if (ur->rung_list_size <= (ur->avail_index + 2) * sizeof(ElsRungNode)) {
// remember rung_node position
ptrdiff_t pos = rung_node - ur->rem_rung_list;
if (ur->rung_list_size <= (ur->avail_index + 2) * sizeof(ElsRungNode)) {
// remember rung_node position
ptrdiff_t pos = rung_node - ur->rem_rung_list;