patch 7.4.1476
Problem:    Function arguments marked as unused while they are not.
Solution:   Remove UNUSED. (Yegappan Lakshmanan)
diff --git a/src/diff.c b/src/diff.c
index be7e38c..92e1a05 100644
--- a/src/diff.c
+++ b/src/diff.c
@@ -641,7 +641,7 @@
  */
     void
 ex_diffupdate(
-    exarg_T	*eap UNUSED)	    /* can be NULL */
+    exarg_T	*eap)	    /* can be NULL */
 {
     buf_T	*buf;
     int		idx_orig;