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 [ -m68hc11 | -m68hc12 ]
272 [ --force-long-branchs ] [ --short-branchs ] [ --strict-direct-mode ]
273 [ --print-insn-syntax ] [ --print-opcodes ] [ --generate-example ]
276 [ -nocpp ] [ -EL ] [ -EB ] [ -G @var{num} ] [ -mcpu=@var{CPU} ]
277 [ -mips1 ] [ -mips2 ] [ -mips3 ] [ -m4650 ] [ -no-m4650 ]
278 [ --trap ] [ --break ]
279 [ --emulation=@var{name} ]
281 [ -- | @var{files} @dots{} ]
286 Turn on listings, in any of a variety of ways:
290 omit false conditionals
293 omit debugging directives
296 include high-level source
302 include macro expansions
305 omit forms processing
311 set the name of the listing file
314 You may combine these options; for example, use @samp{-aln} for assembly
315 listing without forms processing. The @samp{=file} option, if used, must be
316 the last one. By itself, @samp{-a} defaults to @samp{-ahls}.
319 Ignored. This option is accepted for script compatibility with calls to
322 @item --defsym @var{sym}=@var{value}
323 Define the symbol @var{sym} to be @var{value} before assembling the input file.
324 @var{value} must be an integer constant. As in C, a leading @samp{0x}
325 indicates a hexadecimal value, and a leading @samp{0} indicates an octal value.
328 ``fast''---skip whitespace and comment preprocessing (assume source is
332 Generate stabs debugging information for each assembler line. This
333 may help debugging assembler code, if the debugger can handle it.
336 Generate DWARF2 debugging information for each assembler line. This
337 may help debugging assembler code, if the debugger can handle it.
340 Print a summary of the command line options and exit.
343 Add directory @var{dir} to the search list for @code{.include} directives.
346 Don't warn about signed overflow.
349 @ifclear DIFF-TBL-KLUGE
350 This option is accepted but has no effect on the @value{TARGET} family.
352 @ifset DIFF-TBL-KLUGE
353 Issue warnings when difference tables altered for long displacements.
358 Keep (in the symbol table) local symbols. On traditional a.out systems
359 these start with @samp{L}, but different systems have different local
362 @item -o @var{objfile}
363 Name the object-file output from @code{@value{AS}} @var{objfile}.
366 Fold the data section into the text section.
369 Print the maximum space (in bytes) and total time (in seconds) used by
372 @item --strip-local-absolute
373 Remove local absolute symbols from the outgoing symbol table.
377 Print the @code{as} version.
380 Print the @code{as} version and exit.
384 Suppress warning messages.
386 @item --fatal-warnings
387 Treat warnings as errors.
390 Don't suppress warning messages or treat them as errors.
399 Generate an object file even after errors.
401 @item -- | @var{files} @dots{}
402 Standard input, or source files to assemble.
407 The following options are available when @value{AS} is configured for
412 @cindex ARC endianness
413 @cindex endianness, ARC
414 @cindex big endian output, ARC
416 Generate ``big endian'' format output.
418 @cindex little endian output, ARC
419 @item -mlittle-endian
420 Generate ``little endian'' format output.
426 The following options are available when @value{AS} is configured for the ARM
430 @item -m[arm][1|2|3|6|7|8|9][...]
431 Specify which ARM processor variant is the target.
432 @item -m[arm]v[2|2a|3|3m|4|4t|5|5t]
433 Specify which ARM architecture variant is used by the target.
434 @item -mthumb | -mall
435 Enable or disable Thumb only instruction decoding.
436 @item -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu
437 Select which Floating Point architcture is the target.
438 @item -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi
439 Select which procedure calling convention is in use.
441 Select either big-endian (-EB) or little-endian (-EL) output.
442 @item -mthumb-interwork
443 Specify that the code has been generated with interworking between Thumb and
446 Specify that PIC code has been generated.
451 The following options are available when @value{AS} is configured for
454 @cindex D10V optimization
455 @cindex optimization, D10V
457 Optimize output by parallelizing instructions.
462 The following options are available when @value{AS} is configured for a D30V
465 @cindex D30V optimization
466 @cindex optimization, D30V
468 Optimize output by parallelizing instructions.
472 Warn when nops are generated.
474 @cindex D30V nops after 32-bit multiply
476 Warn when a nop after a 32-bit multiply instruction is generated.
481 The following options are available when @value{AS} is configured for the
482 Intel 80960 processor.
485 @item -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC
486 Specify which variant of the 960 architecture is the target.
489 Add code to collect statistics about branches taken.
492 Do not alter compare-and-branch instructions for long displacements;
499 The following options are available when @value{AS} is configured for the
500 Mitsubishi M32R series.
505 Specify which processor in the M32R family is the target. The default
506 is normally the M32R, but this option changes it to the M32RX.
508 @item --warn-explicit-parallel-conflicts or --Wp
509 Produce warning messages when questionable parallel constructs are
512 @item --no-warn-explicit-parallel-conflicts or --Wnp
513 Do not produce warning messages when questionable parallel constructs are
520 The following options are available when @value{AS} is configured for the
521 Motorola 68000 series.
526 Shorten references to undefined symbols, to one word instead of two.
528 @item -m68000 | -m68008 | -m68010 | -m68020 | -m68030 | -m68040 | -m68060
529 @itemx | -m68302 | -m68331 | -m68332 | -m68333 | -m68340 | -mcpu32 | -m5200
530 Specify what processor in the 68000 family is the target. The default
531 is normally the 68020, but this can be changed at configuration time.
533 @item -m68881 | -m68882 | -mno-68881 | -mno-68882
534 The target machine does (or does not) have a floating-point coprocessor.
535 The default is to assume a coprocessor for 68020, 68030, and cpu32. Although
536 the basic 68000 is not compatible with the 68881, a combination of the
537 two can be specified, since it's possible to do emulation of the
538 coprocessor instructions with the main processor.
540 @item -m68851 | -mno-68851
541 The target machine does (or does not) have a memory-management
542 unit coprocessor. The default is to assume an MMU for 68020 and up.
548 The following options are available when @value{AS} is configured for
549 a picoJava processor.
553 @cindex PJ endianness
554 @cindex endianness, PJ
555 @cindex big endian output, PJ
557 Generate ``big endian'' format output.
559 @cindex little endian output, PJ
561 Generate ``little endian'' format output.
567 The following options are available when @value{AS} is configured for the
568 Motorola 68HC11 or 68HC12 series.
572 @item -m68hc11 | -m68hc12
573 Specify what processor is the target. The default is
574 defined by the configuration option when building the assembler.
576 @item --force-long-branchs
577 Relative branches are turned into absolute ones. This concerns
578 conditional branches, unconditional branches and branches to a
581 @item -S | --short-branchs
582 Do not turn relative branchs into absolute ones
583 when the offset is out of range.
585 @item --strict-direct-mode
586 Do not turn the direct addressing mode into extended addressing mode
587 when the instruction does not support direct addressing mode.
589 @item --print-insn-syntax
590 Print the syntax of instruction in case of error.
592 @item --print-opcodes
593 print the list of instructions with syntax and then exit.
595 @item --generate-example
596 print an example of instruction for each possible instruction and then exit.
597 This option is only useful for testing @code{@value{AS}}.
603 The following options are available when @code{@value{AS}} is configured
604 for the SPARC architecture:
607 @item -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
608 @itemx -Av8plus | -Av8plusa | -Av9 | -Av9a
609 Explicitly select a variant of the SPARC architecture.
611 @samp{-Av8plus} and @samp{-Av8plusa} select a 32 bit environment.
612 @samp{-Av9} and @samp{-Av9a} select a 64 bit environment.
614 @samp{-Av8plusa} and @samp{-Av9a} enable the SPARC V9 instruction set with
615 UltraSPARC extensions.
617 @item -xarch=v8plus | -xarch=v8plusa
618 For compatibility with the Solaris v9 assembler. These options are
619 equivalent to -Av8plus and -Av8plusa, respectively.
622 Warn when the assembler switches to another architecture.
627 The following options are available when @value{AS} is configured for
632 This option sets the largest size of an object that can be referenced
633 implicitly with the @code{gp} register. It is only accepted for targets that
634 use ECOFF format, such as a DECstation running Ultrix. The default value is 8.
636 @cindex MIPS endianness
637 @cindex endianness, MIPS
638 @cindex big endian output, MIPS
640 Generate ``big endian'' format output.
642 @cindex little endian output, MIPS
644 Generate ``little endian'' format output.
650 Generate code for a particular MIPS Instruction Set Architecture level.
651 @samp{-mips1} corresponds to the @sc{r2000} and @sc{r3000} processors,
652 @samp{-mips2} to the @sc{r6000} processor, and @samp{-mips3} to the @sc{r4000}
657 Generate code for the MIPS @sc{r4650} chip. This tells the assembler to accept
658 the @samp{mad} and @samp{madu} instruction, and to not schedule @samp{nop}
659 instructions around accesses to the @samp{HI} and @samp{LO} registers.
660 @samp{-no-m4650} turns off this option.
662 @item -mcpu=@var{CPU}
663 Generate code for a particular MIPS cpu. This has little effect on the
664 assembler, but it is passed by @code{@value{GCC}}.
667 @item --emulation=@var{name}
668 This option causes @code{@value{AS}} to emulate @code{@value{AS}} configured
669 for some other target, in all respects, including output format (choosing
670 between ELF and ECOFF only), handling of pseudo-opcodes which may generate
671 debugging information or store symbol table information, and default
672 endianness. The available configuration names are: @samp{mipsecoff},
673 @samp{mipself}, @samp{mipslecoff}, @samp{mipsbecoff}, @samp{mipslelf},
674 @samp{mipsbelf}. The first two do not alter the default endianness from that
675 of the primary target for which the assembler was configured; the others change
676 the default to little- or big-endian as indicated by the @samp{b} or @samp{l}
677 in the name. Using @samp{-EB} or @samp{-EL} will override the endianness
678 selection in any case.
680 This option is currently supported only when the primary target
681 @code{@value{AS}} is configured for is a MIPS ELF or ECOFF target.
682 Furthermore, the primary target or others specified with
683 @samp{--enable-targets=@dots{}} at configuration time must include support for
684 the other format, if both are to be available. For example, the Irix 5
685 configuration includes support for both.
687 Eventually, this option will support more configurations, with more
688 fine-grained control over the assembler's behavior, and will be supported for
692 @code{@value{AS}} ignores this option. It is accepted for compatibility with
700 Control how to deal with multiplication overflow and division by zero.
701 @samp{--trap} or @samp{--no-break} (which are synonyms) take a trap exception
702 (and only work for Instruction Set Architecture level 2 and higher);
703 @samp{--break} or @samp{--no-trap} (also synonyms, and the default) take a
709 The following options are available when @value{AS} is configured for
715 Enable or disable the JSRI to BSR transformation. By default this is enabled.
716 The command line option @samp{-nojsri2bsr} can be used to disable it.
720 Enable or disable the silicon filter behaviour. By default this is disabled.
721 The default can be overidden by the @samp{-sifilter} command line option.
724 Alter jump instructions for long displacements.
726 @item -mcpu=[210|340]
727 Select the cpu type on the target hardware. This controls which instructions
731 Assemble for a big endian target.
734 Assemble for a little endian target.
740 * Manual:: Structure of this Manual
741 * GNU Assembler:: The GNU Assembler
742 * Object Formats:: Object File Formats
743 * Command Line:: Command Line
744 * Input Files:: Input Files
745 * Object:: Output (Object) File
746 * Errors:: Error and Warning Messages
750 @section Structure of this Manual
752 @cindex manual, structure and purpose
753 This manual is intended to describe what you need to know to use
754 @sc{gnu} @code{@value{AS}}. We cover the syntax expected in source files, including
755 notation for symbols, constants, and expressions; the directives that
756 @code{@value{AS}} understands; and of course how to invoke @code{@value{AS}}.
759 We also cover special features in the @value{TARGET}
760 configuration of @code{@value{AS}}, including assembler directives.
763 This manual also describes some of the machine-dependent features of
764 various flavors of the assembler.
767 @cindex machine instructions (not covered)
768 On the other hand, this manual is @emph{not} intended as an introduction
769 to programming in assembly language---let alone programming in general!
770 In a similar vein, we make no attempt to introduce the machine
771 architecture; we do @emph{not} describe the instruction set, standard
772 mnemonics, registers or addressing modes that are standard to a
773 particular architecture.
775 You may want to consult the manufacturer's
776 machine architecture manual for this information.
780 For information on the H8/300 machine instruction set, see @cite{H8/300
781 Series Programming Manual} (Hitachi ADE--602--025). For the H8/300H,
782 see @cite{H8/300H Series Programming Manual} (Hitachi).
785 For information on the H8/500 machine instruction set, see @cite{H8/500
786 Series Programming Manual} (Hitachi M21T001).
789 For information on the Hitachi SH machine instruction set, see
790 @cite{SH-Microcomputer User's Manual} (Hitachi Micro Systems, Inc.).
793 For information on the Z8000 machine instruction set, see @cite{Z8000 CPU Technical Manual}
797 @c I think this is premature---doc@cygnus.com, 17jan1991
799 Throughout this manual, we assume that you are running @dfn{GNU},
800 the portable operating system from the @dfn{Free Software
801 Foundation, Inc.}. This restricts our attention to certain kinds of
802 computer (in particular, the kinds of computers that @sc{gnu} can run on);
803 once this assumption is granted examples and definitions need less
806 @code{@value{AS}} is part of a team of programs that turn a high-level
807 human-readable series of instructions into a low-level
808 computer-readable series of instructions. Different versions of
809 @code{@value{AS}} are used for different kinds of computer.
812 @c There used to be a section "Terminology" here, which defined
813 @c "contents", "byte", "word", and "long". Defining "word" to any
814 @c particular size is confusing when the .word directive may generate 16
815 @c bits on one machine and 32 bits on another; in general, for the user
816 @c version of this manual, none of these terms seem essential to define.
817 @c They were used very little even in the former draft of the manual;
818 @c this draft makes an effort to avoid them (except in names of
822 @section The GNU Assembler
824 @sc{gnu} @code{as} is really a family of assemblers.
826 This manual describes @code{@value{AS}}, a member of that family which is
827 configured for the @value{TARGET} architectures.
829 If you use (or have used) the @sc{gnu} assembler on one architecture, you
830 should find a fairly similar environment when you use it on another
831 architecture. Each version has much in common with the others,
832 including object file formats, most assembler directives (often called
833 @dfn{pseudo-ops}) and assembler syntax.@refill
835 @cindex purpose of @sc{gnu} assembler
836 @code{@value{AS}} is primarily intended to assemble the output of the
837 @sc{gnu} C compiler @code{@value{GCC}} for use by the linker
838 @code{@value{LD}}. Nevertheless, we've tried to make @code{@value{AS}}
839 assemble correctly everything that other assemblers for the same
840 machine would assemble.
842 Any exceptions are documented explicitly (@pxref{Machine Dependencies}).
845 @c This remark should appear in generic version of manual; assumption
846 @c here is that generic version sets M680x0.
847 This doesn't mean @code{@value{AS}} always uses the same syntax as another
848 assembler for the same architecture; for example, we know of several
849 incompatible versions of 680x0 assembly language syntax.
852 Unlike older assemblers, @code{@value{AS}} is designed to assemble a source
853 program in one pass of the source file. This has a subtle impact on the
854 @kbd{.org} directive (@pxref{Org,,@code{.org}}).
857 @section Object File Formats
859 @cindex object file format
860 The @sc{gnu} assembler can be configured to produce several alternative
861 object file formats. For the most part, this does not affect how you
862 write assembly language programs; but directives for debugging symbols
863 are typically different in different file formats. @xref{Symbol
864 Attributes,,Symbol Attributes}.
867 On the @value{TARGET}, @code{@value{AS}} is configured to produce
868 @value{OBJ-NAME} format object files.
870 @c The following should exhaust all configs that set MULTI-OBJ, ideally
872 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
873 @code{a.out} or COFF format object files.
876 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
877 @code{b.out} or COFF format object files.
880 On the @value{TARGET}, @code{@value{AS}} can be configured to produce either
881 SOM or ELF format object files.
886 @section Command Line
888 @cindex command line conventions
889 After the program name @code{@value{AS}}, the command line may contain
890 options and file names. Options may appear in any order, and may be
891 before, after, or between file names. The order of file names is
894 @cindex standard input, as input file
896 @file{--} (two hyphens) by itself names the standard input file
897 explicitly, as one of the files for @code{@value{AS}} to assemble.
899 @cindex options, command line
900 Except for @samp{--} any command line argument that begins with a
901 hyphen (@samp{-}) is an option. Each option changes the behavior of
902 @code{@value{AS}}. No option changes the way another option works. An
903 option is a @samp{-} followed by one or more letters; the case of
904 the letter is important. All options are optional.
906 Some options expect exactly one file name to follow them. The file
907 name may either immediately follow the option's letter (compatible
908 with older assemblers) or it may be the next command argument (@sc{gnu}
909 standard). These two command lines are equivalent:
912 @value{AS} -o my-object-file.o mumble.s
913 @value{AS} -omy-object-file.o mumble.s
920 @cindex source program
922 We use the phrase @dfn{source program}, abbreviated @dfn{source}, to
923 describe the program input to one run of @code{@value{AS}}. The program may
924 be in one or more files; how the source is partitioned into files
925 doesn't change the meaning of the source.
927 @c I added "con" prefix to "catenation" just to prove I can overcome my
928 @c APL training... doc@cygnus.com
929 The source program is a concatenation of the text in all the files, in the
932 Each time you run @code{@value{AS}} it assembles exactly one source
933 program. The source program is made up of one or more files.
934 (The standard input is also a file.)
936 You give @code{@value{AS}} a command line that has zero or more input file
937 names. The input files are read (from left file name to right). A
938 command line argument (in any position) that has no special meaning
939 is taken to be an input file name.
941 If you give @code{@value{AS}} no file names it attempts to read one input file
942 from the @code{@value{AS}} standard input, which is normally your terminal. You
943 may have to type @key{ctl-D} to tell @code{@value{AS}} there is no more program
946 Use @samp{--} if you need to explicitly name the standard input file
947 in your command line.
949 If the source is empty, @code{@value{AS}} produces a small, empty object
952 @subheading Filenames and Line-numbers
954 @cindex input file linenumbers
955 @cindex line numbers, in input files
956 There are two ways of locating a line in the input file (or files) and
957 either may be used in reporting error messages. One way refers to a line
958 number in a physical file; the other refers to a line number in a
959 ``logical'' file. @xref{Errors, ,Error and Warning Messages}.
961 @dfn{Physical files} are those files named in the command line given
962 to @code{@value{AS}}.
964 @dfn{Logical files} are simply names declared explicitly by assembler
965 directives; they bear no relation to physical files. Logical file names help
966 error messages reflect the original source file, when @code{@value{AS}} source
967 is itself synthesized from other files. @code{@value{AS}} understands the
968 @samp{#} directives emitted by the @code{@value{GCC}} preprocessor. See also
969 @ref{File,,@code{.file}}.
972 @section Output (Object) File
978 Every time you run @code{@value{AS}} it produces an output file, which is
979 your assembly language program translated into numbers. This file
980 is the object file. Its default name is
988 @code{b.out} when @code{@value{AS}} is configured for the Intel 80960.
990 You can give it another name by using the @code{-o} option. Conventionally,
991 object file names end with @file{.o}. The default name is used for historical
992 reasons: older assemblers were capable of assembling self-contained programs
993 directly into a runnable program. (For some formats, this isn't currently
994 possible, but it can be done for the @code{a.out} format.)
998 The object file is meant for input to the linker @code{@value{LD}}. It contains
999 assembled program code, information to help @code{@value{LD}} integrate
1000 the assembled program into a runnable file, and (optionally) symbolic
1001 information for the debugger.
1003 @c link above to some info file(s) like the description of a.out.
1004 @c don't forget to describe @sc{gnu} info as well as Unix lossage.
1007 @section Error and Warning Messages
1009 @cindex error messsages
1010 @cindex warning messages
1011 @cindex messages from assembler
1012 @code{@value{AS}} may write warnings and error messages to the standard error
1013 file (usually your terminal). This should not happen when a compiler
1014 runs @code{@value{AS}} automatically. Warnings report an assumption made so
1015 that @code{@value{AS}} could keep assembling a flawed program; errors report a
1016 grave problem that stops the assembly.
