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tuple (_Head_base<>): Default specialization condition at type declaration.

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2016-06-07  François Dumont  <fdumont@gcc.gnu.org>

	* include/std/tuple (_Head_base<>): Default specialization condition at
	type declaration.

From-SVN: r237184
This commit is contained in:
François Dumont 2016-06-07 20:19:19 +00:00
parent a23e6f1c59
commit 373c00952c
2 changed files with 27 additions and 21 deletions
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5
libstdc++-v3/ChangeLog
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@ -1,3 +1,8 @@
2016-06-07 François Dumont <fdumont@gcc.gnu.org>
* include/std/tuple (_Head_base<>): Default specialization condition at
type declaration.
2016-06-06 Ville Voutilainen <ville.voutilainen@gmail.com>
Support allocators in tuples of zero size.

43
libstdc++-v3/include/std/tuple
View file

@ -48,7 +48,24 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
* @{
*/
template<std::size_t _Idx, typename _Head, bool _IsEmptyNotFinal>
template<typename... _Elements>
class tuple;
template<typename _Tp>
struct __is_empty_non_tuple : is_empty<_Tp> { };
// Using EBO for elements that are tuples causes ambiguous base errors.
template<typename _El0, typename... _El>
struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
// Use the Empty Base-class Optimization for empty, non-final types.
template<typename _Tp>
using __empty_not_final
= typename conditional<__is_final(_Tp), false_type,
__is_empty_non_tuple<_Tp>>::type;
template<std::size_t _Idx, typename _Head,
bool = __empty_not_final<_Head>::value>
struct _Head_base;
template<std::size_t _Idx, typename _Head>
@ -158,19 +175,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<std::size_t _Idx, typename... _Elements>
struct _Tuple_impl;
template<typename _Tp>
struct __is_empty_non_tuple : is_empty<_Tp> { };
// Using EBO for elements that are tuples causes ambiguous base errors.
template<typename _El0, typename... _El>
struct __is_empty_non_tuple<tuple<_El0, _El...>> : false_type { };
// Use the Empty Base-class Optimization for empty, non-final types.
template<typename _Tp>
using __empty_not_final
= typename conditional<__is_final(_Tp), false_type,
__is_empty_non_tuple<_Tp>>::type;
/**
* Recursive tuple implementation. Here we store the @c Head element
* and derive from a @c Tuple_impl containing the remaining elements
@ -179,12 +183,12 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
template<std::size_t _Idx, typename _Head, typename... _Tail>
struct _Tuple_impl<_Idx, _Head, _Tail...>
: public _Tuple_impl<_Idx + 1, _Tail...>,
private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
private _Head_base<_Idx, _Head>
{
template<std::size_t, typename...> friend class _Tuple_impl;
typedef _Tuple_impl<_Idx + 1, _Tail...> _Inherited;
typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
typedef _Head_base<_Idx, _Head> _Base;
static constexpr _Head&
_M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
@ -336,11 +340,11 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
// Basis case of inheritance recursion.
template<std::size_t _Idx, typename _Head>
struct _Tuple_impl<_Idx, _Head>
: private _Head_base<_Idx, _Head, __empty_not_final<_Head>::value>
: private _Head_base<_Idx, _Head>
{
template<std::size_t, typename...> friend class _Tuple_impl;
typedef _Head_base<_Idx, _Head, __empty_not_final<_Head>::value> _Base;
typedef _Head_base<_Idx, _Head> _Base;
static constexpr _Head&
_M_head(_Tuple_impl& __t) noexcept { return _Base::_M_head(__t); }
@ -457,9 +461,6 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
}
};
template<typename... _Elements>
class tuple;
// Concept utility functions, reused in conditionally-explicit
// constructors.
template<bool, typename... _Elements>