nested-type-alignment-rs-crepr

main.rs

#[repr(C)]
struct CRepr {
    a: u16, // 2 bytes
    b: u32, // 4 bytes
    c: u16, // 2 bytes
    d: u32, // 4 bytes
}

fn address<T>(r: &T) -> isize {
    r as *const _ as isize
}

fn main() {
    let object = CRepr { a: 0, b: 0, c: 0, d: 0 };
    let offset = |p| p - address(&object);
    println!("Rust struct with C-like layout:\n");
    println!("  offset of a: {:2} bytes", offset(address(&object.a)));
    println!("  offset of b: {:2} bytes", offset(address(&object.b)));
    println!("  offset of c: {:2} bytes", offset(address(&object.c)));
    println!("  offset of d: {:2} bytes", offset(address(&object.d)));
    println!("  total size:  {:2} bytes", std::mem::size_of::<CRepr>());
}