# again __P isn't defined anywhere else
--- opendkim-2.10.3/opendkim/config.h	2022-02-05 20:11:14.668189198 +0000
+++ opendkim-2.10.3/opendkim/config.h.new	2022-02-05 20:14:36.784798073 +0000
@@ -18,6 +18,16 @@
 #endif /* HAVE_STDBOOL_H */
 #include <stdio.h>
 
+#ifdef __STDC__
+# ifndef __P
+#  define __P(x)  x
+# endif /* ! __P */
+#else /* __STDC__ */
+# ifndef __P
+#  define __P(x)  ()
+# endif /* ! __P */
+#endif /* __STDC__ */
+
 /* types and things */
 #define	CONFIG_TYPE_STRING	0
 #define	CONFIG_TYPE_INTEGER	1