DOCUMENT:Q87554  03-MAY-2001  [visualc]
TITLE   :BUG: CArchiveException for Read-only and Write-only Files
PRODUCT :Microsoft C Compiler
PROD/VER:winnt:
OPER/SYS:
KEYWORDS:kbnokeyword kbFileIO kbMFC kbVC100bug kbVC150bug kbVC200bug kbVC400bug kbVC410bug kbGrp

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The information in this article applies to:

 - The Microsoft Foundation Classes (MFC), used with:
    - Microsoft Visual C++ for Windows 
    - Microsoft Visual C++ 32-bit Edition 
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SYMPTOMS
========

The CArchiveExceptions for read-only and write-only archives are not thrown by
the Microsoft Foundation Class Library. This condition can be caught by checking
for an access denied CFileException.

CAUSE
=====

This is an oversight of the MFC libraries. The CArchive class does not utilize a
try/catch block in its member functions that actually perform the serialization.
Thus, a CArchiveException will never be thrown for read-only and write-only
archives.

RESOLUTION
==========

To test for this condition, look for a CFileException with an m_cause value of
CFileException::accessDenied.

STATUS
======

Microsoft has confirmed this to be a problem in the versions of the Microsoft
Foundation Classes listed above. We are researching this problem and will post
new information here in the Microsoft Knowledge Base as it becomes available.

MORE INFORMATION
================

The CArchiveException class is used to handle exceptions that happen when using
the CArchive class. The cause of the CArchiveException can be found by checking
the m_cause data member of CArchiveException. Two of the values listed for
m_cause are CArchiveException::readOnly and CArchiveException::writeOnly. For
more information, refer to the Visual C++ Books Online topics for CArchive and
CArchiveException.

Additional query words:

======================================================================
Keywords          : kbnokeyword kbFileIO kbMFC kbVC100bug kbVC150bug kbVC200bug kbVC400bug kbVC410bug kbGrpDSMFCATL 
Technology        : kbAudDeveloper kbMFC
Version           : winnt:
Issue type        : kbbug

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