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[Runtime] Fix premature snapshot destruction in StableAddressConcurrentReadableHashMap::find. #35345

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merged 1 commit into from
Jan 11, 2021
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[Runtime] Fix premature snapshot destruction in StableAddressConcurrentReadableHashMap::find. #35345

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19 changes: 14 additions & 5 deletions include/swift/Runtime/Concurrent.h
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Original file line number Diff line number Diff line change
Expand Up @@ -488,9 +488,13 @@ template <class ElemTy> struct ConcurrentReadableArray {
~Snapshot() {
Array->decrementReaders();
}

const ElemTy *begin() { return Start; }
const ElemTy *end() { return Start + Count; }

// These are marked as ref-qualified (the &) to make sure they can't be
// called on temporaries, since the temporary would be destroyed before the
// return value can be used, making it invalid.
const ElemTy *begin() & { return Start; }
const ElemTy *end() & { return Start + Count; }

size_t count() { return Count; }
};

Expand Down Expand Up @@ -974,7 +978,11 @@ struct ConcurrentReadableHashMap {

/// Search for an element matching the given key. Returns a pointer to the
/// found element, or nullptr if no matching element exists.
template <class KeyTy> const ElemTy *find(const KeyTy &key) {
//
// This is marked as ref-qualified (the &) to make sure it can't be called
// on temporaries, since the temporary would be destroyed before the return
// value can be used, making it invalid.
template <class KeyTy> const ElemTy *find(const KeyTy &key) & {
if (!Indices.Value || !ElementCount || !Elements)
return nullptr;
return ConcurrentReadableHashMap::find(key, Indices, ElementCount,
Expand Down Expand Up @@ -1181,7 +1189,8 @@ struct StableAddressConcurrentReadableHashMap
}

template <class KeyTy> ElemTy *find(const KeyTy &key) {
auto result = this->snapshot().find(key);
auto snapshot = this->snapshot();
auto result = snapshot.find(key);
if (!result)
return nullptr;
return result->Ptr;
Expand Down