gh-149786: Fixes venvlauncher builds on Windows free-threaded

Lib/test/test_venv.py

@@ -301,9 +301,9 @@ def test_sysconfig(self):
                 self.assertEqual(out.strip(), expected, err)
         for attr, expected in (
             ('executable', self.envpy()),
-            # Usually compare to sys.executable, but if we're running in our own
-            # venv then we really need to compare to our base executable
-            ('_base_executable', sys._base_executable),
+            # Usually compare to sys.prefix, but if we're running in our own
+            # venv then we really need to compare to our base prefix
+            ('base_prefix', sys.base_prefix),
         ):
             with self.subTest(attr):
                 cmd[2] = f'import sys; print(sys.{attr})'
@@ -916,10 +916,10 @@ def test_venvwlauncher(self):
             exename = exename.replace("python", "pythonw")
         envpyw = os.path.join(self.env_dir, self.bindir, exename)
         try:
-            subprocess.check_call([envpyw, "-c", "import sys; "
-                "assert sys._base_executable.endswith('%s')" % exename])
+            subprocess.check_call([envpyw, "-c", "import fnmatch, sys; "
+                "assert fnmatch.fnmatch(sys._base_executable, '**/pythonw*.exe')"])
         except subprocess.CalledProcessError:
-            self.fail("venvwlauncher.exe did not run %s" % exename)
+            self.fail("venvwlauncher.exe did not run pythonw.exe")
 
 
 @requireVenvCreate

Misc/NEWS.d/next/Windows/2026-05-14-22-09-46.gh-issue-149786.UI-HZM.rst

@@ -0,0 +1 @@
+Fixes virtual environment launchers on Windows free-threaded builds.

PC/layout/support/options.py

@@ -108,6 +108,7 @@ def public(f):
             "venv",
             "dev",
             "html-doc",
+            "alias",
             "install-json",
         ],
     },
@@ -123,6 +124,7 @@ def public(f):
             "html-doc",
             "symbols",
             "tests",
+            "alias",
             "install-test-json",
         ],
     },

PC/layout/support/pymanager.py

@@ -66,8 +66,9 @@ def calculate_install_json(ns, *, for_embed=False, for_test=False):
     if ns.include_freethreaded:
         # Free-threaded distro comes with a tag suffix
         TAG_SUFFIX = "t"
-        TARGET = f"python{VER_MAJOR}.{VER_MINOR}t.exe"
-        TARGETW = f"pythonw{VER_MAJOR}.{VER_MINOR}t.exe"
+        if not ns.include_alias:
+            TARGET = f"python{VER_MAJOR}.{VER_MINOR}t.exe"
+            TARGETW = f"pythonw{VER_MAJOR}.{VER_MINOR}t.exe"
         DISPLAY_TAGS.append("free-threaded")
         FILE_SUFFIX = f"t-{ns.arch}"
 

PCbuild/python.vcxproj

@@ -135,6 +135,14 @@
 set PYTHONPATH=$(PySourcePath)Lib
 "$(OutDir)$(PyExeName)$(PyDebugExt).exe" "$(PySourcePath)PC\validate_ucrtbase.py" $(UcrtName)' ContinueOnError="true" />
   </Target>
+  <Target Name="CopyFreethreadedBinary" AfterTargets="AfterBuild"
+          Condition="$(DisableGil) == 'true' and $(Configuration) != 'PGInstrument'">
+    <Message Text="Duplicating $(TargetPath) to $(PyExeName)$(MajorVersionNumber).$(MinorVersionNumber)t$(PyDebugExt).exe for free-threaded compatibility" />
+    <Copy SourceFiles="$(TargetPath)"
+          DestinationFiles="$(OutDir)\$(PyExeName)$(MajorVersionNumber).$(MinorVersionNumber)t$(PyDebugExt).exe"
+          SkipUnchangedFiles="true"
+          UseHardLinksIfPossible="true" />
+  </Target>
   <Target Name="GeneratePythonBat" AfterTargets="AfterBuild">
     <PropertyGroup>
       <_Content>@rem This script invokes the most recently built Python with all arguments

PCbuild/pythonw.vcxproj

@@ -115,4 +115,12 @@
   <Import Project="$(VCTargetsPath)\Microsoft.Cpp.targets" />
   <ImportGroup Label="ExtensionTargets">
   </ImportGroup>
+  <Target Name="CopyFreethreadedBinary" AfterTargets="AfterBuild"
+          Condition="$(DisableGil) == 'true' and $(Configuration) != 'PGInstrument'">
+    <Message Text="Duplicating $(TargetPath) to $(PyWExeName)$(MajorVersionNumber).$(MinorVersionNumber)t$(PyDebugExt).exe for free-threaded compatibility" />
+    <Copy SourceFiles="$(TargetPath)"
+          DestinationFiles="$(OutDir)\$(PyWExeName)$(MajorVersionNumber).$(MinorVersionNumber)t$(PyDebugExt).exe"
+          SkipUnchangedFiles="true"
+          UseHardLinksIfPossible="true" />
+  </Target>
 </Project>

PCbuild/venvlauncher.vcxproj

@@ -89,10 +89,13 @@
     <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
     <Import Project="pyproject.props" />
   </ImportGroup>
-  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup Label="UserMacros">
+    <ExeName>$(PyExeName)$(PyDebugExt).exe</ExeName>
+    <ExeName Condition="$(DisableGil) == 'true'">$(PyExeName)$(MajorVersionNumber).$(MinorVersionNumber)t$(PyDebugExt).exe</ExeName>
+  </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
-      <PreprocessorDefinitions>EXENAME=L"$(PyExeName)$(PyDebugExt).exe";_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>EXENAME=L"$(ExeName)";_CONSOLE;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
     </ClCompile>
     <ResourceCompile>

PCbuild/venvwlauncher.vcxproj

@@ -89,10 +89,13 @@
     <Import Project="$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props" Condition="exists('$(UserRootDir)\Microsoft.Cpp.$(Platform).user.props')" Label="LocalAppDataPlatform" />
     <Import Project="pyproject.props" />
   </ImportGroup>
-  <PropertyGroup Label="UserMacros" />
+  <PropertyGroup Label="UserMacros">
+    <ExeName>$(PyWExeName)$(PyDebugExt).exe</ExeName>
+    <ExeName Condition="$(DisableGil) == 'true'">$(PyWExeName)$(MajorVersionNumber).$(MinorVersionNumber)t$(PyDebugExt).exe</ExeName>
+  </PropertyGroup>
   <ItemDefinitionGroup>
     <ClCompile>
-      <PreprocessorDefinitions>EXENAME=L"$(PyWExeName)$(PyDebugExt).exe";_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
+      <PreprocessorDefinitions>EXENAME=L"$(ExeName)";_WINDOWS;%(PreprocessorDefinitions)</PreprocessorDefinitions>
       <RuntimeLibrary>MultiThreaded</RuntimeLibrary>
     </ClCompile>
     <ResourceCompile>