The _Has_addressof trait only detected an overloaded operator&() as a member function, this also checks for a non-member.
Tested x86_64-linux, committed to trunk.
commit 32b294e3eddf7789c25f3b751ae6b2a2c5c43275 Author: Jonathan Wakely <jwak...@redhat.com> Date: Mon Nov 10 19:02:02 2014 +0000 * include/experimental/optional (_Has_addressof): Check for non-member operator&. * testsuite/experimental/optional/observers/2.cc: Add operator&. * testsuite/experimental/optional/constexpr/observers/2.cc: Likewise. diff --git a/libstdc++-v3/include/experimental/optional b/libstdc++-v3/include/experimental/optional index 7e01abe..2d3127a 100644 --- a/libstdc++-v3/include/experimental/optional +++ b/libstdc++-v3/include/experimental/optional @@ -127,13 +127,23 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION __throw_bad_optional_access(const char* __s) { _GLIBCXX_THROW_OR_ABORT(bad_optional_access(__s)); } - template<typename _Tp, typename _Sfinae = void> - struct _Has_addressof_impl : std::false_type { }; + template<typename _Tp, typename = void> + struct _Has_addressof_mem : std::false_type { }; template<typename _Tp> - struct _Has_addressof_impl<_Tp, - decltype( std::declval<const _Tp&>().operator&(), void() )> - : std::true_type { }; + struct _Has_addressof_mem<_Tp, + __void_t<decltype( std::declval<const _Tp&>().operator&() )> + > + : std::true_type { }; + + template<typename _Tp, typename = void> + struct _Has_addressof_free : std::false_type { }; + + template<typename _Tp> + struct _Has_addressof_free<_Tp, + __void_t<decltype( operator&(std::declval<const _Tp&>()) )> + > + : std::true_type { }; /** * @brief Trait that detects the presence of an overloaded unary operator&. @@ -143,7 +153,9 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION * declval<_Tp * const&>().operator&()). */ template<typename _Tp> - struct _Has_addressof : _Has_addressof_impl<_Tp>::type { }; + struct _Has_addressof + : std::__or_<_Has_addressof_mem<_Tp>, _Has_addressof_free<_Tp>>::type + { }; /** * @brief An overload that attempts to take the address of an lvalue as a diff --git a/libstdc++-v3/testsuite/experimental/optional/constexpr/observers/2.cc b/libstdc++-v3/testsuite/experimental/optional/constexpr/observers/2.cc index 14b5e3b..2c9215c 100644 --- a/libstdc++-v3/testsuite/experimental/optional/constexpr/observers/2.cc +++ b/libstdc++-v3/testsuite/experimental/optional/constexpr/observers/2.cc @@ -26,6 +26,8 @@ struct value_type { int i; + + void* operator&() { return nullptr; } // N.B. non-const }; int main() diff --git a/libstdc++-v3/testsuite/experimental/optional/observers/2.cc b/libstdc++-v3/testsuite/experimental/optional/observers/2.cc index 8499b47..9fb2edb 100644 --- a/libstdc++-v3/testsuite/experimental/optional/observers/2.cc +++ b/libstdc++-v3/testsuite/experimental/optional/observers/2.cc @@ -26,6 +26,8 @@ struct value_type int i; }; +void* operator&(const value_type&) = delete; + int main() { std::experimental::optional<value_type> o { value_type { 51 } };