namespace
boost
    {
    template <class E>
    std::string diagnostic_information( E const & e, bool verbose=true );
    
    std::string diagnostic_information( exception_ptr const & p, bool verbose=true );
    }

Returns:

A string value that contains varying amount of diagnostic information about the passed object:

The string representation of each error_info object is deduced by an unqualified call to to_string(x), where x is of type error_info<Tag,T>, for which Boost Exception defines a generic overload. It converts x.value() to string, attempting to bind (at the time the error_info<Tag,T> template is instantiated) the following functions in order:

The first successfully bound function is used at the time diagnostic_information is called; if both overload resolutions are unsuccessful, the system is unable to convert the error_info object to string, and an unspecified stub string value is used without issuing a compile error.

The exception_ptr overload of diagnostic_information is equivalent to:

if( p )
    try
        {
        rethrow_exception(p);
        }
    catch(...)
        {
        return current_exception_diagnostic_information(verbose);
        }
else return <unspecified-string-value>;

example_io.cpp(70): Throw in function class boost::shared_ptr<struct _iobuf> __cdecl my_fopen(const char *,const char *)
Dynamic exception type: class boost::exception_detail::clone_impl<struct fopen_error>
std::exception::what: example_io error
[struct boost::errinfo_api_function_ *] = fopen
[struct boost::errinfo_errno_ *] = 2, "No such file or directory"
[struct boost::errinfo_file_name_ *] = tmp1.txt
[struct boost::errinfo_file_open_mode_ *] = rb