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This is, produced by makeinfo version 4.0 from as.texinfo.
* As: (as). The GNU assembler.
This file documents the GNU Assembler "as".
Copyright (C) 1991, 92, 93, 94, 95, 96, 97, 98, 99, 2000, 2001 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:, Node: Top, Next: Overview, Up: (dir)
Using as
This file is a user guide to the GNU assembler `as' version 2.11.2.
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:, Node: Overview, Next: Invoking, Prev: Top, Up: Top
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 ]
[ --keep-locals ] [ -o OBJFILE ] [ -R ] [ --statistics ] [ -v ]
[ -version ] [ --version ] [ -W ] [ --warn ] [ --fatal-warnings ]
[ -w ] [ -x ] [ -Z ] [ --target-help ]
[ -marc[5|6|7|8] ]
[ -EB | -EL ]
[ -m[arm]1 | -m[arm]2 | -m[arm]250 | -m[arm]3 | -m[arm]6 | -m[arm]60 |
-m[arm]600 | -m[arm]610 | -m[arm]620 | -m[arm]7[t][[d]m[i]][fe] | -m[arm]70 |
-m[arm]700 | -m[arm]710[c] | -m[arm]7100 | -m[arm]7500 | -m[arm]8 |
-m[arm]810 | -m[arm]9 | -m[arm]920 | -m[arm]920t | -m[arm]9tdmi |
-mstrongarm | -mstrongarm110 | -mstrongarm1100 ]
[ -m[arm]v2 | -m[arm]v2a | -m[arm]v3 | -m[arm]v3m | -m[arm]v4 | -m[arm]v4t |
-m[arm]v5 | -[arm]v5t | -[arm]v5te ]
[ -mthumb | -mall ]
[ -mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu ]
[ -EB | -EL ]
[ -mapcs-32 | -mapcs-26 | -mapcs-float | -mapcs-reentrant ]
[ -mthumb-interwork ]
[ -moabi ]
[ -k ]
[ -O ]
[ -O | -n | -N ]
[ -mb | -me ]
[ -Av6 | -Av7 | -Av8 | -Asparclet | -Asparclite
-Av8plus | -Av8plusa | -Av9 | -Av9a ]
[ -xarch=v8plus | -xarch=v8plusa ] [ -bump ] [ -32 | -64 ]
[ -ACA | -ACA_A | -ACB | -ACC | -AKA | -AKB | -AKC | -AMC ]
[ -b ] [ -no-relax ]
[ --m32rx | --[no-]warn-explicit-parallel-conflicts | --W[n]p ]
[ -l ] [ -m68000 | -m68010 | -m68020 | ... ]
[ -jsri2bsr ] [ -sifilter ] [ -relax ]
[ -mcpu=[210|340] ]
[ -m68hc11 | -m68hc12 ]
[ --force-long-branchs ] [ --short-branchs ] [ --strict-direct-mode ]
[ --print-insn-syntax ] [ --print-opcodes ] [ --generate-example ]
[ -nocpp ] [ -EL ] [ -EB ] [ -G NUM ] [ -mcpu=CPU ]
[ -mips1 ] [ -mips2 ] [ -mips3 ] [ -mips4 ] [ -mips5 ]
[ -mips32 ] [ -mips64 ]
[ -m4650 ] [ -no-m4650 ]
[ --trap ] [ --break ]
[ --emulation=NAME ]
[ -- | FILES ... ]
Turn on listings, in any of a variety of ways:
omit false conditionals
omit debugging directives
include high-level source
include assembly
include macro expansions
omit forms processing
include symbols
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'.
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.
"fast"--skip whitespace and comment preprocessing (assume source is
compiler output).
Generate stabs debugging information for each assembler line. This
may help debugging assembler code, if the debugger can handle it.
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.
Print a summary of the command line options and exit.
Print a summary of all target specific options and exit.
`-I DIR'
Add directory DIR to the search list for `.include' directives.
Don't warn about signed overflow.
Issue warnings when difference tables altered for long
Keep (in the symbol table) local symbols. On traditional a.out
systems these start with `L', but different systems have different
local label prefixes.
Name the object-file output from `as' OBJFILE.
Fold the data section into the text section.
Print the maximum space (in bytes) and total time (in seconds)
used by assembly.
Remove local absolute symbols from the outgoing symbol table.
Print the `as' version.
Print the `as' version and exit.
Suppress warning messages.
Treat warnings as errors.
Don't suppress warning messages or treat them as errors.
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
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.
Specify which ARM processor variant is the target.
Specify which ARM architecture variant is used by the target.
`-mthumb | -mall'
Enable or disable Thumb only instruction decoding.
`-mfpa10 | -mfpa11 | -mfpe-old | -mno-fpu'
Select which Floating Point architecture is the target.
`-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.
