tests/ui/print_type_sizes/repr-align.rs

   1 // compile-flags: -Z print-type-sizes --crate-type=lib
   2 // build-pass
   3 // ignore-pass
   4 // ^-- needed because `--pass check` does not emit the output needed.
   5 //     FIXME: consider using an attribute instead of side-effects.
   6
   7 // This file illustrates how padding is handled: alignment
   8 // requirements can lead to the introduction of padding, either before
   9 // fields or at the end of the structure as a whole.
  10 //
  11 // It avoids using u64/i64 because on some targets that is only 4-byte
  12 // aligned (while on most it is 8-byte aligned) and so the resulting
  13 // padding and overall computed sizes can be quite different.
  14
  15 #![allow(dead_code)]
  16
  17 #[repr(align(16))]
  18 #[derive(Default)]
  19 struct A(i32);
  20
  21 enum E {
  22     A(i32),
  23     B(A)
  24 }
  25
  26 #[derive(Default)]
  27 pub struct S {
  28     a: i32,
  29     b: i32,
  30     c: A,
  31     d: i8,
  32 }