Comma omitted in variadic function declaration in C++

Question

I am used to declaring variadic functions like this:

int f(int n, ...);

When reading The C++ Programming Language I found that the dec

Answer 1

With int f(int n, ...); and int f(int n...);, as you can see, both , ... and ... has the same meaning. Comma is optional.

But this int printz(...); is valid in C++ while int printz(,...); is not (at least one named parameter must appear before the ellipsis parameter). That's why you can have just (...), even though the arguments passed to such function are not accessible.