In C++ 20 mode if the array is empty the resulting variadic data will be empty.
#include <boost/preprocessor/array/enum.hpp>
#define ARRAY (5,(B,O,O,S,T))
BOOST_PP_ARRAY_ENUM(ARRAY) // expands to B, O, O, S, T
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)