The C standard description does not allow a function that does not have at least one normal argument before the variadic arguments. Conceptually, something mus

The C standard description does not allow a function that does not have at least one normal argument before the variadic arguments. Conceptually, something must indicate to the function how many arguments it is supposed to request next, and with what types. Yes, you could write a function where this information is passed through a static-lifetime variable, but in practice the first mandatory argument is almost always used for that anyway.