Boost Exception

virtual char const * diagnostic_information() const throw();

A string representation of all data stored in the boost::exception object by the operator<< function. See "Diagnostic Information" for details.

Nothing.

The return value remains valid until the exception object from which it was obtained is destroyed or modified.
The header boost/exception/diagnostic_information.hpp provides a namespace-scope function diagnostic_information which takes a std::exception. It calls exception::diagnostic_information if its argument can be converted to boost::exception; otherwise it returns a string that combines the value of std::exception::what and the exception's dynamic type.

Boost C++ Libraries