[libcxx] Fix __compressed_pair so it doesn't copy the argument multiple times, and add constexpr.
Summary:
__compressed_pair takes and passes it's constructor arguments by value. This causes arguments to be moved 3 times instead of once. This patch addresses that issue and fixes `constexpr` on the constructors.
I would rather have this fix than D27564, and I'm fairly confident it's not ABI breaking but I'm not 100% sure.
I prefer this solution because it removes a lot of code and makes the implementation *much* smaller.
Reviewers: mclow.lists, K-ballo
Reviewed By: K-ballo
Subscribers: K-ballo, cfe-commits
Differential Revision: https://reviews.llvm.org/D27565
llvm-svn: 300140
Cr-Mirrored-From: sso://chromium.googlesource.com/_direct/external/github.com/llvm/llvm-project
Cr-Mirrored-Commit: c88580c400cec2d06fdc3477db9efa5350770c65
diff --git a/include/memory b/include/memory
index 6eb2184..0688765 100644
--- a/include/memory
+++ b/include/memory
@@ -653,7 +653,7 @@
#include <tuple>
#include <stdexcept>
#include <cstring>
-
+#include <cassert>
#if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
# include <atomic>
#endif
@@ -2070,307 +2070,174 @@
};
#endif
-template <class _T1, class _T2, bool = is_same<typename remove_cv<_T1>::type,
- typename remove_cv<_T2>::type>::value,
- bool = is_empty<_T1>::value
- && !__libcpp_is_final<_T1>::value,
- bool = is_empty<_T2>::value
- && !__libcpp_is_final<_T2>::value
- >
-struct __libcpp_compressed_pair_switch;
+template <class _Tp, int _Idx,
+ bool _CanBeEmptyBase =
+ is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
+struct __compressed_pair_elem {
+ typedef _Tp _ParamT;
+ typedef _Tp& reference;
+ typedef const _Tp& const_reference;
-template <class _T1, class _T2, bool IsSame>
-struct __libcpp_compressed_pair_switch<_T1, _T2, IsSame, false, false> {enum {value = 0};};
+#ifndef _LIBCPP_CXX03_LANG
+ __compressed_pair_elem() = default;
-template <class _T1, class _T2, bool IsSame>
-struct __libcpp_compressed_pair_switch<_T1, _T2, IsSame, true, false> {enum {value = 1};};
+ template <class _Up, class = typename enable_if<
+ !is_same<__compressed_pair_elem, _Up>::value>::type>
+ _LIBCPP_CONSTEXPR explicit
+ __compressed_pair_elem(_Up&& __u)
+ : __value_(_VSTD::forward<_Up>(__u)){};
-template <class _T1, class _T2, bool IsSame>
-struct __libcpp_compressed_pair_switch<_T1, _T2, IsSame, false, true> {enum {value = 2};};
+ template <class... _Args, size_t... _Indexes>
+ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+ __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
+ __tuple_indices<_Indexes...>)
+ : __value_(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
+#else
+ __compressed_pair_elem() : __value_() {}
+ __compressed_pair_elem(_ParamT __p) : __value_(std::forward<_ParamT>(__p)) {}
+#endif
-template <class _T1, class _T2>
-struct __libcpp_compressed_pair_switch<_T1, _T2, false, true, true> {enum {value = 3};};
+ reference __get() _NOEXCEPT { return __value_; }
+ const_reference __get() const _NOEXCEPT { return __value_; }
-template <class _T1, class _T2>
-struct __libcpp_compressed_pair_switch<_T1, _T2, true, true, true> {enum {value = 1};};
-
-template <class _T1, class _T2, unsigned = __libcpp_compressed_pair_switch<_T1, _T2>::value>
-class __libcpp_compressed_pair_imp;
-
-template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 0>
-{
private:
- _T1 __first_;
- _T2 __second_;
-public:
- typedef _T1 _T1_param;
- typedef _T2 _T2_param;
-
- typedef typename remove_reference<_T1>::type& _T1_reference;
- typedef typename remove_reference<_T2>::type& _T2_reference;
-
