https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88736
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- (In reply to Jonathan Wakely from comment #5) > We cannot remove it from <cstddef> without removing it from <stddef.h>, and > that's what the unresolved library issue is about. As Drea suggested, we could remove it from GCC's stddef.h and put it in libstdc++'s stddef.h instead, and then change the makefiles so that libstdc++'s stddef.h is actually installed. That would mean it's available when including <stddef.h> (because that will find the libstdc++ version of that header first), but not when including <cstddef> (because that uses #include_next <stddef.h> so includes GCC's stddef.h, not the libstdc++ version). But that still means removing it from GCC's stddef.h, and also changing which headers libstdc++ installs.
