Merge to upstream r350972.

Test: ./run_tests.py --bitness 32
Test: ./run_tests.py --bitness 64
Test: ./run_tests.py --bitness 64 --host
Bug: None
Change-Id: I96552544c8305853be519855982caf716930519e

CMakeLists.txt

@@ -283,6 +283,9 @@ endif()
 option(LIBCXX_CONFIGURE_IDE "Configure libcxx for use within an IDE"
       ${LIBCXX_CONFIGURE_IDE_DEFAULT})
 
+option(LIBCXX_HERMETIC_STATIC_LIBRARY
+  "Do not export any symbols from the static library." OFF)
+
 #===============================================================================
 # Check option configurations
 #===============================================================================

benchmarks/algorithms.partition_point.bench.cpp

@@ -0,0 +1,124 @@
+#include <array>
+#include <algorithm>
+#include <cassert>
+#include <cstdint>
+#include <tuple>
+#include <vector>
+
+#include "benchmark/benchmark.h"
+
+#include "CartesianBenchmarks.hpp"
+#include "GenerateInput.hpp"
+
+namespace {
+
+template <typename I, typename N>
+std::array<I, 10> every_10th_percentile_N(I first, N n) {
+  N step = n / 10;
+  std::array<I, 10> res;
+
+  for (size_t i = 0; i < 10; ++i) {
+    res[i] = first;
+    std::advance(first, step);
+  }
+
+  return res;
+}
+
+template <class IntT>
+struct TestIntBase {
+  static std::vector<IntT> generateInput(size_t size) {
+    std::vector<IntT> Res(size);
+    std::generate(Res.begin(), Res.end(),
+                  [] { return getRandomInteger<IntT>(); });
+    return Res;
+  }
+};
+
+struct TestInt32 : TestIntBase<std::int32_t> {
+  static constexpr const char* Name = "TestInt32";
+};
+
+struct TestInt64 : TestIntBase<std::int64_t> {
+  static constexpr const char* Name = "TestInt64";
+};
+
+struct TestUint32 : TestIntBase<std::uint32_t> {
+  static constexpr const char* Name = "TestUint32";
+};
+
+struct TestMediumString {
+  static constexpr const char* Name = "TestMediumString";
+  static constexpr size_t StringSize = 32;
+
+  static std::vector<std::string> generateInput(size_t size) {
+    std::vector<std::string> Res(size);
+    std::generate(Res.begin(), Res.end(), [] { return getRandomString(StringSize); });
+    return Res;
+  }
+};
+
+using AllTestTypes = std::tuple<TestInt32, TestInt64, TestUint32, TestMediumString>;
+
+struct LowerBoundAlg {
+  template <class I, class V>
+  I operator()(I first, I last, const V& value) const {
+    return std::lower_bound(first, last, value);
+  }
+
+  static constexpr const char* Name = "LowerBoundAlg";
+};
+
+struct UpperBoundAlg {
+  template <class I, class V>
+  I operator()(I first, I last, const V& value) const {
+    return std::upper_bound(first, last, value);
+  }
+
+  static constexpr const char* Name = "UpperBoundAlg";
+};
+
+struct EqualRangeAlg {
+  template <class I, class V>
+  std::pair<I, I> operator()(I first, I last, const V& value) const {
+    return std::equal_range(first, last, value);
+  }
+
+  static constexpr const char* Name = "EqualRangeAlg";
+};
+
+using AllAlgs = std::tuple<LowerBoundAlg, UpperBoundAlg, EqualRangeAlg>;
+
+template <class Alg, class TestType>
+struct PartitionPointBench {
+  size_t Quantity;
+
+  std::string name() const {
+    return std::string("PartitionPointBench_") + Alg::Name + "_" +
+           TestType::Name + '/' + std::to_string(Quantity);
+  }
+
+  void run(benchmark::State& state) const {
+    auto Data = TestType::generateInput(Quantity);
+    std::sort(Data.begin(), Data.end());
+    auto Every10Percentile = every_10th_percentile_N(Data.begin(), Data.size());
+
+    for (auto _ : state) {
+      for (auto Test : Every10Percentile)
+        benchmark::DoNotOptimize(Alg{}(Data.begin(), Data.end(), *Test));
+    }
+  }
+};
+
+} // namespace
+
+int main(int argc, char** argv) {
+  benchmark::Initialize(&argc, argv);
+  if (benchmark::ReportUnrecognizedArguments(argc, argv))
+    return 1;
+
+  const std::vector<size_t> Quantities = {1 << 8, 1 << 10, 1 << 20};
+  makeCartesianProductBenchmark<PartitionPointBench, AllAlgs, AllTestTypes>(
+      Quantities);
+  benchmark::RunSpecifiedBenchmarks();
+}

docs/BuildingLibcxx.rst

@@ -222,6 +222,15 @@ libc++ specific options
 
   Define libc++ destination prefix.
 
+.. option:: LIBCXX_HERMETIC_STATIC_LIBRARY:BOOL
+
+  **Default**: ``OFF``
+
+  Do not export any symbols from the static libc++ library. This is useful when
+  This is useful when the static libc++ library is being linked into shared
+  libraries that may be used in with other shared libraries that use different
+  C++ library. We want to avoid avoid exporting any libc++ symbols in that case.
+
 .. _libc++experimental options:
 
 libc++experimental Specific Options

docs/DesignDocs/AvailabilityMarkup.rst

@@ -55,7 +55,7 @@ or on a particular symbol:
 Testing
 =======
 
-Some parameters can be passed to lit to run the test-suite and exercising the
+Some parameters can be passed to lit to run the test-suite and exercise the
 availability.
 
 * The `platform` parameter controls the deployment target. For example lit can
@@ -69,8 +69,7 @@ availability.
 Tests can be marked as XFAIL based on multiple features made available by lit:
 
 
-* if `use_system_cxx_lib` is passed to lit, assuming `--param=platform=macosx10.8`
+* if `--param=platform=macosx10.8` is passed, the following features will be available:
-  is passed as well the following features will be available:
 
   - availability
   - availability=x86_64
@@ -82,8 +81,8 @@ Tests can be marked as XFAIL based on multiple features made available by lit:
   This feature is used to XFAIL a test that *is* using a class or a method marked
   as unavailable *and* that is expected to *fail* if deployed on an older system.
 
-* if `use_system_cxx_lib` is passed to lit, the following features will also
+* if `use_system_cxx_lib` and `--param=platform=macosx10.8` are passed to lit,
-  be available:
+  the following features will also be available:
 
   - with_system_cxx_lib
   - with_system_cxx_lib=x86_64
@@ -94,19 +93,7 @@ Tests can be marked as XFAIL based on multiple features made available by lit:
 
   This feature is used to XFAIL a test that is *not* using a class or a method
   marked as unavailable *but* that is expected to fail if deployed on an older
-  system. For example if we know that it exhibits a bug in the libc on a
+  system. For example, if the test exhibits a bug in the libc on a particular
-  particular system version.
+  system version, or if the test uses a symbol that is not available on an
-
+  older version of the dylib (but for which there is no availability markup,
-* if `with_availability` is passed to lit, the following features will also
+  otherwise the XFAIL should use `availability` above).
-  be available:
-
-  - availability_markup
-  - availability_markup=x86_64
-  - availability_markup=macosx
-  - availability_markup=x86_64-macosx
-  - availability_markup=x86_64-apple-macosx10.8
-  - availability_markup=macosx10.8
-
-  This feature is used to XFAIL a test that *is* using a class or a method
-  marked as unavailable *but* that is expected to *pass* if deployed on an older
-  system. For example if it is using a symbol in a statically evaluated context.

docs/TestingLibcxx.rst

@@ -138,8 +138,7 @@ configuration. Passing the option on the command line will override the default.
   Specify the directory of the libc++ library to use at runtime. This directory
   is not added to the linkers search path. This can be used to compile tests
   against one version of libc++ and run them using another. The default value
-  for this option is `cxx_library_root`. This option cannot be used
+  for this option is `cxx_library_root`.
-  when use_system_cxx_lib is provided.
 
 .. option:: use_system_cxx_lib=<bool>
 
@@ -155,14 +154,6 @@ configuration. Passing the option on the command line will override the default.
   the default value. Otherwise the default value is True on Windows and False
   on every other platform.
 
-.. option:: no_default_flags=<bool>
-
-  **Default**: False
-
-  Disable all default compile and link flags from being added. When this
-  option is used only flags specified using the compile_flags and link_flags
-  will be used.
-
 .. option:: compile_flags="<list-of-args>"
 
   Specify additional compile flags as a space delimited string.

docs/UsingLibcxx.rst

@@ -203,8 +203,10 @@ thread safety annotations.
   This macro disables the additional diagnostics generated by libc++ using the
   `diagnose_if` attribute. These additional diagnostics include checks for:
 
-    * Giving `set`, `map`, `multiset`, `multimap` a comparator which is not
+    * Giving `set`, `map`, `multiset`, `multimap` and their `unordered_`
-      const callable.
+      counterparts a comparator which is not const callable.
+    * Giving an unordered associative container a hasher that is not const
+      callable.
 
 **_LIBCPP_NO_VCRUNTIME**:
   Microsoft's C and C++ headers are fairly entangled, and some of their C++

include/__config

@@ -95,6 +95,8 @@
 // Use the smallest possible integer type to represent the index of the variant.
 // Previously libc++ used "unsigned int" exclusivly.
 #  define _LIBCPP_ABI_VARIANT_INDEX_TYPE_OPTIMIZATION
+// Unstable attempt to provide a more optimized std::function
+#  define _LIBCPP_ABI_OPTIMIZED_FUNCTION
 #elif _LIBCPP_ABI_VERSION == 1
 #  if !defined(_LIBCPP_OBJECT_FORMAT_COFF)
 // Enable compiling copies of now inline methods into the dylib to support
@@ -713,7 +715,11 @@ typedef __char32_t char32_t;
 #endif
 
 #ifndef _LIBCPP_EXPORTED_FROM_ABI
+#  if !defined(_LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS)
 #    define _LIBCPP_EXPORTED_FROM_ABI __attribute__((__visibility__("default")))
+#  else
+#    define _LIBCPP_EXPORTED_FROM_ABI
+#  endif
 #endif
 
 #ifndef _LIBCPP_OVERRIDABLE_FUNC_VIS
@@ -971,14 +977,14 @@ template <unsigned> struct __static_assert_check {};
 // If we are getting operator new from the MSVC CRT, then allocation overloads
 // for align_val_t were added in 19.12, aka VS 2017 version 15.3.
 #if defined(_LIBCPP_MSVCRT) && defined(_MSC_VER) && _MSC_VER < 1912
-#define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+#  define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
 #elif defined(_LIBCPP_ABI_MICROSOFT) && !defined(_LIBCPP_NO_VCRUNTIME)
-#define _LIBCPP_DEFER_NEW_TO_VCRUNTIME
+#  define _LIBCPP_DEFER_NEW_TO_VCRUNTIME
-#if !defined(__cpp_aligned_new)
+#  if !defined(__cpp_aligned_new)
-// We're defering to Microsoft's STL to provide aligned new et al. We don't
+     // We're defering to Microsoft's STL to provide aligned new et al. We don't
-// have it unless the language feature test macro is defined.
+     // have it unless the language feature test macro is defined.
-#define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
+#    define _LIBCPP_HAS_NO_LIBRARY_ALIGNED_ALLOCATION
-#endif
+#  endif
 #endif
 
 #if defined(__APPLE__)
@@ -1002,6 +1008,10 @@ template <unsigned> struct __static_assert_check {};
 #define _LIBCPP_WCTYPE_IS_MASK
 #endif
 
+#if _LIBCPP_STD_VER <= 17 || !defined(__cpp_char8_t)
+#define _LIBCPP_NO_HAS_CHAR8_T
+#endif
+
 // Deprecation macros.
 // Deprecations warnings are only enabled when _LIBCPP_ENABLE_DEPRECATION_WARNINGS is defined.
 #if defined(_LIBCPP_ENABLE_DEPRECATION_WARNINGS)
@@ -1359,16 +1369,19 @@ _LIBCPP_FUNC_VIS extern "C" void __sanitizer_annotate_contiguous_container(
 #  define _LIBCPP_AVAILABILITY_THROW_BAD_VARIANT_ACCESS  _LIBCPP_AVAILABILITY_BAD_VARIANT_ACCESS
 #endif
 
-// Availability of stream API in the dylib got dropped and re-added.  The
+// The stream API was dropped and re-added in the dylib shipped on macOS
-// extern template should effectively be available at:
+// and iOS. We can only assume the dylib to provide these definitions for
-//    availability(macosx,introduced=10.9)
+// macosx >= 10.9 and ios >= 7.0. Otherwise, the definitions are available
-//    availability(ios,introduced=7.0)
+// from the headers, but not from the dylib. Explicit instantiation
-#if defined(_LIBCPP_USE_AVAILABILITY_APPLE) &&                                 \
+// declarations for streams exist conditionally to this; if we provide
+// an explicit instantiation declaration and we try to deploy to a dylib
+// that does not provide those symbols, we'll get a load-time error.
+#if !defined(_LIBCPP_BUILDING_LIBRARY) &&                                      \
     ((defined(__ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__) &&                \
       __ENVIRONMENT_MAC_OS_X_VERSION_MIN_REQUIRED__ < 1090) ||                 \
      (defined(__ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__) &&               \
       __ENVIRONMENT_IPHONE_OS_VERSION_MIN_REQUIRED__ < 70000))
-#define _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#  define _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 #endif
 
 #if defined(_LIBCPP_COMPILER_IBM)

include/__hash_table

@@ -35,15 +35,6 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 template <class _Key, class _Tp>
 struct __hash_value_type;
 
-template <class _Key, class _Cp, class _Hash,
-          bool =  is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value>
-class __unordered_map_hasher;
-
-template <class _Key, class _Cp, class _Pred,
-          bool = is_empty<_Pred>::value && !__libcpp_is_final<_Pred>::value
-         >
-class __unordered_map_equal;
-
 #ifndef _LIBCPP_CXX03_LANG
 template <class _Tp>
 struct __is_hash_value_type_imp : false_type {};
@@ -871,35 +862,32 @@ struct __generic_container_node_destructor<__hash_node<_Tp, _VoidPtr>, _Alloc>
 };
 #endif
 
+template <class _Key, class _Hash, class _Equal>
+struct __enforce_unordered_container_requirements {
 #ifndef _LIBCPP_CXX03_LANG
-template <class _Key, class _Hash, class _Equal, class _Alloc>
-struct __diagnose_hash_table_helper {
-  static constexpr bool __trigger_diagnostics()
-    _LIBCPP_DIAGNOSE_WARNING(__check_hash_requirements<_Key, _Hash>::value
-                         && !__invokable<_Hash const&, _Key const&>::value,
-      "the specified hash functor does not provide a const call operator")
-    _LIBCPP_DIAGNOSE_WARNING(is_copy_constructible<_Equal>::value
-                          && !__invokable<_Equal const&, _Key const&, _Key const&>::value,
-      "the specified comparator type does not provide a const call operator")
-  {
     static_assert(__check_hash_requirements<_Key, _Hash>::value,
     "the specified hash does not meet the Hash requirements");
     static_assert(is_copy_constructible<_Equal>::value,
     "the specified comparator is required to be copy constructible");
-    return true;
+#endif
-  }
+    typedef int type;
 };
 
-template <class _Key, class _Value, class _Hash, class _Equal, class _Alloc>
+template <class _Key, class _Hash, class _Equal>
-struct __diagnose_hash_table_helper<
+#ifndef _LIBCPP_CXX03_LANG
-  __hash_value_type<_Key, _Value>,
+    _LIBCPP_DIAGNOSE_WARNING(!__invokable<_Equal const&, _Key const&, _Key const&>::value,
-  __unordered_map_hasher<_Key, __hash_value_type<_Key, _Value>, _Hash>,
+    "the specified comparator type does not provide a const call operator")
-  __unordered_map_equal<_Key, __hash_value_type<_Key, _Value>, _Equal>,
+    _LIBCPP_DIAGNOSE_WARNING(!__invokable<_Hash const&, _Key const&>::value,
-  _Alloc>
+    "the specified hash functor does not provide a const call operator")
-: __diagnose_hash_table_helper<_Key, _Hash, _Equal, _Alloc>
+#endif
-{
+typename __enforce_unordered_container_requirements<_Key, _Hash, _Equal>::type
-};
+__diagnose_unordered_container_requirements(int);
-#endif // _LIBCPP_CXX03_LANG
+
+// This dummy overload is used so that the compiler won't emit a spurious
+// "no matching function for call to __diagnose_unordered_xxx" diagnostic
+// when the overload above causes a hard error.
+template <class _Key, class _Hash, class _Equal>
+int __diagnose_unordered_container_requirements(void*);
 
 template <class _Tp, class _Hash, class _Equal, class _Alloc>
 class __hash_table
@@ -963,10 +951,6 @@ private:
     typedef allocator_traits<__pointer_allocator>          __pointer_alloc_traits;
     typedef typename __bucket_list_deleter::pointer       __node_pointer_pointer;
 
