BUG: ASSERT in Strex.cpp, Line 690 with CString::Format

• The Microsoft Foundation Classes (MFC), included with:
  • Microsoft Visual C++, 32-bit Editions, version 6.0, used with:
    • Microsoft Visual Studio versions 6.0, 6.0 SP3

SYMPTOMS

Using CString::Format, gives an assertion in Strex.cpp, line 690. This problem occurs when the %+f format string is used. Previous versions of Visual C++ do not give this assertion. Also, only the Service Pack 3 (SP3) debug version of MFC gives this assertion; the SP3 retail version does not give the assertion.

CAUSE

This problem is due to a bug in the parsing of the format string in the MFC code.

RESOLUTION

The following are three workarounds:

• Use code similar to the following:

  
   	CString myStr;
  #ifdef _DEBUG
  	myStr.GetBufferSetLength(9);
  	myStr.ReleaseBuffer();
  #endif
  	myStr.Format("%+f", 1.0); 




• Use the format string %+.6f instead of %+f.



• Build the project in release configurations because the assertion does not occur with a release build.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article.

MORE INFORMATION

Steps to Reproduce Behavior

1. Create a new MFC AppWizard project.



2. In the InitInstance function, add the following two lines at the top of the function:

   
   CString str;
   str.Format("%+f", 1.0); 




3. Build the project and ensure that a debug build configuration is specified.

Additional query words: SP3only parse format string floating point

Keywords : kbMFC kbVC600 kbVS600sp3bug kbDSupport kbGrpMFCATL
Version : winnt:6.0
Platform : winnt
Issue type : kbbug