Merge pull request #4463 from pypa/bugfix/distutils-34f9518ef

Merge with distutils@34f9518ef

newsfragments/+4571b0f4.bugfix.rst

@@ -0,0 +1 @@
+Bugfix for building Cython extension on Windows (pypa/distutils#268).

setuptools/_distutils/sysconfig.py

@@ -293,7 +293,9 @@ def customize_compiler(compiler):  # noqa: C901
     Mainly needed on Unix, so we can plug in the information that
     varies across Unices and is stored in Python's Makefile.
     """
-    if compiler.compiler_type in ["unix", "cygwin", "mingw32"]:
+    if compiler.compiler_type in ["unix", "cygwin"] or (
+        compiler.compiler_type == "mingw32" and is_mingw()
+    ):
         _customize_macos()
 
         (

setuptools/_distutils/tests/test_mingwccompiler.py

@@ -2,6 +2,7 @@
 
 from distutils.util import split_quoted, is_mingw
 from distutils.errors import DistutilsPlatformError, CCompilerError
+from distutils import sysconfig
 
 
 class TestMingw32CCompiler:
@@ -43,3 +44,12 @@ def test_cygwincc_error(self, monkeypatch):
 
         with pytest.raises(CCompilerError):
             distutils.cygwinccompiler.Mingw32CCompiler()
+
+    def test_customize_compiler_with_msvc_python(self):
+        from distutils.cygwinccompiler import Mingw32CCompiler
+
+        # In case we have an MSVC Python build, but still want to use
+        # Mingw32CCompiler, then customize_compiler() shouldn't fail at least.
+        # https://github.com/pypa/setuptools/issues/4456
+        compiler = Mingw32CCompiler()
+        sysconfig.customize_compiler(compiler)