$OpenBSD: patch-support_sys-mman_c,v 1.1 2014/07/09 11:39:17 robert Exp $
--- support/sys-mman.c.orig	Tue Jul  8 13:07:33 2014
+++ support/sys-mman.c	Tue Jul  8 13:10:35 2014
@@ -9,13 +9,15 @@
 
 #include <config.h>
 
+#if !defined(__OpenBSD__)
 #define _XOPEN_SOURCE 600
+#endif
 
 #ifdef PLATFORM_MACOSX
 /* For mincore () */
 #define _DARWIN_C_SOURCE
 #endif
-#ifdef __FreeBSD__
+#if defined(__FreeBSD__) || defined(__OpenBSD__)
 /* For mincore () */
 #define __BSD_VISIBLE 1
 #endif
