re2c  3.0
About: re2c is a lexer generator for C, C++ and Go. It compiles regular expressions to deterministic finite automata and encodes the automata in the form of a program in the target language.
  Fossies Dox: re2c-3.0.tar.xz  ("unofficial" and yet experimental doxygen-generated source code documentation)  

re2c Documentation

Some Fossies usage hints in advance:

  1. To see the Doxygen generated documentation please click on one of the items in the steelblue colored "quick index" bar above or use the side panel at the left which displays a hierarchical tree-like index structure and is adjustable in width.
  2. If you want to search for something by keyword rather than browse for it you can use the client side search facility (using Javascript and DHTML) that provides live searching, i.e. the search results are presented and adapted as you type in the Search input field at the top right.
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re2c is a free and open-source lexer generator for C/C++, Go and Rust.

Its main goal is generating fast lexers: at least as fast as their reasonably optimized hand-coded counterparts. Instead of using traditional table-driven approach, re2c encodes the generated finite state automata directly in the form of conditional jumps and comparisons. The resulting programs are faster and often smaller than their table-driven analogues, and they are much easier to debug and understand. re2c applies quite a few optimizations in order to speed up and compress the generated code.

Another distinctive feature is its flexible interface: instead of assuming a fixed program template, re2c lets the programmer write most of the interface code and adapt the generated lexer to any particular environment.


Official re2c website is It has a lot of examples.


Release tarballs:

Source code:

$ git clone
$ git clone

Github is the main repo, sourceforge is a mirror and can be slightly outdated.


re2c is an Open Source, community-driven project. See for details about contributions to this repository.


See or the online docs for instructions how to build re2c.



Mailing lists:

IRC channels:


You are welcome to ask for help or share your thoughts and ideas.


re2c was originally written by Peter Bumbulis Since then many volunteers have contributed to the project. The current maintainer is Ulya Trofimovich