This chapter describes command-line options available in all versions of the GNU assembler; see section Machine Dependent Features, 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
emits a listing to standard output with high-level and assembly source.
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.)
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'.
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.
Use this option to add a path to the list of directories
as searches for files specified in
directives (see section
.include "file"). You may use
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 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$'. `;' for the ARM family;
--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:
ashandles 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.
ENDpseudo-op specifying start address The MRI
ENDpseudo-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
-eoption to the linker, or in a linker script.
NAMEpseudo-ops The MRI
NAMEpseudo-ops assign a module name to the output file. This is not supported by other object file formats.
ORGpseudo-op The m68k MRI
ORGpseudo-op begins an absolute section at a given address. This differs from the usual
.orgpseudo-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.
DCB.Ppseudo-ops are not supported.
FEQUpseudo-op The m68k
FEQUpseudo-op is not supported.
NOOBJpseudo-op The m68k
NOOBJpseudo-op is not supported.
OPTbranch control options The m68k
OPTbranch control options---
asautomatically relaxes all branches, whether forward or backward, to an appropriate size, so these options serve no purpose.
OPTlist control options The following m68k
OPTlist control options are ignored:
OPToptions The following m68k
OPToptions are ignored:
Doption is default The m68k
Doption is the default, unlike the MRI assembler.
OPT NODmay be used to turn it off.
XREFpseudo-op. The m68k
XREFpseudo-op is ignored.
.debugpseudo-op The i960
.debugpseudo-op is not supported.
.extendedpseudo-op The i960
.extendedpseudo-op is not supported.
.listpseudo-op. The various options of the i960
.listpseudo-op are not supported.
.optimizepseudo-op The i960
.optimizepseudo-op is not supported.
.outputpseudo-op The i960
.outputpseudo-op is not supported.
.setrealpseudo-op The i960
.setrealpseudo-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 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 this option, no warnings are issued. This option only
affects the warning messages: it does not change any particular of how
as assembles your file. Errors, which stop the assembly, are
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.'
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