DOCUMENT:Q266713  28-JUN-2001  [visualc]
TITLE   :BUG: IDispatch::GetIDsOfNames() May Return E_FAIL When Successfu
PRODUCT :Microsoft C Compiler
PROD/VER:WINDOWS:3.0
OPER/SYS:
KEYWORDS:kbATL kbVC600 kbVC600bug kbATL300 kbATL300bug kbGrpDSMFCATL

======================================================================
-------------------------------------------------------------------------------
The information in this article applies to:

 - The Microsoft Active Template Library (ATL) 3.0, included with:
    - Microsoft Visual C++, 32-bit Enterprise Edition, version 6.0 
    - Microsoft Visual C++, 32-bit Professional Edition, version 6.0 
    - Microsoft Visual C++, 32-bit Learning Edition, version 6.0 
-------------------------------------------------------------------------------

SYMPTOMS
========

The way in which ATL implements the IDispatch::GetIDsOfNames function may result
in E_FAIL being returned, even when the call succeeds.

CAUSE
=====

When multiple threads call into an object's IDispatch::GetIDsOfNames function,
the CComTypeInfoHolder::GetTI function is eventually called to load the type
library and get the ITypeInfo interface. Because loading the type library and
retrieving the interface are protected by a critical section, the second thread
waits for the first thread to finish. Once the first thread releases the
critical section, the second thread enters the critical section, finds m_pInfo
is non-NULL (set by the first thread), and returns the hRes, which is set to
E_FAIL. The IDispatch::GetIDsNames function eventually returns this E_FAIL.

RESOLUTION
==========

To work around this problem, the CComTypeInfoHolder::GetTI function in the
Atlcom.h file must be modified as follows (all changes are marked with the
comments "ADD" and "END ADD"):

   inline HRESULT CComTypeInfoHolder::GetTI(LCID lcid)
   {
      // If this assert occurs, probably didn't initialize properly.
      ATLASSERT(m_plibid != NULL && m_pguid != NULL);
      ATLASSERT(!InlineIsEqualGUID(*m_plibid, GUID_NULL)
          && "Did you forget to pass the LIBID to CComModule::Init?");

      if (m_pInfo != NULL)
         return S_OK;
      HRESULT hRes = E_FAIL;
      EnterCriticalSection(&_Module.m_csTypeInfoHolder);
      if (m_pInfo == NULL)
      {
         ITypeLib* pTypeLib;
         hRes = LoadRegTypeLib(*m_plibid, m_wMajor, m_wMinor, lcid, &pTypeLib);
         if (SUCCEEDED(hRes))
         {
   	 CComPtr<ITypeInfo> spTypeInfo;
   	 hRes = pTypeLib->GetTypeInfoOfGuid(*m_pguid, &spTypeInfo);
   	 if (SUCCEEDED(hRes))
   	 {
   	    CComPtr<ITypeInfo> spInfo(spTypeInfo);
   	    CComPtr<ITypeInfo2> spTypeInfo2;
   	    if (SUCCEEDED(spTypeInfo->QueryInterface(&spTypeInfo2)))
   	        spInfo = spTypeInfo2;

     	    LoadNameCache(spInfo);
   	    m_pInfo = spInfo.Detach();
   	 }
   	 pTypeLib->Release();
         }
       }
       //ADD
       else
       {
    	hRes = S_OK;
       }
       //END ADD
       LeaveCriticalSection(&_Module.m_csTypeInfoHolder);
       _Module.AddTermFunc(Cleanup, (DWORD)this);
       return hRes;
   }

Make these modifications to a copy of the Atlcom.h file (for example,
Fixatlcom.h). Comment out Atlcom.h in the Stdafx.h file, and then use
Fixatlcom.h instead, as follows:

   //#include <atlcom.h>
   #include "FixAtlCom.h"

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article.

Additional query words: IDispatch Invoke 0x80004005 80004005

======================================================================
Keywords          : kbATL kbVC600 kbVC600bug kbATL300 kbATL300bug kbGrpDSMFCATL 
Technology        : kbVCsearch kbAudDeveloper kbATLsearch
Version           : WINDOWS:3.0
Issue type        : kbbug
Solution Type     : kbpending

=============================================================================

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