_Spec<_CharT> _M_spec{};
};
+ // Decide how 128-bit floating-point types should be formatted (or not).
+ // When supported, the typedef __format::__float128_t is the type that
+ // format arguments should be converted to for storage in basic_format_arg.
+ // Define the macro _GLIBCXX_FORMAT_F128 to say they're supported.
+ // _GLIBCXX_FORMAT_F128=1 means __float128, _Float128 etc. will be formatted
+ // by converting them to long double (or __ieee128 for powerpc64le).
+ // _GLIBCXX_FORMAT_F128=2 means basic_format_arg needs to enable explicit
+ // support for _Float128, rather than formatting it as another type.
+#undef _GLIBCXX_FORMAT_F128
+
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
-# define _GLIBCXX_FORMAT_F128 1
+
+ // Format 128-bit floating-point types using __ieee128.
using __float128_t = __ieee128;
-#elif defined _GLIBCXX_LDOUBLE_IS_IEEE_BINARY128
# define _GLIBCXX_FORMAT_F128 1
- using __float128_t = long double;
-#elif __FLT128_DIG__
-# define _GLIBCXX_FORMAT_F128 2
- using __float128_t = _Float128;
-#else
-# undef _GLIBCXX_FORMAT_F128
-#endif
-#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
- template<typename _Tp>
- concept __extended_floating_point = __is_same(_Tp, _Float128)
- || __is_same(_Tp, __ibm128)
- || __is_same(_Tp, __ieee128);
-#elif _GLIBCXX_FORMAT_F128
- template<typename _Tp>
- concept __extended_floating_point = __is_same(_Tp, __float128_t);
-#else
- template<typename _Tp>
- concept __extended_floating_point = false;
-#endif
+#elif defined _GLIBCXX_LDOUBLE_IS_IEEE_BINARY128
- template<typename _Tp>
- concept __floating_point = std::floating_point<_Tp>
- || __extended_floating_point<_Tp>;
+ // Format 128-bit floating-point types using long double.
+ using __float128_t = long double;
+# define _GLIBCXX_FORMAT_F128 1
- using std::to_chars;
+#elif __FLT128_DIG__ && defined(__GLIBC_PREREQ) // see floating_to_chars.cc
+
+ // Format 128-bit floating-point types using _Float128.
+ using __float128_t = _Float128;
+# define _GLIBCXX_FORMAT_F128 2
-#if _GLIBCXX_FORMAT_F128 == 2 \
- && (__cplusplus == 202002L || !defined(_GLIBCXX_HAVE_FLOAT128_MATH))
+# if __cplusplus == 202002L || !defined(_GLIBCXX_HAVE_FLOAT128_MATH)
// These overloads exist in the library, but are not declared for C++20.
// Make them available as std::__format::to_chars.
to_chars_result
to_chars_result
to_chars(char*, char*, _Float128, chars_format, int) noexcept
__asm("_ZSt8to_charsPcS_DF128_St12chars_formati");
+# endif
#endif
+ using std::to_chars;
+
+ // We can format a floating-point type iff it is usable with to_chars.
+ template<typename _Tp>
+ concept __formattable_float = requires (_Tp __t, char* __p)
+ { __format::to_chars(__p, __p, __t, chars_format::scientific, 6); };
+
template<__char _CharT>
struct __formatter_fp
{
#endif
/// Format a floating-point value.
- template<__format::__floating_point _Tp, __format::__char _CharT>
+ template<__format::__formattable_float _Tp, __format::__char _CharT>
struct formatter<_Tp, _CharT>
{
formatter() = default;
#ifdef _GLIBCXX_LONG_DOUBLE_ALT128_COMPAT
__ieee128 _M_f128;
__ibm128 _M_ibm128;
-#elif _GLIBCXX_FORMAT_F128
+#elif _GLIBCXX_FORMAT_F128 == 2
__float128_t _M_f128;
#endif
};
else if constexpr (is_same_v<_Tp, unsigned __int128>)
return __u._M_u128;
#endif
-#if _GLIBCXX_FORMAT_F128
+#if _GLIBCXX_FORMAT_F128 == 2
else if constexpr (is_same_v<_Tp, __float128_t>)
return __u._M_f128;
#endif
return type_identity<_Float64>();
# endif
#endif
-#ifdef __FLT128_DIG__
+#if _GLIBCXX_FORMAT_F128
+# if __FLT128_DIG__
else if constexpr (is_same_v<_Td, _Float128>)
return type_identity<__format::__float128_t>();
-#endif
-#if _GLIBCXX_USE_FLOAT128
+# endif
+# if __SIZEOF_FLOAT128__
else if constexpr (is_same_v<_Td, __float128>)
return type_identity<__format::__float128_t>();
+# endif
#endif
else if constexpr (__is_specialization_of<_Td, basic_string_view>)
return type_identity<basic_string_view<_CharT>>();
else if constexpr (is_same_v<_Tp, _Float64>)
return _Arg_f64;
#endif
-#if _GLIBCXX_FORMAT_F128
+#if _GLIBCXX_FORMAT_F128 == 2
else if constexpr (is_same_v<_Tp, __format::__float128_t>)
return _Arg_f128;
#endif
#endif
// TODO _Arg_f16 etc.
-#if _GLIBCXX_FORMAT_F128
+#if _GLIBCXX_FORMAT_F128 == 2
case _Arg_f128:
return std::forward<_Visitor>(__vis)(_M_val._M_f128);
#endif