anchor.diff:  -spec rep_spawn(fun()) -> pid().
   
   rep_spawn(Fun) ->
  +    %% XXX: Possible race between `yield` message of child and
  +    %%      `spawn` message of parent.
       Pid = spawn(fun() -> rep_yield(), Fun() end),
       sched ! #sched{msg = spawn, pid = self(), misc = [Pid]},
       rep_yield(),
  
positive.code: stop(Reason) ->
      log:log("-----------------------~n"),
      log:log("Run terminated (~p).~n~n", [Reason]),
      case Reason of
          normal -> ?RET_NORMAL;
          _ -> ?RET_HEISENBUG
  
negative.code: %% of them into the `states` table.
  %% Returns the process to be run next.
  search(#info{active = Active, state = State} = Info) ->
      ?debug("(Search) active set: ~p~n", [sets:to_list(Active)]),
      %% Remove a process from the `actives` set and run it.
      {Next, NewActive} = set_pop(Active),
      %% Store all other possible successor states in `states` table for later
      %% exploration.
      state_insert_succ(Info#info{active = NewActive, state = State}),
      Next.
  
  %% Block message handler.
  