_M_string.swap(__tmp);
_M_sync(const_cast<char_type*>(_M_string.data()),
this->gptr() - this->eback(), this->pptr() - this->pbase());
_M_string.swap(__tmp);
_M_sync(const_cast<char_type*>(_M_string.data()),
this->gptr() - this->eback(), this->pptr() - this->pbase());