Brock Peabody wrote:
That's true. I'm still a little uncomfortable with the idea of a static register though. How, for instance, would you share a register between dynamic link libraries if the register is static?
I may or may not be right, but I don't expect this problem to occur frequently in practice, if the recommendation is to use throw_transportable_exception, with register_ only being used when it is not possible to modify the throw statement. The architecture I'm picturing in my mind differs slightly from your implementation (and probably Sam's, I haven't had time to look at it). I envisage a (reusable, perhaps) exception translator that catches all registered and standard exceptions, wraps them in a new shiny transportable_exception package, and rethrows, something like template<class F> void translate_exceptions(F f) { try { f(); } catch(transportable_exception const &) { throw; } catch(registered_exception_1 const & e) { throw_transportable_exception(e); } // and so on } with the optional< variant<R, ...> > of your implementation replaced by an optional<R>, auto_ptr<transportable_exception> pair. The unfortunate author of a DLL that calls sourceless throwing functions but needs to register_ exceptions can just wrap the functions in his own exception translator, if all else fails. We may even provide a generator exception_translator_generator<X1, X2, ..., Xn>::translate(f);
If there is an excepted exception list, do you think it makes sense to have the library automatically register the types in this list?
Possibly, but I'm not sure how useful that would be. I'd usually only put abstract base classes in that list. :-)
Now I'm confused again :) My understanding was that there is no way to transport a user defined abstract base class unless you derive it from transportable_exception, in which case it wouldn't need to be registered at all.
I'm just saying that I'd probably use the expected list strictly as a "whether" mechanism, as I'd prefer to specify the "how" only once, not per thread creation point. But that's just my opinion.