Commit 2289036a40

Andrew Kelley <andrew@ziglang.org>
2020-02-14 16:34:21
update libcxx to llvm10.0.0rc2
1 parent 74619cc
lib/libcxx/include/experimental/coroutine
@@ -51,7 +51,6 @@ template <class P> struct hash<coroutine_handle<P>>;
 #include <functional>
 #include <memory> // for hash<T*>
 #include <cstddef>
-#include <cassert>
 #include <__debug>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
lib/libcxx/include/experimental/functional
@@ -112,7 +112,7 @@ template<class _ForwardIterator, class _BinaryPredicate = equal_to<>>
 class _LIBCPP_TYPE_VIS default_searcher {
 public:
     _LIBCPP_INLINE_VISIBILITY
-    default_searcher(_ForwardIterator __f, _ForwardIterator __l, 
+    default_searcher(_ForwardIterator __f, _ForwardIterator __l,
                        _BinaryPredicate __p = _BinaryPredicate())
         : __first_(__f), __last_(__l), __pred_(__p) {}
 
@@ -151,12 +151,12 @@ public: // TODO private:
 
     const _Value __default_value_;
     std::unordered_map<_Key, _Value, _Hash, _BinaryPredicate> __table;
-    
+
 public:
     _LIBCPP_INLINE_VISIBILITY
     _BMSkipTable(std::size_t __sz, _Value __default, _Hash __hf, _BinaryPredicate __pred)
         : __default_value_(__default), __table(__sz, __hf, __pred) {}
-    
+
     _LIBCPP_INLINE_VISIBILITY
     void insert(const key_type &__key, value_type __val)
     {
@@ -170,7 +170,7 @@ public:
         return __it == __table.end() ? __default_value_ : __it->second;
     }
 };
-    
+
 
 //  Special case small numeric values; use an array
 template<class _Key, typename _Value, class _Hash, class _BinaryPredicate>
@@ -189,7 +189,7 @@ public:
     {
         std::fill_n(__table.begin(), __table.size(), __default);
     }
-    
+
     _LIBCPP_INLINE_VISIBILITY
     void insert(key_type __key, value_type __val)
     {
@@ -204,8 +204,8 @@ public:
 };
 
 
-template <class _RandomAccessIterator1, 
-          class _Hash = hash<typename iterator_traits<_RandomAccessIterator1>::value_type>, 
+template <class _RandomAccessIterator1,
+          class _Hash = hash<typename iterator_traits<_RandomAccessIterator1>::value_type>,
           class _BinaryPredicate = equal_to<>>
 class _LIBCPP_TYPE_VIS boyer_moore_searcher {
 private:
@@ -217,9 +217,9 @@ private:
                     is_same<_Hash, hash<value_type>>::value &&
                     is_same<_BinaryPredicate, equal_to<>>::value
             > skip_table_type;
-    
+
 public:
-    boyer_moore_searcher(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l, 
+    boyer_moore_searcher(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l,
                 _Hash __hf = _Hash(), _BinaryPredicate __pred = _BinaryPredicate())
             : __first_(__f), __last_(__l), __pred_(__pred),
               __pattern_length_(_VSTD::distance(__first_, __last_)),
@@ -232,13 +232,13 @@ public:
 
         this->__build_suffix_table ( __first_, __last_, __pred_ );
         }
-        
+
     template <typename _RandomAccessIterator2>
     pair<_RandomAccessIterator2, _RandomAccessIterator2>
     operator ()(_RandomAccessIterator2 __f, _RandomAccessIterator2 __l) const
     {
         static_assert ( std::is_same<
-                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator1>::value_type>::type, 
+                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator1>::value_type>::type,
                 typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator2>::value_type>::type
                     >::value,
                 "Corpus and Pattern iterators must point to the same type" );
@@ -247,13 +247,13 @@ public:
         if (__first_ == __last_) return make_pair(__f, __f); // empty pattern
 
     //  If the pattern is larger than the corpus, we can't find it!
-        if ( __pattern_length_ > _VSTD::distance (__f, __l)) 
+        if ( __pattern_length_ > _VSTD::distance (__f, __l))
             return make_pair(__l, __l);
 
-    //  Do the search 
+    //  Do the search
         return this->__search(__f, __l);
     }
-        
+
 public: // TODO private:
     _RandomAccessIterator1               __first_;
     _RandomAccessIterator1               __last_;
@@ -270,7 +270,7 @@ public: // TODO private:
         const _RandomAccessIterator2 __last = __l - __pattern_length_;
         const skip_table_type &         __skip   = *__skip_.get();
         const vector<difference_type> & __suffix = *__suffix_.get();
-        
+
         while (__cur <= __last)
         {
 
@@ -282,7 +282,7 @@ public: // TODO private:
                 if ( __j == 0 )
                     return make_pair(__cur, __cur + __pattern_length_);
                 }
-            
+
         //  Since we didn't match, figure out how far to skip forward
             difference_type __k = __skip[__cur [ __j - 1 ]];
             difference_type __m = __j - __k - 1;
@@ -291,7 +291,7 @@ public: // TODO private:
             else
                 __cur += __suffix[ __j ];
         }
-    
+
         return make_pair(__l, __l);     // We didn't find anything
     }
 
@@ -300,21 +300,21 @@ public: // TODO private:
     void __compute_bm_prefix ( _Iterator __f, _Iterator __l, _BinaryPredicate __pred, _Container &__prefix )
     {
         const std::size_t __count = _VSTD::distance(__f, __l);
-                        
+
         __prefix[0] = 0;
         std::size_t __k = 0;
         for ( std::size_t __i = 1; __i < __count; ++__i )
         {
             while ( __k > 0 && !__pred ( __f[__k], __f[__i] ))
                 __k = __prefix [ __k - 1 ];
-                
+
             if ( __pred ( __f[__k], __f[__i] ))
                 __k++;
             __prefix [ __i ] = __k;
         }
     }
 
-    void __build_suffix_table(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l, 
+    void __build_suffix_table(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l,
                                                     _BinaryPredicate __pred)
     {
         const std::size_t __count = _VSTD::distance(__f, __l);
@@ -322,19 +322,19 @@ public: // TODO private:
         if (__count > 0)
         {
             _VSTD::vector<value_type> __scratch(__count);
-            
+
             __compute_bm_prefix(__f, __l, __pred, __scratch);
             for ( std::size_t __i = 0; __i <= __count; __i++ )
                 __suffix[__i] = __count - __scratch[__count-1];
-    
+
             typedef _VSTD::reverse_iterator<_RandomAccessIterator1> _RevIter;
             __compute_bm_prefix(_RevIter(__l), _RevIter(__f), __pred, __scratch);
-     
+
             for ( std::size_t __i = 0; __i < __count; __i++ )
             {
                 const std::size_t     __j = __count - __scratch[__i];
                 const difference_type __k = __i     - __scratch[__i] + 1;
-     
+
                 if (__suffix[__j] > __k)
                     __suffix[__j] = __k;
             }
@@ -343,20 +343,20 @@ public: // TODO private:
 
 };
 
-template<class _RandomAccessIterator, 
-         class _Hash = hash<typename iterator_traits<_RandomAccessIterator>::value_type>, 
+template<class _RandomAccessIterator,
+         class _Hash = hash<typename iterator_traits<_RandomAccessIterator>::value_type>,
          class _BinaryPredicate = equal_to<>>
 _LIBCPP_INLINE_VISIBILITY
 boyer_moore_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>
-make_boyer_moore_searcher( _RandomAccessIterator __f, _RandomAccessIterator __l, 
+make_boyer_moore_searcher( _RandomAccessIterator __f, _RandomAccessIterator __l,
                     _Hash __hf = _Hash(), _BinaryPredicate __p = _BinaryPredicate ())
 {
     return boyer_moore_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>(__f, __l, __hf, __p);
 }
 
 // boyer-moore-horspool
-template <class _RandomAccessIterator1, 
-          class _Hash = hash<typename iterator_traits<_RandomAccessIterator1>::value_type>, 
+template <class _RandomAccessIterator1,
+          class _Hash = hash<typename iterator_traits<_RandomAccessIterator1>::value_type>,
           class _BinaryPredicate = equal_to<>>
 class _LIBCPP_TYPE_VIS boyer_moore_horspool_searcher {
 private:
@@ -370,7 +370,7 @@ private:
             > skip_table_type;
 
 public:
-    boyer_moore_horspool_searcher(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l, 
+    boyer_moore_horspool_searcher(_RandomAccessIterator1 __f, _RandomAccessIterator1 __l,
                 _Hash __hf = _Hash(), _BinaryPredicate __pred = _BinaryPredicate())
             : __first_(__f), __last_(__l), __pred_(__pred),
               __pattern_length_(_VSTD::distance(__first_, __last_)),
@@ -384,13 +384,13 @@ public:
                     __skip_->insert(*__f, __pattern_length_ - 1 - __i);
             }
         }
-            
+
     template <typename _RandomAccessIterator2>
     pair<_RandomAccessIterator2, _RandomAccessIterator2>
     operator ()(_RandomAccessIterator2 __f, _RandomAccessIterator2 __l) const
     {
         static_assert ( std::is_same<
-                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator1>::value_type>::type, 
+                typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator1>::value_type>::type,
                 typename std::__uncvref<typename std::iterator_traits<_RandomAccessIterator2>::value_type>::type
                     >::value,
                 "Corpus and Pattern iterators must point to the same type" );
@@ -399,13 +399,13 @@ public:
         if (__first_ == __last_) return make_pair(__f, __f); // empty pattern
 
     //  If the pattern is larger than the corpus, we can't find it!
-        if ( __pattern_length_ > _VSTD::distance (__f, __l)) 
+        if ( __pattern_length_ > _VSTD::distance (__f, __l))
             return make_pair(__l, __l);
 
-    //  Do the search 
+    //  Do the search
         return this->__search(__f, __l);
     }
-        
+
 private:
     _RandomAccessIterator1      __first_;
     _RandomAccessIterator1      __last_;
@@ -433,17 +433,17 @@ private:
             }
             __cur += __skip[__cur[__pattern_length_-1]];
         }
-        
+
         return make_pair(__l, __l);
     }
 };
 
-template<class _RandomAccessIterator, 
-         class _Hash = hash<typename iterator_traits<_RandomAccessIterator>::value_type>, 
+template<class _RandomAccessIterator,
+         class _Hash = hash<typename iterator_traits<_RandomAccessIterator>::value_type>,
          class _BinaryPredicate = equal_to<>>
 _LIBCPP_INLINE_VISIBILITY
 boyer_moore_horspool_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>
-make_boyer_moore_horspool_searcher( _RandomAccessIterator __f, _RandomAccessIterator __l, 
+make_boyer_moore_horspool_searcher( _RandomAccessIterator __f, _RandomAccessIterator __l,
                     _Hash __hf = _Hash(), _BinaryPredicate __p = _BinaryPredicate ())
 {
     return boyer_moore_horspool_searcher<_RandomAccessIterator, _Hash, _BinaryPredicate>(__f, __l, __hf, __p);
lib/libcxx/include/experimental/iterator
@@ -26,19 +26,19 @@ namespace std {
          typedef void                         difference_type;
          typedef void                         pointer;
          typedef void                         reference;
-      
+
          ostream_joiner(ostream_type& s, const DelimT& delimiter);
          ostream_joiner(ostream_type& s, DelimT&& delimiter);
 
-         template<typename T>  
+         template<typename T>
          ostream_joiner& operator=(const T& value);
 
          ostream_joiner& operator*() noexcept;
          ostream_joiner& operator++() noexcept;
          ostream_joiner& operator++(int) noexcept;
    private:
-      ostream_type* out_stream;   // exposition only 
-      DelimT delim;               // exposition only 
+      ostream_type* out_stream;   // exposition only
+      DelimT delim;               // exposition only
       bool first_element;         // exposition only
    };
 
@@ -75,10 +75,10 @@ public:
 
     ostream_joiner(ostream_type& __os, _Delim&& __d)
         : __output_iter(_VSTD::addressof(__os)), __delim(_VSTD::move(__d)), __first(true) {}
-        
+
     ostream_joiner(ostream_type& __os, const _Delim& __d)
         : __output_iter(_VSTD::addressof(__os)), __delim(__d), __first(true) {}
-    
+
 
     template<typename _Tp>
     ostream_joiner& operator=(const _Tp& __v)
lib/libcxx/include/experimental/propagate_const
@@ -575,4 +575,3 @@ _LIBCPP_END_NAMESPACE_STD
 
 #endif // _LIBCPP_STD_VER > 11
 #endif // _LIBCPP_EXPERIMENTAL_PROPAGATE_CONST
-
lib/libcxx/include/experimental/type_traits
@@ -60,7 +60,7 @@ inline namespace fundamentals_v1 {
      using is_detected_convertible = is_convertible<detected_t<Op, Args...>, To>;
   template <class To, template<class...> class Op, class... Args>
      constexpr bool is_detected_convertible_v
-       = is_detected_convertible<To, Op, Args...>::value;  
+       = is_detected_convertible<To, Op, Args...>::value;
 
 } // namespace fundamentals_v1
 } // namespace experimental
@@ -122,7 +122,7 @@ struct _DETECTOR<_Default, void_t<_Op<_Args...>>, _Op, _Args...> {
    using value_t = true_type;
    using type = _Op<_Args...>;
    };
-     
+
 
 template <template<class...> class _Op, class... _Args>
   using is_detected = typename _DETECTOR<nonesuch, void, _Op, _Args...>::value_t;
@@ -144,7 +144,7 @@ template <class Expected, template<class...> class _Op, class... _Args>
 template <class To, template<class...> class _Op, class... _Args>
   using is_detected_convertible = is_convertible<detected_t<_Op, _Args...>, To>;
 template <class To, template<class...> class _Op, class... _Args>
-  _LIBCPP_CONSTEXPR bool is_detected_convertible_v = is_detected_convertible<To, _Op, _Args...>::value;  
+  _LIBCPP_CONSTEXPR bool is_detected_convertible_v = is_detected_convertible<To, _Op, _Args...>::value;
 
 
 _LIBCPP_END_NAMESPACE_LFTS
lib/libcxx/include/ext/hash_map
@@ -39,14 +39,17 @@ public:
     typedef /unspecified/ iterator;
     typedef /unspecified/ const_iterator;
 
-    explicit hash_map(size_type n = 193, const hasher& hf = hasher(),
+    hash_map();
+    explicit hash_map(size_type n, const hasher& hf = hasher(),
                            const key_equal& eql = key_equal(),
                            const allocator_type& a = allocator_type());
     template <class InputIterator>
-        hash_map(InputIterator f, InputIterator l,
-                      size_type n = 193, const hasher& hf = hasher(),
-                      const key_equal& eql = key_equal(),
-                      const allocator_type& a = allocator_type());
+    hash_map(InputIterator f, InputIterator l);
+    template <class InputIterator>
+    hash_map(InputIterator f, InputIterator l,
+                size_type n, const hasher& hf = hasher(),
+                const key_equal& eql = key_equal(),
+                const allocator_type& a = allocator_type());
     hash_map(const hash_map&);
     ~hash_map();
     hash_map& operator=(const hash_map&);
@@ -315,12 +318,13 @@ private:
 
     allocator_type& __na_;
 
-    __hash_map_node_destructor& operator=(const __hash_map_node_destructor&);
-
 public:
     bool __first_constructed;
     bool __second_constructed;
 
+    __hash_map_node_destructor(__hash_map_node_destructor const&) = default;
+    __hash_map_node_destructor& operator=(const __hash_map_node_destructor&) = delete;
+
     _LIBCPP_INLINE_VISIBILITY
     explicit __hash_map_node_destructor(allocator_type& __na)
         : __na_(__na),
@@ -391,10 +395,10 @@ public:
         return __t;
     }
 
-    friend _LIBCPP_INLINE_VISIBILITY 
+    friend _LIBCPP_INLINE_VISIBILITY
     bool operator==(const __hash_map_iterator& __x, const __hash_map_iterator& __y)
         {return __x.__i_ == __y.__i_;}
-    friend _LIBCPP_INLINE_VISIBILITY 
+    friend _LIBCPP_INLINE_VISIBILITY
     bool operator!=(const __hash_map_iterator& __x, const __hash_map_iterator& __y)
         {return __x.__i_ != __y.__i_;}
 
@@ -502,7 +506,7 @@ public:
     typedef __hash_map_iterator<typename __table::iterator>       iterator;
     typedef __hash_map_const_iterator<typename __table::const_iterator> const_iterator;
 
-    _LIBCPP_INLINE_VISIBILITY hash_map() {__table_.rehash(193);}
+    _LIBCPP_INLINE_VISIBILITY hash_map() { }
     explicit hash_map(size_type __n, const hasher& __hf = hasher(),
                            const key_equal& __eql = key_equal());
     hash_map(size_type __n, const hasher& __hf,
@@ -623,7 +627,6 @@ template <class _InputIterator>
 hash_map<_Key, _Tp, _Hash, _Pred, _Alloc>::hash_map(
         _InputIterator __first, _InputIterator __last)
 {
-    __table_.rehash(193);
     insert(__first, __last);
 }
 
@@ -775,7 +778,7 @@ public:
     typedef __hash_map_const_iterator<typename __table::const_iterator> const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
-    hash_multimap() {__table_.rehash(193);}
+    hash_multimap() { }
     explicit hash_multimap(size_type __n, const hasher& __hf = hasher(),
                                 const key_equal& __eql = key_equal());
     hash_multimap(size_type __n, const hasher& __hf,
@@ -890,7 +893,6 @@ template <class _InputIterator>
 hash_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>::hash_multimap(
         _InputIterator __first, _InputIterator __last)
 {
-    __table_.rehash(193);
     insert(__first, __last);
 }
 
lib/libcxx/include/ext/hash_set
@@ -237,7 +237,7 @@ public:
     typedef typename __table::const_iterator       const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
-    hash_set() {__table_.rehash(193);}
+    hash_set() { }
     explicit hash_set(size_type __n, const hasher& __hf = hasher(),
                            const key_equal& __eql = key_equal());
     hash_set(size_type __n, const hasher& __hf, const key_equal& __eql,
@@ -347,7 +347,6 @@ template <class _InputIterator>
 hash_set<_Value, _Hash, _Pred, _Alloc>::hash_set(
         _InputIterator __first, _InputIterator __last)
 {
-    __table_.rehash(193);
     insert(__first, __last);
 }
 
@@ -459,7 +458,7 @@ public:
     typedef typename __table::const_iterator       const_iterator;
 
     _LIBCPP_INLINE_VISIBILITY
-    hash_multiset() {__table_.rehash(193);}
+    hash_multiset() { }
     explicit hash_multiset(size_type __n, const hasher& __hf = hasher(),
                                 const key_equal& __eql = key_equal());
     hash_multiset(size_type __n, const hasher& __hf,
@@ -569,7 +568,6 @@ template <class _InputIterator>
 hash_multiset<_Value, _Hash, _Pred, _Alloc>::hash_multiset(
         _InputIterator __first, _InputIterator __last)
 {
-    __table_.rehash(193);
     insert(__first, __last);
 }
 
lib/libcxx/include/support/android/locale_bionic.h
@@ -27,7 +27,9 @@ extern "C" {
 
 #include <android/api-level.h>
 #include <android/ndk-version.h>
+#if __ANDROID_API__ < 21
 #include <support/xlocale/__posix_l_fallback.h>
+#endif
 // In NDK versions later than 16, locale-aware functions are provided by
 // legacy_stdlib_inlines.h
 #if __NDK_MAJOR__ <= 16
lib/libcxx/include/support/ibm/xlocale.h
@@ -87,7 +87,7 @@ int isxdigit_l(int c, locale_t locale)
 static inline
 int iswalnum_l(wchar_t wc, locale_t locale)
 {
-  return __xiswalnum(locale, wc); 
+  return __xiswalnum(locale, wc);
 }
 
 static inline
@@ -159,7 +159,7 @@ int iswxdigit_l(wchar_t wc, locale_t locale)
 static inline
 int iswctype_l(wint_t wc, wctype_t desc, locale_t locale)
 {
-  return __xiswctype(locale, wc, desc); 
+  return __xiswctype(locale, wc, desc);
 }
 
 static inline
@@ -261,7 +261,7 @@ int vasprintf(char **strp, const char *fmt, va_list ap)
     str_size = vsnprintf(*strp, str_size + 1, fmt,  ap);
   }
   return str_size;
-}  
+}
 
 #ifdef __cplusplus
 }
lib/libcxx/include/support/solaris/wchar.h
@@ -26,7 +26,7 @@
 #define wctype sun_wctype
 #define _WCHAR_T 1
 #include_next "wchar.h"
-#undef iswalpha 
+#undef iswalpha
 #undef iswupper
 #undef iswlower
 #undef iswdigit
lib/libcxx/include/support/win32/locale_win32.h
@@ -28,14 +28,72 @@
                      | LC_NUMERIC_MASK \
                      | LC_TIME_MASK )
 
+class __lconv_storage {
+public:
+    __lconv_storage(const lconv *__lc_input) {
+        __lc = *__lc_input;
+
+        __decimal_point = __lc_input->decimal_point;
+        __thousands_sep = __lc_input->thousands_sep;
+        __grouping = __lc_input->grouping;
+        __int_curr_symbol = __lc_input->int_curr_symbol;
+        __currency_symbol = __lc_input->currency_symbol;
+        __mon_decimal_point = __lc_input->mon_decimal_point;
+        __mon_thousands_sep = __lc_input->mon_thousands_sep;
+        __mon_grouping = __lc_input->mon_grouping;
+        __positive_sign = __lc_input->positive_sign;
+        __negative_sign = __lc_input->negative_sign;
+
+        __lc.decimal_point = const_cast<char *>(__decimal_point.c_str());
+        __lc.thousands_sep = const_cast<char *>(__thousands_sep.c_str());
+        __lc.grouping = const_cast<char *>(__grouping.c_str());
+        __lc.int_curr_symbol = const_cast<char *>(__int_curr_symbol.c_str());
+        __lc.currency_symbol = const_cast<char *>(__currency_symbol.c_str());
+        __lc.mon_decimal_point = const_cast<char *>(__mon_decimal_point.c_str());
+        __lc.mon_thousands_sep = const_cast<char *>(__mon_thousands_sep.c_str());
+        __lc.mon_grouping = const_cast<char *>(__mon_grouping.c_str());
+        __lc.positive_sign = const_cast<char *>(__positive_sign.c_str());
+        __lc.negative_sign = const_cast<char *>(__negative_sign.c_str());
+    }
+
+    lconv *__get() {
+        return &__lc;
+    }
+private:
+    lconv __lc;
+    std::string __decimal_point;
+    std::string __thousands_sep;
+    std::string __grouping;
+    std::string __int_curr_symbol;
+    std::string __currency_symbol;
+    std::string __mon_decimal_point;
+    std::string __mon_thousands_sep;
+    std::string __mon_grouping;
+    std::string __positive_sign;
+    std::string __negative_sign;
+};
+
 class locale_t {
 public:
     locale_t()
-        : __locale(nullptr), __locale_str(nullptr) {}
+        : __locale(nullptr), __locale_str(nullptr), __lc(nullptr) {}
     locale_t(std::nullptr_t)
-        : __locale(nullptr), __locale_str(nullptr) {}
+        : __locale(nullptr), __locale_str(nullptr), __lc(nullptr) {}
     locale_t(_locale_t __xlocale, const char* __xlocale_str)
-        : __locale(__xlocale), __locale_str(__xlocale_str) {}
+        : __locale(__xlocale), __locale_str(__xlocale_str), __lc(nullptr) {}
+    locale_t(const locale_t &__l)
+        : __locale(__l.__locale), __locale_str(__l.__locale_str), __lc(nullptr) {}
+
+    ~locale_t() {
+        delete __lc;
+    }
+
+    locale_t &operator =(const locale_t &__l) {
+        __locale = __l.__locale;
+        __locale_str = __l.__locale_str;
+        // __lc not copied
+        return *this;
+    }
 
     friend bool operator==(const locale_t& __left, const locale_t& __right) {
         return __left.__locale == __right.__locale;
@@ -94,9 +152,16 @@ public:
     operator _locale_t() const {
         return __locale;
     }
+
+    lconv *__store_lconv(const lconv *__input_lc) {
+        delete __lc;
+        __lc = new __lconv_storage(__input_lc);
+        return __lc->__get();
+    }
 private:
     _locale_t __locale;
     const char* __locale_str;
+    __lconv_storage *__lc = nullptr;
 };
 
 // Locale management functions
@@ -109,7 +174,7 @@ locale_t newlocale( int mask, const char * locale, locale_t base );
 // We can still implement raii even without uselocale though.
 
 
-lconv *localeconv_l( locale_t loc );
+lconv *localeconv_l( locale_t &loc );
 size_t mbrlen_l( const char *__restrict s, size_t n,
                  mbstate_t *__restrict ps, locale_t loc);
 size_t mbsrtowcs_l( wchar_t *__restrict dst, const char **__restrict src,
@@ -173,7 +238,8 @@ isupper_l(int c, _locale_t loc)
 #define towupper_l _towupper_l
 #define towlower_l _towlower_l
 #if defined(__MINGW32__) && __MSVCRT_VERSION__ < 0x0800
-#define strftime_l( __s, __l, __f, __tm, __loc ) strftime( __s, __l, __f, __tm )
+_LIBCPP_FUNC_VIS size_t strftime_l(char *ret, size_t n, const char *format,
+                                   const struct tm *tm, locale_t loc);
 #else
 #define strftime_l _strftime_l
 #endif
lib/libcxx/include/__bit_reference
@@ -47,6 +47,9 @@ class __bit_reference
     friend class __bit_const_reference<_Cp>;
     friend class __bit_iterator<_Cp, false>;
 public:
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_reference(const __bit_reference&) = default;
+
     _LIBCPP_INLINE_VISIBILITY operator bool() const _NOEXCEPT
         {return static_cast<bool>(*__seg_ & __mask_);}
     _LIBCPP_INLINE_VISIBILITY bool operator ~() const _NOEXCEPT
@@ -132,6 +135,9 @@ class __bit_const_reference
     friend typename _Cp::__self;
     friend class __bit_iterator<_Cp, true>;
 public:
+    _LIBCPP_INLINE_VISIBILITY
+    __bit_const_reference(const __bit_const_reference&) = default;
+
     _LIBCPP_INLINE_VISIBILITY
     __bit_const_reference(const __bit_reference<_Cp>& __x) _NOEXCEPT
         : __seg_(__x.__seg_), __mask_(__x.__mask_) {}
@@ -147,7 +153,7 @@ private:
     __bit_const_reference(__storage_pointer __s, __storage_type __m) _NOEXCEPT
         : __seg_(__s), __mask_(__m) {}
 
-    __bit_const_reference& operator=(const __bit_const_reference& __x);
+    __bit_const_reference& operator=(const __bit_const_reference&) = delete;
 };
 
 // find
@@ -332,7 +338,7 @@ __fill_n_false(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
     }
     // do middle whole words
     __storage_type __nw = __n / __bits_per_word;
-    _VSTD::memset(_VSTD::__to_raw_pointer(__first.__seg_), 0, __nw * sizeof(__storage_type));
+    _VSTD::memset(_VSTD::__to_address(__first.__seg_), 0, __nw * sizeof(__storage_type));
     __n -= __nw * __bits_per_word;
     // do last partial word
     if (__n > 0)
@@ -362,7 +368,7 @@ __fill_n_true(__bit_iterator<_Cp, false> __first, typename _Cp::size_type __n)
     }
     // do middle whole words
     __storage_type __nw = __n / __bits_per_word;
-    _VSTD::memset(_VSTD::__to_raw_pointer(__first.__seg_), -1, __nw * sizeof(__storage_type));
+    _VSTD::memset(_VSTD::__to_address(__first.__seg_), -1, __nw * sizeof(__storage_type));
     __n -= __nw * __bits_per_word;
     // do last partial word
     if (__n > 0)
@@ -429,8 +435,8 @@ __copy_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_Cp, _IsCon
         // __first.__ctz_ == 0;
         // do middle words
         __storage_type __nw = __n / __bits_per_word;
-        _VSTD::memmove(_VSTD::__to_raw_pointer(__result.__seg_),
-                       _VSTD::__to_raw_pointer(__first.__seg_),
+        _VSTD::memmove(_VSTD::__to_address(__result.__seg_),
+                       _VSTD::__to_address(__first.__seg_),
                        __nw * sizeof(__storage_type));
         __n -= __nw * __bits_per_word;
         __result.__seg_ += __nw;
@@ -570,8 +576,8 @@ __copy_backward_aligned(__bit_iterator<_Cp, _IsConst> __first, __bit_iterator<_C
         __storage_type __nw = __n / __bits_per_word;
         __result.__seg_ -= __nw;
         __last.__seg_ -= __nw;
-        _VSTD::memmove(_VSTD::__to_raw_pointer(__result.__seg_),
-                       _VSTD::__to_raw_pointer(__last.__seg_),
+        _VSTD::memmove(_VSTD::__to_address(__result.__seg_),
+                       _VSTD::__to_address(__last.__seg_),
                        __nw * sizeof(__storage_type));
         __n -= __nw * __bits_per_word;
         // do last word
@@ -1108,8 +1114,12 @@ public:
 #endif
     {}
 
+    // avoid re-declaring a copy constructor for the non-const version.
+    using __type_for_copy_to_const =
+      _If<_IsConst, __bit_iterator<_Cp, false>, struct __private_nat>;
+
     _LIBCPP_INLINE_VISIBILITY
-    __bit_iterator(const __bit_iterator<_Cp, false>& __it) _NOEXCEPT
+    __bit_iterator(const __type_for_copy_to_const& __it) _NOEXCEPT
         : __seg_(__it.__seg_), __ctz_(__it.__ctz_) {}
 
     _LIBCPP_INLINE_VISIBILITY reference operator*() const _NOEXCEPT
lib/libcxx/include/__config
@@ -32,7 +32,7 @@
 #  define _GNUC_VER_NEW 0
 #endif
 
-#define _LIBCPP_VERSION 9000
+#define _LIBCPP_VERSION 10000
 
 #ifndef _LIBCPP_ABI_VERSION
 #  define _LIBCPP_ABI_VERSION 1
@@ -183,10 +183,6 @@
 #  define _LIBCPP_COMPILER_IBM
 #endif
 
-#ifndef _LIBCPP_CLANG_VER
-#define _LIBCPP_CLANG_VER 0
-#endif
-
 #if defined(_LIBCPP_COMPILER_GCC) && __cplusplus < 201103L
 #error "libc++ does not support using GCC with C++03. Please enable C++11"
 #endif
@@ -246,6 +242,7 @@
 
 #ifdef __FreeBSD__
 #  include <sys/endian.h>
+#  include <osreldate.h>
 #  if _BYTE_ORDER == _LITTLE_ENDIAN
 #    define _LIBCPP_LITTLE_ENDIAN
 #  else  // _BYTE_ORDER == _LITTLE_ENDIAN
@@ -263,7 +260,6 @@
 #  else  // _BYTE_ORDER == _LITTLE_ENDIAN
 #    define _LIBCPP_BIG_ENDIAN
 #  endif  // _BYTE_ORDER == _LITTLE_ENDIAN
-#  define _LIBCPP_HAS_QUICK_EXIT
 #endif  // __NetBSD__
 
 #if defined(_WIN32)
@@ -343,9 +339,26 @@
 
 #if __ISO_C_VISIBLE >= 2011 || __cplusplus >= 201103L
 #  if defined(__FreeBSD__)
+#    define _LIBCPP_HAS_ALIGNED_ALLOC
 #    define _LIBCPP_HAS_QUICK_EXIT
 #    define _LIBCPP_HAS_C11_FEATURES
-#  elif defined(__Fuchsia__) || defined(__wasi__)
+#    if __FreeBSD_version >= 1300064 || \
+       (__FreeBSD_version >= 1201504 && __FreeBSD_version < 1300000)
+#      define _LIBCPP_HAS_TIMESPEC_GET
+#    endif
+#  elif defined(__BIONIC__)
+#    define _LIBCPP_HAS_C11_FEATURES
+#    if __ANDROID_API__ >= 21
+#      define _LIBCPP_HAS_QUICK_EXIT
+#    endif
+#    if __ANDROID_API__ >= 28
+#      define _LIBCPP_HAS_ALIGNED_ALLOC
+#    endif
+#    if __ANDROID_API__ >= 29
+#      define _LIBCPP_HAS_TIMESPEC_GET
+#    endif
+#  elif defined(__Fuchsia__) || defined(__wasi__) || defined(__NetBSD__)
+#    define _LIBCPP_HAS_ALIGNED_ALLOC
 #    define _LIBCPP_HAS_QUICK_EXIT
 #    define _LIBCPP_HAS_TIMESPEC_GET
 #    define _LIBCPP_HAS_C11_FEATURES
@@ -355,10 +368,12 @@
 #        define _LIBCPP_HAS_QUICK_EXIT
 #      endif
 #      if _LIBCPP_GLIBC_PREREQ(2, 17)
+#        define _LIBCPP_HAS_ALIGNED_ALLOC
 #        define _LIBCPP_HAS_C11_FEATURES
 #        define _LIBCPP_HAS_TIMESPEC_GET
 #      endif
 #    else // defined(_LIBCPP_HAS_MUSL_LIBC)
+#      define _LIBCPP_HAS_ALIGNED_ALLOC
 #      define _LIBCPP_HAS_QUICK_EXIT
 #      define _LIBCPP_HAS_TIMESPEC_GET
 #      define _LIBCPP_HAS_C11_FEATURES
@@ -483,11 +498,14 @@ typedef __char32_t char32_t;
 
 #define _LIBCPP_ALWAYS_INLINE __attribute__ ((__always_inline__))
 
-// No apple compilers support ""d and ""y at this time.
-#if _LIBCPP_CLANG_VER < 800 || defined(__apple_build_version__)
-#define	_LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS
+// Literal operators ""d and ""y are supported starting with LLVM Clang 8 and AppleClang 10.0.1
+#if (defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER < 800) || \
+    (defined(__apple_build_version__) && __apple_build_version__ < 10010000)
+#define _LIBCPP_HAS_NO_CXX20_CHRONO_LITERALS
 #endif
 
+#define _LIBCPP_DISABLE_EXTENSION_WARNING __extension__
+
 #elif defined(_LIBCPP_COMPILER_GCC)
 
 #define _ALIGNAS(x) __attribute__((__aligned__(x)))
@@ -523,6 +541,8 @@ typedef __char32_t char32_t;
 
 #define _LIBCPP_ALWAYS_INLINE __attribute__ ((__always_inline__))
 
+#define _LIBCPP_DISABLE_EXTENSION_WARNING __extension__
+
 #elif defined(_LIBCPP_COMPILER_MSVC)
 
 #define _LIBCPP_TOSTRING2(x) #x
@@ -548,6 +568,8 @@ typedef __char32_t char32_t;
 
 #define _LIBCPP_HAS_NO_VECTOR_EXTENSION
 
+#define _LIBCPP_DISABLE_EXTENSION_WARNING
+
 #elif defined(_LIBCPP_COMPILER_IBM)
 
 #define _ALIGNAS(x) __attribute__((__aligned__(x)))
@@ -568,6 +590,8 @@ typedef __char32_t char32_t;
 
 #define _LIBCPP_HAS_NO_VECTOR_EXTENSION
 
+#define _LIBCPP_DISABLE_EXTENSION_WARNING
+
 #endif // _LIBCPP_COMPILER_[CLANG|GCC|MSVC|IBM]
 
 #if defined(_LIBCPP_OBJECT_FORMAT_COFF)
@@ -860,6 +884,10 @@ typedef unsigned int   char32_t;
 #  endif
 #endif
 
+#ifndef _LIBCPP_DEBUG_LEVEL
+# define _LIBCPP_DEBUG_LEVEL 0
+#endif
+
 #ifdef _LIBCPP_DISABLE_EXTERN_TEMPLATE
 #define _LIBCPP_EXTERN_TEMPLATE(...)
 #define _LIBCPP_EXTERN_TEMPLATE2(...)
@@ -958,6 +986,20 @@ typedef unsigned int   char32_t;
 #  define _LIBCPP_DEPRECATED_IN_CXX17
 #endif
 
+// Macros to enter and leave a state where deprecation warnings are suppressed.
+#if !defined(_LIBCPP_SUPPRESS_DEPRECATED_PUSH) && \
+    (defined(_LIBCPP_COMPILER_CLANG) || defined(_LIBCPP_COMPILER_GCC))
+#  define _LIBCPP_SUPPRESS_DEPRECATED_PUSH \
+    _Pragma("GCC diagnostic push") \
+    _Pragma("GCC diagnostic ignored \"-Wdeprecated\"")
+#  define _LIBCPP_SUPPRESS_DEPRECATED_POP \
+    _Pragma("GCC diagnostic pop")
+#endif
+#if !defined(_LIBCPP_SUPPRESS_DEPRECATED_PUSH)
+#  define _LIBCPP_SUPPRESS_DEPRECATED_PUSH
+#  define _LIBCPP_SUPPRESS_DEPRECATED_POP
+#endif
+
 #if _LIBCPP_STD_VER <= 11
 #  define _LIBCPP_EXPLICIT_AFTER_CXX11
 #else
@@ -982,6 +1024,14 @@ typedef unsigned int   char32_t;
 #  define _LIBCPP_CONSTEXPR_AFTER_CXX17
 #endif
 
+#if _LIBCPP_STD_VER > 17 && \
+    !defined(_LIBCPP_HAS_NO_CXX14_CONSTEXPR) && \
+    !defined(_LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED)
+#  define _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED constexpr
+#else
+#  define _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+#endif
+
 // The _LIBCPP_NODISCARD_ATTRIBUTE should only be used to define other
 // NODISCARD macros to the correct attribute.
 #if __has_cpp_attribute(nodiscard) || defined(_LIBCPP_COMPILER_MSVC)
@@ -1065,7 +1115,6 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
     !defined(_LIBCPP_HAS_THREAD_API_WIN32) && \
     !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
 #  if defined(__FreeBSD__) || \
-      defined(__Fuchsia__) || \
       defined(__wasi__) || \
       defined(__NetBSD__) || \
       defined(__linux__) || \
@@ -1075,6 +1124,8 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
       defined(__sun__) || \
       (defined(__MINGW32__) && __has_include(<pthread.h>))
 #    define _LIBCPP_HAS_THREAD_API_PTHREAD
+#  elif defined(__Fuchsia__)
+#    define _LIBCPP_HAS_THREAD_API_C11
 #  elif defined(_LIBCPP_WIN32API)
 #    define _LIBCPP_HAS_THREAD_API_WIN32
 #  else
@@ -1082,6 +1133,16 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #  endif // _LIBCPP_HAS_THREAD_API
 #endif // _LIBCPP_HAS_NO_THREADS
 
+#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+#if defined(__ANDROID__) && __ANDROID_API__ >= 30
+#define _LIBCPP_HAS_COND_CLOCKWAIT
+#elif defined(_LIBCPP_GLIBC_PREREQ)
+#if _LIBCPP_GLIBC_PREREQ(2, 30)
+#define _LIBCPP_HAS_COND_CLOCKWAIT
+#endif
+#endif
+#endif
+
 #if defined(_LIBCPP_HAS_NO_THREADS) && defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
 #error _LIBCPP_HAS_THREAD_API_PTHREAD may only be defined when \
        _LIBCPP_HAS_NO_THREADS is not defined.
@@ -1097,20 +1158,40 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
        _LIBCPP_HAS_NO_THREADS is defined.
 #endif
 
-// The Apple, glibc, and Bionic implementation of pthreads implements
+#if defined(__STDCPP_THREADS__) && defined(_LIBCPP_HAS_NO_THREADS)
+#error _LIBCPP_HAS_NO_THREADS cannot be set when __STDCPP_THREADS__ is set.
+#endif
+
+#if !defined(_LIBCPP_HAS_NO_THREADS) && !defined(__STDCPP_THREADS__)
+#define __STDCPP_THREADS__ 1
+#endif
+
+// The glibc and Bionic implementation of pthreads implements
 // pthread_mutex_destroy as nop for regular mutexes. Additionally, Win32
 // mutexes have no destroy mechanism.
-// TODO(EricWF): Enable this optimization on Apple and Bionic platforms after
-// speaking to their respective stakeholders.
+//
+// This optimization can't be performed on Apple platforms, where
+// pthread_mutex_destroy can allow the kernel to release resources.
+// See https://llvm.org/D64298 for details.
+//
+// TODO(EricWF): Enable this optimization on Bionic after speaking to their
+//               respective stakeholders.
 #if (defined(_LIBCPP_HAS_THREAD_API_PTHREAD) && defined(__GLIBC__)) \
+  || (defined(_LIBCPP_HAS_THREAD_API_C11) && defined(__Fuchsia__)) \
   || defined(_LIBCPP_HAS_THREAD_API_WIN32)
 # define _LIBCPP_HAS_TRIVIAL_MUTEX_DESTRUCTION
 #endif
 
