Comma omitted in variadic function declaration in C++

According to § 8.3.5.4 of the C++ standard (current draft):

Where syntactically correct and where “…” is not part of
an abstract-declarator, “, …” is synonymous with “…”.

In short, in C++ ... (ellipsis) is an operator in its own right and so can be used without the comma, but use of the comma is retained for backwards compatibility.