Update libcxx to revision 187959, 2013-08-08.

1 files changed, 225 insertions, 40 deletions

diff --git a/system/include/libcxx/utility b/system/include/libcxx/utility
index 2df4b361..d36cf9dd 100644
--- a/system/include/libcxx/utility
+++ b/system/include/libcxx/utility
@@ -38,10 +38,10 @@ template <class T, size_t N>
 void
 swap(T (&a)[N], T (&b)[N]) noexcept(noexcept(swap(*a, *b)));
 
-template <class T> T&& forward(typename remove_reference<T>::type& t) noexcept;
-template <class T> T&& forward(typename remove_reference<T>::type&& t) noexcept;
+template <class T> T&& forward(typename remove_reference<T>::type& t) noexcept;  // constexpr in C++14
+template <class T> T&& forward(typename remove_reference<T>::type&& t) noexcept; // constexpr in C++14
 
-template <class T> typename remove_reference<T>::type&& move(T&&) noexcept;
+template <class T> typename remove_reference<T>::type&& move(T&&) noexcept;      // constexpr in C++14
 
 template <class T>
     typename conditional
@@ -50,7 +50,7 @@ template <class T>
         const T&,
         T&&
     >::type
-    move_if_noexcept(T& x) noexcept;
+    move_if_noexcept(T& x) noexcept; // constexpr in C++14
 
 template <class T> typename add_rvalue_reference<T>::type declval() noexcept;
 
@@ -66,10 +66,10 @@ struct pair
     pair(const pair&) = default;
     pair(pair&&) = default;
     constexpr pair();
-    pair(const T1& x, const T2& y);
-    template <class U, class V> pair(U&& x, V&& y);
-    template <class U, class V> pair(const pair<U, V>& p);
-    template <class U, class V> pair(pair<U, V>&& p);
+    pair(const T1& x, const T2& y);                          // constexpr in C++14
+    template <class U, class V> pair(U&& x, V&& y);          // constexpr in C++14
+    template <class U, class V> pair(const pair<U, V>& p);   // constexpr in C++14
+    template <class U, class V> pair(pair<U, V>&& p);        // constexpr in C++14
     template <class... Args1, class... Args2>
         pair(piecewise_construct_t, tuple<Args1...> first_args,
              tuple<Args2...> second_args);
@@ -83,14 +83,14 @@ struct pair
                                 noexcept(swap(second, p.second)));
 };
 
-template <class T1, class T2> bool operator==(const pair<T1,T2>&, const pair<T1,T2>&);
-template <class T1, class T2> bool operator!=(const pair<T1,T2>&, const pair<T1,T2>&);
-template <class T1, class T2> bool operator< (const pair<T1,T2>&, const pair<T1,T2>&);
-template <class T1, class T2> bool operator> (const pair<T1,T2>&, const pair<T1,T2>&);
-template <class T1, class T2> bool operator>=(const pair<T1,T2>&, const pair<T1,T2>&);
-template <class T1, class T2> bool operator<=(const pair<T1,T2>&, const pair<T1,T2>&);
+template <class T1, class T2> bool operator==(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
+template <class T1, class T2> bool operator!=(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
+template <class T1, class T2> bool operator< (const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
+template <class T1, class T2> bool operator> (const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
+template <class T1, class T2> bool operator>=(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
+template <class T1, class T2> bool operator<=(const pair<T1,T2>&, const pair<T1,T2>&); // constexpr in C++14
 
-template <class T1, class T2> pair<V1, V2> make_pair(T1&&, T2&&);
+template <class T1, class T2> pair<V1, V2> make_pair(T1&&, T2&&);   // constexpr in C++14
 template <class T1, class T2>
 void
 swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
@@ -107,16 +107,48 @@ template <class T1, class T2> struct tuple_element<1, std::pair<T1, T2> >;
 
 template<size_t I, class T1, class T2>
     typename tuple_element<I, std::pair<T1, T2> >::type&
-    get(std::pair<T1, T2>&) noexcept;
+    get(std::pair<T1, T2>&) noexcept; // constexpr in C++14
 
 template<size_t I, class T1, class T2>
     const typename const tuple_element<I, std::pair<T1, T2> >::type&
-    get(const std::pair<T1, T2>&) noexcept;
+    get(const std::pair<T1, T2>&) noexcept; // constexpr in C++14
 
 template<size_t I, class T1, class T2>
     typename tuple_element<I, std::pair<T1, T2> >::type&&
-    get(std::pair<T1, T2>&&) noexcept;
+    get(std::pair<T1, T2>&&) noexcept; // constexpr in C++14
 
