extern BOOL string_format(uschar *, int, const char *, ...) ALMOST_PRINTF(3,4);
extern uschar *string_format_size(int, uschar *);
extern int string_interpret_escape(uschar **);
-extern int string_is_ip_address(uschar *, int *);
+extern int string_is_ip_address(const uschar *, int *);
extern uschar *string_log_address(address_item *, BOOL, BOOL);
extern uschar *string_nextinlist(uschar **, int *, uschar *, int);
extern uschar *string_open_failed(int, const char *, ...) PRINTF_FUNCTION(2,3);