Vendor import of libc++ release_40 branch r292009:vendor/libc++/libc++-release_40-r292009

https://llvm.org/svn/llvm-project/libcxx/branches/release_40@292009

30 files changed, 473 insertions, 81 deletions

diff --git a/CMakeLists.txt b/CMakeLists.txt
index 9fa0ed37e58e..a692f1b57a28 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -24,7 +24,7 @@ if (CMAKE_SOURCE_DIR STREQUAL CMAKE_CURRENT_SOURCE_DIR)
   project(libcxx CXX C)
 
   set(PACKAGE_NAME libcxx)
-  set(PACKAGE_VERSION 4.0.0svn)
+  set(PACKAGE_VERSION 4.0.0)
   set(PACKAGE_STRING "${PACKAGE_NAME} ${PACKAGE_VERSION}")
   set(PACKAGE_BUGREPORT "llvm-bugs@lists.llvm.org")
 
diff --git a/cmake/Modules/HandleOutOfTreeLLVM.cmake b/cmake/Modules/HandleOutOfTreeLLVM.cmake
index c772143244ae..7fee839d2732 100644
--- a/cmake/Modules/HandleOutOfTreeLLVM.cmake
+++ b/cmake/Modules/HandleOutOfTreeLLVM.cmake
@@ -38,7 +38,18 @@ macro(find_llvm_parts)
     set(LLVM_INCLUDE_DIR ${INCLUDE_DIR} CACHE PATH "Path to llvm/include")
     set(LLVM_BINARY_DIR ${LLVM_OBJ_ROOT} CACHE PATH "Path to LLVM build tree")
     set(LLVM_MAIN_SRC_DIR ${MAIN_SRC_DIR} CACHE PATH "Path to LLVM source tree")
-    set(LLVM_CMAKE_PATH "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
+
+    # --cmakedir is supported since llvm r291218 (4.0 release)
+    execute_process(
+      COMMAND ${LLVM_CONFIG_PATH} --cmakedir
+      RESULT_VARIABLE HAD_ERROR
+      OUTPUT_VARIABLE CONFIG_OUTPUT)
+    if(NOT HAD_ERROR)
+      string(STRIP "${CONFIG_OUTPUT}" LLVM_CMAKE_PATH)
+    else()
+      set(LLVM_CMAKE_PATH
+          "${LLVM_BINARY_DIR}/lib${LLVM_LIBDIR_SUFFIX}/cmake/llvm")
+    endif()
   else()
     set(LLVM_FOUND OFF)
     message(WARNING "UNSUPPORTED LIBCXX CONFIGURATION DETECTED: "
diff --git a/include/__config b/include/__config
index fedec61126e1..b30b15c6fdb9 100644
--- a/include/__config
+++ b/include/__config
@@ -396,6 +396,15 @@ namespace std {
 #define _LIBCPP_DISABLE_UBSAN_UNSIGNED_INTEGER_CHECK __attribute__((__no_sanitize__("unsigned-integer-overflow")))
 #endif 
 
+// A constexpr version of __builtin_memcmp was added in clang 4.0
+#if __has_builtin(__builtin_memcmp)
+# ifdef __apple_build_version__
+// No shipping version of Apple's clang has constexpr __builtin_memcmp
+# elif __clang_major__ > 3
+#  define _LIBCPP_BUILTIN_MEMCMP_ISCONSTEXPR
+# endif
+#endif
+
 #elif defined(_LIBCPP_COMPILER_GCC)
 
 #define _ALIGNAS(x) __attribute__((__aligned__(x)))
@@ -763,7 +772,7 @@ template <unsigned> struct __static_assert_check {};
 #define _NOALIAS
 #endif
 
-#if __has_extension(cxx_explicit_conversions) || defined(__IBMCPP__) || \
+#if __has_feature(cxx_explicit_conversions) || defined(__IBMCPP__) || \
     (!defined(_LIBCPP_CXX03_LANG) && defined(__GNUC__)) // All supported GCC versions
 #   define _LIBCPP_EXPLICIT explicit
 #else
diff --git a/include/__mutex_base b/include/__mutex_base
index cce928784a46..21638ee3292d 100644
--- a/include/__mutex_base
+++ b/include/__mutex_base
@@ -410,8 +410,8 @@ condition_variable::wait_for(unique_lock<mutex>& __lk,
     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();
-    system_clock::time_point __s_now = system_clock::now();
     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
diff --git a/include/__string b/include/__string
index 0b851b9f9e2b..c85b874f054b 100644
--- a/include/__string
+++ b/include/__string
@@ -26,13 +26,14 @@ struct char_traits
     typedef streampos pos_type;
     typedef mbstate_t state_type;
 