+template<class T1, class T2>
+    constexpr T1& get(std::pair<T1, T2>&) noexcept; // C++14
+
+template<size_t I, class T1, class T2>
+    constexpr T1 const& get(std::pair<T1, T2> const &) noexcept; // C++14
+
+template<size_t I, class T1, class T2>
+    constexpr T1&& get(std::pair<T1, T2>&&) noexcept; // C++14
+
+// C++14
+
+template<class T, T... I>
+struct integer_sequence
+{
+    typedef T value_type;
+
+    static constexpr size_t size() noexcept;
+};
+
+template<size_t... I>
+  using index_sequence = integer_sequence<size_t, I...>;
+
+template<class T, T N>
+  using make_integer_sequence = integer_sequence<T, 0, 1, ..., N-1>;
+template<size_t N>
+  using make_index_sequence = make_integer_sequence<size_t, N>;
+
+template<class... T>
+  using index_sequence_for = make_index_sequence<sizeof...(T)>;
+
+template<class T, class U=T> 
+    T exchange(T& obj, U&& new_value);
 }  // std
 
 */
@@ -189,7 +221,7 @@ swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::v
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 typename conditional
 <
@@ -226,11 +258,12 @@ struct _LIBCPP_TYPE_VIS pair
 
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR pair() : first(), second() {}
 
-    _LIBCPP_INLINE_VISIBILITY pair(const _T1& __x, const _T2& __y)
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
+    pair(const _T1& __x, const _T2& __y)
         : first(__x), second(__y) {}
 
     template<class _U1, class _U2>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         pair(const pair<_U1, _U2>& __p
 #ifndef _LIBCPP_HAS_NO_ADVANCED_SFINAE
                  ,typename enable_if<is_convertible<const _U1&, _T1>::value &&
@@ -239,6 +272,10 @@ struct _LIBCPP_TYPE_VIS pair
                                       )
             : first(__p.first), second(__p.second) {}
 
+#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+    _LIBCPP_INLINE_VISIBILITY
+    pair(const pair& __p) = default;
+#else
     _LIBCPP_INLINE_VISIBILITY
     pair(const pair& __p)
         _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
@@ -247,6 +284,7 @@ struct _LIBCPP_TYPE_VIS pair
           second(__p.second)
     {
     }
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     pair& operator=(const pair& __p)
@@ -263,20 +301,24 @@ struct _LIBCPP_TYPE_VIS pair
     template <class _U1, class _U2,
               class = typename enable_if<is_convertible<_U1, first_type>::value &&
                                          is_convertible<_U2, second_type>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         pair(_U1&& __u1, _U2&& __u2)
             : first(_VSTD::forward<_U1>(__u1)),
               second(_VSTD::forward<_U2>(__u2))
             {}
 
     template<class _U1, class _U2>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         pair(pair<_U1, _U2>&& __p,
                  typename enable_if<is_convertible<_U1, _T1>::value &&
                                     is_convertible<_U2, _T2>::value>::type* = 0)
             : first(_VSTD::forward<_U1>(__p.first)),
               second(_VSTD::forward<_U2>(__p.second)) {}
 
+#ifndef _LIBCPP_HAS_NO_DEFAULTED_FUNCTIONS
+    _LIBCPP_INLINE_VISIBILITY
+    pair(pair&& __p) = default;
+#else
     _LIBCPP_INLINE_VISIBILITY
     pair(pair&& __p) _NOEXCEPT_(is_nothrow_move_constructible<first_type>::value &&
                                 is_nothrow_move_constructible<second_type>::value)
@@ -284,6 +326,7 @@ struct _LIBCPP_TYPE_VIS pair
           second(_VSTD::forward<second_type>(__p.second))
     {
     }
+#endif
 
     _LIBCPP_INLINE_VISIBILITY
     pair&
@@ -299,7 +342,7 @@ struct _LIBCPP_TYPE_VIS pair
 
     template<class _Tuple,
              class = typename enable_if<__tuple_convertible<_Tuple, pair>::value>::type>
-        _LIBCPP_INLINE_VISIBILITY
+        _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
         pair(_Tuple&& __p)
             : first(_VSTD::forward<typename tuple_element<0,
                                   typename __make_tuple_types<_Tuple>::type>::type>(get<0>(__p))),
@@ -355,7 +398,7 @@ private:
 };
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
 operator==(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 {
@@ -363,7 +406,7 @@ operator==(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 }
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
 operator!=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 {
@@ -371,7 +414,7 @@ operator!=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 }
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
 operator< (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 {
@@ -379,7 +422,7 @@ operator< (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 }
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
 operator> (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 {
@@ -387,7 +430,7 @@ operator> (const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 }
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
 operator>=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 {
@@ -395,7 +438,7 @@ operator>=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 }
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 bool
 operator<=(const pair<_T1,_T2>& __x, const pair<_T1,_T2>& __y)
 {
@@ -440,7 +483,7 @@ struct __make_pair_return
 };
 
 template <class _T1, class _T2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 pair<typename __make_pair_return<_T1>::type, typename __make_pair_return<_T2>::type>
 make_pair(_T1&& __t1, _T2&& __t2)
 {
@@ -503,13 +546,13 @@ struct __get_pair<0>
 {
     template <class _T1, class _T2>
     static
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     _T1&
     get(pair<_T1, _T2>& __p) _NOEXCEPT {return __p.first;}
 
     template <class _T1, class _T2>
     static
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     const _T1&
     get(const pair<_T1, _T2>& __p) _NOEXCEPT {return __p.first;}
 
