C / C++ / MFC

void viPrintf(const char* fmt,...)
{
  va_list v;
  va_start(v,fmt);
  vprintf(fmt,v);
  va_end(v);
}

// constructs a va_list composed of an int and a char * and
// passes it along to printf
// warning: non-tested, might need some adjustment with
// respect to the order in which parameters are stuffed
 
char vargs[10000]; // enough space to hold all the parms
char *pargs=&vargs[0];
 
// stuff an int
 
int x=5;
*((int *)pargs)=x;
pargs+=sizeof(x);
 
// stuff a char*
 
char *pc;
*((char **)pargs)=pc;
pargs+=sizeof(pc);
 
//call printf
printf("%d %s",args);

1. Open a Windows Explorer and locate a .xxx file.
   
2. Right click on it while pressing the shift key. Select "Open with..."
   
3. A dialog box appears for selecting the program to open the file with. Select program A and tick on the checkbox "Use always this program..." (sort of, my OS is in Spanish).

1. The definition is actually lacking.
   
2. The definition is in some file that is not being linked (maybe you deleted from the project accidentally).
   
3. Sometimes the precompiled headers feature makes funny thing and a "Rebuild all" drives it back to sanity.