> On 4 Jan 2025, at 13:27, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > > > > On Sat, 4 Jan 2025, 09:48 Hans Åberg, <haberg_1@xxxxxxxxxx> wrote: > > > On 30 Dec 2024, at 16:11, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > > > >> On Mon, 30 Dec 2024, 14:28 Hans Åberg, <haberg_1@xxxxxxxxxx> wrote: > >> > >>> On 30 Dec 2024, at 14:24, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > >>> > >>> On Sun, 29 Dec 2024 at 14:57, Hans Åberg <haberg_1@xxxxxxxxxx> wrote: > >>>> > >>>> > >>>>> On 29 Dec 2024, at 15:16, Jonathan Wakely <jwakely.gcc@xxxxxxxxx> wrote: > >>>>> > >>>>> On Sun, 29 Dec 2024 at 10:01, Hans Åberg via Gcc-help > >>>>> <gcc-help@xxxxxxxxxxx> wrote: > >>>>>> > >>>>>> When checking the GCC 14.2 implementation of C++23 fixed width floating-point types in the header <stdfloat> [1]: > >>>>>> > >>>>>> The page [2] says that one should be able to write std::float128_t using std::formatter as it is using std::to_chars which is required to support all arithmetic type, but it does not work with GCC. > >>>>> > >>>>> It works fine for me. > >>>>> > >>>>>> But the wording suggests it has been working with GCC. > >>>>> > >>>>> And still is working. > >>>>> > >>>>> If it's not working for you, it must be a limitation of your OS, which > >>>>> you haven't told us. > >>>> > >>>> It is MacOS 15.2, Silicon, but I think the error is the same on Intel, with > >>>> % g++ --version > >>>> g++ (MacPorts gcc14 14.2.0_3+stdlib_flag) 14.2.0 > >>> > >>> That's the problem then. std::to_chars is only defined for float128 > >>> under these conditions: > >>> > >>> #if defined(__STDCPP_FLOAT128_T__) && > >>> defined(_GLIBCXX_LDOUBLE_IS_IEEE_BINARY128) > >>> ... > >>> #elif defined(__STDCPP_FLOAT128_T__) && defined(_GLIBCXX_HAVE_FLOAT128_MATH) > >>> ... > >>> #endif > >>> > >>> The HAVE_FLOAT128_MATH macro is currently only defined for Glibc 2.26 > >>> and later, on targets that support __float128. > > The C++ features are not implemented for some reason, as one can use the GNU <quadmath.h> library and adding to g++ the library option -lquadmath, as in this example: > https://stackoverflow.com/questions/5451447/quadruple-precision-in-c-gcc > > That has nothing to do with std::to_chars or std::format. Could they not be implemented on top of that?
