anchor.diff:            ?debug_flag(?loop, sending_kill_to_cancel),
             ets:delete(Timers, Ref),
             Pid ! {exit_signal, #message{data = kill}, self()},
  -          receive {trapping, false} -> ok end
  +          false = receive_message_ack()
         end,
         {1, Info}
     end;
  
positive.code: send_message_ack(Notify, Trapping) ->
    case Notify =/= ?notify_none of
      true ->
        Notify ! {trapping, Trapping},
        ok;
      false -> ok
    end.
  
  get_leader(#concuerror_info{processes = Processes}, P) ->
  
negative.code:     case Recipient =:= Self of
        true ->
          %% Instant delivery to self
          send_message_ack(Self, element(2, Instant)),
          ?notify_none;
        false -> Self
      end,
    Recipient ! {Type, Message, Notify},
    receive
      {message_ack, Trapping} ->
        NewMessageEvent = MessageEvent#message_event{trapping = Trapping},
        NewSpecial =
          case already_known_delivery(Message, Special) of
  