src/test/ui/union/union-overwrite.rs

   1 // run-pass
   2
   3 #[repr(C)]
   4 #[derive(Copy, Clone)]
   5 struct Pair<T, U>(T, U);
   6 #[repr(C)]
   7 #[derive(Copy, Clone)]
   8 struct Triple<T>(T, T, T);
   9
  10 #[repr(C)]
  11 union U<A, B>
  12 where
  13     A: Copy, B: Copy
  14 {
  15     a: Pair<A, A>,
  16     b: B,
  17 }
  18
  19 #[repr(C)]
  20 union W<A, B>
  21 where
  22     A: Copy, B: Copy
  23 {
  24     a: A,
  25     b: B,
  26 }
  27
  28 #[cfg(target_endian = "little")]
  29 unsafe fn check() {
  30     let mut u = U::<u8, u16> { b: 0xDE_DE };
  31     u.a.0 = 0xBE;
  32     assert_eq!(u.b, 0xDE_BE);
  33
  34     let mut u = U::<u16, u32> { b: 0xDEAD_DEAD };
  35     u.a.0 = 0xBEEF;
  36     assert_eq!(u.b, 0xDEAD_BEEF);
  37
  38     let mut u = U::<u32, u64> { b: 0xDEADBEEF_DEADBEEF };
  39     u.a.0 = 0xBAADF00D;
  40     assert_eq!(u.b, 0xDEADBEEF_BAADF00D);
  41
  42     let mut w = W::<Pair<Triple<u8>, u8>, u32> { b: 0xDEAD_DEAD };
  43     w.a.0 = Triple(0, 0, 0);
  44     assert_eq!(w.b, 0xDE00_0000);
  45
  46     let mut w = W::<Pair<u8, Triple<u8>>, u32> { b: 0xDEAD_DEAD };
  47     w.a.1 = Triple(0, 0, 0);
  48     assert_eq!(w.b, 0x0000_00AD);
  49 }
  50
  51 #[cfg(target_endian = "big")]
  52 unsafe fn check() {
  53     let mut u = U::<u8, u16> { b: 0xDE_DE };
  54     u.a.0 = 0xBE;
  55     assert_eq!(u.b, 0xBE_DE);
  56
  57     let mut u = U::<u16, u32> { b: 0xDEAD_DEAD };
  58     u.a.0 = 0xBEEF;
  59     assert_eq!(u.b, 0xBEEF_DEAD);
  60
  61     let mut u = U::<u32, u64> { b: 0xDEADBEEF_DEADBEEF };
  62     u.a.0 = 0xBAADF00D;
  63     assert_eq!(u.b, 0xBAADF00D_DEADBEEF);
  64
  65     let mut w = W::<Pair<Triple<u8>, u8>, u32> { b: 0xDEAD_DEAD };
  66     w.a.0 = Triple(0, 0, 0);
  67     assert_eq!(w.b, 0x0000_00AD);
  68
  69     let mut w = W::<Pair<u8, Triple<u8>>, u32> { b: 0xDEAD_DEAD };
  70     w.a.1 = Triple(0, 0, 0);
  71     assert_eq!(w.b, 0xDE00_0000);
  72 }
  73
  74 fn main() {
  75     unsafe {
  76         check();
  77     }
  78 }