[libc++][charconv] Granularizes the header.

[Mordante]

Summary

Having the header granularized makes it possible to remove the
dependency on this header in <format>. This <format> header gets
included in more headers due to more usage of std::formatter in the
library. This should reduce the number of transitive includes.

Note formatting the new headers will be done in a followup patch.

[Mordante]

Retrigger CI.

[philnik]

libcxx/include/__charconv/to_chars_integral.h

318–335

I think we should put these and the floating point overloads in a __fwd/to_chars.h header to avoid having a different overload set depending on what file is included. A linker error is a lot better than a program that compiler but is subtly wrong.

libcxx/include/__charconv/traits.h

2

FWIW I'd be fine with formatting the files in this patch.

libcxx/include/module.modulemap.in

690–692

Why do you deviate from the normal style here?

[Mordante]

libcxx/include/__charconv/to_chars_integral.h

318–335

I did this on purpose, when I use the floating point formatter, I can include that light header. I don't see a huge issue with this approach. This is only used in the library internally.

libcxx/include/__charconv/traits.h

2

I really prefer to do it separately. I also want to format the other headers in this directory.
(I will only make a draft of it to test the CI and land it so no additional reviewing is required.)

libcxx/include/module.modulemap.in

690–692

Good point, I should increment the indention of the others.

[Mordante]

CI fixes and addresses review comments.

[philnik]

libcxx/include/__charconv/to_chars_integral.h

318–335

Adding two forward declarations doesn't make this much heavier. My concern is that someone might rely on this being included transitively, and they get unexpected behaviour.

[Mordante]

libcxx/include/__charconv/to_chars_integral.h

318–335

I tried it, but then Clang (rightfully) complains about duplicated default arguments. It also pulls in some headers for the floating-point case. So for now I keep it as is.

[Mordante]

CI fixes.

[philnik]

libcxx/include/__charconv/to_chars_integral.h

318–335

The default arguments shouldn't be a problem. Simply set the defaults in the forward declaration and include the forward-declaration header when you define them.
What headers are pulled in by that? If it's just __type_traits/enable_if.h and __type_traits/is_integral.h, I don't think that's a real problem. These headers are tiny.

[Mordante]

CI fixes and adresses a review comment.

[Mordante]

libcxx/include/__charconv/to_chars_integral.h

318–335

I just dislike that solution where we have two declarations.

Instead I added a new to_chars.h private header including them both. So you can pick that one or if you know what you're doing the even more specialized ones.

[ldionne]

LGTM -- I am fine with either splitting the floating point to_chars and the integral ones or not splitting them. I think the current approach with a combined header that includes the floating-point/integral headers is a fine compromise.

[Mordante]

In D145590#4193285, @ldionne wrote:

LGTM -- I am fine with either splitting the floating point to_chars and the integral ones or not splitting them. I think the current approach with a combined header that includes the floating-point/integral headers is a fine compromise.

Thanks for the review!

[Mordante]

Rebasing gave merge conflicts, give it another CI run.

[philnik]

libcxx/include/__charconv/to_chars_integral.h

318–335

I really don't get why you are so vehemently against this. It's really not a lot of work and could easily fix super subtle bugs. I also don't think that adding another header is a fix for this. It still splits up the interface.

[Mordante]

Retrigger CI.

[Mordante]

CI Fixes.

libcxx/include/CMakeLists.txt

set(files
   __bit/endian.h
   __bit/has_single_bit.h
   __bit/popcount.h
   __bit/rotate.h
   __bit_reference
   __bsd_locale_defaults.h
   __bsd_locale_fallbacks.h
   __charconv/chars_format.h
+  __charconv/from_chars_integral.h
   __charconv/from_chars_result.h
   __charconv/tables.h
+  __charconv/to_chars.h
   __charconv/to_chars_base_10.h
+  __charconv/to_chars_floating_point.h
+  __charconv/to_chars_integral.h
   __charconv/to_chars_result.h
+  __charconv/traits.h
   __chrono/calendar.h
   __chrono/concepts.h
   __chrono/convert_to_timespec.h
   __chrono/convert_to_tm.h
   __chrono/day.h
   __chrono/duration.h
   __chrono/file_clock.h
   __chrono/formatter.h