 // Destroying a condvar is a nop on Windows.
+//
+// This optimization can't be performed on Apple platforms, where
+// pthread_cond_destroy can allow the kernel to release resources.
+// See https://llvm.org/D64298 for details.
+//
 // TODO(EricWF): This is potentially true for some pthread implementations
 // as well.
-#if defined(_LIBCPP_HAS_THREAD_API_WIN32)
+#if (defined(_LIBCPP_HAS_THREAD_API_C11) && defined(__Fuchsia__)) || \
+     defined(_LIBCPP_HAS_THREAD_API_WIN32)
 # define _LIBCPP_HAS_TRIVIAL_CONDVAR_DESTRUCTION
 #endif
 
@@ -1129,6 +1210,14 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #define _LIBCPP_HAS_NO_STDOUT
 #endif
 
+// Some systems do not provide gets() in their C library, for security reasons.
+#ifndef _LIBCPP_C_HAS_NO_GETS
+#  if defined(_LIBCPP_MSVCRT) || \
+      (defined(__FreeBSD_version) && __FreeBSD_version >= 1300043)
+#    define _LIBCPP_C_HAS_NO_GETS
+#  endif
+#endif
+
 #if defined(__BIONIC__) || defined(__CloudABI__) ||                            \
     defined(__Fuchsia__) || defined(__wasi__) || defined(_LIBCPP_HAS_MUSL_LIBC)
 #define _LIBCPP_PROVIDES_DEFAULT_RUNE_TABLE
@@ -1175,6 +1264,14 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #  endif
 #endif
 
+#ifndef _LIBCPP_THREAD_SAFETY_ANNOTATION
+#  ifdef _LIBCPP_HAS_THREAD_SAFETY_ANNOTATIONS
+#    define _LIBCPP_THREAD_SAFETY_ANNOTATION(x) __attribute__((x))
+#  else
+#    define _LIBCPP_THREAD_SAFETY_ANNOTATION(x)
+#  endif
+#endif  // _LIBCPP_THREAD_SAFETY_ANNOTATION
+
 #if __has_attribute(require_constant_initialization)
 #  define _LIBCPP_SAFE_STATIC __attribute__((__require_constant_initialization__))
 #else
@@ -1210,7 +1307,7 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #  define _LIBCPP_FALLTHROUGH() [[fallthrough]]
 #elif __has_cpp_attribute(clang::fallthrough)
 #  define _LIBCPP_FALLTHROUGH() [[clang::fallthrough]]
-#elif __has_attribute(fallthough) || _GNUC_VER >= 700
+#elif __has_attribute(fallthrough) || _GNUC_VER >= 700
 #  define _LIBCPP_FALLTHROUGH() __attribute__((__fallthrough__))
 #else
 #  define _LIBCPP_FALLTHROUGH() ((void)0)
@@ -1224,7 +1321,7 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 
 #ifndef _LIBCPP_NODEBUG_TYPE
 #if __has_attribute(__nodebug__) && \
-    (defined(_LIBCPP_COMPILER_CLANG) && _LIBCPP_CLANG_VER >= 900)
+    (defined(_LIBCPP_CLANG_VER) && _LIBCPP_CLANG_VER >= 900)
 #define _LIBCPP_NODEBUG_TYPE __attribute__((nodebug))
 #else
 #define _LIBCPP_NODEBUG_TYPE
@@ -1257,10 +1354,9 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #define _LIBCPP_HAS_NO_COROUTINES
 #endif
 
-// FIXME: Correct this macro when either (A) a feature test macro for the
-// spaceship operator is provided, or (B) a compiler provides a complete
-// implementation.
+#if !defined(__cpp_impl_three_way_comparison) || __cpp_impl_three_way_comparison < 201907L
 #define _LIBCPP_HAS_NO_SPACESHIP_OPERATOR
+#endif
 
 // Decide whether to use availability macros.
 #if !defined(_LIBCPP_BUILDING_LIBRARY) &&                                      \
@@ -1411,6 +1507,17 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 
 #define _LIBCPP_UNUSED_VAR(x) ((void)(x))
 
+// Configures the fopen close-on-exec mode character, if any. This string will
+// be appended to any mode string used by fstream for fopen/fdopen.
+//
+// Not all platforms support this, but it helps avoid fd-leaks on platforms that
+// do.
+#if defined(__BIONIC__)
+#  define _LIBCPP_FOPEN_CLOEXEC_MODE "e"
+#else
+#  define _LIBCPP_FOPEN_CLOEXEC_MODE
+#endif
+
 #endif // __cplusplus
 
 #endif // _LIBCPP_CONFIG
lib/libcxx/include/__config_site.in
@@ -29,6 +29,7 @@
 #cmakedefine _LIBCPP_NO_VCRUNTIME
 #cmakedefine01 _LIBCPP_HAS_MERGED_TYPEINFO_NAMES_DEFAULT
 #cmakedefine _LIBCPP_ABI_NAMESPACE @_LIBCPP_ABI_NAMESPACE@
+#cmakedefine _LIBCPP_HAS_PARALLEL_ALGORITHMS
 
 @_LIBCPP_ABI_DEFINES@
 
lib/libcxx/include/__debug
@@ -276,4 +276,3 @@ _LIBCPP_FUNC_VIS const __libcpp_db* __get_const_db();
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_DEBUG_H
-
lib/libcxx/include/__functional_03
@@ -104,7 +104,7 @@ class __func<_Fp, _Alloc, _Rp()>
 {
     __compressed_pair<_Fp, _Alloc> __f_;
 public:
-    explicit __func(_Fp __f) : __f_(_VSTD::move(__f)) {}
+    explicit __func(_Fp __f) : __f_(_VSTD::move(__f), __default_init_tag()) {}
     explicit __func(_Fp __f, _Alloc __a) : __f_(_VSTD::move(__f), _VSTD::move(__a)) {}
     virtual __base<_Rp()>* __clone() const;
     virtual void __clone(__base<_Rp()>*) const;
@@ -189,7 +189,7 @@ class __func<_Fp, _Alloc, _Rp(_A0)>
 {
     __compressed_pair<_Fp, _Alloc> __f_;
 public:
-    _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f) : __f_(_VSTD::move(__f)) {}
+    _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f) : __f_(_VSTD::move(__f), __default_init_tag()) {}
     _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f, _Alloc __a)
         : __f_(_VSTD::move(__f), _VSTD::move(__a)) {}
     virtual __base<_Rp(_A0)>* __clone() const;
@@ -275,7 +275,7 @@ class __func<_Fp, _Alloc, _Rp(_A0, _A1)>
 {
     __compressed_pair<_Fp, _Alloc> __f_;
 public:
-    _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f) : __f_(_VSTD::move(__f)) {}
+    _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f) : __f_(_VSTD::move(__f), __default_init_tag()) {}
     _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f, _Alloc __a)
         : __f_(_VSTD::move(__f), _VSTD::move(__a)) {}
     virtual __base<_Rp(_A0, _A1)>* __clone() const;
@@ -361,7 +361,7 @@ class __func<_Fp, _Alloc, _Rp(_A0, _A1, _A2)>
 {
     __compressed_pair<_Fp, _Alloc> __f_;
 public:
-    _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f) : __f_(_VSTD::move(__f)) {}
+    _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f) : __f_(_VSTD::move(__f), __default_init_tag()) {}
     _LIBCPP_INLINE_VISIBILITY explicit __func(_Fp __f, _Alloc __a)
         : __f_(_VSTD::move(__f), _VSTD::move(__a)) {}
     virtual __base<_Rp(_A0, _A1, _A2)>* __clone() const;
lib/libcxx/include/__functional_base
@@ -558,7 +558,7 @@ struct __is_transparent<_Tp, _Up,
 
 // allocator_arg_t
 
-struct _LIBCPP_TEMPLATE_VIS allocator_arg_t { };
+struct _LIBCPP_TEMPLATE_VIS allocator_arg_t { explicit allocator_arg_t() = default; };
 
 #if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
 extern _LIBCPP_EXPORTED_FROM_ABI const allocator_arg_t allocator_arg;
lib/libcxx/include/__hash_table
@@ -776,7 +776,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     __bucket_list_deallocator()
         _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
-        : __data_(0) {}
+        : __data_(0, __default_init_tag()) {}
 
     _LIBCPP_INLINE_VISIBILITY
     __bucket_list_deallocator(const allocator_type& __a, size_type __size)
@@ -825,11 +825,13 @@ private:
 
     allocator_type& __na_;
 
-    __hash_node_destructor& operator=(const __hash_node_destructor&);
-
 public:
     bool __value_constructed;
 
+    __hash_node_destructor(__hash_node_destructor const&) = default;
+    __hash_node_destructor& operator=(const __hash_node_destructor&) = delete;
+
+
     _LIBCPP_INLINE_VISIBILITY
     explicit __hash_node_destructor(allocator_type& __na,
                                     bool __constructed = false) _NOEXCEPT
@@ -1416,8 +1418,8 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table()
         is_nothrow_default_constructible<__node_allocator>::value &&
         is_nothrow_default_constructible<hasher>::value &&
         is_nothrow_default_constructible<key_equal>::value)
-    : __p2_(0),
-      __p3_(1.0f)
+    : __p2_(0, __default_init_tag()),
+      __p3_(1.0f, __default_init_tag())
 {
 }
 
@@ -1437,7 +1439,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const hasher& __hf,
                                                        const key_equal& __eql,
                                                        const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__second_tag(), __node_allocator(__a)),
+      __p1_(__default_init_tag(), __node_allocator(__a)),
       __p2_(0, __hf),
       __p3_(1.0f, __eql)
 {
@@ -1446,9 +1448,9 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const hasher& __hf,
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__second_tag(), __node_allocator(__a)),
-      __p2_(0),
-      __p3_(1.0f)
+      __p1_(__default_init_tag(), __node_allocator(__a)),
+      __p2_(0, __default_init_tag()),
+      __p3_(1.0f, __default_init_tag())
 {
 }
 
@@ -1458,7 +1460,7 @@ __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const __hash_table& __u)
           __bucket_list_deleter(allocator_traits<__pointer_allocator>::
               select_on_container_copy_construction(
                   __u.__bucket_list_.get_deleter().__alloc()), 0)),
-      __p1_(__second_tag(), allocator_traits<__node_allocator>::
+      __p1_(__default_init_tag(), allocator_traits<__node_allocator>::
           select_on_container_copy_construction(__u.__node_alloc())),
       __p2_(0, __u.hash_function()),
       __p3_(__u.__p3_)
@@ -1469,7 +1471,7 @@ template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(const __hash_table& __u,
                                                        const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__second_tag(), __node_allocator(__a)),
+      __p1_(__default_init_tag(), __node_allocator(__a)),
       __p2_(0, __u.hash_function()),
       __p3_(__u.__p3_)
 {
@@ -1503,7 +1505,7 @@ template <class _Tp, class _Hash, class _Equal, class _Alloc>
 __hash_table<_Tp, _Hash, _Equal, _Alloc>::__hash_table(__hash_table&& __u,
                                                        const allocator_type& __a)
     : __bucket_list_(nullptr, __bucket_list_deleter(__pointer_allocator(__a), 0)),
-      __p1_(__second_tag(), __node_allocator(__a)),
+      __p1_(__default_init_tag(), __node_allocator(__a)),
       __p2_(0, _VSTD::move(__u.hash_function())),
       __p3_(_VSTD::move(__u.__p3_))
 {
lib/libcxx/include/__libcpp_version
@@ -1,1 +1,1 @@
-9000
+10000
lib/libcxx/include/__locale
@@ -409,7 +409,7 @@ public:
     static const mask xdigit = _ISxdigit;
     static const mask blank  = _ISblank;
 #if defined(__mips__)
-    static const mask __regex_word = static_cast<char_class_type>(_ISbit(15));
+    static const mask __regex_word = static_cast<mask>(_ISbit(15));
 #else
     static const mask __regex_word = 0x80;
 #endif
lib/libcxx/include/__mutex_base
@@ -15,6 +15,7 @@
 #include <system_error>
 #include <__threading_support>
 
+#include <time.h>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -28,15 +29,6 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 
 #ifndef _LIBCPP_HAS_NO_THREADS
 
-#ifndef _LIBCPP_THREAD_SAFETY_ANNOTATION
-#  ifdef _LIBCPP_HAS_THREAD_SAFETY_ANNOTATIONS
-#    define _LIBCPP_THREAD_SAFETY_ANNOTATION(x) __attribute__((x))
-#  else
-#    define _LIBCPP_THREAD_SAFETY_ANNOTATION(x)
-#  endif
-#endif  // _LIBCPP_THREAD_SAFETY_ANNOTATION
-
-
 class _LIBCPP_TYPE_VIS _LIBCPP_THREAD_SAFETY_ANNOTATION(capability("mutex")) mutex
 {
     __libcpp_mutex_t __m_ = _LIBCPP_MUTEX_INITIALIZER;
@@ -65,9 +57,9 @@ public:
 static_assert(is_nothrow_default_constructible<mutex>::value,
               "the default constructor for std::mutex must be nothrow");
 
-struct _LIBCPP_TYPE_VIS defer_lock_t {};
-struct _LIBCPP_TYPE_VIS try_to_lock_t {};
-struct _LIBCPP_TYPE_VIS adopt_lock_t {};
+struct _LIBCPP_TYPE_VIS defer_lock_t { explicit defer_lock_t() = default; };
+struct _LIBCPP_TYPE_VIS try_to_lock_t { explicit try_to_lock_t() = default; };
+struct _LIBCPP_TYPE_VIS adopt_lock_t { explicit adopt_lock_t() = default; };
 
 #if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
 
@@ -94,10 +86,11 @@ private:
     mutex_type& __m_;
 public:
 
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY
     explicit lock_guard(mutex_type& __m) _LIBCPP_THREAD_SAFETY_ANNOTATION(acquire_capability(__m))
         : __m_(__m) {__m_.lock();}
-    _LIBCPP_INLINE_VISIBILITY
+
+    _LIBCPP_NODISCARD_EXT _LIBCPP_INLINE_VISIBILITY
     lock_guard(mutex_type& __m, adopt_lock_t) _LIBCPP_THREAD_SAFETY_ANNOTATION(requires_capability(__m))
         : __m_(__m) {}
     _LIBCPP_INLINE_VISIBILITY
@@ -336,23 +329,75 @@ public:
 private:
     void __do_timed_wait(unique_lock<mutex>& __lk,
        chrono::time_point<chrono::system_clock, chrono::nanoseconds>) _NOEXCEPT;
+#if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+    void __do_timed_wait(unique_lock<mutex>& __lk,
+       chrono::time_point<chrono::steady_clock, chrono::nanoseconds>) _NOEXCEPT;
+#endif
+    template <class _Clock>
+    void __do_timed_wait(unique_lock<mutex>& __lk,
+       chrono::time_point<_Clock, chrono::nanoseconds>) _NOEXCEPT;
 };
 #endif // !_LIBCPP_HAS_NO_THREADS
 
-template <class _To, class _Rep, class _Period>
+template <class _Rep, class _Period>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
-    chrono::__is_duration<_To>::value,
-    _To
+    is_floating_point<_Rep>::value,
+    chrono::nanoseconds
 >::type
-__ceil(chrono::duration<_Rep, _Period> __d)
+__safe_nanosecond_cast(chrono::duration<_Rep, _Period> __d)
 {
     using namespace chrono;
-    _To __r = duration_cast<_To>(__d);
-    if (__r < __d)
-        ++__r;
-    return __r;
+    using __ratio = ratio_divide<_Period, nano>;
+    using __ns_rep = nanoseconds::rep;
+    _Rep __result_float = __d.count() * __ratio::num / __ratio::den;
+
+    _Rep __result_max = numeric_limits<__ns_rep>::max();
+    if (__result_float >= __result_max) {
+        return nanoseconds::max();
+    }
+
+    _Rep __result_min = numeric_limits<__ns_rep>::min();
+    if (__result_float <= __result_min) {
+        return nanoseconds::min();
+    }
+
+    return nanoseconds(static_cast<__ns_rep>(__result_float));
+}
+
+template <class _Rep, class _Period>
+inline _LIBCPP_INLINE_VISIBILITY
+typename enable_if
+<
+    !is_floating_point<_Rep>::value,
+    chrono::nanoseconds
+>::type
+__safe_nanosecond_cast(chrono::duration<_Rep, _Period> __d)
+{
+    using namespace chrono;
+    if (__d.count() == 0) {
+        return nanoseconds(0);
+    }
+
+    using __ratio = ratio_divide<_Period, nano>;
+    using __ns_rep = nanoseconds::rep;
+    __ns_rep __result_max = std::numeric_limits<__ns_rep>::max();
+    if (__d.count() > 0 && __d.count() > __result_max / __ratio::num) {
+        return nanoseconds::max();
+    }
+
+    __ns_rep __result_min = std::numeric_limits<__ns_rep>::min();
+    if (__d.count() < 0 && __d.count() < __result_min / __ratio::num) {
+        return nanoseconds::min();
+    }
+
+    __ns_rep __result = __d.count() * __ratio::num / __ratio::den;
+    if (__result == 0) {
+        return nanoseconds(1);
+    }
+
+    return nanoseconds(__result);
 }
 
 #ifndef _LIBCPP_HAS_NO_THREADS
@@ -370,7 +415,15 @@ condition_variable::wait_until(unique_lock<mutex>& __lk,
                                const chrono::time_point<_Clock, _Duration>& __t)
 {
     using namespace chrono;
-    wait_for(__lk, __t - _Clock::now());
+    using __clock_tp_ns = time_point<_Clock, nanoseconds>;
+
+    typename _Clock::time_point __now = _Clock::now();
+    if (__t <= __now)
+        return cv_status::timeout;
+
+    __clock_tp_ns __t_ns = __clock_tp_ns(__safe_nanosecond_cast(__t.time_since_epoch()));
+
+    __do_timed_wait(__lk, __t_ns);
     return _Clock::now() < __t ? cv_status::no_timeout : cv_status::timeout;
 }
 
@@ -396,15 +449,25 @@ condition_variable::wait_for(unique_lock<mutex>& __lk,
     using namespace chrono;
     if (__d <= __d.zero())
         return cv_status::timeout;
-    typedef time_point<system_clock, duration<long double, nano> > __sys_tpf;
-    typedef time_point<system_clock, nanoseconds> __sys_tpi;
-    __sys_tpf _Max = __sys_tpi::max();
+    using __ns_rep = nanoseconds::rep;
     steady_clock::time_point __c_now = steady_clock::now();
-    system_clock::time_point __s_now = system_clock::now();
-    if (_Max - __d > __s_now)
-        __do_timed_wait(__lk, __s_now + __ceil<nanoseconds>(__d));
-    else
-        __do_timed_wait(__lk, __sys_tpi::max());
+
+#if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+    using __clock_tp_ns = time_point<steady_clock, nanoseconds>;
+    __ns_rep __now_count_ns = __safe_nanosecond_cast(__c_now.time_since_epoch()).count();
+#else
+    using __clock_tp_ns = time_point<system_clock, nanoseconds>;
+    __ns_rep __now_count_ns = __safe_nanosecond_cast(system_clock::now().time_since_epoch()).count();
+#endif
+
+    __ns_rep __d_ns_count = __safe_nanosecond_cast(__d).count();
+
+    if (__now_count_ns > numeric_limits<__ns_rep>::max() - __d_ns_count) {
+        __do_timed_wait(__lk, __clock_tp_ns::max());
+    } else {
+        __do_timed_wait(__lk, __clock_tp_ns(nanoseconds(__now_count_ns + __d_ns_count)));
+    }
+
     return steady_clock::now() - __c_now < __d ? cv_status::no_timeout :
                                                  cv_status::timeout;
 }
@@ -420,6 +483,46 @@ condition_variable::wait_for(unique_lock<mutex>& __lk,
                       _VSTD::move(__pred));
 }
 
+#if defined(_LIBCPP_HAS_COND_CLOCKWAIT)
+inline
+void
+condition_variable::__do_timed_wait(unique_lock<mutex>& __lk,
+     chrono::time_point<chrono::steady_clock, chrono::nanoseconds> __tp) _NOEXCEPT
+{
+    using namespace chrono;
+    if (!__lk.owns_lock())
+        __throw_system_error(EPERM,
+                            "condition_variable::timed wait: mutex not locked");
+    nanoseconds __d = __tp.time_since_epoch();
+    timespec __ts;
+    seconds __s = duration_cast<seconds>(__d);
+    using __ts_sec = decltype(__ts.tv_sec);
+    const __ts_sec __ts_sec_max = numeric_limits<__ts_sec>::max();
+    if (__s.count() < __ts_sec_max)
+    {
+        __ts.tv_sec = static_cast<__ts_sec>(__s.count());
+        __ts.tv_nsec = (__d - __s).count();
+    }
+    else
+    {
+        __ts.tv_sec = __ts_sec_max;
+        __ts.tv_nsec = giga::num - 1;
+    }
+    int __ec = pthread_cond_clockwait(&__cv_, __lk.mutex()->native_handle(), CLOCK_MONOTONIC, &__ts);
+    if (__ec != 0 && __ec != ETIMEDOUT)
+        __throw_system_error(__ec, "condition_variable timed_wait failed");
+}
+#endif // _LIBCPP_HAS_COND_CLOCKWAIT
+
+template <class _Clock>
+inline
+void
+condition_variable::__do_timed_wait(unique_lock<mutex>& __lk,
+     chrono::time_point<_Clock, chrono::nanoseconds> __tp) _NOEXCEPT
+{
+    wait_for(__lk, __tp - _Clock::now());
+}
+
 #endif // !_LIBCPP_HAS_NO_THREADS
 
 _LIBCPP_END_NAMESPACE_STD
lib/libcxx/include/__split_buffer
@@ -116,15 +116,15 @@ public:
     template <class _InputIter>
         typename enable_if
         <
-            __is_input_iterator<_InputIter>::value &&
-           !__is_forward_iterator<_InputIter>::value,
+            __is_cpp17_input_iterator<_InputIter>::value &&
+           !__is_cpp17_forward_iterator<_InputIter>::value,
             void
         >::type
         __construct_at_end(_InputIter __first, _InputIter __last);
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value,
+            __is_cpp17_forward_iterator<_ForwardIterator>::value,
             void
         >::type
         __construct_at_end(_ForwardIterator __first, _ForwardIterator __last);
@@ -161,6 +161,19 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     void __move_assign_alloc(__split_buffer&, false_type) _NOEXCEPT
         {}
+
+    struct _ConstructTransaction {
+      explicit _ConstructTransaction(pointer* __p, size_type __n) _NOEXCEPT
+      : __pos_(*__p), __end_(*__p + __n), __dest_(__p) {
+      }
+      ~_ConstructTransaction() {
+        *__dest_ = __pos_;
+      }
+      pointer __pos_;
+     const pointer __end_;
+    private:
+     pointer *__dest_;
+    };
 };
 
 template <class _Tp, class _Allocator>
@@ -197,13 +210,10 @@ template <class _Tp, class _Allocator>
 void
 __split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n)
 {
-    __alloc_rr& __a = this->__alloc();
-    do
-    {
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_));
-        ++this->__end_;
-        --__n;
-    } while (__n > 0);
+    _ConstructTransaction __tx(&this->__end_, __n);
+    for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
+        __alloc_traits::construct(this->__alloc(), _VSTD::__to_address(__tx.__pos_));
+    }
 }
 
 //  Copy constructs __n objects starting at __end_ from __x
@@ -216,21 +226,19 @@ template <class _Tp, class _Allocator>
 void
 __split_buffer<_Tp, _Allocator>::__construct_at_end(size_type __n, const_reference __x)
 {
-    __alloc_rr& __a = this->__alloc();
-    do
-    {
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), __x);
-        ++this->__end_;
-        --__n;
-    } while (__n > 0);
+    _ConstructTransaction __tx(&this->__end_, __n);
+    for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
+        __alloc_traits::construct(this->__alloc(),
+            _VSTD::__to_address(__tx.__pos_), __x);
+    }
 }
 
 template <class _Tp, class _Allocator>
 template <class _InputIter>
 typename enable_if
 <
-     __is_input_iterator<_InputIter>::value &&
-    !__is_forward_iterator<_InputIter>::value,
+     __is_cpp17_input_iterator<_InputIter>::value &&
+    !__is_cpp17_forward_iterator<_InputIter>::value,
     void
 >::type
 __split_buffer<_Tp, _Allocator>::__construct_at_end(_InputIter __first, _InputIter __last)
@@ -245,10 +253,10 @@ __split_buffer<_Tp, _Allocator>::__construct_at_end(_InputIter __first, _InputIt
             __split_buffer __buf(__new_cap, 0, __a);
             for (pointer __p = __begin_; __p != __end_; ++__p, ++__buf.__end_)
                 __alloc_traits::construct(__buf.__alloc(),
-                        _VSTD::__to_raw_pointer(__buf.__end_), _VSTD::move(*__p));
+                        _VSTD::__to_address(__buf.__end_), _VSTD::move(*__p));
             swap(__buf);
         }
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), *__first);
+        __alloc_traits::construct(__a, _VSTD::__to_address(this->__end_), *__first);
         ++this->__end_;
     }
 }
@@ -257,16 +265,15 @@ template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value,
+    __is_cpp17_forward_iterator<_ForwardIterator>::value,
     void
 >::type
 __split_buffer<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last)
 {
-    __alloc_rr& __a = this->__alloc();
-    for (; __first != __last; ++__first)
-    {
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), *__first);
-        ++this->__end_;
+    _ConstructTransaction __tx(&this->__end_, std::distance(__first, __last));
+    for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_, ++__first) {
+        __alloc_traits::construct(this->__alloc(),
+            _VSTD::__to_address(__tx.__pos_), *__first);
     }
 }
 
@@ -276,7 +283,7 @@ void
 __split_buffer<_Tp, _Allocator>::__destruct_at_begin(pointer __new_begin, false_type)
 {
     while (__begin_ != __new_begin)
-        __alloc_traits::destroy(__alloc(), __to_raw_pointer(__begin_++));
+        __alloc_traits::destroy(__alloc(), __to_address(__begin_++));
 }
 
 template <class _Tp, class _Allocator>
@@ -293,7 +300,7 @@ void
 __split_buffer<_Tp, _Allocator>::__destruct_at_end(pointer __new_last, false_type) _NOEXCEPT
 {
     while (__new_last != __end_)
-        __alloc_traits::destroy(__alloc(), __to_raw_pointer(--__end_));
+        __alloc_traits::destroy(__alloc(), __to_address(--__end_));
 }
 
 template <class _Tp, class _Allocator>
@@ -317,7 +324,7 @@ template <class _Tp, class _Allocator>
 inline
 __split_buffer<_Tp, _Allocator>::__split_buffer()
     _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
-    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr)
+    : __first_(nullptr), __begin_(nullptr), __end_(nullptr), __end_cap_(nullptr, __default_init_tag())
 {
 }
 
@@ -361,7 +368,7 @@ __split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c)
 
 template <class _Tp, class _Allocator>
 __split_buffer<_Tp, _Allocator>::__split_buffer(__split_buffer&& __c, const __alloc_rr& __a)
-    : __end_cap_(__second_tag(), __a)
+    : __end_cap_(nullptr, __a)
 {
     if (__a == __c.__alloc())
     {
@@ -488,7 +495,7 @@ __split_buffer<_Tp, _Allocator>::push_front(const_reference __x)
             _VSTD::swap(__end_cap(), __t.__end_cap());
         }
     }
-    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__begin_-1), __x);
+    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__begin_-1), __x);
     --__begin_;
 }
 
@@ -519,7 +526,7 @@ __split_buffer<_Tp, _Allocator>::push_front(value_type&& __x)
             _VSTD::swap(__end_cap(), __t.__end_cap());
         }
     }
-    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__begin_-1),
+    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__begin_-1),
             _VSTD::move(__x));
     --__begin_;
 }
@@ -552,7 +559,7 @@ __split_buffer<_Tp, _Allocator>::push_back(const_reference __x)
             _VSTD::swap(__end_cap(), __t.__end_cap());
         }
     }
-    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__end_), __x);
+    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__end_), __x);
     ++__end_;
 }
 
@@ -583,7 +590,7 @@ __split_buffer<_Tp, _Allocator>::push_back(value_type&& __x)
             _VSTD::swap(__end_cap(), __t.__end_cap());
         }
     }
-    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__end_),
+    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__end_),
             _VSTD::move(__x));
     ++__end_;
 }
@@ -614,7 +621,7 @@ __split_buffer<_Tp, _Allocator>::emplace_back(_Args&&... __args)
             _VSTD::swap(__end_cap(), __t.__end_cap());
         }
     }
-    __alloc_traits::construct(__alloc(), _VSTD::__to_raw_pointer(__end_),
+    __alloc_traits::construct(__alloc(), _VSTD::__to_address(__end_),
                               _VSTD::forward<_Args>(__args)...);
     ++__end_;
 }
lib/libcxx/include/__string
@@ -31,11 +31,12 @@ struct char_traits
 
     static constexpr int    compare(const char_type* s1, const char_type* s2, size_t n);
     static constexpr size_t length(const char_type* s);
-    static constexpr const char_type* 
+    static constexpr const char_type*
                             find(const char_type* s, size_t n, const char_type& a);
-    static char_type*       move(char_type* s1, const char_type* s2, size_t n);
-    static char_type*       copy(char_type* s1, const char_type* s2, size_t n);
-    static char_type*       assign(char_type* s, size_t n, char_type a);
+
+    static constexpr char_type* move(char_type* s1, const char_type* s2, size_t n); // constexpr in C++20
+    static constexpr char_type* copy(char_type* s1, const char_type* s2, size_t n); // constexpr in C++20
+    static constexpr char_type* assign(char_type* s, size_t n, char_type a);        // constexpr in C++20
 
     static constexpr int_type  not_eof(int_type c) noexcept;
     static constexpr char_type to_char_type(int_type c) noexcept;
@@ -93,11 +94,14 @@ struct _LIBCPP_TEMPLATE_VIS char_traits
     size_t length(const char_type* __s);
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
     const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
-    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n);
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17
+    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n);
     _LIBCPP_INLINE_VISIBILITY
-    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17
+    char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
     _LIBCPP_INLINE_VISIBILITY
-    static char_type*       assign(char_type* __s, size_t __n, char_type __a);
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17
+    char_type*       assign(char_type* __s, size_t __n, char_type __a);
 
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
         {return eq_int_type(__c, eof()) ? ~eof() : __c;}
@@ -151,9 +155,10 @@ char_traits<_CharT>::find(const char_type* __s, size_t __n, const char_type& __a
 }
 
 template <class _CharT>
-_CharT*
+_LIBCPP_CONSTEXPR_AFTER_CXX17 _CharT*
 char_traits<_CharT>::move(char_type* __s1, const char_type* __s2, size_t __n)
 {
+    if (__n == 0) return __s1;
     char_type* __r = __s1;
     if (__s1 < __s2)
     {
@@ -171,7 +176,7 @@ char_traits<_CharT>::move(char_type* __s1, const char_type* __s2, size_t __n)
 }
 
 template <class _CharT>
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 _CharT*
 char_traits<_CharT>::copy(char_type* __s1, const char_type* __s2, size_t __n)
 {
@@ -183,7 +188,7 @@ char_traits<_CharT>::copy(char_type* __s1, const char_type* __s2, size_t __n)
 }
 
 template <class _CharT>
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 _CharT*
 char_traits<_CharT>::assign(char_type* __s, size_t __n, char_type __a)
 {
@@ -193,6 +198,37 @@ char_traits<_CharT>::assign(char_type* __s, size_t __n, char_type __a)
     return __r;
 }
 
+// constexpr versions of move/copy/assign.
+
+template <class _CharT>
+static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+_CharT* __move_constexpr(_CharT* __s1, const _CharT* __s2, size_t __n) _NOEXCEPT
+{
+    if (__n == 0) return __s1;
+    if (__s1 < __s2) {
+      _VSTD::copy(__s2, __s2 + __n, __s1);
+    } else if (__s2 < __s1) {
+      _VSTD::copy_backward(__s2, __s2 + __n, __s1 + __n);
+    }
+    return __s1;
+}
+
+template <class _CharT>
+static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+_CharT* __copy_constexpr(_CharT* __s1, const _CharT* __s2, size_t __n) _NOEXCEPT
+{
+    _VSTD::copy_n(__s2, __n, __s1);
+    return __s1;
+}
+
+template <class _CharT>
+static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+_CharT* __assign_constexpr(_CharT* __s, size_t __n, _CharT __a) _NOEXCEPT
+{
+     _VSTD::fill_n(__s, __n, __a);
+     return __s;
+}
+
 // char_traits<char>
 
 template <>
@@ -217,15 +253,28 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char>
     length(const char_type* __s)  _NOEXCEPT {return __builtin_strlen(__s);}
     static _LIBCPP_CONSTEXPR_AFTER_CXX14
     const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
-    static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
-        {return __n == 0 ? __s1 : (char_type*) memmove(__s1, __s2, __n);}
-    static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {
+            return __libcpp_is_constant_evaluated()
+                       ? __move_constexpr(__s1, __s2, __n)
+                       : __n == 0 ? __s1 : (char_type*)memmove(__s1, __s2, __n);
+        }
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
         {
             _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-            return __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
+            return __libcpp_is_constant_evaluated()
+                       ? __copy_constexpr(__s1, __s2, __n)
+                       : __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
+        }
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+        {
+            return __libcpp_is_constant_evaluated()
+                       ? __assign_constexpr(__s, __n, __a)
+                       : __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);
         }
-    static inline char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
-        {return __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);}
 
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
         {return eq_int_type(__c, eof()) ? ~eof() : __c;}
@@ -307,16 +356,28 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<wchar_t>
     size_t length(const char_type* __s) _NOEXCEPT;
     static _LIBCPP_CONSTEXPR_AFTER_CXX14
     const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
-    static inline char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
-        {return __n == 0 ? __s1 : (char_type*)wmemmove(__s1, __s2, __n);}
-    static inline char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type* move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {
+            return __libcpp_is_constant_evaluated()
+                       ? __move_constexpr(__s1, __s2, __n)
+                       : __n == 0 ? __s1 : wmemmove(__s1, __s2, __n);
+        }
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type* copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
         {
             _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-            return __n == 0 ? __s1 : (char_type*)wmemcpy(__s1, __s2, __n);
+            return __libcpp_is_constant_evaluated()
+                       ? __copy_constexpr(__s1, __s2, __n)
+                       : __n == 0 ? __s1 : wmemcpy(__s1, __s2, __n);
+        }
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+        {
+            return __libcpp_is_constant_evaluated()
+                       ? __assign_constexpr(__s, __n, __a)
+                       : __n == 0 ? __s : wmemset(__s, __a, __n);
         }
-    static inline char_type* assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
-        {return __n == 0 ? __s : (char_type*)wmemset(__s, __a, __n);}
-
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
         {return eq_int_type(__c, eof()) ? ~eof() : __c;}
     static inline _LIBCPP_CONSTEXPR char_type to_char_type(int_type __c) _NOEXCEPT
@@ -351,6 +412,18 @@ char_traits<wchar_t>::compare(const char_type* __s1, const char_type* __s2, size
 #endif
 }
 
+
+template <class _Traits>
+_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_CONSTEXPR
+inline size_t __char_traits_length_checked(const typename _Traits::char_type* __s) _NOEXCEPT {
+#if _LIBCPP_DEBUG_LEVEL >= 1
+  return __s ? _Traits::length(__s) : (_VSTD::__libcpp_debug_function(_VSTD::__libcpp_debug_info(__FILE__, __LINE__, "p == nullptr", "null pointer pass to non-null argument of char_traits<...>::length")), 0);
+#else
+  return _Traits::length(__s);
+#endif
+}
+
 inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 size_t
 char_traits<wchar_t>::length(const char_type* __s) _NOEXCEPT
@@ -412,21 +485,34 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char8_t>
 
     static constexpr
     size_t           length(const char_type* __s) _NOEXCEPT;
- 
+
     _LIBCPP_INLINE_VISIBILITY static constexpr
     const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
- 
-    static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
-        {return __n == 0 ? __s1 : (char_type*) memmove(__s1, __s2, __n);}
- 
-    static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+        {
+            return __libcpp_is_constant_evaluated()
+                       ? __move_constexpr(__s1, __s2, __n)
+                       : __n == 0 ? __s1 : (char_type*)memmove(__s1, __s2, __n);
+        }
+
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
        {
             _LIBCPP_ASSERT(__s2 < __s1 || __s2 >= __s1+__n, "char_traits::copy overlapped range");
-            return __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
-       }
- 
-    static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
-        {return __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);}
+            return __libcpp_is_constant_evaluated()
+                       ? __copy_constexpr(__s1, __s2, __n)
+                       : __n == 0 ? __s1 : (char_type*)memcpy(__s1, __s2, __n);
+        }
+
+    static _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
+    char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
+        {
+            return __libcpp_is_constant_evaluated()
+                       ? __assign_constexpr(__s, __n, __a)
+                       : __n == 0 ? __s : (char_type*)memset(__s, to_int_type(__a), __n);
+        }
 
     static inline constexpr int_type  not_eof(int_type __c) noexcept
         {return eq_int_type(__c, eof()) ? ~eof() : __c;}
@@ -509,11 +595,11 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char16_t>
     size_t           length(const char_type* __s) _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
     const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT;
 
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
@@ -565,10 +651,11 @@ char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& _
     return 0;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 char16_t*
 char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
+    if (__n == 0) return __s1;
     char_type* __r = __s1;
     if (__s1 < __s2)
     {
@@ -585,7 +672,7 @@ char_traits<char16_t>::move(char_type* __s1, const char_type* __s2, size_t __n)
     return __r;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 char16_t*
 char_traits<char16_t>::copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
@@ -596,7 +683,7 @@ char_traits<char16_t>::copy(char_type* __s1, const char_type* __s2, size_t __n)
     return __r;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 char16_t*
 char_traits<char16_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
 {
@@ -628,11 +715,11 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char32_t>
     size_t           length(const char_type* __s) _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
     const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
     static char_type*       assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT;
 
     static inline _LIBCPP_CONSTEXPR int_type  not_eof(int_type __c) _NOEXCEPT
@@ -684,10 +771,11 @@ char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& _
     return 0;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 char32_t*
 char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
+    if (__n == 0) return __s1;
     char_type* __r = __s1;
     if (__s1 < __s2)
     {
@@ -704,7 +792,7 @@ char_traits<char32_t>::move(char_type* __s1, const char_type* __s2, size_t __n)
     return __r;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 char32_t*
 char_traits<char32_t>::copy(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
@@ -715,7 +803,7 @@ char_traits<char32_t>::copy(char_type* __s1, const char_type* __s2, size_t __n)
     return __r;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX17
 char32_t*
 char_traits<char32_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCEPT
 {
@@ -732,7 +820,7 @@ char_traits<char32_t>::assign(char_type* __s, size_t __n, char_type __a) _NOEXCE
 // __str_find
 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find(const _CharT *__p, _SizeT __sz, 
+__str_find(const _CharT *__p, _SizeT __sz,
              _CharT __c, _SizeT __pos) _NOEXCEPT
 {
     if (__pos >= __sz)
@@ -784,7 +872,7 @@ __search_substring(const _CharT *__first1, const _CharT *__last1,
 
 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_find(const _CharT *__p, _SizeT __sz, 
+__str_find(const _CharT *__p, _SizeT __sz,
        const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
 {
     if (__pos > __sz)
@@ -806,7 +894,7 @@ __str_find(const _CharT *__p, _SizeT __sz,
 