@@ -517,7 +560,7 @@ struct __get_pair<0>
 
     template <class _T1, class _T2>
     static
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     _T1&&
     get(pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<_T1>(__p.first);}
 
@@ -529,13 +572,13 @@ struct __get_pair<1>
 {
     template <class _T1, class _T2>
     static
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     _T2&
     get(pair<_T1, _T2>& __p) _NOEXCEPT {return __p.second;}
 
     template <class _T1, class _T2>
     static
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     const _T2&
     get(const pair<_T1, _T2>& __p) _NOEXCEPT {return __p.second;}
 
@@ -543,7 +586,7 @@ struct __get_pair<1>
 
     template <class _T1, class _T2>
     static
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     _T2&&
     get(pair<_T1, _T2>&& __p) _NOEXCEPT {return _VSTD::forward<_T2>(__p.second);}
 
@@ -551,7 +594,7 @@ struct __get_pair<1>
 };
 
 template <size_t _Ip, class _T1, class _T2>
-_LIBCPP_INLINE_VISIBILITY inline
+_LIBCPP_INLINE_VISIBILITY inline _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, pair<_T1, _T2> >::type&
 get(pair<_T1, _T2>& __p) _NOEXCEPT
 {
@@ -559,7 +602,7 @@ get(pair<_T1, _T2>& __p) _NOEXCEPT
 }
 
 template <size_t _Ip, class _T1, class _T2>
-_LIBCPP_INLINE_VISIBILITY inline
+_LIBCPP_INLINE_VISIBILITY inline _LIBCPP_CONSTEXPR_AFTER_CXX11
 const typename tuple_element<_Ip, pair<_T1, _T2> >::type&
 get(const pair<_T1, _T2>& __p) _NOEXCEPT
 {
@@ -569,7 +612,7 @@ get(const pair<_T1, _T2>& __p) _NOEXCEPT
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
 template <size_t _Ip, class _T1, class _T2>
-_LIBCPP_INLINE_VISIBILITY inline
+_LIBCPP_INLINE_VISIBILITY inline _LIBCPP_CONSTEXPR_AFTER_CXX11
 typename tuple_element<_Ip, pair<_T1, _T2> >::type&&
 get(pair<_T1, _T2>&& __p) _NOEXCEPT
 {
@@ -578,6 +621,148 @@ get(pair<_T1, _T2>&& __p) _NOEXCEPT
 
