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rui314 / 8cc


A Small C Compiler


8cc C Compiler

8cc is a compiler for the C programming language. It's intended to support all C11 language features while keeping the code as small and simple as possible.

The compiler is able to compile itself. You can see its code both as an implementation of the C language and as an example of what this compiler is able to compile.

8cc's source code is carefully written to be as concise and easy-to-read as possible, so that the source code becomes good study material to learn about various techniques used in compilers. You may find the lexer, the preprocessor and the parser are already useful to learn how C source code is processed at each stage.

It's not an optimizing compiler. Generated code is usually 2x or more slower than GCC. I plan to implement a reasonable level of optimization in the future.

8cc supports x86-64 Linux only. I have no plan to make it portable until I fix all known miscompilations and implement an optimization pass. As of 2015, I'm using Ubuntu 14 as my development platform. It should work on other x86-64 Linux distributions though.

Note: Do not have high expectations on this compiler. If you try to compile a program other than the compiler itself, there's a good chance to see compile errors or miscompilations. This is basically a one-man project, and I have spent only a few months of my spare time so far.


Run make to build:


8cc comes with unit tests. To run the tests, give "test" as an argument:

make test

The following target builds 8cc three times to verify that stage1 compiler can build stage2, and stage2 can build stage3. It then compares stage2 and stage3 binaries byte-by-byte to verify that we reach a fixed point.

make fulltest


Rui Ueyama

Links for C compiler development

Besides popular books about compiler, such as the Dragon Book, I found the following books/documents are very useful to develop a C compiler. Note that the standard draft versions are very close to the ratified versions. You can practically use them as the standard documents.