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
39 @set abnormal-separator
43 @settitle Using @value{AS}
46 @settitle Using @value{AS} (@value{TARGET})
48 @setchapternewpage odd
53 @c WARE! Some of the machine-dependent sections contain tables of machine
54 @c instructions. Except in multi-column format, these tables look silly.
55 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
56 @c the multi-col format is faked within @example sections.
58 @c Again unfortunately, the natural size that fits on a page, for these tables,
59 @c is different depending on whether or not smallbook is turned on.
60 @c This matters, because of order: text flow switches columns at each page
63 @c The format faked in this source works reasonably well for smallbook,
64 @c not well for the default large-page format. This manual expects that if you
65 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
66 @c tables in question. You can turn on one without the other at your
67 @c discretion, of course.
70 @c the insn tables look just as silly in info files regardless of smallbook,
71 @c might as well show 'em anyways.
77 * As: (as). The GNU assembler.
86 This file documents the GNU Assembler "@value{AS}".
88 Copyright (C) 1991, 92, 93, 94, 95, 96, 1997 Free Software Foundation, Inc.
90 Permission is granted to make and distribute verbatim copies of
91 this manual provided the copyright notice and this permission notice
92 are preserved on all copies.
95 Permission is granted to process this file through Tex and print the
96 results, provided the printed document carries copying permission
97 notice identical to this one except for the removal of this paragraph
98 (this paragraph not being relevant to the printed manual).
101 Permission is granted to copy and distribute modified versions of this manual
102 under the conditions for verbatim copying, provided that the entire resulting
103 derived work is distributed under the terms of a permission notice identical to
106 Permission is granted to copy and distribute translations of this manual
107 into another language, under the above conditions for modified versions.
111 @title Using @value{AS}
112 @subtitle The @sc{gnu} Assembler
114 @subtitle for the @value{TARGET} family
117 @subtitle January 1994
120 The Free Software Foundation Inc. thanks The Nice Computer
121 Company of Australia for loaning Dean Elsner to write the
122 first (Vax) version of @code{as} for Project @sc{gnu}.
123 The proprietors, management and staff of TNCCA thank FSF for
124 distracting the boss while they got some work
127 @author Dean Elsner, Jay Fenlason & friends
131 \hfill {\it Using {\tt @value{AS}}}\par
132 \hfill Edited by Cygnus Support\par
134 %"boxit" macro for figures:
135 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
136 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
137 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
138 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
139 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
142 @vskip 0pt plus 1filll
143 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 1997 Free Software Foundation, Inc.
145 Permission is granted to make and distribute verbatim copies of
146 this manual provided the copyright notice and this permission notice
147 are preserved on all copies.
149 Permission is granted to copy and distribute modified versions of this manual
150 under the conditions for verbatim copying, provided that the entire resulting
151 derived work is distributed under the terms of a permission notice identical to
154 Permission is granted to copy and distribute translations of this manual
155 into another language, under the above conditions for modified versions.
160 @top Using @value{AS}
162 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
164 This version of the file describes @code{@value{AS}} configured to generate
165 code for @value{TARGET} architectures.
168 * Overview:: Overview
169 * Invoking:: Command-Line Options
171 * Sections:: Sections and Relocation
173 * Expressions:: Expressions
174 * Pseudo Ops:: Assembler Directives
175 * Machine Dependencies:: Machine Dependent Features
176 * Reporting Bugs:: Reporting Bugs
177 * Acknowledgements:: Who Did What
185 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
187 This version of the manual describes @code{@value{AS}} configured to generate
188 code for @value{TARGET} architectures.
192 @cindex invocation summary
193 @cindex option summary
194 @cindex summary of options
195 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
196 @pxref{Invoking,,Comand-Line Options}.
198 @c We don't use deffn and friends for the following because they seem
199 @c to be limited to one line for the header.
201 @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
202 [ -f ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
203 [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ] [ -version ]
204 [ --version ] [ -W ] [ -w ] [ -x ] [ -Z ]
206 @c am29k has no machine-dependent assembler options
209 [ -mbig-endian | -mlittle-endian ]
212 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m[i]] ]
213 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t ]
215 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
217 [ -mapcs-32 | -mapcs-26 ]
224 @c Hitachi family chips have no machine-dependent assembler options
227 @c HPPA has no machine-dependent assembler options (yet).
230 @c The order here is important. See c-sparc.texi.
231 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite | -Av9 | -Av9a ]
232 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ]
235 @c Z8000 has no machine-dependent assembler options
238 @c see md_parse_option in tc-i960.c
239 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
243 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
246 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
247 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
248 [ --trap ] [ --break ]
249 [ --emulation=@var{name} ]
251 [ -- | @var{files} @dots{} ]
256 Turn on listings, in any of a variety of ways:
260 omit debugging directives
263 include high-level source
269 omit forms processing
275 set the name of the listing file
278 You may combine these options; for example, use @samp{-aln} for assembly
279 listing without forms processing. The @samp{=file} option, if used, must be
280 the last one. By itself, @samp{-a} defaults to @samp{-ahls}---that is, all
284 Ignored. This option is accepted for script compatibility with calls to
287 @item --defsym @var{sym}=@var{value}
288 Define the symbol @var{sym} to be @var{value} before assembling the input file.
289 @var{value} must be an integer constant. As in C, a leading @samp{0x}
290 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
293 ``fast''---skip whitespace and comment preprocessing (assume source is
297 Print a summary of the command line options and exit.
300 Add directory @var{dir} to the search list for @code{.include} directives.
303 Don't warn about signed overflow.
306 @ifclear DIFF-TBL-KLUGE
307 This option is accepted but has no effect on the @value{TARGET} family.
309 @ifset DIFF-TBL-KLUGE
310 Issue warnings when difference tables altered for long displacements.
314 Keep (in the symbol table) local symbols, starting with @samp{L}.
316 @item -o @var{objfile}
317 Name the object-file output from @code{@value{AS}} @var{objfile}.
320 Fold the data section into the text section.
323 Print the maximum space (in bytes) and total time (in seconds) used by
328 Print the @code{as} version.
331 Print the @code{as} version and exit.
334 Suppress warning messages.
343 Generate an object file even after errors.
345 @item -- | @var{files} @dots{}
346 Standard input, or source files to assemble.
351 The following options are available when @value{AS} is configured for
356 @cindex ARC endianness
357 @cindex endianness, ARC
358 @cindex big endian output, ARC
360 Generate ``big endian'' format output.
362 @cindex little endian output, ARC
363 @item -mlittle-endian
364 Generate ``little endian'' format output.
370 The following options are available when @value{AS} is configured for the ARM
374 @item -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]7[t][[d]m] | -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t
375 Specify which variant of the ARM architecture is the target.
376 @item -mthumb | -mall
377 Enable or disable Thumb only instruction decoding.
378 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
379 Select which Floating Point architcture is the target.
380 @item -mapcs-32 | -mapcs-26
381 Select which procedure calling convention is in use.
383 Select either big-endian (-EB) or little-endian (-EL) output.
388 The following options are available when @value{AS} is configured for
391 @cindex D10V optimization
392 @cindex optimization, D10V
394 Optimize output by parallelizing instructions.
399 The following options are available when @value{AS} is configured for the
400 Intel 80960 processor.
403 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
404 Specify which variant of the 960 architecture is the target.
407 Add code to collect statistics about branches taken.
410 Do not alter compare-and-branch instructions for long displacements;
417 The following options are available when @value{AS} is configured for the
418 Motorola 68000 series.
423 Shorten references to undefined symbols, to one word instead of two.
425 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
426 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
427 Specify what processor in the 68000 family is the target. The default
428 is normally the 68020, but this can be changed at configuration time.
430 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
431 The target machine does (or does not) have a floating-point coprocessor.
432 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
433 the basic 68000 is not compatible with the 68881, a combination of the
434 two can be specified, since it's possible to do emulation of the
435 coprocessor instructions with the main processor.
437 @item -m68851 | -mno-68851
438 The target machine does (or does not) have a memory-management
439 unit coprocessor. The default is to assume an MMU for 68020 and up.
445 The following options are available when @code{@value{AS}} is configured
446 for the SPARC architecture:
449 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite | -Av9 | -Av9a
450 Explicitly select a variant of the SPARC architecture.
452 @item -xarch=v8plus | -xarch=v8plusa
453 For compatibility with the Solaris v9 assembler. These options are
454 equivalent to -Av9 and -Av9a, respectively.
457 Warn when the assembler switches to another architecture.
462 The following options are available when @value{AS} is configured for
467 This option sets the largest size of an object that can be referenced
468 implicitly with the @code{gp} register. It is only accepted for targets that
469 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
471 @cindex MIPS endianness
472 @cindex endianness, MIPS
473 @cindex big endian output, MIPS
475 Generate ``big endian'' format output.
477 @cindex little endian output, MIPS
479 Generate ``little endian'' format output.
485 Generate code for a particular MIPS Instruction Set Architecture level.
486 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
487 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
492 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
493 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
494 instructions around accesses to the @samp{HI} and @samp{LO} registers.
495 @samp{-no-m4650} turns off this option.
497 @item -mcpu=@var{CPU}
498 Generate code for a particular MIPS cpu. This has little effect on the
499 assembler, but it is passed by @code{@value{GCC}}.
502 @item --emulation=@var{name}
503 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
504 for some other target, in all respects, including output format (choosing
505 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
506 debugging information or store symbol table information, and default
507 endianness. The available configuration names are: @samp{mipsecoff},
508 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
509 @samp{mipsbelf}. The first two do not alter the default endianness from that
510 of the primary target for which the assembler was configured; the others change
511 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
512 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
513 selection in any case.
515 This option is currently supported only when the primary target
516 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
517 Furthermore, the primary target or others specified with
518 @samp{--enable-targets=@dots{}} at configuration time must include support for
519 the other format, if both are to be available. For example, the Irix 5
520 configuration includes support for both.
522 Eventually, this option will support more configurations, with more
523 fine-grained control over the assembler's behavior, and will be supported for
527 @code{@value{AS}} ignores this option. It is accepted for compatibility with
535 Control how to deal with multiplication overflow and division by zero.
536 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
537 (and only work for Instruction Set Architecture level 2 and higher);
538 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
544 * Manual:: Structure of this Manual
545 * GNU Assembler:: The GNU Assembler
546 * Object Formats:: Object File Formats
547 * Command Line:: Command Line
548 * Input Files:: Input Files
549 * Object:: Output (Object) File
550 * Errors:: Error and Warning Messages
554 @section Structure of this Manual
556 @cindex manual, structure and purpose
557 This manual is intended to describe what you need to know to use
558 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
559 notation for symbols, constants, and expressions; the directives that
560 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
563 We also cover special features in the @value{TARGET}
564 configuration of @code{@value{AS}}, including assembler directives.
567 This manual also describes some of the machine-dependent features of
568 various flavors of the assembler.
571 @cindex machine instructions (not covered)
572 On the other hand, this manual is @emph{not} intended as an introduction
573 to programming in assembly language---let alone programming in general!
574 In a similar vein, we make no attempt to introduce the machine
575 architecture; we do @emph{not} describe the instruction set, standard
576 mnemonics, registers or addressing modes that are standard to a
577 particular architecture.
579 You may want to consult the manufacturer's
580 machine architecture manual for this information.
584 For information on the H8/300 machine instruction set, see @cite{H8/300
585 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
586 see @cite{H8/300H Series Programming Manual} (Hitachi).
589 For information on the H8/500 machine instruction set, see @cite{H8/500
590 Series Programming Manual} (Hitachi M21T001).
593 For information on the Hitachi SH machine instruction set, see
594 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
597 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
601 @c I think this is premature---doc@cygnus.com, 17jan1991
603 Throughout this manual, we assume that you are running @dfn{GNU},
604 the portable operating system from the @dfn{Free Software
605 Foundation, Inc.}. This restricts our attention to certain kinds of
606 computer (in particular, the kinds of computers that @sc{gnu} can run on);
607 once this assumption is granted examples and definitions need less
610 @code{@value{AS}} is part of a team of programs that turn a high-level
611 human-readable series of instructions into a low-level
612 computer-readable series of instructions. Different versions of
613 @code{@value{AS}} are used for different kinds of computer.
616 @c There used to be a section "Terminology" here, which defined
617 @c "contents", "byte", "word", and "long". Defining "word" to any
618 @c particular size is confusing when the .word directive may generate 16
619 @c bits on one machine and 32 bits on another; in general, for the user
620 @c version of this manual, none of these terms seem essential to define.
621 @c They were used very little even in the former draft of the manual;
622 @c this draft makes an effort to avoid them (except in names of
626 @section The GNU Assembler
628 @sc{gnu} @code{as} is really a family of assemblers.
630 This manual describes @code{@value{AS}}, a member of that family which is
631 configured for the @value{TARGET} architectures.
633 If you use (or have used) the @sc{gnu} assembler on one architecture, you
634 should find a fairly similar environment when you use it on another
635 architecture. Each version has much in common with the others,
636 including object file formats, most assembler directives (often called
637 @dfn{pseudo-ops}) and assembler syntax.@refill
639 @cindex purpose of @sc{gnu} assembler
640 @code{@value{AS}} is primarily intended to assemble the output of the
641 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
642 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
643 assemble correctly everything that other assemblers for the same
644 machine would assemble.
646 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
649 @c This remark should appear in generic version of manual; assumption
650 @c here is that generic version sets M680x0.
651 This doesn't mean @code{@value{AS}} always uses the same syntax as another
652 assembler for the same architecture; for example, we know of several
653 incompatible versions of 680x0 assembly language syntax.
656 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
657 program in one pass of the source file. This has a subtle impact on the
658 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
661 @section Object File Formats
663 @cindex object file format
664 The @sc{gnu} assembler can be configured to produce several alternative
665 object file formats. For the most part, this does not affect how you
666 write assembly language programs; but directives for debugging symbols
667 are typically different in different file formats. @xref{Symbol
668 Attributes,,Symbol Attributes}.
671 On the @value{TARGET}, @code{@value{AS}} is configured to produce
672 @value{OBJ-NAME} format object files.
674 @c The following should exhaust all configs that set MULTI-OBJ, ideally
676 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
677 @code{a.out} or COFF format object files.
680 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
681 @code{b.out} or COFF format object files.
684 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
685 SOM or ELF format object files.
690 @section Command Line
692 @cindex command line conventions
693 After the program name @code{@value{AS}}, the command line may contain
694 options and file names. Options may appear in any order, and may be
695 before, after, or between file names. The order of file names is
698 @cindex standard input, as input file
700 @file{--} (two hyphens) by itself names the standard input file
701 explicitly, as one of the files for @code{@value{AS}} to assemble.
703 @cindex options, command line
704 Except for @samp{--} any command line argument that begins with a
705 hyphen (@samp{-}) is an option. Each option changes the behavior of
706 @code{@value{AS}}. No option changes the way another option works. An
707 option is a @samp{-} followed by one or more letters; the case of
708 the letter is important. All options are optional.
710 Some options expect exactly one file name to follow them. The file
711 name may either immediately follow the option's letter (compatible
712 with older assemblers) or it may be the next command argument (@sc{gnu}
713 standard). These two command lines are equivalent:
716 @value{AS} -o my-object-file.o mumble.s
717 @value{AS} -omy-object-file.o mumble.s
724 @cindex source program
726 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
727 describe the program input to one run of @code{@value{AS}}. The program may
728 be in one or more files; how the source is partitioned into files
729 doesn't change the meaning of the source.
731 @c I added "con" prefix to "catenation" just to prove I can overcome my
732 @c APL training... doc@cygnus.com
733 The source program is a concatenation of the text in all the files, in the
736 Each time you run @code{@value{AS}} it assembles exactly one source
737 program. The source program is made up of one or more files.
738 (The standard input is also a file.)
740 You give @code{@value{AS}} a command line that has zero or more input file
741 names. The input files are read (from left file name to right). A
742 command line argument (in any position) that has no special meaning
743 is taken to be an input file name.
745 If you give @code{@value{AS}} no file names it attempts to read one input file
746 from the @code{@value{AS}} standard input, which is normally your terminal. You
747 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
750 Use @samp{--} if you need to explicitly name the standard input file
751 in your command line.
