G_DEFINE_INTERFACE (Logger, logger, G_TYPE_INVALID);
static void
-logger_logv_default (Logger *self, GLogLevelFlags log_level, const gchar *format, va_list ap);
+logger_logv_default (Logger *self, GLogLevelFlags log_level, const gchar *format, va_list ap) __attribute__ ((format (printf, 3, 0)));
static void
logger_default_init (LoggerInterface *iface)