-void helpmod_message_channel_long(hchannel *hchan, const char *message, ...);
-void helpmod_message_channel(hchannel *hchan, const char *message, ...);
+void helpmod_message_channel_long(hchannel *hchan, const char *message, ...) __attribute__ ((format (printf, 2, 3)));
+void helpmod_message_channel(hchannel *hchan, const char *message, ...) __attribute__ ((format (printf, 2, 3)));