Avoid an undefined behavior of memcpy() in gzappend().
diff --git a/examples/gzappend.c b/examples/gzappend.c
index 662dec3..d7eea3e 100644
--- a/examples/gzappend.c
+++ b/examples/gzappend.c
@@ -137,7 +137,7 @@
     /* do simple left shift by one */
     if (rot == 1) {
         tmp = *list;
-        memcpy(list, list + 1, len - 1);
+        memmove(list, list + 1, len - 1);
         *last = tmp;
         return;
     }