--- libaitsess/configure.in	2008/10/03 17:32:08	1.1.2.2
+++ libaitsess/configure.in	2011/04/30 21:24:21	1.1.2.3
@@ -1,6 +1,6 @@
 #
 # $Author: misho $
-# $Id: configure.in,v 1.1.2.2 2008/10/03 17:32:08 misho Exp $
+# $Id: configure.in,v 1.1.2.3 2011/04/30 21:24:21 misho Exp $
 #
 AC_INIT(libaitsess, 2.0, misho@openbsd-bg.org)
 AC_CONFIG_SRCDIR([src/aitsess.c])
@@ -31,6 +31,20 @@ AC_C_INLINE
 AC_FUNC_MALLOC
 AC_FUNC_MMAP
 AC_CHECK_FUNCS([bzero memset munmap])
+
+# It's stupid, but not all platforms have union semun, even those that need it.
+AC_MSG_CHECKING(looking for union semun in sys/sem.h)
+AC_TRY_COMPILE([
+		#include <sys/types.h>
+		#include <sys/ipc.h>
+		#include <sys/sem.h>
+		],[
+		union semun arg;
+		semctl(0, 0, 0, arg);
+		], [ 
+		AC_DEFINE(HAVE_UNION_SEMUN, $have_union_semun, [union semun])
+		] msg=yes, msg=no )
+AC_MSG_RESULT([$msg])
 
 DEBUG=no
 AC_MSG_CHECKING(Debug Build)