microsoft · StephanTLavavej · Nov 13, 2020 · Nov 10, 2020 · Nov 11, 2020 · Nov 11, 2020
diff --git a/.github/ISSUE_TEMPLATE/cxx20-feature.md → .github/ISSUE_TEMPLATE/cxx23-feature.md b/.github/ISSUE_TEMPLATE/cxx20-feature.md → .github/ISSUE_TEMPLATE/cxx23-feature.md
@@ -1,8 +1,8 @@
 ---
-name: cxx20 Feature
+name: cxx23 Feature
 about: For STL maintainers only
 title: PAPER_NUMBER PAPER_TITLE
-labels: cxx20
+labels: cxx23
 assignees: ''
 
 ---
@@ -22,3 +22,8 @@ the https://wg21.link redirector will start working.
 
 Feature-test macro:
 `#define MACRO_NAME MACRO_VALUE`
+
+Note: We're still working on finishing C++20. Until we're done
+with that (and the compiler implements distinct `/std:c++20` and
+`/std:c++latest` options), we won't be able to review PRs for
+C++23 features.
diff --git a/CMakeLists.txt b/CMakeLists.txt
@@ -5,7 +5,7 @@ if (NOT DEFINED CMAKE_TOOLCHAIN_FILE AND EXISTS "${CMAKE_CURRENT_LIST_DIR}/vcpkg
     set(CMAKE_TOOLCHAIN_FILE "${CMAKE_CURRENT_LIST_DIR}/vcpkg/scripts/buildsystems/vcpkg.cmake")
 endif()
 
-cmake_minimum_required(VERSION 3.17)
+cmake_minimum_required(VERSION 3.18)
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 project(msvc_standard_libraries LANGUAGES CXX)
 

diff --git a/README.md b/README.md
@@ -143,10 +143,10 @@ Just try to follow these rules, so we can spend more time fixing bugs and implem
 The STL uses boost-math headers to provide P0226R1 Mathematical Special Functions. We recommend using [vcpkg][] to
 acquire this dependency.
 
-1. Install Visual Studio 2019 16.8 Preview 5 or later.
+1. Install Visual Studio 2019 16.9 Preview 1 or later.
     * We recommend selecting "C++ CMake tools for Windows" in the VS Installer.
     This will ensure that you're using supported versions of CMake and Ninja.
-    * Otherwise, install [CMake][] 3.17 or later, and [Ninja][] 1.8.2 or later.
+    * Otherwise, install [CMake][] 3.18 or later, and [Ninja][] 1.8.2 or later.
 2. Open Visual Studio, and choose the "Clone or check out code" option. Enter the URL of this repository,
    `https://github.com/microsoft/STL`.
 3. Open a terminal in the IDE with `` Ctrl + ` `` (by default) or press on "View" in the top bar, and then "Terminal".
@@ -158,10 +158,10 @@ acquire this dependency.
 
 # How To Build With A Native Tools Command Prompt
 
-1. Install Visual Studio 2019 16.8 Preview 5 or later.
+1. Install Visual Studio 2019 16.9 Preview 1 or later.
     * We recommend selecting "C++ CMake tools for Windows" in the VS Installer.
     This will ensure that you're using supported versions of CMake and Ninja.
-    * Otherwise, install [CMake][] 3.17 or later, and [Ninja][] 1.8.2 or later.
+    * Otherwise, install [CMake][] 3.18 or later, and [Ninja][] 1.8.2 or later.
 2. Open a command prompt.
 3. Change directories to a location where you'd like a clone of this STL repository.
 4. `git clone https://github.com/microsoft/STL`

diff --git a/azure-devops/create-vmss.ps1 b/azure-devops/create-vmss.ps1
@@ -25,7 +25,7 @@ $LiveVMPrefix = 'BUILD'
 $WindowsServerSku = '2019-Datacenter'
 
 $ProgressActivity = 'Creating Scale Set'
-$TotalProgress = 11
+$TotalProgress = 12
 $CurrentProgress = 1
 
