Use smartlist_asprintf_add() to improve readability.

src/or/control.c

@@ -4015,13 +4015,11 @@ control_event_conf_changed(smartlist_t *elements)
   for (i = 0; i < smartlist_len(elements); i += 2) {
     char *k = smartlist_get(elements, i);
     char *v = smartlist_get(elements, i+1);
-    char *tmp;
     if (v == NULL) {
-      tor_asprintf(&tmp, "650-%s", k);
+      smartlist_asprintf_add(lines, "650-%s", k);
     } else {
-      tor_asprintf(&tmp, "650-%s=%s", k, v);
+      smartlist_asprintf_add(lines, "650-%s=%s", k, v);
     }
-    smartlist_add(lines, tmp);
   }
   result = smartlist_join_strings(lines, "\r\n", 0, NULL);
   send_control_event(EVENT_CONF_CHANGED, 0,