Update Modules/_ctypes/_ctypes.c

Co-authored-by: Petr Viktorin <encukou@gmail.com>

Author: ZeroIntensity

Modules/_ctypes/_ctypes.c

@@ -3117,8 +3117,11 @@ static int
 PyCData_MallocBuffer(CDataObject *obj, StgInfo *info)
 {
     /* We don't have to lock in this function, because it's only
-       used in constructors and therefore does not have concurrent
-       access. */
+     * used in constructors and therefore does not have concurrent
+     * access.
+     */
+   assert (Py_REFCNT(obj) == 1);
+
     if ((size_t)info->size <= sizeof(obj->b_value)) {
         /* No need to call malloc, can use the default buffer */
         obj->b_ptr = (char *)&obj->b_value;