1018 @cindex format of warning messages
1019 Warning messages have the format
1022 file_name:@b{NNN}:Warning Message Text
1026 @cindex line numbers, in warnings/errors
1027 (where @b{NNN} is a line number). If a logical file name has been given
1028 (@pxref{File,,@code{.file}}) it is used for the filename, otherwise the name of
1029 the current input file is used. If a logical line number was given
1031 (@pxref{Line,,@code{.line}})
1035 (@pxref{Line,,@code{.line}})
1038 (@pxref{Ln,,@code{.ln}})
1041 then it is used to calculate the number printed,
1042 otherwise the actual line in the current source file is printed. The
1043 message text is intended to be self explanatory (in the grand Unix
1046 @cindex format of error messages
1047 Error messages have the format
1049 file_name:@b{NNN}:FATAL:Error Message Text
1051 The file name and line number are derived as for warning
1052 messages. The actual message text may be rather less explanatory
1053 because many of them aren't supposed to happen.
1056 @chapter Command-Line Options
1058 @cindex options, all versions of assembler
1059 This chapter describes command-line options available in @emph{all}
1060 versions of the @sc{gnu} assembler; @pxref{Machine Dependencies}, for options specific
1062 to the @value{TARGET}.
1065 to particular machine architectures.
1068 If you are invoking @code{@value{AS}} via the @sc{gnu} C compiler (version 2),
1069 you can use the @samp{-Wa} option to pass arguments through to the assembler.
1070 The assembler arguments must be separated from each other (and the @samp{-Wa})
1071 by commas. For example:
1074 gcc -c -g -O -Wa,-alh,-L file.c
1078 This passes two options to the assembler: @samp{-alh} (emit a listing to
1079 standard output with with high-level and assembly source) and @samp{-L} (retain
1080 local symbols in the symbol table).
1082 Usually you do not need to use this @samp{-Wa} mechanism, since many compiler
1083 command-line options are automatically passed to the assembler by the compiler.
1084 (You can call the @sc{gnu} compiler driver with the @samp{-v} option to see
1085 precisely what options it passes to each compilation pass, including the
1089 * a:: -a[cdhlns] enable listings
1090 * D:: -D for compatibility
1091 * f:: -f to work faster
1092 * I:: -I for .include search path
1093 @ifclear DIFF-TBL-KLUGE
1094 * K:: -K for compatibility
1096 @ifset DIFF-TBL-KLUGE
1097 * K:: -K for difference tables
1100 * L:: -L to retain local labels
1101 * M:: -M or --mri to assemble in MRI compatibility mode
1102 * MD:: --MD for dependency tracking
1103 * o:: -o to name the object file
1104 * R:: -R to join data and text sections
1105 * statistics:: --statistics to see statistics about assembly
1106 * traditional-format:: --traditional-format for compatible output
1107 * v:: -v to announce version
1108 * W:: -W, --no-warn, --warn, --fatal-warnings to control warnings
1109 * Z:: -Z to make object file even after errors
1113 @section Enable Listings: @code{-a[cdhlns]}
1122 @cindex listings, enabling
1123 @cindex assembly listings, enabling
1125 These options enable listing output from the assembler. By itself,
1126 @samp{-a} requests high-level, assembly, and symbols listing.
1127 You can use other letters to select specific options for the list:
1128 @samp{-ah} requests a high-level language listing,
1129 @samp{-al} requests an output-program assembly listing, and
1130 @samp{-as} requests a symbol table listing.
1131 High-level listings require that a compiler debugging option like
1132 @samp{-g} be used, and that assembly listings (@samp{-al}) be requested
1135 Use the @samp{-ac} option to omit false conditionals from a listing. Any lines
1136 which are not assembled because of a false @code{.if} (or @code{.ifdef}, or any
1137 other conditional), or a true @code{.if} followed by an @code{.else}, will be
1138 omitted from the listing.
1140 Use the @samp{-ad} option to omit debugging directives from the
1143 Once you have specified one of these options, you can further control
1144 listing output and its appearance using the directives @code{.list},
1145 @code{.nolist}, @code{.psize}, @code{.eject}, @code{.title}, and
1147 The @samp{-an} option turns off all forms processing.
1148 If you do not request listing output with one of the @samp{-a} options, the
1149 listing-control directives have no effect.
1151 The letters after @samp{-a} may be combined into one option,
1152 @emph{e.g.}, @samp{-aln}.
1158 This option has no effect whatsoever, but it is accepted to make it more
1159 likely that scripts written for other assemblers also work with
1163 @section Work Faster: @code{-f}
1166 @cindex trusted compiler
1167 @cindex faster processing (@code{-f})
1168 @samp{-f} should only be used when assembling programs written by a
1169 (trusted) compiler. @samp{-f} stops the assembler from doing whitespace
1170 and comment preprocessing on
1171 the input file(s) before assembling them. @xref{Preprocessing,
1175 @emph{Warning:} if you use @samp{-f} when the files actually need to be
1176 preprocessed (if they contain comments, for example), @code{@value{AS}} does
1181 @section @code{.include} search path: @code{-I} @var{path}
1183 @kindex -I @var{path}
1184 @cindex paths for @code{.include}
1185 @cindex search path for @code{.include}
1186 @cindex @code{include} directive search path
1187 Use this option to add a @var{path} to the list of directories
1188 @code{@value{AS}} searches for files specified in @code{.include}
1189 directives (@pxref{Include,,@code{.include}}). You may use @code{-I} as
1190 many times as necessary to include a variety of paths. The current
1191 working directory is always searched first; after that, @code{@value{AS}}
1192 searches any @samp{-I} directories in the same order as they were
1193 specified (left to right) on the command line.
1196 @section Difference Tables: @code{-K}
1199 @ifclear DIFF-TBL-KLUGE
1200 On the @value{TARGET} family, this option is allowed, but has no effect. It is
1201 permitted for compatibility with the @sc{gnu} assembler on other platforms,
1202 where it can be used to warn when the assembler alters the machine code
1203 generated for @samp{.word} directives in difference tables. The @value{TARGET}
1204 family does not have the addressing limitations that sometimes lead to this
1205 alteration on other platforms.
1208 @ifset DIFF-TBL-KLUGE
1209 @cindex difference tables, warning
1210 @cindex warning for altered difference tables
1211 @code{@value{AS}} sometimes alters the code emitted for directives of the form
1212 @samp{.word @var{sym1}-@var{sym2}}; @pxref{Word,,@code{.word}}.
1213 You can use the @samp{-K} option if you want a warning issued when this
1218 @section Include Local Labels: @code{-L}
1221 @cindex local labels, retaining in output
1222 Labels beginning with @samp{L} (upper case only) are called @dfn{local
1223 labels}. @xref{Symbol Names}. Normally you do not see such labels when
1224 debugging, because they are intended for the use of programs (like
1225 compilers) that compose assembler programs, not for your notice.
1226 Normally both @code{@value{AS}} and @code{@value{LD}} discard such labels, so you do not
1227 normally debug with them.
1229 This option tells @code{@value{AS}} to retain those @samp{L@dots{}} symbols
1230 in the object file. Usually if you do this you also tell the linker
1231 @code{@value{LD}} to preserve symbols whose names begin with @samp{L}.
1233 By default, a local label is any label beginning with @samp{L}, but each
1234 target is allowed to redefine the local label prefix.
1236 On the HPPA local labels begin with @samp{L$}.
1240 @section Assemble in MRI Compatibility Mode: @code{-M}
1243 @cindex MRI compatibility mode
1244 The @code{-M} or @code{--mri} option selects MRI compatibility mode. This
1245 changes the syntax and pseudo-op handling of @code{@value{AS}} to make it
1246 compatible with the @code{ASM68K} or the @code{ASM960} (depending upon the
1247 configured target) assembler from Microtec Research. The exact nature of the
1248 MRI syntax will not be documented here; see the MRI manuals for more
1249 information. Note in particular that the handling of macros and macro
1250 arguments is somewhat different. The purpose of this option is to permit
1251 assembling existing MRI assembler code using @code{@value{AS}}.
1253 The MRI compatibility is not complete. Certain operations of the MRI assembler
1254 depend upon its object file format, and can not be supported using other object
1255 file formats. Supporting these would require enhancing each object file format
1256 individually. These are:
1259 @item global symbols in common section
1261 The m68k MRI assembler supports common sections which are merged by the linker.
1262 Other object file formats do not support this. @code{@value{AS}} handles
1263 common sections by treating them as a single common symbol. It permits local
1264 symbols to be defined within a common section, but it can not support global
1265 symbols, since it has no way to describe them.
1267 @item complex relocations
1269 The MRI assemblers support relocations against a negated section address, and
1270 relocations which combine the start addresses of two or more sections. These
1271 are not support by other object file formats.
1273 @item @code{END} pseudo-op specifying start address
1275 The MRI @code{END} pseudo-op permits the specification of a start address.
1276 This is not supported by other object file formats. The start address may
1277 instead be specified using the @code{-e} option to the linker, or in a linker
1280 @item @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops
1282 The MRI @code{IDNT}, @code{.ident} and @code{NAME} pseudo-ops assign a module
1283 name to the output file. This is not supported by other object file formats.
1285 @item @code{ORG} pseudo-op
1287 The m68k MRI @code{ORG} pseudo-op begins an absolute section at a given
1288 address. This differs from the usual @code{@value{AS}} @code{.org} pseudo-op,
1289 which changes the location within the current section. Absolute sections are
1290 not supported by other object file formats. The address of a section may be
1291 assigned within a linker script.
1294 There are some other features of the MRI assembler which are not supported by
1295 @code{@value{AS}}, typically either because they are difficult or because they
1296 seem of little consequence. Some of these may be supported in future releases.
1300 @item EBCDIC strings
1302 EBCDIC strings are not supported.
1304 @item packed binary coded decimal
1306 Packed binary coded decimal is not supported. This means that the @code{DC.P}
1307 and @code{DCB.P} pseudo-ops are not supported.
1309 @item @code{FEQU} pseudo-op
1311 The m68k @code{FEQU} pseudo-op is not supported.
1313 @item @code{NOOBJ} pseudo-op
1315 The m68k @code{NOOBJ} pseudo-op is not supported.
1317 @item @code{OPT} branch control options
1319 The m68k @code{OPT} branch control options---@code{B}, @code{BRS}, @code{BRB},
1320 @code{BRL}, and @code{BRW}---are ignored. @code{@value{AS}} automatically
1321 relaxes all branches, whether forward or backward, to an appropriate size, so
1322 these options serve no purpose.
1324 @item @code{OPT} list control options
1326 The following m68k @code{OPT} list control options are ignored: @code{C},
1327 @code{CEX}, @code{CL}, @code{CRE}, @code{E}, @code{G}, @code{I}, @code{M},
1328 @code{MEX}, @code{MC}, @code{MD}, @code{X}.
1330 @item other @code{OPT} options
1332 The following m68k @code{OPT} options are ignored: @code{NEST}, @code{O},
1333 @code{OLD}, @code{OP}, @code{P}, @code{PCO}, @code{PCR}, @code{PCS}, @code{R}.
1335 @item @code{OPT} @code{D} option is default
1337 The m68k @code{OPT} @code{D} option is the default, unlike the MRI assembler.
1338 @code{OPT NOD} may be used to turn it off.
1340 @item @code{XREF} pseudo-op.
1342 The m68k @code{XREF} pseudo-op is ignored.
1344 @item @code{.debug} pseudo-op
1346 The i960 @code{.debug} pseudo-op is not supported.
1348 @item @code{.extended} pseudo-op
1350 The i960 @code{.extended} pseudo-op is not supported.
1352 @item @code{.list} pseudo-op.
1354 The various options of the i960 @code{.list} pseudo-op are not supported.
1356 @item @code{.optimize} pseudo-op
1358 The i960 @code{.optimize} pseudo-op is not supported.
1360 @item @code{.output} pseudo-op
1362 The i960 @code{.output} pseudo-op is not supported.
1364 @item @code{.setreal} pseudo-op
1366 The i960 @code{.setreal} pseudo-op is not supported.
1371 @section Dependency tracking: @code{--MD}
1374 @cindex dependency tracking
1377 @code{@value{AS}} can generate a dependency file for the file it creates. This
1378 file consists of a single rule suitable for @code{make} describing the
1379 dependencies of the main source file.
1381 The rule is written to the file named in its argument.
1383 This feature is used in the automatic updating of makefiles.
1386 @section Name the Object File: @code{-o}
1389 @cindex naming object file
1390 @cindex object file name
1391 There is always one object file output when you run @code{@value{AS}}. By
1392 default it has the name
1395 @file{a.out} (or @file{b.out}, for Intel 960 targets only).
1409 You use this option (which takes exactly one filename) to give the
1410 object file a different name.
1412 Whatever the object file is called, @code{@value{AS}} overwrites any
1413 existing file of the same name.
1416 @section Join Data and Text Sections: @code{-R}
1419 @cindex data and text sections, joining
1420 @cindex text and data sections, joining
1421 @cindex joining text and data sections
1422 @cindex merging text and data sections
1423 @code{-R} tells @code{@value{AS}} to write the object file as if all
1424 data-section data lives in the text section. This is only done at
1425 the very last moment: your binary data are the same, but data
1426 section parts are relocated differently. The data section part of
1427 your object file is zero bytes long because all its bytes are
1428 appended to the text section. (@xref{Sections,,Sections and Relocation}.)
1430 When you specify @code{-R} it would be possible to generate shorter
1431 address displacements (because we do not have to cross between text and
1432 data section). We refrain from doing this simply for compatibility with
1433 older versions of @code{@value{AS}}. In future, @code{-R} may work this way.
1436 When @code{@value{AS}} is configured for COFF output,
1437 this option is only useful if you use sections named @samp{.text} and
1442 @code{-R} is not supported for any of the HPPA targets. Using
1443 @code{-R} generates a warning from @code{@value{AS}}.
1447 @section Display Assembly Statistics: @code{--statistics}
1449 @kindex --statistics
1450 @cindex statistics, about assembly
1451 @cindex time, total for assembly
1452 @cindex space used, maximum for assembly
1453 Use @samp{--statistics} to display two statistics about the resources used by
1454 @code{@value{AS}}: the maximum amount of space allocated during the assembly
1455 (in bytes), and the total execution time taken for the assembly (in @sc{cpu}
1458 @node traditional-format
1459 @section Compatible output: @code{--traditional-format}
1461 @kindex --traditional-format
1462 For some targets, the output of @code{@value{AS}} is different in some ways
1463 from the output of some existing assembler. This switch requests
1464 @code{@value{AS}} to use the traditional format instead.
1466 For example, it disables the exception frame optimizations which
1467 @code{@value{AS}} normally does by default on @code{@value{GCC}} output.
1470 @section Announce Version: @code{-v}
1474 @cindex assembler version
1475 @cindex version of assembler
1476 You can find out what version of as is running by including the
1477 option @samp{-v} (which you can also spell as @samp{-version}) on the
1481 @section Control Warnings: @code{-W}, @code{--warn}, @code{--no-warn}, @code{--fatal-warnings}
1483 @code{@value{AS}} should never give a warning or error message when
1484 assembling compiler output. But programs written by people often
1485 cause @code{@value{AS}} to give a warning that a particular assumption was
1486 made. All such warnings are directed to the standard error file.
1489 @kindex @samp{--no-warn}
1490 @cindex suppressing warnings
1491 @cindex warnings, suppressing
1492 If you use the @code{-W} and @code{--no-warn} options, no warnings are issued.
1493 This only affects the warning messages: it does not change any particular of
1494 how @code{@value{AS}} assembles your file. Errors, which stop the assembly,
1497 @kindex @samp{--fatal-warnings}
1498 @cindex errors, caused by warnings
1499 @cindex warnings, causing error
1500 If you use the @code{--fatal-warnings} option, @code{@value{AS}} considers
1501 files that generate warnings to be in error.
1503 @kindex @samp{--warn}
1504 @cindex warnings, switching on
1505 You can switch these options off again by specifying @code{--warn}, which
1506 causes warnings to be output as usual.
1509 @section Generate Object File in Spite of Errors: @code{-Z}
1510 @cindex object file, after errors
1511 @cindex errors, continuing after
1512 After an error message, @code{@value{AS}} normally produces no output. If for
1513 some reason you are interested in object file output even after
1514 @code{@value{AS}} gives an error message on your program, use the @samp{-Z}
1515 option. If there are any errors, @code{@value{AS}} continues anyways, and
1516 writes an object file after a final warning message of the form @samp{@var{n}
1517 errors, @var{m} warnings, generating bad object file.}
1522 @cindex machine-independent syntax
1523 @cindex syntax, machine-independent
1524 This chapter describes the machine-independent syntax allowed in a
1525 source file. @code{@value{AS}} syntax is similar to what many other
1526 assemblers use; it is inspired by the BSD 4.2
1531 assembler, except that @code{@value{AS}} does not assemble Vax bit-fields.
1535 * Preprocessing:: Preprocessing
1536 * Whitespace:: Whitespace
1537 * Comments:: Comments
1538 * Symbol Intro:: Symbols
1539 * Statements:: Statements
1540 * Constants:: Constants
1544 @section Preprocessing
1546 @cindex preprocessing
1547 The @code{@value{AS}} internal preprocessor:
1549 @cindex whitespace, removed by preprocessor
1551 adjusts and removes extra whitespace. It leaves one space or tab before
1552 the keywords on a line, and turns any other whitespace on the line into
1555 @cindex comments, removed by preprocessor
1557 removes all comments, replacing them with a single space, or an
1558 appropriate number of newlines.
1560 @cindex constants, converted by preprocessor
1562 converts character constants into the appropriate numeric values.
1565 It does not do macro processing, include file handling, or
1566 anything else you may get from your C compiler's preprocessor. You can
1567 do include file processing with the @code{.include} directive
1568 (@pxref{Include,,@code{.include}}). You can use the @sc{gnu} C compiler driver
1569 to get other ``CPP'' style preprocessing, by giving the input file a
1570 @samp{.S} suffix. @xref{Overall Options,, Options Controlling the Kind of
1571 Output, gcc.info, Using GNU CC}.
1573 Excess whitespace, comments, and character constants
1574 cannot be used in the portions of the input text that are not
1577 @cindex turning preprocessing on and off
1578 @cindex preprocessing, turning on and off
1581 If the first line of an input file is @code{#NO_APP} or if you use the
1582 @samp{-f} option, whitespace and comments are not removed from the input file.
1583 Within an input file, you can ask for whitespace and comment removal in
1584 specific portions of the by putting a line that says @code{#APP} before the
1585 text that may contain whitespace or comments, and putting a line that says
1586 @code{#NO_APP} after this text. This feature is mainly intend to support
1587 @code{asm} statements in compilers whose output is otherwise free of comments
1594 @dfn{Whitespace} is one or more blanks or tabs, in any order.
1595 Whitespace is used to separate symbols, and to make programs neater for
1596 people to read. Unless within character constants
1597 (@pxref{Characters,,Character Constants}), any whitespace means the same
1598 as exactly one space.
1604 There are two ways of rendering comments to @code{@value{AS}}. In both
1605 cases the comment is equivalent to one space.
1607 Anything from @samp{/*} through the next @samp{*/} is a comment.
1608 This means you may not nest these comments.
1612 The only way to include a newline ('\n') in a comment
1613 is to use this sort of comment.
1616 /* This sort of comment does not nest. */
1619 @cindex line comment character
1620 Anything from the @dfn{line comment} character to the next newline
1621 is considered a comment and is ignored. The line comment character is
1623 @samp{;} for the AMD 29K family;
1626 @samp{;} on the ARC;
1629 @samp{@@} on the ARM;
1632 @samp{;} for the H8/300 family;
1635 @samp{!} for the H8/500 family;
1638 @samp{;} for the HPPA;
1641 @samp{#} on the i960;
1644 @samp{;} for picoJava;
1647 @samp{!} for the Hitachi SH;
1650 @samp{!} on the SPARC;
1653 @samp{#} on the m32r;
1656 @samp{|} on the 680x0;
1659 @samp{#} on the 68HC11 and 68HC12;
1662 @samp{#} on the Vax;
1665 @samp{!} for the Z8000;
1668 @samp{#} on the V850;
1670 see @ref{Machine Dependencies}. @refill
1671 @c FIXME What about i386, m88k, i860?