 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_rfind(const _CharT *__p, _SizeT __sz, 
+__str_rfind(const _CharT *__p, _SizeT __sz,
               _CharT __c, _SizeT __pos) _NOEXCEPT
 {
     if (__sz < 1)
@@ -825,7 +913,7 @@ __str_rfind(const _CharT *__p, _SizeT __sz,
 
 template<class _CharT, class _SizeT, class _Traits, _SizeT __npos>
 inline _SizeT _LIBCPP_CONSTEXPR_AFTER_CXX11 _LIBCPP_INLINE_VISIBILITY
-__str_rfind(const _CharT *__p, _SizeT __sz, 
+__str_rfind(const _CharT *__p, _SizeT __sz,
         const _CharT* __s, _SizeT __pos, _SizeT __n) _NOEXCEPT
 {
     __pos = _VSTD::min(__pos, __sz);
@@ -834,7 +922,7 @@ __str_rfind(const _CharT *__p, _SizeT __sz,
     else
         __pos = __sz;
     const _CharT* __r = _VSTD::__find_end(
-                  __p, __p + __pos, __s, __s + __n, _Traits::eq, 
+                  __p, __p + __pos, __s, __s + __n, _Traits::eq,
                         random_access_iterator_tag(), random_access_iterator_tag());
     if (__n > 0 && __r == __p + __pos)
         return __npos;
@@ -963,7 +1051,7 @@ struct __quoted_output_proxy
 
     __quoted_output_proxy(_Iter __f, _Iter __l, _CharT __d, _CharT __e)
     : __first(__f), __last(__l), __delim(__d), __escape(__e) {}
-    //  This would be a nice place for a string_ref 
+    //  This would be a nice place for a string_ref
 };
 
 _LIBCPP_END_NAMESPACE_STD
lib/libcxx/include/__threading_support
@@ -23,16 +23,13 @@
 # include <__external_threading>
 #elif !defined(_LIBCPP_HAS_NO_THREADS)
 
-typedef ::timespec __libcpp_timespec_t;
-
 #if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
 # include <pthread.h>
 # include <sched.h>
+#elif defined(_LIBCPP_HAS_THREAD_API_C11)
+# include <threads.h>
 #endif
 
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
 #if defined(_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL) || \
     defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL) || \
     defined(_LIBCPP_HAS_THREAD_API_WIN32)
@@ -47,8 +44,16 @@ _LIBCPP_PUSH_MACROS
 #define _LIBCPP_NO_THREAD_SAFETY_ANALYSIS
 #endif
 
+typedef ::timespec __libcpp_timespec_t;
+#endif // !defined(_LIBCPP_HAS_NO_THREADS)
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
+#if !defined(_LIBCPP_HAS_NO_THREADS)
+
 #if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
 // Mutex
 typedef pthread_mutex_t __libcpp_mutex_t;
@@ -76,7 +81,36 @@ typedef pthread_t __libcpp_thread_t;
 typedef pthread_key_t __libcpp_tls_key;
 
 #define _LIBCPP_TLS_DESTRUCTOR_CC
-#else
+#elif defined(_LIBCPP_HAS_THREAD_API_C11)
+// Mutex
+typedef mtx_t __libcpp_mutex_t;
+// mtx_t is a struct so using {} for initialization is valid.
+#define _LIBCPP_MUTEX_INITIALIZER {}
+
+typedef mtx_t __libcpp_recursive_mutex_t;
+
+// Condition Variable
+typedef cnd_t __libcpp_condvar_t;
+// cnd_t is a struct so using {} for initialization is valid.
+#define _LIBCPP_CONDVAR_INITIALIZER {}
+
+// Execute once
+typedef once_flag __libcpp_exec_once_flag;
+#define _LIBCPP_EXEC_ONCE_INITIALIZER ONCE_FLAG_INIT
+
+// Thread id
+typedef thrd_t __libcpp_thread_id;
+
+// Thread
+#define _LIBCPP_NULL_THREAD 0U
+
+typedef thrd_t __libcpp_thread_t;
+
+// Thread Local Storage
+typedef tss_t __libcpp_tls_key;
+
+#define _LIBCPP_TLS_DESTRUCTOR_CC
+#elif !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
 // Mutex
 typedef void* __libcpp_mutex_t;
 #define _LIBCPP_MUTEX_INITIALIZER 0
@@ -109,8 +143,9 @@ typedef void* __libcpp_thread_t;
 typedef long __libcpp_tls_key;
 
 #define _LIBCPP_TLS_DESTRUCTOR_CC __stdcall
-#endif
+#endif // !defined(_LIBCPP_HAS_THREAD_API_PTHREAD) && !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
 
+#if !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
 // Mutex
 _LIBCPP_THREAD_ABI_VISIBILITY
 int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m);
@@ -205,9 +240,38 @@ void *__libcpp_tls_get(__libcpp_tls_key __key);
 _LIBCPP_THREAD_ABI_VISIBILITY
 int __libcpp_tls_set(__libcpp_tls_key __key, void *__p);
 
+#endif // !defined(_LIBCPP_HAS_THREAD_API_EXTERNAL)
+
 #if (!defined(_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL) || \
-     defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL)) && \
-    defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
+     defined(_LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL))
+
+namespace __thread_detail {
+
+inline __libcpp_timespec_t __convert_to_timespec(const chrono::nanoseconds& __ns)
+{
+  using namespace chrono;
+  seconds __s = duration_cast<seconds>(__ns);
+  __libcpp_timespec_t __ts;
+  typedef decltype(__ts.tv_sec) __ts_sec;
+  const __ts_sec __ts_sec_max = numeric_limits<__ts_sec>::max();
+
+  if (__s.count() < __ts_sec_max)
+  {
+    __ts.tv_sec = static_cast<__ts_sec>(__s.count());
+    __ts.tv_nsec = static_cast<decltype(__ts.tv_nsec)>((__ns - __s).count());
+  }
+  else
+  {
+    __ts.tv_sec = __ts_sec_max;
+    __ts.tv_nsec = 999999999; // (10^9 - 1)
+  }
+
+  return __ts;
+}
+
+}
+
+#if defined(_LIBCPP_HAS_THREAD_API_PTHREAD)
 
 int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
 {
@@ -357,23 +421,7 @@ void __libcpp_thread_yield()
 
 void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
 {
-   using namespace chrono;
-   seconds __s = duration_cast<seconds>(__ns);
-   __libcpp_timespec_t __ts;
-   typedef decltype(__ts.tv_sec) ts_sec;
-   _LIBCPP_CONSTEXPR ts_sec __ts_sec_max = numeric_limits<ts_sec>::max();
-
-   if (__s.count() < __ts_sec_max)
-   {
-     __ts.tv_sec = static_cast<ts_sec>(__s.count());
-     __ts.tv_nsec = static_cast<decltype(__ts.tv_nsec)>((__ns - __s).count());
-   }
-   else
-   {
-     __ts.tv_sec = __ts_sec_max;
-     __ts.tv_nsec = 999999999; // (10^9 - 1)
-   }
-
+   __libcpp_timespec_t __ts = __thread_detail::__convert_to_timespec(__ns);
    while (nanosleep(&__ts, &__ts) == -1 && errno == EINTR);
 }
 
@@ -393,6 +441,165 @@ int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
     return pthread_setspecific(__key, __p);
 }
 
+#elif defined(_LIBCPP_HAS_THREAD_API_C11)
+
+int __libcpp_recursive_mutex_init(__libcpp_recursive_mutex_t *__m)
+{
+  return mtx_init(__m, mtx_plain | mtx_recursive) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_recursive_mutex_lock(__libcpp_recursive_mutex_t *__m)
+{
+  return mtx_lock(__m) == thrd_success ? 0 : EINVAL;
+}
+
+bool __libcpp_recursive_mutex_trylock(__libcpp_recursive_mutex_t *__m)
+{
+  return mtx_trylock(__m) == thrd_success;
+}
+
+int __libcpp_recursive_mutex_unlock(__libcpp_mutex_t *__m)
+{
+  return mtx_unlock(__m) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m)
+{
+  mtx_destroy(__m);
+  return 0;
+}
+
+int __libcpp_mutex_lock(__libcpp_mutex_t *__m)
+{
+  return mtx_lock(__m) == thrd_success ? 0 : EINVAL;
+}
+
+bool __libcpp_mutex_trylock(__libcpp_mutex_t *__m)
+{
+  return mtx_trylock(__m) == thrd_success;
+}
+
+int __libcpp_mutex_unlock(__libcpp_mutex_t *__m)
+{
+  return mtx_unlock(__m) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_mutex_destroy(__libcpp_mutex_t *__m)
+{
+  mtx_destroy(__m);
+  return 0;
+}
+
+// Condition Variable
+int __libcpp_condvar_signal(__libcpp_condvar_t *__cv)
+{
+  return cnd_signal(__cv) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_condvar_broadcast(__libcpp_condvar_t *__cv)
+{
+  return cnd_broadcast(__cv) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_condvar_wait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m)
+{
+  return cnd_wait(__cv, __m) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_condvar_timedwait(__libcpp_condvar_t *__cv, __libcpp_mutex_t *__m,
+                               timespec *__ts)
+{
+  int __ec = cnd_timedwait(__cv, __m, __ts);
+  return __ec == thrd_timedout ? ETIMEDOUT : __ec;
+}
+
+int __libcpp_condvar_destroy(__libcpp_condvar_t *__cv)
+{
+  cnd_destroy(__cv);
+  return 0;
+}
+
+// Execute once
+int __libcpp_execute_once(__libcpp_exec_once_flag *flag,
+                          void (*init_routine)(void)) {
+  ::call_once(flag, init_routine);
+  return 0;
+}
+
+// Thread id
+// Returns non-zero if the thread ids are equal, otherwise 0
+bool __libcpp_thread_id_equal(__libcpp_thread_id t1, __libcpp_thread_id t2)
+{
+  return thrd_equal(t1, t2) != 0;
+}
+
+// Returns non-zero if t1 < t2, otherwise 0
+bool __libcpp_thread_id_less(__libcpp_thread_id t1, __libcpp_thread_id t2)
+{
+  return t1 < t2;
+}
+
+// Thread
+bool __libcpp_thread_isnull(const __libcpp_thread_t *__t) {
+  return *__t == 0;
+}
+
+int __libcpp_thread_create(__libcpp_thread_t *__t, void *(*__func)(void *),
+                           void *__arg)
+{
+  int __ec = thrd_create(__t, reinterpret_cast<thrd_start_t>(__func), __arg);
+  return __ec == thrd_nomem ? ENOMEM : __ec;
+}
+
+__libcpp_thread_id __libcpp_thread_get_current_id()
+{
+  return thrd_current();
+}
+
+__libcpp_thread_id __libcpp_thread_get_id(const __libcpp_thread_t *__t)
+{
+  return *__t;
+}
+
+int __libcpp_thread_join(__libcpp_thread_t *__t)
+{
+  return thrd_join(*__t, nullptr) == thrd_success ? 0 : EINVAL;
+}
+
+int __libcpp_thread_detach(__libcpp_thread_t *__t)
+{
+  return thrd_detach(*__t) == thrd_success ? 0 : EINVAL;
+}
+
+void __libcpp_thread_yield()
+{
+  thrd_yield();
+}
+
+void __libcpp_thread_sleep_for(const chrono::nanoseconds& __ns)
+{
+   __libcpp_timespec_t __ts = __thread_detail::__convert_to_timespec(__ns);
+  thrd_sleep(&__ts, nullptr);
+}
+
+// Thread local storage
+int __libcpp_tls_create(__libcpp_tls_key *__key, void (*__at_exit)(void *))
+{
+  return tss_create(__key, __at_exit) == thrd_success ? 0 : EINVAL;
+}
+
+void *__libcpp_tls_get(__libcpp_tls_key __key)
+{
+  return tss_get(__key);
+}
+
+int __libcpp_tls_set(__libcpp_tls_key __key, void *__p)
+{
+  return tss_set(__key, __p) == thrd_success ? 0 : EINVAL;
+}
+
+#endif
+
 #endif // !_LIBCPP_HAS_THREAD_LIBRARY_EXTERNAL || _LIBCPP_BUILDING_THREAD_LIBRARY_EXTERNAL
 
 class _LIBCPP_TYPE_VIS thread;
@@ -447,7 +654,7 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     void __reset() { __id_ = 0; }
-    
+
     template<class _CharT, class _Traits>
     friend
     _LIBCPP_INLINE_VISIBILITY
@@ -475,10 +682,10 @@ get_id() _NOEXCEPT
 
 }  // this_thread
 
+#endif // !_LIBCPP_HAS_NO_THREADS
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
-#endif // !_LIBCPP_HAS_NO_THREADS
-
 #endif // _LIBCPP_THREADING_SUPPORT
lib/libcxx/include/__tree
@@ -775,11 +775,14 @@ private:
     typedef __tree_node_types<pointer> _NodeTypes;
     allocator_type& __na_;
 
-    __tree_node_destructor& operator=(const __tree_node_destructor&);
 
 public:
     bool __value_constructed;
 
+
+    __tree_node_destructor(const __tree_node_destructor &) = default;
+    __tree_node_destructor& operator=(const __tree_node_destructor&) = delete;
+
     _LIBCPP_INLINE_VISIBILITY
     explicit __tree_node_destructor(allocator_type& __na, bool __val = false) _NOEXCEPT
         : __na_(__na),
@@ -1574,8 +1577,8 @@ __tree<_Tp, _Compare, _Allocator>::__tree(const value_compare& __comp)
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(const allocator_type& __a)
     : __begin_node_(__iter_pointer()),
-      __pair1_(__second_tag(), __node_allocator(__a)),
-      __pair3_(0)
+      __pair1_(__default_init_tag(), __node_allocator(__a)),
+      __pair3_(0, __default_init_tag())
 {
     __begin_node() = __end_node();
 }
@@ -1584,7 +1587,7 @@ template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(const value_compare& __comp,
                                            const allocator_type& __a)
     : __begin_node_(__iter_pointer()),
-      __pair1_(__second_tag(), __node_allocator(__a)),
+      __pair1_(__default_init_tag(), __node_allocator(__a)),
       __pair3_(0, __comp)
 {
     __begin_node() = __end_node();
@@ -1656,7 +1659,7 @@ __tree<_Tp, _Compare, _Allocator>::__assign_unique(_ForwardIterator __first, _Fo
     typedef typename _ITraits::value_type _ItValueType;
     static_assert((is_same<_ItValueType, __container_value_type>::value),
                   "__assign_unique may only be called with the containers value type");
-    static_assert(__is_forward_iterator<_ForwardIterator>::value,
+    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
                   "__assign_unique requires a forward iterator");
     if (size() != 0)
     {
@@ -1697,7 +1700,7 @@ __tree<_Tp, _Compare, _Allocator>::__assign_multi(_InputIterator __first, _Input
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(const __tree& __t)
     : __begin_node_(__iter_pointer()),
-      __pair1_(__second_tag(), __node_traits::select_on_container_copy_construction(__t.__node_alloc())),
+      __pair1_(__default_init_tag(), __node_traits::select_on_container_copy_construction(__t.__node_alloc())),
       __pair3_(0, __t.value_comp())
 {
     __begin_node() = __end_node();
@@ -1727,7 +1730,7 @@ __tree<_Tp, _Compare, _Allocator>::__tree(__tree&& __t)
 
 template <class _Tp, class _Compare, class _Allocator>
 __tree<_Tp, _Compare, _Allocator>::__tree(__tree&& __t, const allocator_type& __a)
-    : __pair1_(__second_tag(), __node_allocator(__a)),
+    : __pair1_(__default_init_tag(), __node_allocator(__a)),
       __pair3_(0, _VSTD::move(__t.value_comp()))
 {
     if (__a == __t.__alloc())
lib/libcxx/include/__tuple
@@ -477,8 +477,9 @@ using __tuple_like_with_size _LIBCPP_NODEBUG_TYPE = __tuple_like_with_size_imp<
                               >;
 
 struct _LIBCPP_TYPE_VIS __check_tuple_constructor_fail {
-    template <class ...>
-    static constexpr bool __enable_default() { return false; }
+
+    static constexpr bool __enable_explicit_default() { return false; }
+    static constexpr bool __enable_implicit_default() { return false; }
     template <class ...>
     static constexpr bool __enable_explicit() { return false; }
     template <class ...>
lib/libcxx/include/algorithm
@@ -167,20 +167,20 @@ template <class ForwardIterator, class Size, class T, class BinaryPredicate>
              Size count, const T& value, BinaryPredicate pred);
 
 template <class InputIterator, class OutputIterator>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     copy(InputIterator first, InputIterator last, OutputIterator result);
 
 template<class InputIterator, class OutputIterator, class Predicate>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     copy_if(InputIterator first, InputIterator last,
             OutputIterator result, Predicate pred);
 
 template<class InputIterator, class Size, class OutputIterator>
-    OutputIterator
+    constexpr OutputIterator      // constexpr in C++20
     copy_n(InputIterator first, Size n, OutputIterator result);
 
 template <class BidirectionalIterator1, class BidirectionalIterator2>
-    BidirectionalIterator2
+    constexpr BidirectionalIterator2      // constexpr in C++20
     copy_backward(BidirectionalIterator1 first, BidirectionalIterator1 last,
                   BidirectionalIterator2 result);
 
@@ -1631,7 +1631,7 @@ search_n(_ForwardIterator __first, _ForwardIterator __last, _Size __count, const
 
 // copy
 template <class _Iter>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _Iter
 __unwrap_iter(_Iter __i)
 {
@@ -1639,7 +1639,7 @@ __unwrap_iter(_Iter __i)
 }
 
 template <class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if
 <
     is_trivially_copy_assignable<_Tp>::value,
@@ -1693,15 +1693,23 @@ __unwrap_iter(__wrap_iter<_Tp*> __i)
 #endif  // _LIBCPP_DEBUG_LEVEL < 2
 
 template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
-__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+__copy_constexpr(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
     for (; __first != __last; ++__first, (void) ++__result)
         *__result = *__first;
     return __result;
 }
 
+template <class _InputIterator, class _OutputIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+_OutputIterator
+__copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
+{
+    return __copy_constexpr(__first, __last, __result);
+}
+
 template <class _Tp, class _Up>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
@@ -1719,25 +1727,39 @@ __copy(_Tp* __first, _Tp* __last, _Up* __result)
 }
 
 template <class _InputIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
 _OutputIterator
 copy(_InputIterator __first, _InputIterator __last, _OutputIterator __result)
 {
-    return _VSTD::__copy(__unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+    if (__libcpp_is_constant_evaluated()) {
+        return _VSTD::__copy_constexpr(
+            __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+    } else {
+        return _VSTD::__copy(
+            __unwrap_iter(__first), __unwrap_iter(__last), __unwrap_iter(__result));
+    }
 }
 
 // copy_backward
 
 template <class _BidirectionalIterator, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
-__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
+__copy_backward_constexpr(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
 {
     while (__first != __last)
         *--__result = *--__last;
     return __result;
 }
 
+template <class _BidirectionalIterator, class _OutputIterator>
+inline _LIBCPP_INLINE_VISIBILITY
+_OutputIterator
+__copy_backward(_BidirectionalIterator __first, _BidirectionalIterator __last, _OutputIterator __result)
+{
+    return __copy_backward_constexpr(__first, __last, __result);
+}
+
 template <class _Tp, class _Up>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
@@ -1758,20 +1780,26 @@ __copy_backward(_Tp* __first, _Tp* __last, _Up* __result)
 }
 
 template <class _BidirectionalIterator1, class _BidirectionalIterator2>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
 _BidirectionalIterator2
 copy_backward(_BidirectionalIterator1 __first, _BidirectionalIterator1 __last,
               _BidirectionalIterator2 __result)
 {
-    return _VSTD::__copy_backward(__unwrap_iter(__first),
-                                  __unwrap_iter(__last),
-                                  __unwrap_iter(__result));
+    if (__libcpp_is_constant_evaluated()) {
+        return _VSTD::__copy_backward_constexpr(__unwrap_iter(__first),
+                                                __unwrap_iter(__last),
+                                                __unwrap_iter(__result));
+    } else {
+        return _VSTD::__copy_backward(__unwrap_iter(__first),
+                                      __unwrap_iter(__last),
+                                      __unwrap_iter(__result));
+    }
 }
 
 // copy_if
 
 template<class _InputIterator, class _OutputIterator, class _Predicate>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 _OutputIterator
 copy_if(_InputIterator __first, _InputIterator __last,
         _OutputIterator __result, _Predicate __pred)
@@ -1790,11 +1818,11 @@ copy_if(_InputIterator __first, _InputIterator __last,
 // copy_n
 
 template<class _InputIterator, class _Size, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
 typename enable_if
 <
-    __is_input_iterator<_InputIterator>::value &&
-   !__is_random_access_iterator<_InputIterator>::value,
+    __is_cpp17_input_iterator<_InputIterator>::value &&
+   !__is_cpp17_random_access_iterator<_InputIterator>::value,
     _OutputIterator
 >::type
 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
@@ -1816,10 +1844,10 @@ copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
 }
 
 template<class _InputIterator, class _Size, class _OutputIterator>
-inline _LIBCPP_INLINE_VISIBILITY
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17_WITH_IS_CONSTANT_EVALUATED
 typename enable_if
 <
-    __is_random_access_iterator<_InputIterator>::value,
+    __is_cpp17_random_access_iterator<_InputIterator>::value,
     _OutputIterator
 >::type
 copy_n(_InputIterator __first, _Size __orig_n, _OutputIterator __result)
@@ -2492,7 +2520,7 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 _ForwardIterator
 min_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
 {
-    static_assert(__is_forward_iterator<_ForwardIterator>::value,
+    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
         "std::min_element requires a ForwardIterator");
     if (__first != __last)
     {
@@ -2564,7 +2592,7 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
 _ForwardIterator
 max_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
 {
-    static_assert(__is_forward_iterator<_ForwardIterator>::value,
+    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
         "std::max_element requires a ForwardIterator");
     if (__first != __last)
     {
@@ -2659,7 +2687,7 @@ _LIBCPP_NODISCARD_EXT _LIBCPP_CONSTEXPR_AFTER_CXX11
 std::pair<_ForwardIterator, _ForwardIterator>
 minmax_element(_ForwardIterator __first, _ForwardIterator __last, _Compare __comp)
 {
-  static_assert(__is_forward_iterator<_ForwardIterator>::value,
+  static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
         "std::minmax_element requires a ForwardIterator");
   std::pair<_ForwardIterator, _ForwardIterator> __result(__first, __first);
   if (__first != __last)
@@ -3117,10 +3145,10 @@ _SampleIterator __sample(_PopulationIterator __first,
                          input_iterator_tag) {
 
   _Distance __k = 0;
-  for (; __first != __last && __k < __n; ++__first, (void)++__k)
+  for (; __first != __last && __k < __n; ++__first, (void) ++__k)
     __output_iter[__k] = *__first;
   _Distance __sz = __k;
-  for (; __first != __last; ++__first, (void)++__k) {
+  for (; __first != __last; ++__first, (void) ++__k) {
     _Distance __r = _VSTD::uniform_int_distribution<_Distance>(0, __k)(__g);
     if (__r < __sz)
       __output_iter[__r] = *__first;
@@ -3158,8 +3186,8 @@ _SampleIterator __sample(_PopulationIterator __first,
         _PopCategory;
   typedef typename iterator_traits<_PopulationIterator>::difference_type
         _Difference;
-  static_assert(__is_forward_iterator<_PopulationIterator>::value ||
-                __is_random_access_iterator<_SampleIterator>::value,
+  static_assert(__is_cpp17_forward_iterator<_PopulationIterator>::value ||
+                __is_cpp17_random_access_iterator<_SampleIterator>::value,
                 "SampleIterator must meet the requirements of RandomAccessIterator");
   typedef typename common_type<_Distance, _Difference>::type _CommonType;
   _LIBCPP_ASSERT(__n >= 0, "N must be a positive number.");
@@ -3190,7 +3218,7 @@ template<class _RandomAccessIterator, class _UniformRandomNumberGenerator>
     if (__d > 1)
     {
         _Dp __uid;
-        for (--__last, --__d; __first < __last; ++__first, --__d)
+        for (--__last, (void) --__d; __first < __last; ++__first, (void) --__d)
         {
             difference_type __i = __uid(__g, _Pp(0, __d));
             if (__i != difference_type(0))
@@ -3373,7 +3401,7 @@ __stable_partition(_ForwardIterator __first, _ForwardIterator __last, _Predicate
         // All trues now at start of range, all falses in buffer
         // Move falses back into range, but don't mess up __first which points to first false
         __i = __first;
-        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, ++__i)
+        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
             *__i = _VSTD::move(*__t2);
         // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
         return __first;
@@ -3505,7 +3533,7 @@ __stable_partition(_BidirectionalIterator __first, _BidirectionalIterator __last
         __i = ++__first;
         // All trues now at start of range, all falses in buffer
         // Move falses back into range, but don't mess up __first which points to first false
-        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, ++__i)
+        for (value_type* __t2 = __p.first; __t2 < __t; ++__t2, (void) ++__i)
             *__i = _VSTD::move(*__t2);
         // __h destructs moved-from values out of the temp buffer, but doesn't deallocate buffer
         return __first;
@@ -4382,7 +4410,7 @@ merge(_InputIterator1 __first1, _InputIterator1 __last1,
 {
     typedef typename iterator_traits<_InputIterator1>::value_type __v1;
     typedef typename iterator_traits<_InputIterator2>::value_type __v2;
-    return merge(__first1, __last1, __first2, __last2, __result, __less<__v1, __v2>());
+    return _VSTD::merge(__first1, __last1, __first2, __last2, __result, __less<__v1, __v2>());
 }
 
 // inplace_merge
@@ -4428,14 +4456,14 @@ __buffered_inplace_merge(_BidirectionalIterator __first, _BidirectionalIterator
     if (__len1 <= __len2)
     {
         value_type* __p = __buff;
-        for (_BidirectionalIterator __i = __first; __i != __middle; __d.__incr((value_type*)0), (void) ++__i, ++__p)
+        for (_BidirectionalIterator __i = __first; __i != __middle; __d.__incr((value_type*)0), (void) ++__i, (void) ++__p)
             ::new(__p) value_type(_VSTD::move(*__i));
         __half_inplace_merge(__buff, __p, __middle, __last, __first, __comp);
     }
     else
     {
         value_type* __p = __buff;
-        for (_BidirectionalIterator __i = __middle; __i != __last; __d.__incr((value_type*)0), (void) ++__i, ++__p)
+        for (_BidirectionalIterator __i = __middle; __i != __last; __d.__incr((value_type*)0), (void) ++__i, (void) ++__p)
             ::new(__p) value_type(_VSTD::move(*__i));
         typedef reverse_iterator<_BidirectionalIterator> _RBi;
         typedef reverse_iterator<value_type*> _Rv;
@@ -4575,14 +4603,14 @@ __merge_move_construct(_InputIterator1 __first1, _InputIterator1 __last1,
     {
         if (__first1 == __last1)
         {
-            for (; __first2 != __last2; ++__first2, ++__result, __d.__incr((value_type*)0))
+            for (; __first2 != __last2; ++__first2, ++__result, (void) __d.__incr((value_type*)0))
                 ::new (__result) value_type(_VSTD::move(*__first2));
             __h.release();
             return;
         }
         if (__first2 == __last2)
         {
-            for (; __first1 != __last1; ++__first1, ++__result, __d.__incr((value_type*)0))
+            for (; __first1 != __last1; ++__first1, ++__result, (void) __d.__incr((value_type*)0))
                 ::new (__result) value_type(_VSTD::move(*__first1));
             __h.release();
             return;
@@ -4612,7 +4640,7 @@ __merge_move_assign(_InputIterator1 __first1, _InputIterator1 __last1,
     {
         if (__first2 == __last2)
         {
-            for (; __first1 != __last1; ++__first1, ++__result)
+            for (; __first1 != __last1; ++__first1, (void) ++__result)
                 *__result = _VSTD::move(*__first1);
             return;
         }
@@ -4627,7 +4655,7 @@ __merge_move_assign(_InputIterator1 __first1, _InputIterator1 __last1,
             ++__first1;
         }
     }
-    for (; __first2 != __last2; ++__first2, ++__result)
+    for (; __first2 != __last2; ++__first2, (void) ++__result)
         *__result = _VSTD::move(*__first2);
 }
 
@@ -4995,7 +5023,7 @@ void
 __sort_heap(_RandomAccessIterator __first, _RandomAccessIterator __last, _Compare __comp)
 {
     typedef typename iterator_traits<_RandomAccessIterator>::difference_type difference_type;
-    for (difference_type __n = __last - __first; __n > 1; --__last, --__n)
+    for (difference_type __n = __last - __first; __n > 1; --__last, (void) --__n)
         __pop_heap<_Compare>(__first, __last, __comp, __n);
 }
 
@@ -5065,7 +5093,7 @@ __partial_sort_copy(_InputIterator __first, _InputIterator __last,
     _RandomAccessIterator __r = __result_first;
     if (__r != __result_last)
     {
-        for (; __first != __last && __r != __result_last; (void) ++__first, ++__r)
+        for (; __first != __last && __r != __result_last; ++__first, (void) ++__r)
             *__r = *__first;
         __make_heap<_Compare>(__result_first, __r, __comp);
         typename iterator_traits<_RandomAccessIterator>::difference_type __len = __r - __result_first;
@@ -5678,4 +5706,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <__pstl_algorithm>
+#endif
+
 #endif  // _LIBCPP_ALGORITHM
lib/libcxx/include/atomic
@@ -920,7 +920,7 @@ struct __cxx_atomic_base_impl {
 #endif // _LIBCPP_CXX03_LANG
   _LIBCPP_CONSTEXPR explicit __cxx_atomic_base_impl(_Tp value) _NOEXCEPT
     : __a_value(value) {}
-  _Atomic(_Tp) __a_value;
+  _LIBCPP_DISABLE_EXTENSION_WARNING _Atomic(_Tp) __a_value;
 };
 
 #define __cxx_atomic_is_lock_free(__s) __c11_atomic_is_lock_free(__s)
lib/libcxx/include/bit
@@ -42,6 +42,13 @@ namespace std {
   template<class T>
     constexpr int popcount(T x) noexcept;     // C++20
 
+  // 20.15.9, endian
+  enum class endian {
+    little = see below,        // C++20
+    big = see below,           // C++20
+    native = see below         // C++20
+};
+
 } // namespace std
 
 */
@@ -343,7 +350,7 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 bool __ispow2(_Tp __t) _NOEXCEPT
 {
     static_assert(__bitop_unsigned_integer<_Tp>::value, "__ispow2 requires unsigned");
-	return __t != 0 && (((__t & (__t - 1)) == 0)); 
+	return __t != 0 && (((__t & (__t - 1)) == 0));
 }
 
 
@@ -456,6 +463,20 @@ log2p1(_Tp __t) noexcept
     return __t == 0 ? 0 : __bit_log2(__t) + 1;
 }
 
+
+enum class endian
+{
+    little = 0xDEAD,
+    big    = 0xFACE,
+#if defined(_LIBCPP_LITTLE_ENDIAN)
+    native = little
+#elif defined(_LIBCPP_BIG_ENDIAN)
+    native = big
+#else
+    native = 0xCAFE
+#endif
+};
+
 #endif // _LIBCPP_STD_VER > 17
 
 _LIBCPP_END_NAMESPACE_STD
lib/libcxx/include/chrono
@@ -612,13 +612,43 @@ constexpr year_month_weekday_last
 constexpr year_month_weekday_last
   operator/(const month_weekday_last& mwdl, int y) noexcept;
 
-// 25.9, class template time_of_day    // C++20
-template<class Duration> class time_of_day;
+// 26.9, class template hh_mm_ss
+template <class Duration>
+class hh_mm_ss
+{
+    bool            is_neg; // exposition only
+    chrono::hours   h;      // exposition only
+    chrono::minutes m;      // exposition only
+    chrono::seconds s;      // exposition only
+    precision       ss;     // exposition only
+
+public:
+    static unsigned constexpr fractional_width = see below;
+    using precision                            = see below;
+
+    constexpr hh_mm_ss() noexcept : hh_mm_ss{Duration::zero()} {}
+    constexpr explicit hh_mm_ss(Duration d) noexcept;
+
+    constexpr bool is_negative() const noexcept;
+    constexpr chrono::hours hours() const noexcept;
+    constexpr chrono::minutes minutes() const noexcept;
+    constexpr chrono::seconds seconds() const noexcept;
+    constexpr precision subseconds() const noexcept;
+
+    constexpr explicit operator  precision()   const noexcept;
+    constexpr          precision to_duration() const noexcept;
+};
+
+template <class charT, class traits, class Duration>
+  basic_ostream<charT, traits>&
+    operator<<(basic_ostream<charT, traits>& os, hh_mm_ss<Duration> const& hms);
+
+// 26.10, 12/24 hour functions
+constexpr bool is_am(hours const& h) noexcept;
+constexpr bool is_pm(hours const& h) noexcept;
+constexpr hours make12(const hours& h) noexcept;
+constexpr hours make24(const hours& h, bool is_pm) noexcept;
 
-template<> class time_of_day<hours>;
-template<> class time_of_day<minutes>;
-template<> class time_of_day<seconds>;
-template<class Rep, class Period> class time_of_day<duration<Rep, Period>>;
 
 // 25.10.2, time zone database     // C++20
 struct tzdb;
@@ -1428,7 +1458,7 @@ typename enable_if
 >::type
 abs(duration<_Rep, _Period> __d)
 {
-    return __d >= __d.zero() ? __d : -__d;
+    return __d >= __d.zero() ? +__d : -__d;
 }
 #endif
 
@@ -1810,7 +1840,7 @@ private:
     unsigned char __wd;
 public:
   weekday() = default;
-  inline explicit constexpr weekday(unsigned __val) noexcept : __wd(static_cast<unsigned char>(__val)) {}
+  inline explicit constexpr weekday(unsigned __val) noexcept : __wd(static_cast<unsigned char>(__val == 7 ? 0 : __val)) {}
   inline constexpr          weekday(const sys_days& __sysd) noexcept
           : __wd(__weekday_from_days(__sysd.time_since_epoch().count())) {}
   inline explicit constexpr weekday(const local_days& __locd) noexcept
@@ -1822,11 +1852,13 @@ public:
   inline constexpr weekday  operator--(int) noexcept { weekday __tmp = *this; --(*this); return __tmp; }
          constexpr weekday& operator+=(const days& __dd) noexcept;
          constexpr weekday& operator-=(const days& __dd) noexcept;
-  inline explicit constexpr operator unsigned() const noexcept { return __wd; }
+  inline constexpr unsigned c_encoding()   const noexcept { return __wd; }
+  inline constexpr unsigned iso_encoding() const noexcept { return __wd == 0u ? 7 : __wd; }
   inline constexpr bool ok() const noexcept { return __wd <= 6; }
          constexpr weekday_indexed operator[](unsigned __index) const noexcept;
          constexpr weekday_last    operator[](last_spec) const noexcept;
 
+  // TODO: Make private?
   static constexpr unsigned char __weekday_from_days(int __days) noexcept;
 };
 
@@ -1842,7 +1874,7 @@ unsigned char weekday::__weekday_from_days(int __days) noexcept
 
 inline constexpr
 bool operator==(const weekday& __lhs, const weekday& __rhs) noexcept
-{ return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }
+{ return __lhs.c_encoding() == __rhs.c_encoding(); }
 
 inline constexpr
 bool operator!=(const weekday& __lhs, const weekday& __rhs) noexcept
@@ -1850,7 +1882,7 @@ bool operator!=(const weekday& __lhs, const weekday& __rhs) noexcept
 
 inline constexpr
 bool operator< (const weekday& __lhs, const weekday& __rhs) noexcept
-{ return static_cast<unsigned>(__lhs) <  static_cast<unsigned>(__rhs); }
+{ return __lhs.c_encoding() < __rhs.c_encoding(); }
 
 inline constexpr
 bool operator> (const weekday& __lhs, const weekday& __rhs) noexcept
@@ -1866,7 +1898,7 @@ bool operator>=(const weekday& __lhs, const weekday& __rhs) noexcept
 
 constexpr weekday operator+(const weekday& __lhs, const days& __rhs) noexcept
 {
-    auto const __mu = static_cast<long long>(static_cast<unsigned>(__lhs)) + __rhs.count();
+    auto const __mu = static_cast<long long>(__lhs.c_encoding()) + __rhs.count();
     auto const __yr = (__mu >= 0 ? __mu : __mu - 6) / 7;
     return weekday{static_cast<unsigned>(__mu - __yr * 7)};
 }
@@ -1879,7 +1911,7 @@ constexpr weekday operator-(const weekday& __lhs, const days& __rhs) noexcept
 
 constexpr days operator-(const weekday& __lhs, const weekday& __rhs) noexcept
 {
-    const int __wdu = static_cast<unsigned>(__lhs) - static_cast<unsigned>(__rhs);
+    const int __wdu = __lhs.c_encoding() - __rhs.c_encoding();
     const int __wk = (__wdu >= 0 ? __wdu : __wdu-6) / 7;
     return days{__wdu - __wk * 7};
 }
@@ -2537,8 +2569,13 @@ public:
     inline constexpr bool ok() const noexcept
     {
         if (!__y.ok() || !__m.ok() || !__wdi.ok()) return false;
-    //  TODO: make sure it's a valid date
-        return true;
+        if (__wdi.index() <= 4) return true;
+        auto __nth_weekday_day =
+            __wdi.weekday() -
+            chrono::weekday{static_cast<sys_days>(__y / __m / 1)} +
+            days{(__wdi.index() - 1) * 7 + 1};
+        return static_cast<unsigned>(__nth_weekday_day.count()) <=
+               static_cast<unsigned>((__y / __m / last).day());
     }
 
     static constexpr year_month_weekday __from_days(days __d) noexcept;
@@ -2715,6 +2752,84 @@ inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(co
 inline constexpr year_month_weekday_last& year_month_weekday_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
 inline constexpr year_month_weekday_last& year_month_weekday_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
 
+
+template <class _Duration>
+class hh_mm_ss
+{
+private:
+    static_assert(__is_duration<_Duration>::value, "template parameter of hh_mm_ss must be a std::chrono::duration");
+    using __CommonType = common_type_t<_Duration, chrono::seconds>;
+
+    static constexpr uint64_t __pow10(unsigned __exp)
+    {
+        uint64_t __ret = 1;
+        for (unsigned __i = 0; __i < __exp; ++__i)
+            __ret *= 10U;
+        return __ret;
+    }
+
+    static constexpr unsigned __width(uint64_t __n, uint64_t __d = 10, unsigned __w = 0)
+    {
+        if (__n >= 2 && __d != 0 && __w < 19)
+            return 1 + __width(__n, __d % __n * 10, __w+1);
+        return 0;
+    }
+
+public:
+    static unsigned constexpr fractional_width = __width(__CommonType::period::den) < 19 ?
+                                                 __width(__CommonType::period::den) : 6u;
+    using precision = duration<typename __CommonType::rep, ratio<1, __pow10(fractional_width)>>;
+
+    constexpr hh_mm_ss() noexcept : hh_mm_ss{_Duration::zero()} {}
+
+    constexpr explicit hh_mm_ss(_Duration __d) noexcept :
+        __is_neg(__d < _Duration(0)),
+        __h(duration_cast<chrono::hours>  (abs(__d))),
+        __m(duration_cast<chrono::minutes>(abs(__d) - hours())),
+        __s(duration_cast<chrono::seconds>(abs(__d) - hours() - minutes())),
+        __f(duration_cast<precision>      (abs(__d) - hours() - minutes() - seconds()))
+        {}
+
+    constexpr bool is_negative()        const noexcept { return __is_neg; }
+    constexpr chrono::hours hours()     const noexcept { return __h; }
+    constexpr chrono::minutes minutes() const noexcept { return __m; }
+    constexpr chrono::seconds seconds() const noexcept { return __s; }
+    constexpr precision subseconds()    const noexcept { return __f; }
+
+    constexpr precision to_duration() const noexcept
+    {
+        auto __dur = __h + __m + __s + __f;
+        return __is_neg ? -__dur : __dur;
+    }
+
+    constexpr explicit operator precision() const noexcept { return to_duration(); }
+
+private:
+    bool            __is_neg;
+    chrono::hours   __h;
+    chrono::minutes __m;
+    chrono::seconds __s;
+    precision       __f;
+};
+
+constexpr bool is_am(const hours& __h) noexcept { return __h >= hours( 0) && __h < hours(12); }
+constexpr bool is_pm(const hours& __h) noexcept { return __h >= hours(12) && __h < hours(24); }
+
+constexpr hours make12(const hours& __h) noexcept
+{
+    if      (__h == hours( 0)) return hours(12);
+    else if (__h <= hours(12)) return __h;
+    else                       return __h - hours(12);
+}
+
+constexpr hours make24(const hours& __h, bool __is_pm) noexcept
+{
+    if (__is_pm)
+        return __h == hours(12) ? __h : __h + hours(12);
+    else
+        return __h == hours(12) ? hours(0) : __h;
+}
+
 #endif // _LIBCPP_STD_VER > 17
 } // chrono
 