-#ifndef _LIBCPP_CXX03_LANG
-    static_assert(__diagnose_hash_table_helper<_Tp, _Hash, _Equal, _Alloc>::__trigger_diagnostics(), "");
-#endif
-
     // --- Member data begin ---
     __bucket_list                                         __bucket_list_;
     __compressed_pair<__first_node, __node_allocator>     __p1_;

include/__string

@@ -47,6 +47,7 @@ struct char_traits
 
 template <> struct char_traits<char>;
 template <> struct char_traits<wchar_t>;
+template <> struct char_traits<char8_t>;  // c++20
 
 }  // std
 
@@ -389,6 +390,102 @@ char_traits<wchar_t>::find(const char_type* __s, size_t __n, const char_type& __
 }
 
 
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+
+template <>
+struct _LIBCPP_TEMPLATE_VIS char_traits<char8_t>
+{
+    typedef char8_t        char_type;
+    typedef unsigned int   int_type;
+    typedef streamoff      off_type;
+    typedef u8streampos    pos_type;
+    typedef mbstate_t      state_type;
+
+    static inline constexpr void assign(char_type& __c1, const char_type& __c2) noexcept
+        {__c1 = __c2;}
+    static inline constexpr bool eq(char_type __c1, char_type __c2) noexcept
+        {return __c1 == __c2;}
+    static inline constexpr bool lt(char_type __c1, char_type __c2) noexcept
+        {return __c1 < __c2;}
+
+    static constexpr
+    int              compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT;
+
+    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
+       {
+            _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);}
+
+    static inline constexpr int_type  not_eof(int_type __c) noexcept
+        {return eq_int_type(__c, eof()) ? ~eof() : __c;}
+    static inline constexpr char_type to_char_type(int_type __c) noexcept
+        {return char_type(__c);}
+    static inline constexpr int_type to_int_type(char_type __c) noexcept
+        {return int_type(__c);}
+    static inline constexpr bool eq_int_type(int_type __c1, int_type __c2) noexcept
+        {return __c1 == __c2;}
+    static inline constexpr int_type eof() noexcept
+        {return int_type(EOF);}
+};
+
+// TODO use '__builtin_strlen' if it ever supports char8_t ??
+inline constexpr
+size_t
+char_traits<char8_t>::length(const char_type* __s) _NOEXCEPT
+{
+    size_t __len = 0;
+    for (; !eq(*__s, char_type(0)); ++__s)
+        ++__len;
+    return __len;
+}
+
+inline constexpr
+int
+char_traits<char8_t>::compare(const char_type* __s1, const char_type* __s2, size_t __n) _NOEXCEPT
+{
+#if __has_feature(cxx_constexpr_string_builtins)
+    return __builtin_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
+}
+
+// TODO use '__builtin_char_memchr' if it ever supports char8_t ??
+inline constexpr
+const char8_t*
+char_traits<char8_t>::find(const char_type* __s, size_t __n, const char_type& __a) _NOEXCEPT
+{
+    for (; __n; --__n)
+    {
+        if (eq(*__s, __a))
+            return __s;
+        ++__s;
+    }
+    return 0;
+}
+
+#endif // #_LIBCPP_NO_HAS_CHAR8_T
+
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 
 template <>

include/__tree

@@ -40,10 +40,6 @@ template <class _Tp, class _VoidPtr> class __tree_node;
 template <class _Key, class _Value>
 struct __value_type;
 
-template <class _Key, class _CP, class _Compare,
-    bool = is_empty<_Compare>::value && !__libcpp_is_final<_Compare>::value>
-class __map_value_compare;
-
 template <class _Allocator> class __map_node_destructor;
 template <class _TreeIterator> class _LIBCPP_TEMPLATE_VIS __map_iterator;
 template <class _TreeIterator> class _LIBCPP_TEMPLATE_VIS __map_const_iterator;
@@ -966,24 +962,12 @@ private:
 
 };
 
+template<class _Tp, class _Compare>
 #ifndef _LIBCPP_CXX03_LANG
-template <class _Tp, class _Compare, class _Allocator>
+    _LIBCPP_DIAGNOSE_WARNING(!std::__invokable<_Compare const&, _Tp const&, _Tp const&>::value,
-struct __diagnose_tree_helper {
-  static constexpr bool __trigger_diagnostics()
-      _LIBCPP_DIAGNOSE_WARNING(!__invokable<_Compare const&, _Tp const&, _Tp const&>::value,
         "the specified comparator type does not provide a const call operator")
-  { return true; }
+#endif
-};
+int __diagnose_non_const_comparator();
-
-template <class _Key, class _Value, class _KeyComp, class _Alloc>
-struct __diagnose_tree_helper<
-    __value_type<_Key, _Value>,
-    __map_value_compare<_Key, __value_type<_Key, _Value>, _KeyComp>,
-    _Alloc
-> : __diagnose_tree_helper<_Key, _KeyComp, _Alloc>
-{
-};
-#endif // !_LIBCPP_CXX03_LANG
 
 template <class _Tp, class _Compare, class _Allocator>
 class __tree
@@ -1855,10 +1839,6 @@ __tree<_Tp, _Compare, _Allocator>::~__tree()
 {
     static_assert((is_copy_constructible<value_compare>::value),
                  "Comparator must be copy-constructible.");
-#ifndef _LIBCPP_CXX03_LANG
-    static_assert((__diagnose_tree_helper<_Tp, _Compare, _Allocator>::
-                     __trigger_diagnostics()), "");
-#endif
   destroy(__root());
 }
 

include/__tuple

@@ -22,36 +22,36 @@
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size;
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size;
 
 #if !defined(_LIBCPP_CXX03_LANG)
 template <class _Tp, class...>
 using __enable_if_tuple_size_imp = _Tp;
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
     const _Tp,
     typename enable_if<!is_volatile<_Tp>::value>::type,
     integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
     : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
     volatile _Tp,
     typename enable_if<!is_const<_Tp>::value>::type,
     integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
     : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 template <class _Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__enable_if_tuple_size_imp<
     const volatile _Tp,
     integral_constant<size_t, sizeof(tuple_size<_Tp>)>>>
     : public integral_constant<size_t, tuple_size<_Tp>::value> {};
 
 #else
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<const _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size<const _Tp> : public tuple_size<_Tp> {};
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<volatile _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size<volatile _Tp> : public tuple_size<_Tp> {};
-template <class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_size<const volatile _Tp> : public tuple_size<_Tp> {};
+template <class _Tp> struct _LIBCPP_TEMPLATE_VIS tuple_size<const volatile _Tp> : public tuple_size<_Tp> {};
 #endif
 
 template <size_t _Ip, class _Tp> class _LIBCPP_TEMPLATE_VIS tuple_element;
@@ -165,7 +165,7 @@ template <class ..._Tp> class _LIBCPP_TEMPLATE_VIS tuple;
 template <class... _Tp> struct __tuple_like<tuple<_Tp...> > : true_type {};
 
 template <class ..._Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<tuple<_Tp...> >
+struct _LIBCPP_TEMPLATE_VIS tuple_size<tuple<_Tp...> >
     : public integral_constant<size_t, sizeof...(_Tp)>
 {
 };
@@ -291,7 +291,7 @@ public:
 
 
 template <class ..._Tp>
-class _LIBCPP_TEMPLATE_VIS tuple_size<__tuple_types<_Tp...> >
+struct _LIBCPP_TEMPLATE_VIS tuple_size<__tuple_types<_Tp...> >
     : public integral_constant<size_t, sizeof...(_Tp)>
 {
 };

include/algorithm

@@ -750,6 +750,32 @@ public:
     bool operator()(const _T1& __x, const _T2& __y) {return __p_(__y, __x);}
 };
 
+// Perform division by two quickly for positive integers (llvm.org/PR39129)
+
+template <typename _Integral>
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+typename enable_if
+<
+    is_integral<_Integral>::value,
+    _Integral
+>::type
+__half_positive(_Integral __value)
+{
+    return static_cast<_Integral>(static_cast<typename make_unsigned<_Integral>::type>(__value) / 2);
+}
+
+template <typename _Tp>
+_LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+typename enable_if
+<
+    !is_integral<_Tp>::value,
+    _Tp
+>::type
+__half_positive(_Tp __value)
+{
+    return __value / 2;
+}
+
 #ifdef _LIBCPP_DEBUG
 
 template <class _Compare>
@@ -3202,7 +3228,7 @@ partition_point(_ForwardIterator __first, _ForwardIterator __last, _Predicate __
     difference_type __len = _VSTD::distance(__first, __last);
     while (__len != 0)
     {
-        difference_type __l2 = __len / 2;
+        difference_type __l2 = _VSTD::__half_positive(__len);
         _ForwardIterator __m = __first;
         _VSTD::advance(__m, __l2);
         if (__pred(*__m))
@@ -4070,7 +4096,7 @@ __lower_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __va
     difference_type __len = _VSTD::distance(__first, __last);
     while (__len != 0)
     {
-        difference_type __l2 = __len / 2;
+        difference_type __l2 = _VSTD::__half_positive(__len);
         _ForwardIterator __m = __first;
         _VSTD::advance(__m, __l2);
         if (__comp(*__m, __value_))
@@ -4112,7 +4138,7 @@ __upper_bound(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __va
     difference_type __len = _VSTD::distance(__first, __last);
     while (__len != 0)
     {
-        difference_type __l2 = __len / 2;
+        difference_type __l2 = _VSTD::__half_positive(__len);
         _ForwardIterator __m = __first;
         _VSTD::advance(__m, __l2);
         if (__comp(__value_, *__m))
@@ -4154,7 +4180,7 @@ __equal_range(_ForwardIterator __first, _ForwardIterator __last, const _Tp& __va
     difference_type __len = _VSTD::distance(__first, __last);
     while (__len != 0)
     {
-        difference_type __l2 = __len / 2;
+        difference_type __l2 = _VSTD::__half_positive(__len);
         _ForwardIterator __m = __first;
         _VSTD::advance(__m, __l2);
         if (__comp(*__m, __value_))

include/array

@@ -91,7 +91,7 @@ template <class T, size_t N>
 template <class T, size_t N >
   void swap(array<T,N>& x, array<T,N>& y) noexcept(noexcept(x.swap(y))); // C++17
 
-template <class T> class tuple_size;
+template <class T> struct tuple_size;
 template <size_t I, class T> class tuple_element;
 template <class T, size_t N> struct tuple_size<array<T, N>>;
 template <size_t I, class T, size_t N> struct tuple_element<I, array<T, N>>;
@@ -430,7 +430,7 @@ swap(array<_Tp, _Size>& __x, array<_Tp, _Size>& __y)
 }
 
 template <class _Tp, size_t _Size>
-class _LIBCPP_TEMPLATE_VIS tuple_size<array<_Tp, _Size> >
+struct _LIBCPP_TEMPLATE_VIS tuple_size<array<_Tp, _Size> >
     : public integral_constant<size_t, _Size> {};
 
 template <size_t _Ip, class _Tp, size_t _Size>

include/bitset

@@ -991,7 +991,7 @@ inline
 size_t
 bitset<_Size>::count() const _NOEXCEPT
 {
-    return static_cast<size_t>(_VSTD::count(base::__make_iter(0), base::__make_iter(_Size), true));
+    return static_cast<size_t>(__count_bool_true(base::__make_iter(0), _Size));
 }
 
 template <size_t _Size>

include/chrono

@@ -808,6 +808,11 @@ constexpr chrono::year                                  operator ""y(unsigned lo
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>
 
+#ifndef _LIBCPP_CXX03_LANG
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+struct _FilesystemClock;
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+#endif // !_LIBCPP_CXX03_LANG
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
@@ -1581,10 +1586,27 @@ typedef system_clock high_resolution_clock;
 #endif
 
 #if _LIBCPP_STD_VER > 17
+// [time.clock.file], type file_clock
+using file_clock = _VSTD_FS::_FilesystemClock;
+
+template<class _Duration>
+using file_time = time_point<file_clock, _Duration>;
+
+
+template <class _Duration>
+using sys_time    = time_point<system_clock, _Duration>;
+using sys_seconds = sys_time<seconds>;
+using sys_days    = sys_time<days>;
+
+struct local_t {};
+template<class Duration>
+using local_time  = time_point<local_t, Duration>;
+using local_seconds = local_time<seconds>;
+using local_days    = local_time<days>;
+
 
 struct _LIBCPP_TYPE_VIS last_spec { explicit last_spec() = default; };
 
-
 class _LIBCPP_TYPE_VIS day {
 private:
     unsigned char __d;
@@ -1803,21 +1825,36 @@ private:
     unsigned char __wd;
 public:
   weekday() = default;
-  explicit inline constexpr weekday(unsigned __val) noexcept: __wd(static_cast<unsigned char>(__val)) {}
+  inline explicit constexpr weekday(unsigned __val) noexcept : __wd(static_cast<unsigned char>(__val)) {}
-//   inline constexpr weekday(const sys_days& dp) noexcept;
+  inline constexpr          weekday(const sys_days& __sysd) noexcept
-//   explicit constexpr weekday(const local_days& dp) noexcept;
+          : __wd(__weekday_from_days(__sysd.time_since_epoch().count())) {}
+  inline explicit constexpr weekday(const local_days& __locd) noexcept
+          : __wd(__weekday_from_days(__locd.time_since_epoch().count())) {}
+
   inline constexpr weekday& operator++()    noexcept { __wd = (__wd == 6 ? 0 : __wd + 1); return *this; }
   inline constexpr weekday  operator++(int) noexcept { weekday __tmp = *this; ++(*this); return __tmp; }
   inline constexpr weekday& operator--()    noexcept { __wd = (__wd == 0 ? 6 : __wd - 1); return *this; }
   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;
-  explicit inline constexpr operator unsigned() const noexcept { return __wd; }
+  inline explicit constexpr operator unsigned() const noexcept { return __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;
+
+  static constexpr unsigned char __weekday_from_days(int __days) noexcept;
 };
 
+
+// https://howardhinnant.github.io/date_algorithms.html#weekday_from_days
+inline constexpr
+unsigned char weekday::__weekday_from_days(int __days) noexcept
+{
+    return static_cast<unsigned char>(
+              static_cast<unsigned>(__days >= -4 ? (__days+4) % 7 : (__days+5) % 7 + 6)
+           );
+}
+
 inline constexpr
 bool operator==(const weekday& __lhs, const weekday& __rhs) noexcept
 { return static_cast<unsigned>(__lhs) == static_cast<unsigned>(__rhs); }
@@ -2212,6 +2249,7 @@ constexpr year_month operator-(const year_month& __lhs, const months& __rhs) noe
 constexpr year_month operator-(const year_month& __lhs, const years& __rhs) noexcept
 { return __lhs + -__rhs; }
 
+class year_month_day_last;
 
 class _LIBCPP_TYPE_VIS year_month_day {
 private:
@@ -2223,24 +2261,66 @@ public:
      inline constexpr year_month_day(
             const chrono::year& __yval, const chrono::month& __mval, const chrono::day& __dval) noexcept
             : __y{__yval}, __m{__mval}, __d{__dval} {}  
-//   inline constexpr year_month_day(const year_month_day_last& __ymdl) noexcept;
+            constexpr year_month_day(const year_month_day_last& __ymdl) noexcept;
-//   inline constexpr year_month_day(const sys_days& dp) noexcept;
+     inline constexpr year_month_day(const sys_days& __sysd) noexcept
-//   inline explicit constexpr year_month_day(const local_days& dp) noexcept;
+            : year_month_day(__from_days(__sysd.time_since_epoch())) {}
+     inline explicit constexpr year_month_day(const local_days& __locd) noexcept
+            : year_month_day(__from_days(__locd.time_since_epoch())) {}
+
             constexpr year_month_day& operator+=(const months& __dm) noexcept;
             constexpr year_month_day& operator-=(const months& __dm) noexcept;
             constexpr year_month_day& operator+=(const years& __dy)  noexcept;
             constexpr year_month_day& operator-=(const years& __dy)  noexcept;
+
      inline constexpr chrono::year   year() const noexcept { return __y; }
      inline constexpr chrono::month month() const noexcept { return __m; }
      inline constexpr chrono::day     day() const noexcept { return __d; }
-//   inline constexpr operator            sys_days() const noexcept;
+     inline constexpr operator   sys_days() const noexcept          { return   sys_days{__to_days()}; }
-//   inline explicit constexpr operator local_days() const noexcept;
+     inline explicit constexpr operator local_days() const noexcept { return local_days{__to_days()}; }
 
-//   TODO: This is not quite correct; requires the calendar bits to do right
+            constexpr bool             ok() const noexcept;
-//   d_ is in the range [1d, (y_/m_/last).day()],
+
-     inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok() && __d.ok(); }
+     static constexpr year_month_day __from_days(days __d) noexcept;
+     constexpr days __to_days() const noexcept;
 };
 
