https://gcc.gnu.org/bugzilla/show_bug.cgi?id=119246
--- Comment #3 from GCC Commits <cvs-commit at gcc dot gnu.org> --- The master branch has been updated by Tomasz Kaminski <tkami...@gcc.gnu.org>: https://gcc.gnu.org/g:9c9a7316adb99693e237164908893a78b86ba000 commit r16-616-g9c9a7316adb99693e237164908893a78b86ba000 Author: Tomasz KamiÅski <tkami...@redhat.com> Date: Wed Apr 30 10:37:48 2025 +0200 libstdc++: Preserve the argument type in basic_format_args [PR119246] This commits adjust the way how the arguments are stored in the _Arg_value (and thus basic_format_args), by preserving the types of fixed width floating-point types, that were previously converted to float, double, long double. The _Arg_value union now contains alternatives with std::bfloat16_t, std::float16_t, std::float32_t, std::float64_t that use pre-existing _Arg_bf16, _Arg_f16, _Arg_f32, _Arg_f32 argument types. This does not affect formatting, as specialization of formatters for fixed width floating-point types formats them by casting to the corresponding standard floating point type. For the 128bit floating we need to handle the ppc64 architecture, (_GLIBCXX_LONG_DOUBLE_ALT128_COMPAT) for which the long double may (per TU basis) designate either __ibm128 and __ieee128 type, we need to store both types in the _Arg_value and have two _Arg_types (_Arg_ibm128, _Arg_ieee128). On other architectures we use extra enumerator value to store __float128, that is different from long double and _Float128. This is consistent with ppc64, for which __float128, if present, is same type as __ieee128. We use _Arg_float128 _M_float128 names that deviate from _Arg_fN naming scheme, to emphasize that this flag is not used for std::float128_t (_Float128) type, that is consistenly formatted via handle. The __format::__float128_t type is renamed to __format::__flt128_t, to mitigate visual confusion between this type and __float128. We also introduce __bflt16_t typedef instead of using of decltype. We add new alternative for the _Arg_value and allow them to be accessed via _S_get, when the types are available. However, we produce and handle corresponding _Arg_type, only when we can format them. See also r14-3329-g27d0cfcb2b33de. The formatter<_Float128, _CharT> that formats via __format::__flt128_t is always provided, when type is available. It is still correct when __format::__flt128_t is _Float128. We also provide formatter<__float128, _CharT> that formats via __flt128_t. As this type may be disabled (-mno-float128), extra care needs to be taken, for situation when __float128 is same as long double. If the formatter would be defined in such case, the formatter<long double, _CharT> would be generated from different specializations, and have different mangling: * formatter<__float128, _CharT> if __float128 is present, * formatter<__format::__formattable_float, _CharT> otherwise. To best of my knowledge this happens only on ppc64 for __ieee128 and __float128, so the formatter is not defined in this case. static_assert is added to detect other configurations like that. In such case we should replace it with constraint. PR libstdc++/119246 libstdc++-v3/ChangeLog: * include/std/format (__format::__bflt16_t): Define. (_GLIBCXX_FORMAT_F128): Separate value for cases where _Float128 is used. (__format::__float128_t): Renamed to __format::__flt128_t. (std::formatter<_Float128, _CharT>): Define always if there is formattable 128bit float. (std::formatter<__float128, _CharT>): Define. (_Arg_type::_Arg_f128): Rename to _Arg_float128 and adjust value. (_Arg_type::_Arg_ibm128): Change value to _Arg_ldbl. (_Arg_type::_Arg_ieee128): Define as alias to _Arg_float128. (_Arg_value::_M_f128): Replaced with _M_ieee128 and _M_float128. (_Arg_value::_M_ieee128, _Arg_value::_M_float128) (_Arg_value::_M_bf16, _Arg_value::_M_f16, _Arg_value::_M_f32) (_Arg_value::_M_f64): Define. (_Arg_value::_S_get, basic_format_arg::_S_to_enum): Handle __bflt16, _Float16, _Float32, _Float64, and __float128 types. (basic_format_arg::_S_to_arg_type): Preserve _bflt16, _Float16, _Float32, _Float64 and __float128 types. (basic_format_arg::_M_visit): Handle _Arg_float128, _Arg_ieee128, _Arg_b16, _Arg_f16, _Arg_f32, _Arg_f64. * testsuite/std/format/arguments/args.cc: Updated to illustrate that extended floating point types use handles now. Added test for __float128. * testsuite/std/format/parse_ctx.cc: Extended test to cover class to check_dynamic_spec with floating point types and handles. Reviewed-by: Jonathan Wakely <jwak...@redhat.com> Signed-off-by: Tomasz KamiÅski <tkami...@redhat.com>
