Boost Exception

enable_error_info()

namespace
boost
    {
    template <class T>
    ---unspecified--- enable_error_info( T const & x );
    }

Requirements:

T must be a user-defined type with accessible no-throw copy constructor.

Returns:

An object of unspecified type with no-throw copy semantics, which derives publicly from both T, and class boost::exception. The T sub-object is initialized from x by the T copy constructor. If T already derives from boost::exception, then the type of the returned object does not derive boost::exception.

Throws:

Nothing.