Application crashing in between, MFC, VC++

I had an issue before ,where OnTimer () function was not working and I started using thread which is working fine
as of now
http://www.experts-exchange.com/Programming/System/Windows__Programming/MFC/Q_24616997.html

What will be your recommendations?

First I would just pass the window handle and see if that cures your problem.

I've just realised
pWnd->VFSWEbServiceCall();

That is probably the cause of your crash - I suspect you are trying to fill the listbox directly.  

If my guess is correct then you need to use a list (array, some other container) to fill with the items, then when the thread finishes the main app can fill the listbox from the intermediate collection.

yeah ..you are correct..I am filling the listbox directly in "pWnd->VFSWEbServiceCall()"...
This function contains creating request and response messages, calling stored procedures, populating listbox, SSL initialization,

Strip out the bits that add strings/values to the listbox and add them to a list in memory (not a window).  Then when it is done pass the list onto the main window and let that put the entries in there into the listbox.

Actually my problem of crash is different...but I understand that nothing should be UI related in the worker thread...

I will try to be clear..
I have two list boxes on a dialog..which gets called when I click on Button search...

1. List1 fills very quickly from database.
2. List2 takes time around 3-4 seconds..(Webservice)

Now problem is if I click on List1 data lets say in 1 seconds without even allowing List2 to get filled ...the application crashes..

since the dialog box has to close, and list2 data is not populated and windows didn't get the message that web service thread is complete..the application crash...

I don't know if this is possible or not, to get the flag across application...I tried but didn't work
bool  flag = pWnd->PostMessage(WM_WEBSERVICEDONE,0,0);

or May be it is only putting bandage on much bigger problem which can come in later time as referred in the tutorials provided by Dan...

Please let me know your views...

The problem is that MFC is not thread safe.  Directly accessing one MFC based window from a different thread (as you do) can result in crashes.  I don't know the precise details but some things are handled on a thread specific basis, accesing directly from another thread means the information that MFC uses for the window to work is incorrect.  

Just give this a quick try.  Comment out the two lines in your thread starting with pWnd-> and replace with some dummy code eg. sleep(5000) - see if your app still crashes.  


ps.  If you code a thread properly then it will work without problems (same as coding an app really - do something wrong and it can crash).

I commented this code and application does not crash..

//pWnd->VFSWEbServiceCall();

So the problem seems to be what I suggested it could be.

>> Now problem is if I click on List1... the application crashes.

Indeed that is a common problem when secondary threads interact with the U/I in MFC (and actually most kinds of) programs. The specific reasons for the problem are hard to describe, but the symptoms are easy to recognize :-)

If you must use a secondary thread, then do as AndyAinscow suggested: Have it populate, say, a CStringArray or other in-memory array.  When it is done, have it set a flag that the U/I handler (your dialog) can see.  Then have a Window Timer check that flag and when the flag is set, populate the entire listbox from the CStringArray (and kill the timer).

>>>> I commented this code and application does not crash..
>>>> //pWnd->VFSWEbServiceCall();

In the pWnd->VFSWEbServiceCall(); instead of filling the listbox put the entries to a vector<CString>


 void MyCtrl::VFSWEbServiceCall()
 {
      // your code until filling of the listctrl
      ...
      // filling the listctrl
      std::vector<CString> * ptrArr = new std::vector<CString>;
      for (int i = 0; i < numEntriesOfListBox; ++i)
      {
           ptrArr->push_back(StringsToDisplayInListBox[i]);
      }
      // send message to dialog which is the parent of the listbox control
      GetParent(m_hWnd)->PostMessage(WM_FILL_MY_LISTBOX,
                                                                 (LPARAM)ptrArr,
                                                                 (WPARAM)numEntriesOfListBox);
 }

// yourdialog.cpp

BEGIN_MESSAGE_MAP(YourDialog, CDialog)
{
       // existing message handlers
       ....
       // message handler to fill the listbox from vector
       ON_MESSAGE(WM_FILL_MY_LISTBOX, OnFillListBox)
}


void YourDialog::OnFillListBox(LPARAM lp, WPARAM wp)
{
     m_lstBox.ResetContent();
     std::vector<CString> * ptrArr = (std::vector<CString> *)lp;
     for (int i; i < (int)ptrArr->size(); ++i)
     {
          m_lstBox.AddString((*ptrArr)[i]);  
     }
     delete ptrArr;
}

That way you would move the filling from worker thread to main thread.

I am trying to use CStringArray for filling the list control so I have 5 CStringarray for the five column values..

How do I pass the flag to dialog so that the listctrl gets filled on  OnFillListbox ?

I tried using GetParent()->PostMessage(WM_FILL_MY_LISTBOX,0,0); but it is not going into OnFillListBox
function
------------------------------------------------------------------------------------------------------------------
For (i =0;i < 3;i++)
{
arrProgram.Add();
arrProgram.Setat(i, name);

.......................
..........................

}
GetParent()->PostMessage(WM_FILL_MY_LISTBOX,0,0);
}

#define WM_FILL_MY_LISTBOX (WM_USER + 2)
 
BEGIN_MESSAGE_MAP(CDlgFinCoverageSearch, CPDialogSearch)
ON_MESSAGE(WM_FILL_MY_LISTBOX, OnFillListBox)
END MESSAGE
 
LRESULT CDlgFinCoverageSearch::OnFillListBox(WPARAM wParam, LPARAM lParam)
{
 
for  (i=0;i < size;i++
{
m_ListCtrl.AddItem(i, 0,arrProgram.GetAt(j), -1);
		m_ListCtrl.AddItem(i, 1,arrBankName.GetAt(j), -1);
		m_ListCtrl.AddItem(i, 2,arrPhonenum.GetAt(j), -1);
		m_ListCtrl.AddItem(i, 3,arrDescrip.GetAt(j), -1);
		m_ListCtrl.AddItem(i, 4,arrProduct.GetAt(j), -1);
 
		m_ListCtrl.SetItemData(i,j);
j++;
}
}
------------------------------------------------------------------------------------------
For (i =0;i < 3;i++)
{
 
if (eflag == true)
{
 
	arrProgram.Add(enhancement[i]->enhancementName);
	arrProgram.SetAt(j,enhancement[i]->enhancementName);
 
	}
else
{
 
	arrProgram.Add(str);
	arrProgram.SetAt(j,str);
}
 
arrBankName.Add(supplierName.Left(40));
arrBankName.SetAt(j,supplierName.Left(40));
 
if( !phone)
{
 
	arrPhonenum.Add("");
	arrPhonenum.SetAt(j,"");
}
else
{
 
	arrPhonenum.Add(phone[0]->phoneNumber);
	arrPhonenum.SetAt(j,phone[0]->phoneNumber);
}
 
 
arrDescrip.Add(typeName);
arrDescrip.SetAt(j,typeName);
 
arrProduct.Add(productName);
arrProduct.SetAt(j,productName );
}
 
GetParent()->PostMessage(WM_FILL_MY_LISTBOX,0,0);
			
			
			
                                              

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It looks like you are doing it right... however there is one thing you could be getting wrong:

Are you sure that GetParent() will return the dialog that contains the message handler?

In the example, the source code beginning on line 23 is rather anonymous -- we can't tell what object it belongs to.   Since we have no information, it is impossible to say whether  GetParent() will return the CDlgFinCoverageSearch object.