| #![feature(core_intrinsics)] |
| |
| use std::mem; |
| |
| fn main() { |
| let x: Option<Box<[u8]>> = unsafe { |
| let z = std::intrinsics::add_with_overflow(0usize, 0usize); |
| std::mem::transmute::<(usize, bool), Option<Box<[u8]>>>(z) |
| }; |
| let y = &x; |
| // Now read this bytewise. There should be (`ptr_size + 1`) def bytes followed by |
| // (`ptr_size - 1`) undef bytes (the padding after the bool) in there. |
| let z: *const u8 = y as *const _ as *const _; |
| let first_undef = mem::size_of::<usize>() as isize + 1; |
| for i in 0..first_undef { |
| let byte = unsafe { *z.offset(i) }; |
| assert_eq!(byte, 0); |
| } |
| let v = unsafe { *z.offset(first_undef) }; |
| //~^ ERROR: uninitialized |
| if v == 0 { |
| println!("it is zero"); |
| } |
| } |
