In the Boost Exception review process, several people have expressed the opinion that since boost::exception (part of the proposed library) is designed to act as a base class for all Boost exceptions, it should also support cloning. This can be done by adding a clone() virtual function to boost::exception. There are several issues we have to consider. First, should clone() be pure virtual, which would require all deriving exceptions to implement it? This can be achieved by modifying boost::throw_exception to throw a type that derives from the passed exception type and implements clone(). If we go that route, we must make sure that Boost does not contain a "naked" throw statement (that is, a throw that does not call boost::throw_exception.) This should be fine, since Boost libraries are required to call boost::throw_exception anyway. However, the functionality provided by boost::exception would be desirable for user code as well, and thus it would make sense for user-defined exception types to derive it. Which raises my second question: should then user code also be required to throw exceptions by calling boost::throw_exception? Emil Dotchevski