Microsoft KB Archive/111770

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BUG: Serialize in MFC Container-Server Applications May Fail

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Q111770

1.50 1.51 1.52 WINDOWS kbprg kbbuglist -- The information in this article applies to: - The Microsoft Foundation Classes (MFC), included with: Microsoft Visual C++ for Windows, versions 1.5, 1.51, and 1.52 -- SYMPTOMS ======== In an AppWizard-generated OLE (Object Linking and Embedding) 2.0 container- server application, when saving a container-server embedded object that contains another embedded object, the following assertions may occur: OLECLI1.CPP, Line 742 OLECLI1.CPP, Line 747 These assertions indicate that the value of the COleServerDoc member variable m_bCompoundFile is incorrect for the serialization that is being attempted. CAUSE ===== An MFC container-server application typically contains both a COleServerDoc derived class and a COleClientItem derived class. When a server item serializes itself, it assumes it is writing to a flat storage, which could be a file or a substorage in a compound file. This implies that m_bCompoundFile is FALSE. If the COleServerDoc member variable m_bCompoundFile is TRUE [that is, EnableCompoundFiles has been called), its status may be changed during serialization, which could subsequently cause the serialization of embedded objects to fail. RESOLUTION ========== To work around this problem, in the COleServerDoc derived class's Serialize member function, add logic to save and restore the state of m_bCompoundFile before and after the call to the base class Serialize function. For example, in a container-server application where the COleServerDoc class is CConSrvDoc, add the lines marked with asterisks below: /////////////////////////////////////////////////////////// // CConSrvDoc serialization void CConSrvDoc::Serialize(CArchive& ar) { if (ar.IsStoring) { // TODO: add storing code here } else { // TODO: add loading code here } // Calling the base class COleServerDoc enables serialization // of the container document's COleClientItem objects. (*) BOOL bSaveCompound = m_bCompoundFile; (*) m_bCompoundFile = TRUE; COleServerDoc::Serialize(ar); (*) m_bCompoundFile = bSaveCompound; } Note that you do not need to incorporate this workaround if you have removed the "EnableCompoundFiles" line from your document's constructor. STATUS ====== Microsoft has confirmed this to be a bug in the products listed at the beginning of this article. We are researching this bug and will post new information here in the Microsoft Knowledge Base as it becomes available. This is not a problem in the 32-bit MFC classes. Additional reference words: 1.50 2.5 2.50 2.51 2.52 assert KBCategory: kbprg kbbuglist KBSubcategory: MfcOLE

Keywords : kbole kb16bitonly kbMFC kbVC

Issue type : kbbug

Technology : kbAudDeveloper kbMFC