共享枚举

#[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, };

Speaker Notes

  • 在 Rust 端,为共享枚举生成的代码实际上是封装数值的结构体。这是因为在 C++ 中,枚举类存储与所有已列变体不同的值不属于 UB,而 Rust 表示法需要具有相同的行为。