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This is as.info, produced by makeinfo version 4.3 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 2.14.
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
Command-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 IP2K options:_
[-mip2022|-mip2022ext]
_Target M32R options:_
[-m32rx|-[no-]warn-explicit-parallel-conflicts|
-W[n]p]
_Target M680X0 options:_
[-l] [-m68000|-m68010|-m68020|...]
_Target M68HC11 options:_
[-m68hc11|-m68hc12|-m68hcs12]
[-mshort|-mlong]
[-mshort-double|-mlong-double]
[-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] [-mips32r2]
[-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]
_Target TIC54X options:_
[-mcpu=54[123589]|-mcpu=54[56]lp] [-mfar-mode|-mf]
[-merrors-to-file <FILENAME>|-me <FILENAME>]
_Target Xtensa options:_
[-[no-]density] [-[no-]relax] [-[no-]generics]
[-[no-]text-section-literals]
[-[no-]target-align] [-[no-]longcalls]
`-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
Ubicom IP2K series.
`-mip2022ext'
Specifies that the extended IP2022 instructions are allowed.
`-mip2022'
Restores the default behaviour, which restricts the permitted
instructions to just the basic IP2022 ones.
The following options are available when as is configured for the
Renesas M32R (formerly 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 | -m68hcs12'
Specify what processor is the target. The default is defined by
the configuration option when building the assembler.
`-mshort'
Specify to use the 16-bit integer ABI.
`-mlong'
Specify to use the 32-bit integer ABI.
`-mshort-double'
Specify to use the 32-bit double ABI.
`-mlong-double'
Specify to use the 64-bit double ABI.
`--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 the
'c54x architecture.
`-mfar-mode'
Enable extended addressing mode. All addresses and relocations
will assume extended addressing (usually 23 bits).
`-mcpu=CPU_VERSION'
Sets the CPU version being compiled for.
`-merrors-to-file FILENAME'
Redirect error output to a file, for broken systems which don't
support such behaviour in the shell.
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'
`-mips32r2'
`-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',
`-mips32r2', and `-mips64' correspond to generic `MIPS V',
`MIPS32', `MIPS32 Release 2', 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.
The following options are available when as is configured for an
Xtensa processor.
`--density | --no-density'
Enable or disable use of instructions from the Xtensa code density
option. This is enabled by default when the Xtensa processor
supports the code density option.
`--relax | --no-relax'
Enable or disable instruction relaxation. This is enabled by
default. Note: In the current implementation, these options also
control whether assembler optimizations are performed, making
these options equivalent to `--generics' and `--no-generics'.
`--generics | --no-generics'
Enable or disable all assembler transformations of Xtensa
instructions. The default is `--generics'; `--no-generics' should
be used only in the rare cases when the instructions must be
exactly as specified in the assembly source.
`--text-section-literals | --no-text-section-literals'
With `--text-section-literals', literal pools are interspersed in
the text section. The default is `--no-text-section-literals',
which places literals in a separate section in the output file.
`--target-align | --no-target-align'
Enable or disable automatic alignment to reduce branch penalties
at the expense of some code density. The default is
`--target-align'.
`--longcalls | --no-longcalls'
Enable or disable transformation of call instructions to allow
calls across a greater range of addresses. The default is
`--no-longcalls'.
* 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, 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 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 input 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 or ELF 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.