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fix accessing unsized fields

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This commit is contained in:
Ralf Jung 2018-08-16 00:41:26 +02:00
parent 1e137a7966
commit e314a4e75f
1 changed files with 15 additions and 14 deletions
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29
src/librustc_mir/interpret/place.rs
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@ -283,31 +283,32 @@ pub fn mplace_field(
};
// the only way conversion can fail if is this is an array (otherwise we already panicked
// above). In that case, all fields are equal.
let field = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
let field_layout = base.layout.field(self, usize::try_from(field).unwrap_or(0))?;
// Adjust offset
let offset = if field.is_unsized() {
let vtable = match base.extra {
PlaceExtra::Vtable(tab) => tab,
_ => bug!("Unsized place with unsized field must come with vtable"),
};
let (_, align) = self.read_size_and_align_from_vtable(vtable)?;
offset.abi_align(align)
} else {
// No adjustment needed
offset
let offset = match base.extra {
PlaceExtra::Vtable(vtable) => {
let (_, align) = self.read_size_and_align_from_vtable(vtable)?;
// FIXME: Is this right? Should we always do this, or only when actually
// accessing the field to which the vtable applies?
offset.abi_align(align)
}
_ => {
// No adjustment needed
offset
}
};
let ptr = base.ptr.ptr_offset(offset, self)?;
let align = base.align.min(field.align);
let extra = if !field.is_unsized() {
let align = base.align.min(field_layout.align);
let extra = if !field_layout.is_unsized() {
PlaceExtra::None
} else {
assert!(base.extra != PlaceExtra::None, "Expected fat ptr");
base.extra
};
Ok(MPlaceTy { mplace: MemPlace { ptr, align, extra }, layout: field })
Ok(MPlaceTy { mplace: MemPlace { ptr, align, extra }, layout: field_layout })
}
pub fn mplace_subslice(