753 If the source is empty, @code{@value{AS}} produces a small, empty object
756 @subheading Filenames and Line-numbers
758 @cindex input file linenumbers
759 @cindex line numbers, in input files
760 There are two ways of locating a line in the input file (or files) and
761 either may be used in reporting error messages. One way refers to a line
762 number in a physical file; the other refers to a line number in a
763 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
765 @dfn{Physical files} are those files named in the command line given
766 to @code{@value{AS}}.
768 @dfn{Logical files} are simply names declared explicitly by assembler
769 directives; they bear no relation to physical files. Logical file names
770 help error messages reflect the original source file, when @code{@value{AS}}
771 source is itself synthesized from other files.
772 @xref{App-File,,@code{.app-file}}.
775 @section Output (Object) File
781 Every time you run @code{@value{AS}} it produces an output file, which is
782 your assembly language program translated into numbers. This file
783 is the object file. Its default name is
791 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
793 You can give it another name by using the @code{-o} option. Conventionally,
794 object file names end with @file{.o}. The default name is used for historical
795 reasons: older assemblers were capable of assembling self-contained programs
796 directly into a runnable program. (For some formats, this isn't currently
797 possible, but it can be done for the @code{a.out} format.)
801 The object file is meant for input to the linker @code{@value{LD}}. It contains
802 assembled program code, information to help @code{@value{LD}} integrate
803 the assembled program into a runnable file, and (optionally) symbolic
804 information for the debugger.
806 @c link above to some info file(s) like the description of a.out.
807 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
810 @section Error and Warning Messages
812 @cindex error messsages
813 @cindex warning messages
814 @cindex messages from assembler
815 @code{@value{AS}} may write warnings and error messages to the standard error
816 file (usually your terminal). This should not happen when a compiler
817 runs @code{@value{AS}} automatically. Warnings report an assumption made so
818 that @code{@value{AS}} could keep assembling a flawed program; errors report a
819 grave problem that stops the assembly.
821 @cindex format of warning messages
822 Warning messages have the format
825 file_name:@b{NNN}:Warning Message Text
829 @cindex line numbers, in warnings/errors
830 (where @b{NNN} is a line number). If a logical file name has been given
831 (@pxref{App-File,,@code{.app-file}}) it is used for the filename,
832 otherwise the name of the current input file is used. If a logical line
835 (@pxref{Line,,@code{.line}})
839 (@pxref{Line,,@code{.line}})
842 (@pxref{Ln,,@code{.ln}})
845 then it is used to calculate the number printed,
846 otherwise the actual line in the current source file is printed. The
847 message text is intended to be self explanatory (in the grand Unix
850 @cindex format of error messages
851 Error messages have the format
853 file_name:@b{NNN}:FATAL:Error Message Text
855 The file name and line number are derived as for warning
856 messages. The actual message text may be rather less explanatory
857 because many of them aren't supposed to happen.
860 @chapter Command-Line Options
862 @cindex options, all versions of assembler
863 This chapter describes command-line options available in @emph{all}
864 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
866 to the @value{TARGET}.
869 to particular machine architectures.
872 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2), you
873 can use the @samp{-Wa} option to pass arguments through to the
874 assembler. The assembler arguments must be separated from each other
875 (and the @samp{-Wa}) by commas. For example:
878 gcc -c -g -O -Wa,-alh,-L file.c
882 emits a listing to standard output with high-level
885 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
886 command-line options are automatically passed to the assembler by the compiler.
887 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
888 precisely what options it passes to each compilation pass, including the
892 * a:: -a[cdhlns] enable listings
893 * D:: -D for compatibility
894 * f:: -f to work faster
895 * I:: -I for .include search path
896 @ifclear DIFF-TBL-KLUGE
897 * K:: -K for compatibility
899 @ifset DIFF-TBL-KLUGE
900 * K:: -K for difference tables
903 * L:: -L to retain local labels
904 * M:: -M or --mri to assemble in MRI compatibility mode
905 * MD:: --MD for dependency tracking
906 * o:: -o to name the object file
907 * R:: -R to join data and text sections
908 * statistics:: --statistics to see statistics about assembly
909 * v:: -v to announce version
910 * W:: -W to suppress warnings
911 * Z:: -Z to make object file even after errors
915 @section Enable Listings: @code{-a[cdhlns]}
924 @cindex listings, enabling
925 @cindex assembly listings, enabling
927 These options enable listing output from the assembler. By itself,
928 @samp{-a} requests high-level, assembly, and symbols listing.
929 You can use other letters to select specific options for the list:
930 @samp{-ah} requests a high-level language listing,
931 @samp{-al} requests an output-program assembly listing, and
932 @samp{-as} requests a symbol table listing.
933 High-level listings require that a compiler debugging option like
934 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
937 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
938 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
939 other conditional), or a true @code{.if} followed by an @code{.else}, will be
940 omitted from the listing.
942 Use the @samp{-ad} option to omit debugging directives from the
945 Once you have specified one of these options, you can further control
946 listing output and its appearance using the directives @code{.list},
947 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
949 The @samp{-an} option turns off all forms processing.
950 If you do not request listing output with one of the @samp{-a} options, the
951 listing-control directives have no effect.
953 The letters after @samp{-a} may be combined into one option,
954 @emph{e.g.}, @samp{-aln}.
960 This option has no effect whatsoever, but it is accepted to make it more
961 likely that scripts written for other assemblers also work with
965 @section Work Faster: @code{-f}
968 @cindex trusted compiler
969 @cindex faster processing (@code{-f})
970 @samp{-f} should only be used when assembling programs written by a
971 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
972 and comment preprocessing on
973 the input file(s) before assembling them. @xref{Preprocessing,
977 @emph{Warning:} if you use @samp{-f} when the files actually need to be
978 preprocessed (if they contain comments, for example), @code{@value{AS}} does
983 @section @code{.include} search path: @code{-I} @var{path}
985 @kindex -I @var{path}
986 @cindex paths for @code{.include}
987 @cindex search path for @code{.include}
988 @cindex @code{include} directive search path
989 Use this option to add a @var{path} to the list of directories
990 @code{@value{AS}} searches for files specified in @code{.include}
991 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
992 many times as necessary to include a variety of paths. The current
993 working directory is always searched first; after that, @code{@value{AS}}
994 searches any @samp{-I} directories in the same order as they were
995 specified (left to right) on the command line.
998 @section Difference Tables: @code{-K}
1001 @ifclear DIFF-TBL-KLUGE
1002 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1003 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1004 where it can be used to warn when the assembler alters the machine code
1005 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1006 family does not have the addressing limitations that sometimes lead to this
1007 alteration on other platforms.
1010 @ifset DIFF-TBL-KLUGE
1011 @cindex difference tables, warning
1012 @cindex warning for altered difference tables
1013 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1014 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1015 You can use the @samp{-K} option if you want a warning issued when this
1020 @section Include Local Labels: @code{-L}
1023 @cindex local labels, retaining in output
1024 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1025 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1026 debugging, because they are intended for the use of programs (like
1027 compilers) that compose assembler programs, not for your notice.
1028 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1029 normally debug with them.
1031 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1032 in the object file. Usually if you do this you also tell the linker
1033 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1035 By default, a local label is any label beginning with @samp{L}, but each
1036 target is allowed to redefine the local label prefix.
1038 On the HPPA local labels begin with @samp{L$}.
1041 @samp{;} for the ARM family;
1045 @section Assemble in MRI Compatibility Mode: @code{-M}
1048 @cindex MRI compatibility mode
1049 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1050 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1051 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1052 configured target) assembler from Microtec Research. The exact nature of the
1053 MRI syntax will not be documented here; see the MRI manuals for more
1054 information. Note in particular that the handling of macros and macro
1055 arguments is somewhat different. The purpose of this option is to permit
1056 assembling existing MRI assembler code using @code{@value{AS}}.
1058 The MRI compatibility is not complete. Certain operations of the MRI assembler
1059 depend upon its object file format, and can not be supported using other object
1060 file formats. Supporting these would require enhancing each object file format
1061 individually. These are:
1064 @item global symbols in common section
1066 The m68k MRI assembler supports common sections which are merged by the linker.
1067 Other object file formats do not support this. @code{@value{AS}} handles
1068 common sections by treating them as a single common symbol. It permits local
1069 symbols to be defined within a common section, but it can not support global
1070 symbols, since it has no way to describe them.
1072 @item complex relocations
1074 The MRI assemblers support relocations against a negated section address, and
1075 relocations which combine the start addresses of two or more sections. These
1076 are not support by other object file formats.
1078 @item @code{END} pseudo-op specifying start address
1080 The MRI @code{END} pseudo-op permits the specification of a start address.
1081 This is not supported by other object file formats. The start address may
1082 instead be specified using the @code{-e} option to the linker, or in a linker
1085 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1087 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1088 name to the output file. This is not supported by other object file formats.
1090 @item @code{ORG} pseudo-op
1092 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1093 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1094 which changes the location within the current section. Absolute sections are
1095 not supported by other object file formats. The address of a section may be
1096 assigned within a linker script.
1099 There are some other features of the MRI assembler which are not supported by
1100 @code{@value{AS}}, typically either because they are difficult or because they
1101 seem of little consequence. Some of these may be supported in future releases.
1105 @item EBCDIC strings
1107 EBCDIC strings are not supported.
1109 @item packed binary coded decimal
1111 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1112 and @code{DCB.P} pseudo-ops are not supported.
1114 @item @code{FEQU} pseudo-op
1116 The m68k @code{FEQU} pseudo-op is not supported.
1118 @item @code{NOOBJ} pseudo-op
1120 The m68k @code{NOOBJ} pseudo-op is not supported.
1122 @item @code{OPT} branch control options
1124 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1125 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1126 relaxes all branches, whether forward or backward, to an appropriate size, so
1127 these options serve no purpose.
1129 @item @code{OPT} list control options
1131 The following m68k @code{OPT} list control options are ignored: @code{C},
1132 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1133 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1135 @item other @code{OPT} options
1137 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1138 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1140 @item @code{OPT} @code{D} option is default
1142 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1143 @code{OPT NOD} may be used to turn it off.
1145 @item @code{XREF} pseudo-op.
1147 The m68k @code{XREF} pseudo-op is ignored.
1149 @item @code{.debug} pseudo-op
1151 The i960 @code{.debug} pseudo-op is not supported.
1153 @item @code{.extended} pseudo-op
1155 The i960 @code{.extended} pseudo-op is not supported.
1157 @item @code{.list} pseudo-op.
1159 The various options of the i960 @code{.list} pseudo-op are not supported.
1161 @item @code{.optimize} pseudo-op
1163 The i960 @code{.optimize} pseudo-op is not supported.
1165 @item @code{.output} pseudo-op
1167 The i960 @code{.output} pseudo-op is not supported.
1169 @item @code{.setreal} pseudo-op
1171 The i960 @code{.setreal} pseudo-op is not supported.
1176 @section Dependency tracking: @code{--MD}
1179 @cindex dependency tracking
1182 @code{@value{AS}} can generate a dependency file for the file it creates. This
1183 file consists of a single rule suitable for @code{make} describing the
1184 dependencies of the main source file.
1186 The rule is written to the file named in its argument.
1188 This feature is used in the automatic updating of makefiles.
1191 @section Name the Object File: @code{-o}
1194 @cindex naming object file
1195 @cindex object file name
1196 There is always one object file output when you run @code{@value{AS}}. By
1197 default it has the name
1200 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1214 You use this option (which takes exactly one filename) to give the
1215 object file a different name.
1217 Whatever the object file is called, @code{@value{AS}} overwrites any
1218 existing file of the same name.
1221 @section Join Data and Text Sections: @code{-R}
1224 @cindex data and text sections, joining
1225 @cindex text and data sections, joining
1226 @cindex joining text and data sections
1227 @cindex merging text and data sections
1228 @code{-R} tells @code{@value{AS}} to write the object file as if all
1229 data-section data lives in the text section. This is only done at
1230 the very last moment: your binary data are the same, but data
1231 section parts are relocated differently. The data section part of
1232 your object file is zero bytes long because all its bytes are
1233 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1235 When you specify @code{-R} it would be possible to generate shorter
1236 address displacements (because we do not have to cross between text and
1237 data section). We refrain from doing this simply for compatibility with
1238 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1241 When @code{@value{AS}} is configured for COFF output,
1242 this option is only useful if you use sections named @samp{.text} and
1247 @code{-R} is not supported for any of the HPPA targets. Using
1248 @code{-R} generates a warning from @code{@value{AS}}.
1252 @section Display Assembly Statistics: @code{--statistics}
1254 @kindex --statistics
1255 @cindex statistics, about assembly
1256 @cindex time, total for assembly
1257 @cindex space used, maximum for assembly
1258 Use @samp{--statistics} to display two statistics about the resources used by
1259 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1260 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1264 @section Announce Version: @code{-v}
1268 @cindex assembler version
1269 @cindex version of assembler
1270 You can find out what version of as is running by including the
1271 option @samp{-v} (which you can also spell as @samp{-version}) on the
1275 @section Suppress Warnings: @code{-W}
1278 @cindex suppressing warnings
1279 @cindex warnings, suppressing
1280 @code{@value{AS}} should never give a warning or error message when
1281 assembling compiler output. But programs written by people often
1282 cause @code{@value{AS}} to give a warning that a particular assumption was
1283 made. All such warnings are directed to the standard error file.
1284 If you use this option, no warnings are issued. This option only
1285 affects the warning messages: it does not change any particular of how
1286 @code{@value{AS}} assembles your file. Errors, which stop the assembly, are
1290 @section Generate Object File in Spite of Errors: @code{-Z}
1291 @cindex object file, after errors
1292 @cindex errors, continuing after
1293 After an error message, @code{@value{AS}} normally produces no output. If for
1294 some reason you are interested in object file output even after
1295 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1296 option. If there are any errors, @code{@value{AS}} continues anyways, and
1297 writes an object file after a final warning message of the form @samp{@var{n}
1298 errors, @var{m} warnings, generating bad object file.}
1303 @cindex machine-independent syntax
1304 @cindex syntax, machine-independent
1305 This chapter describes the machine-independent syntax allowed in a
1306 source file. @code{@value{AS}} syntax is similar to what many other
1307 assemblers use; it is inspired by the BSD 4.2
1312 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1316 * Preprocessing:: Preprocessing
1317 * Whitespace:: Whitespace
1318 * Comments:: Comments
1319 * Symbol Intro:: Symbols
1320 * Statements:: Statements
1321 * Constants:: Constants
1325 @section Preprocessing
1327 @cindex preprocessing
1328 The @code{@value{AS}} internal preprocessor:
1330 @cindex whitespace, removed by preprocessor
1332 adjusts and removes extra whitespace. It leaves one space or tab before
1333 the keywords on a line, and turns any other whitespace on the line into
1336 @cindex comments, removed by preprocessor
1338 removes all comments, replacing them with a single space, or an
1339 appropriate number of newlines.
1341 @cindex constants, converted by preprocessor
1343 converts character constants into the appropriate numeric values.
1346 It does not do macro processing, include file handling, or
1347 anything else you may get from your C compiler's preprocessor. You can
1348 do include file processing with the @code{.include} directive
1349 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1350 to get other ``CPP'' style preprocessing, by giving the input file a
1351 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1352 Output, gcc.info, Using GNU CC}.
1354 Excess whitespace, comments, and character constants
1355 cannot be used in the portions of the input text that are not
1358 @cindex turning preprocessing on and off
1359 @cindex preprocessing, turning on and off
1362 If the first line of an input file is @code{#NO_APP} or if you use the
1363 @samp{-f} option, whitespace and comments are not removed from the input file.
1364 Within an input file, you can ask for whitespace and comment removal in
1365 specific portions of the by putting a line that says @code{#APP} before the
1366 text that may contain whitespace or comments, and putting a line that says
1367 @code{#NO_APP} after this text. This feature is mainly intend to support
1368 @code{asm} statements in compilers whose output is otherwise free of comments
1375 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1376 Whitespace is used to separate symbols, and to make programs neater for
1377 people to read. Unless within character constants
1378 (@pxref{Characters,,Character Constants}), any whitespace means the same
1379 as exactly one space.
1385 There are two ways of rendering comments to @code{@value{AS}}. In both
1386 cases the comment is equivalent to one space.
