namespace llvm {
+// This implementation of bit_cast is different from the C++17 one in two ways:
+// - It isn't constexpr because that requires compiler support.
+// - It requires trivially-constructible To, to avoid UB in the implementation.
template <typename To, typename From
, typename = typename std::enable_if<sizeof(To) == sizeof(From)>::type
+ , typename = typename std::is_trivially_constructible<To>::type
#if (__has_feature(is_trivially_copyable) && defined(_LIBCPP_VERSION)) || \
(defined(__GNUC__) && __GNUC__ >= 5)
, typename = typename std::enable_if<std::is_trivially_copyable<To>::value>::type
#endif
>
inline To bit_cast(const From &from) noexcept {
- alignas(To) unsigned char storage[sizeof(To)];
- std::memcpy(&storage, &from, sizeof(To));
-#if defined(__GNUC__)
- // Before GCC 7.2, GCC thought that this violated strict aliasing.
-#pragma GCC diagnostic push
-#pragma GCC diagnostic ignored "-Wstrict-aliasing"
-#endif
- return reinterpret_cast<To &>(storage);
-#if defined(__GNUC__)
-#pragma GCC diagnostic pop
-#endif
+ To to;
+ std::memcpy(&to, &from, sizeof(To));
+ return to;
}
} // namespace llvm