags are recognized:
4091 bss section (uninitialized data)
4093 section is not loaded
4104 If no flags are specified, the default flags depend upon the section name. If
4105 the section name is not recognized, the default will be for the section to be
4106 loaded and writable.
4108 If the optional argument to the @code{.section} directive is not quoted, it is
4109 taken as a subsegment number (@pxref{Sub-Sections}).
4113 For ELF targets, the @code{.section} directive is used like this:
4115 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4117 The optional @var{flags} argument is a quoted string which may contain any
4118 combintion of the following characters:
4121 section is allocatable
4125 section is executable
4128 The optional @var{type} argument may contain one of the following constants:
4131 section contains data
4133 section does not contain data (i.e., section only occupies space)
4136 If no flags are specified, the default flags depend upon the section name. If
4137 the section name is not recognized, the default will be for the section to have
4138 none of the above flags: it will not be allocated in memory, nor writable, nor
4139 executable. The section will contain data.
4141 For ELF targets, the assembler supports another type of @code{.section}
4142 directive for compatibility with the Solaris assembler:
4144 .section "@var{name}"[, @var{flags}...]
4146 Note that the section name is quoted. There may be a sequence of comma
4150 section is allocatable
4154 section is executable
4159 @section @code{.set @var{symbol}, @var{expression}}
4161 @cindex @code{set} directive
4162 @cindex symbol value, setting
4163 Set the value of @var{symbol} to @var{expression}. This
4164 changes @var{symbol}'s value and type to conform to
4165 @var{expression}. If @var{symbol} was flagged as external, it remains
4166 flagged (@pxref{Symbol Attributes}).
4168 You may @code{.set} a symbol many times in the same assembly.
4170 If you @code{.set} a global symbol, the value stored in the object
4171 file is the last value stored into it.
4174 The syntax for @code{set} on the HPPA is
4175 @samp{@var{symbol} .set @var{expression}}.
4179 @section @code{.short @var{expressions}}
4181 @cindex @code{short} directive
4183 @code{.short} is normally the same as @samp{.word}.
4184 @xref{Word,,@code{.word}}.
4186 In some configurations, however, @code{.short} and @code{.word} generate
4187 numbers of different lengths; @pxref{Machine Dependencies}.
4191 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4194 This expects zero or more @var{expressions}, and emits
4195 a 16 bit number for each.
4200 @section @code{.single @var{flonums}}
4202 @cindex @code{single} directive
4203 @cindex floating point numbers (single)
4204 This directive assembles zero or more flonums, separated by commas. It
4205 has the same effect as @code{.float}.
4207 The exact kind of floating point numbers emitted depends on how
4208 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4212 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4213 numbers in @sc{ieee} format.
4219 @section @code{.size}
4221 @cindex @code{size} directive
4222 This directive is generated by compilers to include auxiliary debugging
4223 information in the symbol table. It is only permitted inside
4224 @code{.def}/@code{.endef} pairs.
4227 @samp{.size} is only meaningful when generating COFF format output; when
4228 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4233 @ifclear no-space-dir
4235 @section @code{.skip @var{size} , @var{fill}}
4237 @cindex @code{skip} directive
4238 @cindex filling memory
4239 This directive emits @var{size} bytes, each of value @var{fill}. Both
4240 @var{size} and @var{fill} are absolute expressions. If the comma and
4241 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4245 @section @code{.space @var{size} , @var{fill}}
4247 @cindex @code{space} directive
4248 @cindex filling memory
4249 This directive emits @var{size} bytes, each of value @var{fill}. Both
4250 @var{size} and @var{fill} are absolute expressions. If the comma
4251 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4256 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4257 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4258 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4259 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4268 @section @code{.space}
4269 @cindex @code{space} directive
4271 On the AMD 29K, this directive is ignored; it is accepted for
4272 compatibility with other AMD 29K assemblers.
4275 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4276 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4282 @section @code{.stabd, .stabn, .stabs}
4284 @cindex symbolic debuggers, information for
4285 @cindex @code{stab@var{x}} directives
4286 There are three directives that begin @samp{.stab}.
4287 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4288 The symbols are not entered in the @code{@value{AS}} hash table: they
4289 cannot be referenced elsewhere in the source file.