-    static void assign(char_type& c1, const char_type& c2) noexcept;
+    static constexpr void assign(char_type& c1, const char_type& c2) noexcept;
     static constexpr bool eq(char_type c1, char_type c2) noexcept;
     static constexpr bool lt(char_type c1, char_type c2) noexcept;
 
-    static int              compare(const char_type* s1, const char_type* s2, size_t n);
-    static size_t           length(const char_type* s);
-    static const char_type* find(const char_type* s, size_t n, const char_type& a);
+    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* 
+                            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);
@@ -77,18 +78,19 @@ struct _LIBCPP_TEMPLATE_VIS char_traits
     typedef streampos pos_type;
     typedef mbstate_t state_type;
 
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
+    static inline void _LIBCPP_CONSTEXPR_AFTER_CXX14
+        assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
     static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 == __c2;}
     static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 < __c2;}
 
-    static int              compare(const char_type* __s1, const char_type* __s2, size_t __n);
-    _LIBCPP_INLINE_VISIBILITY
-    static size_t           length(const char_type* __s);
-    _LIBCPP_INLINE_VISIBILITY
-    static const char_type* find(const char_type* __s, size_t __n, const char_type& __a);
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int compare(const char_type* __s1, const char_type* __s2, size_t __n);
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    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);
     _LIBCPP_INLINE_VISIBILITY
     static char_type*       copy(char_type* __s1, const char_type* __s2, size_t __n);
@@ -108,7 +110,7 @@ struct _LIBCPP_TEMPLATE_VIS char_traits
 };
 
 template <class _CharT>
-int
+_LIBCPP_CONSTEXPR_AFTER_CXX14 int
 char_traits<_CharT>::compare(const char_type* __s1, const char_type* __s2, size_t __n)
 {
     for (; __n; --__n, ++__s1, ++__s2)
@@ -123,7 +125,7 @@ char_traits<_CharT>::compare(const char_type* __s1, const char_type* __s2, size_
 
 template <class _CharT>
 inline
-size_t
+_LIBCPP_CONSTEXPR_AFTER_CXX14 size_t
 char_traits<_CharT>::length(const char_type* __s)
 {
     size_t __len = 0;
@@ -134,7 +136,7 @@ char_traits<_CharT>::length(const char_type* __s)
 
 template <class _CharT>
 inline
-const _CharT*
+_LIBCPP_CONSTEXPR_AFTER_CXX14 const _CharT*
 char_traits<_CharT>::find(const char_type* __s, size_t __n, const char_type& __a)
 {
     for (; __n; --__n)
@@ -200,18 +202,19 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char>
     typedef streampos pos_type;
     typedef mbstate_t state_type;
 
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
     static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
             {return __c1 == __c2;}
     static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
         {return (unsigned char)__c1 < (unsigned char)__c2;}
 
-    static inline int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
-        {return __n == 0 ? 0 : memcmp(__s1, __s2, __n);}
-    static inline size_t length(const char_type* __s)  _NOEXCEPT {return strlen(__s);}
-    static inline const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
-        {return __n == 0 ? NULL : (const char_type*) memchr(__s, to_int_type(__a), __n);}
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    static inline size_t _LIBCPP_CONSTEXPR_AFTER_CXX14
+    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
@@ -234,6 +237,48 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char>
         {return int_type(EOF);}
 };
 
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+int
+char_traits<char>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    if (__n == 0)
+        return 0;
+#ifdef _LIBCPP_BUILTIN_MEMCMP_ISCONSTEXPR
+    return __builtin_memcmp(__s1, __s2, __n);
+#elif _LIBCPP_STD_VER <= 14
+    return memcmp(__s1, __s2, __n);
+#else
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+#endif
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+const char*
+char_traits<char>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    if (__n == 0)
+        return NULL;
+#if _LIBCPP_STD_VER <= 14
+    return (const char_type*) memchr(__s, to_int_type(__a), __n);
+#else
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return NULL;
+#endif
+}
+
+
 // char_traits<wchar_t>
 
 template <>
@@ -245,19 +290,19 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<wchar_t>
     typedef streampos pos_type;
     typedef mbstate_t state_type;
 
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
     static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 == __c2;}
     static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 < __c2;}
 
-    static inline int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
-        {return __n == 0 ? 0 : wmemcmp(__s1, __s2, __n);}
-    static inline size_t length(const char_type* __s) _NOEXCEPT
-        {return wcslen(__s);}
-    static inline const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
-        {return __n == 0 ? NULL : (const char_type*)wmemchr(__s, __a, __n);}
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    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
@@ -280,6 +325,66 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<wchar_t>
         {return int_type(WEOF);}
 };
 
