http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59177
--- Comment #2 from Jakub Jelinek <jakub at gcc dot gnu.org> --- Just install glibc 2.17 or later if you care about the speed, otherwise it is fixing much more important problem that the clocks had ABI incompatible settings depending on common libstdc++ configure options. If you do have glibc 2.17 or later, clock_gettime(CLOCK_MONOTONIC, &tp); should be used (if not, that would be a bug somewhere), but earlier glibcs have clock_gettime defined only in librt, which is undesirable to require.