 <#
@@ -159,6 +159,14 @@ function Wait-Shutdown {
 }
 
 
+####################################################################################################
+Write-Progress `
+  -Activity $ProgressActivity `
+  -Status 'Setting the subscription context' `
+  -PercentComplete (100 / $TotalProgress * $CurrentProgress++)
+
+Set-AzContext -SubscriptionName CPP_STL_GitHub
+
 ####################################################################################################
 Write-Progress `
   -Activity $ProgressActivity `
@@ -391,6 +399,4 @@ New-AzVmss `
 Write-Progress -Activity $ProgressActivity -Completed
 Write-Host "Location: $Location"
 Write-Host "Resource group name: $ResourceGroupName"
-Write-Host "User name: AdminUser"
-Write-Host "Using generated password: $AdminPW"
 Write-Host 'Finished!'
diff --git a/azure-devops/provision-image.ps1 b/azure-devops/provision-image.ps1
@@ -88,6 +88,9 @@ $Workloads = @(
   'Microsoft.VisualStudio.Component.VC.CMake.Project',
   'Microsoft.VisualStudio.Component.VC.CoreIde',
   'Microsoft.VisualStudio.Component.VC.Llvm.Clang',
+  'Microsoft.VisualStudio.Component.VC.Runtimes.ARM.Spectre',
+  'Microsoft.VisualStudio.Component.VC.Runtimes.ARM64.Spectre',
+  'Microsoft.VisualStudio.Component.VC.Runtimes.x86.x64.Spectre',
   'Microsoft.VisualStudio.Component.VC.Tools.ARM',
   'Microsoft.VisualStudio.Component.VC.Tools.ARM64',
   'Microsoft.VisualStudio.Component.VC.Tools.x86.x64',
@@ -99,6 +102,9 @@ $Sku = 'Enterprise'
 $VisualStudioBootstrapperUrl = 'https://aka.ms/vs/16/pre/vs_enterprise.exe'
 $PythonUrl = 'https://www.python.org/ftp/python/3.9.0/python-3.9.0-amd64.exe'
 
+# https://docs.microsoft.com/en-us/windows-hardware/drivers/download-the-wdk
+$WindowsDriverKitUrl = 'https://go.microsoft.com/fwlink/?linkid=2128854'
+
 $CudaUrl = `
   'https://developer.download.nvidia.com/compute/cuda/10.1/Prod/local_installers/cuda_10.1.243_426.00_win10.exe'
 $CudaFeatures = 'nvcc_10.1 cuobjdump_10.1 nvprune_10.1 cupti_10.1 gpu_library_advisor_10.1 memcheck_10.1 ' + `
@@ -223,6 +229,36 @@ Function InstallPython {
   }
 }
 
+<#
+.SYNOPSIS
+Installs the Windows Driver Kit.
+
+.DESCRIPTION
+InstallWindowsDriverKit installs the Windows Driver Kit from the supplied URL.
+
+.PARAMETER Url
+The URL of the Windows Driver Kit installer.
+#>
+Function InstallWindowsDriverKit {
+  Param(
+    [String]$Url
+  )
+
+  Write-Host 'Downloading the Windows Driver Kit...'
+  [string]$installerPath = Get-TempFilePath -Extension 'exe'
+  curl.exe -L -o $installerPath -s -S $Url
+  Write-Host 'Installing the Windows Driver Kit...'
+  $proc = Start-Process -FilePath $installerPath -ArgumentList `
+  @('/quiet', '/features', 'OptionId.WindowsDriverKitComplete') -Wait -PassThru
+  $exitCode = $proc.ExitCode
+  if ($exitCode -eq 0) {
+    Write-Host 'Installation successful!'
+  }
+  else {
+    Write-Error "Installation failed! Exited with $exitCode."
+  }
+}
+
 <#
 .SYNOPSIS
 Installs NVIDIA's CUDA Toolkit.
@@ -300,6 +336,7 @@ Add-MpPreference -ExclusionProcess python.exe
 
