terminating thread gracefully on main app termination.

Question

I have a modelless dialog that creates a thread, and if the cancel button in the dialog is hit, a variable bCancel is set which the thread in question periodically checks, and then immediately jumps to its clean up code. It works fine. I can even send a WM_COMMAND...ID_CANCEL to the dialog from other places and it works the same. But its not working when I try to send ID_CANCEL to the dialog from the main application window's WM_CLOSE handler (i.e. the user is trying to shut the entire application down while this thread is running.) As best I can tell something is just terminating the thread from outside before it can execute its cleanup code. Does this sound right. What can I do.

(There's a critical section in the dialog's ID_CANCEL handler I didn't mention - not sure how relevant it is. (bCancel is set within this critical section and the thread executes its clean up code within the same critical section.)

Answer 1

After setting the thread's bCancel, your dialog code should wait for the thread handle to get signaled (thus destroyed), so you can use one of the wait### functions on the thread handle (with a sane timeout value of course), thus the app will wait a tiny bit for your thread cleanup to get called.

Answer 2

Not that anyone's still interested, but in the main app WM_CLOSE handler I set bCloseApp=TRUE, then send ID_CANCEL to the dialog and then check if the thread is active. If it is I return 0 (thus bypassing the default DestroyWindow of WM_CLOSE.) Then in the thread exit code I PostMessage(...WM_CLOSE...) to the main app window if bCloseApp==TRUE.

Before implementing the above I found that while in the main app's WM_CLOSE handler, the thread in question is automatically suspended for some reason (which surprised me) and that was a complicating factor as I couldn't wait for the thread to terminate while in the WM_CLOSE handler.