gcc-4.6/gcc/testsuite/g++.dg/warn/unit-1.C

/* { dg-do compile } */
/* { dg-options "-O2 -Wuninitialized" } */

struct a { int mode; };
int sys_msgctl (void)
{
  struct a setbuf;  /* { dg-warning "'setbuf.mode' is used" "" { xfail *-*-* } } */
  return setbuf.mode;
}