1388 Anything from @samp{/*} through the next @samp{*/} is a comment.
1389 This means you may not nest these comments.
1393 The only way to include a newline ('\n') in a comment
1394 is to use this sort of comment.
1397 /* This sort of comment does not nest. */
1400 @cindex line comment character
1401 Anything from the @dfn{line comment} character to the next newline
1402 is considered a comment and is ignored. The line comment character is
1404 @samp{;} for the AMD 29K family;
1407 @samp{;} on the ARC;
1410 @samp{;} for the H8/300 family;
1413 @samp{!} for the H8/500 family;
1416 @samp{;} for the HPPA;
1419 @samp{#} on the i960;
1422 @samp{!} for the Hitachi SH;
1425 @samp{!} on the SPARC;
1428 @samp{|} on the 680x0;
1431 @samp{#} on the Vax;
1434 @samp{!} for the Z8000;
1436 see @ref{Machine Dependencies}. @refill
1437 @c FIXME What about i386, m88k, i860?
1440 On some machines there are two different line comment characters. One
1441 character only begins a comment if it is the first non-whitespace character on
1442 a line, while the other always begins a comment.
1446 @cindex lines starting with @code{#}
1447 @cindex logical line numbers
1448 To be compatible with past assemblers, lines that begin with @samp{#} have a
1449 special interpretation. Following the @samp{#} should be an absolute
1450 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1451 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1452 new logical file name. The rest of the line, if any, should be whitespace.
1454 If the first non-whitespace characters on the line are not numeric,
1455 the line is ignored. (Just like a comment.)
1458 # This is an ordinary comment.
1459 # 42-6 "new_file_name" # New logical file name
1460 # This is logical line # 36.
1462 This feature is deprecated, and may disappear from future versions
1463 of @code{@value{AS}}.
1468 @cindex characters used in symbols
1469 @ifclear SPECIAL-SYMS
1470 A @dfn{symbol} is one or more characters chosen from the set of all
1471 letters (both upper and lower case), digits and the three characters
1477 A @dfn{symbol} is one or more characters chosen from the set of all
1478 letters (both upper and lower case), digits and the three characters
1479 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1485 On most machines, you can also use @code{$} in symbol names; exceptions
1486 are noted in @ref{Machine Dependencies}.
1488 No symbol may begin with a digit. Case is significant.
1489 There is no length limit: all characters are significant. Symbols are
1490 delimited by characters not in that set, or by the beginning of a file
1491 (since the source program must end with a newline, the end of a file is
1492 not a possible symbol delimiter). @xref{Symbols}.
1493 @cindex length of symbols
1498 @cindex statements, structure of
1499 @cindex line separator character
1500 @cindex statement separator character
1502 @ifclear abnormal-separator
1503 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1504 semicolon (@samp{;}). The newline or semicolon is considered part of
1505 the preceding statement. Newlines and semicolons within character
1506 constants are an exception: they do not end statements.
1508 @ifset abnormal-separator
1510 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1511 sign (@samp{@@}). The newline or at sign is considered part of the
1512 preceding statement. Newlines and at signs within character constants
1513 are an exception: they do not end statements.
1516 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1517 point (@samp{!}). The newline or exclamation point is considered part of the
1518 preceding statement. Newlines and exclamation points within character
1519 constants are an exception: they do not end statements.
1522 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1523 H8/300) a dollar sign (@samp{$}); or (for the
1526 (@samp{;}). The newline or separator character is considered part of
1527 the preceding statement. Newlines and separators within character
1528 constants are an exception: they do not end statements.
1533 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1534 separator character. (The line separator is usually @samp{;}, unless
1535 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1536 newline or separator character is considered part of the preceding
1537 statement. Newlines and separators within character constants are an
1538 exception: they do not end statements.
1541 @cindex newline, required at file end
1542 @cindex EOF, newline must precede
1543 It is an error to end any statement with end-of-file: the last
1544 character of any input file should be a newline.@refill
1546 @cindex continuing statements
1547 @cindex multi-line statements
1548 @cindex statement on multiple lines
1549 You may write a statement on more than one line if you put a
1550 backslash (@kbd{\}) immediately in front of any newlines within the
1551 statement. When @code{@value{AS}} reads a backslashed newline both
1552 characters are ignored. You can even put backslashed newlines in
1553 the middle of symbol names without changing the meaning of your
1556 An empty statement is allowed, and may include whitespace. It is ignored.
1558 @cindex instructions and directives
1559 @cindex directives and instructions
1560 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1561 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1563 A statement begins with zero or more labels, optionally followed by a
1564 key symbol which determines what kind of statement it is. The key
1565 symbol determines the syntax of the rest of the statement. If the
1566 symbol begins with a dot @samp{.} then the statement is an assembler
1567 directive: typically valid for any computer. If the symbol begins with
1568 a letter the statement is an assembly language @dfn{instruction}: it
1569 assembles into a machine language instruction.
1571 Different versions of @code{@value{AS}} for different computers
1572 recognize different instructions. In fact, the same symbol may
1573 represent a different instruction in a different computer's assembly
1577 @cindex @code{:} (label)
1578 @cindex label (@code{:})
1579 A label is a symbol immediately followed by a colon (@code{:}).
1580 Whitespace before a label or after a colon is permitted, but you may not
1581 have whitespace between a label's symbol and its colon. @xref{Labels}.
1584 For HPPA targets, labels need not be immediately followed by a colon, but
1585 the definition of a label must begin in column zero. This also implies that
1586 only one label may be defined on each line.
1590 label: .directive followed by something
1591 another_label: # This is an empty statement.
1592 instruction operand_1, operand_2, @dots{}
1599 A constant is a number, written so that its value is known by
1600 inspection, without knowing any context. Like this:
1603 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1604 .ascii "Ring the bell\7" # A string constant.
1605 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1606 .float 0f-314159265358979323846264338327\
1607 95028841971.693993751E-40 # - pi, a flonum.
1612 * Characters:: Character Constants
1613 * Numbers:: Number Constants
1617 @subsection Character Constants
1619 @cindex character constants
1620 @cindex constants, character
1621 There are two kinds of character constants. A @dfn{character} stands
1622 for one character in one byte and its value may be used in
1623 numeric expressions. String constants (properly called string
1624 @emph{literals}) are potentially many bytes and their values may not be
1625 used in arithmetic expressions.
1629 * Chars:: Characters
1633 @subsubsection Strings
1635 @cindex string constants
1636 @cindex constants, string
1637 A @dfn{string} is written between double-quotes. It may contain
1638 double-quotes or null characters. The way to get special characters
1639 into a string is to @dfn{escape} these characters: precede them with
1640 a backslash @samp{\} character. For example @samp{\\} represents
1641 one backslash: the first @code{\} is an escape which tells
1642 @code{@value{AS}} to interpret the second character literally as a backslash
1643 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1644 escape character). The complete list of escapes follows.
1646 @cindex escape codes, character
1647 @cindex character escape codes
1650 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1652 @cindex @code{\b} (backspace character)
1653 @cindex backspace (@code{\b})
1655 Mnemonic for backspace; for ASCII this is octal code 010.
1658 @c Mnemonic for EOText; for ASCII this is octal code 004.
1660 @cindex @code{\f} (formfeed character)
1661 @cindex formfeed (@code{\f})
1663 Mnemonic for FormFeed; for ASCII this is octal code 014.
1665 @cindex @code{\n} (newline character)
1666 @cindex newline (@code{\n})
1668 Mnemonic for newline; for ASCII this is octal code 012.
1671 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1673 @cindex @code{\r} (carriage return character)
1674 @cindex carriage return (@code{\r})
1676 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1679 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1680 @c other assemblers.
1682 @cindex @code{\t} (tab)
1683 @cindex tab (@code{\t})
1685 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1688 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1689 @c @item \x @var{digit} @var{digit} @var{digit}
1690 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1692 @cindex @code{\@var{ddd}} (octal character code)
1693 @cindex octal character code (@code{\@var{ddd}})
1694 @item \ @var{digit} @var{digit} @var{digit}
1695 An octal character code. The numeric code is 3 octal digits.
1696 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1697 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1699 @cindex @code{\@var{xd...}} (hex character code)
1700 @cindex hex character code (@code{\@var{xd...}})
1701 @item \@code{x} @var{hex-digits...}
1702 A hex character code. All trailing hex digits are combined. Either upper or
1703 lower case @code{x} works.
1705 @cindex @code{\\} (@samp{\} character)
1706 @cindex backslash (@code{\\})
1708 Represents one @samp{\} character.
1711 @c Represents one @samp{'} (accent acute) character.
1712 @c This is needed in single character literals
1713 @c (@xref{Characters,,Character Constants}.) to represent
1716 @cindex @code{\"} (doublequote character)
1717 @cindex doublequote (@code{\"})
1719 Represents one @samp{"} character. Needed in strings to represent
1720 this character, because an unescaped @samp{"} would end the string.
1722 @item \ @var{anything-else}
1723 Any other character when escaped by @kbd{\} gives a warning, but
1724 assembles as if the @samp{\} was not present. The idea is that if
1725 you used an escape sequence you clearly didn't want the literal
1726 interpretation of the following character. However @code{@value{AS}} has no
1727 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1728 code and warns you of the fact.
1731 Which characters are escapable, and what those escapes represent,
1732 varies widely among assemblers. The current set is what we think
1733 the BSD 4.2 assembler recognizes, and is a subset of what most C
1734 compilers recognize. If you are in doubt, do not use an escape
1738 @subsubsection Characters
1740 @cindex single character constant
1741 @cindex character, single
1742 @cindex constant, single character
1743 A single character may be written as a single quote immediately
1744 followed by that character. The same escapes apply to characters as
1745 to strings. So if you want to write the character backslash, you
1746 must write @kbd{'\\} where the first @code{\} escapes the second
1747 @code{\}. As you can see, the quote is an acute accent, not a
1748 grave accent. A newline
1750 @ifclear abnormal-separator
1751 (or semicolon @samp{;})
1753 @ifset abnormal-separator
1755 (or at sign @samp{@@})
1758 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1764 immediately following an acute accent is taken as a literal character
1765 and does not count as the end of a statement. The value of a character
1766 constant in a numeric expression is the machine's byte-wide code for
1767 that character. @code{@value{AS}} assumes your character code is ASCII:
1768 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1771 @subsection Number Constants
1773 @cindex constants, number
1774 @cindex number constants
1775 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1776 are stored in the target machine. @emph{Integers} are numbers that
1777 would fit into an @code{int} in the C language. @emph{Bignums} are
1778 integers, but they are stored in more than 32 bits. @emph{Flonums}
1779 are floating point numbers, described below.
1782 * Integers:: Integers
1787 * Bit Fields:: Bit Fields
1793 @subsubsection Integers
1795 @cindex constants, integer
1797 @cindex binary integers
1798 @cindex integers, binary
1799 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1800 the binary digits @samp{01}.
1802 @cindex octal integers
1803 @cindex integers, octal
1804 An octal integer is @samp{0} followed by zero or more of the octal
1805 digits (@samp{01234567}).
1807 @cindex decimal integers
1808 @cindex integers, decimal
1809 A decimal integer starts with a non-zero digit followed by zero or
1810 more digits (@samp{0123456789}).
1812 @cindex hexadecimal integers
1813 @cindex integers, hexadecimal
1814 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
1815 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
1817 Integers have the usual values. To denote a negative integer, use
1818 the prefix operator @samp{-} discussed under expressions
1819 (@pxref{Prefix Ops,,Prefix Operators}).
1822 @subsubsection Bignums
1825 @cindex constants, bignum
1826 A @dfn{bignum} has the same syntax and semantics as an integer
1827 except that the number (or its negative) takes more than 32 bits to
1828 represent in binary. The distinction is made because in some places
1829 integers are permitted while bignums are not.
1832 @subsubsection Flonums
1834 @cindex floating point numbers
1835 @cindex constants, floating point
1837 @cindex precision, floating point
1838 A @dfn{flonum} represents a floating point number. The translation is
1839 indirect: a decimal floating point number from the text is converted by
1840 @code{@value{AS}} to a generic binary floating point number of more than
1841 sufficient precision. This generic floating point number is converted
1842 to a particular computer's floating point format (or formats) by a
1843 portion of @code{@value{AS}} specialized to that computer.
1845 A flonum is written by writing (in order)
1850 (@samp{0} is optional on the HPPA.)
1854 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
1856 @kbd{e} is recommended. Case is not important.
1858 @c FIXME: verify if flonum syntax really this vague for most cases
1859 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
1860 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
1863 On the H8/300, H8/500,
1865 and AMD 29K architectures, the letter must be
1866 one of the letters @samp{DFPRSX} (in upper or lower case).
1868 On the ARC, the letter must be one of the letters @samp{DFRS}
1869 (in upper or lower case).
1871 On the Intel 960 architecture, the letter must be
1872 one of the letters @samp{DFT} (in upper or lower case).
1874 On the HPPA architecture, the letter must be @samp{E} (upper case only).
1878 One of the letters @samp{DFPRSX} (in upper or lower case).
1881 One of the letters @samp{DFRS} (in upper or lower case).
1884 One of the letters @samp{DFPRSX} (in upper or lower case).
1887 The letter @samp{E} (upper case only).
1890 One of the letters @samp{DFT} (in upper or lower case).
1895 An optional sign: either @samp{+} or @samp{-}.
1898 An optional @dfn{integer part}: zero or more decimal digits.
1901 An optional @dfn{fractional part}: @samp{.} followed by zero
1902 or more decimal digits.
1905 An optional exponent, consisting of:
1909 An @samp{E} or @samp{e}.
1910 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
1911 @c principle this can perfectly well be different on different targets.
1913 Optional sign: either @samp{+} or @samp{-}.
1915 One or more decimal digits.
1920 At least one of the integer part or the fractional part must be
1921 present. The floating point number has the usual base-10 value.
1923 @code{@value{AS}} does all processing using integers. Flonums are computed
1924 independently of any floating point hardware in the computer running
1929 @c Bit fields are written as a general facility but are also controlled
1930 @c by a conditional-compilation flag---which is as of now (21mar91)
1931 @c turned on only by the i960 config of GAS.
1933 @subsubsection Bit Fields
1936 @cindex constants, bit field
1937 You can also define numeric constants as @dfn{bit fields}.
1938 specify two numbers separated by a colon---
1940 @var{mask}:@var{value}
1943 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
1946 The resulting number is then packed
1948 @c this conditional paren in case bit fields turned on elsewhere than 960
1949 (in host-dependent byte order)
1951 into a field whose width depends on which assembler directive has the
1952 bit-field as its argument. Overflow (a result from the bitwise and
1953 requiring more binary digits to represent) is not an error; instead,
1954 more constants are generated, of the specified width, beginning with the
1955 least significant digits.@refill
1957 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
1958 @code{.short}, and @code{.word} accept bit-field arguments.
1963 @chapter Sections and Relocation
1968 * Secs Background:: Background
1969 * Ld Sections:: Linker Sections
1970 * As Sections:: Assembler Internal Sections
1971 * Sub-Sections:: Sub-Sections
1975 @node Secs Background
1978 Roughly, a section is a range of addresses, with no gaps; all data
1979 ``in'' those addresses is treated the same for some particular purpose.
1980 For example there may be a ``read only'' section.
1982 @cindex linker, and assembler
1983 @cindex assembler, and linker
1984 The linker @code{@value{LD}} reads many object files (partial programs) and
1985 combines their contents to form a runnable program. When @code{@value{AS}}
1986 emits an object file, the partial program is assumed to start at address 0.
1987 @code{@value{LD}} assigns the final addresses for the partial program, so that
1988 different partial programs do not overlap. This is actually an
1989 oversimplification, but it suffices to explain how @code{@value{AS}} uses
1992 @code{@value{LD}} moves blocks of bytes of your program to their run-time
1993 addresses. These blocks slide to their run-time addresses as rigid
1994 units; their length does not change and neither does the order of bytes
1995 within them. Such a rigid unit is called a @emph{section}. Assigning
1996 run-time addresses to sections is called @dfn{relocation}. It includes
1997 the task of adjusting mentions of object-file addresses so they refer to
1998 the proper run-time addresses.
