anchor.diff:  -spec on_traced_msg(comm:message(), user_state(), gc_state())
                      -> ok.
   on_traced_msg(GCMsg, UState, GCState)
  -  when is_tuple(GCMsg)
  -       andalso '$gen_component' =:= element(1, GCMsg) ->
  +  when is_tuple(GCMsg) andalso '$gen_component' =:= element(1, GCMsg) ->
       on_gc_msg(GCMsg, UState, GCState);
  -on_traced_msg({ping, Pid}, UState, GCState) ->
  -    %% handle failure detector messages
  -    comm:send(Pid, {pong, pid_groups:my_pidname()}, [{channel, prio}]),
  -    MsgTag = erlang:erase('$gen_component_trace_mpath_msg_tag'),
  -    trace_mpath:log_info(self(), {gc_on_done, MsgTag}),
  -    trace_mpath:stop(),
  -    loop(UState, GCState);
  -on_traced_msg({?send_to_group_member, Processname, Msg}, UState, GCState) ->
  -    %% forward a message to group member by its process name
  -    %% initiated via comm:send/3 with group_member
  -    Pid = pid_groups:get_my(Processname),
  -    case Pid of
  -        failed -> ok;
  -        _      -> comm:send_local(Pid, Msg)
  -    end,
  -    MsgTag = erlang:erase('$gen_component_trace_mpath_msg_tag'),
  -    trace_mpath:log_info(self(), {gc_on_done, MsgTag}),
  -    trace_mpath:stop(),
  -    loop(UState, GCState);
   on_traced_msg(Msg, UState, GCState) ->
       T1GCState = on_bp(Msg, UState, GCState),
       Module  = gc_mod(T1GCState),
       Handler = gc_hand(T1GCState),
  -    try Handler(Msg, UState) of
  +    try handle_message(Msg, UState, Handler) of
           kill ->
               log:log(info, "[ gen_component ] ~.0p killed (~.0p:~.0p/2):",
                       [self(), Module, Handler]),
  
positive.code:         _ ->
              Module  = gc_mod(T1GCState),
              Handler = gc_hand(T1GCState),
              try Handler(Msg, UState) of
                  kill ->
                      log:log(info, "[ gen_component ] ~.0p killed (~.0p:~.0p/2):",
                              [self(), Module, Handler]),
  
negative.code:                    gc_bpactive/1, gc_set_bpactive/2,
                     gc_bpqueue/1, gc_set_bpqueue/2,
                     gc_bpstepped/1, gc_set_bpstepped/2,
                     gc_bpstepper/1, gc_set_bpstepper/2,
                     handle_message/3
                    ]}).
  
  -include("scalaris.hrl").
  