https://gcc.gnu.org/bugzilla/show_bug.cgi?id=81193
--- Comment #5 from Peter Bergner <bergner at gcc dot gnu.org> --- Given Alan's comments, I think the best thing to do here is to just emit a warning when using those builtins when the compiler was configured to use an old glibc. If someone disagrees, let me know now, as I'm going to start coding up the change to add the warning.
