This is as.info, produced by makeinfo version 4.2 from as.texinfo.

START-INFO-DIR-ENTRY
* As: (as).                     The GNU assembler.
* Gas: (as).                    The GNU assembler.
END-INFO-DIR-ENTRY

   This file documents the GNU Assembler "as".

   Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001, 2002
Free Software Foundation, Inc.

   Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the section entitled "GNU
Free Documentation License".


File: as.info,  Node: Top,  Next: Overview,  Up: (dir)

Using as
********

   This file is a user guide to the GNU assembler `as' version 2.13.

   This document is distributed under the terms of the GNU Free
Documentation License.  A copy of the license is included in the
section entitled "GNU Free Documentation License".

* Menu:

* Overview::                    Overview
* Invoking::                    Command-Line Options
* Syntax::                      Syntax
* Sections::                    Sections and Relocation
* Symbols::                     Symbols
* Expressions::                 Expressions
* Pseudo Ops::                  Assembler Directives
* Machine Dependencies::        Machine Dependent Features
* Reporting Bugs::              Reporting Bugs
* Acknowledgements::            Who Did What
* GNU Free Documentation License::  GNU Free Documentation License
* Index::                       Index


File: as.info,  Node: Overview,  Next: Invoking,  Prev: Top,  Up: Top

Overview
********

   Here is a brief summary of how to invoke `as'.  For details, *note
Comand-Line Options: Invoking..

     as [-a[cdhlns][=FILE]] [-D] [-defsym SYM=VAL]
      [-f] [-gstabs] [-gdwarf2] [-help] [-I DIR]
      [-J] [-K] [-L]
      [-listing-lhs-width=NUM] [-listing-lhs-width2=NUM]
      [-listing-rhs-width=NUM] [-listing-cont-lines=NUM]
      [-keep-locals] [-o OBJFILE] [-R] [-statistics] [-v]
      [-version] [-version] [-W] [-warn] [-fatal-warnings]
      [-w] [-x] [-Z] [-target-help] [TARGET-OPTIONS]
      [-|FILES ...]
     
     _Target Alpha options:_
        [-mCPU]
        [-mdebug | -no-mdebug]
        [-relax] [-g] [-GSIZE]
        [-F] [-32addr]
     
     _Target ARC options:_
        [-marc[5|6|7|8]]
        [-EB|-EL]
     
     _Target ARM options:_
        [-mcpu=PROCESSOR[+EXTENSION...]]
        [-march=ARCHITECTURE[+EXTENSION...]]
        [-mfpu=FLOATING-POINT-FROMAT]
        [-mthumb]
        [-EB|-EL]
        [-mapcs-32|-mapcs-26|-mapcs-float|
         -mapcs-reentrant]
        [-mthumb-interwork] [-moabi] [-k]
     
     _Target CRIS options:_
        [-underscore | -no-underscore]
        [-pic] [-N]
        [-emulation=criself | -emulation=crisaout]
     
     _Target D10V options:_
        [-O]
     
     _Target D30V options:_
        [-O|-n|-N]
     
     _Target i386 options:_
        [-32|-64]
     
     _Target i960 options:_
        [-ACA|-ACA_A|-ACB|-ACC|-AKA|-AKB|
         -AKC|-AMC]
        [-b] [-no-relax]
     
     _Target M32R options:_
        [-m32rx|-[no-]warn-explicit-parallel-conflicts|
        -W[n]p]
     
     _Target M680X0 options:_
        [-l] [-m68000|-m68010|-m68020|...]
     
     _Target M68HC11 options:_
        [-m68hc11|-m68hc12]
        [-force-long-branchs] [-short-branchs]
        [-strict-direct-mode] [-print-insn-syntax]
        [-print-opcodes] [-generate-example]
     
     _Target MCORE options:_
        [-jsri2bsr] [-sifilter] [-relax]
        [-mcpu=[210|340]]
     
     _Target MIPS options:_
        [-nocpp] [-EL] [-EB] [-n] [-O[OPTIMIZATION LEVEL]]
        [-g[DEBUG LEVEL]] [-G NUM] [-KPIC] [-call_shared]
        [-non_shared] [-xgot] [-membedded-pic]
        [-mabi=ABI] [-32] [-n32] [-64] [-mfp32] [-mgp32]
        [-march=CPU] [-mtune=CPU] [-mips1] [-mips2]
        [-mips3] [-mips4] [-mips5] [-mips32] [-mips64]
        [-construct-floats] [-no-construct-floats]
        [-trap] [-no-break] [-break] [-no-trap]
        [-mfix7000] [-mno-fix7000]
        [-mips16] [-no-mips16]
        [-mips3d] [-no-mips3d]
        [-mdmx] [-no-mdmx]
        [-mdebug] [-no-mdebug]
     
     _Target MMIX options:_
        [-fixed-special-register-names] [-globalize-symbols]
        [-gnu-syntax] [-relax] [-no-predefined-symbols]
        [-no-expand] [-no-merge-gregs] [-x]
        [-linker-allocated-gregs]
     
     _Target PDP11 options:_
        [-mpic|-mno-pic] [-mall] [-mno-extensions]
        [-mEXTENSION|-mno-EXTENSION]
        [-mCPU] [-mMACHINE]
     
     _Target picoJava options:_
        [-mb|-me]
     
     _Target PowerPC options:_
        [-mpwrx|-mpwr2|-mpwr|-m601|-mppc|-mppc32|-m603|-m604|
         -m403|-m405|-mppc64|-m620|-mppc64bridge|-mbooke|
         -mbooke32|-mbooke64]
        [-mcom|-many|-maltivec] [-memb]
        [-mregnames|-mno-regnames]
        [-mrelocatable|-mrelocatable-lib]
        [-mlittle|-mlittle-endian|-mbig|-mbig-endian]
        [-msolaris|-mno-solaris]
     