1674 On some machines there are two different line comment characters. One
1675 character only begins a comment if it is the first non-whitespace character on
1676 a line, while the other always begins a comment.
1680 The V850 assembler also supports a double dash as starting a comment that
1681 extends to the end of the line.
1687 @cindex lines starting with @code{#}
1688 @cindex logical line numbers
1689 To be compatible with past assemblers, lines that begin with @samp{#} have a
1690 special interpretation. Following the @samp{#} should be an absolute
1691 expression (@pxref{Expressions}): the logical line number of the @emph{next}
1692 line. Then a string (@pxref{Strings,, Strings}) is allowed: if present it is a
1693 new logical file name. The rest of the line, if any, should be whitespace.
1695 If the first non-whitespace characters on the line are not numeric,
1696 the line is ignored. (Just like a comment.)
1699 # This is an ordinary comment.
1700 # 42-6 "new_file_name" # New logical file name
1701 # This is logical line # 36.
1703 This feature is deprecated, and may disappear from future versions
1704 of @code{@value{AS}}.
1709 @cindex characters used in symbols
1710 @ifclear SPECIAL-SYMS
1711 A @dfn{symbol} is one or more characters chosen from the set of all
1712 letters (both upper and lower case), digits and the three characters
1718 A @dfn{symbol} is one or more characters chosen from the set of all
1719 letters (both upper and lower case), digits and the three characters
1720 @samp{._$}. (Save that, on the H8/300 only, you may not use @samp{$} in
1726 On most machines, you can also use @code{$} in symbol names; exceptions
1727 are noted in @ref{Machine Dependencies}.
1729 No symbol may begin with a digit. Case is significant.
1730 There is no length limit: all characters are significant. Symbols are
1731 delimited by characters not in that set, or by the beginning of a file
1732 (since the source program must end with a newline, the end of a file is
1733 not a possible symbol delimiter). @xref{Symbols}.
1734 @cindex length of symbols
1739 @cindex statements, structure of
1740 @cindex line separator character
1741 @cindex statement separator character
1743 @ifclear abnormal-separator
1744 A @dfn{statement} ends at a newline character (@samp{\n}) or at a
1745 semicolon (@samp{;}). The newline or semicolon is considered part of
1746 the preceding statement. Newlines and semicolons within character
1747 constants are an exception: they do not end statements.
1749 @ifset abnormal-separator
1751 A @dfn{statement} ends at a newline character (@samp{\n}) or an ``at''
1752 sign (@samp{@@}). The newline or at sign is considered part of the
1753 preceding statement. Newlines and at signs within character constants
1754 are an exception: they do not end statements.
1757 A @dfn{statement} ends at a newline character (@samp{\n}) or an exclamation
1758 point (@samp{!}). The newline or exclamation point is considered part of the
1759 preceding statement. Newlines and exclamation points within character
1760 constants are an exception: they do not end statements.
1763 A @dfn{statement} ends at a newline character (@samp{\n}); or (for the
1764 H8/300) a dollar sign (@samp{$}); or (for the
1767 (@samp{;}). The newline or separator character is considered part of
1768 the preceding statement. Newlines and separators within character
1769 constants are an exception: they do not end statements.
1774 A @dfn{statement} ends at a newline character (@samp{\n}) or line
1775 separator character. (The line separator is usually @samp{;}, unless
1776 this conflicts with the comment character; @pxref{Machine Dependencies}.) The
1777 newline or separator character is considered part of the preceding
1778 statement. Newlines and separators within character constants are an
1779 exception: they do not end statements.
1782 @cindex newline, required at file end
1783 @cindex EOF, newline must precede
1784 It is an error to end any statement with end-of-file: the last
1785 character of any input file should be a newline.@refill
1787 An empty statement is allowed, and may include whitespace. It is ignored.
1789 @cindex instructions and directives
1790 @cindex directives and instructions
1791 @c "key symbol" is not used elsewhere in the document; seems pedantic to
1792 @c @defn{} it in that case, as was done previously... doc@cygnus.com,
1794 A statement begins with zero or more labels, optionally followed by a
1795 key symbol which determines what kind of statement it is. The key
1796 symbol determines the syntax of the rest of the statement. If the
1797 symbol begins with a dot @samp{.} then the statement is an assembler
1798 directive: typically valid for any computer. If the symbol begins with
1799 a letter the statement is an assembly language @dfn{instruction}: it
1800 assembles into a machine language instruction.
1802 Different versions of @code{@value{AS}} for different computers
1803 recognize different instructions. In fact, the same symbol may
1804 represent a different instruction in a different computer's assembly
1808 @cindex @code{:} (label)
1809 @cindex label (@code{:})
1810 A label is a symbol immediately followed by a colon (@code{:}).
1811 Whitespace before a label or after a colon is permitted, but you may not
1812 have whitespace between a label's symbol and its colon. @xref{Labels}.
1815 For HPPA targets, labels need not be immediately followed by a colon, but
1816 the definition of a label must begin in column zero. This also implies that
1817 only one label may be defined on each line.
1821 label: .directive followed by something
1822 another_label: # This is an empty statement.
1823 instruction operand_1, operand_2, @dots{}
1830 A constant is a number, written so that its value is known by
1831 inspection, without knowing any context. Like this:
1834 .byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
1835 .ascii "Ring the bell\7" # A string constant.
1836 .octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
1837 .float 0f-314159265358979323846264338327\
1838 95028841971.693993751E-40 # - pi, a flonum.
1843 * Characters:: Character Constants
1844 * Numbers:: Number Constants
1848 @subsection Character Constants
1850 @cindex character constants
1851 @cindex constants, character
1852 There are two kinds of character constants. A @dfn{character} stands
1853 for one character in one byte and its value may be used in
1854 numeric expressions. String constants (properly called string
1855 @emph{literals}) are potentially many bytes and their values may not be
1856 used in arithmetic expressions.
1860 * Chars:: Characters
1864 @subsubsection Strings
1866 @cindex string constants
1867 @cindex constants, string
1868 A @dfn{string} is written between double-quotes. It may contain
1869 double-quotes or null characters. The way to get special characters
1870 into a string is to @dfn{escape} these characters: precede them with
1871 a backslash @samp{\} character. For example @samp{\\} represents
1872 one backslash: the first @code{\} is an escape which tells
1873 @code{@value{AS}} to interpret the second character literally as a backslash
1874 (which prevents @code{@value{AS}} from recognizing the second @code{\} as an
1875 escape character). The complete list of escapes follows.
1877 @cindex escape codes, character
1878 @cindex character escape codes
1881 @c Mnemonic for ACKnowledge; for ASCII this is octal code 007.
1883 @cindex @code{\b} (backspace character)
1884 @cindex backspace (@code{\b})
1886 Mnemonic for backspace; for ASCII this is octal code 010.
1889 @c Mnemonic for EOText; for ASCII this is octal code 004.
1891 @cindex @code{\f} (formfeed character)
1892 @cindex formfeed (@code{\f})
1894 Mnemonic for FormFeed; for ASCII this is octal code 014.
1896 @cindex @code{\n} (newline character)
1897 @cindex newline (@code{\n})
1899 Mnemonic for newline; for ASCII this is octal code 012.
1902 @c Mnemonic for prefix; for ASCII this is octal code 033, usually known as @code{escape}.
1904 @cindex @code{\r} (carriage return character)
1905 @cindex carriage return (@code{\r})
1907 Mnemonic for carriage-Return; for ASCII this is octal code 015.
1910 @c Mnemonic for space; for ASCII this is octal code 040. Included for compliance with
1911 @c other assemblers.
1913 @cindex @code{\t} (tab)
1914 @cindex tab (@code{\t})
1916 Mnemonic for horizontal Tab; for ASCII this is octal code 011.
1919 @c Mnemonic for Vertical tab; for ASCII this is octal code 013.
1920 @c @item \x @var{digit} @var{digit} @var{digit}
1921 @c A hexadecimal character code. The numeric code is 3 hexadecimal digits.
1923 @cindex @code{\@var{ddd}} (octal character code)
1924 @cindex octal character code (@code{\@var{ddd}})
1925 @item \ @var{digit} @var{digit} @var{digit}
1926 An octal character code. The numeric code is 3 octal digits.
1927 For compatibility with other Unix systems, 8 and 9 are accepted as digits:
1928 for example, @code{\008} has the value 010, and @code{\009} the value 011.
1930 @cindex @code{\@var{xd...}} (hex character code)
1931 @cindex hex character code (@code{\@var{xd...}})
1932 @item \@code{x} @var{hex-digits...}
1933 A hex character code. All trailing hex digits are combined. Either upper or
1934 lower case @code{x} works.
1936 @cindex @code{\\} (@samp{\} character)
1937 @cindex backslash (@code{\\})
1939 Represents one @samp{\} character.
1942 @c Represents one @samp{'} (accent acute) character.
1943 @c This is needed in single character literals
1944 @c (@xref{Characters,,Character Constants}.) to represent
1947 @cindex @code{\"} (doublequote character)
1948 @cindex doublequote (@code{\"})
1950 Represents one @samp{"} character. Needed in strings to represent
1951 this character, because an unescaped @samp{"} would end the string.
1953 @item \ @var{anything-else}
1954 Any other character when escaped by @kbd{\} gives a warning, but
1955 assembles as if the @samp{\} was not present. The idea is that if
1956 you used an escape sequence you clearly didn't want the literal
1957 interpretation of the following character. However @code{@value{AS}} has no
1958 other interpretation, so @code{@value{AS}} knows it is giving you the wrong
1959 code and warns you of the fact.
1962 Which characters are escapable, and what those escapes represent,
1963 varies widely among assemblers. The current set is what we think
1964 the BSD 4.2 assembler recognizes, and is a subset of what most C
1965 compilers recognize. If you are in doubt, do not use an escape
1969 @subsubsection Characters
1971 @cindex single character constant
1972 @cindex character, single
1973 @cindex constant, single character
1974 A single character may be written as a single quote immediately
1975 followed by that character. The same escapes apply to characters as
1976 to strings. So if you want to write the character backslash, you
1977 must write @kbd{'\\} where the first @code{\} escapes the second
1978 @code{\}. As you can see, the quote is an acute accent, not a
1979 grave accent. A newline
1981 @ifclear abnormal-separator
1982 (or semicolon @samp{;})
1984 @ifset abnormal-separator
1986 (or at sign @samp{@@})
1989 (or dollar sign @samp{$}, for the H8/300; or semicolon @samp{;} for the
1995 immediately following an acute accent is taken as a literal character
1996 and does not count as the end of a statement. The value of a character
1997 constant in a numeric expression is the machine's byte-wide code for
1998 that character. @code{@value{AS}} assumes your character code is ASCII:
1999 @kbd{'A} means 65, @kbd{'B} means 66, and so on. @refill
2002 @subsection Number Constants
2004 @cindex constants, number
2005 @cindex number constants
2006 @code{@value{AS}} distinguishes three kinds of numbers according to how they
2007 are stored in the target machine. @emph{Integers} are numbers that
2008 would fit into an @code{int} in the C language. @emph{Bignums} are
2009 integers, but they are stored in more than 32 bits. @emph{Flonums}
2010 are floating point numbers, described below.
2013 * Integers:: Integers
2018 * Bit Fields:: Bit Fields
2024 @subsubsection Integers
2026 @cindex constants, integer
2028 @cindex binary integers
2029 @cindex integers, binary
2030 A binary integer is @samp{0b} or @samp{0B} followed by zero or more of
2031 the binary digits @samp{01}.
2033 @cindex octal integers
2034 @cindex integers, octal
2035 An octal integer is @samp{0} followed by zero or more of the octal
2036 digits (@samp{01234567}).
2038 @cindex decimal integers
2039 @cindex integers, decimal
2040 A decimal integer starts with a non-zero digit followed by zero or
2041 more digits (@samp{0123456789}).
2043 @cindex hexadecimal integers
2044 @cindex integers, hexadecimal
2045 A hexadecimal integer is @samp{0x} or @samp{0X} followed by one or
2046 more hexadecimal digits chosen from @samp{0123456789abcdefABCDEF}.
2048 Integers have the usual values. To denote a negative integer, use
2049 the prefix operator @samp{-} discussed under expressions
2050 (@pxref{Prefix Ops,,Prefix Operators}).
2053 @subsubsection Bignums
2056 @cindex constants, bignum
2057 A @dfn{bignum} has the same syntax and semantics as an integer
2058 except that the number (or its negative) takes more than 32 bits to
2059 represent in binary. The distinction is made because in some places
2060 integers are permitted while bignums are not.
2063 @subsubsection Flonums
2065 @cindex floating point numbers
2066 @cindex constants, floating point
2068 @cindex precision, floating point
2069 A @dfn{flonum} represents a floating point number. The translation is
2070 indirect: a decimal floating point number from the text is converted by
2071 @code{@value{AS}} to a generic binary floating point number of more than
2072 sufficient precision. This generic floating point number is converted
2073 to a particular computer's floating point format (or formats) by a
2074 portion of @code{@value{AS}} specialized to that computer.
2076 A flonum is written by writing (in order)
2081 (@samp{0} is optional on the HPPA.)
2085 A letter, to tell @code{@value{AS}} the rest of the number is a flonum.
2087 @kbd{e} is recommended. Case is not important.
2089 @c FIXME: verify if flonum syntax really this vague for most cases
2090 (Any otherwise illegal letter works here, but that might be changed. Vax BSD
2091 4.2 assembler seems to allow any of @samp{defghDEFGH}.)
2094 On the H8/300, H8/500,
2096 and AMD 29K architectures, the letter must be
2097 one of the letters @samp{DFPRSX} (in upper or lower case).
2099 On the ARC, the letter must be one of the letters @samp{DFRS}
2100 (in upper or lower case).
2102 On the Intel 960 architecture, the letter must be
2103 one of the letters @samp{DFT} (in upper or lower case).
2105 On the HPPA architecture, the letter must be @samp{E} (upper case only).
2109 One of the letters @samp{DFPRSX} (in upper or lower case).
2112 One of the letters @samp{DFRS} (in upper or lower case).
2115 One of the letters @samp{DFPRSX} (in upper or lower case).
2118 The letter @samp{E} (upper case only).
2121 One of the letters @samp{DFT} (in upper or lower case).
2126 An optional sign: either @samp{+} or @samp{-}.
2129 An optional @dfn{integer part}: zero or more decimal digits.
2132 An optional @dfn{fractional part}: @samp{.} followed by zero
2133 or more decimal digits.
2136 An optional exponent, consisting of:
2140 An @samp{E} or @samp{e}.
2141 @c I can't find a config where "EXP_CHARS" is other than 'eE', but in
2142 @c principle this can perfectly well be different on different targets.
2144 Optional sign: either @samp{+} or @samp{-}.
2146 One or more decimal digits.
2151 At least one of the integer part or the fractional part must be
2152 present. The floating point number has the usual base-10 value.
2154 @code{@value{AS}} does all processing using integers. Flonums are computed
2155 independently of any floating point hardware in the computer running
2160 @c Bit fields are written as a general facility but are also controlled
2161 @c by a conditional-compilation flag---which is as of now (21mar91)
2162 @c turned on only by the i960 config of GAS.
2164 @subsubsection Bit Fields
2167 @cindex constants, bit field
2168 You can also define numeric constants as @dfn{bit fields}.
2169 specify two numbers separated by a colon---
2171 @var{mask}:@var{value}
2174 @code{@value{AS}} applies a bitwise @sc{and} between @var{mask} and
2177 The resulting number is then packed
2179 @c this conditional paren in case bit fields turned on elsewhere than 960
2180 (in host-dependent byte order)
2182 into a field whose width depends on which assembler directive has the
2183 bit-field as its argument. Overflow (a result from the bitwise and
2184 requiring more binary digits to represent) is not an error; instead,
2185 more constants are generated, of the specified width, beginning with the
2186 least significant digits.@refill
2188 The directives @code{.byte}, @code{.hword}, @code{.int}, @code{.long},
2189 @code{.short}, and @code{.word} accept bit-field arguments.
2194 @chapter Sections and Relocation
2199 * Secs Background:: Background
2200 * Ld Sections:: Linker Sections
2201 * As Sections:: Assembler Internal Sections
2202 * Sub-Sections:: Sub-Sections
2206 @node Secs Background
2209 Roughly, a section is a range of addresses, with no gaps; all data
2210 ``in'' those addresses is treated the same for some particular purpose.
2211 For example there may be a ``read only'' section.
2213 @cindex linker, and assembler
2214 @cindex assembler, and linker
2215 The linker @code{@value{LD}} reads many object files (partial programs) and
2216 combines their contents to form a runnable program. When @code{@value{AS}}
2217 emits an object file, the partial program is assumed to start at address 0.
2218 @code{@value{LD}} assigns the final addresses for the partial program, so that
2219 different partial programs do not overlap. This is actually an
2220 oversimplification, but it suffices to explain how @code{@value{AS}} uses
2223 @code{@value{LD}} moves blocks of bytes of your program to their run-time
2224 addresses. These blocks slide to their run-time addresses as rigid
2225 units; their length does not change and neither does the order of bytes
2226 within them. Such a rigid unit is called a @emph{section}. Assigning
2227 run-time addresses to sections is called @dfn{relocation}. It includes
2228 the task of adjusting mentions of object-file addresses so they refer to
2229 the proper run-time addresses.
2231 For the H8/300 and H8/500,
2232 and for the Hitachi SH,
2233 @code{@value{AS}} pads sections if needed to
2234 ensure they end on a word (sixteen bit) boundary.
2237 @cindex standard assembler sections
2238 An object file written by @code{@value{AS}} has at least three sections, any
2239 of which may be empty. These are named @dfn{text}, @dfn{data} and
2244 When it generates COFF output,
2246 @code{@value{AS}} can also generate whatever other named sections you specify
2247 using the @samp{.section} directive (@pxref{Section,,@code{.section}}).
2248 If you do not use any directives that place output in the @samp{.text}
2249 or @samp{.data} sections, these sections still exist, but are empty.
2254 When @code{@value{AS}} generates SOM or ELF output for the HPPA,
2256 @code{@value{AS}} can also generate whatever other named sections you
2257 specify using the @samp{.space} and @samp{.subspace} directives. See
2258 @cite{HP9000 Series 800 Assembly Language Reference Manual}
2259 (HP 92432-90001) for details on the @samp{.space} and @samp{.subspace}
2260 assembler directives.
2263 Additionally, @code{@value{AS}} uses different names for the standard
2264 text, data, and bss sections when generating SOM output. Program text
2265 is placed into the @samp{$CODE$} section, data into @samp{$DATA$}, and
2266 BSS into @samp{$BSS$}.
2270 Within the object file, the text section starts at address @code{0}, the
2271 data section follows, and the bss section follows the data section.
2274 When generating either SOM or ELF output files on the HPPA, the text
2275 section starts at address @code{0}, the data section at address
2276 @code{0x4000000}, and the bss section follows the data section.
2279 To let @code{@value{LD}} know which data changes when the sections are
2280 relocated, and how to change that data, @code{@value{AS}} also writes to the
2281 object file details of the relocation needed. To perform relocation
2282 @code{@value{LD}} must know, each time an address in the object
2286 Where in the object file is the beginning of this reference to
2289 How long (in bytes) is this reference?
2291 Which section does the address refer to? What is the numeric value of
2293 (@var{address}) @minus{} (@var{start-address of section})?
2296 Is the reference to an address ``Program-Counter relative''?
2299 @cindex addresses, format of
2300 @cindex section-relative addressing
2301 In fact, every address @code{@value{AS}} ever uses is expressed as
2303 (@var{section}) + (@var{offset into section})
2306 Further, most expressions @code{@value{AS}} computes have this section-relative
2309 (For some object formats, such as SOM for the HPPA, some expressions are
2310 symbol-relative instead.)
2313 In this manual we use the notation @{@var{secname} @var{N}@} to mean ``offset
2314 @var{N} into section @var{secname}.''
