# C API for hyper This provides auxiliary pieces for a C API to use the hyper library. ## Unstable The C API of hyper is currently **unstable**, which means it's not part of the semver contract as the rest of the Rust API is. Because of that, it's only accessible if `--cfg hyper_unstable_ffi` is passed to `rustc` when compiling. The easiest way to do that is setting the `RUSTFLAGS` environment variable. ## Building The C API is part of the Rust library, but isn't compiled by default. Using `cargo`, it can be compiled with the following command: ``` RUSTFLAGS="--cfg hyper_unstable_ffi" cargo build --features client,http1,http2,ffi ```