Dean Michael Berris wrote:
On 7/4/06, Emil Dotchevski <emildotchevski@hotmail.com> wrote:
I don't think it can be completely avoided. If you throw failed<foo>, you should catch(foo &) to handle the exception. At this point you do need a dynamic_cast to get to the exception_info sub-object. You could have a virtual function in foo to get you an exception_info *, but I don't think that this is appropriate.
Let's see:
template <typename _T> class failed : public exception_info, public std::exception { public: failed() { }; explicit failed (const _T & e) : _wrapped_exception(e) { };
// ... other common methods ... };
//... try { ... } catch (exception_info & e) { ... }
But the whole point is that in some scenarios you want to catch T, not exception_info. You are interested in a read_error and have an appropriate response to it ready, but the rest of the exceptions must be propagated unharmed. So you catch( read_error const & r ) and use dynamic_cast to see whether it also contains exception_info. Obviously, if you want to catch all exceptions regardless of type, there is no need for a dynamic_cast. You catch exception_info, std::exception, and ... (in that order.)