#[repr(packed)] pub struct Good { data: u64, ptr: &'static u64, data2: [u64; 2], aligned: [u8; 32], } #[repr(packed(2))] pub struct Packed2 { x: u32, y: u16, z: u8, } fn main() { unsafe { let good = Good { data: 0, ptr: &0, data2: [0, 0], aligned: [0; 32] }; let _ = &good.ptr; //~ ERROR reference to packed field let _ = &good.data; //~ ERROR reference to packed field // Error even when turned into raw pointer immediately. let _ = &good.data as *const _; //~ ERROR reference to packed field let _: *const _ = &good.data; //~ ERROR reference to packed field // Error on method call. let _ = good.data.clone(); //~ ERROR reference to packed field // Error for nested fields. let _ = &good.data2[0]; //~ ERROR reference to packed field let _ = &*good.ptr; // ok, behind a pointer let _ = &good.aligned; // ok, has align 1 let _ = &good.aligned[2]; // ok, has align 1 } unsafe { let packed2 = Packed2 { x: 0, y: 0, z: 0 }; let _ = &packed2.x; //~ ERROR reference to packed field let _ = &packed2.y; // ok, has align 2 in packed(2) struct let _ = &packed2.z; // ok, has align 1 } unsafe { struct U16(u16); impl Drop for U16 { fn drop(&mut self) { println!("{:p}", self); } } struct HasDrop; impl Drop for HasDrop { fn drop(&mut self) {} } #[allow(unused)] struct Wrapper { a: U16, b: HasDrop, } #[allow(unused)] #[repr(packed(2))] struct Wrapper2 { a: U16, b: HasDrop, } // An outer struct with more restrictive packing than the inner struct -- make sure we // notice that! #[repr(packed)] struct Misalign(u8, T); let m1 = Misalign( 0, Wrapper { a: U16(10), b: HasDrop, }, ); let _ref = &m1.1.a; //~ ERROR reference to packed field let m2 = Misalign( 0, Wrapper2 { a: U16(10), b: HasDrop, }, ); let _ref = &m2.1.a; //~ ERROR reference to packed field } }