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This chapter describes command-line options available in all versions of the GNU assembler; see section 8. Machine Dependent Features, 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.)
2.1 Enable Listings: `-a[cdhlns]' -a[cdhlns] enable listings 2.2 `-D' -D for compatibility 2.3 Work Faster: `-f' -f to work faster 2.4
.includeSearch Path: `-I' path
-I for .include search path 2.5 Difference Tables: `-K' -K for difference tables
2.6 Include Local Labels: `-L' -L to retain local labels 2.7 Configuring listing output: `--listing' --listing-XXX to configure listing output 2.8 Assemble in MRI Compatibility Mode: `-M' -M or --mri to assemble in MRI compatibility mode 2.9 Dependency Tracking: `--MD' --MD for dependency tracking 2.10 Name the Object File: `-o' -o to name the object file 2.11 Join Data and Text Sections: `-R' -R to join data and text sections 2.12 Display Assembly Statistics: `--statistics' --statistics to see statistics about assembly 2.13 Compatible Output: `--traditional-format' --traditional-format for compatible output 2.14 Announce Version: `-v' -v to announce version 2.15 Control Warnings: `-W', `--warn', `--no-warn', `--fatal-warnings' -W, --no-warn, --warn, --fatal-warnings to control warnings 2.16 Generate Object File in Spite of Errors: `-Z' -Z to make object file even after errors
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
.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
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.
This option has no effect whatsoever, but it is accepted to make it more
likely that scripts written for other assemblers also work with
`-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. See section Preprocessing.
Warning: if you use `-f' when the files actually need to be preprocessed (if they contain comments, for example),
asdoes not work correctly.
.includeSearch Path: `-I' path
Use this option to add a path to the list of directories
as searches for files specified in
directives (see section
.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,
searches any `-I' directories in the same order as they were
specified (left to right) on the command line.
as sometimes alters the code emitted for directives of the form
`.word sym1-sym2'; see section
You can use the `-K' option if you want a warning issued when this
Labels beginning with `L' (upper case only) are called local
labels. See section 5.3 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.
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$'.
The listing feature of the assembler can be enabled via the command line switch
`-a' (see section 2.1 Enable Listings: `-a[cdhlns]'). 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 (see section 7.58
.list see section 7.91
.title "heading" see section 7.74
see section 7.69
.psize lines , columns see section 7.24
.eject) and also by the following switches:
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
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:
The m68k MRI assembler supports common sections which are merged by the linker.
Other object file formats do not support this.
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.
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.
ENDpseudo-op specifying start address
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
NAME pseudo-ops assign a module
name to the output file. This is not supported by other object file formats.
The m68k MRI
ORG pseudo-op begins an absolute section at a given
address. This differs from the usual
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 are not supported.
Packed binary coded decimal is not supported. This means that the
DCB.P pseudo-ops are not supported.
FEQU pseudo-op is not supported.
NOOBJ pseudo-op is not supported.
OPTbranch control options
OPT branch control options---
relaxes all branches, whether forward or backward, to an appropriate size, so
these options serve no purpose.
OPTlist control options
The following m68k
OPT list control options are ignored:
The following m68k
OPT options are ignored:
Doption is default
D option is the default, unlike the MRI assembler.
OPT NOD may be used to turn it off.
XREF pseudo-op is ignored.
.debug pseudo-op is not supported.
.extended pseudo-op is not supported.
The various options of the i960
.list pseudo-op are not supported.
.optimize pseudo-op is not supported.
.output pseudo-op is not supported.
.setreal pseudo-op is not supported.
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.
There is always one object file output when you run
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.
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. (See section Sections and Relocation.)
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.
as is configured for COFF or ELF output,
this option is only useful if you use sections named `.text' and
`-R' is not supported for any of the HPPA targets. Using
`-R' generates a warning from
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
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
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.
as should never give a warning or error message when
assembling compiler output. But programs written by people often
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
as assembles your file. Errors, which stop the assembly,
are still reported.
If you use the `--fatal-warnings' option,
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.
asnormally produces no output. If for some reason you are interested in object file output even after
asgives an error message on your program, use the `-Z' option. If there are any errors,
ascontinues anyways, and writes an object file after a final warning message of the form `n errors, m warnings, generating bad object file.'
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