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+int
+char_traits<wchar_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+    if (__n == 0)
+        return 0;
+#if __has_builtin(__builtin_wmemcmp)
+    return __builtin_wmemcmp(__s1, __s2, __n);
+#elif _LIBCPP_STD_VER <= 14
+    return wmemcmp(__s1, __s2, __n);
+#else
+    for (; __n; --__n, ++__s1, ++__s2)
+    {
+        if (lt(*__s1, *__s2))
+            return -1;
+        if (lt(*__s2, *__s1))
+            return 1;
+    }
+    return 0;
+#endif
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+size_t
+char_traits<wchar_t>::length(const char_type* __s) _NOEXCEPT
+{
+#if __has_builtin(__builtin_wcslen)
+    return __builtin_wcslen(__s);
+#elif _LIBCPP_STD_VER <= 14
+    return wcslen(__s);
+#else
+    size_t __len = 0;
+    for (; !eq(*__s, char_type(0)); ++__s)
+        ++__len;
+    return __len;
+#endif
+}
+
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+const wchar_t*
+char_traits<wchar_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    if (__n == 0)
+        return NULL;
+#if __has_builtin(__builtin_wmemchr)
+        return __builtin_wmemchr(__s, __a, __n);
+#elif _LIBCPP_STD_VER <= 14
+    return wmemchr(__s, __a, __n);
+#else
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return NULL;
+#endif
+}
+
+
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 
 template <>
@@ -291,19 +396,19 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char16_t>
     typedef u16streampos   pos_type;
     typedef mbstate_t      state_type;
 
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
     static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 == __c2;}
     static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 < __c2;}
 
-    _LIBCPP_INLINE_VISIBILITY
-    static int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
-    static size_t           length(const char_type* __s) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
-    static const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    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
     static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
@@ -323,7 +428,7 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char16_t>
         {return int_type(0xFFFF);}
 };
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 int
 char_traits<char16_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
@@ -337,7 +442,7 @@ char_traits<char16_t>::compare(const char_type* __s1, const char_type* __s2, siz
     return 0;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 size_t
 char_traits<char16_t>::length(const char_type* __s) _NOEXCEPT
 {
@@ -347,7 +452,7 @@ char_traits<char16_t>::length(const char_type* __s) _NOEXCEPT
     return __len;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 const char16_t*
 char_traits<char16_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
 {
@@ -410,19 +515,19 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char32_t>
     typedef u32streampos   pos_type;
     typedef mbstate_t      state_type;
 
-    static inline void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT
-        {__c1 = __c2;}
+    static inline _LIBCPP_CONSTEXPR_AFTER_CXX14
+    void assign(char_type& __c1, const char_type& __c2) _NOEXCEPT {__c1 = __c2;}
     static inline _LIBCPP_CONSTEXPR bool eq(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 == __c2;}
     static inline _LIBCPP_CONSTEXPR bool lt(char_type __c1, char_type __c2) _NOEXCEPT
         {return __c1 < __c2;}
 
-    _LIBCPP_INLINE_VISIBILITY
-    static int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
-    static size_t           length(const char_type* __s) _NOEXCEPT;
-    _LIBCPP_INLINE_VISIBILITY
-    static const char_type* find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+    _LIBCPP_INLINE_VISIBILITY static _LIBCPP_CONSTEXPR_AFTER_CXX14
+    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
     static char_type*       move(char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
     _LIBCPP_INLINE_VISIBILITY
@@ -442,7 +547,7 @@ struct _LIBCPP_TEMPLATE_VIS char_traits<char32_t>
         {return int_type(0xFFFFFFFF);}
 };
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 int
 char_traits<char32_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
 {
@@ -456,7 +561,7 @@ char_traits<char32_t>::compare(const char_type* __s1, const char_type* __s2, siz
     return 0;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 size_t
 char_traits<char32_t>::length(const char_type* __s) _NOEXCEPT
 {
@@ -466,7 +571,7 @@ char_traits<char32_t>::length(const char_type* __s) _NOEXCEPT
     return __len;
 }
 
