CO2 language is a backward compatible with C language that has Rust interop features. It uses cargo as its build system and many cargo commands like `cargo test`, `cargo doc`, `cargo miri` and ... are supported.
CO2 uses a rustc fork as its compiler and compiles code to MIR. It is useful if you want to gradually rewrite a C project in Rust, use Rust dependencies in your existing C project, or if you want to manipulate some raw pointers without writing unsafe.