libcxx/include/__charconv/from_chars_integral.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CHARCONV_FROM_CHARS_INTEGRAL_H
+#define _LIBCPP___CHARCONV_FROM_CHARS_INTEGRAL_H
+
+#include <__algorithm/copy_n.h>
+#include <__charconv/from_chars_result.h>
+#include <__charconv/traits.h>
+#include <__config>
+#include <__errc>
+#include <__memory/addressof.h>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_integral.h>
+#include <__type_traits/is_unsigned.h>
+#include <__type_traits/make_unsigned.h>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 17
+
+from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;
+
+template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+__sign_combinator(_It __first, _It __last, _Tp& __value, _Fn __f, _Ts... __args)
+{
+    using __tl = numeric_limits<_Tp>;
+    decltype(std::__to_unsigned_like(__value)) __x;
+
+    bool __neg = (__first != __last && *__first == '-');
+    auto __r = __f(__neg ? __first + 1 : __first, __last, __x, __args...);
+    switch (__r.ec)
+    {
+    case errc::invalid_argument:
+        return {__first, __r.ec};
+    case errc::result_out_of_range:
+        return __r;
+    default:
+        break;
+    }
+
+    if (__neg)
+    {
+        if (__x <= std::__complement(std::__to_unsigned_like(__tl::min())))
+        {
+            __x = std::__complement(__x);
+            std::copy_n(std::addressof(__x), 1, std::addressof(__value));
+            return __r;
+        }
+    }
+    else
+    {
+        if (__x <= std::__to_unsigned_like(__tl::max()))
+        {
+            __value = __x;
+            return __r;
+        }
+    }
+
+    return {__r.ptr, errc::result_out_of_range};
+}
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
+__in_pattern(_Tp __c)
+{
+    return '0' <= __c && __c <= '9';
+}
+
+struct _LIBCPP_HIDDEN __in_pattern_result
+{
+    bool __ok;
+    int __val;
+
+    explicit _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI operator bool() const { return __ok; }
+};
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI __in_pattern_result
+__in_pattern(_Tp __c, int __base)
+{
+    if (__base <= 10)
+        return {'0' <= __c && __c < '0' + __base, __c - '0'};
+    else if (std::__in_pattern(__c))
+        return {true, __c - '0'};
+    else if ('a' <= __c && __c < 'a' + __base - 10)
+        return {true, __c - 'a' + 10};
+    else
+        return {'A' <= __c && __c < 'A' + __base - 10, __c - 'A' + 10};
+}
+
+template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+__subject_seq_combinator(_It __first, _It __last, _Tp& __value, _Fn __f,
+                         _Ts... __args)
+{
+    auto __find_non_zero = [](_It __firstit, _It __lastit) {
+        for (; __firstit != __lastit; ++__firstit)
+            if (*__firstit != '0')
+                break;
+        return __firstit;
+    };
+
+    auto __p = __find_non_zero(__first, __last);
+    if (__p == __last || !std::__in_pattern(*__p, __args...))
+    {
+        if (__p == __first)
+            return {__first, errc::invalid_argument};
+        else
+        {
+            __value = 0;
+            return {__p, {}};
+        }
+    }
+
+    auto __r = __f(__p, __last, __value, __args...);
+    if (__r.ec == errc::result_out_of_range)
+    {
+        for (; __r.ptr != __last; ++__r.ptr)
+        {
+            if (!std::__in_pattern(*__r.ptr, __args...))
+                break;
+        }
+    }
+
+    return __r;
+}
+
+template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
+{
+    using __tx = __itoa::__traits<_Tp>;
+    using __output_type = typename __tx::type;
+
+    return std::__subject_seq_combinator(
+        __first, __last, __value,
+        [](const char* __f, const char* __l,
+           _Tp& __val) -> from_chars_result {
+            __output_type __a, __b;
+            auto __p = __tx::__read(__f, __l, __a, __b);
+            if (__p == __l || !std::__in_pattern(*__p))
+            {
+                __output_type __m = numeric_limits<_Tp>::max();
+                if (__m >= __a && __m - __a >= __b)
+                {
+                    __val = __a + __b;
+                    return {__p, {}};
+                }
+            }
+            return {__p, errc::result_out_of_range};
+        });
+}
+
+template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
+{
+    using __t = decltype(std::__to_unsigned_like(__value));
+    return std::__sign_combinator(__first, __last, __value, __from_chars_atoi<__t>);
+}
+
+
+/*
+// Code used to generate __from_chars_log2f_lut.
+#include <cmath>
+#include <iostream>
+#include <format>
+
+int main() {
+  for (int i = 2; i <= 36; ++i)
+    std::cout << std::format("{},\n", log2f(i));
+}
+*/
+/// log2f table for bases [2, 36].
+inline constexpr float __from_chars_log2f_lut[35] = {
+    1,         1.5849625, 2,         2.321928, 2.5849626, 2.807355, 3,        3.169925,  3.321928,
+    3.4594316, 3.5849626, 3.7004397, 3.807355, 3.9068906, 4,        4.087463, 4.169925,  4.2479277,
+    4.321928,  4.3923173, 4.4594316, 4.523562, 4.5849624, 4.643856, 4.70044,  4.7548876, 4.807355,
+    4.857981,  4.9068904, 4.9541965, 5,        5.044394,  5.087463, 5.129283, 5.169925};
+
+template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
+                      int __base)
+{
+    if (__base == 10)
+        return std::__from_chars_atoi(__first, __last, __value);
+
+    return std::__subject_seq_combinator(
+        __first, __last, __value,
+        [](const char* __p, const char* __lastp, _Tp& __val,
+           int __b) -> from_chars_result {
+            using __tl = numeric_limits<_Tp>;
+            // __base is always between 2 and 36 inclusive.
+            auto __digits = __tl::digits / __from_chars_log2f_lut[__b - 2];
+            _Tp __x = __in_pattern(*__p++, __b).__val, __y = 0;
+
+            for (int __i = 1; __p != __lastp; ++__i, ++__p)
+            {
+                if (auto __c = __in_pattern(*__p, __b))
+                {
+                    if (__i < __digits - 1)
+                        __x = __x * __b + __c.__val;
+                    else
+                    {
+                        if (!__itoa::__mul_overflowed(__x, __b, __x))
+                            ++__p;
+                        __y = __c.__val;
+                        break;
+                    }
+                }
+                else
+                    break;
+            }
+
+            if (__p == __lastp || !__in_pattern(*__p, __b))
+            {
+                if (__tl::max() - __x >= __y)
+                {
+                    __val = __x + __y;
+                    return {__p, {}};
+                }
+            }
+            return {__p, errc::result_out_of_range};
+        },
+        __base);
+}
+
+template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
+                      int __base)
+{
+    using __t = decltype(std::__to_unsigned_like(__value));
+    return std::__sign_combinator(__first, __last, __value,
+                                  __from_chars_integral<__t>, __base);
+}
+
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+from_chars(const char* __first, const char* __last, _Tp& __value)
+{
+    return std::__from_chars_atoi(__first, __last, __value);
+}
+
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
+from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
+{
+    _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
+    return std::__from_chars_integral(__first, __last, __value, __base);
+}
+#endif // _LIBCPP_STD_VER >= 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___CHARCONV_FROM_CHARS_INTEGRAL_H

libcxx/include/__charconv/to_chars.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CHARCONV_TO_CHARS
+#define _LIBCPP___CHARCONV_TO_CHARS
+
+#include <__charconv/to_chars_floating_point.h>
+#include <__charconv/to_chars_integral.h>
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CHARCONV_TO_CHARS

libcxx/include/__charconv/to_chars_floating_point.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CHARCONV_TO_CHARS_FLOATING_POINT_H
+#define _LIBCPP___CHARCONV_TO_CHARS_FLOATING_POINT_H
+
+#include <__availability>
+#include <__charconv/chars_format.h>
+#include <__charconv/to_chars_result.h>
+#include <__config>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 17
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, float __value);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, double __value);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, long double __value);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision);
+
+_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
+to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision);
+#endif // _LIBCPP_STD_VER >= 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+#endif // _LIBCPP___CHARCONV_TO_CHARS_FLOATING_POINT_H

