Re: CThreadLocalObject Crash on Exit

From:

VT <thomasinov@gmail.com>

Newsgroups:

microsoft.public.vc.mfc

Date:

Fri, 27 Jul 2007 18:45:02 -0000

Message-ID:

<1185561902.228024.42840@b79g2000hse.googlegroups.com>

This is valid but m_nSlot is undefined. I get a "m_nSlot CXX0030:
Error: expression cannot be evaluated" message in the watch window.

On Jul 25, 1:39 pm, Joseph M. Newcomer <newco...@flounder.com> wrote:

The problem I had was that I could find no documentation on this class. However, the most
likely cause is that some memory damage has occurred. When you get the crash, what is the
value of 'this', for example?
joe

On Tue, 24 Jul 2007 23:00:02 -0000, VT <thomasi...@gmail.com> wrote:

CNoTrackObject* CThreadLocalObject::GetData(
   CNoTrackObject* (AFXAPI* pfnCreateObject)())
{
   ENSURE(pfnCreateObject);

   if (m_nSlot == 0)
   {
           if (_afxThreadData == NULL)
           {
                   _afxThreadData = new(__afxThreadData) CThreadSlotData;
                   ENSURE(_afxThreadData != NULL);
           }
           m_nSlot = _afxThreadData->AllocSlot();
           ENSURE(m_nSlot != 0);
   }
   CNoTrackObject* pValue = static_cast<CNoTrackObject*>(_afxThreadData-

GetThreadValue(m_nSlot));

   if (pValue == NULL)
   {
           // allocate zero-init object
           pValue = (*pfnCreateObject)();

           // set tls data to newly created object
           _afxThreadData->SetValue(m_nSlot, pValue);
           ASSERT(_afxThreadData->GetThreadValue(m_nSlot) == pValue);
   }
   return pValue;
}

Here is the surrounding code. It breaks at the line if (m_nSlot ==
0).

On Jul 24, 8:39 am, Joseph M. Newcomer <newco...@flounder.com> wrote:

Without seeing the code, and especially the code of CThreadLocalObject, it is hard to even
begin to guess what might be going on there.
joe

On Tue, 24 Jul 2007 00:39:34 -0000, "thomasi...@gmail.com" <thomasi...@gmail.com> wrote:

I recently ported an app from VC2003 to VC2005. My app now crashes on
exit. The following is the stack trace from the app.

mfc80d.dll!CThreadLocalObject::GetData(CNoTrackObject * (void)*
pfnCreateObject=0x78245650) Line 409 + 0x3 bytes C++

mfc80d.dll!CThreadLocal<AFX_MODULE_THREAD_STATE>::GetData() Line 177
+ 0xd bytes C++
mfc80d.dll!AfxGetModuleThreadState() Line 464 + 0x11 bytes C++
mfc80d.dll!AfxWinTerm() Line 47 + 0x5 bytes C++

mfc80d.dll!AfxWinMain(HINSTANCE__ * hInstance=0x00400000, HINSTANCE__
* hPrevInstance=0x00000000, char * lpCmdLine=0x0015233a, int
nCmdShow=1) Line 62 C++

SzSimTool.exe!WinMain(HINSTANCE__ * hInstance=0x00400000, HINSTANCE__
* hPrevInstance=0x00000000, char * lpCmdLine=0x0015233a, int
nCmdShow=1) Line 29 C++

SzSimTool.exe!__tmainCRTStartup() Line 578 + 0x35 bytes C
SzSimTool.exe!WinMainCRTStartup() Line 403 C
kernel32.dll!7c816fd7()
[Frames below may be incorrect and/or missing, no symbols loaded for
kernel32.dll]

It appears that AfxGetModuleThreadState() returns a seemingly valid
AFX_MODULE_THREAD_STATE* object.

However, the memory under it is inaccessible. So, when it gets to
the
GetData() call inside of the CThreadLocalObject, the this pointer is
pointing to memory it has no access to. Therefore, as soon as it
attempts
to execute if (m_nSlot == 0), it crashes with the following
exception:
Unhandled exception at 0x78246d10 (mfc80d.dll) in SzSimTool.exe:
0xC0000005: Access violation reading location 0x05878b48.

Anyone have any ideas as to what is causing this? If not how can I go
about debugging this problem.

Thanks,
V

Joseph M. Newcomer [MVP]
email: newco...@flounder.com
Web:http://www.flounder.com
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Joseph M. Newcomer [MVP]
email: newco...@flounder.com
Web:http://www.flounder.com
MVP Tips:http://www.flounder.com/mvp_tips.htm- Hide quoted text -

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