-inline
+inline _LIBCPP_CONSTEXPR_AFTER_CXX14
 const char32_t*
 char_traits<char32_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
 {
diff --git a/include/__threading_support b/include/__threading_support
index b2c3b1fc6376..a672a9f80eda 100644
--- a/include/__threading_support
+++ b/include/__threading_support
@@ -385,7 +385,7 @@ int __libcpp_recursive_mutex_unlock(__libcpp_recursive_mutex_t *__m)
 
 int __libcpp_recursive_mutex_destroy(__libcpp_recursive_mutex_t *__m)
 {
-  static_cast<void>(__m);
+  DeleteCriticalSection(__m);
   return 0;
 }
 
diff --git a/include/experimental/string_view b/include/experimental/string_view
index 674f6c355fb4..41c0d34d3c84 100644
--- a/include/experimental/string_view
+++ b/include/experimental/string_view
@@ -340,12 +340,7 @@ _LIBCPP_BEGIN_NAMESPACE_LFTS
         // [string.view.ops], string operations:
         template<class _Allocator>
         _LIBCPP_INLINE_VISIBILITY
-        // Clang's extended C++11 explict conversions don't work with
-        // string_view in C++03.
-#ifndef _LIBCPP_CXX03_LANG
-        _LIBCPP_EXPLICIT
-#endif
-        operator basic_string<_CharT, _Traits, _Allocator>() const
+        _LIBCPP_EXPLICIT operator basic_string<_CharT, _Traits, _Allocator>() const
         { return basic_string<_CharT, _Traits, _Allocator>( begin(), end()); }
 
         template<class _Allocator = allocator<_CharT> >
diff --git a/include/ios b/include/ios
index efee39fb533a..bb5ca72e5e4d 100644
--- a/include/ios
+++ b/include/ios
@@ -572,6 +572,13 @@ ios_base::exceptions(iostate __iostate)
     clear(__rdstate_);
 }
 
+#if defined(_LIBCPP_CXX03_LANG)
+struct _LIBCPP_TYPE_VIS __cxx03_bool {
+  typedef void (__cxx03_bool::*__bool_type)();
+  void __true_value() {}
+};
+#endif
+
 template <class _CharT, class _Traits>
 class _LIBCPP_TEMPLATE_VIS basic_ios
     : public ios_base
@@ -585,8 +592,15 @@ public:
     typedef typename traits_type::pos_type pos_type;
     typedef typename traits_type::off_type off_type;
 
+#if defined(_LIBCPP_CXX03_LANG)
+    _LIBCPP_ALWAYS_INLINE
+    operator __cxx03_bool::__bool_type() const {
+        return !fail() ? &__cxx03_bool::__true_value : nullptr;
+    }
+#else
     _LIBCPP_ALWAYS_INLINE
     _LIBCPP_EXPLICIT operator bool() const {return !fail();}
+#endif
 
