1 \input texinfo @c -*-Texinfo-*-
2 @c Copyright (c) 1991, 92, 93, 94, 95, 96, 97, 98, 2000
3 @c Free Software Foundation, Inc.
4 @c UPDATE!! On future updates--
5 @c (1) check for new machine-dep cmdline options in
6 @c md_parse_option definitions in config/tc-*.c
7 @c (2) for platform-specific directives, examine md_pseudo_op
9 @c (3) for object-format specific directives, examine obj_pseudo_op
11 @c (4) portable directives in potable[] in read.c
15 @c defaults, config file may override:
18 @include asconfig.texi
21 @c common OR combinations of conditions
41 @set abnormal-separator
45 @settitle Using @value{AS}
48 @settitle Using @value{AS} (@value{TARGET})
50 @setchapternewpage odd
55 @c WARE! Some of the machine-dependent sections contain tables of machine
56 @c instructions. Except in multi-column format, these tables look silly.
57 @c Unfortunately, Texinfo doesn't have a general-purpose multi-col format, so
58 @c the multi-col format is faked within @example sections.
60 @c Again unfortunately, the natural size that fits on a page, for these tables,
61 @c is different depending on whether or not smallbook is turned on.
62 @c This matters, because of order: text flow switches columns at each page
65 @c The format faked in this source works reasonably well for smallbook,
66 @c not well for the default large-page format. This manual expects that if you
67 @c turn on @smallbook, you will also uncomment the "@set SMALL" to enable the
68 @c tables in question. You can turn on one without the other at your
69 @c discretion, of course.
72 @c the insn tables look just as silly in info files regardless of smallbook,
73 @c might as well show 'em anyways.
79 * As: (as). The GNU assembler.
88 This file documents the GNU Assembler "@value{AS}".
90 Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
92 Permission is granted to make and distribute verbatim copies of
93 this manual provided the copyright notice and this permission notice
94 are preserved on all copies.
97 Permission is granted to process this file through Tex and print the
98 results, provided the printed document carries copying permission
99 notice identical to this one except for the removal of this paragraph
100 (this paragraph not being relevant to the printed manual).
103 Permission is granted to copy and distribute modified versions of this manual
104 under the conditions for verbatim copying, provided that the entire resulting
105 derived work is distributed under the terms of a permission notice identical to
108 Permission is granted to copy and distribute translations of this manual
109 into another language, under the above conditions for modified versions.
113 @title Using @value{AS}
114 @subtitle The @sc{gnu} Assembler
116 @subtitle for the @value{TARGET} family
119 @subtitle Version @value{VERSION}
122 The Free Software Foundation Inc. thanks The Nice Computer
123 Company of Australia for loaning Dean Elsner to write the
124 first (Vax) version of @code{as} for Project @sc{gnu}.
125 The proprietors, management and staff of TNCCA thank FSF for
126 distracting the boss while they got some work
129 @author Dean Elsner, Jay Fenlason & friends
133 \hfill {\it Using {\tt @value{AS}}}\par
134 \hfill Edited by Cygnus Support\par
136 %"boxit" macro for figures:
137 %Modified from Knuth's ``boxit'' macro from TeXbook (answer to exercise 21.3)
138 \gdef\boxit#1#2{\vbox{\hrule\hbox{\vrule\kern3pt
139 \vbox{\parindent=0pt\parskip=0pt\hsize=#1\kern3pt\strut\hfil
140 #2\hfil\strut\kern3pt}\kern3pt\vrule}\hrule}}%box with visible outline
141 \gdef\ibox#1#2{\hbox to #1{#2\hfil}\kern8pt}% invisible box
144 @vskip 0pt plus 1filll
145 Copyright @copyright{} 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000 Free Software Foundation, Inc.
147 Permission is granted to make and distribute verbatim copies of
148 this manual provided the copyright notice and this permission notice
149 are preserved on all copies.
151 Permission is granted to copy and distribute modified versions of this manual
152 under the conditions for verbatim copying, provided that the entire resulting
153 derived work is distributed under the terms of a permission notice identical to
156 Permission is granted to copy and distribute translations of this manual
157 into another language, under the above conditions for modified versions.
162 @top Using @value{AS}
164 This file is a user guide to the @sc{gnu} assembler @code{@value{AS}} version
167 This version of the file describes @code{@value{AS}} configured to generate
168 code for @value{TARGET} architectures.
171 * Overview:: Overview
172 * Invoking:: Command-Line Options
174 * Sections:: Sections and Relocation
176 * Expressions:: Expressions
177 * Pseudo Ops:: Assembler Directives
178 * Machine Dependencies:: Machine Dependent Features
179 * Reporting Bugs:: Reporting Bugs
180 * Acknowledgements:: Who Did What
188 This manual is a user guide to the @sc{gnu} assembler @code{@value{AS}}.
190 This version of the manual describes @code{@value{AS}} configured to generate
191 code for @value{TARGET} architectures.
195 @cindex invocation summary
196 @cindex option summary
197 @cindex summary of options
198 Here is a brief summary of how to invoke @code{@value{AS}}. For details,
199 @pxref{Invoking,,Comand-Line Options}.
201 @c We don't use deffn and friends for the following because they seem
202 @c to be limited to one line for the header.
204 @value{AS} [ -a[cdhlns][=file] ] [ -D ] [ --defsym @var{sym}=@var{val} ]
205 [ -f ] [ --gstabs ] [ --gdwarf2 ] [ --help ] [ -I @var{dir} ] [ -J ] [ -K ] [ -L ]
206 [ --keep-locals ] [ -o @var{objfile} ] [ -R ] [ --statistics ] [ -v ]
207 [ -version ] [ --version ] [ -W ] [ --warn ] [ --fatal-warnings ]
210 @c am29k has no machine-dependent assembler options
213 [ -mbig-endian | -mlittle-endian ]
216 [ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]60 |
217 -m[arm]600 | -m[arm]610 | -m[arm]620 | -m[arm]7[t][[d]m[i]][fe] | -m[arm]70 |
218 -m[arm]700 | -m[arm]710[c] | -m[arm]7100 | -m[arm]7500 | -m[arm]8 |
219 -m[arm]810 | -m[arm]9 | -m[arm]920 | -m[arm]920t | -m[arm]9tdmi |
220 -mstrongarm | -mstrongarm110 | -mstrongarm1100 ]
221 [ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t |
222 -m[arm]v5 | -[arm]v5t ]
224 [ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
226 [ -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant ]
227 [ -mthumb-interwork ]
238 @c Hitachi family chips have no machine-dependent assembler options
241 @c HPPA has no machine-dependent assembler options (yet).
247 @c The order here is important. See c-sparc.texi.
248 [ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
249 -Av8plus | -Av8plusa | -Av9 | -Av9a ]
250 [ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
253 @c Z8000 has no machine-dependent assembler options
256 @c see md_parse_option in tc-i960.c
257 [ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
261 [ --m32rx | --[no-]warn-explicit-parallel-conflicts | --W[n]p ]
264 [ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
267 [ -jsri2bsr ] [ -sifilter ] [ -relax ]
271 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
272 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
273 [ --trap ] [ --break ]
274 [ --emulation=@var{name} ]
276 [ -- | @var{files} @dots{} ]
281 Turn on listings, in any of a variety of ways:
285 omit false conditionals
288 omit debugging directives
291 include high-level source
297 include macro expansions
300 omit forms processing
306 set the name of the listing file
309 You may combine these options; for example, use @samp{-aln} for assembly
310 listing without forms processing. The @samp{=file} option, if used, must be
311 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
314 Ignored. This option is accepted for script compatibility with calls to
317 @item --defsym @var{sym}=@var{value}
318 Define the symbol @var{sym} to be @var{value} before assembling the input file.
319 @var{value} must be an integer constant. As in C, a leading @samp{0x}
320 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
323 ``fast''---skip whitespace and comment preprocessing (assume source is
327 Generate stabs debugging information for each assembler line. This
328 may help debugging assembler code, if the debugger can handle it.
331 Generate DWARF2 debugging information for each assembler line. This
332 may help debugging assembler code, if the debugger can handle it.
335 Print a summary of the command line options and exit.
338 Add directory @var{dir} to the search list for @code{.include} directives.
341 Don't warn about signed overflow.
344 @ifclear DIFF-TBL-KLUGE
345 This option is accepted but has no effect on the @value{TARGET} family.
347 @ifset DIFF-TBL-KLUGE
348 Issue warnings when difference tables altered for long displacements.
353 Keep (in the symbol table) local symbols. On traditional a.out systems
354 these start with @samp{L}, but different systems have different local
357 @item -o @var{objfile}
358 Name the object-file output from @code{@value{AS}} @var{objfile}.
361 Fold the data section into the text section.
364 Print the maximum space (in bytes) and total time (in seconds) used by
367 @item --strip-local-absolute
368 Remove local absolute symbols from the outgoing symbol table.
372 Print the @code{as} version.
375 Print the @code{as} version and exit.
379 Suppress warning messages.
381 @item --fatal-warnings
382 Treat warnings as errors.
385 Don't suppress warning messages or treat them as errors.
394 Generate an object file even after errors.
396 @item -- | @var{files} @dots{}
397 Standard input, or source files to assemble.
402 The following options are available when @value{AS} is configured for
407 @cindex ARC endianness
408 @cindex endianness, ARC
409 @cindex big endian output, ARC
411 Generate ``big endian'' format output.
413 @cindex little endian output, ARC
414 @item -mlittle-endian
415 Generate ``little endian'' format output.
421 The following options are available when @value{AS} is configured for the ARM
425 @item -m[arm][1|2|3|6|7|8|9][...]
426 Specify which ARM processor variant is the target.
427 @item -m[arm]v[2|2a|3|3m|4|4t|5|5t]
428 Specify which ARM architecture variant is used by the target.
429 @item -mthumb | -mall
430 Enable or disable Thumb only instruction decoding.
431 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
432 Select which Floating Point architcture is the target.
433 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
434 Select which procedure calling convention is in use.
436 Select either big-endian (-EB) or little-endian (-EL) output.
437 @item -mthumb-interwork
438 Specify that the code has been generated with interworking between Thumb and
441 Specify that PIC code has been generated.
446 The following options are available when @value{AS} is configured for
449 @cindex D10V optimization
450 @cindex optimization, D10V
452 Optimize output by parallelizing instructions.
457 The following options are available when @value{AS} is configured for a D30V
460 @cindex D30V optimization
461 @cindex optimization, D30V
463 Optimize output by parallelizing instructions.
467 Warn when nops are generated.
469 @cindex D30V nops after 32-bit multiply
471 Warn when a nop after a 32-bit multiply instruction is generated.
476 The following options are available when @value{AS} is configured for the
477 Intel 80960 processor.
480 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
481 Specify which variant of the 960 architecture is the target.
484 Add code to collect statistics about branches taken.
487 Do not alter compare-and-branch instructions for long displacements;
494 The following options are available when @value{AS} is configured for the
495 Mitsubishi M32R series.
500 Specify which processor in the M32R family is the target. The default
501 is normally the M32R, but this option changes it to the M32RX.
503 @item --warn-explicit-parallel-conflicts or --Wp
504 Produce warning messages when questionable parallel constructs are
507 @item --no-warn-explicit-parallel-conflicts or --Wnp
508 Do not produce warning messages when questionable parallel constructs are
515 The following options are available when @value{AS} is configured for the
516 Motorola 68000 series.
521 Shorten references to undefined symbols, to one word instead of two.
523 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
524 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
525 Specify what processor in the 68000 family is the target. The default
526 is normally the 68020, but this can be changed at configuration time.
528 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
529 The target machine does (or does not) have a floating-point coprocessor.
530 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
531 the basic 68000 is not compatible with the 68881, a combination of the
532 two can be specified, since it's possible to do emulation of the
533 coprocessor instructions with the main processor.
535 @item -m68851 | -mno-68851
536 The target machine does (or does not) have a memory-management
537 unit coprocessor. The default is to assume an MMU for 68020 and up.
543 The following options are available when @value{AS} is configured for
544 a picoJava processor.
548 @cindex PJ endianness
549 @cindex endianness, PJ
550 @cindex big endian output, PJ
552 Generate ``big endian'' format output.
554 @cindex little endian output, PJ
556 Generate ``little endian'' format output.
562 The following options are available when @code{@value{AS}} is configured
563 for the SPARC architecture:
566 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
567 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
568 Explicitly select a variant of the SPARC architecture.
570 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
571 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
573 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
574 UltraSPARC extensions.
576 @item -xarch=v8plus | -xarch=v8plusa
577 For compatibility with the Solaris v9 assembler. These options are
578 equivalent to -Av8plus and -Av8plusa, respectively.
581 Warn when the assembler switches to another architecture.
586 The following options are available when @value{AS} is configured for
591 This option sets the largest size of an object that can be referenced
592 implicitly with the @code{gp} register. It is only accepted for targets that
593 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
595 @cindex MIPS endianness
596 @cindex endianness, MIPS
597 @cindex big endian output, MIPS
599 Generate ``big endian'' format output.
601 @cindex little endian output, MIPS
603 Generate ``little endian'' format output.
609 Generate code for a particular MIPS Instruction Set Architecture level.
610 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
611 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
616 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
617 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
618 instructions around accesses to the @samp{HI} and @samp{LO} registers.
619 @samp{-no-m4650} turns off this option.
621 @item -mcpu=@var{CPU}
622 Generate code for a particular MIPS cpu. This has little effect on the
623 assembler, but it is passed by @code{@value{GCC}}.
626 @item --emulation=@var{name}
627 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
628 for some other target, in all respects, including output format (choosing
629 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
630 debugging information or store symbol table information, and default
631 endianness. The available configuration names are: @samp{mipsecoff},
632 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
633 @samp{mipsbelf}. The first two do not alter the default endianness from that
634 of the primary target for which the assembler was configured; the others change
635 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
636 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
637 selection in any case.
639 This option is currently supported only when the primary target
640 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
641 Furthermore, the primary target or others specified with
642 @samp{--enable-targets=@dots{}} at configuration time must include support for
643 the other format, if both are to be available. For example, the Irix 5
644 configuration includes support for both.
646 Eventually, this option will support more configurations, with more
647 fine-grained control over the assembler's behavior, and will be supported for
651 @code{@value{AS}} ignores this option. It is accepted for compatibility with
659 Control how to deal with multiplication overflow and division by zero.
660 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
661 (and only work for Instruction Set Architecture level 2 and higher);
662 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
668 The following options are available when @value{AS} is configured for
674 Enable or disable the JSRI to BSR transformation. By default this is enabled.
675 The command line option @samp{-nojsri2bsr} can be used to disable it.
679 Enable or disable the silicon filter behaviour. By default this is disabled.
680 The default can be overidden by the @samp{-sifilter} command line option.
683 Alter jump instructions for long displacements.
685 @item -mcpu=[210|340]
686 Select the cpu type on the target hardware. This controls which instructions
690 Assemble for a big endian target.
693 Assemble for a little endian target.
699 * Manual:: Structure of this Manual
700 * GNU Assembler:: The GNU Assembler
701 * Object Formats:: Object File Formats
702 * Command Line:: Command Line
703 * Input Files:: Input Files
704 * Object:: Output (Object) File
705 * Errors:: Error and Warning Messages
709 @section Structure of this Manual
711 @cindex manual, structure and purpose
712 This manual is intended to describe what you need to know to use
713 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
714 notation for symbols, constants, and expressions; the directives that
715 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
718 We also cover special features in the @value{TARGET}
719 configuration of @code{@value{AS}}, including assembler directives.
722 This manual also describes some of the machine-dependent features of
723 various flavors of the assembler.
726 @cindex machine instructions (not covered)
727 On the other hand, this manual is @emph{not} intended as an introduction
728 to programming in assembly language---let alone programming in general!
729 In a similar vein, we make no attempt to introduce the machine
730 architecture; we do @emph{not} describe the instruction set, standard
731 mnemonics, registers or addressing modes that are standard to a
732 particular architecture.
734 You may want to consult the manufacturer's
735 machine architecture manual for this information.
739 For information on the H8/300 machine instruction set, see @cite{H8/300
740 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
741 see @cite{H8/300H Series Programming Manual} (Hitachi).
744 For information on the H8/500 machine instruction set, see @cite{H8/500
745 Series Programming Manual} (Hitachi M21T001).
748 For information on the Hitachi SH machine instruction set, see
749 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
752 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
756 @c I think this is premature---doc@cygnus.com, 17jan1991
758 Throughout this manual, we assume that you are running @dfn{GNU},
759 the portable operating system from the @dfn{Free Software
760 Foundation, Inc.}. This restricts our attention to certain kinds of
761 computer (in particular, the kinds of computers that @sc{gnu} can run on);
762 once this assumption is granted examples and definitions need less
765 @code{@value{AS}} is part of a team of programs that turn a high-level
766 human-readable series of instructions into a low-level
767 computer-readable series of instructions. Different versions of
768 @code{@value{AS}} are used for different kinds of computer.
771 @c There used to be a section "Terminology" here, which defined
772 @c "contents", "byte", "word", and "long". Defining "word" to any
773 @c particular size is confusing when the .word directive may generate 16
774 @c bits on one machine and 32 bits on another; in general, for the user
775 @c version of this manual, none of these terms seem essential to define.
776 @c They were used very little even in the former draft of the manual;
777 @c this draft makes an effort to avoid them (except in names of
781 @section The GNU Assembler
783 @sc{gnu} @code{as} is really a family of assemblers.
