class foo =
  object(dummy)
    initializer
      print_string "*** constructor\n";
      Gc.finalise (fun _ -> print_string "*** destructor\n") dummy
  end;;

new foo;;
print_string "Foo was out-scoped.\n";;
Gc.full_major ();;
print_string "Gc was run.\n";;


(* however, this can't really be used as a destructor since the closure *)
(* given to Gc.finalise will retain a reference to the instance if *)
(* anything in his environment reaches the object *)

(* http://caml.inria.fr/pub/ml-archives/caml-list/2002/03/d61da155e0a36f4794e6ff02eed48ade.en.html *)