 InstallPython $PythonUrl
 InstallVisualStudio -Workloads $Workloads -BootstrapperUrl $VisualStudioBootstrapperUrl
+InstallWindowsDriverKit $WindowsDriverKitUrl
 InstallCuda -Url $CudaUrl -Features $CudaFeatures
 
 Write-Host 'Updating PATH...'

diff --git a/azure-pipelines.yml b/azure-pipelines.yml
@@ -6,7 +6,7 @@
 variables:
   tmpDir: 'D:\Temp'
 
-pool: 'StlBuild-2020-10-23'
+pool: 'StlBuild-2020-11-10'
 
 stages:
   - stage: Code_Format

diff --git a/stl/inc/filesystem b/stl/inc/filesystem
@@ -622,7 +622,6 @@ namespace filesystem {
 
     _NODISCARD inline bool _Is_drive_prefix_with_slash_slash_question(const wstring_view _Text) {
         // test if _Text starts with a \\?\X: prefix
-        using namespace _STD string_view_literals; // TRANSITION, VSO-571749
         return _Text.size() >= 6 && _Text._Starts_with(LR"(\\?\)"sv) && _Is_drive_prefix(_Text.data() + 4);
     }
 
@@ -1250,8 +1249,6 @@ namespace filesystem {
         }
 
         _NODISCARD path lexically_normal() const {
-            using namespace _STD string_view_literals; // TRANSITION, VSO-571749
-
             constexpr wstring_view _Dot     = L"."sv;
             constexpr wstring_view _Dot_dot = L".."sv;
 
@@ -1686,8 +1683,6 @@ namespace filesystem {
     }
 
     _NODISCARD inline path path::lexically_relative(const path& _Base) const {
-        using namespace _STD string_view_literals; // TRANSITION, VSO-571749
-
         constexpr wstring_view _Dot     = L"."sv;
         constexpr wstring_view _Dot_dot = L".."sv;
 
@@ -1810,7 +1805,6 @@ namespace filesystem {
 
     private:
         static string _Pretty_message(const string_view _Op, const path& _Path1, const path& _Path2 = {}) {
-            using namespace _STD string_view_literals; // TRANSITION, VSO-571749
             string _Result;
             // Convert the paths to narrow encoding in a way that gracefully handles non-encodable characters
             const auto _Code_page   = __std_fs_code_page();
@@ -2550,7 +2544,6 @@ namespace filesystem {
 
         _NODISCARD static __std_win_error _Open_dir(
             path& _Path, const directory_options _Options_arg, _Find_file_handle& _Dir, __std_fs_find_data& _Data) {
-            using namespace _STD string_view_literals; // TRANSITION, VSO-571749
             const size_t _Null_term_len = _CSTD wcslen(_Path.c_str());
             if (_Null_term_len == 0 || _Null_term_len != _Path.native().size()) {
                 return __std_win_error::_File_not_found;
@@ -3021,7 +3014,6 @@ namespace filesystem {
 
     // FUNCTION canonical
     _NODISCARD inline __std_win_error _Canonical(path& _Result, const wstring& _Text) { // pre: _Result.empty()
-        using namespace _STD string_view_literals; // TRANSITION, VSO-571749
         if (_Text.empty()) {
             return __std_win_error::_Success;
         }

diff --git a/stl/inc/memory_resource b/stl/inc/memory_resource
@@ -661,7 +661,7 @@ namespace pmr {
         }
 
     protected:
-        virtual void* do_allocate(size_t _Bytes, size_t _Align) override { // TRANSITION, DevCom-1159869
+        virtual void* do_allocate(const size_t _Bytes, const size_t _Align) override {
             // allocate from the current buffer or a new larger buffer from upstream
             if (!_STD align(_Align, _Bytes, _Current_buffer, _Space_available)) {
                 _Increase_capacity(_Bytes, _Align);

diff --git a/stl/inc/tuple b/stl/inc/tuple
@@ -684,6 +684,9 @@ public:
     template <size_t _Index, class... _Types>
     friend constexpr const tuple_element_t<_Index, tuple<_Types...>>&& get(const tuple<_Types...>&& _Tuple) noexcept;
 
