+ if (!filter_expression) {
+ /*
+ * Fall back to normal event enabling if no filter
+ * specified.
+ */
+ return lttng_enable_event(handle, event, channel_name);
+ }
+
+ /*
+ * Empty filter string will always be rejected by the parser
+ * anyway, so treat this corner-case early to eliminate
+ * lttng_fmemopen error for 0-byte allocation.
+ */
+ if (handle == NULL || filter_expression[0] == '\0') {