Hello, I have this preprocessor macros: ----------- #include <boost/preprocessor/variadic/to_seq.hpp> #include <boost/preprocessor/seq/for_each_i.hpp> #include <boost/preprocessor/stringize.hpp> #include <iostream> #define TRACE(...) \ std::cout << "foo" \ BOOST_PP_SEQ_FOR_EACH_I(LOG_ARGUMENT,, BOOST_PP_VARIADIC_TO_SEQ(__VA_ARGS__)); #define LOG_ARGUMENT(r, data, i, elem) \ << std::endl << " Argument " << i << ": " << BOOST_PP_STRINGIZE(elem) << " == " << elem int main(int argc, char *argv[]) { TRACE(); return 0; } ----------- They compile when TRACE has arguments, but not without. Problem is, that LOG_ARGUMENT is called even when no args are supplied, leading to the expansion: std::cout << "foo" << std::endl << " Argument " << 0 << ": " << "" << " == " << ;; elem is empty, therefore there is no expression after the last << expected primary-expression before »;« token How can I deal with that? Thanks, Florian