+    template <size_t _Index, class... _Types>
+    friend constexpr decltype(auto) _Tuple_get(tuple<_Types...>&& _Tuple) noexcept;
+
     template <class _Ty, class... _Types>
     friend constexpr _Ty& get(tuple<_Types...>& _Tuple) noexcept;
 
@@ -796,6 +799,14 @@ _NODISCARD constexpr const tuple_element_t<_Index, tuple<_Types...>>&& get(const
     return static_cast<const _Ty&&>(static_cast<const _Ttype&>(_Tuple)._Myfirst._Val);
 }
 
+template <size_t _Index, class... _Types>
+_NODISCARD constexpr decltype(auto) _Tuple_get(tuple<_Types...>&& _Tuple) noexcept {
+    // used by pair's piecewise constructor
+    using _Ty    = tuple_element_t<_Index, tuple<_Types...>>;
+    using _Ttype = typename tuple_element<_Index, tuple<_Types...>>::_Ttype;
+    return static_cast<_Ty&&>(static_cast<_Ttype&>(_Tuple)._Myfirst._Val);
+}
+
 // FUNCTION TEMPLATE get (by type)
 template <class _Ty, class... _Types>
 _NODISCARD constexpr _Ty& get(tuple<_Types...>& _Tuple) noexcept {
@@ -971,19 +982,6 @@ _NODISCARD constexpr _Ty make_from_tuple(_Tuple&& _Tpl) { // construct _Ty from
 }
 #endif // _HAS_CXX17
 
-// TEMPLATE CONSTRUCTOR pair::pair(tuple, tuple, sequence, sequence)
-template <class _Ty1, class _Ty2>
-template <class _Tuple1, class _Tuple2, size_t... _Indexes1, size_t... _Indexes2>
-constexpr pair<_Ty1, _Ty2>::pair(
-    _Tuple1& _Val1, _Tuple2& _Val2, index_sequence<_Indexes1...>, index_sequence<_Indexes2...>)
-    : first(_STD get<_Indexes1>(_STD move(_Val1))...), second(_STD get<_Indexes2>(_STD move(_Val2))...) {}
-
-// TEMPLATE CONSTRUCTOR pair::pair(piecewise_construct_t, tuple, tuple)
-template <class _Ty1, class _Ty2>
-template <class... _Types1, class... _Types2>
-_CONSTEXPR20 pair<_Ty1, _Ty2>::pair(piecewise_construct_t, tuple<_Types1...> _Val1, tuple<_Types2...> _Val2)
-    : pair(_Val1, _Val2, index_sequence_for<_Types1...>{}, index_sequence_for<_Types2...>{}) {}
-
 // STRUCT TEMPLATE uses_allocator
 template <class... _Types, class _Alloc>
 struct uses_allocator<tuple<_Types...>, _Alloc> : true_type {}; // true_type if container allocator enabled

diff --git a/stl/inc/utility b/stl/inc/utility
@@ -123,6 +123,9 @@ _INLINE_VAR constexpr piecewise_construct_t piecewise_construct{};
 template <class...>
 class tuple;
 
+template <size_t _Index, class... _Types>
+_NODISCARD constexpr decltype(auto) _Tuple_get(tuple<_Types...>&& _Tuple) noexcept;
+
 template <class _Ty1, class _Ty2>
 struct pair { // store a pair of values
     using first_type  = _Ty1;
@@ -263,10 +266,12 @@ struct pair { // store a pair of values
 #endif // ^^^ !_HAS_CONDITIONAL_EXPLICIT ^^^
 
     template <class _Tuple1, class _Tuple2, size_t... _Indexes1, size_t... _Indexes2>
-    constexpr pair(_Tuple1& _Val1, _Tuple2& _Val2, index_sequence<_Indexes1...>, index_sequence<_Indexes2...>);
+    constexpr pair(_Tuple1& _Val1, _Tuple2& _Val2, index_sequence<_Indexes1...>, index_sequence<_Indexes2...>)
+        : first(_Tuple_get<_Indexes1>(_STD move(_Val1))...), second(_Tuple_get<_Indexes2>(_STD move(_Val2))...) {}
 