2316 Apart from text, data and bss sections you need to know about the
2317 @dfn{absolute} section. When @code{@value{LD}} mixes partial programs,
2318 addresses in the absolute section remain unchanged. For example, address
2319 @code{@{absolute 0@}} is ``relocated'' to run-time address 0 by
2320 @code{@value{LD}}. Although the linker never arranges two partial programs'
2321 data sections with overlapping addresses after linking, @emph{by definition}
2322 their absolute sections must overlap. Address @code{@{absolute@ 239@}} in one
2323 part of a program is always the same address when the program is running as
2324 address @code{@{absolute@ 239@}} in any other part of the program.
2326 The idea of sections is extended to the @dfn{undefined} section. Any
2327 address whose section is unknown at assembly time is by definition
2328 rendered @{undefined @var{U}@}---where @var{U} is filled in later.
2329 Since numbers are always defined, the only way to generate an undefined
2330 address is to mention an undefined symbol. A reference to a named
2331 common block would be such a symbol: its value is unknown at assembly
2332 time so it has section @emph{undefined}.
2334 By analogy the word @emph{section} is used to describe groups of sections in
2335 the linked program. @code{@value{LD}} puts all partial programs' text
2336 sections in contiguous addresses in the linked program. It is
2337 customary to refer to the @emph{text section} of a program, meaning all
2338 the addresses of all partial programs' text sections. Likewise for
2339 data and bss sections.
2341 Some sections are manipulated by @code{@value{LD}}; others are invented for
2342 use of @code{@value{AS}} and have no meaning except during assembly.
2345 @section Linker Sections
2346 @code{@value{LD}} deals with just four kinds of sections, summarized below.
2351 @cindex named sections
2352 @cindex sections, named
2353 @item named sections
2356 @cindex text section
2357 @cindex data section
2361 These sections hold your program. @code{@value{AS}} and @code{@value{LD}} treat them as
2362 separate but equal sections. Anything you can say of one section is
2365 When the program is running, however, it is
2366 customary for the text section to be unalterable. The
2367 text section is often shared among processes: it contains
2368 instructions, constants and the like. The data section of a running
2369 program is usually alterable: for example, C variables would be stored
2370 in the data section.
2375 This section contains zeroed bytes when your program begins running. It
2376 is used to hold unitialized variables or common storage. The length of
2377 each partial program's bss section is important, but because it starts
2378 out containing zeroed bytes there is no need to store explicit zero
2379 bytes in the object file. The bss section was invented to eliminate
2380 those explicit zeros from object files.
2382 @cindex absolute section
2383 @item absolute section
2384 Address 0 of this section is always ``relocated'' to runtime address 0.
2385 This is useful if you want to refer to an address that @code{@value{LD}} must
2386 not change when relocating. In this sense we speak of absolute
2387 addresses being ``unrelocatable'': they do not change during relocation.
2389 @cindex undefined section
2390 @item undefined section
2391 This ``section'' is a catch-all for address references to objects not in
2392 the preceding sections.
2393 @c FIXME: ref to some other doc on obj-file formats could go here.
2396 @cindex relocation example
2397 An idealized example of three relocatable sections follows.
2399 The example uses the traditional section names @samp{.text} and @samp{.data}.
2401 Memory addresses are on the horizontal axis.
2405 @c END TEXI2ROFF-KILL
2408 partial program # 1: |ttttt|dddd|00|
2415 partial program # 2: |TTT|DDD|000|
2418 +--+---+-----+--+----+---+-----+~~
2419 linked program: | |TTT|ttttt| |dddd|DDD|00000|
2420 +--+---+-----+--+----+---+-----+~~
2422 addresses: 0 @dots{}
2429 \line{\it Partial program \#1: \hfil}
2430 \line{\ibox{2.5cm}{\tt text}\ibox{2cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2431 \line{\boxit{2.5cm}{\tt ttttt}\boxit{2cm}{\tt dddd}\boxit{1cm}{\tt 00}\hfil}
2433 \line{\it Partial program \#2: \hfil}
2434 \line{\ibox{1cm}{\tt text}\ibox{1.5cm}{\tt data}\ibox{1cm}{\tt bss}\hfil}
2435 \line{\boxit{1cm}{\tt TTT}\boxit{1.5cm}{\tt DDDD}\boxit{1cm}{\tt 000}\hfil}
2437 \line{\it linked program: \hfil}
2438 \line{\ibox{.5cm}{}\ibox{1cm}{\tt text}\ibox{2.5cm}{}\ibox{.75cm}{}\ibox{2cm}{\tt data}\ibox{1.5cm}{}\ibox{2cm}{\tt bss}\hfil}
2439 \line{\boxit{.5cm}{}\boxit{1cm}{\tt TTT}\boxit{2.5cm}{\tt
2440 ttttt}\boxit{.75cm}{}\boxit{2cm}{\tt dddd}\boxit{1.5cm}{\tt
2441 DDDD}\boxit{2cm}{\tt 00000}\ \dots\hfil}
2443 \line{\it addresses: \hfil}
2447 @c END TEXI2ROFF-KILL
2450 @section Assembler Internal Sections
2452 @cindex internal assembler sections
2453 @cindex sections in messages, internal
2454 These sections are meant only for the internal use of @code{@value{AS}}. They
2455 have no meaning at run-time. You do not really need to know about these
2456 sections for most purposes; but they can be mentioned in @code{@value{AS}}
2457 warning messages, so it might be helpful to have an idea of their
2458 meanings to @code{@value{AS}}. These sections are used to permit the
2459 value of every expression in your assembly language program to be a
2460 section-relative address.
2463 @cindex assembler internal logic error
2464 @item ASSEMBLER-INTERNAL-LOGIC-ERROR!
2465 An internal assembler logic error has been found. This means there is a
2466 bug in the assembler.
2468 @cindex expr (internal section)
2470 The assembler stores complex expression internally as combinations of
2471 symbols. When it needs to represent an expression as a symbol, it puts
2472 it in the expr section.
2474 @c FIXME item transfer[t] vector preload
2475 @c FIXME item transfer[t] vector postload
2476 @c FIXME item register
2480 @section Sub-Sections
2482 @cindex numbered subsections
2483 @cindex grouping data
2489 fall into two sections: text and data.
2491 You may have separate groups of
2493 data in named sections
2497 data in named sections
2503 that you want to end up near to each other in the object file, even though they
2504 are not contiguous in the assembler source. @code{@value{AS}} allows you to
2505 use @dfn{subsections} for this purpose. Within each section, there can be
2506 numbered subsections with values from 0 to 8192. Objects assembled into the
2507 same subsection go into the object file together with other objects in the same
2508 subsection. For example, a compiler might want to store constants in the text
2509 section, but might not want to have them interspersed with the program being
2510 assembled. In this case, the compiler could issue a @samp{.text 0} before each
2511 section of code being output, and a @samp{.text 1} before each group of
2512 constants being output.
2514 Subsections are optional. If you do not use subsections, everything
2515 goes in subsection number zero.
2518 Each subsection is zero-padded up to a multiple of four bytes.
2519 (Subsections may be padded a different amount on different flavors
2520 of @code{@value{AS}}.)
2524 On the H8/300 and H8/500 platforms, each subsection is zero-padded to a word
2525 boundary (two bytes).
2526 The same is true on the Hitachi SH.
2529 @c FIXME section padding (alignment)?
2530 @c Rich Pixley says padding here depends on target obj code format; that
2531 @c doesn't seem particularly useful to say without further elaboration,
2532 @c so for now I say nothing about it. If this is a generic BFD issue,
2533 @c these paragraphs might need to vanish from this manual, and be
2534 @c discussed in BFD chapter of binutils (or some such).
2537 On the AMD 29K family, no particular padding is added to section or
2538 subsection sizes; @value{AS} forces no alignment on this platform.
2542 Subsections appear in your object file in numeric order, lowest numbered
2543 to highest. (All this to be compatible with other people's assemblers.)
2544 The object file contains no representation of subsections; @code{@value{LD}} and
2545 other programs that manipulate object files see no trace of them.
2546 They just see all your text subsections as a text section, and all your
2547 data subsections as a data section.
2549 To specify which subsection you want subsequent statements assembled
2550 into, use a numeric argument to specify it, in a @samp{.text
2551 @var{expression}} or a @samp{.data @var{expression}} statement.
2554 When generating COFF output, you
2559 can also use an extra subsection
2560 argument with arbitrary named sections: @samp{.section @var{name},
2563 @var{Expression} should be an absolute expression.
2564 (@xref{Expressions}.) If you just say @samp{.text} then @samp{.text 0}
2565 is assumed. Likewise @samp{.data} means @samp{.data 0}. Assembly
2566 begins in @code{text 0}. For instance:
2568 .text 0 # The default subsection is text 0 anyway.
2569 .ascii "This lives in the first text subsection. *"
2571 .ascii "But this lives in the second text subsection."
2573 .ascii "This lives in the data section,"
2574 .ascii "in the first data subsection."
2576 .ascii "This lives in the first text section,"
2577 .ascii "immediately following the asterisk (*)."
2580 Each section has a @dfn{location counter} incremented by one for every byte
2581 assembled into that section. Because subsections are merely a convenience
2582 restricted to @code{@value{AS}} there is no concept of a subsection location
2583 counter. There is no way to directly manipulate a location counter---but the
2584 @code{.align} directive changes it, and any label definition captures its
2585 current value. The location counter of the section where statements are being
2586 assembled is said to be the @dfn{active} location counter.
2589 @section bss Section
2592 @cindex common variable storage
2593 The bss section is used for local common variable storage.
2594 You may allocate address space in the bss section, but you may
2595 not dictate data to load into it before your program executes. When
2596 your program starts running, all the contents of the bss
2597 section are zeroed bytes.
2599 The @code{.lcomm} pseudo-op defines a symbol in the bss section; see
2600 @ref{Lcomm,,@code{.lcomm}}.
2602 The @code{.comm} pseudo-op may be used to declare a common symbol, which is
2603 another form of uninitialized symbol; see @xref{Comm,,@code{.comm}}.
2606 When assembling for a target which supports multiple sections, such as ELF or
2607 COFF, you may switch into the @code{.bss} section and define symbols as usual;
2608 see @ref{Section,,@code{.section}}. You may only assemble zero values into the
2609 section. Typically the section will only contain symbol definitions and
2610 @code{.skip} directives (@pxref{Skip,,@code{.skip}}).
2617 Symbols are a central concept: the programmer uses symbols to name
2618 things, the linker uses symbols to link, and the debugger uses symbols
2622 @cindex debuggers, and symbol order
2623 @emph{Warning:} @code{@value{AS}} does not place symbols in the object file in
2624 the same order they were declared. This may break some debuggers.
2629 * Setting Symbols:: Giving Symbols Other Values
2630 * Symbol Names:: Symbol Names
2631 * Dot:: The Special Dot Symbol
2632 * Symbol Attributes:: Symbol Attributes
2639 A @dfn{label} is written as a symbol immediately followed by a colon
2640 @samp{:}. The symbol then represents the current value of the
2641 active location counter, and is, for example, a suitable instruction
2642 operand. You are warned if you use the same symbol to represent two
2643 different locations: the first definition overrides any other
2647 On the HPPA, the usual form for a label need not be immediately followed by a
2648 colon, but instead must start in column zero. Only one label may be defined on
2649 a single line. To work around this, the HPPA version of @code{@value{AS}} also
2650 provides a special directive @code{.label} for defining labels more flexibly.
2653 @node Setting Symbols
2654 @section Giving Symbols Other Values
2656 @cindex assigning values to symbols
2657 @cindex symbol values, assigning
2658 A symbol can be given an arbitrary value by writing a symbol, followed
2659 by an equals sign @samp{=}, followed by an expression
2660 (@pxref{Expressions}). This is equivalent to using the @code{.set}
2661 directive. @xref{Set,,@code{.set}}.
2664 @section Symbol Names
2666 @cindex symbol names
2667 @cindex names, symbol
2668 @ifclear SPECIAL-SYMS
2669 Symbol names begin with a letter or with one of @samp{._}. On most
2670 machines, you can also use @code{$} in symbol names; exceptions are
2671 noted in @ref{Machine Dependencies}. That character may be followed by any
2672 string of digits, letters, dollar signs (unless otherwise noted in
2673 @ref{Machine Dependencies}), and underscores.
2676 For the AMD 29K family, @samp{?} is also allowed in the
2677 body of a symbol name, though not at its beginning.
2682 Symbol names begin with a letter or with one of @samp{._}. On the
2684 H8/500, you can also use @code{$} in symbol names. That character may
2685 be followed by any string of digits, letters, dollar signs (save on the
2686 H8/300), and underscores.
2690 Case of letters is significant: @code{foo} is a different symbol name
2693 Each symbol has exactly one name. Each name in an assembly language program
2694 refers to exactly one symbol. You may use that symbol name any number of times
2697 @subheading Local Symbol Names
2699 @cindex local symbol names
2700 @cindex symbol names, local
2701 @cindex temporary symbol names
2702 @cindex symbol names, temporary
2703 Local symbols help compilers and programmers use names temporarily.
2704 There are ten local symbol names, which are re-used throughout the
2705 program. You may refer to them using the names @samp{0} @samp{1}
2706 @dots{} @samp{9}. To define a local symbol, write a label of the form
2707 @samp{@b{N}:} (where @b{N} represents any digit). To refer to the most
2708 recent previous definition of that symbol write @samp{@b{N}b}, using the
2709 same digit as when you defined the label. To refer to the next
2710 definition of a local label, write @samp{@b{N}f}---where @b{N} gives you
2711 a choice of 10 forward references. The @samp{b} stands for
2712 ``backwards'' and the @samp{f} stands for ``forwards''.
2714 Local symbols are not emitted by the current @sc{gnu} C compiler.
2716 There is no restriction on how you can use these labels, but
2717 remember that at any point in the assembly you can refer to at most
2718 10 prior local labels and to at most 10 forward local labels.
2720 Local symbol names are only a notation device. They are immediately
2721 transformed into more conventional symbol names before the assembler
2722 uses them. The symbol names stored in the symbol table, appearing in
2723 error messages and optionally emitted to the object file have these
2728 All local labels begin with @samp{L}. Normally both @code{@value{AS}} and
2729 @code{@value{LD}} forget symbols that start with @samp{L}. These labels are
2730 used for symbols you are never intended to see. If you use the
2731 @samp{-L} option then @code{@value{AS}} retains these symbols in the
2732 object file. If you also instruct @code{@value{LD}} to retain these symbols,
2733 you may use them in debugging.
2736 If the label is written @samp{0:} then the digit is @samp{0}.
2737 If the label is written @samp{1:} then the digit is @samp{1}.
2738 And so on up through @samp{9:}.
2741 This unusual character is included so you do not accidentally invent
2742 a symbol of the same name. The character has ASCII value
2745 @item @emph{ordinal number}
2746 This is a serial number to keep the labels distinct. The first
2747 @samp{0:} gets the number @samp{1}; The 15th @samp{0:} gets the
2748 number @samp{15}; @emph{etc.}. Likewise for the other labels @samp{1:}
2752 For instance, the first @code{1:} is named @code{L1@kbd{C-A}1}, the 44th
2753 @code{3:} is named @code{L3@kbd{C-A}44}.
2756 @section The Special Dot Symbol
2758 @cindex dot (symbol)
2759 @cindex @code{.} (symbol)
2760 @cindex current address
2761 @cindex location counter
2762 The special symbol @samp{.} refers to the current address that
2763 @code{@value{AS}} is assembling into. Thus, the expression @samp{melvin:
2764 .long .} defines @code{melvin} to contain its own address.
2765 Assigning a value to @code{.} is treated the same as a @code{.org}
2766 directive. Thus, the expression @samp{.=.+4} is the same as saying
2767 @ifclear no-space-dir
2776 @node Symbol Attributes
2777 @section Symbol Attributes
2779 @cindex symbol attributes
2780 @cindex attributes, symbol
2781 Every symbol has, as well as its name, the attributes ``Value'' and
2782 ``Type''. Depending on output format, symbols can also have auxiliary
2785 The detailed definitions are in @file{a.out.h}.
2788 If you use a symbol without defining it, @code{@value{AS}} assumes zero for
2789 all these attributes, and probably won't warn you. This makes the
2790 symbol an externally defined symbol, which is generally what you
2794 * Symbol Value:: Value
2795 * Symbol Type:: Type
2798 * a.out Symbols:: Symbol Attributes: @code{a.out}
2802 * a.out Symbols:: Symbol Attributes: @code{a.out}
2805 * a.out Symbols:: Symbol Attributes: @code{a.out}, @code{b.out}
2810 * COFF Symbols:: Symbol Attributes for COFF
2813 * SOM Symbols:: Symbol Attributes for SOM
2820 @cindex value of a symbol
2821 @cindex symbol value
2822 The value of a symbol is (usually) 32 bits. For a symbol which labels a
2823 location in the text, data, bss or absolute sections the value is the
2824 number of addresses from the start of that section to the label.
2825 Naturally for text, data and bss sections the value of a symbol changes
2826 as @code{@value{LD}} changes section base addresses during linking. Absolute
2827 symbols' values do not change during linking: that is why they are
2830 The value of an undefined symbol is treated in a special way. If it is
2831 0 then the symbol is not defined in this assembler source file, and
2832 @code{@value{LD}} tries to determine its value from other files linked into the
2833 same program. You make this kind of symbol simply by mentioning a symbol
2834 name without defining it. A non-zero value represents a @code{.comm}
2835 common declaration. The value is how much common storage to reserve, in
2836 bytes (addresses). The symbol refers to the first address of the
2842 @cindex type of a symbol
2844 The type attribute of a symbol contains relocation (section)
2845 information, any flag settings indicating that a symbol is external, and
2846 (optionally), other information for linkers and debuggers. The exact
2847 format depends on the object-code output format in use.
2852 @c The following avoids a "widow" subsection title. @group would be
2853 @c better if it were available outside examples.
2856 @subsection Symbol Attributes: @code{a.out}, @code{b.out}
2858 @cindex @code{b.out} symbol attributes
2859 @cindex symbol attributes, @code{b.out}
2860 These symbol attributes appear only when @code{@value{AS}} is configured for
2861 one of the Berkeley-descended object output formats---@code{a.out} or
2867 @subsection Symbol Attributes: @code{a.out}
2869 @cindex @code{a.out} symbol attributes
2870 @cindex symbol attributes, @code{a.out}
2876 @subsection Symbol Attributes: @code{a.out}
2878 @cindex @code{a.out} symbol attributes
2879 @cindex symbol attributes, @code{a.out}
2883 * Symbol Desc:: Descriptor
2884 * Symbol Other:: Other
2888 @subsubsection Descriptor
2890 @cindex descriptor, of @code{a.out} symbol
2891 This is an arbitrary 16-bit value. You may establish a symbol's
2892 descriptor value by using a @code{.desc} statement
2893 (@pxref{Desc,,@code{.desc}}). A descriptor value means nothing to
2897 @subsubsection Other
2899 @cindex other attribute, of @code{a.out} symbol
2900 This is an arbitrary 8-bit value. It means nothing to @code{@value{AS}}.
2905 @subsection Symbol Attributes for COFF
2907 @cindex COFF symbol attributes
2908 @cindex symbol attributes, COFF
2910 The COFF format supports a multitude of auxiliary symbol attributes;
2911 like the primary symbol attributes, they are set between @code{.def} and
2912 @code{.endef} directives.
2914 @subsubsection Primary Attributes
2916 @cindex primary attributes, COFF symbols
2917 The symbol name is set with @code{.def}; the value and type,
2918 respectively, with @code{.val} and @code{.type}.
2920 @subsubsection Auxiliary Attributes
2922 @cindex auxiliary attributes, COFF symbols
2923 The @code{@value{AS}} directives @code{.dim}, @code{.line}, @code{.scl},
2924 @code{.size}, and @code{.tag} can generate auxiliary symbol table
2925 information for COFF.
2930 @subsection Symbol Attributes for SOM
2932 @cindex SOM symbol attributes
2933 @cindex symbol attributes, SOM
2935 The SOM format for the HPPA supports a multitude of symbol attributes set with
2936 the @code{.EXPORT} and @code{.IMPORT} directives.
2938 The attributes are described in @cite{HP9000 Series 800 Assembly
2939 Language Reference Manual} (HP 92432-90001) under the @code{IMPORT} and
2940 @code{EXPORT} assembler directive documentation.
