anchor.diff:  -include("sighandler.hrl").
   
   %% API
  --export([start_link/0, stop/0, install/2, remove/1, remove/2, lookup_term/1]).
  +-export([start_link/0, stop/0, install/2, remove/1, remove/2, lookup_term/1, registered/0]).
   
   %% gen_server callbacks
   -export([init/1, handle_call/3, handle_cast/2, handle_info/2,
  
positive.code:     {ok, State0} = remove(Sig, Fun, State),
      {reply, ok, State0};
  handle_call(stop, _From, State) -> {stop, normal, ok, State};
  handle_call(Request, _From, State) ->
      error_logger:info_msg(?MODULE_STRING " ~p ignoring call: ~p~n",
  			  [self(), Request]),
  
negative.code:     lists:foreach(Fun, sighandler_nif:module_info(exports)).
  
  %% State management
  install(Sig, Fun, Ref, #state{handlers = Handlers, port = Port} = State) ->
      Installed = case sighandler_drv:status(Port, Sig) of
  		    active -> installed;
  