README

chibicc: A Small C Compiler

(The old master has moved to
historical/old
branch. This is a new one uploaded in September 2020.)

chibicc is yet another small C compiler that implements most C11
features. Even though it still probably falls into the "toy compilers"
category just like other small compilers do, chibicc can compile
several real-world programs, including Git,
SQLite,
libpng and chibicc
itself, without making modifications to the compiled programs.
Generated executables of these programs pass their corresponding test
suites. So, chibicc actually supports a wide variety of C11 features
and is able to compile hundreds of thousands of lines of real-world C
code correctly.

chibicc is developed as the reference implementation for a book I'm
currently writing about the C compiler and the low-level programming.
The book covers the vast topic with an incremental approach; in the first
chapter, readers will implement a "compiler" that accepts just a single
number as a "language", which will then gain one feature at a time in each
section of the book until the language that the compiler accepts matches
what the C11 spec specifies. I took this incremental approach from the
paper by Abdulaziz
Ghuloum.

Each commit of this project corresponds to a section of the book. For this
purpose, not only the final state of the project but each commit was
carefully written with readability in mind. Readers should be able to learn
how a C language feature can be implemented just by reading one or a few
commits of this project. For example, this is how
while,
[[]](https://github.com/rui314/chibicc/commit/75fbd3dd6efde12eac8225d8b5723093836170a5),
?:,
and thread-local
variable
are implemented. If you have plenty of spare time, it might be fun to read
it from the first
commit.

If you like this project, please consider purchasing a copy of the book
when it becomes available! 😀 I publish the source code here to give people
early access to it, because I was planing to do that anyway with a
permissive open-source license after publishing the book. If I don't charge
for the source code, it doesn't make much sense to me to keep it private. I
hope to publish the book in 2021.
You can sign up here to receive a
notification when a free chapter is available online or the book is published.

I pronounce chibicc as _chee bee cee cee_. "chibi" means "mini" or
"small" in Japanese. "cc" stands for C compiler.

 Status

chibicc supports almost all mandatory features and most optional
features of C11 as well as a few GCC language extensions.

Features that are often missing in a small compiler but supported by
chibicc include (but not limited to):

- Preprocessor
- float, double and long double (x87 80-bit floating point numbers)
- Bit-fields
- alloca()
- Variable-length arrays
- Compound literals
- Thread-local variables
- Atomic variables
- Common symbols
- Designated initializers
- L, u, U and u8 string literals
- Functions that take or return structs as values, as specified