bpo-32869: Fix incorrect dst buffer size for MultiByteToWideChar (#5739)

This function expects the destination buffer size to be given
in wide characters, not bytes.

diff --git a/Python/fileutils.c b/Python/fileutils.c
index 3cf8b7a8b69d73d46a92d2e1ae2c15a878507671..32aeea4f10374b6353a4186bf09ea91dcce656b8 100644 (file)
--- a/Python/fileutils.c
+++ b/Python/fileutils.c
@@ -1289,7 +1289,8 @@ _Py_fopen_obj(PyObject *path, const char *mode)
     if (wpath == NULL)
         return NULL;
 
-    usize = MultiByteToWideChar(CP_ACP, 0, mode, -1, wmode, sizeof(wmode));
+    usize = MultiByteToWideChar(CP_ACP, 0, mode, -1,
+                                wmode, Py_ARRAY_LENGTH(wmode));
     if (usize == 0) {
         PyErr_SetFromWindowsErr(0);
         return NULL;