785 This manual describes @code{@value{AS}}, a member of that family which is
786 configured for the @value{TARGET} architectures.
788 If you use (or have used) the @sc{gnu} assembler on one architecture, you
789 should find a fairly similar environment when you use it on another
790 architecture. Each version has much in common with the others,
791 including object file formats, most assembler directives (often called
792 @dfn{pseudo-ops}) and assembler syntax.@refill
794 @cindex purpose of @sc{gnu} assembler
795 @code{@value{AS}} is primarily intended to assemble the output of the
796 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
797 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
798 assemble correctly everything that other assemblers for the same
799 machine would assemble.
801 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
804 @c This remark should appear in generic version of manual; assumption
805 @c here is that generic version sets M680x0.
806 This doesn't mean @code{@value{AS}} always uses the same syntax as another
807 assembler for the same architecture; for example, we know of several
808 incompatible versions of 680x0 assembly language syntax.
811 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
812 program in one pass of the source file. This has a subtle impact on the
813 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
816 @section Object File Formats
818 @cindex object file format
819 The @sc{gnu} assembler can be configured to produce several alternative
820 object file formats. For the most part, this does not affect how you
821 write assembly language programs; but directives for debugging symbols
822 are typically different in different file formats. @xref{Symbol
823 Attributes,,Symbol Attributes}.
826 On the @value{TARGET}, @code{@value{AS}} is configured to produce
827 @value{OBJ-NAME} format object files.
829 @c The following should exhaust all configs that set MULTI-OBJ, ideally
831 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
832 @code{a.out} or COFF format object files.
835 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
836 @code{b.out} or COFF format object files.
839 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
840 SOM or ELF format object files.
845 @section Command Line
847 @cindex command line conventions
848 After the program name @code{@value{AS}}, the command line may contain
849 options and file names. Options may appear in any order, and may be
850 before, after, or between file names. The order of file names is
853 @cindex standard input, as input file
855 @file{--} (two hyphens) by itself names the standard input file
856 explicitly, as one of the files for @code{@value{AS}} to assemble.
858 @cindex options, command line
859 Except for @samp{--} any command line argument that begins with a
860 hyphen (@samp{-}) is an option. Each option changes the behavior of
861 @code{@value{AS}}. No option changes the way another option works. An
862 option is a @samp{-} followed by one or more letters; the case of
863 the letter is important. All options are optional.
865 Some options expect exactly one file name to follow them. The file
866 name may either immediately follow the option's letter (compatible
867 with older assemblers) or it may be the next command argument (@sc{gnu}
868 standard). These two command lines are equivalent:
871 @value{AS} -o my-object-file.o mumble.s
872 @value{AS} -omy-object-file.o mumble.s
879 @cindex source program
881 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
882 describe the program input to one run of @code{@value{AS}}. The program may
883 be in one or more files; how the source is partitioned into files
884 doesn't change the meaning of the source.
886 @c I added "con" prefix to "catenation" just to prove I can overcome my
887 @c APL training... doc@cygnus.com
888 The source program is a concatenation of the text in all the files, in the
891 Each time you run @code{@value{AS}} it assembles exactly one source
892 program. The source program is made up of one or more files.
893 (The standard input is also a file.)
895 You give @code{@value{AS}} a command line that has zero or more input file
896 names. The input files are read (from left file name to right). A
897 command line argument (in any position) that has no special meaning
898 is taken to be an input file name.
900 If you give @code{@value{AS}} no file names it attempts to read one input file
901 from the @code{@value{AS}} standard input, which is normally your terminal. You
902 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
905 Use @samp{--} if you need to explicitly name the standard input file
906 in your command line.
908 If the source is empty, @code{@value{AS}} produces a small, empty object
911 @subheading Filenames and Line-numbers
913 @cindex input file linenumbers
914 @cindex line numbers, in input files
915 There are two ways of locating a line in the input file (or files) and
916 either may be used in reporting error messages. One way refers to a line
917 number in a physical file; the other refers to a line number in a
918 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
920 @dfn{Physical files} are those files named in the command line given
921 to @code{@value{AS}}.
923 @dfn{Logical files} are simply names declared explicitly by assembler
924 directives; they bear no relation to physical files. Logical file names help
925 error messages reflect the original source file, when @code{@value{AS}} source
926 is itself synthesized from other files. @code{@value{AS}} understands the
927 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
928 @ref{File,,@code{.file}}.
931 @section Output (Object) File
937 Every time you run @code{@value{AS}} it produces an output file, which is
938 your assembly language program translated into numbers. This file
939 is the object file. Its default name is
947 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
949 You can give it another name by using the @code{-o} option. Conventionally,
950 object file names end with @file{.o}. The default name is used for historical
951 reasons: older assemblers were capable of assembling self-contained programs
952 directly into a runnable program. (For some formats, this isn't currently
953 possible, but it can be done for the @code{a.out} format.)
957 The object file is meant for input to the linker @code{@value{LD}}. It contains
958 assembled program code, information to help @code{@value{LD}} integrate
959 the assembled program into a runnable file, and (optionally) symbolic
960 information for the debugger.
962 @c link above to some info file(s) like the description of a.out.
963 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
966 @section Error and Warning Messages
968 @cindex error messsages
969 @cindex warning messages
970 @cindex messages from assembler
971 @code{@value{AS}} may write warnings and error messages to the standard error
972 file (usually your terminal). This should not happen when a compiler
973 runs @code{@value{AS}} automatically. Warnings report an assumption made so
974 that @code{@value{AS}} could keep assembling a flawed program; errors report a
975 grave problem that stops the assembly.
977 @cindex format of warning messages
978 Warning messages have the format
981 file_name:@b{NNN}:Warning Message Text
985 @cindex line numbers, in warnings/errors
986 (where @b{NNN} is a line number). If a logical file name has been given
987 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
988 the current input file is used. If a logical line number was given
990 (@pxref{Line,,@code{.line}})
994 (@pxref{Line,,@code{.line}})
997 (@pxref{Ln,,@code{.ln}})
1000 then it is used to calculate the number printed,
1001 otherwise the actual line in the current source file is printed. The
1002 message text is intended to be self explanatory (in the grand Unix
1005 @cindex format of error messages
1006 Error messages have the format
1008 file_name:@b{NNN}:FATAL:Error Message Text
1010 The file name and line number are derived as for warning
1011 messages. The actual message text may be rather less explanatory
1012 because many of them aren't supposed to happen.
1015 @chapter Command-Line Options
1017 @cindex options, all versions of assembler
1018 This chapter describes command-line options available in @emph{all}
1019 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1021 to the @value{TARGET}.
1024 to particular machine architectures.
1027 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
1028 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1029 The assembler arguments must be separated from each other (and the @samp{-Wa})
1030 by commas. For example:
1033 gcc -c -g -O -Wa,-alh,-L file.c
1037 This passes two options to the assembler: @samp{-alh} (emit a listing to
1038 standard output with with high-level and assembly source) and @samp{-L} (retain
1039 local symbols in the symbol table).
1041 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1042 command-line options are automatically passed to the assembler by the compiler.
1043 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1044 precisely what options it passes to each compilation pass, including the
1048 * a:: -a[cdhlns] enable listings
1049 * D:: -D for compatibility
1050 * f:: -f to work faster
1051 * I:: -I for .include search path
1052 @ifclear DIFF-TBL-KLUGE
1053 * K:: -K for compatibility
1055 @ifset DIFF-TBL-KLUGE
1056 * K:: -K for difference tables
1059 * L:: -L to retain local labels
1060 * M:: -M or --mri to assemble in MRI compatibility mode
1061 * MD:: --MD for dependency tracking
1062 * o:: -o to name the object file
1063 * R:: -R to join data and text sections
1064 * statistics:: --statistics to see statistics about assembly
1065 * traditional-format:: --traditional-format for compatible output
1066 * v:: -v to announce version
1067 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1068 * Z:: -Z to make object file even after errors
1072 @section Enable Listings: @code{-a[cdhlns]}
1081 @cindex listings, enabling
1082 @cindex assembly listings, enabling
1084 These options enable listing output from the assembler. By itself,
1085 @samp{-a} requests high-level, assembly, and symbols listing.
1086 You can use other letters to select specific options for the list:
1087 @samp{-ah} requests a high-level language listing,
1088 @samp{-al} requests an output-program assembly listing, and
1089 @samp{-as} requests a symbol table listing.
1090 High-level listings require that a compiler debugging option like
1091 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1094 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1095 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1096 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1097 omitted from the listing.
1099 Use the @samp{-ad} option to omit debugging directives from the
1102 Once you have specified one of these options, you can further control
1103 listing output and its appearance using the directives @code{.list},
1104 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1106 The @samp{-an} option turns off all forms processing.
1107 If you do not request listing output with one of the @samp{-a} options, the
1108 listing-control directives have no effect.
1110 The letters after @samp{-a} may be combined into one option,
1111 @emph{e.g.}, @samp{-aln}.
1117 This option has no effect whatsoever, but it is accepted to make it more
1118 likely that scripts written for other assemblers also work with
1122 @section Work Faster: @code{-f}
1125 @cindex trusted compiler
1126 @cindex faster processing (@code{-f})
1127 @samp{-f} should only be used when assembling programs written by a
1128 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1129 and comment preprocessing on
1130 the input file(s) before assembling them. @xref{Preprocessing,
1134 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1135 preprocessed (if they contain comments, for example), @code{@value{AS}} does
1140 @section @code{.include} search path: @code{-I} @var{path}
1142 @kindex -I @var{path}
1143 @cindex paths for @code{.include}
1144 @cindex search path for @code{.include}
1145 @cindex @code{include} directive search path
1146 Use this option to add a @var{path} to the list of directories
1147 @code{@value{AS}} searches for files specified in @code{.include}
1148 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
1149 many times as necessary to include a variety of paths. The current
1150 working directory is always searched first; after that, @code{@value{AS}}
1151 searches any @samp{-I} directories in the same order as they were
1152 specified (left to right) on the command line.
1155 @section Difference Tables: @code{-K}
1158 @ifclear DIFF-TBL-KLUGE
1159 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1160 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1161 where it can be used to warn when the assembler alters the machine code
1162 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1163 family does not have the addressing limitations that sometimes lead to this
1164 alteration on other platforms.
1167 @ifset DIFF-TBL-KLUGE
1168 @cindex difference tables, warning
1169 @cindex warning for altered difference tables
1170 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1171 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1172 You can use the @samp{-K} option if you want a warning issued when this
1177 @section Include Local Labels: @code{-L}
1180 @cindex local labels, retaining in output
1181 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1182 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1183 debugging, because they are intended for the use of programs (like
1184 compilers) that compose assembler programs, not for your notice.
1185 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1186 normally debug with them.
1188 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1189 in the object file. Usually if you do this you also tell the linker
1190 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1192 By default, a local label is any label beginning with @samp{L}, but each
1193 target is allowed to redefine the local label prefix.
1195 On the HPPA local labels begin with @samp{L$}.
1198 @samp{;} for the ARM family;
1202 @section Assemble in MRI Compatibility Mode: @code{-M}
1205 @cindex MRI compatibility mode
1206 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1207 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1208 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1209 configured target) assembler from Microtec Research. The exact nature of the
1210 MRI syntax will not be documented here; see the MRI manuals for more
1211 information. Note in particular that the handling of macros and macro
1212 arguments is somewhat different. The purpose of this option is to permit
1213 assembling existing MRI assembler code using @code{@value{AS}}.
1215 The MRI compatibility is not complete. Certain operations of the MRI assembler
1216 depend upon its object file format, and can not be supported using other object
1217 file formats. Supporting these would require enhancing each object file format
1218 individually. These are:
1221 @item global symbols in common section
1223 The m68k MRI assembler supports common sections which are merged by the linker.
1224 Other object file formats do not support this. @code{@value{AS}} handles
1225 common sections by treating them as a single common symbol. It permits local
1226 symbols to be defined within a common section, but it can not support global
1227 symbols, since it has no way to describe them.
1229 @item complex relocations
1231 The MRI assemblers support relocations against a negated section address, and
1232 relocations which combine the start addresses of two or more sections. These
1233 are not support by other object file formats.
1235 @item @code{END} pseudo-op specifying start address
1237 The MRI @code{END} pseudo-op permits the specification of a start address.
1238 This is not supported by other object file formats. The start address may
1239 instead be specified using the @code{-e} option to the linker, or in a linker
1242 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1244 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1245 name to the output file. This is not supported by other object file formats.
1247 @item @code{ORG} pseudo-op
1249 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1250 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1251 which changes the location within the current section. Absolute sections are
1252 not supported by other object file formats. The address of a section may be
1253 assigned within a linker script.
1256 There are some other features of the MRI assembler which are not supported by
1257 @code{@value{AS}}, typically either because they are difficult or because they
1258 seem of little consequence. Some of these may be supported in future releases.
1262 @item EBCDIC strings
1264 EBCDIC strings are not supported.
1266 @item packed binary coded decimal
1268 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1269 and @code{DCB.P} pseudo-ops are not supported.
1271 @item @code{FEQU} pseudo-op
1273 The m68k @code{FEQU} pseudo-op is not supported.
1275 @item @code{NOOBJ} pseudo-op
1277 The m68k @code{NOOBJ} pseudo-op is not supported.
1279 @item @code{OPT} branch control options
1281 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1282 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1283 relaxes all branches, whether forward or backward, to an appropriate size, so
1284 these options serve no purpose.
1286 @item @code{OPT} list control options
1288 The following m68k @code{OPT} list control options are ignored: @code{C},
1289 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1290 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1292 @item other @code{OPT} options
1294 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1295 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1297 @item @code{OPT} @code{D} option is default
1299 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1300 @code{OPT NOD} may be used to turn it off.
1302 @item @code{XREF} pseudo-op.
1304 The m68k @code{XREF} pseudo-op is ignored.
1306 @item @code{.debug} pseudo-op
1308 The i960 @code{.debug} pseudo-op is not supported.
1310 @item @code{.extended} pseudo-op
1312 The i960 @code{.extended} pseudo-op is not supported.
1314 @item @code{.list} pseudo-op.
1316 The various options of the i960 @code{.list} pseudo-op are not supported.
1318 @item @code{.optimize} pseudo-op
1320 The i960 @code{.optimize} pseudo-op is not supported.
1322 @item @code{.output} pseudo-op
1324 The i960 @code{.output} pseudo-op is not supported.
1326 @item @code{.setreal} pseudo-op
1328 The i960 @code{.setreal} pseudo-op is not supported.
1333 @section Dependency tracking: @code{--MD}
1336 @cindex dependency tracking
1339 @code{@value{AS}} can generate a dependency file for the file it creates. This
1340 file consists of a single rule suitable for @code{make} describing the
1341 dependencies of the main source file.
1343 The rule is written to the file named in its argument.
1345 This feature is used in the automatic updating of makefiles.
1348 @section Name the Object File: @code{-o}
1351 @cindex naming object file
1352 @cindex object file name
1353 There is always one object file output when you run @code{@value{AS}}. By
1354 default it has the name
1357 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1371 You use this option (which takes exactly one filename) to give the
1372 object file a different name.
1374 Whatever the object file is called, @code{@value{AS}} overwrites any
1375 existing file of the same name.
1378 @section Join Data and Text Sections: @code{-R}
1381 @cindex data and text sections, joining
1382 @cindex text and data sections, joining
1383 @cindex joining text and data sections
1384 @cindex merging text and data sections
1385 @code{-R} tells @code{@value{AS}} to write the object file as if all
1386 data-section data lives in the text section. This is only done at
1387 the very last moment: your binary data are the same, but data
1388 section parts are relocated differently. The data section part of
1389 your object file is zero bytes long because all its bytes are
1390 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1392 When you specify @code{-R} it would be possible to generate shorter
1393 address displacements (because we do not have to cross between text and
1394 data section). We refrain from doing this simply for compatibility with
1395 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1398 When @code{@value{AS}} is configured for COFF output,
1399 this option is only useful if you use sections named @samp{.text} and
1404 @code{-R} is not supported for any of the HPPA targets. Using
1405 @code{-R} generates a warning from @code{@value{AS}}.
1409 @section Display Assembly Statistics: @code{--statistics}
1411 @kindex --statistics
1412 @cindex statistics, about assembly
1413 @cindex time, total for assembly
1414 @cindex space used, maximum for assembly
1415 Use @samp{--statistics} to display two statistics about the resources used by
1416 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1417 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1420 @node traditional-format
1421 @section Compatible output: @code{--traditional-format}
1423 @kindex --traditional-format
1424 For some targets, the output of @code{@value{AS}} is different in some ways
1425 from the output of some existing assembler. This switch requests
1426 @code{@value{AS}} to use the traditional format instead.
1428 For example, it disables the exception frame optimizations which
1429 @code{@value{AS}} normally does by default on @code{@value{GCC}} output.
1432 @section Announce Version: @code{-v}
1436 @cindex assembler version
1437 @cindex version of assembler
1438 You can find out what version of as is running by including the
1439 option @samp{-v} (which you can also spell as @samp{-version}) on the
1443 @section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings}
1445 @code{@value{AS}} should never give a warning or error message when
1446 assembling compiler output. But programs written by people often
1447 cause @code{@value{AS}} to give a warning that a particular assumption was
1448 made. All such warnings are directed to the standard error file.