4290 Up to five fields are required:
4294 This is the symbol's name. It may contain any character except
4295 @samp{\000}, so is more general than ordinary symbol names. Some
4296 debuggers used to code arbitrarily complex structures into symbol names
4300 An absolute expression. The symbol's type is set to the low 8 bits of
4301 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4302 and debuggers choke on silly bit patterns.
4305 An absolute expression. The symbol's ``other'' attribute is set to the
4306 low 8 bits of this expression.
4309 An absolute expression. The symbol's descriptor is set to the low 16
4310 bits of this expression.
4313 An absolute expression which becomes the symbol's value.
4316 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4317 or @code{.stabs} statement, the symbol has probably already been created;
4318 you get a half-formed symbol in your object file. This is
4319 compatible with earlier assemblers!
4322 @cindex @code{stabd} directive
4323 @item .stabd @var{type} , @var{other} , @var{desc}
4325 The ``name'' of the symbol generated is not even an empty string.
4326 It is a null pointer, for compatibility. Older assemblers used a
4327 null pointer so they didn't waste space in object files with empty
4330 The symbol's value is set to the location counter,
4331 relocatably. When your program is linked, the value of this symbol
4332 is the address of the location counter when the @code{.stabd} was
4335 @cindex @code{stabn} directive
4336 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4337 The name of the symbol is set to the empty string @code{""}.
4339 @cindex @code{stabs} directive
4340 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4341 All five fields are specified.
4347 @section @code{.string} "@var{str}"
4349 @cindex string, copying to object file
4350 @cindex @code{string} directive
4352 Copy the characters in @var{str} to the object file. You may specify more than
4353 one string to copy, separated by commas. Unless otherwise specified for a
4354 particular machine, the assembler marks the end of each string with a 0 byte.
4355 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4359 @section @code{.symver}
4360 @cindex @code{symver} directive
4361 @cindex symbol versioning
4362 @cindex versions of symbols
4363 Use the @code{.symver} directive to bind symbols to specific version nodes
4364 within a source file. This is only supported on ELF platforms, and is
4365 typically used when assembling files to be linked into a shared library.
4366 There are cases where it may make sense to use this in objects to be bound
4367 into an application itself so as to override a versioned symbol from a
4370 For ELF targets, the @code{.symver} directive is used like this:
4372 .symver @var{name}, @var{name2@@nodename}
4374 In this case, the symbol @var{name} must exist and be defined within the file
4375 being assembled. The @code{.versym} directive effectively creates a symbol
4376 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4377 just don't try and create a regular alias is that the @var{@@} character isn't
4378 permitted in symbol names. The @var{name2} part of the name is the actual name
4379 of the symbol by which it will be externally referenced. The name @var{name}
4380 itself is merely a name of convenience that is used so that it is possible to
4381 have definitions for multiple versions of a function within a single source
4382 file, and so that the compiler can unambiguously know which version of a
4383 function is being mentioned. The @var{nodename} portion of the alias should be
4384 the name of a node specified in the version script supplied to the linker when
4385 building a shared library. If you are attempting to override a versioned
4386 symbol from a shared library, then @var{nodename} should correspond to the
4387 nodename of the symbol you are trying to override.
4392 @section @code{.tag @var{structname}}
4394 @cindex COFF structure debugging
4395 @cindex structure debugging, COFF
4396 @cindex @code{tag} directive
4397 This directive is generated by compilers to include auxiliary debugging
4398 information in the symbol table. It is only permitted inside
4399 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4400 definitions in the symbol table with instances of those structures.
4403 @samp{.tag} is only used when generating COFF format output; when
4404 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4410 @section @code{.text @var{subsection}}
4412 @cindex @code{text} directive
4413 Tells @code{@value{AS}} to assemble the following statements onto the end of
4414 the text subsection numbered @var{subsection}, which is an absolute
4415 expression. If @var{subsection} is omitted, subsection number zero
4419 @section @code{.title "@var{heading}"}
4421 @cindex @code{title} directive
4422 @cindex listing control: title line
4423 Use @var{heading} as the title (second line, immediately after the
4424 source file name and pagenumber) when generating assembly listings.