     _Target SPARC options:_
        [-Av6|-Av7|-Av8|-Asparclet|-Asparclite
         -Av8plus|-Av8plusa|-Av9|-Av9a]
        [-xarch=v8plus|-xarch=v8plusa] [-bump]
        [-32|-64]

`-a[cdhlmns]'
     Turn on listings, in any of a variety of ways:

    `-ac'
          omit false conditionals

    `-ad'
          omit debugging directives

    `-ah'
          include high-level source

    `-al'
          include assembly

    `-am'
          include macro expansions

    `-an'
          omit forms processing

    `-as'
          include symbols

    `=file'
          set the name of the listing file

     You may combine these options; for example, use `-aln' for assembly
     listing without forms processing.  The `=file' option, if used,
     must be the last one.  By itself, `-a' defaults to `-ahls'.

`-D'
     Ignored.  This option is accepted for script compatibility with
     calls to other assemblers.

`--defsym SYM=VALUE'
     Define the symbol SYM to be VALUE before assembling the input file.
     VALUE must be an integer constant.  As in C, a leading `0x'
     indicates a hexadecimal value, and a leading `0' indicates an
     octal value.

`-f'
     "fast"--skip whitespace and comment preprocessing (assume source is
     compiler output).

`--gstabs'
     Generate stabs debugging information for each assembler line.  This
     may help debugging assembler code, if the debugger can handle it.

`--gdwarf2'
     Generate DWARF2 debugging information for each assembler line.
     This may help debugging assembler code, if the debugger can handle
     it.  Note - this option is only supported by some targets, not all
     of them.

`--help'
     Print a summary of the command line options and exit.

`--target-help'
     Print a summary of all target specific options and exit.

`-I DIR'
     Add directory DIR to the search list for `.include' directives.

`-J'
     Don't warn about signed overflow.

`-K'
     Issue warnings when difference tables altered for long
     displacements.

`-L'
`--keep-locals'
     Keep (in the symbol table) local symbols.  On traditional a.out
     systems these start with `L', but different systems have different
     local label prefixes.

`--listing-lhs-width=NUMBER'
     Set the maximum width, in words, of the output data column for an
     assembler listing to NUMBER.

`--listing-lhs-width2=NUMBER'
     Set the maximum width, in words, of the output data column for
     continuation lines in an assembler listing to NUMBER.

`--listing-rhs-width=NUMBER'
     Set the maximum width of an input source line, as displayed in a
     listing, to NUMBER bytes.

`--listing-cont-lines=NUMBER'
     Set the maximum number of lines printed in a listing for a single
     line of input to NUMBER + 1.

`-o OBJFILE'
     Name the object-file output from `as' OBJFILE.

`-R'
     Fold the data section into the text section.

`--statistics'
     Print the maximum space (in bytes) and total time (in seconds)
     used by assembly.

`--strip-local-absolute'
     Remove local absolute symbols from the outgoing symbol table.

`-v'
`-version'
     Print the `as' version.

`--version'
     Print the `as' version and exit.

`-W'
`--no-warn'
     Suppress warning messages.

`--fatal-warnings'
     Treat warnings as errors.

`--warn'
     Don't suppress warning messages or treat them as errors.

`-w'
     Ignored.

`-x'
     Ignored.

`-Z'
     Generate an object file even after errors.

`-- | FILES ...'
     Standard input, or source files to assemble.

   The following options are available when as is configured for an ARC
processor.

`-marc[5|6|7|8]'
     This option selects the core processor variant.

`-EB | -EL'
     Select either big-endian (-EB) or little-endian (-EL) output.

   The following options are available when as is configured for the ARM
processor family.

`-mcpu=PROCESSOR[+EXTENSION...]'
     Specify which ARM processor variant is the target.

`-march=ARCHITECTURE[+EXTENSION...]'
     Specify which ARM architecture variant is used by the target.

`-mfpu=FLOATING-POINT-FORMAT'
     Select which Floating Point architecture is the target.

`-mthumb'
     Enable Thumb only instruction decoding.

`-mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant | -moabi'
     Select which procedure calling convention is in use.

`-EB | -EL'
     Select either big-endian (-EB) or little-endian (-EL) output.

`-mthumb-interwork'
     Specify that the code has been generated with interworking between
     Thumb and ARM code in mind.

`-k'
     Specify that PIC code has been generated.

   See the info pages for documentation of the CRIS-specific options.

   The following options are available when as is configured for a D10V
processor.
`-O'
     Optimize output by parallelizing instructions.

   The following options are available when as is configured for a D30V
processor.
`-O'
     Optimize output by parallelizing instructions.

`-n'
     Warn when nops are generated.

`-N'
     Warn when a nop after a 32-bit multiply instruction is generated.

   The following options are available when as is configured for the
Intel 80960 processor.

`-ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC'
     Specify which variant of the 960 architecture is the target.

`-b'
     Add code to collect statistics about branches taken.

`-no-relax'
     Do not alter compare-and-branch instructions for long
     displacements; error if necessary.

   The following options are available when as is configured for the
Mitsubishi M32R series.

`--m32rx'
     Specify which processor in the M32R family is the target.  The
     default is normally the M32R, but this option changes it to the
     M32RX.

`--warn-explicit-parallel-conflicts or --Wp'
     Produce warning messages when questionable parallel constructs are
     encountered.

`--no-warn-explicit-parallel-conflicts or --Wnp'
     Do not produce warning messages when questionable parallel
     constructs are encountered.