2000 For the H8/300 and H8/500,
2001 and for the Hitachi SH,
2002 @code{@value{AS}} pads sections if needed to
2003 ensure they end on a word (sixteen bit) boundary.
2006 @cindex standard assembler sections
2007 An object file written by @code{@value{AS}} has at least three sections, any
2008 of which may be empty. These are named @dfn{text}, @dfn{data} and
2013 When it generates COFF output,
2015 @code{@value{AS}} can also generate whatever other named sections you specify
2016 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2017 If you do not use any directives that place output in the @samp{.text}
2018 or @samp{.data} sections, these sections still exist, but are empty.
2023 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2025 @code{@value{AS}} can also generate whatever other named sections you
2026 specify using the @samp{.space} and @samp{.subspace} directives. See
2027 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2028 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2029 assembler directives.
2032 Additionally, @code{@value{AS}} uses different names for the standard
2033 text, data, and bss sections when generating SOM output. Program text
2034 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2035 BSS into @samp{$BSS$}.
2039 Within the object file, the text section starts at address @code{0}, the
2040 data section follows, and the bss section follows the data section.
2043 When generating either SOM or ELF output files on the HPPA, the text
2044 section starts at address @code{0}, the data section at address
2045 @code{0x4000000}, and the bss section follows the data section.
2048 To let @code{@value{LD}} know which data changes when the sections are
2049 relocated, and how to change that data, @code{@value{AS}} also writes to the
2050 object file details of the relocation needed. To perform relocation
2051 @code{@value{LD}} must know, each time an address in the object
2055 Where in the object file is the beginning of this reference to
2058 How long (in bytes) is this reference?
2060 Which section does the address refer to? What is the numeric value of
2062 (@var{address}) @minus{} (@var{start-address of section})?
2065 Is the reference to an address ``Program-Counter relative''?
2068 @cindex addresses, format of
2069 @cindex section-relative addressing
2070 In fact, every address @code{@value{AS}} ever uses is expressed as
2072 (@var{section}) + (@var{offset into section})
2075 Further, most expressions @code{@value{AS}} computes have this section-relative
2078 (For some object formats, such as SOM for the HPPA, some expressions are
2079 symbol-relative instead.)
2082 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2083 @var{N} into section @var{secname}.''
2085 Apart from text, data and bss sections you need to know about the
2086 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2087 addresses in the absolute section remain unchanged. For example, address
2088 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2089 @code{@value{LD}}. Although the linker never arranges two partial programs'
2090 data sections with overlapping addresses after linking, @emph{by definition}
2091 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2092 part of a program is always the same address when the program is running as
2093 address @code{@{absolute@ 239@}} in any other part of the program.
2095 The idea of sections is extended to the @dfn{undefined} section. Any
2096 address whose section is unknown at assembly time is by definition
2097 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2098 Since numbers are always defined, the only way to generate an undefined
2099 address is to mention an undefined symbol. A reference to a named
2100 common block would be such a symbol: its value is unknown at assembly
2101 time so it has section @emph{undefined}.
2103 By analogy the word @emph{section} is used to describe groups of sections in
2104 the linked program. @code{@value{LD}} puts all partial programs' text
2105 sections in contiguous addresses in the linked program. It is
2106 customary to refer to the @emph{text section} of a program, meaning all
2107 the addresses of all partial programs' text sections. Likewise for
2108 data and bss sections.
2110 Some sections are manipulated by @code{@value{LD}}; others are invented for
2111 use of @code{@value{AS}} and have no meaning except during assembly.
2114 @section Linker Sections
2115 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2120 @cindex named sections
2121 @cindex sections, named
2122 @item named sections
2125 @cindex text section
2126 @cindex data section
2130 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2131 separate but equal sections. Anything you can say of one section is
2134 When the program is running, however, it is
2135 customary for the text section to be unalterable. The
2136 text section is often shared among processes: it contains
2137 instructions, constants and the like. The data section of a running
2138 program is usually alterable: for example, C variables would be stored
2139 in the data section.
2144 This section contains zeroed bytes when your program begins running. It
2145 is used to hold unitialized variables or common storage. The length of
2146 each partial program's bss section is important, but because it starts
2147 out containing zeroed bytes there is no need to store explicit zero
2148 bytes in the object file. The bss section was invented to eliminate
2149 those explicit zeros from object files.
2151 @cindex absolute section
2152 @item absolute section
2153 Address 0 of this section is always ``relocated'' to runtime address 0.
2154 This is useful if you want to refer to an address that @code{@value{LD}} must
2155 not change when relocating. In this sense we speak of absolute
2156 addresses being ``unrelocatable'': they do not change during relocation.
2158 @cindex undefined section
2159 @item undefined section
2160 This ``section'' is a catch-all for address references to objects not in
2161 the preceding sections.
2162 @c FIXME: ref to some other doc on obj-file formats could go here.
2165 @cindex relocation example
2166 An idealized example of three relocatable sections follows.
2168 The example uses the traditional section names @samp{.text} and @samp{.data}.
2170 Memory addresses are on the horizontal axis.
2174 @c END TEXI2ROFF-KILL
2177 partial program # 1: |ttttt|dddd|00|
2184 partial program # 2: |TTT|DDD|000|
2187 +--+---+-----+--+----+---+-----+~~
2188 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2189 +--+---+-----+--+----+---+-----+~~
2191 addresses: 0 @dots{}
2198 \line{\it Partial program \#1: \hfil}
2199 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2200 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2202 \line{\it Partial program \#2: \hfil}
2203 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2204 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2206 \line{\it linked program: \hfil}
2207 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2208 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2209 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2210 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2212 \line{\it addresses: \hfil}
2216 @c END TEXI2ROFF-KILL
2219 @section Assembler Internal Sections
2221 @cindex internal assembler sections
2222 @cindex sections in messages, internal
2223 These sections are meant only for the internal use of @code{@value{AS}}. They
2224 have no meaning at run-time. You do not really need to know about these
2225 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2226 warning messages, so it might be helpful to have an idea of their
2227 meanings to @code{@value{AS}}. These sections are used to permit the
2228 value of every expression in your assembly language program to be a
2229 section-relative address.
2232 @cindex assembler internal logic error
2233 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2234 An internal assembler logic error has been found. This means there is a
2235 bug in the assembler.
2237 @cindex expr (internal section)
2239 The assembler stores complex expression internally as combinations of
2240 symbols. When it needs to represent an expression as a symbol, it puts
2241 it in the expr section.
2243 @c FIXME item transfer[t] vector preload
2244 @c FIXME item transfer[t] vector postload
2245 @c FIXME item register
2249 @section Sub-Sections
2251 @cindex numbered subsections
2252 @cindex grouping data
2258 fall into two sections: text and data.
2260 You may have separate groups of
2262 data in named sections
2266 data in named sections
2272 that you want to end up near to each other in the object file, even though they
2273 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2274 use @dfn{subsections} for this purpose. Within each section, there can be
2275 numbered subsections with values from 0 to 8192. Objects assembled into the
2276 same subsection go into the object file together with other objects in the same
2277 subsection. For example, a compiler might want to store constants in the text
2278 section, but might not want to have them interspersed with the program being
2279 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2280 section of code being output, and a @samp{.text 1} before each group of
2281 constants being output.
2283 Subsections are optional. If you do not use subsections, everything
2284 goes in subsection number zero.
2287 Each subsection is zero-padded up to a multiple of four bytes.
2288 (Subsections may be padded a different amount on different flavors
2289 of @code{@value{AS}}.)
2293 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2294 boundary (two bytes).
2295 The same is true on the Hitachi SH.
2298 @c FIXME section padding (alignment)?
2299 @c Rich Pixley says padding here depends on target obj code format; that
2300 @c doesn't seem particularly useful to say without further elaboration,
2301 @c so for now I say nothing about it. If this is a generic BFD issue,
2302 @c these paragraphs might need to vanish from this manual, and be
2303 @c discussed in BFD chapter of binutils (or some such).
2306 On the AMD 29K family, no particular padding is added to section or
2307 subsection sizes; @value{AS} forces no alignment on this platform.
2311 Subsections appear in your object file in numeric order, lowest numbered
2312 to highest. (All this to be compatible with other people's assemblers.)
2313 The object file contains no representation of subsections; @code{@value{LD}} and
2314 other programs that manipulate object files see no trace of them.
2315 They just see all your text subsections as a text section, and all your
2316 data subsections as a data section.
2318 To specify which subsection you want subsequent statements assembled
2319 into, use a numeric argument to specify it, in a @samp{.text
2320 @var{expression}} or a @samp{.data @var{expression}} statement.
2323 When generating COFF output, you
2328 can also use an extra subsection
2329 argument with arbitrary named sections: @samp{.section @var{name},
2332 @var{Expression} should be an absolute expression.
2333 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2334 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2335 begins in @code{text 0}. For instance:
2337 .text 0 # The default subsection is text 0 anyway.
2338 .ascii "This lives in the first text subsection. *"
2340 .ascii "But this lives in the second text subsection."
2342 .ascii "This lives in the data section,"
2343 .ascii "in the first data subsection."
2345 .ascii "This lives in the first text section,"
2346 .ascii "immediately following the asterisk (*)."
2349 Each section has a @dfn{location counter} incremented by one for every byte
2350 assembled into that section. Because subsections are merely a convenience
2351 restricted to @code{@value{AS}} there is no concept of a subsection location
2352 counter. There is no way to directly manipulate a location counter---but the
2353 @code{.align} directive changes it, and any label definition captures its
2354 current value. The location counter of the section where statements are being
2355 assembled is said to be the @dfn{active} location counter.
2358 @section bss Section
2361 @cindex common variable storage
2362 The bss section is used for local common variable storage.
2363 You may allocate address space in the bss section, but you may
2364 not dictate data to load into it before your program executes. When
2365 your program starts running, all the contents of the bss
2366 section are zeroed bytes.
2368 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2369 @ref{Lcomm,,@code{.lcomm}}.
2371 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2372 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2375 When assembling for a target which supports multiple sections, such as ELF or
2376 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2377 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2378 section. Typically the section will only contain symbol definitions and
2379 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2386 Symbols are a central concept: the programmer uses symbols to name
2387 things, the linker uses symbols to link, and the debugger uses symbols
2391 @cindex debuggers, and symbol order
2392 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2393 the same order they were declared. This may break some debuggers.
2398 * Setting Symbols:: Giving Symbols Other Values
2399 * Symbol Names:: Symbol Names
2400 * Dot:: The Special Dot Symbol
2401 * Symbol Attributes:: Symbol Attributes
2408 A @dfn{label} is written as a symbol immediately followed by a colon
2409 @samp{:}. The symbol then represents the current value of the
2410 active location counter, and is, for example, a suitable instruction
2411 operand. You are warned if you use the same symbol to represent two
2412 different locations: the first definition overrides any other
2416 On the HPPA, the usual form for a label need not be immediately followed by a
2417 colon, but instead must start in column zero. Only one label may be defined on
2418 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2419 provides a special directive @code{.label} for defining labels more flexibly.
2422 @node Setting Symbols
2423 @section Giving Symbols Other Values
2425 @cindex assigning values to symbols
2426 @cindex symbol values, assigning
2427 A symbol can be given an arbitrary value by writing a symbol, followed
2428 by an equals sign @samp{=}, followed by an expression
2429 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2430 directive. @xref{Set,,@code{.set}}.
2433 @section Symbol Names
2435 @cindex symbol names
2436 @cindex names, symbol
2437 @ifclear SPECIAL-SYMS
2438 Symbol names begin with a letter or with one of @samp{._}. On most
2439 machines, you can also use @code{$} in symbol names; exceptions are
2440 noted in @ref{Machine Dependencies}. That character may be followed by any
2441 string of digits, letters, dollar signs (unless otherwise noted in
2442 @ref{Machine Dependencies}), and underscores.
2445 For the AMD 29K family, @samp{?} is also allowed in the
2446 body of a symbol name, though not at its beginning.
2451 Symbol names begin with a letter or with one of @samp{._}. On the
2453 H8/500, you can also use @code{$} in symbol names. That character may
2454 be followed by any string of digits, letters, dollar signs (save on the
2455 H8/300), and underscores.
2459 Case of letters is significant: @code{foo} is a different symbol name
2462 Each symbol has exactly one name. Each name in an assembly language program
2463 refers to exactly one symbol. You may use that symbol name any number of times
2466 @subheading Local Symbol Names
2468 @cindex local symbol names
2469 @cindex symbol names, local
2470 @cindex temporary symbol names
2471 @cindex symbol names, temporary
2472 Local symbols help compilers and programmers use names temporarily.
2473 There are ten local symbol names, which are re-used throughout the
2474 program. You may refer to them using the names @samp{0} @samp{1}
2475 @dots{} @samp{9}. To define a local symbol, write a label of the form
2476 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2477 recent previous definition of that symbol write @samp{@b{N}b}, using the
2478 same digit as when you defined the label. To refer to the next
2479 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2480 a choice of 10 forward references. The @samp{b} stands for
2481 ``backwards'' and the @samp{f} stands for ``forwards''.
2483 Local symbols are not emitted by the current @sc{gnu} C compiler.
2485 There is no restriction on how you can use these labels, but
2486 remember that at any point in the assembly you can refer to at most
2487 10 prior local labels and to at most 10 forward local labels.
2489 Local symbol names are only a notation device. They are immediately
2490 transformed into more conventional symbol names before the assembler
2491 uses them. The symbol names stored in the symbol table, appearing in
2492 error messages and optionally emitted to the object file have these
2497 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2498 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2499 used for symbols you are never intended to see. If you use the
2500 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2501 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2502 you may use them in debugging.
2505 If the label is written @samp{0:} then the digit is @samp{0}.
2506 If the label is written @samp{1:} then the digit is @samp{1}.
2507 And so on up through @samp{9:}.
2510 This unusual character is included so you do not accidentally invent
2511 a symbol of the same name. The character has ASCII value
2514 @item @emph{ordinal number}
2515 This is a serial number to keep the labels distinct. The first
2516 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2517 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2521 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2522 @code{3:} is named @code{L3@kbd{C-A}44}.
2525 @section The Special Dot Symbol
2527 @cindex dot (symbol)
2528 @cindex @code{.} (symbol)
2529 @cindex current address
2530 @cindex location counter
2531 The special symbol @samp{.} refers to the current address that
2532 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2533 .long .} defines @code{melvin} to contain its own address.
2534 Assigning a value to @code{.} is treated the same as a @code{.org}
2535 directive. Thus, the expression @samp{.=.+4} is the same as saying
2536 @ifclear no-space-dir
2545 @node Symbol Attributes
2546 @section Symbol Attributes
2548 @cindex symbol attributes
2549 @cindex attributes, symbol
2550 Every symbol has, as well as its name, the attributes ``Value'' and
2551 ``Type''. Depending on output format, symbols can also have auxiliary
2554 The detailed definitions are in @file{a.out.h}.
2557 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2558 all these attributes, and probably won't warn you. This makes the
2559 symbol an externally defined symbol, which is generally what you
2563 * Symbol Value:: Value
2564 * Symbol Type:: Type
2567 * a.out Symbols:: Symbol Attributes: @code{a.out}
2571 * a.out Symbols:: Symbol Attributes: @code{a.out}
2574 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2579 * COFF Symbols:: Symbol Attributes for COFF
2582 * SOM Symbols:: Symbol Attributes for SOM
2589 @cindex value of a symbol
2590 @cindex symbol value
2591 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2592 location in the text, data, bss or absolute sections the value is the
2593 number of addresses from the start of that section to the label.
2594 Naturally for text, data and bss sections the value of a symbol changes
2595 as @code{@value{LD}} changes section base addresses during linking. Absolute
2596 symbols' values do not change during linking: that is why they are
2599 The value of an undefined symbol is treated in a special way. If it is
2600 0 then the symbol is not defined in this assembler source file, and
2601 @code{@value{LD}} tries to determine its value from other files linked into the
2602 same program. You make this kind of symbol simply by mentioning a symbol
2603 name without defining it. A non-zero value represents a @code{.comm}
2604 common declaration. The value is how much common storage to reserve, in
2605 bytes (addresses). The symbol refers to the first address of the
2611 @cindex type of a symbol
2613 The type attribute of a symbol contains relocation (section)
2614 information, any flag settings indicating that a symbol is external, and
2615 (optionally), other information for linkers and debuggers. The exact
2616 format depends on the object-code output format in use.
