Rust enums are not compatible with C, even with `#[repr(C)]`. Values not explicitly present in the enum are not allowed. Casting them to a Rust enum is UB, and

Rust enums are not compatible with C, even with `#[repr(C)]`. Values not explicitly present in the enum are not allowed. Casting them to a Rust enum is UB, and it does actually cause miscompilation, because `match` can be a jump table.