@@ -2825,6 +2940,7 @@ struct _FilesystemClock {
   typedef chrono::duration<rep, period> duration;
   typedef chrono::time_point<_FilesystemClock> time_point;
 
+  _LIBCPP_EXPORTED_FROM_ABI
   static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;
 
   _LIBCPP_AVAILABILITY_FILESYSTEM _LIBCPP_FUNC_VIS static time_point now() noexcept;
lib/libcxx/include/cmath
@@ -303,11 +303,15 @@ long double    truncl(long double x);
 #include <__config>
 #include <math.h>
 #include <version>
+#include <type_traits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
 #endif
 
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 using ::signbit;
@@ -632,6 +636,38 @@ lerp(long double __a, long double __b, long double __t) _NOEXCEPT { return __ler
 
 #endif // _LIBCPP_STD_VER > 17
 
+template <class _IntT, class _FloatT,
+    bool _FloatBigger = (numeric_limits<_FloatT>::digits > numeric_limits<_IntT>::digits),
+    int _Bits = (numeric_limits<_IntT>::digits - numeric_limits<_FloatT>::digits)>
+_LIBCPP_INLINE_VISIBILITY
+_LIBCPP_CONSTEXPR _IntT __max_representable_int_for_float() _NOEXCEPT {
+  static_assert(is_floating_point<_FloatT>::value, "must be a floating point type");
+  static_assert(is_integral<_IntT>::value, "must be an integral type");
+  static_assert(numeric_limits<_FloatT>::radix == 2, "FloatT has incorrect radix");
+  static_assert((_IsSame<_FloatT, float>::value || _IsSame<_FloatT, double>::value
+                 || _IsSame<_FloatT,long double>::value), "unsupported floating point type");
+  return _FloatBigger ? numeric_limits<_IntT>::max() :  (numeric_limits<_IntT>::max() >> _Bits << _Bits);
+}
+
+// Convert a floating point number to the specified integral type after
+// clamping to the integral types representable range.
+//
+// The behavior is undefined if `__r` is NaN.
+template <class _IntT, class _RealT>
+_LIBCPP_INLINE_VISIBILITY
+_IntT __clamp_to_integral(_RealT __r) _NOEXCEPT {
+  using _Lim = std::numeric_limits<_IntT>;
+  const _IntT _MaxVal = std::__max_representable_int_for_float<_IntT, _RealT>();
+  if (__r >= ::nextafter(static_cast<_RealT>(_MaxVal), INFINITY)) {
+    return _Lim::max();
+  } else if (__r <= _Lim::lowest()) {
+    return _Lim::min();
+  }
+  return static_cast<_IntT>(__r);
+}
+
 _LIBCPP_END_NAMESPACE_STD
 
+_LIBCPP_POP_MACROS
+
 #endif  // _LIBCPP_CMATH
lib/libcxx/include/cstdio
@@ -152,7 +152,7 @@ using ::tmpnam;
 
 #ifndef _LIBCPP_HAS_NO_STDIN
 using ::getchar;
-#if _LIBCPP_STD_VER <= 11 && !defined(_LIBCPP_MSVCRT)
+#if _LIBCPP_STD_VER <= 11 && !defined(_LIBCPP_C_HAS_NO_GETS)
 using ::gets;
 #endif
 using ::scanf;
lib/libcxx/include/cstdlib
@@ -154,7 +154,7 @@ using ::wcstombs;
 using ::at_quick_exit;
 using ::quick_exit;
 #endif
-#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_C11_FEATURES)
+#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_ALIGNED_ALLOC)
 using ::aligned_alloc;
 #endif
 
lib/libcxx/include/ctime
@@ -18,7 +18,7 @@ Macros:
     NULL
     CLOCKS_PER_SEC
     TIME_UTC // C++17
-    
+
 namespace std
 {
 
@@ -29,7 +29,7 @@ Types:
     time_t
     tm
     timespec // C++17
-    
+
 clock_t clock();
 double difftime(time_t time1, time_t time0);
 time_t mktime(tm* timeptr);
@@ -58,7 +58,7 @@ using ::clock_t;
 using ::size_t;
 using ::time_t;
 using ::tm;
-#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_C11_FEATURES)
+#if _LIBCPP_STD_VER > 14 && defined(_LIBCPP_HAS_TIMESPEC_GET)
 using ::timespec;
 #endif
 using ::clock;
lib/libcxx/include/deque
@@ -190,7 +190,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 copy(_RAIter __f,
      _RAIter __l,
      __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-     typename enable_if<__is_random_access_iterator<_RAIter>::value>::type* = 0);
+     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
 
 template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
           class _OutputIterator>
@@ -212,7 +212,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 copy_backward(_RAIter __f,
               _RAIter __l,
               __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-              typename enable_if<__is_random_access_iterator<_RAIter>::value>::type* = 0);
+              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
 
 template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
           class _OutputIterator>
@@ -234,7 +234,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 move(_RAIter __f,
      _RAIter __l,
      __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-     typename enable_if<__is_random_access_iterator<_RAIter>::value>::type* = 0);
+     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
 
 template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
           class _OutputIterator>
@@ -256,7 +256,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 move_backward(_RAIter __f,
               _RAIter __l,
               __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-              typename enable_if<__is_random_access_iterator<_RAIter>::value>::type* = 0);
+              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
 
 template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
           class _OutputIterator>
@@ -450,7 +450,7 @@ private:
     copy(_RAIter __f,
          _RAIter __l,
          __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-         typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*);
+         typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
 
     template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
               class _OutputIterator>
@@ -475,7 +475,7 @@ private:
     copy_backward(_RAIter __f,
                   _RAIter __l,
                   __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-                  typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*);
+                  typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
 
     template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
               class _OutputIterator>
@@ -500,7 +500,7 @@ private:
     move(_RAIter __f,
          _RAIter __l,
          __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-         typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*);
+         typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
 
     template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
               class _OutputIterator>
@@ -525,7 +525,7 @@ private:
     move_backward(_RAIter __f,
                   _RAIter __l,
                   __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-                  typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*);
+                  typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*);
 
     template <class _V1, class _P1, class _R1, class _M1, class _D1, _D1 _B1,
               class _OutputIterator>
@@ -558,7 +558,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 copy(_RAIter __f,
      _RAIter __l,
      __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-     typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*)
+     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
 {
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
@@ -646,7 +646,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 copy_backward(_RAIter __f,
               _RAIter __l,
               __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-              typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*)
+              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
 {
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
@@ -734,7 +734,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 move(_RAIter __f,
      _RAIter __l,
      __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-     typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*)
+     typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
 {
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
@@ -822,7 +822,7 @@ __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>
 move_backward(_RAIter __f,
               _RAIter __l,
               __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2> __r,
-              typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*)
+              typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
 {
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::difference_type difference_type;
     typedef typename __deque_iterator<_V2, _P2, _R2, _M2, _D2, _B2>::pointer pointer;
@@ -934,7 +934,7 @@ public:
     typedef _Allocator                               allocator_type;
     typedef allocator_traits<allocator_type>         __alloc_traits;
     typedef typename __alloc_traits::size_type       size_type;
-protected:
+
     typedef _Tp                                      value_type;
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
@@ -956,6 +956,74 @@ protected:
     typedef __deque_iterator<value_type, const_pointer, const_reference, __map_const_pointer,
                              difference_type>    const_iterator;
 
+    struct __deque_block_range {
+      explicit __deque_block_range(pointer __b, pointer __e) _NOEXCEPT : __begin_(__b), __end_(__e) {}
+      const pointer __begin_;
+      const pointer __end_;
+    };
+
+    struct __deque_range {
+      iterator __pos_;
+      const iterator __end_;
+
+      __deque_range(iterator __pos, iterator __e) _NOEXCEPT
+        : __pos_(__pos), __end_(__e) {}
+
+      explicit operator bool() const _NOEXCEPT {
+        return __pos_ != __end_;
+      }
+
+      __deque_range begin() const {
+        return *this;
+      }
+
+      __deque_range end() const {
+        return __deque_range(__end_, __end_);
+      }
+      __deque_block_range operator*() const _NOEXCEPT {
+         if (__pos_.__m_iter_ == __end_.__m_iter_) {
+          return __deque_block_range(__pos_.__ptr_, __end_.__ptr_);
+        }
+        return __deque_block_range(__pos_.__ptr_, *__pos_.__m_iter_ + __block_size);
+      }
+
+      __deque_range& operator++() _NOEXCEPT {
+        if (__pos_.__m_iter_ == __end_.__m_iter_) {
+          __pos_ = __end_;
+        } else {
+          ++__pos_.__m_iter_;
+          __pos_.__ptr_ = *__pos_.__m_iter_;
+        }
+        return *this;
+      }
+
+
+      friend bool operator==(__deque_range const& __lhs, __deque_range const& __rhs) {
+        return __lhs.__pos_ == __rhs.__pos_;
+      }
+      friend bool operator!=(__deque_range const& __lhs, __deque_range const& __rhs) {
+        return !(__lhs == __rhs);
+      }
+    };
+
+
+
+    struct _ConstructTransaction {
+      _ConstructTransaction(__deque_base* __db, __deque_block_range& __r)
+        : __pos_(__r.__begin_), __end_(__r.__end_), __begin_(__r.__begin_), __base_(__db) {}
+
+
+      ~_ConstructTransaction() {
+        __base_->size() += (__pos_ - __begin_);
+      }
+
+      pointer __pos_;
+      const pointer __end_;
+    private:
+      const pointer __begin_;
+      __deque_base * const __base_;
+    };
+
 protected:
     __map __map_;
     size_type __start_;
@@ -1103,7 +1171,7 @@ template <class _Tp, class _Allocator>
 inline
 __deque_base<_Tp, _Allocator>::__deque_base()
     _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
-    : __start_(0), __size_(0) {}
+    : __start_(0), __size_(0, __default_init_tag()) {}
 
 template <class _Tp, class _Allocator>
 inline
@@ -1222,6 +1290,10 @@ public:
     typedef _VSTD::reverse_iterator<iterator>       reverse_iterator;
     typedef _VSTD::reverse_iterator<const_iterator> const_reverse_iterator;
 
+    using typename __base::__deque_range;
+    using typename __base::__deque_block_range;
+    using typename __base::_ConstructTransaction;
+
     // construct/copy/destroy:
     _LIBCPP_INLINE_VISIBILITY
     deque()
@@ -1236,10 +1308,10 @@ public:
     deque(size_type __n, const value_type& __v, const allocator_type& __a);
     template <class _InputIter>
         deque(_InputIter __f, _InputIter __l,
-              typename enable_if<__is_input_iterator<_InputIter>::value>::type* = 0);
+              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type* = 0);
     template <class _InputIter>
         deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
-              typename enable_if<__is_input_iterator<_InputIter>::value>::type* = 0);
+              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type* = 0);
     deque(const deque& __c);
     deque(const deque& __c, const allocator_type& __a);
 
@@ -1267,11 +1339,11 @@ public:
 
     template <class _InputIter>
         void assign(_InputIter __f, _InputIter __l,
-                    typename enable_if<__is_input_iterator<_InputIter>::value &&
-                                      !__is_random_access_iterator<_InputIter>::value>::type* = 0);
+                    typename enable_if<__is_cpp17_input_iterator<_InputIter>::value &&
+                                      !__is_cpp17_random_access_iterator<_InputIter>::value>::type* = 0);
     template <class _RAIter>
         void assign(_RAIter __f, _RAIter __l,
-                    typename enable_if<__is_random_access_iterator<_RAIter>::value>::type* = 0);
+                    typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type* = 0);
     void assign(size_type __n, const value_type& __v);
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1371,15 +1443,15 @@ public:
     iterator insert(const_iterator __p, size_type __n, const value_type& __v);
     template <class _InputIter>
         iterator insert(const_iterator __p, _InputIter __f, _InputIter __l,
-                         typename enable_if<__is_input_iterator<_InputIter>::value
-                                         &&!__is_forward_iterator<_InputIter>::value>::type* = 0);
+                         typename enable_if<__is_cpp17_input_iterator<_InputIter>::value
+                                         &&!__is_cpp17_forward_iterator<_InputIter>::value>::type* = 0);
     template <class _ForwardIterator>
         iterator insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l,
-                               typename enable_if<__is_forward_iterator<_ForwardIterator>::value
-                                         &&!__is_bidirectional_iterator<_ForwardIterator>::value>::type* = 0);
+                               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value
+                                         &&!__is_cpp17_bidirectional_iterator<_ForwardIterator>::value>::type* = 0);
     template <class _BiIter>
         iterator insert(const_iterator __p, _BiIter __f, _BiIter __l,
-                         typename enable_if<__is_bidirectional_iterator<_BiIter>::value>::type* = 0);
+                         typename enable_if<__is_cpp17_bidirectional_iterator<_BiIter>::value>::type* = 0);
 
     void pop_front();
     void pop_back();
@@ -1399,7 +1471,7 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     bool __invariants() const {return __base::__invariants();}
-private:
+
     typedef typename __base::__map_const_pointer __map_const_pointer;
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1412,24 +1484,62 @@ private:
     {
         return __base::__map_.size() == 0 ? 0 : __base::__map_.size() * __base::__block_size - 1;
     }
+    _LIBCPP_INLINE_VISIBILITY
+    size_type __block_count() const
+    {
+        return __base::__map_.size();
+    }
+
     _LIBCPP_INLINE_VISIBILITY
     size_type __front_spare() const
     {
         return __base::__start_;
     }
     _LIBCPP_INLINE_VISIBILITY
+    size_type __front_spare_blocks() const {
+      return __front_spare() / __base::__block_size;
+    }
+    _LIBCPP_INLINE_VISIBILITY
     size_type __back_spare() const
     {
         return __capacity() - (__base::__start_ + __base::size());
     }
+    _LIBCPP_INLINE_VISIBILITY
+    size_type __back_spare_blocks() const {
+      return __back_spare() / __base::__block_size;
+    }
+
+ private:
+    _LIBCPP_INLINE_VISIBILITY
+    bool __maybe_remove_front_spare(bool __keep_one = true) {
+      if (__front_spare_blocks() >= 2 || (!__keep_one && __front_spare_blocks())) {
+        __alloc_traits::deallocate(__base::__alloc(), __base::__map_.front(),
+                                   __base::__block_size);
+        __base::__map_.pop_front();
+        __base::__start_ -= __base::__block_size;
+        return true;
+      }
+      return false;
+    }
+
+    _LIBCPP_INLINE_VISIBILITY
+    bool __maybe_remove_back_spare(bool __keep_one = true) {
+      if (__back_spare_blocks() >= 2 || (!__keep_one && __back_spare_blocks())) {
+        __alloc_traits::deallocate(__base::__alloc(), __base::__map_.back(),
+                                   __base::__block_size);
+        __base::__map_.pop_back();
+        return true;
+      }
+      return false;
+    }
 
     template <class _InpIter>
         void __append(_InpIter __f, _InpIter __l,
-                 typename enable_if<__is_input_iterator<_InpIter>::value &&
-                                   !__is_forward_iterator<_InpIter>::value>::type* = 0);
+                 typename enable_if<__is_cpp17_input_iterator<_InpIter>::value &&
+                                   !__is_cpp17_forward_iterator<_InpIter>::value>::type* = 0);
     template <class _ForIter>
         void __append(_ForIter __f, _ForIter __l,
-                      typename enable_if<__is_forward_iterator<_ForIter>::value>::type* = 0);
+                      typename enable_if<__is_cpp17_forward_iterator<_ForIter>::value>::type* = 0);
     void __append(size_type __n);
     void __append(size_type __n, const value_type& __v);
     void __erase_to_end(const_iterator __f);
@@ -1524,7 +1634,7 @@ deque<_Tp, _Allocator>::deque(size_type __n, const value_type& __v, const alloca
 template <class _Tp, class _Allocator>
 template <class _InputIter>
 deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l,
-              typename enable_if<__is_input_iterator<_InputIter>::value>::type*)
+              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type*)
 {
     __append(__f, __l);
 }
@@ -1532,7 +1642,7 @@ deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l,
 template <class _Tp, class _Allocator>
 template <class _InputIter>
 deque<_Tp, _Allocator>::deque(_InputIter __f, _InputIter __l, const allocator_type& __a,
-              typename enable_if<__is_input_iterator<_InputIter>::value>::type*)
+              typename enable_if<__is_cpp17_input_iterator<_InputIter>::value>::type*)
     : __base(__a)
 {
     __append(__f, __l);
@@ -1640,8 +1750,8 @@ template <class _Tp, class _Allocator>
 template <class _InputIter>
 void
 deque<_Tp, _Allocator>::assign(_InputIter __f, _InputIter __l,
-                               typename enable_if<__is_input_iterator<_InputIter>::value &&
-                                                 !__is_random_access_iterator<_InputIter>::value>::type*)
+                               typename enable_if<__is_cpp17_input_iterator<_InputIter>::value &&
+                                                 !__is_cpp17_random_access_iterator<_InputIter>::value>::type*)
 {
     iterator __i = __base::begin();
     iterator __e = __base::end();
@@ -1657,7 +1767,7 @@ template <class _Tp, class _Allocator>
 template <class _RAIter>
 void
 deque<_Tp, _Allocator>::assign(_RAIter __f, _RAIter __l,
-                               typename enable_if<__is_random_access_iterator<_RAIter>::value>::type*)
+                               typename enable_if<__is_cpp17_random_access_iterator<_RAIter>::value>::type*)
 {
     if (static_cast<size_type>(__l - __f) > __base::size())
     {
@@ -1727,17 +1837,8 @@ deque<_Tp, _Allocator>::shrink_to_fit() _NOEXCEPT
     }
     else
     {
-        if (__front_spare() >= __base::__block_size)
-        {
-            __alloc_traits::deallocate(__a, __base::__map_.front(), __base::__block_size);
-            __base::__map_.pop_front();
-            __base::__start_ -= __base::__block_size;
-        }
-        if (__back_spare() >= __base::__block_size)
-        {
-            __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
-            __base::__map_.pop_back();
-        }
+      __maybe_remove_front_spare(/*__keep_one=*/false);
+      __maybe_remove_back_spare(/*__keep_one=*/false);
     }
     __base::__map_.shrink_to_fit();
 }
@@ -2151,8 +2252,8 @@ template <class _Tp, class _Allocator>
 template <class _InputIter>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, _InputIter __f, _InputIter __l,
-                               typename enable_if<__is_input_iterator<_InputIter>::value
-                                               &&!__is_forward_iterator<_InputIter>::value>::type*)
+                               typename enable_if<__is_cpp17_input_iterator<_InputIter>::value
+                                               &&!__is_cpp17_forward_iterator<_InputIter>::value>::type*)
 {
     __split_buffer<value_type, allocator_type&> __buf(__base::__alloc());
     __buf.__construct_at_end(__f, __l);
@@ -2164,8 +2265,8 @@ template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, _ForwardIterator __f, _ForwardIterator __l,
-                               typename enable_if<__is_forward_iterator<_ForwardIterator>::value
-                                               &&!__is_bidirectional_iterator<_ForwardIterator>::value>::type*)
+                               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value
+                                               &&!__is_cpp17_bidirectional_iterator<_ForwardIterator>::value>::type*)
 {
     size_type __n = _VSTD::distance(__f, __l);
     __split_buffer<value_type, allocator_type&> __buf(__n, 0, __base::__alloc());
@@ -2178,7 +2279,7 @@ template <class _Tp, class _Allocator>
 template <class _BiIter>
 typename deque<_Tp, _Allocator>::iterator
 deque<_Tp, _Allocator>::insert(const_iterator __p, _BiIter __f, _BiIter __l,
-                               typename enable_if<__is_bidirectional_iterator<_BiIter>::value>::type*)
+                               typename enable_if<__is_cpp17_bidirectional_iterator<_BiIter>::value>::type*)
 {
     size_type __n = _VSTD::distance(__f, __l);
     size_type __pos = __p - __base::begin();
@@ -2247,8 +2348,8 @@ template <class _Tp, class _Allocator>
 template <class _InpIter>
 void
 deque<_Tp, _Allocator>::__append(_InpIter __f, _InpIter __l,
-                                 typename enable_if<__is_input_iterator<_InpIter>::value &&
-                                                   !__is_forward_iterator<_InpIter>::value>::type*)
+                                 typename enable_if<__is_cpp17_input_iterator<_InpIter>::value &&
+                                                   !__is_cpp17_forward_iterator<_InpIter>::value>::type*)
 {
     for (; __f != __l; ++__f)
 #ifdef _LIBCPP_CXX03_LANG
@@ -2262,7 +2363,7 @@ template <class _Tp, class _Allocator>
 template <class _ForIter>
 void
 deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l,
-                                 typename enable_if<__is_forward_iterator<_ForIter>::value>::type*)
+                                 typename enable_if<__is_cpp17_forward_iterator<_ForIter>::value>::type*)
 {
     size_type __n = _VSTD::distance(__f, __l);
     allocator_type& __a = __base::__alloc();
@@ -2270,8 +2371,12 @@ deque<_Tp, _Allocator>::__append(_ForIter __f, _ForIter __l,
     if (__n > __back_capacity)
         __add_back_capacity(__n - __back_capacity);
     // __n <= __back_capacity
-    for (iterator __i = __base::end(); __f != __l; ++__i, (void) ++__f, ++__base::size())
-        __alloc_traits::construct(__a, _VSTD::addressof(*__i), *__f);
+    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
+      _ConstructTransaction __tx(this, __br);
+      for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_, (void)++__f) {
+        __alloc_traits::construct(__a, std::__to_address(__tx.__pos_), *__f);
+      }
+    }
 }
 
 template <class _Tp, class _Allocator>
@@ -2283,8 +2388,12 @@ deque<_Tp, _Allocator>::__append(size_type __n)
     if (__n > __back_capacity)
         __add_back_capacity(__n - __back_capacity);
     // __n <= __back_capacity
-    for (iterator __i = __base::end(); __n; --__n, ++__i, ++__base::size())
-        __alloc_traits::construct(__a, _VSTD::addressof(*__i));
+    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
+      _ConstructTransaction __tx(this, __br);
+      for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
+        __alloc_traits::construct(__a, std::__to_address(__tx.__pos_));
+      }
+    }
 }
 
 template <class _Tp, class _Allocator>
@@ -2296,8 +2405,13 @@ deque<_Tp, _Allocator>::__append(size_type __n, const value_type& __v)
     if (__n > __back_capacity)
         __add_back_capacity(__n - __back_capacity);
     // __n <= __back_capacity
-    for (iterator __i = __base::end(); __n; --__n, ++__i, ++__base::size())
-        __alloc_traits::construct(__a, _VSTD::addressof(*__i), __v);
+    for (__deque_block_range __br : __deque_range(__base::end(), __base::end() + __n)) {
+      _ConstructTransaction __tx(this, __br);
+      for (; __tx.__pos_ != __tx.__end_; ++__tx.__pos_) {
+        __alloc_traits::construct(__a, std::__to_address(__tx.__pos_), __v);
+      }
+    }
+
 }
 
 // Create front capacity for one block of elements.
@@ -2592,16 +2706,12 @@ void
 deque<_Tp, _Allocator>::pop_front()
 {
     allocator_type& __a = __base::__alloc();
-    __alloc_traits::destroy(__a, __to_raw_pointer(*(__base::__map_.begin() +
+    __alloc_traits::destroy(__a, __to_address(*(__base::__map_.begin() +
                                                     __base::__start_ / __base::__block_size) +
                                                     __base::__start_ % __base::__block_size));
     --__base::size();
-    if (++__base::__start_ >= 2 * __base::__block_size)
-    {
-        __alloc_traits::deallocate(__a, __base::__map_.front(), __base::__block_size);
-        __base::__map_.pop_front();
-        __base::__start_ -= __base::__block_size;
-    }
+    ++__base::__start_;
+    __maybe_remove_front_spare();
 }
 
 template <class _Tp, class _Allocator>
@@ -2611,15 +2721,11 @@ deque<_Tp, _Allocator>::pop_back()
     _LIBCPP_ASSERT(!empty(), "deque::pop_back called for empty deque");
     allocator_type& __a = __base::__alloc();
     size_type __p = __base::size() + __base::__start_ - 1;
-    __alloc_traits::destroy(__a, __to_raw_pointer(*(__base::__map_.begin() +
+    __alloc_traits::destroy(__a, __to_address(*(__base::__map_.begin() +
                                                     __p / __base::__block_size) +
                                                     __p % __base::__block_size));
     --__base::size();
-    if (__back_spare() >= 2 * __base::__block_size)
-    {
-        __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
-        __base::__map_.pop_back();
-    }
+    __maybe_remove_back_spare();
 }
 
 // move assign [__f, __l) to [__r, __r + (__l-__f)).
@@ -2768,23 +2874,14 @@ deque<_Tp, _Allocator>::erase(const_iterator __f)
         __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
         --__base::size();
         ++__base::__start_;
-        if (__front_spare() >= 2 * __base::__block_size)
-        {
-            __alloc_traits::deallocate(__a, __base::__map_.front(), __base::__block_size);
-            __base::__map_.pop_front();
-            __base::__start_ -= __base::__block_size;
-        }
+        __maybe_remove_front_spare();
     }
     else
     {   // erase from back
         iterator __i = _VSTD::move(_VSTD::next(__p), __base::end(), __p);
         __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
         --__base::size();
-        if (__back_spare() >= 2 * __base::__block_size)
-        {
-            __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
-            __base::__map_.pop_back();
-        }
+        __maybe_remove_back_spare();
     }
     return __base::begin() + __pos;
 }
@@ -2807,11 +2904,7 @@ deque<_Tp, _Allocator>::erase(const_iterator __f, const_iterator __l)
                 __alloc_traits::destroy(__a, _VSTD::addressof(*__b));
             __base::size() -= __n;
             __base::__start_ += __n;
-            while (__front_spare() >= 2 * __base::__block_size)
-            {
-                __alloc_traits::deallocate(__a, __base::__map_.front(), __base::__block_size);
-                __base::__map_.pop_front();
-                __base::__start_ -= __base::__block_size;
+            while (__maybe_remove_front_spare()) {
             }
         }
         else
@@ -2820,10 +2913,7 @@ deque<_Tp, _Allocator>::erase(const_iterator __f, const_iterator __l)
             for (iterator __e = __base::end(); __i != __e; ++__i)
                 __alloc_traits::destroy(__a, _VSTD::addressof(*__i));
             __base::size() -= __n;
-            while (__back_spare() >= 2 * __base::__block_size)
-            {
-                __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
-                __base::__map_.pop_back();
+            while (__maybe_remove_back_spare()) {
             }
         }
     }
@@ -2844,10 +2934,7 @@ deque<_Tp, _Allocator>::__erase_to_end(const_iterator __f)
         for (iterator __p = __b + __pos; __p != __e; ++__p)
             __alloc_traits::destroy(__a, _VSTD::addressof(*__p));
         __base::size() -= __n;
-        while (__back_spare() >= 2 * __base::__block_size)
-        {
-            __alloc_traits::deallocate(__a, __base::__map_.back(), __base::__block_size);
-            __base::__map_.pop_back();
+        while (__maybe_remove_back_spare()) {
         }
     }
 }
lib/libcxx/include/execution
@@ -0,0 +1,19 @@
+// -*- C++ -*-
+//===------------------------- execution ---------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP_EXECUTION
+#define _LIBCPP_EXECUTION
+
+#include <__config>
+
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <__pstl_execution>
+#endif
+
+#endif // _LIBCPP_EXECUTION
lib/libcxx/include/filesystem
@@ -625,7 +625,7 @@ struct __is_pathable_char_array<_Source, _ECharT*, _UPtr, true>
   static _ECharT __first_or_null(const _ECharT* __b) { return *__b; }
 };
 
-template <class _Iter, bool _IsIt = __is_input_iterator<_Iter>::value,
+template <class _Iter, bool _IsIt = __is_cpp17_input_iterator<_Iter>::value,
           class = void>
 struct __is_pathable_iter : false_type {};
 
@@ -708,14 +708,14 @@ template <>
 struct _PathCVT<char> {
 
   template <class _Iter>
-  static typename enable_if<__is_exactly_input_iterator<_Iter>::value>::type
+  static typename enable_if<__is_exactly_cpp17_input_iterator<_Iter>::value>::type
   __append_range(string& __dest, _Iter __b, _Iter __e) {
     for (; __b != __e; ++__b)
       __dest.push_back(*__b);
   }
 
   template <class _Iter>
-  static typename enable_if<__is_forward_iterator<_Iter>::value>::type
+  static typename enable_if<__is_cpp17_forward_iterator<_Iter>::value>::type
   __append_range(string& __dest, _Iter __b, _Iter __e) {
     __dest.__append_forward_unsafe(__b, __e);
   }
@@ -2583,6 +2583,7 @@ public:
   void disable_recursion_pending() { __rec_ = false; }
 
 private:
+  _LIBCPP_FUNC_VIS
   recursive_directory_iterator(const path& __p, directory_options __opt,
                                error_code* __ec);
 
lib/libcxx/include/forward_list
@@ -490,7 +490,7 @@ protected:
     _LIBCPP_INLINE_VISIBILITY
     __forward_list_base()
         _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
-        : __before_begin_(__begin_node()) {}
+        : __before_begin_(__begin_node(), __default_init_tag()) {}
     _LIBCPP_INLINE_VISIBILITY
     explicit __forward_list_base(const allocator_type& __a)
         : __before_begin_(__begin_node(), __node_allocator(__a)) {}
@@ -670,13 +670,13 @@ public:
     template <class _InputIterator>
         forward_list(_InputIterator __f, _InputIterator __l,
                      typename enable_if<
-                       __is_input_iterator<_InputIterator>::value
+                       __is_cpp17_input_iterator<_InputIterator>::value
                      >::type* = nullptr);
     template <class _InputIterator>
         forward_list(_InputIterator __f, _InputIterator __l,
                      const allocator_type& __a,
                      typename enable_if<
-                       __is_input_iterator<_InputIterator>::value
+                       __is_cpp17_input_iterator<_InputIterator>::value
                      >::type* = nullptr);
     forward_list(const forward_list& __x);
     forward_list(const forward_list& __x, const allocator_type& __a);
@@ -711,7 +711,7 @@ public:
     template <class _InputIterator>
         typename enable_if
         <
-            __is_input_iterator<_InputIterator>::value,
+            __is_cpp17_input_iterator<_InputIterator>::value,
             void
         >::type
         assign(_InputIterator __f, _InputIterator __l);
@@ -792,7 +792,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         typename enable_if
         <
-            __is_input_iterator<_InputIterator>::value,
+            __is_cpp17_input_iterator<_InputIterator>::value,
             iterator
         >::type
         insert_after(const_iterator __p, _InputIterator __f, _InputIterator __l);
@@ -950,7 +950,7 @@ template <class _Tp, class _Alloc>
 template <class _InputIterator>
 forward_list<_Tp, _Alloc>::forward_list(_InputIterator __f, _InputIterator __l,
                                         typename enable_if<
-                                          __is_input_iterator<_InputIterator>::value
+                                          __is_cpp17_input_iterator<_InputIterator>::value
                                         >::type*)
 {
     insert_after(cbefore_begin(), __f, __l);
@@ -961,7 +961,7 @@ template <class _InputIterator>
 forward_list<_Tp, _Alloc>::forward_list(_InputIterator __f, _InputIterator __l,
                                         const allocator_type& __a,
                                         typename enable_if<
-                                          __is_input_iterator<_InputIterator>::value
+                                          __is_cpp17_input_iterator<_InputIterator>::value
                                         >::type*)
     : base(__a)
 {
@@ -1074,7 +1074,7 @@ template <class _Tp, class _Alloc>
 template <class _InputIterator>
 typename enable_if
 <
-    __is_input_iterator<_InputIterator>::value,
+    __is_cpp17_input_iterator<_InputIterator>::value,
     void
 >::type
 forward_list<_Tp, _Alloc>::assign(_InputIterator __f, _InputIterator __l)
@@ -1270,7 +1270,7 @@ template <class _Tp, class _Alloc>
 template <class _InputIterator>
 typename enable_if
 <
-    __is_input_iterator<_InputIterator>::value,
+    __is_cpp17_input_iterator<_InputIterator>::value,
     typename forward_list<_Tp, _Alloc>::iterator
 >::type
 forward_list<_Tp, _Alloc>::insert_after(const_iterator __p,
@@ -1525,7 +1525,7 @@ forward_list<_Tp, _Alloc>::remove(const value_type& __v)
         else
             ++__i;
     }
-    
+
     return (__remove_return_type) __count_removed;
 }
 
@@ -1553,7 +1553,7 @@ forward_list<_Tp, _Alloc>::remove_if(_Predicate __pred)
         else
             ++__i;
     }
-    
+
     return (__remove_return_type) __count_removed;
 }
 
@@ -1573,7 +1573,7 @@ forward_list<_Tp, _Alloc>::unique(_BinaryPredicate __binary_pred)
             __deleted_nodes.splice_after(__deleted_nodes.before_begin(), *this, __i, __j);
         __i = __j;
     }
-    
+
     return (__remove_return_type) __count_removed;
 }
 
lib/libcxx/include/fstream
@@ -508,34 +508,34 @@ const char* basic_filebuf<_CharT, _Traits>::__make_mdstring(
   switch (__mode & ~ios_base::ate) {
   case ios_base::out:
   case ios_base::out | ios_base::trunc:
-    return "w";
+    return "w" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::out | ios_base::app:
   case ios_base::app:
-    return "a";
+    return "a" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in:
-    return "r";
+    return "r" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out:
-    return "r+";
+    return "r+" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::trunc:
-    return "w+";
+    return "w+" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::app:
   case ios_base::in | ios_base::app:
-    return "a+";
+    return "a+" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::out | ios_base::binary:
   case ios_base::out | ios_base::trunc | ios_base::binary:
-    return "wb";
+    return "wb" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::out | ios_base::app | ios_base::binary:
   case ios_base::app | ios_base::binary:
-    return "ab";
+    return "ab" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::binary:
-    return "rb";
+    return "rb" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::binary:
-    return "r+b";
+    return "r+b" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::trunc | ios_base::binary:
-    return "w+b";
+    return "w+b" _LIBCPP_FOPEN_CLOEXEC_MODE;
   case ios_base::in | ios_base::out | ios_base::app | ios_base::binary:
   case ios_base::in | ios_base::app | ios_base::binary:
-    return "a+b";
+    return "a+b" _LIBCPP_FOPEN_CLOEXEC_MODE;
   default:
     return nullptr;
   }
@@ -697,10 +697,9 @@ basic_filebuf<_CharT, _Traits>::close()
         unique_ptr<FILE, int(*)(FILE*)> __h(__file_, fclose);
         if (sync())
             __rt = 0;
-        if (fclose(__h.release()) == 0)
-            __file_ = 0;
-        else
+        if (fclose(__h.release()))
             __rt = 0;
+        __file_ = 0;
         setbuf(0, 0);
     }
     return __rt;
lib/libcxx/include/functional
@@ -440,6 +440,13 @@ public:
     template <typename T> const T* target() const noexcept;
 };
 
+// Deduction guides
+template<class R, class ...Args>
+function(R(*)(Args...)) -> function<R(Args...)>; // since C++17
+
+template<class F>
+function(F) -> function<see-below>; // since C++17
+
 // Null pointer comparisons:
 template <class R, class ... ArgTypes>
   bool operator==(const function<R(ArgTypes...)>&, nullptr_t) noexcept;
@@ -2335,6 +2342,53 @@ public:
 #endif  // _LIBCPP_NO_RTTI
 };
 
+#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
+template<class _Rp, class ..._Ap>
+function(_Rp(*)(_Ap...)) -> function<_Rp(_Ap...)>;
+
+template<class _Fp>
+struct __strip_signature;
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...)> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile> { using type = _Rp(_Ap...); };
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) &> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const &> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile &> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile &> { using type = _Rp(_Ap...); };
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile noexcept> { using type = _Rp(_Ap...); };
+
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) & noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const & noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) volatile & noexcept> { using type = _Rp(_Ap...); };
+template<class _Rp, class _Gp, class ..._Ap>
+struct __strip_signature<_Rp (_Gp::*) (_Ap...) const volatile & noexcept> { using type = _Rp(_Ap...); };
+
+template<class _Fp, class _Stripped = typename __strip_signature<decltype(&_Fp::operator())>::type>
+function(_Fp) -> function<_Stripped>;
+#endif // !_LIBCPP_HAS_NO_DEDUCTION_GUIDES
+
 template<class _Rp, class ..._ArgTypes>
 function<_Rp(_ArgTypes...)>::function(const function& __f) : __f_(__f.__f_) {}
 
lib/libcxx/include/future
@@ -611,7 +611,7 @@ __assoc_sub_state::wait_for(const chrono::duration<_Rep, _Period>& __rel_time) c
 }
 
 template <class _Rp>
-class _LIBCPP_AVAILABILITY_FUTURE __assoc_state
+class _LIBCPP_AVAILABILITY_FUTURE _LIBCPP_HIDDEN __assoc_state
     : public __assoc_sub_state
 {
     typedef __assoc_sub_state base;
@@ -1060,7 +1060,7 @@ template <class _Rp> class _LIBCPP_TEMPLATE_VIS shared_future;
 template <class _Rp> class _LIBCPP_TEMPLATE_VIS future;
 
 template <class _Rp, class _Fp>
-future<_Rp>
+_LIBCPP_INLINE_VISIBILITY future<_Rp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 __make_deferred_assoc_state(_Fp&& __f);
 #else
@@ -1068,7 +1068,7 @@ __make_deferred_assoc_state(_Fp __f);
 #endif
 
 template <class _Rp, class _Fp>
-future<_Rp>
+_LIBCPP_INLINE_VISIBILITY future<_Rp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 __make_async_assoc_state(_Fp&& __f);
 #else
@@ -1767,9 +1767,9 @@ class _LIBCPP_AVAILABILITY_FUTURE __packaged_task_func<_Fp, _Alloc, _Rp(_ArgType
     __compressed_pair<_Fp, _Alloc> __f_;
 public:
     _LIBCPP_INLINE_VISIBILITY
-    explicit __packaged_task_func(const _Fp& __f) : __f_(__f) {}
+    explicit __packaged_task_func(const _Fp& __f) : __f_(__f, __default_init_tag()) {}
     _LIBCPP_INLINE_VISIBILITY
-    explicit __packaged_task_func(_Fp&& __f) : __f_(_VSTD::move(__f)) {}
+    explicit __packaged_task_func(_Fp&& __f) : __f_(_VSTD::move(__f), __default_init_tag()) {}
     _LIBCPP_INLINE_VISIBILITY
     __packaged_task_func(const _Fp& __f, const _Alloc& __a)
         : __f_(__f, __a) {}
@@ -2266,7 +2266,7 @@ struct _LIBCPP_TEMPLATE_VIS uses_allocator<packaged_task<_Callable>, _Alloc>
     : public true_type {};
 
 template <class _Rp, class _Fp>
-future<_Rp>
+_LIBCPP_INLINE_VISIBILITY future<_Rp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 __make_deferred_assoc_state(_Fp&& __f)
 #else
@@ -2279,7 +2279,7 @@ __make_deferred_assoc_state(_Fp __f)
 }
 
 template <class _Rp, class _Fp>
-future<_Rp>
+_LIBCPP_INLINE_VISIBILITY future<_Rp>
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
 __make_async_assoc_state(_Fp&& __f)
 #else
@@ -2293,7 +2293,7 @@ __make_async_assoc_state(_Fp __f)
 }
 
 template <class _Fp, class... _Args>
-class __async_func
+class _LIBCPP_HIDDEN __async_func
 {
     tuple<_Fp, _Args...> __f_;
 
lib/libcxx/include/istream
@@ -1619,7 +1619,7 @@ operator>>(basic_istream<_CharT, _Traits>& __is, bitset<_Size>& __x)
                  __is.rdbuf()->sbumpc();
             }
             __x = bitset<_Size>(__str);
-            if (__c == 0)
+            if (_Size > 0 && __c == 0)
                __state |= ios_base::failbit;
 #ifndef _LIBCPP_NO_EXCEPTIONS
         }
lib/libcxx/include/iterator
@@ -434,12 +434,65 @@ template <class E> constexpr const E* data(initializer_list<E> il) noexcept;
 #endif
 
