FAQ 9.03 What happens to objects in stack frames that become unwound during the throw catch process?

FAQ 9.03 What happens to objects in stack frames that become unwound during the throw / catch process?

They are properly destructed.

Local objects that reside on the stack between the throw and the catch are properly destructed in stack order; last constructed, first destructed. The result is an extension of the C++ destructor discipline, and allocated resources can be safely kept in an object whose destructor releases the resource. This resource is often memory, but it could also be files that need to be closed, semaphores that need to be unlocked, and so on. For example, a local auto_ptr should be used to hold the pointer to an allocated object, as shown in FAQ 2.07.