extern int rev_same_tree_as_empty(struct rev_info *, struct tree *t1);
extern int rev_compare_tree(struct rev_info *, struct tree *t1, struct tree *t2);
extern int rev_same_tree_as_empty(struct rev_info *, struct tree *t1);
extern int rev_compare_tree(struct rev_info *, struct tree *t1, struct tree *t2);