Proposed resolution:

Addressed by paper n3168.

Addresses US-139

Resolve issue LWG 1328 one way or the other, but preferably in the direction outlined in the proposed resolution, which, however, is not complete as-is: in any case, the sentry must not set ok_ = false if is.good() == false, otherwise istream::seekg, being an unformatted input function, does not take any action because the sentry object returns false when converted to type bool. Thus, it remains impossible to seek away from end of file.