+
+// https://howardhinnant.github.io/date_algorithms.html#civil_from_days
+inline constexpr
+year_month_day
+year_month_day::__from_days(days __d) noexcept
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18, "");
+    static_assert(std::numeric_limits<int>::digits >= 20     , "");
+    const int      __z = __d.count() + 719468;
+    const int      __era = (__z >= 0 ? __z : __z - 146096) / 146097;
+    const unsigned __doe = static_cast<unsigned>(__z - __era * 146097);              // [0, 146096]
+    const unsigned __yoe = (__doe - __doe/1460 + __doe/36524 - __doe/146096) / 365;  // [0, 399]
+    const int      __yr = static_cast<int>(__yoe) + __era * 400;
+    const unsigned __doy = __doe - (365 * __yoe + __yoe/4 - __yoe/100);              // [0, 365]
+    const unsigned __mp = (5 * __doy + 2)/153;                                       // [0, 11]
+    const unsigned __dy = __doy - (153 * __mp + 2)/5 + 1;                            // [1, 31]
+    const unsigned __mth = __mp + (__mp < 10 ? 3 : -9);                              // [1, 12]
+    return year_month_day{chrono::year{__yr + (__mth <= 2)}, chrono::month{__mth}, chrono::day{__dy}};
+}
+
+// https://howardhinnant.github.io/date_algorithms.html#days_from_civil
+inline constexpr days year_month_day::__to_days() const noexcept
+{
+    static_assert(std::numeric_limits<unsigned>::digits >= 18, "");
+    static_assert(std::numeric_limits<int>::digits >= 20     , "");
+
+    const int      __yr  = static_cast<int>(__y) - (__m <= February);
+    const unsigned __mth = static_cast<unsigned>(__m);
+    const unsigned __dy  = static_cast<unsigned>(__d);
+
+    const int      __era = (__yr >= 0 ? __yr : __yr - 399) / 400;
+    const unsigned __yoe = static_cast<unsigned>(__yr - __era * 400);                // [0, 399]
+    const unsigned __doy = (153 * (__mth + (__mth > 2 ? -3 : 9)) + 2) / 5 + __dy-1;  // [0, 365]
+    const unsigned __doe = __yoe * 365 + __yoe/4 - __yoe/100 + __doy;                // [0, 146096]
+    return days{__era * 146097 + static_cast<int>(__doe) - 719468};
+}
+
 inline constexpr
 bool operator==(const year_month_day& __lhs, const year_month_day& __rhs) noexcept
 { return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.day() == __rhs.day(); }
@@ -2338,15 +2418,29 @@ public:
      constexpr year_month_day_last& operator+=(const years& __y)  noexcept;
      constexpr year_month_day_last& operator-=(const years& __y)  noexcept;
 
-     constexpr chrono::year           year()           const noexcept { return __y; }
+     inline constexpr chrono::year                     year() const noexcept { return __y; }
-     constexpr chrono::month          month()          const noexcept { return __mdl.month(); }
+     inline constexpr chrono::month                   month() const noexcept { return __mdl.month(); }
-     constexpr chrono::month_day_last month_day_last() const noexcept { return __mdl; }
+     inline constexpr chrono::month_day_last month_day_last() const noexcept { return __mdl; }
-//   constexpr chrono::day            day()            const noexcept;
+            constexpr chrono::day                       day() const noexcept;
-//   constexpr          operator sys_days()   const noexcept;
+     inline constexpr operator                     sys_days() const noexcept { return   sys_days{year()/month()/day()}; }
-//   explicit constexpr operator local_days() const noexcept;
+     inline explicit constexpr operator          local_days() const noexcept { return local_days{year()/month()/day()}; }
-     constexpr bool ok() const noexcept { return __y.ok() && __mdl.ok(); }
+     inline constexpr bool                               ok() const noexcept { return __y.ok() && __mdl.ok(); }
 };
 
+inline constexpr
+chrono::day year_month_day_last::day() const noexcept
+{
+    constexpr chrono::day __d[] =
+    {
+        chrono::day(31), chrono::day(28), chrono::day(31),
+        chrono::day(30), chrono::day(31), chrono::day(30),
+        chrono::day(31), chrono::day(31), chrono::day(30),
+        chrono::day(31), chrono::day(30), chrono::day(31)
+    };
+    return month() != February || !__y.is_leap() ?
+        __d[static_cast<unsigned>(month()) - 1] : chrono::day{29};
+}
+
 inline constexpr
 bool operator==(const year_month_day_last& __lhs, const year_month_day_last& __rhs) noexcept
 { return __lhs.year() == __rhs.year() && __lhs.month_day_last() == __rhs.month_day_last(); }
@@ -2420,6 +2514,15 @@ inline constexpr year_month_day_last& year_month_day_last::operator-=(const mont
 inline constexpr year_month_day_last& year_month_day_last::operator+=(const years& __dy)  noexcept { *this = *this + __dy; return *this; }
 inline constexpr year_month_day_last& year_month_day_last::operator-=(const years& __dy)  noexcept { *this = *this - __dy; return *this; }
 
+inline constexpr year_month_day::year_month_day(const year_month_day_last& __ymdl) noexcept
+    : __y{__ymdl.year()}, __m{__ymdl.month()}, __d{__ymdl.day()} {}  
+
+inline constexpr bool year_month_day::ok() const noexcept
+{
+    if (!__y.ok() || !__m.ok()) return false;
+    return chrono::day{1} <= __d && __d <= (__y / __m / last).day();
+}
+
 class _LIBCPP_TYPE_VIS year_month_weekday {
     chrono::year            __y;
     chrono::month           __m;
@@ -2429,8 +2532,10 @@ public:
     constexpr year_month_weekday(const chrono::year& __yval, const chrono::month& __mval,
                                const chrono::weekday_indexed& __wdival) noexcept
         : __y{__yval}, __m{__mval}, __wdi{__wdival} {}
-//  constexpr year_month_weekday(const sys_days& dp) noexcept;
+    constexpr year_month_weekday(const sys_days& __sysd) noexcept
-//  explicit constexpr year_month_weekday(const local_days& dp) noexcept;
+            : year_month_weekday(__from_days(__sysd.time_since_epoch())) {}
+    inline explicit constexpr year_month_weekday(const local_days& __locd) noexcept
+            : year_month_weekday(__from_days(__locd.time_since_epoch())) {}
     constexpr year_month_weekday& operator+=(const months& m) noexcept;
     constexpr year_month_weekday& operator-=(const months& m) noexcept;
     constexpr year_month_weekday& operator+=(const years& y)  noexcept;
@@ -2442,16 +2547,37 @@ public:
     inline constexpr unsigned                          index() const noexcept { return __wdi.index(); }
     inline constexpr chrono::weekday_indexed weekday_indexed() const noexcept { return __wdi; }
 
-//  constexpr          operator sys_days()   const noexcept;
+    inline constexpr                       operator sys_days() const noexcept { return   sys_days{__to_days()}; }
-//  explicit constexpr operator local_days() const noexcept;
+    inline explicit constexpr operator            local_days() const noexcept { return local_days{__to_days()}; }
     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;
     }
+
+    static constexpr year_month_weekday __from_days(days __d) noexcept;
+    constexpr days __to_days() const noexcept;
 };
 
+inline constexpr
+year_month_weekday year_month_weekday::__from_days(days __d) noexcept
+{
+    const sys_days      __sysd{__d};
+    const chrono::weekday __wd = chrono::weekday(__sysd);
+    const year_month_day __ymd = year_month_day(__sysd);
+    return year_month_weekday{__ymd.year(), __ymd.month(), 
+                              __wd[(static_cast<unsigned>(__ymd.day())-1)/7+1]};
+}
+
+inline constexpr
+days year_month_weekday::__to_days() const noexcept
+{
+    const sys_days __sysd = sys_days(__y/__m/1);
+    return (__sysd + (__wdi.weekday() - chrono::weekday(__sysd) + days{(__wdi.index()-1)*7}))
+                .time_since_epoch();
+}
+
 inline constexpr
 bool operator==(const year_month_weekday& __lhs, const year_month_weekday& __rhs) noexcept
 { return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.weekday_indexed() == __rhs.weekday_indexed(); }
@@ -2529,11 +2655,22 @@ public:
     inline constexpr chrono::month               month() const noexcept { return __m; }
     inline constexpr chrono::weekday           weekday() const noexcept { return __wdl.weekday(); }
     inline constexpr chrono::weekday_last weekday_last() const noexcept { return __wdl; }
-//  constexpr          operator sys_days()   const noexcept;
+    inline constexpr operator                 sys_days() const noexcept { return   sys_days{__to_days()}; }
-//  explicit constexpr operator local_days() const noexcept;
+    inline explicit constexpr operator      local_days() const noexcept { return local_days{__to_days()}; }
     inline constexpr bool ok() const noexcept { return __y.ok() && __m.ok() && __wdl.ok(); }
+    
+    constexpr days __to_days() const noexcept;
+    
 };
 
+inline constexpr
+days year_month_weekday_last::__to_days() const noexcept
+{
+    const sys_days __last = sys_days{__y/__m/last};
+    return (__last - (chrono::weekday{__last} - __wdl.weekday())).time_since_epoch();
+
+}
+
 inline constexpr
 bool operator==(const year_month_weekday_last& __lhs, const year_month_weekday_last& __rhs) noexcept
 { return __lhs.year() == __rhs.year() && __lhs.month() == __rhs.month() && __lhs.weekday_last() == __rhs.weekday_last(); }
@@ -2689,6 +2826,40 @@ namespace chrono { // hoist the literals into namespace std::chrono
 
 _LIBCPP_END_NAMESPACE_STD
 
+#ifndef _LIBCPP_CXX03_LANG
+_LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
+struct _FilesystemClock {
+#if !defined(_LIBCPP_HAS_NO_INT128)
+  typedef __int128_t rep;
+  typedef nano period;
+#else
+  typedef long long rep;
+  typedef nano period;
+#endif
+
+  typedef chrono::duration<rep, period> duration;
+  typedef chrono::time_point<_FilesystemClock> time_point;
+
+  static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;
+
+  _LIBCPP_FUNC_VIS static time_point now() noexcept;
+
+  _LIBCPP_INLINE_VISIBILITY
+  static time_t to_time_t(const time_point& __t) noexcept {
+      typedef chrono::duration<rep> __secs;
+      return time_t(
+          chrono::duration_cast<__secs>(__t.time_since_epoch()).count());
+  }
+
+  _LIBCPP_INLINE_VISIBILITY
+  static time_point from_time_t(time_t __t) noexcept {
+      typedef chrono::duration<rep> __secs;
+      return time_point(__secs(__t));
+  }
+};
+_LIBCPP_END_NAMESPACE_FILESYSTEM
+#endif // !_LIBCPP_CXX03_LANG
+
 _LIBCPP_POP_MACROS
 
 #endif  // _LIBCPP_CHRONO

include/deque

@@ -150,6 +150,11 @@ template <class T, class Allocator>
     void swap(deque<T,Allocator>& x, deque<T,Allocator>& y)
          noexcept(noexcept(x.swap(y)));
 
+template <class T, class Allocator, class U>
+    void erase(deque<T, Allocator>& c, const U& value);       // C++20
+template <class T, class Allocator, class Predicate>
+    void erase_if(deque<T, Allocator>& c, Predicate pred);    // C++20
+
 }  // std
 
 */
@@ -2604,6 +2609,7 @@ template <class _Tp, class _Allocator>
 void
 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() +
@@ -2927,6 +2933,19 @@ swap(deque<_Tp, _Allocator>& __x, deque<_Tp, _Allocator>& __y)
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Tp, class _Allocator, class _Up>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase(deque<_Tp, _Allocator>& __c, const _Up& __v)
+{ __c.erase(_VSTD::remove(__c.begin(), __c.end(), __v), __c.end()); }
+
+template <class _Tp, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(deque<_Tp, _Allocator>& __c, _Predicate __pred)
+{ __c.erase(_VSTD::remove_if(__c.begin(), __c.end(), __pred), __c.end()); }
+#endif
+
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

include/experimental/any

@@ -1,11 +1,21 @@
 // -*- C++ -*-
-//===------------------------------ any -----------------------------------===//
+//===------------------------------- any ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file is distributed under the University of Illinois Open Source
+// This file is dual licensed under the MIT and the University of Illinois Open
-// License. See LICENSE.TXT for details.
+// Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_ANY
+#define _LIBCPP_EXPERIMENTAL_ANY
 
-#error "<experimental/any> has been removed. Use <any> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/any> has been removed. Use <any> instead.")
+#else
+# warning "<experimental/any> has been removed. Use <any> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_ANY

include/experimental/chrono

@@ -1,11 +1,21 @@
 // -*- C++ -*-
-//===------------------------------ chrono ---------------------------------===//
+//===---------------------------- chrono ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file is distributed under the University of Illinois Open Source
+// This file is dual licensed under the MIT and the University of Illinois Open
-// License. See LICENSE.TXT for details.
+// Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_CHRONO
+#define _LIBCPP_EXPERIMENTAL_CHRONO
 
-#error "<experimental/chrono> has been removed. Use <chrono> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/chrono> has been removed. Use <chrono> instead.")
+#else
+# warning "<experimental/chrono> has been removed. Use <chrono> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_CHRONO

include/experimental/numeric

@@ -7,5 +7,15 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_NUMERIC
+#define _LIBCPP_EXPERIMENTAL_NUMERIC
 
-#error "<experimental/numeric> has been removed. Use <numeric> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/numeric> has been removed. Use <numeric> instead.")
+#else
+# warning "<experimental/numeric> has been removed. Use <numeric> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_NUMERIC

include/experimental/optional

@@ -7,5 +7,15 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_OPTIONAL
+#define _LIBCPP_EXPERIMENTAL_OPTIONAL
 
-#error "<experimental/optional> has been removed. Use <optional> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/optional> has been removed. Use <optional> instead.")
+#else
+# warning "<experimental/optional> has been removed. Use <optional> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_OPTIONAL

include/experimental/ratio

@@ -1,11 +1,21 @@
 // -*- C++ -*-
-//===------------------------------ ratio ---------------------------------===//
+//===----------------------------- ratio ----------------------------------===//
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file is distributed under the University of Illinois Open Source
+// This file is dual licensed under the MIT and the University of Illinois Open
-// License. See LICENSE.TXT for details.
+// Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_RATIO
+#define _LIBCPP_EXPERIMENTAL_RATIO
 
-#error "<experimental/ratio> has been removed. Use <ratio> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/ratio> has been removed. Use <ratio> instead.")
+#else
+# warning "<experimental/ratio> has been removed. Use <ratio> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_RATIO

include/experimental/string_view

@@ -3,9 +3,19 @@
 //
 //                     The LLVM Compiler Infrastructure
 //
-// This file is distributed under the University of Illinois Open Source
+// This file is dual licensed under the MIT and the University of Illinois Open
-// License. See LICENSE.TXT for details.
+// Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_STRING_VIEW
+#define _LIBCPP_EXPERIMENTAL_STRING_VIEW
 
-#error "<experimental/string_view> has been removed. Use <string_view> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/string_view> has been removed. Use <string_view> instead.")
+#else
+# warning "<experimental/string_view> has been removed. Use <string_view> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_STRING_VIEW

include/experimental/system_error

@@ -7,5 +7,15 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_SYSTEM_ERROR
+#define _LIBCPP_EXPERIMENTAL_SYSTEM_ERROR
 
-#error "<experimental/system_error> has been removed. Use <system_error> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/system_error> has been removed. Use <system_error> instead.")
+#else
+# warning "<experimental/system_error> has been removed. Use <system_error> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_SYSTEM_ERROR

include/experimental/tuple

@@ -7,5 +7,15 @@
 // Source Licenses. See LICENSE.TXT for details.
 //
 //===----------------------------------------------------------------------===//
+#ifndef _LIBCPP_EXPERIMENTAL_TUPLE
+#define _LIBCPP_EXPERIMENTAL_TUPLE
 
-#error "<experimental/tuple> has been removed. Use <tuple> instead."
+#include <__config>
+
+#ifdef _LIBCPP_WARNING
+_LIBCPP_WARNING("<experimental/tuple> has been removed. Use <tuple> instead.")
+#else
+# warning "<experimental/tuple> has been removed. Use <tuple> instead."
+#endif
+
+#endif // _LIBCPP_EXPERIMENTAL_TUPLE

include/filesystem

@@ -259,36 +259,6 @@ _LIBCPP_PUSH_MACROS
 
 _LIBCPP_BEGIN_NAMESPACE_FILESYSTEM
 
-struct _FilesystemClock {
-#if !defined(_LIBCPP_HAS_NO_INT128)
-  typedef __int128_t rep;
-  typedef nano period;
-#else
-  typedef long long rep;
-  typedef nano period;
-#endif
-
-  typedef chrono::duration<rep, period> duration;
-  typedef chrono::time_point<_FilesystemClock> time_point;
-
-  static _LIBCPP_CONSTEXPR_AFTER_CXX11 const bool is_steady = false;
-
-  _LIBCPP_FUNC_VIS static time_point now() noexcept;
-
-  _LIBCPP_INLINE_VISIBILITY
-  static time_t to_time_t(const time_point& __t) noexcept {
-    typedef chrono::duration<rep> __secs;
-    return time_t(
-        chrono::duration_cast<__secs>(__t.time_since_epoch()).count());
-  }
-
-  _LIBCPP_INLINE_VISIBILITY
-  static time_point from_time_t(time_t __t) noexcept {
-    typedef chrono::duration<rep> __secs;
-    return time_point(__secs(__t));
-  }
-};
-
 typedef chrono::time_point<_FilesystemClock> file_time_type;
 
 struct _LIBCPP_TYPE_VIS space_info {
@@ -1181,6 +1151,31 @@ public:
     return __is;
   }
 
