--- gdbtk_orig/generic/gdbtk-stack.c	2012-03-05 09:19:01.000000000 +0100
+++ gdbtk/generic/gdbtk-stack.c	2012-03-14 11:56:31.851248200 +0100
@@ -289,7 +289,7 @@
       return TCL_ERROR;
     }
 
-  arguments = (long) clientData;
+  arguments = clientData!=NULL?1:0;
 
   /* Initialize the result pointer to an empty list. */