1  typedef union
       2  {
       3    int __lock;
       4  } pthread_mutex_t;
       5  
       6  extern void abort (void);
       7  
       8  int main()
       9  {
      10      struct { int c; pthread_mutex_t m; } r = { .m = 0 };
      11      if (r.c != 0)
      12        abort ();
      13      return 0;
      14  }