     _LIBCPP_ALWAYS_INLINE bool operator!() const    {return  fail();}
     _LIBCPP_ALWAYS_INLINE iostate rdstate() const   {return ios_base::rdstate();}
diff --git a/include/memory b/include/memory
index 54fd7bf49e89..2a25f0ecb507 100644
--- a/include/memory
+++ b/include/memory
@@ -3884,6 +3884,7 @@ class _LIBCPP_TEMPLATE_VIS shared_ptr
 {
 public:
     typedef _Tp element_type;
+
 #if _LIBCPP_STD_VER > 14
     typedef weak_ptr<_Tp> weak_type;
 #endif
@@ -3914,17 +3915,17 @@ public:
     template<class _Yp>
         _LIBCPP_INLINE_VISIBILITY
         shared_ptr(const shared_ptr<_Yp>& __r,
-                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type = __nat())
+                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type = __nat())
                        _NOEXCEPT;
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     _LIBCPP_INLINE_VISIBILITY
     shared_ptr(shared_ptr&& __r) _NOEXCEPT;
     template<class _Yp> _LIBCPP_INLINE_VISIBILITY  shared_ptr(shared_ptr<_Yp>&& __r,
-                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type = __nat())
+                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type = __nat())
                        _NOEXCEPT;
 #endif  // _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template<class _Yp> explicit shared_ptr(const weak_ptr<_Yp>& __r,
-                   typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type= __nat());
+                   typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type= __nat());
 #ifndef _LIBCPP_HAS_NO_RVALUE_REFERENCES
     template<class _Yp>
         shared_ptr(auto_ptr<_Yp>&& __r,
@@ -4316,7 +4317,7 @@ template<class _Tp>
 template<class _Yp>
 inline
 shared_ptr<_Tp>::shared_ptr(const shared_ptr<_Yp>& __r,
-                            typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type)
+                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
@@ -4341,7 +4342,7 @@ template<class _Tp>
 template<class _Yp>
 inline
 shared_ptr<_Tp>::shared_ptr(shared_ptr<_Yp>&& __r,
-                            typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type)
+                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
          _NOEXCEPT
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_)
@@ -4639,7 +4640,7 @@ template<class _Yp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(const shared_ptr<_Yp>& __r) _NOEXCEPT
@@ -4664,7 +4665,7 @@ template<class _Yp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(shared_ptr<_Yp>&& __r)
@@ -4679,7 +4680,7 @@ inline
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>
 >::type&
 shared_ptr<_Tp>::operator=(auto_ptr<_Yp>&& __r)
@@ -4694,7 +4695,8 @@ inline
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, _Tp*>::value,
+    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, 
+                   typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(unique_ptr<_Yp, _Dp>&& __r)
@@ -4711,7 +4713,7 @@ inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(auto_ptr<_Yp> __r)
@@ -4726,7 +4728,8 @@ inline _LIBCPP_INLINE_VISIBILITY
 typename enable_if
 <
     !is_array<_Yp>::value &&
-    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, _Tp*>::value,
+    is_convertible<typename unique_ptr<_Yp, _Dp>::pointer, 
+                   typename shared_ptr<_Tp>::element_type*>::value,
     shared_ptr<_Tp>&
 >::type
 shared_ptr<_Tp>::operator=(unique_ptr<_Yp, _Dp> __r)
@@ -4759,7 +4762,7 @@ template<class _Yp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     void
 >::type
 shared_ptr<_Tp>::reset(_Yp* __p)
@@ -4772,7 +4775,7 @@ template<class _Yp, class _Dp>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     void
 >::type
 shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d)
@@ -4785,7 +4788,7 @@ template<class _Yp, class _Dp, class _Alloc>
 inline
 typename enable_if
 <
-    is_convertible<_Yp*, _Tp*>::value,
+    is_convertible<_Yp*, typename shared_ptr<_Tp>::element_type*>::value,
     void
 >::type
 shared_ptr<_Tp>::reset(_Yp* __p, _Dp __d, _Alloc __a)
@@ -5350,7 +5353,7 @@ weak_ptr<_Tp>::reset() _NOEXCEPT
 template<class _Tp>
 template<class _Yp>
 shared_ptr<_Tp>::shared_ptr(const weak_ptr<_Yp>& __r,
-                            typename enable_if<is_convertible<_Yp*, _Tp*>::value, __nat>::type)
+                            typename enable_if<is_convertible<_Yp*, element_type*>::value, __nat>::type)
     : __ptr_(__r.__ptr_),
       __cntrl_(__r.__cntrl_ ? __r.__cntrl_->lock() : __r.__cntrl_)
 {
diff --git a/include/mutex b/include/mutex
index 8526533f1402..3b878c642cce 100644
--- a/include/mutex
+++ b/include/mutex
@@ -559,6 +559,7 @@ public:
 #endif
 
 template <class _Fp>
+inline _LIBCPP_INLINE_VISIBILITY
 void
 __call_once_proxy(void* __vp)
 {
diff --git a/src/chrono.cpp b/src/chrono.cpp
index df5cabdb1845..9b277a610cd2 100644
--- a/src/chrono.cpp
+++ b/src/chrono.cpp
@@ -42,7 +42,7 @@
 #include <winapifamily.h>
 #endif
 #else
-#if !defined(CLOCK_REALTIME)
+#if !defined(CLOCK_REALTIME) || !defined(_LIBCXX_USE_CLOCK_GETTIME)
 #include <sys/time.h>        // for gettimeofday and timeval
 #endif // !defined(CLOCK_REALTIME)
 #endif // defined(_LIBCPP_WIN32API)
diff --git a/src/new.cpp b/src/new.cpp
index 782aac90fb7a..2ef8939fdcb3 100644
--- a/src/new.cpp
+++ b/src/new.cpp
@@ -198,7 +198,11 @@ void
 operator delete(void* ptr, std::align_val_t) _NOEXCEPT
 {
     if (ptr)
+#if defined(_LIBCPP_MSVCRT)
+        ::_aligned_free(ptr);
+#else
         ::free(ptr);
+#endif
 }
 
 _LIBCPP_WEAK
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/assign2.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/assign2.pass.cpp
index 2c3deaefd063..311064ceb614 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/assign2.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/assign2.pass.cpp
@@ -11,14 +11,30 @@
 
 // template<> struct char_traits<char>
 
-// static void assign(char_type& c1, const char_type& c2);
+// static constexpr void assign(char_type& c1, const char_type& c2); // constexpr in C++17
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    char c = '1';
+    std::char_traits<char>::assign(c, 'a');
+    return c == 'a';
+}
+#endif
+
 int main()
 {
     char c = '\0';
     std::char_traits<char>::assign(c, 'a');
     assert(c == 'a');
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/compare.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/compare.pass.cpp
index ba58684b8e2e..71ab24898d60 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/compare.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/compare.pass.cpp
@@ -12,10 +12,22 @@
 // template<> struct char_traits<char>
 
