Re: Reading Serial Port

From:

clinisbut <clinisbut@gmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 4 Feb 2008 08:19:06 -0800 (PST)

Message-ID:

<8ba4ccd1-e1e2-4e5d-807d-d6d53e8a7e9f@i12g2000prf.googlegroups.com>

On Feb 4, 4:12 pm, "Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
wrote:

"clinisbut" <clinis...@gmail.com> wrote in message

news:76012220-ac65-4870-9126-e322cbba1b82@n20g2000hsh.googlegroups.com...

By the way, I think I'm not deleting correctly my UI thread. I'm
always getting a "huge" memory leak of about 200bytes every time I
close the app. This is what I do to create my UI thread from GUI:

(MySerial*) pMySerial = (MySerial*)
AfxBeginThread( RUNTIME_CLASS( MySerial), THREAD_PRIORITY_NORMAL, 0,
CREATE_SUSPENDED );
pMyThread->ResumeThread();

And this is what I write to kill my thread in his destructor:
First I stop the reader thread:
MySerial::Stop()
{
SetEvent( ShutdownEvent );
WaitForSingleObject( ShutdownEvent, INFINITE );
}

Then I close the app and this should be executed:
MySerial::~MySerial()
{
CloseHandle(ShutdownEvent);
CloseHandle(ReadEvent);
CloseHandle(WriteEvent);

// Wait for the thread to exit before deleting
WaitForSingleObject( this->m_hThread, INFINITE );
delete this;
}

The WaitForSingleObject in Stop accomplishes nothing and should be removed.

The WaitForSingleObject in ~MySerial has some problems. In order to make
sure that you don't have memory leaks you need to synchronize the thread
shutdown so the main thread does not exit until after the serial thread has
exited. You can move the WaitForSingleObject to the main thread, such as in
OnClose. But, CWinThread autodeletes itself and does CloseHandle on its
m_hThread, so your code is in danger of waiting on a handle and deleting
things that are already deleted. To fix this add pMyThread->m_bAutoDelete =
FALSE just before the ResumeThread statement.

--
Scott McPhillips [VC++ MVP]

I've already have a m_bAutoDelete = FALSE inside InitInstance (is it
enough "before"?).
About moving WFSO outside my class... I'd like that the user of this
class doesn't have to deal with this kind of things, I want a more
encapsulate thing.

you need to synchronize the thread shutdown so the main thread does not exit until after the serial thread has exited.

The SetEventShutdown is for stop the worker thread inside MySerial
that is reading all time. I though I should put that WFSO after
SetEvent. Why is it dispensable?
Maybe I need another Event that tells me when the reader thread is
actually stopped?

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