Toolset update: MSVC Compiler 19.51.36014

CMakeLists.txt

@@ -1,13 +1,13 @@
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-cmake_minimum_required(VERSION 4.1.2)
+cmake_minimum_required(VERSION 4.2.1)
 
 set(CMAKE_TRY_COMPILE_TARGET_TYPE STATIC_LIBRARY)
 project(msvc_standard_libraries LANGUAGES CXX)
 
-if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "19.50.35722")
-    message(FATAL_ERROR "The STL must be built with MSVC Compiler 19.50.35722 or later.")
+if(CMAKE_CXX_COMPILER_VERSION VERSION_LESS "19.51.36014")
+    message(FATAL_ERROR "The STL must be built with MSVC Compiler 19.51.36014 or later.")
 endif()
 
 include(CheckCXXSourceCompiles)

CMakePresets.json

@@ -10,7 +10,11 @@
       "name": "base",
       "hidden": true,
       "generator": "Ninja",
-      "binaryDir": "${sourceDir}/out/${presetName}"
+      "binaryDir": "${sourceDir}/out/${presetName}",
+      "toolset": {
+        "strategy": "external",
+        "value": "version=preview"
+      }
     },
     {
       "name": "x64",

README.md

@@ -145,13 +145,13 @@ Just try to follow these rules, so we can spend more time fixing bugs and implem
   + **You must install Insiders for STL development.** *See Note 1 below.*
   + Select the "Desktop development with C++" workload.
   + Select the following components at a minimum:
-    - "MSVC Build Tools for x64/x86 (Latest)"
+    - "MSVC Build Tools for x64/x86 (Preview)"
     - "C++ CMake tools for Windows"
     - "MSVC AddressSanitizer"
     - "Windows 11 SDK (10.0.26100)" or later
     - "C++ Clang tools for Windows (20.1.8 - x64/x86)"
-    - *Optional, see Note 2 below:* "MSVC Build Tools for ARM64/ARM64EC (Latest)"
-* Install [Python][] 3.14.2 or later.
+    - *Optional, see Note 2 below:* "MSVC Build Tools for ARM64/ARM64EC (Preview)"
+* Install [Python][] 3.14.3 or later.
   + Select "Add python.exe to PATH" if you want to follow the instructions below that invoke `python`.
     Otherwise, you should be familiar with alternative methods.
 
@@ -170,7 +170,7 @@ For example, `<atomic>` has conditionally compiled code for the `_M_ARM64` and `
 4. Use the IDE's dropdown menu to choose the architecture you want to build. We recommend x64 for general development.
 5. Build > Build All.
 
-# How To Build With A Native Tools Command Prompt
+# How To Build With The Command Prompt
 
 1. Open a command prompt.
 2. Change directories to a location where you'd like a clone of this STL repository.
@@ -180,33 +180,35 @@ If you installed VS to a non-default location, change the `vcvarsall.bat` paths
 
 To build the x64 target (recommended):
 
-1. `"C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build\vcvarsall.bat" x64`
-    * Or open an "x64 Native Tools Command Prompt for VS 18 Insiders".
-2. Change directories to the previously cloned `STL` directory.
-3. `cmake --preset x64`
-4. `cmake --build --preset x64`
+1. `pushd "%ProgramFiles%\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build"`
+1. `vcvarsall.bat x64 -vcvars_ver=preview`
+1. Change directories to the previously cloned `STL` directory.
+1. `cmake --preset x64`
+1. `cmake --build --preset x64`
 
 To build the x86 target:
 
-1. `"C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build\vcvarsall.bat" x86`
-    * Or open an "x86 Native Tools Command Prompt for VS 18 Insiders".
-2. Change directories to the previously cloned `STL` directory.
-3. `cmake --preset x86`
-4. `cmake --build --preset x86`
+1. `pushd "%ProgramFiles%\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build"`
+1. `vcvarsall.bat x86 -vcvars_ver=preview`
+1. Change directories to the previously cloned `STL` directory.
+1. `cmake --preset x86`
+1. `cmake --build --preset x86`
 
 To build the ARM64 target:
 
-1. `"C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build\vcvarsall.bat" x64_arm64`
-2. Change directories to the previously cloned `STL` directory.
-3. `cmake --preset ARM64`
-4. `cmake --build --preset ARM64`
+1. `pushd "%ProgramFiles%\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build"`
+1. `vcvarsall.bat x64_arm64 -vcvars_ver=preview`
+1. Change directories to the previously cloned `STL` directory.
+1. `cmake --preset ARM64`
+1. `cmake --build --preset ARM64`
 
 To build the ARM64EC target:
 
