--- a/src/pt-exp-base.h
+++ b/src/pt-exp-base.h
@@ -24,10 +24,6 @@
 #if !defined (octave_tree_expr_h)
 #define octave_tree_expr_h 1
 
-#if defined (__GNUG__)
-#pragma interface
-#endif
-
 #include <time.h>
 #include <stdio.h>
 #include <iostream.h>
@@ -117,7 +113,7 @@
       etype = unknown;
     }
 
-  ~tree_expression (void) { }
+  virtual ~tree_expression (void) { }
 
   virtual int is_multi_val_ret_expression (void) const
     { return 0; }
@@ -268,8 +264,6 @@
       maybe_do_ans_assign = 0;
     }
 
-  ~tree_identifier (void) { }
-
   int is_identifier (void) const
     { return 1; }
 
@@ -777,8 +771,6 @@
   tree_builtin (int i_max, int o_max, Octave_builtin_fcn f,
 		const char *nm = 0);
 
-  ~tree_builtin (void) { }
-
 //  int is_builtin (void) const;
 
   int is_mapper_function (void) const
@@ -843,8 +835,6 @@
 	 cmd_list = cl;
        }
 
-  ~tree_function (void) { }
-
 //  tree_function *define (tree_statement_list *t);
   tree_function *define_param_list (tree_parameter_list *t);
   tree_function *define_ret_list (tree_parameter_list *t);