https://gcc.gnu.org/bugzilla/show_bug.cgi?id=84949
--- Comment #4 from Jonathan Wakely <redi at gcc dot gnu.org> --- std::numeric_limits<float> defines: static _GLIBCXX_USE_CONSTEXPR bool has_infinity = __FLT_HAS_INFINITY__; static _GLIBCXX_USE_CONSTEXPR bool has_quiet_NaN = __FLT_HAS_QUIET_NAN__; static _GLIBCXX_USE_CONSTEXPR bool has_signaling_NaN = has_quiet_NaN; static _GLIBCXX_USE_CONSTEXPR float_denorm_style has_denorm = bool(__FLT_HAS_DENORM__) ? denorm_present : denorm_absent; //... static _GLIBCXX_USE_CONSTEXPR bool is_iec559 = has_infinity && has_quiet_NaN && has_denorm == denorm_present; And that seems to be the right thing to do. If the compiler tells us the type has infinities and NaNs then we expose that through std::numeric_limits. I don't think we want the C++ library to be inconsistent with the compiler here. So maybe any change should be in the compiler not libstdc++.