-1. `"C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build\vcvarsall.bat" x64_arm64`
-2. Change directories to the previously cloned `STL` directory.
-3. `cmake --preset ARM64EC`
-4. `cmake --build --preset ARM64EC`
+1. `pushd "%ProgramFiles%\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build"`
+1. `vcvarsall.bat x64_arm64 -vcvars_ver=preview`
+1. Change directories to the previously cloned `STL` directory.
+1. `cmake --preset ARM64EC`
+1. `cmake --build --preset ARM64EC`
 
 # How To Consume
 
@@ -227,21 +229,30 @@ your .exe would "win" over the versions in System32.
 The compiler looks for include directories according to the `INCLUDE` environment variable, and the linker looks for
 import library directories according to the `LIB` environment variable, and the Windows loader will (eventually) look
 for DLL dependencies according to directories in the `PATH` environment variable.
-The build generates a batch script named `set_environment.bat` in the output directory. If you run this script in a VS
-Developer Command Prompt, it will insert the proper directories into the `INCLUDE`, `LIB`, and `PATH` environment
+The build generates a batch script named `set_environment.bat` in the output directory. If you run this script,
+it will insert the proper directories into the `INCLUDE`, `LIB`, and `PATH` environment
 variables to ensure that the built headers and libraries are used.
 
 ## Complete Example Using x64 DLL Flavor
 
-From an "x64 Native Tools Command Prompt for VS 18 Insiders":
-
 ```
+C:\Temp>pushd "%ProgramFiles%\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build"
+
+C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build>vcvarsall.bat x64 -vcvars_ver=preview
+**********************************************************************
+** Visual Studio 2026 Developer Command Prompt v18.4.0-insiders
+** Copyright (c) 2026 Microsoft Corporation
+**********************************************************************
+[vcvarsall.bat] Environment initialized for: 'x64'
+
+C:\Program Files\Microsoft Visual Studio\18\Insiders\VC\Auxiliary\Build>pushd D:\GitHub\STL
+
 D:\GitHub\STL>cmake --preset x64
 [...]
 -- Build files have been written to: D:/GitHub/STL/out/x64
 
 D:\GitHub\STL>cmake --build --preset x64
-[1028/1028] Linking CXX static library out\lib\amd64\libcpmtd0.lib
+[762/762] Linking CXX static library out\lib\amd64\libcpmtd0.lib
 
 D:\GitHub\STL>out\x64\set_environment.bat
 
@@ -264,7 +275,7 @@ C:\Temp>dumpbin /DEPENDENTS .\example.exe | findstr msvcp
     msvcp140d_oss.dll
 ```
 
-# How To Run The Tests With A Native Tools Command Prompt
+# How To Run The Tests
 
 Our tests are currently split across three test suites that are located at `tests\std`, `tests\tr1`, and
 `llvm-project\libcxx\test\std`. The test runner `${PROJECT_BINARY_DIR}\tests\utils\stl-lit\stl-lit.py` accepts paths to

azure-devops/asan-pipeline.yml

@@ -1,7 +1,7 @@
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-# Build STL targeting x86 and x64, and run extra ASan testing
+# Build STL targeting x64, x86, and arm64, then run extra ASan testing
 
 variables:
   - template: config.yml
@@ -16,8 +16,9 @@ schedules:
     - main
 
 stages:
-  - stage: Build_And_Test_x64
-    displayName: 'Build and Test x64'
+  - stage: Test_x64_ASan
+    displayName: 'Test x64 ASan'
+    dependsOn: []
     pool:
       name: ${{ variables.poolName }}
       demands: ${{ variables.poolDemands }}
@@ -30,8 +31,8 @@ stages:
           asanBuild: true
           testTargets: STL-ASan-CI
 
-  - stage: Build_And_Test_x86
-    displayName: 'Build and Test x86'
+  - stage: Test_x86_ASan
+    displayName: 'Test x86 ASan'
     dependsOn: []
     pool:
       name: ${{ variables.poolName }}
@@ -45,4 +46,17 @@ stages:
           asanBuild: true
           testTargets: STL-ASan-CI
 
