FIX: Incorrect Return Values from COleDateTime Members

ID: Q152781

The information in this article applies to:

The Microsoft Foundation Classes (MFC), included with:
- Microsoft Visual C++, 32-bit Editions, versions 4.0, 4.1, 4.2

SYMPTOMS

When you call the COleDateTime members (SetDate, SetTime, and SetDateTime), the return value indicates failure even though the call is successful. This may cause code that checks the return value to believe incorrectly that the call failed.

CAUSE

This behavior is caused by a problem in the COleDateTime code. COleDateTime defines the following enumeration:


    enum DateTimeStatus
    {
        valid = 0,
        invalid = 1,    // Invalid date (out of range, etc.)
        null = 2,       // Literally has no value
    };

The problem occurs because SetDate, SetTime, and SetDateTime all return 'valid' if successful. However 'valid' is defined to be 0 in the DateTimeStatus enumeration, which translates to a Boolean FALSE. The code should check for success and return TRUE or FALSE.

RESOLUTION

Call COleDateTime::GetStatus after each call to SetDate, SetTime, or SetDateTime. Then compare the value returned by GetStatus() against 'valid' to check for success. The "More Information" section of this article provides an example.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This bug has been corrected in the Visual C++ 4.2b technology update.

MORE INFORMATION

Because of the problem outlined previously in this article, code that checks the return value from these functions may believe that a failure has occurred when in fact the Date/Time was set correctly. For example, the following code will ASSERT even though the call was successful:


   COleDateTime myodt;
   VERIFY(myodt.SetDateTime(96,1,1,10,45,0));

To work around this problem, test the success of the call by calling the COleDateTime::GetStatus() member. Compare the value returned by GetStatus() against 'valid' to check for success as shown in this example:


    COleDateTime myodt;
    myodt.SetDateTime(95,6,1,23,45,0);
    VERIFY(myodt.GetStatus() == COleDateTime.valid);

Additional query words: kbVC400bug

Keywords : kbole kbMFC kbVC kbVC420fix
Version : 4.0 4.1 4.2
Platform : NT WINDOWS
Issue type : kbbug