PRB: Do not Call ODBC Within DLL_PROCESS_DETACH Case (177135)
The information in this article applies to:
- Microsoft Visual C++, 32-bit Enterprise Edition 5.0
- Microsoft Visual C++, 32-bit Enterprise Edition 6.0
- Microsoft Visual C++, 32-bit Professional Edition 5.0
- Microsoft Visual C++, 32-bit Professional Edition 6.0
- Microsoft Visual C++, 32-bit Learning Edition 6.0
- Microsoft Data Access Components 2.5
- Microsoft Data Access Components 2.6
This article was previously published under Q177135 SYMPTOMS
When using the MFC Database classes or calling ODBC functions within the
DLL_PROCESS_DETACH case of the DllMain() function, an access violation can
occur especially if the DLL links to the MFC DLL (which does a LoadLibrary
call to call ODBC). For example, calling CDatabase::Close() from the
destructor of a global static object in the DLL causes an access violation
error in ODBC32.DLL.
CAUSE
Because there are no guarantees of the order by which DLLs receive the
DLL_PROCESS_DETACH case, it is possible that the ODBC handle memory can be
freed before your DLL's DllMain() function gets called with
DLL_PROCESS_DETACH. Therefore, any calls to ODBC using those handles can
cause a crash.
RESOLUTION
Do not call ODBC functions or use the MFC ODBC classes in destructors of
global objects within DLLs or in the DllMain() DLL_PROCESS_DETACH case.
Instead use a termination function in the DLL which the application can
call before exiting.
STATUS
This behavior is by design.
| Modification Type: | Major | Last Reviewed: | 12/8/2003 |
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| Keywords: | kbDatabase kbprb KB177135 |
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