- * If the call is successful, then the filter string's address is put
- * in *filter_string. If the event has no filter string, *filter_string
- * is set to NULL. The caller does NOT own *filter_string.
+ * If the call is successful, then the filter expression's address is put
+ * in *filter_expression. If the event has no filter expression,
+ * *filter_expression is set to NULL. The caller does NOT own
+ * *filter_expression.