   The following options are available when as is configured for the
Motorola 68000 series.

`-l'
     Shorten references to undefined symbols, to one word instead of
     two.

`-m68000 | -m68008 | -m68010 | -m68020 | -m68030'
`| -m68040 | -m68060 | -m68302 | -m68331 | -m68332'
`| -m68333 | -m68340 | -mcpu32 | -m5200'
     Specify what processor in the 68000 family is the target.  The
     default is normally the 68020, but this can be changed at
     configuration time.

`-m68881 | -m68882 | -mno-68881 | -mno-68882'
     The target machine does (or does not) have a floating-point
     coprocessor.  The default is to assume a coprocessor for 68020,
     68030, and cpu32.  Although the basic 68000 is not compatible with
     the 68881, a combination of the two can be specified, since it's
     possible to do emulation of the coprocessor instructions with the
     main processor.

`-m68851 | -mno-68851'
     The target machine does (or does not) have a memory-management
     unit coprocessor.  The default is to assume an MMU for 68020 and
     up.

   For details about the PDP-11 machine dependent features options, see
*Note PDP-11-Options::.

`-mpic | -mno-pic'
     Generate position-independent (or position-dependent) code.  The
     default is `-mpic'.

`-mall'
`-mall-extensions'
     Enable all instruction set extensions.  This is the default.

`-mno-extensions'
     Disable all instruction set extensions.

`-mEXTENSION | -mno-EXTENSION'
     Enable (or disable) a particular instruction set extension.

`-mCPU'
     Enable the instruction set extensions supported by a particular
     CPU, and disable all other extensions.

`-mMACHINE'
     Enable the instruction set extensions supported by a particular
     machine model, and disable all other extensions.

   The following options are available when as is configured for a
picoJava processor.

`-mb'
     Generate "big endian" format output.

`-ml'
     Generate "little endian" format output.

   The following options are available when as is configured for the
Motorola 68HC11 or 68HC12 series.

`-m68hc11 | -m68hc12'
     Specify what processor is the target.  The default is defined by
     the configuration option when building the assembler.

`--force-long-branchs'
     Relative branches are turned into absolute ones. This concerns
     conditional branches, unconditional branches and branches to a sub
     routine.

`-S | --short-branchs'
     Do not turn relative branchs into absolute ones when the offset is
     out of range.

`--strict-direct-mode'
     Do not turn the direct addressing mode into extended addressing
     mode when the instruction does not support direct addressing mode.

`--print-insn-syntax'
     Print the syntax of instruction in case of error.

`--print-opcodes'
     print the list of instructions with syntax and then exit.

`--generate-example'
     print an example of instruction for each possible instruction and
     then exit.  This option is only useful for testing `as'.

   The following options are available when `as' is configured for the
SPARC architecture:

`-Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite'
`-Av8plus | -Av8plusa | -Av9 | -Av9a'
     Explicitly select a variant of the SPARC architecture.

     `-Av8plus' and `-Av8plusa' select a 32 bit environment.  `-Av9'
     and `-Av9a' select a 64 bit environment.

     `-Av8plusa' and `-Av9a' enable the SPARC V9 instruction set with
     UltraSPARC extensions.

`-xarch=v8plus | -xarch=v8plusa'
     For compatibility with the Solaris v9 assembler.  These options are
     equivalent to -Av8plus and -Av8plusa, respectively.

`-bump'
     Warn when the assembler switches to another architecture.

   The following options are available when as is configured for a MIPS
processor.

`-G NUM'
     This option sets the largest size of an object that can be
     referenced implicitly with the `gp' register.  It is only accepted
     for targets that use ECOFF format, such as a DECstation running
     Ultrix.  The default value is 8.

`-EB'
     Generate "big endian" format output.

`-EL'
     Generate "little endian" format output.

`-mips1'
`-mips2'
`-mips3'
`-mips4'
`-mips5'
`-mips32'
`-mips64'
     Generate code for a particular MIPS Instruction Set Architecture
     level.  `-mips1' is an alias for `-march=r3000', `-mips2' is an
     alias for `-march=r6000', `-mips3' is an alias for `-march=r4000'
     and `-mips4' is an alias for `-march=r8000'.  `-mips5', `-mips32',
     and `-mips64' correspond to generic `MIPS V', `MIPS32', and
     `MIPS64' ISA processors, respectively.

`-march=CPU'
     Generate code for a particular MIPS cpu.

`-mtune=CPU'
     Schedule and tune for a particular MIPS cpu.

`-mfix7000'
`-mno-fix7000'
     Cause nops to be inserted if the read of the destination register
     of an mfhi or mflo instruction occurs in the following two
     instructions.

`-mdebug'
`-no-mdebug'
     Cause stabs-style debugging output to go into an ECOFF-style
     .mdebug section instead of the standard ELF .stabs sections.

`-mgp32'
`-mfp32'
     The register sizes are normally inferred from the ISA and ABI, but
     these flags force a certain group of registers to be treated as 32
     bits wide at all times.  `-mgp32' controls the size of
     general-purpose registers and `-mfp32' controls the size of
     floating-point registers.

`-mips16'
`-no-mips16'
     Generate code for the MIPS 16 processor.  This is equivalent to
     putting `.set mips16' at the start of the assembly file.
     `-no-mips16' turns off this option.

`-mips3d'
`-no-mips3d'
     Generate code for the MIPS-3D Application Specific Extension.
     This tells the assembler to accept MIPS-3D instructions.
     `-no-mips3d' turns off this option.

`-mdmx'
`-no-mdmx'
     Generate code for the MDMX Application Specific Extension.  This
     tells the assembler to accept MDMX instructions.  `-no-mdmx' turns
     off this option.

