"Terje Slettebų" <[EMAIL PROTECTED]> wrote in message 00e001c2a04e$92f9c190$60fb5dd5@pc">news:00e001c2a04e$92f9c190$60fb5dd5@pc... > >From: "Johan Nilsson" <[EMAIL PROTECTED]> > > > > The hack makes no 'fixed' assumptions on binary object > > layout, rather, it relies on the fact that any polymorphic type can be > > queried for an implemented interface (aka 'base class'). It does, however, > > make the assumption that the location of the rtti itself data is fixed for > a > > specific c++ implementation across different polymorphic types. > > > > Sample usage (demonstrating syntax only): > > -------------- > > > > void foo(void*) > > { > > try > > { > > IMyBaseClass* pmc = dynamic_void_cast<IMyClass>(pv); > > > > if (pmc) > > { > > pmc-MyFn(); > > } > > } > > catch (std::exception&) > > {} > > } > > > > > > The hack: > > ------ > > template<typename T> > > T* dynamic_void_cast(void* pv) > > { > > struct rtti_obj__ > > { > > virtual ~rtti_obj__() = 0; > > }; > > > > rtti_obj__* pro = static_cast<rtti_obj__*>(pv); > > > > try > > { > > return dynamic_cast<T*>(pro); > > } > > catch (bad_cast&) > > { > > throw; > > } > > catch (exception& e) > > { > > throw bad_cast(e.what()); > > } > > } > > > > ---------- > > Why do you catch, and just rethrow exceptions? Why not just let them > propagate (no try/catch), or turning them into return zero? Also, what other > exception, besides bad_cast, can dynamic_cast throw, which necessitates the > second catch clause?
This is rather platform specific, but in VC.NET, you can get the exception __non_rtti_object (which is derived from bad_typeid)thrown as well. I preferred throwing bad_cast exceptions only. // Johan _______________________________________________ Unsubscribe & other changes: http://lists.boost.org/mailman/listinfo.cgi/boost
