SYNOPSIS
yasm [-f format] [-o outfile] [options...] [infile]
yasm -h
DESCRIPTION
The YASM Modular Assembler is a portable, retargetable assembler
written under the “new” (2 or 3 clause) BSD license. It is designed
from the ground up to allow for multiple assembler syntaxes (parsers)
to be supported in addition to multiple output object formats and
multiple instruction sets. Another primary module of the overall design
is an optimizer module.
YASM consists of the yasm command, libyasm, the core backend library,
and a large number of loadable modules. On some platforms, libyasm and
the loadable modules are statically built into the yasm executable
rather than being dynamically loaded.
The yasm command assembles the file infile and directs output to the
file outfile if specified. If outfile is not specified, yasm will
derive a default output file name from the name of its input file,
usually by appending .o or .obj, or by removing all extensions for a
raw binary file. Failing that, the output file name will be yasm.out.
If called without an infile, yasm assembles the standard input and
directs output to the file outfile, or yasm.out if no outfile is
specified.
OPTIONS
Many options may be given in one of two forms: either a dash followed
by a single letter, or two dashes followed by a long option name.
The following general options are available:
--version
Prints yasm version information and license summary to standard
output. All other options are ignored, and no output file is
generated.
-h or --help
Prints a summary of invocation options. All other options are
ignored, and no output file is generated.
-a arch or --arch=arch
Selects the target architecture. The default architecture is “x86”,
which supports both the IA-32 and derivatives and AMD64 instruction
sets. To print a list of available architectures to standard output,
use “help” as arch. See yasm_arch(7) for more details.
-p parser or --parser=parser
Selects the parser (the assembler syntax). The default parser is
“nasm”, which emulates the syntax of NASM, the Netwide Assembler. To
Selects the output object format. The default object format is
“bin”, which is a flat format binary with no relocation. To print a
list of available object formats to standard output, use “help” as
format.
-g debug or --dformat=debug
Selects the debugging format for debug information. Debugging
information can be used by a debugger to associate executable code
back to the source file or get data structure and type information.
Available debug formats vary between different object formats; yasm
will error when an invalid combination is selected. The default
object format is selected by the object format. To print a list of
available debugging formats to standard output, use “help” as debug.
-L list or --lformat=list
Selects the format/style of the output list file. List files
typically intermix the original source with the machine code
generated by the assembler. The default list format is “nasm”, which
mimics the NASM list file format. To print a list of available list
file formats to standard output, use “help” as list.
-o filename or --objfile=filename
Specifies the name of the output file, overriding any default name
selected by yasm.
-l listfile or --list=listfile
Specifies the name of the output list file. If this option is not
used, no list file is generated.
-m machine or --machine=machine
Selects the target machine architecture. Essentially a subtype of
the selected architecture, the machine type selects between major
subsets of an architecture. For example, for the “x86” architecture,
the two available machines are “x86”, which is used for the IA-32
and derivative 32-bit instruction set, and “amd64”, which is used
for the 64-bit instruction set. This differentiation is required to
generate the proper object file for relocatable object formats such
as COFF and ELF. To print a list of available machines for a given
architecture to standard output, use “help” as machine and the given
architecture using -a arch. See yasm_arch(7) for more details.
WARNING OPTIONS
-W options have two contrary forms: -Wname and -Wno-name. Only the
non-default forms are shown here.
-w Inhibits all warning messages.
-Werror
Treats warnings as errors.
-Wno-unrecognized-char
Causes yasm to not warn on unrecognized characters found in the
PREPROCESSOR OPTIONS
-e or --preproc-only
Stops assembly after the preprocessing stage; preprocessed output is
sent to the specified output name or, if no output name is
specified, the standard output. No object file is produced.
-I path
Adds directory path to the search path for include files.
-P filename
Pre-includes file filename, making it look as though filename was
prepended to the input.
-D macro[=value]
Pre-defines a single-line macro.
-U macro
Undefines a single-line macro.
EXAMPLES
To assemble NASM syntax, 32-bit x86 source source.asm into ELF file
source.o, warning on orphan labels:
yasm -f elf -Worphan-labels source.asm
To assemble NASM syntax AMD64 source x.asm into AMD64 Win32 file
object.obj:
yasm -m amd64 -f win32 -o object.obj x.asm
To assemble already preprocessed NASM syntax 32-bit x86 source y.asm
into flat binary file y.com:
yasm -f bin -r raw -o y.com y.asm
DIAGNOSTICS
The yasm command exits 0 on success, and nonzero if an error occurs.
COMPATIBILITY
YASM’s NASM parser and preprocessor, while they strive to be as
compatible as possible with NASM, have a few incompatibilities due to
YASM’s different internal structure.
RESTRICTIONS
As object files are often architecture and machine dependent, not all
combinations of object formats, architectures, and machines are legal;
trying to use an invalid combination will result in an error.
There is no support for list files or symbol maps.
Relocatable object formats are limited to static linking applications,
as YASM cannot generate relocations for dynamic linking.
COPYRIGHT
Copyright © 2004 Peter Johnson
YASM September 2004 YASM(1)
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