patch 7.4.2051
Problem:    No proper testing of trunc_string().
Solution:   Add a unittest for message.c.
diff --git a/src/message.c b/src/message.c
index 72cd79e..fe72e43 100644
--- a/src/message.c
+++ b/src/message.c
@@ -260,7 +260,7 @@
 	    return;
 	}
 	n = ptr2cells(s + e);
-	if (len + n >= half)
+	if (len + n > half)
 	    break;
 	len += n;
 	buf[e] = s[e];