+  friend _LIBCPP_INLINE_VISIBILITY bool operator==(const path& __lhs, const path& __rhs) noexcept {
+    return __lhs.compare(__rhs) == 0;
+  }
+  friend _LIBCPP_INLINE_VISIBILITY bool operator!=(const path& __lhs, const path& __rhs) noexcept {
+    return __lhs.compare(__rhs) != 0;
+  }
+  friend _LIBCPP_INLINE_VISIBILITY bool operator<(const path& __lhs, const path& __rhs) noexcept {
+    return __lhs.compare(__rhs) < 0;
+  }
+  friend _LIBCPP_INLINE_VISIBILITY bool operator<=(const path& __lhs, const path& __rhs) noexcept {
+    return __lhs.compare(__rhs) <= 0;
+  }
+  friend _LIBCPP_INLINE_VISIBILITY bool operator>(const path& __lhs, const path& __rhs) noexcept {
+    return __lhs.compare(__rhs) > 0;
+  }
+  friend _LIBCPP_INLINE_VISIBILITY bool operator>=(const path& __lhs, const path& __rhs) noexcept {
+    return __lhs.compare(__rhs) >= 0;
+  }
+
+  friend _LIBCPP_INLINE_VISIBILITY path operator/(const path& __lhs,
+                                                  const path& __rhs) {
+    path __result(__lhs);
+    __result /= __rhs;
+    return __result;
+  }
 private:
   inline _LIBCPP_INLINE_VISIBILITY path&
   __assign_view(__string_view const& __s) noexcept {
@@ -1197,43 +1192,6 @@ inline _LIBCPP_INLINE_VISIBILITY void swap(path& __lhs, path& __rhs) noexcept {
 _LIBCPP_FUNC_VIS
 size_t hash_value(const path& __p) noexcept;
 
-inline _LIBCPP_INLINE_VISIBILITY bool operator==(const path& __lhs,
-                                                 const path& __rhs) noexcept {
-  return __lhs.compare(__rhs) == 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY bool operator!=(const path& __lhs,
-                                                 const path& __rhs) noexcept {
-  return __lhs.compare(__rhs) != 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY bool operator<(const path& __lhs,
-                                                const path& __rhs) noexcept {
-  return __lhs.compare(__rhs) < 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY bool operator<=(const path& __lhs,
-                                                 const path& __rhs) noexcept {
-  return __lhs.compare(__rhs) <= 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY bool operator>(const path& __lhs,
-                                                const path& __rhs) noexcept {
-  return __lhs.compare(__rhs) > 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY bool operator>=(const path& __lhs,
-                                                 const path& __rhs) noexcept {
-  return __lhs.compare(__rhs) >= 0;
-}
-
-inline _LIBCPP_INLINE_VISIBILITY path operator/(const path& __lhs,
-                                                const path& __rhs) {
-  path __result(__lhs);
-  __result /= __rhs;
-  return __result;
-}
-
 template <class _Source>
 _LIBCPP_INLINE_VISIBILITY
     typename enable_if<__is_pathable<_Source>::value, path>::type

include/forward_list

@@ -167,6 +167,11 @@ template <class T, class Allocator>
     void swap(forward_list<T, Allocator>& x, forward_list<T, Allocator>& y)
          noexcept(noexcept(x.swap(y)));
 
+template <class T, class Allocator, class U>
+    void erase(forward_list<T, Allocator>& c, const U& value);       // C++20
+template <class T, class Allocator, class Predicate>
+    void erase_if(forward_list<T, Allocator>& c, Predicate pred);    // C++20
+
 }  // std
 
 */
@@ -1744,6 +1749,18 @@ swap(forward_list<_Tp, _Alloc>& __x, forward_list<_Tp, _Alloc>& __y)
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Tp, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(forward_list<_Tp, _Allocator>& __c, _Predicate __pred)
+{ __c.remove_if(__pred); }
+
+template <class _Tp, class _Allocator, class _Up>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase(forward_list<_Tp, _Allocator>& __c, const _Up& __v)
+{ _VSTD::erase_if(__c, [&](auto& __elem) { return __elem == __v; }); }
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

include/fstream

@@ -702,6 +702,7 @@ basic_filebuf<_CharT, _Traits>::close()
             __file_ = 0;
         else
             __rt = 0;
+        setbuf(0, 0);
     }
     return __rt;
 }

include/iosfwd

@@ -18,6 +18,12 @@ namespace std
 {
 
 template<class charT> struct char_traits;
+template<>            struct char_traits<char>;
+template<>            struct char_traits<char8_t>;  // C++20
+template<>            struct char_traits<char16_t>;
+template<>            struct char_traits<char32_t>;
+template<>            struct char_traits<wchar_t>;
+
 template<class T>     class allocator;
 
 class ios_base;
@@ -98,6 +104,14 @@ _LIBCPP_BEGIN_NAMESPACE_STD
 class _LIBCPP_TYPE_VIS ios_base;
 
 template<class _CharT>  struct _LIBCPP_TEMPLATE_VIS char_traits;
+template<> struct char_traits<char>;
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+template<> struct char_traits<char8_t>;
+#endif
+template<> struct char_traits<char16_t>;
+template<> struct char_traits<char32_t>;
+template<> struct char_traits<wchar_t>;
+
 template<class _Tp>     class _LIBCPP_TEMPLATE_VIS allocator;
 
 template <class _CharT, class _Traits = char_traits<_CharT> >
@@ -175,6 +189,9 @@ typedef basic_fstream<wchar_t>       wfstream;
 template <class _State>             class _LIBCPP_TEMPLATE_VIS fpos;
 typedef fpos<mbstate_t>    streampos;
 typedef fpos<mbstate_t>    wstreampos;
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+typedef fpos<mbstate_t>    u8streampos;
+#endif
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 typedef fpos<mbstate_t>    u16streampos;
 typedef fpos<mbstate_t>    u32streampos;

include/istream

@@ -160,6 +160,7 @@ template <class charT, class traits, class T>
 */
 
 #include <__config>
+#include <version>
 #include <ostream>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
@@ -1504,7 +1505,7 @@ operator>>(basic_istream<_CharT, _Traits>& __is, bitset<_Size>& __x)
     return __is;
 }
 
-#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#ifndef _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istream<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_istream<wchar_t>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_iostream<char>)

include/limits

@@ -119,6 +119,7 @@ template<> class numeric_limits<cv long double>;
 
 _LIBCPP_PUSH_MACROS
 #include <__undef_macros>
+#include <version>
 
 
 _LIBCPP_BEGIN_NAMESPACE_STD

include/list

@@ -169,6 +169,11 @@ template <class T, class Alloc>
     void swap(list<T,Alloc>& x, list<T,Alloc>& y)
          noexcept(noexcept(x.swap(y)));
 
+template <class T, class Allocator, class U>
+    void erase(list<T, Allocator>& c, const U& value);       // C++20
+template <class T, class Allocator, class Predicate>
+    void erase_if(list<T, Allocator>& c, Predicate pred);    // C++20
+
 }  // std
 
 */
@@ -2450,6 +2455,18 @@ swap(list<_Tp, _Alloc>& __x, list<_Tp, _Alloc>& __y)
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Tp, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(list<_Tp, _Allocator>& __c, _Predicate __pred)
+{ __c.remove_if(__pred); }
+
+template <class _Tp, class _Allocator, class _Up>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase(list<_Tp, _Allocator>& __c, const _Up& __v)
+{ _VSTD::erase_if(__c, [&](auto& __elem) { return __elem == __v; }); }
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

include/locale

@@ -187,6 +187,7 @@ template <class charT> class messages_byname;
 #include <streambuf>
 #include <iterator>
 #include <limits>
+#include <version>
 #ifndef __APPLE__
 #include <cstdarg>
 #endif

include/map

@@ -254,6 +254,10 @@ void
 swap(map<Key, T, Compare, Allocator>& x, map<Key, T, Compare, Allocator>& y)
     noexcept(noexcept(x.swap(y)));
 
+template <class Key, class T, class Compare, class Allocator, class Predicate>
+  void erase_if(map<Key, T, Compare, Allocator>& c, Predicate pred);  // C++20
+
+
 template <class Key, class T, class Compare = less<Key>,
           class Allocator = allocator<pair<const Key, T>>>
 class multimap
@@ -465,6 +469,9 @@ swap(multimap<Key, T, Compare, Allocator>& x,
      multimap<Key, T, Compare, Allocator>& y)
     noexcept(noexcept(x.swap(y)));
 
+template <class Key, class T, class Compare, class Allocator, class Predicate>
+  void erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);  // C++20
+
 }  // std
 
 */
@@ -486,7 +493,8 @@ swap(multimap<Key, T, Compare, Allocator>& x,
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Key, class _CP, class _Compare, bool _IsSmall>
+template <class _Key, class _CP, class _Compare,
+          bool = is_empty<_Compare>::value && !__libcpp_is_final<_Compare>::value>
 class __map_value_compare
     : private _Compare
 {
@@ -900,6 +908,7 @@ public:
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
 
+    static_assert(sizeof(__diagnose_non_const_comparator<_Key, _Compare>()), "");
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
@@ -1612,6 +1621,14 @@ swap(map<_Key, _Tp, _Compare, _Allocator>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Key, class _Tp, class _Compare, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(map<_Key, _Tp, _Compare, _Allocator>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
+
 template <class _Key, class _Tp, class _Compare = less<_Key>,
           class _Allocator = allocator<pair<const _Key, _Tp> > >
 class _LIBCPP_TEMPLATE_VIS multimap
@@ -1626,6 +1643,7 @@ public:
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
 
+    static_assert(sizeof(__diagnose_non_const_comparator<_Key, _Compare>()), "");
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
@@ -2148,6 +2166,13 @@ swap(multimap<_Key, _Tp, _Compare, _Allocator>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Key, class _Tp, class _Compare, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(multimap<_Key, _Tp, _Compare, _Allocator>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_MAP

include/memory

@@ -1460,29 +1460,21 @@ struct __has_select_on_container_copy_construction
 
 #else  // _LIBCPP_CXX03_LANG
 
-#ifndef _LIBCPP_HAS_NO_VARIADICS
+template <class _Alloc, class _Pointer, class _Tp, class = void>
+struct __has_construct : std::false_type {};
 
-template <class _Alloc, class _Pointer, class ..._Args>
+template <class _Alloc, class _Pointer, class _Tp>
-struct __has_construct
+struct __has_construct<_Alloc, _Pointer, _Tp, typename __void_t<
-    : false_type
+    decltype(_VSTD::declval<_Alloc>().construct(_VSTD::declval<_Pointer>(), _VSTD::declval<_Tp>()))
-{
+>::type> : std::true_type {};
-};
 
-#else  // _LIBCPP_HAS_NO_VARIADICS
+template <class _Alloc, class _Pointer, class = void>
-
+struct __has_destroy : false_type {};
-template <class _Alloc, class _Pointer, class _Args>
-struct __has_construct
-    : false_type
-{
-};
-
-#endif  // _LIBCPP_HAS_NO_VARIADICS
 
 template <class _Alloc, class _Pointer>
-struct __has_destroy
+struct __has_destroy<_Alloc, _Pointer, typename __void_t<
-    : false_type
+    decltype(_VSTD::declval<_Alloc>().destroy(_VSTD::declval<_Pointer>()))
-{
+>::type> : std::true_type {};
-};
 
 template <class _Alloc>
 struct __has_max_size
@@ -1510,6 +1502,12 @@ struct __alloc_traits_difference_type<_Alloc, _Ptr, true>
     typedef typename _Alloc::difference_type type;
 };
 
+template <class _Tp>
+struct __is_default_allocator : false_type {};
+
+template <class _Tp>
+struct __is_default_allocator<_VSTD::allocator<_Tp> > : true_type {};
+
 template <class _Alloc>
 struct _LIBCPP_TEMPLATE_VIS allocator_traits
 {
@@ -1571,9 +1569,10 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
             }
     template <class _Tp, class _A0>
         _LIBCPP_INLINE_VISIBILITY
-        static void construct(allocator_type&, _Tp* __p, const _A0& __a0)
+        static void construct(allocator_type& __a, _Tp* __p, const _A0& __a0)
             {
-                ::new ((void*)__p) _Tp(__a0);
+                __construct(__has_construct<allocator_type, _Tp*, const _A0&>(),
+                            __a, __p, __a0);
             }
     template <class _Tp, class _A0, class _A1>
         _LIBCPP_INLINE_VISIBILITY
@@ -1613,7 +1612,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
         void
         __construct_forward(allocator_type& __a, _Ptr __begin1, _Ptr __end1, _Ptr& __begin2)
         {
-            for (; __begin1 != __end1; ++__begin1, ++__begin2)
+            for (; __begin1 != __end1; ++__begin1, (void) ++__begin2)
                 construct(__a, _VSTD::__to_raw_pointer(__begin2), _VSTD::move_if_noexcept(*__begin1));
         }
 
@@ -1622,7 +1621,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
         static
         typename enable_if
         <
-            (is_same<allocator_type, allocator<_Tp> >::value
+            (__is_default_allocator<allocator_type>::value
                 || !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
              is_trivially_move_constructible<_Tp>::value,
             void
@@ -1647,23 +1646,25 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
                 construct(__a, _VSTD::__to_raw_pointer(__begin2), *__begin1);
         }
 
-    template <class _Tp>
+    template <class _SourceTp, class _DestTp,
+              class _RawSourceTp = typename remove_const<_SourceTp>::type,
+              class _RawDestTp = typename remove_const<_DestTp>::type>
         _LIBCPP_INLINE_VISIBILITY
         static
         typename enable_if
         <
-            (is_same<allocator_type, allocator<_Tp> >::value
+            is_trivially_move_constructible<_DestTp>::value &&
-                || !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
+            is_same<_RawSourceTp, _RawDestTp>::value &&
-             is_trivially_move_constructible<_Tp>::value,
+            (__is_default_allocator<allocator_type>::value ||
+             !__has_construct<allocator_type, _DestTp*, _SourceTp&>::value),
             void
         >::type
-        __construct_range_forward(allocator_type&, _Tp* __begin1, _Tp* __end1, _Tp*& __begin2)
+        __construct_range_forward(allocator_type&, _SourceTp* __begin1, _SourceTp* __end1, _DestTp*& __begin2)
         {
-            typedef typename remove_const<_Tp>::type _Vp;
             ptrdiff_t _Np = __end1 - __begin1;
             if (_Np > 0)
             {
-                _VSTD::memcpy(const_cast<_Vp*>(__begin2), __begin1, _Np * sizeof(_Tp));
+                _VSTD::memcpy(const_cast<_RawDestTp*>(__begin2), __begin1, _Np * sizeof(_DestTp));
                 __begin2 += _Np;
             }
         }
@@ -1686,7 +1687,7 @@ struct _LIBCPP_TEMPLATE_VIS allocator_traits
         static
         typename enable_if
         <
-            (is_same<allocator_type, allocator<_Tp> >::value
+            (__is_default_allocator<allocator_type>::value
                 || !__has_construct<allocator_type, _Tp*, _Tp>::value) &&
              is_trivially_move_constructible<_Tp>::value,
             void
@@ -1721,6 +1722,19 @@ private:
             {
                 ::new ((void*)__p) _Tp(_VSTD::forward<_Args>(__args)...);
             }
+#else  // _LIBCPP_HAS_NO_VARIADICS
+    template <class _Tp, class _A0>
+        _LIBCPP_INLINE_VISIBILITY
+        static void __construct(true_type, allocator_type& __a, _Tp* __p,
+                                const _A0& __a0)
+            {__a.construct(__p, __a0);}
+    template <class _Tp, class _A0>
+        _LIBCPP_INLINE_VISIBILITY
+        static void __construct(false_type, allocator_type&, _Tp* __p,
+                                const _A0& __a0)
+            {
+                ::new ((void*)__p) _Tp(__a0);
+            }
 #endif  // _LIBCPP_HAS_NO_VARIADICS
 
     template <class _Tp>

include/optional

@@ -105,8 +105,8 @@ namespace std {
 
     // 23.6.3.3, assignment
     optional &operator=(nullopt_t) noexcept;
-    optional &operator=(const optional &);
+    optional &operator=(const optional &);                // constexpr in C++20
-    optional &operator=(optional &&) noexcept(see below );
+    optional &operator=(optional &&) noexcept(see below); // constexpr in C++20
     template <class U = T> optional &operator=(U &&);
     template <class U> optional &operator=(const optional<U> &);
     template <class U> optional &operator=(optional<U> &&);

include/ostream

@@ -140,6 +140,7 @@ template <class charT, class traits, class T>
 #include <locale>
 #include <iterator>
 #include <bitset>
+#include <version>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #pragma GCC system_header
@@ -1092,7 +1093,7 @@ operator<<(basic_ostream<_CharT, _Traits>& __os, const bitset<_Size>& __x)
                          use_facet<ctype<_CharT> >(__os.getloc()).widen('1'));
 }
 
