Moving data from a CDateTimeCtrl to a CTime object in VC++ 6 - mfc

Question

Working with VS6 I noticed that some of my dialog boxes would crash when the date was changed in a CDateTimeCtrl object. Investigating this revealed that the call to DDX_DateTimeCtrl was moving 12 bytes of data onto a CTime object that is 4 bytes wide. Can anyone explain why this might be happening? Does anyone know how to correct it?
Header:
#if !defined(AFX_DATEDIALOG_H__B9373304_D774_4447_A4D1_BB4E1FB3404F__INCLUDED_)
#define AFX_DATEDIALOG_H__B9373304_D774_4447_A4D1_BB4E1FB3404F__INCLUDED_
#if _MSC_VER > 1000
#pragma once
#endif // _MSC_VER > 1000
// DateDialog.h : header file
//
/////////////////////////////////////////////////////////////////////////////
// CDateDialog dialog
class CDateDialog : public CDialog
{
// Construction
public:
CDateDialog(CWnd* pParent = NULL); // standard constructor
// Dialog Data
//{{AFX_DATA(CDateDialog)
enum { IDD = IDD_DIALOG_DATE };
CDateTimeCtrl m_StartDate;
CDateTimeCtrl m_EndDate;
CTime m_tmEndDate;
CTime m_tmStartDate;
//}}AFX_DATA
// Overrides
// ClassWizard generated virtual function overrides
//{{AFX_VIRTUAL(CDateDialog)
protected:
virtual void DoDataExchange(CDataExchange* pDX); // DDX/DDV support
//}}AFX_VIRTUAL
// Implementation
protected:
// Generated message map functions
//{{AFX_MSG(CDateDialog)
afx_msg void OnButtonBack();
afx_msg void OnDatetimechangeEndDate(NMHDR* pNMHDR, LRESULT* pResult);
afx_msg void OnDatetimechangeStartDate(NMHDR* pNMHDR, LRESULT* pResult);
afx_msg void OnCloseupStartDate(NMHDR* pNMHDR, LRESULT* pResult);
afx_msg void OnCloseupEndDate(NMHDR* pNMHDR, LRESULT* pResult);
//}}AFX_MSG
DECLARE_MESSAGE_MAP()
private:
// the range limits for the dates; these are set to the values found
// in m_tmStartDate and m_tmEndDate in OnInitDialog
CTime m_tmStart; // beginning of the range
CTime m_tmEnd; // end of the range
};
//{{AFX_INSERT_LOCATION}}
// Microsoft Visual C++ will insert additional declarations immediately before the previous line.
#endif // !defined(AFX_DATEDIALOG_H__B9373304_D774_4447_A4D1_BB4E1FB3404F__INCLUDED_)
Code:
// DateDialog.cpp : implementation file
//
#include "stdafx.h"
#include "CustomerSales.h"
#include "DateDialog.h"
#ifdef _DEBUG
#define new DEBUG_NEW
#undef THIS_FILE
static char THIS_FILE[] = __FILE__;
#endif
/////////////////////////////////////////////////////////////////////////////
// CDateDialog dialog
CDateDialog::CDateDialog(CWnd* pParent /*=NULL*/)
: CDialog(CDateDialog::IDD, pParent)
{
//{{AFX_DATA_INIT(CDateDialog)
m_tmEndDate = 0;
m_tmStartDate = 0;
//}}AFX_DATA_INIT
}
void CDateDialog::DoDataExchange(CDataExchange* pDX)
{
CDialog::DoDataExchange(pDX);
//{{AFX_DATA_MAP(CDateDialog)
DDX_Control(pDX, IDC_START_DATE, m_StartDate);
DDX_Control(pDX, IDC_END_DATE, m_EndDate);
DDX_DateTimeCtrl(pDX, IDC_END_DATE, m_tmEndDate);
DDX_DateTimeCtrl(pDX, IDC_START_DATE, m_tmStartDate);
//}}AFX_DATA_MAP
}
BEGIN_MESSAGE_MAP(CDateDialog, CDialog)
//{{AFX_MSG_MAP(CDateDialog)
ON_BN_CLICKED(IDC_BUTTON_BACK, OnButtonBack)
ON_NOTIFY(DTN_DATETIMECHANGE, IDC_END_DATE, OnDatetimechangeEndDate)
ON_NOTIFY(DTN_DATETIMECHANGE, IDC_START_DATE, OnDatetimechangeStartDate)
ON_NOTIFY(DTN_CLOSEUP, IDC_START_DATE, OnCloseupStartDate)
ON_NOTIFY(DTN_CLOSEUP, IDC_END_DATE, OnCloseupEndDate)
//}}AFX_MSG_MAP
END_MESSAGE_MAP()
/////////////////////////////////////////////////////////////////////////////
// CDateDialog message handlers
void CDateDialog::OnButtonBack()
{
// exit with our buton ID
EndDialog(IDC_BUTTON_BACK);
}
void CDateDialog::OnDatetimechangeEndDate(NMHDR* pNMHDR, LRESULT* pResult)
{
if(m_EndDate.GetMonthCalCtrl() == NULL)
{
UpdateData();
if(m_tmStartDate > m_tmEndDate)
m_tmStartDate = m_tmEndDate;
UpdateData(FALSE);
}
*pResult = 0;
}
void CDateDialog::OnDatetimechangeStartDate(NMHDR* pNMHDR, LRESULT* pResult)
{
if(m_StartDate.GetMonthCalCtrl() == NULL)
{
UpdateData();
if(m_tmEndDate < m_tmStartDate)
m_tmEndDate = m_tmStartDate;
UpdateData(FALSE);
}
*pResult = 0;
}
void CDateDialog::OnCloseupStartDate(NMHDR* pNMHDR, LRESULT* pResult)
{
UpdateData();
if(m_tmEndDate < m_tmStartDate)
m_tmEndDate = m_tmStartDate;
UpdateData(FALSE);
*pResult = 0;
}
void CDateDialog::OnCloseupEndDate(NMHDR* pNMHDR, LRESULT* pResult)
{
UpdateData();
if(m_tmStartDate > m_tmEndDate)
m_tmStartDate = m_tmEndDate;
UpdateData(FALSE);
*pResult = 0;
}

Answer 1

I have observed the bug with the CDateTimeCtrl a long time ago. The GetTime method of the class would crash if used with the CTime variable. I remember that at that time I have found a reference in the Internet related to this problem. I cannot find it now. The proposed solution was to use COleDateTime.
It seems that the similar problem exists with the DDE/DDX exchanges, and it has not been fixed in the latest MFC.
The simplest workaround for me at that time was to use the COleDateTime variables.
The DDX_DateTimeCtrl works with CTime and COleDateTime, so the solution for you will be to use the COleDateTime for your m_tmEndDate and m_tmStartDate variables.