basic_ostream::sentry::sentry

#include <ostream>

namespace std
{
    template < class CharT, class Traits = std::char_traits < CharT > >
    class basic_ostream
        : virtual public std::basic_ios < CharT, Traits >
    {
    public:
        class sentry
        {
        public:
            explicit sentry( std::basic_ostream < CharT, Traits >& os );
        };
    };
}