Claudes C Compiler — Development skill for Claude Code

CCC — Claude's C Compiler

A C compiler written entirely from scratch in Rust, targeting x86-64, i686, AArch64, and RISC-V 64. Zero compiler-specific dependencies — the frontend, SSA-based IR, optimizer, code generator, peephole optimizers, assembler, linker, and DWARF debug info generation are all implemented from scratch. Claude's C Compiler produces ELF executables without any external toolchain.

Note: With the exception of this one paragraph that was written by a human, 100% of the code and documentation in this repository was written by Claude Opus 4.6. A human guided some of this process by writing test cases that Claude was told to pass, but never interactively pair-programmed with Claude to debug or to provide feedback on code quality. As a result, I do not recommend you use this code! None of it has been validated for correctness. Claude wrote this exclusively on a Linux host; it probably will not work on MacOS/Windows — neither I nor Claude have tried. The docs may be wrong and make claims that are false. See [our blog post](https://anthropic.com/engineering/building-c-compiler) for more detail.

Prerequisites

• Rust (stable, 2021 edition) — install via rustup
• Linux host — the compiler targets Linux ELF executables and relies on Linux system headers / C runtime libraries (glibc or musl) being installed on the host
• For cross-compilation targets (ARM, RISC-V, i686), the corresponding cross-compilation sysroots should be installed (e.g., aarch64-linux-gnu-gcc, riscv64-linux-gnu-gcc)

Building

cargo build --release

This produces five binaries in `target/release/`, all compiled from the same source. The target architecture is selected by the binary name at runtime:

Binary	Target
ccc	x86-64 (default)
ccc-x86	x86-64
ccc-arm	AArch64
ccc-riscv	RISC-V 64
ccc-i686	i686 (32-bit x86)

Quick Start

Compile and run a simple C progr