libcxx/include/__charconv/to_chars_integral.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CHARCONV_TO_CHARS_INTEGRAL_H
+#define _LIBCPP___CHARCONV_TO_CHARS_INTEGRAL_H
+
+#include <__algorithm/copy_n.h>
+#include <__bit/countl.h>
+#include <__charconv/tables.h>
+#include <__charconv/to_chars_base_10.h>
+#include <__charconv/to_chars_result.h>
+#include <__charconv/traits.h>
+#include <__config>
+#include <__errc>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/integral_constant.h>
+#include <__type_traits/is_same.h>
+#include <__type_traits/make_32_64_or_128_bit.h>
+#include <__type_traits/make_unsigned.h>
+#include <__utility/unreachable.h>
+#include <cstddef>
+#include <cstdint>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 17
+
+to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type);
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_itoa(char* __first, char* __last, _Tp __value, true_type)
+{
+    auto __x = std::__to_unsigned_like(__value);
+    if (__value < 0 && __first != __last)
+    {
+        *__first++ = '-';
+        __x = std::__complement(__x);
+    }
+
+    return std::__to_chars_itoa(__first, __last, __x, false_type());
+}
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type)
+{
+    using __tx = __itoa::__traits<_Tp>;
+    auto __diff = __last - __first;
+
+    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
+        return {__tx::__convert(__first, __value), errc(0)};
+    else
+        return {__last, errc::value_too_large};
+}
+
+#  ifndef _LIBCPP_HAS_NO_INT128
+template <>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_itoa(char* __first, char* __last, __uint128_t __value, false_type)
+{
+    // When the value fits in 64-bits use the 64-bit code path. This reduces
+    // the number of expensive calculations on 128-bit values.
+    //
+    // NOTE the 128-bit code path requires this optimization.
+    if(__value <= numeric_limits<uint64_t>::max())
+        return __to_chars_itoa(__first, __last, static_cast<uint64_t>(__value), false_type());
+
+    using __tx = __itoa::__traits<__uint128_t>;
+    auto __diff = __last - __first;
+
+    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
+        return {__tx::__convert(__first, __value), errc(0)};
+    else
+        return {__last, errc::value_too_large};
+}
+#endif
+
+template <class _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value, int __base, false_type);
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
+                    true_type)
+{
+    auto __x = std::__to_unsigned_like(__value);
+    if (__value < 0 && __first != __last)
+    {
+        *__first++ = '-';
+        __x = std::__complement(__x);
+    }
+
+    return std::__to_chars_integral(__first, __last, __x, __base, false_type());
+}
+
+namespace __itoa {
+
+template <unsigned _Base>
+struct _LIBCPP_HIDDEN __integral;
+
+template <>
+struct _LIBCPP_HIDDEN __integral<2> {
+  template <typename _Tp>
+  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
+    // If value == 0 still need one digit. If the value != this has no
+    // effect since the code scans for the most significant bit set. (Note
+    // that __libcpp_clz doesn't work for 0.)
+    return numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1);
+  }
+
+  template <typename _Tp>
+  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
+    ptrdiff_t __cap = __last - __first;
+    int __n = __width(__value);
+    if (__n > __cap)
+      return {__last, errc::value_too_large};
+
+    __last = __first + __n;
+    char* __p = __last;
+    const unsigned __divisor = 16;
+    while (__value > __divisor) {
+      unsigned __c = __value % __divisor;
+      __value /= __divisor;
+      __p -= 4;
+      std::copy_n(&__base_2_lut[4 * __c], 4, __p);
+    }
+    do {
+      unsigned __c = __value % 2;
+      __value /= 2;
+      *--__p = "01"[__c];
+    } while (__value != 0);
+    return {__last, errc(0)};
+  }
+};
+
+template <>
+struct _LIBCPP_HIDDEN __integral<8> {
+  template <typename _Tp>
+  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
+    // If value == 0 still need one digit. If the value != this has no
+    // effect since the code scans for the most significat bit set. (Note
+    // that __libcpp_clz doesn't work for 0.)
+    return ((numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1)) + 2) / 3;
+  }
+
+  template <typename _Tp>
+  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
+    ptrdiff_t __cap = __last - __first;
+    int __n = __width(__value);
+    if (__n > __cap)
+      return {__last, errc::value_too_large};
+
+    __last = __first + __n;
+    char* __p = __last;
+    unsigned __divisor = 64;
+    while (__value > __divisor) {
+      unsigned __c = __value % __divisor;
+      __value /= __divisor;
+      __p -= 2;
+      std::copy_n(&__base_8_lut[2 * __c], 2, __p);
+    }
+    do {
+      unsigned __c = __value % 8;
+      __value /= 8;
+      *--__p = "01234567"[__c];
+    } while (__value != 0);
+    return {__last, errc(0)};
+  }
+
+};
+
+template <>
+struct _LIBCPP_HIDDEN __integral<16> {
+  template <typename _Tp>
+  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
+    // If value == 0 still need one digit. If the value != this has no
+    // effect since the code scans for the most significat bit set. (Note
+    // that __libcpp_clz doesn't work for 0.)
+    return (numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1) + 3) / 4;
+  }
+
+  template <typename _Tp>
+  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
+    ptrdiff_t __cap = __last - __first;
+    int __n = __width(__value);
+    if (__n > __cap)
+      return {__last, errc::value_too_large};
+
+    __last = __first + __n;
+    char* __p = __last;
+    unsigned __divisor = 256;
+    while (__value > __divisor) {
+      unsigned __c = __value % __divisor;
+      __value /= __divisor;
+      __p -= 2;
+      std::copy_n(&__base_16_lut[2 * __c], 2, __p);
+    }
+    if (__first != __last)
+      do {
+        unsigned __c = __value % 16;
+        __value /= 16;
+        *--__p = "0123456789abcdef"[__c];
+      } while (__value != 0);
+    return {__last, errc(0)};
+  }
+};
+
+} // namespace __itoa
+
+template <unsigned _Base, typename _Tp,
+          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
+__to_chars_integral_width(_Tp __value) {
+  return __itoa::__integral<_Base>::__width(__value);
+}
+
+template <unsigned _Base, typename _Tp,
+          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
+__to_chars_integral_width(_Tp __value) {
+  return std::__to_chars_integral_width<_Base>(static_cast<unsigned>(__value));
+}
+
+template <unsigned _Base, typename _Tp,
+          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value) {
+  return __itoa::__integral<_Base>::__to_chars(__first, __last, __value);
+}
+
+template <unsigned _Base, typename _Tp,
+          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value) {
+  return std::__to_chars_integral<_Base>(__first, __last, static_cast<unsigned>(__value));
+}
+
+template <typename _Tp>
+_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
+__to_chars_integral_width(_Tp __value, unsigned __base) {
+  _LIBCPP_ASSERT(__value >= 0, "The function requires a non-negative value.");
+
+  unsigned __base_2 = __base * __base;
+  unsigned __base_3 = __base_2 * __base;
+  unsigned __base_4 = __base_2 * __base_2;
+
+  int __r = 0;
+  while (true) {
+    if (__value < __base)
+      return __r + 1;
+    if (__value < __base_2)
+      return __r + 2;
+    if (__value < __base_3)
+      return __r + 3;
+    if (__value < __base_4)
+      return __r + 4;
+
+    __value /= __base_4;
+    __r += 4;
+  }
+
+  __libcpp_unreachable();
+}
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
+                    false_type)
+{
+  if (__base == 10) [[likely]]
+    return std::__to_chars_itoa(__first, __last, __value, false_type());
+
+  switch (__base) {
+  case 2:
+    return std::__to_chars_integral<2>(__first, __last, __value);
+  case 8:
+    return std::__to_chars_integral<8>(__first, __last, __value);
+  case 16:
+    return std::__to_chars_integral<16>(__first, __last, __value);
+  }
+
+  ptrdiff_t __cap = __last - __first;
+  int __n = std::__to_chars_integral_width(__value, __base);
+  if (__n > __cap)
+    return {__last, errc::value_too_large};
+
+  __last = __first + __n;
+  char* __p = __last;
+  do {
+    unsigned __c = __value % __base;
+    __value /= __base;
+    *--__p = "0123456789abcdefghijklmnopqrstuvwxyz"[__c];
+  } while (__value != 0);
+  return {__last, errc(0)};
+}
+
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+to_chars(char* __first, char* __last, _Tp __value)
+{
+  using _Type = __make_32_64_or_128_bit_t<_Tp>;
+  static_assert(!is_same<_Type, void>::value, "unsupported integral type used in to_chars");
+  return std::__to_chars_itoa(__first, __last, static_cast<_Type>(__value), is_signed<_Tp>());
+}
+
+template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
+to_chars(char* __first, char* __last, _Tp __value, int __base)
+{
+  _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
+
+  using _Type = __make_32_64_or_128_bit_t<_Tp>;
+  return std::__to_chars_integral(__first, __last, static_cast<_Type>(__value), __base, is_signed<_Tp>());
+}
+
+#endif // _LIBCPP_STD_VER >= 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___CHARCONV_TO_CHARS_INTEGRAL_H

