Q168004: FIX: "Unable to initialize DAO/Jet db engine" Error

Article: Q168004
Product(s): Microsoft C Compiler
Version(s): 4.2 4.2b 5.0
Operating System(s): 
Keyword(s): kberrmsg kbDAOsearch kbDatabase kbMFC kbVC kbVS97sp1fix kbVS97sp2fix
Last Modified: 17-JUL-2001

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The information in this article applies to:

- Microsoft Visual C++, 32-bit Enterprise Edition, versions 4.2, 4.2b, 5.0 
- Microsoft Visual C++, 32-bit Professional Edition, versions 4.2, 4.2b, 5.0 
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SYMPTOMS
========

When you run a Visual C++ version 4.2 or 4.2b application on a machine that has
the 4.21.7022 version of the MFC DLL (MFC42.DLL), the following message appears
when you try to use MFC DAO classes:

  Unable to initialize DAO/Jet db engine

CAUSE
=====

Version 4.21.7022 of the MFC DLL (MFC42.DLL), which comes with Visual C++ 5.0,
always incorrectly tries to use DAO 3.5. Visual C++ 4.2 applications use DAO 3.0
and, therefore, DAO 3.0 is installed rather than DAO 3.5. When MFC tries to load
DAO 3.5 and it is not there, the error message shown above appears.

RESOLUTION
==========

Visual C++ applications that are statically linked with MFC do not use the
MFC42.DLL and do not see the problem. Also, the MFC DLL (MFC42.DLL) that comes
with Visual C++ 4.2 can be placed in the directory of the application so that it
is used, rather than the newer MFC DLL.

It is possible to fix the problem by installing DAO 3.5 on the machine as well.
However, keep in mind that this means you will be using a new Jet database
engine, which may introduce new problems with the application that was tested
using DAO 3.0.

STATUS
======

Microsoft has confirmed this to be a bug in the Microsoft products listed at the
beginning of this article. This bug has been corrected in Visual Studio 97
Service Pack 1.

For additional information about the Visual Studio 97 Service Pack 1, please see
the following article in the Microsoft Knowledge Base:

  Q170365 INFO: Visual Studio 97 Service Packs - What, Where, and Why

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

You can see the bug with the MFC42.DLL by looking in the DAOCORE.CPP file
included with Visual C++ 5.0. In several places in the file you can see the
following code:

        // Determine whether to use DAO 3.5 or 3.0
        // Use DAO 3.0 if DLL build and not
        // built with MFC 4.21 or later
        BOOL bUseDao30 = FALSE;

     #ifdef _AFXDLL
        AFX_MODULE_STATE* pModuleState = AfxGetModuleState();
        if (pModuleState->m_dwVersion < 421)
           bUseDao30 = TRUE;
     #endif // _AFXDLL

Notice that the version checking is incorrect. The version is checked against
'421' instead of '0x0421'. This means that bUseDao30 will always be FALSE and
this causes DAO 3.5 to be used.

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Keywords          : kberrmsg kbDAOsearch kbDatabase kbMFC kbVC kbVS97sp1fix kbVS97sp2fix 
Technology        : kbVCsearch kbAudDeveloper kbVC420 kbVC500 kbVC32bitSearch kbVC420b kbVC500Search
Version           : 4.2 4.2b 5.0
Issue type        : kbbug
Solution Type     : kbfix

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