C snippet that reproduces the problem

test.c (text/x-csrc), 418 bytes, created by Ole Christensen on 2015-06-20 12:18:51 UTC

int            g  = 0;
int * volatile gp = &g;

extern int write (int, const void *, unsigned count);

void
func (void)
{
  int *lp = &g;

  *lp = 0;
  // uncomment this to make the program run Ok
  //printf ("func: %d\n", *lp);

  *gp = 1;
}

int
main (void)
{
  unsigned long *p = (unsigned long *) &g;

  func ();

  if (((int) *p) == 1)
    write (1, "Ok\n", 3);
  else
    write (1, "ERROR\n", 6);

  return 0;
}