detail::fixedstring::checkOverflow(pos, that.size_);
count = detail::fixedstring::checkOverflowOrNpos(count, that.size_ - pos);
detail::fixedstring::checkOverflow(count, N - size_);
detail::fixedstring::checkOverflow(pos, that.size_);
count = detail::fixedstring::checkOverflowOrNpos(count, that.size_ - pos);
detail::fixedstring::checkOverflow(count, N - size_);