This is a fork of Rui Ueyama's chibicc with fixes and improvements, including:

• C99 features: VLA parameters, VLA de-allocation, K&R old-style functions.
• C11 features: _Static_assert(), over-aligned locals, _Generic with qualifiers.
• C23 features: constexpr, enum:T{}, #embed, auto type-inference, etc.
• C2Y/TS features: defer(as _Defer), __VA_TAIL__
• GNU features: inline asm, cleanup
• Basic optimizations: const folding, reg-alloc for temporaries, instruction selection.

Project goal

• Compile correct code correctly.
• Code readability.
• Build real world projects, test with their suites.
• Implement GNU extensions and C23 features if doable.
• Match GCC / Clang's behavior to improve compatibility with existing code in the wild.

Building & Running

• Should just work on recent glibc-based (2.28+) x86-64 Linux. Also see porting
• Test script needs bash; depending on the distro, file and/or glibc-static packages may be required.

git clone --depth 1 https://github.com/fuhsnn/slimcc
cd slimcc
make test-stage2 -j4

Run it in base directory like CC=~/slimcc/slimcc, since internal header path is hardcoded for simplicity.

What can it build?

slimcc should be able to compile most C89 to C11 projects not requiring optional or compiler-specific features.

A CI workflow is set up to make test real-world projects in a Debian container with cc gcc cpp uninstalled. The lineup includes Curl, Git, OpenSSL, PHP, Perl, Python, PostgreSQL, and continues to grow. Please have a look a the workflow, dockerfile, and build instructions to verify this claim.

musl is also buildable sans complex numbers, it's a goal to set up a self-hosted slimcc-musl environment.

Can it pass csmith?

1M tests were run with --no-packed-struct flag, all issues found were fixed.

How optimized are the generated binaries?

Binary size is roughly among TinyCC's and GCC/Clang at -O0, no claims about speed.

How optimized is the compiler itself?

The compiler leaks all allocations, it gets bad for large translation units, I'm looking for a clean way to remedy this.

Can it be built with another small C compiler?

Here's some I've tried:

• TinyCC, kefir, vanilla chibicc: can build with cc *.c, make test will fail but not big deal.
• pcc: has a bug parsing escaped sequence in a comment, otherwise can build.
• cproc: can't build, lacks long double support.
• mir, xcc: missing header.

Porting

musl Linux and BSDs should be doable. Check hard-coded paths in main.c, and pre-defined macros in preprocessor.c.

The widcc branch is a less noisy codebase than slimcc that should be more appealing for developers to hack on.