fixes

pl/listing.yap

@@ -63,8 +63,8 @@ listing :-
     Mod \= prolog,
     Mod \= system,
     \+ '$hidden_atom'( Mod ),
-    '$current_predicate'(_,Mod,Pred, user),
-    '$undefined'(Pred, prolog), % skip predicates exported from prolog.
+    current_predicate( Name, Mod:Pred ),
+    \+ '$undefined'(Pred, Mod), % skip predicates exported from prolog.
     functor(Pred,Name,Arity),
     '$listing'(Name,Arity,Mod,Stream),
     fail.
@@ -108,7 +108,9 @@ listing(Stream, [MV|MVs]) :- !,
     ).
 
 '$do_listing'(Stream, M, Name/Arity) :-
-    ( current_predicate(M:Name/Arity),
+    ( current_predicate(Name, M:Pred),
+      functor( Pred, Name, Arity),
+      \+ '$undefined'(Pred, M),
       '$listing'(Name,Arity,M,Stream),
       fail
    ;