2621 @c The following avoids a "widow" subsection title. @group would be
2622 @c better if it were available outside examples.
2625 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2627 @cindex @code{b.out} symbol attributes
2628 @cindex symbol attributes, @code{b.out}
2629 These symbol attributes appear only when @code{@value{AS}} is configured for
2630 one of the Berkeley-descended object output formats---@code{a.out} or
2636 @subsection Symbol Attributes: @code{a.out}
2638 @cindex @code{a.out} symbol attributes
2639 @cindex symbol attributes, @code{a.out}
2645 @subsection Symbol Attributes: @code{a.out}
2647 @cindex @code{a.out} symbol attributes
2648 @cindex symbol attributes, @code{a.out}
2652 * Symbol Desc:: Descriptor
2653 * Symbol Other:: Other
2657 @subsubsection Descriptor
2659 @cindex descriptor, of @code{a.out} symbol
2660 This is an arbitrary 16-bit value. You may establish a symbol's
2661 descriptor value by using a @code{.desc} statement
2662 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2666 @subsubsection Other
2668 @cindex other attribute, of @code{a.out} symbol
2669 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2674 @subsection Symbol Attributes for COFF
2676 @cindex COFF symbol attributes
2677 @cindex symbol attributes, COFF
2679 The COFF format supports a multitude of auxiliary symbol attributes;
2680 like the primary symbol attributes, they are set between @code{.def} and
2681 @code{.endef} directives.
2683 @subsubsection Primary Attributes
2685 @cindex primary attributes, COFF symbols
2686 The symbol name is set with @code{.def}; the value and type,
2687 respectively, with @code{.val} and @code{.type}.
2689 @subsubsection Auxiliary Attributes
2691 @cindex auxiliary attributes, COFF symbols
2692 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2693 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2694 information for COFF.
2699 @subsection Symbol Attributes for SOM
2701 @cindex SOM symbol attributes
2702 @cindex symbol attributes, SOM
2704 The SOM format for the HPPA supports a multitude of symbol attributes set with
2705 the @code{.EXPORT} and @code{.IMPORT} directives.
2707 The attributes are described in @cite{HP9000 Series 800 Assembly
2708 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2709 @code{EXPORT} assembler directive documentation.
2713 @chapter Expressions
2717 @cindex numeric values
2718 An @dfn{expression} specifies an address or numeric value.
2719 Whitespace may precede and/or follow an expression.
2721 The result of an expression must be an absolute number, or else an offset into
2722 a particular section. If an expression is not absolute, and there is not
2723 enough information when @code{@value{AS}} sees the expression to know its
2724 section, a second pass over the source program might be necessary to interpret
2725 the expression---but the second pass is currently not implemented.
2726 @code{@value{AS}} aborts with an error message in this situation.
2729 * Empty Exprs:: Empty Expressions
2730 * Integer Exprs:: Integer Expressions
2734 @section Empty Expressions
2736 @cindex empty expressions
2737 @cindex expressions, empty
2738 An empty expression has no value: it is just whitespace or null.
2739 Wherever an absolute expression is required, you may omit the
2740 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2741 is compatible with other assemblers.
2744 @section Integer Expressions
2746 @cindex integer expressions
2747 @cindex expressions, integer
2748 An @dfn{integer expression} is one or more @emph{arguments} delimited
2749 by @emph{operators}.
2752 * Arguments:: Arguments
2753 * Operators:: Operators
2754 * Prefix Ops:: Prefix Operators
2755 * Infix Ops:: Infix Operators
2759 @subsection Arguments
2761 @cindex expression arguments
2762 @cindex arguments in expressions
2763 @cindex operands in expressions
2764 @cindex arithmetic operands
2765 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2766 contexts arguments are sometimes called ``arithmetic operands''. In
2767 this manual, to avoid confusing them with the ``instruction operands'' of
2768 the machine language, we use the term ``argument'' to refer to parts of
2769 expressions only, reserving the word ``operand'' to refer only to machine
2770 instruction operands.
2772 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2773 @var{section} is one of text, data, bss, absolute,
2774 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2777 Numbers are usually integers.
2779 A number can be a flonum or bignum. In this case, you are warned
2780 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2781 these 32 bits are an integer. You may write integer-manipulating
2782 instructions that act on exotic constants, compatible with other
2785 @cindex subexpressions
2786 Subexpressions are a left parenthesis @samp{(} followed by an integer
2787 expression, followed by a right parenthesis @samp{)}; or a prefix
2788 operator followed by an argument.
2791 @subsection Operators
2793 @cindex operators, in expressions
2794 @cindex arithmetic functions
2795 @cindex functions, in expressions
2796 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2797 operators are followed by an argument. Infix operators appear
2798 between their arguments. Operators may be preceded and/or followed by
2802 @subsection Prefix Operator
2804 @cindex prefix operators
2805 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2806 one argument, which must be absolute.
2808 @c the tex/end tex stuff surrounding this small table is meant to make
2809 @c it align, on the printed page, with the similar table in the next
2810 @c section (which is inside an enumerate).
2812 \global\advance\leftskip by \itemindent
2817 @dfn{Negation}. Two's complement negation.
2819 @dfn{Complementation}. Bitwise not.
2823 \global\advance\leftskip by -\itemindent
2827 @subsection Infix Operators
2829 @cindex infix operators
2830 @cindex operators, permitted arguments
2831 @dfn{Infix operators} take two arguments, one on either side. Operators
2832 have precedence, but operations with equal precedence are performed left
2833 to right. Apart from @code{+} or @code{-}, both arguments must be
2834 absolute, and the result is absolute.
2837 @cindex operator precedence
2838 @cindex precedence of operators
2845 @dfn{Multiplication}.
2848 @dfn{Division}. Truncation is the same as the C operator @samp{/}
2855 @dfn{Shift Left}. Same as the C operator @samp{<<}.
2859 @dfn{Shift Right}. Same as the C operator @samp{>>}.
2863 Intermediate precedence
2868 @dfn{Bitwise Inclusive Or}.
2874 @dfn{Bitwise Exclusive Or}.
2877 @dfn{Bitwise Or Not}.
2884 @cindex addition, permitted arguments
2885 @cindex plus, permitted arguments
2886 @cindex arguments for addition
2888 @dfn{Addition}. If either argument is absolute, the result has the section of
2889 the other argument. You may not add together arguments from different
2892 @cindex subtraction, permitted arguments
2893 @cindex minus, permitted arguments
2894 @cindex arguments for subtraction
2896 @dfn{Subtraction}. If the right argument is absolute, the
2897 result has the section of the left argument.
2898 If both arguments are in the same section, the result is absolute.
2899 You may not subtract arguments from different sections.
2900 @c FIXME is there still something useful to say about undefined - undefined ?
2904 In short, it's only meaningful to add or subtract the @emph{offsets} in an
2905 address; you can only have a defined section in one of the two arguments.
2908 @chapter Assembler Directives
2910 @cindex directives, machine independent
2911 @cindex pseudo-ops, machine independent
2912 @cindex machine independent directives
2913 All assembler directives have names that begin with a period (@samp{.}).
2914 The rest of the name is letters, usually in lower case.
2916 This chapter discusses directives that are available regardless of the
2917 target machine configuration for the @sc{gnu} assembler.
2919 Some machine configurations provide additional directives.
2920 @xref{Machine Dependencies}.
2923 @ifset machine-directives
2924 @xref{Machine Dependencies} for additional directives.
2929 * Abort:: @code{.abort}
2931 * ABORT:: @code{.ABORT}
2934 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
2935 * App-File:: @code{.app-file @var{string}}
2936 * Ascii:: @code{.ascii "@var{string}"}@dots{}
2937 * Asciz:: @code{.asciz "@var{string}"}@dots{}
2938 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
2939 * Byte:: @code{.byte @var{expressions}}
2940 * Comm:: @code{.comm @var{symbol} , @var{length} }
2941 * Data:: @code{.data @var{subsection}}
2943 * Def:: @code{.def @var{name}}
2946 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
2952 * Double:: @code{.double @var{flonums}}
2953 * Eject:: @code{.eject}
2954 * Else:: @code{.else}
2956 * Endef:: @code{.endef}
2959 * Endif:: @code{.endif}
2960 * Equ:: @code{.equ @var{symbol}, @var{expression}}
2961 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
2963 * Extern:: @code{.extern}
2964 @ifclear no-file-dir
2965 * File:: @code{.file @var{string}}
2968 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
2969 * Float:: @code{.float @var{flonums}}
2970 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
2971 * hword:: @code{.hword @var{expressions}}
2972 * Ident:: @code{.ident}
2973 * If:: @code{.if @var{absolute expression}}
2974 * Include:: @code{.include "@var{file}"}
2975 * Int:: @code{.int @var{expressions}}
2976 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
2977 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
2978 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
2979 * Lflags:: @code{.lflags}
2980 @ifclear no-line-dir
2981 * Line:: @code{.line @var{line-number}}
2984 * Ln:: @code{.ln @var{line-number}}
2985 * Linkonce:: @code{.linkonce [@var{type}]}
2986 * List:: @code{.list}
2987 * Long:: @code{.long @var{expressions}}
2989 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
2992 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
2993 * MRI:: @code{.mri @var{val}}
2995 * Nolist:: @code{.nolist}
2996 * Octa:: @code{.octa @var{bignums}}
2997 * Org:: @code{.org @var{new-lc} , @var{fill}}
2998 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
2999 * Psize:: @code{.psize @var{lines}, @var{columns}}
3000 * Quad:: @code{.quad @var{bignums}}
3001 * Rept:: @code{.rept @var{count}}
3002 * Sbttl:: @code{.sbttl "@var{subheading}"}
3004 * Scl:: @code{.scl @var{class}}
3005 * Section:: @code{.section @var{name}, @var{subsection}}
3008 * Set:: @code{.set @var{symbol}, @var{expression}}
3009 * Short:: @code{.short @var{expressions}}
3010 * Single:: @code{.single @var{flonums}}
3012 * Size:: @code{.size}
3015 * Skip:: @code{.skip @var{size} , @var{fill}}
3016 * Sleb128:: @code{.sleb128 @var{expressions}}
3017 * Space:: @code{.space @var{size} , @var{fill}}
3019 * Stab:: @code{.stabd, .stabn, .stabs}
3022 * String:: @code{.string "@var{str}"}
3024 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3027 * Tag:: @code{.tag @var{structname}}
3030 * Text:: @code{.text @var{subsection}}
3031 * Title:: @code{.title "@var{heading}"}
3033 * Type:: @code{.type @var{int}}
3034 * Val:: @code{.val @var{addr}}
3037 * Uleb128:: @code{.uleb128 @var{expressions}}
3038 * Word:: @code{.word @var{expressions}}
3039 * Deprecated:: Deprecated Directives
3043 @section @code{.abort}
3045 @cindex @code{abort} directive
3046 @cindex stopping the assembly
3047 This directive stops the assembly immediately. It is for
3048 compatibility with other assemblers. The original idea was that the
3049 assembly language source would be piped into the assembler. If the sender
3050 of the source quit, it could use this directive tells @code{@value{AS}} to
3051 quit also. One day @code{.abort} will not be supported.
3055 @section @code{.ABORT}
3057 @cindex @code{ABORT} directive
3058 When producing COFF output, @code{@value{AS}} accepts this directive as a
3059 synonym for @samp{.abort}.
3062 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3068 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3070 @cindex padding the location counter
3071 @cindex @code{align} directive
3072 Pad the location counter (in the current subsection) to a particular storage
3073 boundary. The first expression (which must be absolute) is the alignment
3074 required, as described below.
3076 The second expression (also absolute) gives the fill value to be stored in the
3077 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3078 padding bytes are normally zero. However, on some systems, if the section is
3079 marked as containing code and the fill value is omitted, the space is filled
3080 with no-op instructions.
3082 The third expression is also absolute, and is also optional. If it is present,
3083 it is the maximum number of bytes that should be skipped by this alignment
3084 directive. If doing the alignment would require skipping more bytes than the
3085 specified maximum, then the alignment is not done at all. You can omit the
3086 fill value (the second argument) entirely by simply using two commas after the
3087 required alignment; this can be useful if you want the alignment to be filled
3088 with no-op instructions when appropriate.
3090 The way the required alignment is specified varies from system to system.
3091 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3093 the first expression is the
3094 alignment request in bytes. For example @samp{.align 8} advances
3095 the location counter until it is a multiple of 8. If the location counter
3096 is already a multiple of 8, no change is needed.
3098 For other systems, including the i386 using a.out format, it is the
3099 number of low-order zero bits the location counter must have after
3100 advancement. For example @samp{.align 3} advances the location
3101 counter until it a multiple of 8. If the location counter is already a
3102 multiple of 8, no change is needed.
3104 This inconsistency is due to the different behaviors of the various
3105 native assemblers for these systems which GAS must emulate.
3106 GAS also provides @code{.balign} and @code{.p2align} directives,
3107 described later, which have a consistent behavior across all
3108 architectures (but are specific to GAS).
3111 @section @code{.app-file @var{string}}
3113 @cindex logical file name
3114 @cindex file name, logical
3115 @cindex @code{app-file} directive
3117 @ifclear no-file-dir
3118 (which may also be spelled @samp{.file})
3120 tells @code{@value{AS}} that we are about to start a new
3121 logical file. @var{string} is the new file name. In general, the
3122 filename is recognized whether or not it is surrounded by quotes @samp{"};
3123 but if you wish to specify an empty file name is permitted,
3124 you must give the quotes--@code{""}. This statement may go away in
3125 future: it is only recognized to be compatible with old @code{@value{AS}}
3129 @section @code{.ascii "@var{string}"}@dots{}
3131 @cindex @code{ascii} directive
3132 @cindex string literals
3133 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3134 separated by commas. It assembles each string (with no automatic
3135 trailing zero byte) into consecutive addresses.
3138 @section @code{.asciz "@var{string}"}@dots{}
3140 @cindex @code{asciz} directive
3141 @cindex zero-terminated strings
3142 @cindex null-terminated strings
3143 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3144 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3147 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3149 @cindex padding the location counter given number of bytes
3150 @cindex @code{balign} directive
3151 Pad the location counter (in the current subsection) to a particular
3152 storage boundary. The first expression (which must be absolute) is the
3153 alignment request in bytes. For example @samp{.balign 8} advances
3154 the location counter until it is a multiple of 8. If the location counter
3155 is already a multiple of 8, no change is needed.
3157 The second expression (also absolute) gives the fill value to be stored in the
3158 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3159 padding bytes are normally zero. However, on some systems, if the section is
3160 marked as containing code and the fill value is omitted, the space is filled
3161 with no-op instructions.
3163 The third expression is also absolute, and is also optional. If it is present,
3164 it is the maximum number of bytes that should be skipped by this alignment
3165 directive. If doing the alignment would require skipping more bytes than the
3166 specified maximum, then the alignment is not done at all. You can omit the
3167 fill value (the second argument) entirely by simply using two commas after the
3168 required alignment; this can be useful if you want the alignment to be filled
3169 with no-op instructions when appropriate.
3171 @cindex @code{balignw} directive
3172 @cindex @code{balignl} directive
3173 The @code{.balignw} and @code{.balignl} directives are variants of the
3174 @code{.balign} directive. The @code{.balignw} directive treats the fill
3175 pattern as a two byte word value. The @code{.balignl} directives treats the
3176 fill pattern as a four byte longword value. For example, @code{.balignw
3177 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3178 filled in with the value 0x368d (the exact placement of the bytes depends upon
3179 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3183 @section @code{.byte @var{expressions}}
3185 @cindex @code{byte} directive
3186 @cindex integers, one byte
3187 @code{.byte} expects zero or more expressions, separated by commas.
3188 Each expression is assembled into the next byte.
3191 @section @code{.comm @var{symbol} , @var{length} }
3193 @cindex @code{comm} directive
3194 @cindex symbol, common
3195 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3196 common symbol in one object file may be merged with a defined or common symbol
3197 of the same name in another object file. If @code{@value{LD}} does not see a
3198 definition for the symbol--just one or more common symbols--then it will
3199 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3200 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3201 the same name, and they do not all have the same size, it will allocate space
3202 using the largest size.
