: VALUE rb_ensure(VALUE (*body)(), VALUE data1, VALUE (*ensure)(), VALUE data2)
    ensure  C ǤǤޤ body(data1) ¹Ԥ
    㳰 exit ȤƤ ensure(data2) μ¤
    ¹Ԥޤ ( body() ｪλƤ¹Ԥޤ)

