On Tue, 11 Mar 2025 at 12:22, Tomasz Kamiński wrote: > > Floating points types _Float16, _Float32, _Float64, and bfloat16, > can be formatted only if std::to_chars overloads for such types > where provided. Currently this is only the case for architectures
Spelling: "were provided" With that fixed, OK for trunk, thanks for noticing this. I think we also want this on the gcc-14 and gcc-13 branches, but after it's sat on trunk for a while. > where float and double are 32-bits and 64-bits IEEE floating points types. > > This patch updates the preprocessing checks for formatters > for above types to check _GLIBCXX_FLOAT_IS_IEEE_BINARY32 > and _GLIBCXX_DOUBLE_IS_IEEE_BINARY64. Making them non-formattable > on non-IEEE architectures. > > Remove a potential UB, where we could produce basic_format_arg > with _M_type set to _Arg_fp32 or _Arg_fp64, that was later not > handled by `_M_visit`. > > libstdc++-v3/ChangeLog: > > * include/std/format (formatter<_Float16, _CharT>): Define only if > _GLIBCXX_FLOAT_IS_IEEE_BINARY32 macro is defined. > (formatter<_Float16, _CharT>): As above. > (formatter<__gnu_cxx::__bfloat16_t, _CharT>): As above. > (formatter<_Float64, _CharT>): Define only if > _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 is defined. > (basic_format_arg::_S_to_arg_type): Normalize _Float32 and _Float64 > only to float and double respectivelly. > (basic_format_arg::_S_to_enum): Remove handling of _Float32 and > _Float64. > --- > Tested on x86_64-linux. OK for trunk? > > libstdc++-v3/include/std/format | 32 ++++++++------------------------ > 1 file changed, 8 insertions(+), 24 deletions(-) > > diff --git a/libstdc++-v3/include/std/format b/libstdc++-v3/include/std/format > index e7e0d2d142b..1809f040077 100644 > --- a/libstdc++-v3/include/std/format > +++ b/libstdc++-v3/include/std/format > @@ -2276,7 +2276,7 @@ namespace __format > }; > #endif > > -#ifdef __STDCPP_FLOAT16_T__ > +#if defined(__STDCPP_FLOAT16_T__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32) > // Reuse __formatter_fp<C>::format<float, Out> for _Float16. > template<__format::__char _CharT> > struct formatter<_Float16, _CharT> > @@ -2298,7 +2298,7 @@ namespace __format > }; > #endif > > -#if defined(__FLT32_DIG__) > +#if defined(__FLT32_DIG__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32) > // Reuse __formatter_fp<C>::format<float, Out> for _Float32. > template<__format::__char _CharT> > struct formatter<_Float32, _CharT> > @@ -2320,7 +2320,7 @@ namespace __format > }; > #endif > > -#if defined(__FLT64_DIG__) > +#if defined(__FLT64_DIG__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64) > // Reuse __formatter_fp<C>::format<double, Out> for _Float64. > template<__format::__char _CharT> > struct formatter<_Float64, _CharT> > @@ -2364,7 +2364,7 @@ namespace __format > }; > #endif > > -#ifdef __STDCPP_BFLOAT16_T__ > +#if defined(__STDCPP_BFLOAT16_T__) && > defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32) > // Reuse __formatter_fp<C>::format<float, Out> for bfloat16_t. > template<__format::__char _CharT> > struct formatter<__gnu_cxx::__bfloat16_t, _CharT> > @@ -3443,22 +3443,16 @@ namespace __format > return type_identity<float>(); > #endif > > -#ifdef __FLT32_DIG__ > +#if defined(__FLT32_DIG__) && defined(_GLIBCXX_FLOAT_IS_IEEE_BINARY32) > else if constexpr (is_same_v<_Td, _Float32>) > -# ifdef _GLIBCXX_FLOAT_IS_IEEE_BINARY32 > return type_identity<float>(); > -# else > - return type_identity<_Float32>(); > -# endif > #endif > -#ifdef __FLT64_DIG__ > + > +#if defined(__FLT64_DIG__) && defined(_GLIBCXX_DOUBLE_IS_IEEE_BINARY64) > else if constexpr (is_same_v<_Td, _Float64>) > -# ifdef _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 > return type_identity<double>(); > -# else > - return type_identity<_Float64>(); > -# endif > #endif > + > #if _GLIBCXX_FORMAT_F128 > # if __FLT128_DIG__ > else if constexpr (is_same_v<_Td, _Float128>) > @@ -3538,16 +3532,6 @@ namespace __format > return _Arg_u128; > #endif > > - // N.B. some of these types will never actually be used here, > - // because they get normalized to a standard floating-point type. > -#if defined __FLT32_DIG__ && ! _GLIBCXX_FLOAT_IS_IEEE_BINARY32 > - else if constexpr (is_same_v<_Tp, _Float32>) > - return _Arg_f32; > -#endif > -#if defined __FLT64_DIG__ && ! _GLIBCXX_DOUBLE_IS_IEEE_BINARY64 > - else if constexpr (is_same_v<_Tp, _Float64>) > - return _Arg_f64; > -#endif > #if _GLIBCXX_FORMAT_F128 == 2 > else if constexpr (is_same_v<_Tp, __format::__float128_t>) > return _Arg_f128; > -- > 2.48.1 >
