If an exception occurs, and the thread suddenly transfers out of the current context, the pool associated with that context is drained. However, if that pool is not the top pool on the thread's stack, all the pools above the drained pool are also drained (releasing all their objects in the process). The top autorelease pool on the thread's stack then becomes the pool previously underneath the drained pool associated with the exceptional condition. Because of this behavior, exception handlers do not need to release objects that were sent autorelease. Neither is it necessary or even desirable for an exception handler to send release to its autorelease pool, unless the handler is re-raising the exception.