Subj : Re: Question about: createthread/beginthread/beginthreadex ?
To   : comp.programming.threads
From : m_pll
Date : Tue Mar 15 2005 12:02 am

mandatory wrote:

> Well - now we have two different answers out of two posts?
> can see why im confused ?

For the sake of completeness, let me give you a third answer:
use CreateThread.

If you're not using any MFC code you shouldn't care about
AfxBeginThread. It's true that MFC objects can only be used
from threads created by MFC but that's an MFC limitation.
It basically means that MFC is unsuitable for building
reusable components that can be invoked on arbitrary threads.
It would be ridiculous to require all win32 code in the world
to link to MFC just to make this scenario work, especially
when you consider the fact that many system components
create threads that might call user code (e.g. things like
QueueUserWorkItem, COM/RPC thread pools etc) and all of
them use plain CreateThread.

Now, the _beginthreadex part. If you use CRT functions from
a thread created with CreateThread, there are only two cases
where this could leak memory:

#1. If the CRT instance that you're using is statically linked
into an executable (that is, a program, not a DLL).

- or -

#2. If the CRT is statically linked into a DLL that has also
called DisableThreadLibraryCalls in its DllMain.

The recommended way to use CRT from multithreaded programs
is to link to the CRT DLL (using /MD compiler option). If you
do this you will have no problems with CreateThread.

Even if you link statically, you will be fine as long as your
module is a DLL and you don't call DisableThreadLibraryCalls.

(All of this is kind of documented in CreateThread docs, even
though it's a bit difficult to figure out what the're talking
about)

Doing #1 or #2 makes your code MFC-like in that it can only be
used by threads that you created yourself. Even if everybody
else was dutifully using _beginthreadex (which, again, is not
the case), it wouldn't help you because *your* statically
linked instance of CRT won't be notified when somebody else
calls _endthreadex in *their* instance.

So, to summarize, here are the rules for writing multithreaded
win32 code:

1. Use /MD

2. Use CreateThread

3. Don't use MFC

.