This is a fork of Rui Ueyama's chibicc with fixes and enhancements, 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, _BitInt, nullptr, ={}
• C2Y features: named loops, if declarations, _Countof.
• defer: enable with -fdefer-ts, or use _Defer.
• WG14 proposals: __VA_TAIL__, #def #enddef.
• GNU features: inline assembly, commonly used __attribute__'s.
• MSVC features: #pragma pack, anonymous struct.
• Basic codegen optimizations (close to GCC/Clang at -O0).

Compiling real C projects with slimcc has been a major focus, the CI workflow now regularly build-test a healthy collection of familiar names, for bragging rights:

• Core system commands (GNU coreutils, busybox, toybox)
• Developer tools (binutils, Bash, Curl, Git, jq, wget, Zsh)
• Programming languages (Python, Go, Lua, Perl, Ruby, PHP, Ocaml, Zig)
• Gamedev/graphics libraries (SDL3, glfw, stb, raylib, sokol)
• Critical infrastructure softwares (Redis, Valkey, Nginx, PostgreSQL)

slimcc-musl-bootstrap is a minimal statically-linked chroot environment with musl, binutils, toybox entirely compiled with slimcc.

• Recent GNU binutils is required.
• Find a relevant preset in platform/, copy/symlink to platform.c or create one, hit make.
• On recent glibc Linux, this should just work:

ln -s platform/linux-glibc-generic.c platform.c
make

• For simplicity, built-in headers are searched relative to the binary, it's intended to be executed in-tree like:

~/slimcc/slimcc *.c
CC=~/slimcc/slimcc ./configure
cmake -DCMAKE_C_COMPILER=/home/username/slimcc/slimcc

• For installing/symlinking/packaging, please edit platform.c with absolute paths.
• make slimcc-asan/test-asan build and run tests with address sanitizer, recommended if you are hacking the source.

• Autoconf based projects might fail to build due to -fPIC or -Wl not being passed. If there is a block in ./configure that looks like below, append -Wl,, -fPIC, -static respectively and re-configure:

  lt_prog_compiler_wl=
lt_prog_compiler_pic=
lt_prog_compiler_static=

• It might be necessary to configure with CFLAGS=-fPIC, for CMake, -DCMAKE_C_FLAGS=-fPIC.
• CMake find_package() might fail to find installed libraries, help it with -DCMAKE_PREFIX_PATH.
• Meson: see mesonbuild/meson#5406. Try Muon or hope for slimcc to join the club.
• Projects with deep GCC assumptions might actually work if you carefully opt in/out of #if __GNUC__ blocks, see the CI test scripts for a taste of hacks that can be done.
• Some projects adopt an idiom that globally set -fvisibility=hidden then selectively export public API with __attribute__((visibility("default"))). slimcc support both, yet a problem arises when the former is probed by build system while the latter hardcoded in #if __GNUC__ blocks regardless of the build system's decision. An option -fdisable-visibility is added to simply disable both features to prevent the conflict.

The coding style is highly influenced by chibicc, which means in the eyes of C veterans there might be all kinds of inefficiencies in the name of readability. While micro-optimizing is fun, I only commit changes that noticeably improve fully-optimized builds.

As such, optimization flags and custom allocators have great impact on its performance, make lto/lto-mi/lto-je is provided for optimized builds. It's usually faster than Clang/GCC for common tasks, but only by doing way less internally.

• It's written in C99 with several POSIX 2008 functions.
• TinyCC(mob branch), kefir, pcc, and vanilla chibicc should be able to compile it.
• cproc is blocked by the lack of long double support in its backend, QBE.