libcxx/include/__charconv/traits.h

+// -*- C++ -*-
+//===----------------------------------------------------------------------===//
+//
+// Part of the LLVM Project, under the Apache License v2.0 with LLVM Exceptions.
+// See https://llvm.org/LICENSE.txt for license information.
+// SPDX-License-Identifier: Apache-2.0 WITH LLVM-exception
+//
+//===----------------------------------------------------------------------===//
+
+#ifndef _LIBCPP___CHARCONV_TRAITS
+#define _LIBCPP___CHARCONV_TRAITS
+
+#include <__bit/countl.h>
+#include <__charconv/tables.h>
+#include <__charconv/to_chars_base_10.h>
+#include <__config>
+#include <__type_traits/enable_if.h>
+#include <__type_traits/is_unsigned.h>
+#include <cstdint>
+#include <limits>
+
+#if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
+#  pragma GCC system_header
+#endif
+
+_LIBCPP_PUSH_MACROS
+#include <__undef_macros>
+
+_LIBCPP_BEGIN_NAMESPACE_STD
+
+#if _LIBCPP_STD_VER >= 17
+
+namespace __itoa
+{
+
+template <typename _Tp, typename = void>
+struct _LIBCPP_HIDDEN __traits_base;
+
+template <typename _Tp>
+struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) <= sizeof(uint32_t)>>
+{
+    using type = uint32_t;
+
+    /// The width estimation using a log10 algorithm.
+    ///
+    /// The algorithm is based on
+    /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
+    /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
+    /// function requires its input to have at least one bit set the value of
+    /// zero is set to one. This means the first element of the lookup table is
+    /// zero.
+    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
+    {
+        auto __t = (32 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
+        return __t - (__v < __itoa::__pow10_32[__t]) + 1;
+    }
+
+    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v)
+    {
+        return __itoa::__base_10_u32(__p, __v);
+    }
+
+    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_32)& __pow() { return __itoa::__pow10_32; }
+};
+
+template <typename _Tp>
+struct _LIBCPP_HIDDEN
+    __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uint64_t)>> {
+  using type = uint64_t;
+
+  /// The width estimation using a log10 algorithm.
+  ///
+  /// The algorithm is based on
+  /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
+  /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
+  /// function requires its input to have at least one bit set the value of
+  /// zero is set to one. This means the first element of the lookup table is
+  /// zero.
+  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
+    auto __t = (64 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
+    return __t - (__v < __itoa::__pow10_64[__t]) + 1;
+  }
+
+  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) { return __itoa::__base_10_u64(__p, __v); }
+
+  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_64)& __pow() { return __itoa::__pow10_64; }
+};
+
+
+#  ifndef _LIBCPP_HAS_NO_INT128
+template <typename _Tp>
+struct _LIBCPP_HIDDEN
+    __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(__uint128_t)> > {
+  using type = __uint128_t;
+
+  /// The width estimation using a log10 algorithm.
+  ///
+  /// The algorithm is based on
+  /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
+  /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
+  /// function requires its input to have at least one bit set the value of
+  /// zero is set to one. This means the first element of the lookup table is
+  /// zero.
+  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
+    _LIBCPP_ASSERT(__v > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fail when this isn't true.");
+    // There's always a bit set in the upper 64-bits.
+    auto __t = (128 - std::__libcpp_clz(static_cast<uint64_t>(__v >> 64))) * 1233 >> 12;
+    _LIBCPP_ASSERT(__t >= __itoa::__pow10_128_offset, "Index out of bounds");
+    // __t is adjusted since the lookup table misses the lower entries.
+    return __t - (__v < __itoa::__pow10_128[__t - __itoa::__pow10_128_offset]) + 1;
+  }
+
+  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) { return __itoa::__base_10_u128(__p, __v); }
+
+  // TODO FMT This pow function should get an index.
+  // By moving this to its own header it can be reused by the pow function in to_chars_base_10.
+  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_128)& __pow() { return __itoa::__pow10_128; }
+};
+#endif
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
+__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r)
+{
+    auto __c = __a * __b;
+    __r = __c;
+    return __c > numeric_limits<unsigned char>::max();
+}
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
+__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r)
+{
+    auto __c = __a * __b;
+    __r = __c;
+    return __c > numeric_limits<unsigned short>::max();
+}
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
+__mul_overflowed(_Tp __a, _Tp __b, _Tp& __r)
+{
+    static_assert(is_unsigned<_Tp>::value, "");
+    return __builtin_mul_overflow(__a, __b, &__r);
+}
+
+template <typename _Tp, typename _Up>
+inline _LIBCPP_HIDE_FROM_ABI bool
+_LIBCPP_CONSTEXPR_SINCE_CXX23 __mul_overflowed(_Tp __a, _Up __b, _Tp& __r)
+{
+    return __itoa::__mul_overflowed(__a, static_cast<_Tp>(__b), __r);
+}
+
+template <typename _Tp>
+struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp>
+{
+    static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
+    using __traits_base<_Tp>::__pow;
+    using typename __traits_base<_Tp>::type;
+
+    // precondition: at least one non-zero character available
+    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char const*
+    __read(char const* __p, char const* __ep, type& __a, type& __b)
+    {
+        type __cprod[digits];
+        int __j = digits - 1;
+        int __i = digits;
+        do
+        {
+            if (*__p < '0' || *__p > '9')
+                break;
+            __cprod[--__i] = *__p++ - '0';
+        } while (__p != __ep && __i != 0);
+
+        __a = __inner_product(__cprod + __i + 1, __cprod + __j, __pow() + 1,
+                              __cprod[__i]);
+        if (__itoa::__mul_overflowed(__cprod[__j], __pow()[__j - __i], __b))
+            --__p;
+        return __p;
+    }
+
+    template <typename _It1, typename _It2, class _Up>
+    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Up
+    __inner_product(_It1 __first1, _It1 __last1, _It2 __first2, _Up __init)
+    {
+        for (; __first1 < __last1; ++__first1, ++__first2)
+            __init = __init + *__first1 * *__first2;
+        return __init;
+    }
+};
+
+}  // namespace __itoa
+
+template <typename _Tp>
+inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Tp
+__complement(_Tp __x)
+{
+    static_assert(is_unsigned<_Tp>::value, "cast to unsigned first");
+    return _Tp(~__x + 1);
+}
+
+
+#endif // _LIBCPP_STD_VER >= 17
+
+_LIBCPP_END_NAMESPACE_STD
+
+_LIBCPP_POP_MACROS
+
+#endif // _LIBCPP___CHARCONV_TRAITS

libcxx/include/__format/formatter_integral.h

 
 #include <__concepts/arithmetic.h>
 #include <__concepts/same_as.h>
 #include <__config>
 #include <__format/concepts.h>
 #include <__format/format_error.h>
 #include <__format/formatter_output.h>
 #include <__format/parser_std_format_spec.h>
+#include <__type_traits/make_unsigned.h>
 #include <__utility/unreachable.h>
 #include <array>
 #include <charconv>
 #include <limits>
 #include <string>
 #include <string_view>
 
 #ifndef _LIBCPP_HAS_NO_LOCALIZATION

libcxx/include/charconv

namespace std {
 
   constexpr from_chars_result from_chars(const char* first, const char* last,
                                see below& value, int base = 10);                         // constexpr since C++23
 
 } // namespace std
 
 */
 
-#include <__algorithm/copy_n.h>
 #include <__assert> // all public C++ headers provide the assertion handler
-#include <__availability>
-#include <__bit/countl.h>
 #include <__charconv/chars_format.h>
+#include <__charconv/from_chars_integral.h>
 #include <__charconv/from_chars_result.h>
 #include <__charconv/tables.h>
+#include <__charconv/to_chars.h>
 #include <__charconv/to_chars_base_10.h>
+#include <__charconv/to_chars_floating_point.h>
+#include <__charconv/to_chars_integral.h>
 #include <__charconv/to_chars_result.h>
+#include <__charconv/traits.h>
 #include <__config>
 #include <__debug>
 #include <__errc>
-#include <__memory/addressof.h>
-#include <__type_traits/is_unsigned.h>
-#include <__type_traits/make_32_64_or_128_bit.h>
-#include <__type_traits/make_unsigned.h>
-#include <__utility/unreachable.h>
 #include <cmath> // for log2f
 #include <cstdint>
 #include <cstdlib>
 #include <limits>
 
