PRB: CString::LoadString Fails in Console Application

The information in this article applies to:

• The Microsoft Foundation Classes (MFC), included with: Microsoft Visual C++, 32-bit Edition, versions 2.0, 2.1, 2.2, 4.0, 4.1

SYMPTOMS

CString::LoadString() generates an MFC assert in debug mode console applications or fails in release mode console applications.

CAUSE

CString::LoadString() relies on MFC global resource handles that are initialized in AfxWinMain(), which is only called in MFC GUI-based applications.

RESOLUTION

The resource string is loaded using the Win32 API ::LoadString() function. This method does not require any extra MFC initialization.

Example #1 below uses this method.

It is possible to initialize the MFC global resource handles by calling the undocumented AfxWinInit() function. In this case, it is advisable to declare an instance of a CWinApp class.

Example #2 below demonstrates this method.

STATUS

This behavior is by design.

WORKAROUND

Sample Code - Example #1

   /* Compile options needed: /MT
   */
   #include <afx.h>
   #include <stdio.h>
   #include <conio.h>

   #define IDS_HELLO 1

   BOOL LoadStringResource(CString &cszString, UINT nID)
   {
       int nSize = 0;
       int nLen = -1;

       cszString.Empty();

       //Keep looping until we have the whole string
       while ((nLen != 0) && (nLen == nSize - 1))
       {
           //Grow buffer by 256 bytes
           nSize += 256;

           //Load String Resource
           nLen = ::LoadString( GetModuleHandle(NULL), nID,
                                cszString.GetBuffer(nSize-1), nSize);
       }
       cszString.ReleaseBuffer();

       return (BOOL) nLen;
   }

   void main(void)
   {
       AfxInitialize();

       CString cszString;

       // IDS_HELLO is a string resource attached to the console
   application
       if (LoadStringResource(cszString, IDS_HELLO))
           printf("The string was loaded\n%s\n", (LPCTSTR) cszString);
       else
           printf("Error loading string");

       getch();
   }

Sample Code - Example #2

   /* Compile options needed: /MT
   */
   #include <afx.h>
   #include <afxwin.h>
   #include <conio.h>

   #define IDS_HELLO 1

   CWinApp theApp;

   void main()
   {
       if (!AfxWinInit(GetModuleHandle(NULL), NULL,
           ::GetCommandLine(), 0))
       {
           printf("Couldn't initialize MFC!\n");
           return;
       }

       CString cszString;

       // IDS_HELLO is a string resource attached to the console
   application
       if (cszString.LoadString(IDS_HELLO))
           printf("The string was loaded\n%s\n", (LPCTSTR) cszString);
       else
           printf("Error loading string");

       getch();
   }