2944 @chapter Expressions
2948 @cindex numeric values
2949 An @dfn{expression} specifies an address or numeric value.
2950 Whitespace may precede and/or follow an expression.
2952 The result of an expression must be an absolute number, or else an offset into
2953 a particular section. If an expression is not absolute, and there is not
2954 enough information when @code{@value{AS}} sees the expression to know its
2955 section, a second pass over the source program might be necessary to interpret
2956 the expression---but the second pass is currently not implemented.
2957 @code{@value{AS}} aborts with an error message in this situation.
2960 * Empty Exprs:: Empty Expressions
2961 * Integer Exprs:: Integer Expressions
2965 @section Empty Expressions
2967 @cindex empty expressions
2968 @cindex expressions, empty
2969 An empty expression has no value: it is just whitespace or null.
2970 Wherever an absolute expression is required, you may omit the
2971 expression, and @code{@value{AS}} assumes a value of (absolute) 0. This
2972 is compatible with other assemblers.
2975 @section Integer Expressions
2977 @cindex integer expressions
2978 @cindex expressions, integer
2979 An @dfn{integer expression} is one or more @emph{arguments} delimited
2980 by @emph{operators}.
2983 * Arguments:: Arguments
2984 * Operators:: Operators
2985 * Prefix Ops:: Prefix Operators
2986 * Infix Ops:: Infix Operators
2990 @subsection Arguments
2992 @cindex expression arguments
2993 @cindex arguments in expressions
2994 @cindex operands in expressions
2995 @cindex arithmetic operands
2996 @dfn{Arguments} are symbols, numbers or subexpressions. In other
2997 contexts arguments are sometimes called ``arithmetic operands''. In
2998 this manual, to avoid confusing them with the ``instruction operands'' of
2999 the machine language, we use the term ``argument'' to refer to parts of
3000 expressions only, reserving the word ``operand'' to refer only to machine
3001 instruction operands.
3003 Symbols are evaluated to yield @{@var{section} @var{NNN}@} where
3004 @var{section} is one of text, data, bss, absolute,
3005 or undefined. @var{NNN} is a signed, 2's complement 32 bit
3008 Numbers are usually integers.
3010 A number can be a flonum or bignum. In this case, you are warned
3011 that only the low order 32 bits are used, and @code{@value{AS}} pretends
3012 these 32 bits are an integer. You may write integer-manipulating
3013 instructions that act on exotic constants, compatible with other
3016 @cindex subexpressions
3017 Subexpressions are a left parenthesis @samp{(} followed by an integer
3018 expression, followed by a right parenthesis @samp{)}; or a prefix
3019 operator followed by an argument.
3022 @subsection Operators
3024 @cindex operators, in expressions
3025 @cindex arithmetic functions
3026 @cindex functions, in expressions
3027 @dfn{Operators} are arithmetic functions, like @code{+} or @code{%}. Prefix
3028 operators are followed by an argument. Infix operators appear
3029 between their arguments. Operators may be preceded and/or followed by
3033 @subsection Prefix Operator
3035 @cindex prefix operators
3036 @code{@value{AS}} has the following @dfn{prefix operators}. They each take
3037 one argument, which must be absolute.
3039 @c the tex/end tex stuff surrounding this small table is meant to make
3040 @c it align, on the printed page, with the similar table in the next
3041 @c section (which is inside an enumerate).
3043 \global\advance\leftskip by \itemindent
3048 @dfn{Negation}. Two's complement negation.
3050 @dfn{Complementation}. Bitwise not.
3054 \global\advance\leftskip by -\itemindent
3058 @subsection Infix Operators
3060 @cindex infix operators
3061 @cindex operators, permitted arguments
3062 @dfn{Infix operators} take two arguments, one on either side. Operators
3063 have precedence, but operations with equal precedence are performed left
3064 to right. Apart from @code{+} or @code{-}, both arguments must be
3065 absolute, and the result is absolute.
3068 @cindex operator precedence
3069 @cindex precedence of operators
3076 @dfn{Multiplication}.
3079 @dfn{Division}. Truncation is the same as the C operator @samp{/}
3086 @dfn{Shift Left}. Same as the C operator @samp{<<}.
3090 @dfn{Shift Right}. Same as the C operator @samp{>>}.
3094 Intermediate precedence
3099 @dfn{Bitwise Inclusive Or}.
3105 @dfn{Bitwise Exclusive Or}.
3108 @dfn{Bitwise Or Not}.
3115 @cindex addition, permitted arguments
3116 @cindex plus, permitted arguments
3117 @cindex arguments for addition
3119 @dfn{Addition}. If either argument is absolute, the result has the section of
3120 the other argument. You may not add together arguments from different
3123 @cindex subtraction, permitted arguments
3124 @cindex minus, permitted arguments
3125 @cindex arguments for subtraction
3127 @dfn{Subtraction}. If the right argument is absolute, the
3128 result has the section of the left argument.
3129 If both arguments are in the same section, the result is absolute.
3130 You may not subtract arguments from different sections.
3131 @c FIXME is there still something useful to say about undefined - undefined ?
3135 In short, it's only meaningful to add or subtract the @emph{offsets} in an
3136 address; you can only have a defined section in one of the two arguments.
3139 @chapter Assembler Directives
3141 @cindex directives, machine independent
3142 @cindex pseudo-ops, machine independent
3143 @cindex machine independent directives
3144 All assembler directives have names that begin with a period (@samp{.}).
3145 The rest of the name is letters, usually in lower case.
3147 This chapter discusses directives that are available regardless of the
3148 target machine configuration for the @sc{gnu} assembler.
3150 Some machine configurations provide additional directives.
3151 @xref{Machine Dependencies}.
3154 @ifset machine-directives
3155 @xref{Machine Dependencies} for additional directives.
3160 * Abort:: @code{.abort}
3162 * ABORT:: @code{.ABORT}
3165 * Align:: @code{.align @var{abs-expr} , @var{abs-expr}}
3166 * Ascii:: @code{.ascii "@var{string}"}@dots{}
3167 * Asciz:: @code{.asciz "@var{string}"}@dots{}
3168 * Balign:: @code{.balign @var{abs-expr} , @var{abs-expr}}
3169 * Byte:: @code{.byte @var{expressions}}
3170 * Comm:: @code{.comm @var{symbol} , @var{length} }
3171 * Data:: @code{.data @var{subsection}}
3173 * Def:: @code{.def @var{name}}
3176 * Desc:: @code{.desc @var{symbol}, @var{abs-expression}}
3182 * Double:: @code{.double @var{flonums}}
3183 * Eject:: @code{.eject}
3184 * Else:: @code{.else}
3185 * Elseif:: @code{.elseif}
3188 * Endef:: @code{.endef}
3191 * Endfunc:: @code{.endfunc}
3192 * Endif:: @code{.endif}
3193 * Equ:: @code{.equ @var{symbol}, @var{expression}}
3194 * Equiv:: @code{.equiv @var{symbol}, @var{expression}}
3196 * Exitm:: @code{.exitm}
3197 * Extern:: @code{.extern}
3198 * Fail:: @code{.fail}
3199 @ifclear no-file-dir
3200 * File:: @code{.file @var{string}}
3203 * Fill:: @code{.fill @var{repeat} , @var{size} , @var{value}}
3204 * Float:: @code{.float @var{flonums}}
3205 * Func:: @code{.func}
3206 * Global:: @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3207 * hword:: @code{.hword @var{expressions}}
3208 * Ident:: @code{.ident}
3209 * If:: @code{.if @var{absolute expression}}
3210 * Include:: @code{.include "@var{file}"}
3211 * Int:: @code{.int @var{expressions}}
3212 * Irp:: @code{.irp @var{symbol},@var{values}}@dots{}
3213 * Irpc:: @code{.irpc @var{symbol},@var{values}}@dots{}
3214 * Lcomm:: @code{.lcomm @var{symbol} , @var{length}}
3215 * Lflags:: @code{.lflags}
3216 @ifclear no-line-dir
3217 * Line:: @code{.line @var{line-number}}
3220 * Ln:: @code{.ln @var{line-number}}
3221 * Linkonce:: @code{.linkonce [@var{type}]}
3222 * List:: @code{.list}
3223 * Long:: @code{.long @var{expressions}}
3225 * Lsym:: @code{.lsym @var{symbol}, @var{expression}}
3228 * Macro:: @code{.macro @var{name} @var{args}}@dots{}
3229 * MRI:: @code{.mri @var{val}}
3231 * Nolist:: @code{.nolist}
3232 * Octa:: @code{.octa @var{bignums}}
3233 * Org:: @code{.org @var{new-lc} , @var{fill}}
3234 * P2align:: @code{.p2align @var{abs-expr} , @var{abs-expr}}
3235 * Print:: @code{.print @var{string}}
3236 * Psize:: @code{.psize @var{lines}, @var{columns}}
3237 * Purgem:: @code{.purgem @var{name}}
3238 * Quad:: @code{.quad @var{bignums}}
3239 * Rept:: @code{.rept @var{count}}
3240 * Sbttl:: @code{.sbttl "@var{subheading}"}
3242 * Scl:: @code{.scl @var{class}}
3243 * Section:: @code{.section @var{name}, @var{subsection}}
3246 * Set:: @code{.set @var{symbol}, @var{expression}}
3247 * Short:: @code{.short @var{expressions}}
3248 * Single:: @code{.single @var{flonums}}
3250 * Size:: @code{.size}
3253 * Skip:: @code{.skip @var{size} , @var{fill}}
3254 * Sleb128:: @code{.sleb128 @var{expressions}}
3255 * Space:: @code{.space @var{size} , @var{fill}}
3257 * Stab:: @code{.stabd, .stabn, .stabs}
3260 * String:: @code{.string "@var{str}"}
3261 * Struct:: @code{.struct @var{expression}}
3263 * Symver:: @code{.symver @var{name},@var{name2@@nodename}}
3266 * Tag:: @code{.tag @var{structname}}
3269 * Text:: @code{.text @var{subsection}}
3270 * Title:: @code{.title "@var{heading}"}
3272 * Type:: @code{.type @var{int}}
3273 * Val:: @code{.val @var{addr}}
3276 * Visibility:: @code{.internal @var{name}, .hidden @var{name}, .protected @var{name}}
3279 * Uleb128:: @code{.uleb128 @var{expressions}}
3280 * Word:: @code{.word @var{expressions}}
3281 * Deprecated:: Deprecated Directives
3285 @section @code{.abort}
3287 @cindex @code{abort} directive
3288 @cindex stopping the assembly
3289 This directive stops the assembly immediately. It is for
3290 compatibility with other assemblers. The original idea was that the
3291 assembly language source would be piped into the assembler. If the sender
3292 of the source quit, it could use this directive tells @code{@value{AS}} to
3293 quit also. One day @code{.abort} will not be supported.
3297 @section @code{.ABORT}
3299 @cindex @code{ABORT} directive
3300 When producing COFF output, @code{@value{AS}} accepts this directive as a
3301 synonym for @samp{.abort}.
3304 When producing @code{b.out} output, @code{@value{AS}} accepts this directive,
3310 @section @code{.align @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3312 @cindex padding the location counter
3313 @cindex @code{align} directive
3314 Pad the location counter (in the current subsection) to a particular storage
3315 boundary. The first expression (which must be absolute) is the alignment
3316 required, as described below.
3318 The second expression (also absolute) gives the fill value to be stored in the
3319 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3320 padding bytes are normally zero. However, on some systems, if the section is
3321 marked as containing code and the fill value is omitted, the space is filled
3322 with no-op instructions.
3324 The third expression is also absolute, and is also optional. If it is present,
3325 it is the maximum number of bytes that should be skipped by this alignment
3326 directive. If doing the alignment would require skipping more bytes than the
3327 specified maximum, then the alignment is not done at all. You can omit the
3328 fill value (the second argument) entirely by simply using two commas after the
3329 required alignment; this can be useful if you want the alignment to be filled
3330 with no-op instructions when appropriate.
3332 The way the required alignment is specified varies from system to system.
3333 For the a29k, hppa, m68k, m88k, w65, sparc, and Hitachi SH, and i386 using ELF
3335 the first expression is the
3336 alignment request in bytes. For example @samp{.align 8} advances
3337 the location counter until it is a multiple of 8. If the location counter
3338 is already a multiple of 8, no change is needed.
3340 For other systems, including the i386 using a.out format, and the arm and
3341 strongarm, it is the
3342 number of low-order zero bits the location counter must have after
3343 advancement. For example @samp{.align 3} advances the location
3344 counter until it a multiple of 8. If the location counter is already a
3345 multiple of 8, no change is needed.
3347 This inconsistency is due to the different behaviors of the various
3348 native assemblers for these systems which GAS must emulate.
3349 GAS also provides @code{.balign} and @code{.p2align} directives,
3350 described later, which have a consistent behavior across all
3351 architectures (but are specific to GAS).
3354 @section @code{.ascii "@var{string}"}@dots{}
3356 @cindex @code{ascii} directive
3357 @cindex string literals
3358 @code{.ascii} expects zero or more string literals (@pxref{Strings})
3359 separated by commas. It assembles each string (with no automatic
3360 trailing zero byte) into consecutive addresses.
3363 @section @code{.asciz "@var{string}"}@dots{}
3365 @cindex @code{asciz} directive
3366 @cindex zero-terminated strings
3367 @cindex null-terminated strings
3368 @code{.asciz} is just like @code{.ascii}, but each string is followed by
3369 a zero byte. The ``z'' in @samp{.asciz} stands for ``zero''.
3372 @section @code{.balign[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
3374 @cindex padding the location counter given number of bytes
3375 @cindex @code{balign} directive
3376 Pad the location counter (in the current subsection) to a particular
3377 storage boundary. The first expression (which must be absolute) is the
3378 alignment request in bytes. For example @samp{.balign 8} advances
3379 the location counter until it is a multiple of 8. If the location counter
3380 is already a multiple of 8, no change is needed.
3382 The second expression (also absolute) gives the fill value to be stored in the
3383 padding bytes. It (and the comma) may be omitted. If it is omitted, the
3384 padding bytes are normally zero. However, on some systems, if the section is
3385 marked as containing code and the fill value is omitted, the space is filled
3386 with no-op instructions.
3388 The third expression is also absolute, and is also optional. If it is present,
3389 it is the maximum number of bytes that should be skipped by this alignment
3390 directive. If doing the alignment would require skipping more bytes than the
3391 specified maximum, then the alignment is not done at all. You can omit the
3392 fill value (the second argument) entirely by simply using two commas after the
3393 required alignment; this can be useful if you want the alignment to be filled
3394 with no-op instructions when appropriate.
3396 @cindex @code{balignw} directive
3397 @cindex @code{balignl} directive
3398 The @code{.balignw} and @code{.balignl} directives are variants of the
3399 @code{.balign} directive. The @code{.balignw} directive treats the fill
3400 pattern as a two byte word value. The @code{.balignl} directives treats the
3401 fill pattern as a four byte longword value. For example, @code{.balignw
3402 4,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
3403 filled in with the value 0x368d (the exact placement of the bytes depends upon
3404 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
3408 @section @code{.byte @var{expressions}}
3410 @cindex @code{byte} directive
3411 @cindex integers, one byte
3412 @code{.byte} expects zero or more expressions, separated by commas.
3413 Each expression is assembled into the next byte.
3416 @section @code{.comm @var{symbol} , @var{length} }
3418 @cindex @code{comm} directive
3419 @cindex symbol, common
3420 @code{.comm} declares a common symbol named @var{symbol}. When linking, a
3421 common symbol in one object file may be merged with a defined or common symbol
3422 of the same name in another object file. If @code{@value{LD}} does not see a
3423 definition for the symbol--just one or more common symbols--then it will
3424 allocate @var{length} bytes of uninitialized memory. @var{length} must be an
3425 absolute expression. If @code{@value{LD}} sees multiple common symbols with
3426 the same name, and they do not all have the same size, it will allocate space
3427 using the largest size.
3430 When using ELF, the @code{.comm} directive takes an optional third argument.
3431 This is the desired alignment of the symbol, specified as a byte boundary (for
3432 example, an alignment of 16 means that the least significant 4 bits of the
3433 address should be zero). The alignment must be an absolute expression, and it
3434 must be a power of two. If @code{@value{LD}} allocates uninitialized memory
3435 for the common symbol, it will use the alignment when placing the symbol. If
3436 no alignment is specified, @code{@value{AS}} will set the alignment to the
3437 largest power of two less than or equal to the size of the symbol, up to a
3442 The syntax for @code{.comm} differs slightly on the HPPA. The syntax is
3443 @samp{@var{symbol} .comm, @var{length}}; @var{symbol} is optional.
3447 @section @code{.data @var{subsection}}
3449 @cindex @code{data} directive
3450 @code{.data} tells @code{@value{AS}} to assemble the following statements onto the
3451 end of the data subsection numbered @var{subsection} (which is an
3452 absolute expression). If @var{subsection} is omitted, it defaults
3457 @section @code{.def @var{name}}
3459 @cindex @code{def} directive
3460 @cindex COFF symbols, debugging
3461 @cindex debugging COFF symbols
3462 Begin defining debugging information for a symbol @var{name}; the
3463 definition extends until the @code{.endef} directive is encountered.
3466 This directive is only observed when @code{@value{AS}} is configured for COFF
3467 format output; when producing @code{b.out}, @samp{.def} is recognized,
3474 @section @code{.desc @var{symbol}, @var{abs-expression}}
3476 @cindex @code{desc} directive
3477 @cindex COFF symbol descriptor
3478 @cindex symbol descriptor, COFF
3479 This directive sets the descriptor of the symbol (@pxref{Symbol Attributes})
3480 to the low 16 bits of an absolute expression.
3483 The @samp{.desc} directive is not available when @code{@value{AS}} is
3484 configured for COFF output; it is only for @code{a.out} or @code{b.out}
3485 object format. For the sake of compatibility, @code{@value{AS}} accepts
3486 it, but produces no output, when configured for COFF.
3492 @section @code{.dim}
3494 @cindex @code{dim} directive
3495 @cindex COFF auxiliary symbol information
3496 @cindex auxiliary symbol information, COFF
3497 This directive is generated by compilers to include auxiliary debugging
3498 information in the symbol table. It is only permitted inside
3499 @code{.def}/@code{.endef} pairs.
3502 @samp{.dim} is only meaningful when generating COFF format output; when
3503 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
3509 @section @code{.double @var{flonums}}
3511 @cindex @code{double} directive
3512 @cindex floating point numbers (double)
3513 @code{.double} expects zero or more flonums, separated by commas. It
3514 assembles floating point numbers.
3516 The exact kind of floating point numbers emitted depends on how
3517 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
3521 On the @value{TARGET} family @samp{.double} emits 64-bit floating-point numbers
3522 in @sc{ieee} format.
3527 @section @code{.eject}
3529 @cindex @code{eject} directive
3530 @cindex new page, in listings
3531 @cindex page, in listings
3532 @cindex listing control: new page
3533 Force a page break at this point, when generating assembly listings.
3536 @section @code{.else}
3538 @cindex @code{else} directive
3539 @code{.else} is part of the @code{@value{AS}} support for conditional
3540 assembly; @pxref{If,,@code{.if}}. It marks the beginning of a section
3541 of code to be assembled if the condition for the preceding @code{.if}
3545 @section @code{.elseif}
3547 @cindex @code{elseif} directive
3548 @code{.elseif} is part of the @code{@value{AS}} support for conditional
3549 assembly; @pxref{If,,@code{.if}}. It is shorthand for beginning a new
3550 @code{.if} block that would otherwise fill the entire @code{.else} section.
3553 @section @code{.end}
3555 @cindex @code{end} directive
3556 @code{.end} marks the end of the assembly file. @code{@value{AS}} does not
3557 process anything in the file past the @code{.end} directive.
3561 @section @code{.endef}
3563 @cindex @code{endef} directive
3564 This directive flags the end of a symbol definition begun with
3568 @samp{.endef} is only meaningful when generating COFF format output; if
3569 @code{@value{AS}} is configured to generate @code{b.out}, it accepts this
3570 directive but ignores it.
3575 @section @code{.endfunc}
3576 @cindex @code{endfunc} directive
3577 @code{.endfunc} marks the end of a function specified with @code{.func}.
3580 @section @code{.endif}
3582 @cindex @code{endif} directive
3583 @code{.endif} is part of the @code{@value{AS}} support for conditional assembly;
3584 it marks the end of a block of code that is only assembled
3585 conditionally. @xref{If,,@code{.if}}.
