Microsoft KB Archive/136080

= FIX: Memory Leak Reported in PLEX.CPP When Using CSocket =

Article ID: 136080

Article Last Modified on 11/21/2006

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APPLIES TO

 Microsoft Foundation Class Library 4.2, when used with:  Microsoft Visual C++ 2.1

 Microsoft Visual C++ 2.2 

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This article was previously published under Q136080



SYMPTOMS
Running an application that uses the CSocket class causes a memory leak report to be generated when the application exits. The memory leak report will be similar to this:

{1555} plex.cpp(28) : non-object block at $002ECC8C, 132 bytes long



CAUSE
The CSocket class will queue up socket notification messages while it waits for a particular socket operation to complete. These messages are stored in CPtrList (m_listSocketNotifications) on a per-thread basis. This object is destroyed when the thread-state information for that thread is cleaned-up. Unfortunately the thread-state information for the primary thread is not cleaned-up until after the memory leak detection is performed.

Because MFC does not take care to free the plex objects associated with this list before the list is destroyed, the perceived memory leak is reported.

Because the problem is related to the frequency and sequence of the socket notification messages being received, the memory leak message might not occur every time the program is executed. It might only be seen under certain circumstances.



RESOLUTION
This message will only occur when CSocket objects are used in the primary thread. The message can be safely ignored because the m_listSocketNotifications object is actually being safely deleted before the application exits, so the memory will be freed then.

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STATUS
Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem was fixed in Microsoft Visual C++, 32-bit Edition, version 4.0.

Additional query words: 2.10 2.20 3.10 3.20 3.1 3.2

Keywords: kbbug kbfix kbnoupdate kbvc400fix kbwinsock KB136080

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