 _LIBCPP_BEGIN_NAMESPACE_STD
+template <class _Iter>
+struct _LIBCPP_TEMPLATE_VIS iterator_traits;
 
 struct _LIBCPP_TEMPLATE_VIS input_iterator_tag {};
 struct _LIBCPP_TEMPLATE_VIS output_iterator_tag {};
 struct _LIBCPP_TEMPLATE_VIS forward_iterator_tag       : public input_iterator_tag {};
 struct _LIBCPP_TEMPLATE_VIS bidirectional_iterator_tag : public forward_iterator_tag {};
 struct _LIBCPP_TEMPLATE_VIS random_access_iterator_tag : public bidirectional_iterator_tag {};
+#if _LIBCPP_STD_VER > 17
+// TODO(EricWF)  contiguous_iterator_tag is provided as an extension prior to
+//  C++20 to allow optimizations for users providing wrapped iterator types.
+struct _LIBCPP_TEMPLATE_VIS contiguous_iterator_tag: public random_access_iterator_tag { };
+#endif
+
+template <class _Iter>
+struct __iter_traits_cache {
+  using type = _If<
+    __is_primary_template<iterator_traits<_Iter> >::value,
+    _Iter,
+    iterator_traits<_Iter>
+  >;
+};
+template <class _Iter>
+using _ITER_TRAITS = typename __iter_traits_cache<_Iter>::type;
+
+struct __iter_concept_concept_test {
+  template <class _Iter>
+  using _Apply = typename _ITER_TRAITS<_Iter>::iterator_concept;
+};
+struct __iter_concept_category_test {
+  template <class _Iter>
+  using _Apply = typename _ITER_TRAITS<_Iter>::iterator_category;
+};
+struct __iter_concept_random_fallback {
+  template <class _Iter>
+  using _Apply = _EnableIf<
+                          __is_primary_template<iterator_traits<_Iter> >::value,
+                          random_access_iterator_tag
+                        >;
+};
+
+template <class _Iter, class _Tester> struct __test_iter_concept
+    : _IsValidExpansion<_Tester::template _Apply, _Iter>,
+      _Tester
+{
+};
+
+template <class _Iter>
+struct __iter_concept_cache {
+  using type = _Or<
+    __test_iter_concept<_Iter, __iter_concept_concept_test>,
+    __test_iter_concept<_Iter, __iter_concept_category_test>,
+    __test_iter_concept<_Iter, __iter_concept_random_fallback>
+  >;
+};
+
+template <class _Iter>
+using _ITER_CONCEPT = typename __iter_concept_cache<_Iter>::type::template _Apply<_Iter>;
+
 
 template <class _Tp>
 struct __has_iterator_typedefs
@@ -500,7 +553,10 @@ struct __iterator_traits<_Iter, true>
 
 template <class _Iter>
 struct _LIBCPP_TEMPLATE_VIS iterator_traits
-    : __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> {};
+    : __iterator_traits<_Iter, __has_iterator_typedefs<_Iter>::value> {
+
+  using __primary_template = iterator_traits;
+};
 
 template<class _Tp>
 struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
@@ -510,6 +566,9 @@ struct _LIBCPP_TEMPLATE_VIS iterator_traits<_Tp*>
     typedef _Tp* pointer;
     typedef _Tp& reference;
     typedef random_access_iterator_tag iterator_category;
+#if _LIBCPP_STD_VER > 17
+    typedef contiguous_iterator_tag    iterator_concept;
+#endif
 };
 
 template <class _Tp, class _Up, bool = __has_iterator_category<iterator_traits<_Tp> >::value>
@@ -521,19 +580,28 @@ template <class _Tp, class _Up>
 struct __has_iterator_category_convertible_to<_Tp, _Up, false> : public false_type {};
 
 template <class _Tp>
-struct __is_input_iterator : public __has_iterator_category_convertible_to<_Tp, input_iterator_tag> {};
+struct __is_cpp17_input_iterator : public __has_iterator_category_convertible_to<_Tp, input_iterator_tag> {};
 
 template <class _Tp>
-struct __is_forward_iterator : public __has_iterator_category_convertible_to<_Tp, forward_iterator_tag> {};
+struct __is_cpp17_forward_iterator : public __has_iterator_category_convertible_to<_Tp, forward_iterator_tag> {};
 
 template <class _Tp>
-struct __is_bidirectional_iterator : public __has_iterator_category_convertible_to<_Tp, bidirectional_iterator_tag> {};
+struct __is_cpp17_bidirectional_iterator : public __has_iterator_category_convertible_to<_Tp, bidirectional_iterator_tag> {};
 
 template <class _Tp>
-struct __is_random_access_iterator : public __has_iterator_category_convertible_to<_Tp, random_access_iterator_tag> {};
+struct __is_cpp17_random_access_iterator : public __has_iterator_category_convertible_to<_Tp, random_access_iterator_tag> {};
+
+#if _LIBCPP_STD_VER > 17
+template <class _Tp>
+struct __is_cpp17_contiguous_iterator : public __has_iterator_category_convertible_to<_Tp, contiguous_iterator_tag> {};
+#else
+template <class _Tp>
+struct __is_cpp17_contiguous_iterator : public false_type {};
+#endif
+
 
 template <class _Tp>
-struct __is_exactly_input_iterator
+struct __is_exactly_cpp17_input_iterator
     : public integral_constant<bool,
          __has_iterator_category_convertible_to<_Tp, input_iterator_tag>::value &&
         !__has_iterator_category_convertible_to<_Tp, forward_iterator_tag>::value> {};
@@ -600,7 +668,7 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 void advance(_InputIter& __i,
              typename iterator_traits<_InputIter>::difference_type __n)
 {
-    _LIBCPP_ASSERT(__n >= 0 || __is_bidirectional_iterator<_InputIter>::value,
+    _LIBCPP_ASSERT(__n >= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
                        "Attempt to advance(it, -n) on a non-bidi iterator");
     __advance(__i, __n, typename iterator_traits<_InputIter>::iterator_category());
 }
@@ -636,13 +704,13 @@ template <class _InputIter>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 typename enable_if
 <
-    __is_input_iterator<_InputIter>::value,
+    __is_cpp17_input_iterator<_InputIter>::value,
     _InputIter
 >::type
 next(_InputIter __x,
      typename iterator_traits<_InputIter>::difference_type __n = 1)
 {
-    _LIBCPP_ASSERT(__n >= 0 || __is_bidirectional_iterator<_InputIter>::value,
+    _LIBCPP_ASSERT(__n >= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
                        "Attempt to next(it, -n) on a non-bidi iterator");
 
     _VSTD::advance(__x, __n);
@@ -653,13 +721,13 @@ template <class _InputIter>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
 typename enable_if
 <
-    __is_input_iterator<_InputIter>::value,
+    __is_cpp17_input_iterator<_InputIter>::value,
     _InputIter
 >::type
 prev(_InputIter __x,
      typename iterator_traits<_InputIter>::difference_type __n = 1)
 {
-    _LIBCPP_ASSERT(__n <= 0 || __is_bidirectional_iterator<_InputIter>::value,
+    _LIBCPP_ASSERT(__n <= 0 || __is_cpp17_bidirectional_iterator<_InputIter>::value,
                        "Attempt to prev(it, +n) on a non-bidi iterator");
     _VSTD::advance(__x, -__n);
     return __x;
@@ -1304,8 +1372,8 @@ _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_IF_NODEBUG
 __wrap_iter<_Iter>
 operator+(typename __wrap_iter<_Iter>::difference_type, __wrap_iter<_Iter>) _NOEXCEPT;
 
-template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY copy(_Ip, _Ip, _Op);
-template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY copy_backward(_B1, _B1, _B2);
+template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 copy(_Ip, _Ip, _Op);
+template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17 copy_backward(_B1, _B1, _B2);
 template <class _Ip, class _Op> _Op _LIBCPP_INLINE_VISIBILITY move(_Ip, _Ip, _Op);
 template <class _B1, class _B2> _B2 _LIBCPP_INLINE_VISIBILITY move_backward(_B1, _B1, _B2);
 
@@ -1515,8 +1583,8 @@ private:
     __wrap_iter<_Iter1>
     operator+(typename __wrap_iter<_Iter1>::difference_type, __wrap_iter<_Iter1>) _NOEXCEPT;
 
-    template <class _Ip, class _Op> friend _Op copy(_Ip, _Ip, _Op);
-    template <class _B1, class _B2> friend _B2 copy_backward(_B1, _B1, _B2);
+    template <class _Ip, class _Op> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _Op copy(_Ip, _Ip, _Op);
+    template <class _B1, class _B2> friend _LIBCPP_CONSTEXPR_AFTER_CXX17 _B2 copy_backward(_B1, _B1, _B2);
     template <class _Ip, class _Op> friend _Op move(_Ip, _Ip, _Op);
     template <class _B1, class _B2> friend _B2 move_backward(_B1, _B1, _B2);
 
lib/libcxx/include/list
@@ -715,7 +715,7 @@ template <class _Tp, class _Alloc>
 inline
 __list_imp<_Tp, _Alloc>::__list_imp()
         _NOEXCEPT_(is_nothrow_default_constructible<__node_allocator>::value)
-    : __size_alloc_(0)
+    : __size_alloc_(0, __default_init_tag())
 {
 }
 
@@ -887,10 +887,10 @@ public:
     list(size_type __n, const value_type& __x, const allocator_type& __a);
     template <class _InpIter>
         list(_InpIter __f, _InpIter __l,
-             typename enable_if<__is_input_iterator<_InpIter>::value>::type* = 0);
+             typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type* = 0);
     template <class _InpIter>
         list(_InpIter __f, _InpIter __l, const allocator_type& __a,
-             typename enable_if<__is_input_iterator<_InpIter>::value>::type* = 0);
+             typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type* = 0);
 
     list(const list& __c);
     list(const list& __c, const allocator_type& __a);
@@ -922,7 +922,7 @@ public:
 
     template <class _InpIter>
         void assign(_InpIter __f, _InpIter __l,
-             typename enable_if<__is_input_iterator<_InpIter>::value>::type* = 0);
+             typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type* = 0);
     void assign(size_type __n, const value_type& __x);
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1039,7 +1039,7 @@ public:
     iterator insert(const_iterator __p, size_type __n, const value_type& __x);
     template <class _InpIter>
         iterator insert(const_iterator __p, _InpIter __f, _InpIter __l,
-             typename enable_if<__is_input_iterator<_InpIter>::value>::type* = 0);
+             typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type* = 0);
 
     _LIBCPP_INLINE_VISIBILITY
     void swap(list& __c)
@@ -1252,7 +1252,7 @@ list<_Tp, _Alloc>::list(size_type __n, const value_type& __x, const allocator_ty
 template <class _Tp, class _Alloc>
 template <class _InpIter>
 list<_Tp, _Alloc>::list(_InpIter __f, _InpIter __l,
-                        typename enable_if<__is_input_iterator<_InpIter>::value>::type*)
+                        typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type*)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
@@ -1264,7 +1264,7 @@ list<_Tp, _Alloc>::list(_InpIter __f, _InpIter __l,
 template <class _Tp, class _Alloc>
 template <class _InpIter>
 list<_Tp, _Alloc>::list(_InpIter __f, _InpIter __l, const allocator_type& __a,
-                        typename enable_if<__is_input_iterator<_InpIter>::value>::type*)
+                        typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type*)
     : base(__a)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1403,7 +1403,7 @@ template <class _Tp, class _Alloc>
 template <class _InpIter>
 void
 list<_Tp, _Alloc>::assign(_InpIter __f, _InpIter __l,
-                          typename enable_if<__is_input_iterator<_InpIter>::value>::type*)
+                          typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type*)
 {
     iterator __i = begin();
     iterator __e = end();
@@ -1532,7 +1532,7 @@ template <class _Tp, class _Alloc>
 template <class _InpIter>
 typename list<_Tp, _Alloc>::iterator
 list<_Tp, _Alloc>::insert(const_iterator __p, _InpIter __f, _InpIter __l,
-             typename enable_if<__is_input_iterator<_InpIter>::value>::type*)
+             typename enable_if<__is_cpp17_input_iterator<_InpIter>::value>::type*)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     _LIBCPP_ASSERT(__get_const_db()->__find_c_from_i(&__p) == this,
@@ -2211,7 +2211,7 @@ list<_Tp, _Alloc>::unique(_BinaryPred __binary_pred)
             __i = __j;
             }
     }
-    
+
     return (__remove_return_type) __deleted_nodes.size();
 }
 
lib/libcxx/include/map
@@ -1474,26 +1474,26 @@ private:
 #ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
 template<class _InputIterator, class _Compare = less<__iter_key_type<_InputIterator>>,
          class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
-         class = enable_if_t<!__is_allocator<_Compare>::value, void>,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>,
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 map(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Compare, _Allocator>;
 
 template<class _Key, class _Tp, class _Compare = less<remove_const_t<_Key>>,
          class _Allocator = allocator<pair<const _Key, _Tp>>,
-         class = enable_if_t<!__is_allocator<_Compare>::value, void>,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>,
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 map(initializer_list<pair<_Key, _Tp>>, _Compare = _Compare(), _Allocator = _Allocator())
   -> map<remove_const_t<_Key>, _Tp, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 map(_InputIterator, _InputIterator, _Allocator)
   -> map<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
          less<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Tp, class _Allocator,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 map(initializer_list<pair<_Key, _Tp>>, _Allocator)
   -> map<remove_const_t<_Key>, _Tp, less<remove_const_t<_Key>>, _Allocator>;
 #endif
@@ -2131,26 +2131,26 @@ private:
 #ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
 template<class _InputIterator, class _Compare = less<__iter_key_type<_InputIterator>>,
          class _Allocator = allocator<__iter_to_alloc_type<_InputIterator>>,
-         class = enable_if_t<!__is_allocator<_Compare>::value, void>,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>,
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 multimap(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>, _Compare, _Allocator>;
 
 template<class _Key, class _Tp, class _Compare = less<remove_const_t<_Key>>,
          class _Allocator = allocator<pair<const _Key, _Tp>>,
-         class = enable_if_t<!__is_allocator<_Compare>::value, void>,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>,
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 multimap(initializer_list<pair<_Key, _Tp>>, _Compare = _Compare(), _Allocator = _Allocator())
   -> multimap<remove_const_t<_Key>, _Tp, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 multimap(_InputIterator, _InputIterator, _Allocator)
   -> multimap<__iter_key_type<_InputIterator>, __iter_mapped_type<_InputIterator>,
          less<__iter_key_type<_InputIterator>>, _Allocator>;
 
 template<class _Key, class _Tp, class _Allocator,
-         class = enable_if_t<__is_allocator<_Allocator>::value, void>>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 multimap(initializer_list<pair<_Key, _Tp>>, _Allocator)
   -> multimap<remove_const_t<_Key>, _Tp, less<remove_const_t<_Key>>, _Allocator>;
 #endif
lib/libcxx/include/math.h
@@ -510,7 +510,11 @@ _LIBCPP_INLINE_VISIBILITY
 bool
 __libcpp_isnan(_A1 __lcpp_x) _NOEXCEPT
 {
+#if __has_builtin(__builtin_isnan)
+    return __builtin_isnan(__lcpp_x);
+#else
     return isnan(__lcpp_x);
+#endif
 }
 
 #undef isnan
lib/libcxx/include/memory
@@ -662,7 +662,6 @@ void* align(size_t alignment, size_t size, void*& ptr, size_t& space);
 #include <tuple>
 #include <stdexcept>
 #include <cstring>
-#include <cassert>
 #if !defined(_LIBCPP_HAS_NO_ATOMIC_HEADER)
 #  include <atomic>
 #endif
@@ -1099,40 +1098,51 @@ struct __const_void_pointer<_Ptr, _Alloc, false>
 #endif
 };
 
+
+template <bool _UsePointerTraits> struct __to_address_helper;
+
+template <> struct __to_address_helper<true> {
+    template <class _Pointer>
+    using __return_type = decltype(pointer_traits<_Pointer>::to_address(std::declval<const _Pointer&>()));
+
+    template <class _Pointer>
+    _LIBCPP_CONSTEXPR
+    static __return_type<_Pointer>
+    __do_it(const _Pointer &__p) _NOEXCEPT { return pointer_traits<_Pointer>::to_address(__p); }
+};
+
+template <class _Pointer, bool _Dummy = true>
+using __choose_to_address = __to_address_helper<_IsValidExpansion<__to_address_helper<_Dummy>::template __return_type, _Pointer>::value>;
+
+
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
 _Tp*
-__to_raw_pointer(_Tp* __p) _NOEXCEPT
+__to_address(_Tp* __p) _NOEXCEPT
 {
+    static_assert(!is_function<_Tp>::value, "_Tp is a function type");
     return __p;
 }
 
-#if _LIBCPP_STD_VER <= 17
-template <class _Pointer>
-inline _LIBCPP_INLINE_VISIBILITY
-typename pointer_traits<_Pointer>::element_type*
-__to_raw_pointer(_Pointer __p) _NOEXCEPT
-{
-    return _VSTD::__to_raw_pointer(__p.operator->());
-}
-#else
 template <class _Pointer>
-inline _LIBCPP_INLINE_VISIBILITY
-auto
-__to_raw_pointer(const _Pointer& __p) _NOEXCEPT
--> decltype(pointer_traits<_Pointer>::to_address(__p))
-{
-    return pointer_traits<_Pointer>::to_address(__p);
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+typename __choose_to_address<_Pointer>::template __return_type<_Pointer>
+__to_address(const _Pointer& __p) _NOEXCEPT {
+  return __choose_to_address<_Pointer>::__do_it(__p);
 }
 
-template <class _Pointer, class... _None>
-inline _LIBCPP_INLINE_VISIBILITY
-auto
-__to_raw_pointer(const _Pointer& __p, _None...) _NOEXCEPT
-{
-    return _VSTD::__to_raw_pointer(__p.operator->());
-}
+template <> struct __to_address_helper<false> {
+    template <class _Pointer>
+    using __return_type = typename pointer_traits<_Pointer>::element_type*;
 
+    template <class _Pointer>
+    _LIBCPP_CONSTEXPR
+    static __return_type<_Pointer>
+    __do_it(const _Pointer &__p) _NOEXCEPT { return std::__to_address(__p.operator->()); }
+};
+
+
+#if _LIBCPP_STD_VER > 17
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY constexpr
 _Tp*
@@ -1147,7 +1157,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 auto
 to_address(const _Pointer& __p) _NOEXCEPT
 {
-    return _VSTD::__to_raw_pointer(__p);
+    return _VSTD::__to_address(__p);
 }
 #endif
 
@@ -1507,6 +1517,31 @@ struct __is_default_allocator : false_type {};
 template <class _Tp>
 struct __is_default_allocator<_VSTD::allocator<_Tp> > : true_type {};
 
+
+
+template <class _Alloc,
+    bool = __has_construct<_Alloc, typename _Alloc::value_type*,  typename _Alloc::value_type&&>::value && !__is_default_allocator<_Alloc>::value
+    >
+struct __is_cpp17_move_insertable;
+template <class _Alloc>
+struct __is_cpp17_move_insertable<_Alloc, true> : std::true_type {};
+template <class _Alloc>
+struct __is_cpp17_move_insertable<_Alloc, false> : std::is_move_constructible<typename _Alloc::value_type> {};
+
+template <class _Alloc,
+    bool = __has_construct<_Alloc, typename _Alloc::value_type*, const typename _Alloc::value_type&>::value && !__is_default_allocator<_Alloc>::value
+    >
+struct __is_cpp17_copy_insertable;
+template <class _Alloc>
+struct __is_cpp17_copy_insertable<_Alloc, true> : __is_cpp17_move_insertable<_Alloc> {};
+template <class _Alloc>
+struct __is_cpp17_copy_insertable<_Alloc, false> : integral_constant<bool,
+    std::is_copy_constructible<typename _Alloc::value_type>::value &&
+    __is_cpp17_move_insertable<_Alloc>::value>
+  {};
+
+
+
 template <class _Alloc>
 struct _LIBCPP_TEMPLATE_VIS allocator_traits
 {
@@ -1609,10 +1644,18 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
         _LIBCPP_INLINE_VISIBILITY
         static
         void
-        __construct_forward(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2)
+        __construct_forward_with_exception_guarantees(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2)
         {
+            static_assert(__is_cpp17_move_insertable<allocator_type>::value,
+              "The specified type does not meet the requirements of Cpp17MoveInsertible");
             for (; __begin1 != __end1; ++__begin1, (void) ++__begin2)
-                construct(__a, _VSTD::__to_raw_pointer(__begin2), _VSTD::move_if_noexcept(*__begin1));
+              construct(__a, _VSTD::__to_address(__begin2),
+#ifdef _LIBCPP_NO_EXCEPTIONS
+                        _VSTD::move(*__begin1)
+#else
+                        _VSTD::move_if_noexcept(*__begin1)
+#endif
+                        );
         }
 
     template <class _Tp>
@@ -1625,7 +1668,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
              is_trivially_move_constructible<_Tp>::value,
             void
         >::type
-        __construct_forward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
+        __construct_forward_with_exception_guarantees(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
         {
             ptrdiff_t _Np = __end1 - __begin1;
             if (_Np > 0)
@@ -1642,7 +1685,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
         __construct_range_forward(allocator_type& __a, _Iter __begin1, _Iter __end1, _Ptr& __begin2)
         {
             for (; __begin1 != __end1; ++__begin1, (void) ++__begin2)
-                construct(__a, _VSTD::__to_raw_pointer(__begin2), *__begin1);
+                construct(__a, _VSTD::__to_address(__begin2), *__begin1);
         }
 
     template <class _SourceTp, class _DestTp,
@@ -1672,12 +1715,20 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
         _LIBCPP_INLINE_VISIBILITY
         static
         void
-        __construct_backward(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __end2)
+        __construct_backward_with_exception_guarantees(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __end2)
         {
+            static_assert(__is_cpp17_move_insertable<allocator_type>::value,
+              "The specified type does not meet the requirements of Cpp17MoveInsertable");
             while (__end1 != __begin1)
             {
-                construct(__a, _VSTD::__to_raw_pointer(__end2-1), _VSTD::move_if_noexcept(*--__end1));
-                --__end2;
+              construct(__a, _VSTD::__to_address(__end2 - 1),
+#ifdef _LIBCPP_NO_EXCEPTIONS
+                        _VSTD::move(*--__end1)
+#else
+                        _VSTD::move_if_noexcept(*--__end1)
+#endif
+                        );
+              --__end2;
             }
         }
 
@@ -1691,7 +1742,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
              is_trivially_move_constructible<_Tp>::value,
             void
         >::type
-        __construct_backward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
+        __construct_backward_with_exception_guarantees(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __end2)
         {
             ptrdiff_t _Np = __end1 - __begin1;
             __end2 -= _Np;
@@ -2127,6 +2178,10 @@ public:
 };
 #endif
 
+// Tag used to default initialize one or both of the pair's elements.
+struct __default_init_tag {};
+struct __value_init_tag {};
+
 template <class _Tp, int _Idx,
           bool _CanBeEmptyBase =
               is_empty<_Tp>::value && !__libcpp_is_final<_Tp>::value>
@@ -2135,30 +2190,31 @@ struct __compressed_pair_elem {
   typedef _Tp& reference;
   typedef const _Tp& const_reference;
 
-#ifndef _LIBCPP_CXX03_LANG
-  _LIBCPP_INLINE_VISIBILITY constexpr __compressed_pair_elem() : __value_() {}
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+  __compressed_pair_elem(__default_init_tag) {}
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+  __compressed_pair_elem(__value_init_tag) : __value_() {}
 
   template <class _Up, class = typename enable_if<
       !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
   >::type>
   _LIBCPP_INLINE_VISIBILITY
-  constexpr explicit
+  _LIBCPP_CONSTEXPR explicit
   __compressed_pair_elem(_Up&& __u)
       : __value_(_VSTD::forward<_Up>(__u))
     {
     }
 
+
+#ifndef _LIBCPP_CXX03_LANG
   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
-  _LIBCPP_INLINE_VISIBILITY __compressed_pair_elem() : __value_() {}
-  _LIBCPP_INLINE_VISIBILITY
-  __compressed_pair_elem(_ParamT __p) : __value_(std::forward<_ParamT>(__p)) {}
 #endif
 
+
   _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return __value_; }
   _LIBCPP_INLINE_VISIBILITY
   const_reference __get() const _NOEXCEPT { return __value_; }
@@ -2174,28 +2230,27 @@ struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
   typedef const _Tp& const_reference;
   typedef _Tp __value_type;
 
-#ifndef _LIBCPP_CXX03_LANG
-  _LIBCPP_INLINE_VISIBILITY constexpr __compressed_pair_elem() = default;
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR __compressed_pair_elem() = default;
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+  __compressed_pair_elem(__default_init_tag) {}
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+  __compressed_pair_elem(__value_init_tag) : __value_type() {}
 
   template <class _Up, class = typename enable_if<
         !is_same<__compressed_pair_elem, typename decay<_Up>::type>::value
   >::type>
   _LIBCPP_INLINE_VISIBILITY
-  constexpr explicit
+  _LIBCPP_CONSTEXPR explicit
   __compressed_pair_elem(_Up&& __u)
       : __value_type(_VSTD::forward<_Up>(__u))
   {}
 
+#ifndef _LIBCPP_CXX03_LANG
   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
-  _LIBCPP_INLINE_VISIBILITY __compressed_pair_elem() : __value_type() {}
-  _LIBCPP_INLINE_VISIBILITY
-  __compressed_pair_elem(_ParamT __p)
-      : __value_type(std::forward<_ParamT>(__p)) {}
 #endif
 
   _LIBCPP_INLINE_VISIBILITY reference __get() _NOEXCEPT { return *this; }
@@ -2203,9 +2258,6 @@ struct __compressed_pair_elem<_Tp, _Idx, true> : private _Tp {
   const_reference __get() const _NOEXCEPT { return *this; }
 };
 
-// Tag used to construct the second element of the compressed pair.
-struct __second_tag {};
-
 template <class _T1, class _T2>
 class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
                           private __compressed_pair_elem<_T2, 1> {
@@ -2222,33 +2274,21 @@ class __compressed_pair : private __compressed_pair_elem<_T1, 0>,
     "implementation for this configuration");
 
 public:
-#ifndef _LIBCPP_CXX03_LANG
-  template <bool _Dummy = true,
+    template <bool _Dummy = true,
       class = typename enable_if<
           __dependent_type<is_default_constructible<_T1>, _Dummy>::value &&
           __dependent_type<is_default_constructible<_T2>, _Dummy>::value
       >::type
   >
   _LIBCPP_INLINE_VISIBILITY
-  constexpr __compressed_pair() {}
-
-  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() {}
-
-  template <class _Tp>
-  _LIBCPP_INLINE_VISIBILITY constexpr
-  __compressed_pair(__second_tag, _Tp&& __t)
-      : _Base1(), _Base2(std::forward<_Tp>(__t)) {}
+  _LIBCPP_CONSTEXPR __compressed_pair() : _Base1(__value_init_tag()), _Base2(__value_init_tag()) {}
 
   template <class _U1, class _U2>
-  _LIBCPP_INLINE_VISIBILITY constexpr
+  _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
   __compressed_pair(_U1&& __t1, _U2&& __t2)
       : _Base1(std::forward<_U1>(__t1)), _Base2(std::forward<_U2>(__t2)) {}
 
+#ifndef _LIBCPP_CXX03_LANG
   template <class... _Args1, class... _Args2>
   _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX14
   __compressed_pair(piecewise_construct_t __pc, tuple<_Args1...> __first_args,
@@ -2257,21 +2297,6 @@ public:
                typename __make_tuple_indices<sizeof...(_Args1)>::type()),
         _Base2(__pc, _VSTD::move(__second_args),
                typename __make_tuple_indices<sizeof...(_Args2)>::type()) {}
-
-#else
-  _LIBCPP_INLINE_VISIBILITY
-  __compressed_pair() {}
-
-  _LIBCPP_INLINE_VISIBILITY explicit
-  __compressed_pair(_T1 __t1) : _Base1(_VSTD::forward<_T1>(__t1)) {}
-
-  _LIBCPP_INLINE_VISIBILITY
-  __compressed_pair(__second_tag, _T2 __t2)
-      : _Base1(), _Base2(_VSTD::forward<_T2>(__t2)) {}
-
-  _LIBCPP_INLINE_VISIBILITY
-  __compressed_pair(_T1 __t1, _T2 __t2)
-      : _Base1(_VSTD::forward<_T1>(__t1)), _Base2(_VSTD::forward<_T2>(__t2)) {}
 #endif
 
   _LIBCPP_INLINE_VISIBILITY
@@ -2452,17 +2477,17 @@ public:
   template <bool _Dummy = true,
             class = _EnableIfDeleterDefaultConstructible<_Dummy> >
   _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(pointer()) {}
+  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}
 
   template <bool _Dummy = true,
             class = _EnableIfDeleterDefaultConstructible<_Dummy> >
   _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(pointer()) {}
+  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}
 
   template <bool _Dummy = true,
             class = _EnableIfDeleterDefaultConstructible<_Dummy> >
   _LIBCPP_INLINE_VISIBILITY
-  explicit unique_ptr(pointer __p) _NOEXCEPT : __ptr_(__p) {}
+  explicit unique_ptr(pointer __p) _NOEXCEPT : __ptr_(__p, __default_init_tag()) {}
 
   template <bool _Dummy = true,
             class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> > >
@@ -2504,7 +2529,7 @@ public:
              typename enable_if<is_convertible<_Up*, _Tp*>::value &&
                                     is_same<_Dp, default_delete<_Tp> >::value,
                                 __nat>::type = __nat()) _NOEXCEPT
-      : __ptr_(__p.release()) {}
+      : __ptr_(__p.release(), __default_init_tag()) {}
 #endif
 
   _LIBCPP_INLINE_VISIBILITY
@@ -2675,19 +2700,19 @@ public:
   template <bool _Dummy = true,
             class = _EnableIfDeleterDefaultConstructible<_Dummy> >
   _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(pointer()) {}
+  _LIBCPP_CONSTEXPR unique_ptr() _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}
 
   template <bool _Dummy = true,
             class = _EnableIfDeleterDefaultConstructible<_Dummy> >
   _LIBCPP_INLINE_VISIBILITY
-  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(pointer()) {}
+  _LIBCPP_CONSTEXPR unique_ptr(nullptr_t) _NOEXCEPT : __ptr_(pointer(), __default_init_tag()) {}
 
   template <class _Pp, bool _Dummy = true,
             class = _EnableIfDeleterDefaultConstructible<_Dummy>,
             class = _EnableIfPointerConvertible<_Pp> >
   _LIBCPP_INLINE_VISIBILITY
   explicit unique_ptr(_Pp __p) _NOEXCEPT
-      : __ptr_(__p) {}
+      : __ptr_(__p, __default_init_tag()) {}
 
   template <class _Pp, bool _Dummy = true,
             class = _EnableIfDeleterConstructible<_LValRefType<_Dummy> >,
@@ -3531,24 +3556,20 @@ class __shared_ptr_emplace
 {
     __compressed_pair<_Alloc, _Tp> __data_;
 public:
-#ifndef _LIBCPP_HAS_NO_VARIADICS
 
     _LIBCPP_INLINE_VISIBILITY
     __shared_ptr_emplace(_Alloc __a)
-        :  __data_(_VSTD::move(__a)) {}
+        :  __data_(_VSTD::move(__a), __value_init_tag()) {}
+
 
+#ifndef _LIBCPP_HAS_NO_VARIADICS
     template <class ..._Args>
         _LIBCPP_INLINE_VISIBILITY
         __shared_ptr_emplace(_Alloc __a, _Args&& ...__args)
             :  __data_(piecewise_construct, _VSTD::forward_as_tuple(__a),
                    _VSTD::forward_as_tuple(_VSTD::forward<_Args>(__args)...)) {}
-
 #else  // _LIBCPP_HAS_NO_VARIADICS
 
-    _LIBCPP_INLINE_VISIBILITY
-    __shared_ptr_emplace(_Alloc __a)
-        :  __data_(__a) {}
-
     template <class _A0>
         _LIBCPP_INLINE_VISIBILITY
         __shared_ptr_emplace(_Alloc __a, _A0& __a0)
@@ -3831,49 +3852,22 @@ public:
                       : nullptr);}
 #endif  // _LIBCPP_NO_RTTI
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
-    template<class ..._Args>
-        static
-        shared_ptr<_Tp>
-        make_shared(_Args&& ...__args);
+    template<class _Yp, class _CntrlBlk>
+    static shared_ptr<_Tp>
+    __create_with_control_block(_Yp* __p, _CntrlBlk* __cntrl)
+    {
+        shared_ptr<_Tp> __r;
+        __r.__ptr_ = __p;
+        __r.__cntrl_ = __cntrl;
+        __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
+        return __r;
+    }
 
     template<class _Alloc, class ..._Args>
         static
         shared_ptr<_Tp>
         allocate_shared(const _Alloc& __a, _Args&& ...__args);
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
-
-    static shared_ptr<_Tp> make_shared();
-
-    template<class _A0>
-        static shared_ptr<_Tp> make_shared(_A0&);
-
-    template<class _A0, class _A1>
-        static shared_ptr<_Tp> make_shared(_A0&, _A1&);
-
-    template<class _A0, class _A1, class _A2>
-        static shared_ptr<_Tp> make_shared(_A0&, _A1&, _A2&);
-
-    template<class _Alloc>
-        static shared_ptr<_Tp>
-        allocate_shared(const _Alloc& __a);
-
-    template<class _Alloc, class _A0>
-        static shared_ptr<_Tp>
-        allocate_shared(const _Alloc& __a, _A0& __a0);
-
-    template<class _Alloc, class _A0, class _A1>
-        static shared_ptr<_Tp>
-        allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1);
-
-    template<class _Alloc, class _A0, class _A1, class _A2>
-        static shared_ptr<_Tp>
-        allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1, _A2& __a2);
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 private:
     template <class _Yp, bool = is_function<_Yp>::value>
         struct __shared_ptr_default_allocator
@@ -4186,27 +4180,6 @@ shared_ptr<_Tp>::shared_ptr(unique_ptr<_Yp, _Dp> __r,
     __r.release();
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
-template<class _Tp>
-template<class ..._Args>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::make_shared(_Args&& ...__args)
-{
-    static_assert( is_constructible<_Tp, _Args...>::value, "Can't construct object in make_shared" );
-    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
-    typedef allocator<_CntrlBlk> _A2;
-    typedef __allocator_destructor<_A2> _D2;
-    _A2 __a2;
-    unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
-    ::new(__hold2.get()) _CntrlBlk(__a2, _VSTD::forward<_Args>(__args)...);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = __hold2.release();
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
 template<class _Tp>
 template<class _Alloc, class ..._Args>
 shared_ptr<_Tp>
@@ -4227,165 +4200,6 @@ shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _Args&& ...__args)
     return __r;
 }
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
-
-template<class _Tp>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::make_shared()
-{
-    static_assert((is_constructible<_Tp>::value), "Can't construct object in make_shared" );
-    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
-    typedef allocator<_CntrlBlk> _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2;
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(__hold2.get()) _CntrlBlk(__alloc2);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = __hold2.release();
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _A0>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::make_shared(_A0& __a0)
-{
-    static_assert((is_constructible<_Tp, _A0>::value), "Can't construct object in make_shared" );
-    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
-    typedef allocator<_CntrlBlk> _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2;
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(__hold2.get()) _CntrlBlk(__alloc2, __a0);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = __hold2.release();
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _A0, class _A1>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::make_shared(_A0& __a0, _A1& __a1)
-{
-    static_assert((is_constructible<_Tp, _A0, _A1>::value), "Can't construct object in make_shared" );
-    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
-    typedef allocator<_CntrlBlk> _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2;
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(__hold2.get()) _CntrlBlk(__alloc2, __a0, __a1);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = __hold2.release();
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _A0, class _A1, class _A2>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::make_shared(_A0& __a0, _A1& __a1, _A2& __a2)
-{
-    static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in make_shared" );
-    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
-    typedef allocator<_CntrlBlk> _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2;
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(__hold2.get()) _CntrlBlk(__alloc2, __a0, __a1, __a2);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = __hold2.release();
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _Alloc>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::allocate_shared(const _Alloc& __a)
-{
-    static_assert((is_constructible<_Tp>::value), "Can't construct object in allocate_shared" );
-    typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
-    typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2(__a);
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
-        _CntrlBlk(__a);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = _VSTD::addressof(*__hold2.release());
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _Alloc, class _A0>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _A0& __a0)
-{
-    static_assert((is_constructible<_Tp, _A0>::value), "Can't construct object in allocate_shared" );
-    typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
-    typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2(__a);
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
-        _CntrlBlk(__a, __a0);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = _VSTD::addressof(*__hold2.release());
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _Alloc, class _A0, class _A1>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1)
-{
-    static_assert((is_constructible<_Tp, _A0, _A1>::value), "Can't construct object in allocate_shared" );
-    typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
-    typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2(__a);
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
-        _CntrlBlk(__a, __a0, __a1);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = _VSTD::addressof(*__hold2.release());
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-template<class _Tp>
-template<class _Alloc, class _A0, class _A1, class _A2>
-shared_ptr<_Tp>
-shared_ptr<_Tp>::allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1, _A2& __a2)
-{
-    static_assert((is_constructible<_Tp, _A0, _A1, _A2>::value), "Can't construct object in allocate_shared" );
-    typedef __shared_ptr_emplace<_Tp, _Alloc> _CntrlBlk;
-    typedef typename __allocator_traits_rebind<_Alloc, _CntrlBlk>::type _Alloc2;
-    typedef __allocator_destructor<_Alloc2> _D2;
-    _Alloc2 __alloc2(__a);
-    unique_ptr<_CntrlBlk, _D2> __hold2(__alloc2.allocate(1), _D2(__alloc2, 1));
-    ::new(static_cast<void*>(_VSTD::addressof(*__hold2.get())))
-        _CntrlBlk(__a, __a0, __a1, __a2);
-    shared_ptr<_Tp> __r;
-    __r.__ptr_ = __hold2.get()->get();
-    __r.__cntrl_ = _VSTD::addressof(*__hold2.release());
-    __r.__enable_weak_this(__r.__ptr_, __r.__ptr_);
-    return __r;
-}
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 template<class _Tp>
 shared_ptr<_Tp>::~shared_ptr()
 {
@@ -4567,8 +4381,6 @@ shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d, _Alloc __a)
     shared_ptr(__p, __d, __a).swap(*this);
 }
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
-
 template<class _Tp, class ..._Args>
 inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
@@ -4578,7 +4390,17 @@ typename enable_if
 >::type
 make_shared(_Args&& ...__args)
 {
-    return shared_ptr<_Tp>::make_shared(_VSTD::forward<_Args>(__args)...);
+    static_assert(is_constructible<_Tp, _Args...>::value, "Can't construct object in make_shared");
+    typedef __shared_ptr_emplace<_Tp, allocator<_Tp> > _CntrlBlk;
+    typedef allocator<_CntrlBlk> _A2;
+    typedef __allocator_destructor<_A2> _D2;
+
+    _A2 __a2;
+    unique_ptr<_CntrlBlk, _D2> __hold2(__a2.allocate(1), _D2(__a2, 1));
+    ::new(__hold2.get()) _CntrlBlk(__a2, _VSTD::forward<_Args>(__args)...);
+
+    _Tp *__ptr = __hold2.get()->get();
+    return shared_ptr<_Tp>::__create_with_control_block(__ptr, __hold2.release());
 }
 
 template<class _Tp, class _Alloc, class ..._Args>
@@ -4593,74 +4415,6 @@ allocate_shared(const _Alloc& __a, _Args&& ...__args)
     return shared_ptr<_Tp>::allocate_shared(__a, _VSTD::forward<_Args>(__args)...);
 }
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
-
-template<class _Tp>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-make_shared()
-{
-    return shared_ptr<_Tp>::make_shared();
-}
-
-template<class _Tp, class _A0>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-make_shared(_A0& __a0)
-{
-    return shared_ptr<_Tp>::make_shared(__a0);
-}
-
-template<class _Tp, class _A0, class _A1>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-make_shared(_A0& __a0, _A1& __a1)
-{
-    return shared_ptr<_Tp>::make_shared(__a0, __a1);
-}
-
-template<class _Tp, class _A0, class _A1, class _A2>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-make_shared(_A0& __a0, _A1& __a1, _A2& __a2)
-{
-    return shared_ptr<_Tp>::make_shared(__a0, __a1, __a2);
-}
-
-template<class _Tp, class _Alloc>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-allocate_shared(const _Alloc& __a)
-{
-    return shared_ptr<_Tp>::allocate_shared(__a);
-}
-
-template<class _Tp, class _Alloc, class _A0>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-allocate_shared(const _Alloc& __a, _A0& __a0)
-{
-    return shared_ptr<_Tp>::allocate_shared(__a, __a0);
-}
-
-template<class _Tp, class _Alloc, class _A0, class _A1>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1)
-{
-    return shared_ptr<_Tp>::allocate_shared(__a, __a0, __a1);
-}
-
-template<class _Tp, class _Alloc, class _A0, class _A1, class _A2>
-inline _LIBCPP_INLINE_VISIBILITY
-shared_ptr<_Tp>
-allocate_shared(const _Alloc& __a, _A0& __a0, _A1& __a1, _A2& __a2)
-{
-    return shared_ptr<_Tp>::allocate_shared(__a, __a0, __a1, __a2);
-}
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
-
 template<class _Tp, class _Up>
 inline _LIBCPP_INLINE_VISIBILITY
 bool
@@ -5590,4 +5344,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <__pstl_memory>
+#endif
+
 #endif  // _LIBCPP_MEMORY
lib/libcxx/include/module.modulemap
@@ -275,6 +275,10 @@ module std [system] {
     header "exception"
     export *
   }
+  module execution {
+    header "execution"
+    export *
+  }
   module filesystem {
     header "filesystem"
     export *
lib/libcxx/include/mutex
@@ -86,9 +86,9 @@ public:
     void unlock();
 };
 
