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YASM(1)			  The Yasm Modular Assembler		       YASM(1)

NAME
       yasm - The Yasm Modular Assembler

SYNOPSIS

       yasm [-f	format]	[-o outfile] [other options...]	{infile}

       yasm -h

DESCRIPTION
       The Yasm	Modular	Assembler is a portable, retargetable assembler
       written under the "new" (2 or 3 clause) BSD license. Yasm currently
       supports	the x86	and AMD64 instruction sets, accepts NASM and GAS
       assembler syntaxes, outputs binary, ELF32, ELF64, COFF, Win32, and
       Win64 object formats, and generates source debugging information	in
       STABS, DWARF 2, and CodeView 8 formats.

       YASM consists of	the yasm command, libyasm, the core backend library,
       and a large number of modules. Currently, libyasm and the loadable
       modules are statically built into the yasm executable.

       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 with an infile	of "-",	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.
       Options are listed in alphabetical order.

   General Options
       -a arch or --arch=arch: Select target architecture
	   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 a list of
	   supported architectures.

       -f format or --oformat=format: Select object format
	   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. See yasm_objfmts(7) for a list of supported object formats.

       -g debug	or --dformat=debug: Select debugging format
	   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. See yasm_dbgfmts(7) for a list of supported debugging
	   formats.

       -L list or --lformat=list: Select list file format
	   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.

       -l listfile or --list=listfile: Specify list filename
	   Specifies the name of the output list file. If this option is not
	   used, no list file is generated.

       -m machine or --machine=machine:	Select target machine architecture
	   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.

       -o filename or --objfile=filename: Specify object filename
	   Specifies the name of the output file, overriding any default name
	   generated by	Yasm.

       -p parser or --parser=parser: Select parser
	   Selects the parser (the assembler syntax). The default parser is
	   "nasm", which emulates the syntax of	NASM, the Netwide Assembler.
	   Another available parser is "gas", which emulates the syntax	of GNU
	   AS. To print	a list of available parsers to standard	output,	use
	   "help" as parser. See yasm_parsers(7) for a list of supported
	   parsers.

       -r preproc or --preproc=preproc:	Select preprocessor
	   Selects the preprocessor to use on the input	file before passing it
	   to the parser. Preprocessors	often provide macro functionality that
	   is not included in the main parser. The default preprocessor	is
	   "nasm", which is an imported	version	of the actual NASM
	   preprocessor. A "raw" preprocessor is also available, which simply
	   skips the preprocessing step, passing the input file	directly to
	   the parser. To print	a list of available preprocessors to standard
	   output, use "help" as preproc.

       -h or --help: Print a summary of	options
	   Prints a summary of invocation options. All other options are
	   ignored, and	no output file is generated.

       --version: Get the Yasm version
	   This	option causes Yasm to prints the version number	of Yasm	as
	   well	as a license summary to	standard output. All other options are
	   ignored, and	no output file is generated.

   Warning Options
       -W options have two contrary forms: -Wname and -Wno-name. Only the
       non-default forms are shown here.

       The warning options are handled in the order given on the command line,
       so if -w	is followed by -Worphan-labels,	all warnings are turned	off
       except for orphan-labels.

       -w: Inhibit all warning messages
	   This	option causes Yasm to inhibit all warning messages. As
	   discussed above, this option	may be followed	by other options to
	   re-enable specified warnings.

       -Werror:	Treat warnings as errors
	   This	option causes Yasm to treat all	warnings as errors. Normally
	   warnings do not prevent an object file from being generated and do
	   not result in a failure exit	status from yasm, whereas errors do.
	   This	option makes warnings equivalent to errors in terms of this
	   behavior.

       -Wno-unrecognized-char: Do not warn on unrecognized input characters
	   Causes Yasm to not warn on unrecognized characters found in the
	   input. Normally Yasm	will generate a	warning	for any	non-ASCII
	   character found in the input	file.

       -Worphan-labels:	Warn on	labels lacking a trailing option
	   When	using the NASM-compatible parser, causes Yasm to warn about
	   labels found	alone on a line	without	a trailing colon. While	these
	   are legal labels in NASM syntax, they may be	unintentional, due to
	   typos or macro definition ordering.

       -X style: Change	error/warning reporting	style
	   Selects a specific output style for error and warning messages. The
	   default is "gnu" style, which mimics	the output of gcc. The "vc"
	   style is also available, which mimics the output of Microsoft's
	   Visual C++ compiler.

	   This	option is available so that Yasm integrates more naturally
	   into	IDE environments such as Visual	Studio or Emacs, allowing the
	   IDE to correctly recognize the error/warning	message	as such	and
	   link	back to	the offending line of source code.

   Preprocessor	Options
       While these preprocessor	options	theoretically will affect any
       preprocessor, the only preprocessor currently in	Yasm is	the "nasm"
       preprocessor.

       -D macro[=value]: Pre-define a macro
	   Pre-defines a single-line macro. The	value is optional (if no value
	   is given, the macro is still	defined, but to	an empty value).

       -e or --preproc-only: Only preprocess
	   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:	Add include file path
	   Adds	directory path to the search path for include files. The
	   search path defaults	to only	including the directory	in which the
	   source file resides.

       -P filename: Pre-include	a file
	   Pre-includes	file filename, making it look as though	filename was
	   prepended to	the input. Can be useful for prepending	multi-line
	   macros that the -D can't support.

       -U macro: Undefine a macro
	   Undefines a single-line macro (may be either	a built-in macro or
	   one defined earlier in the command line with	-D.

EXAMPLES
       To assemble NASM	syntax,	32-bit x86 source source.asm into ELF file
       source.o, warning on orphan labels:

	   yasm	-f elf32 -Worphan-labels source.asm

       To assemble NASM	syntax AMD64 source x.asm into Win64 file object.obj:

	   yasm	-f win64 -o object.obj x.asm

       To assemble already preprocessed	NASM syntax 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.

       Yasm's GAS parser and preprocessor are missing a	number of features
       present in GNU AS.

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 symbol maps.

SEE ALSO
       yasm_arch(7), yasm_dbgfmts(7), yasm_objfmts(7), yasm_parsers(7)

       Related tools: as(1), ld(1), nasm(1)

BUGS
       When using the "x86" architecture, it is	overly easy to generate	AMD64
       code (using the BITS 64 directive) and generate a 32-bit	object file
       (by failing to specify -m amd64 or selecting a 64-bit object format
       such as ELF64 on	the command line).

AUTHOR
       Peter Johnson <peter@tortall.net>
	   Author.

COPYRIGHT
       Copyright (C) 2004, 2005, 2006, 2007 Peter Johnson

Yasm				  April	2007			       YASM(1)

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