Random crash for MFC dialog member variable not in scope - c++

Question

I have a MFC application with property window. I property window I have implemented a custom CMFCPropertyGridProperty, So that whenever user click the button added in that property, another dialog pops up.
void CMFCPropertyGridCustomProperty::OnClickButton(CPoint point) {
CSampleDlg* configDlg = new CSampleDlg(NULL);
INT_PTR bResult = configDlg->DoModal();
if(bResult != 1) //If user cancels bResult is 2 ,if select ok bResult is 1
{
return;
}
CString selectedOutput = configDlg->GetSelectionOutput();
CString configValue = configDlg->GetSelectionElemValue();
but the problem is , When I am running in debug mode, sometimes it is working fine but some times it crashes on configDlg->GetSelectionOutput() line. In callStack, I found that the variable is out of scope at that time.
Here is part of my dialog code:
IMPLEMENT_DYNAMIC(CSomeClassDlg, CDialogEx)
CSomeClassDlg::CSomeClassDlg(CWnd* pParent /*=NULL*/)
: CDialogEx(CSomeClassDlg::IDD, pParent)
{
m_DevNameStr = "";
m_ElemValue = "";
}
CSomeClassDlg::~CSomeClassDlg()
{
delete m_DataXMLTree;
m_DataXMLTree = NULL;
delete m_TemplateXMLTree;
m_TemplateXMLTree = NULL;
}
void CSomeClassDlg::OnItemchangedElementList(NMHDR *pNMHDR, LRESULT *pResult)
{
LPNMLISTVIEW pNMLV = reinterpret_cast<LPNMLISTVIEW>(pNMHDR);
int nPos = -1;
nPos = m_ElementListCtrl.GetNextItem(-1,LVNI_SELECTED);
if(nPos != -1)
{
elemDataNode = (CTreeNode*)(m_ElementListCtrl.GetItemData(nSelectedItemIndex));
elemTepmplateNode = GetTemplateElement(elemDataNode);
ShowElemDescription(elemDataNode,elemTepmplateNode);
}
else
{
return;
}
*pResult = 0;
}
void CSomeClassDlg::ShowElemDescription(CTreeNode* dataElemNode, CTreeNode* templateElemNode)
{
if(dataElemNode==NULL || templateElemNode==NULL)
{
m_DescEditCtrl.SetWindowTextA("");
return;
}
CString PIXITStr = templateElemNode->GetAttributeValue("AssociatedPixit");
CString descriptionStr = templateElemNode->GetAttributeValue("Description");
CString valueStr = dataElemNode->GetAttributeValue("Value");
m_DescEditCtrl.SetWindowTextA(descriptionStr);
m_DevNameStr = PIXITStr;
m_ElemValue = valueStr;
}
CString CSomeClassDlg::GetSelectionOutput()
{
return m_DevNameStr;
}
CString CSomeClassDlg::GetSelectionElemValue()
{
return m_ElemValue;
}
But I don't understand if that is the problem then why it is not happening each time. And if it is really the problem what is the best wat to get multiple member variable after doing doModal() . Please help.

Answer 1

Finally I have made some changes which had solved this issue.
1.changes the constructor of custom CMFCPropertyGridProperty class , parameter specially of type COleVariant.
2.Changed the dialog class constructor to take a CTreeNode* and store it as member variable. Somehow that pointer was getting corrupted after DoModal.
3.Added some Assert() to check the validity and a Redraw() in onclickbutton() of custom CMFCPropertyGridProperty class.
I do not know the exact reason for all these changes. Found a reference code in Google code
Here is the OnClickButton of the custom CMFCPropertyGridProperty class:
void CMFCPropertyGridPropertyCustomClass::OnClickButton(CPoint point)
{
ASSERT_VALID(this);
ASSERT_VALID(m_pWndList);
ASSERT_VALID(m_pWndInPlace);
ASSERT(::IsWindow(m_pWndInPlace->GetSafeHwnd()));
m_bButtonIsDown = TRUE;
Redraw();
BOOL bUpdate = FALSE;
CString selOutput = "";
CSomeClassDlg* configDlg = new CSomeClassDlg(m_selNode);
INT_PTR bResult = configDlg->DoModal();
if(bResult == IDOK)
{
bUpdate = TRUE;
//Do Something
}
if (bUpdate)
{
if (m_pWndInPlace != NULL)
{
m_pWndInPlace->SetWindowText(selOutput);
}
m_varValue = (LPCTSTR) selOutput;
}
m_bButtonIsDown = FALSE;
Redraw();
if (m_pWndInPlace != NULL)
{
m_pWndInPlace->SetFocus();
}
else
{
m_pWndList->SetFocus();
}
}
Here is the constructor of the custom CMFCPropertyGridProperty class:
CMFCPropertyGridPropertyCustomClass::CMFCPropertyGridPropertyCustomClass(CTreeNode* pNode, const CString& strName, const CString& varValue, const CString& description) : CMFCPropertyGridProperty(strName, COleVariant((LPCTSTR)varValue), description)
{
//some initialization
}