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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 `-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$'.
--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. 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.
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
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
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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