-  # no coverage for ARM64
+  - stage: Test_ARM64_ASan
+    displayName: 'Test ARM64 ASan'
+    dependsOn: []
+    pool:
+      name: ${{ variables.arm64PoolName }}
+      demands: ${{ variables.poolDemands }}
+    jobs:
+      - template: build-and-test.yml
+        parameters:
+          hostArch: arm64
+          targetArch: arm64
+          targetPlatform: arm64
+          asanBuild: true
+          testTargets: STL-ASan-CI

azure-devops/build-and-test.yml

@@ -22,7 +22,7 @@ parameters:
   default: 'STL-CI'
 - name: numShards
   type: number
-  default: 8
+  default: 10
 - name: configureTesting
   type: boolean
   default: true

azure-devops/config.yml

@@ -5,10 +5,10 @@
 
 variables:
 - name: poolName
-  value: 'Stl-2026-01-13T1248-x64-Pool'
+  value: 'Stl-2026-02-20T0952-x64-Pool'
   readonly: true
 - name: arm64PoolName
-  value: 'Stl-2026-01-13T1248-arm64-Pool'
+  value: 'Stl-2026-02-20T0952-arm64-Pool'
   readonly: true
 - name: poolDemands
   value: 'EnableSpotVM -equals false'

azure-devops/create-1es-hosted-pool.ps1

@@ -31,7 +31,7 @@ if ($Arch -ieq 'x64') {
 } else {
   # CPP_STL_GitHub has quota for 672 cores (21 VMs) in westcentralus, not currently used.
   $AvailableLocations = @('eastus2', 'northeurope') # Locations where CPP_STL_GitHub has quota for 1024 cores (32 VMs).
-  $AvailableLocationIdx = 4 # Increment for each new pool, to cycle through the available locations.
+  $AvailableLocationIdx = 5 # Increment for each new pool, to cycle through the available locations.
   $Location = $AvailableLocations[$AvailableLocationIdx % $AvailableLocations.Length]
   $VMSize = 'Standard_D32ps_v6'
   $PoolSize = 32

azure-devops/provision-image.ps1

@@ -36,13 +36,12 @@ if ($Arch -ieq 'x64') {
 
 $VisualStudioWorkloads = @(
   'Microsoft.VisualStudio.Component.VC.ASAN',
-  'Microsoft.VisualStudio.Component.VC.CLI.Support',
   'Microsoft.VisualStudio.Component.VC.CMake.Project',
   'Microsoft.VisualStudio.Component.VC.CoreIde',
   'Microsoft.VisualStudio.Component.VC.Llvm.Clang',
-  'Microsoft.VisualStudio.Component.VC.Tools.ARM64',
-  'Microsoft.VisualStudio.Component.VC.Tools.ARM64EC',
-  'Microsoft.VisualStudio.Component.VC.Tools.x86.x64',
+  'Microsoft.VisualStudio.Component.VC.Preview.ARM64',
+  'Microsoft.VisualStudio.Component.VC.Preview.CLI.Support',
+  'Microsoft.VisualStudio.Component.VC.Preview.Tools.x86.x64',
   'Microsoft.VisualStudio.Component.Windows11SDK.26100'
 )
 
@@ -67,9 +66,9 @@ $PowerShellArgs = @('/quiet', '/norestart')
 
 # https://www.python.org
 if ($Provisioning_x64) {
-  $PythonUrl = 'https://www.python.org/ftp/python/3.14.2/python-3.14.2-amd64.exe'
+  $PythonUrl = 'https://www.python.org/ftp/python/3.14.3/python-3.14.3-amd64.exe'
 } else {
-  $PythonUrl = 'https://www.python.org/ftp/python/3.14.2/python-3.14.2-arm64.exe'
+  $PythonUrl = 'https://www.python.org/ftp/python/3.14.3/python-3.14.3-arm64.exe'
 }
 $PythonArgs = @('/quiet', 'InstallAllUsers=1', 'PrependPath=1', 'CompileAll=1', 'Include_doc=0')
 
@@ -186,6 +185,13 @@ if ($Provisioning_x64) {
   EnableNativeNVMe
 }
 
+# TRANSITION, patch Launch-VsDevShell.ps1 to pass `-vcvars_ver=preview` before a proper parameter is available.
+Write-Host 'Patching Launch-VsDevShell.ps1...'
+$launchVsDevShell = 'C:\Program Files\Microsoft Visual Studio\18\Insiders\Common7\Tools\Launch-VsDevShell.ps1'
+$paramRegex = 'VsInstanceId = \$instanceId'
+$paramSubst = '$&; DevCmdArguments = "-vcvars_ver=preview";'
+(Get-Content -Raw $launchVsDevShell) -creplace $paramRegex, $paramSubst | Set-Content -NoNewLine $launchVsDevShell
+
 # Tell create-1es-hosted-pool.ps1 that we succeeded.
 Write-Host 'PROVISION_IMAGE_SUCCEEDED'
 

azure-pipelines.yml

@@ -1,7 +1,7 @@
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-# Build STL targeting x86, x64, arm64, arm64ec
+# Build STL targeting x64, x86, arm64, arm64ec
 
 variables:
   - template: azure-devops/config.yml
@@ -173,7 +173,6 @@ stages:
           hostArch: arm64
           targetArch: arm64
           targetPlatform: arm64
-          numShards: 10
 
