https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105281
--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> --- Thanks for the survey! (In reply to Jiang An from comment #2) > constexpr in C++23, lack constexpr (for some overloads) in libstdc++: > abs > modf > remquo > frexp Also imaxabs and imaxdiv, assuming https://cplusplus.github.io/LWG/issue3834 gets approved. These are handled by the front-end though, so they work in constexpr anyway. Even if we add constexpr to the additional overloads in <cmath>, it won't be present on ::modf(double) which is declared in libc and added to namespace std with a using-declaration. The implicit constexpr added by the front-end only works if you use don't use -fno-builtin
