rustc: do not raise the alignment of optimized enums to the niche's alignment. #46809
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r? @estebank (rust_highfive has picked a reviewer for you, use r? to override) |
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@bors r+ |
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📌 Commit 090a192 has been approved by |
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@bors r_ |
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@bors r- |
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(don't mind me, just Travis-cycling the PR) |
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rustc: ensure optimized enums have a properly aligned size. Fixes #46769 by padding the optimized enums wrapping packed data as necessary. Note that this is not the only way to solve this - on nightly, #46436 makes it easier to fix without adding new padding because of the replacement of `packed` flags with a non-redundant scheme. But because it can't be backported, the optimal fix will be in a separate nightly-only PR (#46809).
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#46808 has been merged. |
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Could you please add a test that the size of a packed enum is what it's supposed to be? @bors r- |
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Something like this: // This struct has a single niche - the dealigned pointer within. Check that
// it is null-pointer-optimized correctly
struct Interesting {
packed: Packed<&'static ()>,
other: u8
}
assert_eq!(mem::size_of::<Interesting>(), mem::size_of::<Option<Interesting>>()); |
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rustc: do not raise the alignment of optimized enums to the niche's alignment. This is the improved fix for rust-lang#46769 that does not increase the size of any types (see also rust-lang#46808).
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This is the improved fix for #46769 that does not increase the size of any types (see also #46808).