`--construct-floats'
`--no-construct-floats'
     The `--no-construct-floats' option disables the construction of
     double width floating point constants by loading the two halves of
     the value into the two single width floating point registers that
     make up the double width register.  By default
     `--construct-floats' is selected, allowing construction of these
     floating point constants.

`--emulation=NAME'
     This option causes `as' to emulate `as' configured for some other
     target, in all respects, including output format (choosing between
     ELF and ECOFF only), handling of pseudo-opcodes which may generate
     debugging information or store symbol table information, and
     default endianness.  The available configuration names are:
     `mipsecoff', `mipself', `mipslecoff', `mipsbecoff', `mipslelf',
     `mipsbelf'.  The first two do not alter the default endianness
     from that of the primary target for which the assembler was
     configured; the others change the default to little- or big-endian
     as indicated by the `b' or `l' in the name.  Using `-EB' or `-EL'
     will override the endianness selection in any case.

     This option is currently supported only when the primary target
     `as' is configured for is a MIPS ELF or ECOFF target.
     Furthermore, the primary target or others specified with
     `--enable-targets=...' at configuration time must include support
     for the other format, if both are to be available.  For example,
     the Irix 5 configuration includes support for both.

     Eventually, this option will support more configurations, with more
     fine-grained control over the assembler's behavior, and will be
     supported for more processors.

`-nocpp'
     `as' ignores this option.  It is accepted for compatibility with
     the native tools.

`--trap'
`--no-trap'
`--break'
`--no-break'
     Control how to deal with multiplication overflow and division by
     zero.  `--trap' or `--no-break' (which are synonyms) take a trap
     exception (and only work for Instruction Set Architecture level 2
     and higher); `--break' or `--no-trap' (also synonyms, and the
     default) take a break exception.

`-n'
     When this option is used, `as' will issue a warning every time it
     generates a nop instruction from a macro.

   The following options are available when as is configured for an
MCore processor.

`-jsri2bsr'
`-nojsri2bsr'
     Enable or disable the JSRI to BSR transformation.  By default this
     is enabled.  The command line option `-nojsri2bsr' can be used to
     disable it.

`-sifilter'
`-nosifilter'
     Enable or disable the silicon filter behaviour.  By default this
     is disabled.  The default can be overridden by the `-sifilter'
     command line option.

`-relax'
     Alter jump instructions for long displacements.

`-mcpu=[210|340]'
     Select the cpu type on the target hardware.  This controls which
     instructions can be assembled.

`-EB'
     Assemble for a big endian target.

`-EL'
     Assemble for a little endian target.

   See the info pages for documentation of the MMIX-specific options.

* Menu:

* Manual::                      Structure of this Manual
* GNU Assembler::               The GNU Assembler
* Object Formats::              Object File Formats
* Command Line::                Command Line
* Input Files::                 Input Files
* Object::                      Output (Object) File
* Errors::                      Error and Warning Messages


File: as.info,  Node: Manual,  Next: GNU Assembler,  Up: Overview

Structure of this Manual
========================

   This manual is intended to describe what you need to know to use GNU
`as'.  We cover the syntax expected in source files, including notation
for symbols, constants, and expressions; the directives that `as'
understands; and of course how to invoke `as'.

   This manual also describes some of the machine-dependent features of
various flavors of the assembler.

   On the other hand, this manual is _not_ intended as an introduction
to programming in assembly language--let alone programming in general!
In a similar vein, we make no attempt to introduce the machine
architecture; we do _not_ describe the instruction set, standard
mnemonics, registers or addressing modes that are standard to a
particular architecture.  You may want to consult the manufacturer's
machine architecture manual for this information.


File: as.info,  Node: GNU Assembler,  Next: Object Formats,  Prev: Manual,  Up: Overview

The GNU Assembler
=================

   GNU `as' is really a family of assemblers.  If you use (or have
used) the GNU assembler on one architecture, you should find a fairly
similar environment when you use it on another architecture.  Each
version has much in common with the others, including object file
formats, most assembler directives (often called "pseudo-ops") and
assembler syntax.

   `as' is primarily intended to assemble the output of the GNU C
compiler `gcc' for use by the linker `ld'.  Nevertheless, we've tried
to make `as' assemble correctly everything that other assemblers for
the same machine would assemble.  Any exceptions are documented
explicitly (*note Machine Dependencies::).  This doesn't mean `as'
always uses the same syntax as another assembler for the same
architecture; for example, we know of several incompatible versions of
680x0 assembly language syntax.

   Unlike older assemblers, `as' is designed to assemble a source
program in one pass of the source file.  This has a subtle impact on the
`.org' directive (*note `.org': Org.).


File: as.info,  Node: Object Formats,  Next: Command Line,  Prev: GNU Assembler,  Up: Overview

Object File Formats
===================

   The GNU assembler can be configured to produce several alternative
object file formats.  For the most part, this does not affect how you
write assembly language programs; but directives for debugging symbols
are typically different in different file formats.  *Note Symbol
Attributes: Symbol Attributes.


File: as.info,  Node: Command Line,  Next: Input Files,  Prev: Object Formats,  Up: Overview

Command Line
============

   After the program name `as', the command line may contain options
and file names.  Options may appear in any order, and may be before,
after, or between file names.  The order of file names is significant.

   `--' (two hyphens) by itself names the standard input file
explicitly, as one of the files for `as' to assemble.

   Except for `--' any command line argument that begins with a hyphen
(`-') is an option.  Each option changes the behavior of `as'.  No
option changes the way another option works.  An option is a `-'
followed by one or more letters; the case of the letter is important.
All options are optional.

