How to pop and destroy

This document describes how to pop and destroy objects on the cleanup stack.

In general, it is recommended that any objects which are accessed only through an automatic pointer are pushed onto the cleanup stack immediately, before being used, and only popped before they must be destroyed.

You can use the single function CleanupStack::PopAndDestroy() to both pop the object from the cleanup stack and destroy it. This operation is the usual thing to do when an object on the cleanup stack has been finished with.

void doExampleL()
 {
 // allocate and leave if could not
 CExample* myExample = new (ELeave) CExample;

 // this cannot leave - no protection needed
 myExample->iInt = 5; 
 
 // do something that might leave, protected by cleanup stack
 CleanupStack::PushL(myExample); // push pointer to stack

 myExample->DoSomethingL()); // something that might leave 

 // pop from cleanup stack, and destroy, in one operation
 CleanupStack::PopAndDestroy();  
 }

Note

Pop() on its own is nevertheless useful: it is safe to pop an object from the cleanup stack when you are sure that it will either be destroyed, or a reference stored to it, before any operations are performed on it which might leave. This way, an object can never be orphaned (which is our aim). In the former case, you get pop-and-destroy all in one, which it is worthwhile for the system to provide. In the latter case, you need to store a pointer. This is what happens, for instance, in two-phase construction.