Re: threads won't close and then reopen correctly...
On Mon, 22 Sep 2008 13:45:03 -0700 (PDT), RAB <rabmissouri@yahoo.com>
wrote:
I have a MFC VC++ project that has a thread started in the
OnInitDialog() function of a dialog box.
AfxBeginThread(ThreadProcess, (LPVOID) this, 0);
I handle the thread in the the following function
UINT Questions::ThreadProcess(LPVOID param)
{
//do some stuff
AfxEndThread(0);
return 0;
}
Everything works well until I close the dialog box and then reopen
it. When I do that the thread doesn't work as it should the second
time around. Anyone have any thoughts on why I am getting this
unwanted behavior and what I can do to correct it?
"Doesn't work as it should" == "unwanted behavior", and neither tells me
anything specific that would help me help you. I will guess that there
should be only one instance of this thread active at a time, and you're
doing nothing to enforce this. In general, you should join with secondary
threads at some point, and it doesn't appear that you're doing this. For
more on this and other CWinThread issues, see:
http://members.cox.net/doug_web/threads.htm
In addition, calling AfxEndThread() is a bad idea, and it's nonsensical to
write a return statement immediately following it. If MS didn't declare
AfxEndThread __declspec(noreturn), they should have, and then the compiler
wouldn't complain about a missing return statement. But it would still be a
bad idea to call AfxEndThread(), because a return statement is all you need
inside the thread controlling function, and returning normally ensures
local variables are properly destroyed. If for some reason I needed to end
a thread in some deeply nested function call, I would probably throw an
exception of a type that only the thread controlling function will ever
catch. This means always rethrowing from catch(...).
--
Doug Harrison
Visual C++ MVP