Specify that the code has been generated with interworking between
Thumb and ARM code in mind.
Specify that PIC code has been generated.
The following options are available when as is configured for a D10V
Optimize output by parallelizing instructions.
The following options are available when as is configured for a D30V
Optimize output by parallelizing instructions.
Warn when nops are generated.
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.
Add code to collect statistics about branches taken.
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.
Specify which processor in the M32R family is the target. The
default is normally the M32R, but this option changes it to the
`--warn-explicit-parallel-conflicts or --Wp'
Produce warning messages when questionable parallel constructs are
`--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.
Shorten references to undefined symbols, to one word instead of
`-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
The following options are available when as is configured for a
picoJava processor.
Generate "big endian" format output.
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.
Relative branches are turned into absolute ones. This concerns
conditional branches, unconditional branches and branches to a sub
`-S | --short-branchs'
Do not turn relative branchs into absolute ones when the offset is
out of range.
Do not turn the direct addressing mode into extended addressing
mode when the instruction does not support direct addressing mode.
Print the syntax of instruction in case of error.
print the list of instructions with syntax and then exit.
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.
Warn when the assembler switches to another architecture.
The following options are available when as is configured for a MIPS
`-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.
Generate "big endian" format output.
Generate "little endian" format output.
Generate code for a particular MIPS Instruction Set Architecture
level. `-mips1' corresponds to the R2000 and R3000 processors,
`-mips2' to the R6000 processor, and `-mips3' to the R4000
processor. `-mips5', `-mips32', and `-mips64' correspond to
generic MIPS V, MIPS32, and MIPS64 ISA processors, respectively.
Generate code for the MIPS R4650 chip. This tells the assembler
to accept the `mad' and `madu' instruction, and to not schedule
`nop' instructions around accesses to the `HI' and `LO' registers.
`-no-m4650' turns off this option.
Generate code for a particular MIPS cpu. It is exactly equivalent
to `-mCPU', except that there are more value of CPU understood.
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.
`as' ignores this option. It is accepted for compatibility with
the native tools.
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.
The following options are available when as is configured for an
MCore processor.
Enable or disable the JSRI to BSR transformation. By default this
is enabled. The command line option `-nojsri2bsr' can be used to
disable it.
Enable or disable the silicon filter behaviour. By default this
is disabled. The default can be overridden by the `-sifilter'
command line option.
Alter jump instructions for long displacements.
Select the cpu type on the target hardware. This controls which
instructions can be assembled.
Assemble for a big endian target.
Assemble for a little endian target.
* 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:, 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:, 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:, 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:, 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:, 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
"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:, 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:, 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
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:, 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
* 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:, 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._,