   Some options expect exactly one file name to follow them.  The file
name may either immediately follow the option's letter (compatible with
older assemblers) or it may be the next command argument (GNU
standard).  These two command lines are equivalent:

     as -o my-object-file.o mumble.s
     as -omy-object-file.o mumble.s


File: as.info,  Node: Input Files,  Next: Object,  Prev: Command Line,  Up: Overview

Input Files
===========

   We use the phrase "source program", abbreviated "source", to
describe the program input to one run of `as'.  The program may be in
one or more files; how the source is partitioned into files doesn't
change the meaning of the source.

   The source program is a concatenation of the text in all the files,
in the order specified.

   Each time you run `as' it assembles exactly one source program.  The
source program is made up of one or more files.  (The standard input is
also a file.)

   You give `as' a command line that has zero or more input file names.
The input files are read (from left file name to right).  A command
line argument (in any position) that has no special meaning is taken to
be an input file name.

   If you give `as' no file names it attempts to read one input file
from the `as' standard input, which is normally your terminal.  You may
have to type <ctl-D> to tell `as' there is no more program to assemble.

   Use `--' if you need to explicitly name the standard input file in
your command line.

   If the source is empty, `as' produces a small, empty object file.

Filenames and Line-numbers
--------------------------

   There are two ways of locating a line in the input file (or files)
and either may be used in reporting error messages.  One way refers to
a line number in a physical file; the other refers to a line number in a
"logical" file.  *Note Error and Warning Messages: Errors.

   "Physical files" are those files named in the command line given to
`as'.

   "Logical files" are simply names declared explicitly by assembler
directives; they bear no relation to physical files.  Logical file
names help error messages reflect the original source file, when `as'
source is itself synthesized from other files.  `as' understands the
`#' directives emitted by the `gcc' preprocessor.  See also *Note
`.file': File.


File: as.info,  Node: Object,  Next: Errors,  Prev: Input Files,  Up: Overview

Output (Object) File
====================

   Every time you run `as' it produces an output file, which is your
assembly language program translated into numbers.  This file is the
object file.  Its default name is `a.out', or `b.out' when `as' is
configured for the Intel 80960.  You can give it another name by using
the `-o' option.  Conventionally, object file names end with `.o'.  The
default name is used for historical reasons: older assemblers were
capable of assembling self-contained programs directly into a runnable
program.  (For some formats, this isn't currently possible, but it can
be done for the `a.out' format.)

   The object file is meant for input to the linker `ld'.  It contains
assembled program code, information to help `ld' integrate the
assembled program into a runnable file, and (optionally) symbolic
information for the debugger.


File: as.info,  Node: Errors,  Prev: Object,  Up: Overview

Error and Warning Messages
==========================

   `as' may write warnings and error messages to the standard error
file (usually your terminal).  This should not happen when  a compiler
runs `as' automatically.  Warnings report an assumption made so that
`as' could keep assembling a flawed program; errors report a grave
problem that stops the assembly.

   Warning messages have the format

     file_name:NNN:Warning Message Text

(where NNN is a line number).  If a logical file name has been given
(*note `.file': File.) it is used for the filename, otherwise the name
of the current input file is used.  If a logical line number was given
(*note `.line': Line.)  then it is used to calculate the number printed,
otherwise the actual line in the current source file is printed.  The
message text is intended to be self explanatory (in the grand Unix
tradition).

   Error messages have the format
     file_name:NNN:FATAL:Error Message Text
   The file name and line number are derived as for warning messages.
The actual message text may be rather less explanatory because many of
them aren't supposed to happen.


File: as.info,  Node: Invoking,  Next: Syntax,  Prev: Overview,  Up: Top

Command-Line Options
********************

   This chapter describes command-line options available in _all_
versions of the GNU assembler; *note Machine Dependencies::, for
options specific to particular machine architectures.

   If you are invoking `as' via the GNU C compiler (version 2), you can
use the `-Wa' option to pass arguments through to the assembler.  The
assembler arguments must be separated from each other (and the `-Wa')
by commas.  For example:

     gcc -c -g -O -Wa,-alh,-L file.c

This passes two options to the assembler: `-alh' (emit a listing to
standard output with with high-level and assembly source) and `-L'
(retain local symbols in the symbol table).

   Usually you do not need to use this `-Wa' mechanism, since many
compiler command-line options are automatically passed to the assembler
by the compiler.  (You can call the GNU compiler driver with the `-v'
option to see precisely what options it passes to each compilation
pass, including the assembler.)

* Menu:

* a::             -a[cdhlns] enable listings
* D::             -D for compatibility
* f::             -f to work faster
* I::             -I for .include search path

* K::             -K for difference tables

* L::             -L to retain local labels
* listing::       --listing-XXX to configure listing output
* M::		  -M or --mri to assemble in MRI compatibility mode
* MD::            --MD for dependency tracking
* o::             -o to name the object file
* R::             -R to join data and text sections
* statistics::    --statistics to see statistics about assembly
* traditional-format:: --traditional-format for compatible output
* v::             -v to announce version
* W::             -W, --no-warn, --warn, --fatal-warnings to control warnings
* Z::             -Z to make object file even after errors


File: as.info,  Node: a,  Next: D,  Up: Invoking

Enable Listings: `-a[cdhlns]'
=============================

   These options enable listing output from the assembler.  By itself,
`-a' requests high-level, assembly, and symbols listing.  You can use
other letters to select specific options for the list: `-ah' requests a
high-level language listing, `-al' requests an output-program assembly
listing, and `-as' requests a symbol table listing.  High-level
listings require that a compiler debugging option like `-g' be used,
and that assembly listings (`-al') be requested also.

