mirror of https://github.com/rust-lang/rust
37 lines
1.5 KiB
Rust
37 lines
1.5 KiB
Rust
//@ run-pass
|
|
#[repr(packed)]
|
|
struct Packed<T: Copy>(#[allow(dead_code)] T);
|
|
|
|
impl<T: Copy> Copy for Packed<T> {}
|
|
impl<T: Copy> Clone for Packed<T> {
|
|
fn clone(&self) -> Self { *self }
|
|
}
|
|
|
|
fn sanity_check_size<T: Copy>(one: T) {
|
|
let two = [one, one];
|
|
let stride = (&two[1] as *const _ as usize) - (&two[0] as *const _ as usize);
|
|
let (size, align) = (std::mem::size_of::<T>(), std::mem::align_of::<T>());
|
|
assert_eq!(stride, size);
|
|
assert_eq!(size % align, 0);
|
|
}
|
|
|
|
fn main() {
|
|
// This can fail if rustc and LLVM disagree on the size of a type.
|
|
// In this case, `Option<Packed<(&(), u32)>>` was erroneously not
|
|
// marked as packed despite needing alignment `1` and containing
|
|
// its `&()` discriminant, which has alignment larger than `1`.
|
|
sanity_check_size((Some(Packed((&(), 0))), true));
|
|
|
|
// In #46769, `Option<(Packed<&()>, bool)>` was found to have
|
|
// pointer alignment, without actually being aligned in size.
|
|
// e.g., on 64-bit platforms, it had alignment `8` but size `9`.
|
|
type PackedRefAndBool<'a> = (Packed<&'a ()>, bool);
|
|
sanity_check_size::<Option<PackedRefAndBool>>(Some((Packed(&()), true)));
|
|
|
|
// Make sure we don't pay for the enum optimization in size,
|
|
// e.g., we shouldn't need extra padding after the packed data.
|
|
assert_eq!(std::mem::align_of::<Option<PackedRefAndBool>>(), 1);
|
|
assert_eq!(std::mem::size_of::<Option<PackedRefAndBool>>(),
|
|
std::mem::size_of::<PackedRefAndBool>());
|
|
}
|