 // static int compare(const char_type* s1, const char_type* s2, size_t n);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<char>::compare("123", "223", 3) < 0
+        && std::char_traits<char>::compare("223", "123", 3) > 0
+        && std::char_traits<char>::compare("123", "123", 3) == 0;
+}
+#endif
+
 int main()
 {
     assert(std::char_traits<char>::compare("", "", 0) == 0);
@@ -38,4 +50,8 @@ int main()
     assert(std::char_traits<char>::compare("223", "123", 3) > 0);
     assert(std::char_traits<char>::compare("133", "123", 3) > 0);
     assert(std::char_traits<char>::compare("124", "123", 3) > 0);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/find.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/find.pass.cpp
index a640af28d8ac..714202e25685 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/find.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/find.pass.cpp
@@ -12,10 +12,24 @@
 // template<> struct char_traits<char>
 
 // static const char_type* find(const char_type* s, size_t n, const char_type& a);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    constexpr const char *p = "123";
+    return std::char_traits<char>::find(p, 3, '1') == p
+        && std::char_traits<char>::find(p, 3, '2') == p + 1
+        && std::char_traits<char>::find(p, 3, '3') == p + 2
+        && std::char_traits<char>::find(p, 3, '4') == nullptr;
+}
+#endif
+
 int main()
 {
     char s1[] = {1, 2, 3};
@@ -25,4 +39,8 @@ int main()
     assert(std::char_traits<char>::find(s1, 3, char(4)) == 0);
     assert(std::char_traits<char>::find(s1, 3, char(0)) == 0);
     assert(std::char_traits<char>::find(NULL, 0, char(0)) == 0);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/length.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/length.pass.cpp
index 56844ef46644..d93e499873b6 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/length.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char/length.pass.cpp
@@ -12,10 +12,22 @@
 // template<> struct char_traits<char>
 
 // static size_t length(const char_type* s);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<char>::length("") == 0
+        && std::char_traits<char>::length("abcd") == 4;
+}
+#endif
+
+
 int main()
 {
     assert(std::char_traits<char>::length("") == 0);
@@ -23,4 +35,8 @@ int main()
     assert(std::char_traits<char>::length("aa") == 2);
     assert(std::char_traits<char>::length("aaa") == 3);
     assert(std::char_traits<char>::length("aaaa") == 4);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/assign2.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/assign2.pass.cpp
index 7f223af57414..e28f906c05bb 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/assign2.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/assign2.pass.cpp
@@ -12,12 +12,22 @@
 // template<> struct char_traits<char16_t>
 
 // static void assign(char_type& c1, const char_type& c2);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
 #include "test_macros.h"
 
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    char16_t c = u'1';
+    std::char_traits<char16_t>::assign(c, u'a');
+    return c == u'a';
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -26,5 +36,9 @@ int main()
     std::char_traits<char16_t>::assign(c, u'a');
     assert(c == u'a');
 #endif
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/compare.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/compare.pass.cpp
index 7356097a6677..b4be1402ad1c 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/compare.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/compare.pass.cpp
@@ -12,12 +12,23 @@
 // template<> struct char_traits<char16_t>
 
 // static int compare(const char_type* s1, const char_type* s2, size_t n);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
 #include "test_macros.h"
 
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<char16_t>::compare(u"123", u"223", 3) < 0
+        && std::char_traits<char16_t>::compare(u"223", u"123", 3) > 0
+        && std::char_traits<char16_t>::compare(u"123", u"123", 3) == 0;
+}
+#endif
+
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -43,5 +54,9 @@ int main()
     assert(std::char_traits<char16_t>::compare(u"133", u"123", 3) > 0);
     assert(std::char_traits<char16_t>::compare(u"124", u"123", 3) > 0);
 #endif
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/find.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/find.pass.cpp
index 22db05b55a87..852451cb827e 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/find.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/find.pass.cpp
@@ -12,10 +12,24 @@
 // template<> struct char_traits<char16_t>
 
 // static const char_type* find(const char_type* s, size_t n, const char_type& a);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    constexpr const char16_t *p = u"123";
+    return std::char_traits<char16_t>::find(p, 3, u'1') == p
+        && std::char_traits<char16_t>::find(p, 3, u'2') == p + 1
+        && std::char_traits<char16_t>::find(p, 3, u'3') == p + 2
+        && std::char_traits<char16_t>::find(p, 3, u'4') == nullptr;
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -26,5 +40,9 @@ int main()
     assert(std::char_traits<char16_t>::find(s1, 3, char16_t(4)) == 0);
     assert(std::char_traits<char16_t>::find(s1, 3, char16_t(0)) == 0);
     assert(std::char_traits<char16_t>::find(NULL, 0, char16_t(0)) == 0);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/length.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/length.pass.cpp
index ff5a2a934a9f..5d882bde2f5a 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/length.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char16_t/length.pass.cpp
@@ -12,12 +12,21 @@
 // template<> struct char_traits<char16_t>
 
