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Constrain optional's __constexpr_addressof in its return type and use a constexpr addressof for optional, if available. 

Constrain optional's __constexpr_addressof in its return type
and use a constexpr addressof for optional, if available.
* include/experimental/optional (__constexpr_addressof):
Constrain in the return type instead of in a template parameter.
(_Has_addressof_mem)
(_Has_addressof_free, _Has_addressof, __constexpr_addressof):
Guard with #ifndef __cpp_lib_addressof_constexpr.
(operator->()): Use std::__addressof if it's constexpr.

From-SVN: r243298
This commit is contained in:
Ville Voutilainen 2016-12-06 14:47:54 +02:00 committed by Ville Voutilainen
parent b01af236b7
commit 1637d42545
2 changed files with 28 additions and 5 deletions
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11
libstdc++-v3/ChangeLog
View File

@ -1,3 +1,14 @@
2016-12-06 Ville Voutilainen <ville.voutilainen@gmail.com>
Constrain optional's __constexpr_addressof in its return type
and use a constexpr addressof for optional, if available.
* include/experimental/optional (__constexpr_addressof):
Constrain in the return type instead of in a template parameter.
(_Has_addressof_mem)
(_Has_addressof_free, _Has_addressof, __constexpr_addressof):
Guard with #ifndef __cpp_lib_addressof_constexpr.
(operator->()): Use std::__addressof if it's constexpr.
2016-11-27 Tim Shen <timshen@google.com>
* include/std/variant (visit): Make visit constexpr. Also cleanup

22
libstdc++-v3/include/experimental/optional
View File

@ -134,6 +134,7 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
__throw_bad_optional_access(const char* __s)
{ _GLIBCXX_THROW_OR_ABORT(bad_optional_access(__s)); }
#ifndef __cpp_lib_addressof_constexpr
template<typename _Tp, typename = void>
struct _Has_addressof_mem : std::false_type { };
@ -170,16 +171,21 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* overloaded addressof operator (unary operator&), in which case the call
* will not be a constant expression.
*/
template<typename _Tp, enable_if_t<!_Has_addressof<_Tp>::value, int>...>
constexpr _Tp* __constexpr_addressof(_Tp& __t)
template<typename _Tp>
constexpr
enable_if_t<!_Has_addressof<_Tp>::value, _Tp*>
__constexpr_addressof(_Tp& __t)
{ return &__t; }
/**
* @brief Fallback overload that defers to __addressof.
*/
template<typename _Tp, enable_if_t<_Has_addressof<_Tp>::value, int>...>
inline _Tp* __constexpr_addressof(_Tp& __t)
template<typename _Tp>
inline
enable_if_t<_Has_addressof<_Tp>::value, _Tp*>
__constexpr_addressof(_Tp& __t)
{ return std::__addressof(__t); }
#endif // __cpp_lib_addressof_constexpr
/**
* @brief Class template that holds the necessary state for @ref optional
@ -705,7 +711,13 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// [X.Y.4.5] Observers.
constexpr const _Tp*
operator->() const
{ return __constexpr_addressof(this->_M_get()); }
{
#ifndef __cpp_lib_addressof_constexpr
return __constexpr_addressof(this->_M_get());
#else
return std::__addressof(this->_M_get());
#endif
}
_Tp*
operator->()