Boost Exception

#include <boost/exception/error_info.hpp>
#include <string>

namespace
boost
    {
    typedef error_info<struct errinfo_file_open_mode_,std::string> errinfo_file_open_mode;
    }

This type is designed to be used as a standard error_info instance for transporting the string passed as a second argument to fopen in exceptions indicating fopen failures and deriving from boost::exception.