Thread: Beginner Question: CreateWindowEx Fails.

>>> how to display the Integer it returns in a Message Box.

Code:

#include <stdio.h>
...
char Error[10];
int LastError;
...
LastError = GetLastError();
sprintf(Error, "%d", LastError);
MessageBox(NULL, Error, "Error is", MB_OK);

Or use something like this(not my code, author unknown):

Code:

#include <windows.h>
#include <stdarg.h>
#include <stdio.h>
#include <tchar.h>

int CDECL MessageBoxPrintf (TCHAR * szFormat, ...)
{
     TCHAR   szBuffer [1024] ;
     va_list pArgList ;

     va_start (pArgList, szFormat) ;

     _vsntprintf (szBuffer, sizeof (szBuffer) / sizeof (TCHAR), 
                  szFormat, pArgList) ;

     szBuffer[(sizeof (szBuffer) / sizeof (TCHAR)) - 1] = TEXT('\0') ;

     va_end (pArgList) ;

     return MessageBox (NULL, szBuffer, TEXT("Debug Message"), 0) ;
}

Code:

MessageBoxPrintf("The error returned was %d.", GetLastError());

EDIT:
Nul termination added as pointed out by JasonD.

The code may have been taken from Petzold. Here is his code:

Code:

int CDECL MessageBoxPrintf (TCHAR * szCaption, TCHAR * szFormat, ...)
{
     TCHAR   szBuffer [1024] ;
     va_list pArgList ;

          // The va_start macro (defined in STDARG.H) is usually equivalent to:
          // pArgList = (char *) &szFormat + sizeof (szFormat) ;

     va_start (pArgList, szFormat) ;

          // The last argument to wvsprintf points to the arguments

     _vsntprintf (szBuffer, sizeof (szBuffer) / sizeof (TCHAR), 
                  szFormat, pArgList) ;

          // The va_end macro just zeroes out pArgList for no good reason

     va_end (pArgList) ;

     return MessageBox (NULL, szBuffer, szCaption, 0) ;
}

Notice that this code avoids buffer overflow by using the _vsntprintf function with appropriate use of the sizeof operator. However, the above code is not perfect, as it does not guarantee NULL termination. So, you should force this yourself by setting the last character in szBuffer to NULL. That reminds me, I should add this to my errata list for Programming Windows...