problem with gtk_signal_connect

[Jean Michel LECONTE <Jean-Michel Leconte lambda-systems com>]

I have probs to pass a structure (PlTerm)  through a signal_connect as the 
argument of the function i want to connect to the signal
it seems that the argument *goal  is reinitialized when i fall in the 
function callback_signals

Why ?

Thanks a lot 

void callback_signals(GtkWidget *widg, gpointer *goal)
{
   PlTerm *arg;
 int functor,arity;
 int result;
 printf("salut ");
 arg=Rd_Callable_Check(*(PlTerm *)goal,&functor,&arity);

 result=Pl_Query_Start(functor,arity,arg,FALSE);
 Pl_Query_End(PL_KEEP_FOR_PROLOG);

}

Bool set_signal_connect(int internal_number,char *signal,PlTerm *goal)
{

    gtk_signal_connect (GTK_OBJECT (tableofelements[internal_number]), signal,
                        GTK_SIGNAL_FUNC(callback_signals),
                        (gpointer)(goal));
    return TRUE;
}