1451 @kindex @samp{--no-warn}
1452 @cindex suppressing warnings
1453 @cindex warnings, suppressing
1454 If you use the @code{-W} and @code{--no-warn} options, no warnings are issued.
1455 This only affects the warning messages: it does not change any particular of
1456 how @code{@value{AS}} assembles your file. Errors, which stop the assembly,
1459 @kindex @samp{--fatal-warnings}
1460 @cindex errors, caused by warnings
1461 @cindex warnings, causing error
1462 If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers
1463 files that generate warnings to be in error.
1465 @kindex @samp{--warn}
1466 @cindex warnings, switching on
1467 You can switch these options off again by specifying @code{--warn}, which
1468 causes warnings to be output as usual.
1471 @section Generate Object File in Spite of Errors: @code{-Z}
1472 @cindex object file, after errors
1473 @cindex errors, continuing after
1474 After an error message, @code{@value{AS}} normally produces no output. If for
1475 some reason you are interested in object file output even after
1476 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1477 option. If there are any errors, @code{@value{AS}} continues anyways, and
1478 writes an object file after a final warning message of the form @samp{@var{n}
1479 errors, @var{m} warnings, generating bad object file.}
1484 @cindex machine-independent syntax
1485 @cindex syntax, machine-independent
1486 This chapter describes the machine-independent syntax allowed in a
1487 source file. @code{@value{AS}} syntax is similar to what many other
1488 assemblers use; it is inspired by the BSD 4.2
1493 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1497 * Preprocessing:: Preprocessing
1498 * Whitespace:: Whitespace
1499 * Comments:: Comments
1500 * Symbol Intro:: Symbols
1501 * Statements:: Statements
1502 * Constants:: Constants
1506 @section Preprocessing
1508 @cindex preprocessing
1509 The @code{@value{AS}} internal preprocessor:
1511 @cindex whitespace, removed by preprocessor
1513 adjusts and removes extra whitespace. It leaves one space or tab before
1514 the keywords on a line, and turns any other whitespace on the line into
1517 @cindex comments, removed by preprocessor
1519 removes all comments, replacing them with a single space, or an
1520 appropriate number of newlines.
1522 @cindex constants, converted by preprocessor
1524 converts character constants into the appropriate numeric values.
1527 It does not do macro processing, include file handling, or
1528 anything else you may get from your C compiler's preprocessor. You can
1529 do include file processing with the @code{.include} directive
1530 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1531 to get other ``CPP'' style preprocessing, by giving the input file a
1532 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1533 Output, gcc.info, Using GNU CC}.
1535 Excess whitespace, comments, and character constants
1536 cannot be used in the portions of the input text that are not
1539 @cindex turning preprocessing on and off
1540 @cindex preprocessing, turning on and off
1543 If the first line of an input file is @code{#NO_APP} or if you use the
1544 @samp{-f} option, whitespace and comments are not removed from the input file.
1545 Within an input file, you can ask for whitespace and comment removal in
1546 specific portions of the by putting a line that says @code{#APP} before the
1547 text that may contain whitespace or comments, and putting a line that says
1548 @code{#NO_APP} after this text. This feature is mainly intend to support
1549 @code{asm} statements in compilers whose output is otherwise free of comments
1556 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1557 Whitespace is used to separate symbols, and to make programs neater for
1558 people to read. Unless within character constants
1559 (@pxref{Characters,,Character Constants}), any whitespace means the same
1560 as exactly one space.
1566 There are two ways of rendering comments to @code{@value{AS}}. In both
1567 cases the comment is equivalent to one space.
1569 Anything from @samp{/*} through the next @samp{*/} is a comment.
1570 This means you may not nest these comments.
1574 The only way to include a newline ('\n') in a comment
1575 is to use this sort of comment.
1578 /* This sort of comment does not nest. */
1581 @cindex line comment character
1582 Anything from the @dfn{line comment} character to the next newline
1583 is considered a comment and is ignored. The line comment character is
1585 @samp{;} for the AMD 29K family;
1588 @samp{;} on the ARC;
1591 @samp{@@} on the ARM;
1594 @samp{;} for the H8/300 family;
1597 @samp{!} for the H8/500 family;
1600 @samp{;} for the HPPA;
1603 @samp{#} on the i960;
1606 @samp{;} for picoJava;
1609 @samp{!} for the Hitachi SH;
1612 @samp{!} on the SPARC;
1615 @samp{#} on the m32r;
1618 @samp{|} on the 680x0;
1621 @samp{#} on the Vax;
1624 @samp{!} for the Z8000;
1627 @samp{#} on the V850;
1629 see @ref{Machine Dependencies}. @refill
1630 @c FIXME What about i386, m88k, i860?
1633 On some machines there are two different line comment characters. One
1634 character only begins a comment if it is the first non-whitespace character on
1635 a line, while the other always begins a comment.
1639 The V850 assembler also supports a double dash as starting a comment that
1640 extends to the end of the line.
1646 @cindex lines starting with @code{#}
1647 @cindex logical line numbers
1648 To be compatible with past assemblers, lines that begin with @samp{#} have a
1649 special interpretation. Following the @samp{#} should be an absolute
1650 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1651 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1652 new logical file name. The rest of the line, if any, should be whitespace.
1654 If the first non-whitespace characters on the line are not numeric,
1655 the line is ignored. (Just like a comment.)
1658 # This is an ordinary comment.
1659 # 42-6 "new_file_name" # New logical file name
1660 # This is logical line # 36.
1662 This feature is deprecated, and may disappear from future versions
1663 of @code{@value{AS}}.
1668 @cindex characters used in symbols
1669 @ifclear SPECIAL-SYMS
1670 A @dfn{symbol} is one or more characters chosen from the set of all
1671 letters (both upper and lower case), digits and the three characters
1677 A @dfn{symbol} is one or more characters chosen from the set of all
1678 letters (both upper and lower case), digits and the three characters
1679 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1685 On most machines, you can also use @code{$} in symbol names; exceptions
1686 are noted in @ref{Machine Dependencies}.
1688 No symbol may begin with a digit. Case is significant.
1689 There is no length limit: all characters are significant. Symbols are
1690 delimited by characters not in that set, or by the beginning of a file
1691 (since the source program must end with a newline, the end of a file is
1692 not a possible symbol delimiter). @xref{Symbols}.
1693 @cindex length of symbols
1698 @cindex statements, structure of
1699 @cindex line separator character
1700 @cindex statement separator character
1702 @ifclear abnormal-separator
1703 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1704 semicolon (@samp{;}). The newline or semicolon is considered part of
1705 the preceding statement. Newlines and semicolons within character
1706 constants are an exception: they do not end statements.
1708 @ifset abnormal-separator
1710 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1711 sign (@samp{@@}). The newline or at sign is considered part of the
1712 preceding statement. Newlines and at signs within character constants
1713 are an exception: they do not end statements.
1716 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1717 point (@samp{!}). The newline or exclamation point is considered part of the
1718 preceding statement. Newlines and exclamation points within character
1719 constants are an exception: they do not end statements.
1722 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1723 H8/300) a dollar sign (@samp{$}); or (for the
1726 (@samp{;}). The newline or separator character is considered part of
1727 the preceding statement. Newlines and separators within character
1728 constants are an exception: they do not end statements.
1733 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1734 separator character. (The line separator is usually @samp{;}, unless
1735 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1736 newline or separator character is considered part of the preceding
1737 statement. Newlines and separators within character constants are an
1738 exception: they do not end statements.
1741 @cindex newline, required at file end
1742 @cindex EOF, newline must precede
1743 It is an error to end any statement with end-of-file: the last
1744 character of any input file should be a newline.@refill
1746 An empty statement is allowed, and may include whitespace. It is ignored.
1748 @cindex instructions and directives
1749 @cindex directives and instructions
1750 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1751 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1753 A statement begins with zero or more labels, optionally followed by a
1754 key symbol which determines what kind of statement it is. The key
1755 symbol determines the syntax of the rest of the statement. If the
1756 symbol begins with a dot @samp{.} then the statement is an assembler
1757 directive: typically valid for any computer. If the symbol begins with
1758 a letter the statement is an assembly language @dfn{instruction}: it
1759 assembles into a machine language instruction.
1761 Different versions of @code{@value{AS}} for different computers
1762 recognize different instructions. In fact, the same symbol may
1763 represent a different instruction in a different computer's assembly
1767 @cindex @code{:} (label)
1768 @cindex label (@code{:})
1769 A label is a symbol immediately followed by a colon (@code{:}).
1770 Whitespace before a label or after a colon is permitted, but you may not
1771 have whitespace between a label's symbol and its colon. @xref{Labels}.
1774 For HPPA targets, labels need not be immediately followed by a colon, but
1775 the definition of a label must begin in column zero. This also implies that
1776 only one label may be defined on each line.
1780 label: .directive followed by something
1781 another_label: # This is an empty statement.
1782 instruction operand_1, operand_2, @dots{}
1789 A constant is a number, written so that its value is known by
1790 inspection, without knowing any context. Like this:
1793 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1794 .ascii "Ring the bell\7" # A string constant.
1795 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1796 .float 0f-314159265358979323846264338327\
1797 95028841971.693993751E-40 # - pi, a flonum.
1802 * Characters:: Character Constants
1803 * Numbers:: Number Constants
1807 @subsection Character Constants
1809 @cindex character constants
1810 @cindex constants, character
1811 There are two kinds of character constants. A @dfn{character} stands
1812 for one character in one byte and its value may be used in
1813 numeric expressions. String constants (properly called string
1814 @emph{literals}) are potentially many bytes and their values may not be
1815 used in arithmetic expressions.
1819 * Chars:: Characters
1823 @subsubsection Strings
1825 @cindex string constants
1826 @cindex constants, string
1827 A @dfn{string} is written between double-quotes. It may contain
1828 double-quotes or null characters. The way to get special characters
1829 into a string is to @dfn{escape} these characters: precede them with
1830 a backslash @samp{\} character. For example @samp{\\} represents
1831 one backslash: the first @code{\} is an escape which tells
1832 @code{@value{AS}} to interpret the second character literally as a backslash
1833 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1834 escape character). The complete list of escapes follows.
1836 @cindex escape codes, character
1837 @cindex character escape codes
1840 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1842 @cindex @code{\b} (backspace character)
1843 @cindex backspace (@code{\b})
1845 Mnemonic for backspace; for ASCII this is octal code 010.
1848 @c Mnemonic for EOText; for ASCII this is octal code 004.
1850 @cindex @code{\f} (formfeed character)
1851 @cindex formfeed (@code{\f})
1853 Mnemonic for FormFeed; for ASCII this is octal code 014.
1855 @cindex @code{\n} (newline character)
1856 @cindex newline (@code{\n})
1858 Mnemonic for newline; for ASCII this is octal code 012.
1861 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1863 @cindex @code{\r} (carriage return character)
1864 @cindex carriage return (@code{\r})
1866 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1869 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1870 @c other assemblers.
1872 @cindex @code{\t} (tab)
1873 @cindex tab (@code{\t})
1875 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1878 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1879 @c @item \x @var{digit} @var{digit} @var{digit}
1880 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1882 @cindex @code{\@var{ddd}} (octal character code)
1883 @cindex octal character code (@code{\@var{ddd}})
1884 @item \ @var{digit} @var{digit} @var{digit}
1885 An octal character code. The numeric code is 3 octal digits.
1886 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1887 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1889 @cindex @code{\@var{xd...}} (hex character code)
1890 @cindex hex character code (@code{\@var{xd...}})
1891 @item \@code{x} @var{hex-digits...}
1892 A hex character code. All trailing hex digits are combined. Either upper or
1893 lower case @code{x} works.
1895 @cindex @code{\\} (@samp{\} character)
1896 @cindex backslash (@code{\\})
1898 Represents one @samp{\} character.
1901 @c Represents one @samp{'} (accent acute) character.
1902 @c This is needed in single character literals
1903 @c (@xref{Characters,,Character Constants}.) to represent
1906 @cindex @code{\"} (doublequote character)
1907 @cindex doublequote (@code{\"})
1909 Represents one @samp{"} character. Needed in strings to represent
1910 this character, because an unescaped @samp{"} would end the string.
1912 @item \ @var{anything-else}
1913 Any other character when escaped by @kbd{\} gives a warning, but
1914 assembles as if the @samp{\} was not present. The idea is that if
1915 you used an escape sequence you clearly didn't want the literal
1916 interpretation of the following character. However @code{@value{AS}} has no
1917 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1918 code and warns you of the fact.
1921 Which characters are escapable, and what those escapes represent,
1922 varies widely among assemblers. The current set is what we think
1923 the BSD 4.2 assembler recognizes, and is a subset of what most C
1924 compilers recognize. If you are in doubt, do not use an escape
1928 @subsubsection Characters
1930 @cindex single character constant
1931 @cindex character, single
1932 @cindex constant, single character
1933 A single character may be written as a single quote immediately
1934 followed by that character. The same escapes apply to characters as
1935 to strings. So if you want to write the character backslash, you
1936 must write @kbd{'\\} where the first @code{\} escapes the second
1937 @code{\}. As you can see, the quote is an acute accent, not a
1938 grave accent. A newline
1940 @ifclear abnormal-separator
1941 (or semicolon @samp{;})
1943 @ifset abnormal-separator
1945 (or at sign @samp{@@})
1948 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1954 immediately following an acute accent is taken as a literal character
1955 and does not count as the end of a statement. The value of a character
1956 constant in a numeric expression is the machine's byte-wide code for
1957 that character. @code{@value{AS}} assumes your character code is ASCII:
1958 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
1961 @subsection Number Constants
1963 @cindex constants, number
1964 @cindex number constants
1965 @code{@value{AS}} distinguishes three kinds of numbers according to how they
1966 are stored in the target machine. @emph{Integers} are numbers that
1967 would fit into an @code{int} in the C language. @emph{Bignums} are
1968 integers, but they are stored in more than 32 bits. @emph{Flonums}
1969 are floating point numbers, described below.
1972 * Integers:: Integers
1977 * Bit Fields:: Bit Fields
1983 @subsubsection Integers
1985 @cindex constants, integer
1987 @cindex binary integers
1988 @cindex integers, binary
1989 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
1990 the binary digits @samp{01}.
1992 @cindex octal integers
1993 @cindex integers, octal
1994 An octal integer is @samp{0} followed by zero or more of the octal
1995 digits (@samp{01234567}).
1997 @cindex decimal integers
1998 @cindex integers, decimal
1999 A decimal integer starts with a non-zero digit followed by zero or
2000 more digits (@samp{0123456789}).
2002 @cindex hexadecimal integers
2003 @cindex integers, hexadecimal
2004 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2005 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2007 Integers have the usual values. To denote a negative integer, use
2008 the prefix operator @samp{-} discussed under expressions
2009 (@pxref{Prefix Ops,,Prefix Operators}).
2012 @subsubsection Bignums
2015 @cindex constants, bignum
2016 A @dfn{bignum} has the same syntax and semantics as an integer
2017 except that the number (or its negative) takes more than 32 bits to
2018 represent in binary. The distinction is made because in some places
2019 integers are permitted while bignums are not.
2022 @subsubsection Flonums
2024 @cindex floating point numbers
2025 @cindex constants, floating point
2027 @cindex precision, floating point
2028 A @dfn{flonum} represents a floating point number. The translation is
2029 indirect: a decimal floating point number from the text is converted by
2030 @code{@value{AS}} to a generic binary floating point number of more than
2031 sufficient precision. This generic floating point number is converted
2032 to a particular computer's floating point format (or formats) by a
2033 portion of @code{@value{AS}} specialized to that computer.
2035 A flonum is written by writing (in order)
2040 (@samp{0} is optional on the HPPA.)
2044 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
2046 @kbd{e} is recommended. Case is not important.
2048 @c FIXME: verify if flonum syntax really this vague for most cases
2049 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2050 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2053 On the H8/300, H8/500,
2055 and AMD 29K architectures, the letter must be
2056 one of the letters @samp{DFPRSX} (in upper or lower case).
2058 On the ARC, the letter must be one of the letters @samp{DFRS}
2059 (in upper or lower case).
2061 On the Intel 960 architecture, the letter must be
2062 one of the letters @samp{DFT} (in upper or lower case).
2064 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2068 One of the letters @samp{DFPRSX} (in upper or lower case).
2071 One of the letters @samp{DFRS} (in upper or lower case).
2074 One of the letters @samp{DFPRSX} (in upper or lower case).
2077 The letter @samp{E} (upper case only).
2080 One of the letters @samp{DFT} (in upper or lower case).
2085 An optional sign: either @samp{+} or @samp{-}.
2088 An optional @dfn{integer part}: zero or more decimal digits.
2091 An optional @dfn{fractional part}: @samp{.} followed by zero
2092 or more decimal digits.
2095 An optional exponent, consisting of:
2099 An @samp{E} or @samp{e}.
2100 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2101 @c principle this can perfectly well be different on different targets.
2103 Optional sign: either @samp{+} or @samp{-}.
2105 One or more decimal digits.
2110 At least one of the integer part or the fractional part must be
2111 present. The floating point number has the usual base-10 value.
2113 @code{@value{AS}} does all processing using integers. Flonums are computed
2114 independently of any floating point hardware in the computer running
2119 @c Bit fields are written as a general facility but are also controlled
2120 @c by a conditional-compilation flag---which is as of now (21mar91)
2121 @c turned on only by the i960 config of GAS.