3588 @section @code{.equ @var{symbol}, @var{expression}}
3590 @cindex @code{equ} directive
3591 @cindex assigning values to symbols
3592 @cindex symbols, assigning values to
3593 This directive sets the value of @var{symbol} to @var{expression}.
3594 It is synonymous with @samp{.set}; @pxref{Set,,@code{.set}}.
3597 The syntax for @code{equ} on the HPPA is
3598 @samp{@var{symbol} .equ @var{expression}}.
3602 @section @code{.equiv @var{symbol}, @var{expression}}
3603 @cindex @code{equiv} directive
3604 The @code{.equiv} directive is like @code{.equ} and @code{.set}, except that
3605 the assembler will signal an error if @var{symbol} is already defined.
3607 Except for the contents of the error message, this is roughly equivalent to
3616 @section @code{.err}
3617 @cindex @code{err} directive
3618 If @code{@value{AS}} assembles a @code{.err} directive, it will print an error
3619 message and, unless the @code{-Z} option was used, it will not generate an
3620 object file. This can be used to signal error an conditionally compiled code.
3623 @section @code{.exitm}
3624 Exit early from the current macro definition. @xref{Macro}.
3627 @section @code{.extern}
3629 @cindex @code{extern} directive
3630 @code{.extern} is accepted in the source program---for compatibility
3631 with other assemblers---but it is ignored. @code{@value{AS}} treats
3632 all undefined symbols as external.
3635 @section @code{.fail @var{expression}}
3637 @cindex @code{fail} directive
3638 Generates an error or a warning. If the value of the @var{expression} is 500
3639 or more, @code{@value{AS}} will print a warning message. If the value is less
3640 than 500, @code{@value{AS}} will print an error message. The message will
3641 include the value of @var{expression}. This can occasionally be useful inside
3642 complex nested macros or conditional assembly.
3644 @ifclear no-file-dir
3646 @section @code{.file @var{string}}
3648 @cindex @code{file} directive
3649 @cindex logical file name
3650 @cindex file name, logical
3651 @code{.file} tells @code{@value{AS}} that we are about to start a new logical
3652 file. @var{string} is the new file name. In general, the filename is
3653 recognized whether or not it is surrounded by quotes @samp{"}; but if you wish
3654 to specify an empty file name, you must give the quotes--@code{""}. This
3655 statement may go away in future: it is only recognized to be compatible with
3656 old @code{@value{AS}} programs.
3658 In some configurations of @code{@value{AS}}, @code{.file} has already been
3659 removed to avoid conflicts with other assemblers. @xref{Machine Dependencies}.
3664 @section @code{.fill @var{repeat} , @var{size} , @var{value}}
3666 @cindex @code{fill} directive
3667 @cindex writing patterns in memory
3668 @cindex patterns, writing in memory
3669 @var{result}, @var{size} and @var{value} are absolute expressions.
3670 This emits @var{repeat} copies of @var{size} bytes. @var{Repeat}
3671 may be zero or more. @var{Size} may be zero or more, but if it is
3672 more than 8, then it is deemed to have the value 8, compatible with
3673 other people's assemblers. The contents of each @var{repeat} bytes
3674 is taken from an 8-byte number. The highest order 4 bytes are
3675 zero. The lowest order 4 bytes are @var{value} rendered in the
3676 byte-order of an integer on the computer @code{@value{AS}} is assembling for.
3677 Each @var{size} bytes in a repetition is taken from the lowest order
3678 @var{size} bytes of this number. Again, this bizarre behavior is
3679 compatible with other people's assemblers.
3681 @var{size} and @var{value} are optional.
3682 If the second comma and @var{value} are absent, @var{value} is
3683 assumed zero. If the first comma and following tokens are absent,
3684 @var{size} is assumed to be 1.
3687 @section @code{.float @var{flonums}}
3689 @cindex floating point numbers (single)
3690 @cindex @code{float} directive
3691 This directive assembles zero or more flonums, separated by commas. It
3692 has the same effect as @code{.single}.
3694 The exact kind of floating point numbers emitted depends on how
3695 @code{@value{AS}} is configured.
3696 @xref{Machine Dependencies}.
3700 On the @value{TARGET} family, @code{.float} emits 32-bit floating point numbers
3701 in @sc{ieee} format.
3706 @section @code{.func @var{name}[,@var{label}]}
3707 @cindex @code{func} directive
3708 @code{.func} emits debugging information to denote function @var{name}, and
3709 is ignored unless the file is assembled with debugging enabled.
3710 Only @samp{--gstabs} is currently supported.
3711 @var{label} is the entry point of the function and if omitted @var{name}
3712 prepended with the @samp{leading char} is used.
3713 @samp{leading char} is usually @code{_} or nothing, depending on the target.
3714 All functions are currently defined to have @code{void} return type.
3715 The function must be terminated with @code{.endfunc}.
3718 @section @code{.global @var{symbol}}, @code{.globl @var{symbol}}
3720 @cindex @code{global} directive
3721 @cindex symbol, making visible to linker
3722 @code{.global} makes the symbol visible to @code{@value{LD}}. If you define
3723 @var{symbol} in your partial program, its value is made available to
3724 other partial programs that are linked with it. Otherwise,
3725 @var{symbol} takes its attributes from a symbol of the same name
3726 from another file linked into the same program.
3728 Both spellings (@samp{.globl} and @samp{.global}) are accepted, for
3729 compatibility with other assemblers.
3732 On the HPPA, @code{.global} is not always enough to make it accessible to other
3733 partial programs. You may need the HPPA-only @code{.EXPORT} directive as well.
3734 @xref{HPPA Directives,, HPPA Assembler Directives}.
3738 @section @code{.hword @var{expressions}}
3740 @cindex @code{hword} directive
3741 @cindex integers, 16-bit
3742 @cindex numbers, 16-bit
3743 @cindex sixteen bit integers
3744 This expects zero or more @var{expressions}, and emits
3745 a 16 bit number for each.
3748 This directive is a synonym for @samp{.short}; depending on the target
3749 architecture, it may also be a synonym for @samp{.word}.
3753 This directive is a synonym for @samp{.short}.
3756 This directive is a synonym for both @samp{.short} and @samp{.word}.
3761 @section @code{.ident}
3763 @cindex @code{ident} directive
3764 This directive is used by some assemblers to place tags in object files.
3765 @code{@value{AS}} simply accepts the directive for source-file
3766 compatibility with such assemblers, but does not actually emit anything
3770 @section @code{.if @var{absolute expression}}
3772 @cindex conditional assembly
3773 @cindex @code{if} directive
3774 @code{.if} marks the beginning of a section of code which is only
3775 considered part of the source program being assembled if the argument
3776 (which must be an @var{absolute expression}) is non-zero. The end of
3777 the conditional section of code must be marked by @code{.endif}
3778 (@pxref{Endif,,@code{.endif}}); optionally, you may include code for the
3779 alternative condition, flagged by @code{.else} (@pxref{Else,,@code{.else}}).
3780 If you have several conditions to check, @code{.elseif} may be used to avoid
3781 nesting blocks if/else within each subsequent @code{.else} block.
3783 The following variants of @code{.if} are also supported:
3785 @cindex @code{ifdef} directive
3786 @item .ifdef @var{symbol}
3787 Assembles the following section of code if the specified @var{symbol}
3790 @cindex @code{ifc} directive
3791 @item .ifc @var{string1},@var{string2}
3792 Assembles the following section of code if the two strings are the same. The
3793 strings may be optionally quoted with single quotes. If they are not quoted,
3794 the first string stops at the first comma, and the second string stops at the
3795 end of the line. Strings which contain whitespace should be quoted. The
3796 string comparison is case sensitive.
3798 @cindex @code{ifeq} directive
3799 @item .ifeq @var{absolute expression}
3800 Assembles the following section of code if the argument is zero.
3802 @cindex @code{ifeqs} directive
3803 @item .ifeqs @var{string1},@var{string2}
3804 Another form of @code{.ifc}. The strings must be quoted using double quotes.
3806 @cindex @code{ifge} directive
3807 @item .ifge @var{absolute expression}
3808 Assembles the following section of code if the argument is greater than or
3811 @cindex @code{ifgt} directive
3812 @item .ifgt @var{absolute expression}
3813 Assembles the following section of code if the argument is greater than zero.
3815 @cindex @code{ifle} directive
3816 @item .ifle @var{absolute expression}
3817 Assembles the following section of code if the argument is less than or equal
3820 @cindex @code{iflt} directive
3821 @item .iflt @var{absolute expression}
3822 Assembles the following section of code if the argument is less than zero.
3824 @cindex @code{ifnc} directive
3825 @item .ifnc @var{string1},@var{string2}.
3826 Like @code{.ifc}, but the sense of the test is reversed: this assembles the
3827 following section of code if the two strings are not the same.
3829 @cindex @code{ifndef} directive
3830 @cindex @code{ifnotdef} directive
3831 @item .ifndef @var{symbol}
3832 @itemx .ifnotdef @var{symbol}
3833 Assembles the following section of code if the specified @var{symbol}
3834 has not been defined. Both spelling variants are equivalent.
3836 @cindex @code{ifne} directive
3837 @item .ifne @var{absolute expression}
3838 Assembles the following section of code if the argument is not equal to zero
3839 (in other words, this is equivalent to @code{.if}).
3841 @cindex @code{ifnes} directive
3842 @item .ifnes @var{string1},@var{string2}
3843 Like @code{.ifeqs}, but the sense of the test is reversed: this assembles the
3844 following section of code if the two strings are not the same.
3848 @section @code{.include "@var{file}"}
3850 @cindex @code{include} directive
3851 @cindex supporting files, including
3852 @cindex files, including
3853 This directive provides a way to include supporting files at specified
3854 points in your source program. The code from @var{file} is assembled as
3855 if it followed the point of the @code{.include}; when the end of the
3856 included file is reached, assembly of the original file continues. You
3857 can control the search paths used with the @samp{-I} command-line option
3858 (@pxref{Invoking,,Command-Line Options}). Quotation marks are required
3862 @section @code{.int @var{expressions}}
3864 @cindex @code{int} directive
3865 @cindex integers, 32-bit
3866 Expect zero or more @var{expressions}, of any section, separated by commas.
3867 For each expression, emit a number that, at run time, is the value of that
3868 expression. The byte order and bit size of the number depends on what kind
3869 of target the assembly is for.
3873 On the H8/500 and most forms of the H8/300, @code{.int} emits 16-bit
3874 integers. On the H8/300H and the Hitachi SH, however, @code{.int} emits
3880 @section @code{.irp @var{symbol},@var{values}}@dots{}
3882 @cindex @code{irp} directive
3883 Evaluate a sequence of statements assigning different values to @var{symbol}.
3884 The sequence of statements starts at the @code{.irp} directive, and is
3885 terminated by an @code{.endr} directive. For each @var{value}, @var{symbol} is
3886 set to @var{value}, and the sequence of statements is assembled. If no
3887 @var{value} is listed, the sequence of statements is assembled once, with
3888 @var{symbol} set to the null string. To refer to @var{symbol} within the
3889 sequence of statements, use @var{\symbol}.
3891 For example, assembling
3899 is equivalent to assembling
3908 @section @code{.irpc @var{symbol},@var{values}}@dots{}
3910 @cindex @code{irpc} directive
3911 Evaluate a sequence of statements assigning different values to @var{symbol}.
3912 The sequence of statements starts at the @code{.irpc} directive, and is
3913 terminated by an @code{.endr} directive. For each character in @var{value},
3914 @var{symbol} is set to the character, and the sequence of statements is
3915 assembled. If no @var{value} is listed, the sequence of statements is
3916 assembled once, with @var{symbol} set to the null string. To refer to
3917 @var{symbol} within the sequence of statements, use @var{\symbol}.
3919 For example, assembling
3927 is equivalent to assembling
3936 @section @code{.lcomm @var{symbol} , @var{length}}
3938 @cindex @code{lcomm} directive
3939 @cindex local common symbols
3940 @cindex symbols, local common
3941 Reserve @var{length} (an absolute expression) bytes for a local common
3942 denoted by @var{symbol}. The section and value of @var{symbol} are
3943 those of the new local common. The addresses are allocated in the bss
3944 section, so that at run-time the bytes start off zeroed. @var{Symbol}
3945 is not declared global (@pxref{Global,,@code{.global}}), so is normally
3946 not visible to @code{@value{LD}}.
3949 Some targets permit a third argument to be used with @code{.lcomm}. This
3950 argument specifies the desired alignment of the symbol in the bss section.
3954 The syntax for @code{.lcomm} differs slightly on the HPPA. The syntax is
3955 @samp{@var{symbol} .lcomm, @var{length}}; @var{symbol} is optional.
3959 @section @code{.lflags}
3961 @cindex @code{lflags} directive (ignored)
3962 @code{@value{AS}} accepts this directive, for compatibility with other
3963 assemblers, but ignores it.
3965 @ifclear no-line-dir
3967 @section @code{.line @var{line-number}}
3969 @cindex @code{line} directive
3973 @section @code{.ln @var{line-number}}
3975 @cindex @code{ln} directive
3977 @cindex logical line number
3979 Change the logical line number. @var{line-number} must be an absolute
3980 expression. The next line has that logical line number. Therefore any other
3981 statements on the current line (after a statement separator character) are
3982 reported as on logical line number @var{line-number} @minus{} 1. One day
3983 @code{@value{AS}} will no longer support this directive: it is recognized only
3984 for compatibility with existing assembler programs.
3988 @emph{Warning:} In the AMD29K configuration of @value{AS}, this command is
3989 not available; use the synonym @code{.ln} in that context.
3994 @ifclear no-line-dir
3995 Even though this is a directive associated with the @code{a.out} or
3996 @code{b.out} object-code formats, @code{@value{AS}} still recognizes it
3997 when producing COFF output, and treats @samp{.line} as though it
3998 were the COFF @samp{.ln} @emph{if} it is found outside a
3999 @code{.def}/@code{.endef} pair.
4001 Inside a @code{.def}, @samp{.line} is, instead, one of the directives
4002 used by compilers to generate auxiliary symbol information for
4007 @section @code{.linkonce [@var{type}]}
4009 @cindex @code{linkonce} directive
4010 @cindex common sections
4011 Mark the current section so that the linker only includes a single copy of it.
4012 This may be used to include the same section in several different object files,
4013 but ensure that the linker will only include it once in the final output file.
4014 The @code{.linkonce} pseudo-op must be used for each instance of the section.
4015 Duplicate sections are detected based on the section name, so it should be
4018 This directive is only supported by a few object file formats; as of this
4019 writing, the only object file format which supports it is the Portable
4020 Executable format used on Windows NT.
4022 The @var{type} argument is optional. If specified, it must be one of the
4023 following strings. For example:
4027 Not all types may be supported on all object file formats.
4031 Silently discard duplicate sections. This is the default.
4034 Warn if there are duplicate sections, but still keep only one copy.
4037 Warn if any of the duplicates have different sizes.
4040 Warn if any of the duplicates do not have exactly the same contents.
4044 @section @code{.ln @var{line-number}}
4046 @cindex @code{ln} directive
4047 @ifclear no-line-dir
4048 @samp{.ln} is a synonym for @samp{.line}.
4051 Tell @code{@value{AS}} to change the logical line number. @var{line-number}
4052 must be an absolute expression. The next line has that logical
4053 line number, so any other statements on the current line (after a
4054 statement separator character @code{;}) are reported as on logical
4055 line number @var{line-number} @minus{} 1.
4058 This directive is accepted, but ignored, when @code{@value{AS}} is
4059 configured for @code{b.out}; its effect is only associated with COFF
4065 @section @code{.mri @var{val}}
4067 @cindex @code{mri} directive
4068 @cindex MRI mode, temporarily
4069 If @var{val} is non-zero, this tells @code{@value{AS}} to enter MRI mode. If
4070 @var{val} is zero, this tells @code{@value{AS}} to exit MRI mode. This change
4071 affects code assembled until the next @code{.mri} directive, or until the end
4072 of the file. @xref{M, MRI mode, MRI mode}.
4075 @section @code{.list}
4077 @cindex @code{list} directive
4078 @cindex listing control, turning on
4079 Control (in conjunction with the @code{.nolist} directive) whether or
4080 not assembly listings are generated. These two directives maintain an
4081 internal counter (which is zero initially). @code{.list} increments the
4082 counter, and @code{.nolist} decrements it. Assembly listings are
4083 generated whenever the counter is greater than zero.
4085 By default, listings are disabled. When you enable them (with the
4086 @samp{-a} command line option; @pxref{Invoking,,Command-Line Options}),
4087 the initial value of the listing counter is one.
4090 @section @code{.long @var{expressions}}
4092 @cindex @code{long} directive
4093 @code{.long} is the same as @samp{.int}, @pxref{Int,,@code{.int}}.
4096 @c no one seems to know what this is for or whether this description is
4097 @c what it really ought to do
4099 @section @code{.lsym @var{symbol}, @var{expression}}
4101 @cindex @code{lsym} directive
4102 @cindex symbol, not referenced in assembly
4103 @code{.lsym} creates a new symbol named @var{symbol}, but does not put it in
4104 the hash table, ensuring it cannot be referenced by name during the
4105 rest of the assembly. This sets the attributes of the symbol to be
4106 the same as the expression value:
4108 @var{other} = @var{descriptor} = 0
4109 @var{type} = @r{(section of @var{expression})}
4110 @var{value} = @var{expression}
4113 The new symbol is not flagged as external.
4117 @section @code{.macro}
4120 The commands @code{.macro} and @code{.endm} allow you to define macros that
4121 generate assembly output. For example, this definition specifies a macro
4122 @code{sum} that puts a sequence of numbers into memory:
4125 .macro sum from=0, to=5
4134 With that definition, @samp{SUM 0,5} is equivalent to this assembly input:
4146 @item .macro @var{macname}
4147 @itemx .macro @var{macname} @var{macargs} @dots{}
4148 @cindex @code{macro} directive
4149 Begin the definition of a macro called @var{macname}. If your macro
4150 definition requires arguments, specify their names after the macro name,
4151 separated by commas or spaces. You can supply a default value for any
4152 macro argument by following the name with @samp{=@var{deflt}}. For
4153 example, these are all valid @code{.macro} statements:
4157 Begin the definition of a macro called @code{comm}, which takes no
4160 @item .macro plus1 p, p1
4161 @itemx .macro plus1 p p1
4162 Either statement begins the definition of a macro called @code{plus1},
4163 which takes two arguments; within the macro definition, write
4164 @samp{\p} or @samp{\p1} to evaluate the arguments.
4166 @item .macro reserve_str p1=0 p2
4167 Begin the definition of a macro called @code{reserve_str}, with two
4168 arguments. The first argument has a default value, but not the second.
4169 After the definition is complete, you can call the macro either as
4170 @samp{reserve_str @var{a},@var{b}} (with @samp{\p1} evaluating to
4171 @var{a} and @samp{\p2} evaluating to @var{b}), or as @samp{reserve_str
4172 ,@var{b}} (with @samp{\p1} evaluating as the default, in this case
4173 @samp{0}, and @samp{\p2} evaluating to @var{b}).
4176 When you call a macro, you can specify the argument values either by
4177 position, or by keyword. For example, @samp{sum 9,17} is equivalent to
4178 @samp{sum to=17, from=9}.
4181 @cindex @code{endm} directive
4182 Mark the end of a macro definition.
4185 @cindex @code{exitm} directive
4186 Exit early from the current macro definition.
4188 @cindex number of macros executed
4189 @cindex macros, count executed
4191 @code{@value{AS}} maintains a counter of how many macros it has
4192 executed in this pseudo-variable; you can copy that number to your
4193 output with @samp{\@@}, but @emph{only within a macro definition}.
4196 @item LOCAL @var{name} [ , @dots{} ]
4197 @emph{Warning: @code{LOCAL} is only available if you select ``alternate
4198 macro syntax'' with @samp{-a} or @samp{--alternate}.} @xref{Alternate,,
4199 Alternate macro syntax}.
4201 Generate a string replacement for each of the @var{name} arguments, and
4202 replace any instances of @var{name} in each macro expansion. The
4203 replacement string is unique in the assembly, and different for each
4204 separate macro expansion. @code{LOCAL} allows you to write macros that
4205 define symbols, without fear of conflict between separate macro expansions.
