workaround "empty macro argument" warning
workaround "empty macro argument" warning

madlib/eigen_backup,madlib/eigen_backup,rotorliu/eigen,rotorliu/eigen,rotorliu/eigen,rotorliu/eigen,mjbshaw/Eigen,mjbshaw/Eigen,mjbshaw/Eigen,madlib/eigen_backup,mjbshaw/Eigen,madlib/eigen_backup