4426 This directive affects subsequent pages, as well as the current page if
4427 it appears within ten lines of the top of a page.
4431 @section @code{.type @var{int}}
4433 @cindex COFF symbol type
4434 @cindex symbol type, COFF
4435 @cindex @code{type} directive
4436 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4437 records the integer @var{int} as the type attribute of a symbol table entry.
4440 @samp{.type} is associated only with COFF format output; when
4441 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4442 directive but ignores it.
4448 @section @code{.val @var{addr}}
4450 @cindex @code{val} directive
4451 @cindex COFF value attribute
4452 @cindex value attribute, COFF
4453 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4454 records the address @var{addr} as the value attribute of a symbol table
4458 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4459 configured for @code{b.out}, it accepts this directive but ignores it.
4464 @section @code{.word @var{expressions}}
4466 @cindex @code{word} directive
4467 This directive expects zero or more @var{expressions}, of any section,
4468 separated by commas.
4471 For each expression, @code{@value{AS}} emits a 32-bit number.
4474 For each expression, @code{@value{AS}} emits a 16-bit number.
4479 The size of the number emitted, and its byte order,
4480 depend on what target computer the assembly is for.
4483 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4484 @c happen---32-bit addressability, period; no long/short jumps.
4485 @ifset DIFF-TBL-KLUGE
4486 @cindex difference tables altered
4487 @cindex altered difference tables
4489 @emph{Warning: Special Treatment to support Compilers}
4493 Machines with a 32-bit address space, but that do less than 32-bit
4494 addressing, require the following special treatment. If the machine of
4495 interest to you does 32-bit addressing (or doesn't require it;
4496 @pxref{Machine Dependencies}), you can ignore this issue.
4499 In order to assemble compiler output into something that works,
4500 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4501 Directives of the form @samp{.word sym1-sym2} are often emitted by
4502 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4503 directive of the form @samp{.word sym1-sym2}, and the difference between
4504 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4505 creates a @dfn{secondary jump table}, immediately before the next label.
4506 This secondary jump table is preceded by a short-jump to the
4507 first byte after the secondary table. This short-jump prevents the flow
4508 of control from accidentally falling into the new table. Inside the
4509 table is a long-jump to @code{sym2}. The original @samp{.word}
4510 contains @code{sym1} minus the address of the long-jump to
4513 If there were several occurrences of @samp{.word sym1-sym2} before the
4514 secondary jump table, all of them are adjusted. If there was a
4515 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4516 long-jump to @code{sym4} is included in the secondary jump table,
4517 and the @code{.word} directives are adjusted to contain @code{sym3}
4518 minus the address of the long-jump to @code{sym4}; and so on, for as many
4519 entries in the original jump table as necessary.
4522 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4523 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4524 assembly language programmers.
4527 @c end DIFF-TBL-KLUGE
4530 @section Deprecated Directives
4532 @cindex deprecated directives
4533 @cindex obsolescent directives
4534 One day these directives won't work.
4535 They are included for compatibility with older assemblers.
4543 @node Machine Dependencies
4544 @chapter Machine Dependent Features
4546 @cindex machine dependencies
4547 The machine instruction sets are (almost by definition) different on
4548 each machine where @code{@value{AS}} runs. Floating point representations
4549 vary as well, and @code{@value{AS}} often supports a few additional
4550 directives or command-line options for compatibility with other
4551 assemblers on a particular platform. Finally, some versions of
4552 @code{@value{AS}} support special pseudo-instructions for branch
4555 This chapter discusses most of these differences, though it does not
4556 include details on any machine's instruction set. For details on that
4557 subject, see the hardware manufacturer's manual.
