https://gcc.gnu.org/bugzilla/show_bug.cgi?id=60637
--- Comment #7 from Jonathan Wakely <redi at gcc dot gnu.org> --- To be clear, I'm not opposed to reusing the C++11 code for the non-standard C++98 functions (all of them, not just signbit). That seems like a reasonable project to undertake in stage 1, if someone is interested, but that wouldn't help fix this bug in 4.9 and 5.
