anchor.diff:      T1State = on_bp(Msg, State),
       Module  = gc_mod(T1State),
       Handler = gc_hand(T1State),
  +    UState = gc_ustate(T1State),
       T2State =
  -        try Handler(Msg, gc_ustate(T1State))
  +        try Handler(Msg, UState)
           catch Level:Reason ->
                   Stacktrace = erlang:get_stacktrace(),
  +                io:format("Stacktrace ~.0p~n", [Stacktrace]),
                   case Stacktrace of
                       %% erlang < R15 : {Module, Handler, [Msg, State]}
                       %% erlang >= R15: {Module, Handler, [Msg, State], _}
                       [T | _] when
                             erlang:element(1, T) =:= Module andalso
  -                          erlang:element(2, T) =:= Handler andalso
  -                          erlang:element(3, T) =:= [Msg, T1State] andalso
  +                          %% erlang:element(2, T) =:= Handler andalso
  +                          erlang:element(3, T) =:= [Msg, UState] andalso
                             Reason =:= function_clause andalso
                             Level =:= error ->
                           {'$gc_unknown_event',
  
positive.code:             "~n** Exception:~n ~.0p:~.0p~n"
              "** Current message:~n ~.0p~n"
              "** Module:~n ~.0p~n"
              "** Source linetrace (enable in scalaris.hrl):~n ~.0p~n"
              "** State:~n ~.0p~n"
              "** Handler:~n ~.0p~n"
              "** Stacktrace:~n ~.0p~n",
              [Level, Reason,
               Msg,
               gc_mod(State),
               erlang:get(test_server_loc),
               State,
               gc_hand(State),
               Stacktrace]),
      State.
  
  
negative.code:             end;
          {'$gc_unknown_event', NewState} -> NewState;
          {'$gc_exception', NewState} ->     NewState;
          unknown_event ->
              %% drop T2State, as it contains the error message
              TmpState = on_unknown_event(Msg, T1State),
              bp_step_done(Msg, TmpState);
          NewUState ->
              bp_step_done(Msg, gc_set_ustate(T1State, NewUState))
      end.
  