Hello (Thomas Heller, Joel de Guzman :-) ) In /usr/include/boost/phoenix/object/construct.hpp, there appears this preprocessor test on this macro BOOST_PHOENIX_NO_VARIADIC_EXPRESSION whereby the code either: 1. includes boost/phoenix/object/detail/cpp03/construct_expr.hpp , or 2. defines a expression inline Is that macro used to workaround some compiler limitations (and/or c++ std version) back in the day? I work with g++7 and std=c++14, and boost 1.64, and yet somehow boost/phoenix/object/detail/cpp03/construct_expr.hpp is included, and somewhere down the line a compilation error happens. The cpp03 is unnerving. Rds, MM