 // static size_t length(const char_type* s);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
 #include "test_macros.h"
 
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<char16_t>::length(u"") == 0
+        && std::char_traits<char16_t>::length(u"abcd") == 4;
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -28,5 +37,9 @@ int main()
     assert(std::char_traits<char16_t>::length(u"aaa") == 3);
     assert(std::char_traits<char16_t>::length(u"aaaa") == 4);
 #endif
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/assign2.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/assign2.pass.cpp
index 6cd55ea58bff..373931169d81 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/assign2.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/assign2.pass.cpp
@@ -12,12 +12,22 @@
 // template<> struct char_traits<char32_t>
 
 // static void assign(char_type& c1, const char_type& c2);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
 #include "test_macros.h"
 
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    char32_t c = U'1';
+    std::char_traits<char32_t>::assign(c, U'a');
+    return c == U'a';
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -26,5 +36,9 @@ int main()
     std::char_traits<char32_t>::assign(c, U'a');
     assert(c == U'a');
 #endif
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/compare.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/compare.pass.cpp
index 2671b5624100..1730d06cc16a 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/compare.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/compare.pass.cpp
@@ -12,12 +12,22 @@
 // template<> struct char_traits<char32_t>
 
 // static int compare(const char_type* s1, const char_type* s2, size_t n);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
 #include "test_macros.h"
 
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<char32_t>::compare(U"123", U"223", 3) < 0
+        && std::char_traits<char32_t>::compare(U"223", U"123", 3) > 0
+        && std::char_traits<char32_t>::compare(U"123", U"123", 3) == 0;
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -43,5 +53,9 @@ int main()
     assert(std::char_traits<char32_t>::compare(U"133", U"123", 3) > 0);
     assert(std::char_traits<char32_t>::compare(U"124", U"123", 3) > 0);
 #endif
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/find.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/find.pass.cpp
index d0b17999d3e1..6d201db62efc 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/find.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/find.pass.cpp
@@ -12,10 +12,24 @@
 // template<> struct char_traits<char32_t>
 
 // static const char_type* find(const char_type* s, size_t n, const char_type& a);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    constexpr const char32_t *p = U"123";
+    return std::char_traits<char32_t>::find(p, 3, U'1') == p
+        && std::char_traits<char32_t>::find(p, 3, U'2') == p + 1
+        && std::char_traits<char32_t>::find(p, 3, U'3') == p + 2
+        && std::char_traits<char32_t>::find(p, 3, U'4') == nullptr;
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -26,5 +40,9 @@ int main()
     assert(std::char_traits<char32_t>::find(s1, 3, char32_t(4)) == 0);
     assert(std::char_traits<char32_t>::find(s1, 3, char32_t(0)) == 0);
     assert(std::char_traits<char32_t>::find(NULL, 0, char32_t(0)) == 0);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/length.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/length.pass.cpp
index e0bee5dc5080..9d691aca4ec9 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/length.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.char32_t/length.pass.cpp
@@ -12,12 +12,21 @@
 // template<> struct char_traits<char32_t>
 
 // static size_t length(const char_type* s);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
 #include "test_macros.h"
 
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<char32_t>::length(U"") == 0
+        && std::char_traits<char32_t>::length(U"abcd") == 4;
+}
+#endif
+
 int main()
 {
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
@@ -28,5 +37,9 @@ int main()
     assert(std::char_traits<char32_t>::length(U"aaa") == 3);
     assert(std::char_traits<char32_t>::length(U"aaaa") == 4);
 #endif
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/assign2.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/assign2.pass.cpp
index 7dcf08c2e76f..7a317f0d66de 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/assign2.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/assign2.pass.cpp
@@ -12,13 +12,29 @@
 // template<> struct char_traits<wchar_t>
 
 // static void assign(char_type& c1, const char_type& c2);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    wchar_t c = L'1';
+    std::char_traits<wchar_t>::assign(c, L'a');
+    return c == L'a';
+}
+#endif
+
 int main()
 {
     wchar_t c = L'\0';
     std::char_traits<wchar_t>::assign(c, L'a');
     assert(c == L'a');
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/compare.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/compare.pass.cpp
index 124201bb82f3..894560d69396 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/compare.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/compare.pass.cpp
@@ -12,10 +12,22 @@
 // template<> struct char_traits<wchar_t>
 
