RE: vb6 usercontrol gives access violation when handling events

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Date: Thu, 20 Jan 2005 02:11:02 -0800

Hi,

thanks for the response.

It is odd that you can't reproduce the problem yet I can obtain the same
results on several machines. Upgrading to SP6 is not an option to be taken
lightly as the real application has been deployed to many sites using sp5
runtimes and the machines here are used to maintain that application.

The small example app that I posted was the result of paring away the
structure of our main application to try and determine the cause of the main
fault that we are experiencing which is that the VBVM enters an endless loop
during form unload. The looping problem does not manifest itself on every run
of the application so appears to be dependant on the VM state becoming
corrupted after continued use of the application.

A search of Google groups shows a couple of other instances where the same
occurs but they have no resolution so I have no clues as to further
investigation. A couple of those instances have suggested using a timer on
the form to perform the unload thus removing the nested event handlers and
this does seem to work, however, I have concerns that any pending events
(e.g. should the user accidentally triple click rather than double) will be
able to sneak in ahead of the timer.

The nested user control access violation was found during testing of the
application using the C++ debugger as there are a large number of COM objects
written in C++ in use as well as the VB front end. My concern is that the
violation I am experiencing with the form unload leads to the VM looping
problem which is causing our customers problems. The access violation may
indeed have nothing to do with the looping VM problem but a search of Google
with respect to that issue also shows a couple of instances from other users.
Once again, however, there is no resolution to the problem so no suggestions
as to how to proceed with the investigation.

So in summary, I have two problems which can be treated in isolation,
however, there is the concern that one problem eventually leads to the other
after running the application for a period of time. Any other suggestions for
potential causes that can be investigated would be welcomed.

Many thanks in advance for your help

Andrew

""Peter Huang" [MSFT]" wrote:

> Hi
>
> I have tested on both windbg, vc++7.0 debugger and vc6.0 debugger, but I
> can not reproduce the problem.
> So far I think you may try to refresh the most recently service pack(sp6
> for vs6) to see if that works for you.
> Also here I attach my test project in the attament, you may have a try.
>
>
> Best regards,
>
> Perter Huang
> Microsoft Online Partner Support
>
> Get Secure! - www.microsoft.com/security
> This posting is provided "AS IS" with no warranties, and confers no rights

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