If your application uses exception handling, it is recommended that you always add a catch(...) statement after all the existing catch statements. Remember that even if your code contains the appropriate handlers for expected exception, exceptions of unexpected types may be thrown by standard functions, algorithms and containers. By adding a catch(...) statement at the end of existing handlers you guarantee that no exception is left unhandled. Furthermore, a catch(...) statement ensures that the program properly destroys all local objects and closes open files and streams as part of the stack unwinding process in the event of an exception. For example:
catch(DerivedEx& de) //most derived exception
catch(...) //catch any other unexpected exception
Note that catch(...) cannot detect the type of the exception it handles. Therefore, you should perform only general cleanup and logging operations inside a catch(...) block.