https://gcc.gnu.org/bugzilla/show_bug.cgi?id=69413
Jonathan Wakely <redi at gcc dot gnu.org> changed: What |Removed |Added ---------------------------------------------------------------------------- Status|UNCONFIRMED |RESOLVED Resolution|--- |FIXED --- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> --- GCC 6 will now work if it is built against glibc <= 2.22 and then glibc is upgraded to >= 2.23 Using recent glibc 2.22 snapshots from git still requires rebuilding libstdc++. Specifically, if you build GCC against glibc before https://sourceware.org/git/gitweb.cgi?p=glibc.git;h=d9b965fa56350d6eea9f7f438a0714c7ffbb183f and then update glibc to a snapshot of 2.22 from git master after that commit, libstdc++ will not work. In that case glibc still reports itself as 2.22 and libstdc++ won't detect that the isinf and isnan declarations are gone, so must be reconfigured and rebuilt against the new glibc headers. When glibc releases 2.23 it weill be possible to upgrade to that without rebuilding libstdc++, because the version bump will tell libstdc++ the functions are gone.