https://gcc.gnu.org/bugzilla/show_bug.cgi?id=82092
--- Comment #5 from Jürgen Reuter <juergen.reuter at desy dot de> --- Interestingly, I get the problem only with Xcode 9.0 and MAC OS X Sierra Darwin 16.6, but not with Xcode 9.0 and Mac OS X High Sierra Darwin 16.7.