===================================================================
RCS file: /cvsrepo/anoncvs/cvs/src/usr.bin/m4/m4.1,v
retrieving revision 1.33
retrieving revision 1.34
diff -u -r1.33 -r1.34
--- src/usr.bin/m4/m4.1	2003/06/27 21:22:52	1.33
+++ src/usr.bin/m4/m4.1	2003/06/29 11:04:03	1.34
@@ -1,4 +1,4 @@
-.\"	@(#) $OpenBSD: m4.1,v 1.33 2003/06/27 21:22:52 jmc Exp $
+.\"	@(#) $OpenBSD: m4.1,v 1.34 2003/06/29 11:04:03 espie Exp $
 .\"
 .\" Copyright (c) 1989, 1993
 .\"	The Regents of the University of California.  All rights reserved.
@@ -394,6 +394,19 @@
 to allow
 .Nm autoconf
 to work.
+.Pp
+The built-ins
+.Ic pushdef
+and
+.Ic popdef
+handle macro definitions as a stack.
+However,
+.Ic define
+interacts with the stack in an undefined way.
+In this implementation,
+.Ic define
+replaces the top-most definition only.
+Other implementations may erase all definitions on the stack instead.
 .Pp
 For portability, one should not use the macros
 .Ic builtin ,