bpo-36085: Enable better DLL resolution on Windows (GH-12302)

1 files changed, 37 insertions, 0 deletions

diff --git a/Lib/os.py b/Lib/os.py
index 7741c75..79ff7a2 100644
--- a/Lib/os.py
+++ b/Lib/os.py
@@ -1070,3 +1070,40 @@ class PathLike(abc.ABC):
     @classmethod
     def __subclasshook__(cls, subclass):
         return hasattr(subclass, '__fspath__')
+
+
+if name == 'nt':
+    class _AddedDllDirectory:
+        def __init__(self, path, cookie, remove_dll_directory):
+            self.path = path
+            self._cookie = cookie
+            self._remove_dll_directory = remove_dll_directory
+        def close(self):
+            self._remove_dll_directory(self._cookie)
+            self.path = None
+        def __enter__(self):
+            return self
+        def __exit__(self, *args):
+            self.close()
+        def __repr__(self):
+            if self.path:
+                return "<AddedDllDirectory({!r})>".format(self.path)
+            return "<AddedDllDirectory()>"
+
+    def add_dll_directory(path):
+        """Add a path to the DLL search path.
+
+        This search path is used when resolving dependencies for imported
+        extension modules (the module itself is resolved through sys.path),
+        and also by ctypes.
+
+        Remove the directory by calling close() on the returned object or
+        using it in a with statement.
+        """
+        import nt
+        cookie = nt._add_dll_directory(path)
+        return _AddedDllDirectory(
+            path,
+            cookie,
+            nt._remove_dll_directory
+        )