FIX: Assertion Using Multiple %1 (or %2) in AfxFormatString1

WINDOWS   | WINDOWS NT

The information in this article applies to:

• The Microsoft Foundation Classes (MFC) included with:

      - Microsoft Visual C++ for Windows, versions 1.0 and 1.5
      - Microsoft Visual C++, 32-bit Edition, version 1.0
  

SYMPTOMS

When you use the AfxFormatString1() or AfxFormatString2() function, with more than one %1 or %2 parameter in the template string, the following assertion occurs:

   File strcore1.cpp, Line 269, Assertion Failed!

CAUSE

These functions do not allocate enough memory for multiple parameters to be used. However, in the case of AfxFormatString2(), two parameters may be used (one %1 and one %2) successfully. It is the use of two %1's or two %2's that causes the problem.

STATUS

Microsoft has confirmed this to be a bug in the Microsoft products listed at the beginning of this article. This problem has been corrected in MFC 3.0, included with Visual C++ version 2.0.

MORE INFORMATION

You can reproduce the problem by using the following steps:

1. Create a .CPP file using the sample code provided below.

2. Create a new Windows project that uses MFC, and add the .CPP that you just created to the project.

3. Use App Studio to create a string table that includes the following two entries:

         IDS_THETEMPLATE = File %1 has some text associated with it.
         IDS_THENEWTEMPLATE = File %1 and %1 have associated text.
   

4. Save the string information in an .RC file.

5. Add the newly created .RC file to the project by choosing Edit from the Project menu.

6. Perform a build. Visual Workbench creates a .DEF file for you if you do not supply your own .DEF file.

7. Run the program to view the assertion.

Sample Code

/* Compile options needed: Default MFC-Windows project options
*/
   /////////////////////////////////////////////////////////////////////
   // main cpp file
   /////////////////////////////////////////////////////////////////////
   #include <afxwin.h>          // Provide access to MFC
   #include "resource.h"     // App Studio puts resource ID's here

   // myWinApp hooks us into the MFC application processing
   class myWinApp : CWinApp
   {
   public:
        BOOL InitInstance();
   };

   BOOL myWinApp::InitInstance()
   {
     CString theOutputString;

     // This works fine
     AfxFormatString1( theOutputString, IDS_THETEMPLATE,
                       "filename.ext" );
     TRACE("theOutputString=%s\n", theOutputString);

     // Comment this out to avoid Assertion
     AfxFormatString1( theOutputString, IDS_THENEWTEMPLATE,
                       "filename.ext");
     TRACE("theOutputString=%s.\n", theOutputString);

     return FALSE; // Terminate the program
   }

   myWinApp theApp;

   /////////////////////////////////////////////////////////////////////