def _reset_cache():
    _pointer_type_cache.clear()
    _c_functype_cache.clear()
    if _os.name in ("nt", "ce"):
        _win_functype_cache.clear()
    # _SimpleCData.c_wchar_p_from_param
    POINTER(c_wchar).from_param = c_wchar_p.from_param
    # _SimpleCData.c_char_p_from_param
    POINTER(c_char).from_param = c_char_p.from_param
    _pointer_type_cache[None] = c_void_p
    # XXX for whatever reasons, creating the first instance of a callback
    # function is needed for the unittests on Win64 to succeed.  This MAY
    # be a compiler bug, since the problem occurs only when _ctypes is
    # compiled with the MS SDK compiler.  Or an uninitialized variable?
    CFUNCTYPE(c_int)(lambda: None)