[committed] libstdc++: Make std::move_only_function never valueless in std::variant
Commit Message
Tested powerpc64le-linux, pushed to trunk.
-- >8 --
This is not suitable to backport, as it affects the ABI of std::variant
and so isn't appropriate for a release branch.
libstdc++-v3/ChangeLog:
* include/bits/move_only_function.h (_Never_valueless_alt):
Define partial specialization for std::move_only_function.
---
libstdc++-v3/include/bits/move_only_function.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
@@ -183,6 +183,18 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
constexpr bool __is_move_only_function_v<move_only_function<_Tp>> = true;
/// @endcond
+ namespace __detail::__variant
+ {
+ template<typename> struct _Never_valueless_alt; // see <variant>
+
+ // Provide the strong exception-safety guarantee when emplacing a
+ // move_only_function into a variant.
+ template<typename... _Signature>
+ struct _Never_valueless_alt<std::move_only_function<_Signature...>>
+ : true_type
+ { };
+ } // namespace __detail::__variant
+
_GLIBCXX_END_NAMESPACE_VERSION
} // namespace std