FIX: CComQIPtr operator= Causes an Access Violation (174891)

The information in this article applies to:

The Microsoft Active Template Library (ATL) 2.0
The Microsoft Active Template Library (ATL) 2.1

This article was previously published under Q174891

SYMPTOMS

When a CComQIPtr is assigned a NULL pointer, an access violation occurs.

CAUSE

When a CComQIPtr is assigned a NULL pointer, no check is done, and a QueryInterface is attempted with the NULL pointer. This behavior causes the access violation.

RESOLUTION

Do not assign NULL pointer to a CComQIPtr object.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been fixed in Visual Studio 97 Service Pack 3.

For more information, please see the following article in the Microsoft Knowledge Base:

170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

MORE INFORMATION

Steps to Reproduce Behavior

   CComQIPtr<IMyInterface, IID_IMyInterface> ptr;
   IUnknown* pUnk = NULL;
   ptr = pUnk;

Modification Type:	Major	Last Reviewed:	10/2/2003
Keywords:	kbArchitecture kbATL300fix kbBug kbfix kbVS97sp2fix KB174891