[Bug libstdc++/65883] New: numeric_limits::max() returns incorrect value

[john at johnmaddock dot co.uk]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65883

            Bug ID: 65883
           Summary: numeric_limits<unsigned __int128>::max() returns
                    incorrect value
           Product: gcc
           Version: 5.1.0
            Status: UNCONFIRMED
          Severity: blocker
          Priority: P3
         Component: libstdc++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: john at johnmaddock dot co.uk

std::numeric_limits<unsigned __int128>::max() returns
0x7fffffffffffffffffffffffffffffff which is definitely not 2^128-1.  Looks like
a cut and paste error from numeric_limits<__int128>?

This is on Xubuntu 64-bit.

This is a showstopper for Boost.Multiprecision which has asserts that are
incorrectly triggered by the bug.

Regards, John Maddock.