llvm-gcc-4.2/gcc/testsuite/gcc.dg/gomp/appendix-a/a.17.2.c

/* { dg-do compile } */

void
a17_2_wrong ()
{
  int x;
  int *i;
  float *r;
  i = &x;
  r = (float *) &x;
#pragma omp parallel
  {
#pragma omp atomic
    *i += 1;
#pragma omp atomic
    *r += 1.0;
/* Incorrect because the atomic constructs reference the same location
     through incompatible types */
  }
}