Q139693: FIX: Assertion Failed, Line 505 of Sockcore.cpp

Article: Q139693
Product(s): Microsoft C Compiler
Version(s): winnt:2.1,2.2
Operating System(s): 
Keyword(s): kbMFC kbVC152bug kbVC200bug kbVC210bug kbVC220bug kbVC400fix kbWinsock kbGrpDSMFCATL kb
Last Modified: 06-MAY-2001

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The information in this article applies to:

- The Microsoft Foundation Classes (MFC), used with:
   - Microsoft Visual C++ for Windows, 16-bit edition, version 1.52 
   - Microsoft Visual C++, 32-bit Editions, versions 2.1, 2.2 
-------------------------------------------------------------------------------

SYMPTOMS
========

An MFC application that uses the socket classes fails with a message similar to
the following:

In MFC 3.1 or 3.2, the assertion appears as:

  Assertion Failed: <app name>: File sockcore.cpp, Line 505

In MFC 2.52, the assertion appears as:

  Assertion Failed: <app name>: File sockcore.cpp, Line 484

CAUSE
=====

When all sockets are closed, the socket handle maps are emptied and the socket
notification window is destroyed.

MFC maintains an auxiliary queue of socket notification messages. If any messages
remain in this queue when the last socket is closed, then this assertion failure
will occur when any new sockets are opened and an attempt is made to process
these left-over notifications.

RESOLUTION
==========

Purge the auxiliary queue of all messages when the last socket is closed. In
this context, last does not mean previous; it means the socket that was closed,
leaving no sockets open for that thread.

This problem can be remedied by overriding the CAsyncSocket::Close member
function in your CAsyncSocket-derived or CSocket-derived class. The following
implementation of this override will take care of the problem:

  void CMySocket::Close()
  {
    // If Deriving from CSocket, then use:
    CSocket::Close();
    // Otherwise, use:
    // CAsyncSocket::Close();
    AFX_THREAD_STATE* pThreadState = AfxGetThreadState();
    if (pThreadState->m_mapSocketHandle.IsEmpty())
    {   // **** LAST SOCKET ****
      while (!pThreadState->m_listSocketNotifications.IsEmpty())
        delete pThreadState->m_listSocketNotifications.RemoveHead();
      pThreadState->m_listSocketNotifications.RemoveAll();
    }
  }


To handle the case where a socket object is deleted before Close is called, also
override the virtual destructor to make sure the correct version of Close is
called:

  CMySocket::~CMySocket()
  {
    if (m_hSocket != INVALID_SOCKET)
      Close();
  }

STATUS
======

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

Additional query words: 1.52 2.10 2.20 2.52 3.10 3.20 4.00 CSocket CAsyncSocket

======================================================================
Keywords          : kbMFC kbVC152bug kbVC200bug 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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