You wrote (in your message from Tuesday 1)
 > Hi Folks,
 > 	I have traced down the source of this problem. If I revert
 > sys/featuretest.h back to version 1.2 before Jason's change, xdm under xfree
 > 4 now compiles. I have no idea what to do about it though.

Apply this patch to dm.h. I agree with Jason in
<http://mail-index.netbsd.org/source-changes/2001/12/26/0065.html> 
that XFree86 should not play games with _POSIX_SOURCE there. 

Index: xc/programs/xdm/dm.h
===================================================================
RCS file: /home/x-cvs/xc/programs/xdm/dm.h,v
retrieving revision 3.27
diff -u -r3.27 dm.h
--- xc/programs/xdm/dm.h	2001/12/14 20:01:21	3.27
+++ xc/programs/xdm/dm.h	2002/01/01 14:13:04
@@ -26,7 +26,7 @@
 from The Open Group.
 
 */
-/* $XFree86: xc/programs/xdm/dm.h,v 3.27 2001/12/14 20:01:21 dawes Exp $ */
+/* $XFree86: dm.h,v 3.27 2001/12/14 20:01:21 dawes Exp $ */
 
 /*
  * xdm - display manager daemon
@@ -52,15 +52,8 @@
 #include <limits.h>
 #undef _POSIX_C_SOURCE
 #else
-#if defined(X_NOT_POSIX) || defined(_POSIX_SOURCE)
 #include <setjmp.h>
 #include <limits.h>
-#else
-#define _POSIX_SOURCE
-#include <setjmp.h>
-#include <limits.h>
-#undef _POSIX_SOURCE
-#endif
 #endif
 #include <time.h>
 #define Time_t time_t
-- 
					Matthieu