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don't UB on dangling ptr deref, instead check inbounds on projections

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This commit is contained in:
Ralf Jung 2023-08-01 17:11:00 +02:00
parent a48396984a
commit b1ebf002c3
102 changed files with 531 additions and 469 deletions
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12
compiler/rustc_const_eval/src/interpret/operand.rs
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@ -219,6 +219,17 @@ impl<'tcx, Prov: Provenance> ImmTy<'tcx, Prov> {
/// given layout.
// Not called `offset` to avoid confusion with the trait method.
fn offset_(&self, offset: Size, layout: TyAndLayout<'tcx>, cx: &impl HasDataLayout) -> Self {
debug_assert!(layout.is_sized(), "unsized immediates are not a thing");
// `ImmTy` have already been checked to be in-bounds, so we can just check directly if this
// remains in-bounds. This cannot actually be violated since projections are type-checked
// and bounds-checked.
assert!(
offset + layout.size <= self.layout.size,
"attempting to project to field at offset {} with size {} into immediate with layout {:#?}",
offset.bytes(),
layout.size.bytes(),
self.layout,
);
// This makes several assumptions about what layouts we will encounter; we match what
// codegen does as good as we can (see `extract_field` in `rustc_codegen_ssa/src/mir/operand.rs`).
let inner_val: Immediate<_> = match (**self, self.layout.abi) {
@ -387,7 +398,6 @@ impl<'tcx, Prov: Provenance> Projectable<'tcx, Prov> for OpTy<'tcx, Prov> {
match self.as_mplace_or_imm() {
Left(mplace) => Ok(mplace.offset_with_meta(offset, meta, layout, ecx)?.into()),
Right(imm) => {
debug_assert!(layout.is_sized(), "unsized immediates are not a thing");
assert_matches!(meta, MemPlaceMeta::None); // no place to store metadata here
// Every part of an uninit is uninit.
Ok(imm.offset_(offset, layout, ecx).into())