- typedef typename remove_reference<typename add_const<_T1>::type>::type& _T1_const_reference;
- typedef typename remove_reference<typename add_const<_T2>::type>::type& _T2_const_reference;
-
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() : __first_(), __second_() {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
- : __first_(_VSTD::forward<_T1_param>(__t1)), __second_() {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
- : __first_(), __second_(_VSTD::forward<_T2_param>(__t2)) {}
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
- : __first_(_VSTD::forward<_T1_param>(__t1)), __second_(_VSTD::forward<_T2_param>(__t2)) {}
-
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
- template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
- _LIBCPP_INLINE_VISIBILITY
- __libcpp_compressed_pair_imp(piecewise_construct_t,
- tuple<_Args1...> __first_args,
- tuple<_Args2...> __second_args,
- __tuple_indices<_I1...>,
- __tuple_indices<_I2...>)
- : __first_(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...),
- __second_(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
- {}
-
-#endif // _LIBCPP_HAS_NO_VARIADICS
-
- _LIBCPP_INLINE_VISIBILITY _T1_reference first() _NOEXCEPT {return __first_;}
- _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return __first_;}
-
- _LIBCPP_INLINE_VISIBILITY _T2_reference second() _NOEXCEPT {return __second_;}
- _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return __second_;}
-
- _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp& __x)
- _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
- __is_nothrow_swappable<_T2>::value)
- {
- using _VSTD::swap;
- swap(__first_, __x.__first_);
- swap(__second_, __x.__second_);
- }
+ _Tp __value_;
};
-template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 1>
- : private _T1
-{
-private:
- _T2 __second_;
-public:
- typedef _T1 _T1_param;
- typedef _T2 _T2_param;
+template <class _Tp, int _Idx>
+struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
+ typedef _Tp _ParamT;
+ typedef _Tp& reference;
+ typedef const _Tp& const_reference;
+ typedef _Tp __value_type;
- typedef _T1& _T1_reference;
- typedef typename remove_reference<_T2>::type& _T2_reference;
+#ifndef _LIBCPP_CXX03_LANG
+ __compressed_pair_elem() = default;
- typedef const _T1& _T1_const_reference;
- typedef typename remove_reference<typename add_const<_T2>::type>::type&
- _T2_const_reference;
+ template <class _Up, class = typename enable_if<
+ !is_same<__compressed_pair_elem, _Up>::value>::type>
+ _LIBCPP_CONSTEXPR explicit
+ __compressed_pair_elem(_Up&& __u)
+ : __value_type(_VSTD::forward<_Up>(__u)){};
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() : __second_() {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
- : _T1(_VSTD::forward<_T1_param>(__t1)), __second_() {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
- : __second_(_VSTD::forward<_T2_param>(__t2)) {}
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
- : _T1(_VSTD::forward<_T1_param>(__t1)), __second_(_VSTD::forward<_T2_param>(__t2)) {}
+ template <class... _Args, size_t... _Indexes>
+ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+ __compressed_pair_elem(piecewise_construct_t, tuple<_Args...> __args,
+ __tuple_indices<_Indexes...>)
+ : __value_type(_VSTD::forward<_Args>(_VSTD::get<_Indexes>(__args))...) {}
+#else
+ __compressed_pair_elem() : __value_type() {}
+ __compressed_pair_elem(_ParamT __p)
+ : __value_type(std::forward<_ParamT>(__p)) {}
+#endif
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
- template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
- _LIBCPP_INLINE_VISIBILITY
