int observer_test_second_observer = 0;
int observer_test_third_observer = 0;
+/* Provide prototypes to silence -Wmissing-prototypes. */
+extern void observer_test_first_notification_function (int arg);
+extern void observer_test_second_notification_function (int arg);
+extern void observer_test_third_notification_function (int arg);
+
void
observer_test_first_notification_function (int arg)
{