   - stage: Test_ARM64EC
     dependsOn:
@@ -189,4 +188,3 @@ stages:
           hostArch: arm64
           targetArch: arm64
           targetPlatform: arm64ec
-          numShards: 10

benchmarks/CMakeLists.txt

@@ -1,7 +1,7 @@
 # Copyright (c) Microsoft Corporation.
 # SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
 
-cmake_minimum_required(VERSION 4.1.2)
+cmake_minimum_required(VERSION 4.2.1)
 project(msvc_standard_libraries_benchmarks LANGUAGES CXX)
 
 if(DEFINED STL_BINARY_DIR)

stl/inc/__msvc_formatter.hpp

@@ -146,14 +146,6 @@ struct formatter {
 };
 
 _FMT_P2286_BEGIN
-// TRANSITION, VSO-1236041: Avoid declaring and defining member functions in different headers.
-template <_Basic_format_arg_type _ArgType, class _CharT, class _Pc>
-constexpr _Pc::iterator _Formatter_base_parse(_Dynamic_format_specs<_CharT>& _Specs, _Pc& _ParseCtx);
-
-template <class _Ty, class _CharT, class _FormatContext>
-_FormatContext::iterator _Formatter_base_format(
-    const _Dynamic_format_specs<_CharT>& _Specs, const _Ty& _Val, _FormatContext& _FormatCtx);
-
 template <class _Ty, class _CharT, _Basic_format_arg_type _ArgType>
 struct _Formatter_base {
 public:
@@ -165,15 +157,11 @@ struct _Formatter_base {
     }
 #endif // _HAS_CXX23
 
-    template <class _Pc = basic_format_parse_context<_CharT>>
-    constexpr _Pc::iterator parse(type_identity_t<_Pc&> _ParseCtx) {
-        return _Formatter_base_parse<_ArgType>(_Specs, _ParseCtx);
-    }
+    template <class _ParseContext = basic_format_parse_context<_CharT>>
+    constexpr _ParseContext::iterator parse(type_identity_t<_ParseContext&> _Parse_ctx); // defined in <format>
 
     template <class _FormatContext>
-    _FormatContext::iterator format(const _Ty& _Val, _FormatContext& _FormatCtx) const {
-        return _Formatter_base_format(_Specs, _Val, _FormatCtx);
-    }
+    _FormatContext::iterator format(const _Ty& _Val, _FormatContext& _Format_ctx) const; // defined in <format>
 
 private:
     _Dynamic_format_specs<_CharT> _Specs;
@@ -419,30 +407,17 @@ struct _Fill_align_and_width_specs {
     _CharT _Fill[4 / sizeof(_CharT)]{' '};
 };
 
-// TRANSITION, VSO-1236041: Avoid declaring and defining member functions in different headers.
-template <class _CharT, class _Pc>
-_NODISCARD constexpr _Pc::iterator _Fill_align_and_width_formatter_parse(
-    _Fill_align_and_width_specs<_CharT>& _Specs, _Pc& _Parse_ctx);
-
-template <class _CharT, class _FormatContext, class _Func>
-_NODISCARD _FormatContext::iterator _Fill_align_and_width_formatter_format(
-    const _Fill_align_and_width_specs<_CharT>& _Specs, _FormatContext& _Format_ctx, int _Width,
-    _Fmt_align _Default_align, _Func&& _Fn);
-
 template <class _CharT>
 struct _Fill_align_and_width_formatter {
 public:
     template <class _ParseContext = basic_format_parse_context<_CharT>> // improves throughput, see GH-5003
-    _NODISCARD constexpr _ParseContext::iterator _Parse(type_identity_t<_ParseContext&> _Parse_ctx) {
-        return _STD _Fill_align_and_width_formatter_parse(_Specs, _Parse_ctx);
-    }
+    _NODISCARD constexpr _ParseContext::iterator _Parse(
+        type_identity_t<_ParseContext&> _Parse_ctx); // defined in <format>
 
     template <class _FormatContext, class _Func>
-    _NODISCARD constexpr auto _Format(
-        _FormatContext& _Format_ctx, const int _Width, _Fmt_align _Default_align, _Func&& _Fn) const {
-        return _STD _Fill_align_and_width_formatter_format(
-            _Specs, _Format_ctx, _Width, _Default_align, _STD forward<_Func>(_Fn));
-    }
+    _NODISCARD _FormatContext::iterator _Format(_FormatContext& _Format_ctx, const int _Width,
+        _Fmt_align _Default_align,
+        _Func&& _Fn) const; // defined in <format>
 
 private:
     _Fill_align_and_width_specs<_CharT> _Specs;