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rustc: do not raise the alignment of optimized enums to the niche's alignment.

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This commit is contained in:
Eduard-Mihai Burtescu 2017-12-18 15:17:29 +02:00
parent b39c4bc123
commit 5c3dcfaf85
2 changed files with 16 additions and 9 deletions
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13
src/test/run-pass/packed-struct-optimized-enum.rs
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@ -19,7 +19,9 @@ impl<T: Copy> Clone for Packed<T> {
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);
assert_eq!(stride, std::mem::size_of_val(&one));
let (size, align) = (std::mem::size_of::<T>(), std::mem::align_of::<T>());
assert_eq!(stride, size);
assert_eq!(size % align, 0);
}
fn main() {
@ -32,5 +34,12 @@ fn main() {
// 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`.
sanity_check_size(Some((Packed(&()), true)));
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>());
}