| // compile-flags: -Z print-type-sizes |
| // compile-pass |
| // ignore-pass |
| // ^-- needed because `--pass check` does not emit the output needed. |
| // FIXME: consider using an attribute instead of side-effects. |
| |
| // This file illustrates how packing is handled; it should cause |
| // the elimination of padding that would normally be introduced |
| // to satisfy alignment desirata. |
| // |
| // It avoids using u64/i64 because on some targets that is only 4-byte |
| // aligned (while on most it is 8-byte aligned) and so the resulting |
| // padding and overall computed sizes can be quite different. |
| |
| #![allow(dead_code)] |
| #![feature(start)] |
| |
| #[derive(Default)] |
| #[repr(packed)] |
| struct Packed1 { |
| a: u8, |
| b: u8, |
| g: i32, |
| c: u8, |
| h: i16, |
| d: u8, |
| } |
| |
| #[derive(Default)] |
| #[repr(packed(2))] |
| struct Packed2 { |
| a: u8, |
| b: u8, |
| g: i32, |
| c: u8, |
| h: i16, |
| d: u8, |
| } |
| |
| #[derive(Default)] |
| #[repr(packed(2))] |
| #[repr(C)] |
| struct Packed2C { |
| a: u8, |
| b: u8, |
| g: i32, |
| c: u8, |
| h: i16, |
| d: u8, |
| } |
| |
| #[derive(Default)] |
| struct Padded { |
| a: u8, |
| b: u8, |
| g: i32, |
| c: u8, |
| h: i16, |
| d: u8, |
| } |
| |
| #[start] |
| fn start(_: isize, _: *const *const u8) -> isize { |
| let _c: Packed1 = Default::default(); |
| let _d: Packed2 = Default::default(); |
| let _e: Packed2C = Default::default(); |
| let _f: Padded = Default::default(); |
| 0 |
| } |