   Use the `-ac' option to omit false conditionals from a listing.  Any
lines which are not assembled because of a false `.if' (or `.ifdef', or
any other conditional), or a true `.if' followed by an `.else', will be
omitted from the listing.

   Use the `-ad' option to omit debugging directives from the listing.

   Once you have specified one of these options, you can further control
listing output and its appearance using the directives `.list',
`.nolist', `.psize', `.eject', `.title', and `.sbttl'.  The `-an'
option turns off all forms processing.  If you do not request listing
output with one of the `-a' options, the listing-control directives
have no effect.

   The letters after `-a' may be combined into one option, _e.g._,
`-aln'.

   Note if the assembler source is coming from the standard input (eg
because it is being created by `gcc' and the `-pipe' command line switch
is being used) then the listing will not contain any comments or
preprocessor directives.  This is because the listing code buffers
input source lines from stdin only after they have been preprocessed by
the assembler.  This reduces memory usage and makes the code more
efficient.


File: as.info,  Node: D,  Next: f,  Prev: a,  Up: Invoking

`-D'
====

   This option has no effect whatsoever, but it is accepted to make it
more likely that scripts written for other assemblers also work with
`as'.


File: as.info,  Node: f,  Next: I,  Prev: D,  Up: Invoking

Work Faster: `-f'
=================

   `-f' should only be used when assembling programs written by a
(trusted) compiler.  `-f' stops the assembler from doing whitespace and
comment preprocessing on the input file(s) before assembling them.
*Note Preprocessing: Preprocessing.

     _Warning:_ if you use `-f' when the files actually need to be
     preprocessed (if they contain comments, for example), `as' does
     not work correctly.


File: as.info,  Node: I,  Next: K,  Prev: f,  Up: Invoking

`.include' search path: `-I' PATH
=================================

   Use this option to add a PATH to the list of directories `as'
searches for files specified in `.include' directives (*note
`.include': Include.).  You may use `-I' as many times as necessary to
include a variety of paths.  The current working directory is always
searched first; after that, `as' searches any `-I' directories in the
same order as they were specified (left to right) on the command line.


File: as.info,  Node: K,  Next: L,  Prev: I,  Up: Invoking

Difference Tables: `-K'
=======================

   `as' sometimes alters the code emitted for directives of the form
`.word SYM1-SYM2'; *note `.word': Word..  You can use the `-K' option
if you want a warning issued when this is done.


File: as.info,  Node: L,  Next: listing,  Prev: K,  Up: Invoking

Include Local Labels: `-L'
==========================

   Labels beginning with `L' (upper case only) are called "local
labels". *Note Symbol Names::.  Normally you do not see such labels when
debugging, because they are intended for the use of programs (like
compilers) that compose assembler programs, not for your notice.
Normally both `as' and `ld' discard such labels, so you do not normally
debug with them.

   This option tells `as' to retain those `L...' symbols in the object
file.  Usually if you do this you also tell the linker `ld' to preserve
symbols whose names begin with `L'.

   By default, a local label is any label beginning with `L', but each
target is allowed to redefine the local label prefix.  On the HPPA
local labels begin with `L$'.


File: as.info,  Node: listing,  Next: M,  Prev: L,  Up: Invoking

Configuring listing output: `--listing'
=======================================

   The listing feature of the assembler can be enabled via the command
line switch `-a' (*note a::).  This feature combines the input source
file(s) with a hex dump of the corresponding locations in the output
object file, and displays them as a listing file.  The format of this
listing can be controlled by pseudo ops inside the assembler source
(*note List:: *note Title:: *note Sbttl:: *note Psize:: *note Eject::)
and also by the following switches:

`--listing-lhs-width=`number''
     Sets the maximum width, in words, of the first line of the hex
     byte dump.  This dump appears on the left hand side of the listing
     output.

`--listing-lhs-width2=`number''
     Sets the maximum width, in words, of any further lines of the hex
     byte dump for a given inut source line.  If this value is not
     specified, it defaults to being the same as the value specified
     for `--listing-lhs-width'.  If neither switch is used the default
     is to one.

`--listing-rhs-width=`number''
     Sets the maximum width, in characters, of the source line that is
     displayed alongside the hex dump.  The default value for this
     parameter is 100.  The source line is displayed on the right hand
     side of the listing output.

`--listing-cont-lines=`number''
     Sets the maximum number of continuation lines of hex dump that
     will be displayed for a given single line of source input.  The
     default value is 4.


File: as.info,  Node: M,  Next: MD,  Prev: listing,  Up: Invoking

Assemble in MRI Compatibility Mode: `-M'
========================================

   The `-M' or `--mri' option selects MRI compatibility mode.  This
changes the syntax and pseudo-op handling of `as' to make it compatible
with the `ASM68K' or the `ASM960' (depending upon the configured
target) assembler from Microtec Research.  The exact nature of the MRI
syntax will not be documented here; see the MRI manuals for more
information.  Note in particular that the handling of macros and macro
arguments is somewhat different.  The purpose of this option is to
permit assembling existing MRI assembler code using `as'.

   The MRI compatibility is not complete.  Certain operations of the
MRI assembler depend upon its object file format, and can not be
supported using other object file formats.  Supporting these would
require enhancing each object file format individually.  These are:

   * global symbols in common section

     The m68k MRI assembler supports common sections which are merged
     by the linker.  Other object file formats do not support this.
     `as' handles common sections by treating them as a single common
     symbol.  It permits local symbols to be defined within a common
     section, but it can not support global symbols, since it has no
     way to describe them.