 #if !defined(_LIBCPP_HAS_NO_PRAGMA_SYSTEM_HEADER)
 #  pragma GCC system_header
 #endif
 
-_LIBCPP_PUSH_MACROS
-#include <__undef_macros>
-
 _LIBCPP_BEGIN_NAMESPACE_STD
 
-#if _LIBCPP_STD_VER >= 17
-
-to_chars_result to_chars(char*, char*, bool, int = 10) = delete;
-from_chars_result from_chars(const char*, const char*, bool, int = 10) = delete;
-
-namespace __itoa
-{
-
-template <typename _Tp, typename = void>
-struct _LIBCPP_HIDDEN __traits_base;
-
-template <typename _Tp>
-struct _LIBCPP_HIDDEN __traits_base<_Tp, __enable_if_t<sizeof(_Tp) <= sizeof(uint32_t)>>
-{
-    using type = uint32_t;
-
-    /// The width estimation using a log10 algorithm.
-    ///
-    /// The algorithm is based on
-    /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
-    /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
-    /// function requires its input to have at least one bit set the value of
-    /// zero is set to one. This means the first element of the lookup table is
-    /// zero.
-    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v)
-    {
-        auto __t = (32 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
-        return __t - (__v < __itoa::__pow10_32[__t]) + 1;
-    }
-
-    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v)
-    {
-        return __itoa::__base_10_u32(__p, __v);
-    }
-
-    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_32)& __pow() { return __itoa::__pow10_32; }
-};
-
-template <typename _Tp>
-struct _LIBCPP_HIDDEN
-    __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(uint64_t)>> {
-  using type = uint64_t;
-
-  /// The width estimation using a log10 algorithm.
-  ///
-  /// The algorithm is based on
-  /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
-  /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
-  /// function requires its input to have at least one bit set the value of
-  /// zero is set to one. This means the first element of the lookup table is
-  /// zero.
-  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
-    auto __t = (64 - std::__libcpp_clz(static_cast<type>(__v | 1))) * 1233 >> 12;
-    return __t - (__v < __itoa::__pow10_64[__t]) + 1;
-  }
-
-  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) { return __itoa::__base_10_u64(__p, __v); }
-
-  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_64)& __pow() { return __itoa::__pow10_64; }
-};
-
-
-#  ifndef _LIBCPP_HAS_NO_INT128
-template <typename _Tp>
-struct _LIBCPP_HIDDEN
-    __traits_base<_Tp, __enable_if_t<sizeof(_Tp) == sizeof(__uint128_t)> > {
-  using type = __uint128_t;
-
-  /// The width estimation using a log10 algorithm.
-  ///
-  /// The algorithm is based on
-  /// http://graphics.stanford.edu/~seander/bithacks.html#IntegerLog10
-  /// Instead of using IntegerLogBase2 it uses __libcpp_clz. Since that
-  /// function requires its input to have at least one bit set the value of
-  /// zero is set to one. This means the first element of the lookup table is
-  /// zero.
-  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int __width(_Tp __v) {
-    _LIBCPP_ASSERT(__v > numeric_limits<uint64_t>::max(), "The optimizations for this algorithm fail when this isn't true.");
-    // There's always a bit set in the upper 64-bits.
-    auto __t = (128 - std::__libcpp_clz(static_cast<uint64_t>(__v >> 64))) * 1233 >> 12;
-    _LIBCPP_ASSERT(__t >= __itoa::__pow10_128_offset, "Index out of bounds");
-    // __t is adjusted since the lookup table misses the lower entries.
-    return __t - (__v < __itoa::__pow10_128[__t - __itoa::__pow10_128_offset]) + 1;
-  }
-
-  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char* __convert(char* __p, _Tp __v) { return __itoa::__base_10_u128(__p, __v); }
-
-  // TODO FMT This pow function should get an index.
-  // By moving this to its own header it can be reused by the pow function in to_chars_base_10.
-  static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI decltype(__pow10_128)& __pow() { return __itoa::__pow10_128; }
-};
-#endif
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
-__mul_overflowed(unsigned char __a, _Tp __b, unsigned char& __r)
-{
-    auto __c = __a * __b;
-    __r = __c;
-    return __c > numeric_limits<unsigned char>::max();
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
-__mul_overflowed(unsigned short __a, _Tp __b, unsigned short& __r)
-{
-    auto __c = __a * __b;
-    __r = __c;
-    return __c > numeric_limits<unsigned short>::max();
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
-__mul_overflowed(_Tp __a, _Tp __b, _Tp& __r)
-{
-    static_assert(is_unsigned<_Tp>::value, "");
-    return __builtin_mul_overflow(__a, __b, &__r);
-}
-
-template <typename _Tp, typename _Up>
-inline _LIBCPP_HIDE_FROM_ABI bool
-_LIBCPP_CONSTEXPR_SINCE_CXX23 __mul_overflowed(_Tp __a, _Up __b, _Tp& __r)
-{
-    return __itoa::__mul_overflowed(__a, static_cast<_Tp>(__b), __r);
-}
-
-template <typename _Tp>
-struct _LIBCPP_HIDDEN __traits : __traits_base<_Tp>
-{
-    static constexpr int digits = numeric_limits<_Tp>::digits10 + 1;
-    using __traits_base<_Tp>::__pow;
-    using typename __traits_base<_Tp>::type;
-
-    // precondition: at least one non-zero character available
-    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI char const*
-    __read(char const* __p, char const* __ep, type& __a, type& __b)
-    {
-        type __cprod[digits];
-        int __j = digits - 1;
-        int __i = digits;
-        do
-        {
-            if (*__p < '0' || *__p > '9')
-                break;
-            __cprod[--__i] = *__p++ - '0';
-        } while (__p != __ep && __i != 0);
-
-        __a = __inner_product(__cprod + __i + 1, __cprod + __j, __pow() + 1,
-                              __cprod[__i]);
-        if (__itoa::__mul_overflowed(__cprod[__j], __pow()[__j - __i], __b))
-            --__p;
-        return __p;
-    }
-
-    template <typename _It1, typename _It2, class _Up>
-    static _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Up
-    __inner_product(_It1 __first1, _It1 __last1, _It2 __first2, _Up __init)
-    {
-        for (; __first1 < __last1; ++__first1, ++__first2)
-            __init = __init + *__first1 * *__first2;
-        return __init;
-    }
-};
-
-}  // namespace __itoa
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI _Tp
-__complement(_Tp __x)
-{
-    static_assert(is_unsigned<_Tp>::value, "cast to unsigned first");
-    return _Tp(~__x + 1);
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type);
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_itoa(char* __first, char* __last, _Tp __value, true_type)
-{
-    auto __x = std::__to_unsigned_like(__value);
-    if (__value < 0 && __first != __last)
-    {
-        *__first++ = '-';
-        __x = std::__complement(__x);
-    }
-
-    return std::__to_chars_itoa(__first, __last, __x, false_type());
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_itoa(char* __first, char* __last, _Tp __value, false_type)
-{
-    using __tx = __itoa::__traits<_Tp>;
-    auto __diff = __last - __first;
-
-    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
-        return {__tx::__convert(__first, __value), errc(0)};
-    else
-        return {__last, errc::value_too_large};
-}
-
-#  ifndef _LIBCPP_HAS_NO_INT128
-template <>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_itoa(char* __first, char* __last, __uint128_t __value, false_type)
-{
-    // When the value fits in 64-bits use the 64-bit code path. This reduces
-    // the number of expensive calculations on 128-bit values.
-    //
-    // NOTE the 128-bit code path requires this optimization.
-    if(__value <= numeric_limits<uint64_t>::max())
-        return __to_chars_itoa(__first, __last, static_cast<uint64_t>(__value), false_type());
-
-    using __tx = __itoa::__traits<__uint128_t>;
-    auto __diff = __last - __first;
