In order to find the correct fix for bug 18753, I've been examining the shutdown process on Windows. I have written a program that logs the messages sent to it, and I've run it on Windows 7. What I found was that a shutdown produces the following sequence of events: * We get a 0x3b message. DefWindowProc sends a WM_QUERYENDSESSION message. We return 1, allowing the session to end. * We get another 0x3b message, which leads to a WM_ENDSESSION. * Nothing else happens, but for some reason the program exits.
I added a trace after the message loop returns to see if the program gets a WM_QUIT. It doesn't.
Apparently, my test program was killed.
I tried changing the window proc so that it loops infinitely when it gets WM_ENDSESSION. Windows 7 sees this as "blocking shutdown". (Naturally, it responds the same way if I return 0 from WM_QUERYENDSESSION.)
This leads me to believe that Windows 7, when shutting down, immediately kills any process that returns from a WM_ENDSESSION message.
Does that seem sane?
I've posted my test program (source code and .exe file) at http://madewokherd.nfshost.com/msgtest.zip, and I'd like to hear if other Windows versions behave the same way Windows 7 does.