   * complex relocations

     The MRI assemblers support relocations against a negated section
     address, and relocations which combine the start addresses of two
     or more sections.  These are not support by other object file
     formats.

   * `END' pseudo-op specifying start address

     The MRI `END' pseudo-op permits the specification of a start
     address.  This is not supported by other object file formats.  The
     start address may instead be specified using the `-e' option to
     the linker, or in a linker script.

   * `IDNT', `.ident' and `NAME' pseudo-ops

     The MRI `IDNT', `.ident' and `NAME' pseudo-ops assign a module
     name to the output file.  This is not supported by other object
     file formats.

   * `ORG' pseudo-op

     The m68k MRI `ORG' pseudo-op begins an absolute section at a given
     address.  This differs from the usual `as' `.org' pseudo-op, which
     changes the location within the current section.  Absolute
     sections are not supported by other object file formats.  The
     address of a section may be assigned within a linker script.

   There are some other features of the MRI assembler which are not
supported by `as', typically either because they are difficult or
because they seem of little consequence.  Some of these may be
supported in future releases.

   * EBCDIC strings

     EBCDIC strings are not supported.

   * packed binary coded decimal

     Packed binary coded decimal is not supported.  This means that the
     `DC.P' and `DCB.P' pseudo-ops are not supported.

   * `FEQU' pseudo-op

     The m68k `FEQU' pseudo-op is not supported.

   * `NOOBJ' pseudo-op

     The m68k `NOOBJ' pseudo-op is not supported.

   * `OPT' branch control options

     The m68k `OPT' branch control options--`B', `BRS', `BRB', `BRL',
     and `BRW'--are ignored.  `as' automatically relaxes all branches,
     whether forward or backward, to an appropriate size, so these
     options serve no purpose.

   * `OPT' list control options

     The following m68k `OPT' list control options are ignored: `C',
     `CEX', `CL', `CRE', `E', `G', `I', `M', `MEX', `MC', `MD', `X'.

   * other `OPT' options

     The following m68k `OPT' options are ignored: `NEST', `O', `OLD',
     `OP', `P', `PCO', `PCR', `PCS', `R'.

   * `OPT' `D' option is default

     The m68k `OPT' `D' option is the default, unlike the MRI assembler.
     `OPT NOD' may be used to turn it off.

   * `XREF' pseudo-op.

     The m68k `XREF' pseudo-op is ignored.

   * `.debug' pseudo-op

     The i960 `.debug' pseudo-op is not supported.

   * `.extended' pseudo-op

     The i960 `.extended' pseudo-op is not supported.

   * `.list' pseudo-op.

     The various options of the i960 `.list' pseudo-op are not
     supported.

   * `.optimize' pseudo-op

     The i960 `.optimize' pseudo-op is not supported.

   * `.output' pseudo-op

     The i960 `.output' pseudo-op is not supported.

   * `.setreal' pseudo-op

     The i960 `.setreal' pseudo-op is not supported.



File: as.info,  Node: MD,  Next: o,  Prev: M,  Up: Invoking

Dependency tracking: `--MD'
===========================

   `as' can generate a dependency file for the file it creates.  This
file consists of a single rule suitable for `make' describing the
dependencies of the main source file.

   The rule is written to the file named in its argument.

   This feature is used in the automatic updating of makefiles.


File: as.info,  Node: o,  Next: R,  Prev: MD,  Up: Invoking

Name the Object File: `-o'
==========================

   There is always one object file output when you run `as'.  By
default it has the name `a.out' (or `b.out', for Intel 960 targets
only).  You use this option (which takes exactly one filename) to give
the object file a different name.

   Whatever the object file is called, `as' overwrites any existing
file of the same name.


File: as.info,  Node: R,  Next: statistics,  Prev: o,  Up: Invoking

Join Data and Text Sections: `-R'
=================================

   `-R' tells `as' to write the object file as if all data-section data
lives in the text section.  This is only done at the very last moment:
your binary data are the same, but data section parts are relocated
differently.  The data section part of your object file is zero bytes
long because all its bytes are appended to the text section.  (*Note
Sections and Relocation: Sections.)

   When you specify `-R' it would be possible to generate shorter
address displacements (because we do not have to cross between text and
data section).  We refrain from doing this simply for compatibility with
older versions of `as'.  In future, `-R' may work this way.

   When `as' is configured for COFF output, this option is only useful
if you use sections named `.text' and `.data'.

   `-R' is not supported for any of the HPPA targets.  Using `-R'
generates a warning from `as'.


File: as.info,  Node: statistics,  Next: traditional-format,  Prev: R,  Up: Invoking

Display Assembly Statistics: `--statistics'
===========================================

   Use `--statistics' to display two statistics about the resources
used by `as': the maximum amount of space allocated during the assembly
(in bytes), and the total execution time taken for the assembly (in CPU
seconds).


File: as.info,  Node: traditional-format,  Next: v,  Prev: statistics,  Up: Invoking

Compatible output: `--traditional-format'
=========================================

   For some targets, the output of `as' is different in some ways from
the output of some existing assembler.  This switch requests `as' to
use the traditional format instead.

   For example, it disables the exception frame optimizations which
`as' normally does by default on `gcc' output.


File: as.info,  Node: v,  Next: W,  Prev: traditional-format,  Up: Invoking

Announce Version: `-v'
======================

   You can find out what version of as is running by including the
option `-v' (which you can also spell as `-version') on the command
line.


File: as.info,  Node: W,  Next: Z,  Prev: v,  Up: Invoking

Control Warnings: `-W', `--warn', `--no-warn', `--fatal-warnings'
=================================================================

   `as' should never give a warning or error message when assembling
compiler output.  But programs written by people often cause `as' to
give a warning that a particular assumption was made.  All such
warnings are directed to the standard error file.