File:, Node: D, Next: f, Prev: a, Up: Invoking
This option has no effect whatsoever, but it is accepted to make it
more likely that scripts written for other assemblers also work with

File:, 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:, 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:, 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:, Node: L, Next: M, 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:, Node: M, Next: MD, Prev: L, 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
* `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
* `.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:, 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:, 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:, 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:, 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

File:, 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:, 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

File:, 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:, 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:, Node: Syntax, Next: Sections, Prev: Invoking, Up: Top
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:, Node: Preprocessing, Next: Whitespace, Up: Syntax
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:
( 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:, Node: Whitespace, Next: Comments, Prev: Preprocessing, Up: Syntax
"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

File:, Node: Comments, Next: Symbol Intro, Prev: Whitespace, Up: Syntax
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 picoJava; `!' for the Hitachi
SH; `!' on the SPARC; `#' on the m32r; `|' on the 680x0; `#' on the
68HC11 and 68HC12; `#' 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
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:, Node: Symbol Intro, Next: Statements, Prev: Comments, Up: Syntax
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::.

File:, Node: Statements, Next: Constants, Prev: Symbol Intro, Up: Syntax
A "statement" ends at a newline character (`\n') or line separator
character. (The line separator is usually `;', unless this conflicts
with the comment character; *note Machine Dependencies::.) The newline
or separator character is considered part of the preceding statement.
Newlines and separators within character constants are an exception:
they do not end statements.
It is an error to end any statement with end-of-file: the last
character of any input file should be a newline.
An empty statement is allowed, and may include whitespace. It is
A statement begins with zero or more labels, optionally followed by a
key symbol which determines what kind of statement it is. The key
symbol determines the syntax of the rest of the statement. If the
symbol begins with a dot `.' then the statement is an assembler
directive: typically valid for any computer. If the symbol begins with
a letter the statement is an assembly language "instruction": it
assembles into a machine language instruction. Different versions of
`as' for different computers recognize different instructions. In
fact, the same symbol may represent a different instruction in a
different computer's assembly language.
A label is a symbol immediately followed by a colon (`:').
Whitespace before a label or after a colon is permitted, but you may not
have whitespace between a label's symbol and its colon. *Note Labels::.
For HPPA targets, labels need not be immediately followed by a
colon, but the definition of a label must begin in column zero. This
also implies that only one label may be defined on each line.
label: .directive followed by something
another_label: # This is an empty statement.
instruction operand_1, operand_2, ...

File:, Node: Constants, Prev: Statements, Up: Syntax
A constant is a number, written so that its value is known by
inspection, without knowing any context. Like this:
.byte 74, 0112, 092, 0x4A, 0X4a, 'J, '\J # All the same value.
.ascii "Ring the bell\7" # A string constant.
.octa 0x123456789abcdef0123456789ABCDEF0 # A bignum.
.float 0f-314159265358979323846264338327\
95028841971.693993751E-40 # - pi, a flonum.
* Menu:
* Characters:: Character Constants
* Numbers:: Number Constants

File:, Node: Characters, Next: Numbers, Up: Constants
Character Constants
There are two kinds of character constants. A "character" stands
for one character in one byte and its value may be used in numeric
expressions. String constants (properly called string _literals_) are
potentially many bytes and their values may not be used in arithmetic
* Menu:
* Strings:: Strings
* Chars:: Characters

File:, Node: Strings, Next: Chars, Up: Characters
A "string" is written between double-quotes. It may contain
double-quotes or null characters. The way to get special characters
into a string is to "escape" these characters: precede them with a
backslash `\' character. For example `\\' represents one backslash:
the first `\' is an escape which tells `as' to interpret the second
character literally as a backslash (which prevents `as' from
recognizing the second `\' as an escape character). The complete list
of escapes follows.
Mnemonic for backspace; for ASCII this is octal code 010.
Mnemonic for FormFeed; for ASCII this is octal code 014.
Mnemonic for newline; for ASCII this is octal code 012.
Mnemonic for carriage-Return; for ASCII this is octal code 015.
Mnemonic for horizontal Tab; for ASCII this is octal code 011.
An octal character code. The numeric code is 3 octal digits. For
compatibility with other Unix systems, 8 and 9 are accepted as
digits: for example, `\008' has the value 010, and `\009' the
value 011.
`\`x' HEX-DIGITS...'
A hex character code. All trailing hex digits are combined.
Either upper or lower case `x' works.
Represents one `\' character.
Represents one `"' character. Needed in strings to represent this
character, because an unescaped `"' would end the string.
Any other character when escaped by `\' gives a warning, but
assembles as if the `\' was not present. The idea is that if you
used an escape sequence you clearly didn't want the literal
interpretation of the following character. However `as' has no
other interpretation, so `as' knows it is giving you the wrong
code and warns you of the fact.
Which characters are escapable, and what those escapes represent,
varies widely among assemblers. The current set is what we think the
BSD 4.2 assembler recognizes, and is a subset of what most C compilers
recognize. If you are in doubt, do not use an escape sequence.

File:, Node: Chars, Prev: Strings, Up: Characters
A single character may be written as a single quote immediately
followed by that character. The same escapes apply to characters as to
strings. So if you want to write the character backslash, you must
write `'\\' where the first `\' escapes the second `\'. As you can
see, the quote is an acute accent, not a grave accent. A newline
immediately following an acute accent is taken as a literal character
and does not count as the end of a statement. The value of a character
constant in a numeric expression is the machine's byte-wide code for
that character. `as' assumes your character code is ASCII: `'A' means
65, `'B' means 66, and so on.

File:, Node: Numbers, Prev: Characters, Up: Constants
Number Constants
`as' distinguishes three kinds of numbers according to how they are
stored in the target machine. _Integers_ are numbers that would fit
into an `int' in the C language. _Bignums_ are integers, but they are
stored in more than 32 bits. _Flonums_ are floating point numbers,
described below.
* Menu:
* Integers:: Integers
* Bignums:: Bignums
* Flonums:: Flonums