From: "E. Gladyshev" <eegg@comcast.net>
Your solution
try{...} catch(...) { try { throw; } catch( type1 ) { ... } }
is very different from
try{...} catch( type1 ) {...}
One of the differences is that in the first case, the stack unwinding will be triggered for any exception. In the second case, it is not necessarily the case.
Not at all. From 15.2/1: As control passes from a throwexpression to a handler, destructors are invoked for all automatic objects constructed since the try block was entered. In order to enter any handler, stack unwinding occurs. In the first case, stack unwinding occurs immediately because "catch (...)" matches all exceptions. In the second case, only if there wasn't a handler for a particular exception would stack unwinding be delayed while the search continued for another handler (including unexpected()). IOW, stack unwinding will occur for both forms, it's just a question as to where the handler will be found. Let me make this more concrete. Assume the only expected excceptions are type1, type2, and type3. Then this: try { ... } catch (...) { // stack unwinding has occurred by the time we get here // this is actually in a separate function, of course try { throw; } catch (type1 const &) { ... } catch (type2 const &) { ... } catch (type3 const &) { ... } catch (...) { throw; } } does exactly the same thing, wrt stack unwinding, as this: try { ... } catch (type1 const &) { // stack unwinding has occurred by the time we get here ... } catch (type2 const &) { // stack unwinding has occurred by the time we get here ... } catch (type3 const &) { // stack unwinding has occurred by the time we get here ... } If the function called by the first form handles a different set of exceptions, then the only change is where the handler is for the active exception. Stack unwinding will have occurred by the time that handler is entered. If both forms provide the same set of handlers, then the only difference is where the handler is found. Given that the former approach captures common exception handling in a single function that rethrows the exception, it is merely shorthand for having to write the same handlers repeatedly. -- Rob Stewart stewart@sig.com Software Engineer http://www.sig.com Susquehanna International Group, LLP using std::disclaimer;