Article: Q196836
Product(s): Microsoft C Compiler
Version(s): winnt:4.0,4.1,4.2,5.0,6.0
Operating System(s):
Keyword(s): kbDLL kbMFC kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 kbWinsock kbGrpDSMFCATL
Last Modified: 17-JUL-2001
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The information in this article applies to:
- The Microsoft Foundation Classes (MFC), used with:
- Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1
- Microsoft Visual C++, 32-bit Enterprise Edition, version 4.2
- Microsoft Visual C++, 32-bit Professional Edition, version 4.2
- Microsoft Visual C++, 32-bit Enterprise Edition, version 5.0
- Microsoft Visual C++, 32-bit Professional Edition, version 5.0
- 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
========
When you call MFC socket functions from ExitInstance of a DLL, the functions may
fail and return an error.
CAUSE
=====
In an MFC DLL, the CWinApp::ExitInstance function is called from the DllMain
function in response to the DLL_PROCESS_DETACH case.
The MFC socket functions call the WinSock APIs implemented in wsock32.dll. When
an application shuts down, the DllMain with DLL_PROCESS_DETACH of the WinSock
DLL may be called before the DllMain of the MFC regular DLL. This can cause some
process specific information to be lost.
NOTE: This problem applies to non-MFC DLLs and non-MFC sockets as well.
RESOLUTION
==========
Do not call socket functions from CWinApp::ExitInstance (DLL_PROCESS_DETACH).
Provide a cleanup function that the application can call to perform the last
socket functions.
STATUS
======
This behavior is by design.
MORE INFORMATION
================
A common mistake is to call the CSocket::Close (or CAsyncSocket::Close) function
in CWinApp::ExitInstance. This can generate an assertion in sockcore.cpp line
856 in Microsoft Visual C++ 5.0, and line 667 in Microsoft Visual C++ 6.0.
(c) Microsoft Corporation 1998, All Rights Reserved. Contributions by Adam Kim,
Microsoft Corporation.
Additional query words:
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Keywords : kbDLL kbMFC kbVC400 kbVC410 kbVC420 kbVC500 kbVC600 kbWinsock kbGrpDSMFCATL
Technology : kbAudDeveloper kbMFC
Version : winnt:4.0,4.1,4.2,5.0,6.0
Issue type : kbprb
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