4561 * AMD29K-Dependent:: AMD 29K Dependent Features
4563 @c start-sanitize-arc
4565 * ARC-Dependent:: ARC Dependent Features
4569 * D10V-Dependent:: D10V Dependent Features
4572 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4575 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4578 * HPPA-Dependent:: HPPA Dependent Features
4581 * i386-Dependent:: Intel 80386 Dependent Features
4584 * i960-Dependent:: Intel 80960 Dependent Features
4587 * M68K-Dependent:: M680x0 Dependent Features
4590 * MIPS-Dependent:: MIPS Dependent Features
4593 * SH-Dependent:: Hitachi SH Dependent Features
4596 * Sparc-Dependent:: SPARC Dependent Features
4599 * Z8000-Dependent:: Z8000 Dependent Features
4602 * Vax-Dependent:: VAX Dependent Features
4609 @c The following major nodes are *sections* in the GENERIC version, *chapters*
4610 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
4611 @c peculiarity: to preserve cross-references, there must be a node called
4612 @c "Machine Dependencies". Hence the conditional nodenames in each
4613 @c major node below. Node defaulting in makeinfo requires adjacency of
4614 @c node and sectioning commands; hence the repetition of @chapter BLAH
4615 @c in both conditional blocks.
4617 @c start-sanitize-arc
4622 @chapter ARC Dependent Features
4625 @node Machine Dependencies
4626 @chapter ARC Dependent Features
4631 * ARC-Opts:: Options
4632 * ARC-Float:: Floating Point
4633 * ARC-Directives:: Sparc Machine Directives
4639 @cindex options for ARC
4641 @cindex architectures, ARC
4642 @cindex ARC architectures
4643 The ARC chip family includes several successive levels (or other
4644 variants) of chip, using the same core instruction set, but including
4645 a few additional instructions at each level.
4647 By default, @code{@value{AS}} assumes the core instruction set (ARC
4648 base). The @code{.cpu} pseudo-op is used to select a different variant.
4651 @cindex @code{-mbig-endian} option (ARC)
4652 @cindex @code{-mlittle-endian} option (ARC)
4653 @cindex ARC big-endian output
4654 @cindex ARC little-endian output
4655 @cindex big-endian output, ARC
4656 @cindex little-endian output, ARC
4658 @itemx -mlittle-endian
4659 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
4660 little-endian output at run time (unlike most other @sc{gnu} development
4661 tools, which must be configured for one or the other). Use
4662 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
4667 @section Floating Point
4669 @cindex floating point, ARC (@sc{ieee})
4670 @cindex ARC floating point (@sc{ieee})
4671 The ARC cpu family currently does not have hardware floating point
4672 support. Software floating point support is provided by @code{GCC}
4673 and uses @sc{ieee} floating-point numbers.
4675 @node ARC-Directives
4676 @section ARC Machine Directives
4678 @cindex ARC machine directives
4679 @cindex machine directives, ARC
4680 The ARC version of @code{@value{AS}} supports the following additional
4685 @cindex @code{cpu} directive, SPARC
4686 This must be followed by the desired cpu. It must be one of
4687 @code{base}, @code{host}, @code{graphics}, or @code{audio}.
4695 @include c-a29k.texi
4700 @node Machine Dependencies
4701 @chapter Machine Dependent Features
4703 The machine instruction sets are different on each Hitachi chip family,
4704 and there are also some syntax differences among the families. This
4705 chapter describes the specific @code{@value{AS}} features for each
4709 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4710 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4711 * SH-Dependent:: Hitachi SH Dependent Features
4718 @include c-d10v.texi
4722 @include c-h8300.texi
4726 @include c-h8500.texi
4730 @include c-hppa.texi
4734 @include c-i386.texi
4738 @include c-i960.texi
4742 @include c-m68k.texi
4746 @include c-mips.texi
4750 @include c-ns32k.texi
4758 @include c-sparc.texi
4770 @c reverse effect of @down at top of generic Machine-Dep chapter
4774 @node Reporting Bugs
4775 @chapter Reporting Bugs
4776 @cindex bugs in @code{@value{AS}}
4777 @cindex reporting bugs in @code{@value{AS}}
4779 Your bug reports play an essential role in making @code{@value{AS}} reliable.
4781 Reporting a bug may help you by bringing a solution to your problem, or it may
4782 not. But in any case the principal function of a bug report is to help the
4783 entire community by making the next version of @code{@value{AS}} work better.
4784 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
4786 In order for a bug report to serve its purpose, you must include the
4787 information that enables us to fix the bug.
