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miri: lift restriction on extern types being the only field in a struct

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This commit is contained in:
Tomasz Miąsko 2021-12-14 00:00:00 +00:00
parent c5ecc15704
commit fd47d247d8
3 changed files with 69 additions and 27 deletions
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16
compiler/rustc_const_eval/src/interpret/eval_context.rs
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@ -616,19 +616,9 @@ impl<'mir, 'tcx: 'mir, M: Machine<'mir, 'tcx>> InterpCx<'mir, 'tcx, M> {
match self.size_and_align_of(metadata, &field)? {
Some(size_and_align) => size_and_align,
None => {
// A field with extern type. If this field is at offset 0, we behave
// like the underlying extern type.
// FIXME: Once we have made decisions for how to handle size and alignment
// of `extern type`, this should be adapted. It is just a temporary hack
// to get some code to work that probably ought to work.
if sized_size == Size::ZERO {
return Ok(None);
} else {
span_bug!(
self.cur_span(),
"Fields cannot be extern types, unless they are at offset 0"
)
}
// A field with an extern type. We don't know the actual dynamic size
// or the alignment.
return Ok(None);
}
};

22
compiler/rustc_const_eval/src/interpret/place.rs
View file

@ -362,21 +362,15 @@ where
// Re-use parent metadata to determine dynamic field layout.
// With custom DSTS, this *will* execute user-defined code, but the same
// happens at run-time so that's okay.
let align = match self.size_and_align_of(&base.meta, &field_layout)? {
Some((_, align)) => align,
None if offset == Size::ZERO => {
// An extern type at offset 0, we fall back to its static alignment.
// FIXME: Once we have made decisions for how to handle size and alignment
// of `extern type`, this should be adapted. It is just a temporary hack
// to get some code to work that probably ought to work.
field_layout.align.abi
match self.size_and_align_of(&base.meta, &field_layout)? {
Some((_, 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.
assert!(matches!(base.meta, MemPlaceMeta::None));
(base.meta, offset)
}
None => span_bug!(
self.cur_span(),
"cannot compute offset for extern type field at non-0 offset"
),
};
(base.meta, offset.align_to(align))
}
} else {
// base.meta could be present; we might be accessing a sized field of an unsized
// struct.