-void sendmessagetouser(nick *source, nick *target, char *format, ... );
-void sendsecuremessagetouser(nick *source, nick *target, char *servername, char *format, ... );
-void sendnoticetouser(nick *source, nick *target, char *format, ... );
-void killuser(nick *source, nick *target, char *format, ... );
+void sendmessagetouser(nick *source, nick *target, char *format, ... ) __attribute__ ((format (printf, 3, 4)));
+void sendsecuremessagetouser(nick *source, nick *target, char *servername, char *format, ... ) __attribute__ ((format (printf, 4, 5)));
+void sendnoticetouser(nick *source, nick *target, char *format, ... ) __attribute__ ((format (printf, 3, 4)));
+void killuser(nick *source, nick *target, char *format, ... ) __attribute__ ((format (printf, 3, 4)));