The next problem is that gnulib defines: inline int signbit (float f) { return _gl_cxx_signbitf (f); } inline int signbit (double d) { return _gl_cxx_signbitd (d); } inline int signbit (long double l) { return _gl_cxx_signbitl (l); } GCC 6 provides a standard-conforming <math.h> which defines the same signbit overloads (as required by C++11 and C++14). So the gnulib header is incompatible with any conforming C++11 implementation. -- devel mailing list devel@xxxxxxxxxxxxxxxxxxxxxxx http://lists.fedoraproject.org/admin/lists/devel@xxxxxxxxxxxxxxxxxxxxxxx