4790 * Bug Criteria:: Have you found a bug?
4791 * Bug Reporting:: How to report bugs
4795 @section Have you found a bug?
4796 @cindex bug criteria
4798 If you are not sure whether you have found a bug, here are some guidelines:
4801 @cindex fatal signal
4802 @cindex assembler crash
4803 @cindex crash of assembler
4805 If the assembler gets a fatal signal, for any input whatever, that is a
4806 @code{@value{AS}} bug. Reliable assemblers never crash.
4808 @cindex error on valid input
4810 If @code{@value{AS}} produces an error message for valid input, that is a bug.
4812 @cindex invalid input
4814 If @code{@value{AS}} does not produce an error message for invalid input, that
4815 is a bug. However, you should note that your idea of ``invalid input'' might
4816 be our idea of ``an extension'' or ``support for traditional practice''.
4819 If you are an experienced user of assemblers, your suggestions for improvement
4820 of @code{@value{AS}} are welcome in any case.
4824 @section How to report bugs
4826 @cindex @code{@value{AS}} bugs, reporting
4828 A number of companies and individuals offer support for @sc{gnu} products. If
4829 you obtained @code{@value{AS}} from a support organization, we recommend you
4830 contact that organization first.
4832 You can find contact information for many support companies and
4833 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
4836 In any event, we also recommend that you send bug reports for @code{@value{AS}}
4837 to @samp{bug-gnu-utils@@prep.ai.mit.edu}.
4839 The fundamental principle of reporting bugs usefully is this:
4840 @strong{report all the facts}. If you are not sure whether to state a
4841 fact or leave it out, state it!
4843 Often people omit facts because they think they know what causes the problem
4844 and assume that some details do not matter. Thus, you might assume that the
4845 name of a symbol you use in an example does not matter. Well, probably it does
4846 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
4847 happens to fetch from the location where that name is stored in memory;
4848 perhaps, if the name were different, the contents of that location would fool
4849 the assembler into doing the right thing despite the bug. Play it safe and
4850 give a specific, complete example. That is the easiest thing for you to do,
4851 and the most helpful.
4853 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
4854 it is new to us. Therefore, always write your bug reports on the assumption
4855 that the bug has not been reported previously.
4857 Sometimes people give a few sketchy facts and ask, ``Does this ring a
4858 bell?'' Those bug reports are useless, and we urge everyone to
4859 @emph{refuse to respond to them} except to chide the sender to report
4862 To enable us to fix the bug, you should include all these things:
4866 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
4867 it with the @samp{--version} argument.
4869 Without this, we will not know whether there is any point in looking for
4870 the bug in the current version of @code{@value{AS}}.
4873 Any patches you may have applied to the @code{@value{AS}} source.
4876 The type of machine you are using, and the operating system name and
4880 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
4884 The command arguments you gave the assembler to assemble your example and
4885 observe the bug. To guarantee you will not omit something important, list them
4886 all. A copy of the Makefile (or the output from make) is sufficient.
4888 If we were to try to guess the arguments, we would probably guess wrong
4889 and then we might not encounter the bug.
4892 A complete input file that will reproduce the bug. If the bug is observed when
4893 the assembler is invoked via a compiler, send the assembler source, not the
4894 high level language source. Most compilers will produce the assembler source
4895 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
4896 the options @samp{-v --save-temps}; this will save the assembler source in a
4897 file with an extension of @file{.s}, and also show you exactly how
4898 @code{@value{AS}} is being run.
4901 A description of what behavior you observe that you believe is
4902 incorrect. For example, ``It gets a fatal signal.''
4904 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
4905 will certainly notice it. But if the bug is incorrect output, we might not
4906 notice unless it is glaringly wrong. You might as well not give us a chance to
4909 Even if the problem you experience is a fatal signal, you should still say so
4910 explicitly. Suppose something strange is going on, such as, your copy of
4911 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
4912 library on your system. (This has happened!) Your copy might crash and ours
4913 would not. If you told us to expect a crash, then when ours fails to crash, we
4914 would know that the bug was not happening for us. If you had not told us to
4915 expect a crash, then we would not be able to draw any conclusion from our
4919 If you wish to suggest changes to the @code{@value{AS}} source, send us context
4920 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
4921 option. Always send diffs from the old file to the new file. If you even
4922 discuss something in the @code{@value{AS}} source, refer to it by context, not
4925 The line numbers in our development sources will not match those in your
4926 sources. Your line numbers would convey no useful information to us.
