diff options
Diffstat (limited to 'absl/base/casts.h')
| -rw-r--r-- | absl/base/casts.h | 18 |
1 files changed, 14 insertions, 4 deletions
diff --git a/absl/base/casts.h b/absl/base/casts.h index b16af233..bf100efa 100644 --- a/absl/base/casts.h +++ b/absl/base/casts.h @@ -44,8 +44,12 @@ struct is_bitcastable bool, sizeof(Dest) == sizeof(Source) && type_traits_internal::is_trivially_copyable<Source>::value && - type_traits_internal::is_trivially_copyable<Dest>::value && - std::is_default_constructible<Dest>::value> {}; + type_traits_internal::is_trivially_copyable<Dest>::value +#if !ABSL_HAVE_BUILTIN(__builtin_bit_cast) + && std::is_default_constructible<Dest>::value +#endif + > { +}; } // namespace internal_casts @@ -147,20 +151,26 @@ constexpr To implicit_cast(typename absl::internal::identity_t<To> to) { // introducing this undefined behavior (since the original value is never // accessed in the wrong way). // -// NOTE: The requirements here are stricter than the bit_cast of standard -// proposal P0476 due to the need for workarounds and lack of intrinsics. +// NOTE: The requirements here are more strict than the bit_cast of standard +// proposal P0476 when __builtin_bit_cast is not available. // Specifically, this implementation also requires `Dest` to be // default-constructible. template < typename Dest, typename Source, typename std::enable_if<internal_casts::is_bitcastable<Dest, Source>::value, int>::type = 0> +#if ABSL_HAVE_BUILTIN(__builtin_bit_cast) +inline constexpr Dest bit_cast(const Source& source) { + return __builtin_bit_cast(Dest, source); +} +#else inline Dest bit_cast(const Source& source) { Dest dest; memcpy(static_cast<void*>(std::addressof(dest)), static_cast<const void*>(std::addressof(source)), sizeof(dest)); return dest; } +#endif // NOTE: This overload is only picked if the requirements of bit_cast are // not met. It is therefore UB, but is provided temporarily as previous |