The Yasm Modular Assembler Project

Yasm is a complete rewrite of the NASM assembler under the "new" BSD License (some portions are under other licenses, see COPYING for details). Yasm currently supports the x86 and AMD64 instruction sets, accepts NASM and GAS assembler syntaxes, outputs binary, ELF32, ELF64, 32 and 64-bit Mach-O, RDOFF2, COFF, Win32, and Win64 object formats, and generates source debugging information in STABS, DWARF 2, and CodeView? 8 formats. Yasm can be easily integrated into Visual Studio 2005 (see VisualStudio2005) for assembly of NASM or GAS syntax code into Win32 or Win64 object files.

Key Current User-Visible Features

• Nearly feature-complete lexing and parsing of NASM syntax.
• Nearly feature-complete lexing and parsing of GAS (GNU assembler) syntax.
• AMD64 support (enabled using "BITS 64", "-m amd64", or selecting an explicitly 64-bit object format output such as "-f win64" or "-f elf64")
• 64-bit (and larger) integer constants allowed (including math operations).
• A fast jump size optimizer equivalent to or better than other assemblers' multi-pass optimizers.
• Support for multiple object formats:
  • Binary object file output (NASM style).
  • COFF object file? output, for use with DJGPP.
  • Win32 object file? output.
  • Win64/AMD64 aka "x64" object file? output.
    • Supports structured exception handling
  • RDOFF2 object file? output.
  • ELF32 and ELF64 object file output.
  • 32 and 64-bit Mach-O object file? output.
• STABS, DWARF2, and CodeView? debug formats.
• Portability; currently compilable on:
  • UNIX and compatibles (32-bit and 64-bit FreeBSD and Linux tested, GNU configure based autoconfiguration)
  • DOS (using DJGPP)
  • Windows (using Visual C++ or CygWin).
• Internationalization support via GNU gettext.

Key Internal Features

The core focus of Yasm is not the "yasm" commandline frontend; rather, it is the Libyasm library and associated LoadableModules? (see the ProgrammerReferences for documentation). Libyasm and the modules are intended for reuse in other sorts of programs dealing with code at the assembly level (compilers, debuggers, etc). Someday, libyasm may be packaged separately from the rest of Yasm.

• A NASM syntax and GAS syntax recursive-descent parser.
• Architecture-specific instruction parsers hand-written for simplicity and size, as well as to make it easy to add additional architectures while retaining the same front-end syntax. The blend of recursive descent for syntax and a hand-written parser for instructions strikes a great balance between the strengths and weaknesses of each approach.
• A NASM syntax lexer written in re2c. A highly efficient scanner generator (almost always faster than lex/flex), it's also very embeddable due to its code generation methodology, allowing a number of re2c scanners to be used in various places in yasm without any worries about naming conflicts.
• A GAS syntax lexer written in re2c.
• Many of the modular interfaces at least superficially finished. This is still an area that needs a lot of work.
• A small set of portable equivalents of useful functions that are standard on some systems (detected via configure), such as the queue(3) set of functions, strdup, strcasecmp, and mergesort.
• A decent (and growing) set of assembler test input files to test the entire assembler as well as specific modules.

Wiki

For a complete list of local wiki pages, see TitleIndex.

Q: Now what is this wiki thing? And why is there an edit button that I can use? Is there an error in the setup or should it be that way?

A: Yes, you currently may edit many pages here, and even create new ones. The main goal of the wiki is making editing text easier and encouraging people to contribute and annotate text content for the project. See the Wiki article at Wikipedia or WhyWikiWorks for more information about the wiki philosophy.