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