2123 @subsubsection Bit Fields
2126 @cindex constants, bit field
2127 You can also define numeric constants as @dfn{bit fields}.
2128 specify two numbers separated by a colon---
2130 @var{mask}:@var{value}
2133 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2136 The resulting number is then packed
2138 @c this conditional paren in case bit fields turned on elsewhere than 960
2139 (in host-dependent byte order)
2141 into a field whose width depends on which assembler directive has the
2142 bit-field as its argument. Overflow (a result from the bitwise and
2143 requiring more binary digits to represent) is not an error; instead,
2144 more constants are generated, of the specified width, beginning with the
2145 least significant digits.@refill
2147 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2148 @code{.short}, and @code{.word} accept bit-field arguments.
2153 @chapter Sections and Relocation
2158 * Secs Background:: Background
2159 * Ld Sections:: Linker Sections
2160 * As Sections:: Assembler Internal Sections
2161 * Sub-Sections:: Sub-Sections
2165 @node Secs Background
2168 Roughly, a section is a range of addresses, with no gaps; all data
2169 ``in'' those addresses is treated the same for some particular purpose.
2170 For example there may be a ``read only'' section.
2172 @cindex linker, and assembler
2173 @cindex assembler, and linker
2174 The linker @code{@value{LD}} reads many object files (partial programs) and
2175 combines their contents to form a runnable program. When @code{@value{AS}}
2176 emits an object file, the partial program is assumed to start at address 0.
2177 @code{@value{LD}} assigns the final addresses for the partial program, so that
2178 different partial programs do not overlap. This is actually an
2179 oversimplification, but it suffices to explain how @code{@value{AS}} uses
2182 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2183 addresses. These blocks slide to their run-time addresses as rigid
2184 units; their length does not change and neither does the order of bytes
2185 within them. Such a rigid unit is called a @emph{section}. Assigning
2186 run-time addresses to sections is called @dfn{relocation}. It includes
2187 the task of adjusting mentions of object-file addresses so they refer to
2188 the proper run-time addresses.
2190 For the H8/300 and H8/500,
2191 and for the Hitachi SH,
2192 @code{@value{AS}} pads sections if needed to
2193 ensure they end on a word (sixteen bit) boundary.
2196 @cindex standard assembler sections
2197 An object file written by @code{@value{AS}} has at least three sections, any
2198 of which may be empty. These are named @dfn{text}, @dfn{data} and
2203 When it generates COFF output,
2205 @code{@value{AS}} can also generate whatever other named sections you specify
2206 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2207 If you do not use any directives that place output in the @samp{.text}
2208 or @samp{.data} sections, these sections still exist, but are empty.
2213 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2215 @code{@value{AS}} can also generate whatever other named sections you
2216 specify using the @samp{.space} and @samp{.subspace} directives. See
2217 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2218 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2219 assembler directives.
2222 Additionally, @code{@value{AS}} uses different names for the standard
2223 text, data, and bss sections when generating SOM output. Program text
2224 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2225 BSS into @samp{$BSS$}.
2229 Within the object file, the text section starts at address @code{0}, the
2230 data section follows, and the bss section follows the data section.
2233 When generating either SOM or ELF output files on the HPPA, the text
2234 section starts at address @code{0}, the data section at address
2235 @code{0x4000000}, and the bss section follows the data section.
2238 To let @code{@value{LD}} know which data changes when the sections are
2239 relocated, and how to change that data, @code{@value{AS}} also writes to the
2240 object file details of the relocation needed. To perform relocation
2241 @code{@value{LD}} must know, each time an address in the object
2245 Where in the object file is the beginning of this reference to
2248 How long (in bytes) is this reference?
2250 Which section does the address refer to? What is the numeric value of
2252 (@var{address}) @minus{} (@var{start-address of section})?
2255 Is the reference to an address ``Program-Counter relative''?
2258 @cindex addresses, format of
2259 @cindex section-relative addressing
2260 In fact, every address @code{@value{AS}} ever uses is expressed as
2262 (@var{section}) + (@var{offset into section})
2265 Further, most expressions @code{@value{AS}} computes have this section-relative
2268 (For some object formats, such as SOM for the HPPA, some expressions are
2269 symbol-relative instead.)
2272 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2273 @var{N} into section @var{secname}.''
2275 Apart from text, data and bss sections you need to know about the
2276 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2277 addresses in the absolute section remain unchanged. For example, address
2278 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2279 @code{@value{LD}}. Although the linker never arranges two partial programs'
2280 data sections with overlapping addresses after linking, @emph{by definition}
2281 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2282 part of a program is always the same address when the program is running as
2283 address @code{@{absolute@ 239@}} in any other part of the program.
2285 The idea of sections is extended to the @dfn{undefined} section. Any
2286 address whose section is unknown at assembly time is by definition
2287 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2288 Since numbers are always defined, the only way to generate an undefined
2289 address is to mention an undefined symbol. A reference to a named
2290 common block would be such a symbol: its value is unknown at assembly
2291 time so it has section @emph{undefined}.
2293 By analogy the word @emph{section} is used to describe groups of sections in
2294 the linked program. @code{@value{LD}} puts all partial programs' text
2295 sections in contiguous addresses in the linked program. It is
2296 customary to refer to the @emph{text section} of a program, meaning all
2297 the addresses of all partial programs' text sections. Likewise for
2298 data and bss sections.
2300 Some sections are manipulated by @code{@value{LD}}; others are invented for
2301 use of @code{@value{AS}} and have no meaning except during assembly.
2304 @section Linker Sections
2305 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2310 @cindex named sections
2311 @cindex sections, named
2312 @item named sections
2315 @cindex text section
2316 @cindex data section
2320 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2321 separate but equal sections. Anything you can say of one section is
2324 When the program is running, however, it is
2325 customary for the text section to be unalterable. The
2326 text section is often shared among processes: it contains
2327 instructions, constants and the like. The data section of a running
2328 program is usually alterable: for example, C variables would be stored
2329 in the data section.
2334 This section contains zeroed bytes when your program begins running. It
2335 is used to hold unitialized variables or common storage. The length of
2336 each partial program's bss section is important, but because it starts
2337 out containing zeroed bytes there is no need to store explicit zero
2338 bytes in the object file. The bss section was invented to eliminate
2339 those explicit zeros from object files.
2341 @cindex absolute section
2342 @item absolute section
2343 Address 0 of this section is always ``relocated'' to runtime address 0.
2344 This is useful if you want to refer to an address that @code{@value{LD}} must
2345 not change when relocating. In this sense we speak of absolute
2346 addresses being ``unrelocatable'': they do not change during relocation.
2348 @cindex undefined section
2349 @item undefined section
2350 This ``section'' is a catch-all for address references to objects not in
2351 the preceding sections.
2352 @c FIXME: ref to some other doc on obj-file formats could go here.
2355 @cindex relocation example
2356 An idealized example of three relocatable sections follows.
2358 The example uses the traditional section names @samp{.text} and @samp{.data}.
2360 Memory addresses are on the horizontal axis.
2364 @c END TEXI2ROFF-KILL
2367 partial program # 1: |ttttt|dddd|00|
2374 partial program # 2: |TTT|DDD|000|
2377 +--+---+-----+--+----+---+-----+~~
2378 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2379 +--+---+-----+--+----+---+-----+~~
2381 addresses: 0 @dots{}
2388 \line{\it Partial program \#1: \hfil}
2389 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2390 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2392 \line{\it Partial program \#2: \hfil}
2393 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2394 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2396 \line{\it linked program: \hfil}
2397 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2398 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2399 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2400 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2402 \line{\it addresses: \hfil}
2406 @c END TEXI2ROFF-KILL
2409 @section Assembler Internal Sections
2411 @cindex internal assembler sections
2412 @cindex sections in messages, internal
2413 These sections are meant only for the internal use of @code{@value{AS}}. They
2414 have no meaning at run-time. You do not really need to know about these
2415 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2416 warning messages, so it might be helpful to have an idea of their
2417 meanings to @code{@value{AS}}. These sections are used to permit the
2418 value of every expression in your assembly language program to be a
2419 section-relative address.
2422 @cindex assembler internal logic error
2423 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2424 An internal assembler logic error has been found. This means there is a
2425 bug in the assembler.
2427 @cindex expr (internal section)
2429 The assembler stores complex expression internally as combinations of
2430 symbols. When it needs to represent an expression as a symbol, it puts
2431 it in the expr section.
2433 @c FIXME item transfer[t] vector preload
2434 @c FIXME item transfer[t] vector postload
2435 @c FIXME item register
2439 @section Sub-Sections
2441 @cindex numbered subsections
2442 @cindex grouping data
2448 fall into two sections: text and data.
2450 You may have separate groups of
2452 data in named sections
2456 data in named sections
2462 that you want to end up near to each other in the object file, even though they
2463 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2464 use @dfn{subsections} for this purpose. Within each section, there can be
2465 numbered subsections with values from 0 to 8192. Objects assembled into the
2466 same subsection go into the object file together with other objects in the same
2467 subsection. For example, a compiler might want to store constants in the text
2468 section, but might not want to have them interspersed with the program being
2469 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2470 section of code being output, and a @samp{.text 1} before each group of
2471 constants being output.
2473 Subsections are optional. If you do not use subsections, everything
2474 goes in subsection number zero.
2477 Each subsection is zero-padded up to a multiple of four bytes.
2478 (Subsections may be padded a different amount on different flavors
2479 of @code{@value{AS}}.)
2483 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2484 boundary (two bytes).
2485 The same is true on the Hitachi SH.
2488 @c FIXME section padding (alignment)?
2489 @c Rich Pixley says padding here depends on target obj code format; that
2490 @c doesn't seem particularly useful to say without further elaboration,
2491 @c so for now I say nothing about it. If this is a generic BFD issue,
2492 @c these paragraphs might need to vanish from this manual, and be
2493 @c discussed in BFD chapter of binutils (or some such).
2496 On the AMD 29K family, no particular padding is added to section or
2497 subsection sizes; @value{AS} forces no alignment on this platform.
2501 Subsections appear in your object file in numeric order, lowest numbered
2502 to highest. (All this to be compatible with other people's assemblers.)
2503 The object file contains no representation of subsections; @code{@value{LD}} and
2504 other programs that manipulate object files see no trace of them.
2505 They just see all your text subsections as a text section, and all your
2506 data subsections as a data section.
2508 To specify which subsection you want subsequent statements assembled
2509 into, use a numeric argument to specify it, in a @samp{.text
2510 @var{expression}} or a @samp{.data @var{expression}} statement.
2513 When generating COFF output, you
2518 can also use an extra subsection
2519 argument with arbitrary named sections: @samp{.section @var{name},
2522 @var{Expression} should be an absolute expression.
2523 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2524 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2525 begins in @code{text 0}. For instance:
2527 .text 0 # The default subsection is text 0 anyway.
2528 .ascii "This lives in the first text subsection. *"
2530 .ascii "But this lives in the second text subsection."
2532 .ascii "This lives in the data section,"
2533 .ascii "in the first data subsection."
2535 .ascii "This lives in the first text section,"
2536 .ascii "immediately following the asterisk (*)."
2539 Each section has a @dfn{location counter} incremented by one for every byte
2540 assembled into that section. Because subsections are merely a convenience
2541 restricted to @code{@value{AS}} there is no concept of a subsection location
2542 counter. There is no way to directly manipulate a location counter---but the
2543 @code{.align} directive changes it, and any label definition captures its
2544 current value. The location counter of the section where statements are being
2545 assembled is said to be the @dfn{active} location counter.
2548 @section bss Section
2551 @cindex common variable storage
2552 The bss section is used for local common variable storage.
2553 You may allocate address space in the bss section, but you may
2554 not dictate data to load into it before your program executes. When
2555 your program starts running, all the contents of the bss
2556 section are zeroed bytes.
2558 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2559 @ref{Lcomm,,@code{.lcomm}}.
2561 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2562 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2565 When assembling for a target which supports multiple sections, such as ELF or
2566 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2567 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2568 section. Typically the section will only contain symbol definitions and
2569 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2576 Symbols are a central concept: the programmer uses symbols to name
2577 things, the linker uses symbols to link, and the debugger uses symbols
2581 @cindex debuggers, and symbol order
2582 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2583 the same order they were declared. This may break some debuggers.
2588 * Setting Symbols:: Giving Symbols Other Values
2589 * Symbol Names:: Symbol Names
2590 * Dot:: The Special Dot Symbol
2591 * Symbol Attributes:: Symbol Attributes
2598 A @dfn{label} is written as a symbol immediately followed by a colon
2599 @samp{:}. The symbol then represents the current value of the
2600 active location counter, and is, for example, a suitable instruction
2601 operand. You are warned if you use the same symbol to represent two
2602 different locations: the first definition overrides any other
2606 On the HPPA, the usual form for a label need not be immediately followed by a
2607 colon, but instead must start in column zero. Only one label may be defined on
2608 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2609 provides a special directive @code{.label} for defining labels more flexibly.
2612 @node Setting Symbols
2613 @section Giving Symbols Other Values
2615 @cindex assigning values to symbols
2616 @cindex symbol values, assigning
2617 A symbol can be given an arbitrary value by writing a symbol, followed
2618 by an equals sign @samp{=}, followed by an expression
2619 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2620 directive. @xref{Set,,@code{.set}}.
2623 @section Symbol Names
2625 @cindex symbol names
2626 @cindex names, symbol
2627 @ifclear SPECIAL-SYMS
2628 Symbol names begin with a letter or with one of @samp{._}. On most
2629 machines, you can also use @code{$} in symbol names; exceptions are
2630 noted in @ref{Machine Dependencies}. That character may be followed by any
2631 string of digits, letters, dollar signs (unless otherwise noted in
2632 @ref{Machine Dependencies}), and underscores.
2635 For the AMD 29K family, @samp{?} is also allowed in the
2636 body of a symbol name, though not at its beginning.
2641 Symbol names begin with a letter or with one of @samp{._}. On the
2643 H8/500, you can also use @code{$} in symbol names. That character may
2644 be followed by any string of digits, letters, dollar signs (save on the
2645 H8/300), and underscores.
2649 Case of letters is significant: @code{foo} is a different symbol name
2652 Each symbol has exactly one name. Each name in an assembly language program
2653 refers to exactly one symbol. You may use that symbol name any number of times
2656 @subheading Local Symbol Names
2658 @cindex local symbol names
2659 @cindex symbol names, local
2660 @cindex temporary symbol names
2661 @cindex symbol names, temporary
2662 Local symbols help compilers and programmers use names temporarily.
2663 There are ten local symbol names, which are re-used throughout the
2664 program. You may refer to them using the names @samp{0} @samp{1}
2665 @dots{} @samp{9}. To define a local symbol, write a label of the form
2666 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2667 recent previous definition of that symbol write @samp{@b{N}b}, using the
2668 same digit as when you defined the label. To refer to the next
2669 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2670 a choice of 10 forward references. The @samp{b} stands for
2671 ``backwards'' and the @samp{f} stands for ``forwards''.
2673 Local symbols are not emitted by the current @sc{gnu} C compiler.
2675 There is no restriction on how you can use these labels, but
2676 remember that at any point in the assembly you can refer to at most
2677 10 prior local labels and to at most 10 forward local labels.
2679 Local symbol names are only a notation device. They are immediately
2680 transformed into more conventional symbol names before the assembler
2681 uses them. The symbol names stored in the symbol table, appearing in
2682 error messages and optionally emitted to the object file have these
2687 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2688 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2689 used for symbols you are never intended to see. If you use the
2690 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2691 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2692 you may use them in debugging.
2695 If the label is written @samp{0:} then the digit is @samp{0}.
2696 If the label is written @samp{1:} then the digit is @samp{1}.
2697 And so on up through @samp{9:}.
2700 This unusual character is included so you do not accidentally invent
2701 a symbol of the same name. The character has ASCII value
2704 @item @emph{ordinal number}
2705 This is a serial number to keep the labels distinct. The first
2706 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2707 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2711 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2712 @code{3:} is named @code{L3@kbd{C-A}44}.
2715 @section The Special Dot Symbol
2717 @cindex dot (symbol)
2718 @cindex @code{.} (symbol)
2719 @cindex current address
2720 @cindex location counter
2721 The special symbol @samp{.} refers to the current address that
2722 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2723 .long .} defines @code{melvin} to contain its own address.
2724 Assigning a value to @code{.} is treated the same as a @code{.org}
2725 directive. Thus, the expression @samp{.=.+4} is the same as saying
2726 @ifclear no-space-dir
2735 @node Symbol Attributes
2736 @section Symbol Attributes
2738 @cindex symbol attributes
2739 @cindex attributes, symbol
2740 Every symbol has, as well as its name, the attributes ``Value'' and
2741 ``Type''. Depending on output format, symbols can also have auxiliary
2744 The detailed definitions are in @file{a.out.h}.
2747 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2748 all these attributes, and probably won't warn you. This makes the
2749 symbol an externally defined symbol, which is generally what you
2753 * Symbol Value:: Value
2754 * Symbol Type:: Type
2757 * a.out Symbols:: Symbol Attributes: @code{a.out}
2761 * a.out Symbols:: Symbol Attributes: @code{a.out}
2764 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2769 * COFF Symbols:: Symbol Attributes for COFF
2772 * SOM Symbols:: Symbol Attributes for SOM
2779 @cindex value of a symbol
2780 @cindex symbol value
2781 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2782 location in the text, data, bss or absolute sections the value is the
2783 number of addresses from the start of that section to the label.
