Here is a generic exception_ptr implementation based on a registry of exception types. (http://joshuanapoli.com/exception/) The registry is
If boost::throw_exception is modified such that its postcondition is that the exception object it throws derives from boost::exception (I can't think of a reason not to), cloning can be implemented intrusively without a need for registration.
I would hope to save exceptions thrown from 3rd party libraries. An intrusive approach wouldn't work.
For boost::throw_exception to be able to register the exception type from 3rd party libraries, they must call boost::throw_exception. If they call boost::throw_exception then we have the concrete type they wish to throw (as a template parameter) and we can wrap that type in something else which implements the cloning. This would be very similar to the current semantics of boost::enable_error_info (part of boost::exception.) -- Emil Dotchevski Reverge Studios, Inc. http://www.revergestudios.com/reblog/index.php?n=ReCode