FIX: Access Violation Firing an Error Event in OLE Control

MORE INFORMATION

To reproduce this problem, add the stock Error event to an OLE Control using ClassWizard's OLE Events tab. The name given the member function to fire the event will be FireError. In the OnLButtonDown handler of the OLE Control, call FireError() and pass the following parameters: This causes the SCODE of the error to be 0x800A0007 (CTL_E_OUTOFMEMORY), and the description string to be " ", a single space followed by a NULL byte. The rest of the parameters will be defaults.

Now, run the test container, insert your control, and click the control's client area. In Release builds, this causes an access violation on the first occurrence of the event. In Debug, it takes several occurrences before the access violation is seen.

Sample Code

Below is the OnLButtonDown handler for the Circ3 tutorial sample, modified to call the error event.

/* Compile options needed:
*/ 
void CCirc3Ctrl::OnLButtonDown(UINT nFlags, CPoint point)
{
   /*  Comment the tutorial.
        CDC* pdc;
   // Flash the color of the control if within the
           ellipse.
   if (InCircle(point))
   {
      pdc = GetDC();
      FlashColor(pdc);
      ReleaseDC(pdc);
      // Fire the ClickIn event
      FireClickIn(point.x, point.y);
   }
   else
      // Fire the ClickOut event
      FireClickOut();
        */ 
        // Here's the call.
   FireError(CTL_E_OUTOFMEMORY, " ");
   COleControl::OnLButtonDown(nFlags, point);
}