-extern uschar *b64encode(uschar *, int);
-extern int b64decode(uschar *, uschar **);
-extern int bdat_getc(void);
+#ifdef EXPERIMENTAL_ARC
+extern gstring *authres_arc(gstring *);
+#endif
+#ifndef DISABLE_DKIM
+extern gstring *authres_dkim(gstring *);
+#endif
+#ifdef EXPERIMENTAL_DMARC
+extern gstring *authres_dmarc(gstring *);
+#endif
+extern gstring *authres_smtpauth(gstring *);
+#ifdef SUPPORT_SPF
+extern gstring *authres_spf(gstring *);
+#endif
+
+extern uschar *b64encode(const uschar *, int);
+extern int b64decode(const uschar *, uschar **);
+extern int bdat_getc(unsigned);
+extern uschar *bdat_getbuf(unsigned *);
+extern int bdat_ungetc(int);
+extern void bdat_flush_data(void);
+