- __libcpp_compressed_pair_imp(piecewise_construct_t,
- tuple<_Args1...> __first_args,
- tuple<_Args2...> __second_args,
- __tuple_indices<_I1...>,
- __tuple_indices<_I2...>)
- : _T1(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...),
- __second_(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
- {}
-
-#endif // _LIBCPP_HAS_NO_VARIADICS
-
- _LIBCPP_INLINE_VISIBILITY _T1_reference first() _NOEXCEPT {return *this;}
- _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return *this;}
-
- _LIBCPP_INLINE_VISIBILITY _T2_reference second() _NOEXCEPT {return __second_;}
- _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return __second_;}
-
- _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp& __x)
- _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
- __is_nothrow_swappable<_T2>::value)
- {
- using _VSTD::swap;
- swap(__second_, __x.__second_);
- }
+ reference __get() _NOEXCEPT { return *this; }
+ const_reference __get() const _NOEXCEPT { return *this; }
};
-template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 2>
- : private _T2
-{
-private:
- _T1 __first_;
-public:
- typedef _T1 _T1_param;
- typedef _T2 _T2_param;
-
- typedef typename remove_reference<_T1>::type& _T1_reference;
- typedef _T2& _T2_reference;
-
- typedef typename remove_reference<typename add_const<_T1>::type>::type&
- _T1_const_reference;
- typedef const _T2& _T2_const_reference;
-
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() : __first_() {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
- : __first_(_VSTD::forward<_T1_param>(__t1)) {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
- : _T2(_VSTD::forward<_T2_param>(__t2)), __first_() {}
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
- _NOEXCEPT_(is_nothrow_move_constructible<_T1>::value &&
- is_nothrow_move_constructible<_T2>::value)
- : _T2(_VSTD::forward<_T2_param>(__t2)), __first_(_VSTD::forward<_T1_param>(__t1)) {}
-
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
- template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
- _LIBCPP_INLINE_VISIBILITY
- __libcpp_compressed_pair_imp(piecewise_construct_t,
- tuple<_Args1...> __first_args,
- tuple<_Args2...> __second_args,
- __tuple_indices<_I1...>,
- __tuple_indices<_I2...>)
- : _T2(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...),
- __first_(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...)
-
- {}
-
-#endif // _LIBCPP_HAS_NO_VARIADICS
-
- _LIBCPP_INLINE_VISIBILITY _T1_reference first() _NOEXCEPT {return __first_;}
- _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return __first_;}
-
- _LIBCPP_INLINE_VISIBILITY _T2_reference second() _NOEXCEPT {return *this;}
- _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return *this;}
-
- _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp& __x)
- _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
- __is_nothrow_swappable<_T2>::value)
- {
- using _VSTD::swap;
- swap(__first_, __x.__first_);
- }
-};
+// Tag used to construct the second element of the compressed pair.
+struct __second_tag {};
template <class _T1, class _T2>
-class __libcpp_compressed_pair_imp<_T1, _T2, 3>
- : private _T1,
- private _T2
-{
+class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
+ private __compressed_pair_elem<_T2, 1> {
+ typedef __compressed_pair_elem<_T1, 0> _Base1;
+ typedef __compressed_pair_elem<_T2, 1> _Base2;
+
+ // NOTE: This static assert should never fire because __compressed_pair
+ // is *almost never* used in a scenario where it's possible for T1 == T2.
+ // (The exception is std::function where it is possible that the function
+ // object and the allocator have the same type).
