anchor.diff:  get_next_event(Event, [{Pair, Queue}|_], _ActiveProcesses, State) ->
     %% Pending messages can always be sent
     MessageEvent = queue:get(Queue),
  -  %% XXX: Sending to an uninstrumented process should be caught here
     Special = {message_delivered, MessageEvent},
     UpdatedEvent =
       Event#event{
  
positive.code: max_cv(D1, D2) ->
    Merger = fun(_Key, V1, V2) -> max(V1, V2) end,
    orddict:merge(Merger, D1, D2).
  
negative.code: %% Between scheduler and an instrumented process
  %%------------------------------------------------------------------------------
  
  get_next_event_backend(#event{actor = {_Sender, Recipient}} = Event, _State) ->
    #event{event_info = EventInfo} = Event,
    #message_event{message = Message, type = Type} = EventInfo,
    %% Message delivery always succeeds
    Recipient ! {Type, Message},
    UpdatedEvent =
      receive
        {trapping, Trapping} ->
          NewEventInfo = EventInfo#message_event{trapping = Trapping},
          Event#event{event_info = NewEventInfo};
        {system_reply, From, Reply} ->
          #event{special = Special} = Event,
          case is_list(Special) of
            true ->
              #message_event{message = #message{data = OldReply}} =
                proplists:get_value(message, Special),
              case OldReply =:= Reply of
                true -> Event;
                false ->
                  error({system_reply_differs, OldReply, Reply})
              end;
            false ->
              MessageEvent =
                #message_event{
                   cause_label = Event#event.label,
                   message = #message{data = Reply, message_id = make_ref()},
                   sender = Recipient,
                   recipient = From},
              Event#event{special = [{message, MessageEvent},Special]}
          end
      after
        2000 ->
          error(too_late)
      end,
    {ok, UpdatedEvent};
  get_next_event_backend(#event{actor = Pid} = Event, State) when is_pid(Pid) ->
    Pid ! Event,
    get_next_event_backend_loop(Event, State).
  