-struct defer_lock_t {};
-struct try_to_lock_t {};
-struct adopt_lock_t {};
+struct defer_lock_t { explicit defer_lock_t() = default; };
+struct try_to_lock_t { explicit try_to_lock_t() = default; };
+struct adopt_lock_t { explicit adopt_lock_t() = default; };
 
 inline constexpr defer_lock_t  defer_lock{};
 inline constexpr try_to_lock_t try_to_lock{};
@@ -650,7 +650,7 @@ public:
 #endif
 
 template <class _Fp>
-void
+void _LIBCPP_INLINE_VISIBILITY
 __call_once_proxy(void* __vp)
 {
     __call_once_param<_Fp>* __p = static_cast<__call_once_param<_Fp>*>(__vp);
lib/libcxx/include/new
@@ -39,7 +39,7 @@ struct destroying_delete_t { // C++20
 };
 inline constexpr destroying_delete_t destroying_delete{}; // C++20
 
-struct nothrow_t {};
+struct nothrow_t { explicit nothrow_t() = default; };
 extern const nothrow_t nothrow;
 typedef void (*new_handler)();
 new_handler set_new_handler(new_handler new_p) noexcept;
@@ -126,7 +126,7 @@ namespace std  // purposefully not using versioning namespace
 {
 
 #if !defined(_LIBCPP_ABI_VCRUNTIME)
-struct _LIBCPP_TYPE_VIS nothrow_t {};
+struct _LIBCPP_TYPE_VIS nothrow_t { explicit nothrow_t() = default; };
 extern _LIBCPP_FUNC_VIS const nothrow_t nothrow;
 
 class _LIBCPP_EXCEPTION_ABI bad_alloc
lib/libcxx/include/numeric
@@ -532,17 +532,14 @@ midpoint(_Tp __a, _Tp __b) noexcept
 _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK
 {
     using _Up = std::make_unsigned_t<_Tp>;
+    constexpr _Up __bitshift = std::numeric_limits<_Up>::digits - 1;
 
-    int __sign = 1;
-    _Up __m = __a;
-    _Up __M = __b;
-    if (__a > __b)
-    {
-        __sign = -1;
-        __m = __b;
-        __M = __a;
-    }
-     return __a + __sign * _Tp(_Up(__M-__m) >> 1);
+    _Up __diff = _Up(__b) - _Up(__a);
+    _Up __sign_bit = __b < __a;
+
+    _Up __half_diff = (__diff / 2) + (__sign_bit << __bitshift) + (__sign_bit & __diff);
+
+    return __a + __half_diff;
 }
 
 
@@ -576,7 +573,7 @@ midpoint(_Fp __a, _Fp __b) noexcept
     return __fp_abs(__a) <= __hi && __fp_abs(__b) <= __hi ?  // typical case: overflow is impossible
       (__a + __b)/2 :                                        // always correctly rounded
       __fp_abs(__a) < __lo ? __a + __b/2 :                   // not safe to halve a
-      __fp_abs(__a) < __lo ? __a/2 + __b :                   // not safe to halve b
+      __fp_abs(__b) < __lo ? __a/2 + __b :                   // not safe to halve b
       __a/2 + __b/2;                                         // otherwise correctly rounded
 }
 
@@ -586,4 +583,8 @@ _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS
 
+#if defined(_LIBCPP_HAS_PARALLEL_ALGORITHMS) && _LIBCPP_STD_VER >= 17
+#   include <__pstl_numeric>
+#endif
+
 #endif  // _LIBCPP_NUMERIC
lib/libcxx/include/ostream
@@ -1055,7 +1055,7 @@ operator<<(basic_ostream<_CharT, _Traits>& __os,
 template<class _CharT, class _Traits>
 basic_ostream<_CharT, _Traits>&
 operator<<(basic_ostream<_CharT, _Traits>& __os,
-           const basic_string_view<_CharT, _Traits> __sv)
+           basic_string_view<_CharT, _Traits> __sv)
 {
     return _VSTD::__put_character_sequence(__os, __sv.data(), __sv.size());
 }
lib/libcxx/include/queue
@@ -562,7 +562,7 @@ priority_queue(_Compare, _Container)
 template<class _InputIterator,
          class _Compare   = less<typename iterator_traits<_InputIterator>::value_type>,
          class _Container = vector<typename iterator_traits<_InputIterator>::value_type>,
-         class = typename enable_if< __is_input_iterator<_InputIterator>::value, nullptr_t>::type,
+         class = typename enable_if< __is_cpp17_input_iterator<_InputIterator>::value, nullptr_t>::type,
          class = typename enable_if<!__is_allocator<_Compare>::value, nullptr_t>::type,
          class = typename enable_if<!__is_allocator<_Container>::value, nullptr_t>::type
 >
lib/libcxx/include/random
@@ -3645,7 +3645,7 @@ generate_canonical(_URNG& __g)
     const size_t __logR = __log2<uint64_t, _URNG::max() - _URNG::min() + uint64_t(1)>::value;
 #endif
     const size_t __k = __b / __logR + (__b % __logR != 0) + (__b == 0);
-    const _RealType _Rp = _URNG::max() - _URNG::min() + _RealType(1);
+    const _RealType _Rp = static_cast<_RealType>(_URNG::max() - _URNG::min()) + _RealType(1);
     _RealType __base = _Rp;
     _RealType _Sp = __g() - _URNG::min();
     for (size_t __i = 1; __i < __k; ++__i, __base *= _Rp)
@@ -4592,7 +4592,10 @@ public:
 
 template<class _IntType>
 poisson_distribution<_IntType>::param_type::param_type(double __mean)
-    : __mean_(__mean)
+    // According to the standard `inf` is a valid input, but it causes the
+    // distribution to hang, so we replace it with the maximum representable
+    // mean.
+    : __mean_(isinf(__mean) ? numeric_limits<double>::max() : __mean)
 {
     if (__mean_ < 10)
     {
@@ -4610,7 +4613,7 @@ poisson_distribution<_IntType>::param_type::param_type(double __mean)
     {
         __s_ = _VSTD::sqrt(__mean_);
         __d_ = 6 * __mean_ * __mean_;
-        __l_ = static_cast<result_type>(__mean_ - 1.1484);
+        __l_ = std::trunc(__mean_ - 1.1484);
         __omega_ = .3989423 / __s_;
         double __b1_ = .4166667E-1 / __mean_;
         double __b2_ = .3 * __b1_ * __b1_;
@@ -4627,12 +4630,12 @@ template<class _URNG>
 _IntType
 poisson_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr)
 {
-    result_type __x;
+    double __tx;
     uniform_real_distribution<double> __urd;
     if (__pr.__mean_ < 10)
     {
-         __x = 0;
-        for (double __p = __urd(__urng); __p > __pr.__l_; ++__x)
+         __tx = 0;
+        for (double __p = __urd(__urng); __p > __pr.__l_; ++__tx)
             __p *= __urd(__urng);
     }
     else
@@ -4642,19 +4645,19 @@ poisson_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr
         double __u;
         if (__g > 0)
         {
-            __x = static_cast<result_type>(__g);
-            if (__x >= __pr.__l_)
-                return __x;
-            __difmuk = __pr.__mean_ - __x;
+            __tx = std::trunc(__g);
+            if (__tx >= __pr.__l_)
+                return std::__clamp_to_integral<result_type>(__tx);
+            __difmuk = __pr.__mean_ - __tx;
             __u = __urd(__urng);
             if (__pr.__d_ * __u >= __difmuk * __difmuk * __difmuk)
-                return __x;
+                return std::__clamp_to_integral<result_type>(__tx);
         }
         exponential_distribution<double> __edist;
         for (bool __using_exp_dist = false; true; __using_exp_dist = true)
         {
             double __e;
-            if (__using_exp_dist || __g < 0)
+            if (__using_exp_dist || __g <= 0)
             {
                 double __t;
                 do
@@ -4664,31 +4667,31 @@ poisson_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr
                     __u += __u - 1;
                     __t = 1.8 + (__u < 0 ? -__e : __e);
                 } while (__t <= -.6744);
-                __x = __pr.__mean_ + __pr.__s_ * __t;
-                __difmuk = __pr.__mean_ - __x;
+                __tx = std::trunc(__pr.__mean_ + __pr.__s_ * __t);
+                __difmuk = __pr.__mean_ - __tx;
                 __using_exp_dist = true;
             }
             double __px;
             double __py;
-            if (__x < 10)
+            if (__tx < 10 && __tx >= 0)
             {
                 const double __fac[] = {1, 1, 2, 6, 24, 120, 720, 5040,
                                              40320, 362880};
                 __px = -__pr.__mean_;
-                __py = _VSTD::pow(__pr.__mean_, (double)__x) / __fac[__x];
+                __py = _VSTD::pow(__pr.__mean_, (double)__tx) / __fac[static_cast<int>(__tx)];
             }
             else
             {
-                double __del = .8333333E-1 / __x;
+                double __del = .8333333E-1 / __tx;
                 __del -= 4.8 * __del * __del * __del;
-                double __v = __difmuk / __x;
+                double __v = __difmuk / __tx;
                 if (_VSTD::abs(__v) > 0.25)
-                    __px = __x * _VSTD::log(1 + __v) - __difmuk - __del;
+                    __px = __tx * _VSTD::log(1 + __v) - __difmuk - __del;
                 else
-                    __px = __x * __v * __v * (((((((.1250060 * __v + -.1384794) *
+                    __px = __tx * __v * __v * (((((((.1250060 * __v + -.1384794) *
                            __v + .1421878) * __v + -.1661269) * __v + .2000118) *
                            __v + -.2500068) * __v + .3333333) * __v + -.5) - __del;
-                __py = .3989423 / _VSTD::sqrt(__x);
+                __py = .3989423 / _VSTD::sqrt(__tx);
             }
             double __r = (0.5 - __difmuk) / __pr.__s_;
             double __r2 = __r * __r;
@@ -4708,7 +4711,7 @@ poisson_distribution<_IntType>::operator()(_URNG& __urng, const param_type& __pr
             }
         }
     }
-    return __x;
+    return std::__clamp_to_integral<result_type>(__tx);
 }
 
 template <class _CharT, class _Traits, class _IntType>
@@ -6102,6 +6105,7 @@ public:
         template<class _UnaryOperation>
             param_type(size_t __nw, result_type __xmin, result_type __xmax,
                        _UnaryOperation __fw);
+        param_type(param_type const&) = default;
         param_type & operator=(const param_type& __rhs);
 
         _LIBCPP_INLINE_VISIBILITY
@@ -6425,6 +6429,7 @@ public:
         template<class _UnaryOperation>
             param_type(size_t __nw, result_type __xmin, result_type __xmax,
                        _UnaryOperation __fw);
+        param_type(param_type const&) = default;
         param_type & operator=(const param_type& __rhs);
 
         _LIBCPP_INLINE_VISIBILITY
lib/libcxx/include/regex
@@ -169,15 +169,15 @@ public:
     // assign:
     basic_regex& assign(const basic_regex& that);
     basic_regex& assign(basic_regex&& that) noexcept;
-    basic_regex& assign(const charT* ptr, flag_type f = regex_constants::ECMAScript);
-    basic_regex& assign(const charT* p, size_t len, flag_type f);
+    basic_regex& assign(const charT* ptr,           flag_type f = regex_constants::ECMAScript);
+    basic_regex& assign(const charT* p, size_t len, flag_type f = regex_constants::ECMAScript);
     template <class string_traits, class A>
         basic_regex& assign(const basic_string<charT, string_traits, A>& s,
-                            flag_type f = regex_constants::ECMAScript);
+                                                    flag_type f = regex_constants::ECMAScript);
     template <class InputIterator>
         basic_regex& assign(InputIterator first, InputIterator last,
-                            flag_type f = regex_constants::ECMAScript);
-    basic_regex& assign(initializer_list<charT>, flag_type = regex_constants::ECMAScript);
+                                                    flag_type f = regex_constants::ECMAScript);
+    basic_regex& assign(initializer_list<charT>,    flag_type f = regex_constants::ECMAScript);
 
     // const operations:
     unsigned mark_count() const;
@@ -965,7 +965,8 @@ enum error_type
     error_stack,
     __re_err_grammar,
     __re_err_empty,
-    __re_err_unknown
+    __re_err_unknown,
+    __re_err_parse
 };
 
 }  // regex_constants
@@ -2539,8 +2540,7 @@ public:
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {
-        if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
-        __parse(__p, __p + __traits_.length(__p));
+        __init(__p, __p + __traits_.length(__p));
         }
 
     _LIBCPP_INLINE_VISIBILITY
@@ -2548,8 +2548,7 @@ public:
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {
-        if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
-        __parse(__p, __p + __len);
+        __init(__p, __p + __len);
         }
 
 //     basic_regex(const basic_regex&) = default;
@@ -2561,8 +2560,7 @@ public:
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {
-        if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
-        __parse(__p.begin(), __p.end());
+        __init(__p.begin(), __p.end());
         }
 
     template <class _ForwardIterator>
@@ -2572,8 +2570,7 @@ public:
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {
-        if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
-        __parse(__first, __last);
+        __init(__first, __last);
         }
 #ifndef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
@@ -2582,8 +2579,7 @@ public:
         : __flags_(__f), __marked_count_(0), __loop_count_(0), __open_count_(0),
           __end_(0)
         {
-        if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
-        __parse(__il.begin(), __il.end());
+        __init(__il.begin(), __il.end());
         }
 #endif  // _LIBCPP_CXX03_LANG
 
@@ -2617,7 +2613,7 @@ public:
     basic_regex& assign(const value_type* __p, flag_type __f = regex_constants::ECMAScript)
         {return assign(__p, __p + __traits_.length(__p), __f);}
     _LIBCPP_INLINE_VISIBILITY
-    basic_regex& assign(const value_type* __p, size_t __len, flag_type __f)
+    basic_regex& assign(const value_type* __p, size_t __len, flag_type __f = regex_constants::ECMAScript)
         {return assign(__p, __p + __len, __f);}
     template <class _ST, class _SA>
         _LIBCPP_INLINE_VISIBILITY
@@ -2629,8 +2625,8 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         typename enable_if
         <
-             __is_input_iterator  <_InputIterator>::value &&
-            !__is_forward_iterator<_InputIterator>::value,
+             __is_cpp17_input_iterator  <_InputIterator>::value &&
+            !__is_cpp17_forward_iterator<_InputIterator>::value,
             basic_regex&
         >::type
         assign(_InputIterator __first, _InputIterator __last,
@@ -2656,7 +2652,7 @@ public:
         _LIBCPP_INLINE_VISIBILITY
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value,
+            __is_cpp17_forward_iterator<_ForwardIterator>::value,
             basic_regex&
         >::type
         assign(_ForwardIterator __first, _ForwardIterator __last,
@@ -2698,6 +2694,9 @@ private:
     _LIBCPP_INLINE_VISIBILITY
     unsigned __loop_count() const {return __loop_count_;}
 
+    template <class _ForwardIterator>
+        void
+        __init(_ForwardIterator __first, _ForwardIterator __last);
     template <class _ForwardIterator>
         _ForwardIterator
         __parse(_ForwardIterator __first, _ForwardIterator __last);
@@ -2953,7 +2952,7 @@ private:
 
 #ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
 template <class _ForwardIterator,
-          class = typename enable_if<__is_forward_iterator<_ForwardIterator>::value, nullptr_t>::type
+          class = typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value, nullptr_t>::type
 >
 basic_regex(_ForwardIterator, _ForwardIterator,
             regex_constants::syntax_option_type = regex_constants::ECMAScript)
@@ -3054,6 +3053,17 @@ __lookahead<_CharT, _Traits>::__exec(__state& __s) const
     }
 }
 
+template <class _CharT, class _Traits>
+template <class _ForwardIterator>
+void
+basic_regex<_CharT, _Traits>::__init(_ForwardIterator __first, _ForwardIterator __last)
+{
+    if (__get_grammar(__flags_) == 0) __flags_ |= regex_constants::ECMAScript;
+    _ForwardIterator __temp = __parse(__first, __last);
+    if ( __temp != __last)
+        __throw_regex_error<regex_constants::__re_err_parse>();
+}
+
 template <class _CharT, class _Traits>
 template <class _ForwardIterator>
 _ForwardIterator
lib/libcxx/include/set
@@ -852,26 +852,26 @@ public:
 template<class _InputIterator,
          class _Compare = less<typename iterator_traits<_InputIterator>::value_type>,
          class _Allocator = allocator<typename iterator_traits<_InputIterator>::value_type>,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
-         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>,
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>>
 set(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> set<typename iterator_traits<_InputIterator>::value_type, _Compare, _Allocator>;
 
 template<class _Key, class _Compare = less<_Key>,
          class _Allocator = allocator<_Key>,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
-         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>,
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>>
 set(initializer_list<_Key>, _Compare = _Compare(), _Allocator = _Allocator())
   -> set<_Key, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 set(_InputIterator, _InputIterator, _Allocator)
   -> set<typename iterator_traits<_InputIterator>::value_type,
          less<typename iterator_traits<_InputIterator>::value_type>, _Allocator>;
 
 template<class _Key, class _Allocator,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 set(initializer_list<_Key>, _Allocator)
   -> set<_Key, less<_Key>, _Allocator>;
 #endif
@@ -1377,26 +1377,26 @@ public:
 template<class _InputIterator,
          class _Compare = less<typename iterator_traits<_InputIterator>::value_type>,
          class _Allocator = allocator<typename iterator_traits<_InputIterator>::value_type>,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
-         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>,
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>>
 multiset(_InputIterator, _InputIterator, _Compare = _Compare(), _Allocator = _Allocator())
   -> multiset<typename iterator_traits<_InputIterator>::value_type, _Compare, _Allocator>;
 
 template<class _Key, class _Compare = less<_Key>,
          class _Allocator = allocator<_Key>,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type,
-         class = typename enable_if<!__is_allocator<_Compare>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>,
+         class = _EnableIf<!__is_allocator<_Compare>::value, void>>
 multiset(initializer_list<_Key>, _Compare = _Compare(), _Allocator = _Allocator())
   -> multiset<_Key, _Compare, _Allocator>;
 
 template<class _InputIterator, class _Allocator,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 multiset(_InputIterator, _InputIterator, _Allocator)
   -> multiset<typename iterator_traits<_InputIterator>::value_type,
          less<typename iterator_traits<_InputIterator>::value_type>, _Allocator>;
 
 template<class _Key, class _Allocator,
-         class = typename enable_if<__is_allocator<_Allocator>::value, void>::type>
+         class = _EnableIf<__is_allocator<_Allocator>::value, void>>
 multiset(initializer_list<_Key>, _Allocator)
   -> multiset<_Key, less<_Key>, _Allocator>;
 #endif
lib/libcxx/include/span
@@ -39,7 +39,7 @@ public:
     // constants and types
     using element_type = ElementType;
     using value_type = remove_cv_t<ElementType>;
-    using index_type = size_t;
+    using size_type = size_t;
     using difference_type = ptrdiff_t;
     using pointer = element_type*;
     using const_pointer = const element_type*;
@@ -49,11 +49,11 @@ public:
     using const_iterator = implementation-defined;
     using reverse_iterator = std::reverse_iterator<iterator>;
     using const_reverse_iterator = std::reverse_iterator<const_iterator>;
-    static constexpr index_type extent = Extent;
+    static constexpr size_type extent = Extent;
 
     // [span.cons], span constructors, copy, assignment, and destructor
     constexpr span() noexcept;
-    constexpr span(pointer ptr, index_type count);
+    constexpr span(pointer ptr, size_type count);
     constexpr span(pointer firstElem, pointer lastElem);
     template <size_t N>
         constexpr span(element_type (&arr)[N]) noexcept;
@@ -79,17 +79,17 @@ public:
     template <size_t Offset, size_t Count = dynamic_extent>
         constexpr span<element_type, see below> subspan() const;
 
-    constexpr span<element_type, dynamic_extent> first(index_type count) const;
-    constexpr span<element_type, dynamic_extent> last(index_type count) const;
-    constexpr span<element_type, dynamic_extent> subspan(index_type offset, index_type count = dynamic_extent) const;
+    constexpr span<element_type, dynamic_extent> first(size_type count) const;
+    constexpr span<element_type, dynamic_extent> last(size_type count) const;
+    constexpr span<element_type, dynamic_extent> subspan(size_type offset, size_type count = dynamic_extent) const;
 
     // [span.obs], span observers
-    constexpr index_type size() const noexcept;
-    constexpr index_type size_bytes() const noexcept;
+    constexpr size_type size() const noexcept;
+    constexpr size_type size_bytes() const noexcept;
     constexpr bool empty() const noexcept;
 
     // [span.elem], span element access
-    constexpr reference operator[](index_type idx) const;
+    constexpr reference operator[](size_type idx) const;
     constexpr reference front() const;
     constexpr reference back() const;
     constexpr pointer data() const noexcept;
@@ -105,8 +105,8 @@ public:
     constexpr const_reverse_iterator crend() const noexcept;
 
 private:
-    pointer data_;     // exposition only
-    index_type size_;  // exposition only
+    pointer data_;    // exposition only
+    size_type size_;  // exposition only
 };
 
 template<class T, size_t N>
@@ -195,7 +195,7 @@ public:
 //  constants and types
     using element_type           = _Tp;
     using value_type             = remove_cv_t<_Tp>;
-    using index_type             = size_t;
+    using size_type              = size_t;
     using difference_type        = ptrdiff_t;
     using pointer                = _Tp *;
     using const_pointer          = const _Tp *;
@@ -206,7 +206,7 @@ public:
     using reverse_iterator       = _VSTD::reverse_iterator<iterator>;
     using const_reverse_iterator = _VSTD::reverse_iterator<const_iterator>;
 
-    static constexpr index_type extent = _Extent;
+    static constexpr size_type extent = _Extent;
 
 // [span.cons], span constructors, copy, assignment, and destructor
     _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}
@@ -215,7 +215,7 @@ public:
     constexpr span           (const span&) noexcept = default;
     constexpr span& operator=(const span&) noexcept = default;
 
-    _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, index_type __count) : __data{__ptr}
+    _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, size_type __count) : __data{__ptr}
         { (void)__count; _LIBCPP_ASSERT(_Extent == __count, "size mismatch in span's constructor (ptr, len)"); }
     _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}
         { (void)__l;     _LIBCPP_ASSERT(_Extent == distance(__f, __l), "size mismatch in span's constructor (ptr, ptr)"); }
@@ -260,14 +260,14 @@ public:
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    constexpr span<element_type, dynamic_extent> first(index_type __count) const noexcept
+    constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
     {
         _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
         return {data(), __count};
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    constexpr span<element_type, dynamic_extent> last(index_type __count) const noexcept
+    constexpr span<element_type, dynamic_extent> last(size_type __count) const noexcept
     {
         _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
         return {data() + size() - __count, __count};
@@ -285,7 +285,7 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     constexpr span<element_type, dynamic_extent>
-       subspan(index_type __offset, index_type __count = dynamic_extent) const noexcept
+       subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
     {
         _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
         _LIBCPP_ASSERT(__count  <= size() || __count == dynamic_extent, "Count out of range in span::subspan(offset, count)");
@@ -295,11 +295,11 @@ public:
         return {data() + __offset, __count};
     }
 
-    _LIBCPP_INLINE_VISIBILITY constexpr index_type size()       const noexcept { return _Extent; }
-    _LIBCPP_INLINE_VISIBILITY constexpr index_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
-    _LIBCPP_INLINE_VISIBILITY constexpr bool empty()            const noexcept { return _Extent == 0; }
+    _LIBCPP_INLINE_VISIBILITY constexpr size_type size()       const noexcept { return _Extent; }
+    _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return _Extent * sizeof(element_type); }
+    _LIBCPP_INLINE_VISIBILITY constexpr bool empty()           const noexcept { return _Extent == 0; }
 
-    _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](index_type __idx) const noexcept
+    _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
     {
         _LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T,N>[] index out of bounds");
         return __data[__idx];
@@ -356,7 +356,7 @@ public:
 //  constants and types
     using element_type           = _Tp;
     using value_type             = remove_cv_t<_Tp>;
-    using index_type             = size_t;
+    using size_type              = size_t;
     using difference_type        = ptrdiff_t;
     using pointer                = _Tp *;
     using const_pointer          = const _Tp *;
@@ -367,7 +367,7 @@ public:
     using reverse_iterator       = _VSTD::reverse_iterator<iterator>;
     using const_reverse_iterator = _VSTD::reverse_iterator<const_iterator>;
 
-    static constexpr index_type extent = dynamic_extent;
+    static constexpr size_type extent = dynamic_extent;
 
 // [span.cons], span constructors, copy, assignment, and destructor
     _LIBCPP_INLINE_VISIBILITY constexpr span() noexcept : __data{nullptr}, __size{0} {}
@@ -375,7 +375,7 @@ public:
     constexpr span           (const span&) noexcept = default;
     constexpr span& operator=(const span&) noexcept = default;
 
-    _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, index_type __count) : __data{__ptr}, __size{__count} {}
+    _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __ptr, size_type __count) : __data{__ptr}, __size{__count} {}
     _LIBCPP_INLINE_VISIBILITY constexpr span(pointer __f, pointer __l) : __data{__f}, __size{static_cast<size_t>(distance(__f, __l))} {}
 
     template <size_t _Sz>
@@ -394,13 +394,13 @@ public:
     _LIBCPP_INLINE_VISIBILITY
         constexpr span(      _Container& __c,
             enable_if_t<__is_span_compatible_container<_Container, _Tp>::value, nullptr_t> = nullptr)
-        : __data{_VSTD::data(__c)}, __size{(index_type) _VSTD::size(__c)} {}
+        : __data{_VSTD::data(__c)}, __size{(size_type) _VSTD::size(__c)} {}
 
     template <class _Container>
     _LIBCPP_INLINE_VISIBILITY
         constexpr span(const _Container& __c,
             enable_if_t<__is_span_compatible_container<const _Container, _Tp>::value, nullptr_t> = nullptr)
-        : __data{_VSTD::data(__c)}, __size{(index_type) _VSTD::size(__c)} {}
+        : __data{_VSTD::data(__c)}, __size{(size_type) _VSTD::size(__c)} {}
 
 
     template <class _OtherElementType, size_t _OtherExtent>
@@ -430,14 +430,14 @@ public:
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    constexpr span<element_type, dynamic_extent> first(index_type __count) const noexcept
+    constexpr span<element_type, dynamic_extent> first(size_type __count) const noexcept
     {
         _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::first(count)");
         return {data(), __count};
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    constexpr span<element_type, dynamic_extent> last (index_type __count) const noexcept
+    constexpr span<element_type, dynamic_extent> last (size_type __count) const noexcept
     {
         _LIBCPP_ASSERT(__count <= size(), "Count out of range in span::last(count)");
         return {data() + size() - __count, __count};
@@ -454,7 +454,7 @@ public:
 
     constexpr span<element_type, dynamic_extent>
     _LIBCPP_INLINE_VISIBILITY
-    subspan(index_type __offset, index_type __count = dynamic_extent) const noexcept
+    subspan(size_type __offset, size_type __count = dynamic_extent) const noexcept
     {
         _LIBCPP_ASSERT(__offset <= size(), "Offset out of range in span::subspan(offset, count)");
         _LIBCPP_ASSERT(__count  <= size() || __count == dynamic_extent, "count out of range in span::subspan(offset, count)");
@@ -464,11 +464,11 @@ public:
         return {data() + __offset, __count};
     }
 
-    _LIBCPP_INLINE_VISIBILITY constexpr index_type size()       const noexcept { return __size; }
-    _LIBCPP_INLINE_VISIBILITY constexpr index_type size_bytes() const noexcept { return __size * sizeof(element_type); }
-    _LIBCPP_INLINE_VISIBILITY constexpr bool empty()            const noexcept { return __size == 0; }
+    _LIBCPP_INLINE_VISIBILITY constexpr size_type size()       const noexcept { return __size; }
+    _LIBCPP_INLINE_VISIBILITY constexpr size_type size_bytes() const noexcept { return __size * sizeof(element_type); }
+    _LIBCPP_INLINE_VISIBILITY constexpr bool empty()           const noexcept { return __size == 0; }
 
-    _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](index_type __idx) const noexcept
+    _LIBCPP_INLINE_VISIBILITY constexpr reference operator[](size_type __idx) const noexcept
     {
         _LIBCPP_ASSERT(__idx >= 0 && __idx < size(), "span<T>[] index out of bounds");
         return __data[__idx];
@@ -505,7 +505,7 @@ public:
         __data = __other.__data;
         __other.__data = __p;
 
-        index_type __sz = __size;
+        size_type __sz = __size;
         __size = __other.__size;
         __other.__size = __sz;
     }
@@ -517,8 +517,8 @@ public:
     { return {reinterpret_cast<byte *>(data()), size_bytes()}; }
 
 private:
-    pointer    __data;
-    index_type __size;
+    pointer   __data;
+    size_type __size;
 };
 
 //  tuple interface
lib/libcxx/include/string
@@ -625,7 +625,7 @@ struct __libcpp_string_gets_noexcept_iterator_impl : public true_type {};
 template <class _Iter>
 struct __libcpp_string_gets_noexcept_iterator_impl : public false_type {};
 #else
-template <class _Iter, bool = __is_forward_iterator<_Iter>::value>
+template <class _Iter, bool = __is_cpp17_forward_iterator<_Iter>::value>
 struct __libcpp_string_gets_noexcept_iterator_impl : public _LIBCPP_BOOL_CONSTANT((
     noexcept(++(declval<_Iter&>())) &&
     is_nothrow_assignable<_Iter&, _Iter>::value &&
@@ -812,11 +812,9 @@ public:
     basic_string(basic_string&& __str, const allocator_type& __a);
 #endif  // _LIBCPP_CXX03_LANG
 
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
     template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
-#endif
     _LIBCPP_INLINE_VISIBILITY
-    basic_string(const _CharT* __s) {
+    basic_string(const _CharT* __s) : __r_(__default_init_tag(), __default_init_tag()) {
       _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*) detected nullptr");
       __init(__s, traits_type::length(__s));
 #   if _LIBCPP_DEBUG_LEVEL >= 2
@@ -824,9 +822,7 @@ public:
 #   endif
     }
 
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
     template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
-#endif
         _LIBCPP_INLINE_VISIBILITY
         basic_string(const _CharT* __s, const _Allocator& __a);
 
@@ -837,9 +833,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     basic_string(size_type __n, _CharT __c);
 
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
     template <class = typename enable_if<__is_allocator<_Allocator>::value, nullptr_t>::type>
-#endif
         _LIBCPP_INLINE_VISIBILITY
         basic_string(size_type __n, _CharT __c, const _Allocator& __a);
 
@@ -862,10 +856,10 @@ public:
         _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
         explicit basic_string(const _Tp& __t, const allocator_type& __a);
 
-    template<class _InputIterator, class = typename enable_if<__is_input_iterator<_InputIterator>::value>::type>
+    template<class _InputIterator, class = typename enable_if<__is_cpp17_input_iterator<_InputIterator>::value>::type>
         _LIBCPP_INLINE_VISIBILITY
         basic_string(_InputIterator __first, _InputIterator __last);
-    template<class _InputIterator, class = typename enable_if<__is_input_iterator<_InputIterator>::value>::type>
+    template<class _InputIterator, class = typename enable_if<__is_cpp17_input_iterator<_InputIterator>::value>::type>
         _LIBCPP_INLINE_VISIBILITY
         basic_string(_InputIterator __first, _InputIterator __last, const allocator_type& __a);
 #ifndef _LIBCPP_CXX03_LANG
@@ -1029,7 +1023,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-            __is_exactly_input_iterator<_InputIterator>::value
+            __is_exactly_cpp17_input_iterator<_InputIterator>::value
                 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
             basic_string&
         >::type
@@ -1043,7 +1037,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value
+            __is_cpp17_forward_iterator<_ForwardIterator>::value
                 && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
             basic_string&
         >::type
@@ -1097,7 +1091,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-           __is_exactly_input_iterator<_InputIterator>::value
+           __is_exactly_cpp17_input_iterator<_InputIterator>::value
                 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
             basic_string&
         >::type
@@ -1106,7 +1100,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value
+            __is_cpp17_forward_iterator<_ForwardIterator>::value
                  && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
             basic_string&
         >::type
@@ -1148,7 +1142,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-           __is_exactly_input_iterator<_InputIterator>::value
+           __is_exactly_cpp17_input_iterator<_InputIterator>::value
                 || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
             iterator
         >::type
@@ -1157,7 +1151,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value
+            __is_cpp17_forward_iterator<_ForwardIterator>::value
                  && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
             iterator
         >::type
@@ -1219,7 +1213,7 @@ public:
     _LIBCPP_METHOD_TEMPLATE_IMPLICIT_INSTANTIATION_VIS
     typename enable_if
         <
-            __is_input_iterator<_InputIterator>::value,
+            __is_cpp17_input_iterator<_InputIterator>::value,
             basic_string&
         >::type
         replace(const_iterator __i1, const_iterator __i2, _InputIterator __j1, _InputIterator __j2);
@@ -1245,10 +1239,10 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     const value_type* c_str() const _NOEXCEPT {return data();}
     _LIBCPP_INLINE_VISIBILITY
-    const value_type* data() const _NOEXCEPT  {return _VSTD::__to_raw_pointer(__get_pointer());}
+    const value_type* data() const _NOEXCEPT  {return _VSTD::__to_address(__get_pointer());}
 #if _LIBCPP_STD_VER > 14 || defined(_LIBCPP_BUILDING_LIBRARY)
     _LIBCPP_INLINE_VISIBILITY
-    value_type* data()             _NOEXCEPT  {return _VSTD::__to_raw_pointer(__get_pointer());}
+    value_type* data()             _NOEXCEPT  {return _VSTD::__to_address(__get_pointer());}
 #endif
 
     _LIBCPP_INLINE_VISIBILITY
@@ -1553,7 +1547,7 @@ private:
     inline
     typename enable_if
     <
-        __is_exactly_input_iterator<_InputIterator>::value,
+        __is_exactly_cpp17_input_iterator<_InputIterator>::value,
         void
     >::type
     __init(_InputIterator __first, _InputIterator __last);
@@ -1562,7 +1556,7 @@ private:
     inline
     typename enable_if
     <
-        __is_forward_iterator<_ForwardIterator>::value,
+        __is_cpp17_forward_iterator<_ForwardIterator>::value,
         void
     >::type
     __init(_ForwardIterator __first, _ForwardIterator __last);
@@ -1658,7 +1652,7 @@ private:
 template<class _InputIterator,
          class _CharT = typename iterator_traits<_InputIterator>::value_type,
          class _Allocator = allocator<_CharT>,
-         class = typename enable_if<__is_input_iterator<_InputIterator>::value, void>::type,
+         class = typename enable_if<__is_cpp17_input_iterator<_InputIterator>::value, void>::type,
          class = typename enable_if<__is_allocator<_Allocator>::value, void>::type
          >
 basic_string(_InputIterator, _InputIterator, _Allocator = _Allocator())
@@ -1727,6 +1721,7 @@ template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string()
     _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
+     : __r_(__default_init_tag(), __default_init_tag())
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
@@ -1742,7 +1737,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const allocator_type& __
 #else
         _NOEXCEPT
 #endif
-: __r_(__second_tag(), __a)
+: __r_(__default_init_tag(), __a)
 {
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
@@ -1771,7 +1766,7 @@ void basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s,
         __set_long_cap(__cap+1);
         __set_long_size(__sz);
     }
-    traits_type::copy(_VSTD::__to_raw_pointer(__p), __s, __sz);
+    traits_type::copy(_VSTD::__to_address(__p), __s, __sz);
     traits_type::assign(__p[__sz], value_type());
 }
 
