In the second Chapter of Charles Petzold's "Programming Windows", 5th
Edition, we have the following listing:

/*-----------------------------------------------------
   SCRNSIZE.C -- Displays screen size in a message box
                 (c) Charles Petzold, 1998
  -----------------------------------------------------*/

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

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) ;
}

int WINAPI WinMain (HINSTANCE hInstance, HINSTANCE hPrevInstance,
                    PSTR szCmdLine, int iCmdShow)
{
     int cxScreen, cyScreen ;

     cxScreen = GetSystemMetrics (SM_CXSCREEN) ;
     cyScreen = GetSystemMetrics (SM_CYSCREEN) ;
     MessageBoxPrintf (TEXT ("ScrnSize"),
                       TEXT ("The screen is %i pixels wide by %i pixels
high."),
                       cxScreen, cyScreen) ;
     return 0 ;
}

I'm able to compile this with VC++ 7.1 without defining the UNICODE
macro. However, when I define this macro, it does not compile. I get the
following error:

error C2664: '_vsnprintf' : cannot convert parameter 1 from 'TCHAR
[1024]' to 'char *'
        Types pointed to are unrelated; conversion requires
reinterpret_cast, C-style cast or function-style cast

AFAICS, it should compile. Any ideas as to why this is happening?

Thanks,
Sumit.