newgen[0] = egid; memcpy (&newgen[1], _hurd_id.gen.gids, (ngen - 1) * sizeof (gid_t)); newaux[0] = rgid; memcpy (&newaux[1], _hurd_id.aux.gids, (naux - 1) * sizeof (gid_t));
newgen = _hurd_id.gen.gids; ngen = _hurd_id.gen.ngids; if (egid != -1) { if (_hurd_id.gen.ngids == 0) {  newgen = &egid; ngen = 1; } else { _hurd_id.gen.gids[0] = egid; _hurd_id.valid = 0; } }  newaux = _hurd_id.aux.gids; naux = _hurd_id.aux.ngids; if (rgid != -1) { if (_hurd_id.aux.ngids == 0) { newaux = &rgid; naux = 1; } else { _hurd_id.aux.gids[0] = rgid; _hurd_id.valid = 0; } }
__setregid (gid_t rgid, gid_t egid){  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 RGID as the real gid,	 and EGID as the first element in the list of effective gids.  */      size_t ngen = _hurd_id.gen.ngids < 1 ? 1 : _hurd_id.gen.ngids;      size_t naux = _hurd_id.aux.ngids < 1 ? 1 : _hurd_id.aux.ngids;      gid_t newaux[naux], newgen[ngen];      newgen[0] = egid;      memcpy (&newgen[1], _hurd_id.gen.gids, (ngen - 1) * sizeof (gid_t));      newaux[0] = rgid;      memcpy (&newaux[1], _hurd_id.aux.gids, (naux - 1) * sizeof (gid_t));      err = __USEPORT (AUTH, __auth_makeauth		       (port, NULL, MACH_MSG_TYPE_COPY_SEND, 0,			_hurd_id.gen.gids, _hurd_id.gen.ngids,			_hurd_id.aux.gids, _hurd_id.aux.ngids,			newgen, ngen,			newaux, naux,			&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;}