OptionalStorage implementation for trivial type, take III
This is another attempt at implementating optional storage
for trivially copyable type, using an union instead of a
raw buffer to hold the actual storage. This make it possible
to get rid of the reinterpret_cast, and hopefully to fix the UB
of the previous attempts.
This validates fine on my laptop for gcc 8.2 and gcc 4.8, I'll
revert if it breaks the validation.
git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354137 91177308-0d34-0410-b5e6-96231b3b80d8
diff --git a/include/llvm/ADT/Optional.h b/include/llvm/ADT/Optional.h
index 25a3185..55bbfc5 100644
--- a/include/llvm/ADT/Optional.h
+++ b/include/llvm/ADT/Optional.h
@@ -109,6 +109,54 @@
}
};
+template <typename T> struct OptionalStorage<T, true> {
+ struct empty_type {};
+ union {
+ empty_type empty;
+ T value;
+ };
+ bool hasVal = false;
+
+ OptionalStorage() : empty{} {}
+
+ OptionalStorage(const T &y) : hasVal(true) {
+ new ((void*)std::addressof(value)) T(y);
+ }
+ OptionalStorage(const OptionalStorage &O) = default;
+ OptionalStorage(T &&y) : hasVal(true) {
+ new ((void*)std::addressof(value)) T(std::move(y));
+ }
+
+ OptionalStorage(OptionalStorage &&O) = default;
+
+ OptionalStorage &operator=(T &&y) {
+ hasVal = true;
+ new ((void*)std::addressof(value)) T(std::move(y));
+ return *this;
+ }
+ OptionalStorage &operator=(OptionalStorage &&O) = default;
+
+ OptionalStorage &operator=(const T &y) {
+ hasVal = true;
+ new ((void*)std::addressof(value)) T(y);
+ return *this;
+ }
+ OptionalStorage &operator=(const OptionalStorage &O) = default;
+
+ ~OptionalStorage() = default;
+
+ T *getPointer() {
+ assert(hasVal);
+ return &value;
+ }
+ const T *getPointer() const {
+ assert(hasVal);
+ return &value;
+ }
+
+ void reset() { hasVal = false; }
+};
+
} // namespace optional_detail
template <typename T> class Optional {
@@ -153,11 +201,11 @@
const T *getPointer() const {
assert(Storage.hasVal);
- return reinterpret_cast<const T *>(Storage.storage.buffer);
+ return Storage.getPointer();
}
T *getPointer() {
assert(Storage.hasVal);
- return reinterpret_cast<T *>(Storage.storage.buffer);
+ return Storage.getPointer();
}
const T &getValue() const LLVM_LVALUE_FUNCTION { return *getPointer(); }
T &getValue() LLVM_LVALUE_FUNCTION { return *getPointer(); }
