start_link(M, A) ->
    spawn_link(
      fun () ->
              ProxyPid = self(),
              Ref = make_ref(),
              Pid = spawn_link(
                      fun () -> mainloop(
                                  ProxyPid, Ref, M,
                                  M:init(ProxyPid, A))
                      end),
              proxy_loop(Ref, Pid, empty)
      end).