Re: Reading Serial Port

From:
"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>
Newsgroups:
microsoft.public.vc.mfc
Date:
Mon, 4 Feb 2008 12:00:04 -0500
Message-ID:
<u8ehn90ZIHA.4696@TK2MSFTNGP05.phx.gbl>
"clinisbut" <clinisbut@gmail.com> wrote in message
news:8ba4ccd1-e1e2-4e5d-807d-d6d53e8a7e9f@i12g2000prf.googlegroups.com...

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.


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?


The WFSO will always return immediately because it tests the event that you
just set in the previous line. That doesn't accomplish anything.

You probably want to test this->m_hThread instead: It seems like you are
trying to detect thread stop in two different places. You can move your
destructor code into the Stop function and do it all right there.

--
Scott McPhillips [VC++ MVP]

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