--- /dev/null
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+int main ()
+{
+struct base {
+ int basic;
+};
+
+struct derived {
+ struct base common;
+ char extra;
+};
+
+volatile struct base b;
+volatile struct base *bp;
+
+bp = (struct base *)&b;
+
+bp->basic = 10;
+((struct derived volatile *)bp)->extra = 'x';
+return 0;
+}
+/* { dg-output "mudflap violation 1.*" } */
+/* { dg-output "Nearby object 1.*" } */
+/* { dg-output "mudflap object.*.main. b.*" } */
+/* { dg-do run { xfail *-*-* } } */