https://gcc.gnu.org/bugzilla/show_bug.cgi?id=100361
--- Comment #6 from Jonathan Wakely <redi at gcc dot gnu.org> --- That patch isn't OK, because the declarations in <charconv> would still be present, but using them would give linker errors. I think we should just check __SIZE_WIDTH__ < 32 (in that .cc file and in the header). If somebody wants to contribute an implementation that doesn't use the tables and trades off time for space then we can support them, but I don't think that's a good use of Patrick's time.
