In C++
        20 mode the variadic data can be empty and
      the result will be 0.
    
#include <boost/preprocessor/variadic/size.hpp>
#define VAR_DATA x, y, z
BOOST_PP_VARIADIC_SIZE(VAR_DATA) // expands to 3
Distributed under the Boost Software License, Version 1.0. (See accompanying file LICENSE_1_0.txt or copy at www.boost.org/LICENSE_1_0.txt)