boost::log::operator<< — Output operator.
// In header: <boost/log/utility/string_literal.hpp> template<typename CharT, typename StrmTraitsT, typename LitTraitsT> std::basic_ostream< CharT, StrmTraitsT > & operator<<(std::basic_ostream< CharT, StrmTraitsT > & strm, basic_string_literal< CharT, LitTraitsT > const & lit);