     template <class... _Types1, class... _Types2>
-    _CONSTEXPR20 pair(piecewise_construct_t, tuple<_Types1...> _Val1, tuple<_Types2...> _Val2);
+    _CONSTEXPR20 pair(piecewise_construct_t, tuple<_Types1...> _Val1, tuple<_Types2...> _Val2)
+        : pair(_Val1, _Val2, index_sequence_for<_Types1...>{}, index_sequence_for<_Types2...>{}) {}
 
     pair& operator=(const volatile pair&) = delete;
 

diff --git a/stl/inc/yvals_core.h b/stl/inc/yvals_core.h
@@ -1184,12 +1184,8 @@
 #define __cpp_lib_constexpr_tuple       201811L
 #define __cpp_lib_constexpr_utility     201811L
 
-#ifdef __cpp_impl_coroutine // TRANSITION, Clang and EDG coroutine support
-#if __cpp_impl_coroutine >= 201902L
+#ifdef __cpp_impl_coroutine // TRANSITION, Clang coroutine support
 #define __cpp_lib_coroutine 201902L
-#else // ^^^ __cpp_impl_coroutine >= 201902L ^^^ / vvv __cpp_impl_coroutine < 201902L vvv
-#define __cpp_lib_coroutine 197000L // TRANSITION, VS 2019 16.8 Preview 4
-#endif // ^^^ __cpp_impl_coroutine < 201902L ^^^
 #endif // __cpp_impl_coroutine
 
 #define __cpp_lib_destroying_delete            201806L

diff --git a/tests/libcxx/expected_results.txt b/tests/libcxx/expected_results.txt
@@ -501,7 +501,7 @@ std/utilities/memory/allocator.traits/allocator.traits.members/destroy.pass.cpp
 std/utilities/memory/allocator.traits/allocator.traits.members/max_size.pass.cpp FAIL
 std/utilities/memory/allocator.traits/allocator.traits.members/select_on_container_copy_construction.pass.cpp FAIL
 std/utilities/memory/default.allocator/allocator.globals/eq.pass.cpp FAIL
-std/utilities/memory/default.allocator/allocator.members/allocate.pass.cpp FAIL
+std/utilities/memory/default.allocator/allocator.members/allocate.pass.cpp:1 FAIL
 std/utilities/memory/specialized.algorithms/specialized.construct/construct_at.pass.cpp FAIL
 std/utilities/memory/specialized.algorithms/specialized.destroy/destroy.pass.cpp FAIL
 std/utilities/memory/specialized.algorithms/specialized.destroy/destroy_at.pass.cpp FAIL

diff --git a/tests/std/tests/P0433R2_deduction_guides/test.cpp b/tests/std/tests/P0433R2_deduction_guides/test.cpp
@@ -91,14 +91,12 @@ long add(short x, int y) {
     return x + y;
 }
 
-struct UniqueTagCanDeduceFrom {}; // TRANSITION, VSO-587956
-
 template <typename Void, template <typename...> class ClassTemplate, typename... CtorArgs>
 struct CanDeduceFromHelper : false_type {};
 
 template <template <typename...> class ClassTemplate, typename... CtorArgs>
-struct CanDeduceFromHelper<void_t<UniqueTagCanDeduceFrom, decltype(ClassTemplate(declval<CtorArgs>()...))>,
-    ClassTemplate, CtorArgs...> : true_type {};
+struct CanDeduceFromHelper<void_t<decltype(ClassTemplate(declval<CtorArgs>()...))>, ClassTemplate, CtorArgs...>
+    : true_type {};
 
 template <template <typename...> class ClassTemplate, typename... CtorArgs>
 constexpr bool CanDeduceFrom = CanDeduceFromHelper<void, ClassTemplate, CtorArgs...>::value;

