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Fixed build_ext assumption that cross-compilation on Windows always uses MSVCCompiler#399

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Avasam wants to merge 1 commit intopypa:mainfrom
Avasam:patch-1
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Fixed build_ext assumption that cross-compilation on Windows always uses MSVCCompiler#399
Avasam wants to merge 1 commit intopypa:mainfrom
Avasam:patch-1

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@Avasam Avasam commented Feb 20, 2026 •
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Fixes the following error if providing --plat-name when using msys2-mingw on Windows:

Traceback (most recent call last):
  File "D:/a/_temp/msys64/mingw64/lib/python3.12/site-packages/pyproject_hooks/_in_process/_in_process.py", line 389, in <module>
    main()
  File "D:/a/_temp/msys64/mingw64/lib/python3.12/site-packages/pyproject_hooks/_in_process/_in_process.py", line 373, in main
    json_out["return_val"] = hook(**hook_input["kwargs"])
                             ^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:/a/_temp/msys64/mingw64/lib/python3.12/site-packages/pyproject_hooks/_in_process/_in_process.py", line 280, in build_wheel
    return _build_backend().build_wheel(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/build_meta.py", line 438, in build_wheel
    return _build(['bdist_wheel'])
           ^^^^^^^^^^^^^^^^^^^^^^^
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/build_meta.py", line 429, in _build
    return self._build_with_temp_dir(
           ^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/build_meta.py", line 410, in _build_with_temp_dir
    self.run_setup()
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/build_meta.py", line 317, in run_setup
    exec(code, locals())
  File "<string>", line 1963, in <module>
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/__init__.py", line 117, in setup
    return distutils.core.setup(**attrs)  # type: ignore[return-value]
           ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/core.py", line 186, in setup
    return run_commands(dist)
           ^^^^^^^^^^^^^^^^^^
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/core.py", line 202, in run_commands
    dist.run_commands()
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1000, in run_commands
    self.run_command(cmd)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/dist.py", line 1107, in run_command
    super().run_command(command)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1019, in run_command
    cmd_obj.run()
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/command/bdist_wheel.py", line 370, in run
    self.run_command("build")
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/cmd.py", line 341, in run_command
    self.distribution.run_command(command)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/dist.py", line 1107, in run_command
    super().run_command(command)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1019, in run_command
    cmd_obj.run()
  File "<string>", line 354, in run
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/command/build.py", line 135, in run
    self.run_command(cmd_name)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/cmd.py", line 341, in run_command
    self.distribution.run_command(command)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/dist.py", line 1107, in run_command
    super().run_command(command)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/dist.py", line 1019, in run_command
    cmd_obj.run()
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/command/build_ext.py", line 97, in run
    _build_ext.run(self)
  File "D:/a/_temp/msys64/tmp/build-env-g6pjoax9/lib/python3.12/site-packages/setuptools/_distutils/command/build_ext.py", line 336, in run
    self.compiler.initialize(self.plat_name)
    ^^^^^^^^^^^^^^^^^^^^^^^^
AttributeError: 'MinGW32Compiler' object has no attribute 'initialize'

This could've been caught with static type checking, but attr-defined is currently disabled in mypy

@Avasam Avasam mentioned this pull request Feb 20, 2026
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Avasam
Avasam commented Feb 26, 2026
View reviewed changes
distutils/command/build_ext.py
# late initialization of compiler even if they shouldn't...)
self.plat_name != get_platform()
# Initialization is a MSVCCompiler specific concept
and hasattr(self.compiler, "initialize")
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@Avasam Avasam Feb 26, 2026

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I would've done

Suggested change
and hasattr(self.compiler, "initialize")
and isinstance(MSVCCompiler, self.compiler)

But who knows if someone downstream added a custom non-MSVCCompiler with .initialize that relies on being called.

Or it could be considered so internal that it's fine to do the more "proper" check that also helps static checkers.

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