Shared Enums
#[cxx::bridge]
mod ffi {
enum Suit {
Clubs,
Diamonds,
Hearts,
Spades,
}
}
Generated Rust:
#![allow(unused)] fn main() { #[derive(Copy, Clone, PartialEq, Eq)] #[repr(transparent)] pub struct Suit { pub repr: u8, } #[allow(non_upper_case_globals)] impl Suit { pub const Clubs: Self = Suit { repr: 0 }; pub const Diamonds: Self = Suit { repr: 1 }; pub const Hearts: Self = Suit { repr: 2 }; pub const Spades: Self = Suit { repr: 3 }; } }
Generated C++:
enum class Suit : uint8_t {
Clubs = 0,
Diamonds = 1,
Hearts = 2,
Spades = 3,
};
- On the Rust side, the code generated for shared enums is actually a struct wrapping a numeric value. This is because it is not UB in C++ for an enum class to hold a value different from all of the listed variants, and our Rust representation needs to have the same behavior.