2784 Naturally for text, data and bss sections the value of a symbol changes
2785 as @code{@value{LD}} changes section base addresses during linking. Absolute
2786 symbols' values do not change during linking: that is why they are
2789 The value of an undefined symbol is treated in a special way. If it is
2790 0 then the symbol is not defined in this assembler source file, and
2791 @code{@value{LD}} tries to determine its value from other files linked into the
2792 same program. You make this kind of symbol simply by mentioning a symbol
2793 name without defining it. A non-zero value represents a @code{.comm}
2794 common declaration. The value is how much common storage to reserve, in
2795 bytes (addresses). The symbol refers to the first address of the
2801 @cindex type of a symbol
2803 The type attribute of a symbol contains relocation (section)
2804 information, any flag settings indicating that a symbol is external, and
2805 (optionally), other information for linkers and debuggers. The exact
2806 format depends on the object-code output format in use.
2811 @c The following avoids a "widow" subsection title. @group would be
2812 @c better if it were available outside examples.
2815 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2817 @cindex @code{b.out} symbol attributes
2818 @cindex symbol attributes, @code{b.out}
2819 These symbol attributes appear only when @code{@value{AS}} is configured for
2820 one of the Berkeley-descended object output formats---@code{a.out} or
2826 @subsection Symbol Attributes: @code{a.out}
2828 @cindex @code{a.out} symbol attributes
2829 @cindex symbol attributes, @code{a.out}
2835 @subsection Symbol Attributes: @code{a.out}
2837 @cindex @code{a.out} symbol attributes
2838 @cindex symbol attributes, @code{a.out}
2842 * Symbol Desc:: Descriptor
2843 * Symbol Other:: Other
2847 @subsubsection Descriptor
2849 @cindex descriptor, of @code{a.out} symbol
2850 This is an arbitrary 16-bit value. You may establish a symbol's
2851 descriptor value by using a @code{.desc} statement
2852 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2856 @subsubsection Other
2858 @cindex other attribute, of @code{a.out} symbol
2859 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2864 @subsection Symbol Attributes for COFF
2866 @cindex COFF symbol attributes
2867 @cindex symbol attributes, COFF
2869 The COFF format supports a multitude of auxiliary symbol attributes;
2870 like the primary symbol attributes, they are set between @code{.def} and
2871 @code{.endef} directives.
2873 @subsubsection Primary Attributes
2875 @cindex primary attributes, COFF symbols
2876 The symbol name is set with @code{.def}; the value and type,
2877 respectively, with @code{.val} and @code{.type}.
2879 @subsubsection Auxiliary Attributes
2881 @cindex auxiliary attributes, COFF symbols
2882 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2883 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2884 information for COFF.
2889 @subsection Symbol Attributes for SOM
2891 @cindex SOM symbol attributes
2892 @cindex symbol attributes, SOM
2894 The SOM format for the HPPA supports a multitude of symbol attributes set with
2895 the @code{.EXPORT} and @code{.IMPORT} directives.
2897 The attributes are described in @cite{HP9000 Series 800 Assembly
2898 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2899 @code{EXPORT} assembler directive documentation.
2903 @chapter Expressions
2907 @cindex numeric values
2908 An @dfn{expression} specifies an address or numeric value.
2909 Whitespace may precede and/or follow an expression.
2911 The result of an expression must be an absolute number, or else an offset into
2912 a particular section. If an expression is not absolute, and there is not
2913 enough information when @code{@value{AS}} sees the expression to know its
2914 section, a second pass over the source program might be necessary to interpret
2915 the expression---but the second pass is currently not implemented.
2916 @code{@value{AS}} aborts with an error message in this situation.
2919 * Empty Exprs:: Empty Expressions
2920 * Integer Exprs:: Integer Expressions
2924 @section Empty Expressions
2926 @cindex empty expressions
2927 @cindex expressions, empty
2928 An empty expression has no value: it is just whitespace or null.
2929 Wherever an absolute expression is required, you may omit the
2930 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2931 is compatible with other assemblers.
2934 @section Integer Expressions
2936 @cindex integer expressions
2937 @cindex expressions, integer
2938 An @dfn{integer expression} is one or more @emph{arguments} delimited
2939 by @emph{operators}.
2942 * Arguments:: Arguments
2943 * Operators:: Operators
2944 * Prefix Ops:: Prefix Operators
2945 * Infix Ops:: Infix Operators
2949 @subsection Arguments
2951 @cindex expression arguments
2952 @cindex arguments in expressions
2953 @cindex operands in expressions
2954 @cindex arithmetic operands
2955 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2956 contexts arguments are sometimes called ``arithmetic operands''. In
2957 this manual, to avoid confusing them with the ``instruction operands'' of
2958 the machine language, we use the term ``argument'' to refer to parts of
2959 expressions only, reserving the word ``operand'' to refer only to machine
2960 instruction operands.
2962 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
2963 @var{section} is one of text, data, bss, absolute,
2964 or undefined. @var{NNN} is a signed, 2's complement 32 bit
2967 Numbers are usually integers.
2969 A number can be a flonum or bignum. In this case, you are warned
2970 that only the low order 32 bits are used, and @code{@value{AS}} pretends
2971 these 32 bits are an integer. You may write integer-manipulating
2972 instructions that act on exotic constants, compatible with other
2975 @cindex subexpressions
2976 Subexpressions are a left parenthesis @samp{(} followed by an integer
2977 expression, followed by a right parenthesis @samp{)}; or a prefix
2978 operator followed by an argument.
2981 @subsection Operators
2983 @cindex operators, in expressions
2984 @cindex arithmetic functions
2985 @cindex functions, in expressions
2986 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
2987 operators are followed by an argument. Infix operators appear
2988 between their arguments. Operators may be preceded and/or followed by
2992 @subsection Prefix Operator
2994 @cindex prefix operators
2995 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
2996 one argument, which must be absolute.
2998 @c the tex/end tex stuff surrounding this small table is meant to make
2999 @c it align, on the printed page, with the similar table in the next
3000 @c section (which is inside an enumerate).
3002 \global\advance\leftskip by \itemindent
3007 @dfn{Negation}. Two's complement negation.
3009 @dfn{Complementation}. Bitwise not.
3013 \global\advance\leftskip by -\itemindent
3017 @subsection Infix Operators
3019 @cindex infix operators
3020 @cindex operators, permitted arguments
3021 @dfn{Infix operators} take two arguments, one on either side. Operators
3022 have precedence, but operations with equal precedence are performed left
3023 to right. Apart from @code{+} or @code{-}, both arguments must be
3024 absolute, and the result is absolute.
3027 @cindex operator precedence
3028 @cindex precedence of operators
3035 @dfn{Multiplication}.
3038 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3045 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3049 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3053 Intermediate precedence
3058 @dfn{Bitwise Inclusive Or}.
3064 @dfn{Bitwise Exclusive Or}.
3067 @dfn{Bitwise Or Not}.
3074 @cindex addition, permitted arguments
3075 @cindex plus, permitted arguments
3076 @cindex arguments for addition
3078 @dfn{Addition}. If either argument is absolute, the result has the section of
3079 the other argument. You may not add together arguments from different
3082 @cindex subtraction, permitted arguments
3083 @cindex minus, permitted arguments
3084 @cindex arguments for subtraction
3086 @dfn{Subtraction}. If the right argument is absolute, the
3087 result has the section of the left argument.
3088 If both arguments are in the same section, the result is absolute.
3089 You may not subtract arguments from different sections.
3090 @c FIXME is there still something useful to say about undefined - undefined ?
3094 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3095 address; you can only have a defined section in one of the two arguments.
3098 @chapter Assembler Directives
3100 @cindex directives, machine independent
3101 @cindex pseudo-ops, machine independent
3102 @cindex machine independent directives
3103 All assembler directives have names that begin with a period (@samp{.}).
3104 The rest of the name is letters, usually in lower case.
3106 This chapter discusses directives that are available regardless of the
3107 target machine configuration for the @sc{gnu} assembler.
3109 Some machine configurations provide additional directives.
3110 @xref{Machine Dependencies}.
3113 @ifset machine-directives
3114 @xref{Machine Dependencies} for additional directives.
3119 * Abort:: @code{.abort}
3121 * ABORT:: @code{.ABORT}
3124 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3125 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3126 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3127 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3128 * Byte:: @code{.byte @var{expressions}}
3129 * Comm:: @code{.comm @var{symbol} , @var{length} }
3130 * Data:: @code{.data @var{subsection}}
3132 * Def:: @code{.def @var{name}}
3135 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3141 * Double:: @code{.double @var{flonums}}
3142 * Eject:: @code{.eject}
3143 * Else:: @code{.else}
3144 * Elseif:: @code{.elseif}
3147 * Endef:: @code{.endef}
3150 * Endfunc:: @code{.endfunc}
3151 * Endif:: @code{.endif}
3152 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3153 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3155 * Exitm:: @code{.exitm}
3156 * Extern:: @code{.extern}
3157 * Fail:: @code{.fail}
3158 @ifclear no-file-dir
3159 * File:: @code{.file @var{string}}
3162 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3163 * Float:: @code{.float @var{flonums}}
3164 * Func:: @code{.func}
3165 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3166 * hword:: @code{.hword @var{expressions}}
3167 * Ident:: @code{.ident}
3168 * If:: @code{.if @var{absolute expression}}
3169 * Include:: @code{.include "@var{file}"}
3170 * Int:: @code{.int @var{expressions}}
3171 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3172 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3173 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3174 * Lflags:: @code{.lflags}
3175 @ifclear no-line-dir
3176 * Line:: @code{.line @var{line-number}}
3179 * Ln:: @code{.ln @var{line-number}}
3180 * Linkonce:: @code{.linkonce [@var{type}]}
3181 * List:: @code{.list}
3182 * Long:: @code{.long @var{expressions}}
3184 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3187 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3188 * MRI:: @code{.mri @var{val}}
3190 * Nolist:: @code{.nolist}
3191 * Octa:: @code{.octa @var{bignums}}
3192 * Org:: @code{.org @var{new-lc} , @var{fill}}
3193 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3194 * Print:: @code{.print @var{string}}
3195 * Psize:: @code{.psize @var{lines}, @var{columns}}
3196 * Purgem:: @code{.purgem @var{name}}
3197 * Quad:: @code{.quad @var{bignums}}
3198 * Rept:: @code{.rept @var{count}}
3199 * Sbttl:: @code{.sbttl "@var{subheading}"}
3201 * Scl:: @code{.scl @var{class}}
3202 * Section:: @code{.section @var{name}, @var{subsection}}
3205 * Set:: @code{.set @var{symbol}, @var{expression}}
3206 * Short:: @code{.short @var{expressions}}
3207 * Single:: @code{.single @var{flonums}}
3209 * Size:: @code{.size}
3212 * Skip:: @code{.skip @var{size} , @var{fill}}
3213 * Sleb128:: @code{.sleb128 @var{expressions}}
3214 * Space:: @code{.space @var{size} , @var{fill}}
3216 * Stab:: @code{.stabd, .stabn, .stabs}
3219 * String:: @code{.string "@var{str}"}
3220 * Struct:: @code{.struct @var{expression}}
3222 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3225 * Tag:: @code{.tag @var{structname}}
3228 * Text:: @code{.text @var{subsection}}
3229 * Title:: @code{.title "@var{heading}"}
3231 * Type:: @code{.type @var{int}}
3232 * Val:: @code{.val @var{addr}}
3235 * Visibility:: @code{.internal @var{name}, .hidden @var{name}, .protected @var{name}}
3238 * Uleb128:: @code{.uleb128 @var{expressions}}
3239 * Word:: @code{.word @var{expressions}}
3240 * Deprecated:: Deprecated Directives
3244 @section @code{.abort}
3246 @cindex @code{abort} directive
3247 @cindex stopping the assembly
3248 This directive stops the assembly immediately. It is for
3249 compatibility with other assemblers. The original idea was that the
3250 assembly language source would be piped into the assembler. If the sender
3251 of the source quit, it could use this directive tells @code{@value{AS}} to
3252 quit also. One day @code{.abort} will not be supported.
3256 @section @code{.ABORT}
3258 @cindex @code{ABORT} directive
3259 When producing COFF output, @code{@value{AS}} accepts this directive as a
3260 synonym for @samp{.abort}.
3263 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3269 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3271 @cindex padding the location counter
3272 @cindex @code{align} directive
3273 Pad the location counter (in the current subsection) to a particular storage
3274 boundary. The first expression (which must be absolute) is the alignment
3275 required, as described below.
3277 The second expression (also absolute) gives the fill value to be stored in the
3278 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3279 padding bytes are normally zero. However, on some systems, if the section is
3280 marked as containing code and the fill value is omitted, the space is filled
3281 with no-op instructions.
3283 The third expression is also absolute, and is also optional. If it is present,
3284 it is the maximum number of bytes that should be skipped by this alignment
3285 directive. If doing the alignment would require skipping more bytes than the
3286 specified maximum, then the alignment is not done at all. You can omit the
3287 fill value (the second argument) entirely by simply using two commas after the
3288 required alignment; this can be useful if you want the alignment to be filled
3289 with no-op instructions when appropriate.
3291 The way the required alignment is specified varies from system to system.
3292 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3294 the first expression is the
3295 alignment request in bytes. For example @samp{.align 8} advances
3296 the location counter until it is a multiple of 8. If the location counter
3297 is already a multiple of 8, no change is needed.
3299 For other systems, including the i386 using a.out format, and the arm and
3300 strongarm, it is the
3301 number of low-order zero bits the location counter must have after
3302 advancement. For example @samp{.align 3} advances the location
3303 counter until it a multiple of 8. If the location counter is already a
3304 multiple of 8, no change is needed.
3306 This inconsistency is due to the different behaviors of the various
3307 native assemblers for these systems which GAS must emulate.
3308 GAS also provides @code{.balign} and @code{.p2align} directives,
3309 described later, which have a consistent behavior across all
3310 architectures (but are specific to GAS).
3313 @section @code{.ascii "@var{string}"}@dots{}
3315 @cindex @code{ascii} directive
3316 @cindex string literals
3317 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3318 separated by commas. It assembles each string (with no automatic
3319 trailing zero byte) into consecutive addresses.
3322 @section @code{.asciz "@var{string}"}@dots{}
3324 @cindex @code{asciz} directive
3325 @cindex zero-terminated strings
3326 @cindex null-terminated strings
3327 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3328 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3331 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3333 @cindex padding the location counter given number of bytes
3334 @cindex @code{balign} directive
3335 Pad the location counter (in the current subsection) to a particular
3336 storage boundary. The first expression (which must be absolute) is the
3337 alignment request in bytes. For example @samp{.balign 8} advances
3338 the location counter until it is a multiple of 8. If the location counter
3339 is already a multiple of 8, no change is needed.
3341 The second expression (also absolute) gives the fill value to be stored in the
3342 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3343 padding bytes are normally zero. However, on some systems, if the section is
3344 marked as containing code and the fill value is omitted, the space is filled
3345 with no-op instructions.
3347 The third expression is also absolute, and is also optional. If it is present,
3348 it is the maximum number of bytes that should be skipped by this alignment
3349 directive. If doing the alignment would require skipping more bytes than the
3350 specified maximum, then the alignment is not done at all. You can omit the
3351 fill value (the second argument) entirely by simply using two commas after the
3352 required alignment; this can be useful if you want the alignment to be filled
3353 with no-op instructions when appropriate.
3355 @cindex @code{balignw} directive
3356 @cindex @code{balignl} directive
3357 The @code{.balignw} and @code{.balignl} directives are variants of the
3358 @code{.balign} directive. The @code{.balignw} directive treats the fill
3359 pattern as a two byte word value. The @code{.balignl} directives treats the
3360 fill pattern as a four byte longword value. For example, @code{.balignw
3361 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3362 filled in with the value 0x368d (the exact placement of the bytes depends upon
3363 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3367 @section @code{.byte @var{expressions}}
3369 @cindex @code{byte} directive
3370 @cindex integers, one byte
3371 @code{.byte} expects zero or more expressions, separated by commas.
3372 Each expression is assembled into the next byte.
3375 @section @code{.comm @var{symbol} , @var{length} }
3377 @cindex @code{comm} directive
3378 @cindex symbol, common
3379 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3380 common symbol in one object file may be merged with a defined or common symbol
3381 of the same name in another object file. If @code{@value{LD}} does not see a
3382 definition for the symbol--just one or more common symbols--then it will
3383 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3384 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3385 the same name, and they do not all have the same size, it will allocate space
3386 using the largest size.
3389 When using ELF, the @code{.comm} directive takes an optional third argument.
3390 This is the desired alignment of the symbol, specified as a byte boundary (for
3391 example, an alignment of 16 means that the least significant 4 bits of the
3392 address should be zero). The alignment must be an absolute expression, and it
3393 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3394 for the common symbol, it will use the alignment when placing the symbol. If
3395 no alignment is specified, @code{@value{AS}} will set the alignment to the
3396 largest power of two less than or equal to the size of the symbol, up to a
3401 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3402 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3406 @section @code{.data @var{subsection}}
3408 @cindex @code{data} directive
3409 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3410 end of the data subsection numbered @var{subsection} (which is an
3411 absolute expression). If @var{subsection} is omitted, it defaults
3416 @section @code{.def @var{name}}
3418 @cindex @code{def} directive
3419 @cindex COFF symbols, debugging
3420 @cindex debugging COFF symbols
3421 Begin defining debugging information for a symbol @var{name}; the
3422 definition extends until the @code{.endef} directive is encountered.
