pathfinder: use os.add_dll_directory() instead of raw kernel32 call

Per @leofang's review question: replace the direct ctypes
kernel32.AddDllDirectory() call with the stdlib os.add_dll_directory()
wrapper. Both call the same Win32 API, but the stdlib version drops the
hand-maintained argtypes/restype binding and reports failure as OSError
instead of a NULL cookie + GetLastError() check. Behavior is unchanged:
the returned handle is intentionally discarded (it has no finalizer, so
the directory stays on the search path for the process lifetime), and the
PATH mutation + failure warning are preserved.

Also strip an internal issue number from a test docstring.

Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>

Author: rparolin

cuda_pathfinder/cuda/pathfinder/_dynamic_libs/load_dl_windows.py

@@ -44,10 +44,6 @@
 ]
 kernel32.GetModuleFileNameW.restype = ctypes.wintypes.DWORD
 
-# AddDllDirectory (Windows 7+)
-kernel32.AddDllDirectory.argtypes = [ctypes.wintypes.LPCWSTR]
-kernel32.AddDllDirectory.restype = ctypes.c_void_p  # DLL_DIRECTORY_COOKIE
-
 
 def ctypes_handle_to_unsigned_int(handle: ctypes.wintypes.HMODULE) -> int:
     """Convert ctypes HMODULE to unsigned int."""
@@ -70,16 +66,19 @@ def add_dll_directory(dll_abs_path: str) -> None:
     dirpath = os.path.dirname(dll_abs_path)
     assert os.path.isdir(dirpath), dll_abs_path
 
-    # Add the DLL directory to the native search path. AddDllDirectory only
-    # affects the LOAD_LIBRARY_SEARCH_USER_DIRS search; PATH is updated
-    # unconditionally below to also cover legacy dependent-DLL resolution.
-    cookie = kernel32.AddDllDirectory(dirpath)
-    if not cookie:
+    # Add the DLL directory to the native search path via the stdlib wrapper
+    # around AddDllDirectory. This only affects the LOAD_LIBRARY_SEARCH_USER_DIRS
+    # search; PATH is updated unconditionally below to also cover legacy
+    # dependent-DLL resolution. The returned handle is intentionally discarded:
+    # the directory must stay on the search path for the process lifetime, and
+    # the handle has no finalizer, so dropping it does not remove the directory.
+    try:
+        os.add_dll_directory(dirpath)  # type: ignore[attr-defined]
+    except OSError as e:
         # Warn instead of failing silently; the PATH update below is a weaker
         # fallback that newer loaders may ignore.
-        error_code = ctypes.GetLastError()  # type: ignore[attr-defined]
         warnings.warn(
-            f"AddDllDirectory({dirpath!r}) failed (error code: {error_code}); "
+            f"os.add_dll_directory({dirpath!r}) failed ({e}); "
             "falling back to process-global PATH mutation for dependent-DLL resolution.",
             RuntimeWarning,
             stacklevel=2,

cuda_pathfinder/tests/test_find_nvidia_binaries.py

@@ -373,7 +373,7 @@ def test_caching_per_utility():
 
 
 def test_resolve_in_trusted_dirs_returns_absolute_path(tmp_path, monkeypatch, mocker):
-    """#374: a match found under a relative search dir must be absolutized.
+    """A match found under a relative search dir must be absolutized.
 
     ``find_nvidia_binary_utility`` documents an absolute, separator-resolved
     result. A relative search dir (e.g. a relative ``CUDA_HOME``) previously