-#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#ifndef _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_ostream<wchar_t>)
 #endif

include/regex

@@ -996,6 +996,10 @@ public:
     static const char_class_type __regex_word = 0x8000;
 #elif defined(__mips__) && defined(__GLIBC__)
     static const char_class_type __regex_word = static_cast<char_class_type>(_ISbit(15));
+#elif defined(__NetBSD__)
+    // NetBSD defines classes up to 0x2000
+    // see sys/ctype_bits.h, _CTYPE_Q
+    static const char_class_type __regex_word = 0x8000;
 #else
     static const char_class_type __regex_word = 0x80;
 #endif

include/set

@@ -216,6 +216,9 @@ void
 swap(set<Key, Compare, Allocator>& x, set<Key, Compare, Allocator>& y)
     noexcept(noexcept(x.swap(y)));
 
+template <class Key, class Compare, class Allocator, class Predicate>
+  void erase_if(set<Key, Compare, Allocator>& c, Predicate pred);  // C++20
+
 template <class Key, class Compare = less<Key>,
           class Allocator = allocator<Key>>
 class multiset
@@ -412,6 +415,9 @@ void
 swap(multiset<Key, Compare, Allocator>& x, multiset<Key, Compare, Allocator>& y)
     noexcept(noexcept(x.swap(y)));
 
+template <class Key, class Compare, class Allocator, class Predicate>
+  void erase_if(multiset<Key, Compare, Allocator>& c, Predicate pred);  // C++20
+
 }  // std
 
 */
@@ -445,6 +451,7 @@ public:
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
 
+    static_assert(sizeof(__diagnose_non_const_comparator<_Key, _Compare>()), "");
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
@@ -911,6 +918,13 @@ swap(set<_Key, _Compare, _Allocator>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Key, class _Compare, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(set<_Key, _Compare, _Allocator>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 template <class _Key, class _Compare = less<_Key>,
           class _Allocator = allocator<_Key> >
 class _LIBCPP_TEMPLATE_VIS multiset
@@ -925,6 +939,7 @@ public:
     typedef value_type&                              reference;
     typedef const value_type&                        const_reference;
 
+    static_assert(sizeof(__diagnose_non_const_comparator<_Key, _Compare>()), "");
     static_assert((is_same<typename allocator_type::value_type, value_type>::value),
                   "Allocator::value_type must be same type as value_type");
 
@@ -1390,6 +1405,13 @@ swap(multiset<_Key, _Compare, _Allocator>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Key, class _Compare, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(multiset<_Key, _Compare, _Allocator>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 #endif  // _LIBCPP_SET

include/streambuf

@@ -486,7 +486,7 @@ basic_streambuf<_CharT, _Traits>::overflow(int_type)
     return traits_type::eof();
 }
 
-#ifndef _LIBCPP_AVAILABILITY_NO_STREAMS_EXTERN_TEMPLATE
+#ifndef _LIBCPP_DO_NOT_ASSUME_STREAMS_EXPLICIT_INSTANTIATION_IN_DYLIB
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_streambuf<char>)
 _LIBCPP_EXTERN_TEMPLATE(class _LIBCPP_EXTERN_TEMPLATE_TYPE_VIS basic_streambuf<wchar_t>)
 

include/string

@@ -437,6 +437,11 @@ template<class charT, class traits, class Allocator>
 basic_istream<charT, traits>&
 getline(basic_istream<charT, traits>& is, basic_string<charT, traits, Allocator>& str);
 
+template<class charT, class traits, class Allocator, class U>
+void erase(basic_string<charT, traits, Allocator>& c, const U& value); // C++20
+template<class charT, class traits, class Allocator, class Predicate>
+void erase_if(basic_string<charT, traits, Allocator>& c, Predicate pred); // C++20
+
 typedef basic_string<char>    string;
 typedef basic_string<wchar_t> wstring;
 typedef basic_string<char16_t> u16string;
@@ -4170,11 +4175,13 @@ swap(basic_string<_CharT, _Traits, _Allocator>& __lhs,
     __lhs.swap(__rhs);
 }
 
-#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+typedef basic_string<char8_t> u8string;
+#endif
 
+#ifndef _LIBCPP_HAS_NO_UNICODE_CHARS
 typedef basic_string<char16_t> u16string;
 typedef basic_string<char32_t> u32string;
-
 #endif  // _LIBCPP_HAS_NO_UNICODE_CHARS
 
 _LIBCPP_FUNC_VIS int                stoi  (const string& __str, size_t* __idx = 0, int __base = 10);
@@ -4274,6 +4281,18 @@ getline(basic_istream<_CharT, _Traits>&& __is,
 
 #endif  // _LIBCPP_CXX03_LANG
 
+#if _LIBCPP_STD_VER > 17
+template<class _CharT, class _Traits, class _Allocator, class _Up>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase(basic_string<_CharT, _Traits, _Allocator>& __str, const _Up& __v)
+{ __str.erase(_VSTD::remove(__str.begin(), __str.end(), __v), __str.end()); }
+
+template<class _CharT, class _Traits, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(basic_string<_CharT, _Traits, _Allocator>& __str, _Predicate __pred)
+{ __str.erase(_VSTD::remove_if(__str.begin(), __str.end(), __pred), __str.end()); }
+#endif
+
 #if _LIBCPP_DEBUG_LEVEL >= 2
 
 template<class _CharT, class _Traits, class _Allocator>
@@ -4331,6 +4350,14 @@ inline namespace literals
         return basic_string<wchar_t> (__str, __len);
     }
 
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+    inline _LIBCPP_INLINE_VISIBILITY
+    basic_string<char8_t> operator "" s(const char8_t *__str, size_t __len) _NOEXCEPT
+    {
+        return basic_string<char8_t> (__str, __len);
+    }
+#endif
+
     inline _LIBCPP_INLINE_VISIBILITY
     basic_string<char16_t> operator "" s( const char16_t *__str, size_t __len )
     {

include/string_view

@@ -769,6 +769,9 @@ bool operator>=(typename common_type<basic_string_view<_CharT, _Traits> >::type
 }
 
 typedef basic_string_view<char>     string_view;
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+typedef basic_string_view<char8_t>  u8string_view;
+#endif
 typedef basic_string_view<char16_t> u16string_view;
 typedef basic_string_view<char32_t> u32string_view;
 typedef basic_string_view<wchar_t>  wstring_view;
@@ -802,6 +805,14 @@ inline namespace literals
         return basic_string_view<wchar_t> (__str, __len);
     }
 
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+    inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
+    basic_string_view<char8_t> operator "" sv(const char8_t *__str, size_t __len) _NOEXCEPT
+    {
+        return basic_string_view<char8_t> (__str, __len);
+    }
+#endif
+
     inline _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
     basic_string_view<char16_t> operator "" sv(const char16_t *__str, size_t __len) _NOEXCEPT
     {

include/tuple

@@ -84,8 +84,8 @@ template <class T, class Tuple>
   constexpr T make_from_tuple(Tuple&& t); // C++17
 
 // 20.4.1.4, tuple helper classes:
-template <class T> class tuple_size; // undefined
+template <class T> struct tuple_size; // undefined
-template <class... T> class tuple_size<tuple<T...>>;
+template <class... T> struct tuple_size<tuple<T...>>;
 template <class T>
  inline constexpr size_t tuple_size_v = tuple_size<T>::value; // C++17
 template <size_t I, class T> class tuple_element; // undefined

include/type_traits

@@ -709,7 +709,7 @@ template <>          struct __libcpp_is_integral<char>               : public tr
 template <>          struct __libcpp_is_integral<signed char>        : public true_type {};
 template <>          struct __libcpp_is_integral<unsigned char>      : public true_type {};
 template <>          struct __libcpp_is_integral<wchar_t>            : public true_type {};
-#if _LIBCPP_STD_VER > 17 && defined(__cpp_char8_t)
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
 template <>          struct __libcpp_is_integral<char8_t>            : public true_type {};
 #endif
 #ifndef _LIBCPP_HAS_NO_UNICODE_CHARS

include/typeinfo

@@ -73,12 +73,8 @@ public:
 #include <vcruntime_typeinfo.h>
 #else
 
-#if !defined(_LIBCPP_ABI_MICROSOFT)
+#if defined(_LIBCPP_NONUNIQUE_RTTI_BIT) && !defined(_LIBCPP_ABI_MICROSOFT)
-#if defined(_LIBCPP_NONUNIQUE_RTTI_BIT)
+#   define _LIBCPP_HAS_NONUNIQUE_TYPEINFO
-#define _LIBCPP_HAS_NONUNIQUE_TYPEINFO
-#else
-#define _LIBCPP_HAS_UNIQUE_TYPEINFO
-#endif
 #endif
 
 namespace std  // purposefully not using versioning namespace

include/unordered_map

@@ -384,6 +384,12 @@ template <class Key, class T, class Hash, class Pred, class Alloc>
               unordered_multimap<Key, T, Hash, Pred, Alloc>& y)
               noexcept(noexcept(x.swap(y)));
 
+template <class K, class T, class H, class P, class A, class Predicate>
+    void erase_if(unordered_set<K, T, H, P, A>& c, Predicate pred);       // C++20
+
+template <class K, class T, class H, class P, class A, class Predicate>
+    void erase_if(unordered_multiset<K, T, H, P, A>& c, Predicate pred);  // C++20
+
 template <class Key, class T, class Hash, class Pred, class Alloc>
     bool
     operator==(const unordered_multimap<Key, T, Hash, Pred, Alloc>& x,
@@ -414,7 +420,8 @@ template <class Key, class T, class Hash, class Pred, class Alloc>
 
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-template <class _Key, class _Cp, class _Hash, bool _IsEmpty>
+template <class _Key, class _Cp, class _Hash,
+          bool = is_empty<_Hash>::value && !__libcpp_is_final<_Hash>::value>
 class __unordered_map_hasher
     : private _Hash
 {
@@ -482,7 +489,8 @@ swap(__unordered_map_hasher<_Key, _Cp, _Hash, __b>& __x,
     __x.swap(__y);
 }
 
-template <class _Key, class _Cp, class _Pred, bool _IsEmpty>
+template <class _Key, class _Cp, class _Pred,
+          bool = is_empty<_Pred>::value && !__libcpp_is_final<_Pred>::value>
 class __unordered_map_equal
     : private _Pred
 {
@@ -845,6 +853,7 @@ public:
     typedef const value_type&                              const_reference;
     static_assert((is_same<value_type, typename allocator_type::value_type>::value),
                   "Invalid allocator::value_type");
+    static_assert(sizeof(__diagnose_unordered_container_requirements<_Key, _Hash, _Pred>(0)), "");
 
 private:
     typedef __hash_value_type<key_type, mapped_type>                 __value_type;
@@ -1623,6 +1632,13 @@ swap(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 bool
 operator==(const unordered_map<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
@@ -1667,6 +1683,7 @@ public:
     typedef const value_type&                              const_reference;
     static_assert((is_same<value_type, typename allocator_type::value_type>::value),
                   "Invalid allocator::value_type");
+    static_assert(sizeof(__diagnose_unordered_container_requirements<_Key, _Hash, _Pred>(0)), "");
 
 private:
     typedef __hash_value_type<key_type, mapped_type>                 __value_type;
@@ -2239,6 +2256,13 @@ swap(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 template <class _Key, class _Tp, class _Hash, class _Pred, class _Alloc>
 bool
 operator==(const unordered_multimap<_Key, _Tp, _Hash, _Pred, _Alloc>& __x,

include/unordered_set

@@ -339,6 +339,13 @@ template <class Value, class Hash, class Pred, class Alloc>
               unordered_multiset<Value, Hash, Pred, Alloc>& y)
               noexcept(noexcept(x.swap(y)));
 
+template <class K, class T, class H, class P, class A, class Predicate>
+    void erase_if(unordered_set<K, T, H, P, A>& c, Predicate pred);       // C++20
+
+template <class K, class T, class H, class P, class A, class Predicate>
+    void erase_if(unordered_multiset<K, T, H, P, A>& c, Predicate pred);  // C++20
+
+
 template <class Value, class Hash, class Pred, class Alloc>
     bool
     operator==(const unordered_multiset<Value, Hash, Pred, Alloc>& x,
@@ -384,6 +391,7 @@ public:
     typedef const value_type&                                          const_reference;
     static_assert((is_same<value_type, typename allocator_type::value_type>::value),
                   "Invalid allocator::value_type");
+    static_assert(sizeof(__diagnose_unordered_container_requirements<_Value, _Hash, _Pred>(0)), "");
 
 private:
     typedef __hash_table<value_type, hasher, key_equal, allocator_type> __table;
@@ -933,6 +941,13 @@ swap(unordered_set<_Value, _Hash, _Pred, _Alloc>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Value, class _Hash, class _Pred, class _Alloc, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(unordered_set<_Value, _Hash, _Pred, _Alloc>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 bool
 operator==(const unordered_set<_Value, _Hash, _Pred, _Alloc>& __x,
@@ -976,6 +991,7 @@ public:
     typedef const value_type&                                          const_reference;
     static_assert((is_same<value_type, typename allocator_type::value_type>::value),
                   "Invalid allocator::value_type");
+    static_assert(sizeof(__diagnose_unordered_container_requirements<_Value, _Hash, _Pred>(0)), "");
 
 private:
     typedef __hash_table<value_type, hasher, key_equal, allocator_type> __table;
@@ -1495,6 +1511,13 @@ swap(unordered_multiset<_Value, _Hash, _Pred, _Alloc>& __x,
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Value, class _Hash, class _Pred, class _Alloc, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(unordered_multiset<_Value, _Hash, _Pred, _Alloc>& __c, _Predicate __pred)
+{ __libcpp_erase_if_container(__c, __pred); }
+#endif
+
 template <class _Value, class _Hash, class _Pred, class _Alloc>
 bool
 operator==(const unordered_multiset<_Value, _Hash, _Pred, _Alloc>& __x,

include/utility

@@ -103,7 +103,7 @@ swap(pair<T1, T2>& x, pair<T1, T2>& y) noexcept(noexcept(x.swap(y)));
 struct piecewise_construct_t { };
 inline constexpr piecewise_construct_t piecewise_construct = piecewise_construct_t();
 
-template <class T> class tuple_size;
+template <class T> struct tuple_size;
 template <size_t I, class T> class tuple_element;
 
 template <class T1, class T2> struct tuple_size<pair<T1, T2> >;
@@ -409,13 +409,17 @@ struct _LIBCPP_TEMPLATE_VIS pair
             _CheckArgsDep<_Dummy>::template __enable_default<_T1, _T2>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR
-    pair() : first(), second() {}
+    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>::template __enable_explicit<_T1 const&, _T2 const&>()
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(_T1 const& __t1, _T2 const& __t2)
+        _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
+                   is_nothrow_copy_constructible<second_type>::value)
         : first(__t1), second(__t2) {}
 
     template<bool _Dummy = true, _EnableB<
@@ -423,6 +427,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(_T1 const& __t1, _T2 const& __t2)
+        _NOEXCEPT_(is_nothrow_copy_constructible<first_type>::value &&
+                   is_nothrow_copy_constructible<second_type>::value)
         : first(__t1), second(__t2) {}
 
     template<class _U1, class _U2, _EnableB<
@@ -430,6 +436,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(_U1&& __u1, _U2&& __u2)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1>::value &&
+                    is_nothrow_constructible<second_type, _U2>::value))
         : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
 
     template<class _U1, class _U2, _EnableB<
@@ -437,6 +445,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(_U1&& __u1, _U2&& __u2)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1>::value &&
+                    is_nothrow_constructible<second_type, _U2>::value))
         : first(_VSTD::forward<_U1>(__u1)), second(_VSTD::forward<_U2>(__u2)) {}
 
     template<class _U1, class _U2, _EnableB<
@@ -444,6 +454,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(pair<_U1, _U2> const& __p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1 const&>::value &&
+                    is_nothrow_constructible<second_type, _U2 const&>::value))
         : first(__p.first), second(__p.second) {}
 
     template<class _U1, class _U2, _EnableB<
@@ -451,6 +463,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(pair<_U1, _U2> const& __p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1 const&>::value &&
+                    is_nothrow_constructible<second_type, _U2 const&>::value))
         : first(__p.first), second(__p.second) {}
 
     template<class _U1, class _U2, _EnableB<
@@ -458,6 +472,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     explicit pair(pair<_U1, _U2>&&__p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1&&>::value &&
+                    is_nothrow_constructible<second_type, _U2&&>::value))
         : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
 
     template<class _U1, class _U2, _EnableB<
@@ -465,6 +481,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     > = false>
     _LIBCPP_INLINE_VISIBILITY _LIBCPP_CONSTEXPR_AFTER_CXX11
     pair(pair<_U1, _U2>&& __p)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _U1&&>::value &&
+                    is_nothrow_constructible<second_type, _U2&&>::value))
         : first(_VSTD::forward<_U1>(__p.first)), second(_VSTD::forward<_U2>(__p.second)) {}
 
     template<class _Tuple, _EnableB<
@@ -487,6 +505,8 @@ struct _LIBCPP_TEMPLATE_VIS pair
     _LIBCPP_INLINE_VISIBILITY
     pair(piecewise_construct_t __pc,
          tuple<_Args1...> __first_args, tuple<_Args2...> __second_args)
+        _NOEXCEPT_((is_nothrow_constructible<first_type, _Args1...>::value &&
+                    is_nothrow_constructible<second_type, _Args2...>::value))
         : pair(__pc, __first_args, __second_args,
                 typename __make_tuple_indices<sizeof...(_Args1)>::type(),
                 typename __make_tuple_indices<sizeof...(_Args2) >::type()) {}
@@ -663,7 +683,7 @@ make_pair(_T1 __x, _T2 __y)
 #endif  // _LIBCPP_CXX03_LANG
 
 template <class _T1, class _T2>
-  class _LIBCPP_TEMPLATE_VIS tuple_size<pair<_T1, _T2> >
+  struct _LIBCPP_TEMPLATE_VIS tuple_size<pair<_T1, _T2> >
     : public integral_constant<size_t, 2> {};
 
 template <size_t _Ip, class _T1, class _T2>

include/variant

@@ -23,8 +23,8 @@ namespace std {
 
     // 20.7.2.1, constructors
     constexpr variant() noexcept(see below);
-    variant(const variant&);
+    variant(const variant&);                // constexpr in C++20
-    variant(variant&&) noexcept(see below);
+    variant(variant&&) noexcept(see below); // constexpr in C++20
 
     template <class T> constexpr variant(T&&) noexcept(see below);
 