-
-    if (__tx::digits <= __diff || __tx::__width(__value) <= __diff)
-        return {__tx::__convert(__first, __value), errc(0)};
-    else
-        return {__last, errc::value_too_large};
-}
-#endif
-
-template <class _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_integral(char* __first, char* __last, _Tp __value, int __base, false_type);
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
-                    true_type)
-{
-    auto __x = std::__to_unsigned_like(__value);
-    if (__value < 0 && __first != __last)
-    {
-        *__first++ = '-';
-        __x = std::__complement(__x);
-    }
-
-    return std::__to_chars_integral(__first, __last, __x, __base, false_type());
-}
-
-namespace __itoa {
-
-template <unsigned _Base>
-struct _LIBCPP_HIDDEN __integral;
-
-template <>
-struct _LIBCPP_HIDDEN __integral<2> {
-  template <typename _Tp>
-  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
-    // If value == 0 still need one digit. If the value != this has no
-    // effect since the code scans for the most significant bit set. (Note
-    // that __libcpp_clz doesn't work for 0.)
-    return numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1);
-  }
-
-  template <typename _Tp>
-  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
-    ptrdiff_t __cap = __last - __first;
-    int __n = __width(__value);
-    if (__n > __cap)
-      return {__last, errc::value_too_large};
-
-    __last = __first + __n;
-    char* __p = __last;
-    const unsigned __divisor = 16;
-    while (__value > __divisor) {
-      unsigned __c = __value % __divisor;
-      __value /= __divisor;
-      __p -= 4;
-      std::copy_n(&__base_2_lut[4 * __c], 4, __p);
-    }
-    do {
-      unsigned __c = __value % 2;
-      __value /= 2;
-      *--__p = "01"[__c];
-    } while (__value != 0);
-    return {__last, errc(0)};
-  }
-};
-
-template <>
-struct _LIBCPP_HIDDEN __integral<8> {
-  template <typename _Tp>
-  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
-    // If value == 0 still need one digit. If the value != this has no
-    // effect since the code scans for the most significat bit set. (Note
-    // that __libcpp_clz doesn't work for 0.)
-    return ((numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1)) + 2) / 3;
-  }
-
-  template <typename _Tp>
-  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
-    ptrdiff_t __cap = __last - __first;
-    int __n = __width(__value);
-    if (__n > __cap)
-      return {__last, errc::value_too_large};
-
-    __last = __first + __n;
-    char* __p = __last;
-    unsigned __divisor = 64;
-    while (__value > __divisor) {
-      unsigned __c = __value % __divisor;
-      __value /= __divisor;
-      __p -= 2;
-      std::copy_n(&__base_8_lut[2 * __c], 2, __p);
-    }
-    do {
-      unsigned __c = __value % 8;
-      __value /= 8;
-      *--__p = "01234567"[__c];
-    } while (__value != 0);
-    return {__last, errc(0)};
-  }
-
-};
-
-template <>
-struct _LIBCPP_HIDDEN __integral<16> {
-  template <typename _Tp>
-  _LIBCPP_HIDE_FROM_ABI static constexpr int __width(_Tp __value) noexcept {
-    // If value == 0 still need one digit. If the value != this has no
-    // effect since the code scans for the most significat bit set. (Note
-    // that __libcpp_clz doesn't work for 0.)
-    return (numeric_limits<_Tp>::digits - std::__libcpp_clz(__value | 1) + 3) / 4;
-  }
-
-  template <typename _Tp>
-  _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI static to_chars_result __to_chars(char* __first, char* __last, _Tp __value) {
-    ptrdiff_t __cap = __last - __first;
-    int __n = __width(__value);
-    if (__n > __cap)
-      return {__last, errc::value_too_large};
-
-    __last = __first + __n;
-    char* __p = __last;
-    unsigned __divisor = 256;
-    while (__value > __divisor) {
-      unsigned __c = __value % __divisor;
-      __value /= __divisor;
-      __p -= 2;
-      std::copy_n(&__base_16_lut[2 * __c], 2, __p);
-    }
-    if (__first != __last)
-      do {
-        unsigned __c = __value % 16;
-        __value /= 16;
-        *--__p = "0123456789abcdef"[__c];
-      } while (__value != 0);
-    return {__last, errc(0)};
-  }
-};
-
-} // namespace __itoa
-
-template <unsigned _Base, typename _Tp,
-          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
-__to_chars_integral_width(_Tp __value) {
-  return __itoa::__integral<_Base>::__width(__value);
-}
-
-template <unsigned _Base, typename _Tp,
-          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
-__to_chars_integral_width(_Tp __value) {
-  return std::__to_chars_integral_width<_Base>(static_cast<unsigned>(__value));
-}
-
-template <unsigned _Base, typename _Tp,
-          typename enable_if<(sizeof(_Tp) >= sizeof(unsigned)), int>::type = 0>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_integral(char* __first, char* __last, _Tp __value) {
-  return __itoa::__integral<_Base>::__to_chars(__first, __last, __value);
-}
-
-template <unsigned _Base, typename _Tp,
-          typename enable_if<(sizeof(_Tp) < sizeof(unsigned)), int>::type = 0>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_integral(char* __first, char* __last, _Tp __value) {
-  return std::__to_chars_integral<_Base>(__first, __last, static_cast<unsigned>(__value));
-}
-
-template <typename _Tp>
-_LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI int
-__to_chars_integral_width(_Tp __value, unsigned __base) {
-  _LIBCPP_ASSERT(__value >= 0, "The function requires a non-negative value.");
-
-  unsigned __base_2 = __base * __base;
-  unsigned __base_3 = __base_2 * __base;
-  unsigned __base_4 = __base_2 * __base_2;
-
-  int __r = 0;
-  while (true) {
-    if (__value < __base)
-      return __r + 1;
-    if (__value < __base_2)
-      return __r + 2;
-    if (__value < __base_3)
-      return __r + 3;
-    if (__value < __base_4)
-      return __r + 4;
-
-    __value /= __base_4;
-    __r += 4;
-  }
-
-  __libcpp_unreachable();
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-__to_chars_integral(char* __first, char* __last, _Tp __value, int __base,
-                    false_type)
-{
-  if (__base == 10) [[likely]]
-    return std::__to_chars_itoa(__first, __last, __value, false_type());
-
-  switch (__base) {
-  case 2:
-    return std::__to_chars_integral<2>(__first, __last, __value);
-  case 8:
-    return std::__to_chars_integral<8>(__first, __last, __value);
-  case 16:
-    return std::__to_chars_integral<16>(__first, __last, __value);
-  }
-
-  ptrdiff_t __cap = __last - __first;
-  int __n = std::__to_chars_integral_width(__value, __base);
-  if (__n > __cap)
-    return {__last, errc::value_too_large};
-
-  __last = __first + __n;
-  char* __p = __last;
-  do {
-    unsigned __c = __value % __base;
-    __value /= __base;
-    *--__p = "0123456789abcdefghijklmnopqrstuvwxyz"[__c];
-  } while (__value != 0);
-  return {__last, errc(0)};
-}
-
-template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-to_chars(char* __first, char* __last, _Tp __value)
-{
-  using _Type = __make_32_64_or_128_bit_t<_Tp>;
-  static_assert(!is_same<_Type, void>::value, "unsupported integral type used in to_chars");
-  return std::__to_chars_itoa(__first, __last, static_cast<_Type>(__value), is_signed<_Tp>());
-}
-
-template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI to_chars_result
-to_chars(char* __first, char* __last, _Tp __value, int __base)
-{
-  _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
-
-  using _Type = __make_32_64_or_128_bit_t<_Tp>;
-  return std::__to_chars_integral(__first, __last, static_cast<_Type>(__value), __base, is_signed<_Tp>());
-}
-
-template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-__sign_combinator(_It __first, _It __last, _Tp& __value, _Fn __f, _Ts... __args)
-{
-    using __tl = numeric_limits<_Tp>;