@@ -1795,16 +1790,14 @@ basic_string<_CharT, _Traits, _Allocator>::__init(const value_type* __s, size_ty
         __set_long_cap(__cap+1);
         __set_long_size(__sz);
     }
-    traits_type::copy(_VSTD::__to_raw_pointer(__p), __s, __sz);
+    traits_type::copy(_VSTD::__to_address(__p), __s, __sz);
     traits_type::assign(__p[__sz], value_type());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
 template <class>
-#endif
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     _LIBCPP_ASSERT(__s != nullptr, "basic_string(const char*, allocator) detected nullptr");
     __init(__s, traits_type::length(__s));
@@ -1816,6 +1809,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, const
 template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n)
+     : __r_(__default_init_tag(), __default_init_tag())
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n) detected nullptr");
     __init(__s, __n);
@@ -1827,7 +1821,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_
 template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_type __n, const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     _LIBCPP_ASSERT(__n == 0 || __s != nullptr, "basic_string(const char*, n, allocator) detected nullptr");
     __init(__s, __n);
@@ -1838,12 +1832,12 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _CharT* __s, size_
 
 template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str)
-    : __r_(__second_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc()))
+    : __r_(__default_init_tag(), __alloc_traits::select_on_container_copy_construction(__str.__alloc()))
 {
     if (!__str.__is_long())
         __r_.first().__r = __str.__r_.first().__r;
     else
-        __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
+        __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
 #endif
@@ -1852,12 +1846,12 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __st
 template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(
     const basic_string& __str, const allocator_type& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     if (!__str.__is_long())
         __r_.first().__r = __str.__r_.first().__r;
     else
-        __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
+        __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
 #if _LIBCPP_DEBUG_LEVEL >= 2
     __get_db()->__insert_c(this);
 #endif
@@ -1886,10 +1880,10 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str)
 template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(basic_string&& __str, const allocator_type& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     if (__str.__is_long() && __a != __str.__alloc()) // copy, not move
-        __init(_VSTD::__to_raw_pointer(__str.__get_long_pointer()), __str.__get_long_size());
+        __init(_VSTD::__to_address(__str.__get_long_pointer()), __str.__get_long_size());
     else
     {
         __r_.first().__r = __str.__r_.first().__r;
@@ -1924,13 +1918,14 @@ basic_string<_CharT, _Traits, _Allocator>::__init(size_type __n, value_type __c)
         __set_long_cap(__cap+1);
         __set_long_size(__n);
     }
-    traits_type::assign(_VSTD::__to_raw_pointer(__p), __n, __c);
+    traits_type::assign(_VSTD::__to_address(__p), __n, __c);
     traits_type::assign(__p[__n], value_type());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c)
+     : __r_(__default_init_tag(), __default_init_tag())
 {
     __init(__n, __c);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1939,11 +1934,9 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __
 }
 
 template <class _CharT, class _Traits, class _Allocator>
-#ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
 template <class>
-#endif
 basic_string<_CharT, _Traits, _Allocator>::basic_string(size_type __n, _CharT __c, const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     __init(__n, __c);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -1955,7 +1948,7 @@ template <class _CharT, class _Traits, class _Allocator>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str,
                                                         size_type __pos, size_type __n,
                                                         const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     size_type __str_sz = __str.size();
     if (__pos > __str_sz)
@@ -1970,7 +1963,7 @@ template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const basic_string& __str, size_type __pos,
                                                         const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     size_type __str_sz = __str.size();
     if (__pos > __str_sz)
@@ -1985,7 +1978,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template <class _Tp, class>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(
              const _Tp& __t, size_type __pos, size_type __n, const allocator_type& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     __self_view __sv0 = __t;
     __self_view __sv = __sv0.substr(__pos, __n);
@@ -1998,6 +1991,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(
 template <class _CharT, class _Traits, class _Allocator>
 template <class _Tp, class>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t)
+     : __r_(__default_init_tag(), __default_init_tag())
 {
     __self_view __sv = __t;
     __init(__sv.data(), __sv.size());
@@ -2009,7 +2003,7 @@ basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t)
 template <class _CharT, class _Traits, class _Allocator>
 template <class _Tp, class>
 basic_string<_CharT, _Traits, _Allocator>::basic_string(const _Tp & __t, const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     __self_view __sv = __t;
     __init(__sv.data(), __sv.size());
@@ -2022,7 +2016,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template <class _InputIterator>
 typename enable_if
 <
-    __is_exactly_input_iterator<_InputIterator>::value,
+    __is_exactly_cpp17_input_iterator<_InputIterator>::value,
     void
 >::type
 basic_string<_CharT, _Traits, _Allocator>::__init(_InputIterator __first, _InputIterator __last)
@@ -2049,7 +2043,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value,
+    __is_cpp17_forward_iterator<_ForwardIterator>::value,
     void
 >::type
 basic_string<_CharT, _Traits, _Allocator>::__init(_ForwardIterator __first, _ForwardIterator __last)
@@ -2080,6 +2074,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template<class _InputIterator, class>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last)
+     : __r_(__default_init_tag(), __default_init_tag())
 {
     __init(__first, __last);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2092,7 +2087,7 @@ template<class _InputIterator, class>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(_InputIterator __first, _InputIterator __last,
                                                         const allocator_type& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     __init(__first, __last);
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2106,6 +2101,7 @@ template <class _CharT, class _Traits, class _Allocator>
 inline
 basic_string<_CharT, _Traits, _Allocator>::basic_string(
     initializer_list<_CharT> __il)
+     : __r_(__default_init_tag(), __default_init_tag())
 {
     __init(__il.begin(), __il.end());
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2118,7 +2114,7 @@ inline
 
 basic_string<_CharT, _Traits, _Allocator>::basic_string(
     initializer_list<_CharT> __il, const _Allocator& __a)
-    : __r_(__second_tag(), __a)
+    : __r_(__default_init_tag(), __a)
 {
     __init(__il.begin(), __il.end());
 #if _LIBCPP_DEBUG_LEVEL >= 2
@@ -2154,14 +2150,14 @@ basic_string<_CharT, _Traits, _Allocator>::__grow_by_and_replace
     pointer __p = __alloc_traits::allocate(__alloc(), __cap+1);
     __invalidate_all_iterators();
     if (__n_copy != 0)
-        traits_type::copy(_VSTD::__to_raw_pointer(__p),
-                          _VSTD::__to_raw_pointer(__old_p), __n_copy);
+        traits_type::copy(_VSTD::__to_address(__p),
+                          _VSTD::__to_address(__old_p), __n_copy);
     if (__n_add != 0)
-        traits_type::copy(_VSTD::__to_raw_pointer(__p) + __n_copy, __p_new_stuff, __n_add);
+        traits_type::copy(_VSTD::__to_address(__p) + __n_copy, __p_new_stuff, __n_add);
     size_type __sec_cp_sz = __old_sz - __n_del - __n_copy;
     if (__sec_cp_sz != 0)
-        traits_type::copy(_VSTD::__to_raw_pointer(__p) + __n_copy + __n_add,
-                          _VSTD::__to_raw_pointer(__old_p) + __n_copy + __n_del, __sec_cp_sz);
+        traits_type::copy(_VSTD::__to_address(__p) + __n_copy + __n_add,
+                          _VSTD::__to_address(__old_p) + __n_copy + __n_del, __sec_cp_sz);
     if (__old_cap+1 != __min_cap)
         __alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
     __set_long_pointer(__p);
@@ -2186,12 +2182,12 @@ basic_string<_CharT, _Traits, _Allocator>::__grow_by(size_type __old_cap, size_t
     pointer __p = __alloc_traits::allocate(__alloc(), __cap+1);
     __invalidate_all_iterators();
     if (__n_copy != 0)
-        traits_type::copy(_VSTD::__to_raw_pointer(__p),
-                          _VSTD::__to_raw_pointer(__old_p), __n_copy);
+        traits_type::copy(_VSTD::__to_address(__p),
+                          _VSTD::__to_address(__old_p), __n_copy);
     size_type __sec_cp_sz = __old_sz - __n_del - __n_copy;
     if (__sec_cp_sz != 0)
-        traits_type::copy(_VSTD::__to_raw_pointer(__p) + __n_copy + __n_add,
-                          _VSTD::__to_raw_pointer(__old_p) + __n_copy + __n_del,
+        traits_type::copy(_VSTD::__to_address(__p) + __n_copy + __n_add,
+                          _VSTD::__to_address(__old_p) + __n_copy + __n_del,
                           __sec_cp_sz);
     if (__old_cap+1 != __min_cap)
         __alloc_traits::deallocate(__alloc(), __old_p, __old_cap+1);
@@ -2209,7 +2205,7 @@ basic_string<_CharT, _Traits, _Allocator>::assign(const value_type* __s, size_ty
     size_type __cap = capacity();
     if (__cap >= __n)
     {
-        value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
+        value_type* __p = _VSTD::__to_address(__get_pointer());
         traits_type::move(__p, __s, __n);
         traits_type::assign(__p[__n], value_type());
         __set_size(__n);
@@ -2235,7 +2231,7 @@ basic_string<_CharT, _Traits, _Allocator>::assign(size_type __n, value_type __c)
     }
     else
         __invalidate_iterators_past(__n);
-    value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
+    value_type* __p = _VSTD::__to_address(__get_pointer());
     traits_type::assign(__p, __n, __c);
     traits_type::assign(__p[__n], value_type());
     __set_size(__n);
@@ -2270,7 +2266,7 @@ basic_string<_CharT, _Traits, _Allocator>::operator=(const basic_string& __str)
     if (this != &__str)
     {
         __copy_assign_alloc(__str);
-        assign(__str.data(), __str.size());
+        return assign(__str.data(), __str.size());
     }
     return *this;
 }
@@ -2299,10 +2295,20 @@ basic_string<_CharT, _Traits, _Allocator>::__move_assign(basic_string& __str, tr
     _NOEXCEPT_(is_nothrow_move_assignable<allocator_type>::value)
 #endif
 {
-    __clear_and_shrink();
-    __r_.first() = __str.__r_.first();
-    __move_assign_alloc(__str);
-    __str.__zero();
+  if (__is_long()) {
+    __alloc_traits::deallocate(__alloc(), __get_long_pointer(),
+                               __get_long_cap());
+#if _LIBCPP_STD_VER <= 14
+    if (!is_nothrow_move_assignable<allocator_type>::value) {
+      __set_short_size(0);
+      traits_type::assign(__get_short_pointer()[0], value_type());
+    }
+#endif
+  }
+  __move_assign_alloc(__str);
+  __r_.first() = __str.__r_.first();
+  __str.__set_short_size(0);
+  traits_type::assign(__str.__get_short_pointer()[0], value_type());
 }
 
 template <class _CharT, class _Traits, class _Allocator>
@@ -2322,7 +2328,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template<class _InputIterator>
 typename enable_if
 <
-     __is_exactly_input_iterator <_InputIterator>::value
+     __is_exactly_cpp17_input_iterator <_InputIterator>::value
           || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
     basic_string<_CharT, _Traits, _Allocator>&
 >::type
@@ -2337,7 +2343,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template<class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value
+    __is_cpp17_forward_iterator<_ForwardIterator>::value
          && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
     basic_string<_CharT, _Traits, _Allocator>&
 >::type
@@ -2408,7 +2414,7 @@ basic_string<_CharT, _Traits, _Allocator>::append(const value_type* __s, size_ty
     {
         if (__n)
         {
-            value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
+            value_type* __p = _VSTD::__to_address(__get_pointer());
             traits_type::copy(__p + __sz, __s, __n);
             __sz += __n;
             __set_size(__sz);
@@ -2431,7 +2437,7 @@ basic_string<_CharT, _Traits, _Allocator>::append(size_type __n, value_type __c)
         if (__cap - __sz < __n)
             __grow_by(__cap, __sz + __n - __cap, __sz, __sz, 0);
         pointer __p = __get_pointer();
-        traits_type::assign(_VSTD::__to_raw_pointer(__p) + __sz, __n, __c);
+        traits_type::assign(_VSTD::__to_address(__p) + __sz, __n, __c);
         __sz += __n;
         __set_size(__sz);
         traits_type::assign(__p[__sz], value_type());
@@ -2511,7 +2517,7 @@ basic_string<_CharT, _Traits, _Allocator>&
 basic_string<_CharT, _Traits, _Allocator>::__append_forward_unsafe(
     _ForwardIterator __first, _ForwardIterator __last)
 {
-    static_assert(__is_forward_iterator<_ForwardIterator>::value,
+    static_assert(__is_cpp17_forward_iterator<_ForwardIterator>::value,
                   "function requires a ForwardIterator");
     size_type __sz = size();
     size_type __cap = capacity();
@@ -2596,7 +2602,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, const value_t
     {
         if (__n)
         {
-            value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
+            value_type* __p = _VSTD::__to_address(__get_pointer());
             size_type __n_move = __sz - __pos;
             if (__n_move != 0)
             {
@@ -2628,7 +2634,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, size_type __n
         value_type* __p;
         if (__cap - __sz >= __n)
         {
-            __p = _VSTD::__to_raw_pointer(__get_pointer());
+            __p = _VSTD::__to_address(__get_pointer());
             size_type __n_move = __sz - __pos;
             if (__n_move != 0)
                 traits_type::move(__p + __pos + __n, __p + __pos, __n_move);
@@ -2636,7 +2642,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(size_type __pos, size_type __n
         else
         {
             __grow_by(__cap, __sz + __n - __cap, __sz, __pos, 0, __n);
-            __p = _VSTD::__to_raw_pointer(__get_long_pointer());
+            __p = _VSTD::__to_address(__get_long_pointer());
         }
         traits_type::assign(__p + __pos, __n, __c);
         __sz += __n;
@@ -2650,7 +2656,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template<class _InputIterator>
 typename enable_if
 <
-   __is_exactly_input_iterator<_InputIterator>::value
+   __is_exactly_cpp17_input_iterator<_InputIterator>::value
         || !__libcpp_string_gets_noexcept_iterator<_InputIterator>::value,
    typename basic_string<_CharT, _Traits, _Allocator>::iterator
 >::type
@@ -2669,7 +2675,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template<class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value
+    __is_cpp17_forward_iterator<_ForwardIterator>::value
         && __libcpp_string_gets_noexcept_iterator<_ForwardIterator>::value,
     typename basic_string<_CharT, _Traits, _Allocator>::iterator
 >::type
@@ -2697,7 +2703,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _Forward
         value_type* __p;
         if (__cap - __sz >= __n)
         {
-            __p = _VSTD::__to_raw_pointer(__get_pointer());
+            __p = _VSTD::__to_address(__get_pointer());
             size_type __n_move = __sz - __ip;
             if (__n_move != 0)
                 traits_type::move(__p + __ip + __n, __p + __ip, __n_move);
@@ -2705,7 +2711,7 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, _Forward
         else
         {
             __grow_by(__cap, __sz + __n - __cap, __sz, __ip, 0, __n);
-            __p = _VSTD::__to_raw_pointer(__get_long_pointer());
+            __p = _VSTD::__to_address(__get_long_pointer());
         }
         __sz += __n;
         __set_size(__sz);
@@ -2771,11 +2777,11 @@ basic_string<_CharT, _Traits, _Allocator>::insert(const_iterator __pos, value_ty
     if (__cap == __sz)
     {
         __grow_by(__cap, 1, __sz, __ip, 0, 1);
-        __p = _VSTD::__to_raw_pointer(__get_long_pointer());
+        __p = _VSTD::__to_address(__get_long_pointer());
     }
     else
     {
-        __p = _VSTD::__to_raw_pointer(__get_pointer());
+        __p = _VSTD::__to_address(__get_pointer());
         size_type __n_move = __sz - __ip;
         if (__n_move != 0)
             traits_type::move(__p + __ip + 1, __p + __ip, __n_move);
@@ -2816,7 +2822,7 @@ basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __
     size_type __cap = capacity();
     if (__cap - __sz + __n1 >= __n2)
     {
-        value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
+        value_type* __p = _VSTD::__to_address(__get_pointer());
         if (__n1 != __n2)
         {
             size_type __n_move = __sz - __pos - __n1;
@@ -2871,7 +2877,7 @@ basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __
     value_type* __p;
     if (__cap - __sz + __n1 >= __n2)
     {
-        __p = _VSTD::__to_raw_pointer(__get_pointer());
+        __p = _VSTD::__to_address(__get_pointer());
         if (__n1 != __n2)
         {
             size_type __n_move = __sz - __pos - __n1;
@@ -2882,7 +2888,7 @@ basic_string<_CharT, _Traits, _Allocator>::replace(size_type __pos, size_type __
     else
     {
         __grow_by(__cap, __sz - __n1 + __n2 - __cap, __sz, __pos, __n1, __n2);
-        __p = _VSTD::__to_raw_pointer(__get_long_pointer());
+        __p = _VSTD::__to_address(__get_long_pointer());
     }
     traits_type::assign(__p + __pos, __n2, __c);
     __sz += __n2 - __n1;
@@ -2896,7 +2902,7 @@ template <class _CharT, class _Traits, class _Allocator>
 template<class _InputIterator>
 typename enable_if
 <
-    __is_input_iterator<_InputIterator>::value,
+    __is_cpp17_input_iterator<_InputIterator>::value,
     basic_string<_CharT, _Traits, _Allocator>&
 >::type
 basic_string<_CharT, _Traits, _Allocator>::replace(const_iterator __i1, const_iterator __i2,
@@ -2994,7 +3000,7 @@ basic_string<_CharT, _Traits, _Allocator>::erase(size_type __pos, size_type __n)
         this->__throw_out_of_range();
     if (__n)
     {
-        value_type* __p = _VSTD::__to_raw_pointer(__get_pointer());
+        value_type* __p = _VSTD::__to_address(__get_pointer());
         __n = _VSTD::min(__n, __sz - __pos);
         size_type __n_move = __sz - __pos - __n;
         if (__n_move != 0)
@@ -3182,8 +3188,8 @@ basic_string<_CharT, _Traits, _Allocator>::reserve(size_type __res_arg)
             __was_long = __is_long();
             __p = __get_pointer();
         }
-        traits_type::copy(_VSTD::__to_raw_pointer(__new_data),
-                          _VSTD::__to_raw_pointer(__p), size()+1);
+        traits_type::copy(_VSTD::__to_address(__new_data),
+                          _VSTD::__to_address(__p), size()+1);
         if (__was_long)
             __alloc_traits::deallocate(__alloc(), __p, __cap+1);
         if (__now_long)
@@ -4294,23 +4300,23 @@ template<class _CharT, class _Traits, class _Allocator>
 bool
 basic_string<_CharT, _Traits, _Allocator>::__dereferenceable(const const_iterator* __i) const
 {
-    return this->data() <= _VSTD::__to_raw_pointer(__i->base()) &&
-           _VSTD::__to_raw_pointer(__i->base()) < this->data() + this->size();
+    return this->data() <= _VSTD::__to_address(__i->base()) &&
+           _VSTD::__to_address(__i->base()) < this->data() + this->size();
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 bool
 basic_string<_CharT, _Traits, _Allocator>::__decrementable(const const_iterator* __i) const
 {
-    return this->data() < _VSTD::__to_raw_pointer(__i->base()) &&
-           _VSTD::__to_raw_pointer(__i->base()) <= this->data() + this->size();
+    return this->data() < _VSTD::__to_address(__i->base()) &&
+           _VSTD::__to_address(__i->base()) <= this->data() + this->size();
 }
 
 template<class _CharT, class _Traits, class _Allocator>
 bool
 basic_string<_CharT, _Traits, _Allocator>::__addable(const const_iterator* __i, ptrdiff_t __n) const
 {
-    const value_type* __p = _VSTD::__to_raw_pointer(__i->base()) + __n;
+    const value_type* __p = _VSTD::__to_address(__i->base()) + __n;
     return this->data() <= __p && __p <= this->data() + this->size();
 }
 
@@ -4318,7 +4324,7 @@ template<class _CharT, class _Traits, class _Allocator>
 bool
 basic_string<_CharT, _Traits, _Allocator>::__subscriptable(const const_iterator* __i, ptrdiff_t __n) const
 {
-    const value_type* __p = _VSTD::__to_raw_pointer(__i->base()) + __n;
+    const value_type* __p = _VSTD::__to_address(__i->base()) + __n;
     return this->data() <= __p && __p < this->data() + this->size();
 }
 
lib/libcxx/include/string_view
@@ -173,6 +173,7 @@ namespace std {
 
 #include <__config>
 #include <__string>
+#include <iosfwd>
 #include <algorithm>
 #include <iterator>
 #include <limits>
@@ -235,7 +236,7 @@ public:
 
     _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
     basic_string_view(const _CharT* __s)
-        : __data(__s), __size(_Traits::length(__s)) {}
+        : __data(__s), __size(std::__char_traits_length_checked<_Traits>(__s)) {}
 
     // [string.view.iterators], iterators
     _LIBCPP_CONSTEXPR _LIBCPP_INLINE_VISIBILITY
@@ -767,6 +768,12 @@ bool operator>=(typename common_type<basic_string_view<_CharT, _Traits> >::type
     return __lhs.compare(__rhs) >= 0;
 }
 
+
+template<class _CharT, class _Traits>
+basic_ostream<_CharT, _Traits>&
+operator<<(basic_ostream<_CharT, _Traits>& __os,
+           basic_string_view<_CharT, _Traits> __str);
+
 typedef basic_string_view<char>     string_view;
 #ifndef _LIBCPP_NO_HAS_CHAR8_T
 typedef basic_string_view<char8_t>  u8string_view;
lib/libcxx/include/thread
@@ -14,8 +14,6 @@
 
     thread synopsis
 
-#define __STDCPP_THREADS__ __cplusplus
-
 namespace std
 {
 
@@ -107,8 +105,6 @@ void sleep_for(const chrono::duration<Rep, Period>& rel_time);
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>
 
-#define __STDCPP_THREADS__ __cplusplus
-
 #ifdef _LIBCPP_HAS_NO_THREADS
 #error <thread> is not supported on this single threaded system
 #else // !_LIBCPP_HAS_NO_THREADS
@@ -278,6 +274,7 @@ __thread_execute(tuple<_TSp, _Fp, _Args...>& __t, __tuple_indices<_Indices...>)
 }
 
 template <class _Fp>
+_LIBCPP_INLINE_VISIBILITY
 void* __thread_proxy(void* __vp)
 {
     // _Fp = std::tuple< unique_ptr<__thread_struct>, Functor, Args...>
lib/libcxx/include/tuple
@@ -19,40 +19,40 @@ namespace std
 template <class... T>
 class tuple {
 public:
-    constexpr tuple();
-    explicit tuple(const T&...);  // constexpr in C++14
+    explicit(see-below) constexpr tuple();
+    explicit(see-below) tuple(const T&...);  // constexpr in C++14
     template <class... U>
-        explicit tuple(U&&...);  // constexpr in C++14
+        explicit(see-below) tuple(U&&...);  // constexpr in C++14
     tuple(const tuple&) = default;
     tuple(tuple&&) = default;
     template <class... U>
-        tuple(const tuple<U...>&);  // constexpr in C++14
+        explicit(see-below) tuple(const tuple<U...>&);  // constexpr in C++14
     template <class... U>
-        tuple(tuple<U...>&&);  // constexpr in C++14
+        explicit(see-below) tuple(tuple<U...>&&);  // constexpr in C++14
     template <class U1, class U2>
-        tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2 // constexpr in C++14
+        explicit(see-below) tuple(const pair<U1, U2>&); // iff sizeof...(T) == 2 // constexpr in C++14
     template <class U1, class U2>
-        tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2  // constexpr in C++14
+        explicit(see-below) tuple(pair<U1, U2>&&); // iff sizeof...(T) == 2  // constexpr in C++14
 
     // allocator-extended constructors
     template <class Alloc>
         tuple(allocator_arg_t, const Alloc& a);
     template <class Alloc>
-        tuple(allocator_arg_t, const Alloc& a, const T&...);
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const T&...);
     template <class Alloc, class... U>
-        tuple(allocator_arg_t, const Alloc& a, U&&...);
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, U&&...);
     template <class Alloc>
         tuple(allocator_arg_t, const Alloc& a, const tuple&);
     template <class Alloc>
         tuple(allocator_arg_t, const Alloc& a, tuple&&);
     template <class Alloc, class... U>
-        tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const tuple<U...>&);
     template <class Alloc, class... U>
-        tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, tuple<U...>&&);
     template <class Alloc, class U1, class U2>
-        tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, const pair<U1, U2>&);
     template <class Alloc, class U1, class U2>
-        tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);
+        explicit(see-below) tuple(allocator_arg_t, const Alloc& a, pair<U1, U2>&&);
 
     tuple& operator=(const tuple&);
     tuple&
@@ -69,6 +69,17 @@ public:
     void swap(tuple&) noexcept(AND(swap(declval<T&>(), declval<T&>())...));
 };
 
+template <class ...T>
+tuple(T...) -> tuple<T...>;                                         // since C++17
+template <class T1, class T2>
+tuple(pair<T1, T2>) -> tuple<T1, T2>;                               // since C++17
+template <class Alloc, class ...T>
+tuple(allocator_arg_t, Alloc, T...) -> tuple<T...>;                 // since C++17
+template <class Alloc, class T1, class T2>
+tuple(allocator_arg_t, Alloc, pair<T1, T2>) -> tuple<T1, T2>;       // since C++17
+template <class Alloc, class ...T>
+tuple(allocator_arg_t, Alloc, tuple<T...>) -> tuple<T...>;          // since C++17
+
 inline constexpr unspecified ignore;
 
 template <class... T> tuple<V...>  make_tuple(T&&...); // constexpr in C++14
@@ -488,11 +499,19 @@ class _LIBCPP_TEMPLATE_VIS tuple
     template <class _Dummy>
     struct _CheckArgsConstructor<true, _Dummy>
     {
-        template <class ..._Args>
-        static constexpr bool __enable_default() {
-            return __all<is_default_constructible<_Args>::value...>::value;
+        template <int&...>
+        static constexpr bool __enable_implicit_default() {
+           return __all<__is_implicitly_default_constructible<_Tp>::value... >::value;
+        }
+
+        template <int&...>
+        static constexpr bool __enable_explicit_default() {
+            return
+                __all<is_default_constructible<_Tp>::value...>::value &&
+                !__enable_implicit_default< >();
         }
 
+
         template <class ..._Args>
         static constexpr bool __enable_explicit() {
             return
@@ -630,22 +649,26 @@ class _LIBCPP_TEMPLATE_VIS tuple
         const typename tuple_element<_Jp, tuple<_Up...> >::type&& get(const tuple<_Up...>&&) _NOEXCEPT;
 public:
 
-    template <bool _Dummy = true, class = typename enable_if<
-        _CheckArgsConstructor<_Dummy>::template __enable_default<_Tp...>()
-    >::type>
-    _LIBCPP_INLINE_VISIBILITY
-    _LIBCPP_CONSTEXPR tuple()
+    template <bool _Dummy = true, _EnableIf<
+        _CheckArgsConstructor<_Dummy>::__enable_implicit_default()
+    , void*> = nullptr>
+    _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    tuple()
+        _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
+
+    template <bool _Dummy = true, _EnableIf<
+        _CheckArgsConstructor<_Dummy>::__enable_explicit_default()
+    , void*> = nullptr>
+    explicit _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    tuple()
         _NOEXCEPT_(__all<is_nothrow_default_constructible<_Tp>::value...>::value) {}
 
     tuple(tuple const&) = default;
     tuple(tuple&&) = default;
 
-    template <class _AllocArgT, class _Alloc, bool _Dummy = true, class = _EnableIf<
-        _And<
-            _IsSame<allocator_arg_t, _AllocArgT>,
-           __dependent_type<is_default_constructible<_Tp>, _Dummy>...
-       >::value
-      >
+    template <class _AllocArgT, class _Alloc, _EnableIf<
+             _CheckArgsConstructor<_IsSame<allocator_arg_t, _AllocArgT>::value >::__enable_implicit_default()
+      , void*> = nullptr
     >
     _LIBCPP_INLINE_VISIBILITY
     tuple(_AllocArgT, _Alloc const& __a)
@@ -654,6 +677,17 @@ public:
                     typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
                     __tuple_types<_Tp...>()) {}
 
+    template <class _AllocArgT, class _Alloc, _EnableIf<
+             _CheckArgsConstructor<_IsSame<allocator_arg_t, _AllocArgT>::value>::__enable_explicit_default()
+      , void*> = nullptr
+    >
+    explicit _LIBCPP_INLINE_VISIBILITY
+    tuple(_AllocArgT, _Alloc const& __a)
+      : __base_(allocator_arg_t(), __a,
+                    __tuple_indices<>(), __tuple_types<>(),
+                    typename __make_tuple_indices<sizeof...(_Tp), 0>::type(),
+                    __tuple_types<_Tp...>()) {}
+
     template <bool _Dummy = true,
               typename enable_if
                       <
@@ -943,13 +977,16 @@ public:
 };
 
 #ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
-// NOTE: These are not yet standardized, but are required to simulate the
-// implicit deduction guide that should be generated had libc++ declared the
-// tuple-like constructors "correctly"
-template <class _Alloc, class ..._Args>
-tuple(allocator_arg_t, const _Alloc&, tuple<_Args...> const&) -> tuple<_Args...>;
-template <class _Alloc, class ..._Args>
-tuple(allocator_arg_t, const _Alloc&, tuple<_Args...>&&) -> tuple<_Args...>;
+template <class ..._Tp>
+tuple(_Tp...) -> tuple<_Tp...>;
+template <class _Tp1, class _Tp2>
+tuple(pair<_Tp1, _Tp2>) -> tuple<_Tp1, _Tp2>;
+template <class _Alloc, class ..._Tp>
+tuple(allocator_arg_t, _Alloc, _Tp...) -> tuple<_Tp...>;
+template <class _Alloc, class _Tp1, class _Tp2>
+tuple(allocator_arg_t, _Alloc, pair<_Tp1, _Tp2>) -> tuple<_Tp1, _Tp2>;
+template <class _Alloc, class ..._Tp>
+tuple(allocator_arg_t, _Alloc, tuple<_Tp...>) -> tuple<_Tp...>;
 #endif
 
 template <class ..._Tp>
@@ -1312,8 +1349,9 @@ struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J
     typename __tuple_cat_return_ref<tuple<_Types...>&&, _Tuple0&&>::type
     operator()(tuple<_Types...> __t, _Tuple0&& __t0)
     {
-        return forward_as_tuple(_VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
-                                      _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...);
+        return _VSTD::forward_as_tuple(
+            _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
+            _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...);
     }
 
     template <class _Tuple0, class _Tuple1, class ..._Tuples>
@@ -1324,15 +1362,16 @@ struct __tuple_cat<tuple<_Types...>, __tuple_indices<_I0...>, __tuple_indices<_J
         typedef _LIBCPP_NODEBUG_TYPE typename remove_reference<_Tuple0>::type _T0;
         typedef _LIBCPP_NODEBUG_TYPE typename remove_reference<_Tuple1>::type _T1;
         return __tuple_cat<
-           tuple<_Types..., typename __apply_cv<_Tuple0, typename tuple_element<_J0, _T0>::type>::type&&...>,
-           typename __make_tuple_indices<sizeof ...(_Types) + tuple_size<_T0>::value>::type,
-           typename __make_tuple_indices<tuple_size<_T1>::value>::type>()
-                           (forward_as_tuple(
-                              _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
-                              _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...
-                            ),
-                            _VSTD::forward<_Tuple1>(__t1),
-                            _VSTD::forward<_Tuples>(__tpls)...);
+            tuple<_Types...,
+                  typename __apply_cv<_Tuple0, typename tuple_element<
+                                                   _J0, _T0>::type>::type&&...>,
+            typename __make_tuple_indices<sizeof...(_Types) +
+                                          tuple_size<_T0>::value>::type,
+            typename __make_tuple_indices<tuple_size<_T1>::value>::type>()(
+            _VSTD::forward_as_tuple(
+                _VSTD::forward<_Types>(_VSTD::get<_I0>(__t))...,
+                _VSTD::get<_J0>(_VSTD::forward<_Tuple0>(__t0))...),
+            _VSTD::forward<_Tuple1>(__t1), _VSTD::forward<_Tuples>(__tpls)...);
     }
 };
 
lib/libcxx/include/type_traits
@@ -427,7 +427,6 @@ template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS pair;
 template <class _Tp> class _LIBCPP_TEMPLATE_VIS reference_wrapper;
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS hash;
 
-
 template <class _Tp, _Tp __v>
 struct _LIBCPP_TEMPLATE_VIS integral_constant
 {
@@ -509,8 +508,8 @@ struct _Lazy : _Func<_Args...> {};
 
 // Member detector base
 
-template <template <class...> class _Templ, class ..._Args>
-true_type __sfinae_test_impl(_FirstType<int, _Templ<_Args...> >);
+template <template <class...> class _Templ, class ..._Args, class = _Templ<_Args...> >
+true_type __sfinae_test_impl(int);
 template <template <class...> class, class ...>
 false_type __sfinae_test_impl(...);
 
@@ -526,6 +525,7 @@ struct __identity { typedef _Tp type; };
 template <class _Tp, bool>
 struct _LIBCPP_TEMPLATE_VIS __dependent_type : public _Tp {};
 
+
 template <bool _Bp, class _If, class _Then>
     struct _LIBCPP_TEMPLATE_VIS conditional {typedef _If type;};
 template <class _If, class _Then>
@@ -570,6 +570,17 @@ using _IsNotSame = _BoolConstant<
     !_VSTD::is_same<_Tp, _Up>::value
 #endif
 >;
+
+
+template <class _Tp>
+using __test_for_primary_template = _EnableIf<
+    _IsSame<_Tp, typename _Tp::__primary_template>::value
+  >;
+template <class _Tp>
+using __is_primary_template = _IsValidExpansion<
+    __test_for_primary_template, _Tp
+  >;
+
 // addressof
 #ifndef _LIBCPP_HAS_NO_BUILTIN_ADDRESSOF
 
@@ -720,7 +731,7 @@ template <class _Tp>
 _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_null_pointer_v
     = is_null_pointer<_Tp>::value;
 #endif
-#endif
+#endif // _LIBCPP_STD_VER > 11
 
 // is_integral
 
@@ -886,28 +897,15 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_class_v
 
 // is_function
 
-namespace __libcpp_is_function_imp
-{
-struct __dummy_type {};
-template <class _Tp> char  __test(_Tp*);
-template <class _Tp> char __test(__dummy_type);
-template <class _Tp> __two __test(...);
-template <class _Tp> _Tp&  __source(int);
-template <class _Tp> __dummy_type __source(...);
-}
-
-template <class _Tp, bool = is_class<_Tp>::value ||
-                            is_union<_Tp>::value ||
-                            is_void<_Tp>::value  ||
-                            is_reference<_Tp>::value ||
-                            __is_nullptr_t<_Tp>::value >
-struct __libcpp_is_function
-    : public integral_constant<bool, sizeof(__libcpp_is_function_imp::__test<_Tp>(__libcpp_is_function_imp::__source<_Tp>(0))) == 1>
-    {};
-template <class _Tp> struct __libcpp_is_function<_Tp, true> : public false_type {};
-
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_function
-    : public __libcpp_is_function<_Tp> {};
+    : public _BoolConstant<
+#ifdef __clang__
+    __is_function(_Tp)
+#else
+ !(is_reference<_Tp>::value || is_const<const _Tp>::value)
+#endif
+    > {};
+
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
@@ -915,27 +913,24 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_function_v
     = is_function<_Tp>::value;
 #endif
 
-// is_member_function_pointer
-
-// template <class _Tp> struct            __libcpp_is_member_function_pointer             : public false_type {};
-// template <class _Tp, class _Up> struct __libcpp_is_member_function_pointer<_Tp _Up::*> : public is_function<_Tp> {};
-//
-
-template <class _MP, bool _IsMemberFunctionPtr, bool _IsMemberObjectPtr>
-struct __member_pointer_traits_imp
-{  // forward declaration; specializations later
+template <class _Tp> struct __libcpp_is_member_pointer {
+  enum {
+    __is_member = false,
+    __is_func = false,
+    __is_obj = false
+  };
+};
+template <class _Tp, class _Up> struct __libcpp_is_member_pointer<_Tp _Up::*> {
+  enum {
+    __is_member = true,
+    __is_func = is_function<_Tp>::value,
+    __is_obj = !__is_func,
+  };
 };
 
 
-template <class _Tp> struct __libcpp_is_member_function_pointer
-    : public false_type {};
-
-template <class _Ret, class _Class>
-struct __libcpp_is_member_function_pointer<_Ret _Class::*>
-    : public is_function<_Ret> {};
-
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_function_pointer
-    : public __libcpp_is_member_function_pointer<typename remove_cv<_Tp>::type>::type {};
+    : public _BoolConstant< __libcpp_is_member_pointer<typename remove_cv<_Tp>::type>::__is_func > {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
@@ -945,11 +940,8 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_member_function_pointer_v
 
 // is_member_pointer
 
-template <class _Tp>            struct __libcpp_is_member_pointer             : public false_type {};
-template <class _Tp, class _Up> struct __libcpp_is_member_pointer<_Tp _Up::*> : public true_type {};
-
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_pointer
-    : public __libcpp_is_member_pointer<typename remove_cv<_Tp>::type> {};
+ : public _BoolConstant< __libcpp_is_member_pointer<typename remove_cv<_Tp>::type>::__is_member > {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
@@ -960,8 +952,7 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_member_pointer_v
 // is_member_object_pointer
 
 template <class _Tp> struct _LIBCPP_TEMPLATE_VIS is_member_object_pointer
-    : public integral_constant<bool, is_member_pointer<_Tp>::value &&
-                                    !is_member_function_pointer<_Tp>::value> {};
+    : public _BoolConstant< __libcpp_is_member_pointer<typename remove_cv<_Tp>::type>::__is_obj >  {};
 
 #if _LIBCPP_STD_VER > 14 && !defined(_LIBCPP_HAS_NO_VARIABLE_TEMPLATES)
 template <class _Tp>
@@ -1080,16 +1071,9 @@ struct __is_referenceable : integral_constant<bool,
 
 // add_const
 
-template <class _Tp, bool = is_reference<_Tp>::value ||
-                            is_function<_Tp>::value  ||
-                            is_const<_Tp>::value     >
-struct __add_const             {typedef _LIBCPP_NODEBUG_TYPE  _Tp type;};
-
-template <class _Tp>
-struct __add_const<_Tp, false> {typedef _LIBCPP_NODEBUG_TYPE  const _Tp type;};
-
-template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_const
-    {typedef _LIBCPP_NODEBUG_TYPE  typename __add_const<_Tp>::type type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_const {
+  typedef _LIBCPP_NODEBUG_TYPE const _Tp type;
+};
 
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using add_const_t = typename add_const<_Tp>::type;
@@ -1097,25 +1081,18 @@ template <class _Tp> using add_const_t = typename add_const<_Tp>::type;
 
 // add_volatile
 
-template <class _Tp, bool = is_reference<_Tp>::value ||
-                            is_function<_Tp>::value  ||
-                            is_volatile<_Tp>::value  >
-struct __add_volatile             {typedef _Tp type;};
-
-template <class _Tp>
-struct __add_volatile<_Tp, false> {typedef volatile _Tp type;};
-
-template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_volatile
-    {typedef _LIBCPP_NODEBUG_TYPE typename __add_volatile<_Tp>::type type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_volatile {
+  typedef _LIBCPP_NODEBUG_TYPE volatile _Tp type;
+};
 
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using add_volatile_t = typename add_volatile<_Tp>::type;
 #endif
 
 // add_cv
-
-template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_cv
-    {typedef _LIBCPP_NODEBUG_TYPE typename add_const<typename add_volatile<_Tp>::type>::type type;};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_cv {
+  typedef _LIBCPP_NODEBUG_TYPE const volatile _Tp type;
+};
 
 #if _LIBCPP_STD_VER > 11
 template <class _Tp> using add_cv_t = typename add_cv<_Tp>::type;
@@ -1153,8 +1130,12 @@ template <class _Tp> struct _LIBCPP_TEMPLATE_VIS add_rvalue_reference
 template <class _Tp> using add_rvalue_reference_t = typename add_rvalue_reference<_Tp>::type;
 #endif
 
+// Suppress deprecation notice for volatile-qualified return type resulting
+// from volatile-qualified types _Tp.
+_LIBCPP_SUPPRESS_DEPRECATED_PUSH
 template <class _Tp> _Tp&& __declval(int);
 template <class _Tp> _Tp   __declval(long);
+_LIBCPP_SUPPRESS_DEPRECATED_POP
 
 template <class _Tp>
 decltype(_VSTD::__declval<_Tp>(0))
@@ -1448,8 +1429,7 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_base_of_v
 #if __has_feature(is_convertible_to) && !defined(_LIBCPP_USE_IS_CONVERTIBLE_FALLBACK)
 
 template <class _T1, class _T2> struct _LIBCPP_TEMPLATE_VIS is_convertible
-    : public integral_constant<bool, __is_convertible_to(_T1, _T2) &&
-                                     !is_abstract<_T2>::value> {};
+    : public integral_constant<bool, __is_convertible_to(_T1, _T2)> {};
 
 #else  // __has_feature(is_convertible_to)
 
@@ -2307,6 +2287,11 @@ __decay_copy(_Tp&& __t)
     return _VSTD::forward<_Tp>(__t);
 }
 
+template <class _MP, bool _IsMemberFunctionPtr, bool _IsMemberObjectPtr>
+struct __member_pointer_traits_imp
+{
+};
+
 template <class _Rp, class _Class, class ..._Param>
 struct __member_pointer_traits_imp<_Rp (_Class::*)(_Param...), true, false>
 {
@@ -2836,6 +2821,30 @@ _LIBCPP_INLINE_VAR _LIBCPP_CONSTEXPR bool is_default_constructible_v
     = is_default_constructible<_Tp>::value;
 #endif
 
+#ifndef _LIBCPP_CXX03_LANG
+// First of all, we can't implement this check in C++03 mode because the {}
+// default initialization syntax isn't valid.
+// Second, we implement the trait in a funny manner with two defaulted template
+// arguments to workaround Clang's PR43454.
+template <class _Tp>
+void __test_implicit_default_constructible(_Tp);
+
+template <class _Tp, class = void, bool = is_default_constructible<_Tp>::value>
+struct __is_implicitly_default_constructible
+    : false_type
+{ };
+
+template <class _Tp>
+struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), true>
+    : true_type
+{ };
+
+template <class _Tp>
+struct __is_implicitly_default_constructible<_Tp, decltype(__test_implicit_default_constructible<_Tp const&>({})), false>
+    : false_type
+{ };
+#endif // !C++03
+
 // is_copy_constructible
 
 template <class _Tp>
@@ -3681,6 +3690,13 @@ _LIBCPP_INLINE_VAR constexpr bool is_nothrow_invocable_r_v
 template <class _Tp> struct __is_swappable;
 template <class _Tp> struct __is_nothrow_swappable;
 