3205 When using ELF, the @code{.comm} directive takes an optional third argument.
3206 This is the desired alignment of the symbol, specified as a byte boundary (for
3207 example, an alignment of 16 means that the least significant 4 bits of the
3208 address should be zero). The alignment must be an absolute expression, and it
3209 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3210 for the common symbol, it will use the alignment when placing the symbol. If
3211 no alignment is specified, @code{@value{AS}} will set the alignment to the
3212 largest power of two less than or equal to the size of the symbol, up to a
3217 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3218 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3222 @section @code{.data @var{subsection}}
3224 @cindex @code{data} directive
3225 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3226 end of the data subsection numbered @var{subsection} (which is an
3227 absolute expression). If @var{subsection} is omitted, it defaults
3232 @section @code{.def @var{name}}
3234 @cindex @code{def} directive
3235 @cindex COFF symbols, debugging
3236 @cindex debugging COFF symbols
3237 Begin defining debugging information for a symbol @var{name}; the
3238 definition extends until the @code{.endef} directive is encountered.
3241 This directive is only observed when @code{@value{AS}} is configured for COFF
3242 format output; when producing @code{b.out}, @samp{.def} is recognized,
3249 @section @code{.desc @var{symbol}, @var{abs-expression}}
3251 @cindex @code{desc} directive
3252 @cindex COFF symbol descriptor
3253 @cindex symbol descriptor, COFF
3254 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3255 to the low 16 bits of an absolute expression.
3258 The @samp{.desc} directive is not available when @code{@value{AS}} is
3259 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3260 object format. For the sake of compatibility, @code{@value{AS}} accepts
3261 it, but produces no output, when configured for COFF.
3267 @section @code{.dim}
3269 @cindex @code{dim} directive
3270 @cindex COFF auxiliary symbol information
3271 @cindex auxiliary symbol information, COFF
3272 This directive is generated by compilers to include auxiliary debugging
3273 information in the symbol table. It is only permitted inside
3274 @code{.def}/@code{.endef} pairs.
3277 @samp{.dim} is only meaningful when generating COFF format output; when
3278 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3284 @section @code{.double @var{flonums}}
3286 @cindex @code{double} directive
3287 @cindex floating point numbers (double)
3288 @code{.double} expects zero or more flonums, separated by commas. It
3289 assembles floating point numbers.
3291 The exact kind of floating point numbers emitted depends on how
3292 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3296 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3297 in @sc{ieee} format.
3302 @section @code{.eject}
3304 @cindex @code{eject} directive
3305 @cindex new page, in listings
3306 @cindex page, in listings
3307 @cindex listing control: new page
3308 Force a page break at this point, when generating assembly listings.
3311 @section @code{.else}
3313 @cindex @code{else} directive
3314 @code{.else} is part of the @code{@value{AS}} support for conditional
3315 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3316 of code to be assembled if the condition for the preceding @code{.if}
3320 @node End, Endef, Else, Pseudo Ops
3321 @section @code{.end}
3323 @cindex @code{end} directive
3324 This doesn't do anything---but isn't an s_ignore, so I suspect it's
3325 meant to do something eventually (which is why it isn't documented here
3326 as "for compatibility with blah").
3331 @section @code{.endef}
3333 @cindex @code{endef} directive
3334 This directive flags the end of a symbol definition begun with
3338 @samp{.endef} is only meaningful when generating COFF format output; if
3339 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3340 directive but ignores it.
3345 @section @code{.endif}
3347 @cindex @code{endif} directive
3348 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3349 it marks the end of a block of code that is only assembled
3350 conditionally. @xref{If,,@code{.if}}.
3353 @section @code{.equ @var{symbol}, @var{expression}}
3355 @cindex @code{equ} directive
3356 @cindex assigning values to symbols
3357 @cindex symbols, assigning values to
3358 This directive sets the value of @var{symbol} to @var{expression}.
3359 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3362 The syntax for @code{equ} on the HPPA is
3363 @samp{@var{symbol} .equ @var{expression}}.
3367 @section @code{.equiv @var{symbol}, @var{expression}}
3368 @cindex @code{equiv} directive
3369 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3370 the assembler will signal an error if @var{symbol} is already defined.
3372 Except for the contents of the error message, this is roughly equivalent to
3381 @section @code{.err}
3382 @cindex @code{err} directive
3383 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3384 message and, unless the @code{-Z} option was used, it will not generate an
3385 object file. This can be used to signal error an conditionally compiled code.
3388 @section @code{.extern}
3390 @cindex @code{extern} directive
3391 @code{.extern} is accepted in the source program---for compatibility
3392 with other assemblers---but it is ignored. @code{@value{AS}} treats
3393 all undefined symbols as external.
3395 @ifclear no-file-dir
3397 @section @code{.file @var{string}}
3399 @cindex @code{file} directive
3400 @cindex logical file name
3401 @cindex file name, logical
3402 @code{.file} (which may also be spelled @samp{.app-file}) tells
3403 @code{@value{AS}} that we are about to start a new logical file.
3404 @var{string} is the new file name. In general, the filename is
3405 recognized whether or not it is surrounded by quotes @samp{"}; but if
3406 you wish to specify an empty file name, you must give the
3407 quotes--@code{""}. This statement may go away in future: it is only
3408 recognized to be compatible with old @code{@value{AS}} programs.
3410 In some configurations of @code{@value{AS}}, @code{.file} has already been
3411 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3416 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3418 @cindex @code{fill} directive
3419 @cindex writing patterns in memory
3420 @cindex patterns, writing in memory
3421 @var{result}, @var{size} and @var{value} are absolute expressions.
3422 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3423 may be zero or more. @var{Size} may be zero or more, but if it is
3424 more than 8, then it is deemed to have the value 8, compatible with
3425 other people's assemblers. The contents of each @var{repeat} bytes
3426 is taken from an 8-byte number. The highest order 4 bytes are
3427 zero. The lowest order 4 bytes are @var{value} rendered in the
3428 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3429 Each @var{size} bytes in a repetition is taken from the lowest order
3430 @var{size} bytes of this number. Again, this bizarre behavior is
3431 compatible with other people's assemblers.
3433 @var{size} and @var{value} are optional.
3434 If the second comma and @var{value} are absent, @var{value} is
3435 assumed zero. If the first comma and following tokens are absent,
3436 @var{size} is assumed to be 1.
3439 @section @code{.float @var{flonums}}
3441 @cindex floating point numbers (single)
3442 @cindex @code{float} directive
3443 This directive assembles zero or more flonums, separated by commas. It
3444 has the same effect as @code{.single}.
3446 The exact kind of floating point numbers emitted depends on how
3447 @code{@value{AS}} is configured.
3448 @xref{Machine Dependencies}.
3452 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3453 in @sc{ieee} format.
3458 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3460 @cindex @code{global} directive
3461 @cindex symbol, making visible to linker
3462 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3463 @var{symbol} in your partial program, its value is made available to
3464 other partial programs that are linked with it. Otherwise,
3465 @var{symbol} takes its attributes from a symbol of the same name
3466 from another file linked into the same program.
3468 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3469 compatibility with other assemblers.
3472 On the HPPA, @code{.global} is not always enough to make it accessible to other
3473 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3474 @xref{HPPA Directives,, HPPA Assembler Directives}.
3478 @section @code{.hword @var{expressions}}
3480 @cindex @code{hword} directive
3481 @cindex integers, 16-bit
3482 @cindex numbers, 16-bit
3483 @cindex sixteen bit integers
3484 This expects zero or more @var{expressions}, and emits
3485 a 16 bit number for each.
3488 This directive is a synonym for @samp{.short}; depending on the target
3489 architecture, it may also be a synonym for @samp{.word}.
3493 This directive is a synonym for @samp{.short}.
3496 This directive is a synonym for both @samp{.short} and @samp{.word}.
3501 @section @code{.ident}
3503 @cindex @code{ident} directive
3504 This directive is used by some assemblers to place tags in object files.
3505 @code{@value{AS}} simply accepts the directive for source-file
3506 compatibility with such assemblers, but does not actually emit anything
3510 @section @code{.if @var{absolute expression}}
3512 @cindex conditional assembly
3513 @cindex @code{if} directive
3514 @code{.if} marks the beginning of a section of code which is only
3515 considered part of the source program being assembled if the argument
3516 (which must be an @var{absolute expression}) is non-zero. The end of
3517 the conditional section of code must be marked by @code{.endif}
3518 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3519 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3521 The following variants of @code{.if} are also supported:
3523 @cindex @code{ifdef} directive
3524 @item .ifdef @var{symbol}
3525 Assembles the following section of code if the specified @var{symbol}
3529 @cindex @code{ifeqs} directive
3531 Not yet implemented.
3534 @cindex @code{ifndef} directive
3535 @cindex @code{ifnotdef} directive
3536 @item .ifndef @var{symbol}
3537 @itemx .ifnotdef @var{symbol}
3538 Assembles the following section of code if the specified @var{symbol}
3539 has not been defined. Both spelling variants are equivalent.
3543 Not yet implemented.
3548 @section @code{.include "@var{file}"}
3550 @cindex @code{include} directive
3551 @cindex supporting files, including
3552 @cindex files, including
3553 This directive provides a way to include supporting files at specified
3554 points in your source program. The code from @var{file} is assembled as
3555 if it followed the point of the @code{.include}; when the end of the
3556 included file is reached, assembly of the original file continues. You
3557 can control the search paths used with the @samp{-I} command-line option
3558 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3562 @section @code{.int @var{expressions}}
3564 @cindex @code{int} directive
3565 @cindex integers, 32-bit
3566 Expect zero or more @var{expressions}, of any section, separated by commas.
3567 For each expression, emit a number that, at run time, is the value of that
3568 expression. The byte order and bit size of the number depends on what kind
3569 of target the assembly is for.
3573 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3574 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3580 @section @code{.irp @var{symbol},@var{values}}@dots{}
3582 @cindex @code{irp} directive
3583 Evaluate a sequence of statements assigning different values to @var{symbol}.
3584 The sequence of statements starts at the @code{.irp} directive, and is
3585 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3586 set to @var{value}, and the sequence of statements is assembled. If no
3587 @var{value} is listed, the sequence of statements is assembled once, with
3588 @var{symbol} set to the null string. To refer to @var{symbol} within the
3589 sequence of statements, use @var{\symbol}.
3591 For example, assembling
3599 is equivalent to assembling
3608 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3610 @cindex @code{irpc} directive
3611 Evaluate a sequence of statements assigning different values to @var{symbol}.
3612 The sequence of statements starts at the @code{.irpc} directive, and is
3613 terminated by an @code{.endr} directive. For each character in @var{value},
3614 @var{symbol} is set to the character, and the sequence of statements is
3615 assembled. If no @var{value} is listed, the sequence of statements is
3616 assembled once, with @var{symbol} set to the null string. To refer to
3617 @var{symbol} within the sequence of statements, use @var{\symbol}.
3619 For example, assembling
3627 is equivalent to assembling
3636 @section @code{.lcomm @var{symbol} , @var{length}}
3638 @cindex @code{lcomm} directive
3639 @cindex local common symbols
3640 @cindex symbols, local common
3641 Reserve @var{length} (an absolute expression) bytes for a local common
3642 denoted by @var{symbol}. The section and value of @var{symbol} are
3643 those of the new local common. The addresses are allocated in the bss
3644 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3645 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3646 not visible to @code{@value{LD}}.
3649 Some targets permit a third argument to be used with @code{.lcomm}. This
3650 argument specifies the desired alignment of the symbol in the bss section.
3654 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3655 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3659 @section @code{.lflags}
3661 @cindex @code{lflags} directive (ignored)
3662 @code{@value{AS}} accepts this directive, for compatibility with other
3663 assemblers, but ignores it.
3665 @ifclear no-line-dir
3667 @section @code{.line @var{line-number}}
3669 @cindex @code{line} directive
3673 @section @code{.ln @var{line-number}}
3675 @cindex @code{ln} directive
3677 @cindex logical line number
3679 Change the logical line number. @var{line-number} must be an absolute
3680 expression. The next line has that logical line number. Therefore any other
3681 statements on the current line (after a statement separator character) are
3682 reported as on logical line number @var{line-number} @minus{} 1. One day
3683 @code{@value{AS}} will no longer support this directive: it is recognized only
3684 for compatibility with existing assembler programs.
3688 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3689 not available; use the synonym @code{.ln} in that context.
3694 @ifclear no-line-dir
3695 Even though this is a directive associated with the @code{a.out} or
3696 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3697 when producing COFF output, and treats @samp{.line} as though it
3698 were the COFF @samp{.ln} @emph{if} it is found outside a
3699 @code{.def}/@code{.endef} pair.
3701 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3702 used by compilers to generate auxiliary symbol information for
3707 @section @code{.linkonce [@var{type}]}
3709 @cindex @code{linkonce} directive
3710 @cindex common sections
3711 Mark the current section so that the linker only includes a single copy of it.
3712 This may be used to include the same section in several different object files,
3713 but ensure that the linker will only include it once in the final output file.
3714 The @code{.linkonce} pseudo-op must be used for each instance of the section.
3715 Duplicate sections are detected based on the section name, so it should be
3718 This directive is only supported by a few object file formats; as of this
3719 writing, the only object file format which supports it is the Portable
3720 Executable format used on Windows NT.
3722 The @var{type} argument is optional. If specified, it must be one of the
3723 following strings. For example:
3727 Not all types may be supported on all object file formats.
3731 Silently discard duplicate sections. This is the default.
3734 Warn if there are duplicate sections, but still keep only one copy.
3737 Warn if any of the duplicates have different sizes.
3740 Warn if any of the duplicates do not have exactly the same contents.
3744 @section @code{.ln @var{line-number}}
3746 @cindex @code{ln} directive
3747 @ifclear no-line-dir
3748 @samp{.ln} is a synonym for @samp{.line}.
3751 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
3752 must be an absolute expression. The next line has that logical
3753 line number, so any other statements on the current line (after a
3754 statement separator character @code{;}) are reported as on logical
3755 line number @var{line-number} @minus{} 1.
3758 This directive is accepted, but ignored, when @code{@value{AS}} is
3759 configured for @code{b.out}; its effect is only associated with COFF
3765 @section @code{.mri @var{val}}
3767 @cindex @code{mri} directive
3768 @cindex MRI mode, temporarily
3769 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
3770 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
3771 affects code assembled until the next @code{.mri} directive, or until the end
3772 of the file. @xref{M, MRI mode, MRI mode}.
3775 @section @code{.list}
3777 @cindex @code{list} directive
3778 @cindex listing control, turning on
3779 Control (in conjunction with the @code{.nolist} directive) whether or
3780 not assembly listings are generated. These two directives maintain an
3781 internal counter (which is zero initially). @code{.list} increments the
3782 counter, and @code{.nolist} decrements it. Assembly listings are
3783 generated whenever the counter is greater than zero.
3785 By default, listings are disabled. When you enable them (with the
3786 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
3787 the initial value of the listing counter is one.
3790 @section @code{.long @var{expressions}}
3792 @cindex @code{long} directive
3793 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
3796 @c no one seems to know what this is for or whether this description is
3797 @c what it really ought to do
3799 @section @code{.lsym @var{symbol}, @var{expression}}
3801 @cindex @code{lsym} directive
3802 @cindex symbol, not referenced in assembly
3803 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
3804 the hash table, ensuring it cannot be referenced by name during the
3805 rest of the assembly. This sets the attributes of the symbol to be
3806 the same as the expression value:
3808 @var{other} = @var{descriptor} = 0
3809 @var{type} = @r{(section of @var{expression})}
3810 @var{value} = @var{expression}
3813 The new symbol is not flagged as external.
3817 @section @code{.macro}
3820 The commands @code{.macro} and @code{.endm} allow you to define macros that
3821 generate assembly output. For example, this definition specifies a macro
3822 @code{sum} that puts a sequence of numbers into memory:
3825 .macro sum from=0, to=5
3834 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
3846 @item .macro @var{macname}
3847 @itemx .macro @var{macname} @var{macargs} @dots{}
3848 @cindex @code{macro} directive
3849 Begin the definition of a macro called @var{macname}. If your macro
3850 definition requires arguments, specify their names after the macro name,
3851 separated by commas or spaces. You can supply a default value for any
3852 macro argument by following the name with @samp{=@var{deflt}}. For
3853 example, these are all valid @code{.macro} statements:
3857 Begin the definition of a macro called @code{comm}, which takes no
3860 @item .macro plus1 p, p1
3861 @itemx .macro plus1 p p1
3862 Either statement begins the definition of a macro called @code{plus1},
3863 which takes two arguments; within the macro definition, write
3864 @samp{\p} or @samp{\p1} to evaluate the arguments.