@@ -46,8 +46,8 @@ namespace std {
     ~variant();
 
     // 20.7.2.3, assignment
-    variant& operator=(const variant&);
+    variant& operator=(const variant&);                // constexpr in C++20
-    variant& operator=(variant&&) noexcept(see below);
+    variant& operator=(variant&&) noexcept(see below); // constexpr in C++20
 
     template <class T> variant& operator=(T&&) noexcept(see below);
 
@@ -1066,7 +1066,7 @@ public:
 #ifndef _LIBCPP_NO_EXCEPTIONS
       // EXTENSION: When the move construction of `__lhs` into `__rhs` throws
       // and `__tmp` is nothrow move constructible then we move `__tmp` back
-      // into `__rhs` and provide the strong exception safety guarentee.
+      // into `__rhs` and provide the strong exception safety guarantee.
       try {
         this->__generic_construct(*__rhs, _VSTD::move(*__lhs));
       } catch (...) {

include/vector

@@ -261,6 +261,11 @@ template <class T, class Allocator>
 void swap(vector<T,Allocator>& x, vector<T,Allocator>& y)
     noexcept(noexcept(x.swap(y)));
 
+template <class T, class Allocator, class U>
+    void erase(vector<T, Allocator>& c, const U& value);       // C++20
+template <class T, class Allocator, class Predicate>
+    void erase_if(vector<T, Allocator>& c, Predicate pred);    // C++20
+
 }  // std
 
 */
@@ -3408,6 +3413,18 @@ swap(vector<_Tp, _Allocator>& __x, vector<_Tp, _Allocator>& __y)
     __x.swap(__y);
 }
 
+#if _LIBCPP_STD_VER > 17
+template <class _Tp, class _Allocator, class _Up>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase(vector<_Tp, _Allocator>& __c, const _Up& __v)
+{ __c.erase(_VSTD::remove(__c.begin(), __c.end(), __v), __c.end()); }
+
+template <class _Tp, class _Allocator, class _Predicate>
+inline _LIBCPP_INLINE_VISIBILITY
+void erase_if(vector<_Tp, _Allocator>& __c, _Predicate __pred)
+{ __c.erase(_VSTD::remove_if(__c.begin(), __c.end(), __pred), __c.end()); }
+#endif
+
 _LIBCPP_END_NAMESPACE_STD
 
 _LIBCPP_POP_MACROS

include/version

@@ -30,6 +30,8 @@ __cpp_lib_bit_cast                          201806L <bit>
 __cpp_lib_bool_constant                     201505L <type_traits>
 __cpp_lib_boyer_moore_searcher              201603L <functional>
 __cpp_lib_byte                              201603L <cstddef>
+__cpp_lib_char8_t                           201811L <atomic> <filesystem> <istream> <limits>
+                                                    <locale> <ostream> <string> <string_view>
 __cpp_lib_chrono                            201611L <chrono>
 __cpp_lib_chrono_udls                       201304L <chrono>
 __cpp_lib_clamp                             201603L <algorithm>
@@ -37,6 +39,9 @@ __cpp_lib_complex_udls                      201309L <complex>
 __cpp_lib_concepts                          201806L <concepts>
 __cpp_lib_constexpr_swap_algorithms         201806L <algorithm>
 __cpp_lib_enable_shared_from_this           201603L <memory>
+__cpp_lib_erase_if                          201811L <string> <deque> <forward_list> <list> 
+                                                    <vector> <map> <set> <unordered_map> 
+                                                    <unordered_set>
 __cpp_lib_exchange_function                 201304L <utility>
 __cpp_lib_execution                         201603L <execution>
 __cpp_lib_filesystem                        201703L <filesystem>
@@ -114,6 +119,10 @@ __cpp_lib_void_t                            201411L <type_traits>
 #endif
 
 #if _LIBCPP_STD_VER > 17
+#ifndef _LIBCPP_NO_HAS_CHAR8_T
+# define __cpp_lib_char8_t                              201811L
+#endif
+#define  __cpp_lib_erase_if                             201811L
 #endif
 
 #endif  // _LIBCPP_VERSIONH

lib/CMakeLists.txt

@@ -175,13 +175,16 @@ endif()
 split_list(LIBCXX_COMPILE_FLAGS)
 split_list(LIBCXX_LINK_FLAGS)
 
-# Add an object library that contains the compiled source files.
+macro(cxx_object_library name)
-add_library(cxx_objects OBJECT ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
+  cmake_parse_arguments(ARGS "" "" "DEFINES;FLAGS" ${ARGN})
-if(LIBCXX_CXX_ABI_HEADER_TARGET)
+
-  add_dependencies(cxx_objects ${LIBCXX_CXX_ABI_HEADER_TARGET})
+  # Add an object library that contains the compiled source files.
-endif()
+  add_library(${name} OBJECT ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
-if(WIN32 AND NOT MINGW)
+  if(LIBCXX_CXX_ABI_HEADER_TARGET)
-  target_compile_definitions(cxx_objects
+    add_dependencies(${name} ${LIBCXX_CXX_ABI_HEADER_TARGET})
+  endif()
+  if(WIN32 AND NOT MINGW)
+    target_compile_definitions(${name}
                                PRIVATE
                                  # Ignore the -MSC_VER mismatch, as we may build
                                  # with a different compatibility version.
@@ -201,16 +204,40 @@ if(WIN32 AND NOT MINGW)
                                  # Use the ISO conforming behaviour for conversion
                                  # in printf, scanf.
                                  _CRT_STDIO_ISO_WIDE_SPECIFIERS)
-endif()
+  endif()
 
-set_target_properties(cxx_objects
+  if(ARGS_DEFINES)
+    target_compile_definitions(${name} PRIVATE ${ARGS_DEFINES})
+  endif()
+
+  set_target_properties(${name}
     PROPERTIES
-    COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
+      COMPILE_FLAGS ${LIBCXX_COMPILE_FLAGS}
-)
+  )
+
+  if(ARGS_FLAGS)
+    target_compile_options(${name} PRIVATE ${ARGS_FLAGS})
+  endif()
+endmacro()
+
+if(LIBCXX_HERMETIC_STATIC_LIBRARY)
+  append_flags_if_supported(CXX_STATIC_OBJECTS_FLAGS -fvisibility=hidden)
+  append_flags_if_supported(CXX_STATIC_OBJECTS_FLAGS -fvisibility-global-new-delete-hidden)
+  cxx_object_library(cxx_static_objects
+    DEFINES _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS
+    FLAGS ${CXX_STATIC_OBJECTS_FLAGS})
+  cxx_object_library(cxx_shared_objects)
+  set(cxx_static_sources $<TARGET_OBJECTS:cxx_static_objects>)
+  set(cxx_shared_sources $<TARGET_OBJECTS:cxx_shared_objects>)
+else()
+  cxx_object_library(cxx_objects)
+  set(cxx_static_sources $<TARGET_OBJECTS:cxx_objects>)
+  set(cxx_shared_sources $<TARGET_OBJECTS:cxx_objects>)
+endif()
 
 # Build the shared library.
 if (LIBCXX_ENABLE_SHARED)
-  add_library(cxx_shared SHARED $<TARGET_OBJECTS:cxx_objects>)
+  add_library(cxx_shared SHARED ${cxx_shared_sources})
   if(COMMAND llvm_setup_rpath)
     llvm_setup_rpath(cxx_shared)
   endif()
@@ -237,7 +264,7 @@ endif()
 
 # Build the static library.
 if (LIBCXX_ENABLE_STATIC)
-  add_library(cxx_static STATIC $<TARGET_OBJECTS:cxx_objects>)
+  add_library(cxx_static STATIC ${cxx_static_sources})
   target_link_libraries(cxx_static ${LIBCXX_LIBRARIES})
   set(CMAKE_STATIC_LIBRARY_PREFIX "lib")
   set_target_properties(cxx_static

src/filesystem/operations.cpp

@@ -206,8 +206,20 @@ public:
     return *this;
   }
 
+  bool atEnd() const noexcept {
+    return State == PS_AtEnd;
+  }
+
+  bool inRootDir() const noexcept {
+    return State == PS_InRootDir;
+  }
+
+  bool inRootName() const noexcept {
+    return State == PS_InRootName;
+  }
+
   bool inRootPath() const noexcept {
-    return State == PS_InRootDir || State == PS_InRootName;
+    return inRootName() || inRootDir();
   }
 
 private:
@@ -1294,7 +1306,19 @@ string_view_t path::__root_path_raw() const {
   return {};
 }
 
+static bool ConsumeRootName(PathParser *PP) {
+  static_assert(PathParser::PS_BeforeBegin == 1 &&
+      PathParser::PS_InRootName == 2,
+      "Values for enums are incorrect");
+  while (PP->State <= PathParser::PS_InRootName)
+    ++(*PP);
+  return PP->State == PathParser::PS_AtEnd;
+}
+
 static bool ConsumeRootDir(PathParser* PP) {
+  static_assert(PathParser::PS_BeforeBegin == 1 &&
+                PathParser::PS_InRootName == 2 &&
+                PathParser::PS_InRootDir == 3, "Values for enums are incorrect");
   while (PP->State <= PathParser::PS_InRootDir)
     ++(*PP);
   return PP->State == PathParser::PS_AtEnd;
@@ -1454,7 +1478,7 @@ static int DetermineLexicalElementCount(PathParser PP) {
     auto Elem = *PP;
     if (Elem == "..")
       --Count;
-    else if (Elem != ".")
+    else if (Elem != "." && Elem != "")
       ++Count;
   }
   return Count;
@@ -1468,8 +1492,7 @@ path path::lexically_relative(const path& base) const {
       return PP.State != PPBase.State &&
              (PP.inRootPath() || PPBase.inRootPath());
     };
-    if (PP.State == PathParser::PS_InRootName &&
+    if (PP.inRootName() && PPBase.inRootName()) {
-        PPBase.State == PathParser::PS_InRootName) {
       if (*PP != *PPBase)
         return {};
     } else if (CheckIterMismatchAtBase())
@@ -1501,6 +1524,10 @@ path path::lexically_relative(const path& base) const {
   if (ElemCount < 0)
     return {};
 
+  // if n == 0 and (a == end() || a->empty()), returns path("."); otherwise
+  if (ElemCount == 0 && (PP.atEnd() || *PP == ""))
+    return ".";
+
   // return a path constructed with 'n' dot-dot elements, followed by the the
   // elements of '*this' after the mismatch.
   path Result;
@@ -1514,21 +1541,68 @@ path path::lexically_relative(const path& base) const {
 
 ////////////////////////////////////////////////////////////////////////////
 // path.comparisons
-int path::__compare(string_view_t __s) const {
+static int CompareRootName(PathParser *LHS, PathParser *RHS) {
-  auto PP = PathParser::CreateBegin(__pn_);
+  if (!LHS->inRootName() && !RHS->inRootName())
-  auto PP2 = PathParser::CreateBegin(__s);
-  while (PP && PP2) {
-    int res = (*PP).compare(*PP2);
-    if (res != 0)
-      return res;
-    ++PP;
-    ++PP2;
-  }
-  if (PP.State == PP2.State && !PP)
     return 0;
-  if (!PP)
+
+  auto GetRootName = [](PathParser *Parser) -> string_view_t {
+    return Parser->inRootName() ? **Parser : "";
+  };
+  int res = GetRootName(LHS).compare(GetRootName(RHS));
+  ConsumeRootName(LHS);
+  ConsumeRootName(RHS);
+  return res;
+}
+
+static int CompareRootDir(PathParser *LHS, PathParser *RHS) {
+  if (!LHS->inRootDir() && RHS->inRootDir())
     return -1;
+  else if (LHS->inRootDir() && !RHS->inRootDir())
     return 1;
+  else {
+    ConsumeRootDir(LHS);
+    ConsumeRootDir(RHS);
+    return 0;
+  }
+}
+
+static int CompareRelative(PathParser *LHSPtr, PathParser *RHSPtr) {
+  auto &LHS = *LHSPtr;
+  auto &RHS = *RHSPtr;
+  
+  int res;
+  while (LHS && RHS) {
+    if ((res = (*LHS).compare(*RHS)) != 0)
+      return res;
+    ++LHS;
+    ++RHS;
+  }
+  return 0;
+}
+
+static int CompareEndState(PathParser *LHS, PathParser *RHS) {
+  if (LHS->atEnd() && !RHS->atEnd())
+    return -1;
+  else if (!LHS->atEnd() && RHS->atEnd())
+    return 1;
+  return 0;
+}
+
+int path::__compare(string_view_t __s) const {
+  auto LHS = PathParser::CreateBegin(__pn_);
+  auto RHS = PathParser::CreateBegin(__s);
+  int res;
+
+  if ((res = CompareRootName(&LHS, &RHS)) != 0)
+    return res;
+
+  if ((res = CompareRootDir(&LHS, &RHS)) != 0)
+    return res;
+
+  if ((res = CompareRelative(&LHS, &RHS)) != 0)
+    return res;
+
+  return CompareEndState(&LHS, &RHS);
 }
 
 ////////////////////////////////////////////////////////////////////////////

test/libcxx/algorithms/half_positive.pass.cpp

@@ -0,0 +1,56 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <algorithm>
+
+// __half_positive divides an integer number by 2 as unsigned number for known types.
+// It can be an important optimization for lower bound, for example.
+
+#include <algorithm>
+#include <cassert>
+#include <limits>
+#include <type_traits>
+
+#include "test_macros.h"
+#include "user_defined_integral.hpp"
+
+namespace {
+
+template <class IntType, class UnderlyingType = IntType>
+TEST_CONSTEXPR bool test(IntType max_v = IntType(std::numeric_limits<UnderlyingType>::max())) {
+    return std::__half_positive(max_v) == max_v / 2;
+}
+
+}  // namespace
+
+int main()
+{
+    {
+        assert(test<char>());
+        assert(test<int>());
+        assert(test<long>());
+        assert((test<UserDefinedIntegral<int>, int>()));
+        assert(test<size_t>());
+#if !defined(_LIBCPP_HAS_NO_INT128)
+        assert(test<__int128_t>());
+#endif  // !defined(_LIBCPP_HAS_NO_INT128)
+    }
+
+#if TEST_STD_VER >= 11
+    {
+        static_assert(test<char>(), "");
+        static_assert(test<int>(), "");
+        static_assert(test<long>(), "");
+        static_assert(test<size_t>(), "");
+#if !defined(_LIBCPP_HAS_NO_INT128)
+        static_assert(test<__int128_t>(), "");
+#endif  // !defined(_LIBCPP_HAS_NO_INT128)
+    }
+#endif // TEST_STD_VER >= 11
+}

test/libcxx/containers/associative/non_const_comparator.fail.cpp

@@ -27,7 +27,8 @@ int main() {
   static_assert(!std::__invokable<BadCompare const&, int const&, int const&>::value, "");
   static_assert(std::__invokable<BadCompare&, int const&, int const&>::value, "");
 