3425 This directive is only observed when @code{@value{AS}} is configured for COFF
3426 format output; when producing @code{b.out}, @samp{.def} is recognized,
3433 @section @code{.desc @var{symbol}, @var{abs-expression}}
3435 @cindex @code{desc} directive
3436 @cindex COFF symbol descriptor
3437 @cindex symbol descriptor, COFF
3438 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3439 to the low 16 bits of an absolute expression.
3442 The @samp{.desc} directive is not available when @code{@value{AS}} is
3443 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3444 object format. For the sake of compatibility, @code{@value{AS}} accepts
3445 it, but produces no output, when configured for COFF.
3451 @section @code{.dim}
3453 @cindex @code{dim} directive
3454 @cindex COFF auxiliary symbol information
3455 @cindex auxiliary symbol information, COFF
3456 This directive is generated by compilers to include auxiliary debugging
3457 information in the symbol table. It is only permitted inside
3458 @code{.def}/@code{.endef} pairs.
3461 @samp{.dim} is only meaningful when generating COFF format output; when
3462 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3468 @section @code{.double @var{flonums}}
3470 @cindex @code{double} directive
3471 @cindex floating point numbers (double)
3472 @code{.double} expects zero or more flonums, separated by commas. It
3473 assembles floating point numbers.
3475 The exact kind of floating point numbers emitted depends on how
3476 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3480 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3481 in @sc{ieee} format.
3486 @section @code{.eject}
3488 @cindex @code{eject} directive
3489 @cindex new page, in listings
3490 @cindex page, in listings
3491 @cindex listing control: new page
3492 Force a page break at this point, when generating assembly listings.
3495 @section @code{.else}
3497 @cindex @code{else} directive
3498 @code{.else} is part of the @code{@value{AS}} support for conditional
3499 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3500 of code to be assembled if the condition for the preceding @code{.if}
3504 @section @code{.elseif}
3506 @cindex @code{elseif} directive
3507 @code{.elseif} is part of the @code{@value{AS}} support for conditional
3508 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
3509 @code{.if} block that would otherwise fill the entire @code{.else} section.
3512 @section @code{.end}
3514 @cindex @code{end} directive
3515 @code{.end} marks the end of the assembly file. @code{@value{AS}} does not
3516 process anything in the file past the @code{.end} directive.
3520 @section @code{.endef}
3522 @cindex @code{endef} directive
3523 This directive flags the end of a symbol definition begun with
3527 @samp{.endef} is only meaningful when generating COFF format output; if
3528 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3529 directive but ignores it.
3534 @section @code{.endfunc}
3535 @cindex @code{endfunc} directive
3536 @code{.endfunc} marks the end of a function specified with @code{.func}.
3539 @section @code{.endif}
3541 @cindex @code{endif} directive
3542 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3543 it marks the end of a block of code that is only assembled
3544 conditionally. @xref{If,,@code{.if}}.
3547 @section @code{.equ @var{symbol}, @var{expression}}
3549 @cindex @code{equ} directive
3550 @cindex assigning values to symbols
3551 @cindex symbols, assigning values to
3552 This directive sets the value of @var{symbol} to @var{expression}.
3553 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3556 The syntax for @code{equ} on the HPPA is
3557 @samp{@var{symbol} .equ @var{expression}}.
3561 @section @code{.equiv @var{symbol}, @var{expression}}
3562 @cindex @code{equiv} directive
3563 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3564 the assembler will signal an error if @var{symbol} is already defined.
3566 Except for the contents of the error message, this is roughly equivalent to
3575 @section @code{.err}
3576 @cindex @code{err} directive
3577 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3578 message and, unless the @code{-Z} option was used, it will not generate an
3579 object file. This can be used to signal error an conditionally compiled code.
3582 @section @code{.exitm}
3583 Exit early from the current macro definition. @xref{Macro}.
3586 @section @code{.extern}
3588 @cindex @code{extern} directive
3589 @code{.extern} is accepted in the source program---for compatibility
3590 with other assemblers---but it is ignored. @code{@value{AS}} treats
3591 all undefined symbols as external.
3594 @section @code{.fail @var{expression}}
3596 @cindex @code{fail} directive
3597 Generates an error or a warning. If the value of the @var{expression} is 500
3598 or more, @code{@value{AS}} will print a warning message. If the value is less
3599 than 500, @code{@value{AS}} will print an error message. The message will
3600 include the value of @var{expression}. This can occasionally be useful inside
3601 complex nested macros or conditional assembly.
3603 @ifclear no-file-dir
3605 @section @code{.file @var{string}}
3607 @cindex @code{file} directive
3608 @cindex logical file name
3609 @cindex file name, logical
3610 @code{.file} tells @code{@value{AS}} that we are about to start a new logical
3611 file. @var{string} is the new file name. In general, the filename is
3612 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
3613 to specify an empty file name, you must give the quotes--@code{""}. This
3614 statement may go away in future: it is only recognized to be compatible with
3615 old @code{@value{AS}} programs.
3617 In some configurations of @code{@value{AS}}, @code{.file} has already been
3618 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3623 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3625 @cindex @code{fill} directive
3626 @cindex writing patterns in memory
3627 @cindex patterns, writing in memory
3628 @var{result}, @var{size} and @var{value} are absolute expressions.
3629 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3630 may be zero or more. @var{Size} may be zero or more, but if it is
3631 more than 8, then it is deemed to have the value 8, compatible with
3632 other people's assemblers. The contents of each @var{repeat} bytes
3633 is taken from an 8-byte number. The highest order 4 bytes are
3634 zero. The lowest order 4 bytes are @var{value} rendered in the
3635 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3636 Each @var{size} bytes in a repetition is taken from the lowest order
3637 @var{size} bytes of this number. Again, this bizarre behavior is
3638 compatible with other people's assemblers.
3640 @var{size} and @var{value} are optional.
3641 If the second comma and @var{value} are absent, @var{value} is
3642 assumed zero. If the first comma and following tokens are absent,
3643 @var{size} is assumed to be 1.
3646 @section @code{.float @var{flonums}}
3648 @cindex floating point numbers (single)
3649 @cindex @code{float} directive
3650 This directive assembles zero or more flonums, separated by commas. It
3651 has the same effect as @code{.single}.
3653 The exact kind of floating point numbers emitted depends on how
3654 @code{@value{AS}} is configured.
3655 @xref{Machine Dependencies}.
3659 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3660 in @sc{ieee} format.
3665 @section @code{.func @var{name}[,@var{label}]}
3666 @cindex @code{func} directive
3667 @code{.func} emits debugging information to denote function @var{name}, and
3668 is ignored unless the file is assembled with debugging enabled.
3669 Only @samp{--gstabs} is currently supported.
3670 @var{label} is the entry point of the function and if omitted @var{name}
3671 prepended with the @samp{leading char} is used.
3672 @samp{leading char} is usually @code{_} or nothing, depending on the target.
3673 All functions are currently defined to have @code{void} return type.
3674 The function must be terminated with @code{.endfunc}.
3677 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3679 @cindex @code{global} directive
3680 @cindex symbol, making visible to linker
3681 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3682 @var{symbol} in your partial program, its value is made available to
3683 other partial programs that are linked with it. Otherwise,
3684 @var{symbol} takes its attributes from a symbol of the same name
3685 from another file linked into the same program.
3687 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3688 compatibility with other assemblers.
3691 On the HPPA, @code{.global} is not always enough to make it accessible to other
3692 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3693 @xref{HPPA Directives,, HPPA Assembler Directives}.
3697 @section @code{.hword @var{expressions}}
3699 @cindex @code{hword} directive
3700 @cindex integers, 16-bit
3701 @cindex numbers, 16-bit
3702 @cindex sixteen bit integers
3703 This expects zero or more @var{expressions}, and emits
3704 a 16 bit number for each.
3707 This directive is a synonym for @samp{.short}; depending on the target
3708 architecture, it may also be a synonym for @samp{.word}.
3712 This directive is a synonym for @samp{.short}.
3715 This directive is a synonym for both @samp{.short} and @samp{.word}.
3720 @section @code{.ident}
3722 @cindex @code{ident} directive
3723 This directive is used by some assemblers to place tags in object files.
3724 @code{@value{AS}} simply accepts the directive for source-file
3725 compatibility with such assemblers, but does not actually emit anything
3729 @section @code{.if @var{absolute expression}}
3731 @cindex conditional assembly
3732 @cindex @code{if} directive
3733 @code{.if} marks the beginning of a section of code which is only
3734 considered part of the source program being assembled if the argument
3735 (which must be an @var{absolute expression}) is non-zero. The end of
3736 the conditional section of code must be marked by @code{.endif}
3737 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3738 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3739 If you have several conditions to check, @code{.elseif} may be used to avoid
3740 nesting blocks if/else within each subsequent @code{.else} block.
3742 The following variants of @code{.if} are also supported:
3744 @cindex @code{ifdef} directive
3745 @item .ifdef @var{symbol}
3746 Assembles the following section of code if the specified @var{symbol}
3749 @cindex @code{ifc} directive
3750 @item .ifc @var{string1},@var{string2}
3751 Assembles the following section of code if the two strings are the same. The
3752 strings may be optionally quoted with single quotes. If they are not quoted,
3753 the first string stops at the first comma, and the second string stops at the
3754 end of the line. Strings which contain whitespace should be quoted. The
3755 string comparison is case sensitive.
3757 @cindex @code{ifeq} directive
3758 @item .ifeq @var{absolute expression}
3759 Assembles the following section of code if the argument is zero.
3761 @cindex @code{ifeqs} directive
3762 @item .ifeqs @var{string1},@var{string2}
3763 Another form of @code{.ifc}. The strings must be quoted using double quotes.
3765 @cindex @code{ifge} directive
3766 @item .ifge @var{absolute expression}
3767 Assembles the following section of code if the argument is greater than or
3770 @cindex @code{ifgt} directive
3771 @item .ifgt @var{absolute expression}
3772 Assembles the following section of code if the argument is greater than zero.
3774 @cindex @code{ifle} directive
3775 @item .ifle @var{absolute expression}
3776 Assembles the following section of code if the argument is less than or equal
3779 @cindex @code{iflt} directive
3780 @item .iflt @var{absolute expression}
3781 Assembles the following section of code if the argument is less than zero.
3783 @cindex @code{ifnc} directive
3784 @item .ifnc @var{string1},@var{string2}.
3785 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
3786 following section of code if the two strings are not the same.
3788 @cindex @code{ifndef} directive
3789 @cindex @code{ifnotdef} directive
3790 @item .ifndef @var{symbol}
3791 @itemx .ifnotdef @var{symbol}
3792 Assembles the following section of code if the specified @var{symbol}
3793 has not been defined. Both spelling variants are equivalent.
3795 @cindex @code{ifne} directive
3796 @item .ifne @var{absolute expression}
3797 Assembles the following section of code if the argument is not equal to zero
3798 (in other words, this is equivalent to @code{.if}).
3800 @cindex @code{ifnes} directive
3801 @item .ifnes @var{string1},@var{string2}
3802 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
3803 following section of code if the two strings are not the same.
3807 @section @code{.include "@var{file}"}
3809 @cindex @code{include} directive
3810 @cindex supporting files, including
3811 @cindex files, including
3812 This directive provides a way to include supporting files at specified
3813 points in your source program. The code from @var{file} is assembled as
3814 if it followed the point of the @code{.include}; when the end of the
3815 included file is reached, assembly of the original file continues. You
3816 can control the search paths used with the @samp{-I} command-line option
3817 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3821 @section @code{.int @var{expressions}}
3823 @cindex @code{int} directive
3824 @cindex integers, 32-bit
3825 Expect zero or more @var{expressions}, of any section, separated by commas.
3826 For each expression, emit a number that, at run time, is the value of that
3827 expression. The byte order and bit size of the number depends on what kind
3828 of target the assembly is for.
3832 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3833 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3839 @section @code{.irp @var{symbol},@var{values}}@dots{}
3841 @cindex @code{irp} directive
3842 Evaluate a sequence of statements assigning different values to @var{symbol}.
3843 The sequence of statements starts at the @code{.irp} directive, and is
3844 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3845 set to @var{value}, and the sequence of statements is assembled. If no
3846 @var{value} is listed, the sequence of statements is assembled once, with
3847 @var{symbol} set to the null string. To refer to @var{symbol} within the
3848 sequence of statements, use @var{\symbol}.
3850 For example, assembling
3858 is equivalent to assembling
3867 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3869 @cindex @code{irpc} directive
3870 Evaluate a sequence of statements assigning different values to @var{symbol}.
3871 The sequence of statements starts at the @code{.irpc} directive, and is
3872 terminated by an @code{.endr} directive. For each character in @var{value},
3873 @var{symbol} is set to the character, and the sequence of statements is
3874 assembled. If no @var{value} is listed, the sequence of statements is
3875 assembled once, with @var{symbol} set to the null string. To refer to
3876 @var{symbol} within the sequence of statements, use @var{\symbol}.
3878 For example, assembling
3886 is equivalent to assembling
3895 @section @code{.lcomm @var{symbol} , @var{length}}
3897 @cindex @code{lcomm} directive
3898 @cindex local common symbols
3899 @cindex symbols, local common
3900 Reserve @var{length} (an absolute expression) bytes for a local common
3901 denoted by @var{symbol}. The section and value of @var{symbol} are
3902 those of the new local common. The addresses are allocated in the bss
3903 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3904 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3905 not visible to @code{@value{LD}}.
3908 Some targets permit a third argument to be used with @code{.lcomm}. This
3909 argument specifies the desired alignment of the symbol in the bss section.
3913 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3914 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3918 @section @code{.lflags}
3920 @cindex @code{lflags} directive (ignored)
3921 @code{@value{AS}} accepts this directive, for compatibility with other
3922 assemblers, but ignores it.
3924 @ifclear no-line-dir
3926 @section @code{.line @var{line-number}}
3928 @cindex @code{line} directive
3932 @section @code{.ln @var{line-number}}
3934 @cindex @code{ln} directive
3936 @cindex logical line number
3938 Change the logical line number. @var{line-number} must be an absolute
3939 expression. The next line has that logical line number. Therefore any other
3940 statements on the current line (after a statement separator character) are
3941 reported as on logical line number @var{line-number} @minus{} 1. One day
3942 @code{@value{AS}} will no longer support this directive: it is recognized only
3943 for compatibility with existing assembler programs.
3947 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3948 not available; use the synonym @code{.ln} in that context.
3953 @ifclear no-line-dir
3954 Even though this is a directive associated with the @code{a.out} or
3955 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3956 when producing COFF output, and treats @samp{.line} as though it
3957 were the COFF @samp{.ln} @emph{if} it is found outside a
3958 @code{.def}/@code{.endef} pair.
3960 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
3961 used by compilers to generate auxiliary symbol information for
3966 @section @code{.linkonce [@var{type}]}
3968 @cindex @code{linkonce} directive
3969 @cindex common sections
3970 Mark the current section so that the linker only includes a single copy of it.
3971 This may be used to include the same section in several different object files,
3972 but ensure that the linker will only include it once in the final output file.
3973 The @code{.linkonce} pseudo-op must be used for each instance of the section.
3974 Duplicate sections are detected based on the section name, so it should be
3977 This directive is only supported by a few object file formats; as of this
3978 writing, the only object file format which supports it is the Portable
3979 Executable format used on Windows NT.
3981 The @var{type} argument is optional. If specified, it must be one of the
3982 following strings. For example:
3986 Not all types may be supported on all object file formats.
3990 Silently discard duplicate sections. This is the default.
3993 Warn if there are duplicate sections, but still keep only one copy.
3996 Warn if any of the duplicates have different sizes.
3999 Warn if any of the duplicates do not have exactly the same contents.
4003 @section @code{.ln @var{line-number}}
4005 @cindex @code{ln} directive
4006 @ifclear no-line-dir
4007 @samp{.ln} is a synonym for @samp{.line}.
4010 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
4011 must be an absolute expression. The next line has that logical
4012 line number, so any other statements on the current line (after a
4013 statement separator character @code{;}) are reported as on logical
4014 line number @var{line-number} @minus{} 1.
4017 This directive is accepted, but ignored, when @code{@value{AS}} is
4018 configured for @code{b.out}; its effect is only associated with COFF
4024 @section @code{.mri @var{val}}
4026 @cindex @code{mri} directive
4027 @cindex MRI mode, temporarily
4028 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
4029 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
4030 affects code assembled until the next @code{.mri} directive, or until the end
4031 of the file. @xref{M, MRI mode, MRI mode}.
4034 @section @code{.list}
4036 @cindex @code{list} directive
4037 @cindex listing control, turning on
4038 Control (in conjunction with the @code{.nolist} directive) whether or
4039 not assembly listings are generated. These two directives maintain an
4040 internal counter (which is zero initially). @code{.list} increments the
4041 counter, and @code{.nolist} decrements it. Assembly listings are
4042 generated whenever the counter is greater than zero.
4044 By default, listings are disabled. When you enable them (with the
4045 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4046 the initial value of the listing counter is one.