3866 @item .macro reserve_str p1=0 p2
3867 Begin the definition of a macro called @code{reserve_str}, with two
3868 arguments. The first argument has a default value, but not the second.
3869 After the definition is complete, you can call the macro either as
3870 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
3871 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
3872 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
3873 @samp{0}, and @samp{\p2} evaluating to @var{b}).
3876 When you call a macro, you can specify the argument values either by
3877 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
3878 @samp{sum to=17, from=9}.
3881 @cindex @code{endm} directive
3882 Mark the end of a macro definition.
3885 @cindex @code{exitm} directive
3886 Exit early from the current macro definition.
3888 @cindex number of macros executed
3889 @cindex macros, count executed
3891 @code{@value{AS}} maintains a counter of how many macros it has
3892 executed in this pseudo-variable; you can copy that number to your
3893 output with @samp{\@@}, but @emph{only within a macro definition}.
3896 @item LOCAL @var{name} [ , @dots{} ]
3897 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
3898 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
3899 Alternate macro syntax}.
3901 Generate a string replacement for each of the @var{name} arguments, and
3902 replace any instances of @var{name} in each macro expansion. The
3903 replacement string is unique in the assembly, and different for each
3904 separate macro expansion. @code{LOCAL} allows you to write macros that
3905 define symbols, without fear of conflict between separate macro expansions.
3910 @section @code{.nolist}
3912 @cindex @code{nolist} directive
3913 @cindex listing control, turning off
3914 Control (in conjunction with the @code{.list} directive) whether or
3915 not assembly listings are generated. These two directives maintain an
3916 internal counter (which is zero initially). @code{.list} increments the
3917 counter, and @code{.nolist} decrements it. Assembly listings are
3918 generated whenever the counter is greater than zero.
3921 @section @code{.octa @var{bignums}}
3923 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
3924 @cindex @code{octa} directive
3925 @cindex integer, 16-byte
3926 @cindex sixteen byte integer
3927 This directive expects zero or more bignums, separated by commas. For each
3928 bignum, it emits a 16-byte integer.
3930 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
3931 hence @emph{octa}-word for 16 bytes.
3934 @section @code{.org @var{new-lc} , @var{fill}}
3936 @cindex @code{org} directive
3937 @cindex location counter, advancing
3938 @cindex advancing location counter
3939 @cindex current address, advancing
3940 Advance the location counter of the current section to
3941 @var{new-lc}. @var{new-lc} is either an absolute expression or an
3942 expression with the same section as the current subsection. That is,
3943 you can't use @code{.org} to cross sections: if @var{new-lc} has the
3944 wrong section, the @code{.org} directive is ignored. To be compatible
3945 with former assemblers, if the section of @var{new-lc} is absolute,
3946 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
3947 is the same as the current subsection.
3949 @code{.org} may only increase the location counter, or leave it
3950 unchanged; you cannot use @code{.org} to move the location counter
3953 @c double negative used below "not undefined" because this is a specific
3954 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
3955 @c section. doc@cygnus.com 18feb91
3956 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
3957 may not be undefined. If you really detest this restriction we eagerly await
3958 a chance to share your improved assembler.
3960 Beware that the origin is relative to the start of the section, not
3961 to the start of the subsection. This is compatible with other
3962 people's assemblers.
3964 When the location counter (of the current subsection) is advanced, the
3965 intervening bytes are filled with @var{fill} which should be an
3966 absolute expression. If the comma and @var{fill} are omitted,
3967 @var{fill} defaults to zero.
3970 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3972 @cindex padding the location counter given a power of two
3973 @cindex @code{p2align} directive
3974 Pad the location counter (in the current subsection) to a particular
3975 storage boundary. The first expression (which must be absolute) is the
3976 number of low-order zero bits the location counter must have after
3977 advancement. For example @samp{.p2align 3} advances the location
3978 counter until it a multiple of 8. If the location counter is already a
3979 multiple of 8, no change is needed.
3981 The second expression (also absolute) gives the fill value to be stored in the
3982 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3983 padding bytes are normally zero. However, on some systems, if the section is
3984 marked as containing code and the fill value is omitted, the space is filled
3985 with no-op instructions.
3987 The third expression is also absolute, and is also optional. If it is present,
3988 it is the maximum number of bytes that should be skipped by this alignment
3989 directive. If doing the alignment would require skipping more bytes than the
3990 specified maximum, then the alignment is not done at all. You can omit the
3991 fill value (the second argument) entirely by simply using two commas after the
3992 required alignment; this can be useful if you want the alignment to be filled
3993 with no-op instructions when appropriate.
3995 @cindex @code{p2alignw} directive
3996 @cindex @code{p2alignl} directive
3997 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
3998 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
3999 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4000 fill pattern as a four byte longword value. For example, @code{.p2alignw
4001 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4002 filled in with the value 0x368d (the exact placement of the bytes depends upon
4003 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4007 @section @code{.psize @var{lines} , @var{columns}}
4009 @cindex @code{psize} directive
4010 @cindex listing control: paper size
4011 @cindex paper size, for listings
4012 Use this directive to declare the number of lines---and, optionally, the
4013 number of columns---to use for each page, when generating listings.
4015 If you do not use @code{.psize}, listings use a default line-count
4016 of 60. You may omit the comma and @var{columns} specification; the
4017 default width is 200 columns.
4019 @code{@value{AS}} generates formfeeds whenever the specified number of
4020 lines is exceeded (or whenever you explicitly request one, using
4023 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4024 those explicitly specified with @code{.eject}.
4027 @section @code{.quad @var{bignums}}
4029 @cindex @code{quad} directive
4030 @code{.quad} expects zero or more bignums, separated by commas. For
4031 each bignum, it emits
4033 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4034 warning message; and just takes the lowest order 8 bytes of the bignum.
4035 @cindex eight-byte integer
4036 @cindex integer, 8-byte
4038 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4039 hence @emph{quad}-word for 8 bytes.
4042 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4043 warning message; and just takes the lowest order 16 bytes of the bignum.
4044 @cindex sixteen-byte integer
4045 @cindex integer, 16-byte
4049 @section @code{.rept @var{count}}
4051 @cindex @code{rept} directive
4052 Repeat the sequence of lines between the @code{.rept} directive and the next
4053 @code{.endr} directive @var{count} times.
4055 For example, assembling
4063 is equivalent to assembling
4072 @section @code{.sbttl "@var{subheading}"}
4074 @cindex @code{sbttl} directive
4075 @cindex subtitles for listings
4076 @cindex listing control: subtitle
4077 Use @var{subheading} as the title (third line, immediately after the
4078 title line) when generating assembly listings.
4080 This directive affects subsequent pages, as well as the current page if
4081 it appears within ten lines of the top of a page.
4085 @section @code{.scl @var{class}}
4087 @cindex @code{scl} directive
4088 @cindex symbol storage class (COFF)
4089 @cindex COFF symbol storage class
4090 Set the storage-class value for a symbol. This directive may only be
4091 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4092 whether a symbol is static or external, or it may record further
4093 symbolic debugging information.
4096 The @samp{.scl} directive is primarily associated with COFF output; when
4097 configured to generate @code{b.out} output format, @code{@value{AS}}
4098 accepts this directive but ignores it.
4103 @section @code{.section @var{name}}
4105 @cindex @code{section} directive
4106 @cindex named section
4107 Use the @code{.section} directive to assemble the following code into a section
4110 This directive is only supported for targets that actually support arbitrarily
4111 named sections; on @code{a.out} targets, for example, it is not accepted, even
4112 with a standard @code{a.out} section name.
4115 For COFF targets, the @code{.section} directive is used in one of the following
4118 .section @var{name}[, "@var{flags}"]
4119 .section @var{name}[, @var{subsegment}]
4122 If the optional argument is quoted, it is taken as flags to use for the
4123 section. Each flag is a single character. The following flags are recognized:
4126 bss section (uninitialized data)
4128 section is not loaded
4139 If no flags are specified, the default flags depend upon the section name. If
4140 the section name is not recognized, the default will be for the section to be
4141 loaded and writable.
4143 If the optional argument to the @code{.section} directive is not quoted, it is
4144 taken as a subsegment number (@pxref{Sub-Sections}).
4148 For ELF targets, the @code{.section} directive is used like this:
4150 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4152 The optional @var{flags} argument is a quoted string which may contain any
4153 combintion of the following characters:
4156 section is allocatable
4160 section is executable
4163 The optional @var{type} argument may contain one of the following constants:
4166 section contains data
4168 section does not contain data (i.e., section only occupies space)
4171 If no flags are specified, the default flags depend upon the section name. If
4172 the section name is not recognized, the default will be for the section to have
4173 none of the above flags: it will not be allocated in memory, nor writable, nor
4174 executable. The section will contain data.
4176 For ELF targets, the assembler supports another type of @code{.section}
4177 directive for compatibility with the Solaris assembler:
4179 .section "@var{name}"[, @var{flags}...]
4181 Note that the section name is quoted. There may be a sequence of comma
4185 section is allocatable
4189 section is executable
4194 @section @code{.set @var{symbol}, @var{expression}}
4196 @cindex @code{set} directive
4197 @cindex symbol value, setting
4198 Set the value of @var{symbol} to @var{expression}. This
4199 changes @var{symbol}'s value and type to conform to
4200 @var{expression}. If @var{symbol} was flagged as external, it remains
4201 flagged (@pxref{Symbol Attributes}).
4203 You may @code{.set} a symbol many times in the same assembly.
4205 If you @code{.set} a global symbol, the value stored in the object
4206 file is the last value stored into it.
4209 The syntax for @code{set} on the HPPA is
4210 @samp{@var{symbol} .set @var{expression}}.
4214 @section @code{.short @var{expressions}}
4216 @cindex @code{short} directive
4218 @code{.short} is normally the same as @samp{.word}.
4219 @xref{Word,,@code{.word}}.
4221 In some configurations, however, @code{.short} and @code{.word} generate
4222 numbers of different lengths; @pxref{Machine Dependencies}.
4226 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4229 This expects zero or more @var{expressions}, and emits
4230 a 16 bit number for each.
4235 @section @code{.single @var{flonums}}
4237 @cindex @code{single} directive
4238 @cindex floating point numbers (single)
4239 This directive assembles zero or more flonums, separated by commas. It
4240 has the same effect as @code{.float}.
4242 The exact kind of floating point numbers emitted depends on how
4243 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4247 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4248 numbers in @sc{ieee} format.
4254 @section @code{.size}
4256 @cindex @code{size} directive
4257 This directive is generated by compilers to include auxiliary debugging
4258 information in the symbol table. It is only permitted inside
4259 @code{.def}/@code{.endef} pairs.
4262 @samp{.size} is only meaningful when generating COFF format output; when
4263 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4269 @section @code{.sleb128 @var{expressions}}
4271 @cindex @code{sleb128} directive
4272 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4273 compact, variable length representation of numbers used by the DWARF
4274 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
4276 @ifclear no-space-dir
4278 @section @code{.skip @var{size} , @var{fill}}
4280 @cindex @code{skip} directive
4281 @cindex filling memory
4282 This directive emits @var{size} bytes, each of value @var{fill}. Both
4283 @var{size} and @var{fill} are absolute expressions. If the comma and
4284 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4288 @section @code{.space @var{size} , @var{fill}}
4290 @cindex @code{space} directive
4291 @cindex filling memory
4292 This directive emits @var{size} bytes, each of value @var{fill}. Both
4293 @var{size} and @var{fill} are absolute expressions. If the comma
4294 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4299 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4300 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4301 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4302 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4311 @section @code{.space}
4312 @cindex @code{space} directive
4314 On the AMD 29K, this directive is ignored; it is accepted for
4315 compatibility with other AMD 29K assemblers.
4318 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4319 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4325 @section @code{.stabd, .stabn, .stabs}
4327 @cindex symbolic debuggers, information for
4328 @cindex @code{stab@var{x}} directives
4329 There are three directives that begin @samp{.stab}.
4330 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4331 The symbols are not entered in the @code{@value{AS}} hash table: they
4332 cannot be referenced elsewhere in the source file.
4333 Up to five fields are required:
4337 This is the symbol's name. It may contain any character except
4338 @samp{\000}, so is more general than ordinary symbol names. Some
4339 debuggers used to code arbitrarily complex structures into symbol names
4343 An absolute expression. The symbol's type is set to the low 8 bits of
4344 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4345 and debuggers choke on silly bit patterns.
4348 An absolute expression. The symbol's ``other'' attribute is set to the
4349 low 8 bits of this expression.
4352 An absolute expression. The symbol's descriptor is set to the low 16
4353 bits of this expression.
4356 An absolute expression which becomes the symbol's value.
4359 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4360 or @code{.stabs} statement, the symbol has probably already been created;
4361 you get a half-formed symbol in your object file. This is
4362 compatible with earlier assemblers!
4365 @cindex @code{stabd} directive
4366 @item .stabd @var{type} , @var{other} , @var{desc}
4368 The ``name'' of the symbol generated is not even an empty string.
4369 It is a null pointer, for compatibility. Older assemblers used a
4370 null pointer so they didn't waste space in object files with empty
4373 The symbol's value is set to the location counter,
4374 relocatably. When your program is linked, the value of this symbol
4375 is the address of the location counter when the @code{.stabd} was
4378 @cindex @code{stabn} directive
4379 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4380 The name of the symbol is set to the empty string @code{""}.
4382 @cindex @code{stabs} directive
4383 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4384 All five fields are specified.
4390 @section @code{.string} "@var{str}"
4392 @cindex string, copying to object file
4393 @cindex @code{string} directive
4395 Copy the characters in @var{str} to the object file. You may specify more than
4396 one string to copy, separated by commas. Unless otherwise specified for a
4397 particular machine, the assembler marks the end of each string with a 0 byte.
4398 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4402 @section @code{.symver}
4403 @cindex @code{symver} directive
4404 @cindex symbol versioning
4405 @cindex versions of symbols
4406 Use the @code{.symver} directive to bind symbols to specific version nodes
4407 within a source file. This is only supported on ELF platforms, and is
4408 typically used when assembling files to be linked into a shared library.
4409 There are cases where it may make sense to use this in objects to be bound
4410 into an application itself so as to override a versioned symbol from a
4413 For ELF targets, the @code{.symver} directive is used like this:
4415 .symver @var{name}, @var{name2@@nodename}
4417 In this case, the symbol @var{name} must exist and be defined within the file
4418 being assembled. The @code{.versym} directive effectively creates a symbol
4419 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4420 just don't try and create a regular alias is that the @var{@@} character isn't
4421 permitted in symbol names. The @var{name2} part of the name is the actual name
4422 of the symbol by which it will be externally referenced. The name @var{name}
4423 itself is merely a name of convenience that is used so that it is possible to
4424 have definitions for multiple versions of a function within a single source
4425 file, and so that the compiler can unambiguously know which version of a
4426 function is being mentioned. The @var{nodename} portion of the alias should be
4427 the name of a node specified in the version script supplied to the linker when
4428 building a shared library. If you are attempting to override a versioned
4429 symbol from a shared library, then @var{nodename} should correspond to the
4430 nodename of the symbol you are trying to override.
4435 @section @code{.tag @var{structname}}
4437 @cindex COFF structure debugging
4438 @cindex structure debugging, COFF
4439 @cindex @code{tag} directive
4440 This directive is generated by compilers to include auxiliary debugging
4441 information in the symbol table. It is only permitted inside
4442 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4443 definitions in the symbol table with instances of those structures.
