Q266713: BUG: IDispatch::GetIDsOfNames() May Return E_FAIL When Successfu

Article: Q266713
Product(s): Microsoft C Compiler
Version(s): WINDOWS:3.0
Operating System(s): 
Keyword(s): kbATL kbVC600 kbVC600bug kbATL300 kbATL300bug kbGrpDSMFCATL
Last Modified: 28-JUN-2001

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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 
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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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