-  // expected-warning@__tree:* 4 {{the specified comparator type does not provide a const call operator}}
+  // expected-warning@set:* 2 {{the specified comparator type does not provide a const call operator}}
+  // expected-warning@map:* 2 {{the specified comparator type does not provide a const call operator}}
   {
     using C = std::set<int, BadCompare>;
     C s;

test/libcxx/containers/sequences/deque/pop_back_empty.pass.cpp

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <deque>
+
+// pop_back() more than the number of elements in a deque
+
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+
+#include <cstdlib>
+#include <deque>
+
+
+int main() {
+    std::deque<int> q;
+    q.push_back(0);
+    q.pop_back();
+    q.pop_back();
+    std::exit(1);
+}

test/libcxx/containers/sequences/vector/pop_back_empty.pass.cpp

@@ -0,0 +1,26 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// pop_back() more than the number of elements in a vector
+
+#define _LIBCPP_ASSERT(x, m) ((x) ? (void)0 : std::exit(0))
+
+#include <cstdlib>
+#include <vector>
+
+
+int main() {
+    std::vector<int> v;
+    v.push_back(0);
+    v.pop_back();
+    v.pop_back();
+    std::exit(1);
+}

test/libcxx/containers/sequences/vector/vector.cons/construct_iter_iter.pass.cpp

@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// template <class InputIter> vector(InputIter first, InputIter last);
+
+#include <vector>
+#include <cassert>
+
+#include "min_allocator.h"
+
+void test_ctor_under_alloc() {
+  int arr1[] = {42};
+  int arr2[] = {1, 101, 42};
+  {
+    typedef std::vector<int, cpp03_allocator<int> > C;
+    typedef C::allocator_type Alloc;
+    {
+      Alloc::construct_called = false;
+      C v(arr1, arr1 + 1);
+      assert(Alloc::construct_called);
+    }
+    {
+      Alloc::construct_called = false;
+      C v(arr2, arr2 + 3);
+      assert(Alloc::construct_called);
+    }
+  }
+  {
+    typedef std::vector<int, cpp03_overload_allocator<int> > C;
+    typedef C::allocator_type Alloc;
+    {
+      Alloc::construct_called = false;
+      C v(arr1, arr1 + 1);
+      assert(Alloc::construct_called);
+    }
+    {
+      Alloc::construct_called = false;
+      C v(arr2, arr2 + 3);
+      assert(Alloc::construct_called);
+    }
+  }
+}
+
+int main() {
+  test_ctor_under_alloc();
+}

test/libcxx/containers/sequences/vector/vector.cons/construct_iter_iter_alloc.pass.cpp

@@ -0,0 +1,57 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <vector>
+
+// template <class InputIter> vector(InputIter first, InputIter last,
+//                                   const allocator_type& a);
+
+#include <vector>
+#include <cassert>
+
+#include "min_allocator.h"
+
+void test_ctor_under_alloc() {
+  int arr1[] = {42};
+  int arr2[] = {1, 101, 42};
+  {
+    typedef std::vector<int, cpp03_allocator<int> > C;
+    typedef C::allocator_type Alloc;
+    Alloc a;
+    {
+      Alloc::construct_called = false;
+      C v(arr1, arr1 + 1, a);
+      assert(Alloc::construct_called);
+    }
+    {
+      Alloc::construct_called = false;
+      C v(arr2, arr2 + 3, a);
+      assert(Alloc::construct_called);
+    }
+  }
+  {
+    typedef std::vector<int, cpp03_overload_allocator<int> > C;
+    typedef C::allocator_type Alloc;
+    Alloc a;
+    {
+      Alloc::construct_called = false;
+      C v(arr1, arr1 + 1, a);
+      assert(Alloc::construct_called);
+    }
+    {
+      Alloc::construct_called = false;
+      C v(arr2, arr2 + 3, a);
+      assert(Alloc::construct_called);
+    }
+  }
+}
+
+int main() {
+  test_ctor_under_alloc();
+}

test/libcxx/containers/unord/non_const_comparator.fail.cpp

@@ -11,7 +11,7 @@
 // REQUIRES: diagnose-if-support, verify-support
 
 // Test that libc++ generates a warning diagnostic when the container is
-// provided a non-const callable comparator.
+// provided a non-const callable comparator or a non-const hasher.
 
 #include <unordered_set>
 #include <unordered_map>
@@ -34,8 +34,10 @@ int main() {
   static_assert(!std::__invokable<BadEqual const&, int const&, int const&>::value, "");
   static_assert(std::__invokable<BadEqual&, int const&, int const&>::value, "");
 
-  // expected-warning@__hash_table:* 4 {{the specified comparator type does not provide a const call operator}}
+  // expected-warning@unordered_set:* 2 {{the specified comparator type does not provide a const call operator}}
-  // expected-warning@__hash_table:* 4 {{the specified hash functor does not provide a const call operator}}
+  // expected-warning@unordered_map:* 2 {{the specified comparator type does not provide a const call operator}}
+  // expected-warning@unordered_set:* 2 {{the specified hash functor does not provide a const call operator}}
+  // expected-warning@unordered_map:* 2 {{the specified hash functor does not provide a const call operator}}
 
   {
     using C = std::unordered_set<int, BadHash, BadEqual>;

test/libcxx/experimental/diagnostics/syserr/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/system_error>
+
+#include <experimental/system_error>
+
+// expected-error@experimental/system_error:* {{"<experimental/system_error> has been removed. Use <system_error> instead."}}
+
+int main() {}

test/libcxx/experimental/diagnostics/syserr/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/system_error>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/system_error>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/numerics/numeric.ops/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/numeric>
+
+#include <experimental/numeric>
+
+// expected-error@experimental/numeric:* {{"<experimental/numeric> has been removed. Use <numeric> instead."}}
+
+int main() {}

test/libcxx/experimental/numerics/numeric.ops/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/numeric>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/numeric>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/strings/string.view/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/string_view>
+
+#include <experimental/string_view>
+
+// expected-error@experimental/string_view:* {{"<experimental/string_view> has been removed. Use <string_view> instead."}}
+
+int main() {}

test/libcxx/experimental/strings/string.view/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/string_view>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/string_view>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/utilities/any/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/any>
+
+#include <experimental/any>
+
+// expected-error@experimental/any:* {{"<experimental/any> has been removed. Use <any> instead."}}
+
+int main() {}

test/libcxx/experimental/utilities/any/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/any>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/any>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/utilities/optional/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/optional>
+
+#include <experimental/optional>
+
+// expected-error@experimental/optional:* {{"<experimental/optional> has been removed. Use <optional> instead."}}
+
+int main() {}

test/libcxx/experimental/utilities/optional/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/optional>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/optional>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/utilities/ratio/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/ratio>
+
+#include <experimental/ratio>
+
+// expected-error@experimental/ratio:* {{"<experimental/ratio> has been removed. Use <ratio> instead."}}
+
+int main() {}

test/libcxx/experimental/utilities/ratio/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/ratio>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/ratio>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/utilities/time/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/chrono>
+
+#include <experimental/chrono>
+
+// expected-error@experimental/chrono:* {{"<experimental/chrono> has been removed. Use <chrono> instead."}}
+
+int main() {}

test/libcxx/experimental/utilities/time/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/chrono>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/chrono>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/experimental/utilities/tuple/use_header_warning.fail.cpp

@@ -0,0 +1,18 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// REQUIRES: verify-support
+
+// <experimental/tuple>
+
+#include <experimental/tuple>
+
+// expected-error@experimental/tuple:* {{"<experimental/tuple> has been removed. Use <tuple> instead."}}
+
+int main() {}

test/libcxx/experimental/utilities/tuple/version.pass.cpp

@@ -0,0 +1,21 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// <experimental/tuple>
+
+#ifdef __GNUC__
+#pragma GCC diagnostic ignored "-W#warnings"
+#endif
+#include <experimental/tuple>
+
+#ifndef _LIBCPP_VERSION
+#error _LIBCPP_VERSION not defined
+#endif
+
+int main() {}

test/libcxx/input.output/file.streams/fstreams/fstream.close.pass.cpp

@@ -0,0 +1,35 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// <fstream>
+
+// template <class charT, class traits = char_traits<charT> >
+// class basic_fstream
+
+// close();
+
+//	Inspired by PR#38052 - std::fstream still good after closing and updating content
+
+#include <fstream>
+#include <cassert>
+#include "platform_support.h"
+
+int main()
+{
+    std::string temp = get_temp_file_name();
+
+    std::fstream ofs(temp, std::ios::out | std::ios::trunc);
+    ofs << "Hello, World!\n";
+    assert( ofs.good());
+    ofs.close();
+    assert( ofs.good());
+    ofs << "Hello, World!\n";
+    assert(!ofs.good());
+
+    std::remove(temp.c_str());
+}

test/libcxx/language.support/cxa_deleted_virtual.pass.cpp

@@ -12,6 +12,7 @@
 // Test exporting the symbol: "__cxa_deleted_virtual" in macosx
 // But don't expect the symbol to be exported in previous versions.
 //
+// XFAIL: with_system_cxx_lib=macosx10.14
 // XFAIL: with_system_cxx_lib=macosx10.13
 // XFAIL: with_system_cxx_lib=macosx10.12
 // XFAIL: with_system_cxx_lib=macosx10.11

test/libcxx/language.support/support.dynamic/libcpp_deallocate.sh.cpp

@@ -14,10 +14,6 @@
 // definitions, which does not yet provide aligned allocation
 // XFAIL: LIBCXX-WINDOWS-FIXME
 
-// Clang 10 (and older) will trigger an availability error when the deployment
-// target does not support aligned allocation, even if we pass `-faligned-allocation`.
-// XFAIL: apple-clang-10 && availability=macosx10.12
-
 // The dylibs shipped before macosx10.14 do not contain the aligned allocation
 // functions, so trying to force using those with -faligned-allocation results
 // in a link error.

test/libcxx/memory/aligned_allocation_macro.pass.cpp

@@ -9,13 +9,17 @@
 
 // UNSUPPORTED: c++98, c++03, c++11, c++14
 
-// aligned allocation functions are not provided prior to macosx10.13
+// AppleClang <= 10 enables aligned allocation regardless of the deployment
-// UNSUPPORTED: macosx10.12
+// target, so this test would fail.
-// UNSUPPORTED: macosx10.11
+// UNSUPPORTED: apple-clang-9, apple-clang-10
-// UNSUPPORTED: macosx10.10
+
-// UNSUPPORTED: macosx10.9
+// XFAIL: availability=macosx10.13
-// UNSUPPORTED: macosx10.8
+// XFAIL: availability=macosx10.12
-// UNSUPPORTED: macosx10.7
+// XFAIL: availability=macosx10.11
+// XFAIL: availability=macosx10.10
+// XFAIL: availability=macosx10.9
+// XFAIL: availability=macosx10.8
+// XFAIL: availability=macosx10.7
 
 #include <new>
 

test/libcxx/utilities/optional/optional.object/triviality.abi.pass.cpp

@@ -8,8 +8,18 @@
 //===----------------------------------------------------------------------===//
 
 // UNSUPPORTED: c++98, c++03, c++11, c++14
+
 // <optional>
 
+// This test asserts the triviality of special member functions of optional<T>
+// whenever T has these special member functions trivial. The goal of this test
+// is to make sure that we do not change the triviality of those, since that
+// constitues an ABI break (small enough optionals would be passed by registers).
+//
+// constexpr optional(const optional& rhs);
+// constexpr optional(optional&& rhs) noexcept(see below);
+// constexpr optional<T>& operator=(const optional& rhs);
+// constexpr optional<T>& operator=(optional&& rhs) noexcept(see below);
 
 #include <optional>
 #include <type_traits>
@@ -21,41 +31,27 @@ template <class T>
 struct SpecialMemberTest {
     using O = std::optional<T>;
 
-    static_assert(std::is_default_constructible_v<O>,
-        "optional is always default constructible.");
-    static_assert(std::is_copy_constructible_v<O> == std::is_copy_constructible_v<T>,
-        "optional<T> is copy constructible if and only if T is copy constructible.");
-    static_assert(std::is_move_constructible_v<O> ==
-        (std::is_copy_constructible_v<T> || std::is_move_constructible_v<T>),
-        "optional<T> is move constructible if and only if T is copy or move constructible.");
-    static_assert(std::is_copy_assignable_v<O> ==
-        (std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T>),
-        "optional<T> is copy assignable if and only if T is both copy "
-        "constructible and copy assignable.");
-    static_assert(std::is_move_assignable_v<O> ==
-        ((std::is_move_constructible_v<T> && std::is_move_assignable_v<T>) ||
-         (std::is_copy_constructible_v<T> && std::is_copy_assignable_v<T>)),
-        "optional<T> is move assignable if and only if T is both move constructible and "
-        "move assignable, or both copy constructible and copy assignable.");
-
-    // The following tests are for not-yet-standardized behavior (P0602):
     static_assert(std::is_trivially_destructible_v<O> ==
         std::is_trivially_destructible_v<T>,
         "optional<T> is trivially destructible if and only if T is.");
+
     static_assert(std::is_trivially_copy_constructible_v<O> ==
         std::is_trivially_copy_constructible_v<T>,
         "optional<T> is trivially copy constructible if and only if T is.");
+
     static_assert(std::is_trivially_move_constructible_v<O> ==
         std::is_trivially_move_constructible_v<T> ||
         (!std::is_move_constructible_v<T> && std::is_trivially_copy_constructible_v<T>),
         "optional<T> is trivially move constructible if T is trivially move constructible, "
         "or if T is trivially copy constructible and is not move constructible.");
+
     static_assert(std::is_trivially_copy_assignable_v<O> ==
         (std::is_trivially_destructible_v<T> &&
          std::is_trivially_copy_constructible_v<T> &&
          std::is_trivially_copy_assignable_v<T>),
         "optional<T> is trivially copy assignable if and only if T is trivially destructible, "
         "trivially copy constructible, and trivially copy assignable.");
+
     static_assert(std::is_trivially_move_assignable_v<O> ==
         (std::is_trivially_destructible_v<T> &&
          ((std::is_trivially_move_constructible_v<T> && std::is_trivially_move_assignable_v<T>) ||

test/libcxx/utilities/utility/pairs/pairs.pair/U_V.pass.cpp

@@ -0,0 +1,54 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template<class U, class V> pair(U&& x, V&& y);
+
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>, int, int>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>, int, int>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>, int, int>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>, int, int>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>, int, int>::value, "");
+    }
+}

test/libcxx/utilities/utility/pairs/pairs.pair/const_first_const_second.pass.cpp

@@ -0,0 +1,62 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// pair(const T1& x, const T2& y);
+
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    constexpr explicit ExplicitT(ExplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    constexpr ImplicitT(ImplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(ExplicitNothrowT const&) noexcept {}
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(ImplicitNothrowT const&) noexcept {}
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
+                                                     ExplicitT const&, ExplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>,
+                                                     ExplicitNothrowT const&, ExplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>,
+                                                     ExplicitT const&, ExplicitNothrowT const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>,
+                                                     ExplicitNothrowT const&, ExplicitNothrowT const&>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>,
+                                                     ImplicitT const&, ImplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>,
+                                                     ImplicitNothrowT const&, ImplicitT const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>,
+                                                     ImplicitT const&, ImplicitNothrowT const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
+                                                     ImplicitNothrowT const&, ImplicitNothrowT const&>::value, "");
+    }
+}

test/libcxx/utilities/utility/pairs/pairs.pair/const_pair_U_V.pass.cpp

@@ -0,0 +1,64 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template <class U, class V> EXPLICIT constexpr pair(const pair<U, V>& p);
+
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    constexpr explicit ExplicitT(ExplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    constexpr ImplicitT(ImplicitT const& o) : value(o.value) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
+                                                     std::pair<int, int> const&>::value, "");
+    }
+}

test/libcxx/utilities/utility/pairs/pairs.pair/default.pass.cpp

@@ -0,0 +1,36 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// constexpr pair();
+
+#include <utility>
+#include <type_traits>
+
+
+struct ThrowingDefault {
+  ThrowingDefault() { }
+};
+
+struct NonThrowingDefault {
+  NonThrowingDefault() noexcept { }
+};
+
+int main() {
+
+    static_assert(!std::is_nothrow_default_constructible<std::pair<ThrowingDefault, ThrowingDefault>>::value, "");
+    static_assert(!std::is_nothrow_default_constructible<std::pair<NonThrowingDefault, ThrowingDefault>>::value, "");
+    static_assert(!std::is_nothrow_default_constructible<std::pair<ThrowingDefault, NonThrowingDefault>>::value, "");
+    static_assert( std::is_nothrow_default_constructible<std::pair<NonThrowingDefault, NonThrowingDefault>>::value, "");
+}

test/libcxx/utilities/utility/pairs/pairs.pair/pair.tuple_element.fail.cpp

@@ -20,6 +20,6 @@ int main()
     {
     typedef std::pair<int, double> P;
     std::tuple_element<2, P>::type foo; // expected-note {{requested here}}
-        // expected-error@utility:* {{static_assert failed "Index out of bounds in std::tuple_element<std::pair<T1, T2>>"}}
+        // expected-error-re@utility:* {{static_assert failed{{( due to requirement '2U[L]{0,2} < 2')?}} "Index out of bounds in std::tuple_element<std::pair<T1, T2>>"}}
     }
 }

test/libcxx/utilities/utility/pairs/pairs.pair/piecewise.pass.cpp

@@ -0,0 +1,38 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template <class... Args1, class... Args2>
+//     pair(piecewise_construct_t, tuple<Args1...> first_args,
+//                                 tuple<Args2...> second_args);
+
+#include <tuple>
+#include <type_traits>
+#include <utility>
+
+#include "archetypes.hpp"
+
+
+int main() {
+    using NonThrowingConvert = NonThrowingTypes::ConvertingType;
+    using ThrowingConvert = NonTrivialTypes::ConvertingType;
+    static_assert(!std::is_nothrow_constructible<std::pair<ThrowingConvert, ThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+    static_assert(!std::is_nothrow_constructible<std::pair<NonThrowingConvert, ThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+    static_assert(!std::is_nothrow_constructible<std::pair<ThrowingConvert, NonThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+    static_assert( std::is_nothrow_constructible<std::pair<NonThrowingConvert, NonThrowingConvert>,
+                                                 std::piecewise_construct_t, std::tuple<int, int>, std::tuple<long, long>>::value, "");
+}

test/libcxx/utilities/utility/pairs/pairs.pair/rv_pair_U_V.pass.cpp

@@ -0,0 +1,63 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+
+// UNSUPPORTED: c++98, c++03
+
+// <utility>
+
+// template <class T1, class T2> struct pair
+
+// template <class U, class V> pair(pair<U, V>&& p);
+
+#include <type_traits>
+#include <utility>
+
+
+struct ExplicitT {
+    constexpr explicit ExplicitT(int x) : value(x) {}
+    int value;
+};
+
+struct ImplicitT {
+    constexpr ImplicitT(int x) : value(x) {}
+    int value;
+};
+
+struct ExplicitNothrowT {
+    explicit ExplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+struct ImplicitNothrowT {
+    ImplicitNothrowT(int x) noexcept : value(x) {}
+    int value;
+};
+
+int main() {
+    { // explicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitT>,
+                                                     std::pair<int, int>&&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitT>,
+                                                     std::pair<int, int>&&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ExplicitT, ExplicitNothrowT>,
+                                                     std::pair<int, int>&&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ExplicitNothrowT, ExplicitNothrowT>,
+                                                     std::pair<int, int>&&>::value, "");
+    }
+    { // implicit noexcept test
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitT>,
+                                                     std::pair<int, int>&&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitT>,
+                                                     std::pair<int, int>&&>::value, "");
+        static_assert(!std::is_nothrow_constructible<std::pair<ImplicitT, ImplicitNothrowT>,
+                                                     std::pair<int, int>&&>::value, "");
+        static_assert( std::is_nothrow_constructible<std::pair<ImplicitNothrowT, ImplicitNothrowT>,
+                                                     std::pair<int, int>&&>::value, "");
+    }
+}

test/libcxx/utilities/variant/variant.variant/variant.helper/variant_alternative.fail.cpp

