https://gcc.gnu.org/bugzilla/show_bug.cgi?id=123987
--- Comment #10 from Richard Earnshaw <rearnsha at gcc dot gnu.org> --- additionally, gcc provides __builtin_isinf_sign() &c. I suspect that if gcc wants the compiler to respect its extended semantics for isinf, then its headers should arrange for the function to be remapped accordingly. But that makes this a glibc bug.
