================
@@ -31,8 +31,10 @@ class WeakInfo {
: alias(Alias), loc(Loc) {}
inline const IdentifierInfo *getAlias() const { return alias; }
inline SourceLocation getLocation() const { return loc; }
- bool operator==(WeakInfo RHS) const = delete;
- bool operator!=(WeakInfo RHS) const = delete;
+ bool operator==(const WeakInfo &RHS) const {
+ return getAlias() == RHS.getAlias() && getLocation() == RHS.getLocation();
+ }
----------------
eugeneepshteyn wrote:
(This comment was generated with the help of AI)
This `operator==` disagrees with the set this type is stored in.
`Sema::WeakUndeclaredIdentifiers` hashes with
`WeakInfo::DenseMapInfoByAliasOnly`, so a second `#pragma weak` for the same
alias at another location is rejected by the set, but `find` cannot locate the
stored entry and `insert` returns `{end(), false}`. The `= delete` was
deliberate (commit ce21c926f8ef, D121927: one record per alias name). No caller
reads `.first` yet, so this is latent, but the new contract does not hold for
any `SetVector` whose element `operator==` is stricter than its set's equality.
```cpp
#include "llvm/ADT/DenseSet.h"
#include "llvm/ADT/SetVector.h"
#include <cstdio>
// operator== is stricter than the set's equality, as with WeakInfo
// (alias + location) vs. WeakInfo::DenseMapInfoByAliasOnly (alias only).
struct Rec {
int Key, Loc;
bool operator==(const Rec &O) const { return Key == O.Key && Loc == O.Loc; }
};
struct ByKeyOnly {
static unsigned getHashValue(const Rec &R) { return R.Key; }
static bool isEqual(const Rec &L, const Rec &R) { return L.Key == R.Key; }
};
int main() {
llvm::SetVector<Rec, llvm::SmallVector<Rec, 1>,
llvm::SmallDenseSet<Rec, 2, ByKeyOnly>>
S;
S.insert({1, 100});
auto [It, Inserted] = S.insert({1, 200});
std::printf("inserted=%d iterator_is_end=%d\n", Inserted, It == S.end());
}
```
```console
$ clang++ -std=c++17 -I llvm/include -I build/include weak-equality.cpp
build/lib/libLLVMSupport.a && ./a.out
inserted=0 iterator_is_end=1
```
https://github.com/llvm/llvm-project/pull/232372
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