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.

       -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.

       -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.

       --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)