@@ -31,6 +31,6 @@ int main()
     {
         typedef std::variant<int, double> T;
         std::variant_alternative<2, T>::type foo; // expected-note {{requested here}}
-        // expected-error@variant:* {{static_assert failed "Index out of bounds in std::variant_alternative<>"}}
+        // expected-error-re@variant:* {{static_assert failed{{( due to requirement '2U[L]{0,2} < sizeof...\(_Types\)')?}} "Index out of bounds in std::variant_alternative<>"}}
     }
 }

test/libcxx/utilities/variant/variant.variant/variant_size.pass.cpp

@@ -24,7 +24,8 @@ struct make_variant_imp;
 
 template <size_t ...Indices>
 struct make_variant_imp<std::integer_sequence<size_t, Indices...>> {
-  using type = std::variant<decltype((Indices, char(0)))...>;
+  template <size_t> using AlwaysChar = char;
+  using type = std::variant<AlwaysChar<Indices>...>;
 };
 
 template <size_t N>

test/std/algorithms/alg.modifying.operations/alg.random.sample/sample.fail.cpp

@@ -34,7 +34,7 @@ template <class PopulationIterator, class SampleIterator> void test() {
 }
 
 int main() {
-  // expected-error@algorithm:* {{static_assert failed "SampleIterator must meet the requirements of RandomAccessIterator"}}
+  // expected-error-re@algorithm:* {{static_assert failed{{( due to requirement '.*')?}} "SampleIterator must meet the requirements of RandomAccessIterator"}}
   // expected-error@algorithm:* 2 {{does not provide a subscript operator}}
   // expected-error@algorithm:* {{invalid operands}}
   test<input_iterator<int *>, output_iterator<int *> >();

test/std/algorithms/alg.nonmodifying/alg.find.end/find_end_pred.pass.cpp

@@ -16,6 +16,7 @@
 //   find_end(Iter1 first1, Iter1 last1, Iter2 first2, Iter2 last2, Pred pred);
 
 #include <algorithm>
+#include <functional>
 #include <cassert>
 
 #include "test_macros.h"

test/std/atomics/atomics.lockfree/isalwayslockfree.pass.cpp

@@ -59,7 +59,7 @@ void checkLongLongTypes() {
   static_assert((0 != ATOMIC_LLONG_LOCK_FREE) == ExpectLockFree, "");
 }
 
-int main()
+void run()
 {
 // structs and unions can't be defined in the template invocation.
 // Work around this with a typedef.
@@ -134,3 +134,5 @@ int main()
     static_assert(std::atomic<void*>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE));
     static_assert(std::atomic<std::nullptr_t>::is_always_lock_free == (2 == ATOMIC_POINTER_LOCK_FREE));
 }
+
+int main() { run(); }

test/std/containers/associative/map/map.erasure/erase_if.pass.cpp

@@ -0,0 +1,79 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <map>
+
+// template <class Key, class T, class Compare, class Allocator, class Predicate>
+//   void erase_if(map<Key, T, Compare, Allocator>& c, Predicate pred);
+
+#include <map>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+using Init = std::initializer_list<int>;
+template <typename M>
+M make (Init vals)
+{
+    M ret;
+    for (int v : vals)
+        ret[v] = v + 10;
+    return ret;
+}
+
+template <typename M, typename Pred>
+void
+test0(Init vals, Pred p, Init expected)
+{
+    M s = make<M> (vals);
+    ASSERT_SAME_TYPE(void, decltype(std::erase_if(s, p)));
+    std::erase_if(s, p);
+    assert(s == make<M>(expected));
+}
+
+template <typename S>
+void test()
+{
+    auto is1 = [](auto v) { return v.first == 1;};
+    auto is2 = [](auto v) { return v.first == 2;};
+    auto is3 = [](auto v) { return v.first == 3;};
+    auto is4 = [](auto v) { return v.first == 4;};
+    auto True  = [](auto) { return true; };
+    auto False = [](auto) { return false; };
+    
+    test0<S>({}, is1, {});
+
+    test0<S>({1}, is1, {});
+    test0<S>({1}, is2, {1});
+
+    test0<S>({1,2}, is1, {2});
+    test0<S>({1,2}, is2, {1});
+    test0<S>({1,2}, is3, {1,2});
+
+    test0<S>({1,2,3}, is1, {2,3});
+    test0<S>({1,2,3}, is2, {1,3});
+    test0<S>({1,2,3}, is3, {1,2});
+    test0<S>({1,2,3}, is4, {1,2,3});
+
+    test0<S>({1,2,3}, True,  {});
+    test0<S>({1,2,3}, False, {1,2,3});
+}
+
+int main()
+{
+    test<std::map<int, int>>();
+    test<std::map<int, int, std::less<int>, min_allocator<std::pair<const int, int>>>> ();
+    test<std::map<int, int, std::less<int>, test_allocator<std::pair<const int, int>>>> ();
+
+    test<std::map<long, short>>();
+    test<std::map<short, double>>();
+}
+

test/std/containers/associative/multimap/multimap.erasure/erase_if.pass.cpp

@@ -0,0 +1,89 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <map>
+
+//   template <class Key, class T, class Compare, class Allocator, class Predicate>
+//     void erase_if(multimap<Key, T, Compare, Allocator>& c, Predicate pred);
+
+#include <map>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+using Init = std::initializer_list<int>;
+template <typename M>
+M make (Init vals)
+{
+    M ret;
+    for (int v : vals)
+        ret.insert(typename M::value_type(v, v + 10));
+    return ret;
+}
+
+template <typename M, typename Pred>
+void
+test0(Init vals, Pred p, Init expected)
+{
+    M s = make<M> (vals);
+    ASSERT_SAME_TYPE(void, decltype(std::erase_if(s, p)));
+    std::erase_if(s, p);
+    assert(s == make<M>(expected));
+}
+
+template <typename S>
+void test()
+{
+    auto is1 = [](auto v) { return v.first == 1;};
+    auto is2 = [](auto v) { return v.first == 2;};
+    auto is3 = [](auto v) { return v.first == 3;};
+    auto is4 = [](auto v) { return v.first == 4;};
+    auto True  = [](auto) { return true; };
+    auto False = [](auto) { return false; };
+    
+    test0<S>({}, is1, {});
+
+    test0<S>({1}, is1, {});
+    test0<S>({1}, is2, {1});
+
+    test0<S>({1,2}, is1, {2});
+    test0<S>({1,2}, is2, {1});
+    test0<S>({1,2}, is3, {1,2});
+    test0<S>({1,1}, is1, {});
+    test0<S>({1,1}, is3, {1,1});
+
+    test0<S>({1,2,3}, is1, {2,3});
+    test0<S>({1,2,3}, is2, {1,3});
+    test0<S>({1,2,3}, is3, {1,2});
+    test0<S>({1,2,3}, is4, {1,2,3});
+
+    test0<S>({1,1,1}, is1, {});
+    test0<S>({1,1,1}, is2, {1,1,1});
+    test0<S>({1,1,2}, is1, {2});
+    test0<S>({1,1,2}, is2, {1,1});
+    test0<S>({1,1,2}, is3, {1,1,2});
+    test0<S>({1,2,2}, is1, {2,2});
+    test0<S>({1,2,2}, is2, {1});
+    test0<S>({1,2,2}, is3, {1,2,2});
+    
+    test0<S>({1,2,3}, True,  {});
+    test0<S>({1,2,3}, False, {1,2,3});
+}
+
+int main()
+{
+    test<std::multimap<int, int>>();
+    test<std::multimap<int, int, std::less<int>, min_allocator<std::pair<const int, int>>>> ();
+    test<std::multimap<int, int, std::less<int>, test_allocator<std::pair<const int, int>>>> ();
+
+    test<std::multimap<long, short>>();
+    test<std::multimap<short, double>>();
+}

test/std/containers/associative/multiset/multiset.erasure/erase_if.pass.cpp

@@ -0,0 +1,78 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <set>
+
+// template <class T, class Compare, class Allocator, class Predicate>
+//   void erase_if(multiset<T, Compare, Allocator>& c, Predicate pred);
+
+#include <set>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+template <class S, class Pred>
+void
+test0(S s, Pred p, S expected)
+{
+    ASSERT_SAME_TYPE(void, decltype(std::erase_if(s, p)));
+    std::erase_if(s, p);
+    assert(s == expected);
+}
+
+template <typename S>
+void test()
+{
+    auto is1 = [](auto v) { return v == 1;};
+    auto is2 = [](auto v) { return v == 2;};
+    auto is3 = [](auto v) { return v == 3;};
+    auto is4 = [](auto v) { return v == 4;};
+    auto True  = [](auto) { return true; };
+    auto False = [](auto) { return false; };
+    
+    test0(S(), is1, S());
+
+    test0(S({1}), is1, S());
+    test0(S({1}), is2, S({1}));
+
+    test0(S({1,2}), is1, S({2}));
+    test0(S({1,2}), is2, S({1}));
+    test0(S({1,2}), is3, S({1,2}));
+    test0(S({1,1}), is1, S());
+    test0(S({1,1}), is3, S({1,1}));
+
+    test0(S({1,2,3}), is1, S({2,3}));
+    test0(S({1,2,3}), is2, S({1,3}));
+    test0(S({1,2,3}), is3, S({1,2}));
+    test0(S({1,2,3}), is4, S({1,2,3}));
+
+    test0(S({1,1,1}), is1, S());
+    test0(S({1,1,1}), is2, S({1,1,1}));
+    test0(S({1,1,2}), is1, S({2}));
+    test0(S({1,1,2}), is2, S({1,1}));
+    test0(S({1,1,2}), is3, S({1,1,2}));
+    test0(S({1,2,2}), is1, S({2,2}));
+    test0(S({1,2,2}), is2, S({1}));
+    test0(S({1,2,2}), is3, S({1,2,2}));
+    
+    test0(S({1,2,3}), True,  S());
+    test0(S({1,2,3}), False, S({1,2,3}));
+}
+
+int main()
+{
+    test<std::multiset<int>>();
+    test<std::multiset<int, std::less<int>, min_allocator<int>>> ();
+    test<std::multiset<int, std::less<int>, test_allocator<int>>> ();
+
+    test<std::multiset<long>>();
+    test<std::multiset<double>>();
+}

test/std/containers/associative/set/set.erasure/erase_if.pass.cpp

@@ -0,0 +1,67 @@
+//===----------------------------------------------------------------------===//
+//
+//                     The LLVM Compiler Infrastructure
+//
+// This file is dual licensed under the MIT and the University of Illinois Open
+// Source Licenses. See LICENSE.TXT for details.
+//
+//===----------------------------------------------------------------------===//
+// UNSUPPORTED: c++98, c++03, c++11, c++14, c++17
+
+// <set>
+
+// template <class T, class Compare, class Allocator, class Predicate>
+//   void erase_if(set<T, Compare, Allocator>& c, Predicate pred);
+
+#include <set>
+
+#include "test_macros.h"
+#include "test_allocator.h"
+#include "min_allocator.h"
+
+template <class S, class Pred>
+void
+test0(S s, Pred p, S expected)
+{
+    ASSERT_SAME_TYPE(void, decltype(std::erase_if(s, p)));
+    std::erase_if(s, p);
+    assert(s == expected);
+}
+
+template <typename S>
+void test()
+{
+    auto is1 = [](auto v) { return v == 1;};
+    auto is2 = [](auto v) { return v == 2;};
+    auto is3 = [](auto v) { return v == 3;};
+    auto is4 = [](auto v) { return v == 4;};
+    auto True  = [](auto) { return true; };
+    auto False = [](auto) { return false; };
+    
+    test0(S(), is1, S());
+
+    test0(S({1}), is1, S());
+    test0(S({1}), is2, S({1}));
+
+    test0(S({1,2}), is1, S({2}));
+    test0(S({1,2}), is2, S({1}));
+    test0(S({1,2}), is3, S({1,2}));
+
+    test0(S({1,2,3}), is1, S({2,3}));
+    test0(S({1,2,3}), is2, S({1,3}));
+    test0(S({1,2,3}), is3, S({1,2}));
+    test0(S({1,2,3}), is4, S({1,2,3}));
+
+    test0(S({1,2,3}), True,  S());
+    test0(S({1,2,3}), False, S({1,2,3}));
+}
+
+int main()
+{
+    test<std::set<int>>();
+    test<std::set<int, std::less<int>, min_allocator<int>>> ();
+    test<std::set<int, std::less<int>, test_allocator<int>>> ();
+
+    test<std::set<long>>();
+    test<std::set<double>>();
+}

test/std/containers/sequences/array/array.data/data.pass.cpp

@@ -42,7 +42,7 @@ int main()
         typedef std::array<T, 0> C;
         C c = {};
         T* p = c.data();
-        assert(p != nullptr);
+        LIBCPP_ASSERT(p != nullptr);
     }
     {
       typedef double T;
@@ -50,14 +50,14 @@ int main()
       C c = {{}};
       const T* p = c.data();
       static_assert((std::is_same<decltype(c.data()), const T*>::value), "");
-      assert(p != nullptr);
+      LIBCPP_ASSERT(p != nullptr);
     }
   {
       typedef std::max_align_t T;
       typedef std::array<T, 0> C;
       const C c = {};
       const T* p = c.data();
-      assert(p != nullptr);
+      LIBCPP_ASSERT(p != nullptr);
       std::uintptr_t pint = reinterpret_cast<std::uintptr_t>(p);
       assert(pint % TEST_ALIGNOF(std::max_align_t) == 0);
     }
@@ -66,6 +66,6 @@ int main()
       typedef std::array<T, 0> C;
       C c = {};
       T* p = c.data();
-      assert(p != nullptr);
+      LIBCPP_ASSERT(p != nullptr);
     }
 }

test/std/containers/sequences/array/array.data/data_const.pass.cpp

@@ -48,14 +48,14 @@ int main()
       typedef std::array<T, 0> C;
       const C c = {};
       const T* p = c.data();
-      assert(p != nullptr);
+      LIBCPP_ASSERT(p != nullptr);
     }
     {
       typedef std::max_align_t T;
       typedef std::array<T, 0> C;
       const C c = {};
       const T* p = c.data();
-      assert(p != nullptr);
+      LIBCPP_ASSERT(p != nullptr);
       std::uintptr_t pint = reinterpret_cast<std::uintptr_t>(p);
       assert(pint % TEST_ALIGNOF(std::max_align_t) == 0);
     }

test/std/containers/sequences/array/array.tuple/get.fail.cpp

@@ -31,6 +31,6 @@ int main()
         typedef std::array<T, 3> C;
         C c = {1, 2, 3.5};
         std::get<3>(c) = 5.5; // expected-note {{requested here}}
-        // expected-error@array:* {{static_assert failed "Index out of bounds in std::get<> (std::array)"}}
+        // expected-error-re@array:* {{static_assert failed{{( due to requirement '3U[L]{0,2} < 3U[L]{0,2}')?}} "Index out of bounds in std::get<> (std::array)"}}
     }
 }