+ static_assert(!is_same<_T1, _T2>::value,
+ "__compressed_pair cannot be instantated when T1 and T2 are the same type; "
+ "The current implementation is NOT ABI-compatible with the previous "
+ "implementation for this configuration");
+
public:
- typedef _T1 _T1_param;
- typedef _T2 _T2_param;
+#ifndef _LIBCPP_CXX03_LANG
+ _LIBCPP_INLINE_VISIBILITY
+ __compressed_pair() = default;
- typedef _T1& _T1_reference;
- typedef _T2& _T2_reference;
+ template <class _Tp, typename enable_if<!is_same<typename decay<_Tp>::type,
+ __compressed_pair>::value,
+ bool>::type = true>
+ _LIBCPP_INLINE_VISIBILITY constexpr explicit
+ __compressed_pair(_Tp&& __t)
+ : _Base1(std::forward<_Tp>(__t)), _Base2() {}
- typedef const _T1& _T1_const_reference;
- typedef const _T2& _T2_const_reference;
+ template <class _Tp>
+ _LIBCPP_INLINE_VISIBILITY constexpr
+ __compressed_pair(__second_tag, _Tp&& __t)
+ : _Base1(), _Base2(std::forward<_Tp>(__t)) {}
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp() {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T1_param __t1)
- : _T1(_VSTD::forward<_T1_param>(__t1)) {}
- _LIBCPP_INLINE_VISIBILITY explicit __libcpp_compressed_pair_imp(_T2_param __t2)
- : _T2(_VSTD::forward<_T2_param>(__t2)) {}
- _LIBCPP_INLINE_VISIBILITY __libcpp_compressed_pair_imp(_T1_param __t1, _T2_param __t2)
- : _T1(_VSTD::forward<_T1_param>(__t1)), _T2(_VSTD::forward<_T2_param>(__t2)) {}
+ template <class _U1, class _U2>
+ _LIBCPP_INLINE_VISIBILITY constexpr
+ __compressed_pair(_U1&& __t1, _U2&& __t2)
+ : _Base1(std::forward<_U1>(__t1)), _Base2(std::forward<_U2>(__t2)) {}
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+ template <class... _Args1, class... _Args2>
+ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
+ __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
+ tuple<_Args2...> __second_args)
+ : _Base1(__pc, _VSTD::move(__first_args),
+ typename __make_tuple_indices<sizeof...(_Args1)>::type()),
+ _Base2(__pc, _VSTD::move(__second_args),
+ typename __make_tuple_indices<sizeof...(_Args2)>::type()) {}
- template <class... _Args1, class... _Args2, size_t... _I1, size_t... _I2>
- _LIBCPP_INLINE_VISIBILITY
- __libcpp_compressed_pair_imp(piecewise_construct_t,
- tuple<_Args1...> __first_args,
- tuple<_Args2...> __second_args,
- __tuple_indices<_I1...>,
- __tuple_indices<_I2...>)
- : _T1(_VSTD::forward<_Args1>(_VSTD::get<_I1>(__first_args))...),
- _T2(_VSTD::forward<_Args2>(_VSTD::get<_I2>(__second_args))...)
- {}
+#else
+ _LIBCPP_INLINE_VISIBILITY
+ __compressed_pair() {}
-#endif // _LIBCPP_HAS_NO_VARIADICS
+ _LIBCPP_INLINE_VISIBILITY explicit
+ __compressed_pair(_T1 __t1) : _Base1(_VSTD::forward<_T1>(__t1)) {}
- _LIBCPP_INLINE_VISIBILITY _T1_reference first() _NOEXCEPT {return *this;}
- _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return *this;}
+ _LIBCPP_INLINE_VISIBILITY
+ __compressed_pair(__second_tag, _T2 __t2)
+ : _Base1(), _Base2(_VSTD::forward<_T2>(__t2)) {}
- _LIBCPP_INLINE_VISIBILITY _T2_reference second() _NOEXCEPT {return *this;}
- _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return *this;}
+ _LIBCPP_INLINE_VISIBILITY
+ __compressed_pair(_T1 __t1, _T2 __t2)
+ : _Base1(_VSTD::forward<_T1>(__t1)), _Base2(_VSTD::forward<_T2>(__t2)) {}
+#endif
- _LIBCPP_INLINE_VISIBILITY void swap(__libcpp_compressed_pair_imp&)
- _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
- __is_nothrow_swappable<_T2>::value)
- {
- }
-};
+ _LIBCPP_INLINE_VISIBILITY
+ typename _Base1::reference first() _NOEXCEPT {
+ return static_cast<_Base1&>(*this).__get();
+ }
-template <class _T1, class _T2>