diff --git a/tests/std/tests/P0896R4_ranges_range_machinery/test.cpp b/tests/std/tests/P0896R4_ranges_range_machinery/test.cpp
@@ -1498,8 +1498,8 @@ namespace borrowed_range_testing {
     STATIC_ASSERT(test_borrowed_range<std::span<int>, std::span<int>::iterator>());
     STATIC_ASSERT(test_borrowed_range<std::span<int, 42>, std::span<int, 42>::iterator>());
     STATIC_ASSERT(test_borrowed_range<ranges::subrange<int*, int*>, int*>());
-#if 0 // TRANSITION, future
     STATIC_ASSERT(test_borrowed_range<ranges::ref_view<int[42]>, int*>());
+#if 0 // TRANSITION, future
     STATIC_ASSERT(test_borrowed_range<ranges::iota_view<int, int>, ...>());
 #endif // TRANSITION, future
 

diff --git a/tests/std/tests/P0896R4_views_common/test.cpp b/tests/std/tests/P0896R4_views_common/test.cpp
@@ -357,9 +357,6 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
         }
 
         // Validate common_view::base() && (NB: do this last since it leaves r moved-from)
-#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, DevCom-1159442
-        (void) 42;
-#endif // TRANSITION, DevCom-1159442
         same_as<V> auto b2 = move(r).base();
         static_assert(noexcept(move(r).base()) == is_nothrow_move_constructible_v<V>);
         if (!is_empty) {

diff --git a/tests/std/tests/P0896R4_views_drop_while/test.cpp b/tests/std/tests/P0896R4_views_drop_while/test.cpp
@@ -152,9 +152,6 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
     }
 
     // Validate deduction guide
-#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, DevCom-1159442
-    (void) 42;
-#endif // TRANSITION, DevCom-1159442
     same_as<R> auto r = drop_while_view{forward<Rng>(rng), is_less_than<3>};
     assert(ranges::equal(r, expected));
     if constexpr (forward_range<V>) {

diff --git a/tests/std/tests/P0896R4_views_filter/test.cpp b/tests/std/tests/P0896R4_views_filter/test.cpp
@@ -149,9 +149,6 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
     }
 
     // Validate deduction guide
-#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, DevCom-1159442
-    (void) 42;
-#endif // TRANSITION, DevCom-1159442
     same_as<F> auto r = filter_view{forward<Rng>(rng), is_even};
     assert(ranges::equal(r, expected));
     if constexpr (forward_range<V>) {
@@ -263,9 +260,6 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
     }
 
     // Validate filter_view::base() && (NB: do this last since it leaves r moved-from)
-#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, DevCom-1159442
-    (void) 42;
-#endif // TRANSITION, DevCom-1159442
     if (forward_range<V>) { // intentionally not if constexpr
         same_as<V> auto b2 = move(r).base();
         STATIC_ASSERT(noexcept(move(r).base()) == is_nothrow_move_constructible_v<V>);

diff --git a/tests/std/tests/P0896R4_views_reverse/test.cpp b/tests/std/tests/P0896R4_views_reverse/test.cpp
@@ -160,9 +160,6 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
     }
 
     // Validate deduction guide
-#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, DevCom-1159442
-    (void) 42;
-#endif // TRANSITION, DevCom-1159442
     same_as<R> auto r = reverse_view{forward<Rng>(rng)};
     assert(ranges::equal(r, expected));
 
@@ -294,9 +291,6 @@ constexpr bool test_one(Rng&& rng, Expected&& expected) {
     }
 
     // Validate reverse_view::base() && (NB: do this last since it leaves r moved-from)
-#if !defined(__clang__) && !defined(__EDG__) // TRANSITION, DevCom-1159442
-    (void) 42;
-#endif // TRANSITION, DevCom-1159442
     same_as<V> auto b2 = move(r).base();
     static_assert(noexcept(move(r).base()) == is_nothrow_move_constructible_v<V>);
     if (!is_empty) {