4049 @section @code{.long @var{expressions}}
4051 @cindex @code{long} directive
4052 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4055 @c no one seems to know what this is for or whether this description is
4056 @c what it really ought to do
4058 @section @code{.lsym @var{symbol}, @var{expression}}
4060 @cindex @code{lsym} directive
4061 @cindex symbol, not referenced in assembly
4062 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4063 the hash table, ensuring it cannot be referenced by name during the
4064 rest of the assembly. This sets the attributes of the symbol to be
4065 the same as the expression value:
4067 @var{other} = @var{descriptor} = 0
4068 @var{type} = @r{(section of @var{expression})}
4069 @var{value} = @var{expression}
4072 The new symbol is not flagged as external.
4076 @section @code{.macro}
4079 The commands @code{.macro} and @code{.endm} allow you to define macros that
4080 generate assembly output. For example, this definition specifies a macro
4081 @code{sum} that puts a sequence of numbers into memory:
4084 .macro sum from=0, to=5
4093 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4105 @item .macro @var{macname}
4106 @itemx .macro @var{macname} @var{macargs} @dots{}
4107 @cindex @code{macro} directive
4108 Begin the definition of a macro called @var{macname}. If your macro
4109 definition requires arguments, specify their names after the macro name,
4110 separated by commas or spaces. You can supply a default value for any
4111 macro argument by following the name with @samp{=@var{deflt}}. For
4112 example, these are all valid @code{.macro} statements:
4116 Begin the definition of a macro called @code{comm}, which takes no
4119 @item .macro plus1 p, p1
4120 @itemx .macro plus1 p p1
4121 Either statement begins the definition of a macro called @code{plus1},
4122 which takes two arguments; within the macro definition, write
4123 @samp{\p} or @samp{\p1} to evaluate the arguments.
4125 @item .macro reserve_str p1=0 p2
4126 Begin the definition of a macro called @code{reserve_str}, with two
4127 arguments. The first argument has a default value, but not the second.
4128 After the definition is complete, you can call the macro either as
4129 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4130 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4131 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4132 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4135 When you call a macro, you can specify the argument values either by
4136 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4137 @samp{sum to=17, from=9}.
4140 @cindex @code{endm} directive
4141 Mark the end of a macro definition.
4144 @cindex @code{exitm} directive
4145 Exit early from the current macro definition.
4147 @cindex number of macros executed
4148 @cindex macros, count executed
4150 @code{@value{AS}} maintains a counter of how many macros it has
4151 executed in this pseudo-variable; you can copy that number to your
4152 output with @samp{\@@}, but @emph{only within a macro definition}.
4155 @item LOCAL @var{name} [ , @dots{} ]
4156 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4157 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4158 Alternate macro syntax}.
4160 Generate a string replacement for each of the @var{name} arguments, and
4161 replace any instances of @var{name} in each macro expansion. The
4162 replacement string is unique in the assembly, and different for each
4163 separate macro expansion. @code{LOCAL} allows you to write macros that
4164 define symbols, without fear of conflict between separate macro expansions.
4169 @section @code{.nolist}
4171 @cindex @code{nolist} directive
4172 @cindex listing control, turning off
4173 Control (in conjunction with the @code{.list} directive) whether or
4174 not assembly listings are generated. These two directives maintain an
4175 internal counter (which is zero initially). @code{.list} increments the
4176 counter, and @code{.nolist} decrements it. Assembly listings are
4177 generated whenever the counter is greater than zero.
4180 @section @code{.octa @var{bignums}}
4182 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4183 @cindex @code{octa} directive
4184 @cindex integer, 16-byte
4185 @cindex sixteen byte integer
4186 This directive expects zero or more bignums, separated by commas. For each
4187 bignum, it emits a 16-byte integer.
4189 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4190 hence @emph{octa}-word for 16 bytes.
4193 @section @code{.org @var{new-lc} , @var{fill}}
4195 @cindex @code{org} directive
4196 @cindex location counter, advancing
4197 @cindex advancing location counter
4198 @cindex current address, advancing
4199 Advance the location counter of the current section to
4200 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4201 expression with the same section as the current subsection. That is,
4202 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4203 wrong section, the @code{.org} directive is ignored. To be compatible
4204 with former assemblers, if the section of @var{new-lc} is absolute,
4205 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4206 is the same as the current subsection.
4208 @code{.org} may only increase the location counter, or leave it
4209 unchanged; you cannot use @code{.org} to move the location counter
4212 @c double negative used below "not undefined" because this is a specific
4213 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4214 @c section. doc@cygnus.com 18feb91
4215 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4216 may not be undefined. If you really detest this restriction we eagerly await
4217 a chance to share your improved assembler.
4219 Beware that the origin is relative to the start of the section, not
4220 to the start of the subsection. This is compatible with other
4221 people's assemblers.
4223 When the location counter (of the current subsection) is advanced, the
4224 intervening bytes are filled with @var{fill} which should be an
4225 absolute expression. If the comma and @var{fill} are omitted,
4226 @var{fill} defaults to zero.
4229 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4231 @cindex padding the location counter given a power of two
4232 @cindex @code{p2align} directive
4233 Pad the location counter (in the current subsection) to a particular
4234 storage boundary. The first expression (which must be absolute) is the
4235 number of low-order zero bits the location counter must have after
4236 advancement. For example @samp{.p2align 3} advances the location
4237 counter until it a multiple of 8. If the location counter is already a
4238 multiple of 8, no change is needed.
4240 The second expression (also absolute) gives the fill value to be stored in the
4241 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4242 padding bytes are normally zero. However, on some systems, if the section is
4243 marked as containing code and the fill value is omitted, the space is filled
4244 with no-op instructions.
4246 The third expression is also absolute, and is also optional. If it is present,
4247 it is the maximum number of bytes that should be skipped by this alignment
4248 directive. If doing the alignment would require skipping more bytes than the
4249 specified maximum, then the alignment is not done at all. You can omit the
4250 fill value (the second argument) entirely by simply using two commas after the
4251 required alignment; this can be useful if you want the alignment to be filled
4252 with no-op instructions when appropriate.
4254 @cindex @code{p2alignw} directive
4255 @cindex @code{p2alignl} directive
4256 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4257 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4258 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4259 fill pattern as a four byte longword value. For example, @code{.p2alignw
4260 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4261 filled in with the value 0x368d (the exact placement of the bytes depends upon
4262 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4266 @section @code{.print @var{string}}
4268 @cindex @code{print} directive
4269 @code{@value{AS}} will print @var{string} on the standard output during
4270 assembly. You must put @var{string} in double quotes.
4273 @section @code{.psize @var{lines} , @var{columns}}
4275 @cindex @code{psize} directive
4276 @cindex listing control: paper size
4277 @cindex paper size, for listings
4278 Use this directive to declare the number of lines---and, optionally, the
4279 number of columns---to use for each page, when generating listings.
4281 If you do not use @code{.psize}, listings use a default line-count
4282 of 60. You may omit the comma and @var{columns} specification; the
4283 default width is 200 columns.
4285 @code{@value{AS}} generates formfeeds whenever the specified number of
4286 lines is exceeded (or whenever you explicitly request one, using
4289 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4290 those explicitly specified with @code{.eject}.
4293 @section @code{.purgem @var{name}}
4295 @cindex @code{purgem} directive
4296 Undefine the macro @var{name}, so that later uses of the string will not be
4297 expanded. @xref{Macro}.
4300 @section @code{.quad @var{bignums}}
4302 @cindex @code{quad} directive
4303 @code{.quad} expects zero or more bignums, separated by commas. For
4304 each bignum, it emits
4306 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4307 warning message; and just takes the lowest order 8 bytes of the bignum.
4308 @cindex eight-byte integer
4309 @cindex integer, 8-byte
4311 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4312 hence @emph{quad}-word for 8 bytes.
4315 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4316 warning message; and just takes the lowest order 16 bytes of the bignum.
4317 @cindex sixteen-byte integer
4318 @cindex integer, 16-byte
4322 @section @code{.rept @var{count}}
4324 @cindex @code{rept} directive
4325 Repeat the sequence of lines between the @code{.rept} directive and the next
4326 @code{.endr} directive @var{count} times.
4328 For example, assembling
4336 is equivalent to assembling
4345 @section @code{.sbttl "@var{subheading}"}
4347 @cindex @code{sbttl} directive
4348 @cindex subtitles for listings
4349 @cindex listing control: subtitle
4350 Use @var{subheading} as the title (third line, immediately after the
4351 title line) when generating assembly listings.
4353 This directive affects subsequent pages, as well as the current page if
4354 it appears within ten lines of the top of a page.
4358 @section @code{.scl @var{class}}
4360 @cindex @code{scl} directive
4361 @cindex symbol storage class (COFF)
4362 @cindex COFF symbol storage class
4363 Set the storage-class value for a symbol. This directive may only be
4364 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4365 whether a symbol is static or external, or it may record further
4366 symbolic debugging information.
4369 The @samp{.scl} directive is primarily associated with COFF output; when
4370 configured to generate @code{b.out} output format, @code{@value{AS}}
4371 accepts this directive but ignores it.
4376 @section @code{.section @var{name}}
4378 @cindex @code{section} directive
4379 @cindex named section
4380 Use the @code{.section} directive to assemble the following code into a section
4383 This directive is only supported for targets that actually support arbitrarily
4384 named sections; on @code{a.out} targets, for example, it is not accepted, even
4385 with a standard @code{a.out} section name.
4388 For COFF targets, the @code{.section} directive is used in one of the following
4391 .section @var{name}[, "@var{flags}"]
4392 .section @var{name}[, @var{subsegment}]
4395 If the optional argument is quoted, it is taken as flags to use for the
4396 section. Each flag is a single character. The following flags are recognized:
4399 bss section (uninitialized data)
4401 section is not loaded
4411 shared section (meaningful for PE targets)
4414 If no flags are specified, the default flags depend upon the section name. If
4415 the section name is not recognized, the default will be for the section to be
4416 loaded and writable.
4418 If the optional argument to the @code{.section} directive is not quoted, it is
4419 taken as a subsegment number (@pxref{Sub-Sections}).
4423 For ELF targets, the @code{.section} directive is used like this:
4425 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4427 The optional @var{flags} argument is a quoted string which may contain any
4428 combintion of the following characters:
4431 section is allocatable
4435 section is executable
4438 The optional @var{type} argument may contain one of the following constants:
4441 section contains data
4443 section does not contain data (i.e., section only occupies space)
4446 If no flags are specified, the default flags depend upon the section name. If
4447 the section name is not recognized, the default will be for the section to have
4448 none of the above flags: it will not be allocated in memory, nor writable, nor
4449 executable. The section will contain data.
4451 For ELF targets, the assembler supports another type of @code{.section}
4452 directive for compatibility with the Solaris assembler:
4454 .section "@var{name}"[, @var{flags}...]
4456 Note that the section name is quoted. There may be a sequence of comma
4460 section is allocatable
4464 section is executable
4469 @section @code{.set @var{symbol}, @var{expression}}
4471 @cindex @code{set} directive
4472 @cindex symbol value, setting
4473 Set the value of @var{symbol} to @var{expression}. This
4474 changes @var{symbol}'s value and type to conform to
4475 @var{expression}. If @var{symbol} was flagged as external, it remains
4476 flagged (@pxref{Symbol Attributes}).
4478 You may @code{.set} a symbol many times in the same assembly.
4480 If you @code{.set} a global symbol, the value stored in the object
4481 file is the last value stored into it.
4484 The syntax for @code{set} on the HPPA is
4485 @samp{@var{symbol} .set @var{expression}}.
4489 @section @code{.short @var{expressions}}
4491 @cindex @code{short} directive
4493 @code{.short} is normally the same as @samp{.word}.
4494 @xref{Word,,@code{.word}}.
4496 In some configurations, however, @code{.short} and @code{.word} generate
4497 numbers of different lengths; @pxref{Machine Dependencies}.
4501 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4504 This expects zero or more @var{expressions}, and emits
4505 a 16 bit number for each.
4510 @section @code{.single @var{flonums}}
4512 @cindex @code{single} directive
4513 @cindex floating point numbers (single)
4514 This directive assembles zero or more flonums, separated by commas. It
4515 has the same effect as @code{.float}.
4517 The exact kind of floating point numbers emitted depends on how
4518 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4522 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4523 numbers in @sc{ieee} format.
4529 @section @code{.size}
4531 @cindex @code{size} directive
4532 This directive is generated by compilers to include auxiliary debugging
4533 information in the symbol table. It is only permitted inside
4534 @code{.def}/@code{.endef} pairs.
4537 @samp{.size} is only meaningful when generating COFF format output; when
4538 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4544 @section @code{.sleb128 @var{expressions}}
4546 @cindex @code{sleb128} directive
4547 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4548 compact, variable length representation of numbers used by the DWARF
4549 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
4551 @ifclear no-space-dir
4553 @section @code{.skip @var{size} , @var{fill}}
4555 @cindex @code{skip} directive
4556 @cindex filling memory
4557 This directive emits @var{size} bytes, each of value @var{fill}. Both
4558 @var{size} and @var{fill} are absolute expressions. If the comma and
4559 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4563 @section @code{.space @var{size} , @var{fill}}
4565 @cindex @code{space} directive
4566 @cindex filling memory
4567 This directive emits @var{size} bytes, each of value @var{fill}. Both
4568 @var{size} and @var{fill} are absolute expressions. If the comma
4569 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4574 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4575 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4576 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4577 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4586 @section @code{.space}
4587 @cindex @code{space} directive
4589 On the AMD 29K, this directive is ignored; it is accepted for
4590 compatibility with other AMD 29K assemblers.
4593 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4594 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4600 @section @code{.stabd, .stabn, .stabs}
4602 @cindex symbolic debuggers, information for
4603 @cindex @code{stab@var{x}} directives
4604 There are three directives that begin @samp{.stab}.
4605 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4606 The symbols are not entered in the @code{@value{AS}} hash table: they
4607 cannot be referenced elsewhere in the source file.
4608 Up to five fields are required:
4612 This is the symbol's name. It may contain any character except
4613 @samp{\000}, so is more general than ordinary symbol names. Some
4614 debuggers used to code arbitrarily complex structures into symbol names
4618 An absolute expression. The symbol's type is set to the low 8 bits of
4619 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4620 and debuggers choke on silly bit patterns.
4623 An absolute expression. The symbol's ``other'' attribute is set to the
4624 low 8 bits of this expression.
4627 An absolute expression. The symbol's descriptor is set to the low 16
4628 bits of this expression.
4631 An absolute expression which becomes the symbol's value.
4634 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4635 or @code{.stabs} statement, the symbol has probably already been created;
4636 you get a half-formed symbol in your object file. This is
4637 compatible with earlier assemblers!
4640 @cindex @code{stabd} directive
4641 @item .stabd @var{type} , @var{other} , @var{desc}
4643 The ``name'' of the symbol generated is not even an empty string.
4644 It is a null pointer, for compatibility. Older assemblers used a
4645 null pointer so they didn't waste space in object files with empty
4648 The symbol's value is set to the location counter,
4649 relocatably. When your program is linked, the value of this symbol
4650 is the address of the location counter when the @code{.stabd} was
4653 @cindex @code{stabn} directive
4654 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4655 The name of the symbol is set to the empty string @code{""}.
4657 @cindex @code{stabs} directive
4658 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4659 All five fields are specified.
4665 @section @code{.string} "@var{str}"
4667 @cindex string, copying to object file
4668 @cindex @code{string} directive
4670 Copy the characters in @var{str} to the object file. You may specify more than
4671 one string to copy, separated by commas. Unless otherwise specified for a
4672 particular machine, the assembler marks the end of each string with a 0 byte.
4673 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4676 @section @code{.struct @var{expression}}
4678 @cindex @code{struct} directive
4679 Switch to the absolute section, and set the section offset to @var{expression},
4680 which must be an absolute expression. You might use this as follows:
4689 This would define the symbol @code{field1} to have the value 0, the symbol
4690 @code{field2} to have the value 4, and the symbol @code{field3} to have the
4691 value 8. Assembly would be left in the absolute section, and you would need to
4692 use a @code{.section} directive of some sort to change to some other section
4693 before further assembly.
4697 @section @code{.symver}
4698 @cindex @code{symver} directive
4699 @cindex symbol versioning
4700 @cindex versions of symbols
4701 Use the @code{.symver} directive to bind symbols to specific version nodes
4702 within a source file. This is only supported on ELF platforms, and is
4703 typically used when assembling files to be linked into a shared library.
4704 There are cases where it may make sense to use this in objects to be bound
4705 into an application itself so as to override a versioned symbol from a
4708 For ELF targets, the @code{.symver} directive is used like this:
4710 .symver @var{name}, @var{name2@@nodename}
4712 In this case, the symbol @var{name} must exist and be defined within the file
4713 being assembled. The @code{.versym} directive effectively creates a symbol
4714 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4715 just don't try and create a regular alias is that the @var{@@} character isn't
4716 permitted in symbol names. The @var{name2} part of the name is the actual name
4717 of the symbol by which it will be externally referenced. The name @var{name}
4718 itself is merely a name of convenience that is used so that it is possible to
4719 have definitions for multiple versions of a function within a single source
4720 file, and so that the compiler can unambiguously know which version of a
4721 function is being mentioned. The @var{nodename} portion of the alias should be
4722 the name of a node specified in the version script supplied to the linker when
4723 building a shared library. If you are attempting to override a versioned
4724 symbol from a shared library, then @var{nodename} should correspond to the
4725 nodename of the symbol you are trying to override.
4730 @section @code{.tag @var{structname}}
4732 @cindex COFF structure debugging
4733 @cindex structure debugging, COFF
4734 @cindex @code{tag} directive
4735 This directive is generated by compilers to include auxiliary debugging
4736 information in the symbol table. It is only permitted inside
4737 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4738 definitions in the symbol table with instances of those structures.
