CThreadLocalObject Crash on Exit
in [MFC]
|
From: Joseph M. Newcomer on 29 Jul 2007 21:07 There are enough bugs in the memory display logic that I would not trust that message unless I knew the exact value that was shown. I find that sometimes it just gratuitously issues that message, because it has a symbol-table lookup problem (the error can arise from symbol table lookup or a bad pointer) joe On Fri, 27 Jul 2007 18:45:02 -0000, VT <thomasinov(a)gmail.com> wrote: >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...(a)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...(a)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...(a)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...(a)gmail.com" <thomasi...(a)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...(a)flounder.com >> >> Web:http://www.flounder.com >> >> MVP Tips:http://www.flounder.com/mvp_tips.htm-Hide quoted text - >> >> >> - Show quoted text - >> >> Joseph M. Newcomer [MVP] >> email: newco...(a)flounder.com >> Web:http://www.flounder.com >> MVP Tips:http://www.flounder.com/mvp_tips.htm- Hide quoted text - >> >> - Show quoted text - > Joseph M. Newcomer [MVP] email: newcomer(a)flounder.com Web: http://www.flounder.com MVP Tips: http://www.flounder.com/mvp_tips.htm
From: Joseph M. Newcomer on 29 Jul 2007 21:09
Note that 'this' might be a valid pointer to storage that is already freed, or storage that has been accidentally overwritten, in which case the error message *is* legitimate. So EXACT content is required. m_nSlot has an actual value. If nothing else, you can use a memory window to examine the conents, but the report as it stands is insufficient. joe On Fri, 27 Jul 2007 18:45:02 -0000, VT <thomasinov(a)gmail.com> wrote: >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...(a)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...(a)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...(a)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...(a)gmail.com" <thomasi...(a)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...(a)flounder.com >> >> Web:http://www.flounder.com >> >> MVP Tips:http://www.flounder.com/mvp_tips.htm-Hide quoted text - >> >> >> - Show quoted text - >> >> Joseph M. Newcomer [MVP] >> email: newco...(a)flounder.com >> Web:http://www.flounder.com >> MVP Tips:http://www.flounder.com/mvp_tips.htm- Hide quoted text - >> >> - Show quoted text - > Joseph M. Newcomer [MVP] email: newcomer(a)flounder.com Web: http://www.flounder.com MVP Tips: http://www.flounder.com/mvp_tips.htm |