-class __compressed_pair
- : private __libcpp_compressed_pair_imp<_T1, _T2>
-{
- typedef __libcpp_compressed_pair_imp<_T1, _T2> base;
-public:
- typedef typename base::_T1_param _T1_param;
- typedef typename base::_T2_param _T2_param;
+ _LIBCPP_INLINE_VISIBILITY
+ typename _Base1::const_reference first() const _NOEXCEPT {
+ return static_cast<_Base1 const&>(*this).__get();
+ }
- typedef typename base::_T1_reference _T1_reference;
- typedef typename base::_T2_reference _T2_reference;
+ _LIBCPP_INLINE_VISIBILITY
+ typename _Base2::reference second() _NOEXCEPT {
+ return static_cast<_Base2&>(*this).__get();
+ }
- typedef typename base::_T1_const_reference _T1_const_reference;
- typedef typename base::_T2_const_reference _T2_const_reference;
+ _LIBCPP_INLINE_VISIBILITY
+ typename _Base2::const_reference second() const _NOEXCEPT {
+ return static_cast<_Base2 const&>(*this).__get();
+ }
- _LIBCPP_INLINE_VISIBILITY __compressed_pair() {}
- _LIBCPP_INLINE_VISIBILITY explicit __compressed_pair(_T1_param __t1)
- : base(_VSTD::forward<_T1_param>(__t1)) {}
- _LIBCPP_INLINE_VISIBILITY explicit __compressed_pair(_T2_param __t2)
- : base(_VSTD::forward<_T2_param>(__t2)) {}
- _LIBCPP_INLINE_VISIBILITY __compressed_pair(_T1_param __t1, _T2_param __t2)
- : base(_VSTD::forward<_T1_param>(__t1), _VSTD::forward<_T2_param>(__t2)) {}
-
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
- template <class... _Args1, class... _Args2>
- _LIBCPP_INLINE_VISIBILITY
- __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
- tuple<_Args2...> __second_args)
- : base(__pc, _VSTD::move(__first_args), _VSTD::move(__second_args),
- typename __make_tuple_indices<sizeof...(_Args1)>::type(),
- typename __make_tuple_indices<sizeof...(_Args2) >::type())
- {}
-
-#endif // _LIBCPP_HAS_NO_VARIADICS
-
- _LIBCPP_INLINE_VISIBILITY _T1_reference first() _NOEXCEPT {return base::first();}
- _LIBCPP_INLINE_VISIBILITY _T1_const_reference first() const _NOEXCEPT {return base::first();}
-
- _LIBCPP_INLINE_VISIBILITY _T2_reference second() _NOEXCEPT {return base::second();}
- _LIBCPP_INLINE_VISIBILITY _T2_const_reference second() const _NOEXCEPT {return base::second();}
-
- _LIBCPP_INLINE_VISIBILITY void swap(__compressed_pair& __x)
- _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
- __is_nothrow_swappable<_T2>::value)
- {base::swap(__x);}
+ _LIBCPP_INLINE_VISIBILITY
+ void swap(__compressed_pair& __x)
+ _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
+ __is_nothrow_swappable<_T2>::value)
+ {
+ using std::swap;
+ swap(first(), __x.first());
+ swap(second(), __x.second());
+ }
};
template <class _T1, class _T2>
inline _LIBCPP_INLINE_VISIBILITY
-void
-swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
- _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
- __is_nothrow_swappable<_T2>::value)
- {__x.swap(__y);}
+void swap(__compressed_pair<_T1, _T2>& __x, __compressed_pair<_T1, _T2>& __y)
+ _NOEXCEPT_(__is_nothrow_swappable<_T1>::value &&
+ __is_nothrow_swappable<_T2>::value) {
+ __x.swap(__y);
+}
// __same_or_less_cv_qualified
@@ -2401,7 +2268,7 @@
template <class _Tp>
struct _LIBCPP_TEMPLATE_VIS default_delete
{
-#ifndef _LIBCPP_CXX03_LANG
+#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT = default;
#else
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT {}
@@ -2421,7 +2288,7 @@
struct _LIBCPP_TEMPLATE_VIS default_delete<_Tp[]>
{
public:
-#ifndef _LIBCPP_CXX03_LANG
+#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT = default;
#else
_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR default_delete() _NOEXCEPT {}