Ensure Windows SDK directories are not cleared when caller specifies include/library dirs

distutils/_msvccompiler.py

@@ -224,6 +224,18 @@ def __init__(self, verbose=0, dry_run=0, force=0):
         self.plat_name = None
         self.initialized = False
 
+    @classmethod
+    def _configure(cls, vc_env):
+        """
+        Set class-level include/lib dirs.
+        """
+        cls.include_dirs = cls._parse_path(vc_env.get('include', ''))
+        cls.library_dirs = cls._parse_path(vc_env.get('lib', ''))
+
+    @staticmethod
+    def _parse_path(val):
+        return [dir.rstrip(os.sep) for dir in val.split(os.pathsep) if dir]
+
     def initialize(self, plat_name=None):
         # multi-init means we would need to check platform same each time...
         assert not self.initialized, "don't init multiple times"
@@ -243,6 +255,7 @@ def initialize(self, plat_name=None):
             raise DistutilsPlatformError(
                 "Unable to find a compatible " "Visual Studio installation."
             )
+        self._configure(vc_env)
 
         self._paths = vc_env.get('path', '')
         paths = self._paths.split(os.pathsep)
@@ -253,14 +266,6 @@ def initialize(self, plat_name=None):
         self.mc = _find_exe("mc.exe", paths)  # message compiler
         self.mt = _find_exe("mt.exe", paths)  # message compiler
 
-        for dir in vc_env.get('include', '').split(os.pathsep):
-            if dir:
-                self.add_include_dir(dir.rstrip(os.sep))
-
-        for dir in vc_env.get('lib', '').split(os.pathsep):
-            if dir:
-                self.add_library_dir(dir.rstrip(os.sep))
-
         self.preprocess_options = None
         # bpo-38597: Always compile with dynamic linking
         # Future releases of Python 3.x will include all past

distutils/ccompiler.py

@@ -91,6 +91,16 @@ class CCompiler:
     }
     language_order = ["c++", "objc", "c"]
 
+    include_dirs = []
+    """
+    include dirs specific to this compiler class
+    """
+
+    library_dirs = []
+    """
+    library dirs specific to this compiler class
+    """
+
     def __init__(self, verbose=0, dry_run=0, force=0):
         self.dry_run = dry_run
         self.force = force
@@ -324,24 +334,7 @@ def set_link_objects(self, objects):
 
     def _setup_compile(self, outdir, macros, incdirs, sources, depends, extra):
         """Process arguments and decide which source files to compile."""
-        if outdir is None:
-            outdir = self.output_dir
-        elif not isinstance(outdir, str):
-            raise TypeError("'output_dir' must be a string or None")
-
-        if macros is None:
-            macros = self.macros
-        elif isinstance(macros, list):
-            macros = macros + (self.macros or [])
-        else:
-            raise TypeError("'macros' (if supplied) must be a list of tuples")
-
-        if incdirs is None:
-            incdirs = self.include_dirs
-        elif isinstance(incdirs, (list, tuple)):
-            incdirs = list(incdirs) + (self.include_dirs or [])
-        else:
-            raise TypeError("'include_dirs' (if supplied) must be a list of strings")
+        outdir, macros, incdirs = self._fix_compile_args(outdir, macros, incdirs)
 
         if extra is None:
             extra = []
@@ -400,6 +393,9 @@ def _fix_compile_args(self, output_dir, macros, include_dirs):
         else:
             raise TypeError("'include_dirs' (if supplied) must be a list of strings")
 
+        # add include dirs for class
+        include_dirs += self.__class__.include_dirs
+
         return output_dir, macros, include_dirs
 
     def _prep_compile(self, sources, output_dir, depends=None):
@@ -456,6 +452,9 @@ def _fix_lib_args(self, libraries, library_dirs, runtime_library_dirs):
         else:
             raise TypeError("'library_dirs' (if supplied) must be a list of strings")
 
+        # add library dirs for class
+        library_dirs += self.__class__.library_dirs
+
         if runtime_library_dirs is None:
             runtime_library_dirs = self.runtime_library_dirs
         elif isinstance(runtime_library_dirs, (list, tuple)):

distutils/tests/test_ccompiler.py

@@ -0,0 +1,55 @@
+import os
+import sys
+import platform
+import textwrap
+import sysconfig
+
+import pytest
+
+from distutils import ccompiler
+
+
+def _make_strs(paths):
+    """
+    Convert paths to strings for legacy compatibility.
+    """
+    if sys.version_info > (3, 8) and platform.system() != "Windows":
+        return paths
+    return list(map(os.fspath, paths))
+
+
+@pytest.fixture
+def c_file(tmp_path):
+    c_file = tmp_path / 'foo.c'
+    gen_headers = ('Python.h',)
+    is_windows = platform.system() == "Windows"
+    plat_headers = ('windows.h',) * is_windows
+    all_headers = gen_headers + plat_headers
+    headers = '\n'.join(f'#include <{header}>\n' for header in all_headers)
+    payload = (
+        textwrap.dedent(
+            """
+        #headers
+        void PyInit_foo(void) {}
+        """
+        )
+        .lstrip()
+        .replace('#headers', headers)
+    )
+    c_file.write_text(payload)
+    return c_file
+
+
+def test_set_include_dirs(c_file):
+    """
+    Extensions should build even if set_include_dirs is invoked.
+    In particular, compiler-specific paths should not be overridden.
+    """
+    compiler = ccompiler.new_compiler()
+    python = sysconfig.get_paths()['include']
+    compiler.set_include_dirs([python])
+    compiler.compile(_make_strs([c_file]))
+
+    # do it again, setting include dirs after any initialization
+    compiler.set_include_dirs([python])
+    compiler.compile(_make_strs([c_file]))