1  /* { dg-do compile } */
       2  /* { dg-options "-O2 -fno-strict-aliasing -fwrapv -fexcess-precision=standard" } */
       3  extern int foo();
       4  typedef struct {
       5    char id;
       6    unsigned char fork_flags;
       7    short data_length;
       8  } Header;
       9  int a;
      10  void X() {
      11    do {
      12      char* b;
      13      Header c;
      14      if (a)
      15        c.fork_flags |= 1;
      16      __builtin_memcpy(b, &c, __builtin_offsetof(Header, data_length));
      17      b += foo();
      18    } while (1);
      19  }