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Auto merge of #71274 - RalfJung:raw-init-check-aggregate, r=petrochenkov

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might_permit_raw_init: also check aggregate fields

This is the next step for https://github.com/rust-lang/rust/issues/66151: when doing `mem::zeroed`/`mem::uninitialized`, also recursively check fields of aggregates (except for arrays) for whether they permit zero/uninit initialization.
This commit is contained in:
bors 2020-09-27 10:17:09 +00:00
commit b8363295d5
3 changed files with 59 additions and 8 deletions
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23
compiler/rustc_target/src/abi/mod.rs
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@ -1135,16 +1135,31 @@ impl<'a, Ty> TyAndLayout<'a, Ty> {
Abi::Scalar(s) => scalar_allows_raw_init(s),
Abi::ScalarPair(s1, s2) => scalar_allows_raw_init(s1) && scalar_allows_raw_init(s2),
Abi::Vector { element: s, count } => *count == 0 || scalar_allows_raw_init(s),
Abi::Aggregate { .. } => true, // Cannot be excluded *right now*.
Abi::Aggregate { .. } => true, // Fields are checked below.
};
if !valid {
// This is definitely not okay.
trace!("might_permit_raw_init({:?}, zero={}): not valid", self.layout, zero);
return Ok(false);
}
// If we have not found an error yet, we need to recursively descend.
// FIXME(#66151): For now, we are conservative and do not do this.
// If we have not found an error yet, we need to recursively descend into fields.
match &self.fields {
FieldsShape::Primitive | FieldsShape::Union { .. } => {}
FieldsShape::Array { .. } => {
// FIXME(#66151): For now, we are conservative and do not check arrays.
}
FieldsShape::Arbitrary { offsets, .. } => {
for idx in 0..offsets.len() {
let field = self.field(cx, idx).to_result()?;
if !field.might_permit_raw_init(cx, zero)? {
// We found a field that is unhappy with this kind of initialization.
return Ok(false);
}
}
}
}
// FIXME(#66151): For now, we are conservative and do not check `self.variants`.
Ok(true)
}
}