Re: problem with CMtex and CSingle lock - WAIT_ABANDONED
On Wed, 30 Aug 2006 17:02:08 +0100, "Tom Widmer [VC++ MVP]"
<tom_usenet@hotmail.com> wrote:
Ok, I've looked a bit more closely, and you've hit a VC6 MFC problem in
addition to the general problem of the mystery WAIT_ABANDONED: Lock
should probably TRUE when WAIT_ABANDONED is returned (since the mutex is
actually locked by the caller in this case), but it in fact returns
FALSE, and hence the destructor of the lock doesn't attempt to release
the mutex. I note this has been changed since VC6, and it returns TRUE
for WAIT_ABANDONED under VC8.
Yes, the boolean return type is one of the many flaws afflicting the MFC
synchronization classes. On a related note, I'd love to take a poll and see
what people think this does, where mx is a mutex:
CSingleLock lk(mx);
But, if WAIT_ABANDONED is returned, you have such a serious problem that
you should probably exit immediately anyway, since you are probably
dealing with corrupt data (an alternative would be to restart the service).
I agree. If you receive WAIT_ABANDONED, the data must be regarded as
corrupt, and it's dead wrong for the "fixed" version of Lock to return true
when it receives WAIT_ABANDONED; throwing an exception would be more
appropriate.
--
Doug Harrison
Visual C++ MVP