GNU nano 4.2 :D                              /usr/lib/gcc/x86_64-pc-linux-gnu/9.2.0/include/g++-v9/bits/ostream.tcc
{
_GLIBCXX_BEGIN_NAMESPACE_VERSION

  template<typename _CharT, typename _Traits>
    basic_ostream<_CharT, _Traits>::sentry::
    sentry(basic_ostream<_CharT, _Traits>& __os)
    : _M_ok(false), _M_os(__os)
    {
      // XXX MT
      if (__os.tie() && __os.good())
        __os.tie()->flush();

      if (__os.good())
        _M_ok = true;
      else
        __os.setstate(ios_base::failbit);
    }

  template<typename _CharT, typename _Traits>
    template<typename _ValueT>
      basic_ostream<_CharT, _Traits>&
      basic_ostream<_CharT, _Traits>::
      _M_insert(_ValueT __v)
      {
        sentry __cerb(*this);
        if (__cerb)
          {
            ios_base::iostate __err = ios_base::goodbit;
            __try
              {
                const __num_put_type& __np = __check_facet(this->_M_num_put);
                if (__np.put(*this, *this, this->fill(), __v).failed())
                  __err |= ios_base::badbit;
              }
            __catch(__cxxabiv1::__forced_unwind&)
              {