4446 @samp{.tag} is only used when generating COFF format output; when
4447 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4453 @section @code{.text @var{subsection}}
4455 @cindex @code{text} directive
4456 Tells @code{@value{AS}} to assemble the following statements onto the end of
4457 the text subsection numbered @var{subsection}, which is an absolute
4458 expression. If @var{subsection} is omitted, subsection number zero
4462 @section @code{.title "@var{heading}"}
4464 @cindex @code{title} directive
4465 @cindex listing control: title line
4466 Use @var{heading} as the title (second line, immediately after the
4467 source file name and pagenumber) when generating assembly listings.
4469 This directive affects subsequent pages, as well as the current page if
4470 it appears within ten lines of the top of a page.
4474 @section @code{.type @var{int}}
4476 @cindex COFF symbol type
4477 @cindex symbol type, COFF
4478 @cindex @code{type} directive
4479 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4480 records the integer @var{int} as the type attribute of a symbol table entry.
4483 @samp{.type} is associated only with COFF format output; when
4484 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4485 directive but ignores it.
4491 @section @code{.val @var{addr}}
4493 @cindex @code{val} directive
4494 @cindex COFF value attribute
4495 @cindex value attribute, COFF
4496 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4497 records the address @var{addr} as the value attribute of a symbol table
4501 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4502 configured for @code{b.out}, it accepts this directive but ignores it.
4507 @section @code{.uleb128 @var{expressions}}
4509 @cindex @code{uleb128} directive
4510 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
4511 compact, variable length representation of numbers used by the DWARF
4512 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
4515 @section @code{.word @var{expressions}}
4517 @cindex @code{word} directive
4518 This directive expects zero or more @var{expressions}, of any section,
4519 separated by commas.
4522 For each expression, @code{@value{AS}} emits a 32-bit number.
4525 For each expression, @code{@value{AS}} emits a 16-bit number.
4530 The size of the number emitted, and its byte order,
4531 depend on what target computer the assembly is for.
4534 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4535 @c happen---32-bit addressability, period; no long/short jumps.
4536 @ifset DIFF-TBL-KLUGE
4537 @cindex difference tables altered
4538 @cindex altered difference tables
4540 @emph{Warning: Special Treatment to support Compilers}
4544 Machines with a 32-bit address space, but that do less than 32-bit
4545 addressing, require the following special treatment. If the machine of
4546 interest to you does 32-bit addressing (or doesn't require it;
4547 @pxref{Machine Dependencies}), you can ignore this issue.
4550 In order to assemble compiler output into something that works,
4551 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4552 Directives of the form @samp{.word sym1-sym2} are often emitted by
4553 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4554 directive of the form @samp{.word sym1-sym2}, and the difference between
4555 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4556 creates a @dfn{secondary jump table}, immediately before the next label.
4557 This secondary jump table is preceded by a short-jump to the
4558 first byte after the secondary table. This short-jump prevents the flow
4559 of control from accidentally falling into the new table. Inside the
4560 table is a long-jump to @code{sym2}. The original @samp{.word}
4561 contains @code{sym1} minus the address of the long-jump to
4564 If there were several occurrences of @samp{.word sym1-sym2} before the
4565 secondary jump table, all of them are adjusted. If there was a
4566 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4567 long-jump to @code{sym4} is included in the secondary jump table,
4568 and the @code{.word} directives are adjusted to contain @code{sym3}
4569 minus the address of the long-jump to @code{sym4}; and so on, for as many
4570 entries in the original jump table as necessary.
4573 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4574 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4575 assembly language programmers.
4578 @c end DIFF-TBL-KLUGE
4581 @section Deprecated Directives
4583 @cindex deprecated directives
4584 @cindex obsolescent directives
4585 One day these directives won't work.
4586 They are included for compatibility with older assemblers.
4594 @node Machine Dependencies
4595 @chapter Machine Dependent Features
4597 @cindex machine dependencies
4598 The machine instruction sets are (almost by definition) different on
4599 each machine where @code{@value{AS}} runs. Floating point representations
4600 vary as well, and @code{@value{AS}} often supports a few additional
4601 directives or command-line options for compatibility with other
4602 assemblers on a particular platform. Finally, some versions of
4603 @code{@value{AS}} support special pseudo-instructions for branch
4606 This chapter discusses most of these differences, though it does not
4607 include details on any machine's instruction set. For details on that
4608 subject, see the hardware manufacturer's manual.
4612 * AMD29K-Dependent:: AMD 29K Dependent Features
4615 * ARC-Dependent:: ARC Dependent Features
4618 * ARM-Dependent:: ARM Dependent Features
4621 * D10V-Dependent:: D10V Dependent Features
4624 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4627 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4630 * HPPA-Dependent:: HPPA Dependent Features
4633 * i386-Dependent:: Intel 80386 Dependent Features
4636 * i960-Dependent:: Intel 80960 Dependent Features
4639 * M68K-Dependent:: M680x0 Dependent Features
4642 * MIPS-Dependent:: MIPS Dependent Features
4645 * SH-Dependent:: Hitachi SH Dependent Features
4648 * Sparc-Dependent:: SPARC Dependent Features
4651 * Z8000-Dependent:: Z8000 Dependent Features
4654 * Vax-Dependent:: VAX Dependent Features
4661 @c The following major nodes are *sections* in the GENERIC version, *chapters*
4662 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
4663 @c peculiarity: to preserve cross-references, there must be a node called
4664 @c "Machine Dependencies". Hence the conditional nodenames in each
4665 @c major node below. Node defaulting in makeinfo requires adjacency of
4666 @c node and sectioning commands; hence the repetition of @chapter BLAH
4667 @c in both conditional blocks.
4673 @chapter ARC Dependent Features
4676 @node Machine Dependencies
4677 @chapter ARC Dependent Features
4682 * ARC-Opts:: Options
4683 * ARC-Float:: Floating Point
4684 * ARC-Directives:: Sparc Machine Directives
4690 @cindex options for ARC
4692 @cindex architectures, ARC
4693 @cindex ARC architectures
4694 The ARC chip family includes several successive levels (or other
4695 variants) of chip, using the same core instruction set, but including
4696 a few additional instructions at each level.
4698 By default, @code{@value{AS}} assumes the core instruction set (ARC
4699 base). The @code{.cpu} pseudo-op is intended to be used to select
4703 @cindex @code{-mbig-endian} option (ARC)
4704 @cindex @code{-mlittle-endian} option (ARC)
4705 @cindex ARC big-endian output
4706 @cindex ARC little-endian output
4707 @cindex big-endian output, ARC
4708 @cindex little-endian output, ARC
4710 @itemx -mlittle-endian
4711 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
4712 little-endian output at run time (unlike most other @sc{gnu} development
4713 tools, which must be configured for one or the other). Use
4714 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
4719 @section Floating Point
4721 @cindex floating point, ARC (@sc{ieee})
4722 @cindex ARC floating point (@sc{ieee})
4723 The ARC cpu family currently does not have hardware floating point
4724 support. Software floating point support is provided by @code{GCC}
4725 and uses @sc{ieee} floating-point numbers.
4727 @node ARC-Directives
4728 @section ARC Machine Directives
4730 @cindex ARC machine directives
4731 @cindex machine directives, ARC
4732 The ARC version of @code{@value{AS}} supports the following additional
4737 @cindex @code{cpu} directive, SPARC
4738 This must be followed by the desired cpu.
4739 The ARC is intended to be customizable, @code{.cpu} is used to
4740 select the desired variant [though currently there are none].
4747 @include c-a29k.texi
4756 @node Machine Dependencies
4757 @chapter Machine Dependent Features
4759 The machine instruction sets are different on each Hitachi chip family,
4760 and there are also some syntax differences among the families. This
4761 chapter describes the specific @code{@value{AS}} features for each
4765 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4766 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4767 * SH-Dependent:: Hitachi SH Dependent Features
4774 @include c-d10v.texi
4778 @include c-h8300.texi
4782 @include c-h8500.texi
4786 @include c-hppa.texi
4790 @include c-i386.texi
4794 @include c-i960.texi
4798 @include c-m68k.texi
4802 @include c-mips.texi
4806 @include c-ns32k.texi
4814 @include c-sparc.texi
4826 @c reverse effect of @down at top of generic Machine-Dep chapter
4830 @node Reporting Bugs
4831 @chapter Reporting Bugs
4832 @cindex bugs in assembler
4833 @cindex reporting bugs in assembler
4835 Your bug reports play an essential role in making @code{@value{AS}} reliable.
4837 Reporting a bug may help you by bringing a solution to your problem, or it may
4838 not. But in any case the principal function of a bug report is to help the
4839 entire community by making the next version of @code{@value{AS}} work better.
4840 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
4842 In order for a bug report to serve its purpose, you must include the
4843 information that enables us to fix the bug.
4846 * Bug Criteria:: Have you found a bug?
4847 * Bug Reporting:: How to report bugs
4851 @section Have you found a bug?
4852 @cindex bug criteria
4854 If you are not sure whether you have found a bug, here are some guidelines:
4857 @cindex fatal signal
4858 @cindex assembler crash
4859 @cindex crash of assembler
4861 If the assembler gets a fatal signal, for any input whatever, that is a
4862 @code{@value{AS}} bug. Reliable assemblers never crash.
4864 @cindex error on valid input
4866 If @code{@value{AS}} produces an error message for valid input, that is a bug.
4868 @cindex invalid input
4870 If @code{@value{AS}} does not produce an error message for invalid input, that
4871 is a bug. However, you should note that your idea of ``invalid input'' might
4872 be our idea of ``an extension'' or ``support for traditional practice''.
4875 If you are an experienced user of assemblers, your suggestions for improvement
4876 of @code{@value{AS}} are welcome in any case.
4880 @section How to report bugs
4882 @cindex assembler bugs, reporting
4884 A number of companies and individuals offer support for @sc{gnu} products. If
4885 you obtained @code{@value{AS}} from a support organization, we recommend you
4886 contact that organization first.
4888 You can find contact information for many support companies and
4889 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
4892 In any event, we also recommend that you send bug reports for @code{@value{AS}}
4893 to @samp{bug-gnu-utils@@prep.ai.mit.edu}.
4895 The fundamental principle of reporting bugs usefully is this:
4896 @strong{report all the facts}. If you are not sure whether to state a
4897 fact or leave it out, state it!
4899 Often people omit facts because they think they know what causes the problem
4900 and assume that some details do not matter. Thus, you might assume that the
4901 name of a symbol you use in an example does not matter. Well, probably it does
4902 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
4903 happens to fetch from the location where that name is stored in memory;
4904 perhaps, if the name were different, the contents of that location would fool
4905 the assembler into doing the right thing despite the bug. Play it safe and
4906 give a specific, complete example. That is the easiest thing for you to do,
4907 and the most helpful.
4909 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
4910 it is new to us. Therefore, always write your bug reports on the assumption
4911 that the bug has not been reported previously.
4913 Sometimes people give a few sketchy facts and ask, ``Does this ring a
4914 bell?'' Those bug reports are useless, and we urge everyone to
4915 @emph{refuse to respond to them} except to chide the sender to report
4918 To enable us to fix the bug, you should include all these things:
4922 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
4923 it with the @samp{--version} argument.
4925 Without this, we will not know whether there is any point in looking for
4926 the bug in the current version of @code{@value{AS}}.
4929 Any patches you may have applied to the @code{@value{AS}} source.
4932 The type of machine you are using, and the operating system name and
4936 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
4940 The command arguments you gave the assembler to assemble your example and
4941 observe the bug. To guarantee you will not omit something important, list them
4942 all. A copy of the Makefile (or the output from make) is sufficient.
4944 If we were to try to guess the arguments, we would probably guess wrong
4945 and then we might not encounter the bug.
4948 A complete input file that will reproduce the bug. If the bug is observed when
4949 the assembler is invoked via a compiler, send the assembler source, not the
4950 high level language source. Most compilers will produce the assembler source
4951 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
4952 the options @samp{-v --save-temps}; this will save the assembler source in a
4953 file with an extension of @file{.s}, and also show you exactly how
4954 @code{@value{AS}} is being run.
4957 A description of what behavior you observe that you believe is
4958 incorrect. For example, ``It gets a fatal signal.''
4960 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
4961 will certainly notice it. But if the bug is incorrect output, we might not
4962 notice unless it is glaringly wrong. You might as well not give us a chance to
4965 Even if the problem you experience is a fatal signal, you should still say so
4966 explicitly. Suppose something strange is going on, such as, your copy of
4967 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
4968 library on your system. (This has happened!) Your copy might crash and ours
4969 would not. If you told us to expect a crash, then when ours fails to crash, we
4970 would know that the bug was not happening for us. If you had not told us to
4971 expect a crash, then we would not be able to draw any conclusion from our
4975 If you wish to suggest changes to the @code{@value{AS}} source, send us context
4976 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
4977 option. Always send diffs from the old file to the new file. If you even
4978 discuss something in the @code{@value{AS}} source, refer to it by context, not
4981 The line numbers in our development sources will not match those in your
4982 sources. Your line numbers would convey no useful information to us.
4985 Here are some things that are not necessary:
4989 A description of the envelope of the bug.
4991 Often people who encounter a bug spend a lot of time investigating
4992 which changes to the input file will make the bug go away and which
4993 changes will not affect it.
4995 This is often time consuming and not very useful, because the way we
4996 will find the bug is by running a single example under the debugger
4997 with breakpoints, not by pure deduction from a series of examples.
4998 We recommend that you save your time for something else.
5000 Of course, if you can find a simpler example to report @emph{instead}
5001 of the original one, that is a convenience for us. Errors in the
5002 output will be easier to spot, running under the debugger will take
5003 less time, and so on.
5005 However, simplification is not vital; if you do not want to do this,
5006 report the bug anyway and send us the entire test case you used.
5009 A patch for the bug.
5011 A patch for the bug does help us if it is a good one. But do not omit
5012 the necessary information, such as the test case, on the assumption that
5013 a patch is all we need. We might see problems with your patch and decide
5014 to fix the problem another way, or we might not understand it at all.
5016 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5017 construct an example that will make the program follow a certain path through
5018 the code. If you do not send us the example, we will not be able to construct
5019 one, so we will not be able to verify that the bug is fixed.
5021 And if we cannot understand what bug you are trying to fix, or why your
5022 patch should be an improvement, we will not install it. A test case will
5023 help us to understand.
5026 A guess about what the bug is or what it depends on.
5028 Such guesses are usually wrong. Even we cannot guess right about such
5029 things without first using the debugger to find the facts.
5032 @node Acknowledgements
5033 @chapter Acknowledgements
5035 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5036 it is not meant as a slight. We just don't know about it. Send mail to the
5037 maintainer, and we'll correct the situation. Currently
5039 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5041 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5044 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5045 information and the 68k series machines, most of the preprocessing pass, and
5046 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5048 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5049 many bug fixes, including merging support for several processors, breaking GAS
5050 up to handle multiple object file format back ends (including heavy rewrite,
5051 testing, an integration of the coff and b.out back ends), adding configuration
5052 including heavy testing and verification of cross assemblers and file splits
5053 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5054 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5055 port (including considerable amounts of reverse engineering), a SPARC opcode
5056 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5057 assertions and made them work, much other reorganization, cleanup, and lint.
5059 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5060 in format-specific I/O modules.
5062 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5063 has done much work with it since.
5065 The Intel 80386 machine description was written by Eliot Dresselhaus.
5067 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5069 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5070 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5072 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5073 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5074 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5075 support a.out format.
5077 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5078 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5079 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5080 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5083 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5084 simplified the configuration of which versions accept which directives. He
5085 updated the 68k machine description so that Motorola's opcodes always produced
5086 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5087 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5088 cross-compilation support, and one bug in relaxation that took a week and
5089 required the proverbial one-bit fix.
5091 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5092 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5093 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5094 PowerPC assembler, and made a few other minor patches.
5096 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5098 Hewlett-Packard contributed support for the HP9000/300.
5100 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5101 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5102 formats). This work was supported by both the Center for Software Science at
5103 the University of Utah and Cygnus Support.
5105 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5106 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5107 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5108 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5109 and some initial 64-bit support).
5111 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5112 support for openVMS/Alpha.
5114 Several engineers at Cygnus Support have also provided many small bug fixes and
5115 configuration enhancements.
5117 Many others have contributed large or small bugfixes and enhancements. If
5118 you have contributed significant work and are not mentioned on this list, and
5119 want to be, let us know. Some of the history has been lost; we are not
5120 intentionally leaving anyone out.