[Bug libstdc++/50951] New: state of subtract_with_carry_engine not saved correctly to output stream

[dariomelu at hotmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50951

             Bug #: 50951
           Summary: state of subtract_with_carry_engine not saved
                    correctly to output stream
    Classification: Unclassified
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: libstdc++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: dariomelu@hotmail.com


the value of __x._M_p is not written to output stream __os by

operator<<(std::basic_ostream<_CharT, _Traits>& __os,const
subtract_with_carry_engine<_UIntType,__w,__s,__r>& __x) 

in 4.6.1/include/c++/bits/random.tcc.

Consequently, the state of the random engine is not fully restored by the
corresponding operator>>.

One way to fix the problem is to write __x._M_p to output stream __os.
Alternatively, the contents of the ring buffer could be saved and restored
always beginning at index __x._M_p, whatever its value, and then wrapping
around the ring buffer as necessary.