_hurd_id.aux.uids[0] = _hurd_id.aux.uids[1] = uid;
newaux[0] = newaux[1] = uid;
DEFUN(__setuid, (uid), uid_t uid){  auth_t newauth;  error_t err;  HURD_CRITICAL_BEGIN;  __mutex_lock (&_hurd_id.lock);  err = _hurd_check_ids ();  if (!err)    {      /* Make a new auth handle which has UID as the real uid,	 and as the first element in the list of effective uids.  */      uid_t *newgen, *newaux, auxbuf[2];      size_t ngen, naux;      newaux = _hurd_id.aux.uids;      naux = _hurd_id.aux.nuids;      if (_hurd_id.gen.nuids == 0)	{	  /* No effective uids now.  The new set will be just UID.  */	  newgen = &uid;	  ngen = 1;	}      else if (_hurd_id.gen.uids[0] == 0)	{	  /* We are root; set the effective, real, and saved to UID.  */	  _hurd_id.gen.uids[0] = uid;	  _hurd_id.valid = 0;	  newgen = _hurd_id.gen.uids;	  ngen = _hurd_id.gen.nuids;	  if (_hurd_id.aux.nuids < 2)	    {	      newaux = auxbuf;	      naux = 2;	    }	  _hurd_id.aux.uids[0] = _hurd_id.aux.uids[1] = uid;	}      else	{	  /* We are not root; just change the effective UID.  */	  _hurd_id.gen.uids[0] = uid;	  _hurd_id.valid = 0;	  newgen = _hurd_id.gen.uids;	  ngen = _hurd_id.gen.nuids;	}      err = __USEPORT (AUTH, __auth_makeauth		       (port, NULL, MACH_MSG_TYPE_COPY_SEND, 0,			newgen, ngen, newaux, naux,			_hurd_id.gen.gids, _hurd_id.gen.ngids,			_hurd_id.aux.gids, _hurd_id.aux.ngids,			&newauth));    }  __mutex_unlock (&_hurd_id.lock);  HURD_CRITICAL_END;  if (err)    return __hurd_fail (err);  /* Install the new handle and reauthenticate everything.  */  err = __setauth (newauth);  __mach_port_deallocate (__mach_task_self (), newauth);  return err;}