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Co-authored-by: Ralf Jung <post@ralfj.de>
This commit is contained in:
Oli Scherer 2021-01-03 14:20:51 +01:00 • committed by oli
parent ba3a876592
commit e5330a4f52
2 changed files with 9 additions and 4 deletions
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11
compiler/rustc_mir/src/transform/check_consts/validation.rs
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@ -584,14 +584,19 @@ impl Visitor<'tcx> for Validator<'mir, 'tcx> {
if borrowed_place_has_mut_interior {
match self.const_kind() {
// In a const fn all borrows are transient or point to the places given via
// references in the arguments. The borrow checker guarantees that.
// references in the arguments (so we already checked them with
// TransientCellBorrow/CellBorrow as appropriate).
// The borrow checker guarantees that no new non-transient borrows are created.
// NOTE: Once we have heap allocations during CTFE we need to figure out
// how to prevent `const fn` to create long-lived allocations that point
// to (interior) mutable memory.
hir::ConstContext::ConstFn => self.check_op(ops::TransientCellBorrow),
_ => {
// Locals without StorageDead follow the "enclosing scope" rule, meaning
// they are essentially anonymous static items themselves.
// Locals StorageDead are known to not leak to the final constant, and
// it is thus inherently safe to permit such locals to have their
// address taken as we can't end up with a reference to them in the
// final value without creating a dangling pointer, which will cause
// errors during validation.
// Note: This is only sound if every local that has a `StorageDead` has a
// `StorageDead` in every control flow path leading to a `return` terminator.
if self.local_has_storage_dead(place.local) {