4929 Here are some things that are not necessary:
4933 A description of the envelope of the bug.
4935 Often people who encounter a bug spend a lot of time investigating
4936 which changes to the input file will make the bug go away and which
4937 changes will not affect it.
4939 This is often time consuming and not very useful, because the way we
4940 will find the bug is by running a single example under the debugger
4941 with breakpoints, not by pure deduction from a series of examples.
4942 We recommend that you save your time for something else.
4944 Of course, if you can find a simpler example to report @emph{instead}
4945 of the original one, that is a convenience for us. Errors in the
4946 output will be easier to spot, running under the debugger will take
4947 less time, and so on.
4949 However, simplification is not vital; if you do not want to do this,
4950 report the bug anyway and send us the entire test case you used.
4953 A patch for the bug.
4955 A patch for the bug does help us if it is a good one. But do not omit
4956 the necessary information, such as the test case, on the assumption that
4957 a patch is all we need. We might see problems with your patch and decide
4958 to fix the problem another way, or we might not understand it at all.
4960 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
4961 construct an example that will make the program follow a certain path through
4962 the code. If you do not send us the example, we will not be able to construct
4963 one, so we will not be able to verify that the bug is fixed.
4965 And if we cannot understand what bug you are trying to fix, or why your
4966 patch should be an improvement, we will not install it. A test case will
4967 help us to understand.
4970 A guess about what the bug is or what it depends on.
4972 Such guesses are usually wrong. Even we cannot guess right about such
4973 things without first using the debugger to find the facts.
4976 @node Acknowledgements
4977 @chapter Acknowledgements
4979 If you have contributed to @code{@value{AS}} and your name isn't listed here,
4980 it is not meant as a slight. We just don't know about it. Send mail to the
4981 maintainer, and we'll correct the situation. Currently
4983 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
4985 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
4988 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
4989 information and the 68k series machines, most of the preprocessing pass, and
4990 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
4992 K. Richard Pixley maintained GAS for a while, adding various enhancements and
4993 many bug fixes, including merging support for several processors, breaking GAS
4994 up to handle multiple object file format back ends (including heavy rewrite,
4995 testing, an integration of the coff and b.out back ends), adding configuration
4996 including heavy testing and verification of cross assemblers and file splits
4997 and renaming, converted GAS to strictly ANSI C including full prototypes, added
4998 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
4999 port (including considerable amounts of reverse engineering), a SPARC opcode
5000 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5001 assertions and made them work, much other reorganization, cleanup, and lint.
5003 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5004 in format-specific I/O modules.
5006 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5007 has done much work with it since.
5009 The Intel 80386 machine description was written by Eliot Dresselhaus.
5011 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5013 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5014 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5016 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5017 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5018 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5019 support a.out format.
5021 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5022 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5023 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5024 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5027 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5028 simplified the configuration of which versions accept which directives. He
5029 updated the 68k machine description so that Motorola's opcodes always produced
5030 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5031 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5032 cross-compilation support, and one bug in relaxation that took a week and
5033 required the proverbial one-bit fix.
5035 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5036 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5037 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5038 PowerPC assembler, and made a few other minor patches.
5040 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5042 Hewlett-Packard contributed support for the HP9000/300.
5044 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5045 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5046 formats). This work was supported by both the Center for Software Science at
5047 the University of Utah and Cygnus Support.
5049 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5050 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5051 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5052 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5053 and some initial 64-bit support).
5055 Richard Henderson rewrote the Alpha assembler.
5057 Several engineers at Cygnus Support have also provided many small bug fixes and
5058 configuration enhancements.
5060 Many others have contributed large or small bugfixes and enhancements. If
5061 you have contributed significant work and are not mentioned on this list, and
5062 want to be, let us know. Some of the history has been lost; we are not
5063 intentionally leaving anyone out.