A C compiler written in Ruby
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URCC Compiler


version: 0.0.0


  • Ruby 1.9 +
  • Ruby gem 1.8 +
  • parseconfig
  • LLVM 3.3 +
  • Clang 3.3 +


URCC is a source-to-source C compiler written in Ruby. It can use GCC and LLVM as front-ends. The current distribution assumes the use of LLVM, which it uses to parse C source code into LLVM IR. Then it creates the URCC intermediate representation and supports user-defined passes for optimization. It generates C code after optimization.

Instead of writing compiler passes in C/C++, users could implement and test optimization passes in Ruby, which is easier to program and experiment and helps compiler prototyping and teaching.


Installation requires Ruby Rake and ParseConfig installed. If you don't have them, run following to install.

[sudo] gem install rake
[sudo] gem install parseconfig

And then run rake to install:

git clone https://github.com/dcompiler/urcc.git
rake install

Test if your installation works.

urcc --version



For first time run, URCC will add config folder to $HOME/.urcc, and add a config file and a PASSES folder where pass files are defined.

Compiling C code

Run urcc *.c to compile C source file. The default outputs includes:

  • Un-optimized version of IR;
  • Un-optimized version of IR C dump;
  • Un-optimized version of compiled binary;
  • Optimized version of IR;
  • Optimized version of IR C dump;
  • Optimized version of compiled binary;

The output could be defined in config file.

Adding your own passes

By default, passes are contained in $HOME/.urcc/PASSES, and are defined individually as ruby files. Edit the config file if you want to include your pass file names in PASS > passes, separated by commas.

A pass should be defined as a ruby Proc named 'Pass', inside a module named 'PassModule'. The 'Pass' Proc takes the AST tree of the program as input.

Following is an example pass which does nothing.

# Define a HelloWorld pass                                                                                                              
module PassModule

  Pass = Proc.new do |prog|

    p prog



To include this pass, save it as "HelloWorld.rb" under PASSES directory, and add HelloWorld to config file PASSES > passes.

IR documentation

The intermedite representation (IR) is abstract syntax tree (AST). An easy way to browse AST classes and functions is to use rdoc to generate code documentation:

cd [repos]/lib/ast
rdoc *.rb

Open doc/table_of_contents.html in a Web browser.