   If you use the `-W' and `--no-warn' options, no warnings are issued.
This only affects the warning messages: it does not change any
particular of how `as' assembles your file.  Errors, which stop the
assembly, are still reported.

   If you use the `--fatal-warnings' option, `as' considers files that
generate warnings to be in error.

   You can switch these options off again by specifying `--warn', which
causes warnings to be output as usual.


File: as.info,  Node: Z,  Prev: W,  Up: Invoking

Generate Object File in Spite of Errors: `-Z'
=============================================

   After an error message, `as' normally produces no output.  If for
some reason you are interested in object file output even after `as'
gives an error message on your program, use the `-Z' option.  If there
are any errors, `as' continues anyways, and writes an object file after
a final warning message of the form `N errors, M warnings, generating
bad object file.'


File: as.info,  Node: Syntax,  Next: Sections,  Prev: Invoking,  Up: Top

Syntax
******

   This chapter describes the machine-independent syntax allowed in a
source file.  `as' syntax is similar to what many other assemblers use;
it is inspired by the BSD 4.2 assembler, except that `as' does not
assemble Vax bit-fields.

* Menu:

* Preprocessing::              Preprocessing
* Whitespace::                  Whitespace
* Comments::                    Comments
* Symbol Intro::                Symbols
* Statements::                  Statements
* Constants::                   Constants


File: as.info,  Node: Preprocessing,  Next: Whitespace,  Up: Syntax

Preprocessing
=============

   The `as' internal preprocessor:
   * adjusts and removes extra whitespace.  It leaves one space or tab
     before the keywords on a line, and turns any other whitespace on
     the line into a single space.

   * removes all comments, replacing them with a single space, or an
     appropriate number of newlines.

   * converts character constants into the appropriate numeric values.

   It does not do macro processing, include file handling, or anything
else you may get from your C compiler's preprocessor.  You can do
include file processing with the `.include' directive (*note
`.include': Include.).  You can use the GNU C compiler driver to get
other "CPP" style preprocessing, by giving the input file a `.S'
suffix.  *Note Options Controlling the Kind of Output:
(gcc.info)Overall Options.

   Excess whitespace, comments, and character constants cannot be used
in the portions of the input text that are not preprocessed.

   If the first line of an input file is `#NO_APP' or if you use the
`-f' option, whitespace and comments are not removed from the input
file.  Within an input file, you can ask for whitespace and comment
removal in specific portions of the by putting a line that says `#APP'
before the text that may contain whitespace or comments, and putting a
line that says `#NO_APP' after this text.  This feature is mainly
intend to support `asm' statements in compilers whose output is
otherwise free of comments and whitespace.


File: as.info,  Node: Whitespace,  Next: Comments,  Prev: Preprocessing,  Up: Syntax

Whitespace
==========

   "Whitespace" is one or more blanks or tabs, in any order.
Whitespace is used to separate symbols, and to make programs neater for
people to read.  Unless within character constants (*note Character
Constants: Characters.), any whitespace means the same as exactly one
space.


File: as.info,  Node: Comments,  Next: Symbol Intro,  Prev: Whitespace,  Up: Syntax

Comments
========

   There are two ways of rendering comments to `as'.  In both cases the
comment is equivalent to one space.

   Anything from `/*' through the next `*/' is a comment.  This means
you may not nest these comments.

     /*
       The only way to include a newline ('\n') in a comment
       is to use this sort of comment.
     */
     
     /* This sort of comment does not nest. */

   Anything from the "line comment" character to the next newline is
considered a comment and is ignored.  The line comment character is `;'
for the AMD 29K family; `;' on the ARC; `@' on the ARM; `;' for the
H8/300 family; `!' for the H8/500 family; `;' for the HPPA; `#' on the
i386 and x86-64; `#' on the i960; `;' for the PDP-11; `;' for picoJava;
`;' for Motorola PowerPC; `!' for the Hitachi SH; `!' on the SPARC; `#'
on the m32r; `|' on the 680x0; `#' on the 68HC11 and 68HC12; `;' on the
M880x0; `#' on the Vax; `!' for the Z8000; `#' on the V850; see *Note
Machine Dependencies::.

   On some machines there are two different line comment characters.
One character only begins a comment if it is the first non-whitespace
character on a line, while the other always begins a comment.

   The V850 assembler also supports a double dash as starting a comment
that extends to the end of the line.

   `--';

   To be compatible with past assemblers, lines that begin with `#'
have a special interpretation.  Following the `#' should be an absolute
expression (*note Expressions::): the logical line number of the _next_
line.  Then a string (*note Strings: Strings.) is allowed: if present
it is a new logical file name.  The rest of the line, if any, should be
whitespace.

   If the first non-whitespace characters on the line are not numeric,
the line is ignored.  (Just like a comment.)

                               # This is an ordinary comment.
     # 42-6 "new_file_name"    # New logical file name
                               # This is logical line # 36.
   This feature is deprecated, and may disappear from future versions
of `as'.


File: as.info,  Node: Symbol Intro,  Next: Statements,  Prev: Comments,  Up: Syntax

Symbols
=======

   A "symbol" is one or more characters chosen from the set of all
letters (both upper and lower case), digits and the three characters
`_.$'.  On most machines, you can also use `$' in symbol names;
exceptions are noted in *Note Machine Dependencies::.  No symbol may
begin with a digit.  Case is significant.  There is no length limit:
all characters are significant.  Symbols are delimited by characters
not in that set, or by the beginning of a file (since the source
program must end with a newline, the end of a file is not a possible
symbol delimiter).  *Note Symbols::.