-    decltype(std::__to_unsigned_like(__value)) __x;
-
-    bool __neg = (__first != __last && *__first == '-');
-    auto __r = __f(__neg ? __first + 1 : __first, __last, __x, __args...);
-    switch (__r.ec)
-    {
-    case errc::invalid_argument:
-        return {__first, __r.ec};
-    case errc::result_out_of_range:
-        return __r;
-    default:
-        break;
-    }
-
-    if (__neg)
-    {
-        if (__x <= std::__complement(std::__to_unsigned_like(__tl::min())))
-        {
-            __x = std::__complement(__x);
-            std::copy_n(std::addressof(__x), 1, std::addressof(__value));
-            return __r;
-        }
-    }
-    else
-    {
-        if (__x <= std::__to_unsigned_like(__tl::max()))
-        {
-            __value = __x;
-            return __r;
-        }
-    }
-
-    return {__r.ptr, errc::result_out_of_range};
-}
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI bool
-__in_pattern(_Tp __c)
-{
-    return '0' <= __c && __c <= '9';
-}
-
-struct _LIBCPP_HIDDEN __in_pattern_result
-{
-    bool __ok;
-    int __val;
-
-    explicit _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI operator bool() const { return __ok; }
-};
-
-template <typename _Tp>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI __in_pattern_result
-__in_pattern(_Tp __c, int __base)
-{
-    if (__base <= 10)
-        return {'0' <= __c && __c < '0' + __base, __c - '0'};
-    else if (std::__in_pattern(__c))
-        return {true, __c - '0'};
-    else if ('a' <= __c && __c < 'a' + __base - 10)
-        return {true, __c - 'a' + 10};
-    else
-        return {'A' <= __c && __c < 'A' + __base - 10, __c - 'A' + 10};
-}
-
-template <typename _It, typename _Tp, typename _Fn, typename... _Ts>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-__subject_seq_combinator(_It __first, _It __last, _Tp& __value, _Fn __f,
-                         _Ts... __args)
-{
-    auto __find_non_zero = [](_It __firstit, _It __lastit) {
-        for (; __firstit != __lastit; ++__firstit)
-            if (*__firstit != '0')
-                break;
-        return __firstit;
-    };
-
-    auto __p = __find_non_zero(__first, __last);
-    if (__p == __last || !std::__in_pattern(*__p, __args...))
-    {
-        if (__p == __first)
-            return {__first, errc::invalid_argument};
-        else
-        {
-            __value = 0;
-            return {__p, {}};
-        }
-    }
-
-    auto __r = __f(__p, __last, __value, __args...);
-    if (__r.ec == errc::result_out_of_range)
-    {
-        for (; __r.ptr != __last; ++__r.ptr)
-        {
-            if (!std::__in_pattern(*__r.ptr, __args...))
-                break;
-        }
-    }
-
-    return __r;
-}
-
-template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
-{
-    using __tx = __itoa::__traits<_Tp>;
-    using __output_type = typename __tx::type;
-
-    return std::__subject_seq_combinator(
-        __first, __last, __value,
-        [](const char* __f, const char* __l,
-           _Tp& __val) -> from_chars_result {
-            __output_type __a, __b;
-            auto __p = __tx::__read(__f, __l, __a, __b);
-            if (__p == __l || !std::__in_pattern(*__p))
-            {
-                __output_type __m = numeric_limits<_Tp>::max();
-                if (__m >= __a && __m - __a >= __b)
-                {
-                    __val = __a + __b;
-                    return {__p, {}};
-                }
-            }
-            return {__p, errc::result_out_of_range};
-        });
-}
-
-template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-__from_chars_atoi(const char* __first, const char* __last, _Tp& __value)
-{
-    using __t = decltype(std::__to_unsigned_like(__value));
-    return std::__sign_combinator(__first, __last, __value, __from_chars_atoi<__t>);
-}
-
-
-/*
-// Code used to generate __from_chars_log2f_lut.
-#include <cmath>
-#include <iostream>
-#include <format>
-
-int main() {
-  for (int i = 2; i <= 36; ++i)
-    std::cout << std::format("{},\n", log2f(i));
-}
-*/
-/// log2f table for bases [2, 36].
-inline constexpr float __from_chars_log2f_lut[35] = {
-    1,         1.5849625, 2,         2.321928, 2.5849626, 2.807355, 3,        3.169925,  3.321928,
-    3.4594316, 3.5849626, 3.7004397, 3.807355, 3.9068906, 4,        4.087463, 4.169925,  4.2479277,
-    4.321928,  4.3923173, 4.4594316, 4.523562, 4.5849624, 4.643856, 4.70044,  4.7548876, 4.807355,
-    4.857981,  4.9068904, 4.9541965, 5,        5.044394,  5.087463, 5.129283, 5.169925};
-
-template <typename _Tp, typename enable_if<is_unsigned<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
-                      int __base)
-{
-    if (__base == 10)
-        return std::__from_chars_atoi(__first, __last, __value);
-
-    return std::__subject_seq_combinator(
-        __first, __last, __value,
-        [](const char* __p, const char* __lastp, _Tp& __val,
-           int __b) -> from_chars_result {
-            using __tl = numeric_limits<_Tp>;
-            // __base is always between 2 and 36 inclusive.
-            auto __digits = __tl::digits / __from_chars_log2f_lut[__b - 2];
-            _Tp __x = __in_pattern(*__p++, __b).__val, __y = 0;
-
-            for (int __i = 1; __p != __lastp; ++__i, ++__p)
-            {
-                if (auto __c = __in_pattern(*__p, __b))
-                {
-                    if (__i < __digits - 1)
-                        __x = __x * __b + __c.__val;
-                    else
-                    {
-                        if (!__itoa::__mul_overflowed(__x, __b, __x))
-                            ++__p;
-                        __y = __c.__val;
-                        break;
-                    }
-                }
-                else
-                    break;
-            }
-
-            if (__p == __lastp || !__in_pattern(*__p, __b))
-            {
-                if (__tl::max() - __x >= __y)
-                {
-                    __val = __x + __y;
-                    return {__p, {}};
-                }
-            }
-            return {__p, errc::result_out_of_range};
-        },
-        __base);
-}
-
-template <typename _Tp, typename enable_if<is_signed<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-__from_chars_integral(const char* __first, const char* __last, _Tp& __value,
-                      int __base)
-{
-    using __t = decltype(std::__to_unsigned_like(__value));
-    return std::__sign_combinator(__first, __last, __value,
-                                  __from_chars_integral<__t>, __base);
-}
-
-template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-from_chars(const char* __first, const char* __last, _Tp& __value)
-{
-    return std::__from_chars_atoi(__first, __last, __value);
-}
-
-template <typename _Tp, typename enable_if<is_integral<_Tp>::value, int>::type = 0>
-inline _LIBCPP_CONSTEXPR_SINCE_CXX23 _LIBCPP_HIDE_FROM_ABI from_chars_result
-from_chars(const char* __first, const char* __last, _Tp& __value, int __base)
-{
-    _LIBCPP_ASSERT(2 <= __base && __base <= 36, "base not in [2, 36]");
-    return std::__from_chars_integral(__first, __last, __value, __base);
-}
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, float __value);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, double __value);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, long double __value);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, float __value, chars_format __fmt, int __precision);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, double __value, chars_format __fmt, int __precision);
-
-_LIBCPP_AVAILABILITY_TO_CHARS_FLOATING_POINT _LIBCPP_FUNC_VIS
-to_chars_result to_chars(char* __first, char* __last, long double __value, chars_format __fmt, int __precision);
-
-#endif // _LIBCPP_STD_VER >= 17
-
 _LIBCPP_END_NAMESPACE_STD
 