 // static int compare(const char_type* s1, const char_type* s2, size_t n);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<wchar_t>::compare(L"123", L"223", 3) < 0
+        && std::char_traits<wchar_t>::compare(L"223", L"123", 3) > 0
+        && std::char_traits<wchar_t>::compare(L"123", L"123", 3) == 0;
+}
+#endif
+
 int main()
 {
     assert(std::char_traits<wchar_t>::compare(L"", L"", 0) == 0);
@@ -38,4 +50,8 @@ int main()
     assert(std::char_traits<wchar_t>::compare(L"223", L"123", 3) > 0);
     assert(std::char_traits<wchar_t>::compare(L"133", L"123", 3) > 0);
     assert(std::char_traits<wchar_t>::compare(L"124", L"123", 3) > 0);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/find.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/find.pass.cpp
index ead3f32fcc72..80aca0ea7f9d 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/find.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/find.pass.cpp
@@ -12,10 +12,24 @@
 // template<> struct char_traits<wchar_t>
 
 // static const char_type* find(const char_type* s, size_t n, const char_type& a);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    constexpr const wchar_t *p = L"123";
+    return std::char_traits<wchar_t>::find(p, 3, L'1') == p
+        && std::char_traits<wchar_t>::find(p, 3, L'2') == p + 1
+        && std::char_traits<wchar_t>::find(p, 3, L'3') == p + 2
+        && std::char_traits<wchar_t>::find(p, 3, L'4') == nullptr;
+}
+#endif
+
 int main()
 {
     wchar_t s1[] = {1, 2, 3};
@@ -25,4 +39,8 @@ int main()
     assert(std::char_traits<wchar_t>::find(s1, 3, wchar_t(4)) == 0);
     assert(std::char_traits<wchar_t>::find(s1, 3, wchar_t(0)) == 0);
     assert(std::char_traits<wchar_t>::find(NULL, 0, wchar_t(0)) == 0);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/length.pass.cpp b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/length.pass.cpp
index 691e968ed246..35cbb2d5fd47 100644
--- a/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/length.pass.cpp
+++ b/test/std/strings/char.traits/char.traits.specializations/char.traits.specializations.wchar.t/length.pass.cpp
@@ -12,10 +12,21 @@
 // template<> struct char_traits<wchar_t>
 
 // static size_t length(const char_type* s);
+// constexpr in C++17
 
 #include <string>
 #include <cassert>
 
+#include "test_macros.h"
+
+#if TEST_STD_VER > 14
+constexpr bool test_constexpr()
+{
+    return std::char_traits<wchar_t>::length(L"") == 0
+        && std::char_traits<wchar_t>::length(L"abcd") == 4;
+}
+#endif
+
 int main()
 {
     assert(std::char_traits<wchar_t>::length(L"") == 0);
@@ -23,4 +34,8 @@ int main()
     assert(std::char_traits<wchar_t>::length(L"aa") == 2);
     assert(std::char_traits<wchar_t>::length(L"aaa") == 3);
     assert(std::char_traits<wchar_t>::length(L"aaaa") == 4);
+
+#if TEST_STD_VER > 14
+    static_assert(test_constexpr(), "" );
+#endif
 }
diff --git a/test/std/thread/futures/futures.shared_future/dtor.pass.cpp b/test/std/thread/futures/futures.shared_future/dtor.pass.cpp
index af061268410d..39a8e517daef 100644
--- a/test/std/thread/futures/futures.shared_future/dtor.pass.cpp
+++ b/test/std/thread/futures/futures.shared_future/dtor.pass.cpp
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: libcpp-no-exceptions
+// UNSUPPORTED: libcpp-no-exceptions
 // UNSUPPORTED: libcpp-has-no-threads
 // UNSUPPORTED: c++98, c++03
 
diff --git a/test/std/thread/futures/futures.unique_future/dtor.pass.cpp b/test/std/thread/futures/futures.unique_future/dtor.pass.cpp
index 03d7c915cb61..af908d7e77ad 100644
--- a/test/std/thread/futures/futures.unique_future/dtor.pass.cpp
+++ b/test/std/thread/futures/futures.unique_future/dtor.pass.cpp
@@ -7,7 +7,7 @@
 //
 //===----------------------------------------------------------------------===//
 //
-// XFAIL: libcpp-no-exceptions
+// UNSUPPORTED: libcpp-no-exceptions
 // UNSUPPORTED: libcpp-has-no-threads
 // UNSUPPORTED: c++98, c++03