Solving AccessViolationException

>>>> The problem is that an exception happens inside an OpenGL function.

The exception happens in OpenGL but the reason in 99 percent of all these cases is in your calling one of the OpenGL function where you

- pass a NULL pointer where a valid pointer was required
- pass a pointer already deleted
- pass a pointer of an object which has run out of local scope
- wrote beyond array bounds thus has destroyed some heap data

One of these probably happened in the unmanaged code parts perhaps called or invoked from CsGL.OpenGL.OpenGLControl.OnPaint(PaintEventArgs pevent). If you have the code for this function you may log before and after each function call (or, firstly you do a log at begin and end of the function and if it was sure that the begin was logged but not the end, you narrow both logs until you finally have spotted the statement which causes the expection. If it is a function call where you have the source repeat the procedure.

itsmeandnobodyelse,
How do you explain the link to the sleep(10)? Please note that the sleep is actually performed on a totally different thread.

Regards,
Edo

>>>> How do you explain the link to the sleep(10)?
Hmmm. I would need to see the code to maybe find the explanation.

But for example a sleep would solve the issues which may occur when passing addresses of local variables to callback functions or to other functions which run asynchronously or deferred. The sleep would keep the addresses valid while otherwise they were destroyed prematurely.

>>>> the sleep is actually performed on a totally different thread.
If the DeviceIOControl invokes some asynchronous things, the sleep would help to get them finished before returning and freeing all local resources of the thread function and rolling back the stack variables. All this could help to not corrupting memory of the main thread which for example could use any of the free resources used in your thread fucntion.

Check the thread function where you added the sleep. None of the calls made there should pass any local data variables or their addresses. If they do, change these variables to static variables what should help.

itsmeandnobodyelse, thanks for you're help!

Below you can see the code snippet that does the DeviceIOControl. If I place the sleep before this function things go crazy. If I place it after (even after the CloseHandle) things are OK. Does it make sense?

Regards,
Edo

	DeviceIoControl(DeviceHandle, IOCTL_ADAPT_SEND_NON_EP0_TRANSFER,
                    pTransfer, iXmitBufSize,
                    pTransfer, iXmitBufSize,
                    ReturnSize, ov);
 
    // Blocking mode, wait for timeout or complition
    if WaitForSingleObject(Overlapped.hEvent, Timeout) = WAIT_OBJECT_0 then
    begin
      // Retrive result from OL
      if GetOverlappedResult(DeviceHandle, Overlapped, RetVal, False) then
        Result := Retval - Sizeof(TSingleTransfer);
    end
    else
    begin
      // Timeout happed
      CancelXfer(pTransfer.EndpointAddress);
    end;
 
    // Release Overlapped handle
    CloseHandle(Overlapped.hEvent);
                                              

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hi to alll

i had the same problem exactly, c# with openGL and USB device connection.
i got the same exeption Edo got.
The only thing that solved my problem is changing the openGL object to public instead of private
and i tried everything!!!!
thanks to itsmeandnobodyelse advice

Regards
Eran