Sizes of pthreads-win32 structs
-------------------------------
                     pthread_t   16
                ptw32_thread_t  432
               pthread_attr_t_   40
                        sem_t_   24
              pthread_mutex_t_   48
          pthread_mutexattr_t_   12
           pthread_spinlock_t_   16
            pthread_barrier_t_   64
        pthread_barrierattr_t_    4
                pthread_key_t_   32
               pthread_cond_t_   56
           pthread_condattr_t_    4
             pthread_rwlock_t_   40
         pthread_rwlockattr_t_    4
               pthread_once_t_   24
               ptw32_cleanup_t   24
             ptw32_mcs_node_t_   32
                   sched_param    4
-------------------------------