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
 
+#if _LIBCPP_STD_VER > 11
+template <class _T1, class _T2>
+_LIBCPP_INLINE_VISIBILITY inline
+constexpr _T1 & get(pair<_T1, _T2>& __p) _NOEXCEPT
+{
+    return __get_pair<0>::get(__p);
+}
+
+template <class _T1, class _T2>
+_LIBCPP_INLINE_VISIBILITY inline
+constexpr _T1 const & get(pair<_T1, _T2> const& __p) _NOEXCEPT
+{
+    return __get_pair<0>::get(__p);
+}
+
+template <class _T1, class _T2>
+_LIBCPP_INLINE_VISIBILITY inline
+constexpr _T1 && get(pair<_T1, _T2>&& __p) _NOEXCEPT
+{
+    return __get_pair<0>::get(_VSTD::move(__p));
+}
+
+template <class _T1, class _T2>
+_LIBCPP_INLINE_VISIBILITY inline
+constexpr _T1 & get(pair<_T2, _T1>& __p) _NOEXCEPT
+{
+    return __get_pair<1>::get(__p);
+}
+
+template <class _T1, class _T2>
+_LIBCPP_INLINE_VISIBILITY inline
+constexpr _T1 const & get(pair<_T2, _T1> const& __p) _NOEXCEPT
+{
+    return __get_pair<1>::get(__p);
+}
+
+template <class _T1, class _T2>
+_LIBCPP_INLINE_VISIBILITY inline
+constexpr _T1 && get(pair<_T2, _T1>&& __p) _NOEXCEPT
+{
+    return __get_pair<1>::get(_VSTD::move(__p));
+}
+
+#endif
+
+#if _LIBCPP_STD_VER > 11
+
+template<class _Tp, _Tp... _Ip>
+struct _LIBCPP_TYPE_VIS integer_sequence
+{
+    typedef _Tp value_type;
+    static_assert( is_integral<_Tp>::value,
+                  "std::integer_sequence can only be instantiated with an integral type" );
+    static
+    _LIBCPP_INLINE_VISIBILITY
+    constexpr
+    size_t
+    size() noexcept { return sizeof...(_Ip); }
+};
+
+template<size_t... _Ip>
+    using index_sequence = integer_sequence<size_t, _Ip...>;
+
+namespace __detail {
+
+template<typename _Tp, size_t ..._Extra> struct __repeat;
+template<typename _Tp, _Tp ..._Np, size_t ..._Extra> struct __repeat<integer_sequence<_Tp, _Np...>, _Extra...> {
+  typedef integer_sequence<_Tp,
+                           _Np...,
+                           sizeof...(_Np) + _Np...,
+                           2 * sizeof...(_Np) + _Np...,
+                           3 * sizeof...(_Np) + _Np...,
+                           4 * sizeof...(_Np) + _Np...,
+                           5 * sizeof...(_Np) + _Np...,
+                           6 * sizeof...(_Np) + _Np...,
+                           7 * sizeof...(_Np) + _Np...,
+                           _Extra...> type;
+};
+
+template<size_t _Np> struct __parity;
+template<size_t _Np> struct __make : __parity<_Np % 8>::template __pmake<_Np> {};
+
+template<> struct __make<0> { typedef integer_sequence<size_t> type; };
+template<> struct __make<1> { typedef integer_sequence<size_t, 0> type; };
+template<> struct __make<2> { typedef integer_sequence<size_t, 0, 1> type; };
+template<> struct __make<3> { typedef integer_sequence<size_t, 0, 1, 2> type; };
+template<> struct __make<4> { typedef integer_sequence<size_t, 0, 1, 2, 3> type; };
+template<> struct __make<5> { typedef integer_sequence<size_t, 0, 1, 2, 3, 4> type; };
+template<> struct __make<6> { typedef integer_sequence<size_t, 0, 1, 2, 3, 4, 5> type; };
+template<> struct __make<7> { typedef integer_sequence<size_t, 0, 1, 2, 3, 4, 5, 6> type; };
+
+template<> struct __parity<0> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type> {}; };
+template<> struct __parity<1> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 1> {}; };
+template<> struct __parity<2> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<3> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<4> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<5> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<6> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+template<> struct __parity<7> { template<size_t _Np> struct __pmake : __repeat<typename __make<_Np / 8>::type, _Np - 7, _Np - 6, _Np - 5, _Np - 4, _Np - 3, _Np - 2, _Np - 1> {}; };
+
+template<typename _Tp, typename _Up> struct __convert {
+  template<typename> struct __result;
+  template<_Tp ..._Np> struct __result<integer_sequence<_Tp, _Np...> > { typedef integer_sequence<_Up, _Np...> type; };
+};
+template<typename _Tp> struct __convert<_Tp, _Tp> { template<typename _Up> struct __result { typedef _Up type; }; };
+
+}
+
+template<typename _Tp, _Tp _Np> using __make_integer_sequence_unchecked =
+  typename __detail::__convert<size_t, _Tp>::template __result<typename __detail::__make<_Np>::type>::type;
+
+template <class _Tp, _Tp _Ep>
+struct __make_integer_sequence
+{
+    static_assert(is_integral<_Tp>::value,
+                  "std::make_integer_sequence can only be instantiated with an integral type" );
+    static_assert(0 <= _Ep, "std::make_integer_sequence input shall not be negative");
+    typedef __make_integer_sequence_unchecked<_Tp, _Ep> type;
+};
+
+template<class _Tp, _Tp _Np>
+    using make_integer_sequence = typename __make_integer_sequence<_Tp, _Np>::type;
+
+template<size_t _Np>
+    using make_index_sequence = make_integer_sequence<size_t, _Np>;
+
+template<class... _Tp>
+    using index_sequence_for = make_index_sequence<sizeof...(_Tp)>;
+  
+#endif  // _LIBCPP_STD_VER > 11
+
+#if _LIBCPP_STD_VER > 11
+template<class _T1, class _T2 = _T1>
+_LIBCPP_INLINE_VISIBILITY inline
+_T1 exchange(_T1& __obj, _T2 && __new_value)
+{
+    _T1 __old_value = _VSTD::move(__obj);
+    __obj = _VSTD::forward<_T2>(__new_value);
+    return __old_value;
+}    
+#endif  // _LIBCPP_STD_VER > 11
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_UTILITY