4741 @samp{.tag} is only used when generating COFF format output; when
4742 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4748 @section @code{.text @var{subsection}}
4750 @cindex @code{text} directive
4751 Tells @code{@value{AS}} to assemble the following statements onto the end of
4752 the text subsection numbered @var{subsection}, which is an absolute
4753 expression. If @var{subsection} is omitted, subsection number zero
4757 @section @code{.title "@var{heading}"}
4759 @cindex @code{title} directive
4760 @cindex listing control: title line
4761 Use @var{heading} as the title (second line, immediately after the
4762 source file name and pagenumber) when generating assembly listings.
4764 This directive affects subsequent pages, as well as the current page if
4765 it appears within ten lines of the top of a page.
4769 @section @code{.type @var{int}}
4771 @cindex COFF symbol type
4772 @cindex symbol type, COFF
4773 @cindex @code{type} directive
4774 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4775 records the integer @var{int} as the type attribute of a symbol table entry.
4778 @samp{.type} is associated only with COFF format output; when
4779 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4780 directive but ignores it.
4786 @section @code{.val @var{addr}}
4788 @cindex @code{val} directive
4789 @cindex COFF value attribute
4790 @cindex value attribute, COFF
4791 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4792 records the address @var{addr} as the value attribute of a symbol table
4796 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4797 configured for @code{b.out}, it accepts this directive but ignores it.
4802 @section @code{.uleb128 @var{expressions}}
4804 @cindex @code{uleb128} directive
4805 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
4806 compact, variable length representation of numbers used by the DWARF
4807 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
4811 @section @code{.internal}, @code{.hidden}, @code{.protected}
4812 @cindex @code{internal} directive
4813 @cindex @code{hidden} directive
4814 @cindex @code{protected} directive
4815 @cindex symbol visibility
4817 These directives can be used to set the visibility of a specified symbol. By
4818 default a symbol's visibility is set by its binding (local, global or weak),
4819 but these directives can be used to override that.
4821 A visibility of @code{protected} means that any references to the symbol from
4822 within the component that defines the symbol must be resolved to the definition
4823 in that component, even if a definition in another component would normally
4826 A visibility of @code{hidden} means that the symbol is not visible to other
4827 components. Such a symbol is always considered to be protected as well.
4829 A visibility of @code{internal} is the same as a visibility of @code{hidden},
4830 except that some extra, processor specific processing must also be performed
4833 For ELF targets, the directives are used like this:
4836 .internal @var{name}
4838 .protected @var{name}
4844 @section @code{.word @var{expressions}}
4846 @cindex @code{word} directive
4847 This directive expects zero or more @var{expressions}, of any section,
4848 separated by commas.
4851 For each expression, @code{@value{AS}} emits a 32-bit number.
4854 For each expression, @code{@value{AS}} emits a 16-bit number.
4859 The size of the number emitted, and its byte order,
4860 depend on what target computer the assembly is for.
4863 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4864 @c happen---32-bit addressability, period; no long/short jumps.
4865 @ifset DIFF-TBL-KLUGE
4866 @cindex difference tables altered
4867 @cindex altered difference tables
4869 @emph{Warning: Special Treatment to support Compilers}
4873 Machines with a 32-bit address space, but that do less than 32-bit
4874 addressing, require the following special treatment. If the machine of
4875 interest to you does 32-bit addressing (or doesn't require it;
4876 @pxref{Machine Dependencies}), you can ignore this issue.
4879 In order to assemble compiler output into something that works,
4880 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4881 Directives of the form @samp{.word sym1-sym2} are often emitted by
4882 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4883 directive of the form @samp{.word sym1-sym2}, and the difference between
4884 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4885 creates a @dfn{secondary jump table}, immediately before the next label.
4886 This secondary jump table is preceded by a short-jump to the
4887 first byte after the secondary table. This short-jump prevents the flow
4888 of control from accidentally falling into the new table. Inside the
4889 table is a long-jump to @code{sym2}. The original @samp{.word}
4890 contains @code{sym1} minus the address of the long-jump to
4893 If there were several occurrences of @samp{.word sym1-sym2} before the
4894 secondary jump table, all of them are adjusted. If there was a
4895 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4896 long-jump to @code{sym4} is included in the secondary jump table,
4897 and the @code{.word} directives are adjusted to contain @code{sym3}
4898 minus the address of the long-jump to @code{sym4}; and so on, for as many
4899 entries in the original jump table as necessary.
4902 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4903 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4904 assembly language programmers.
4907 @c end DIFF-TBL-KLUGE
4910 @section Deprecated Directives
4912 @cindex deprecated directives
4913 @cindex obsolescent directives
4914 One day these directives won't work.
4915 They are included for compatibility with older assemblers.
4922 @node Machine Dependencies
4923 @chapter Machine Dependent Features
4925 @cindex machine dependencies
4926 The machine instruction sets are (almost by definition) different on
4927 each machine where @code{@value{AS}} runs. Floating point representations
4928 vary as well, and @code{@value{AS}} often supports a few additional
4929 directives or command-line options for compatibility with other
4930 assemblers on a particular platform. Finally, some versions of
4931 @code{@value{AS}} support special pseudo-instructions for branch
4934 This chapter discusses most of these differences, though it does not
4935 include details on any machine's instruction set. For details on that
4936 subject, see the hardware manufacturer's manual.
4940 * AMD29K-Dependent:: AMD 29K Dependent Features
4943 * ARC-Dependent:: ARC Dependent Features
4946 * ARM-Dependent:: ARM Dependent Features
4949 * D10V-Dependent:: D10V Dependent Features
4952 * D30V-Dependent:: D30V Dependent Features
4955 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4958 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
4961 * HPPA-Dependent:: HPPA Dependent Features
4964 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
4967 * i386-Dependent:: Intel 80386 Dependent Features
4970 * i960-Dependent:: Intel 80960 Dependent Features
4973 * M32R-Dependent:: M32R Dependent Features
4976 * M68K-Dependent:: M680x0 Dependent Features
4979 * MIPS-Dependent:: MIPS Dependent Features
4982 * SH-Dependent:: Hitachi SH Dependent Features
4985 * PJ-Dependent:: picoJava Dependent Features
4988 * Sparc-Dependent:: SPARC Dependent Features
4991 * V850-Dependent:: V850 Dependent Features
4994 * Z8000-Dependent:: Z8000 Dependent Features
4997 * Vax-Dependent:: VAX Dependent Features
5004 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5005 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5006 @c peculiarity: to preserve cross-references, there must be a node called
5007 @c "Machine Dependencies". Hence the conditional nodenames in each
5008 @c major node below. Node defaulting in makeinfo requires adjacency of
5009 @c node and sectioning commands; hence the repetition of @chapter BLAH
5010 @c in both conditional blocks.
5016 @chapter ARC Dependent Features
5019 @node Machine Dependencies
5020 @chapter ARC Dependent Features
5025 * ARC-Opts:: Options
5026 * ARC-Float:: Floating Point
5027 * ARC-Directives:: Sparc Machine Directives
5033 @cindex options for ARC
5035 @cindex architectures, ARC
5036 @cindex ARC architectures
5037 The ARC chip family includes several successive levels (or other
5038 variants) of chip, using the same core instruction set, but including
5039 a few additional instructions at each level.
5041 By default, @code{@value{AS}} assumes the core instruction set (ARC
5042 base). The @code{.cpu} pseudo-op is intended to be used to select
5046 @cindex @code{-mbig-endian} option (ARC)
5047 @cindex @code{-mlittle-endian} option (ARC)
5048 @cindex ARC big-endian output
5049 @cindex ARC little-endian output
5050 @cindex big-endian output, ARC
5051 @cindex little-endian output, ARC
5053 @itemx -mlittle-endian
5054 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
5055 little-endian output at run time (unlike most other @sc{gnu} development
5056 tools, which must be configured for one or the other). Use
5057 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
5062 @section Floating Point
5064 @cindex floating point, ARC (@sc{ieee})
5065 @cindex ARC floating point (@sc{ieee})
5066 The ARC cpu family currently does not have hardware floating point
5067 support. Software floating point support is provided by @code{GCC}
5068 and uses @sc{ieee} floating-point numbers.
5070 @node ARC-Directives
5071 @section ARC Machine Directives
5073 @cindex ARC machine directives
5074 @cindex machine directives, ARC
5075 The ARC version of @code{@value{AS}} supports the following additional
5080 @cindex @code{cpu} directive, SPARC
5081 This must be followed by the desired cpu.
5082 The ARC is intended to be customizable, @code{.cpu} is used to
5083 select the desired variant [though currently there are none].
5090 @include c-a29k.texi
5099 @node Machine Dependencies
5100 @chapter Machine Dependent Features
5102 The machine instruction sets are different on each Hitachi chip family,
5103 and there are also some syntax differences among the families. This
5104 chapter describes the specific @code{@value{AS}} features for each
5108 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5109 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5110 * SH-Dependent:: Hitachi SH Dependent Features
5117 @include c-d10v.texi
5121 @include c-d30v.texi
5125 @include c-h8300.texi
5129 @include c-h8500.texi
5133 @include c-hppa.texi
5137 @include c-i370.texi
5141 @include c-i386.texi
5145 @include c-i960.texi
5149 @include c-m32r.texi
5153 @include c-m68k.texi
5157 @include c-mips.texi
5161 @include c-ns32k.texi
5173 @include c-sparc.texi
5185 @include c-v850.texi
5189 @c reverse effect of @down at top of generic Machine-Dep chapter
5193 @node Reporting Bugs
5194 @chapter Reporting Bugs
5195 @cindex bugs in assembler
5196 @cindex reporting bugs in assembler
5198 Your bug reports play an essential role in making @code{@value{AS}} reliable.
5200 Reporting a bug may help you by bringing a solution to your problem, or it may
5201 not. But in any case the principal function of a bug report is to help the
5202 entire community by making the next version of @code{@value{AS}} work better.
5203 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
5205 In order for a bug report to serve its purpose, you must include the
5206 information that enables us to fix the bug.
5209 * Bug Criteria:: Have you found a bug?
5210 * Bug Reporting:: How to report bugs
5214 @section Have you found a bug?
5215 @cindex bug criteria
5217 If you are not sure whether you have found a bug, here are some guidelines:
5220 @cindex fatal signal
5221 @cindex assembler crash
5222 @cindex crash of assembler
5224 If the assembler gets a fatal signal, for any input whatever, that is a
5225 @code{@value{AS}} bug. Reliable assemblers never crash.
5227 @cindex error on valid input
5229 If @code{@value{AS}} produces an error message for valid input, that is a bug.
5231 @cindex invalid input
5233 If @code{@value{AS}} does not produce an error message for invalid input, that
5234 is a bug. However, you should note that your idea of ``invalid input'' might
5235 be our idea of ``an extension'' or ``support for traditional practice''.
5238 If you are an experienced user of assemblers, your suggestions for improvement
5239 of @code{@value{AS}} are welcome in any case.
5243 @section How to report bugs
5245 @cindex assembler bugs, reporting
5247 A number of companies and individuals offer support for @sc{gnu} products. If
5248 you obtained @code{@value{AS}} from a support organization, we recommend you
5249 contact that organization first.
5251 You can find contact information for many support companies and
5252 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5255 In any event, we also recommend that you send bug reports for @code{@value{AS}}
5256 to @samp{bug-gnu-utils@@gnu.org}.
5258 The fundamental principle of reporting bugs usefully is this:
5259 @strong{report all the facts}. If you are not sure whether to state a
5260 fact or leave it out, state it!
5262 Often people omit facts because they think they know what causes the problem
5263 and assume that some details do not matter. Thus, you might assume that the
5264 name of a symbol you use in an example does not matter. Well, probably it does
5265 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5266 happens to fetch from the location where that name is stored in memory;
5267 perhaps, if the name were different, the contents of that location would fool
5268 the assembler into doing the right thing despite the bug. Play it safe and
5269 give a specific, complete example. That is the easiest thing for you to do,
5270 and the most helpful.
5272 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5273 it is new to us. Therefore, always write your bug reports on the assumption
5274 that the bug has not been reported previously.
5276 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5277 bell?'' Those bug reports are useless, and we urge everyone to
5278 @emph{refuse to respond to them} except to chide the sender to report
5281 To enable us to fix the bug, you should include all these things:
5285 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
5286 it with the @samp{--version} argument.
5288 Without this, we will not know whether there is any point in looking for
5289 the bug in the current version of @code{@value{AS}}.
5292 Any patches you may have applied to the @code{@value{AS}} source.
5295 The type of machine you are using, and the operating system name and
5299 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
5303 The command arguments you gave the assembler to assemble your example and
5304 observe the bug. To guarantee you will not omit something important, list them
5305 all. A copy of the Makefile (or the output from make) is sufficient.
5307 If we were to try to guess the arguments, we would probably guess wrong
5308 and then we might not encounter the bug.
5311 A complete input file that will reproduce the bug. If the bug is observed when
5312 the assembler is invoked via a compiler, send the assembler source, not the
5313 high level language source. Most compilers will produce the assembler source
5314 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5315 the options @samp{-v --save-temps}; this will save the assembler source in a
5316 file with an extension of @file{.s}, and also show you exactly how
5317 @code{@value{AS}} is being run.
5320 A description of what behavior you observe that you believe is
5321 incorrect. For example, ``It gets a fatal signal.''
5323 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
5324 will certainly notice it. But if the bug is incorrect output, we might not
5325 notice unless it is glaringly wrong. You might as well not give us a chance to
5328 Even if the problem you experience is a fatal signal, you should still say so
5329 explicitly. Suppose something strange is going on, such as, your copy of
5330 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
5331 library on your system. (This has happened!) Your copy might crash and ours
5332 would not. If you told us to expect a crash, then when ours fails to crash, we
5333 would know that the bug was not happening for us. If you had not told us to
5334 expect a crash, then we would not be able to draw any conclusion from our
5338 If you wish to suggest changes to the @code{@value{AS}} source, send us context
5339 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
5340 option. Always send diffs from the old file to the new file. If you even
5341 discuss something in the @code{@value{AS}} source, refer to it by context, not
5344 The line numbers in our development sources will not match those in your
5345 sources. Your line numbers would convey no useful information to us.
5348 Here are some things that are not necessary:
5352 A description of the envelope of the bug.
5354 Often people who encounter a bug spend a lot of time investigating
5355 which changes to the input file will make the bug go away and which
5356 changes will not affect it.
5358 This is often time consuming and not very useful, because the way we
5359 will find the bug is by running a single example under the debugger
5360 with breakpoints, not by pure deduction from a series of examples.
5361 We recommend that you save your time for something else.
5363 Of course, if you can find a simpler example to report @emph{instead}
5364 of the original one, that is a convenience for us. Errors in the
5365 output will be easier to spot, running under the debugger will take
5366 less time, and so on.
5368 However, simplification is not vital; if you do not want to do this,
5369 report the bug anyway and send us the entire test case you used.
5372 A patch for the bug.
5374 A patch for the bug does help us if it is a good one. But do not omit
5375 the necessary information, such as the test case, on the assumption that
5376 a patch is all we need. We might see problems with your patch and decide
5377 to fix the problem another way, or we might not understand it at all.
5379 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5380 construct an example that will make the program follow a certain path through
5381 the code. If you do not send us the example, we will not be able to construct
5382 one, so we will not be able to verify that the bug is fixed.
5384 And if we cannot understand what bug you are trying to fix, or why your
5385 patch should be an improvement, we will not install it. A test case will
5386 help us to understand.
5389 A guess about what the bug is or what it depends on.
5391 Such guesses are usually wrong. Even we cannot guess right about such
5392 things without first using the debugger to find the facts.
5395 @node Acknowledgements
5396 @chapter Acknowledgements
5398 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5399 it is not meant as a slight. We just don't know about it. Send mail to the
5400 maintainer, and we'll correct the situation. Currently
5402 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5404 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5407 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5408 information and the 68k series machines, most of the preprocessing pass, and
5409 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5411 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5412 many bug fixes, including merging support for several processors, breaking GAS
5413 up to handle multiple object file format back ends (including heavy rewrite,
5414 testing, an integration of the coff and b.out back ends), adding configuration
5415 including heavy testing and verification of cross assemblers and file splits
5416 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5417 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5418 port (including considerable amounts of reverse engineering), a SPARC opcode
5419 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5420 assertions and made them work, much other reorganization, cleanup, and lint.
5422 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5423 in format-specific I/O modules.
5425 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5426 has done much work with it since.
5428 The Intel 80386 machine description was written by Eliot Dresselhaus.
5430 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5432 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5433 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5435 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5436 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5437 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5438 support a.out format.
5440 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5441 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5442 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5443 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5446 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5447 simplified the configuration of which versions accept which directives. He
5448 updated the 68k machine description so that Motorola's opcodes always produced
5449 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5450 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5451 cross-compilation support, and one bug in relaxation that took a week and
5452 required the proverbial one-bit fix.
5454 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5455 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5456 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5457 PowerPC assembler, and made a few other minor patches.
5459 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5461 Hewlett-Packard contributed support for the HP9000/300.
5463 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5464 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5465 formats). This work was supported by both the Center for Software Science at
5466 the University of Utah and Cygnus Support.
5468 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5469 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5470 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5471 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5472 and some initial 64-bit support).
5474 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
5476 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5477 support for openVMS/Alpha.
5479 Several engineers at Cygnus Support have also provided many small bug fixes and
5480 configuration enhancements.
5482 Many others have contributed large or small bugfixes and enhancements. If
5483 you have contributed significant work and are not mentioned on this list, and
5484 want to be, let us know. Some of the history has been lost; we are not
5485 intentionally leaving anyone out.
projects / external / binutils.git / blob