Re: Synchronization problems

"Doug Harrison [MVP]" <>
Fri, 04 Jan 2008 18:08:14 -0600
On Sat, 5 Jan 2008 01:46:48 +0200, "Kurz" <> wrote:

I have a main MFC executable which loads and run few Dll's. In the main
program I have a thread that uses a try/catch block. When the thread fails
it jumps to an exception in the catch block, then the thread terminates. I
want it to hold its termination inside the exception block, until certain
conditions occur in the dll's. Specifically, I want it to wait until any of
2 routines in some dll (which run periodically) are not in the middle of
I have few questions regarding that-

Is it legal to call dll exported functions from an exception block?

Yes. Note that to catch C++ exceptions across module (EXE/DLL) boundaries,
all the modules should link to the same CRT DLL.

Can I use system events for that? If so, how would the event state in the
dll, be known by the main program?

You would have to devise a way for the modules to use the same event
objects; for example, the main program could create them all and pass their
handles to the DLL via some exported initialization function. As for
checking state, you would use WaitForSingleObject,
(Msg)?WaitForMultipleObjects, etc.

Can I use simple flags for that?

You could, but there's no way to wait on them efficiently. You'd have to
poll them in a loop, and since multiple threads will be using these
objects, you'd have to deal with synchronization. Using events circumvents
these problems.

Doug Harrison
Visual C++ MVP

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