Re: debug assertion error in threads of c++ under windows

From:

"Scott McPhillips [MVP]" <org-dot-mvps-at-scottmcp>

Newsgroups:

microsoft.public.vc.mfc

Date:

Mon, 12 Mar 2007 09:57:01 -0400

Message-ID:

<##QpH6KZHHA.3268@TK2MSFTNGP04.phx.gbl>

Pushpa wrote:

Hi All,

This my part of the c++ program using threads in windows :

//modified by pushpa
struct structExrdDoc
{
    CExrdDoc* spDoc;
    LPCTSTR sstrFileName;

    structExrdDoc():spDoc(NULL),sstrFileName(""){}
};
structExrdDoc sp;

volatile bool running;

UINT CExcelExport::run(LPVOID p)
{
    CExrdDoc* me = sp.spDoc;
    me->OnSaveDocument ((LPCTSTR)sp.sstrFileName);
    running = FALSE;
    return 0;
}
//modified by pushpa

void CExcelExport::SaveExcelFile (CExrdDoc* pDoc, const string&
strFileName)
{
    sp.spDoc = pDoc; //modified by pushpa
    sp.sstrFileName = strFileName.c_str(); //modified by pushpa
    running = TRUE; //modified by pushpa
    AfxBeginThread(run,NULL); //modified by pushpa
    //pDoc->OnSaveDocument (strFileName.c_str()); //modified by pushpa
}

Here the line of code I have commented was taking lot of time, so I hv
tried to use threads and I am new to this.

This is the declaration in the .h file

    static UINT CExcelExport::run(LPVOID p);

After some struggle I could compile the application, but when it is
run I am getting a Debug assertion error.

debug assertion failed!
program:d:\amsa\amsa\bin\gageanalysisdlld.exe
file:wincore.cpp
line:888
for information on how your program can cause an assertion failure,
see the visual c++ documentation on asserts.

Could you please help me with this.

Thanking you in advance,
Pushpa.

In addition to the bug described by Wim...

OnSaveDocument is not designed to be executed from a secondary thread.
The problem is related to accessing windows created in the main thread,
which is not permitted by MFC. If you look in the stack window when the
assert happens you will see where in the CDocument code a window is
accessed.

You could write a new document function to save your data without
accessing any windows, or you could save the data in the thread function
without calling the CDocument function.

--
Scott McPhillips [VC++ MVP]

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