-extern char *ad_dir __P((char *));
-extern char *ad_path __P((char *, int));
-extern int ad_mode __P((char *, int));
-extern int ad_mkdir __P((char *, int));
-extern int ad_open __P((char *, int, int, int, struct adouble *));
+extern char *ad_dir __P((const char *));
+extern char *ad_path __P((const char *, int));
+extern int ad_mode __P((const char *, int));
+extern int ad_mkdir __P((const char *, int));
+extern int ad_open __P((const char *, int, int, int, struct adouble *));