document message "unknown architecture"

diff --git a/usr.bin/mandoc/mandoc.1 b/usr.bin/mandoc/mandoc.1
index c41e431..3e3f479 100644 (file)
--- a/usr.bin/mandoc/mandoc.1
+++ b/usr.bin/mandoc/mandoc.1
@@ -1,4 +1,4 @@
-.\"    $OpenBSD: mandoc.1,v 1.127 2017/06/24 15:59:28 schwarze Exp $
+.\"    $OpenBSD: mandoc.1,v 1.128 2017/06/24 19:05:36 schwarze Exp $
 .\"
 .\" Copyright (c) 2009, 2010, 2011 Kristaps Dzonsons <kristaps@bsd.lv>
 .\" Copyright (c) 2012, 2014-2017 Ingo Schwarze <schwarze@openbsd.org>
@@ -816,6 +816,12 @@ macro does not use CVS
 keyword substitution, but using it is conventionally expected in the
 .Ox
 base system.
+.It Sy "unknown architecture"
+.Pq mdoc , Ox , Nx
+The third argument of the
+.Ic \&Dt
+macro does not match any of the architectures this operating system
+is running on.
 .It Sy "operating system explicitly specified"
 .Pq mdoc , Ox , Nx
 The