4210 @section @code{.nolist}
4212 @cindex @code{nolist} directive
4213 @cindex listing control, turning off
4214 Control (in conjunction with the @code{.list} directive) whether or
4215 not assembly listings are generated. These two directives maintain an
4216 internal counter (which is zero initially). @code{.list} increments the
4217 counter, and @code{.nolist} decrements it. Assembly listings are
4218 generated whenever the counter is greater than zero.
4221 @section @code{.octa @var{bignums}}
4223 @c FIXME: double size emitted for "octa" on i960, others? Or warn?
4224 @cindex @code{octa} directive
4225 @cindex integer, 16-byte
4226 @cindex sixteen byte integer
4227 This directive expects zero or more bignums, separated by commas. For each
4228 bignum, it emits a 16-byte integer.
4230 The term ``octa'' comes from contexts in which a ``word'' is two bytes;
4231 hence @emph{octa}-word for 16 bytes.
4234 @section @code{.org @var{new-lc} , @var{fill}}
4236 @cindex @code{org} directive
4237 @cindex location counter, advancing
4238 @cindex advancing location counter
4239 @cindex current address, advancing
4240 Advance the location counter of the current section to
4241 @var{new-lc}. @var{new-lc} is either an absolute expression or an
4242 expression with the same section as the current subsection. That is,
4243 you can't use @code{.org} to cross sections: if @var{new-lc} has the
4244 wrong section, the @code{.org} directive is ignored. To be compatible
4245 with former assemblers, if the section of @var{new-lc} is absolute,
4246 @code{@value{AS}} issues a warning, then pretends the section of @var{new-lc}
4247 is the same as the current subsection.
4249 @code{.org} may only increase the location counter, or leave it
4250 unchanged; you cannot use @code{.org} to move the location counter
4253 @c double negative used below "not undefined" because this is a specific
4254 @c reference to "undefined" (as SEG_UNKNOWN is called in this manual)
4255 @c section. doc@cygnus.com 18feb91
4256 Because @code{@value{AS}} tries to assemble programs in one pass, @var{new-lc}
4257 may not be undefined. If you really detest this restriction we eagerly await
4258 a chance to share your improved assembler.
4260 Beware that the origin is relative to the start of the section, not
4261 to the start of the subsection. This is compatible with other
4262 people's assemblers.
4264 When the location counter (of the current subsection) is advanced, the
4265 intervening bytes are filled with @var{fill} which should be an
4266 absolute expression. If the comma and @var{fill} are omitted,
4267 @var{fill} defaults to zero.
4270 @section @code{.p2align[wl] @var{abs-expr}, @var{abs-expr}, @var{abs-expr}}
4272 @cindex padding the location counter given a power of two
4273 @cindex @code{p2align} directive
4274 Pad the location counter (in the current subsection) to a particular
4275 storage boundary. The first expression (which must be absolute) is the
4276 number of low-order zero bits the location counter must have after
4277 advancement. For example @samp{.p2align 3} advances the location
4278 counter until it a multiple of 8. If the location counter is already a
4279 multiple of 8, no change is needed.
4281 The second expression (also absolute) gives the fill value to be stored in the
4282 padding bytes. It (and the comma) may be omitted. If it is omitted, the
4283 padding bytes are normally zero. However, on some systems, if the section is
4284 marked as containing code and the fill value is omitted, the space is filled
4285 with no-op instructions.
4287 The third expression is also absolute, and is also optional. If it is present,
4288 it is the maximum number of bytes that should be skipped by this alignment
4289 directive. If doing the alignment would require skipping more bytes than the
4290 specified maximum, then the alignment is not done at all. You can omit the
4291 fill value (the second argument) entirely by simply using two commas after the
4292 required alignment; this can be useful if you want the alignment to be filled
4293 with no-op instructions when appropriate.
4295 @cindex @code{p2alignw} directive
4296 @cindex @code{p2alignl} directive
4297 The @code{.p2alignw} and @code{.p2alignl} directives are variants of the
4298 @code{.p2align} directive. The @code{.p2alignw} directive treats the fill
4299 pattern as a two byte word value. The @code{.p2alignl} directives treats the
4300 fill pattern as a four byte longword value. For example, @code{.p2alignw
4301 2,0x368d} will align to a multiple of 4. If it skips two bytes, they will be
4302 filled in with the value 0x368d (the exact placement of the bytes depends upon
4303 the endianness of the processor). If it skips 1 or 3 bytes, the fill value is
4307 @section @code{.print @var{string}}
4309 @cindex @code{print} directive
4310 @code{@value{AS}} will print @var{string} on the standard output during
4311 assembly. You must put @var{string} in double quotes.
4314 @section @code{.psize @var{lines} , @var{columns}}
4316 @cindex @code{psize} directive
4317 @cindex listing control: paper size
4318 @cindex paper size, for listings
4319 Use this directive to declare the number of lines---and, optionally, the
4320 number of columns---to use for each page, when generating listings.
4322 If you do not use @code{.psize}, listings use a default line-count
4323 of 60. You may omit the comma and @var{columns} specification; the
4324 default width is 200 columns.
4326 @code{@value{AS}} generates formfeeds whenever the specified number of
4327 lines is exceeded (or whenever you explicitly request one, using
4330 If you specify @var{lines} as @code{0}, no formfeeds are generated save
4331 those explicitly specified with @code{.eject}.
4334 @section @code{.purgem @var{name}}
4336 @cindex @code{purgem} directive
4337 Undefine the macro @var{name}, so that later uses of the string will not be
4338 expanded. @xref{Macro}.
4341 @section @code{.quad @var{bignums}}
4343 @cindex @code{quad} directive
4344 @code{.quad} expects zero or more bignums, separated by commas. For
4345 each bignum, it emits
4347 an 8-byte integer. If the bignum won't fit in 8 bytes, it prints a
4348 warning message; and just takes the lowest order 8 bytes of the bignum.
4349 @cindex eight-byte integer
4350 @cindex integer, 8-byte
4352 The term ``quad'' comes from contexts in which a ``word'' is two bytes;
4353 hence @emph{quad}-word for 8 bytes.
4356 a 16-byte integer. If the bignum won't fit in 16 bytes, it prints a
4357 warning message; and just takes the lowest order 16 bytes of the bignum.
4358 @cindex sixteen-byte integer
4359 @cindex integer, 16-byte
4363 @section @code{.rept @var{count}}
4365 @cindex @code{rept} directive
4366 Repeat the sequence of lines between the @code{.rept} directive and the next
4367 @code{.endr} directive @var{count} times.
4369 For example, assembling
4377 is equivalent to assembling
4386 @section @code{.sbttl "@var{subheading}"}
4388 @cindex @code{sbttl} directive
4389 @cindex subtitles for listings
4390 @cindex listing control: subtitle
4391 Use @var{subheading} as the title (third line, immediately after the
4392 title line) when generating assembly listings.
4394 This directive affects subsequent pages, as well as the current page if
4395 it appears within ten lines of the top of a page.
4399 @section @code{.scl @var{class}}
4401 @cindex @code{scl} directive
4402 @cindex symbol storage class (COFF)
4403 @cindex COFF symbol storage class
4404 Set the storage-class value for a symbol. This directive may only be
4405 used inside a @code{.def}/@code{.endef} pair. Storage class may flag
4406 whether a symbol is static or external, or it may record further
4407 symbolic debugging information.
4410 The @samp{.scl} directive is primarily associated with COFF output; when
4411 configured to generate @code{b.out} output format, @code{@value{AS}}
4412 accepts this directive but ignores it.
4417 @section @code{.section @var{name}}
4419 @cindex @code{section} directive
4420 @cindex named section
4421 Use the @code{.section} directive to assemble the following code into a section
4424 This directive is only supported for targets that actually support arbitrarily
4425 named sections; on @code{a.out} targets, for example, it is not accepted, even
4426 with a standard @code{a.out} section name.
4429 For COFF targets, the @code{.section} directive is used in one of the following
4432 .section @var{name}[, "@var{flags}"]
4433 .section @var{name}[, @var{subsegment}]
4436 If the optional argument is quoted, it is taken as flags to use for the
4437 section. Each flag is a single character. The following flags are recognized:
4440 bss section (uninitialized data)
4442 section is not loaded
4452 shared section (meaningful for PE targets)
4455 If no flags are specified, the default flags depend upon the section name. If
4456 the section name is not recognized, the default will be for the section to be
4457 loaded and writable.
4459 If the optional argument to the @code{.section} directive is not quoted, it is
4460 taken as a subsegment number (@pxref{Sub-Sections}).
4464 For ELF targets, the @code{.section} directive is used like this:
4466 .section @var{name}[, "@var{flags}"[, @@@var{type}]]
4468 The optional @var{flags} argument is a quoted string which may contain any
4469 combintion of the following characters:
4472 section is allocatable
4476 section is executable
4479 The optional @var{type} argument may contain one of the following constants:
4482 section contains data
4484 section does not contain data (i.e., section only occupies space)
4487 If no flags are specified, the default flags depend upon the section name. If
4488 the section name is not recognized, the default will be for the section to have
4489 none of the above flags: it will not be allocated in memory, nor writable, nor
4490 executable. The section will contain data.
4492 For ELF targets, the assembler supports another type of @code{.section}
4493 directive for compatibility with the Solaris assembler:
4495 .section "@var{name}"[, @var{flags}...]
4497 Note that the section name is quoted. There may be a sequence of comma
4501 section is allocatable
4505 section is executable
4510 @section @code{.set @var{symbol}, @var{expression}}
4512 @cindex @code{set} directive
4513 @cindex symbol value, setting
4514 Set the value of @var{symbol} to @var{expression}. This
4515 changes @var{symbol}'s value and type to conform to
4516 @var{expression}. If @var{symbol} was flagged as external, it remains
4517 flagged (@pxref{Symbol Attributes}).
4519 You may @code{.set} a symbol many times in the same assembly.
4521 If you @code{.set} a global symbol, the value stored in the object
4522 file is the last value stored into it.
4525 The syntax for @code{set} on the HPPA is
4526 @samp{@var{symbol} .set @var{expression}}.
4530 @section @code{.short @var{expressions}}
4532 @cindex @code{short} directive
4534 @code{.short} is normally the same as @samp{.word}.
4535 @xref{Word,,@code{.word}}.
4537 In some configurations, however, @code{.short} and @code{.word} generate
4538 numbers of different lengths; @pxref{Machine Dependencies}.
4542 @code{.short} is the same as @samp{.word}. @xref{Word,,@code{.word}}.
4545 This expects zero or more @var{expressions}, and emits
4546 a 16 bit number for each.
4551 @section @code{.single @var{flonums}}
4553 @cindex @code{single} directive
4554 @cindex floating point numbers (single)
4555 This directive assembles zero or more flonums, separated by commas. It
4556 has the same effect as @code{.float}.
4558 The exact kind of floating point numbers emitted depends on how
4559 @code{@value{AS}} is configured. @xref{Machine Dependencies}.
4563 On the @value{TARGET} family, @code{.single} emits 32-bit floating point
4564 numbers in @sc{ieee} format.
4570 @section @code{.size}
4572 @cindex @code{size} directive
4573 This directive is generated by compilers to include auxiliary debugging
4574 information in the symbol table. It is only permitted inside
4575 @code{.def}/@code{.endef} pairs.
4578 @samp{.size} is only meaningful when generating COFF format output; when
4579 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4585 @section @code{.sleb128 @var{expressions}}
4587 @cindex @code{sleb128} directive
4588 @var{sleb128} stands for ``signed little endian base 128.'' This is a
4589 compact, variable length representation of numbers used by the DWARF
4590 symbolic debugging format. @xref{Uleb128,@code{.uleb128}}.
4592 @ifclear no-space-dir
4594 @section @code{.skip @var{size} , @var{fill}}
4596 @cindex @code{skip} directive
4597 @cindex filling memory
4598 This directive emits @var{size} bytes, each of value @var{fill}. Both
4599 @var{size} and @var{fill} are absolute expressions. If the comma and
4600 @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same as
4604 @section @code{.space @var{size} , @var{fill}}
4606 @cindex @code{space} directive
4607 @cindex filling memory
4608 This directive emits @var{size} bytes, each of value @var{fill}. Both
4609 @var{size} and @var{fill} are absolute expressions. If the comma
4610 and @var{fill} are omitted, @var{fill} is assumed to be zero. This is the same
4615 @emph{Warning:} @code{.space} has a completely different meaning for HPPA
4616 targets; use @code{.block} as a substitute. See @cite{HP9000 Series 800
4617 Assembly Language Reference Manual} (HP 92432-90001) for the meaning of the
4618 @code{.space} directive. @xref{HPPA Directives,,HPPA Assembler Directives},
4627 @section @code{.space}
4628 @cindex @code{space} directive
4630 On the AMD 29K, this directive is ignored; it is accepted for
4631 compatibility with other AMD 29K assemblers.
4634 @emph{Warning:} In most versions of the @sc{gnu} assembler, the directive
4635 @code{.space} has the effect of @code{.block} @xref{Machine Dependencies}.
4641 @section @code{.stabd, .stabn, .stabs}
4643 @cindex symbolic debuggers, information for
4644 @cindex @code{stab@var{x}} directives
4645 There are three directives that begin @samp{.stab}.
4646 All emit symbols (@pxref{Symbols}), for use by symbolic debuggers.
4647 The symbols are not entered in the @code{@value{AS}} hash table: they
4648 cannot be referenced elsewhere in the source file.
4649 Up to five fields are required:
4653 This is the symbol's name. It may contain any character except
4654 @samp{\000}, so is more general than ordinary symbol names. Some
4655 debuggers used to code arbitrarily complex structures into symbol names
4659 An absolute expression. The symbol's type is set to the low 8 bits of
4660 this expression. Any bit pattern is permitted, but @code{@value{LD}}
4661 and debuggers choke on silly bit patterns.
4664 An absolute expression. The symbol's ``other'' attribute is set to the
4665 low 8 bits of this expression.
4668 An absolute expression. The symbol's descriptor is set to the low 16
4669 bits of this expression.
4672 An absolute expression which becomes the symbol's value.
4675 If a warning is detected while reading a @code{.stabd}, @code{.stabn},
4676 or @code{.stabs} statement, the symbol has probably already been created;
4677 you get a half-formed symbol in your object file. This is
4678 compatible with earlier assemblers!
4681 @cindex @code{stabd} directive
4682 @item .stabd @var{type} , @var{other} , @var{desc}
4684 The ``name'' of the symbol generated is not even an empty string.
4685 It is a null pointer, for compatibility. Older assemblers used a
4686 null pointer so they didn't waste space in object files with empty
4689 The symbol's value is set to the location counter,
4690 relocatably. When your program is linked, the value of this symbol
4691 is the address of the location counter when the @code{.stabd} was
4694 @cindex @code{stabn} directive
4695 @item .stabn @var{type} , @var{other} , @var{desc} , @var{value}
4696 The name of the symbol is set to the empty string @code{""}.
4698 @cindex @code{stabs} directive
4699 @item .stabs @var{string} , @var{type} , @var{other} , @var{desc} , @var{value}
4700 All five fields are specified.
4706 @section @code{.string} "@var{str}"
4708 @cindex string, copying to object file
4709 @cindex @code{string} directive
4711 Copy the characters in @var{str} to the object file. You may specify more than
4712 one string to copy, separated by commas. Unless otherwise specified for a
4713 particular machine, the assembler marks the end of each string with a 0 byte.
4714 You can use any of the escape sequences described in @ref{Strings,,Strings}.
4717 @section @code{.struct @var{expression}}
4719 @cindex @code{struct} directive
4720 Switch to the absolute section, and set the section offset to @var{expression},
4721 which must be an absolute expression. You might use this as follows:
4730 This would define the symbol @code{field1} to have the value 0, the symbol
4731 @code{field2} to have the value 4, and the symbol @code{field3} to have the
4732 value 8. Assembly would be left in the absolute section, and you would need to
4733 use a @code{.section} directive of some sort to change to some other section
4734 before further assembly.
4738 @section @code{.symver}
4739 @cindex @code{symver} directive
4740 @cindex symbol versioning
4741 @cindex versions of symbols
4742 Use the @code{.symver} directive to bind symbols to specific version nodes
4743 within a source file. This is only supported on ELF platforms, and is
4744 typically used when assembling files to be linked into a shared library.
4745 There are cases where it may make sense to use this in objects to be bound
4746 into an application itself so as to override a versioned symbol from a
4749 For ELF targets, the @code{.symver} directive is used like this:
4751 .symver @var{name}, @var{name2@@nodename}
4753 In this case, the symbol @var{name} must exist and be defined within the file
4754 being assembled. The @code{.versym} directive effectively creates a symbol
4755 alias with the name @var{name2@@nodename}, and in fact the main reason that we
4756 just don't try and create a regular alias is that the @var{@@} character isn't
4757 permitted in symbol names. The @var{name2} part of the name is the actual name
4758 of the symbol by which it will be externally referenced. The name @var{name}
4759 itself is merely a name of convenience that is used so that it is possible to
4760 have definitions for multiple versions of a function within a single source
4761 file, and so that the compiler can unambiguously know which version of a
4762 function is being mentioned. The @var{nodename} portion of the alias should be
4763 the name of a node specified in the version script supplied to the linker when
4764 building a shared library. If you are attempting to override a versioned
4765 symbol from a shared library, then @var{nodename} should correspond to the
4766 nodename of the symbol you are trying to override.
4771 @section @code{.tag @var{structname}}
4773 @cindex COFF structure debugging
4774 @cindex structure debugging, COFF
4775 @cindex @code{tag} directive
4776 This directive is generated by compilers to include auxiliary debugging
4777 information in the symbol table. It is only permitted inside
4778 @code{.def}/@code{.endef} pairs. Tags are used to link structure
4779 definitions in the symbol table with instances of those structures.
4782 @samp{.tag} is only used when generating COFF format output; when
4783 @code{@value{AS}} is generating @code{b.out}, it accepts this directive but
4789 @section @code{.text @var{subsection}}
4791 @cindex @code{text} directive
4792 Tells @code{@value{AS}} to assemble the following statements onto the end of
4793 the text subsection numbered @var{subsection}, which is an absolute
4794 expression. If @var{subsection} is omitted, subsection number zero
4798 @section @code{.title "@var{heading}"}
4800 @cindex @code{title} directive
4801 @cindex listing control: title line
4802 Use @var{heading} as the title (second line, immediately after the
4803 source file name and pagenumber) when generating assembly listings.
4805 This directive affects subsequent pages, as well as the current page if
4806 it appears within ten lines of the top of a page.
4810 @section @code{.type @var{int}}
4812 @cindex COFF symbol type
4813 @cindex symbol type, COFF
4814 @cindex @code{type} directive
4815 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4816 records the integer @var{int} as the type attribute of a symbol table entry.
4819 @samp{.type} is associated only with COFF format output; when
4820 @code{@value{AS}} is configured for @code{b.out} output, it accepts this
4821 directive but ignores it.
4827 @section @code{.val @var{addr}}
4829 @cindex @code{val} directive
4830 @cindex COFF value attribute
4831 @cindex value attribute, COFF
4832 This directive, permitted only within @code{.def}/@code{.endef} pairs,
4833 records the address @var{addr} as the value attribute of a symbol table
4837 @samp{.val} is used only for COFF output; when @code{@value{AS}} is
4838 configured for @code{b.out}, it accepts this directive but ignores it.
4843 @section @code{.uleb128 @var{expressions}}
4845 @cindex @code{uleb128} directive
4846 @var{uleb128} stands for ``unsigned little endian base 128.'' This is a
4847 compact, variable length representation of numbers used by the DWARF
4848 symbolic debugging format. @xref{Sleb128,@code{.sleb128}}.
4852 @section @code{.internal}, @code{.hidden}, @code{.protected}
4853 @cindex @code{internal} directive
4854 @cindex @code{hidden} directive
4855 @cindex @code{protected} directive
4856 @cindex symbol visibility
4858 These directives can be used to set the visibility of a specified symbol. By
4859 default a symbol's visibility is set by its binding (local, global or weak),
4860 but these directives can be used to override that.
4862 A visibility of @code{protected} means that any references to the symbol from
4863 within the component that defines the symbol must be resolved to the definition
4864 in that component, even if a definition in another component would normally
4867 A visibility of @code{hidden} means that the symbol is not visible to other
4868 components. Such a symbol is always considered to be protected as well.
