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Q136080: FIX: Memory Leak Reported in PLEX.CPP When Using CSocket

Article: Q136080
Product(s): Microsoft C Compiler
Version(s): winnt:2.1,2.2
Operating System(s): 
Keyword(s): kbnokeyword kbMFC kbVC210bug kbVC220bug kbVC400fix kbWinsock kbGrpDSMFCATL kbNoUpdatekb
Last Modified: 06-MAY-2001

-------------------------------------------------------------------------------
The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++, 32-bit Editions, versions 2.1, 2.2 
-------------------------------------------------------------------------------

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.

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          : kbnokeyword kbMFC kbVC210bug kbVC220bug kbVC400fix kbWinsock kbGrpDSMFCATL kbNoUpdate kbbuglist kbfixlist
Technology        : kbAudDeveloper kbMFC
Version           : winnt:2.1,2.2
Issue type        : kbbug
Solution Type     : kbfix

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