Hi Jonathan,
> On 14/05/25 10:01 +0200, Tomasz Kamiński wrote:
>>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.
>>---
>>I believe I have fixed all the typos. OK for trunk?
>
>
> OK, thanks
this patch broke Solaris bootstrap, both i386-pc-solaris2.11 and
sparc-sun-solaris2.11:
In file included from
/vol/gcc/src/hg/master/local/libstdc++-v3/src/c++20/format.cc:29:
/var/gcc/regression/master/11.4-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/format:
In member function ‘typename std::basic_format_context<_Out, _CharT>::iterator
std::formatter<__float128, _CharT>::format(__float128,
std::basic_format_context<_Out, _CharT>&) const’:
/var/gcc/regression/master/11.4-gcc/build/i386-pc-solaris2.11/libstdc++-v3/include/format:2994:41:
error: ‘__flt128_t’ is not a member of ‘std::__format’; did you mean
‘__bflt16_t’? [-Wtemplate-body]
2994 | { return _M_f.format((__format::__flt128_t)__u, __fc); }
| ^~~~~~~~~~
| __bflt16_t
and one more instance.
Rainer
--
-----------------------------------------------------------------------------
Rainer Orth, Center for Biotechnology, Bielefeld University