4870 A visibility of @code{internal} is the same as a visibility of @code{hidden},
4871 except that some extra, processor specific processing must also be performed
4874 For ELF targets, the directives are used like this:
4877 .internal @var{name}
4879 .protected @var{name}
4885 @section @code{.word @var{expressions}}
4887 @cindex @code{word} directive
4888 This directive expects zero or more @var{expressions}, of any section,
4889 separated by commas.
4892 For each expression, @code{@value{AS}} emits a 32-bit number.
4895 For each expression, @code{@value{AS}} emits a 16-bit number.
4900 The size of the number emitted, and its byte order,
4901 depend on what target computer the assembly is for.
4904 @c on amd29k, i960, sparc the "special treatment to support compilers" doesn't
4905 @c happen---32-bit addressability, period; no long/short jumps.
4906 @ifset DIFF-TBL-KLUGE
4907 @cindex difference tables altered
4908 @cindex altered difference tables
4910 @emph{Warning: Special Treatment to support Compilers}
4914 Machines with a 32-bit address space, but that do less than 32-bit
4915 addressing, require the following special treatment. If the machine of
4916 interest to you does 32-bit addressing (or doesn't require it;
4917 @pxref{Machine Dependencies}), you can ignore this issue.
4920 In order to assemble compiler output into something that works,
4921 @code{@value{AS}} occasionlly does strange things to @samp{.word} directives.
4922 Directives of the form @samp{.word sym1-sym2} are often emitted by
4923 compilers as part of jump tables. Therefore, when @code{@value{AS}} assembles a
4924 directive of the form @samp{.word sym1-sym2}, and the difference between
4925 @code{sym1} and @code{sym2} does not fit in 16 bits, @code{@value{AS}}
4926 creates a @dfn{secondary jump table}, immediately before the next label.
4927 This secondary jump table is preceded by a short-jump to the
4928 first byte after the secondary table. This short-jump prevents the flow
4929 of control from accidentally falling into the new table. Inside the
4930 table is a long-jump to @code{sym2}. The original @samp{.word}
4931 contains @code{sym1} minus the address of the long-jump to
4934 If there were several occurrences of @samp{.word sym1-sym2} before the
4935 secondary jump table, all of them are adjusted. If there was a
4936 @samp{.word sym3-sym4}, that also did not fit in sixteen bits, a
4937 long-jump to @code{sym4} is included in the secondary jump table,
4938 and the @code{.word} directives are adjusted to contain @code{sym3}
4939 minus the address of the long-jump to @code{sym4}; and so on, for as many
4940 entries in the original jump table as necessary.
4943 @emph{This feature may be disabled by compiling @code{@value{AS}} with the
4944 @samp{-DWORKING_DOT_WORD} option.} This feature is likely to confuse
4945 assembly language programmers.
4948 @c end DIFF-TBL-KLUGE
4951 @section Deprecated Directives
4953 @cindex deprecated directives
4954 @cindex obsolescent directives
4955 One day these directives won't work.
4956 They are included for compatibility with older assemblers.
4963 @node Machine Dependencies
4964 @chapter Machine Dependent Features
4966 @cindex machine dependencies
4967 The machine instruction sets are (almost by definition) different on
4968 each machine where @code{@value{AS}} runs. Floating point representations
4969 vary as well, and @code{@value{AS}} often supports a few additional
4970 directives or command-line options for compatibility with other
4971 assemblers on a particular platform. Finally, some versions of
4972 @code{@value{AS}} support special pseudo-instructions for branch
4975 This chapter discusses most of these differences, though it does not
4976 include details on any machine's instruction set. For details on that
4977 subject, see the hardware manufacturer's manual.
4981 * AMD29K-Dependent:: AMD 29K Dependent Features
4984 * ARC-Dependent:: ARC Dependent Features
4987 * ARM-Dependent:: ARM Dependent Features
4990 * D10V-Dependent:: D10V Dependent Features
4993 * D30V-Dependent:: D30V Dependent Features
4996 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
4999 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5002 * HPPA-Dependent:: HPPA Dependent Features
5005 * ESA/390-Dependent:: IBM ESA/390 Dependent Features
5008 * i386-Dependent:: Intel 80386 Dependent Features
5011 * i960-Dependent:: Intel 80960 Dependent Features
5014 * M32R-Dependent:: M32R Dependent Features
5017 * M68K-Dependent:: M680x0 Dependent Features
5020 * M68HC11-Dependent:: M68HC11 and 68HC12 Dependent Features
5023 * MIPS-Dependent:: MIPS Dependent Features
5026 * SH-Dependent:: Hitachi SH Dependent Features
5029 * PJ-Dependent:: picoJava Dependent Features
5032 * Sparc-Dependent:: SPARC Dependent Features
5035 * V850-Dependent:: V850 Dependent Features
5038 * Z8000-Dependent:: Z8000 Dependent Features
5041 * Vax-Dependent:: VAX Dependent Features
5048 @c The following major nodes are *sections* in the GENERIC version, *chapters*
5049 @c in single-cpu versions. This is mainly achieved by @lowersections. There is a
5050 @c peculiarity: to preserve cross-references, there must be a node called
5051 @c "Machine Dependencies". Hence the conditional nodenames in each
5052 @c major node below. Node defaulting in makeinfo requires adjacency of
5053 @c node and sectioning commands; hence the repetition of @chapter BLAH
5054 @c in both conditional blocks.
5060 @chapter ARC Dependent Features
5063 @node Machine Dependencies
5064 @chapter ARC Dependent Features
5069 * ARC-Opts:: Options
5070 * ARC-Float:: Floating Point
5071 * ARC-Directives:: Sparc Machine Directives
5077 @cindex options for ARC
5079 @cindex architectures, ARC
5080 @cindex ARC architectures
5081 The ARC chip family includes several successive levels (or other
5082 variants) of chip, using the same core instruction set, but including
5083 a few additional instructions at each level.
5085 By default, @code{@value{AS}} assumes the core instruction set (ARC
5086 base). The @code{.cpu} pseudo-op is intended to be used to select
5090 @cindex @code{-mbig-endian} option (ARC)
5091 @cindex @code{-mlittle-endian} option (ARC)
5092 @cindex ARC big-endian output
5093 @cindex ARC little-endian output
5094 @cindex big-endian output, ARC
5095 @cindex little-endian output, ARC
5097 @itemx -mlittle-endian
5098 Any @sc{arc} configuration of @code{@value{AS}} can select big-endian or
5099 little-endian output at run time (unlike most other @sc{gnu} development
5100 tools, which must be configured for one or the other). Use
5101 @samp{-mbig-endian} to select big-endian output, and @samp{-mlittle-endian}
5106 @section Floating Point
5108 @cindex floating point, ARC (@sc{ieee})
5109 @cindex ARC floating point (@sc{ieee})
5110 The ARC cpu family currently does not have hardware floating point
5111 support. Software floating point support is provided by @code{GCC}
5112 and uses @sc{ieee} floating-point numbers.
5114 @node ARC-Directives
5115 @section ARC Machine Directives
5117 @cindex ARC machine directives
5118 @cindex machine directives, ARC
5119 The ARC version of @code{@value{AS}} supports the following additional
5124 @cindex @code{cpu} directive, SPARC
5125 This must be followed by the desired cpu.
5126 The ARC is intended to be customizable, @code{.cpu} is used to
5127 select the desired variant [though currently there are none].
5134 @include c-a29k.texi
5143 @node Machine Dependencies
5144 @chapter Machine Dependent Features
5146 The machine instruction sets are different on each Hitachi chip family,
5147 and there are also some syntax differences among the families. This
5148 chapter describes the specific @code{@value{AS}} features for each
5152 * H8/300-Dependent:: Hitachi H8/300 Dependent Features
5153 * H8/500-Dependent:: Hitachi H8/500 Dependent Features
5154 * SH-Dependent:: Hitachi SH Dependent Features
5161 @include c-d10v.texi
5165 @include c-d30v.texi
5169 @include c-h8300.texi
5173 @include c-h8500.texi
5177 @include c-hppa.texi
5181 @include c-i370.texi
5185 @include c-i386.texi
5189 @include c-i960.texi
5193 @include c-m32r.texi
5197 @include c-m68k.texi
5201 @include c-m68hc11.texi
5205 @include c-mips.texi
5209 @include c-ns32k.texi
5221 @include c-sparc.texi
5233 @include c-v850.texi
5237 @c reverse effect of @down at top of generic Machine-Dep chapter
5241 @node Reporting Bugs
5242 @chapter Reporting Bugs
5243 @cindex bugs in assembler
5244 @cindex reporting bugs in assembler
5246 Your bug reports play an essential role in making @code{@value{AS}} reliable.
5248 Reporting a bug may help you by bringing a solution to your problem, or it may
5249 not. But in any case the principal function of a bug report is to help the
5250 entire community by making the next version of @code{@value{AS}} work better.
5251 Bug reports are your contribution to the maintenance of @code{@value{AS}}.
5253 In order for a bug report to serve its purpose, you must include the
5254 information that enables us to fix the bug.
5257 * Bug Criteria:: Have you found a bug?
5258 * Bug Reporting:: How to report bugs
5262 @section Have you found a bug?
5263 @cindex bug criteria
5265 If you are not sure whether you have found a bug, here are some guidelines:
5268 @cindex fatal signal
5269 @cindex assembler crash
5270 @cindex crash of assembler
5272 If the assembler gets a fatal signal, for any input whatever, that is a
5273 @code{@value{AS}} bug. Reliable assemblers never crash.
5275 @cindex error on valid input
5277 If @code{@value{AS}} produces an error message for valid input, that is a bug.
5279 @cindex invalid input
5281 If @code{@value{AS}} does not produce an error message for invalid input, that
5282 is a bug. However, you should note that your idea of ``invalid input'' might
5283 be our idea of ``an extension'' or ``support for traditional practice''.
5286 If you are an experienced user of assemblers, your suggestions for improvement
5287 of @code{@value{AS}} are welcome in any case.
5291 @section How to report bugs
5293 @cindex assembler bugs, reporting
5295 A number of companies and individuals offer support for @sc{gnu} products. If
5296 you obtained @code{@value{AS}} from a support organization, we recommend you
5297 contact that organization first.
5299 You can find contact information for many support companies and
5300 individuals in the file @file{etc/SERVICE} in the @sc{gnu} Emacs
5303 In any event, we also recommend that you send bug reports for @code{@value{AS}}
5304 to @samp{bug-gnu-utils@@gnu.org}.
5306 The fundamental principle of reporting bugs usefully is this:
5307 @strong{report all the facts}. If you are not sure whether to state a
5308 fact or leave it out, state it!
5310 Often people omit facts because they think they know what causes the problem
5311 and assume that some details do not matter. Thus, you might assume that the
5312 name of a symbol you use in an example does not matter. Well, probably it does
5313 not, but one cannot be sure. Perhaps the bug is a stray memory reference which
5314 happens to fetch from the location where that name is stored in memory;
5315 perhaps, if the name were different, the contents of that location would fool
5316 the assembler into doing the right thing despite the bug. Play it safe and
5317 give a specific, complete example. That is the easiest thing for you to do,
5318 and the most helpful.
5320 Keep in mind that the purpose of a bug report is to enable us to fix the bug if
5321 it is new to us. Therefore, always write your bug reports on the assumption
5322 that the bug has not been reported previously.
5324 Sometimes people give a few sketchy facts and ask, ``Does this ring a
5325 bell?'' Those bug reports are useless, and we urge everyone to
5326 @emph{refuse to respond to them} except to chide the sender to report
5329 To enable us to fix the bug, you should include all these things:
5333 The version of @code{@value{AS}}. @code{@value{AS}} announces it if you start
5334 it with the @samp{--version} argument.
5336 Without this, we will not know whether there is any point in looking for
5337 the bug in the current version of @code{@value{AS}}.
5340 Any patches you may have applied to the @code{@value{AS}} source.
5343 The type of machine you are using, and the operating system name and
5347 What compiler (and its version) was used to compile @code{@value{AS}}---e.g.
5351 The command arguments you gave the assembler to assemble your example and
5352 observe the bug. To guarantee you will not omit something important, list them
5353 all. A copy of the Makefile (or the output from make) is sufficient.
5355 If we were to try to guess the arguments, we would probably guess wrong
5356 and then we might not encounter the bug.
5359 A complete input file that will reproduce the bug. If the bug is observed when
5360 the assembler is invoked via a compiler, send the assembler source, not the
5361 high level language source. Most compilers will produce the assembler source
5362 when run with the @samp{-S} option. If you are using @code{@value{GCC}}, use
5363 the options @samp{-v --save-temps}; this will save the assembler source in a
5364 file with an extension of @file{.s}, and also show you exactly how
5365 @code{@value{AS}} is being run.
5368 A description of what behavior you observe that you believe is
5369 incorrect. For example, ``It gets a fatal signal.''
5371 Of course, if the bug is that @code{@value{AS}} gets a fatal signal, then we
5372 will certainly notice it. But if the bug is incorrect output, we might not
5373 notice unless it is glaringly wrong. You might as well not give us a chance to
5376 Even if the problem you experience is a fatal signal, you should still say so
5377 explicitly. Suppose something strange is going on, such as, your copy of
5378 @code{@value{AS}} is out of synch, or you have encountered a bug in the C
5379 library on your system. (This has happened!) Your copy might crash and ours
5380 would not. If you told us to expect a crash, then when ours fails to crash, we
5381 would know that the bug was not happening for us. If you had not told us to
5382 expect a crash, then we would not be able to draw any conclusion from our
5386 If you wish to suggest changes to the @code{@value{AS}} source, send us context
5387 diffs, as generated by @code{diff} with the @samp{-u}, @samp{-c}, or @samp{-p}
5388 option. Always send diffs from the old file to the new file. If you even
5389 discuss something in the @code{@value{AS}} source, refer to it by context, not
5392 The line numbers in our development sources will not match those in your
5393 sources. Your line numbers would convey no useful information to us.
5396 Here are some things that are not necessary:
5400 A description of the envelope of the bug.
5402 Often people who encounter a bug spend a lot of time investigating
5403 which changes to the input file will make the bug go away and which
5404 changes will not affect it.
5406 This is often time consuming and not very useful, because the way we
5407 will find the bug is by running a single example under the debugger
5408 with breakpoints, not by pure deduction from a series of examples.
5409 We recommend that you save your time for something else.
5411 Of course, if you can find a simpler example to report @emph{instead}
5412 of the original one, that is a convenience for us. Errors in the
5413 output will be easier to spot, running under the debugger will take
5414 less time, and so on.
5416 However, simplification is not vital; if you do not want to do this,
5417 report the bug anyway and send us the entire test case you used.
5420 A patch for the bug.
5422 A patch for the bug does help us if it is a good one. But do not omit
5423 the necessary information, such as the test case, on the assumption that
5424 a patch is all we need. We might see problems with your patch and decide
5425 to fix the problem another way, or we might not understand it at all.
5427 Sometimes with a program as complicated as @code{@value{AS}} it is very hard to
5428 construct an example that will make the program follow a certain path through
5429 the code. If you do not send us the example, we will not be able to construct
5430 one, so we will not be able to verify that the bug is fixed.
5432 And if we cannot understand what bug you are trying to fix, or why your
5433 patch should be an improvement, we will not install it. A test case will
5434 help us to understand.
5437 A guess about what the bug is or what it depends on.
5439 Such guesses are usually wrong. Even we cannot guess right about such
5440 things without first using the debugger to find the facts.
5443 @node Acknowledgements
5444 @chapter Acknowledgements
5446 If you have contributed to @code{@value{AS}} and your name isn't listed here,
5447 it is not meant as a slight. We just don't know about it. Send mail to the
5448 maintainer, and we'll correct the situation. Currently
5450 the maintainer is Ken Raeburn (email address @code{raeburn@@cygnus.com}).
5452 Dean Elsner wrote the original @sc{gnu} assembler for the VAX.@footnote{Any
5455 Jay Fenlason maintained GAS for a while, adding support for GDB-specific debug
5456 information and the 68k series machines, most of the preprocessing pass, and
5457 extensive changes in @file{messages.c}, @file{input-file.c}, @file{write.c}.
5459 K. Richard Pixley maintained GAS for a while, adding various enhancements and
5460 many bug fixes, including merging support for several processors, breaking GAS
5461 up to handle multiple object file format back ends (including heavy rewrite,
5462 testing, an integration of the coff and b.out back ends), adding configuration
5463 including heavy testing and verification of cross assemblers and file splits
5464 and renaming, converted GAS to strictly ANSI C including full prototypes, added
5465 support for m680[34]0 and cpu32, did considerable work on i960 including a COFF
5466 port (including considerable amounts of reverse engineering), a SPARC opcode
5467 file rewrite, DECstation, rs6000, and hp300hpux host ports, updated ``know''
5468 assertions and made them work, much other reorganization, cleanup, and lint.
5470 Ken Raeburn wrote the high-level BFD interface code to replace most of the code
5471 in format-specific I/O modules.
5473 The original VMS support was contributed by David L. Kashtan. Eric Youngdale
5474 has done much work with it since.
5476 The Intel 80386 machine description was written by Eliot Dresselhaus.
5478 Minh Tran-Le at IntelliCorp contributed some AIX 386 support.
5480 The Motorola 88k machine description was contributed by Devon Bowen of Buffalo
5481 University and Torbjorn Granlund of the Swedish Institute of Computer Science.
5483 Keith Knowles at the Open Software Foundation wrote the original MIPS back end
5484 (@file{tc-mips.c}, @file{tc-mips.h}), and contributed Rose format support
5485 (which hasn't been merged in yet). Ralph Campbell worked with the MIPS code to
5486 support a.out format.
5488 Support for the Zilog Z8k and Hitachi H8/300 and H8/500 processors (tc-z8k,
5489 tc-h8300, tc-h8500), and IEEE 695 object file format (obj-ieee), was written by
5490 Steve Chamberlain of Cygnus Support. Steve also modified the COFF back end to
5491 use BFD for some low-level operations, for use with the H8/300 and AMD 29k
5494 John Gilmore built the AMD 29000 support, added @code{.include} support, and
5495 simplified the configuration of which versions accept which directives. He
5496 updated the 68k machine description so that Motorola's opcodes always produced
5497 fixed-size instructions (e.g. @code{jsr}), while synthetic instructions
5498 remained shrinkable (@code{jbsr}). John fixed many bugs, including true tested
5499 cross-compilation support, and one bug in relaxation that took a week and
5500 required the proverbial one-bit fix.
5502 Ian Lance Taylor of Cygnus Support merged the Motorola and MIT syntax for the
5503 68k, completed support for some COFF targets (68k, i386 SVR3, and SCO Unix),
5504 added support for MIPS ECOFF and ELF targets, wrote the initial RS/6000 and
5505 PowerPC assembler, and made a few other minor patches.
5507 Steve Chamberlain made @code{@value{AS}} able to generate listings.
5509 Hewlett-Packard contributed support for the HP9000/300.
5511 Jeff Law wrote GAS and BFD support for the native HPPA object format (SOM)
5512 along with a fairly extensive HPPA testsuite (for both SOM and ELF object
5513 formats). This work was supported by both the Center for Software Science at
5514 the University of Utah and Cygnus Support.
5516 Support for ELF format files has been worked on by Mark Eichin of Cygnus
5517 Support (original, incomplete implementation for SPARC), Pete Hoogenboom and
5518 Jeff Law at the University of Utah (HPPA mainly), Michael Meissner of the Open
5519 Software Foundation (i386 mainly), and Ken Raeburn of Cygnus Support (sparc,
5520 and some initial 64-bit support).
5522 Linas Vepstas added GAS support for the ESA/390 "IBM 370" architecture.
5524 Richard Henderson rewrote the Alpha assembler. Klaus Kaempf wrote GAS and BFD
5525 support for openVMS/Alpha.
5527 Several engineers at Cygnus Support have also provided many small bug fixes and
5528 configuration enhancements.
5530 Many others have contributed large or small bugfixes and enhancements. If
5531 you have contributed significant work and are not mentioned on this list, and
5532 want to be, let us know. Some of the history has been lost; we are not
5533 intentionally leaving anyone out.
projects / deliverable / binutils-gdb.git / blob