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codegen, miri: fix computing the offset of an unsized field in a packed struct

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Ralf Jung 2023-12-02 14:24:17 +01:00
parent 0919ad1838
commit ef15a8182b
6 changed files with 171 additions and 11 deletions
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12
compiler/rustc_const_eval/src/interpret/projection.rs
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@ -163,7 +163,17 @@ where
// With custom DSTS, this *will* execute user-defined code, but the same
// happens at run-time so that's okay.
match self.size_and_align_of(&base_meta, &field_layout)? {
Some((_, align)) => (base_meta, offset.align_to(align)),
Some((_, align)) => {
// For packed types, we need to cap alignment.
let align = if let ty::Adt(def, _) = base.layout().ty.kind()
&& let Some(packed) = def.repr().pack
{
align.min(packed)
} else {
align
};
(base_meta, offset.align_to(align))
}
None => {
// For unsized types with an extern type tail we perform no adjustments.
// NOTE: keep this in sync with `PlaceRef::project_field` in the codegen backend.