+// swap, swap_ranges
+
+template <class _ForwardIterator1, class _ForwardIterator2>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+_ForwardIterator2
+swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2);
+
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY
 #ifndef _LIBCPP_CXX03_LANG
@@ -3706,7 +3722,22 @@ inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
 typename enable_if<
     __is_swappable<_Tp>::value
 >::type
-swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value);
+swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value)
+{
+    _VSTD::swap_ranges(__a, __a + _Np, __b);
+}
+
+template <class _ForwardIterator1, class _ForwardIterator2>
+inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
+_ForwardIterator2
+swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2)
+{
+    for(; __first1 != __last1; ++__first1, (void) ++__first2)
+        swap(*__first1, *__first2);
+    return __first2;
+}
+
+// iter_swap
 
 template <class _ForwardIterator1, class _ForwardIterator2>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
@@ -3985,21 +4016,6 @@ struct __can_extract_map_key<_ValTy, _Key, _Key, _RawValTy>
 
 #endif
 
-#if _LIBCPP_STD_VER > 17
-enum class endian
-{
-    little = 0xDEAD,
-    big    = 0xFACE,
-#if defined(_LIBCPP_LITTLE_ENDIAN)
-    native = little
-#elif defined(_LIBCPP_BIG_ENDIAN)
-    native = big
-#else
-    native = 0xCAFE
-#endif
-};
-#endif
-
 #ifndef _LIBCPP_HAS_NO_BUILTIN_IS_CONSTANT_EVALUATED
 #if _LIBCPP_STD_VER > 17
 _LIBCPP_INLINE_VISIBILITY
lib/libcxx/include/utility
@@ -69,11 +69,11 @@ struct pair
 
     pair(const pair&) = default;
     pair(pair&&) = default;
-    constexpr pair();
-    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
+    explicit(see-below) constexpr pair();
+    explicit(see-below) pair(const T1& x, const T2& y);                          // constexpr in C++14
+    template <class U, class V> explicit(see-below) pair(U&& x, V&& y);          // constexpr in C++14
+    template <class U, class V> explicit(see-below) pair(const pair<U, V>& p);   // constexpr in C++14
+    template <class U, class V> explicit(see-below) 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);
@@ -99,7 +99,7 @@ template <class T1, class T2>
 void
 swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
 
-struct piecewise_construct_t { };
+struct piecewise_construct_t { explicit piecewise_construct_t() = default; };
 inline constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
 
 template <class T> struct tuple_size;
@@ -248,29 +248,11 @@ operator>=(const _Tp& __x, const _Tp& __y)
 
 }  // rel_ops
 
-// swap_ranges
+// swap_ranges is defined in <type_traits>`
 
+// swap is defined in <type_traits>
 
-template <class _ForwardIterator1, class _ForwardIterator2>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-_ForwardIterator2
-swap_ranges(_ForwardIterator1 __first1, _ForwardIterator1 __last1, _ForwardIterator2 __first2)
-{
-    for(; __first1 != __last1; ++__first1, (void) ++__first2)
-        swap(*__first1, *__first2);
-    return __first2;
-}
-
-// forward declared in <type_traits>
-template<class _Tp, size_t _Np>
-inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX17
-typename enable_if<
-    __is_swappable<_Tp>::value
->::type
-swap(_Tp (&__a)[_Np], _Tp (&__b)[_Np]) _NOEXCEPT_(__is_nothrow_swappable<_Tp>::value)
-{
-    _VSTD::swap_ranges(__a, __a + _Np, __b);
-}
+// move_if_noexcept
 
 template <class _Tp>
 inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
@@ -294,7 +276,7 @@ template <class _Tp> constexpr add_const_t<_Tp>& as_const(_Tp& __t) noexcept { r
 template <class _Tp>                        void as_const(const _Tp&&) = delete;
 #endif
 
-struct _LIBCPP_TEMPLATE_VIS piecewise_construct_t { };
+struct _LIBCPP_TEMPLATE_VIS piecewise_construct_t { explicit piecewise_construct_t() = default; };
 #if defined(_LIBCPP_CXX03_LANG) || defined(_LIBCPP_BUILDING_LIBRARY)
 extern _LIBCPP_EXPORTED_FROM_ABI const piecewise_construct_t piecewise_construct;// = piecewise_construct_t();
 #else
@@ -352,10 +334,17 @@ struct _LIBCPP_TEMPLATE_VIS pair
     using _EnableB _LIBCPP_NODEBUG_TYPE = typename enable_if<_Val, bool>::type;
 
     struct _CheckArgs {
-      template <class _U1, class _U2>
-      static constexpr bool __enable_default() {
-          return is_default_constructible<_U1>::value
-              && is_default_constructible<_U2>::value;
+      template <int&...>
+      static constexpr bool __enable_explicit_default() {
+          return is_default_constructible<_T1>::value
+              && is_default_constructible<_T2>::value
+              && !__enable_implicit_default<>();
+      }
+
+      template <int&...>
+      static constexpr bool __enable_implicit_default() {
+          return __is_implicitly_default_constructible<_T1>::value
+              && __is_implicitly_default_constructible<_T2>::value;
       }
 
       template <class _U1, class _U2>
@@ -406,7 +395,15 @@ struct _LIBCPP_TEMPLATE_VIS pair
     >::type;
 
     template<bool _Dummy = true, _EnableB<
-            _CheckArgsDep<_Dummy>::template __enable_default<_T1, _T2>()
+            _CheckArgsDep<_Dummy>::__enable_explicit_default()
+    > = false>
+    explicit _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    pair() _NOEXCEPT_(is_nothrow_default_constructible<first_type>::value &&
+                      is_nothrow_default_constructible<second_type>::value)
+        : first(), second() {}
+
+    template<bool _Dummy = true, _EnableB<
+            _CheckArgsDep<_Dummy>::__enable_implicit_default()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     pair() _NOEXCEPT_(is_nothrow_default_constructible<first_type>::value &&
lib/libcxx/include/valarray
@@ -1256,6 +1256,8 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     operator>>=(const _Expr& __v) const;
 
+    slice_array(slice_array const&) = default;
+
     _LIBCPP_INLINE_VISIBILITY
     const slice_array& operator=(const slice_array& __sa) const;
 
@@ -1505,11 +1507,6 @@ public:
 
 #endif  // _LIBCPP_CXX03_LANG
 
-//  gslice(const gslice&)            = default;
-//  gslice(gslice&&)                 = default;
-//  gslice& operator=(const gslice&) = default;
-//  gslice& operator=(gslice&&)      = default;
-
     _LIBCPP_INLINE_VISIBILITY
     size_t           start()  const {return __1d_.size() ? __1d_[0] : 0;}
 
@@ -1645,10 +1642,7 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     void operator=(const value_type& __x) const;
 
-//  gslice_array(const gslice_array&)            = default;
-//  gslice_array(gslice_array&&)                 = default;
-//  gslice_array& operator=(const gslice_array&) = default;
-//  gslice_array& operator=(gslice_array&&)      = default;
+    gslice_array(const gslice_array&)            = default;
 
 private:
     gslice_array(const gslice& __gs, const valarray<value_type>& __v)
@@ -1977,17 +1971,14 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     operator>>=(const _Expr& __v) const;
 
+    mask_array(const mask_array&) = default;
+
     _LIBCPP_INLINE_VISIBILITY
     const mask_array& operator=(const mask_array& __ma) const;
 
     _LIBCPP_INLINE_VISIBILITY
     void operator=(const value_type& __x) const;
 
-//  mask_array(const mask_array&)            = default;
-//  mask_array(mask_array&&)                 = default;
-//  mask_array& operator=(const mask_array&) = default;
-//  mask_array& operator=(mask_array&&)      = default;
-
 private:
     _LIBCPP_INLINE_VISIBILITY
     mask_array(const valarray<bool>& __vb, const valarray<value_type>& __v)
@@ -2336,17 +2327,14 @@ public:
     _LIBCPP_INLINE_VISIBILITY
     operator>>=(const _Expr& __v) const;
 
+    indirect_array(const indirect_array&) = default;
+
     _LIBCPP_INLINE_VISIBILITY
     const indirect_array& operator=(const indirect_array& __ia) const;
 
     _LIBCPP_INLINE_VISIBILITY
     void operator=(const value_type& __x) const;
 
-//  indirect_array(const indirect_array&)            = default;
-//  indirect_array(indirect_array&&)                 = default;
-//  indirect_array& operator=(const indirect_array&) = default;
-//  indirect_array& operator=(indirect_array&&)      = default;
-
 private:
      _LIBCPP_INLINE_VISIBILITY
    indirect_array(const valarray<size_t>& __ia, const valarray<value_type>& __v)
lib/libcxx/include/vector
@@ -297,7 +297,7 @@ _LIBCPP_PUSH_MACROS
 _LIBCPP_BEGIN_NAMESPACE_STD
 
 template <bool>
-class __vector_base_common
+class _LIBCPP_TEMPLATE_VIS __vector_base_common
 {
 protected:
     _LIBCPP_INLINE_VISIBILITY __vector_base_common() {}
@@ -423,7 +423,7 @@ __vector_base<_Tp, _Allocator>::__destruct_at_end(pointer __new_last) _NOEXCEPT
 {
     pointer __soon_to_be_end = __end_;
     while (__new_last != __soon_to_be_end)
-        __alloc_traits::destroy(__alloc(), _VSTD::__to_raw_pointer(--__soon_to_be_end));
+        __alloc_traits::destroy(__alloc(), _VSTD::__to_address(--__soon_to_be_end));
     __end_ = __new_last;
 }
 
@@ -433,7 +433,7 @@ __vector_base<_Tp, _Allocator>::__vector_base()
         _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
     : __begin_(nullptr),
       __end_(nullptr),
-      __end_cap_(nullptr)
+      __end_cap_(nullptr, __default_init_tag())
 {
 }
 
@@ -518,29 +518,29 @@ public:
     vector(size_type __n, const value_type& __x, const allocator_type& __a);
     template <class _InputIterator>
         vector(_InputIterator __first,
-               typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                                 !__is_forward_iterator<_InputIterator>::value &&
+               typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                                 !__is_cpp17_forward_iterator<_InputIterator>::value &&
                                  is_constructible<
                                     value_type,
                                     typename iterator_traits<_InputIterator>::reference>::value,
                                  _InputIterator>::type __last);
     template <class _InputIterator>
         vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-               typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                                 !__is_forward_iterator<_InputIterator>::value &&
+               typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                                 !__is_cpp17_forward_iterator<_InputIterator>::value &&
                                  is_constructible<
                                     value_type,
                                     typename iterator_traits<_InputIterator>::reference>::value>::type* = 0);
     template <class _ForwardIterator>
         vector(_ForwardIterator __first,
-               typename enable_if<__is_forward_iterator<_ForwardIterator>::value &&
+               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
                                  is_constructible<
                                     value_type,
                                     typename iterator_traits<_ForwardIterator>::reference>::value,
                                  _ForwardIterator>::type __last);
     template <class _ForwardIterator>
         vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
-               typename enable_if<__is_forward_iterator<_ForwardIterator>::value &&
+               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
                                  is_constructible<
                                     value_type,
                                     typename iterator_traits<_ForwardIterator>::reference>::value>::type* = 0);
@@ -589,8 +589,8 @@ public:
     template <class _InputIterator>
         typename enable_if
         <
-             __is_input_iterator  <_InputIterator>::value &&
-            !__is_forward_iterator<_InputIterator>::value &&
+             __is_cpp17_input_iterator  <_InputIterator>::value &&
+            !__is_cpp17_forward_iterator<_InputIterator>::value &&
             is_constructible<
                  value_type,
                  typename iterator_traits<_InputIterator>::reference>::value,
@@ -600,7 +600,7 @@ public:
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value &&
+            __is_cpp17_forward_iterator<_ForwardIterator>::value &&
             is_constructible<
                  value_type,
                  typename iterator_traits<_ForwardIterator>::reference>::value,
@@ -692,10 +692,10 @@ public:
 
     _LIBCPP_INLINE_VISIBILITY
     value_type*       data() _NOEXCEPT
-        {return _VSTD::__to_raw_pointer(this->__begin_);}
+        {return _VSTD::__to_address(this->__begin_);}
     _LIBCPP_INLINE_VISIBILITY
     const value_type* data() const _NOEXCEPT
-        {return _VSTD::__to_raw_pointer(this->__begin_);}
+        {return _VSTD::__to_address(this->__begin_);}
 
 #ifdef _LIBCPP_CXX03_LANG
     _LIBCPP_INLINE_VISIBILITY
@@ -737,8 +737,8 @@ public:
     template <class _InputIterator>
         typename enable_if
         <
-             __is_input_iterator  <_InputIterator>::value &&
-            !__is_forward_iterator<_InputIterator>::value &&
+             __is_cpp17_input_iterator  <_InputIterator>::value &&
+            !__is_cpp17_forward_iterator<_InputIterator>::value &&
             is_constructible<
                  value_type,
                  typename iterator_traits<_InputIterator>::reference>::value,
@@ -748,7 +748,7 @@ public:
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value &&
+            __is_cpp17_forward_iterator<_ForwardIterator>::value &&
             is_constructible<
                  value_type,
                  typename iterator_traits<_ForwardIterator>::reference>::value,
@@ -808,7 +808,7 @@ private:
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value,
+            __is_cpp17_forward_iterator<_ForwardIterator>::value,
             void
         >::type
         __construct_at_end(_ForwardIterator __first, _ForwardIterator __last, size_type __n);
@@ -864,58 +864,67 @@ private:
 #else
     _LIBCPP_INLINE_VISIBILITY
     void __annotate_contiguous_container(const void*, const void*, const void*,
-                                         const void*) const {}
+                                         const void*) const _NOEXCEPT {}
 #endif
     _LIBCPP_INLINE_VISIBILITY
-    void __annotate_new(size_type __current_size) const {
+    void __annotate_new(size_type __current_size) const _NOEXCEPT {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + capacity(), data() + __current_size);
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    void __annotate_delete() const {
+    void __annotate_delete() const _NOEXCEPT {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + size(), data() + capacity());
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    void __annotate_increase(size_type __n) const
+    void __annotate_increase(size_type __n) const _NOEXCEPT
     {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + size(), data() + size() + __n);
     }
 
     _LIBCPP_INLINE_VISIBILITY
-    void __annotate_shrink(size_type __old_size) const
+    void __annotate_shrink(size_type __old_size) const _NOEXCEPT
     {
       __annotate_contiguous_container(data(), data() + capacity(),
                                       data() + __old_size, data() + size());
     }
+
+  struct _ConstructTransaction {
+    explicit _ConstructTransaction(vector &__v, size_type __n)
+      : __v_(__v),  __pos_(__v.__end_), __new_end_(__v.__end_ + __n) {
 #ifndef _LIBCPP_HAS_NO_ASAN
-    // The annotation for size increase should happen before the actual increase,
-    // but if an exception is thrown after that the annotation has to be undone.
-    struct __RAII_IncreaseAnnotator {
-      __RAII_IncreaseAnnotator(const vector &__v, size_type __n = 1)
-        : __commit(false), __v(__v), __old_size(__v.size() + __n) {
-        __v.__annotate_increase(__n);
-      }
-      void __done() { __commit = true; }
-      ~__RAII_IncreaseAnnotator() {
-        if (__commit) return;
-        __v.__annotate_shrink(__old_size);
+      __v_.__annotate_increase(__n);
+#endif
+    }
+    ~_ConstructTransaction() {
+      __v_.__end_ = __pos_;
+#ifndef _LIBCPP_HAS_NO_ASAN
+      if (__pos_ != __new_end_) {
+        __v_.__annotate_shrink(__new_end_ - __v_.__begin_);
       }
-      bool __commit;
-      const vector &__v;
-      size_type __old_size;
-    };
-#else
-    struct __RAII_IncreaseAnnotator {
-      _LIBCPP_INLINE_VISIBILITY
-      __RAII_IncreaseAnnotator(const vector &, size_type = 1) {}
-      _LIBCPP_INLINE_VISIBILITY void __done() {}
-    };
 #endif
+    }
 
+    vector &__v_;
+    pointer __pos_;
+    const_pointer const __new_end_;
+
+  private:
+    _ConstructTransaction(_ConstructTransaction const&) = delete;
+    _ConstructTransaction& operator=(_ConstructTransaction const&) = delete;
+  };
+
+  template <class ..._Args>
+  _LIBCPP_INLINE_VISIBILITY
+  void __construct_one_at_end(_Args&& ...__args) {
+    _ConstructTransaction __tx(*this, 1);
+    __alloc_traits::construct(this->__alloc(), _VSTD::__to_address(__tx.__pos_),
+        _VSTD::forward<_Args>(__args)...);
+    ++__tx.__pos_;
+  }
 };
 
 #ifndef _LIBCPP_HAS_NO_DEDUCTION_GUIDES
@@ -938,8 +947,10 @@ template <class _Tp, class _Allocator>
 void
 vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, allocator_type&>& __v)
 {
+
     __annotate_delete();
-    __alloc_traits::__construct_backward(this->__alloc(), this->__begin_, this->__end_, __v.__begin_);
+    __alloc_traits::__construct_backward_with_exception_guarantees(
+        this->__alloc(), this->__begin_, this->__end_, __v.__begin_);
     _VSTD::swap(this->__begin_, __v.__begin_);
     _VSTD::swap(this->__end_, __v.__end_);
     _VSTD::swap(this->__end_cap(), __v.__end_cap());
@@ -954,8 +965,10 @@ vector<_Tp, _Allocator>::__swap_out_circular_buffer(__split_buffer<value_type, a
 {
     __annotate_delete();
     pointer __r = __v.__begin_;
-    __alloc_traits::__construct_backward(this->__alloc(), this->__begin_, __p, __v.__begin_);
-    __alloc_traits::__construct_forward(this->__alloc(), __p, this->__end_, __v.__end_);
+    __alloc_traits::__construct_backward_with_exception_guarantees(
+        this->__alloc(), this->__begin_, __p, __v.__begin_);
+    __alloc_traits::__construct_forward_with_exception_guarantees(
+        this->__alloc(), __p, this->__end_, __v.__end_);
     _VSTD::swap(this->__begin_, __v.__begin_);
     _VSTD::swap(this->__end_, __v.__end_);
     _VSTD::swap(this->__end_cap(), __v.__end_cap());
@@ -1027,15 +1040,10 @@ template <class _Tp, class _Allocator>
 void
 vector<_Tp, _Allocator>::__construct_at_end(size_type __n)
 {
-    allocator_type& __a = this->__alloc();
-    do
-    {
-        __RAII_IncreaseAnnotator __annotator(*this);
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_));
-        ++this->__end_;
-        --__n;
-        __annotator.__done();
-    } while (__n > 0);
+    _ConstructTransaction __tx(*this, __n);
+    for (; __tx.__pos_ != __tx.__new_end_; ++__tx.__pos_) {
+      __alloc_traits::construct(this->__alloc(), _VSTD::__to_address(__tx.__pos_));
+    }
 }
 
 //  Copy constructs __n objects starting at __end_ from __x
@@ -1049,30 +1057,23 @@ inline
 void
 vector<_Tp, _Allocator>::__construct_at_end(size_type __n, const_reference __x)
 {
-    allocator_type& __a = this->__alloc();
-    do
-    {
-        __RAII_IncreaseAnnotator __annotator(*this);
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_), __x);
-        ++this->__end_;
-        --__n;
-        __annotator.__done();
-    } while (__n > 0);
+    _ConstructTransaction __tx(*this, __n);
+    for (; __tx.__pos_ != __tx.__new_end_; ++__tx.__pos_) {
+        __alloc_traits::construct(this->__alloc(), _VSTD::__to_address(__tx.__pos_), __x);
+    }
 }
 
 template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value,
+    __is_cpp17_forward_iterator<_ForwardIterator>::value,
     void
 >::type
 vector<_Tp, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last, size_type __n)
 {
-    allocator_type& __a = this->__alloc();
-    __RAII_IncreaseAnnotator __annotator(*this, __n);
-    __alloc_traits::__construct_range_forward(__a, __first, __last, this->__end_);
-    __annotator.__done();
+    _ConstructTransaction __tx(*this, __n);
+    __alloc_traits::__construct_range_forward(this->__alloc(), __first, __last, __tx.__pos_);
 }
 
 //  Default constructs __n objects starting at __end_
@@ -1172,8 +1173,8 @@ vector<_Tp, _Allocator>::vector(size_type __n, const value_type& __x, const allo
 template <class _Tp, class _Allocator>
 template <class _InputIterator>
 vector<_Tp, _Allocator>::vector(_InputIterator __first,
-       typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                         !__is_forward_iterator<_InputIterator>::value &&
+       typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                         !__is_cpp17_forward_iterator<_InputIterator>::value &&
                          is_constructible<
                             value_type,
                             typename iterator_traits<_InputIterator>::reference>::value,
@@ -1189,8 +1190,8 @@ vector<_Tp, _Allocator>::vector(_InputIterator __first,
 template <class _Tp, class _Allocator>
 template <class _InputIterator>
 vector<_Tp, _Allocator>::vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-       typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                         !__is_forward_iterator<_InputIterator>::value &&
+       typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                         !__is_cpp17_forward_iterator<_InputIterator>::value &&
                          is_constructible<
                             value_type,
                             typename iterator_traits<_InputIterator>::reference>::value>::type*)
@@ -1206,7 +1207,7 @@ vector<_Tp, _Allocator>::vector(_InputIterator __first, _InputIterator __last, c
 template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 vector<_Tp, _Allocator>::vector(_ForwardIterator __first,
-                                typename enable_if<__is_forward_iterator<_ForwardIterator>::value &&
+                                typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
                                 is_constructible<
                                    value_type,
                                    typename iterator_traits<_ForwardIterator>::reference>::value,
@@ -1226,7 +1227,7 @@ vector<_Tp, _Allocator>::vector(_ForwardIterator __first,
 template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 vector<_Tp, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
-                                typename enable_if<__is_forward_iterator<_ForwardIterator>::value &&
+                                typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value &&
                                 is_constructible<
                                    value_type,
                                    typename iterator_traits<_ForwardIterator>::reference>::value>::type*)
@@ -1409,8 +1410,8 @@ template <class _Tp, class _Allocator>
 template <class _InputIterator>
 typename enable_if
 <
-     __is_input_iterator  <_InputIterator>::value &&
-    !__is_forward_iterator<_InputIterator>::value &&
+     __is_cpp17_input_iterator  <_InputIterator>::value &&
+    !__is_cpp17_forward_iterator<_InputIterator>::value &&
     is_constructible<
        _Tp,
        typename iterator_traits<_InputIterator>::reference>::value,
@@ -1427,7 +1428,7 @@ template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value &&
+    __is_cpp17_forward_iterator<_ForwardIterator>::value &&
     is_constructible<
        _Tp,
        typename iterator_traits<_ForwardIterator>::reference>::value,
@@ -1621,7 +1622,7 @@ vector<_Tp, _Allocator>::__push_back_slow_path(_Up& __x)
     allocator_type& __a = this->__alloc();
     __split_buffer<value_type, allocator_type&> __v(__recommend(size() + 1), size(), __a);
     // __v.push_back(_VSTD::forward<_Up>(__x));
-    __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(__v.__end_), _VSTD::forward<_Up>(__x));
+    __alloc_traits::construct(__a, _VSTD::__to_address(__v.__end_), _VSTD::forward<_Up>(__x));
     __v.__end_++;
     __swap_out_circular_buffer(__v);
 }
@@ -1633,11 +1634,7 @@ vector<_Tp, _Allocator>::push_back(const_reference __x)
 {
     if (this->__end_ != this->__end_cap())
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
-        __alloc_traits::construct(this->__alloc(),
-                                  _VSTD::__to_raw_pointer(this->__end_), __x);
-        __annotator.__done();
-        ++this->__end_;
+        __construct_one_at_end(__x);
     }
     else
         __push_back_slow_path(__x);
@@ -1652,12 +1649,7 @@ vector<_Tp, _Allocator>::push_back(value_type&& __x)
 {
     if (this->__end_ < this->__end_cap())
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
-        __alloc_traits::construct(this->__alloc(),
-                                  _VSTD::__to_raw_pointer(this->__end_),
-                                  _VSTD::move(__x));
-        __annotator.__done();
-        ++this->__end_;
+        __construct_one_at_end(_VSTD::move(__x));
     }
     else
         __push_back_slow_path(_VSTD::move(__x));
@@ -1671,7 +1663,7 @@ vector<_Tp, _Allocator>::__emplace_back_slow_path(_Args&&... __args)
     allocator_type& __a = this->__alloc();
     __split_buffer<value_type, allocator_type&> __v(__recommend(size() + 1), size(), __a);
 //    __v.emplace_back(_VSTD::forward<_Args>(__args)...);
-    __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(__v.__end_), _VSTD::forward<_Args>(__args)...);
+    __alloc_traits::construct(__a, _VSTD::__to_address(__v.__end_), _VSTD::forward<_Args>(__args)...);
     __v.__end_++;
     __swap_out_circular_buffer(__v);
 }
@@ -1688,12 +1680,7 @@ vector<_Tp, _Allocator>::emplace_back(_Args&&... __args)
 {
     if (this->__end_ < this->__end_cap())
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
-        __alloc_traits::construct(this->__alloc(),
-                                  _VSTD::__to_raw_pointer(this->__end_),
-                                  _VSTD::forward<_Args>(__args)...);
-        __annotator.__done();
-        ++this->__end_;
+        __construct_one_at_end(_VSTD::forward<_Args>(__args)...);
     }
     else
         __emplace_back_slow_path(_VSTD::forward<_Args>(__args)...);
@@ -1761,10 +1748,15 @@ vector<_Tp, _Allocator>::__move_range(pointer __from_s, pointer __from_e, pointe
 {
     pointer __old_last = this->__end_;
     difference_type __n = __old_last - __to;
-    for (pointer __i = __from_s + __n; __i < __from_e; ++__i, ++this->__end_)
-        __alloc_traits::construct(this->__alloc(),
-                                  _VSTD::__to_raw_pointer(this->__end_),
-                                  _VSTD::move(*__i));
+    {
+      pointer __i = __from_s + __n;
+      _ConstructTransaction __tx(*this, __from_e - __i);
+      for (; __i < __from_e; ++__i, ++__tx.__pos_) {
+          __alloc_traits::construct(this->__alloc(),
+                                    _VSTD::__to_address(__tx.__pos_),
+                                    _VSTD::move(*__i));
+      }
+    }
     _VSTD::move_backward(__from_s, __from_s + __n, __old_last);
 }
 
@@ -1780,12 +1772,9 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, const_reference __x)
     pointer __p = this->__begin_ + (__position - begin());
     if (this->__end_ < this->__end_cap())
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
         if (__p == this->__end_)
         {
-            __alloc_traits::construct(this->__alloc(),
-                                      _VSTD::__to_raw_pointer(this->__end_), __x);
-            ++this->__end_;
+            __construct_one_at_end(__x);
         }
         else
         {
@@ -1795,7 +1784,6 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, const_reference __x)
                 ++__xr;
             *__p = *__xr;
         }
-        __annotator.__done();
     }
     else
     {
@@ -1821,20 +1809,15 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, value_type&& __x)
     pointer __p = this->__begin_ + (__position - begin());
     if (this->__end_ < this->__end_cap())
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
         if (__p == this->__end_)
         {
-            __alloc_traits::construct(this->__alloc(),
-                                      _VSTD::__to_raw_pointer(this->__end_),
-                                      _VSTD::move(__x));
-            ++this->__end_;
+            __construct_one_at_end(_VSTD::move(__x));
         }
         else
         {
             __move_range(__p, this->__end_, __p + 1);
             *__p = _VSTD::move(__x);
         }
-        __annotator.__done();
     }
     else
     {
@@ -1859,13 +1842,9 @@ vector<_Tp, _Allocator>::emplace(const_iterator __position, _Args&&... __args)
     pointer __p = this->__begin_ + (__position - begin());
     if (this->__end_ < this->__end_cap())
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
         if (__p == this->__end_)
         {
-            __alloc_traits::construct(this->__alloc(),
-                                      _VSTD::__to_raw_pointer(this->__end_),
-                                      _VSTD::forward<_Args>(__args)...);
-            ++this->__end_;
+            __construct_one_at_end(_VSTD::forward<_Args>(__args)...);
         }
         else
         {
@@ -1873,7 +1852,6 @@ vector<_Tp, _Allocator>::emplace(const_iterator __position, _Args&&... __args)
             __move_range(__p, this->__end_, __p + 1);
             *__p = _VSTD::move(__tmp.get());
         }
-        __annotator.__done();
     }
     else
     {
@@ -1911,9 +1889,7 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, size_type __n, const_
             }
             if (__n > 0)
             {
-                __RAII_IncreaseAnnotator __annotator(*this, __n);
                 __move_range(__p, __old_last, __p + __old_n);
-                __annotator.__done();
                 const_pointer __xr = pointer_traits<const_pointer>::pointer_to(__x);
                 if (__p <= __xr && __xr < this->__end_)
                     __xr += __old_n;
@@ -1935,8 +1911,8 @@ template <class _Tp, class _Allocator>
 template <class _InputIterator>
 typename enable_if
 <
-     __is_input_iterator  <_InputIterator>::value &&
-    !__is_forward_iterator<_InputIterator>::value &&
+     __is_cpp17_input_iterator  <_InputIterator>::value &&
+    !__is_cpp17_forward_iterator<_InputIterator>::value &&
     is_constructible<
        _Tp,
        typename iterator_traits<_InputIterator>::reference>::value,
@@ -1955,11 +1931,7 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, _InputIterator __firs
     pointer __old_last = this->__end_;
     for (; this->__end_ != this->__end_cap() && __first != __last; ++__first)
     {
-        __RAII_IncreaseAnnotator __annotator(*this);
-        __alloc_traits::construct(__a, _VSTD::__to_raw_pointer(this->__end_),
-                                  *__first);
-        ++this->__end_;
-        __annotator.__done();
+        __construct_one_at_end(*__first);
     }
     __split_buffer<value_type, allocator_type&> __v(__a);
     if (__first != __last)
@@ -1993,7 +1965,7 @@ template <class _Tp, class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value &&
+    __is_cpp17_forward_iterator<_ForwardIterator>::value &&
     is_constructible<
        _Tp,
        typename iterator_traits<_ForwardIterator>::reference>::value,
@@ -2026,9 +1998,7 @@ vector<_Tp, _Allocator>::insert(const_iterator __position, _ForwardIterator __fi
             }
             if (__n > 0)
             {
-                __RAII_IncreaseAnnotator __annotator(*this, __n);
                 __move_range(__p, __old_last, __p + __old_n);
-                __annotator.__done();
                 _VSTD::copy(__first, __m, __p);
             }
         }
@@ -2261,18 +2231,18 @@ public:
     vector(size_type __n, const value_type& __v, const allocator_type& __a);
     template <class _InputIterator>
         vector(_InputIterator __first, _InputIterator __last,
-               typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                                 !__is_forward_iterator<_InputIterator>::value>::type* = 0);
+               typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                                 !__is_cpp17_forward_iterator<_InputIterator>::value>::type* = 0);
     template <class _InputIterator>
         vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-               typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                                 !__is_forward_iterator<_InputIterator>::value>::type* = 0);
+               typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                                 !__is_cpp17_forward_iterator<_InputIterator>::value>::type* = 0);
     template <class _ForwardIterator>
         vector(_ForwardIterator __first, _ForwardIterator __last,
-               typename enable_if<__is_forward_iterator<_ForwardIterator>::value>::type* = 0);
+               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value>::type* = 0);
     template <class _ForwardIterator>
         vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
-               typename enable_if<__is_forward_iterator<_ForwardIterator>::value>::type* = 0);
+               typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value>::type* = 0);
 
     vector(const vector& __v);
     vector(const vector& __v, const allocator_type& __a);
@@ -2303,15 +2273,15 @@ public:
     template <class _InputIterator>
         typename enable_if
         <
-            __is_input_iterator<_InputIterator>::value &&
-           !__is_forward_iterator<_InputIterator>::value,
+            __is_cpp17_input_iterator<_InputIterator>::value &&
+           !__is_cpp17_forward_iterator<_InputIterator>::value,
            void
         >::type
         assign(_InputIterator __first, _InputIterator __last);
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value,
+            __is_cpp17_forward_iterator<_ForwardIterator>::value,
            void
         >::type
         assign(_ForwardIterator __first, _ForwardIterator __last);
@@ -2419,15 +2389,15 @@ public:
     template <class _InputIterator>
         typename enable_if
         <
-             __is_input_iterator  <_InputIterator>::value &&
-            !__is_forward_iterator<_InputIterator>::value,
+             __is_cpp17_input_iterator  <_InputIterator>::value &&
+            !__is_cpp17_forward_iterator<_InputIterator>::value,
             iterator
         >::type
         insert(const_iterator __position, _InputIterator __first, _InputIterator __last);
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value,
+            __is_cpp17_forward_iterator<_ForwardIterator>::value,
             iterator
         >::type
         insert(const_iterator __position, _ForwardIterator __first, _ForwardIterator __last);
@@ -2470,7 +2440,7 @@ private:
     template <class _ForwardIterator>
         typename enable_if
         <
-            __is_forward_iterator<_ForwardIterator>::value,
+            __is_cpp17_forward_iterator<_ForwardIterator>::value,
             void
         >::type
         __construct_at_end(_ForwardIterator __first, _ForwardIterator __last);
@@ -2629,7 +2599,7 @@ template <class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value,
+    __is_cpp17_forward_iterator<_ForwardIterator>::value,
     void
 >::type
 vector<bool, _Allocator>::__construct_at_end(_ForwardIterator __first, _ForwardIterator __last)
@@ -2652,7 +2622,7 @@ vector<bool, _Allocator>::vector()
     _NOEXCEPT_(is_nothrow_default_constructible<allocator_type>::value)
     : __begin_(nullptr),
       __size_(0),
-      __cap_alloc_(0)
+      __cap_alloc_(0, __default_init_tag())
 {
 }
 
@@ -2674,7 +2644,7 @@ template <class _Allocator>
 vector<bool, _Allocator>::vector(size_type __n)
     : __begin_(nullptr),
       __size_(0),
-      __cap_alloc_(0)
+      __cap_alloc_(0, __default_init_tag())
 {
     if (__n > 0)
     {
@@ -2702,7 +2672,7 @@ template <class _Allocator>
 vector<bool, _Allocator>::vector(size_type __n, const value_type& __x)
     : __begin_(nullptr),
       __size_(0),
-      __cap_alloc_(0)
+      __cap_alloc_(0, __default_init_tag())
 {
     if (__n > 0)
     {
@@ -2727,11 +2697,11 @@ vector<bool, _Allocator>::vector(size_type __n, const value_type& __x, const all
 template <class _Allocator>
 template <class _InputIterator>
 vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last,
-       typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                         !__is_forward_iterator<_InputIterator>::value>::type*)
+       typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                         !__is_cpp17_forward_iterator<_InputIterator>::value>::type*)
     : __begin_(nullptr),
       __size_(0),
-      __cap_alloc_(0)
+      __cap_alloc_(0, __default_init_tag())
 {
 #ifndef _LIBCPP_NO_EXCEPTIONS
     try
@@ -2754,8 +2724,8 @@ vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last,
 template <class _Allocator>
 template <class _InputIterator>
 vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last, const allocator_type& __a,
-       typename enable_if<__is_input_iterator  <_InputIterator>::value &&
-                         !__is_forward_iterator<_InputIterator>::value>::type*)
+       typename enable_if<__is_cpp17_input_iterator  <_InputIterator>::value &&
+                         !__is_cpp17_forward_iterator<_InputIterator>::value>::type*)
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, static_cast<__storage_allocator>(__a))
@@ -2781,10 +2751,10 @@ vector<bool, _Allocator>::vector(_InputIterator __first, _InputIterator __last,
 template <class _Allocator>
 template <class _ForwardIterator>
 vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last,
-                                typename enable_if<__is_forward_iterator<_ForwardIterator>::value>::type*)
+                                typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value>::type*)
     : __begin_(nullptr),
       __size_(0),
-      __cap_alloc_(0)
+      __cap_alloc_(0, __default_init_tag())
 {
     size_type __n = static_cast<size_type>(_VSTD::distance(__first, __last));
     if (__n > 0)
@@ -2797,7 +2767,7 @@ vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __la
 template <class _Allocator>
 template <class _ForwardIterator>
 vector<bool, _Allocator>::vector(_ForwardIterator __first, _ForwardIterator __last, const allocator_type& __a,
-                                typename enable_if<__is_forward_iterator<_ForwardIterator>::value>::type*)
+                                typename enable_if<__is_cpp17_forward_iterator<_ForwardIterator>::value>::type*)
     : __begin_(nullptr),
       __size_(0),
       __cap_alloc_(0, static_cast<__storage_allocator>(__a))
@@ -2816,7 +2786,7 @@ template <class _Allocator>
 vector<bool, _Allocator>::vector(initializer_list<value_type> __il)
     : __begin_(nullptr),
       __size_(0),
-      __cap_alloc_(0)
+      __cap_alloc_(0, __default_init_tag())
 {
     size_type __n = static_cast<size_type>(__il.size());
     if (__n > 0)
@@ -2998,8 +2968,8 @@ template <class _Allocator>
 template <class _InputIterator>
 typename enable_if
 <
-    __is_input_iterator<_InputIterator>::value &&
-   !__is_forward_iterator<_InputIterator>::value,
+    __is_cpp17_input_iterator<_InputIterator>::value &&
+   !__is_cpp17_forward_iterator<_InputIterator>::value,
    void
 >::type
 vector<bool, _Allocator>::assign(_InputIterator __first, _InputIterator __last)
@@ -3013,7 +2983,7 @@ template <class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value,
+    __is_cpp17_forward_iterator<_ForwardIterator>::value,
    void
 >::type
 vector<bool, _Allocator>::assign(_ForwardIterator __first, _ForwardIterator __last)
@@ -3150,8 +3120,8 @@ template <class _Allocator>
 template <class _InputIterator>
 typename enable_if
 <
-     __is_input_iterator  <_InputIterator>::value &&
-    !__is_forward_iterator<_InputIterator>::value,
+     __is_cpp17_input_iterator  <_InputIterator>::value &&
+    !__is_cpp17_forward_iterator<_InputIterator>::value,
     typename vector<bool, _Allocator>::iterator
 >::type
 vector<bool, _Allocator>::insert(const_iterator __position, _InputIterator __first, _InputIterator __last)
@@ -3195,7 +3165,7 @@ template <class _Allocator>
 template <class _ForwardIterator>
 typename enable_if
 <
-    __is_forward_iterator<_ForwardIterator>::value,
+    __is_cpp17_forward_iterator<_ForwardIterator>::value,
     typename vector<bool, _Allocator>::iterator
 >::type
 vector<bool, _Allocator>::insert(const_iterator __position, _ForwardIterator __first, _ForwardIterator __last)
lib/libcxx/include/version
@@ -43,6 +43,7 @@ __cpp_lib_constexpr_misc                                201811L <array> <functio
 __cpp_lib_constexpr_swap_algorithms                     201806L <algorithm>
 __cpp_lib_destroying_delete                             201806L <new>
 __cpp_lib_enable_shared_from_this                       201603L <memory>
+__cpp_lib_endian                                        201907L <bit>
 __cpp_lib_erase_if                                      201811L <string> <deque> <forward_list>
                                                                 <list> <vector> <map>
                                                                 <set> <unordered_map> <unordered_set>
@@ -223,6 +224,7 @@ __cpp_lib_void_t                                        201411L <type_traits>
 # if _LIBCPP_STD_VER > 17 && defined(__cpp_impl_destroying_delete) && __cpp_impl_destroying_delete >= 201806L
 #   define __cpp_lib_destroying_delete                  201806L
 # endif
+# define __cpp_lib_endian                               201907L
 # define __cpp_lib_erase_if                             201811L
 // # define __cpp_lib_generic_unordered_lookup             201811L
 # define __cpp_lib_interpolate                          201902L