Question

Let’s say I want to do something like this

void my_printf(char *fmt,...) {
 char buf[big enough];
 sprintf(buf,fmt,...);  
}

What is the proper way of passing the variable number of arguments directly to a function with accepts variable arguments?

Answer 1

sprintf has a va_list form called vsprintf. Pass the va_list you construct locally to it as the last argument.

void my_printf(char *fmt,...) {
 va_list ap;
 va_start(ap, fmt);

 char buf[big enough];
 vsprintf(buf,fmt,ap);

 va_end(ap);
}