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* [gcc r13-1288] libstdc++: Make std::move_only_function never valueless in std::variant
@ 2022-06-27 10:16 Jonathan Wakely
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From: Jonathan Wakely @ 2022-06-27 10:16 UTC (permalink / raw)
To: gcc-cvs, libstdc++-cvs
https://gcc.gnu.org/g:a364488f7a70ebf6c1fd59fed9f6a8a477591087
commit r13-1288-ga364488f7a70ebf6c1fd59fed9f6a8a477591087
Author: Jonathan Wakely <jwakely@redhat.com>
Date: Thu Jun 23 18:42:55 2022 +0100
libstdc++: Make std::move_only_function never valueless in std::variant
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.
Diff:
---
libstdc++-v3/include/bits/move_only_function.h | 12 ++++++++++++
1 file changed, 12 insertions(+)
diff --git a/libstdc++-v3/include/bits/move_only_function.h b/libstdc++-v3/include/bits/move_only_function.h
index f96552a7c89..71d52074978 100644
--- a/libstdc++-v3/include/bits/move_only_function.h
+++ b/libstdc++-v3/include/bits/move_only_function.h
@@ -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
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