-_LIBCPP_POP_MACROS
-
 #if !defined(_LIBCPP_REMOVE_TRANSITIVE_INCLUDES) && _LIBCPP_STD_VER <= 20
 #  include <concepts>
 #  include <cstring>
 #  include <iosfwd>
 #  include <type_traits>
 #endif
 
 #endif // _LIBCPP_CHARCONV

libcxx/include/module.modulemap.in

module bitset {
     export *
   }
   // No submodule for cassert. It fundamentally needs repeated, textual inclusion.
   module charconv {
     header "charconv"
     export *
 
     module __charconv {
-      module chars_format      { private header "__charconv/chars_format.h" }
-      module from_chars_result { private header "__charconv/from_chars_result.h" }
-      module tables            { private header "__charconv/tables.h" }
-      module to_chars_base_10  { private header "__charconv/to_chars_base_10.h" }
-      module to_chars_result   { private header "__charconv/to_chars_result.h" }
+      module chars_format            { private header "__charconv/chars_format.h" }
+      module from_chars_integral     { private header "__charconv/from_chars_integral.h" }
+      module from_chars_result       { private header "__charconv/from_chars_result.h" }
+      module tables                  { private header "__charconv/tables.h" }
+      module to_chars                { private header "__charconv/to_chars.h" }
+      module to_chars_base_10        { private header "__charconv/to_chars_base_10.h" }
+      module to_chars_floating_point { private header "__charconv/to_chars_floating_point.h" }
+      module to_chars_integral       { private header "__charconv/to_chars_integral.h" }
+      module to_chars_result         { private header "__charconv/to_chars_result.h" }
+      module traits                  { private header "__charconv/traits.h" }
     }
 
   }
   module chrono {
     header "chrono"
     export *
 
     module __chrono {

libcxx/test/libcxx/private_headers.verify.cpp

 #include <__bit/countl.h> // expected-error@*:* {{use of private header from outside its module: '__bit/countl.h'}}
 #include <__bit/countr.h> // expected-error@*:* {{use of private header from outside its module: '__bit/countr.h'}}
 #include <__bit/endian.h> // expected-error@*:* {{use of private header from outside its module: '__bit/endian.h'}}
 #include <__bit/has_single_bit.h> // expected-error@*:* {{use of private header from outside its module: '__bit/has_single_bit.h'}}
 #include <__bit/popcount.h> // expected-error@*:* {{use of private header from outside its module: '__bit/popcount.h'}}
 #include <__bit/rotate.h> // expected-error@*:* {{use of private header from outside its module: '__bit/rotate.h'}}
 #include <__bit_reference> // expected-error@*:* {{use of private header from outside its module: '__bit_reference'}}
 #include <__charconv/chars_format.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/chars_format.h'}}
+#include <__charconv/from_chars_integral.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/from_chars_integral.h'}}
 #include <__charconv/from_chars_result.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/from_chars_result.h'}}
 #include <__charconv/tables.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/tables.h'}}
+#include <__charconv/to_chars.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/to_chars.h'}}
 #include <__charconv/to_chars_base_10.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/to_chars_base_10.h'}}
+#include <__charconv/to_chars_floating_point.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/to_chars_floating_point.h'}}
+#include <__charconv/to_chars_integral.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/to_chars_integral.h'}}
 #include <__charconv/to_chars_result.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/to_chars_result.h'}}
+#include <__charconv/traits.h> // expected-error@*:* {{use of private header from outside its module: '__charconv/traits.h'}}
 #include <__chrono/calendar.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/calendar.h'}}
 #include <__chrono/concepts.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/concepts.h'}}
 #include <__chrono/convert_to_timespec.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/convert_to_timespec.h'}}
 #include <__chrono/convert_to_tm.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/convert_to_tm.h'}}
 #include <__chrono/day.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/day.h'}}
 #include <__chrono/duration.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/duration.h'}}
 #include <__chrono/file_clock.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/file_clock.h'}}
 #include <__chrono/formatter.h> // expected-error@*:* {{use of private header from outside its module: '__chrono/formatter.h'}}

libcxx/test/support/charconv_test_helpers.h

 
 #include <algorithm>
 #include <charconv>
 #include <cassert>
 #include <limits>
 #include <numeric>
 #include <string.h>
 #include <stdlib.h>
+#include <type_traits>
 
 #include "test_macros.h"
 
 #if TEST_STD_VER < 11
 #error This file requires C++11
 #endif
 
 using std::false_type;

libcxx/utils/data/ignore_format.txt

 libcxx/include/__bit/endian.h
 libcxx/include/__bit/popcount.h
 libcxx/include/__bit_reference
 libcxx/include/__bit/rotate.h
 libcxx/include/bitset
 libcxx/include/__bsd_locale_defaults.h
 libcxx/include/__bsd_locale_fallbacks.h
 libcxx/include/cctype
-libcxx/include/charconv
 libcxx/include/__charconv/chars_format.h
+libcxx/include/__charconv/from_chars_integral.h
 libcxx/include/__charconv/from_chars_result.h
 libcxx/include/__charconv/tables.h
 libcxx/include/__charconv/to_chars_base_10.h
+libcxx/include/__charconv/to_chars_floating_point.h
+libcxx/include/__charconv/to_chars_integral.h
 libcxx/include/__charconv/to_chars_result.h
+libcxx/include/__charconv/traits.h
 libcxx/include/chrono
 libcxx/include/__chrono/calendar.h
 libcxx/include/__chrono/convert_to_timespec.h
 libcxx/include/__chrono/day.h
 libcxx/include/__chrono/duration.h
 libcxx/include/__chrono/file_clock.h
 libcxx/include/__chrono/formatter.h
 libcxx/include/__chrono/hh_mm_ss.h