[Bug libstdc++/12297] New: istream::sentry::sentry() handles eof() incorrectly.

["peturr02 at ru dot is" <gcc-bugzilla at gcc dot gnu dot org>]

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http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12297

           Summary: istream::sentry::sentry() handles eof() incorrectly.
           Product: gcc
           Version: 3.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: libstdc++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: peturr02 at ru dot is
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i686-pc-linux-gnu
  GCC host triplet: i686-pc-linux-gnu
GCC target triplet: i686-pc-linux-gnu

According to the resolution to DR 195:

http://anubis.dkuug.dk/jtc1/sc22/wg21/docs/lwg-defects.html#195

basic_istream::sentry::sentry() should call setstate(failbit | eofbit) if
is.rdbuf()->sgetc() or is.rdbuf()->sbumpc() return eof(). Currently, the
sentry constructor calls is.setstate(eofbit) and later calls
is.setstate(failbit). This means that failbit will not be set in is.rdstate()
as it should if the call to setstate(eofbit) throws an exception.