Stopping an MFC thread

Question

I understand the problem with just killing the thread directly (via AfxEndThread or other means), and I've seen the examples using CEvent objects to signal the thread and then having the thread clean itself up. The problem I have is that using CEvent to signal the thread seems to require a loop where you check to see if the thread is signaled at the end of the loop. The problem is, my thread doesn't loop. It just runs, and the processing could take a while (which is why I'd like to be able to stop it).

Also, if I were to just kill the thread, I realize that anything I've allocated will not have a chance to clean itself up. It seems to me like any locals I've been using that happen to have put stuff on the heap will also not be able to clean themselves up. Is this the case?

Answer 1

Locals would be placed on the stack and, hence, WOULD be freed on forcing the thread shut (I think). Destructors won't get called though and any critical sections the thread holds will not get released.

If the thread is ONLY doing things with simple data types on the stack, however, it IS a safe thing to be doing.

Answer 2

Does your thread ever exit? If so, you could set an event in the thread at exit and have the main process wait for that event via waitforsingleevent. This is best to do with a timeout so the main process doesn't appear to lockup when it's closing. At the timeout event, kill the thread via AfxKillThread. You'll have to determine what a reasonable timeout is, though.

Since you don't loop in the thread this seems to me to be the only way to do this. Of course, you could something like set a boolean flag in the main process and have the thread periodically check this flag, but then your thread code will be littered with "if(!canRun) return;" type code.

If the thread never exits, then AfxKillThread/AfxTerminateThread is the only way to stop the thread.

Answer 3

There is no secret magic knowledge here.

Just check the event object periodically throughout the function code, where you deem it is safe to exit.